id,content,language
0,symtable Access to the compiler s symbol tables Source code Lib symtable py Symbol tables are generated by the compiler from AST just before bytecode is generated The symbol table is responsible for calculating the scope of every identifier in the code symtable provides an interface to examine these tables Generating Symbol Tables symtable symtable code filename compile_type Return the toplevel SymbolTable for the Python source code filename is the name of the file containing the code compile_type is like the mode argument to compile Examining Symbol Tables class symtable SymbolTable A namespace table for a block The constructor is not public get_type Return the type of the symbol table Possible values are class module function annotation TypeVar bound type alias and type parameter The latter four refer to different flavors of annotation scopes Changed in version 3 12 Added annotation TypeVar bound type alias and type parameter as possible return values get_id Return the table s identifier get_name Return the table s name This is the name of the class if the table is for a class the name of the function if the table is for a function or top if the table is global get_type returns module For type parameter scopes which are used for generic classes functions and type aliases it is the name of the underlying class function or type alias For type alias scopes it is the name of the type alias For TypeVar bound scopes it is the name of the TypeVar get_lineno Return the number of the first line in the block this table represents is_optimized Return True if the locals in this table can be optimized is_nested Return True if the block is a nested class or function has_children Return True if the block has nested namespaces within it These can be obtained with get_children get_identifiers Return a view object containing the names of symbols in the table See the documentation of view objects lookup name Lookup name in the table and return a Symbol instance get_symbols Return a list of Symbol instances for names in the table get_children Return a list of the nested symbol tables class symtable Function A namespace for a function or method This class inherits from SymbolTable get_parameters Return a tuple containing names of parameters to this function get_locals Return a tuple containing names of locals in this function get_globals Return a tuple containing names of globals in this function get_nonlocals Return a tuple containing names of nonlocals in this function get_frees Return a tuple containing names of free variables in this function class symtable Class A namespace of a class This class inherits from SymbolTable get_methods Return a tuple containing the names of methods declared in the class class symtable Symbol An entry in a SymbolTable corresponding to an identifier in the source The constructor is not public get_name Return the symbol s name is_referenced Return True if the symbol is used in its block is_imported Return True if the symbol is created from an import statement is_parameter Return True if the symbol is a parameter is_global Return True if the symbol is global is_nonlocal Return True if the symbol is nonlocal is_declared_global Return True if the symbol is declared global with a global statement is_local Return True if the symbol is local to its block is_annotated Return True if the symbol is annotated New in version 3 6 is_free Return True if the symbol is referenced in its block but not assigned to is_assigned Return True if the symbol is assigned to in its block is_namespace Return True if name binding introduces new namespace If the name is used as the target of a function or class statement this will be true For example table symtable symtable def some_func pass string exec table lookup some_func is_namespace True Note that a single name can be bound to multiple objects If the result is True the name may also be bound to other objects like an int or list that does not introduce a new namespace get_namespaces Return a list of namespaces bound to this name get_namespace Return the namespace bound to this na,en
1,me If more than one or no namespace is bound to this name a ValueError is raised,en
2,lzma Compression using the LZMA algorithm New in version 3 3 Source code Lib lzma py This module provides classes and convenience functions for compressing and decompressing data using the LZMA compression algorithm Also included is a file interface supporting the xz and legacy lzma file formats used by the xz utility as well as raw compressed streams The interface provided by this module is very similar to that of the bz2 module Note that LZMAFile and bz2 BZ2File are not thread safe so if you need to use a single LZMAFile instance from multiple threads it is necessary to protect it with a lock exception lzma LZMAError This exception is raised when an error occurs during compression or decompression or while initializing the compressor decompressor state Reading and writing compressed files lzma open filename mode rb format None check 1 preset None filters None encoding None errors None newline None Open an LZMA compressed file in binary or text mode returning a file object The filename argument can be either an actual file name given as a str bytes or path like object in which case the named file is opened or it can be an existing file object to read from or write to The mode argument can be any of r rb w wb x xb a or ab for binary mode or rt wt xt or at for text mode The default is rb When opening a file for reading the format and filters arguments have the same meanings as for LZMADecompressor In this case the check and preset arguments should not be used When opening a file for writing the format check preset and filters arguments have the same meanings as for LZMACompressor For binary mode this function is equivalent to the LZMAFile constructor LZMAFile filename mode In this case the encoding errors and newline arguments must not be provided For text mode a LZMAFile object is created and wrapped in an io TextIOWrapper instance with the specified encoding error handling behavior and line ending s Changed in version 3 4 Added support for the x xb and xt modes Changed in version 3 6 Accepts a path like object class lzma LZMAFile filename None mode r format None check 1 preset None filters None Open an LZMA compressed file in binary mode An LZMAFile can wrap an already open file object or operate directly on a named file The filename argument specifies either the file object to wrap or the name of the file to open as a str bytes or path like object When wrapping an existing file object the wrapped file will not be closed when the LZMAFile is closed The mode argument can be either r for reading default w for overwriting x for exclusive creation or a for appending These can equivalently be given as rb wb xb and ab respectively If filename is a file object rather than an actual file name a mode of w does not truncate the file and is instead equivalent to a When opening a file for reading the input file may be the concatenation of multiple separate compressed streams These are transparently decoded as a single logical stream When opening a file for reading the format and filters arguments have the same meanings as for LZMADecompressor In this case the check and preset arguments should not be used When opening a file for writing the format check preset and filters arguments have the same meanings as for LZMACompressor LZMAFile supports all the members specified by io BufferedIOBase except for detach and truncate Iteration and the with statement are supported The following method is also provided peek size 1 Return buffered data without advancing the file position At least one byte of data will be returned unless EOF has been reached The exact number of bytes returned is unspecified the size argument is ignored Note While calling peek does not change the file position of the LZMAFile it may change the position of the underlying file object e g if the LZMAFile was constructed by passing a file object for filename Changed in version 3 4 Added support for the x and xb modes Changed in version 3 5 The read method now accepts an argument of None Changed in version 3 6 Accepts a path like object Compressing and decompressing data i,en
3,n memory class lzma LZMACompressor format FORMAT_XZ check 1 preset None filters None Create a compressor object which can be used to compress data incrementally For a more convenient way of compressing a single chunk of data see compress The format argument specifies what container format should be used Possible values are FORMAT_XZ The xz container format This is the default format FORMAT_ALONE The legacy lzma container format This format is more limited than xz it does not support integrity checks or multiple filters FORMAT_RAW A raw data stream not using any container format This format specifier does not support integrity checks and requires that you always specify a custom filter chain for both compression and decompression Additionally data compressed in this manner cannot be decompressed using FORMAT_AUTO see LZMADecompressor The check argument specifies the type of integrity check to include in the compressed data This check is used when decompressing to ensure that the data has not been corrupted Possible values are CHECK_NONE No integrity check This is the default and the only acceptable value for FORMAT_ALONE and FORMAT_RAW CHECK_CRC32 32 bit Cyclic Redundancy Check CHECK_CRC64 64 bit Cyclic Redundancy Check This is the default for FORMAT_XZ CHECK_SHA256 256 bit Secure Hash Algorithm If the specified check is not supported an LZMAError is raised The compression settings can be specified either as a preset compression level with the preset argument or in detail as a custom filter chain with the filters argument The preset argument if provided should be an integer between 0 and 9 inclusive optionally OR ed with the constant PRESET_EXTREME If neither preset nor filters are given the default behavior is to use PRESET_DEFAULT preset level 6 Higher presets produce smaller output but make the compression process slower Note In addition to being more CPU intensive compression with higher presets also requires much more memory and produces output that needs more memory to decompress With preset 9 for example the overhead for an LZMACompressor object can be as high as 800 MiB For this reason it is generally best to stick with the default preset The filters argument if provided should be a filter chain specifier See Specifying custom filter chains for details compress data Compress data a bytes object returning a bytes object containing compressed data for at least part of the input Some of data may be buffered internally for use in later calls to compress and flush The returned data should be concatenated with the output of any previous calls to compress flush Finish the compression process returning a bytes object containing any data stored in the compressor s internal buffers The compressor cannot be used after this method has been called class lzma LZMADecompressor format FORMAT_AUTO memlimit None filters None Create a decompressor object which can be used to decompress data incrementally For a more convenient way of decompressing an entire compressed stream at once see decompress The format argument specifies the container format that should be used The default is FORMAT_AUTO which can decompress both xz and lzma files Other possible values are FORMAT_XZ FORMAT_ALONE and FORMAT_RAW The memlimit argument specifies a limit in bytes on the amount of memory that the decompressor can use When this argument is used decompression will fail with an LZMAError if it is not possible to decompress the input within the given memory limit The filters argument specifies the filter chain that was used to create the stream being decompressed This argument is required if format is FORMAT_RAW but should not be used for other formats See Specifying custom filter chains for more information about filter chains Note This class does not transparently handle inputs containing multiple compressed streams unlike decompress and LZMAFile To decompress a multi stream input with LZMADecompressor you must create a new decompressor for each stream decompress data max_length 1 Decompress data a bytes like object returning uncompressed data as bytes,en
4, Some of data may be buffered internally for use in later calls to decompress The returned data should be concatenated with the output of any previous calls to decompress If max_length is nonnegative returns at most max_length bytes of decompressed data If this limit is reached and further output can be produced the needs_input attribute will be set to False In this case the next call to decompress may provide data as b to obtain more of the output If all of the input data was decompressed and returned either because this was less than max_length bytes or because max_length was negative the needs_input attribute will be set to True Attempting to decompress data after the end of stream is reached raises an EOFError Any data found after the end of the stream is ignored and saved in the unused_data attribute Changed in version 3 5 Added the max_length parameter check The ID of the integrity check used by the input stream This may be CHECK_UNKNOWN until enough of the input has been decoded to determine what integrity check it uses eof True if the end of stream marker has been reached unused_data Data found after the end of the compressed stream Before the end of the stream is reached this will be b needs_input False if the decompress method can provide more decompressed data before requiring new uncompressed input New in version 3 5 lzma compress data format FORMAT_XZ check 1 preset None filters None Compress data a bytes object returning the compressed data as a bytes object See LZMACompressor above for a description of the format check preset and filters arguments lzma decompress data format FORMAT_AUTO memlimit None filters None Decompress data a bytes object returning the uncompressed data as a bytes object If data is the concatenation of multiple distinct compressed streams decompress all of these streams and return the concatenation of the results See LZMADecompressor above for a description of the format memlimit and filters arguments Miscellaneous lzma is_check_supported check Return True if the given integrity check is supported on this system CHECK_NONE and CHECK_CRC32 are always supported CHECK_CRC64 and CHECK_SHA256 may be unavailable if you are using a version of liblzma that was compiled with a limited feature set Specifying custom filter chains A filter chain specifier is a sequence of dictionaries where each dictionary contains the ID and options for a single filter Each dictionary must contain the key id and may contain additional keys to specify filter dependent options Valid filter IDs are as follows Compression filters FILTER_LZMA1 for use with FORMAT_ALONE FILTER_LZMA2 for use with FORMAT_XZ and FORMAT_RAW Delta filter FILTER_DELTA Branch Call Jump BCJ filters FILTER_X86 FILTER_IA64 FILTER_ARM FILTER_ARMTHUMB FILTER_POWERPC FILTER_SPARC A filter chain can consist of up to 4 filters and cannot be empty The last filter in the chain must be a compression filter and any other filters must be delta or BCJ filters Compression filters support the following options specified as additional entries in the dictionary representing the filter preset A compression preset to use as a source of default values for options that are not specified explicitly dict_size Dictionary size in bytes This should be between 4 KiB and 1 5 GiB inclusive lc Number of literal context bits lp Number of literal position bits The sum lc lp must be at most 4 pb Number of position bits must be at most 4 mode MODE_FAST or MODE_NORMAL nice_len What should be considered a nice length for a match This should be 273 or less mf What match finder to use MF_HC3 MF_HC4 MF_BT2 MF_BT3 or MF_BT4 depth Maximum search depth used by match finder 0 default means to select automatically based on other filter options The delta filter stores the differences between bytes producing more repetitive input for the compressor in certain circumstances It supports one option dist This indicates the distance between bytes to be subtracted The default is 1 i e take the differences between adjacent bytes The BCJ filters are intended to be applied to machine code They co,en
5,nvert relative branches calls and jumps in the code to use absolute addressing with the aim of increasing the redundancy that can be exploited by the compressor These filters support one option start_offset This specifies the address that should be mapped to the beginning of the input data The default is 0 Examples Reading in a compressed file import lzma with lzma open file xz as f file_content f read Creating a compressed file import lzma data b Insert Data Here with lzma open file xz w as f f write data Compressing data in memory import lzma data_in b Insert Data Here data_out lzma compress data_in Incremental compression import lzma lzc lzma LZMACompressor out1 lzc compress b Some data n out2 lzc compress b Another piece of data n out3 lzc compress b Even more data n out4 lzc flush Concatenate all the partial results result b join out1 out2 out3 out4 Writing compressed data to an already open file import lzma with open file xz wb as f f write b This data will not be compressed n with lzma open f w as lzf lzf write b This will be compressed n f write b Not compressed n Creating a compressed file using a custom filter chain import lzma my_filters id lzma FILTER_DELTA dist 5 id lzma FILTER_LZMA2 preset 7 lzma PRESET_EXTREME with lzma open file xz w filters my_filters as f f write b blah blah blah,en
6,keyword Testing for Python keywords Source code Lib keyword py This module allows a Python program to determine if a string is a keyword or soft keyword keyword iskeyword s Return True if s is a Python keyword keyword kwlist Sequence containing all the keywords defined for the interpreter If any keywords are defined to only be active when particular __future__ statements are in effect these will be included as well keyword issoftkeyword s Return True if s is a Python soft keyword New in version 3 9 keyword softkwlist Sequence containing all the soft keywords defined for the interpreter If any soft keywords are defined to only be active when particular __future__ statements are in effect these will be included as well New in version 3 9,en
7,Design and History FAQ Why does Python use indentation for grouping of statements Guido van Rossum believes that using indentation for grouping is extremely elegant and contributes a lot to the clarity of the average Python program Most people learn to love this feature after a while Since there are no begin end brackets there cannot be a disagreement between grouping perceived by the parser and the human reader Occasionally C programmers will encounter a fragment of code like this if x y x y z Only the x statement is executed if the condition is true but the indentation leads many to believe otherwise Even experienced C programmers will sometimes stare at it a long time wondering as to why y is being decremented even for x y Because there are no begin end brackets Python is much less prone to coding style conflicts In C there are many different ways to place the braces After becoming used to reading and writing code using a particular style it is normal to feel somewhat uneasy when reading or being required to write in a different one Many coding styles place begin end brackets on a line by themselves This makes programs considerably longer and wastes valuable screen space making it harder to get a good overview of a program Ideally a function should fit on one screen say 20 30 lines 20 lines of Python can do a lot more work than 20 lines of C This is not solely due to the lack of begin end brackets the lack of declarations and the high level data types are also responsible but the indentation based syntax certainly helps Why am I getting strange results with simple arithmetic operations See the next question Why are floating point calculations so inaccurate Users are often surprised by results like this 1 2 1 0 0 19999999999999996 and think it is a bug in Python It s not This has little to do with Python and much more to do with how the underlying platform handles floating point numbers The float type in CPython uses a C double for storage A float object s value is stored in binary floating point with a fixed precision typically 53 bits and Python uses C operations which in turn rely on the hardware implementation in the processor to perform floating point operations This means that as far as floating point operations are concerned Python behaves like many popular languages including C and Java Many numbers that can be written easily in decimal notation cannot be expressed exactly in binary floating point For example after x 1 2 the value stored for x is a very good approximation to the decimal value 1 2 but is not exactly equal to it On a typical machine the actual stored value is 1 0011001100110011001100110011001100110011001100110011 binary which is exactly 1 1999999999999999555910790149937383830547332763671875 decimal The typical precision of 53 bits provides Python floats with 15 16 decimal digits of accuracy For a fuller explanation please see the floating point arithmetic chapter in the Python tutorial Why are Python strings immutable There are several advantages One is performance knowing that a string is immutable means we can allocate space for it at creation time and the storage requirements are fixed and unchanging This is also one of the reasons for the distinction between tuples and lists Another advantage is that strings in Python are considered as elemental as numbers No amount of activity will change the value 8 to anything else and in Python no amount of activity will change the string eight to anything else Why must self be used explicitly in method definitions and calls The idea was borrowed from Modula 3 It turns out to be very useful for a variety of reasons First it s more obvious that you are using a method or instance attribute instead of a local variable Reading self x or self meth makes it absolutely clear that an instance variable or method is used even if you don t know the class definition by heart In C you can sort of tell by the lack of a local variable declaration assuming globals are rare or easily recognizable but in Python there are no local variable declarations so you d have to look,en
8, up the class definition to be sure Some C and Java coding standards call for instance attributes to have an m_ prefix so this explicitness is still useful in those languages too Second it means that no special syntax is necessary if you want to explicitly reference or call the method from a particular class In C if you want to use a method from a base class which is overridden in a derived class you have to use the operator in Python you can write baseclass methodname self argument list This is particularly useful for __init__ methods and in general in cases where a derived class method wants to extend the base class method of the same name and thus has to call the base class method somehow Finally for instance variables it solves a syntactic problem with assignment since local variables in Python are by definition those variables to which a value is assigned in a function body and that aren t explicitly declared global there has to be some way to tell the interpreter that an assignment was meant to assign to an instance variable instead of to a local variable and it should preferably be syntactic for efficiency reasons C does this through declarations but Python doesn t have declarations and it would be a pity having to introduce them just for this purpose Using the explicit self var solves this nicely Similarly for using instance variables having to write self var means that references to unqualified names inside a method don t have to search the instance s directories To put it another way local variables and instance variables live in two different namespaces and you need to tell Python which namespace to use Why can t I use an assignment in an expression Starting in Python 3 8 you can Assignment expressions using the walrus operator assign a variable in an expression while chunk fp read 200 print chunk See PEP 572 for more information Why does Python use methods for some functionality e g list index but functions for other e g len list As Guido said a For some operations prefix notation just reads better than postfix prefix and infix operations have a long tradition in mathematics which likes notations where the visuals help the mathematician thinking about a problem Compare the easy with which we rewrite a formula like x a b into x a x b to the clumsiness of doing the same thing using a raw OO notation b When I read code that says len x I know that it is asking for the length of something This tells me two things the result is an integer and the argument is some kind of container To the contrary when I read x len I have to already know that x is some kind of container implementing an interface or inheriting from a class that has a standard len Witness the confusion we occasionally have when a class that is not implementing a mapping has a get or keys method or something that isn t a file has a write method https mail python org pipermail python 3000 2006 November 004 643 html Why is join a string method instead of a list or tuple method Strings became much more like other standard types starting in Python 1 6 when methods were added which give the same functionality that has always been available using the functions of the string module Most of these new methods have been widely accepted but the one which appears to make some programmers feel uncomfortable is join 1 2 4 8 16 which gives the result 1 2 4 8 16 There are two common arguments against this usage The first runs along the lines of It looks really ugly using a method of a string literal string constant to which the answer is that it might but a string literal is just a fixed value If the methods are to be allowed on names bound to strings there is no logical reason to make them unavailable on literals The second objection is typically cast as I am really telling a sequence to join its members together with a string constant Sadly you aren t For some reason there seems to be much less difficulty with having split as a string method since in that case it is easy to see that 1 2 4 8 16 split is an instruction to a string literal to return the substrings deli,en
9,mited by the given separator or by default arbitrary runs of white space join is a string method because in using it you are telling the separator string to iterate over a sequence of strings and insert itself between adjacent elements This method can be used with any argument which obeys the rules for sequence objects including any new classes you might define yourself Similar methods exist for bytes and bytearray objects How fast are exceptions A try except block is extremely efficient if no exceptions are raised Actually catching an exception is expensive In versions of Python prior to 2 0 it was common to use this idiom try value mydict key except KeyError mydict key getvalue key value mydict key This only made sense when you expected the dict to have the key almost all the time If that wasn t the case you coded it like this if key in mydict value mydict key else value mydict key getvalue key For this specific case you could also use value dict setdefault key getvalue key but only if the getvalue call is cheap enough because it is evaluated in all cases Why isn t there a switch or case statement in Python In general structured switch statements execute one block of code when an expression has a particular value or set of values Since Python 3 10 one can easily match literal values or constants within a namespace with a match case statement An older alternative is a sequence of if elif elif else For cases where you need to choose from a very large number of possibilities you can create a dictionary mapping case values to functions to call For example functions a function_1 b function_2 c self method_1 func functions value func For calling methods on objects you can simplify yet further by using the getattr built in to retrieve methods with a particular name class MyVisitor def visit_a self def dispatch self value method_name visit_ str value method getattr self method_name method It s suggested that you use a prefix for the method names such as visit_ in this example Without such a prefix if values are coming from an untrusted source an attacker would be able to call any method on your object Imitating switch with fallthrough as with C s switch case default is possible much harder and less needed Can t you emulate threads in the interpreter instead of relying on an OS specific thread implementation Answer 1 Unfortunately the interpreter pushes at least one C stack frame for each Python stack frame Also extensions can call back into Python at almost random moments Therefore a complete threads implementation requires thread support for C Answer 2 Fortunately there is Stackless Python which has a completely redesigned interpreter loop that avoids the C stack Why can t lambda expressions contain statements Python lambda expressions cannot contain statements because Python s syntactic framework can t handle statements nested inside expressions However in Python this is not a serious problem Unlike lambda forms in other languages where they add functionality Python lambdas are only a shorthand notation if you re too lazy to define a function Functions are already first class objects in Python and can be declared in a local scope Therefore the only advantage of using a lambda instead of a locally defined function is that you don t need to invent a name for the function but that s just a local variable to which the function object which is exactly the same type of object that a lambda expression yields is assigned Can Python be compiled to machine code C or some other language Cython compiles a modified version of Python with optional annotations into C extensions Nuitka is an up and coming compiler of Python into C code aiming to support the full Python language How does Python manage memory The details of Python memory management depend on the implementation The standard implementation of Python CPython uses reference counting to detect inaccessible objects and another mechanism to collect reference cycles periodically executing a cycle detection algorithm which looks for inaccessible cycles and deletes the objects involved,en
10, The gc module provides functions to perform a garbage collection obtain debugging statistics and tune the collector s parameters Other implementations such as Jython or PyPy however can rely on a different mechanism such as a full blown garbage collector This difference can cause some subtle porting problems if your Python code depends on the behavior of the reference counting implementation In some Python implementations the following code which is fine in CPython will probably run out of file descriptors for file in very_long_list_of_files f open file c f read 1 Indeed using CPython s reference counting and destructor scheme each new assignment to f closes the previous file With a traditional GC however those file objects will only get collected and closed at varying and possibly long intervals If you want to write code that will work with any Python implementation you should explicitly close the file or use the with statement this will work regardless of memory management scheme for file in very_long_list_of_files with open file as f c f read 1 Why doesn t CPython use a more traditional garbage collection scheme For one thing this is not a C standard feature and hence it s not portable Yes we know about the Boehm GC library It has bits of assembler code for most common platforms not for all of them and although it is mostly transparent it isn t completely transparent patches are required to get Python to work with it Traditional GC also becomes a problem when Python is embedded into other applications While in a standalone Python it s fine to replace the standard malloc and free with versions provided by the GC library an application embedding Python may want to have its own substitute for malloc and free and may not want Python s Right now CPython works with anything that implements malloc and free properly Why isn t all memory freed when CPython exits Objects referenced from the global namespaces of Python modules are not always deallocated when Python exits This may happen if there are circular references There are also certain bits of memory that are allocated by the C library that are impossible to free e g a tool like Purify will complain about these Python is however aggressive about cleaning up memory on exit and does try to destroy every single object If you want to force Python to delete certain things on deallocation use the atexit module to run a function that will force those deletions Why are there separate tuple and list data types Lists and tuples while similar in many respects are generally used in fundamentally different ways Tuples can be thought of as being similar to Pascal records or C structs they re small collections of related data which may be of different types which are operated on as a group For example a Cartesian coordinate is appropriately represented as a tuple of two or three numbers Lists on the other hand are more like arrays in other languages They tend to hold a varying number of objects all of which have the same type and which are operated on one by one For example os listdir returns a list of strings representing the files in the current directory Functions which operate on this output would generally not break if you added another file or two to the directory Tuples are immutable meaning that once a tuple has been created you can t replace any of its elements with a new value Lists are mutable meaning that you can always change a list s elements Only immutable elements can be used as dictionary keys and hence only tuples and not lists can be used as keys How are lists implemented in CPython CPython s lists are really variable length arrays not Lisp style linked lists The implementation uses a contiguous array of references to other objects and keeps a pointer to this array and the array s length in a list head structure This makes indexing a list a i an operation whose cost is independent of the size of the list or the value of the index When items are appended or inserted the array of references is resized Some cleverness is applied to improve the performance of appending it,en
11,ems repeatedly when the array must be grown some extra space is allocated so the next few times don t require an actual resize How are dictionaries implemented in CPython CPython s dictionaries are implemented as resizable hash tables Compared to B trees this gives better performance for lookup the most common operation by far under most circumstances and the implementation is simpler Dictionaries work by computing a hash code for each key stored in the dictionary using the hash built in function The hash code varies widely depending on the key and a per process seed for example Python could hash to 539294296 while python a string that differs by a single bit could hash to 1142331976 The hash code is then used to calculate a location in an internal array where the value will be stored Assuming that you re storing keys that all have different hash values this means that dictionaries take constant time O 1 in Big O notation to retrieve a key Why must dictionary keys be immutable The hash table implementation of dictionaries uses a hash value calculated from the key value to find the key If the key were a mutable object its value could change and thus its hash could also change But since whoever changes the key object can t tell that it was being used as a dictionary key it can t move the entry around in the dictionary Then when you try to look up the same object in the dictionary it won t be found because its hash value is different If you tried to look up the old value it wouldn t be found either because the value of the object found in that hash bin would be different If you want a dictionary indexed with a list simply convert the list to a tuple first the function tuple L creates a tuple with the same entries as the list L Tuples are immutable and can therefore be used as dictionary keys Some unacceptable solutions that have been proposed Hash lists by their address object ID This doesn t work because if you construct a new list with the same value it won t be found e g mydict 1 2 12 print mydict 1 2 would raise a KeyError exception because the id of the 1 2 used in the second line differs from that in the first line In other words dictionary keys should be compared using not using is Make a copy when using a list as a key This doesn t work because the list being a mutable object could contain a reference to itself and then the copying code would run into an infinite loop Allow lists as keys but tell the user not to modify them This would allow a class of hard to track bugs in programs when you forgot or modified a list by accident It also invalidates an important invariant of dictionaries every value in d keys is usable as a key of the dictionary Mark lists as read only once they are used as a dictionary key The problem is that it s not just the top level object that could change its value you could use a tuple containing a list as a key Entering anything as a key into a dictionary would require marking all objects reachable from there as read only and again self referential objects could cause an infinite loop There is a trick to get around this if you need to but use it at your own risk You can wrap a mutable structure inside a class instance which has both a __eq__ and a __hash__ method You must then make sure that the hash value for all such wrapper objects that reside in a dictionary or other hash based structure remain fixed while the object is in the dictionary or other structure class ListWrapper def __init__ self the_list self the_list the_list def __eq__ self other return self the_list other the_list def __hash__ self l self the_list result 98767 len l 555 for i el in enumerate l try result result hash el 9999999 1001 i except Exception result result 7777777 i 333 return result Note that the hash computation is complicated by the possibility that some members of the list may be unhashable and also by the possibility of arithmetic overflow Furthermore it must always be the case that if o1 o2 ie o1 __eq__ o2 is True then hash o1 hash o2 ie o1 __hash__ o2 __hash__ regardless of whether the object is in a diction,en
12,ary or not If you fail to meet these restrictions dictionaries and other hash based structures will misbehave In the case of ListWrapper whenever the wrapper object is in a dictionary the wrapped list must not change to avoid anomalies Don t do this unless you are prepared to think hard about the requirements and the consequences of not meeting them correctly Consider yourself warned Why doesn t list sort return the sorted list In situations where performance matters making a copy of the list just to sort it would be wasteful Therefore list sort sorts the list in place In order to remind you of that fact it does not return the sorted list This way you won t be fooled into accidentally overwriting a list when you need a sorted copy but also need to keep the unsorted version around If you want to return a new list use the built in sorted function instead This function creates a new list from a provided iterable sorts it and returns it For example here s how to iterate over the keys of a dictionary in sorted order for key in sorted mydict do whatever with mydict key How do you specify and enforce an interface spec in Python An interface specification for a module as provided by languages such as C and Java describes the prototypes for the methods and functions of the module Many feel that compile time enforcement of interface specifications helps in the construction of large programs Python 2 6 adds an abc module that lets you define Abstract Base Classes ABCs You can then use isinstance and issubclass to check whether an instance or a class implements a particular ABC The collections abc module defines a set of useful ABCs such as Iterable Container and MutableMapping For Python many of the advantages of interface specifications can be obtained by an appropriate test discipline for components A good test suite for a module can both provide a regression test and serve as a module interface specification and a set of examples Many Python modules can be run as a script to provide a simple self test Even modules which use complex external interfaces can often be tested in isolation using trivial stub emulations of the external interface The doctest and unittest modules or third party test frameworks can be used to construct exhaustive test suites that exercise every line of code in a module An appropriate testing discipline can help build large complex applications in Python as well as having interface specifications would In fact it can be better because an interface specification cannot test certain properties of a program For example the list append method is expected to add new elements to the end of some internal list an interface specification cannot test that your list append implementation will actually do this correctly but it s trivial to check this property in a test suite Writing test suites is very helpful and you might want to design your code to make it easily tested One increasingly popular technique test driven development calls for writing parts of the test suite first before you write any of the actual code Of course Python allows you to be sloppy and not write test cases at all Why is there no goto In the 1970s people realized that unrestricted goto could lead to messy spaghetti code that was hard to understand and revise In a high level language it is also unneeded as long as there are ways to branch in Python with if statements and or and and if else expressions and loop with while and for statements possibly containing continue and break One can also use exceptions to provide a structured goto that works even across function calls Many feel that exceptions can conveniently emulate all reasonable uses of the go or goto constructs of C Fortran and other languages For example class label Exception pass declare a label try if condition raise label goto label except label where to goto pass This doesn t allow you to jump into the middle of a loop but that s usually considered an abuse of goto anyway Use sparingly Why can t raw strings r strings end with a backslash More precisely they can t end with an odd nu,en
13,mber of backslashes the unpaired backslash at the end escapes the closing quote character leaving an unterminated string Raw strings were designed to ease creating input for processors chiefly regular expression engines that want to do their own backslash escape processing Such processors consider an unmatched trailing backslash to be an error anyway so raw strings disallow that In return they allow you to pass on the string quote character by escaping it with a backslash These rules work well when r strings are used for their intended purpose If you re trying to build Windows pathnames note that all Windows system calls accept forward slashes too f open mydir file txt works fine If you re trying to build a pathname for a DOS command try e g one of dir r this is my dos dir dir r this is my dos dir 1 dir this is my dos dir Why doesn t Python have a with statement for attribute assignments Python has a with statement that wraps the execution of a block calling code on the entrance and exit from the block Some languages have a construct that looks like this with obj a 1 equivalent to obj a 1 total total 1 obj total obj total 1 In Python such a construct would be ambiguous Other languages such as Object Pascal Delphi and C use static types so it s possible to know in an unambiguous way what member is being assigned to This is the main point of static typing the compiler always knows the scope of every variable at compile time Python uses dynamic types It is impossible to know in advance which attribute will be referenced at runtime Member attributes may be added or removed from objects on the fly This makes it impossible to know from a simple reading what attribute is being referenced a local one a global one or a member attribute For instance take the following incomplete snippet def foo a with a print x The snippet assumes that a must have a member attribute called x However there is nothing in Python that tells the interpreter this What should happen if a is let us say an integer If there is a global variable named x will it be used inside the with block As you see the dynamic nature of Python makes such choices much harder The primary benefit of with and similar language features reduction of code volume can however easily be achieved in Python by assignment Instead of function args mydict index index a 21 function args mydict index index b 42 function args mydict index index c 63 write this ref function args mydict index index ref a 21 ref b 42 ref c 63 This also has the side effect of increasing execution speed because name bindings are resolved at run time in Python and the second version only needs to perform the resolution once Similar proposals that would introduce syntax to further reduce code volume such as using a leading dot have been rejected in favour of explicitness see https mail python org pipermail python ideas 2016 May 040070 html Why don t generators support the with statement For technical reasons a generator used directly as a context manager would not work correctly When as is most common a generator is used as an iterator run to completion no closing is needed When it is wrap it as contextlib closing generator in the with statement Why are colons required for the if while def class statements The colon is required primarily to enhance readability one of the results of the experimental ABC language Consider this if a b print a versus if a b print a Notice how the second one is slightly easier to read Notice further how a colon sets off the example in this FAQ answer it s a standard usage in English Another minor reason is that the colon makes it easier for editors with syntax highlighting they can look for colons to decide when indentation needs to be increased instead of having to do a more elaborate parsing of the program text Why does Python allow commas at the end of lists and tuples Python lets you add a trailing comma at the end of lists tuples and dictionaries 1 2 3 a b c d A 1 5 B 6 7 last trailing comma is optional but good style There are several reasons to allow this When you have a litera,en
14,l value for a list tuple or dictionary spread across multiple lines it s easier to add more elements because you don t have to remember to add a comma to the previous line The lines can also be reordered without creating a syntax error Accidentally omitting the comma can lead to errors that are hard to diagnose For example x fee fie foo fum This list looks like it has four elements but it actually contains three fee fiefoo and fum Always adding the comma avoids this source of error Allowing the trailing comma may also make programmatic code generation easier,en
15,plistlib Generate and parse Apple plist files Source code Lib plistlib py This module provides an interface for reading and writing the property list files used by Apple primarily on macOS and iOS This module supports both binary and XML plist files The property list plist file format is a simple serialization supporting basic object types like dictionaries lists numbers and strings Usually the top level object is a dictionary To write out and to parse a plist file use the dump and load functions To work with plist data in bytes objects use dumps and loads Values can be strings integers floats booleans tuples lists dictionaries but only with string keys bytes bytearray or datetime datetime objects Changed in version 3 4 New API old API deprecated Support for binary format plists added Changed in version 3 8 Support added for reading and writing UID tokens in binary plists as used by NSKeyedArchiver and NSKeyedUnarchiver Changed in version 3 9 Old API removed See also PList manual page Apple s documentation of the file format This module defines the following functions plistlib load fp fmt None dict_type dict Read a plist file fp should be a readable and binary file object Return the unpacked root object which usually is a dictionary The fmt is the format of the file and the following values are valid None Autodetect the file format FMT_XML XML file format FMT_BINARY Binary plist format The dict_type is the type used for dictionaries that are read from the plist file XML data for the FMT_XML format is parsed using the Expat parser from xml parsers expat see its documentation for possible exceptions on ill formed XML Unknown elements will simply be ignored by the plist parser The parser for the binary format raises InvalidFileException when the file cannot be parsed New in version 3 4 plistlib loads data fmt None dict_type dict Load a plist from a bytes object See load for an explanation of the keyword arguments New in version 3 4 plistlib dump value fp fmt FMT_XML sort_keys True skipkeys False Write value to a plist file Fp should be a writable binary file object The fmt argument specifies the format of the plist file and can be one of the following values FMT_XML XML formatted plist file FMT_BINARY Binary formatted plist file When sort_keys is true the default the keys for dictionaries will be written to the plist in sorted order otherwise they will be written in the iteration order of the dictionary When skipkeys is false the default the function raises TypeError when a key of a dictionary is not a string otherwise such keys are skipped A TypeError will be raised if the object is of an unsupported type or a container that contains objects of unsupported types An OverflowError will be raised for integer values that cannot be represented in binary plist files New in version 3 4 plistlib dumps value fmt FMT_XML sort_keys True skipkeys False Return value as a plist formatted bytes object See the documentation for dump for an explanation of the keyword arguments of this function New in version 3 4 The following classes are available class plistlib UID data Wraps an int This is used when reading or writing NSKeyedArchiver encoded data which contains UID see PList manual It has one attribute data which can be used to retrieve the int value of the UID data must be in the range 0 data 2 64 New in version 3 8 The following constants are available plistlib FMT_XML The XML format for plist files New in version 3 4 plistlib FMT_BINARY The binary format for plist files New in version 3 4 Examples Generating a plist import datetime import plistlib pl dict aString Doodah aList A B 12 32 1 1 2 3 aFloat 0 1 anInt 728 aDict dict anotherString hello hi there aThirdString M xe4ssig Ma xdf aTrueValue True aFalseValue False someData b binary gunk someMoreData b lots of binary gunk 10 aDate datetime datetime now print plistlib dumps pl decode Parsing a plist import plistlib plist b plist version 1 0 dict key foo key string bar string dict plist pl plistlib loads plist print pl foo,en
16,shelve Python object persistence Source code Lib shelve py A shelf is a persistent dictionary like object The difference with dbm databases is that the values not the keys in a shelf can be essentially arbitrary Python objects anything that the pickle module can handle This includes most class instances recursive data types and objects containing lots of shared sub objects The keys are ordinary strings shelve open filename flag c protocol None writeback False Open a persistent dictionary The filename specified is the base filename for the underlying database As a side effect an extension may be added to the filename and more than one file may be created By default the underlying database file is opened for reading and writing The optional flag parameter has the same interpretation as the flag parameter of dbm open By default pickles created with pickle DEFAULT_PROTOCOL are used to serialize values The version of the pickle protocol can be specified with the protocol parameter Because of Python semantics a shelf cannot know when a mutable persistent dictionary entry is modified By default modified objects are written only when assigned to the shelf see Example If the optional writeback parameter is set to True all entries accessed are also cached in memory and written back on sync and close this can make it handier to mutate mutable entries in the persistent dictionary but if many entries are accessed it can consume vast amounts of memory for the cache and it can make the close operation very slow since all accessed entries are written back there is no way to determine which accessed entries are mutable nor which ones were actually mutated Changed in version 3 10 pickle DEFAULT_PROTOCOL is now used as the default pickle protocol Changed in version 3 11 Accepts path like object for filename Note Do not rely on the shelf being closed automatically always call close explicitly when you don t need it any more or use shelve open as a context manager with shelve open spam as db db eggs eggs Warning Because the shelve module is backed by pickle it is insecure to load a shelf from an untrusted source Like with pickle loading a shelf can execute arbitrary code Shelf objects support most of methods and operations supported by dictionaries except copying constructors and operators and This eases the transition from dictionary based scripts to those requiring persistent storage Two additional methods are supported Shelf sync Write back all entries in the cache if the shelf was opened with writeback set to True Also empty the cache and synchronize the persistent dictionary on disk if feasible This is called automatically when the shelf is closed with close Shelf close Synchronize and close the persistent dict object Operations on a closed shelf will fail with a ValueError See also Persistent dictionary recipe with widely supported storage formats and having the speed of native dictionaries Restrictions The choice of which database package will be used such as dbm ndbm or dbm gnu depends on which interface is available Therefore it is not safe to open the database directly using dbm The database is also unfortunately subject to the limitations of dbm if it is used this means that the pickled representation of the objects stored in the database should be fairly small and in rare cases key collisions may cause the database to refuse updates The shelve module does not support concurrent read write access to shelved objects Multiple simultaneous read accesses are safe When a program has a shelf open for writing no other program should have it open for reading or writing Unix file locking can be used to solve this but this differs across Unix versions and requires knowledge about the database implementation used On macOS dbm ndbm can silently corrupt the database file on updates which can cause hard crashes when trying to read from the database class shelve Shelf dict protocol None writeback False keyencoding utf 8 A subclass of collections abc MutableMapping which stores pickled values in the dict object By default pickles created with pic,en
17,kle DEFAULT_PROTOCOL are used to serialize values The version of the pickle protocol can be specified with the protocol parameter See the pickle documentation for a discussion of the pickle protocols If the writeback parameter is True the object will hold a cache of all entries accessed and write them back to the dict at sync and close times This allows natural operations on mutable entries but can consume much more memory and make sync and close take a long time The keyencoding parameter is the encoding used to encode keys before they are used with the underlying dict A Shelf object can also be used as a context manager in which case it will be automatically closed when the with block ends Changed in version 3 2 Added the keyencoding parameter previously keys were always encoded in UTF 8 Changed in version 3 4 Added context manager support Changed in version 3 10 pickle DEFAULT_PROTOCOL is now used as the default pickle protocol class shelve BsdDbShelf dict protocol None writeback False keyencoding utf 8 A subclass of Shelf which exposes first next previous last and set_location methods These are available in the third party bsddb module from pybsddb but not in other database modules The dict object passed to the constructor must support those methods This is generally accomplished by calling one of bsddb hashopen bsddb btopen or bsddb rnopen The optional protocol writeback and keyencoding parameters have the same interpretation as for the Shelf class class shelve DbfilenameShelf filename flag c protocol None writeback False A subclass of Shelf which accepts a filename instead of a dict like object The underlying file will be opened using dbm open By default the file will be created and opened for both read and write The optional flag parameter has the same interpretation as for the open function The optional protocol and writeback parameters have the same interpretation as for the Shelf class Example To summarize the interface key is a string data is an arbitrary object import shelve d shelve open filename open file may get suffix added by low level library d key data store data at key overwrites old data if using an existing key data d key retrieve a COPY of data at key raise KeyError if no such key del d key delete data stored at key raises KeyError if no such key flag key in d true if the key exists klist list d keys a list of all existing keys slow as d was opened WITHOUT writeback True beware d xx 0 1 2 this works as expected but d xx append 3 this doesn t d xx is STILL 0 1 2 having opened d without writeback True you need to code carefully temp d xx extracts the copy temp append 5 mutates the copy d xx temp stores the copy right back to persist it or d shelve open filename writeback True would let you just code d xx append 5 and have it work as expected BUT it would also consume more memory and make the d close operation slower d close close it See also Module dbm Generic interface to dbm style databases Module pickle Object serialization used by shelve,en
18,dis Disassembler for Python bytecode Source code Lib dis py The dis module supports the analysis of CPython bytecode by disassembling it The CPython bytecode which this module takes as an input is defined in the file Include opcode h and used by the compiler and the interpreter CPython implementation detail Bytecode is an implementation detail of the CPython interpreter No guarantees are made that bytecode will not be added removed or changed between versions of Python Use of this module should not be considered to work across Python VMs or Python releases Changed in version 3 6 Use 2 bytes for each instruction Previously the number of bytes varied by instruction Changed in version 3 10 The argument of jump exception handling and loop instructions is now the instruction offset rather than the byte offset Changed in version 3 11 Some instructions are accompanied by one or more inline cache entries which take the form of CACHE instructions These instructions are hidden by default but can be shown by passing show_caches True to any dis utility Furthermore the interpreter now adapts the bytecode to specialize it for different runtime conditions The adaptive bytecode can be shown by passing adaptive True Changed in version 3 12 The argument of a jump is the offset of the target instruction relative to the instruction that appears immediately after the jump instruction s CACHE entries As a consequence the presence of the CACHE instructions is transparent for forward jumps but needs to be taken into account when reasoning about backward jumps Example Given the function myfunc def myfunc alist return len alist the following command can be used to display the disassembly of myfunc dis dis myfunc 2 0 RESUME 0 3 2 LOAD_GLOBAL 1 NULL len 12 LOAD_FAST 0 alist 14 CALL 1 22 RETURN_VALUE The 2 is a line number Command line interface The dis module can be invoked as a script from the command line python m dis h infile The following options are accepted h help Display usage and exit If infile is specified its disassembled code will be written to stdout Otherwise disassembly is performed on compiled source code recieved from stdin Bytecode analysis New in version 3 4 The bytecode analysis API allows pieces of Python code to be wrapped in a Bytecode object that provides easy access to details of the compiled code class dis Bytecode x first_line None current_offset None show_caches False adaptive False Analyse the bytecode corresponding to a function generator asynchronous generator coroutine method string of source code or a code object as returned by compile This is a convenience wrapper around many of the functions listed below most notably get_instructions as iterating over a Bytecode instance yields the bytecode operations as Instruction instances If first_line is not None it indicates the line number that should be reported for the first source line in the disassembled code Otherwise the source line information if any is taken directly from the disassembled code object If current_offset is not None it refers to an instruction offset in the disassembled code Setting this means dis will display a current instruction marker against the specified opcode If show_caches is True dis will display inline cache entries used by the interpreter to specialize the bytecode If adaptive is True dis will display specialized bytecode that may be different from the original bytecode classmethod from_traceback tb show_caches False Construct a Bytecode instance from the given traceback setting current_offset to the instruction responsible for the exception codeobj The compiled code object first_line The first source line of the code object if available dis Return a formatted view of the bytecode operations the same as printed by dis dis but returned as a multi line string info Return a formatted multi line string with detailed information about the code object like code_info Changed in version 3 7 This can now handle coroutine and asynchronous generator objects Changed in version 3 11 Added the show_caches and adaptive parameters Example bytecode dis Bytec,en
19,ode myfunc for instr in bytecode print instr opname RESUME LOAD_GLOBAL LOAD_FAST CALL RETURN_VALUE Analysis functions The dis module also defines the following analysis functions that convert the input directly to the desired output They can be useful if only a single operation is being performed so the intermediate analysis object isn t useful dis code_info x Return a formatted multi line string with detailed code object information for the supplied function generator asynchronous generator coroutine method source code string or code object Note that the exact contents of code info strings are highly implementation dependent and they may change arbitrarily across Python VMs or Python releases New in version 3 2 Changed in version 3 7 This can now handle coroutine and asynchronous generator objects dis show_code x file None Print detailed code object information for the supplied function method source code string or code object to file or sys stdout if file is not specified This is a convenient shorthand for print code_info x file file intended for interactive exploration at the interpreter prompt New in version 3 2 Changed in version 3 4 Added file parameter dis dis x None file None depth None show_caches False adaptive False Disassemble the x object x can denote either a module a class a method a function a generator an asynchronous generator a coroutine a code object a string of source code or a byte sequence of raw bytecode For a module it disassembles all functions For a class it disassembles all methods including class and static methods For a code object or sequence of raw bytecode it prints one line per bytecode instruction It also recursively disassembles nested code objects These can include generator expressions nested functions the bodies of nested classes and the code objects used for annotation scopes Strings are first compiled to code objects with the compile built in function before being disassembled If no object is provided this function disassembles the last traceback The disassembly is written as text to the supplied file argument if provided and to sys stdout otherwise The maximal depth of recursion is limited by depth unless it is None depth 0 means no recursion If show_caches is True this function will display inline cache entries used by the interpreter to specialize the bytecode If adaptive is True this function will display specialized bytecode that may be different from the original bytecode Changed in version 3 4 Added file parameter Changed in version 3 7 Implemented recursive disassembling and added depth parameter Changed in version 3 7 This can now handle coroutine and asynchronous generator objects Changed in version 3 11 Added the show_caches and adaptive parameters dis distb tb None file None show_caches False adaptive False Disassemble the top of stack function of a traceback using the last traceback if none was passed The instruction causing the exception is indicated The disassembly is written as text to the supplied file argument if provided and to sys stdout otherwise Changed in version 3 4 Added file parameter Changed in version 3 11 Added the show_caches and adaptive parameters dis disassemble code lasti 1 file None show_caches False adaptive False dis disco code lasti 1 file None show_caches False adaptive False Disassemble a code object indicating the last instruction if lasti was provided The output is divided in the following columns 1 the line number for the first instruction of each line 2 the current instruction indicated as 3 a labelled instruction indicated with 4 the address of the instruction 5 the operation code name 6 operation parameters and 7 interpretation of the parameters in parentheses The parameter interpretation recognizes local and global variable names constant values branch targets and compare operators The disassembly is written as text to the supplied file argument if provided and to sys stdout otherwise Changed in version 3 4 Added file parameter Changed in version 3 11 Added the show_caches and adaptive parameters dis get_instructions x first_line None,en
20, show_caches False adaptive False Return an iterator over the instructions in the supplied function method source code string or code object The iterator generates a series of Instruction named tuples giving the details of each operation in the supplied code If first_line is not None it indicates the line number that should be reported for the first source line in the disassembled code Otherwise the source line information if any is taken directly from the disassembled code object The show_caches and adaptive parameters work as they do in dis New in version 3 4 Changed in version 3 11 Added the show_caches and adaptive parameters dis findlinestarts code This generator function uses the co_lines method of the code object code to find the offsets which are starts of lines in the source code They are generated as offset lineno pairs Changed in version 3 6 Line numbers can be decreasing Before they were always increasing Changed in version 3 10 The PEP 626 co_lines method is used instead of the co_firstlineno and co_lnotab attributes of the code object dis findlabels code Detect all offsets in the raw compiled bytecode string code which are jump targets and return a list of these offsets dis stack_effect opcode oparg None jump None Compute the stack effect of opcode with argument oparg If the code has a jump target and jump is True stack_effect will return the stack effect of jumping If jump is False it will return the stack effect of not jumping And if jump is None default it will return the maximal stack effect of both cases New in version 3 4 Changed in version 3 8 Added jump parameter Python Bytecode Instructions The get_instructions function and Bytecode class provide details of bytecode instructions as Instruction instances class dis Instruction Details for a bytecode operation opcode numeric code for operation corresponding to the opcode values listed below and the bytecode values in the Opcode collections opname human readable name for operation arg numeric argument to operation if any otherwise None argval resolved arg value if any otherwise None argrepr human readable description of operation argument if any otherwise an empty string offset start index of operation within bytecode sequence starts_line line started by this opcode if any otherwise None is_jump_target True if other code jumps to here otherwise False positions dis Positions object holding the start and end locations that are covered by this instruction New in version 3 4 Changed in version 3 11 Field positions is added class dis Positions In case the information is not available some fields might be None lineno end_lineno col_offset end_col_offset New in version 3 11 The Python compiler currently generates the following bytecode instructions General instructions In the following We will refer to the interpreter stack as STACK and describe operations on it as if it was a Python list The top of the stack corresponds to STACK 1 in this language NOP Do nothing code Used as a placeholder by the bytecode optimizer and to generate line tracing events POP_TOP Removes the top of stack item STACK pop END_FOR Removes the top two values from the stack Equivalent to POP_TOP POP_TOP Used to clean up at the end of loops hence the name New in version 3 12 END_SEND Implements del STACK 2 Used to clean up when a generator exits New in version 3 12 COPY i Push the i th item to the top of the stack without removing it from its original location assert i 0 STACK append STACK i New in version 3 11 SWAP i Swap the top of the stack with the i th element STACK i STACK 1 STACK 1 STACK i New in version 3 11 CACHE Rather than being an actual instruction this opcode is used to mark extra space for the interpreter to cache useful data directly in the bytecode itself It is automatically hidden by all dis utilities but can be viewed with show_caches True Logically this space is part of the preceding instruction Many opcodes expect to be followed by an exact number of caches and will instruct the interpreter to skip over them at runtime Populated caches can look like arbitrary instruc,en
21,tions so great care should be taken when reading or modifying raw adaptive bytecode containing quickened data New in version 3 11 Unary operations Unary operations take the top of the stack apply the operation and push the result back on the stack UNARY_NEGATIVE Implements STACK 1 STACK 1 UNARY_NOT Implements STACK 1 not STACK 1 UNARY_INVERT Implements STACK 1 STACK 1 GET_ITER Implements STACK 1 iter STACK 1 GET_YIELD_FROM_ITER If STACK 1 is a generator iterator or coroutine object it is left as is Otherwise implements STACK 1 iter STACK 1 New in version 3 5 Binary and in place operations Binary operations remove the top two items from the stack STACK 1 and STACK 2 They perform the operation then put the result back on the stack In place operations are like binary operations but the operation is done in place when STACK 2 supports it and the resulting STACK 1 may be but does not have to be the original STACK 2 BINARY_OP op Implements the binary and in place operators depending on the value of op rhs STACK pop lhs STACK pop STACK append lhs op rhs New in version 3 11 BINARY_SUBSCR Implements key STACK pop container STACK pop STACK append container key STORE_SUBSCR Implements key STACK pop container STACK pop value STACK pop container key value DELETE_SUBSCR Implements key STACK pop container STACK pop del container key BINARY_SLICE Implements end STACK pop start STACK pop container STACK pop STACK append container start end New in version 3 12 STORE_SLICE Implements end STACK pop start STACK pop container STACK pop values STACK pop container start end value New in version 3 12 Coroutine opcodes GET_AWAITABLE where Implements STACK 1 get_awaitable STACK 1 where get_awaitable o returns o if o is a coroutine object or a generator object with the CO_ITERABLE_COROUTINE flag or resolves o __await__ If the where operand is nonzero it indicates where the instruction occurs 1 After a call to __aenter__ 2 After a call to __aexit__ New in version 3 5 Changed in version 3 11 Previously this instruction did not have an oparg GET_AITER Implements STACK 1 STACK 1 __aiter__ New in version 3 5 Changed in version 3 7 Returning awaitable objects from __aiter__ is no longer supported GET_ANEXT Implement STACK append get_awaitable STACK 1 __anext__ to the stack See GET_AWAITABLE for details about get_awaitable New in version 3 5 END_ASYNC_FOR Terminates an async for loop Handles an exception raised when awaiting a next item The stack contains the async iterable in STACK 2 and the raised exception in STACK 1 Both are popped If the exception is not StopAsyncIteration it is re raised New in version 3 8 Changed in version 3 11 Exception representation on the stack now consist of one not three items CLEANUP_THROW Handles an exception raised during a throw or close call through the current frame If STACK 1 is an instance of StopIteration pop three values from the stack and push its value member Otherwise re raise STACK 1 New in version 3 12 BEFORE_ASYNC_WITH Resolves __aenter__ and __aexit__ from STACK 1 Pushes __aexit__ and result of __aenter__ to the stack STACK extend __aexit__ __aenter__ New in version 3 5 Miscellaneous opcodes SET_ADD i Implements item STACK pop set add STACK i item Used to implement set comprehensions LIST_APPEND i Implements item STACK pop list append STACK i item Used to implement list comprehensions MAP_ADD i Implements value STACK pop key STACK pop dict __setitem__ STACK i key value Used to implement dict comprehensions New in version 3 1 Changed in version 3 8 Map value is STACK 1 and map key is STACK 2 Before those were reversed For all of the SET_ADD LIST_APPEND and MAP_ADD instructions while the added value or key value pair is popped off the container object remains on the stack so that it is available for further iterations of the loop RETURN_VALUE Returns with STACK 1 to the caller of the function RETURN_CONST consti Returns with co_consts consti to the caller of the function New in version 3 12 YIELD_VALUE Yields STACK pop from a generator Changed in version 3 11 oparg set to be the stack depth Changed in version ,en
22,3 12 oparg set to be the exception block depth for efficient closing of generators SETUP_ANNOTATIONS Checks whether __annotations__ is defined in locals if not it is set up to an empty dict This opcode is only emitted if a class or module body contains variable annotations statically New in version 3 6 POP_EXCEPT Pops a value from the stack which is used to restore the exception state Changed in version 3 11 Exception representation on the stack now consist of one not three items RERAISE Re raises the exception currently on top of the stack If oparg is non zero pops an additional value from the stack which is used to set f_lasti of the current frame New in version 3 9 Changed in version 3 11 Exception representation on the stack now consist of one not three items PUSH_EXC_INFO Pops a value from the stack Pushes the current exception to the top of the stack Pushes the value originally popped back to the stack Used in exception handlers New in version 3 11 CHECK_EXC_MATCH Performs exception matching for except Tests whether the STACK 2 is an exception matching STACK 1 Pops STACK 1 and pushes the boolean result of the test New in version 3 11 CHECK_EG_MATCH Performs exception matching for except Applies split STACK 1 on the exception group representing STACK 2 In case of a match pops two items from the stack and pushes the non matching subgroup None in case of full match followed by the matching subgroup When there is no match pops one item the match type and pushes None New in version 3 11 WITH_EXCEPT_START Calls the function in position 4 on the stack with arguments type val tb representing the exception at the top of the stack Used to implement the call context_manager __exit__ exc_info when an exception has occurred in a with statement New in version 3 9 Changed in version 3 11 The __exit__ function is in position 4 of the stack rather than 7 Exception representation on the stack now consist of one not three items LOAD_ASSERTION_ERROR Pushes AssertionError onto the stack Used by the assert statement New in version 3 9 LOAD_BUILD_CLASS Pushes builtins __build_class__ onto the stack It is later called to construct a class BEFORE_WITH This opcode performs several operations before a with block starts First it loads __exit__ from the context manager and pushes it onto the stack for later use by WITH_EXCEPT_START Then __enter__ is called Finally the result of calling the __enter__ method is pushed onto the stack New in version 3 11 GET_LEN Perform STACK append len STACK 1 New in version 3 10 MATCH_MAPPING If STACK 1 is an instance of collections abc Mapping or more technically if it has the Py_TPFLAGS_MAPPING flag set in its tp_flags push True onto the stack Otherwise push False New in version 3 10 MATCH_SEQUENCE If STACK 1 is an instance of collections abc Sequence and is not an instance of str bytes bytearray or more technically if it has the Py_TPFLAGS_SEQUENCE flag set in its tp_flags push True onto the stack Otherwise push False New in version 3 10 MATCH_KEYS STACK 1 is a tuple of mapping keys and STACK 2 is the match subject If STACK 2 contains all of the keys in STACK 1 push a tuple containing the corresponding values Otherwise push None New in version 3 10 Changed in version 3 11 Previously this instruction also pushed a boolean value indicating success True or failure False STORE_NAME namei Implements name STACK pop namei is the index of name in the attribute co_names of the code object The compiler tries to use STORE_FAST or STORE_GLOBAL if possible DELETE_NAME namei Implements del name where namei is the index into co_names attribute of the code object UNPACK_SEQUENCE count Unpacks STACK 1 into count individual values which are put onto the stack right to left Require there to be exactly count values assert len STACK 1 count STACK extend STACK pop count 1 1 UNPACK_EX counts Implements assignment with a starred target Unpacks an iterable in STACK 1 into individual values where the total number of values can be smaller than the number of items in the iterable one of the new values will be a list of all leftover item,en
23,s The number of values before and after the list value is limited to 255 The number of values before the list value is encoded in the argument of the opcode The number of values after the list if any is encoded using an EXTENDED_ARG As a consequence the argument can be seen as a two bytes values where the low byte of counts is the number of values before the list value the high byte of counts the number of values after it The extracted values are put onto the stack right to left i e a b c d will be stored after execution as STACK extend a b c STORE_ATTR namei Implements obj STACK pop value STACK pop obj name value where namei is the index of name in co_names of the code object DELETE_ATTR namei Implements obj STACK pop del obj name where namei is the index of name into co_names of the code object STORE_GLOBAL namei Works as STORE_NAME but stores the name as a global DELETE_GLOBAL namei Works as DELETE_NAME but deletes a global name LOAD_CONST consti Pushes co_consts consti onto the stack LOAD_NAME namei Pushes the value associated with co_names namei onto the stack The name is looked up within the locals then the globals then the builtins LOAD_LOCALS Pushes a reference to the locals dictionary onto the stack This is used to prepare namespace dictionaries for LOAD_FROM_DICT_OR_DEREF and LOAD_FROM_DICT_OR_GLOBALS New in version 3 12 LOAD_FROM_DICT_OR_GLOBALS i Pops a mapping off the stack and looks up the value for co_names namei If the name is not found there looks it up in the globals and then the builtins similar to LOAD_GLOBAL This is used for loading global variables in annotation scopes within class bodies New in version 3 12 BUILD_TUPLE count Creates a tuple consuming count items from the stack and pushes the resulting tuple onto the stack assert count 0 STACK values STACK count STACK count STACK append tuple values BUILD_LIST count Works as BUILD_TUPLE but creates a list BUILD_SET count Works as BUILD_TUPLE but creates a set BUILD_MAP count Pushes a new dictionary object onto the stack Pops 2 count items so that the dictionary holds count entries STACK 4 STACK 3 STACK 2 STACK 1 Changed in version 3 5 The dictionary is created from stack items instead of creating an empty dictionary pre sized to hold count items BUILD_CONST_KEY_MAP count The version of BUILD_MAP specialized for constant keys Pops the top element on the stack which contains a tuple of keys then starting from STACK 2 pops count values to form values in the built dictionary New in version 3 6 BUILD_STRING count Concatenates count strings from the stack and pushes the resulting string onto the stack New in version 3 6 LIST_EXTEND i Implements seq STACK pop list extend STACK i seq Used to build lists New in version 3 9 SET_UPDATE i Implements seq STACK pop set update STACK i seq Used to build sets New in version 3 9 DICT_UPDATE i Implements map STACK pop dict update STACK i map Used to build dicts New in version 3 9 DICT_MERGE i Like DICT_UPDATE but raises an exception for duplicate keys New in version 3 9 LOAD_ATTR namei If the low bit of namei is not set this replaces STACK 1 with getattr STACK 1 co_names namei 1 If the low bit of namei is set this will attempt to load a method named co_names namei 1 from the STACK 1 object STACK 1 is popped This bytecode distinguishes two cases if STACK 1 has a method with the correct name the bytecode pushes the unbound method and STACK 1 STACK 1 will be used as the first argument self by CALL when calling the unbound method Otherwise NULL and the object returned by the attribute lookup are pushed Changed in version 3 12 If the low bit of namei is set then a NULL or self is pushed to the stack before the attribute or unbound method respectively LOAD_SUPER_ATTR namei This opcode implements super both in its zero argument and two argument forms e g super method super attr and super cls self method super cls self attr It pops three values from the stack from top of stack down self the first argument to the current method cls the class within which the current method was defined the global super With respect to its argum,en
24,ent it works similarly to LOAD_ATTR except that namei is shifted left by 2 bits instead of 1 The low bit of namei signals to attempt a method load as with LOAD_ATTR which results in pushing None and the loaded method When it is unset a single value is pushed to the stack The second low bit of namei if set means that this was a two argument call to super unset means zero argument New in version 3 12 COMPARE_OP opname Performs a Boolean operation The operation name can be found in cmp_op opname IS_OP invert Performs is comparison or is not if invert is 1 New in version 3 9 CONTAINS_OP invert Performs in comparison or not in if invert is 1 New in version 3 9 IMPORT_NAME namei Imports the module co_names namei STACK 1 and STACK 2 are popped and provide the fromlist and level arguments of __import__ The module object is pushed onto the stack The current namespace is not affected for a proper import statement a subsequent STORE_FAST instruction modifies the namespace IMPORT_FROM namei Loads the attribute co_names namei from the module found in STACK 1 The resulting object is pushed onto the stack to be subsequently stored by a STORE_FAST instruction JUMP_FORWARD delta Increments bytecode counter by delta JUMP_BACKWARD delta Decrements bytecode counter by delta Checks for interrupts New in version 3 11 JUMP_BACKWARD_NO_INTERRUPT delta Decrements bytecode counter by delta Does not check for interrupts New in version 3 11 POP_JUMP_IF_TRUE delta If STACK 1 is true increments the bytecode counter by delta STACK 1 is popped Changed in version 3 11 The oparg is now a relative delta rather than an absolute target This opcode is a pseudo instruction replaced in final bytecode by the directed versions forward backward Changed in version 3 12 This is no longer a pseudo instruction POP_JUMP_IF_FALSE delta If STACK 1 is false increments the bytecode counter by delta STACK 1 is popped Changed in version 3 11 The oparg is now a relative delta rather than an absolute target This opcode is a pseudo instruction replaced in final bytecode by the directed versions forward backward Changed in version 3 12 This is no longer a pseudo instruction POP_JUMP_IF_NOT_NONE delta If STACK 1 is not None increments the bytecode counter by delta STACK 1 is popped This opcode is a pseudo instruction replaced in final bytecode by the directed versions forward backward New in version 3 11 Changed in version 3 12 This is no longer a pseudo instruction POP_JUMP_IF_NONE delta If STACK 1 is None increments the bytecode counter by delta STACK 1 is popped This opcode is a pseudo instruction replaced in final bytecode by the directed versions forward backward New in version 3 11 Changed in version 3 12 This is no longer a pseudo instruction FOR_ITER delta STACK 1 is an iterator Call its __next__ method If this yields a new value push it on the stack leaving the iterator below it If the iterator indicates it is exhausted then the byte code counter is incremented by delta Changed in version 3 12 Up until 3 11 the iterator was popped when it was exhausted LOAD_GLOBAL namei Loads the global named co_names namei 1 onto the stack Changed in version 3 11 If the low bit of namei is set then a NULL is pushed to the stack before the global variable LOAD_FAST var_num Pushes a reference to the local co_varnames var_num onto the stack Changed in version 3 12 This opcode is now only used in situations where the local variable is guaranteed to be initialized It cannot raise UnboundLocalError LOAD_FAST_CHECK var_num Pushes a reference to the local co_varnames var_num onto the stack raising an UnboundLocalError if the local variable has not been initialized New in version 3 12 LOAD_FAST_AND_CLEAR var_num Pushes a reference to the local co_varnames var_num onto the stack or pushes NULL onto the stack if the local variable has not been initialized and sets co_varnames var_num to NULL New in version 3 12 STORE_FAST var_num Stores STACK pop into the local co_varnames var_num DELETE_FAST var_num Deletes local co_varnames var_num MAKE_CELL i Creates a new cell in slot i If that slot is nonemp,en
25,ty then that value is stored into the new cell New in version 3 11 LOAD_CLOSURE i Pushes a reference to the cell contained in slot i of the fast locals storage The name of the variable is co_fastlocalnames i Note that LOAD_CLOSURE is effectively an alias for LOAD_FAST It exists to keep bytecode a little more readable Changed in version 3 11 i is no longer offset by the length of co_varnames LOAD_DEREF i Loads the cell contained in slot i of the fast locals storage Pushes a reference to the object the cell contains on the stack Changed in version 3 11 i is no longer offset by the length of co_varnames LOAD_FROM_DICT_OR_DEREF i Pops a mapping off the stack and looks up the name associated with slot i of the fast locals storage in this mapping If the name is not found there loads it from the cell contained in slot i similar to LOAD_DEREF This is used for loading free variables in class bodies which previously used LOAD_CLASSDEREF and in annotation scopes within class bodies New in version 3 12 STORE_DEREF i Stores STACK pop into the cell contained in slot i of the fast locals storage Changed in version 3 11 i is no longer offset by the length of co_varnames DELETE_DEREF i Empties the cell contained in slot i of the fast locals storage Used by the del statement New in version 3 2 Changed in version 3 11 i is no longer offset by the length of co_varnames COPY_FREE_VARS n Copies the n free variables from the closure into the frame Removes the need for special code on the caller s side when calling closures New in version 3 11 RAISE_VARARGS argc Raises an exception using one of the 3 forms of the raise statement depending on the value of argc 0 raise re raise previous exception 1 raise STACK 1 raise exception instance or type at STACK 1 2 raise STACK 2 from STACK 1 raise exception instance or type at STACK 2 with __cause__ set to STACK 1 CALL argc Calls a callable object with the number of arguments specified by argc including the named arguments specified by the preceding KW_NAMES if any On the stack are in ascending order either NULL The callable The positional arguments The named arguments or The callable self The remaining positional arguments The named arguments argc is the total of the positional and named arguments excluding self when a NULL is not present CALL pops all arguments and the callable object off the stack calls the callable object with those arguments and pushes the return value returned by the callable object New in version 3 11 CALL_FUNCTION_EX flags Calls a callable object with variable set of positional and keyword arguments If the lowest bit of flags is set the top of the stack contains a mapping object containing additional keyword arguments Before the callable is called the mapping object and iterable object are each unpacked and their contents passed in as keyword and positional arguments respectively CALL_FUNCTION_EX pops all arguments and the callable object off the stack calls the callable object with those arguments and pushes the return value returned by the callable object New in version 3 6 PUSH_NULL Pushes a NULL to the stack Used in the call sequence to match the NULL pushed by LOAD_METHOD for non method calls New in version 3 11 KW_NAMES consti Prefixes CALL Stores a reference to co_consts consti into an internal variable for use by CALL co_consts consti must be a tuple of strings New in version 3 11 MAKE_FUNCTION flags Pushes a new function object on the stack From bottom to top the consumed stack must consist of values if the argument carries a specified flag value 0x01 a tuple of default values for positional only and positional or keyword parameters in positional order 0x02 a dictionary of keyword only parameters default values 0x04 a tuple of strings containing parameters annotations 0x08 a tuple containing cells for free variables making a closure the code associated with the function at STACK 1 Changed in version 3 10 Flag value 0x04 is a tuple of strings instead of dictionary Changed in version 3 11 Qualified name at STACK 1 was removed BUILD_SLICE argc Pushes a slice object on the s,en
26,tack argc must be 2 or 3 If it is 2 implements end STACK pop start STACK pop STACK append slice start stop if it is 3 implements step STACK pop end STACK pop start STACK pop STACK append slice start end step See the slice built in function for more information EXTENDED_ARG ext Prefixes any opcode which has an argument too big to fit into the default one byte ext holds an additional byte which act as higher bits in the argument For each opcode at most three prefixal EXTENDED_ARG are allowed forming an argument from two byte to four byte FORMAT_VALUE flags Used for implementing formatted literal strings f strings Pops an optional fmt_spec from the stack then a required value flags is interpreted as follows flags 0x03 0x00 value is formatted as is flags 0x03 0x01 call str on value before formatting it flags 0x03 0x02 call repr on value before formatting it flags 0x03 0x03 call ascii on value before formatting it flags 0x04 0x04 pop fmt_spec from the stack and use it else use an empty fmt_spec Formatting is performed using PyObject_Format The result is pushed on the stack New in version 3 6 MATCH_CLASS count STACK 1 is a tuple of keyword attribute names STACK 2 is the class being matched against and STACK 3 is the match subject count is the number of positional sub patterns Pop STACK 1 STACK 2 and STACK 3 If STACK 3 is an instance of STACK 2 and has the positional and keyword attributes required by count and STACK 1 push a tuple of extracted attributes Otherwise push None New in version 3 10 Changed in version 3 11 Previously this instruction also pushed a boolean value indicating success True or failure False RESUME where A no op Performs internal tracing debugging and optimization checks The where operand marks where the RESUME occurs 0 The start of a function which is neither a generator coroutine nor an async generator 1 After a yield expression 2 After a yield from expression 3 After an await expression New in version 3 11 RETURN_GENERATOR Create a generator coroutine or async generator from the current frame Used as first opcode of in code object for the above mentioned callables Clear the current frame and return the newly created generator New in version 3 11 SEND delta Equivalent to STACK 1 STACK 2 send STACK 1 Used in yield from and await statements If the call raises StopIteration pop the top value from the stack push the exception s value attribute and increment the bytecode counter by delta New in version 3 11 HAVE_ARGUMENT This is not really an opcode It identifies the dividing line between opcodes in the range 0 255 which don t use their argument and those that do HAVE_ARGUMENT and HAVE_ARGUMENT respectively If your application uses pseudo instructions use the hasarg collection instead Changed in version 3 6 Now every instruction has an argument but opcodes HAVE_ARGUMENT ignore it Before only opcodes HAVE_ARGUMENT had an argument Changed in version 3 12 Pseudo instructions were added to the dis module and for them it is not true that comparison with HAVE_ARGUMENT indicates whether they use their arg CALL_INTRINSIC_1 Calls an intrinsic function with one argument Passes STACK 1 as the argument and sets STACK 1 to the result Used to implement functionality that is not performance critical The operand determines which intrinsic function is called Operand Description INTRINSIC_1_INVALID Not valid INTRINSIC_PRINT Prints the argument to standard out Used in the REPL INTRINSIC_IMPORT_STAR Performs import for the named module INTRINSIC_STOPITERATION_ERROR Extracts the return value from a StopIteration exception INTRINSIC_ASYNC_GEN_WRAP Wraps an aync generator value INTRINSIC_UNARY_POSITIVE Performs the unary operation INTRINSIC_LIST_TO_TUPLE Converts a list to a tuple INTRINSIC_TYPEVAR Creates a typing TypeVar INTRINSIC_PARAMSPEC Creates a typing ParamSpec INTRINSIC_TYPEVARTUPLE Creates a typing TypeVarTuple INTRINSIC_SUBSCRIPT_GENERIC Returns typing Generic subscripted with the argument INTRINSIC_TYPEALIAS Creates a typing TypeAliasType used in the type statement The argument is a tuple of the type alias s name type p,en
27,arameters and value New in version 3 12 CALL_INTRINSIC_2 Calls an intrinsic function with two arguments Used to implement functionality that is not performance critical arg2 STACK pop arg1 STACK pop result intrinsic2 arg1 arg2 STACK push result The operand determines which intrinsic function is called Operand Description INTRINSIC_2_INVALID Not valid INTRINSIC_PREP_RERAISE_STAR Calculates the ExceptionGroup to raise from a try except INTRINSIC_TYPEVAR_WITH_BOUND Creates a typing TypeVar with a bound INTRINSIC_TYPEVAR_WITH_CONSTRAINTS Creates a typing TypeVar with constraints INTRINSIC_SET_FUNCTION_TYPE_PARAMS Sets the __type_params__ attribute of a function New in version 3 12 Pseudo instructions These opcodes do not appear in Python bytecode They are used by the compiler but are replaced by real opcodes or removed before bytecode is generated SETUP_FINALLY target Set up an exception handler for the following code block If an exception occurs the value stack level is restored to its current state and control is transferred to the exception handler at target SETUP_CLEANUP target Like SETUP_FINALLY but in case of an exception also pushes the last instruction lasti to the stack so that RERAISE can restore it If an exception occurs the value stack level and the last instruction on the frame are restored to their current state and control is transferred to the exception handler at target SETUP_WITH target Like SETUP_CLEANUP but in case of an exception one more item is popped from the stack before control is transferred to the exception handler at target This variant is used in with and async with constructs which push the return value of the context manager s __enter__ or __aenter__ to the stack POP_BLOCK Marks the end of the code block associated with the last SETUP_FINALLY SETUP_CLEANUP or SETUP_WITH JUMP JUMP_NO_INTERRUPT Undirected relative jump instructions which are replaced by their directed forward backward counterparts by the assembler LOAD_METHOD Optimized unbound method lookup Emitted as a LOAD_ATTR opcode with a flag set in the arg Opcode collections These collections are provided for automatic introspection of bytecode instructions Changed in version 3 12 The collections now contain pseudo instructions and instrumented instructions as well These are opcodes with values MIN_PSEUDO_OPCODE and MIN_INSTRUMENTED_OPCODE dis opname Sequence of operation names indexable using the bytecode dis opmap Dictionary mapping operation names to bytecodes dis cmp_op Sequence of all compare operation names dis hasarg Sequence of bytecodes that use their argument New in version 3 12 dis hasconst Sequence of bytecodes that access a constant dis hasfree Sequence of bytecodes that access a free variable free in this context refers to names in the current scope that are referenced by inner scopes or names in outer scopes that are referenced from this scope It does not include references to global or builtin scopes dis hasname Sequence of bytecodes that access an attribute by name dis hasjrel Sequence of bytecodes that have a relative jump target dis hasjabs Sequence of bytecodes that have an absolute jump target dis haslocal Sequence of bytecodes that access a local variable dis hascompare Sequence of bytecodes of Boolean operations dis hasexc Sequence of bytecodes that set an exception handler New in version 3 12,en
28,typing Support for type hints New in version 3 5 Source code Lib typing py Note The Python runtime does not enforce function and variable type annotations They can be used by third party tools such as type checkers IDEs linters etc This module provides runtime support for type hints For the original specification of the typing system see PEP 484 For a simplified introduction to type hints see PEP 483 The function below takes and returns a string and is annotated as follows def greeting name str str return Hello name In the function greeting the argument name is expected to be of type str and the return type str Subtypes are accepted as arguments New features are frequently added to the typing module The typing_extensions package provides backports of these new features to older versions of Python For a summary of deprecated features and a deprecation timeline please see Deprecation Timeline of Major Features See also Typing cheat sheet A quick overview of type hints hosted at the mypy docs Type System Reference section of the mypy docs The Python typing system is standardised via PEPs so this reference should broadly apply to most Python type checkers Some parts may still be specific to mypy Static Typing with Python Type checker agnostic documentation written by the community detailing type system features useful typing related tools and typing best practices Relevant PEPs Since the initial introduction of type hints in PEP 484 and PEP 483 a number of PEPs have modified and enhanced Python s framework for type annotations PEP 526 Syntax for Variable Annotations Introducing syntax for annotating variables outside of function definitions and ClassVar PEP 544 Protocols Structural subtyping static duck typing Introducing Protocol and the runtime_checkable decorator PEP 585 Type Hinting Generics In Standard Collections Introducing types GenericAlias and the ability to use standard library classes as generic types PEP 586 Literal Types Introducing Literal PEP 589 TypedDict Type Hints for Dictionaries with a Fixed Set of Keys Introducing TypedDict PEP 591 Adding a final qualifier to typing Introducing Final and the final decorator PEP 593 Flexible function and variable annotations Introducing Annotated PEP 604 Allow writing union types as X Y Introducing types UnionType and the ability to use the binary or operator to signify a union of types PEP 612 Parameter Specification Variables Introducing ParamSpec and Concatenate PEP 613 Explicit Type Aliases Introducing TypeAlias PEP 646 Variadic Generics Introducing TypeVarTuple PEP 647 User Defined Type Guards Introducing TypeGuard PEP 655 Marking individual TypedDict items as required or potentially missing Introducing Required and NotRequired PEP 673 Self type Introducing Self PEP 675 Arbitrary Literal String Type Introducing LiteralString PEP 681 Data Class Transforms Introducing the dataclass_transform decorator PEP 692 Using TypedDict for more precise kwargs typing Introducing a new way of typing kwargs with Unpack and TypedDict PEP 695 Type Parameter Syntax Introducing builtin syntax for creating generic functions classes and type aliases PEP 698 Adding an override decorator to typing Introducing the override decorator Type aliases A type alias is defined using the type statement which creates an instance of TypeAliasType In this example Vector and list float will be treated equivalently by static type checkers type Vector list float def scale scalar float vector Vector Vector return scalar num for num in vector passes type checking a list of floats qualifies as a Vector new_vector scale 2 0 1 0 4 2 5 4 Type aliases are useful for simplifying complex type signatures For example from collections abc import Sequence type ConnectionOptions dict str str type Address tuple str int type Server tuple Address ConnectionOptions def broadcast_message message str servers Sequence Server None The static type checker will treat the previous type signature as being exactly equivalent to this one def broadcast_message message str servers Sequence tuple tuple str int dict str str None The typ,en
29,e statement is new in Python 3 12 For backwards compatibility type aliases can also be created through simple assignment Vector list float Or marked with TypeAlias to make it explicit that this is a type alias not a normal variable assignment from typing import TypeAlias Vector TypeAlias list float NewType Use the NewType helper to create distinct types from typing import NewType UserId NewType UserId int some_id UserId 524313 The static type checker will treat the new type as if it were a subclass of the original type This is useful in helping catch logical errors def get_user_name user_id UserId str passes type checking user_a get_user_name UserId 42351 fails type checking an int is not a UserId user_b get_user_name 1 You may still perform all int operations on a variable of type UserId but the result will always be of type int This lets you pass in a UserId wherever an int might be expected but will prevent you from accidentally creating a UserId in an invalid way output is of type int not UserId output UserId 23413 UserId 54341 Note that these checks are enforced only by the static type checker At runtime the statement Derived NewType Derived Base will make Derived a callable that immediately returns whatever parameter you pass it That means the expression Derived some_value does not create a new class or introduce much overhead beyond that of a regular function call More precisely the expression some_value is Derived some_value is always true at runtime It is invalid to create a subtype of Derived from typing import NewType UserId NewType UserId int Fails at runtime and does not pass type checking class AdminUserId UserId pass However it is possible to create a NewType based on a derived NewType from typing import NewType UserId NewType UserId int ProUserId NewType ProUserId UserId and typechecking for ProUserId will work as expected See PEP 484 for more details Note Recall that the use of a type alias declares two types to be equivalent to one another Doing type Alias Original will make the static type checker treat Alias as being exactly equivalent to Original in all cases This is useful when you want to simplify complex type signatures In contrast NewType declares one type to be a subtype of another Doing Derived NewType Derived Original will make the static type checker treat Derived as a subclass of Original which means a value of type Original cannot be used in places where a value of type Derived is expected This is useful when you want to prevent logic errors with minimal runtime cost New in version 3 5 2 Changed in version 3 10 NewType is now a class rather than a function As a result there is some additional runtime cost when calling NewType over a regular function Changed in version 3 11 The performance of calling NewType has been restored to its level in Python 3 9 Annotating callable objects Functions or other callable objects can be annotated using collections abc Callable or typing Callable Callable int str signifies a function that takes a single parameter of type int and returns a str For example from collections abc import Callable Awaitable def feeder get_next_item Callable str None Body def async_query on_success Callable int None on_error Callable int Exception None None Body async def on_update value str None Body callback Callable str Awaitable None on_update The subscription syntax must always be used with exactly two values the argument list and the return type The argument list must be a list of types a ParamSpec Concatenate or an ellipsis The return type must be a single type If a literal ellipsis is given as the argument list it indicates that a callable with any arbitrary parameter list would be acceptable def concat x str y str str return x y x Callable str x str OK x concat Also OK Callable cannot express complex signatures such as functions that take a variadic number of arguments overloaded functions or functions that have keyword only parameters However these signatures can be expressed by defining a Protocol class with a __call__ method from collections abc import Iterable from typ,en
30,ing import Protocol class Combiner Protocol def __call__ self vals bytes maxlen int None None list bytes def batch_proc data Iterable bytes cb_results Combiner bytes for item in data def good_cb vals bytes maxlen int None None list bytes def bad_cb vals bytes maxitems int None list bytes batch_proc good_cb OK batch_proc bad_cb Error Argument 2 has incompatible type because of different name and kind in the callback Callables which take other callables as arguments may indicate that their parameter types are dependent on each other using ParamSpec Additionally if that callable adds or removes arguments from other callables the Concatenate operator may be used They take the form Callable ParamSpecVariable ReturnType and Callable Concatenate Arg1Type Arg2Type ParamSpecVariable ReturnType respectively Changed in version 3 10 Callable now supports ParamSpec and Concatenate See PEP 612 for more details See also The documentation for ParamSpec and Concatenate provides examples of usage in Callable Generics Since type information about objects kept in containers cannot be statically inferred in a generic way many container classes in the standard library support subscription to denote the expected types of container elements from collections abc import Mapping Sequence class Employee Sequence Employee indicates that all elements in the sequence must be instances of Employee Mapping str str indicates that all keys and all values in the mapping must be strings def notify_by_email employees Sequence Employee overrides Mapping str str None Generic functions and classes can be parameterized by using type parameter syntax from collections abc import Sequence def first T l Sequence T T Function is generic over the TypeVar T return l 0 Or by using the TypeVar factory directly from collections abc import Sequence from typing import TypeVar U TypeVar U Declare type variable U def second l Sequence U U Function is generic over the TypeVar U return l 1 Changed in version 3 12 Syntactic support for generics is new in Python 3 12 Annotating tuples For most containers in Python the typing system assumes that all elements in the container will be of the same type For example from collections abc import Mapping Type checker will infer that all elements in x are meant to be ints x list int Type checker error list only accepts a single type argument y list int str 1 foo Type checker will infer that all keys in z are meant to be strings and that all values in z are meant to be either strings or ints z Mapping str str int list only accepts one type argument so a type checker would emit an error on the y assignment above Similarly Mapping only accepts two type arguments the first indicates the type of the keys and the second indicates the type of the values Unlike most other Python containers however it is common in idiomatic Python code for tuples to have elements which are not all of the same type For this reason tuples are special cased in Python s typing system tuple accepts any number of type arguments OK x is assigned to a tuple of length 1 where the sole element is an int x tuple int 5 OK y is assigned to a tuple of length 2 element 1 is an int element 2 is a str y tuple int str 5 foo Error the type annotation indicates a tuple of length 1 but z has been assigned to a tuple of length 3 z tuple int 1 2 3 To denote a tuple which could be of any length and in which all elements are of the same type T use tuple T To denote an empty tuple use tuple Using plain tuple as an annotation is equivalent to using tuple Any x tuple int 1 2 These reassignments are OK tuple int indicates x can be of any length x 1 2 3 x This reassignment is an error all elements in x must be ints x foo bar y can only ever be assigned to an empty tuple y tuple z tuple foo bar These reassignments are OK plain tuple is equivalent to tuple Any z 1 2 3 z The type of class objects A variable annotated with C may accept a value of type C In contrast a variable annotated with type C or typing Type C may accept values that are classes themselves specifically it will accept the class o,en
31,bject of C For example a 3 Has type int b int Has type type int c type a Also has type type int Note that type C is covariant class User class ProUser User class TeamUser User def make_new_user user_class type User User return user_class make_new_user User OK make_new_user ProUser Also OK type ProUser is a subtype of type User make_new_user TeamUser Still fine make_new_user User Error expected type User but got User make_new_user int Error type int is not a subtype of type User The only legal parameters for type are classes Any type variables and unions of any of these types For example def new_non_team_user user_class type BasicUser ProUser new_non_team_user BasicUser OK new_non_team_user ProUser OK new_non_team_user TeamUser Error type TeamUser is not a subtype of type BasicUser ProUser new_non_team_user User Also an error type Any is equivalent to type which is the root of Python s metaclass hierarchy User defined generic types A user defined class can be defined as a generic class from logging import Logger class LoggedVar T def __init__ self value T name str logger Logger None self name name self logger logger self value value def set self new T None self log Set repr self value self value new def get self T self log Get repr self value return self value def log self message str None self logger info s s self name message This syntax indicates that the class LoggedVar is parameterised around a single type variable T This also makes T valid as a type within the class body Generic classes implicitly inherit from Generic For compatibility with Python 3 11 and lower it is also possible to inherit explicitly from Generic to indicate a generic class from typing import TypeVar Generic T TypeVar T class LoggedVar Generic T Generic classes have __class_getitem__ methods meaning they can be parameterised at runtime e g LoggedVar int below from collections abc import Iterable def zero_all_vars vars Iterable LoggedVar int None for var in vars var set 0 A generic type can have any number of type variables All varieties of TypeVar are permissible as parameters for a generic type from typing import TypeVar Generic Sequence class WeirdTrio T B Sequence bytes S int str OldT TypeVar OldT contravariant True OldB TypeVar OldB bound Sequence bytes covariant True OldS TypeVar OldS int str class OldWeirdTrio Generic OldT OldB OldS Each type variable argument to Generic must be distinct This is thus invalid from typing import TypeVar Generic class Pair M M SyntaxError T TypeVar T class Pair Generic T T INVALID Generic classes can also inherit from other classes from collections abc import Sized class LinkedList T Sized When inheriting from generic classes some type parameters could be fixed from collections abc import Mapping class MyDict T Mapping str T In this case MyDict has a single parameter T Using a generic class without specifying type parameters assumes Any for each position In the following example MyIterable is not generic but implicitly inherits from Iterable Any from collections abc import Iterable class MyIterable Iterable Same as Iterable Any User defined generic type aliases are also supported Examples from collections abc import Iterable type Response S Iterable S int Return type here is same as Iterable str int def response query str Response str type Vec T Iterable tuple T T def inproduct T int float complex v Vec T T Same as Iterable tuple T T return sum x y for x y in v For backward compatibility generic type aliases can also be created through a simple assignment from collections abc import Iterable from typing import TypeVar S TypeVar S Response Iterable S int Changed in version 3 7 Generic no longer has a custom metaclass Changed in version 3 12 Syntactic support for generics and type aliases is new in version 3 12 Previously generic classes had to explicitly inherit from Generic or contain a type variable in one of their bases User defined generics for parameter expressions are also supported via parameter specification variables in the form P The behavior is consistent with type variables described above as parame,en
32,ter specification variables are treated by the typing module as a specialized type variable The one exception to this is that a list of types can be used to substitute a ParamSpec class Z T P T is a TypeVar P is a ParamSpec Z int dict float __main__ Z int dict float Classes generic over a ParamSpec can also be created using explicit inheritance from Generic In this case is not used from typing import ParamSpec Generic P ParamSpec P class Z Generic P Another difference between TypeVar and ParamSpec is that a generic with only one parameter specification variable will accept parameter lists in the forms X Type1 Type2 and also X Type1 Type2 for aesthetic reasons Internally the latter is converted to the former so the following are equivalent class X P X int str __main__ X int str X int str __main__ X int str Note that generics with ParamSpec may not have correct __parameters__ after substitution in some cases because they are intended primarily for static type checking Changed in version 3 10 Generic can now be parameterized over parameter expressions See ParamSpec and PEP 612 for more details A user defined generic class can have ABCs as base classes without a metaclass conflict Generic metaclasses are not supported The outcome of parameterizing generics is cached and most types in the typing module are hashable and comparable for equality The Any type A special kind of type is Any A static type checker will treat every type as being compatible with Any and Any as being compatible with every type This means that it is possible to perform any operation or method call on a value of type Any and assign it to any variable from typing import Any a Any None a OK a 2 OK s str s a OK def foo item Any int Passes type checking item could be any type and that type might have a bar method item bar Notice that no type checking is performed when assigning a value of type Any to a more precise type For example the static type checker did not report an error when assigning a to s even though s was declared to be of type str and receives an int value at runtime Furthermore all functions without a return type or parameter types will implicitly default to using Any def legacy_parser text return data A static type checker will treat the above as having the same signature as def legacy_parser text Any Any return data This behavior allows Any to be used as an escape hatch when you need to mix dynamically and statically typed code Contrast the behavior of Any with the behavior of object Similar to Any every type is a subtype of object However unlike Any the reverse is not true object is not a subtype of every other type That means when the type of a value is object a type checker will reject almost all operations on it and assigning it to a variable or using it as a return value of a more specialized type is a type error For example def hash_a item object int Fails type checking an object does not have a magic method item magic def hash_b item Any int Passes type checking item magic Passes type checking since ints and strs are subclasses of object hash_a 42 hash_a foo Passes type checking since Any is compatible with all types hash_b 42 hash_b foo Use object to indicate that a value could be any type in a typesafe manner Use Any to indicate that a value is dynamically typed Nominal vs structural subtyping Initially PEP 484 defined the Python static type system as using nominal subtyping This means that a class A is allowed where a class B is expected if and only if A is a subclass of B This requirement previously also applied to abstract base classes such as Iterable The problem with this approach is that a class had to be explicitly marked to support them which is unpythonic and unlike what one would normally do in idiomatic dynamically typed Python code For example this conforms to PEP 484 from collections abc import Sized Iterable Iterator class Bucket Sized Iterable int def __len__ self int def __iter__ self Iterator int PEP 544 allows to solve this problem by allowing users to write the above code without explicit base classes in the class ,en
33,definition allowing Bucket to be implicitly considered a subtype of both Sized and Iterable int by static type checkers This is known as structural subtyping or static duck typing from collections abc import Iterator Iterable class Bucket Note no base classes def __len__ self int def __iter__ self Iterator int def collect items Iterable int int result collect Bucket Passes type check Moreover by subclassing a special class Protocol a user can define new custom protocols to fully enjoy structural subtyping see examples below Module contents The typing module defines the following classes functions and decorators Special typing primitives Special types These can be used as types in annotations They do not support subscription using typing Any Special type indicating an unconstrained type Every type is compatible with Any Any is compatible with every type Changed in version 3 11 Any can now be used as a base class This can be useful for avoiding type checker errors with classes that can duck type anywhere or are highly dynamic typing AnyStr A constrained type variable Definition AnyStr TypeVar AnyStr str bytes AnyStr is meant to be used for functions that may accept str or bytes arguments but cannot allow the two to mix For example def concat a AnyStr b AnyStr AnyStr return a b concat foo bar OK output has type str concat b foo b bar OK output has type bytes concat foo b bar Error cannot mix str and bytes Note that despite its name AnyStr has nothing to do with the Any type nor does it mean any string In particular AnyStr and str bytes are different from each other and have different use cases Invalid use of AnyStr The type variable is used only once in the function signature so cannot be solved by the type checker def greet_bad cond bool AnyStr return hi there if cond else b greetings The better way of annotating this function def greet_proper cond bool str bytes return hi there if cond else b greetings typing LiteralString Special type that includes only literal strings Any string literal is compatible with LiteralString as is another LiteralString However an object typed as just str is not A string created by composing LiteralString typed objects is also acceptable as a LiteralString Example def run_query sql LiteralString None def caller arbitrary_string str literal_string LiteralString None run_query SELECT FROM students OK run_query literal_string OK run_query SELECT FROM literal_string OK run_query arbitrary_string type checker error run_query type checker error f SELECT FROM students WHERE name arbitrary_string LiteralString is useful for sensitive APIs where arbitrary user generated strings could generate problems For example the two cases above that generate type checker errors could be vulnerable to an SQL injection attack See PEP 675 for more details New in version 3 11 typing Never The bottom type a type that has no members This can be used to define a function that should never be called or a function that never returns from typing import Never def never_call_me arg Never None pass def int_or_str arg int str None never_call_me arg type checker error match arg case int print It s an int case str print It s a str case _ never_call_me arg OK arg is of type Never New in version 3 11 On older Python versions NoReturn may be used to express the same concept Never was added to make the intended meaning more explicit typing NoReturn Special type indicating that a function never returns For example from typing import NoReturn def stop NoReturn raise RuntimeError no way NoReturn can also be used as a bottom type a type that has no values Starting in Python 3 11 the Never type should be used for this concept instead Type checkers should treat the two equivalently New in version 3 6 2 typing Self Special type to represent the current enclosed class For example from typing import Self reveal_type class Foo def return_self self Self return self class SubclassOfFoo Foo pass reveal_type Foo return_self Revealed type is Foo reveal_type SubclassOfFoo return_self Revealed type is SubclassOfFoo This annotation is semantically equ,en
34,ivalent to the following albeit in a more succinct fashion from typing import TypeVar Self TypeVar Self bound Foo class Foo def return_self self Self Self return self In general if something returns self as in the above examples you should use Self as the return annotation If Foo return_self was annotated as returning Foo then the type checker would infer the object returned from SubclassOfFoo return_self as being of type Foo rather than SubclassOfFoo Other common use cases include classmethod s that are used as alternative constructors and return instances of the cls parameter Annotating an __enter__ method which returns self You should not use Self as the return annotation if the method is not guaranteed to return an instance of a subclass when the class is subclassed class Eggs Self would be an incorrect return annotation here as the object returned is always an instance of Eggs even in subclasses def returns_eggs self Eggs return Eggs See PEP 673 for more details New in version 3 11 typing TypeAlias Special annotation for explicitly declaring a type alias For example from typing import TypeAlias Factors TypeAlias list int TypeAlias is particularly useful on older Python versions for annotating aliases that make use of forward references as it can be hard for type checkers to distinguish these from normal variable assignments from typing import Generic TypeAlias TypeVar T TypeVar T Box does not exist yet so we have to use quotes for the forward reference on Python 3 12 Using TypeAlias tells the type checker that this is a type alias declaration not a variable assignment to a string BoxOfStrings TypeAlias Box str class Box Generic T classmethod def make_box_of_strings cls BoxOfStrings See PEP 613 for more details New in version 3 10 Deprecated since version 3 12 TypeAlias is deprecated in favor of the type statement which creates instances of TypeAliasType and which natively supports forward references Note that while TypeAlias and TypeAliasType serve similar purposes and have similar names they are distinct and the latter is not the type of the former Removal of TypeAlias is not currently planned but users are encouraged to migrate to type statements Special forms These can be used as types in annotations They all support subscription using but each has a unique syntax typing Union Union type Union X Y is equivalent to X Y and means either X or Y To define a union use e g Union int str or the shorthand int str Using that shorthand is recommended Details The arguments must be types and there must be at least one Unions of unions are flattened e g Union Union int str float Union int str float Unions of a single argument vanish e g Union int int The constructor actually returns int Redundant arguments are skipped e g Union int str int Union int str int str When comparing unions the argument order is ignored e g Union int str Union str int You cannot subclass or instantiate a Union You cannot write Union X Y Changed in version 3 7 Don t remove explicit subclasses from unions at runtime Changed in version 3 10 Unions can now be written as X Y See union type expressions typing Optional Optional X is equivalent to X None or Union X None Note that this is not the same concept as an optional argument which is one that has a default An optional argument with a default does not require the Optional qualifier on its type annotation just because it is optional For example def foo arg int 0 None On the other hand if an explicit value of None is allowed the use of Optional is appropriate whether the argument is optional or not For example def foo arg Optional int None None Changed in version 3 10 Optional can now be written as X None See union type expressions typing Concatenate Special form for annotating higher order functions Concatenate can be used in conjunction with Callable and ParamSpec to annotate a higher order callable which adds removes or transforms parameters of another callable Usage is in the form Concatenate Arg1Type Arg2Type ParamSpecVariable Concatenate is currently only valid when used as the first argument to a ,en
35,Callable The last parameter to Concatenate must be a ParamSpec or ellipsis For example to annotate a decorator with_lock which provides a threading Lock to the decorated function Concatenate can be used to indicate that with_lock expects a callable which takes in a Lock as the first argument and returns a callable with a different type signature In this case the ParamSpec indicates that the returned callable s parameter types are dependent on the parameter types of the callable being passed in from collections abc import Callable from threading import Lock from typing import Concatenate Use this lock to ensure that only one thread is executing a function at any time my_lock Lock def with_lock P R f Callable Concatenate Lock P R Callable P R A type safe decorator which provides a lock def inner args P args kwargs P kwargs R Provide the lock as the first argument return f my_lock args kwargs return inner with_lock def sum_threadsafe lock Lock numbers list float float Add a list of numbers together in a thread safe manner with lock return sum numbers We don t need to pass in the lock ourselves thanks to the decorator sum_threadsafe 1 1 2 2 3 3 New in version 3 10 See also PEP 612 Parameter Specification Variables the PEP which introduced ParamSpec and Concatenate ParamSpec Annotating callable objects typing Literal Special typing form to define literal types Literal can be used to indicate to type checkers that the annotated object has a value equivalent to one of the provided literals For example def validate_simple data Any Literal True always returns True type Mode Literal r rb w wb def open_helper file str mode Mode str open_helper some path r Passes type check open_helper other path typo Error in type checker Literal cannot be subclassed At runtime an arbitrary value is allowed as type argument to Literal but type checkers may impose restrictions See PEP 586 for more details about literal types New in version 3 8 Changed in version 3 9 1 Literal now de duplicates parameters Equality comparisons of Literal objects are no longer order dependent Literal objects will now raise a TypeError exception during equality comparisons if one of their parameters are not hashable typing ClassVar Special type construct to mark class variables As introduced in PEP 526 a variable annotation wrapped in ClassVar indicates that a given attribute is intended to be used as a class variable and should not be set on instances of that class Usage class Starship stats ClassVar dict str int class variable damage int 10 instance variable ClassVar accepts only types and cannot be further subscribed ClassVar is not a class itself and should not be used with isinstance or issubclass ClassVar does not change Python runtime behavior but it can be used by third party type checkers For example a type checker might flag the following code as an error enterprise_d Starship 3000 enterprise_d stats Error setting class variable on instance Starship stats This is OK New in version 3 5 3 typing Final Special typing construct to indicate final names to type checkers Final names cannot be reassigned in any scope Final names declared in class scopes cannot be overridden in subclasses For example MAX_SIZE Final 9000 MAX_SIZE 1 Error reported by type checker class Connection TIMEOUT Final int 10 class FastConnector Connection TIMEOUT 1 Error reported by type checker There is no runtime checking of these properties See PEP 591 for more details New in version 3 8 typing Required Special typing construct to mark a TypedDict key as required This is mainly useful for total False TypedDicts See TypedDict and PEP 655 for more details New in version 3 11 typing NotRequired Special typing construct to mark a TypedDict key as potentially missing See TypedDict and PEP 655 for more details New in version 3 11 typing Annotated Special typing form to add context specific metadata to an annotation Add metadata x to a given type T by using the annotation Annotated T x Metadata added using Annotated can be used by static analysis tools or at runtime At runtime the metadata is stored,en
36, in a __metadata__ attribute If a library or tool encounters an annotation Annotated T x and has no special logic for the metadata it should ignore the metadata and simply treat the annotation as T As such Annotated can be useful for code that wants to use annotations for purposes outside Python s static typing system Using Annotated T x as an annotation still allows for static typechecking of T as type checkers will simply ignore the metadata x In this way Annotated differs from the no_type_check decorator which can also be used for adding annotations outside the scope of the typing system but completely disables typechecking for a function or class The responsibility of how to interpret the metadata lies with the tool or library encountering an Annotated annotation A tool or library encountering an Annotated type can scan through the metadata elements to determine if they are of interest e g using isinstance Annotated type metadata Here is an example of how you might use Annotated to add metadata to type annotations if you were doing range analysis dataclass class ValueRange lo int hi int T1 Annotated int ValueRange 10 5 T2 Annotated T1 ValueRange 20 3 Details of the syntax The first argument to Annotated must be a valid type Multiple metadata elements can be supplied Annotated supports variadic arguments dataclass class ctype kind str Annotated int ValueRange 3 10 ctype char It is up to the tool consuming the annotations to decide whether the client is allowed to add multiple metadata elements to one annotation and how to merge those annotations Annotated must be subscripted with at least two arguments Annotated int is not valid The order of the metadata elements is preserved and matters for equality checks assert Annotated int ValueRange 3 10 ctype char Annotated int ctype char ValueRange 3 10 Nested Annotated types are flattened The order of the metadata elements starts with the innermost annotation assert Annotated Annotated int ValueRange 3 10 ctype char Annotated int ValueRange 3 10 ctype char Duplicated metadata elements are not removed assert Annotated int ValueRange 3 10 Annotated int ValueRange 3 10 ValueRange 3 10 Annotated can be used with nested and generic aliases dataclass class MaxLen value int type Vec T Annotated list tuple T T MaxLen 10 When used in a type annotation a type checker will treat V the same as Annotated list tuple int int MaxLen 10 type V Vec int Annotated cannot be used with an unpacked TypeVarTuple type Variadic Ts Annotated Ts Ann1 NOT valid This would be equivalent to Annotated T1 T2 T3 Ann1 where T1 T2 etc are TypeVars This would be invalid only one type should be passed to Annotated By default get_type_hints strips the metadata from annotations Pass include_extras True to have the metadata preserved from typing import Annotated get_type_hints def func x Annotated int metadata None pass get_type_hints func x class int return class NoneType get_type_hints func include_extras True x typing Annotated int metadata return class NoneType At runtime the metadata associated with an Annotated type can be retrieved via the __metadata__ attribute from typing import Annotated X Annotated int very important metadata X typing Annotated int very important metadata X __metadata__ very important metadata See also PEP 593 Flexible function and variable annotations The PEP introducing Annotated to the standard library New in version 3 9 typing TypeGuard Special typing construct for marking user defined type guard functions TypeGuard can be used to annotate the return type of a user defined type guard function TypeGuard only accepts a single type argument At runtime functions marked this way should return a boolean TypeGuard aims to benefit type narrowing a technique used by static type checkers to determine a more precise type of an expression within a program s code flow Usually type narrowing is done by analyzing conditional code flow and applying the narrowing to a block of code The conditional expression here is sometimes referred to as a type guard def is_str val str float isinstance type guard i,en
37,f isinstance val str Type of val is narrowed to str else Else type of val is narrowed to float Sometimes it would be convenient to use a user defined boolean function as a type guard Such a function should use TypeGuard as its return type to alert static type checkers to this intention Using TypeGuard tells the static type checker that for a given function 1 The return value is a boolean 2 If the return value is True the type of its argument is the type inside TypeGuard For example def is_str_list val list object TypeGuard list str Determines whether all objects in the list are strings return all isinstance x str for x in val def func1 val list object if is_str_list val Type of val is narrowed to list str print join val else Type of val remains as list object print Not a list of strings If is_str_list is a class or instance method then the type in TypeGuard maps to the type of the second parameter after cls or self In short the form def foo arg TypeA TypeGuard TypeB means that if foo arg returns True then arg narrows from TypeA to TypeB Note TypeB need not be a narrower form of TypeA it can even be a wider form The main reason is to allow for things like narrowing list object to list str even though the latter is not a subtype of the former since list is invariant The responsibility of writing type safe type guards is left to the user TypeGuard also works with type variables See PEP 647 for more details New in version 3 10 typing Unpack Typing operator to conceptually mark an object as having been unpacked For example using the unpack operator on a type variable tuple is equivalent to using Unpack to mark the type variable tuple as having been unpacked Ts TypeVarTuple Ts tup tuple Ts Effectively does tup tuple Unpack Ts In fact Unpack can be used interchangeably with in the context of typing TypeVarTuple and builtins tuple types You might see Unpack being used explicitly in older versions of Python where couldn t be used in certain places In older versions of Python TypeVarTuple and Unpack are located in the typing_extensions backports package from typing_extensions import TypeVarTuple Unpack Ts TypeVarTuple Ts tup tuple Ts Syntax error on Python 3 10 tup tuple Unpack Ts Semantically equivalent and backwards compatible Unpack can also be used along with typing TypedDict for typing kwargs in a function signature from typing import TypedDict Unpack class Movie TypedDict name str year int This function expects two keyword arguments name of type str and year of type int def foo kwargs Unpack Movie See PEP 692 for more details on using Unpack for kwargs typing New in version 3 11 Building generic types and type aliases The following classes should not be used directly as annotations Their intended purpose is to be building blocks for creating generic types and type aliases These objects can be created through special syntax type parameter lists and the type statement For compatibility with Python 3 11 and earlier they can also be created without the dedicated syntax as documented below class typing Generic Abstract base class for generic types A generic type is typically declared by adding a list of type parameters after the class name class Mapping KT VT def __getitem__ self key KT VT Etc Such a class implicitly inherits from Generic The runtime semantics of this syntax are discussed in the Language Reference This class can then be used as follows def lookup_name X Y mapping Mapping X Y key X default Y Y try return mapping key except KeyError return default Here the brackets after the function name indicate a generic function For backwards compatibility generic classes can also be declared by explicitly inheriting from Generic In this case the type parameters must be declared separately KT TypeVar KT VT TypeVar VT class Mapping Generic KT VT def __getitem__ self key KT VT Etc class typing TypeVar name constraints bound None covariant False contravariant False infer_variance False Type variable The preferred way to construct a type variable is via the dedicated syntax for generic functions generic classes and generic type ali,en
38,ases class Sequence T T is a TypeVar This syntax can also be used to create bound and constrained type variables class StrSequence S str S is a TypeVar bound to str class StrOrBytesSequence A str bytes A is a TypeVar constrained to str or bytes However if desired reusable type variables can also be constructed manually like so T TypeVar T Can be anything S TypeVar S bound str Can be any subtype of str A TypeVar A str bytes Must be exactly str or bytes Type variables exist primarily for the benefit of static type checkers They serve as the parameters for generic types as well as for generic function and type alias definitions See Generic for more information on generic types Generic functions work as follows def repeat T x T n int Sequence T Return a list containing n references to x return x n def print_capitalized S str x S S Print x capitalized and return x print x capitalize return x def concatenate A str bytes x A y A A Add two strings or bytes objects together return x y Note that type variables can be bound constrained or neither but cannot be both bound and constrained The variance of type variables is inferred by type checkers when they are created through the type parameter syntax or when infer_variance True is passed Manually created type variables may be explicitly marked covariant or contravariant by passing covariant True or contravariant True By default manually created type variables are invariant See PEP 484 and PEP 695 for more details Bound type variables and constrained type variables have different semantics in several important ways Using a bound type variable means that the TypeVar will be solved using the most specific type possible x print_capitalized a string reveal_type x revealed type is str class StringSubclass str pass y print_capitalized StringSubclass another string reveal_type y revealed type is StringSubclass z print_capitalized 45 error int is not a subtype of str Type variables can be bound to concrete types abstract types ABCs or protocols and even unions of types Can be anything with an __abs__ method def print_abs T SupportsAbs arg T None print Absolute value abs arg U TypeVar U bound str bytes Can be any subtype of the union str bytes V TypeVar V bound SupportsAbs Can be anything with an __abs__ method Using a constrained type variable however means that the TypeVar can only ever be solved as being exactly one of the constraints given a concatenate one two reveal_type a revealed type is str b concatenate StringSubclass one StringSubclass two reveal_type b revealed type is str despite StringSubclass being passed in c concatenate one b two error type variable A can be either str or bytes in a function call but not both At runtime isinstance x T will raise TypeError __name__ The name of the type variable __covariant__ Whether the type var has been explicitly marked as covariant __contravariant__ Whether the type var has been explicitly marked as contravariant __infer_variance__ Whether the type variable s variance should be inferred by type checkers New in version 3 12 __bound__ The bound of the type variable if any Changed in version 3 12 For type variables created through type parameter syntax the bound is evaluated only when the attribute is accessed not when the type variable is created see Lazy evaluation __constraints__ A tuple containing the constraints of the type variable if any Changed in version 3 12 For type variables created through type parameter syntax the constraints are evaluated only when the attribute is accessed not when the type variable is created see Lazy evaluation Changed in version 3 12 Type variables can now be declared using the type parameter syntax introduced by PEP 695 The infer_variance parameter was added class typing TypeVarTuple name Type variable tuple A specialized form of type variable that enables variadic generics Type variable tuples can be declared in type parameter lists using a single asterisk before the name def move_first_element_to_last T Ts tup tuple T Ts tuple Ts T return tup 1 tup 0 Or by explicitly invoking the TypeVarTuple constructor,en
39, T TypeVar T Ts TypeVarTuple Ts def move_first_element_to_last tup tuple T Ts tuple Ts T return tup 1 tup 0 A normal type variable enables parameterization with a single type A type variable tuple in contrast allows parameterization with an arbitrary number of types by acting like an arbitrary number of type variables wrapped in a tuple For example T is bound to int Ts is bound to Return value is 1 which has type tuple int move_first_element_to_last tup 1 T is bound to int Ts is bound to str Return value is spam 1 which has type tuple str int move_first_element_to_last tup 1 spam T is bound to int Ts is bound to str float Return value is spam 3 0 1 which has type tuple str float int move_first_element_to_last tup 1 spam 3 0 This fails to type check and fails at runtime because tuple is not compatible with tuple T Ts at least one element is required move_first_element_to_last tup Note the use of the unpacking operator in tuple T Ts Conceptually you can think of Ts as a tuple of type variables T1 T2 tuple T Ts would then become tuple T T1 T2 which is equivalent to tuple T T1 T2 Note that in older versions of Python you might see this written using Unpack instead as Unpack Ts Type variable tuples must always be unpacked This helps distinguish type variable tuples from normal type variables x Ts Not valid x tuple Ts Not valid x tuple Ts The correct way to do it Type variable tuples can be used in the same contexts as normal type variables For example in class definitions arguments and return types class Array Shape def __getitem__ self key tuple Shape float def __abs__ self Array Shape def get_shape self tuple Shape Type variable tuples can be happily combined with normal type variables class Array DType Shape This is fine pass class Array2 Shape DType This would also be fine pass class Height class Width float_array_1d Array float Height Array Totally fine int_array_2d Array int Height Width Array Yup fine too However note that at most one type variable tuple may appear in a single list of type arguments or type parameters x tuple Ts Ts Not valid class Array Shape Shape Not valid pass Finally an unpacked type variable tuple can be used as the type annotation of args def call_soon Ts callback Callable Ts None args Ts None callback args In contrast to non unpacked annotations of args e g args int which would specify that all arguments are int args Ts enables reference to the types of the individual arguments in args Here this allows us to ensure the types of the args passed to call_soon match the types of the positional arguments of callback See PEP 646 for more details on type variable tuples __name__ The name of the type variable tuple New in version 3 11 Changed in version 3 12 Type variable tuples can now be declared using the type parameter syntax introduced by PEP 695 class typing ParamSpec name bound None covariant False contravariant False Parameter specification variable A specialized version of type variables In type parameter lists parameter specifications can be declared with two asterisks type IntFunc P Callable P int For compatibility with Python 3 11 and earlier ParamSpec objects can also be created as follows P ParamSpec P Parameter specification variables exist primarily for the benefit of static type checkers They are used to forward the parameter types of one callable to another callable a pattern commonly found in higher order functions and decorators They are only valid when used in Concatenate or as the first argument to Callable or as parameters for user defined Generics See Generic for more information on generic types For example to add basic logging to a function one can create a decorator add_logging to log function calls The parameter specification variable tells the type checker that the callable passed into the decorator and the new callable returned by it have inter dependent type parameters from collections abc import Callable import logging def add_logging T P f Callable P T Callable P T A type safe decorator to add logging to a function def inner args P args kwargs P kwargs T logging info f f,en
40, __name__ was called return f args kwargs return inner add_logging def add_two x float y float float Add two numbers together return x y Without ParamSpec the simplest way to annotate this previously was to use a TypeVar with bound Callable Any However this causes two problems 1 The type checker can t type check the inner function because args and kwargs have to be typed Any 2 cast may be required in the body of the add_logging decorator when returning the inner function or the static type checker must be told to ignore the return inner args kwargs Since ParamSpec captures both positional and keyword parameters P args and P kwargs can be used to split a ParamSpec into its components P args represents the tuple of positional parameters in a given call and should only be used to annotate args P kwargs represents the mapping of keyword parameters to their values in a given call and should be only be used to annotate kwargs Both attributes require the annotated parameter to be in scope At runtime P args and P kwargs are instances respectively of ParamSpecArgs and ParamSpecKwargs __name__ The name of the parameter specification Parameter specification variables created with covariant True or contravariant True can be used to declare covariant or contravariant generic types The bound argument is also accepted similar to TypeVar However the actual semantics of these keywords are yet to be decided New in version 3 10 Changed in version 3 12 Parameter specifications can now be declared using the type parameter syntax introduced by PEP 695 Note Only parameter specification variables defined in global scope can be pickled See also PEP 612 Parameter Specification Variables the PEP which introduced ParamSpec and Concatenate Concatenate Annotating callable objects typing ParamSpecArgs typing ParamSpecKwargs Arguments and keyword arguments attributes of a ParamSpec The P args attribute of a ParamSpec is an instance of ParamSpecArgs and P kwargs is an instance of ParamSpecKwargs They are intended for runtime introspection and have no special meaning to static type checkers Calling get_origin on either of these objects will return the original ParamSpec from typing import ParamSpec get_origin P ParamSpec P get_origin P args is P True get_origin P kwargs is P True New in version 3 10 class typing TypeAliasType name value type_params The type of type aliases created through the type statement Example type Alias int type Alias class typing TypeAliasType New in version 3 12 __name__ The name of the type alias type Alias int Alias __name__ Alias __module__ The module in which the type alias was defined type Alias int Alias __module__ __main__ __type_params__ The type parameters of the type alias or an empty tuple if the alias is not generic type ListOrSet T list T set T ListOrSet __type_params__ T type NotGeneric int NotGeneric __type_params__ __value__ The type alias s value This is lazily evaluated so names used in the definition of the alias are not resolved until the __value__ attribute is accessed type Mutually Recursive type Recursive Mutually Mutually Mutually Recursive Recursive Mutually __value__ Recursive Recursive __value__ Mutually Other special directives These functions and classes should not be used directly as annotations Their intended purpose is to be building blocks for creating and declaring types class typing NamedTuple Typed version of collections namedtuple Usage class Employee NamedTuple name str id int This is equivalent to Employee collections namedtuple Employee name id To give a field a default value you can assign to it in the class body class Employee NamedTuple name str id int 3 employee Employee Guido assert employee id 3 Fields with a default value must come after any fields without a default The resulting class has an extra attribute __annotations__ giving a dict that maps the field names to the field types The field names are in the _fields attribute and the default values are in the _field_defaults attribute both of which are part of the namedtuple API NamedTuple subclasses can also have docstrings and meth,en
41,ods class Employee NamedTuple Represents an employee name str id int 3 def __repr__ self str return f Employee self name id self id NamedTuple subclasses can be generic class Group T NamedTuple key T group list T Backward compatible usage For creating a generic NamedTuple on Python 3 11 or lower class Group NamedTuple Generic T key T group list T A functional syntax is also supported Employee NamedTuple Employee name str id int Changed in version 3 6 Added support for PEP 526 variable annotation syntax Changed in version 3 6 1 Added support for default values methods and docstrings Changed in version 3 8 The _field_types and __annotations__ attributes are now regular dictionaries instead of instances of OrderedDict Changed in version 3 9 Removed the _field_types attribute in favor of the more standard __annotations__ attribute which has the same information Changed in version 3 11 Added support for generic namedtuples class typing NewType name tp Helper class to create low overhead distinct types A NewType is considered a distinct type by a typechecker At runtime however calling a NewType returns its argument unchanged Usage UserId NewType UserId int Declare the NewType UserId first_user UserId 1 UserId returns the argument unchanged at runtime __module__ The module in which the new type is defined __name__ The name of the new type __supertype__ The type that the new type is based on New in version 3 5 2 Changed in version 3 10 NewType is now a class rather than a function class typing Protocol Generic Base class for protocol classes Protocol classes are defined like this class Proto Protocol def meth self int Such classes are primarily used with static type checkers that recognize structural subtyping static duck typing for example class C def meth self int return 0 def func x Proto int return x meth func C Passes static type check See PEP 544 for more details Protocol classes decorated with runtime_checkable described later act as simple minded runtime protocols that check only the presence of given attributes ignoring their type signatures Protocol classes can be generic for example class GenProto T Protocol def meth self T In code that needs to be compatible with Python 3 11 or older generic Protocols can be written as follows T TypeVar T class GenProto Protocol T def meth self T New in version 3 8 typing runtime_checkable Mark a protocol class as a runtime protocol Such a protocol can be used with isinstance and issubclass This raises TypeError when applied to a non protocol class This allows a simple minded structural check very similar to one trick ponies in collections abc such as Iterable For example runtime_checkable class Closable Protocol def close self assert isinstance open some file Closable runtime_checkable class Named Protocol name str import threading assert isinstance threading Thread name Bob Named Note runtime_checkable will check only the presence of the required methods or attributes not their type signatures or types For example ssl SSLObject is a class therefore it passes an issubclass check against Callable However the ssl SSLObject __init__ method exists only to raise a TypeError with a more informative message therefore making it impossible to call instantiate ssl SSLObject Note An isinstance check against a runtime checkable protocol can be surprisingly slow compared to an isinstance check against a non protocol class Consider using alternative idioms such as hasattr calls for structural checks in performance sensitive code New in version 3 8 Changed in version 3 12 The internal implementation of isinstance checks against runtime checkable protocols now uses inspect getattr_static to look up attributes previously hasattr was used As a result some objects which used to be considered instances of a runtime checkable protocol may no longer be considered instances of that protocol on Python 3 12 and vice versa Most users are unlikely to be affected by this change Changed in version 3 12 The members of a runtime checkable protocol are now considered frozen at runtime as soon as the class has been,en
42, created Monkey patching attributes onto a runtime checkable protocol will still work but will have no impact on isinstance checks comparing objects to the protocol See What s new in Python 3 12 for more details class typing TypedDict dict Special construct to add type hints to a dictionary At runtime it is a plain dict TypedDict declares a dictionary type that expects all of its instances to have a certain set of keys where each key is associated with a value of a consistent type This expectation is not checked at runtime but is only enforced by type checkers Usage class Point2D TypedDict x int y int label str a Point2D x 1 y 2 label good OK b Point2D z 3 label bad Fails type check assert Point2D x 1 y 2 label first dict x 1 y 2 label first To allow using this feature with older versions of Python that do not support PEP 526 TypedDict supports two additional equivalent syntactic forms Using a literal dict as the second argument Point2D TypedDict Point2D x int y int label str Using keyword arguments Point2D TypedDict Point2D x int y int label str Deprecated since version 3 11 will be removed in version 3 13 The keyword argument syntax is deprecated in 3 11 and will be removed in 3 13 It may also be unsupported by static type checkers The functional syntax should also be used when any of the keys are not valid identifiers for example because they are keywords or contain hyphens Example raises SyntaxError class Point2D TypedDict in int in is a keyword x y int name with hyphens OK functional syntax Point2D TypedDict Point2D in int x y int By default all keys must be present in a TypedDict It is possible to mark individual keys as non required using NotRequired class Point2D TypedDict x int y int label NotRequired str Alternative syntax Point2D TypedDict Point2D x int y int label NotRequired str This means that a Point2D TypedDict can have the label key omitted It is also possible to mark all keys as non required by default by specifying a totality of False class Point2D TypedDict total False x int y int Alternative syntax Point2D TypedDict Point2D x int y int total False This means that a Point2D TypedDict can have any of the keys omitted A type checker is only expected to support a literal False or True as the value of the total argument True is the default and makes all items defined in the class body required Individual keys of a total False TypedDict can be marked as required using Required class Point2D TypedDict total False x Required int y Required int label str Alternative syntax Point2D TypedDict Point2D x Required int y Required int label str total False It is possible for a TypedDict type to inherit from one or more other TypedDict types using the class based syntax Usage class Point3D Point2D z int Point3D has three items x y and z It is equivalent to this definition class Point3D TypedDict x int y int z int A TypedDict cannot inherit from a non TypedDict class except for Generic For example class X TypedDict x int class Y TypedDict y int class Z object pass A non TypedDict class class XY X Y pass OK class XZ X Z pass raises TypeError A TypedDict can be generic class Group T TypedDict key T group list T To create a generic TypedDict that is compatible with Python 3 11 or lower inherit from Generic explicitly T TypeVar T class Group TypedDict Generic T key T group list T A TypedDict can be introspected via annotations dicts see Annotations Best Practices for more information on annotations best practices __total__ __required_keys__ and __optional_keys__ __total__ Point2D __total__ gives the value of the total argument Example from typing import TypedDict class Point2D TypedDict pass Point2D __total__ True class Point2D TypedDict total False pass Point2D __total__ False class Point3D Point2D pass Point3D __total__ True This attribute reflects only the value of the total argument to the current TypedDict class not whether the class is semantically total For example a TypedDict with __total__ set to True may have keys marked with NotRequired or it may inherit from another TypedDict with total False Therefore it is g,en
43,enerally better to use __required_keys__ and __optional_keys__ for introspection __required_keys__ New in version 3 9 __optional_keys__ Point2D __required_keys__ and Point2D __optional_keys__ return frozenset objects containing required and non required keys respectively Keys marked with Required will always appear in __required_keys__ and keys marked with NotRequired will always appear in __optional_keys__ For backwards compatibility with Python 3 10 and below it is also possible to use inheritance to declare both required and non required keys in the same TypedDict This is done by declaring a TypedDict with one value for the total argument and then inheriting from it in another TypedDict with a different value for total class Point2D TypedDict total False x int y int class Point3D Point2D z int Point3D __required_keys__ frozenset z True Point3D __optional_keys__ frozenset x y True New in version 3 9 Note If from __future__ import annotations is used or if annotations are given as strings annotations are not evaluated when the TypedDict is defined Therefore the runtime introspection that __required_keys__ and __optional_keys__ rely on may not work properly and the values of the attributes may be incorrect See PEP 589 for more examples and detailed rules of using TypedDict New in version 3 8 Changed in version 3 11 Added support for marking individual keys as Required or NotRequired See PEP 655 Changed in version 3 11 Added support for generic TypedDict s Protocols The following protocols are provided by the typing module All are decorated with runtime_checkable class typing SupportsAbs An ABC with one abstract method __abs__ that is covariant in its return type class typing SupportsBytes An ABC with one abstract method __bytes__ class typing SupportsComplex An ABC with one abstract method __complex__ class typing SupportsFloat An ABC with one abstract method __float__ class typing SupportsIndex An ABC with one abstract method __index__ New in version 3 8 class typing SupportsInt An ABC with one abstract method __int__ class typing SupportsRound An ABC with one abstract method __round__ that is covariant in its return type ABCs for working with IO class typing IO class typing TextIO class typing BinaryIO Generic type IO AnyStr and its subclasses TextIO IO str and BinaryIO IO bytes represent the types of I O streams such as returned by open Functions and decorators typing cast typ val Cast a value to a type This returns the value unchanged To the type checker this signals that the return value has the designated type but at runtime we intentionally don t check anything we want this to be as fast as possible typing assert_type val typ Ask a static type checker to confirm that val has an inferred type of typ At runtime this does nothing it returns the first argument unchanged with no checks or side effects no matter the actual type of the argument When a static type checker encounters a call to assert_type it emits an error if the value is not of the specified type def greet name str None assert_type name str OK inferred type of name is str assert_type name int type checker error This function is useful for ensuring the type checker s understanding of a script is in line with the developer s intentions def complex_function arg object Do some complex type narrowing logic after which we hope the inferred type will be int Test whether the type checker correctly understands our function assert_type arg int New in version 3 11 typing assert_never arg Ask a static type checker to confirm that a line of code is unreachable Example def int_or_str arg int str None match arg case int print It s an int case str print It s a str case _ as unreachable assert_never unreachable Here the annotations allow the type checker to infer that the last case can never execute because arg is either an int or a str and both options are covered by earlier cases If a type checker finds that a call to assert_never is reachable it will emit an error For example if the type annotation for arg was instead int str float the type checker would emit an error ,en
44,pointing out that unreachable is of type float For a call to assert_never to pass type checking the inferred type of the argument passed in must be the bottom type Never and nothing else At runtime this throws an exception when called See also Unreachable Code and Exhaustiveness Checking has more information about exhaustiveness checking with static typing New in version 3 11 typing reveal_type obj Ask a static type checker to reveal the inferred type of an expression When a static type checker encounters a call to this function it emits a diagnostic with the inferred type of the argument For example x int 1 reveal_type x Revealed type is builtins int This can be useful when you want to debug how your type checker handles a particular piece of code At runtime this function prints the runtime type of its argument to sys stderr and returns the argument unchanged allowing the call to be used within an expression x reveal_type 1 prints Runtime type is int print x prints 1 Note that the runtime type may be different from more or less specific than the type statically inferred by a type checker Most type checkers support reveal_type anywhere even if the name is not imported from typing Importing the name from typing however allows your code to run without runtime errors and communicates intent more clearly New in version 3 11 typing dataclass_transform eq_default True order_default False kw_only_default False frozen_default False field_specifiers kwargs Decorator to mark an object as providing dataclass like behavior dataclass_transform may be used to decorate a class metaclass or a function that is itself a decorator The presence of dataclass_transform tells a static type checker that the decorated object performs runtime magic that transforms a class in a similar way to dataclasses dataclass Example usage with a decorator function dataclass_transform def create_model T cls type T type T return cls create_model class CustomerModel id int name str On a base class dataclass_transform class ModelBase class CustomerModel ModelBase id int name str On a metaclass dataclass_transform class ModelMeta type class ModelBase metaclass ModelMeta class CustomerModel ModelBase id int name str The CustomerModel classes defined above will be treated by type checkers similarly to classes created with dataclasses dataclass For example type checkers will assume these classes have __init__ methods that accept id and name The decorated class metaclass or function may accept the following bool arguments which type checkers will assume have the same effect as they would have on the dataclasses dataclass decorator init eq order unsafe_hash frozen match_args kw_only and slots It must be possible for the value of these arguments True or False to be statically evaluated The arguments to the dataclass_transform decorator can be used to customize the default behaviors of the decorated class metaclass or function Parameters eq_default bool Indicates whether the eq parameter is assumed to be True or False if it is omitted by the caller Defaults to True order_default bool Indicates whether the order parameter is assumed to be True or False if it is omitted by the caller Defaults to False kw_only_default bool Indicates whether the kw_only parameter is assumed to be True or False if it is omitted by the caller Defaults to False frozen_default bool Indicates whether the frozen parameter is assumed to be True or False if it is omitted by the caller Defaults to False New in version 3 12 field_specifiers tuple Callable Any Specifies a static list of supported classes or functions that describe fields similar to dataclasses field Defaults to kwargs Any Arbitrary other keyword arguments are accepted in order to allow for possible future extensions Type checkers recognize the following optional parameters on field specifiers Recognised parameters for field specifiers Parameter name Description init Indicates whether the field should be included in the synthesized __init__ method If unspecified init defaults to True default Provides the default value for the field def,en
45,ault_factory Provides a runtime callback that returns the default value for the field If neither default nor default_factory are specified the field is assumed to have no default value and must be provided a value when the class is instantiated factory An alias for the default_factory parameter on field specifiers kw_only Indicates whether the field should be marked as keyword only If True the field will be keyword only If False it will not be keyword only If unspecified the value of the kw_only parameter on the object decorated with dataclass_transform will be used or if that is unspecified the value of kw_only_default on dataclass_transform will be used alias Provides an alternative name for the field This alternative name is used in the synthesized __init__ method At runtime this decorator records its arguments in the __dataclass_transform__ attribute on the decorated object It has no other runtime effect See PEP 681 for more details New in version 3 11 typing overload Decorator for creating overloaded functions and methods The overload decorator allows describing functions and methods that support multiple different combinations of argument types A series of overload decorated definitions must be followed by exactly one non overload decorated definition for the same function method overload decorated definitions are for the benefit of the type checker only since they will be overwritten by the non overload decorated definition The non overload decorated definition meanwhile will be used at runtime but should be ignored by a type checker At runtime calling an overload decorated function directly will raise NotImplementedError An example of overload that gives a more precise type than can be expressed using a union or a type variable overload def process response None None overload def process response int tuple int str overload def process response bytes str def process response actual implementation goes here See PEP 484 for more details and comparison with other typing semantics Changed in version 3 11 Overloaded functions can now be introspected at runtime using get_overloads typing get_overloads func Return a sequence of overload decorated definitions for func func is the function object for the implementation of the overloaded function For example given the definition of process in the documentation for overload get_overloads process will return a sequence of three function objects for the three defined overloads If called on a function with no overloads get_overloads returns an empty sequence get_overloads can be used for introspecting an overloaded function at runtime New in version 3 11 typing clear_overloads Clear all registered overloads in the internal registry This can be used to reclaim the memory used by the registry New in version 3 11 typing final Decorator to indicate final methods and final classes Decorating a method with final indicates to a type checker that the method cannot be overridden in a subclass Decorating a class with final indicates that it cannot be subclassed For example class Base final def done self None class Sub Base def done self None Error reported by type checker final class Leaf class Other Leaf Error reported by type checker There is no runtime checking of these properties See PEP 591 for more details New in version 3 8 Changed in version 3 11 The decorator will now attempt to set a __final__ attribute to True on the decorated object Thus a check like if getattr obj __final__ False can be used at runtime to determine whether an object obj has been marked as final If the decorated object does not support setting attributes the decorator returns the object unchanged without raising an exception typing no_type_check Decorator to indicate that annotations are not type hints This works as a class or function decorator With a class it applies recursively to all methods and classes defined in that class but not to methods defined in its superclasses or subclasses Type checkers will ignore all annotations in a function or class with this decorator no_type_check mutates the decorated o,en
46,bject in place typing no_type_check_decorator Decorator to give another decorator the no_type_check effect This wraps the decorator with something that wraps the decorated function in no_type_check typing override Decorator to indicate that a method in a subclass is intended to override a method or attribute in a superclass Type checkers should emit an error if a method decorated with override does not in fact override anything This helps prevent bugs that may occur when a base class is changed without an equivalent change to a child class For example class Base def log_status self None class Sub Base override def log_status self None Okay overrides Base log_status override def done self None Error reported by type checker There is no runtime checking of this property The decorator will attempt to set an __override__ attribute to True on the decorated object Thus a check like if getattr obj __override__ False can be used at runtime to determine whether an object obj has been marked as an override If the decorated object does not support setting attributes the decorator returns the object unchanged without raising an exception See PEP 698 for more details New in version 3 12 typing type_check_only Decorator to mark a class or function as unavailable at runtime This decorator is itself not available at runtime It is mainly intended to mark classes that are defined in type stub files if an implementation returns an instance of a private class type_check_only class Response private or not available at runtime code int def get_header self name str str def fetch_response Response Note that returning instances of private classes is not recommended It is usually preferable to make such classes public Introspection helpers typing get_type_hints obj globalns None localns None include_extras False Return a dictionary containing type hints for a function method module or class object This is often the same as obj __annotations__ In addition forward references encoded as string literals are handled by evaluating them in globals and locals namespaces For a class C return a dictionary constructed by merging all the __annotations__ along C __mro__ in reverse order The function recursively replaces all Annotated T with T unless include_extras is set to True see Annotated for more information For example class Student NamedTuple name Annotated str some marker assert get_type_hints Student name str assert get_type_hints Student include_extras False name str assert get_type_hints Student include_extras True name Annotated str some marker Note get_type_hints does not work with imported type aliases that include forward references Enabling postponed evaluation of annotations PEP 563 may remove the need for most forward references Changed in version 3 9 Added include_extras parameter as part of PEP 593 See the documentation on Annotated for more information Changed in version 3 11 Previously Optional t was added for function and method annotations if a default value equal to None was set Now the annotation is returned unchanged typing get_origin tp Get the unsubscripted version of a type for a typing object of the form X Y Z return X If X is a typing module alias for a builtin or collections class it will be normalized to the original class If X is an instance of ParamSpecArgs or ParamSpecKwargs return the underlying ParamSpec Return None for unsupported objects Examples assert get_origin str is None assert get_origin Dict str int is dict assert get_origin Union int str is Union P ParamSpec P assert get_origin P args is P assert get_origin P kwargs is P New in version 3 8 typing get_args tp Get type arguments with all substitutions performed for a typing object of the form X Y Z return Y Z If X is a union or Literal contained in another generic type the order of Y Z may be different from the order of the original arguments Y Z due to type caching Return for unsupported objects Examples assert get_args int assert get_args Dict int str int str assert get_args Union int str int str New in version 3 8 typing is_typeddict tp Check if a type is a Ty,en
47,pedDict For example class Film TypedDict title str year int assert is_typeddict Film assert not is_typeddict list str TypedDict is a factory for creating typed dicts not a typed dict itself assert not is_typeddict TypedDict New in version 3 10 class typing ForwardRef Class used for internal typing representation of string forward references For example List SomeClass is implicitly transformed into List ForwardRef SomeClass ForwardRef should not be instantiated by a user but may be used by introspection tools Note PEP 585 generic types such as list SomeClass will not be implicitly transformed into list ForwardRef SomeClass and thus will not automatically resolve to list SomeClass New in version 3 7 4 Constant typing TYPE_CHECKING A special constant that is assumed to be True by 3rd party static type checkers It is False at runtime Usage if TYPE_CHECKING import expensive_mod def fun arg expensive_mod SomeType None local_var expensive_mod AnotherType other_fun The first type annotation must be enclosed in quotes making it a forward reference to hide the expensive_mod reference from the interpreter runtime Type annotations for local variables are not evaluated so the second annotation does not need to be enclosed in quotes Note If from __future__ import annotations is used annotations are not evaluated at function definition time Instead they are stored as strings in __annotations__ This makes it unnecessary to use quotes around the annotation see PEP 563 New in version 3 5 2 Deprecated aliases This module defines several deprecated aliases to pre existing standard library classes These were originally included in the typing module in order to support parameterizing these generic classes using However the aliases became redundant in Python 3 9 when the corresponding pre existing classes were enhanced to support see PEP 585 The redundant types are deprecated as of Python 3 9 However while the aliases may be removed at some point removal of these aliases is not currently planned As such no deprecation warnings are currently issued by the interpreter for these aliases If at some point it is decided to remove these deprecated aliases a deprecation warning will be issued by the interpreter for at least two releases prior to removal The aliases are guaranteed to remain in the typing module without deprecation warnings until at least Python 3 14 Type checkers are encouraged to flag uses of the deprecated types if the program they are checking targets a minimum Python version of 3 9 or newer Aliases to built in types class typing Dict dict MutableMapping KT VT Deprecated alias to dict Note that to annotate arguments it is preferred to use an abstract collection type such as Mapping rather than to use dict or typing Dict This type can be used as follows def count_words text str Dict str int Deprecated since version 3 9 builtins dict now supports subscripting See PEP 585 and Generic Alias Type class typing List list MutableSequence T Deprecated alias to list Note that to annotate arguments it is preferred to use an abstract collection type such as Sequence or Iterable rather than to use list or typing List This type may be used as follows def vec2 T int float x T y T List T return x y def keep_positives T int float vector Sequence T List T return item for item in vector if item 0 Deprecated since version 3 9 builtins list now supports subscripting See PEP 585 and Generic Alias Type class typing Set set MutableSet T Deprecated alias to builtins set Note that to annotate arguments it is preferred to use an abstract collection type such as AbstractSet rather than to use set or typing Set Deprecated since version 3 9 builtins set now supports subscripting See PEP 585 and Generic Alias Type class typing FrozenSet frozenset AbstractSet T_co Deprecated alias to builtins frozenset Deprecated since version 3 9 builtins frozenset now supports subscripting See PEP 585 and Generic Alias Type typing Tuple Deprecated alias for tuple tuple and Tuple are special cased in the type system see Annotating tuples for more details Deprecated since version ,en
48,3 9 builtins tuple now supports subscripting See PEP 585 and Generic Alias Type class typing Type Generic CT_co Deprecated alias to type See The type of class objects for details on using type or typing Type in type annotations New in version 3 5 2 Deprecated since version 3 9 builtins type now supports subscripting See PEP 585 and Generic Alias Type Aliases to types in collections class typing DefaultDict collections defaultdict MutableMapping KT VT Deprecated alias to collections defaultdict New in version 3 5 2 Deprecated since version 3 9 collections defaultdict now supports subscripting See PEP 585 and Generic Alias Type class typing OrderedDict collections OrderedDict MutableMapping KT VT Deprecated alias to collections OrderedDict New in version 3 7 2 Deprecated since version 3 9 collections OrderedDict now supports subscripting See PEP 585 and Generic Alias Type class typing ChainMap collections ChainMap MutableMapping KT VT Deprecated alias to collections ChainMap New in version 3 6 1 Deprecated since version 3 9 collections ChainMap now supports subscripting See PEP 585 and Generic Alias Type class typing Counter collections Counter Dict T int Deprecated alias to collections Counter New in version 3 6 1 Deprecated since version 3 9 collections Counter now supports subscripting See PEP 585 and Generic Alias Type class typing Deque deque MutableSequence T Deprecated alias to collections deque New in version 3 6 1 Deprecated since version 3 9 collections deque now supports subscripting See PEP 585 and Generic Alias Type Aliases to other concrete types Deprecated since version 3 8 will be removed in version 3 13 The typing io namespace is deprecated and will be removed These types should be directly imported from typing instead class typing Pattern class typing Match Deprecated aliases corresponding to the return types from re compile and re match These types and the corresponding functions are generic over AnyStr Pattern can be specialised as Pattern str or Pattern bytes Match can be specialised as Match str or Match bytes Deprecated since version 3 8 will be removed in version 3 13 The typing re namespace is deprecated and will be removed These types should be directly imported from typing instead Deprecated since version 3 9 Classes Pattern and Match from re now support See PEP 585 and Generic Alias Type class typing Text Deprecated alias for str Text is provided to supply a forward compatible path for Python 2 code in Python 2 Text is an alias for unicode Use Text to indicate that a value must contain a unicode string in a manner that is compatible with both Python 2 and Python 3 def add_unicode_checkmark text Text Text return text u u2713 New in version 3 5 2 Deprecated since version 3 11 Python 2 is no longer supported and most type checkers also no longer support type checking Python 2 code Removal of the alias is not currently planned but users are encouraged to use str instead of Text Aliases to container ABCs in collections abc class typing AbstractSet Collection T_co Deprecated alias to collections abc Set Deprecated since version 3 9 collections abc Set now supports subscripting See PEP 585 and Generic Alias Type class typing ByteString Sequence int This type represents the types bytes bytearray and memoryview of byte sequences Deprecated since version 3 9 will be removed in version 3 14 Prefer collections abc Buffer or a union like bytes bytearray memoryview class typing Collection Sized Iterable T_co Container T_co Deprecated alias to collections abc Collection New in version 3 6 Deprecated since version 3 9 collections abc Collection now supports subscripting See PEP 585 and Generic Alias Type class typing Container Generic T_co Deprecated alias to collections abc Container Deprecated since version 3 9 collections abc Container now supports subscripting See PEP 585 and Generic Alias Type class typing ItemsView MappingView AbstractSet tuple KT_co VT_co Deprecated alias to collections abc ItemsView Deprecated since version 3 9 collections abc ItemsView now supports subscripting See PEP 585 and Generic ,en
49,Alias Type class typing KeysView MappingView AbstractSet KT_co Deprecated alias to collections abc KeysView Deprecated since version 3 9 collections abc KeysView now supports subscripting See PEP 585 and Generic Alias Type class typing Mapping Collection KT Generic KT VT_co Deprecated alias to collections abc Mapping This type can be used as follows def get_position_in_index word_list Mapping str int word str int return word_list word Deprecated since version 3 9 collections abc Mapping now supports subscripting See PEP 585 and Generic Alias Type class typing MappingView Sized Deprecated alias to collections abc MappingView Deprecated since version 3 9 collections abc MappingView now supports subscripting See PEP 585 and Generic Alias Type class typing MutableMapping Mapping KT VT Deprecated alias to collections abc MutableMapping Deprecated since version 3 9 collections abc MutableMapping now supports subscripting See PEP 585 and Generic Alias Type class typing MutableSequence Sequence T Deprecated alias to collections abc MutableSequence Deprecated since version 3 9 collections abc MutableSequence now supports subscripting See PEP 585 and Generic Alias Type class typing MutableSet AbstractSet T Deprecated alias to collections abc MutableSet Deprecated since version 3 9 collections abc MutableSet now supports subscripting See PEP 585 and Generic Alias Type class typing Sequence Reversible T_co Collection T_co Deprecated alias to collections abc Sequence Deprecated since version 3 9 collections abc Sequence now supports subscripting See PEP 585 and Generic Alias Type class typing ValuesView MappingView Collection _VT_co Deprecated alias to collections abc ValuesView Deprecated since version 3 9 collections abc ValuesView now supports subscripting See PEP 585 and Generic Alias Type Aliases to asynchronous ABCs in collections abc class typing Coroutine Awaitable ReturnType Generic YieldType SendType ReturnType Deprecated alias to collections abc Coroutine The variance and order of type variables correspond to those of Generator for example from collections abc import Coroutine c Coroutine list str str int Some coroutine defined elsewhere x c send hi Inferred type of x is list str async def bar None y await c Inferred type of y is int New in version 3 5 3 Deprecated since version 3 9 collections abc Coroutine now supports subscripting See PEP 585 and Generic Alias Type class typing AsyncGenerator AsyncIterator YieldType Generic YieldType SendType Deprecated alias to collections abc AsyncGenerator An async generator can be annotated by the generic type AsyncGenerator YieldType SendType For example async def echo_round AsyncGenerator int float sent yield 0 while sent 0 0 rounded await round sent sent yield rounded Unlike normal generators async generators cannot return a value so there is no ReturnType type parameter As with Generator the SendType behaves contravariantly If your generator will only yield values set the SendType to None async def infinite_stream start int AsyncGenerator int None while True yield start start await increment start Alternatively annotate your generator as having a return type of either AsyncIterable YieldType or AsyncIterator YieldType async def infinite_stream start int AsyncIterator int while True yield start start await increment start New in version 3 6 1 Deprecated since version 3 9 collections abc AsyncGenerator now supports subscripting See PEP 585 and Generic Alias Type class typing AsyncIterable Generic T_co Deprecated alias to collections abc AsyncIterable New in version 3 5 2 Deprecated since version 3 9 collections abc AsyncIterable now supports subscripting See PEP 585 and Generic Alias Type class typing AsyncIterator AsyncIterable T_co Deprecated alias to collections abc AsyncIterator New in version 3 5 2 Deprecated since version 3 9 collections abc AsyncIterator now supports subscripting See PEP 585 and Generic Alias Type class typing Awaitable Generic T_co Deprecated alias to collections abc Awaitable New in version 3 5 2 Deprecated since version 3 9 collections abc Awaitable now ,en
50,supports subscripting See PEP 585 and Generic Alias Type Aliases to other ABCs in collections abc class typing Iterable Generic T_co Deprecated alias to collections abc Iterable Deprecated since version 3 9 collections abc Iterable now supports subscripting See PEP 585 and Generic Alias Type class typing Iterator Iterable T_co Deprecated alias to collections abc Iterator Deprecated since version 3 9 collections abc Iterator now supports subscripting See PEP 585 and Generic Alias Type typing Callable Deprecated alias to collections abc Callable See Annotating callable objects for details on how to use collections abc Callable and typing Callable in type annotations Deprecated since version 3 9 collections abc Callable now supports subscripting See PEP 585 and Generic Alias Type Changed in version 3 10 Callable now supports ParamSpec and Concatenate See PEP 612 for more details class typing Generator Iterator YieldType Generic YieldType SendType ReturnType Deprecated alias to collections abc Generator A generator can be annotated by the generic type Generator YieldType SendType ReturnType For example def echo_round Generator int float str sent yield 0 while sent 0 sent yield round sent return Done Note that unlike many other generics in the typing module the SendType of Generator behaves contravariantly not covariantly or invariantly If your generator will only yield values set the SendType and ReturnType to None def infinite_stream start int Generator int None None while True yield start start 1 Alternatively annotate your generator as having a return type of either Iterable YieldType or Iterator YieldType def infinite_stream start int Iterator int while True yield start start 1 Deprecated since version 3 9 collections abc Generator now supports subscripting See PEP 585 and Generic Alias Type class typing Hashable Deprecated alias to collections abc Hashable Deprecated since version 3 12 Use collections abc Hashable directly instead class typing Reversible Iterable T_co Deprecated alias to collections abc Reversible Deprecated since version 3 9 collections abc Reversible now supports subscripting See PEP 585 and Generic Alias Type class typing Sized Deprecated alias to collections abc Sized Deprecated since version 3 12 Use collections abc Sized directly instead Aliases to contextlib ABCs class typing ContextManager Generic T_co Deprecated alias to contextlib AbstractContextManager New in version 3 5 4 Deprecated since version 3 9 contextlib AbstractContextManager now supports subscripting See PEP 585 and Generic Alias Type class typing AsyncContextManager Generic T_co Deprecated alias to contextlib AbstractAsyncContextManager New in version 3 6 2 Deprecated since version 3 9 contextlib AbstractAsyncContextManager now supports subscripting See PEP 585 and Generic Alias Type Deprecation Timeline of Major Features Certain features in typing are deprecated and may be removed in a future version of Python The following table summarizes major deprecations for your convenience This is subject to change and not all deprecations are listed Feature Deprecated in Projected removal PEP issue typing io and 3 8 3 13 bpo 38291 typing re submodules typing versions of 3 9 Undecided see Deprecated PEP 585 standard collections aliases for more information typing ByteString 3 9 3 14 gh 91896 typing Text 3 11 Undecided gh 92332 typing Hashable and 3 12 Undecided gh 94309 typing Sized typing TypeAlias 3 12 Undecided PEP 695,en
51,warnings Warning control Source code Lib warnings py Warning messages are typically issued in situations where it is useful to alert the user of some condition in a program where that condition normally doesn t warrant raising an exception and terminating the program For example one might want to issue a warning when a program uses an obsolete module Python programmers issue warnings by calling the warn function defined in this module C programmers use PyErr_WarnEx see Exception Handling for details Warning messages are normally written to sys stderr but their disposition can be changed flexibly from ignoring all warnings to turning them into exceptions The disposition of warnings can vary based on the warning category the text of the warning message and the source location where it is issued Repetitions of a particular warning for the same source location are typically suppressed There are two stages in warning control first each time a warning is issued a determination is made whether a message should be issued or not next if a message is to be issued it is formatted and printed using a user settable hook The determination whether to issue a warning message is controlled by the warning filter which is a sequence of matching rules and actions Rules can be added to the filter by calling filterwarnings and reset to its default state by calling resetwarnings The printing of warning messages is done by calling showwarning which may be overridden the default implementation of this function formats the message by calling formatwarning which is also available for use by custom implementations See also logging captureWarnings allows you to handle all warnings with the standard logging infrastructure Warning Categories There are a number of built in exceptions that represent warning categories This categorization is useful to be able to filter out groups of warnings While these are technically built in exceptions they are documented here because conceptually they belong to the warnings mechanism User code can define additional warning categories by subclassing one of the standard warning categories A warning category must always be a subclass of the Warning class The following warnings category classes are currently defined Class Description Warning This is the base class of all warning category classes It is a subclass of Exception UserWarning The default category for warn DeprecationWarning Base category for warnings about deprecated features when those warnings are intended for other Python developers ignored by default unless triggered by code in __main__ SyntaxWarning Base category for warnings about dubious syntactic features RuntimeWarning Base category for warnings about dubious runtime features FutureWarning Base category for warnings about deprecated features when those warnings are intended for end users of applications that are written in Python PendingDeprecationWarning Base category for warnings about features that will be deprecated in the future ignored by default ImportWarning Base category for warnings triggered during the process of importing a module ignored by default UnicodeWarning Base category for warnings related to Unicode BytesWarning Base category for warnings related to bytes and bytearray ResourceWarning Base category for warnings related to resource usage ignored by default Changed in version 3 7 Previously DeprecationWarning and FutureWarning were distinguished based on whether a feature was being removed entirely or changing its behaviour They are now distinguished based on their intended audience and the way they re handled by the default warnings filters The Warnings Filter The warnings filter controls whether warnings are ignored displayed or turned into errors raising an exception Conceptually the warnings filter maintains an ordered list of filter specifications any specific warning is matched against each filter specification in the list in turn until a match is found the filter determines the disposition of the match Each entry is a tuple of the form action message category module lineno w,en
52,here action is one of the following strings Value Disposition default print the first occurrence of matching warnings for each location module line number where the warning is issued error turn matching warnings into exceptions ignore never print matching warnings always always print matching warnings module print the first occurrence of matching warnings for each module where the warning is issued regardless of line number once print only the first occurrence of matching warnings regardless of location message is a string containing a regular expression that the start of the warning message must match case insensitively In W and PYTHONWARNINGS message is a literal string that the start of the warning message must contain case insensitively ignoring any whitespace at the start or end of message category is a class a subclass of Warning of which the warning category must be a subclass in order to match module is a string containing a regular expression that the start of the fully qualified module name must match case sensitively In W and PYTHONWARNINGS module is a literal string that the fully qualified module name must be equal to case sensitively ignoring any whitespace at the start or end of module lineno is an integer that the line number where the warning occurred must match or 0 to match all line numbers Since the Warning class is derived from the built in Exception class to turn a warning into an error we simply raise category message If a warning is reported and doesn t match any registered filter then the default action is applied hence its name Describing Warning Filters The warnings filter is initialized by W options passed to the Python interpreter command line and the PYTHONWARNINGS environment variable The interpreter saves the arguments for all supplied entries without interpretation in sys warnoptions the warnings module parses these when it is first imported invalid options are ignored after printing a message to sys stderr Individual warnings filters are specified as a sequence of fields separated by colons action message category module line The meaning of each of these fields is as described in The Warnings Filter When listing multiple filters on a single line as for PYTHONWARNINGS the individual filters are separated by commas and the filters listed later take precedence over those listed before them as they re applied left to right and the most recently applied filters take precedence over earlier ones Commonly used warning filters apply to either all warnings warnings in a particular category or warnings raised by particular modules or packages Some examples default Show all warnings even those ignored by default ignore Ignore all warnings error Convert all warnings to errors error ResourceWarning Treat ResourceWarning messages as errors default DeprecationWarning Show DeprecationWarning messages ignore default mymodule Only report warnings triggered by mymodule error mymodule Convert warnings to errors in mymodule Default Warning Filter By default Python installs several warning filters which can be overridden by the W command line option the PYTHONWARNINGS environment variable and calls to filterwarnings In regular release builds the default warning filter has the following entries in order of precedence default DeprecationWarning __main__ ignore DeprecationWarning ignore PendingDeprecationWarning ignore ImportWarning ignore ResourceWarning In a debug build the list of default warning filters is empty Changed in version 3 2 DeprecationWarning is now ignored by default in addition to PendingDeprecationWarning Changed in version 3 7 DeprecationWarning is once again shown by default when triggered directly by code in __main__ Changed in version 3 7 BytesWarning no longer appears in the default filter list and is instead configured via sys warnoptions when b is specified twice Overriding the default filter Developers of applications written in Python may wish to hide all Python level warnings from their users by default and only display them when running tests or otherwise working on the application T,en
53,he sys warnoptions attribute used to pass filter configurations to the interpreter can be used as a marker to indicate whether or not warnings should be disabled import sys if not sys warnoptions import warnings warnings simplefilter ignore Developers of test runners for Python code are advised to instead ensure that all warnings are displayed by default for the code under test using code like import sys if not sys warnoptions import os warnings warnings simplefilter default Change the filter in this process os environ PYTHONWARNINGS default Also affect subprocesses Finally developers of interactive shells that run user code in a namespace other than __main__ are advised to ensure that DeprecationWarning messages are made visible by default using code like the following where user_ns is the module used to execute code entered interactively import warnings warnings filterwarnings default category DeprecationWarning module user_ns get __name__ Temporarily Suppressing Warnings If you are using code that you know will raise a warning such as a deprecated function but do not want to see the warning even when warnings have been explicitly configured via the command line then it is possible to suppress the warning using the catch_warnings context manager import warnings def fxn warnings warn deprecated DeprecationWarning with warnings catch_warnings warnings simplefilter ignore fxn While within the context manager all warnings will simply be ignored This allows you to use known deprecated code without having to see the warning while not suppressing the warning for other code that might not be aware of its use of deprecated code Note this can only be guaranteed in a single threaded application If two or more threads use the catch_warnings context manager at the same time the behavior is undefined Testing Warnings To test warnings raised by code use the catch_warnings context manager With it you can temporarily mutate the warnings filter to facilitate your testing For instance do the following to capture all raised warnings to check import warnings def fxn warnings warn deprecated DeprecationWarning with warnings catch_warnings record True as w Cause all warnings to always be triggered warnings simplefilter always Trigger a warning fxn Verify some things assert len w 1 assert issubclass w 1 category DeprecationWarning assert deprecated in str w 1 message One can also cause all warnings to be exceptions by using error instead of always One thing to be aware of is that if a warning has already been raised because of a once default rule then no matter what filters are set the warning will not be seen again unless the warnings registry related to the warning has been cleared Once the context manager exits the warnings filter is restored to its state when the context was entered This prevents tests from changing the warnings filter in unexpected ways between tests and leading to indeterminate test results The showwarning function in the module is also restored to its original value Note this can only be guaranteed in a single threaded application If two or more threads use the catch_warnings context manager at the same time the behavior is undefined When testing multiple operations that raise the same kind of warning it is important to test them in a manner that confirms each operation is raising a new warning e g set warnings to be raised as exceptions and check the operations raise exceptions check that the length of the warning list continues to increase after each operation or else delete the previous entries from the warnings list before each new operation Updating Code For New Versions of Dependencies Warning categories that are primarily of interest to Python developers rather than end users of applications written in Python are ignored by default Notably this ignored by default list includes DeprecationWarning for every module except __main__ which means developers should make sure to test their code with typically ignored warnings made visible in order to receive timely notifications of future breaking API changes whether in ,en
54,the standard library or third party packages In the ideal case the code will have a suitable test suite and the test runner will take care of implicitly enabling all warnings when running tests the test runner provided by the unittest module does this In less ideal cases applications can be checked for use of deprecated interfaces by passing Wd to the Python interpreter this is shorthand for W default or setting PYTHONWARNINGS default in the environment This enables default handling for all warnings including those that are ignored by default To change what action is taken for encountered warnings you can change what argument is passed to W e g W error See the W flag for more details on what is possible Available Functions warnings warn message category None stacklevel 1 source None skip_file_prefixes None Issue a warning or maybe ignore it or raise an exception The category argument if given must be a warning category class it defaults to UserWarning Alternatively message can be a Warning instance in which case category will be ignored and message __class__ will be used In this case the message text will be str message This function raises an exception if the particular warning issued is changed into an error by the warnings filter The stacklevel argument can be used by wrapper functions written in Python like this def deprecated_api message warnings warn message DeprecationWarning stacklevel 2 This makes the warning refer to deprecated_api s caller rather than to the source of deprecated_api itself since the latter would defeat the purpose of the warning message The skip_file_prefixes keyword argument can be used to indicate which stack frames are ignored when counting stack levels This can be useful when you want the warning to always appear at call sites outside of a package when a constant stacklevel does not fit all call paths or is otherwise challenging to maintain If supplied it must be a tuple of strings When prefixes are supplied stacklevel is implicitly overridden to be max 2 stacklevel To cause a warning to be attributed to the caller from outside of the current package you might write example lower py _warn_skips os path dirname __file__ def one_way r_luxury_yacht None t_wobbler_mangrove None if r_luxury_yacht warnings warn Please migrate to t_wobbler_mangrove skip_file_prefixes _warn_skips example higher py from import lower def another_way kw lower one_way kw This makes the warning refer to both the example lower one_way and package higher another_way call sites only from calling code living outside of example package source if supplied is the destroyed object which emitted a ResourceWarning Changed in version 3 6 Added source parameter Changed in version 3 12 Added skip_file_prefixes warnings warn_explicit message category filename lineno module None registry None module_globals None source None This is a low level interface to the functionality of warn passing in explicitly the message category filename and line number and optionally the module name and the registry which should be the __warningregistry__ dictionary of the module The module name defaults to the filename with py stripped if no registry is passed the warning is never suppressed message must be a string and category a subclass of Warning or message may be a Warning instance in which case category will be ignored module_globals if supplied should be the global namespace in use by the code for which the warning is issued This argument is used to support displaying source for modules found in zipfiles or other non filesystem import sources source if supplied is the destroyed object which emitted a ResourceWarning Changed in version 3 6 Add the source parameter warnings showwarning message category filename lineno file None line None Write a warning to a file The default implementation calls formatwarning message category filename lineno line and writes the resulting string to file which defaults to sys stderr You may replace this function with any callable by assigning to warnings showwarning line is a line of source code to be included in the,en
55, warning message if line is not supplied showwarning will try to read the line specified by filename and lineno warnings formatwarning message category filename lineno line None Format a warning the standard way This returns a string which may contain embedded newlines and ends in a newline line is a line of source code to be included in the warning message if line is not supplied formatwarning will try to read the line specified by filename and lineno warnings filterwarnings action message category Warning module lineno 0 append False Insert an entry into the list of warnings filter specifications The entry is inserted at the front by default if append is true it is inserted at the end This checks the types of the arguments compiles the message and module regular expressions and inserts them as a tuple in the list of warnings filters Entries closer to the front of the list override entries later in the list if both match a particular warning Omitted arguments default to a value that matches everything warnings simplefilter action category Warning lineno 0 append False Insert a simple entry into the list of warnings filter specifications The meaning of the function parameters is as for filterwarnings but regular expressions are not needed as the filter inserted always matches any message in any module as long as the category and line number match warnings resetwarnings Reset the warnings filter This discards the effect of all previous calls to filterwarnings including that of the W command line options and calls to simplefilter Available Context Managers class warnings catch_warnings record False module None action None category Warning lineno 0 append False A context manager that copies and upon exit restores the warnings filter and the showwarning function If the record argument is False the default the context manager returns None on entry If record is True a list is returned that is progressively populated with objects as seen by a custom showwarning function which also suppresses output to sys stdout Each object in the list has attributes with the same names as the arguments to showwarning The module argument takes a module that will be used instead of the module returned when you import warnings whose filter will be protected This argument exists primarily for testing the warnings module itself If the action argument is not None the remaining arguments are passed to simplefilter as if it were called immediately on entering the context Note The catch_warnings manager works by replacing and then later restoring the module s showwarning function and internal list of filter specifications This means the context manager is modifying global state and therefore is not thread safe Changed in version 3 11 Added the action category lineno and append parameters,en
56,urllib parse Parse URLs into components Source code Lib urllib parse py This module defines a standard interface to break Uniform Resource Locator URL strings up in components addressing scheme network location path etc to combine the components back into a URL string and to convert a relative URL to an absolute URL given a base URL The module has been designed to match the internet RFC on Relative Uniform Resource Locators It supports the following URL schemes file ftp gopher hdl http https imap mailto mms news nntp prospero rsync rtsp rtsps rtspu sftp shttp sip sips snews svn svn ssh telnet wais ws wss The urllib parse module defines functions that fall into two broad categories URL parsing and URL quoting These are covered in detail in the following sections URL Parsing The URL parsing functions focus on splitting a URL string into its components or on combining URL components into a URL string urllib parse urlparse urlstring scheme allow_fragments True Parse a URL into six components returning a 6 item named tuple This corresponds to the general structure of a URL scheme netloc path parameters query fragment Each tuple item is a string possibly empty The components are not broken up into smaller parts for example the network location is a single string and escapes are not expanded The delimiters as shown above are not part of the result except for a leading slash in the path component which is retained if present For example from urllib parse import urlparse urlparse scheme netloc path parameters query fragment ParseResult scheme scheme netloc netloc path path parameters params query query fragment fragment o urlparse http docs python org 80 3 library urllib parse html highlight params url parsing o ParseResult scheme http netloc docs python org 80 path 3 library urllib parse html params query highlight params fragment url parsing o scheme http o netloc docs python org 80 o hostname docs python org o port 80 o _replace fragment geturl http docs python org 80 3 library urllib parse html highlight params Following the syntax specifications in RFC 1808 urlparse recognizes a netloc only if it is properly introduced by Otherwise the input is presumed to be a relative URL and thus to start with a path component from urllib parse import urlparse urlparse www cwi nl 80 7Eguido Python html ParseResult scheme netloc www cwi nl 80 path 7Eguido Python html params query fragment urlparse www cwi nl 7Eguido Python html ParseResult scheme netloc path www cwi nl 7Eguido Python html params query fragment urlparse help Python html ParseResult scheme netloc path help Python html params query fragment The scheme argument gives the default addressing scheme to be used only if the URL does not specify one It should be the same type text or bytes as urlstring except that the default value is always allowed and is automatically converted to b if appropriate If the allow_fragments argument is false fragment identifiers are not recognized Instead they are parsed as part of the path parameters or query component and fragment is set to the empty string in the return value The return value is a named tuple which means that its items can be accessed by index or as named attributes which are Attribute Index Value Value if not present scheme 0 URL scheme specifier scheme parameter netloc 1 Network location part empty string path 2 Hierarchical path empty string params 3 Parameters for last path empty string element query 4 Query component empty string fragment 5 Fragment identifier empty string username User name None password Password None hostname Host name lower case None port Port number as integer None if present Reading the port attribute will raise a ValueError if an invalid port is specified in the URL See section Structured Parse Results for more information on the result object Unmatched square brackets in the netloc attribute will raise a ValueError Characters in the netloc attribute that decompose under NFKC normalization as used by the IDNA encoding into any of or will raise a ValueError If the URL is decomposed before parsing no error,en
57, will be raised As is the case with all named tuples the subclass has a few additional methods and attributes that are particularly useful One such method is _replace The _replace method will return a new ParseResult object replacing specified fields with new values from urllib parse import urlparse u urlparse www cwi nl 80 7Eguido Python html u ParseResult scheme netloc www cwi nl 80 path 7Eguido Python html params query fragment u _replace scheme http ParseResult scheme http netloc www cwi nl 80 path 7Eguido Python html params query fragment Warning urlparse does not perform validation See URL parsing security for details Changed in version 3 2 Added IPv6 URL parsing capabilities Changed in version 3 3 The fragment is now parsed for all URL schemes unless allow_fragment is false in accordance with RFC 3986 Previously an allowlist of schemes that support fragments existed Changed in version 3 6 Out of range port numbers now raise ValueError instead of returning None Changed in version 3 8 Characters that affect netloc parsing under NFKC normalization will now raise ValueError urllib parse parse_qs qs keep_blank_values False strict_parsing False encoding utf 8 errors replace max_num_fields None separator Parse a query string given as a string argument data of type application x www form urlencoded Data are returned as a dictionary The dictionary keys are the unique query variable names and the values are lists of values for each name The optional argument keep_blank_values is a flag indicating whether blank values in percent encoded queries should be treated as blank strings A true value indicates that blanks should be retained as blank strings The default false value indicates that blank values are to be ignored and treated as if they were not included The optional argument strict_parsing is a flag indicating what to do with parsing errors If false the default errors are silently ignored If true errors raise a ValueError exception The optional encoding and errors parameters specify how to decode percent encoded sequences into Unicode characters as accepted by the bytes decode method The optional argument max_num_fields is the maximum number of fields to read If set then throws a ValueError if there are more than max_num_fields fields read The optional argument separator is the symbol to use for separating the query arguments It defaults to Use the urllib parse urlencode function with the doseq parameter set to True to convert such dictionaries into query strings Changed in version 3 2 Add encoding and errors parameters Changed in version 3 8 Added max_num_fields parameter Changed in version 3 10 Added separator parameter with the default value of Python versions earlier than Python 3 10 allowed using both and as query parameter separator This has been changed to allow only a single separator key with as the default separator urllib parse parse_qsl qs keep_blank_values False strict_parsing False encoding utf 8 errors replace max_num_fields None separator Parse a query string given as a string argument data of type application x www form urlencoded Data are returned as a list of name value pairs The optional argument keep_blank_values is a flag indicating whether blank values in percent encoded queries should be treated as blank strings A true value indicates that blanks should be retained as blank strings The default false value indicates that blank values are to be ignored and treated as if they were not included The optional argument strict_parsing is a flag indicating what to do with parsing errors If false the default errors are silently ignored If true errors raise a ValueError exception The optional encoding and errors parameters specify how to decode percent encoded sequences into Unicode characters as accepted by the bytes decode method The optional argument max_num_fields is the maximum number of fields to read If set then throws a ValueError if there are more than max_num_fields fields read The optional argument separator is the symbol to use for separating the query arguments It defaults to Use the urllib pars,en
58,e urlencode function to convert such lists of pairs into query strings Changed in version 3 2 Add encoding and errors parameters Changed in version 3 8 Added max_num_fields parameter Changed in version 3 10 Added separator parameter with the default value of Python versions earlier than Python 3 10 allowed using both and as query parameter separator This has been changed to allow only a single separator key with as the default separator urllib parse urlunparse parts Construct a URL from a tuple as returned by urlparse The parts argument can be any six item iterable This may result in a slightly different but equivalent URL if the URL that was parsed originally had unnecessary delimiters for example a with an empty query the RFC states that these are equivalent urllib parse urlsplit urlstring scheme allow_fragments True This is similar to urlparse but does not split the params from the URL This should generally be used instead of urlparse if the more recent URL syntax allowing parameters to be applied to each segment of the path portion of the URL see RFC 2396 is wanted A separate function is needed to separate the path segments and parameters This function returns a 5 item named tuple addressing scheme network location path query fragment identifier The return value is a named tuple its items can be accessed by index or as named attributes Attribute Index Value Value if not present scheme 0 URL scheme specifier scheme parameter netloc 1 Network location part empty string path 2 Hierarchical path empty string query 3 Query component empty string fragment 4 Fragment identifier empty string username User name None password Password None hostname Host name lower case None port Port number as integer None if present Reading the port attribute will raise a ValueError if an invalid port is specified in the URL See section Structured Parse Results for more information on the result object Unmatched square brackets in the netloc attribute will raise a ValueError Characters in the netloc attribute that decompose under NFKC normalization as used by the IDNA encoding into any of or will raise a ValueError If the URL is decomposed before parsing no error will be raised Following some of the WHATWG spec that updates RFC 3986 leading C0 control and space characters are stripped from the URL n r and tab t characters are removed from the URL at any position Warning urlsplit does not perform validation See URL parsing security for details Changed in version 3 6 Out of range port numbers now raise ValueError instead of returning None Changed in version 3 8 Characters that affect netloc parsing under NFKC normalization will now raise ValueError Changed in version 3 10 ASCII newline and tab characters are stripped from the URL Changed in version 3 12 Leading WHATWG C0 control and space characters are stripped from the URL urllib parse urlunsplit parts Combine the elements of a tuple as returned by urlsplit into a complete URL as a string The parts argument can be any five item iterable This may result in a slightly different but equivalent URL if the URL that was parsed originally had unnecessary delimiters for example a with an empty query the RFC states that these are equivalent urllib parse urljoin base url allow_fragments True Construct a full absolute URL by combining a base URL base with another URL url Informally this uses components of the base URL in particular the addressing scheme the network location and part of the path to provide missing components in the relative URL For example from urllib parse import urljoin urljoin http www cwi nl 7Eguido Python html FAQ html http www cwi nl 7Eguido FAQ html The allow_fragments argument has the same meaning and default as for urlparse Note If url is an absolute URL that is it starts with or scheme the url s hostname and or scheme will be present in the result For example urljoin http www cwi nl 7Eguido Python html www python org 7Eguido http www python org 7Eguido If you do not want that behavior preprocess the url with urlsplit and urlunsplit removing possible scheme and netloc parts Chan,en
59,ged in version 3 5 Behavior updated to match the semantics defined in RFC 3986 urllib parse urldefrag url If url contains a fragment identifier return a modified version of url with no fragment identifier and the fragment identifier as a separate string If there is no fragment identifier in url return url unmodified and an empty string The return value is a named tuple its items can be accessed by index or as named attributes Attribute Index Value Value if not present url 0 URL with no fragment empty string fragment 1 Fragment identifier empty string See section Structured Parse Results for more information on the result object Changed in version 3 2 Result is a structured object rather than a simple 2 tuple urllib parse unwrap url Extract the url from a wrapped URL that is a string formatted as URL scheme host path scheme host path URL scheme host path or scheme host path If url is not a wrapped URL it is returned without changes URL parsing security The urlsplit and urlparse APIs do not perform validation of inputs They may not raise errors on inputs that other applications consider invalid They may also succeed on some inputs that might not be considered URLs elsewhere Their purpose is for practical functionality rather than purity Instead of raising an exception on unusual input they may instead return some component parts as empty strings Or components may contain more than perhaps they should We recommend that users of these APIs where the values may be used anywhere with security implications code defensively Do some verification within your code before trusting a returned component part Does that scheme make sense Is that a sensible path Is there anything strange about that hostname etc What constitutes a URL is not universally well defined Different applications have different needs and desired constraints For instance the living WHATWG spec describes what user facing web clients such as a web browser require While RFC 3986 is more general These functions incorporate some aspects of both but cannot be claimed compliant with either The APIs and existing user code with expectations on specific behaviors predate both standards leading us to be very cautious about making API behavior changes Parsing ASCII Encoded Bytes The URL parsing functions were originally designed to operate on character strings only In practice it is useful to be able to manipulate properly quoted and encoded URLs as sequences of ASCII bytes Accordingly the URL parsing functions in this module all operate on bytes and bytearray objects in addition to str objects If str data is passed in the result will also contain only str data If bytes or bytearray data is passed in the result will contain only bytes data Attempting to mix str data with bytes or bytearray in a single function call will result in a TypeError being raised while attempting to pass in non ASCII byte values will trigger UnicodeDecodeError To support easier conversion of result objects between str and bytes all return values from URL parsing functions provide either an encode method when the result contains str data or a decode method when the result contains bytes data The signatures of these methods match those of the corresponding str and bytes methods except that the default encoding is ascii rather than utf 8 Each produces a value of a corresponding type that contains either bytes data for encode methods or str data for decode methods Applications that need to operate on potentially improperly quoted URLs that may contain non ASCII data will need to do their own decoding from bytes to characters before invoking the URL parsing methods The behaviour described in this section applies only to the URL parsing functions The URL quoting functions use their own rules when producing or consuming byte sequences as detailed in the documentation of the individual URL quoting functions Changed in version 3 2 URL parsing functions now accept ASCII encoded byte sequences Structured Parse Results The result objects from the urlparse urlsplit and urldefrag functions are subclasses of the tup,en
60,le type These subclasses add the attributes listed in the documentation for those functions the encoding and decoding support described in the previous section as well as an additional method urllib parse SplitResult geturl Return the re combined version of the original URL as a string This may differ from the original URL in that the scheme may be normalized to lower case and empty components may be dropped Specifically empty parameters queries and fragment identifiers will be removed For urldefrag results only empty fragment identifiers will be removed For urlsplit and urlparse results all noted changes will be made to the URL returned by this method The result of this method remains unchanged if passed back through the original parsing function from urllib parse import urlsplit url HTTP www Python org doc r1 urlsplit url r1 geturl http www Python org doc r2 urlsplit r1 geturl r2 geturl http www Python org doc The following classes provide the implementations of the structured parse results when operating on str objects class urllib parse DefragResult url fragment Concrete class for urldefrag results containing str data The encode method returns a DefragResultBytes instance New in version 3 2 class urllib parse ParseResult scheme netloc path params query fragment Concrete class for urlparse results containing str data The encode method returns a ParseResultBytes instance class urllib parse SplitResult scheme netloc path query fragment Concrete class for urlsplit results containing str data The encode method returns a SplitResultBytes instance The following classes provide the implementations of the parse results when operating on bytes or bytearray objects class urllib parse DefragResultBytes url fragment Concrete class for urldefrag results containing bytes data The decode method returns a DefragResult instance New in version 3 2 class urllib parse ParseResultBytes scheme netloc path params query fragment Concrete class for urlparse results containing bytes data The decode method returns a ParseResult instance New in version 3 2 class urllib parse SplitResultBytes scheme netloc path query fragment Concrete class for urlsplit results containing bytes data The decode method returns a SplitResult instance New in version 3 2 URL Quoting The URL quoting functions focus on taking program data and making it safe for use as URL components by quoting special characters and appropriately encoding non ASCII text They also support reversing these operations to recreate the original data from the contents of a URL component if that task isn t already covered by the URL parsing functions above urllib parse quote string safe encoding None errors None Replace special characters in string using the xx escape Letters digits and the characters _ are never quoted By default this function is intended for quoting the path section of a URL The optional safe parameter specifies additional ASCII characters that should not be quoted its default value is string may be either a str or a bytes object Changed in version 3 7 Moved from RFC 2396 to RFC 3986 for quoting URL strings is now included in the set of unreserved characters The optional encoding and errors parameters specify how to deal with non ASCII characters as accepted by the str encode method encoding defaults to utf 8 errors defaults to strict meaning unsupported characters raise a UnicodeEncodeError encoding and errors must not be supplied if string is a bytes or a TypeError is raised Note that quote string safe encoding errors is equivalent to quote_from_bytes string encode encoding errors safe Example quote El Niño yields El 20Ni C3 B1o urllib parse quote_plus string safe encoding None errors None Like quote but also replace spaces with plus signs as required for quoting HTML form values when building up a query string to go into a URL Plus signs in the original string are escaped unless they are included in safe It also does not have safe default to Example quote_plus El Niño yields 2FEl Ni C3 B1o 2F urllib parse quote_from_bytes bytes safe Like quote but accepts a bytes object ra,en
61,ther than a str and does not perform string to bytes encoding Example quote_from_bytes b a xef yields a 26 EF urllib parse unquote string encoding utf 8 errors replace Replace xx escapes with their single character equivalent The optional encoding and errors parameters specify how to decode percent encoded sequences into Unicode characters as accepted by the bytes decode method string may be either a str or a bytes object encoding defaults to utf 8 errors defaults to replace meaning invalid sequences are replaced by a placeholder character Example unquote El 20Ni C3 B1o yields El Niño Changed in version 3 9 string parameter supports bytes and str objects previously only str urllib parse unquote_plus string encoding utf 8 errors replace Like unquote but also replace plus signs with spaces as required for unquoting HTML form values string must be a str Example unquote_plus El Ni C3 B1o yields El Niño urllib parse unquote_to_bytes string Replace xx escapes with their single octet equivalent and return a bytes object string may be either a str or a bytes object If it is a str unescaped non ASCII characters in string are encoded into UTF 8 bytes Example unquote_to_bytes a 26 EF yields b a xef urllib parse urlencode query doseq False safe encoding None errors None quote_via quote_plus Convert a mapping object or a sequence of two element tuples which may contain str or bytes objects to a percent encoded ASCII text string If the resultant string is to be used as a data for POST operation with the urlopen function then it should be encoded to bytes otherwise it would result in a TypeError The resulting string is a series of key value pairs separated by characters where both key and value are quoted using the quote_via function By default quote_plus is used to quote the values which means spaces are quoted as a character and characters are encoded as 2F which follows the standard for GET requests application x www form urlencoded An alternate function that can be passed as quote_via is quote which will encode spaces as 20 and not encode characters For maximum control of what is quoted use quote and specify a value for safe When a sequence of two element tuples is used as the query argument the first element of each tuple is a key and the second is a value The value element in itself can be a sequence and in that case if the optional parameter doseq evaluates to True individual key value pairs separated by are generated for each element of the value sequence for the key The order of parameters in the encoded string will match the order of parameter tuples in the sequence The safe encoding and errors parameters are passed down to quote_via the encoding and errors parameters are only passed when a query element is a str To reverse this encoding process parse_qs and parse_qsl are provided in this module to parse query strings into Python data structures Refer to urllib examples to find out how the urllib parse urlencode method can be used for generating the query string of a URL or data for a POST request Changed in version 3 2 query supports bytes and string objects Changed in version 3 5 Added the quote_via parameter See also WHATWG URL Living standard Working Group for the URL Standard that defines URLs domains IP addresses the application x www form urlencoded format and their API RFC 3986 Uniform Resource Identifiers This is the current standard STD66 Any changes to urllib parse module should conform to this Certain deviations could be observed which are mostly for backward compatibility purposes and for certain de facto parsing requirements as commonly observed in major browsers RFC 2732 Format for Literal IPv6 Addresses in URL s This specifies the parsing requirements of IPv6 URLs RFC 2396 Uniform Resource Identifiers URI Generic Syntax Document describing the generic syntactic requirements for both Uniform Resource Names URNs and Uniform Resource Locators URLs RFC 2368 The mailto URL scheme Parsing requirements for mailto URL schemes RFC 1808 Relative Uniform Resource Locators This Request For Comments includes the rules for ,en
62,joining an absolute and a relative URL including a fair number of Abnormal Examples which govern the treatment of border cases RFC 1738 Uniform Resource Locators URL This specifies the formal syntax and semantics of absolute URLs,en
63,spwd The shadow password database Deprecated since version 3 11 will be removed in version 3 13 The spwd module is deprecated see PEP 594 for details and alternatives This module provides access to the Unix shadow password database It is available on various Unix versions Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information You must have enough privileges to access the shadow password database this usually means you have to be root Shadow password database entries are reported as a tuple like object whose attributes correspond to the members of the spwd structure Attribute field below see shadow h Index Attribute Meaning 0 sp_namp Login name 1 sp_pwdp Encrypted password 2 sp_lstchg Date of last change 3 sp_min Minimal number of days between changes 4 sp_max Maximum number of days between changes 5 sp_warn Number of days before password expires to warn user about it 6 sp_inact Number of days after password expires until account is disabled 7 sp_expire Number of days since 1970 01 01 when account expires 8 sp_flag Reserved The sp_namp and sp_pwdp items are strings all others are integers KeyError is raised if the entry asked for cannot be found The following functions are defined spwd getspnam name Return the shadow password database entry for the given user name Changed in version 3 6 Raises a PermissionError instead of KeyError if the user doesn t have privileges spwd getspall Return a list of all available shadow password database entries in arbitrary order See also Module grp An interface to the group database similar to this Module pwd An interface to the normal password database similar to this,en
64,logging handlers Logging handlers Source code Lib logging handlers py Important This page contains only reference information For tutorials please see Basic Tutorial Advanced Tutorial Logging Cookbook The following useful handlers are provided in the package Note that three of the handlers StreamHandler FileHandler and NullHandler are actually defined in the logging module itself but have been documented here along with the other handlers StreamHandler The StreamHandler class located in the core logging package sends logging output to streams such as sys stdout sys stderr or any file like object or more precisely any object which supports write and flush methods class logging StreamHandler stream None Returns a new instance of the StreamHandler class If stream is specified the instance will use it for logging output otherwise sys stderr will be used emit record If a formatter is specified it is used to format the record The record is then written to the stream followed by terminator If exception information is present it is formatted using traceback print_exception and appended to the stream flush Flushes the stream by calling its flush method Note that the close method is inherited from Handler and so does no output so an explicit flush call may be needed at times setStream stream Sets the instance s stream to the specified value if it is different The old stream is flushed before the new stream is set Parameters stream The stream that the handler should use Returns the old stream if the stream was changed or None if it wasn t New in version 3 7 terminator String used as the terminator when writing a formatted record to a stream Default value is n If you don t want a newline termination you can set the handler instance s terminator attribute to the empty string In earlier versions the terminator was hardcoded as n New in version 3 2 FileHandler The FileHandler class located in the core logging package sends logging output to a disk file It inherits the output functionality from StreamHandler class logging FileHandler filename mode a encoding None delay False errors None Returns a new instance of the FileHandler class The specified file is opened and used as the stream for logging If mode is not specified a is used If encoding is not None it is used to open the file with that encoding If delay is true then file opening is deferred until the first call to emit By default the file grows indefinitely If errors is specified it s used to determine how encoding errors are handled Changed in version 3 6 As well as string values Path objects are also accepted for the filename argument Changed in version 3 9 The errors parameter was added close Closes the file emit record Outputs the record to the file Note that if the file was closed due to logging shutdown at exit and the file mode is w the record will not be emitted see bpo 42378 NullHandler New in version 3 1 The NullHandler class located in the core logging package does not do any formatting or output It is essentially a no op handler for use by library developers class logging NullHandler Returns a new instance of the NullHandler class emit record This method does nothing handle record This method does nothing createLock This method returns None for the lock since there is no underlying I O to which access needs to be serialized See Configuring Logging for a Library for more information on how to use NullHandler WatchedFileHandler The WatchedFileHandler class located in the logging handlers module is a FileHandler which watches the file it is logging to If the file changes it is closed and reopened using the file name A file change can happen because of usage of programs such as newsyslog and logrotate which perform log file rotation This handler intended for use under Unix Linux watches the file to see if it has changed since the last emit A file is deemed to have changed if its device or inode have changed If the file has changed the old file stream is closed and the file opened to get a new stream This handler is not appropriate for use under Windows because under Window,en
65,s open log files cannot be moved or renamed logging opens the files with exclusive locks and so there is no need for such a handler Furthermore ST_INO is not supported under Windows stat always returns zero for this value class logging handlers WatchedFileHandler filename mode a encoding None delay False errors None Returns a new instance of the WatchedFileHandler class The specified file is opened and used as the stream for logging If mode is not specified a is used If encoding is not None it is used to open the file with that encoding If delay is true then file opening is deferred until the first call to emit By default the file grows indefinitely If errors is provided it determines how encoding errors are handled Changed in version 3 6 As well as string values Path objects are also accepted for the filename argument Changed in version 3 9 The errors parameter was added reopenIfNeeded Checks to see if the file has changed If it has the existing stream is flushed and closed and the file opened again typically as a precursor to outputting the record to the file New in version 3 6 emit record Outputs the record to the file but first calls reopenIfNeeded to reopen the file if it has changed BaseRotatingHandler The BaseRotatingHandler class located in the logging handlers module is the base class for the rotating file handlers RotatingFileHandler and TimedRotatingFileHandler You should not need to instantiate this class but it has attributes and methods you may need to override class logging handlers BaseRotatingHandler filename mode encoding None delay False errors None The parameters are as for FileHandler The attributes are namer If this attribute is set to a callable the rotation_filename method delegates to this callable The parameters passed to the callable are those passed to rotation_filename Note The namer function is called quite a few times during rollover so it should be as simple and as fast as possible It should also return the same output every time for a given input otherwise the rollover behaviour may not work as expected It s also worth noting that care should be taken when using a namer to preserve certain attributes in the filename which are used during rotation For example RotatingFileHandler expects to have a set of log files whose names contain successive integers so that rotation works as expected and TimedRotatingFileHandler deletes old log files based on the backupCount parameter passed to the handler s initializer by determining the oldest files to delete For this to happen the filenames should be sortable using the date time portion of the filename and a namer needs to respect this If a namer is wanted that doesn t respect this scheme it will need to be used in a subclass of TimedRotatingFileHandler which overrides the getFilesToDelete method to fit in with the custom naming scheme New in version 3 3 rotator If this attribute is set to a callable the rotate method delegates to this callable The parameters passed to the callable are those passed to rotate New in version 3 3 rotation_filename default_name Modify the filename of a log file when rotating This is provided so that a custom filename can be provided The default implementation calls the namer attribute of the handler if it s callable passing the default name to it If the attribute isn t callable the default is None the name is returned unchanged Parameters default_name The default name for the log file New in version 3 3 rotate source dest When rotating rotate the current log The default implementation calls the rotator attribute of the handler if it s callable passing the source and dest arguments to it If the attribute isn t callable the default is None the source is simply renamed to the destination Parameters source The source filename This is normally the base filename e g test log dest The destination filename This is normally what the source is rotated to e g test log 1 New in version 3 3 The reason the attributes exist is to save you having to subclass you can use the same callables for instances of RotatingFileHandler and TimedRo,en
66,tatingFileHandler If either the namer or rotator callable raises an exception this will be handled in the same way as any other exception during an emit call i e via the handleError method of the handler If you need to make more significant changes to rotation processing you can override the methods For an example see Using a rotator and namer to customize log rotation processing RotatingFileHandler The RotatingFileHandler class located in the logging handlers module supports rotation of disk log files class logging handlers RotatingFileHandler filename mode a maxBytes 0 backupCount 0 encoding None delay False errors None Returns a new instance of the RotatingFileHandler class The specified file is opened and used as the stream for logging If mode is not specified a is used If encoding is not None it is used to open the file with that encoding If delay is true then file opening is deferred until the first call to emit By default the file grows indefinitely If errors is provided it determines how encoding errors are handled You can use the maxBytes and backupCount values to allow the file to rollover at a predetermined size When the size is about to be exceeded the file is closed and a new file is silently opened for output Rollover occurs whenever the current log file is nearly maxBytes in length but if either of maxBytes or backupCount is zero rollover never occurs so you generally want to set backupCount to at least 1 and have a non zero maxBytes When backupCount is non zero the system will save old log files by appending the extensions 1 2 etc to the filename For example with a backupCount of 5 and a base file name of app log you would get app log app log 1 app log 2 up to app log 5 The file being written to is always app log When this file is filled it is closed and renamed to app log 1 and if files app log 1 app log 2 etc exist then they are renamed to app log 2 app log 3 etc respectively Changed in version 3 6 As well as string values Path objects are also accepted for the filename argument Changed in version 3 9 The errors parameter was added doRollover Does a rollover as described above emit record Outputs the record to the file catering for rollover as described previously TimedRotatingFileHandler The TimedRotatingFileHandler class located in the logging handlers module supports rotation of disk log files at certain timed intervals class logging handlers TimedRotatingFileHandler filename when h interval 1 backupCount 0 encoding None delay False utc False atTime None errors None Returns a new instance of the TimedRotatingFileHandler class The specified file is opened and used as the stream for logging On rotating it also sets the filename suffix Rotating happens based on the product of when and interval You can use the when to specify the type of interval The list of possible values is below Note that they are not case sensitive Value Type of interval If how atTime is used S Seconds Ignored M Minutes Ignored H Hours Ignored D Days Ignored W0 W6 Weekday 0 Monday Used to compute initial rollover time midnight Roll over at midnight if Used to compute initial atTime not specified else rollover time at time atTime When using weekday based rotation specify W0 for Monday W1 for Tuesday and so on up to W6 for Sunday In this case the value passed for interval isn t used The system will save old log files by appending extensions to the filename The extensions are date and time based using the strftime format Y m d_ H M S or a leading portion thereof depending on the rollover interval When computing the next rollover time for the first time when the handler is created the last modification time of an existing log file or else the current time is used to compute when the next rotation will occur If the utc argument is true times in UTC will be used otherwise local time is used If backupCount is nonzero at most backupCount files will be kept and if more would be created when rollover occurs the oldest one is deleted The deletion logic uses the interval to determine which files to delete so changing the interval may leave old ,en
67,files lying around If delay is true then file opening is deferred until the first call to emit If atTime is not None it must be a datetime time instance which specifies the time of day when rollover occurs for the cases where rollover is set to happen at midnight or on a particular weekday Note that in these cases the atTime value is effectively used to compute the initial rollover and subsequent rollovers would be calculated via the normal interval calculation If errors is specified it s used to determine how encoding errors are handled Note Calculation of the initial rollover time is done when the handler is initialised Calculation of subsequent rollover times is done only when rollover occurs and rollover occurs only when emitting output If this is not kept in mind it might lead to some confusion For example if an interval of every minute is set that does not mean you will always see log files with times in the filename separated by a minute if during application execution logging output is generated more frequently than once a minute then you can expect to see log files with times separated by a minute If on the other hand logging messages are only output once every five minutes say then there will be gaps in the file times corresponding to the minutes where no output and hence no rollover occurred Changed in version 3 4 atTime parameter was added Changed in version 3 6 As well as string values Path objects are also accepted for the filename argument Changed in version 3 9 The errors parameter was added doRollover Does a rollover as described above emit record Outputs the record to the file catering for rollover as described above getFilesToDelete Returns a list of filenames which should be deleted as part of rollover These are the absolute paths of the oldest backup log files written by the handler SocketHandler The SocketHandler class located in the logging handlers module sends logging output to a network socket The base class uses a TCP socket class logging handlers SocketHandler host port Returns a new instance of the SocketHandler class intended to communicate with a remote machine whose address is given by host and port Changed in version 3 4 If port is specified as None a Unix domain socket is created using the value in host otherwise a TCP socket is created close Closes the socket emit Pickles the record s attribute dictionary and writes it to the socket in binary format If there is an error with the socket silently drops the packet If the connection was previously lost re establishes the connection To unpickle the record at the receiving end into a LogRecord use the makeLogRecord function handleError Handles an error which has occurred during emit The most likely cause is a lost connection Closes the socket so that we can retry on the next event makeSocket This is a factory method which allows subclasses to define the precise type of socket they want The default implementation creates a TCP socket socket SOCK_STREAM makePickle record Pickles the record s attribute dictionary in binary format with a length prefix and returns it ready for transmission across the socket The details of this operation are equivalent to data pickle dumps record_attr_dict 1 datalen struct pack L len data return datalen data Note that pickles aren t completely secure If you are concerned about security you may want to override this method to implement a more secure mechanism For example you can sign pickles using HMAC and then verify them on the receiving end or alternatively you can disable unpickling of global objects on the receiving end send packet Send a pickled byte string packet to the socket The format of the sent byte string is as described in the documentation for makePickle This function allows for partial sends which can happen when the network is busy createSocket Tries to create a socket on failure uses an exponential back off algorithm On initial failure the handler will drop the message it was trying to send When subsequent messages are handled by the same instance it will not try connecting until some time has pass,en
68,ed The default parameters are such that the initial delay is one second and if after that delay the connection still can t be made the handler will double the delay each time up to a maximum of 30 seconds This behaviour is controlled by the following handler attributes retryStart initial delay defaulting to 1 0 seconds retryFactor multiplier defaulting to 2 0 retryMax maximum delay defaulting to 30 0 seconds This means that if the remote listener starts up after the handler has been used you could lose messages since the handler won t even attempt a connection until the delay has elapsed but just silently drop messages during the delay period DatagramHandler The DatagramHandler class located in the logging handlers module inherits from SocketHandler to support sending logging messages over UDP sockets class logging handlers DatagramHandler host port Returns a new instance of the DatagramHandler class intended to communicate with a remote machine whose address is given by host and port Note As UDP is not a streaming protocol there is no persistent connection between an instance of this handler and host For this reason when using a network socket a DNS lookup might have to be made each time an event is logged which can introduce some latency into the system If this affects you you can do a lookup yourself and initialize this handler using the looked up IP address rather than the hostname Changed in version 3 4 If port is specified as None a Unix domain socket is created using the value in host otherwise a UDP socket is created emit Pickles the record s attribute dictionary and writes it to the socket in binary format If there is an error with the socket silently drops the packet To unpickle the record at the receiving end into a LogRecord use the makeLogRecord function makeSocket The factory method of SocketHandler is here overridden to create a UDP socket socket SOCK_DGRAM send s Send a pickled byte string to a socket The format of the sent byte string is as described in the documentation for SocketHandler makePickle SysLogHandler The SysLogHandler class located in the logging handlers module supports sending logging messages to a remote or local Unix syslog class logging handlers SysLogHandler address localhost SYSLOG_UDP_PORT facility LOG_USER socktype socket SOCK_DGRAM Returns a new instance of the SysLogHandler class intended to communicate with a remote Unix machine whose address is given by address in the form of a host port tuple If address is not specified localhost 514 is used The address is used to open a socket An alternative to providing a host port tuple is providing an address as a string for example dev log In this case a Unix domain socket is used to send the message to the syslog If facility is not specified LOG_USER is used The type of socket opened depends on the socktype argument which defaults to socket SOCK_DGRAM and thus opens a UDP socket To open a TCP socket for use with the newer syslog daemons such as rsyslog specify a value of socket SOCK_STREAM Note that if your server is not listening on UDP port 514 SysLogHandler may appear not to work In that case check what address you should be using for a domain socket it s system dependent For example on Linux it s usually dev log but on OS X it s var run syslog You ll need to check your platform and use the appropriate address you may need to do this check at runtime if your application needs to run on several platforms On Windows you pretty much have to use the UDP option Note On macOS 12 x Monterey Apple has changed the behaviour of their syslog daemon it no longer listens on a domain socket Therefore you cannot expect SysLogHandler to work on this system See gh 91070 for more information Changed in version 3 2 socktype was added close Closes the socket to the remote host createSocket Tries to create a socket and if it s not a datagram socket connect it to the other end This method is called during handler initialization but it s not regarded as an error if the other end isn t listening at this point the method will be called again when emitting an e,en
69,vent if there is no socket at that point New in version 3 11 emit record The record is formatted and then sent to the syslog server If exception information is present it is not sent to the server Changed in version 3 2 1 See bpo 12168 In earlier versions the message sent to the syslog daemons was always terminated with a NUL byte because early versions of these daemons expected a NUL terminated message even though it s not in the relevant specification RFC 5424 More recent versions of these daemons don t expect the NUL byte but strip it off if it s there and even more recent daemons which adhere more closely to RFC 5424 pass the NUL byte on as part of the message To enable easier handling of syslog messages in the face of all these differing daemon behaviours the appending of the NUL byte has been made configurable through the use of a class level attribute append_nul This defaults to True preserving the existing behaviour but can be set to False on a SysLogHandler instance in order for that instance to not append the NUL terminator Changed in version 3 3 See bpo 12419 In earlier versions there was no facility for an ident or tag prefix to identify the source of the message This can now be specified using a class level attribute defaulting to to preserve existing behaviour but which can be overridden on a SysLogHandler instance in order for that instance to prepend the ident to every message handled Note that the provided ident must be text not bytes and is prepended to the message exactly as is encodePriority facility priority Encodes the facility and priority into an integer You can pass in strings or integers if strings are passed internal mapping dictionaries are used to convert them to integers The symbolic LOG_ values are defined in SysLogHandler and mirror the values defined in the sys syslog h header file Priorities Name string Symbolic value alert LOG_ALERT crit or critical LOG_CRIT debug LOG_DEBUG emerg or panic LOG_EMERG err or error LOG_ERR info LOG_INFO notice LOG_NOTICE warn or warning LOG_WARNING Facilities Name string Symbolic value auth LOG_AUTH authpriv LOG_AUTHPRIV cron LOG_CRON daemon LOG_DAEMON ftp LOG_FTP kern LOG_KERN lpr LOG_LPR mail LOG_MAIL news LOG_NEWS syslog LOG_SYSLOG user LOG_USER uucp LOG_UUCP local0 LOG_LOCAL0 local1 LOG_LOCAL1 local2 LOG_LOCAL2 local3 LOG_LOCAL3 local4 LOG_LOCAL4 local5 LOG_LOCAL5 local6 LOG_LOCAL6 local7 LOG_LOCAL7 mapPriority levelname Maps a logging level name to a syslog priority name You may need to override this if you are using custom levels or if the default algorithm is not suitable for your needs The default algorithm maps DEBUG INFO WARNING ERROR and CRITICAL to the equivalent syslog names and all other level names to warning NTEventLogHandler The NTEventLogHandler class located in the logging handlers module supports sending logging messages to a local Windows NT Windows 2000 or Windows XP event log Before you can use it you need Mark Hammond s Win32 extensions for Python installed class logging handlers NTEventLogHandler appname dllname None logtype Application Returns a new instance of the NTEventLogHandler class The appname is used to define the application name as it appears in the event log An appropriate registry entry is created using this name The dllname should give the fully qualified pathname of a dll or exe which contains message definitions to hold in the log if not specified win32service pyd is used this is installed with the Win32 extensions and contains some basic placeholder message definitions Note that use of these placeholders will make your event logs big as the entire message source is held in the log If you want slimmer logs you have to pass in the name of your own dll or exe which contains the message definitions you want to use in the event log The logtype is one of Application System or Security and defaults to Application close At this point you can remove the application name from the registry as a source of event log entries However if you do this you will not be able to see the events as you intended in the Event Log Viewer it n,en
70,eeds to be able to access the registry to get the dll name The current version does not do this emit record Determines the message ID event category and event type and then logs the message in the NT event log getEventCategory record Returns the event category for the record Override this if you want to specify your own categories This version returns 0 getEventType record Returns the event type for the record Override this if you want to specify your own types This version does a mapping using the handler s typemap attribute which is set up in __init__ to a dictionary which contains mappings for DEBUG INFO WARNING ERROR and CRITICAL If you are using your own levels you will either need to override this method or place a suitable dictionary in the handler s typemap attribute getMessageID record Returns the message ID for the record If you are using your own messages you could do this by having the msg passed to the logger being an ID rather than a format string Then in here you could use a dictionary lookup to get the message ID This version returns 1 which is the base message ID in win32service pyd SMTPHandler The SMTPHandler class located in the logging handlers module supports sending logging messages to an email address via SMTP class logging handlers SMTPHandler mailhost fromaddr toaddrs subject credentials None secure None timeout 1 0 Returns a new instance of the SMTPHandler class The instance is initialized with the from and to addresses and subject line of the email The toaddrs should be a list of strings To specify a non standard SMTP port use the host port tuple format for the mailhost argument If you use a string the standard SMTP port is used If your SMTP server requires authentication you can specify a username password tuple for the credentials argument To specify the use of a secure protocol TLS pass in a tuple to the secure argument This will only be used when authentication credentials are supplied The tuple should be either an empty tuple or a single value tuple with the name of a keyfile or a 2 value tuple with the names of the keyfile and certificate file This tuple is passed to the smtplib SMTP starttls method A timeout can be specified for communication with the SMTP server using the timeout argument Changed in version 3 3 Added the timeout parameter emit record Formats the record and sends it to the specified addressees getSubject record If you want to specify a subject line which is record dependent override this method MemoryHandler The MemoryHandler class located in the logging handlers module supports buffering of logging records in memory periodically flushing them to a target handler Flushing occurs whenever the buffer is full or when an event of a certain severity or greater is seen MemoryHandler is a subclass of the more general BufferingHandler which is an abstract class This buffers logging records in memory Whenever each record is added to the buffer a check is made by calling shouldFlush to see if the buffer should be flushed If it should then flush is expected to do the flushing class logging handlers BufferingHandler capacity Initializes the handler with a buffer of the specified capacity Here capacity means the number of logging records buffered emit record Append the record to the buffer If shouldFlush returns true call flush to process the buffer flush For a BufferingHandler instance flushing means that it sets the buffer to an empty list This method can be overwritten to implement more useful flushing behavior shouldFlush record Return True if the buffer is up to capacity This method can be overridden to implement custom flushing strategies class logging handlers MemoryHandler capacity flushLevel ERROR target None flushOnClose True Returns a new instance of the MemoryHandler class The instance is initialized with a buffer size of capacity number of records buffered If flushLevel is not specified ERROR is used If no target is specified the target will need to be set using setTarget before this handler does anything useful If flushOnClose is specified as False then the buffer is no,en
71,t flushed when the handler is closed If not specified or specified as True the previous behaviour of flushing the buffer will occur when the handler is closed Changed in version 3 6 The flushOnClose parameter was added close Calls flush sets the target to None and clears the buffer flush For a MemoryHandler instance flushing means just sending the buffered records to the target if there is one The buffer is also cleared when buffered records are sent to the target Override if you want different behavior setTarget target Sets the target handler for this handler shouldFlush record Checks for buffer full or a record at the flushLevel or higher HTTPHandler The HTTPHandler class located in the logging handlers module supports sending logging messages to a web server using either GET or POST semantics class logging handlers HTTPHandler host url method GET secure False credentials None context None Returns a new instance of the HTTPHandler class The host can be of the form host port should you need to use a specific port number If no method is specified GET is used If secure is true a HTTPS connection will be used The context parameter may be set to a ssl SSLContext instance to configure the SSL settings used for the HTTPS connection If credentials is specified it should be a 2 tuple consisting of userid and password which will be placed in a HTTP Authorization header using Basic authentication If you specify credentials you should also specify secure True so that your userid and password are not passed in cleartext across the wire Changed in version 3 5 The context parameter was added mapLogRecord record Provides a dictionary based on record which is to be URL encoded and sent to the web server The default implementation just returns record __dict__ This method can be overridden if e g only a subset of LogRecord is to be sent to the web server or if more specific customization of what s sent to the server is required emit record Sends the record to the web server as a URL encoded dictionary The mapLogRecord method is used to convert the record to the dictionary to be sent Note Since preparing a record for sending it to a web server is not the same as a generic formatting operation using setFormatter to specify a Formatter for a HTTPHandler has no effect Instead of calling format this handler calls mapLogRecord and then urllib parse urlencode to encode the dictionary in a form suitable for sending to a web server QueueHandler New in version 3 2 The QueueHandler class located in the logging handlers module supports sending logging messages to a queue such as those implemented in the queue or multiprocessing modules Along with the QueueListener class QueueHandler can be used to let handlers do their work on a separate thread from the one which does the logging This is important in web applications and also other service applications where threads servicing clients need to respond as quickly as possible while any potentially slow operations such as sending an email via SMTPHandler are done on a separate thread class logging handlers QueueHandler queue Returns a new instance of the QueueHandler class The instance is initialized with the queue to send messages to The queue can be any queue like object it s used as is by the enqueue method which needs to know how to send messages to it The queue is not required to have the task tracking API which means that you can use SimpleQueue instances for queue Note If you are using multiprocessing you should avoid using SimpleQueue and instead use multiprocessing Queue emit record Enqueues the result of preparing the LogRecord Should an exception occur e g because a bounded queue has filled up the handleError method is called to handle the error This can result in the record silently being dropped if logging raiseExceptions is False or a message printed to sys stderr if logging raiseExceptions is True prepare record Prepares a record for queuing The object returned by this method is enqueued The base implementation formats the record to merge the message arguments exception and stack informati,en
72,on if present It also removes unpickleable items from the record in place Specifically it overwrites the record s msg and message attributes with the merged message obtained by calling the handler s format method and sets the args exc_info and exc_text attributes to None You might want to override this method if you want to convert the record to a dict or JSON string or send a modified copy of the record while leaving the original intact Note The base implementation formats the message with arguments sets the message and msg attributes to the formatted message and sets the args and exc_text attributes to None to allow pickling and to prevent further attempts at formatting This means that a handler on the QueueListener side won t have the information to do custom formatting e g of exceptions You may wish to subclass QueueHandler and override this method to e g avoid setting exc_text to None Note that the message msg args changes are related to ensuring the record is pickleable and you might or might not be able to avoid doing that depending on whether your args are pickleable Note that you may have to consider not only your own code but also code in any libraries that you use enqueue record Enqueues the record on the queue using put_nowait you may want to override this if you want to use blocking behaviour or a timeout or a customized queue implementation listener When created via configuration using dictConfig this attribute will contain a QueueListener instance for use with this handler Otherwise it will be None New in version 3 12 QueueListener New in version 3 2 The QueueListener class located in the logging handlers module supports receiving logging messages from a queue such as those implemented in the queue or multiprocessing modules The messages are received from a queue in an internal thread and passed on the same thread to one or more handlers for processing While QueueListener is not itself a handler it is documented here because it works hand in hand with QueueHandler Along with the QueueHandler class QueueListener can be used to let handlers do their work on a separate thread from the one which does the logging This is important in web applications and also other service applications where threads servicing clients need to respond as quickly as possible while any potentially slow operations such as sending an email via SMTPHandler are done on a separate thread class logging handlers QueueListener queue handlers respect_handler_level False Returns a new instance of the QueueListener class The instance is initialized with the queue to send messages to and a list of handlers which will handle entries placed on the queue The queue can be any queue like object it s passed as is to the dequeue method which needs to know how to get messages from it The queue is not required to have the task tracking API though it s used if available which means that you can use SimpleQueue instances for queue Note If you are using multiprocessing you should avoid using SimpleQueue and instead use multiprocessing Queue If respect_handler_level is True a handler s level is respected compared with the level for the message when deciding whether to pass messages to that handler otherwise the behaviour is as in previous Python versions to always pass each message to each handler Changed in version 3 5 The respect_handler_level argument was added dequeue block Dequeues a record and return it optionally blocking The base implementation uses get You may want to override this method if you want to use timeouts or work with custom queue implementations prepare record Prepare a record for handling This implementation just returns the passed in record You may want to override this method if you need to do any custom marshalling or manipulation of the record before passing it to the handlers handle record Handle a record This just loops through the handlers offering them the record to handle The actual object passed to the handlers is that which is returned from prepare start Starts the listener This starts up a background thread to monitor the ,en
73,queue for LogRecords to process stop Stops the listener This asks the thread to terminate and then waits for it to do so Note that if you don t call this before your application exits there may be some records still left on the queue which won t be processed enqueue_sentinel Writes a sentinel to the queue to tell the listener to quit This implementation uses put_nowait You may want to override this method if you want to use timeouts or work with custom queue implementations New in version 3 3 See also Module logging API reference for the logging module Module logging config Configuration API for the logging module,en
74,shutil High level file operations Source code Lib shutil py The shutil module offers a number of high level operations on files and collections of files In particular functions are provided which support file copying and removal For operations on individual files see also the os module Warning Even the higher level file copying functions shutil copy shutil copy2 cannot copy all file metadata On POSIX platforms this means that file owner and group are lost as well as ACLs On Mac OS the resource fork and other metadata are not used This means that resources will be lost and file type and creator codes will not be correct On Windows file owners ACLs and alternate data streams are not copied Directory and files operations shutil copyfileobj fsrc fdst length Copy the contents of the file like object fsrc to the file like object fdst The integer length if given is the buffer size In particular a negative length value means to copy the data without looping over the source data in chunks by default the data is read in chunks to avoid uncontrolled memory consumption Note that if the current file position of the fsrc object is not 0 only the contents from the current file position to the end of the file will be copied shutil copyfile src dst follow_symlinks True Copy the contents no metadata of the file named src to a file named dst and return dst in the most efficient way possible src and dst are path like objects or path names given as strings dst must be the complete target file name look at copy for a copy that accepts a target directory path If src and dst specify the same file SameFileError is raised The destination location must be writable otherwise an OSError exception will be raised If dst already exists it will be replaced Special files such as character or block devices and pipes cannot be copied with this function If follow_symlinks is false and src is a symbolic link a new symbolic link will be created instead of copying the file src points to Raises an auditing event shutil copyfile with arguments src dst Changed in version 3 3 IOError used to be raised instead of OSError Added follow_symlinks argument Now returns dst Changed in version 3 4 Raise SameFileError instead of Error Since the former is a subclass of the latter this change is backward compatible Changed in version 3 8 Platform specific fast copy syscalls may be used internally in order to copy the file more efficiently See Platform dependent efficient copy operations section exception shutil SameFileError This exception is raised if source and destination in copyfile are the same file New in version 3 4 shutil copymode src dst follow_symlinks True Copy the permission bits from src to dst The file contents owner and group are unaffected src and dst are path like objects or path names given as strings If follow_symlinks is false and both src and dst are symbolic links copymode will attempt to modify the mode of dst itself rather than the file it points to This functionality is not available on every platform please see copystat for more information If copymode cannot modify symbolic links on the local platform and it is asked to do so it will do nothing and return Raises an auditing event shutil copymode with arguments src dst Changed in version 3 3 Added follow_symlinks argument shutil copystat src dst follow_symlinks True Copy the permission bits last access time last modification time and flags from src to dst On Linux copystat also copies the extended attributes where possible The file contents owner and group are unaffected src and dst are path like objects or path names given as strings If follow_symlinks is false and src and dst both refer to symbolic links copystat will operate on the symbolic links themselves rather than the files the symbolic links refer to reading the information from the src symbolic link and writing the information to the dst symbolic link Note Not all platforms provide the ability to examine and modify symbolic links Python itself can tell you what functionality is locally available If os chmod in os supports_follow_symlinks is,en
75, True copystat can modify the permission bits of a symbolic link If os utime in os supports_follow_symlinks is True copystat can modify the last access and modification times of a symbolic link If os chflags in os supports_follow_symlinks is True copystat can modify the flags of a symbolic link os chflags is not available on all platforms On platforms where some or all of this functionality is unavailable when asked to modify a symbolic link copystat will copy everything it can copystat never returns failure Please see os supports_follow_symlinks for more information Raises an auditing event shutil copystat with arguments src dst Changed in version 3 3 Added follow_symlinks argument and support for Linux extended attributes shutil copy src dst follow_symlinks True Copies the file src to the file or directory dst src and dst should be path like objects or strings If dst specifies a directory the file will be copied into dst using the base filename from src If dst specifies a file that already exists it will be replaced Returns the path to the newly created file If follow_symlinks is false and src is a symbolic link dst will be created as a symbolic link If follow_symlinks is true and src is a symbolic link dst will be a copy of the file src refers to copy copies the file data and the file s permission mode see os chmod Other metadata like the file s creation and modification times is not preserved To preserve all file metadata from the original use copy2 instead Raises an auditing event shutil copyfile with arguments src dst Raises an auditing event shutil copymode with arguments src dst Changed in version 3 3 Added follow_symlinks argument Now returns path to the newly created file Changed in version 3 8 Platform specific fast copy syscalls may be used internally in order to copy the file more efficiently See Platform dependent efficient copy operations section shutil copy2 src dst follow_symlinks True Identical to copy except that copy2 also attempts to preserve file metadata When follow_symlinks is false and src is a symbolic link copy2 attempts to copy all metadata from the src symbolic link to the newly created dst symbolic link However this functionality is not available on all platforms On platforms where some or all of this functionality is unavailable copy2 will preserve all the metadata it can copy2 never raises an exception because it cannot preserve file metadata copy2 uses copystat to copy the file metadata Please see copystat for more information about platform support for modifying symbolic link metadata Raises an auditing event shutil copyfile with arguments src dst Raises an auditing event shutil copystat with arguments src dst Changed in version 3 3 Added follow_symlinks argument try to copy extended file system attributes too currently Linux only Now returns path to the newly created file Changed in version 3 8 Platform specific fast copy syscalls may be used internally in order to copy the file more efficiently See Platform dependent efficient copy operations section shutil ignore_patterns patterns This factory function creates a function that can be used as a callable for copytree s ignore argument ignoring files and directories that match one of the glob style patterns provided See the example below shutil copytree src dst symlinks False ignore None copy_function copy2 ignore_dangling_symlinks False dirs_exist_ok False Recursively copy an entire directory tree rooted at src to a directory named dst and return the destination directory All intermediate directories needed to contain dst will also be created by default Permissions and times of directories are copied with copystat individual files are copied using copy2 If symlinks is true symbolic links in the source tree are represented as symbolic links in the new tree and the metadata of the original links will be copied as far as the platform allows if false or omitted the contents and metadata of the linked files are copied to the new tree When symlinks is false if the file pointed by the symlink doesn t exist an exception will be added in the list,en
76, of errors raised in an Error exception at the end of the copy process You can set the optional ignore_dangling_symlinks flag to true if you want to silence this exception Notice that this option has no effect on platforms that don t support os symlink If ignore is given it must be a callable that will receive as its arguments the directory being visited by copytree and a list of its contents as returned by os listdir Since copytree is called recursively the ignore callable will be called once for each directory that is copied The callable must return a sequence of directory and file names relative to the current directory i e a subset of the items in its second argument these names will then be ignored in the copy process ignore_patterns can be used to create such a callable that ignores names based on glob style patterns If exception s occur an Error is raised with a list of reasons If copy_function is given it must be a callable that will be used to copy each file It will be called with the source path and the destination path as arguments By default copy2 is used but any function that supports the same signature like copy can be used If dirs_exist_ok is false the default and dst already exists a FileExistsError is raised If dirs_exist_ok is true the copying operation will continue if it encounters existing directories and files within the dst tree will be overwritten by corresponding files from the src tree Raises an auditing event shutil copytree with arguments src dst Changed in version 3 2 Added the copy_function argument to be able to provide a custom copy function Added the ignore_dangling_symlinks argument to silence dangling symlinks errors when symlinks is false Changed in version 3 3 Copy metadata when symlinks is false Now returns dst Changed in version 3 8 Platform specific fast copy syscalls may be used internally in order to copy the file more efficiently See Platform dependent efficient copy operations section Changed in version 3 8 Added the dirs_exist_ok parameter shutil rmtree path ignore_errors False onerror None onexc None dir_fd None Delete an entire directory tree path must point to a directory but not a symbolic link to a directory If ignore_errors is true errors resulting from failed removals will be ignored if false or omitted such errors are handled by calling a handler specified by onexc or onerror or if both are omitted exceptions are propagated to the caller This function can support paths relative to directory descriptors Note On platforms that support the necessary fd based functions a symlink attack resistant version of rmtree is used by default On other platforms the rmtree implementation is susceptible to a symlink attack given proper timing and circumstances attackers can manipulate symlinks on the filesystem to delete files they wouldn t be able to access otherwise Applications can use the rmtree avoids_symlink_attacks function attribute to determine which case applies If onexc is provided it must be a callable that accepts three parameters function path and excinfo The first parameter function is the function which raised the exception it depends on the platform and implementation The second parameter path will be the path name passed to function The third parameter excinfo is the exception that was raised Exceptions raised by onexc will not be caught The deprecated onerror is similar to onexc except that the third parameter it receives is the tuple returned from sys exc_info Raises an auditing event shutil rmtree with arguments path dir_fd Changed in version 3 3 Added a symlink attack resistant version that is used automatically if platform supports fd based functions Changed in version 3 8 On Windows will no longer delete the contents of a directory junction before removing the junction Changed in version 3 11 The dir_fd parameter Changed in version 3 12 Added the onexc parameter deprecated onerror rmtree avoids_symlink_attacks Indicates whether the current platform and implementation provides a symlink attack resistant version of rmtree Currently this is only true for platforms ,en
77,supporting fd based directory access functions New in version 3 3 shutil move src dst copy_function copy2 Recursively move a file or directory src to another location and return the destination If dst is an existing directory or a symlink to a directory then src is moved inside that directory The destination path in that directory must not already exist If dst already exists but is not a directory it may be overwritten depending on os rename semantics If the destination is on the current filesystem then os rename is used Otherwise src is copied to the destination using copy_function and then removed In case of symlinks a new symlink pointing to the target of src will be created as the destination and src will be removed If copy_function is given it must be a callable that takes two arguments src and the destination and will be used to copy src to the destination if os rename cannot be used If the source is a directory copytree is called passing it the copy_function The default copy_function is copy2 Using copy as the copy_function allows the move to succeed when it is not possible to also copy the metadata at the expense of not copying any of the metadata Raises an auditing event shutil move with arguments src dst Changed in version 3 3 Added explicit symlink handling for foreign filesystems thus adapting it to the behavior of GNU s mv Now returns dst Changed in version 3 5 Added the copy_function keyword argument Changed in version 3 8 Platform specific fast copy syscalls may be used internally in order to copy the file more efficiently See Platform dependent efficient copy operations section Changed in version 3 9 Accepts a path like object for both src and dst shutil disk_usage path Return disk usage statistics about the given path as a named tuple with the attributes total used and free which are the amount of total used and free space in bytes path may be a file or a directory Note On Unix filesystems path must point to a path within a mounted filesystem partition On those platforms CPython doesn t attempt to retrieve disk usage information from non mounted filesystems New in version 3 3 Changed in version 3 8 On Windows path can now be a file or directory Availability Unix Windows shutil chown path user None group None Change owner user and or group of the given path user can be a system user name or a uid the same applies to group At least one argument is required See also os chown the underlying function Raises an auditing event shutil chown with arguments path user group Availability Unix New in version 3 3 shutil which cmd mode os F_OK os X_OK path None Return the path to an executable which would be run if the given cmd was called If no cmd would be called return None mode is a permission mask passed to os access by default determining if the file exists and executable When no path is specified the results of os environ are used returning either the PATH value or a fallback of os defpath On Windows the current directory is prepended to the path if mode does not include os X_OK When the mode does include os X_OK the Windows API NeedCurrentDirectoryForExePathW will be consulted to determine if the current directory should be prepended to path To avoid consulting the current working directory for executables set the environment variable NoDefaultCurrentDirectoryInExePath Also on Windows the PATHEXT variable is used to resolve commands that may not already include an extension For example if you call shutil which python which will search PATHEXT to know that it should look for python exe within the path directories For example on Windows shutil which python C Python33 python EXE This is also applied when cmd is a path that contains a directory component shutil which C Python33 python C Python33 python EXE New in version 3 3 Changed in version 3 8 The bytes type is now accepted If cmd type is bytes the result type is also bytes Changed in version 3 12 On Windows the current directory is no longer prepended to the search path if mode includes os X_OK and WinAPI NeedCurrentDirectoryForExePathW cmd is false else the c,en
78,urrent directory is prepended even if it is already in the search path PATHEXT is used now even when cmd includes a directory component or ends with an extension that is in PATHEXT and filenames that have no extension can now be found Changed in version 3 12 1 On Windows if mode includes os X_OK executables with an extension in PATHEXT will be preferred over executables without a matching extension This brings behavior closer to that of Python 3 11 exception shutil Error This exception collects exceptions that are raised during a multi file operation For copytree the exception argument is a list of 3 tuples srcname dstname exception Platform dependent efficient copy operations Starting from Python 3 8 all functions involving a file copy copyfile copy copy2 copytree and move may use platform specific fast copy syscalls in order to copy the file more efficiently see bpo 33671 fast copy means that the copying operation occurs within the kernel avoiding the use of userspace buffers in Python as in outfd write infd read On macOS fcopyfile is used to copy the file content not metadata On Linux os sendfile is used On Windows shutil copyfile uses a bigger default buffer size 1 MiB instead of 64 KiB and a memoryview based variant of shutil copyfileobj is used If the fast copy operation fails and no data was written in the destination file then shutil will silently fallback on using less efficient copyfileobj function internally Changed in version 3 8 copytree example An example that uses the ignore_patterns helper from shutil import copytree ignore_patterns copytree source destination ignore ignore_patterns pyc tmp This will copy everything except pyc files and files or directories whose name starts with tmp Another example that uses the ignore argument to add a logging call from shutil import copytree import logging def _logpath path names logging info Working in s path return nothing will be ignored copytree source destination ignore _logpath rmtree example This example shows how to remove a directory tree on Windows where some of the files have their read only bit set It uses the onexc callback to clear the readonly bit and reattempt the remove Any subsequent failure will propagate import os stat import shutil def remove_readonly func path _ Clear the readonly bit and reattempt the removal os chmod path stat S_IWRITE func path shutil rmtree directory onexc remove_readonly Archiving operations New in version 3 2 Changed in version 3 5 Added support for the xztar format High level utilities to create and read compressed and archived files are also provided They rely on the zipfile and tarfile modules shutil make_archive base_name format root_dir base_dir verbose dry_run owner group logger Create an archive file such as zip or tar and return its name base_name is the name of the file to create including the path minus any format specific extension format is the archive format one of zip if the zlib module is available tar gztar if the zlib module is available bztar if the bz2 module is available or xztar if the lzma module is available root_dir is a directory that will be the root directory of the archive all paths in the archive will be relative to it for example we typically chdir into root_dir before creating the archive base_dir is the directory where we start archiving from i e base_dir will be the common prefix of all files and directories in the archive base_dir must be given relative to root_dir See Archiving example with base_dir for how to use base_dir and root_dir together root_dir and base_dir both default to the current directory If dry_run is true no archive is created but the operations that would be executed are logged to logger owner and group are used when creating a tar archive By default uses the current owner and group logger must be an object compatible with PEP 282 usually an instance of logging Logger The verbose argument is unused and deprecated Raises an auditing event shutil make_archive with arguments base_name format root_dir base_dir Note This function is not thread safe when custom archivers registe,en
79,red with register_archive_format do not support the root_dir argument In this case it temporarily changes the current working directory of the process to root_dir to perform archiving Changed in version 3 8 The modern pax POSIX 1 2001 format is now used instead of the legacy GNU format for archives created with format tar Changed in version 3 10 6 This function is now made thread safe during creation of standard zip and tar archives shutil get_archive_formats Return a list of supported formats for archiving Each element of the returned sequence is a tuple name description By default shutil provides these formats zip ZIP file if the zlib module is available tar Uncompressed tar file Uses POSIX 1 2001 pax format for new archives gztar gzip ed tar file if the zlib module is available bztar bzip2 ed tar file if the bz2 module is available xztar xz ed tar file if the lzma module is available You can register new formats or provide your own archiver for any existing formats by using register_archive_format shutil register_archive_format name function extra_args description Register an archiver for the format name function is the callable that will be used to unpack archives The callable will receive the base_name of the file to create followed by the base_dir which defaults to os curdir to start archiving from Further arguments are passed as keyword arguments owner group dry_run and logger as passed in make_archive If function has the custom attribute function supports_root_dir set to True the root_dir argument is passed as a keyword argument Otherwise the current working directory of the process is temporarily changed to root_dir before calling function In this case make_archive is not thread safe If given extra_args is a sequence of name value pairs that will be used as extra keywords arguments when the archiver callable is used description is used by get_archive_formats which returns the list of archivers Defaults to an empty string Changed in version 3 12 Added support for functions supporting the root_dir argument shutil unregister_archive_format name Remove the archive format name from the list of supported formats shutil unpack_archive filename extract_dir format filter Unpack an archive filename is the full path of the archive extract_dir is the name of the target directory where the archive is unpacked If not provided the current working directory is used format is the archive format one of zip tar gztar bztar or xztar Or any other format registered with register_unpack_format If not provided unpack_archive will use the archive file name extension and see if an unpacker was registered for that extension In case none is found a ValueError is raised The keyword only filter argument is passed to the underlying unpacking function For zip files filter is not accepted For tar files it is recommended to set it to data unless using features specific to tar and UNIX like filesystems See Extraction filters for details The data filter will become the default for tar files in Python 3 14 Raises an auditing event shutil unpack_archive with arguments filename extract_dir format Warning Never extract archives from untrusted sources without prior inspection It is possible that files are created outside of the path specified in the extract_dir argument e g members that have absolute filenames starting with or filenames with two dots Changed in version 3 7 Accepts a path like object for filename and extract_dir Changed in version 3 12 Added the filter argument shutil register_unpack_format name extensions function extra_args description Registers an unpack format name is the name of the format and extensions is a list of extensions corresponding to the format like zip for Zip files function is the callable that will be used to unpack archives The callable will receive the path of the archive as a positional argument the directory the archive must be extracted to as a positional argument possibly a filter keyword argument if it was given to unpack_archive additional keyword arguments specified by extra_args as a sequence of name value t,en
80,uples description can be provided to describe the format and will be returned by the get_unpack_formats function shutil unregister_unpack_format name Unregister an unpack format name is the name of the format shutil get_unpack_formats Return a list of all registered formats for unpacking Each element of the returned sequence is a tuple name extensions description By default shutil provides these formats zip ZIP file unpacking compressed files works only if the corresponding module is available tar uncompressed tar file gztar gzip ed tar file if the zlib module is available bztar bzip2 ed tar file if the bz2 module is available xztar xz ed tar file if the lzma module is available You can register new formats or provide your own unpacker for any existing formats by using register_unpack_format Archiving example In this example we create a gzip ed tar file archive containing all files found in the ssh directory of the user from shutil import make_archive import os archive_name os path expanduser os path join myarchive root_dir os path expanduser os path join ssh make_archive archive_name gztar root_dir Users tarek myarchive tar gz The resulting archive contains tar tzvf Users tarek myarchive tar gz drwx tarek staff 0 2010 02 01 16 23 40 rw r r tarek staff 609 2008 06 09 13 26 54 authorized_keys rwxr xr x tarek staff 65 2008 06 09 13 26 54 config rwx tarek staff 668 2008 06 09 13 26 54 id_dsa rwxr xr x tarek staff 609 2008 06 09 13 26 54 id_dsa pub rw tarek staff 1675 2008 06 09 13 26 54 id_rsa rw r r tarek staff 397 2008 06 09 13 26 54 id_rsa pub rw r r tarek staff 37192 2010 02 06 18 23 10 known_hosts Archiving example with base_dir In this example similar to the one above we show how to use make_archive but this time with the usage of base_dir We now have the following directory structure tree tmp tmp root structure content please_add txt do_not_add txt In the final archive please_add txt should be included but do_not_add txt should not Therefore we use the following from shutil import make_archive import os archive_name os path expanduser os path join myarchive make_archive archive_name tar root_dir tmp root base_dir structure content Users tarek my_archive tar Listing the files in the resulting archive gives us python m tarfile l Users tarek myarchive tar structure content structure content please_add txt Querying the size of the output terminal shutil get_terminal_size fallback columns lines Get the size of the terminal window For each of the two dimensions the environment variable COLUMNS and LINES respectively is checked If the variable is defined and the value is a positive integer it is used When COLUMNS or LINES is not defined which is the common case the terminal connected to sys __stdout__ is queried by invoking os get_terminal_size If the terminal size cannot be successfully queried either because the system doesn t support querying or because we are not connected to a terminal the value given in fallback parameter is used fallback defaults to 80 24 which is the default size used by many terminal emulators The value returned is a named tuple of type os terminal_size See also The Single UNIX Specification Version 2 Other Environment Variables New in version 3 3 Changed in version 3 11 The fallback values are also used if os get_terminal_size returns zeroes,en
81,datetime Basic date and time types Source code Lib datetime py The datetime module supplies classes for manipulating dates and times While date and time arithmetic is supported the focus of the implementation is on efficient attribute extraction for output formatting and manipulation Tip Skip to the format codes See also Module calendar General calendar related functions Module time Time access and conversions Module zoneinfo Concrete time zones representing the IANA time zone database Package dateutil Third party library with expanded time zone and parsing support Package DateType Third party library that introduces distinct static types to e g allow static type checkers to differentiate between naive and aware datetimes Aware and Naive Objects Date and time objects may be categorized as aware or naive depending on whether or not they include timezone information With sufficient knowledge of applicable algorithmic and political time adjustments such as time zone and daylight saving time information an aware object can locate itself relative to other aware objects An aware object represents a specific moment in time that is not open to interpretation 1 A naive object does not contain enough information to unambiguously locate itself relative to other date time objects Whether a naive object represents Coordinated Universal Time UTC local time or time in some other timezone is purely up to the program just like it is up to the program whether a particular number represents metres miles or mass Naive objects are easy to understand and to work with at the cost of ignoring some aspects of reality For applications requiring aware objects datetime and time objects have an optional time zone information attribute tzinfo that can be set to an instance of a subclass of the abstract tzinfo class These tzinfo objects capture information about the offset from UTC time the time zone name and whether daylight saving time is in effect Only one concrete tzinfo class the timezone class is supplied by the datetime module The timezone class can represent simple timezones with fixed offsets from UTC such as UTC itself or North American EST and EDT timezones Supporting timezones at deeper levels of detail is up to the application The rules for time adjustment across the world are more political than rational change frequently and there is no standard suitable for every application aside from UTC Constants The datetime module exports the following constants datetime MINYEAR The smallest year number allowed in a date or datetime object MINYEAR is 1 datetime MAXYEAR The largest year number allowed in a date or datetime object MAXYEAR is 9999 datetime UTC Alias for the UTC timezone singleton datetime timezone utc New in version 3 11 Available Types class datetime date An idealized naive date assuming the current Gregorian calendar always was and always will be in effect Attributes year month and day class datetime time An idealized time independent of any particular day assuming that every day has exactly 24 60 60 seconds There is no notion of leap seconds here Attributes hour minute second microsecond and tzinfo class datetime datetime A combination of a date and a time Attributes year month day hour minute second microsecond and tzinfo class datetime timedelta A duration expressing the difference between two datetime or date instances to microsecond resolution class datetime tzinfo An abstract base class for time zone information objects These are used by the datetime and time classes to provide a customizable notion of time adjustment for example to account for time zone and or daylight saving time class datetime timezone A class that implements the tzinfo abstract base class as a fixed offset from the UTC New in version 3 2 Objects of these types are immutable Subclass relationships object timedelta tzinfo timezone time date datetime Common Properties The date datetime time and timezone types share these common features Objects of these types are immutable Objects of these types are hashable meaning that they can be used as dictionary keys O,en
82,bjects of these types support efficient pickling via the pickle module Determining if an Object is Aware or Naive Objects of the date type are always naive An object of type time or datetime may be aware or naive A datetime object d is aware if both of the following hold 1 d tzinfo is not None 2 d tzinfo utcoffset d does not return None Otherwise d is naive A time object t is aware if both of the following hold 1 t tzinfo is not None 2 t tzinfo utcoffset None does not return None Otherwise t is naive The distinction between aware and naive doesn t apply to timedelta objects timedelta Objects A timedelta object represents a duration the difference between two datetime or date instances class datetime timedelta days 0 seconds 0 microseconds 0 milliseconds 0 minutes 0 hours 0 weeks 0 All arguments are optional and default to 0 Arguments may be integers or floats and may be positive or negative Only days seconds and microseconds are stored internally Arguments are converted to those units A millisecond is converted to 1000 microseconds A minute is converted to 60 seconds An hour is converted to 3600 seconds A week is converted to 7 days and days seconds and microseconds are then normalized so that the representation is unique with 0 microseconds 1000000 0 seconds 3600 24 the number of seconds in one day 999999999 days 999999999 The following example illustrates how any arguments besides days seconds and microseconds are merged and normalized into those three resulting attributes from datetime import timedelta delta timedelta days 50 seconds 27 microseconds 10 milliseconds 29000 minutes 5 hours 8 weeks 2 Only days seconds and microseconds remain delta datetime timedelta days 64 seconds 29156 microseconds 10 If any argument is a float and there are fractional microseconds the fractional microseconds left over from all arguments are combined and their sum is rounded to the nearest microsecond using round half to even tiebreaker If no argument is a float the conversion and normalization processes are exact no information is lost If the normalized value of days lies outside the indicated range OverflowError is raised Note that normalization of negative values may be surprising at first For example from datetime import timedelta d timedelta microseconds 1 d days d seconds d microseconds 1 86399 999999 Class attributes timedelta min The most negative timedelta object timedelta 999999999 timedelta max The most positive timedelta object timedelta days 999999999 hours 23 minutes 59 seconds 59 microseconds 999999 timedelta resolution The smallest possible difference between non equal timedelta objects timedelta microseconds 1 Note that because of normalization timedelta max timedelta min timedelta max is not representable as a timedelta object Instance attributes read only Attribute Value days Between 999999999 and 999999999 inclusive seconds Between 0 and 86399 inclusive microseconds Between 0 and 999999 inclusive Supported operations Operation Result t1 t2 t3 Sum of t2 and t3 Afterwards t1 t2 t3 and t1 t3 t2 are true 1 t1 t2 t3 Difference of t2 and t3 Afterwards t1 t2 t3 and t2 t1 t3 are true 1 6 t1 t2 i or t1 i t2 Delta multiplied by an integer Afterwards t1 i t2 is true provided i 0 In general t1 i t1 i 1 t1 is true 1 t1 t2 f or t1 f t2 Delta multiplied by a float The result is rounded to the nearest multiple of timedelta resolution using round half to even f t2 t3 Division 3 of overall duration t2 by interval unit t3 Returns a float object t1 t2 f or t1 t2 i Delta divided by a float or an int The result is rounded to the nearest multiple of timedelta resolution using round half to even t1 t2 i or t1 t2 The floor is computed and the remainder if t3 any is thrown away In the second case an integer is returned 3 t1 t2 t3 The remainder is computed as a timedelta object 3 q r divmod t1 t2 Computes the quotient and the remainder q t1 t2 3 and r t1 t2 q is an integer and r is a timedelta object t1 Returns a timedelta object with the same value 2 t1 equivalent to timedelta t1 days t1 seconds t1 microseconds and to t1 1 1 4 abs t equivalen,en
83,t to t when t days 0 and to t when t days 0 2 str t Returns a string in the form D day s H H MM SS UUUUUU where D is negative for negative t 5 repr t Returns a string representation of the timedelta object as a constructor call with canonical attribute values Notes 1 This is exact but may overflow 2 This is exact and cannot overflow 3 Division by 0 raises ZeroDivisionError 4 timedelta max is not representable as a timedelta object 5 String representations of timedelta objects are normalized similarly to their internal representation This leads to somewhat unusual results for negative timedeltas For example timedelta hours 5 datetime timedelta days 1 seconds 68400 print _ 1 day 19 00 00 6 The expression t2 t3 will always be equal to the expression t2 t3 except when t3 is equal to timedelta max in that case the former will produce a result while the latter will overflow In addition to the operations listed above timedelta objects support certain additions and subtractions with date and datetime objects see below Changed in version 3 2 Floor division and true division of a timedelta object by another timedelta object are now supported as are remainder operations and the divmod function True division and multiplication of a timedelta object by a float object are now supported timedelta objects support equality and order comparisons In Boolean contexts a timedelta object is considered to be true if and only if it isn t equal to timedelta 0 Instance methods timedelta total_seconds Return the total number of seconds contained in the duration Equivalent to td timedelta seconds 1 For interval units other than seconds use the division form directly e g td timedelta microseconds 1 Note that for very large time intervals greater than 270 years on most platforms this method will lose microsecond accuracy New in version 3 2 Examples of usage timedelta An additional example of normalization Components of another_year add up to exactly 365 days from datetime import timedelta year timedelta days 365 another_year timedelta weeks 40 days 84 hours 23 minutes 50 seconds 600 year another_year True year total_seconds 31536000 0 Examples of timedelta arithmetic from datetime import timedelta year timedelta days 365 ten_years 10 year ten_years datetime timedelta days 3650 ten_years days 365 10 nine_years ten_years year nine_years datetime timedelta days 3285 three_years nine_years 3 three_years three_years days 365 datetime timedelta days 1095 3 date Objects A date object represents a date year month and day in an idealized calendar the current Gregorian calendar indefinitely extended in both directions January 1 of year 1 is called day number 1 January 2 of year 1 is called day number 2 and so on 2 class datetime date year month day All arguments are required Arguments must be integers in the following ranges MINYEAR year MAXYEAR 1 month 12 1 day number of days in the given month and year If an argument outside those ranges is given ValueError is raised Other constructors all class methods classmethod date today Return the current local date This is equivalent to date fromtimestamp time time classmethod date fromtimestamp timestamp Return the local date corresponding to the POSIX timestamp such as is returned by time time This may raise OverflowError if the timestamp is out of the range of values supported by the platform C localtime function and OSError on localtime failure It s common for this to be restricted to years from 1970 through 2038 Note that on non POSIX systems that include leap seconds in their notion of a timestamp leap seconds are ignored by fromtimestamp Changed in version 3 3 Raise OverflowError instead of ValueError if the timestamp is out of the range of values supported by the platform C localtime function Raise OSError instead of ValueError on localtime failure classmethod date fromordinal ordinal Return the date corresponding to the proleptic Gregorian ordinal where January 1 of year 1 has ordinal 1 ValueError is raised unless 1 ordinal date max toordinal For any date d date fromordinal d toordinal d classmethod date from,en
84,isoformat date_string Return a date corresponding to a date_string given in any valid ISO 8601 format with the following exceptions 1 Reduced precision dates are not currently supported YYYY MM YYYY 2 Extended date representations are not currently supported YYYYYY MM DD 3 Ordinal dates are not currently supported YYYY OOO Examples from datetime import date date fromisoformat 2019 12 04 datetime date 2019 12 4 date fromisoformat 20191204 datetime date 2019 12 4 date fromisoformat 2021 W01 1 datetime date 2021 1 4 New in version 3 7 Changed in version 3 11 Previously this method only supported the format YYYY MM DD classmethod date fromisocalendar year week day Return a date corresponding to the ISO calendar date specified by year week and day This is the inverse of the function date isocalendar New in version 3 8 Class attributes date min The earliest representable date date MINYEAR 1 1 date max The latest representable date date MAXYEAR 12 31 date resolution The smallest possible difference between non equal date objects timedelta days 1 Instance attributes read only date year Between MINYEAR and MAXYEAR inclusive date month Between 1 and 12 inclusive date day Between 1 and the number of days in the given month of the given year Supported operations Operation Result date2 date1 timedelta date2 will be timedelta days days after date1 1 date2 date1 timedelta Computes date2 such that date2 timedelta date1 2 timedelta date1 date2 3 date1 date2 date1 Equality comparison 4 date2 date1 date2 date1 date2 Order comparison 5 date1 date2 date1 date2 Notes 1 date2 is moved forward in time if timedelta days 0 or backward if timedelta days 0 Afterward date2 date1 timedelta days timedelta seconds and timedelta microseconds are ignored OverflowError is raised if date2 year would be smaller than MINYEAR or larger than MAXYEAR 2 timedelta seconds and timedelta microseconds are ignored 3 This is exact and cannot overflow timedelta seconds and timedelta microseconds are 0 and date2 timedelta date1 after 4 date objects are equal if they represent the same date 5 date1 is considered less than date2 when date1 precedes date2 in time In other words date1 date2 if and only if date1 toordinal date2 toordinal In Boolean contexts all date objects are considered to be true Instance methods date replace year self year month self month day self day Return a date with the same value except for those parameters given new values by whichever keyword arguments are specified Example from datetime import date d date 2002 12 31 d replace day 26 datetime date 2002 12 26 date timetuple Return a time struct_time such as returned by time localtime The hours minutes and seconds are 0 and the DST flag is 1 d timetuple is equivalent to time struct_time d year d month d day 0 0 0 d weekday yday 1 where yday d toordinal date d year 1 1 toordinal 1 is the day number within the current year starting with 1 for January 1st date toordinal Return the proleptic Gregorian ordinal of the date where January 1 of year 1 has ordinal 1 For any date object d date fromordinal d toordinal d date weekday Return the day of the week as an integer where Monday is 0 and Sunday is 6 For example date 2002 12 4 weekday 2 a Wednesday See also isoweekday date isoweekday Return the day of the week as an integer where Monday is 1 and Sunday is 7 For example date 2002 12 4 isoweekday 3 a Wednesday See also weekday isocalendar date isocalendar Return a named tuple object with three components year week and weekday The ISO calendar is a widely used variant of the Gregorian calendar 3 The ISO year consists of 52 or 53 full weeks and where a week starts on a Monday and ends on a Sunday The first week of an ISO year is the first Gregorian calendar week of a year containing a Thursday This is called week number 1 and the ISO year of that Thursday is the same as its Gregorian year For example 2004 begins on a Thursday so the first week of ISO year 2004 begins on Monday 29 Dec 2003 and ends on Sunday 4 Jan 2004 from datetime import date date 2003 12 29 isocalendar datetime IsoCalendarDate year 2004 we,en
85,ek 1 weekday 1 date 2004 1 4 isocalendar datetime IsoCalendarDate year 2004 week 1 weekday 7 Changed in version 3 9 Result changed from a tuple to a named tuple date isoformat Return a string representing the date in ISO 8601 format YYYY MM DD from datetime import date date 2002 12 4 isoformat 2002 12 04 date __str__ For a date d str d is equivalent to d isoformat date ctime Return a string representing the date from datetime import date date 2002 12 4 ctime Wed Dec 4 00 00 00 2002 d ctime is equivalent to time ctime time mktime d timetuple on platforms where the native C ctime function which time ctime invokes but which date ctime does not invoke conforms to the C standard date strftime format Return a string representing the date controlled by an explicit format string Format codes referring to hours minutes or seconds will see 0 values See also strftime and strptime Behavior and date isoformat date __format__ format Same as date strftime This makes it possible to specify a format string for a date object in formatted string literals and when using str format See also strftime and strptime Behavior and date isoformat Examples of Usage date Example of counting days to an event import time from datetime import date today date today today datetime date 2007 12 5 today date fromtimestamp time time True my_birthday date today year 6 24 if my_birthday today my_birthday my_birthday replace year today year 1 my_birthday datetime date 2008 6 24 time_to_birthday abs my_birthday today time_to_birthday days 202 More examples of working with date from datetime import date d date fromordinal 730920 730920th day after 1 1 0001 d datetime date 2002 3 11 Methods related to formatting string output d isoformat 2002 03 11 d strftime d m y 11 03 02 d strftime A d B Y Monday 11 March 2002 d ctime Mon Mar 11 00 00 00 2002 The 1 is 0 d the 2 is 0 B format d day month The day is 11 the month is March Methods for to extracting components under different calendars t d timetuple for i in t print i 2002 year 3 month 11 day 0 0 0 0 weekday 0 Monday 70 70th day in the year 1 ic d isocalendar for i in ic print i 2002 ISO year 11 ISO week number 1 ISO day number 1 Monday A date object is immutable all operations produce a new object d replace year 2005 datetime date 2005 3 11 datetime Objects A datetime object is a single object containing all the information from a date object and a time object Like a date object datetime assumes the current Gregorian calendar extended in both directions like a time object datetime assumes there are exactly 3600 24 seconds in every day Constructor class datetime datetime year month day hour 0 minute 0 second 0 microsecond 0 tzinfo None fold 0 The year month and day arguments are required tzinfo may be None or an instance of a tzinfo subclass The remaining arguments must be integers in the following ranges MINYEAR year MAXYEAR 1 month 12 1 day number of days in the given month and year 0 hour 24 0 minute 60 0 second 60 0 microsecond 1000000 fold in 0 1 If an argument outside those ranges is given ValueError is raised Changed in version 3 6 Added the fold parameter Other constructors all class methods classmethod datetime today Return the current local datetime with tzinfo None Equivalent to datetime fromtimestamp time time See also now fromtimestamp This method is functionally equivalent to now but without a tz parameter classmethod datetime now tz None Return the current local date and time If optional argument tz is None or not specified this is like today but if possible supplies more precision than can be gotten from going through a time time timestamp for example this may be possible on platforms supplying the C gettimeofday function If tz is not None it must be an instance of a tzinfo subclass and the current date and time are converted to tz s time zone This function is preferred over today and utcnow classmethod datetime utcnow Return the current UTC date and time with tzinfo None This is like now but returns the current UTC date and time as a naive datetime object An aware current UTC datetime can be obtaine,en
86,d by calling datetime now timezone utc See also now Warning Because naive datetime objects are treated by many datetime methods as local times it is preferred to use aware datetimes to represent times in UTC As such the recommended way to create an object representing the current time in UTC is by calling datetime now timezone utc Deprecated since version 3 12 Use datetime now with UTC instead classmethod datetime fromtimestamp timestamp tz None Return the local date and time corresponding to the POSIX timestamp such as is returned by time time If optional argument tz is None or not specified the timestamp is converted to the platform s local date and time and the returned datetime object is naive If tz is not None it must be an instance of a tzinfo subclass and the timestamp is converted to tz s time zone fromtimestamp may raise OverflowError if the timestamp is out of the range of values supported by the platform C localtime or gmtime functions and OSError on localtime or gmtime failure It s common for this to be restricted to years in 1970 through 2038 Note that on non POSIX systems that include leap seconds in their notion of a timestamp leap seconds are ignored by fromtimestamp and then it s possible to have two timestamps differing by a second that yield identical datetime objects This method is preferred over utcfromtimestamp Changed in version 3 3 Raise OverflowError instead of ValueError if the timestamp is out of the range of values supported by the platform C localtime or gmtime functions Raise OSError instead of ValueError on localtime or gmtime failure Changed in version 3 6 fromtimestamp may return instances with fold set to 1 classmethod datetime utcfromtimestamp timestamp Return the UTC datetime corresponding to the POSIX timestamp with tzinfo None The resulting object is naive This may raise OverflowError if the timestamp is out of the range of values supported by the platform C gmtime function and OSError on gmtime failure It s common for this to be restricted to years in 1970 through 2038 To get an aware datetime object call fromtimestamp datetime fromtimestamp timestamp timezone utc On the POSIX compliant platforms it is equivalent to the following expression datetime 1970 1 1 tzinfo timezone utc timedelta seconds timestamp except the latter formula always supports the full years range between MINYEAR and MAXYEAR inclusive Warning Because naive datetime objects are treated by many datetime methods as local times it is preferred to use aware datetimes to represent times in UTC As such the recommended way to create an object representing a specific timestamp in UTC is by calling datetime fromtimestamp timestamp tz timezone utc Changed in version 3 3 Raise OverflowError instead of ValueError if the timestamp is out of the range of values supported by the platform C gmtime function Raise OSError instead of ValueError on gmtime failure Deprecated since version 3 12 Use datetime fromtimestamp with UTC instead classmethod datetime fromordinal ordinal Return the datetime corresponding to the proleptic Gregorian ordinal where January 1 of year 1 has ordinal 1 ValueError is raised unless 1 ordinal datetime max toordinal The hour minute second and microsecond of the result are all 0 and tzinfo is None classmethod datetime combine date time tzinfo time tzinfo Return a new datetime object whose date components are equal to the given date object s and whose time components are equal to the given time object s If the tzinfo argument is provided its value is used to set the tzinfo attribute of the result otherwise the tzinfo attribute of the time argument is used If the date argument is a datetime object its time components and tzinfo attributes are ignored For any datetime object d d datetime combine d date d time d tzinfo Changed in version 3 6 Added the tzinfo argument classmethod datetime fromisoformat date_string Return a datetime corresponding to a date_string in any valid ISO 8601 format with the following exceptions 1 Time zone offsets may have fractional seconds 2 The T separator may be replaced by any singl,en
87,e unicode character 3 Fractional hours and minutes are not supported 4 Reduced precision dates are not currently supported YYYY MM YYYY 5 Extended date representations are not currently supported YYYYYY MM DD 6 Ordinal dates are not currently supported YYYY OOO Examples from datetime import datetime datetime fromisoformat 2011 11 04 datetime datetime 2011 11 4 0 0 datetime fromisoformat 20111104 datetime datetime 2011 11 4 0 0 datetime fromisoformat 2011 11 04T00 05 23 datetime datetime 2011 11 4 0 5 23 datetime fromisoformat 2011 11 04T00 05 23Z datetime datetime 2011 11 4 0 5 23 tzinfo datetime timezone utc datetime fromisoformat 20111104T000523 datetime datetime 2011 11 4 0 5 23 datetime fromisoformat 2011 W01 2T00 05 23 283 datetime datetime 2011 1 4 0 5 23 283000 datetime fromisoformat 2011 11 04 00 05 23 283 datetime datetime 2011 11 4 0 5 23 283000 datetime fromisoformat 2011 11 04 00 05 23 283 00 00 datetime datetime 2011 11 4 0 5 23 283000 tzinfo datetime timezone utc datetime fromisoformat 2011 11 04T00 05 23 04 00 datetime datetime 2011 11 4 0 5 23 tzinfo datetime timezone datetime timedelta seconds 14400 New in version 3 7 Changed in version 3 11 Previously this method only supported formats that could be emitted by date isoformat or datetime isoformat classmethod datetime fromisocalendar year week day Return a datetime corresponding to the ISO calendar date specified by year week and day The non date components of the datetime are populated with their normal default values This is the inverse of the function datetime isocalendar New in version 3 8 classmethod datetime strptime date_string format Return a datetime corresponding to date_string parsed according to format If format does not contain microseconds or timezone information this is equivalent to datetime time strptime date_string format 0 6 ValueError is raised if the date_string and format can t be parsed by time strptime or if it returns a value which isn t a time tuple See also strftime and strptime Behavior and datetime fromisoformat Class attributes datetime min The earliest representable datetime datetime MINYEAR 1 1 tzinfo None datetime max The latest representable datetime datetime MAXYEAR 12 31 23 59 59 999999 tzinfo None datetime resolution The smallest possible difference between non equal datetime objects timedelta microseconds 1 Instance attributes read only datetime year Between MINYEAR and MAXYEAR inclusive datetime month Between 1 and 12 inclusive datetime day Between 1 and the number of days in the given month of the given year datetime hour In range 24 datetime minute In range 60 datetime second In range 60 datetime microsecond In range 1000000 datetime tzinfo The object passed as the tzinfo argument to the datetime constructor or None if none was passed datetime fold In 0 1 Used to disambiguate wall times during a repeated interval A repeated interval occurs when clocks are rolled back at the end of daylight saving time or when the UTC offset for the current zone is decreased for political reasons The value 0 1 represents the earlier later of the two moments with the same wall time representation New in version 3 6 Supported operations Operation Result datetime2 datetime1 timedelta 1 datetime2 datetime1 timedelta 2 timedelta datetime1 datetime2 3 datetime1 datetime2 datetime1 Equality comparison 4 datetime2 datetime1 datetime2 datetime1 Order comparison 5 datetime2 datetime1 datetime2 datetime1 datetime2 1 datetime2 is a duration of timedelta removed from datetime1 moving forward in time if timedelta days 0 or backward if timedelta days 0 The result has the same tzinfo attribute as the input datetime and datetime2 datetime1 timedelta after OverflowError is raised if datetime2 year would be smaller than MINYEAR or larger than MAXYEAR Note that no time zone adjustments are done even if the input is an aware object 2 Computes the datetime2 such that datetime2 timedelta datetime1 As for addition the result has the same tzinfo attribute as the input datetime and no time zone adjustments are done even if the input is aware 3 Subtraction o,en
88,f a datetime from a datetime is defined only if both operands are naive or if both are aware If one is aware and the other is naive TypeError is raised If both are naive or both are aware and have the same tzinfo attribute the tzinfo attributes are ignored and the result is a timedelta object t such that datetime2 t datetime1 No time zone adjustments are done in this case If both are aware and have different tzinfo attributes a b acts as if a and b were first converted to naive UTC datetimes The result is a replace tzinfo None a utcoffset b replace tzinfo None b utcoffset except that the implementation never overflows 4 datetime objects are equal if they represent the same date and time taking into account the time zone Naive and aware datetime objects are never equal datetime objects are never equal to date objects that are not also datetime instances even if they represent the same date If both comparands are aware and have the same tzinfo attribute the tzinfo and fold attributes are ignored and the base datetimes are compared If both comparands are aware and have different tzinfo attributes the comparison acts as comparands were first converted to UTC datetimes except that the implementation never overflows datetime instances in a repeated interval are never equal to datetime instances in other time zone 5 datetime1 is considered less than datetime2 when datetime1 precedes datetime2 in time taking into account the time zone Order comparison between naive and aware datetime objects as well as a datetime object and a date object that is not also a datetime instance raises TypeError If both comparands are aware and have the same tzinfo attribute the tzinfo and fold attributes are ignored and the base datetimes are compared If both comparands are aware and have different tzinfo attributes the comparison acts as comparands were first converted to UTC datetimes except that the implementation never overflows Changed in version 3 3 Equality comparisons between aware and naive datetime instances don t raise TypeError Instance methods datetime date Return date object with same year month and day datetime time Return time object with same hour minute second microsecond and fold tzinfo is None See also method timetz Changed in version 3 6 The fold value is copied to the returned time object datetime timetz Return time object with same hour minute second microsecond fold and tzinfo attributes See also method time Changed in version 3 6 The fold value is copied to the returned time object datetime replace year self year month self month day self day hour self hour minute self minute second self second microsecond self microsecond tzinfo self tzinfo fold 0 Return a datetime with the same attributes except for those attributes given new values by whichever keyword arguments are specified Note that tzinfo None can be specified to create a naive datetime from an aware datetime with no conversion of date and time data Changed in version 3 6 Added the fold parameter datetime astimezone tz None Return a datetime object with new tzinfo attribute tz adjusting the date and time data so the result is the same UTC time as self but in tz s local time If provided tz must be an instance of a tzinfo subclass and its utcoffset and dst methods must not return None If self is naive it is presumed to represent time in the system timezone If called without arguments or with tz None the system local timezone is assumed for the target timezone The tzinfo attribute of the converted datetime instance will be set to an instance of timezone with the zone name and offset obtained from the OS If self tzinfo is tz self astimezone tz is equal to self no adjustment of date or time data is performed Else the result is local time in the timezone tz representing the same UTC time as self after astz dt astimezone tz astz astz utcoffset will have the same date and time data as dt dt utcoffset If you merely want to attach a time zone object tz to a datetime dt without adjustment of date and time data use dt replace tzinfo tz If you merely want to remove the time zone o,en
89,bject from an aware datetime dt without conversion of date and time data use dt replace tzinfo None Note that the default tzinfo fromutc method can be overridden in a tzinfo subclass to affect the result returned by astimezone Ignoring error cases astimezone acts like def astimezone self tz if self tzinfo is tz return self Convert self to UTC and attach the new time zone object utc self self utcoffset replace tzinfo tz Convert from UTC to tz s local time return tz fromutc utc Changed in version 3 3 tz now can be omitted Changed in version 3 6 The astimezone method can now be called on naive instances that are presumed to represent system local time datetime utcoffset If tzinfo is None returns None else returns self tzinfo utcoffset self and raises an exception if the latter doesn t return None or a timedelta object with magnitude less than one day Changed in version 3 7 The UTC offset is not restricted to a whole number of minutes datetime dst If tzinfo is None returns None else returns self tzinfo dst self and raises an exception if the latter doesn t return None or a timedelta object with magnitude less than one day Changed in version 3 7 The DST offset is not restricted to a whole number of minutes datetime tzname If tzinfo is None returns None else returns self tzinfo tzname self raises an exception if the latter doesn t return None or a string object datetime timetuple Return a time struct_time such as returned by time localtime d timetuple is equivalent to time struct_time d year d month d day d hour d minute d second d weekday yday dst where yday d toordinal date d year 1 1 toordinal 1 is the day number within the current year starting with 1 for January 1st The tm_isdst flag of the result is set according to the dst method tzinfo is None or dst returns None tm_isdst is set to 1 else if dst returns a non zero value tm_isdst is set to 1 else tm_isdst is set to 0 datetime utctimetuple If datetime instance d is naive this is the same as d timetuple except that tm_isdst is forced to 0 regardless of what d dst returns DST is never in effect for a UTC time If d is aware d is normalized to UTC time by subtracting d utcoffset and a time struct_time for the normalized time is returned tm_isdst is forced to 0 Note that an OverflowError may be raised if d year was MINYEAR or MAXYEAR and UTC adjustment spills over a year boundary Warning Because naive datetime objects are treated by many datetime methods as local times it is preferred to use aware datetimes to represent times in UTC as a result using datetime utctimetuple may give misleading results If you have a naive datetime representing UTC use datetime replace tzinfo timezone utc to make it aware at which point you can use datetime timetuple datetime toordinal Return the proleptic Gregorian ordinal of the date The same as self date toordinal datetime timestamp Return POSIX timestamp corresponding to the datetime instance The return value is a float similar to that returned by time time Naive datetime instances are assumed to represent local time and this method relies on the platform C mktime function to perform the conversion Since datetime supports wider range of values than mktime on many platforms this method may raise OverflowError or OSError for times far in the past or far in the future For aware datetime instances the return value is computed as dt datetime 1970 1 1 tzinfo timezone utc total_seconds New in version 3 3 Changed in version 3 6 The timestamp method uses the fold attribute to disambiguate the times during a repeated interval Note There is no method to obtain the POSIX timestamp directly from a naive datetime instance representing UTC time If your application uses this convention and your system timezone is not set to UTC you can obtain the POSIX timestamp by supplying tzinfo timezone utc timestamp dt replace tzinfo timezone utc timestamp or by calculating the timestamp directly timestamp dt datetime 1970 1 1 timedelta seconds 1 datetime weekday Return the day of the week as an integer where Monday is 0 and Sunday is 6 The same as self date weekday See,en
90, also isoweekday datetime isoweekday Return the day of the week as an integer where Monday is 1 and Sunday is 7 The same as self date isoweekday See also weekday isocalendar datetime isocalendar Return a named tuple with three components year week and weekday The same as self date isocalendar datetime isoformat sep T timespec auto Return a string representing the date and time in ISO 8601 format YYYY MM DDTHH MM SS ffffff if microsecond is not 0 YYYY MM DDTHH MM SS if microsecond is 0 If utcoffset does not return None a string is appended giving the UTC offset YYYY MM DDTHH MM SS ffffff HH MM SS ffffff if microsecond is not 0 YYYY MM DDTHH MM SS HH MM SS ffffff if microsecond is 0 Examples from datetime import datetime timezone datetime 2019 5 18 15 17 8 132263 isoformat 2019 05 18T15 17 08 132263 datetime 2019 5 18 15 17 tzinfo timezone utc isoformat 2019 05 18T15 17 00 00 00 The optional argument sep default T is a one character separator placed between the date and time portions of the result For example from datetime import tzinfo timedelta datetime class TZ tzinfo A time zone with an arbitrary constant 06 39 offset def utcoffset self dt return timedelta hours 6 minutes 39 datetime 2002 12 25 tzinfo TZ isoformat 2002 12 25 00 00 00 06 39 datetime 2009 11 27 microsecond 100 tzinfo TZ isoformat 2009 11 27T00 00 00 000100 06 39 The optional argument timespec specifies the number of additional components of the time to include the default is auto It can be one of the following auto Same as seconds if microsecond is 0 same as microseconds otherwise hours Include the hour in the two digit HH format minutes Include hour and minute in HH MM format seconds Include hour minute and second in HH MM SS format milliseconds Include full time but truncate fractional second part to milliseconds HH MM SS sss format microseconds Include full time in HH MM SS ffffff format Note Excluded time components are truncated not rounded ValueError will be raised on an invalid timespec argument from datetime import datetime datetime now isoformat timespec minutes 2002 12 25T00 00 dt datetime 2015 1 1 12 30 59 0 dt isoformat timespec microseconds 2015 01 01T12 30 59 000000 Changed in version 3 6 Added the timespec parameter datetime __str__ For a datetime instance d str d is equivalent to d isoformat datetime ctime Return a string representing the date and time from datetime import datetime datetime 2002 12 4 20 30 40 ctime Wed Dec 4 20 30 40 2002 The output string will not include time zone information regardless of whether the input is aware or naive d ctime is equivalent to time ctime time mktime d timetuple on platforms where the native C ctime function which time ctime invokes but which datetime ctime does not invoke conforms to the C standard datetime strftime format Return a string representing the date and time controlled by an explicit format string See also strftime and strptime Behavior and datetime isoformat datetime __format__ format Same as datetime strftime This makes it possible to specify a format string for a datetime object in formatted string literals and when using str format See also strftime and strptime Behavior and datetime isoformat Examples of Usage datetime Examples of working with datetime objects from datetime import datetime date time timezone Using datetime combine d date 2005 7 14 t time 12 30 datetime combine d t datetime datetime 2005 7 14 12 30 Using datetime now datetime now datetime datetime 2007 12 6 16 29 43 79043 GMT 1 datetime now timezone utc datetime datetime 2007 12 6 15 29 43 79060 tzinfo datetime timezone utc Using datetime strptime dt datetime strptime 21 11 06 16 30 d m y H M dt datetime datetime 2006 11 21 16 30 Using datetime timetuple to get tuple of all attributes tt dt timetuple for it in tt print it 2006 year 11 month 21 day 16 hour 30 minute 0 second 1 weekday 0 Monday 325 number of days since 1st January 1 dst method tzinfo dst returned None Date in ISO format ic dt isocalendar for it in ic print it 2006 ISO year 47 ISO week 2 ISO weekday Formatting a datetime dt strftime A d B Y I M p Tuesd,en
91,ay 21 November 2006 04 30PM The 1 is 0 d the 2 is 0 B the 3 is 0 I M p format dt day month time The day is 21 the month is November the time is 04 30PM The example below defines a tzinfo subclass capturing time zone information for Kabul Afghanistan which used 4 UTC until 1945 and then 4 30 UTC thereafter from datetime import timedelta datetime tzinfo timezone class KabulTz tzinfo Kabul used 4 until 1945 when they moved to 4 30 UTC_MOVE_DATE datetime 1944 12 31 20 tzinfo timezone utc def utcoffset self dt if dt year 1945 return timedelta hours 4 elif 1945 1 1 0 0 dt timetuple 5 1945 1 1 0 30 An ambiguous imaginary half hour range representing a fold in time due to the shift from 4 to 4 30 If dt falls in the imaginary range use fold to decide how to resolve See PEP495 return timedelta hours 4 minutes 30 if dt fold else 0 else return timedelta hours 4 minutes 30 def fromutc self dt Follow same validations as in datetime tzinfo if not isinstance dt datetime raise TypeError fromutc requires a datetime argument if dt tzinfo is not self raise ValueError dt tzinfo is not self A custom implementation is required for fromutc as the input to this function is a datetime with utc values but with a tzinfo set to self See datetime astimezone or fromtimestamp if dt replace tzinfo timezone utc self UTC_MOVE_DATE return dt timedelta hours 4 minutes 30 else return dt timedelta hours 4 def dst self dt Kabul does not observe daylight saving time return timedelta 0 def tzname self dt if dt self UTC_MOVE_DATE return 04 30 return 04 Usage of KabulTz from above tz1 KabulTz Datetime before the change dt1 datetime 1900 11 21 16 30 tzinfo tz1 print dt1 utcoffset 4 00 00 Datetime after the change dt2 datetime 2006 6 14 13 0 tzinfo tz1 print dt2 utcoffset 4 30 00 Convert datetime to another time zone dt3 dt2 astimezone timezone utc dt3 datetime datetime 2006 6 14 8 30 tzinfo datetime timezone utc dt2 datetime datetime 2006 6 14 13 0 tzinfo KabulTz dt2 dt3 True time Objects A time object represents a local time of day independent of any particular day and subject to adjustment via a tzinfo object class datetime time hour 0 minute 0 second 0 microsecond 0 tzinfo None fold 0 All arguments are optional tzinfo may be None or an instance of a tzinfo subclass The remaining arguments must be integers in the following ranges 0 hour 24 0 minute 60 0 second 60 0 microsecond 1000000 fold in 0 1 If an argument outside those ranges is given ValueError is raised All default to 0 except tzinfo which defaults to None Class attributes time min The earliest representable time time 0 0 0 0 time max The latest representable time time 23 59 59 999999 time resolution The smallest possible difference between non equal time objects timedelta microseconds 1 although note that arithmetic on time objects is not supported Instance attributes read only time hour In range 24 time minute In range 60 time second In range 60 time microsecond In range 1000000 time tzinfo The object passed as the tzinfo argument to the time constructor or None if none was passed time fold In 0 1 Used to disambiguate wall times during a repeated interval A repeated interval occurs when clocks are rolled back at the end of daylight saving time or when the UTC offset for the current zone is decreased for political reasons The value 0 1 represents the earlier later of the two moments with the same wall time representation New in version 3 6 time objects support equality and order comparisons where a is considered less than b when a precedes b in time Naive and aware time objects are never equal Order comparison between naive and aware time objects raises TypeError If both comparands are aware and have the same tzinfo attribute the tzinfo and fold attributes are ignored and the base times are compared If both comparands are aware and have different tzinfo attributes the comparands are first adjusted by subtracting their UTC offsets obtained from self utcoffset Changed in version 3 3 Equality comparisons between aware and naive time instances don t raise TypeError In Boolean contexts a time object is always,en
92, considered to be true Changed in version 3 5 Before Python 3 5 a time object was considered to be false if it represented midnight in UTC This behavior was considered obscure and error prone and has been removed in Python 3 5 See bpo 13936 for full details Other constructor classmethod time fromisoformat time_string Return a time corresponding to a time_string in any valid ISO 8601 format with the following exceptions 1 Time zone offsets may have fractional seconds 2 The leading T normally required in cases where there may be ambiguity between a date and a time is not required 3 Fractional seconds may have any number of digits anything beyond 6 will be truncated 4 Fractional hours and minutes are not supported Examples from datetime import time time fromisoformat 04 23 01 datetime time 4 23 1 time fromisoformat T04 23 01 datetime time 4 23 1 time fromisoformat T042301 datetime time 4 23 1 time fromisoformat 04 23 01 000384 datetime time 4 23 1 384 time fromisoformat 04 23 01 000384 datetime time 4 23 1 384 time fromisoformat 04 23 01 04 00 datetime time 4 23 1 tzinfo datetime timezone datetime timedelta seconds 14400 time fromisoformat 04 23 01Z datetime time 4 23 1 tzinfo datetime timezone utc time fromisoformat 04 23 01 00 00 datetime time 4 23 1 tzinfo datetime timezone utc New in version 3 7 Changed in version 3 11 Previously this method only supported formats that could be emitted by time isoformat Instance methods time replace hour self hour minute self minute second self second microsecond self microsecond tzinfo self tzinfo fold 0 Return a time with the same value except for those attributes given new values by whichever keyword arguments are specified Note that tzinfo None can be specified to create a naive time from an aware time without conversion of the time data Changed in version 3 6 Added the fold parameter time isoformat timespec auto Return a string representing the time in ISO 8601 format one of HH MM SS ffffff if microsecond is not 0 HH MM SS if microsecond is 0 HH MM SS ffffff HH MM SS ffffff if utcoffset does not return None HH MM SS HH MM SS ffffff if microsecond is 0 and utcoffset does not return None The optional argument timespec specifies the number of additional components of the time to include the default is auto It can be one of the following auto Same as seconds if microsecond is 0 same as microseconds otherwise hours Include the hour in the two digit HH format minutes Include hour and minute in HH MM format seconds Include hour minute and second in HH MM SS format milliseconds Include full time but truncate fractional second part to milliseconds HH MM SS sss format microseconds Include full time in HH MM SS ffffff format Note Excluded time components are truncated not rounded ValueError will be raised on an invalid timespec argument Example from datetime import time time hour 12 minute 34 second 56 microsecond 123456 isoformat timespec minutes 12 34 dt time hour 12 minute 34 second 56 microsecond 0 dt isoformat timespec microseconds 12 34 56 000000 dt isoformat timespec auto 12 34 56 Changed in version 3 6 Added the timespec parameter time __str__ For a time t str t is equivalent to t isoformat time strftime format Return a string representing the time controlled by an explicit format string See also strftime and strptime Behavior and time isoformat time __format__ format Same as time strftime This makes it possible to specify a format string for a time object in formatted string literals and when using str format See also strftime and strptime Behavior and time isoformat time utcoffset If tzinfo is None returns None else returns self tzinfo utcoffset None and raises an exception if the latter doesn t return None or a timedelta object with magnitude less than one day Changed in version 3 7 The UTC offset is not restricted to a whole number of minutes time dst If tzinfo is None returns None else returns self tzinfo dst None and raises an exception if the latter doesn t return None or a timedelta object with magnitude less than one day Changed in version 3 7 The DST offset is not restricted,en
93, to a whole number of minutes time tzname If tzinfo is None returns None else returns self tzinfo tzname None or raises an exception if the latter doesn t return None or a string object Examples of Usage time Examples of working with a time object from datetime import time tzinfo timedelta class TZ1 tzinfo def utcoffset self dt return timedelta hours 1 def dst self dt return timedelta 0 def tzname self dt return 01 00 def __repr__ self return f self __class__ __name__ t time 12 10 30 tzinfo TZ1 t datetime time 12 10 30 tzinfo TZ1 t isoformat 12 10 30 01 00 t dst datetime timedelta 0 t tzname 01 00 t strftime H M S Z 12 10 30 01 00 The is H M format time t The time is 12 10 tzinfo Objects class datetime tzinfo This is an abstract base class meaning that this class should not be instantiated directly Define a subclass of tzinfo to capture information about a particular time zone An instance of a concrete subclass of tzinfo can be passed to the constructors for datetime and time objects The latter objects view their attributes as being in local time and the tzinfo object supports methods revealing offset of local time from UTC the name of the time zone and DST offset all relative to a date or time object passed to them You need to derive a concrete subclass and at least supply implementations of the standard tzinfo methods needed by the datetime methods you use The datetime module provides timezone a simple concrete subclass of tzinfo which can represent timezones with fixed offset from UTC such as UTC itself or North American EST and EDT Special requirement for pickling A tzinfo subclass must have an __init__ method that can be called with no arguments otherwise it can be pickled but possibly not unpickled again This is a technical requirement that may be relaxed in the future A concrete subclass of tzinfo may need to implement the following methods Exactly which methods are needed depends on the uses made of aware datetime objects If in doubt simply implement all of them tzinfo utcoffset dt Return offset of local time from UTC as a timedelta object that is positive east of UTC If local time is west of UTC this should be negative This represents the total offset from UTC for example if a tzinfo object represents both time zone and DST adjustments utcoffset should return their sum If the UTC offset isn t known return None Else the value returned must be a timedelta object strictly between timedelta hours 24 and timedelta hours 24 the magnitude of the offset must be less than one day Most implementations of utcoffset will probably look like one of these two return CONSTANT fixed offset class return CONSTANT self dst dt daylight aware class If utcoffset does not return None dst should not return None either The default implementation of utcoffset raises NotImplementedError Changed in version 3 7 The UTC offset is not restricted to a whole number of minutes tzinfo dst dt Return the daylight saving time DST adjustment as a timedelta object or None if DST information isn t known Return timedelta 0 if DST is not in effect If DST is in effect return the offset as a timedelta object see utcoffset for details Note that DST offset if applicable has already been added to the UTC offset returned by utcoffset so there s no need to consult dst unless you re interested in obtaining DST info separately For example datetime timetuple calls its tzinfo attribute s dst method to determine how the tm_isdst flag should be set and tzinfo fromutc calls dst to account for DST changes when crossing time zones An instance tz of a tzinfo subclass that models both standard and daylight times must be consistent in this sense tz utcoffset dt tz dst dt must return the same result for every datetime dt with dt tzinfo tz For sane tzinfo subclasses this expression yields the time zone s standard offset which should not depend on the date or the time but only on geographic location The implementation of datetime astimezone relies on this but cannot detect violations it s the programmer s responsibility to ensure it If a tzinfo subclass cannot guarantee this i,en
94,t may be able to override the default implementation of tzinfo fromutc to work correctly with astimezone regardless Most implementations of dst will probably look like one of these two def dst self dt a fixed offset class doesn t account for DST return timedelta 0 or def dst self dt Code to set dston and dstoff to the time zone s DST transition times based on the input dt year and expressed in standard local time if dston dt replace tzinfo None dstoff return timedelta hours 1 else return timedelta 0 The default implementation of dst raises NotImplementedError Changed in version 3 7 The DST offset is not restricted to a whole number of minutes tzinfo tzname dt Return the time zone name corresponding to the datetime object dt as a string Nothing about string names is defined by the datetime module and there s no requirement that it mean anything in particular For example GMT UTC 500 5 00 EDT US Eastern America New York are all valid replies Return None if a string name isn t known Note that this is a method rather than a fixed string primarily because some tzinfo subclasses will wish to return different names depending on the specific value of dt passed especially if the tzinfo class is accounting for daylight time The default implementation of tzname raises NotImplementedError These methods are called by a datetime or time object in response to their methods of the same names A datetime object passes itself as the argument and a time object passes None as the argument A tzinfo subclass s methods should therefore be prepared to accept a dt argument of None or of class datetime When None is passed it s up to the class designer to decide the best response For example returning None is appropriate if the class wishes to say that time objects don t participate in the tzinfo protocols It may be more useful for utcoffset None to return the standard UTC offset as there is no other convention for discovering the standard offset When a datetime object is passed in response to a datetime method dt tzinfo is the same object as self tzinfo methods can rely on this unless user code calls tzinfo methods directly The intent is that the tzinfo methods interpret dt as being in local time and not need worry about objects in other timezones There is one more tzinfo method that a subclass may wish to override tzinfo fromutc dt This is called from the default datetime astimezone implementation When called from that dt tzinfo is self and dt s date and time data are to be viewed as expressing a UTC time The purpose of fromutc is to adjust the date and time data returning an equivalent datetime in self s local time Most tzinfo subclasses should be able to inherit the default fromutc implementation without problems It s strong enough to handle fixed offset time zones and time zones accounting for both standard and daylight time and the latter even if the DST transition times differ in different years An example of a time zone the default fromutc implementation may not handle correctly in all cases is one where the standard offset from UTC depends on the specific date and time passed which can happen for political reasons The default implementations of astimezone and fromutc may not produce the result you want if the result is one of the hours straddling the moment the standard offset changes Skipping code for error cases the default fromutc implementation acts like def fromutc self dt raise ValueError error if dt tzinfo is not self dtoff dt utcoffset dtdst dt dst raise ValueError if dtoff is None or dtdst is None delta dtoff dtdst this is self s standard offset if delta dt delta convert to standard local time dtdst dt dst raise ValueError if dtdst is None if dtdst return dt dtdst else return dt In the following tzinfo_examples py file there are some examples of tzinfo classes from datetime import tzinfo timedelta datetime ZERO timedelta 0 HOUR timedelta hours 1 SECOND timedelta seconds 1 A class capturing the platform s idea of local time May result in wrong values on historical times in timezones where UTC offset and or the DST rules had changed ,en
95,in the past import time as _time STDOFFSET timedelta seconds _time timezone if _time daylight DSTOFFSET timedelta seconds _time altzone else DSTOFFSET STDOFFSET DSTDIFF DSTOFFSET STDOFFSET class LocalTimezone tzinfo def fromutc self dt assert dt tzinfo is self stamp dt datetime 1970 1 1 tzinfo self SECOND args _time localtime stamp 6 dst_diff DSTDIFF SECOND Detect fold fold args _time localtime stamp dst_diff return datetime args microsecond dt microsecond tzinfo self fold fold def utcoffset self dt if self _isdst dt return DSTOFFSET else return STDOFFSET def dst self dt if self _isdst dt return DSTDIFF else return ZERO def tzname self dt return _time tzname self _isdst dt def _isdst self dt tt dt year dt month dt day dt hour dt minute dt second dt weekday 0 0 stamp _time mktime tt tt _time localtime stamp return tt tm_isdst 0 Local LocalTimezone A complete implementation of current DST rules for major US time zones def first_sunday_on_or_after dt days_to_go 6 dt weekday if days_to_go dt timedelta days_to_go return dt US DST Rules This is a simplified i e wrong for a few cases set of rules for US DST start and end times For a complete and up to date set of DST rules and timezone definitions visit the Olson Database or try pytz http www twinsun com tz tz link htm https sourceforge net projects pytz might not be up to date In the US since 2007 DST starts at 2am standard time on the second Sunday in March which is the first Sunday on or after Mar 8 DSTSTART_2007 datetime 1 3 8 2 and ends at 2am DST time on the first Sunday of Nov DSTEND_2007 datetime 1 11 1 2 From 1987 to 2006 DST used to start at 2am standard time on the first Sunday in April and to end at 2am DST time on the last Sunday of October which is the first Sunday on or after Oct 25 DSTSTART_1987_2006 datetime 1 4 1 2 DSTEND_1987_2006 datetime 1 10 25 2 From 1967 to 1986 DST used to start at 2am standard time on the last Sunday in April the one on or after April 24 and to end at 2am DST time on the last Sunday of October which is the first Sunday on or after Oct 25 DSTSTART_1967_1986 datetime 1 4 24 2 DSTEND_1967_1986 DSTEND_1987_2006 def us_dst_range year Find start and end times for US DST For years before 1967 return start end for no DST if 2006 year dststart dstend DSTSTART_2007 DSTEND_2007 elif 1986 year 2007 dststart dstend DSTSTART_1987_2006 DSTEND_1987_2006 elif 1966 year 1987 dststart dstend DSTSTART_1967_1986 DSTEND_1967_1986 else return datetime year 1 1 2 start first_sunday_on_or_after dststart replace year year end first_sunday_on_or_after dstend replace year year return start end class USTimeZone tzinfo def __init__ self hours reprname stdname dstname self stdoffset timedelta hours hours self reprname reprname self stdname stdname self dstname dstname def __repr__ self return self reprname def tzname self dt if self dst dt return self dstname else return self stdname def utcoffset self dt return self stdoffset self dst dt def dst self dt if dt is None or dt tzinfo is None An exception may be sensible here in one or both cases It depends on how you want to treat them The default fromutc implementation called by the default astimezone implementation passes a datetime with dt tzinfo is self return ZERO assert dt tzinfo is self start end us_dst_range dt year Can t compare naive to aware objects so strip the timezone from dt first dt dt replace tzinfo None if start HOUR dt end HOUR DST is in effect return HOUR if end HOUR dt end Fold an ambiguous hour use dt fold to disambiguate return ZERO if dt fold else HOUR if start dt start HOUR Gap a non existent hour reverse the fold rule return HOUR if dt fold else ZERO DST is off return ZERO def fromutc self dt assert dt tzinfo is self start end us_dst_range dt year start start replace tzinfo self end end replace tzinfo self std_time dt self stdoffset dst_time std_time HOUR if end dst_time end HOUR Repeated hour return std_time replace fold 1 if std_time start or dst_time end Standard time return std_time if start std_time end HOUR Daylight saving time return dst_time Eastern USTimeZone 5 Eastern EST EDT Central,en
96, USTimeZone 6 Central CST CDT Mountain USTimeZone 7 Mountain MST MDT Pacific USTimeZone 8 Pacific PST PDT Note that there are unavoidable subtleties twice per year in a tzinfo subclass accounting for both standard and daylight time at the DST transition points For concreteness consider US Eastern UTC 0500 where EDT begins the minute after 1 59 EST on the second Sunday in March and ends the minute after 1 59 EDT on the first Sunday in November UTC 3 MM 4 MM 5 MM 6 MM 7 MM 8 MM EST 22 MM 23 MM 0 MM 1 MM 2 MM 3 MM EDT 23 MM 0 MM 1 MM 2 MM 3 MM 4 MM start 22 MM 23 MM 0 MM 1 MM 3 MM 4 MM end 23 MM 0 MM 1 MM 1 MM 2 MM 3 MM When DST starts the start line the local wall clock leaps from 1 59 to 3 00 A wall time of the form 2 MM doesn t really make sense on that day so astimezone Eastern won t deliver a result with hour 2 on the day DST begins For example at the Spring forward transition of 2016 we get from datetime import datetime timezone from tzinfo_examples import HOUR Eastern u0 datetime 2016 3 13 5 tzinfo timezone utc for i in range 4 u u0 i HOUR t u astimezone Eastern print u time UTC t time t tzname 05 00 00 UTC 00 00 00 EST 06 00 00 UTC 01 00 00 EST 07 00 00 UTC 03 00 00 EDT 08 00 00 UTC 04 00 00 EDT When DST ends the end line there s a potentially worse problem there s an hour that can t be spelled unambiguously in local wall time the last hour of daylight time In Eastern that s times of the form 5 MM UTC on the day daylight time ends The local wall clock leaps from 1 59 daylight time back to 1 00 standard time again Local times of the form 1 MM are ambiguous astimezone mimics the local clock s behavior by mapping two adjacent UTC hours into the same local hour then In the Eastern example UTC times of the form 5 MM and 6 MM both map to 1 MM when converted to Eastern but earlier times have the fold attribute set to 0 and the later times have it set to 1 For example at the Fall back transition of 2016 we get u0 datetime 2016 11 6 4 tzinfo timezone utc for i in range 4 u u0 i HOUR t u astimezone Eastern print u time UTC t time t tzname t fold 04 00 00 UTC 00 00 00 EDT 0 05 00 00 UTC 01 00 00 EDT 0 06 00 00 UTC 01 00 00 EST 1 07 00 00 UTC 02 00 00 EST 0 Note that the datetime instances that differ only by the value of the fold attribute are considered equal in comparisons Applications that can t bear wall time ambiguities should explicitly check the value of the fold attribute or avoid using hybrid tzinfo subclasses there are no ambiguities when using timezone or any other fixed offset tzinfo subclass such as a class representing only EST fixed offset 5 hours or only EDT fixed offset 4 hours See also zoneinfo The datetime module has a basic timezone class for handling arbitrary fixed offsets from UTC and its timezone utc attribute a UTC timezone instance zoneinfo brings the IANA timezone database also known as the Olson database to Python and its usage is recommended IANA timezone database The Time Zone Database often called tz tzdata or zoneinfo contains code and data that represent the history of local time for many representative locations around the globe It is updated periodically to reflect changes made by political bodies to time zone boundaries UTC offsets and daylight saving rules timezone Objects The timezone class is a subclass of tzinfo each instance of which represents a timezone defined by a fixed offset from UTC Objects of this class cannot be used to represent timezone information in the locations where different offsets are used in different days of the year or where historical changes have been made to civil time class datetime timezone offset name None The offset argument must be specified as a timedelta object representing the difference between the local time and UTC It must be strictly between timedelta hours 24 and timedelta hours 24 otherwise ValueError is raised The name argument is optional If specified it must be a string that will be used as the value returned by the datetime tzname method New in version 3 2 Changed in version 3 7 The UTC offset is not restricted to a whole number of minutes time,en
97,zone utcoffset dt Return the fixed value specified when the timezone instance is constructed The dt argument is ignored The return value is a timedelta instance equal to the difference between the local time and UTC Changed in version 3 7 The UTC offset is not restricted to a whole number of minutes timezone tzname dt Return the fixed value specified when the timezone instance is constructed If name is not provided in the constructor the name returned by tzname dt is generated from the value of the offset as follows If offset is timedelta 0 the name is UTC otherwise it is a string in the format UTC HH MM where is the sign of offset HH and MM are two digits of offset hours and offset minutes respectively Changed in version 3 6 Name generated from offset timedelta 0 is now plain UTC not UTC 00 00 timezone dst dt Always returns None timezone fromutc dt Return dt offset The dt argument must be an aware datetime instance with tzinfo set to self Class attributes timezone utc The UTC timezone timezone timedelta 0 strftime and strptime Behavior date datetime and time objects all support a strftime format method to create a string representing the time under the control of an explicit format string Conversely the datetime strptime class method creates a datetime object from a string representing a date and time and a corresponding format string The table below provides a high level comparison of strftime versus strptime strftime strptime Usage Convert object to a string according to a given format Parse a string into a datetime object given a corresponding format Type of method Instance method Class method Method of date datetime time datetime Signature strftime format strptime date_string format strftime and strptime Format Codes These methods accept format codes that can be used to parse and format dates datetime strptime 31 01 22 23 59 59 999999 d m y H M S f datetime datetime 2022 1 31 23 59 59 999999 _ strftime a d b Y I M p Mon 31 Jan 2022 11 59PM The following is a list of all the format codes that the 1989 C standard requires and these work on all platforms with a standard C implementation Directive Meaning Example Notes a Weekday as locale s abbreviated Sun Mon Sat 1 name en_US So Mo Sa de_DE A Weekday as locale s full name Sunday Monday 1 Saturday en_US Sonntag Montag Samstag de_DE w Weekday as a decimal number 0 1 6 where 0 is Sunday and 6 is Saturday d Day of the month as a zero 01 02 31 9 padded decimal number b Month as locale s abbreviated Jan Feb Dec 1 name en_US Jan Feb Dez de_DE B Month as locale s full name January February 1 December en_US Januar Februar Dezember de_DE m Month as a zero padded decimal 01 02 12 9 number y Year without century as a zero 00 01 99 9 padded decimal number Y Year with century as a decimal 0001 0002 2013 2 number 2014 9998 9999 H Hour 24 hour clock as a zero 00 01 23 9 padded decimal number I Hour 12 hour clock as a zero 01 02 12 9 padded decimal number p Locale s equivalent of either AM AM PM en_US am pm 1 or PM de_DE 3 M Minute as a zero padded decimal 00 01 59 9 number S Second as a zero padded decimal 00 01 59 4 number 9 f Microsecond as a decimal number 000000 000001 5 zero padded to 6 digits 999999 z UTC offset in the form empty 0000 0400 6 HHMM SS ffffff empty 1030 063415 string if the object is naive 030712 345216 Z Time zone name empty string if empty UTC GMT 6 the object is naive j Day of the year as a zero padded 001 002 366 9 decimal number U Week number of the year Sunday 00 01 53 7 as the first day of the week as 9 a zero padded decimal number All days in a new year preceding the first Sunday are considered to be in week 0 W Week number of the year Monday 00 01 53 7 as the first day of the week as 9 a zero padded decimal number All days in a new year preceding the first Monday are considered to be in week 0 c Locale s appropriate date and Tue Aug 16 21 30 00 1988 1 time representation en_US Di 16 Aug 21 30 00 1988 de_DE x Locale s appropriate date 08 16 88 None 1 representation 08 16 1988 en_US 16 08 1988 de_DE X Locale s appropriate time 21 30 00 en_US 1 representation,en
98, 21 30 00 de_DE A literal character Several additional directives not required by the C89 standard are included for convenience These parameters all correspond to ISO 8601 date values Directive Meaning Example Notes G ISO 8601 year with century 0001 0002 2013 8 representing the year that 2014 9998 9999 contains the greater part of the ISO week V u ISO 8601 weekday as a decimal 1 2 7 number where 1 is Monday V ISO 8601 week as a decimal 01 02 53 8 number with Monday as the first 9 day of the week Week 01 is the week containing Jan 4 z UTC offset in the form empty 00 00 04 00 6 HH MM SS ffffff empty 10 30 06 34 15 string if the object is naive 03 07 12 345216 These may not be available on all platforms when used with the strftime method The ISO 8601 year and ISO 8601 week directives are not interchangeable with the year and week number directives above Calling strptime with incomplete or ambiguous ISO 8601 directives will raise a ValueError The full set of format codes supported varies across platforms because Python calls the platform C library s strftime function and platform variations are common To see the full set of format codes supported on your platform consult the strftime 3 documentation There are also differences between platforms in handling of unsupported format specifiers New in version 3 6 G u and V were added New in version 3 12 z was added Technical Detail Broadly speaking d strftime fmt acts like the time module s time strftime fmt d timetuple although not all objects support a timetuple method For the datetime strptime class method the default value is 1900 01 01T00 00 00 000 any components not specified in the format string will be pulled from the default value 4 Using datetime strptime date_string format is equivalent to datetime time strptime date_string format 0 6 except when the format includes sub second components or timezone offset information which are supported in datetime strptime but are discarded by time strptime For time objects the format codes for year month and day should not be used as time objects have no such values If they re used anyway 1900 is substituted for the year and 1 for the month and day For date objects the format codes for hours minutes seconds and microseconds should not be used as date objects have no such values If they re used anyway 0 is substituted for them For the same reason handling of format strings containing Unicode code points that can t be represented in the charset of the current locale is also platform dependent On some platforms such code points are preserved intact in the output while on others strftime may raise UnicodeError or return an empty string instead Notes 1 Because the format depends on the current locale care should be taken when making assumptions about the output value Field orderings will vary for example month day year versus day month year and the output may contain non ASCII characters 2 The strptime method can parse years in the full 1 9999 range but years 1000 must be zero filled to 4 digit width Changed in version 3 2 In previous versions strftime method was restricted to years 1900 Changed in version 3 3 In version 3 2 strftime method was restricted to years 1000 3 When used with the strptime method the p directive only affects the output hour field if the I directive is used to parse the hour 4 Unlike the time module the datetime module does not support leap seconds 5 When used with the strptime method the f directive accepts from one to six digits and zero pads on the right f is an extension to the set of format characters in the C standard but implemented separately in datetime objects and therefore always available 6 For a naive object the z z and Z format codes are replaced by empty strings For an aware object z utcoffset is transformed into a string of the form HHMM SS ffffff where HH is a 2 digit string giving the number of UTC offset hours MM is a 2 digit string giving the number of UTC offset minutes SS is a 2 digit string giving the number of UTC offset seconds and ffffff is a 6 digit string giving the number of UTC offset ,en
99,microseconds The ffffff part is omitted when the offset is a whole number of seconds and both the ffffff and the SS part is omitted when the offset is a whole number of minutes For example if utcoffset returns timedelta hours 3 minutes 30 z is replaced with the string 0330 Changed in version 3 7 The UTC offset is not restricted to a whole number of minutes Changed in version 3 7 When the z directive is provided to the strptime method the UTC offsets can have a colon as a separator between hours minutes and seconds For example 01 00 00 will be parsed as an offset of one hour In addition providing Z is identical to 00 00 z Behaves exactly as z but has a colon separator added between hours minutes and seconds Z In strftime Z is replaced by an empty string if tzname returns None otherwise Z is replaced by the returned value which must be a string strptime only accepts certain values for Z 1 any value in time tzname for your machine s locale 2 the hard coded values UTC and GMT So someone living in Japan may have JST UTC and GMT as valid values but probably not EST It will raise ValueError for invalid values Changed in version 3 2 When the z directive is provided to the strptime method an aware datetime object will be produced The tzinfo of the result will be set to a timezone instance 7 When used with the strptime method U and W are only used in calculations when the day of the week and the calendar year Y are specified 8 Similar to U and W V is only used in calculations when the day of the week and the ISO year G are specified in a strptime format string Also note that G and Y are not interchangeable 9 When used with the strptime method the leading zero is optional for formats d m H I M S j U W and V Format y does require a leading zero Footnotes 1 If that is we ignore the effects of Relativity 2 This matches the definition of the proleptic Gregorian calendar in Dershowitz and Reingold s book Calendrical Calculations where it s the base calendar for all computations See the book for algorithms for converting between proleptic Gregorian ordinals and many other calendar systems 3 See R H van Gent s guide to the mathematics of the ISO 8601 calendar for a good explanation 4 Passing datetime strptime Feb 29 b d will fail since 1900 is not a leap year,en
100,optparse Parser for command line options Source code Lib optparse py Deprecated since version 3 2 The optparse module is deprecated and will not be developed further development will continue with the argparse module optparse is a more convenient flexible and powerful library for parsing command line options than the old getopt module optparse uses a more declarative style of command line parsing you create an instance of OptionParser populate it with options and parse the command line optparse allows users to specify options in the conventional GNU POSIX syntax and additionally generates usage and help messages for you Here s an example of using optparse in a simple script from optparse import OptionParser parser OptionParser parser add_option f file dest filename help write report to FILE metavar FILE parser add_option q quiet action store_false dest verbose default True help don t print status messages to stdout options args parser parse_args With these few lines of code users of your script can now do the usual thing on the command line for example yourscript file outfile q As it parses the command line optparse sets attributes of the options object returned by parse_args based on user supplied command line values When parse_args returns from parsing this command line options filename will be outfile and options verbose will be False optparse supports both long and short options allows short options to be merged together and allows options to be associated with their arguments in a variety of ways Thus the following command lines are all equivalent to the above example yourscript f outfile quiet yourscript quiet file outfile yourscript q foutfile yourscript qfoutfile Additionally users can run one of the following yourscript h yourscript help and optparse will print out a brief summary of your script s options Usage yourscript options Options h help show this help message and exit f FILE file FILE write report to FILE q quiet don t print status messages to stdout where the value of yourscript is determined at runtime normally from sys argv 0 Background optparse was explicitly designed to encourage the creation of programs with straightforward conventional command line interfaces To that end it supports only the most common command line syntax and semantics conventionally used under Unix If you are unfamiliar with these conventions read this section to acquaint yourself with them Terminology argument a string entered on the command line and passed by the shell to execl or execv In Python arguments are elements of sys argv 1 sys argv 0 is the name of the program being executed Unix shells also use the term word It is occasionally desirable to substitute an argument list other than sys argv 1 so you should read argument as an element of sys argv 1 or of some other list provided as a substitute for sys argv 1 option an argument used to supply extra information to guide or customize the execution of a program There are many different syntaxes for options the traditional Unix syntax is a hyphen followed by a single letter e g x or F Also traditional Unix syntax allows multiple options to be merged into a single argument e g x F is equivalent to xF The GNU project introduced followed by a series of hyphen separated words e g file or dry run These are the only two option syntaxes provided by optparse Some other option syntaxes that the world has seen include a hyphen followed by a few letters e g pf this is not the same as multiple options merged into a single argument a hyphen followed by a whole word e g file this is technically equivalent to the previous syntax but they aren t usually seen in the same program a plus sign followed by a single letter or a few letters or a word e g f rgb a slash followed by a letter or a few letters or a word e g f file These option syntaxes are not supported by optparse and they never will be This is deliberate the first three are non standard on any environment and the last only makes sense if you re exclusively targeting Windows or certain legacy platforms e g VMS MS DOS option argument a,en
101,n argument that follows an option is closely associated with that option and is consumed from the argument list when that option is With optparse option arguments may either be in a separate argument from their option f foo file foo or included in the same argument ffoo file foo Typically a given option either takes an argument or it doesn t Lots of people want an optional option arguments feature meaning that some options will take an argument if they see it and won t if they don t This is somewhat controversial because it makes parsing ambiguous if a takes an optional argument and b is another option entirely how do we interpret ab Because of this ambiguity optparse does not support this feature positional argument something leftover in the argument list after options have been parsed i e after options and their arguments have been parsed and removed from the argument list required option an option that must be supplied on the command line note that the phrase required option is self contradictory in English optparse doesn t prevent you from implementing required options but doesn t give you much help at it either For example consider this hypothetical command line prog v report report txt foo bar v and report are both options Assuming that report takes one argument report txt is an option argument foo and bar are positional arguments What are options for Options are used to provide extra information to tune or customize the execution of a program In case it wasn t clear options are usually optional A program should be able to run just fine with no options whatsoever Pick a random program from the Unix or GNU toolsets Can it run without any options at all and still make sense The main exceptions are find tar and dd all of which are mutant oddballs that have been rightly criticized for their non standard syntax and confusing interfaces Lots of people want their programs to have required options Think about it If it s required then it s not optional If there is a piece of information that your program absolutely requires in order to run successfully that s what positional arguments are for As an example of good command line interface design consider the humble cp utility for copying files It doesn t make much sense to try to copy files without supplying a destination and at least one source Hence cp fails if you run it with no arguments However it has a flexible useful syntax that does not require any options at all cp SOURCE DEST cp SOURCE DEST DIR You can get pretty far with just that Most cp implementations provide a bunch of options to tweak exactly how the files are copied you can preserve mode and modification time avoid following symlinks ask before clobbering existing files etc But none of this distracts from the core mission of cp which is to copy either one file to another or several files to another directory What are positional arguments for Positional arguments are for those pieces of information that your program absolutely positively requires to run A good user interface should have as few absolute requirements as possible If your program requires 17 distinct pieces of information in order to run successfully it doesn t much matter how you get that information from the user most people will give up and walk away before they successfully run the program This applies whether the user interface is a command line a configuration file or a GUI if you make that many demands on your users most of them will simply give up In short try to minimize the amount of information that users are absolutely required to supply use sensible defaults whenever possible Of course you also want to make your programs reasonably flexible That s what options are for Again it doesn t matter if they are entries in a config file widgets in the Preferences dialog of a GUI or command line options the more options you implement the more flexible your program is and the more complicated its implementation becomes Too much flexibility has drawbacks as well of course too many options can overwhelm users and make your code much harder to main,en
102,tain Tutorial While optparse is quite flexible and powerful it s also straightforward to use in most cases This section covers the code patterns that are common to any optparse based program First you need to import the OptionParser class then early in the main program create an OptionParser instance from optparse import OptionParser parser OptionParser Then you can start defining options The basic syntax is parser add_option opt_str attr value Each option has one or more option strings such as f or file and several option attributes that tell optparse what to expect and what to do when it encounters that option on the command line Typically each option will have one short option string and one long option string e g parser add_option f file You re free to define as many short option strings and as many long option strings as you like including zero as long as there is at least one option string overall The option strings passed to OptionParser add_option are effectively labels for the option defined by that call For brevity we will frequently refer to encountering an option on the command line in reality optparse encounters option strings and looks up options from them Once all of your options are defined instruct optparse to parse your program s command line options args parser parse_args If you like you can pass a custom argument list to parse_args but that s rarely necessary by default it uses sys argv 1 parse_args returns two values options an object containing values for all of your options e g if file takes a single string argument then options file will be the filename supplied by the user or None if the user did not supply that option args the list of positional arguments leftover after parsing options This tutorial section only covers the four most important option attributes action type dest destination and help Of these action is the most fundamental Understanding option actions Actions tell optparse what to do when it encounters an option on the command line There is a fixed set of actions hard coded into optparse adding new actions is an advanced topic covered in section Extending optparse Most actions tell optparse to store a value in some variable for example take a string from the command line and store it in an attribute of options If you don t specify an option action optparse defaults to store The store action The most common option action is store which tells optparse to take the next argument or the remainder of the current argument ensure that it is of the correct type and store it to your chosen destination For example parser add_option f file action store type string dest filename Now let s make up a fake command line and ask optparse to parse it args f foo txt options args parser parse_args args When optparse sees the option string f it consumes the next argument foo txt and stores it in options filename So after this call to parse_args options filename is foo txt Some other option types supported by optparse are int and float Here s an option that expects an integer argument parser add_option n type int dest num Note that this option has no long option string which is perfectly acceptable Also there s no explicit action since the default is store Let s parse another fake command line This time we ll jam the option argument right up against the option since n42 one argument is equivalent to n 42 two arguments the code options args parser parse_args n42 print options num will print 42 If you don t specify a type optparse assumes string Combined with the fact that the default action is store that means our first example can be a lot shorter parser add_option f file dest filename If you don t supply a destination optparse figures out a sensible default from the option strings if the first long option string is foo bar then the default destination is foo_bar If there are no long option strings optparse looks at the first short option string the default destination for f is f optparse also includes the built in complex type Adding types is covered in section Extending optparse Handling boolean flag o,en
103,ptions Flag options set a variable to true or false when a particular option is seen are quite common optparse supports them with two separate actions store_true and store_false For example you might have a verbose flag that is turned on with v and off with q parser add_option v action store_true dest verbose parser add_option q action store_false dest verbose Here we have two different options with the same destination which is perfectly OK It just means you have to be a bit careful when setting default values see below When optparse encounters v on the command line it sets options verbose to True when it encounters q options verbose is set to False Other actions Some other actions supported by optparse are store_const store a constant value pre set via Option const append append this option s argument to a list count increment a counter by one callback call a specified function These are covered in section Reference Guide and section Option Callbacks Default values All of the above examples involve setting some variable the destination when certain command line options are seen What happens if those options are never seen Since we didn t supply any defaults they are all set to None This is usually fine but sometimes you want more control optparse lets you supply a default value for each destination which is assigned before the command line is parsed First consider the verbose quiet example If we want optparse to set verbose to True unless q is seen then we can do this parser add_option v action store_true dest verbose default True parser add_option q action store_false dest verbose Since default values apply to the destination rather than to any particular option and these two options happen to have the same destination this is exactly equivalent parser add_option v action store_true dest verbose parser add_option q action store_false dest verbose default True Consider this parser add_option v action store_true dest verbose default False parser add_option q action store_false dest verbose default True Again the default value for verbose will be True the last default value supplied for any particular destination is the one that counts A clearer way to specify default values is the set_defaults method of OptionParser which you can call at any time before calling parse_args parser set_defaults verbose True parser add_option options args parser parse_args As before the last value specified for a given option destination is the one that counts For clarity try to use one method or the other of setting default values not both Generating help optparse s ability to generate help and usage text automatically is useful for creating user friendly command line interfaces All you have to do is supply a help value for each option and optionally a short usage message for your whole program Here s an OptionParser populated with user friendly documented options usage usage prog options arg1 arg2 parser OptionParser usage usage parser add_option v verbose action store_true dest verbose default True help make lots of noise default parser add_option q quiet action store_false dest verbose help be vewwy quiet I m hunting wabbits parser add_option f filename metavar FILE help write output to FILE parser add_option m mode default intermediate help interaction mode novice intermediate or expert default default If optparse encounters either h or help on the command line or if you just call parser print_help it prints the following to standard output Usage yourscript options arg1 arg2 Options h help show this help message and exit v verbose make lots of noise default q quiet be vewwy quiet I m hunting wabbits f FILE filename FILE write output to FILE m MODE mode MODE interaction mode novice intermediate or expert default intermediate If the help output is triggered by a help option optparse exits after printing the help text There s a lot going on here to help optparse generate the best possible help message the script defines its own usage message usage usage prog options arg1 arg2 optparse expands prog in the usage string to the name of the cu,en
104,rrent program i e os path basename sys argv 0 The expanded string is then printed before the detailed option help If you don t supply a usage string optparse uses a bland but sensible default Usage prog options which is fine if your script doesn t take any positional arguments every option defines a help string and doesn t worry about line wrapping optparse takes care of wrapping lines and making the help output look good options that take a value indicate this fact in their automatically generated help message e g for the mode option m MODE mode MODE Here MODE is called the meta variable it stands for the argument that the user is expected to supply to m mode By default optparse converts the destination variable name to uppercase and uses that for the meta variable Sometimes that s not what you want for example the filename option explicitly sets metavar FILE resulting in this automatically generated option description f FILE filename FILE This is important for more than just saving space though the manually written help text uses the meta variable FILE to clue the user in that there s a connection between the semi formal syntax f FILE and the informal semantic description write output to FILE This is a simple but effective way to make your help text a lot clearer and more useful for end users options that have a default value can include default in the help string optparse will replace it with str of the option s default value If an option has no default value or the default value is None default expands to none Grouping Options When dealing with many options it is convenient to group these options for better help output An OptionParser can contain several option groups each of which can contain several options An option group is obtained using the class OptionGroup class optparse OptionGroup parser title description None where parser is the OptionParser instance the group will be inserted in to title is the group title description optional is a long description of the group OptionGroup inherits from OptionContainer like OptionParser and so the add_option method can be used to add an option to the group Once all the options are declared using the OptionParser method add_option_group the group is added to the previously defined parser Continuing with the parser defined in the previous section adding an OptionGroup to a parser is easy group OptionGroup parser Dangerous Options Caution use these options at your own risk It is believed that some of them bite group add_option g action store_true help Group option parser add_option_group group This would result in the following help output Usage yourscript options arg1 arg2 Options h help show this help message and exit v verbose make lots of noise default q quiet be vewwy quiet I m hunting wabbits f FILE filename FILE write output to FILE m MODE mode MODE interaction mode novice intermediate or expert default intermediate Dangerous Options Caution use these options at your own risk It is believed that some of them bite g Group option A bit more complete example might involve using more than one group still extending the previous example group OptionGroup parser Dangerous Options Caution use these options at your own risk It is believed that some of them bite group add_option g action store_true help Group option parser add_option_group group group OptionGroup parser Debug Options group add_option d debug action store_true help Print debug information group add_option s sql action store_true help Print all SQL statements executed group add_option e action store_true help Print every action done parser add_option_group group that results in the following output Usage yourscript options arg1 arg2 Options h help show this help message and exit v verbose make lots of noise default q quiet be vewwy quiet I m hunting wabbits f FILE filename FILE write output to FILE m MODE mode MODE interaction mode novice intermediate or expert default intermediate Dangerous Options Caution use these options at your own risk It is believed that some of them bite g Group option Debug Options d deb,en
105,ug Print debug information s sql Print all SQL statements executed e Print every action done Another interesting method in particular when working programmatically with option groups is OptionParser get_option_group opt_str Return the OptionGroup to which the short or long option string opt_str e g o or option belongs If there s no such OptionGroup return None Printing a version string Similar to the brief usage string optparse can also print a version string for your program You have to supply the string as the version argument to OptionParser parser OptionParser usage prog f q version prog 1 0 prog is expanded just like it is in usage Apart from that version can contain anything you like When you supply it optparse automatically adds a version option to your parser If it encounters this option on the command line it expands your version string by replacing prog prints it to stdout and exits For example if your script is called usr bin foo usr bin foo version foo 1 0 The following two methods can be used to print and get the version string OptionParser print_version file None Print the version message for the current program self version to file default stdout As with print_usage any occurrence of prog in self version is replaced with the name of the current program Does nothing if self version is empty or undefined OptionParser get_version Same as print_version but returns the version string instead of printing it How optparse handles errors There are two broad classes of errors that optparse has to worry about programmer errors and user errors Programmer errors are usually erroneous calls to OptionParser add_option e g invalid option strings unknown option attributes missing option attributes etc These are dealt with in the usual way raise an exception either optparse OptionError or TypeError and let the program crash Handling user errors is much more important since they are guaranteed to happen no matter how stable your code is optparse can automatically detect some user errors such as bad option arguments passing n 4x where n takes an integer argument missing arguments n at the end of the command line where n takes an argument of any type Also you can call OptionParser error to signal an application defined error condition options args parser parse_args if options a and options b parser error options a and b are mutually exclusive In either case optparse handles the error the same way it prints the program s usage message and an error message to standard error and exits with error status 2 Consider the first example above where the user passes 4x to an option that takes an integer usr bin foo n 4x Usage foo options foo error option n invalid integer value 4x Or where the user fails to pass a value at all usr bin foo n Usage foo options foo error n option requires an argument optparse generated error messages take care always to mention the option involved in the error be sure to do the same when calling OptionParser error from your application code If optparse s default error handling behaviour does not suit your needs you ll need to subclass OptionParser and override its exit and or error methods Putting it all together Here s what optparse based scripts usually look like from optparse import OptionParser def main usage usage prog options arg parser OptionParser usage parser add_option f file dest filename help read data from FILENAME parser add_option v verbose action store_true dest verbose parser add_option q quiet action store_false dest verbose options args parser parse_args if len args 1 parser error incorrect number of arguments if options verbose print reading s options filename if __name__ __main__ main Reference Guide Creating the parser The first step in using optparse is to create an OptionParser instance class optparse OptionParser The OptionParser constructor has no required arguments but a number of optional keyword arguments You should always pass them as keyword arguments i e do not rely on the order in which the arguments are declared usage default prog options The usage summary to print when you,en
106,r program is run incorrectly or with a help option When optparse prints the usage string it expands prog to os path basename sys argv 0 or to prog if you passed that keyword argument To suppress a usage message pass the special value optparse SUPPRESS_USAGE option_list default A list of Option objects to populate the parser with The options in option_list are added after any options in standard_option_list a class attribute that may be set by OptionParser subclasses but before any version or help options Deprecated use add_option after creating the parser instead option_class default optparse Option Class to use when adding options to the parser in add_option version default None A version string to print when the user supplies a version option If you supply a true value for version optparse automatically adds a version option with the single option string version The substring prog is expanded the same as for usage conflict_handler default error Specifies what to do when options with conflicting option strings are added to the parser see section Conflicts between options description default None A paragraph of text giving a brief overview of your program optparse reformats this paragraph to fit the current terminal width and prints it when the user requests help after usage but before the list of options formatter default a new IndentedHelpFormatter An instance of optparse HelpFormatter that will be used for printing help text optparse provides two concrete classes for this purpose IndentedHelpFormatter and TitledHelpFormatter add_help_option default True If true optparse will add a help option with option strings h and help to the parser prog The string to use when expanding prog in usage and version instead of os path basename sys argv 0 epilog default None A paragraph of help text to print after the option help Populating the parser There are several ways to populate the parser with options The preferred way is by using OptionParser add_option as shown in section Tutorial add_option can be called in one of two ways pass it an Option instance as returned by make_option pass it any combination of positional and keyword arguments that are acceptable to make_option i e to the Option constructor and it will create the Option instance for you The other alternative is to pass a list of pre constructed Option instances to the OptionParser constructor as in option_list make_option f filename action store type string dest filename make_option q quiet action store_false dest verbose parser OptionParser option_list option_list make_option is a factory function for creating Option instances currently it is an alias for the Option constructor A future version of optparse may split Option into several classes and make_option will pick the right class to instantiate Do not instantiate Option directly Defining options Each Option instance represents a set of synonymous command line option strings e g f and file You can specify any number of short or long option strings but you must specify at least one overall option string The canonical way to create an Option instance is with the add_option method of OptionParser OptionParser add_option option OptionParser add_option opt_str attr value To define an option with only a short option string parser add_option f attr value And to define an option with only a long option string parser add_option foo attr value The keyword arguments define attributes of the new Option object The most important option attribute is action and it largely determines which other attributes are relevant or required If you pass irrelevant option attributes or fail to pass required ones optparse raises an OptionError exception explaining your mistake An option s action determines what optparse does when it encounters this option on the command line The standard option actions hard coded into optparse are store store this option s argument default store_const store a constant value pre set via Option const store_true store True store_false store False append append this option s argument to a list append_const appe,en
107,nd a constant value to a list pre set via Option const count increment a counter by one callback call a specified function help print a usage message including all options and the documentation for them If you don t supply an action the default is store For this action you may also supply type and dest option attributes see Standard option actions As you can see most actions involve storing or updating a value somewhere optparse always creates a special object for this conventionally called options which is an instance of optparse Values class optparse Values An object holding parsed argument names and values as attributes Normally created by calling when calling OptionParser parse_args and can be overridden by a custom subclass passed to the values argument of OptionParser parse_args as described in Parsing arguments Option arguments and various other values are stored as attributes of this object according to the dest destination option attribute For example when you call parser parse_args one of the first things optparse does is create the options object options Values If one of the options in this parser is defined with parser add_option f file action store type string dest filename and the command line being parsed includes any of the following ffoo f foo file foo file foo then optparse on seeing this option will do the equivalent of options filename foo The type and dest option attributes are almost as important as action but action is the only one that makes sense for all options Option attributes class optparse Option A single command line argument with various attributes passed by keyword to the constructor Normally created with OptionParser add_option rather than directly and can be overridden by a custom class via the option_class argument to OptionParser The following option attributes may be passed as keyword arguments to OptionParser add_option If you pass an option attribute that is not relevant to a particular option or fail to pass a required option attribute optparse raises OptionError Option action default store Determines optparse s behaviour when this option is seen on the command line the available options are documented here Option type default string The argument type expected by this option e g string or int the available option types are documented here Option dest default derived from option strings If the option s action implies writing or modifying a value somewhere this tells optparse where to write it dest names an attribute of the options object that optparse builds as it parses the command line Option default The value to use for this option s destination if the option is not seen on the command line See also OptionParser set_defaults Option nargs default 1 How many arguments of type type should be consumed when this option is seen If 1 optparse will store a tuple of values to dest Option const For actions that store a constant value the constant value to store Option choices For options of type choice the list of strings the user may choose from Option callback For options with action callback the callable to call when this option is seen See section Option Callbacks for detail on the arguments passed to the callable Option callback_args Option callback_kwargs Additional positional and keyword arguments to pass to callback after the four standard callback arguments Option help Help text to print for this option when listing all available options after the user supplies a help option such as help If no help text is supplied the option will be listed without help text To hide this option use the special value optparse SUPPRESS_HELP Option metavar default derived from option strings Stand in for the option argument s to use when printing help text See section Tutorial for an example Standard option actions The various option actions all have slightly different requirements and effects Most actions have several relevant option attributes which you may specify to guide optparse s behaviour a few have required attributes which you must specify for any option using that action store relevant ty,en
108,pe dest nargs choices The option must be followed by an argument which is converted to a value according to type and stored in dest If nargs 1 multiple arguments will be consumed from the command line all will be converted according to type and stored to dest as a tuple See the Standard option types section If choices is supplied a list or tuple of strings the type defaults to choice If type is not supplied it defaults to string If dest is not supplied optparse derives a destination from the first long option string e g foo bar implies foo_bar If there are no long option strings optparse derives a destination from the first short option string e g f implies f Example parser add_option f parser add_option p type float nargs 3 dest point As it parses the command line f foo txt p 1 3 5 4 fbar txt optparse will set options f foo txt options point 1 0 3 5 4 0 options f bar txt store_const required const relevant dest The value const is stored in dest Example parser add_option q quiet action store_const const 0 dest verbose parser add_option v verbose action store_const const 1 dest verbose parser add_option noisy action store_const const 2 dest verbose If noisy is seen optparse will set options verbose 2 store_true relevant dest A special case of store_const that stores True to dest store_false relevant dest Like store_true but stores False Example parser add_option clobber action store_true dest clobber parser add_option no clobber action store_false dest clobber append relevant type dest nargs choices The option must be followed by an argument which is appended to the list in dest If no default value for dest is supplied an empty list is automatically created when optparse first encounters this option on the command line If nargs 1 multiple arguments are consumed and a tuple of length nargs is appended to dest The defaults for type and dest are the same as for the store action Example parser add_option t tracks action append type int If t3 is seen on the command line optparse does the equivalent of options tracks options tracks append int 3 If a little later on tracks 4 is seen it does options tracks append int 4 The append action calls the append method on the current value of the option This means that any default value specified must have an append method It also means that if the default value is non empty the default elements will be present in the parsed value for the option with any values from the command line appended after those default values parser add_option files action append default mypkg defaults opts args parser parse_args files overrides mypkg opts files mypkg defaults overrides mypkg append_const required const relevant dest Like store_const but the value const is appended to dest as with append dest defaults to None and an empty list is automatically created the first time the option is encountered count relevant dest Increment the integer stored at dest If no default value is supplied dest is set to zero before being incremented the first time Example parser add_option v action count dest verbosity The first time v is seen on the command line optparse does the equivalent of options verbosity 0 options verbosity 1 Every subsequent occurrence of v results in options verbosity 1 callback required callback relevant type nargs callback_args callback_kwargs Call the function specified by callback which is called as func option opt_str value parser args kwargs See section Option Callbacks for more detail help Prints a complete help message for all the options in the current option parser The help message is constructed from the usage string passed to OptionParser s constructor and the help string passed to every option If no help string is supplied for an option it will still be listed in the help message To omit an option entirely use the special value optparse SUPPRESS_HELP optparse automatically adds a help option to all OptionParsers so you do not normally need to create one Example from optparse import OptionParser SUPPRESS_HELP usually a help option is added automatically but that can be suppressed usin,en
109,g the add_help_option argument parser OptionParser add_help_option False parser add_option h help action help parser add_option v action store_true dest verbose help Be moderately verbose parser add_option file dest filename help Input file to read data from parser add_option secret help SUPPRESS_HELP If optparse sees either h or help on the command line it will print something like the following help message to stdout assuming sys argv 0 is foo py Usage foo py options Options h help Show this help message and exit v Be moderately verbose file FILENAME Input file to read data from After printing the help message optparse terminates your process with sys exit 0 version Prints the version number supplied to the OptionParser to stdout and exits The version number is actually formatted and printed by the print_version method of OptionParser Generally only relevant if the version argument is supplied to the OptionParser constructor As with help options you will rarely create version options since optparse automatically adds them when needed Standard option types optparse has five built in option types string int choice float and complex If you need to add new option types see section Extending optparse Arguments to string options are not checked or converted in any way the text on the command line is stored in the destination or passed to the callback as is Integer arguments type int are parsed as follows if the number starts with 0x it is parsed as a hexadecimal number if the number starts with 0 it is parsed as an octal number if the number starts with 0b it is parsed as a binary number otherwise the number is parsed as a decimal number The conversion is done by calling int with the appropriate base 2 8 10 or 16 If this fails so will optparse although with a more useful error message float and complex option arguments are converted directly with float and complex with similar error handling choice options are a subtype of string options The choices option attribute a sequence of strings defines the set of allowed option arguments optparse check_choice compares user supplied option arguments against this master list and raises OptionValueError if an invalid string is given Parsing arguments The whole point of creating and populating an OptionParser is to call its parse_args method OptionParser parse_args args None values None Parse the command line options found in args The input parameters are args the list of arguments to process default sys argv 1 values an Values object to store option arguments in default a new instance of Values if you give an existing object the option defaults will not be initialized on it and the return value is a pair options args where options the same object that was passed in as values or the optparse Values instance created by optparse args the leftover positional arguments after all options have been processed The most common usage is to supply neither keyword argument If you supply values it will be modified with repeated setattr calls roughly one for every option argument stored to an option destination and returned by parse_args If parse_args encounters any errors in the argument list it calls the OptionParser s error method with an appropriate end user error message This ultimately terminates your process with an exit status of 2 the traditional Unix exit status for command line errors Querying and manipulating your option parser The default behavior of the option parser can be customized slightly and you can also poke around your option parser and see what s there OptionParser provides several methods to help you out OptionParser disable_interspersed_args Set parsing to stop on the first non option For example if a and b are both simple options that take no arguments optparse normally accepts this syntax prog a arg1 b arg2 and treats it as equivalent to prog a b arg1 arg2 To disable this feature call disable_interspersed_args This restores traditional Unix syntax where option parsing stops with the first non option argument Use this if you have a command processor which runs another comma,en
110,nd which has options of its own and you want to make sure these options don t get confused For example each command might have a different set of options OptionParser enable_interspersed_args Set parsing to not stop on the first non option allowing interspersing switches with command arguments This is the default behavior OptionParser get_option opt_str Returns the Option instance with the option string opt_str or None if no options have that option string OptionParser has_option opt_str Return True if the OptionParser has an option with option string opt_str e g q or verbose OptionParser remove_option opt_str If the OptionParser has an option corresponding to opt_str that option is removed If that option provided any other option strings all of those option strings become invalid If opt_str does not occur in any option belonging to this OptionParser raises ValueError Conflicts between options If you re not careful it s easy to define options with conflicting option strings parser add_option n dry run parser add_option n noisy This is particularly true if you ve defined your own OptionParser subclass with some standard options Every time you add an option optparse checks for conflicts with existing options If it finds any it invokes the current conflict handling mechanism You can set the conflict handling mechanism either in the constructor parser OptionParser conflict_handler handler or with a separate call parser set_conflict_handler handler The available conflict handlers are error default assume option conflicts are a programming error and raise OptionConflictError resolve resolve option conflicts intelligently see below As an example let s define an OptionParser that resolves conflicts intelligently and add conflicting options to it parser OptionParser conflict_handler resolve parser add_option n dry run help do no harm parser add_option n noisy help be noisy At this point optparse detects that a previously added option is already using the n option string Since conflict_handler is resolve it resolves the situation by removing n from the earlier option s list of option strings Now dry run is the only way for the user to activate that option If the user asks for help the help message will reflect that Options dry run do no harm n noisy be noisy It s possible to whittle away the option strings for a previously added option until there are none left and the user has no way of invoking that option from the command line In that case optparse removes that option completely so it doesn t show up in help text or anywhere else Carrying on with our existing OptionParser parser add_option dry run help new dry run option At this point the original n dry run option is no longer accessible so optparse removes it leaving this help text Options n noisy be noisy dry run new dry run option Cleanup OptionParser instances have several cyclic references This should not be a problem for Python s garbage collector but you may wish to break the cyclic references explicitly by calling destroy on your OptionParser once you are done with it This is particularly useful in long running applications where large object graphs are reachable from your OptionParser Other methods OptionParser supports several other public methods OptionParser set_usage usage Set the usage string according to the rules described above for the usage constructor keyword argument Passing None sets the default usage string use optparse SUPPRESS_USAGE to suppress a usage message OptionParser print_usage file None Print the usage message for the current program self usage to file default stdout Any occurrence of the string prog in self usage is replaced with the name of the current program Does nothing if self usage is empty or not defined OptionParser get_usage Same as print_usage but returns the usage string instead of printing it OptionParser set_defaults dest value Set default values for several option destinations at once Using set_defaults is the preferred way to set default values for options since multiple options can share the same destination For example if severa,en
111,l mode options all set the same destination any one of them can set the default and the last one wins parser add_option advanced action store_const dest mode const advanced default novice overridden below parser add_option novice action store_const dest mode const novice default advanced overrides above setting To avoid this confusion use set_defaults parser set_defaults mode advanced parser add_option advanced action store_const dest mode const advanced parser add_option novice action store_const dest mode const novice Option Callbacks When optparse s built in actions and types aren t quite enough for your needs you have two choices extend optparse or define a callback option Extending optparse is more general but overkill for a lot of simple cases Quite often a simple callback is all you need There are two steps to defining a callback option define the option itself using the callback action write the callback this is a function or method that takes at least four arguments as described below Defining a callback option As always the easiest way to define a callback option is by using the OptionParser add_option method Apart from action the only option attribute you must specify is callback the function to call parser add_option c action callback callback my_callback callback is a function or other callable object so you must have already defined my_callback when you create this callback option In this simple case optparse doesn t even know if c takes any arguments which usually means that the option takes no arguments the mere presence of c on the command line is all it needs to know In some circumstances though you might want your callback to consume an arbitrary number of command line arguments This is where writing callbacks gets tricky it s covered later in this section optparse always passes four particular arguments to your callback and it will only pass additional arguments if you specify them via callback_args and callback_kwargs Thus the minimal callback function signature is def my_callback option opt value parser The four arguments to a callback are described below There are several other option attributes that you can supply when you define a callback option type has its usual meaning as with the store or append actions it instructs optparse to consume one argument and convert it to type Rather than storing the converted value s anywhere though optparse passes it to your callback function nargs also has its usual meaning if it is supplied and 1 optparse will consume nargs arguments each of which must be convertible to type It then passes a tuple of converted values to your callback callback_args a tuple of extra positional arguments to pass to the callback callback_kwargs a dictionary of extra keyword arguments to pass to the callback How callbacks are called All callbacks are called as follows func option opt_str value parser args kwargs where option is the Option instance that s calling the callback opt_str is the option string seen on the command line that s triggering the callback If an abbreviated long option was used opt_str will be the full canonical option string e g if the user puts foo on the command line as an abbreviation for foobar then opt_str will be foobar value is the argument to this option seen on the command line optparse will only expect an argument if type is set the type of value will be the type implied by the option s type If type for this option is None no argument expected then value will be None If nargs 1 value will be a tuple of values of the appropriate type parser is the OptionParser instance driving the whole thing mainly useful because you can access some other interesting data through its instance attributes parser largs the current list of leftover arguments ie arguments that have been consumed but are neither options nor option arguments Feel free to modify parser largs e g by adding more arguments to it This list will become args the second return value of parse_args parser rargs the current list of remaining arguments ie with opt_str and value if applicable removed and ,en
112,only the arguments following them still there Feel free to modify parser rargs e g by consuming more arguments parser values the object where option values are by default stored an instance of optparse OptionValues This lets callbacks use the same mechanism as the rest of optparse for storing option values you don t need to mess around with globals or closures You can also access or modify the value s of any options already encountered on the command line args is a tuple of arbitrary positional arguments supplied via the callback_args option attribute kwargs is a dictionary of arbitrary keyword arguments supplied via callback_kwargs Raising errors in a callback The callback function should raise OptionValueError if there are any problems with the option or its argument s optparse catches this and terminates the program printing the error message you supply to stderr Your message should be clear concise accurate and mention the option at fault Otherwise the user will have a hard time figuring out what they did wrong Callback example 1 trivial callback Here s an example of a callback option that takes no arguments and simply records that the option was seen def record_foo_seen option opt_str value parser parser values saw_foo True parser add_option foo action callback callback record_foo_seen Of course you could do that with the store_true action Callback example 2 check option order Here s a slightly more interesting example record the fact that a is seen but blow up if it comes after b in the command line def check_order option opt_str value parser if parser values b raise OptionValueError can t use a after b parser values a 1 parser add_option a action callback callback check_order parser add_option b action store_true dest b Callback example 3 check option order generalized If you want to re use this callback for several similar options set a flag but blow up if b has already been seen it needs a bit of work the error message and the flag that it sets must be generalized def check_order option opt_str value parser if parser values b raise OptionValueError can t use s after b opt_str setattr parser values option dest 1 parser add_option a action callback callback check_order dest a parser add_option b action store_true dest b parser add_option c action callback callback check_order dest c Callback example 4 check arbitrary condition Of course you could put any condition in there you re not limited to checking the values of already defined options For example if you have options that should not be called when the moon is full all you have to do is this def check_moon option opt_str value parser if is_moon_full raise OptionValueError s option invalid when moon is full opt_str setattr parser values option dest 1 parser add_option foo action callback callback check_moon dest foo The definition of is_moon_full is left as an exercise for the reader Callback example 5 fixed arguments Things get slightly more interesting when you define callback options that take a fixed number of arguments Specifying that a callback option takes arguments is similar to defining a store or append option if you define type then the option takes one argument that must be convertible to that type if you further define nargs then the option takes nargs arguments Here s an example that just emulates the standard store action def store_value option opt_str value parser setattr parser values option dest value parser add_option foo action callback callback store_value type int nargs 3 dest foo Note that optparse takes care of consuming 3 arguments and converting them to integers for you all you have to do is store them Or whatever obviously you don t need a callback for this example Callback example 6 variable arguments Things get hairy when you want an option to take a variable number of arguments For this case you must write a callback as optparse doesn t provide any built in capabilities for it And you have to deal with certain intricacies of conventional Unix command line parsing that optparse normally handles for you In particular callbacks should,en
113, implement the conventional rules for bare and arguments either or can be option arguments bare if not the argument to some option halt command line processing and discard the bare if not the argument to some option halt command line processing but keep the append it to parser largs If you want an option that takes a variable number of arguments there are several subtle tricky issues to worry about The exact implementation you choose will be based on which trade offs you re willing to make for your application which is why optparse doesn t support this sort of thing directly Nevertheless here s a stab at a callback for an option with variable arguments def vararg_callback option opt_str value parser assert value is None value def floatable str try float str return True except ValueError return False for arg in parser rargs stop on foo like options if arg 2 and len arg 2 break stop on a but not on 3 or 3 0 if arg 1 and len arg 1 and not floatable arg break value append arg del parser rargs len value setattr parser values option dest value parser add_option c callback dest vararg_attr action callback callback vararg_callback Extending optparse Since the two major controlling factors in how optparse interprets command line options are the action and type of each option the most likely direction of extension is to add new actions and new types Adding new types To add new types you need to define your own subclass of optparse s Option class This class has a couple of attributes that define optparse s types TYPES and TYPE_CHECKER Option TYPES A tuple of type names in your subclass simply define a new tuple TYPES that builds on the standard one Option TYPE_CHECKER A dictionary mapping type names to type checking functions A type checking function has the following signature def check_mytype option opt value where option is an Option instance opt is an option string e g f and value is the string from the command line that must be checked and converted to your desired type check_mytype should return an object of the hypothetical type mytype The value returned by a type checking function will wind up in the OptionValues instance returned by OptionParser parse_args or be passed to a callback as the value parameter Your type checking function should raise OptionValueError if it encounters any problems OptionValueError takes a single string argument which is passed as is to OptionParser s error method which in turn prepends the program name and the string error and prints everything to stderr before terminating the process Here s a silly example that demonstrates adding a complex option type to parse Python style complex numbers on the command line This is even sillier than it used to be because optparse 1 3 added built in support for complex numbers but never mind First the necessary imports from copy import copy from optparse import Option OptionValueError You need to define your type checker first since it s referred to later in the TYPE_CHECKER class attribute of your Option subclass def check_complex option opt value try return complex value except ValueError raise OptionValueError option s invalid complex value r opt value Finally the Option subclass class MyOption Option TYPES Option TYPES complex TYPE_CHECKER copy Option TYPE_CHECKER TYPE_CHECKER complex check_complex If we didn t make a copy of Option TYPE_CHECKER we would end up modifying the TYPE_CHECKER attribute of optparse s Option class This being Python nothing stops you from doing that except good manners and common sense That s it Now you can write a script that uses the new option type just like any other optparse based script except you have to instruct your OptionParser to use MyOption instead of Option parser OptionParser option_class MyOption parser add_option c type complex Alternately you can build your own option list and pass it to OptionParser if you don t use add_option in the above way you don t need to tell OptionParser which option class to use option_list MyOption c action store type complex dest c parser OptionParser option_list option_list Adding ne,en
114,w actions Adding new actions is a bit trickier because you have to understand that optparse has a couple of classifications for actions store actions actions that result in optparse storing a value to an attribute of the current OptionValues instance these options require a dest attribute to be supplied to the Option constructor typed actions actions that take a value from the command line and expect it to be of a certain type or rather a string that can be converted to a certain type These options require a type attribute to the Option constructor These are overlapping sets some default store actions are store store_const append and count while the default typed actions are store append and callback When you add an action you need to categorize it by listing it in at least one of the following class attributes of Option all are lists of strings Option ACTIONS All actions must be listed in ACTIONS Option STORE_ACTIONS store actions are additionally listed here Option TYPED_ACTIONS typed actions are additionally listed here Option ALWAYS_TYPED_ACTIONS Actions that always take a type i e whose options always take a value are additionally listed here The only effect of this is that optparse assigns the default type string to options with no explicit type whose action is listed in ALWAYS_TYPED_ACTIONS In order to actually implement your new action you must override Option s take_action method and add a case that recognizes your action For example let s add an extend action This is similar to the standard append action but instead of taking a single value from the command line and appending it to an existing list extend will take multiple values in a single comma delimited string and extend an existing list with them That is if names is an extend option of type string the command line names foo bar names blah names ding dong would result in a list foo bar blah ding dong Again we define a subclass of Option class MyOption Option ACTIONS Option ACTIONS extend STORE_ACTIONS Option STORE_ACTIONS extend TYPED_ACTIONS Option TYPED_ACTIONS extend ALWAYS_TYPED_ACTIONS Option ALWAYS_TYPED_ACTIONS extend def take_action self action dest opt value values parser if action extend lvalue value split values ensure_value dest extend lvalue else Option take_action self action dest opt value values parser Features of note extend both expects a value on the command line and stores that value somewhere so it goes in both STORE_ACTIONS and TYPED_ACTIONS to ensure that optparse assigns the default type of string to extend actions we put the extend action in ALWAYS_TYPED_ACTIONS as well MyOption take_action implements just this one new action and passes control back to Option take_action for the standard optparse actions values is an instance of the optparse_parser Values class which provides the very useful ensure_value method ensure_value is essentially getattr with a safety valve it is called as values ensure_value attr value If the attr attribute of values doesn t exist or is None then ensure_value first sets it to value and then returns value This is very handy for actions like extend append and count all of which accumulate data in a variable and expect that variable to be of a certain type a list for the first two an integer for the latter Using ensure_value means that scripts using your action don t have to worry about setting a default value for the option destinations in question they can just leave the default as None and ensure_value will take care of getting it right when it s needed Exceptions exception optparse OptionError Raised if an Option instance is created with invalid or inconsistent arguments exception optparse OptionConflictError Raised if conflicting options are added to an OptionParser exception optparse OptionValueError Raised if an invalid option value is encountered on the command line exception optparse BadOptionError Raised if an invalid option is passed on the command line exception optparse AmbiguousOptionError Raised if an ambiguous option is passed on the command line,en
115,What s New In Python 3 10 Editor Pablo Galindo Salgado This article explains the new features in Python 3 10 compared to 3 9 Python 3 10 was released on October 4 2021 For full details see the changelog Summary Release highlights New syntax features PEP 634 Structural Pattern Matching Specification PEP 635 Structural Pattern Matching Motivation and Rationale PEP 636 Structural Pattern Matching Tutorial bpo 12782 Parenthesized context managers are now officially allowed New features in the standard library PEP 618 Add Optional Length Checking To zip Interpreter improvements PEP 626 Precise line numbers for debugging and other tools New typing features PEP 604 Allow writing union types as X Y PEP 612 Parameter Specification Variables PEP 613 Explicit Type Aliases PEP 647 User Defined Type Guards Important deprecations removals or restrictions PEP 644 Require OpenSSL 1 1 1 or newer PEP 632 Deprecate distutils module PEP 623 Deprecate and prepare for the removal of the wstr member in PyUnicodeObject PEP 624 Remove Py_UNICODE encoder APIs PEP 597 Add optional EncodingWarning New Features Parenthesized context managers Using enclosing parentheses for continuation across multiple lines in context managers is now supported This allows formatting a long collection of context managers in multiple lines in a similar way as it was previously possible with import statements For instance all these examples are now valid with CtxManager as example with CtxManager1 CtxManager2 with CtxManager1 as example CtxManager2 with CtxManager1 CtxManager2 as example with CtxManager1 as example1 CtxManager2 as example2 it is also possible to use a trailing comma at the end of the enclosed group with CtxManager1 as example1 CtxManager2 as example2 CtxManager3 as example3 This new syntax uses the non LL 1 capacities of the new parser Check PEP 617 for more details Contributed by Guido van Rossum Pablo Galindo and Lysandros Nikolaou in bpo 12782 and bpo 40334 Better error messages SyntaxErrors When parsing code that contains unclosed parentheses or brackets the interpreter now includes the location of the unclosed bracket of parentheses instead of displaying SyntaxError unexpected EOF while parsing or pointing to some incorrect location For instance consider the following code notice the unclosed expected 9 1 18 2 19 2 27 3 28 3 29 3 36 4 37 4 38 4 39 4 45 5 46 5 47 5 48 5 49 5 54 6 some_other_code foo Previous versions of the interpreter reported confusing places as the location of the syntax error File example py line 3 some_other_code foo SyntaxError invalid syntax but in Python 3 10 a more informative error is emitted File example py line 1 expected 9 1 18 2 19 2 27 3 28 3 29 3 36 4 37 4 SyntaxError was never closed In a similar way errors involving unclosed string literals single and triple quoted now point to the start of the string instead of reporting EOF EOL These improvements are inspired by previous work in the PyPy interpreter Contributed by Pablo Galindo in bpo 42864 and Batuhan Taskaya in bpo 40176 SyntaxError exceptions raised by the interpreter will now highlight the full error range of the expression that constitutes the syntax error itself instead of just where the problem is detected In this way instead of displaying before Python 3 10 foo x z for z in range 10 t w File stdin line 1 foo x z for z in range 10 t w SyntaxError Generator expression must be parenthesized now Python 3 10 will display the exception as foo x z for z in range 10 t w File stdin line 1 foo x z for z in range 10 t w SyntaxError Generator expression must be parenthesized This improvement was contributed by Pablo Galindo in bpo 43914 A considerable amount of new specialized messages for SyntaxError exceptions have been incorporated Some of the most notable ones are as follows Missing before blocks if rocket position event_horizon File stdin line 1 if rocket position event_horizon SyntaxError expected Contributed by Pablo Galindo in bpo 42997 Unparenthesised tuples in comprehensions targets x y for x y in zip abcd 1234 File stdin line 1 x y for x y in zip abcd 123,en
116,4 SyntaxError did you forget parentheses around the comprehension target Contributed by Pablo Galindo in bpo 43017 Missing commas in collection literals and between expressions items x 1 y 2 z 3 File stdin line 3 y 2 SyntaxError invalid syntax Perhaps you forgot a comma Contributed by Pablo Galindo in bpo 43822 Multiple Exception types without parentheses try build_dyson_sphere except NotEnoughScienceError NotEnoughResourcesError File stdin line 3 except NotEnoughScienceError NotEnoughResourcesError SyntaxError multiple exception types must be parenthesized Contributed by Pablo Galindo in bpo 43149 Missing and values in dictionary literals values x 1 y 2 z File stdin line 4 z SyntaxError expression expected after dictionary key and values x 1 y 2 z w 3 File stdin line 1 values x 1 y 2 z w 3 SyntaxError expected after dictionary key Contributed by Pablo Galindo in bpo 43823 try blocks without except or finally blocks try x 2 something 3 File stdin line 3 something 3 SyntaxError expected except or finally block Contributed by Pablo Galindo in bpo 44305 Usage of instead of in comparisons if rocket position event_horizon File stdin line 1 if rocket position event_horizon SyntaxError cannot assign to attribute here Maybe you meant instead of Contributed by Pablo Galindo in bpo 43797 Usage of in f strings f Black holes all_black_holes and revelations File stdin line 1 all_black_holes SyntaxError f string cannot use starred expression here Contributed by Pablo Galindo in bpo 41064 IndentationErrors Many IndentationError exceptions now have more context regarding what kind of block was expecting an indentation including the location of the statement def foo if lel x 2 File stdin line 3 x 2 IndentationError expected an indented block after if statement in line 2 AttributeErrors When printing AttributeError PyErr_Display will offer suggestions of similar attribute names in the object that the exception was raised from collections namedtoplo Traceback most recent call last File stdin line 1 in module AttributeError module collections has no attribute namedtoplo Did you mean namedtuple Contributed by Pablo Galindo in bpo 38530 Warning Notice this won t work if PyErr_Display is not called to display the error which can happen if some other custom error display function is used This is a common scenario in some REPLs like IPython NameErrors When printing NameError raised by the interpreter PyErr_Display will offer suggestions of similar variable names in the function that the exception was raised from schwarzschild_black_hole None schwarschild_black_hole Traceback most recent call last File stdin line 1 in module NameError name schwarschild_black_hole is not defined Did you mean schwarzschild_black_hole Contributed by Pablo Galindo in bpo 38530 Warning Notice this won t work if PyErr_Display is not called to display the error which can happen if some other custom error display function is used This is a common scenario in some REPLs like IPython PEP 626 Precise line numbers for debugging and other tools PEP 626 brings more precise and reliable line numbers for debugging profiling and coverage tools Tracing events with the correct line number are generated for all lines of code executed and only for lines of code that are executed The f_lineno attribute of frame objects will always contain the expected line number The co_lnotab attribute of code objects is deprecated and will be removed in 3 12 Code that needs to convert from offset to line number should use the new co_lines method instead PEP 634 Structural Pattern Matching Structural pattern matching has been added in the form of a match statement and case statements of patterns with associated actions Patterns consist of sequences mappings primitive data types as well as class instances Pattern matching enables programs to extract information from complex data types branch on the structure of data and apply specific actions based on different forms of data Syntax and operations The generic syntax of pattern matching is match subject case pattern_1 action_1 case pattern_2 action_2 ca,en
117,se pattern_3 action_3 case _ action_wildcard A match statement takes an expression and compares its value to successive patterns given as one or more case blocks Specifically pattern matching operates by 1 using data with type and shape the subject 2 evaluating the subject in the match statement 3 comparing the subject with each pattern in a case statement from top to bottom until a match is confirmed 4 executing the action associated with the pattern of the confirmed match 5 If an exact match is not confirmed the last case a wildcard _ if provided will be used as the matching case If an exact match is not confirmed and a wildcard case does not exist the entire match block is a no op Declarative approach Readers may be aware of pattern matching through the simple example of matching a subject data object to a literal pattern with the switch statement found in C Java or JavaScript and many other languages Often the switch statement is used for comparison of an object expression with case statements containing literals More powerful examples of pattern matching can be found in languages such as Scala and Elixir With structural pattern matching the approach is declarative and explicitly states the conditions the patterns for data to match While an imperative series of instructions using nested if statements could be used to accomplish something similar to structural pattern matching it is less clear than the declarative approach Instead the declarative approach states the conditions to meet for a match and is more readable through its explicit patterns While structural pattern matching can be used in its simplest form comparing a variable to a literal in a case statement its true value for Python lies in its handling of the subject s type and shape Simple pattern match to a literal Let s look at this example as pattern matching in its simplest form a value the subject being matched to several literals the patterns In the example below status is the subject of the match statement The patterns are each of the case statements where literals represent request status codes The associated action to the case is executed after a match def http_error status match status case 400 return Bad request case 404 return Not found case 418 return I m a teapot case _ return Something s wrong with the internet If the above function is passed a status of 418 I m a teapot is returned If the above function is passed a status of 500 the case statement with _ will match as a wildcard and Something s wrong with the internet is returned Note the last block the variable name _ acts as a wildcard and insures the subject will always match The use of _ is optional You can combine several literals in a single pattern using or case 401 403 404 return Not allowed Behavior without the wildcard If we modify the above example by removing the last case block the example becomes def http_error status match status case 400 return Bad request case 404 return Not found case 418 return I m a teapot Without the use of _ in a case statement a match may not exist If no match exists the behavior is a no op For example if status of 500 is passed a no op occurs Patterns with a literal and variable Patterns can look like unpacking assignments and a pattern may be used to bind variables In this example a data point can be unpacked to its x coordinate and y coordinate point is an x y tuple match point case 0 0 print Origin case 0 y print f Y y case x 0 print f X x case x y print f X x Y y case _ raise ValueError Not a point The first pattern has two literals 0 0 and may be thought of as an extension of the literal pattern shown above The next two patterns combine a literal and a variable and the variable binds a value from the subject point The fourth pattern captures two values which makes it conceptually similar to the unpacking assignment x y point Patterns and classes If you are using classes to structure your data you can use as a pattern the class name followed by an argument list resembling a constructor This pattern has the ability to capture class attributes into v,en
118,ariables class Point x int y int def location point match point case Point x 0 y 0 print Origin is the point s location case Point x 0 y y print f Y y and the point is on the y axis case Point x x y 0 print f X x and the point is on the x axis case Point print The point is located somewhere else on the plane case _ print Not a point Patterns with positional parameters You can use positional parameters with some builtin classes that provide an ordering for their attributes e g dataclasses You can also define a specific position for attributes in patterns by setting the __match_args__ special attribute in your classes If it s set to x y the following patterns are all equivalent and all bind the y attribute to the var variable Point 1 var Point 1 y var Point x 1 y var Point y var x 1 Nested patterns Patterns can be arbitrarily nested For example if our data is a short list of points it could be matched like this match points case print No points in the list case Point 0 0 print The origin is the only point in the list case Point x y print f A single point x y is in the list case Point 0 y1 Point 0 y2 print f Two points on the Y axis at y1 y2 are in the list case _ print Something else is found in the list Complex patterns and the wildcard To this point the examples have used _ alone in the last case statement A wildcard can be used in more complex patterns such as error code _ For example match test_variable case warning code 40 print A warning has been received case error code _ print f An error code occurred In the above case test_variable will match for error code 100 and error code 800 Guard We can add an if clause to a pattern known as a guard If the guard is false match goes on to try the next case block Note that value capture happens before the guard is evaluated match point case Point x y if x y print f The point is located on the diagonal Y X at x case Point x y print f Point is not on the diagonal Other Key Features Several other key features Like unpacking assignments tuple and list patterns have exactly the same meaning and actually match arbitrary sequences Technically the subject must be a sequence Therefore an important exception is that patterns don t match iterators Also to prevent a common mistake sequence patterns don t match strings Sequence patterns support wildcards x y rest and x y rest work similar to wildcards in unpacking assignments The name after may also be _ so x y _ matches a sequence of at least two items without binding the remaining items Mapping patterns bandwidth b latency l captures the bandwidth and latency values from a dict Unlike sequence patterns extra keys are ignored A wildcard rest is also supported But _ would be redundant so is not allowed Subpatterns may be captured using the as keyword case Point x1 y1 Point x2 y2 as p2 This binds x1 y1 x2 y2 like you would expect without the as clause and p2 to the entire second item of the subject Most literals are compared by equality However the singletons True False and None are compared by identity Named constants may be used in patterns These named constants must be dotted names to prevent the constant from being interpreted as a capture variable from enum import Enum class Color Enum RED 0 GREEN 1 BLUE 2 color Color GREEN match color case Color RED print I see red case Color GREEN print Grass is green case Color BLUE print I m feeling the blues For the full specification see PEP 634 Motivation and rationale are in PEP 635 and a longer tutorial is in PEP 636 Optional EncodingWarning and encoding locale option The default encoding of TextIOWrapper and open is platform and locale dependent Since UTF 8 is used on most Unix platforms omitting encoding option when opening UTF 8 files e g JSON YAML TOML Markdown is a very common bug For example BUG rb mode or encoding utf 8 should be used with open data json as f data json load f To find this type of bug an optional EncodingWarning is added It is emitted when sys flags warn_default_encoding is true and locale specific default encoding is used X warn_default_encoding option and PYTHONWARNDEF,en
119,AULTENCODING are added to enable the warning See Text Encoding for more information New Features Related to Type Hints This section covers major changes affecting PEP 484 type hints and the typing module PEP 604 New Type Union Operator A new type union operator was introduced which enables the syntax X Y This provides a cleaner way of expressing either type X or type Y instead of using typing Union especially in type hints In previous versions of Python to apply a type hint for functions accepting arguments of multiple types typing Union was used def square number Union int float Union int float return number 2 Type hints can now be written in a more succinct manner def square number int float int float return number 2 This new syntax is also accepted as the second argument to isinstance and issubclass isinstance 1 int str True See Union Type and PEP 604 for more details Contributed by Maggie Moss and Philippe Prados in bpo 41428 with additions by Yurii Karabas and Serhiy Storchaka in bpo 44490 PEP 612 Parameter Specification Variables Two new options to improve the information provided to static type checkers for PEP 484 s Callable have been added to the typing module The first is the parameter specification variable They are used to forward the parameter types of one callable to another callable a pattern commonly found in higher order functions and decorators Examples of usage can be found in typing ParamSpec Previously there was no easy way to type annotate dependency of parameter types in such a precise manner The second option is the new Concatenate operator It s used in conjunction with parameter specification variables to type annotate a higher order callable which adds or removes parameters of another callable Examples of usage can be found in typing Concatenate See typing Callable typing ParamSpec typing Concatenate typing ParamSpecArgs typing ParamSpecKwargs and PEP 612 for more details Contributed by Ken Jin in bpo 41559 with minor enhancements by Jelle Zijlstra in bpo 43783 PEP written by Mark Mendoza PEP 613 TypeAlias PEP 484 introduced the concept of type aliases only requiring them to be top level unannotated assignments This simplicity sometimes made it difficult for type checkers to distinguish between type aliases and ordinary assignments especially when forward references or invalid types were involved Compare StrCache Cache str a type alias LOG_PREFIX LOG DEBUG a module constant Now the typing module has a special value TypeAlias which lets you declare type aliases more explicitly StrCache TypeAlias Cache str a type alias LOG_PREFIX LOG DEBUG a module constant See PEP 613 for more details Contributed by Mikhail Golubev in bpo 41923 PEP 647 User Defined Type Guards TypeGuard has been added to the typing module to annotate type guard functions and improve information provided to static type checkers during type narrowing For more information please see TypeGuard s documentation and PEP 647 Contributed by Ken Jin and Guido van Rossum in bpo 43766 PEP written by Eric Traut Other Language Changes The int type has a new method int bit_count returning the number of ones in the binary expansion of a given integer also known as the population count Contributed by Niklas Fiekas in bpo 29882 The views returned by dict keys dict values and dict items now all have a mapping attribute that gives a types MappingProxyType object wrapping the original dictionary Contributed by Dennis Sweeney in bpo 40890 PEP 618 The zip function now has an optional strict flag used to require that all the iterables have an equal length Builtin and extension functions that take integer arguments no longer accept Decimal s Fraction s and other objects that can be converted to integers only with a loss e g that have the __int__ method but do not have the __index__ method Contributed by Serhiy Storchaka in bpo 37999 If object __ipow__ returns NotImplemented the operator will correctly fall back to object __pow__ and object __rpow__ as expected Contributed by Alex Shkop in bpo 38302 Assignment expressions can now be used unparenthesized w,en
120,ithin set literals and set comprehensions as well as in sequence indexes but not slices Functions have a new __builtins__ attribute which is used to look for builtin symbols when a function is executed instead of looking into __globals__ __builtins__ The attribute is initialized from __globals__ __builtins__ if it exists else from the current builtins Contributed by Mark Shannon in bpo 42990 Two new builtin functions aiter and anext have been added to provide asynchronous counterparts to iter and next respectively Contributed by Joshua Bronson Daniel Pope and Justin Wang in bpo 31861 Static methods staticmethod and class methods classmethod now inherit the method attributes __module__ __name__ __qualname__ __doc__ __annotations__ and have a new __wrapped__ attribute Moreover static methods are now callable as regular functions Contributed by Victor Stinner in bpo 43682 Annotations for complex targets everything beside simple name targets defined by PEP 526 no longer cause any runtime effects with from __future__ import annotations Contributed by Batuhan Taskaya in bpo 42737 Class and module objects now lazy create empty annotations dicts on demand The annotations dicts are stored in the object s __dict__ for backwards compatibility This improves the best practices for working with __annotations__ for more information please see Annotations Best Practices Contributed by Larry Hastings in bpo 43901 Annotations consist of yield yield from await or named expressions are now forbidden under from __future__ import annotations due to their side effects Contributed by Batuhan Taskaya in bpo 42725 Usage of unbound variables super and other expressions that might alter the processing of symbol table as annotations are now rendered effectless under from __future__ import annotations Contributed by Batuhan Taskaya in bpo 42725 Hashes of NaN values of both float type and decimal Decimal type now depend on object identity Formerly they always hashed to 0 even though NaN values are not equal to one another This caused potentially quadratic runtime behavior due to excessive hash collisions when creating dictionaries and sets containing multiple NaNs Contributed by Raymond Hettinger in bpo 43475 A SyntaxError instead of a NameError will be raised when deleting the __debug__ constant Contributed by Donghee Na in bpo 45000 SyntaxError exceptions now have end_lineno and end_offset attributes They will be None if not determined Contributed by Pablo Galindo in bpo 43914 New Modules None Improved Modules asyncio Add missing connect_accepted_socket method Contributed by Alex Grönholm in bpo 41332 argparse Misleading phrase optional arguments was replaced with options in argparse help Some tests might require adaptation if they rely on exact output match Contributed by Raymond Hettinger in bpo 9694 array The index method of array array now has optional start and stop parameters Contributed by Anders Lorentsen and Zackery Spytz in bpo 31956 asynchat asyncore smtpd These modules have been marked as deprecated in their module documentation since Python 3 6 An import time DeprecationWarning has now been added to all three of these modules base64 Add base64 b32hexencode and base64 b32hexdecode to support the Base32 Encoding with Extended Hex Alphabet bdb Add clearBreakpoints to reset all set breakpoints Contributed by Irit Katriel in bpo 24160 bisect Added the possibility of providing a key function to the APIs in the bisect module Contributed by Raymond Hettinger in bpo 4356 codecs Add a codecs unregister function to unregister a codec search function Contributed by Hai Shi in bpo 41842 collections abc The __args__ of the parameterized generic for collections abc Callable are now consistent with typing Callable collections abc Callable generic now flattens type parameters similar to what typing Callable currently does This means that collections abc Callable int str str will have __args__ of int str str previously this was int str str To allow this change types GenericAlias can now be subclassed and a subclass will be returned when subscripting the ,en
121,collections abc Callable type Note that a TypeError may be raised for invalid forms of parameterizing collections abc Callable which may have passed silently in Python 3 9 Contributed by Ken Jin in bpo 42195 contextlib Add a contextlib aclosing context manager to safely close async generators and objects representing asynchronously released resources Contributed by Joongi Kim and John Belmonte in bpo 41229 Add asynchronous context manager support to contextlib nullcontext Contributed by Tom Gringauz in bpo 41543 Add AsyncContextDecorator for supporting usage of async context managers as decorators curses The extended color functions added in ncurses 6 1 will be used transparently by curses color_content curses init_color curses init_pair and curses pair_content A new function curses has_extended_color_support indicates whether extended color support is provided by the underlying ncurses library Contributed by Jeffrey Kintscher and Hans Petter Jansson in bpo 36982 The BUTTON5_ constants are now exposed in the curses module if they are provided by the underlying curses library Contributed by Zackery Spytz in bpo 39273 dataclasses __slots__ Added slots parameter in dataclasses dataclass decorator Contributed by Yurii Karabas in bpo 42269 Keyword only fields dataclasses now supports fields that are keyword only in the generated __init__ method There are a number of ways of specifying keyword only fields You can say that every field is keyword only from dataclasses import dataclass dataclass kw_only True class Birthday name str birthday datetime date Both name and birthday are keyword only parameters to the generated __init__ method You can specify keyword only on a per field basis from dataclasses import dataclass field dataclass class Birthday name str birthday datetime date field kw_only True Here only birthday is keyword only If you set kw_only on individual fields be aware that there are rules about re ordering fields due to keyword only fields needing to follow non keyword only fields See the full dataclasses documentation for details You can also specify that all fields following a KW_ONLY marker are keyword only This will probably be the most common usage from dataclasses import dataclass KW_ONLY dataclass class Point x float y float _ KW_ONLY z float 0 0 t float 0 0 Here z and t are keyword only parameters while x and y are not Contributed by Eric V Smith in bpo 43532 distutils The entire distutils package is deprecated to be removed in Python 3 12 Its functionality for specifying package builds has already been completely replaced by third party packages setuptools and packaging and most other commonly used APIs are available elsewhere in the standard library such as platform shutil subprocess or sysconfig There are no plans to migrate any other functionality from distutils and applications that are using other functions should plan to make private copies of the code Refer to PEP 632 for discussion The bdist_wininst command deprecated in Python 3 8 has been removed The bdist_wheel command is now recommended to distribute binary packages on Windows Contributed by Victor Stinner in bpo 42802 doctest When a module does not define __loader__ fall back to __spec__ loader Contributed by Brett Cannon in bpo 42133 encodings encodings normalize_encoding now ignores non ASCII characters Contributed by Hai Shi in bpo 39337 enum Enum __repr__ now returns enum_name member_name and __str__ now returns member_name Stdlib enums available as module constants have a repr of module_name member_name Contributed by Ethan Furman in bpo 40066 Add enum StrEnum for enums where all members are strings Contributed by Ethan Furman in bpo 41816 fileinput Add encoding and errors parameters in fileinput input and fileinput FileInput Contributed by Inada Naoki in bpo 43712 fileinput hook_compressed now returns TextIOWrapper object when mode is r and file is compressed like uncompressed files Contributed by Inada Naoki in bpo 5758 faulthandler The faulthandler module now detects if a fatal error occurs during a garbage collector collection Contribu,en
122,ted by Victor Stinner in bpo 44466 gc Add audit hooks for gc get_objects gc get_referrers and gc get_referents Contributed by Pablo Galindo in bpo 43439 glob Add the root_dir and dir_fd parameters in glob and iglob which allow to specify the root directory for searching Contributed by Serhiy Storchaka in bpo 38144 hashlib The hashlib module requires OpenSSL 1 1 1 or newer Contributed by Christian Heimes in PEP 644 and bpo 43669 The hashlib module has preliminary support for OpenSSL 3 0 0 Contributed by Christian Heimes in bpo 38820 and other issues The pure Python fallback of pbkdf2_hmac is deprecated In the future PBKDF2 HMAC will only be available when Python has been built with OpenSSL support Contributed by Christian Heimes in bpo 43880 hmac The hmac module now uses OpenSSL s HMAC implementation internally Contributed by Christian Heimes in bpo 40645 IDLE and idlelib Make IDLE invoke sys excepthook when started without n User hooks were previously ignored Contributed by Ken Hilton in bpo 43008 Rearrange the settings dialog Split the General tab into Windows and Shell Ed tabs Move help sources which extend the Help menu to the Extensions tab Make space for new options and shorten the dialog The latter makes the dialog better fit small screens Contributed by Terry Jan Reedy in bpo 40468 Move the indent space setting from the Font tab to the new Windows tab Contributed by Mark Roseman and Terry Jan Reedy in bpo 33962 The changes above were backported to a 3 9 maintenance release Add a Shell sidebar Move the primary prompt to the sidebar Add secondary prompts to the sidebar Left click and optional drag selects one or more lines of text as with the editor line number sidebar Right click after selecting text lines displays a context menu with copy with prompts This zips together prompts from the sidebar with lines from the selected text This option also appears on the context menu for the text Contributed by Tal Einat in bpo 37903 Use spaces instead of tabs to indent interactive code This makes interactive code entries look right Making this feasible was a major motivation for adding the shell sidebar Contributed by Terry Jan Reedy in bpo 37892 Highlight the new soft keywords match case and _ in pattern matching statements However this highlighting is not perfect and will be incorrect in some rare cases including some _ s in case patterns Contributed by Tal Einat in bpo 44010 New in 3 10 maintenance releases Apply syntax highlighting to pyi files Contributed by Alex Waygood and Terry Jan Reedy in bpo 45447 Include prompts when saving Shell with inputs and outputs Contributed by Terry Jan Reedy in gh 95191 importlib metadata Feature parity with importlib_metadata 4 6 history importlib metadata entry points now provide a nicer experience for selecting entry points by group and name through a new importlib metadata EntryPoints class See the Compatibility Note in the docs for more info on the deprecation and usage Added importlib metadata packages_distributions for resolving top level Python modules and packages to their importlib metadata Distribution inspect When a module does not define __loader__ fall back to __spec__ loader Contributed by Brett Cannon in bpo 42133 Add inspect get_annotations which safely computes the annotations defined on an object It works around the quirks of accessing the annotations on various types of objects and makes very few assumptions about the object it examines inspect get_annotations can also correctly un stringize stringized annotations inspect get_annotations is now considered best practice for accessing the annotations dict defined on any Python object for more information on best practices for working with annotations please see Annotations Best Practices Relatedly inspect signature inspect Signature from_callable and inspect Signature from_function now call inspect get_annotations to retrieve annotations This means inspect signature and inspect Signature from_callable can also now un stringize stringized annotations Contributed by Larry Hastings in bpo 43817 itertools Add itertools pair,en
123,wise Contributed by Raymond Hettinger in bpo 38200 linecache When a module does not define __loader__ fall back to __spec__ loader Contributed by Brett Cannon in bpo 42133 os Add os cpu_count support for VxWorks RTOS Contributed by Peixing Xin in bpo 41440 Add a new function os eventfd and related helpers to wrap the eventfd2 syscall on Linux Contributed by Christian Heimes in bpo 41001 Add os splice that allows to move data between two file descriptors without copying between kernel address space and user address space where one of the file descriptors must refer to a pipe Contributed by Pablo Galindo in bpo 41625 Add O_EVTONLY O_FSYNC O_SYMLINK and O_NOFOLLOW_ANY for macOS Contributed by Donghee Na in bpo 43106 os path os path realpath now accepts a strict keyword only argument When set to True OSError is raised if a path doesn t exist or a symlink loop is encountered Contributed by Barney Gale in bpo 43757 pathlib Add slice support to PurePath parents Contributed by Joshua Cannon in bpo 35498 Add negative indexing support to PurePath parents Contributed by Yaroslav Pankovych in bpo 21041 Add Path hardlink_to method that supersedes link_to The new method has the same argument order as symlink_to Contributed by Barney Gale in bpo 39950 pathlib Path stat and chmod now accept a follow_symlinks keyword only argument for consistency with corresponding functions in the os module Contributed by Barney Gale in bpo 39906 platform Add platform freedesktop_os_release to retrieve operation system identification from freedesktop org os release standard file Contributed by Christian Heimes in bpo 28468 pprint pprint pprint now accepts a new underscore_numbers keyword argument Contributed by sblondon in bpo 42914 pprint can now pretty print dataclasses dataclass instances Contributed by Lewis Gaul in bpo 43080 py_compile Add quiet option to command line interface of py_compile Contributed by Gregory Schevchenko in bpo 38731 pyclbr Add an end_lineno attribute to the Function and Class objects in the tree returned by pyclbr readmodule and pyclbr readmodule_ex It matches the existing start lineno Contributed by Aviral Srivastava in bpo 38307 shelve The shelve module now uses pickle DEFAULT_PROTOCOL by default instead of pickle protocol 3 when creating shelves Contributed by Zackery Spytz in bpo 34204 statistics Add covariance Pearson s correlation and simple linear_regression functions Contributed by Tymoteusz Wołodźko in bpo 38490 site When a module does not define __loader__ fall back to __spec__ loader Contributed by Brett Cannon in bpo 42133 socket The exception socket timeout is now an alias of TimeoutError Contributed by Christian Heimes in bpo 42413 Add option to create MPTCP sockets with IPPROTO_MPTCP Contributed by Rui Cunha in bpo 43571 Add IP_RECVTOS option to receive the type of service ToS or DSCP ECN fields Contributed by Georg Sauthoff in bpo 44077 ssl The ssl module requires OpenSSL 1 1 1 or newer Contributed by Christian Heimes in PEP 644 and bpo 43669 The ssl module has preliminary support for OpenSSL 3 0 0 and new option OP_IGNORE_UNEXPECTED_EOF Contributed by Christian Heimes in bpo 38820 bpo 43794 bpo 43788 bpo 43791 bpo 43799 bpo 43920 bpo 43789 and bpo 43811 Deprecated function and use of deprecated constants now result in a DeprecationWarning ssl SSLContext options has OP_NO_SSLv2 and OP_NO_SSLv3 set by default and therefore cannot warn about setting the flag again The deprecation section has a list of deprecated features Contributed by Christian Heimes in bpo 43880 The ssl module now has more secure default settings Ciphers without forward secrecy or SHA 1 MAC are disabled by default Security level 2 prohibits weak RSA DH and ECC keys with less than 112 bits of security SSLContext defaults to minimum protocol version TLS 1 2 Settings are based on Hynek Schlawack s research Contributed by Christian Heimes in bpo 43998 The deprecated protocols SSL 3 0 TLS 1 0 and TLS 1 1 are no longer officially supported Python does not block them actively However OpenSSL build options distro configurations vendor patches and cip,en
124,her suites may prevent a successful handshake Add a timeout parameter to the ssl get_server_certificate function Contributed by Zackery Spytz in bpo 31870 The ssl module uses heap types and multi phase initialization Contributed by Christian Heimes in bpo 42333 A new verify flag VERIFY_X509_PARTIAL_CHAIN has been added Contributed by l0x in bpo 40849 sqlite3 Add audit events for connect handle enable_load_extension and load_extension Contributed by Erlend E Aasland in bpo 43762 sys Add sys orig_argv attribute the list of the original command line arguments passed to the Python executable Contributed by Victor Stinner in bpo 23427 Add sys stdlib_module_names containing the list of the standard library module names Contributed by Victor Stinner in bpo 42955 _thread _thread interrupt_main now takes an optional signal number to simulate the default is still signal SIGINT Contributed by Antoine Pitrou in bpo 43356 threading Add threading gettrace and threading getprofile to retrieve the functions set by threading settrace and threading setprofile respectively Contributed by Mario Corchero in bpo 42251 Add threading __excepthook__ to allow retrieving the original value of threading excepthook in case it is set to a broken or a different value Contributed by Mario Corchero in bpo 42308 traceback The format_exception format_exception_only and print_exception functions can now take an exception object as a positional only argument Contributed by Zackery Spytz and Matthias Bussonnier in bpo 26389 types Reintroduce the types EllipsisType types NoneType and types NotImplementedType classes providing a new set of types readily interpretable by type checkers Contributed by Bas van Beek in bpo 41810 typing For major changes see New Features Related to Type Hints The behavior of typing Literal was changed to conform with PEP 586 and to match the behavior of static type checkers specified in the PEP 1 Literal now de duplicates parameters 2 Equality comparisons between Literal objects are now order independent 3 Literal comparisons now respect types For example Literal 0 Literal False previously evaluated to True It is now False To support this change the internally used type cache now supports differentiating types 4 Literal objects will now raise a TypeError exception during equality comparisons if any of their parameters are not hashable Note that declaring Literal with unhashable parameters will not throw an error from typing import Literal Literal 0 Literal 0 Literal False Traceback most recent call last File stdin line 1 in module TypeError unhashable type set Contributed by Yurii Karabas in bpo 42345 Add new function typing is_typeddict to introspect if an annotation is a typing TypedDict Contributed by Patrick Reader in bpo 41792 Subclasses of typing Protocol which only have data variables declared will now raise a TypeError when checked with isinstance unless they are decorated with runtime_checkable Previously these checks passed silently Users should decorate their subclasses with the runtime_checkable decorator if they want runtime protocols Contributed by Yurii Karabas in bpo 38908 Importing from the typing io and typing re submodules will now emit DeprecationWarning These submodules have been deprecated since Python 3 8 and will be removed in a future version of Python Anything belonging to those submodules should be imported directly from typing instead Contributed by Sebastian Rittau in bpo 38291 unittest Add new method assertNoLogs to complement the existing assertLogs Contributed by Kit Yan Choi in bpo 39385 urllib parse Python versions earlier than Python 3 10 allowed using both and as query parameter separators in urllib parse parse_qs and urllib parse parse_qsl Due to security concerns and to conform with newer W3C recommendations this has been changed to allow only a single separator key with as the default This change also affects cgi parse and cgi parse_multipart as they use the affected functions internally For more details please see their respective documentation Contributed by Adam Goldschmidt Senthil Kumaran a,en
125,nd Ken Jin in bpo 42967 The presence of newline or tab characters in parts of a URL allows for some forms of attacks Following the WHATWG specification that updates RFC 3986 ASCII newline n r and tab t characters are stripped from the URL by the parser in urllib parse preventing such attacks The removal characters are controlled by a new module level variable urllib parse _UNSAFE_URL_BYTES_TO_REMOVE See gh 88048 xml Add a LexicalHandler class to the xml sax handler module Contributed by Jonathan Gossage and Zackery Spytz in bpo 35018 zipimport Add methods related to PEP 451 find_spec zipimport zipimporter create_module and zipimport zipimporter exec_module Contributed by Brett Cannon in bpo 42131 Add invalidate_caches method Contributed by Desmond Cheong in bpo 14678 Optimizations Constructors str bytes and bytearray are now faster around 30 40 for small objects Contributed by Serhiy Storchaka in bpo 41334 The runpy module now imports fewer modules The python3 m module name command startup time is 1 4x faster in average On Linux python3 I m module name imports 69 modules on Python 3 9 whereas it only imports 51 modules 18 on Python 3 10 Contributed by Victor Stinner in bpo 41006 and bpo 41718 The LOAD_ATTR instruction now uses new per opcode cache mechanism It is about 36 faster now for regular attributes and 44 faster for slots Contributed by Pablo Galindo and Yury Selivanov in bpo 42093 and Guido van Rossum in bpo 42927 based on ideas implemented originally in PyPy and MicroPython When building Python with enable optimizations now fno semantic interposition is added to both the compile and link line This speeds builds of the Python interpreter created with enable shared with gcc by up to 30 See this article for more details Contributed by Victor Stinner and Pablo Galindo in bpo 38980 Use a new output buffer management code for bz2 lzma zlib modules and add readall function to _compression DecompressReader class bz2 decompression is now 1 09x 1 17x faster lzma decompression 1 20x 1 32x faster GzipFile read 1 1 11x 1 18x faster Contributed by Ma Lin reviewed by Gregory P Smith in bpo 41486 When using stringized annotations annotations dicts for functions are no longer created when the function is created Instead they are stored as a tuple of strings and the function object lazily converts this into the annotations dict on demand This optimization cuts the CPU time needed to define an annotated function by half Contributed by Yurii Karabas and Inada Naoki in bpo 42202 Substring search functions such as str1 in str2 and str2 find str1 now sometimes use Crochemore Perrin s Two Way string searching algorithm to avoid quadratic behavior on long strings Contributed by Dennis Sweeney in bpo 41972 Add micro optimizations to _PyType_Lookup to improve type attribute cache lookup performance in the common case of cache hits This makes the interpreter 1 04 times faster on average Contributed by Dino Viehland in bpo 43452 The following built in functions now support the faster PEP 590 vectorcall calling convention map filter reversed bool and float Contributed by Donghee Na and Jeroen Demeyer in bpo 43575 bpo 43287 bpo 41922 bpo 41873 and bpo 41870 BZ2File performance is improved by removing internal RLock This makes BZ2File thread unsafe in the face of multiple simultaneous readers or writers just like its equivalent classes in gzip and lzma have always been Contributed by Inada Naoki in bpo 43785 Deprecated Currently Python accepts numeric literals immediately followed by keywords for example 0in x 1or x 0if 1else 2 It allows confusing and ambiguous expressions like 0x1for x in y which can be interpreted as 0x1 for x in y or 0x1f or x in y Starting in this release a deprecation warning is raised if the numeric literal is immediately followed by one of keywords and else for if in is and or In future releases it will be changed to syntax warning and finally to syntax error Contributed by Serhiy Storchaka in bpo 43833 Starting in this release there will be a concerted effort to begin cleaning up old import semantics that were kept for,en
126, Python 2 7 compatibility Specifically find_loader find_module superseded by find_spec load_module superseded by exec_module module_repr which the import system takes care of for you the __package__ attribute superseded by __spec__ parent the __loader__ attribute superseded by __spec__ loader and the __cached__ attribute superseded by __spec__ cached will slowly be removed as well as other classes and methods in importlib ImportWarning and or DeprecationWarning will be raised as appropriate to help identify code which needs updating during this transition The entire distutils namespace is deprecated to be removed in Python 3 12 Refer to the module changes section for more information Non integer arguments to random randrange are deprecated The ValueError is deprecated in favor of a TypeError Contributed by Serhiy Storchaka and Raymond Hettinger in bpo 37319 The various load_module methods of importlib have been documented as deprecated since Python 3 6 but will now also trigger a DeprecationWarning Use exec_module instead Contributed by Brett Cannon in bpo 26131 zimport zipimporter load_module has been deprecated in preference for exec_module Contributed by Brett Cannon in bpo 26131 The use of load_module by the import system now triggers an ImportWarning as exec_module is preferred Contributed by Brett Cannon in bpo 26131 The use of importlib abc MetaPathFinder find_module and importlib abc PathEntryFinder find_module by the import system now trigger an ImportWarning as importlib abc MetaPathFinder find_spec and importlib abc PathEntryFinder find_spec are preferred respectively You can use importlib util spec_from_loader to help in porting Contributed by Brett Cannon in bpo 42134 The use of importlib abc PathEntryFinder find_loader by the import system now triggers an ImportWarning as importlib abc PathEntryFinder find_spec is preferred You can use importlib util spec_from_loader to help in porting Contributed by Brett Cannon in bpo 43672 The various implementations of importlib abc MetaPathFinder find_module importlib machinery BuiltinImporter find_module importlib machinery FrozenImporter find_module importlib machinery WindowsRegistryFinder find_module importlib machinery PathFinder find_module importlib abc MetaPathFinder find_module importlib abc PathEntryFinder find_module importlib machinery FileFinder find_module and importlib abc PathEntryFinder find_loader importlib machinery FileFinder find_loader now raise DeprecationWarning and are slated for removal in Python 3 12 previously they were documented as deprecated in Python 3 4 Contributed by Brett Cannon in bpo 42135 importlib abc Finder is deprecated including its sole method find_module Both importlib abc MetaPathFinder and importlib abc PathEntryFinder no longer inherit from the class Users should inherit from one of these two classes as appropriate instead Contributed by Brett Cannon in bpo 42135 The deprecations of imp importlib find_loader importlib util set_package_wrapper importlib util set_loader_wrapper importlib util module_for_loader pkgutil ImpImporter and pkgutil ImpLoader have all been updated to list Python 3 12 as the slated version of removal they began raising DeprecationWarning in previous versions of Python Contributed by Brett Cannon in bpo 43720 The import system now uses the __spec__ attribute on modules before falling back on module_repr for a module s __repr__ method Removal of the use of module_repr is scheduled for Python 3 12 Contributed by Brett Cannon in bpo 42137 importlib abc Loader module_repr importlib machinery FrozenLoader module_repr and importlib machinery BuiltinLoader module_repr are deprecated and slated for removal in Python 3 12 Contributed by Brett Cannon in bpo 42136 sqlite3 OptimizedUnicode has been undocumented and obsolete since Python 3 3 when it was made an alias to str It is now deprecated scheduled for removal in Python 3 12 Contributed by Erlend E Aasland in bpo 42264 The undocumented built in function sqlite3 enable_shared_cache is now deprecated scheduled for removal in Python 3 12 Its use is strongly dis,en
127,couraged by the SQLite3 documentation See the SQLite3 docs for more details If a shared cache must be used open the database in URI mode using the cache shared query parameter Contributed by Erlend E Aasland in bpo 24464 The following threading methods are now deprecated threading currentThread threading current_thread threading activeCount threading active_count threading Condition notifyAll threading Condition notify_all threading Event isSet threading Event is_set threading Thread setName threading Thread name threading thread getName threading Thread name threading Thread isDaemon threading Thread daemon threading Thread setDaemon threading Thread daemon Contributed by Jelle Zijlstra in gh 87889 pathlib Path link_to is deprecated and slated for removal in Python 3 12 Use pathlib Path hardlink_to instead Contributed by Barney Gale in bpo 39950 cgi log is deprecated and slated for removal in Python 3 12 Contributed by Inada Naoki in bpo 41139 The following ssl features have been deprecated since Python 3 6 Python 3 7 or OpenSSL 1 1 0 and will be removed in 3 11 OP_NO_SSLv2 OP_NO_SSLv3 OP_NO_TLSv1 OP_NO_TLSv1_1 OP_NO_TLSv1_2 and OP_NO_TLSv1_3 are replaced by sslSSLContext minimum_version and sslSSLContext maximum_version PROTOCOL_SSLv2 PROTOCOL_SSLv3 PROTOCOL_SSLv23 PROTOCOL_TLSv1 PROTOCOL_TLSv1_1 PROTOCOL_TLSv1_2 and PROTOCOL_TLS are deprecated in favor of PROTOCOL_TLS_CLIENT and PROTOCOL_TLS_SERVER wrap_socket is replaced by ssl SSLContext wrap_socket match_hostname RAND_pseudo_bytes RAND_egd NPN features like ssl SSLSocket selected_npn_protocol and ssl SSLContext set_npn_protocols are replaced by ALPN The threading debug PYTHONTHREADDEBUG environment variable is deprecated in Python 3 10 and will be removed in Python 3 12 This feature requires a debug build of Python Contributed by Victor Stinner in bpo 44584 Importing from the typing io and typing re submodules will now emit DeprecationWarning These submodules will be removed in a future version of Python Anything belonging to these submodules should be imported directly from typing instead Contributed by Sebastian Rittau in bpo 38291 Removed Removed special methods __int__ __float__ __floordiv__ __mod__ __divmod__ __rfloordiv__ __rmod__ and __rdivmod__ of the complex class They always raised a TypeError Contributed by Serhiy Storchaka in bpo 41974 The ParserBase error method from the private and undocumented _markupbase module has been removed html parser HTMLParser is the only subclass of ParserBase and its error implementation was already removed in Python 3 5 Contributed by Berker Peksag in bpo 31844 Removed the unicodedata ucnhash_CAPI attribute which was an internal PyCapsule object The related private _PyUnicode_Name_CAPI structure was moved to the internal C API Contributed by Victor Stinner in bpo 42157 Removed the parser module which was deprecated in 3 9 due to the switch to the new PEG parser as well as all the C source and header files that were only being used by the old parser including node h parser h graminit h and grammar h Removed the Public C API functions PyParser_SimpleParseStringFlags PyParser_SimpleParseStringFlagsFilename PyParser_SimpleParseFileFlags and PyNode_Compile that were deprecated in 3 9 due to the switch to the new PEG parser Removed the formatter module which was deprecated in Python 3 4 It is somewhat obsolete little used and not tested It was originally scheduled to be removed in Python 3 6 but such removals were delayed until after Python 2 7 EOL Existing users should copy whatever classes they use into their code Contributed by Donghee Na and Terry J Reedy in bpo 42299 Removed the PyModule_GetWarningsModule function that was useless now due to the _warnings module was converted to a builtin module in 2 6 Contributed by Hai Shi in bpo 42599 Remove deprecated aliases to Collections Abstract Base Classes from the collections module Contributed by Victor Stinner in bpo 37324 The loop parameter has been removed from most of asyncio s high level API following deprecation in Python 3 8 The motivation behind this change is multifold ,en
128,1 This simplifies the high level API 2 The functions in the high level API have been implicitly getting the current thread s running event loop since Python 3 7 There isn t a need to pass the event loop to the API in most normal use cases 3 Event loop passing is error prone especially when dealing with loops running in different threads Note that the low level API will still accept loop See Changes in the Python API for examples of how to replace existing code Contributed by Yurii Karabas Andrew Svetlov Yury Selivanov and Kyle Stanley in bpo 42392 Porting to Python 3 10 This section lists previously described changes and other bugfixes that may require changes to your code Changes in the Python syntax Deprecation warning is now emitted when compiling previously valid syntax if the numeric literal is immediately followed by a keyword like in 0in x In future releases it will be changed to syntax warning and finally to a syntax error To get rid of the warning and make the code compatible with future releases just add a space between the numeric literal and the following keyword Contributed by Serhiy Storchaka in bpo 43833 Changes in the Python API The etype parameters of the format_exception format_exception_only and print_exception functions in the traceback module have been renamed to exc Contributed by Zackery Spytz and Matthias Bussonnier in bpo 26389 atexit At Python exit if a callback registered with atexit register fails its exception is now logged Previously only some exceptions were logged and the last exception was always silently ignored Contributed by Victor Stinner in bpo 42639 collections abc Callable generic now flattens type parameters similar to what typing Callable currently does This means that collections abc Callable int str str will have __args__ of int str str previously this was int str str Code which accesses the arguments via typing get_args or __args__ need to account for this change Furthermore TypeError may be raised for invalid forms of parameterizing collections abc Callable which may have passed silently in Python 3 9 Contributed by Ken Jin in bpo 42195 socket htons and socket ntohs now raise OverflowError instead of DeprecationWarning if the given parameter will not fit in a 16 bit unsigned integer Contributed by Erlend E Aasland in bpo 42393 The loop parameter has been removed from most of asyncio s high level API following deprecation in Python 3 8 A coroutine that currently looks like this async def foo loop await asyncio sleep 1 loop loop Should be replaced with this async def foo await asyncio sleep 1 If foo was specifically designed not to run in the current thread s running event loop e g running in another thread s event loop consider using asyncio run_coroutine_threadsafe instead Contributed by Yurii Karabas Andrew Svetlov Yury Selivanov and Kyle Stanley in bpo 42392 The types FunctionType constructor now inherits the current builtins if the globals dictionary has no __builtins__ key rather than using None None as builtins same behavior as eval and exec functions Defining a function with def function in Python is not affected globals cannot be overridden with this syntax it also inherits the current builtins Contributed by Victor Stinner in bpo 42990 Changes in the C API The C API functions PyParser_SimpleParseStringFlags PyParser_SimpleParseStringFlagsFilename PyParser_SimpleParseFileFlags PyNode_Compile and the type used by these functions struct _node were removed due to the switch to the new PEG parser Source should be now be compiled directly to a code object using for example Py_CompileString The resulting code object can then be evaluated using for example PyEval_EvalCode Specifically A call to PyParser_SimpleParseStringFlags followed by PyNode_Compile can be replaced by calling Py_CompileString There is no direct replacement for PyParser_SimpleParseFileFlags To compile code from a FILE argument you will need to read the file in C and pass the resulting buffer to Py_CompileString To compile a file given a char filename explicitly open the file read it and compile the result O,en
129,ne way to do this is using the io module with PyImport_ImportModule PyObject_CallMethod PyBytes_AsString and Py_CompileString as sketched below Declarations and error handling are omitted io_module Import_ImportModule io fileobject PyObject_CallMethod io_module open ss filename rb source_bytes_object PyObject_CallMethod fileobject read result PyObject_CallMethod fileobject close source_buf PyBytes_AsString source_bytes_object code Py_CompileString source_buf filename Py_file_input For FrameObject objects the f_lasti member now represents a wordcode offset instead of a simple offset into the bytecode string This means that this number needs to be multiplied by 2 to be used with APIs that expect a byte offset instead like PyCode_Addr2Line for example Notice as well that the f_lasti member of FrameObject objects is not considered stable please use PyFrame_GetLineNumber instead CPython bytecode changes The MAKE_FUNCTION instruction now accepts either a dict or a tuple of strings as the function s annotations Contributed by Yurii Karabas and Inada Naoki in bpo 42202 Build Changes PEP 644 Python now requires OpenSSL 1 1 1 or newer OpenSSL 1 0 2 is no longer supported Contributed by Christian Heimes in bpo 43669 The C99 functions snprintf and vsnprintf are now required to build Python Contributed by Victor Stinner in bpo 36020 sqlite3 requires SQLite 3 7 15 or higher Contributed by Sergey Fedoseev and Erlend E Aasland in bpo 40744 and bpo 40810 The atexit module must now always be built as a built in module Contributed by Victor Stinner in bpo 42639 Add disable test modules option to the configure script don t build nor install test modules Contributed by Xavier de Gaye Thomas Petazzoni and Peixing Xin in bpo 27640 Add with wheel pkg dir PATH option to the configure script If specified the ensurepip module looks for setuptools and pip wheel packages in this directory if both are present these wheel packages are used instead of ensurepip bundled wheel packages Some Linux distribution packaging policies recommend against bundling dependencies For example Fedora installs wheel packages in the usr share python wheels directory and don t install the ensurepip _bundled package Contributed by Victor Stinner in bpo 42856 Add a new configure without static libpython option to not build the libpythonMAJOR MINOR a static library and not install the python o object file Contributed by Victor Stinner in bpo 43103 The configure script now uses the pkg config utility if available to detect the location of Tcl Tk headers and libraries As before those locations can be explicitly specified with the with tcltk includes and with tcltk libs configuration options Contributed by Manolis Stamatogiannakis in bpo 42603 Add with openssl rpath option to configure script The option simplifies building Python with a custom OpenSSL installation e g configure with openssl path to openssl with openssl rpath auto Contributed by Christian Heimes in bpo 43466 C API Changes PEP 652 Maintaining the Stable ABI The Stable ABI Application Binary Interface for extension modules or embedding Python is now explicitly defined C API Stability describes C API and ABI stability guarantees along with best practices for using the Stable ABI Contributed by Petr Viktorin in PEP 652 and bpo 43795 New Features The result of PyNumber_Index now always has exact type int Previously the result could have been an instance of a subclass of int Contributed by Serhiy Storchaka in bpo 40792 Add a new orig_argv member to the PyConfig structure the list of the original command line arguments passed to the Python executable Contributed by Victor Stinner in bpo 23427 The PyDateTime_DATE_GET_TZINFO and PyDateTime_TIME_GET_TZINFO macros have been added for accessing the tzinfo attributes of datetime datetime and datetime time objects Contributed by Zackery Spytz in bpo 30155 Add a PyCodec_Unregister function to unregister a codec search function Contributed by Hai Shi in bpo 41842 The PyIter_Send function was added to allow sending value into iterator without raising StopIteration exception Cont,en
130,ributed by Vladimir Matveev in bpo 41756 Add PyUnicode_AsUTF8AndSize to the limited C API Contributed by Alex Gaynor in bpo 41784 Add PyModule_AddObjectRef function similar to PyModule_AddObject but don t steal a reference to the value on success Contributed by Victor Stinner in bpo 1635741 Add Py_NewRef and Py_XNewRef functions to increment the reference count of an object and return the object Contributed by Victor Stinner in bpo 42262 The PyType_FromSpecWithBases and PyType_FromModuleAndSpec functions now accept a single class as the bases argument Contributed by Serhiy Storchaka in bpo 42423 The PyType_FromModuleAndSpec function now accepts NULL tp_doc slot Contributed by Hai Shi in bpo 41832 The PyType_GetSlot function can accept static types Contributed by Hai Shi and Petr Viktorin in bpo 41073 Add a new PySet_CheckExact function to the C API to check if an object is an instance of set but not an instance of a subtype Contributed by Pablo Galindo in bpo 43277 Add PyErr_SetInterruptEx which allows passing a signal number to simulate Contributed by Antoine Pitrou in bpo 43356 The limited C API is now supported if Python is built in debug mode if the Py_DEBUG macro is defined In the limited C API the Py_INCREF and Py_DECREF functions are now implemented as opaque function calls rather than accessing directly the PyObject ob_refcnt member if Python is built in debug mode and the Py_LIMITED_API macro targets Python 3 10 or newer It became possible to support the limited C API in debug mode because the PyObject structure is the same in release and debug mode since Python 3 8 see bpo 36465 The limited C API is still not supported in the with trace refs special build Py_TRACE_REFS macro Contributed by Victor Stinner in bpo 43688 Add the Py_Is x y function to test if the x object is the y object the same as x is y in Python Add also the Py_IsNone Py_IsTrue Py_IsFalse functions to test if an object is respectively the None singleton the True singleton or the False singleton Contributed by Victor Stinner in bpo 43753 Add new functions to control the garbage collector from C code PyGC_Enable PyGC_Disable PyGC_IsEnabled These functions allow to activate deactivate and query the state of the garbage collector from C code without having to import the gc module Add a new Py_TPFLAGS_DISALLOW_INSTANTIATION type flag to disallow creating type instances Contributed by Victor Stinner in bpo 43916 Add a new Py_TPFLAGS_IMMUTABLETYPE type flag for creating immutable type objects type attributes cannot be set nor deleted Contributed by Victor Stinner and Erlend E Aasland in bpo 43908 Porting to Python 3 10 The PY_SSIZE_T_CLEAN macro must now be defined to use PyArg_ParseTuple and Py_BuildValue formats which use es et s u y z U and Z See Parsing arguments and building values and PEP 353 Contributed by Victor Stinner in bpo 40943 Since Py_REFCNT is changed to the inline static function Py_REFCNT obj new_refcnt must be replaced with Py_SET_REFCNT obj new_refcnt see Py_SET_REFCNT available since Python 3 9 For backward compatibility this macro can be used if PY_VERSION_HEX 0x030900A4 define Py_SET_REFCNT obj refcnt Py_REFCNT obj refcnt void 0 endif Contributed by Victor Stinner in bpo 39573 Calling PyDict_GetItem without GIL held had been allowed for historical reason It is no longer allowed Contributed by Victor Stinner in bpo 40839 PyUnicode_FromUnicode NULL size and PyUnicode_FromStringAndSize NULL size raise DeprecationWarning now Use PyUnicode_New to allocate Unicode object without initial data Contributed by Inada Naoki in bpo 36346 The private _PyUnicode_Name_CAPI structure of the PyCapsule API unicodedata ucnhash_CAPI has been moved to the internal C API Contributed by Victor Stinner in bpo 42157 Py_GetPath Py_GetPrefix Py_GetExecPrefix Py_GetProgramFullPath Py_GetPythonHome and Py_GetProgramName functions now return NULL if called before Py_Initialize before Python is initialized Use the new Python Initialization Configuration API to get the Python Path Configuration Contributed by Victor Stinner in bpo 42260 PyList_SET_ITEM PyTuple_S,en
131,ET_ITEM and PyCell_SET macros can no longer be used as l value or r value For example x PyList_SET_ITEM a b c and PyList_SET_ITEM a b c x now fail with a compiler error It prevents bugs like if PyList_SET_ITEM a b c 0 test Contributed by Zackery Spytz and Victor Stinner in bpo 30459 The non limited API files odictobject h parser_interface h picklebufobject h pyarena h pyctype h pydebug h pyfpe h and pytime h have been moved to the Include cpython directory These files must not be included directly as they are already included in Python h see Include Files If they have been included directly consider including Python h instead Contributed by Nicholas Sim in bpo 35134 Use the Py_TPFLAGS_IMMUTABLETYPE type flag to create immutable type objects Do not rely on Py_TPFLAGS_HEAPTYPE to decide if a type object is mutable or not check if Py_TPFLAGS_IMMUTABLETYPE is set instead Contributed by Victor Stinner and Erlend E Aasland in bpo 43908 The undocumented function Py_FrozenMain has been removed from the limited API The function is mainly useful for custom builds of Python Contributed by Petr Viktorin in bpo 26241 Deprecated The PyUnicode_InternImmortal function is now deprecated and will be removed in Python 3 12 use PyUnicode_InternInPlace instead Contributed by Victor Stinner in bpo 41692 Removed Removed Py_UNICODE_str functions manipulating Py_UNICODE strings Contributed by Inada Naoki in bpo 41123 Py_UNICODE_strlen use PyUnicode_GetLength or PyUnicode_GET_LENGTH Py_UNICODE_strcat use PyUnicode_CopyCharacters or PyUnicode_FromFormat Py_UNICODE_strcpy Py_UNICODE_strncpy use PyUnicode_CopyCharacters or PyUnicode_Substring Py_UNICODE_strcmp use PyUnicode_Compare Py_UNICODE_strncmp use PyUnicode_Tailmatch Py_UNICODE_strchr Py_UNICODE_strrchr use PyUnicode_FindChar Removed PyUnicode_GetMax Please migrate to new PEP 393 APIs Contributed by Inada Naoki in bpo 41103 Removed PyLong_FromUnicode Please migrate to PyLong_FromUnicodeObject Contributed by Inada Naoki in bpo 41103 Removed PyUnicode_AsUnicodeCopy Please use PyUnicode_AsUCS4Copy or PyUnicode_AsWideCharString Contributed by Inada Naoki in bpo 41103 Removed _Py_CheckRecursionLimit variable it has been replaced by ceval recursion_limit of the PyInterpreterState structure Contributed by Victor Stinner in bpo 41834 Removed undocumented macros Py_ALLOW_RECURSION and Py_END_ALLOW_RECURSION and the recursion_critical field of the PyInterpreterState structure Contributed by Serhiy Storchaka in bpo 41936 Removed the undocumented PyOS_InitInterrupts function Initializing Python already implicitly installs signal handlers see PyConfig install_signal_handlers Contributed by Victor Stinner in bpo 41713 Remove the PyAST_Validate function It is no longer possible to build a AST object mod_ty type with the public C API The function was already excluded from the limited C API PEP 384 Contributed by Victor Stinner in bpo 43244 Remove the symtable h header file and the undocumented functions PyST_GetScope PySymtable_Build PySymtable_BuildObject PySymtable_Free Py_SymtableString Py_SymtableStringObject The Py_SymtableString function was part the stable ABI by mistake but it could not be used because the symtable h header file was excluded from the limited C API Use Python symtable module instead Contributed by Victor Stinner in bpo 43244 Remove PyOS_ReadlineFunctionPointer from the limited C API headers and from python3 dll the library that provides the stable ABI on Windows Since the function takes a FILE argument its ABI stability cannot be guaranteed Contributed by Petr Viktorin in bpo 43868 Remove ast h asdl h and Python ast h header files These functions were undocumented and excluded from the limited C API Most names defined by these header files were not prefixed by Py and so could create names conflicts For example Python ast h defined a Yield macro which was conflict with the Yield name used by the Windows winbase h header Use the Python ast module instead Contributed by Victor Stinner in bpo 43244 Remove the compiler and parser functions using struct _mod type because the public AST C AP,en
132,I was removed PyAST_Compile PyAST_CompileEx PyAST_CompileObject PyFuture_FromAST PyFuture_FromASTObject PyParser_ASTFromFile PyParser_ASTFromFileObject PyParser_ASTFromFilename PyParser_ASTFromString PyParser_ASTFromStringObject These functions were undocumented and excluded from the limited C API Contributed by Victor Stinner in bpo 43244 Remove the pyarena h header file with functions PyArena_New PyArena_Free PyArena_Malloc PyArena_AddPyObject These functions were undocumented excluded from the limited C API and were only used internally by the compiler Contributed by Victor Stinner in bpo 43244 The PyThreadState use_tracing member has been removed to optimize Python Contributed by Mark Shannon in bpo 43760 Notable security feature in 3 10 7 Converting between int and str in bases other than 2 binary 4 8 octal 16 hexadecimal or 32 such as base 10 decimal now raises a ValueError if the number of digits in string form is above a limit to avoid potential denial of service attacks due to the algorithmic complexity This is a mitigation for CVE 2020 10735 This limit can be configured or disabled by environment variable command line flag or sys APIs See the integer string conversion length limitation documentation The default limit is 4300 digits in string form Notable security feature in 3 10 8 The deprecated mailcap module now refuses to inject unsafe text filenames MIME types parameters into shell commands Instead of using such text it will warn and act as if a match was not found or for test commands as if the test failed Contributed by Petr Viktorin in gh 98966 Notable changes in 3 10 12 tarfile The extraction methods in tarfile and shutil unpack_archive have a new a filter argument that allows limiting tar features than may be surprising or dangerous such as creating files outside the destination directory See Extraction filters for details In Python 3 12 use without the filter argument will show a DeprecationWarning In Python 3 14 the default will switch to data Contributed by Petr Viktorin in PEP 706,en
133,errno Standard errno system symbols This module makes available standard errno system symbols The value of each symbol is the corresponding integer value The names and descriptions are borrowed from linux include errno h which should be all inclusive errno errorcode Dictionary providing a mapping from the errno value to the string name in the underlying system For instance errno errorcode errno EPERM maps to EPERM To translate a numeric error code to an error message use os strerror Of the following list symbols that are not used on the current platform are not defined by the module The specific list of defined symbols is available as errno errorcode keys Symbols available can include errno EPERM Operation not permitted This error is mapped to the exception PermissionError errno ENOENT No such file or directory This error is mapped to the exception FileNotFoundError errno ESRCH No such process This error is mapped to the exception ProcessLookupError errno EINTR Interrupted system call This error is mapped to the exception InterruptedError errno EIO I O error errno ENXIO No such device or address errno E2BIG Arg list too long errno ENOEXEC Exec format error errno EBADF Bad file number errno ECHILD No child processes This error is mapped to the exception ChildProcessError errno EAGAIN Try again This error is mapped to the exception BlockingIOError errno ENOMEM Out of memory errno EACCES Permission denied This error is mapped to the exception PermissionError errno EFAULT Bad address errno ENOTBLK Block device required errno EBUSY Device or resource busy errno EEXIST File exists This error is mapped to the exception FileExistsError errno EXDEV Cross device link errno ENODEV No such device errno ENOTDIR Not a directory This error is mapped to the exception NotADirectoryError errno EISDIR Is a directory This error is mapped to the exception IsADirectoryError errno EINVAL Invalid argument errno ENFILE File table overflow errno EMFILE Too many open files errno ENOTTY Not a typewriter errno ETXTBSY Text file busy errno EFBIG File too large errno ENOSPC No space left on device errno ESPIPE Illegal seek errno EROFS Read only file system errno EMLINK Too many links errno EPIPE Broken pipe This error is mapped to the exception BrokenPipeError errno EDOM Math argument out of domain of func errno ERANGE Math result not representable errno EDEADLK Resource deadlock would occur errno ENAMETOOLONG File name too long errno ENOLCK No record locks available errno ENOSYS Function not implemented errno ENOTEMPTY Directory not empty errno ELOOP Too many symbolic links encountered errno EWOULDBLOCK Operation would block This error is mapped to the exception BlockingIOError errno ENOMSG No message of desired type errno EIDRM Identifier removed errno ECHRNG Channel number out of range errno EL2NSYNC Level 2 not synchronized errno EL3HLT Level 3 halted errno EL3RST Level 3 reset errno ELNRNG Link number out of range errno EUNATCH Protocol driver not attached errno ENOCSI No CSI structure available errno EL2HLT Level 2 halted errno EBADE Invalid exchange errno EBADR Invalid request descriptor errno EXFULL Exchange full errno ENOANO No anode errno EBADRQC Invalid request code errno EBADSLT Invalid slot errno EDEADLOCK File locking deadlock error errno EBFONT Bad font file format errno ENOSTR Device not a stream errno ENODATA No data available errno ETIME Timer expired errno ENOSR Out of streams resources errno ENONET Machine is not on the network errno ENOPKG Package not installed errno EREMOTE Object is remote errno ENOLINK Link has been severed errno EADV Advertise error errno ESRMNT Srmount error errno ECOMM Communication error on send errno EPROTO Protocol error errno EMULTIHOP Multihop attempted errno EDOTDOT RFS specific error errno EBADMSG Not a data message errno EOVERFLOW Value too large for defined data type errno ENOTUNIQ Name not unique on network errno EBADFD File descriptor in bad state errno EREMCHG Remote address changed errno ELIBACC Can not access a needed shared library errno ELIBBAD Accessing a corrupted shared library errno ELIBS,en
134,CN lib section in a out corrupted errno ELIBMAX Attempting to link in too many shared libraries errno ELIBEXEC Cannot exec a shared library directly errno EILSEQ Illegal byte sequence errno ERESTART Interrupted system call should be restarted errno ESTRPIPE Streams pipe error errno EUSERS Too many users errno ENOTSOCK Socket operation on non socket errno EDESTADDRREQ Destination address required errno EMSGSIZE Message too long errno EPROTOTYPE Protocol wrong type for socket errno ENOPROTOOPT Protocol not available errno EPROTONOSUPPORT Protocol not supported errno ESOCKTNOSUPPORT Socket type not supported errno EOPNOTSUPP Operation not supported on transport endpoint errno ENOTSUP Operation not supported New in version 3 2 errno EPFNOSUPPORT Protocol family not supported errno EAFNOSUPPORT Address family not supported by protocol errno EADDRINUSE Address already in use errno EADDRNOTAVAIL Cannot assign requested address errno ENETDOWN Network is down errno ENETUNREACH Network is unreachable errno ENETRESET Network dropped connection because of reset errno ECONNABORTED Software caused connection abort This error is mapped to the exception ConnectionAbortedError errno ECONNRESET Connection reset by peer This error is mapped to the exception ConnectionResetError errno ENOBUFS No buffer space available errno EISCONN Transport endpoint is already connected errno ENOTCONN Transport endpoint is not connected errno ESHUTDOWN Cannot send after transport endpoint shutdown This error is mapped to the exception BrokenPipeError errno ETOOMANYREFS Too many references cannot splice errno ETIMEDOUT Connection timed out This error is mapped to the exception TimeoutError errno ECONNREFUSED Connection refused This error is mapped to the exception ConnectionRefusedError errno EHOSTDOWN Host is down errno EHOSTUNREACH No route to host errno EALREADY Operation already in progress This error is mapped to the exception BlockingIOError errno EINPROGRESS Operation now in progress This error is mapped to the exception BlockingIOError errno ESTALE Stale NFS file handle errno EUCLEAN Structure needs cleaning errno ENOTNAM Not a XENIX named type file errno ENAVAIL No XENIX semaphores available errno EISNAM Is a named type file errno EREMOTEIO Remote I O error errno EDQUOT Quota exceeded errno EQFULL Interface output queue is full New in version 3 11 errno ENOTCAPABLE Capabilities insufficient This error is mapped to the exception PermissionError Availability WASI FreeBSD New in version 3 11 1 errno ECANCELED Operation canceled New in version 3 2 errno EOWNERDEAD Owner died New in version 3 2 errno ENOTRECOVERABLE State not recoverable New in version 3 2,en
135,pickle Python object serialization Source code Lib pickle py The pickle module implements binary protocols for serializing and de serializing a Python object structure Pickling is the process whereby a Python object hierarchy is converted into a byte stream and unpickling is the inverse operation whereby a byte stream from a binary file or bytes like object is converted back into an object hierarchy Pickling and unpickling is alternatively known as serialization marshalling 1 or flattening however to avoid confusion the terms used here are pickling and unpickling Warning The pickle module is not secure Only unpickle data you trust It is possible to construct malicious pickle data which will execute arbitrary code during unpickling Never unpickle data that could have come from an untrusted source or that could have been tampered with Consider signing data with hmac if you need to ensure that it has not been tampered with Safer serialization formats such as json may be more appropriate if you are processing untrusted data See Comparison with json Relationship to other Python modules Comparison with marshal Python has a more primitive serialization module called marshal but in general pickle should always be the preferred way to serialize Python objects marshal exists primarily to support Python s pyc files The pickle module differs from marshal in several significant ways The pickle module keeps track of the objects it has already serialized so that later references to the same object won t be serialized again marshal doesn t do this This has implications both for recursive objects and object sharing Recursive objects are objects that contain references to themselves These are not handled by marshal and in fact attempting to marshal recursive objects will crash your Python interpreter Object sharing happens when there are multiple references to the same object in different places in the object hierarchy being serialized pickle stores such objects only once and ensures that all other references point to the master copy Shared objects remain shared which can be very important for mutable objects marshal cannot be used to serialize user defined classes and their instances pickle can save and restore class instances transparently however the class definition must be importable and live in the same module as when the object was stored The marshal serialization format is not guaranteed to be portable across Python versions Because its primary job in life is to support pyc files the Python implementers reserve the right to change the serialization format in non backwards compatible ways should the need arise The pickle serialization format is guaranteed to be backwards compatible across Python releases provided a compatible pickle protocol is chosen and pickling and unpickling code deals with Python 2 to Python 3 type differences if your data is crossing that unique breaking change language boundary Comparison with json There are fundamental differences between the pickle protocols and JSON JavaScript Object Notation JSON is a text serialization format it outputs unicode text although most of the time it is then encoded to utf 8 while pickle is a binary serialization format JSON is human readable while pickle is not JSON is interoperable and widely used outside of the Python ecosystem while pickle is Python specific JSON by default can only represent a subset of the Python built in types and no custom classes pickle can represent an extremely large number of Python types many of them automatically by clever usage of Python s introspection facilities complex cases can be tackled by implementing specific object APIs Unlike pickle deserializing untrusted JSON does not in itself create an arbitrary code execution vulnerability See also The json module a standard library module allowing JSON serialization and deserialization Data stream format The data format used by pickle is Python specific This has the advantage that there are no restrictions imposed by external standards such as JSON or XDR which can t represent pointer sharing ho,en
136,wever it means that non Python programs may not be able to reconstruct pickled Python objects By default the pickle data format uses a relatively compact binary representation If you need optimal size characteristics you can efficiently compress pickled data The module pickletools contains tools for analyzing data streams generated by pickle pickletools source code has extensive comments about opcodes used by pickle protocols There are currently 6 different protocols which can be used for pickling The higher the protocol used the more recent the version of Python needed to read the pickle produced Protocol version 0 is the original human readable protocol and is backwards compatible with earlier versions of Python Protocol version 1 is an old binary format which is also compatible with earlier versions of Python Protocol version 2 was introduced in Python 2 3 It provides much more efficient pickling of new style classes Refer to PEP 307 for information about improvements brought by protocol 2 Protocol version 3 was added in Python 3 0 It has explicit support for bytes objects and cannot be unpickled by Python 2 x This was the default protocol in Python 3 0 3 7 Protocol version 4 was added in Python 3 4 It adds support for very large objects pickling more kinds of objects and some data format optimizations It is the default protocol starting with Python 3 8 Refer to PEP 3154 for information about improvements brought by protocol 4 Protocol version 5 was added in Python 3 8 It adds support for out of band data and speedup for in band data Refer to PEP 574 for information about improvements brought by protocol 5 Note Serialization is a more primitive notion than persistence although pickle reads and writes file objects it does not handle the issue of naming persistent objects nor the even more complicated issue of concurrent access to persistent objects The pickle module can transform a complex object into a byte stream and it can transform the byte stream into an object with the same internal structure Perhaps the most obvious thing to do with these byte streams is to write them onto a file but it is also conceivable to send them across a network or store them in a database The shelve module provides a simple interface to pickle and unpickle objects on DBM style database files Module Interface To serialize an object hierarchy you simply call the dumps function Similarly to de serialize a data stream you call the loads function However if you want more control over serialization and de serialization you can create a Pickler or an Unpickler object respectively The pickle module provides the following constants pickle HIGHEST_PROTOCOL An integer the highest protocol version available This value can be passed as a protocol value to functions dump and dumps as well as the Pickler constructor pickle DEFAULT_PROTOCOL An integer the default protocol version used for pickling May be less than HIGHEST_PROTOCOL Currently the default protocol is 4 first introduced in Python 3 4 and incompatible with previous versions Changed in version 3 0 The default protocol is 3 Changed in version 3 8 The default protocol is 4 The pickle module provides the following functions to make the pickling process more convenient pickle dump obj file protocol None fix_imports True buffer_callback None Write the pickled representation of the object obj to the open file object file This is equivalent to Pickler file protocol dump obj Arguments file protocol fix_imports and buffer_callback have the same meaning as in the Pickler constructor Changed in version 3 8 The buffer_callback argument was added pickle dumps obj protocol None fix_imports True buffer_callback None Return the pickled representation of the object obj as a bytes object instead of writing it to a file Arguments protocol fix_imports and buffer_callback have the same meaning as in the Pickler constructor Changed in version 3 8 The buffer_callback argument was added pickle load file fix_imports True encoding ASCII errors strict buffers None Read the pickled representation of an object from the o,en
137,pen file object file and return the reconstituted object hierarchy specified therein This is equivalent to Unpickler file load The protocol version of the pickle is detected automatically so no protocol argument is needed Bytes past the pickled representation of the object are ignored Arguments file fix_imports encoding errors strict and buffers have the same meaning as in the Unpickler constructor Changed in version 3 8 The buffers argument was added pickle loads data fix_imports True encoding ASCII errors strict buffers None Return the reconstituted object hierarchy of the pickled representation data of an object data must be a bytes like object The protocol version of the pickle is detected automatically so no protocol argument is needed Bytes past the pickled representation of the object are ignored Arguments fix_imports encoding errors strict and buffers have the same meaning as in the Unpickler constructor Changed in version 3 8 The buffers argument was added The pickle module defines three exceptions exception pickle PickleError Common base class for the other pickling exceptions It inherits from Exception exception pickle PicklingError Error raised when an unpicklable object is encountered by Pickler It inherits from PickleError Refer to What can be pickled and unpickled to learn what kinds of objects can be pickled exception pickle UnpicklingError Error raised when there is a problem unpickling an object such as a data corruption or a security violation It inherits from PickleError Note that other exceptions may also be raised during unpickling including but not necessarily limited to AttributeError EOFError ImportError and IndexError The pickle module exports three classes Pickler Unpickler and PickleBuffer class pickle Pickler file protocol None fix_imports True buffer_callback None This takes a binary file for writing a pickle data stream The optional protocol argument an integer tells the pickler to use the given protocol supported protocols are 0 to HIGHEST_PROTOCOL If not specified the default is DEFAULT_PROTOCOL If a negative number is specified HIGHEST_PROTOCOL is selected The file argument must have a write method that accepts a single bytes argument It can thus be an on disk file opened for binary writing an io BytesIO instance or any other custom object that meets this interface If fix_imports is true and protocol is less than 3 pickle will try to map the new Python 3 names to the old module names used in Python 2 so that the pickle data stream is readable with Python 2 If buffer_callback is None the default buffer views are serialized into file as part of the pickle stream If buffer_callback is not None then it can be called any number of times with a buffer view If the callback returns a false value such as None the given buffer is out of band otherwise the buffer is serialized in band i e inside the pickle stream It is an error if buffer_callback is not None and protocol is None or smaller than 5 Changed in version 3 8 The buffer_callback argument was added dump obj Write the pickled representation of obj to the open file object given in the constructor persistent_id obj Do nothing by default This exists so a subclass can override it If persistent_id returns None obj is pickled as usual Any other value causes Pickler to emit the returned value as a persistent ID for obj The meaning of this persistent ID should be defined by Unpickler persistent_load Note that the value returned by persistent_id cannot itself have a persistent ID See Persistence of External Objects for details and examples of uses dispatch_table A pickler object s dispatch table is a registry of reduction functions of the kind which can be declared using copyreg pickle It is a mapping whose keys are classes and whose values are reduction functions A reduction function takes a single argument of the associated class and should conform to the same interface as a __reduce__ method By default a pickler object will not have a dispatch_table attribute and it will instead use the global dispatch table managed by the copyreg module However ,en
138,to customize the pickling for a specific pickler object one can set the dispatch_table attribute to a dict like object Alternatively if a subclass of Pickler has a dispatch_table attribute then this will be used as the default dispatch table for instances of that class See Dispatch Tables for usage examples New in version 3 3 reducer_override obj Special reducer that can be defined in Pickler subclasses This method has priority over any reducer in the dispatch_table It should conform to the same interface as a __reduce__ method and can optionally return NotImplemented to fallback on dispatch_table registered reducers to pickle obj For a detailed example see Custom Reduction for Types Functions and Other Objects New in version 3 8 fast Deprecated Enable fast mode if set to a true value The fast mode disables the usage of memo therefore speeding the pickling process by not generating superfluous PUT opcodes It should not be used with self referential objects doing otherwise will cause Pickler to recurse infinitely Use pickletools optimize if you need more compact pickles class pickle Unpickler file fix_imports True encoding ASCII errors strict buffers None This takes a binary file for reading a pickle data stream The protocol version of the pickle is detected automatically so no protocol argument is needed The argument file must have three methods a read method that takes an integer argument a readinto method that takes a buffer argument and a readline method that requires no arguments as in the io BufferedIOBase interface Thus file can be an on disk file opened for binary reading an io BytesIO object or any other custom object that meets this interface The optional arguments fix_imports encoding and errors are used to control compatibility support for pickle stream generated by Python 2 If fix_imports is true pickle will try to map the old Python 2 names to the new names used in Python 3 The encoding and errors tell pickle how to decode 8 bit string instances pickled by Python 2 these default to ASCII and strict respectively The encoding can be bytes to read these 8 bit string instances as bytes objects Using encoding latin1 is required for unpickling NumPy arrays and instances of datetime date and time pickled by Python 2 If buffers is None the default then all data necessary for deserialization must be contained in the pickle stream This means that the buffer_callback argument was None when a Pickler was instantiated or when dump or dumps was called If buffers is not None it should be an iterable of buffer enabled objects that is consumed each time the pickle stream references an out of band buffer view Such buffers have been given in order to the buffer_callback of a Pickler object Changed in version 3 8 The buffers argument was added load Read the pickled representation of an object from the open file object given in the constructor and return the reconstituted object hierarchy specified therein Bytes past the pickled representation of the object are ignored persistent_load pid Raise an UnpicklingError by default If defined persistent_load should return the object specified by the persistent ID pid If an invalid persistent ID is encountered an UnpicklingError should be raised See Persistence of External Objects for details and examples of uses find_class module name Import module if necessary and return the object called name from it where the module and name arguments are str objects Note unlike its name suggests find_class is also used for finding functions Subclasses may override this to gain control over what type of objects and how they can be loaded potentially reducing security risks Refer to Restricting Globals for details Raises an auditing event pickle find_class with arguments module name class pickle PickleBuffer buffer A wrapper for a buffer representing picklable data buffer must be a buffer providing object such as a bytes like object or a N dimensional array PickleBuffer is itself a buffer provider therefore it is possible to pass it to other APIs expecting a buffer providing object such as memoryview ,en
139,PickleBuffer objects can only be serialized using pickle protocol 5 or higher They are eligible for out of band serialization New in version 3 8 raw Return a memoryview of the memory area underlying this buffer The returned object is a one dimensional C contiguous memoryview with format B unsigned bytes BufferError is raised if the buffer is neither C nor Fortran contiguous release Release the underlying buffer exposed by the PickleBuffer object What can be pickled and unpickled The following types can be pickled built in constants None True False Ellipsis and NotImplemented integers floating point numbers complex numbers strings bytes bytearrays tuples lists sets and dictionaries containing only picklable objects functions built in and user defined accessible from the top level of a module using def not lambda classes accessible from the top level of a module instances of such classes whose the result of calling __getstate__ is picklable see section Pickling Class Instances for details Attempts to pickle unpicklable objects will raise the PicklingError exception when this happens an unspecified number of bytes may have already been written to the underlying file Trying to pickle a highly recursive data structure may exceed the maximum recursion depth a RecursionError will be raised in this case You can carefully raise this limit with sys setrecursionlimit Note that functions built in and user defined are pickled by fully qualified name not by value 2 This means that only the function name is pickled along with the name of the containing module and classes Neither the function s code nor any of its function attributes are pickled Thus the defining module must be importable in the unpickling environment and the module must contain the named object otherwise an exception will be raised 3 Similarly classes are pickled by fully qualified name so the same restrictions in the unpickling environment apply Note that none of the class s code or data is pickled so in the following example the class attribute attr is not restored in the unpickling environment class Foo attr A class attribute picklestring pickle dumps Foo These restrictions are why picklable functions and classes must be defined at the top level of a module Similarly when class instances are pickled their class s code and data are not pickled along with them Only the instance data are pickled This is done on purpose so you can fix bugs in a class or add methods to the class and still load objects that were created with an earlier version of the class If you plan to have long lived objects that will see many versions of a class it may be worthwhile to put a version number in the objects so that suitable conversions can be made by the class s __setstate__ method Pickling Class Instances In this section we describe the general mechanisms available to you to define customize and control how class instances are pickled and unpickled In most cases no additional code is needed to make instances picklable By default pickle will retrieve the class and the attributes of an instance via introspection When a class instance is unpickled its __init__ method is usually not invoked The default behaviour first creates an uninitialized instance and then restores the saved attributes The following code shows an implementation of this behaviour def save obj return obj __class__ obj __dict__ def restore cls attributes obj cls __new__ cls obj __dict__ update attributes return obj Classes can alter the default behaviour by providing one or several special methods object __getnewargs_ex__ In protocols 2 and newer classes that implements the __getnewargs_ex__ method can dictate the values passed to the __new__ method upon unpickling The method must return a pair args kwargs where args is a tuple of positional arguments and kwargs a dictionary of named arguments for constructing the object Those will be passed to the __new__ method upon unpickling You should implement this method if the __new__ method of your class requires keyword only arguments Otherwise it is recommended for compatibility,en
140, to implement __getnewargs__ Changed in version 3 6 __getnewargs_ex__ is now used in protocols 2 and 3 object __getnewargs__ This method serves a similar purpose as __getnewargs_ex__ but supports only positional arguments It must return a tuple of arguments args which will be passed to the __new__ method upon unpickling __getnewargs__ will not be called if __getnewargs_ex__ is defined Changed in version 3 6 Before Python 3 6 __getnewargs__ was called instead of __getnewargs_ex__ in protocols 2 and 3 object __getstate__ Classes can further influence how their instances are pickled by overriding the method __getstate__ It is called and the returned object is pickled as the contents for the instance instead of a default state There are several cases For a class that has no instance __dict__ and no __slots__ the default state is None For a class that has an instance __dict__ and no __slots__ the default state is self __dict__ For a class that has an instance __dict__ and __slots__ the default state is a tuple consisting of two dictionaries self __dict__ and a dictionary mapping slot names to slot values Only slots that have a value are included in the latter For a class that has __slots__ and no instance __dict__ the default state is a tuple whose first item is None and whose second item is a dictionary mapping slot names to slot values described in the previous bullet Changed in version 3 11 Added the default implementation of the __getstate__ method in the object class object __setstate__ state Upon unpickling if the class defines __setstate__ it is called with the unpickled state In that case there is no requirement for the state object to be a dictionary Otherwise the pickled state must be a dictionary and its items are assigned to the new instance s dictionary Note If __reduce__ returns a state with value None at pickling the __setstate__ method will not be called upon unpickling Refer to the section Handling Stateful Objects for more information about how to use the methods __getstate__ and __setstate__ Note At unpickling time some methods like __getattr__ __getattribute__ or __setattr__ may be called upon the instance In case those methods rely on some internal invariant being true the type should implement __new__ to establish such an invariant as __init__ is not called when unpickling an instance As we shall see pickle does not use directly the methods described above In fact these methods are part of the copy protocol which implements the __reduce__ special method The copy protocol provides a unified interface for retrieving the data necessary for pickling and copying objects 4 Although powerful implementing __reduce__ directly in your classes is error prone For this reason class designers should use the high level interface i e __getnewargs_ex__ __getstate__ and __setstate__ whenever possible We will show however cases where using __reduce__ is the only option or leads to more efficient pickling or both object __reduce__ The interface is currently defined as follows The __reduce__ method takes no argument and shall return either a string or preferably a tuple the returned object is often referred to as the reduce value If a string is returned the string should be interpreted as the name of a global variable It should be the object s local name relative to its module the pickle module searches the module namespace to determine the object s module This behaviour is typically useful for singletons When a tuple is returned it must be between two and six items long Optional items can either be omitted or None can be provided as their value The semantics of each item are in order A callable object that will be called to create the initial version of the object A tuple of arguments for the callable object An empty tuple must be given if the callable does not accept any argument Optionally the object s state which will be passed to the object s __setstate__ method as previously described If the object has no such method then the value must be a dictionary and it will be added to the object s __dict__ attribute Optionally ,en
141,an iterator and not a sequence yielding successive items These items will be appended to the object either using obj append item or in batch using obj extend list_of_items This is primarily used for list subclasses but may be used by other classes as long as they have append and extend methods with the appropriate signature Whether append or extend is used depends on which pickle protocol version is used as well as the number of items to append so both must be supported Optionally an iterator not a sequence yielding successive key value pairs These items will be stored to the object using obj key value This is primarily used for dictionary subclasses but may be used by other classes as long as they implement __setitem__ Optionally a callable with a obj state signature This callable allows the user to programmatically control the state updating behavior of a specific object instead of using obj s static __setstate__ method If not None this callable will have priority over obj s __setstate__ New in version 3 8 The optional sixth tuple item obj state was added object __reduce_ex__ protocol Alternatively a __reduce_ex__ method may be defined The only difference is this method should take a single integer argument the protocol version When defined pickle will prefer it over the __reduce__ method In addition __reduce__ automatically becomes a synonym for the extended version The main use for this method is to provide backwards compatible reduce values for older Python releases Persistence of External Objects For the benefit of object persistence the pickle module supports the notion of a reference to an object outside the pickled data stream Such objects are referenced by a persistent ID which should be either a string of alphanumeric characters for protocol 0 5 or just an arbitrary object for any newer protocol The resolution of such persistent IDs is not defined by the pickle module it will delegate this resolution to the user defined methods on the pickler and unpickler persistent_id and persistent_load respectively To pickle objects that have an external persistent ID the pickler must have a custom persistent_id method that takes an object as an argument and returns either None or the persistent ID for that object When None is returned the pickler simply pickles the object as normal When a persistent ID string is returned the pickler will pickle that object along with a marker so that the unpickler will recognize it as a persistent ID To unpickle external objects the unpickler must have a custom persistent_load method that takes a persistent ID object and returns the referenced object Here is a comprehensive example presenting how persistent ID can be used to pickle external objects by reference Simple example presenting how persistent ID can be used to pickle external objects by reference import pickle import sqlite3 from collections import namedtuple Simple class representing a record in our database MemoRecord namedtuple MemoRecord key task class DBPickler pickle Pickler def persistent_id self obj Instead of pickling MemoRecord as a regular class instance we emit a persistent ID if isinstance obj MemoRecord Here our persistent ID is simply a tuple containing a tag and a key which refers to a specific record in the database return MemoRecord obj key else If obj does not have a persistent ID return None This means obj needs to be pickled as usual return None class DBUnpickler pickle Unpickler def __init__ self file connection super __init__ file self connection connection def persistent_load self pid This method is invoked whenever a persistent ID is encountered Here pid is the tuple returned by DBPickler cursor self connection cursor type_tag key_id pid if type_tag MemoRecord Fetch the referenced record from the database and return it cursor execute SELECT FROM memos WHERE key str key_id key task cursor fetchone return MemoRecord key task else Always raises an error if you cannot return the correct object Otherwise the unpickler will think None is the object referenced by the persistent ID raise pickle UnpicklingError un,en
142,supported persistent object def main import io import pprint Initialize and populate our database conn sqlite3 connect memory cursor conn cursor cursor execute CREATE TABLE memos key INTEGER PRIMARY KEY task TEXT tasks give food to fish prepare group meeting fight with a zebra for task in tasks cursor execute INSERT INTO memos VALUES NULL task Fetch the records to be pickled cursor execute SELECT FROM memos memos MemoRecord key task for key task in cursor Save the records using our custom DBPickler file io BytesIO DBPickler file dump memos print Pickled records pprint pprint memos Update a record just for good measure cursor execute UPDATE memos SET task learn italian WHERE key 1 Load the records from the pickle data stream file seek 0 memos DBUnpickler file conn load print Unpickled records pprint pprint memos if __name__ __main__ main Dispatch Tables If one wants to customize pickling of some classes without disturbing any other code which depends on pickling then one can create a pickler with a private dispatch table The global dispatch table managed by the copyreg module is available as copyreg dispatch_table Therefore one may choose to use a modified copy of copyreg dispatch_table as a private dispatch table For example f io BytesIO p pickle Pickler f p dispatch_table copyreg dispatch_table copy p dispatch_table SomeClass reduce_SomeClass creates an instance of pickle Pickler with a private dispatch table which handles the SomeClass class specially Alternatively the code class MyPickler pickle Pickler dispatch_table copyreg dispatch_table copy dispatch_table SomeClass reduce_SomeClass f io BytesIO p MyPickler f does the same but all instances of MyPickler will by default share the private dispatch table On the other hand the code copyreg pickle SomeClass reduce_SomeClass f io BytesIO p pickle Pickler f modifies the global dispatch table shared by all users of the copyreg module Handling Stateful Objects Here s an example that shows how to modify pickling behavior for a class The TextReader class below opens a text file and returns the line number and line contents each time its readline method is called If a TextReader instance is pickled all attributes except the file object member are saved When the instance is unpickled the file is reopened and reading resumes from the last location The __setstate__ and __getstate__ methods are used to implement this behavior class TextReader Print and number lines in a text file def __init__ self filename self filename filename self file open filename self lineno 0 def readline self self lineno 1 line self file readline if not line return None if line endswith n line line 1 return i s self lineno line def __getstate__ self Copy the object s state from self __dict__ which contains all our instance attributes Always use the dict copy method to avoid modifying the original state state self __dict__ copy Remove the unpicklable entries del state file return state def __setstate__ self state Restore instance attributes i e filename and lineno self __dict__ update state Restore the previously opened file s state To do so we need to reopen it and read from it until the line count is restored file open self filename for _ in range self lineno file readline Finally save the file self file file A sample usage might be something like this reader TextReader hello txt reader readline 1 Hello world reader readline 2 I am line number two new_reader pickle loads pickle dumps reader new_reader readline 3 Goodbye Custom Reduction for Types Functions and Other Objects New in version 3 8 Sometimes dispatch_table may not be flexible enough In particular we may want to customize pickling based on another criterion than the object s type or we may want to customize the pickling of functions and classes For those cases it is possible to subclass from the Pickler class and implement a reducer_override method This method can return an arbitrary reduction tuple see __reduce__ It can alternatively return NotImplemented to fallback to the traditional behavior If both the dispatch_table and reducer_override a,en
143,re defined then reducer_override method takes priority Note For performance reasons reducer_override may not be called for the following objects None True False and exact instances of int float bytes str dict set frozenset list and tuple Here is a simple example where we allow pickling and reconstructing a given class import io import pickle class MyClass my_attribute 1 class MyPickler pickle Pickler def reducer_override self obj Custom reducer for MyClass if getattr obj __name__ None MyClass return type obj __name__ obj __bases__ my_attribute obj my_attribute else For any other object fallback to usual reduction return NotImplemented f io BytesIO p MyPickler f p dump MyClass del MyClass unpickled_class pickle loads f getvalue assert isinstance unpickled_class type assert unpickled_class __name__ MyClass assert unpickled_class my_attribute 1 Out of band Buffers New in version 3 8 In some contexts the pickle module is used to transfer massive amounts of data Therefore it can be important to minimize the number of memory copies to preserve performance and resource consumption However normal operation of the pickle module as it transforms a graph like structure of objects into a sequential stream of bytes intrinsically involves copying data to and from the pickle stream This constraint can be eschewed if both the provider the implementation of the object types to be transferred and the consumer the implementation of the communications system support the out of band transfer facilities provided by pickle protocol 5 and higher Provider API The large data objects to be pickled must implement a __reduce_ex__ method specialized for protocol 5 and higher which returns a PickleBuffer instance instead of e g a bytes object for any large data A PickleBuffer object signals that the underlying buffer is eligible for out of band data transfer Those objects remain compatible with normal usage of the pickle module However consumers can also opt in to tell pickle that they will handle those buffers by themselves Consumer API A communications system can enable custom handling of the PickleBuffer objects generated when serializing an object graph On the sending side it needs to pass a buffer_callback argument to Pickler or to the dump or dumps function which will be called with each PickleBuffer generated while pickling the object graph Buffers accumulated by the buffer_callback will not see their data copied into the pickle stream only a cheap marker will be inserted On the receiving side it needs to pass a buffers argument to Unpickler or to the load or loads function which is an iterable of the buffers which were passed to buffer_callback That iterable should produce buffers in the same order as they were passed to buffer_callback Those buffers will provide the data expected by the reconstructors of the objects whose pickling produced the original PickleBuffer objects Between the sending side and the receiving side the communications system is free to implement its own transfer mechanism for out of band buffers Potential optimizations include the use of shared memory or datatype dependent compression Example Here is a trivial example where we implement a bytearray subclass able to participate in out of band buffer pickling class ZeroCopyByteArray bytearray def __reduce_ex__ self protocol if protocol 5 return type self _reconstruct PickleBuffer self None else PickleBuffer is forbidden with pickle protocols 4 return type self _reconstruct bytearray self classmethod def _reconstruct cls obj with memoryview obj as m Get a handle over the original buffer object obj m obj if type obj is cls Original buffer object is a ZeroCopyByteArray return it as is return obj else return cls obj The reconstructor the _reconstruct class method returns the buffer s providing object if it has the right type This is an easy way to simulate zero copy behaviour on this toy example On the consumer side we can pickle those objects the usual way which when unserialized will give us a copy of the original object b ZeroCopyByteArray b abc data pickle dumps b protocol ,en
144,5 new_b pickle loads data print b new_b True print b is new_b False a copy was made But if we pass a buffer_callback and then give back the accumulated buffers when unserializing we are able to get back the original object b ZeroCopyByteArray b abc buffers data pickle dumps b protocol 5 buffer_callback buffers append new_b pickle loads data buffers buffers print b new_b True print b is new_b True no copy was made This example is limited by the fact that bytearray allocates its own memory you cannot create a bytearray instance that is backed by another object s memory However third party datatypes such as NumPy arrays do not have this limitation and allow use of zero copy pickling or making as few copies as possible when transferring between distinct processes or systems See also PEP 574 Pickle protocol 5 with out of band data Restricting Globals By default unpickling will import any class or function that it finds in the pickle data For many applications this behaviour is unacceptable as it permits the unpickler to import and invoke arbitrary code Just consider what this hand crafted pickle data stream does when loaded import pickle pickle loads b cos nsystem n S echo hello world ntR hello world 0 In this example the unpickler imports the os system function and then apply the string argument echo hello world Although this example is inoffensive it is not difficult to imagine one that could damage your system For this reason you may want to control what gets unpickled by customizing Unpickler find_class Unlike its name suggests Unpickler find_class is called whenever a global i e a class or a function is requested Thus it is possible to either completely forbid globals or restrict them to a safe subset Here is an example of an unpickler allowing only few safe classes from the builtins module to be loaded import builtins import io import pickle safe_builtins range complex set frozenset slice class RestrictedUnpickler pickle Unpickler def find_class self module name Only allow safe classes from builtins if module builtins and name in safe_builtins return getattr builtins name Forbid everything else raise pickle UnpicklingError global s s is forbidden module name def restricted_loads s Helper function analogous to pickle loads return RestrictedUnpickler io BytesIO s load A sample usage of our unpickler working as intended restricted_loads pickle dumps 1 2 range 15 1 2 range 0 15 restricted_loads b cos nsystem n S echo hello world ntR Traceback most recent call last pickle UnpicklingError global os system is forbidden restricted_loads b cbuiltins neval n b S getattr __import__ os system b echo hello world ntR Traceback most recent call last pickle UnpicklingError global builtins eval is forbidden As our examples shows you have to be careful with what you allow to be unpickled Therefore if security is a concern you may want to consider alternatives such as the marshalling API in xmlrpc client or third party solutions Performance Recent versions of the pickle protocol from protocol 2 and upwards feature efficient binary encodings for several common features and built in types Also the pickle module has a transparent optimizer written in C Examples For the simplest code use the dump and load functions import pickle An arbitrary collection of objects supported by pickle data a 1 2 0 3 4j b character string b byte string c None True False with open data pickle wb as f Pickle the data dictionary using the highest protocol available pickle dump data f pickle HIGHEST_PROTOCOL The following example reads the resulting pickled data import pickle with open data pickle rb as f The protocol version used is detected automatically so we do not have to specify it data pickle load f See also Module copyreg Pickle interface constructor registration for extension types Module pickletools Tools for working with and analyzing pickled data Module shelve Indexed databases of objects uses pickle Module copy Shallow and deep object copying Module marshal High performance serialization of built in types Footnotes 1 Don t confuse this with the marshal ,en
145,module 2 This is why lambda functions cannot be pickled all lambda functions share the same name lambda 3 The exception raised will likely be an ImportError or an AttributeError but it could be something else 4 The copy module uses this protocol for shallow and deep copying operations 5 The limitation on alphanumeric characters is due to the fact that persistent IDs in protocol 0 are delimited by the newline character Therefore if any kind of newline characters occurs in persistent IDs the resulting pickled data will become unreadable,en
146,Tkinter Dialogs tkinter simpledialog Standard Tkinter input dialogs Source code Lib tkinter simpledialog py The tkinter simpledialog module contains convenience classes and functions for creating simple modal dialogs to get a value from the user tkinter simpledialog askfloat title prompt kw tkinter simpledialog askinteger title prompt kw tkinter simpledialog askstring title prompt kw The above three functions provide dialogs that prompt the user to enter a value of the desired type class tkinter simpledialog Dialog parent title None The base class for custom dialogs body master Override to construct the dialog s interface and return the widget that should have initial focus buttonbox Default behaviour adds OK and Cancel buttons Override for custom button layouts tkinter filedialog File selection dialogs Source code Lib tkinter filedialog py The tkinter filedialog module provides classes and factory functions for creating file directory selection windows Native Load Save Dialogs The following classes and functions provide file dialog windows that combine a native look and feel with configuration options to customize behaviour The following keyword arguments are applicable to the classes and functions listed below parent the window to place the dialog on top of title the title of the window initialdir the directory that the dialog starts in initialfile the file selected upon opening of the dialog filetypes a sequence of label pattern tuples wildcard is allowed defaultextension default extension to append to file save dialogs multiple when true selection of multiple items is allowed Static factory functions The below functions when called create a modal native look and feel dialog wait for the user s selection then return the selected value s or None to the caller tkinter filedialog askopenfile mode r options tkinter filedialog askopenfiles mode r options The above two functions create an Open dialog and return the opened file object s in read only mode tkinter filedialog asksaveasfile mode w options Create a SaveAs dialog and return a file object opened in write only mode tkinter filedialog askopenfilename options tkinter filedialog askopenfilenames options The above two functions create an Open dialog and return the selected filename s that correspond to existing file s tkinter filedialog asksaveasfilename options Create a SaveAs dialog and return the selected filename tkinter filedialog askdirectory options Prompt user to select a directory Additional keyword option mustexist determines if selection must be an existing directory class tkinter filedialog Open master None options class tkinter filedialog SaveAs master None options The above two classes provide native dialog windows for saving and loading files Convenience classes The below classes are used for creating file directory windows from scratch These do not emulate the native look and feel of the platform class tkinter filedialog Directory master None options Create a dialog prompting the user to select a directory Note The FileDialog class should be subclassed for custom event handling and behaviour class tkinter filedialog FileDialog master title None Create a basic file selection dialog cancel_command event None Trigger the termination of the dialog window dirs_double_event event Event handler for double click event on directory dirs_select_event event Event handler for click event on directory files_double_event event Event handler for double click event on file files_select_event event Event handler for single click event on file filter_command event None Filter the files by directory get_filter Retrieve the file filter currently in use get_selection Retrieve the currently selected item go dir_or_file os curdir pattern default key None Render dialog and start event loop ok_event event Exit dialog returning current selection quit how None Exit dialog returning filename if any set_filter dir pat Set the file filter set_selection file Update the current file selection to file class tkinter filedialog LoadFileDialog master title None A subclass of FileDialog tha,en
147,t creates a dialog window for selecting an existing file ok_command Test that a file is provided and that the selection indicates an already existing file class tkinter filedialog SaveFileDialog master title None A subclass of FileDialog that creates a dialog window for selecting a destination file ok_command Test whether or not the selection points to a valid file that is not a directory Confirmation is required if an already existing file is selected tkinter commondialog Dialog window templates Source code Lib tkinter commondialog py The tkinter commondialog module provides the Dialog class that is the base class for dialogs defined in other supporting modules class tkinter commondialog Dialog master None options show color None options Render the Dialog window See also Modules tkinter messagebox Reading and Writing Files,en
148,5 The import system Python code in one module gains access to the code in another module by the process of importing it The import statement is the most common way of invoking the import machinery but it is not the only way Functions such as importlib import_module and built in __import__ can also be used to invoke the import machinery The import statement combines two operations it searches for the named module then it binds the results of that search to a name in the local scope The search operation of the import statement is defined as a call to the __import__ function with the appropriate arguments The return value of __import__ is used to perform the name binding operation of the import statement See the import statement for the exact details of that name binding operation A direct call to __import__ performs only the module search and if found the module creation operation While certain side effects may occur such as the importing of parent packages and the updating of various caches including sys modules only the import statement performs a name binding operation When an import statement is executed the standard builtin __import__ function is called Other mechanisms for invoking the import system such as importlib import_module may choose to bypass __import__ and use their own solutions to implement import semantics When a module is first imported Python searches for the module and if found it creates a module object 1 initializing it If the named module cannot be found a ModuleNotFoundError is raised Python implements various strategies to search for the named module when the import machinery is invoked These strategies can be modified and extended by using various hooks described in the sections below Changed in version 3 3 The import system has been updated to fully implement the second phase of PEP 302 There is no longer any implicit import machinery the full import system is exposed through sys meta_path In addition native namespace package support has been implemented see PEP 420 5 1 importlib The importlib module provides a rich API for interacting with the import system For example importlib import_module provides a recommended simpler API than built in __import__ for invoking the import machinery Refer to the importlib library documentation for additional detail 5 2 Packages Python has only one type of module object and all modules are of this type regardless of whether the module is implemented in Python C or something else To help organize modules and provide a naming hierarchy Python has a concept of packages You can think of packages as the directories on a file system and modules as files within directories but don t take this analogy too literally since packages and modules need not originate from the file system For the purposes of this documentation we ll use this convenient analogy of directories and files Like file system directories packages are organized hierarchically and packages may themselves contain subpackages as well as regular modules It s important to keep in mind that all packages are modules but not all modules are packages Or put another way packages are just a special kind of module Specifically any module that contains a __path__ attribute is considered a package All modules have a name Subpackage names are separated from their parent package name by a dot akin to Python s standard attribute access syntax Thus you might have a package called email which in turn has a subpackage called email mime and a module within that subpackage called email mime text 5 2 1 Regular packages Python defines two types of packages regular packages and namespace packages Regular packages are traditional packages as they existed in Python 3 2 and earlier A regular package is typically implemented as a directory containing an __init__ py file When a regular package is imported this __init__ py file is implicitly executed and the objects it defines are bound to names in the package s namespace The __init__ py file can contain the same Python code that any other module can contain and Python will add so,en
149,me additional attributes to the module when it is imported For example the following file system layout defines a top level parent package with three subpackages parent __init__ py one __init__ py two __init__ py three __init__ py Importing parent one will implicitly execute parent __init__ py and parent one __init__ py Subsequent imports of parent two or parent three will execute parent two __init__ py and parent three __init__ py respectively 5 2 2 Namespace packages A namespace package is a composite of various portions where each portion contributes a subpackage to the parent package Portions may reside in different locations on the file system Portions may also be found in zip files on the network or anywhere else that Python searches during import Namespace packages may or may not correspond directly to objects on the file system they may be virtual modules that have no concrete representation Namespace packages do not use an ordinary list for their __path__ attribute They instead use a custom iterable type which will automatically perform a new search for package portions on the next import attempt within that package if the path of their parent package or sys path for a top level package changes With namespace packages there is no parent __init__ py file In fact there may be multiple parent directories found during import search where each one is provided by a different portion Thus parent one may not be physically located next to parent two In this case Python will create a namespace package for the top level parent package whenever it or one of its subpackages is imported See also PEP 420 for the namespace package specification 5 3 Searching To begin the search Python needs the fully qualified name of the module or package but for the purposes of this discussion the difference is immaterial being imported This name may come from various arguments to the import statement or from the parameters to the importlib import_module or __import__ functions This name will be used in various phases of the import search and it may be the dotted path to a submodule e g foo bar baz In this case Python first tries to import foo then foo bar and finally foo bar baz If any of the intermediate imports fail a ModuleNotFoundError is raised 5 3 1 The module cache The first place checked during import search is sys modules This mapping serves as a cache of all modules that have been previously imported including the intermediate paths So if foo bar baz was previously imported sys modules will contain entries for foo foo bar and foo bar baz Each key will have as its value the corresponding module object During import the module name is looked up in sys modules and if present the associated value is the module satisfying the import and the process completes However if the value is None then a ModuleNotFoundError is raised If the module name is missing Python will continue searching for the module sys modules is writable Deleting a key may not destroy the associated module as other modules may hold references to it but it will invalidate the cache entry for the named module causing Python to search anew for the named module upon its next import The key can also be assigned to None forcing the next import of the module to result in a ModuleNotFoundError Beware though as if you keep a reference to the module object invalidate its cache entry in sys modules and then re import the named module the two module objects will not be the same By contrast importlib reload will reuse the same module object and simply reinitialise the module contents by rerunning the module s code 5 3 2 Finders and loaders If the named module is not found in sys modules then Python s import protocol is invoked to find and load the module This protocol consists of two conceptual objects finders and loaders A finder s job is to determine whether it can find the named module using whatever strategy it knows about Objects that implement both of these interfaces are referred to as importers they return themselves when they find that they can load the requested module Pyt,en
150,hon includes a number of default finders and importers The first one knows how to locate built in modules and the second knows how to locate frozen modules A third default finder searches an import path for modules The import path is a list of locations that may name file system paths or zip files It can also be extended to search for any locatable resource such as those identified by URLs The import machinery is extensible so new finders can be added to extend the range and scope of module searching Finders do not actually load modules If they can find the named module they return a module spec an encapsulation of the module s import related information which the import machinery then uses when loading the module The following sections describe the protocol for finders and loaders in more detail including how you can create and register new ones to extend the import machinery Changed in version 3 4 In previous versions of Python finders returned loaders directly whereas now they return module specs which contain loaders Loaders are still used during import but have fewer responsibilities 5 3 3 Import hooks The import machinery is designed to be extensible the primary mechanism for this are the import hooks There are two types of import hooks meta hooks and import path hooks Meta hooks are called at the start of import processing before any other import processing has occurred other than sys modules cache look up This allows meta hooks to override sys path processing frozen modules or even built in modules Meta hooks are registered by adding new finder objects to sys meta_path as described below Import path hooks are called as part of sys path or package __path__ processing at the point where their associated path item is encountered Import path hooks are registered by adding new callables to sys path_hooks as described below 5 3 4 The meta path When the named module is not found in sys modules Python next searches sys meta_path which contains a list of meta path finder objects These finders are queried in order to see if they know how to handle the named module Meta path finders must implement a method called find_spec which takes three arguments a name an import path and optionally a target module The meta path finder can use any strategy it wants to determine whether it can handle the named module or not If the meta path finder knows how to handle the named module it returns a spec object If it cannot handle the named module it returns None If sys meta_path processing reaches the end of its list without returning a spec then a ModuleNotFoundError is raised Any other exceptions raised are simply propagated up aborting the import process The find_spec method of meta path finders is called with two or three arguments The first is the fully qualified name of the module being imported for example foo bar baz The second argument is the path entries to use for the module search For top level modules the second argument is None but for submodules or subpackages the second argument is the value of the parent package s __path__ attribute If the appropriate __path__ attribute cannot be accessed a ModuleNotFoundError is raised The third argument is an existing module object that will be the target of loading later The import system passes in a target module only during reload The meta path may be traversed multiple times for a single import request For example assuming none of the modules involved has already been cached importing foo bar baz will first perform a top level import calling mpf find_spec foo None None on each meta path finder mpf After foo has been imported foo bar will be imported by traversing the meta path a second time calling mpf find_spec foo bar foo __path__ None Once foo bar has been imported the final traversal will call mpf find_spec foo bar baz foo bar __path__ None Some meta path finders only support top level imports These importers will always return None when anything other than None is passed as the second argument Python s default sys meta_path has three meta path finders one that knows how to impor,en
151,t built in modules one that knows how to import frozen modules and one that knows how to import modules from an import path i e the path based finder Changed in version 3 4 The find_spec method of meta path finders replaced find_module which is now deprecated While it will continue to work without change the import machinery will try it only if the finder does not implement find_spec Changed in version 3 10 Use of find_module by the import system now raises ImportWarning Changed in version 3 12 find_module has been removed Use find_spec instead 5 4 Loading If and when a module spec is found the import machinery will use it and the loader it contains when loading the module Here is an approximation of what happens during the loading portion of import module None if spec loader is not None and hasattr spec loader create_module It is assumed exec_module will also be defined on the loader module spec loader create_module spec if module is None module ModuleType spec name The import related module attributes get set here _init_module_attrs spec module if spec loader is None unsupported raise ImportError if spec origin is None and spec submodule_search_locations is not None namespace package sys modules spec name module elif not hasattr spec loader exec_module module spec loader load_module spec name else sys modules spec name module try spec loader exec_module module except BaseException try del sys modules spec name except KeyError pass raise return sys modules spec name Note the following details If there is an existing module object with the given name in sys modules import will have already returned it The module will exist in sys modules before the loader executes the module code This is crucial because the module code may directly or indirectly import itself adding it to sys modules beforehand prevents unbounded recursion in the worst case and multiple loading in the best If loading fails the failing module and only the failing module gets removed from sys modules Any module already in the sys modules cache and any module that was successfully loaded as a side effect must remain in the cache This contrasts with reloading where even the failing module is left in sys modules After the module is created but before execution the import machinery sets the import related module attributes _init_module_attrs in the pseudo code example above as summarized in a later section Module execution is the key moment of loading in which the module s namespace gets populated Execution is entirely delegated to the loader which gets to decide what gets populated and how The module created during loading and passed to exec_module may not be the one returned at the end of import 2 Changed in version 3 4 The import system has taken over the boilerplate responsibilities of loaders These were previously performed by the importlib abc Loader load_module method 5 4 1 Loaders Module loaders provide the critical function of loading module execution The import machinery calls the importlib abc Loader exec_module method with a single argument the module object to execute Any value returned from exec_module is ignored Loaders must satisfy the following requirements If the module is a Python module as opposed to a built in module or a dynamically loaded extension the loader should execute the module s code in the module s global name space module __dict__ If the loader cannot execute the module it should raise an ImportError although any other exception raised during exec_module will be propagated In many cases the finder and loader can be the same object in such cases the find_spec method would just return a spec with the loader set to self Module loaders may opt in to creating the module object during loading by implementing a create_module method It takes one argument the module spec and returns the new module object to use during loading create_module does not need to set any attributes on the module object If the method returns None the import machinery will create the new module itself New in version 3 4 The create_module method of loaders Change,en
152,d in version 3 4 The load_module method was replaced by exec_module and the import machinery assumed all the boilerplate responsibilities of loading For compatibility with existing loaders the import machinery will use the load_module method of loaders if it exists and the loader does not also implement exec_module However load_module has been deprecated and loaders should implement exec_module instead The load_module method must implement all the boilerplate loading functionality described above in addition to executing the module All the same constraints apply with some additional clarification If there is an existing module object with the given name in sys modules the loader must use that existing module Otherwise importlib reload will not work correctly If the named module does not exist in sys modules the loader must create a new module object and add it to sys modules The module must exist in sys modules before the loader executes the module code to prevent unbounded recursion or multiple loading If loading fails the loader must remove any modules it has inserted into sys modules but it must remove only the failing module s and only if the loader itself has loaded the module s explicitly Changed in version 3 5 A DeprecationWarning is raised when exec_module is defined but create_module is not Changed in version 3 6 An ImportError is raised when exec_module is defined but create_module is not Changed in version 3 10 Use of load_module will raise ImportWarning 5 4 2 Submodules When a submodule is loaded using any mechanism e g importlib APIs the import or import from statements or built in __import__ a binding is placed in the parent module s namespace to the submodule object For example if package spam has a submodule foo after importing spam foo spam will have an attribute foo which is bound to the submodule Let s say you have the following directory structure spam __init__ py foo py and spam __init__ py has the following line in it from foo import Foo then executing the following puts name bindings for foo and Foo in the spam module import spam spam foo module spam foo from tmp imports spam foo py spam Foo class spam foo Foo Given Python s familiar name binding rules this might seem surprising but it s actually a fundamental feature of the import system The invariant holding is that if you have sys modules spam and sys modules spam foo as you would after the above import the latter must appear as the foo attribute of the former 5 4 3 Module spec The import machinery uses a variety of information about each module during import especially before loading Most of the information is common to all modules The purpose of a module s spec is to encapsulate this import related information on a per module basis Using a spec during import allows state to be transferred between import system components e g between the finder that creates the module spec and the loader that executes it Most importantly it allows the import machinery to perform the boilerplate operations of loading whereas without a module spec the loader had that responsibility The module s spec is exposed as the __spec__ attribute on a module object See ModuleSpec for details on the contents of the module spec New in version 3 4 5 4 4 Import related module attributes The import machinery fills in these attributes on each module object during loading based on the module s spec before the loader executes the module It is strongly recommended that you rely on __spec__ and its attributes instead of any of the other individual attributes listed below __name__ The __name__ attribute must be set to the fully qualified name of the module This name is used to uniquely identify the module in the import system __loader__ The __loader__ attribute must be set to the loader object that the import machinery used when loading the module This is mostly for introspection but can be used for additional loader specific functionality for example getting data associated with a loader It is strongly recommended that you rely on __spec__ instead of this attribute Changed in version,en
153, 3 12 The value of __loader__ is expected to be the same as __spec__ loader The use of __loader__ is deprecated and slated for removal in Python 3 14 __package__ The module s __package__ attribute may be set Its value must be a string but it can be the same value as its __name__ When the module is a package its __package__ value should be set to its __name__ When the module is not a package __package__ should be set to the empty string for top level modules or for submodules to the parent package s name See PEP 366 for further details This attribute is used instead of __name__ to calculate explicit relative imports for main modules as defined in PEP 366 It is strongly recommended that you rely on __spec__ instead of this attribute Changed in version 3 6 The value of __package__ is expected to be the same as __spec__ parent Changed in version 3 10 ImportWarning is raised if import falls back to __package__ instead of parent Changed in version 3 12 Raise DeprecationWarning instead of ImportWarning when falling back to __package__ __spec__ The __spec__ attribute must be set to the module spec that was used when importing the module Setting __spec__ appropriately applies equally to modules initialized during interpreter startup The one exception is __main__ where __spec__ is set to None in some cases When __spec__ parent is not set __package__ is used as a fallback New in version 3 4 Changed in version 3 6 __spec__ parent is used as a fallback when __package__ is not defined __path__ If the module is a package either regular or namespace the module object s __path__ attribute must be set The value must be iterable but may be empty if __path__ has no further significance If __path__ is not empty it must produce strings when iterated over More details on the semantics of __path__ are given below Non package modules should not have a __path__ attribute __file__ __cached__ __file__ is optional if set value must be a string It indicates the pathname of the file from which the module was loaded if loaded from a file or the pathname of the shared library file for extension modules loaded dynamically from a shared library It might be missing for certain types of modules such as C modules that are statically linked into the interpreter and the import system may opt to leave it unset if it has no semantic meaning e g a module loaded from a database If __file__ is set then the __cached__ attribute might also be set which is the path to any compiled version of the code e g byte compiled file The file does not need to exist to set this attribute the path can simply point to where the compiled file would exist see PEP 3147 Note that __cached__ may be set even if __file__ is not set However that scenario is quite atypical Ultimately the loader is what makes use of the module spec provided by the finder from which __file__ and __cached__ are derived So if a loader can load from a cached module but otherwise does not load from a file that atypical scenario may be appropriate It is strongly recommended that you rely on __spec__ instead of __cached__ 5 4 5 module __path__ By definition if a module has a __path__ attribute it is a package A package s __path__ attribute is used during imports of its subpackages Within the import machinery it functions much the same as sys path i e providing a list of locations to search for modules during import However __path__ is typically much more constrained than sys path __path__ must be an iterable of strings but it may be empty The same rules used for sys path also apply to a package s __path__ and sys path_hooks described below are consulted when traversing a package s __path__ A package s __init__ py file may set or alter the package s __path__ attribute and this was typically the way namespace packages were implemented prior to PEP 420 With the adoption of PEP 420 namespace packages no longer need to supply __init__ py files containing only __path__ manipulation code the import machinery automatically sets __path__ correctly for the namespace package 5 4 6 Module reprs By default all modules have a us,en
154,able repr however depending on the attributes set above and in the module s spec you can more explicitly control the repr of module objects If the module has a spec __spec__ the import machinery will try to generate a repr from it If that fails or there is no spec the import system will craft a default repr using whatever information is available on the module It will try to use the module __name__ module __file__ and module __loader__ as input into the repr with defaults for whatever information is missing Here are the exact rules used If the module has a __spec__ attribute the information in the spec is used to generate the repr The name loader origin and has_location attributes are consulted If the module has a __file__ attribute this is used as part of the module s repr If the module has no __file__ but does have a __loader__ that is not None then the loader s repr is used as part of the module s repr Otherwise just use the module s __name__ in the repr Changed in version 3 12 Use of module_repr having been deprecated since Python 3 4 was removed in Python 3 12 and is no longer called during the resolution of a module s repr 5 4 7 Cached bytecode invalidation Before Python loads cached bytecode from a pyc file it checks whether the cache is up to date with the source py file By default Python does this by storing the source s last modified timestamp and size in the cache file when writing it At runtime the import system then validates the cache file by checking the stored metadata in the cache file against the source s metadata Python also supports hash based cache files which store a hash of the source file s contents rather than its metadata There are two variants of hash based pyc files checked and unchecked For checked hash based pyc files Python validates the cache file by hashing the source file and comparing the resulting hash with the hash in the cache file If a checked hash based cache file is found to be invalid Python regenerates it and writes a new checked hash based cache file For unchecked hash based pyc files Python simply assumes the cache file is valid if it exists Hash based pyc files validation behavior may be overridden with the check hash based pycs flag Changed in version 3 7 Added hash based pyc files Previously Python only supported timestamp based invalidation of bytecode caches 5 5 The Path Based Finder As mentioned previously Python comes with several default meta path finders One of these called the path based finder PathFinder searches an import path which contains a list of path entries Each path entry names a location to search for modules The path based finder itself doesn t know how to import anything Instead it traverses the individual path entries associating each of them with a path entry finder that knows how to handle that particular kind of path The default set of path entry finders implement all the semantics for finding modules on the file system handling special file types such as Python source code py files Python byte code pyc files and shared libraries e g so files When supported by the zipimport module in the standard library the default path entry finders also handle loading all of these file types other than shared libraries from zipfiles Path entries need not be limited to file system locations They can refer to URLs database queries or any other location that can be specified as a string The path based finder provides additional hooks and protocols so that you can extend and customize the types of searchable path entries For example if you wanted to support path entries as network URLs you could write a hook that implements HTTP semantics to find modules on the web This hook a callable would return a path entry finder supporting the protocol described below which was then used to get a loader for the module from the web A word of warning this section and the previous both use the term finder distinguishing between them by using the terms meta path finder and path entry finder These two types of finders are very similar support similar protocols and function in similar,en
155, ways during the import process but it s important to keep in mind that they are subtly different In particular meta path finders operate at the beginning of the import process as keyed off the sys meta_path traversal By contrast path entry finders are in a sense an implementation detail of the path based finder and in fact if the path based finder were to be removed from sys meta_path none of the path entry finder semantics would be invoked 5 5 1 Path entry finders The path based finder is responsible for finding and loading Python modules and packages whose location is specified with a string path entry Most path entries name locations in the file system but they need not be limited to this As a meta path finder the path based finder implements the find_spec protocol previously described however it exposes additional hooks that can be used to customize how modules are found and loaded from the import path Three variables are used by the path based finder sys path sys path_hooks and sys path_importer_cache The __path__ attributes on package objects are also used These provide additional ways that the import machinery can be customized sys path contains a list of strings providing search locations for modules and packages It is initialized from the PYTHONPATH environment variable and various other installation and implementation specific defaults Entries in sys path can name directories on the file system zip files and potentially other locations see the site module that should be searched for modules such as URLs or database queries Only strings should be present on sys path all other data types are ignored The path based finder is a meta path finder so the import machinery begins the import path search by calling the path based finder s find_spec method as described previously When the path argument to find_spec is given it will be a list of string paths to traverse typically a package s __path__ attribute for an import within that package If the path argument is None this indicates a top level import and sys path is used The path based finder iterates over every entry in the search path and for each of these looks for an appropriate path entry finder PathEntryFinder for the path entry Because this can be an expensive operation e g there may be stat call overheads for this search the path based finder maintains a cache mapping path entries to path entry finders This cache is maintained in sys path_importer_cache despite the name this cache actually stores finder objects rather than being limited to importer objects In this way the expensive search for a particular path entry location s path entry finder need only be done once User code is free to remove cache entries from sys path_importer_cache forcing the path based finder to perform the path entry search again If the path entry is not present in the cache the path based finder iterates over every callable in sys path_hooks Each of the path entry hooks in this list is called with a single argument the path entry to be searched This callable may either return a path entry finder that can handle the path entry or it may raise ImportError An ImportError is used by the path based finder to signal that the hook cannot find a path entry finder for that path entry The exception is ignored and import path iteration continues The hook should expect either a string or bytes object the encoding of bytes objects is up to the hook e g it may be a file system encoding UTF 8 or something else and if the hook cannot decode the argument it should raise ImportError If sys path_hooks iteration ends with no path entry finder being returned then the path based finder s find_spec method will store None in sys path_importer_cache to indicate that there is no finder for this path entry and return None indicating that this meta path finder could not find the module If a path entry finder is returned by one of the path entry hook callables on sys path_hooks then the following protocol is used to ask the finder for a module spec which is then used when loading the module The current working di,en
156,rectory denoted by an empty string is handled slightly differently from other entries on sys path First if the current working directory is found to not exist no value is stored in sys path_importer_cache Second the value for the current working directory is looked up fresh for each module lookup Third the path used for sys path_importer_cache and returned by importlib machinery PathFinder find_spec will be the actual current working directory and not the empty string 5 5 2 Path entry finder protocol In order to support imports of modules and initialized packages and also to contribute portions to namespace packages path entry finders must implement the find_spec method find_spec takes two arguments the fully qualified name of the module being imported and the optional target module find_spec returns a fully populated spec for the module This spec will always have loader set with one exception To indicate to the import machinery that the spec represents a namespace portion the path entry finder sets submodule_search_locations to a list containing the portion Changed in version 3 4 find_spec replaced find_loader and find_module both of which are now deprecated but will be used if find_spec is not defined Older path entry finders may implement one of these two deprecated methods instead of find_spec The methods are still respected for the sake of backward compatibility However if find_spec is implemented on the path entry finder the legacy methods are ignored find_loader takes one argument the fully qualified name of the module being imported find_loader returns a 2 tuple where the first item is the loader and the second item is a namespace portion For backwards compatibility with other implementations of the import protocol many path entry finders also support the same traditional find_module method that meta path finders support However path entry finder find_module methods are never called with a path argument they are expected to record the appropriate path information from the initial call to the path hook The find_module method on path entry finders is deprecated as it does not allow the path entry finder to contribute portions to namespace packages If both find_loader and find_module exist on a path entry finder the import system will always call find_loader in preference to find_module Changed in version 3 10 Calls to find_module and find_loader by the import system will raise ImportWarning Changed in version 3 12 find_module and find_loader have been removed 5 6 Replacing the standard import system The most reliable mechanism for replacing the entire import system is to delete the default contents of sys meta_path replacing them entirely with a custom meta path hook If it is acceptable to only alter the behaviour of import statements without affecting other APIs that access the import system then replacing the builtin __import__ function may be sufficient This technique may also be employed at the module level to only alter the behaviour of import statements within that module To selectively prevent the import of some modules from a hook early on the meta path rather than disabling the standard import system entirely it is sufficient to raise ModuleNotFoundError directly from find_spec instead of returning None The latter indicates that the meta path search should continue while raising an exception terminates it immediately 5 7 Package Relative Imports Relative imports use leading dots A single leading dot indicates a relative import starting with the current package Two or more leading dots indicate a relative import to the parent s of the current package one level per dot after the first For example given the following package layout package __init__ py subpackage1 __init__ py moduleX py moduleY py subpackage2 __init__ py moduleZ py moduleA py In either subpackage1 moduleX py or subpackage1 __init__ py the following are valid relative imports from moduleY import spam from moduleY import spam as ham from import moduleY from subpackage1 import moduleY from subpackage2 moduleZ import eggs from moduleA import foo A,en
157,bsolute imports may use either the import or from import syntax but relative imports may only use the second form the reason for this is that import XXX YYY ZZZ should expose XXX YYY ZZZ as a usable expression but moduleY is not a valid expression 5 8 Special considerations for __main__ The __main__ module is a special case relative to Python s import system As noted elsewhere the __main__ module is directly initialized at interpreter startup much like sys and builtins However unlike those two it doesn t strictly qualify as a built in module This is because the manner in which __main__ is initialized depends on the flags and other options with which the interpreter is invoked 5 8 1 __main__ __spec__ Depending on how __main__ is initialized __main__ __spec__ gets set appropriately or to None When Python is started with the m option __spec__ is set to the module spec of the corresponding module or package __spec__ is also populated when the __main__ module is loaded as part of executing a directory zipfile or other sys path entry In the remaining cases __main__ __spec__ is set to None as the code used to populate the __main__ does not correspond directly with an importable module interactive prompt c option running from stdin running directly from a source or bytecode file Note that __main__ __spec__ is always None in the last case even if the file could technically be imported directly as a module instead Use the m switch if valid module metadata is desired in __main__ Note also that even when __main__ corresponds with an importable module and __main__ __spec__ is set accordingly they re still considered distinct modules This is due to the fact that blocks guarded by if __name__ __main__ checks only execute when the module is used to populate the __main__ namespace and not during normal import 5 9 References The import machinery has evolved considerably since Python s early days The original specification for packages is still available to read although some details have changed since the writing of that document The original specification for sys meta_path was PEP 302 with subsequent extension in PEP 420 PEP 420 introduced namespace packages for Python 3 3 PEP 420 also introduced the find_loader protocol as an alternative to find_module PEP 366 describes the addition of the __package__ attribute for explicit relative imports in main modules PEP 328 introduced absolute and explicit relative imports and initially proposed __name__ for semantics PEP 366 would eventually specify for __package__ PEP 338 defines executing modules as scripts PEP 451 adds the encapsulation of per module import state in spec objects It also off loads most of the boilerplate responsibilities of loaders back onto the import machinery These changes allow the deprecation of several APIs in the import system and also addition of new methods to finders and loaders Footnotes 1 See types ModuleType 2 The importlib implementation avoids using the return value directly Instead it gets the module object by looking the module name up in sys modules The indirect effect of this is that an imported module may replace itself in sys modules This is implementation specific behavior that is not guaranteed to work in other Python implementations,en
158,fnmatch Unix filename pattern matching Source code Lib fnmatch py This module provides support for Unix shell style wildcards which are not the same as regular expressions which are documented in the re module The special characters used in shell style wildcards are Pattern Meaning matches everything matches any single character seq matches any character in seq seq matches any character not in seq For a literal match wrap the meta characters in brackets For example matches the character Note that the filename separator on Unix is not special to this module See module glob for pathname expansion glob uses filter to match pathname segments Similarly filenames starting with a period are not special for this module and are matched by the and patterns Also note that functools lru_cache with the maxsize of 32768 is used to cache the compiled regex patterns in the following functions fnmatch fnmatchcase filter fnmatch fnmatch name pat Test whether the filename string name matches the pattern string pat returning True or False Both parameters are case normalized using os path normcase fnmatchcase can be used to perform a case sensitive comparison regardless of whether that s standard for the operating system This example will print all file names in the current directory with the extension txt import fnmatch import os for file in os listdir if fnmatch fnmatch file txt print file fnmatch fnmatchcase name pat Test whether the filename string name matches the pattern string pat returning True or False the comparison is case sensitive and does not apply os path normcase fnmatch filter names pat Construct a list from those elements of the iterable names that match pattern pat It is the same as n for n in names if fnmatch n pat but implemented more efficiently fnmatch translate pat Return the shell style pattern pat converted to a regular expression for using with re match Example import fnmatch re regex fnmatch translate txt regex s txt Z reobj re compile regex reobj match foobar txt re Match object span 0 10 match foobar txt See also Module glob Unix shell style path expansion,en
159,sqlite3 DB API 2 0 interface for SQLite databases Source code Lib sqlite3 SQLite is a C library that provides a lightweight disk based database that doesn t require a separate server process and allows accessing the database using a nonstandard variant of the SQL query language Some applications can use SQLite for internal data storage It s also possible to prototype an application using SQLite and then port the code to a larger database such as PostgreSQL or Oracle The sqlite3 module was written by Gerhard Häring It provides an SQL interface compliant with the DB API 2 0 specification described by PEP 249 and requires SQLite 3 7 15 or newer This document includes four main sections Tutorial teaches how to use the sqlite3 module Reference describes the classes and functions this module defines How to guides details how to handle specific tasks Explanation provides in depth background on transaction control See also https www sqlite org The SQLite web page the documentation describes the syntax and the available data types for the supported SQL dialect https www w3schools com sql Tutorial reference and examples for learning SQL syntax PEP 249 Database API Specification 2 0 PEP written by Marc André Lemburg Tutorial In this tutorial you will create a database of Monty Python movies using basic sqlite3 functionality It assumes a fundamental understanding of database concepts including cursors and transactions First we need to create a new database and open a database connection to allow sqlite3 to work with it Call sqlite3 connect to create a connection to the database tutorial db in the current working directory implicitly creating it if it does not exist import sqlite3 con sqlite3 connect tutorial db The returned Connection object con represents the connection to the on disk database In order to execute SQL statements and fetch results from SQL queries we will need to use a database cursor Call con cursor to create the Cursor cur con cursor Now that we ve got a database connection and a cursor we can create a database table movie with columns for title release year and review score For simplicity we can just use column names in the table declaration thanks to the flexible typing feature of SQLite specifying the data types is optional Execute the CREATE TABLE statement by calling cur execute cur execute CREATE TABLE movie title year score We can verify that the new table has been created by querying the sqlite_master table built in to SQLite which should now contain an entry for the movie table definition see The Schema Table for details Execute that query by calling cur execute assign the result to res and call res fetchone to fetch the resulting row res cur execute SELECT name FROM sqlite_master res fetchone movie We can see that the table has been created as the query returns a tuple containing the table s name If we query sqlite_master for a non existent table spam res fetchone will return None res cur execute SELECT name FROM sqlite_master WHERE name spam res fetchone is None True Now add two rows of data supplied as SQL literals by executing an INSERT statement once again by calling cur execute cur execute INSERT INTO movie VALUES Monty Python and the Holy Grail 1975 8 2 And Now for Something Completely Different 1971 7 5 The INSERT statement implicitly opens a transaction which needs to be committed before changes are saved in the database see Transaction control for details Call con commit on the connection object to commit the transaction con commit We can verify that the data was inserted correctly by executing a SELECT query Use the now familiar cur execute to assign the result to res and call res fetchall to return all resulting rows res cur execute SELECT score FROM movie res fetchall 8 2 7 5 The result is a list of two tuple s one per row each containing that row s score value Now insert three more rows by calling cur executemany data Monty Python Live at the Hollywood Bowl 1982 7 9 Monty Python s The Meaning of Life 1983 7 5 Monty Python s Life of Brian 1979 8 0 cur executemany INSERT INTO movie VALUES data ,en
160,con commit Remember to commit the transaction after executing INSERT Notice that placeholders are used to bind data to the query Always use placeholders instead of string formatting to bind Python values to SQL statements to avoid SQL injection attacks see How to use placeholders to bind values in SQL queries for more details We can verify that the new rows were inserted by executing a SELECT query this time iterating over the results of the query for row in cur execute SELECT year title FROM movie ORDER BY year print row 1971 And Now for Something Completely Different 1975 Monty Python and the Holy Grail 1979 Monty Python s Life of Brian 1982 Monty Python Live at the Hollywood Bowl 1983 Monty Python s The Meaning of Life Each row is a two item tuple of year title matching the columns selected in the query Finally verify that the database has been written to disk by calling con close to close the existing connection opening a new one creating a new cursor then querying the database con close new_con sqlite3 connect tutorial db new_cur new_con cursor res new_cur execute SELECT title year FROM movie ORDER BY score DESC title year res fetchone print f The highest scoring Monty Python movie is title r released in year The highest scoring Monty Python movie is Monty Python and the Holy Grail released in 1975 You ve now created an SQLite database using the sqlite3 module inserted data and retrieved values from it in multiple ways See also How to guides for further reading How to use placeholders to bind values in SQL queries How to adapt custom Python types to SQLite values How to convert SQLite values to custom Python types How to use the connection context manager How to create and use row factories Explanation for in depth background on transaction control Reference Module functions sqlite3 connect database timeout 5 0 detect_types 0 isolation_level DEFERRED check_same_thread True factory sqlite3 Connection cached_statements 128 uri False autocommit sqlite3 LEGACY_TRANSACTION_CONTROL Open a connection to an SQLite database Parameters database path like object The path to the database file to be opened You can pass memory to create an SQLite database existing only in memory and open a connection to it timeout float How many seconds the connection should wait before raising an OperationalError when a table is locked If another connection opens a transaction to modify a table that table will be locked until the transaction is committed Default five seconds detect_types int Control whether and how data types not natively supported by SQLite are looked up to be converted to Python types using the converters registered with register_converter Set it to any combination using bitwise or of PARSE_DECLTYPES and PARSE_COLNAMES to enable this Column names takes precedence over declared types if both flags are set Types cannot be detected for generated fields for example max data even when the detect_types parameter is set str will be returned instead By default 0 type detection is disabled isolation_level str None Control legacy transaction handling behaviour See Connection isolation_level and Transaction control via the isolation_level attribute for more information Can be DEFERRED default EXCLUSIVE or IMMEDIATE or None to disable opening transactions implicitly Has no effect unless Connection autocommit is set to LEGACY_TRANSACTION_CONTROL the default check_same_thread bool If True default ProgrammingError will be raised if the database connection is used by a thread other than the one that created it If False the connection may be accessed in multiple threads write operations may need to be serialized by the user to avoid data corruption See threadsafety for more information factory Connection A custom subclass of Connection to create the connection with if not the default Connection class cached_statements int The number of statements that sqlite3 should internally cache for this connection to avoid parsing overhead By default 128 statements uri bool If set to True database is interpreted as a URI Uniform Resource Identifier with a,en
161, file path and an optional query string The scheme part must be file and the path can be relative or absolute The query string allows passing parameters to SQLite enabling various How to work with SQLite URIs autocommit bool Control PEP 249 transaction handling behaviour See Connection autocommit and Transaction control via the autocommit attribute for more information autocommit currently defaults to LEGACY_TRANSACTION_CONTROL The default will change to False in a future Python release Return type Connection Raises an auditing event sqlite3 connect with argument database Raises an auditing event sqlite3 connect handle with argument connection_handle Changed in version 3 4 Added the uri parameter Changed in version 3 7 database can now also be a path like object not only a string Changed in version 3 10 Added the sqlite3 connect handle auditing event Changed in version 3 12 Added the autocommit parameter sqlite3 complete_statement statement Return True if the string statement appears to contain one or more complete SQL statements No syntactic verification or parsing of any kind is performed other than checking that there are no unclosed string literals and the statement is terminated by a semicolon For example sqlite3 complete_statement SELECT foo FROM bar True sqlite3 complete_statement SELECT foo False This function may be useful during command line input to determine if the entered text seems to form a complete SQL statement or if additional input is needed before calling execute See runsource in Lib sqlite3 __main__ py for real world use sqlite3 enable_callback_tracebacks flag Enable or disable callback tracebacks By default you will not get any tracebacks in user defined functions aggregates converters authorizer callbacks etc If you want to debug them you can call this function with flag set to True Afterwards you will get tracebacks from callbacks on sys stderr Use False to disable the feature again Register an unraisable hook handler for an improved debug experience sqlite3 enable_callback_tracebacks True con sqlite3 connect memory def evil_trace stmt 5 0 con set_trace_callback evil_trace def debug unraisable print f unraisable exc_value r in callback unraisable object __name__ print f Error message unraisable err_msg import sys sys unraisablehook debug cur con execute SELECT 1 ZeroDivisionError division by zero in callback evil_trace Error message None sqlite3 register_adapter type adapter Register an adapter callable to adapt the Python type type into an SQLite type The adapter is called with a Python object of type type as its sole argument and must return a value of a type that SQLite natively understands sqlite3 register_converter typename converter Register the converter callable to convert SQLite objects of type typename into a Python object of a specific type The converter is invoked for all SQLite values of type typename it is passed a bytes object and should return an object of the desired Python type Consult the parameter detect_types of connect for information regarding how type detection works Note typename and the name of the type in your query are matched case insensitively Module constants sqlite3 LEGACY_TRANSACTION_CONTROL Set autocommit to this constant to select old style pre Python 3 12 transaction control behaviour See Transaction control via the isolation_level attribute for more information sqlite3 PARSE_COLNAMES Pass this flag value to the detect_types parameter of connect to look up a converter function by using the type name parsed from the query column name as the converter dictionary key The type name must be wrapped in square brackets SELECT p as p point FROM test will look up converter point This flag may be combined with PARSE_DECLTYPES using the bitwise or operator sqlite3 PARSE_DECLTYPES Pass this flag value to the detect_types parameter of connect to look up a converter function using the declared types for each column The types are declared when the database table is created sqlite3 will look up a converter function using the first word of the declared type as the converter dict,en
162,ionary key For example CREATE TABLE test i integer primary key will look up a converter named integer p point will look up a converter named point n number 10 will look up a converter named number This flag may be combined with PARSE_COLNAMES using the bitwise or operator sqlite3 SQLITE_OK sqlite3 SQLITE_DENY sqlite3 SQLITE_IGNORE Flags that should be returned by the authorizer_callback callable passed to Connection set_authorizer to indicate whether Access is allowed SQLITE_OK The SQL statement should be aborted with an error SQLITE_DENY The column should be treated as a NULL value SQLITE_IGNORE sqlite3 apilevel String constant stating the supported DB API level Required by the DB API Hard coded to 2 0 sqlite3 paramstyle String constant stating the type of parameter marker formatting expected by the sqlite3 module Required by the DB API Hard coded to qmark Note The named DB API parameter style is also supported sqlite3 sqlite_version Version number of the runtime SQLite library as a string sqlite3 sqlite_version_info Version number of the runtime SQLite library as a tuple of integers sqlite3 threadsafety Integer constant required by the DB API 2 0 stating the level of thread safety the sqlite3 module supports This attribute is set based on the default threading mode the underlying SQLite library is compiled with The SQLite threading modes are 1 Single thread In this mode all mutexes are disabled and SQLite is unsafe to use in more than a single thread at once 2 Multi thread In this mode SQLite can be safely used by multiple threads provided that no single database connection is used simultaneously in two or more threads 3 Serialized In serialized mode SQLite can be safely used by multiple threads with no restriction The mappings from SQLite threading modes to DB API 2 0 threadsafety levels are as follows SQLite threading threadsafety SQLITE_THREADSAFE DB API 2 0 meaning mode single thread 0 0 Threads may not share the module multi thread 1 2 Threads may share the module but not connections serialized 3 1 Threads may share the module connections and cursors Changed in version 3 11 Set threadsafety dynamically instead of hard coding it to 1 sqlite3 version Version number of this module as a string This is not the version of the SQLite library Deprecated since version 3 12 will be removed in version 3 14 This constant used to reflect the version number of the pysqlite package a third party library which used to upstream changes to sqlite3 Today it carries no meaning or practical value sqlite3 version_info Version number of this module as a tuple of integers This is not the version of the SQLite library Deprecated since version 3 12 will be removed in version 3 14 This constant used to reflect the version number of the pysqlite package a third party library which used to upstream changes to sqlite3 Today it carries no meaning or practical value sqlite3 SQLITE_DBCONFIG_DEFENSIVE sqlite3 SQLITE_DBCONFIG_DQS_DDL sqlite3 SQLITE_DBCONFIG_DQS_DML sqlite3 SQLITE_DBCONFIG_ENABLE_FKEY sqlite3 SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER sqlite3 SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION sqlite3 SQLITE_DBCONFIG_ENABLE_QPSG sqlite3 SQLITE_DBCONFIG_ENABLE_TRIGGER sqlite3 SQLITE_DBCONFIG_ENABLE_VIEW sqlite3 SQLITE_DBCONFIG_LEGACY_ALTER_TABLE sqlite3 SQLITE_DBCONFIG_LEGACY_FILE_FORMAT sqlite3 SQLITE_DBCONFIG_NO_CKPT_ON_CLOSE sqlite3 SQLITE_DBCONFIG_RESET_DATABASE sqlite3 SQLITE_DBCONFIG_TRIGGER_EQP sqlite3 SQLITE_DBCONFIG_TRUSTED_SCHEMA sqlite3 SQLITE_DBCONFIG_WRITABLE_SCHEMA These constants are used for the Connection setconfig and getconfig methods The availability of these constants varies depending on the version of SQLite Python was compiled with New in version 3 12 See also https www sqlite org c3ref c_dbconfig_defensive html SQLite docs Database Connection Configuration Options Connection objects class sqlite3 Connection Each open SQLite database is represented by a Connection object which is created using sqlite3 connect Their main purpose is creating Cursor objects and Transaction control See also How to use connection shortcut methods How ,en
163,to use the connection context manager An SQLite database connection has the following attributes and methods cursor factory Cursor Create and return a Cursor object The cursor method accepts a single optional parameter factory If supplied this must be a callable returning an instance of Cursor or its subclasses blobopen table column row readonly False name main Open a Blob handle to an existing BLOB Binary Large OBject Parameters table str The name of the table where the blob is located column str The name of the column where the blob is located row str The name of the row where the blob is located readonly bool Set to True if the blob should be opened without write permissions Defaults to False name str The name of the database where the blob is located Defaults to main Raises OperationalError When trying to open a blob in a WITHOUT ROWID table Return type Blob Note The blob size cannot be changed using the Blob class Use the SQL function zeroblob to create a blob with a fixed size New in version 3 11 commit Commit any pending transaction to the database If autocommit is True or there is no open transaction this method does nothing If autocommit is False a new transaction is implicitly opened if a pending transaction was committed by this method rollback Roll back to the start of any pending transaction If autocommit is True or there is no open transaction this method does nothing If autocommit is False a new transaction is implicitly opened if a pending transaction was rolled back by this method close Close the database connection If autocommit is False any pending transaction is implicitly rolled back If autocommit is True or LEGACY_TRANSACTION_CONTROL no implicit transaction control is executed Make sure to commit before closing to avoid losing pending changes execute sql parameters Create a new Cursor object and call execute on it with the given sql and parameters Return the new cursor object executemany sql parameters Create a new Cursor object and call executemany on it with the given sql and parameters Return the new cursor object executescript sql_script Create a new Cursor object and call executescript on it with the given sql_script Return the new cursor object create_function name narg func deterministic False Create or remove a user defined SQL function Parameters name str The name of the SQL function narg int The number of arguments the SQL function can accept If 1 it may take any number of arguments func callback None A callable that is called when the SQL function is invoked The callable must return a type natively supported by SQLite Set to None to remove an existing SQL function deterministic bool If True the created SQL function is marked as deterministic which allows SQLite to perform additional optimizations Raises NotSupportedError If deterministic is used with SQLite versions older than 3 8 3 Changed in version 3 8 Added the deterministic parameter Example import hashlib def md5sum t return hashlib md5 t hexdigest con sqlite3 connect memory con create_function md5 1 md5sum for row in con execute SELECT md5 b foo print row acbd18db4cc2f85cedef654fccc4a4d8 create_aggregate name n_arg aggregate_class Create or remove a user defined SQL aggregate function Parameters name str The name of the SQL aggregate function n_arg int The number of arguments the SQL aggregate function can accept If 1 it may take any number of arguments aggregate_class class None A class must implement the following methods step Add a row to the aggregate finalize Return the final result of the aggregate as a type natively supported by SQLite The number of arguments that the step method must accept is controlled by n_arg Set to None to remove an existing SQL aggregate function Example class MySum def __init__ self self count 0 def step self value self count value def finalize self return self count con sqlite3 connect memory con create_aggregate mysum 1 MySum cur con execute CREATE TABLE test i cur execute INSERT INTO test i VALUES 1 cur execute INSERT INTO test i VALUES 2 cur execute SELECT mysum i FROM test print cur fetchone 0 c,en
164,on close create_window_function name num_params aggregate_class Create or remove a user defined aggregate window function Parameters name str The name of the SQL aggregate window function to create or remove num_params int The number of arguments the SQL aggregate window function can accept If 1 it may take any number of arguments aggregate_class class None A class that must implement the following methods step Add a row to the current window value Return the current value of the aggregate inverse Remove a row from the current window finalize Return the final result of the aggregate as a type natively supported by SQLite The number of arguments that the step and value methods must accept is controlled by num_params Set to None to remove an existing SQL aggregate window function Raises NotSupportedError If used with a version of SQLite older than 3 25 0 which does not support aggregate window functions New in version 3 11 Example Example taken from https www sqlite org windowfunctions html udfwinfunc class WindowSumInt def __init__ self self count 0 def step self value Add a row to the current window self count value def value self Return the current value of the aggregate return self count def inverse self value Remove a row from the current window self count value def finalize self Return the final value of the aggregate Any clean up actions should be placed here return self count con sqlite3 connect memory cur con execute CREATE TABLE test x y values a 4 b 5 c 3 d 8 e 1 cur executemany INSERT INTO test VALUES values con create_window_function sumint 1 WindowSumInt cur execute SELECT x sumint y OVER ORDER BY x ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING AS sum_y FROM test ORDER BY x print cur fetchall create_collation name callable Create a collation named name using the collating function callable callable is passed two string arguments and it should return an integer 1 if the first is ordered higher than the second 1 if the first is ordered lower than the second 0 if they are ordered equal The following example shows a reverse sorting collation def collate_reverse string1 string2 if string1 string2 return 0 elif string1 string2 return 1 else return 1 con sqlite3 connect memory con create_collation reverse collate_reverse cur con execute CREATE TABLE test x cur executemany INSERT INTO test x VALUES a b cur execute SELECT x FROM test ORDER BY x COLLATE reverse for row in cur print row con close Remove a collation function by setting callable to None Changed in version 3 11 The collation name can contain any Unicode character Earlier only ASCII characters were allowed interrupt Call this method from a different thread to abort any queries that might be executing on the connection Aborted queries will raise an OperationalError set_authorizer authorizer_callback Register callable authorizer_callback to be invoked for each attempt to access a column of a table in the database The callback should return one of SQLITE_OK SQLITE_DENY or SQLITE_IGNORE to signal how access to the column should be handled by the underlying SQLite library The first argument to the callback signifies what kind of operation is to be authorized The second and third argument will be arguments or None depending on the first argument The 4th argument is the name of the database main temp etc if applicable The 5th argument is the name of the inner most trigger or view that is responsible for the access attempt or None if this access attempt is directly from input SQL code Please consult the SQLite documentation about the possible values for the first argument and the meaning of the second and third argument depending on the first one All necessary constants are available in the sqlite3 module Passing None as authorizer_callback will disable the authorizer Changed in version 3 11 Added support for disabling the authorizer using None set_progress_handler progress_handler n Register callable progress_handler to be invoked for every n instructions of the SQLite virtual machine This is useful if you want to get called from SQLite during long running operations f,en
165,or example to update a GUI If you want to clear any previously installed progress handler call the method with None for progress_handler Returning a non zero value from the handler function will terminate the currently executing query and cause it to raise a DatabaseError exception set_trace_callback trace_callback Register callable trace_callback to be invoked for each SQL statement that is actually executed by the SQLite backend The only argument passed to the callback is the statement as str that is being executed The return value of the callback is ignored Note that the backend does not only run statements passed to the Cursor execute methods Other sources include the transaction management of the sqlite3 module and the execution of triggers defined in the current database Passing None as trace_callback will disable the trace callback Note Exceptions raised in the trace callback are not propagated As a development and debugging aid use enable_callback_tracebacks to enable printing tracebacks from exceptions raised in the trace callback New in version 3 3 enable_load_extension enabled Enable the SQLite engine to load SQLite extensions from shared libraries if enabled is True else disallow loading SQLite extensions SQLite extensions can define new functions aggregates or whole new virtual table implementations One well known extension is the fulltext search extension distributed with SQLite Note The sqlite3 module is not built with loadable extension support by default because some platforms notably macOS have SQLite libraries which are compiled without this feature To get loadable extension support you must pass the enable loadable sqlite extensions option to configure Raises an auditing event sqlite3 enable_load_extension with arguments connection enabled New in version 3 2 Changed in version 3 10 Added the sqlite3 enable_load_extension auditing event con enable_load_extension True Load the fulltext search extension con execute select load_extension fts3 so alternatively you can load the extension using an API call con load_extension fts3 so disable extension loading again con enable_load_extension False example from SQLite wiki con execute CREATE VIRTUAL TABLE recipe USING fts3 name ingredients con executescript INSERT INTO recipe name ingredients VALUES broccoli stew broccoli peppers cheese tomatoes INSERT INTO recipe name ingredients VALUES pumpkin stew pumpkin onions garlic celery INSERT INTO recipe name ingredients VALUES broccoli pie broccoli cheese onions flour INSERT INTO recipe name ingredients VALUES pumpkin pie pumpkin sugar flour butter for row in con execute SELECT rowid name ingredients FROM recipe WHERE name MATCH pie print row con close load_extension path entrypoint None Load an SQLite extension from a shared library Enable extension loading with enable_load_extension before calling this method Parameters path str The path to the SQLite extension entrypoint str None Entry point name If None the default SQLite will come up with an entry point name of its own see the SQLite docs Loading an Extension for details Raises an auditing event sqlite3 load_extension with arguments connection path New in version 3 2 Changed in version 3 10 Added the sqlite3 load_extension auditing event Changed in version 3 12 Added the entrypoint parameter iterdump Return an iterator to dump the database as SQL source code Useful when saving an in memory database for later restoration Similar to the dump command in the sqlite3 shell Example Convert file example db to SQL dump file dump sql con sqlite3 connect example db with open dump sql w as f for line in con iterdump f write s n line con close See also How to handle non UTF 8 text encodings backup target pages 1 progress None name main sleep 0 250 Create a backup of an SQLite database Works even if the database is being accessed by other clients or concurrently by the same connection Parameters target Connection The database connection to save the backup to pages int The number of pages to copy at a time If equal to or less than 0 the entire database is copied in a single s,en
166,tep Defaults to 1 progress callback None If set to a callable it is invoked with three integer arguments for every backup iteration the status of the last iteration the remaining number of pages still to be copied and the total number of pages Defaults to None name str The name of the database to back up Either main the default for the main database temp for the temporary database or the name of a custom database as attached using the ATTACH DATABASE SQL statement sleep float The number of seconds to sleep between successive attempts to back up remaining pages Example 1 copy an existing database into another def progress status remaining total print f Copied total remaining of total pages src sqlite3 connect example db dst sqlite3 connect backup db with dst src backup dst pages 1 progress progress dst close src close Example 2 copy an existing database into a transient copy src sqlite3 connect example db dst sqlite3 connect memory src backup dst New in version 3 7 See also How to handle non UTF 8 text encodings getlimit category Get a connection runtime limit Parameters category int The SQLite limit category to be queried Return type int Raises ProgrammingError If category is not recognised by the underlying SQLite library Example query the maximum length of an SQL statement for Connection con the default is 1000000000 con getlimit sqlite3 SQLITE_LIMIT_SQL_LENGTH 1000000000 New in version 3 11 setlimit category limit Set a connection runtime limit Attempts to increase a limit above its hard upper bound are silently truncated to the hard upper bound Regardless of whether or not the limit was changed the prior value of the limit is returned Parameters category int The SQLite limit category to be set limit int The value of the new limit If negative the current limit is unchanged Return type int Raises ProgrammingError If category is not recognised by the underlying SQLite library Example limit the number of attached databases to 1 for Connection con the default limit is 10 con setlimit sqlite3 SQLITE_LIMIT_ATTACHED 1 10 con getlimit sqlite3 SQLITE_LIMIT_ATTACHED 1 New in version 3 11 getconfig op Query a boolean connection configuration option Parameters op int A SQLITE_DBCONFIG code Return type bool New in version 3 12 setconfig op enable True Set a boolean connection configuration option Parameters op int A SQLITE_DBCONFIG code enable bool True if the configuration option should be enabled default False if it should be disabled New in version 3 12 serialize name main Serialize a database into a bytes object For an ordinary on disk database file the serialization is just a copy of the disk file For an in memory database or a temp database the serialization is the same sequence of bytes which would be written to disk if that database were backed up to disk Parameters name str The database name to be serialized Defaults to main Return type bytes Note This method is only available if the underlying SQLite library has the serialize API New in version 3 11 deserialize data name main Deserialize a serialized database into a Connection This method causes the database connection to disconnect from database name and reopen name as an in memory database based on the serialization contained in data Parameters data bytes A serialized database name str The database name to deserialize into Defaults to main Raises OperationalError If the database connection is currently involved in a read transaction or a backup operation DatabaseError If data does not contain a valid SQLite database OverflowError If len data is larger than 2 63 1 Note This method is only available if the underlying SQLite library has the deserialize API New in version 3 11 autocommit This attribute controls PEP 249 compliant transaction behaviour autocommit has three allowed values False Select PEP 249 compliant transaction behaviour implying that sqlite3 ensures a transaction is always open Use commit and rollback to close transactions This is the recommended value of autocommit True Use SQLite s autocommit mode commit and rollback have no effect in this mode LEGACY_T,en
167,RANSACTION_CONTROL Pre Python 3 12 non PEP 249 compliant transaction control See isolation_level for more details This is currently the default value of autocommit Changing autocommit to False will open a new transaction and changing it to True will commit any pending transaction See Transaction control via the autocommit attribute for more details Note The isolation_level attribute has no effect unless autocommit is LEGACY_TRANSACTION_CONTROL New in version 3 12 in_transaction This read only attribute corresponds to the low level SQLite autocommit mode True if a transaction is active there are uncommitted changes False otherwise New in version 3 2 isolation_level Controls the legacy transaction handling mode of sqlite3 If set to None transactions are never implicitly opened If set to one of DEFERRED IMMEDIATE or EXCLUSIVE corresponding to the underlying SQLite transaction behaviour implicit transaction management is performed If not overridden by the isolation_level parameter of connect the default is which is an alias for DEFERRED Note Using autocommit to control transaction handling is recommended over using isolation_level isolation_level has no effect unless autocommit is set to LEGACY_TRANSACTION_CONTROL the default row_factory The initial row_factory for Cursor objects created from this connection Assigning to this attribute does not affect the row_factory of existing cursors belonging to this connection only new ones Is None by default meaning each row is returned as a tuple See How to create and use row factories for more details text_factory A callable that accepts a bytes parameter and returns a text representation of it The callable is invoked for SQLite values with the TEXT data type By default this attribute is set to str See How to handle non UTF 8 text encodings for more details total_changes Return the total number of database rows that have been modified inserted or deleted since the database connection was opened Cursor objects A Cursor object represents a database cursor which is used to execute SQL statements and manage the context of a fetch operation Cursors are created using Connection cursor or by using any of the connection shortcut methods Cursor objects are iterators meaning that if you execute a SELECT query you can simply iterate over the cursor to fetch the resulting rows for row in cur execute SELECT t FROM data print row class sqlite3 Cursor A Cursor instance has the following attributes and methods execute sql parameters Execute a single SQL statement optionally binding Python values using placeholders Parameters sql str A single SQL statement parameters dict sequence Python values to bind to placeholders in sql A dict if named placeholders are used A sequence if unnamed placeholders are used See How to use placeholders to bind values in SQL queries Raises ProgrammingError If sql contains more than one SQL statement If autocommit is LEGACY_TRANSACTION_CONTROL isolation_level is not None sql is an INSERT UPDATE DELETE or REPLACE statement and there is no open transaction a transaction is implicitly opened before executing sql Deprecated since version 3 12 will be removed in version 3 14 DeprecationWarning is emitted if named placeholders are used and parameters is a sequence instead of a dict Starting with Python 3 14 ProgrammingError will be raised instead Use executescript to execute multiple SQL statements executemany sql parameters For every item in parameters repeatedly execute the parameterized DML Data Manipulation Language SQL statement sql Uses the same implicit transaction handling as execute Parameters sql str A single SQL DML statement parameters iterable An iterable of parameters to bind with the placeholders in sql See How to use placeholders to bind values in SQL queries Raises ProgrammingError If sql contains more than one SQL statement or is not a DML statement Example rows row1 row2 cur is an sqlite3 Cursor object cur executemany INSERT INTO data VALUES rows Note Any resulting rows are discarded including DML statements with RETURNING clauses Deprecated since version 3 1,en
168,2 will be removed in version 3 14 DeprecationWarning is emitted if named placeholders are used and the items in parameters are sequences instead of dict s Starting with Python 3 14 ProgrammingError will be raised instead executescript sql_script Execute the SQL statements in sql_script If the autocommit is LEGACY_TRANSACTION_CONTROL and there is a pending transaction an implicit COMMIT statement is executed first No other implicit transaction control is performed any transaction control must be added to sql_script sql_script must be a string Example cur is an sqlite3 Cursor object cur executescript BEGIN CREATE TABLE person firstname lastname age CREATE TABLE book title author published CREATE TABLE publisher name address COMMIT fetchone If row_factory is None return the next row query result set as a tuple Else pass it to the row factory and return its result Return None if no more data is available fetchmany size cursor arraysize Return the next set of rows of a query result as a list Return an empty list if no more rows are available The number of rows to fetch per call is specified by the size parameter If size is not given arraysize determines the number of rows to be fetched If fewer than size rows are available as many rows as are available are returned Note there are performance considerations involved with the size parameter For optimal performance it is usually best to use the arraysize attribute If the size parameter is used then it is best for it to retain the same value from one fetchmany call to the next fetchall Return all remaining rows of a query result as a list Return an empty list if no rows are available Note that the arraysize attribute can affect the performance of this operation close Close the cursor now rather than whenever __del__ is called The cursor will be unusable from this point forward a ProgrammingError exception will be raised if any operation is attempted with the cursor setinputsizes sizes Required by the DB API Does nothing in sqlite3 setoutputsize size column None Required by the DB API Does nothing in sqlite3 arraysize Read write attribute that controls the number of rows returned by fetchmany The default value is 1 which means a single row would be fetched per call connection Read only attribute that provides the SQLite database Connection belonging to the cursor A Cursor object created by calling con cursor will have a connection attribute that refers to con con sqlite3 connect memory cur con cursor cur connection con True description Read only attribute that provides the column names of the last query To remain compatible with the Python DB API it returns a 7 tuple for each column where the last six items of each tuple are None It is set for SELECT statements without any matching rows as well lastrowid Read only attribute that provides the row id of the last inserted row It is only updated after successful INSERT or REPLACE statements using the execute method For other statements after executemany or executescript or if the insertion failed the value of lastrowid is left unchanged The initial value of lastrowid is None Note Inserts into WITHOUT ROWID tables are not recorded Changed in version 3 6 Added support for the REPLACE statement rowcount Read only attribute that provides the number of modified rows for INSERT UPDATE DELETE and REPLACE statements is 1 for other statements including CTE Common Table Expression queries It is only updated by the execute and executemany methods after the statement has run to completion This means that any resulting rows must be fetched in order for rowcount to be updated row_factory Control how a row fetched from this Cursor is represented If None a row is represented as a tuple Can be set to the included sqlite3 Row or a callable that accepts two arguments a Cursor object and the tuple of row values and returns a custom object representing an SQLite row Defaults to what Connection row_factory was set to when the Cursor was created Assigning to this attribute does not affect Connection row_factory of the parent connection See How to create and,en
169, use row factories for more details Row objects class sqlite3 Row A Row instance serves as a highly optimized row_factory for Connection objects It supports iteration equality testing len and mapping access by column name and index Two Row objects compare equal if they have identical column names and values See How to create and use row factories for more details keys Return a list of column names as strings Immediately after a query it is the first member of each tuple in Cursor description Changed in version 3 5 Added support of slicing Blob objects class sqlite3 Blob New in version 3 11 A Blob instance is a file like object that can read and write data in an SQLite BLOB Binary Large OBject Call len blob to get the size number of bytes of the blob Use indices and slices for direct access to the blob data Use the Blob as a context manager to ensure that the blob handle is closed after use con sqlite3 connect memory con execute CREATE TABLE test blob_col blob con execute INSERT INTO test blob_col VALUES zeroblob 13 Write to our blob using two write operations with con blobopen test blob_col 1 as blob blob write b hello blob write b world Modify the first and last bytes of our blob blob 0 ord H blob 1 ord Read the contents of our blob with con blobopen test blob_col 1 as blob greeting blob read print greeting outputs b Hello world close Close the blob The blob will be unusable from this point onward An Error or subclass exception will be raised if any further operation is attempted with the blob read length 1 Read length bytes of data from the blob at the current offset position If the end of the blob is reached the data up to EOF End of File will be returned When length is not specified or is negative read will read until the end of the blob write data Write data to the blob at the current offset This function cannot change the blob length Writing beyond the end of the blob will raise ValueError tell Return the current access position of the blob seek offset origin os SEEK_SET Set the current access position of the blob to offset The origin argument defaults to os SEEK_SET absolute blob positioning Other values for origin are os SEEK_CUR seek relative to the current position and os SEEK_END seek relative to the blob s end PrepareProtocol objects class sqlite3 PrepareProtocol The PrepareProtocol type s single purpose is to act as a PEP 246 style adaption protocol for objects that can adapt themselves to native SQLite types Exceptions The exception hierarchy is defined by the DB API 2 0 PEP 249 exception sqlite3 Warning This exception is not currently raised by the sqlite3 module but may be raised by applications using sqlite3 for example if a user defined function truncates data while inserting Warning is a subclass of Exception exception sqlite3 Error The base class of the other exceptions in this module Use this to catch all errors with one single except statement Error is a subclass of Exception If the exception originated from within the SQLite library the following two attributes are added to the exception sqlite_errorcode The numeric error code from the SQLite API New in version 3 11 sqlite_errorname The symbolic name of the numeric error code from the SQLite API New in version 3 11 exception sqlite3 InterfaceError Exception raised for misuse of the low level SQLite C API In other words if this exception is raised it probably indicates a bug in the sqlite3 module InterfaceError is a subclass of Error exception sqlite3 DatabaseError Exception raised for errors that are related to the database This serves as the base exception for several types of database errors It is only raised implicitly through the specialised subclasses DatabaseError is a subclass of Error exception sqlite3 DataError Exception raised for errors caused by problems with the processed data like numeric values out of range and strings which are too long DataError is a subclass of DatabaseError exception sqlite3 OperationalError Exception raised for errors that are related to the database s operation and not necessarily under the control of the progr,en
170,ammer For example the database path is not found or a transaction could not be processed OperationalError is a subclass of DatabaseError exception sqlite3 IntegrityError Exception raised when the relational integrity of the database is affected e g a foreign key check fails It is a subclass of DatabaseError exception sqlite3 InternalError Exception raised when SQLite encounters an internal error If this is raised it may indicate that there is a problem with the runtime SQLite library InternalError is a subclass of DatabaseError exception sqlite3 ProgrammingError Exception raised for sqlite3 API programming errors for example supplying the wrong number of bindings to a query or trying to operate on a closed Connection ProgrammingError is a subclass of DatabaseError exception sqlite3 NotSupportedError Exception raised in case a method or database API is not supported by the underlying SQLite library For example setting deterministic to True in create_function if the underlying SQLite library does not support deterministic functions NotSupportedError is a subclass of DatabaseError SQLite and Python types SQLite natively supports the following types NULL INTEGER REAL TEXT BLOB The following Python types can thus be sent to SQLite without any problem Python type SQLite type None NULL int INTEGER float REAL str TEXT bytes BLOB This is how SQLite types are converted to Python types by default SQLite type Python type NULL None INTEGER int REAL float TEXT depends on text_factory str by default BLOB bytes The type system of the sqlite3 module is extensible in two ways you can store additional Python types in an SQLite database via object adapters and you can let the sqlite3 module convert SQLite types to Python types via converters Default adapters and converters deprecated Note The default adapters and converters are deprecated as of Python 3 12 Instead use the Adapter and converter recipes and tailor them to your needs The deprecated default adapters and converters consist of An adapter for datetime date objects to strings in ISO 8601 format An adapter for datetime datetime objects to strings in ISO 8601 format A converter for declared date types to datetime date objects A converter for declared timestamp types to datetime datetime objects Fractional parts will be truncated to 6 digits microsecond precision Note The default timestamp converter ignores UTC offsets in the database and always returns a naive datetime datetime object To preserve UTC offsets in timestamps either leave converters disabled or register an offset aware converter with register_converter Deprecated since version 3 12 Command line interface The sqlite3 module can be invoked as a script using the interpreter s m switch in order to provide a simple SQLite shell The argument signature is as follows python m sqlite3 h v filename sql Type quit or CTRL D to exit the shell h help Print CLI help v version Print underlying SQLite library version New in version 3 12 How to guides How to use placeholders to bind values in SQL queries SQL operations usually need to use values from Python variables However beware of using Python s string operations to assemble queries as they are vulnerable to SQL injection attacks For example an attacker can simply close the single quote and inject OR TRUE to select all rows Never do this insecure symbol input OR TRUE sql SELECT FROM stocks WHERE symbol s symbol print sql SELECT FROM stocks WHERE symbol OR TRUE cur execute sql Instead use the DB API s parameter substitution To insert a variable into a query string use a placeholder in the string and substitute the actual values into the query by providing them as a tuple of values to the second argument of the cursor s execute method An SQL statement may use one of two kinds of placeholders question marks qmark style or named placeholders named style For the qmark style parameters must be a sequence whose length must match the number of placeholders or a ProgrammingError is raised For the named style parameters must be an instance of a dict or a subclass which must contain keys for all,en
171, named parameters any extra items are ignored Here s an example of both styles con sqlite3 connect memory cur con execute CREATE TABLE lang name first_appeared This is the named style used with executemany data name C year 1972 name Fortran year 1957 name Python year 1991 name Go year 2009 cur executemany INSERT INTO lang VALUES name year data This is the qmark style used in a SELECT query params 1972 cur execute SELECT FROM lang WHERE first_appeared params print cur fetchall Note PEP 249 numeric placeholders are not supported If used they will be interpreted as named placeholders How to adapt custom Python types to SQLite values SQLite supports only a limited set of data types natively To store custom Python types in SQLite databases adapt them to one of the Python types SQLite natively understands There are two ways to adapt Python objects to SQLite types letting your object adapt itself or using an adapter callable The latter will take precedence above the former For a library that exports a custom type it may make sense to enable that type to adapt itself As an application developer it may make more sense to take direct control by registering custom adapter functions How to write adaptable objects Suppose we have a Point class that represents a pair of coordinates x and y in a Cartesian coordinate system The coordinate pair will be stored as a text string in the database using a semicolon to separate the coordinates This can be implemented by adding a __conform__ self protocol method which returns the adapted value The object passed to protocol will be of type PrepareProtocol class Point def __init__ self x y self x self y x y def __conform__ self protocol if protocol is sqlite3 PrepareProtocol return f self x self y con sqlite3 connect memory cur con cursor cur execute SELECT Point 4 0 3 2 print cur fetchone 0 How to register adapter callables The other possibility is to create a function that converts the Python object to an SQLite compatible type This function can then be registered using register_adapter class Point def __init__ self x y self x self y x y def adapt_point point return f point x point y sqlite3 register_adapter Point adapt_point con sqlite3 connect memory cur con cursor cur execute SELECT Point 1 0 2 5 print cur fetchone 0 How to convert SQLite values to custom Python types Writing an adapter lets you convert from custom Python types to SQLite values To be able to convert from SQLite values to custom Python types we use converters Let s go back to the Point class We stored the x and y coordinates separated via semicolons as strings in SQLite First we ll define a converter function that accepts the string as a parameter and constructs a Point object from it Note Converter functions are always passed a bytes object no matter the underlying SQLite data type def convert_point s x y map float s split b return Point x y We now need to tell sqlite3 when it should convert a given SQLite value This is done when connecting to a database using the detect_types parameter of connect There are three options Implicit set detect_types to PARSE_DECLTYPES Explicit set detect_types to PARSE_COLNAMES Both set detect_types to sqlite3 PARSE_DECLTYPES sqlite3 PARSE_COLNAMES Column names take precedence over declared types The following example illustrates the implicit and explicit approaches class Point def __init__ self x y self x self y x y def __repr__ self return f Point self x self y def adapt_point point return f point x point y def convert_point s x y list map float s split b return Point x y Register the adapter and converter sqlite3 register_adapter Point adapt_point sqlite3 register_converter point convert_point 1 Parse using declared types p Point 4 0 3 2 con sqlite3 connect memory detect_types sqlite3 PARSE_DECLTYPES cur con execute CREATE TABLE test p point cur execute INSERT INTO test p VALUES p cur execute SELECT p FROM test print with declared types cur fetchone 0 cur close con close 2 Parse using column names con sqlite3 connect memory detect_types sqlite3 PARSE_COLNAMES cur con execute CREATE TABLE test,en
172, p cur execute INSERT INTO test p VALUES p cur execute SELECT p AS p point FROM test print with column names cur fetchone 0 Adapter and converter recipes This section shows recipes for common adapters and converters import datetime import sqlite3 def adapt_date_iso val Adapt datetime date to ISO 8601 date return val isoformat def adapt_datetime_iso val Adapt datetime datetime to timezone naive ISO 8601 date return val isoformat def adapt_datetime_epoch val Adapt datetime datetime to Unix timestamp return int val timestamp sqlite3 register_adapter datetime date adapt_date_iso sqlite3 register_adapter datetime datetime adapt_datetime_iso sqlite3 register_adapter datetime datetime adapt_datetime_epoch def convert_date val Convert ISO 8601 date to datetime date object return datetime date fromisoformat val decode def convert_datetime val Convert ISO 8601 datetime to datetime datetime object return datetime datetime fromisoformat val decode def convert_timestamp val Convert Unix epoch timestamp to datetime datetime object return datetime datetime fromtimestamp int val sqlite3 register_converter date convert_date sqlite3 register_converter datetime convert_datetime sqlite3 register_converter timestamp convert_timestamp How to use connection shortcut methods Using the execute executemany and executescript methods of the Connection class your code can be written more concisely because you don t have to create the often superfluous Cursor objects explicitly Instead the Cursor objects are created implicitly and these shortcut methods return the cursor objects This way you can execute a SELECT statement and iterate over it directly using only a single call on the Connection object Create and fill the table con sqlite3 connect memory con execute CREATE TABLE lang name first_appeared data C 1985 Objective C 1984 con executemany INSERT INTO lang name first_appeared VALUES data Print the table contents for row in con execute SELECT name first_appeared FROM lang print row print I just deleted con execute DELETE FROM lang rowcount rows close is not a shortcut method and it s not called automatically the connection object should be closed manually con close How to use the connection context manager A Connection object can be used as a context manager that automatically commits or rolls back open transactions when leaving the body of the context manager If the body of the with statement finishes without exceptions the transaction is committed If this commit fails or if the body of the with statement raises an uncaught exception the transaction is rolled back If autocommit is False a new transaction is implicitly opened after committing or rolling back If there is no open transaction upon leaving the body of the with statement or if autocommit is True the context manager does nothing Note The context manager neither implicitly opens a new transaction nor closes the connection If you need a closing context manager consider using contextlib closing con sqlite3 connect memory con execute CREATE TABLE lang id INTEGER PRIMARY KEY name VARCHAR UNIQUE Successful con commit is called automatically afterwards with con con execute INSERT INTO lang name VALUES Python con rollback is called after the with block finishes with an exception the exception is still raised and must be caught try with con con execute INSERT INTO lang name VALUES Python except sqlite3 IntegrityError print couldn t add Python twice Connection object used as context manager only commits or rollbacks transactions so the connection object should be closed manually con close How to work with SQLite URIs Some useful URI tricks include Open a database in read only mode con sqlite3 connect file tutorial db mode ro uri True con execute CREATE TABLE readonly data Traceback most recent call last OperationalError attempt to write a readonly database Do not implicitly create a new database file if it does not already exist will raise OperationalError if unable to create a new file con sqlite3 connect file nosuchdb db mode rw uri True Traceback most recent call last OperationalError unable ,en
173,to open database file Create a shared named in memory database db file mem1 mode memory cache shared con1 sqlite3 connect db uri True con2 sqlite3 connect db uri True with con1 con1 execute CREATE TABLE shared data con1 execute INSERT INTO shared VALUES 28 res con2 execute SELECT data FROM shared assert res fetchone 28 More information about this feature including a list of parameters can be found in the SQLite URI documentation How to create and use row factories By default sqlite3 represents each row as a tuple If a tuple does not suit your needs you can use the sqlite3 Row class or a custom row_factory While row_factory exists as an attribute both on the Cursor and the Connection it is recommended to set Connection row_factory so all cursors created from the connection will use the same row factory Row provides indexed and case insensitive named access to columns with minimal memory overhead and performance impact over a tuple To use Row as a row factory assign it to the row_factory attribute con sqlite3 connect memory con row_factory sqlite3 Row Queries now return Row objects res con execute SELECT Earth AS name 6378 AS radius row res fetchone row keys name radius row 0 Access by index Earth row name Access by name Earth row RADIUS Column names are case insensitive 6378 Note The FROM clause can be omitted in the SELECT statement as in the above example In such cases SQLite returns a single row with columns defined by expressions e g literals with the given aliases expr AS alias You can create a custom row_factory that returns each row as a dict with column names mapped to values def dict_factory cursor row fields column 0 for column in cursor description return key value for key value in zip fields row Using it queries now return a dict instead of a tuple con sqlite3 connect memory con row_factory dict_factory for row in con execute SELECT 1 AS a 2 AS b print row a 1 b 2 The following row factory returns a named tuple from collections import namedtuple def namedtuple_factory cursor row fields column 0 for column in cursor description cls namedtuple Row fields return cls _make row namedtuple_factory can be used as follows con sqlite3 connect memory con row_factory namedtuple_factory cur con execute SELECT 1 AS a 2 AS b row cur fetchone row Row a 1 b 2 row 0 Indexed access 1 row b Attribute access 2 With some adjustments the above recipe can be adapted to use a dataclass or any other custom class instead of a namedtuple How to handle non UTF 8 text encodings By default sqlite3 uses str to adapt SQLite values with the TEXT data type This works well for UTF 8 encoded text but it might fail for other encodings and invalid UTF 8 You can use a custom text_factory to handle such cases Because of SQLite s flexible typing it is not uncommon to encounter table columns with the TEXT data type containing non UTF 8 encodings or even arbitrary data To demonstrate let s assume we have a database with ISO 8859 2 Latin 2 encoded text for example a table of Czech English dictionary entries Assuming we now have a Connection instance con connected to this database we can decode the Latin 2 encoded text using this text_factory con text_factory lambda data str data encoding latin2 For invalid UTF 8 or arbitrary data in stored in TEXT table columns you can use the following technique borrowed from the Unicode HOWTO con text_factory lambda data str data errors surrogateescape Note The sqlite3 module API does not support strings containing surrogates See also Unicode HOWTO Explanation Transaction control sqlite3 offers multiple methods of controlling whether when and how database transactions are opened and closed Transaction control via the autocommit attribute is recommended while Transaction control via the isolation_level attribute retains the pre Python 3 12 behaviour Transaction control via the autocommit attribute The recommended way of controlling transaction behaviour is through the Connection autocommit attribute which should preferably be set using the autocommit parameter of connect It is suggested to set autocommit to False which,en
174, implies PEP 249 compliant transaction control This means sqlite3 ensures that a transaction is always open so connect Connection commit and Connection rollback will implicitly open a new transaction immediately after closing the pending one for the latter two sqlite3 uses BEGIN DEFERRED statements when opening transactions Transactions should be committed explicitly using commit Transactions should be rolled back explicitly using rollback An implicit rollback is performed if the database is close ed with pending changes Set autocommit to True to enable SQLite s autocommit mode In this mode Connection commit and Connection rollback have no effect Note that SQLite s autocommit mode is distinct from the PEP 249 compliant Connection autocommit attribute use Connection in_transaction to query the low level SQLite autocommit mode Set autocommit to LEGACY_TRANSACTION_CONTROL to leave transaction control behaviour to the Connection isolation_level attribute See Transaction control via the isolation_level attribute for more information Transaction control via the isolation_level attribute Note The recommended way of controlling transactions is via the autocommit attribute See Transaction control via the autocommit attribute If Connection autocommit is set to LEGACY_TRANSACTION_CONTROL the default transaction behaviour is controlled using the Connection isolation_level attribute Otherwise isolation_level has no effect If the connection attribute isolation_level is not None new transactions are implicitly opened before execute and executemany executes INSERT UPDATE DELETE or REPLACE statements for other statements no implicit transaction handling is performed Use the commit and rollback methods to respectively commit and roll back pending transactions You can choose the underlying SQLite transaction behaviour that is whether and what type of BEGIN statements sqlite3 implicitly executes via the isolation_level attribute If isolation_level is set to None no transactions are implicitly opened at all This leaves the underlying SQLite library in autocommit mode but also allows the user to perform their own transaction handling using explicit SQL statements The underlying SQLite library autocommit mode can be queried using the in_transaction attribute The executescript method implicitly commits any pending transaction before execution of the given SQL script regardless of the value of isolation_level Changed in version 3 6 sqlite3 used to implicitly commit an open transaction before DDL statements This is no longer the case Changed in version 3 12 The recommended way of controlling transactions is now via the autocommit attribute,en
175,4 Using Python on Windows This document aims to give an overview of Windows specific behaviour you should know about when using Python on Microsoft Windows Unlike most Unix systems and services Windows does not include a system supported installation of Python To make Python available the CPython team has compiled Windows installers with every release for many years These installers are primarily intended to add a per user installation of Python with the core interpreter and library being used by a single user The installer is also able to install for all users of a single machine and a separate ZIP file is available for application local distributions As specified in PEP 11 a Python release only supports a Windows platform while Microsoft considers the platform under extended support This means that Python 3 12 supports Windows 8 1 and newer If you require Windows 7 support please install Python 3 8 There are a number of different installers available for Windows each with certain benefits and downsides The full installer contains all components and is the best option for developers using Python for any kind of project The Microsoft Store package is a simple installation of Python that is suitable for running scripts and packages and using IDLE or other development environments It requires Windows 10 and above but can be safely installed without corrupting other programs It also provides many convenient commands for launching Python and its tools The nuget org packages are lightweight installations intended for continuous integration systems It can be used to build Python packages or run scripts but is not updateable and has no user interface tools The embeddable package is a minimal package of Python suitable for embedding into a larger application 4 1 The full installer 4 1 1 Installation steps Four Python 3 12 installers are available for download two each for the 32 bit and 64 bit versions of the interpreter The web installer is a small initial download and it will automatically download the required components as necessary The offline installer includes the components necessary for a default installation and only requires an internet connection for optional features See Installing Without Downloading for other ways to avoid downloading during installation After starting the installer one of two options may be selected image If you select Install Now You will not need to be an administrator unless a system update for the C Runtime Library is required or you install the Python Launcher for Windows for all users Python will be installed into your user directory The Python Launcher for Windows will be installed according to the option at the bottom of the first page The standard library test suite launcher and pip will be installed If selected the install directory will be added to your PATH Shortcuts will only be visible for the current user Selecting Customize installation will allow you to select the features to install the installation location and other options or post install actions To install debugging symbols or binaries you will need to use this option To perform an all users installation you should select Customize installation In this case You may be required to provide administrative credentials or approval Python will be installed into the Program Files directory The Python Launcher for Windows will be installed into the Windows directory Optional features may be selected during installation The standard library can be pre compiled to bytecode If selected the install directory will be added to the system PATH Shortcuts are available for all users 4 1 2 Removing the MAX_PATH Limitation Windows historically has limited path lengths to 260 characters This meant that paths longer than this would not resolve and errors would result In the latest versions of Windows this limitation can be expanded to approximately 32 000 characters Your administrator will need to activate the Enable Win32 long paths group policy or set LongPathsEnabled to 1 in the registry key HKEY_LOCAL_MACHINE SYSTEM CurrentControlSet Control,en
176, FileSystem This allows the open function the os module and most other path functionality to accept and return paths longer than 260 characters After changing the above option no further configuration is required Changed in version 3 6 Support for long paths was enabled in Python 4 1 3 Installing Without UI All of the options available in the installer UI can also be specified from the command line allowing scripted installers to replicate an installation on many machines without user interaction These options may also be set without suppressing the UI in order to change some of the defaults The following options found by executing the installer with can be passed into the installer Name Description passive to display progress without requiring user interaction quiet to install uninstall without displaying any UI simple to prevent user customization uninstall to remove Python without confirmation layout directory to pre download all components log filename to specify log files location All other options are passed as name value where the value is usually 0 to disable a feature 1 to enable a feature or a path The full list of available options is shown below Name Description Default InstallAllUsers Perform a system wide installation 0 TargetDir The installation directory Selected based on InstallAllUsers DefaultAllUsersTargetDir The default installation directory for ProgramFiles Python all user installs X Y or ProgramFiles x8 6 Python X Y DefaultJustForMeTargetDir The default install directory for LocalAppData Programs just for me installs Python PythonXY or Loc alAppData Programs Pytho n PythonXY 32 or Local AppData Programs Python PythonXY 64 DefaultCustomTargetDir The default custom install directory empty displayed in the UI AssociateFiles Create file associations if the 1 launcher is also installed CompileAll Compile all py files to pyc 0 PrependPath Prepend install and Scripts 0 directories to PATH and add PY to PATHEXT AppendPath Append install and Scripts directories 0 to PATH and add PY to PATHEXT Shortcuts Create shortcuts for the interpreter 1 documentation and IDLE if installed Include_doc Install Python manual 1 Include_debug Install debug binaries 0 Include_dev Install developer headers and 1 libraries Omitting this may lead to an unusable installation Include_exe Install python exe and related 1 files Omitting this may lead to an unusable installation Include_launcher Install Python Launcher for Windows 1 InstallLauncherAllUsers Installs the launcher for all users 1 Also requires Include_launcher to be set to 1 Include_lib Install standard library and extension 1 modules Omitting this may lead to an unusable installation Include_pip Install bundled pip and setuptools 1 Include_symbols Install debugging symbols pdb 0 Include_tcltk Install Tcl Tk support and IDLE 1 Include_test Install standard library test suite 1 Include_tools Install utility scripts 1 LauncherOnly Only installs the launcher This will 0 override most other options SimpleInstall Disable most install UI 0 SimpleInstallDescription A custom message to display when the empty simplified install UI is used For example to silently install a default system wide Python installation you could use the following command from an elevated command prompt python 3 9 0 exe quiet InstallAllUsers 1 PrependPath 1 Include_test 0 To allow users to easily install a personal copy of Python without the test suite you could provide a shortcut with the following command This will display a simplified initial page and disallow customization python 3 9 0 exe InstallAllUsers 0 Include_launcher 0 Include_test 0 SimpleInstall 1 SimpleInstallDescription Just for me no test suite Note that omitting the launcher also omits file associations and is only recommended for per user installs when there is also a system wide installation that included the launcher The options listed above can also be provided in a file named unattend xml alongside the executable This file specifies a list of options and values When a value is provided as an attribute it will be converted to a numbe,en
177,r if possible Values provided as element text are always left as strings This example file sets the same options as the previous example Options Option Name InstallAllUsers Value no Option Name Include_launcher Value 0 Option Name Include_test Value no Option Name SimpleInstall Value yes Option Name SimpleInstallDescription Just for me no test suite Option Options 4 1 4 Installing Without Downloading As some features of Python are not included in the initial installer download selecting those features may require an internet connection To avoid this need all possible components may be downloaded on demand to create a complete layout that will no longer require an internet connection regardless of the selected features Note that this download may be bigger than required but where a large number of installations are going to be performed it is very useful to have a locally cached copy Execute the following command from Command Prompt to download all possible required files Remember to substitute python 3 9 0 exe for the actual name of your installer and to create layouts in their own directories to avoid collisions between files with the same name python 3 9 0 exe layout optional target directory You may also specify the quiet option to hide the progress display 4 1 5 Modifying an install Once Python has been installed you can add or remove features through the Programs and Features tool that is part of Windows Select the Python entry and choose Uninstall Change to open the installer in maintenance mode Modify allows you to add or remove features by modifying the checkboxes unchanged checkboxes will not install or remove anything Some options cannot be changed in this mode such as the install directory to modify these you will need to remove and then reinstall Python completely Repair will verify all the files that should be installed using the current settings and replace any that have been removed or modified Uninstall will remove Python entirely with the exception of the Python Launcher for Windows which has its own entry in Programs and Features 4 2 The Microsoft Store package New in version 3 7 2 The Microsoft Store package is an easily installable Python interpreter that is intended mainly for interactive use for example by students To install the package ensure you have the latest Windows 10 updates and search the Microsoft Store app for Python 3 12 Ensure that the app you select is published by the Python Software Foundation and install it Warning Python will always be available for free on the Microsoft Store If you are asked to pay for it you have not selected the correct package After installation Python may be launched by finding it in Start Alternatively it will be available from any Command Prompt or PowerShell session by typing python Further pip and IDLE may be used by typing pip or idle IDLE can also be found in Start All three commands are also available with version number suffixes for example as python3 exe and python3 x exe as well as python exe where 3 x is the specific version you want to launch such as 3 12 Open Manage App Execution Aliases through Start to select which version of Python is associated with each command It is recommended to make sure that pip and idle are consistent with whichever version of python is selected Virtual environments can be created with python m venv and activated and used as normal If you have installed another version of Python and added it to your PATH variable it will be available as python exe rather than the one from the Microsoft Store To access the new installation use python3 exe or python3 x exe The py exe launcher will detect this Python installation but will prefer installations from the traditional installer To remove Python open Settings and use Apps and Features or else find Python in Start and right click to select Uninstall Uninstalling will remove all packages you installed directly into this Python installation but will not remove any virtual environments 4 2 1 Known issues 4 2 1 1 Redirection of local data registry and temporary paths Because of rest,en
178,rictions on Microsoft Store apps Python scripts may not have full write access to shared locations such as TEMP and the registry Instead it will write to a private copy If your scripts must modify the shared locations you will need to install the full installer At runtime Python will use a private copy of well known Windows folders and the registry For example if the environment variable APPDATA is c Users user AppData then when writing to C Users user AppData Local will write to C Users user AppDat a Local Packages PythonSoftwareFoundation Python 3 8_qbz5n2kfra8p0 Lo calCache Local When reading files Windows will return the file from the private folder or if that does not exist the real Windows directory For example reading C Windows System32 returns the contents of C Windows System32 plus the contents of C Program Files WindowsApps package_name VFS SystemX86 You can find the real path of any existing file using os path realpath import os test_file C Users example AppData Local test txt os path realpath test_file C Users example AppData Local Packages PythonSoftwareFoundation Python 3 8_qbz5n2kfra8p0 LocalCache Local test txt When writing to the Windows Registry the following behaviors exist Reading from HKLM Software is allowed and results are merged with the registry dat file in the package Writing to HKLM Software is not allowed if the corresponding key value exists i e modifying existing keys Writing to HKLM Software is allowed as long as a corresponding key value does not exist in the package and the user has the correct access permissions For more detail on the technical basis for these limitations please consult Microsoft s documentation on packaged full trust apps currently available at docs microsoft com en us windows msix desktop desktop to uwp behind the scenes 4 3 The nuget org packages New in version 3 5 2 The nuget org package is a reduced size Python environment intended for use on continuous integration and build systems that do not have a system wide install of Python While nuget is the package manager for NET it also works perfectly fine for packages containing build time tools Visit nuget org for the most up to date information on using nuget What follows is a summary that is sufficient for Python developers The nuget exe command line tool may be downloaded directly from https aka ms nugetclidl for example using curl or PowerShell With the tool the latest version of Python for 64 bit or 32 bit machines is installed using nuget exe install python ExcludeVersion OutputDirectory nuget exe install pythonx86 ExcludeVersion OutputDirectory To select a particular version add a Version 3 x y The output directory may be changed from and the package will be installed into a subdirectory By default the subdirectory is named the same as the package and without the ExcludeVersion option this name will include the specific version installed Inside the subdirectory is a tools directory that contains the Python installation Without ExcludeVersion python 3 5 2 tools python exe V Python 3 5 2 With ExcludeVersion python tools python exe V Python 3 5 2 In general nuget packages are not upgradeable and newer versions should be installed side by side and referenced using the full path Alternatively delete the package directory manually and install it again Many CI systems will do this automatically if they do not preserve files between builds Alongside the tools directory is a build native directory This contains a MSBuild properties file python props that can be used in a C project to reference the Python install Including the settings will automatically use the headers and import libraries in your build The package information pages on nuget org are www nuget org packages python for the 64 bit version and www nuget org packages pythonx86 for the 32 bit version 4 4 The embeddable package New in version 3 5 The embedded distribution is a ZIP file containing a minimal Python environment It is intended for acting as part of another application rather than being directly accessed by end users When extracted the embedded distr,en
179,ibution is almost fully isolated from the user s system including environment variables system registry settings and installed packages The standard library is included as pre compiled and optimized pyc files in a ZIP and python3 dll python37 dll python exe and pythonw exe are all provided Tcl tk including all dependents such as Idle pip and the Python documentation are not included Note The embedded distribution does not include the Microsoft C Runtime and it is the responsibility of the application installer to provide this The runtime may have already been installed on a user s system previously or automatically via Windows Update and can be detected by finding ucrtbase dll in the system directory Third party packages should be installed by the application installer alongside the embedded distribution Using pip to manage dependencies as for a regular Python installation is not supported with this distribution though with some care it may be possible to include and use pip for automatic updates In general third party packages should be treated as part of the application vendoring so that the developer can ensure compatibility with newer versions before providing updates to users The two recommended use cases for this distribution are described below 4 4 1 Python Application An application written in Python does not necessarily require users to be aware of that fact The embedded distribution may be used in this case to include a private version of Python in an install package Depending on how transparent it should be or conversely how professional it should appear there are two options Using a specialized executable as a launcher requires some coding but provides the most transparent experience for users With a customized launcher there are no obvious indications that the program is running on Python icons can be customized company and version information can be specified and file associations behave properly In most cases a custom launcher should simply be able to call Py_Main with a hard coded command line The simpler approach is to provide a batch file or generated shortcut that directly calls the python exe or pythonw exe with the required command line arguments In this case the application will appear to be Python and not its actual name and users may have trouble distinguishing it from other running Python processes or file associations With the latter approach packages should be installed as directories alongside the Python executable to ensure they are available on the path With the specialized launcher packages can be located in other locations as there is an opportunity to specify the search path before launching the application 4 4 2 Embedding Python Applications written in native code often require some form of scripting language and the embedded Python distribution can be used for this purpose In general the majority of the application is in native code and some part will either invoke python exe or directly use python3 dll For either case extracting the embedded distribution to a subdirectory of the application installation is sufficient to provide a loadable Python interpreter As with the application use packages can be installed to any location as there is an opportunity to specify search paths before initializing the interpreter Otherwise there is no fundamental differences between using the embedded distribution and a regular installation 4 5 Alternative bundles Besides the standard CPython distribution there are modified packages including additional functionality The following is a list of popular versions and their key features ActivePython Installer with multi platform compatibility documentation PyWin32 Anaconda Popular scientific modules such as numpy scipy and pandas and the conda package manager Enthought Deployment Manager The Next Generation Python Environment and Package Manager Previously Enthought provided Canopy but it reached end of life in 2016 WinPython Windows specific distribution with prebuilt scientific packages and tools for building packages Note that these packages may not inclu,en
180,de the latest versions of Python or other libraries and are not maintained or supported by the core Python team 4 6 Configuring Python To run Python conveniently from a command prompt you might consider changing some default environment variables in Windows While the installer provides an option to configure the PATH and PATHEXT variables for you this is only reliable for a single system wide installation If you regularly use multiple versions of Python consider using the Python Launcher for Windows 4 6 1 Excursus Setting environment variables Windows allows environment variables to be configured permanently at both the User level and the System level or temporarily in a command prompt To temporarily set environment variables open Command Prompt and use the set command C set PATH C Program Files Python 3 9 PATH C set PYTHONPATH PYTHONPATH C My_python_lib C python These changes will apply to any further commands executed in that console and will be inherited by any applications started from the console Including the variable name within percent signs will expand to the existing value allowing you to add your new value at either the start or the end Modifying PATH by adding the directory containing python exe to the start is a common way to ensure the correct version of Python is launched To permanently modify the default environment variables click Start and search for edit environment variables or open System properties Advanced system settings and click the Environment Variables button In this dialog you can add or modify User and System variables To change System variables you need non restricted access to your machine i e Administrator rights Note Windows will concatenate User variables after System variables which may cause unexpected results when modifying PATH The PYTHONPATH variable is used by all versions of Python so you should not permanently configure it unless the listed paths only include code that is compatible with all of your installed Python versions See also https docs microsoft com en us windows win32 procthread environment variables Overview of environment variables on Windows https docs microsoft com en us windows server administration windows commands set_1 The set command for temporarily modifying environment variables https docs microsoft com en us windows server administration windows commands setx The setx command for permanently modifying environment variables 4 6 2 Finding the Python executable Changed in version 3 5 Besides using the automatically created start menu entry for the Python interpreter you might want to start Python in the command prompt The installer has an option to set that up for you On the first page of the installer an option labelled Add Python to PATH may be selected to have the installer add the install location into the PATH The location of the Scripts folder is also added This allows you to type python to run the interpreter and pip for the package installer Thus you can also execute your scripts with command line options see Command line documentation If you don t enable this option at install time you can always re run the installer select Modify and enable it Alternatively you can manually modify the PATH using the directions in Excursus Setting environment variables You need to set your PATH environment variable to include the directory of your Python installation delimited by a semicolon from other entries An example variable could look like this assuming the first two entries already existed C WINDOWS system32 C WINDOWS C Program Files Python 3 9 4 7 UTF 8 mode New in version 3 7 Windows still uses legacy encodings for the system encoding the ANSI Code Page Python uses it for the default encoding of text files e g locale getencoding This may cause issues because UTF 8 is widely used on the internet and most Unix systems including WSL Windows Subsystem for Linux You can use the Python UTF 8 Mode to change the default text encoding to UTF 8 You can enable the Python UTF 8 Mode via the X utf8 command line option or the PYTHONUTF8 1 environment variable See PYTHONUTF,en
181,8 for enabling UTF 8 mode and Excursus Setting environment variables for how to modify environment variables When the Python UTF 8 Mode is enabled you can still use the system encoding the ANSI Code Page via the mbcs codec Note that adding PYTHONUTF8 1 to the default environment variables will affect all Python 3 7 applications on your system If you have any Python 3 7 applications which rely on the legacy system encoding it is recommended to set the environment variable temporarily or use the X utf8 command line option Note Even when UTF 8 mode is disabled Python uses UTF 8 by default on Windows for Console I O including standard I O see PEP 528 for details The filesystem encoding see PEP 529 for details 4 8 Python Launcher for Windows New in version 3 3 The Python launcher for Windows is a utility which aids in locating and executing of different Python versions It allows scripts or the command line to indicate a preference for a specific Python version and will locate and execute that version Unlike the PATH variable the launcher will correctly select the most appropriate version of Python It will prefer per user installations over system wide ones and orders by language version rather than using the most recently installed version The launcher was originally specified in PEP 397 4 8 1 Getting started 4 8 1 1 From the command line Changed in version 3 6 System wide installations of Python 3 3 and later will put the launcher on your PATH The launcher is compatible with all available versions of Python so it does not matter which version is installed To check that the launcher is available execute the following command in Command Prompt py You should find that the latest version of Python you have installed is started it can be exited as normal and any additional command line arguments specified will be sent directly to Python If you have multiple versions of Python installed e g 3 7 and 3 12 you will have noticed that Python 3 12 was started to launch Python 3 7 try the command py 3 7 If you want the latest version of Python 2 you have installed try the command py 2 If you see the following error you do not have the launcher installed py is not recognized as an internal or external command operable program or batch file The command py list displays the currently installed version s of Python The x y argument is the short form of the V Company Tag argument which allows selecting a specific Python runtime including those that may have come from somewhere other than python org Any runtime registered by following PEP 514 will be discoverable The list command lists all available runtimes using the V format When using the V argument specifying the Company will limit selection to runtimes from that provider while specifying only the Tag will select from all providers Note that omitting the slash implies a tag Select any 3 tagged runtime py V 3 Select any PythonCore released runtime py V PythonCore Select PythonCore s latest Python 3 runtime py V PythonCore 3 The short form of the argument 3 only ever selects from core Python releases and not other distributions However the longer form V 3 will select from any The Company is matched on the full string case insenitive The Tag is matched oneither the full string or a prefix provided the next character is a dot or a hyphen This allows V 3 1 to match 3 1 32 but not 3 10 Tags are sorted using numerical ordering 3 10 is newer than 3 1 but are compared using text V 3 01 does not match 3 1 4 8 1 2 Virtual environments New in version 3 5 If the launcher is run with no explicit Python version specification and a virtual environment created with the standard library venv module or the external virtualenv tool active the launcher will run the virtual environment s interpreter rather than the global one To run the global interpreter either deactivate the virtual environment or explicitly specify the global Python version 4 8 1 3 From a script Let s create a test Python script create a file called hello py with the following contents python import sys sys stdout write hello from Python s n ,en
182,sys version From the directory in which hello py lives execute the command py hello py You should notice the version number of your latest Python 2 x installation is printed Now try changing the first line to be python3 Re executing the command should now print the latest Python 3 x information As with the above command line examples you can specify a more explicit version qualifier Assuming you have Python 3 7 installed try changing the first line to python3 7 and you should find the 3 7 version information printed Note that unlike interactive use a bare python will use the latest version of Python 2 x that you have installed This is for backward compatibility and for compatibility with Unix where the command python typically refers to Python 2 4 8 1 4 From file associations The launcher should have been associated with Python files i e py pyw pyc files when it was installed This means that when you double click on one of these files from Windows explorer the launcher will be used and therefore you can use the same facilities described above to have the script specify the version which should be used The key benefit of this is that a single launcher can support multiple Python versions at the same time depending on the contents of the first line 4 8 2 Shebang Lines If the first line of a script file starts with it is known as a shebang line Linux and other Unix like operating systems have native support for such lines and they are commonly used on such systems to indicate how a script should be executed This launcher allows the same facilities to be used with Python scripts on Windows and the examples above demonstrate their use To allow shebang lines in Python scripts to be portable between Unix and Windows this launcher supports a number of virtual commands to specify which interpreter to use The supported virtual commands are usr bin env usr bin python usr local bin python python For example if the first line of your script starts with usr bin python The default Python will be located and used As many Python scripts written to work on Unix will already have this line you should find these scripts can be used by the launcher without modification If you are writing a new script on Windows which you hope will be useful on Unix you should use one of the shebang lines starting with usr Any of the above virtual commands can be suffixed with an explicit version either just the major version or the major and minor version Furthermore the 32 bit version can be requested by adding 32 after the minor version I e usr bin python3 7 32 will request usage of the 32 bit python 3 7 New in version 3 7 Beginning with python launcher 3 7 it is possible to request 64 bit version by the 64 suffix Furthermore it is possible to specify a major and architecture without minor i e usr bin python3 64 Changed in version 3 11 The 64 suffix is deprecated and now implies any architecture that is not provably i386 32 bit To request a specific environment use the new V TAG argument with the complete tag The usr bin env form of shebang line has one further special property Before looking for installed Python interpreters this form will search the executable PATH for a Python executable matching the name provided as the first argument This corresponds to the behaviour of the Unix env program which performs a PATH search If an executable matching the first argument after the env command cannot be found but the argument starts with python it will be handled as described for the other virtual commands The environment variable PYLAUNCHER_NO_SEARCH_PATH may be set to any value to skip this search of PATH Shebang lines that do not match any of these patterns are looked up in the commands section of the launcher s INI file This may be used to handle certain commands in a way that makes sense for your system The name of the command must be a single argument no spaces in the shebang executable and the value substituted is the full path to the executable additional arguments specified in the INI will be quoted as part of the filename commands bin xpython C Progr,en
183,am Files XPython python exe Any commands not found in the INI file are treated as Windows executable paths that are absolute or relative to the directory containing the script file This is a convenience for Windows only scripts such as those generated by an installer since the behavior is not compatible with Unix style shells These paths may be quoted and may include multiple arguments after which the path to the script and any additional arguments will be appended 4 8 3 Arguments in shebang lines The shebang lines can also specify additional options to be passed to the Python interpreter For example if you have a shebang line usr bin python v Then Python will be started with the v option 4 8 4 Customization 4 8 4 1 Customization via INI files Two ini files will be searched by the launcher py ini in the current user s application data directory LOCALAPPDATA or env LocalAppData and py ini in the same directory as the launcher The same ini files are used for both the console version of the launcher i e py exe and for the windows version i e pyw exe Customization specified in the application directory will have precedence over the one next to the executable so a user who may not have write access to the ini file next to the launcher can override commands in that global ini file 4 8 4 2 Customizing default Python versions In some cases a version qualifier can be included in a command to dictate which version of Python will be used by the command A version qualifier starts with a major version number and can optionally be followed by a period and a minor version specifier Furthermore it is possible to specify if a 32 or 64 bit implementation shall be requested by adding 32 or 64 For example a shebang line of python has no version qualifier while python3 has a version qualifier which specifies only a major version If no version qualifiers are found in a command the environment variable PY_PYTHON can be set to specify the default version qualifier If it is not set the default is 3 The variable can specify any value that may be passed on the command line such as 3 3 7 3 7 32 or 3 7 64 Note that the 64 option is only available with the launcher included with Python 3 7 or newer If no minor version qualifiers are found the environment variable PY_PYTHON major where major is the current major version qualifier as determined above can be set to specify the full version If no such option is found the launcher will enumerate the installed Python versions and use the latest minor release found for the major version which is likely although not guaranteed to be the most recently installed version in that family On 64 bit Windows with both 32 bit and 64 bit implementations of the same major minor Python version installed the 64 bit version will always be preferred This will be true for both 32 bit and 64 bit implementations of the launcher a 32 bit launcher will prefer to execute a 64 bit Python installation of the specified version if available This is so the behavior of the launcher can be predicted knowing only what versions are installed on the PC and without regard to the order in which they were installed i e without knowing whether a 32 or 64 bit version of Python and corresponding launcher was installed last As noted above an optional 32 or 64 suffix can be used on a version specifier to change this behaviour Examples If no relevant options are set the commands python and python2 will use the latest Python 2 x version installed and the command python3 will use the latest Python 3 x installed The command python3 7 will not consult any options at all as the versions are fully specified If PY_PYTHON 3 the commands python and python3 will both use the latest installed Python 3 version If PY_PYTHON 3 7 32 the command python will use the 32 bit implementation of 3 7 whereas the command python3 will use the latest installed Python PY_PYTHON was not considered at all as a major version was specified If PY_PYTHON 3 and PY_PYTHON3 3 7 the commands python and python3 will both use specifically 3 7 In addition to environment variables the sa,en
184,me settings can be configured in the INI file used by the launcher The section in the INI file is called defaults and the key name will be the same as the environment variables without the leading PY_ prefix and note that the key names in the INI file are case insensitive The contents of an environment variable will override things specified in the INI file For example Setting PY_PYTHON 3 7 is equivalent to the INI file containing defaults python 3 7 Setting PY_PYTHON 3 and PY_PYTHON3 3 7 is equivalent to the INI file containing defaults python 3 python3 3 7 4 8 5 Diagnostics If an environment variable PYLAUNCHER_DEBUG is set to any value the launcher will print diagnostic information to stderr i e to the console While this information manages to be simultaneously verbose and terse it should allow you to see what versions of Python were located why a particular version was chosen and the exact command line used to execute the target Python It is primarily intended for testing and debugging 4 8 6 Dry Run If an environment variable PYLAUNCHER_DRYRUN is set to any value the launcher will output the command it would have run but will not actually launch Python This may be useful for tools that want to use the launcher to detect and then launch Python directly Note that the command written to standard output is always encoded using UTF 8 and may not render correctly in the console 4 8 7 Install on demand If an environment variable PYLAUNCHER_ALLOW_INSTALL is set to any value and the requested Python version is not installed but is available on the Microsoft Store the launcher will attempt to install it This may require user interaction to complete and you may need to run the command again An additional PYLAUNCHER_ALWAYS_INSTALL variable causes the launcher to always try to install Python even if it is detected This is mainly intended for testing and should be used with PYLAUNCHER_DRYRUN 4 8 8 Return codes The following exit codes may be returned by the Python launcher Unfortunately there is no way to distinguish these from the exit code of Python itself The names of codes are as used in the sources and are only for reference There is no way to access or resolve them apart from reading this page Entries are listed in alphabetical order of names Name Value Description RC_BAD_VENV_CFG 107 A pyvenv cfg was found but is corrupt RC_CREATE_PROCESS 101 Failed to launch Python RC_INSTALLING 111 An install was started but the command will need to be re run after it completes RC_INTERNAL_ERROR 109 Unexpected error Please report a bug RC_NO_COMMANDLINE 108 Unable to obtain command line from the operating system RC_NO_PYTHON 103 Unable to locate the requested version RC_NO_VENV_CFG 106 A pyvenv cfg was required but not found 4 9 Finding modules These notes supplement the description at The initialization of the sys path module search path with detailed Windows notes When no _pth file is found this is how sys path is populated on Windows An empty entry is added at the start which corresponds to the current directory If the environment variable PYTHONPATH exists as described in Environment variables its entries are added next Note that on Windows paths in this variable must be separated by semicolons to distinguish them from the colon used in drive identifiers C etc Additional application paths can be added in the registry as subkeys of SOFTWARE Python PythonCore version PythonPath under both the HKEY_CURRENT_USER and HKEY_LOCAL_MACHINE hives Subkeys which have semicolon delimited path strings as their default value will cause each path to be added to sys path Note that all known installers only use HKLM so HKCU is typically empty If the environment variable PYTHONHOME is set it is assumed as Python Home Otherwise the path of the main Python executable is used to locate a landmark file either Lib os py or pythonXY zip to deduce the Python Home If a Python home is found the relevant sub directories added to sys path Lib plat win etc are based on that folder Otherwise the core Python path is constructed from the PythonPath stored in the regis,en
185,try If the Python Home cannot be located no PYTHONPATH is specified in the environment and no registry entries can be found a default path with relative entries is used e g Lib plat win etc If a pyvenv cfg file is found alongside the main executable or in the directory one level above the executable the following variations apply If home is an absolute path and PYTHONHOME is not set this path is used instead of the path to the main executable when deducing the home location The end result of all this is When running python exe or any other exe in the main Python directory either an installed version or directly from the PCbuild directory the core path is deduced and the core paths in the registry are ignored Other application paths in the registry are always read When Python is hosted in another exe different directory embedded via COM etc the Python Home will not be deduced so the core path from the registry is used Other application paths in the registry are always read If Python can t find its home and there are no registry value frozen exe some very strange installation setup you get a path with some default but relative paths For those who want to bundle Python into their application or distribution the following advice will prevent conflicts with other installations Include a _pth file alongside your executable containing the directories to include This will ignore paths listed in the registry and environment variables and also ignore site unless import site is listed If you are loading python3 dll or python37 dll in your own executable explicitly call Py_SetPath or at least Py_SetProgramName before Py_Initialize Clear and or overwrite PYTHONPATH and set PYTHONHOME before launching python exe from your application If you cannot use the previous suggestions for example you are a distribution that allows people to run python exe directly ensure that the landmark file Lib os py exists in your install directory Note that it will not be detected inside a ZIP file but a correctly named ZIP file will be detected instead These will ensure that the files in a system wide installation will not take precedence over the copy of the standard library bundled with your application Otherwise your users may experience problems using your application Note that the first suggestion is the best as the others may still be susceptible to non standard paths in the registry and user site packages Changed in version 3 6 Add _pth file support and removes applocal option from pyvenv cfg Changed in version 3 6 Add python XX zip as a potential landmark when directly adjacent to the executable Deprecated since version 3 6 Modules specified in the registry under Modules not PythonPath may be imported by importlib machinery WindowsRegistryFinder This finder is enabled on Windows in 3 6 0 and earlier but may need to be explicitly added to sys meta_path in the future 4 10 Additional modules Even though Python aims to be portable among all platforms there are features that are unique to Windows A couple of modules both in the standard library and external and snippets exist to use these features The Windows specific standard modules are documented in MS Windows Specific Services 4 10 1 PyWin32 The PyWin32 module by Mark Hammond is a collection of modules for advanced Windows specific support This includes utilities for Component Object Model COM Win32 API calls Registry Event log Microsoft Foundation Classes MFC user interfaces PythonWin is a sample MFC application shipped with PyWin32 It is an embeddable IDE with a built in debugger See also Win32 How Do I by Tim Golden Python and COM by David and Paul Boddie 4 10 2 cx_Freeze cx_Freeze wraps Python scripts into executable Windows programs exe files When you have done this you can distribute your application without requiring your users to install Python 4 11 Compiling Python on Windows If you want to compile CPython yourself first thing you should do is get the source You can download either the latest release s source or just grab a fresh checkout The source tree contains a build solution and proj,en
186,ect files for Microsoft Visual Studio which is the compiler used to build the official Python releases These files are in the PCbuild directory Check PCbuild readme txt for general information on the build process For extension modules consult Building C and C Extensions on Windows 4 12 Other Platforms With ongoing development of Python some platforms that used to be supported earlier are no longer supported due to the lack of users or developers Check PEP 11 for details on all unsupported platforms Windows CE is no longer supported since Python 3 if it ever was The Cygwin installer offers to install the Python interpreter as well See Python for Windows for detailed information about platforms with pre compiled installers,en
187,Binary Data Services The modules described in this chapter provide some basic services operations for manipulation of binary data Other operations on binary data specifically in relation to file formats and network protocols are described in the relevant sections Some libraries described under Text Processing Services also work with either ASCII compatible binary formats for example re or all binary data for example difflib In addition see the documentation for Python s built in binary data types in Binary Sequence Types bytes bytearray memoryview struct Interpret bytes as packed binary data Functions and Exceptions Format Strings Byte Order Size and Alignment Format Characters Examples Applications Native Formats Standard Formats Classes codecs Codec registry and base classes Codec Base Classes Error Handlers Stateless Encoding and Decoding Incremental Encoding and Decoding IncrementalEncoder Objects IncrementalDecoder Objects Stream Encoding and Decoding StreamWriter Objects StreamReader Objects StreamReaderWriter Objects StreamRecoder Objects Encodings and Unicode Standard Encodings Python Specific Encodings Text Encodings Binary Transforms Text Transforms encodings idna Internationalized Domain Names in Applications encodings mbcs Windows ANSI codepage encodings utf_8_sig UTF 8 codec with BOM signature,en
188,gettext Multilingual internationalization services Source code Lib gettext py The gettext module provides internationalization I18N and localization L10N services for your Python modules and applications It supports both the GNU gettext message catalog API and a higher level class based API that may be more appropriate for Python files The interface described below allows you to write your module and application messages in one natural language and provide a catalog of translated messages for running under different natural languages Some hints on localizing your Python modules and applications are also given GNU gettext API The gettext module defines the following API which is very similar to the GNU gettext API If you use this API you will affect the translation of your entire application globally Often this is what you want if your application is monolingual with the choice of language dependent on the locale of your user If you are localizing a Python module or if your application needs to switch languages on the fly you probably want to use the class based API instead gettext bindtextdomain domain localedir None Bind the domain to the locale directory localedir More concretely gettext will look for binary mo files for the given domain using the path on Unix localedir language LC_MESSAGES domain mo where language is searched for in the environment variables LANGUAGE LC_ALL LC_MESSAGES and LANG respectively If localedir is omitted or None then the current binding for domain is returned 1 gettext textdomain domain None Change or query the current global domain If domain is None then the current global domain is returned otherwise the global domain is set to domain which is returned gettext gettext message Return the localized translation of message based on the current global domain language and locale directory This function is usually aliased as _ in the local namespace see examples below gettext dgettext domain message Like gettext but look the message up in the specified domain gettext ngettext singular plural n Like gettext but consider plural forms If a translation is found apply the plural formula to n and return the resulting message some languages have more than two plural forms If no translation is found return singular if n is 1 return plural otherwise The Plural formula is taken from the catalog header It is a C or Python expression that has a free variable n the expression evaluates to the index of the plural in the catalog See the GNU gettext documentation for the precise syntax to be used in po files and the formulas for a variety of languages gettext dngettext domain singular plural n Like ngettext but look the message up in the specified domain gettext pgettext context message gettext dpgettext domain context message gettext npgettext context singular plural n gettext dnpgettext domain context singular plural n Similar to the corresponding functions without the p in the prefix that is gettext dgettext ngettext dngettext but the translation is restricted to the given message context New in version 3 8 Note that GNU gettext also defines a dcgettext method but this was deemed not useful and so it is currently unimplemented Here s an example of typical usage for this API import gettext gettext bindtextdomain myapplication path to my language directory gettext textdomain myapplication _ gettext gettext print _ This is a translatable string Class based API The class based API of the gettext module gives you more flexibility and greater convenience than the GNU gettext API It is the recommended way of localizing your Python applications and modules gettext defines a GNUTranslations class which implements the parsing of GNU mo format files and has methods for returning strings Instances of this class can also install themselves in the built in namespace as the function _ gettext find domain localedir None languages None all False This function implements the standard mo file search algorithm It takes a domain identical to what textdomain takes Optional localedir is as in bindtextdomain Optional languages is a ,en
189,list of strings where each string is a language code If localedir is not given then the default system locale directory is used 2 If languages is not given then the following environment variables are searched LANGUAGE LC_ALL LC_MESSAGES and LANG The first one returning a non empty value is used for the languages variable The environment variables should contain a colon separated list of languages which will be split on the colon to produce the expected list of language code strings find then expands and normalizes the languages and then iterates through them searching for an existing file built of these components localedir language LC_MESSAGES domain mo The first such file name that exists is returned by find If no such file is found then None is returned If all is given it returns a list of all file names in the order in which they appear in the languages list or the environment variables gettext translation domain localedir None languages None class_ None fallback False Return a Translations instance based on the domain localedir and languages which are first passed to find to get a list of the associated mo file paths Instances with identical mo file names are cached The actual class instantiated is class_ if provided otherwise GNUTranslations The class s constructor must take a single file object argument If multiple files are found later files are used as fallbacks for earlier ones To allow setting the fallback copy copy is used to clone each translation object from the cache the actual instance data is still shared with the cache If no mo file is found this function raises OSError if fallback is false which is the default and returns a NullTranslations instance if fallback is true Changed in version 3 3 IOError used to be raised it is now an alias of OSError Changed in version 3 11 codeset parameter is removed gettext install domain localedir None names None This installs the function _ in Python s builtins namespace based on domain and localedir which are passed to the function translation For the names parameter please see the description of the translation object s install method As seen below you usually mark the strings in your application that are candidates for translation by wrapping them in a call to the _ function like this print _ This string will be translated For convenience you want the _ function to be installed in Python s builtins namespace so it is easily accessible in all modules of your application Changed in version 3 11 names is now a keyword only parameter The NullTranslations class Translation classes are what actually implement the translation of original source file message strings to translated message strings The base class used by all translation classes is NullTranslations this provides the basic interface you can use to write your own specialized translation classes Here are the methods of NullTranslations class gettext NullTranslations fp None Takes an optional file object fp which is ignored by the base class Initializes protected instance variables _info and _charset which are set by derived classes as well as _fallback which is set through add_fallback It then calls self _parse fp if fp is not None _parse fp No op in the base class this method takes file object fp and reads the data from the file initializing its message catalog If you have an unsupported message catalog file format you should override this method to parse your format add_fallback fallback Add fallback as the fallback object for the current translation object A translation object should consult the fallback if it cannot provide a translation for a given message gettext message If a fallback has been set forward gettext to the fallback Otherwise return message Overridden in derived classes ngettext singular plural n If a fallback has been set forward ngettext to the fallback Otherwise return singular if n is 1 return plural otherwise Overridden in derived classes pgettext context message If a fallback has been set forward pgettext to the fallback Otherwise return the translated message Overridden in derived class,en
190,es New in version 3 8 npgettext context singular plural n If a fallback has been set forward npgettext to the fallback Otherwise return the translated message Overridden in derived classes New in version 3 8 info Return a dictionary containing the metadata found in the message catalog file charset Return the encoding of the message catalog file install names None This method installs gettext into the built in namespace binding it to _ If the names parameter is given it must be a sequence containing the names of functions you want to install in the builtins namespace in addition to _ Supported names are gettext ngettext pgettext and npgettext Note that this is only one way albeit the most convenient way to make the _ function available to your application Because it affects the entire application globally and specifically the built in namespace localized modules should never install _ Instead they should use this code to make _ available to their module import gettext t gettext translation mymodule _ t gettext This puts _ only in the module s global namespace and so only affects calls within this module Changed in version 3 8 Added pgettext and npgettext The GNUTranslations class The gettext module provides one additional class derived from NullTranslations GNUTranslations This class overrides _parse to enable reading GNU gettext format mo files in both big endian and little endian format GNUTranslations parses optional metadata out of the translation catalog It is convention with GNU gettext to include metadata as the translation for the empty string This metadata is in RFC 822 style key value pairs and should contain the Project Id Version key If the key Content Type is found then the charset property is used to initialize the protected _charset instance variable defaulting to None if not found If the charset encoding is specified then all message ids and message strings read from the catalog are converted to Unicode using this encoding else ASCII is assumed Since message ids are read as Unicode strings too all gettext methods will assume message ids as Unicode strings not byte strings The entire set of key value pairs are placed into a dictionary and set as the protected _info instance variable If the mo file s magic number is invalid the major version number is unexpected or if other problems occur while reading the file instantiating a GNUTranslations class can raise OSError class gettext GNUTranslations The following methods are overridden from the base class implementation gettext message Look up the message id in the catalog and return the corresponding message string as a Unicode string If there is no entry in the catalog for the message id and a fallback has been set the look up is forwarded to the fallback s gettext method Otherwise the message id is returned ngettext singular plural n Do a plural forms lookup of a message id singular is used as the message id for purposes of lookup in the catalog while n is used to determine which plural form to use The returned message string is a Unicode string If the message id is not found in the catalog and a fallback is specified the request is forwarded to the fallback s ngettext method Otherwise when n is 1 singular is returned and plural is returned in all other cases Here is an example n len os listdir cat GNUTranslations somefile message cat ngettext There is num d file in this directory There are num d files in this directory n num n pgettext context message Look up the context and message id in the catalog and return the corresponding message string as a Unicode string If there is no entry in the catalog for the message id and context and a fallback has been set the look up is forwarded to the fallback s pgettext method Otherwise the message id is returned New in version 3 8 npgettext context singular plural n Do a plural forms lookup of a message id singular is used as the message id for purposes of lookup in the catalog while n is used to determine which plural form to use If the message id for context is not found in the catalog and a fallback is specified the ,en
191,request is forwarded to the fallback s npgettext method Otherwise when n is 1 singular is returned and plural is returned in all other cases New in version 3 8 Solaris message catalog support The Solaris operating system defines its own binary mo file format but since no documentation can be found on this format it is not supported at this time The Catalog constructor GNOME uses a version of the gettext module by James Henstridge but this version has a slightly different API Its documented usage was import gettext cat gettext Catalog domain localedir _ cat gettext print _ hello world For compatibility with this older module the function Catalog is an alias for the translation function described above One difference between this module and Henstridge s his catalog objects supported access through a mapping API but this appears to be unused and so is not currently supported Internationalizing your programs and modules Internationalization I18N refers to the operation by which a program is made aware of multiple languages Localization L10N refers to the adaptation of your program once internationalized to the local language and cultural habits In order to provide multilingual messages for your Python programs you need to take the following steps 1 prepare your program or module by specially marking translatable strings 2 run a suite of tools over your marked files to generate raw messages catalogs 3 create language specific translations of the message catalogs 4 use the gettext module so that message strings are properly translated In order to prepare your code for I18N you need to look at all the strings in your files Any string that needs to be translated should be marked by wrapping it in _ that is a call to the function _ For example filename mylog txt message _ writing a log message with open filename w as fp fp write message In this example the string writing a log message is marked as a candidate for translation while the strings mylog txt and w are not There are a few tools to extract the strings meant for translation The original GNU gettext only supported C or C source code but its extended version xgettext scans code written in a number of languages including Python to find strings marked as translatable Babel is a Python internationalization library that includes a pybabel script to extract and compile message catalogs François Pinard s program called xpot does a similar job and is available as part of his po utils package Python also includes pure Python versions of these programs called pygettext py and msgfmt py some Python distributions will install them for you pygettext py is similar to xgettext but only understands Python source code and cannot handle other programming languages such as C or C pygettext py supports a command line interface similar to xgettext for details on its use run pygettext py help msgfmt py is binary compatible with GNU msgfmt With these two programs you may not need the GNU gettext package to internationalize your Python applications xgettext pygettext and similar tools generate po files that are message catalogs They are structured human readable files that contain every marked string in the source code along with a placeholder for the translated versions of these strings Copies of these po files are then handed over to the individual human translators who write translations for every supported natural language They send back the completed language specific versions as a language name po file that s compiled into a machine readable mo binary catalog file using the msgfmt program The mo files are used by the gettext module for the actual translation processing at run time How you use the gettext module in your code depends on whether you are internationalizing a single module or your entire application The next two sections will discuss each case Localizing your module If you are localizing your module you must take care not to make global changes e g to the built in namespace You should not use the GNU gettext API but instead the class based API Let s say your module is called spa,en
192,m and the module s various natural language translation mo files reside in usr share locale in GNU gettext format Here s what you would put at the top of your module import gettext t gettext translation spam usr share locale _ t gettext Localizing your application If you are localizing your application you can install the _ function globally into the built in namespace usually in the main driver file of your application This will let all your application specific files just use _ without having to explicitly install it in each file In the simple case then you need only add the following bit of code to the main driver file of your application import gettext gettext install myapplication If you need to set the locale directory you can pass it into the install function import gettext gettext install myapplication usr share locale Changing languages on the fly If your program needs to support many languages at the same time you may want to create multiple translation instances and then switch between them explicitly like so import gettext lang1 gettext translation myapplication languages en lang2 gettext translation myapplication languages fr lang3 gettext translation myapplication languages de start by using language1 lang1 install time goes by user selects language 2 lang2 install more time goes by user selects language 3 lang3 install Deferred translations In most coding situations strings are translated where they are coded Occasionally however you need to mark strings for translation but defer actual translation until later A classic example is animals mollusk albatross rat penguin python for a in animals print a Here you want to mark the strings in the animals list as being translatable but you don t actually want to translate them until they are printed Here is one way you can handle this situation def _ message return message animals _ mollusk _ albatross _ rat _ penguin _ python del _ for a in animals print _ a This works because the dummy definition of _ simply returns the string unchanged And this dummy definition will temporarily override any definition of _ in the built in namespace until the del command Take care though if you have a previous definition of _ in the local namespace Note that the second use of _ will not identify a as being translatable to the gettext program because the parameter is not a string literal Another way to handle this is with the following example def N_ message return message animals N_ mollusk N_ albatross N_ rat N_ penguin N_ python for a in animals print _ a In this case you are marking translatable strings with the function N_ which won t conflict with any definition of _ However you will need to teach your message extraction program to look for translatable strings marked with N_ xgettext pygettext pybabel extract and xpot all support this through the use of the k command line switch The choice of N_ here is totally arbitrary it could have just as easily been MarkThisStringForTranslation Acknowledgements The following people contributed code feedback design suggestions previous implementations and valuable experience to the creation of this module Peter Funk James Henstridge Juan David Ibáñez Palomar Marc André Lemburg Martin von Löwis François Pinard Barry Warsaw Gustavo Niemeyer Footnotes 1 The default locale directory is system dependent for example on Red Hat Linux it is usr share locale but on Solaris it is usr lib locale The gettext module does not try to support these system dependent defaults instead its default is sys base_prefix share locale see sys base_prefix For this reason it is always best to call bindtextdomain with an explicit absolute path at the start of your application 2 See the footnote for bindtextdomain above,en
193,urllib robotparser Parser for robots txt Source code Lib urllib robotparser py This module provides a single class RobotFileParser which answers questions about whether or not a particular user agent can fetch a URL on the web site that published the robots txt file For more details on the structure of robots txt files see http www robotstxt org orig html class urllib robotparser RobotFileParser url This class provides methods to read parse and answer questions about the robots txt file at url set_url url Sets the URL referring to a robots txt file read Reads the robots txt URL and feeds it to the parser parse lines Parses the lines argument can_fetch useragent url Returns True if the useragent is allowed to fetch the url according to the rules contained in the parsed robots txt file mtime Returns the time the robots txt file was last fetched This is useful for long running web spiders that need to check for new robots txt files periodically modified Sets the time the robots txt file was last fetched to the current time crawl_delay useragent Returns the value of the Crawl delay parameter from robots txt for the useragent in question If there is no such parameter or it doesn t apply to the useragent specified or the robots txt entry for this parameter has invalid syntax return None New in version 3 6 request_rate useragent Returns the contents of the Request rate parameter from robots txt as a named tuple RequestRate requests seconds If there is no such parameter or it doesn t apply to the useragent specified or the robots txt entry for this parameter has invalid syntax return None New in version 3 6 site_maps Returns the contents of the Sitemap parameter from robots txt in the form of a list If there is no such parameter or the robots txt entry for this parameter has invalid syntax return None New in version 3 8 The following example demonstrates basic use of the RobotFileParser class import urllib robotparser rp urllib robotparser RobotFileParser rp set_url http www musi cal com robots txt rp read rrate rp request_rate rrate requests 3 rrate seconds 20 rp crawl_delay 6 rp can_fetch http www musi cal com cgi bin search city San Francisco False rp can_fetch http www musi cal com True,en
194,Superseded Modules The modules described in this chapter are deprecated and only kept for backwards compatibility They have been superseded by other modules aifc Read and write AIFF and AIFC files audioop Manipulate raw audio data cgi Common Gateway Interface support cgitb Traceback manager for CGI scripts chunk Read IFF chunked data crypt Function to check Unix passwords imghdr Determine the type of an image mailcap Mailcap file handling msilib Read and write Microsoft Installer files nis Interface to Sun s NIS Yellow Pages nntplib NNTP protocol client optparse Parser for command line options ossaudiodev Access to OSS compatible audio devices pipes Interface to shell pipelines sndhdr Determine type of sound file spwd The shadow password database sunau Read and write Sun AU files telnetlib Telnet client uu Encode and decode uuencode files xdrlib Encode and decode XDR data,en
195,email message Message Representing an email message using the compat32 API The Message class is very similar to the EmailMessage class without the methods added by that class and with the default behavior of certain other methods being slightly different We also document here some methods that while supported by the EmailMessage class are not recommended unless you are dealing with legacy code The philosophy and structure of the two classes is otherwise the same This document describes the behavior under the default for Message policy Compat32 If you are going to use another policy you should be using the EmailMessage class instead An email message consists of headers and a payload Headers must be RFC 5322 style names and values where the field name and value are separated by a colon The colon is not part of either the field name or the field value The payload may be a simple text message or a binary object or a structured sequence of sub messages each with their own set of headers and their own payload The latter type of payload is indicated by the message having a MIME type such as multipart or message rfc822 The conceptual model provided by a Message object is that of an ordered dictionary of headers with additional methods for accessing both specialized information from the headers for accessing the payload for generating a serialized version of the message and for recursively walking over the object tree Note that duplicate headers are supported but special methods must be used to access them The Message pseudo dictionary is indexed by the header names which must be ASCII values The values of the dictionary are strings that are supposed to contain only ASCII characters there is some special handling for non ASCII input but it doesn t always produce the correct results Headers are stored and returned in case preserving form but field names are matched case insensitively There may also be a single envelope header also known as the Unix From header or the From_ header The payload is either a string or bytes in the case of simple message objects or a list of Message objects for MIME container documents e g multipart and message rfc822 Here are the methods of the Message class class email message Message policy compat32 If policy is specified it must be an instance of a policy class use the rules it specifies to update and serialize the representation of the message If policy is not set use the compat32 policy which maintains backward compatibility with the Python 3 2 version of the email package For more information see the policy documentation Changed in version 3 3 The policy keyword argument was added as_string unixfrom False maxheaderlen 0 policy None Return the entire message flattened as a string When optional unixfrom is true the envelope header is included in the returned string unixfrom defaults to False For backward compatibility reasons maxheaderlen defaults to 0 so if you want a different value you must override it explicitly the value specified for max_line_length in the policy will be ignored by this method The policy argument may be used to override the default policy obtained from the message instance This can be used to control some of the formatting produced by the method since the specified policy will be passed to the Generator Flattening the message may trigger changes to the Message if defaults need to be filled in to complete the transformation to a string for example MIME boundaries may be generated or modified Note that this method is provided as a convenience and may not always format the message the way you want For example by default it does not do the mangling of lines that begin with From that is required by the Unix mbox format For more flexibility instantiate a Generator instance and use its flatten method directly For example from io import StringIO from email generator import Generator fp StringIO g Generator fp mangle_from_ True maxheaderlen 60 g flatten msg text fp getvalue If the message object contains binary data that is not encoded according to RFC standards the non compliant data,en
196, will be replaced by unicode unknown character code points See also as_bytes and BytesGenerator Changed in version 3 4 the policy keyword argument was added __str__ Equivalent to as_string Allows str msg to produce a string containing the formatted message as_bytes unixfrom False policy None Return the entire message flattened as a bytes object When optional unixfrom is true the envelope header is included in the returned string unixfrom defaults to False The policy argument may be used to override the default policy obtained from the message instance This can be used to control some of the formatting produced by the method since the specified policy will be passed to the BytesGenerator Flattening the message may trigger changes to the Message if defaults need to be filled in to complete the transformation to a string for example MIME boundaries may be generated or modified Note that this method is provided as a convenience and may not always format the message the way you want For example by default it does not do the mangling of lines that begin with From that is required by the Unix mbox format For more flexibility instantiate a BytesGenerator instance and use its flatten method directly For example from io import BytesIO from email generator import BytesGenerator fp BytesIO g BytesGenerator fp mangle_from_ True maxheaderlen 60 g flatten msg text fp getvalue New in version 3 4 __bytes__ Equivalent to as_bytes Allows bytes msg to produce a bytes object containing the formatted message New in version 3 4 is_multipart Return True if the message s payload is a list of sub Message objects otherwise return False When is_multipart returns False the payload should be a string object which might be a CTE encoded binary payload Note that is_multipart returning True does not necessarily mean that msg get_content_maintype multipart will return the True For example is_multipart will return True when the Message is of type message rfc822 set_unixfrom unixfrom Set the message s envelope header to unixfrom which should be a string get_unixfrom Return the message s envelope header Defaults to None if the envelope header was never set attach payload Add the given payload to the current payload which must be None or a list of Message objects before the call After the call the payload will always be a list of Message objects If you want to set the payload to a scalar object e g a string use set_payload instead This is a legacy method On the EmailMessage class its functionality is replaced by set_content and the related make and add methods get_payload i None decode False Return the current payload which will be a list of Message objects when is_multipart is True or a string when is_multipart is False If the payload is a list and you mutate the list object you modify the message s payload in place With optional argument i get_payload will return the i th element of the payload counting from zero if is_multipart is True An IndexError will be raised if i is less than 0 or greater than or equal to the number of items in the payload If the payload is a string i e is_multipart is False and i is given a TypeError is raised Optional decode is a flag indicating whether the payload should be decoded or not according to the Content Transfer Encoding header When True and the message is not a multipart the payload will be decoded if this header s value is quoted printable or base64 If some other encoding is used or Content Transfer Encoding header is missing the payload is returned as is undecoded In all cases the returned value is binary data If the message is a multipart and the decode flag is True then None is returned If the payload is base64 and it was not perfectly formed missing padding characters outside the base64 alphabet then an appropriate defect will be added to the message s defect property InvalidBase64PaddingDefect or InvalidBase64CharactersDefect respectively When decode is False the default the body is returned as a string without decoding the Content Transfer Encoding However for a Content Transfer Encoding of 8bit an attempt is ma,en
197,de to decode the original bytes using the charset specified by the Content Type header using the replace error handler If no charset is specified or if the charset given is not recognized by the email package the body is decoded using the default ASCII charset This is a legacy method On the EmailMessage class its functionality is replaced by get_content and iter_parts set_payload payload charset None Set the entire message object s payload to payload It is the client s responsibility to ensure the payload invariants Optional charset sets the message s default character set see set_charset for details This is a legacy method On the EmailMessage class its functionality is replaced by set_content set_charset charset Set the character set of the payload to charset which can either be a Charset instance see email charset a string naming a character set or None If it is a string it will be converted to a Charset instance If charset is None the charset parameter will be removed from the Content Type header the message will not be otherwise modified Anything else will generate a TypeError If there is no existing MIME Version header one will be added If there is no existing Content Type header one will be added with a value of text plain Whether the Content Type header already exists or not its charset parameter will be set to charset output_charset If charset input_charset and charset output_charset differ the payload will be re encoded to the output_charset If there is no existing Content Transfer Encoding header then the payload will be transfer encoded if needed using the specified Charset and a header with the appropriate value will be added If a Content Transfer Encoding header already exists the payload is assumed to already be correctly encoded using that Content Transfer Encoding and is not modified This is a legacy method On the EmailMessage class its functionality is replaced by the charset parameter of the email emailmessage EmailMessage set_content method get_charset Return the Charset instance associated with the message s payload This is a legacy method On the EmailMessage class it always returns None The following methods implement a mapping like interface for accessing the message s RFC 2822 headers Note that there are some semantic differences between these methods and a normal mapping i e dictionary interface For example in a dictionary there are no duplicate keys but here there may be duplicate message headers Also in dictionaries there is no guaranteed order to the keys returned by keys but in a Message object headers are always returned in the order they appeared in the original message or were added to the message later Any header deleted and then re added are always appended to the end of the header list These semantic differences are intentional and are biased toward maximal convenience Note that in all cases any envelope header present in the message is not included in the mapping interface In a model generated from bytes any header values that in contravention of the RFCs contain non ASCII bytes will when retrieved through this interface be represented as Header objects with a charset of unknown 8bit __len__ Return the total number of headers including duplicates __contains__ name Return True if the message object has a field named name Matching is done case insensitively and name should not include the trailing colon Used for the in operator e g if message id in myMessage print Message ID myMessage message id __getitem__ name Return the value of the named header field name should not include the colon field separator If the header is missing None is returned a KeyError is never raised Note that if the named field appears more than once in the message s headers exactly which of those field values will be returned is undefined Use the get_all method to get the values of all the extant named headers __setitem__ name val Add a header to the message with field name name and value val The field is appended to the end of the message s existing fields Note that this does not overwrite or delete any existing he,en
198,ader with the same name If you want to ensure that the new header is the only one present in the message with field name name delete the field first e g del msg subject msg subject Python roolz __delitem__ name Delete all occurrences of the field with name name from the message s headers No exception is raised if the named field isn t present in the headers keys Return a list of all the message s header field names values Return a list of all the message s field values items Return a list of 2 tuples containing all the message s field headers and values get name failobj None Return the value of the named header field This is identical to __getitem__ except that optional failobj is returned if the named header is missing defaults to None Here are some additional useful methods get_all name failobj None Return a list of all the values for the field named name If there are no such named headers in the message failobj is returned defaults to None add_header _name _value _params Extended header setting This method is similar to __setitem__ except that additional header parameters can be provided as keyword arguments _name is the header field to add and _value is the primary value for the header For each item in the keyword argument dictionary _params the key is taken as the parameter name with underscores converted to dashes since dashes are illegal in Python identifiers Normally the parameter will be added as key value unless the value is None in which case only the key will be added If the value contains non ASCII characters it can be specified as a three tuple in the format CHARSET LANGUAGE VALUE where CHARSET is a string naming the charset to be used to encode the value LANGUAGE can usually be set to None or the empty string see RFC 2231 for other possibilities and VALUE is the string value containing non ASCII code points If a three tuple is not passed and the value contains non ASCII characters it is automatically encoded in RFC 2231 format using a CHARSET of utf 8 and a LANGUAGE of None Here s an example msg add_header Content Disposition attachment filename bud gif This will add a header that looks like Content Disposition attachment filename bud gif An example with non ASCII characters msg add_header Content Disposition attachment filename iso 8859 1 Fußballer ppt Which produces Content Disposition attachment filename iso 8859 1 Fu DFballer ppt replace_header _name _value Replace a header Replace the first header found in the message that matches _name retaining header order and field name case If no matching header was found a KeyError is raised get_content_type Return the message s content type The returned string is coerced to lower case of the form maintype subtype If there was no Content Type header in the message the default type as given by get_default_type will be returned Since according to RFC 2045 messages always have a default type get_content_type will always return a value RFC 2045 defines a message s default type to be text plain unless it appears inside a multipart digest container in which case it would be message rfc822 If the Content Type header has an invalid type specification RFC 2045 mandates that the default type be text plain get_content_maintype Return the message s main content type This is the maintype part of the string returned by get_content_type get_content_subtype Return the message s sub content type This is the subtype part of the string returned by get_content_type get_default_type Return the default content type Most messages have a default content type of text plain except for messages that are subparts of multipart digest containers Such subparts have a default content type of message rfc822 set_default_type ctype Set the default content type ctype should either be text plain or message rfc822 although this is not enforced The default content type is not stored in the Content Type header get_params failobj None header content type unquote True Return the message s Content Type parameters as a list The elements of the returned list are 2 tuples of key value pairs as split on the ,en
199,sign The left hand side of the is the key while the right hand side is the value If there is no sign in the parameter the value is the empty string otherwise the value is as described in get_param and is unquoted if optional unquote is True the default Optional failobj is the object to return if there is no Content Type header Optional header is the header to search instead of Content Type This is a legacy method On the EmailMessage class its functionality is replaced by the params property of the individual header objects returned by the header access methods get_param param failobj None header content type unquote True Return the value of the Content Type header s parameter param as a string If the message has no Content Type header or if there is no such parameter then failobj is returned defaults to None Optional header if given specifies the message header to use instead of Content Type Parameter keys are always compared case insensitively The return value can either be a string or a 3 tuple if the parameter was RFC 2231 encoded When it s a 3 tuple the elements of the value are of the form CHARSET LANGUAGE VALUE Note that both CHARSET and LANGUAGE can be None in which case you should consider VALUE to be encoded in the us ascii charset You can usually ignore LANGUAGE If your application doesn t care whether the parameter was encoded as in RFC 2231 you can collapse the parameter value by calling email utils collapse_rfc2231_value passing in the return value from get_param This will return a suitably decoded Unicode string when the value is a tuple or the original string unquoted if it isn t For example rawparam msg get_param foo param email utils collapse_rfc2231_value rawparam In any case the parameter value either the returned string or the VALUE item in the 3 tuple is always unquoted unless unquote is set to False This is a legacy method On the EmailMessage class its functionality is replaced by the params property of the individual header objects returned by the header access methods set_param param value header Content Type requote True charset None language replace False Set a parameter in the Content Type header If the parameter already exists in the header its value will be replaced with value If the Content Type header as not yet been defined for this message it will be set to text plain and the new parameter value will be appended as per RFC 2045 Optional header specifies an alternative header to Content Type and all parameters will be quoted as necessary unless optional requote is False the default is True If optional charset is specified the parameter will be encoded according to RFC 2231 Optional language specifies the RFC 2231 language defaulting to the empty string Both charset and language should be strings If replace is False the default the header is moved to the end of the list of headers If replace is True the header will be updated in place Changed in version 3 4 replace keyword was added del_param param header content type requote True Remove the given parameter completely from the Content Type header The header will be re written in place without the parameter or its value All values will be quoted as necessary unless requote is False the default is True Optional header specifies an alternative to Content Type set_type type header Content Type requote True Set the main type and subtype for the Content Type header type must be a string in the form maintype subtype otherwise a ValueError is raised This method replaces the Content Type header keeping all the parameters in place If requote is False this leaves the existing header s quoting as is otherwise the parameters will be quoted the default An alternative header can be specified in the header argument When the Content Type header is set a MIME Version header is also added This is a legacy method On the EmailMessage class its functionality is replaced by the make_ and add_ methods get_filename failobj None Return the value of the filename parameter of the Content Disposition header of the message If the header does not have a filename paramete,en
200,r this method falls back to looking for the name parameter on the Content Type header If neither is found or the header is missing then failobj is returned The returned string will always be unquoted as per email utils unquote get_boundary failobj None Return the value of the boundary parameter of the Content Type header of the message or failobj if either the header is missing or has no boundary parameter The returned string will always be unquoted as per email utils unquote set_boundary boundary Set the boundary parameter of the Content Type header to boundary set_boundary will always quote boundary if necessary A HeaderParseError is raised if the message object has no Content Type header Note that using this method is subtly different than deleting the old Content Type header and adding a new one with the new boundary via add_header because set_boundary preserves the order of the Content Type header in the list of headers However it does not preserve any continuation lines which may have been present in the original Content Type header get_content_charset failobj None Return the charset parameter of the Content Type header coerced to lower case If there is no Content Type header or if that header has no charset parameter failobj is returned Note that this method differs from get_charset which returns the Charset instance for the default encoding of the message body get_charsets failobj None Return a list containing the character set names in the message If the message is a multipart then the list will contain one element for each subpart in the payload otherwise it will be a list of length 1 Each item in the list will be a string which is the value of the charset parameter in the Content Type header for the represented subpart However if the subpart has no Content Type header no charset parameter or is not of the text main MIME type then that item in the returned list will be failobj get_content_disposition Return the lowercased value without parameters of the message s Content Disposition header if it has one or None The possible values for this method are inline attachment or None if the message follows RFC 2183 New in version 3 5 walk The walk method is an all purpose generator which can be used to iterate over all the parts and subparts of a message object tree in depth first traversal order You will typically use walk as the iterator in a for loop each iteration returns the next subpart Here s an example that prints the MIME type of every part of a multipart message structure for part in msg walk print part get_content_type multipart report text plain message delivery status text plain text plain message rfc822 text plain walk iterates over the subparts of any part where is_multipart returns True even though msg get_content_maintype multipart may return False We can see this in our example by making use of the _structure debug helper function for part in msg walk print part get_content_maintype multipart part is_multipart True True False False False True False False False False False True False False _structure msg multipart report text plain message delivery status text plain text plain message rfc822 text plain Here the message parts are not multiparts but they do contain subparts is_multipart returns True and walk descends into the subparts Message objects can also optionally contain two instance attributes which can be used when generating the plain text of a MIME message preamble The format of a MIME document allows for some text between the blank line following the headers and the first multipart boundary string Normally this text is never visible in a MIME aware mail reader because it falls outside the standard MIME armor However when viewing the raw text of the message or when viewing the message in a non MIME aware reader this text can become visible The preamble attribute contains this leading extra armor text for MIME documents When the Parser discovers some text after the headers but before the first boundary string it assigns this text to the message s preamble attribute When the Generator is writing,en
201, out the plain text representation of a MIME message and it finds the message has a preamble attribute it will write this text in the area between the headers and the first boundary See email parser and email generator for details Note that if the message object has no preamble the preamble attribute will be None epilogue The epilogue attribute acts the same way as the preamble attribute except that it contains text that appears between the last boundary and the end of the message You do not need to set the epilogue to the empty string in order for the Generator to print a newline at the end of the file defects The defects attribute contains a list of all the problems found when parsing this message See email errors for a detailed description of the possible parsing defects,en
202,Python HOWTOs Python HOWTOs are documents that cover a single specific topic and attempt to cover it fairly completely Modelled on the Linux Documentation Project s HOWTO collection this collection is an effort to foster documentation that s more detailed than the Python Library Reference Currently the HOWTOs are Porting Extension Modules to Python 3 Curses Programming with Python Descriptor Guide Debugging C API extensions and CPython Internals with GDB Enum HOWTO Functional Programming HOWTO Logging HOWTO Logging Cookbook Regular Expression HOWTO Socket Programming HOWTO Sorting Techniques Unicode HOWTO HOWTO Fetch Internet Resources Using The urllib Package Argparse Tutorial An introduction to the ipaddress module Instrumenting CPython with DTrace and SystemTap Python support for the Linux perf profiler Annotations Best Practices Isolating Extension Modules,en
203,2 Defining Extension Types Tutorial Python allows the writer of a C extension module to define new types that can be manipulated from Python code much like the built in str and list types The code for all extension types follows a pattern but there are some details that you need to understand before you can get started This document is a gentle introduction to the topic 2 1 The Basics The CPython runtime sees all Python objects as variables of type PyObject which serves as a base type for all Python objects The PyObject structure itself only contains the object s reference count and a pointer to the object s type object This is where the action is the type object determines which C functions get called by the interpreter when for instance an attribute gets looked up on an object a method called or it is multiplied by another object These C functions are called type methods So if you want to define a new extension type you need to create a new type object This sort of thing can only be explained by example so here s a minimal but complete module that defines a new type named Custom inside a C extension module custom Note What we re showing here is the traditional way of defining static extension types It should be adequate for most uses The C API also allows defining heap allocated extension types using the PyType_FromSpec function which isn t covered in this tutorial define PY_SSIZE_T_CLEAN include Python h typedef struct PyObject_HEAD Type specific fields go here CustomObject static PyTypeObject CustomType ob_base PyVarObject_HEAD_INIT NULL 0 tp_name custom Custom tp_doc PyDoc_STR Custom objects tp_basicsize sizeof CustomObject tp_itemsize 0 tp_flags Py_TPFLAGS_DEFAULT tp_new PyType_GenericNew static PyModuleDef custommodule m_base PyModuleDef_HEAD_INIT m_name custom m_doc Example module that creates an extension type m_size 1 PyMODINIT_FUNC PyInit_custom void PyObject m if PyType_Ready CustomType 0 return NULL m PyModule_Create custommodule if m NULL return NULL Py_INCREF CustomType if PyModule_AddObject m Custom PyObject CustomType 0 Py_DECREF CustomType Py_DECREF m return NULL return m Now that s quite a bit to take in at once but hopefully bits will seem familiar from the previous chapter This file defines three things 1 What a Custom object contains this is the CustomObject struct which is allocated once for each Custom instance 2 How the Custom type behaves this is the CustomType struct which defines a set of flags and function pointers that the interpreter inspects when specific operations are requested 3 How to initialize the custom module this is the PyInit_custom function and the associated custommodule struct The first bit is typedef struct PyObject_HEAD CustomObject This is what a Custom object will contain PyObject_HEAD is mandatory at the start of each object struct and defines a field called ob_base of type PyObject containing a pointer to a type object and a reference count these can be accessed using the macros Py_TYPE and Py_REFCNT respectively The reason for the macro is to abstract away the layout and to enable additional fields in debug builds Note There is no semicolon above after the PyObject_HEAD macro Be wary of adding one by accident some compilers will complain Of course objects generally store additional data besides the standard PyObject_HEAD boilerplate for example here is the definition for standard Python floats typedef struct PyObject_HEAD double ob_fval PyFloatObject The second bit is the definition of the type object static PyTypeObject CustomType ob_base PyVarObject_HEAD_INIT NULL 0 tp_name custom Custom tp_doc PyDoc_STR Custom objects tp_basicsize sizeof CustomObject tp_itemsize 0 tp_flags Py_TPFLAGS_DEFAULT tp_new PyType_GenericNew Note We recommend using C99 style designated initializers as above to avoid listing all the PyTypeObject fields that you don t care about and also to avoid caring about the fields declaration order The actual definition of PyTypeObject in object h has many more fields than the definition above The remaining fields will be filled with zeros by the C compil,en
204,er and it s common practice to not specify them explicitly unless you need them We re going to pick it apart one field at a time ob_base PyVarObject_HEAD_INIT NULL 0 This line is mandatory boilerplate to initialize the ob_base field mentioned above tp_name custom Custom The name of our type This will appear in the default textual representation of our objects and in some error messages for example custom Custom Traceback most recent call last File stdin line 1 in module TypeError can only concatenate str not custom Custom to str Note that the name is a dotted name that includes both the module name and the name of the type within the module The module in this case is custom and the type is Custom so we set the type name to custom Custom Using the real dotted import path is important to make your type compatible with the pydoc and pickle modules tp_basicsize sizeof CustomObject tp_itemsize 0 This is so that Python knows how much memory to allocate when creating new Custom instances tp_itemsize is only used for variable sized objects and should otherwise be zero Note If you want your type to be subclassable from Python and your type has the same tp_basicsize as its base type you may have problems with multiple inheritance A Python subclass of your type will have to list your type first in its __bases__ or else it will not be able to call your type s __new__ method without getting an error You can avoid this problem by ensuring that your type has a larger value for tp_basicsize than its base type does Most of the time this will be true anyway because either your base type will be object or else you will be adding data members to your base type and therefore increasing its size We set the class flags to Py_TPFLAGS_DEFAULT tp_flags Py_TPFLAGS_DEFAULT All types should include this constant in their flags It enables all of the members defined until at least Python 3 3 If you need further members you will need to OR the corresponding flags We provide a doc string for the type in tp_doc tp_doc PyDoc_STR Custom objects To enable object creation we have to provide a tp_new handler This is the equivalent of the Python method __new__ but has to be specified explicitly In this case we can just use the default implementation provided by the API function PyType_GenericNew tp_new PyType_GenericNew Everything else in the file should be familiar except for some code in PyInit_custom if PyType_Ready CustomType 0 return This initializes the Custom type filling in a number of members to the appropriate default values including ob_type that we initially set to NULL Py_INCREF CustomType if PyModule_AddObject m Custom PyObject CustomType 0 Py_DECREF CustomType Py_DECREF m return NULL This adds the type to the module dictionary This allows us to create Custom instances by calling the Custom class import custom mycustom custom Custom That s it All that remains is to build it put the above code in a file called custom c build system requires setuptools build backend setuptools build_meta project name custom version 1 in a file called pyproject toml and from setuptools import Extension setup setup ext_modules Extension custom custom c in a file called setup py then typing python m pip install in a shell should produce a file custom so in a subdirectory and install it now fire up Python you should be able to import custom and play around with Custom objects That wasn t so hard was it Of course the current Custom type is pretty uninteresting It has no data and doesn t do anything It can t even be subclassed 2 2 Adding data and methods to the Basic example Let s extend the basic example to add some data and methods Let s also make the type usable as a base class We ll create a new module custom2 that adds these capabilities define PY_SSIZE_T_CLEAN include Python h include stddef h for offsetof typedef struct PyObject_HEAD PyObject first first name PyObject last last name int number CustomObject static void Custom_dealloc CustomObject self Py_XDECREF self first Py_XDECREF self last Py_TYPE self tp_free PyObject self static PyObject Custom_new PyTypeObje,en
205,ct type PyObject args PyObject kwds CustomObject self self CustomObject type tp_alloc type 0 if self NULL self first PyUnicode_FromString if self first NULL Py_DECREF self return NULL self last PyUnicode_FromString if self last NULL Py_DECREF self return NULL self number 0 return PyObject self static int Custom_init CustomObject self PyObject args PyObject kwds static char kwlist first last number NULL PyObject first NULL last NULL if PyArg_ParseTupleAndKeywords args kwds OOi kwlist first last self number return 1 if first Py_XSETREF self first Py_NewRef first if last Py_XSETREF self last Py_NewRef last return 0 static PyMemberDef Custom_members first Py_T_OBJECT_EX offsetof CustomObject first 0 first name last Py_T_OBJECT_EX offsetof CustomObject last 0 last name number Py_T_INT offsetof CustomObject number 0 custom number NULL Sentinel static PyObject Custom_name CustomObject self PyObject Py_UNUSED ignored if self first NULL PyErr_SetString PyExc_AttributeError first return NULL if self last NULL PyErr_SetString PyExc_AttributeError last return NULL return PyUnicode_FromFormat S S self first self last static PyMethodDef Custom_methods name PyCFunction Custom_name METH_NOARGS Return the name combining the first and last name NULL Sentinel static PyTypeObject CustomType ob_base PyVarObject_HEAD_INIT NULL 0 tp_name custom2 Custom tp_doc PyDoc_STR Custom objects tp_basicsize sizeof CustomObject tp_itemsize 0 tp_flags Py_TPFLAGS_DEFAULT Py_TPFLAGS_BASETYPE tp_new Custom_new tp_init initproc Custom_init tp_dealloc destructor Custom_dealloc tp_members Custom_members tp_methods Custom_methods static PyModuleDef custommodule m_base PyModuleDef_HEAD_INIT m_name custom2 m_doc Example module that creates an extension type m_size 1 PyMODINIT_FUNC PyInit_custom2 void PyObject m if PyType_Ready CustomType 0 return NULL m PyModule_Create custommodule if m NULL return NULL if PyModule_AddObjectRef m Custom PyObject CustomType 0 Py_DECREF m return NULL return m This version of the module has a number of changes The Custom type now has three data attributes in its C struct first last and number The first and last variables are Python strings containing first and last names The number attribute is a C integer The object structure is updated accordingly typedef struct PyObject_HEAD PyObject first first name PyObject last last name int number CustomObject Because we now have data to manage we have to be more careful about object allocation and deallocation At a minimum we need a deallocation method static void Custom_dealloc CustomObject self Py_XDECREF self first Py_XDECREF self last Py_TYPE self tp_free PyObject self which is assigned to the tp_dealloc member tp_dealloc destructor Custom_dealloc This method first clears the reference counts of the two Python attributes Py_XDECREF correctly handles the case where its argument is NULL which might happen here if tp_new failed midway It then calls the tp_free member of the object s type computed by Py_TYPE self to free the object s memory Note that the object s type might not be CustomType because the object may be an instance of a subclass Note The explicit cast to destructor above is needed because we defined Custom_dealloc to take a CustomObject argument but the tp_dealloc function pointer expects to receive a PyObject argument Otherwise the compiler will emit a warning This is object oriented polymorphism in C We want to make sure that the first and last names are initialized to empty strings so we provide a tp_new implementation static PyObject Custom_new PyTypeObject type PyObject args PyObject kwds CustomObject self self CustomObject type tp_alloc type 0 if self NULL self first PyUnicode_FromString if self first NULL Py_DECREF self return NULL self last PyUnicode_FromString if self last NULL Py_DECREF self return NULL self number 0 return PyObject self and install it in the tp_new member tp_new Custom_new The tp_new handler is responsible for creating as opposed to initializing objects of the type It is exposed in Python as the __new__ method It is not required to define a tp_new memb,en
206,er and indeed many extension types will simply reuse PyType_GenericNew as done in the first version of the Custom type above In this case we use the tp_new handler to initialize the first and last attributes to non NULL default values tp_new is passed the type being instantiated not necessarily CustomType if a subclass is instantiated and any arguments passed when the type was called and is expected to return the instance created tp_new handlers always accept positional and keyword arguments but they often ignore the arguments leaving the argument handling to initializer a k a tp_init in C or __init__ in Python methods Note tp_new shouldn t call tp_init explicitly as the interpreter will do it itself The tp_new implementation calls the tp_alloc slot to allocate memory self CustomObject type tp_alloc type 0 Since memory allocation may fail we must check the tp_alloc result against NULL before proceeding Note We didn t fill the tp_alloc slot ourselves Rather PyType_Ready fills it for us by inheriting it from our base class which is object by default Most types use the default allocation strategy Note If you are creating a co operative tp_new one that calls a base type s tp_new or __new__ you must not try to determine what method to call using method resolution order at runtime Always statically determine what type you are going to call and call its tp_new directly or via type tp_base tp_new If you do not do this Python subclasses of your type that also inherit from other Python defined classes may not work correctly Specifically you may not be able to create instances of such subclasses without getting a TypeError We also define an initialization function which accepts arguments to provide initial values for our instance static int Custom_init CustomObject self PyObject args PyObject kwds static char kwlist first last number NULL PyObject first NULL last NULL tmp if PyArg_ParseTupleAndKeywords args kwds OOi kwlist first last self number return 1 if first tmp self first Py_INCREF first self first first Py_XDECREF tmp if last tmp self last Py_INCREF last self last last Py_XDECREF tmp return 0 by filling the tp_init slot tp_init initproc Custom_init The tp_init slot is exposed in Python as the __init__ method It is used to initialize an object after it s created Initializers always accept positional and keyword arguments and they should return either 0 on success or 1 on error Unlike the tp_new handler there is no guarantee that tp_init is called at all for example the pickle module by default doesn t call __init__ on unpickled instances It can also be called multiple times Anyone can call the __init__ method on our objects For this reason we have to be extra careful when assigning the new attribute values We might be tempted for example to assign the first member like this if first Py_XDECREF self first Py_INCREF first self first first But this would be risky Our type doesn t restrict the type of the first member so it could be any kind of object It could have a destructor that causes code to be executed that tries to access the first member or that destructor could release the Global interpreter Lock and let arbitrary code run in other threads that accesses and modifies our object To be paranoid and protect ourselves against this possibility we almost always reassign members before decrementing their reference counts When don t we have to do this when we absolutely know that the reference count is greater than 1 when we know that deallocation of the object 1 will neither release the GIL nor cause any calls back into our type s code when decrementing a reference count in a tp_dealloc handler on a type which doesn t support cyclic garbage collection 2 We want to expose our instance variables as attributes There are a number of ways to do that The simplest way is to define member definitions static PyMemberDef Custom_members first Py_T_OBJECT_EX offsetof CustomObject first 0 first name last Py_T_OBJECT_EX offsetof CustomObject last 0 last name number Py_T_INT offsetof CustomObject number 0 custom number NULL Sentinel and put t,en
207,he definitions in the tp_members slot tp_members Custom_members Each member definition has a member name type offset access flags and documentation string See the Generic Attribute Management section below for details A disadvantage of this approach is that it doesn t provide a way to restrict the types of objects that can be assigned to the Python attributes We expect the first and last names to be strings but any Python objects can be assigned Further the attributes can be deleted setting the C pointers to NULL Even though we can make sure the members are initialized to non NULL values the members can be set to NULL if the attributes are deleted We define a single method Custom name that outputs the objects name as the concatenation of the first and last names static PyObject Custom_name CustomObject self PyObject Py_UNUSED ignored if self first NULL PyErr_SetString PyExc_AttributeError first return NULL if self last NULL PyErr_SetString PyExc_AttributeError last return NULL return PyUnicode_FromFormat S S self first self last The method is implemented as a C function that takes a Custom or Custom subclass instance as the first argument Methods always take an instance as the first argument Methods often take positional and keyword arguments as well but in this case we don t take any and don t need to accept a positional argument tuple or keyword argument dictionary This method is equivalent to the Python method def name self return s s self first self last Note that we have to check for the possibility that our first and last members are NULL This is because they can be deleted in which case they are set to NULL It would be better to prevent deletion of these attributes and to restrict the attribute values to be strings We ll see how to do that in the next section Now that we ve defined the method we need to create an array of method definitions static PyMethodDef Custom_methods name PyCFunction Custom_name METH_NOARGS Return the name combining the first and last name NULL Sentinel note that we used the METH_NOARGS flag to indicate that the method is expecting no arguments other than self and assign it to the tp_methods slot tp_methods Custom_methods Finally we ll make our type usable as a base class for subclassing We ve written our methods carefully so far so that they don t make any assumptions about the type of the object being created or used so all we need to do is to add the Py_TPFLAGS_BASETYPE to our class flag definition tp_flags Py_TPFLAGS_DEFAULT Py_TPFLAGS_BASETYPE We rename PyInit_custom to PyInit_custom2 update the module name in the PyModuleDef struct and update the full class name in the PyTypeObject struct Finally we update our setup py file to include the new module from setuptools import Extension setup setup ext_modules Extension custom custom c Extension custom2 custom2 c and then we re install so that we can import custom2 python m pip install 2 3 Providing finer control over data attributes In this section we ll provide finer control over how the first and last attributes are set in the Custom example In the previous version of our module the instance variables first and last could be set to non string values or even deleted We want to make sure that these attributes always contain strings define PY_SSIZE_T_CLEAN include Python h include stddef h for offsetof typedef struct PyObject_HEAD PyObject first first name PyObject last last name int number CustomObject static void Custom_dealloc CustomObject self Py_XDECREF self first Py_XDECREF self last Py_TYPE self tp_free PyObject self static PyObject Custom_new PyTypeObject type PyObject args PyObject kwds CustomObject self self CustomObject type tp_alloc type 0 if self NULL self first PyUnicode_FromString if self first NULL Py_DECREF self return NULL self last PyUnicode_FromString if self last NULL Py_DECREF self return NULL self number 0 return PyObject self static int Custom_init CustomObject self PyObject args PyObject kwds static char kwlist first last number NULL PyObject first NULL last NULL if PyArg_ParseTupleAndKeywords args kwds UUi kwlist ,en
208,first last self number return 1 if first Py_SETREF self first Py_NewRef first if last Py_SETREF self last Py_NewRef last return 0 static PyMemberDef Custom_members number Py_T_INT offsetof CustomObject number 0 custom number NULL Sentinel static PyObject Custom_getfirst CustomObject self void closure return Py_NewRef self first static int Custom_setfirst CustomObject self PyObject value void closure if value NULL PyErr_SetString PyExc_TypeError Cannot delete the first attribute return 1 if PyUnicode_Check value PyErr_SetString PyExc_TypeError The first attribute value must be a string return 1 Py_SETREF self first Py_NewRef value return 0 static PyObject Custom_getlast CustomObject self void closure return Py_NewRef self last static int Custom_setlast CustomObject self PyObject value void closure if value NULL PyErr_SetString PyExc_TypeError Cannot delete the last attribute return 1 if PyUnicode_Check value PyErr_SetString PyExc_TypeError The last attribute value must be a string return 1 Py_SETREF self last Py_NewRef value return 0 static PyGetSetDef Custom_getsetters first getter Custom_getfirst setter Custom_setfirst first name NULL last getter Custom_getlast setter Custom_setlast last name NULL NULL Sentinel static PyObject Custom_name CustomObject self PyObject Py_UNUSED ignored return PyUnicode_FromFormat S S self first self last static PyMethodDef Custom_methods name PyCFunction Custom_name METH_NOARGS Return the name combining the first and last name NULL Sentinel static PyTypeObject CustomType ob_base PyVarObject_HEAD_INIT NULL 0 tp_name custom3 Custom tp_doc PyDoc_STR Custom objects tp_basicsize sizeof CustomObject tp_itemsize 0 tp_flags Py_TPFLAGS_DEFAULT Py_TPFLAGS_BASETYPE tp_new Custom_new tp_init initproc Custom_init tp_dealloc destructor Custom_dealloc tp_members Custom_members tp_methods Custom_methods tp_getset Custom_getsetters static PyModuleDef custommodule m_base PyModuleDef_HEAD_INIT m_name custom3 m_doc Example module that creates an extension type m_size 1 PyMODINIT_FUNC PyInit_custom3 void PyObject m if PyType_Ready CustomType 0 return NULL m PyModule_Create custommodule if m NULL return NULL if PyModule_AddObjectRef m Custom PyObject CustomType 0 Py_DECREF m return NULL return m To provide greater control over the first and last attributes we ll use custom getter and setter functions Here are the functions for getting and setting the first attribute static PyObject Custom_getfirst CustomObject self void closure Py_INCREF self first return self first static int Custom_setfirst CustomObject self PyObject value void closure PyObject tmp if value NULL PyErr_SetString PyExc_TypeError Cannot delete the first attribute return 1 if PyUnicode_Check value PyErr_SetString PyExc_TypeError The first attribute value must be a string return 1 tmp self first Py_INCREF value self first value Py_DECREF tmp return 0 The getter function is passed a Custom object and a closure which is a void pointer In this case the closure is ignored The closure supports an advanced usage in which definition data is passed to the getter and setter This could for example be used to allow a single set of getter and setter functions that decide the attribute to get or set based on data in the closure The setter function is passed the Custom object the new value and the closure The new value may be NULL in which case the attribute is being deleted In our setter we raise an error if the attribute is deleted or if its new value is not a string We create an array of PyGetSetDef structures static PyGetSetDef Custom_getsetters first getter Custom_getfirst setter Custom_setfirst first name NULL last getter Custom_getlast setter Custom_setlast last name NULL NULL Sentinel and register it in the tp_getset slot tp_getset Custom_getsetters The last item in a PyGetSetDef structure is the closure mentioned above In this case we aren t using a closure so we just pass NULL We also remove the member definitions for these attributes static PyMemberDef Custom_members number Py_T_INT offsetof CustomObject number 0 custom number NULL Sentinel We also n,en
209,eed to update the tp_init handler to only allow strings 3 to be passed static int Custom_init CustomObject self PyObject args PyObject kwds static char kwlist first last number NULL PyObject first NULL last NULL tmp if PyArg_ParseTupleAndKeywords args kwds UUi kwlist first last self number return 1 if first tmp self first Py_INCREF first self first first Py_DECREF tmp if last tmp self last Py_INCREF last self last last Py_DECREF tmp return 0 With these changes we can assure that the first and last members are never NULL so we can remove checks for NULL values in almost all cases This means that most of the Py_XDECREF calls can be converted to Py_DECREF calls The only place we can t change these calls is in the tp_dealloc implementation where there is the possibility that the initialization of these members failed in tp_new We also rename the module initialization function and module name in the initialization function as we did before and we add an extra definition to the setup py file 2 4 Supporting cyclic garbage collection Python has a cyclic garbage collector GC that can identify unneeded objects even when their reference counts are not zero This can happen when objects are involved in cycles For example consider l l append l del l In this example we create a list that contains itself When we delete it it still has a reference from itself Its reference count doesn t drop to zero Fortunately Python s cyclic garbage collector will eventually figure out that the list is garbage and free it In the second version of the Custom example we allowed any kind of object to be stored in the first or last attributes 4 Besides in the second and third versions we allowed subclassing Custom and subclasses may add arbitrary attributes For any of those two reasons Custom objects can participate in cycles import custom3 class Derived custom3 Custom pass n Derived n some_attribute n To allow a Custom instance participating in a reference cycle to be properly detected and collected by the cyclic GC our Custom type needs to fill two additional slots and to enable a flag that enables these slots define PY_SSIZE_T_CLEAN include Python h include stddef h for offsetof typedef struct PyObject_HEAD PyObject first first name PyObject last last name int number CustomObject static int Custom_traverse CustomObject self visitproc visit void arg Py_VISIT self first Py_VISIT self last return 0 static int Custom_clear CustomObject self Py_CLEAR self first Py_CLEAR self last return 0 static void Custom_dealloc CustomObject self PyObject_GC_UnTrack self Custom_clear self Py_TYPE self tp_free PyObject self static PyObject Custom_new PyTypeObject type PyObject args PyObject kwds CustomObject self self CustomObject type tp_alloc type 0 if self NULL self first PyUnicode_FromString if self first NULL Py_DECREF self return NULL self last PyUnicode_FromString if self last NULL Py_DECREF self return NULL self number 0 return PyObject self static int Custom_init CustomObject self PyObject args PyObject kwds static char kwlist first last number NULL PyObject first NULL last NULL if PyArg_ParseTupleAndKeywords args kwds UUi kwlist first last self number return 1 if first Py_SETREF self first Py_NewRef first if last Py_SETREF self last Py_NewRef last return 0 static PyMemberDef Custom_members number Py_T_INT offsetof CustomObject number 0 custom number NULL Sentinel static PyObject Custom_getfirst CustomObject self void closure return Py_NewRef self first static int Custom_setfirst CustomObject self PyObject value void closure if value NULL PyErr_SetString PyExc_TypeError Cannot delete the first attribute return 1 if PyUnicode_Check value PyErr_SetString PyExc_TypeError The first attribute value must be a string return 1 Py_XSETREF self first Py_NewRef value return 0 static PyObject Custom_getlast CustomObject self void closure return Py_NewRef self last static int Custom_setlast CustomObject self PyObject value void closure if value NULL PyErr_SetString PyExc_TypeError Cannot delete the last attribute return 1 if PyUnicode_Check value PyErr_SetString PyExc_TypeErro,en
210,r The last attribute value must be a string return 1 Py_XSETREF self last Py_NewRef value return 0 static PyGetSetDef Custom_getsetters first getter Custom_getfirst setter Custom_setfirst first name NULL last getter Custom_getlast setter Custom_setlast last name NULL NULL Sentinel static PyObject Custom_name CustomObject self PyObject Py_UNUSED ignored return PyUnicode_FromFormat S S self first self last static PyMethodDef Custom_methods name PyCFunction Custom_name METH_NOARGS Return the name combining the first and last name NULL Sentinel static PyTypeObject CustomType ob_base PyVarObject_HEAD_INIT NULL 0 tp_name custom4 Custom tp_doc PyDoc_STR Custom objects tp_basicsize sizeof CustomObject tp_itemsize 0 tp_flags Py_TPFLAGS_DEFAULT Py_TPFLAGS_BASETYPE Py_TPFLAGS_HAVE_GC tp_new Custom_new tp_init initproc Custom_init tp_dealloc destructor Custom_dealloc tp_traverse traverseproc Custom_traverse tp_clear inquiry Custom_clear tp_members Custom_members tp_methods Custom_methods tp_getset Custom_getsetters static PyModuleDef custommodule m_base PyModuleDef_HEAD_INIT m_name custom4 m_doc Example module that creates an extension type m_size 1 PyMODINIT_FUNC PyInit_custom4 void PyObject m if PyType_Ready CustomType 0 return NULL m PyModule_Create custommodule if m NULL return NULL if PyModule_AddObjectRef m Custom PyObject CustomType 0 Py_DECREF m return NULL return m First the traversal method lets the cyclic GC know about subobjects that could participate in cycles static int Custom_traverse CustomObject self visitproc visit void arg int vret if self first vret visit self first arg if vret 0 return vret if self last vret visit self last arg if vret 0 return vret return 0 For each subobject that can participate in cycles we need to call the visit function which is passed to the traversal method The visit function takes as arguments the subobject and the extra argument arg passed to the traversal method It returns an integer value that must be returned if it is non zero Python provides a Py_VISIT macro that automates calling visit functions With Py_VISIT we can minimize the amount of boilerplate in Custom_traverse static int Custom_traverse CustomObject self visitproc visit void arg Py_VISIT self first Py_VISIT self last return 0 Note The tp_traverse implementation must name its arguments exactly visit and arg in order to use Py_VISIT Second we need to provide a method for clearing any subobjects that can participate in cycles static int Custom_clear CustomObject self Py_CLEAR self first Py_CLEAR self last return 0 Notice the use of the Py_CLEAR macro It is the recommended and safe way to clear data attributes of arbitrary types while decrementing their reference counts If you were to call Py_XDECREF instead on the attribute before setting it to NULL there is a possibility that the attribute s destructor would call back into code that reads the attribute again especially if there is a reference cycle Note You could emulate Py_CLEAR by writing PyObject tmp tmp self first self first NULL Py_XDECREF tmp Nevertheless it is much easier and less error prone to always use Py_CLEAR when deleting an attribute Don t try to micro optimize at the expense of robustness The deallocator Custom_dealloc may call arbitrary code when clearing attributes It means the circular GC can be triggered inside the function Since the GC assumes reference count is not zero we need to untrack the object from the GC by calling PyObject_GC_UnTrack before clearing members Here is our reimplemented deallocator using PyObject_GC_UnTrack and Custom_clear static void Custom_dealloc CustomObject self PyObject_GC_UnTrack self Custom_clear self Py_TYPE self tp_free PyObject self Finally we add the Py_TPFLAGS_HAVE_GC flag to the class flags tp_flags Py_TPFLAGS_DEFAULT Py_TPFLAGS_BASETYPE Py_TPFLAGS_HAVE_GC That s pretty much it If we had written custom tp_alloc or tp_free handlers we d need to modify them for cyclic garbage collection Most extensions will use the versions automatically provided 2 5 Subclassing other types It is possible to create new extension types t,en
211,hat are derived from existing types It is easiest to inherit from the built in types since an extension can easily use the PyTypeObject it needs It can be difficult to share these PyTypeObject structures between extension modules In this example we will create a SubList type that inherits from the built in list type The new type will be completely compatible with regular lists but will have an additional increment method that increases an internal counter import sublist s sublist SubList range 3 s extend s print len s 6 print s increment 1 print s increment 2 define PY_SSIZE_T_CLEAN include Python h typedef struct PyListObject list int state SubListObject static PyObject SubList_increment SubListObject self PyObject unused self state return PyLong_FromLong self state static PyMethodDef SubList_methods increment PyCFunction SubList_increment METH_NOARGS PyDoc_STR increment state counter NULL static int SubList_init SubListObject self PyObject args PyObject kwds if PyList_Type tp_init PyObject self args kwds 0 return 1 self state 0 return 0 static PyTypeObject SubListType PyVarObject_HEAD_INIT NULL 0 tp_name sublist SubList tp_doc PyDoc_STR SubList objects tp_basicsize sizeof SubListObject tp_itemsize 0 tp_flags Py_TPFLAGS_DEFAULT Py_TPFLAGS_BASETYPE tp_init initproc SubList_init tp_methods SubList_methods static PyModuleDef sublistmodule PyModuleDef_HEAD_INIT m_name sublist m_doc Example module that creates an extension type m_size 1 PyMODINIT_FUNC PyInit_sublist void PyObject m SubListType tp_base PyList_Type if PyType_Ready SubListType 0 return NULL m PyModule_Create sublistmodule if m NULL return NULL Py_INCREF SubListType if PyModule_AddObject m SubList PyObject SubListType 0 Py_DECREF SubListType Py_DECREF m return NULL return m As you can see the source code closely resembles the Custom examples in previous sections We will break down the main differences between them typedef struct PyListObject list int state SubListObject The primary difference for derived type objects is that the base type s object structure must be the first value The base type will already include the PyObject_HEAD at the beginning of its structure When a Python object is a SubList instance its PyObject pointer can be safely cast to both PyListObject and SubListObject static int SubList_init SubListObject self PyObject args PyObject kwds if PyList_Type tp_init PyObject self args kwds 0 return 1 self state 0 return 0 We see above how to call through to the __init__ method of the base type This pattern is important when writing a type with custom tp_new and tp_dealloc members The tp_new handler should not actually create the memory for the object with its tp_alloc but let the base class handle it by calling its own tp_new The PyTypeObject struct supports a tp_base specifying the type s concrete base class Due to cross platform compiler issues you can t fill that field directly with a reference to PyList_Type it should be done later in the module initialization function PyMODINIT_FUNC PyInit_sublist void PyObject m SubListType tp_base PyList_Type if PyType_Ready SubListType 0 return NULL m PyModule_Create sublistmodule if m NULL return NULL Py_INCREF SubListType if PyModule_AddObject m SubList PyObject SubListType 0 Py_DECREF SubListType Py_DECREF m return NULL return m Before calling PyType_Ready the type structure must have the tp_base slot filled in When we are deriving an existing type it is not necessary to fill out the tp_alloc slot with PyType_GenericNew the allocation function from the base type will be inherited After that calling PyType_Ready and adding the type object to the module is the same as with the basic Custom examples Footnotes 1 This is true when we know that the object is a basic type like a string or a float 2 We relied on this in the tp_dealloc handler in this example because our type doesn t support garbage collection 3 We now know that the first and last members are strings so perhaps we could be less careful about decrementing their reference counts however we accept instances of string subclasses Even though deallocatin,en
212,g normal strings won t call back into our objects we can t guarantee that deallocating an instance of a string subclass won t call back into our objects 4 Also even with our attributes restricted to strings instances the user could pass arbitrary str subclasses and therefore still create reference cycles,en
213,platform Access to underlying platform s identifying data Source code Lib platform py Note Specific platforms listed alphabetically with Linux included in the Unix section Cross Platform platform architecture executable sys executable bits linkage Queries the given executable defaults to the Python interpreter binary for various architecture information Returns a tuple bits linkage which contain information about the bit architecture and the linkage format used for the executable Both values are returned as strings Values that cannot be determined are returned as given by the parameter presets If bits is given as the sizeof pointer or sizeof long on Python version 1 5 2 is used as indicator for the supported pointer size The function relies on the system s file command to do the actual work This is available on most if not all Unix platforms and some non Unix platforms and then only if the executable points to the Python interpreter Reasonable defaults are used when the above needs are not met Note On macOS and perhaps other platforms executable files may be universal files containing multiple architectures To get at the 64 bitness of the current interpreter it is more reliable to query the sys maxsize attribute is_64bits sys maxsize 2 32 platform machine Returns the machine type e g AMD64 An empty string is returned if the value cannot be determined platform node Returns the computer s network name may not be fully qualified An empty string is returned if the value cannot be determined platform platform aliased False terse False Returns a single string identifying the underlying platform with as much useful information as possible The output is intended to be human readable rather than machine parseable It may look different on different platforms and this is intended If aliased is true the function will use aliases for various platforms that report system names which differ from their common names for example SunOS will be reported as Solaris The system_alias function is used to implement this Setting terse to true causes the function to return only the absolute minimum information needed to identify the platform Changed in version 3 8 On macOS the function now uses mac_ver if it returns a non empty release string to get the macOS version rather than the darwin version platform processor Returns the real processor name e g amdk6 An empty string is returned if the value cannot be determined Note that many platforms do not provide this information or simply return the same value as for machine NetBSD does this platform python_build Returns a tuple buildno builddate stating the Python build number and date as strings platform python_compiler Returns a string identifying the compiler used for compiling Python platform python_branch Returns a string identifying the Python implementation SCM branch platform python_implementation Returns a string identifying the Python implementation Possible return values are CPython IronPython Jython PyPy platform python_revision Returns a string identifying the Python implementation SCM revision platform python_version Returns the Python version as string major minor patchlevel Note that unlike the Python sys version the returned value will always include the patchlevel it defaults to 0 platform python_version_tuple Returns the Python version as tuple major minor patchlevel of strings Note that unlike the Python sys version the returned value will always include the patchlevel it defaults to 0 platform release Returns the system s release e g 2 2 0 or NT An empty string is returned if the value cannot be determined platform system Returns the system OS name such as Linux Darwin Java Windows An empty string is returned if the value cannot be determined platform system_alias system release version Returns system release version aliased to common marketing names used for some systems It also does some reordering of the information in some cases where it would otherwise cause confusion platform version Returns the system s release version e g 3 on degas An empty string is returned if the value,en
214, cannot be determined platform uname Fairly portable uname interface Returns a namedtuple containing six attributes system node release version machine and processor processor is resolved late on demand Note the first two attribute names differ from the names presented by os uname where they are named sysname and nodename Entries which cannot be determined are set to Changed in version 3 3 Result changed from a tuple to a namedtuple Changed in version 3 9 processor is resolved late instead of immediately Java Platform platform java_ver release vendor vminfo osinfo Version interface for Jython Returns a tuple release vendor vminfo osinfo with vminfo being a tuple vm_name vm_release vm_vendor and osinfo being a tuple os_name os_version os_arch Values which cannot be determined are set to the defaults given as parameters which all default to Windows Platform platform win32_ver release version csd ptype Get additional version information from the Windows Registry and return a tuple release version csd ptype referring to OS release version number CSD level service pack and OS type multi single processor Values which cannot be determined are set to the defaults given as parameters which all default to an empty string As a hint ptype is Uniprocessor Free on single processor NT machines and Multiprocessor Free on multi processor machines The Free refers to the OS version being free of debugging code It could also state Checked which means the OS version uses debugging code i e code that checks arguments ranges etc platform win32_edition Returns a string representing the current Windows edition or None if the value cannot be determined Possible values include but are not limited to Enterprise IoTUAP ServerStandard and nanoserver New in version 3 8 platform win32_is_iot Return True if the Windows edition returned by win32_edition is recognized as an IoT edition New in version 3 8 macOS Platform platform mac_ver release versioninfo machine Get macOS version information and return it as tuple release versioninfo machine with versioninfo being a tuple version dev_stage non_release_version Entries which cannot be determined are set to All tuple entries are strings Unix Platforms platform libc_ver executable sys executable lib version chunksize 16384 Tries to determine the libc version against which the file executable defaults to the Python interpreter is linked Returns a tuple of strings lib version which default to the given parameters in case the lookup fails Note that this function has intimate knowledge of how different libc versions add symbols to the executable is probably only usable for executables compiled using gcc The file is read and scanned in chunks of chunksize bytes Linux Platforms platform freedesktop_os_release Get operating system identification from os release file and return it as a dict The os release file is a freedesktop org standard and is available in most Linux distributions A noticeable exception is Android and Android based distributions Raises OSError or subclass when neither etc os release nor usr lib os release can be read On success the function returns a dictionary where keys and values are strings Values have their special characters like and unquoted The fields NAME ID and PRETTY_NAME are always defined according to the standard All other fields are optional Vendors may include additional fields Note that fields like NAME VERSION and VARIANT are strings suitable for presentation to users Programs should use fields like ID ID_LIKE VERSION_ID or VARIANT_ID to identify Linux distributions Example def get_like_distro info platform freedesktop_os_release ids info ID if ID_LIKE in info ids are space separated and ordered by precedence ids extend info ID_LIKE split return ids New in version 3 10,en
215,tkinter ttk Tk themed widgets Source code Lib tkinter ttk py The tkinter ttk module provides access to the Tk themed widget set introduced in Tk 8 5 It provides additional benefits including anti aliased font rendering under X11 and window transparency requiring a composition window manager on X11 The basic idea for tkinter ttk is to separate to the extent possible the code implementing a widget s behavior from the code implementing its appearance See also Tk Widget Styling Support A document introducing theming support for Tk Using Ttk To start using Ttk import its module from tkinter import ttk To override the basic Tk widgets the import should follow the Tk import from tkinter import from tkinter ttk import That code causes several tkinter ttk widgets Button Checkbutton Entry Frame Label LabelFrame Menubutton PanedWindow Radiobutton Scale and Scrollbar to automatically replace the Tk widgets This has the direct benefit of using the new widgets which gives a better look and feel across platforms however the replacement widgets are not completely compatible The main difference is that widget options such as fg bg and others related to widget styling are no longer present in Ttk widgets Instead use the ttk Style class for improved styling effects See also Converting existing applications to use Tile widgets A monograph using Tcl terminology about differences typically encountered when moving applications to use the new widgets Ttk Widgets Ttk comes with 18 widgets twelve of which already existed in tkinter Button Checkbutton Entry Frame Label LabelFrame Menubutton PanedWindow Radiobutton Scale Scrollbar and Spinbox The other six are new Combobox Notebook Progressbar Separator Sizegrip and Treeview And all them are subclasses of Widget Using the Ttk widgets gives the application an improved look and feel As discussed above there are differences in how the styling is coded Tk code l1 tkinter Label text Test fg black bg white l2 tkinter Label text Test fg black bg white Ttk code style ttk Style style configure BW TLabel foreground black background white l1 ttk Label text Test style BW TLabel l2 ttk Label text Test style BW TLabel For more information about TtkStyling see the Style class documentation Widget ttk Widget defines standard options and methods supported by Tk themed widgets and is not supposed to be directly instantiated Standard Options All the ttk Widgets accept the following options Option Description class Specifies the window class The class is used when querying the option database for the window s other options to determine the default bindtags for the window and to select the widget s default layout and style This option is read only and may only be specified when the window is created cursor Specifies the mouse cursor to be used for the widget If set to the empty string the default the cursor is inherited for the parent widget takefocus Determines whether the window accepts the focus during keyboard traversal 0 1 or an empty string is returned If 0 is returned it means that the window should be skipped entirely during keyboard traversal If 1 it means that the window should receive the input focus as long as it is viewable And an empty string means that the traversal scripts make the decision about whether or not to focus on the window style May be used to specify a custom widget style Scrollable Widget Options The following options are supported by widgets that are controlled by a scrollbar Option Description xscrollcommand Used to communicate with horizontal scrollbars When the view in the widget s window change the widget will generate a Tcl command based on the scrollcommand Usually this option consists of the method Scrollbar set of some scrollbar This will cause the scrollbar to be updated whenever the view in the window changes yscrollcommand Used to communicate with vertical scrollbars For some more information see above Label Options The following options are supported by labels buttons and other button like widgets Option Description text Specifies a text string to be displayed inside the widget,en
216, textvariable Specifies a name whose value will be used in place of the text option resource underline If set specifies the index 0 based of a character to underline in the text string The underline character is used for mnemonic activation image Specifies an image to display This is a list of 1 or more elements The first element is the default image name The rest of the list if a sequence of statespec value pairs as defined by Style map specifying different images to use when the widget is in a particular state or a combination of states All images in the list should have the same size compound Specifies how to display the image relative to the text in the case both text and images options are present Valid values are text display text only image display image only top bottom left right display image above below left of or right of the text respectively none the default display the image if present otherwise the text width If greater than zero specifies how much space in character widths to allocate for the text label if less than zero specifies a minimum width If zero or unspecified the natural width of the text label is used Compatibility Options Option Description state May be set to normal or disabled to control the disabled state bit This is a write only option setting it changes the widget state but the Widget state method does not affect this option Widget States The widget state is a bitmap of independent state flags Flag Description active The mouse cursor is over the widget and pressing a mouse button will cause some action to occur disabled Widget is disabled under program control focus Widget has keyboard focus pressed Widget is being pressed selected On true or current for things like Checkbuttons and radiobuttons background Windows and Mac have a notion of an active or foreground window The background state is set for widgets in a background window and cleared for those in the foreground window readonly Widget should not allow user modification alternate A widget specific alternate display format invalid The widget s value is invalid A state specification is a sequence of state names optionally prefixed with an exclamation point indicating that the bit is off ttk Widget Besides the methods described below the ttk Widget supports the methods tkinter Widget cget and tkinter Widget configure class tkinter ttk Widget identify x y Returns the name of the element at position x y or the empty string if the point does not lie within any element x and y are pixel coordinates relative to the widget instate statespec callback None args kw Test the widget s state If a callback is not specified returns True if the widget state matches statespec and False otherwise If callback is specified then it is called with args if widget state matches statespec state statespec None Modify or inquire widget state If statespec is specified sets the widget state according to it and return a new statespec indicating which flags were changed If statespec is not specified returns the currently enabled state flags statespec will usually be a list or a tuple Combobox The ttk Combobox widget combines a text field with a pop down list of values This widget is a subclass of Entry Besides the methods inherited from Widget Widget cget Widget configure Widget identify Widget instate and Widget state and the following inherited from Entry Entry bbox Entry delete Entry icursor Entry index Entry insert Entry selection Entry xview it has some other methods described at ttk Combobox Options This widget accepts the following specific options Option Description exportselection Boolean value If set the widget selection is linked to the Window Manager selection which can be returned by invoking Misc selection_get for example justify Specifies how the text is aligned within the widget One of left center or right height Specifies the height of the pop down listbox in rows postcommand A script possibly registered with Misc register that is called immediately before displaying the values It may specify which values to display state One of normal readonly or,en
217, disabled In the readonly state the value may not be edited directly and the user can only selection of the values from the dropdown list In the normal state the text field is directly editable In the disabled state no interaction is possible textvariable Specifies a name whose value is linked to the widget value Whenever the value associated with that name changes the widget value is updated and vice versa See tkinter StringVar values Specifies the list of values to display in the drop down listbox width Specifies an integer value indicating the desired width of the entry window in average size characters of the widget s font Virtual events The combobox widgets generates a ComboboxSelected virtual event when the user selects an element from the list of values ttk Combobox class tkinter ttk Combobox current newindex None If newindex is specified sets the combobox value to the element position newindex Otherwise returns the index of the current value or 1 if the current value is not in the values list get Returns the current value of the combobox set value Sets the value of the combobox to value Spinbox The ttk Spinbox widget is a ttk Entry enhanced with increment and decrement arrows It can be used for numbers or lists of string values This widget is a subclass of Entry Besides the methods inherited from Widget Widget cget Widget configure Widget identify Widget instate and Widget state and the following inherited from Entry Entry bbox Entry delete Entry icursor Entry index Entry insert Entry xview it has some other methods described at ttk Spinbox Options This widget accepts the following specific options Option Description from Float value If set this is the minimum value to which the decrement button will decrement Must be spelled as from_ when used as an argument since from is a Python keyword to Float value If set this is the maximum value to which the increment button will increment increment Float value Specifies the amount which the increment decrement buttons change the value Defaults to 1 0 values Sequence of string or float values If specified the increment decrement buttons will cycle through the items in this sequence rather than incrementing or decrementing numbers wrap Boolean value If True increment and decrement buttons will cycle from the to value to the from value or the from value to the to value respectively format String value This specifies the format of numbers set by the increment decrement buttons It must be in the form W Pf where W is the padded width of the value P is the precision and and f are literal command Python callable Will be called with no arguments whenever either of the increment or decrement buttons are pressed Virtual events The spinbox widget generates an Increment virtual event when the user presses Up and a Decrement virtual event when the user presses Down ttk Spinbox class tkinter ttk Spinbox get Returns the current value of the spinbox set value Sets the value of the spinbox to value Notebook Ttk Notebook widget manages a collection of windows and displays a single one at a time Each child window is associated with a tab which the user may select to change the currently displayed window Options This widget accepts the following specific options Option Description height If present and greater than zero specifies the desired height of the pane area not including internal padding or tabs Otherwise the maximum height of all panes is used padding Specifies the amount of extra space to add around the outside of the notebook The padding is a list up to four length specifications left top right bottom If fewer than four elements are specified bottom defaults to top right defaults to left and top defaults to left width If present and greater than zero specified the desired width of the pane area not including internal padding Otherwise the maximum width of all panes is used Tab Options There are also specific options for tabs Option Description state Either normal disabled or hidden If disabled then the tab is not selectable If hidden then the tab is not shown sticky Specifies how ,en
218,the child window is positioned within the pane area Value is a string containing zero or more of the characters n s e or w Each letter refers to a side north south east or west that the child window will stick to as per the grid geometry manager padding Specifies the amount of extra space to add between the notebook and this pane Syntax is the same as for the option padding used by this widget text Specifies a text to be displayed in the tab image Specifies an image to display in the tab See the option image described in Widget compound Specifies how to display the image relative to the text in the case both options text and image are present See Label Options for legal values underline Specifies the index 0 based of a character to underline in the text string The underlined character is used for mnemonic activation if Notebook enable_traversal is called Tab Identifiers The tab_id present in several methods of ttk Notebook may take any of the following forms An integer between zero and the number of tabs The name of a child window A positional specification of the form x y which identifies the tab The literal string current which identifies the currently selected tab The literal string end which returns the number of tabs only valid for Notebook index Virtual Events This widget generates a NotebookTabChanged virtual event after a new tab is selected ttk Notebook class tkinter ttk Notebook add child kw Adds a new tab to the notebook If window is currently managed by the notebook but hidden it is restored to its previous position See Tab Options for the list of available options forget tab_id Removes the tab specified by tab_id unmaps and unmanages the associated window hide tab_id Hides the tab specified by tab_id The tab will not be displayed but the associated window remains managed by the notebook and its configuration remembered Hidden tabs may be restored with the add command identify x y Returns the name of the tab element at position x y or the empty string if none index tab_id Returns the numeric index of the tab specified by tab_id or the total number of tabs if tab_id is the string end insert pos child kw Inserts a pane at the specified position pos is either the string end an integer index or the name of a managed child If child is already managed by the notebook moves it to the specified position See Tab Options for the list of available options select tab_id None Selects the specified tab_id The associated child window will be displayed and the previously selected window if different is unmapped If tab_id is omitted returns the widget name of the currently selected pane tab tab_id option None kw Query or modify the options of the specific tab_id If kw is not given returns a dictionary of the tab option values If option is specified returns the value of that option Otherwise sets the options to the corresponding values tabs Returns a list of windows managed by the notebook enable_traversal Enable keyboard traversal for a toplevel window containing this notebook This will extend the bindings for the toplevel window containing the notebook as follows Control Tab selects the tab following the currently selected one Shift Control Tab selects the tab preceding the currently selected one Alt K where K is the mnemonic underlined character of any tab will select that tab Multiple notebooks in a single toplevel may be enabled for traversal including nested notebooks However notebook traversal only works properly if all panes have the notebook they are in as master Progressbar The ttk Progressbar widget shows the status of a long running operation It can operate in two modes 1 the determinate mode which shows the amount completed relative to the total amount of work to be done and 2 the indeterminate mode which provides an animated display to let the user know that work is progressing Options This widget accepts the following specific options Option Description orient One of horizontal or vertical Specifies the orientation of the progress bar length Specifies the length of the long axis of the progress bar width if hori,en
219,zontal height if vertical mode One of determinate or indeterminate maximum A number specifying the maximum value Defaults to 100 value The current value of the progress bar In determinate mode this represents the amount of work completed In indeterminate mode it is interpreted as modulo maximum that is the progress bar completes one cycle when its value increases by maximum variable A name which is linked to the option value If specified the value of the progress bar is automatically set to the value of this name whenever the latter is modified phase Read only option The widget periodically increments the value of this option whenever its value is greater than 0 and in determinate mode less than maximum This option may be used by the current theme to provide additional animation effects ttk Progressbar class tkinter ttk Progressbar start interval None Begin autoincrement mode schedules a recurring timer event that calls Progressbar step every interval milliseconds If omitted interval defaults to 50 milliseconds step amount None Increments the progress bar s value by amount amount defaults to 1 0 if omitted stop Stop autoincrement mode cancels any recurring timer event initiated by Progressbar start for this progress bar Separator The ttk Separator widget displays a horizontal or vertical separator bar It has no other methods besides the ones inherited from ttk Widget Options This widget accepts the following specific option Option Description orient One of horizontal or vertical Specifies the orientation of the separator Sizegrip The ttk Sizegrip widget also known as a grow box allows the user to resize the containing toplevel window by pressing and dragging the grip This widget has neither specific options nor specific methods besides the ones inherited from ttk Widget Platform specific notes On macOS toplevel windows automatically include a built in size grip by default Adding a Sizegrip is harmless since the built in grip will just mask the widget Bugs If the containing toplevel s position was specified relative to the right or bottom of the screen e g the Sizegrip widget will not resize the window This widget supports only southeast resizing Treeview The ttk Treeview widget displays a hierarchical collection of items Each item has a textual label an optional image and an optional list of data values The data values are displayed in successive columns after the tree label The order in which data values are displayed may be controlled by setting the widget option displaycolumns The tree widget can also display column headings Columns may be accessed by number or symbolic names listed in the widget option columns See Column Identifiers Each item is identified by a unique name The widget will generate item IDs if they are not supplied by the caller There is a distinguished root item named The root item itself is not displayed its children appear at the top level of the hierarchy Each item also has a list of tags which can be used to associate event bindings with individual items and control the appearance of the item The Treeview widget supports horizontal and vertical scrolling according to the options described in Scrollable Widget Options and the methods Treeview xview and Treeview yview Options This widget accepts the following specific options Option Description columns A list of column identifiers specifying the number of columns and their names displaycolumns A list of column identifiers either symbolic or integer indices specifying which data columns are displayed and the order in which they appear or the string all height Specifies the number of rows which should be visible Note the requested width is determined from the sum of the column widths padding Specifies the internal padding for the widget The padding is a list of up to four length specifications selectmode Controls how the built in class bindings manage the selection One of extended browse or none If set to extended the default multiple items may be selected If browse only a single item will be selected at a time If none the selection will not be chang,en
220,ed Note that the application code and tag bindings can set the selection however they wish regardless of the value of this option show A list containing zero or more of the following values specifying which elements of the tree to display tree display tree labels in column 0 headings display the heading row The default is tree headings i e show all elements Note Column 0 always refers to the tree column even if show tree is not specified Item Options The following item options may be specified for items in the insert and item widget commands Option Description text The textual label to display for the item image A Tk Image displayed to the left of the label values The list of values associated with the item Each item should have the same number of values as the widget option columns If there are fewer values than columns the remaining values are assumed empty If there are more values than columns the extra values are ignored open True False value indicating whether the item s children should be displayed or hidden tags A list of tags associated with this item Tag Options The following options may be specified on tags Option Description foreground Specifies the text foreground color background Specifies the cell or item background color font Specifies the font to use when drawing text image Specifies the item image in case the item s image option is empty Column Identifiers Column identifiers take any of the following forms A symbolic name from the list of columns option An integer n specifying the nth data column A string of the form n where n is an integer specifying the nth display column Notes Item s option values may be displayed in a different order than the order in which they are stored Column 0 always refers to the tree column even if show tree is not specified A data column number is an index into an item s option values list a display column number is the column number in the tree where the values are displayed Tree labels are displayed in column 0 If option displaycolumns is not set then data column n is displayed in column n 1 Again column 0 always refers to the tree column Virtual Events The Treeview widget generates the following virtual events Event Description TreeviewSelect Generated whenever the selection changes TreeviewOpen Generated just before settings the focus item to open True TreeviewClose Generated just after setting the focus item to open False The Treeview focus and Treeview selection methods can be used to determine the affected item or items ttk Treeview class tkinter ttk Treeview bbox item column None Returns the bounding box relative to the treeview widget s window of the specified item in the form x y width height If column is specified returns the bounding box of that cell If the item is not visible i e if it is a descendant of a closed item or is scrolled offscreen returns an empty string get_children item None Returns the list of children belonging to item If item is not specified returns root children set_children item newchildren Replaces item s child with newchildren Children present in item that are not present in newchildren are detached from the tree No items in newchildren may be an ancestor of item Note that not specifying newchildren results in detaching item s children column column option None kw Query or modify the options for the specified column If kw is not given returns a dict of the column option values If option is specified then the value for that option is returned Otherwise sets the options to the corresponding values The valid options values are id Returns the column name This is a read only option anchor One of the standard Tk anchor values Specifies how the text in this column should be aligned with respect to the cell minwidth width The minimum width of the column in pixels The treeview widget will not make the column any smaller than specified by this option when the widget is resized or the user drags a column stretch True False Specifies whether the column s width should be adjusted when the widget is resized width width The width of the column in pixels To,en
221, configure the tree column call this with column 0 delete items Delete all specified items and all their descendants The root item may not be deleted detach items Unlinks all of the specified items from the tree The items and all of their descendants are still present and may be reinserted at another point in the tree but will not be displayed The root item may not be detached exists item Returns True if the specified item is present in the tree focus item None If item is specified sets the focus item to item Otherwise returns the current focus item or if there is none heading column option None kw Query or modify the heading options for the specified column If kw is not given returns a dict of the heading option values If option is specified then the value for that option is returned Otherwise sets the options to the corresponding values The valid options values are text text The text to display in the column heading image imageName Specifies an image to display to the right of the column heading anchor anchor Specifies how the heading text should be aligned One of the standard Tk anchor values command callback A callback to be invoked when the heading label is pressed To configure the tree column heading call this with column 0 identify component x y Returns a description of the specified component under the point given by x and y or the empty string if no such component is present at that position identify_row y Returns the item ID of the item at position y identify_column x Returns the data column identifier of the cell at position x The tree column has ID 0 identify_region x y Returns one of region meaning heading Tree heading area separator Space between two columns headings tree The tree area cell A data cell Availability Tk 8 6 identify_element x y Returns the element at position x y Availability Tk 8 6 index item Returns the integer index of item within its parent s list of children insert parent index iid None kw Creates a new item and returns the item identifier of the newly created item parent is the item ID of the parent item or the empty string to create a new top level item index is an integer or the value end specifying where in the list of parent s children to insert the new item If index is less than or equal to zero the new node is inserted at the beginning if index is greater than or equal to the current number of children it is inserted at the end If iid is specified it is used as the item identifier iid must not already exist in the tree Otherwise a new unique identifier is generated See Item Options for the list of available options item item option None kw Query or modify the options for the specified item If no options are given a dict with options values for the item is returned If option is specified then the value for that option is returned Otherwise sets the options to the corresponding values as given by kw move item parent index Moves item to position index in parent s list of children It is illegal to move an item under one of its descendants If index is less than or equal to zero item is moved to the beginning if greater than or equal to the number of children it is moved to the end If item was detached it is reattached next item Returns the identifier of item s next sibling or if item is the last child of its parent parent item Returns the ID of the parent of item or if item is at the top level of the hierarchy prev item Returns the identifier of item s previous sibling or if item is the first child of its parent reattach item parent index An alias for Treeview move see item Ensure that item is visible Sets all of item s ancestors open option to True and scrolls the widget if necessary so that item is within the visible portion of the tree selection Returns a tuple of selected items Changed in version 3 8 selection no longer takes arguments For changing the selection state use the following selection methods selection_set items items becomes the new selection Changed in version 3 6 items can be passed as separate arguments not just as a single tuple selection_add items Add items to the ,en
222,selection Changed in version 3 6 items can be passed as separate arguments not just as a single tuple selection_remove items Remove items from the selection Changed in version 3 6 items can be passed as separate arguments not just as a single tuple selection_toggle items Toggle the selection state of each item in items Changed in version 3 6 items can be passed as separate arguments not just as a single tuple set item column None value None With one argument returns a dictionary of column value pairs for the specified item With two arguments returns the current value of the specified column With three arguments sets the value of given column in given item to the specified value tag_bind tagname sequence None callback None Bind a callback for the given event sequence to the tag tagname When an event is delivered to an item the callbacks for each of the item s tags option are called tag_configure tagname option None kw Query or modify the options for the specified tagname If kw is not given returns a dict of the option settings for tagname If option is specified returns the value for that option for the specified tagname Otherwise sets the options to the corresponding values for the given tagname tag_has tagname item None If item is specified returns 1 or 0 depending on whether the specified item has the given tagname Otherwise returns a list of all items that have the specified tag Availability Tk 8 6 xview args Query or modify horizontal position of the treeview yview args Query or modify vertical position of the treeview Ttk Styling Each widget in ttk is assigned a style which specifies the set of elements making up the widget and how they are arranged along with dynamic and default settings for element options By default the style name is the same as the widget s class name but it may be overridden by the widget s style option If you don t know the class name of a widget use the method Misc winfo_class somewidget winfo_class See also Tcl 2004 conference presentation This document explains how the theme engine works class tkinter ttk Style This class is used to manipulate the style database configure style query_opt None kw Query or set the default value of the specified option s in style Each key in kw is an option and each value is a string identifying the value for that option For example to change every default button to be a flat button with some padding and a different background color from tkinter import ttk import tkinter root tkinter Tk ttk Style configure TButton padding 6 relief flat background ccc btn ttk Button text Sample btn pack root mainloop map style query_opt None kw Query or sets dynamic values of the specified option s in style Each key in kw is an option and each value should be a list or a tuple usually containing statespecs grouped in tuples lists or some other preference A statespec is a compound of one or more states and then a value An example may make it more understandable import tkinter from tkinter import ttk root tkinter Tk style ttk Style style map C TButton foreground pressed red active blue background pressed disabled black active white colored_btn ttk Button text Test style C TButton pack root mainloop Note that the order of the states value sequences for an option does matter if the order is changed to active blue pressed red in the foreground option for example the result would be a blue foreground when the widget were in active or pressed states lookup style option state None default None Returns the value specified for option in style If state is specified it is expected to be a sequence of one or more states If the default argument is set it is used as a fallback value in case no specification for option is found To check what font a Button uses by default from tkinter import ttk print ttk Style lookup TButton font layout style layoutspec None Define the widget layout for given style If layoutspec is omitted return the layout specification for given style layoutspec if specified is expected to be a list or some other sequence type excluding strings where each item should be a tup,en
223,le and the first item is the layout name and the second item should have the format described in Layouts To understand the format see the following example it is not intended to do anything useful from tkinter import ttk import tkinter root tkinter Tk style ttk Style style layout TMenubutton Menubutton background None Menubutton button children Menubutton focus children Menubutton padding children Menubutton label side left expand 1 mbtn ttk Menubutton text Text mbtn pack root mainloop element_create elementname etype args kw Create a new element in the current theme of the given etype which is expected to be either image or from If image is used args should contain the default image name followed by statespec value pairs this is the imagespec and kw may have the following options border padding padding is a list of up to four integers specifying the left top right and bottom borders respectively height height Specifies a minimum height for the element If less than zero the base image s height is used as a default padding padding Specifies the element s interior padding Defaults to border s value if not specified sticky spec Specifies how the image is placed within the final parcel spec contains zero or more characters n s w or e width width Specifies a minimum width for the element If less than zero the base image s width is used as a default Example img1 tkinter PhotoImage master root file button png img1 tkinter PhotoImage master root file button pressed png img1 tkinter PhotoImage master root file button active png style ttk Style root style element_create Button button image img1 pressed img2 active img3 border 2 4 sticky we If from is used as the value of etype element_create will clone an existing element args is expected to contain a themename from which the element will be cloned and optionally an element to clone from If this element to clone from is not specified an empty element will be used kw is discarded Example style ttk Style root style element_create plain background from default element_names Returns the list of elements defined in the current theme element_options elementname Returns the list of elementname s options theme_create themename parent None settings None Create a new theme It is an error if themename already exists If parent is specified the new theme will inherit styles elements and layouts from the parent theme If settings are present they are expected to have the same syntax used for theme_settings theme_settings themename settings Temporarily sets the current theme to themename apply specified settings and then restore the previous theme Each key in settings is a style and each value may contain the keys configure map layout and element create and they are expected to have the same format as specified by the methods Style configure Style map Style layout and Style element_create respectively As an example let s change the Combobox for the default theme a bit from tkinter import ttk import tkinter root tkinter Tk style ttk Style style theme_settings default TCombobox configure padding 5 map background active green2 disabled green4 fieldbackground disabled green3 foreground focus OliveDrab1 disabled OliveDrab2 combo ttk Combobox pack root mainloop theme_names Returns a list of all known themes theme_use themename None If themename is not given returns the theme in use Otherwise sets the current theme to themename refreshes all widgets and emits a ThemeChanged event Layouts A layout can be just None if it takes no options or a dict of options specifying how to arrange the element The layout mechanism uses a simplified version of the pack geometry manager given an initial cavity each element is allocated a parcel The valid options values are side whichside Specifies which side of the cavity to place the element one of top right bottom or left If omitted the element occupies the entire cavity sticky nswe Specifies where the element is placed inside its allocated parcel unit 0 or 1 If set to 1 causes the element and all of its descendants to be treated as a single element for the purposes of ,en
224,Widget identify et al It s used for things like scrollbar thumbs with grips children sublayout Specifies a list of elements to place inside the element Each element is a tuple or other sequence type where the first item is the layout name and the other is a Layout,en
225,Function Objects There are a few functions specific to Python functions type PyFunctionObject The C structure used for functions PyTypeObject PyFunction_Type This is an instance of PyTypeObject and represents the Python function type It is exposed to Python programmers as types FunctionType int PyFunction_Check PyObject o Return true if o is a function object has type PyFunction_Type The parameter must not be NULL This function always succeeds PyObject PyFunction_New PyObject code PyObject globals Return value New reference Return a new function object associated with the code object code globals must be a dictionary with the global variables accessible to the function The function s docstring and name are retrieved from the code object __module__ is retrieved from globals The argument defaults annotations and closure are set to NULL __qualname__ is set to the same value as the code object s co_qualname field PyObject PyFunction_NewWithQualName PyObject code PyObject globals PyObject qualname Return value New reference As PyFunction_New but also allows setting the function object s __qualname__ attribute qualname should be a unicode object or NULL if NULL the __qualname__ attribute is set to the same value as the code object s co_qualname field New in version 3 3 PyObject PyFunction_GetCode PyObject op Return value Borrowed reference Return the code object associated with the function object op PyObject PyFunction_GetGlobals PyObject op Return value Borrowed reference Return the globals dictionary associated with the function object op PyObject PyFunction_GetModule PyObject op Return value Borrowed reference Return a borrowed reference to the __module__ attribute of the function object op It can be NULL This is normally a string containing the module name but can be set to any other object by Python code PyObject PyFunction_GetDefaults PyObject op Return value Borrowed reference Return the argument default values of the function object op This can be a tuple of arguments or NULL int PyFunction_SetDefaults PyObject op PyObject defaults Set the argument default values for the function object op defaults must be Py_None or a tuple Raises SystemError and returns 1 on failure void PyFunction_SetVectorcall PyFunctionObject func vectorcallfunc vectorcall Set the vectorcall field of a given function object func Warning extensions using this API must preserve the behavior of the unaltered default vectorcall function New in version 3 12 PyObject PyFunction_GetClosure PyObject op Return value Borrowed reference Return the closure associated with the function object op This can be NULL or a tuple of cell objects int PyFunction_SetClosure PyObject op PyObject closure Set the closure associated with the function object op closure must be Py_None or a tuple of cell objects Raises SystemError and returns 1 on failure PyObject PyFunction_GetAnnotations PyObject op Return value Borrowed reference Return the annotations of the function object op This can be a mutable dictionary or NULL int PyFunction_SetAnnotations PyObject op PyObject annotations Set the annotations for the function object op annotations must be a dictionary or Py_None Raises SystemError and returns 1 on failure int PyFunction_AddWatcher PyFunction_WatchCallback callback Register callback as a function watcher for the current interpreter Return an ID which may be passed to PyFunction_ClearWatcher In case of error e g no more watcher IDs available return 1 and set an exception New in version 3 12 int PyFunction_ClearWatcher int watcher_id Clear watcher identified by watcher_id previously returned from PyFunction_AddWatcher for the current interpreter Return 0 on success or 1 and set an exception on error e g if the given watcher_id was never registered New in version 3 12 type PyFunction_WatchEvent Enumeration of possible function watcher events PyFunction_EVENT_CREATE PyFunction_EVENT_DESTROY PyFunction_EVENT_MODIFY_CODE PyFunction_EVENT_MODIFY_DEFAULTS PyFunction_EVENT_MODIFY_KWDEFAULTS New in version 3 12 typedef int PyFunction_WatchCallback PyFunction_WatchEvent event ,en
226,PyFunctionObject func PyObject new_value Type of a function watcher callback function If event is PyFunction_EVENT_CREATE or PyFunction_EVENT_DESTROY then new_value will be NULL Otherwise new_value will hold a borrowed reference to the new value that is about to be stored in func for the attribute that is being modified The callback may inspect but must not modify func doing so could have unpredictable effects including infinite recursion If event is PyFunction_EVENT_CREATE then the callback is invoked after func has been fully initialized Otherwise the callback is invoked before the modification to func takes place so the prior state of func can be inspected The runtime is permitted to optimize away the creation of function objects when possible In such cases no event will be emitted Although this creates the possibility of an observable difference of runtime behavior depending on optimization decisions it does not change the semantics of the Python code being executed If event is PyFunction_EVENT_DESTROY Taking a reference in the callback to the about to be destroyed function will resurrect it preventing it from being freed at this time When the resurrected object is destroyed later any watcher callbacks active at that time will be called again If the callback sets an exception it must return 1 this exception will be printed as an unraisable exception using PyErr_WriteUnraisable Otherwise it should return 0 There may already be a pending exception set on entry to the callback In this case the callback should return 0 with the same exception still set This means the callback may not call any other API that can set an exception unless it saves and clears the exception state first and restores it before returning New in version 3 12,en
227,socketserver A framework for network servers Source code Lib socketserver py The socketserver module simplifies the task of writing network servers Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information There are four basic concrete server classes class socketserver TCPServer server_address RequestHandlerClass bind_and_activate True This uses the internet TCP protocol which provides for continuous streams of data between the client and server If bind_and_activate is true the constructor automatically attempts to invoke server_bind and server_activate The other parameters are passed to the BaseServer base class class socketserver UDPServer server_address RequestHandlerClass bind_and_activate True This uses datagrams which are discrete packets of information that may arrive out of order or be lost while in transit The parameters are the same as for TCPServer class socketserver UnixStreamServer server_address RequestHandlerClass bind_and_activate True class socketserver UnixDatagramServer server_address RequestHandlerClass bind_and_activate True These more infrequently used classes are similar to the TCP and UDP classes but use Unix domain sockets they re not available on non Unix platforms The parameters are the same as for TCPServer These four classes process requests synchronously each request must be completed before the next request can be started This isn t suitable if each request takes a long time to complete because it requires a lot of computation or because it returns a lot of data which the client is slow to process The solution is to create a separate process or thread to handle each request the ForkingMixIn and ThreadingMixIn mix in classes can be used to support asynchronous behaviour Creating a server requires several steps First you must create a request handler class by subclassing the BaseRequestHandler class and overriding its handle method this method will process incoming requests Second you must instantiate one of the server classes passing it the server s address and the request handler class It is recommended to use the server in a with statement Then call the handle_request or serve_forever method of the server object to process one or many requests Finally call server_close to close the socket unless you used a with statement When inheriting from ThreadingMixIn for threaded connection behavior you should explicitly declare how you want your threads to behave on an abrupt shutdown The ThreadingMixIn class defines an attribute daemon_threads which indicates whether or not the server should wait for thread termination You should set the flag explicitly if you would like threads to behave autonomously the default is False meaning that Python will not exit until all threads created by ThreadingMixIn have exited Server classes have the same external methods and attributes no matter what network protocol they use Server Creation Notes There are five classes in an inheritance diagram four of which represent synchronous servers of four types BaseServer v TCPServer UnixStreamServer v UDPServer UnixDatagramServer Note that UnixDatagramServer derives from UDPServer not from UnixStreamServer the only difference between an IP and a Unix server is the address family class socketserver ForkingMixIn class socketserver ThreadingMixIn Forking and threading versions of each type of server can be created using these mix in classes For instance ThreadingUDPServer is created as follows class ThreadingUDPServer ThreadingMixIn UDPServer pass The mix in class comes first since it overrides a method defined in UDPServer Setting the various attributes also changes the behavior of the underlying server mechanism ForkingMixIn and the Forking classes mentioned below are only available on POSIX platforms that support fork block_on_close ForkingMixIn server_close waits until all child processes complete except if block_on_close attribute is False ThreadingMixIn server_close waits until all non daem,en
228,on threads complete except if block_on_close attribute is False daemon_threads For ThreadingMixIn use daemonic threads by setting ThreadingMixIn daemon_threads to True to not wait until threads complete Changed in version 3 7 ForkingMixIn server_close and ThreadingMixIn server_close now waits until all child processes and non daemonic threads complete Add a new ForkingMixIn block_on_close class attribute to opt in for the pre 3 7 behaviour class socketserver ForkingTCPServer class socketserver ForkingUDPServer class socketserver ThreadingTCPServer class socketserver ThreadingUDPServer class socketserver ForkingUnixStreamServer class socketserver ForkingUnixDatagramServer class socketserver ThreadingUnixStreamServer class socketserver ThreadingUnixDatagramServer These classes are pre defined using the mix in classes New in version 3 12 The ForkingUnixStreamServer and ForkingUnixDatagramServer classes were added To implement a service you must derive a class from BaseRequestHandler and redefine its handle method You can then run various versions of the service by combining one of the server classes with your request handler class The request handler class must be different for datagram or stream services This can be hidden by using the handler subclasses StreamRequestHandler or DatagramRequestHandler Of course you still have to use your head For instance it makes no sense to use a forking server if the service contains state in memory that can be modified by different requests since the modifications in the child process would never reach the initial state kept in the parent process and passed to each child In this case you can use a threading server but you will probably have to use locks to protect the integrity of the shared data On the other hand if you are building an HTTP server where all data is stored externally for instance in the file system a synchronous class will essentially render the service deaf while one request is being handled which may be for a very long time if a client is slow to receive all the data it has requested Here a threading or forking server is appropriate In some cases it may be appropriate to process part of a request synchronously but to finish processing in a forked child depending on the request data This can be implemented by using a synchronous server and doing an explicit fork in the request handler class handle method Another approach to handling multiple simultaneous requests in an environment that supports neither threads nor fork or where these are too expensive or inappropriate for the service is to maintain an explicit table of partially finished requests and to use selectors to decide which request to work on next or whether to handle a new incoming request This is particularly important for stream services where each client can potentially be connected for a long time if threads or subprocesses cannot be used Server Objects class socketserver BaseServer server_address RequestHandlerClass This is the superclass of all Server objects in the module It defines the interface given below but does not implement most of the methods which is done in subclasses The two parameters are stored in the respective server_address and RequestHandlerClass attributes fileno Return an integer file descriptor for the socket on which the server is listening This function is most commonly passed to selectors to allow monitoring multiple servers in the same process handle_request Process a single request This function calls the following methods in order get_request verify_request and process_request If the user provided handle method of the handler class raises an exception the server s handle_error method will be called If no request is received within timeout seconds handle_timeout will be called and handle_request will return serve_forever poll_interval 0 5 Handle requests until an explicit shutdown request Poll for shutdown every poll_interval seconds Ignores the timeout attribute It also calls service_actions which may be used by a subclass or mixin to provide actions specific to a given servic,en
229,e For example the ForkingMixIn class uses service_actions to clean up zombie child processes Changed in version 3 3 Added service_actions call to the serve_forever method service_actions This is called in the serve_forever loop This method can be overridden by subclasses or mixin classes to perform actions specific to a given service such as cleanup actions New in version 3 3 shutdown Tell the serve_forever loop to stop and wait until it does shutdown must be called while serve_forever is running in a different thread otherwise it will deadlock server_close Clean up the server May be overridden address_family The family of protocols to which the server s socket belongs Common examples are socket AF_INET and socket AF_UNIX RequestHandlerClass The user provided request handler class an instance of this class is created for each request server_address The address on which the server is listening The format of addresses varies depending on the protocol family see the documentation for the socket module for details For internet protocols this is a tuple containing a string giving the address and an integer port number 127 0 0 1 80 for example socket The socket object on which the server will listen for incoming requests The server classes support the following class variables allow_reuse_address Whether the server will allow the reuse of an address This defaults to False and can be set in subclasses to change the policy request_queue_size The size of the request queue If it takes a long time to process a single request any requests that arrive while the server is busy are placed into a queue up to request_queue_size requests Once the queue is full further requests from clients will get a Connection denied error The default value is usually 5 but this can be overridden by subclasses socket_type The type of socket used by the server socket SOCK_STREAM and socket SOCK_DGRAM are two common values timeout Timeout duration measured in seconds or None if no timeout is desired If handle_request receives no incoming requests within the timeout period the handle_timeout method is called There are various server methods that can be overridden by subclasses of base server classes like TCPServer these methods aren t useful to external users of the server object finish_request request client_address Actually processes the request by instantiating RequestHandlerClass and calling its handle method get_request Must accept a request from the socket and return a 2 tuple containing the new socket object to be used to communicate with the client and the client s address handle_error request client_address This function is called if the handle method of a RequestHandlerClass instance raises an exception The default action is to print the traceback to standard error and continue handling further requests Changed in version 3 6 Now only called for exceptions derived from the Exception class handle_timeout This function is called when the timeout attribute has been set to a value other than None and the timeout period has passed with no requests being received The default action for forking servers is to collect the status of any child processes that have exited while in threading servers this method does nothing process_request request client_address Calls finish_request to create an instance of the RequestHandlerClass If desired this function can create a new process or thread to handle the request the ForkingMixIn and ThreadingMixIn classes do this server_activate Called by the server s constructor to activate the server The default behavior for a TCP server just invokes listen on the server s socket May be overridden server_bind Called by the server s constructor to bind the socket to the desired address May be overridden verify_request request client_address Must return a Boolean value if the value is True the request will be processed and if it s False the request will be denied This function can be overridden to implement access controls for a server The default implementation always returns True Changed in version 3 6 Support for the context ,en
230,manager protocol was added Exiting the context manager is equivalent to calling server_close Request Handler Objects class socketserver BaseRequestHandler This is the superclass of all request handler objects It defines the interface given below A concrete request handler subclass must define a new handle method and can override any of the other methods A new instance of the subclass is created for each request setup Called before the handle method to perform any initialization actions required The default implementation does nothing handle This function must do all the work required to service a request The default implementation does nothing Several instance attributes are available to it the request is available as request the client address as client_address and the server instance as server in case it needs access to per server information The type of request is different for datagram or stream services For stream services request is a socket object for datagram services request is a pair of string and socket finish Called after the handle method to perform any clean up actions required The default implementation does nothing If setup raises an exception this function will not be called request The new socket socket object to be used to communicate with the client client_address Client address returned by BaseServer get_request server BaseServer object used for handling the request class socketserver StreamRequestHandler class socketserver DatagramRequestHandler These BaseRequestHandler subclasses override the setup and finish methods and provide rfile and wfile attributes rfile A file object from which receives the request is read Support the io BufferedIOBase readable interface wfile A file object to which the reply is written Support the io BufferedIOBase writable interface Changed in version 3 6 wfile also supports the io BufferedIOBase writable interface Examples socketserver TCPServer Example This is the server side import socketserver class MyTCPHandler socketserver BaseRequestHandler The request handler class for our server It is instantiated once per connection to the server and must override the handle method to implement communication to the client def handle self self request is the TCP socket connected to the client self data self request recv 1024 strip print Received from format self client_address 0 print self data just send back the same data but upper cased self request sendall self data upper if __name__ __main__ HOST PORT localhost 9999 Create the server binding to localhost on port 9999 with socketserver TCPServer HOST PORT MyTCPHandler as server Activate the server this will keep running until you interrupt the program with Ctrl C server serve_forever An alternative request handler class that makes use of streams file like objects that simplify communication by providing the standard file interface class MyTCPHandler socketserver StreamRequestHandler def handle self self rfile is a file like object created by the handler we can now use e g readline instead of raw recv calls self data self rfile readline strip print wrote format self client_address 0 print self data Likewise self wfile is a file like object used to write back to the client self wfile write self data upper The difference is that the readline call in the second handler will call recv multiple times until it encounters a newline character while the single recv call in the first handler will just return what has been received so far from the client s sendall call typically all of it but this is not guaranteed by the TCP protocol This is the client side import socket import sys HOST PORT localhost 9999 data join sys argv 1 Create a socket SOCK_STREAM means a TCP socket with socket socket socket AF_INET socket SOCK_STREAM as sock Connect to server and send data sock connect HOST PORT sock sendall bytes data n utf 8 Receive data from the server and shut down received str sock recv 1024 utf 8 print Sent format data print Received format received The output of the example should look something like this Server python TCPServer py 127 0 0,en
231, 1 wrote b hello world with TCP 127 0 0 1 wrote b python is nice Client python TCPClient py hello world with TCP Sent hello world with TCP Received HELLO WORLD WITH TCP python TCPClient py python is nice Sent python is nice Received PYTHON IS NICE socketserver UDPServer Example This is the server side import socketserver class MyUDPHandler socketserver BaseRequestHandler This class works similar to the TCP handler class except that self request consists of a pair of data and client socket and since there is no connection the client address must be given explicitly when sending data back via sendto def handle self data self request 0 strip socket self request 1 print wrote format self client_address 0 print data socket sendto data upper self client_address if __name__ __main__ HOST PORT localhost 9999 with socketserver UDPServer HOST PORT MyUDPHandler as server server serve_forever This is the client side import socket import sys HOST PORT localhost 9999 data join sys argv 1 SOCK_DGRAM is the socket type to use for UDP sockets sock socket socket socket AF_INET socket SOCK_DGRAM As you can see there is no connect call UDP has no connections Instead data is directly sent to the recipient via sendto sock sendto bytes data n utf 8 HOST PORT received str sock recv 1024 utf 8 print Sent format data print Received format received The output of the example should look exactly like for the TCP server example Asynchronous Mixins To build asynchronous handlers use the ThreadingMixIn and ForkingMixIn classes An example for the ThreadingMixIn class import socket import threading import socketserver class ThreadedTCPRequestHandler socketserver BaseRequestHandler def handle self data str self request recv 1024 ascii cur_thread threading current_thread response bytes format cur_thread name data ascii self request sendall response class ThreadedTCPServer socketserver ThreadingMixIn socketserver TCPServer pass def client ip port message with socket socket socket AF_INET socket SOCK_STREAM as sock sock connect ip port sock sendall bytes message ascii response str sock recv 1024 ascii print Received format response if __name__ __main__ Port 0 means to select an arbitrary unused port HOST PORT localhost 0 server ThreadedTCPServer HOST PORT ThreadedTCPRequestHandler with server ip port server server_address Start a thread with the server that thread will then start one more thread for each request server_thread threading Thread target server serve_forever Exit the server thread when the main thread terminates server_thread daemon True server_thread start print Server loop running in thread server_thread name client ip port Hello World 1 client ip port Hello World 2 client ip port Hello World 3 server shutdown The output of the example should look something like this python ThreadedTCPServer py Server loop running in thread Thread 1 Received Thread 2 Hello World 1 Received Thread 3 Hello World 2 Received Thread 4 Hello World 3 The ForkingMixIn class is used in the same way except that the server will spawn a new process for each request Available only on POSIX platforms that support fork,en
232,argparse Parser for command line options arguments and sub commands New in version 3 2 Source code Lib argparse py Tutorial This page contains the API reference information For a more gentle introduction to Python command line parsing have a look at the argparse tutorial The argparse module makes it easy to write user friendly command line interfaces The program defines what arguments it requires and argparse will figure out how to parse those out of sys argv The argparse module also automatically generates help and usage messages The module will also issue errors when users give the program invalid arguments Core Functionality The argparse module s support for command line interfaces is built around an instance of argparse ArgumentParser It is a container for argument specifications and has options that apply to the parser as whole parser argparse ArgumentParser prog ProgramName description What the program does epilog Text at the bottom of help The ArgumentParser add_argument method attaches individual argument specifications to the parser It supports positional arguments options that accept values and on off flags parser add_argument filename positional argument parser add_argument c count option that takes a value parser add_argument v verbose action store_true on off flag The ArgumentParser parse_args method runs the parser and places the extracted data in a argparse Namespace object args parser parse_args print args filename args count args verbose Quick Links for add_argument Name Description Values action Specify how an argument should be handled store store_const store_true append append_const count help version choices Limit values to a specific set of choices foo bar range 1 10 or Container instance const Store a constant value default Default value used when an argument is not provided Defaults to None dest Specify the attribute name used in the result namespace help Help message for an argument metavar Alternate display name for the argument as shown in help nargs Number of times the argument can be used int or required Indicate whether an argument is required or optional True or False type Automatically convert an argument to the given type int float argparse FileType w or callable function Example The following code is a Python program that takes a list of integers and produces either the sum or the max import argparse parser argparse ArgumentParser description Process some integers parser add_argument integers metavar N type int nargs help an integer for the accumulator parser add_argument sum dest accumulate action store_const const sum default max help sum the integers default find the max args parser parse_args print args accumulate args integers Assuming the above Python code is saved into a file called prog py it can be run at the command line and it provides useful help messages python prog py h usage prog py h sum N N Process some integers positional arguments N an integer for the accumulator options h help show this help message and exit sum sum the integers default find the max When run with the appropriate arguments it prints either the sum or the max of the command line integers python prog py 1 2 3 4 4 python prog py 1 2 3 4 sum 10 If invalid arguments are passed in an error will be displayed python prog py a b c usage prog py h sum N N prog py error argument N invalid int value a The following sections walk you through this example Creating a parser The first step in using the argparse is creating an ArgumentParser object parser argparse ArgumentParser description Process some integers The ArgumentParser object will hold all the information necessary to parse the command line into Python data types Adding arguments Filling an ArgumentParser with information about program arguments is done by making calls to the add_argument method Generally these calls tell the ArgumentParser how to take the strings on the command line and turn them into objects This information is stored and used when parse_args is called For example parser add_argument integers metavar N type int nargs help an integer for t,en
233,he accumulator parser add_argument sum dest accumulate action store_const const sum default max help sum the integers default find the max Later calling parse_args will return an object with two attributes integers and accumulate The integers attribute will be a list of one or more integers and the accumulate attribute will be either the sum function if sum was specified at the command line or the max function if it was not Parsing arguments ArgumentParser parses arguments through the parse_args method This will inspect the command line convert each argument to the appropriate type and then invoke the appropriate action In most cases this means a simple Namespace object will be built up from attributes parsed out of the command line parser parse_args sum 7 1 42 Namespace accumulate built in function sum integers 7 1 42 In a script parse_args will typically be called with no arguments and the ArgumentParser will automatically determine the command line arguments from sys argv ArgumentParser objects class argparse ArgumentParser prog None usage None description None epilog None parents formatter_class argparse HelpFormatter prefix_chars fromfile_prefix_chars None argument_default None conflict_handler error add_help True allow_abbrev True exit_on_error True Create a new ArgumentParser object All parameters should be passed as keyword arguments Each parameter has its own more detailed description below but in short they are prog The name of the program default os path basename sys argv 0 usage The string describing the program usage default generated from arguments added to parser description Text to display before the argument help by default no text epilog Text to display after the argument help by default no text parents A list of ArgumentParser objects whose arguments should also be included formatter_class A class for customizing the help output prefix_chars The set of characters that prefix optional arguments default fromfile_prefix_chars The set of characters that prefix files from which additional arguments should be read default None argument_default The global default value for arguments default None conflict_handler The strategy for resolving conflicting optionals usually unnecessary add_help Add a h help option to the parser default True allow_abbrev Allows long options to be abbreviated if the abbreviation is unambiguous default True exit_on_error Determines whether or not ArgumentParser exits with error info when an error occurs default True Changed in version 3 5 allow_abbrev parameter was added Changed in version 3 8 In previous versions allow_abbrev also disabled grouping of short flags such as vv to mean v v Changed in version 3 9 exit_on_error parameter was added The following sections describe how each of these are used prog By default ArgumentParser objects use sys argv 0 to determine how to display the name of the program in help messages This default is almost always desirable because it will make the help messages match how the program was invoked on the command line For example consider a file named myprogram py with the following code import argparse parser argparse ArgumentParser parser add_argument foo help foo help args parser parse_args The help for this program will display myprogram py as the program name regardless of where the program was invoked from python myprogram py help usage myprogram py h foo FOO options h help show this help message and exit foo FOO foo help cd python subdir myprogram py help usage myprogram py h foo FOO options h help show this help message and exit foo FOO foo help To change this default behavior another value can be supplied using the prog argument to ArgumentParser parser argparse ArgumentParser prog myprogram parser print_help usage myprogram h options h help show this help message and exit Note that the program name whether determined from sys argv 0 or from the prog argument is available to help messages using the prog s format specifier parser argparse ArgumentParser prog myprogram parser add_argument foo help foo of the prog s program parser print_help usa,en
234,ge myprogram h foo FOO options h help show this help message and exit foo FOO foo of the myprogram program usage By default ArgumentParser calculates the usage message from the arguments it contains parser argparse ArgumentParser prog PROG parser add_argument foo nargs help foo help parser add_argument bar nargs help bar help parser print_help usage PROG h foo FOO bar bar positional arguments bar bar help options h help show this help message and exit foo FOO foo help The default message can be overridden with the usage keyword argument parser argparse ArgumentParser prog PROG usage prog s options parser add_argument foo nargs help foo help parser add_argument bar nargs help bar help parser print_help usage PROG options positional arguments bar bar help options h help show this help message and exit foo FOO foo help The prog s format specifier is available to fill in the program name in your usage messages description Most calls to the ArgumentParser constructor will use the description keyword argument This argument gives a brief description of what the program does and how it works In help messages the description is displayed between the command line usage string and the help messages for the various arguments parser argparse ArgumentParser description A foo that bars parser print_help usage argparse py h A foo that bars options h help show this help message and exit By default the description will be line wrapped so that it fits within the given space To change this behavior see the formatter_class argument epilog Some programs like to display additional description of the program after the description of the arguments Such text can be specified using the epilog argument to ArgumentParser parser argparse ArgumentParser description A foo that bars epilog And that s how you d foo a bar parser print_help usage argparse py h A foo that bars options h help show this help message and exit And that s how you d foo a bar As with the description argument the epilog text is by default line wrapped but this behavior can be adjusted with the formatter_class argument to ArgumentParser parents Sometimes several parsers share a common set of arguments Rather than repeating the definitions of these arguments a single parser with all the shared arguments and passed to parents argument to ArgumentParser can be used The parents argument takes a list of ArgumentParser objects collects all the positional and optional actions from them and adds these actions to the ArgumentParser object being constructed parent_parser argparse ArgumentParser add_help False parent_parser add_argument parent type int foo_parser argparse ArgumentParser parents parent_parser foo_parser add_argument foo foo_parser parse_args parent 2 XXX Namespace foo XXX parent 2 bar_parser argparse ArgumentParser parents parent_parser bar_parser add_argument bar bar_parser parse_args bar YYY Namespace bar YYY parent None Note that most parent parsers will specify add_help False Otherwise the ArgumentParser will see two h help options one in the parent and one in the child and raise an error Note You must fully initialize the parsers before passing them via parents If you change the parent parsers after the child parser those changes will not be reflected in the child formatter_class ArgumentParser objects allow the help formatting to be customized by specifying an alternate formatting class Currently there are four such classes class argparse RawDescriptionHelpFormatter class argparse RawTextHelpFormatter class argparse ArgumentDefaultsHelpFormatter class argparse MetavarTypeHelpFormatter RawDescriptionHelpFormatter and RawTextHelpFormatter give more control over how textual descriptions are displayed By default ArgumentParser objects line wrap the description and epilog texts in command line help messages parser argparse ArgumentParser prog PROG description this description was indented weird but that is okay epilog likewise for this epilog whose whitespace will be cleaned up and whose words will be wrapped across a couple lines parser print_help usage PROG h this descripti,en
235,on was indented weird but that is okay options h help show this help message and exit likewise for this epilog whose whitespace will be cleaned up and whose words will be wrapped across a couple lines Passing RawDescriptionHelpFormatter as formatter_class indicates that description and epilog are already correctly formatted and should not be line wrapped parser argparse ArgumentParser prog PROG formatter_class argparse RawDescriptionHelpFormatter description textwrap dedent Please do not mess up this text I have indented it exactly the way I want it parser print_help usage PROG h Please do not mess up this text I have indented it exactly the way I want it options h help show this help message and exit RawTextHelpFormatter maintains whitespace for all sorts of help text including argument descriptions However multiple new lines are replaced with one If you wish to preserve multiple blank lines add spaces between the newlines ArgumentDefaultsHelpFormatter automatically adds information about default values to each of the argument help messages parser argparse ArgumentParser prog PROG formatter_class argparse ArgumentDefaultsHelpFormatter parser add_argument foo type int default 42 help FOO parser add_argument bar nargs default 1 2 3 help BAR parser print_help usage PROG h foo FOO bar positional arguments bar BAR default 1 2 3 options h help show this help message and exit foo FOO FOO default 42 MetavarTypeHelpFormatter uses the name of the type argument for each argument as the display name for its values rather than using the dest as the regular formatter does parser argparse ArgumentParser prog PROG formatter_class argparse MetavarTypeHelpFormatter parser add_argument foo type int parser add_argument bar type float parser print_help usage PROG h foo int float positional arguments float options h help show this help message and exit foo int prefix_chars Most command line options will use as the prefix e g f foo Parsers that need to support different or additional prefix characters e g for options like f or foo may specify them using the prefix_chars argument to the ArgumentParser constructor parser argparse ArgumentParser prog PROG prefix_chars parser add_argument f parser add_argument bar parser parse_args f X bar Y split Namespace bar Y f X The prefix_chars argument defaults to Supplying a set of characters that does not include will cause f foo options to be disallowed fromfile_prefix_chars Sometimes when dealing with a particularly long argument list it may make sense to keep the list of arguments in a file rather than typing it out at the command line If the fromfile_prefix_chars argument is given to the ArgumentParser constructor then arguments that start with any of the specified characters will be treated as files and will be replaced by the arguments they contain For example with open args txt w encoding sys getfilesystemencoding as fp fp write f nbar parser argparse ArgumentParser fromfile_prefix_chars parser add_argument f parser parse_args f foo args txt Namespace f bar Arguments read from a file must by default be one per line but see also convert_arg_line_to_args and are treated as if they were in the same place as the original file referencing argument on the command line So in the example above the expression f foo args txt is considered equivalent to the expression f foo f bar ArgumentParser uses filesystem encoding and error handler to read the file containing arguments The fromfile_prefix_chars argument defaults to None meaning that arguments will never be treated as file references Changed in version 3 12 ArgumentParser changed encoding and errors to read arguments files from default e g locale getpreferredencoding False and strict to filesystem encoding and error handler Arguments file should be encoded in UTF 8 instead of ANSI Codepage on Windows argument_default Generally argument defaults are specified either by passing a default to add_argument or by calling the set_defaults methods with a specific set of name value pairs Sometimes however it may be useful to specify a single parser wide default f,en
236,or arguments This can be accomplished by passing the argument_default keyword argument to ArgumentParser For example to globally suppress attribute creation on parse_args calls we supply argument_default SUPPRESS parser argparse ArgumentParser argument_default argparse SUPPRESS parser add_argument foo parser add_argument bar nargs parser parse_args foo 1 BAR Namespace bar BAR foo 1 parser parse_args Namespace allow_abbrev Normally when you pass an argument list to the parse_args method of an ArgumentParser it recognizes abbreviations of long options This feature can be disabled by setting allow_abbrev to False parser argparse ArgumentParser prog PROG allow_abbrev False parser add_argument foobar action store_true parser add_argument foonley action store_false parser parse_args foon usage PROG h foobar foonley PROG error unrecognized arguments foon New in version 3 5 conflict_handler ArgumentParser objects do not allow two actions with the same option string By default ArgumentParser objects raise an exception if an attempt is made to create an argument with an option string that is already in use parser argparse ArgumentParser prog PROG parser add_argument f foo help old foo help parser add_argument foo help new foo help Traceback most recent call last ArgumentError argument foo conflicting option string s foo Sometimes e g when using parents it may be useful to simply override any older arguments with the same option string To get this behavior the value resolve can be supplied to the conflict_handler argument of ArgumentParser parser argparse ArgumentParser prog PROG conflict_handler resolve parser add_argument f foo help old foo help parser add_argument foo help new foo help parser print_help usage PROG h f FOO foo FOO options h help show this help message and exit f FOO old foo help foo FOO new foo help Note that ArgumentParser objects only remove an action if all of its option strings are overridden So in the example above the old f foo action is retained as the f action because only the foo option string was overridden add_help By default ArgumentParser objects add an option which simply displays the parser s help message For example consider a file named myprogram py containing the following code import argparse parser argparse ArgumentParser parser add_argument foo help foo help args parser parse_args If h or help is supplied at the command line the ArgumentParser help will be printed python myprogram py help usage myprogram py h foo FOO options h help show this help message and exit foo FOO foo help Occasionally it may be useful to disable the addition of this help option This can be achieved by passing False as the add_help argument to ArgumentParser parser argparse ArgumentParser prog PROG add_help False parser add_argument foo help foo help parser print_help usage PROG foo FOO options foo FOO foo help The help option is typically h help The exception to this is if the prefix_chars is specified and does not include in which case h and help are not valid options In this case the first character in prefix_chars is used to prefix the help options parser argparse ArgumentParser prog PROG prefix_chars parser print_help usage PROG h options h help show this help message and exit exit_on_error Normally when you pass an invalid argument list to the parse_args method of an ArgumentParser it will exit with error info If the user would like to catch errors manually the feature can be enabled by setting exit_on_error to False parser argparse ArgumentParser exit_on_error False parser add_argument integers type int _StoreAction option_strings integers dest integers nargs None const None default None type class int choices None help None metavar None try parser parse_args integers a split except argparse ArgumentError print Catching an argumentError Catching an argumentError New in version 3 9 The add_argument method ArgumentParser add_argument name or flags action nargs const default type choices required help metavar dest Define how a single command line argument should be parsed Each parameter has its own more detailed de,en
237,scription below but in short they are name or flags Either a name or a list of option strings e g foo or f foo action The basic type of action to be taken when this argument is encountered at the command line nargs The number of command line arguments that should be consumed const A constant value required by some action and nargs selections default The value produced if the argument is absent from the command line and if it is absent from the namespace object type The type to which the command line argument should be converted choices A sequence of the allowable values for the argument required Whether or not the command line option may be omitted optionals only help A brief description of what the argument does metavar A name for the argument in usage messages dest The name of the attribute to be added to the object returned by parse_args The following sections describe how each of these are used name or flags The add_argument method must know whether an optional argument like f or foo or a positional argument like a list of filenames is expected The first arguments passed to add_argument must therefore be either a series of flags or a simple argument name For example an optional argument could be created like parser add_argument f foo while a positional argument could be created like parser add_argument bar When parse_args is called optional arguments will be identified by the prefix and the remaining arguments will be assumed to be positional parser argparse ArgumentParser prog PROG parser add_argument f foo parser add_argument bar parser parse_args BAR Namespace bar BAR foo None parser parse_args BAR foo FOO Namespace bar BAR foo FOO parser parse_args foo FOO usage PROG h f FOO bar PROG error the following arguments are required bar action ArgumentParser objects associate command line arguments with actions These actions can do just about anything with the command line arguments associated with them though most actions simply add an attribute to the object returned by parse_args The action keyword argument specifies how the command line arguments should be handled The supplied actions are store This just stores the argument s value This is the default action For example parser argparse ArgumentParser parser add_argument foo parser parse_args foo 1 split Namespace foo 1 store_const This stores the value specified by the const keyword argument note that the const keyword argument defaults to None The store_const action is most commonly used with optional arguments that specify some sort of flag For example parser argparse ArgumentParser parser add_argument foo action store_const const 42 parser parse_args foo Namespace foo 42 store_true and store_false These are special cases of store_const used for storing the values True and False respectively In addition they create default values of False and True respectively For example parser argparse ArgumentParser parser add_argument foo action store_true parser add_argument bar action store_false parser add_argument baz action store_false parser parse_args foo bar split Namespace foo True bar False baz True append This stores a list and appends each argument value to the list It is useful to allow an option to be specified multiple times If the default value is non empty the default elements will be present in the parsed value for the option with any values from the command line appended after those default values Example usage parser argparse ArgumentParser parser add_argument foo action append parser parse_args foo 1 foo 2 split Namespace foo 1 2 append_const This stores a list and appends the value specified by the const keyword argument to the list note that the const keyword argument defaults to None The append_const action is typically useful when multiple arguments need to store constants to the same list For example parser argparse ArgumentParser parser add_argument str dest types action append_const const str parser add_argument int dest types action append_const const int parser parse_args str int split Namespace types class str class int count This counts the numb,en
238,er of times a keyword argument occurs For example this is useful for increasing verbosity levels parser argparse ArgumentParser parser add_argument verbose v action count default 0 parser parse_args vvv Namespace verbose 3 Note the default will be None unless explicitly set to 0 help This prints a complete help message for all the options in the current parser and then exits By default a help action is automatically added to the parser See ArgumentParser for details of how the output is created version This expects a version keyword argument in the add_argument call and prints version information and exits when invoked import argparse parser argparse ArgumentParser prog PROG parser add_argument version action version version prog s 2 0 parser parse_args version PROG 2 0 extend This stores a list and extends each argument value to the list Example usage parser argparse ArgumentParser parser add_argument foo action extend nargs type str parser parse_args foo f1 foo f2 f3 f4 Namespace foo f1 f2 f3 f4 New in version 3 8 You may also specify an arbitrary action by passing an Action subclass or other object that implements the same interface The BooleanOptionalAction is available in argparse and adds support for boolean actions such as foo and no foo import argparse parser argparse ArgumentParser parser add_argument foo action argparse BooleanOptionalAction parser parse_args no foo Namespace foo False New in version 3 9 The recommended way to create a custom action is to extend Action overriding the __call__ method and optionally the __init__ and format_usage methods An example of a custom action class FooAction argparse Action def __init__ self option_strings dest nargs None kwargs if nargs is not None raise ValueError nargs not allowed super __init__ option_strings dest kwargs def __call__ self parser namespace values option_string None print r r r namespace values option_string setattr namespace self dest values parser argparse ArgumentParser parser add_argument foo action FooAction parser add_argument bar action FooAction args parser parse_args 1 foo 2 split Namespace bar None foo None 1 None Namespace bar 1 foo None 2 foo args Namespace bar 1 foo 2 For more details see Action nargs ArgumentParser objects usually associate a single command line argument with a single action to be taken The nargs keyword argument associates a different number of command line arguments with a single action See also Specifying ambiguous arguments The supported values are N an integer N arguments from the command line will be gathered together into a list For example parser argparse ArgumentParser parser add_argument foo nargs 2 parser add_argument bar nargs 1 parser parse_args c foo a b split Namespace bar c foo a b Note that nargs 1 produces a list of one item This is different from the default in which the item is produced by itself One argument will be consumed from the command line if possible and produced as a single item If no command line argument is present the value from default will be produced Note that for optional arguments there is an additional case the option string is present but not followed by a command line argument In this case the value from const will be produced Some examples to illustrate this parser argparse ArgumentParser parser add_argument foo nargs const c default d parser add_argument bar nargs default d parser parse_args XX foo YY Namespace bar XX foo YY parser parse_args XX foo Namespace bar XX foo c parser parse_args Namespace bar d foo d One of the more common uses of nargs is to allow optional input and output files parser argparse ArgumentParser parser add_argument infile nargs type argparse FileType r default sys stdin parser add_argument outfile nargs type argparse FileType w default sys stdout parser parse_args input txt output txt Namespace infile _io TextIOWrapper name input txt encoding UTF 8 outfile _io TextIOWrapper name output txt encoding UTF 8 parser parse_args Namespace infile _io TextIOWrapper name stdin encoding UTF 8 outfile _io TextIOWrapper name stdout encoding UTF 8 All command line argum,en
239,ents present are gathered into a list Note that it generally doesn t make much sense to have more than one positional argument with nargs but multiple optional arguments with nargs is possible For example parser argparse ArgumentParser parser add_argument foo nargs parser add_argument bar nargs parser add_argument baz nargs parser parse_args a b foo x y bar 1 2 split Namespace bar 1 2 baz a b foo x y Just like all command line args present are gathered into a list Additionally an error message will be generated if there wasn t at least one command line argument present For example parser argparse ArgumentParser prog PROG parser add_argument foo nargs parser parse_args a b Namespace foo a b parser parse_args usage PROG h foo foo PROG error the following arguments are required foo If the nargs keyword argument is not provided the number of arguments consumed is determined by the action Generally this means a single command line argument will be consumed and a single item not a list will be produced const The const argument of add_argument is used to hold constant values that are not read from the command line but are required for the various ArgumentParser actions The two most common uses of it are When add_argument is called with action store_const or action append_const These actions add the const value to one of the attributes of the object returned by parse_args See the action description for examples If const is not provided to add_argument it will receive a default value of None When add_argument is called with option strings like f or foo and nargs This creates an optional argument that can be followed by zero or one command line arguments When parsing the command line if the option string is encountered with no command line argument following it the value of const will be assumed to be None instead See the nargs description for examples Changed in version 3 11 const None by default including when action append_const or action store_const default All optional arguments and some positional arguments may be omitted at the command line The default keyword argument of add_argument whose value defaults to None specifies what value should be used if the command line argument is not present For optional arguments the default value is used when the option string was not present at the command line parser argparse ArgumentParser parser add_argument foo default 42 parser parse_args foo 2 Namespace foo 2 parser parse_args Namespace foo 42 If the target namespace already has an attribute set the action default will not over write it parser argparse ArgumentParser parser add_argument foo default 42 parser parse_args namespace argparse Namespace foo 101 Namespace foo 101 If the default value is a string the parser parses the value as if it were a command line argument In particular the parser applies any type conversion argument if provided before setting the attribute on the Namespace return value Otherwise the parser uses the value as is parser argparse ArgumentParser parser add_argument length default 10 type int parser add_argument width default 10 5 type int parser parse_args Namespace length 10 width 10 5 For positional arguments with nargs equal to or the default value is used when no command line argument was present parser argparse ArgumentParser parser add_argument foo nargs default 42 parser parse_args a Namespace foo a parser parse_args Namespace foo 42 Providing default argparse SUPPRESS causes no attribute to be added if the command line argument was not present parser argparse ArgumentParser parser add_argument foo default argparse SUPPRESS parser parse_args Namespace parser parse_args foo 1 Namespace foo 1 type By default the parser reads command line arguments in as simple strings However quite often the command line string should instead be interpreted as another type such as a float or int The type keyword for add_argument allows any necessary type checking and type conversions to be performed If the type keyword is used with the default keyword the type converter is only applied if the default is a string The ,en
240,argument to type can be any callable that accepts a single string If the function raises ArgumentTypeError TypeError or ValueError the exception is caught and a nicely formatted error message is displayed No other exception types are handled Common built in types and functions can be used as type converters import argparse import pathlib parser argparse ArgumentParser parser add_argument count type int parser add_argument distance type float parser add_argument street type ascii parser add_argument code_point type ord parser add_argument source_file type open parser add_argument dest_file type argparse FileType w encoding latin 1 parser add_argument datapath type pathlib Path User defined functions can be used as well def hyphenated string return join word 4 for word in string casefold split parser argparse ArgumentParser _ parser add_argument short_title type hyphenated parser parse_args The Tale of Two Cities Namespace short_title the tale of two citi The bool function is not recommended as a type converter All it does is convert empty strings to False and non empty strings to True This is usually not what is desired In general the type keyword is a convenience that should only be used for simple conversions that can only raise one of the three supported exceptions Anything with more interesting error handling or resource management should be done downstream after the arguments are parsed For example JSON or YAML conversions have complex error cases that require better reporting than can be given by the type keyword A JSONDecodeError would not be well formatted and a FileNotFoundError exception would not be handled at all Even FileType has its limitations for use with the type keyword If one argument uses FileType and then a subsequent argument fails an error is reported but the file is not automatically closed In this case it would be better to wait until after the parser has run and then use the with statement to manage the files For type checkers that simply check against a fixed set of values consider using the choices keyword instead choices Some command line arguments should be selected from a restricted set of values These can be handled by passing a sequence object as the choices keyword argument to add_argument When the command line is parsed argument values will be checked and an error message will be displayed if the argument was not one of the acceptable values parser argparse ArgumentParser prog game py parser add_argument move choices rock paper scissors parser parse_args rock Namespace move rock parser parse_args fire usage game py h rock paper scissors game py error argument move invalid choice fire choose from rock paper scissors Note that inclusion in the choices sequence is checked after any type conversions have been performed so the type of the objects in the choices sequence should match the type specified parser argparse ArgumentParser prog doors py parser add_argument door type int choices range 1 4 print parser parse_args 3 Namespace door 3 parser parse_args 4 usage doors py h 1 2 3 doors py error argument door invalid choice 4 choose from 1 2 3 Any sequence can be passed as the choices value so list objects tuple objects and custom sequences are all supported Use of enum Enum is not recommended because it is difficult to control its appearance in usage help and error messages Formatted choices override the default metavar which is normally derived from dest This is usually what you want because the user never sees the dest parameter If this display isn t desirable perhaps because there are many choices just specify an explicit metavar required In general the argparse module assumes that flags like f and bar indicate optional arguments which can always be omitted at the command line To make an option required True can be specified for the required keyword argument to add_argument parser argparse ArgumentParser parser add_argument foo required True parser parse_args foo BAR Namespace foo BAR parser parse_args usage h foo FOO error the following arguments are required foo As the example shows if ,en
241,an option is marked as required parse_args will report an error if that option is not present at the command line Note Required options are generally considered bad form because users expect options to be optional and thus they should be avoided when possible help The help value is a string containing a brief description of the argument When a user requests help usually by using h or help at the command line these help descriptions will be displayed with each argument parser argparse ArgumentParser prog frobble parser add_argument foo action store_true help foo the bars before frobbling parser add_argument bar nargs help one of the bars to be frobbled parser parse_args h usage frobble h foo bar bar positional arguments bar one of the bars to be frobbled options h help show this help message and exit foo foo the bars before frobbling The help strings can include various format specifiers to avoid repetition of things like the program name or the argument default The available specifiers include the program name prog s and most keyword arguments to add_argument e g default s type s etc parser argparse ArgumentParser prog frobble parser add_argument bar nargs type int default 42 help the bar to prog s default default s parser print_help usage frobble h bar positional arguments bar the bar to frobble default 42 options h help show this help message and exit As the help string supports formatting if you want a literal to appear in the help string you must escape it as argparse supports silencing the help entry for certain options by setting the help value to argparse SUPPRESS parser argparse ArgumentParser prog frobble parser add_argument foo help argparse SUPPRESS parser print_help usage frobble h options h help show this help message and exit metavar When ArgumentParser generates help messages it needs some way to refer to each expected argument By default ArgumentParser objects use the dest value as the name of each object By default for positional argument actions the dest value is used directly and for optional argument actions the dest value is uppercased So a single positional argument with dest bar will be referred to as bar A single optional argument foo that should be followed by a single command line argument will be referred to as FOO An example parser argparse ArgumentParser parser add_argument foo parser add_argument bar parser parse_args X foo Y split Namespace bar X foo Y parser print_help usage h foo FOO bar positional arguments bar options h help show this help message and exit foo FOO An alternative name can be specified with metavar parser argparse ArgumentParser parser add_argument foo metavar YYY parser add_argument bar metavar XXX parser parse_args X foo Y split Namespace bar X foo Y parser print_help usage h foo YYY XXX positional arguments XXX options h help show this help message and exit foo YYY Note that metavar only changes the displayed name the name of the attribute on the parse_args object is still determined by the dest value Different values of nargs may cause the metavar to be used multiple times Providing a tuple to metavar specifies a different display for each of the arguments parser argparse ArgumentParser prog PROG parser add_argument x nargs 2 parser add_argument foo nargs 2 metavar bar baz parser print_help usage PROG h x X X foo bar baz options h help show this help message and exit x X X foo bar baz dest Most ArgumentParser actions add some value as an attribute of the object returned by parse_args The name of this attribute is determined by the dest keyword argument of add_argument For positional argument actions dest is normally supplied as the first argument to add_argument parser argparse ArgumentParser parser add_argument bar parser parse_args XXX Namespace bar XXX For optional argument actions the value of dest is normally inferred from the option strings ArgumentParser generates the value of dest by taking the first long option string and stripping away the initial string If no long option strings were supplied dest will be derived from the first short option string by stripp,en
242,ing the initial character Any internal characters will be converted to _ characters to make sure the string is a valid attribute name The examples below illustrate this behavior parser argparse ArgumentParser parser add_argument f foo bar foo parser add_argument x y parser parse_args f 1 x 2 split Namespace foo_bar 1 x 2 parser parse_args foo 1 y 2 split Namespace foo_bar 1 x 2 dest allows a custom attribute name to be provided parser argparse ArgumentParser parser add_argument foo dest bar parser parse_args foo XXX split Namespace bar XXX Action classes Action classes implement the Action API a callable which returns a callable which processes arguments from the command line Any object which follows this API may be passed as the action parameter to add_argument class argparse Action option_strings dest nargs None const None default None type None choices None required False help None metavar None Action objects are used by an ArgumentParser to represent the information needed to parse a single argument from one or more strings from the command line The Action class must accept the two positional arguments plus any keyword arguments passed to ArgumentParser add_argument except for the action itself Instances of Action or return value of any callable to the action parameter should have attributes dest option_strings default type required help etc defined The easiest way to ensure these attributes are defined is to call Action __init__ Action instances should be callable so subclasses must override the __call__ method which should accept four parameters parser The ArgumentParser object which contains this action namespace The Namespace object that will be returned by parse_args Most actions add an attribute to this object using setattr values The associated command line arguments with any type conversions applied Type conversions are specified with the type keyword argument to add_argument option_string The option string that was used to invoke this action The option_string argument is optional and will be absent if the action is associated with a positional argument The __call__ method may perform arbitrary actions but will typically set attributes on the namespace based on dest and values Action subclasses can define a format_usage method that takes no argument and return a string which will be used when printing the usage of the program If such method is not provided a sensible default will be used The parse_args method ArgumentParser parse_args args None namespace None Convert argument strings to objects and assign them as attributes of the namespace Return the populated namespace Previous calls to add_argument determine exactly what objects are created and how they are assigned See the documentation for add_argument for details args List of strings to parse The default is taken from sys argv namespace An object to take the attributes The default is a new empty Namespace object Option value syntax The parse_args method supports several ways of specifying the value of an option if it takes one In the simplest case the option and its value are passed as two separate arguments parser argparse ArgumentParser prog PROG parser add_argument x parser add_argument foo parser parse_args x X Namespace foo None x X parser parse_args foo FOO Namespace foo FOO x None For long options options with names longer than a single character the option and value can also be passed as a single command line argument using to separate them parser parse_args foo FOO Namespace foo FOO x None For short options options only one character long the option and its value can be concatenated parser parse_args xX Namespace foo None x X Several short options can be joined together using only a single prefix as long as only the last option or none of them requires a value parser argparse ArgumentParser prog PROG parser add_argument x action store_true parser add_argument y action store_true parser add_argument z parser parse_args xyzZ Namespace x True y True z Z Invalid arguments While parsing the command line parse_args checks for a variety of errors incl,en
243,uding ambiguous options invalid types invalid options wrong number of positional arguments etc When it encounters such an error it exits and prints the error along with a usage message parser argparse ArgumentParser prog PROG parser add_argument foo type int parser add_argument bar nargs invalid type parser parse_args foo spam usage PROG h foo FOO bar PROG error argument foo invalid int value spam invalid option parser parse_args bar usage PROG h foo FOO bar PROG error no such option bar wrong number of arguments parser parse_args spam badger usage PROG h foo FOO bar PROG error extra arguments found badger Arguments containing The parse_args method attempts to give errors whenever the user has clearly made a mistake but some situations are inherently ambiguous For example the command line argument 1 could either be an attempt to specify an option or an attempt to provide a positional argument The parse_args method is cautious here positional arguments may only begin with if they look like negative numbers and there are no options in the parser that look like negative numbers parser argparse ArgumentParser prog PROG parser add_argument x parser add_argument foo nargs no negative number options so 1 is a positional argument parser parse_args x 1 Namespace foo None x 1 no negative number options so 1 and 5 are positional arguments parser parse_args x 1 5 Namespace foo 5 x 1 parser argparse ArgumentParser prog PROG parser add_argument 1 dest one parser add_argument foo nargs negative number options present so 1 is an option parser parse_args 1 X Namespace foo None one X negative number options present so 2 is an option parser parse_args 2 usage PROG h 1 ONE foo PROG error no such option 2 negative number options present so both 1s are options parser parse_args 1 1 usage PROG h 1 ONE foo PROG error argument 1 expected one argument If you have positional arguments that must begin with and don t look like negative numbers you can insert the pseudo argument which tells parse_args that everything after that is a positional argument parser parse_args f Namespace foo f one None See also the argparse howto on ambiguous arguments for more details Argument abbreviations prefix matching The parse_args method by default allows long options to be abbreviated to a prefix if the abbreviation is unambiguous the prefix matches a unique option parser argparse ArgumentParser prog PROG parser add_argument bacon parser add_argument badger parser parse_args bac MMM split Namespace bacon MMM badger None parser parse_args bad WOOD split Namespace bacon None badger WOOD parser parse_args ba BA split usage PROG h bacon BACON badger BADGER PROG error ambiguous option ba could match badger bacon An error is produced for arguments that could produce more than one options This feature can be disabled by setting allow_abbrev to False Beyond sys argv Sometimes it may be useful to have an ArgumentParser parse arguments other than those of sys argv This can be accomplished by passing a list of strings to parse_args This is useful for testing at the interactive prompt parser argparse ArgumentParser parser add_argument integers metavar int type int choices range 10 nargs help an integer in the range 0 9 parser add_argument sum dest accumulate action store_const const sum default max help sum the integers default find the max parser parse_args 1 2 3 4 Namespace accumulate built in function max integers 1 2 3 4 parser parse_args 1 2 3 4 sum Namespace accumulate built in function sum integers 1 2 3 4 The Namespace object class argparse Namespace Simple class used by default by parse_args to create an object holding attributes and return it This class is deliberately simple just an object subclass with a readable string representation If you prefer to have dict like view of the attributes you can use the standard Python idiom vars parser argparse ArgumentParser parser add_argument foo args parser parse_args foo BAR vars args foo BAR It may also be useful to have an ArgumentParser assign attributes to an already existing object rather than a new Namespace object Th,en
244,is can be achieved by specifying the namespace keyword argument class C pass c C parser argparse ArgumentParser parser add_argument foo parser parse_args args foo BAR namespace c c foo BAR Other utilities Sub commands ArgumentParser add_subparsers title description prog parser_class action option_strings dest required help metavar Many programs split up their functionality into a number of sub commands for example the svn program can invoke sub commands like svn checkout svn update and svn commit Splitting up functionality this way can be a particularly good idea when a program performs several different functions which require different kinds of command line arguments ArgumentParser supports the creation of such sub commands with the add_subparsers method The add_subparsers method is normally called with no arguments and returns a special action object This object has a single method add_parser which takes a command name and any ArgumentParser constructor arguments and returns an ArgumentParser object that can be modified as usual Description of parameters title title for the sub parser group in help output by default subcommands if description is provided otherwise uses title for positional arguments description description for the sub parser group in help output by default None prog usage information that will be displayed with sub command help by default the name of the program and any positional arguments before the subparser argument parser_class class which will be used to create sub parser instances by default the class of the current parser e g ArgumentParser action the basic type of action to be taken when this argument is encountered at the command line dest name of the attribute under which sub command name will be stored by default None and no value is stored required Whether or not a subcommand must be provided by default False added in 3 7 help help for sub parser group in help output by default None metavar string presenting available sub commands in help by default it is None and presents sub commands in form cmd1 cmd2 Some example usage create the top level parser parser argparse ArgumentParser prog PROG parser add_argument foo action store_true help foo help subparsers parser add_subparsers help sub command help create the parser for the a command parser_a subparsers add_parser a help a help parser_a add_argument bar type int help bar help create the parser for the b command parser_b subparsers add_parser b help b help parser_b add_argument baz choices XYZ help baz help parse some argument lists parser parse_args a 12 Namespace bar 12 foo False parser parse_args foo b baz Z Namespace baz Z foo True Note that the object returned by parse_args will only contain attributes for the main parser and the subparser that was selected by the command line and not any other subparsers So in the example above when the a command is specified only the foo and bar attributes are present and when the b command is specified only the foo and baz attributes are present Similarly when a help message is requested from a subparser only the help for that particular parser will be printed The help message will not include parent parser or sibling parser messages A help message for each subparser command however can be given by supplying the help argument to add_parser as above parser parse_args help usage PROG h foo a b positional arguments a b sub command help a a help b b help options h help show this help message and exit foo foo help parser parse_args a help usage PROG a h bar positional arguments bar bar help options h help show this help message and exit parser parse_args b help usage PROG b h baz X Y Z options h help show this help message and exit baz X Y Z baz help The add_subparsers method also supports title and description keyword arguments When either is present the subparser s commands will appear in their own group in the help output For example parser argparse ArgumentParser subparsers parser add_subparsers title subcommands description valid subcommands help additional help subparsers add_parser foo subparsers,en
245, add_parser bar parser parse_args h usage h foo bar options h help show this help message and exit subcommands valid subcommands foo bar additional help Furthermore add_parser supports an additional aliases argument which allows multiple strings to refer to the same subparser This example like svn aliases co as a shorthand for checkout parser argparse ArgumentParser subparsers parser add_subparsers checkout subparsers add_parser checkout aliases co checkout add_argument foo parser parse_args co bar Namespace foo bar One particularly effective way of handling sub commands is to combine the use of the add_subparsers method with calls to set_defaults so that each subparser knows which Python function it should execute For example sub command functions def foo args print args x args y def bar args print s args z create the top level parser parser argparse ArgumentParser subparsers parser add_subparsers required True create the parser for the foo command parser_foo subparsers add_parser foo parser_foo add_argument x type int default 1 parser_foo add_argument y type float parser_foo set_defaults func foo create the parser for the bar command parser_bar subparsers add_parser bar parser_bar add_argument z parser_bar set_defaults func bar parse the args and call whatever function was selected args parser parse_args foo 1 x 2 split args func args 2 0 parse the args and call whatever function was selected args parser parse_args bar XYZYX split args func args XYZYX This way you can let parse_args do the job of calling the appropriate function after argument parsing is complete Associating functions with actions like this is typically the easiest way to handle the different actions for each of your subparsers However if it is necessary to check the name of the subparser that was invoked the dest keyword argument to the add_subparsers call will work parser argparse ArgumentParser subparsers parser add_subparsers dest subparser_name subparser1 subparsers add_parser 1 subparser1 add_argument x subparser2 subparsers add_parser 2 subparser2 add_argument y parser parse_args 2 frobble Namespace subparser_name 2 y frobble Changed in version 3 7 New required keyword argument FileType objects class argparse FileType mode r bufsize 1 encoding None errors None The FileType factory creates objects that can be passed to the type argument of ArgumentParser add_argument Arguments that have FileType objects as their type will open command line arguments as files with the requested modes buffer sizes encodings and error handling see the open function for more details parser argparse ArgumentParser parser add_argument raw type argparse FileType wb 0 parser add_argument out type argparse FileType w encoding UTF 8 parser parse_args raw raw dat file txt Namespace out _io TextIOWrapper name file txt mode w encoding UTF 8 raw _io FileIO name raw dat mode wb FileType objects understand the pseudo argument and automatically convert this into sys stdin for readable FileType objects and sys stdout for writable FileType objects parser argparse ArgumentParser parser add_argument infile type argparse FileType r parser parse_args Namespace infile _io TextIOWrapper name stdin encoding UTF 8 Changed in version 3 4 Added the encodings and errors parameters Argument groups ArgumentParser add_argument_group title None description None By default ArgumentParser groups command line arguments into positional arguments and options when displaying help messages When there is a better conceptual grouping of arguments than this default one appropriate groups can be created using the add_argument_group method parser argparse ArgumentParser prog PROG add_help False group parser add_argument_group group group add_argument foo help foo help group add_argument bar help bar help parser print_help usage PROG foo FOO bar group bar bar help foo FOO foo help The add_argument_group method returns an argument group object which has an add_argument method just like a regular ArgumentParser When an argument is added to the group the parser treats it just like a normal argument but displays ,en
246,the argument in a separate group for help messages The add_argument_group method accepts title and description arguments which can be used to customize this display parser argparse ArgumentParser prog PROG add_help False group1 parser add_argument_group group1 group1 description group1 add_argument foo help foo help group2 parser add_argument_group group2 group2 description group2 add_argument bar help bar help parser print_help usage PROG bar BAR foo group1 group1 description foo foo help group2 group2 description bar BAR bar help Note that any arguments not in your user defined groups will end up back in the usual positional arguments and optional arguments sections Changed in version 3 11 Calling add_argument_group on an argument group is deprecated This feature was never supported and does not always work correctly The function exists on the API by accident through inheritance and will be removed in the future Mutual exclusion ArgumentParser add_mutually_exclusive_group required False Create a mutually exclusive group argparse will make sure that only one of the arguments in the mutually exclusive group was present on the command line parser argparse ArgumentParser prog PROG group parser add_mutually_exclusive_group group add_argument foo action store_true group add_argument bar action store_false parser parse_args foo Namespace bar True foo True parser parse_args bar Namespace bar False foo False parser parse_args foo bar usage PROG h foo bar PROG error argument bar not allowed with argument foo The add_mutually_exclusive_group method also accepts a required argument to indicate that at least one of the mutually exclusive arguments is required parser argparse ArgumentParser prog PROG group parser add_mutually_exclusive_group required True group add_argument foo action store_true group add_argument bar action store_false parser parse_args usage PROG h foo bar PROG error one of the arguments foo bar is required Note that currently mutually exclusive argument groups do not support the title and description arguments of add_argument_group However a mutually exclusive group can be added to an argument group that has a title and description For example parser argparse ArgumentParser prog PROG group parser add_argument_group Group title Group description exclusive_group group add_mutually_exclusive_group required True exclusive_group add_argument foo help foo help exclusive_group add_argument bar help bar help parser print_help usage PROG h foo FOO bar BAR options h help show this help message and exit Group title Group description foo FOO foo help bar BAR bar help Changed in version 3 11 Calling add_argument_group or add_mutually_exclusive_group on a mutually exclusive group is deprecated These features were never supported and do not always work correctly The functions exist on the API by accident through inheritance and will be removed in the future Parser defaults ArgumentParser set_defaults kwargs Most of the time the attributes of the object returned by parse_args will be fully determined by inspecting the command line arguments and the argument actions set_defaults allows some additional attributes that are determined without any inspection of the command line to be added parser argparse ArgumentParser parser add_argument foo type int parser set_defaults bar 42 baz badger parser parse_args 736 Namespace bar 42 baz badger foo 736 Note that parser level defaults always override argument level defaults parser argparse ArgumentParser parser add_argument foo default bar parser set_defaults foo spam parser parse_args Namespace foo spam Parser level defaults can be particularly useful when working with multiple parsers See the add_subparsers method for an example of this type ArgumentParser get_default dest Get the default value for a namespace attribute as set by either add_argument or by set_defaults parser argparse ArgumentParser parser add_argument foo default badger parser get_default foo badger Printing help In most typical applications parse_args will take care of formatting and printing any usage or error messages ,en
247,However several formatting methods are available ArgumentParser print_usage file None Print a brief description of how the ArgumentParser should be invoked on the command line If file is None sys stdout is assumed ArgumentParser print_help file None Print a help message including the program usage and information about the arguments registered with the ArgumentParser If file is None sys stdout is assumed There are also variants of these methods that simply return a string instead of printing it ArgumentParser format_usage Return a string containing a brief description of how the ArgumentParser should be invoked on the command line ArgumentParser format_help Return a string containing a help message including the program usage and information about the arguments registered with the ArgumentParser Partial parsing ArgumentParser parse_known_args args None namespace None Sometimes a script may only parse a few of the command line arguments passing the remaining arguments on to another script or program In these cases the parse_known_args method can be useful It works much like parse_args except that it does not produce an error when extra arguments are present Instead it returns a two item tuple containing the populated namespace and the list of remaining argument strings parser argparse ArgumentParser parser add_argument foo action store_true parser add_argument bar parser parse_known_args foo badger BAR spam Namespace bar BAR foo True badger spam Warning Prefix matching rules apply to parse_known_args The parser may consume an option even if it s just a prefix of one of its known options instead of leaving it in the remaining arguments list Customizing file parsing ArgumentParser convert_arg_line_to_args arg_line Arguments that are read from a file see the fromfile_prefix_chars keyword argument to the ArgumentParser constructor are read one argument per line convert_arg_line_to_args can be overridden for fancier reading This method takes a single argument arg_line which is a string read from the argument file It returns a list of arguments parsed from this string The method is called once per line read from the argument file in order A useful override of this method is one that treats each space separated word as an argument The following example demonstrates how to do this class MyArgumentParser argparse ArgumentParser def convert_arg_line_to_args self arg_line return arg_line split Exiting methods ArgumentParser exit status 0 message None This method terminates the program exiting with the specified status and if given it prints a message before that The user can override this method to handle these steps differently class ErrorCatchingArgumentParser argparse ArgumentParser def exit self status 0 message None if status raise Exception f Exiting because of an error message exit status ArgumentParser error message This method prints a usage message including the message to the standard error and terminates the program with a status code of 2 Intermixed parsing ArgumentParser parse_intermixed_args args None namespace None ArgumentParser parse_known_intermixed_args args None namespace None A number of Unix commands allow the user to intermix optional arguments with positional arguments The parse_intermixed_args and parse_known_intermixed_args methods support this parsing style These parsers do not support all the argparse features and will raise exceptions if unsupported features are used In particular subparsers and mutually exclusive groups that include both optionals and positionals are not supported The following example shows the difference between parse_known_args and parse_intermixed_args the former returns 2 3 as unparsed arguments while the latter collects all the positionals into rest parser argparse ArgumentParser parser add_argument foo parser add_argument cmd parser add_argument rest nargs type int parser parse_known_args doit 1 foo bar 2 3 split Namespace cmd doit foo bar rest 1 2 3 parser parse_intermixed_args doit 1 foo bar 2 3 split Namespace cmd doit foo bar rest 1 2 3 parse_known_intermixed_args returns a ,en
248,two item tuple containing the populated namespace and the list of remaining argument strings parse_intermixed_args raises an error if there are any remaining unparsed argument strings New in version 3 7 Upgrading optparse code Originally the argparse module had attempted to maintain compatibility with optparse However optparse was difficult to extend transparently particularly with the changes required to support the new nargs specifiers and better usage messages When most everything in optparse had either been copy pasted over or monkey patched it no longer seemed practical to try to maintain the backwards compatibility The argparse module improves on the standard library optparse module in a number of ways including Handling positional arguments Supporting sub commands Allowing alternative option prefixes like and Handling zero or more and one or more style arguments Producing more informative usage messages Providing a much simpler interface for custom type and action A partial upgrade path from optparse to argparse Replace all optparse OptionParser add_option calls with ArgumentParser add_argument calls Replace options args parser parse_args with args parser parse_args and add additional ArgumentParser add_argument calls for the positional arguments Keep in mind that what was previously called options now in the argparse context is called args Replace optparse OptionParser disable_interspersed_args by using parse_intermixed_args instead of parse_args Replace callback actions and the callback_ keyword arguments with type or action arguments Replace string names for type keyword arguments with the corresponding type objects e g int float complex etc Replace optparse Values with Namespace and optparse OptionError and optparse OptionValueError with ArgumentError Replace strings with implicit arguments such as default or prog with the standard Python syntax to use dictionaries to format strings that is default s and prog s Replace the OptionParser constructor version argument with a call to parser add_argument version action version version the version Exceptions exception argparse ArgumentError An error from creating or using an argument optional or positional The string value of this exception is the message augmented with information about the argument that caused it exception argparse ArgumentTypeError Raised when something goes wrong converting a command line string to a type,en
249,mmap Memory mapped file support Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information Memory mapped file objects behave like both bytearray and like file objects You can use mmap objects in most places where bytearray are expected for example you can use the re module to search through a memory mapped file You can also change a single byte by doing obj index 97 or change a subsequence by assigning to a slice obj i1 i2 b You can also read and write data starting at the current file position and seek through the file to different positions A memory mapped file is created by the mmap constructor which is different on Unix and on Windows In either case you must provide a file descriptor for a file opened for update If you wish to map an existing Python file object use its fileno method to obtain the correct value for the fileno parameter Otherwise you can open the file using the os open function which returns a file descriptor directly the file still needs to be closed when done Note If you want to create a memory mapping for a writable buffered file you should flush the file first This is necessary to ensure that local modifications to the buffers are actually available to the mapping For both the Unix and Windows versions of the constructor access may be specified as an optional keyword parameter access accepts one of four values ACCESS_READ ACCESS_WRITE or ACCESS_COPY to specify read only write through or copy on write memory respectively or ACCESS_DEFAULT to defer to prot access can be used on both Unix and Windows If access is not specified Windows mmap returns a write through mapping The initial memory values for all three access types are taken from the specified file Assignment to an ACCESS_READ memory map raises a TypeError exception Assignment to an ACCESS_WRITE memory map affects both memory and the underlying file Assignment to an ACCESS_COPY memory map affects memory but does not update the underlying file Changed in version 3 7 Added ACCESS_DEFAULT constant To map anonymous memory 1 should be passed as the fileno along with the length class mmap mmap fileno length tagname None access ACCESS_DEFAULT offset Windows version Maps length bytes from the file specified by the file handle fileno and creates a mmap object If length is larger than the current size of the file the file is extended to contain length bytes If length is 0 the maximum length of the map is the current size of the file except that if the file is empty Windows raises an exception you cannot create an empty mapping on Windows tagname if specified and not None is a string giving a tag name for the mapping Windows allows you to have many different mappings against the same file If you specify the name of an existing tag that tag is opened otherwise a new tag of this name is created If this parameter is omitted or None the mapping is created without a name Avoiding the use of the tagname parameter will assist in keeping your code portable between Unix and Windows offset may be specified as a non negative integer offset mmap references will be relative to the offset from the beginning of the file offset defaults to 0 offset must be a multiple of the ALLOCATIONGRANULARITY Raises an auditing event mmap __new__ with arguments fileno length access offset class mmap mmap fileno length flags MAP_SHARED prot PROT_WRITE PROT_READ access ACCESS_DEFAULT offset Unix version Maps length bytes from the file specified by the file descriptor fileno and returns a mmap object If length is 0 the maximum length of the map will be the current size of the file when mmap is called flags specifies the nature of the mapping MAP_PRIVATE creates a private copy on write mapping so changes to the contents of the mmap object will be private to this process and MAP_SHARED creates a mapping that s shared with all other processes mapping the same areas of the file The default value is MAP_SHARED Some systems have additional possible flags with the f,en
250,ull list specified in MAP_ constants prot if specified gives the desired memory protection the two most useful values are PROT_READ and PROT_WRITE to specify that the pages may be read or written prot defaults to PROT_READ PROT_WRITE access may be specified in lieu of flags and prot as an optional keyword parameter It is an error to specify both flags prot and access See the description of access above for information on how to use this parameter offset may be specified as a non negative integer offset mmap references will be relative to the offset from the beginning of the file offset defaults to 0 offset must be a multiple of ALLOCATIONGRANULARITY which is equal to PAGESIZE on Unix systems To ensure validity of the created memory mapping the file specified by the descriptor fileno is internally automatically synchronized with the physical backing store on macOS This example shows a simple way of using mmap import mmap write a simple example file with open hello txt wb as f f write b Hello Python n with open hello txt r b as f memory map the file size 0 means whole file mm mmap mmap f fileno 0 read content via standard file methods print mm readline prints b Hello Python n read content via slice notation print mm 5 prints b Hello update content using slice notation note that new content must have same size mm 6 b world n and read again using standard file methods mm seek 0 print mm readline prints b Hello world n close the map mm close mmap can also be used as a context manager in a with statement import mmap with mmap mmap 1 13 as mm mm write b Hello world New in version 3 2 Context manager support The next example demonstrates how to create an anonymous map and exchange data between the parent and child processes import mmap import os mm mmap mmap 1 13 mm write b Hello world pid os fork if pid 0 In a child process mm seek 0 print mm readline mm close Raises an auditing event mmap __new__ with arguments fileno length access offset Memory mapped file objects support the following methods close Closes the mmap Subsequent calls to other methods of the object will result in a ValueError exception being raised This will not close the open file closed True if the file is closed New in version 3 2 find sub start end Returns the lowest index in the object where the subsequence sub is found such that sub is contained in the range start end Optional arguments start and end are interpreted as in slice notation Returns 1 on failure Changed in version 3 5 Writable bytes like object is now accepted flush offset size Flushes changes made to the in memory copy of a file back to disk Without use of this call there is no guarantee that changes are written back before the object is destroyed If offset and size are specified only changes to the given range of bytes will be flushed to disk otherwise the whole extent of the mapping is flushed offset must be a multiple of the PAGESIZE or ALLOCATIONGRANULARITY None is returned to indicate success An exception is raised when the call failed Changed in version 3 8 Previously a nonzero value was returned on success zero was returned on error under Windows A zero value was returned on success an exception was raised on error under Unix madvise option start length Send advice option to the kernel about the memory region beginning at start and extending length bytes option must be one of the MADV_ constants available on the system If start and length are omitted the entire mapping is spanned On some systems including Linux start must be a multiple of the PAGESIZE Availability Systems with the madvise system call New in version 3 8 move dest src count Copy the count bytes starting at offset src to the destination index dest If the mmap was created with ACCESS_READ then calls to move will raise a TypeError exception read n Return a bytes containing up to n bytes starting from the current file position If the argument is omitted None or negative return all bytes from the current file position to the end of the mapping The file position is updated to point after the bytes that were returned Changed in ,en
251,version 3 3 Argument can be omitted or None read_byte Returns a byte at the current file position as an integer and advances the file position by 1 readline Returns a single line starting at the current file position and up to the next newline The file position is updated to point after the bytes that were returned resize newsize Resizes the map and the underlying file if any If the mmap was created with ACCESS_READ or ACCESS_COPY resizing the map will raise a TypeError exception On Windows Resizing the map will raise an OSError if there are other maps against the same named file Resizing an anonymous map ie against the pagefile will silently create a new map with the original data copied over up to the length of the new size Changed in version 3 11 Correctly fails if attempting to resize when another map is held Allows resize against an anonymous map on Windows rfind sub start end Returns the highest index in the object where the subsequence sub is found such that sub is contained in the range start end Optional arguments start and end are interpreted as in slice notation Returns 1 on failure Changed in version 3 5 Writable bytes like object is now accepted seek pos whence Set the file s current position whence argument is optional and defaults to os SEEK_SET or 0 absolute file positioning other values are os SEEK_CUR or 1 seek relative to the current position and os SEEK_END or 2 seek relative to the file s end size Return the length of the file which can be larger than the size of the memory mapped area tell Returns the current position of the file pointer write bytes Write the bytes in bytes into memory at the current position of the file pointer and return the number of bytes written never less than len bytes since if the write fails a ValueError will be raised The file position is updated to point after the bytes that were written If the mmap was created with ACCESS_READ then writing to it will raise a TypeError exception Changed in version 3 5 Writable bytes like object is now accepted Changed in version 3 6 The number of bytes written is now returned write_byte byte Write the integer byte into memory at the current position of the file pointer the file position is advanced by 1 If the mmap was created with ACCESS_READ then writing to it will raise a TypeError exception MADV_ Constants mmap MADV_NORMAL mmap MADV_RANDOM mmap MADV_SEQUENTIAL mmap MADV_WILLNEED mmap MADV_DONTNEED mmap MADV_REMOVE mmap MADV_DONTFORK mmap MADV_DOFORK mmap MADV_HWPOISON mmap MADV_MERGEABLE mmap MADV_UNMERGEABLE mmap MADV_SOFT_OFFLINE mmap MADV_HUGEPAGE mmap MADV_NOHUGEPAGE mmap MADV_DONTDUMP mmap MADV_DODUMP mmap MADV_FREE mmap MADV_NOSYNC mmap MADV_AUTOSYNC mmap MADV_NOCORE mmap MADV_CORE mmap MADV_PROTECT mmap MADV_FREE_REUSABLE mmap MADV_FREE_REUSE These options can be passed to mmap madvise Not every option will be present on every system Availability Systems with the madvise system call New in version 3 8 MAP_ Constants mmap MAP_SHARED mmap MAP_PRIVATE mmap MAP_DENYWRITE mmap MAP_EXECUTABLE mmap MAP_ANON mmap MAP_ANONYMOUS mmap MAP_POPULATE mmap MAP_STACK mmap MAP_ALIGNED_SUPER mmap MAP_CONCEAL These are the various flags that can be passed to mmap mmap MAP_ALIGNED_SUPER is only available at FreeBSD and MAP_CONCEAL is only available at OpenBSD Note that some options might not be present on some systems Changed in version 3 10 Added MAP_POPULATE constant New in version 3 11 Added MAP_STACK constant New in version 3 12 Added MAP_ALIGNED_SUPER constant Added MAP_CONCEAL constant,en
252,ast Abstract Syntax Trees Source code Lib ast py The ast module helps Python applications to process trees of the Python abstract syntax grammar The abstract syntax itself might change with each Python release this module helps to find out programmatically what the current grammar looks like An abstract syntax tree can be generated by passing ast PyCF_ONLY_AST as a flag to the compile built in function or using the parse helper provided in this module The result will be a tree of objects whose classes all inherit from ast AST An abstract syntax tree can be compiled into a Python code object using the built in compile function Abstract Grammar The abstract grammar is currently defined as follows ASDL s 4 builtin types are identifier int string constant module Python mod Module stmt body type_ignore type_ignores Interactive stmt body Expression expr body FunctionType expr argtypes expr returns stmt FunctionDef identifier name arguments args stmt body expr decorator_list expr returns string type_comment type_param type_params AsyncFunctionDef identifier name arguments args stmt body expr decorator_list expr returns string type_comment type_param type_params ClassDef identifier name expr bases keyword keywords stmt body expr decorator_list type_param type_params Return expr value Delete expr targets Assign expr targets expr value string type_comment TypeAlias expr name type_param type_params expr value AugAssign expr target operator op expr value simple indicates that we annotate simple name without parens AnnAssign expr target expr annotation expr value int simple use orelse because else is a keyword in target languages For expr target expr iter stmt body stmt orelse string type_comment AsyncFor expr target expr iter stmt body stmt orelse string type_comment While expr test stmt body stmt orelse If expr test stmt body stmt orelse With withitem items stmt body string type_comment AsyncWith withitem items stmt body string type_comment Match expr subject match_case cases Raise expr exc expr cause Try stmt body excepthandler handlers stmt orelse stmt finalbody TryStar stmt body excepthandler handlers stmt orelse stmt finalbody Assert expr test expr msg Import alias names ImportFrom identifier module alias names int level Global identifier names Nonlocal identifier names Expr expr value Pass Break Continue col_offset is the byte offset in the utf8 string the parser uses attributes int lineno int col_offset int end_lineno int end_col_offset BoolOp can use left right expr BoolOp boolop op expr values NamedExpr expr target expr value BinOp expr left operator op expr right UnaryOp unaryop op expr operand Lambda arguments args expr body IfExp expr test expr body expr orelse Dict expr keys expr values Set expr elts ListComp expr elt comprehension generators SetComp expr elt comprehension generators DictComp expr key expr value comprehension generators GeneratorExp expr elt comprehension generators the grammar constrains where yield expressions can occur Await expr value Yield expr value YieldFrom expr value need sequences for compare to distinguish between x 4 3 and x 4 3 Compare expr left cmpop ops expr comparators Call expr func expr args keyword keywords FormattedValue expr value int conversion expr format_spec JoinedStr expr values Constant constant value string kind the following expression can appear in assignment context Attribute expr value identifier attr expr_context ctx Subscript expr value expr slice expr_context ctx Starred expr value expr_context ctx Name identifier id expr_context ctx List expr elts expr_context ctx Tuple expr elts expr_context ctx can appear only in Subscript Slice expr lower expr upper expr step col_offset is the byte offset in the utf8 string the parser uses attributes int lineno int col_offset int end_lineno int end_col_offset expr_context Load Store Del boolop And Or operator Add Sub Mult MatMult Div Mod Pow LShift RShift BitOr BitXor BitAnd FloorDiv unaryop Invert Not UAdd USub cmpop Eq NotEq Lt LtE Gt GtE Is IsNot In NotIn comprehension expr target expr iter expr ifs int is_async excepthandler Ex,en
253,ceptHandler expr type identifier name stmt body attributes int lineno int col_offset int end_lineno int end_col_offset arguments arg posonlyargs arg args arg vararg arg kwonlyargs expr kw_defaults arg kwarg expr defaults arg identifier arg expr annotation string type_comment attributes int lineno int col_offset int end_lineno int end_col_offset keyword arguments supplied to call NULL identifier for kwargs keyword identifier arg expr value attributes int lineno int col_offset int end_lineno int end_col_offset import name with optional as alias alias identifier name identifier asname attributes int lineno int col_offset int end_lineno int end_col_offset withitem expr context_expr expr optional_vars match_case pattern pattern expr guard stmt body pattern MatchValue expr value MatchSingleton constant value MatchSequence pattern patterns MatchMapping expr keys pattern patterns identifier rest MatchClass expr cls pattern patterns identifier kwd_attrs pattern kwd_patterns MatchStar identifier name The optional rest MatchMapping parameter handles capturing extra mapping keys MatchAs pattern pattern identifier name MatchOr pattern patterns attributes int lineno int col_offset int end_lineno int end_col_offset type_ignore TypeIgnore int lineno string tag type_param TypeVar identifier name expr bound ParamSpec identifier name TypeVarTuple identifier name attributes int lineno int col_offset int end_lineno int end_col_offset Node classes class ast AST This is the base of all AST node classes The actual node classes are derived from the Parser Python asdl file which is reproduced above They are defined in the _ast C module and re exported in ast There is one class defined for each left hand side symbol in the abstract grammar for example ast stmt or ast expr In addition there is one class defined for each constructor on the right hand side these classes inherit from the classes for the left hand side trees For example ast BinOp inherits from ast expr For production rules with alternatives aka sums the left hand side class is abstract only instances of specific constructor nodes are ever created _fields Each concrete class has an attribute _fields which gives the names of all child nodes Each instance of a concrete class has one attribute for each child node of the type as defined in the grammar For example ast BinOp instances have an attribute left of type ast expr If these attributes are marked as optional in the grammar using a question mark the value might be None If the attributes can have zero or more values marked with an asterisk the values are represented as Python lists All possible attributes must be present and have valid values when compiling an AST with compile lineno col_offset end_lineno end_col_offset Instances of ast expr and ast stmt subclasses have lineno col_offset end_lineno and end_col_offset attributes The lineno and end_lineno are the first and last line numbers of source text span 1 indexed so the first line is line 1 and the col_offset and end_col_offset are the corresponding UTF 8 byte offsets of the first and last tokens that generated the node The UTF 8 offset is recorded because the parser uses UTF 8 internally Note that the end positions are not required by the compiler and are therefore optional The end offset is after the last symbol for example one can get the source segment of a one line expression node using source_line node col_offset node end_col_offset The constructor of a class ast T parses its arguments as follows If there are positional arguments there must be as many as there are items in T _fields they will be assigned as attributes of these names If there are keyword arguments they will set the attributes of the same names to the given values For example to create and populate an ast UnaryOp node you could use node ast UnaryOp node op ast USub node operand ast Constant node operand value 5 node operand lineno 0 node operand col_offset 0 node lineno 0 node col_offset 0 or the more compact node ast UnaryOp ast USub ast Constant 5 lineno 0 col_offset 0 lineno 0 col_offset 0 Changed in version,en
254, 3 8 Class ast Constant is now used for all constants Changed in version 3 9 Simple indices are represented by their value extended slices are represented as tuples Deprecated since version 3 8 Old classes ast Num ast Str ast Bytes ast NameConstant and ast Ellipsis are still available but they will be removed in future Python releases In the meantime instantiating them will return an instance of a different class Deprecated since version 3 9 Old classes ast Index and ast ExtSlice are still available but they will be removed in future Python releases In the meantime instantiating them will return an instance of a different class Note The descriptions of the specific node classes displayed here were initially adapted from the fantastic Green Tree Snakes project and all its contributors Root nodes class ast Module body type_ignores A Python module as with file input Node type generated by ast parse in the default exec mode body is a list of the module s Statements type_ignores is a list of the module s type ignore comments see ast parse for more details print ast dump ast parse x 1 indent 4 Module body Assign targets Name id x ctx Store value Constant value 1 type_ignores class ast Expression body A single Python expression input Node type generated by ast parse when mode is eval body is a single node one of the expression types print ast dump ast parse 123 mode eval indent 4 Expression body Constant value 123 class ast Interactive body A single interactive input like in Interactive Mode Node type generated by ast parse when mode is single body is a list of statement nodes print ast dump ast parse x 1 y 2 mode single indent 4 Interactive body Assign targets Name id x ctx Store value Constant value 1 Assign targets Name id y ctx Store value Constant value 2 class ast FunctionType argtypes returns A representation of an old style type comments for functions as Python versions prior to 3 5 didn t support PEP 484 annotations Node type generated by ast parse when mode is func_type Such type comments would look like this def sum_two_number a b type int int int return a b argtypes is a list of expression nodes returns is a single expression node print ast dump ast parse int str List int mode func_type indent 4 FunctionType argtypes Name id int ctx Load Name id str ctx Load returns Subscript value Name id List ctx Load slice Name id int ctx Load ctx Load New in version 3 8 Literals class ast Constant value A constant value The value attribute of the Constant literal contains the Python object it represents The values represented can be simple types such as a number string or None but also immutable container types tuples and frozensets if all of their elements are constant print ast dump ast parse 123 mode eval indent 4 Expression body Constant value 123 class ast FormattedValue value conversion format_spec Node representing a single formatting field in an f string If the string contains a single formatting field and nothing else the node can be isolated otherwise it appears in JoinedStr value is any expression node such as a literal a variable or a function call conversion is an integer 1 no formatting 115 s string formatting 114 r repr formatting 97 a ascii formatting format_spec is a JoinedStr node representing the formatting of the value or None if no format was specified Both conversion and format_spec can be set at the same time class ast JoinedStr values An f string comprising a series of FormattedValue and Constant nodes print ast dump ast parse f sin a is sin a 3 mode eval indent 4 Expression body JoinedStr values Constant value sin FormattedValue value Name id a ctx Load conversion 1 Constant value is FormattedValue value Call func Name id sin ctx Load args Name id a ctx Load keywords conversion 1 format_spec JoinedStr values Constant value 3 class ast List elts ctx class ast Tuple elts ctx A list or tuple elts holds a list of nodes representing the elements ctx is Store if the container is an assignment target i e x y something and Load otherwise print ast dump ast parse 1 2 3 mode eval indent 4 Expression body List elts,en
255, Constant value 1 Constant value 2 Constant value 3 ctx Load print ast dump ast parse 1 2 3 mode eval indent 4 Expression body Tuple elts Constant value 1 Constant value 2 Constant value 3 ctx Load class ast Set elts A set elts holds a list of nodes representing the set s elements print ast dump ast parse 1 2 3 mode eval indent 4 Expression body Set elts Constant value 1 Constant value 2 Constant value 3 class ast Dict keys values A dictionary keys and values hold lists of nodes representing the keys and the values respectively in matching order what would be returned when calling dictionary keys and dictionary values When doing dictionary unpacking using dictionary literals the expression to be expanded goes in the values list with a None at the corresponding position in keys print ast dump ast parse a 1 d mode eval indent 4 Expression body Dict keys Constant value a None values Constant value 1 Name id d ctx Load Variables class ast Name id ctx A variable name id holds the name as a string and ctx is one of the following types class ast Load class ast Store class ast Del Variable references can be used to load the value of a variable to assign a new value to it or to delete it Variable references are given a context to distinguish these cases print ast dump ast parse a indent 4 Module body Expr value Name id a ctx Load type_ignores print ast dump ast parse a 1 indent 4 Module body Assign targets Name id a ctx Store value Constant value 1 type_ignores print ast dump ast parse del a indent 4 Module body Delete targets Name id a ctx Del type_ignores class ast Starred value ctx A var variable reference value holds the variable typically a Name node This type must be used when building a Call node with args print ast dump ast parse a b it indent 4 Module body Assign targets Tuple elts Name id a ctx Store Starred value Name id b ctx Store ctx Store ctx Store value Name id it ctx Load type_ignores Expressions class ast Expr value When an expression such as a function call appears as a statement by itself with its return value not used or stored it is wrapped in this container value holds one of the other nodes in this section a Constant a Name a Lambda a Yield or YieldFrom node print ast dump ast parse a indent 4 Module body Expr value UnaryOp op USub operand Name id a ctx Load type_ignores class ast UnaryOp op operand A unary operation op is the operator and operand any expression node class ast UAdd class ast USub class ast Not class ast Invert Unary operator tokens Not is the not keyword Invert is the operator print ast dump ast parse not x mode eval indent 4 Expression body UnaryOp op Not operand Name id x ctx Load class ast BinOp left op right A binary operation like addition or division op is the operator and left and right are any expression nodes print ast dump ast parse x y mode eval indent 4 Expression body BinOp left Name id x ctx Load op Add right Name id y ctx Load class ast Add class ast Sub class ast Mult class ast Div class ast FloorDiv class ast Mod class ast Pow class ast LShift class ast RShift class ast BitOr class ast BitXor class ast BitAnd class ast MatMult Binary operator tokens class ast BoolOp op values A boolean operation or or and op is Or or And values are the values involved Consecutive operations with the same operator such as a or b or c are collapsed into one node with several values This doesn t include not which is a UnaryOp print ast dump ast parse x or y mode eval indent 4 Expression body BoolOp op Or values Name id x ctx Load Name id y ctx Load class ast And class ast Or Boolean operator tokens class ast Compare left ops comparators A comparison of two or more values left is the first value in the comparison ops the list of operators and comparators the list of values after the first element in the comparison print ast dump ast parse 1 a 10 mode eval indent 4 Expression body Compare left Constant value 1 ops LtE Lt comparators Name id a ctx Load Constant value 10 class ast Eq class ast NotEq class ast Lt class ast LtE class ast Gt class ast GtE class ast Is class ast IsNot class ast In cl,en
256,ass ast NotIn Comparison operator tokens class ast Call func args keywords A function call func is the function which will often be a Name or Attribute object Of the arguments args holds a list of the arguments passed by position keywords holds a list of keyword objects representing arguments passed by keyword When creating a Call node args and keywords are required but they can be empty lists print ast dump ast parse func a b c d e mode eval indent 4 Expression body Call func Name id func ctx Load args Name id a ctx Load Starred value Name id d ctx Load ctx Load keywords keyword arg b value Name id c ctx Load keyword value Name id e ctx Load class ast keyword arg value A keyword argument to a function call or class definition arg is a raw string of the parameter name value is a node to pass in class ast IfExp test body orelse An expression such as a if b else c Each field holds a single node so in the following example all three are Name nodes print ast dump ast parse a if b else c mode eval indent 4 Expression body IfExp test Name id b ctx Load body Name id a ctx Load orelse Name id c ctx Load class ast Attribute value attr ctx Attribute access e g d keys value is a node typically a Name attr is a bare string giving the name of the attribute and ctx is Load Store or Del according to how the attribute is acted on print ast dump ast parse snake colour mode eval indent 4 Expression body Attribute value Name id snake ctx Load attr colour ctx Load class ast NamedExpr target value A named expression This AST node is produced by the assignment expressions operator also known as the walrus operator As opposed to the Assign node in which the first argument can be multiple nodes in this case both target and value must be single nodes print ast dump ast parse x 4 mode eval indent 4 Expression body NamedExpr target Name id x ctx Store value Constant value 4 New in version 3 8 Subscripting class ast Subscript value slice ctx A subscript such as l 1 value is the subscripted object usually sequence or mapping slice is an index slice or key It can be a Tuple and contain a Slice ctx is Load Store or Del according to the action performed with the subscript print ast dump ast parse l 1 2 3 mode eval indent 4 Expression body Subscript value Name id l ctx Load slice Tuple elts Slice lower Constant value 1 upper Constant value 2 Constant value 3 ctx Load ctx Load class ast Slice lower upper step Regular slicing on the form lower upper or lower upper step Can occur only inside the slice field of Subscript either directly or as an element of Tuple print ast dump ast parse l 1 2 mode eval indent 4 Expression body Subscript value Name id l ctx Load slice Slice lower Constant value 1 upper Constant value 2 ctx Load Comprehensions class ast ListComp elt generators class ast SetComp elt generators class ast GeneratorExp elt generators class ast DictComp key value generators List and set comprehensions generator expressions and dictionary comprehensions elt or key and value is a single node representing the part that will be evaluated for each item generators is a list of comprehension nodes print ast dump ast parse x for x in numbers mode eval indent 4 Expression body ListComp elt Name id x ctx Load generators comprehension target Name id x ctx Store iter Name id numbers ctx Load ifs is_async 0 print ast dump ast parse x x 2 for x in numbers mode eval indent 4 Expression body DictComp key Name id x ctx Load value BinOp left Name id x ctx Load op Pow right Constant value 2 generators comprehension target Name id x ctx Store iter Name id numbers ctx Load ifs is_async 0 print ast dump ast parse x for x in numbers mode eval indent 4 Expression body SetComp elt Name id x ctx Load generators comprehension target Name id x ctx Store iter Name id numbers ctx Load ifs is_async 0 class ast comprehension target iter ifs is_async One for clause in a comprehension target is the reference to use for each element typically a Name or Tuple node iter is the object to iterate over ifs is a list of test expressions each for clause can have multiple ifs is_async indi,en
257,cates a comprehension is asynchronous using an async for instead of for The value is an integer 0 or 1 print ast dump ast parse ord c for line in file for c in line mode eval indent 4 Multiple comprehensions in one Expression body ListComp elt Call func Name id ord ctx Load args Name id c ctx Load keywords generators comprehension target Name id line ctx Store iter Name id file ctx Load ifs is_async 0 comprehension target Name id c ctx Store iter Name id line ctx Load ifs is_async 0 print ast dump ast parse n 2 for n in it if n 5 if n 10 mode eval indent 4 generator comprehension Expression body GeneratorExp elt BinOp left Name id n ctx Load op Pow right Constant value 2 generators comprehension target Name id n ctx Store iter Name id it ctx Load ifs Compare left Name id n ctx Load ops Gt comparators Constant value 5 Compare left Name id n ctx Load ops Lt comparators Constant value 10 is_async 0 print ast dump ast parse i async for i in soc mode eval indent 4 Async comprehension Expression body ListComp elt Name id i ctx Load generators comprehension target Name id i ctx Store iter Name id soc ctx Load ifs is_async 1 Statements class ast Assign targets value type_comment An assignment targets is a list of nodes and value is a single node Multiple nodes in targets represents assigning the same value to each Unpacking is represented by putting a Tuple or List within targets type_comment type_comment is an optional string with the type annotation as a comment print ast dump ast parse a b 1 indent 4 Multiple assignment Module body Assign targets Name id a ctx Store Name id b ctx Store value Constant value 1 type_ignores print ast dump ast parse a b c indent 4 Unpacking Module body Assign targets Tuple elts Name id a ctx Store Name id b ctx Store ctx Store value Name id c ctx Load type_ignores class ast AnnAssign target annotation value simple An assignment with a type annotation target is a single node and can be a Name a Attribute or a Subscript annotation is the annotation such as a Constant or Name node value is a single optional node simple is a boolean integer set to True for a Name node in target that do not appear in between parenthesis and are hence pure names and not expressions print ast dump ast parse c int indent 4 Module body AnnAssign target Name id c ctx Store annotation Name id int ctx Load simple 1 type_ignores print ast dump ast parse a int 1 indent 4 Annotation with parenthesis Module body AnnAssign target Name id a ctx Store annotation Name id int ctx Load value Constant value 1 simple 0 type_ignores print ast dump ast parse a b int indent 4 Attribute annotation Module body AnnAssign target Attribute value Name id a ctx Load attr b ctx Store annotation Name id int ctx Load simple 0 type_ignores print ast dump ast parse a 1 int indent 4 Subscript annotation Module body AnnAssign target Subscript value Name id a ctx Load slice Constant value 1 ctx Store annotation Name id int ctx Load simple 0 type_ignores class ast AugAssign target op value Augmented assignment such as a 1 In the following example target is a Name node for x with the Store context op is Add and value is a Constant with value for 1 The target attribute cannot be of class Tuple or List unlike the targets of Assign print ast dump ast parse x 2 indent 4 Module body AugAssign target Name id x ctx Store op Add value Constant value 2 type_ignores class ast Raise exc cause A raise statement exc is the exception object to be raised normally a Call or Name or None for a standalone raise cause is the optional part for y in raise x from y print ast dump ast parse raise x from y indent 4 Module body Raise exc Name id x ctx Load cause Name id y ctx Load type_ignores class ast Assert test msg An assertion test holds the condition such as a Compare node msg holds the failure message print ast dump ast parse assert x y indent 4 Module body Assert test Name id x ctx Load msg Name id y ctx Load type_ignores class ast Delete targets Represents a del statement targets is a list of nodes such as Name Attribute or Subscript nodes print ast dump ast parse del x y,en
258, z indent 4 Module body Delete targets Name id x ctx Del Name id y ctx Del Name id z ctx Del type_ignores class ast Pass A pass statement print ast dump ast parse pass indent 4 Module body Pass type_ignores class ast TypeAlias name type_params value A type alias created through the type statement name is the name of the alias type_params is a list of type parameters and value is the value of the type alias print ast dump ast parse type Alias int indent 4 Module body TypeAlias name Name id Alias ctx Store type_params value Name id int ctx Load type_ignores New in version 3 12 Other statements which are only applicable inside functions or loops are described in other sections Imports class ast Import names An import statement names is a list of alias nodes print ast dump ast parse import x y z indent 4 Module body Import names alias name x alias name y alias name z type_ignores class ast ImportFrom module names level Represents from x import y module is a raw string of the from name without any leading dots or None for statements such as from import foo level is an integer holding the level of the relative import 0 means absolute import print ast dump ast parse from y import x y z indent 4 Module body ImportFrom module y names alias name x alias name y alias name z level 0 type_ignores class ast alias name asname Both parameters are raw strings of the names asname can be None if the regular name is to be used print ast dump ast parse from foo bar import a as b c indent 4 Module body ImportFrom module foo bar names alias name a asname b alias name c level 2 type_ignores Control flow Note Optional clauses such as else are stored as an empty list if they re not present class ast If test body orelse An if statement test holds a single node such as a Compare node body and orelse each hold a list of nodes elif clauses don t have a special representation in the AST but rather appear as extra If nodes within the orelse section of the previous one print ast dump ast parse if x elif y else indent 4 Module body If test Name id x ctx Load body Expr value Constant value Ellipsis orelse If test Name id y ctx Load body Expr value Constant value Ellipsis orelse Expr value Constant value Ellipsis type_ignores class ast For target iter body orelse type_comment A for loop target holds the variable s the loop assigns to as a single Name Tuple List Attribute or Subscript node iter holds the item to be looped over again as a single node body and orelse contain lists of nodes to execute Those in orelse are executed if the loop finishes normally rather than via a break statement type_comment type_comment is an optional string with the type annotation as a comment print ast dump ast parse for x in y else indent 4 Module body For target Name id x ctx Store iter Name id y ctx Load body Expr value Constant value Ellipsis orelse Expr value Constant value Ellipsis type_ignores class ast While test body orelse A while loop test holds the condition such as a Compare node print ast dump ast parse while x else indent 4 Module body While test Name id x ctx Load body Expr value Constant value Ellipsis orelse Expr value Constant value Ellipsis type_ignores class ast Break class ast Continue The break and continue statements print ast dump ast parse for a in b if a 5 break else continue indent 4 Module body For target Name id a ctx Store iter Name id b ctx Load body If test Compare left Name id a ctx Load ops Gt comparators Constant value 5 body Break orelse Continue orelse type_ignores class ast Try body handlers orelse finalbody try blocks All attributes are list of nodes to execute except for handlers which is a list of ExceptHandler nodes print ast dump ast parse try except Exception except OtherException as e else finally indent 4 Module body Try body Expr value Constant value Ellipsis handlers ExceptHandler type Name id Exception ctx Load body Expr value Constant value Ellipsis ExceptHandler type Name id OtherException ctx Load name e body Expr value Constant value Ellipsis orelse Expr value Constant value Ellipsis finalbody Expr value Constant value Ell,en
259,ipsis type_ignores class ast TryStar body handlers orelse finalbody try blocks which are followed by except clauses The attributes are the same as for Try but the ExceptHandler nodes in handlers are interpreted as except blocks rather then except print ast dump ast parse try except Exception indent 4 Module body TryStar body Expr value Constant value Ellipsis handlers ExceptHandler type Name id Exception ctx Load body Expr value Constant value Ellipsis orelse finalbody type_ignores New in version 3 11 class ast ExceptHandler type name body A single except clause type is the exception type it will match typically a Name node or None for a catch all except clause name is a raw string for the name to hold the exception or None if the clause doesn t have as foo body is a list of nodes print ast dump ast parse try a 1 except TypeError pass indent 4 Module body Try body Expr value BinOp left Name id a ctx Load op Add right Constant value 1 handlers ExceptHandler type Name id TypeError ctx Load body Pass orelse finalbody type_ignores class ast With items body type_comment A with block items is a list of withitem nodes representing the context managers and body is the indented block inside the context type_comment type_comment is an optional string with the type annotation as a comment class ast withitem context_expr optional_vars A single context manager in a with block context_expr is the context manager often a Call node optional_vars is a Name Tuple or List for the as foo part or None if that isn t used print ast dump ast parse with a as b c as d something b d indent 4 Module body With items withitem context_expr Name id a ctx Load optional_vars Name id b ctx Store withitem context_expr Name id c ctx Load optional_vars Name id d ctx Store body Expr value Call func Name id something ctx Load args Name id b ctx Load Name id d ctx Load keywords type_ignores Pattern matching class ast Match subject cases A match statement subject holds the subject of the match the object that is being matched against the cases and cases contains an iterable of match_case nodes with the different cases New in version 3 10 class ast match_case pattern guard body A single case pattern in a match statement pattern contains the match pattern that the subject will be matched against Note that the AST nodes produced for patterns differ from those produced for expressions even when they share the same syntax The guard attribute contains an expression that will be evaluated if the pattern matches the subject body contains a list of nodes to execute if the pattern matches and the result of evaluating the guard expression is true print ast dump ast parse match x case x if x 0 case tuple indent 4 Module body Match subject Name id x ctx Load cases match_case pattern MatchSequence patterns MatchAs name x guard Compare left Name id x ctx Load ops Gt comparators Constant value 0 body Expr value Constant value Ellipsis match_case pattern MatchClass cls Name id tuple ctx Load patterns kwd_attrs kwd_patterns body Expr value Constant value Ellipsis type_ignores New in version 3 10 class ast MatchValue value A match literal or value pattern that compares by equality value is an expression node Permitted value nodes are restricted as described in the match statement documentation This pattern succeeds if the match subject is equal to the evaluated value print ast dump ast parse match x case Relevant indent 4 Module body Match subject Name id x ctx Load cases match_case pattern MatchValue value Constant value Relevant body Expr value Constant value Ellipsis type_ignores New in version 3 10 class ast MatchSingleton value A match literal pattern that compares by identity value is the singleton to be compared against None True or False This pattern succeeds if the match subject is the given constant print ast dump ast parse match x case None indent 4 Module body Match subject Name id x ctx Load cases match_case pattern MatchSingleton value None body Expr value Constant value Ellipsis type_ignores New in version 3 10 class ast MatchSequence patterns A match sequence patte,en
260,rn patterns contains the patterns to be matched against the subject elements if the subject is a sequence Matches a variable length sequence if one of the subpatterns is a MatchStar node otherwise matches a fixed length sequence print ast dump ast parse match x case 1 2 indent 4 Module body Match subject Name id x ctx Load cases match_case pattern MatchSequence patterns MatchValue value Constant value 1 MatchValue value Constant value 2 body Expr value Constant value Ellipsis type_ignores New in version 3 10 class ast MatchStar name Matches the rest of the sequence in a variable length match sequence pattern If name is not None a list containing the remaining sequence elements is bound to that name if the overall sequence pattern is successful print ast dump ast parse match x case 1 2 rest case _ indent 4 Module body Match subject Name id x ctx Load cases match_case pattern MatchSequence patterns MatchValue value Constant value 1 MatchValue value Constant value 2 MatchStar name rest body Expr value Constant value Ellipsis match_case pattern MatchSequence patterns MatchStar body Expr value Constant value Ellipsis type_ignores New in version 3 10 class ast MatchMapping keys patterns rest A match mapping pattern keys is a sequence of expression nodes patterns is a corresponding sequence of pattern nodes rest is an optional name that can be specified to capture the remaining mapping elements Permitted key expressions are restricted as described in the match statement documentation This pattern succeeds if the subject is a mapping all evaluated key expressions are present in the mapping and the value corresponding to each key matches the corresponding subpattern If rest is not None a dict containing the remaining mapping elements is bound to that name if the overall mapping pattern is successful print ast dump ast parse match x case 1 _ 2 _ case rest indent 4 Module body Match subject Name id x ctx Load cases match_case pattern MatchMapping keys Constant value 1 Constant value 2 patterns MatchAs MatchAs body Expr value Constant value Ellipsis match_case pattern MatchMapping keys patterns rest rest body Expr value Constant value Ellipsis type_ignores New in version 3 10 class ast MatchClass cls patterns kwd_attrs kwd_patterns A match class pattern cls is an expression giving the nominal class to be matched patterns is a sequence of pattern nodes to be matched against the class defined sequence of pattern matching attributes kwd_attrs is a sequence of additional attributes to be matched specified as keyword arguments in the class pattern kwd_patterns are the corresponding patterns specified as keyword values in the class pattern This pattern succeeds if the subject is an instance of the nominated class all positional patterns match the corresponding class defined attributes and any specified keyword attributes match their corresponding pattern Note classes may define a property that returns self in order to match a pattern node against the instance being matched Several builtin types are also matched that way as described in the match statement documentation print ast dump ast parse match x case Point2D 0 0 case Point3D x 0 y 0 z 0 indent 4 Module body Match subject Name id x ctx Load cases match_case pattern MatchClass cls Name id Point2D ctx Load patterns MatchValue value Constant value 0 MatchValue value Constant value 0 kwd_attrs kwd_patterns body Expr value Constant value Ellipsis match_case pattern MatchClass cls Name id Point3D ctx Load patterns kwd_attrs x y z kwd_patterns MatchValue value Constant value 0 MatchValue value Constant value 0 MatchValue value Constant value 0 body Expr value Constant value Ellipsis type_ignores New in version 3 10 class ast MatchAs pattern name A match as pattern capture pattern or wildcard pattern pattern contains the match pattern that the subject will be matched against If the pattern is None the node represents a capture pattern i e a bare name and will always succeed The name attribute contains the name that will be bound if the pattern is successful If name is None pattern must also ,en
261,be None and the node represents the wildcard pattern print ast dump ast parse match x case x as y case _ indent 4 Module body Match subject Name id x ctx Load cases match_case pattern MatchAs pattern MatchSequence patterns MatchAs name x name y body Expr value Constant value Ellipsis match_case pattern MatchAs body Expr value Constant value Ellipsis type_ignores New in version 3 10 class ast MatchOr patterns A match or pattern An or pattern matches each of its subpatterns in turn to the subject until one succeeds The or pattern is then deemed to succeed If none of the subpatterns succeed the or pattern fails The patterns attribute contains a list of match pattern nodes that will be matched against the subject print ast dump ast parse match x case x y indent 4 Module body Match subject Name id x ctx Load cases match_case pattern MatchOr patterns MatchSequence patterns MatchAs name x MatchAs name y body Expr value Constant value Ellipsis type_ignores New in version 3 10 Type parameters Type parameters can exist on classes functions and type aliases class ast TypeVar name bound A typing TypeVar name is the name of the type variable bound is the bound or constraints if any If bound is a Tuple it represents constraints otherwise it represents the bound print ast dump ast parse type Alias T int list T indent 4 Module body TypeAlias name Name id Alias ctx Store type_params TypeVar name T bound Name id int ctx Load value Subscript value Name id list ctx Load slice Name id T ctx Load ctx Load type_ignores New in version 3 12 class ast ParamSpec name A typing ParamSpec name is the name of the parameter specification print ast dump ast parse type Alias P Callable P int indent 4 Module body TypeAlias name Name id Alias ctx Store type_params ParamSpec name P value Subscript value Name id Callable ctx Load slice Tuple elts Name id P ctx Load Name id int ctx Load ctx Load ctx Load type_ignores New in version 3 12 class ast TypeVarTuple name A typing TypeVarTuple name is the name of the type variable tuple print ast dump ast parse type Alias Ts tuple Ts indent 4 Module body TypeAlias name Name id Alias ctx Store type_params TypeVarTuple name Ts value Subscript value Name id tuple ctx Load slice Tuple elts Starred value Name id Ts ctx Load ctx Load ctx Load ctx Load type_ignores New in version 3 12 Function and class definitions class ast FunctionDef name args body decorator_list returns type_comment type_params A function definition name is a raw string of the function name args is an arguments node body is the list of nodes inside the function decorator_list is the list of decorators to be applied stored outermost first i e the first in the list will be applied last returns is the return annotation type_params is a list of type parameters type_comment type_comment is an optional string with the type annotation as a comment Changed in version 3 12 Added type_params class ast Lambda args body lambda is a minimal function definition that can be used inside an expression Unlike FunctionDef body holds a single node print ast dump ast parse lambda x y indent 4 Module body Expr value Lambda args arguments posonlyargs args arg arg x arg arg y kwonlyargs kw_defaults defaults body Constant value Ellipsis type_ignores class ast arguments posonlyargs args vararg kwonlyargs kw_defaults kwarg defaults The arguments for a function posonlyargs args and kwonlyargs are lists of arg nodes vararg and kwarg are single arg nodes referring to the args kwargs parameters kw_defaults is a list of default values for keyword only arguments If one is None the corresponding argument is required defaults is a list of default values for arguments that can be passed positionally If there are fewer defaults they correspond to the last n arguments class ast arg arg annotation type_comment A single argument in a list arg is a raw string of the argument name annotation is its annotation such as a Name node type_comment type_comment is an optional string with the type annotation as a comment print ast dump ast parse decorator1 decorator2 def f a annotation b 1 c 2 d e f 3 ,en
262,g return annotation pass indent 4 Module body FunctionDef name f args arguments posonlyargs args arg arg a annotation Constant value annotation arg arg b arg arg c vararg arg arg d kwonlyargs arg arg e arg arg f kw_defaults None Constant value 3 kwarg arg arg g defaults Constant value 1 Constant value 2 body Pass decorator_list Name id decorator1 ctx Load Name id decorator2 ctx Load returns Constant value return annotation type_params type_ignores class ast Return value A return statement print ast dump ast parse return 4 indent 4 Module body Return value Constant value 4 type_ignores class ast Yield value class ast YieldFrom value A yield or yield from expression Because these are expressions they must be wrapped in a Expr node if the value sent back is not used print ast dump ast parse yield x indent 4 Module body Expr value Yield value Name id x ctx Load type_ignores print ast dump ast parse yield from x indent 4 Module body Expr value YieldFrom value Name id x ctx Load type_ignores class ast Global names class ast Nonlocal names global and nonlocal statements names is a list of raw strings print ast dump ast parse global x y z indent 4 Module body Global names x y z type_ignores print ast dump ast parse nonlocal x y z indent 4 Module body Nonlocal names x y z type_ignores class ast ClassDef name bases keywords body decorator_list type_params A class definition name is a raw string for the class name bases is a list of nodes for explicitly specified base classes keywords is a list of keyword nodes principally for metaclass Other keywords will be passed to the metaclass as per PEP 3115 body is a list of nodes representing the code within the class definition decorator_list is a list of nodes as in FunctionDef type_params is a list of type parameters print ast dump ast parse decorator1 decorator2 class Foo base1 base2 metaclass meta pass indent 4 Module body ClassDef name Foo bases Name id base1 ctx Load Name id base2 ctx Load keywords keyword arg metaclass value Name id meta ctx Load body Pass decorator_list Name id decorator1 ctx Load Name id decorator2 ctx Load type_params type_ignores Changed in version 3 12 Added type_params Async and await class ast AsyncFunctionDef name args body decorator_list returns type_comment type_params An async def function definition Has the same fields as FunctionDef Changed in version 3 12 Added type_params class ast Await value An await expression value is what it waits for Only valid in the body of an AsyncFunctionDef print ast dump ast parse async def f await other_func indent 4 Module body AsyncFunctionDef name f args arguments posonlyargs args kwonlyargs kw_defaults defaults body Expr value Await value Call func Name id other_func ctx Load args keywords decorator_list type_params type_ignores class ast AsyncFor target iter body orelse type_comment class ast AsyncWith items body type_comment async for loops and async with context managers They have the same fields as For and With respectively Only valid in the body of an AsyncFunctionDef Note When a string is parsed by ast parse operator nodes subclasses of ast operator ast unaryop ast cmpop ast boolop and ast expr_context on the returned tree will be singletons Changes to one will be reflected in all other occurrences of the same value e g ast Add ast Helpers Apart from the node classes the ast module defines these utility functions and classes for traversing abstract syntax trees ast parse source filename unknown mode exec type_comments False feature_version None Parse the source into an AST node Equivalent to compile source filename mode ast PyCF_ONLY_AST If type_comments True is given the parser is modified to check and return type comments as specified by PEP 484 and PEP 526 This is equivalent to adding ast PyCF_TYPE_COMMENTS to the flags passed to compile This will report syntax errors for misplaced type comments Without this flag type comments will be ignored and the type_comment field on selected AST nodes will always be None In addition the locations of type ignore comments will be returned as the type_ignores attribute of,en
263, Module otherwise it is always an empty list In addition if mode is func_type the input syntax is modified to correspond to PEP 484 signature type comments e g str int List str Setting feature_version to a tuple major minor will result in a best effort attempt to parse using that Python version s grammar For example setting feature_version 3 9 will attempt to disallow parsing of match statements Currently major must equal to 3 The lowest supported version is 3 4 and this may increase in future Python versions the highest is sys version_info 0 2 Best effort attempt means there is no guarantee that the parse or success of the parse is the same as when run on the Python version corresponding to feature_version If source contains a null character 0 ValueError is raised Warning Note that successfully parsing source code into an AST object doesn t guarantee that the source code provided is valid Python code that can be executed as the compilation step can raise further SyntaxError exceptions For instance the source return 42 generates a valid AST node for a return statement but it cannot be compiled alone it needs to be inside a function node In particular ast parse won t do any scoping checks which the compilation step does Warning It is possible to crash the Python interpreter with a sufficiently large complex string due to stack depth limitations in Python s AST compiler Changed in version 3 8 Added type_comments mode func_type and feature_version ast unparse ast_obj Unparse an ast AST object and generate a string with code that would produce an equivalent ast AST object if parsed back with ast parse Warning The produced code string will not necessarily be equal to the original code that generated the ast AST object without any compiler optimizations such as constant tuples frozensets Warning Trying to unparse a highly complex expression would result with RecursionError New in version 3 9 ast literal_eval node_or_string Evaluate an expression node or a string containing only a Python literal or container display The string or node provided may only consist of the following Python literal structures strings bytes numbers tuples lists dicts sets booleans None and Ellipsis This can be used for evaluating strings containing Python values without the need to parse the values oneself It is not capable of evaluating arbitrarily complex expressions for example involving operators or indexing This function had been documented as safe in the past without defining what that meant That was misleading This is specifically designed not to execute Python code unlike the more general eval There is no namespace no name lookups or ability to call out But it is not free from attack A relatively small input can lead to memory exhaustion or to C stack exhaustion crashing the process There is also the possibility for excessive CPU consumption denial of service on some inputs Calling it on untrusted data is thus not recommended Warning It is possible to crash the Python interpreter due to stack depth limitations in Python s AST compiler It can raise ValueError TypeError SyntaxError MemoryError and RecursionError depending on the malformed input Changed in version 3 2 Now allows bytes and set literals Changed in version 3 9 Now supports creating empty sets with set Changed in version 3 10 For string inputs leading spaces and tabs are now stripped ast get_docstring node clean True Return the docstring of the given node which must be a FunctionDef AsyncFunctionDef ClassDef or Module node or None if it has no docstring If clean is true clean up the docstring s indentation with inspect cleandoc Changed in version 3 5 AsyncFunctionDef is now supported ast get_source_segment source node padded False Get source code segment of the source that generated node If some location information lineno end_lineno col_offset or end_col_offset is missing return None If padded is True the first line of a multi line statement will be padded with spaces to match its original position New in version 3 8 ast fix_missing_locations node When you compile a node tree with co,en
264,mpile the compiler expects lineno and col_offset attributes for every node that supports them This is rather tedious to fill in for generated nodes so this helper adds these attributes recursively where not already set by setting them to the values of the parent node It works recursively starting at node ast increment_lineno node n 1 Increment the line number and end line number of each node in the tree starting at node by n This is useful to move code to a different location in a file ast copy_location new_node old_node Copy source location lineno col_offset end_lineno and end_col_offset from old_node to new_node if possible and return new_node ast iter_fields node Yield a tuple of fieldname value for each field in node _fields that is present on node ast iter_child_nodes node Yield all direct child nodes of node that is all fields that are nodes and all items of fields that are lists of nodes ast walk node Recursively yield all descendant nodes in the tree starting at node including node itself in no specified order This is useful if you only want to modify nodes in place and don t care about the context class ast NodeVisitor A node visitor base class that walks the abstract syntax tree and calls a visitor function for every node found This function may return a value which is forwarded by the visit method This class is meant to be subclassed with the subclass adding visitor methods visit node Visit a node The default implementation calls the method called self visit_ classname where classname is the name of the node class or generic_visit if that method doesn t exist generic_visit node This visitor calls visit on all children of the node Note that child nodes of nodes that have a custom visitor method won t be visited unless the visitor calls generic_visit or visits them itself visit_Constant node Handles all constant nodes Don t use the NodeVisitor if you want to apply changes to nodes during traversal For this a special visitor exists NodeTransformer that allows modifications Deprecated since version 3 8 Methods visit_Num visit_Str visit_Bytes visit_NameConstant and visit_Ellipsis are deprecated now and will not be called in future Python versions Add the visit_Constant method to handle all constant nodes class ast NodeTransformer A NodeVisitor subclass that walks the abstract syntax tree and allows modification of nodes The NodeTransformer will walk the AST and use the return value of the visitor methods to replace or remove the old node If the return value of the visitor method is None the node will be removed from its location otherwise it is replaced with the return value The return value may be the original node in which case no replacement takes place Here is an example transformer that rewrites all occurrences of name lookups foo to data foo class RewriteName NodeTransformer def visit_Name self node return Subscript value Name id data ctx Load slice Constant value node id ctx node ctx Keep in mind that if the node you re operating on has child nodes you must either transform the child nodes yourself or call the generic_visit method for the node first For nodes that were part of a collection of statements that applies to all statement nodes the visitor may also return a list of nodes rather than just a single node If NodeTransformer introduces new nodes that weren t part of original tree without giving them location information such as lineno fix_missing_locations should be called with the new sub tree to recalculate the location information tree ast parse foo mode eval new_tree fix_missing_locations RewriteName visit tree Usually you use the transformer like this node YourTransformer visit node ast dump node annotate_fields True include_attributes False indent None Return a formatted dump of the tree in node This is mainly useful for debugging purposes If annotate_fields is true by default the returned string will show the names and the values for fields If annotate_fields is false the result string will be more compact by omitting unambiguous field names Attributes such as line numbers and column offsets are,en
265, not dumped by default If this is wanted include_attributes can be set to true If indent is a non negative integer or string then the tree will be pretty printed with that indent level An indent level of 0 negative or will only insert newlines None the default selects the single line representation Using a positive integer indent indents that many spaces per level If indent is a string such as t that string is used to indent each level Changed in version 3 9 Added the indent option Compiler Flags The following flags may be passed to compile in order to change effects on the compilation of a program ast PyCF_ALLOW_TOP_LEVEL_AWAIT Enables support for top level await async for async with and async comprehensions New in version 3 8 ast PyCF_ONLY_AST Generates and returns an abstract syntax tree instead of returning a compiled code object ast PyCF_TYPE_COMMENTS Enables support for PEP 484 and PEP 526 style type comments type type type ignore stuff New in version 3 8 Command Line Usage New in version 3 9 The ast module can be executed as a script from the command line It is as simple as python m ast m mode a infile The following options are accepted h help Show the help message and exit m mode mode mode Specify what kind of code must be compiled like the mode argument in parse no type comments Don t parse type comments a include attributes Include attributes such as line numbers and column offsets i indent indent indent Indentation of nodes in AST number of spaces If infile is specified its contents are parsed to AST and dumped to stdout Otherwise the content is read from stdin See also Green Tree Snakes an external documentation resource has good details on working with Python ASTs ASTTokens annotates Python ASTs with the positions of tokens and text in the source code that generated them This is helpful for tools that make source code transformations leoAst py unifies the token based and parse tree based views of python programs by inserting two way links between tokens and ast nodes LibCST parses code as a Concrete Syntax Tree that looks like an ast tree and keeps all formatting details It s useful for building automated refactoring codemod applications and linters Parso is a Python parser that supports error recovery and round trip parsing for different Python versions in multiple Python versions Parso is also able to list multiple syntax errors in your python file,en
266,email contentmanager Managing MIME Content Source code Lib email contentmanager py New in version 3 6 1 class email contentmanager ContentManager Base class for content managers Provides the standard registry mechanisms to register converters between MIME content and other representations as well as the get_content and set_content dispatch methods get_content msg args kw Look up a handler function based on the mimetype of msg see next paragraph call it passing through all arguments and return the result of the call The expectation is that the handler will extract the payload from msg and return an object that encodes information about the extracted data To find the handler look for the following keys in the registry stopping with the first one found the string representing the full MIME type maintype subtype the string representing the maintype the empty string If none of these keys produce a handler raise a KeyError for the full MIME type set_content msg obj args kw If the maintype is multipart raise a TypeError otherwise look up a handler function based on the type of obj see next paragraph call clear_content on the msg and call the handler function passing through all arguments The expectation is that the handler will transform and store obj into msg possibly making other changes to msg as well such as adding various MIME headers to encode information needed to interpret the stored data To find the handler obtain the type of obj typ type obj and look for the following keys in the registry stopping with the first one found the type itself typ the type s fully qualified name typ __module__ typ __qualname__ the type s qualname typ __qualname__ the type s name typ __name__ If none of the above match repeat all of the checks above for each of the types in the MRO typ __mro__ Finally if no other key yields a handler check for a handler for the key None If there is no handler for None raise a KeyError for the fully qualified name of the type Also add a MIME Version header if one is not present see also MIMEPart add_get_handler key handler Record the function handler as the handler for key For the possible values of key see get_content add_set_handler typekey handler Record handler as the function to call when an object of a type matching typekey is passed to set_content For the possible values of typekey see set_content Content Manager Instances Currently the email package provides only one concrete content manager raw_data_manager although more may be added in the future raw_data_manager is the content_manager provided by EmailPolicy and its derivatives email contentmanager raw_data_manager This content manager provides only a minimum interface beyond that provided by Message itself it deals only with text raw byte strings and Message objects Nevertheless it provides significant advantages compared to the base API get_content on a text part will return a unicode string without the application needing to manually decode it set_content provides a rich set of options for controlling the headers added to a part and controlling the content transfer encoding and it enables the use of the various add_ methods thereby simplifying the creation of multipart messages email contentmanager get_content msg errors replace Return the payload of the part as either a string for text parts an EmailMessage object for message rfc822 parts or a bytes object for all other non multipart types Raise a KeyError if called on a multipart If the part is a text part and errors is specified use it as the error handler when decoding the payload to unicode The default error handler is replace email contentmanager set_content msg str subtype plain charset utf 8 cte None disposition None filename None cid None params None headers None email contentmanager set_content msg bytes maintype subtype cte base64 disposition None filename None cid None params None headers None email contentmanager set_content msg EmailMessage cte None disposition None filename None cid None params None headers None Add headers and payload to msg Add a Content Type header with a maint,en
267,ype subtype value For str set the MIME maintype to text and set the subtype to subtype if it is specified or plain if it is not For bytes use the specified maintype and subtype or raise a TypeError if they are not specified For EmailMessage objects set the maintype to message and set the subtype to subtype if it is specified or rfc822 if it is not If subtype is partial raise an error bytes objects must be used to construct message partial parts If charset is provided which is valid only for str encode the string to bytes using the specified character set The default is utf 8 If the specified charset is a known alias for a standard MIME charset name use the standard charset instead If cte is set encode the payload using the specified content transfer encoding and set the Content Transfer Encoding header to that value Possible values for cte are quoted printable base64 7bit 8bit and binary If the input cannot be encoded in the specified encoding for example specifying a cte of 7bit for an input that contains non ASCII values raise a ValueError For str objects if cte is not set use heuristics to determine the most compact encoding For EmailMessage per RFC 2046 raise an error if a cte of quoted printable or base64 is requested for subtype rfc822 and for any cte other than 7bit for subtype external body For message rfc822 use 8bit if cte is not specified For all other values of subtype use 7bit Note A cte of binary does not actually work correctly yet The EmailMessage object as modified by set_content is correct but BytesGenerator does not serialize it correctly If disposition is set use it as the value of the Content Disposition header If not specified and filename is specified add the header with the value attachment If disposition is not specified and filename is also not specified do not add the header The only valid values for disposition are attachment and inline If filename is specified use it as the value of the filename parameter of the Content Disposition header If cid is specified add a Content ID header with cid as its value If params is specified iterate its items method and use the resulting key value pairs to set additional parameters on the Content Type header If headers is specified and is a list of strings of the form headername headervalue or a list of header objects distinguished from strings by having a name attribute add the headers to msg Footnotes 1 Originally added in 3 4 as a provisional module,en
268,pipes Interface to shell pipelines Source code Lib pipes py Deprecated since version 3 11 will be removed in version 3 13 The pipes module is deprecated see PEP 594 for details Please use the subprocess module instead The pipes module defines a class to abstract the concept of a pipeline a sequence of converters from one file to another Because the module uses bin sh command lines a POSIX or compatible shell for os system and os popen is required Availability Unix not VxWorks The pipes module defines the following class class pipes Template An abstraction of a pipeline Example import pipes t pipes Template t append tr a z A Z f t open pipefile w f write hello world f close open pipefile read HELLO WORLD Template Objects Template objects following methods Template reset Restore a pipeline template to its initial state Template clone Return a new equivalent pipeline template Template debug flag If flag is true turn debugging on Otherwise turn debugging off When debugging is on commands to be executed are printed and the shell is given set x command to be more verbose Template append cmd kind Append a new action at the end The cmd variable must be a valid bourne shell command The kind variable consists of two letters The first letter can be either of which means the command reads its standard input f which means the commands reads a given file on the command line or which means the commands reads no input and hence must be first Similarly the second letter can be either of which means the command writes to standard output f which means the command writes a file on the command line or which means the command does not write anything and hence must be last Template prepend cmd kind Add a new action at the beginning See append for explanations of the arguments Template open file mode Return a file like object open to file but read from or written to by the pipeline Note that only one of r w may be given Template copy infile outfile Copy infile to outfile through the pipe,en
269,DateTime Objects Various date and time objects are supplied by the datetime module Before using any of these functions the header file datetime h must be included in your source note that this is not included by Python h and the macro PyDateTime_IMPORT must be invoked usually as part of the module initialisation function The macro puts a pointer to a C structure into a static variable PyDateTimeAPI that is used by the following macros type PyDateTime_Date This subtype of PyObject represents a Python date object type PyDateTime_DateTime This subtype of PyObject represents a Python datetime object type PyDateTime_Time This subtype of PyObject represents a Python time object type PyDateTime_Delta This subtype of PyObject represents the difference between two datetime values PyTypeObject PyDateTime_DateType This instance of PyTypeObject represents the Python date type it is the same object as datetime date in the Python layer PyTypeObject PyDateTime_DateTimeType This instance of PyTypeObject represents the Python datetime type it is the same object as datetime datetime in the Python layer PyTypeObject PyDateTime_TimeType This instance of PyTypeObject represents the Python time type it is the same object as datetime time in the Python layer PyTypeObject PyDateTime_DeltaType This instance of PyTypeObject represents Python type for the difference between two datetime values it is the same object as datetime timedelta in the Python layer PyTypeObject PyDateTime_TZInfoType This instance of PyTypeObject represents the Python time zone info type it is the same object as datetime tzinfo in the Python layer Macro for access to the UTC singleton PyObject PyDateTime_TimeZone_UTC Returns the time zone singleton representing UTC the same object as datetime timezone utc New in version 3 7 Type check macros int PyDate_Check PyObject ob Return true if ob is of type PyDateTime_DateType or a subtype of PyDateTime_DateType ob must not be NULL This function always succeeds int PyDate_CheckExact PyObject ob Return true if ob is of type PyDateTime_DateType ob must not be NULL This function always succeeds int PyDateTime_Check PyObject ob Return true if ob is of type PyDateTime_DateTimeType or a subtype of PyDateTime_DateTimeType ob must not be NULL This function always succeeds int PyDateTime_CheckExact PyObject ob Return true if ob is of type PyDateTime_DateTimeType ob must not be NULL This function always succeeds int PyTime_Check PyObject ob Return true if ob is of type PyDateTime_TimeType or a subtype of PyDateTime_TimeType ob must not be NULL This function always succeeds int PyTime_CheckExact PyObject ob Return true if ob is of type PyDateTime_TimeType ob must not be NULL This function always succeeds int PyDelta_Check PyObject ob Return true if ob is of type PyDateTime_DeltaType or a subtype of PyDateTime_DeltaType ob must not be NULL This function always succeeds int PyDelta_CheckExact PyObject ob Return true if ob is of type PyDateTime_DeltaType ob must not be NULL This function always succeeds int PyTZInfo_Check PyObject ob Return true if ob is of type PyDateTime_TZInfoType or a subtype of PyDateTime_TZInfoType ob must not be NULL This function always succeeds int PyTZInfo_CheckExact PyObject ob Return true if ob is of type PyDateTime_TZInfoType ob must not be NULL This function always succeeds Macros to create objects PyObject PyDate_FromDate int year int month int day Return value New reference Return a datetime date object with the specified year month and day PyObject PyDateTime_FromDateAndTime int year int month int day int hour int minute int second int usecond Return value New reference Return a datetime datetime object with the specified year month day hour minute second and microsecond PyObject PyDateTime_FromDateAndTimeAndFold int year int month int day int hour int minute int second int usecond int fold Return value New reference Return a datetime datetime object with the specified year month day hour minute second microsecond and fold New in version 3 6 PyObject PyTime_FromTime int hour int minute int second int usecond Retu,en
270,rn value New reference Return a datetime time object with the specified hour minute second and microsecond PyObject PyTime_FromTimeAndFold int hour int minute int second int usecond int fold Return value New reference Return a datetime time object with the specified hour minute second microsecond and fold New in version 3 6 PyObject PyDelta_FromDSU int days int seconds int useconds Return value New reference Return a datetime timedelta object representing the given number of days seconds and microseconds Normalization is performed so that the resulting number of microseconds and seconds lie in the ranges documented for datetime timedelta objects PyObject PyTimeZone_FromOffset PyObject offset Return value New reference Return a datetime timezone object with an unnamed fixed offset represented by the offset argument New in version 3 7 PyObject PyTimeZone_FromOffsetAndName PyObject offset PyObject name Return value New reference Return a datetime timezone object with a fixed offset represented by the offset argument and with tzname name New in version 3 7 Macros to extract fields from date objects The argument must be an instance of PyDateTime_Date including subclasses such as PyDateTime_DateTime The argument must not be NULL and the type is not checked int PyDateTime_GET_YEAR PyDateTime_Date o Return the year as a positive int int PyDateTime_GET_MONTH PyDateTime_Date o Return the month as an int from 1 through 12 int PyDateTime_GET_DAY PyDateTime_Date o Return the day as an int from 1 through 31 Macros to extract fields from datetime objects The argument must be an instance of PyDateTime_DateTime including subclasses The argument must not be NULL and the type is not checked int PyDateTime_DATE_GET_HOUR PyDateTime_DateTime o Return the hour as an int from 0 through 23 int PyDateTime_DATE_GET_MINUTE PyDateTime_DateTime o Return the minute as an int from 0 through 59 int PyDateTime_DATE_GET_SECOND PyDateTime_DateTime o Return the second as an int from 0 through 59 int PyDateTime_DATE_GET_MICROSECOND PyDateTime_DateTime o Return the microsecond as an int from 0 through 999999 int PyDateTime_DATE_GET_FOLD PyDateTime_DateTime o Return the fold as an int from 0 through 1 New in version 3 6 PyObject PyDateTime_DATE_GET_TZINFO PyDateTime_DateTime o Return the tzinfo which may be None New in version 3 10 Macros to extract fields from time objects The argument must be an instance of PyDateTime_Time including subclasses The argument must not be NULL and the type is not checked int PyDateTime_TIME_GET_HOUR PyDateTime_Time o Return the hour as an int from 0 through 23 int PyDateTime_TIME_GET_MINUTE PyDateTime_Time o Return the minute as an int from 0 through 59 int PyDateTime_TIME_GET_SECOND PyDateTime_Time o Return the second as an int from 0 through 59 int PyDateTime_TIME_GET_MICROSECOND PyDateTime_Time o Return the microsecond as an int from 0 through 999999 int PyDateTime_TIME_GET_FOLD PyDateTime_Time o Return the fold as an int from 0 through 1 New in version 3 6 PyObject PyDateTime_TIME_GET_TZINFO PyDateTime_Time o Return the tzinfo which may be None New in version 3 10 Macros to extract fields from time delta objects The argument must be an instance of PyDateTime_Delta including subclasses The argument must not be NULL and the type is not checked int PyDateTime_DELTA_GET_DAYS PyDateTime_Delta o Return the number of days as an int from 999999999 to 999999999 New in version 3 3 int PyDateTime_DELTA_GET_SECONDS PyDateTime_Delta o Return the number of seconds as an int from 0 through 86399 New in version 3 3 int PyDateTime_DELTA_GET_MICROSECONDS PyDateTime_Delta o Return the number of microseconds as an int from 0 through 999999 New in version 3 3 Macros for the convenience of modules implementing the DB API PyObject PyDateTime_FromTimestamp PyObject args Return value New reference Create and return a new datetime datetime object given an argument tuple suitable for passing to datetime datetime fromtimestamp PyObject PyDate_FromTimestamp PyObject args Return value New reference Create and return a new datetime date object given an ar,en
271,gument tuple suitable for passing to datetime date fromtimestamp,fr
272,sched Event scheduler Source code Lib sched py The sched module defines a class which implements a general purpose event scheduler class sched scheduler timefunc time monotonic delayfunc time sleep The scheduler class defines a generic interface to scheduling events It needs two functions to actually deal with the outside world timefunc should be callable without arguments and return a number the time in any units whatsoever The delayfunc function should be callable with one argument compatible with the output of timefunc and should delay that many time units delayfunc will also be called with the argument 0 after each event is run to allow other threads an opportunity to run in multi threaded applications Changed in version 3 3 timefunc and delayfunc parameters are optional Changed in version 3 3 scheduler class can be safely used in multi threaded environments Example import sched time s sched scheduler time time time sleep def print_time a default print From print_time time time a def print_some_times print time time s enter 10 1 print_time s enter 5 2 print_time argument positional despite having higher priority keyword runs after positional as enter is relative s enter 5 1 print_time kwargs a keyword s enterabs 1_650_000_000 10 print_time argument first enterabs s enterabs 1_650_000_000 5 print_time argument second enterabs s run print time time print_some_times 1652342830 3640375 From print_time 1652342830 3642538 second enterabs From print_time 1652342830 3643398 first enterabs From print_time 1652342835 3694863 positional From print_time 1652342835 3696074 keyword From print_time 1652342840 369612 default 1652342840 3697174 Scheduler Objects scheduler instances have the following methods and attributes scheduler enterabs time priority action argument kwargs Schedule a new event The time argument should be a numeric type compatible with the return value of the timefunc function passed to the constructor Events scheduled for the same time will be executed in the order of their priority A lower number represents a higher priority Executing the event means executing action argument kwargs argument is a sequence holding the positional arguments for action kwargs is a dictionary holding the keyword arguments for action Return value is an event which may be used for later cancellation of the event see cancel Changed in version 3 3 argument parameter is optional Changed in version 3 3 kwargs parameter was added scheduler enter delay priority action argument kwargs Schedule an event for delay more time units Other than the relative time the other arguments the effect and the return value are the same as those for enterabs Changed in version 3 3 argument parameter is optional Changed in version 3 3 kwargs parameter was added scheduler cancel event Remove the event from the queue If event is not an event currently in the queue this method will raise a ValueError scheduler empty Return True if the event queue is empty scheduler run blocking True Run all scheduled events This method will wait using the delayfunc function passed to the constructor for the next event then execute it and so on until there are no more scheduled events If blocking is false executes the scheduled events due to expire soonest if any and then return the deadline of the next scheduled call in the scheduler if any Either action or delayfunc can raise an exception In either case the scheduler will maintain a consistent state and propagate the exception If an exception is raised by action the event will not be attempted in future calls to run If a sequence of events takes longer to run than the time available before the next event the scheduler will simply fall behind No events will be dropped the calling code is responsible for canceling events which are no longer pertinent Changed in version 3 3 blocking parameter was added scheduler queue Read only attribute returning a list of upcoming events in the order they will be run Each event is shown as a named tuple with the following fields time priority action argument kwargs,en
273,3 Configure Python 3 1 Build Requirements Features required to build CPython A C11 compiler Optional C11 features are not required Support for IEEE 754 floating point numbers and floating point Not a Number NaN Support for threads OpenSSL 1 1 1 or newer for the ssl and hashlib modules On Windows Microsoft Visual Studio 2017 or later is required Changed in version 3 5 On Windows Visual Studio 2015 or later is required Changed in version 3 6 Selected C99 features are now required like stdint h and static inline functions Changed in version 3 7 Thread support and OpenSSL 1 0 2 are now required Changed in version 3 10 OpenSSL 1 1 1 is now required Changed in version 3 11 C11 compiler IEEE 754 and NaN support are now required On Windows Visual Studio 2017 or later is required See also PEP 7 Style Guide for C Code and PEP 11 CPython platform support 3 2 Generated files To reduce build dependencies Python source code contains multiple generated files Commands to regenerate all generated files make regen all make regen stdlib module names make regen limited abi make regen configure The Makefile pre in file documents generated files their inputs and tools used to regenerate them Search for regen make targets 3 2 1 configure script The make regen configure command regenerates the aclocal m4 file and the configure script using the Tools build regen configure sh shell script which uses an Ubuntu container to get the same tools versions and have a reproducible output The container is optional the following command can be run locally autoreconf ivf Werror The generated files can change depending on the exact autoconf archive aclocal and pkg config versions 3 3 Configure Options List all configure script options using configure help See also the Misc SpecialBuilds txt in the Python source distribution 3 3 1 General Options enable loadable sqlite extensions Support loadable extensions in the _sqlite extension module default is no of the sqlite3 module See the sqlite3 Connection enable_load_extension method of the sqlite3 module New in version 3 6 disable ipv6 Disable IPv6 support enabled by default if supported see the socket module enable big digits 15 30 Define the size in bits of Python int digits 15 or 30 bits By default the digit size is 30 Define the PYLONG_BITS_IN_DIGIT to 15 or 30 See sys int_info bits_per_digit with suffix SUFFIX Set the Python executable suffix to SUFFIX The default suffix is exe on Windows and macOS python exe executable js on Emscripten node html on Emscripten browser wasm on WASI and an empty string on other platforms python executable Changed in version 3 11 The default suffix on WASM platform is one of js html or wasm with tzpath list of absolute paths separated by pathsep Select the default time zone search path for zoneinfo TZPATH See the Compile time configuration of the zoneinfo module Default usr share zoneinfo usr lib zoneinfo usr share lib zon einfo etc zoneinfo See os pathsep path separator New in version 3 9 without decimal contextvar Build the _decimal extension module using a thread local context rather than a coroutine local context default see the decimal module See decimal HAVE_CONTEXTVAR and the contextvars module New in version 3 9 with dbmliborder list of backend names Override order to check db backends for the dbm module A valid value is a colon separated string with the backend names ndbm gdbm bdb without c locale coercion Disable C locale coercion to a UTF 8 based locale enabled by default Don t define the PY_COERCE_C_LOCALE macro See PYTHONCOERCECLOCALE and the PEP 538 without freelists Disable all freelists except the empty tuple singleton New in version 3 11 with platlibdir DIRNAME Python library directory name default is lib Fedora and SuSE use lib64 on 64 bit platforms See sys platlibdir New in version 3 9 with wheel pkg dir PATH Directory of wheel packages used by the ensurepip module none by default Some Linux distribution packaging policies recommend against bundling dependencies For example Fedora installs wheel packages in the usr share python wheels directory and don t inst,en
274,all the ensurepip _bundled package New in version 3 10 with pkg config check yes no Whether configure should use pkg config to detect build dependencies check default pkg config is optional yes pkg config is mandatory no configure does not use pkg config even when present New in version 3 11 enable pystats Turn on internal statistics gathering The statistics will be dumped to a arbitrary probably unique file in tmp py_stats or C temp py_stats on Windows If that directory does not exist results will be printed on stdout Use Tools scripts summarize_stats py to read the stats New in version 3 11 3 3 2 WebAssembly Options with emscripten target browser node Set build flavor for wasm32 emscripten browser default preload minimal stdlib default MEMFS node NODERAWFS and pthread support New in version 3 11 enable wasm dynamic linking Turn on dynamic linking support for WASM Dynamic linking enables dlopen File size of the executable increases due to limited dead code elimination and additional features New in version 3 11 enable wasm pthreads Turn on pthreads support for WASM New in version 3 11 3 3 3 Install Options prefix PREFIX Install architecture independent files in PREFIX On Unix it defaults to usr local This value can be retrieved at runtime using sys prefix As an example one can use prefix HOME local to install a Python in its home directory exec prefix EPREFIX Install architecture dependent files in EPREFIX defaults to prefix This value can be retrieved at runtime using sys exec_prefix disable test modules Don t build nor install test modules like the test package or the _testcapi extension module built and installed by default New in version 3 10 with ensurepip upgrade install no Select the ensurepip command run on Python installation upgrade default run python m ensurepip altinstall upgrade command install run python m ensurepip altinstall command no don t run ensurepip New in version 3 6 3 3 4 Performance options Configuring Python using enable optimizations with lto PGO LTO is recommended for best performance The experimental enable bolt flag can also be used to improve performance enable optimizations Enable Profile Guided Optimization PGO using PROFILE_TASK disabled by default The C compiler Clang requires llvm profdata program for PGO On macOS GCC also requires it GCC is just an alias to Clang on macOS Disable also semantic interposition in libpython if enable shared and GCC is used add fno semantic interposition to the compiler and linker flags New in version 3 6 Changed in version 3 10 Use fno semantic interposition on GCC PROFILE_TASK Environment variable used in the Makefile Python command line arguments for the PGO generation task Default m test pgo timeout TESTTIMEOUT New in version 3 8 with lto full thin no yes Enable Link Time Optimization LTO in any build disabled by default The C compiler Clang requires llvm ar for LTO ar on macOS as well as an LTO aware linker ld gold or lld New in version 3 6 New in version 3 11 To use ThinLTO feature use with lto thin on Clang Changed in version 3 12 Use ThinLTO as the default optimization policy on Clang if the compiler accepts the flag enable bolt Enable usage of the BOLT post link binary optimizer disabled by default BOLT is part of the LLVM project but is not always included in their binary distributions This flag requires that llvm bolt and merge fdata are available BOLT is still a fairly new project so this flag should be considered experimental for now Because this tool operates on machine code its success is dependent on a combination of the build environment the other optimization configure args the CPU architecture and not all combinations are supported BOLT versions before LLVM 16 are known to crash BOLT under some scenarios Use of LLVM 16 or newer for BOLT optimization is strongly encouraged The BOLT_INSTRUMENT_FLAGS and BOLT_APPLY_FLAGS configure variables can be defined to override the default set of arguments for llvm bolt to instrument and apply BOLT data to binaries respectively New in version 3 12 with computed gotos Enable computed gotos in evaluati,en
275,on loop enabled by default on supported compilers without pymalloc Disable the specialized Python memory allocator pymalloc enabled by default See also PYTHONMALLOC environment variable without doc strings Disable static documentation strings to reduce the memory footprint enabled by default Documentation strings defined in Python are not affected Don t define the WITH_DOC_STRINGS macro See the PyDoc_STRVAR macro enable profiling Enable C level code profiling with gprof disabled by default with strict overflow Add fstrict overflow to the C compiler flags by default we add fno strict overflow instead 3 3 5 Python Debug Build A debug build is Python built with the with pydebug configure option Effects of a debug build Display all warnings by default the list of default warning filters is empty in the warnings module Add d to sys abiflags Add sys gettotalrefcount function Add X showrefcount command line option Add d command line option and PYTHONDEBUG environment variable to debug the parser Add support for the __lltrace__ variable enable low level tracing in the bytecode evaluation loop if the variable is defined Install debug hooks on memory allocators to detect buffer overflow and other memory errors Define Py_DEBUG and Py_REF_DEBUG macros Add runtime checks code surrounded by ifdef Py_DEBUG and endif Enable assert and _PyObject_ASSERT assertions don t set the NDEBUG macro see also the with assertions configure option Main runtime checks Add sanity checks on the function arguments Unicode and int objects are created with their memory filled with a pattern to detect usage of uninitialized objects Ensure that functions which can clear or replace the current exception are not called with an exception raised Check that deallocator functions don t change the current exception The garbage collector gc collect function runs some basic checks on objects consistency The Py_SAFE_DOWNCAST macro checks for integer underflow and overflow when downcasting from wide types to narrow types See also the Python Development Mode and the with trace refs configure option Changed in version 3 8 Release builds and debug builds are now ABI compatible defining the Py_DEBUG macro no longer implies the Py_TRACE_REFS macro see the with trace refs option which introduces the only ABI incompatibility 3 3 6 Debug options with pydebug Build Python in debug mode define the Py_DEBUG macro disabled by default with trace refs Enable tracing references for debugging purpose disabled by default Effects Define the Py_TRACE_REFS macro Add sys getobjects function Add PYTHONDUMPREFS environment variable This build is not ABI compatible with release build default build or debug build Py_DEBUG and Py_REF_DEBUG macros New in version 3 8 with assertions Build with C assertions enabled default is no assert and _PyObject_ASSERT If set the NDEBUG macro is not defined in the OPT compiler variable See also the with pydebug option debug build which also enables assertions New in version 3 6 with valgrind Enable Valgrind support default is no with dtrace Enable DTrace support default is no See Instrumenting CPython with DTrace and SystemTap New in version 3 6 with address sanitizer Enable AddressSanitizer memory error detector asan default is no New in version 3 6 with memory sanitizer Enable MemorySanitizer allocation error detector msan default is no New in version 3 6 with undefined behavior sanitizer Enable UndefinedBehaviorSanitizer undefined behaviour detector ubsan default is no New in version 3 6 3 3 7 Linker options enable shared Enable building a shared Python library libpython default is no without static libpython Do not build libpythonMAJOR MINOR a and do not install python o built and enabled by default New in version 3 10 3 3 8 Libraries options with libs lib1 Link against additional libraries default is no with system expat Build the pyexpat module using an installed expat library default is no with system libmpdec Build the _decimal extension module using an installed mpdec library see the decimal module default is no New in version 3 3 with readline editli,en
276,ne Use editline library for backend of the readline module Define the WITH_EDITLINE macro New in version 3 10 without readline Don t build the readline module built by default Don t define the HAVE_LIBREADLINE macro New in version 3 10 with libm STRING Override libm math library to STRING default is system dependent with libc STRING Override libc C library to STRING default is system dependent with openssl DIR Root of the OpenSSL directory New in version 3 7 with openssl rpath no auto DIR Set runtime library directory rpath for OpenSSL libraries no default don t set rpath auto auto detect rpath from with openssl and pkg config DIR set an explicit rpath New in version 3 10 3 3 9 Security Options with hash algorithm fnv siphash13 siphash24 Select hash algorithm for use in Python pyhash c siphash13 default siphash24 fnv New in version 3 4 New in version 3 11 siphash13 is added and it is the new default with builtin hashlib hashes md5 sha1 sha256 sha512 sha3 blake2 Built in hash modules md5 sha1 sha256 sha512 sha3 with shake blake2 New in version 3 9 with ssl default suites python openssl STRING Override the OpenSSL default cipher suites string python default use Python s preferred selection openssl leave OpenSSL s defaults untouched STRING use a custom string See the ssl module New in version 3 7 Changed in version 3 10 The settings python and STRING also set TLS 1 2 as minimum protocol version 3 3 10 macOS Options See Mac README rst enable universalsdk enable universalsdk SDKDIR Create a universal binary build SDKDIR specifies which macOS SDK should be used to perform the build default is no enable framework enable framework INSTALLDIR Create a Python framework rather than a traditional Unix install Optional INSTALLDIR specifies the installation path default is no with universal archs ARCH Specify the kind of universal binary that should be created This option is only valid when enable universalsdk is set Options universal2 32 bit 64 bit 3 way intel intel 32 intel 64 all with framework name FRAMEWORK Specify the name for the python framework on macOS only valid when enable framework is set default Python 3 3 11 Cross Compiling Options Cross compiling also known as cross building can be used to build Python for another CPU architecture or platform Cross compiling requires a Python interpreter for the build platform The version of the build Python must match the version of the cross compiled host Python build BUILD configure for building on BUILD usually guessed by config guess host HOST cross compile to build programs to run on HOST target platform with build python path to python path to build python binary for cross compiling New in version 3 11 CONFIG_SITE file An environment variable that points to a file with configure overrides Example config site file config site aarch64 ac_cv_buggy_getaddrinfo no ac_cv_file__dev_ptmx yes ac_cv_file__dev_ptc no Cross compiling example CONFIG_SITE config site aarch64 configure build x86_64 pc linux gnu host aarch64 unknown linux gnu with build python x86_64 python 3 4 Python Build System 3 4 1 Main files of the build system configure ac configure Makefile pre in Makefile created by configure pyconfig h created by configure Modules Setup C extensions built by the Makefile using Module makesetup shell script 3 4 2 Main build steps C files c are built as object files o A static libpython library a is created from objects files python o and the static libpython library are linked into the final python program C extensions are built by the Makefile see Modules Setup 3 4 3 Main Makefile targets make Build Python with the standard library make platform build the python program but don t build the standard library extension modules make profile opt build Python using Profile Guided Optimization PGO You can use the configure enable optimizations option to make this the default target of the make command make all or just make make buildbottest Build Python and run the Python test suite the same way than buildbots test Python Set TESTTIMEOUT variable in seconds to change the test timeout 1200 by,en
277, default 20 minutes make install Build and install Python make regen all Regenerate almost all generated files make regen stdlib module names and autoconf must be run separately for the remaining generated files make clean Remove built files make distclean Same than make clean but remove also files created by the configure script 3 4 4 C extensions Some C extensions are built as built in modules like the sys module They are built with the Py_BUILD_CORE_BUILTIN macro defined Built in modules have no __file__ attribute import sys sys module sys built in sys __file__ Traceback most recent call last File stdin line 1 in module AttributeError module sys has no attribute __file__ Other C extensions are built as dynamic libraries like the _asyncio module They are built with the Py_BUILD_CORE_MODULE macro defined Example on Linux x86 64 import _asyncio _asyncio module _asyncio from usr lib64 python3 9 lib dynload _asyncio cpython 39 x86_64 linux gnu so _asyncio __file__ usr lib64 python3 9 lib dynload _asyncio cpython 39 x86_64 linux gnu so Modules Setup is used to generate Makefile targets to build C extensions At the beginning of the files C extensions are built as built in modules Extensions defined after the shared marker are built as dynamic libraries The PyAPI_FUNC PyAPI_DATA and PyMODINIT_FUNC macros of Include exports h are defined differently depending if the Py_BUILD_CORE_MODULE macro is defined Use Py_EXPORTED_SYMBOL if the Py_BUILD_CORE_MODULE is defined Use Py_IMPORTED_SYMBOL otherwise If the Py_BUILD_CORE_BUILTIN macro is used by mistake on a C extension built as a shared library its PyInit_ xxx function is not exported causing an ImportError on import 3 5 Compiler and linker flags Options set by the configure script and environment variables and used by Makefile 3 5 1 Preprocessor flags CONFIGURE_CPPFLAGS Value of CPPFLAGS variable passed to the configure script New in version 3 6 CPPFLAGS Objective C C preprocessor flags e g I include_dir if you have headers in a nonstandard directory include_dir Both CPPFLAGS and LDFLAGS need to contain the shell s value to be able to build extension modules using the directories specified in the environment variables BASECPPFLAGS New in version 3 4 PY_CPPFLAGS Extra preprocessor flags added for building the interpreter object files Default BASECPPFLAGS I I srcdir Include CONFIGURE_CPPFLAGS CPPFLAGS New in version 3 2 3 5 2 Compiler flags CC C compiler command Example gcc pthread CXX C compiler command Example g pthread CFLAGS C compiler flags CFLAGS_NODIST CFLAGS_NODIST is used for building the interpreter and stdlib C extensions Use it when a compiler flag should not be part of CFLAGS once Python is installed gh 65320 In particular CFLAGS should not contain the compiler flag I for setting the search path for include files The I flags are processed from left to right and any flags in CFLAGS would take precedence over user and package supplied I flags hardening flags such as Werror because distributions cannot control whether packages installed by users conform to such heightened standards New in version 3 5 COMPILEALL_OPTS Options passed to the compileall command line when building PYC files in make install Default j0 New in version 3 12 EXTRA_CFLAGS Extra C compiler flags CONFIGURE_CFLAGS Value of CFLAGS variable passed to the configure script New in version 3 2 CONFIGURE_CFLAGS_NODIST Value of CFLAGS_NODIST variable passed to the configure script New in version 3 5 BASECFLAGS Base compiler flags OPT Optimization flags CFLAGS_ALIASING Strict or non strict aliasing flags used to compile Python dtoa c New in version 3 7 CCSHARED Compiler flags used to build a shared library For example fPIC is used on Linux and on BSD CFLAGSFORSHARED Extra C flags added for building the interpreter object files Default CCSHARED when enable shared is used or an empty string otherwise PY_CFLAGS Default BASECFLAGS OPT CONFIGURE_CFLAGS CFLAGS EXTRA_CFLAGS PY_CFLAGS_NODIST Default CONFIGURE_CFLAGS_NODIST CFLAGS_NODIST I srcdir Include internal New in version 3 5 PY_STDMODULE_CFLAGS C flags used for b,en
278,uilding the interpreter object files Default PY_CFLAGS PY_CFLAGS_NODIST PY_CPPFLAGS CFLAGSFORSHARED New in version 3 7 PY_CORE_CFLAGS Default PY_STDMODULE_CFLAGS DPy_BUILD_CORE New in version 3 2 PY_BUILTIN_MODULE_CFLAGS Compiler flags to build a standard library extension module as a built in module like the posix module Default PY_STDMODULE_CFLAGS DPy_BUILD_CORE_BUILTIN New in version 3 8 PURIFY Purify command Purify is a memory debugger program Default empty string not used 3 5 3 Linker flags LINKCC Linker command used to build programs like python and _testembed Default PURIFY CC CONFIGURE_LDFLAGS Value of LDFLAGS variable passed to the configure script Avoid assigning CFLAGS LDFLAGS etc so users can use them on the command line to append to these values without stomping the pre set values New in version 3 2 LDFLAGS_NODIST LDFLAGS_NODIST is used in the same manner as CFLAGS_NODIST Use it when a linker flag should not be part of LDFLAGS once Python is installed gh 65320 In particular LDFLAGS should not contain the compiler flag L for setting the search path for libraries The L flags are processed from left to right and any flags in LDFLAGS would take precedence over user and package supplied L flags CONFIGURE_LDFLAGS_NODIST Value of LDFLAGS_NODIST variable passed to the configure script New in version 3 8 LDFLAGS Linker flags e g L lib_dir if you have libraries in a nonstandard directory lib_dir Both CPPFLAGS and LDFLAGS need to contain the shell s value to be able to build extension modules using the directories specified in the environment variables LIBS Linker flags to pass libraries to the linker when linking the Python executable Example lrt LDSHARED Command to build a shared library Default LDSHARED PY_LDFLAGS BLDSHARED Command to build libpython shared library Default BLDSHARED PY_CORE_LDFLAGS PY_LDFLAGS Default CONFIGURE_LDFLAGS LDFLAGS PY_LDFLAGS_NODIST Default CONFIGURE_LDFLAGS_NODIST LDFLAGS_NODIST New in version 3 8 PY_CORE_LDFLAGS Linker flags used for building the interpreter object files New in version 3 8,en
279,Logging Cookbook Author Vinay Sajip vinay_sajip at red dove dot com This page contains a number of recipes related to logging which have been found useful in the past For links to tutorial and reference information please see Other resources Using logging in multiple modules Multiple calls to logging getLogger someLogger return a reference to the same logger object This is true not only within the same module but also across modules as long as it is in the same Python interpreter process It is true for references to the same object additionally application code can define and configure a parent logger in one module and create but not configure a child logger in a separate module and all logger calls to the child will pass up to the parent Here is a main module import logging import auxiliary_module create logger with spam_application logger logging getLogger spam_application logger setLevel logging DEBUG create file handler which logs even debug messages fh logging FileHandler spam log fh setLevel logging DEBUG create console handler with a higher log level ch logging StreamHandler ch setLevel logging ERROR create formatter and add it to the handlers formatter logging Formatter asctime s name s levelname s message s fh setFormatter formatter ch setFormatter formatter add the handlers to the logger logger addHandler fh logger addHandler ch logger info creating an instance of auxiliary_module Auxiliary a auxiliary_module Auxiliary logger info created an instance of auxiliary_module Auxiliary logger info calling auxiliary_module Auxiliary do_something a do_something logger info finished auxiliary_module Auxiliary do_something logger info calling auxiliary_module some_function auxiliary_module some_function logger info done with auxiliary_module some_function Here is the auxiliary module import logging create logger module_logger logging getLogger spam_application auxiliary class Auxiliary def __init__ self self logger logging getLogger spam_application auxiliary Auxiliary self logger info creating an instance of Auxiliary def do_something self self logger info doing something a 1 1 self logger info done doing something def some_function module_logger info received a call to some_function The output looks like this 2005 03 23 23 47 11 663 spam_application INFO creating an instance of auxiliary_module Auxiliary 2005 03 23 23 47 11 665 spam_application auxiliary Auxiliary INFO creating an instance of Auxiliary 2005 03 23 23 47 11 665 spam_application INFO created an instance of auxiliary_module Auxiliary 2005 03 23 23 47 11 668 spam_application INFO calling auxiliary_module Auxiliary do_something 2005 03 23 23 47 11 668 spam_application auxiliary Auxiliary INFO doing something 2005 03 23 23 47 11 669 spam_application auxiliary Auxiliary INFO done doing something 2005 03 23 23 47 11 670 spam_application INFO finished auxiliary_module Auxiliary do_something 2005 03 23 23 47 11 671 spam_application INFO calling auxiliary_module some_function 2005 03 23 23 47 11 672 spam_application auxiliary INFO received a call to some_function 2005 03 23 23 47 11 673 spam_application INFO done with auxiliary_module some_function Logging from multiple threads Logging from multiple threads requires no special effort The following example shows logging from the main initial thread and another thread import logging import threading import time def worker arg while not arg stop logging debug Hi from myfunc time sleep 0 5 def main logging basicConfig level logging DEBUG format relativeCreated 6d threadName s message s info stop False thread threading Thread target worker args info thread start while True try logging debug Hello from main time sleep 0 75 except KeyboardInterrupt info stop True break thread join if __name__ __main__ main When run the script should print something like the following 0 Thread 1 Hi from myfunc 3 MainThread Hello from main 505 Thread 1 Hi from myfunc 755 MainThread Hello from main 1007 Thread 1 Hi from myfunc 1507 MainThread Hello from main 1508 Thread 1 Hi from myfunc 2010 Thread 1 Hi from myfunc 2258 MainThread Hello fro,en
280,m main 2512 Thread 1 Hi from myfunc 3009 MainThread Hello from main 3013 Thread 1 Hi from myfunc 3515 Thread 1 Hi from myfunc 3761 MainThread Hello from main 4017 Thread 1 Hi from myfunc 4513 MainThread Hello from main 4518 Thread 1 Hi from myfunc This shows the logging output interspersed as one might expect This approach works for more threads than shown here of course Multiple handlers and formatters Loggers are plain Python objects The addHandler method has no minimum or maximum quota for the number of handlers you may add Sometimes it will be beneficial for an application to log all messages of all severities to a text file while simultaneously logging errors or above to the console To set this up simply configure the appropriate handlers The logging calls in the application code will remain unchanged Here is a slight modification to the previous simple module based configuration example import logging logger logging getLogger simple_example logger setLevel logging DEBUG create file handler which logs even debug messages fh logging FileHandler spam log fh setLevel logging DEBUG create console handler with a higher log level ch logging StreamHandler ch setLevel logging ERROR create formatter and add it to the handlers formatter logging Formatter asctime s name s levelname s message s ch setFormatter formatter fh setFormatter formatter add the handlers to logger logger addHandler ch logger addHandler fh application code logger debug debug message logger info info message logger warning warn message logger error error message logger critical critical message Notice that the application code does not care about multiple handlers All that changed was the addition and configuration of a new handler named fh The ability to create new handlers with higher or lower severity filters can be very helpful when writing and testing an application Instead of using many print statements for debugging use logger debug Unlike the print statements which you will have to delete or comment out later the logger debug statements can remain intact in the source code and remain dormant until you need them again At that time the only change that needs to happen is to modify the severity level of the logger and or handler to debug Logging to multiple destinations Let s say you want to log to console and file with different message formats and in differing circumstances Say you want to log messages with levels of DEBUG and higher to file and those messages at level INFO and higher to the console Let s also assume that the file should contain timestamps but the console messages should not Here s how you can achieve this import logging set up logging to file see previous section for more details logging basicConfig level logging DEBUG format asctime s name 12s levelname 8s message s datefmt m d H M filename tmp myapp log filemode w define a Handler which writes INFO messages or higher to the sys stderr console logging StreamHandler console setLevel logging INFO set a format which is simpler for console use formatter logging Formatter name 12s levelname 8s message s tell the handler to use this format console setFormatter formatter add the handler to the root logger logging getLogger addHandler console Now we can log to the root logger or any other logger First the root logging info Jackdaws love my big sphinx of quartz Now define a couple of other loggers which might represent areas in your application logger1 logging getLogger myapp area1 logger2 logging getLogger myapp area2 logger1 debug Quick zephyrs blow vexing daft Jim logger1 info How quickly daft jumping zebras vex logger2 warning Jail zesty vixen who grabbed pay from quack logger2 error The five boxing wizards jump quickly When you run this on the console you will see root INFO Jackdaws love my big sphinx of quartz myapp area1 INFO How quickly daft jumping zebras vex myapp area2 WARNING Jail zesty vixen who grabbed pay from quack myapp area2 ERROR The five boxing wizards jump quickly and in the file you will see something like 10 22 22 19 root INFO Jackdaws love my big sphinx of quartz 1,en
281,0 22 22 19 myapp area1 DEBUG Quick zephyrs blow vexing daft Jim 10 22 22 19 myapp area1 INFO How quickly daft jumping zebras vex 10 22 22 19 myapp area2 WARNING Jail zesty vixen who grabbed pay from quack 10 22 22 19 myapp area2 ERROR The five boxing wizards jump quickly As you can see the DEBUG message only shows up in the file The other messages are sent to both destinations This example uses console and file handlers but you can use any number and combination of handlers you choose Note that the above choice of log filename tmp myapp log implies use of a standard location for temporary files on POSIX systems On Windows you may need to choose a different directory name for the log just ensure that the directory exists and that you have the permissions to create and update files in it Custom handling of levels Sometimes you might want to do something slightly different from the standard handling of levels in handlers where all levels above a threshold get processed by a handler To do this you need to use filters Let s look at a scenario where you want to arrange things as follows Send messages of severity INFO and WARNING to sys stdout Send messages of severity ERROR and above to sys stderr Send messages of severity DEBUG and above to file app log Suppose you configure logging with the following JSON version 1 disable_existing_loggers false formatters simple format levelname 8s message s handlers stdout class logging StreamHandler level INFO formatter simple stream ext sys stdout stderr class logging StreamHandler level ERROR formatter simple stream ext sys stderr file class logging FileHandler formatter simple filename app log mode w root level DEBUG handlers stderr stdout file This configuration does almost what we want except that sys stdout would show messages of severity ERROR and above as well as INFO and WARNING messages To prevent this we can set up a filter which excludes those messages and add it to the relevant handler This can be configured by adding a filters section parallel to formatters and handlers filters warnings_and_below __main__ filter_maker level WARNING and changing the section on the stdout handler to add it stdout class logging StreamHandler level INFO formatter simple stream ext sys stdout filters warnings_and_below A filter is just a function so we can define the filter_maker a factory function as follows def filter_maker level level getattr logging level def filter record return record levelno level return filter This converts the string argument passed in to a numeric level and returns a function which only returns True if the level of the passed in record is at or below the specified level Note that in this example I have defined the filter_maker in a test script main py that I run from the command line so its module will be __main__ hence the __main__ filter_maker in the filter configuration You will need to change that if you define it in a different module With the filter added we can run main py which in full is import json import logging import logging config CONFIG version 1 disable_existing_loggers false formatters simple format levelname 8s message s filters warnings_and_below __main__ filter_maker level WARNING handlers stdout class logging StreamHandler level INFO formatter simple stream ext sys stdout filters warnings_and_below stderr class logging StreamHandler level ERROR formatter simple stream ext sys stderr file class logging FileHandler formatter simple filename app log mode w root level DEBUG handlers stderr stdout file def filter_maker level level getattr logging level def filter record return record levelno level return filter logging config dictConfig json loads CONFIG logging debug A DEBUG message logging info An INFO message logging warning A WARNING message logging error An ERROR message logging critical A CRITICAL message And after running it like this python main py 2 stderr log stdout log We can see the results are as expected more log app log DEBUG A DEBUG message INFO An INFO message WARNING A WARNING message ERROR An ERROR message CRITICAL A CRITICAL message s,en
282,tderr log ERROR An ERROR message CRITICAL A CRITICAL message stdout log INFO An INFO message WARNING A WARNING message Configuration server example Here is an example of a module using the logging configuration server import logging import logging config import time import os read initial config file logging config fileConfig logging conf create and start listener on port 9999 t logging config listen 9999 t start logger logging getLogger simpleExample try loop through logging calls to see the difference new configurations make until Ctrl C is pressed while True logger debug debug message logger info info message logger warning warn message logger error error message logger critical critical message time sleep 5 except KeyboardInterrupt cleanup logging config stopListening t join And here is a script that takes a filename and sends that file to the server properly preceded with the binary encoded length as the new logging configuration usr bin env python import socket sys struct with open sys argv 1 rb as f data_to_send f read HOST localhost PORT 9999 s socket socket socket AF_INET socket SOCK_STREAM print connecting s connect HOST PORT print sending config s send struct pack L len data_to_send s send data_to_send s close print complete Dealing with handlers that block Sometimes you have to get your logging handlers to do their work without blocking the thread you re logging from This is common in web applications though of course it also occurs in other scenarios A common culprit which demonstrates sluggish behaviour is the SMTPHandler sending emails can take a long time for a number of reasons outside the developer s control for example a poorly performing mail or network infrastructure But almost any network based handler can block Even a SocketHandler operation may do a DNS query under the hood which is too slow and this query can be deep in the socket library code below the Python layer and outside your control One solution is to use a two part approach For the first part attach only a QueueHandler to those loggers which are accessed from performance critical threads They simply write to their queue which can be sized to a large enough capacity or initialized with no upper bound to their size The write to the queue will typically be accepted quickly though you will probably need to catch the queue Full exception as a precaution in your code If you are a library developer who has performance critical threads in their code be sure to document this together with a suggestion to attach only QueueHandlers to your loggers for the benefit of other developers who will use your code The second part of the solution is QueueListener which has been designed as the counterpart to QueueHandler A QueueListener is very simple it s passed a queue and some handlers and it fires up an internal thread which listens to its queue for LogRecords sent from QueueHandlers or any other source of LogRecords for that matter The LogRecords are removed from the queue and passed to the handlers for processing The advantage of having a separate QueueListener class is that you can use the same instance to service multiple QueueHandlers This is more resource friendly than say having threaded versions of the existing handler classes which would eat up one thread per handler for no particular benefit An example of using these two classes follows imports omitted que queue Queue 1 no limit on size queue_handler QueueHandler que handler logging StreamHandler listener QueueListener que handler root logging getLogger root addHandler queue_handler formatter logging Formatter threadName s message s handler setFormatter formatter listener start The log output will display the thread which generated the event the main thread rather than the internal thread which monitors the internal queue This is what you want to happen root warning Look out listener stop which when run will produce MainThread Look out Note Although the earlier discussion wasn t specifically talking about async code but rather about slow logging handlers it should be noted that when logging fro,en
283,m async code network and even file handlers could lead to problems blocking the event loop because some logging is done from asyncio internals It might be best if any async code is used in an application to use the above approach for logging so that any blocking code runs only in the QueueListener thread Changed in version 3 5 Prior to Python 3 5 the QueueListener always passed every message received from the queue to every handler it was initialized with This was because it was assumed that level filtering was all done on the other side where the queue is filled From 3 5 onwards this behaviour can be changed by passing a keyword argument respect_handler_level True to the listener s constructor When this is done the listener compares the level of each message with the handler s level and only passes a message to a handler if it s appropriate to do so Sending and receiving logging events across a network Let s say you want to send logging events across a network and handle them at the receiving end A simple way of doing this is attaching a SocketHandler instance to the root logger at the sending end import logging logging handlers rootLogger logging getLogger rootLogger setLevel logging DEBUG socketHandler logging handlers SocketHandler localhost logging handlers DEFAULT_TCP_LOGGING_PORT don t bother with a formatter since a socket handler sends the event as an unformatted pickle rootLogger addHandler socketHandler Now we can log to the root logger or any other logger First the root logging info Jackdaws love my big sphinx of quartz Now define a couple of other loggers which might represent areas in your application logger1 logging getLogger myapp area1 logger2 logging getLogger myapp area2 logger1 debug Quick zephyrs blow vexing daft Jim logger1 info How quickly daft jumping zebras vex logger2 warning Jail zesty vixen who grabbed pay from quack logger2 error The five boxing wizards jump quickly At the receiving end you can set up a receiver using the socketserver module Here is a basic working example import pickle import logging import logging handlers import socketserver import struct class LogRecordStreamHandler socketserver StreamRequestHandler Handler for a streaming logging request This basically logs the record using whatever logging policy is configured locally def handle self Handle multiple requests each expected to be a 4 byte length followed by the LogRecord in pickle format Logs the record according to whatever policy is configured locally while True chunk self connection recv 4 if len chunk 4 break slen struct unpack L chunk 0 chunk self connection recv slen while len chunk slen chunk chunk self connection recv slen len chunk obj self unPickle chunk record logging makeLogRecord obj self handleLogRecord record def unPickle self data return pickle loads data def handleLogRecord self record if a name is specified we use the named logger rather than the one implied by the record if self server logname is not None name self server logname else name record name logger logging getLogger name N B EVERY record gets logged This is because Logger handle is normally called AFTER logger level filtering If you want to do filtering do it at the client end to save wasting cycles and network bandwidth logger handle record class LogRecordSocketReceiver socketserver ThreadingTCPServer Simple TCP socket based logging receiver suitable for testing allow_reuse_address True def __init__ self host localhost port logging handlers DEFAULT_TCP_LOGGING_PORT handler LogRecordStreamHandler socketserver ThreadingTCPServer __init__ self host port handler self abort 0 self timeout 1 self logname None def serve_until_stopped self import select abort 0 while not abort rd wr ex select select self socket fileno self timeout if rd self handle_request abort self abort def main logging basicConfig format relativeCreated 5d name 15s levelname 8s message s tcpserver LogRecordSocketReceiver print About to start TCP server tcpserver serve_until_stopped if __name__ __main__ main First run the server and then the client On the client side nothing is pr,en
284,inted on the console on the server side you should see something like About to start TCP server 59 root INFO Jackdaws love my big sphinx of quartz 59 myapp area1 DEBUG Quick zephyrs blow vexing daft Jim 69 myapp area1 INFO How quickly daft jumping zebras vex 69 myapp area2 WARNING Jail zesty vixen who grabbed pay from quack 69 myapp area2 ERROR The five boxing wizards jump quickly Note that there are some security issues with pickle in some scenarios If these affect you you can use an alternative serialization scheme by overriding the makePickle method and implementing your alternative there as well as adapting the above script to use your alternative serialization Running a logging socket listener in production To run a logging listener in production you may need to use a process management tool such as Supervisor Here is a Gist which provides the bare bones files to run the above functionality using Supervisor It consists of the following files File Purpose prepare sh A Bash script to prepare the environment for testing supervisor conf The Supervisor configuration file which has entries for the listener and a multi process web application ensure_app sh A Bash script to ensure that Supervisor is running with the above configuration log_listener py The socket listener program which receives log events and records them to a file main py A simple web application which performs logging via a socket connected to the listener webapp json A JSON configuration file for the web application client py A Python script to exercise the web application The web application uses Gunicorn which is a popular web application server that starts multiple worker processes to handle requests This example setup shows how the workers can write to the same log file without conflicting with one another they all go through the socket listener To test these files do the following in a POSIX environment 1 Download the Gist as a ZIP archive using the Download ZIP button 2 Unzip the above files from the archive into a scratch directory 3 In the scratch directory run bash prepare sh to get things ready This creates a run subdirectory to contain Supervisor related and log files and a venv subdirectory to contain a virtual environment into which bottle gunicorn and supervisor are installed 4 Run bash ensure_app sh to ensure that Supervisor is running with the above configuration 5 Run venv bin python client py to exercise the web application which will lead to records being written to the log 6 Inspect the log files in the run subdirectory You should see the most recent log lines in files matching the pattern app log They won t be in any particular order since they have been handled concurrently by different worker processes in a non deterministic way 7 You can shut down the listener and the web application by running venv bin supervisorctl c supervisor conf shutdown You may need to tweak the configuration files in the unlikely event that the configured ports clash with something else in your test environment Adding contextual information to your logging output Sometimes you want logging output to contain contextual information in addition to the parameters passed to the logging call For example in a networked application it may be desirable to log client specific information in the log e g remote client s username or IP address Although you could use the extra parameter to achieve this it s not always convenient to pass the information in this way While it might be tempting to create Logger instances on a per connection basis this is not a good idea because these instances are not garbage collected While this is not a problem in practice when the number of Logger instances is dependent on the level of granularity you want to use in logging an application it could be hard to manage if the number of Logger instances becomes effectively unbounded Using LoggerAdapters to impart contextual information An easy way in which you can pass contextual information to be output along with logging event information is to use the LoggerAdapter class This class is desig,en
285,ned to look like a Logger so that you can call debug info warning error exception critical and log These methods have the same signatures as their counterparts in Logger so you can use the two types of instances interchangeably When you create an instance of LoggerAdapter you pass it a Logger instance and a dict like object which contains your contextual information When you call one of the logging methods on an instance of LoggerAdapter it delegates the call to the underlying instance of Logger passed to its constructor and arranges to pass the contextual information in the delegated call Here s a snippet from the code of LoggerAdapter def debug self msg args kwargs Delegate a debug call to the underlying logger after adding contextual information from this adapter instance msg kwargs self process msg kwargs self logger debug msg args kwargs The process method of LoggerAdapter is where the contextual information is added to the logging output It s passed the message and keyword arguments of the logging call and it passes back potentially modified versions of these to use in the call to the underlying logger The default implementation of this method leaves the message alone but inserts an extra key in the keyword argument whose value is the dict like object passed to the constructor Of course if you had passed an extra keyword argument in the call to the adapter it will be silently overwritten The advantage of using extra is that the values in the dict like object are merged into the LogRecord instance s __dict__ allowing you to use customized strings with your Formatter instances which know about the keys of the dict like object If you need a different method e g if you want to prepend or append the contextual information to the message string you just need to subclass LoggerAdapter and override process to do what you need Here is a simple example class CustomAdapter logging LoggerAdapter This example adapter expects the passed in dict like object to have a connid key whose value in brackets is prepended to the log message def process self msg kwargs return s s self extra connid msg kwargs which you can use like this logger logging getLogger __name__ adapter CustomAdapter logger connid some_conn_id Then any events that you log to the adapter will have the value of some_conn_id prepended to the log messages Using objects other than dicts to pass contextual information You don t need to pass an actual dict to a LoggerAdapter you could pass an instance of a class which implements __getitem__ and __iter__ so that it looks like a dict to logging This would be useful if you want to generate values dynamically whereas the values in a dict would be constant Using Filters to impart contextual information You can also add contextual information to log output using a user defined Filter Filter instances are allowed to modify the LogRecords passed to them including adding additional attributes which can then be output using a suitable format string or if needed a custom Formatter For example in a web application the request being processed or at least the interesting parts of it can be stored in a threadlocal threading local variable and then accessed from a Filter to add say information from the request say the remote IP address and remote user s username to the LogRecord using the attribute names ip and user as in the LoggerAdapter example above In that case the same format string can be used to get similar output to that shown above Here s an example script import logging from random import choice class ContextFilter logging Filter This is a filter which injects contextual information into the log Rather than use actual contextual information we just use random data in this demo USERS jim fred sheila IPS 123 231 231 123 127 0 0 1 192 168 0 1 def filter self record record ip choice ContextFilter IPS record user choice ContextFilter USERS return True if __name__ __main__ levels logging DEBUG logging INFO logging WARNING logging ERROR logging CRITICAL logging basicConfig level logging DEBUG format asctime 15s name 5s levelname 8s I,en
286,P ip 15s User user 8s message s a1 logging getLogger a b c a2 logging getLogger d e f f ContextFilter a1 addFilter f a2 addFilter f a1 debug A debug message a1 info An info message with s some parameters for x in range 10 lvl choice levels lvlname logging getLevelName lvl a2 log lvl A message at s level with d s lvlname 2 parameters which when run produces something like 2010 09 06 22 38 15 292 a b c DEBUG IP 123 231 231 123 User fred A debug message 2010 09 06 22 38 15 300 a b c INFO IP 192 168 0 1 User sheila An info message with some parameters 2010 09 06 22 38 15 300 d e f CRITICAL IP 127 0 0 1 User sheila A message at CRITICAL level with 2 parameters 2010 09 06 22 38 15 300 d e f ERROR IP 127 0 0 1 User jim A message at ERROR level with 2 parameters 2010 09 06 22 38 15 300 d e f DEBUG IP 127 0 0 1 User sheila A message at DEBUG level with 2 parameters 2010 09 06 22 38 15 300 d e f ERROR IP 123 231 231 123 User fred A message at ERROR level with 2 parameters 2010 09 06 22 38 15 300 d e f CRITICAL IP 192 168 0 1 User jim A message at CRITICAL level with 2 parameters 2010 09 06 22 38 15 300 d e f CRITICAL IP 127 0 0 1 User sheila A message at CRITICAL level with 2 parameters 2010 09 06 22 38 15 300 d e f DEBUG IP 192 168 0 1 User jim A message at DEBUG level with 2 parameters 2010 09 06 22 38 15 301 d e f ERROR IP 127 0 0 1 User sheila A message at ERROR level with 2 parameters 2010 09 06 22 38 15 301 d e f DEBUG IP 123 231 231 123 User fred A message at DEBUG level with 2 parameters 2010 09 06 22 38 15 301 d e f INFO IP 123 231 231 123 User fred A message at INFO level with 2 parameters Use of contextvars Since Python 3 7 the contextvars module has provided context local storage which works for both threading and asyncio processing needs This type of storage may thus be generally preferable to thread locals The following example shows how in a multi threaded environment logs can populated with contextual information such as for example request attributes handled by web applications For the purposes of illustration say that you have different web applications each independent of the other but running in the same Python process and using a library common to them How can each of these applications have their own log where all logging messages from the library and other request processing code are directed to the appropriate application s log file while including in the log additional contextual information such as client IP HTTP request method and client username Let s assume that the library can be simulated by the following code webapplib py import logging import time logger logging getLogger __name__ def useful Just a representative event logged from the library logger debug Hello from webapplib Just sleep for a bit so other threads get to run time sleep 0 01 We can simulate the multiple web applications by means of two simple classes Request and WebApp These simulate how real threaded web applications work each request is handled by a thread main py import argparse from contextvars import ContextVar import logging import os from random import choice import threading import webapplib logger logging getLogger __name__ root logging getLogger root setLevel logging DEBUG class Request A simple dummy request class which just holds dummy HTTP request method client IP address and client username def __init__ self method ip user self method method self ip ip self user user A dummy set of requests which will be used in the simulation we ll just pick from this list randomly Note that all GET requests are from 192 168 2 XXX addresses whereas POST requests are from 192 16 3 XXX addresses Three users are represented in the sample requests REQUESTS Request GET 192 168 2 20 jim Request POST 192 168 3 20 fred Request GET 192 168 2 21 sheila Request POST 192 168 3 21 jim Request GET 192 168 2 22 fred Request POST 192 168 3 22 sheila Note that the format string includes references to request context information such as HTTP method client IP and username formatter logging Formatter threadName 11s appName s name 9s user 6s ip s method 4s,en
287, message s Create our context variables These will be filled at the start of request processing and used in the logging that happens during that processing ctx_request ContextVar request ctx_appname ContextVar appname class InjectingFilter logging Filter A filter which injects context specific information into logs and ensures that only information for a specific webapp is included in its log def __init__ self app self app app def filter self record request ctx_request get record method request method record ip request ip record user request user record appName appName ctx_appname get return appName self app name class WebApp A dummy web application class which has its own handler and filter for a webapp specific log def __init__ self name self name name handler logging FileHandler name log w f InjectingFilter self handler setFormatter formatter handler addFilter f root addHandler handler self num_requests 0 def process_request self request This is the dummy method for processing a request It s called on a different thread for every request We store the context information into the context vars before doing anything else ctx_request set request ctx_appname set self name self num_requests 1 logger debug Request processing started webapplib useful logger debug Request processing finished def main fn os path splitext os path basename __file__ 0 adhf argparse ArgumentDefaultsHelpFormatter ap argparse ArgumentParser formatter_class adhf prog fn description Simulate a couple of web applications handling some requests showing how request context can be used to populate logs aa ap add_argument aa count c type int default 100 help How many requests to simulate options ap parse_args Create the dummy webapps and put them in a list which we can use to select from randomly app1 WebApp app1 app2 WebApp app2 apps app1 app2 threads Add a common handler which will capture all events handler logging FileHandler app log w handler setFormatter formatter root addHandler handler Generate calls to process requests for i in range options count try Pick an app at random and a request for it to process app choice apps request choice REQUESTS Process the request in its own thread t threading Thread target app process_request args request threads append t t start except KeyboardInterrupt break Wait for the threads to terminate for t in threads t join for app in apps print s processed s requests app name app num_requests if __name__ __main__ main If you run the above you should find that roughly half the requests go into app1 log and the rest into app2 log and the all the requests are logged to app log Each webapp specific log will contain only log entries for only that webapp and the request information will be displayed consistently in the log i e the information in each dummy request will always appear together in a log line This is illustrated by the following shell output logging contextual webapp python main py app1 processed 51 requests app2 processed 49 requests logging contextual webapp wc l log 153 app1 log 147 app2 log 300 app log 600 total logging contextual webapp head 3 app1 log Thread 3 process_request app1 __main__ jim 192 168 3 21 POST Request processing started Thread 3 process_request app1 webapplib jim 192 168 3 21 POST Hello from webapplib Thread 5 process_request app1 __main__ jim 192 168 3 21 POST Request processing started logging contextual webapp head 3 app2 log Thread 1 process_request app2 __main__ sheila 192 168 2 21 GET Request processing started Thread 1 process_request app2 webapplib sheila 192 168 2 21 GET Hello from webapplib Thread 2 process_request app2 __main__ jim 192 168 2 20 GET Request processing started logging contextual webapp head app log Thread 1 process_request app2 __main__ sheila 192 168 2 21 GET Request processing started Thread 1 process_request app2 webapplib sheila 192 168 2 21 GET Hello from webapplib Thread 2 process_request app2 __main__ jim 192 168 2 20 GET Request processing started Thread 3 process_request app1 __main__ jim 192 168 3 21 POST Request processing started Thread 2 process_reques,en
288,t app2 webapplib jim 192 168 2 20 GET Hello from webapplib Thread 3 process_request app1 webapplib jim 192 168 3 21 POST Hello from webapplib Thread 4 process_request app2 __main__ fred 192 168 2 22 GET Request processing started Thread 5 process_request app1 __main__ jim 192 168 3 21 POST Request processing started Thread 4 process_request app2 webapplib fred 192 168 2 22 GET Hello from webapplib Thread 6 process_request app1 __main__ jim 192 168 3 21 POST Request processing started logging contextual webapp grep app1 app1 log wc l 153 logging contextual webapp grep app2 app2 log wc l 147 logging contextual webapp grep app1 app log wc l 153 logging contextual webapp grep app2 app log wc l 147 Imparting contextual information in handlers Each Handler has its own chain of filters If you want to add contextual information to a LogRecord without leaking it to other handlers you can use a filter that returns a new LogRecord instead of modifying it in place as shown in the following script import copy import logging def filter record logging LogRecord record copy copy record record user jim return record if __name__ __main__ logger logging getLogger logger setLevel logging INFO handler logging StreamHandler formatter logging Formatter message s from user 8s handler setFormatter formatter handler addFilter filter logger addHandler handler logger info A log message Logging to a single file from multiple processes Although logging is thread safe and logging to a single file from multiple threads in a single process is supported logging to a single file from multiple processes is not supported because there is no standard way to serialize access to a single file across multiple processes in Python If you need to log to a single file from multiple processes one way of doing this is to have all the processes log to a SocketHandler and have a separate process which implements a socket server which reads from the socket and logs to file If you prefer you can dedicate one thread in one of the existing processes to perform this function This section documents this approach in more detail and includes a working socket receiver which can be used as a starting point for you to adapt in your own applications You could also write your own handler which uses the Lock class from the multiprocessing module to serialize access to the file from your processes The existing FileHandler and subclasses do not make use of multiprocessing at present though they may do so in the future Note that at present the multiprocessing module does not provide working lock functionality on all platforms see https bugs python org issue3770 Alternatively you can use a Queue and a QueueHandler to send all logging events to one of the processes in your multi process application The following example script demonstrates how you can do this in the example a separate listener process listens for events sent by other processes and logs them according to its own logging configuration Although the example only demonstrates one way of doing it for example you may want to use a listener thread rather than a separate listener process the implementation would be analogous it does allow for completely different logging configurations for the listener and the other processes in your application and can be used as the basis for code meeting your own specific requirements You ll need these imports in your own code import logging import logging handlers import multiprocessing Next two import lines for this demo only from random import choice random import time Because you ll want to define the logging configurations for listener and workers the listener and worker process functions take a configurer parameter which is a callable for configuring logging for that process These functions are also passed the queue which they use for communication In practice you can configure the listener however you want but note that in this simple example the listener does not apply level or filter logic to received records In practice you would probably want to do this logic in the worker processes,en
289, to avoid sending events which would be filtered out between processes The size of the rotated files is made small so you can see the results easily def listener_configurer root logging getLogger h logging handlers RotatingFileHandler mptest log a 300 10 f logging Formatter asctime s processName 10s name s levelname 8s message s h setFormatter f root addHandler h This is the listener process top level loop wait for logging events LogRecords on the queue and handle them quit when you get a None for a LogRecord def listener_process queue configurer configurer while True try record queue get if record is None We send this as a sentinel to tell the listener to quit break logger logging getLogger record name logger handle record No level or filter logic applied just do it except Exception import sys traceback print Whoops Problem file sys stderr traceback print_exc file sys stderr Arrays used for random selections in this demo LEVELS logging DEBUG logging INFO logging WARNING logging ERROR logging CRITICAL LOGGERS a b c d e f MESSAGES Random message 1 Random message 2 Random message 3 The worker configuration is done at the start of the worker process run Note that on Windows you can t rely on fork semantics so each process will run the logging configuration code when it starts def worker_configurer queue h logging handlers QueueHandler queue Just the one handler needed root logging getLogger root addHandler h send all messages for demo no other level or filter logic applied root setLevel logging DEBUG This is the worker process top level loop which just logs ten events with random intervening delays before terminating The print messages are just so you know it s doing something def worker_process queue configurer configurer queue name multiprocessing current_process name print Worker started s name for i in range 10 time sleep random logger logging getLogger choice LOGGERS level choice LEVELS message choice MESSAGES logger log level message print Worker finished s name Here s where the demo gets orchestrated Create the queue create and start the listener create ten workers and start them wait for them to finish then send a None to the queue to tell the listener to finish def main queue multiprocessing Queue 1 listener multiprocessing Process target listener_process args queue listener_configurer listener start workers for i in range 10 worker multiprocessing Process target worker_process args queue worker_configurer workers append worker worker start for w in workers w join queue put_nowait None listener join if __name__ __main__ main A variant of the above script keeps the logging in the main process in a separate thread import logging import logging config import logging handlers from multiprocessing import Process Queue import random import threading import time def logger_thread q while True record q get if record is None break logger logging getLogger record name logger handle record def worker_process q qh logging handlers QueueHandler q root logging getLogger root setLevel logging DEBUG root addHandler qh levels logging DEBUG logging INFO logging WARNING logging ERROR logging CRITICAL loggers foo foo bar foo bar baz spam spam ham spam ham eggs for i in range 100 lvl random choice levels logger logging getLogger random choice loggers logger log lvl Message no d i if __name__ __main__ q Queue d version 1 formatters detailed class logging Formatter format asctime s name 15s levelname 8s processName 10s message s handlers console class logging StreamHandler level INFO file class logging FileHandler filename mplog log mode w formatter detailed foofile class logging FileHandler filename mplog foo log mode w formatter detailed errors class logging FileHandler filename mplog errors log mode w level ERROR formatter detailed loggers foo handlers foofile root level DEBUG handlers console file errors workers for i in range 5 wp Process target worker_process name worker d i 1 args q workers append wp wp start logging config dictConfig d lp threading Thread target logger_thread args q lp start At this point the main process could d,en
290,o some useful work of its own Once it s done that it can wait for the workers to terminate for wp in workers wp join And now tell the logging thread to finish up too q put None lp join This variant shows how you can e g apply configuration for particular loggers e g the foo logger has a special handler which stores all events in the foo subsystem in a file mplog foo log This will be used by the logging machinery in the main process even though the logging events are generated in the worker processes to direct the messages to the appropriate destinations Using concurrent futures ProcessPoolExecutor If you want to use concurrent futures ProcessPoolExecutor to start your worker processes you need to create the queue slightly differently Instead of queue multiprocessing Queue 1 you should use queue multiprocessing Manager Queue 1 also works with the examples above and you can then replace the worker creation from this workers for i in range 10 worker multiprocessing Process target worker_process args queue worker_configurer workers append worker worker start for w in workers w join to this remembering to first import concurrent futures with concurrent futures ProcessPoolExecutor max_workers 10 as executor for i in range 10 executor submit worker_process queue worker_configurer Deploying Web applications using Gunicorn and uWSGI When deploying Web applications using Gunicorn or uWSGI or similar multiple worker processes are created to handle client requests In such environments avoid creating file based handlers directly in your web application Instead use a SocketHandler to log from the web application to a listener in a separate process This can be set up using a process management tool such as Supervisor see Running a logging socket listener in production for more details Using file rotation Sometimes you want to let a log file grow to a certain size then open a new file and log to that You may want to keep a certain number of these files and when that many files have been created rotate the files so that the number of files and the size of the files both remain bounded For this usage pattern the logging package provides a RotatingFileHandler import glob import logging import logging handlers LOG_FILENAME logging_rotatingfile_example out Set up a specific logger with our desired output level my_logger logging getLogger MyLogger my_logger setLevel logging DEBUG Add the log message handler to the logger handler logging handlers RotatingFileHandler LOG_FILENAME maxBytes 20 backupCount 5 my_logger addHandler handler Log some messages for i in range 20 my_logger debug i d i See what files are created logfiles glob glob s LOG_FILENAME for filename in logfiles print filename The result should be 6 separate files each with part of the log history for the application logging_rotatingfile_example out logging_rotatingfile_example out 1 logging_rotatingfile_example out 2 logging_rotatingfile_example out 3 logging_rotatingfile_example out 4 logging_rotatingfile_example out 5 The most current file is always logging_rotatingfile_example out and each time it reaches the size limit it is renamed with the suffix 1 Each of the existing backup files is renamed to increment the suffix 1 becomes 2 etc and the 6 file is erased Obviously this example sets the log length much too small as an extreme example You would want to set maxBytes to an appropriate value Use of alternative formatting styles When logging was added to the Python standard library the only way of formatting messages with variable content was to use the formatting method Since then Python has gained two new formatting approaches string Template added in Python 2 4 and str format added in Python 2 6 Logging as of 3 2 provides improved support for these two additional formatting styles The Formatter class been enhanced to take an additional optional keyword parameter named style This defaults to but other possible values are and which correspond to the other two formatting styles Backwards compatibility is maintained by default as you would expect but by explicitly specifying a st,en
291,yle parameter you get the ability to specify format strings which work with str format or string Template Here s an example console session to show the possibilities import logging root logging getLogger root setLevel logging DEBUG handler logging StreamHandler bf logging Formatter asctime name levelname 8s message style handler setFormatter bf root addHandler handler logger logging getLogger foo bar logger debug This is a DEBUG message 2010 10 28 15 11 55 341 foo bar DEBUG This is a DEBUG message logger critical This is a CRITICAL message 2010 10 28 15 12 11 526 foo bar CRITICAL This is a CRITICAL message df logging Formatter asctime name levelname message style handler setFormatter df logger debug This is a DEBUG message 2010 10 28 15 13 06 924 foo bar DEBUG This is a DEBUG message logger critical This is a CRITICAL message 2010 10 28 15 13 11 494 foo bar CRITICAL This is a CRITICAL message Note that the formatting of logging messages for final output to logs is completely independent of how an individual logging message is constructed That can still use formatting as shown here logger error This is an s s s other ERROR message 2010 10 28 15 19 29 833 foo bar ERROR This is another ERROR message Logging calls logger debug logger info etc only take positional parameters for the actual logging message itself with keyword parameters used only for determining options for how to handle the actual logging call e g the exc_info keyword parameter to indicate that traceback information should be logged or the extra keyword parameter to indicate additional contextual information to be added to the log So you cannot directly make logging calls using str format or string Template syntax because internally the logging package uses formatting to merge the format string and the variable arguments There would be no changing this while preserving backward compatibility since all logging calls which are out there in existing code will be using format strings There is however a way that you can use and formatting to construct your individual log messages Recall that for a message you can use an arbitrary object as a message format string and that the logging package will call str on that object to get the actual format string Consider the following two classes class BraceMessage def __init__ self fmt args kwargs self fmt fmt self args args self kwargs kwargs def __str__ self return self fmt format self args self kwargs class DollarMessage def __init__ self fmt kwargs self fmt fmt self kwargs kwargs def __str__ self from string import Template return Template self fmt substitute self kwargs Either of these can be used in place of a format string to allow or formatting to be used to build the actual message part which appears in the formatted log output in place of message s or message or message It s a little unwieldy to use the class names whenever you want to log something but it s quite palatable if you use an alias such as __ double underscore not to be confused with _ the single underscore used as a synonym alias for gettext gettext or its brethren The above classes are not included in Python though they re easy enough to copy and paste into your own code They can be used as follows assuming that they re declared in a module called wherever from wherever import BraceMessage as __ print __ Message with 0 name 2 name placeholders Message with 2 placeholders class Point pass p Point p x 0 5 p y 0 5 print __ Message with coordinates point x 2f point y 2f point p Message with coordinates 0 50 0 50 from wherever import DollarMessage as __ print __ Message with num what num 2 what placeholders Message with 2 placeholders While the above examples use print to show how the formatting works you would of course use logger debug or similar to actually log using this approach One thing to note is that you pay no significant performance penalty with this approach the actual formatting happens not when you make the logging call but when and if the logged message is actually about to be output to a log by a handler So the only slightly unusual thing ,en
292,which might trip you up is that the parentheses go around the format string and the arguments not just the format string That s because the __ notation is just syntax sugar for a constructor call to one of the XXX Message classes If you prefer you can use a LoggerAdapter to achieve a similar effect to the above as in the following example import logging class Message def __init__ self fmt args self fmt fmt self args args def __str__ self return self fmt format self args class StyleAdapter logging LoggerAdapter def log self level msg args stacklevel 1 kwargs if self isEnabledFor level msg kwargs self process msg kwargs self logger log level Message msg args kwargs stacklevel stacklevel 1 logger StyleAdapter logging getLogger __name__ def main logger debug Hello world if __name__ __main__ logging basicConfig level logging DEBUG main The above script should log the message Hello world when run with Python 3 8 or later Customizing LogRecord Every logging event is represented by a LogRecord instance When an event is logged and not filtered out by a logger s level a LogRecord is created populated with information about the event and then passed to the handlers for that logger and its ancestors up to and including the logger where further propagation up the hierarchy is disabled Before Python 3 2 there were only two places where this creation was done Logger makeRecord which is called in the normal process of logging an event This invoked LogRecord directly to create an instance makeLogRecord which is called with a dictionary containing attributes to be added to the LogRecord This is typically invoked when a suitable dictionary has been received over the network e g in pickle form via a SocketHandler or in JSON form via an HTTPHandler This has usually meant that if you need to do anything special with a LogRecord you ve had to do one of the following Create your own Logger subclass which overrides Logger makeRecord and set it using setLoggerClass before any loggers that you care about are instantiated Add a Filter to a logger or handler which does the necessary special manipulation you need when its filter method is called The first approach would be a little unwieldy in the scenario where say several different libraries wanted to do different things Each would attempt to set its own Logger subclass and the one which did this last would win The second approach works reasonably well for many cases but does not allow you to e g use a specialized subclass of LogRecord Library developers can set a suitable filter on their loggers but they would have to remember to do this every time they introduced a new logger which they would do simply by adding new packages or modules and doing logger logging getLogger __name__ at module level It s probably one too many things to think about Developers could also add the filter to a NullHandler attached to their top level logger but this would not be invoked if an application developer attached a handler to a lower level library logger so output from that handler would not reflect the intentions of the library developer In Python 3 2 and later LogRecord creation is done through a factory which you can specify The factory is just a callable you can set with setLogRecordFactory and interrogate with getLogRecordFactory The factory is invoked with the same signature as the LogRecord constructor as LogRecord is the default setting for the factory This approach allows a custom factory to control all aspects of LogRecord creation For example you could return a subclass or just add some additional attributes to the record once created using a pattern similar to this old_factory logging getLogRecordFactory def record_factory args kwargs record old_factory args kwargs record custom_attribute 0xdecafbad return record logging setLogRecordFactory record_factory This pattern allows different libraries to chain factories together and as long as they don t overwrite each other s attributes or unintentionally overwrite the attributes provided as standard there should be no surprises However it should be borne in,en
293, mind that each link in the chain adds run time overhead to all logging operations and the technique should only be used when the use of a Filter does not provide the desired result Subclassing QueueHandler a ZeroMQ example You can use a QueueHandler subclass to send messages to other kinds of queues for example a ZeroMQ publish socket In the example below the socket is created separately and passed to the handler as its queue import zmq using pyzmq the Python binding for ZeroMQ import json for serializing records portably ctx zmq Context sock zmq Socket ctx zmq PUB or zmq PUSH or other suitable value sock bind tcp 5556 or wherever class ZeroMQSocketHandler QueueHandler def enqueue self record self queue send_json record __dict__ handler ZeroMQSocketHandler sock Of course there are other ways of organizing this for example passing in the data needed by the handler to create the socket class ZeroMQSocketHandler QueueHandler def __init__ self uri socktype zmq PUB ctx None self ctx ctx or zmq Context socket zmq Socket self ctx socktype socket bind uri super __init__ socket def enqueue self record self queue send_json record __dict__ def close self self queue close Subclassing QueueListener a ZeroMQ example You can also subclass QueueListener to get messages from other kinds of queues for example a ZeroMQ subscribe socket Here s an example class ZeroMQSocketListener QueueListener def __init__ self uri handlers kwargs self ctx kwargs get ctx or zmq Context socket zmq Socket self ctx zmq SUB socket setsockopt_string zmq SUBSCRIBE subscribe to everything socket connect uri super __init__ socket handlers kwargs def dequeue self msg self queue recv_json return logging makeLogRecord msg See also Module logging API reference for the logging module Module logging config Configuration API for the logging module Module logging handlers Useful handlers included with the logging module A basic logging tutorial A more advanced logging tutorial An example dictionary based configuration Below is an example of a logging configuration dictionary it s taken from the documentation on the Django project This dictionary is passed to dictConfig to put the configuration into effect LOGGING version 1 disable_existing_loggers False formatters verbose format levelname asctime module process d thread d message style simple format levelname message style filters special project logging SpecialFilter foo bar handlers console level INFO class logging StreamHandler formatter simple mail_admins level ERROR class django utils log AdminEmailHandler filters special loggers django handlers console propagate True django request handlers mail_admins level ERROR propagate False myproject custom handlers console mail_admins level INFO filters special For more information about this configuration you can see the relevant section of the Django documentation Using a rotator and namer to customize log rotation processing An example of how you can define a namer and rotator is given in the following runnable script which shows gzip compression of the log file import gzip import logging import logging handlers import os import shutil def namer name return name gz def rotator source dest with open source rb as f_in with gzip open dest wb as f_out shutil copyfileobj f_in f_out os remove source rh logging handlers RotatingFileHandler rotated log maxBytes 128 backupCount 5 rh rotator rotator rh namer namer root logging getLogger root setLevel logging INFO root addHandler rh f logging Formatter asctime s message s rh setFormatter f for i in range 1000 root info f Message no i 1 After running this you will see six new files five of which are compressed ls rotated log rotated log rotated log 2 gz rotated log 4 gz rotated log 1 gz rotated log 3 gz rotated log 5 gz zcat rotated log 1 gz 2023 01 20 02 28 17 767 Message no 996 2023 01 20 02 28 17 767 Message no 997 2023 01 20 02 28 17 767 Message no 998 A more elaborate multiprocessing example The following working example shows how logging can be used with multiprocessing using configuration files The configurations are fairly si,en
294,mple but serve to illustrate how more complex ones could be implemented in a real multiprocessing scenario In the example the main process spawns a listener process and some worker processes Each of the main process the listener and the workers have three separate configurations the workers all share the same configuration We can see logging in the main process how the workers log to a QueueHandler and how the listener implements a QueueListener and a more complex logging configuration and arranges to dispatch events received via the queue to the handlers specified in the configuration Note that these configurations are purely illustrative but you should be able to adapt this example to your own scenario Here s the script the docstrings and the comments hopefully explain how it works import logging import logging config import logging handlers from multiprocessing import Process Queue Event current_process import os import random import time class MyHandler A simple handler for logging events It runs in the listener process and dispatches events to loggers based on the name in the received record which then get dispatched by the logging system to the handlers configured for those loggers def handle self record if record name root logger logging getLogger else logger logging getLogger record name if logger isEnabledFor record levelno The process name is transformed just to show that it s the listener doing the logging to files and console record processName s for s current_process name record processName logger handle record def listener_process q stop_event config This could be done in the main process but is just done in a separate process for illustrative purposes This initialises logging according to the specified configuration starts the listener and waits for the main process to signal completion via the event The listener is then stopped and the process exits logging config dictConfig config listener logging handlers QueueListener q MyHandler listener start if os name posix On POSIX the setup logger will have been configured in the parent process but should have been disabled following the dictConfig call On Windows since fork isn t used the setup logger won t exist in the child so it would be created and the message would appear hence the if posix clause logger logging getLogger setup logger critical Should not appear because of disabled logger stop_event wait listener stop def worker_process config A number of these are spawned for the purpose of illustration In practice they could be a heterogeneous bunch of processes rather than ones which are identical to each other This initialises logging according to the specified configuration and logs a hundred messages with random levels to randomly selected loggers A small sleep is added to allow other processes a chance to run This is not strictly needed but it mixes the output from the different processes a bit more than if it s left out logging config dictConfig config levels logging DEBUG logging INFO logging WARNING logging ERROR logging CRITICAL loggers foo foo bar foo bar baz spam spam ham spam ham eggs if os name posix On POSIX the setup logger will have been configured in the parent process but should have been disabled following the dictConfig call On Windows since fork isn t used the setup logger won t exist in the child so it would be created and the message would appear hence the if posix clause logger logging getLogger setup logger critical Should not appear because of disabled logger for i in range 100 lvl random choice levels logger logging getLogger random choice loggers logger log lvl Message no d i time sleep 0 01 def main q Queue The main process gets a simple configuration which prints to the console config_initial version 1 handlers console class logging StreamHandler level INFO root handlers console level DEBUG The worker process configuration is just a QueueHandler attached to the root logger which allows all messages to be sent to the queue We disable existing loggers to disable the setup logger used in the parent process This is needed on POSIX,en
295, because the logger will be there in the child following a fork config_worker version 1 disable_existing_loggers True handlers queue class logging handlers QueueHandler queue q root handlers queue level DEBUG The listener process configuration shows that the full flexibility of logging configuration is available to dispatch events to handlers however you want We disable existing loggers to disable the setup logger used in the parent process This is needed on POSIX because the logger will be there in the child following a fork config_listener version 1 disable_existing_loggers True formatters detailed class logging Formatter format asctime s name 15s levelname 8s processName 10s message s simple class logging Formatter format name 15s levelname 8s processName 10s message s handlers console class logging StreamHandler formatter simple level INFO file class logging FileHandler filename mplog log mode w formatter detailed foofile class logging FileHandler filename mplog foo log mode w formatter detailed errors class logging FileHandler filename mplog errors log mode w formatter detailed level ERROR loggers foo handlers foofile root handlers console file errors level DEBUG Log some initial events just to show that logging in the parent works normally logging config dictConfig config_initial logger logging getLogger setup logger info About to create workers workers for i in range 5 wp Process target worker_process name worker d i 1 args config_worker workers append wp wp start logger info Started worker s wp name logger info About to create listener stop_event Event lp Process target listener_process name listener args q stop_event config_listener lp start logger info Started listener We now hang around for the workers to finish their work for wp in workers wp join Workers all done listening can now stop Logging in the parent still works normally logger info Telling listener to stop stop_event set lp join logger info All done if __name__ __main__ main Inserting a BOM into messages sent to a SysLogHandler RFC 5424 requires that a Unicode message be sent to a syslog daemon as a set of bytes which have the following structure an optional pure ASCII component followed by a UTF 8 Byte Order Mark BOM followed by Unicode encoded using UTF 8 See the relevant section of the specification In Python 3 1 code was added to SysLogHandler to insert a BOM into the message but unfortunately it was implemented incorrectly with the BOM appearing at the beginning of the message and hence not allowing any pure ASCII component to appear before it As this behaviour is broken the incorrect BOM insertion code is being removed from Python 3 2 4 and later However it is not being replaced and if you want to produce RFC 5424 compliant messages which include a BOM an optional pure ASCII sequence before it and arbitrary Unicode after it encoded using UTF 8 then you need to do the following 1 Attach a Formatter instance to your SysLogHandler instance with a format string such as ASCII section ufeffUnicode section The Unicode code point U FEFF when encoded using UTF 8 will be encoded as a UTF 8 BOM the byte string b xef xbb xbf 2 Replace the ASCII section with whatever placeholders you like but make sure that the data that appears in there after substitution is always ASCII that way it will remain unchanged after UTF 8 encoding 3 Replace the Unicode section with whatever placeholders you like if the data which appears there after substitution contains characters outside the ASCII range that s fine it will be encoded using UTF 8 The formatted message will be encoded using UTF 8 encoding by SysLogHandler If you follow the above rules you should be able to produce RFC 5424 compliant messages If you don t logging may not complain but your messages will not be RFC 5424 compliant and your syslog daemon may complain Implementing structured logging Although most logging messages are intended for reading by humans and thus not readily machine parseable there might be circumstances where you want to output messages in a structured format which is capable of being parse,en
296,d by a program without needing complex regular expressions to parse the log message This is straightforward to achieve using the logging package There are a number of ways in which this could be achieved but the following is a simple approach which uses JSON to serialise the event in a machine parseable manner import json import logging class StructuredMessage def __init__ self message kwargs self message message self kwargs kwargs def __str__ self return s s self message json dumps self kwargs _ StructuredMessage optional to improve readability logging basicConfig level logging INFO format message s logging info _ message 1 foo bar bar baz num 123 fnum 123 456 If the above script is run it prints message 1 fnum 123 456 num 123 bar baz foo bar Note that the order of items might be different according to the version of Python used If you need more specialised processing you can use a custom JSON encoder as in the following complete example import json import logging class Encoder json JSONEncoder def default self o if isinstance o set return tuple o elif isinstance o str return o encode unicode_escape decode ascii return super default o class StructuredMessage def __init__ self message kwargs self message message self kwargs kwargs def __str__ self s Encoder encode self kwargs return s s self message s _ StructuredMessage optional to improve readability def main logging basicConfig level logging INFO format message s logging info _ message 1 set_value 1 2 3 snowman u2603 if __name__ __main__ main When the above script is run it prints message 1 snowman u2603 set_value 1 2 3 Note that the order of items might be different according to the version of Python used Customizing handlers with dictConfig There are times when you want to customize logging handlers in particular ways and if you use dictConfig you may be able to do this without subclassing As an example consider that you may want to set the ownership of a log file On POSIX this is easily done using shutil chown but the file handlers in the stdlib don t offer built in support You can customize handler creation using a plain function such as def owned_file_handler filename mode a encoding None owner None if owner if not os path exists filename open filename a close shutil chown filename owner return logging FileHandler filename mode encoding You can then specify in a logging configuration passed to dictConfig that a logging handler be created by calling this function LOGGING version 1 disable_existing_loggers False formatters default format asctime s levelname s name s message s handlers file The values below are popped from this dictionary and used to create the handler set the handler s level and its formatter owned_file_handler level DEBUG formatter default The values below are passed to the handler creator callable as keyword arguments owner pulse pulse filename chowntest log mode w encoding utf 8 root handlers file level DEBUG In this example I am setting the ownership using the pulse user and group just for the purposes of illustration Putting it together into a working script chowntest py import logging logging config os shutil def owned_file_handler filename mode a encoding None owner None if owner if not os path exists filename open filename a close shutil chown filename owner return logging FileHandler filename mode encoding LOGGING version 1 disable_existing_loggers False formatters default format asctime s levelname s name s message s handlers file The values below are popped from this dictionary and used to create the handler set the handler s level and its formatter owned_file_handler level DEBUG formatter default The values below are passed to the handler creator callable as keyword arguments owner pulse pulse filename chowntest log mode w encoding utf 8 root handlers file level DEBUG logging config dictConfig LOGGING logger logging getLogger mylogger logger debug A debug message To run this you will probably need to run as root sudo python3 3 chowntest py cat chowntest log 2013 11 05 09 34 51 128 DEBUG mylogger A debug message ls l chowntest log rw r r,en
297, 1 pulse pulse 55 2013 11 05 09 34 chowntest log Note that this example uses Python 3 3 because that s where shutil chown makes an appearance This approach should work with any Python version that supports dictConfig namely Python 2 7 3 2 or later With pre 3 3 versions you would need to implement the actual ownership change using e g os chown In practice the handler creating function may be in a utility module somewhere in your project Instead of the line in the configuration owned_file_handler you could use e g ext project util owned_file_handler where project util can be replaced with the actual name of the package where the function resides In the above working script using ext __main__ owned_file_handler should work Here the actual callable is resolved by dictConfig from the ext specification This example hopefully also points the way to how you could implement other types of file change e g setting specific POSIX permission bits in the same way using os chmod Of course the approach could also be extended to types of handler other than a FileHandler for example one of the rotating file handlers or a different type of handler altogether Using particular formatting styles throughout your application In Python 3 2 the Formatter gained a style keyword parameter which while defaulting to for backward compatibility allowed the specification of or to support the formatting approaches supported by str format and string Template Note that this governs the formatting of logging messages for final output to logs and is completely orthogonal to how an individual logging message is constructed Logging calls debug info etc only take positional parameters for the actual logging message itself with keyword parameters used only for determining options for how to handle the logging call e g the exc_info keyword parameter to indicate that traceback information should be logged or the extra keyword parameter to indicate additional contextual information to be added to the log So you cannot directly make logging calls using str format or string Template syntax because internally the logging package uses formatting to merge the format string and the variable arguments There would be no changing this while preserving backward compatibility since all logging calls which are out there in existing code will be using format strings There have been suggestions to associate format styles with specific loggers but that approach also runs into backward compatibility problems because any existing code could be using a given logger name and using formatting For logging to work interoperably between any third party libraries and your code decisions about formatting need to be made at the level of the individual logging call This opens up a couple of ways in which alternative formatting styles can be accommodated Using LogRecord factories In Python 3 2 along with the Formatter changes mentioned above the logging package gained the ability to allow users to set their own LogRecord subclasses using the setLogRecordFactory function You can use this to set your own subclass of LogRecord which does the Right Thing by overriding the getMessage method The base class implementation of this method is where the msg args formatting happens and where you can substitute your alternate formatting however you should be careful to support all formatting styles and allow formatting as the default to ensure interoperability with other code Care should also be taken to call str self msg just as the base implementation does Refer to the reference documentation on setLogRecordFactory and LogRecord for more information Using custom message objects There is another perhaps simpler way that you can use and formatting to construct your individual log messages You may recall from Using arbitrary objects as messages that when logging you can use an arbitrary object as a message format string and that the logging package will call str on that object to get the actual format string Consider the following two classes class BraceMessage def __init__ self fmt args kwargs self fmt fm,en
298,t self args args self kwargs kwargs def __str__ self return self fmt format self args self kwargs class DollarMessage def __init__ self fmt kwargs self fmt fmt self kwargs kwargs def __str__ self from string import Template return Template self fmt substitute self kwargs Either of these can be used in place of a format string to allow or formatting to be used to build the actual message part which appears in the formatted log output in place of message s or message or message If you find it a little unwieldy to use the class names whenever you want to log something you can make it more palatable if you use an alias such as M or _ for the message or perhaps __ if you are using _ for localization Examples of this approach are given below Firstly formatting with str format __ BraceMessage print __ Message with 0 1 2 placeholders Message with 2 placeholders class Point pass p Point p x 0 5 p y 0 5 print __ Message with coordinates point x 2f point y 2f point p Message with coordinates 0 50 0 50 Secondly formatting with string Template __ DollarMessage print __ Message with num what num 2 what placeholders Message with 2 placeholders One thing to note is that you pay no significant performance penalty with this approach the actual formatting happens not when you make the logging call but when and if the logged message is actually about to be output to a log by a handler So the only slightly unusual thing which might trip you up is that the parentheses go around the format string and the arguments not just the format string That s because the __ notation is just syntax sugar for a constructor call to one of the XXX Message classes shown above Configuring filters with dictConfig You can configure filters using dictConfig though it might not be obvious at first glance how to do it hence this recipe Since Filter is the only filter class included in the standard library and it is unlikely to cater to many requirements it s only there as a base class you will typically need to define your own Filter subclass with an overridden filter method To do this specify the key in the configuration dictionary for the filter specifying a callable which will be used to create the filter a class is the most obvious but you can provide any callable which returns a Filter instance Here is a complete example import logging import logging config import sys class MyFilter logging Filter def __init__ self param None self param param def filter self record if self param is None allow True else allow self param not in record msg if allow record msg changed record msg return allow LOGGING version 1 filters myfilter MyFilter param noshow handlers console class logging StreamHandler filters myfilter root level DEBUG handlers console if __name__ __main__ logging config dictConfig LOGGING logging debug hello logging debug hello noshow This example shows how you can pass configuration data to the callable which constructs the instance in the form of keyword parameters When run the above script will print changed hello which shows that the filter is working as configured A couple of extra points to note If you can t refer to the callable directly in the configuration e g if it lives in a different module and you can t import it directly where the configuration dictionary is you can use the form ext as described in Access to external objects For example you could have used the text ext __main__ MyFilter instead of MyFilter in the above example As well as for filters this technique can also be used to configure custom handlers and formatters See User defined objects for more information on how logging supports using user defined objects in its configuration and see the other cookbook recipe Customizing handlers with dictConfig above Customized exception formatting There might be times when you want to do customized exception formatting for argument s sake let s say you want exactly one line per logged event even when exception information is present You can do this with a custom formatter class as shown in the following example import logging class OneLineExcept,en
299,ionFormatter logging Formatter def formatException self exc_info Format an exception so that it prints on a single line result super formatException exc_info return repr result or format into one line however you want to def format self record s super format record if record exc_text s s replace n return s def configure_logging fh logging FileHandler output txt w f OneLineExceptionFormatter asctime s levelname s message s d m Y H M S fh setFormatter f root logging getLogger root setLevel logging DEBUG root addHandler fh def main configure_logging logging info Sample message try x 1 0 except ZeroDivisionError as e logging exception ZeroDivisionError s e if __name__ __main__ main When run this produces a file with exactly two lines 28 01 2015 07 21 23 INFO Sample message 28 01 2015 07 21 23 ERROR ZeroDivisionError integer division or modulo by zero Traceback most recent call last n File logtest7 py line 30 in main n x 1 0 nZeroDivisionError integer division or modulo by zero While the above treatment is simplistic it points the way to how exception information can be formatted to your liking The traceback module may be helpful for more specialized needs Speaking logging messages There might be situations when it is desirable to have logging messages rendered in an audible rather than a visible format This is easy to do if you have text to speech TTS functionality available in your system even if it doesn t have a Python binding Most TTS systems have a command line program you can run and this can be invoked from a handler using subprocess It s assumed here that TTS command line programs won t expect to interact with users or take a long time to complete and that the frequency of logged messages will be not so high as to swamp the user with messages and that it s acceptable to have the messages spoken one at a time rather than concurrently The example implementation below waits for one message to be spoken before the next is processed and this might cause other handlers to be kept waiting Here is a short example showing the approach which assumes that the espeak TTS package is available import logging import subprocess import sys class TTSHandler logging Handler def emit self record msg self format record Speak slowly in a female English voice cmd espeak s150 ven f3 msg p subprocess Popen cmd stdout subprocess PIPE stderr subprocess STDOUT wait for the program to finish p communicate def configure_logging h TTSHandler root logging getLogger root addHandler h the default formatter just returns the message root setLevel logging DEBUG def main logging info Hello logging debug Goodbye if __name__ __main__ configure_logging sys exit main When run this script should say Hello and then Goodbye in a female voice The above approach can of course be adapted to other TTS systems and even other systems altogether which can process messages via external programs run from a command line Buffering logging messages and outputting them conditionally There might be situations where you want to log messages in a temporary area and only output them if a certain condition occurs For example you may want to start logging debug events in a function and if the function completes without errors you don t want to clutter the log with the collected debug information but if there is an error you want all the debug information to be output as well as the error Here is an example which shows how you could do this using a decorator for your functions where you want logging to behave this way It makes use of the logging handlers MemoryHandler which allows buffering of logged events until some condition occurs at which point the buffered events are flushed passed to another handler the target handler for processing By default the MemoryHandler flushed when its buffer gets filled up or an event whose level is greater than or equal to a specified threshold is seen You can use this recipe with a more specialised subclass of MemoryHandler if you want custom flushing behavior The example script has a simple function foo which just cycles through all the logging,en
300, levels writing to sys stderr to say what level it s about to log at and then actually logging a message at that level You can pass a parameter to foo which if true will log at ERROR and CRITICAL levels otherwise it only logs at DEBUG INFO and WARNING levels The script just arranges to decorate foo with a decorator which will do the conditional logging that s required The decorator takes a logger as a parameter and attaches a memory handler for the duration of the call to the decorated function The decorator can be additionally parameterised using a target handler a level at which flushing should occur and a capacity for the buffer number of records buffered These default to a StreamHandler which writes to sys stderr logging ERROR and 100 respectively Here s the script import logging from logging handlers import MemoryHandler import sys logger logging getLogger __name__ logger addHandler logging NullHandler def log_if_errors logger target_handler None flush_level None capacity None if target_handler is None target_handler logging StreamHandler if flush_level is None flush_level logging ERROR if capacity is None capacity 100 handler MemoryHandler capacity flushLevel flush_level target target_handler def decorator fn def wrapper args kwargs logger addHandler handler try return fn args kwargs except Exception logger exception call failed raise finally super MemoryHandler handler flush logger removeHandler handler return wrapper return decorator def write_line s sys stderr write s n s def foo fail False write_line about to log at DEBUG logger debug Actually logged at DEBUG write_line about to log at INFO logger info Actually logged at INFO write_line about to log at WARNING logger warning Actually logged at WARNING if fail write_line about to log at ERROR logger error Actually logged at ERROR write_line about to log at CRITICAL logger critical Actually logged at CRITICAL return fail decorated_foo log_if_errors logger foo if __name__ __main__ logger setLevel logging DEBUG write_line Calling undecorated foo with False assert not foo False write_line Calling undecorated foo with True assert foo True write_line Calling decorated foo with False assert not decorated_foo False write_line Calling decorated foo with True assert decorated_foo True When this script is run the following output should be observed Calling undecorated foo with False about to log at DEBUG about to log at INFO about to log at WARNING Calling undecorated foo with True about to log at DEBUG about to log at INFO about to log at WARNING about to log at ERROR about to log at CRITICAL Calling decorated foo with False about to log at DEBUG about to log at INFO about to log at WARNING Calling decorated foo with True about to log at DEBUG about to log at INFO about to log at WARNING about to log at ERROR Actually logged at DEBUG Actually logged at INFO Actually logged at WARNING Actually logged at ERROR about to log at CRITICAL Actually logged at CRITICAL As you can see actual logging output only occurs when an event is logged whose severity is ERROR or greater but in that case any previous events at lower severities are also logged You can of course use the conventional means of decoration log_if_errors logger def foo fail False Sending logging messages to email with buffering To illustrate how you can send log messages via email so that a set number of messages are sent per email you can subclass BufferingHandler In the following example which you can adapt to suit your specific needs a simple test harness is provided which allows you to run the script with command line arguments specifying what you typically need to send things via SMTP Run the downloaded script with the h argument to see the required and optional arguments import logging import logging handlers import smtplib class BufferingSMTPHandler logging handlers BufferingHandler def __init__ self mailhost port username password fromaddr toaddrs subject capacity logging handlers BufferingHandler __init__ self capacity self mailhost mailhost self mailport port self username username self password password se,en
301,lf fromaddr fromaddr if isinstance toaddrs str toaddrs toaddrs self toaddrs toaddrs self subject subject self setFormatter logging Formatter asctime s levelname 5s message s def flush self if len self buffer 0 try smtp smtplib SMTP self mailhost self mailport smtp starttls smtp login self username self password msg From s r nTo s r nSubject s r n r n self fromaddr join self toaddrs self subject for record in self buffer s self format record msg msg s r n smtp sendmail self fromaddr self toaddrs msg smtp quit except Exception if logging raiseExceptions raise self buffer if __name__ __main__ import argparse ap argparse ArgumentParser aa ap add_argument aa host metavar HOST help SMTP server aa port p type int default 587 help SMTP port aa user metavar USER help SMTP username aa password metavar PASSWORD help SMTP password aa to metavar TO help Addressee for emails aa sender metavar SENDER help Sender email address aa subject s default Test Logging email from Python logging module buffering help Subject of email options ap parse_args logger logging getLogger logger setLevel logging DEBUG h BufferingSMTPHandler options host options port options user options password options sender options to options subject 10 logger addHandler h for i in range 102 logger info Info index d i h flush h close If you run this script and your SMTP server is correctly set up you should find that it sends eleven emails to the addressee you specify The first ten emails will each have ten log messages and the eleventh will have two messages That makes up 102 messages as specified in the script Formatting times using UTC GMT via configuration Sometimes you want to format times using UTC which can be done using a class such as UTCFormatter shown below import logging import time class UTCFormatter logging Formatter converter time gmtime and you can then use the UTCFormatter in your code instead of Formatter If you want to do that via configuration you can use the dictConfig API with an approach illustrated by the following complete example import logging import logging config import time class UTCFormatter logging Formatter converter time gmtime LOGGING version 1 disable_existing_loggers False formatters utc UTCFormatter format asctime s message s local format asctime s message s handlers console1 class logging StreamHandler formatter utc console2 class logging StreamHandler formatter local root handlers console1 console2 if __name__ __main__ logging config dictConfig LOGGING logging warning The local time is s time asctime When this script is run it should print something like 2015 10 17 12 53 29 501 The local time is Sat Oct 17 13 53 29 2015 2015 10 17 13 53 29 501 The local time is Sat Oct 17 13 53 29 2015 showing how the time is formatted both as local time and UTC one for each handler Using a context manager for selective logging There are times when it would be useful to temporarily change the logging configuration and revert it back after doing something For this a context manager is the most obvious way of saving and restoring the logging context Here is a simple example of such a context manager which allows you to optionally change the logging level and add a logging handler purely in the scope of the context manager import logging import sys class LoggingContext def __init__ self logger level None handler None close True self logger logger self level level self handler handler self close close def __enter__ self if self level is not None self old_level self logger level self logger setLevel self level if self handler self logger addHandler self handler def __exit__ self et ev tb if self level is not None self logger setLevel self old_level if self handler self logger removeHandler self handler if self handler and self close self handler close implicit return of None don t swallow exceptions If you specify a level value the logger s level is set to that value in the scope of the with block covered by the context manager If you specify a handler it is added to the logger on entry to the block and removed on exit from the block You can also ask ,en
302,the manager to close the handler for you on block exit you could do this if you don t need the handler any more To illustrate how it works we can add the following block of code to the above if __name__ __main__ logger logging getLogger foo logger addHandler logging StreamHandler logger setLevel logging INFO logger info 1 This should appear just once on stderr logger debug 2 This should not appear with LoggingContext logger level logging DEBUG logger debug 3 This should appear once on stderr logger debug 4 This should not appear h logging StreamHandler sys stdout with LoggingContext logger level logging DEBUG handler h close True logger debug 5 This should appear twice once on stderr and once on stdout logger info 6 This should appear just once on stderr logger debug 7 This should not appear We initially set the logger s level to INFO so message 1 appears and message 2 doesn t We then change the level to DEBUG temporarily in the following with block and so message 3 appears After the block exits the logger s level is restored to INFO and so message 4 doesn t appear In the next with block we set the level to DEBUG again but also add a handler writing to sys stdout Thus message 5 appears twice on the console once via stderr and once via stdout After the with statement s completion the status is as it was before so message 6 appears like message 1 whereas message 7 doesn t just like message 2 If we run the resulting script the result is as follows python logctx py 1 This should appear just once on stderr 3 This should appear once on stderr 5 This should appear twice once on stderr and once on stdout 5 This should appear twice once on stderr and once on stdout 6 This should appear just once on stderr If we run it again but pipe stderr to dev null we see the following which is the only message written to stdout python logctx py 2 dev null 5 This should appear twice once on stderr and once on stdout Once again but piping stdout to dev null we get python logctx py dev null 1 This should appear just once on stderr 3 This should appear once on stderr 5 This should appear twice once on stderr and once on stdout 6 This should appear just once on stderr In this case the message 5 printed to stdout doesn t appear as expected Of course the approach described here can be generalised for example to attach logging filters temporarily Note that the above code works in Python 2 as well as Python 3 A CLI application starter template Here s an example which shows how you can Use a logging level based on command line arguments Dispatch to multiple subcommands in separate files all logging at the same level in a consistent way Make use of simple minimal configuration Suppose we have a command line application whose job is to stop start or restart some services This could be organised for the purposes of illustration as a file app py that is the main script for the application with individual commands implemented in start py stop py and restart py Suppose further that we want to control the verbosity of the application via a command line argument defaulting to logging INFO Here s one way that app py could be written import argparse import importlib import logging import os import sys def main args None scriptname os path basename __file__ parser argparse ArgumentParser scriptname levels DEBUG INFO WARNING ERROR CRITICAL parser add_argument log level default INFO choices levels subparsers parser add_subparsers dest command help Available commands start_cmd subparsers add_parser start help Start a service start_cmd add_argument name metavar NAME help Name of service to start stop_cmd subparsers add_parser stop help Stop one or more services stop_cmd add_argument names metavar NAME nargs help Name of service to stop restart_cmd subparsers add_parser restart help Restart one or more services restart_cmd add_argument names metavar NAME nargs help Name of service to restart options parser parse_args the code to dispatch commands could all be in this file For the purposes of illustration only we implement each command in a separate module try mod impo,en
303,rtlib import_module options command cmd getattr mod command except ImportError AttributeError print Unable to find the code for command s options command return 1 Could get fancy here and load configuration from file or dictionary logging basicConfig level options log_level format levelname s name s message s cmd options if __name__ __main__ sys exit main And the start stop and restart commands can be implemented in separate modules like so for starting start py import logging logger logging getLogger __name__ def command options logger debug About to start s options name actually do the command processing here logger info Started the s service options name and thus for stopping stop py import logging logger logging getLogger __name__ def command options n len options names if n 1 plural services s options names 0 else plural s services join s name for name in options names i services rfind services services i and services i 2 logger debug About to stop s services actually do the command processing here logger info Stopped the s service s services plural and similarly for restarting restart py import logging logger logging getLogger __name__ def command options n len options names if n 1 plural services s options names 0 else plural s services join s name for name in options names i services rfind services services i and services i 2 logger debug About to restart s services actually do the command processing here logger info Restarted the s service s services plural If we run this application with the default log level we get output like this python app py start foo INFO start Started the foo service python app py stop foo bar INFO stop Stopped the foo and bar services python app py restart foo bar baz INFO restart Restarted the foo bar and baz services The first word is the logging level and the second word is the module or package name of the place where the event was logged If we change the logging level then we can change the information sent to the log For example if we want more information python app py log level DEBUG start foo DEBUG start About to start foo INFO start Started the foo service python app py log level DEBUG stop foo bar DEBUG stop About to stop foo and bar INFO stop Stopped the foo and bar services python app py log level DEBUG restart foo bar baz DEBUG restart About to restart foo bar and baz INFO restart Restarted the foo bar and baz services And if we want less python app py log level WARNING start foo python app py log level WARNING stop foo bar python app py log level WARNING restart foo bar baz In this case the commands don t print anything to the console since nothing at WARNING level or above is logged by them A Qt GUI for logging A question that comes up from time to time is about how to log to a GUI application The Qt framework is a popular cross platform UI framework with Python bindings using PySide2 or PyQt5 libraries The following example shows how to log to a Qt GUI This introduces a simple QtHandler class which takes a callable which should be a slot in the main thread that does GUI updates A worker thread is also created to show how you can log to the GUI from both the UI itself via a button for manual logging as well as a worker thread doing work in the background here just logging messages at random levels with random short delays in between The worker thread is implemented using Qt s QThread class rather than the threading module as there are circumstances where one has to use QThread which offers better integration with other Qt components The code should work with recent releases of either PySide6 PyQt6 PySide2 or PyQt5 You should be able to adapt the approach to earlier versions of Qt Please refer to the comments in the code snippet for more detailed information import datetime import logging import random import sys import time Deal with minor differences between different Qt packages try from PySide6 import QtCore QtGui QtWidgets Signal QtCore Signal Slot QtCore Slot except ImportError try from PyQt6 import QtCore QtGui QtWidgets Signal QtCore pyqtSignal Slot QtCore pyqtSlo,en
304,t except ImportError try from PySide2 import QtCore QtGui QtWidgets Signal QtCore Signal Slot QtCore Slot except ImportError from PyQt5 import QtCore QtGui QtWidgets Signal QtCore pyqtSignal Slot QtCore pyqtSlot logger logging getLogger __name__ Signals need to be contained in a QObject or subclass in order to be correctly initialized class Signaller QtCore QObject signal Signal str logging LogRecord Output to a Qt GUI is only supposed to happen on the main thread So this handler is designed to take a slot function which is set up to run in the main thread In this example the function takes a string argument which is a formatted log message and the log record which generated it The formatted string is just a convenience you could format a string for output any way you like in the slot function itself You specify the slot function to do whatever GUI updates you want The handler doesn t know or care about specific UI elements class QtHandler logging Handler def __init__ self slotfunc args kwargs super __init__ args kwargs self signaller Signaller self signaller signal connect slotfunc def emit self record s self format record self signaller signal emit s record This example uses QThreads which means that the threads at the Python level are named something like Dummy 1 The function below gets the Qt name of the current thread def ctname return QtCore QThread currentThread objectName Used to generate random levels for logging LEVELS logging DEBUG logging INFO logging WARNING logging ERROR logging CRITICAL This worker class represents work that is done in a thread separate to the main thread The way the thread is kicked off to do work is via a button press that connects to a slot in the worker Because the default threadName value in the LogRecord isn t much use we add a qThreadName which contains the QThread name as computed above and pass that value in an extra dictionary which is used to update the LogRecord with the QThread name This example worker just outputs messages sequentially interspersed with random delays of the order of a few seconds class Worker QtCore QObject Slot def start self extra qThreadName ctname logger debug Started work extra extra i 1 Let the thread run until interrupted This allows reasonably clean thread termination while not QtCore QThread currentThread isInterruptionRequested delay 0 5 random random 2 time sleep delay try if random random 0 1 raise ValueError Exception raised d i else level random choice LEVELS logger log level Message after delay of 3 1f d delay i extra extra except ValueError as e logger exception Failed s e extra extra i 1 Implement a simple UI for this cookbook example This contains A read only text edit window which holds formatted log messages A button to start work and log stuff in a separate thread A button to log something from the main thread A button to clear the log window class Window QtWidgets QWidget COLORS logging DEBUG black logging INFO blue logging WARNING orange logging ERROR red logging CRITICAL purple def __init__ self app super __init__ self app app self textedit te QtWidgets QPlainTextEdit self Set whatever the default monospace font is for the platform f QtGui QFont nosuchfont if hasattr f Monospace f setStyleHint f Monospace else f setStyleHint f StyleHint Monospace for Qt6 te setFont f te setReadOnly True PB QtWidgets QPushButton self work_button PB Start background work self self log_button PB Log a message at a random level self self clear_button PB Clear log window self self handler h QtHandler self update_status Remember to use qThreadName rather than threadName in the format string fs asctime s qThreadName 12s levelname 8s message s formatter logging Formatter fs h setFormatter formatter logger addHandler h Set up to terminate the QThread when we exit app aboutToQuit connect self force_quit Lay out all the widgets layout QtWidgets QVBoxLayout self layout addWidget te layout addWidget self work_button layout addWidget self log_button layout addWidget self clear_button self setFixedSize 900 400 Connect the non worker slots and signals self log_button ,en
305,clicked connect self manual_update self clear_button clicked connect self clear_display Start a new worker thread and connect the slots for the worker self start_thread self work_button clicked connect self worker start Once started the button should be disabled self work_button clicked connect lambda self work_button setEnabled False def start_thread self self worker Worker self worker_thread QtCore QThread self worker setObjectName Worker self worker_thread setObjectName WorkerThread for qThreadName self worker moveToThread self worker_thread This will start an event loop in the worker thread self worker_thread start def kill_thread self Just tell the worker to stop then tell it to quit and wait for that to happen self worker_thread requestInterruption if self worker_thread isRunning self worker_thread quit self worker_thread wait else print worker has already exited def force_quit self For use when the window is closed if self worker_thread isRunning self kill_thread The functions below update the UI and run in the main thread because that s where the slots are set up Slot str logging LogRecord def update_status self status record color self COLORS get record levelno black s pre font color s s font pre color status self textedit appendHtml s Slot def manual_update self This function uses the formatted message passed in but also uses information from the record to format the message in an appropriate color according to its severity level level random choice LEVELS extra qThreadName ctname logger log level Manually logged extra extra Slot def clear_display self self textedit clear def main QtCore QThread currentThread setObjectName MainThread logging getLogger setLevel logging DEBUG app QtWidgets QApplication sys argv example Window app example show if hasattr app exec rc app exec else rc app exec_ sys exit rc if __name__ __main__ main Logging to syslog with RFC5424 support Although RFC 5424 dates from 2009 most syslog servers are configured by default to use the older RFC 3164 which hails from 2001 When logging was added to Python in 2003 it supported the earlier and only existing protocol at the time Since RFC5424 came out as there has not been widespread deployment of it in syslog servers the SysLogHandler functionality has not been updated RFC 5424 contains some useful features such as support for structured data and if you need to be able to log to a syslog server with support for it you can do so with a subclassed handler which looks something like this import datetime import logging handlers import re import socket import time class SysLogHandler5424 logging handlers SysLogHandler tz_offset re compile r d 2 d 2 escaped re compile r def __init__ self args kwargs self msgid kwargs pop msgid None self appname kwargs pop appname None super __init__ args kwargs def format self record version 1 asctime datetime datetime fromtimestamp record created isoformat m self tz_offset match time strftime z has_offset False if m and time timezone hrs mins m groups if int hrs or int mins has_offset True if not has_offset asctime Z else asctime f hrs mins try hostname socket gethostname except Exception hostname appname self appname or procid record process msgid msg super format record sdata if hasattr record structured_data sd record structured_data This should be a dict where the keys are SD ID and the value is a dict mapping PARAM NAME to PARAM VALUE refer to the RFC for what these mean There s no error checking here it s purely for illustration and you can adapt this code for use in production environments parts def replacer m g m groups return g 0 for sdid dv in sd items part f sdid for k v in dv items s str v s self escaped sub replacer s part f k s part parts append part sdata join parts return f version asctime hostname appname procid msgid sdata msg You ll need to be familiar with RFC 5424 to fully understand the above code and it may be that you have slightly different needs e g for how you pass structural data to the log Nevertheless the above should be adaptable to your speciric needs With the above handler you d pass ,en
306,structured data using something like this sd foo 12345 bar baz baz bozz fizz r buzz foo 54321 rab baz zab bozz zzif r buzz extra structured_data sd i 1 logger debug Message d i extra extra How to treat a logger like an output stream Sometimes you need to interface to a third party API which expects a file like object to write to but you want to direct the API s output to a logger You can do this using a class which wraps a logger with a file like API Here s a short script illustrating such a class import logging class LoggerWriter def __init__ self logger level self logger logger self level level def write self message if message n avoid printing bare newlines if you like self logger log self level message def flush self doesn t actually do anything but might be expected of a file like object so optional depending on your situation pass def close self doesn t actually do anything but might be expected of a file like object so optional depending on your situation You might want to set a flag so that later calls to write raise an exception pass def main logging basicConfig level logging DEBUG logger logging getLogger demo info_fp LoggerWriter logger logging INFO debug_fp LoggerWriter logger logging DEBUG print An INFO message file info_fp print A DEBUG message file debug_fp if __name__ __main__ main When this script is run it prints INFO demo An INFO message DEBUG demo A DEBUG message You could also use LoggerWriter to redirect sys stdout and sys stderr by doing something like this import sys sys stdout LoggerWriter logger logging INFO sys stderr LoggerWriter logger logging WARNING You should do this after configuring logging for your needs In the above example the basicConfig call does this using the sys stderr value before it is overwritten by a LoggerWriter instance Then you d get this kind of result print Foo INFO demo Foo print Bar file sys stderr WARNING demo Bar Of course the examples above show output according to the format used by basicConfig but you can use a different formatter when you configure logging Note that with the above scheme you are somewhat at the mercy of buffering and the sequence of write calls which you are intercepting For example with the definition of LoggerWriter above if you have the snippet sys stderr LoggerWriter logger logging WARNING 1 0 then running the script results in WARNING demo Traceback most recent call last WARNING demo File home runner cookbook loggerwriter test py line 53 in module WARNING demo WARNING demo main WARNING demo File home runner cookbook loggerwriter test py line 49 in main WARNING demo WARNING demo 1 0 WARNING demo ZeroDivisionError WARNING demo WARNING demo division by zero As you can see this output isn t ideal That s because the underlying code which writes to sys stderr makes multiple writes each of which results in a separate logged line for example the last three lines above To get around this problem you need to buffer things and only output log lines when newlines are seen Let s use a slghtly better implementation of LoggerWriter class BufferingLoggerWriter LoggerWriter def __init__ self logger level super __init__ logger level self buffer def write self message if n not in message self buffer message else parts message split n if self buffer s self buffer parts pop 0 self logger log self level s self buffer parts pop for part in parts self logger log self level part This just buffers up stuff until a newline is seen and then logs complete lines With this approach you get better output WARNING demo Traceback most recent call last WARNING demo File home runner cookbook loggerwriter main py line 55 in module WARNING demo main WARNING demo File home runner cookbook loggerwriter main py line 52 in main WARNING demo 1 0 WARNING demo ZeroDivisionError division by zero Patterns to avoid Although the preceding sections have described ways of doing things you might need to do or deal with it is worth mentioning some usage patterns which are unhelpful and which should therefore be avoided in most cases The following sections are in no particular order Opening the ,en
307,same log file multiple times On Windows you will generally not be able to open the same file multiple times as this will lead to a file is in use by another process error However on POSIX platforms you ll not get any errors if you open the same file multiple times This could be done accidentally for example by Adding a file handler more than once which references the same file e g by a copy paste forget to change error Opening two files that look different as they have different names but are the same because one is a symbolic link to the other Forking a process following which both parent and child have a reference to the same file This might be through use of the multiprocessing module for example Opening a file multiple times might appear to work most of the time but can lead to a number of problems in practice Logging output can be garbled because multiple threads or processes try to write to the same file Although logging guards against concurrent use of the same handler instance by multiple threads there is no such protection if concurrent writes are attempted by two different threads using two different handler instances which happen to point to the same file An attempt to delete a file e g during file rotation silently fails because there is another reference pointing to it This can lead to confusion and wasted debugging time log entries end up in unexpected places or are lost altogether Or a file that was supposed to be moved remains in place and grows in size unexpectedly despite size based rotation being supposedly in place Use the techniques outlined in Logging to a single file from multiple processes to circumvent such issues Using loggers as attributes in a class or passing them as parameters While there might be unusual cases where you ll need to do this in general there is no point because loggers are singletons Code can always access a given logger instance by name using logging getLogger name so passing instances around and holding them as instance attributes is pointless Note that in other languages such as Java and C loggers are often static class attributes However this pattern doesn t make sense in Python where the module and not the class is the unit of software decomposition Adding handlers other than NullHandler to a logger in a library Configuring logging by adding handlers formatters and filters is the responsibility of the application developer not the library developer If you are maintaining a library ensure that you don t add handlers to any of your loggers other than a NullHandler instance Creating a lot of loggers Loggers are singletons that are never freed during a script execution and so creating lots of loggers will use up memory which can t then be freed Rather than create a logger per e g file processed or network connection made use the existing mechanisms for passing contextual information into your logs and restrict the loggers created to those describing areas within your application generally modules but occasionally slightly more fine grained than that Other resources See also Module logging API reference for the logging module Module logging config Configuration API for the logging module Module logging handlers Useful handlers included with the logging module Basic Tutorial Advanced Tutorial,en
308,pyclbr Python module browser support Source code Lib pyclbr py The pyclbr module provides limited information about the functions classes and methods defined in a Python coded module The information is sufficient to implement a module browser The information is extracted from the Python source code rather than by importing the module so this module is safe to use with untrusted code This restriction makes it impossible to use this module with modules not implemented in Python including all standard and optional extension modules pyclbr readmodule module path None Return a dictionary mapping module level class names to class descriptors If possible descriptors for imported base classes are included Parameter module is a string with the name of the module to read it may be the name of a module within a package If given path is a sequence of directory paths prepended to sys path which is used to locate the module source code This function is the original interface and is only kept for back compatibility It returns a filtered version of the following pyclbr readmodule_ex module path None Return a dictionary based tree containing a function or class descriptors for each function and class defined in the module with a def or class statement The returned dictionary maps module level function and class names to their descriptors Nested objects are entered into the children dictionary of their parent As with readmodule module names the module to be read and path is prepended to sys path If the module being read is a package the returned dictionary has a key __path__ whose value is a list containing the package search path New in version 3 7 Descriptors for nested definitions They are accessed through the new children attribute Each has a new parent attribute The descriptors returned by these functions are instances of Function and Class classes Users are not expected to create instances of these classes Function Objects class pyclbr Function Class Function instances describe functions defined by def statements They have the following attributes file Name of the file in which the function is defined module The name of the module defining the function described name The name of the function lineno The line number in the file where the definition starts parent For top level functions None For nested functions the parent New in version 3 7 children A dictionary mapping names to descriptors for nested functions and classes New in version 3 7 is_async True for functions that are defined with the async prefix False otherwise New in version 3 10 Class Objects class pyclbr Class Class Class instances describe classes defined by class statements They have the same attributes as Functions and two more file Name of the file in which the class is defined module The name of the module defining the class described name The name of the class lineno The line number in the file where the definition starts parent For top level classes None For nested classes the parent New in version 3 7 children A dictionary mapping names to descriptors for nested functions and classes New in version 3 7 super A list of Class objects which describe the immediate base classes of the class being described Classes which are named as superclasses but which are not discoverable by readmodule_ex are listed as a string with the class name instead of as Class objects methods A dictionary mapping method names to line numbers This can be derived from the newer children dictionary but remains for back compatibility,en
309,Bytes Objects These functions raise TypeError when expecting a bytes parameter and called with a non bytes parameter type PyBytesObject This subtype of PyObject represents a Python bytes object PyTypeObject PyBytes_Type Part of the Stable ABI This instance of PyTypeObject represents the Python bytes type it is the same object as bytes in the Python layer int PyBytes_Check PyObject o Return true if the object o is a bytes object or an instance of a subtype of the bytes type This function always succeeds int PyBytes_CheckExact PyObject o Return true if the object o is a bytes object but not an instance of a subtype of the bytes type This function always succeeds PyObject PyBytes_FromString const char v Return value New reference Part of the Stable ABI Return a new bytes object with a copy of the string v as value on success and NULL on failure The parameter v must not be NULL it will not be checked PyObject PyBytes_FromStringAndSize const char v Py_ssize_t len Return value New reference Part of the Stable ABI Return a new bytes object with a copy of the string v as value and length len on success and NULL on failure If v is NULL the contents of the bytes object are uninitialized PyObject PyBytes_FromFormat const char format Return value New reference Part of the Stable ABI Take a C printf style format string and a variable number of arguments calculate the size of the resulting Python bytes object and return a bytes object with the values formatted into it The variable arguments must be C types and must correspond exactly to the format characters in the format string The following format characters are allowed Format Characters Type Comment n a The literal character c int A single byte represented as a C int d int Equivalent to printf d 1 u unsigned int Equivalent to printf u 1 ld long Equivalent to printf ld 1 lu unsigned long Equivalent to printf lu 1 zd Py_ssize_t Equivalent to printf zd 1 zu size_t Equivalent to printf zu 1 i int Equivalent to printf i 1 x int Equivalent to printf x 1 s const char A null terminated C character array p const void The hex representation of a C pointer Mostly equivalent to printf p except that it is guaranteed to start with the literal 0x regardless of what the platform s printf yields An unrecognized format character causes all the rest of the format string to be copied as is to the result object and any extra arguments discarded 1 For integer specifiers d u ld lu zd zu i x the 0 conversion flag has effect even when a precision is given PyObject PyBytes_FromFormatV const char format va_list vargs Return value New reference Part of the Stable ABI Identical to PyBytes_FromFormat except that it takes exactly two arguments PyObject PyBytes_FromObject PyObject o Return value New reference Part of the Stable ABI Return the bytes representation of object o that implements the buffer protocol Py_ssize_t PyBytes_Size PyObject o Part of the Stable ABI Return the length of the bytes in bytes object o Py_ssize_t PyBytes_GET_SIZE PyObject o Similar to PyBytes_Size but without error checking char PyBytes_AsString PyObject o Part of the Stable ABI Return a pointer to the contents of o The pointer refers to the internal buffer of o which consists of len o 1 bytes The last byte in the buffer is always null regardless of whether there are any other null bytes The data must not be modified in any way unless the object was just created using PyBytes_FromStringAndSize NULL size It must not be deallocated If o is not a bytes object at all PyBytes_AsString returns NULL and raises TypeError char PyBytes_AS_STRING PyObject string Similar to PyBytes_AsString but without error checking int PyBytes_AsStringAndSize PyObject obj char buffer Py_ssize_t length Part of the Stable ABI Return the null terminated contents of the object obj through the output variables buffer and length Returns 0 on success If length is NULL the bytes object may not contain embedded null bytes if it does the function returns 1 and a ValueError is raised The buffer refers to an internal buffer of obj which includes an additional null byte at,en
310, the end not counted in length The data must not be modified in any way unless the object was just created using PyBytes_FromStringAndSize NULL size It must not be deallocated If obj is not a bytes object at all PyBytes_AsStringAndSize returns 1 and raises TypeError Changed in version 3 5 Previously TypeError was raised when embedded null bytes were encountered in the bytes object void PyBytes_Concat PyObject bytes PyObject newpart Part of the Stable ABI Create a new bytes object in bytes containing the contents of newpart appended to bytes the caller will own the new reference The reference to the old value of bytes will be stolen If the new object cannot be created the old reference to bytes will still be discarded and the value of bytes will be set to NULL the appropriate exception will be set void PyBytes_ConcatAndDel PyObject bytes PyObject newpart Part of the Stable ABI Create a new bytes object in bytes containing the contents of newpart appended to bytes This version releases the strong reference to newpart i e decrements its reference count int _PyBytes_Resize PyObject bytes Py_ssize_t newsize A way to resize a bytes object even though it is immutable Only use this to build up a brand new bytes object don t use this if the bytes may already be known in other parts of the code It is an error to call this function if the refcount on the input bytes object is not one Pass the address of an existing bytes object as an lvalue it may be written into and the new size desired On success bytes holds the resized bytes object and 0 is returned the address in bytes may differ from its input value If the reallocation fails the original bytes object at bytes is deallocated bytes is set to NULL MemoryError is set and 1 is returned,en
311,3 An Informal Introduction to Python In the following examples input and output are distinguished by the presence or absence of prompts and to repeat the example you must type everything after the prompt when the prompt appears lines that do not begin with a prompt are output from the interpreter Note that a secondary prompt on a line by itself in an example means you must type a blank line this is used to end a multi line command Many of the examples in this manual even those entered at the interactive prompt include comments Comments in Python start with the hash character and extend to the end of the physical line A comment may appear at the start of a line or following whitespace or code but not within a string literal A hash character within a string literal is just a hash character Since comments are to clarify code and are not interpreted by Python they may be omitted when typing in examples Some examples this is the first comment spam 1 and this is the second comment and now a third text This is not a comment because it s inside quotes 3 1 Using Python as a Calculator Let s try some simple Python commands Start the interpreter and wait for the primary prompt It shouldn t take long 3 1 1 Numbers The interpreter acts as a simple calculator you can type an expression at it and it will write the value Expression syntax is straightforward the operators and can be used to perform arithmetic parentheses can be used for grouping For example 2 2 4 50 5 6 20 50 5 6 4 5 0 8 5 division always returns a floating point number 1 6 The integer numbers e g 2 4 20 have type int the ones with a fractional part e g 5 0 1 6 have type float We will see more about numeric types later in the tutorial Division always returns a float To do floor division and get an integer result you can use the operator to calculate the remainder you can use 17 3 classic division returns a float 5 666666666666667 17 3 floor division discards the fractional part 5 17 3 the operator returns the remainder of the division 2 5 3 2 floored quotient divisor remainder 17 With Python it is possible to use the operator to calculate powers 1 5 2 5 squared 25 2 7 2 to the power of 7 128 The equal sign is used to assign a value to a variable Afterwards no result is displayed before the next interactive prompt width 20 height 5 9 width height 900 If a variable is not defined assigned a value trying to use it will give you an error n try to access an undefined variable Traceback most recent call last File stdin line 1 in module NameError name n is not defined There is full support for floating point operators with mixed type operands convert the integer operand to floating point 4 3 75 1 14 0 In interactive mode the last printed expression is assigned to the variable _ This means that when you are using Python as a desk calculator it is somewhat easier to continue calculations for example tax 12 5 100 price 100 50 price tax 12 5625 price _ 113 0625 round _ 2 113 06 This variable should be treated as read only by the user Don t explicitly assign a value to it you would create an independent local variable with the same name masking the built in variable with its magic behavior In addition to int and float Python supports other types of numbers such as Decimal and Fraction Python also has built in support for complex numbers and uses the j or J suffix to indicate the imaginary part e g 3 5j 3 1 2 Text Python can manipulate text represented by type str so called strings as well as numbers This includes characters words rabbit names Paris sentences Got your back etc Yay They can be enclosed in single quotes or double quotes with the same result 2 spam eggs single quotes spam eggs Paris rabbit got your back Yay double quotes Paris rabbit got your back Yay 1975 digits and numerals enclosed in quotes are also strings 1975 To quote a quote we need to escape it by preceding it with Alternatively we can use the other type of quotation marks doesn t use to escape the single quote doesn t doesn t or use double quotes instead doesn t Yes they said Yes they said Yes they said Yes th,en
312,ey said Isn t they said Isn t they said In the Python shell the string definition and output string can look different The print function produces a more readable output by omitting the enclosing quotes and by printing escaped and special characters s First line nSecond line n means newline s without print special characters are included in the string First line nSecond line print s with print special characters are interpreted so n produces new line First line Second line If you don t want characters prefaced by to be interpreted as special characters you can use raw strings by adding an r before the first quote print C some name here n means newline C some ame print r C some name note the r before the quote C some name There is one subtle aspect to raw strings a raw string may not end in an odd number of characters see the FAQ entry for more information and workarounds String literals can span multiple lines One way is using triple quotes or End of lines are automatically included in the string but it s possible to prevent this by adding a at the end of the line The following example print Usage thingy OPTIONS h Display this usage message H hostname Hostname to connect to produces the following output note that the initial newline is not included Usage thingy OPTIONS h Display this usage message H hostname Hostname to connect to Strings can be concatenated glued together with the operator and repeated with 3 times un followed by ium 3 un ium unununium Two or more string literals i e the ones enclosed between quotes next to each other are automatically concatenated Py thon Python This feature is particularly useful when you want to break long strings text Put several strings within parentheses to have them joined together text Put several strings within parentheses to have them joined together This only works with two literals though not with variables or expressions prefix Py prefix thon can t concatenate a variable and a string literal File stdin line 1 prefix thon SyntaxError invalid syntax un 3 ium File stdin line 1 un 3 ium SyntaxError invalid syntax If you want to concatenate variables or a variable and a literal use prefix thon Python Strings can be indexed subscripted with the first character having index 0 There is no separate character type a character is simply a string of size one word Python word 0 character in position 0 P word 5 character in position 5 n Indices may also be negative numbers to start counting from the right word 1 last character n word 2 second last character o word 6 P Note that since 0 is the same as 0 negative indices start from 1 In addition to indexing slicing is also supported While indexing is used to obtain individual characters slicing allows you to obtain a substring word 0 2 characters from position 0 included to 2 excluded Py word 2 5 characters from position 2 included to 5 excluded tho Slice indices have useful defaults an omitted first index defaults to zero an omitted second index defaults to the size of the string being sliced word 2 character from the beginning to position 2 excluded Py word 4 characters from position 4 included to the end on word 2 characters from the second last included to the end on Note how the start is always included and the end always excluded This makes sure that s i s i is always equal to s word 2 word 2 Python word 4 word 4 Python One way to remember how slices work is to think of the indices as pointing between characters with the left edge of the first character numbered 0 Then the right edge of the last character of a string of n characters has index n for example P y t h o n 0 1 2 3 4 5 6 6 5 4 3 2 1 The first row of numbers gives the position of the indices 0 6 in the string the second row gives the corresponding negative indices The slice from i to j consists of all characters between the edges labeled i and j respectively For non negative indices the length of a slice is the difference of the indices if both are within bounds For example the length of word 1 3 is 2 Attempting to use an index that is too large will result in an error word,en
313, 42 the word only has 6 characters Traceback most recent call last File stdin line 1 in module IndexError string index out of range However out of range slice indexes are handled gracefully when used for slicing word 4 42 on word 42 Python strings cannot be changed they are immutable Therefore assigning to an indexed position in the string results in an error word 0 J Traceback most recent call last File stdin line 1 in module TypeError str object does not support item assignment word 2 py Traceback most recent call last File stdin line 1 in module TypeError str object does not support item assignment If you need a different string you should create a new one J word 1 Jython word 2 py Pypy The built in function len returns the length of a string s supercalifragilisticexpialidocious len s 34 See also Text Sequence Type str Strings are examples of sequence types and support the common operations supported by such types String Methods Strings support a large number of methods for basic transformations and searching f strings String literals that have embedded expressions Format String Syntax Information about string formatting with str format printf style String Formatting The old formatting operations invoked when strings are the left operand of the operator are described in more detail here 3 1 3 Lists Python knows a number of compound data types used to group together other values The most versatile is the list which can be written as a list of comma separated values items between square brackets Lists might contain items of different types but usually the items all have the same type squares 1 4 9 16 25 squares 1 4 9 16 25 Like strings and all other built in sequence types lists can be indexed and sliced squares 0 indexing returns the item 1 squares 1 25 squares 3 slicing returns a new list 9 16 25 Lists also support operations like concatenation squares 36 49 64 81 100 1 4 9 16 25 36 49 64 81 100 Unlike strings which are immutable lists are a mutable type i e it is possible to change their content cubes 1 8 27 65 125 something s wrong here 4 3 the cube of 4 is 64 not 65 64 cubes 3 64 replace the wrong value cubes 1 8 27 64 125 You can also add new items at the end of the list by using the list append method we will see more about methods later cubes append 216 add the cube of 6 cubes append 7 3 and the cube of 7 cubes 1 8 27 64 125 216 343 Simple assignment in Python never copies data When you assign a list to a variable the variable refers to the existing list Any changes you make to the list through one variable will be seen through all other variables that refer to it rgb Red Green Blue rgba rgb id rgb id rgba they reference the same object True rgba append Alph rgb Red Green Blue Alph All slice operations return a new list containing the requested elements This means that the following slice returns a shallow copy of the list correct_rgba rgba correct_rgba 1 Alpha correct_rgba Red Green Blue Alpha rgba Red Green Blue Alph Assignment to slices is also possible and this can even change the size of the list or clear it entirely letters a b c d e f g letters a b c d e f g replace some values letters 2 5 C D E letters a b C D E f g now remove them letters 2 5 letters a b f g clear the list by replacing all the elements with an empty list letters letters The built in function len also applies to lists letters a b c d len letters 4 It is possible to nest lists create lists containing other lists for example a a b c n 1 2 3 x a n x a b c 1 2 3 x 0 a b c x 0 1 b 3 2 First Steps Towards Programming Of course we can use Python for more complicated tasks than adding two and two together For instance we can write an initial sub sequence of the Fibonacci series as follows Fibonacci series the sum of two elements defines the next a b 0 1 while a 10 print a a b b a b 0 1 1 2 3 5 8 This example introduces several new features The first line contains a multiple assignment the variables a and b simultaneously get the new values 0 and 1 On the last line this is used again demonstrating that the expressions on the right hand side are a,en
314,ll evaluated first before any of the assignments take place The right hand side expressions are evaluated from the left to the right The while loop executes as long as the condition here a 10 remains true In Python like in C any non zero integer value is true zero is false The condition may also be a string or list value in fact any sequence anything with a non zero length is true empty sequences are false The test used in the example is a simple comparison The standard comparison operators are written the same as in C less than greater than equal to less than or equal to greater than or equal to and not equal to The body of the loop is indented indentation is Python s way of grouping statements At the interactive prompt you have to type a tab or space s for each indented line In practice you will prepare more complicated input for Python with a text editor all decent text editors have an auto indent facility When a compound statement is entered interactively it must be followed by a blank line to indicate completion since the parser cannot guess when you have typed the last line Note that each line within a basic block must be indented by the same amount The print function writes the value of the argument s it is given It differs from just writing the expression you want to write as we did earlier in the calculator examples in the way it handles multiple arguments floating point quantities and strings Strings are printed without quotes and a space is inserted between items so you can format things nicely like this i 256 256 print The value of i is i The value of i is 65536 The keyword argument end can be used to avoid the newline after the output or end the output with a different string a b 0 1 while a 1000 print a end a b b a b 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 Footnotes 1 Since has higher precedence than 3 2 will be interpreted as 3 2 and thus result in 9 To avoid this and get 9 you can use 3 2 2 Unlike other languages special characters such as n have the same meaning with both single and double quotes The only difference between the two is that within single quotes you don t need to escape but you have to escape and vice versa,en
315,Subprocesses Source code Lib asyncio subprocess py Lib asyncio base_subprocess py This section describes high level async await asyncio APIs to create and manage subprocesses Here s an example of how asyncio can run a shell command and obtain its result import asyncio async def run cmd proc await asyncio create_subprocess_shell cmd stdout asyncio subprocess PIPE stderr asyncio subprocess PIPE stdout stderr await proc communicate print f cmd r exited with proc returncode if stdout print f stdout n stdout decode if stderr print f stderr n stderr decode asyncio run run ls zzz will print ls zzz exited with 1 stderr ls zzz No such file or directory Because all asyncio subprocess functions are asynchronous and asyncio provides many tools to work with such functions it is easy to execute and monitor multiple subprocesses in parallel It is indeed trivial to modify the above example to run several commands simultaneously async def main await asyncio gather run ls zzz run sleep 1 echo hello asyncio run main See also the Examples subsection Creating Subprocesses coroutine asyncio create_subprocess_exec program args stdin None stdout None stderr None limit None kwds Create a subprocess The limit argument sets the buffer limit for StreamReader wrappers for Process stdout and Process stderr if subprocess PIPE is passed to stdout and stderr arguments Return a Process instance See the documentation of loop subprocess_exec for other parameters Changed in version 3 10 Removed the loop parameter coroutine asyncio create_subprocess_shell cmd stdin None stdout None stderr None limit None kwds Run the cmd shell command The limit argument sets the buffer limit for StreamReader wrappers for Process stdout and Process stderr if subprocess PIPE is passed to stdout and stderr arguments Return a Process instance See the documentation of loop subprocess_shell for other parameters Important It is the application s responsibility to ensure that all whitespace and special characters are quoted appropriately to avoid shell injection vulnerabilities The shlex quote function can be used to properly escape whitespace and special shell characters in strings that are going to be used to construct shell commands Changed in version 3 10 Removed the loop parameter Note Subprocesses are available for Windows if a ProactorEventLoop is used See Subprocess Support on Windows for details See also asyncio also has the following low level APIs to work with subprocesses loop subprocess_exec loop subprocess_shell loop connect_read_pipe loop connect_write_pipe as well as the Subprocess Transports and Subprocess Protocols Constants asyncio subprocess PIPE Can be passed to the stdin stdout or stderr parameters If PIPE is passed to stdin argument the Process stdin attribute will point to a StreamWriter instance If PIPE is passed to stdout or stderr arguments the Process stdout and Process stderr attributes will point to StreamReader instances asyncio subprocess STDOUT Special value that can be used as the stderr argument and indicates that standard error should be redirected into standard output asyncio subprocess DEVNULL Special value that can be used as the stdin stdout or stderr argument to process creation functions It indicates that the special file os devnull will be used for the corresponding subprocess stream Interacting with Subprocesses Both create_subprocess_exec and create_subprocess_shell functions return instances of the Process class Process is a high level wrapper that allows communicating with subprocesses and watching for their completion class asyncio subprocess Process An object that wraps OS processes created by the create_subprocess_exec and create_subprocess_shell functions This class is designed to have a similar API to the subprocess Popen class but there are some notable differences unlike Popen Process instances do not have an equivalent to the poll method the communicate and wait methods don t have a timeout parameter use the wait_for function the Process wait method is asynchronous whereas subprocess Popen wait method is implemented as a blockin,en
316,g busy loop the universal_newlines parameter is not supported This class is not thread safe See also the Subprocess and Threads section coroutine wait Wait for the child process to terminate Set and return the returncode attribute Note This method can deadlock when using stdout PIPE or stderr PIPE and the child process generates so much output that it blocks waiting for the OS pipe buffer to accept more data Use the communicate method when using pipes to avoid this condition coroutine communicate input None Interact with process 1 send data to stdin if input is not None 2 closes stdin 3 read data from stdout and stderr until EOF is reached 4 wait for process to terminate The optional input argument is the data bytes object that will be sent to the child process Return a tuple stdout_data stderr_data If either BrokenPipeError or ConnectionResetError exception is raised when writing input into stdin the exception is ignored This condition occurs when the process exits before all data are written into stdin If it is desired to send data to the process stdin the process needs to be created with stdin PIPE Similarly to get anything other than None in the result tuple the process has to be created with stdout PIPE and or stderr PIPE arguments Note that the data read is buffered in memory so do not use this method if the data size is large or unlimited Changed in version 3 12 stdin gets closed when input None too send_signal signal Sends the signal signal to the child process Note On Windows SIGTERM is an alias for terminate CTRL_C_EVENT and CTRL_BREAK_EVENT can be sent to processes started with a creationflags parameter which includes CREATE_NEW_PROCESS_GROUP terminate Stop the child process On POSIX systems this method sends SIGTERM to the child process On Windows the Win32 API function TerminateProcess is called to stop the child process kill Kill the child process On POSIX systems this method sends SIGKILL to the child process On Windows this method is an alias for terminate stdin Standard input stream StreamWriter or None if the process was created with stdin None stdout Standard output stream StreamReader or None if the process was created with stdout None stderr Standard error stream StreamReader or None if the process was created with stderr None Warning Use the communicate method rather than process stdin write await process stdout read or await process stderr read This avoids deadlocks due to streams pausing reading or writing and blocking the child process pid Process identification number PID Note that for processes created by the create_subprocess_shell function this attribute is the PID of the spawned shell returncode Return code of the process when it exits A None value indicates that the process has not terminated yet A negative value N indicates that the child was terminated by signal N POSIX only Subprocess and Threads Standard asyncio event loop supports running subprocesses from different threads by default On Windows subprocesses are provided by ProactorEventLoop only default SelectorEventLoop has no subprocess support On UNIX child watchers are used for subprocess finish waiting see Process Watchers for more info Changed in version 3 8 UNIX switched to use ThreadedChildWatcher for spawning subprocesses from different threads without any limitation Spawning a subprocess with inactive current child watcher raises RuntimeError Note that alternative event loop implementations might have own limitations please refer to their documentation See also The Concurrency and multithreading in asyncio section Examples An example using the Process class to control a subprocess and the StreamReader class to read from its standard output The subprocess is created by the create_subprocess_exec function import asyncio import sys async def get_date code import datetime print datetime datetime now Create the subprocess redirect the standard output into a pipe proc await asyncio create_subprocess_exec sys executable c code stdout asyncio subprocess PIPE Read one line of output data await proc stdout readline line data decode as,en
317,cii rstrip Wait for the subprocess exit await proc wait return line date asyncio run get_date print f Current date date See also the same example written using low level APIs,en
318,chunk Read IFF chunked data Source code Lib chunk py Deprecated since version 3 11 will be removed in version 3 13 The chunk module is deprecated see PEP 594 for details This module provides an interface for reading files that use EA IFF 85 chunks 1 This format is used in at least the Audio Interchange File Format AIFF AIFF C and the Real Media File Format RMFF The WAVE audio file format is closely related and can also be read using this module A chunk has the following structure Offset Length Contents 0 4 Chunk ID 4 4 Size of chunk in big endian byte order not including the header 8 n Data bytes where n is the size given in the preceding field 8 n 0 or 1 Pad byte needed if n is odd and chunk alignment is used The ID is a 4 byte string which identifies the type of chunk The size field a 32 bit value encoded using big endian byte order gives the size of the chunk data not including the 8 byte header Usually an IFF type file consists of one or more chunks The proposed usage of the Chunk class defined here is to instantiate an instance at the start of each chunk and read from the instance until it reaches the end after which a new instance can be instantiated At the end of the file creating a new instance will fail with an EOFError exception class chunk Chunk file align True bigendian True inclheader False Class which represents a chunk The file argument is expected to be a file like object An instance of this class is specifically allowed The only method that is needed is read If the methods seek and tell are present and don t raise an exception they are also used If these methods are present and raise an exception they are expected to not have altered the object If the optional argument align is true chunks are assumed to be aligned on 2 byte boundaries If align is false no alignment is assumed The default value is true If the optional argument bigendian is false the chunk size is assumed to be in little endian order This is needed for WAVE audio files The default value is true If the optional argument inclheader is true the size given in the chunk header includes the size of the header The default value is false A Chunk object supports the following methods getname Returns the name ID of the chunk This is the first 4 bytes of the chunk getsize Returns the size of the chunk close Close and skip to the end of the chunk This does not close the underlying file The remaining methods will raise OSError if called after the close method has been called Before Python 3 3 they used to raise IOError now an alias of OSError isatty Returns False seek pos whence 0 Set the chunk s current position The whence argument is optional and defaults to 0 absolute file positioning other values are 1 seek relative to the current position and 2 seek relative to the file s end There is no return value If the underlying file does not allow seek only forward seeks are allowed tell Return the current position into the chunk read size 1 Read at most size bytes from the chunk less if the read hits the end of the chunk before obtaining size bytes If the size argument is negative or omitted read all data until the end of the chunk An empty bytes object is returned when the end of the chunk is encountered immediately skip Skip to the end of the chunk All further calls to read for the chunk will return b If you are not interested in the contents of the chunk this method should be called so that the file points to the start of the next chunk Footnotes 1 EA IFF 85 Standard for Interchange Format Files Jerry Morrison Electronic Arts January 1985,en
319,ensurepip Bootstrapping the pip installer New in version 3 4 Source code Lib ensurepip The ensurepip package provides support for bootstrapping the pip installer into an existing Python installation or virtual environment This bootstrapping approach reflects the fact that pip is an independent project with its own release cycle and the latest available stable version is bundled with maintenance and feature releases of the CPython reference interpreter In most cases end users of Python shouldn t need to invoke this module directly as pip should be bootstrapped by default but it may be needed if installing pip was skipped when installing Python or when creating a virtual environment or after explicitly uninstalling pip Note This module does not access the internet All of the components needed to bootstrap pip are included as internal parts of the package See also Installing Python Modules The end user guide for installing Python packages PEP 453 Explicit bootstrapping of pip in Python installations The original rationale and specification for this module Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information Command line interface The command line interface is invoked using the interpreter s m switch The simplest possible invocation is python m ensurepip This invocation will install pip if it is not already installed but otherwise does nothing To ensure the installed version of pip is at least as recent as the one available in ensurepip pass the upgrade option python m ensurepip upgrade By default pip is installed into the current virtual environment if one is active or into the system site packages if there is no active virtual environment The installation location can be controlled through two additional command line options root dir Installs pip relative to the given root directory rather than the root of the currently active virtual environment if any or the default root for the current Python installation user Installs pip into the user site packages directory rather than globally for the current Python installation this option is not permitted inside an active virtual environment By default the scripts pipX and pipX Y will be installed where X Y stands for the version of Python used to invoke ensurepip The scripts installed can be controlled through two additional command line options altinstall if an alternate installation is requested the pipX script will not be installed default pip if a default pip installation is requested the pip script will be installed in addition to the two regular scripts Providing both of the script selection options will trigger an exception Module API ensurepip exposes two functions for programmatic use ensurepip version Returns a string specifying the available version of pip that will be installed when bootstrapping an environment ensurepip bootstrap root None upgrade False user False altinstall False default_pip False verbosity 0 Bootstraps pip into the current or designated environment root specifies an alternative root directory to install relative to If root is None then installation uses the default install location for the current environment upgrade indicates whether or not to upgrade an existing installation of an earlier version of pip to the available version user indicates whether to use the user scheme rather than installing globally By default the scripts pipX and pipX Y will be installed where X Y stands for the current version of Python If altinstall is set then pipX will not be installed If default_pip is set then pip will be installed in addition to the two regular scripts Setting both altinstall and default_pip will trigger ValueError verbosity controls the level of output to sys stdout from the bootstrapping operation Raises an auditing event ensurepip bootstrap with argument root Note The bootstrapping process has side effects on both sys path and os environ Invoking the command line interface in a subprocess instead allows these side,en
320, effects to be avoided Note The bootstrapping process may install additional modules required by pip but other software should not assume those dependencies will always be present by default as the dependencies may be removed in a future version of pip,en
321,posix The most common POSIX system calls This module provides access to operating system functionality that is standardized by the C Standard and the POSIX standard a thinly disguised Unix interface Availability Unix Do not import this module directly Instead import the module os which provides a portable version of this interface On Unix the os module provides a superset of the posix interface On non Unix operating systems the posix module is not available but a subset is always available through the os interface Once os is imported there is no performance penalty in using it instead of posix In addition os provides some additional functionality such as automatically calling putenv when an entry in os environ is changed Errors are reported as exceptions the usual exceptions are given for type errors while errors reported by the system calls raise OSError Large File Support Several operating systems including AIX and Solaris provide support for files that are larger than 2 GiB from a C programming model where int and long are 32 bit values This is typically accomplished by defining the relevant size and offset types as 64 bit values Such files are sometimes referred to as large files Large file support is enabled in Python when the size of an off_t is larger than a long and the long long is at least as large as an off_t It may be necessary to configure and compile Python with certain compiler flags to enable this mode For example with Solaris 2 6 and 2 7 you need to do something like CFLAGS getconf LFS_CFLAGS OPT g O2 CFLAGS configure On large file capable Linux systems this might work CFLAGS D_LARGEFILE64_SOURCE D_FILE_OFFSET_BITS 64 OPT g O2 CFLAGS configure Notable Module Contents In addition to many functions described in the os module documentation posix defines the following data item posix environ A dictionary representing the string environment at the time the interpreter was started Keys and values are bytes on Unix and str on Windows For example environ b HOME environ HOME on Windows is the pathname of your home directory equivalent to getenv HOME in C Modifying this dictionary does not affect the string environment passed on by execv popen or system if you need to change the environment pass environ to execve or add variable assignments and export statements to the command string for system or popen Changed in version 3 2 On Unix keys and values are bytes Note The os module provides an alternate implementation of environ which updates the environment on modification Note also that updating os environ will render this dictionary obsolete Use of the os module version of this is recommended over direct access to the posix module,en
322,5 Using Python on a Mac Author Bob Savage bobsavage mac com Python on a Mac running macOS is in principle very similar to Python on any other Unix platform but there are a number of additional features such as the integrated development environment IDE and the Package Manager that are worth pointing out 5 1 Getting and Installing Python macOS used to come with Python 2 7 pre installed between versions 10 8 and 12 3 You are invited to install the most recent version of Python 3 from the Python website A current universal2 binary build of Python which runs natively on the Mac s new Apple Silicon and legacy Intel processors is available there What you get after installing is a number of things A Python 3 12 folder in your Applications folder In here you find IDLE the development environment that is a standard part of official Python distributions and Python Launcher which handles double clicking Python scripts from the Finder A framework Library Frameworks Python framework which includes the Python executable and libraries The installer adds this location to your shell path To uninstall Python you can remove these three things A symlink to the Python executable is placed in usr local bin Note On macOS 10 8 12 3 the Apple provided build of Python is installed in System Library Frameworks Python framework and usr bin python respectively You should never modify or delete these as they are Apple controlled and are used by Apple or third party software Remember that if you choose to install a newer Python version from python org you will have two different but functional Python installations on your computer so it will be important that your paths and usages are consistent with what you want to do IDLE includes a Help menu that allows you to access Python documentation If you are completely new to Python you should start reading the tutorial introduction in that document If you are familiar with Python on other Unix platforms you should read the section on running Python scripts from the Unix shell 5 1 1 How to run a Python script Your best way to get started with Python on macOS is through the IDLE integrated development environment see section The IDE and use the Help menu when the IDE is running If you want to run Python scripts from the Terminal window command line or from the Finder you first need an editor to create your script macOS comes with a number of standard Unix command line editors vim nano among them If you want a more Mac like editor BBEdit from Bare Bones Software see https www barebones com products bbedit index html are good choices as is TextMate see https macromates com Other editors include MacVim https macvim org and Aquamacs https aquamacs org To run your script from the Terminal window you must make sure that usr local bin is in your shell search path To run your script from the Finder you have two options Drag it to Python Launcher Select Python Launcher as the default application to open your script or any py script through the finder Info window and double click it Python Launcher has various preferences to control how your script is launched Option dragging allows you to change these for one invocation or use its Preferences menu to change things globally 5 1 2 Running scripts with a GUI With older versions of Python there is one macOS quirk that you need to be aware of programs that talk to the Aqua window manager in other words anything that has a GUI need to be run in a special way Use pythonw instead of python to start such scripts With Python 3 9 you can use either python or pythonw 5 1 3 Configuration Python on macOS honors all standard Unix environment variables such as PYTHONPATH but setting these variables for programs started from the Finder is non standard as the Finder does not read your profile or cshrc at startup You need to create a file MacOSX environment plist See Apple s Technical Q A QA1067 for details For more information on installation Python packages see section Installing Additional Python Packages 5 2 The IDE Python ships with the standard IDLE development environment A good,en
323, introduction to using IDLE can be found at https www hashcollision org hkn python idle_intro index html 5 3 Installing Additional Python Packages This section has moved to the Python Packaging User Guide 5 4 GUI Programming There are several options for building GUI applications on the Mac with Python PyObjC is a Python binding to Apple s Objective C Cocoa framework which is the foundation of most modern Mac development Information on PyObjC is available from https pypi org project pyobjc The standard Python GUI toolkit is tkinter based on the cross platform Tk toolkit https www tcl tk An Aqua native version of Tk is bundled with macOS by Apple and the latest version can be downloaded and installed from https www activestate com it can also be built from source wxPython is another popular cross platform GUI toolkit that runs natively on macOS Packages and documentation are available from https www wxpython org PyQt is another popular cross platform GUI toolkit that runs natively on macOS More information can be found at https riverbankcomputing com software pyqt intro PySide is another cross platform Qt based toolkit More information at https www qt io qt for python 5 5 Distributing Python Applications The standard tool for deploying standalone Python applications on the Mac is py2app More information on installing and using py2app can be found at https pypi org project py2app 5 6 Other Resources The Pythonmac SIG mailing list is an excellent support resource for Python users and developers on the Mac https www python org community sigs current pythonmac sig Another useful resource is the MacPython wiki https wiki python org moin MacPython,en
324,curses Terminal handling for character cell displays Source code Lib curses The curses module provides an interface to the curses library the de facto standard for portable advanced terminal handling While curses is most widely used in the Unix environment versions are available for Windows DOS and possibly other systems as well This extension module is designed to match the API of ncurses an open source curses library hosted on Linux and the BSD variants of Unix Note Whenever the documentation mentions a character it can be specified as an integer a one character Unicode string or a one byte byte string Whenever the documentation mentions a character string it can be specified as a Unicode string or a byte string See also Module curses ascii Utilities for working with ASCII characters regardless of your locale settings Module curses panel A panel stack extension that adds depth to curses windows Module curses textpad Editable text widget for curses supporting Emacs like bindings Curses Programming with Python Tutorial material on using curses with Python by Andrew Kuchling and Eric Raymond Functions The module curses defines the following exception exception curses error Exception raised when a curses library function returns an error Note Whenever x or y arguments to a function or a method are optional they default to the current cursor location Whenever attr is optional it defaults to A_NORMAL The module curses defines the following functions curses baudrate Return the output speed of the terminal in bits per second On software terminal emulators it will have a fixed high value Included for historical reasons in former times it was used to write output loops for time delays and occasionally to change interfaces depending on the line speed curses beep Emit a short attention sound curses can_change_color Return True or False depending on whether the programmer can change the colors displayed by the terminal curses cbreak Enter cbreak mode In cbreak mode sometimes called rare mode normal tty line buffering is turned off and characters are available to be read one by one However unlike raw mode special characters interrupt quit suspend and flow control retain their effects on the tty driver and calling program Calling first raw then cbreak leaves the terminal in cbreak mode curses color_content color_number Return the intensity of the red green and blue RGB components in the color color_number which must be between 0 and COLORS 1 Return a 3 tuple containing the R G B values for the given color which will be between 0 no component and 1000 maximum amount of component curses color_pair pair_number Return the attribute value for displaying text in the specified color pair Only the first 256 color pairs are supported This attribute value can be combined with A_STANDOUT A_REVERSE and the other A_ attributes pair_number is the counterpart to this function curses curs_set visibility Set the cursor state visibility can be set to 0 1 or 2 for invisible normal or very visible If the terminal supports the visibility requested return the previous cursor state otherwise raise an exception On many terminals the visible mode is an underline cursor and the very visible mode is a block cursor curses def_prog_mode Save the current terminal mode as the program mode the mode when the running program is using curses Its counterpart is the shell mode for when the program is not in curses Subsequent calls to reset_prog_mode will restore this mode curses def_shell_mode Save the current terminal mode as the shell mode the mode when the running program is not using curses Its counterpart is the program mode when the program is using curses capabilities Subsequent calls to reset_shell_mode will restore this mode curses delay_output ms Insert an ms millisecond pause in output curses doupdate Update the physical screen The curses library keeps two data structures one representing the current physical screen contents and a virtual screen representing the desired next state The doupdate ground updates the physical screen to match the virtual screen The,en
325, virtual screen may be updated by a noutrefresh call after write operations such as addstr have been performed on a window The normal refresh call is simply noutrefresh followed by doupdate if you have to update multiple windows you can speed performance and perhaps reduce screen flicker by issuing noutrefresh calls on all windows followed by a single doupdate curses echo Enter echo mode In echo mode each character input is echoed to the screen as it is entered curses endwin De initialize the library and return terminal to normal status curses erasechar Return the user s current erase character as a one byte bytes object Under Unix operating systems this is a property of the controlling tty of the curses program and is not set by the curses library itself curses filter The filter routine if used must be called before initscr is called The effect is that during those calls LINES is set to 1 the capabilities clear cup cud cud1 cuu1 cuu vpa are disabled and the home string is set to the value of cr The effect is that the cursor is confined to the current line and so are screen updates This may be used for enabling character at a time line editing without touching the rest of the screen curses flash Flash the screen That is change it to reverse video and then change it back in a short interval Some people prefer such as visible bell to the audible attention signal produced by beep curses flushinp Flush all input buffers This throws away any typeahead that has been typed by the user and has not yet been processed by the program curses getmouse After getch returns KEY_MOUSE to signal a mouse event this method should be called to retrieve the queued mouse event represented as a 5 tuple id x y z bstate id is an ID value used to distinguish multiple devices and x y z are the event s coordinates z is currently unused bstate is an integer value whose bits will be set to indicate the type of event and will be the bitwise OR of one or more of the following constants where n is the button number from 1 to 5 BUTTONn_PRESSED BUTTONn_RELEASED BUTTONn_CLICKED BUTTONn_DOUBLE_CLICKED BUTTONn_TRIPLE_CLICKED BUTTON_SHIFT BUTTON_CTRL BUTTON_ALT Changed in version 3 10 The BUTTON5_ constants are now exposed if they are provided by the underlying curses library curses getsyx Return the current coordinates of the virtual screen cursor as a tuple y x If leaveok is currently True then return 1 1 curses getwin file Read window related data stored in the file by an earlier window putwin call The routine then creates and initializes a new window using that data returning the new window object curses has_colors Return True if the terminal can display colors otherwise return False curses has_extended_color_support Return True if the module supports extended colors otherwise return False Extended color support allows more than 256 color pairs for terminals that support more than 16 colors e g xterm 256color Extended color support requires ncurses version 6 1 or later New in version 3 10 curses has_ic Return True if the terminal has insert and delete character capabilities This function is included for historical reasons only as all modern software terminal emulators have such capabilities curses has_il Return True if the terminal has insert and delete line capabilities or can simulate them using scrolling regions This function is included for historical reasons only as all modern software terminal emulators have such capabilities curses has_key ch Take a key value ch and return True if the current terminal type recognizes a key with that value curses halfdelay tenths Used for half delay mode which is similar to cbreak mode in that characters typed by the user are immediately available to the program However after blocking for tenths tenths of seconds raise an exception if nothing has been typed The value of tenths must be a number between 1 and 255 Use nocbreak to leave half delay mode curses init_color color_number r g b Change the definition of a color taking the number of the color to be changed followed by three RGB values for the amounts of red gree,en
326,n and blue components The value of color_number must be between 0 and COLORS 1 Each of r g b must be a value between 0 and 1000 When init_color is used all occurrences of that color on the screen immediately change to the new definition This function is a no op on most terminals it is active only if can_change_color returns True curses init_pair pair_number fg bg Change the definition of a color pair It takes three arguments the number of the color pair to be changed the foreground color number and the background color number The value of pair_number must be between 1 and COLOR_PAIRS 1 the 0 color pair is wired to white on black and cannot be changed The value of fg and bg arguments must be between 0 and COLORS 1 or after calling use_default_colors 1 If the color pair was previously initialized the screen is refreshed and all occurrences of that color pair are changed to the new definition curses initscr Initialize the library Return a window object which represents the whole screen Note If there is an error opening the terminal the underlying curses library may cause the interpreter to exit curses is_term_resized nlines ncols Return True if resize_term would modify the window structure False otherwise curses isendwin Return True if endwin has been called that is the curses library has been deinitialized curses keyname k Return the name of the key numbered k as a bytes object The name of a key generating printable ASCII character is the key s character The name of a control key combination is a two byte bytes object consisting of a caret b followed by the corresponding printable ASCII character The name of an alt key combination 128 255 is a bytes object consisting of the prefix b M followed by the name of the corresponding ASCII character curses killchar Return the user s current line kill character as a one byte bytes object Under Unix operating systems this is a property of the controlling tty of the curses program and is not set by the curses library itself curses longname Return a bytes object containing the terminfo long name field describing the current terminal The maximum length of a verbose description is 128 characters It is defined only after the call to initscr curses meta flag If flag is True allow 8 bit characters to be input If flag is False allow only 7 bit chars curses mouseinterval interval Set the maximum time in milliseconds that can elapse between press and release events in order for them to be recognized as a click and return the previous interval value The default value is 200 milliseconds or one fifth of a second curses mousemask mousemask Set the mouse events to be reported and return a tuple availmask oldmask availmask indicates which of the specified mouse events can be reported on complete failure it returns 0 oldmask is the previous value of the given window s mouse event mask If this function is never called no mouse events are ever reported curses napms ms Sleep for ms milliseconds curses newpad nlines ncols Create and return a pointer to a new pad data structure with the given number of lines and columns Return a pad as a window object A pad is like a window except that it is not restricted by the screen size and is not necessarily associated with a particular part of the screen Pads can be used when a large window is needed and only a part of the window will be on the screen at one time Automatic refreshes of pads such as from scrolling or echoing of input do not occur The refresh and noutrefresh methods of a pad require 6 arguments to specify the part of the pad to be displayed and the location on the screen to be used for the display The arguments are pminrow pmincol sminrow smincol smaxrow smaxcol the p arguments refer to the upper left corner of the pad region to be displayed and the s arguments define a clipping box on the screen within which the pad region is to be displayed curses newwin nlines ncols curses newwin nlines ncols begin_y begin_x Return a new window whose left upper corner is at begin_y begin_x and whose height width is nlines ncols By default the window will extend ,en
327,from the specified position to the lower right corner of the screen curses nl Enter newline mode This mode translates the return key into newline on input and translates newline into return and line feed on output Newline mode is initially on curses nocbreak Leave cbreak mode Return to normal cooked mode with line buffering curses noecho Leave echo mode Echoing of input characters is turned off curses nonl Leave newline mode Disable translation of return into newline on input and disable low level translation of newline into newline return on output but this does not change the behavior of addch n which always does the equivalent of return and line feed on the virtual screen With translation off curses can sometimes speed up vertical motion a little also it will be able to detect the return key on input curses noqiflush When the noqiflush routine is used normal flush of input and output queues associated with the INTR QUIT and SUSP characters will not be done You may want to call noqiflush in a signal handler if you want output to continue as though the interrupt had not occurred after the handler exits curses noraw Leave raw mode Return to normal cooked mode with line buffering curses pair_content pair_number Return a tuple fg bg containing the colors for the requested color pair The value of pair_number must be between 0 and COLOR_PAIRS 1 curses pair_number attr Return the number of the color pair set by the attribute value attr color_pair is the counterpart to this function curses putp str Equivalent to tputs str 1 putchar emit the value of a specified terminfo capability for the current terminal Note that the output of putp always goes to standard output curses qiflush flag If flag is False the effect is the same as calling noqiflush If flag is True or no argument is provided the queues will be flushed when these control characters are read curses raw Enter raw mode In raw mode normal line buffering and processing of interrupt quit suspend and flow control keys are turned off characters are presented to curses input functions one by one curses reset_prog_mode Restore the terminal to program mode as previously saved by def_prog_mode curses reset_shell_mode Restore the terminal to shell mode as previously saved by def_shell_mode curses resetty Restore the state of the terminal modes to what it was at the last call to savetty curses resize_term nlines ncols Backend function used by resizeterm performing most of the work when resizing the windows resize_term blank fills the areas that are extended The calling application should fill in these areas with appropriate data The resize_term function attempts to resize all windows However due to the calling convention of pads it is not possible to resize these without additional interaction with the application curses resizeterm nlines ncols Resize the standard and current windows to the specified dimensions and adjusts other bookkeeping data used by the curses library that record the window dimensions in particular the SIGWINCH handler curses savetty Save the current state of the terminal modes in a buffer usable by resetty curses get_escdelay Retrieves the value set by set_escdelay New in version 3 9 curses set_escdelay ms Sets the number of milliseconds to wait after reading an escape character to distinguish between an individual escape character entered on the keyboard from escape sequences sent by cursor and function keys New in version 3 9 curses get_tabsize Retrieves the value set by set_tabsize New in version 3 9 curses set_tabsize size Sets the number of columns used by the curses library when converting a tab character to spaces as it adds the tab to a window New in version 3 9 curses setsyx y x Set the virtual screen cursor to y x If y and x are both 1 then leaveok is set True curses setupterm term None fd 1 Initialize the terminal term is a string giving the terminal name or None if omitted or None the value of the TERM environment variable will be used fd is the file descriptor to which any initialization sequences will be sent if not supplied or 1 the file descri,en
328,ptor for sys stdout will be used curses start_color Must be called if the programmer wants to use colors and before any other color manipulation routine is called It is good practice to call this routine right after initscr start_color initializes eight basic colors black red green yellow blue magenta cyan and white and two global variables in the curses module COLORS and COLOR_PAIRS containing the maximum number of colors and color pairs the terminal can support It also restores the colors on the terminal to the values they had when the terminal was just turned on curses termattrs Return a logical OR of all video attributes supported by the terminal This information is useful when a curses program needs complete control over the appearance of the screen curses termname Return the value of the environment variable TERM as a bytes object truncated to 14 characters curses tigetflag capname Return the value of the Boolean capability corresponding to the terminfo capability name capname as an integer Return the value 1 if capname is not a Boolean capability or 0 if it is canceled or absent from the terminal description curses tigetnum capname Return the value of the numeric capability corresponding to the terminfo capability name capname as an integer Return the value 2 if capname is not a numeric capability or 1 if it is canceled or absent from the terminal description curses tigetstr capname Return the value of the string capability corresponding to the terminfo capability name capname as a bytes object Return None if capname is not a terminfo string capability or is canceled or absent from the terminal description curses tparm str Instantiate the bytes object str with the supplied parameters where str should be a parameterized string obtained from the terminfo database E g tparm tigetstr cup 5 3 could result in b 033 6 4H the exact result depending on terminal type curses typeahead fd Specify that the file descriptor fd be used for typeahead checking If fd is 1 then no typeahead checking is done The curses library does line breakout optimization by looking for typeahead periodically while updating the screen If input is found and it is coming from a tty the current update is postponed until refresh or doupdate is called again allowing faster response to commands typed in advance This function allows specifying a different file descriptor for typeahead checking curses unctrl ch Return a bytes object which is a printable representation of the character ch Control characters are represented as a caret followed by the character for example as b C Printing characters are left as they are curses ungetch ch Push ch so the next getch will return it Note Only one ch can be pushed before getch is called curses update_lines_cols Update the LINES and COLS module variables Useful for detecting manual screen resize New in version 3 5 curses unget_wch ch Push ch so the next get_wch will return it Note Only one ch can be pushed before get_wch is called New in version 3 3 curses ungetmouse id x y z bstate Push a KEY_MOUSE event onto the input queue associating the given state data with it curses use_env flag If used this function should be called before initscr or newterm are called When flag is False the values of lines and columns specified in the terminfo database will be used even if environment variables LINES and COLUMNS used by default are set or if curses is running in a window in which case default behavior would be to use the window size if LINES and COLUMNS are not set curses use_default_colors Allow use of default values for colors on terminals supporting this feature Use this to support transparency in your application The default color is assigned to the color number 1 After calling this function init_pair x curses COLOR_RED 1 initializes for instance color pair x to a red foreground color on the default background curses wrapper func args kwargs Initialize curses and call another callable object func which should be the rest of your curses using application If the application raises an exception this function will restore t,en
329,he terminal to a sane state before re raising the exception and generating a traceback The callable object func is then passed the main window stdscr as its first argument followed by any other arguments passed to wrapper Before calling func wrapper turns on cbreak mode turns off echo enables the terminal keypad and initializes colors if the terminal has color support On exit whether normally or by exception it restores cooked mode turns on echo and disables the terminal keypad Window Objects Window objects as returned by initscr and newwin above have the following methods and attributes window addch ch attr window addch y x ch attr Paint character ch at y x with attributes attr overwriting any character previously painted at that location By default the character position and attributes are the current settings for the window object Note Writing outside the window subwindow or pad raises a curses error Attempting to write to the lower right corner of a window subwindow or pad will cause an exception to be raised after the character is printed window addnstr str n attr window addnstr y x str n attr Paint at most n characters of the character string str at y x with attributes attr overwriting anything previously on the display window addstr str attr window addstr y x str attr Paint the character string str at y x with attributes attr overwriting anything previously on the display Note Writing outside the window subwindow or pad raises curses error Attempting to write to the lower right corner of a window subwindow or pad will cause an exception to be raised after the string is printed A bug in ncurses the backend for this Python module can cause SegFaults when resizing windows This is fixed in ncurses 6 1 20190511 If you are stuck with an earlier ncurses you can avoid triggering this if you do not call addstr with a str that has embedded newlines Instead call addstr separately for each line window attroff attr Remove attribute attr from the background set applied to all writes to the current window window attron attr Add attribute attr from the background set applied to all writes to the current window window attrset attr Set the background set of attributes to attr This set is initially 0 no attributes window bkgd ch attr Set the background property of the window to the character ch with attributes attr The change is then applied to every character position in that window The attribute of every character in the window is changed to the new background attribute Wherever the former background character appears it is changed to the new background character window bkgdset ch attr Set the window s background A window s background consists of a character and any combination of attributes The attribute part of the background is combined OR ed with all non blank characters that are written into the window Both the character and attribute parts of the background are combined with the blank characters The background becomes a property of the character and moves with the character through any scrolling and insert delete line character operations window border ls rs ts bs tl tr bl br Draw a border around the edges of the window Each parameter specifies the character to use for a specific part of the border see the table below for more details Note A 0 value for any parameter will cause the default character to be used for that parameter Keyword parameters can not be used The defaults are listed in this table Parameter Description Default value ls Left side ACS_VLINE rs Right side ACS_VLINE ts Top ACS_HLINE bs Bottom ACS_HLINE tl Upper left corner ACS_ULCORNER tr Upper right corner ACS_URCORNER bl Bottom left corner ACS_LLCORNER br Bottom right corner ACS_LRCORNER window box vertch horch Similar to border but both ls and rs are vertch and both ts and bs are horch The default corner characters are always used by this function window chgat attr window chgat num attr window chgat y x attr window chgat y x num attr Set the attributes of num characters at the current cursor position or at position y x if supplied If num is not given or is,en
330, 1 the attribute will be set on all the characters to the end of the line This function moves cursor to position y x if supplied The changed line will be touched using the touchline method so that the contents will be redisplayed by the next window refresh window clear Like erase but also cause the whole window to be repainted upon next call to refresh window clearok flag If flag is True the next call to refresh will clear the window completely window clrtobot Erase from cursor to the end of the window all lines below the cursor are deleted and then the equivalent of clrtoeol is performed window clrtoeol Erase from cursor to the end of the line window cursyncup Update the current cursor position of all the ancestors of the window to reflect the current cursor position of the window window delch y x Delete any character at y x window deleteln Delete the line under the cursor All following lines are moved up by one line window derwin begin_y begin_x window derwin nlines ncols begin_y begin_x An abbreviation for derive window derwin is the same as calling subwin except that begin_y and begin_x are relative to the origin of the window rather than relative to the entire screen Return a window object for the derived window window echochar ch attr Add character ch with attribute attr and immediately call refresh on the window window enclose y x Test whether the given pair of screen relative character cell coordinates are enclosed by the given window returning True or False It is useful for determining what subset of the screen windows enclose the location of a mouse event Changed in version 3 10 Previously it returned 1 or 0 instead of True or False window encoding Encoding used to encode method arguments Unicode strings and characters The encoding attribute is inherited from the parent window when a subwindow is created for example with window subwin By default current locale encoding is used see locale getencoding New in version 3 3 window erase Clear the window window getbegyx Return a tuple y x of co ordinates of upper left corner window getbkgd Return the given window s current background character attribute pair window getch y x Get a character Note that the integer returned does not have to be in ASCII range function keys keypad keys and so on are represented by numbers higher than 255 In no delay mode return 1 if there is no input otherwise wait until a key is pressed window get_wch y x Get a wide character Return a character for most keys or an integer for function keys keypad keys and other special keys In no delay mode raise an exception if there is no input New in version 3 3 window getkey y x Get a character returning a string instead of an integer as getch does Function keys keypad keys and other special keys return a multibyte string containing the key name In no delay mode raise an exception if there is no input window getmaxyx Return a tuple y x of the height and width of the window window getparyx Return the beginning coordinates of this window relative to its parent window as a tuple y x Return 1 1 if this window has no parent window getstr window getstr n window getstr y x window getstr y x n Read a bytes object from the user with primitive line editing capacity window getyx Return a tuple y x of current cursor position relative to the window s upper left corner window hline ch n window hline y x ch n Display a horizontal line starting at y x with length n consisting of the character ch window idcok flag If flag is False curses no longer considers using the hardware insert delete character feature of the terminal if flag is True use of character insertion and deletion is enabled When curses is first initialized use of character insert delete is enabled by default window idlok flag If flag is True curses will try and use hardware line editing facilities Otherwise line insertion deletion are disabled window immedok flag If flag is True any change in the window image automatically causes the window to be refreshed you no longer have to call refresh yourself However it may degrade performance considerably due to,en
331, repeated calls to wrefresh This option is disabled by default window inch y x Return the character at the given position in the window The bottom 8 bits are the character proper and upper bits are the attributes window insch ch attr window insch y x ch attr Paint character ch at y x with attributes attr moving the line from position x right by one character window insdelln nlines Insert nlines lines into the specified window above the current line The nlines bottom lines are lost For negative nlines delete nlines lines starting with the one under the cursor and move the remaining lines up The bottom nlines lines are cleared The current cursor position remains the same window insertln Insert a blank line under the cursor All following lines are moved down by one line window insnstr str n attr window insnstr y x str n attr Insert a character string as many characters as will fit on the line before the character under the cursor up to n characters If n is zero or negative the entire string is inserted All characters to the right of the cursor are shifted right with the rightmost characters on the line being lost The cursor position does not change after moving to y x if specified window insstr str attr window insstr y x str attr Insert a character string as many characters as will fit on the line before the character under the cursor All characters to the right of the cursor are shifted right with the rightmost characters on the line being lost The cursor position does not change after moving to y x if specified window instr n window instr y x n Return a bytes object of characters extracted from the window starting at the current cursor position or at y x if specified Attributes are stripped from the characters If n is specified instr returns a string at most n characters long exclusive of the trailing NUL window is_linetouched line Return True if the specified line was modified since the last call to refresh otherwise return False Raise a curses error exception if line is not valid for the given window window is_wintouched Return True if the specified window was modified since the last call to refresh otherwise return False window keypad flag If flag is True escape sequences generated by some keys keypad function keys will be interpreted by curses If flag is False escape sequences will be left as is in the input stream window leaveok flag If flag is True cursor is left where it is on update instead of being at cursor position This reduces cursor movement where possible If possible the cursor will be made invisible If flag is False cursor will always be at cursor position after an update window move new_y new_x Move cursor to new_y new_x window mvderwin y x Move the window inside its parent window The screen relative parameters of the window are not changed This routine is used to display different parts of the parent window at the same physical position on the screen window mvwin new_y new_x Move the window so its upper left corner is at new_y new_x window nodelay flag If flag is True getch will be non blocking window notimeout flag If flag is True escape sequences will not be timed out If flag is False after a few milliseconds an escape sequence will not be interpreted and will be left in the input stream as is window noutrefresh Mark for refresh but wait This function updates the data structure representing the desired state of the window but does not force an update of the physical screen To accomplish that call doupdate window overlay destwin sminrow smincol dminrow dmincol dmaxrow dmaxcol Overlay the window on top of destwin The windows need not be the same size only the overlapping region is copied This copy is non destructive which means that the current background character does not overwrite the old contents of destwin To get fine grained control over the copied region the second form of overlay can be used sminrow and smincol are the upper left coordinates of the source window and the other variables mark a rectangle in the destination window window overwrite destwin sminrow smincol dminrow dmincol dmaxrow dmaxc,en
332,ol Overwrite the window on top of destwin The windows need not be the same size in which case only the overlapping region is copied This copy is destructive which means that the current background character overwrites the old contents of destwin To get fine grained control over the copied region the second form of overwrite can be used sminrow and smincol are the upper left coordinates of the source window the other variables mark a rectangle in the destination window window putwin file Write all data associated with the window into the provided file object This information can be later retrieved using the getwin function window redrawln beg num Indicate that the num screen lines starting at line beg are corrupted and should be completely redrawn on the next refresh call window redrawwin Touch the entire window causing it to be completely redrawn on the next refresh call window refresh pminrow pmincol sminrow smincol smaxrow smaxcol Update the display immediately sync actual screen with previous drawing deleting methods The 6 optional arguments can only be specified when the window is a pad created with newpad The additional parameters are needed to indicate what part of the pad and screen are involved pminrow and pmincol specify the upper left hand corner of the rectangle to be displayed in the pad sminrow smincol smaxrow and smaxcol specify the edges of the rectangle to be displayed on the screen The lower right hand corner of the rectangle to be displayed in the pad is calculated from the screen coordinates since the rectangles must be the same size Both rectangles must be entirely contained within their respective structures Negative values of pminrow pmincol sminrow or smincol are treated as if they were zero window resize nlines ncols Reallocate storage for a curses window to adjust its dimensions to the specified values If either dimension is larger than the current values the window s data is filled with blanks that have the current background rendition as set by bkgdset merged into them window scroll lines 1 Scroll the screen or scrolling region upward by lines lines window scrollok flag Control what happens when the cursor of a window is moved off the edge of the window or scrolling region either as a result of a newline action on the bottom line or typing the last character of the last line If flag is False the cursor is left on the bottom line If flag is True the window is scrolled up one line Note that in order to get the physical scrolling effect on the terminal it is also necessary to call idlok window setscrreg top bottom Set the scrolling region from line top to line bottom All scrolling actions will take place in this region window standend Turn off the standout attribute On some terminals this has the side effect of turning off all attributes window standout Turn on attribute A_STANDOUT window subpad begin_y begin_x window subpad nlines ncols begin_y begin_x Return a sub window whose upper left corner is at begin_y begin_x and whose width height is ncols nlines window subwin begin_y begin_x window subwin nlines ncols begin_y begin_x Return a sub window whose upper left corner is at begin_y begin_x and whose width height is ncols nlines By default the sub window will extend from the specified position to the lower right corner of the window window syncdown Touch each location in the window that has been touched in any of its ancestor windows This routine is called by refresh so it should almost never be necessary to call it manually window syncok flag If flag is True then syncup is called automatically whenever there is a change in the window window syncup Touch all locations in ancestors of the window that have been changed in the window window timeout delay Set blocking or non blocking read behavior for the window If delay is negative blocking read is used which will wait indefinitely for input If delay is zero then non blocking read is used and getch will return 1 if no input is waiting If delay is positive then getch will block for delay milliseconds and return 1 if there is still no input at the en,en
333,d of that time window touchline start count changed Pretend count lines have been changed starting with line start If changed is supplied it specifies whether the affected lines are marked as having been changed changed True or unchanged changed False window touchwin Pretend the whole window has been changed for purposes of drawing optimizations window untouchwin Mark all lines in the window as unchanged since the last call to refresh window vline ch n attr window vline y x ch n attr Display a vertical line starting at y x with length n consisting of the character ch with attributes attr Constants The curses module defines the following data members curses ERR Some curses routines that return an integer such as getch return ERR upon failure curses OK Some curses routines that return an integer such as napms return OK upon success curses version curses __version__ A bytes object representing the current version of the module curses ncurses_version A named tuple containing the three components of the ncurses library version major minor and patch All values are integers The components can also be accessed by name so curses ncurses_version 0 is equivalent to curses ncurses_version major and so on Availability if the ncurses library is used New in version 3 8 curses COLORS The maximum number of colors the terminal can support It is defined only after the call to start_color curses COLOR_PAIRS The maximum number of color pairs the terminal can support It is defined only after the call to start_color curses COLS The width of the screen i e the number of columns It is defined only after the call to initscr Updated by update_lines_cols resizeterm and resize_term curses LINES The height of the screen i e the number of lines It is defined only after the call to initscr Updated by update_lines_cols resizeterm and resize_term Some constants are available to specify character cell attributes The exact constants available are system dependent Attribute Meaning curses A_ALTCHARSET Alternate character set mode curses A_BLINK Blink mode curses A_BOLD Bold mode curses A_DIM Dim mode curses A_INVIS Invisible or blank mode curses A_ITALIC Italic mode curses A_NORMAL Normal attribute curses A_PROTECT Protected mode curses A_REVERSE Reverse background and foreground colors curses A_STANDOUT Standout mode curses A_UNDERLINE Underline mode curses A_HORIZONTAL Horizontal highlight curses A_LEFT Left highlight curses A_LOW Low highlight curses A_RIGHT Right highlight curses A_TOP Top highlight curses A_VERTICAL Vertical highlight New in version 3 7 A_ITALIC was added Several constants are available to extract corresponding attributes returned by some methods Bit mask Meaning curses A_ATTRIBUTES Bit mask to extract attributes curses A_CHARTEXT Bit mask to extract a character curses A_COLOR Bit mask to extract color pair field information Keys are referred to by integer constants with names starting with KEY_ The exact keycaps available are system dependent Key constant Key curses KEY_MIN Minimum key value curses KEY_BREAK Break key unreliable curses KEY_DOWN Down arrow curses KEY_UP Up arrow curses KEY_LEFT Left arrow curses KEY_RIGHT Right arrow curses KEY_HOME Home key upward left arrow curses KEY_BACKSPACE Backspace unreliable curses KEY_F0 Function keys Up to 64 function keys are supported curses KEY_Fn Value of function key n curses KEY_DL Delete line curses KEY_IL Insert line curses KEY_DC Delete character curses KEY_IC Insert char or enter insert mode curses KEY_EIC Exit insert char mode curses KEY_CLEAR Clear screen curses KEY_EOS Clear to end of screen curses KEY_EOL Clear to end of line curses KEY_SF Scroll 1 line forward curses KEY_SR Scroll 1 line backward reverse curses KEY_NPAGE Next page curses KEY_PPAGE Previous page curses KEY_STAB Set tab curses KEY_CTAB Clear tab curses KEY_CATAB Clear all tabs curses KEY_ENTER Enter or send unreliable curses KEY_SRESET Soft partial reset unreliable curses KEY_RESET Reset or hard reset unreliable curses KEY_PRINT Print curses KEY_LL Home down or bottom lower left curses KEY_A1 Upper left of keypa,en
334,d curses KEY_A3 Upper right of keypad curses KEY_B2 Center of keypad curses KEY_C1 Lower left of keypad curses KEY_C3 Lower right of keypad curses KEY_BTAB Back tab curses KEY_BEG Beg beginning curses KEY_CANCEL Cancel curses KEY_CLOSE Close curses KEY_COMMAND Cmd command curses KEY_COPY Copy curses KEY_CREATE Create curses KEY_END End curses KEY_EXIT Exit curses KEY_FIND Find curses KEY_HELP Help curses KEY_MARK Mark curses KEY_MESSAGE Message curses KEY_MOVE Move curses KEY_NEXT Next curses KEY_OPEN Open curses KEY_OPTIONS Options curses KEY_PREVIOUS Prev previous curses KEY_REDO Redo curses KEY_REFERENCE Ref reference curses KEY_REFRESH Refresh curses KEY_REPLACE Replace curses KEY_RESTART Restart curses KEY_RESUME Resume curses KEY_SAVE Save curses KEY_SBEG Shifted Beg beginning curses KEY_SCANCEL Shifted Cancel curses KEY_SCOMMAND Shifted Command curses KEY_SCOPY Shifted Copy curses KEY_SCREATE Shifted Create curses KEY_SDC Shifted Delete char curses KEY_SDL Shifted Delete line curses KEY_SELECT Select curses KEY_SEND Shifted End curses KEY_SEOL Shifted Clear line curses KEY_SEXIT Shifted Exit curses KEY_SFIND Shifted Find curses KEY_SHELP Shifted Help curses KEY_SHOME Shifted Home curses KEY_SIC Shifted Input curses KEY_SLEFT Shifted Left arrow curses KEY_SMESSAGE Shifted Message curses KEY_SMOVE Shifted Move curses KEY_SNEXT Shifted Next curses KEY_SOPTIONS Shifted Options curses KEY_SPREVIOUS Shifted Prev curses KEY_SPRINT Shifted Print curses KEY_SREDO Shifted Redo curses KEY_SREPLACE Shifted Replace curses KEY_SRIGHT Shifted Right arrow curses KEY_SRSUME Shifted Resume curses KEY_SSAVE Shifted Save curses KEY_SSUSPEND Shifted Suspend curses KEY_SUNDO Shifted Undo curses KEY_SUSPEND Suspend curses KEY_UNDO Undo curses KEY_MOUSE Mouse event has occurred curses KEY_RESIZE Terminal resize event curses KEY_MAX Maximum key value On VT100s and their software emulations such as X terminal emulators there are normally at least four function keys KEY_F1 KEY_F2 KEY_F3 KEY_F4 available and the arrow keys mapped to KEY_UP KEY_DOWN KEY_LEFT and KEY_RIGHT in the obvious way If your machine has a PC keyboard it is safe to expect arrow keys and twelve function keys older PC keyboards may have only ten function keys also the following keypad mappings are standard Keycap Constant Insert KEY_IC Delete KEY_DC Home KEY_HOME End KEY_END Page Up KEY_PPAGE Page Down KEY_NPAGE The following table lists characters from the alternate character set These are inherited from the VT100 terminal and will generally be available on software emulations such as X terminals When there is no graphic available curses falls back on a crude printable ASCII approximation Note These are available only after initscr has been called ACS code Meaning curses ACS_BBSS alternate name for upper right corner curses ACS_BLOCK solid square block curses ACS_BOARD board of squares curses ACS_BSBS alternate name for horizontal line curses ACS_BSSB alternate name for upper left corner curses ACS_BSSS alternate name for top tee curses ACS_BTEE bottom tee curses ACS_BULLET bullet curses ACS_CKBOARD checker board stipple curses ACS_DARROW arrow pointing down curses ACS_DEGREE degree symbol curses ACS_DIAMOND diamond curses ACS_GEQUAL greater than or equal to curses ACS_HLINE horizontal line curses ACS_LANTERN lantern symbol curses ACS_LARROW left arrow curses ACS_LEQUAL less than or equal to curses ACS_LLCORNER lower left hand corner curses ACS_LRCORNER lower right hand corner curses ACS_LTEE left tee curses ACS_NEQUAL not equal sign curses ACS_PI letter pi curses ACS_PLMINUS plus or minus sign curses ACS_PLUS big plus sign curses ACS_RARROW right arrow curses ACS_RTEE right tee curses ACS_S1 scan line 1 curses ACS_S3 scan line 3 curses ACS_S7 scan line 7 curses ACS_S9 scan line 9 curses ACS_SBBS alternate name for lower right corner curses ACS_SBSB alternate name for vertical line curses ACS_SBSS alternate name for right tee curses ACS_SSBB alternate name for lower left corner curses ACS_SSBS alternate name for bottom tee curses ACS_SSSB alternate name for left tee curs,en
335,es ACS_SSSS alternate name for crossover or big plus curses ACS_STERLING pound sterling curses ACS_TTEE top tee curses ACS_UARROW up arrow curses ACS_ULCORNER upper left corner curses ACS_URCORNER upper right corner curses ACS_VLINE vertical line The following table lists mouse button constants used by getmouse Mouse button constant Meaning curses BUTTONn_PRESSED Mouse button n pressed curses BUTTONn_RELEASED Mouse button n released curses BUTTONn_CLICKED Mouse button n clicked curses BUTTONn_DOUBLE_CLICKED Mouse button n double clicked curses BUTTONn_TRIPLE_CLICKED Mouse button n triple clicked curses BUTTON_SHIFT Shift was down during button state change curses BUTTON_CTRL Control was down during button state change curses BUTTON_ALT Control was down during button state change Changed in version 3 10 The BUTTON5_ constants are now exposed if they are provided by the underlying curses library The following table lists the predefined colors Constant Color curses COLOR_BLACK Black curses COLOR_BLUE Blue curses COLOR_CYAN Cyan light greenish blue curses COLOR_GREEN Green curses COLOR_MAGENTA Magenta purplish red curses COLOR_RED Red curses COLOR_WHITE White curses COLOR_YELLOW Yellow curses textpad Text input widget for curses programs The curses textpad module provides a Textbox class that handles elementary text editing in a curses window supporting a set of keybindings resembling those of Emacs thus also of Netscape Navigator BBedit 6 x FrameMaker and many other programs The module also provides a rectangle drawing function useful for framing text boxes or for other purposes The module curses textpad defines the following function curses textpad rectangle win uly ulx lry lrx Draw a rectangle The first argument must be a window object the remaining arguments are coordinates relative to that window The second and third arguments are the y and x coordinates of the upper left hand corner of the rectangle to be drawn the fourth and fifth arguments are the y and x coordinates of the lower right hand corner The rectangle will be drawn using VT100 IBM PC forms characters on terminals that make this possible including xterm and most other software terminal emulators Otherwise it will be drawn with ASCII dashes vertical bars and plus signs Textbox objects You can instantiate a Textbox object as follows class curses textpad Textbox win Return a textbox widget object The win argument should be a curses window object in which the textbox is to be contained The edit cursor of the textbox is initially located at the upper left hand corner of the containing window with coordinates 0 0 The instance s stripspaces flag is initially on Textbox objects have the following methods edit validator This is the entry point you will normally use It accepts editing keystrokes until one of the termination keystrokes is entered If validator is supplied it must be a function It will be called for each keystroke entered with the keystroke as a parameter command dispatch is done on the result This method returns the window contents as a string whether blanks in the window are included is affected by the stripspaces attribute do_command ch Process a single command keystroke Here are the supported special keystrokes Keystroke Action Control A Go to left edge of window Control B Cursor left wrapping to previous line if appropriate Control D Delete character under cursor Control E Go to right edge stripspaces off or end of line stripspaces on Control F Cursor right wrapping to next line when appropriate Control G Terminate returning the window contents Control H Delete character backward Control J Terminate if the window is 1 line otherwise insert newline Control K If line is blank delete it otherwise clear to end of line Control L Refresh screen Control N Cursor down move down one line Control O Insert a blank line at cursor location Control P Cursor up move up one line Move operations do nothing if the cursor is at an edge where the movement is not possible The following synonyms are supported where possible Constant Keystroke KEY_LEFT Control B KEY_RIGHT,en
336, Control F KEY_UP Control P KEY_DOWN Control N KEY_BACKSPACE Control h All other keystrokes are treated as a command to insert the given character and move right with line wrapping gather Return the window contents as a string whether blanks in the window are included is affected by the stripspaces member stripspaces This attribute is a flag which controls the interpretation of blanks in the window When it is on trailing blanks on each line are ignored any cursor motion that would land the cursor on a trailing blank goes to the end of that line instead and trailing blanks are stripped when the window contents are gathered,en
337,inspect Inspect live objects Source code Lib inspect py The inspect module provides several useful functions to help get information about live objects such as modules classes methods functions tracebacks frame objects and code objects For example it can help you examine the contents of a class retrieve the source code of a method extract and format the argument list for a function or get all the information you need to display a detailed traceback There are four main kinds of services provided by this module type checking getting source code inspecting classes and functions and examining the interpreter stack Types and members The getmembers function retrieves the members of an object such as a class or module The functions whose names begin with is are mainly provided as convenient choices for the second argument to getmembers They also help you determine when you can expect to find the following special attributes see Import related module attributes for module attributes Type Attribute Description class __doc__ documentation string __name__ name with which this class was defined __qualname__ qualified name __module__ name of module in which this class was defined method __doc__ documentation string __name__ name with which this method was defined __qualname__ qualified name __func__ function object containing implementation of method __self__ instance to which this method is bound or None __module__ name of module in which this method was defined function __doc__ documentation string __name__ name with which this function was defined __qualname__ qualified name __code__ code object containing compiled function bytecode __defaults__ tuple of any default values for positional or keyword parameters __kwdefaults__ mapping of any default values for keyword only parameters __globals__ global namespace in which this function was defined __builtins__ builtins namespace __annotations__ mapping of parameters names to annotations return key is reserved for return annotations __module__ name of module in which this function was defined traceback tb_frame frame object at this level tb_lasti index of last attempted instruction in bytecode tb_lineno current line number in Python source code tb_next next inner traceback object called by this level frame f_back next outer frame object this frame s caller f_builtins builtins namespace seen by this frame f_code code object being executed in this frame f_globals global namespace seen by this frame f_lasti index of last attempted instruction in bytecode f_lineno current line number in Python source code f_locals local namespace seen by this frame f_trace tracing function for this frame or None code co_argcount number of arguments not including keyword only arguments or args co_code string of raw compiled bytecode co_cellvars tuple of names of cell variables referenced by containing scopes co_consts tuple of constants used in the bytecode co_filename name of file in which this code object was created co_firstlineno number of first line in Python source code co_flags bitmap of CO_ flags read more here co_lnotab encoded mapping of line numbers to bytecode indices co_freevars tuple of names of free variables referenced via a function s closure co_posonlyargcount number of positional only arguments co_kwonlyargcount number of keyword only arguments not including arg co_name name with which this code object was defined co_qualname fully qualified name with which this code object was defined co_names tuple of names other than arguments and function locals co_nlocals number of local variables co_stacksize virtual machine stack space required co_varnames tuple of names of arguments and local variables generator __name__ name __qualname__ qualified name gi_frame frame gi_running is the generator running gi_code code gi_yieldfrom object being iterated by yield from or None coroutine __name__ name __qualname__ qualified name cr_await object being awaited on or None cr_frame frame cr_running is the coroutine running cr_code code cr_origin where coroutine was created or None See s ys set_coroutine_ori,en
338,gin_tr acking_depth builtin __doc__ documentation string __name__ original name of this function or method __qualname__ qualified name __self__ instance to which a method is bound or None Changed in version 3 5 Add __qualname__ and gi_yieldfrom attributes to generators The __name__ attribute of generators is now set from the function name instead of the code name and it can now be modified Changed in version 3 7 Add cr_origin attribute to coroutines Changed in version 3 10 Add __builtins__ attribute to functions inspect getmembers object predicate Return all the members of an object in a list of name value pairs sorted by name If the optional predicate argument which will be called with the value object of each member is supplied only members for which the predicate returns a true value are included Note getmembers will only return class attributes defined in the metaclass when the argument is a class and those attributes have been listed in the metaclass custom __dir__ inspect getmembers_static object predicate Return all the members of an object in a list of name value pairs sorted by name without triggering dynamic lookup via the descriptor protocol __getattr__ or __getattribute__ Optionally only return members that satisfy a given predicate Note getmembers_static may not be able to retrieve all members that getmembers can fetch like dynamically created attributes and may find members that getmembers can t like descriptors that raise AttributeError It can also return descriptor objects instead of instance members in some cases New in version 3 11 inspect getmodulename path Return the name of the module named by the file path without including the names of enclosing packages The file extension is checked against all of the entries in importlib machinery all_suffixes If it matches the final path component is returned with the extension removed Otherwise None is returned Note that this function only returns a meaningful name for actual Python modules paths that potentially refer to Python packages will still return None Changed in version 3 3 The function is based directly on importlib inspect ismodule object Return True if the object is a module inspect isclass object Return True if the object is a class whether built in or created in Python code inspect ismethod object Return True if the object is a bound method written in Python inspect isfunction object Return True if the object is a Python function which includes functions created by a lambda expression inspect isgeneratorfunction object Return True if the object is a Python generator function Changed in version 3 8 Functions wrapped in functools partial now return True if the wrapped function is a Python generator function inspect isgenerator object Return True if the object is a generator inspect iscoroutinefunction object Return True if the object is a coroutine function a function defined with an async def syntax a functools partial wrapping a coroutine function or a sync function marked with markcoroutinefunction New in version 3 5 Changed in version 3 8 Functions wrapped in functools partial now return True if the wrapped function is a coroutine function Changed in version 3 12 Sync functions marked with markcoroutinefunction now return True inspect markcoroutinefunction func Decorator to mark a callable as a coroutine function if it would not otherwise be detected by iscoroutinefunction This may be of use for sync functions that return a coroutine if the function is passed to an API that requires iscoroutinefunction When possible using an async def function is preferred Also acceptable is calling the function and testing the return with iscoroutine New in version 3 12 inspect iscoroutine object Return True if the object is a coroutine created by an async def function New in version 3 5 inspect isawaitable object Return True if the object can be used in await expression Can also be used to distinguish generator based coroutines from regular generators import types def gen yield types coroutine def gen_coro yield assert not isawaitable gen assert isawaitable ge,en
339,n_coro New in version 3 5 inspect isasyncgenfunction object Return True if the object is an asynchronous generator function for example async def agen yield 1 inspect isasyncgenfunction agen True New in version 3 6 Changed in version 3 8 Functions wrapped in functools partial now return True if the wrapped function is a asynchronous generator function inspect isasyncgen object Return True if the object is an asynchronous generator iterator created by an asynchronous generator function New in version 3 6 inspect istraceback object Return True if the object is a traceback inspect isframe object Return True if the object is a frame inspect iscode object Return True if the object is a code inspect isbuiltin object Return True if the object is a built in function or a bound built in method inspect ismethodwrapper object Return True if the type of object is a MethodWrapperType These are instances of MethodWrapperType such as __str__ __eq__ and __repr__ New in version 3 11 inspect isroutine object Return True if the object is a user defined or built in function or method inspect isabstract object Return True if the object is an abstract base class inspect ismethoddescriptor object Return True if the object is a method descriptor but not if ismethod isclass isfunction or isbuiltin are true This for example is true of int __add__ An object passing this test has a __get__ method but not a __set__ method but beyond that the set of attributes varies A __name__ attribute is usually sensible and __doc__ often is Methods implemented via descriptors that also pass one of the other tests return False from the ismethoddescriptor test simply because the other tests promise more you can e g count on having the __func__ attribute etc when an object passes ismethod inspect isdatadescriptor object Return True if the object is a data descriptor Data descriptors have a __set__ or a __delete__ method Examples are properties defined in Python getsets and members The latter two are defined in C and there are more specific tests available for those types which is robust across Python implementations Typically data descriptors will also have __name__ and __doc__ attributes properties getsets and members have both of these attributes but this is not guaranteed inspect isgetsetdescriptor object Return True if the object is a getset descriptor CPython implementation detail getsets are attributes defined in extension modules via PyGetSetDef structures For Python implementations without such types this method will always return False inspect ismemberdescriptor object Return True if the object is a member descriptor CPython implementation detail Member descriptors are attributes defined in extension modules via PyMemberDef structures For Python implementations without such types this method will always return False Retrieving source code inspect getdoc object Get the documentation string for an object cleaned up with cleandoc If the documentation string for an object is not provided and the object is a class a method a property or a descriptor retrieve the documentation string from the inheritance hierarchy Return None if the documentation string is invalid or missing Changed in version 3 5 Documentation strings are now inherited if not overridden inspect getcomments object Return in a single string any lines of comments immediately preceding the object s source code for a class function or method or at the top of the Python source file if the object is a module If the object s source code is unavailable return None This could happen if the object has been defined in C or the interactive shell inspect getfile object Return the name of the text or binary file in which an object was defined This will fail with a TypeError if the object is a built in module class or function inspect getmodule object Try to guess which module an object was defined in Return None if the module cannot be determined inspect getsourcefile object Return the name of the Python source file in which an object was defined or None if no way can be identified to get the source This will ,en
340,fail with a TypeError if the object is a built in module class or function inspect getsourcelines object Return a list of source lines and starting line number for an object The argument may be a module class method function traceback frame or code object The source code is returned as a list of the lines corresponding to the object and the line number indicates where in the original source file the first line of code was found An OSError is raised if the source code cannot be retrieved A TypeError is raised if the object is a built in module class or function Changed in version 3 3 OSError is raised instead of IOError now an alias of the former inspect getsource object Return the text of the source code for an object The argument may be a module class method function traceback frame or code object The source code is returned as a single string An OSError is raised if the source code cannot be retrieved A TypeError is raised if the object is a built in module class or function Changed in version 3 3 OSError is raised instead of IOError now an alias of the former inspect cleandoc doc Clean up indentation from docstrings that are indented to line up with blocks of code All leading whitespace is removed from the first line Any leading whitespace that can be uniformly removed from the second line onwards is removed Empty lines at the beginning and end are subsequently removed Also all tabs are expanded to spaces Introspecting callables with the Signature object New in version 3 3 The Signature object represents the call signature of a callable object and its return annotation To retrieve a Signature object use the signature function inspect signature callable follow_wrapped True globals None locals None eval_str False Return a Signature object for the given callable from inspect import signature def foo a b int kwargs pass sig signature foo str sig a b int kwargs str sig parameters b b int sig parameters b annotation class int Accepts a wide range of Python callables from plain functions and classes to functools partial objects For objects defined in modules using stringized annotations from __future__ import annotations signature will attempt to automatically un stringize the annotations using get_annotations The globals locals and eval_str parameters are passed into get_annotations when resolving the annotations see the documentation for get_annotations for instructions on how to use these parameters Raises ValueError if no signature can be provided and TypeError if that type of object is not supported Also if the annotations are stringized and eval_str is not false the eval call s to un stringize the annotations in get_annotations could potentially raise any kind of exception A slash in the signature of a function denotes that the parameters prior to it are positional only For more info see the FAQ entry on positional only parameters Changed in version 3 5 The follow_wrapped parameter was added Pass False to get a signature of callable specifically callable __wrapped__ will not be used to unwrap decorated callables Changed in version 3 10 The globals locals and eval_str parameters were added Note Some callables may not be introspectable in certain implementations of Python For example in CPython some built in functions defined in C provide no metadata about their arguments CPython implementation detail If the passed object has a __signature__ attribute we may use it to create the signature The exact semantics are an implementation detail and are subject to unannounced changes Consult the source code for current semantics class inspect Signature parameters None return_annotation Signature empty A Signature object represents the call signature of a function and its return annotation For each parameter accepted by the function it stores a Parameter object in its parameters collection The optional parameters argument is a sequence of Parameter objects which is validated to check that there are no parameters with duplicate names and that the parameters are in the right order i e positional only first then positional or keyword,en
341, and that parameters with defaults follow parameters without defaults The optional return_annotation argument can be an arbitrary Python object It represents the return annotation of the callable Signature objects are immutable Use Signature replace to make a modified copy Changed in version 3 5 Signature objects are now picklable and hashable empty A special class level marker to specify absence of a return annotation parameters An ordered mapping of parameters names to the corresponding Parameter objects Parameters appear in strict definition order including keyword only parameters Changed in version 3 7 Python only explicitly guaranteed that it preserved the declaration order of keyword only parameters as of version 3 7 although in practice this order had always been preserved in Python 3 return_annotation The return annotation for the callable If the callable has no return annotation this attribute is set to Signature empty bind args kwargs Create a mapping from positional and keyword arguments to parameters Returns BoundArguments if args and kwargs match the signature or raises a TypeError bind_partial args kwargs Works the same way as Signature bind but allows the omission of some required arguments mimics functools partial behavior Returns BoundArguments or raises a TypeError if the passed arguments do not match the signature replace parameters return_annotation Create a new Signature instance based on the instance replace was invoked on It is possible to pass different parameters and or return_annotation to override the corresponding properties of the base signature To remove return_annotation from the copied Signature pass in Signature empty def test a b pass sig signature test new_sig sig replace return_annotation new return anno str new_sig a b new return anno classmethod from_callable obj follow_wrapped True globals None locals None eval_str False Return a Signature or its subclass object for a given callable obj This method simplifies subclassing of Signature class MySignature Signature pass sig MySignature from_callable sum assert isinstance sig MySignature Its behavior is otherwise identical to that of signature New in version 3 5 Changed in version 3 10 The globals locals and eval_str parameters were added class inspect Parameter name kind default Parameter empty annotation Parameter empty Parameter objects are immutable Instead of modifying a Parameter object you can use Parameter replace to create a modified copy Changed in version 3 5 Parameter objects are now picklable and hashable empty A special class level marker to specify absence of default values and annotations name The name of the parameter as a string The name must be a valid Python identifier CPython implementation detail CPython generates implicit parameter names of the form 0 on the code objects used to implement comprehensions and generator expressions Changed in version 3 6 These parameter names are now exposed by this module as names like implicit0 default The default value for the parameter If the parameter has no default value this attribute is set to Parameter empty annotation The annotation for the parameter If the parameter has no annotation this attribute is set to Parameter empty kind Describes how argument values are bound to the parameter The possible values are accessible via Parameter like Parameter KEYWORD_ONLY and support comparison and ordering in the following order Name Meaning POSITIONAL_ONLY Value must be supplied as a positional argument Positional only parameters are those which appear before a entry if present in a Python function definition POSITIONAL_OR_KEYWORD Value may be supplied as either a keyword or positional argument this is the standard binding behaviour for functions implemented in Python VAR_POSITIONAL A tuple of positional arguments that aren t bound to any other parameter This corresponds to a args parameter in a Python function definition KEYWORD_ONLY Value must be supplied as a keyword argument Keyword only parameters are those which appear after a or args entry in a Python function definition VAR_K,en
342,EYWORD A dict of keyword arguments that aren t bound to any other parameter This corresponds to a kwargs parameter in a Python function definition Example print all keyword only arguments without default values def foo a b c d 10 pass sig signature foo for param in sig parameters values if param kind param KEYWORD_ONLY and param default is param empty print Parameter param Parameter c kind description Describes a enum value of Parameter kind New in version 3 8 Example print all descriptions of arguments def foo a b c d 10 pass sig signature foo for param in sig parameters values print param kind description positional or keyword positional or keyword keyword only keyword only replace name kind default annotation Create a new Parameter instance based on the instance replaced was invoked on To override a Parameter attribute pass the corresponding argument To remove a default value or and an annotation from a Parameter pass Parameter empty from inspect import Parameter param Parameter foo Parameter KEYWORD_ONLY default 42 str param foo 42 str param replace Will create a shallow copy of param foo 42 str param replace default Parameter empty annotation spam foo spam Changed in version 3 4 In Python 3 3 Parameter objects were allowed to have name set to None if their kind was set to POSITIONAL_ONLY This is no longer permitted class inspect BoundArguments Result of a Signature bind or Signature bind_partial call Holds the mapping of arguments to the function s parameters arguments A mutable mapping of parameters names to arguments values Contains only explicitly bound arguments Changes in arguments will reflect in args and kwargs Should be used in conjunction with Signature parameters for any argument processing purposes Note Arguments for which Signature bind or Signature bind_partial relied on a default value are skipped However if needed use BoundArguments apply_defaults to add them Changed in version 3 9 arguments is now of type dict Formerly it was of type collections OrderedDict args A tuple of positional arguments values Dynamically computed from the arguments attribute kwargs A dict of keyword arguments values Dynamically computed from the arguments attribute signature A reference to the parent Signature object apply_defaults Set default values for missing arguments For variable positional arguments args the default is an empty tuple For variable keyword arguments kwargs the default is an empty dict def foo a b ham args pass ba inspect signature foo bind spam ba apply_defaults ba arguments a spam b ham args New in version 3 5 The args and kwargs properties can be used to invoke functions def test a b sig signature test ba sig bind 10 b 20 test ba args ba kwargs See also PEP 362 Function Signature Object The detailed specification implementation details and examples Classes and functions inspect getclasstree classes unique False Arrange the given list of classes into a hierarchy of nested lists Where a nested list appears it contains classes derived from the class whose entry immediately precedes the list Each entry is a 2 tuple containing a class and a tuple of its base classes If the unique argument is true exactly one entry appears in the returned structure for each class in the given list Otherwise classes using multiple inheritance and their descendants will appear multiple times inspect getfullargspec func Get the names and default values of a Python function s parameters A named tuple is returned FullArgSpec args varargs varkw defaults kwonlyargs kwonlydefaults annotations args is a list of the positional parameter names varargs is the name of the parameter or None if arbitrary positional arguments are not accepted varkw is the name of the parameter or None if arbitrary keyword arguments are not accepted defaults is an n tuple of default argument values corresponding to the last n positional parameters or None if there are no such defaults defined kwonlyargs is a list of keyword only parameter names in declaration order kwonlydefaults is a dictionary mapping parameter names from kwonlyargs to the default values us,en
343,ed if no argument is supplied annotations is a dictionary mapping parameter names to annotations The special key return is used to report the function return value annotation if any Note that signature and Signature Object provide the recommended API for callable introspection and support additional behaviours like positional only arguments that are sometimes encountered in extension module APIs This function is retained primarily for use in code that needs to maintain compatibility with the Python 2 inspect module API Changed in version 3 4 This function is now based on signature but still ignores __wrapped__ attributes and includes the already bound first parameter in the signature output for bound methods Changed in version 3 6 This method was previously documented as deprecated in favour of signature in Python 3 5 but that decision has been reversed in order to restore a clearly supported standard interface for single source Python 2 3 code migrating away from the legacy getargspec API Changed in version 3 7 Python only explicitly guaranteed that it preserved the declaration order of keyword only parameters as of version 3 7 although in practice this order had always been preserved in Python 3 inspect getargvalues frame Get information about arguments passed into a particular frame A named tuple ArgInfo args varargs keywords locals is returned args is a list of the argument names varargs and keywords are the names of the and arguments or None locals is the locals dictionary of the given frame Note This function was inadvertently marked as deprecated in Python 3 5 inspect formatargvalues args varargs varkw locals formatarg formatvarargs formatvarkw formatvalue Format a pretty argument spec from the four values returned by getargvalues The format arguments are the corresponding optional formatting functions that are called to turn names and values into strings Note This function was inadvertently marked as deprecated in Python 3 5 inspect getmro cls Return a tuple of class cls s base classes including cls in method resolution order No class appears more than once in this tuple Note that the method resolution order depends on cls s type Unless a very peculiar user defined metatype is in use cls will be the first element of the tuple inspect getcallargs func args kwds Bind the args and kwds to the argument names of the Python function or method func as if it was called with them For bound methods bind also the first argument typically named self to the associated instance A dict is returned mapping the argument names including the names of the and arguments if any to their values from args and kwds In case of invoking func incorrectly i e whenever func args kwds would raise an exception because of incompatible signature an exception of the same type and the same or similar message is raised For example from inspect import getcallargs def f a b 1 pos named pass getcallargs f 1 2 3 a 1 named b 2 pos 3 True getcallargs f a 2 x 4 a 2 named x 4 b 1 pos True getcallargs f Traceback most recent call last TypeError f missing 1 required positional argument a New in version 3 2 Deprecated since version 3 5 Use Signature bind and Signature bind_partial instead inspect getclosurevars func Get the mapping of external name references in a Python function or method func to their current values A named tuple ClosureVars nonlocals globals builtins unbound is returned nonlocals maps referenced names to lexical closure variables globals to the function s module globals and builtins to the builtins visible from the function body unbound is the set of names referenced in the function that could not be resolved at all given the current module globals and builtins TypeError is raised if func is not a Python function or method New in version 3 3 inspect unwrap func stop None Get the object wrapped by func It follows the chain of __wrapped__ attributes returning the last object in the chain stop is an optional callback accepting an object in the wrapper chain as its sole argument that allows the unwrapping to be terminated early if the callback ,en
344,returns a true value If the callback never returns a true value the last object in the chain is returned as usual For example signature uses this to stop unwrapping if any object in the chain has a __signature__ attribute defined ValueError is raised if a cycle is encountered New in version 3 4 inspect get_annotations obj globals None locals None eval_str False Compute the annotations dict for an object obj may be a callable class or module Passing in an object of any other type raises TypeError Returns a dict get_annotations returns a new dict every time it s called calling it twice on the same object will return two different but equivalent dicts This function handles several details for you If eval_str is true values of type str will be un stringized using eval This is intended for use with stringized annotations from __future__ import annotations If obj doesn t have an annotations dict returns an empty dict Functions and methods always have an annotations dict classes modules and other types of callables may not Ignores inherited annotations on classes If a class doesn t have its own annotations dict returns an empty dict All accesses to object members and dict values are done using getattr and dict get for safety Always always always returns a freshly created dict eval_str controls whether or not values of type str are replaced with the result of calling eval on those values If eval_str is true eval is called on values of type str Note that get_annotations doesn t catch exceptions if eval raises an exception it will unwind the stack past the get_annotations call If eval_str is false the default values of type str are unchanged globals and locals are passed in to eval see the documentation for eval for more information If globals or locals is None this function may replace that value with a context specific default contingent on type obj If obj is a module globals defaults to obj __dict__ If obj is a class globals defaults to sys modules obj __module__ __dict__ and locals defaults to the obj class namespace If obj is a callable globals defaults to obj __globals__ although if obj is a wrapped function using functools update_wrapper it is first unwrapped Calling get_annotations is best practice for accessing the annotations dict of any object See Annotations Best Practices for more information on annotations best practices New in version 3 10 The interpreter stack Some of the following functions return FrameInfo objects For backwards compatibility these objects allow tuple like operations on all attributes except positions This behavior is considered deprecated and may be removed in the future class inspect FrameInfo frame The frame object that the record corresponds to filename The file name associated with the code being executed by the frame this record corresponds to lineno The line number of the current line associated with the code being executed by the frame this record corresponds to function The function name that is being executed by the frame this record corresponds to code_context A list of lines of context from the source code that s being executed by the frame this record corresponds to index The index of the current line being executed in the code_context list positions A dis Positions object containing the start line number end line number start column offset and end column offset associated with the instruction being executed by the frame this record corresponds to Changed in version 3 5 Return a named tuple instead of a tuple Changed in version 3 11 FrameInfo is now a class instance that is backwards compatible with the previous named tuple class inspect Traceback filename The file name associated with the code being executed by the frame this traceback corresponds to lineno The line number of the current line associated with the code being executed by the frame this traceback corresponds to function The function name that is being executed by the frame this traceback corresponds to code_context A list of lines of context from the source code that s being executed by the frame this traceback correspon,en
345,ds to index The index of the current line being executed in the code_context list positions A dis Positions object containing the start line number end line number start column offset and end column offset associated with the instruction being executed by the frame this traceback corresponds to Changed in version 3 11 Traceback is now a class instance that is backwards compatible with the previous named tuple Note Keeping references to frame objects as found in the first element of the frame records these functions return can cause your program to create reference cycles Once a reference cycle has been created the lifespan of all objects which can be accessed from the objects which form the cycle can become much longer even if Python s optional cycle detector is enabled If such cycles must be created it is important to ensure they are explicitly broken to avoid the delayed destruction of objects and increased memory consumption which occurs Though the cycle detector will catch these destruction of the frames and local variables can be made deterministic by removing the cycle in a finally clause This is also important if the cycle detector was disabled when Python was compiled or using gc disable For example def handle_stackframe_without_leak frame inspect currentframe try do something with the frame finally del frame If you want to keep the frame around for example to print a traceback later you can also break reference cycles by using the frame clear method The optional context argument supported by most of these functions specifies the number of lines of context to return which are centered around the current line inspect getframeinfo frame context 1 Get information about a frame or traceback object A Traceback object is returned Changed in version 3 11 A Traceback object is returned instead of a named tuple inspect getouterframes frame context 1 Get a list of FrameInfo objects for a frame and all outer frames These frames represent the calls that lead to the creation of frame The first entry in the returned list represents frame the last entry represents the outermost call on frame s stack Changed in version 3 5 A list of named tuples FrameInfo frame filename lineno function code_context index is returned Changed in version 3 11 A list of FrameInfo objects is returned inspect getinnerframes traceback context 1 Get a list of FrameInfo objects for a traceback s frame and all inner frames These frames represent calls made as a consequence of frame The first entry in the list represents traceback the last entry represents where the exception was raised Changed in version 3 5 A list of named tuples FrameInfo frame filename lineno function code_context index is returned Changed in version 3 11 A list of FrameInfo objects is returned inspect currentframe Return the frame object for the caller s stack frame CPython implementation detail This function relies on Python stack frame support in the interpreter which isn t guaranteed to exist in all implementations of Python If running in an implementation without Python stack frame support this function returns None inspect stack context 1 Return a list of FrameInfo objects for the caller s stack The first entry in the returned list represents the caller the last entry represents the outermost call on the stack Changed in version 3 5 A list of named tuples FrameInfo frame filename lineno function code_context index is returned Changed in version 3 11 A list of FrameInfo objects is returned inspect trace context 1 Return a list of FrameInfo objects for the stack between the current frame and the frame in which an exception currently being handled was raised in The first entry in the list represents the caller the last entry represents where the exception was raised Changed in version 3 5 A list of named tuples FrameInfo frame filename lineno function code_context index is returned Changed in version 3 11 A list of FrameInfo objects is returned Fetching attributes statically Both getattr and hasattr can trigger code execution when fetching or checking for the existence of attributes,en
346, Descriptors like properties will be invoked and __getattr__ and __getattribute__ may be called For cases where you want passive introspection like documentation tools this can be inconvenient getattr_static has the same signature as getattr but avoids executing code when it fetches attributes inspect getattr_static obj attr default None Retrieve attributes without triggering dynamic lookup via the descriptor protocol __getattr__ or __getattribute__ Note this function may not be able to retrieve all attributes that getattr can fetch like dynamically created attributes and may find attributes that getattr can t like descriptors that raise AttributeError It can also return descriptors objects instead of instance members If the instance __dict__ is shadowed by another member for example a property then this function will be unable to find instance members New in version 3 2 getattr_static does not resolve descriptors for example slot descriptors or getset descriptors on objects implemented in C The descriptor object is returned instead of the underlying attribute You can handle these with code like the following Note that for arbitrary getset descriptors invoking these may trigger code execution example code for resolving the builtin descriptor types class _foo __slots__ foo slot_descriptor type _foo foo getset_descriptor type type open __file__ name wrapper_descriptor type str __dict__ __add__ descriptor_types slot_descriptor getset_descriptor wrapper_descriptor result getattr_static some_object foo if type result in descriptor_types try result result __get__ except AttributeError descriptors can raise AttributeError to indicate there is no underlying value in which case the descriptor itself will have to do pass Current State of Generators Coroutines and Asynchronous Generators When implementing coroutine schedulers and for other advanced uses of generators it is useful to determine whether a generator is currently executing is waiting to start or resume or execution or has already terminated getgeneratorstate allows the current state of a generator to be determined easily inspect getgeneratorstate generator Get current state of a generator iterator Possible states are GEN_CREATED Waiting to start execution GEN_RUNNING Currently being executed by the interpreter GEN_SUSPENDED Currently suspended at a yield expression GEN_CLOSED Execution has completed New in version 3 2 inspect getcoroutinestate coroutine Get current state of a coroutine object The function is intended to be used with coroutine objects created by async def functions but will accept any coroutine like object that has cr_running and cr_frame attributes Possible states are CORO_CREATED Waiting to start execution CORO_RUNNING Currently being executed by the interpreter CORO_SUSPENDED Currently suspended at an await expression CORO_CLOSED Execution has completed New in version 3 5 inspect getasyncgenstate agen Get current state of an asynchronous generator object The function is intended to be used with asynchronous iterator objects created by async def functions which use the yield statement but will accept any asynchronous generator like object that has ag_running and ag_frame attributes Possible states are AGEN_CREATED Waiting to start execution AGEN_RUNNING Currently being executed by the interpreter AGEN_SUSPENDED Currently suspended at a yield expression AGEN_CLOSED Execution has completed New in version 3 12 The current internal state of the generator can also be queried This is mostly useful for testing purposes to ensure that internal state is being updated as expected inspect getgeneratorlocals generator Get the mapping of live local variables in generator to their current values A dictionary is returned that maps from variable names to values This is the equivalent of calling locals in the body of the generator and all the same caveats apply If generator is a generator with no currently associated frame then an empty dictionary is returned TypeError is raised if generator is not a Python generator object CPython implementation detail This function r,en
347,elies on the generator exposing a Python stack frame for introspection which isn t guaranteed to be the case in all implementations of Python In such cases this function will always return an empty dictionary New in version 3 3 inspect getcoroutinelocals coroutine This function is analogous to getgeneratorlocals but works for coroutine objects created by async def functions New in version 3 5 inspect getasyncgenlocals agen This function is analogous to getgeneratorlocals but works for asynchronous generator objects created by async def functions which use the yield statement New in version 3 12 Code Objects Bit Flags Python code objects have a co_flags attribute which is a bitmap of the following flags inspect CO_OPTIMIZED The code object is optimized using fast locals inspect CO_NEWLOCALS If set a new dict will be created for the frame s f_locals when the code object is executed inspect CO_VARARGS The code object has a variable positional parameter args like inspect CO_VARKEYWORDS The code object has a variable keyword parameter kwargs like inspect CO_NESTED The flag is set when the code object is a nested function inspect CO_GENERATOR The flag is set when the code object is a generator function i e a generator object is returned when the code object is executed inspect CO_COROUTINE The flag is set when the code object is a coroutine function When the code object is executed it returns a coroutine object See PEP 492 for more details New in version 3 5 inspect CO_ITERABLE_COROUTINE The flag is used to transform generators into generator based coroutines Generator objects with this flag can be used in await expression and can yield from coroutine objects See PEP 492 for more details New in version 3 5 inspect CO_ASYNC_GENERATOR The flag is set when the code object is an asynchronous generator function When the code object is executed it returns an asynchronous generator object See PEP 525 for more details New in version 3 6 Note The flags are specific to CPython and may not be defined in other Python implementations Furthermore the flags are an implementation detail and can be removed or deprecated in future Python releases It s recommended to use public APIs from the inspect module for any introspection needs Buffer flags class inspect BufferFlags This is an enum IntFlag that represents the flags that can be passed to the __buffer__ method of objects implementing the buffer protocol The meaning of the flags is explained at Buffer request types SIMPLE WRITABLE FORMAT ND STRIDES C_CONTIGUOUS F_CONTIGUOUS ANY_CONTIGUOUS INDIRECT CONTIG CONTIG_RO STRIDED STRIDED_RO RECORDS RECORDS_RO FULL FULL_RO READ WRITE New in version 3 12 Command Line Interface The inspect module also provides a basic introspection capability from the command line By default accepts the name of a module and prints the source of that module A class or function within the module can be printed instead by appended a colon and the qualified name of the target object details Print information about the specified object rather than the source code,en
348,timeit Measure execution time of small code snippets Source code Lib timeit py This module provides a simple way to time small bits of Python code It has both a Command Line Interface as well as a callable one It avoids a number of common traps for measuring execution times See also Tim Peters introduction to the Algorithms chapter in the second edition of Python Cookbook published by O Reilly Basic Examples The following example shows how the Command Line Interface can be used to compare three different expressions python m timeit join str n for n in range 100 10000 loops best of 5 30 2 usec per loop python m timeit join str n for n in range 100 10000 loops best of 5 27 5 usec per loop python m timeit join map str range 100 10000 loops best of 5 23 2 usec per loop This can be achieved from the Python Interface with import timeit timeit timeit join str n for n in range 100 number 10000 0 3018611848820001 timeit timeit join str n for n in range 100 number 10000 0 2727368790656328 timeit timeit join map str range 100 number 10000 0 23702679807320237 A callable can also be passed from the Python Interface timeit timeit lambda join map str range 100 number 10000 0 19665591977536678 Note however that timeit will automatically determine the number of repetitions only when the command line interface is used In the Examples section you can find more advanced examples Python Interface The module defines three convenience functions and a public class timeit timeit stmt pass setup pass timer default timer number 1000000 globals None Create a Timer instance with the given statement setup code and timer function and run its timeit method with number executions The optional globals argument specifies a namespace in which to execute the code Changed in version 3 5 The optional globals parameter was added timeit repeat stmt pass setup pass timer default timer repeat 5 number 1000000 globals None Create a Timer instance with the given statement setup code and timer function and run its repeat method with the given repeat count and number executions The optional globals argument specifies a namespace in which to execute the code Changed in version 3 5 The optional globals parameter was added Changed in version 3 7 Default value of repeat changed from 3 to 5 timeit default_timer The default timer which is always time perf_counter returns float seconds An alternative time perf_counter_ns returns integer nanoseconds Changed in version 3 3 time perf_counter is now the default timer class timeit Timer stmt pass setup pass timer timer function globals None Class for timing execution speed of small code snippets The constructor takes a statement to be timed an additional statement used for setup and a timer function Both statements default to pass the timer function is platform dependent see the module doc string stmt and setup may also contain multiple statements separated by or newlines as long as they don t contain multi line string literals The statement will by default be executed within timeit s namespace this behavior can be controlled by passing a namespace to globals To measure the execution time of the first statement use the timeit method The repeat and autorange methods are convenience methods to call timeit multiple times The execution time of setup is excluded from the overall timed execution run The stmt and setup parameters can also take objects that are callable without arguments This will embed calls to them in a timer function that will then be executed by timeit Note that the timing overhead is a little larger in this case because of the extra function calls Changed in version 3 5 The optional globals parameter was added timeit number 1000000 Time number executions of the main statement This executes the setup statement once and then returns the time it takes to execute the main statement a number of times The default timer returns seconds as a float The argument is the number of times through the loop defaulting to one million The main statement the setup statement and the timer function to be used are passed to the construc,en
349,tor Note By default timeit temporarily turns off garbage collection during the timing The advantage of this approach is that it makes independent timings more comparable The disadvantage is that GC may be an important component of the performance of the function being measured If so GC can be re enabled as the first statement in the setup string For example timeit Timer for i in range 10 oct i gc enable timeit autorange callback None Automatically determine how many times to call timeit This is a convenience function that calls timeit repeatedly so that the total time 0 2 second returning the eventual number of loops time taken for that number of loops It calls timeit with increasing numbers from the sequence 1 2 5 10 20 50 until the time taken is at least 0 2 seconds If callback is given and is not None it will be called after each trial with two arguments callback number time_taken New in version 3 6 repeat repeat 5 number 1000000 Call timeit a few times This is a convenience function that calls the timeit repeatedly returning a list of results The first argument specifies how many times to call timeit The second argument specifies the number argument for timeit Note It s tempting to calculate mean and standard deviation from the result vector and report these However this is not very useful In a typical case the lowest value gives a lower bound for how fast your machine can run the given code snippet higher values in the result vector are typically not caused by variability in Python s speed but by other processes interfering with your timing accuracy So the min of the result is probably the only number you should be interested in After that you should look at the entire vector and apply common sense rather than statistics Changed in version 3 7 Default value of repeat changed from 3 to 5 print_exc file None Helper to print a traceback from the timed code Typical use t Timer outside the try except try t timeit or t repeat except Exception t print_exc The advantage over the standard traceback is that source lines in the compiled template will be displayed The optional file argument directs where the traceback is sent it defaults to sys stderr Command Line Interface When called as a program from the command line the following form is used python m timeit n N r N u U s S p v h statement Where the following options are understood n N number N how many times to execute statement r N repeat N how many times to repeat the timer default 5 s S setup S statement to be executed once initially default pass p process measure process time not wallclock time using time process_time instead of time perf_counter which is the default New in version 3 3 u unit U specify a time unit for timer output can select nsec usec msec or sec New in version 3 5 v verbose print raw timing results repeat for more digits precision h help print a short usage message and exit A multi line statement may be given by specifying each line as a separate statement argument indented lines are possible by enclosing an argument in quotes and using leading spaces Multiple s options are treated similarly If n is not given a suitable number of loops is calculated by trying increasing numbers from the sequence 1 2 5 10 20 50 until the total time is at least 0 2 seconds default_timer measurements can be affected by other programs running on the same machine so the best thing to do when accurate timing is necessary is to repeat the timing a few times and use the best time The r option is good for this the default of 5 repetitions is probably enough in most cases You can use time process_time to measure CPU time Note There is a certain baseline overhead associated with executing a pass statement The code here doesn t try to hide it but you should be aware of it The baseline overhead can be measured by invoking the program without arguments and it might differ between Python versions Examples It is possible to provide a setup statement that is executed only once at the beginning python m timeit s text sample string char g char in text 5000000 loops best of 5 0 0877 usec,en
350, per loop python m timeit s text sample string char g text find char 1000000 loops best of 5 0 342 usec per loop In the output there are three fields The loop count which tells you how many times the statement body was run per timing loop repetition The repetition count best of 5 which tells you how many times the timing loop was repeated and finally the time the statement body took on average within the best repetition of the timing loop That is the time the fastest repetition took divided by the loop count import timeit timeit timeit char in text setup text sample string char g 0 41440500499993504 timeit timeit text find char setup text sample string char g 1 7246671520006203 The same can be done using the Timer class and its methods import timeit t timeit Timer char in text setup text sample string char g t timeit 0 3955516149999312 t repeat 0 40183617287970225 0 37027556854118704 0 38344867356679524 0 3712595970846668 0 37866875250654886 The following examples show how to time expressions that contain multiple lines Here we compare the cost of using hasattr vs try except to test for missing and present object attributes python m timeit try str __bool__ except AttributeError pass 20000 loops best of 5 15 7 usec per loop python m timeit if hasattr str __bool__ pass 50000 loops best of 5 4 26 usec per loop python m timeit try int __bool__ except AttributeError pass 200000 loops best of 5 1 43 usec per loop python m timeit if hasattr int __bool__ pass 100000 loops best of 5 2 23 usec per loop import timeit attribute is missing s try str __bool__ except AttributeError pass timeit timeit stmt s number 100000 0 9138244460009446 s if hasattr str __bool__ pass timeit timeit stmt s number 100000 0 5829014980008651 attribute is present s try int __bool__ except AttributeError pass timeit timeit stmt s number 100000 0 04215312199994514 s if hasattr int __bool__ pass timeit timeit stmt s number 100000 0 08588060699912603 To give the timeit module access to functions you define you can pass a setup parameter which contains an import statement def test Stupid test function L i for i in range 100 if __name__ __main__ import timeit print timeit timeit test setup from __main__ import test Another option is to pass globals to the globals parameter which will cause the code to be executed within your current global namespace This can be more convenient than individually specifying imports def f x return x 2 def g x return x 4 def h x return x 8 import timeit print timeit timeit func 42 for func in f g h globals globals,en
351,File and Directory Access The modules described in this chapter deal with disk files and directories For example there are modules for reading the properties of files manipulating paths in a portable way and creating temporary files The full list of modules in this chapter is pathlib Object oriented filesystem paths Basic use Pure paths General properties Operators Accessing individual parts Methods and properties Concrete paths Methods Correspondence to tools in the os module os path Common pathname manipulations fileinput Iterate over lines from multiple input streams stat Interpreting stat results filecmp File and Directory Comparisons The dircmp class tempfile Generate temporary files and directories Examples Deprecated functions and variables glob Unix style pathname pattern expansion fnmatch Unix filename pattern matching linecache Random access to text lines shutil High level file operations Directory and files operations Platform dependent efficient copy operations copytree example rmtree example Archiving operations Archiving example Archiving example with base_dir Querying the size of the output terminal See also Module os Operating system interfaces including functions to work with files at a lower level than Python file objects Module io Python s built in I O library including both abstract classes and some concrete classes such as file I O Built in function open The standard way to open files for reading and writing with Python,en
352,Generic Operating System Services The modules described in this chapter provide interfaces to operating system features that are available on almost all operating systems such as files and a clock The interfaces are generally modeled after the Unix or C interfaces but they are available on most other systems as well Here s an overview os Miscellaneous operating system interfaces File Names Command Line Arguments and Environment Variables Python UTF 8 Mode Process Parameters File Object Creation File Descriptor Operations Querying the size of a terminal Inheritance of File Descriptors Files and Directories Linux extended attributes Process Management Interface to the scheduler Miscellaneous System Information Random numbers io Core tools for working with streams Overview Text I O Binary I O Raw I O Text Encoding Opt in EncodingWarning High level Module Interface Class hierarchy I O Base Classes Raw File I O Buffered Streams Text I O Performance Binary I O Text I O Multi threading Reentrancy time Time access and conversions Functions Clock ID Constants Timezone Constants argparse Parser for command line options arguments and sub commands Core Functionality Quick Links for add_argument Example Creating a parser Adding arguments Parsing arguments ArgumentParser objects prog usage description epilog parents formatter_class prefix_chars fromfile_prefix_chars argument_default allow_abbrev conflict_handler add_help exit_on_error The add_argument method name or flags action nargs const default type choices required help metavar dest Action classes The parse_args method Option value syntax Invalid arguments Arguments containing Argument abbreviations prefix matching Beyond sys argv The Namespace object Other utilities Sub commands FileType objects Argument groups Mutual exclusion Parser defaults Printing help Partial parsing Customizing file parsing Exiting methods Intermixed parsing Upgrading optparse code Exceptions getopt C style parser for command line options logging Logging facility for Python Logger Objects Logging Levels Handler Objects Formatter Objects Filter Objects LogRecord Objects LogRecord attributes LoggerAdapter Objects Thread Safety Module Level Functions Module Level Attributes Integration with the warnings module logging config Logging configuration Configuration functions Security considerations Configuration dictionary schema Dictionary Schema Details Incremental Configuration Object connections User defined objects Handler configuration order Access to external objects Access to internal objects Import resolution and custom importers Configuring QueueHandler and QueueListener Configuration file format logging handlers Logging handlers StreamHandler FileHandler NullHandler WatchedFileHandler BaseRotatingHandler RotatingFileHandler TimedRotatingFileHandler SocketHandler DatagramHandler SysLogHandler NTEventLogHandler SMTPHandler MemoryHandler HTTPHandler QueueHandler QueueListener getpass Portable password input curses Terminal handling for character cell displays Functions Window Objects Constants curses textpad Text input widget for curses programs Textbox objects curses ascii Utilities for ASCII characters curses panel A panel stack extension for curses Functions Panel Objects platform Access to underlying platform s identifying data Cross Platform Java Platform Windows Platform macOS Platform Unix Platforms Linux Platforms errno Standard errno system symbols ctypes A foreign function library for Python ctypes tutorial Loading dynamic link libraries Accessing functions from loaded dlls Calling functions Fundamental data types Calling functions continued Calling variadic functions Calling functions with your own custom data types Specifying the required argument types function prototypes Return types Passing pointers or passing parameters by reference Structures and unions Structure union alignment and byte order Bit fields in structures and unions Arrays Pointers Type conversions Incomplete Types Callback functions Accessing values exported from dlls Surprises Variable sized data types ctypes reference Find,en
353,ing shared libraries Loading shared libraries Foreign functions Function prototypes Utility functions Data types Fundamental data types Structured data types Arrays and pointers,en
354,sndhdr Determine type of sound file Source code Lib sndhdr py Deprecated since version 3 11 will be removed in version 3 13 The sndhdr module is deprecated see PEP 594 for details and alternatives The sndhdr provides utility functions which attempt to determine the type of sound data which is in a file When these functions are able to determine what type of sound data is stored in a file they return a namedtuple containing five attributes filetype framerate nchannels nframes sampwidth The value for type indicates the data type and will be one of the strings aifc aiff au hcom sndr sndt voc wav 8svx sb ub or ul The sampling_rate will be either the actual value or 0 if unknown or difficult to decode Similarly channels will be either the number of channels or 0 if it cannot be determined or if the value is difficult to decode The value for frames will be either the number of frames or 1 The last item in the tuple bits_per_sample will either be the sample size in bits or A for A LAW or U for u LAW sndhdr what filename Determines the type of sound data stored in the file filename using whathdr If it succeeds returns a namedtuple as described above otherwise None is returned Changed in version 3 5 Result changed from a tuple to a namedtuple sndhdr whathdr filename Determines the type of sound data stored in a file based on the file header The name of the file is given by filename This function returns a namedtuple as described above on success or None Changed in version 3 5 Result changed from a tuple to a namedtuple The following sound header types are recognized as listed below with the return value from whathdr and what Value Sound header format aifc Compressed Audio Interchange Files aiff Audio Interchange Files au Au Files hcom HCOM Files sndt Sndtool Sound Files voc Creative Labs Audio Files wav Waveform Audio File Format Files 8svx 8 Bit Sampled Voice Files sb Signed Byte Audio Data Files ub UB Files ul uLAW Audio Files sndhdr tests A list of functions performing the individual tests Each function takes two arguments the byte stream and an open file like object When what is called with a byte stream the file like object will be None The test function should return a string describing the image type if the test succeeded or None if it failed Example import sndhdr imghdr what bass wav wav imghdr whathdr bass wav wav,en
355,7 Input and Output There are several ways to present the output of a program data can be printed in a human readable form or written to a file for future use This chapter will discuss some of the possibilities 7 1 Fancier Output Formatting So far we ve encountered two ways of writing values expression statements and the print function A third way is using the write method of file objects the standard output file can be referenced as sys stdout See the Library Reference for more information on this Often you ll want more control over the formatting of your output than simply printing space separated values There are several ways to format output To use formatted string literals begin a string with f or F before the opening quotation mark or triple quotation mark Inside this string you can write a Python expression between and characters that can refer to variables or literal values year 2016 event Referendum f Results of the year event Results of the 2016 Referendum The str format method of strings requires more manual effort You ll still use and to mark where a variable will be substituted and can provide detailed formatting directives but you ll also need to provide the information to be formatted yes_votes 42_572_654 no_votes 43_132_495 percentage yes_votes yes_votes no_votes 9 YES votes 2 2 format yes_votes percentage 42572654 YES votes 49 67 Finally you can do all the string handling yourself by using string slicing and concatenation operations to create any layout you can imagine The string type has some methods that perform useful operations for padding strings to a given column width When you don t need fancy output but just want a quick display of some variables for debugging purposes you can convert any value to a string with the repr or str functions The str function is meant to return representations of values which are fairly human readable while repr is meant to generate representations which can be read by the interpreter or will force a SyntaxError if there is no equivalent syntax For objects which don t have a particular representation for human consumption str will return the same value as repr Many values such as numbers or structures like lists and dictionaries have the same representation using either function Strings in particular have two distinct representations Some examples s Hello world str s Hello world repr s Hello world str 1 7 0 14285714285714285 x 10 3 25 y 200 200 s The value of x is repr x and y is repr y print s The value of x is 32 5 and y is 40000 The repr of a string adds string quotes and backslashes hello hello world n hellos repr hello print hellos hello world n The argument to repr may be any Python object repr x y spam eggs 32 5 40000 spam eggs The string module contains a Template class that offers yet another way to substitute values into strings using placeholders like x and replacing them with values from a dictionary but offers much less control of the formatting 7 1 1 Formatted String Literals Formatted string literals also called f strings for short let you include the value of Python expressions inside a string by prefixing the string with f or F and writing expressions as expression An optional format specifier can follow the expression This allows greater control over how the value is formatted The following example rounds pi to three places after the decimal import math print f The value of pi is approximately math pi 3f The value of pi is approximately 3 142 Passing an integer after the will cause that field to be a minimum number of characters wide This is useful for making columns line up table Sjoerd 4127 Jack 4098 Dcab 7678 for name phone in table items print f name 10 phone 10d Sjoerd 4127 Jack 4098 Dcab 7678 Other modifiers can be used to convert the value before it is formatted a applies ascii s applies str and r applies repr animals eels print f My hovercraft is full of animals My hovercraft is full of eels print f My hovercraft is full of animals r My hovercraft is full of eels The specifier can be used to expand an expression to the text of the expression an,en
356, equal sign then the representation of the evaluated expression bugs roaches count 13 area living room print f Debugging bugs count area Debugging bugs roaches count 13 area living room See self documenting expressions for more information on the specifier For a reference on these format specifications see the reference guide for the Format Specification Mini Language 7 1 2 The String format Method Basic usage of the str format method looks like this print We are the who say format knights Ni We are the knights who say Ni The brackets and characters within them called format fields are replaced with the objects passed into the str format method A number in the brackets can be used to refer to the position of the object passed into the str format method print 0 and 1 format spam eggs spam and eggs print 1 and 0 format spam eggs eggs and spam If keyword arguments are used in the str format method their values are referred to by using the name of the argument print This food is adjective format food spam adjective absolutely horrible This spam is absolutely horrible Positional and keyword arguments can be arbitrarily combined print The story of 0 1 and other format Bill Manfred other Georg The story of Bill Manfred and Georg If you have a really long format string that you don t want to split up it would be nice if you could reference the variables to be formatted by name instead of by position This can be done by simply passing the dict and using square brackets to access the keys table Sjoerd 4127 Jack 4098 Dcab 8637678 print Jack 0 Jack d Sjoerd 0 Sjoerd d Dcab 0 Dcab d format table Jack 4098 Sjoerd 4127 Dcab 8637678 This could also be done by passing the table dictionary as keyword arguments with the notation table Sjoerd 4127 Jack 4098 Dcab 8637678 print Jack Jack d Sjoerd Sjoerd d Dcab Dcab d format table Jack 4098 Sjoerd 4127 Dcab 8637678 This is particularly useful in combination with the built in function vars which returns a dictionary containing all local variables As an example the following lines produce a tidily aligned set of columns giving integers and their squares and cubes for x in range 1 11 print 0 2d 1 3d 2 4d format x x x x x x 1 1 1 2 4 8 3 9 27 4 16 64 5 25 125 6 36 216 7 49 343 8 64 512 9 81 729 10 100 1000 For a complete overview of string formatting with str format see Format String Syntax 7 1 3 Manual String Formatting Here s the same table of squares and cubes formatted manually for x in range 1 11 print repr x rjust 2 repr x x rjust 3 end Note use of end on previous line print repr x x x rjust 4 1 1 1 2 4 8 3 9 27 4 16 64 5 25 125 6 36 216 7 49 343 8 64 512 9 81 729 10 100 1000 Note that the one space between each column was added by the way print works it always adds spaces between its arguments The str rjust method of string objects right justifies a string in a field of a given width by padding it with spaces on the left There are similar methods str ljust and str center These methods do not write anything they just return a new string If the input string is too long they don t truncate it but return it unchanged this will mess up your column lay out but that s usually better than the alternative which would be lying about a value If you really want truncation you can always add a slice operation as in x ljust n n There is another method str zfill which pads a numeric string on the left with zeros It understands about plus and minus signs 12 zfill 5 00012 3 14 zfill 7 003 14 3 14159265359 zfill 5 3 14159265359 7 1 4 Old string formatting The operator modulo can also be used for string formatting Given string values instances of in string are replaced with zero or more elements of values This operation is commonly known as string interpolation For example import math print The value of pi is approximately 5 3f math pi The value of pi is approximately 3 142 More information can be found in the printf style String Formatting section 7 2 Reading and Writing Files open returns a file object and is most commonly used with two positional arguments and one keyword argument open filename mode encodi,en
357,ng None f open workfile w encoding utf 8 The first argument is a string containing the filename The second argument is another string containing a few characters describing the way in which the file will be used mode can be r when the file will only be read w for only writing an existing file with the same name will be erased and a opens the file for appending any data written to the file is automatically added to the end r opens the file for both reading and writing The mode argument is optional r will be assumed if it s omitted Normally files are opened in text mode that means you read and write strings from and to the file which are encoded in a specific encoding If encoding is not specified the default is platform dependent see open Because UTF 8 is the modern de facto standard encoding utf 8 is recommended unless you know that you need to use a different encoding Appending a b to the mode opens the file in binary mode Binary mode data is read and written as bytes objects You can not specify encoding when opening file in binary mode In text mode the default when reading is to convert platform specific line endings n on Unix r n on Windows to just n When writing in text mode the default is to convert occurrences of n back to platform specific line endings This behind the scenes modification to file data is fine for text files but will corrupt binary data like that in JPEG or EXE files Be very careful to use binary mode when reading and writing such files It is good practice to use the with keyword when dealing with file objects The advantage is that the file is properly closed after its suite finishes even if an exception is raised at some point Using with is also much shorter than writing equivalent try finally blocks with open workfile encoding utf 8 as f read_data f read We can check that the file has been automatically closed f closed True If you re not using the with keyword then you should call f close to close the file and immediately free up any system resources used by it Warning Calling f write without using the with keyword or calling f close might result in the arguments of f write not being completely written to the disk even if the program exits successfully After a file object is closed either by a with statement or by calling f close attempts to use the file object will automatically fail f close f read Traceback most recent call last File stdin line 1 in module ValueError I O operation on closed file 7 2 1 Methods of File Objects The rest of the examples in this section will assume that a file object called f has already been created To read a file s contents call f read size which reads some quantity of data and returns it as a string in text mode or bytes object in binary mode size is an optional numeric argument When size is omitted or negative the entire contents of the file will be read and returned it s your problem if the file is twice as large as your machine s memory Otherwise at most size characters in text mode or size bytes in binary mode are read and returned If the end of the file has been reached f read will return an empty string f read This is the entire file n f read f readline reads a single line from the file a newline character n is left at the end of the string and is only omitted on the last line of the file if the file doesn t end in a newline This makes the return value unambiguous if f readline returns an empty string the end of the file has been reached while a blank line is represented by n a string containing only a single newline f readline This is the first line of the file n f readline Second line of the file n f readline For reading lines from a file you can loop over the file object This is memory efficient fast and leads to simple code for line in f print line end This is the first line of the file Second line of the file If you want to read all the lines of a file in a list you can also use list f or f readlines f write string writes the contents of string to the file returning the number of characters written f write This is a test n 15 Other types of objects need ,en
358,to be converted either to a string in text mode or a bytes object in binary mode before writing them value the answer 42 s str value convert the tuple to string f write s 18 f tell returns an integer giving the file object s current position in the file represented as number of bytes from the beginning of the file when in binary mode and an opaque number when in text mode To change the file object s position use f seek offset whence The position is computed from adding offset to a reference point the reference point is selected by the whence argument A whence value of 0 measures from the beginning of the file 1 uses the current file position and 2 uses the end of the file as the reference point whence can be omitted and defaults to 0 using the beginning of the file as the reference point f open workfile rb f write b 0123456789abcdef 16 f seek 5 Go to the 6th byte in the file 5 f read 1 b 5 f seek 3 2 Go to the 3rd byte before the end 13 f read 1 b d In text files those opened without a b in the mode string only seeks relative to the beginning of the file are allowed the exception being seeking to the very file end with seek 0 2 and the only valid offset values are those returned from the f tell or zero Any other offset value produces undefined behaviour File objects have some additional methods such as isatty and truncate which are less frequently used consult the Library Reference for a complete guide to file objects 7 2 2 Saving structured data with json Strings can easily be written to and read from a file Numbers take a bit more effort since the read method only returns strings which will have to be passed to a function like int which takes a string like 123 and returns its numeric value 123 When you want to save more complex data types like nested lists and dictionaries parsing and serializing by hand becomes complicated Rather than having users constantly writing and debugging code to save complicated data types to files Python allows you to use the popular data interchange format called JSON JavaScript Object Notation The standard module called json can take Python data hierarchies and convert them to string representations this process is called serializing Reconstructing the data from the string representation is called deserializing Between serializing and deserializing the string representing the object may have been stored in a file or data or sent over a network connection to some distant machine Note The JSON format is commonly used by modern applications to allow for data exchange Many programmers are already familiar with it which makes it a good choice for interoperability If you have an object x you can view its JSON string representation with a simple line of code import json x 1 simple list json dumps x 1 simple list Another variant of the dumps function called dump simply serializes the object to a text file So if f is a text file object opened for writing we can do this json dump x f To decode the object again if f is a binary file or text file object which has been opened for reading x json load f Note JSON files must be encoded in UTF 8 Use encoding utf 8 when opening JSON file as a text file for both of reading and writing This simple serialization technique can handle lists and dictionaries but serializing arbitrary class instances in JSON requires a bit of extra effort The reference for the json module contains an explanation of this See also pickle the pickle module Contrary to JSON pickle is a protocol which allows the serialization of arbitrarily complex Python objects As such it is specific to Python and cannot be used to communicate with applications written in other languages It is also insecure by default deserializing pickle data coming from an untrusted source can execute arbitrary code if the data was crafted by a skilled attacker,en
359,getpass Portable password input Source code Lib getpass py Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information The getpass module provides two functions getpass getpass prompt Password stream None Prompt the user for a password without echoing The user is prompted using the string prompt which defaults to Password On Unix the prompt is written to the file like object stream using the replace error handler if needed stream defaults to the controlling terminal dev tty or if that is unavailable to sys stderr this argument is ignored on Windows If echo free input is unavailable getpass falls back to printing a warning message to stream and reading from sys stdin and issuing a GetPassWarning Note If you call getpass from within IDLE the input may be done in the terminal you launched IDLE from rather than the idle window itself exception getpass GetPassWarning A UserWarning subclass issued when password input may be echoed getpass getuser Return the login name of the user This function checks the environment variables LOGNAME USER LNAME and USERNAME in order and returns the value of the first one which is set to a non empty string If none are set the login name from the password database is returned on systems which support the pwd module otherwise an exception is raised In general this function should be preferred over os getlogin,en
360,HOWTO Fetch Internet Resources Using The urllib Package Author Michael Foord Introduction Related Articles You may also find useful the following article on fetching web resources with Python Basic Authentication A tutorial on Basic Authentication with examples in Python urllib request is a Python module for fetching URLs Uniform Resource Locators It offers a very simple interface in the form of the urlopen function This is capable of fetching URLs using a variety of different protocols It also offers a slightly more complex interface for handling common situations like basic authentication cookies proxies and so on These are provided by objects called handlers and openers urllib request supports fetching URLs for many URL schemes identified by the string before the in URL for example ftp is the URL scheme of ftp python org using their associated network protocols e g FTP HTTP This tutorial focuses on the most common case HTTP For straightforward situations urlopen is very easy to use But as soon as you encounter errors or non trivial cases when opening HTTP URLs you will need some understanding of the HyperText Transfer Protocol The most comprehensive and authoritative reference to HTTP is RFC 2616 This is a technical document and not intended to be easy to read This HOWTO aims to illustrate using urllib with enough detail about HTTP to help you through It is not intended to replace the urllib request docs but is supplementary to them Fetching URLs The simplest way to use urllib request is as follows import urllib request with urllib request urlopen http python org as response html response read If you wish to retrieve a resource via URL and store it in a temporary location you can do so via the shutil copyfileobj and tempfile NamedTemporaryFile functions import shutil import tempfile import urllib request with urllib request urlopen http python org as response with tempfile NamedTemporaryFile delete False as tmp_file shutil copyfileobj response tmp_file with open tmp_file name as html pass Many uses of urllib will be that simple note that instead of an http URL we could have used a URL starting with ftp file etc However it s the purpose of this tutorial to explain the more complicated cases concentrating on HTTP HTTP is based on requests and responses the client makes requests and servers send responses urllib request mirrors this with a Request object which represents the HTTP request you are making In its simplest form you create a Request object that specifies the URL you want to fetch Calling urlopen with this Request object returns a response object for the URL requested This response is a file like object which means you can for example call read on the response import urllib request req urllib request Request http python org with urllib request urlopen req as response the_page response read Note that urllib request makes use of the same Request interface to handle all URL schemes For example you can make an FTP request like so req urllib request Request ftp example com In the case of HTTP there are two extra things that Request objects allow you to do First you can pass data to be sent to the server Second you can pass extra information metadata about the data or about the request itself to the server this information is sent as HTTP headers Let s look at each of these in turn Data Sometimes you want to send data to a URL often the URL will refer to a CGI Common Gateway Interface script or other web application With HTTP this is often done using what s known as a POST request This is often what your browser does when you submit a HTML form that you filled in on the web Not all POSTs have to come from forms you can use a POST to transmit arbitrary data to your own application In the common case of HTML forms the data needs to be encoded in a standard way and then passed to the Request object as the data argument The encoding is done using a function from the urllib parse library import urllib parse import urllib request url http www someserver com cgi bin register cgi values name Michael Foord location Northampto,en
361,n language Python data urllib parse urlencode values data data encode ascii data should be bytes req urllib request Request url data with urllib request urlopen req as response the_page response read Note that other encodings are sometimes required e g for file upload from HTML forms see HTML Specification Form Submission for more details If you do not pass the data argument urllib uses a GET request One way in which GET and POST requests differ is that POST requests often have side effects they change the state of the system in some way for example by placing an order with the website for a hundredweight of tinned spam to be delivered to your door Though the HTTP standard makes it clear that POSTs are intended to always cause side effects and GET requests never to cause side effects nothing prevents a GET request from having side effects nor a POST requests from having no side effects Data can also be passed in an HTTP GET request by encoding it in the URL itself This is done as follows import urllib request import urllib parse data data name Somebody Here data location Northampton data language Python url_values urllib parse urlencode data print url_values The order may differ from below name Somebody Here language Python location Northampton url http www example com example cgi full_url url url_values data urllib request urlopen full_url Notice that the full URL is created by adding a to the URL followed by the encoded values Headers We ll discuss here one particular HTTP header to illustrate how to add headers to your HTTP request Some websites 1 dislike being browsed by programs or send different versions to different browsers 2 By default urllib identifies itself as Python urllib x y where x and y are the major and minor version numbers of the Python release e g Python urllib 2 5 which may confuse the site or just plain not work The way a browser identifies itself is through the User Agent header 3 When you create a Request object you can pass a dictionary of headers in The following example makes the same request as above but identifies itself as a version of Internet Explorer 4 import urllib parse import urllib request url http www someserver com cgi bin register cgi user_agent Mozilla 5 0 Windows NT 6 1 Win64 x64 values name Michael Foord location Northampton language Python headers User Agent user_agent data urllib parse urlencode values data data encode ascii req urllib request Request url data headers with urllib request urlopen req as response the_page response read The response also has two useful methods See the section on info and geturl which comes after we have a look at what happens when things go wrong Handling Exceptions urlopen raises URLError when it cannot handle a response though as usual with Python APIs built in exceptions such as ValueError TypeError etc may also be raised HTTPError is the subclass of URLError raised in the specific case of HTTP URLs The exception classes are exported from the urllib error module URLError Often URLError is raised because there is no network connection no route to the specified server or the specified server doesn t exist In this case the exception raised will have a reason attribute which is a tuple containing an error code and a text error message e g req urllib request Request http www pretend_server org try urllib request urlopen req except urllib error URLError as e print e reason 4 getaddrinfo failed HTTPError Every HTTP response from the server contains a numeric status code Sometimes the status code indicates that the server is unable to fulfil the request The default handlers will handle some of these responses for you for example if the response is a redirection that requests the client fetch the document from a different URL urllib will handle that for you For those it can t handle urlopen will raise an HTTPError Typical errors include 404 page not found 403 request forbidden and 401 authentication required See section 10 of RFC 2616 for a reference on all the HTTP error codes The HTTPError instance raised will have an integer code attribute which co,en
362,rresponds to the error sent by the server Error Codes Because the default handlers handle redirects codes in the 300 range and codes in the 100 299 range indicate success you will usually only see error codes in the 400 599 range http server BaseHTTPRequestHandler responses is a useful dictionary of response codes in that shows all the response codes used by RFC 2616 The dictionary is reproduced here for convenience Table mapping response codes to messages entries have the form code shortmessage longmessage responses 100 Continue Request received please continue 101 Switching Protocols Switching to new protocol obey Upgrade header 200 OK Request fulfilled document follows 201 Created Document created URL follows 202 Accepted Request accepted processing continues off line 203 Non Authoritative Information Request fulfilled from cache 204 No Content Request fulfilled nothing follows 205 Reset Content Clear input form for further input 206 Partial Content Partial content follows 300 Multiple Choices Object has several resources see URI list 301 Moved Permanently Object moved permanently see URI list 302 Found Object moved temporarily see URI list 303 See Other Object moved see Method and URL list 304 Not Modified Document has not changed since given time 305 Use Proxy You must use proxy specified in Location to access this resource 307 Temporary Redirect Object moved temporarily see URI list 400 Bad Request Bad request syntax or unsupported method 401 Unauthorized No permission see authorization schemes 402 Payment Required No payment see charging schemes 403 Forbidden Request forbidden authorization will not help 404 Not Found Nothing matches the given URI 405 Method Not Allowed Specified method is invalid for this server 406 Not Acceptable URI not available in preferred format 407 Proxy Authentication Required You must authenticate with this proxy before proceeding 408 Request Timeout Request timed out try again later 409 Conflict Request conflict 410 Gone URI no longer exists and has been permanently removed 411 Length Required Client must specify Content Length 412 Precondition Failed Precondition in headers is false 413 Request Entity Too Large Entity is too large 414 Request URI Too Long URI is too long 415 Unsupported Media Type Entity body in unsupported format 416 Requested Range Not Satisfiable Cannot satisfy request range 417 Expectation Failed Expect condition could not be satisfied 500 Internal Server Error Server got itself in trouble 501 Not Implemented Server does not support this operation 502 Bad Gateway Invalid responses from another server proxy 503 Service Unavailable The server cannot process the request due to a high load 504 Gateway Timeout The gateway server did not receive a timely response 505 HTTP Version Not Supported Cannot fulfill request When an error is raised the server responds by returning an HTTP error code and an error page You can use the HTTPError instance as a response on the page returned This means that as well as the code attribute it also has read geturl and info methods as returned by the urllib response module req urllib request Request http www python org fish html try urllib request urlopen req except urllib error HTTPError as e print e code print e read 404 b DOCTYPE html PUBLIC W3C DTD XHTML 1 0 Transitional EN http www w3 org TR xhtml1 DTD xhtml1 transitional dtd n n n html title Page Not Found title n Wrapping it Up So if you want to be prepared for HTTPError or URLError there are two basic approaches I prefer the second approach Number 1 from urllib request import Request urlopen from urllib error import URLError HTTPError req Request someurl try response urlopen req except HTTPError as e print The server couldn t fulfill the request print Error code e code except URLError as e print We failed to reach a server print Reason e reason else everything is fine Note The except HTTPError must come first otherwise except URLError will also catch an HTTPError Number 2 from urllib request import Request urlopen from urllib error import URLError req Request someurl try response ur,en
363,lopen req except URLError as e if hasattr e reason print We failed to reach a server print Reason e reason elif hasattr e code print The server couldn t fulfill the request print Error code e code else everything is fine info and geturl The response returned by urlopen or the HTTPError instance has two useful methods info and geturl and is defined in the module urllib response geturl this returns the real URL of the page fetched This is useful because urlopen or the opener object used may have followed a redirect The URL of the page fetched may not be the same as the URL requested info this returns a dictionary like object that describes the page fetched particularly the headers sent by the server It is currently an http client HTTPMessage instance Typical headers include Content length Content type and so on See the Quick Reference to HTTP Headers for a useful listing of HTTP headers with brief explanations of their meaning and use Openers and Handlers When you fetch a URL you use an opener an instance of the perhaps confusingly named urllib request OpenerDirector Normally we have been using the default opener via urlopen but you can create custom openers Openers use handlers All the heavy lifting is done by the handlers Each handler knows how to open URLs for a particular URL scheme http ftp etc or how to handle an aspect of URL opening for example HTTP redirections or HTTP cookies You will want to create openers if you want to fetch URLs with specific handlers installed for example to get an opener that handles cookies or to get an opener that does not handle redirections To create an opener instantiate an OpenerDirector and then call add_handler some_handler_instance repeatedly Alternatively you can use build_opener which is a convenience function for creating opener objects with a single function call build_opener adds several handlers by default but provides a quick way to add more and or override the default handlers Other sorts of handlers you might want to can handle proxies authentication and other common but slightly specialised situations install_opener can be used to make an opener object the global default opener This means that calls to urlopen will use the opener you have installed Opener objects have an open method which can be called directly to fetch urls in the same way as the urlopen function there s no need to call install_opener except as a convenience Basic Authentication To illustrate creating and installing a handler we will use the HTTPBasicAuthHandler For a more detailed discussion of this subject including an explanation of how Basic Authentication works see the Basic Authentication Tutorial When authentication is required the server sends a header as well as the 401 error code requesting authentication This specifies the authentication scheme and a realm The header looks like WWW Authenticate SCHEME realm REALM e g WWW Authenticate Basic realm cPanel Users The client should then retry the request with the appropriate name and password for the realm included as a header in the request This is basic authentication In order to simplify this process we can create an instance of HTTPBasicAuthHandler and an opener to use this handler The HTTPBasicAuthHandler uses an object called a password manager to handle the mapping of URLs and realms to passwords and usernames If you know what the realm is from the authentication header sent by the server then you can use a HTTPPasswordMgr Frequently one doesn t care what the realm is In that case it is convenient to use HTTPPasswordMgrWithDefaultRealm This allows you to specify a default username and password for a URL This will be supplied in the absence of you providing an alternative combination for a specific realm We indicate this by providing None as the realm argument to the add_password method The top level URL is the first URL that requires authentication URLs deeper than the URL you pass to add_password will also match create a password manager password_mgr urllib request HTTPPasswordMgrWithDefaultRealm Add the username and password If we knew the ,en
364,realm we could use it instead of None top_level_url http example com foo password_mgr add_password None top_level_url username password handler urllib request HTTPBasicAuthHandler password_mgr create opener OpenerDirector instance opener urllib request build_opener handler use the opener to fetch a URL opener open a_url Install the opener Now all calls to urllib request urlopen use our opener urllib request install_opener opener Note In the above example we only supplied our HTTPBasicAuthHandler to build_opener By default openers have the handlers for normal situations ProxyHandler if a proxy setting such as an http_proxy environment variable is set UnknownHandler HTTPHandler HTTPDefaultErrorHandler HTTPRedirectHandler FTPHandler FileHandler DataHandler HTTPErrorProcessor top_level_url is in fact either a full URL including the http scheme component and the hostname and optionally the port number e g http example com or an authority i e the hostname optionally including the port number e g example com or example com 8080 the latter example includes a port number The authority if present must NOT contain the userinfo component for example joe password example com is not correct Proxies urllib will auto detect your proxy settings and use those This is through the ProxyHandler which is part of the normal handler chain when a proxy setting is detected Normally that s a good thing but there are occasions when it may not be helpful 5 One way to do this is to setup our own ProxyHandler with no proxies defined This is done using similar steps to setting up a Basic Authentication handler proxy_support urllib request ProxyHandler opener urllib request build_opener proxy_support urllib request install_opener opener Note Currently urllib request does not support fetching of https locations through a proxy However this can be enabled by extending urllib request as shown in the recipe 6 Note HTTP_PROXY will be ignored if a variable REQUEST_METHOD is set see the documentation on getproxies Sockets and Layers The Python support for fetching resources from the web is layered urllib uses the http client library which in turn uses the socket library As of Python 2 3 you can specify how long a socket should wait for a response before timing out This can be useful in applications which have to fetch web pages By default the socket module has no timeout and can hang Currently the socket timeout is not exposed at the http client or urllib request levels However you can set the default timeout globally for all sockets using import socket import urllib request timeout in seconds timeout 10 socket setdefaulttimeout timeout this call to urllib request urlopen now uses the default timeout we have set in the socket module req urllib request Request http www voidspace org uk response urllib request urlopen req Footnotes This document was reviewed and revised by John Lee 1 Google for example 2 Browser sniffing is a very bad practice for website design building sites using web standards is much more sensible Unfortunately a lot of sites still send different versions to different browsers 3 The user agent for MSIE 6 is Mozilla 4 0 compatible MSIE 6 0 Windows NT 5 1 SV1 NET CLR 1 1 4322 4 For details of more HTTP request headers see Quick Reference to HTTP Headers 5 In my case I have to use a proxy to access the internet at work If you attempt to fetch localhost URLs through this proxy it blocks them IE is set to use the proxy which urllib picks up on In order to test scripts with a localhost server I have to prevent urllib from using the proxy 6 urllib opener for SSL proxy CONNECT method ASPN Cookbook Recipe,en
365,concurrent futures Launching parallel tasks New in version 3 2 Source code Lib concurrent futures thread py and Lib concurrent futures process py The concurrent futures module provides a high level interface for asynchronously executing callables The asynchronous execution can be performed with threads using ThreadPoolExecutor or separate processes using ProcessPoolExecutor Both implement the same interface which is defined by the abstract Executor class Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information Executor Objects class concurrent futures Executor An abstract class that provides methods to execute calls asynchronously It should not be used directly but through its concrete subclasses submit fn args kwargs Schedules the callable fn to be executed as fn args kwargs and returns a Future object representing the execution of the callable with ThreadPoolExecutor max_workers 1 as executor future executor submit pow 323 1235 print future result map fn iterables timeout None chunksize 1 Similar to map fn iterables except the iterables are collected immediately rather than lazily fn is executed asynchronously and several calls to fn may be made concurrently The returned iterator raises a TimeoutError if __next__ is called and the result isn t available after timeout seconds from the original call to Executor map timeout can be an int or a float If timeout is not specified or None there is no limit to the wait time If a fn call raises an exception then that exception will be raised when its value is retrieved from the iterator When using ProcessPoolExecutor this method chops iterables into a number of chunks which it submits to the pool as separate tasks The approximate size of these chunks can be specified by setting chunksize to a positive integer For very long iterables using a large value for chunksize can significantly improve performance compared to the default size of 1 With ThreadPoolExecutor chunksize has no effect Changed in version 3 5 Added the chunksize argument shutdown wait True cancel_futures False Signal the executor that it should free any resources that it is using when the currently pending futures are done executing Calls to Executor submit and Executor map made after shutdown will raise RuntimeError If wait is True then this method will not return until all the pending futures are done executing and the resources associated with the executor have been freed If wait is False then this method will return immediately and the resources associated with the executor will be freed when all pending futures are done executing Regardless of the value of wait the entire Python program will not exit until all pending futures are done executing If cancel_futures is True this method will cancel all pending futures that the executor has not started running Any futures that are completed or running won t be cancelled regardless of the value of cancel_futures If both cancel_futures and wait are True all futures that the executor has started running will be completed prior to this method returning The remaining futures are cancelled You can avoid having to call this method explicitly if you use the with statement which will shutdown the Executor waiting as if Executor shutdown were called with wait set to True import shutil with ThreadPoolExecutor max_workers 4 as e e submit shutil copy src1 txt dest1 txt e submit shutil copy src2 txt dest2 txt e submit shutil copy src3 txt dest3 txt e submit shutil copy src4 txt dest4 txt Changed in version 3 9 Added cancel_futures ThreadPoolExecutor ThreadPoolExecutor is an Executor subclass that uses a pool of threads to execute calls asynchronously Deadlocks can occur when the callable associated with a Future waits on the results of another Future For example import time def wait_on_b time sleep 5 print b result b will never complete because it is waiting on a return 5 def wait_on_a time sleep 5 print a result a will never complete because it is w,en
366,aiting on b return 6 executor ThreadPoolExecutor max_workers 2 a executor submit wait_on_b b executor submit wait_on_a And def wait_on_future f executor submit pow 5 2 This will never complete because there is only one worker thread and it is executing this function print f result executor ThreadPoolExecutor max_workers 1 executor submit wait_on_future class concurrent futures ThreadPoolExecutor max_workers None thread_name_prefix initializer None initargs An Executor subclass that uses a pool of at most max_workers threads to execute calls asynchronously All threads enqueued to ThreadPoolExecutor will be joined before the interpreter can exit Note that the exit handler which does this is executed before any exit handlers added using atexit This means exceptions in the main thread must be caught and handled in order to signal threads to exit gracefully For this reason it is recommended that ThreadPoolExecutor not be used for long running tasks initializer is an optional callable that is called at the start of each worker thread initargs is a tuple of arguments passed to the initializer Should initializer raise an exception all currently pending jobs will raise a BrokenThreadPool as well as any attempt to submit more jobs to the pool Changed in version 3 5 If max_workers is None or not given it will default to the number of processors on the machine multiplied by 5 assuming that ThreadPoolExecutor is often used to overlap I O instead of CPU work and the number of workers should be higher than the number of workers for ProcessPoolExecutor Changed in version 3 6 Added the thread_name_prefix parameter to allow users to control the threading Thread names for worker threads created by the pool for easier debugging Changed in version 3 7 Added the initializer and initargs arguments Changed in version 3 8 Default value of max_workers is changed to min 32 os cpu_count 4 This default value preserves at least 5 workers for I O bound tasks It utilizes at most 32 CPU cores for CPU bound tasks which release the GIL And it avoids using very large resources implicitly on many core machines ThreadPoolExecutor now reuses idle worker threads before starting max_workers worker threads too ThreadPoolExecutor Example import concurrent futures import urllib request URLS http www foxnews com http www cnn com http europe wsj com http www bbc co uk http nonexistant subdomain python org Retrieve a single page and report the URL and contents def load_url url timeout with urllib request urlopen url timeout timeout as conn return conn read We can use a with statement to ensure threads are cleaned up promptly with concurrent futures ThreadPoolExecutor max_workers 5 as executor Start the load operations and mark each future with its URL future_to_url executor submit load_url url 60 url for url in URLS for future in concurrent futures as_completed future_to_url url future_to_url future try data future result except Exception as exc print r generated an exception s url exc else print r page is d bytes url len data ProcessPoolExecutor The ProcessPoolExecutor class is an Executor subclass that uses a pool of processes to execute calls asynchronously ProcessPoolExecutor uses the multiprocessing module which allows it to side step the Global Interpreter Lock but also means that only picklable objects can be executed and returned The __main__ module must be importable by worker subprocesses This means that ProcessPoolExecutor will not work in the interactive interpreter Calling Executor or Future methods from a callable submitted to a ProcessPoolExecutor will result in deadlock class concurrent futures ProcessPoolExecutor max_workers None mp_context None initializer None initargs max_tasks_per_child None An Executor subclass that executes calls asynchronously using a pool of at most max_workers processes If max_workers is None or not given it will default to the number of processors on the machine If max_workers is less than or equal to 0 then a ValueError will be raised On Windows max_workers must be less than or equal to 61 If it is not then ValueError will,en
367, be raised If max_workers is None then the default chosen will be at most 61 even if more processors are available mp_context can be a multiprocessing context or None It will be used to launch the workers If mp_context is None or not given the default multiprocessing context is used See Contexts and start methods initializer is an optional callable that is called at the start of each worker process initargs is a tuple of arguments passed to the initializer Should initializer raise an exception all currently pending jobs will raise a BrokenProcessPool as well as any attempt to submit more jobs to the pool max_tasks_per_child is an optional argument that specifies the maximum number of tasks a single process can execute before it will exit and be replaced with a fresh worker process By default max_tasks_per_child is None which means worker processes will live as long as the pool When a max is specified the spawn multiprocessing start method will be used by default in absence of a mp_context parameter This feature is incompatible with the fork start method Changed in version 3 3 When one of the worker processes terminates abruptly a BrokenProcessPool error is now raised Previously behaviour was undefined but operations on the executor or its futures would often freeze or deadlock Changed in version 3 7 The mp_context argument was added to allow users to control the start_method for worker processes created by the pool Added the initializer and initargs arguments Note The default multiprocessing start method see Contexts and start methods will change away from fork in Python 3 14 Code that requires fork be used for their ProcessPoolExecutor should explicitly specify that by passing a mp_context multiprocessing get_context fork parameter Changed in version 3 11 The max_tasks_per_child argument was added to allow users to control the lifetime of workers in the pool Changed in version 3 12 On POSIX systems if your application has multiple threads and the multiprocessing context uses the fork start method The os fork function called internally to spawn workers may raise a DeprecationWarning Pass a mp_context configured to use a different start method See the os fork documentation for further explanation ProcessPoolExecutor Example import concurrent futures import math PRIMES 112272535095293 112582705942171 112272535095293 115280095190773 115797848077099 1099726899285419 def is_prime n if n 2 return False if n 2 return True if n 2 0 return False sqrt_n int math floor math sqrt n for i in range 3 sqrt_n 1 2 if n i 0 return False return True def main with concurrent futures ProcessPoolExecutor as executor for number prime in zip PRIMES executor map is_prime PRIMES print d is prime s number prime if __name__ __main__ main Future Objects The Future class encapsulates the asynchronous execution of a callable Future instances are created by Executor submit class concurrent futures Future Encapsulates the asynchronous execution of a callable Future instances are created by Executor submit and should not be created directly except for testing cancel Attempt to cancel the call If the call is currently being executed or finished running and cannot be cancelled then the method will return False otherwise the call will be cancelled and the method will return True cancelled Return True if the call was successfully cancelled running Return True if the call is currently being executed and cannot be cancelled done Return True if the call was successfully cancelled or finished running result timeout None Return the value returned by the call If the call hasn t yet completed then this method will wait up to timeout seconds If the call hasn t completed in timeout seconds then a TimeoutError will be raised timeout can be an int or float If timeout is not specified or None there is no limit to the wait time If the future is cancelled before completing then CancelledError will be raised If the call raised an exception this method will raise the same exception exception timeout None Return the exception raised by the call If the call hasn t yet complet,en
368,ed then this method will wait up to timeout seconds If the call hasn t completed in timeout seconds then a TimeoutError will be raised timeout can be an int or float If timeout is not specified or None there is no limit to the wait time If the future is cancelled before completing then CancelledError will be raised If the call completed without raising None is returned add_done_callback fn Attaches the callable fn to the future fn will be called with the future as its only argument when the future is cancelled or finishes running Added callables are called in the order that they were added and are always called in a thread belonging to the process that added them If the callable raises an Exception subclass it will be logged and ignored If the callable raises a BaseException subclass the behavior is undefined If the future has already completed or been cancelled fn will be called immediately The following Future methods are meant for use in unit tests and Executor implementations set_running_or_notify_cancel This method should only be called by Executor implementations before executing the work associated with the Future and by unit tests If the method returns False then the Future was cancelled i e Future cancel was called and returned True Any threads waiting on the Future completing i e through as_completed or wait will be woken up If the method returns True then the Future was not cancelled and has been put in the running state i e calls to Future running will return True This method can only be called once and cannot be called after Future set_result or Future set_exception have been called set_result result Sets the result of the work associated with the Future to result This method should only be used by Executor implementations and unit tests Changed in version 3 8 This method raises concurrent futures InvalidStateError if the Future is already done set_exception exception Sets the result of the work associated with the Future to the Exception exception This method should only be used by Executor implementations and unit tests Changed in version 3 8 This method raises concurrent futures InvalidStateError if the Future is already done Module Functions concurrent futures wait fs timeout None return_when ALL_COMPLETED Wait for the Future instances possibly created by different Executor instances given by fs to complete Duplicate futures given to fs are removed and will be returned only once Returns a named 2 tuple of sets The first set named done contains the futures that completed finished or cancelled futures before the wait completed The second set named not_done contains the futures that did not complete pending or running futures timeout can be used to control the maximum number of seconds to wait before returning timeout can be an int or float If timeout is not specified or None there is no limit to the wait time return_when indicates when this function should return It must be one of the following constants Constant Description concurrent futures FIRST_COMPLETED The function will return when any future finishes or is cancelled concurrent futures FIRST_EXCEPTION The function will return when any future finishes by raising an exception If no future raises an exception then it is equivalent to ALL_COMPLETED concurrent futures ALL_COMPLETED The function will return when all futures finish or are cancelled concurrent futures as_completed fs timeout None Returns an iterator over the Future instances possibly created by different Executor instances given by fs that yields futures as they complete finished or cancelled futures Any futures given by fs that are duplicated will be returned once Any futures that completed before as_completed is called will be yielded first The returned iterator raises a TimeoutError if __next__ is called and the result isn t available after timeout seconds from the original call to as_completed timeout can be an int or float If timeout is not specified or None there is no limit to the wait time See also PEP 3148 futures execute computations asynchronously The proposal which described thi,en
369,s feature for inclusion in the Python standard library Exception classes exception concurrent futures CancelledError Raised when a future is cancelled exception concurrent futures TimeoutError A deprecated alias of TimeoutError raised when a future operation exceeds the given timeout Changed in version 3 11 This class was made an alias of TimeoutError exception concurrent futures BrokenExecutor Derived from RuntimeError this exception class is raised when an executor is broken for some reason and cannot be used to submit or execute new tasks New in version 3 7 exception concurrent futures InvalidStateError Raised when an operation is performed on a future that is not allowed in the current state New in version 3 8 exception concurrent futures thread BrokenThreadPool Derived from BrokenExecutor this exception class is raised when one of the workers of a ThreadPoolExecutor has failed initializing New in version 3 7 exception concurrent futures process BrokenProcessPool Derived from BrokenExecutor formerly RuntimeError this exception class is raised when one of the workers of a ProcessPoolExecutor has terminated in a non clean fashion for example if it was killed from the outside New in version 3 3,en
370,Context Variables Objects New in version 3 7 Changed in version 3 7 1 Note In Python 3 7 1 the signatures of all context variables C APIs were changed to use PyObject pointers instead of PyContext PyContextVar and PyContextToken e g in 3 7 0 PyContext PyContext_New void in 3 7 1 PyObject PyContext_New void See bpo 34762 for more details This section details the public C API for the contextvars module type PyContext The C structure used to represent a contextvars Context object type PyContextVar The C structure used to represent a contextvars ContextVar object type PyContextToken The C structure used to represent a contextvars Token object PyTypeObject PyContext_Type The type object representing the context type PyTypeObject PyContextVar_Type The type object representing the context variable type PyTypeObject PyContextToken_Type The type object representing the context variable token type Type check macros int PyContext_CheckExact PyObject o Return true if o is of type PyContext_Type o must not be NULL This function always succeeds int PyContextVar_CheckExact PyObject o Return true if o is of type PyContextVar_Type o must not be NULL This function always succeeds int PyContextToken_CheckExact PyObject o Return true if o is of type PyContextToken_Type o must not be NULL This function always succeeds Context object management functions PyObject PyContext_New void Return value New reference Create a new empty context object Returns NULL if an error has occurred PyObject PyContext_Copy PyObject ctx Return value New reference Create a shallow copy of the passed ctx context object Returns NULL if an error has occurred PyObject PyContext_CopyCurrent void Return value New reference Create a shallow copy of the current thread context Returns NULL if an error has occurred int PyContext_Enter PyObject ctx Set ctx as the current context for the current thread Returns 0 on success and 1 on error int PyContext_Exit PyObject ctx Deactivate the ctx context and restore the previous context as the current context for the current thread Returns 0 on success and 1 on error Context variable functions PyObject PyContextVar_New const char name PyObject def Return value New reference Create a new ContextVar object The name parameter is used for introspection and debug purposes The def parameter specifies a default value for the context variable or NULL for no default If an error has occurred this function returns NULL int PyContextVar_Get PyObject var PyObject default_value PyObject value Get the value of a context variable Returns 1 if an error has occurred during lookup and 0 if no error occurred whether or not a value was found If the context variable was found value will be a pointer to it If the context variable was not found value will point to default_value if not NULL the default value of var if not NULL NULL Except for NULL the function returns a new reference PyObject PyContextVar_Set PyObject var PyObject value Return value New reference Set the value of var to value in the current context Returns a new token object for this change or NULL if an error has occurred int PyContextVar_Reset PyObject var PyObject token Reset the state of the var context variable to that it was in before PyContextVar_Set that returned the token was called This function returns 0 on success and 1 on error,en
371,Old Buffer Protocol Deprecated since version 3 0 These functions were part of the old buffer protocol API in Python 2 In Python 3 this protocol doesn t exist anymore but the functions are still exposed to ease porting 2 x code They act as a compatibility wrapper around the new buffer protocol but they don t give you control over the lifetime of the resources acquired when a buffer is exported Therefore it is recommended that you call PyObject_GetBuffer or the y or w format codes with the PyArg_ParseTuple family of functions to get a buffer view over an object and PyBuffer_Release when the buffer view can be released int PyObject_AsCharBuffer PyObject obj const char buffer Py_ssize_t buffer_len Part of the Stable ABI Returns a pointer to a read only memory location usable as character based input The obj argument must support the single segment character buffer interface On success returns 0 sets buffer to the memory location and buffer_len to the buffer length Returns 1 and sets a TypeError on error int PyObject_AsReadBuffer PyObject obj const void buffer Py_ssize_t buffer_len Part of the Stable ABI Returns a pointer to a read only memory location containing arbitrary data The obj argument must support the single segment readable buffer interface On success returns 0 sets buffer to the memory location and buffer_len to the buffer length Returns 1 and sets a TypeError on error int PyObject_CheckReadBuffer PyObject o Part of the Stable ABI Returns 1 if o supports the single segment readable buffer interface Otherwise returns 0 This function always succeeds Note that this function tries to get and release a buffer and exceptions which occur while calling corresponding functions will get suppressed To get error reporting use PyObject_GetBuffer instead int PyObject_AsWriteBuffer PyObject obj void buffer Py_ssize_t buffer_len Part of the Stable ABI Returns a pointer to a writable memory location The obj argument must support the single segment character buffer interface On success returns 0 sets buffer to the memory location and buffer_len to the buffer length Returns 1 and sets a TypeError on error,en
372,Coroutines and Tasks This section outlines high level asyncio APIs to work with coroutines and Tasks Coroutines Awaitables Creating Tasks Task Cancellation Task Groups Sleeping Running Tasks Concurrently Eager Task Factory Shielding From Cancellation Timeouts Waiting Primitives Running in Threads Scheduling From Other Threads Introspection Task Object Coroutines Source code Lib asyncio coroutines py Coroutines declared with the async await syntax is the preferred way of writing asyncio applications For example the following snippet of code prints hello waits 1 second and then prints world import asyncio async def main print hello await asyncio sleep 1 print world asyncio run main hello world Note that simply calling a coroutine will not schedule it to be executed main coroutine object main at 0x1053bb7c8 To actually run a coroutine asyncio provides the following mechanisms The asyncio run function to run the top level entry point main function see the above example Awaiting on a coroutine The following snippet of code will print hello after waiting for 1 second and then print world after waiting for another 2 seconds import asyncio import time async def say_after delay what await asyncio sleep delay print what async def main print f started at time strftime X await say_after 1 hello await say_after 2 world print f finished at time strftime X asyncio run main Expected output started at 17 13 52 hello world finished at 17 13 55 The asyncio create_task function to run coroutines concurrently as asyncio Tasks Let s modify the above example and run two say_after coroutines concurrently async def main task1 asyncio create_task say_after 1 hello task2 asyncio create_task say_after 2 world print f started at time strftime X Wait until both tasks are completed should take around 2 seconds await task1 await task2 print f finished at time strftime X Note that expected output now shows that the snippet runs 1 second faster than before started at 17 14 32 hello world finished at 17 14 34 The asyncio TaskGroup class provides a more modern alternative to create_task Using this API the last example becomes async def main async with asyncio TaskGroup as tg task1 tg create_task say_after 1 hello task2 tg create_task say_after 2 world print f started at time strftime X The await is implicit when the context manager exits print f finished at time strftime X The timing and output should be the same as for the previous version New in version 3 11 asyncio TaskGroup Awaitables We say that an object is an awaitable object if it can be used in an await expression Many asyncio APIs are designed to accept awaitables There are three main types of awaitable objects coroutines Tasks and Futures Coroutines Python coroutines are awaitables and therefore can be awaited from other coroutines import asyncio async def nested return 42 async def main Nothing happens if we just call nested A coroutine object is created but not awaited so it won t run at all nested Let s do it differently now and await it print await nested will print 42 asyncio run main Important In this documentation the term coroutine can be used for two closely related concepts a coroutine function an async def function a coroutine object an object returned by calling a coroutine function Tasks Tasks are used to schedule coroutines concurrently When a coroutine is wrapped into a Task with functions like asyncio create_task the coroutine is automatically scheduled to run soon import asyncio async def nested return 42 async def main Schedule nested to run soon concurrently with main task asyncio create_task nested task can now be used to cancel nested or can simply be awaited to wait until it is complete await task asyncio run main Futures A Future is a special low level awaitable object that represents an eventual result of an asynchronous operation When a Future object is awaited it means that the coroutine will wait until the Future is resolved in some other place Future objects in asyncio are needed to allow callback based code to be used with async await Normally there is no need to cre,en
373,ate Future objects at the application level code Future objects sometimes exposed by libraries and some asyncio APIs can be awaited async def main await function_that_returns_a_future_object this is also valid await asyncio gather function_that_returns_a_future_object some_python_coroutine A good example of a low level function that returns a Future object is loop run_in_executor Creating Tasks Source code Lib asyncio tasks py asyncio create_task coro name None context None Wrap the coro coroutine into a Task and schedule its execution Return the Task object If name is not None it is set as the name of the task using Task set_name An optional keyword only context argument allows specifying a custom contextvars Context for the coro to run in The current context copy is created when no context is provided The task is executed in the loop returned by get_running_loop RuntimeError is raised if there is no running loop in current thread Note asyncio TaskGroup create_task is a new alternative leveraging structural concurrency it allows for waiting for a group of related tasks with strong safety guarantees Important Save a reference to the result of this function to avoid a task disappearing mid execution The event loop only keeps weak references to tasks A task that isn t referenced elsewhere may get garbage collected at any time even before it s done For reliable fire and forget background tasks gather them in a collection background_tasks set for i in range 10 task asyncio create_task some_coro param i Add task to the set This creates a strong reference background_tasks add task To prevent keeping references to finished tasks forever make each task remove its own reference from the set after completion task add_done_callback background_tasks discard New in version 3 7 Changed in version 3 8 Added the name parameter Changed in version 3 11 Added the context parameter Task Cancellation Tasks can easily and safely be cancelled When a task is cancelled asyncio CancelledError will be raised in the task at the next opportunity It is recommended that coroutines use try finally blocks to robustly perform clean up logic In case asyncio CancelledError is explicitly caught it should generally be propagated when clean up is complete asyncio CancelledError directly subclasses BaseException so most code will not need to be aware of it The asyncio components that enable structured concurrency like asyncio TaskGroup and asyncio timeout are implemented using cancellation internally and might misbehave if a coroutine swallows asyncio CancelledError Similarly user code should not generally call uncancel However in cases when suppressing asyncio CancelledError is truly desired it is necessary to also call uncancel to completely remove the cancellation state Task Groups Task groups combine a task creation API with a convenient and reliable way to wait for all tasks in the group to finish class asyncio TaskGroup An asynchronous context manager holding a group of tasks Tasks can be added to the group using create_task All tasks are awaited when the context manager exits New in version 3 11 create_task coro name None context None Create a task in this task group The signature matches that of asyncio create_task Example async def main async with asyncio TaskGroup as tg task1 tg create_task some_coro task2 tg create_task another_coro print f Both tasks have completed now task1 result task2 result The async with statement will wait for all tasks in the group to finish While waiting new tasks may still be added to the group for example by passing tg into one of the coroutines and calling tg create_task in that coroutine Once the last task has finished and the async with block is exited no new tasks may be added to the group The first time any of the tasks belonging to the group fails with an exception other than asyncio CancelledError the remaining tasks in the group are cancelled No further tasks can then be added to the group At this point if the body of the async with statement is still active i e __aexit__ hasn t been called yet the task directly c,en
374,ontaining the async with statement is also cancelled The resulting asyncio CancelledError will interrupt an await but it will not bubble out of the containing async with statement Once all tasks have finished if any tasks have failed with an exception other than asyncio CancelledError those exceptions are combined in an ExceptionGroup or BaseExceptionGroup as appropriate see their documentation which is then raised Two base exceptions are treated specially If any task fails with KeyboardInterrupt or SystemExit the task group still cancels the remaining tasks and waits for them but then the initial KeyboardInterrupt or SystemExit is re raised instead of ExceptionGroup or BaseExceptionGroup If the body of the async with statement exits with an exception so __aexit__ is called with an exception set this is treated the same as if one of the tasks failed the remaining tasks are cancelled and then waited for and non cancellation exceptions are grouped into an exception group and raised The exception passed into __aexit__ unless it is asyncio CancelledError is also included in the exception group The same special case is made for KeyboardInterrupt and SystemExit as in the previous paragraph Sleeping coroutine asyncio sleep delay result None Block for delay seconds If result is provided it is returned to the caller when the coroutine completes sleep always suspends the current task allowing other tasks to run Setting the delay to 0 provides an optimized path to allow other tasks to run This can be used by long running functions to avoid blocking the event loop for the full duration of the function call Example of coroutine displaying the current date every second for 5 seconds import asyncio import datetime async def display_date loop asyncio get_running_loop end_time loop time 5 0 while True print datetime datetime now if loop time 1 0 end_time break await asyncio sleep 1 asyncio run display_date Changed in version 3 10 Removed the loop parameter Running Tasks Concurrently awaitable asyncio gather aws return_exceptions False Run awaitable objects in the aws sequence concurrently If any awaitable in aws is a coroutine it is automatically scheduled as a Task If all awaitables are completed successfully the result is an aggregate list of returned values The order of result values corresponds to the order of awaitables in aws If return_exceptions is False default the first raised exception is immediately propagated to the task that awaits on gather Other awaitables in the aws sequence won t be cancelled and will continue to run If return_exceptions is True exceptions are treated the same as successful results and aggregated in the result list If gather is cancelled all submitted awaitables that have not completed yet are also cancelled If any Task or Future from the aws sequence is cancelled it is treated as if it raised CancelledError the gather call is not cancelled in this case This is to prevent the cancellation of one submitted Task Future to cause other Tasks Futures to be cancelled Note A new alternative to create and run tasks concurrently and wait for their completion is asyncio TaskGroup TaskGroup provides stronger safety guarantees than gather for scheduling a nesting of subtasks if a task or a subtask a task scheduled by a task raises an exception TaskGroup will while gather will not cancel the remaining scheduled tasks Example import asyncio async def factorial name number f 1 for i in range 2 number 1 print f Task name Compute factorial number currently i i await asyncio sleep 1 f i print f Task name factorial number f return f async def main Schedule three calls concurrently L await asyncio gather factorial A 2 factorial B 3 factorial C 4 print L asyncio run main Expected output Task A Compute factorial 2 currently i 2 Task B Compute factorial 3 currently i 2 Task C Compute factorial 4 currently i 2 Task A factorial 2 2 Task B Compute factorial 3 currently i 3 Task C Compute factorial 4 currently i 3 Task B factorial 3 6 Task C Compute factorial 4 currently i 4 Task C factorial 4 24 2 6 24 Note If return_exceptions i,en
375,s False cancelling gather after it has been marked done won t cancel any submitted awaitables For instance gather can be marked done after propagating an exception to the caller therefore calling gather cancel after catching an exception raised by one of the awaitables from gather won t cancel any other awaitables Changed in version 3 7 If the gather itself is cancelled the cancellation is propagated regardless of return_exceptions Changed in version 3 10 Removed the loop parameter Deprecated since version 3 10 Deprecation warning is emitted if no positional arguments are provided or not all positional arguments are Future like objects and there is no running event loop Eager Task Factory asyncio eager_task_factory loop coro name None context None A task factory for eager task execution When using this factory via loop set_task_factory asyncio eager_task_factory coroutines begin execution synchronously during Task construction Tasks are only scheduled on the event loop if they block This can be a performance improvement as the overhead of loop scheduling is avoided for coroutines that complete synchronously A common example where this is beneficial is coroutines which employ caching or memoization to avoid actual I O when possible Note Immediate execution of the coroutine is a semantic change If the coroutine returns or raises the task is never scheduled to the event loop If the coroutine execution blocks the task is scheduled to the event loop This change may introduce behavior changes to existing applications For example the application s task execution order is likely to change New in version 3 12 asyncio create_eager_task_factory custom_task_constructor Create an eager task factory similar to eager_task_factory using the provided custom_task_constructor when creating a new task instead of the default Task custom_task_constructor must be a callable with the signature matching the signature of Task __init__ The callable must return a asyncio Task compatible object This function returns a callable intended to be used as a task factory of an event loop via loop set_task_factory factory New in version 3 12 Shielding From Cancellation awaitable asyncio shield aw Protect an awaitable object from being cancelled If aw is a coroutine it is automatically scheduled as a Task The statement task asyncio create_task something res await shield task is equivalent to res await something except that if the coroutine containing it is cancelled the Task running in something is not cancelled From the point of view of something the cancellation did not happen Although its caller is still cancelled so the await expression still raises a CancelledError If something is cancelled by other means i e from within itself that would also cancel shield If it is desired to completely ignore cancellation not recommended the shield function should be combined with a try except clause as follows task asyncio create_task something try res await shield task except CancelledError res None Important Save a reference to tasks passed to this function to avoid a task disappearing mid execution The event loop only keeps weak references to tasks A task that isn t referenced elsewhere may get garbage collected at any time even before it s done Changed in version 3 10 Removed the loop parameter Deprecated since version 3 10 Deprecation warning is emitted if aw is not Future like object and there is no running event loop Timeouts asyncio timeout delay Return an asynchronous context manager that can be used to limit the amount of time spent waiting on something delay can either be None or a float int number of seconds to wait If delay is None no time limit will be applied this can be useful if the delay is unknown when the context manager is created In either case the context manager can be rescheduled after creation using Timeout reschedule Example async def main async with asyncio timeout 10 await long_running_task If long_running_task takes more than 10 seconds to complete the context manager will cancel the current task and handle the resulting asyncio Cancelle,en
376,dError internally transforming it into a TimeoutError which can be caught and handled Note The asyncio timeout context manager is what transforms the asyncio CancelledError into a TimeoutError which means the TimeoutError can only be caught outside of the context manager Example of catching TimeoutError async def main try async with asyncio timeout 10 await long_running_task except TimeoutError print The long operation timed out but we ve handled it print This statement will run regardless The context manager produced by asyncio timeout can be rescheduled to a different deadline and inspected class asyncio Timeout when An asynchronous context manager for cancelling overdue coroutines when should be an absolute time at which the context should time out as measured by the event loop s clock If when is None the timeout will never trigger If when loop time the timeout will trigger on the next iteration of the event loop when float None Return the current deadline or None if the current deadline is not set reschedule when float None Reschedule the timeout expired bool Return whether the context manager has exceeded its deadline expired Example async def main try We do not know the timeout when starting so we pass None async with asyncio timeout None as cm We know the timeout now so we reschedule it new_deadline get_running_loop time 10 cm reschedule new_deadline await long_running_task except TimeoutError pass if cm expired print Looks like we haven t finished on time Timeout context managers can be safely nested New in version 3 11 asyncio timeout_at when Similar to asyncio timeout except when is the absolute time to stop waiting or None Example async def main loop get_running_loop deadline loop time 20 try async with asyncio timeout_at deadline await long_running_task except TimeoutError print The long operation timed out but we ve handled it print This statement will run regardless New in version 3 11 coroutine asyncio wait_for aw timeout Wait for the aw awaitable to complete with a timeout If aw is a coroutine it is automatically scheduled as a Task timeout can either be None or a float or int number of seconds to wait for If timeout is None block until the future completes If a timeout occurs it cancels the task and raises TimeoutError To avoid the task cancellation wrap it in shield The function will wait until the future is actually cancelled so the total wait time may exceed the timeout If an exception happens during cancellation it is propagated If the wait is cancelled the future aw is also cancelled Example async def eternity Sleep for one hour await asyncio sleep 3600 print yay async def main Wait for at most 1 second try await asyncio wait_for eternity timeout 1 0 except TimeoutError print timeout asyncio run main Expected output timeout Changed in version 3 7 When aw is cancelled due to a timeout wait_for waits for aw to be cancelled Previously it raised TimeoutError immediately Changed in version 3 10 Removed the loop parameter Changed in version 3 11 Raises TimeoutError instead of asyncio TimeoutError Waiting Primitives coroutine asyncio wait aws timeout None return_when ALL_COMPLETED Run Future and Task instances in the aws iterable concurrently and block until the condition specified by return_when The aws iterable must not be empty Returns two sets of Tasks Futures done pending Usage done pending await asyncio wait aws timeout a float or int if specified can be used to control the maximum number of seconds to wait before returning Note that this function does not raise TimeoutError Futures or Tasks that aren t done when the timeout occurs are simply returned in the second set return_when indicates when this function should return It must be one of the following constants Constant Description asyncio FIRST_COMPLETED The function will return when any future finishes or is cancelled asyncio FIRST_EXCEPTION The function will return when any future finishes by raising an exception If no future raises an exception then it is equivalent to ALL_COMPLETED asyncio ALL_COMPLETED The function will return when all futur,en
377,es finish or are cancelled Unlike wait_for wait does not cancel the futures when a timeout occurs Changed in version 3 10 Removed the loop parameter Changed in version 3 11 Passing coroutine objects to wait directly is forbidden Changed in version 3 12 Added support for generators yielding tasks asyncio as_completed aws timeout None Run awaitable objects in the aws iterable concurrently Return an iterator of coroutines Each coroutine returned can be awaited to get the earliest next result from the iterable of the remaining awaitables Raises TimeoutError if the timeout occurs before all Futures are done Example for coro in as_completed aws earliest_result await coro Changed in version 3 10 Removed the loop parameter Deprecated since version 3 10 Deprecation warning is emitted if not all awaitable objects in the aws iterable are Future like objects and there is no running event loop Changed in version 3 12 Added support for generators yielding tasks Running in Threads coroutine asyncio to_thread func args kwargs Asynchronously run function func in a separate thread Any args and kwargs supplied for this function are directly passed to func Also the current contextvars Context is propagated allowing context variables from the event loop thread to be accessed in the separate thread Return a coroutine that can be awaited to get the eventual result of func This coroutine function is primarily intended to be used for executing IO bound functions methods that would otherwise block the event loop if they were run in the main thread For example def blocking_io print f start blocking_io at time strftime X Note that time sleep can be replaced with any blocking IO bound operation such as file operations time sleep 1 print f blocking_io complete at time strftime X async def main print f started main at time strftime X await asyncio gather asyncio to_thread blocking_io asyncio sleep 1 print f finished main at time strftime X asyncio run main Expected output started main at 19 50 53 start blocking_io at 19 50 53 blocking_io complete at 19 50 54 finished main at 19 50 54 Directly calling blocking_io in any coroutine would block the event loop for its duration resulting in an additional 1 second of run time Instead by using asyncio to_thread we can run it in a separate thread without blocking the event loop Note Due to the GIL asyncio to_thread can typically only be used to make IO bound functions non blocking However for extension modules that release the GIL or alternative Python implementations that don t have one asyncio to_thread can also be used for CPU bound functions New in version 3 9 Scheduling From Other Threads asyncio run_coroutine_threadsafe coro loop Submit a coroutine to the given event loop Thread safe Return a concurrent futures Future to wait for the result from another OS thread This function is meant to be called from a different OS thread than the one where the event loop is running Example Create a coroutine coro asyncio sleep 1 result 3 Submit the coroutine to a given loop future asyncio run_coroutine_threadsafe coro loop Wait for the result with an optional timeout argument assert future result timeout 3 If an exception is raised in the coroutine the returned Future will be notified It can also be used to cancel the task in the event loop try result future result timeout except TimeoutError print The coroutine took too long cancelling the task future cancel except Exception as exc print f The coroutine raised an exception exc r else print f The coroutine returned result r See the concurrency and multithreading section of the documentation Unlike other asyncio functions this function requires the loop argument to be passed explicitly New in version 3 5 1 Introspection asyncio current_task loop None Return the currently running Task instance or None if no task is running If loop is None get_running_loop is used to get the current loop New in version 3 7 asyncio all_tasks loop None Return a set of not yet finished Task objects run by the loop If loop is None get_running_loop is used for getting current loop New in ver,en
378,sion 3 7 asyncio iscoroutine obj Return True if obj is a coroutine object New in version 3 4 Task Object class asyncio Task coro loop None name None context None eager_start False A Future like object that runs a Python coroutine Not thread safe Tasks are used to run coroutines in event loops If a coroutine awaits on a Future the Task suspends the execution of the coroutine and waits for the completion of the Future When the Future is done the execution of the wrapped coroutine resumes Event loops use cooperative scheduling an event loop runs one Task at a time While a Task awaits for the completion of a Future the event loop runs other Tasks callbacks or performs IO operations Use the high level asyncio create_task function to create Tasks or the low level loop create_task or ensure_future functions Manual instantiation of Tasks is discouraged To cancel a running Task use the cancel method Calling it will cause the Task to throw a CancelledError exception into the wrapped coroutine If a coroutine is awaiting on a Future object during cancellation the Future object will be cancelled cancelled can be used to check if the Task was cancelled The method returns True if the wrapped coroutine did not suppress the CancelledError exception and was actually cancelled asyncio Task inherits from Future all of its APIs except Future set_result and Future set_exception An optional keyword only context argument allows specifying a custom contextvars Context for the coro to run in If no context is provided the Task copies the current context and later runs its coroutine in the copied context An optional keyword only eager_start argument allows eagerly starting the execution of the asyncio Task at task creation time If set to True and the event loop is running the task will start executing the coroutine immediately until the first time the coroutine blocks If the coroutine returns or raises without blocking the task will be finished eagerly and will skip scheduling to the event loop Changed in version 3 7 Added support for the contextvars module Changed in version 3 8 Added the name parameter Deprecated since version 3 10 Deprecation warning is emitted if loop is not specified and there is no running event loop Changed in version 3 11 Added the context parameter Changed in version 3 12 Added the eager_start parameter done Return True if the Task is done A Task is done when the wrapped coroutine either returned a value raised an exception or the Task was cancelled result Return the result of the Task If the Task is done the result of the wrapped coroutine is returned or if the coroutine raised an exception that exception is re raised If the Task has been cancelled this method raises a CancelledError exception If the Task s result isn t yet available this method raises a InvalidStateError exception exception Return the exception of the Task If the wrapped coroutine raised an exception that exception is returned If the wrapped coroutine returned normally this method returns None If the Task has been cancelled this method raises a CancelledError exception If the Task isn t done yet this method raises an InvalidStateError exception add_done_callback callback context None Add a callback to be run when the Task is done This method should only be used in low level callback based code See the documentation of Future add_done_callback for more details remove_done_callback callback Remove callback from the callbacks list This method should only be used in low level callback based code See the documentation of Future remove_done_callback for more details get_stack limit None Return the list of stack frames for this Task If the wrapped coroutine is not done this returns the stack where it is suspended If the coroutine has completed successfully or was cancelled this returns an empty list If the coroutine was terminated by an exception this returns the list of traceback frames The frames are always ordered from oldest to newest Only one stack frame is returned for a suspended coroutine The optional limit argument sets the maximum number of frames to ,en
379,return by default all available frames are returned The ordering of the returned list differs depending on whether a stack or a traceback is returned the newest frames of a stack are returned but the oldest frames of a traceback are returned This matches the behavior of the traceback module print_stack limit None file None Print the stack or traceback for this Task This produces output similar to that of the traceback module for the frames retrieved by get_stack The limit argument is passed to get_stack directly The file argument is an I O stream to which the output is written by default output is written to sys stdout get_coro Return the coroutine object wrapped by the Task Note This will return None for Tasks which have already completed eagerly See the Eager Task Factory New in version 3 8 Changed in version 3 12 Newly added eager task execution means result may be None get_context Return the contextvars Context object associated with the task New in version 3 12 get_name Return the name of the Task If no name has been explicitly assigned to the Task the default asyncio Task implementation generates a default name during instantiation New in version 3 8 set_name value Set the name of the Task The value argument can be any object which is then converted to a string In the default Task implementation the name will be visible in the repr output of a task object New in version 3 8 cancel msg None Request the Task to be cancelled This arranges for a CancelledError exception to be thrown into the wrapped coroutine on the next cycle of the event loop The coroutine then has a chance to clean up or even deny the request by suppressing the exception with a try except CancelledError finally block Therefore unlike Future cancel Task cancel does not guarantee that the Task will be cancelled although suppressing cancellation completely is not common and is actively discouraged Should the coroutine nevertheless decide to suppress the cancellation it needs to call Task uncancel in addition to catching the exception Changed in version 3 9 Added the msg parameter Changed in version 3 11 The msg parameter is propagated from cancelled task to its awaiter The following example illustrates how coroutines can intercept the cancellation request async def cancel_me print cancel_me before sleep try Wait for 1 hour await asyncio sleep 3600 except asyncio CancelledError print cancel_me cancel sleep raise finally print cancel_me after sleep async def main Create a cancel_me Task task asyncio create_task cancel_me Wait for 1 second await asyncio sleep 1 task cancel try await task except asyncio CancelledError print main cancel_me is cancelled now asyncio run main Expected output cancel_me before sleep cancel_me cancel sleep cancel_me after sleep main cancel_me is cancelled now cancelled Return True if the Task is cancelled The Task is cancelled when the cancellation was requested with cancel and the wrapped coroutine propagated the CancelledError exception thrown into it uncancel Decrement the count of cancellation requests to this Task Returns the remaining number of cancellation requests Note that once execution of a cancelled task completed further calls to uncancel are ineffective New in version 3 11 This method is used by asyncio s internals and isn t expected to be used by end user code In particular if a Task gets successfully uncancelled this allows for elements of structured concurrency like Task Groups and asyncio timeout to continue running isolating cancellation to the respective structured block For example async def make_request_with_timeout try async with asyncio timeout 1 Structured block affected by the timeout await make_request await make_another_request except TimeoutError log There was a timeout Outer code not affected by the timeout await unrelated_code While the block with make_request and make_another_request might get cancelled due to the timeout unrelated_code should continue running even in case of the timeout This is implemented with uncancel TaskGroup context managers use uncancel in a similar fashion If end user code ,en
380,is for some reason suppresing cancellation by catching CancelledError it needs to call this method to remove the cancellation state cancelling Return the number of pending cancellation requests to this Task i e the number of calls to cancel less the number of uncancel calls Note that if this number is greater than zero but the Task is still executing cancelled will still return False This is because this number can be lowered by calling uncancel which can lead to the task not being cancelled after all if the cancellation requests go down to zero This method is used by asyncio s internals and isn t expected to be used by end user code See uncancel for more details New in version 3 11,en
381,math Mathematical functions This module provides access to the mathematical functions defined by the C standard These functions cannot be used with complex numbers use the functions of the same name from the cmath module if you require support for complex numbers The distinction between functions which support complex numbers and those which don t is made since most users do not want to learn quite as much mathematics as required to understand complex numbers Receiving an exception instead of a complex result allows earlier detection of the unexpected complex number used as a parameter so that the programmer can determine how and why it was generated in the first place The following functions are provided by this module Except when explicitly noted otherwise all return values are floats Number theoretic and representation functions math ceil x Return the ceiling of x the smallest integer greater than or equal to x If x is not a float delegates to x __ceil__ which should return an Integral value math comb n k Return the number of ways to choose k items from n items without repetition and without order Evaluates to n k n k when k n and evaluates to zero when k n Also called the binomial coefficient because it is equivalent to the coefficient of k th term in polynomial expansion of 1 x ⁿ Raises TypeError if either of the arguments are not integers Raises ValueError if either of the arguments are negative New in version 3 8 math copysign x y Return a float with the magnitude absolute value of x but the sign of y On platforms that support signed zeros copysign 1 0 0 0 returns 1 0 math fabs x Return the absolute value of x math factorial n Return n factorial as an integer Raises ValueError if n is not integral or is negative Deprecated since version 3 9 Accepting floats with integral values like 5 0 is deprecated math floor x Return the floor of x the largest integer less than or equal to x If x is not a float delegates to x __floor__ which should return an Integral value math fmod x y Return fmod x y as defined by the platform C library Note that the Python expression x y may not return the same result The intent of the C standard is that fmod x y be exactly mathematically to infinite precision equal to x n y for some integer n such that the result has the same sign as x and magnitude less than abs y Python s x y returns a result with the sign of y instead and may not be exactly computable for float arguments For example fmod 1e 100 1e100 is 1e 100 but the result of Python s 1e 100 1e100 is 1e100 1e 100 which cannot be represented exactly as a float and rounds to the surprising 1e100 For this reason function fmod is generally preferred when working with floats while Python s x y is preferred when working with integers math frexp x Return the mantissa and exponent of x as the pair m e m is a float and e is an integer such that x m 2 e exactly If x is zero returns 0 0 0 otherwise 0 5 abs m 1 This is used to pick apart the internal representation of a float in a portable way math fsum iterable Return an accurate floating point sum of values in the iterable Avoids loss of precision by tracking multiple intermediate partial sums The algorithm s accuracy depends on IEEE 754 arithmetic guarantees and the typical case where the rounding mode is half even On some non Windows builds the underlying C library uses extended precision addition and may occasionally double round an intermediate sum causing it to be off in its least significant bit For further discussion and two alternative approaches see the ASPN cookbook recipes for accurate floating point summation math gcd integers Return the greatest common divisor of the specified integer arguments If any of the arguments is nonzero then the returned value is the largest positive integer that is a divisor of all arguments If all arguments are zero then the returned value is 0 gcd without arguments returns 0 New in version 3 5 Changed in version 3 9 Added support for an arbitrary number of arguments Formerly only two arguments were supported math isclose a b rel_tol 1e 09 abs_tol 0 0 Ret,en
382,urn True if the values a and b are close to each other and False otherwise Whether or not two values are considered close is determined according to given absolute and relative tolerances rel_tol is the relative tolerance it is the maximum allowed difference between a and b relative to the larger absolute value of a or b For example to set a tolerance of 5 pass rel_tol 0 05 The default tolerance is 1e 09 which assures that the two values are the same within about 9 decimal digits rel_tol must be greater than zero abs_tol is the minimum absolute tolerance useful for comparisons near zero abs_tol must be at least zero If no errors occur the result will be abs a b max rel_tol max abs a abs b abs_tol The IEEE 754 special values of NaN inf and inf will be handled according to IEEE rules Specifically NaN is not considered close to any other value including NaN inf and inf are only considered close to themselves New in version 3 5 See also PEP 485 A function for testing approximate equality math isfinite x Return True if x is neither an infinity nor a NaN and False otherwise Note that 0 0 is considered finite New in version 3 2 math isinf x Return True if x is a positive or negative infinity and False otherwise math isnan x Return True if x is a NaN not a number and False otherwise math isqrt n Return the integer square root of the nonnegative integer n This is the floor of the exact square root of n or equivalently the greatest integer a such that a ² n For some applications it may be more convenient to have the least integer a such that n a ² or in other words the ceiling of the exact square root of n For positive n this can be computed using a 1 isqrt n 1 New in version 3 8 math lcm integers Return the least common multiple of the specified integer arguments If all arguments are nonzero then the returned value is the smallest positive integer that is a multiple of all arguments If any of the arguments is zero then the returned value is 0 lcm without arguments returns 1 New in version 3 9 math ldexp x i Return x 2 i This is essentially the inverse of function frexp math modf x Return the fractional and integer parts of x Both results carry the sign of x and are floats math nextafter x y steps 1 Return the floating point value steps steps after x towards y If x is equal to y return y unless steps is zero Examples math nextafter x math inf goes up towards positive infinity math nextafter x math inf goes down towards minus infinity math nextafter x 0 0 goes towards zero math nextafter x math copysign math inf x goes away from zero See also math ulp New in version 3 9 Changed in version 3 12 Added the steps argument math perm n k None Return the number of ways to choose k items from n items without repetition and with order Evaluates to n n k when k n and evaluates to zero when k n If k is not specified or is None then k defaults to n and the function returns n Raises TypeError if either of the arguments are not integers Raises ValueError if either of the arguments are negative New in version 3 8 math prod iterable start 1 Calculate the product of all the elements in the input iterable The default start value for the product is 1 When the iterable is empty return the start value This function is intended specifically for use with numeric values and may reject non numeric types New in version 3 8 math remainder x y Return the IEEE 754 style remainder of x with respect to y For finite x and finite nonzero y this is the difference x n y where n is the closest integer to the exact value of the quotient x y If x y is exactly halfway between two consecutive integers the nearest even integer is used for n The remainder r remainder x y thus always satisfies abs r 0 5 abs y Special cases follow IEEE 754 in particular remainder x math inf is x for any finite x and remainder x 0 and remainder math inf x raise ValueError for any non NaN x If the result of the remainder operation is zero that zero will have the same sign as x On platforms using IEEE 754 binary floating point the result of this operation is always exactly representable no roun,en
383,ding error is introduced New in version 3 7 math sumprod p q Return the sum of products of values from two iterables p and q Raises ValueError if the inputs do not have the same length Roughly equivalent to sum itertools starmap operator mul zip p q strict True For float and mixed int float inputs the intermediate products and sums are computed with extended precision New in version 3 12 math trunc x Return x with the fractional part removed leaving the integer part This rounds toward 0 trunc is equivalent to floor for positive x and equivalent to ceil for negative x If x is not a float delegates to x __trunc__ which should return an Integral value math ulp x Return the value of the least significant bit of the float x If x is a NaN not a number return x If x is negative return ulp x If x is a positive infinity return x If x is equal to zero return the smallest positive denormalized representable float smaller than the minimum positive normalized float sys float_info min If x is equal to the largest positive representable float return the value of the least significant bit of x such that the first float smaller than x is x ulp x Otherwise x is a positive finite number return the value of the least significant bit of x such that the first float bigger than x is x ulp x ULP stands for Unit in the Last Place See also math nextafter and sys float_info epsilon New in version 3 9 Note that frexp and modf have a different call return pattern than their C equivalents they take a single argument and return a pair of values rather than returning their second return value through an output parameter there is no such thing in Python For the ceil floor and modf functions note that all floating point numbers of sufficiently large magnitude are exact integers Python floats typically carry no more than 53 bits of precision the same as the platform C double type in which case any float x with abs x 2 52 necessarily has no fractional bits Power and logarithmic functions math cbrt x Return the cube root of x New in version 3 11 math exp x Return e raised to the power x where e 2 718281 is the base of natural logarithms This is usually more accurate than math e x or pow math e x math exp2 x Return 2 raised to the power x New in version 3 11 math expm1 x Return e raised to the power x minus 1 Here e is the base of natural logarithms For small floats x the subtraction in exp x 1 can result in a significant loss of precision the expm1 function provides a way to compute this quantity to full precision from math import exp expm1 exp 1e 5 1 gives result accurate to 11 places 1 0000050000069649e 05 expm1 1e 5 result accurate to full precision 1 0000050000166668e 05 New in version 3 2 math log x base With one argument return the natural logarithm of x to base e With two arguments return the logarithm of x to the given base calculated as log x log base math log1p x Return the natural logarithm of 1 x base e The result is calculated in a way which is accurate for x near zero math log2 x Return the base 2 logarithm of x This is usually more accurate than log x 2 New in version 3 3 See also int bit_length returns the number of bits necessary to represent an integer in binary excluding the sign and leading zeros math log10 x Return the base 10 logarithm of x This is usually more accurate than log x 10 math pow x y Return x raised to the power y Exceptional cases follow the IEEE 754 standard as far as possible In particular pow 1 0 x and pow x 0 0 always return 1 0 even when x is a zero or a NaN If both x and y are finite x is negative and y is not an integer then pow x y is undefined and raises ValueError Unlike the built in operator math pow converts both its arguments to type float Use or the built in pow function for computing exact integer powers Changed in version 3 11 The special cases pow 0 0 inf and pow 0 0 inf were changed to return inf instead of raising ValueError for consistency with IEEE 754 math sqrt x Return the square root of x Trigonometric functions math acos x Return the arc cosine of x in radians The result is between 0 and pi math a,en
384,sin x Return the arc sine of x in radians The result is between pi 2 and pi 2 math atan x Return the arc tangent of x in radians The result is between pi 2 and pi 2 math atan2 y x Return atan y x in radians The result is between pi and pi The vector in the plane from the origin to point x y makes this angle with the positive X axis The point of atan2 is that the signs of both inputs are known to it so it can compute the correct quadrant for the angle For example atan 1 and atan2 1 1 are both pi 4 but atan2 1 1 is 3 pi 4 math cos x Return the cosine of x radians math dist p q Return the Euclidean distance between two points p and q each given as a sequence or iterable of coordinates The two points must have the same dimension Roughly equivalent to sqrt sum px qx 2 0 for px qx in zip p q New in version 3 8 math hypot coordinates Return the Euclidean norm sqrt sum x 2 for x in coordinates This is the length of the vector from the origin to the point given by the coordinates For a two dimensional point x y this is equivalent to computing the hypotenuse of a right triangle using the Pythagorean theorem sqrt x x y y Changed in version 3 8 Added support for n dimensional points Formerly only the two dimensional case was supported Changed in version 3 10 Improved the algorithm s accuracy so that the maximum error is under 1 ulp unit in the last place More typically the result is almost always correctly rounded to within 1 2 ulp math sin x Return the sine of x radians math tan x Return the tangent of x radians Angular conversion math degrees x Convert angle x from radians to degrees math radians x Convert angle x from degrees to radians Hyperbolic functions Hyperbolic functions are analogs of trigonometric functions that are based on hyperbolas instead of circles math acosh x Return the inverse hyperbolic cosine of x math asinh x Return the inverse hyperbolic sine of x math atanh x Return the inverse hyperbolic tangent of x math cosh x Return the hyperbolic cosine of x math sinh x Return the hyperbolic sine of x math tanh x Return the hyperbolic tangent of x Special functions math erf x Return the error function at x The erf function can be used to compute traditional statistical functions such as the cumulative standard normal distribution def phi x Cumulative distribution function for the standard normal distribution return 1 0 erf x sqrt 2 0 2 0 New in version 3 2 math erfc x Return the complementary error function at x The complementary error function is defined as 1 0 erf x It is used for large values of x where a subtraction from one would cause a loss of significance New in version 3 2 math gamma x Return the Gamma function at x New in version 3 2 math lgamma x Return the natural logarithm of the absolute value of the Gamma function at x New in version 3 2 Constants math pi The mathematical constant π 3 141592 to available precision math e The mathematical constant e 2 718281 to available precision math tau The mathematical constant τ 6 283185 to available precision Tau is a circle constant equal to 2 π the ratio of a circle s circumference to its radius To learn more about Tau check out Vi Hart s video Pi is still Wrong and start celebrating Tau day by eating twice as much pie New in version 3 6 math inf A floating point positive infinity For negative infinity use math inf Equivalent to the output of float inf New in version 3 5 math nan A floating point not a number NaN value Equivalent to the output of float nan Due to the requirements of the IEEE 754 standard math nan and float nan are not considered to equal to any other numeric value including themselves To check whether a number is a NaN use the isnan function to test for NaNs instead of is or Example import math math nan math nan False float nan float nan False math isnan math nan True math isnan float nan True New in version 3 5 Changed in version 3 11 It is now always available CPython implementation detail The math module consists mostly of thin wrappers around the platform C math library functions Behavior in exceptional cases follows Annex F of the C99 standar,en
385,d where appropriate The current implementation will raise ValueError for invalid operations like sqrt 1 0 or log 0 0 where C99 Annex F recommends signaling invalid operation or divide by zero and OverflowError for results that overflow for example exp 1000 0 A NaN will not be returned from any of the functions above unless one or more of the input arguments was a NaN in that case most functions will return a NaN but again following C99 Annex F there are some exceptions to this rule for example pow float nan 0 0 or hypot float nan float inf Note that Python makes no effort to distinguish signaling NaNs from quiet NaNs and behavior for signaling NaNs remains unspecified Typical behavior is to treat all NaNs as though they were quiet See also Module cmath Complex number versions of many of these functions,en
386,Built in Constants A small number of constants live in the built in namespace They are False The false value of the bool type Assignments to False are illegal and raise a SyntaxError True The true value of the bool type Assignments to True are illegal and raise a SyntaxError None An object frequently used to represent the absence of a value as when default arguments are not passed to a function Assignments to None are illegal and raise a SyntaxError None is the sole instance of the NoneType type NotImplemented A special value which should be returned by the binary special methods e g __eq__ __lt__ __add__ __rsub__ etc to indicate that the operation is not implemented with respect to the other type may be returned by the in place binary special methods e g __imul__ __iand__ etc for the same purpose It should not be evaluated in a boolean context NotImplemented is the sole instance of the types NotImplementedType type Note When a binary or in place method returns NotImplemented the interpreter will try the reflected operation on the other type or some other fallback depending on the operator If all attempts return NotImplemented the interpreter will raise an appropriate exception Incorrectly returning NotImplemented will result in a misleading error message or the NotImplemented value being returned to Python code See Implementing the arithmetic operations for examples Note NotImplementedError and NotImplemented are not interchangeable even though they have similar names and purposes See NotImplementedError for details on when to use it Changed in version 3 9 Evaluating NotImplemented in a boolean context is deprecated While it currently evaluates as true it will emit a DeprecationWarning It will raise a TypeError in a future version of Python Ellipsis The same as the ellipsis literal Special value used mostly in conjunction with extended slicing syntax for user defined container data types Ellipsis is the sole instance of the types EllipsisType type __debug__ This constant is true if Python was not started with an O option See also the assert statement Note The names None False True and __debug__ cannot be reassigned assignments to them even as an attribute name raise SyntaxError so they can be considered true constants Constants added by the site module The site module which is imported automatically during startup except if the S command line option is given adds several constants to the built in namespace They are useful for the interactive interpreter shell and should not be used in programs quit code None exit code None Objects that when printed print a message like Use quit or Ctrl D i e EOF to exit and when called raise SystemExit with the specified exit code copyright credits Objects that when printed or called print the text of copyright or credits respectively license Object that when printed prints the message Type license to see the full license text and when called displays the full license text in a pager like fashion one screen at a time,en
387,locale Internationalization services Source code Lib locale py The locale module opens access to the POSIX locale database and functionality The POSIX locale mechanism allows programmers to deal with certain cultural issues in an application without requiring the programmer to know all the specifics of each country where the software is executed The locale module is implemented on top of the _locale module which in turn uses an ANSI C locale implementation if available The locale module defines the following exception and functions exception locale Error Exception raised when the locale passed to setlocale is not recognized locale setlocale category locale None If locale is given and not None setlocale modifies the locale setting for the category The available categories are listed in the data description below locale may be a string or an iterable of two strings language code and encoding If it s an iterable it s converted to a locale name using the locale aliasing engine An empty string specifies the user s default settings If the modification of the locale fails the exception Error is raised If successful the new locale setting is returned If locale is omitted or None the current setting for category is returned setlocale is not thread safe on most systems Applications typically start with a call of import locale locale setlocale locale LC_ALL This sets the locale for all categories to the user s default setting typically specified in the LANG environment variable If the locale is not changed thereafter using multithreading should not cause problems locale localeconv Returns the database of the local conventions as a dictionary This dictionary has the following strings as keys Category Key Meaning LC_NUMERIC decimal_point Decimal point character grouping Sequence of numbers specifying which relative positions the thousands_sep is expected If the sequence is terminated with CHAR_MAX no further grouping is performed If the sequence terminates with a 0 the last group size is repeatedly used thousands_sep Character used between groups LC_MONETARY int_curr_symbol International currency symbol currency_symbol Local currency symbol p_cs_precedes n_cs_precedes Whether the currency symbol precedes the value for positive resp negative values p_sep_by_space n_sep_by_space Whether the currency symbol is separated from the value by a space for positive resp negative values mon_decimal_point Decimal point used for monetary values frac_digits Number of fractional digits used in local formatting of monetary values int_frac_digits Number of fractional digits used in international formatting of monetary values mon_thousands_sep Group separator used for monetary values mon_grouping Equivalent to grouping used for monetary values positive_sign Symbol used to annotate a positive monetary value negative_sign Symbol used to annotate a negative monetary value p_sign_posn n_sign_posn The position of the sign for positive resp negative values see below All numeric values can be set to CHAR_MAX to indicate that there is no value specified in this locale The possible values for p_sign_posn and n_sign_posn are given below Value Explanation 0 Currency and value are surrounded by parentheses 1 The sign should precede the value and currency symbol 2 The sign should follow the value and currency symbol 3 The sign should immediately precede the value 4 The sign should immediately follow the value CHAR_MAX Nothing is specified in this locale The function temporarily sets the LC_CTYPE locale to the LC_NUMERIC locale or the LC_MONETARY locale if locales are different and numeric or monetary strings are non ASCII This temporary change affects other threads Changed in version 3 7 The function now temporarily sets the LC_CTYPE locale to the LC_NUMERIC locale in some cases locale nl_langinfo option Return some locale specific information as a string This function is not available on all systems and the set of possible options might also vary across platforms The possible argument values are numbers for which symbolic constants are available in the locale mod,en
388,ule The nl_langinfo function accepts one of the following keys Most descriptions are taken from the corresponding description in the GNU C library locale CODESET Get a string with the name of the character encoding used in the selected locale locale D_T_FMT Get a string that can be used as a format string for time strftime to represent date and time in a locale specific way locale D_FMT Get a string that can be used as a format string for time strftime to represent a date in a locale specific way locale T_FMT Get a string that can be used as a format string for time strftime to represent a time in a locale specific way locale T_FMT_AMPM Get a format string for time strftime to represent time in the am pm format locale DAY_1 locale DAY_2 locale DAY_3 locale DAY_4 locale DAY_5 locale DAY_6 locale DAY_7 Get the name of the n th day of the week Note This follows the US convention of DAY_1 being Sunday not the international convention ISO 8601 that Monday is the first day of the week locale ABDAY_1 locale ABDAY_2 locale ABDAY_3 locale ABDAY_4 locale ABDAY_5 locale ABDAY_6 locale ABDAY_7 Get the abbreviated name of the n th day of the week locale MON_1 locale MON_2 locale MON_3 locale MON_4 locale MON_5 locale MON_6 locale MON_7 locale MON_8 locale MON_9 locale MON_10 locale MON_11 locale MON_12 Get the name of the n th month locale ABMON_1 locale ABMON_2 locale ABMON_3 locale ABMON_4 locale ABMON_5 locale ABMON_6 locale ABMON_7 locale ABMON_8 locale ABMON_9 locale ABMON_10 locale ABMON_11 locale ABMON_12 Get the abbreviated name of the n th month locale RADIXCHAR Get the radix character decimal dot decimal comma etc locale THOUSEP Get the separator character for thousands groups of three digits locale YESEXPR Get a regular expression that can be used with the regex function to recognize a positive response to a yes no question locale NOEXPR Get a regular expression that can be used with the regex 3 function to recognize a negative response to a yes no question Note The regular expressions for YESEXPR and NOEXPR use syntax suitable for the regex function from the C library which might differ from the syntax used in re locale CRNCYSTR Get the currency symbol preceded by if the symbol should appear before the value if the symbol should appear after the value or if the symbol should replace the radix character locale ERA Get a string that represents the era used in the current locale Most locales do not define this value An example of a locale which does define this value is the Japanese one In Japan the traditional representation of dates includes the name of the era corresponding to the then emperor s reign Normally it should not be necessary to use this value directly Specifying the E modifier in their format strings causes the time strftime function to use this information The format of the returned string is not specified and therefore you should not assume knowledge of it on different systems locale ERA_D_T_FMT Get a format string for time strftime to represent date and time in a locale specific era based way locale ERA_D_FMT Get a format string for time strftime to represent a date in a locale specific era based way locale ERA_T_FMT Get a format string for time strftime to represent a time in a locale specific era based way locale ALT_DIGITS Get a representation of up to 100 values used to represent the values 0 to 99 locale getdefaultlocale envvars Tries to determine the default locale settings and returns them as a tuple of the form language code encoding According to POSIX a program which has not called setlocale LC_ALL runs using the portable C locale Calling setlocale LC_ALL lets it use the default locale as defined by the LANG variable Since we do not want to interfere with the current locale setting we thus emulate the behavior in the way described above To maintain compatibility with other platforms not only the LANG variable is tested but a list of variables given as envvars parameter The first found to be defined will be used envvars defaults to the search path used in GNU gettext it must always contain the varia,en
389,ble name LANG The GNU gettext search path contains LC_ALL LC_CTYPE LANG and LANGUAGE in that order Except for the code C the language code corresponds to RFC 1766 language code and encoding may be None if their values cannot be determined Deprecated since version 3 11 will be removed in version 3 15 locale getlocale category LC_CTYPE Returns the current setting for the given locale category as sequence containing language code encoding category may be one of the LC_ values except LC_ALL It defaults to LC_CTYPE Except for the code C the language code corresponds to RFC 1766 language code and encoding may be None if their values cannot be determined locale getpreferredencoding do_setlocale True Return the locale encoding used for text data according to user preferences User preferences are expressed differently on different systems and might not be available programmatically on some systems so this function only returns a guess On some systems it is necessary to invoke setlocale to obtain the user preferences so this function is not thread safe If invoking setlocale is not necessary or desired do_setlocale should be set to False On Android or if the Python UTF 8 Mode is enabled always return utf 8 the locale encoding and the do_setlocale argument are ignored The Python preinitialization configures the LC_CTYPE locale See also the filesystem encoding and error handler Changed in version 3 7 The function now always returns utf 8 on Android or if the Python UTF 8 Mode is enabled locale getencoding Get the current locale encoding On Android and VxWorks return utf 8 On Unix return the encoding of the current LC_CTYPE locale Return utf 8 if nl_langinfo CODESET returns an empty string for example if the current LC_CTYPE locale is not supported On Windows return the ANSI code page The Python preinitialization configures the LC_CTYPE locale See also the filesystem encoding and error handler This function is similar to getpreferredencoding False except this function ignores the Python UTF 8 Mode New in version 3 11 locale normalize localename Returns a normalized locale code for the given locale name The returned locale code is formatted for use with setlocale If normalization fails the original name is returned unchanged If the given encoding is not known the function defaults to the default encoding for the locale code just like setlocale locale resetlocale category LC_ALL Sets the locale for category to the default setting The default setting is determined by calling getdefaultlocale category defaults to LC_ALL Deprecated since version 3 11 will be removed in version 3 13 locale strcoll string1 string2 Compares two strings according to the current LC_COLLATE setting As any other compare function returns a negative or a positive value or 0 depending on whether string1 collates before or after string2 or is equal to it locale strxfrm string Transforms a string to one that can be used in locale aware comparisons For example strxfrm s1 strxfrm s2 is equivalent to strcoll s1 s2 0 This function can be used when the same string is compared repeatedly e g when collating a sequence of strings locale format_string format val grouping False monetary False Formats a number val according to the current LC_NUMERIC setting The format follows the conventions of the operator For floating point values the decimal point is modified if appropriate If grouping is True also takes the grouping into account If monetary is true the conversion uses monetary thousands separator and grouping strings Processes formatting specifiers as in format val but takes the current locale settings into account Changed in version 3 7 The monetary keyword parameter was added locale currency val symbol True grouping False international False Formats a number val according to the current LC_MONETARY settings The returned string includes the currency symbol if symbol is true which is the default If grouping is True which is not the default grouping is done with the value If international is True which is not the default the international currency symbol is used Note This fun,en
390,ction will not work with the C locale so you have to set a locale via setlocale first locale str float Formats a floating point number using the same format as the built in function str float but takes the decimal point into account locale delocalize string Converts a string into a normalized number string following the LC_NUMERIC settings New in version 3 5 locale localize string grouping False monetary False Converts a normalized number string into a formatted string following the LC_NUMERIC settings New in version 3 10 locale atof string func float Converts a string to a number following the LC_NUMERIC settings by calling func on the result of calling delocalize on string locale atoi string Converts a string to an integer following the LC_NUMERIC conventions locale LC_CTYPE Locale category for the character type functions Most importantly this category defines the text encoding i e how bytes are interpreted as Unicode codepoints See PEP 538 and PEP 540 for how this variable might be automatically coerced to C UTF 8 to avoid issues created by invalid settings in containers or incompatible settings passed over remote SSH connections Python doesn t internally use locale dependent character transformation functions from ctype h Instead an internal pyctype h provides locale independent equivalents like Py_TOLOWER locale LC_COLLATE Locale category for sorting strings The functions strcoll and strxfrm of the locale module are affected locale LC_TIME Locale category for the formatting of time The function time strftime follows these conventions locale LC_MONETARY Locale category for formatting of monetary values The available options are available from the localeconv function locale LC_MESSAGES Locale category for message display Python currently does not support application specific locale aware messages Messages displayed by the operating system like those returned by os strerror might be affected by this category This value may not be available on operating systems not conforming to the POSIX standard most notably Windows locale LC_NUMERIC Locale category for formatting numbers The functions format_string atoi atof and str of the locale module are affected by that category All other numeric formatting operations are not affected locale LC_ALL Combination of all locale settings If this flag is used when the locale is changed setting the locale for all categories is attempted If that fails for any category no category is changed at all When the locale is retrieved using this flag a string indicating the setting for all categories is returned This string can be later used to restore the settings locale CHAR_MAX This is a symbolic constant used for different values returned by localeconv Example import locale loc locale getlocale get current locale use German locale name might vary with platform locale setlocale locale LC_ALL de_DE locale strcoll f xe4n foo compare a string containing an umlaut locale setlocale locale LC_ALL use user s preferred locale locale setlocale locale LC_ALL C use default C locale locale setlocale locale LC_ALL loc restore saved locale Background details hints tips and caveats The C standard defines the locale as a program wide property that may be relatively expensive to change On top of that some implementations are broken in such a way that frequent locale changes may cause core dumps This makes the locale somewhat painful to use correctly Initially when a program is started the locale is the C locale no matter what the user s preferred locale is There is one exception the LC_CTYPE category is changed at startup to set the current locale encoding to the user s preferred locale encoding The program must explicitly say that it wants the user s preferred locale settings for other categories by calling setlocale LC_ALL It is generally a bad idea to call setlocale in some library routine since as a side effect it affects the entire program Saving and restoring it is almost as bad it is expensive and affects other threads that happen to run before the settings have been restored If when coding a module fo,en
391,r general use you need a locale independent version of an operation that is affected by the locale such as certain formats used with time strftime you will have to find a way to do it without using the standard library routine Even better is convincing yourself that using locale settings is okay Only as a last resort should you document that your module is not compatible with non C locale settings The only way to perform numeric operations according to the locale is to use the special functions defined by this module atof atoi format_string str There is no way to perform case conversions and character classifications according to the locale For Unicode text strings these are done according to the character value only while for byte strings the conversions and classifications are done according to the ASCII value of the byte and bytes whose high bit is set i e non ASCII bytes are never converted or considered part of a character class such as letter or whitespace For extension writers and programs that embed Python Extension modules should never call setlocale except to find out what the current locale is But since the return value can only be used portably to restore it that is not very useful except perhaps to find out whether or not the locale is C When Python code uses the locale module to change the locale this also affects the embedding application If the embedding application doesn t want this to happen it should remove the _locale extension module which does all the work from the table of built in modules in the config c file and make sure that the _locale module is not accessible as a shared library Access to message catalogs locale gettext msg locale dgettext domain msg locale dcgettext domain msg category locale textdomain domain locale bindtextdomain domain dir locale bind_textdomain_codeset domain codeset The locale module exposes the C library s gettext interface on systems that provide this interface It consists of the functions gettext dgettext dcgettext textdomain bindtextdomain and bind_textdomain_codeset These are similar to the same functions in the gettext module but use the C library s binary format for message catalogs and the C library s search algorithms for locating message catalogs Python applications should normally find no need to invoke these functions and should use gettext instead A known exception to this rule are applications that link with additional C libraries which internally invoke C functions gettext or dcgettext For these applications it may be necessary to bind the text domain so that the libraries can properly locate their message catalogs,en
392,Cryptographic Services The modules described in this chapter implement various algorithms of a cryptographic nature They are available at the discretion of the installation On Unix systems the crypt module may also be available Here s an overview hashlib Secure hashes and message digests Hash algorithms Usage Constructors Attributes Hash Objects SHAKE variable length digests File hashing Key derivation BLAKE2 Creating hash objects Constants Examples Simple hashing Using different digest sizes Keyed hashing Randomized hashing Personalization Tree mode Credits hmac Keyed Hashing for Message Authentication secrets Generate secure random numbers for managing secrets Random numbers Generating tokens How many bytes should tokens use Other functions Recipes and best practices,en
393,time Time access and conversions This module provides various time related functions For related functionality see also the datetime and calendar modules Although this module is always available not all functions are available on all platforms Most of the functions defined in this module call platform C library functions with the same name It may sometimes be helpful to consult the platform documentation because the semantics of these functions varies among platforms An explanation of some terminology and conventions is in order The epoch is the point where the time starts the return value of time gmtime 0 It is January 1 1970 00 00 00 UTC on all platforms The term seconds since the epoch refers to the total number of elapsed seconds since the epoch typically excluding leap seconds Leap seconds are excluded from this total on all POSIX compliant platforms The functions in this module may not handle dates and times before the epoch or far in the future The cut off point in the future is determined by the C library for 32 bit systems it is typically in 2038 Function strptime can parse 2 digit years when given y format code When 2 digit years are parsed they are converted according to the POSIX and ISO C standards values 69 99 are mapped to 1969 1999 and values 0 68 are mapped to 2000 2068 UTC is Coordinated Universal Time formerly known as Greenwich Mean Time or GMT The acronym UTC is not a mistake but a compromise between English and French DST is Daylight Saving Time an adjustment of the timezone by usually one hour during part of the year DST rules are magic determined by local law and can change from year to year The C library has a table containing the local rules often it is read from a system file for flexibility and is the only source of True Wisdom in this respect The precision of the various real time functions may be less than suggested by the units in which their value or argument is expressed E g on most Unix systems the clock ticks only 50 or 100 times a second On the other hand the precision of time and sleep is better than their Unix equivalents times are expressed as floating point numbers time returns the most accurate time available using Unix gettimeofday where available and sleep will accept a time with a nonzero fraction Unix select is used to implement this where available The time value as returned by gmtime localtime and strptime and accepted by asctime mktime and strftime is a sequence of 9 integers The return values of gmtime localtime and strptime also offer attribute names for individual fields See struct_time for a description of these objects Changed in version 3 3 The struct_time type was extended to provide the tm_gmtoff and tm_zone attributes when platform supports corresponding struct tm members Changed in version 3 6 The struct_time attributes tm_gmtoff and tm_zone are now available on all platforms Use the following functions to convert between time representations From To Use seconds since the epoch struct_time in UTC gmtime seconds since the epoch struct_time in local localtime time struct_time in UTC seconds since the epoch calendar timegm struct_time in local seconds since the epoch mktime time Functions time asctime t Convert a tuple or struct_time representing a time as returned by gmtime or localtime to a string of the following form Sun Jun 20 23 21 05 1993 The day field is two characters long and is space padded if the day is a single digit e g Wed Jun 9 04 26 40 1993 If t is not provided the current time as returned by localtime is used Locale information is not used by asctime Note Unlike the C function of the same name asctime does not add a trailing newline time pthread_getcpuclockid thread_id Return the clk_id of the thread specific CPU time clock for the specified thread_id Use threading get_ident or the ident attribute of threading Thread objects to get a suitable value for thread_id Warning Passing an invalid or expired thread_id may result in undefined behavior such as segmentation fault Availability Unix See the man page for pthread_getcpuclockid 3 for further informa,en
394,tion New in version 3 7 time clock_getres clk_id Return the resolution precision of the specified clock clk_id Refer to Clock ID Constants for a list of accepted values for clk_id Availability Unix New in version 3 3 time clock_gettime clk_id float Return the time of the specified clock clk_id Refer to Clock ID Constants for a list of accepted values for clk_id Use clock_gettime_ns to avoid the precision loss caused by the float type Availability Unix New in version 3 3 time clock_gettime_ns clk_id int Similar to clock_gettime but return time as nanoseconds Availability Unix New in version 3 7 time clock_settime clk_id time float Set the time of the specified clock clk_id Currently CLOCK_REALTIME is the only accepted value for clk_id Use clock_settime_ns to avoid the precision loss caused by the float type Availability Unix New in version 3 3 time clock_settime_ns clk_id time int Similar to clock_settime but set time with nanoseconds Availability Unix New in version 3 7 time ctime secs Convert a time expressed in seconds since the epoch to a string of a form Sun Jun 20 23 21 05 1993 representing local time The day field is two characters long and is space padded if the day is a single digit e g Wed Jun 9 04 26 40 1993 If secs is not provided or None the current time as returned by time is used ctime secs is equivalent to asctime localtime secs Locale information is not used by ctime time get_clock_info name Get information on the specified clock as a namespace object Supported clock names and the corresponding functions to read their value are monotonic time monotonic perf_counter time perf_counter process_time time process_time thread_time time thread_time time time time The result has the following attributes adjustable True if the clock can be changed automatically e g by a NTP daemon or manually by the system administrator False otherwise implementation The name of the underlying C function used to get the clock value Refer to Clock ID Constants for possible values monotonic True if the clock cannot go backward False otherwise resolution The resolution of the clock in seconds float New in version 3 3 time gmtime secs Convert a time expressed in seconds since the epoch to a struct_time in UTC in which the dst flag is always zero If secs is not provided or None the current time as returned by time is used Fractions of a second are ignored See above for a description of the struct_time object See calendar timegm for the inverse of this function time localtime secs Like gmtime but converts to local time If secs is not provided or None the current time as returned by time is used The dst flag is set to 1 when DST applies to the given time localtime may raise OverflowError if the timestamp is outside the range of values supported by the platform C localtime or gmtime functions and OSError on localtime or gmtime failure It s common for this to be restricted to years between 1970 and 2038 time mktime t This is the inverse function of localtime Its argument is the struct_time or full 9 tuple since the dst flag is needed use 1 as the dst flag if it is unknown which expresses the time in local time not UTC It returns a floating point number for compatibility with time If the input value cannot be represented as a valid time either OverflowError or ValueError will be raised which depends on whether the invalid value is caught by Python or the underlying C libraries The earliest date for which it can generate a time is platform dependent time monotonic float Return the value in fractional seconds of a monotonic clock i e a clock that cannot go backwards The clock is not affected by system clock updates The reference point of the returned value is undefined so that only the difference between the results of two calls is valid Use monotonic_ns to avoid the precision loss caused by the float type New in version 3 3 Changed in version 3 5 The function is now always available and always system wide Changed in version 3 10 On macOS the function is now system wide time monotonic_ns int Similar to monotonic but return time as nanoseconds,en
395, New in version 3 7 time perf_counter float Return the value in fractional seconds of a performance counter i e a clock with the highest available resolution to measure a short duration It does include time elapsed during sleep and is system wide The reference point of the returned value is undefined so that only the difference between the results of two calls is valid Use perf_counter_ns to avoid the precision loss caused by the float type New in version 3 3 Changed in version 3 10 On Windows the function is now system wide time perf_counter_ns int Similar to perf_counter but return time as nanoseconds New in version 3 7 time process_time float Return the value in fractional seconds of the sum of the system and user CPU time of the current process It does not include time elapsed during sleep It is process wide by definition The reference point of the returned value is undefined so that only the difference between the results of two calls is valid Use process_time_ns to avoid the precision loss caused by the float type New in version 3 3 time process_time_ns int Similar to process_time but return time as nanoseconds New in version 3 7 time sleep secs Suspend execution of the calling thread for the given number of seconds The argument may be a floating point number to indicate a more precise sleep time If the sleep is interrupted by a signal and no exception is raised by the signal handler the sleep is restarted with a recomputed timeout The suspension time may be longer than requested by an arbitrary amount because of the scheduling of other activity in the system On Windows if secs is zero the thread relinquishes the remainder of its time slice to any other thread that is ready to run If there are no other threads ready to run the function returns immediately and the thread continues execution On Windows 8 1 and newer the implementation uses a high resolution timer which provides resolution of 100 nanoseconds If secs is zero Sleep 0 is used Unix implementation Use clock_nanosleep if available resolution 1 nanosecond Or use nanosleep if available resolution 1 nanosecond Or use select resolution 1 microsecond Changed in version 3 5 The function now sleeps at least secs even if the sleep is interrupted by a signal except if the signal handler raises an exception see PEP 475 for the rationale Changed in version 3 11 On Unix the clock_nanosleep and nanosleep functions are now used if available On Windows a waitable timer is now used time strftime format t Convert a tuple or struct_time representing a time as returned by gmtime or localtime to a string as specified by the format argument If t is not provided the current time as returned by localtime is used format must be a string ValueError is raised if any field in t is outside of the allowed range 0 is a legal argument for any position in the time tuple if it is normally illegal the value is forced to a correct one The following directives can be embedded in the format string They are shown without the optional field width and precision specification and are replaced by the indicated characters in the strftime result Directive Meaning Notes a Locale s abbreviated weekday name A Locale s full weekday name b Locale s abbreviated month name B Locale s full month name c Locale s appropriate date and time representation d Day of the month as a decimal number 01 31 f Microseconds as a decimal number 1 000000 999999 H Hour 24 hour clock as a decimal number 00 23 I Hour 12 hour clock as a decimal number 01 12 j Day of the year as a decimal number 001 366 m Month as a decimal number 01 12 M Minute as a decimal number 00 59 p Locale s equivalent of either AM or PM 2 S Second as a decimal number 00 61 3 U Week number of the year Sunday as the first day 4 of the week as a decimal number 00 53 All days in a new year preceding the first Sunday are considered to be in week 0 w Weekday as a decimal number 0 Sunday 6 W Week number of the year Monday as the first day 4 of the week as a decimal number 00 53 All days in a new year preceding the first Monday are considered to be in week 0 x L,en
396,ocale s appropriate date representation X Locale s appropriate time representation y Year without century as a decimal number 00 99 Y Year with century as a decimal number z Time zone offset indicating a positive or negative time difference from UTC GMT of the form HHMM or HHMM where H represents decimal hour digits and M represents decimal minute digits 23 59 23 59 1 Z Time zone name no characters if no time zone exists Deprecated 1 A literal character Notes 1 The f format directive only applies to strptime not to strftime However see also datetime datetime strptime and datetime datetime strftime where the f format directive applies to microseconds 2 When used with the strptime function the p directive only affects the output hour field if the I directive is used to parse the hour 3 The range really is 0 to 61 value 60 is valid in timestamps representing leap seconds and value 61 is supported for historical reasons 4 When used with the strptime function U and W are only used in calculations when the day of the week and the year are specified Here is an example a format for dates compatible with that specified in the RFC 2822 Internet email standard 1 from time import gmtime strftime strftime a d b Y H M S 0000 gmtime Thu 28 Jun 2001 14 17 15 0000 Additional directives may be supported on certain platforms but only the ones listed here have a meaning standardized by ANSI C To see the full set of format codes supported on your platform consult the strftime 3 documentation On some platforms an optional field width and precision specification can immediately follow the initial of a directive in the following order this is also not portable The field width is normally 2 except for j where it is 3 time strptime string format Parse a string representing a time according to a format The return value is a struct_time as returned by gmtime or localtime The format parameter uses the same directives as those used by strftime it defaults to a b d H M S Y which matches the formatting returned by ctime If string cannot be parsed according to format or if it has excess data after parsing ValueError is raised The default values used to fill in any missing data when more accurate values cannot be inferred are 1900 1 1 0 0 0 0 1 1 Both string and format must be strings For example import time time strptime 30 Nov 00 d b y time struct_time tm_year 2000 tm_mon 11 tm_mday 30 tm_hour 0 tm_min 0 tm_sec 0 tm_wday 3 tm_yday 335 tm_isdst 1 Support for the Z directive is based on the values contained in tzname and whether daylight is true Because of this it is platform specific except for recognizing UTC and GMT which are always known and are considered to be non daylight savings timezones Only the directives specified in the documentation are supported Because strftime is implemented per platform it can sometimes offer more directives than those listed But strptime is independent of any platform and thus does not necessarily support all directives available that are not documented as supported class time struct_time The type of the time value sequence returned by gmtime localtime and strptime It is an object with a named tuple interface values can be accessed by index and by attribute name The following values are present Index Attribute Values 0 tm_year for example 1993 1 tm_mon range 1 12 2 tm_day range 1 31 3 tm_hour range 0 23 4 tm_min range 0 59 5 tm_sec range 0 61 see Note 2 in strftime 6 tm_wday range 0 6 Monday is 0 7 tm_yday range 1 366 8 tm_isdst 0 1 or 1 see below N A tm_zone abbreviation of timezone name N A tm_gmtoff offset east of UTC in seconds Note that unlike the C structure the month value is a range of 1 12 not 0 11 In calls to mktime tm_isdst may be set to 1 when daylight savings time is in effect and 0 when it is not A value of 1 indicates that this is not known and will usually result in the correct state being filled in When a tuple with an incorrect length is passed to a function expecting a struct_time or having elements of the wrong type a TypeError is raised time time float Return the time in seconds since the epoch as ,en
397,a floating point number The handling of leap seconds is platform dependent On Windows and most Unix systems the leap seconds are not counted towards the time in seconds since the epoch This is commonly referred to as Unix time Note that even though the time is always returned as a floating point number not all systems provide time with a better precision than 1 second While this function normally returns non decreasing values it can return a lower value than a previous call if the system clock has been set back between the two calls The number returned by time may be converted into a more common time format i e year month day hour etc in UTC by passing it to gmtime function or in local time by passing it to the localtime function In both cases a struct_time object is returned from which the components of the calendar date may be accessed as attributes Use time_ns to avoid the precision loss caused by the float type time time_ns int Similar to time but returns time as an integer number of nanoseconds since the epoch New in version 3 7 time thread_time float Return the value in fractional seconds of the sum of the system and user CPU time of the current thread It does not include time elapsed during sleep It is thread specific by definition The reference point of the returned value is undefined so that only the difference between the results of two calls in the same thread is valid Use thread_time_ns to avoid the precision loss caused by the float type Availability Linux Unix Windows Unix systems supporting CLOCK_THREAD_CPUTIME_ID New in version 3 7 time thread_time_ns int Similar to thread_time but return time as nanoseconds New in version 3 7 time tzset Reset the time conversion rules used by the library routines The environment variable TZ specifies how this is done It will also set the variables tzname from the TZ environment variable timezone non DST seconds West of UTC altzone DST seconds west of UTC and daylight to 0 if this timezone does not have any daylight saving time rules or to nonzero if there is a time past present or future when daylight saving time applies Availability Unix Note Although in many cases changing the TZ environment variable may affect the output of functions like localtime without calling tzset this behavior should not be relied on The TZ environment variable should contain no whitespace The standard format of the TZ environment variable is whitespace added for clarity std offset dst offset start time end time Where the components are std and dst Three or more alphanumerics giving the timezone abbreviations These will be propagated into time tzname offset The offset has the form hh mm ss This indicates the value added the local time to arrive at UTC If preceded by a the timezone is east of the Prime Meridian otherwise it is west If no offset follows dst summer time is assumed to be one hour ahead of standard time start time end time Indicates when to change to and back from DST The format of the start and end dates are one of the following J n The Julian day n 1 n 365 Leap days are not counted so in all years February 28 is day 59 and March 1 is day 60 n The zero based Julian day 0 n 365 Leap days are counted and it is possible to refer to February 29 M m n d The d th day 0 d 6 of week n of month m of the year 1 n 5 1 m 12 where week 5 means the last d day in month m which may occur in either the fourth or the fifth week Week 1 is the first week in which the d th day occurs Day zero is a Sunday time has the same format as offset except that no leading sign or is allowed The default if time is not given is 02 00 00 os environ TZ EST 05EDT M4 1 0 M10 5 0 time tzset time strftime X x Z 02 07 36 05 08 03 EDT os environ TZ AEST 10AEDT 11 M10 5 0 M3 5 0 time tzset time strftime X x Z 16 08 12 05 08 03 AEST On many Unix systems including BSD Linux Solaris and Darwin it is more convenient to use the system s zoneinfo tzfile 5 database to specify the timezone rules To do this set the TZ environment variable to the path of the required timezone datafile relative to the root of the systems zoneinfo time,en
398,zone database usually located at usr share zoneinfo For example US Eastern Australia Melbourne Egypt or Europe Amsterdam os environ TZ US Eastern time tzset time tzname EST EDT os environ TZ Egypt time tzset time tzname EET EEST Clock ID Constants These constants are used as parameters for clock_getres and clock_gettime time CLOCK_BOOTTIME Identical to CLOCK_MONOTONIC except it also includes any time that the system is suspended This allows applications to get a suspend aware monotonic clock without having to deal with the complications of CLOCK_REALTIME which may have discontinuities if the time is changed using settimeofday or similar Availability Linux 2 6 39 New in version 3 7 time CLOCK_HIGHRES The Solaris OS has a CLOCK_HIGHRES timer that attempts to use an optimal hardware source and may give close to nanosecond resolution CLOCK_HIGHRES is the nonadjustable high resolution clock Availability Solaris New in version 3 3 time CLOCK_MONOTONIC Clock that cannot be set and represents monotonic time since some unspecified starting point Availability Unix New in version 3 3 time CLOCK_MONOTONIC_RAW Similar to CLOCK_MONOTONIC but provides access to a raw hardware based time that is not subject to NTP adjustments Availability Linux 2 6 28 macOS 10 12 New in version 3 3 time CLOCK_PROCESS_CPUTIME_ID High resolution per process timer from the CPU Availability Unix New in version 3 3 time CLOCK_PROF High resolution per process timer from the CPU Availability FreeBSD NetBSD 7 OpenBSD New in version 3 7 time CLOCK_TAI International Atomic Time The system must have a current leap second table in order for this to give the correct answer PTP or NTP software can maintain a leap second table Availability Linux New in version 3 9 time CLOCK_THREAD_CPUTIME_ID Thread specific CPU time clock Availability Unix New in version 3 3 time CLOCK_UPTIME Time whose absolute value is the time the system has been running and not suspended providing accurate uptime measurement both absolute and interval Availability FreeBSD OpenBSD 5 5 New in version 3 7 time CLOCK_UPTIME_RAW Clock that increments monotonically tracking the time since an arbitrary point unaffected by frequency or time adjustments and not incremented while the system is asleep Availability macOS 10 12 New in version 3 8 The following constant is the only parameter that can be sent to clock_settime time CLOCK_REALTIME System wide real time clock Setting this clock requires appropriate privileges Availability Unix New in version 3 3 Timezone Constants time altzone The offset of the local DST timezone in seconds west of UTC if one is defined This is negative if the local DST timezone is east of UTC as in Western Europe including the UK Only use this if daylight is nonzero See note below time daylight Nonzero if a DST timezone is defined See note below time timezone The offset of the local non DST timezone in seconds west of UTC negative in most of Western Europe positive in the US zero in the UK See note below time tzname A tuple of two strings the first is the name of the local non DST timezone the second is the name of the local DST timezone If no DST timezone is defined the second string should not be used See note below Note For the above Timezone constants altzone daylight timezone and tzname the value is determined by the timezone rules in effect at module load time or the last time tzset is called and may be incorrect for times in the past It is recommended to use the tm_gmtoff and tm_zone results from localtime to obtain timezone information See also Module datetime More object oriented interface to dates and times Module locale Internationalization services The locale setting affects the interpretation of many format specifiers in strftime and strptime Module calendar General calendar related functions timegm is the inverse of gmtime from this module Footnotes 1 The use of Z is now deprecated but the z escape that expands to the preferred hour minute offset is not supported by all ANSI C libraries Also a strict reading of the original 1982 RFC 822 standard calls for a two digi,en
399,t year y rather than Y but practice moved to 4 digit years long before the year 2000 After that RFC 822 became obsolete and the 4 digit year has been first recommended by RFC 1123 and then mandated by RFC 2822,en
400,2 Using the Python Interpreter 2 1 Invoking the Interpreter The Python interpreter is usually installed as usr local bin python3 12 on those machines where it is available putting usr local bin in your Unix shell s search path makes it possible to start it by typing the command python3 12 to the shell 1 Since the choice of the directory where the interpreter lives is an installation option other places are possible check with your local Python guru or system administrator E g usr local python is a popular alternative location On Windows machines where you have installed Python from the Microsoft Store the python3 12 command will be available If you have the py exe launcher installed you can use the py command See Excursus Setting environment variables for other ways to launch Python Typing an end of file character Control D on Unix Control Z on Windows at the primary prompt causes the interpreter to exit with a zero exit status If that doesn t work you can exit the interpreter by typing the following command quit The interpreter s line editing features include interactive editing history substitution and code completion on systems that support the GNU Readline library Perhaps the quickest check to see whether command line editing is supported is typing Control P to the first Python prompt you get If it beeps you have command line editing see Appendix Interactive Input Editing and History Substitution for an introduction to the keys If nothing appears to happen or if P is echoed command line editing isn t available you ll only be able to use backspace to remove characters from the current line The interpreter operates somewhat like the Unix shell when called with standard input connected to a tty device it reads and executes commands interactively when called with a file name argument or with a file as standard input it reads and executes a script from that file A second way of starting the interpreter is python c command arg which executes the statement s in command analogous to the shell s c option Since Python statements often contain spaces or other characters that are special to the shell it is usually advised to quote command in its entirety Some Python modules are also useful as scripts These can be invoked using python m module arg which executes the source file for module as if you had spelled out its full name on the command line When a script file is used it is sometimes useful to be able to run the script and enter interactive mode afterwards This can be done by passing i before the script All command line options are described in Command line and environment 2 1 1 Argument Passing When known to the interpreter the script name and additional arguments thereafter are turned into a list of strings and assigned to the argv variable in the sys module You can access this list by executing import sys The length of the list is at least one when no script and no arguments are given sys argv 0 is an empty string When the script name is given as meaning standard input sys argv 0 is set to When c command is used sys argv 0 is set to c When m module is used sys argv 0 is set to the full name of the located module Options found after c command or m module are not consumed by the Python interpreter s option processing but left in sys argv for the command or module to handle 2 1 2 Interactive Mode When commands are read from a tty the interpreter is said to be in interactive mode In this mode it prompts for the next command with the primary prompt usually three greater than signs for continuation lines it prompts with the secondary prompt by default three dots The interpreter prints a welcome message stating its version number and a copyright notice before printing the first prompt python3 12 Python 3 12 default April 4 2022 09 25 04 GCC 10 2 0 on linux Type help copyright credits or license for more information Continuation lines are needed when entering a multi line construct As an example take a look at this if statement the_world_is_flat True if the_world_is_flat print Be careful not to fall off Be careful not to fall of,en
401,f For more on interactive mode see Interactive Mode 2 2 The Interpreter and Its Environment 2 2 1 Source Code Encoding By default Python source files are treated as encoded in UTF 8 In that encoding characters of most languages in the world can be used simultaneously in string literals identifiers and comments although the standard library only uses ASCII characters for identifiers a convention that any portable code should follow To display all these characters properly your editor must recognize that the file is UTF 8 and it must use a font that supports all the characters in the file To declare an encoding other than the default one a special comment line should be added as the first line of the file The syntax is as follows coding encoding where encoding is one of the valid codecs supported by Python For example to declare that Windows 1252 encoding is to be used the first line of your source code file should be coding cp1252 One exception to the first line rule is when the source code starts with a UNIX shebang line In this case the encoding declaration should be added as the second line of the file For example usr bin env python3 coding cp1252 Footnotes 1 On Unix the Python 3 x interpreter is by default not installed with the executable named python so that it does not conflict with a simultaneously installed Python 2 x executable,en
402,doctest Test interactive Python examples Source code Lib doctest py The doctest module searches for pieces of text that look like interactive Python sessions and then executes those sessions to verify that they work exactly as shown There are several common ways to use doctest To check that a module s docstrings are up to date by verifying that all interactive examples still work as documented To perform regression testing by verifying that interactive examples from a test file or a test object work as expected To write tutorial documentation for a package liberally illustrated with input output examples Depending on whether the examples or the expository text are emphasized this has the flavor of literate testing or executable documentation Here s a complete but small example module This is the example module The example module supplies one function factorial For example factorial 5 120 def factorial n Return the factorial of n an exact integer 0 factorial n for n in range 6 1 1 2 6 24 120 factorial 30 265252859812191058636308480000000 factorial 1 Traceback most recent call last ValueError n must be 0 Factorials of floats are OK but the float must be an exact integer factorial 30 1 Traceback most recent call last ValueError n must be exact integer factorial 30 0 265252859812191058636308480000000 It must also not be ridiculously large factorial 1e100 Traceback most recent call last OverflowError n too large import math if not n 0 raise ValueError n must be 0 if math floor n n raise ValueError n must be exact integer if n 1 n catch a value like 1e300 raise OverflowError n too large result 1 factor 2 while factor n result factor factor 1 return result if __name__ __main__ import doctest doctest testmod If you run example py directly from the command line doctest works its magic python example py There s no output That s normal and it means all the examples worked Pass v to the script and doctest prints a detailed log of what it s trying and prints a summary at the end python example py v Trying factorial 5 Expecting 120 ok Trying factorial n for n in range 6 Expecting 1 1 2 6 24 120 ok And so on eventually ending with Trying factorial 1e100 Expecting Traceback most recent call last OverflowError n too large ok 2 items passed all tests 1 tests in __main__ 8 tests in __main__ factorial 9 tests in 2 items 9 passed and 0 failed Test passed That s all you need to know to start making productive use of doctest Jump in The following sections provide full details Note that there are many examples of doctests in the standard Python test suite and libraries Especially useful examples can be found in the standard test file Lib test test_doctest test_doctest py Simple Usage Checking Examples in Docstrings The simplest way to start using doctest but not necessarily the way you ll continue to do it is to end each module M with if __name__ __main__ import doctest doctest testmod doctest then examines docstrings in module M Running the module as a script causes the examples in the docstrings to get executed and verified python M py This won t display anything unless an example fails in which case the failing example s and the cause s of the failure s are printed to stdout and the final line of output is Test Failed N failures where N is the number of examples that failed Run it with the v switch instead python M py v and a detailed report of all examples tried is printed to standard output along with assorted summaries at the end You can force verbose mode by passing verbose True to testmod or prohibit it by passing verbose False In either of those cases sys argv is not examined by testmod so passing v or not has no effect There is also a command line shortcut for running testmod You can instruct the Python interpreter to run the doctest module directly from the standard library and pass the module name s on the command line python m doctest v example py This will import example py as a standalone module and run testmod on it Note that this may not work correctly if the file is part of a package and imports other submodules from that pack,en
403,age For more information on testmod see section Basic API Simple Usage Checking Examples in a Text File Another simple application of doctest is testing interactive examples in a text file This can be done with the testfile function import doctest doctest testfile example txt That short script executes and verifies any interactive Python examples contained in the file example txt The file content is treated as if it were a single giant docstring the file doesn t need to contain a Python program For example perhaps example txt contains this The example module Using factorial This is an example text file in reStructuredText format First import factorial from the example module from example import factorial Now use it factorial 6 120 Running doctest testfile example txt then finds the error in this documentation File example txt line 14 in example txt Failed example factorial 6 Expected 120 Got 720 As with testmod testfile won t display anything unless an example fails If an example does fail then the failing example s and the cause s of the failure s are printed to stdout using the same format as testmod By default testfile looks for files in the calling module s directory See section Basic API for a description of the optional arguments that can be used to tell it to look for files in other locations Like testmod testfile s verbosity can be set with the v command line switch or with the optional keyword argument verbose There is also a command line shortcut for running testfile You can instruct the Python interpreter to run the doctest module directly from the standard library and pass the file name s on the command line python m doctest v example txt Because the file name does not end with py doctest infers that it must be run with testfile not testmod For more information on testfile see section Basic API How It Works This section examines in detail how doctest works which docstrings it looks at how it finds interactive examples what execution context it uses how it handles exceptions and how option flags can be used to control its behavior This is the information that you need to know to write doctest examples for information about actually running doctest on these examples see the following sections Which Docstrings Are Examined The module docstring and all function class and method docstrings are searched Objects imported into the module are not searched In addition there are cases when you want tests to be part of a module but not part of the help text which requires that the tests not be included in the docstring Doctest looks for a module level variable called __test__ and uses it to locate other tests If M __test__ exists it must be a dict and each entry maps a string name to a function object class object or string Function and class object docstrings found from M __test__ are searched and strings are treated as if they were docstrings In output a key K in M __test__ appears with name M __test__ K For example place this block of code at the top of example py __test__ numbers factorial 6 720 factorial n for n in range 6 1 1 2 6 24 120 The value of example __test__ numbers will be treated as a docstring and all the tests inside it will be run It is important to note that the value can be mapped to a function class object or module if so doctest searches them recursively for docstrings which are then scanned for tests Any classes found are recursively searched similarly to test docstrings in their contained methods and nested classes How are Docstring Examples Recognized In most cases a copy and paste of an interactive console session works fine but doctest isn t trying to do an exact emulation of any specific Python shell comments are ignored x 12 x 12 if x 13 print yes else print no print NO print NO no NO NO Any expected output must immediately follow the final or line containing the code and the expected output if any extends to the next or all whitespace line The fine print Expected output cannot contain an all whitespace line since such a line is taken to signal the end of expected output If expected output d,en
404,oes contain a blank line put BLANKLINE in your doctest example each place a blank line is expected All hard tab characters are expanded to spaces using 8 column tab stops Tabs in output generated by the tested code are not modified Because any hard tabs in the sample output are expanded this means that if the code output includes hard tabs the only way the doctest can pass is if the NORMALIZE_WHITESPACE option or directive is in effect Alternatively the test can be rewritten to capture the output and compare it to an expected value as part of the test This handling of tabs in the source was arrived at through trial and error and has proven to be the least error prone way of handling them It is possible to use a different algorithm for handling tabs by writing a custom DocTestParser class Output to stdout is captured but not output to stderr exception tracebacks are captured via a different means If you continue a line via backslashing in an interactive session or for any other reason use a backslash you should use a raw docstring which will preserve your backslashes exactly as you type them def f x r Backslashes in a raw docstring m n print f __doc__ Backslashes in a raw docstring m n Otherwise the backslash will be interpreted as part of the string For example the n above would be interpreted as a newline character Alternatively you can double each backslash in the doctest version and not use a raw string def f x Backslashes in a raw docstring m n print f __doc__ Backslashes in a raw docstring m n The starting column doesn t matter assert Easy import math math floor 1 9 1 and as many leading whitespace characters are stripped from the expected output as appeared in the initial line that started the example What s the Execution Context By default each time doctest finds a docstring to test it uses a shallow copy of M s globals so that running tests doesn t change the module s real globals and so that one test in M can t leave behind crumbs that accidentally allow another test to work This means examples can freely use any names defined at top level in M and names defined earlier in the docstring being run Examples cannot see names defined in other docstrings You can force use of your own dict as the execution context by passing globs your_dict to testmod or testfile instead What About Exceptions No problem provided that the traceback is the only output produced by the example just paste in the traceback 1 Since tracebacks contain details that are likely to change rapidly for example exact file paths and line numbers this is one case where doctest works hard to be flexible in what it accepts Simple example 1 2 3 remove 42 Traceback most recent call last File stdin line 1 in module ValueError list remove x x not in list That doctest succeeds if ValueError is raised with the list remove x x not in list detail as shown The expected output for an exception must start with a traceback header which may be either of the following two lines indented the same as the first line of the example Traceback most recent call last Traceback innermost last The traceback header is followed by an optional traceback stack whose contents are ignored by doctest The traceback stack is typically omitted or copied verbatim from an interactive session The traceback stack is followed by the most interesting part the line s containing the exception type and detail This is usually the last line of a traceback but can extend across multiple lines if the exception has a multi line detail raise ValueError multi n line ndetail Traceback most recent call last File stdin line 1 in module ValueError multi line detail The last three lines starting with ValueError are compared against the exception s type and detail and the rest are ignored Best practice is to omit the traceback stack unless it adds significant documentation value to the example So the last example is probably better as raise ValueError multi n line ndetail Traceback most recent call last ValueError multi line detail Note that tracebacks are treated very specially In particular in the rewritte,en
405,n example the use of is independent of doctest s ELLIPSIS option The ellipsis in that example could be left out or could just as well be three or three hundred commas or digits or an indented transcript of a Monty Python skit Some details you should read once but won t need to remember Doctest can t guess whether your expected output came from an exception traceback or from ordinary printing So e g an example that expects ValueError 42 is prime will pass whether ValueError is actually raised or if the example merely prints that traceback text In practice ordinary output rarely begins with a traceback header line so this doesn t create real problems Each line of the traceback stack if present must be indented further than the first line of the example or start with a non alphanumeric character The first line following the traceback header indented the same and starting with an alphanumeric is taken to be the start of the exception detail Of course this does the right thing for genuine tracebacks When the IGNORE_EXCEPTION_DETAIL doctest option is specified everything following the leftmost colon and any module information in the exception name is ignored The interactive shell omits the traceback header line for some SyntaxError s But doctest uses the traceback header line to distinguish exceptions from non exceptions So in the rare case where you need to test a SyntaxError that omits the traceback header you will need to manually add the traceback header line to your test example For some exceptions Python displays the position of the error using markers and tildes 1 None File stdin line 1 1 None TypeError unsupported operand type s for int and NoneType Since the lines showing the position of the error come before the exception type and detail they are not checked by doctest For example the following test would pass even though it puts the marker in the wrong location 1 None File stdin line 1 1 None TypeError unsupported operand type s for int and NoneType Option Flags A number of option flags control various aspects of doctest s behavior Symbolic names for the flags are supplied as module constants which can be bitwise ORed together and passed to various functions The names can also be used in doctest directives and may be passed to the doctest command line interface via the o option New in version 3 4 The o command line option The first group of options define test semantics controlling aspects of how doctest decides whether actual output matches an example s expected output doctest DONT_ACCEPT_TRUE_FOR_1 By default if an expected output block contains just 1 an actual output block containing just 1 or just True is considered to be a match and similarly for 0 versus False When DONT_ACCEPT_TRUE_FOR_1 is specified neither substitution is allowed The default behavior caters to that Python changed the return type of many functions from integer to boolean doctests expecting little integer output still work in these cases This option will probably go away but not for several years doctest DONT_ACCEPT_BLANKLINE By default if an expected output block contains a line containing only the string BLANKLINE then that line will match a blank line in the actual output Because a genuinely blank line delimits the expected output this is the only way to communicate that a blank line is expected When DONT_ACCEPT_BLANKLINE is specified this substitution is not allowed doctest NORMALIZE_WHITESPACE When specified all sequences of whitespace blanks and newlines are treated as equal Any sequence of whitespace within the expected output will match any sequence of whitespace within the actual output By default whitespace must match exactly NORMALIZE_WHITESPACE is especially useful when a line of expected output is very long and you want to wrap it across multiple lines in your source doctest ELLIPSIS When specified an ellipsis marker in the expected output can match any substring in the actual output This includes substrings that span line boundaries and empty substrings so it s best to keep usage of this simple Complicated uses can lead to the s,en
406,ame kinds of oops it matched too much surprises that is prone to in regular expressions doctest IGNORE_EXCEPTION_DETAIL When specified doctests expecting exceptions pass so long as an exception of the expected type is raised even if the details message and fully qualified exception name don t match For example an example expecting ValueError 42 will pass if the actual exception raised is ValueError 3 14 but will fail if say a TypeError is raised instead It will also ignore any fully qualified name included before the exception class which can vary between implementations and versions of Python and the code libraries in use Hence all three of these variations will work with the flag specified raise Exception message Traceback most recent call last Exception message raise Exception message Traceback most recent call last builtins Exception message raise Exception message Traceback most recent call last __main__ Exception message Note that ELLIPSIS can also be used to ignore the details of the exception message but such a test may still fail based on whether the module name is present or matches exactly Changed in version 3 2 IGNORE_EXCEPTION_DETAIL now also ignores any information relating to the module containing the exception under test doctest SKIP When specified do not run the example at all This can be useful in contexts where doctest examples serve as both documentation and test cases and an example should be included for documentation purposes but should not be checked E g the example s output might be random or the example might depend on resources which would be unavailable to the test driver The SKIP flag can also be used for temporarily commenting out examples doctest COMPARISON_FLAGS A bitmask or ing together all the comparison flags above The second group of options controls how test failures are reported doctest REPORT_UDIFF When specified failures that involve multi line expected and actual outputs are displayed using a unified diff doctest REPORT_CDIFF When specified failures that involve multi line expected and actual outputs will be displayed using a context diff doctest REPORT_NDIFF When specified differences are computed by difflib Differ using the same algorithm as the popular ndiff py utility This is the only method that marks differences within lines as well as across lines For example if a line of expected output contains digit 1 where actual output contains letter l a line is inserted with a caret marking the mismatching column positions doctest REPORT_ONLY_FIRST_FAILURE When specified display the first failing example in each doctest but suppress output for all remaining examples This will prevent doctest from reporting correct examples that break because of earlier failures but it might also hide incorrect examples that fail independently of the first failure When REPORT_ONLY_FIRST_FAILURE is specified the remaining examples are still run and still count towards the total number of failures reported only the output is suppressed doctest FAIL_FAST When specified exit after the first failing example and don t attempt to run the remaining examples Thus the number of failures reported will be at most 1 This flag may be useful during debugging since examples after the first failure won t even produce debugging output The doctest command line accepts the option f as a shorthand for o FAIL_FAST New in version 3 4 doctest REPORTING_FLAGS A bitmask or ing together all the reporting flags above There is also a way to register new option flag names though this isn t useful unless you intend to extend doctest internals via subclassing doctest register_optionflag name Create a new option flag with a given name and return the new flag s integer value register_optionflag can be used when subclassing OutputChecker or DocTestRunner to create new options that are supported by your subclasses register_optionflag should always be called using the following idiom MY_FLAG register_optionflag MY_FLAG Directives Doctest directives may be used to modify the option flags for an individual example Doctest directives are sp,en
407,ecial Python comments following an example s source code directive doctest directive_options directive_options directive_option directive_option directive_option on_or_off directive_option_name on_or_off directive_option_name DONT_ACCEPT_BLANKLINE NORMALIZE_WHITESPACE Whitespace is not allowed between the or and the directive option name The directive option name can be any of the option flag names explained above An example s doctest directives modify doctest s behavior for that single example Use to enable the named behavior or to disable it For example this test passes print list range 20 doctest NORMALIZE_WHITESPACE 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Without the directive it would fail both because the actual output doesn t have two blanks before the single digit list elements and because the actual output is on a single line This test also passes and also requires a directive to do so print list range 20 doctest ELLIPSIS 0 1 18 19 Multiple directives can be used on a single physical line separated by commas print list range 20 doctest ELLIPSIS NORMALIZE_WHITESPACE 0 1 18 19 If multiple directive comments are used for a single example then they are combined print list range 20 doctest ELLIPSIS doctest NORMALIZE_WHITESPACE 0 1 18 19 As the previous example shows you can add lines to your example containing only directives This can be useful when an example is too long for a directive to comfortably fit on the same line print list range 5 list range 10 20 list range 30 40 doctest ELLIPSIS 0 4 10 19 30 39 Note that since all options are disabled by default and directives apply only to the example they appear in enabling options via in a directive is usually the only meaningful choice However option flags can also be passed to functions that run doctests establishing different defaults In such cases disabling an option via in a directive can be useful Warnings doctest is serious about requiring exact matches in expected output If even a single character doesn t match the test fails This will probably surprise you a few times as you learn exactly what Python does and doesn t guarantee about output For example when printing a set Python doesn t guarantee that the element is printed in any particular order so a test like foo Hermione Harry is vulnerable One workaround is to do foo Hermione Harry True instead Another is to do d sorted foo d Harry Hermione There are others but you get the idea Another bad idea is to print things that embed an object address like id 1 0 certain to fail some of the time 7948648 class C pass C the default repr for instances embeds an address C object at 0x00AC18F0 The ELLIPSIS directive gives a nice approach for the last example C doctest ELLIPSIS C object at 0x Floating point numbers are also subject to small output variations across platforms because Python defers to the platform C library for float formatting and C libraries vary widely in quality here 1 7 risky 0 14285714285714285 print 1 7 safer 0 142857142857 print round 1 7 6 much safer 0 142857 Numbers of the form I 2 J are safe across all platforms and I often contrive doctest examples to produce numbers of that form 3 4 utterly safe 0 75 Simple fractions are also easier for people to understand and that makes for better documentation Basic API The functions testmod and testfile provide a simple interface to doctest that should be sufficient for most basic uses For a less formal introduction to these two functions see sections Simple Usage Checking Examples in Docstrings and Simple Usage Checking Examples in a Text File doctest testfile filename module_relative True name None package None globs None verbose None report True optionflags 0 extraglobs None raise_on_error False parser DocTestParser encoding None All arguments except filename are optional and should be specified in keyword form Test examples in the file named filename Return failure_count test_count Optional argument module_relative specifies how the filename should be interpreted If module_relative is True the default then filename specifies an OS independent,en
408, module relative path By default this path is relative to the calling module s directory but if the package argument is specified then it is relative to that package To ensure OS independence filename should use characters to separate path segments and may not be an absolute path i e it may not begin with If module_relative is False then filename specifies an OS specific path The path may be absolute or relative relative paths are resolved with respect to the current working directory Optional argument name gives the name of the test by default or if None os path basename filename is used Optional argument package is a Python package or the name of a Python package whose directory should be used as the base directory for a module relative filename If no package is specified then the calling module s directory is used as the base directory for module relative filenames It is an error to specify package if module_relative is False Optional argument globs gives a dict to be used as the globals when executing examples A new shallow copy of this dict is created for the doctest so its examples start with a clean slate By default or if None a new empty dict is used Optional argument extraglobs gives a dict merged into the globals used to execute examples This works like dict update if globs and extraglobs have a common key the associated value in extraglobs appears in the combined dict By default or if None no extra globals are used This is an advanced feature that allows parameterization of doctests For example a doctest can be written for a base class using a generic name for the class then reused to test any number of subclasses by passing an extraglobs dict mapping the generic name to the subclass to be tested Optional argument verbose prints lots of stuff if true and prints only failures if false by default or if None it s true if and only if v is in sys argv Optional argument report prints a summary at the end when true else prints nothing at the end In verbose mode the summary is detailed else the summary is very brief in fact empty if all tests passed Optional argument optionflags default value 0 takes the bitwise OR of option flags See section Option Flags Optional argument raise_on_error defaults to false If true an exception is raised upon the first failure or unexpected exception in an example This allows failures to be post mortem debugged Default behavior is to continue running examples Optional argument parser specifies a DocTestParser or subclass that should be used to extract tests from the files It defaults to a normal parser i e DocTestParser Optional argument encoding specifies an encoding that should be used to convert the file to unicode doctest testmod m None name None globs None verbose None report True optionflags 0 extraglobs None raise_on_error False exclude_empty False All arguments are optional and all except for m should be specified in keyword form Test examples in docstrings in functions and classes reachable from module m or module __main__ if m is not supplied or is None starting with m __doc__ Also test examples reachable from dict m __test__ if it exists m __test__ maps names strings to functions classes and strings function and class docstrings are searched for examples strings are searched directly as if they were docstrings Only docstrings attached to objects belonging to module m are searched Return failure_count test_count Optional argument name gives the name of the module by default or if None m __name__ is used Optional argument exclude_empty defaults to false If true objects for which no doctests are found are excluded from consideration The default is a backward compatibility hack so that code still using doctest master summarize in conjunction with testmod continues to get output for objects with no tests The exclude_empty argument to the newer DocTestFinder constructor defaults to true Optional arguments extraglobs verbose report optionflags raise_on_error and globs are the same as for function testfile above except that globs defaults to m __dict__ doctest run_docstring_examples ,en
409,f globs verbose False name NoName compileflags None optionflags 0 Test examples associated with object f for example f may be a string a module a function or a class object A shallow copy of dictionary argument globs is used for the execution context Optional argument name is used in failure messages and defaults to NoName If optional argument verbose is true output is generated even if there are no failures By default output is generated only in case of an example failure Optional argument compileflags gives the set of flags that should be used by the Python compiler when running the examples By default or if None flags are deduced corresponding to the set of future features found in globs Optional argument optionflags works as for function testfile above Unittest API As your collection of doctest ed modules grows you ll want a way to run all their doctests systematically doctest provides two functions that can be used to create unittest test suites from modules and text files containing doctests To integrate with unittest test discovery include a load_tests function in your test module import unittest import doctest import my_module_with_doctests def load_tests loader tests ignore tests addTests doctest DocTestSuite my_module_with_doctests return tests There are two main functions for creating unittest TestSuite instances from text files and modules with doctests doctest DocFileSuite paths module_relative True package None setUp None tearDown None globs None optionflags 0 parser DocTestParser encoding None Convert doctest tests from one or more text files to a unittest TestSuite The returned unittest TestSuite is to be run by the unittest framework and runs the interactive examples in each file If an example in any file fails then the synthesized unit test fails and a failureException exception is raised showing the name of the file containing the test and a sometimes approximate line number Pass one or more paths as strings to text files to be examined Options may be provided as keyword arguments Optional argument module_relative specifies how the filenames in paths should be interpreted If module_relative is True the default then each filename in paths specifies an OS independent module relative path By default this path is relative to the calling module s directory but if the package argument is specified then it is relative to that package To ensure OS independence each filename should use characters to separate path segments and may not be an absolute path i e it may not begin with If module_relative is False then each filename in paths specifies an OS specific path The path may be absolute or relative relative paths are resolved with respect to the current working directory Optional argument package is a Python package or the name of a Python package whose directory should be used as the base directory for module relative filenames in paths If no package is specified then the calling module s directory is used as the base directory for module relative filenames It is an error to specify package if module_relative is False Optional argument setUp specifies a set up function for the test suite This is called before running the tests in each file The setUp function will be passed a DocTest object The setUp function can access the test globals as the globs attribute of the test passed Optional argument tearDown specifies a tear down function for the test suite This is called after running the tests in each file The tearDown function will be passed a DocTest object The setUp function can access the test globals as the globs attribute of the test passed Optional argument globs is a dictionary containing the initial global variables for the tests A new copy of this dictionary is created for each test By default globs is a new empty dictionary Optional argument optionflags specifies the default doctest options for the tests created by or ing together individual option flags See section Option Flags See function set_unittest_reportflags below for a better way to set reporting options Optional argument parser specifies a D,en
410,ocTestParser or subclass that should be used to extract tests from the files It defaults to a normal parser i e DocTestParser Optional argument encoding specifies an encoding that should be used to convert the file to unicode The global __file__ is added to the globals provided to doctests loaded from a text file using DocFileSuite doctest DocTestSuite module None globs None extraglobs None test_finder None setUp None tearDown None optionflags 0 checker None Convert doctest tests for a module to a unittest TestSuite The returned unittest TestSuite is to be run by the unittest framework and runs each doctest in the module If any of the doctests fail then the synthesized unit test fails and a failureException exception is raised showing the name of the file containing the test and a sometimes approximate line number Optional argument module provides the module to be tested It can be a module object or a possibly dotted module name If not specified the module calling this function is used Optional argument globs is a dictionary containing the initial global variables for the tests A new copy of this dictionary is created for each test By default globs is a new empty dictionary Optional argument extraglobs specifies an extra set of global variables which is merged into globs By default no extra globals are used Optional argument test_finder is the DocTestFinder object or a drop in replacement that is used to extract doctests from the module Optional arguments setUp tearDown and optionflags are the same as for function DocFileSuite above This function uses the same search technique as testmod Changed in version 3 5 DocTestSuite returns an empty unittest TestSuite if module contains no docstrings instead of raising ValueError exception doctest failureException When doctests which have been converted to unit tests by DocFileSuite or DocTestSuite fail this exception is raised showing the name of the file containing the test and a sometimes approximate line number Under the covers DocTestSuite creates a unittest TestSuite out of doctest DocTestCase instances and DocTestCase is a subclass of unittest TestCase DocTestCase isn t documented here it s an internal detail but studying its code can answer questions about the exact details of unittest integration Similarly DocFileSuite creates a unittest TestSuite out of doctest DocFileCase instances and DocFileCase is a subclass of DocTestCase So both ways of creating a unittest TestSuite run instances of DocTestCase This is important for a subtle reason when you run doctest functions yourself you can control the doctest options in use directly by passing option flags to doctest functions However if you re writing a unittest framework unittest ultimately controls when and how tests get run The framework author typically wants to control doctest reporting options perhaps e g specified by command line options but there s no way to pass options through unittest to doctest test runners For this reason doctest also supports a notion of doctest reporting flags specific to unittest support via this function doctest set_unittest_reportflags flags Set the doctest reporting flags to use Argument flags takes the bitwise OR of option flags See section Option Flags Only reporting flags can be used This is a module global setting and affects all future doctests run by module unittest the runTest method of DocTestCase looks at the option flags specified for the test case when the DocTestCase instance was constructed If no reporting flags were specified which is the typical and expected case doctest s unittest reporting flags are bitwise ORed into the option flags and the option flags so augmented are passed to the DocTestRunner instance created to run the doctest If any reporting flags were specified when the DocTestCase instance was constructed doctest s unittest reporting flags are ignored The value of the unittest reporting flags in effect before the function was called is returned by the function Advanced API The basic API is a simple wrapper that s intended to make doctest easy to use It is fairly,en
411, flexible and should meet most users needs however if you require more fine grained control over testing or wish to extend doctest s capabilities then you should use the advanced API The advanced API revolves around two container classes which are used to store the interactive examples extracted from doctest cases Example A single Python statement paired with its expected output DocTest A collection of Example s typically extracted from a single docstring or text file Additional processing classes are defined to find parse and run and check doctest examples DocTestFinder Finds all docstrings in a given module and uses a DocTestParser to create a DocTest from every docstring that contains interactive examples DocTestParser Creates a DocTest object from a string such as an object s docstring DocTestRunner Executes the examples in a DocTest and uses an OutputChecker to verify their output OutputChecker Compares the actual output from a doctest example with the expected output and decides whether they match The relationships among these processing classes are summarized in the following diagram list of module DocTestFinder DocTest DocTestRunner results printed Example v v DocTestParser Example OutputChecker DocTest Objects class doctest DocTest examples globs name filename lineno docstring A collection of doctest examples that should be run in a single namespace The constructor arguments are used to initialize the attributes of the same names DocTest defines the following attributes They are initialized by the constructor and should not be modified directly examples A list of Example objects encoding the individual interactive Python examples that should be run by this test globs The namespace aka globals that the examples should be run in This is a dictionary mapping names to values Any changes to the namespace made by the examples such as binding new variables will be reflected in globs after the test is run name A string name identifying the DocTest Typically this is the name of the object or file that the test was extracted from filename The name of the file that this DocTest was extracted from or None if the filename is unknown or if the DocTest was not extracted from a file lineno The line number within filename where this DocTest begins or None if the line number is unavailable This line number is zero based with respect to the beginning of the file docstring The string that the test was extracted from or None if the string is unavailable or if the test was not extracted from a string Example Objects class doctest Example source want exc_msg None lineno 0 indent 0 options None A single interactive example consisting of a Python statement and its expected output The constructor arguments are used to initialize the attributes of the same names Example defines the following attributes They are initialized by the constructor and should not be modified directly source A string containing the example s source code This source code consists of a single Python statement and always ends with a newline the constructor adds a newline when necessary want The expected output from running the example s source code either from stdout or a traceback in case of exception want ends with a newline unless no output is expected in which case it s an empty string The constructor adds a newline when necessary exc_msg The exception message generated by the example if the example is expected to generate an exception or None if it is not expected to generate an exception This exception message is compared against the return value of traceback format_exception_only exc_msg ends with a newline unless it s None The constructor adds a newline if needed lineno The line number within the string containing this example where the example begins This line number is zero based with respect to the beginning of the containing string indent The example s indentation in the containing string i e the number of space characters that precede the example s first prompt options A dictionary mapping from option flags to True or False which is used to override def,en
412,ault options for this example Any option flags not contained in this dictionary are left at their default value as specified by the DocTestRunner s optionflags By default no options are set DocTestFinder objects class doctest DocTestFinder verbose False parser DocTestParser recurse True exclude_empty True A processing class used to extract the DocTest s that are relevant to a given object from its docstring and the docstrings of its contained objects DocTest s can be extracted from modules classes functions methods staticmethods classmethods and properties The optional argument verbose can be used to display the objects searched by the finder It defaults to False no output The optional argument parser specifies the DocTestParser object or a drop in replacement that is used to extract doctests from docstrings If the optional argument recurse is false then DocTestFinder find will only examine the given object and not any contained objects If the optional argument exclude_empty is false then DocTestFinder find will include tests for objects with empty docstrings DocTestFinder defines the following method find obj name module globs extraglobs Return a list of the DocTest s that are defined by obj s docstring or by any of its contained objects docstrings The optional argument name specifies the object s name this name will be used to construct names for the returned DocTest s If name is not specified then obj __name__ is used The optional parameter module is the module that contains the given object If the module is not specified or is None then the test finder will attempt to automatically determine the correct module The object s module is used As a default namespace if globs is not specified To prevent the DocTestFinder from extracting DocTests from objects that are imported from other modules Contained objects with modules other than module are ignored To find the name of the file containing the object To help find the line number of the object within its file If module is False no attempt to find the module will be made This is obscure of use mostly in testing doctest itself if module is False or is None but cannot be found automatically then all objects are considered to belong to the non existent module so all contained objects will recursively be searched for doctests The globals for each DocTest is formed by combining globs and extraglobs bindings in extraglobs override bindings in globs A new shallow copy of the globals dictionary is created for each DocTest If globs is not specified then it defaults to the module s __dict__ if specified or otherwise If extraglobs is not specified then it defaults to DocTestParser objects class doctest DocTestParser A processing class used to extract interactive examples from a string and use them to create a DocTest object DocTestParser defines the following methods get_doctest string globs name filename lineno Extract all doctest examples from the given string and collect them into a DocTest object globs name filename and lineno are attributes for the new DocTest object See the documentation for DocTest for more information get_examples string name string Extract all doctest examples from the given string and return them as a list of Example objects Line numbers are 0 based The optional argument name is a name identifying this string and is only used for error messages parse string name string Divide the given string into examples and intervening text and return them as a list of alternating Example s and strings Line numbers for the Example s are 0 based The optional argument name is a name identifying this string and is only used for error messages DocTestRunner objects class doctest DocTestRunner checker None verbose None optionflags 0 A processing class used to execute and verify the interactive examples in a DocTest The comparison between expected outputs and actual outputs is done by an OutputChecker This comparison may be customized with a number of option flags see section Option Flags for more information If the option flags are insufficient then the comparison may also b,en
413,e customized by passing a subclass of OutputChecker to the constructor The test runner s display output can be controlled in two ways First an output function can be passed to run this function will be called with strings that should be displayed It defaults to sys stdout write If capturing the output is not sufficient then the display output can be also customized by subclassing DocTestRunner and overriding the methods report_start report_success report_unexpected_exception and report_failure The optional keyword argument checker specifies the OutputChecker object or drop in replacement that should be used to compare the expected outputs to the actual outputs of doctest examples The optional keyword argument verbose controls the DocTestRunner s verbosity If verbose is True then information is printed about each example as it is run If verbose is False then only failures are printed If verbose is unspecified or None then verbose output is used iff the command line switch v is used The optional keyword argument optionflags can be used to control how the test runner compares expected output to actual output and how it displays failures For more information see section Option Flags DocTestRunner defines the following methods report_start out test example Report that the test runner is about to process the given example This method is provided to allow subclasses of DocTestRunner to customize their output it should not be called directly example is the example about to be processed test is the test containing example out is the output function that was passed to DocTestRunner run report_success out test example got Report that the given example ran successfully This method is provided to allow subclasses of DocTestRunner to customize their output it should not be called directly example is the example about to be processed got is the actual output from the example test is the test containing example out is the output function that was passed to DocTestRunner run report_failure out test example got Report that the given example failed This method is provided to allow subclasses of DocTestRunner to customize their output it should not be called directly example is the example about to be processed got is the actual output from the example test is the test containing example out is the output function that was passed to DocTestRunner run report_unexpected_exception out test example exc_info Report that the given example raised an unexpected exception This method is provided to allow subclasses of DocTestRunner to customize their output it should not be called directly example is the example about to be processed exc_info is a tuple containing information about the unexpected exception as returned by sys exc_info test is the test containing example out is the output function that was passed to DocTestRunner run run test compileflags None out None clear_globs True Run the examples in test a DocTest object and display the results using the writer function out The examples are run in the namespace test globs If clear_globs is true the default then this namespace will be cleared after the test runs to help with garbage collection If you would like to examine the namespace after the test completes then use clear_globs False compileflags gives the set of flags that should be used by the Python compiler when running the examples If not specified then it will default to the set of future import flags that apply to globs The output of each example is checked using the DocTestRunner s output checker and the results are formatted by the DocTestRunner report_ methods summarize verbose None Print a summary of all the test cases that have been run by this DocTestRunner and return a named tuple TestResults failed attempted The optional verbose argument controls how detailed the summary is If the verbosity is not specified then the DocTestRunner s verbosity is used OutputChecker objects class doctest OutputChecker A class used to check the whether the actual output from a doctest example matches the expected output OutputChecker defines two met,en
414,hods check_output which compares a given pair of outputs and returns True if they match and output_difference which returns a string describing the differences between two outputs OutputChecker defines the following methods check_output want got optionflags Return True iff the actual output from an example got matches the expected output want These strings are always considered to match if they are identical but depending on what option flags the test runner is using several non exact match types are also possible See section Option Flags for more information about option flags output_difference example got optionflags Return a string describing the differences between the expected output for a given example example and the actual output got optionflags is the set of option flags used to compare want and got Debugging Doctest provides several mechanisms for debugging doctest examples Several functions convert doctests to executable Python programs which can be run under the Python debugger pdb The DebugRunner class is a subclass of DocTestRunner that raises an exception for the first failing example containing information about that example This information can be used to perform post mortem debugging on the example The unittest cases generated by DocTestSuite support the debug method defined by unittest TestCase You can add a call to pdb set_trace in a doctest example and you ll drop into the Python debugger when that line is executed Then you can inspect current values of variables and so on For example suppose a py contains just this module docstring def f x g x 2 def g x print x 3 import pdb pdb set_trace f 3 9 Then an interactive Python session may look like this import a doctest doctest testmod a Return doctest a 1 3 g None import pdb pdb set_trace Pdb list 1 def g x 2 print x 3 3 import pdb pdb set_trace EOF Pdb p x 6 Pdb step Return doctest a 0 2 f None g x 2 Pdb list 1 def f x 2 g x 2 EOF Pdb p x 3 Pdb step Return doctest a 2 1 None f 3 Pdb cont 0 3 Functions that convert doctests to Python code and possibly run the synthesized code under the debugger doctest script_from_examples s Convert text with examples to a script Argument s is a string containing doctest examples The string is converted to a Python script where doctest examples in s are converted to regular code and everything else is converted to Python comments The generated script is returned as a string For example import doctest print doctest script_from_examples r Set x and y to 1 and 2 x y 1 2 Print their sum print x y 3 displays Set x and y to 1 and 2 x y 1 2 Print their sum print x y Expected 3 This function is used internally by other functions see below but can also be useful when you want to transform an interactive Python session into a Python script doctest testsource module name Convert the doctest for an object to a script Argument module is a module object or dotted name of a module containing the object whose doctests are of interest Argument name is the name within the module of the object with the doctests of interest The result is a string containing the object s docstring converted to a Python script as described for script_from_examples above For example if module a py contains a top level function f then import a doctest print doctest testsource a a f prints a script version of function f s docstring with doctests converted to code and the rest placed in comments doctest debug module name pm False Debug the doctests for an object The module and name arguments are the same as for function testsource above The synthesized Python script for the named object s docstring is written to a temporary file and then that file is run under the control of the Python debugger pdb A shallow copy of module __dict__ is used for both local and global execution context Optional argument pm controls whether post mortem debugging is used If pm has a true value the script file is run directly and the debugger gets involved only if the script terminates via raising an unhandled exception If it does then post mortem debugging is invoked via pdb post_morte,en
415,m passing the traceback object from the unhandled exception If pm is not specified or is false the script is run under the debugger from the start via passing an appropriate exec call to pdb run doctest debug_src src pm False globs None Debug the doctests in a string This is like function debug above except that a string containing doctest examples is specified directly via the src argument Optional argument pm has the same meaning as in function debug above Optional argument globs gives a dictionary to use as both local and global execution context If not specified or None an empty dictionary is used If specified a shallow copy of the dictionary is used The DebugRunner class and the special exceptions it may raise are of most interest to testing framework authors and will only be sketched here See the source code and especially DebugRunner s docstring which is a doctest for more details class doctest DebugRunner checker None verbose None optionflags 0 A subclass of DocTestRunner that raises an exception as soon as a failure is encountered If an unexpected exception occurs an UnexpectedException exception is raised containing the test the example and the original exception If the output doesn t match then a DocTestFailure exception is raised containing the test the example and the actual output For information about the constructor parameters and methods see the documentation for DocTestRunner in section Advanced API There are two exceptions that may be raised by DebugRunner instances exception doctest DocTestFailure test example got An exception raised by DocTestRunner to signal that a doctest example s actual output did not match its expected output The constructor arguments are used to initialize the attributes of the same names DocTestFailure defines the following attributes DocTestFailure test The DocTest object that was being run when the example failed DocTestFailure example The Example that failed DocTestFailure got The example s actual output exception doctest UnexpectedException test example exc_info An exception raised by DocTestRunner to signal that a doctest example raised an unexpected exception The constructor arguments are used to initialize the attributes of the same names UnexpectedException defines the following attributes UnexpectedException test The DocTest object that was being run when the example failed UnexpectedException example The Example that failed UnexpectedException exc_info A tuple containing information about the unexpected exception as returned by sys exc_info Soapbox As mentioned in the introduction doctest has grown to have three primary uses 1 Checking examples in docstrings 2 Regression testing 3 Executable documentation literate testing These uses have different requirements and it is important to distinguish them In particular filling your docstrings with obscure test cases makes for bad documentation When writing a docstring choose docstring examples with care There s an art to this that needs to be learned it may not be natural at first Examples should add genuine value to the documentation A good example can often be worth many words If done with care the examples will be invaluable for your users and will pay back the time it takes to collect them many times over as the years go by and things change I m still amazed at how often one of my doctest examples stops working after a harmless change Doctest also makes an excellent tool for regression testing especially if you don t skimp on explanatory text By interleaving prose and examples it becomes much easier to keep track of what s actually being tested and why When a test fails good prose can make it much easier to figure out what the problem is and how it should be fixed It s true that you could write extensive comments in code based testing but few programmers do Many have found that using doctest approaches instead leads to much clearer tests Perhaps this is simply because doctest makes writing prose a little easier than writing code while writing comments in code is a little harder I think it goes deeper than just that the,en
416, natural attitude when writing a doctest based test is that you want to explain the fine points of your software and illustrate them with examples This in turn naturally leads to test files that start with the simplest features and logically progress to complications and edge cases A coherent narrative is the result instead of a collection of isolated functions that test isolated bits of functionality seemingly at random It s a different attitude and produces different results blurring the distinction between testing and explaining Regression testing is best confined to dedicated objects or files There are several options for organizing tests Write text files containing test cases as interactive examples and test the files using testfile or DocFileSuite This is recommended although is easiest to do for new projects designed from the start to use doctest Define functions named _regrtest_topic that consist of single docstrings containing test cases for the named topics These functions can be included in the same file as the module or separated out into a separate test file Define a __test__ dictionary mapping from regression test topics to docstrings containing test cases When you have placed your tests in a module the module can itself be the test runner When a test fails you can arrange for your test runner to re run only the failing doctest while you debug the problem Here is a minimal example of such a test runner if __name__ __main__ import doctest flags doctest REPORT_NDIFF doctest FAIL_FAST if len sys argv 1 name sys argv 1 if name in globals obj globals name else obj __test__ name doctest run_docstring_examples obj globals name name optionflags flags else fail total doctest testmod optionflags flags print failures out of tests format fail total Footnotes 1 Examples containing both expected output and an exception are not supported Trying to guess where one ends and the other begins is too error prone and that also makes for a confusing test,en
417,MS Windows Specific Services This chapter describes modules that are only available on MS Windows platforms msvcrt Useful routines from the MS VC runtime File Operations Console I O Other Functions winreg Windows registry access Functions Constants HKEY_ Constants Access Rights 64 bit Specific Value Types Registry Handle Objects winsound Sound playing interface for Windows,en
418,The Python Standard Library While The Python Language Reference describes the exact syntax and semantics of the Python language this library reference manual describes the standard library that is distributed with Python It also describes some of the optional components that are commonly included in Python distributions Python s standard library is very extensive offering a wide range of facilities as indicated by the long table of contents listed below The library contains built in modules written in C that provide access to system functionality such as file I O that would otherwise be inaccessible to Python programmers as well as modules written in Python that provide standardized solutions for many problems that occur in everyday programming Some of these modules are explicitly designed to encourage and enhance the portability of Python programs by abstracting away platform specifics into platform neutral APIs The Python installers for the Windows platform usually include the entire standard library and often also include many additional components For Unix like operating systems Python is normally provided as a collection of packages so it may be necessary to use the packaging tools provided with the operating system to obtain some or all of the optional components In addition to the standard library there is an active collection of hundreds of thousands of components from individual programs and modules to packages and entire application development frameworks available from the Python Package Index Introduction Notes on availability Built in Functions Built in Constants Constants added by the site module Built in Types Truth Value Testing Boolean Operations and or not Comparisons Numeric Types int float complex Boolean Type bool Iterator Types Sequence Types list tuple range Text Sequence Type str Binary Sequence Types bytes bytearray memoryview Set Types set frozenset Mapping Types dict Context Manager Types Type Annotation Types Generic Alias Union Other Built in Types Special Attributes Integer string conversion length limitation Built in Exceptions Exception context Inheriting from built in exceptions Base classes Concrete exceptions Warnings Exception groups Exception hierarchy Text Processing Services string Common string operations re Regular expression operations difflib Helpers for computing deltas textwrap Text wrapping and filling unicodedata Unicode Database stringprep Internet String Preparation readline GNU readline interface rlcompleter Completion function for GNU readline Binary Data Services struct Interpret bytes as packed binary data codecs Codec registry and base classes Data Types datetime Basic date and time types zoneinfo IANA time zone support calendar General calendar related functions collections Container datatypes collections abc Abstract Base Classes for Containers heapq Heap queue algorithm bisect Array bisection algorithm array Efficient arrays of numeric values weakref Weak references types Dynamic type creation and names for built in types copy Shallow and deep copy operations pprint Data pretty printer reprlib Alternate repr implementation enum Support for enumerations graphlib Functionality to operate with graph like structures Numeric and Mathematical Modules numbers Numeric abstract base classes math Mathematical functions cmath Mathematical functions for complex numbers decimal Decimal fixed point and floating point arithmetic fractions Rational numbers random Generate pseudo random numbers statistics Mathematical statistics functions Functional Programming Modules itertools Functions creating iterators for efficient looping functools Higher order functions and operations on callable objects operator Standard operators as functions File and Directory Access pathlib Object oriented filesystem paths os path Common pathname manipulations fileinput Iterate over lines from multiple input streams stat Interpreting stat results filecmp File and Directory Comparisons tempfile Generate temporary files and directories glob Unix style pathname pattern expansion fnmatch Unix filename patte,en
419,rn matching linecache Random access to text lines shutil High level file operations Data Persistence pickle Python object serialization copyreg Register pickle support functions shelve Python object persistence marshal Internal Python object serialization dbm Interfaces to Unix databases sqlite3 DB API 2 0 interface for SQLite databases Data Compression and Archiving zlib Compression compatible with gzip gzip Support for gzip files bz2 Support for bzip2 compression lzma Compression using the LZMA algorithm zipfile Work with ZIP archives tarfile Read and write tar archive files File Formats csv CSV File Reading and Writing configparser Configuration file parser tomllib Parse TOML files netrc netrc file processing plistlib Generate and parse Apple plist files Cryptographic Services hashlib Secure hashes and message digests hmac Keyed Hashing for Message Authentication secrets Generate secure random numbers for managing secrets Generic Operating System Services os Miscellaneous operating system interfaces io Core tools for working with streams time Time access and conversions argparse Parser for command line options arguments and sub commands getopt C style parser for command line options logging Logging facility for Python logging config Logging configuration logging handlers Logging handlers getpass Portable password input curses Terminal handling for character cell displays curses textpad Text input widget for curses programs curses ascii Utilities for ASCII characters curses panel A panel stack extension for curses platform Access to underlying platform s identifying data errno Standard errno system symbols ctypes A foreign function library for Python Concurrent Execution threading Thread based parallelism multiprocessing Process based parallelism multiprocessing shared_memory Shared memory for direct access across processes The concurrent package concurrent futures Launching parallel tasks subprocess Subprocess management sched Event scheduler queue A synchronized queue class contextvars Context Variables _thread Low level threading API Networking and Interprocess Communication asyncio Asynchronous I O socket Low level networking interface ssl TLS SSL wrapper for socket objects select Waiting for I O completion selectors High level I O multiplexing signal Set handlers for asynchronous events mmap Memory mapped file support Internet Data Handling email An email and MIME handling package json JSON encoder and decoder mailbox Manipulate mailboxes in various formats mimetypes Map filenames to MIME types base64 Base16 Base32 Base64 Base85 Data Encodings binascii Convert between binary and ASCII quopri Encode and decode MIME quoted printable data Structured Markup Processing Tools html HyperText Markup Language support html parser Simple HTML and XHTML parser html entities Definitions of HTML general entities XML Processing Modules xml etree ElementTree The ElementTree XML API xml dom The Document Object Model API xml dom minidom Minimal DOM implementation xml dom pulldom Support for building partial DOM trees xml sax Support for SAX2 parsers xml sax handler Base classes for SAX handlers xml sax saxutils SAX Utilities xml sax xmlreader Interface for XML parsers xml parsers expat Fast XML parsing using Expat Internet Protocols and Support webbrowser Convenient web browser controller wsgiref WSGI Utilities and Reference Implementation urllib URL handling modules urllib request Extensible library for opening URLs urllib response Response classes used by urllib urllib parse Parse URLs into components urllib error Exception classes raised by urllib request urllib robotparser Parser for robots txt http HTTP modules http client HTTP protocol client ftplib FTP protocol client poplib POP3 protocol client imaplib IMAP4 protocol client smtplib SMTP protocol client uuid UUID objects according to RFC 4122 socketserver A framework for network servers http server HTTP servers http cookies HTTP state management http cookiejar Cookie handling for HTTP clients xmlrpc XMLRPC server and client modules xmlrpc client XML RPC client access xmlrpc ,en
420,server Basic XML RPC servers ipaddress IPv4 IPv6 manipulation library Multimedia Services wave Read and write WAV files colorsys Conversions between color systems Internationalization gettext Multilingual internationalization services locale Internationalization services Program Frameworks turtle Turtle graphics cmd Support for line oriented command interpreters shlex Simple lexical analysis Graphical User Interfaces with Tk tkinter Python interface to Tcl Tk tkinter colorchooser Color choosing dialog tkinter font Tkinter font wrapper Tkinter Dialogs tkinter messagebox Tkinter message prompts tkinter scrolledtext Scrolled Text Widget tkinter dnd Drag and drop support tkinter ttk Tk themed widgets tkinter tix Extension widgets for Tk IDLE Development Tools typing Support for type hints pydoc Documentation generator and online help system Python Development Mode doctest Test interactive Python examples unittest Unit testing framework unittest mock mock object library unittest mock getting started 2to3 Automated Python 2 to 3 code translation test Regression tests package for Python test support Utilities for the Python test suite test support socket_helper Utilities for socket tests test support script_helper Utilities for the Python execution tests test support bytecode_helper Support tools for testing correct bytecode generation test support threading_helper Utilities for threading tests test support os_helper Utilities for os tests test support import_helper Utilities for import tests test support warnings_helper Utilities for warnings tests Debugging and Profiling Audit events table bdb Debugger framework faulthandler Dump the Python traceback pdb The Python Debugger The Python Profilers timeit Measure execution time of small code snippets trace Trace or track Python statement execution tracemalloc Trace memory allocations Software Packaging and Distribution ensurepip Bootstrapping the pip installer venv Creation of virtual environments zipapp Manage executable Python zip archives Python Runtime Services sys System specific parameters and functions sys monitoring Execution event monitoring sysconfig Provide access to Python s configuration information builtins Built in objects __main__ Top level code environment warnings Warning control dataclasses Data Classes contextlib Utilities for with statement contexts abc Abstract Base Classes atexit Exit handlers traceback Print or retrieve a stack traceback __future__ Future statement definitions gc Garbage Collector interface inspect Inspect live objects site Site specific configuration hook Custom Python Interpreters code Interpreter base classes codeop Compile Python code Importing Modules zipimport Import modules from Zip archives pkgutil Package extension utility modulefinder Find modules used by a script runpy Locating and executing Python modules importlib The implementation of import importlib resources Package resource reading opening and access importlib resources abc Abstract base classes for resources importlib metadata Accessing package metadata The initialization of the sys path module search path Python Language Services ast Abstract Syntax Trees symtable Access to the compiler s symbol tables token Constants used with Python parse trees keyword Testing for Python keywords tokenize Tokenizer for Python source tabnanny Detection of ambiguous indentation pyclbr Python module browser support py_compile Compile Python source files compileall Byte compile Python libraries dis Disassembler for Python bytecode pickletools Tools for pickle developers MS Windows Specific Services msvcrt Useful routines from the MS VC runtime winreg Windows registry access winsound Sound playing interface for Windows Unix Specific Services posix The most common POSIX system calls pwd The password database grp The group database termios POSIX style tty control tty Terminal control functions pty Pseudo terminal utilities fcntl The fcntl and ioctl system calls resource Resource usage information syslog Unix syslog library routines Modules command line interface CLI Superseded Modules aifc R,en
421,ead and write AIFF and AIFC files audioop Manipulate raw audio data cgi Common Gateway Interface support cgitb Traceback manager for CGI scripts chunk Read IFF chunked data crypt Function to check Unix passwords imghdr Determine the type of an image mailcap Mailcap file handling msilib Read and write Microsoft Installer files nis Interface to Sun s NIS Yellow Pages nntplib NNTP protocol client optparse Parser for command line options ossaudiodev Access to OSS compatible audio devices pipes Interface to shell pipelines sndhdr Determine type of sound file spwd The shadow password database sunau Read and write Sun AU files telnetlib Telnet client uu Encode and decode uuencode files xdrlib Encode and decode XDR data Security Considerations,en
422,bisect Array bisection algorithm Source code Lib bisect py This module provides support for maintaining a list in sorted order without having to sort the list after each insertion For long lists of items with expensive comparison operations this can be an improvement over linear searches or frequent resorting The module is called bisect because it uses a basic bisection algorithm to do its work Unlike other bisection tools that search for a specific value the functions in this module are designed to locate an insertion point Accordingly the functions never call an __eq__ method to determine whether a value has been found Instead the functions only call the __lt__ method and will return an insertion point between values in an array The following functions are provided bisect bisect_left a x lo 0 hi len a key None Locate the insertion point for x in a to maintain sorted order The parameters lo and hi may be used to specify a subset of the list which should be considered by default the entire list is used If x is already present in a the insertion point will be before to the left of any existing entries The return value is suitable for use as the first parameter to list insert assuming that a is already sorted The returned insertion point ip partitions the array a into two slices such that all elem x for elem in a lo ip is true for the left slice and all elem x for elem in a ip hi is true for the right slice key specifies a key function of one argument that is used to extract a comparison key from each element in the array To support searching complex records the key function is not applied to the x value If key is None the elements are compared directly and no key function is called Changed in version 3 10 Added the key parameter bisect bisect_right a x lo 0 hi len a key None bisect bisect a x lo 0 hi len a key None Similar to bisect_left but returns an insertion point which comes after to the right of any existing entries of x in a The returned insertion point ip partitions the array a into two slices such that all elem x for elem in a lo ip is true for the left slice and all elem x for elem in a ip hi is true for the right slice Changed in version 3 10 Added the key parameter bisect insort_left a x lo 0 hi len a key None Insert x in a in sorted order This function first runs bisect_left to locate an insertion point Next it runs the insert method on a to insert x at the appropriate position to maintain sort order To support inserting records in a table the key function if any is applied to x for the search step but not for the insertion step Keep in mind that the O log n search is dominated by the slow O n insertion step Changed in version 3 10 Added the key parameter bisect insort_right a x lo 0 hi len a key None bisect insort a x lo 0 hi len a key None Similar to insort_left but inserting x in a after any existing entries of x This function first runs bisect_right to locate an insertion point Next it runs the insert method on a to insert x at the appropriate position to maintain sort order To support inserting records in a table the key function if any is applied to x for the search step but not for the insertion step Keep in mind that the O log n search is dominated by the slow O n insertion step Changed in version 3 10 Added the key parameter Performance Notes When writing time sensitive code using bisect and insort keep these thoughts in mind Bisection is effective for searching ranges of values For locating specific values dictionaries are more performant The insort functions are O n because the logarithmic search step is dominated by the linear time insertion step The search functions are stateless and discard key function results after they are used Consequently if the search functions are used in a loop the key function may be called again and again on the same array elements If the key function isn t fast consider wrapping it with functools cache to avoid duplicate computations Alternatively consider searching an array of precomputed keys to locate the insertion point as shown in the examples section below See a,en
423,lso Sorted Collections is a high performance module that uses bisect to managed sorted collections of data The SortedCollection recipe uses bisect to build a full featured collection class with straight forward search methods and support for a key function The keys are precomputed to save unnecessary calls to the key function during searches Searching Sorted Lists The above bisect functions are useful for finding insertion points but can be tricky or awkward to use for common searching tasks The following five functions show how to transform them into the standard lookups for sorted lists def index a x Locate the leftmost value exactly equal to x i bisect_left a x if i len a and a i x return i raise ValueError def find_lt a x Find rightmost value less than x i bisect_left a x if i return a i 1 raise ValueError def find_le a x Find rightmost value less than or equal to x i bisect_right a x if i return a i 1 raise ValueError def find_gt a x Find leftmost value greater than x i bisect_right a x if i len a return a i raise ValueError def find_ge a x Find leftmost item greater than or equal to x i bisect_left a x if i len a return a i raise ValueError Examples The bisect function can be useful for numeric table lookups This example uses bisect to look up a letter grade for an exam score say based on a set of ordered numeric breakpoints 90 and up is an A 80 to 89 is a B and so on def grade score breakpoints 60 70 80 90 grades FDCBA i bisect breakpoints score return grades i grade score for score in 33 99 77 70 89 90 100 F A C C B A A The bisect and insort functions also work with lists of tuples The key argument can serve to extract the field used for ordering records in a table from collections import namedtuple from operator import attrgetter from bisect import bisect insort from pprint import pprint Movie namedtuple Movie name released director movies Movie Jaws 1975 Spielberg Movie Titanic 1997 Cameron Movie The Birds 1963 Hitchcock Movie Aliens 1986 Cameron Find the first movie released after 1960 by_year attrgetter released movies sort key by_year movies bisect movies 1960 key by_year Movie name The Birds released 1963 director Hitchcock Insert a movie while maintaining sort order romance Movie Love Story 1970 Hiller insort movies romance key by_year pprint movies Movie name The Birds released 1963 director Hitchcock Movie name Love Story released 1970 director Hiller Movie name Jaws released 1975 director Spielberg Movie name Aliens released 1986 director Cameron Movie name Titanic released 1997 director Cameron If the key function is expensive it is possible to avoid repeated function calls by searching a list of precomputed keys to find the index of a record data red 5 blue 1 yellow 8 black 0 data sort key lambda r r 1 Or use operator itemgetter 1 keys r 1 for r in data Precompute a list of keys data bisect_left keys 0 black 0 data bisect_left keys 1 blue 1 data bisect_left keys 5 red 5 data bisect_left keys 8 yellow 8,en
424,Extending The main direction for asyncio extending is writing custom event loop classes Asyncio has helpers that could be used to simplify this task Note Third parties should reuse existing asyncio code with caution a new Python version is free to break backward compatibility in internal part of API Writing a Custom Event Loop asyncio AbstractEventLoop declares very many methods Implementing all them from scratch is a tedious job A loop can get many common methods implementation for free by inheriting from asyncio BaseEventLoop In turn the successor should implement a bunch of private methods declared but not implemented in asyncio BaseEventLoop For example loop create_connection checks arguments resolves DNS addresses and calls loop _make_socket_transport that should be implemented by inherited class The _make_socket_transport method is not documented and is considered as an internal API Future and Task private constructors asyncio Future and asyncio Task should be never created directly please use corresponding loop create_future and loop create_task or asyncio create_task factories instead However third party event loops may reuse built in future and task implementations for the sake of getting a complex and highly optimized code for free For this purpose the following private constructors are listed Future __init__ loop None Create a built in future instance loop is an optional event loop instance Task __init__ coro loop None name None context None Create a built in task instance loop is an optional event loop instance The rest of arguments are described in loop create_task description Changed in version 3 11 context argument is added Task lifetime support A third party task implementation should call the following functions to keep a task visible by asyncio all_tasks and asyncio current_task asyncio _register_task task Register a new task as managed by asyncio Call the function from a task constructor asyncio _unregister_task task Unregister a task from asyncio internal structures The function should be called when a task is about to finish asyncio _enter_task loop task Switch the current task to the task argument Call the function just before executing a portion of embedded coroutine coroutine send or coroutine throw asyncio _leave_task loop task Switch the current task back from task to None Call the function just after coroutine send or coroutine throw execution,en
425,Debugging and Profiling These libraries help you with Python development the debugger enables you to step through code analyze stack frames and set breakpoints etc and the profilers run code and give you a detailed breakdown of execution times allowing you to identify bottlenecks in your programs Auditing events provide visibility into runtime behaviors that would otherwise require intrusive debugging or patching Audit events table bdb Debugger framework faulthandler Dump the Python traceback Dumping the traceback Fault handler state Dumping the tracebacks after a timeout Dumping the traceback on a user signal Issue with file descriptors Example pdb The Python Debugger Debugger Commands The Python Profilers Introduction to the profilers Instant User s Manual profile and cProfile Module Reference The Stats Class What Is Deterministic Profiling Limitations Calibration Using a custom timer timeit Measure execution time of small code snippets Basic Examples Python Interface Command Line Interface Examples trace Trace or track Python statement execution Command Line Usage Main options Modifiers Filters Programmatic Interface tracemalloc Trace memory allocations Examples Display the top 10 Compute differences Get the traceback of a memory block Pretty top Record the current and peak size of all traced memory blocks API Functions DomainFilter Filter Frame Snapshot Statistic StatisticDiff Trace Traceback,en
426,string Common string operations Source code Lib string py See also Text Sequence Type str String Methods String constants The constants defined in this module are string ascii_letters The concatenation of the ascii_lowercase and ascii_uppercase constants described below This value is not locale dependent string ascii_lowercase The lowercase letters abcdefghijklmnopqrstuvwxyz This value is not locale dependent and will not change string ascii_uppercase The uppercase letters ABCDEFGHIJKLMNOPQRSTUVWXYZ This value is not locale dependent and will not change string digits The string 0123456789 string hexdigits The string 0123456789abcdefABCDEF string octdigits The string 01234567 string punctuation String of ASCII characters which are considered punctuation characters in the C locale _ string printable String of ASCII characters which are considered printable This is a combination of digits ascii_letters punctuation and whitespace string whitespace A string containing all ASCII characters that are considered whitespace This includes the characters space tab linefeed return formfeed and vertical tab Custom String Formatting The built in string class provides the ability to do complex variable substitutions and value formatting via the format method described in PEP 3101 The Formatter class in the string module allows you to create and customize your own string formatting behaviors using the same implementation as the built in format method class string Formatter The Formatter class has the following public methods format format_string args kwargs The primary API method It takes a format string and an arbitrary set of positional and keyword arguments It is just a wrapper that calls vformat Changed in version 3 7 A format string argument is now positional only vformat format_string args kwargs This function does the actual work of formatting It is exposed as a separate function for cases where you want to pass in a predefined dictionary of arguments rather than unpacking and repacking the dictionary as individual arguments using the args and kwargs syntax vformat does the work of breaking up the format string into character data and replacement fields It calls the various methods described below In addition the Formatter defines a number of methods that are intended to be replaced by subclasses parse format_string Loop over the format_string and return an iterable of tuples literal_text field_name format_spec conversion This is used by vformat to break the string into either literal text or replacement fields The values in the tuple conceptually represent a span of literal text followed by a single replacement field If there is no literal text which can happen if two replacement fields occur consecutively then literal_text will be a zero length string If there is no replacement field then the values of field_name format_spec and conversion will be None get_field field_name args kwargs Given field_name as returned by parse see above convert it to an object to be formatted Returns a tuple obj used_key The default version takes strings of the form defined in PEP 3101 such as 0 name or label title args and kwargs are as passed in to vformat The return value used_key has the same meaning as the key parameter to get_value get_value key args kwargs Retrieve a given field value The key argument will be either an integer or a string If it is an integer it represents the index of the positional argument in args if it is a string then it represents a named argument in kwargs The args parameter is set to the list of positional arguments to vformat and the kwargs parameter is set to the dictionary of keyword arguments For compound field names these functions are only called for the first component of the field name subsequent components are handled through normal attribute and indexing operations So for example the field expression 0 name would cause get_value to be called with a key argument of 0 The name attribute will be looked up after get_value returns by calling the built in getattr function If the index or keyword refers to an item th,en
427,at does not exist then an IndexError or KeyError should be raised check_unused_args used_args args kwargs Implement checking for unused arguments if desired The arguments to this function is the set of all argument keys that were actually referred to in the format string integers for positional arguments and strings for named arguments and a reference to the args and kwargs that was passed to vformat The set of unused args can be calculated from these parameters check_unused_args is assumed to raise an exception if the check fails format_field value format_spec format_field simply calls the global format built in The method is provided so that subclasses can override it convert_field value conversion Converts the value returned by get_field given a conversion type as in the tuple returned by the parse method The default version understands s str r repr and a ascii conversion types Format String Syntax The str format method and the Formatter class share the same syntax for format strings although in the case of Formatter subclasses can define their own format string syntax The syntax is related to that of formatted string literals but it is less sophisticated and in particular does not support arbitrary expressions Format strings contain replacement fields surrounded by curly braces Anything that is not contained in braces is considered literal text which is copied unchanged to the output If you need to include a brace character in the literal text it can be escaped by doubling and The grammar for a replacement field is as follows replacement_field field_name conversion format_spec field_name arg_name attribute_name element_index arg_name identifier digit attribute_name identifier element_index digit index_string index_string any source character except conversion r s a format_spec format spec format_spec In less formal terms the replacement field can start with a field_name that specifies the object whose value is to be formatted and inserted into the output instead of the replacement field The field_name is optionally followed by a conversion field which is preceded by an exclamation point and a format_spec which is preceded by a colon These specify a non default format for the replacement value See also the Format Specification Mini Language section The field_name itself begins with an arg_name that is either a number or a keyword If it s a number it refers to a positional argument and if it s a keyword it refers to a named keyword argument An arg_name is treated as a number if a call to str isdecimal on the string would return true If the numerical arg_names in a format string are 0 1 2 in sequence they can all be omitted not just some and the numbers 0 1 2 will be automatically inserted in that order Because arg_name is not quote delimited it is not possible to specify arbitrary dictionary keys e g the strings 10 or within a format string The arg_name can be followed by any number of index or attribute expressions An expression of the form name selects the named attribute using getattr while an expression of the form index does an index lookup using __getitem__ Changed in version 3 1 The positional argument specifiers can be omitted for str format so format a b is equivalent to 0 1 format a b Changed in version 3 4 The positional argument specifiers can be omitted for Formatter Some simple format string examples First thou shalt count to 0 References first positional argument Bring me a Implicitly references the first positional argument From to Same as From 0 to 1 My quest is name References keyword argument name Weight in tons 0 weight weight attribute of first positional arg Units destroyed players 0 First element of keyword argument players The conversion field causes a type coercion before formatting Normally the job of formatting a value is done by the __format__ method of the value itself However in some cases it is desirable to force a type to be formatted as a string overriding its own definition of formatting By converting the value to a string before calling __format__ the normal formatting logic is bypass,en
428,ed Three conversion flags are currently supported s which calls str on the value r which calls repr and a which calls ascii Some examples Harold s a clever 0 s Calls str on the argument first Bring out the holy name r Calls repr on the argument first More a Calls ascii on the argument first The format_spec field contains a specification of how the value should be presented including such details as field width alignment padding decimal precision and so on Each value type can define its own formatting mini language or interpretation of the format_spec Most built in types support a common formatting mini language which is described in the next section A format_spec field can also include nested replacement fields within it These nested replacement fields may contain a field name conversion flag and format specification but deeper nesting is not allowed The replacement fields within the format_spec are substituted before the format_spec string is interpreted This allows the formatting of a value to be dynamically specified See the Format examples section for some examples Format Specification Mini Language Format specifications are used within replacement fields contained within a format string to define how individual values are presented see Format String Syntax and f strings They can also be passed directly to the built in format function Each formattable type may define how the format specification is to be interpreted Most built in types implement the following options for format specifications although some of the formatting options are only supported by the numeric types A general convention is that an empty format specification produces the same result as if you had called str on the value A non empty format specification typically modifies the result The general form of a standard format specifier is format_spec fill align sign z 0 width grouping_option precision type fill any character align sign width digit grouping_option _ precision digit type b c d e E f F g G n o s x X If a valid align value is specified it can be preceded by a fill character that can be any character and defaults to a space if omitted It is not possible to use a literal curly brace or as the fill character in a formatted string literal or when using the str format method However it is possible to insert a curly brace with a nested replacement field This limitation doesn t affect the format function The meaning of the various alignment options is as follows Option Meaning Forces the field to be left aligned within the available space this is the default for most objects Forces the field to be right aligned within the available space this is the default for numbers Forces the padding to be placed after the sign if any but before the digits This is used for printing fields in the form 000000120 This alignment option is only valid for numeric types It becomes the default for numbers when 0 immediately precedes the field width Forces the field to be centered within the available space Note that unless a minimum field width is defined the field width will always be the same size as the data to fill it so that the alignment option has no meaning in this case The sign option is only valid for number types and can be one of the following Option Meaning indicates that a sign should be used for both positive as well as negative numbers indicates that a sign should be used only for negative numbers this is the default behavior space indicates that a leading space should be used on positive numbers and a minus sign on negative numbers The z option coerces negative zero floating point values to positive zero after rounding to the format precision This option is only valid for floating point presentation types Changed in version 3 11 Added the z option see also PEP 682 The option causes the alternate form to be used for the conversion The alternate form is defined differently for different types This option is only valid for integer float and complex types For integers when binary octal or hexadecimal output is used this option adds the respective prefix 0,en
429,b 0o 0x or 0X to the output value For float and complex the alternate form causes the result of the conversion to always contain a decimal point character even if no digits follow it Normally a decimal point character appears in the result of these conversions only if a digit follows it In addition for g and G conversions trailing zeros are not removed from the result The option signals the use of a comma for a thousands separator For a locale aware separator use the n integer presentation type instead Changed in version 3 1 Added the option see also PEP 378 The _ option signals the use of an underscore for a thousands separator for floating point presentation types and for integer presentation type d For integer presentation types b o x and X underscores will be inserted every 4 digits For other presentation types specifying this option is an error Changed in version 3 6 Added the _ option see also PEP 515 width is a decimal integer defining the minimum total field width including any prefixes separators and other formatting characters If not specified then the field width will be determined by the content When no explicit alignment is given preceding the width field by a zero 0 character enables sign aware zero padding for numeric types This is equivalent to a fill character of 0 with an alignment type of Changed in version 3 10 Preceding the width field by 0 no longer affects the default alignment for strings The precision is a decimal integer indicating how many digits should be displayed after the decimal point for presentation types f and F or before and after the decimal point for presentation types g or G For string presentation types the field indicates the maximum field size in other words how many characters will be used from the field content The precision is not allowed for integer presentation types Finally the type determines how the data should be presented The available string presentation types are Type Meaning s String format This is the default type for strings and may be omitted None The same as s The available integer presentation types are Type Meaning b Binary format Outputs the number in base 2 c Character Converts the integer to the corresponding unicode character before printing d Decimal Integer Outputs the number in base 10 o Octal format Outputs the number in base 8 x Hex format Outputs the number in base 16 using lower case letters for the digits above 9 X Hex format Outputs the number in base 16 using upper case letters for the digits above 9 In case is specified the prefix 0x will be upper cased to 0X as well n Number This is the same as d except that it uses the current locale setting to insert the appropriate number separator characters None The same as d In addition to the above presentation types integers can be formatted with the floating point presentation types listed below except n and None When doing so float is used to convert the integer to a floating point number before formatting The available presentation types for float and Decimal values are Type Meaning e Scientific notation For a given precision p formats the number in scientific notation with the letter e separating the coefficient from the exponent The coefficient has one digit before and p digits after the decimal point for a total of p 1 significant digits With no precision given uses a precision of 6 digits after the decimal point for float and shows all coefficient digits for Decimal If no digits follow the decimal point the decimal point is also removed unless the option is used E Scientific notation Same as e except it uses an upper case E as the separator character f Fixed point notation For a given precision p formats the number as a decimal number with exactly p digits following the decimal point With no precision given uses a precision of 6 digits after the decimal point for float and uses a precision large enough to show all coefficient digits for Decimal If no digits follow the decimal point the decimal point is also removed unless the option is used F Fixed point notation Same as f but converts nan to NAN ,en
430,and inf to INF g General format For a given precision p 1 this rounds the number to p significant digits and then formats the result in either fixed point format or in scientific notation depending on its magnitude A precision of 0 is treated as equivalent to a precision of 1 The precise rules are as follows suppose that the result formatted with presentation type e and precision p 1 would have exponent exp Then if m exp p where m is 4 for floats and 6 for Decimals the number is formatted with presentation type f and precision p 1 exp Otherwise the number is formatted with presentation type e and precision p 1 In both cases insignificant trailing zeros are removed from the significand and the decimal point is also removed if there are no remaining digits following it unless the option is used With no precision given uses a precision of 6 significant digits for float For Decimal the coefficient of the result is formed from the coefficient digits of the value scientific notation is used for values smaller than 1e 6 in absolute value and values where the place value of the least significant digit is larger than 1 and fixed point notation is used otherwise Positive and negative infinity positive and negative zero and nans are formatted as inf inf 0 0 and nan respectively regardless of the precision G General format Same as g except switches to E if the number gets too large The representations of infinity and NaN are uppercased too n Number This is the same as g except that it uses the current locale setting to insert the appropriate number separator characters Percentage Multiplies the number by 100 and displays in fixed f format followed by a percent sign None For float this is the same as g except that when fixed point notation is used to format the result it always includes at least one digit past the decimal point The precision used is as large as needed to represent the given value faithfully For Decimal this is the same as either g or G depending on the value of context capitals for the current decimal context The overall effect is to match the output of str as altered by the other format modifiers Format examples This section contains examples of the str format syntax and comparison with the old formatting In most of the cases the syntax is similar to the old formatting with the addition of the and with used instead of For example 03 2f can be translated to 03 2f The new format syntax also supports new and different options shown in the following examples Accessing arguments by position 0 1 2 format a b c a b c format a b c 3 1 only a b c 2 1 0 format a b c c b a 2 1 0 format abc unpacking argument sequence c b a 0 1 0 format abra cad arguments indices can be repeated abracadabra Accessing arguments by name Coordinates latitude longitude format latitude 37 24N longitude 115 81W Coordinates 37 24N 115 81W coord latitude 37 24N longitude 115 81W Coordinates latitude longitude format coord Coordinates 37 24N 115 81W Accessing arguments attributes c 3 5j The complex number 0 is formed from the real part 0 real and the imaginary part 0 imag format c The complex number 3 5j is formed from the real part 3 0 and the imaginary part 5 0 class Point def __init__ self x y self x self y x y def __str__ self return Point self x self y format self self str Point 4 2 Point 4 2 Accessing arguments items coord 3 5 X 0 0 Y 0 1 format coord X 3 Y 5 Replacing s and r repr shows quotes r str doesn t s format test1 test2 repr shows quotes test1 str doesn t test2 Aligning the text and specifying a width 30 format left aligned left aligned 30 format right aligned right aligned 30 format centered centered 30 format centered use as a fill char centered Replacing f f and f and specifying a sign f f format 3 14 3 14 show it always 3 140000 3 140000 f f format 3 14 3 14 show a space for positive numbers 3 140000 3 140000 f f format 3 14 3 14 show only the minus same as f f 3 140000 3 140000 Replacing x and o and converting the value to different bases format also supports binary numbers int 0 d hex 0 x oct 0 o bin 0 b format 42 int 42 hex 2a oct ,en
431,52 bin 101010 with 0x 0o or 0b as prefix int 0 d hex 0 x oct 0 o bin 0 b format 42 int 42 hex 0x2a oct 0o52 bin 0b101010 Using the comma as a thousands separator format 1234567890 1 234 567 890 Expressing a percentage points 19 total 22 Correct answers 2 format points total Correct answers 86 36 Using type specific formatting import datetime d datetime datetime 2010 7 4 12 15 58 Y m d H M S format d 2010 07 04 12 15 58 Nesting arguments and more complex examples for align text in zip left center right 0 fill align 16 format text fill align align align left center right octets 192 168 0 1 02X 02X 02X 02X format octets C0A80001 int _ 16 3232235521 width 5 for num in range 5 12 for base in dXob print 0 width base format num base base width width end print 5 5 5 101 6 6 6 110 7 7 7 111 8 8 10 1000 9 9 11 1001 10 A 12 1010 11 B 13 1011 Template strings Template strings provide simpler string substitutions as described in PEP 292 A primary use case for template strings is for internationalization i18n since in that context the simpler syntax and functionality makes it easier to translate than other built in string formatting facilities in Python As an example of a library built on template strings for i18n see the flufl i18n package Template strings support based substitutions using the following rules is an escape it is replaced with a single identifier names a substitution placeholder matching a mapping key of identifier By default identifier is restricted to any case insensitive ASCII alphanumeric string including underscores that starts with an underscore or ASCII letter The first non identifier character after the character terminates this placeholder specification identifier is equivalent to identifier It is required when valid identifier characters follow the placeholder but are not part of the placeholder such as noun ification Any other appearance of in the string will result in a ValueError being raised The string module provides a Template class that implements these rules The methods of Template are class string Template template The constructor takes a single argument which is the template string substitute mapping kwds Performs the template substitution returning a new string mapping is any dictionary like object with keys that match the placeholders in the template Alternatively you can provide keyword arguments where the keywords are the placeholders When both mapping and kwds are given and there are duplicates the placeholders from kwds take precedence safe_substitute mapping kwds Like substitute except that if placeholders are missing from mapping and kwds instead of raising a KeyError exception the original placeholder will appear in the resulting string intact Also unlike with substitute any other appearances of the will simply return instead of raising ValueError While other exceptions may still occur this method is called safe because it always tries to return a usable string instead of raising an exception In another sense safe_substitute may be anything other than safe since it will silently ignore malformed templates containing dangling delimiters unmatched braces or placeholders that are not valid Python identifiers is_valid Returns false if the template has invalid placeholders that will cause substitute to raise ValueError New in version 3 11 get_identifiers Returns a list of the valid identifiers in the template in the order they first appear ignoring any invalid identifiers New in version 3 11 Template instances also provide one public data attribute template This is the object passed to the constructor s template argument In general you shouldn t change it but read only access is not enforced Here is an example of how to use a Template from string import Template s Template who likes what s substitute who tim what kung pao tim likes kung pao d dict who tim Template Give who 100 substitute d Traceback most recent call last ValueError Invalid placeholder in string line 1 col 11 Template who likes what substitute d Traceback most recent call last KeyError what Template who likes what safe_substitute,en
432, d tim likes what Advanced usage you can derive subclasses of Template to customize the placeholder syntax delimiter character or the entire regular expression used to parse template strings To do this you can override these class attributes delimiter This is the literal string describing a placeholder introducing delimiter The default value is Note that this should not be a regular expression as the implementation will call re escape on this string as needed Note further that you cannot change the delimiter after class creation i e a different delimiter must be set in the subclass s class namespace idpattern This is the regular expression describing the pattern for non braced placeholders The default value is the regular expression a _a z _a z0 9 If this is given and braceidpattern is None this pattern will also apply to braced placeholders Note Since default flags is re IGNORECASE pattern a z can match with some non ASCII characters That s why we use the local a flag here Changed in version 3 7 braceidpattern can be used to define separate patterns used inside and outside the braces braceidpattern This is like idpattern but describes the pattern for braced placeholders Defaults to None which means to fall back to idpattern i e the same pattern is used both inside and outside braces If given this allows you to define different patterns for braced and unbraced placeholders New in version 3 7 flags The regular expression flags that will be applied when compiling the regular expression used for recognizing substitutions The default value is re IGNORECASE Note that re VERBOSE will always be added to the flags so custom idpattern s must follow conventions for verbose regular expressions New in version 3 2 Alternatively you can provide the entire regular expression pattern by overriding the class attribute pattern If you do this the value must be a regular expression object with four named capturing groups The capturing groups correspond to the rules given above along with the invalid placeholder rule escaped This group matches the escape sequence e g in the default pattern named This group matches the unbraced placeholder name it should not include the delimiter in capturing group braced This group matches the brace enclosed placeholder name it should not include either the delimiter or braces in the capturing group invalid This group matches any other delimiter pattern usually a single delimiter and it should appear last in the regular expression The methods on this class will raise ValueError if the pattern matches the template without one of these named groups matching Helper functions string capwords s sep None Split the argument into words using str split capitalize each word using str capitalize and join the capitalized words using str join If the optional second argument sep is absent or None runs of whitespace characters are replaced by a single space and leading and trailing whitespace are removed otherwise sep is used to split and join the words,en
433,audioop Manipulate raw audio data Deprecated since version 3 11 will be removed in version 3 13 The audioop module is deprecated see PEP 594 for details The audioop module contains some useful operations on sound fragments It operates on sound fragments consisting of signed integer samples 8 16 24 or 32 bits wide stored in bytes like objects All scalar items are integers unless specified otherwise Changed in version 3 4 Support for 24 bit samples was added All functions now accept any bytes like object String input now results in an immediate error This module provides support for a LAW u LAW and Intel DVI ADPCM encodings A few of the more complicated operations only take 16 bit samples otherwise the sample size in bytes is always a parameter of the operation The module defines the following variables and functions exception audioop error This exception is raised on all errors such as unknown number of bytes per sample etc audioop add fragment1 fragment2 width Return a fragment which is the addition of the two samples passed as parameters width is the sample width in bytes either 1 2 3 or 4 Both fragments should have the same length Samples are truncated in case of overflow audioop adpcm2lin adpcmfragment width state Decode an Intel DVI ADPCM coded fragment to a linear fragment See the description of lin2adpcm for details on ADPCM coding Return a tuple sample newstate where the sample has the width specified in width audioop alaw2lin fragment width Convert sound fragments in a LAW encoding to linearly encoded sound fragments a LAW encoding always uses 8 bits samples so width refers only to the sample width of the output fragment here audioop avg fragment width Return the average over all samples in the fragment audioop avgpp fragment width Return the average peak peak value over all samples in the fragment No filtering is done so the usefulness of this routine is questionable audioop bias fragment width bias Return a fragment that is the original fragment with a bias added to each sample Samples wrap around in case of overflow audioop byteswap fragment width Byteswap all samples in a fragment and returns the modified fragment Converts big endian samples to little endian and vice versa New in version 3 4 audioop cross fragment width Return the number of zero crossings in the fragment passed as an argument audioop findfactor fragment reference Return a factor F such that rms add fragment mul reference F is minimal i e return the factor with which you should multiply reference to make it match as well as possible to fragment The fragments should both contain 2 byte samples The time taken by this routine is proportional to len fragment audioop findfit fragment reference Try to match reference as well as possible to a portion of fragment which should be the longer fragment This is conceptually done by taking slices out of fragment using findfactor to compute the best match and minimizing the result The fragments should both contain 2 byte samples Return a tuple offset factor where offset is the integer offset into fragment where the optimal match started and factor is the floating point factor as per findfactor audioop findmax fragment length Search fragment for a slice of length length samples not bytes with maximum energy i e return i for which rms fragment i 2 i length 2 is maximal The fragments should both contain 2 byte samples The routine takes time proportional to len fragment audioop getsample fragment width index Return the value of sample index from the fragment audioop lin2adpcm fragment width state Convert samples to 4 bit Intel DVI ADPCM encoding ADPCM coding is an adaptive coding scheme whereby each 4 bit number is the difference between one sample and the next divided by a varying step The Intel DVI ADPCM algorithm has been selected for use by the IMA so it may well become a standard state is a tuple containing the state of the coder The coder returns a tuple adpcmfrag newstate and the newstate should be passed to the next call of lin2adpcm In the initial call None can be passed as the state adpcmfrag is the AD,en
434,PCM coded fragment packed 2 4 bit values per byte audioop lin2alaw fragment width Convert samples in the audio fragment to a LAW encoding and return this as a bytes object a LAW is an audio encoding format whereby you get a dynamic range of about 13 bits using only 8 bit samples It is used by the Sun audio hardware among others audioop lin2lin fragment width newwidth Convert samples between 1 2 3 and 4 byte formats Note In some audio formats such as WAV files 16 24 and 32 bit samples are signed but 8 bit samples are unsigned So when converting to 8 bit wide samples for these formats you need to also add 128 to the result new_frames audioop lin2lin frames old_width 1 new_frames audioop bias new_frames 1 128 The same in reverse has to be applied when converting from 8 to 16 24 or 32 bit width samples audioop lin2ulaw fragment width Convert samples in the audio fragment to u LAW encoding and return this as a bytes object u LAW is an audio encoding format whereby you get a dynamic range of about 14 bits using only 8 bit samples It is used by the Sun audio hardware among others audioop max fragment width Return the maximum of the absolute value of all samples in a fragment audioop maxpp fragment width Return the maximum peak peak value in the sound fragment audioop minmax fragment width Return a tuple consisting of the minimum and maximum values of all samples in the sound fragment audioop mul fragment width factor Return a fragment that has all samples in the original fragment multiplied by the floating point value factor Samples are truncated in case of overflow audioop ratecv fragment width nchannels inrate outrate state weightA weightB Convert the frame rate of the input fragment state is a tuple containing the state of the converter The converter returns a tuple newfragment newstate and newstate should be passed to the next call of ratecv The initial call should pass None as the state The weightA and weightB arguments are parameters for a simple digital filter and default to 1 and 0 respectively audioop reverse fragment width Reverse the samples in a fragment and returns the modified fragment audioop rms fragment width Return the root mean square of the fragment i e sqrt sum S_i 2 n This is a measure of the power in an audio signal audioop tomono fragment width lfactor rfactor Convert a stereo fragment to a mono fragment The left channel is multiplied by lfactor and the right channel by rfactor before adding the two channels to give a mono signal audioop tostereo fragment width lfactor rfactor Generate a stereo fragment from a mono fragment Each pair of samples in the stereo fragment are computed from the mono sample whereby left channel samples are multiplied by lfactor and right channel samples by rfactor audioop ulaw2lin fragment width Convert sound fragments in u LAW encoding to linearly encoded sound fragments u LAW encoding always uses 8 bits samples so width refers only to the sample width of the output fragment here Note that operations such as mul or max make no distinction between mono and stereo fragments i e all samples are treated equal If this is a problem the stereo fragment should be split into two mono fragments first and recombined later Here is an example of how to do that def mul_stereo sample width lfactor rfactor lsample audioop tomono sample width 1 0 rsample audioop tomono sample width 0 1 lsample audioop mul lsample width lfactor rsample audioop mul rsample width rfactor lsample audioop tostereo lsample width 1 0 rsample audioop tostereo rsample width 0 1 return audioop add lsample rsample width If you use the ADPCM coder to build network packets and you want your protocol to be stateless i e to be able to tolerate packet loss you should not only transmit the data but also the state Note that you should send the initial state the one you passed to lin2adpcm along to the decoder not the final state as returned by the coder If you want to use struct Struct to store the state in binary you can code the first element the predicted value in 16 bits and the second the delta index in 8 The ADPCM coders ,en
435,have never been tried against other ADPCM coders only against themselves It could well be that I misinterpreted the standards in which case they will not be interoperable with the respective standards The find routines might look a bit funny at first sight They are primarily meant to do echo cancellation A reasonably fast way to do this is to pick the most energetic piece of the output sample locate that in the input sample and subtract the whole output sample from the input sample def echocancel outputdata inputdata pos audioop findmax outputdata 800 one tenth second out_test outputdata pos 2 in_test inputdata pos 2 ipos factor audioop findfit in_test out_test Optional for better cancellation factor audioop findfactor in_test ipos 2 ipos 2 len out_test out_test prefill 0 pos ipos 2 postfill 0 len inputdata len prefill len outputdata outputdata prefill audioop mul outputdata 2 factor postfill return audioop add inputdata outputdata 2,en
436,Type Objects Perhaps one of the most important structures of the Python object system is the structure that defines a new type the PyTypeObject structure Type objects can be handled using any of the PyObject_ or PyType_ functions but do not offer much that s interesting to most Python applications These objects are fundamental to how objects behave so they are very important to the interpreter itself and to any extension module that implements new types Type objects are fairly large compared to most of the standard types The reason for the size is that each type object stores a large number of values mostly C function pointers each of which implements a small part of the type s functionality The fields of the type object are examined in detail in this section The fields will be described in the order in which they occur in the structure In addition to the following quick reference the Examples section provides at a glance insight into the meaning and use of PyTypeObject Quick Reference tp slots PyTypeObject Slot Type special Info 2 1 methods attrs O T D I R tp_name const char __name__ X X tp_basicsize Py_ssize_t X X X tp_itemsize Py_ssize_t X X tp_dealloc destructor X X X tp_vectorcall_of Py_ssize_t X X fset tp_getattr getattrfunc __getattribute__ G __getattr__ tp_setattr setattrfunc __setattr__ G __delattr__ tp_as_async PyAsyncMethods sub slots tp_repr reprfunc __repr__ X X X tp_as_number PyNumberMethods sub slots tp_as_sequence PySequenceMethod sub slots s tp_as_mapping PyMappingMethods sub slots tp_hash hashfunc __hash__ X G tp_call ternaryfunc __call__ X X tp_str reprfunc __str__ X X tp_getattro getattrofunc __getattribute__ X X G __getattr__ tp_setattro setattrofunc __setattr__ X X G __delattr__ tp_as_buffer PyBufferProcs tp_flags unsigned long X X tp_doc const char __doc__ X X tp_traverse traverseproc X G tp_clear inquiry X G tp_richcompare richcmpfunc __lt__ __le__ X G __eq__ __ne__ __gt__ __ge__ tp_weaklistoffs Py_ssize_t X et tp_iter getiterfunc __iter__ X tp_iternext iternextfunc __next__ X tp_methods PyMethodDef X X tp_members PyMemberDef X tp_getset PyGetSetDef X X tp_base PyTypeObject __base__ X tp_dict PyObject __dict__ tp_descr_get descrgetfunc __get__ X tp_descr_set descrsetfunc __set__ X __delete__ tp_dictoffset Py_ssize_t X tp_init initproc __init__ X X X tp_alloc allocfunc X tp_new newfunc __new__ X X tp_free freefunc X X tp_is_gc inquiry X X tp_bases PyObject __bases__ tp_mro PyObject __mro__ tp_cache PyObject tp_subclasses void __subclasses__ tp_weaklist PyObject tp_del destructor tp_version_tag unsigned int tp_finalize destructor __del__ X tp_vectorcall vectorcallfunc tp_watched unsigned char 1 A slot name in parentheses indicates it is effectively deprecated Names in angle brackets should be initially set to NULL and treated as read only Names in square brackets are for internal use only R as a prefix means the field is required must be non NULL 2 Columns O set on PyBaseObject_Type T set on PyType_Type D default if slot is set to NULL X PyType_Ready sets this value if it is NULL PyType_Ready always sets this value it should be NULL PyType_Ready may set this value depending on other slots Also see the inheritance column I I inheritance X type slot is inherited via PyType_Ready if defined with a NULL value the slots of the sub struct are inherited individually G inherited but only in combination with other slots see the slot s description it s complicated see the slot s description Note that some slots are effectively inherited through the normal attribute lookup chain sub slots Slot Type special methods am_await unaryfunc __await__ am_aiter unaryfunc __aiter__ am_anext unaryfunc __anext__ am_send sendfunc nb_add binaryfunc __add__ __radd__ nb_inplace_add binaryfunc __iadd__ nb_subtract binaryfunc __sub__ __rsub__ nb_inplace_subtract binaryfunc __isub__ nb_multiply binaryfunc __mul__ __rmul__ nb_inplace_multiply binaryfunc __imul__ nb_remainder binaryfunc __mod__ __rmod__ nb_inplace_remainder binaryfunc __imod__ nb_divmod binaryfunc __divmod__ __rdivmod__ nb_power ternaryfunc __pow__ __rpow__ nb_inpl,en
437,ace_power ternaryfunc __ipow__ nb_negative unaryfunc __neg__ nb_positive unaryfunc __pos__ nb_absolute unaryfunc __abs__ nb_bool inquiry __bool__ nb_invert unaryfunc __invert__ nb_lshift binaryfunc __lshift__ __rlshift__ nb_inplace_lshift binaryfunc __ilshift__ nb_rshift binaryfunc __rshift__ __rrshift__ nb_inplace_rshift binaryfunc __irshift__ nb_and binaryfunc __and__ __rand__ nb_inplace_and binaryfunc __iand__ nb_xor binaryfunc __xor__ __rxor__ nb_inplace_xor binaryfunc __ixor__ nb_or binaryfunc __or__ __ror__ nb_inplace_or binaryfunc __ior__ nb_int unaryfunc __int__ nb_reserved void nb_float unaryfunc __float__ nb_floor_divide binaryfunc __floordiv__ nb_inplace_floor_divide binaryfunc __ifloordiv __ nb_true_divide binaryfunc __truediv__ nb_inplace_true_divide binaryfunc __itruediv__ nb_index unaryfunc __index__ nb_matrix_multiply binaryfunc __matmul__ __rmatmul__ nb_inplace_matrix_multip binaryfunc __imatmul__ ly mp_length lenfunc __len__ mp_subscript binaryfunc __getitem__ mp_ass_subscript objobjargproc __setitem__ __delitem__ sq_length lenfunc __len__ sq_concat binaryfunc __add__ sq_repeat ssizeargfunc __mul__ sq_item ssizeargfunc __getitem__ sq_ass_item ssizeobjargproc __setitem__ __delitem__ sq_contains objobjproc __contains__ sq_inplace_concat binaryfunc __iadd__ sq_inplace_repeat ssizeargfunc __imul__ bf_getbuffer getbufferproc bf_releasebuffer releasebufferpr oc slot typedefs typedef Parameter Types Return Type allocfunc PyTypeObject Py_ssize_t PyObject destructor PyObject void freefunc void void traverseproc PyObject visitproc void int newfunc PyObject PyObject PyObject PyObject initproc PyObject PyObject int PyObject reprfunc PyObject PyObject getattrfunc PyObject const char PyObject setattrfunc PyObject const char int PyObject getattrofunc PyObject PyObject PyObject setattrofunc PyObject PyObject int PyObject descrgetfunc PyObject PyObject PyObject PyObject descrsetfunc PyObject PyObject int PyObject hashfunc PyObject Py_hash_t richcmpfunc PyObject PyObject int PyObject getiterfunc PyObject PyObject iternextfunc PyObject PyObject lenfunc PyObject Py_ssize_t getbufferproc PyObject Py_buffer int int releasebufferproc PyObject Py_buffer void inquiry PyObject int unaryfunc PyObject PyObject binaryfunc PyObject PyObject PyObject ternaryfunc PyObject PyObject PyObject PyObject ssizeargfunc PyObject Py_ssize_t PyObject ssizeobjargproc PyObject Py_ssize_t int PyObject objobjproc PyObject PyObject int objobjargproc PyObject PyObject int PyObject See Slot Type typedefs below for more detail PyTypeObject Definition The structure definition for PyTypeObject can be found in Include object h For convenience of reference this repeats the definition found there typedef struct _typeobject PyObject_VAR_HEAD const char tp_name For printing in format module name Py_ssize_t tp_basicsize tp_itemsize For allocation Methods to implement standard operations destructor tp_dealloc Py_ssize_t tp_vectorcall_offset getattrfunc tp_getattr setattrfunc tp_setattr PyAsyncMethods tp_as_async formerly known as tp_compare Python 2 or tp_reserved Python 3 reprfunc tp_repr Method suites for standard classes PyNumberMethods tp_as_number PySequenceMethods tp_as_sequence PyMappingMethods tp_as_mapping More standard operations here for binary compatibility hashfunc tp_hash ternaryfunc tp_call reprfunc tp_str getattrofunc tp_getattro setattrofunc tp_setattro Functions to access object as input output buffer PyBufferProcs tp_as_buffer Flags to define presence of optional expanded features unsigned long tp_flags const char tp_doc Documentation string Assigned meaning in release 2 0 call function for all accessible objects traverseproc tp_traverse delete references to contained objects inquiry tp_clear Assigned meaning in release 2 1 rich comparisons richcmpfunc tp_richcompare weak reference enabler Py_ssize_t tp_weaklistoffset Iterators getiterfunc tp_iter iternextfunc tp_iternext Attribute descriptor and subclassing stuff struct PyMethodDef tp_methods struct PyMemberDef tp_members struct PyGetSetDef tp_getset Strong reference on a heap type borrowed r,en
438,eference on a static type struct _typeobject tp_base PyObject tp_dict descrgetfunc tp_descr_get descrsetfunc tp_descr_set Py_ssize_t tp_dictoffset initproc tp_init allocfunc tp_alloc newfunc tp_new freefunc tp_free Low level free memory routine inquiry tp_is_gc For PyObject_IS_GC PyObject tp_bases PyObject tp_mro method resolution order PyObject tp_cache PyObject tp_subclasses PyObject tp_weaklist destructor tp_del Type attribute cache version tag Added in version 2 6 unsigned int tp_version_tag destructor tp_finalize vectorcallfunc tp_vectorcall bitset of which type watchers care about this type unsigned char tp_watched PyTypeObject PyObject Slots The type object structure extends the PyVarObject structure The ob_size field is used for dynamic types created by type_new usually called from a class statement Note that PyType_Type the metatype initializes tp_itemsize which means that its instances i e type objects must have the ob_size field Py_ssize_t PyObject ob_refcnt Part of the Stable ABI This is the type object s reference count initialized to 1 by the PyObject_HEAD_INIT macro Note that for statically allocated type objects the type s instances objects whose ob_type points back to the type do not count as references But for dynamically allocated type objects the instances do count as references Inheritance This field is not inherited by subtypes PyTypeObject PyObject ob_type Part of the Stable ABI This is the type s type in other words its metatype It is initialized by the argument to the PyObject_HEAD_INIT macro and its value should normally be PyType_Type However for dynamically loadable extension modules that must be usable on Windows at least the compiler complains that this is not a valid initializer Therefore the convention is to pass NULL to the PyObject_HEAD_INIT macro and to initialize this field explicitly at the start of the module s initialization function before doing anything else This is typically done like this Foo_Type ob_type PyType_Type This should be done before any instances of the type are created PyType_Ready checks if ob_type is NULL and if so initializes it to the ob_type field of the base class PyType_Ready will not change this field if it is non zero Inheritance This field is inherited by subtypes PyObject PyObject _ob_next PyObject PyObject _ob_prev These fields are only present when the macro Py_TRACE_REFS is defined see the configure with trace refs option Their initialization to NULL is taken care of by the PyObject_HEAD_INIT macro For statically allocated objects these fields always remain NULL For dynamically allocated objects these two fields are used to link the object into a doubly linked list of all live objects on the heap This could be used for various debugging purposes currently the only uses are the sys getobjects function and to print the objects that are still alive at the end of a run when the environment variable PYTHONDUMPREFS is set Inheritance These fields are not inherited by subtypes PyVarObject Slots Py_ssize_t PyVarObject ob_size Part of the Stable ABI For statically allocated type objects this should be initialized to zero For dynamically allocated type objects this field has a special internal meaning Inheritance This field is not inherited by subtypes PyTypeObject Slots Each slot has a section describing inheritance If PyType_Ready may set a value when the field is set to NULL then there will also be a Default section Note that many fields set on PyBaseObject_Type and PyType_Type effectively act as defaults const char PyTypeObject tp_name Pointer to a NUL terminated string containing the name of the type For types that are accessible as module globals the string should be the full module name followed by a dot followed by the type name for built in types it should be just the type name If the module is a submodule of a package the full package name is part of the full module name For example a type named T defined in module M in subpackage Q in package P should have the tp_name initializer P Q M T For dynamically allocated type objects this should just be the ty,en
439,pe name and the module name explicitly stored in the type dict as the value for key __module__ For statically allocated type objects the tp_name field should contain a dot Everything before the last dot is made accessible as the __module__ attribute and everything after the last dot is made accessible as the __name__ attribute If no dot is present the entire tp_name field is made accessible as the __name__ attribute and the __module__ attribute is undefined unless explicitly set in the dictionary as explained above This means your type will be impossible to pickle Additionally it will not be listed in module documentations created with pydoc This field must not be NULL It is the only required field in PyTypeObject other than potentially tp_itemsize Inheritance This field is not inherited by subtypes Py_ssize_t PyTypeObject tp_basicsize Py_ssize_t PyTypeObject tp_itemsize These fields allow calculating the size in bytes of instances of the type There are two kinds of types types with fixed length instances have a zero tp_itemsize field types with variable length instances have a non zero tp_itemsize field For a type with fixed length instances all instances have the same size given in tp_basicsize For a type with variable length instances the instances must have an ob_size field and the instance size is tp_basicsize plus N times tp_itemsize where N is the length of the object The value of N is typically stored in the instance s ob_size field There are exceptions for example ints use a negative ob_size to indicate a negative number and N is abs ob_size there Also the presence of an ob_size field in the instance layout doesn t mean that the instance structure is variable length for example the structure for the list type has fixed length instances yet those instances have a meaningful ob_size field The basic size includes the fields in the instance declared by the macro PyObject_HEAD or PyObject_VAR_HEAD whichever is used to declare the instance struct and this in turn includes the _ob_prev and _ob_next fields if they are present This means that the only correct way to get an initializer for the tp_basicsize is to use the sizeof operator on the struct used to declare the instance layout The basic size does not include the GC header size A note about alignment if the variable items require a particular alignment this should be taken care of by the value of tp_basicsize Example suppose a type implements an array of double tp_itemsize is sizeof double It is the programmer s responsibility that tp_basicsize is a multiple of sizeof double assuming this is the alignment requirement for double For any type with variable length instances this field must not be NULL Inheritance These fields are inherited separately by subtypes If the base type has a non zero tp_itemsize it is generally not safe to set tp_itemsize to a different non zero value in a subtype though this depends on the implementation of the base type destructor PyTypeObject tp_dealloc A pointer to the instance destructor function This function must be defined unless the type guarantees that its instances will never be deallocated as is the case for the singletons None and Ellipsis The function signature is void tp_dealloc PyObject self The destructor function is called by the Py_DECREF and Py_XDECREF macros when the new reference count is zero At this point the instance is still in existence but there are no references to it The destructor function should free all references which the instance owns free all memory buffers owned by the instance using the freeing function corresponding to the allocation function used to allocate the buffer and call the type s tp_free function If the type is not subtypable doesn t have the Py_TPFLAGS_BASETYPE flag bit set it is permissible to call the object deallocator directly instead of via tp_free The object deallocator should be the one used to allocate the instance this is normally PyObject_Del if the instance was allocated using PyObject_New or PyObject_NewVar or PyObject_GC_Del if the instance was allocated using PyObject_GC_New or,en
440, PyObject_GC_NewVar If the type supports garbage collection has the Py_TPFLAGS_HAVE_GC flag bit set the destructor should call PyObject_GC_UnTrack before clearing any member fields static void foo_dealloc foo_object self PyObject_GC_UnTrack self Py_CLEAR self ref Py_TYPE self tp_free PyObject self Finally if the type is heap allocated Py_TPFLAGS_HEAPTYPE the deallocator should release the owned reference to its type object via Py_DECREF after calling the type deallocator In order to avoid dangling pointers the recommended way to achieve this is static void foo_dealloc foo_object self PyTypeObject tp Py_TYPE self free references and buffers here tp tp_free self Py_DECREF tp Inheritance This field is inherited by subtypes Py_ssize_t PyTypeObject tp_vectorcall_offset An optional offset to a per instance function that implements calling the object using the vectorcall protocol a more efficient alternative of the simpler tp_call This field is only used if the flag Py_TPFLAGS_HAVE_VECTORCALL is set If so this must be a positive integer containing the offset in the instance of a vectorcallfunc pointer The vectorcallfunc pointer may be NULL in which case the instance behaves as if Py_TPFLAGS_HAVE_VECTORCALL was not set calling the instance falls back to tp_call Any class that sets Py_TPFLAGS_HAVE_VECTORCALL must also set tp_call and make sure its behaviour is consistent with the vectorcallfunc function This can be done by setting tp_call to PyVectorcall_Call Changed in version 3 8 Before version 3 8 this slot was named tp_print In Python 2 x it was used for printing to a file In Python 3 0 to 3 7 it was unused Changed in version 3 12 Before version 3 12 it was not recommended for mutable heap types to implement the vectorcall protocol When a user sets __call__ in Python code only tp_call is updated likely making it inconsistent with the vectorcall function Since 3 12 setting __call__ will disable vectorcall optimization by clearing the Py_TPFLAGS_HAVE_VECTORCALL flag Inheritance This field is always inherited However the Py_TPFLAGS_HAVE_VECTORCALL flag is not always inherited If it s not set then the subclass won t use vectorcall except when PyVectorcall_Call is explicitly called getattrfunc PyTypeObject tp_getattr An optional pointer to the get attribute string function This field is deprecated When it is defined it should point to a function that acts the same as the tp_getattro function but taking a C string instead of a Python string object to give the attribute name Inheritance Group tp_getattr tp_getattro This field is inherited by subtypes together with tp_getattro a subtype inherits both tp_getattr and tp_getattro from its base type when the subtype s tp_getattr and tp_getattro are both NULL setattrfunc PyTypeObject tp_setattr An optional pointer to the function for setting and deleting attributes This field is deprecated When it is defined it should point to a function that acts the same as the tp_setattro function but taking a C string instead of a Python string object to give the attribute name Inheritance Group tp_setattr tp_setattro This field is inherited by subtypes together with tp_setattro a subtype inherits both tp_setattr and tp_setattro from its base type when the subtype s tp_setattr and tp_setattro are both NULL PyAsyncMethods PyTypeObject tp_as_async Pointer to an additional structure that contains fields relevant only to objects which implement awaitable and asynchronous iterator protocols at the C level See Async Object Structures for details New in version 3 5 Formerly known as tp_compare and tp_reserved Inheritance The tp_as_async field is not inherited but the contained fields are inherited individually reprfunc PyTypeObject tp_repr An optional pointer to a function that implements the built in function repr The signature is the same as for PyObject_Repr PyObject tp_repr PyObject self The function must return a string or a Unicode object Ideally this function should return a string that when passed to eval given a suitable environment returns an object with the same value If this is not feasible it sh,en
441,ould return a string starting with and ending with from which both the type and the value of the object can be deduced Inheritance This field is inherited by subtypes Default When this field is not set a string of the form s object at p is returned where s is replaced by the type name and p by the object s memory address PyNumberMethods PyTypeObject tp_as_number Pointer to an additional structure that contains fields relevant only to objects which implement the number protocol These fields are documented in Number Object Structures Inheritance The tp_as_number field is not inherited but the contained fields are inherited individually PySequenceMethods PyTypeObject tp_as_sequence Pointer to an additional structure that contains fields relevant only to objects which implement the sequence protocol These fields are documented in Sequence Object Structures Inheritance The tp_as_sequence field is not inherited but the contained fields are inherited individually PyMappingMethods PyTypeObject tp_as_mapping Pointer to an additional structure that contains fields relevant only to objects which implement the mapping protocol These fields are documented in Mapping Object Structures Inheritance The tp_as_mapping field is not inherited but the contained fields are inherited individually hashfunc PyTypeObject tp_hash An optional pointer to a function that implements the built in function hash The signature is the same as for PyObject_Hash Py_hash_t tp_hash PyObject The value 1 should not be returned as a normal return value when an error occurs during the computation of the hash value the function should set an exception and return 1 When this field is not set and tp_richcompare is not set an attempt to take the hash of the object raises TypeError This is the same as setting it to PyObject_HashNotImplemented This field can be set explicitly to PyObject_HashNotImplemented to block inheritance of the hash method from a parent type This is interpreted as the equivalent of __hash__ None at the Python level causing isinstance o collections Hashable to correctly return False Note that the converse is also true setting __hash__ None on a class at the Python level will result in the tp_hash slot being set to PyObject_HashNotImplemented Inheritance Group tp_hash tp_richcompare This field is inherited by subtypes together with tp_richcompare a subtype inherits both of tp_richcompare and tp_hash when the subtype s tp_richcompare and tp_hash are both NULL ternaryfunc PyTypeObject tp_call An optional pointer to a function that implements calling the object This should be NULL if the object is not callable The signature is the same as for PyObject_Call PyObject tp_call PyObject self PyObject args PyObject kwargs Inheritance This field is inherited by subtypes reprfunc PyTypeObject tp_str An optional pointer to a function that implements the built in operation str Note that str is a type now and str calls the constructor for that type This constructor calls PyObject_Str to do the actual work and PyObject_Str will call this handler The signature is the same as for PyObject_Str PyObject tp_str PyObject self The function must return a string or a Unicode object It should be a friendly string representation of the object as this is the representation that will be used among other things by the print function Inheritance This field is inherited by subtypes Default When this field is not set PyObject_Repr is called to return a string representation getattrofunc PyTypeObject tp_getattro An optional pointer to the get attribute function The signature is the same as for PyObject_GetAttr PyObject tp_getattro PyObject self PyObject attr It is usually convenient to set this field to PyObject_GenericGetAttr which implements the normal way of looking for object attributes Inheritance Group tp_getattr tp_getattro This field is inherited by subtypes together with tp_getattr a subtype inherits both tp_getattr and tp_getattro from its base type when the subtype s tp_getattr and tp_getattro are both NULL Default PyBaseObject_Type uses PyObject_GenericGetAttr setattrof,en
442,unc PyTypeObject tp_setattro An optional pointer to the function for setting and deleting attributes The signature is the same as for PyObject_SetAttr int tp_setattro PyObject self PyObject attr PyObject value In addition setting value to NULL to delete an attribute must be supported It is usually convenient to set this field to PyObject_GenericSetAttr which implements the normal way of setting object attributes Inheritance Group tp_setattr tp_setattro This field is inherited by subtypes together with tp_setattr a subtype inherits both tp_setattr and tp_setattro from its base type when the subtype s tp_setattr and tp_setattro are both NULL Default PyBaseObject_Type uses PyObject_GenericSetAttr PyBufferProcs PyTypeObject tp_as_buffer Pointer to an additional structure that contains fields relevant only to objects which implement the buffer interface These fields are documented in Buffer Object Structures Inheritance The tp_as_buffer field is not inherited but the contained fields are inherited individually unsigned long PyTypeObject tp_flags This field is a bit mask of various flags Some flags indicate variant semantics for certain situations others are used to indicate that certain fields in the type object or in the extension structures referenced via tp_as_number tp_as_sequence tp_as_mapping and tp_as_buffer that were historically not always present are valid if such a flag bit is clear the type fields it guards must not be accessed and must be considered to have a zero or NULL value instead Inheritance Inheritance of this field is complicated Most flag bits are inherited individually i e if the base type has a flag bit set the subtype inherits this flag bit The flag bits that pertain to extension structures are strictly inherited if the extension structure is inherited i e the base type s value of the flag bit is copied into the subtype together with a pointer to the extension structure The Py_TPFLAGS_HAVE_GC flag bit is inherited together with the tp_traverse and tp_clear fields i e if the Py_TPFLAGS_HAVE_GC flag bit is clear in the subtype and the tp_traverse and tp_clear fields in the subtype exist and have NULL values XXX are most flag bits really inherited individually Default PyBaseObject_Type uses Py_TPFLAGS_DEFAULT Py_TPFLAGS_BASETYPE Bit Masks The following bit masks are currently defined these can be ORed together using the operator to form the value of the tp_flags field The macro PyType_HasFeature takes a type and a flags value tp and f and checks whether tp tp_flags f is non zero Py_TPFLAGS_HEAPTYPE This bit is set when the type object itself is allocated on the heap for example types created dynamically using PyType_FromSpec In this case the ob_type field of its instances is considered a reference to the type and the type object is INCREF ed when a new instance is created and DECREF ed when an instance is destroyed this does not apply to instances of subtypes only the type referenced by the instance s ob_type gets INCREF ed or DECREF ed Inheritance Py_TPFLAGS_BASETYPE This bit is set when the type can be used as the base type of another type If this bit is clear the type cannot be subtyped similar to a final class in Java Inheritance Py_TPFLAGS_READY This bit is set when the type object has been fully initialized by PyType_Ready Inheritance Py_TPFLAGS_READYING This bit is set while PyType_Ready is in the process of initializing the type object Inheritance Py_TPFLAGS_HAVE_GC This bit is set when the object supports garbage collection If this bit is set instances must be created using PyObject_GC_New and destroyed using PyObject_GC_Del More information in section Supporting Cyclic Garbage Collection This bit also implies that the GC related fields tp_traverse and tp_clear are present in the type object Inheritance Group Py_TPFLAGS_HAVE_GC tp_traverse tp_clear The Py_TPFLAGS_HAVE_GC flag bit is inherited together with the tp_traverse and tp_clear fields i e if the Py_TPFLAGS_HAVE_GC flag bit is clear in the subtype and the tp_traverse and tp_clear fields in the subtype exist and have NULL values Py_TPFLAGS_,en
443,DEFAULT This is a bitmask of all the bits that pertain to the existence of certain fields in the type object and its extension structures Currently it includes the following bits Py_TPFLAGS_HAVE_STACKLESS_EXTENSION Inheritance Py_TPFLAGS_METHOD_DESCRIPTOR This bit indicates that objects behave like unbound methods If this flag is set for type meth then meth __get__ obj cls args kwds with obj not None must be equivalent to meth obj args kwds meth __get__ None cls args kwds must be equivalent to meth args kwds This flag enables an optimization for typical method calls like obj meth it avoids creating a temporary bound method object for obj meth New in version 3 8 Inheritance This flag is never inherited by types without the Py_TPFLAGS_IMMUTABLETYPE flag set For extension types it is inherited whenever tp_descr_get is inherited Py_TPFLAGS_MANAGED_DICT This bit indicates that instances of the class have a __dict__ attribute and that the space for the dictionary is managed by the VM If this flag is set Py_TPFLAGS_HAVE_GC should also be set New in version 3 12 Inheritance This flag is inherited unless the tp_dictoffset field is set in a superclass Py_TPFLAGS_MANAGED_WEAKREF This bit indicates that instances of the class should be weakly referenceable New in version 3 12 Inheritance This flag is inherited unless the tp_weaklistoffset field is set in a superclass Py_TPFLAGS_ITEMS_AT_END Only usable with variable size types i e ones with non zero tp_itemsize Indicates that the variable sized portion of an instance of this type is at the end of the instance s memory area at an offset of Py_TYPE obj tp_basicsize which may be different in each subclass When setting this flag be sure that all superclasses either use this memory layout or are not variable sized Python does not check this New in version 3 12 Inheritance This flag is inherited Py_TPFLAGS_LONG_SUBCLASS Py_TPFLAGS_LIST_SUBCLASS Py_TPFLAGS_TUPLE_SUBCLASS Py_TPFLAGS_BYTES_SUBCLASS Py_TPFLAGS_UNICODE_SUBCLASS Py_TPFLAGS_DICT_SUBCLASS Py_TPFLAGS_BASE_EXC_SUBCLASS Py_TPFLAGS_TYPE_SUBCLASS These flags are used by functions such as PyLong_Check to quickly determine if a type is a subclass of a built in type such specific checks are faster than a generic check like PyObject_IsInstance Custom types that inherit from built ins should have their tp_flags set appropriately or the code that interacts with such types will behave differently depending on what kind of check is used Py_TPFLAGS_HAVE_FINALIZE This bit is set when the tp_finalize slot is present in the type structure New in version 3 4 Deprecated since version 3 8 This flag isn t necessary anymore as the interpreter assumes the tp_finalize slot is always present in the type structure Py_TPFLAGS_HAVE_VECTORCALL This bit is set when the class implements the vectorcall protocol See tp_vectorcall_offset for details Inheritance This bit is inherited if tp_call is also inherited New in version 3 9 Changed in version 3 12 This flag is now removed from a class when the class s __call__ method is reassigned This flag can now be inherited by mutable classes Py_TPFLAGS_IMMUTABLETYPE This bit is set for type objects that are immutable type attributes cannot be set nor deleted PyType_Ready automatically applies this flag to static types Inheritance This flag is not inherited New in version 3 10 Py_TPFLAGS_DISALLOW_INSTANTIATION Disallow creating instances of the type set tp_new to NULL and don t create the __new__ key in the type dictionary The flag must be set before creating the type not after For example it must be set before PyType_Ready is called on the type The flag is set automatically on static types if tp_base is NULL or PyBaseObject_Type and tp_new is NULL Inheritance This flag is not inherited However subclasses will not be instantiable unless they provide a non NULL tp_new which is only possible via the C API Note To disallow instantiating a class directly but allow instantiating its subclasses e g for an abstract base class do not use this flag Instead make tp_new only succeed for subclasses New in version 3 10 Py_TPFLAGS_MA,en
444,PPING This bit indicates that instances of the class may match mapping patterns when used as the subject of a match block It is automatically set when registering or subclassing collections abc Mapping and unset when registering collections abc Sequence Note Py_TPFLAGS_MAPPING and Py_TPFLAGS_SEQUENCE are mutually exclusive it is an error to enable both flags simultaneously Inheritance This flag is inherited by types that do not already set Py_TPFLAGS_SEQUENCE See also PEP 634 Structural Pattern Matching Specification New in version 3 10 Py_TPFLAGS_SEQUENCE This bit indicates that instances of the class may match sequence patterns when used as the subject of a match block It is automatically set when registering or subclassing collections abc Sequence and unset when registering collections abc Mapping Note Py_TPFLAGS_MAPPING and Py_TPFLAGS_SEQUENCE are mutually exclusive it is an error to enable both flags simultaneously Inheritance This flag is inherited by types that do not already set Py_TPFLAGS_MAPPING See also PEP 634 Structural Pattern Matching Specification New in version 3 10 Py_TPFLAGS_VALID_VERSION_TAG Internal Do not set or unset this flag To indicate that a class has changed call PyType_Modified Warning This flag is present in header files but is an internal feature and should not be used It will be removed in a future version of CPython const char PyTypeObject tp_doc An optional pointer to a NUL terminated C string giving the docstring for this type object This is exposed as the __doc__ attribute on the type and instances of the type Inheritance This field is not inherited by subtypes traverseproc PyTypeObject tp_traverse An optional pointer to a traversal function for the garbage collector This is only used if the Py_TPFLAGS_HAVE_GC flag bit is set The signature is int tp_traverse PyObject self visitproc visit void arg More information about Python s garbage collection scheme can be found in section Supporting Cyclic Garbage Collection The tp_traverse pointer is used by the garbage collector to detect reference cycles A typical implementation of a tp_traverse function simply calls Py_VISIT on each of the instance s members that are Python objects that the instance owns For example this is function local_traverse from the _thread extension module static int local_traverse localobject self visitproc visit void arg Py_VISIT self args Py_VISIT self kw Py_VISIT self dict return 0 Note that Py_VISIT is called only on those members that can participate in reference cycles Although there is also a self key member it can only be NULL or a Python string and therefore cannot be part of a reference cycle On the other hand even if you know a member can never be part of a cycle as a debugging aid you may want to visit it anyway just so the gc module s get_referents function will include it Warning When implementing tp_traverse only the members that the instance owns by having strong references to them must be visited For instance if an object supports weak references via the tp_weaklist slot the pointer supporting the linked list what tp_weaklist points to must not be visited as the instance does not directly own the weak references to itself the weakreference list is there to support the weak reference machinery but the instance has no strong reference to the elements inside it as they are allowed to be removed even if the instance is still alive Note that Py_VISIT requires the visit and arg parameters to local_traverse to have these specific names don t name them just anything Instances of heap allocated types hold a reference to their type Their traversal function must therefore either visit Py_TYPE self or delegate this responsibility by calling tp_traverse of another heap allocated type such as a heap allocated superclass If they do not the type object may not be garbage collected Changed in version 3 9 Heap allocated types are expected to visit Py_TYPE self in tp_traverse In earlier versions of Python due to bug 40217 doing this may lead to crashes in subclasses Inheritance Group Py_TPFLAGS_HAVE_GC tp_traverse tp_cl,en
445,ear This field is inherited by subtypes together with tp_clear and the Py_TPFLAGS_HAVE_GC flag bit the flag bit tp_traverse and tp_clear are all inherited from the base type if they are all zero in the subtype inquiry PyTypeObject tp_clear An optional pointer to a clear function for the garbage collector This is only used if the Py_TPFLAGS_HAVE_GC flag bit is set The signature is int tp_clear PyObject The tp_clear member function is used to break reference cycles in cyclic garbage detected by the garbage collector Taken together all tp_clear functions in the system must combine to break all reference cycles This is subtle and if in any doubt supply a tp_clear function For example the tuple type does not implement a tp_clear function because it s possible to prove that no reference cycle can be composed entirely of tuples Therefore the tp_clear functions of other types must be sufficient to break any cycle containing a tuple This isn t immediately obvious and there s rarely a good reason to avoid implementing tp_clear Implementations of tp_clear should drop the instance s references to those of its members that may be Python objects and set its pointers to those members to NULL as in the following example static int local_clear localobject self Py_CLEAR self key Py_CLEAR self args Py_CLEAR self kw Py_CLEAR self dict return 0 The Py_CLEAR macro should be used because clearing references is delicate the reference to the contained object must not be released via Py_DECREF until after the pointer to the contained object is set to NULL This is because releasing the reference may cause the contained object to become trash triggering a chain of reclamation activity that may include invoking arbitrary Python code due to finalizers or weakref callbacks associated with the contained object If it s possible for such code to reference self again it s important that the pointer to the contained object be NULL at that time so that self knows the contained object can no longer be used The Py_CLEAR macro performs the operations in a safe order Note that tp_clear is not always called before an instance is deallocated For example when reference counting is enough to determine that an object is no longer used the cyclic garbage collector is not involved and tp_dealloc is called directly Because the goal of tp_clear functions is to break reference cycles it s not necessary to clear contained objects like Python strings or Python integers which can t participate in reference cycles On the other hand it may be convenient to clear all contained Python objects and write the type s tp_dealloc function to invoke tp_clear More information about Python s garbage collection scheme can be found in section Supporting Cyclic Garbage Collection Inheritance Group Py_TPFLAGS_HAVE_GC tp_traverse tp_clear This field is inherited by subtypes together with tp_traverse and the Py_TPFLAGS_HAVE_GC flag bit the flag bit tp_traverse and tp_clear are all inherited from the base type if they are all zero in the subtype richcmpfunc PyTypeObject tp_richcompare An optional pointer to the rich comparison function whose signature is PyObject tp_richcompare PyObject self PyObject other int op The first parameter is guaranteed to be an instance of the type that is defined by PyTypeObject The function should return the result of the comparison usually Py_True or Py_False If the comparison is undefined it must return Py_NotImplemented if another error occurred it must return NULL and set an exception condition The following constants are defined to be used as the third argument for tp_richcompare and for PyObject_RichCompare Constant Comparison Py_LT Py_LE Py_EQ Py_NE Py_GT Py_GE The following macro is defined to ease writing rich comparison functions Py_RETURN_RICHCOMPARE VAL_A VAL_B op Return Py_True or Py_False from the function depending on the result of a comparison VAL_A and VAL_B must be orderable by C comparison operators for example they may be C ints or floats The third argument specifies the requested operation as for PyObject_RichCompare The returned value is a ne,en
446,w strong reference On error sets an exception and returns NULL from the function New in version 3 7 Inheritance Group tp_hash tp_richcompare This field is inherited by subtypes together with tp_hash a subtype inherits tp_richcompare and tp_hash when the subtype s tp_richcompare and tp_hash are both NULL Default PyBaseObject_Type provides a tp_richcompare implementation which may be inherited However if only tp_hash is defined not even the inherited function is used and instances of the type will not be able to participate in any comparisons Py_ssize_t PyTypeObject tp_weaklistoffset While this field is still supported Py_TPFLAGS_MANAGED_WEAKREF should be used instead if at all possible If the instances of this type are weakly referenceable this field is greater than zero and contains the offset in the instance structure of the weak reference list head ignoring the GC header if present this offset is used by PyObject_ClearWeakRefs and the PyWeakref_ functions The instance structure needs to include a field of type PyObject which is initialized to NULL Do not confuse this field with tp_weaklist that is the list head for weak references to the type object itself It is an error to set both the Py_TPFLAGS_MANAGED_WEAKREF bit and tp_weaklist Inheritance This field is inherited by subtypes but see the rules listed below A subtype may override this offset this means that the subtype uses a different weak reference list head than the base type Since the list head is always found via tp_weaklistoffset this should not be a problem Default If the Py_TPFLAGS_MANAGED_WEAKREF bit is set in the tp_dict field then tp_weaklistoffset will be set to a negative value to indicate that it is unsafe to use this field getiterfunc PyTypeObject tp_iter An optional pointer to a function that returns an iterator for the object Its presence normally signals that the instances of this type are iterable although sequences may be iterable without this function This function has the same signature as PyObject_GetIter PyObject tp_iter PyObject self Inheritance This field is inherited by subtypes iternextfunc PyTypeObject tp_iternext An optional pointer to a function that returns the next item in an iterator The signature is PyObject tp_iternext PyObject self When the iterator is exhausted it must return NULL a StopIteration exception may or may not be set When another error occurs it must return NULL too Its presence signals that the instances of this type are iterators Iterator types should also define the tp_iter function and that function should return the iterator instance itself not a new iterator instance This function has the same signature as PyIter_Next Inheritance This field is inherited by subtypes struct PyMethodDef PyTypeObject tp_methods An optional pointer to a static NULL terminated array of PyMethodDef structures declaring regular methods of this type For each entry in the array an entry is added to the type s dictionary see tp_dict below containing a method descriptor Inheritance This field is not inherited by subtypes methods are inherited through a different mechanism struct PyMemberDef PyTypeObject tp_members An optional pointer to a static NULL terminated array of PyMemberDef structures declaring regular data members fields or slots of instances of this type For each entry in the array an entry is added to the type s dictionary see tp_dict below containing a member descriptor Inheritance This field is not inherited by subtypes members are inherited through a different mechanism struct PyGetSetDef PyTypeObject tp_getset An optional pointer to a static NULL terminated array of PyGetSetDef structures declaring computed attributes of instances of this type For each entry in the array an entry is added to the type s dictionary see tp_dict below containing a getset descriptor Inheritance This field is not inherited by subtypes computed attributes are inherited through a different mechanism PyTypeObject PyTypeObject tp_base An optional pointer to a base type from which type properties are inherited At this level only single inheritance is su,en
447,pported multiple inheritance require dynamically creating a type object by calling the metatype Note Slot initialization is subject to the rules of initializing globals C99 requires the initializers to be address constants Function designators like PyType_GenericNew with implicit conversion to a pointer are valid C99 address constants However the unary operator applied to a non static variable like PyBaseObject_Type is not required to produce an address constant Compilers may support this gcc does MSVC does not Both compilers are strictly standard conforming in this particular behavior Consequently tp_base should be set in the extension module s init function Inheritance This field is not inherited by subtypes obviously Default This field defaults to PyBaseObject_Type which to Python programmers is known as the type object PyObject PyTypeObject tp_dict The type s dictionary is stored here by PyType_Ready This field should normally be initialized to NULL before PyType_Ready is called it may also be initialized to a dictionary containing initial attributes for the type Once PyType_Ready has initialized the type extra attributes for the type may be added to this dictionary only if they don t correspond to overloaded operations like __add__ Once initialization for the type has finished this field should be treated as read only Some types may not store their dictionary in this slot Use PyType_GetDict to retrieve the dictionary for an arbitrary type Changed in version 3 12 Internals detail For static builtin types this is always NULL Instead the dict for such types is stored on PyInterpreterState Use PyType_GetDict to get the dict for an arbitrary type Inheritance This field is not inherited by subtypes though the attributes defined in here are inherited through a different mechanism Default If this field is NULL PyType_Ready will assign a new dictionary to it Warning It is not safe to use PyDict_SetItem on or otherwise modify tp_dict with the dictionary C API descrgetfunc PyTypeObject tp_descr_get An optional pointer to a descriptor get function The function signature is PyObject tp_descr_get PyObject self PyObject obj PyObject type Inheritance This field is inherited by subtypes descrsetfunc PyTypeObject tp_descr_set An optional pointer to a function for setting and deleting a descriptor s value The function signature is int tp_descr_set PyObject self PyObject obj PyObject value The value argument is set to NULL to delete the value Inheritance This field is inherited by subtypes Py_ssize_t PyTypeObject tp_dictoffset While this field is still supported Py_TPFLAGS_MANAGED_DICT should be used instead if at all possible If the instances of this type have a dictionary containing instance variables this field is non zero and contains the offset in the instances of the type of the instance variable dictionary this offset is used by PyObject_GenericGetAttr Do not confuse this field with tp_dict that is the dictionary for attributes of the type object itself The value specifies the offset of the dictionary from the start of the instance structure The tp_dictoffset should be regarded as write only To get the pointer to the dictionary call PyObject_GenericGetDict Calling PyObject_GenericGetDict may need to allocate memory for the dictionary so it is may be more efficient to call PyObject_GetAttr when accessing an attribute on the object It is an error to set both the Py_TPFLAGS_MANAGED_WEAKREF bit and tp_dictoffset Inheritance This field is inherited by subtypes A subtype should not override this offset doing so could be unsafe if C code tries to access the dictionary at the previous offset To properly support inheritance use Py_TPFLAGS_MANAGED_DICT Default This slot has no default For static types if the field is NULL then no __dict__ gets created for instances If the Py_TPFLAGS_MANAGED_DICT bit is set in the tp_dict field then tp_dictoffset will be set to 1 to indicate that it is unsafe to use this field initproc PyTypeObject tp_init An optional pointer to an instance initialization function This function corresponds to the __init__ ,en
448,method of classes Like __init__ it is possible to create an instance without calling __init__ and it is possible to reinitialize an instance by calling its __init__ method again The function signature is int tp_init PyObject self PyObject args PyObject kwds The self argument is the instance to be initialized the args and kwds arguments represent positional and keyword arguments of the call to __init__ The tp_init function if not NULL is called when an instance is created normally by calling its type after the type s tp_new function has returned an instance of the type If the tp_new function returns an instance of some other type that is not a subtype of the original type no tp_init function is called if tp_new returns an instance of a subtype of the original type the subtype s tp_init is called Returns 0 on success 1 and sets an exception on error Inheritance This field is inherited by subtypes Default For static types this field does not have a default allocfunc PyTypeObject tp_alloc An optional pointer to an instance allocation function The function signature is PyObject tp_alloc PyTypeObject self Py_ssize_t nitems Inheritance This field is inherited by static subtypes but not by dynamic subtypes subtypes created by a class statement Default For dynamic subtypes this field is always set to PyType_GenericAlloc to force a standard heap allocation strategy For static subtypes PyBaseObject_Type uses PyType_GenericAlloc That is the recommended value for all statically defined types newfunc PyTypeObject tp_new An optional pointer to an instance creation function The function signature is PyObject tp_new PyTypeObject subtype PyObject args PyObject kwds The subtype argument is the type of the object being created the args and kwds arguments represent positional and keyword arguments of the call to the type Note that subtype doesn t have to equal the type whose tp_new function is called it may be a subtype of that type but not an unrelated type The tp_new function should call subtype tp_alloc subtype nitems to allocate space for the object and then do only as much further initialization as is absolutely necessary Initialization that can safely be ignored or repeated should be placed in the tp_init handler A good rule of thumb is that for immutable types all initialization should take place in tp_new while for mutable types most initialization should be deferred to tp_init Set the Py_TPFLAGS_DISALLOW_INSTANTIATION flag to disallow creating instances of the type in Python Inheritance This field is inherited by subtypes except it is not inherited by static types whose tp_base is NULL or PyBaseObject_Type Default For static types this field has no default This means if the slot is defined as NULL the type cannot be called to create new instances presumably there is some other way to create instances like a factory function freefunc PyTypeObject tp_free An optional pointer to an instance deallocation function Its signature is void tp_free void self An initializer that is compatible with this signature is PyObject_Free Inheritance This field is inherited by static subtypes but not by dynamic subtypes subtypes created by a class statement Default In dynamic subtypes this field is set to a deallocator suitable to match PyType_GenericAlloc and the value of the Py_TPFLAGS_HAVE_GC flag bit For static subtypes PyBaseObject_Type uses PyObject_Del inquiry PyTypeObject tp_is_gc An optional pointer to a function called by the garbage collector The garbage collector needs to know whether a particular object is collectible or not Normally it is sufficient to look at the object s type s tp_flags field and check the Py_TPFLAGS_HAVE_GC flag bit But some types have a mixture of statically and dynamically allocated instances and the statically allocated instances are not collectible Such types should define this function it should return 1 for a collectible instance and 0 for a non collectible instance The signature is int tp_is_gc PyObject self The only example of this are types themselves The metatype PyType_Type defines this function to distinguis,en
449,h between statically and dynamically allocated types Inheritance This field is inherited by subtypes Default This slot has no default If this field is NULL Py_TPFLAGS_HAVE_GC is used as the functional equivalent PyObject PyTypeObject tp_bases Tuple of base types This field should be set to NULL and treated as read only Python will fill it in when the type is initialized For dynamically created classes the Py_tp_bases slot can be used instead of the bases argument of PyType_FromSpecWithBases The argument form is preferred Warning Multiple inheritance does not work well for statically defined types If you set tp_bases to a tuple Python will not raise an error but some slots will only be inherited from the first base Inheritance This field is not inherited PyObject PyTypeObject tp_mro Tuple containing the expanded set of base types starting with the type itself and ending with object in Method Resolution Order This field should be set to NULL and treated as read only Python will fill it in when the type is initialized Inheritance This field is not inherited it is calculated fresh by PyType_Ready PyObject PyTypeObject tp_cache Unused Internal use only Inheritance This field is not inherited void PyTypeObject tp_subclasses A collection of subclasses Internal use only May be an invalid pointer To get a list of subclasses call the Python method __subclasses__ Changed in version 3 12 For some types this field does not hold a valid PyObject The type was changed to void to indicate this Inheritance This field is not inherited PyObject PyTypeObject tp_weaklist Weak reference list head for weak references to this type object Not inherited Internal use only Changed in version 3 12 Internals detail For the static builtin types this is always NULL even if weakrefs are added Instead the weakrefs for each are stored on PyInterpreterState Use the public C API or the internal _PyObject_GET_WEAKREFS_LISTPTR macro to avoid the distinction Inheritance This field is not inherited destructor PyTypeObject tp_del This field is deprecated Use tp_finalize instead unsigned int PyTypeObject tp_version_tag Used to index into the method cache Internal use only Inheritance This field is not inherited destructor PyTypeObject tp_finalize An optional pointer to an instance finalization function Its signature is void tp_finalize PyObject self If tp_finalize is set the interpreter calls it once when finalizing an instance It is called either from the garbage collector if the instance is part of an isolated reference cycle or just before the object is deallocated Either way it is guaranteed to be called before attempting to break reference cycles ensuring that it finds the object in a sane state tp_finalize should not mutate the current exception status therefore a recommended way to write a non trivial finalizer is static void local_finalize PyObject self PyObject error_type error_value error_traceback Save the current exception if any PyErr_Fetch error_type error_value error_traceback Restore the saved exception PyErr_Restore error_type error_value error_traceback Also note that in a garbage collected Python tp_dealloc may be called from any Python thread not just the thread which created the object if the object becomes part of a refcount cycle that cycle might be collected by a garbage collection on any thread This is not a problem for Python API calls since the thread on which tp_dealloc is called will own the Global Interpreter Lock GIL However if the object being destroyed in turn destroys objects from some other C or C library care should be taken to ensure that destroying those objects on the thread which called tp_dealloc will not violate any assumptions of the library Inheritance This field is inherited by subtypes New in version 3 4 Changed in version 3 8 Before version 3 8 it was necessary to set the Py_TPFLAGS_HAVE_FINALIZE flags bit in order for this field to be used This is no longer required See also Safe object finalization PEP 442 vectorcallfunc PyTypeObject tp_vectorcall Vectorcall function to use for calls of this type object In other wor,en
450,ds it is used to implement vectorcall for type __call__ If tp_vectorcall is NULL the default call implementation using __new__ and __init__ is used Inheritance This field is never inherited New in version 3 9 the field exists since 3 8 but it s only used since 3 9 unsigned char PyTypeObject tp_watched Internal Do not use New in version 3 12 Static Types Traditionally types defined in C code are static that is a static PyTypeObject structure is defined directly in code and initialized using PyType_Ready This results in types that are limited relative to types defined in Python Static types are limited to one base i e they cannot use multiple inheritance Static type objects but not necessarily their instances are immutable It is not possible to add or modify the type object s attributes from Python Static type objects are shared across sub interpreters so they should not include any subinterpreter specific state Also since PyTypeObject is only part of the Limited API as an opaque struct any extension modules using static types must be compiled for a specific Python minor version Heap Types An alternative to static types is heap allocated types or heap types for short which correspond closely to classes created by Python s class statement Heap types have the Py_TPFLAGS_HEAPTYPE flag set This is done by filling a PyType_Spec structure and calling PyType_FromSpec PyType_FromSpecWithBases PyType_FromModuleAndSpec or PyType_FromMetaclass Number Object Structures type PyNumberMethods This structure holds pointers to the functions which an object uses to implement the number protocol Each function is used by the function of similar name documented in the Number Protocol section Here is the structure definition typedef struct binaryfunc nb_add binaryfunc nb_subtract binaryfunc nb_multiply binaryfunc nb_remainder binaryfunc nb_divmod ternaryfunc nb_power unaryfunc nb_negative unaryfunc nb_positive unaryfunc nb_absolute inquiry nb_bool unaryfunc nb_invert binaryfunc nb_lshift binaryfunc nb_rshift binaryfunc nb_and binaryfunc nb_xor binaryfunc nb_or unaryfunc nb_int void nb_reserved unaryfunc nb_float binaryfunc nb_inplace_add binaryfunc nb_inplace_subtract binaryfunc nb_inplace_multiply binaryfunc nb_inplace_remainder ternaryfunc nb_inplace_power binaryfunc nb_inplace_lshift binaryfunc nb_inplace_rshift binaryfunc nb_inplace_and binaryfunc nb_inplace_xor binaryfunc nb_inplace_or binaryfunc nb_floor_divide binaryfunc nb_true_divide binaryfunc nb_inplace_floor_divide binaryfunc nb_inplace_true_divide unaryfunc nb_index binaryfunc nb_matrix_multiply binaryfunc nb_inplace_matrix_multiply PyNumberMethods Note Binary and ternary functions must check the type of all their operands and implement the necessary conversions at least one of the operands is an instance of the defined type If the operation is not defined for the given operands binary and ternary functions must return Py_NotImplemented if another error occurred they must return NULL and set an exception Note The nb_reserved field should always be NULL It was previously called nb_long and was renamed in Python 3 0 1 binaryfunc PyNumberMethods nb_add binaryfunc PyNumberMethods nb_subtract binaryfunc PyNumberMethods nb_multiply binaryfunc PyNumberMethods nb_remainder binaryfunc PyNumberMethods nb_divmod ternaryfunc PyNumberMethods nb_power unaryfunc PyNumberMethods nb_negative unaryfunc PyNumberMethods nb_positive unaryfunc PyNumberMethods nb_absolute inquiry PyNumberMethods nb_bool unaryfunc PyNumberMethods nb_invert binaryfunc PyNumberMethods nb_lshift binaryfunc PyNumberMethods nb_rshift binaryfunc PyNumberMethods nb_and binaryfunc PyNumberMethods nb_xor binaryfunc PyNumberMethods nb_or unaryfunc PyNumberMethods nb_int void PyNumberMethods nb_reserved unaryfunc PyNumberMethods nb_float binaryfunc PyNumberMethods nb_inplace_add binaryfunc PyNumberMethods nb_inplace_subtract binaryfunc PyNumberMethods nb_inplace_multiply binaryfunc PyNumberMethods nb_inplace_remainder ternaryfunc PyNumberMethods nb_inplace_power binaryfunc PyNumberMethods nb_inplace_lshift binaryfunc PyNumberMethods,en
451, nb_inplace_rshift binaryfunc PyNumberMethods nb_inplace_and binaryfunc PyNumberMethods nb_inplace_xor binaryfunc PyNumberMethods nb_inplace_or binaryfunc PyNumberMethods nb_floor_divide binaryfunc PyNumberMethods nb_true_divide binaryfunc PyNumberMethods nb_inplace_floor_divide binaryfunc PyNumberMethods nb_inplace_true_divide unaryfunc PyNumberMethods nb_index binaryfunc PyNumberMethods nb_matrix_multiply binaryfunc PyNumberMethods nb_inplace_matrix_multiply Mapping Object Structures type PyMappingMethods This structure holds pointers to the functions which an object uses to implement the mapping protocol It has three members lenfunc PyMappingMethods mp_length This function is used by PyMapping_Size and PyObject_Size and has the same signature This slot may be set to NULL if the object has no defined length binaryfunc PyMappingMethods mp_subscript This function is used by PyObject_GetItem and PySequence_GetSlice and has the same signature as PyObject_GetItem This slot must be filled for the PyMapping_Check function to return 1 it can be NULL otherwise objobjargproc PyMappingMethods mp_ass_subscript This function is used by PyObject_SetItem PyObject_DelItem PySequence_SetSlice and PySequence_DelSlice It has the same signature as PyObject_SetItem but v can also be set to NULL to delete an item If this slot is NULL the object does not support item assignment and deletion Sequence Object Structures type PySequenceMethods This structure holds pointers to the functions which an object uses to implement the sequence protocol lenfunc PySequenceMethods sq_length This function is used by PySequence_Size and PyObject_Size and has the same signature It is also used for handling negative indices via the sq_item and the sq_ass_item slots binaryfunc PySequenceMethods sq_concat This function is used by PySequence_Concat and has the same signature It is also used by the operator after trying the numeric addition via the nb_add slot ssizeargfunc PySequenceMethods sq_repeat This function is used by PySequence_Repeat and has the same signature It is also used by the operator after trying numeric multiplication via the nb_multiply slot ssizeargfunc PySequenceMethods sq_item This function is used by PySequence_GetItem and has the same signature It is also used by PyObject_GetItem after trying the subscription via the mp_subscript slot This slot must be filled for the PySequence_Check function to return 1 it can be NULL otherwise Negative indexes are handled as follows if the sq_length slot is filled it is called and the sequence length is used to compute a positive index which is passed to sq_item If sq_length is NULL the index is passed as is to the function ssizeobjargproc PySequenceMethods sq_ass_item This function is used by PySequence_SetItem and has the same signature It is also used by PyObject_SetItem and PyObject_DelItem after trying the item assignment and deletion via the mp_ass_subscript slot This slot may be left to NULL if the object does not support item assignment and deletion objobjproc PySequenceMethods sq_contains This function may be used by PySequence_Contains and has the same signature This slot may be left to NULL in this case PySequence_Contains simply traverses the sequence until it finds a match binaryfunc PySequenceMethods sq_inplace_concat This function is used by PySequence_InPlaceConcat and has the same signature It should modify its first operand and return it This slot may be left to NULL in this case PySequence_InPlaceConcat will fall back to PySequence_Concat It is also used by the augmented assignment after trying numeric in place addition via the nb_inplace_add slot ssizeargfunc PySequenceMethods sq_inplace_repeat This function is used by PySequence_InPlaceRepeat and has the same signature It should modify its first operand and return it This slot may be left to NULL in this case PySequence_InPlaceRepeat will fall back to PySequence_Repeat It is also used by the augmented assignment after trying numeric in place multiplication via the nb_inplace_multiply slot Buffer Object Structures type PyBufferProcs Th,en
452,is structure holds pointers to the functions required by the Buffer protocol The protocol defines how an exporter object can expose its internal data to consumer objects getbufferproc PyBufferProcs bf_getbuffer The signature of this function is int PyObject exporter Py_buffer view int flags Handle a request to exporter to fill in view as specified by flags Except for point 3 an implementation of this function MUST take these steps 1 Check if the request can be met If not raise BufferError set view obj to NULL and return 1 2 Fill in the requested fields 3 Increment an internal counter for the number of exports 4 Set view obj to exporter and increment view obj 5 Return 0 If exporter is part of a chain or tree of buffer providers two main schemes can be used Re export Each member of the tree acts as the exporting object and sets view obj to a new reference to itself Redirect The buffer request is redirected to the root object of the tree Here view obj will be a new reference to the root object The individual fields of view are described in section Buffer structure the rules how an exporter must react to specific requests are in section Buffer request types All memory pointed to in the Py_buffer structure belongs to the exporter and must remain valid until there are no consumers left format shape strides suboffsets and internal are read only for the consumer PyBuffer_FillInfo provides an easy way of exposing a simple bytes buffer while dealing correctly with all request types PyObject_GetBuffer is the interface for the consumer that wraps this function releasebufferproc PyBufferProcs bf_releasebuffer The signature of this function is void PyObject exporter Py_buffer view Handle a request to release the resources of the buffer If no resources need to be released PyBufferProcs bf_releasebuffer may be NULL Otherwise a standard implementation of this function will take these optional steps 1 Decrement an internal counter for the number of exports 2 If the counter is 0 free all memory associated with view The exporter MUST use the internal field to keep track of buffer specific resources This field is guaranteed to remain constant while a consumer MAY pass a copy of the original buffer as the view argument This function MUST NOT decrement view obj since that is done automatically in PyBuffer_Release this scheme is useful for breaking reference cycles PyBuffer_Release is the interface for the consumer that wraps this function Async Object Structures New in version 3 5 type PyAsyncMethods This structure holds pointers to the functions required to implement awaitable and asynchronous iterator objects Here is the structure definition typedef struct unaryfunc am_await unaryfunc am_aiter unaryfunc am_anext sendfunc am_send PyAsyncMethods unaryfunc PyAsyncMethods am_await The signature of this function is PyObject am_await PyObject self The returned object must be an iterator i e PyIter_Check must return 1 for it This slot may be set to NULL if an object is not an awaitable unaryfunc PyAsyncMethods am_aiter The signature of this function is PyObject am_aiter PyObject self Must return an asynchronous iterator object See __anext__ for details This slot may be set to NULL if an object does not implement asynchronous iteration protocol unaryfunc PyAsyncMethods am_anext The signature of this function is PyObject am_anext PyObject self Must return an awaitable object See __anext__ for details This slot may be set to NULL sendfunc PyAsyncMethods am_send The signature of this function is PySendResult am_send PyObject self PyObject arg PyObject result See PyIter_Send for details This slot may be set to NULL New in version 3 10 Slot Type typedefs typedef PyObject allocfunc PyTypeObject cls Py_ssize_t nitems Part of the Stable ABI The purpose of this function is to separate memory allocation from memory initialization It should return a pointer to a block of memory of adequate length for the instance suitably aligned and initialized to zeros but with ob_refcnt set to 1 and ob_type set to the type argument If the type s tp_itemsize is non zero the ,en
453,object s ob_size field should be initialized to nitems and the length of the allocated memory block should be tp_basicsize nitems tp_itemsize rounded up to a multiple of sizeof void otherwise nitems is not used and the length of the block should be tp_basicsize This function should not do any other instance initialization not even to allocate additional memory that should be done by tp_new typedef void destructor PyObject Part of the Stable ABI typedef void freefunc void See tp_free typedef PyObject newfunc PyObject PyObject PyObject Part of the Stable ABI See tp_new typedef int initproc PyObject PyObject PyObject Part of the Stable ABI See tp_init typedef PyObject reprfunc PyObject Part of the Stable ABI See tp_repr typedef PyObject getattrfunc PyObject self char attr Part of the Stable ABI Return the value of the named attribute for the object typedef int setattrfunc PyObject self char attr PyObject value Part of the Stable ABI Set the value of the named attribute for the object The value argument is set to NULL to delete the attribute typedef PyObject getattrofunc PyObject self PyObject attr Part of the Stable ABI Return the value of the named attribute for the object See tp_getattro typedef int setattrofunc PyObject self PyObject attr PyObject value Part of the Stable ABI Set the value of the named attribute for the object The value argument is set to NULL to delete the attribute See tp_setattro typedef PyObject descrgetfunc PyObject PyObject PyObject Part of the Stable ABI See tp_descr_get typedef int descrsetfunc PyObject PyObject PyObject Part of the Stable ABI See tp_descr_set typedef Py_hash_t hashfunc PyObject Part of the Stable ABI See tp_hash typedef PyObject richcmpfunc PyObject PyObject int Part of the Stable ABI See tp_richcompare typedef PyObject getiterfunc PyObject Part of the Stable ABI See tp_iter typedef PyObject iternextfunc PyObject Part of the Stable ABI See tp_iternext typedef Py_ssize_t lenfunc PyObject Part of the Stable ABI typedef int getbufferproc PyObject Py_buffer int Part of the Stable ABI since version 3 12 typedef void releasebufferproc PyObject Py_buffer Part of the Stable ABI since version 3 12 typedef PyObject unaryfunc PyObject Part of the Stable ABI typedef PyObject binaryfunc PyObject PyObject Part of the Stable ABI typedef PySendResult sendfunc PyObject PyObject PyObject See am_send typedef PyObject ternaryfunc PyObject PyObject PyObject Part of the Stable ABI typedef PyObject ssizeargfunc PyObject Py_ssize_t Part of the Stable ABI typedef int ssizeobjargproc PyObject Py_ssize_t PyObject Part of the Stable ABI typedef int objobjproc PyObject PyObject Part of the Stable ABI typedef int objobjargproc PyObject PyObject PyObject Part of the Stable ABI Examples The following are simple examples of Python type definitions They include common usage you may encounter Some demonstrate tricky corner cases For more examples practical info and a tutorial see Defining Extension Types Tutorial and Defining Extension Types Assorted Topics A basic static type typedef struct PyObject_HEAD const char data MyObject static PyTypeObject MyObject_Type PyVarObject_HEAD_INIT NULL 0 tp_name mymod MyObject tp_basicsize sizeof MyObject tp_doc PyDoc_STR My objects tp_new myobj_new tp_dealloc destructor myobj_dealloc tp_repr reprfunc myobj_repr You may also find older code especially in the CPython code base with a more verbose initializer static PyTypeObject MyObject_Type PyVarObject_HEAD_INIT NULL 0 mymod MyObject tp_name sizeof MyObject tp_basicsize 0 tp_itemsize destructor myobj_dealloc tp_dealloc 0 tp_vectorcall_offset 0 tp_getattr 0 tp_setattr 0 tp_as_async reprfunc myobj_repr tp_repr 0 tp_as_number 0 tp_as_sequence 0 tp_as_mapping 0 tp_hash 0 tp_call 0 tp_str 0 tp_getattro 0 tp_setattro 0 tp_as_buffer 0 tp_flags PyDoc_STR My objects tp_doc 0 tp_traverse 0 tp_clear 0 tp_richcompare 0 tp_weaklistoffset 0 tp_iter 0 tp_iternext 0 tp_methods 0 tp_members 0 tp_getset 0 tp_base 0 tp_dict 0 tp_descr_get 0 tp_descr_set 0 tp_dictoffset 0 tp_init 0 tp_alloc myobj_new tp_new A type that supports weakrefs instance,en
454, dicts and hashing typedef struct PyObject_HEAD const char data MyObject static PyTypeObject MyObject_Type PyVarObject_HEAD_INIT NULL 0 tp_name mymod MyObject tp_basicsize sizeof MyObject tp_doc PyDoc_STR My objects tp_flags Py_TPFLAGS_DEFAULT Py_TPFLAGS_BASETYPE Py_TPFLAGS_HAVE_GC Py_TPFLAGS_MANAGED_DICT Py_TPFLAGS_MANAGED_WEAKREF tp_new myobj_new tp_traverse traverseproc myobj_traverse tp_clear inquiry myobj_clear tp_alloc PyType_GenericNew tp_dealloc destructor myobj_dealloc tp_repr reprfunc myobj_repr tp_hash hashfunc myobj_hash tp_richcompare PyBaseObject_Type tp_richcompare A str subclass that cannot be subclassed and cannot be called to create instances e g uses a separate factory func using Py_TPFLAGS_DISALLOW_INSTANTIATION flag typedef struct PyUnicodeObject raw char extra MyStr static PyTypeObject MyStr_Type PyVarObject_HEAD_INIT NULL 0 tp_name mymod MyStr tp_basicsize sizeof MyStr tp_base NULL set to PyUnicode_Type in module init tp_doc PyDoc_STR my custom str tp_flags Py_TPFLAGS_DEFAULT Py_TPFLAGS_DISALLOW_INSTANTIATION tp_repr reprfunc myobj_repr The simplest static type with fixed length instances typedef struct PyObject_HEAD MyObject static PyTypeObject MyObject_Type PyVarObject_HEAD_INIT NULL 0 tp_name mymod MyObject The simplest static type with variable length instances typedef struct PyObject_VAR_HEAD const char data 1 MyObject static PyTypeObject MyObject_Type PyVarObject_HEAD_INIT NULL 0 tp_name mymod MyObject tp_basicsize sizeof MyObject sizeof char tp_itemsize sizeof char,en
455,tkinter scrolledtext Scrolled Text Widget Source code Lib tkinter scrolledtext py The tkinter scrolledtext module provides a class of the same name which implements a basic text widget which has a vertical scroll bar configured to do the right thing Using the ScrolledText class is a lot easier than setting up a text widget and scroll bar directly The text widget and scrollbar are packed together in a Frame and the methods of the Grid and Pack geometry managers are acquired from the Frame object This allows the ScrolledText widget to be used directly to achieve most normal geometry management behavior Should more specific control be necessary the following attributes are available class tkinter scrolledtext ScrolledText master None kw frame The frame which surrounds the text and scroll bar widgets vbar The scroll bar widget,en
456,email policy Policy Objects New in version 3 3 Source code Lib email policy py The email package s prime focus is the handling of email messages as described by the various email and MIME RFCs However the general format of email messages a block of header fields each consisting of a name followed by a colon followed by a value the whole block followed by a blank line and an arbitrary body is a format that has found utility outside of the realm of email Some of these uses conform fairly closely to the main email RFCs some do not Even when working with email there are times when it is desirable to break strict compliance with the RFCs such as generating emails that interoperate with email servers that do not themselves follow the standards or that implement extensions you want to use in ways that violate the standards Policy objects give the email package the flexibility to handle all these disparate use cases A Policy object encapsulates a set of attributes and methods that control the behavior of various components of the email package during use Policy instances can be passed to various classes and methods in the email package to alter the default behavior The settable values and their defaults are described below There is a default policy used by all classes in the email package For all of the parser classes and the related convenience functions and for the Message class this is the Compat32 policy via its corresponding pre defined instance compat32 This policy provides for complete backward compatibility in some cases including bug compatibility with the pre Python3 3 version of the email package This default value for the policy keyword to EmailMessage is the EmailPolicy policy via its pre defined instance default When a Message or EmailMessage object is created it acquires a policy If the message is created by a parser a policy passed to the parser will be the policy used by the message it creates If the message is created by the program then the policy can be specified when it is created When a message is passed to a generator the generator uses the policy from the message by default but you can also pass a specific policy to the generator that will override the one stored on the message object The default value for the policy keyword for the email parser classes and the parser convenience functions will be changing in a future version of Python Therefore you should always specify explicitly which policy you want to use when calling any of the classes and functions described in the parser module The first part of this documentation covers the features of Policy an abstract base class that defines the features that are common to all policy objects including compat32 This includes certain hook methods that are called internally by the email package which a custom policy could override to obtain different behavior The second part describes the concrete classes EmailPolicy and Compat32 which implement the hooks that provide the standard behavior and the backward compatible behavior and features respectively Policy instances are immutable but they can be cloned accepting the same keyword arguments as the class constructor and returning a new Policy instance that is a copy of the original but with the specified attributes values changed As an example the following code could be used to read an email message from a file on disk and pass it to the system sendmail program on a Unix system from email import message_from_binary_file from email generator import BytesGenerator from email import policy from subprocess import Popen PIPE with open mymsg txt rb as f msg message_from_binary_file f policy policy default p Popen sendmail msg To addresses 0 stdin PIPE g BytesGenerator p stdin policy msg policy clone linesep r n g flatten msg p stdin close rc p wait Here we are telling BytesGenerator to use the RFC correct line separator characters when creating the binary string to feed into sendmail s stdin where the default policy would use n line separators Some email package methods accept a policy keyword argument allowing the pol,en
457,icy to be overridden for that method For example the following code uses the as_bytes method of the msg object from the previous example and writes the message to a file using the native line separators for the platform on which it is running import os with open converted txt wb as f f write msg as_bytes policy msg policy clone linesep os linesep 17 Policy objects can also be combined using the addition operator producing a policy object whose settings are a combination of the non default values of the summed objects compat_SMTP policy compat32 clone linesep r n compat_strict policy compat32 clone raise_on_defect True compat_strict_SMTP compat_SMTP compat_strict This operation is not commutative that is the order in which the objects are added matters To illustrate policy100 policy compat32 clone max_line_length 100 policy80 policy compat32 clone max_line_length 80 apolicy policy100 policy80 apolicy max_line_length 80 apolicy policy80 policy100 apolicy max_line_length 100 class email policy Policy kw This is the abstract base class for all policy classes It provides default implementations for a couple of trivial methods as well as the implementation of the immutability property the clone method and the constructor semantics The constructor of a policy class can be passed various keyword arguments The arguments that may be specified are any non method properties on this class plus any additional non method properties on the concrete class A value specified in the constructor will override the default value for the corresponding attribute This class defines the following properties and thus values for the following may be passed in the constructor of any policy class max_line_length The maximum length of any line in the serialized output not counting the end of line character s Default is 78 per RFC 5322 A value of 0 or None indicates that no line wrapping should be done at all linesep The string to be used to terminate lines in serialized output The default is n because that s the internal end of line discipline used by Python though r n is required by the RFCs cte_type Controls the type of Content Transfer Encodings that may be or are required to be used The possible values are 7bit all data must be 7 bit clean ASCII only This means that where necessary data will be encoded using either quoted printable or base64 encoding 8bit data is not constrained to be 7 bit clean Data in headers is still required to be ASCII only and so will be encoded see fold_binary and utf8 below for exceptions but body parts may use the 8bit CTE A cte_type value of 8bit only works with BytesGenerator not Generator because strings cannot contain binary data If a Generator is operating under a policy that specifies cte_type 8bit it will act as if cte_type is 7bit raise_on_defect If True any defects encountered will be raised as errors If False the default defects will be passed to the register_defect method mangle_from_ If True lines starting with From in the body are escaped by putting a in front of them This parameter is used when the message is being serialized by a generator Default False New in version 3 5 message_factory A factory function for constructing a new empty message object Used by the parser when building messages Defaults to None in which case Message is used New in version 3 6 The following Policy method is intended to be called by code using the email library to create policy instances with custom settings clone kw Return a new Policy instance whose attributes have the same values as the current instance except where those attributes are given new values by the keyword arguments The remaining Policy methods are called by the email package code and are not intended to be called by an application using the email package A custom policy must implement all of these methods handle_defect obj defect Handle a defect found on obj When the email package calls this method defect will always be a subclass of Defect The default implementation checks the raise_on_defect flag If it is True defect is raised as an exception If it is False the ,en
458,default obj and defect are passed to register_defect register_defect obj defect Register a defect on obj In the email package defect will always be a subclass of Defect The default implementation calls the append method of the defects attribute of obj When the email package calls handle_defect obj will normally have a defects attribute that has an append method Custom object types used with the email package for example custom Message objects should also provide such an attribute otherwise defects in parsed messages will raise unexpected errors header_max_count name Return the maximum allowed number of headers named name Called when a header is added to an EmailMessage or Message object If the returned value is not 0 or None and there are already a number of headers with the name name greater than or equal to the value returned a ValueError is raised Because the default behavior of Message __setitem__ is to append the value to the list of headers it is easy to create duplicate headers without realizing it This method allows certain headers to be limited in the number of instances of that header that may be added to a Message programmatically The limit is not observed by the parser which will faithfully produce as many headers as exist in the message being parsed The default implementation returns None for all header names header_source_parse sourcelines The email package calls this method with a list of strings each string ending with the line separation characters found in the source being parsed The first line includes the field header name and separator All whitespace in the source is preserved The method should return the name value tuple that is to be stored in the Message to represent the parsed header If an implementation wishes to retain compatibility with the existing email package policies name should be the case preserved name all characters up to the separator while value should be the unfolded value all line separator characters removed but whitespace kept intact stripped of leading whitespace sourcelines may contain surrogateescaped binary data There is no default implementation header_store_parse name value The email package calls this method with the name and value provided by the application program when the application program is modifying a Message programmatically as opposed to a Message created by a parser The method should return the name value tuple that is to be stored in the Message to represent the header If an implementation wishes to retain compatibility with the existing email package policies the name and value should be strings or string subclasses that do not change the content of the passed in arguments There is no default implementation header_fetch_parse name value The email package calls this method with the name and value currently stored in the Message when that header is requested by the application program and whatever the method returns is what is passed back to the application as the value of the header being retrieved Note that there may be more than one header with the same name stored in the Message the method is passed the specific name and value of the header destined to be returned to the application value may contain surrogateescaped binary data There should be no surrogateescaped binary data in the value returned by the method There is no default implementation fold name value The email package calls this method with the name and value currently stored in the Message for a given header The method should return a string that represents that header folded correctly according to the policy settings by composing the name with the value and inserting linesep characters at the appropriate places See RFC 5322 for a discussion of the rules for folding email headers value may contain surrogateescaped binary data There should be no surrogateescaped binary data in the string returned by the method fold_binary name value The same as fold except that the returned value should be a bytes object rather than a string value may contain surrogateescaped binary data These could be converted,en
459, back into binary data in the returned bytes object class email policy EmailPolicy kw This concrete Policy provides behavior that is intended to be fully compliant with the current email RFCs These include but are not limited to RFC 5322 RFC 2047 and the current MIME RFCs This policy adds new header parsing and folding algorithms Instead of simple strings headers are str subclasses with attributes that depend on the type of the field The parsing and folding algorithm fully implement RFC 2047 and RFC 5322 The default value for the message_factory attribute is EmailMessage In addition to the settable attributes listed above that apply to all policies this policy adds the following additional attributes New in version 3 6 1 utf8 If False follow RFC 5322 supporting non ASCII characters in headers by encoding them as encoded words If True follow RFC 6532 and use utf 8 encoding for headers Messages formatted in this way may be passed to SMTP servers that support the SMTPUTF8 extension RFC 6531 refold_source If the value for a header in the Message object originated from a parser as opposed to being set by a program this attribute indicates whether or not a generator should refold that value when transforming the message back into serialized form The possible values are none all source values use original folding long source values that have any line that is longer than max_line_length will be refolded all all values are refolded The default is long header_factory A callable that takes two arguments name and value where name is a header field name and value is an unfolded header field value and returns a string subclass that represents that header A default header_factory see headerregistry is provided that supports custom parsing for the various address and date RFC 5322 header field types and the major MIME header field stypes Support for additional custom parsing will be added in the future content_manager An object with at least two methods get_content and set_content When the get_content or set_content method of an EmailMessage object is called it calls the corresponding method of this object passing it the message object as its first argument and any arguments or keywords that were passed to it as additional arguments By default content_manager is set to raw_data_manager New in version 3 4 The class provides the following concrete implementations of the abstract methods of Policy header_max_count name Returns the value of the max_count attribute of the specialized class used to represent the header with the given name header_source_parse sourcelines The name is parsed as everything up to the and returned unmodified The value is determined by stripping leading whitespace off the remainder of the first line joining all subsequent lines together and stripping any trailing carriage return or linefeed characters header_store_parse name value The name is returned unchanged If the input value has a name attribute and it matches name ignoring case the value is returned unchanged Otherwise the name and value are passed to header_factory and the resulting header object is returned as the value In this case a ValueError is raised if the input value contains CR or LF characters header_fetch_parse name value If the value has a name attribute it is returned to unmodified Otherwise the name and the value with any CR or LF characters removed are passed to the header_factory and the resulting header object is returned Any surrogateescaped bytes get turned into the unicode unknown character glyph fold name value Header folding is controlled by the refold_source policy setting A value is considered to be a source value if and only if it does not have a name attribute having a name attribute means it is a header object of some sort If a source value needs to be refolded according to the policy it is converted into a header object by passing the name and the value with any CR and LF characters removed to the header_factory Folding of a header object is done by calling its fold method with the current policy Source values are split into lines ,en
460,using splitlines If the value is not to be refolded the lines are rejoined using the linesep from the policy and returned The exception is lines containing non ascii binary data In that case the value is refolded regardless of the refold_source setting which causes the binary data to be CTE encoded using the unknown 8bit charset fold_binary name value The same as fold if cte_type is 7bit except that the returned value is bytes If cte_type is 8bit non ASCII binary data is converted back into bytes Headers with binary data are not refolded regardless of the refold_header setting since there is no way to know whether the binary data consists of single byte characters or multibyte characters The following instances of EmailPolicy provide defaults suitable for specific application domains Note that in the future the behavior of these instances in particular the HTTP instance may be adjusted to conform even more closely to the RFCs relevant to their domains email policy default An instance of EmailPolicy with all defaults unchanged This policy uses the standard Python n line endings rather than the RFC correct r n email policy SMTP Suitable for serializing messages in conformance with the email RFCs Like default but with linesep set to r n which is RFC compliant email policy SMTPUTF8 The same as SMTP except that utf8 is True Useful for serializing messages to a message store without using encoded words in the headers Should only be used for SMTP transmission if the sender or recipient addresses have non ASCII characters the smtplib SMTP send_message method handles this automatically email policy HTTP Suitable for serializing headers with for use in HTTP traffic Like SMTP except that max_line_length is set to None unlimited email policy strict Convenience instance The same as default except that raise_on_defect is set to True This allows any policy to be made strict by writing somepolicy policy strict With all of these EmailPolicies the effective API of the email package is changed from the Python 3 2 API in the following ways Setting a header on a Message results in that header being parsed and a header object created Fetching a header value from a Message results in that header being parsed and a header object created and returned Any header object or any header that is refolded due to the policy settings is folded using an algorithm that fully implements the RFC folding algorithms including knowing where encoded words are required and allowed From the application view this means that any header obtained through the EmailMessage is a header object with extra attributes whose string value is the fully decoded unicode value of the header Likewise a header may be assigned a new value or a new header created using a unicode string and the policy will take care of converting the unicode string into the correct RFC encoded form The header objects and their attributes are described in headerregistry class email policy Compat32 kw This concrete Policy is the backward compatibility policy It replicates the behavior of the email package in Python 3 2 The policy module also defines an instance of this class compat32 that is used as the default policy Thus the default behavior of the email package is to maintain compatibility with Python 3 2 The following attributes have values that are different from the Policy default mangle_from_ The default is True The class provides the following concrete implementations of the abstract methods of Policy header_source_parse sourcelines The name is parsed as everything up to the and returned unmodified The value is determined by stripping leading whitespace off the remainder of the first line joining all subsequent lines together and stripping any trailing carriage return or linefeed characters header_store_parse name value The name and value are returned unmodified header_fetch_parse name value If the value contains binary data it is converted into a Header object using the unknown 8bit charset Otherwise it is returned unmodified fold name value Headers are folded using the Header folding algorithm ,en
461,which preserves existing line breaks in the value and wraps each resulting line to the max_line_length Non ASCII binary data are CTE encoded using the unknown 8bit charset fold_binary name value Headers are folded using the Header folding algorithm which preserves existing line breaks in the value and wraps each resulting line to the max_line_length If cte_type is 7bit non ascii binary data is CTE encoded using the unknown 8bit charset Otherwise the original source header is used with its existing line breaks and any RFC invalid binary data it may contain email policy compat32 An instance of Compat32 providing backward compatibility with the behavior of the email package in Python 3 2 Footnotes 1 Originally added in 3 3 as a provisional feature,en
462,asyncio Asynchronous I O Hello World import asyncio async def main print Hello await asyncio sleep 1 print World asyncio run main asyncio is a library to write concurrent code using the async await syntax asyncio is used as a foundation for multiple Python asynchronous frameworks that provide high performance network and web servers database connection libraries distributed task queues etc asyncio is often a perfect fit for IO bound and high level structured network code asyncio provides a set of high level APIs to run Python coroutines concurrently and have full control over their execution perform network IO and IPC control subprocesses distribute tasks via queues synchronize concurrent code Additionally there are low level APIs for library and framework developers to create and manage event loops which provide asynchronous APIs for networking running subprocesses handling OS signals etc implement efficient protocols using transports bridge callback based libraries and code with async await syntax You can experiment with an asyncio concurrent context in the REPL python m asyncio asyncio REPL Use await directly instead of asyncio run Type help copyright credits or license for more information import asyncio await asyncio sleep 10 result hello hello Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information Reference High level APIs Runners Coroutines and Tasks Streams Synchronization Primitives Subprocesses Queues Exceptions Low level APIs Event Loop Futures Transports and Protocols Policies Platform Support Extending Guides and Tutorials High level API Index Low level API Index Developing with asyncio Note The source code for asyncio can be found in Lib asyncio,en
463,Programming FAQ General Questions Is there a source code level debugger with breakpoints single stepping etc Yes Several debuggers for Python are described below and the built in function breakpoint allows you to drop into any of them The pdb module is a simple but adequate console mode debugger for Python It is part of the standard Python library and is documented in the Library Reference Manual You can also write your own debugger by using the code for pdb as an example The IDLE interactive development environment which is part of the standard Python distribution normally available as Tools scripts idle3 includes a graphical debugger PythonWin is a Python IDE that includes a GUI debugger based on pdb The PythonWin debugger colors breakpoints and has quite a few cool features such as debugging non PythonWin programs PythonWin is available as part of pywin32 project and as a part of the ActivePython distribution Eric is an IDE built on PyQt and the Scintilla editing component trepan3k is a gdb like debugger Visual Studio Code is an IDE with debugging tools that integrates with version control software There are a number of commercial Python IDEs that include graphical debuggers They include Wing IDE Komodo IDE PyCharm Are there tools to help find bugs or perform static analysis Yes Pylint and Pyflakes do basic checking that will help you catch bugs sooner Static type checkers such as Mypy Pyre and Pytype can check type hints in Python source code How can I create a stand alone binary from a Python script You don t need the ability to compile Python to C code if all you want is a stand alone program that users can download and run without having to install the Python distribution first There are a number of tools that determine the set of modules required by a program and bind these modules together with a Python binary to produce a single executable One is to use the freeze tool which is included in the Python source tree as Tools freeze It converts Python byte code to C arrays with a C compiler you can embed all your modules into a new program which is then linked with the standard Python modules It works by scanning your source recursively for import statements in both forms and looking for the modules in the standard Python path as well as in the source directory for built in modules It then turns the bytecode for modules written in Python into C code array initializers that can be turned into code objects using the marshal module and creates a custom made config file that only contains those built in modules which are actually used in the program It then compiles the generated C code and links it with the rest of the Python interpreter to form a self contained binary which acts exactly like your script The following packages can help with the creation of console and GUI executables Nuitka Cross platform PyInstaller Cross platform PyOxidizer Cross platform cx_Freeze Cross platform py2app macOS only py2exe Windows only Are there coding standards or a style guide for Python programs Yes The coding style required for standard library modules is documented as PEP 8 Core Language Why am I getting an UnboundLocalError when the variable has a value It can be a surprise to get the UnboundLocalError in previously working code when it is modified by adding an assignment statement somewhere in the body of a function This code x 10 def bar print x bar 10 works but this code x 10 def foo print x x 1 results in an UnboundLocalError foo Traceback most recent call last UnboundLocalError local variable x referenced before assignment This is because when you make an assignment to a variable in a scope that variable becomes local to that scope and shadows any similarly named variable in the outer scope Since the last statement in foo assigns a new value to x the compiler recognizes it as a local variable Consequently when the earlier print x attempts to print the uninitialized local variable and an error results In the example above you can access the outer scope variable by declaring it global x 10 def foobar global x print x x 1 fooba,en
464,r 10 This explicit declaration is required in order to remind you that unlike the superficially analogous situation with class and instance variables you are actually modifying the value of the variable in the outer scope print x 11 You can do a similar thing in a nested scope using the nonlocal keyword def foo x 10 def bar nonlocal x print x x 1 bar print x foo 10 11 What are the rules for local and global variables in Python In Python variables that are only referenced inside a function are implicitly global If a variable is assigned a value anywhere within the function s body it s assumed to be a local unless explicitly declared as global Though a bit surprising at first a moment s consideration explains this On one hand requiring global for assigned variables provides a bar against unintended side effects On the other hand if global was required for all global references you d be using global all the time You d have to declare as global every reference to a built in function or to a component of an imported module This clutter would defeat the usefulness of the global declaration for identifying side effects Why do lambdas defined in a loop with different values all return the same result Assume you use a for loop to define a few different lambdas or even plain functions e g squares for x in range 5 squares append lambda x 2 This gives you a list that contains 5 lambdas that calculate x 2 You might expect that when called they would return respectively 0 1 4 9 and 16 However when you actually try you will see that they all return 16 squares 2 16 squares 4 16 This happens because x is not local to the lambdas but is defined in the outer scope and it is accessed when the lambda is called not when it is defined At the end of the loop the value of x is 4 so all the functions now return 4 2 i e 16 You can also verify this by changing the value of x and see how the results of the lambdas change x 8 squares 2 64 In order to avoid this you need to save the values in variables local to the lambdas so that they don t rely on the value of the global x squares for x in range 5 squares append lambda n x n 2 Here n x creates a new variable n local to the lambda and computed when the lambda is defined so that it has the same value that x had at that point in the loop This means that the value of n will be 0 in the first lambda 1 in the second 2 in the third and so on Therefore each lambda will now return the correct result squares 2 4 squares 4 16 Note that this behaviour is not peculiar to lambdas but applies to regular functions too How do I share global variables across modules The canonical way to share information across modules within a single program is to create a special module often called config or cfg Just import the config module in all modules of your application the module then becomes available as a global name Because there is only one instance of each module any changes made to the module object get reflected everywhere For example config py x 0 Default value of the x configuration setting mod py import config config x 1 main py import config import mod print config x Note that using a module is also the basis for implementing the singleton design pattern for the same reason What are the best practices for using import in a module In general don t use from modulename import Doing so clutters the importer s namespace and makes it much harder for linters to detect undefined names Import modules at the top of a file Doing so makes it clear what other modules your code requires and avoids questions of whether the module name is in scope Using one import per line makes it easy to add and delete module imports but using multiple imports per line uses less screen space It s good practice if you import modules in the following order 1 standard library modules e g sys os argparse re 2 third party library modules anything installed in Python s site packages directory e g dateutil requests PIL Image 3 locally developed modules It is sometimes necessary to move imports to a function or class to avoid problems with circular im,en
465,ports Gordon McMillan says Circular imports are fine where both modules use the import module form of import They fail when the 2nd module wants to grab a name out of the first from module import name and the import is at the top level That s because names in the 1st are not yet available because the first module is busy importing the 2nd In this case if the second module is only used in one function then the import can easily be moved into that function By the time the import is called the first module will have finished initializing and the second module can do its import It may also be necessary to move imports out of the top level of code if some of the modules are platform specific In that case it may not even be possible to import all of the modules at the top of the file In this case importing the correct modules in the corresponding platform specific code is a good option Only move imports into a local scope such as inside a function definition if it s necessary to solve a problem such as avoiding a circular import or are trying to reduce the initialization time of a module This technique is especially helpful if many of the imports are unnecessary depending on how the program executes You may also want to move imports into a function if the modules are only ever used in that function Note that loading a module the first time may be expensive because of the one time initialization of the module but loading a module multiple times is virtually free costing only a couple of dictionary lookups Even if the module name has gone out of scope the module is probably available in sys modules Why are default values shared between objects This type of bug commonly bites neophyte programmers Consider this function def foo mydict Danger shared reference to one dict for all calls compute something mydict key value return mydict The first time you call this function mydict contains a single item The second time mydict contains two items because when foo begins executing mydict starts out with an item already in it It is often expected that a function call creates new objects for default values This is not what happens Default values are created exactly once when the function is defined If that object is changed like the dictionary in this example subsequent calls to the function will refer to this changed object By definition immutable objects such as numbers strings tuples and None are safe from change Changes to mutable objects such as dictionaries lists and class instances can lead to confusion Because of this feature it is good programming practice to not use mutable objects as default values Instead use None as the default value and inside the function check if the parameter is None and create a new list dictionary whatever if it is For example don t write def foo mydict but def foo mydict None if mydict is None mydict create a new dict for local namespace This feature can be useful When you have a function that s time consuming to compute a common technique is to cache the parameters and the resulting value of each call to the function and return the cached value if the same value is requested again This is called memoizing and can be implemented like this Callers can only provide two parameters and optionally pass _cache by keyword def expensive arg1 arg2 _cache if arg1 arg2 in _cache return _cache arg1 arg2 Calculate the value result expensive computation _cache arg1 arg2 result Store result in the cache return result You could use a global variable containing a dictionary instead of the default value it s a matter of taste How can I pass optional or keyword parameters from one function to another Collect the arguments using the and specifiers in the function s parameter list this gives you the positional arguments as a tuple and the keyword arguments as a dictionary You can then pass these arguments when calling another function by using and def f x args kwargs kwargs width 14 3c g x args kwargs What is the difference between arguments and parameters Parameters are defined by the names that appear in a function definit,en
466,ion whereas arguments are the values actually passed to a function when calling it Parameters define what kind of arguments a function can accept For example given the function definition def func foo bar None kwargs pass foo bar and kwargs are parameters of func However when calling func for example func 42 bar 314 extra somevar the values 42 314 and somevar are arguments Why did changing list y also change list x If you wrote code like x y x y append 10 y 10 x 10 you might be wondering why appending an element to y changed x too There are two factors that produce this result 1 Variables are simply names that refer to objects Doing y x doesn t create a copy of the list it creates a new variable y that refers to the same object x refers to This means that there is only one object the list and both x and y refer to it 2 Lists are mutable which means that you can change their content After the call to append the content of the mutable object has changed from to 10 Since both the variables refer to the same object using either name accesses the modified value 10 If we instead assign an immutable object to x x 5 ints are immutable y x x x 1 5 can t be mutated we are creating a new object here x 6 y 5 we can see that in this case x and y are not equal anymore This is because integers are immutable and when we do x x 1 we are not mutating the int 5 by incrementing its value instead we are creating a new object the int 6 and assigning it to x that is changing which object x refers to After this assignment we have two objects the ints 6 and 5 and two variables that refer to them x now refers to 6 but y still refers to 5 Some operations for example y append 10 and y sort mutate the object whereas superficially similar operations for example y y 10 and sorted y create a new object In general in Python and in all cases in the standard library a method that mutates an object will return None to help avoid getting the two types of operations confused So if you mistakenly write y sort thinking it will give you a sorted copy of y you ll instead end up with None which will likely cause your program to generate an easily diagnosed error However there is one class of operations where the same operation sometimes has different behaviors with different types the augmented assignment operators For example mutates lists but not tuples or ints a_list 1 2 3 is equivalent to a_list extend 1 2 3 and mutates a_list whereas some_tuple 1 2 3 and some_int 1 create new objects In other words If we have a mutable object list dict set etc we can use some specific operations to mutate it and all the variables that refer to it will see the change If we have an immutable object str int tuple etc all the variables that refer to it will always see the same value but operations that transform that value into a new value always return a new object If you want to know if two variables refer to the same object or not you can use the is operator or the built in function id How do I write a function with output parameters call by reference Remember that arguments are passed by assignment in Python Since assignment just creates references to objects there s no alias between an argument name in the caller and callee and so no call by reference per se You can achieve the desired effect in a number of ways 1 By returning a tuple of the results def func1 a b a new value a and b are local names b b 1 assigned to new objects return a b return new values x y old value 99 func1 x y new value 100 This is almost always the clearest solution 2 By using global variables This isn t thread safe and is not recommended 3 By passing a mutable changeable in place object def func2 a a 0 new value a references a mutable list a 1 a 1 1 changes a shared object args old value 99 func2 args args new value 100 4 By passing in a dictionary that gets mutated def func3 args args a new value args is a mutable dictionary args b args b 1 change it in place args a old value b 99 func3 args args a new value b 100 5 Or bundle up values in a class instance class Namespace def __init__ self args for ,en
467,key value in args items setattr self key value def func4 args args a new value args is a mutable Namespace args b args b 1 change object in place args Namespace a old value b 99 func4 args vars args a new value b 100 There s almost never a good reason to get this complicated Your best choice is to return a tuple containing the multiple results How do you make a higher order function in Python You have two choices you can use nested scopes or you can use callable objects For example suppose you wanted to define linear a b which returns a function f x that computes the value a x b Using nested scopes def linear a b def result x return a x b return result Or using a callable object class linear def __init__ self a b self a self b a b def __call__ self x return self a x self b In both cases taxes linear 0 3 2 gives a callable object where taxes 10e6 0 3 10e6 2 The callable object approach has the disadvantage that it is a bit slower and results in slightly longer code However note that a collection of callables can share their signature via inheritance class exponential linear __init__ inherited def __call__ self x return self a x self b Object can encapsulate state for several methods class counter value 0 def set self x self value x def up self self value self value 1 def down self self value self value 1 count counter inc dec reset count up count down count set Here inc dec and reset act like functions which share the same counting variable How do I copy an object in Python In general try copy copy or copy deepcopy for the general case Not all objects can be copied but most can Some objects can be copied more easily Dictionaries have a copy method newdict olddict copy Sequences can be copied by slicing new_l l How can I find the methods or attributes of an object For an instance x of a user defined class dir x returns an alphabetized list of the names containing the instance attributes and methods and attributes defined by its class How can my code discover the name of an object Generally speaking it can t because objects don t really have names Essentially assignment always binds a name to a value the same is true of def and class statements but in that case the value is a callable Consider the following code class A pass B A a B b a print b __main__ A object at 0x16D07CC print a __main__ A object at 0x16D07CC Arguably the class has a name even though it is bound to two names and invoked through the name B the created instance is still reported as an instance of class A However it is impossible to say whether the instance s name is a or b since both names are bound to the same value Generally speaking it should not be necessary for your code to know the names of particular values Unless you are deliberately writing introspective programs this is usually an indication that a change of approach might be beneficial In comp lang python Fredrik Lundh once gave an excellent analogy in answer to this question The same way as you get the name of that cat you found on your porch the cat object itself cannot tell you its name and it doesn t really care so the only way to find out what it s called is to ask all your neighbours namespaces if it s their cat object and don t be surprised if you ll find that it s known by many names or no name at all What s up with the comma operator s precedence Comma is not an operator in Python Consider this session a in b a False a Since the comma is not an operator but a separator between expressions the above is evaluated as if you had entered a in b a not a in b a The same is true of the various assignment operators etc They are not truly operators but syntactic delimiters in assignment statements Is there an equivalent of C s ternary operator Yes there is The syntax is as follows on_true if expression else on_false x y 50 25 small x if x y else y Before this syntax was introduced in Python 2 5 a common idiom was to use logical operators expression and on_true or on_false However this idiom is unsafe as it can give wrong results when on_true has a false boolean value Therefore it is always bette,en
468,r to use the if else form Is it possible to write obfuscated one liners in Python Yes Usually this is done by nesting lambda within lambda See the following three examples slightly adapted from Ulf Bartelt from functools import reduce Primes 1000 print list filter None map lambda y y reduce lambda x y x y 0 map lambda x y y y x range 2 int pow y 0 5 1 1 range 2 1000 First 10 Fibonacci numbers print list map lambda x f lambda x f f x 1 f f x 2 f if x 1 else 1 f x f range 10 Mandelbrot set print lambda Ru Ro Iu Io IM Sx Sy reduce lambda x y x n y map lambda y Iu Iu Io Io Ru Ru Ro Ro Sy Sy L lambda yc Iu Iu Io Io Ru Ru Ro Ro i IM Sx Sx Sy Sy reduce lambda x y x y map lambda x xc Ru yc yc Ru Ru Ro Ro i i Sx Sx F lambda xc yc x y k f lambda xc yc x y k f k 0 or x x y y 4 0 or 1 f xc yc x x y y xc 2 0 x y yc k 1 f f xc yc x y k f chr 64 F Ru x Ro Ru Sx yc 0 0 i range Sx L Iu y Io Iu Sy range Sy 2 1 0 7 1 2 1 2 30 80 24 ___ ___ ___ ___ __ lines on screen V V ______ columns on screen __________ maximum of iterations _________________ range on y axis ____________________________ range on x axis Don t try this at home kids What does the slash in the parameter list of a function mean A slash in the argument list of a function denotes that the parameters prior to it are positional only Positional only parameters are the ones without an externally usable name Upon calling a function that accepts positional only parameters arguments are mapped to parameters based solely on their position For example divmod is a function that accepts positional only parameters Its documentation looks like this help divmod Help on built in function divmod in module builtins divmod x y Return the tuple x y x y Invariant div y mod x The slash at the end of the parameter list means that both parameters are positional only Thus calling divmod with keyword arguments would lead to an error divmod x 3 y 4 Traceback most recent call last File stdin line 1 in module TypeError divmod takes no keyword arguments Numbers and strings How do I specify hexadecimal and octal integers To specify an octal digit precede the octal value with a zero and then a lower or uppercase o For example to set the variable a to the octal value 10 8 in decimal type a 0o10 a 8 Hexadecimal is just as easy Simply precede the hexadecimal number with a zero and then a lower or uppercase x Hexadecimal digits can be specified in lower or uppercase For example in the Python interpreter a 0xa5 a 165 b 0XB2 b 178 Why does 22 10 return 3 It s primarily driven by the desire that i j have the same sign as j If you want that and also want i i j j i j then integer division has to return the floor C also requires that identity to hold and then compilers that truncate i j need to make i j have the same sign as i There are few real use cases for i j when j is negative When j is positive there are many and in virtually all of them it s more useful for i j to be 0 If the clock says 10 now what did it say 200 hours ago 190 12 2 is useful 190 12 10 is a bug waiting to bite How do I get int literal attribute instead of SyntaxError Trying to lookup an int literal attribute in the normal manner gives a SyntaxError because the period is seen as a decimal point 1 __class__ File stdin line 1 1 __class__ SyntaxError invalid decimal literal The solution is to separate the literal from the period with either a space or parentheses 1 __class__ class int 1 __class__ class int How do I convert a string to a number For integers use the built in int type constructor e g int 144 144 Similarly float converts to floating point e g float 144 144 0 By default these interpret the number as decimal so that int 0144 144 holds true and int 0x144 raises ValueError int string base takes the base to convert from as a second optional argument so int 0x144 16 324 If the base is specified as 0 the number is interpreted using Python s rules a leading 0o indicates octal and 0x indicates a hex number Do not use the built in function eval if all you need is to convert strings to numbers eval will be significantly slower and it presents a se,en
469,curity risk someone could pass you a Python expression that might have unwanted side effects For example someone could pass __import__ os system rm rf HOME which would erase your home directory eval also has the effect of interpreting numbers as Python expressions so that e g eval 09 gives a syntax error because Python does not allow leading 0 in a decimal number except 0 How do I convert a number to a string To convert e g the number 144 to the string 144 use the built in type constructor str If you want a hexadecimal or octal representation use the built in functions hex or oct For fancy formatting see the f strings and Format String Syntax sections e g 04d format 144 yields 0144 and 3f format 1 0 3 0 yields 0 333 How do I modify a string in place You can t because strings are immutable In most situations you should simply construct a new string from the various parts you want to assemble it from However if you need an object with the ability to modify in place unicode data try using an io StringIO object or the array module import io s Hello world sio io StringIO s sio getvalue Hello world sio seek 7 7 sio write there 6 sio getvalue Hello there import array a array array u s print a array u Hello world a 0 y print a array u yello world a tounicode yello world How do I use strings to call functions methods There are various techniques The best is to use a dictionary that maps strings to functions The primary advantage of this technique is that the strings do not need to match the names of the functions This is also the primary technique used to emulate a case construct def a pass def b pass dispatch go a stop b Note lack of parens for funcs dispatch get_input Note trailing parens to call function Use the built in function getattr import foo getattr foo bar Note that getattr works on any object including classes class instances modules and so on This is used in several places in the standard library like this class Foo def do_foo self def do_bar self f getattr foo_instance do_ opname f Use locals to resolve the function name def myFunc print hello fname myFunc f locals fname f Is there an equivalent to Perl s chomp for removing trailing newlines from strings You can use S rstrip r n to remove all occurrences of any line terminator from the end of the string S without removing other trailing whitespace If the string S represents more than one line with several empty lines at the end the line terminators for all the blank lines will be removed lines line 1 r n r n r n lines rstrip n r line 1 Since this is typically only desired when reading text one line at a time using S rstrip this way works well Is there a scanf or sscanf equivalent Not as such For simple input parsing the easiest approach is usually to split the line into whitespace delimited words using the split method of string objects and then convert decimal strings to numeric values using int or float split supports an optional sep parameter which is useful if the line uses something other than whitespace as a separator For more complicated input parsing regular expressions are more powerful than C s sscanf and better suited for the task What does UnicodeDecodeError or UnicodeEncodeError error mean See the Unicode HOWTO Can I end a raw string with an odd number of backslashes A raw string ending with an odd number of backslashes will escape the string s quote r C this will not work File stdin line 1 r C this will not work SyntaxError unterminated string literal detected at line 1 There are several workarounds for this One is to use regular strings and double the backslashes C this will work C this will work Another is to concatenate a regular string containing an escaped backslash to the raw string r C this will work C this will work It is also possible to use os path join to append a backslash on Windows os path join r C this will work C this will work Note that while a backslash will escape a quote for the purposes of determining where the raw string ends no escaping occurs when interpreting the value of the raw string That is the backslash remains present in ,en
470,the value of the raw string r backslash preserved backslash preserved Also see the specification in the language reference Performance My program is too slow How do I speed it up That s a tough one in general First here are a list of things to remember before diving further Performance characteristics vary across Python implementations This FAQ focuses on CPython Behaviour can vary across operating systems especially when talking about I O or multi threading You should always find the hot spots in your program before attempting to optimize any code see the profile module Writing benchmark scripts will allow you to iterate quickly when searching for improvements see the timeit module It is highly recommended to have good code coverage through unit testing or any other technique before potentially introducing regressions hidden in sophisticated optimizations That being said there are many tricks to speed up Python code Here are some general principles which go a long way towards reaching acceptable performance levels Making your algorithms faster or changing to faster ones can yield much larger benefits than trying to sprinkle micro optimization tricks all over your code Use the right data structures Study documentation for the Built in Types and the collections module When the standard library provides a primitive for doing something it is likely although not guaranteed to be faster than any alternative you may come up with This is doubly true for primitives written in C such as builtins and some extension types For example be sure to use either the list sort built in method or the related sorted function to do sorting and see the Sorting Techniques for examples of moderately advanced usage Abstractions tend to create indirections and force the interpreter to work more If the levels of indirection outweigh the amount of useful work done your program will be slower You should avoid excessive abstraction especially under the form of tiny functions or methods which are also often detrimental to readability If you have reached the limit of what pure Python can allow there are tools to take you further away For example Cython can compile a slightly modified version of Python code into a C extension and can be used on many different platforms Cython can take advantage of compilation and optional type annotations to make your code significantly faster than when interpreted If you are confident in your C programming skills you can also write a C extension module yourself See also The wiki page devoted to performance tips What is the most efficient way to concatenate many strings together str and bytes objects are immutable therefore concatenating many strings together is inefficient as each concatenation creates a new object In the general case the total runtime cost is quadratic in the total string length To accumulate many str objects the recommended idiom is to place them into a list and call str join at the end chunks for s in my_strings chunks append s result join chunks another reasonably efficient idiom is to use io StringIO To accumulate many bytes objects the recommended idiom is to extend a bytearray object using in place concatenation the operator result bytearray for b in my_bytes_objects result b Sequences Tuples Lists How do I convert between tuples and lists The type constructor tuple seq converts any sequence actually any iterable into a tuple with the same items in the same order For example tuple 1 2 3 yields 1 2 3 and tuple abc yields a b c If the argument is a tuple it does not make a copy but returns the same object so it is cheap to call tuple when you aren t sure that an object is already a tuple The type constructor list seq converts any sequence or iterable into a list with the same items in the same order For example list 1 2 3 yields 1 2 3 and list abc yields a b c If the argument is a list it makes a copy just like seq would What s a negative index Python sequences are indexed with positive numbers and negative numbers For positive numbers 0 is the first index 1 is the second index and so forth For neg,en
471,ative indices 1 is the last index and 2 is the penultimate next to last index and so forth Think of seq n as the same as seq len seq n Using negative indices can be very convenient For example S 1 is all of the string except for its last character which is useful for removing the trailing newline from a string How do I iterate over a sequence in reverse order Use the reversed built in function for x in reversed sequence do something with x This won t touch your original sequence but build a new copy with reversed order to iterate over How do you remove duplicates from a list See the Python Cookbook for a long discussion of many ways to do this https code activestate com recipes 52560 If you don t mind reordering the list sort it and then scan from the end of the list deleting duplicates as you go if mylist mylist sort last mylist 1 for i in range len mylist 2 1 1 if last mylist i del mylist i else last mylist i If all elements of the list may be used as set keys i e they are all hashable this is often faster mylist list set mylist This converts the list into a set thereby removing duplicates and then back into a list How do you remove multiple items from a list As with removing duplicates explicitly iterating in reverse with a delete condition is one possibility However it is easier and faster to use slice replacement with an implicit or explicit forward iteration Here are three variations mylist filter keep_function mylist mylist x for x in mylist if keep_condition mylist x for x in mylist if keep_condition The list comprehension may be fastest How do you make an array in Python Use a list this 1 is an array Lists are equivalent to C or Pascal arrays in their time complexity the primary difference is that a Python list can contain objects of many different types The array module also provides methods for creating arrays of fixed types with compact representations but they are slower to index than lists Also note that NumPy and other third party packages define array like structures with various characteristics as well To get Lisp style linked lists you can emulate cons cells using tuples lisp_list like this example None If mutability is desired you could use lists instead of tuples Here the analogue of a Lisp car is lisp_list 0 and the analogue of cdr is lisp_list 1 Only do this if you re sure you really need to because it s usually a lot slower than using Python lists How do I create a multidimensional list You probably tried to make a multidimensional array like this A None 2 3 This looks correct if you print it A None None None None None None But when you assign a value it shows up in multiple places A 0 0 5 A 5 None 5 None 5 None The reason is that replicating a list with doesn t create copies it only creates references to the existing objects The 3 creates a list containing 3 references to the same list of length two Changes to one row will show in all rows which is almost certainly not what you want The suggested approach is to create a list of the desired length first and then fill in each element with a newly created list A None 3 for i in range 3 A i None 2 This generates a list containing 3 different lists of length two You can also use a list comprehension w h 2 3 A None w for i in range h Or you can use an extension that provides a matrix datatype NumPy is the best known How do I apply a method or function to a sequence of objects To call a method or function and accumulate the return values is a list a list comprehension is an elegant solution result obj method for obj in mylist result function obj for obj in mylist To just run the method or function without saving the return values a plain for loop will suffice for obj in mylist obj method for obj in mylist function obj Why does a_tuple i item raise an exception when the addition works This is because of a combination of the fact that augmented assignment operators are assignment operators and the difference between mutable and immutable objects in Python This discussion applies in general when augmented assignment operators are applied to elements of a tu,en
472,ple that point to mutable objects but we ll use a list and as our exemplar If you wrote a_tuple 1 2 a_tuple 0 1 Traceback most recent call last TypeError tuple object does not support item assignment The reason for the exception should be immediately clear 1 is added to the object a_tuple 0 points to 1 producing the result object 2 but when we attempt to assign the result of the computation 2 to element 0 of the tuple we get an error because we can t change what an element of a tuple points to Under the covers what this augmented assignment statement is doing is approximately this result a_tuple 0 1 a_tuple 0 result Traceback most recent call last TypeError tuple object does not support item assignment It is the assignment part of the operation that produces the error since a tuple is immutable When you write something like a_tuple foo bar a_tuple 0 item Traceback most recent call last TypeError tuple object does not support item assignment The exception is a bit more surprising and even more surprising is the fact that even though there was an error the append worked a_tuple 0 foo item To see why this happens you need to know that a if an object implements an __iadd__ magic method it gets called when the augmented assignment is executed and its return value is what gets used in the assignment statement and b for lists __iadd__ is equivalent to calling extend on the list and returning the list That s why we say that for lists is a shorthand for list extend a_list a_list 1 a_list 1 This is equivalent to result a_list __iadd__ 1 a_list result The object pointed to by a_list has been mutated and the pointer to the mutated object is assigned back to a_list The end result of the assignment is a no op since it is a pointer to the same object that a_list was previously pointing to but the assignment still happens Thus in our tuple example what is happening is equivalent to result a_tuple 0 __iadd__ item a_tuple 0 result Traceback most recent call last TypeError tuple object does not support item assignment The __iadd__ succeeds and thus the list is extended but even though result points to the same object that a_tuple 0 already points to that final assignment still results in an error because tuples are immutable I want to do a complicated sort can you do a Schwartzian Transform in Python The technique attributed to Randal Schwartz of the Perl community sorts the elements of a list by a metric which maps each element to its sort value In Python use the key argument for the list sort method Isorted L Isorted sort key lambda s int s 10 15 How can I sort one list by values from another list Merge them into an iterator of tuples sort the resulting list and then pick out the element you want list1 what I m sorting by list2 something else to sort pairs zip list1 list2 pairs sorted pairs pairs I m else by sort sorting to what something result x 1 for x in pairs result else sort to something Objects What is a class A class is the particular object type created by executing a class statement Class objects are used as templates to create instance objects which embody both the data attributes and code methods specific to a datatype A class can be based on one or more other classes called its base class es It then inherits the attributes and methods of its base classes This allows an object model to be successively refined by inheritance You might have a generic Mailbox class that provides basic accessor methods for a mailbox and subclasses such as MboxMailbox MaildirMailbox OutlookMailbox that handle various specific mailbox formats What is a method A method is a function on some object x that you normally call as x name arguments Methods are defined as functions inside the class definition class C def meth self arg return arg 2 self attribute What is self Self is merely a conventional name for the first argument of a method A method defined as meth self a b c should be called as x meth a b c for some instance x of the class in which the definition occurs the called method will think it is called as meth x a b c See also Why must self be ,en
473,used explicitly in method definitions and calls How do I check if an object is an instance of a given class or of a subclass of it Use the built in function isinstance obj cls You can check if an object is an instance of any of a number of classes by providing a tuple instead of a single class e g isinstance obj class1 class2 and can also check whether an object is one of Python s built in types e g isinstance obj str or isinstance obj int float complex Note that isinstance also checks for virtual inheritance from an abstract base class So the test will return True for a registered class even if hasn t directly or indirectly inherited from it To test for true inheritance scan the MRO of the class from collections abc import Mapping class P pass class C P pass Mapping register P c C isinstance c C direct True isinstance c P indirect True isinstance c Mapping virtual True Actual inheritance chain type c __mro__ class C class P class object Test for true inheritance Mapping in type c __mro__ False Note that most programs do not use isinstance on user defined classes very often If you are developing the classes yourself a more proper object oriented style is to define methods on the classes that encapsulate a particular behaviour instead of checking the object s class and doing a different thing based on what class it is For example if you have a function that does something def search obj if isinstance obj Mailbox code to search a mailbox elif isinstance obj Document code to search a document elif A better approach is to define a search method on all the classes and just call it class Mailbox def search self code to search a mailbox class Document def search self code to search a document obj search What is delegation Delegation is an object oriented technique also called a design pattern Let s say you have an object x and want to change the behaviour of just one of its methods You can create a new class that provides a new implementation of the method you re interested in changing and delegates all other methods to the corresponding method of x Python programmers can easily implement delegation For example the following class implements a class that behaves like a file but converts all written data to uppercase class UpperOut def __init__ self outfile self _outfile outfile def write self s self _outfile write s upper def __getattr__ self name return getattr self _outfile name Here the UpperOut class redefines the write method to convert the argument string to uppercase before calling the underlying self _outfile write method All other methods are delegated to the underlying self _outfile object The delegation is accomplished via the __getattr__ method consult the language reference for more information about controlling attribute access Note that for more general cases delegation can get trickier When attributes must be set as well as retrieved the class must define a __setattr__ method too and it must do so carefully The basic implementation of __setattr__ is roughly equivalent to the following class X def __setattr__ self name value self __dict__ name value Most __setattr__ implementations must modify self __dict__ to store local state for self without causing an infinite recursion How do I call a method defined in a base class from a derived class that extends it Use the built in super function class Derived Base def meth self super meth calls Base meth In the example super will automatically determine the instance from which it was called the self value look up the method resolution order MRO with type self __mro__ and return the next in line after Derived in the MRO Base How can I organize my code to make it easier to change the base class You could assign the base class to an alias and derive from the alias Then all you have to change is the value assigned to the alias Incidentally this trick is also handy if you want to decide dynamically e g depending on availability of resources which base class to use Example class Base BaseAlias Base class Derived BaseAlias How do I create static class data and static class meth,en
474,ods Both static data and static methods in the sense of C or Java are supported in Python For static data simply define a class attribute To assign a new value to the attribute you have to explicitly use the class name in the assignment class C count 0 number of times C __init__ called def __init__ self C count C count 1 def getcount self return C count or return self count c count also refers to C count for any c such that isinstance c C holds unless overridden by c itself or by some class on the base class search path from c __class__ back to C Caution within a method of C an assignment like self count 42 creates a new and unrelated instance named count in self s own dict Rebinding of a class static data name must always specify the class whether inside a method or not C count 314 Static methods are possible class C staticmethod def static arg1 arg2 arg3 No self parameter However a far more straightforward way to get the effect of a static method is via a simple module level function def getcount return C count If your code is structured so as to define one class or tightly related class hierarchy per module this supplies the desired encapsulation How can I overload constructors or methods in Python This answer actually applies to all methods but the question usually comes up first in the context of constructors In C you d write class C C cout No arguments n C int i cout Argument is i n In Python you have to write a single constructor that catches all cases using default arguments For example class C def __init__ self i None if i is None print No arguments else print Argument is i This is not entirely equivalent but close enough in practice You could also try a variable length argument list e g def __init__ self args The same approach works for all method definitions I try to use __spam and I get an error about _SomeClassName__spam Variable names with double leading underscores are mangled to provide a simple but effective way to define class private variables Any identifier of the form __spam at least two leading underscores at most one trailing underscore is textually replaced with _classname__spam where classname is the current class name with any leading underscores stripped This doesn t guarantee privacy an outside user can still deliberately access the _classname__spam attribute and private values are visible in the object s __dict__ Many Python programmers never bother to use private variable names at all My class defines __del__ but it is not called when I delete the object There are several possible reasons for this The del statement does not necessarily call __del__ it simply decrements the object s reference count and if this reaches zero __del__ is called If your data structures contain circular links e g a tree where each child has a parent reference and each parent has a list of children the reference counts will never go back to zero Once in a while Python runs an algorithm to detect such cycles but the garbage collector might run some time after the last reference to your data structure vanishes so your __del__ method may be called at an inconvenient and random time This is inconvenient if you re trying to reproduce a problem Worse the order in which object s __del__ methods are executed is arbitrary You can run gc collect to force a collection but there are pathological cases where objects will never be collected Despite the cycle collector it s still a good idea to define an explicit close method on objects to be called whenever you re done with them The close method can then remove attributes that refer to subobjects Don t call __del__ directly __del__ should call close and close should make sure that it can be called more than once for the same object Another way to avoid cyclical references is to use the weakref module which allows you to point to objects without incrementing their reference count Tree data structures for instance should use weak references for their parent and sibling references if they need them Finally if your __del__ method raises an exception a warning message is printed to sy,en
475,s stderr How do I get a list of all instances of a given class Python does not keep track of all instances of a class or of a built in type You can program the class s constructor to keep track of all instances by keeping a list of weak references to each instance Why does the result of id appear to be not unique The id builtin returns an integer that is guaranteed to be unique during the lifetime of the object Since in CPython this is the object s memory address it happens frequently that after an object is deleted from memory the next freshly created object is allocated at the same position in memory This is illustrated by this example id 1000 13901272 id 2000 13901272 The two ids belong to different integer objects that are created before and deleted immediately after execution of the id call To be sure that objects whose id you want to examine are still alive create another reference to the object a 1000 b 2000 id a 13901272 id b 13891296 When can I rely on identity tests with the is operator The is operator tests for object identity The test a is b is equivalent to id a id b The most important property of an identity test is that an object is always identical to itself a is a always returns True Identity tests are usually faster than equality tests And unlike equality tests identity tests are guaranteed to return a boolean True or False However identity tests can only be substituted for equality tests when object identity is assured Generally there are three circumstances where identity is guaranteed 1 Assignments create new names but do not change object identity After the assignment new old it is guaranteed that new is old 2 Putting an object in a container that stores object references does not change object identity After the list assignment s 0 x it is guaranteed that s 0 is x 3 If an object is a singleton it means that only one instance of that object can exist After the assignments a None and b None it is guaranteed that a is b because None is a singleton In most other circumstances identity tests are inadvisable and equality tests are preferred In particular identity tests should not be used to check constants such as int and str which aren t guaranteed to be singletons a 1000 b 500 c b 500 a is c False a Python b Py c b thon a is c False Likewise new instances of mutable containers are never identical a b a is b False In the standard library code you will see several common patterns for correctly using identity tests 1 As recommended by PEP 8 an identity test is the preferred way to check for None This reads like plain English in code and avoids confusion with other objects that may have boolean values that evaluate to false 2 Detecting optional arguments can be tricky when None is a valid input value In those situations you can create a singleton sentinel object guaranteed to be distinct from other objects For example here is how to implement a method that behaves like dict pop _sentinel object def pop self key default _sentinel if key in self value self key del self key return value if default is _sentinel raise KeyError key return default 3 Container implementations sometimes need to augment equality tests with identity tests This prevents the code from being confused by objects such as float NaN that are not equal to themselves For example here is the implementation of collections abc Sequence __contains__ def __contains__ self value for v in self if v is value or v value return True return False How can a subclass control what data is stored in an immutable instance When subclassing an immutable type override the __new__ method instead of the __init__ method The latter only runs after an instance is created which is too late to alter data in an immutable instance All of these immutable classes have a different signature than their parent class from datetime import date class FirstOfMonthDate date Always choose the first day of the month def __new__ cls year month day return super __new__ cls year month 1 class NamedInt int Allow text names for some numbers xlat zero 0 one 1 ten 10 def __new__ cls value,en
476, value cls xlat get value value return super __new__ cls value class TitleStr str Convert str to name suitable for a URL path def __new__ cls s s s lower replace s join c for c in s if c isalnum or c return super __new__ cls s The classes can be used like this FirstOfMonthDate 2012 2 14 FirstOfMonthDate 2012 2 1 NamedInt ten 10 NamedInt 20 20 TitleStr Blog Why Python Rocks blog why python rocks How do I cache method calls The two principal tools for caching methods are functools cached_property and functools lru_cache The former stores results at the instance level and the latter at the class level The cached_property approach only works with methods that do not take any arguments It does not create a reference to the instance The cached method result will be kept only as long as the instance is alive The advantage is that when an instance is no longer used the cached method result will be released right away The disadvantage is that if instances accumulate so too will the accumulated method results They can grow without bound The lru_cache approach works with methods that have hashable arguments It creates a reference to the instance unless special efforts are made to pass in weak references The advantage of the least recently used algorithm is that the cache is bounded by the specified maxsize The disadvantage is that instances are kept alive until they age out of the cache or until the cache is cleared This example shows the various techniques class Weather Lookup weather information on a government website def __init__ self station_id self _station_id station_id The _station_id is private and immutable def current_temperature self Latest hourly observation Do not cache this because old results can be out of date cached_property def location self Return the longitude latitude coordinates of the station Result only depends on the station_id lru_cache maxsize 20 def historic_rainfall self date units mm Rainfall on a given date Depends on the station_id date and units The above example assumes that the station_id never changes If the relevant instance attributes are mutable the cached_property approach can t be made to work because it cannot detect changes to the attributes To make the lru_cache approach work when the station_id is mutable the class needs to define the __eq__ and __hash__ methods so that the cache can detect relevant attribute updates class Weather Example with a mutable station identifier def __init__ self station_id self station_id station_id def change_station self station_id self station_id station_id def __eq__ self other return self station_id other station_id def __hash__ self return hash self station_id lru_cache maxsize 20 def historic_rainfall self date units cm Rainfall on a given date Depends on the station_id date and units Modules How do I create a pyc file When a module is imported for the first time or when the source file has changed since the current compiled file was created a pyc file containing the compiled code should be created in a __pycache__ subdirectory of the directory containing the py file The pyc file will have a filename that starts with the same name as the py file and ends with pyc with a middle component that depends on the particular python binary that created it See PEP 3147 for details One reason that a pyc file may not be created is a permissions problem with the directory containing the source file meaning that the __pycache__ subdirectory cannot be created This can happen for example if you develop as one user but run as another such as if you are testing with a web server Unless the PYTHONDONTWRITEBYTECODE environment variable is set creation of a pyc file is automatic if you re importing a module and Python has the ability permissions free space etc to create a __pycache__ subdirectory and write the compiled module to that subdirectory Running Python on a top level script is not considered an import and no pyc will be created For example if you have a top level module foo py that imports another module xyz py when you run foo by typing python foo py as a shell c,en
477,ommand a pyc will be created for xyz because xyz is imported but no pyc file will be created for foo since foo py isn t being imported If you need to create a pyc file for foo that is to create a pyc file for a module that is not imported you can using the py_compile and compileall modules The py_compile module can manually compile any module One way is to use the compile function in that module interactively import py_compile py_compile compile foo py This will write the pyc to a __pycache__ subdirectory in the same location as foo py or you can override that with the optional parameter cfile You can also automatically compile all files in a directory or directories using the compileall module You can do it from the shell prompt by running compileall py and providing the path of a directory containing Python files to compile python m compileall How do I find the current module name A module can find out its own module name by looking at the predefined global variable __name__ If this has the value __main__ the program is running as a script Many modules that are usually used by importing them also provide a command line interface or a self test and only execute this code after checking __name__ def main print Running test if __name__ __main__ main How can I have modules that mutually import each other Suppose you have the following modules foo py from bar import bar_var foo_var 1 bar py from foo import foo_var bar_var 2 The problem is that the interpreter will perform the following steps main imports foo Empty globals for foo are created foo is compiled and starts executing foo imports bar Empty globals for bar are created bar is compiled and starts executing bar imports foo which is a no op since there already is a module named foo The import mechanism tries to read foo_var from foo globals to set bar foo_var foo foo_var The last step fails because Python isn t done with interpreting foo yet and the global symbol dictionary for foo is still empty The same thing happens when you use import foo and then try to access foo foo_var in global code There are at least three possible workarounds for this problem Guido van Rossum recommends avoiding all uses of from module import and placing all code inside functions Initializations of global variables and class variables should use constants or built in functions only This means everything from an imported module is referenced as module name Jim Roskind suggests performing steps in the following order in each module exports globals functions and classes that don t need imported base classes import statements active code including globals that are initialized from imported values Van Rossum doesn t like this approach much because the imports appear in a strange place but it does work Matthias Urlichs recommends restructuring your code so that the recursive import is not necessary in the first place These solutions are not mutually exclusive __import__ x y z returns module x how do I get z Consider using the convenience function import_module from importlib instead z importlib import_module x y z When I edit an imported module and reimport it the changes don t show up Why does this happen For reasons of efficiency as well as consistency Python only reads the module file on the first time a module is imported If it didn t in a program consisting of many modules where each one imports the same basic module the basic module would be parsed and re parsed many times To force re reading of a changed module do this import importlib import modname importlib reload modname Warning this technique is not 100 fool proof In particular modules containing statements like from modname import some_objects will continue to work with the old version of the imported objects If the module contains class definitions existing class instances will not be updated to use the new class definition This can result in the following paradoxical behaviour import importlib import cls c cls C Create an instance of C importlib reload cls module cls from cls py isinstance c cls C isinstance is false False The natur,en
478,e of the problem is made clear if you print out the identity of the class objects hex id c __class__ 0x7352a0 hex id cls C 0x4198d0,en
479,What s New in Python 2 6 Author A M Kuchling amk at amk ca This article explains the new features in Python 2 6 released on October 1 2008 The release schedule is described in PEP 361 The major theme of Python 2 6 is preparing the migration path to Python 3 0 a major redesign of the language Whenever possible Python 2 6 incorporates new features and syntax from 3 0 while remaining compatible with existing code by not removing older features or syntax When it s not possible to do that Python 2 6 tries to do what it can adding compatibility functions in a future_builtins module and a 3 switch to warn about usages that will become unsupported in 3 0 Some significant new packages have been added to the standard library such as the multiprocessing and json modules but there aren t many new features that aren t related to Python 3 0 in some way Python 2 6 also sees a number of improvements and bugfixes throughout the source A search through the change logs finds there were 259 patches applied and 612 bugs fixed between Python 2 5 and 2 6 Both figures are likely to be underestimates This article doesn t attempt to provide a complete specification of the new features but instead provides a convenient overview For full details you should refer to the documentation for Python 2 6 If you want to understand the rationale for the design and implementation refer to the PEP for a particular new feature Whenever possible What s New in Python links to the bug patch item for each change Python 3 0 The development cycle for Python versions 2 6 and 3 0 was synchronized with the alpha and beta releases for both versions being made on the same days The development of 3 0 has influenced many features in 2 6 Python 3 0 is a far ranging redesign of Python that breaks compatibility with the 2 x series This means that existing Python code will need some conversion in order to run on Python 3 0 However not all the changes in 3 0 necessarily break compatibility In cases where new features won t cause existing code to break they ve been backported to 2 6 and are described in this document in the appropriate place Some of the 3 0 derived features are A __complex__ method for converting objects to a complex number Alternate syntax for catching exceptions except TypeError as exc The addition of functools reduce as a synonym for the built in reduce function Python 3 0 adds several new built in functions and changes the semantics of some existing builtins Functions that are new in 3 0 such as bin have simply been added to Python 2 6 but existing builtins haven t been changed instead the future_builtins module has versions with the new 3 0 semantics Code written to be compatible with 3 0 can do from future_builtins import hex map as necessary A new command line switch 3 enables warnings about features that will be removed in Python 3 0 You can run code with this switch to see how much work will be necessary to port code to 3 0 The value of this switch is available to Python code as the boolean variable sys py3kwarning and to C extension code as Py_Py3kWarningFlag See also The 3 xxx series of PEPs which contains proposals for Python 3 0 PEP 3000 describes the development process for Python 3 0 Start with PEP 3100 that describes the general goals for Python 3 0 and then explore the higher numbered PEPs that propose specific features Changes to the Development Process While 2 6 was being developed the Python development process underwent two significant changes we switched from SourceForge s issue tracker to a customized Roundup installation and the documentation was converted from LaTeX to reStructuredText New Issue Tracker Roundup For a long time the Python developers had been growing increasingly annoyed by SourceForge s bug tracker SourceForge s hosted solution doesn t permit much customization for example it wasn t possible to customize the life cycle of issues The infrastructure committee of the Python Software Foundation therefore posted a call for issue trackers asking volunteers to set up different products and import some of the bugs and patches fro,en
480,m SourceForge Four different trackers were examined Jira Launchpad Roundup and Trac The committee eventually settled on Jira and Roundup as the two candidates Jira is a commercial product that offers no cost hosted instances to free software projects Roundup is an open source project that requires volunteers to administer it and a server to host it After posting a call for volunteers a new Roundup installation was set up at https bugs python org One installation of Roundup can host multiple trackers and this server now also hosts issue trackers for Jython and for the Python web site It will surely find other uses in the future Where possible this edition of What s New in Python links to the bug patch item for each change Hosting of the Python bug tracker is kindly provided by Upfront Systems of Stellenbosch South Africa Martin von Löwis put a lot of effort into importing existing bugs and patches from SourceForge his scripts for this import operation are at https svn python org view tracker importer and may be useful to other projects wishing to move from SourceForge to Roundup See also https bugs python org The Python bug tracker https bugs jython org The Jython bug tracker https roundup sourceforge io Roundup downloads and documentation https svn python org view tracker importer Martin von Löwis s conversion scripts New Documentation Format reStructuredText Using Sphinx The Python documentation was written using LaTeX since the project started around 1989 In the 1980s and early 1990s most documentation was printed out for later study not viewed online LaTeX was widely used because it provided attractive printed output while remaining straightforward to write once the basic rules of the markup were learned Today LaTeX is still used for writing publications destined for printing but the landscape for programming tools has shifted We no longer print out reams of documentation instead we browse through it online and HTML has become the most important format to support Unfortunately converting LaTeX to HTML is fairly complicated and Fred L Drake Jr the long time Python documentation editor spent a lot of time maintaining the conversion process Occasionally people would suggest converting the documentation into SGML and later XML but performing a good conversion is a major task and no one ever committed the time required to finish the job During the 2 6 development cycle Georg Brandl put a lot of effort into building a new toolchain for processing the documentation The resulting package is called Sphinx and is available from https www sphinx doc org Sphinx concentrates on HTML output producing attractively styled and modern HTML printed output is still supported through conversion to LaTeX The input format is reStructuredText a markup syntax supporting custom extensions and directives that is commonly used in the Python community Sphinx is a standalone package that can be used for writing and almost two dozen other projects listed on the Sphinx web site have adopted Sphinx as their documentation tool See also Documenting Python Describes how to write for Python s documentation Sphinx Documentation and code for the Sphinx toolchain Docutils The underlying reStructuredText parser and toolset PEP 343 The with statement The previous version Python 2 5 added the with statement as an optional feature to be enabled by a from __future__ import with_statement directive In 2 6 the statement no longer needs to be specially enabled this means that with is now always a keyword The rest of this section is a copy of the corresponding section from the What s New in Python 2 5 document if you re familiar with the with statement from Python 2 5 you can skip this section The with statement clarifies code that previously would use try finally blocks to ensure that clean up code is executed In this section I ll discuss the statement as it will commonly be used In the next section I ll examine the implementation details and show how to write objects for use with this statement The with statement is a control flow structure whose basic structure i,en
481,s with expression as variable with block The expression is evaluated and it should result in an object that supports the context management protocol that is has __enter__ and __exit__ methods The object s __enter__ is called before with block is executed and therefore can run set up code It also may return a value that is bound to the name variable if given Note carefully that variable is not assigned the result of expression After execution of the with block is finished the object s __exit__ method is called even if the block raised an exception and can therefore run clean up code Some standard Python objects now support the context management protocol and can be used with the with statement File objects are one example with open etc passwd r as f for line in f print line more processing code After this statement has executed the file object in f will have been automatically closed even if the for loop raised an exception part way through the block Note In this case f is the same object created by open because __enter__ returns self The threading module s locks and condition variables also support the with statement lock threading Lock with lock Critical section of code The lock is acquired before the block is executed and always released once the block is complete The localcontext function in the decimal module makes it easy to save and restore the current decimal context which encapsulates the desired precision and rounding characteristics for computations from decimal import Decimal Context localcontext Displays with default precision of 28 digits v Decimal 578 print v sqrt with localcontext Context prec 16 All code in this block uses a precision of 16 digits The original context is restored on exiting the block print v sqrt Writing Context Managers Under the hood the with statement is fairly complicated Most people will only use with in company with existing objects and don t need to know these details so you can skip the rest of this section if you like Authors of new objects will need to understand the details of the underlying implementation and should keep reading A high level explanation of the context management protocol is The expression is evaluated and should result in an object called a context manager The context manager must have __enter__ and __exit__ methods The context manager s __enter__ method is called The value returned is assigned to VAR If no as VAR clause is present the value is simply discarded The code in BLOCK is executed If BLOCK raises an exception the context manager s __exit__ method is called with three arguments the exception details type value traceback the same values returned by sys exc_info which can also be None if no exception occurred The method s return value controls whether an exception is re raised any false value re raises the exception and True will result in suppressing it You ll only rarely want to suppress the exception because if you do the author of the code containing the with statement will never realize anything went wrong If BLOCK didn t raise an exception the __exit__ method is still called but type value and traceback are all None Let s think through an example I won t present detailed code but will only sketch the methods necessary for a database that supports transactions For people unfamiliar with database terminology a set of changes to the database are grouped into a transaction Transactions can be either committed meaning that all the changes are written into the database or rolled back meaning that the changes are all discarded and the database is unchanged See any database textbook for more information Let s assume there s an object representing a database connection Our goal will be to let the user write code like this db_connection DatabaseConnection with db_connection as cursor cursor execute insert into cursor execute delete from more operations The transaction should be committed if the code in the block runs flawlessly or rolled back if there s an exception Here s the basic interface for DatabaseConnection that I ll assume class DatabaseConnection ,en
482,Database interface def cursor self Returns a cursor object and starts a new transaction def commit self Commits current transaction def rollback self Rolls back current transaction The __enter__ method is pretty easy having only to start a new transaction For this application the resulting cursor object would be a useful result so the method will return it The user can then add as cursor to their with statement to bind the cursor to a variable name class DatabaseConnection def __enter__ self Code to start a new transaction cursor self cursor return cursor The __exit__ method is the most complicated because it s where most of the work has to be done The method has to check if an exception occurred If there was no exception the transaction is committed The transaction is rolled back if there was an exception In the code below execution will just fall off the end of the function returning the default value of None None is false so the exception will be re raised automatically If you wished you could be more explicit and add a return statement at the marked location class DatabaseConnection def __exit__ self type value tb if tb is None No exception so commit self commit else Exception occurred so rollback self rollback return False The contextlib module The contextlib module provides some functions and a decorator that are useful when writing objects for use with the with statement The decorator is called contextmanager and lets you write a single generator function instead of defining a new class The generator should yield exactly one value The code up to the yield will be executed as the __enter__ method and the value yielded will be the method s return value that will get bound to the variable in the with statement s as clause if any The code after the yield will be executed in the __exit__ method Any exception raised in the block will be raised by the yield statement Using this decorator our database example from the previous section could be written as from contextlib import contextmanager contextmanager def db_transaction connection cursor connection cursor try yield cursor except connection rollback raise else connection commit db DatabaseConnection with db_transaction db as cursor The contextlib module also has a nested mgr1 mgr2 function that combines a number of context managers so you don t need to write nested with statements In this example the single with statement both starts a database transaction and acquires a thread lock lock threading Lock with nested db_transaction db lock as cursor locked Finally the closing function returns its argument so that it can be bound to a variable and calls the argument s close method at the end of the block import urllib sys from contextlib import closing with closing urllib urlopen http www yahoo com as f for line in f sys stdout write line See also PEP 343 The with statement PEP written by Guido van Rossum and Nick Coghlan implemented by Mike Bland Guido van Rossum and Neal Norwitz The PEP shows the code generated for a with statement which can be helpful in learning how the statement works The documentation for the contextlib module PEP 366 Explicit Relative Imports From a Main Module Python s m switch allows running a module as a script When you ran a module that was located inside a package relative imports didn t work correctly The fix for Python 2 6 adds a __package__ attribute to modules When this attribute is present relative imports will be relative to the value of this attribute instead of the __name__ attribute PEP 302 style importers can then set __package__ as necessary The runpy module that implements the m switch now does this so relative imports will now work correctly in scripts running from inside a package PEP 370 Per user site packages Directory When you run Python the module search path sys path usually includes a directory whose path ends in site packages This directory is intended to hold locally installed packages available to all users using a machine or a particular site installation Python 2 6 introduces a convention for user specific site directo,en
483,ries The directory varies depending on the platform Unix and Mac OS X local Windows APPDATA Python Within this directory there will be version specific subdirectories such as lib python2 6 site packages on Unix Mac OS and Python26 site packages on Windows If you don t like the default directory it can be overridden by an environment variable PYTHONUSERBASE sets the root directory used for all Python versions supporting this feature On Windows the directory for application specific data can be changed by setting the APPDATA environment variable You can also modify the site py file for your Python installation The feature can be disabled entirely by running Python with the s option or setting the PYTHONNOUSERSITE environment variable See also PEP 370 Per user site packages Directory PEP written and implemented by Christian Heimes PEP 371 The multiprocessing Package The new multiprocessing package lets Python programs create new processes that will perform a computation and return a result to the parent The parent and child processes can communicate using queues and pipes synchronize their operations using locks and semaphores and can share simple arrays of data The multiprocessing module started out as an exact emulation of the threading module using processes instead of threads That goal was discarded along the path to Python 2 6 but the general approach of the module is still similar The fundamental class is the Process which is passed a callable object and a collection of arguments The start method sets the callable running in a subprocess after which you can call the is_alive method to check whether the subprocess is still running and the join method to wait for the process to exit Here s a simple example where the subprocess will calculate a factorial The function doing the calculation is written strangely so that it takes significantly longer when the input argument is a multiple of 4 import time from multiprocessing import Process Queue def factorial queue N Compute a factorial If N is a multiple of 4 this function will take much longer if N 4 0 time sleep 05 N 4 Calculate the result fact 1L for i in range 1 N 1 fact fact i Put the result on the queue queue put fact if __name__ __main__ queue Queue N 5 p Process target factorial args queue N p start p join result queue get print Factorial N result A Queue is used to communicate the result of the factorial The Queue object is stored in a global variable The child process will use the value of the variable when the child was created because it s a Queue parent and child can use the object to communicate If the parent were to change the value of the global variable the child s value would be unaffected and vice versa Two other classes Pool and Manager provide higher level interfaces Pool will create a fixed number of worker processes and requests can then be distributed to the workers by calling apply or apply_async to add a single request and map or map_async to add a number of requests The following code uses a Pool to spread requests across 5 worker processes and retrieve a list of results from multiprocessing import Pool def factorial N dictionary Compute a factorial p Pool 5 result p map factorial range 1 1000 10 for v in result print v This produces the following output 1 39916800 51090942171709440000 8222838654177922817725562880000000 33452526613163807108170062053440751665152000000000 The other high level interface the Manager class creates a separate server process that can hold master copies of Python data structures Other processes can then access and modify these data structures using proxy objects The following example creates a shared dictionary by calling the dict method the worker processes then insert values into the dictionary Locking is not done for you automatically which doesn t matter in this example Manager s methods also include Lock RLock and Semaphore to create shared locks import time from multiprocessing import Pool Manager def factorial N dictionary Compute a factorial Calculate the result fact 1L for i in range 1 N 1 fact fact i Store resul,en
484,t in dictionary dictionary N fact if __name__ __main__ p Pool 5 mgr Manager d mgr dict Create shared dictionary Run tasks using the pool for N in range 1 1000 10 p apply_async factorial N d Mark pool as closed no more tasks can be added p close Wait for tasks to exit p join Output results for k v in sorted d items print k v This will produce the output 1 1 11 39916800 21 51090942171709440000 31 8222838654177922817725562880000000 41 33452526613163807108170062053440751665152000000000 51 15511187532873822802242430164693032110632597200169861120000 See also The documentation for the multiprocessing module PEP 371 Addition of the multiprocessing package PEP written by Jesse Noller and Richard Oudkerk implemented by Richard Oudkerk and Jesse Noller PEP 3101 Advanced String Formatting In Python 3 0 the operator is supplemented by a more powerful string formatting method format Support for the str format method has been backported to Python 2 6 In 2 6 both 8 bit and Unicode strings have a format method that treats the string as a template and takes the arguments to be formatted The formatting template uses curly brackets as special characters Substitute positional argument 0 into the string User ID 0 format root User ID root Use the named keyword arguments User ID uid Last seen last_login format uid root last_login 5 Mar 2008 07 20 User ID root Last seen 5 Mar 2008 07 20 Curly brackets can be escaped by doubling them Empty dict format Empty dict Field names can be integers indicating positional arguments such as 0 1 etc or names of keyword arguments You can also supply compound field names that read attributes or access dictionary keys import sys print Platform 0 platform nPython version 0 version format sys Platform darwin Python version 2 6a1 trunk 61261M Mar 5 2008 20 29 41 GCC 4 0 1 Apple Computer Inc build 5367 import mimetypes Content type 0 mp4 format mimetypes types_map Content type video mp4 Note that when using dictionary style notation such as mp4 you don t need to put any quotation marks around the string it will look up the value using mp4 as the key Strings beginning with a number will be converted to an integer You can t write more complicated expressions inside a format string So far we ve shown how to specify which field to substitute into the resulting string The precise formatting used is also controllable by adding a colon followed by a format specifier For example Field 0 left justify pad to 15 characters Field 1 right justify pad to 6 characters fmt 0 15 1 6 fmt format Registration 35 Registration 35 fmt format Tutorial 50 Tutorial 50 fmt format Banquet 125 Banquet 125 Format specifiers can reference other fields through nesting fmt 0 1 width 15 fmt format Invoice 1234 width Invoice 1234 width 35 fmt format Invoice 1234 width Invoice 1234 The alignment of a field within the desired width can be specified Character Effect default Left align Right align Center For numeric types only Pad after the sign Format specifiers can also include a presentation type which controls how the value is formatted For example floating point numbers can be formatted as a general number or in exponential notation 0 g format 3 75 3 75 0 e format 3 75 3 750000e 00 A variety of presentation types are available Consult the 2 6 documentation for a complete list here s a sample b Binary Outputs the number in base 2 c Character Converts the integer to the corresponding Unicode character before printing d Decimal Integer Outputs the number in base 10 o Octal format Outputs the number in base 8 x Hex format Outputs the number in base 16 using lower case letters for the digits above 9 e Exponent notation Prints the number in scientific notation using the letter e to indicate the exponent g General format This prints the number as a fixed point number unless the number is too large in which case it switches to e exponent notation n Number This is the same as g for floats or d for integers except that it uses the current locale setting to insert the appropriate number separator characters Percentage Multiplies the number by 100 and displays ,en
485,in fixed f format followed by a percent sign Classes and types can define a __format__ method to control how they re formatted It receives a single argument the format specifier def __format__ self format_spec if isinstance format_spec unicode return unicode str self else return str self There s also a format builtin that will format a single value It calls the type s __format__ method with the provided specifier format 75 6564 2f 75 66 See also Format String Syntax The reference documentation for format fields PEP 3101 Advanced String Formatting PEP written by Talin Implemented by Eric Smith PEP 3105 print As a Function The print statement becomes the print function in Python 3 0 Making print a function makes it possible to replace the function by doing def print or importing a new function from somewhere else Python 2 6 has a __future__ import that removes print as language syntax letting you use the functional form instead For example from __future__ import print_function print of entries len dictionary file sys stderr The signature of the new function is def print args sep end n file None The parameters are args positional arguments whose values will be printed out sep the separator which will be printed between arguments end the ending text which will be printed after all of the arguments have been output file the file object to which the output will be sent See also PEP 3105 Make print a function PEP written by Georg Brandl PEP 3110 Exception Handling Changes One error that Python programmers occasionally make is writing the following code try except TypeError ValueError Wrong The author is probably trying to catch both TypeError and ValueError exceptions but this code actually does something different it will catch TypeError and bind the resulting exception object to the local name ValueError The ValueError exception will not be caught at all The correct code specifies a tuple of exceptions try except TypeError ValueError This error happens because the use of the comma here is ambiguous does it indicate two different nodes in the parse tree or a single node that s a tuple Python 3 0 makes this unambiguous by replacing the comma with the word as To catch an exception and store the exception object in the variable exc you must write try except TypeError as exc Python 3 0 will only support the use of as and therefore interprets the first example as catching two different exceptions Python 2 6 supports both the comma and as so existing code will continue to work We therefore suggest using as when writing new Python code that will only be executed with 2 6 See also PEP 3110 Catching Exceptions in Python 3000 PEP written and implemented by Collin Winter PEP 3112 Byte Literals Python 3 0 adopts Unicode as the language s fundamental string type and denotes 8 bit literals differently either as b string or using a bytes constructor For future compatibility Python 2 6 adds bytes as a synonym for the str type and it also supports the b notation The 2 6 str differs from 3 0 s bytes type in various ways most notably the constructor is completely different In 3 0 bytes 65 66 67 is 3 elements long containing the bytes representing ABC in 2 6 bytes 65 66 67 returns the 12 byte string representing the str of the list The primary use of bytes in 2 6 will be to write tests of object type such as isinstance x bytes This will help the 2to3 converter which can t tell whether 2 x code intends strings to contain either characters or 8 bit bytes you can now use either bytes or str to represent your intention exactly and the resulting code will also be correct in Python 3 0 There s also a __future__ import that causes all string literals to become Unicode strings This means that u escape sequences can be used to include Unicode characters from __future__ import unicode_literals s u751f u3080 u304e u3000 u751f u3054 u3081 u3000 u751f u305f u307e u3054 print len s 12 Unicode characters At the C level Python 3 0 will rename the existing 8 bit string type called PyStringObject in Python 2 x to PyBytesObject Python 2 6 uses define to support usi,en
486,ng the names PyBytesObject PyBytes_Check PyBytes_FromStringAndSize and all the other functions and macros used with strings Instances of the bytes type are immutable just as strings are A new bytearray type stores a mutable sequence of bytes bytearray 65 66 67 bytearray b ABC b bytearray u u21ef u3244 utf 8 b bytearray b xe2 x87 xaf xe3 x89 x84 b 0 xe3 b bytearray b xe3 x87 xaf xe3 x89 x84 unicode str b utf 8 u u31ef u3244 Byte arrays support most of the methods of string types such as startswith endswith find rfind and some of the methods of lists such as append pop and reverse b bytearray ABC b append d b append ord e b bytearray b ABCde There s also a corresponding C API with PyByteArray_FromObject PyByteArray_FromStringAndSize and various other functions See also PEP 3112 Bytes literals in Python 3000 PEP written by Jason Orendorff backported to 2 6 by Christian Heimes PEP 3116 New I O Library Python s built in file objects support a number of methods but file like objects don t necessarily support all of them Objects that imitate files usually support read and write but they may not support readline for example Python 3 0 introduces a layered I O library in the io module that separates buffering and text handling features from the fundamental read and write operations There are three levels of abstract base classes provided by the io module RawIOBase defines raw I O operations read readinto write seek tell truncate and close Most of the methods of this class will often map to a single system call There are also readable writable and seekable methods for determining what operations a given object will allow Python 3 0 has concrete implementations of this class for files and sockets but Python 2 6 hasn t restructured its file and socket objects in this way BufferedIOBase is an abstract base class that buffers data in memory to reduce the number of system calls used making I O processing more efficient It supports all of the methods of RawIOBase and adds a raw attribute holding the underlying raw object There are five concrete classes implementing this ABC BufferedWriter and BufferedReader are for objects that support write only or read only usage that have a seek method for random access BufferedRandom objects support read and write access upon the same underlying stream and BufferedRWPair is for objects such as TTYs that have both read and write operations acting upon unconnected streams of data The BytesIO class supports reading writing and seeking over an in memory buffer TextIOBase Provides functions for reading and writing strings remember strings will be Unicode in Python 3 0 and supporting universal newlines TextIOBase defines the readline method and supports iteration upon objects There are two concrete implementations TextIOWrapper wraps a buffered I O object supporting all of the methods for text I O and adding a buffer attribute for access to the underlying object StringIO simply buffers everything in memory without ever writing anything to disk In Python 2 6 io StringIO is implemented in pure Python so it s pretty slow You should therefore stick with the existing StringIO module or cStringIO for now At some point Python 3 0 s io module will be rewritten into C for speed and perhaps the C implementation will be backported to the 2 x releases In Python 2 6 the underlying implementations haven t been restructured to build on top of the io module s classes The module is being provided to make it easier to write code that s forward compatible with 3 0 and to save developers the effort of writing their own implementations of buffering and text I O See also PEP 3116 New I O PEP written by Daniel Stutzbach Mike Verdone and Guido van Rossum Code by Guido van Rossum Georg Brandl Walter Doerwald Jeremy Hylton Martin von Löwis Tony Lownds and others PEP 3118 Revised Buffer Protocol The buffer protocol is a C level API that lets Python types exchange pointers into their internal representations A memory mapped file can be viewed as a buffer of characters for example and this lets another module such as re treat memory ,en
487,mapped files as a string of characters to be searched The primary users of the buffer protocol are numeric processing packages such as NumPy which expose the internal representation of arrays so that callers can write data directly into an array instead of going through a slower API This PEP updates the buffer protocol in light of experience from NumPy development adding a number of new features such as indicating the shape of an array or locking a memory region The most important new C API function is PyObject_GetBuffer PyObject obj Py_buffer view int flags which takes an object and a set of flags and fills in the Py_buffer structure with information about the object s memory representation Objects can use this operation to lock memory in place while an external caller could be modifying the contents so there s a corresponding PyBuffer_Release Py_buffer view to indicate that the external caller is done The flags argument to PyObject_GetBuffer specifies constraints upon the memory returned Some examples are PyBUF_WRITABLE indicates that the memory must be writable PyBUF_LOCK requests a read only or exclusive lock on the memory PyBUF_C_CONTIGUOUS and PyBUF_F_CONTIGUOUS requests a C contiguous last dimension varies the fastest or Fortran contiguous first dimension varies the fastest array layout Two new argument codes for PyArg_ParseTuple s and z return locked buffer objects for a parameter See also PEP 3118 Revising the buffer protocol PEP written by Travis Oliphant and Carl Banks implemented by Travis Oliphant PEP 3119 Abstract Base Classes Some object oriented languages such as Java support interfaces declaring that a class has a given set of methods or supports a given access protocol Abstract Base Classes or ABCs are an equivalent feature for Python The ABC support consists of an abc module containing a metaclass called ABCMeta special handling of this metaclass by the isinstance and issubclass builtins and a collection of basic ABCs that the Python developers think will be widely useful Future versions of Python will probably add more ABCs Let s say you have a particular class and wish to know whether it supports dictionary style access The phrase dictionary style is vague however It probably means that accessing items with obj 1 works Does it imply that setting items with obj 2 value works Or that the object will have keys values and items methods What about the iterative variants such as iterkeys copy and update Iterating over the object with iter The Python 2 6 collections module includes a number of different ABCs that represent these distinctions Iterable indicates that a class defines __iter__ and Container means the class defines a __contains__ method and therefore supports x in y expressions The basic dictionary interface of getting items setting items and keys values and items is defined by the MutableMapping ABC You can derive your own classes from a particular ABC to indicate they support that ABC s interface import collections class Storage collections MutableMapping Alternatively you could write the class without deriving from the desired ABC and instead register the class by calling the ABC s register method import collections class Storage collections MutableMapping register Storage For classes that you write deriving from the ABC is probably clearer The register method is useful when you ve written a new ABC that can describe an existing type or class or if you want to declare that some third party class implements an ABC For example if you defined a PrintableType ABC it s legal to do Register Python s types PrintableType register int PrintableType register float PrintableType register str Classes should obey the semantics specified by an ABC but Python can t check this it s up to the class author to understand the ABC s requirements and to implement the code accordingly To check whether an object supports a particular interface you can now write def func d if not isinstance d collections MutableMapping raise ValueError Mapping object expected not r d Don t feel that you must now begin writing lots of,en
488, checks as in the above example Python has a strong tradition of duck typing where explicit type checking is never done and code simply calls methods on an object trusting that those methods will be there and raising an exception if they aren t Be judicious in checking for ABCs and only do it where it s absolutely necessary You can write your own ABCs by using abc ABCMeta as the metaclass in a class definition from abc import ABCMeta abstractmethod class Drawable __metaclass__ ABCMeta abstractmethod def draw self x y scale 1 0 pass def draw_doubled self x y self draw x y scale 2 0 class Square Drawable def draw self x y scale In the Drawable ABC above the draw_doubled method renders the object at twice its size and can be implemented in terms of other methods described in Drawable Classes implementing this ABC therefore don t need to provide their own implementation of draw_doubled though they can do so An implementation of draw is necessary though the ABC can t provide a useful generic implementation You can apply the abstractmethod decorator to methods such as draw that must be implemented Python will then raise an exception for classes that don t define the method Note that the exception is only raised when you actually try to create an instance of a subclass lacking the method class Circle Drawable pass c Circle Traceback most recent call last File stdin line 1 in module TypeError Can t instantiate abstract class Circle with abstract methods draw Abstract data attributes can be declared using the abstractproperty decorator from abc import abstractproperty abstractproperty def readonly self return self _x Subclasses must then define a readonly property See also PEP 3119 Introducing Abstract Base Classes PEP written by Guido van Rossum and Talin Implemented by Guido van Rossum Backported to 2 6 by Benjamin Aranguren with Alex Martelli PEP 3127 Integer Literal Support and Syntax Python 3 0 changes the syntax for octal base 8 integer literals prefixing them with 0o or 0O instead of a leading zero and adds support for binary base 2 integer literals signalled by a 0b or 0B prefix Python 2 6 doesn t drop support for a leading 0 signalling an octal number but it does add support for 0o and 0b 0o21 2 8 1 17 17 0b101111 47 The oct builtin still returns numbers prefixed with a leading zero and a new bin builtin returns the binary representation for a number oct 42 052 future_builtins oct 42 0o52 bin 173 0b10101101 The int and long builtins will now accept the 0o and 0b prefixes when base 8 or base 2 are requested or when the base argument is zero signalling that the base used should be determined from the string int 0o52 0 42 int 1101 2 13 int 0b1101 2 13 int 0b1101 0 13 See also PEP 3127 Integer Literal Support and Syntax PEP written by Patrick Maupin backported to 2 6 by Eric Smith PEP 3129 Class Decorators Decorators have been extended from functions to classes It s now legal to write foo bar class A pass This is equivalent to class A pass A foo bar A See also PEP 3129 Class Decorators PEP written by Collin Winter PEP 3141 A Type Hierarchy for Numbers Python 3 0 adds several abstract base classes for numeric types inspired by Scheme s numeric tower These classes were backported to 2 6 as the numbers module The most general ABC is Number It defines no operations at all and only exists to allow checking if an object is a number by doing isinstance obj Number Complex is a subclass of Number Complex numbers can undergo the basic operations of addition subtraction multiplication division and exponentiation and you can retrieve the real and imaginary parts and obtain a number s conjugate Python s built in complex type is an implementation of Complex Real further derives from Complex and adds operations that only work on real numbers floor trunc rounding taking the remainder mod N floor division and comparisons Rational numbers derive from Real have numerator and denominator properties and can be converted to floats Python 2 6 adds a simple rational number class Fraction in the fractions module It s called Fraction instead of Ratio,en
489,nal to avoid a name clash with numbers Rational Integral numbers derive from Rational and can be shifted left and right with and combined using bitwise operations such as and and can be used as array indexes and slice boundaries In Python 3 0 the PEP slightly redefines the existing builtins round math floor math ceil and adds a new one math trunc that s been backported to Python 2 6 math trunc rounds toward zero returning the closest Integral that s between the function s argument and zero See also PEP 3141 A Type Hierarchy for Numbers PEP written by Jeffrey Yasskin Scheme s numerical tower from the Guile manual Scheme s number datatypes from the R5RS Scheme specification The fractions Module To fill out the hierarchy of numeric types the fractions module provides a rational number class Rational numbers store their values as a numerator and denominator forming a fraction and can exactly represent numbers such as 2 3 that floating point numbers can only approximate The Fraction constructor takes two Integral values that will be the numerator and denominator of the resulting fraction from fractions import Fraction a Fraction 2 3 b Fraction 2 5 float a float b 0 66666666666666663 0 40000000000000002 a b Fraction 16 15 a b Fraction 5 3 For converting floating point numbers to rationals the float type now has an as_integer_ratio method that returns the numerator and denominator for a fraction that evaluates to the same floating point value 2 5 as_integer_ratio 5 2 3 1415 as_integer_ratio 7074029114692207L 2251799813685248L 1 3 as_integer_ratio 6004799503160661L 18014398509481984L Note that values that can only be approximated by floating point numbers such as 1 3 are not simplified to the number being approximated the fraction attempts to match the floating point value exactly The fractions module is based upon an implementation by Sjoerd Mullender that was in Python s Demo classes directory for a long time This implementation was significantly updated by Jeffrey Yasskin Other Language Changes Some smaller changes made to the core Python language are Directories and zip archives containing a __main__ py file can now be executed directly by passing their name to the interpreter The directory or zip archive is automatically inserted as the first entry in sys path Suggestion and initial patch by Andy Chu subsequently revised by Phillip J Eby and Nick Coghlan bpo 1739468 The hasattr function was catching and ignoring all errors under the assumption that they meant a __getattr__ method was failing somehow and the return value of hasattr would therefore be False This logic shouldn t be applied to KeyboardInterrupt and SystemExit however Python 2 6 will no longer discard such exceptions when hasattr encounters them Fixed by Benjamin Peterson bpo 2196 When calling a function using the syntax to provide keyword arguments you are no longer required to use a Python dictionary any mapping will now work def f kw print sorted kw ud UserDict UserDict ud a 1 ud b string f ud a b Contributed by Alexander Belopolsky bpo 1686487 It s also become legal to provide keyword arguments after a args argument to a function call def f args kw print args kw f 1 2 3 4 5 6 keyword 13 1 2 3 4 5 6 keyword 13 Previously this would have been a syntax error Contributed by Amaury Forgeot d Arc bpo 3473 A new builtin next iterator default returns the next item from the specified iterator If the default argument is supplied it will be returned if iterator has been exhausted otherwise the StopIteration exception will be raised Backported in bpo 2719 Tuples now have index and count methods matching the list type s index and count methods t 0 1 2 3 4 0 1 2 t index 3 3 t count 0 2 Contributed by Raymond Hettinger The built in types now have improved support for extended slicing syntax accepting various combinations of start stop step Previously the support was partial and certain corner cases wouldn t work Implemented by Thomas Wouters Properties now have three attributes getter setter and deleter that are decorators providing useful shortcuts for adding a getter set,en
490,ter or deleter function to an existing property You would use them like this class C object property def x self return self _x x setter def x self value self _x value x deleter def x self del self _x class D C C x getter def x self return self _x 2 x setter def x self value self _x value 2 Several methods of the built in set types now accept multiple iterables intersection intersection_update union update difference and difference_update s set 1234567890 s intersection abc123 cdf246 Intersection between all inputs set 2 s difference 246 789 set 1 0 3 5 Contributed by Raymond Hettinger Many floating point features were added The float function will now turn the string nan into an IEEE 754 Not A Number value and inf and inf into positive or negative infinity This works on any platform with IEEE 754 semantics Contributed by Christian Heimes bpo 1635 Other functions in the math module isinf and isnan return true if their floating point argument is infinite or Not A Number bpo 1640 Conversion functions were added to convert floating point numbers into hexadecimal strings bpo 3008 These functions convert floats to and from a string representation without introducing rounding errors from the conversion between decimal and binary Floats have a hex method that returns a string representation and the float fromhex method converts a string back into a number a 3 75 a hex 0x1 e000000000000p 1 float fromhex 0x1 e000000000000p 1 3 75 b 1 3 b hex 0x1 5555555555555p 2 A numerical nicety when creating a complex number from two floats on systems that support signed zeros 0 and 0 the complex constructor will now preserve the sign of the zero Fixed by Mark T Dickinson bpo 1507 Classes that inherit a __hash__ method from a parent class can set __hash__ None to indicate that the class isn t hashable This will make hash obj raise a TypeError and the class will not be indicated as implementing the Hashable ABC You should do this when you ve defined a __cmp__ or __eq__ method that compares objects by their value rather than by identity All objects have a default hash method that uses id obj as the hash value There s no tidy way to remove the __hash__ method inherited from a parent class so assigning None was implemented as an override At the C level extensions can set tp_hash to PyObject_HashNotImplemented Fixed by Nick Coghlan and Amaury Forgeot d Arc bpo 2235 The GeneratorExit exception now subclasses BaseException instead of Exception This means that an exception handler that does except Exception will not inadvertently catch GeneratorExit Contributed by Chad Austin bpo 1537 Generator objects now have a gi_code attribute that refers to the original code object backing the generator Contributed by Collin Winter bpo 1473257 The compile built in function now accepts keyword arguments as well as positional parameters Contributed by Thomas Wouters bpo 1444529 The complex constructor now accepts strings containing parenthesized complex numbers meaning that complex repr cplx will now round trip values For example complex 3 4j now returns the value 3 4j bpo 1491866 The string translate method now accepts None as the translation table parameter which is treated as the identity transformation This makes it easier to carry out operations that only delete characters Contributed by Bengt Richter and implemented by Raymond Hettinger bpo 1193128 The built in dir function now checks for a __dir__ method on the objects it receives This method must return a list of strings containing the names of valid attributes for the object and lets the object control the value that dir produces Objects that have __getattr__ or __getattribute__ methods can use this to advertise pseudo attributes they will honor bpo 1591665 Instance method objects have new attributes for the object and function comprising the method the new synonym for im_self is __self__ and im_func is also available as __func__ The old names are still supported in Python 2 6 but are gone in 3 0 An obscure change when you use the locals function inside a class statement the resulting dictionary no longer r,en
491,eturns free variables Free variables in this case are variables referenced in the class statement that aren t attributes of the class Optimizations The warnings module has been rewritten in C This makes it possible to invoke warnings from the parser and may also make the interpreter s startup faster Contributed by Neal Norwitz and Brett Cannon bpo 1631171 Type objects now have a cache of methods that can reduce the work required to find the correct method implementation for a particular class once cached the interpreter doesn t need to traverse base classes to figure out the right method to call The cache is cleared if a base class or the class itself is modified so the cache should remain correct even in the face of Python s dynamic nature Original optimization implemented by Armin Rigo updated for Python 2 6 by Kevin Jacobs bpo 1700288 By default this change is only applied to types that are included with the Python core Extension modules may not necessarily be compatible with this cache so they must explicitly add Py_TPFLAGS_HAVE_VERSION_TAG to the module s tp_flags field to enable the method cache To be compatible with the method cache the extension module s code must not directly access and modify the tp_dict member of any of the types it implements Most modules don t do this but it s impossible for the Python interpreter to determine that See bpo 1878 for some discussion Function calls that use keyword arguments are significantly faster by doing a quick pointer comparison usually saving the time of a full string comparison Contributed by Raymond Hettinger after an initial implementation by Antoine Pitrou bpo 1819 All of the functions in the struct module have been rewritten in C thanks to work at the Need For Speed sprint Contributed by Raymond Hettinger Some of the standard built in types now set a bit in their type objects This speeds up checking whether an object is a subclass of one of these types Contributed by Neal Norwitz Unicode strings now use faster code for detecting whitespace and line breaks this speeds up the split method by about 25 and splitlines by 35 Contributed by Antoine Pitrou Memory usage is reduced by using pymalloc for the Unicode string s data The with statement now stores the __exit__ method on the stack producing a small speedup Implemented by Jeffrey Yasskin To reduce memory usage the garbage collector will now clear internal free lists when garbage collecting the highest generation of objects This may return memory to the operating system sooner Interpreter Changes Two command line options have been reserved for use by other Python implementations The J switch has been reserved for use by Jython for Jython specific options such as switches that are passed to the underlying JVM X has been reserved for options specific to a particular implementation of Python such as CPython Jython or IronPython If either option is used with Python 2 6 the interpreter will report that the option isn t currently used Python can now be prevented from writing pyc or pyo files by supplying the B switch to the Python interpreter or by setting the PYTHONDONTWRITEBYTECODE environment variable before running the interpreter This setting is available to Python programs as the sys dont_write_bytecode variable and Python code can change the value to modify the interpreter s behaviour Contributed by Neal Norwitz and Georg Brandl The encoding used for standard input output and standard error can be specified by setting the PYTHONIOENCODING environment variable before running the interpreter The value should be a string in the form encoding or encoding errorhandler The encoding part specifies the encoding s name e g utf 8 or latin 1 the optional errorhandler part specifies what to do with characters that can t be handled by the encoding and should be one of error ignore or replace Contributed by Martin von Löwis New and Improved Modules As in every release Python s standard library received a number of enhancements and bug fixes Here s a partial list of the most notable changes sorted alphabetically by module name Cons,en
492,ult the Misc NEWS file in the source tree for a more complete list of changes or look through the Subversion logs for all the details The asyncore and asynchat modules are being actively maintained again and a number of patches and bugfixes were applied Maintained by Josiah Carlson see bpo 1736190 for one patch The bsddb module also has a new maintainer Jesús Cea Avión and the package is now available as a standalone package The web page for the package is www jcea es programacion pybsddb htm The plan is to remove the package from the standard library in Python 3 0 because its pace of releases is much more frequent than Python s The bsddb dbshelve module now uses the highest pickling protocol available instead of restricting itself to protocol 1 Contributed by W Barnes The cgi module will now read variables from the query string of an HTTP POST request This makes it possible to use form actions with URLs that include query strings such as cgi bin add py category 1 Contributed by Alexandre Fiori and Nubis bpo 1817 The parse_qs and parse_qsl functions have been relocated from the cgi module to the urlparse module The versions still available in the cgi module will trigger PendingDeprecationWarning messages in 2 6 bpo 600362 The cmath module underwent extensive revision contributed by Mark Dickinson and Christian Heimes Five new functions were added polar converts a complex number to polar form returning the modulus and argument of the complex number rect does the opposite turning a modulus argument pair back into the corresponding complex number phase returns the argument also called the angle of a complex number isnan returns True if either the real or imaginary part of its argument is a NaN isinf returns True if either the real or imaginary part of its argument is infinite The revisions also improved the numerical soundness of the cmath module For all functions the real and imaginary parts of the results are accurate to within a few units of least precision ulps whenever possible See bpo 1381 for the details The branch cuts for asinh atanh and atan have also been corrected The tests for the module have been greatly expanded nearly 2000 new test cases exercise the algebraic functions On IEEE 754 platforms the cmath module now handles IEEE 754 special values and floating point exceptions in a manner consistent with Annex G of the C99 standard A new data type in the collections module namedtuple typename fieldnames is a factory function that creates subclasses of the standard tuple whose fields are accessible by name as well as index For example var_type collections namedtuple variable id name type size Names are separated by spaces or commas id name type size would also work var_type _fields id name type size var var_type 1 frequency int 4 print var 0 var id Equivalent 1 1 print var 2 var type Equivalent int int var _asdict size 4 type int id 1 name frequency v2 var _replace name amplitude v2 variable id 1 name amplitude type int size 4 Several places in the standard library that returned tuples have been modified to return namedtuple instances For example the Decimal as_tuple method now returns a named tuple with sign digits and exponent fields Contributed by Raymond Hettinger Another change to the collections module is that the deque type now supports an optional maxlen parameter if supplied the deque s size will be restricted to no more than maxlen items Adding more items to a full deque causes old items to be discarded from collections import deque dq deque maxlen 3 dq deque maxlen 3 dq append 1 dq append 2 dq append 3 dq deque 1 2 3 maxlen 3 dq append 4 dq deque 2 3 4 maxlen 3 Contributed by Raymond Hettinger The Cookie module s Morsel objects now support an httponly attribute In some browsers cookies with this attribute set cannot be accessed or manipulated by JavaScript code Contributed by Arvin Schnell bpo 1638033 A new window method in the curses module chgat changes the display attributes for a certain number of characters on a single line Contributed by Fabian Kreutz Boldface text starting at y 0 x 21 and affect,en
493,ing the rest of the line stdscr chgat 0 21 curses A_BOLD The Textbox class in the curses textpad module now supports editing in insert mode as well as overwrite mode Insert mode is enabled by supplying a true value for the insert_mode parameter when creating the Textbox instance The datetime module s strftime methods now support a f format code that expands to the number of microseconds in the object zero padded on the left to six places Contributed by Skip Montanaro bpo 1158 The decimal module was updated to version 1 66 of the General Decimal Specification New features include some methods for some basic mathematical functions such as exp and log10 Decimal 1 exp Decimal 2 718281828459045235360287471 Decimal 2 7182818 ln Decimal 0 9999999895305022877376682436 Decimal 1000 log10 Decimal 3 The as_tuple method of Decimal objects now returns a named tuple with sign digits and exponent fields Implemented by Facundo Batista and Mark Dickinson Named tuple support added by Raymond Hettinger The difflib module s SequenceMatcher class now returns named tuples representing matches with a b and size attributes Contributed by Raymond Hettinger An optional timeout parameter specifying a timeout measured in seconds was added to the ftplib FTP class constructor as well as the connect method Added by Facundo Batista Also the FTP class s storbinary and storlines now take an optional callback parameter that will be called with each block of data after the data has been sent Contributed by Phil Schwartz bpo 1221598 The reduce built in function is also available in the functools module In Python 3 0 the builtin has been dropped and reduce is only available from functools currently there are no plans to drop the builtin in the 2 x series Patched by Christian Heimes bpo 1739906 When possible the getpass module will now use dev tty to print a prompt message and read the password falling back to standard error and standard input If the password may be echoed to the terminal a warning is printed before the prompt is displayed Contributed by Gregory P Smith The glob glob function can now return Unicode filenames if a Unicode path was used and Unicode filenames are matched within the directory bpo 1001604 A new function in the heapq module merge iter1 iter2 takes any number of iterables returning data in sorted order and returns a new generator that returns the contents of all the iterators also in sorted order For example list heapq merge 1 3 5 9 2 8 16 1 2 3 5 8 9 16 Another new function heappushpop heap item pushes item onto heap then pops off and returns the smallest item This is more efficient than making a call to heappush and then heappop heapq is now implemented to only use less than comparison instead of the less than or equal comparison it previously used This makes heapq s usage of a type match the list sort method Contributed by Raymond Hettinger An optional timeout parameter specifying a timeout measured in seconds was added to the httplib HTTPConnection and HTTPSConnection class constructors Added by Facundo Batista Most of the inspect module s functions such as getmoduleinfo and getargs now return named tuples In addition to behaving like tuples the elements of the return value can also be accessed as attributes Contributed by Raymond Hettinger Some new functions in the module include isgenerator isgeneratorfunction and isabstract The itertools module gained several new functions izip_longest iter1 iter2 fillvalue makes tuples from each of the elements if some of the iterables are shorter than others the missing values are set to fillvalue For example tuple itertools izip_longest 1 2 3 1 2 3 4 5 1 1 2 2 3 3 None 4 None 5 product iter1 iter2 repeat N returns the Cartesian product of the supplied iterables a set of tuples containing every possible combination of the elements returned from each iterable list itertools product 1 2 3 4 5 6 1 4 1 5 1 6 2 4 2 5 2 6 3 4 3 5 3 6 The optional repeat keyword argument is used for taking the product of an iterable or a set of iterables with themselves repeated N times With a single iterable argu,en
494,ment N tuples are returned list itertools product 1 2 repeat 3 1 1 1 1 1 2 1 2 1 1 2 2 2 1 1 2 1 2 2 2 1 2 2 2 With two iterables 2N tuples are returned list itertools product 1 2 3 4 repeat 2 1 3 1 3 1 3 1 4 1 3 2 3 1 3 2 4 1 4 1 3 1 4 1 4 1 4 2 3 1 4 2 4 2 3 1 3 2 3 1 4 2 3 2 3 2 3 2 4 2 4 1 3 2 4 1 4 2 4 2 3 2 4 2 4 combinations iterable r returns sub sequences of length r from the elements of iterable list itertools combinations 123 2 1 2 1 3 2 3 list itertools combinations 123 3 1 2 3 list itertools combinations 1234 3 1 2 3 1 2 4 1 3 4 2 3 4 permutations iter r returns all the permutations of length r of the iterable s elements If r is not specified it will default to the number of elements produced by the iterable list itertools permutations 1 2 3 4 2 1 2 1 3 1 4 2 1 2 3 2 4 3 1 3 2 3 4 4 1 4 2 4 3 itertools chain iterables is an existing function in itertools that gained a new constructor in Python 2 6 itertools chain from_iterable iterable takes a single iterable that should return other iterables chain will then return all the elements of the first iterable then all the elements of the second and so on list itertools chain from_iterable 1 2 3 4 5 6 1 2 3 4 5 6 All contributed by Raymond Hettinger The logging module s FileHandler class and its subclasses WatchedFileHandler RotatingFileHandler and TimedRotatingFileHandler now have an optional delay parameter to their constructors If delay is true opening of the log file is deferred until the first emit call is made Contributed by Vinay Sajip TimedRotatingFileHandler also has a utc constructor parameter If the argument is true UTC time will be used in determining when midnight occurs and in generating filenames otherwise local time will be used Several new functions were added to the math module isinf and isnan determine whether a given float is a positive or negative infinity or a NaN Not a Number respectively copysign copies the sign bit of an IEEE 754 number returning the absolute value of x combined with the sign bit of y For example math copysign 1 0 0 returns 1 0 Contributed by Christian Heimes factorial computes the factorial of a number Contributed by Raymond Hettinger bpo 2138 fsum adds up the stream of numbers from an iterable and is careful to avoid loss of precision through using partial sums Contributed by Jean Brouwers Raymond Hettinger and Mark Dickinson bpo 2819 acosh asinh and atanh compute the inverse hyperbolic functions log1p returns the natural logarithm of 1 x base e trunc rounds a number toward zero returning the closest Integral that s between the function s argument and zero Added as part of the backport of PEP 3141 s type hierarchy for numbers The math module has been improved to give more consistent behaviour across platforms especially with respect to handling of floating point exceptions and IEEE 754 special values Whenever possible the module follows the recommendations of the C99 standard about 754 s special values For example sqrt 1 should now give a ValueError across almost all platforms while sqrt float NaN should return a NaN on all IEEE 754 platforms Where Annex F of the C99 standard recommends signaling divide by zero or invalid Python will raise ValueError Where Annex F of the C99 standard recommends signaling overflow Python will raise OverflowError See bpo 711019 and bpo 1640 Contributed by Christian Heimes and Mark Dickinson mmap objects now have a rfind method that searches for a substring beginning at the end of the string and searching backwards The find method also gained an end parameter giving an index at which to stop searching Contributed by John Lenton The operator module gained a methodcaller function that takes a name and an optional set of arguments returning a callable that will call the named function on any arguments passed to it For example Equivalent to lambda s s replace old new replacer operator methodcaller replace old new replacer old wine in old bottles new wine in new bottles Contributed by Georg Brandl after a suggestion by Gregory Petrosyan The attrgetter function now accepts dotted names and perfor,en
495,ms the corresponding attribute lookups inst_name operator attrgetter __class__ __name__ inst_name str inst_name help _Helper Contributed by Georg Brandl after a suggestion by Barry Warsaw The os module now wraps several new system calls fchmod fd mode and fchown fd uid gid change the mode and ownership of an opened file and lchmod path mode changes the mode of a symlink Contributed by Georg Brandl and Christian Heimes chflags and lchflags are wrappers for the corresponding system calls where they re available changing the flags set on a file Constants for the flag values are defined in the stat module some possible values include UF_IMMUTABLE to signal the file may not be changed and UF_APPEND to indicate that data can only be appended to the file Contributed by M Levinson os closerange low high efficiently closes all file descriptors from low to high ignoring any errors and not including high itself This function is now used by the subprocess module to make starting processes faster Contributed by Georg Brandl bpo 1663329 The os environ object s clear method will now unset the environment variables using os unsetenv in addition to clearing the object s keys Contributed by Martin Horcicka bpo 1181 The os walk function now has a followlinks parameter If set to True it will follow symlinks pointing to directories and visit the directory s contents For backward compatibility the parameter s default value is false Note that the function can fall into an infinite recursion if there s a symlink that points to a parent directory bpo 1273829 In the os path module the splitext function has been changed to not split on leading period characters This produces better results when operating on Unix s dot files For example os path splitext ipython now returns ipython instead of ipython bpo 1115886 A new function os path relpath path start returns a relative path from the start path if it s supplied or from the current working directory to the destination path Contributed by Richard Barran bpo 1339796 On Windows os path expandvars will now expand environment variables given in the form var and user will be expanded into the user s home directory path Contributed by Josiah Carlson bpo 957650 The Python debugger provided by the pdb module gained a new command run restarts the Python program being debugged and can optionally take new command line arguments for the program Contributed by Rocky Bernstein bpo 1393667 The pdb post_mortem function used to begin debugging a traceback will now use the traceback returned by sys exc_info if no traceback is supplied Contributed by Facundo Batista bpo 1106316 The pickletools module now has an optimize function that takes a string containing a pickle and removes some unused opcodes returning a shorter pickle that contains the same data structure Contributed by Raymond Hettinger A get_data function was added to the pkgutil module that returns the contents of resource files included with an installed Python package For example import pkgutil print pkgutil get_data test exception_hierarchy txt BaseException SystemExit KeyboardInterrupt GeneratorExit Exception StopIteration StandardError Contributed by Paul Moore bpo 2439 The pyexpat module s Parser objects now allow setting their buffer_size attribute to change the size of the buffer used to hold character data Contributed by Achim Gaedke bpo 1137 The Queue module now provides queue variants that retrieve entries in different orders The PriorityQueue class stores queued items in a heap and retrieves them in priority order and LifoQueue retrieves the most recently added entries first meaning that it behaves like a stack Contributed by Raymond Hettinger The random module s Random objects can now be pickled on a 32 bit system and unpickled on a 64 bit system and vice versa Unfortunately this change also means that Python 2 6 s Random objects can t be unpickled correctly on earlier versions of Python Contributed by Shawn Ligocki bpo 1727780 The new triangular low high mode function returns random numbers following a triangular distribution The returned valu,en
496,es are between low and high not including high itself and with mode as the most frequently occurring value in the distribution Contributed by Wladmir van der Laan and Raymond Hettinger bpo 1681432 Long regular expression searches carried out by the re module will check for signals being delivered so time consuming searches can now be interrupted Contributed by Josh Hoyt and Ralf Schmitt bpo 846388 The regular expression module is implemented by compiling bytecodes for a tiny regex specific virtual machine Untrusted code could create malicious strings of bytecode directly and cause crashes so Python 2 6 includes a verifier for the regex bytecode Contributed by Guido van Rossum from work for Google App Engine bpo 3487 The rlcompleter module s Completer complete method will now ignore exceptions triggered while evaluating a name Fixed by Lorenz Quack bpo 2250 The sched module s scheduler instances now have a read only queue attribute that returns the contents of the scheduler s queue represented as a list of named tuples with the fields time priority action argument Contributed by Raymond Hettinger bpo 1861 The select module now has wrapper functions for the Linux epoll and BSD kqueue system calls modify method was added to the existing poll objects pollobj modify fd eventmask takes a file descriptor or file object and an event mask modifying the recorded event mask for that file Contributed by Christian Heimes bpo 1657 The shutil copytree function now has an optional ignore argument that takes a callable object This callable will receive each directory path and a list of the directory s contents and returns a list of names that will be ignored not copied The shutil module also provides an ignore_patterns function for use with this new parameter ignore_patterns takes an arbitrary number of glob style patterns and returns a callable that will ignore any files and directories that match any of these patterns The following example copies a directory tree but skips both svn directories and Emacs backup files which have names ending with shutil copytree Doc library tmp library ignore shutil ignore_patterns svn Contributed by Tarek Ziadé bpo 2663 Integrating signal handling with GUI handling event loops like those used by Tkinter or GTk has long been a problem most software ends up polling waking up every fraction of a second to check if any GUI events have occurred The signal module can now make this more efficient Calling signal set_wakeup_fd fd sets a file descriptor to be used when a signal is received a byte is written to that file descriptor There s also a C level function PySignal_SetWakeupFd for setting the descriptor Event loops will use this by opening a pipe to create two descriptors one for reading and one for writing The writable descriptor will be passed to set_wakeup_fd and the readable descriptor will be added to the list of descriptors monitored by the event loop via select or poll On receiving a signal a byte will be written and the main event loop will be woken up avoiding the need to poll Contributed by Adam Olsen bpo 1583 The siginterrupt function is now available from Python code and allows changing whether signals can interrupt system calls or not Contributed by Ralf Schmitt The setitimer and getitimer functions have also been added where they re available setitimer allows setting interval timers that will cause a signal to be delivered to the process after a specified time measured in wall clock time consumed process time or combined process system time Contributed by Guilherme Polo bpo 2240 The smtplib module now supports SMTP over SSL thanks to the addition of the SMTP_SSL class This class supports an interface identical to the existing SMTP class Contributed by Monty Taylor Both class constructors also have an optional timeout parameter that specifies a timeout for the initial connection attempt measured in seconds Contributed by Facundo Batista An implementation of the LMTP protocol RFC 2033 was also added to the module LMTP is used in place of SMTP when transferring e mail between agents that don t ma,en
497,nage a mail queue LMTP implemented by Leif Hedstrom bpo 957003 SMTP starttls now complies with RFC 3207 and forgets any knowledge obtained from the server not obtained from the TLS negotiation itself Patch contributed by Bill Fenner bpo 829951 The socket module now supports TIPC https tipc sourceforge net a high performance non IP based protocol designed for use in clustered environments TIPC addresses are 4 or 5 tuples Contributed by Alberto Bertogli bpo 1646 A new function create_connection takes an address and connects to it using an optional timeout value returning the connected socket object This function also looks up the address s type and connects to it using IPv4 or IPv6 as appropriate Changing your code to use create_connection instead of socket socket AF_INET may be all that s required to make your code work with IPv6 The base classes in the SocketServer module now support calling a handle_timeout method after a span of inactivity specified by the server s timeout attribute Contributed by Michael Pomraning The serve_forever method now takes an optional poll interval measured in seconds controlling how often the server will check for a shutdown request Contributed by Pedro Werneck and Jeffrey Yasskin bpo 742598 bpo 1193577 The sqlite3 module maintained by Gerhard Häring has been updated from version 2 3 2 in Python 2 5 to version 2 4 1 The struct module now supports the C99 _Bool type using the format character Contributed by David Remahl The Popen objects provided by the subprocess module now have terminate kill and send_signal methods On Windows send_signal only supports the SIGTERM signal and all these methods are aliases for the Win32 API function TerminateProcess Contributed by Christian Heimes A new variable in the sys module float_info is an object containing information derived from the float h file about the platform s floating point support Attributes of this object include mant_dig number of digits in the mantissa epsilon smallest difference between 1 0 and the next largest value representable and several others Contributed by Christian Heimes bpo 1534 Another new variable dont_write_bytecode controls whether Python writes any pyc or pyo files on importing a module If this variable is true the compiled files are not written The variable is initially set on start up by supplying the B switch to the Python interpreter or by setting the PYTHONDONTWRITEBYTECODE environment variable before running the interpreter Python code can subsequently change the value of this variable to control whether bytecode files are written or not Contributed by Neal Norwitz and Georg Brandl Information about the command line arguments supplied to the Python interpreter is available by reading attributes of a named tuple available as sys flags For example the verbose attribute is true if Python was executed in verbose mode debug is true in debugging mode etc These attributes are all read only Contributed by Christian Heimes A new function getsizeof takes a Python object and returns the amount of memory used by the object measured in bytes Built in objects return correct results third party extensions may not but can define a __sizeof__ method to return the object s size Contributed by Robert Schuppenies bpo 2898 It s now possible to determine the current profiler and tracer functions by calling sys getprofile and sys gettrace Contributed by Georg Brandl bpo 1648 The tarfile module now supports POSIX 1 2001 pax tarfiles in addition to the POSIX 1 1988 ustar and GNU tar formats that were already supported The default format is GNU tar specify the format parameter to open a file using a different format tar tarfile open output tar w format tarfile PAX_FORMAT The new encoding and errors parameters specify an encoding and an error handling scheme for character conversions strict ignore and replace are the three standard ways Python can handle errors utf 8 is a special value that replaces bad characters with their UTF 8 representation Character conversions occur because the PAX format supports Unicode filenames defaulting to UTF 8 ,en
498,encoding The TarFile add method now accepts an exclude argument that s a function that can be used to exclude certain filenames from an archive The function must take a filename and return true if the file should be excluded or false if it should be archived The function is applied to both the name initially passed to add and to the names of files in recursively added directories All changes contributed by Lars Gustäbel An optional timeout parameter was added to the telnetlib Telnet class constructor specifying a timeout measured in seconds Added by Facundo Batista The tempfile NamedTemporaryFile class usually deletes the temporary file it created when the file is closed This behaviour can now be changed by passing delete False to the constructor Contributed by Damien Miller bpo 1537850 A new class SpooledTemporaryFile behaves like a temporary file but stores its data in memory until a maximum size is exceeded On reaching that limit the contents will be written to an on disk temporary file Contributed by Dustin J Mitchell The NamedTemporaryFile and SpooledTemporaryFile classes both work as context managers so you can write with tempfile NamedTemporaryFile as tmp Contributed by Alexander Belopolsky bpo 2021 The test test_support module gained a number of context managers useful for writing tests EnvironmentVarGuard is a context manager that temporarily changes environment variables and automatically restores them to their old values Another context manager TransientResource can surround calls to resources that may or may not be available it will catch and ignore a specified list of exceptions For example a network test may ignore certain failures when connecting to an external web site with test_support TransientResource IOError errno errno ETIMEDOUT f urllib urlopen https sf net Finally check_warnings resets the warning module s warning filters and returns an object that will record all warning messages triggered bpo 3781 with test_support check_warnings as wrec warnings simplefilter always code that triggers a warning assert str wrec message function is outdated assert len wrec warnings 1 Multiple warnings raised Contributed by Brett Cannon The textwrap module can now preserve existing whitespace at the beginnings and ends of the newly created lines by specifying drop_whitespace False as an argument S This sentence has a bunch of extra whitespace print textwrap fill S width 15 This sentence has a bunch of extra whitespace print textwrap fill S drop_whitespace False width 15 This sentence has a bunch of extra whitespace Contributed by Dwayne Bailey bpo 1581073 The threading module API is being changed to use properties such as daemon instead of setDaemon and isDaemon methods and some methods have been renamed to use underscores instead of camel case for example the activeCount method is renamed to active_count Both the 2 6 and 3 0 versions of the module support the same properties and renamed methods but don t remove the old methods No date has been set for the deprecation of the old APIs in Python 3 x the old APIs won t be removed in any 2 x version Carried out by several people most notably Benjamin Peterson The threading module s Thread objects gained an ident property that returns the thread s identifier a nonzero integer Contributed by Gregory P Smith bpo 2871 The timeit module now accepts callables as well as strings for the statement being timed and for the setup code Two convenience functions were added for creating Timer instances repeat stmt setup time repeat number and timeit stmt setup time number create an instance and call the corresponding method Contributed by Erik Demaine bpo 1533909 The Tkinter module now accepts lists and tuples for options separating the elements by spaces before passing the resulting value to Tcl Tk Contributed by Guilherme Polo bpo 2906 The turtle module for turtle graphics was greatly enhanced by Gregor Lingl New features in the module include Better animation of turtle movement and rotation Control over turtle movement using the new delay tracer and speed methods The ability to se,en
499,t new shapes for the turtle and to define a new coordinate system Turtles now have an undo method that can roll back actions Simple support for reacting to input events such as mouse and keyboard activity making it possible to write simple games A turtle cfg file can be used to customize the starting appearance of the turtle s screen The module s docstrings can be replaced by new docstrings that have been translated into another language bpo 1513695 An optional timeout parameter was added to the urllib urlopen function and the urllib ftpwrapper class constructor as well as the urllib2 urlopen function The parameter specifies a timeout measured in seconds For example u urllib2 urlopen http slow example com timeout 3 Traceback most recent call last urllib2 URLError urlopen error timed out Added by Facundo Batista The Unicode database provided by the unicodedata module has been updated to version 5 1 0 Updated by Martin von Löwis bpo 3811 The warnings module s formatwarning and showwarning gained an optional line argument that can be used to supply the line of source code Added as part of bpo 1631171 which re implemented part of the warnings module in C code A new function catch_warnings is a context manager intended for testing purposes that lets you temporarily modify the warning filters and then restore their original values bpo 3781 The XML RPC SimpleXMLRPCServer and DocXMLRPCServer classes can now be prevented from immediately opening and binding to their socket by passing False as the bind_and_activate constructor parameter This can be used to modify the instance s allow_reuse_address attribute before calling the server_bind and server_activate methods to open the socket and begin listening for connections Contributed by Peter Parente bpo 1599845 SimpleXMLRPCServer also has a _send_traceback_header attribute if true the exception and formatted traceback are returned as HTTP headers X Exception and X Traceback This feature is for debugging purposes only and should not be used on production servers because the tracebacks might reveal passwords or other sensitive information Contributed by Alan McIntyre as part of his project for Google s Summer of Code 2007 The xmlrpclib module no longer automatically converts datetime date and datetime time to the xmlrpclib DateTime type the conversion semantics were not necessarily correct for all applications Code using xmlrpclib should convert date and time instances bpo 1330538 The code can also handle dates before 1900 contributed by Ralf Schmitt bpo 2014 and 64 bit integers represented by using i8 in XML RPC responses contributed by Riku Lindblad bpo 2985 The zipfile module s ZipFile class now has extract and extractall methods that will unpack a single file or all the files in the archive to the current directory or to a specified directory z zipfile ZipFile python 251 zip Unpack a single file writing it relative to the tmp directory z extract Python sysmodule c tmp Unpack all the files in the archive z extractall Contributed by Alan McIntyre bpo 467924 The open read and extract methods can now take either a filename or a ZipInfo object This is useful when an archive accidentally contains a duplicated filename Contributed by Graham Horler bpo 1775025 Finally zipfile now supports using Unicode filenames for archived files Contributed by Alexey Borzenkov bpo 1734346 The ast module The ast module provides an Abstract Syntax Tree representation of Python code and Armin Ronacher contributed a set of helper functions that perform a variety of common tasks These will be useful for HTML templating packages code analyzers and similar tools that process Python code The parse function takes an expression and returns an AST The dump function outputs a representation of a tree suitable for debugging import ast t ast parse d for i in abcdefghijklm d i i ord i ord a 1 print d print ast dump t This outputs a deeply nested tree Module body Assign targets Name id d ctx Store value Dict keys values For target Name id i ctx Store iter Str s abcdefghijklm body Assign targets Subscript value Name id ,en
500,d ctx Load slice Index value BinOp left Name id i ctx Load op Add right Name id i ctx Load ctx Store value BinOp left BinOp left Call func Name id ord ctx Load args Name id i ctx Load keywords starargs None kwargs None op Sub right Call func Name id ord ctx Load args Str s a keywords starargs None kwargs None op Add right Num n 1 orelse Print dest None values Name id d ctx Load nl True The literal_eval method takes a string or an AST representing a literal expression parses and evaluates it and returns the resulting value A literal expression is a Python expression containing only strings numbers dictionaries etc but no statements or function calls If you need to evaluate an expression but cannot accept the security risk of using an eval call literal_eval will handle it safely literal a b 2 4 3 8 1 2 print ast literal_eval literal a b 1 2 2 4 3 8 print ast literal_eval a b Traceback most recent call last ValueError malformed string The module also includes NodeVisitor and NodeTransformer classes for traversing and modifying an AST and functions for common transformations such as changing line numbers The future_builtins module Python 3 0 makes many changes to the repertoire of built in functions and most of the changes can t be introduced in the Python 2 x series because they would break compatibility The future_builtins module provides versions of these built in functions that can be imported when writing 3 0 compatible code The functions in this module currently include ascii obj equivalent to repr In Python 3 0 repr will return a Unicode string while ascii will return a pure ASCII bytestring filter predicate iterable map func iterable1 the 3 0 versions return iterators unlike the 2 x builtins which return lists hex value oct value instead of calling the __hex__ or __oct__ methods these versions will call the __index__ method and convert the result to hexadecimal or octal oct will use the new 0o notation for its result The json module JavaScript Object Notation The new json module supports the encoding and decoding of Python types in JSON Javascript Object Notation JSON is a lightweight interchange format often used in web applications For more information about JSON see http www json org json comes with support for decoding and encoding most built in Python types The following example encodes and decodes a dictionary import json data spam foo parrot 42 in_json json dumps data Encode the data in_json parrot 42 spam foo json loads in_json Decode into a Python object spam foo parrot 42 It s also possible to write your own decoders and encoders to support more types Pretty printing of the JSON strings is also supported json originally called simplejson was written by Bob Ippolito The plistlib module A Property List Parser The plist format is commonly used on Mac OS X to store basic data types numbers strings lists and dictionaries by serializing them into an XML based format It resembles the XML RPC serialization of data types Despite being primarily used on Mac OS X the format has nothing Mac specific about it and the Python implementation works on any platform that Python supports so the plistlib module has been promoted to the standard library Using the module is simple import sys import plistlib import datetime Create data structure data_struct dict lastAccessed datetime datetime now version 1 categories Personal Shared Private Create string containing XML plist_str plistlib writePlistToString data_struct new_struct plistlib readPlistFromString plist_str print data_struct print new_struct Write data structure to a file and read it back plistlib writePlist data_struct tmp customizations plist new_struct plistlib readPlist tmp customizations plist read writePlist accepts file like objects as well as paths plistlib writePlist data_struct sys stdout ctypes Enhancements Thomas Heller continued to maintain and enhance the ctypes module ctypes now supports a c_bool datatype that represents the C99 bool type Contributed by David Remahl bpo 1649190 The ctypes string buffer and array types have improved support for extended sli,en
501,cing syntax where various combinations of start stop step are supplied Implemented by Thomas Wouters All ctypes data types now support from_buffer and from_buffer_copy methods that create a ctypes instance based on a provided buffer object from_buffer_copy copies the contents of the object while from_buffer will share the same memory area A new calling convention tells ctypes to clear the errno or Win32 LastError variables at the outset of each wrapped call Implemented by Thomas Heller bpo 1798 You can now retrieve the Unix errno variable after a function call When creating a wrapped function you can supply use_errno True as a keyword parameter to the DLL function and then call the module level methods set_errno and get_errno to set and retrieve the error value The Win32 LastError variable is similarly supported by the DLL OleDLL and WinDLL functions You supply use_last_error True as a keyword parameter and then call the module level methods set_last_error and get_last_error The byref function used to retrieve a pointer to a ctypes instance now has an optional offset parameter that is a byte count that will be added to the returned pointer Improved SSL Support Bill Janssen made extensive improvements to Python 2 6 s support for the Secure Sockets Layer by adding a new module ssl that s built atop the OpenSSL library This new module provides more control over the protocol negotiated the X 509 certificates used and has better support for writing SSL servers as opposed to clients in Python The existing SSL support in the socket module hasn t been removed and continues to work though it will be removed in Python 3 0 To use the new module you must first create a TCP connection in the usual way and then pass it to the ssl wrap_socket function It s possible to specify whether a certificate is required and to obtain certificate info by calling the getpeercert method See also The documentation for the ssl module Deprecations and Removals String exceptions have been removed Attempting to use them raises a TypeError Changes to the Exception interface as dictated by PEP 352 continue to be made For 2 6 the message attribute is being deprecated in favor of the args attribute 3 0 warning mode Python 3 0 will feature a reorganized standard library that will drop many outdated modules and rename others Python 2 6 running in 3 0 warning mode will warn about these modules when they are imported The list of deprecated modules is audiodev bgenlocations buildtools bundlebuilder Canvas compiler dircache dl fpformat gensuitemodule ihooks imageop imgfile linuxaudiodev mhlib mimetools multifile new pure statvfs sunaudiodev test testall and toaiff The gopherlib module has been removed The MimeWriter module and mimify module have been deprecated use the email package instead The md5 module has been deprecated use the hashlib module instead The posixfile module has been deprecated fcntl lockf provides better locking The popen2 module has been deprecated use the subprocess module The rgbimg module has been removed The sets module has been deprecated it s better to use the built in set and frozenset types The sha module has been deprecated use the hashlib module instead Build and C API Changes Changes to Python s build process and to the C API include Python now must be compiled with C89 compilers after 19 years This means that the Python source tree has dropped its own implementations of memmove and strerror which are in the C89 standard library Python 2 6 can be built with Microsoft Visual Studio 2008 version 9 0 and this is the new default compiler See the PCbuild directory for the build files Implemented by Christian Heimes On Mac OS X Python 2 6 can be compiled as a 4 way universal build The configure script can take a with universal archs 32 bit 64 bit all switch controlling whether the binaries are built for 32 bit architectures x86 PowerPC 64 bit x86 64 and PPC 64 or both Contributed by Ronald Oussoren A new function added in Python 2 6 6 PySys_SetArgvEx sets the value of sys argv and can optionally update sys path to include the directory con,en
502,taining the script named by sys argv 0 depending on the value of an updatepath parameter This function was added to close a security hole for applications that embed Python The old function PySys_SetArgv would always update sys path and sometimes it would add the current directory This meant that if you ran an application embedding Python in a directory controlled by someone else attackers could put a Trojan horse module in the directory say a file named os py that your application would then import and run If you maintain a C C application that embeds Python check whether you re calling PySys_SetArgv and carefully consider whether the application should be using PySys_SetArgvEx with updatepath set to false Note that using this function will break compatibility with Python versions 2 6 5 and earlier if you have to continue working with earlier versions you can leave the call to PySys_SetArgv alone and call PyRun_SimpleString sys path pop 0 n afterwards to discard the first sys path component Security issue reported as CVE 2008 5983 discussed in gh 50003 and fixed by Antoine Pitrou The BerkeleyDB module now has a C API object available as bsddb db api This object can be used by other C extensions that wish to use the bsddb module for their own purposes Contributed by Duncan Grisby The new buffer interface previously described in the PEP 3118 section adds PyObject_GetBuffer and PyBuffer_Release as well as a few other functions Python s use of the C stdio library is now thread safe or at least as thread safe as the underlying library is A long standing potential bug occurred if one thread closed a file object while another thread was reading from or writing to the object In 2 6 file objects have a reference count manipulated by the PyFile_IncUseCount and PyFile_DecUseCount functions File objects can t be closed unless the reference count is zero PyFile_IncUseCount should be called while the GIL is still held before carrying out an I O operation using the FILE pointer and PyFile_DecUseCount should be called immediately after the GIL is re acquired Contributed by Antoine Pitrou and Gregory P Smith Importing modules simultaneously in two different threads no longer deadlocks it will now raise an ImportError A new API function PyImport_ImportModuleNoBlock will look for a module in sys modules first then try to import it after acquiring an import lock If the import lock is held by another thread an ImportError is raised Contributed by Christian Heimes Several functions return information about the platform s floating point support PyFloat_GetMax returns the maximum representable floating point value and PyFloat_GetMin returns the minimum positive value PyFloat_GetInfo returns an object containing more information from the float h file such as mant_dig number of digits in the mantissa epsilon smallest difference between 1 0 and the next largest value representable and several others Contributed by Christian Heimes bpo 1534 C functions and methods that use PyComplex_AsCComplex will now accept arguments that have a __complex__ method In particular the functions in the cmath module will now accept objects with this method This is a backport of a Python 3 0 change Contributed by Mark Dickinson bpo 1675423 Python s C API now includes two functions for case insensitive string comparisons PyOS_stricmp char char and PyOS_strnicmp char char Py_ssize_t Contributed by Christian Heimes bpo 1635 Many C extensions define their own little macro for adding integers and strings to the module s dictionary in the init function Python 2 6 finally defines standard macros for adding values to a module PyModule_AddStringMacro and PyModule_AddIntMacro Contributed by Christian Heimes Some macros were renamed in both 3 0 and 2 6 to make it clearer that they are macros not functions Py_Size became Py_SIZE Py_Type became Py_TYPE and Py_Refcnt became Py_REFCNT The mixed case macros are still available in Python 2 6 for backward compatibility bpo 1629 Distutils now places C extensions it builds in a different directory when running on a debug version of Pytho,en
503,n Contributed by Collin Winter bpo 1530959 Several basic data types such as integers and strings maintain internal free lists of objects that can be re used The data structures for these free lists now follow a naming convention the variable is always named free_list the counter is always named numfree and a macro Py typename _MAXFREELIST is always defined A new Makefile target make patchcheck prepares the Python source tree for making a patch it fixes trailing whitespace in all modified py files checks whether the documentation has been changed and reports whether the Misc ACKS and Misc NEWS files have been updated Contributed by Brett Cannon Another new target make profile opt compiles a Python binary using GCC s profile guided optimization It compiles Python with profiling enabled runs the test suite to obtain a set of profiling results and then compiles using these results for optimization Contributed by Gregory P Smith Port Specific Changes Windows The support for Windows 95 98 ME and NT4 has been dropped Python 2 6 requires at least Windows 2000 SP4 The new default compiler on Windows is Visual Studio 2008 version 9 0 The build directories for Visual Studio 2003 version 7 1 and 2005 version 8 0 were moved into the PC directory The new PCbuild directory supports cross compilation for X64 debug builds and Profile Guided Optimization PGO PGO builds are roughly 10 faster than normal builds Contributed by Christian Heimes with help from Amaury Forgeot d Arc and Martin von Löwis The msvcrt module now supports both the normal and wide char variants of the console I O API The getwch function reads a keypress and returns a Unicode value as does the getwche function The putwch function takes a Unicode character and writes it to the console Contributed by Christian Heimes os path expandvars will now expand environment variables in the form var and user will be expanded into the user s home directory path Contributed by Josiah Carlson bpo 957650 The socket module s socket objects now have an ioctl method that provides a limited interface to the WSAIoctl system interface The _winreg module now has a function ExpandEnvironmentStrings that expands environment variable references such as NAME in an input string The handle objects provided by this module now support the context protocol so they can be used in with statements Contributed by Christian Heimes _winreg also has better support for x64 systems exposing the DisableReflectionKey EnableReflectionKey and QueryReflectionKey functions which enable and disable registry reflection for 32 bit processes running on 64 bit systems bpo 1753245 The msilib module s Record object gained GetInteger and GetString methods that return field values as an integer or a string Contributed by Floris Bruynooghe bpo 2125 Port Specific Changes Mac OS X When compiling a framework build of Python you can now specify the framework name to be used by providing the with framework name option to the configure script The macfs module has been removed This in turn required the macostools touched function to be removed because it depended on the macfs module bpo 1490190 Many other Mac OS modules have been deprecated and will be removed in Python 3 0 _builtinSuites aepack aetools aetypes applesingle appletrawmain appletrunner argvemulator Audio_mac autoGIL Carbon cfmfile CodeWarrior ColorPicker EasyDialogs Explorer Finder FrameWork findertools ic icglue icopen macerrors MacOS macfs macostools macresource MiniAEFrame Nav Netscape OSATerminology pimp PixMapWrapper StdSuites SystemEvents Terminal and terminalcommand Port Specific Changes IRIX A number of old IRIX specific modules were deprecated and will be removed in Python 3 0 al and AL cd cddb cdplayer CL and cl DEVICE ERRNO FILE FL and fl flp fm GET GLWS GL and gl IN IOCTL jpeg panelparser readcd SV and sv torgb videoreader and WAIT Porting to Python 2 6 This section lists previously described changes and other bugfixes that may require changes to your code Classes that aren t supposed to be hashable should set __hash__ None in their definitions to indicate ,en
504,the fact String exceptions have been removed Attempting to use them raises a TypeError The __init__ method of collections deque now clears any existing contents of the deque before adding elements from the iterable This change makes the behavior match list __init__ object __init__ previously accepted arbitrary arguments and keyword arguments ignoring them In Python 2 6 this is no longer allowed and will result in a TypeError This will affect __init__ methods that end up calling the corresponding method on object perhaps through using super See bpo 1683368 for discussion The Decimal constructor now accepts leading and trailing whitespace when passed a string Previously it would raise an InvalidOperation exception On the other hand the create_decimal method of Context objects now explicitly disallows extra whitespace raising a ConversionSyntax exception Due to an implementation accident if you passed a file path to the built in __import__ function it would actually import the specified file This was never intended to work however and the implementation now explicitly checks for this case and raises an ImportError C API the PyImport_Import and PyImport_ImportModule functions now default to absolute imports not relative imports This will affect C extensions that import other modules C API extension data types that shouldn t be hashable should define their tp_hash slot to PyObject_HashNotImplemented The socket module exception socket error now inherits from IOError Previously it wasn t a subclass of StandardError but now it is through IOError Implemented by Gregory P Smith bpo 1706815 The xmlrpclib module no longer automatically converts datetime date and datetime time to the xmlrpclib DateTime type the conversion semantics were not necessarily correct for all applications Code using xmlrpclib should convert date and time instances bpo 1330538 3 0 warning mode The Exception class now warns when accessed using slicing or index access having Exception behave like a tuple is being phased out 3 0 warning mode inequality comparisons between two dictionaries or two objects that don t implement comparison methods are reported as warnings dict1 dict2 still works but dict1 dict2 is being phased out Comparisons between cells which are an implementation detail of Python s scoping rules also cause warnings because such comparisons are forbidden entirely in 3 0 For applications that embed Python The PySys_SetArgvEx function was added in Python 2 6 6 letting applications close a security hole when the existing PySys_SetArgv function was used Check whether you re calling PySys_SetArgv and carefully consider whether the application should be using PySys_SetArgvEx with updatepath set to false Acknowledgements The author would like to thank the following people for offering suggestions corrections and assistance with various drafts of this article Georg Brandl Steve Brown Nick Coghlan Ralph Corderoy Jim Jewett Kent Johnson Chris Lambacher Martin Michlmayr Antoine Pitrou Brian Warner,en
505,4 Execution model 4 1 Structure of a program A Python program is constructed from code blocks A block is a piece of Python program text that is executed as a unit The following are blocks a module a function body and a class definition Each command typed interactively is a block A script file a file given as standard input to the interpreter or specified as a command line argument to the interpreter is a code block A script command a command specified on the interpreter command line with the c option is a code block A module run as a top level script as module __main__ from the command line using a m argument is also a code block The string argument passed to the built in functions eval and exec is a code block A code block is executed in an execution frame A frame contains some administrative information used for debugging and determines where and how execution continues after the code block s execution has completed 4 2 Naming and binding 4 2 1 Binding of names Names refer to objects Names are introduced by name binding operations The following constructs bind names formal parameters to functions class definitions function definitions assignment expressions targets that are identifiers if occurring in an assignment for loop header after as in a with statement except clause except clause or in the as pattern in structural pattern matching in a capture pattern in structural pattern matching import statements type statements type parameter lists The import statement of the form from import binds all names defined in the imported module except those beginning with an underscore This form may only be used at the module level A target occurring in a del statement is also considered bound for this purpose though the actual semantics are to unbind the name Each assignment or import statement occurs within a block defined by a class or function definition or at the module level the top level code block If a name is bound in a block it is a local variable of that block unless declared as nonlocal or global If a name is bound at the module level it is a global variable The variables of the module code block are local and global If a variable is used in a code block but not defined there it is a free variable Each occurrence of a name in the program text refers to the binding of that name established by the following name resolution rules 4 2 2 Resolution of names A scope defines the visibility of a name within a block If a local variable is defined in a block its scope includes that block If the definition occurs in a function block the scope extends to any blocks contained within the defining one unless a contained block introduces a different binding for the name When a name is used in a code block it is resolved using the nearest enclosing scope The set of all such scopes visible to a code block is called the block s environment When a name is not found at all a NameError exception is raised If the current scope is a function scope and the name refers to a local variable that has not yet been bound to a value at the point where the name is used an UnboundLocalError exception is raised UnboundLocalError is a subclass of NameError If a name binding operation occurs anywhere within a code block all uses of the name within the block are treated as references to the current block This can lead to errors when a name is used within a block before it is bound This rule is subtle Python lacks declarations and allows name binding operations to occur anywhere within a code block The local variables of a code block can be determined by scanning the entire text of the block for name binding operations See the FAQ entry on UnboundLocalError for examples If the global statement occurs within a block all uses of the names specified in the statement refer to the bindings of those names in the top level namespace Names are resolved in the top level namespace by searching the global namespace i e the namespace of the module containing the code block and the builtins namespace the namespace of the module builtins The global namespace is searched ,en
506,first If the names are not found there the builtins namespace is searched The global statement must precede all uses of the listed names The global statement has the same scope as a name binding operation in the same block If the nearest enclosing scope for a free variable contains a global statement the free variable is treated as a global The nonlocal statement causes corresponding names to refer to previously bound variables in the nearest enclosing function scope SyntaxError is raised at compile time if the given name does not exist in any enclosing function scope Type parameters cannot be rebound with the nonlocal statement The namespace for a module is automatically created the first time a module is imported The main module for a script is always called __main__ Class definition blocks and arguments to exec and eval are special in the context of name resolution A class definition is an executable statement that may use and define names These references follow the normal rules for name resolution with an exception that unbound local variables are looked up in the global namespace The namespace of the class definition becomes the attribute dictionary of the class The scope of names defined in a class block is limited to the class block it does not extend to the code blocks of methods This includes comprehensions and generator expressions but it does not include annotation scopes which have access to their enclosing class scopes This means that the following will fail class A a 42 b list a i for i in range 10 However the following will succeed class A type Alias Nested class Nested pass print A Alias __value__ type A Nested 4 2 3 Annotation scopes Type parameter lists and type statements introduce annotation scopes which behave mostly like function scopes but with some exceptions discussed below Annotations currently do not use annotation scopes but they are expected to use annotation scopes in Python 3 13 when PEP 649 is implemented Annotation scopes are used in the following contexts Type parameter lists for generic type aliases Type parameter lists for generic functions A generic function s annotations are executed within the annotation scope but its defaults and decorators are not Type parameter lists for generic classes A generic class s base classes and keyword arguments are executed within the annotation scope but its decorators are not The bounds and constraints for type variables lazily evaluated The value of type aliases lazily evaluated Annotation scopes differ from function scopes in the following ways Annotation scopes have access to their enclosing class namespace If an annotation scope is immediately within a class scope or within another annotation scope that is immediately within a class scope the code in the annotation scope can use names defined in the class scope as if it were executed directly within the class body This contrasts with regular functions defined within classes which cannot access names defined in the class scope Expressions in annotation scopes cannot contain yield yield from await or expressions These expressions are allowed in other scopes contained within the annotation scope Names defined in annotation scopes cannot be rebound with nonlocal statements in inner scopes This includes only type parameters as no other syntactic elements that can appear within annotation scopes can introduce new names While annotation scopes have an internal name that name is not reflected in the __qualname__ of objects defined within the scope Instead the __qualname__ of such objects is as if the object were defined in the enclosing scope New in version 3 12 Annotation scopes were introduced in Python 3 12 as part of PEP 695 4 2 4 Lazy evaluation The values of type aliases created through the type statement are lazily evaluated The same applies to the bounds and constraints of type variables created through the type parameter syntax This means that they are not evaluated when the type alias or type variable is created Instead they are only evaluated when doing so is necessary to resolve an attribute,en
507, access Example type Alias 1 0 Alias __value__ Traceback most recent call last ZeroDivisionError division by zero def func T 1 0 pass T func __type_params__ 0 T __bound__ Traceback most recent call last ZeroDivisionError division by zero Here the exception is raised only when the __value__ attribute of the type alias or the __bound__ attribute of the type variable is accessed This behavior is primarily useful for references to types that have not yet been defined when the type alias or type variable is created For example lazy evaluation enables creation of mutually recursive type aliases from typing import Literal type SimpleExpr int Parenthesized type Parenthesized tuple Literal Expr Literal type Expr SimpleExpr tuple SimpleExpr Literal Expr Lazily evaluated values are evaluated in annotation scope which means that names that appear inside the lazily evaluated value are looked up as if they were used in the immediately enclosing scope New in version 3 12 4 2 5 Builtins and restricted execution CPython implementation detail Users should not touch __builtins__ it is strictly an implementation detail Users wanting to override values in the builtins namespace should import the builtins module and modify its attributes appropriately The builtins namespace associated with the execution of a code block is actually found by looking up the name __builtins__ in its global namespace this should be a dictionary or a module in the latter case the module s dictionary is used By default when in the __main__ module __builtins__ is the built in module builtins when in any other module __builtins__ is an alias for the dictionary of the builtins module itself 4 2 6 Interaction with dynamic features Name resolution of free variables occurs at runtime not at compile time This means that the following code will print 42 i 10 def f print i i 42 f The eval and exec functions do not have access to the full environment for resolving names Names may be resolved in the local and global namespaces of the caller Free variables are not resolved in the nearest enclosing namespace but in the global namespace 1 The exec and eval functions have optional arguments to override the global and local namespace If only one namespace is specified it is used for both 4 3 Exceptions Exceptions are a means of breaking out of the normal flow of control of a code block in order to handle errors or other exceptional conditions An exception is raised at the point where the error is detected it may be handled by the surrounding code block or by any code block that directly or indirectly invoked the code block where the error occurred The Python interpreter raises an exception when it detects a run time error such as division by zero A Python program can also explicitly raise an exception with the raise statement Exception handlers are specified with the try except statement The finally clause of such a statement can be used to specify cleanup code which does not handle the exception but is executed whether an exception occurred or not in the preceding code Python uses the termination model of error handling an exception handler can find out what happened and continue execution at an outer level but it cannot repair the cause of the error and retry the failing operation except by re entering the offending piece of code from the top When an exception is not handled at all the interpreter terminates execution of the program or returns to its interactive main loop In either case it prints a stack traceback except when the exception is SystemExit Exceptions are identified by class instances The except clause is selected depending on the class of the instance it must reference the class of the instance or a non virtual base class thereof The instance can be received by the handler and can carry additional information about the exceptional condition Note Exception messages are not part of the Python API Their contents may change from one version of Python to the next without warning and should not be relied on by code which will run under multiple versions of the interpreter,en
508, See also the description of the try statement in section The try statement and raise statement in section The raise statement Footnotes 1 This limitation occurs because the code that is executed by these operations is not available at the time the module is compiled,en
509,xml sax xmlreader Interface for XML parsers Source code Lib xml sax xmlreader py SAX parsers implement the XMLReader interface They are implemented in a Python module which must provide a function create_parser This function is invoked by xml sax make_parser with no arguments to create a new parser object class xml sax xmlreader XMLReader Base class which can be inherited by SAX parsers class xml sax xmlreader IncrementalParser In some cases it is desirable not to parse an input source at once but to feed chunks of the document as they get available Note that the reader will normally not read the entire file but read it in chunks as well still parse won t return until the entire document is processed So these interfaces should be used if the blocking behaviour of parse is not desirable When the parser is instantiated it is ready to begin accepting data from the feed method immediately After parsing has been finished with a call to close the reset method must be called to make the parser ready to accept new data either from feed or using the parse method Note that these methods must not be called during parsing that is after parse has been called and before it returns By default the class also implements the parse method of the XMLReader interface using the feed close and reset methods of the IncrementalParser interface as a convenience to SAX 2 0 driver writers class xml sax xmlreader Locator Interface for associating a SAX event with a document location A locator object will return valid results only during calls to DocumentHandler methods at any other time the results are unpredictable If information is not available methods may return None class xml sax xmlreader InputSource system_id None Encapsulation of the information needed by the XMLReader to read entities This class may include information about the public identifier system identifier byte stream possibly with character encoding information and or the character stream of an entity Applications will create objects of this class for use in the XMLReader parse method and for returning from EntityResolver resolveEntity An InputSource belongs to the application the XMLReader is not allowed to modify InputSource objects passed to it from the application although it may make copies and modify those class xml sax xmlreader AttributesImpl attrs This is an implementation of the Attributes interface see section The Attributes Interface This is a dictionary like object which represents the element attributes in a startElement call In addition to the most useful dictionary operations it supports a number of other methods as described by the interface Objects of this class should be instantiated by readers attrs must be a dictionary like object containing a mapping from attribute names to attribute values class xml sax xmlreader AttributesNSImpl attrs qnames Namespace aware variant of AttributesImpl which will be passed to startElementNS It is derived from AttributesImpl but understands attribute names as two tuples of namespaceURI and localname In addition it provides a number of methods expecting qualified names as they appear in the original document This class implements the AttributesNS interface see section The AttributesNS Interface XMLReader Objects The XMLReader interface supports the following methods XMLReader parse source Process an input source producing SAX events The source object can be a system identifier a string identifying the input source typically a file name or a URL a pathlib Path or path like object or an InputSource object When parse returns the input is completely processed and the parser object can be discarded or reset Changed in version 3 5 Added support of character streams Changed in version 3 8 Added support of path like objects XMLReader getContentHandler Return the current ContentHandler XMLReader setContentHandler handler Set the current ContentHandler If no ContentHandler is set content events will be discarded XMLReader getDTDHandler Return the current DTDHandler XMLReader setDTDHandler handler Set the current DTDHandler If no DTDHandler,en
510, is set DTD events will be discarded XMLReader getEntityResolver Return the current EntityResolver XMLReader setEntityResolver handler Set the current EntityResolver If no EntityResolver is set attempts to resolve an external entity will result in opening the system identifier for the entity and fail if it is not available XMLReader getErrorHandler Return the current ErrorHandler XMLReader setErrorHandler handler Set the current error handler If no ErrorHandler is set errors will be raised as exceptions and warnings will be printed XMLReader setLocale locale Allow an application to set the locale for errors and warnings SAX parsers are not required to provide localization for errors and warnings if they cannot support the requested locale however they must raise a SAX exception Applications may request a locale change in the middle of a parse XMLReader getFeature featurename Return the current setting for feature featurename If the feature is not recognized SAXNotRecognizedException is raised The well known featurenames are listed in the module xml sax handler XMLReader setFeature featurename value Set the featurename to value If the feature is not recognized SAXNotRecognizedException is raised If the feature or its setting is not supported by the parser SAXNotSupportedException is raised XMLReader getProperty propertyname Return the current setting for property propertyname If the property is not recognized a SAXNotRecognizedException is raised The well known propertynames are listed in the module xml sax handler XMLReader setProperty propertyname value Set the propertyname to value If the property is not recognized SAXNotRecognizedException is raised If the property or its setting is not supported by the parser SAXNotSupportedException is raised IncrementalParser Objects Instances of IncrementalParser offer the following additional methods IncrementalParser feed data Process a chunk of data IncrementalParser close Assume the end of the document That will check well formedness conditions that can be checked only at the end invoke handlers and may clean up resources allocated during parsing IncrementalParser reset This method is called after close has been called to reset the parser so that it is ready to parse new documents The results of calling parse or feed after close without calling reset are undefined Locator Objects Instances of Locator provide these methods Locator getColumnNumber Return the column number where the current event begins Locator getLineNumber Return the line number where the current event begins Locator getPublicId Return the public identifier for the current event Locator getSystemId Return the system identifier for the current event InputSource Objects InputSource setPublicId id Sets the public identifier of this InputSource InputSource getPublicId Returns the public identifier of this InputSource InputSource setSystemId id Sets the system identifier of this InputSource InputSource getSystemId Returns the system identifier of this InputSource InputSource setEncoding encoding Sets the character encoding of this InputSource The encoding must be a string acceptable for an XML encoding declaration see section 4 3 3 of the XML recommendation The encoding attribute of the InputSource is ignored if the InputSource also contains a character stream InputSource getEncoding Get the character encoding of this InputSource InputSource setByteStream bytefile Set the byte stream a binary file for this input source The SAX parser will ignore this if there is also a character stream specified but it will use a byte stream in preference to opening a URI connection itself If the application knows the character encoding of the byte stream it should set it with the setEncoding method InputSource getByteStream Get the byte stream for this input source The getEncoding method will return the character encoding for this byte stream or None if unknown InputSource setCharacterStream charfile Set the character stream a text file for this input source If there is a character stream specified the SAX parser will ignore any by,en
511,te stream and will not attempt to open a URI connection to the system identifier InputSource getCharacterStream Get the character stream for this input source The Attributes Interface Attributes objects implement a portion of the mapping protocol including the methods copy get __contains__ items keys and values The following methods are also provided Attributes getLength Return the number of attributes Attributes getNames Return the names of the attributes Attributes getType name Returns the type of the attribute name which is normally CDATA Attributes getValue name Return the value of attribute name The AttributesNS Interface This interface is a subtype of the Attributes interface see section The Attributes Interface All methods supported by that interface are also available on AttributesNS objects The following methods are also available AttributesNS getValueByQName name Return the value for a qualified name AttributesNS getNameByQName name Return the namespace localname pair for a qualified name AttributesNS getQNameByName name Return the qualified name for a namespace localname pair AttributesNS getQNames Return the qualified names of all attributes,en
512,base64 Base16 Base32 Base64 Base85 Data Encodings Source code Lib base64 py This module provides functions for encoding binary data to printable ASCII characters and decoding such encodings back to binary data It provides encoding and decoding functions for the encodings specified in RFC 4648 which defines the Base16 Base32 and Base64 algorithms and for the de facto standard Ascii85 and Base85 encodings The RFC 4648 encodings are suitable for encoding binary data so that it can be safely sent by email used as parts of URLs or included as part of an HTTP POST request The encoding algorithm is not the same as the uuencode program There are two interfaces provided by this module The modern interface supports encoding bytes like objects to ASCII bytes and decoding bytes like objects or strings containing ASCII to bytes Both base 64 alphabets defined in RFC 4648 normal and URL and filesystem safe are supported The legacy interface does not support decoding from strings but it does provide functions for encoding and decoding to and from file objects It only supports the Base64 standard alphabet and it adds newlines every 76 characters as per RFC 2045 Note that if you are looking for RFC 2045 support you probably want to be looking at the email package instead Changed in version 3 3 ASCII only Unicode strings are now accepted by the decoding functions of the modern interface Changed in version 3 4 Any bytes like objects are now accepted by all encoding and decoding functions in this module Ascii85 Base85 support added The modern interface provides base64 b64encode s altchars None Encode the bytes like object s using Base64 and return the encoded bytes Optional altchars must be a bytes like object of length 2 which specifies an alternative alphabet for the and characters This allows an application to e g generate URL or filesystem safe Base64 strings The default is None for which the standard Base64 alphabet is used May assert or raise a ValueError if the length of altchars is not 2 Raises a TypeError if altchars is not a bytes like object base64 b64decode s altchars None validate False Decode the Base64 encoded bytes like object or ASCII string s and return the decoded bytes Optional altchars must be a bytes like object or ASCII string of length 2 which specifies the alternative alphabet used instead of the and characters A binascii Error exception is raised if s is incorrectly padded If validate is False the default characters that are neither in the normal base 64 alphabet nor the alternative alphabet are discarded prior to the padding check If validate is True these non alphabet characters in the input result in a binascii Error For more information about the strict base64 check see binascii a2b_base64 May assert or raise a ValueError if the length of altchars is not 2 base64 standard_b64encode s Encode bytes like object s using the standard Base64 alphabet and return the encoded bytes base64 standard_b64decode s Decode bytes like object or ASCII string s using the standard Base64 alphabet and return the decoded bytes base64 urlsafe_b64encode s Encode bytes like object s using the URL and filesystem safe alphabet which substitutes instead of and _ instead of in the standard Base64 alphabet and return the encoded bytes The result can still contain base64 urlsafe_b64decode s Decode bytes like object or ASCII string s using the URL and filesystem safe alphabet which substitutes instead of and _ instead of in the standard Base64 alphabet and return the decoded bytes base64 b32encode s Encode the bytes like object s using Base32 and return the encoded bytes base64 b32decode s casefold False map01 None Decode the Base32 encoded bytes like object or ASCII string s and return the decoded bytes Optional casefold is a flag specifying whether a lowercase alphabet is acceptable as input For security purposes the default is False RFC 4648 allows for optional mapping of the digit 0 zero to the letter O oh and for optional mapping of the digit 1 one to either the letter I eye or letter L el The optional argument map01 when not None specifi,en
513,es which letter the digit 1 should be mapped to when map01 is not None the digit 0 is always mapped to the letter O For security purposes the default is None so that 0 and 1 are not allowed in the input A binascii Error is raised if s is incorrectly padded or if there are non alphabet characters present in the input base64 b32hexencode s Similar to b32encode but uses the Extended Hex Alphabet as defined in RFC 4648 New in version 3 10 base64 b32hexdecode s casefold False Similar to b32decode but uses the Extended Hex Alphabet as defined in RFC 4648 This version does not allow the digit 0 zero to the letter O oh and digit 1 one to either the letter I eye or letter L el mappings all these characters are included in the Extended Hex Alphabet and are not interchangeable New in version 3 10 base64 b16encode s Encode the bytes like object s using Base16 and return the encoded bytes base64 b16decode s casefold False Decode the Base16 encoded bytes like object or ASCII string s and return the decoded bytes Optional casefold is a flag specifying whether a lowercase alphabet is acceptable as input For security purposes the default is False A binascii Error is raised if s is incorrectly padded or if there are non alphabet characters present in the input base64 a85encode b foldspaces False wrapcol 0 pad False adobe False Encode the bytes like object b using Ascii85 and return the encoded bytes foldspaces is an optional flag that uses the special short sequence y instead of 4 consecutive spaces ASCII 0x20 as supported by btoa This feature is not supported by the standard Ascii85 encoding wrapcol controls whether the output should have newline b n characters added to it If this is non zero each output line will be at most this many characters long pad controls whether the input is padded to a multiple of 4 before encoding Note that the btoa implementation always pads adobe controls whether the encoded byte sequence is framed with and which is used by the Adobe implementation New in version 3 4 base64 a85decode b foldspaces False adobe False ignorechars b t n r x0b Decode the Ascii85 encoded bytes like object or ASCII string b and return the decoded bytes foldspaces is a flag that specifies whether the y short sequence should be accepted as shorthand for 4 consecutive spaces ASCII 0x20 This feature is not supported by the standard Ascii85 encoding adobe controls whether the input sequence is in Adobe Ascii85 format i e is framed with and ignorechars should be a bytes like object or ASCII string containing characters to ignore from the input This should only contain whitespace characters and by default contains all whitespace characters in ASCII New in version 3 4 base64 b85encode b pad False Encode the bytes like object b using base85 as used in e g git style binary diffs and return the encoded bytes If pad is true the input is padded with b 0 so its length is a multiple of 4 bytes before encoding New in version 3 4 base64 b85decode b Decode the base85 encoded bytes like object or ASCII string b and return the decoded bytes Padding is implicitly removed if necessary New in version 3 4 The legacy interface base64 decode input output Decode the contents of the binary input file and write the resulting binary data to the output file input and output must be file objects input will be read until input readline returns an empty bytes object base64 decodebytes s Decode the bytes like object s which must contain one or more lines of base64 encoded data and return the decoded bytes New in version 3 1 base64 encode input output Encode the contents of the binary input file and write the resulting base64 encoded data to the output file input and output must be file objects input will be read until input read returns an empty bytes object encode inserts a newline character b n after every 76 bytes of the output as well as ensuring that the output always ends with a newline as per RFC 2045 MIME base64 encodebytes s Encode the bytes like object s which can contain arbitrary binary data and return bytes containing the base64 encoded data with newline,en
514,s b n inserted after every 76 bytes of output and ensuring that there is a trailing newline as per RFC 2045 MIME New in version 3 1 An example usage of the module import base64 encoded base64 b64encode b data to be encoded encoded b ZGF0YSB0byBiZSBlbmNvZGVk data base64 b64decode encoded data b data to be encoded Security Considerations A new security considerations section was added to RFC 4648 section 12 it s recommended to review the security section for any code deployed to production See also Module binascii Support module containing ASCII to binary and binary to ASCII conversions RFC 1521 MIME Multipurpose Internet Mail Extensions Part One Mechanisms for Specifying and Describing the Format of Internet Message Bodies Section 5 2 Base64 Content Transfer Encoding provides the definition of the base64 encoding,en
515,C API Stability Unless documented otherwise Python s C API is covered by the Backwards Compatibility Policy PEP 387 Most changes to it are source compatible typically by only adding new API Changing existing API or removing API is only done after a deprecation period or to fix serious issues CPython s Application Binary Interface ABI is forward and backwards compatible across a minor release if these are compiled the same way see Platform Considerations below So code compiled for Python 3 10 0 will work on 3 10 8 and vice versa but will need to be compiled separately for 3 9 x and 3 11 x There are two tiers of C API with different stability expectations Unstable API may change in minor versions without a deprecation period It is marked by the PyUnstable prefix in names Limited API is compatible across several minor releases When Py_LIMITED_API is defined only this subset is exposed from Python h These are discussed in more detail below Names prefixed by an underscore such as _Py_InternalState are private API that can change without notice even in patch releases If you need to use this API consider reaching out to CPython developers to discuss adding public API for your use case Unstable C API Any API named with the PyUnstable prefix exposes CPython implementation details and may change in every minor release e g from 3 9 to 3 10 without any deprecation warnings However it will not change in a bugfix release e g from 3 10 0 to 3 10 1 It is generally intended for specialized low level tools like debuggers Projects that use this API are expected to follow CPython development and spend extra effort adjusting to changes Stable Application Binary Interface For simplicity this document talks about extensions but the Limited API and Stable ABI work the same way for all uses of the API for example embedding Python Limited C API Python 3 2 introduced the Limited API a subset of Python s C API Extensions that only use the Limited API can be compiled once and work with multiple versions of Python Contents of the Limited API are listed below Py_LIMITED_API Define this macro before including Python h to opt in to only use the Limited API and to select the Limited API version Define Py_LIMITED_API to the value of PY_VERSION_HEX corresponding to the lowest Python version your extension supports The extension will work without recompilation with all Python 3 releases from the specified one onward and can use Limited API introduced up to that version Rather than using the PY_VERSION_HEX macro directly hardcode a minimum minor version e g 0x030A0000 for Python 3 10 for stability when compiling with future Python versions You can also define Py_LIMITED_API to 3 This works the same as 0x03020000 Python 3 2 the version that introduced Limited API Stable ABI To enable this Python provides a Stable ABI a set of symbols that will remain compatible across Python 3 x versions The Stable ABI contains symbols exposed in the Limited API but also other ones for example functions necessary to support older versions of the Limited API On Windows extensions that use the Stable ABI should be linked against python3 dll rather than a version specific library such as python39 dll On some platforms Python will look for and load shared library files named with the abi3 tag e g mymodule abi3 so It does not check if such extensions conform to a Stable ABI The user or their packaging tools need to ensure that for example extensions built with the 3 10 Limited API are not installed for lower versions of Python All functions in the Stable ABI are present as functions in Python s shared library not solely as macros This makes them usable from languages that don t use the C preprocessor Limited API Scope and Performance The goal for the Limited API is to allow everything that is possible with the full C API but possibly with a performance penalty For example while PyList_GetItem is available its unsafe macro variant PyList_GET_ITEM is not The macro can be faster because it can rely on version specific implementation details of the list object Without Py_LIMITED_API d,en
516,efined some C API functions are inlined or replaced by macros Defining Py_LIMITED_API disables this inlining allowing stability as Python s data structures are improved but possibly reducing performance By leaving out the Py_LIMITED_API definition it is possible to compile a Limited API extension with a version specific ABI This can improve performance for that Python version but will limit compatibility Compiling with Py_LIMITED_API will then yield an extension that can be distributed where a version specific one is not available for example for prereleases of an upcoming Python version Limited API Caveats Note that compiling with Py_LIMITED_API is not a complete guarantee that code conforms to the Limited API or the Stable ABI Py_LIMITED_API only covers definitions but an API also includes other issues such as expected semantics One issue that Py_LIMITED_API does not guard against is calling a function with arguments that are invalid in a lower Python version For example consider a function that starts accepting NULL for an argument In Python 3 9 NULL now selects a default behavior but in Python 3 8 the argument will be used directly causing a NULL dereference and crash A similar argument works for fields of structs Another issue is that some struct fields are currently not hidden when Py_LIMITED_API is defined even though they re part of the Limited API For these reasons we recommend testing an extension with all minor Python versions it supports and preferably to build with the lowest such version We also recommend reviewing documentation of all used API to check if it is explicitly part of the Limited API Even with Py_LIMITED_API defined a few private declarations are exposed for technical reasons or even unintentionally as bugs Also note that the Limited API is not necessarily stable compiling with Py_LIMITED_API with Python 3 8 means that the extension will run with Python 3 12 but it will not necessarily compile with Python 3 12 In particular parts of the Limited API may be deprecated and removed provided that the Stable ABI stays stable Platform Considerations ABI stability depends not only on Python but also on the compiler used lower level libraries and compiler options For the purposes of the Stable ABI these details define a platform They usually depend on the OS type and processor architecture It is the responsibility of each particular distributor of Python to ensure that all Python versions on a particular platform are built in a way that does not break the Stable ABI This is the case with Windows and macOS releases from python org and many third party distributors Contents of Limited API Currently the Limited API includes the following items PY_VECTORCALL_ARGUMENTS_OFFSET PyAIter_Check PyArg_Parse PyArg_ParseTuple PyArg_ParseTupleAndKeywords PyArg_UnpackTuple PyArg_VaParse PyArg_VaParseTupleAndKeywords PyArg_ValidateKeywordArguments PyBaseObject_Type PyBool_FromLong PyBool_Type PyBuffer_FillContiguousStrides PyBuffer_FillInfo PyBuffer_FromContiguous PyBuffer_GetPointer PyBuffer_IsContiguous PyBuffer_Release PyBuffer_SizeFromFormat PyBuffer_ToContiguous PyByteArrayIter_Type PyByteArray_AsString PyByteArray_Concat PyByteArray_FromObject PyByteArray_FromStringAndSize PyByteArray_Resize PyByteArray_Size PyByteArray_Type PyBytesIter_Type PyBytes_AsString PyBytes_AsStringAndSize PyBytes_Concat PyBytes_ConcatAndDel PyBytes_DecodeEscape PyBytes_FromFormat PyBytes_FromFormatV PyBytes_FromObject PyBytes_FromString PyBytes_FromStringAndSize PyBytes_Repr PyBytes_Size PyBytes_Type PyCFunction PyCFunctionWithKeywords PyCFunction_Call PyCFunction_GetFlags PyCFunction_GetFunction PyCFunction_GetSelf PyCFunction_New PyCFunction_NewEx PyCFunction_Type PyCMethod_New PyCallIter_New PyCallIter_Type PyCallable_Check PyCapsule_Destructor PyCapsule_GetContext PyCapsule_GetDestructor PyCapsule_GetName PyCapsule_GetPointer PyCapsule_Import PyCapsule_IsValid PyCapsule_New PyCapsule_SetContext PyCapsule_SetDestructor PyCapsule_SetName PyCapsule_SetPointer PyCapsule_Type PyClassMethodDescr_Type PyCodec_BackslashReplaceErrors PyCodec,en
517,_Decode PyCodec_Decoder PyCodec_Encode PyCodec_Encoder PyCodec_IgnoreErrors PyCodec_IncrementalDecoder PyCodec_IncrementalEncoder PyCodec_KnownEncoding PyCodec_LookupError PyCodec_NameReplaceErrors PyCodec_Register PyCodec_RegisterError PyCodec_ReplaceErrors PyCodec_StreamReader PyCodec_StreamWriter PyCodec_StrictErrors PyCodec_Unregister PyCodec_XMLCharRefReplaceErrors PyComplex_FromDoubles PyComplex_ImagAsDouble PyComplex_RealAsDouble PyComplex_Type PyDescr_NewClassMethod PyDescr_NewGetSet PyDescr_NewMember PyDescr_NewMethod PyDictItems_Type PyDictIterItem_Type PyDictIterKey_Type PyDictIterValue_Type PyDictKeys_Type PyDictProxy_New PyDictProxy_Type PyDictRevIterItem_Type PyDictRevIterKey_Type PyDictRevIterValue_Type PyDictValues_Type PyDict_Clear PyDict_Contains PyDict_Copy PyDict_DelItem PyDict_DelItemString PyDict_GetItem PyDict_GetItemString PyDict_GetItemWithError PyDict_Items PyDict_Keys PyDict_Merge PyDict_MergeFromSeq2 PyDict_New PyDict_Next PyDict_SetItem PyDict_SetItemString PyDict_Size PyDict_Type PyDict_Update PyDict_Values PyEllipsis_Type PyEnum_Type PyErr_BadArgument PyErr_BadInternalCall PyErr_CheckSignals PyErr_Clear PyErr_Display PyErr_DisplayException PyErr_ExceptionMatches PyErr_Fetch PyErr_Format PyErr_FormatV PyErr_GetExcInfo PyErr_GetHandledException PyErr_GetRaisedException PyErr_GivenExceptionMatches PyErr_NewException PyErr_NewExceptionWithDoc PyErr_NoMemory PyErr_NormalizeException PyErr_Occurred PyErr_Print PyErr_PrintEx PyErr_ProgramText PyErr_ResourceWarning PyErr_Restore PyErr_SetExcFromWindowsErr PyErr_SetExcFromWindowsErrWithFilename PyErr_SetExcFromWindowsErrWithFilenameObject PyErr_SetExcFromWindowsErrWithFilenameObjects PyErr_SetExcInfo PyErr_SetFromErrno PyErr_SetFromErrnoWithFilename PyErr_SetFromErrnoWithFilenameObject PyErr_SetFromErrnoWithFilenameObjects PyErr_SetFromWindowsErr PyErr_SetFromWindowsErrWithFilename PyErr_SetHandledException PyErr_SetImportError PyErr_SetImportErrorSubclass PyErr_SetInterrupt PyErr_SetInterruptEx PyErr_SetNone PyErr_SetObject PyErr_SetRaisedException PyErr_SetString PyErr_SyntaxLocation PyErr_SyntaxLocationEx PyErr_WarnEx PyErr_WarnExplicit PyErr_WarnFormat PyErr_WriteUnraisable PyEval_AcquireLock PyEval_AcquireThread PyEval_CallFunction PyEval_CallMethod PyEval_CallObjectWithKeywords PyEval_EvalCode PyEval_EvalCodeEx PyEval_EvalFrame PyEval_EvalFrameEx PyEval_GetBuiltins PyEval_GetFrame PyEval_GetFuncDesc PyEval_GetFuncName PyEval_GetGlobals PyEval_GetLocals PyEval_InitThreads PyEval_ReleaseLock PyEval_ReleaseThread PyEval_RestoreThread PyEval_SaveThread PyEval_ThreadsInitialized PyExc_ArithmeticError PyExc_AssertionError PyExc_AttributeError PyExc_BaseException PyExc_BaseExceptionGroup PyExc_BlockingIOError PyExc_BrokenPipeError PyExc_BufferError PyExc_BytesWarning PyExc_ChildProcessError PyExc_ConnectionAbortedError PyExc_ConnectionError PyExc_ConnectionRefusedError PyExc_ConnectionResetError PyExc_DeprecationWarning PyExc_EOFError PyExc_EncodingWarning PyExc_EnvironmentError PyExc_Exception PyExc_FileExistsError PyExc_FileNotFoundError PyExc_FloatingPointError PyExc_FutureWarning PyExc_GeneratorExit PyExc_IOError PyExc_ImportError PyExc_ImportWarning PyExc_IndentationError PyExc_IndexError PyExc_InterruptedError PyExc_IsADirectoryError PyExc_KeyError PyExc_KeyboardInterrupt PyExc_LookupError PyExc_MemoryError PyExc_ModuleNotFoundError PyExc_NameError PyExc_NotADirectoryError PyExc_NotImplementedError PyExc_OSError PyExc_OverflowError PyExc_PendingDeprecationWarning PyExc_PermissionError PyExc_ProcessLookupError PyExc_RecursionError PyExc_ReferenceError PyExc_ResourceWarning PyExc_RuntimeError PyExc_RuntimeWarning PyExc_StopAsyncIteration PyExc_StopIteration PyExc_SyntaxError PyExc_SyntaxWarning PyExc_SystemError PyExc_SystemExit PyExc_TabError PyExc_TimeoutError PyExc_TypeError PyExc_UnboundLocalError PyExc_UnicodeDecodeError PyExc_UnicodeEncodeError PyExc_UnicodeError PyExc_UnicodeTranslateError PyExc_UnicodeWarning PyExc_UserWarning PyExc_ValueError PyExc_Warning PyExc_WindowsError PyExc_ZeroDivisionError PyExceptionClass_Name PyException_GetAr,en
518,gs PyException_GetCause PyException_GetContext PyException_GetTraceback PyException_SetArgs PyException_SetCause PyException_SetContext PyException_SetTraceback PyFile_FromFd PyFile_GetLine PyFile_WriteObject PyFile_WriteString PyFilter_Type PyFloat_AsDouble PyFloat_FromDouble PyFloat_FromString PyFloat_GetInfo PyFloat_GetMax PyFloat_GetMin PyFloat_Type PyFrameObject PyFrame_GetCode PyFrame_GetLineNumber PyFrozenSet_New PyFrozenSet_Type PyGC_Collect PyGC_Disable PyGC_Enable PyGC_IsEnabled PyGILState_Ensure PyGILState_GetThisThreadState PyGILState_Release PyGILState_STATE PyGetSetDef PyGetSetDescr_Type PyImport_AddModule PyImport_AddModuleObject PyImport_AppendInittab PyImport_ExecCodeModule PyImport_ExecCodeModuleEx PyImport_ExecCodeModuleObject PyImport_ExecCodeModuleWithPathnames PyImport_GetImporter PyImport_GetMagicNumber PyImport_GetMagicTag PyImport_GetModule PyImport_GetModuleDict PyImport_Import PyImport_ImportFrozenModule PyImport_ImportFrozenModuleObject PyImport_ImportModule PyImport_ImportModuleLevel PyImport_ImportModuleLevelObject PyImport_ImportModuleNoBlock PyImport_ReloadModule PyIndex_Check PyInterpreterState PyInterpreterState_Clear PyInterpreterState_Delete PyInterpreterState_Get PyInterpreterState_GetDict PyInterpreterState_GetID PyInterpreterState_New PyIter_Check PyIter_Next PyIter_Send PyListIter_Type PyListRevIter_Type PyList_Append PyList_AsTuple PyList_GetItem PyList_GetSlice PyList_Insert PyList_New PyList_Reverse PyList_SetItem PyList_SetSlice PyList_Size PyList_Sort PyList_Type PyLongObject PyLongRangeIter_Type PyLong_AsDouble PyLong_AsLong PyLong_AsLongAndOverflow PyLong_AsLongLong PyLong_AsLongLongAndOverflow PyLong_AsSize_t PyLong_AsSsize_t PyLong_AsUnsignedLong PyLong_AsUnsignedLongLong PyLong_AsUnsignedLongLongMask PyLong_AsUnsignedLongMask PyLong_AsVoidPtr PyLong_FromDouble PyLong_FromLong PyLong_FromLongLong PyLong_FromSize_t PyLong_FromSsize_t PyLong_FromString PyLong_FromUnsignedLong PyLong_FromUnsignedLongLong PyLong_FromVoidPtr PyLong_GetInfo PyLong_Type PyMap_Type PyMapping_Check PyMapping_GetItemString PyMapping_HasKey PyMapping_HasKeyString PyMapping_Items PyMapping_Keys PyMapping_Length PyMapping_SetItemString PyMapping_Size PyMapping_Values PyMem_Calloc PyMem_Free PyMem_Malloc PyMem_Realloc PyMemberDef PyMemberDescr_Type PyMember_GetOne PyMember_SetOne PyMemoryView_FromBuffer PyMemoryView_FromMemory PyMemoryView_FromObject PyMemoryView_GetContiguous PyMemoryView_Type PyMethodDef PyMethodDescr_Type PyModuleDef PyModuleDef_Base PyModuleDef_Init PyModuleDef_Type PyModule_AddFunctions PyModule_AddIntConstant PyModule_AddObject PyModule_AddObjectRef PyModule_AddStringConstant PyModule_AddType PyModule_Create2 PyModule_ExecDef PyModule_FromDefAndSpec2 PyModule_GetDef PyModule_GetDict PyModule_GetFilename PyModule_GetFilenameObject PyModule_GetName PyModule_GetNameObject PyModule_GetState PyModule_New PyModule_NewObject PyModule_SetDocString PyModule_Type PyNumber_Absolute PyNumber_Add PyNumber_And PyNumber_AsSsize_t PyNumber_Check PyNumber_Divmod PyNumber_Float PyNumber_FloorDivide PyNumber_InPlaceAdd PyNumber_InPlaceAnd PyNumber_InPlaceFloorDivide PyNumber_InPlaceLshift PyNumber_InPlaceMatrixMultiply PyNumber_InPlaceMultiply PyNumber_InPlaceOr PyNumber_InPlacePower PyNumber_InPlaceRemainder PyNumber_InPlaceRshift PyNumber_InPlaceSubtract PyNumber_InPlaceTrueDivide PyNumber_InPlaceXor PyNumber_Index PyNumber_Invert PyNumber_Long PyNumber_Lshift PyNumber_MatrixMultiply PyNumber_Multiply PyNumber_Negative PyNumber_Or PyNumber_Positive PyNumber_Power PyNumber_Remainder PyNumber_Rshift PyNumber_Subtract PyNumber_ToBase PyNumber_TrueDivide PyNumber_Xor PyOS_AfterFork PyOS_AfterFork_Child PyOS_AfterFork_Parent PyOS_BeforeFork PyOS_CheckStack PyOS_FSPath PyOS_InputHook PyOS_InterruptOccurred PyOS_double_to_string PyOS_getsig PyOS_mystricmp PyOS_mystrnicmp PyOS_setsig PyOS_sighandler_t PyOS_snprintf PyOS_string_to_double PyOS_strtol PyOS_strtoul PyOS_vsnprintf PyObject PyObject ob_refcnt PyObject ob_type PyObject_ASCII PyObject_AsCharBuffer PyObject_AsFileDescriptor PyObject_AsReadBuffer P,en
519,yObject_AsWriteBuffer PyObject_Bytes PyObject_Call PyObject_CallFunction PyObject_CallFunctionObjArgs PyObject_CallMethod PyObject_CallMethodObjArgs PyObject_CallNoArgs PyObject_CallObject PyObject_Calloc PyObject_CheckBuffer PyObject_CheckReadBuffer PyObject_ClearWeakRefs PyObject_CopyData PyObject_DelItem PyObject_DelItemString PyObject_Dir PyObject_Format PyObject_Free PyObject_GC_Del PyObject_GC_IsFinalized PyObject_GC_IsTracked PyObject_GC_Track PyObject_GC_UnTrack PyObject_GenericGetAttr PyObject_GenericGetDict PyObject_GenericSetAttr PyObject_GenericSetDict PyObject_GetAIter PyObject_GetAttr PyObject_GetAttrString PyObject_GetBuffer PyObject_GetItem PyObject_GetIter PyObject_GetTypeData PyObject_HasAttr PyObject_HasAttrString PyObject_Hash PyObject_HashNotImplemented PyObject_Init PyObject_InitVar PyObject_IsInstance PyObject_IsSubclass PyObject_IsTrue PyObject_Length PyObject_Malloc PyObject_Not PyObject_Realloc PyObject_Repr PyObject_RichCompare PyObject_RichCompareBool PyObject_SelfIter PyObject_SetAttr PyObject_SetAttrString PyObject_SetItem PyObject_Size PyObject_Str PyObject_Type PyObject_Vectorcall PyObject_VectorcallMethod PyProperty_Type PyRangeIter_Type PyRange_Type PyReversed_Type PySeqIter_New PySeqIter_Type PySequence_Check PySequence_Concat PySequence_Contains PySequence_Count PySequence_DelItem PySequence_DelSlice PySequence_Fast PySequence_GetItem PySequence_GetSlice PySequence_In PySequence_InPlaceConcat PySequence_InPlaceRepeat PySequence_Index PySequence_Length PySequence_List PySequence_Repeat PySequence_SetItem PySequence_SetSlice PySequence_Size PySequence_Tuple PySetIter_Type PySet_Add PySet_Clear PySet_Contains PySet_Discard PySet_New PySet_Pop PySet_Size PySet_Type PySlice_AdjustIndices PySlice_GetIndices PySlice_GetIndicesEx PySlice_New PySlice_Type PySlice_Unpack PyState_AddModule PyState_FindModule PyState_RemoveModule PyStructSequence_Desc PyStructSequence_Field PyStructSequence_GetItem PyStructSequence_New PyStructSequence_NewType PyStructSequence_SetItem PyStructSequence_UnnamedField PySuper_Type PySys_AddWarnOption PySys_AddWarnOptionUnicode PySys_AddXOption PySys_FormatStderr PySys_FormatStdout PySys_GetObject PySys_GetXOptions PySys_HasWarnOptions PySys_ResetWarnOptions PySys_SetArgv PySys_SetArgvEx PySys_SetObject PySys_SetPath PySys_WriteStderr PySys_WriteStdout PyThreadState PyThreadState_Clear PyThreadState_Delete PyThreadState_Get PyThreadState_GetDict PyThreadState_GetFrame PyThreadState_GetID PyThreadState_GetInterpreter PyThreadState_New PyThreadState_SetAsyncExc PyThreadState_Swap PyThread_GetInfo PyThread_ReInitTLS PyThread_acquire_lock PyThread_acquire_lock_timed PyThread_allocate_lock PyThread_create_key PyThread_delete_key PyThread_delete_key_value PyThread_exit_thread PyThread_free_lock PyThread_get_key_value PyThread_get_stacksize PyThread_get_thread_ident PyThread_get_thread_native_id PyThread_init_thread PyThread_release_lock PyThread_set_key_value PyThread_set_stacksize PyThread_start_new_thread PyThread_tss_alloc PyThread_tss_create PyThread_tss_delete PyThread_tss_free PyThread_tss_get PyThread_tss_is_created PyThread_tss_set PyTraceBack_Here PyTraceBack_Print PyTraceBack_Type PyTupleIter_Type PyTuple_GetItem PyTuple_GetSlice PyTuple_New PyTuple_Pack PyTuple_SetItem PyTuple_Size PyTuple_Type PyTypeObject PyType_ClearCache PyType_FromMetaclass PyType_FromModuleAndSpec PyType_FromSpec PyType_FromSpecWithBases PyType_GenericAlloc PyType_GenericNew PyType_GetFlags PyType_GetModule PyType_GetModuleState PyType_GetName PyType_GetQualName PyType_GetSlot PyType_GetTypeDataSize PyType_IsSubtype PyType_Modified PyType_Ready PyType_Slot PyType_Spec PyType_Type PyUnicodeDecodeError_Create PyUnicodeDecodeError_GetEncoding PyUnicodeDecodeError_GetEnd PyUnicodeDecodeError_GetObject PyUnicodeDecodeError_GetReason PyUnicodeDecodeError_GetStart PyUnicodeDecodeError_SetEnd PyUnicodeDecodeError_SetReason PyUnicodeDecodeError_SetStart PyUnicodeEncodeError_GetEncoding PyUnicodeEncodeError_GetEnd PyUnicodeEncodeError_GetObject PyUnicodeEncodeError_GetReason PyUnicodeEncodeError_GetSt,en
520,art PyUnicodeEncodeError_SetEnd PyUnicodeEncodeError_SetReason PyUnicodeEncodeError_SetStart PyUnicodeIter_Type PyUnicodeTranslateError_GetEnd PyUnicodeTranslateError_GetObject PyUnicodeTranslateError_GetReason PyUnicodeTranslateError_GetStart PyUnicodeTranslateError_SetEnd PyUnicodeTranslateError_SetReason PyUnicodeTranslateError_SetStart PyUnicode_Append PyUnicode_AppendAndDel PyUnicode_AsASCIIString PyUnicode_AsCharmapString PyUnicode_AsDecodedObject PyUnicode_AsDecodedUnicode PyUnicode_AsEncodedObject PyUnicode_AsEncodedString PyUnicode_AsEncodedUnicode PyUnicode_AsLatin1String PyUnicode_AsMBCSString PyUnicode_AsRawUnicodeEscapeString PyUnicode_AsUCS4 PyUnicode_AsUCS4Copy PyUnicode_AsUTF16String PyUnicode_AsUTF32String PyUnicode_AsUTF8AndSize PyUnicode_AsUTF8String PyUnicode_AsUnicodeEscapeString PyUnicode_AsWideChar PyUnicode_AsWideCharString PyUnicode_BuildEncodingMap PyUnicode_Compare PyUnicode_CompareWithASCIIString PyUnicode_Concat PyUnicode_Contains PyUnicode_Count PyUnicode_Decode PyUnicode_DecodeASCII PyUnicode_DecodeCharmap PyUnicode_DecodeCodePageStateful PyUnicode_DecodeFSDefault PyUnicode_DecodeFSDefaultAndSize PyUnicode_DecodeLatin1 PyUnicode_DecodeLocale PyUnicode_DecodeLocaleAndSize PyUnicode_DecodeMBCS PyUnicode_DecodeMBCSStateful PyUnicode_DecodeRawUnicodeEscape PyUnicode_DecodeUTF16 PyUnicode_DecodeUTF16Stateful PyUnicode_DecodeUTF32 PyUnicode_DecodeUTF32Stateful PyUnicode_DecodeUTF7 PyUnicode_DecodeUTF7Stateful PyUnicode_DecodeUTF8 PyUnicode_DecodeUTF8Stateful PyUnicode_DecodeUnicodeEscape PyUnicode_EncodeCodePage PyUnicode_EncodeFSDefault PyUnicode_EncodeLocale PyUnicode_FSConverter PyUnicode_FSDecoder PyUnicode_Find PyUnicode_FindChar PyUnicode_Format PyUnicode_FromEncodedObject PyUnicode_FromFormat PyUnicode_FromFormatV PyUnicode_FromObject PyUnicode_FromOrdinal PyUnicode_FromString PyUnicode_FromStringAndSize PyUnicode_FromWideChar PyUnicode_GetDefaultEncoding PyUnicode_GetLength PyUnicode_InternFromString PyUnicode_InternInPlace PyUnicode_IsIdentifier PyUnicode_Join PyUnicode_Partition PyUnicode_RPartition PyUnicode_RSplit PyUnicode_ReadChar PyUnicode_Replace PyUnicode_Resize PyUnicode_RichCompare PyUnicode_Split PyUnicode_Splitlines PyUnicode_Substring PyUnicode_Tailmatch PyUnicode_Translate PyUnicode_Type PyUnicode_WriteChar PyVarObject PyVarObject ob_base PyVarObject ob_size PyVectorcall_Call PyVectorcall_NARGS PyWeakReference PyWeakref_GetObject PyWeakref_NewProxy PyWeakref_NewRef PyWrapperDescr_Type PyWrapper_New PyZip_Type Py_AddPendingCall Py_AtExit Py_BEGIN_ALLOW_THREADS Py_BLOCK_THREADS Py_BuildValue Py_BytesMain Py_CompileString Py_DecRef Py_DecodeLocale Py_END_ALLOW_THREADS Py_EncodeLocale Py_EndInterpreter Py_EnterRecursiveCall Py_Exit Py_FatalError Py_FileSystemDefaultEncodeErrors Py_FileSystemDefaultEncoding Py_Finalize Py_FinalizeEx Py_GenericAlias Py_GenericAliasType Py_GetBuildInfo Py_GetCompiler Py_GetCopyright Py_GetExecPrefix Py_GetPath Py_GetPlatform Py_GetPrefix Py_GetProgramFullPath Py_GetProgramName Py_GetPythonHome Py_GetRecursionLimit Py_GetVersion Py_HasFileSystemDefaultEncoding Py_IncRef Py_Initialize Py_InitializeEx Py_Is Py_IsFalse Py_IsInitialized Py_IsNone Py_IsTrue Py_LeaveRecursiveCall Py_Main Py_MakePendingCalls Py_NewInterpreter Py_NewRef Py_ReprEnter Py_ReprLeave Py_SetPath Py_SetProgramName Py_SetPythonHome Py_SetRecursionLimit Py_UCS4 Py_UNBLOCK_THREADS Py_UTF8Mode Py_VaBuildValue Py_Version Py_XNewRef Py_buffer Py_intptr_t Py_ssize_t Py_uintptr_t allocfunc binaryfunc descrgetfunc descrsetfunc destructor getattrfunc getattrofunc getbufferproc getiterfunc getter hashfunc initproc inquiry iternextfunc lenfunc newfunc objobjargproc objobjproc releasebufferproc reprfunc richcmpfunc setattrfunc setattrofunc setter ssizeargfunc ssizeobjargproc ssizessizeargfunc ssizessizeobjargproc symtable ternaryfunc traverseproc unaryfunc vectorcallfunc visitproc,en
521,tabnanny Detection of ambiguous indentation Source code Lib tabnanny py For the time being this module is intended to be called as a script However it is possible to import it into an IDE and use the function check described below Note The API provided by this module is likely to change in future releases such changes may not be backward compatible tabnanny check file_or_dir If file_or_dir is a directory and not a symbolic link then recursively descend the directory tree named by file_or_dir checking all py files along the way If file_or_dir is an ordinary Python source file it is checked for whitespace related problems The diagnostic messages are written to standard output using the print function tabnanny verbose Flag indicating whether to print verbose messages This is incremented by the v option if called as a script tabnanny filename_only Flag indicating whether to print only the filenames of files containing whitespace related problems This is set to true by the q option if called as a script exception tabnanny NannyNag Raised by process_tokens if detecting an ambiguous indent Captured and handled in check tabnanny process_tokens tokens This function is used by check to process tokens generated by the tokenize module See also Module tokenize Lexical scanner for Python source code,en
522,unicodedata Unicode Database This module provides access to the Unicode Character Database UCD which defines character properties for all Unicode characters The data contained in this database is compiled from the UCD version 15 0 0 The module uses the same names and symbols as defined by Unicode Standard Annex 44 Unicode Character Database It defines the following functions unicodedata lookup name Look up character by name If a character with the given name is found return the corresponding character If not found KeyError is raised Changed in version 3 3 Support for name aliases 1 and named sequences 2 has been added unicodedata name chr default Returns the name assigned to the character chr as a string If no name is defined default is returned or if not given ValueError is raised unicodedata decimal chr default Returns the decimal value assigned to the character chr as integer If no such value is defined default is returned or if not given ValueError is raised unicodedata digit chr default Returns the digit value assigned to the character chr as integer If no such value is defined default is returned or if not given ValueError is raised unicodedata numeric chr default Returns the numeric value assigned to the character chr as float If no such value is defined default is returned or if not given ValueError is raised unicodedata category chr Returns the general category assigned to the character chr as string unicodedata bidirectional chr Returns the bidirectional class assigned to the character chr as string If no such value is defined an empty string is returned unicodedata combining chr Returns the canonical combining class assigned to the character chr as integer Returns 0 if no combining class is defined unicodedata east_asian_width chr Returns the east asian width assigned to the character chr as string unicodedata mirrored chr Returns the mirrored property assigned to the character chr as integer Returns 1 if the character has been identified as a mirrored character in bidirectional text 0 otherwise unicodedata decomposition chr Returns the character decomposition mapping assigned to the character chr as string An empty string is returned in case no such mapping is defined unicodedata normalize form unistr Return the normal form form for the Unicode string unistr Valid values for form are NFC NFKC NFD and NFKD The Unicode standard defines various normalization forms of a Unicode string based on the definition of canonical equivalence and compatibility equivalence In Unicode several characters can be expressed in various way For example the character U 00C7 LATIN CAPITAL LETTER C WITH CEDILLA can also be expressed as the sequence U 0043 LATIN CAPITAL LETTER C U 0327 COMBINING CEDILLA For each character there are two normal forms normal form C and normal form D Normal form D NFD is also known as canonical decomposition and translates each character into its decomposed form Normal form C NFC first applies a canonical decomposition then composes pre combined characters again In addition to these two forms there are two additional normal forms based on compatibility equivalence In Unicode certain characters are supported which normally would be unified with other characters For example U 2160 ROMAN NUMERAL ONE is really the same thing as U 0049 LATIN CAPITAL LETTER I However it is supported in Unicode for compatibility with existing character sets e g gb2312 The normal form KD NFKD will apply the compatibility decomposition i e replace all compatibility characters with their equivalents The normal form KC NFKC first applies the compatibility decomposition followed by the canonical composition Even if two unicode strings are normalized and look the same to a human reader if one has combining characters and the other doesn t they may not compare equal unicodedata is_normalized form unistr Return whether the Unicode string unistr is in the normal form form Valid values for form are NFC NFKC NFD and NFKD New in version 3 8 In addition the module exposes the following constant unicodedata unidata_version The version of the ,en
523,Unicode database used in this module unicodedata ucd_3_2_0 This is an object that has the same methods as the entire module but uses the Unicode database version 3 2 instead for applications that require this specific version of the Unicode database such as IDNA Examples import unicodedata unicodedata lookup LEFT CURLY BRACKET unicodedata name SOLIDUS unicodedata decimal 9 9 unicodedata decimal a Traceback most recent call last File stdin line 1 in module ValueError not a decimal unicodedata category A L etter u ppercase Lu unicodedata bidirectional u0660 A rabic N umber AN Footnotes 1 https www unicode org Public 15 0 0 ucd NameAliases txt 2 https www unicode org Public 15 0 0 ucd NamedSequences txt,en
524,statistics Mathematical statistics functions New in version 3 4 Source code Lib statistics py This module provides functions for calculating mathematical statistics of numeric Real valued data The module is not intended to be a competitor to third party libraries such as NumPy SciPy or proprietary full featured statistics packages aimed at professional statisticians such as Minitab SAS and Matlab It is aimed at the level of graphing and scientific calculators Unless explicitly noted these functions support int float Decimal and Fraction Behaviour with other types whether in the numeric tower or not is currently unsupported Collections with a mix of types are also undefined and implementation dependent If your input data consists of mixed types you may be able to use map to ensure a consistent result for example map float input_data Some datasets use NaN not a number values to represent missing data Since NaNs have unusual comparison semantics they cause surprising or undefined behaviors in the statistics functions that sort data or that count occurrences The functions affected are median median_low median_high median_grouped mode multimode and quantiles The NaN values should be stripped before calling these functions from statistics import median from math import isnan from itertools import filterfalse data 20 7 float NaN 19 2 18 3 float NaN 14 4 sorted data This has surprising behavior 20 7 nan 14 4 18 3 19 2 nan median data This result is unexpected 16 35 sum map isnan data Number of missing values 2 clean list filterfalse isnan data Strip NaN values clean 20 7 19 2 18 3 14 4 sorted clean Sorting now works as expected 14 4 18 3 19 2 20 7 median clean This result is now well defined 18 75 Averages and measures of central location These functions calculate an average or typical value from a population or sample mean Arithmetic mean average of data fmean Fast floating point arithmetic mean with optional weighting geometric_mean Geometric mean of data harmonic_mean Harmonic mean of data median Median middle value of data median_low Low median of data median_high High median of data median_grouped Median or 50th percentile of grouped data mode Single mode most common value of discrete or nominal data multimode List of modes most common values of discrete or nominal data quantiles Divide data into intervals with equal probability Measures of spread These functions calculate a measure of how much the population or sample tends to deviate from the typical or average values pstdev Population standard deviation of data pvariance Population variance of data stdev Sample standard deviation of data variance Sample variance of data Statistics for relations between two inputs These functions calculate statistics regarding relations between two inputs covariance Sample covariance for two variables correlation Pearson and Spearman s correlation coefficients linear_regression Slope and intercept for simple linear regression Function details Note The functions do not require the data given to them to be sorted However for reading convenience most of the examples show sorted sequences statistics mean data Return the sample arithmetic mean of data which can be a sequence or iterable The arithmetic mean is the sum of the data divided by the number of data points It is commonly called the average although it is only one of many different mathematical averages It is a measure of the central location of the data If data is empty StatisticsError will be raised Some examples of use mean 1 2 3 4 4 2 8 mean 1 0 2 5 3 25 5 75 2 625 from fractions import Fraction as F mean F 3 7 F 1 21 F 5 3 F 1 3 Fraction 13 21 from decimal import Decimal as D mean D 0 5 D 0 75 D 0 625 D 0 375 Decimal 0 5625 Note The mean is strongly affected by outliers and is not necessarily a typical example of the data points For a more robust although less efficient measure of central tendency see median The sample mean gives an unbiased estimate of the true population mean so that when taken on average over all the possible samples mean sample converges on the true mean of th,en
525,e entire population If data represents the entire population rather than a sample then mean data is equivalent to calculating the true population mean μ statistics fmean data weights None Convert data to floats and compute the arithmetic mean This runs faster than the mean function and it always returns a float The data may be a sequence or iterable If the input dataset is empty raises a StatisticsError fmean 3 5 4 0 5 25 4 25 Optional weighting is supported For example a professor assigns a grade for a course by weighting quizzes at 20 homework at 20 a midterm exam at 30 and a final exam at 30 grades 85 92 83 91 weights 0 20 0 20 0 30 0 30 fmean grades weights 87 6 If weights is supplied it must be the same length as the data or a ValueError will be raised New in version 3 8 Changed in version 3 11 Added support for weights statistics geometric_mean data Convert data to floats and compute the geometric mean The geometric mean indicates the central tendency or typical value of the data using the product of the values as opposed to the arithmetic mean which uses their sum Raises a StatisticsError if the input dataset is empty if it contains a zero or if it contains a negative value The data may be a sequence or iterable No special efforts are made to achieve exact results However this may change in the future round geometric_mean 54 24 36 1 36 0 New in version 3 8 statistics harmonic_mean data weights None Return the harmonic mean of data a sequence or iterable of real valued numbers If weights is omitted or None then equal weighting is assumed The harmonic mean is the reciprocal of the arithmetic mean of the reciprocals of the data For example the harmonic mean of three values a b and c will be equivalent to 3 1 a 1 b 1 c If one of the values is zero the result will be zero The harmonic mean is a type of average a measure of the central location of the data It is often appropriate when averaging ratios or rates for example speeds Suppose a car travels 10 km at 40 km hr then another 10 km at 60 km hr What is the average speed harmonic_mean 40 60 48 0 Suppose a car travels 40 km hr for 5 km and when traffic clears speeds up to 60 km hr for the remaining 30 km of the journey What is the average speed harmonic_mean 40 60 weights 5 30 56 0 StatisticsError is raised if data is empty any element is less than zero or if the weighted sum isn t positive The current algorithm has an early out when it encounters a zero in the input This means that the subsequent inputs are not tested for validity This behavior may change in the future New in version 3 6 Changed in version 3 10 Added support for weights statistics median data Return the median middle value of numeric data using the common mean of middle two method If data is empty StatisticsError is raised data can be a sequence or iterable The median is a robust measure of central location and is less affected by the presence of outliers When the number of data points is odd the middle data point is returned median 1 3 5 3 When the number of data points is even the median is interpolated by taking the average of the two middle values median 1 3 5 7 4 0 This is suited for when your data is discrete and you don t mind that the median may not be an actual data point If the data is ordinal supports order operations but not numeric doesn t support addition consider using median_low or median_high instead statistics median_low data Return the low median of numeric data If data is empty StatisticsError is raised data can be a sequence or iterable The low median is always a member of the data set When the number of data points is odd the middle value is returned When it is even the smaller of the two middle values is returned median_low 1 3 5 3 median_low 1 3 5 7 3 Use the low median when your data are discrete and you prefer the median to be an actual data point rather than interpolated statistics median_high data Return the high median of data If data is empty StatisticsError is raised data can be a sequence or iterable The high median is always a member of the data set When the number of,en
526, data points is odd the middle value is returned When it is even the larger of the two middle values is returned median_high 1 3 5 3 median_high 1 3 5 7 5 Use the high median when your data are discrete and you prefer the median to be an actual data point rather than interpolated statistics median_grouped data interval 1 Return the median of grouped continuous data calculated as the 50th percentile using interpolation If data is empty StatisticsError is raised data can be a sequence or iterable median_grouped 52 52 53 54 52 5 In the following example the data are rounded so that each value represents the midpoint of data classes e g 1 is the midpoint of the class 0 5 1 5 2 is the midpoint of 1 5 2 5 3 is the midpoint of 2 5 3 5 etc With the data given the middle value falls somewhere in the class 3 5 4 5 and interpolation is used to estimate it median_grouped 1 2 2 3 4 4 4 4 4 5 3 7 Optional argument interval represents the class interval and defaults to 1 Changing the class interval naturally will change the interpolation median_grouped 1 3 3 5 7 interval 1 3 25 median_grouped 1 3 3 5 7 interval 2 3 5 This function does not check whether the data points are at least interval apart CPython implementation detail Under some circumstances median_grouped may coerce data points to floats This behaviour is likely to change in the future See also Statistics for the Behavioral Sciences Frederick J Gravetter and Larry B Wallnau 8th Edition The SSMEDIAN function in the Gnome Gnumeric spreadsheet including this discussion statistics mode data Return the single most common data point from discrete or nominal data The mode when it exists is the most typical value and serves as a measure of central location If there are multiple modes with the same frequency returns the first one encountered in the data If the smallest or largest of those is desired instead use min multimode data or max multimode data If the input data is empty StatisticsError is raised mode assumes discrete data and returns a single value This is the standard treatment of the mode as commonly taught in schools mode 1 1 2 3 3 3 3 4 3 The mode is unique in that it is the only statistic in this package that also applies to nominal non numeric data mode red blue blue red green red red red Changed in version 3 8 Now handles multimodal datasets by returning the first mode encountered Formerly it raised StatisticsError when more than one mode was found statistics multimode data Return a list of the most frequently occurring values in the order they were first encountered in the data Will return more than one result if there are multiple modes or an empty list if the data is empty multimode aabbbbccddddeeffffgg b d f multimode New in version 3 8 statistics pstdev data mu None Return the population standard deviation the square root of the population variance See pvariance for arguments and other details pstdev 1 5 2 5 2 5 2 75 3 25 4 75 0 986893273527251 statistics pvariance data mu None Return the population variance of data a non empty sequence or iterable of real valued numbers Variance or second moment about the mean is a measure of the variability spread or dispersion of data A large variance indicates that the data is spread out a small variance indicates it is clustered closely around the mean If the optional second argument mu is given it is typically the mean of the data It can also be used to compute the second moment around a point that is not the mean If it is missing or None the default the arithmetic mean is automatically calculated Use this function to calculate the variance from the entire population To estimate the variance from a sample the variance function is usually a better choice Raises StatisticsError if data is empty Examples data 0 0 0 25 0 25 1 25 1 5 1 75 2 75 3 25 pvariance data 1 25 If you have already calculated the mean of your data you can pass it as the optional second argument mu to avoid recalculation mu mean data pvariance data mu 1 25 Decimals and Fractions are supported from decimal import Decimal as D pvariance D 27 5 D 30 25 D 30 25 D,en
527, 34 5 D 41 75 Decimal 24 815 from fractions import Fraction as F pvariance F 1 4 F 5 4 F 1 2 Fraction 13 72 Note When called with the entire population this gives the population variance σ² When called on a sample instead this is the biased sample variance s² also known as variance with N degrees of freedom If you somehow know the true population mean μ you may use this function to calculate the variance of a sample giving the known population mean as the second argument Provided the data points are a random sample of the population the result will be an unbiased estimate of the population variance statistics stdev data xbar None Return the sample standard deviation the square root of the sample variance See variance for arguments and other details stdev 1 5 2 5 2 5 2 75 3 25 4 75 1 0810874155219827 statistics variance data xbar None Return the sample variance of data an iterable of at least two real valued numbers Variance or second moment about the mean is a measure of the variability spread or dispersion of data A large variance indicates that the data is spread out a small variance indicates it is clustered closely around the mean If the optional second argument xbar is given it should be the mean of data If it is missing or None the default the mean is automatically calculated Use this function when your data is a sample from a population To calculate the variance from the entire population see pvariance Raises StatisticsError if data has fewer than two values Examples data 2 75 1 75 1 25 0 25 0 5 1 25 3 5 variance data 1 3720238095238095 If you have already calculated the mean of your data you can pass it as the optional second argument xbar to avoid recalculation m mean data variance data m 1 3720238095238095 This function does not attempt to verify that you have passed the actual mean as xbar Using arbitrary values for xbar can lead to invalid or impossible results Decimal and Fraction values are supported from decimal import Decimal as D variance D 27 5 D 30 25 D 30 25 D 34 5 D 41 75 Decimal 31 01875 from fractions import Fraction as F variance F 1 6 F 1 2 F 5 3 Fraction 67 108 Note This is the sample variance s² with Bessel s correction also known as variance with N 1 degrees of freedom Provided that the data points are representative e g independent and identically distributed the result should be an unbiased estimate of the true population variance If you somehow know the actual population mean μ you should pass it to the pvariance function as the mu parameter to get the variance of a sample statistics quantiles data n 4 method exclusive Divide data into n continuous intervals with equal probability Returns a list of n 1 cut points separating the intervals Set n to 4 for quartiles the default Set n to 10 for deciles Set n to 100 for percentiles which gives the 99 cuts points that separate data into 100 equal sized groups Raises StatisticsError if n is not least 1 The data can be any iterable containing sample data For meaningful results the number of data points in data should be larger than n Raises StatisticsError if there are not at least two data points The cut points are linearly interpolated from the two nearest data points For example if a cut point falls one third of the distance between two sample values 100 and 112 the cut point will evaluate to 104 The method for computing quantiles can be varied depending on whether the data includes or excludes the lowest and highest possible values from the population The default method is exclusive and is used for data sampled from a population that can have more extreme values than found in the samples The portion of the population falling below the i th of m sorted data points is computed as i m 1 Given nine sample values the method sorts them and assigns the following percentiles 10 20 30 40 50 60 70 80 90 Setting the method to inclusive is used for describing population data or for samples that are known to include the most extreme values from the population The minimum value in data is treated as the 0th percentile and the maximum value is treated as the 1,en
528,00th percentile The portion of the population falling below the i th of m sorted data points is computed as i 1 m 1 Given 11 sample values the method sorts them and assigns the following percentiles 0 10 20 30 40 50 60 70 80 90 100 Decile cut points for empirically sampled data data 105 129 87 86 111 111 89 81 108 92 110 100 75 105 103 109 76 119 99 91 103 129 106 101 84 111 74 87 86 103 103 106 86 111 75 87 102 121 111 88 89 101 106 95 103 107 101 81 109 104 round q 1 for q in quantiles data n 10 81 0 86 2 89 0 99 4 102 5 103 6 106 0 109 8 111 0 New in version 3 8 statistics covariance x y Return the sample covariance of two inputs x and y Covariance is a measure of the joint variability of two inputs Both inputs must be of the same length no less than two otherwise StatisticsError is raised Examples x 1 2 3 4 5 6 7 8 9 y 1 2 3 1 2 3 1 2 3 covariance x y 0 75 z 9 8 7 6 5 4 3 2 1 covariance x z 7 5 covariance z x 7 5 New in version 3 10 statistics correlation x y method linear Return the Pearson s correlation coefficient for two inputs Pearson s correlation coefficient r takes values between 1 and 1 It measures the strength and direction of a linear relationship If method is ranked computes Spearman s rank correlation coefficient for two inputs The data is replaced by ranks Ties are averaged so that equal values receive the same rank The resulting coefficient measures the strength of a monotonic relationship Spearman s correlation coefficient is appropriate for ordinal data or for continuous data that doesn t meet the linear proportion requirement for Pearson s correlation coefficient Both inputs must be of the same length no less than two and need not to be constant otherwise StatisticsError is raised Example with Kepler s laws of planetary motion Mercury Venus Earth Mars Jupiter Saturn Uranus and Neptune orbital_period 88 225 365 687 4331 10_756 30_687 60_190 days dist_from_sun 58 108 150 228 778 1_400 2_900 4_500 million km Show that a perfect monotonic relationship exists correlation orbital_period dist_from_sun method ranked 1 0 Observe that a linear relationship is imperfect round correlation orbital_period dist_from_sun 4 0 9882 Demonstrate Kepler s third law There is a linear correlation between the square of the orbital period and the cube of the distance from the sun period_squared p p for p in orbital_period dist_cubed d d d for d in dist_from_sun round correlation period_squared dist_cubed 4 1 0 New in version 3 10 Changed in version 3 12 Added support for Spearman s rank correlation coefficient statistics linear_regression x y proportional False Return the slope and intercept of simple linear regression parameters estimated using ordinary least squares Simple linear regression describes the relationship between an independent variable x and a dependent variable y in terms of this linear function y slope x intercept noise where slope and intercept are the regression parameters that are estimated and noise represents the variability of the data that was not explained by the linear regression it is equal to the difference between predicted and actual values of the dependent variable Both inputs must be of the same length no less than two and the independent variable x cannot be constant otherwise a StatisticsError is raised For example we can use the release dates of the Monty Python films to predict the cumulative number of Monty Python films that would have been produced by 2019 assuming that they had kept the pace year 1971 1975 1979 1982 1983 films_total 1 2 3 4 5 slope intercept linear_regression year films_total round slope 2019 intercept 16 If proportional is true the independent variable x and the dependent variable y are assumed to be directly proportional The data is fit to a line passing through the origin Since the intercept will always be 0 0 the underlying linear function simplifies to y slope x noise Continuing the example from correlation we look to see how well a model based on major planets can predict the orbital distances for dwarf planets model linear_regression period_squared dist_cubed pr,en
529,oportional True slope model slope Dwarf planets Pluto Eris Makemake Haumea Ceres orbital_periods 90_560 204_199 111_845 103_410 1_680 days predicted_dist math cbrt slope p p for p in orbital_periods list map round predicted_dist 5912 10166 6806 6459 414 5_906 10_152 6_796 6_450 414 actual distance in million km 5906 10152 6796 6450 414 New in version 3 10 Changed in version 3 11 Added support for proportional Exceptions A single exception is defined exception statistics StatisticsError Subclass of ValueError for statistics related exceptions NormalDist objects NormalDist is a tool for creating and manipulating normal distributions of a random variable It is a class that treats the mean and standard deviation of data measurements as a single entity Normal distributions arise from the Central Limit Theorem and have a wide range of applications in statistics class statistics NormalDist mu 0 0 sigma 1 0 Returns a new NormalDist object where mu represents the arithmetic mean and sigma represents the standard deviation If sigma is negative raises StatisticsError mean A read only property for the arithmetic mean of a normal distribution median A read only property for the median of a normal distribution mode A read only property for the mode of a normal distribution stdev A read only property for the standard deviation of a normal distribution variance A read only property for the variance of a normal distribution Equal to the square of the standard deviation classmethod from_samples data Makes a normal distribution instance with mu and sigma parameters estimated from the data using fmean and stdev The data can be any iterable and should consist of values that can be converted to type float If data does not contain at least two elements raises StatisticsError because it takes at least one point to estimate a central value and at least two points to estimate dispersion samples n seed None Generates n random samples for a given mean and standard deviation Returns a list of float values If seed is given creates a new instance of the underlying random number generator This is useful for creating reproducible results even in a multi threading context pdf x Using a probability density function pdf compute the relative likelihood that a random variable X will be near the given value x Mathematically it is the limit of the ratio P x X x dx dx as dx approaches zero The relative likelihood is computed as the probability of a sample occurring in a narrow range divided by the width of the range hence the word density Since the likelihood is relative to other points its value can be greater than 1 0 cdf x Using a cumulative distribution function cdf compute the probability that a random variable X will be less than or equal to x Mathematically it is written P X x inv_cdf p Compute the inverse cumulative distribution function also known as the quantile function or the percent point function Mathematically it is written x P X x p Finds the value x of the random variable X such that the probability of the variable being less than or equal to that value equals the given probability p overlap other Measures the agreement between two normal probability distributions Returns a value between 0 0 and 1 0 giving the overlapping area for the two probability density functions quantiles n 4 Divide the normal distribution into n continuous intervals with equal probability Returns a list of n 1 cut points separating the intervals Set n to 4 for quartiles the default Set n to 10 for deciles Set n to 100 for percentiles which gives the 99 cuts points that separate the normal distribution into 100 equal sized groups zscore x Compute the Standard Score describing x in terms of the number of standard deviations above or below the mean of the normal distribution x mean stdev New in version 3 9 Instances of NormalDist support addition subtraction multiplication and division by a constant These operations are used for translation and scaling For example temperature_february NormalDist 5 2 5 Celsius temperature_february 9 5 32 Fahrenheit NormalDist mu 41 0 sigma 4,en
530, 5 Dividing a constant by an instance of NormalDist is not supported because the result wouldn t be normally distributed Since normal distributions arise from additive effects of independent variables it is possible to add and subtract two independent normally distributed random variables represented as instances of NormalDist For example birth_weights NormalDist from_samples 2 5 3 1 2 1 2 4 2 7 3 5 drug_effects NormalDist 0 4 0 15 combined birth_weights drug_effects round combined mean 1 3 1 round combined stdev 1 0 5 New in version 3 8 NormalDist Examples and Recipes Classic probability problems NormalDist readily solves classic probability problems For example given historical data for SAT exams showing that scores are normally distributed with a mean of 1060 and a standard deviation of 195 determine the percentage of students with test scores between 1100 and 1200 after rounding to the nearest whole number sat NormalDist 1060 195 fraction sat cdf 1200 0 5 sat cdf 1100 0 5 round fraction 100 0 1 18 4 Find the quartiles and deciles for the SAT scores list map round sat quantiles 928 1060 1192 list map round sat quantiles n 10 810 896 958 1011 1060 1109 1162 1224 1310 Monte Carlo inputs for simulations To estimate the distribution for a model than isn t easy to solve analytically NormalDist can generate input samples for a Monte Carlo simulation def model x y z return 3 x 7 x y 5 y 11 z n 100_000 X NormalDist 10 2 5 samples n seed 3652260728 Y NormalDist 15 1 75 samples n seed 4582495471 Z NormalDist 50 1 25 samples n seed 6582483453 quantiles map model X Y Z 1 4591308524824727 1 8035946855390597 2 175091447274739 Approximating binomial distributions Normal distributions can be used to approximate Binomial distributions when the sample size is large and when the probability of a successful trial is near 50 For example an open source conference has 750 attendees and two rooms with a 500 person capacity There is a talk about Python and another about Ruby In previous conferences 65 of the attendees preferred to listen to Python talks Assuming the population preferences haven t changed what is the probability that the Python room will stay within its capacity limits n 750 Sample size p 0 65 Preference for Python q 1 0 p Preference for Ruby k 500 Room capacity Approximation using the cumulative normal distribution from math import sqrt round NormalDist mu n p sigma sqrt n p q cdf k 0 5 4 0 8402 Exact solution using the cumulative binomial distribution from math import comb fsum round fsum comb n r p r q n r for r in range k 1 4 0 8402 Approximation using a simulation from random import seed binomialvariate seed 8675309 mean binomialvariate n p k for i in range 10_000 0 8406 Naive bayesian classifier Normal distributions commonly arise in machine learning problems Wikipedia has a nice example of a Naive Bayesian Classifier The challenge is to predict a person s gender from measurements of normally distributed features including height weight and foot size We re given a training dataset with measurements for eight people The measurements are assumed to be normally distributed so we summarize the data with NormalDist height_male NormalDist from_samples 6 5 92 5 58 5 92 height_female NormalDist from_samples 5 5 5 5 42 5 75 weight_male NormalDist from_samples 180 190 170 165 weight_female NormalDist from_samples 100 150 130 150 foot_size_male NormalDist from_samples 12 11 12 10 foot_size_female NormalDist from_samples 6 8 7 9 Next we encounter a new person whose feature measurements are known but whose gender is unknown ht 6 0 height wt 130 weight fs 8 foot size Starting with a 50 prior probability of being male or female we compute the posterior as the prior times the product of likelihoods for the feature measurements given the gender prior_male 0 5 prior_female 0 5 posterior_male prior_male height_male pdf ht weight_male pdf wt foot_size_male pdf fs posterior_female prior_female height_female pdf ht weight_female pdf wt foot_size_female pdf fs The final prediction goes to the largest posterior This is known as the maximum a po,en
531,steriori or MAP male if posterior_male posterior_female else female female Kernel density estimation It is possible to estimate a continuous probability density function from a fixed number of discrete samples The basic idea is to smooth the data using a kernel function such as a normal distribution triangular distribution or uniform distribution The degree of smoothing is controlled by a scaling parameter h which is called the bandwidth def kde_normal sample h Create a continuous probability density function from a sample Smooth the sample with a normal distribution kernel scaled by h kernel_h NormalDist 0 0 h pdf n len sample def pdf x return sum kernel_h x x_i for x_i in sample n return pdf Wikipedia has an example where we can use the kde_normal recipe to generate and plot a probability density function estimated from a small sample sample 2 1 1 3 0 4 1 9 5 1 6 2 f_hat kde_normal sample h 1 5 xarr i 100 for i in range 750 1100 yarr f_hat x for x in xarr The points in xarr and yarr can be used to make a PDF plot image Scatter plot of the estimated probability density function image,en
532,Introduction The Application Programmer s Interface to Python gives C and C programmers access to the Python interpreter at a variety of levels The API is equally usable from C but for brevity it is generally referred to as the Python C API There are two fundamentally different reasons for using the Python C API The first reason is to write extension modules for specific purposes these are C modules that extend the Python interpreter This is probably the most common use The second reason is to use Python as a component in a larger application this technique is generally referred to as embedding Python in an application Writing an extension module is a relatively well understood process where a cookbook approach works well There are several tools that automate the process to some extent While people have embedded Python in other applications since its early existence the process of embedding Python is less straightforward than writing an extension Many API functions are useful independent of whether you re embedding or extending Python moreover most applications that embed Python will need to provide a custom extension as well so it s probably a good idea to become familiar with writing an extension before attempting to embed Python in a real application Coding standards If you re writing C code for inclusion in CPython you must follow the guidelines and standards defined in PEP 7 These guidelines apply regardless of the version of Python you are contributing to Following these conventions is not necessary for your own third party extension modules unless you eventually expect to contribute them to Python Include Files All function type and macro definitions needed to use the Python C API are included in your code by the following line define PY_SSIZE_T_CLEAN include Python h This implies inclusion of the following standard headers stdio h string h errno h limits h assert h and stdlib h if available Note Since Python may define some pre processor definitions which affect the standard headers on some systems you must include Python h before any standard headers are included It is recommended to always define PY_SSIZE_T_CLEAN before including Python h See Parsing arguments and building values for a description of this macro All user visible names defined by Python h except those defined by the included standard headers have one of the prefixes Py or _Py Names beginning with _Py are for internal use by the Python implementation and should not be used by extension writers Structure member names do not have a reserved prefix Note User code should never define names that begin with Py or _Py This confuses the reader and jeopardizes the portability of the user code to future Python versions which may define additional names beginning with one of these prefixes The header files are typically installed with Python On Unix these are located in the directories prefix include pythonversion and exec_prefix include pythonversion where prefix and exec_prefix are defined by the corresponding parameters to Python s configure script and version is d d sys version_info 2 On Windows the headers are installed in prefix include where prefix is the installation directory specified to the installer To include the headers place both directories if different on your compiler s search path for includes Do not place the parent directories on the search path and then use include pythonX Y Python h this will break on multi platform builds since the platform independent headers under prefix include the platform specific headers from exec_prefix C users should note that although the API is defined entirely using C the header files properly declare the entry points to be extern C As a result there is no need to do anything special to use the API from C Useful macros Several useful macros are defined in the Python header files Many are defined closer to where they are useful e g Py_RETURN_NONE Others of a more general utility are defined here This is not necessarily a complete listing PyMODINIT_FUNC Declare an extension module PyInit initialization functi,en
533,on The function return type is PyObject The macro declares any special linkage declarations required by the platform and for C declares the function as extern C The initialization function must be named PyInit_ name where name is the name of the module and should be the only non static item defined in the module file Example static struct PyModuleDef spam_module PyModuleDef_HEAD_INIT m_name spam PyMODINIT_FUNC PyInit_spam void return PyModule_Create spam_module Py_ABS x Return the absolute value of x New in version 3 3 Py_ALWAYS_INLINE Ask the compiler to always inline a static inline function The compiler can ignore it and decides to not inline the function It can be used to inline performance critical static inline functions when building Python in debug mode with function inlining disabled For example MSC disables function inlining when building in debug mode Marking blindly a static inline function with Py_ALWAYS_INLINE can result in worse performances due to increased code size for example The compiler is usually smarter than the developer for the cost benefit analysis If Python is built in debug mode if the Py_DEBUG macro is defined the Py_ALWAYS_INLINE macro does nothing It must be specified before the function return type Usage static inline Py_ALWAYS_INLINE int random void return 4 New in version 3 11 Py_CHARMASK c Argument must be a character or an integer in the range 128 127 or 0 255 This macro returns c cast to an unsigned char Py_DEPRECATED version Use this for deprecated declarations The macro must be placed before the symbol name Example Py_DEPRECATED 3 8 PyAPI_FUNC int Py_OldFunction void Changed in version 3 8 MSVC support was added Py_GETENV s Like getenv s but returns NULL if E was passed on the command line see PyConfig use_environment Py_MAX x y Return the maximum value between x and y New in version 3 3 Py_MEMBER_SIZE type member Return the size of a structure type member in bytes New in version 3 6 Py_MIN x y Return the minimum value between x and y New in version 3 3 Py_NO_INLINE Disable inlining on a function For example it reduces the C stack consumption useful on LTO PGO builds which heavily inline code see bpo 33720 Usage Py_NO_INLINE static int random void return 4 New in version 3 11 Py_STRINGIFY x Convert x to a C string E g Py_STRINGIFY 123 returns 123 New in version 3 4 Py_UNREACHABLE Use this when you have a code path that cannot be reached by design For example in the default clause in a switch statement for which all possible values are covered in case statements Use this in places where you might be tempted to put an assert 0 or abort call In release mode the macro helps the compiler to optimize the code and avoids a warning about unreachable code For example the macro is implemented with __builtin_unreachable on GCC in release mode A use for Py_UNREACHABLE is following a call a function that never returns but that is not declared _Py_NO_RETURN If a code path is very unlikely code but can be reached under exceptional case this macro must not be used For example under low memory condition or if a system call returns a value out of the expected range In this case it s better to report the error to the caller If the error cannot be reported to caller Py_FatalError can be used New in version 3 7 Py_UNUSED arg Use this for unused arguments in a function definition to silence compiler warnings Example int func int a int Py_UNUSED b return a New in version 3 4 PyDoc_STRVAR name str Creates a variable with name name that can be used in docstrings If Python is built without docstrings the value will be empty Use PyDoc_STRVAR for docstrings to support building Python without docstrings as specified in PEP 7 Example PyDoc_STRVAR pop_doc Remove and return the rightmost element static PyMethodDef deque_methods pop PyCFunction deque_pop METH_NOARGS pop_doc PyDoc_STR str Creates a docstring for the given input string or an empty string if docstrings are disabled Use PyDoc_STR in specifying docstrings to support building Python without docstrings as specified in PEP 7 Example static PyMethodDef pysq,en
534,lite_row_methods keys PyCFunction pysqlite_row_keys METH_NOARGS PyDoc_STR Returns the keys of the row NULL NULL Objects Types and Reference Counts Most Python C API functions have one or more arguments as well as a return value of type PyObject This type is a pointer to an opaque data type representing an arbitrary Python object Since all Python object types are treated the same way by the Python language in most situations e g assignments scope rules and argument passing it is only fitting that they should be represented by a single C type Almost all Python objects live on the heap you never declare an automatic or static variable of type PyObject only pointer variables of type PyObject can be declared The sole exception are the type objects since these must never be deallocated they are typically static PyTypeObject objects All Python objects even Python integers have a type and a reference count An object s type determines what kind of object it is e g an integer a list or a user defined function there are many more as explained in The standard type hierarchy For each of the well known types there is a macro to check whether an object is of that type for instance PyList_Check a is true if and only if the object pointed to by a is a Python list Reference Counts The reference count is important because today s computers have a finite and often severely limited memory size it counts how many different places there are that have a strong reference to an object Such a place could be another object or a global or static C variable or a local variable in some C function When the last strong reference to an object is released i e its reference count becomes zero the object is deallocated If it contains references to other objects those references are released Those other objects may be deallocated in turn if there are no more references to them and so on There s an obvious problem with objects that reference each other here for now the solution is don t do that Reference counts are always manipulated explicitly The normal way is to use the macro Py_INCREF to take a new reference to an object i e increment its reference count by one and Py_DECREF to release that reference i e decrement the reference count by one The Py_DECREF macro is considerably more complex than the incref one since it must check whether the reference count becomes zero and then cause the object s deallocator to be called The deallocator is a function pointer contained in the object s type structure The type specific deallocator takes care of releasing references for other objects contained in the object if this is a compound object type such as a list as well as performing any additional finalization that s needed There s no chance that the reference count can overflow at least as many bits are used to hold the reference count as there are distinct memory locations in virtual memory assuming sizeof Py_ssize_t sizeof void Thus the reference count increment is a simple operation It is not necessary to hold a strong reference i e increment the reference count for every local variable that contains a pointer to an object In theory the object s reference count goes up by one when the variable is made to point to it and it goes down by one when the variable goes out of scope However these two cancel each other out so at the end the reference count hasn t changed The only real reason to use the reference count is to prevent the object from being deallocated as long as our variable is pointing to it If we know that there is at least one other reference to the object that lives at least as long as our variable there is no need to take a new strong reference i e increment the reference count temporarily An important situation where this arises is in objects that are passed as arguments to C functions in an extension module that are called from Python the call mechanism guarantees to hold a reference to every argument for the duration of the call However a common pitfall is to extract an object from a list and hold on to it for a while without taking a new reference ,en
535,Some other operation might conceivably remove the object from the list releasing that reference and possibly deallocating it The real danger is that innocent looking operations may invoke arbitrary Python code which could do this there is a code path which allows control to flow back to the user from a Py_DECREF so almost any operation is potentially dangerous A safe approach is to always use the generic operations functions whose name begins with PyObject_ PyNumber_ PySequence_ or PyMapping_ These operations always create a new strong reference i e increment the reference count of the object they return This leaves the caller with the responsibility to call Py_DECREF when they are done with the result this soon becomes second nature Reference Count Details The reference count behavior of functions in the Python C API is best explained in terms of ownership of references Ownership pertains to references never to objects objects are not owned they are always shared Owning a reference means being responsible for calling Py_DECREF on it when the reference is no longer needed Ownership can also be transferred meaning that the code that receives ownership of the reference then becomes responsible for eventually releasing it by calling Py_DECREF or Py_XDECREF when it s no longer needed or passing on this responsibility usually to its caller When a function passes ownership of a reference on to its caller the caller is said to receive a new reference When no ownership is transferred the caller is said to borrow the reference Nothing needs to be done for a borrowed reference Conversely when a calling function passes in a reference to an object there are two possibilities the function steals a reference to the object or it does not Stealing a reference means that when you pass a reference to a function that function assumes that it now owns that reference and you are not responsible for it any longer Few functions steal references the two notable exceptions are PyList_SetItem and PyTuple_SetItem which steal a reference to the item but not to the tuple or list into which the item is put These functions were designed to steal a reference because of a common idiom for populating a tuple or list with newly created objects for example the code to create the tuple 1 2 three could look like this forgetting about error handling for the moment a better way to code this is shown below PyObject t t PyTuple_New 3 PyTuple_SetItem t 0 PyLong_FromLong 1L PyTuple_SetItem t 1 PyLong_FromLong 2L PyTuple_SetItem t 2 PyUnicode_FromString three Here PyLong_FromLong returns a new reference which is immediately stolen by PyTuple_SetItem When you want to keep using an object although the reference to it will be stolen use Py_INCREF to grab another reference before calling the reference stealing function Incidentally PyTuple_SetItem is the only way to set tuple items PySequence_SetItem and PyObject_SetItem refuse to do this since tuples are an immutable data type You should only use PyTuple_SetItem for tuples that you are creating yourself Equivalent code for populating a list can be written using PyList_New and PyList_SetItem However in practice you will rarely use these ways of creating and populating a tuple or list There s a generic function Py_BuildValue that can create most common objects from C values directed by a format string For example the above two blocks of code could be replaced by the following which also takes care of the error checking PyObject tuple list tuple Py_BuildValue iis 1 2 three list Py_BuildValue iis 1 2 three It is much more common to use PyObject_SetItem and friends with items whose references you are only borrowing like arguments that were passed in to the function you are writing In that case their behaviour regarding references is much saner since you don t have to take a new reference just so you can give that reference away have it be stolen For example this function sets all items of a list actually any mutable sequence to a given item int set_all PyObject target PyObject item Py_ssize_t i n n PyObject_Length target i,en
536,f n 0 return 1 for i 0 i n i PyObject index PyLong_FromSsize_t i if index return 1 if PyObject_SetItem target index item 0 Py_DECREF index return 1 Py_DECREF index return 0 The situation is slightly different for function return values While passing a reference to most functions does not change your ownership responsibilities for that reference many functions that return a reference to an object give you ownership of the reference The reason is simple in many cases the returned object is created on the fly and the reference you get is the only reference to the object Therefore the generic functions that return object references like PyObject_GetItem and PySequence_GetItem always return a new reference the caller becomes the owner of the reference It is important to realize that whether you own a reference returned by a function depends on which function you call only the plumage the type of the object passed as an argument to the function doesn t enter into it Thus if you extract an item from a list using PyList_GetItem you don t own the reference but if you obtain the same item from the same list using PySequence_GetItem which happens to take exactly the same arguments you do own a reference to the returned object Here is an example of how you could write a function that computes the sum of the items in a list of integers once using PyList_GetItem and once using PySequence_GetItem long sum_list PyObject list Py_ssize_t i n long total 0 value PyObject item n PyList_Size list if n 0 return 1 Not a list for i 0 i n i item PyList_GetItem list i Can t fail if PyLong_Check item continue Skip non integers value PyLong_AsLong item if value 1 PyErr_Occurred Integer too big to fit in a C long bail out return 1 total value return total long sum_sequence PyObject sequence Py_ssize_t i n long total 0 value PyObject item n PySequence_Length sequence if n 0 return 1 Has no length for i 0 i n i item PySequence_GetItem sequence i if item NULL return 1 Not a sequence or other failure if PyLong_Check item value PyLong_AsLong item Py_DECREF item if value 1 PyErr_Occurred Integer too big to fit in a C long bail out return 1 total value else Py_DECREF item Discard reference ownership return total Types There are few other data types that play a significant role in the Python C API most are simple C types such as int long double and char A few structure types are used to describe static tables used to list the functions exported by a module or the data attributes of a new object type and another is used to describe the value of a complex number These will be discussed together with the functions that use them type Py_ssize_t Part of the Stable ABI A signed integral type such that sizeof Py_ssize_t sizeof size_t C99 doesn t define such a thing directly size_t is an unsigned integral type See PEP 353 for details PY_SSIZE_T_MAX is the largest positive value of type Py_ssize_t Exceptions The Python programmer only needs to deal with exceptions if specific error handling is required unhandled exceptions are automatically propagated to the caller then to the caller s caller and so on until they reach the top level interpreter where they are reported to the user accompanied by a stack traceback For C programmers however error checking always has to be explicit All functions in the Python C API can raise exceptions unless an explicit claim is made otherwise in a function s documentation In general when a function encounters an error it sets an exception discards any object references that it owns and returns an error indicator If not documented otherwise this indicator is either NULL or 1 depending on the function s return type A few functions return a Boolean true false result with false indicating an error Very few functions return no explicit error indicator or have an ambiguous return value and require explicit testing for errors with PyErr_Occurred These exceptions are always explicitly documented Exception state is maintained in per thread storage this is equivalent to using global storage in an unthreaded application A thread can be in one of ,en
537,two states an exception has occurred or not The function PyErr_Occurred can be used to check for this it returns a borrowed reference to the exception type object when an exception has occurred and NULL otherwise There are a number of functions to set the exception state PyErr_SetString is the most common though not the most general function to set the exception state and PyErr_Clear clears the exception state The full exception state consists of three objects all of which can be NULL the exception type the corresponding exception value and the traceback These have the same meanings as the Python result of sys exc_info however they are not the same the Python objects represent the last exception being handled by a Python try except statement while the C level exception state only exists while an exception is being passed on between C functions until it reaches the Python bytecode interpreter s main loop which takes care of transferring it to sys exc_info and friends Note that starting with Python 1 5 the preferred thread safe way to access the exception state from Python code is to call the function sys exc_info which returns the per thread exception state for Python code Also the semantics of both ways to access the exception state have changed so that a function which catches an exception will save and restore its thread s exception state so as to preserve the exception state of its caller This prevents common bugs in exception handling code caused by an innocent looking function overwriting the exception being handled it also reduces the often unwanted lifetime extension for objects that are referenced by the stack frames in the traceback As a general principle a function that calls another function to perform some task should check whether the called function raised an exception and if so pass the exception state on to its caller It should discard any object references that it owns and return an error indicator but it should not set another exception that would overwrite the exception that was just raised and lose important information about the exact cause of the error A simple example of detecting exceptions and passing them on is shown in the sum_sequence example above It so happens that this example doesn t need to clean up any owned references when it detects an error The following example function shows some error cleanup First to remind you why you like Python we show the equivalent Python code def incr_item dict key try item dict key except KeyError item 0 dict key item 1 Here is the corresponding C code in all its glory int incr_item PyObject dict PyObject key Objects all initialized to NULL for Py_XDECREF PyObject item NULL const_one NULL incremented_item NULL int rv 1 Return value initialized to 1 failure item PyObject_GetItem dict key if item NULL Handle KeyError only if PyErr_ExceptionMatches PyExc_KeyError goto error Clear the error and use zero PyErr_Clear item PyLong_FromLong 0L if item NULL goto error const_one PyLong_FromLong 1L if const_one NULL goto error incremented_item PyNumber_Add item const_one if incremented_item NULL goto error if PyObject_SetItem dict key incremented_item 0 goto error rv 0 Success Continue with cleanup code error Cleanup code shared by success and failure path Use Py_XDECREF to ignore NULL references Py_XDECREF item Py_XDECREF const_one Py_XDECREF incremented_item return rv 1 for error 0 for success This example represents an endorsed use of the goto statement in C It illustrates the use of PyErr_ExceptionMatches and PyErr_Clear to handle specific exceptions and the use of Py_XDECREF to dispose of owned references that may be NULL note the X in the name Py_DECREF would crash when confronted with a NULL reference It is important that the variables used to hold owned references are initialized to NULL for this to work likewise the proposed return value is initialized to 1 failure and only set to success after the final call made is successful Embedding Python The one important task that only embedders as opposed to extension writers of the Python interpreter have to worry ab,en
538,out is the initialization and possibly the finalization of the Python interpreter Most functionality of the interpreter can only be used after the interpreter has been initialized The basic initialization function is Py_Initialize This initializes the table of loaded modules and creates the fundamental modules builtins __main__ and sys It also initializes the module search path sys path Py_Initialize does not set the script argument list sys argv If this variable is needed by Python code that will be executed later setting PyConfig argv and PyConfig parse_argv must be set see Python Initialization Configuration On most systems in particular on Unix and Windows although the details are slightly different Py_Initialize calculates the module search path based upon its best guess for the location of the standard Python interpreter executable assuming that the Python library is found in a fixed location relative to the Python interpreter executable In particular it looks for a directory named lib python X Y relative to the parent directory where the executable named python is found on the shell command search path the environment variable PATH For instance if the Python executable is found in usr local bin python it will assume that the libraries are in usr local lib python X Y In fact this particular path is also the fallback location used when no executable file named python is found along PATH The user can override this behavior by setting the environment variable PYTHONHOME or insert additional directories in front of the standard path by setting PYTHONPATH The embedding application can steer the search by calling Py_SetProgramName file before calling Py_Initialize Note that PYTHONHOME still overrides this and PYTHONPATH is still inserted in front of the standard path An application that requires total control has to provide its own implementation of Py_GetPath Py_GetPrefix Py_GetExecPrefix and Py_GetProgramFullPath all defined in Modules getpath c Sometimes it is desirable to uninitialize Python For instance the application may want to start over make another call to Py_Initialize or the application is simply done with its use of Python and wants to free memory allocated by Python This can be accomplished by calling Py_FinalizeEx The function Py_IsInitialized returns true if Python is currently in the initialized state More information about these functions is given in a later chapter Notice that Py_FinalizeEx does not free all memory allocated by the Python interpreter e g memory allocated by extension modules currently cannot be released Debugging Builds Python can be built with several macros to enable extra checks of the interpreter and extension modules These checks tend to add a large amount of overhead to the runtime so they are not enabled by default A full list of the various types of debugging builds is in the file Misc SpecialBuilds txt in the Python source distribution Builds are available that support tracing of reference counts debugging the memory allocator or low level profiling of the main interpreter loop Only the most frequently used builds will be described in the remainder of this section Py_DEBUG Compiling the interpreter with the Py_DEBUG macro defined produces what is generally meant by a debug build of Python Py_DEBUG is enabled in the Unix build by adding with pydebug to the configure command It is also implied by the presence of the not Python specific _DEBUG macro When Py_DEBUG is enabled in the Unix build compiler optimization is disabled In addition to the reference count debugging described below extra checks are performed see Python Debug Build Defining Py_TRACE_REFS enables reference tracing see the configure with trace refs option When defined a circular doubly linked list of active objects is maintained by adding two extra fields to every PyObject Total allocations are tracked as well Upon exit all existing references are printed In interactive mode this happens after every statement run by the interpreter Please refer to Misc SpecialBuilds txt in the Python source distribution for more,en
539, detailed information,en
540,http cookiejar Cookie handling for HTTP clients Source code Lib http cookiejar py The http cookiejar module defines classes for automatic handling of HTTP cookies It is useful for accessing web sites that require small pieces of data cookies to be set on the client machine by an HTTP response from a web server and then returned to the server in later HTTP requests Both the regular Netscape cookie protocol and the protocol defined by RFC 2965 are handled RFC 2965 handling is switched off by default RFC 2109 cookies are parsed as Netscape cookies and subsequently treated either as Netscape or RFC 2965 cookies according to the policy in effect Note that the great majority of cookies on the internet are Netscape cookies http cookiejar attempts to follow the de facto Netscape cookie protocol which differs substantially from that set out in the original Netscape specification including taking note of the max age and port cookie attributes introduced with RFC 2965 Note The various named parameters found in Set Cookie and Set Cookie2 headers eg domain and expires are conventionally referred to as attributes To distinguish them from Python attributes the documentation for this module uses the term cookie attribute instead The module defines the following exception exception http cookiejar LoadError Instances of FileCookieJar raise this exception on failure to load cookies from a file LoadError is a subclass of OSError Changed in version 3 3 LoadError used to be a subtype of IOError which is now an alias of OSError The following classes are provided class http cookiejar CookieJar policy None policy is an object implementing the CookiePolicy interface The CookieJar class stores HTTP cookies It extracts cookies from HTTP requests and returns them in HTTP responses CookieJar instances automatically expire contained cookies when necessary Subclasses are also responsible for storing and retrieving cookies from a file or database class http cookiejar FileCookieJar filename None delayload None policy None policy is an object implementing the CookiePolicy interface For the other arguments see the documentation for the corresponding attributes A CookieJar which can load cookies from and perhaps save cookies to a file on disk Cookies are NOT loaded from the named file until either the load or revert method is called Subclasses of this class are documented in section FileCookieJar subclasses and co operation with web browsers This should not be initialized directly use its subclasses below instead Changed in version 3 8 The filename parameter supports a path like object class http cookiejar CookiePolicy This class is responsible for deciding whether each cookie should be accepted from returned to the server class http cookiejar DefaultCookiePolicy blocked_domains None allowed_domains None netscape True rfc2965 False rfc2109_as_netscape None hide_cookie2 False strict_domain False strict_rfc2965_unverifiable True strict_ns_unverifiable False strict_ns_domain DefaultCookiePolicy DomainLiberal strict_ns_set_initial_dollar False strict_ns_set_path False secure_protocols https wss Constructor arguments should be passed as keyword arguments only blocked_domains is a sequence of domain names that we never accept cookies from nor return cookies to allowed_domains if not None this is a sequence of the only domains for which we accept and return cookies secure_protocols is a sequence of protocols for which secure cookies can be added to By default https and wss secure websocket are considered secure protocols For all other arguments see the documentation for CookiePolicy and DefaultCookiePolicy objects DefaultCookiePolicy implements the standard accept reject rules for Netscape and RFC 2965 cookies By default RFC 2109 cookies ie cookies received in a Set Cookie header with a version cookie attribute of 1 are treated according to the RFC 2965 rules However if RFC 2965 handling is turned off or rfc2109_as_netscape is True RFC 2109 cookies are downgraded by the CookieJar instance to Netscape cookies by setting the version attribute of the Cookie instance ,en
541,to 0 DefaultCookiePolicy also provides some parameters to allow some fine tuning of policy class http cookiejar Cookie This class represents Netscape RFC 2109 and RFC 2965 cookies It is not expected that users of http cookiejar construct their own Cookie instances Instead if necessary call make_cookies on a CookieJar instance See also Module urllib request URL opening with automatic cookie handling Module http cookies HTTP cookie classes principally useful for server side code The http cookiejar and http cookies modules do not depend on each other https curl se rfc cookie_spec html The specification of the original Netscape cookie protocol Though this is still the dominant protocol the Netscape cookie protocol implemented by all the major browsers and http cookiejar only bears a passing resemblance to the one sketched out in cookie_spec html RFC 2109 HTTP State Management Mechanism Obsoleted by RFC 2965 Uses Set Cookie with version 1 RFC 2965 HTTP State Management Mechanism The Netscape protocol with the bugs fixed Uses Set Cookie2 in place of Set Cookie Not widely used http kristol org cookie errata html Unfinished errata to RFC 2965 RFC 2964 Use of HTTP State Management CookieJar and FileCookieJar Objects CookieJar objects support the iterator protocol for iterating over contained Cookie objects CookieJar has the following methods CookieJar add_cookie_header request Add correct Cookie header to request If policy allows ie the rfc2965 and hide_cookie2 attributes of the CookieJar s CookiePolicy instance are true and false respectively the Cookie2 header is also added when appropriate The request object usually a urllib request Request instance must support the methods get_full_url has_header get_header header_items add_unredirected_header and the attributes host type unverifiable and origin_req_host as documented by urllib request Changed in version 3 3 request object needs origin_req_host attribute Dependency on a deprecated method get_origin_req_host has been removed CookieJar extract_cookies response request Extract cookies from HTTP response and store them in the CookieJar where allowed by policy The CookieJar will look for allowable Set Cookie and Set Cookie2 headers in the response argument and store cookies as appropriate subject to the CookiePolicy set_ok method s approval The response object usually the result of a call to urllib request urlopen or similar should support an info method which returns an email message Message instance The request object usually a urllib request Request instance must support the method get_full_url and the attributes host unverifiable and origin_req_host as documented by urllib request The request is used to set default values for cookie attributes as well as for checking that the cookie is allowed to be set Changed in version 3 3 request object needs origin_req_host attribute Dependency on a deprecated method get_origin_req_host has been removed CookieJar set_policy policy Set the CookiePolicy instance to be used CookieJar make_cookies response request Return sequence of Cookie objects extracted from response object See the documentation for extract_cookies for the interfaces required of the response and request arguments CookieJar set_cookie_if_ok cookie request Set a Cookie if policy says it s OK to do so CookieJar set_cookie cookie Set a Cookie without checking with policy to see whether or not it should be set CookieJar clear domain path name Clear some cookies If invoked without arguments clear all cookies If given a single argument only cookies belonging to that domain will be removed If given two arguments cookies belonging to the specified domain and URL path are removed If given three arguments then the cookie with the specified domain path and name is removed Raises KeyError if no matching cookie exists CookieJar clear_session_cookies Discard all session cookies Discards all contained cookies that have a true discard attribute usually because they had either no max age or expires cookie attribute or an explicit discard cookie attribute For interactive browsers the end of,en
542, a session usually corresponds to closing the browser window Note that the save method won t save session cookies anyway unless you ask otherwise by passing a true ignore_discard argument FileCookieJar implements the following additional methods FileCookieJar save filename None ignore_discard False ignore_expires False Save cookies to a file This base class raises NotImplementedError Subclasses may leave this method unimplemented filename is the name of file in which to save cookies If filename is not specified self filename is used whose default is the value passed to the constructor if any if self filename is None ValueError is raised ignore_discard save even cookies set to be discarded ignore_expires save even cookies that have expired The file is overwritten if it already exists thus wiping all the cookies it contains Saved cookies can be restored later using the load or revert methods FileCookieJar load filename None ignore_discard False ignore_expires False Load cookies from a file Old cookies are kept unless overwritten by newly loaded ones Arguments are as for save The named file must be in the format understood by the class or LoadError will be raised Also OSError may be raised for example if the file does not exist Changed in version 3 3 IOError used to be raised it is now an alias of OSError FileCookieJar revert filename None ignore_discard False ignore_expires False Clear all cookies and reload cookies from a saved file revert can raise the same exceptions as load If there is a failure the object s state will not be altered FileCookieJar instances have the following public attributes FileCookieJar filename Filename of default file in which to keep cookies This attribute may be assigned to FileCookieJar delayload If true load cookies lazily from disk This attribute should not be assigned to This is only a hint since this only affects performance not behaviour unless the cookies on disk are changing A CookieJar object may ignore it None of the FileCookieJar classes included in the standard library lazily loads cookies FileCookieJar subclasses and co operation with web browsers The following CookieJar subclasses are provided for reading and writing class http cookiejar MozillaCookieJar filename None delayload None policy None A FileCookieJar that can load from and save cookies to disk in the Mozilla cookies txt file format which is also used by curl and the Lynx and Netscape browsers Note This loses information about RFC 2965 cookies and also about newer or non standard cookie attributes such as port Warning Back up your cookies before saving if you have cookies whose loss corruption would be inconvenient there are some subtleties which may lead to slight changes in the file over a load save round trip Also note that cookies saved while Mozilla is running will get clobbered by Mozilla class http cookiejar LWPCookieJar filename None delayload None policy None A FileCookieJar that can load from and save cookies to disk in format compatible with the libwww perl library s Set Cookie3 file format This is convenient if you want to store cookies in a human readable file Changed in version 3 8 The filename parameter supports a path like object CookiePolicy Objects Objects implementing the CookiePolicy interface have the following methods CookiePolicy set_ok cookie request Return boolean value indicating whether cookie should be accepted from server cookie is a Cookie instance request is an object implementing the interface defined by the documentation for CookieJar extract_cookies CookiePolicy return_ok cookie request Return boolean value indicating whether cookie should be returned to server cookie is a Cookie instance request is an object implementing the interface defined by the documentation for CookieJar add_cookie_header CookiePolicy domain_return_ok domain request Return False if cookies should not be returned given cookie domain This method is an optimization It removes the need for checking every cookie with a particular domain which might involve reading many files Returning true from domain_return_ok and path,en
543,_return_ok leaves all the work to return_ok If domain_return_ok returns true for the cookie domain path_return_ok is called for the cookie path Otherwise path_return_ok and return_ok are never called for that cookie domain If path_return_ok returns true return_ok is called with the Cookie object itself for a full check Otherwise return_ok is never called for that cookie path Note that domain_return_ok is called for every cookie domain not just for the request domain For example the function might be called with both example com and www example com if the request domain is www example com The same goes for path_return_ok The request argument is as documented for return_ok CookiePolicy path_return_ok path request Return False if cookies should not be returned given cookie path See the documentation for domain_return_ok In addition to implementing the methods above implementations of the CookiePolicy interface must also supply the following attributes indicating which protocols should be used and how All of these attributes may be assigned to CookiePolicy netscape Implement Netscape protocol CookiePolicy rfc2965 Implement RFC 2965 protocol CookiePolicy hide_cookie2 Don t add Cookie2 header to requests the presence of this header indicates to the server that we understand RFC 2965 cookies The most useful way to define a CookiePolicy class is by subclassing from DefaultCookiePolicy and overriding some or all of the methods above CookiePolicy itself may be used as a null policy to allow setting and receiving any and all cookies this is unlikely to be useful DefaultCookiePolicy Objects Implements the standard rules for accepting and returning cookies Both RFC 2965 and Netscape cookies are covered RFC 2965 handling is switched off by default The easiest way to provide your own policy is to override this class and call its methods in your overridden implementations before adding your own additional checks import http cookiejar class MyCookiePolicy http cookiejar DefaultCookiePolicy def set_ok self cookie request if not http cookiejar DefaultCookiePolicy set_ok self cookie request return False if i_dont_want_to_store_this_cookie cookie return False return True In addition to the features required to implement the CookiePolicy interface this class allows you to block and allow domains from setting and receiving cookies There are also some strictness switches that allow you to tighten up the rather loose Netscape protocol rules a little bit at the cost of blocking some benign cookies A domain blocklist and allowlist is provided both off by default Only domains not in the blocklist and present in the allowlist if the allowlist is active participate in cookie setting and returning Use the blocked_domains constructor argument and blocked_domains and set_blocked_domains methods and the corresponding argument and methods for allowed_domains If you set an allowlist you can turn it off again by setting it to None Domains in block or allow lists that do not start with a dot must equal the cookie domain to be matched For example example com matches a blocklist entry of example com but www example com does not Domains that do start with a dot are matched by more specific domains too For example both www example com and www coyote example com match example com but example com itself does not IP addresses are an exception and must match exactly For example if blocked_domains contains 192 168 1 2 and 168 1 2 192 168 1 2 is blocked but 193 168 1 2 is not DefaultCookiePolicy implements the following additional methods DefaultCookiePolicy blocked_domains Return the sequence of blocked domains as a tuple DefaultCookiePolicy set_blocked_domains blocked_domains Set the sequence of blocked domains DefaultCookiePolicy is_blocked domain Return True if domain is on the blocklist for setting or receiving cookies DefaultCookiePolicy allowed_domains Return None or the sequence of allowed domains as a tuple DefaultCookiePolicy set_allowed_domains allowed_domains Set the sequence of allowed domains or None DefaultCookiePolicy is_not_allowed domain Return True ,en
544,if domain is not on the allowlist for setting or receiving cookies DefaultCookiePolicy instances have the following attributes which are all initialised from the constructor arguments of the same name and which may all be assigned to DefaultCookiePolicy rfc2109_as_netscape If true request that the CookieJar instance downgrade RFC 2109 cookies ie cookies received in a Set Cookie header with a version cookie attribute of 1 to Netscape cookies by setting the version attribute of the Cookie instance to 0 The default value is None in which case RFC 2109 cookies are downgraded if and only if RFC 2965 handling is turned off Therefore RFC 2109 cookies are downgraded by default General strictness switches DefaultCookiePolicy strict_domain Don t allow sites to set two component domains with country code top level domains like co uk gov uk co nz etc This is far from perfect and isn t guaranteed to work RFC 2965 protocol strictness switches DefaultCookiePolicy strict_rfc2965_unverifiable Follow RFC 2965 rules on unverifiable transactions usually an unverifiable transaction is one resulting from a redirect or a request for an image hosted on another site If this is false cookies are never blocked on the basis of verifiability Netscape protocol strictness switches DefaultCookiePolicy strict_ns_unverifiable Apply RFC 2965 rules on unverifiable transactions even to Netscape cookies DefaultCookiePolicy strict_ns_domain Flags indicating how strict to be with domain matching rules for Netscape cookies See below for acceptable values DefaultCookiePolicy strict_ns_set_initial_dollar Ignore cookies in Set Cookie headers that have names starting with DefaultCookiePolicy strict_ns_set_path Don t allow setting cookies whose path doesn t path match request URI strict_ns_domain is a collection of flags Its value is constructed by or ing together for example DomainStrictNoDots DomainStrictNonDomain means both flags are set DefaultCookiePolicy DomainStrictNoDots When setting cookies the host prefix must not contain a dot eg www foo bar com can t set a cookie for bar com because www foo contains a dot DefaultCookiePolicy DomainStrictNonDomain Cookies that did not explicitly specify a domain cookie attribute can only be returned to a domain equal to the domain that set the cookie eg spam example com won t be returned cookies from example com that had no domain cookie attribute DefaultCookiePolicy DomainRFC2965Match When setting cookies require a full RFC 2965 domain match The following attributes are provided for convenience and are the most useful combinations of the above flags DefaultCookiePolicy DomainLiberal Equivalent to 0 ie all of the above Netscape domain strictness flags switched off DefaultCookiePolicy DomainStrict Equivalent to DomainStrictNoDots DomainStrictNonDomain Cookie Objects Cookie instances have Python attributes roughly corresponding to the standard cookie attributes specified in the various cookie standards The correspondence is not one to one because there are complicated rules for assigning default values because the max age and expires cookie attributes contain equivalent information and because RFC 2109 cookies may be downgraded by http cookiejar from version 1 to version 0 Netscape cookies Assignment to these attributes should not be necessary other than in rare circumstances in a CookiePolicy method The class does not enforce internal consistency so you should know what you re doing if you do that Cookie version Integer or None Netscape cookies have version 0 RFC 2965 and RFC 2109 cookies have a version cookie attribute of 1 However note that http cookiejar may downgrade RFC 2109 cookies to Netscape cookies in which case version is 0 Cookie name Cookie name a string Cookie value Cookie value a string or None Cookie port String representing a port or a set of ports eg 80 or 80 8080 or None Cookie domain Cookie domain a string Cookie path Cookie path a string eg acme rocket_launchers Cookie secure True if cookie should only be returned over a secure connection Cookie expires Integer expiry date in seconds since epoch or None,en
545, See also the is_expired method Cookie discard True if this is a session cookie Cookie comment String comment from the server explaining the function of this cookie or None Cookie comment_url URL linking to a comment from the server explaining the function of this cookie or None Cookie rfc2109 True if this cookie was received as an RFC 2109 cookie ie the cookie arrived in a Set Cookie header and the value of the Version cookie attribute in that header was 1 This attribute is provided because http cookiejar may downgrade RFC 2109 cookies to Netscape cookies in which case version is 0 Cookie port_specified True if a port or set of ports was explicitly specified by the server in the Set Cookie Set Cookie2 header Cookie domain_specified True if a domain was explicitly specified by the server Cookie domain_initial_dot True if the domain explicitly specified by the server began with a dot Cookies may have additional non standard cookie attributes These may be accessed using the following methods Cookie has_nonstandard_attr name Return True if cookie has the named cookie attribute Cookie get_nonstandard_attr name default None If cookie has the named cookie attribute return its value Otherwise return default Cookie set_nonstandard_attr name value Set the value of the named cookie attribute The Cookie class also defines the following method Cookie is_expired now None True if cookie has passed the time at which the server requested it should expire If now is given in seconds since the epoch return whether the cookie has expired at the specified time Examples The first example shows the most common usage of http cookiejar import http cookiejar urllib request cj http cookiejar CookieJar opener urllib request build_opener urllib request HTTPCookieProcessor cj r opener open http example com This example illustrates how to open a URL using your Netscape Mozilla or Lynx cookies assumes Unix Netscape convention for location of the cookies file import os http cookiejar urllib request cj http cookiejar MozillaCookieJar cj load os path join os path expanduser netscape cookies txt opener urllib request build_opener urllib request HTTPCookieProcessor cj r opener open http example com The next example illustrates the use of DefaultCookiePolicy Turn on RFC 2965 cookies be more strict about domains when setting and returning Netscape cookies and block some domains from setting cookies or having them returned import urllib request from http cookiejar import CookieJar DefaultCookiePolicy policy DefaultCookiePolicy rfc2965 True strict_ns_domain Policy DomainStrict blocked_domains ads net ads net cj CookieJar policy opener urllib request build_opener urllib request HTTPCookieProcessor cj r opener open http example com,en
546,9 Classes Classes provide a means of bundling data and functionality together Creating a new class creates a new type of object allowing new instances of that type to be made Each class instance can have attributes attached to it for maintaining its state Class instances can also have methods defined by its class for modifying its state Compared with other programming languages Python s class mechanism adds classes with a minimum of new syntax and semantics It is a mixture of the class mechanisms found in C and Modula 3 Python classes provide all the standard features of Object Oriented Programming the class inheritance mechanism allows multiple base classes a derived class can override any methods of its base class or classes and a method can call the method of a base class with the same name Objects can contain arbitrary amounts and kinds of data As is true for modules classes partake of the dynamic nature of Python they are created at runtime and can be modified further after creation In C terminology normally class members including the data members are public except see below Private Variables and all member functions are virtual As in Modula 3 there are no shorthands for referencing the object s members from its methods the method function is declared with an explicit first argument representing the object which is provided implicitly by the call As in Smalltalk classes themselves are objects This provides semantics for importing and renaming Unlike C and Modula 3 built in types can be used as base classes for extension by the user Also like in C most built in operators with special syntax arithmetic operators subscripting etc can be redefined for class instances Lacking universally accepted terminology to talk about classes I will make occasional use of Smalltalk and C terms I would use Modula 3 terms since its object oriented semantics are closer to those of Python than C but I expect that few readers have heard of it 9 1 A Word About Names and Objects Objects have individuality and multiple names in multiple scopes can be bound to the same object This is known as aliasing in other languages This is usually not appreciated on a first glance at Python and can be safely ignored when dealing with immutable basic types numbers strings tuples However aliasing has a possibly surprising effect on the semantics of Python code involving mutable objects such as lists dictionaries and most other types This is usually used to the benefit of the program since aliases behave like pointers in some respects For example passing an object is cheap since only a pointer is passed by the implementation and if a function modifies an object passed as an argument the caller will see the change this eliminates the need for two different argument passing mechanisms as in Pascal 9 2 Python Scopes and Namespaces Before introducing classes I first have to tell you something about Python s scope rules Class definitions play some neat tricks with namespaces and you need to know how scopes and namespaces work to fully understand what s going on Incidentally knowledge about this subject is useful for any advanced Python programmer Let s begin with some definitions A namespace is a mapping from names to objects Most namespaces are currently implemented as Python dictionaries but that s normally not noticeable in any way except for performance and it may change in the future Examples of namespaces are the set of built in names containing functions such as abs and built in exception names the global names in a module and the local names in a function invocation In a sense the set of attributes of an object also form a namespace The important thing to know about namespaces is that there is absolutely no relation between names in different namespaces for instance two different modules may both define a function maximize without confusion users of the modules must prefix it with the module name By the way I use the word attribute for any name following a dot for example in the expression z real real is an attribute of the object z Strictly speaking re,en
547,ferences to names in modules are attribute references in the expression modname funcname modname is a module object and funcname is an attribute of it In this case there happens to be a straightforward mapping between the module s attributes and the global names defined in the module they share the same namespace 1 Attributes may be read only or writable In the latter case assignment to attributes is possible Module attributes are writable you can write modname the_answer 42 Writable attributes may also be deleted with the del statement For example del modname the_answer will remove the attribute the_answer from the object named by modname Namespaces are created at different moments and have different lifetimes The namespace containing the built in names is created when the Python interpreter starts up and is never deleted The global namespace for a module is created when the module definition is read in normally module namespaces also last until the interpreter quits The statements executed by the top level invocation of the interpreter either read from a script file or interactively are considered part of a module called __main__ so they have their own global namespace The built in names actually also live in a module this is called builtins The local namespace for a function is created when the function is called and deleted when the function returns or raises an exception that is not handled within the function Actually forgetting would be a better way to describe what actually happens Of course recursive invocations each have their own local namespace A scope is a textual region of a Python program where a namespace is directly accessible Directly accessible here means that an unqualified reference to a name attempts to find the name in the namespace Although scopes are determined statically they are used dynamically At any time during execution there are 3 or 4 nested scopes whose namespaces are directly accessible the innermost scope which is searched first contains the local names the scopes of any enclosing functions which are searched starting with the nearest enclosing scope contain non local but also non global names the next to last scope contains the current module s global names the outermost scope searched last is the namespace containing built in names If a name is declared global then all references and assignments go directly to the next to last scope containing the module s global names To rebind variables found outside of the innermost scope the nonlocal statement can be used if not declared nonlocal those variables are read only an attempt to write to such a variable will simply create a new local variable in the innermost scope leaving the identically named outer variable unchanged Usually the local scope references the local names of the textually current function Outside functions the local scope references the same namespace as the global scope the module s namespace Class definitions place yet another namespace in the local scope It is important to realize that scopes are determined textually the global scope of a function defined in a module is that module s namespace no matter from where or by what alias the function is called On the other hand the actual search for names is done dynamically at run time however the language definition is evolving towards static name resolution at compile time so don t rely on dynamic name resolution In fact local variables are already determined statically A special quirk of Python is that if no global or nonlocal statement is in effect assignments to names always go into the innermost scope Assignments do not copy data they just bind names to objects The same is true for deletions the statement del x removes the binding of x from the namespace referenced by the local scope In fact all operations that introduce new names use the local scope in particular import statements and function definitions bind the module or function name in the local scope The global statement can be used to indicate that particular variables live in the global scope and should be reb,en
548,ound there the nonlocal statement indicates that particular variables live in an enclosing scope and should be rebound there 9 2 1 Scopes and Namespaces Example This is an example demonstrating how to reference the different scopes and namespaces and how global and nonlocal affect variable binding def scope_test def do_local spam local spam def do_nonlocal nonlocal spam spam nonlocal spam def do_global global spam spam global spam spam test spam do_local print After local assignment spam do_nonlocal print After nonlocal assignment spam do_global print After global assignment spam scope_test print In global scope spam The output of the example code is After local assignment test spam After nonlocal assignment nonlocal spam After global assignment nonlocal spam In global scope global spam Note how the local assignment which is default didn t change scope_test s binding of spam The nonlocal assignment changed scope_test s binding of spam and the global assignment changed the module level binding You can also see that there was no previous binding for spam before the global assignment 9 3 A First Look at Classes Classes introduce a little bit of new syntax three new object types and some new semantics 9 3 1 Class Definition Syntax The simplest form of class definition looks like this class ClassName statement 1 statement N Class definitions like function definitions def statements must be executed before they have any effect You could conceivably place a class definition in a branch of an if statement or inside a function In practice the statements inside a class definition will usually be function definitions but other statements are allowed and sometimes useful we ll come back to this later The function definitions inside a class normally have a peculiar form of argument list dictated by the calling conventions for methods again this is explained later When a class definition is entered a new namespace is created and used as the local scope thus all assignments to local variables go into this new namespace In particular function definitions bind the name of the new function here When a class definition is left normally via the end a class object is created This is basically a wrapper around the contents of the namespace created by the class definition we ll learn more about class objects in the next section The original local scope the one in effect just before the class definition was entered is reinstated and the class object is bound here to the class name given in the class definition header ClassName in the example 9 3 2 Class Objects Class objects support two kinds of operations attribute references and instantiation Attribute references use the standard syntax used for all attribute references in Python obj name Valid attribute names are all the names that were in the class s namespace when the class object was created So if the class definition looked like this class MyClass A simple example class i 12345 def f self return hello world then MyClass i and MyClass f are valid attribute references returning an integer and a function object respectively Class attributes can also be assigned to so you can change the value of MyClass i by assignment __doc__ is also a valid attribute returning the docstring belonging to the class A simple example class Class instantiation uses function notation Just pretend that the class object is a parameterless function that returns a new instance of the class For example assuming the above class x MyClass creates a new instance of the class and assigns this object to the local variable x The instantiation operation calling a class object creates an empty object Many classes like to create objects with instances customized to a specific initial state Therefore a class may define a special method named __init__ like this def __init__ self self data When a class defines an __init__ method class instantiation automatically invokes __init__ for the newly created class instance So in this example a new initialized instance can be obtained by x MyClass Of course the __init__ method may have a,en
549,rguments for greater flexibility In that case arguments given to the class instantiation operator are passed on to __init__ For example class Complex def __init__ self realpart imagpart self r realpart self i imagpart x Complex 3 0 4 5 x r x i 3 0 4 5 9 3 3 Instance Objects Now what can we do with instance objects The only operations understood by instance objects are attribute references There are two kinds of valid attribute names data attributes and methods data attributes correspond to instance variables in Smalltalk and to data members in C Data attributes need not be declared like local variables they spring into existence when they are first assigned to For example if x is the instance of MyClass created above the following piece of code will print the value 16 without leaving a trace x counter 1 while x counter 10 x counter x counter 2 print x counter del x counter The other kind of instance attribute reference is a method A method is a function that belongs to an object In Python the term method is not unique to class instances other object types can have methods as well For example list objects have methods called append insert remove sort and so on However in the following discussion we ll use the term method exclusively to mean methods of class instance objects unless explicitly stated otherwise Valid method names of an instance object depend on its class By definition all attributes of a class that are function objects define corresponding methods of its instances So in our example x f is a valid method reference since MyClass f is a function but x i is not since MyClass i is not But x f is not the same thing as MyClass f it is a method object not a function object 9 3 4 Method Objects Usually a method is called right after it is bound x f In the MyClass example this will return the string hello world However it is not necessary to call a method right away x f is a method object and can be stored away and called at a later time For example xf x f while True print xf will continue to print hello world until the end of time What exactly happens when a method is called You may have noticed that x f was called without an argument above even though the function definition for f specified an argument What happened to the argument Surely Python raises an exception when a function that requires an argument is called without any even if the argument isn t actually used Actually you may have guessed the answer the special thing about methods is that the instance object is passed as the first argument of the function In our example the call x f is exactly equivalent to MyClass f x In general calling a method with a list of n arguments is equivalent to calling the corresponding function with an argument list that is created by inserting the method s instance object before the first argument In general methods work as follows When a non data attribute of an instance is referenced the instance s class is searched If the name denotes a valid class attribute that is a function object references to both the instance object and the function object are packed into a method object When the method object is called with an argument list a new argument list is constructed from the instance object and the argument list and the function object is called with this new argument list 9 3 5 Class and Instance Variables Generally speaking instance variables are for data unique to each instance and class variables are for attributes and methods shared by all instances of the class class Dog kind canine class variable shared by all instances def __init__ self name self name name instance variable unique to each instance d Dog Fido e Dog Buddy d kind shared by all dogs canine e kind shared by all dogs canine d name unique to d Fido e name unique to e Buddy As discussed in A Word About Names and Objects shared data can have possibly surprising effects with involving mutable objects such as lists and dictionaries For example the tricks list in the following code should not be used as a class variable because just a single list would be shared,en
550, by all Dog instances class Dog tricks mistaken use of a class variable def __init__ self name self name name def add_trick self trick self tricks append trick d Dog Fido e Dog Buddy d add_trick roll over e add_trick play dead d tricks unexpectedly shared by all dogs roll over play dead Correct design of the class should use an instance variable instead class Dog def __init__ self name self name name self tricks creates a new empty list for each dog def add_trick self trick self tricks append trick d Dog Fido e Dog Buddy d add_trick roll over e add_trick play dead d tricks roll over e tricks play dead 9 4 Random Remarks If the same attribute name occurs in both an instance and in a class then attribute lookup prioritizes the instance class Warehouse purpose storage region west w1 Warehouse print w1 purpose w1 region storage west w2 Warehouse w2 region east print w2 purpose w2 region storage east Data attributes may be referenced by methods as well as by ordinary users clients of an object In other words classes are not usable to implement pure abstract data types In fact nothing in Python makes it possible to enforce data hiding it is all based upon convention On the other hand the Python implementation written in C can completely hide implementation details and control access to an object if necessary this can be used by extensions to Python written in C Clients should use data attributes with care clients may mess up invariants maintained by the methods by stamping on their data attributes Note that clients may add data attributes of their own to an instance object without affecting the validity of the methods as long as name conflicts are avoided again a naming convention can save a lot of headaches here There is no shorthand for referencing data attributes or other methods from within methods I find that this actually increases the readability of methods there is no chance of confusing local variables and instance variables when glancing through a method Often the first argument of a method is called self This is nothing more than a convention the name self has absolutely no special meaning to Python Note however that by not following the convention your code may be less readable to other Python programmers and it is also conceivable that a class browser program might be written that relies upon such a convention Any function object that is a class attribute defines a method for instances of that class It is not necessary that the function definition is textually enclosed in the class definition assigning a function object to a local variable in the class is also ok For example Function defined outside the class def f1 self x y return min x x y class C f f1 def g self return hello world h g Now f g and h are all attributes of class C that refer to function objects and consequently they are all methods of instances of C h being exactly equivalent to g Note that this practice usually only serves to confuse the reader of a program Methods may call other methods by using method attributes of the self argument class Bag def __init__ self self data def add self x self data append x def addtwice self x self add x self add x Methods may reference global names in the same way as ordinary functions The global scope associated with a method is the module containing its definition A class is never used as a global scope While one rarely encounters a good reason for using global data in a method there are many legitimate uses of the global scope for one thing functions and modules imported into the global scope can be used by methods as well as functions and classes defined in it Usually the class containing the method is itself defined in this global scope and in the next section we ll find some good reasons why a method would want to reference its own class Each value is an object and therefore has a class also called its type It is stored as object __class__ 9 5 Inheritance Of course a language feature would not be worthy of the name class without supporting inheritance The syntax for a derived class definition looks like this,en
551, class DerivedClassName BaseClassName statement 1 statement N The name BaseClassName must be defined in a namespace accessible from the scope containing the derived class definition In place of a base class name other arbitrary expressions are also allowed This can be useful for example when the base class is defined in another module class DerivedClassName modname BaseClassName Execution of a derived class definition proceeds the same as for a base class When the class object is constructed the base class is remembered This is used for resolving attribute references if a requested attribute is not found in the class the search proceeds to look in the base class This rule is applied recursively if the base class itself is derived from some other class There s nothing special about instantiation of derived classes DerivedClassName creates a new instance of the class Method references are resolved as follows the corresponding class attribute is searched descending down the chain of base classes if necessary and the method reference is valid if this yields a function object Derived classes may override methods of their base classes Because methods have no special privileges when calling other methods of the same object a method of a base class that calls another method defined in the same base class may end up calling a method of a derived class that overrides it For C programmers all methods in Python are effectively virtual An overriding method in a derived class may in fact want to extend rather than simply replace the base class method of the same name There is a simple way to call the base class method directly just call BaseClassName methodname self arguments This is occasionally useful to clients as well Note that this only works if the base class is accessible as BaseClassName in the global scope Python has two built in functions that work with inheritance Use isinstance to check an instance s type isinstance obj int will be True only if obj __class__ is int or some class derived from int Use issubclass to check class inheritance issubclass bool int is True since bool is a subclass of int However issubclass float int is False since float is not a subclass of int 9 5 1 Multiple Inheritance Python supports a form of multiple inheritance as well A class definition with multiple base classes looks like this class DerivedClassName Base1 Base2 Base3 statement 1 statement N For most purposes in the simplest cases you can think of the search for attributes inherited from a parent class as depth first left to right not searching twice in the same class where there is an overlap in the hierarchy Thus if an attribute is not found in DerivedClassName it is searched for in Base1 then recursively in the base classes of Base1 and if it was not found there it was searched for in Base2 and so on In fact it is slightly more complex than that the method resolution order changes dynamically to support cooperative calls to super This approach is known in some other multiple inheritance languages as call next method and is more powerful than the super call found in single inheritance languages Dynamic ordering is necessary because all cases of multiple inheritance exhibit one or more diamond relationships where at least one of the parent classes can be accessed through multiple paths from the bottommost class For example all classes inherit from object so any case of multiple inheritance provides more than one path to reach object To keep the base classes from being accessed more than once the dynamic algorithm linearizes the search order in a way that preserves the left to right ordering specified in each class that calls each parent only once and that is monotonic meaning that a class can be subclassed without affecting the precedence order of its parents Taken together these properties make it possible to design reliable and extensible classes with multiple inheritance For more detail see https www python org download releases 2 3 mro 9 6 Private Variables Private instance variables that cannot be accessed except from inside an object,en
552, don t exist in Python However there is a convention that is followed by most Python code a name prefixed with an underscore e g _spam should be treated as a non public part of the API whether it is a function a method or a data member It should be considered an implementation detail and subject to change without notice Since there is a valid use case for class private members namely to avoid name clashes of names with names defined by subclasses there is limited support for such a mechanism called name mangling Any identifier of the form __spam at least two leading underscores at most one trailing underscore is textually replaced with _classname__spam where classname is the current class name with leading underscore s stripped This mangling is done without regard to the syntactic position of the identifier as long as it occurs within the definition of a class Name mangling is helpful for letting subclasses override methods without breaking intraclass method calls For example class Mapping def __init__ self iterable self items_list self __update iterable def update self iterable for item in iterable self items_list append item __update update private copy of original update method class MappingSubclass Mapping def update self keys values provides new signature for update but does not break __init__ for item in zip keys values self items_list append item The above example would work even if MappingSubclass were to introduce a __update identifier since it is replaced with _Mapping__update in the Mapping class and _MappingSubclass__update in the MappingSubclass class respectively Note that the mangling rules are designed mostly to avoid accidents it still is possible to access or modify a variable that is considered private This can even be useful in special circumstances such as in the debugger Notice that code passed to exec or eval does not consider the classname of the invoking class to be the current class this is similar to the effect of the global statement the effect of which is likewise restricted to code that is byte compiled together The same restriction applies to getattr setattr and delattr as well as when referencing __dict__ directly 9 7 Odds and Ends Sometimes it is useful to have a data type similar to the Pascal record or C struct bundling together a few named data items The idiomatic approach is to use dataclasses for this purpose from dataclasses import dataclass dataclass class Employee name str dept str salary int john Employee john computer lab 1000 john dept computer lab john salary 1000 A piece of Python code that expects a particular abstract data type can often be passed a class that emulates the methods of that data type instead For instance if you have a function that formats some data from a file object you can define a class with methods read and readline that get the data from a string buffer instead and pass it as an argument Instance method objects have attributes too m __self__ is the instance object with the method m and m __func__ is the function object corresponding to the method 9 8 Iterators By now you have probably noticed that most container objects can be looped over using a for statement for element in 1 2 3 print element for element in 1 2 3 print element for key in one 1 two 2 print key for char in 123 print char for line in open myfile txt print line end This style of access is clear concise and convenient The use of iterators pervades and unifies Python Behind the scenes the for statement calls iter on the container object The function returns an iterator object that defines the method __next__ which accesses elements in the container one at a time When there are no more elements __next__ raises a StopIteration exception which tells the for loop to terminate You can call the __next__ method using the next built in function this example shows how it all works s abc it iter s it str_iterator object at 0x10c90e650 next it a next it b next it c next it Traceback most recent call last File stdin line 1 in module next it StopIteration Having seen the mechanics behind the iterator pr,en
553,otocol it is easy to add iterator behavior to your classes Define an __iter__ method which returns an object with a __next__ method If the class defines __next__ then __iter__ can just return self class Reverse Iterator for looping over a sequence backwards def __init__ self data self data data self index len data def __iter__ self return self def __next__ self if self index 0 raise StopIteration self index self index 1 return self data self index rev Reverse spam iter rev __main__ Reverse object at 0x00A1DB50 for char in rev print char m a p s 9 9 Generators Generators are a simple and powerful tool for creating iterators They are written like regular functions but use the yield statement whenever they want to return data Each time next is called on it the generator resumes where it left off it remembers all the data values and which statement was last executed An example shows that generators can be trivially easy to create def reverse data for index in range len data 1 1 1 yield data index for char in reverse golf print char f l o g Anything that can be done with generators can also be done with class based iterators as described in the previous section What makes generators so compact is that the __iter__ and __next__ methods are created automatically Another key feature is that the local variables and execution state are automatically saved between calls This made the function easier to write and much more clear than an approach using instance variables like self index and self data In addition to automatic method creation and saving program state when generators terminate they automatically raise StopIteration In combination these features make it easy to create iterators with no more effort than writing a regular function 9 10 Generator Expressions Some simple generators can be coded succinctly as expressions using a syntax similar to list comprehensions but with parentheses instead of square brackets These expressions are designed for situations where the generator is used right away by an enclosing function Generator expressions are more compact but less versatile than full generator definitions and tend to be more memory friendly than equivalent list comprehensions Examples sum i i for i in range 10 sum of squares 285 xvec 10 20 30 yvec 7 5 3 sum x y for x y in zip xvec yvec dot product 260 unique_words set word for line in page for word in line split valedictorian max student gpa student name for student in graduates data golf list data i for i in range len data 1 1 1 f l o g Footnotes 1 Except for one thing Module objects have a secret read only attribute called __dict__ which returns the dictionary used to implement the module s namespace the name __dict__ is an attribute but not a global name Obviously using this violates the abstraction of namespace implementation and should be restricted to things like post mortem debuggers,en
554,selectors High level I O multiplexing New in version 3 4 Source code Lib selectors py Introduction This module allows high level and efficient I O multiplexing built upon the select module primitives Users are encouraged to use this module instead unless they want precise control over the OS level primitives used It defines a BaseSelector abstract base class along with several concrete implementations KqueueSelector EpollSelector that can be used to wait for I O readiness notification on multiple file objects In the following file object refers to any object with a fileno method or a raw file descriptor See file object DefaultSelector is an alias to the most efficient implementation available on the current platform this should be the default choice for most users Note The type of file objects supported depends on the platform on Windows sockets are supported but not pipes whereas on Unix both are supported some other types may be supported as well such as fifos or special file devices See also select Low level I O multiplexing module Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information Classes Classes hierarchy BaseSelector SelectSelector PollSelector EpollSelector DevpollSelector KqueueSelector In the following events is a bitwise mask indicating which I O events should be waited for on a given file object It can be a combination of the modules constants below Constant Meaning selectors EVENT_READ Available for read selectors EVENT_WRITE Available for write class selectors SelectorKey A SelectorKey is a namedtuple used to associate a file object to its underlying file descriptor selected event mask and attached data It is returned by several BaseSelector methods fileobj File object registered fd Underlying file descriptor events Events that must be waited for on this file object data Optional opaque data associated to this file object for example this could be used to store a per client session ID class selectors BaseSelector A BaseSelector is used to wait for I O event readiness on multiple file objects It supports file stream registration unregistration and a method to wait for I O events on those streams with an optional timeout It s an abstract base class so cannot be instantiated Use DefaultSelector instead or one of SelectSelector KqueueSelector etc if you want to specifically use an implementation and your platform supports it BaseSelector and its concrete implementations support the context manager protocol abstractmethod register fileobj events data None Register a file object for selection monitoring it for I O events fileobj is the file object to monitor It may either be an integer file descriptor or an object with a fileno method events is a bitwise mask of events to monitor data is an opaque object This returns a new SelectorKey instance or raises a ValueError in case of invalid event mask or file descriptor or KeyError if the file object is already registered abstractmethod unregister fileobj Unregister a file object from selection removing it from monitoring A file object shall be unregistered prior to being closed fileobj must be a file object previously registered This returns the associated SelectorKey instance or raises a KeyError if fileobj is not registered It will raise ValueError if fileobj is invalid e g it has no fileno method or its fileno method has an invalid return value modify fileobj events data None Change a registered file object s monitored events or attached data This is equivalent to BaseSelector unregister fileobj followed by BaseSelector register fileobj events data except that it can be implemented more efficiently This returns a new SelectorKey instance or raises a ValueError in case of invalid event mask or file descriptor or KeyError if the file object is not registered abstractmethod select timeout None Wait until some registered file objects become ready or the timeout expires If timeout 0 this specifies the maximum wait time in seconds If ti,en
555,meout 0 the call won t block and will report the currently ready file objects If timeout is None the call will block until a monitored file object becomes ready This returns a list of key events tuples one for each ready file object key is the SelectorKey instance corresponding to a ready file object events is a bitmask of events ready on this file object Note This method can return before any file object becomes ready or the timeout has elapsed if the current process receives a signal in this case an empty list will be returned Changed in version 3 5 The selector is now retried with a recomputed timeout when interrupted by a signal if the signal handler did not raise an exception see PEP 475 for the rationale instead of returning an empty list of events before the timeout close Close the selector This must be called to make sure that any underlying resource is freed The selector shall not be used once it has been closed get_key fileobj Return the key associated with a registered file object This returns the SelectorKey instance associated to this file object or raises KeyError if the file object is not registered abstractmethod get_map Return a mapping of file objects to selector keys This returns a Mapping instance mapping registered file objects to their associated SelectorKey instance class selectors DefaultSelector The default selector class using the most efficient implementation available on the current platform This should be the default choice for most users class selectors SelectSelector select select based selector class selectors PollSelector select poll based selector class selectors EpollSelector select epoll based selector fileno This returns the file descriptor used by the underlying select epoll object class selectors DevpollSelector select devpoll based selector fileno This returns the file descriptor used by the underlying select devpoll object New in version 3 5 class selectors KqueueSelector select kqueue based selector fileno This returns the file descriptor used by the underlying select kqueue object Examples Here is a simple echo server implementation import selectors import socket sel selectors DefaultSelector def accept sock mask conn addr sock accept Should be ready print accepted conn from addr conn setblocking False sel register conn selectors EVENT_READ read def read conn mask data conn recv 1000 Should be ready if data print echoing repr data to conn conn send data Hope it won t block else print closing conn sel unregister conn conn close sock socket socket sock bind localhost 1234 sock listen 100 sock setblocking False sel register sock selectors EVENT_READ accept while True events sel select for key mask in events callback key data callback key fileobj mask,en
556,email errors Exception and Defect classes Source code Lib email errors py The following exception classes are defined in the email errors module exception email errors MessageError This is the base class for all exceptions that the email package can raise It is derived from the standard Exception class and defines no additional methods exception email errors MessageParseError This is the base class for exceptions raised by the Parser class It is derived from MessageError This class is also used internally by the parser used by headerregistry exception email errors HeaderParseError Raised under some error conditions when parsing the RFC 5322 headers of a message this class is derived from MessageParseError The set_boundary method will raise this error if the content type is unknown when the method is called Header may raise this error for certain base64 decoding errors and when an attempt is made to create a header that appears to contain an embedded header that is there is what is supposed to be a continuation line that has no leading whitespace and looks like a header exception email errors BoundaryError Deprecated and no longer used exception email errors MultipartConversionError Raised when a payload is added to a Message object using add_payload but the payload is already a scalar and the message s Content Type main type is not either multipart or missing MultipartConversionError multiply inherits from MessageError and the built in TypeError Since Message add_payload is deprecated this exception is rarely raised in practice However the exception may also be raised if the attach method is called on an instance of a class derived from MIMENonMultipart e g MIMEImage exception email errors MessageDefect This is the base class for all defects found when parsing email messages It is derived from ValueError exception email errors HeaderDefect This is the base class for all defects found when parsing email headers It is derived from MessageDefect Here is the list of the defects that the FeedParser can find while parsing messages Note that the defects are added to the message where the problem was found so for example if a message nested inside a multipart alternative had a malformed header that nested message object would have a defect but the containing messages would not All defect classes are subclassed from email errors MessageDefect NoBoundaryInMultipartDefect A message claimed to be a multipart but had no boundary parameter StartBoundaryNotFoundDefect The start boundary claimed in the Content Type header was never found CloseBoundaryNotFoundDefect A start boundary was found but no corresponding close boundary was ever found New in version 3 3 FirstHeaderLineIsContinuationDefect The message had a continuation line as its first header line MisplacedEnvelopeHeaderDefect A Unix From header was found in the middle of a header block MissingHeaderBodySeparatorDefect A line was found while parsing headers that had no leading white space but contained no Parsing continues assuming that the line represents the first line of the body New in version 3 3 MalformedHeaderDefect A header was found that was missing a colon or was otherwise malformed Deprecated since version 3 3 This defect has not been used for several Python versions MultipartInvariantViolationDefect A message claimed to be a multipart but no subparts were found Note that when a message has this defect its is_multipart method may return False even though its content type claims to be multipart InvalidBase64PaddingDefect When decoding a block of base64 encoded bytes the padding was not correct Enough padding is added to perform the decode but the resulting decoded bytes may be invalid InvalidBase64CharactersDefect When decoding a block of base64 encoded bytes characters outside the base64 alphabet were encountered The characters are ignored but the resulting decoded bytes may be invalid InvalidBase64LengthDefect When decoding a block of base64 encoded bytes the number of non padding base64 characters was invalid 1 more than a multiple of 4 The encoded block was kept as,en
557, is InvalidDateDefect When decoding an invalid or unparsable date field The original value is kept as is,en
558,textwrap Text wrapping and filling Source code Lib textwrap py The textwrap module provides some convenience functions as well as TextWrapper the class that does all the work If you re just wrapping or filling one or two text strings the convenience functions should be good enough otherwise you should use an instance of TextWrapper for efficiency textwrap wrap text width 70 initial_indent subsequent_indent expand_tabs True replace_whitespace True fix_sentence_endings False break_long_words True drop_whitespace True break_on_hyphens True tabsize 8 max_lines None placeholder Wraps the single paragraph in text a string so every line is at most width characters long Returns a list of output lines without final newlines Optional keyword arguments correspond to the instance attributes of TextWrapper documented below See the TextWrapper wrap method for additional details on how wrap behaves textwrap fill text width 70 initial_indent subsequent_indent expand_tabs True replace_whitespace True fix_sentence_endings False break_long_words True drop_whitespace True break_on_hyphens True tabsize 8 max_lines None placeholder Wraps the single paragraph in text and returns a single string containing the wrapped paragraph fill is shorthand for n join wrap text In particular fill accepts exactly the same keyword arguments as wrap textwrap shorten text width fix_sentence_endings False break_long_words True break_on_hyphens True placeholder Collapse and truncate the given text to fit in the given width First the whitespace in text is collapsed all whitespace is replaced by single spaces If the result fits in the width it is returned Otherwise enough words are dropped from the end so that the remaining words plus the placeholder fit within width textwrap shorten Hello world width 12 Hello world textwrap shorten Hello world width 11 Hello textwrap shorten Hello world width 10 placeholder Hello Optional keyword arguments correspond to the instance attributes of TextWrapper documented below Note that the whitespace is collapsed before the text is passed to the TextWrapper fill function so changing the value of tabsize expand_tabs drop_whitespace and replace_whitespace will have no effect New in version 3 4 textwrap dedent text Remove any common leading whitespace from every line in text This can be used to make triple quoted strings line up with the left edge of the display while still presenting them in the source code in indented form Note that tabs and spaces are both treated as whitespace but they are not equal the lines hello and thello are considered to have no common leading whitespace Lines containing only whitespace are ignored in the input and normalized to a single newline character in the output For example def test end first line with to avoid the empty line s hello world print repr s prints hello n world n print repr dedent s prints hello n world n textwrap indent text prefix predicate None Add prefix to the beginning of selected lines in text Lines are separated by calling text splitlines True By default prefix is added to all lines that do not consist solely of whitespace including any line endings For example s hello n n nworld indent s hello n n n world The optional predicate argument can be used to control which lines are indented For example it is easy to add prefix to even empty and whitespace only lines print indent s lambda line True hello world New in version 3 3 wrap fill and shorten work by creating a TextWrapper instance and calling a single method on it That instance is not reused so for applications that process many text strings using wrap and or fill it may be more efficient to create your own TextWrapper object Text is preferably wrapped on whitespaces and right after the hyphens in hyphenated words only then will long words be broken if necessary unless TextWrapper break_long_words is set to false class textwrap TextWrapper kwargs The TextWrapper constructor accepts a number of optional keyword arguments Each keyword argument corresponds to an instance attribute so for example wrapper TextWrapper initial_indent i,en
559,s the same as wrapper TextWrapper wrapper initial_indent You can re use the same TextWrapper object many times and you can change any of its options through direct assignment to instance attributes between uses The TextWrapper instance attributes and keyword arguments to the constructor are as follows width default 70 The maximum length of wrapped lines As long as there are no individual words in the input text longer than width TextWrapper guarantees that no output line will be longer than width characters expand_tabs default True If true then all tab characters in text will be expanded to spaces using the expandtabs method of text tabsize default 8 If expand_tabs is true then all tab characters in text will be expanded to zero or more spaces depending on the current column and the given tab size New in version 3 3 replace_whitespace default True If true after tab expansion but before wrapping the wrap method will replace each whitespace character with a single space The whitespace characters replaced are as follows tab newline vertical tab formfeed and carriage return t n v f r Note If expand_tabs is false and replace_whitespace is true each tab character will be replaced by a single space which is not the same as tab expansion Note If replace_whitespace is false newlines may appear in the middle of a line and cause strange output For this reason text should be split into paragraphs using str splitlines or similar which are wrapped separately drop_whitespace default True If true whitespace at the beginning and ending of every line after wrapping but before indenting is dropped Whitespace at the beginning of the paragraph however is not dropped if non whitespace follows it If whitespace being dropped takes up an entire line the whole line is dropped initial_indent default String that will be prepended to the first line of wrapped output Counts towards the length of the first line The empty string is not indented subsequent_indent default String that will be prepended to all lines of wrapped output except the first Counts towards the length of each line except the first fix_sentence_endings default False If true TextWrapper attempts to detect sentence endings and ensure that sentences are always separated by exactly two spaces This is generally desired for text in a monospaced font However the sentence detection algorithm is imperfect it assumes that a sentence ending consists of a lowercase letter followed by one of or possibly followed by one of or followed by a space One problem with this algorithm is that it is unable to detect the difference between Dr in Dr Frankenstein s monster and Spot in See Spot See Spot run fix_sentence_endings is false by default Since the sentence detection algorithm relies on string lowercase for the definition of lowercase letter and a convention of using two spaces after a period to separate sentences on the same line it is specific to English language texts break_long_words default True If true then words longer than width will be broken in order to ensure that no lines are longer than width If it is false long words will not be broken and some lines may be longer than width Long words will be put on a line by themselves in order to minimize the amount by which width is exceeded break_on_hyphens default True If true wrapping will occur preferably on whitespaces and right after hyphens in compound words as it is customary in English If false only whitespaces will be considered as potentially good places for line breaks but you need to set break_long_words to false if you want truly insecable words Default behaviour in previous versions was to always allow breaking hyphenated words max_lines default None If not None then the output will contain at most max_lines lines with placeholder appearing at the end of the output New in version 3 4 placeholder default String that will appear at the end of the output text if it has been truncated New in version 3 4 TextWrapper also provides some public methods analogous to the module level convenience functions wrap text Wraps the single paragraph in,en
560, text a string so every line is at most width characters long All wrapping options are taken from instance attributes of the TextWrapper instance Returns a list of output lines without final newlines If the wrapped output has no content the returned list is empty fill text Wraps the single paragraph in text and returns a single string containing the wrapped paragraph,en
561,dbm Interfaces to Unix databases Source code Lib dbm __init__ py dbm is a generic interface to variants of the DBM database dbm gnu or dbm ndbm If none of these modules is installed the slow but simple implementation in module dbm dumb will be used There is a third party interface to the Oracle Berkeley DB exception dbm error A tuple containing the exceptions that can be raised by each of the supported modules with a unique exception also named dbm error as the first item the latter is used when dbm error is raised dbm whichdb filename This function attempts to guess which of the several simple database modules available dbm gnu dbm ndbm or dbm dumb should be used to open a given file Return one of the following values None if the file can t be opened because it s unreadable or doesn t exist the empty string if the file s format can t be guessed a string containing the required module name such as dbm ndbm or dbm gnu Changed in version 3 11 filename accepts a path like object dbm open file flag r mode 0o666 Open a database and return the corresponding database object Parameters file path like object The database file to open If the database file already exists the whichdb function is used to determine its type and the appropriate module is used if it does not exist the first submodule listed above that can be imported is used flag str r default Open existing database for reading only w Open existing database for reading and writing c Open database for reading and writing creating it if it doesn t exist n Always create a new empty database open for reading and writing mode int The Unix file access mode of the file default octal 0o666 used only when the database has to be created Changed in version 3 11 file accepts a path like object The object returned by open supports the same basic functionality as a dict keys and their corresponding values can be stored retrieved and deleted and the in operator and the keys method are available as well as get and setdefault methods Key and values are always stored as bytes This means that when strings are used they are implicitly converted to the default encoding before being stored These objects also support being used in a with statement which will automatically close them when done Changed in version 3 2 get and setdefault methods are now available for all dbm backends Changed in version 3 4 Added native support for the context management protocol to the objects returned by open Changed in version 3 8 Deleting a key from a read only database raises a database module specific exception instead of KeyError The following example records some hostnames and a corresponding title and then prints out the contents of the database import dbm Open database creating it if necessary with dbm open cache c as db Record some values db b hello b there db www python org Python Website db www cnn com Cable News Network Note that the keys are considered bytes now assert db b www python org b Python Website Notice how the value is now in bytes assert db www cnn com b Cable News Network Often used methods of the dict interface work too print db get python org b not present Storing a non string key or value will raise an exception most likely a TypeError db www yahoo com 4 db is automatically closed when leaving the with statement See also Module shelve Persistence module which stores non string data The individual submodules are described in the following sections dbm gnu GNU database manager Source code Lib dbm gnu py The dbm gnu module provides an interface to the GDBM GNU dbm library similar to the dbm ndbm module but with additional functionality like crash tolerance Note The file formats created by dbm gnu and dbm ndbm are incompatible and can not be used interchangeably exception dbm gnu error Raised on dbm gnu specific errors such as I O errors KeyError is raised for general mapping errors like specifying an incorrect key dbm gnu open filename flag r mode 0o666 Open a GDBM database and return a gdbm object Parameters filename path like object The database file to open flag str r default Open exi,en
562,sting database for reading only w Open existing database for reading and writing c Open database for reading and writing creating it if it doesn t exist n Always create a new empty database open for reading and writing The following additional characters may be appended to control how the database is opened f Open the database in fast mode Writes to the database will not be synchronized s Synchronized mode Changes to the database will be written immediately to the file u Do not lock database Not all flags are valid for all versions of GDBM See the open_flags member for a list of supported flag characters mode int The Unix file access mode of the file default octal 0o666 used only when the database has to be created Raises error If an invalid flag argument is passed Changed in version 3 11 filename accepts a path like object dbm gnu open_flags A string of characters the flag parameter of open supports gdbm objects behave similar to mappings but items and values methods are not supported The following methods are also provided gdbm firstkey It s possible to loop over every key in the database using this method and the nextkey method The traversal is ordered by GDBM s internal hash values and won t be sorted by the key values This method returns the starting key gdbm nextkey key Returns the key that follows key in the traversal The following code prints every key in the database db without having to create a list in memory that contains them all k db firstkey while k is not None print k k db nextkey k gdbm reorganize If you have carried out a lot of deletions and would like to shrink the space used by the GDBM file this routine will reorganize the database gdbm objects will not shorten the length of a database file except by using this reorganization otherwise deleted file space will be kept and reused as new key value pairs are added gdbm sync When the database has been opened in fast mode this method forces any unwritten data to be written to the disk gdbm close Close the GDBM database dbm ndbm New Database Manager Source code Lib dbm ndbm py The dbm ndbm module provides an interface to the NDBM New Database Manager library This module can be used with the classic NDBM interface or the GDBM GNU dbm compatibility interface Note The file formats created by dbm gnu and dbm ndbm are incompatible and can not be used interchangeably Warning The NDBM library shipped as part of macOS has an undocumented limitation on the size of values which can result in corrupted database files when storing values larger than this limit Reading such corrupted files can result in a hard crash segmentation fault exception dbm ndbm error Raised on dbm ndbm specific errors such as I O errors KeyError is raised for general mapping errors like specifying an incorrect key dbm ndbm library Name of the NDBM implementation library used dbm ndbm open filename flag r mode 0o666 Open an NDBM database and return an ndbm object Parameters filename path like object The basename of the database file without the dir or pag extensions flag str r default Open existing database for reading only w Open existing database for reading and writing c Open database for reading and writing creating it if it doesn t exist n Always create a new empty database open for reading and writing mode int The Unix file access mode of the file default octal 0o666 used only when the database has to be created ndbm objects behave similar to mappings but items and values methods are not supported The following methods are also provided Changed in version 3 11 Accepts path like object for filename ndbm close Close the NDBM database dbm dumb Portable DBM implementation Source code Lib dbm dumb py Note The dbm dumb module is intended as a last resort fallback for the dbm module when a more robust module is not available The dbm dumb module is not written for speed and is not nearly as heavily used as the other database modules The dbm dumb module provides a persistent dict like interface which is written entirely in Python Unlike other dbm backends such as dbm gnu no external library is req,en
563,uired The dbm dumb module defines the following exception dbm dumb error Raised on dbm dumb specific errors such as I O errors KeyError is raised for general mapping errors like specifying an incorrect key dbm dumb open filename flag c mode 0o666 Open a dbm dumb database The returned database object behaves similar to a mapping in addition to providing sync and close methods Parameters filename The basename of the database file without extensions A new database creates the following files filename dat filename dir flag str r Open existing database for reading only w Open existing database for reading and writing c default Open database for reading and writing creating it if it doesn t exist n Always create a new empty database open for reading and writing mode int The Unix file access mode of the file default octal 0o666 used only when the database has to be created Warning It is possible to crash the Python interpreter when loading a database with a sufficiently large complex entry due to stack depth limitations in Python s AST compiler Changed in version 3 5 open always creates a new database when flag is n Changed in version 3 8 A database opened read only if flag is r A database is not created if it does not exist if flag is r or w Changed in version 3 11 filename accepts a path like object In addition to the methods provided by the collections abc MutableMapping class the following methods are provided dumbdbm sync Synchronize the on disk directory and data files This method is called by the Shelve sync method dumbdbm close Close the database,en
564,multiprocessing shared_memory Shared memory for direct access across processes Source code Lib multiprocessing shared_memory py New in version 3 8 This module provides a class SharedMemory for the allocation and management of shared memory to be accessed by one or more processes on a multicore or symmetric multiprocessor SMP machine To assist with the life cycle management of shared memory especially across distinct processes a BaseManager subclass SharedMemoryManager is also provided in the multiprocessing managers module In this module shared memory refers to POSIX style shared memory blocks though is not necessarily implemented explicitly as such and does not refer to distributed shared memory This style of shared memory permits distinct processes to potentially read and write to a common or shared region of volatile memory Processes are conventionally limited to only have access to their own process memory space but shared memory permits the sharing of data between processes avoiding the need to instead send messages between processes containing that data Sharing data directly via memory can provide significant performance benefits compared to sharing data via disk or socket or other communications requiring the serialization deserialization and copying of data class multiprocessing shared_memory SharedMemory name None create False size 0 Create an instance of the SharedMemory class for either creating a new shared memory block or attaching to an existing shared memory block Each shared memory block is assigned a unique name In this way one process can create a shared memory block with a particular name and a different process can attach to that same shared memory block using that same name As a resource for sharing data across processes shared memory blocks may outlive the original process that created them When one process no longer needs access to a shared memory block that might still be needed by other processes the close method should be called When a shared memory block is no longer needed by any process the unlink method should be called to ensure proper cleanup Parameters name str None The unique name for the requested shared memory specified as a string When creating a new shared memory block if None the default is supplied for the name a novel name will be generated create bool Control whether a new shared memory block is created True or an existing shared memory block is attached False size int The requested number of bytes when creating a new shared memory block Because some platforms choose to allocate chunks of memory based upon that platform s memory page size the exact size of the shared memory block may be larger or equal to the size requested When attaching to an existing shared memory block the size parameter is ignored close Close access to the shared memory from this instance In order to ensure proper cleanup of resources all instances should call close once the instance is no longer needed Note that calling close does not cause the shared memory block itself to be destroyed unlink Request that the underlying shared memory block be destroyed In order to ensure proper cleanup of resources unlink should be called once and only once across all processes which have need for the shared memory block After requesting its destruction a shared memory block may or may not be immediately destroyed and this behavior may differ across platforms Attempts to access data inside the shared memory block after unlink has been called may result in memory access errors Note the last process relinquishing its hold on a shared memory block may call unlink and close in either order buf A memoryview of contents of the shared memory block name Read only access to the unique name of the shared memory block size Read only access to size in bytes of the shared memory block The following example demonstrates low level use of SharedMemory instances from multiprocessing import shared_memory shm_a shared_memory SharedMemory create True size 10 type shm_a buf class memoryview buffer shm_a buf len buffer 10 buffer 4 bytearray 22 ,en
565,33 44 55 Modify multiple at once buffer 4 100 Modify single byte at a time Attach to an existing shared memory block shm_b shared_memory SharedMemory shm_a name import array array array b shm_b buf 5 Copy the data into a new array array array b 22 33 44 55 100 shm_b buf 5 b howdy Modify via shm_b using bytes bytes shm_a buf 5 Access via shm_a b howdy shm_b close Close each SharedMemory instance shm_a close shm_a unlink Call unlink only once to release the shared memory The following example demonstrates a practical use of the SharedMemory class with NumPy arrays accessing the same numpy ndarray from two distinct Python shells In the first Python interactive shell import numpy as np a np array 1 1 2 3 5 8 Start with an existing NumPy array from multiprocessing import shared_memory shm shared_memory SharedMemory create True size a nbytes Now create a NumPy array backed by shared memory b np ndarray a shape dtype a dtype buffer shm buf b a Copy the original data into shared memory b array 1 1 2 3 5 8 type b class numpy ndarray type a class numpy ndarray shm name We did not specify a name so one was chosen for us psm_21467_46075 In either the same shell or a new Python shell on the same machine import numpy as np from multiprocessing import shared_memory Attach to the existing shared memory block existing_shm shared_memory SharedMemory name psm_21467_46075 Note that a shape is 6 and a dtype is np int64 in this example c np ndarray 6 dtype np int64 buffer existing_shm buf c array 1 1 2 3 5 8 c 1 888 c array 1 1 2 3 5 888 Back in the first Python interactive shell b reflects this change b array 1 1 2 3 5 888 Clean up from within the second Python shell del c Unnecessary merely emphasizing the array is no longer used existing_shm close Clean up from within the first Python shell del b Unnecessary merely emphasizing the array is no longer used shm close shm unlink Free and release the shared memory block at the very end class multiprocessing managers SharedMemoryManager address authkey A subclass of multiprocessing managers BaseManager which can be used for the management of shared memory blocks across processes A call to start on a SharedMemoryManager instance causes a new process to be started This new process s sole purpose is to manage the life cycle of all shared memory blocks created through it To trigger the release of all shared memory blocks managed by that process call shutdown on the instance This triggers a unlink call on all of the SharedMemory objects managed by that process and then stops the process itself By creating SharedMemory instances through a SharedMemoryManager we avoid the need to manually track and trigger the freeing of shared memory resources This class provides methods for creating and returning SharedMemory instances and for creating a list like object ShareableList backed by shared memory Refer to BaseManager for a description of the inherited address and authkey optional input arguments and how they may be used to connect to an existing SharedMemoryManager service from other processes SharedMemory size Create and return a new SharedMemory object with the specified size in bytes ShareableList sequence Create and return a new ShareableList object initialized by the values from the input sequence The following example demonstrates the basic mechanisms of a SharedMemoryManager from multiprocessing managers import SharedMemoryManager smm SharedMemoryManager smm start Start the process that manages the shared memory blocks sl smm ShareableList range 4 sl ShareableList 0 1 2 3 name psm_6572_7512 raw_shm smm SharedMemory size 128 another_sl smm ShareableList alpha another_sl ShareableList a l p h a name psm_6572_12221 smm shutdown Calls unlink on sl raw_shm and another_sl The following example depicts a potentially more convenient pattern for using SharedMemoryManager objects via the with statement to ensure that all shared memory blocks are released after they are no longer needed with SharedMemoryManager as smm sl smm ShareableList range 2000 Divide the work among two processes storing partial results ,en
566,in sl p1 Process target do_work args sl 0 1000 p2 Process target do_work args sl 1000 2000 p1 start p2 start A multiprocessing Pool might be more efficient p1 join p2 join Wait for all work to complete in both processes total_result sum sl Consolidate the partial results now in sl When using a SharedMemoryManager in a with statement the shared memory blocks created using that manager are all released when the with statement s code block finishes execution class multiprocessing shared_memory ShareableList sequence None name None Provide a mutable list like object where all values stored within are stored in a shared memory block This constrains storable values to the following built in data types int signed 64 bit float bool str less than 10M bytes each when encoded as UTF 8 bytes less than 10M bytes each None It also notably differs from the built in list type in that these lists can not change their overall length i e no append insert etc and do not support the dynamic creation of new ShareableList instances via slicing sequence is used in populating a new ShareableList full of values Set to None to instead attach to an already existing ShareableList by its unique shared memory name name is the unique name for the requested shared memory as described in the definition for SharedMemory When attaching to an existing ShareableList specify its shared memory block s unique name while leaving sequence set to None Note A known issue exists for bytes and str values If they end with x00 nul bytes or characters those may be silently stripped when fetching them by index from the ShareableList This rstrip b x00 behavior is considered a bug and may go away in the future See gh 106939 For applications where rstripping of trailing nulls is a problem work around it by always unconditionally appending an extra non 0 byte to the end of such values when storing and unconditionally removing it when fetching from multiprocessing import shared_memory nul_bug_demo shared_memory ShareableList x00 b x03 x02 x01 x00 x00 x00 nul_bug_demo 0 nul_bug_demo 1 b x03 x02 x01 nul_bug_demo shm unlink padded shared_memory ShareableList x00 x07 b x03 x02 x01 x00 x00 x00 x07 padded 0 1 x00 padded 1 1 b x03 x02 x01 x00 x00 x00 padded shm unlink count value Return the number of occurrences of value index value Return first index position of value Raise ValueError if value is not present format Read only attribute containing the struct packing format used by all currently stored values shm The SharedMemory instance where the values are stored The following example demonstrates basic use of a ShareableList instance from multiprocessing import shared_memory a shared_memory ShareableList howdy b HoWdY 273 154 100 None True 42 type entry for entry in a class str class bytes class float class int class NoneType class bool class int a 2 273 154 a 2 78 5 a 2 78 5 a 2 dry ice Changing data types is supported as well a 2 dry ice a 2 larger than previously allocated storage space Traceback most recent call last ValueError exceeds available storage for existing str a 2 dry ice len a 7 a index 42 6 a count b howdy 0 a count b HoWdY 1 a shm close a shm unlink del a Use of a ShareableList after call to unlink is unsupported The following example depicts how one two or many processes may access the same ShareableList by supplying the name of the shared memory block behind it b shared_memory ShareableList range 5 In a first process c shared_memory ShareableList name b shm name In a second process c ShareableList 0 1 2 3 4 name c 1 999 b 1 999 b shm close c shm close c shm unlink The following examples demonstrates that ShareableList and underlying SharedMemory objects can be pickled and unpickled if needed Note that it will still be the same shared object This happens because the deserialized object has the same unique name and is just attached to an existing object with the same name if the object is still alive import pickle from multiprocessing import shared_memory sl shared_memory ShareableList range 10 list sl 0 1 2 3 4 5 6 7 8 9 deserialized_sl pickle loads pickle dumps ,en
567,sl list deserialized_sl 0 1 2 3 4 5 6 7 8 9 sl 0 1 deserialized_sl 1 2 list sl 1 2 2 3 4 5 6 7 8 9 list deserialized_sl 1 2 2 3 4 5 6 7 8 9 sl shm close sl shm unlink,en
568,Supporting Cyclic Garbage Collection Python s support for detecting and collecting garbage which involves circular references requires support from object types which are containers for other objects which may also be containers Types which do not store references to other objects or which only store references to atomic types such as numbers or strings do not need to provide any explicit support for garbage collection To create a container type the tp_flags field of the type object must include the Py_TPFLAGS_HAVE_GC and provide an implementation of the tp_traverse handler If instances of the type are mutable a tp_clear implementation must also be provided Py_TPFLAGS_HAVE_GC Objects with a type with this flag set must conform with the rules documented here For convenience these objects will be referred to as container objects Constructors for container types must conform to two rules 1 The memory for the object must be allocated using PyObject_GC_New or PyObject_GC_NewVar 2 Once all the fields which may contain references to other containers are initialized it must call PyObject_GC_Track Similarly the deallocator for the object must conform to a similar pair of rules 1 Before fields which refer to other containers are invalidated PyObject_GC_UnTrack must be called 2 The object s memory must be deallocated using PyObject_GC_Del Warning If a type adds the Py_TPFLAGS_HAVE_GC then it must implement at least a tp_traverse handler or explicitly use one from its subclass or subclasses When calling PyType_Ready or some of the APIs that indirectly call it like PyType_FromSpecWithBases or PyType_FromSpec the interpreter will automatically populate the tp_flags tp_traverse and tp_clear fields if the type inherits from a class that implements the garbage collector protocol and the child class does not include the Py_TPFLAGS_HAVE_GC flag PyObject_GC_New TYPE typeobj Analogous to PyObject_New but for container objects with the Py_TPFLAGS_HAVE_GC flag set PyObject_GC_NewVar TYPE typeobj size Analogous to PyObject_NewVar but for container objects with the Py_TPFLAGS_HAVE_GC flag set PyObject PyUnstable_Object_GC_NewWithExtraData PyTypeObject type size_t extra_size This is Unstable API It may change without warning in minor releases Analogous to PyObject_GC_New but allocates extra_size bytes at the end of the object at offset tp_basicsize The allocated memory is initialized to zeros except for the Python object header The extra data will be deallocated with the object but otherwise it is not managed by Python Warning The function is marked as unstable because the final mechanism for reserving extra data after an instance is not yet decided For allocating a variable number of fields prefer using PyVarObject and tp_itemsize instead New in version 3 12 PyObject_GC_Resize TYPE op newsize Resize an object allocated by PyObject_NewVar Returns the resized object of type TYPE refers to any C type or NULL on failure op must be of type PyVarObject and must not be tracked by the collector yet newsize must be of type Py_ssize_t void PyObject_GC_Track PyObject op Part of the Stable ABI Adds the object op to the set of container objects tracked by the collector The collector can run at unexpected times so objects must be valid while being tracked This should be called once all the fields followed by the tp_traverse handler become valid usually near the end of the constructor int PyObject_IS_GC PyObject obj Returns non zero if the object implements the garbage collector protocol otherwise returns 0 The object cannot be tracked by the garbage collector if this function returns 0 int PyObject_GC_IsTracked PyObject op Part of the Stable ABI since version 3 9 Returns 1 if the object type of op implements the GC protocol and op is being currently tracked by the garbage collector and 0 otherwise This is analogous to the Python function gc is_tracked New in version 3 9 int PyObject_GC_IsFinalized PyObject op Part of the Stable ABI since version 3 9 Returns 1 if the object type of op implements the GC protocol and op has been already finalized by the garbage ,en
569,collector and 0 otherwise This is analogous to the Python function gc is_finalized New in version 3 9 void PyObject_GC_Del void op Part of the Stable ABI Releases memory allocated to an object using PyObject_GC_New or PyObject_GC_NewVar void PyObject_GC_UnTrack void op Part of the Stable ABI Remove the object op from the set of container objects tracked by the collector Note that PyObject_GC_Track can be called again on this object to add it back to the set of tracked objects The deallocator tp_dealloc handler should call this for the object before any of the fields used by the tp_traverse handler become invalid Changed in version 3 8 The _PyObject_GC_TRACK and _PyObject_GC_UNTRACK macros have been removed from the public C API The tp_traverse handler accepts a function parameter of this type typedef int visitproc PyObject object void arg Part of the Stable ABI Type of the visitor function passed to the tp_traverse handler The function should be called with an object to traverse as object and the third parameter to the tp_traverse handler as arg The Python core uses several visitor functions to implement cyclic garbage detection it s not expected that users will need to write their own visitor functions The tp_traverse handler must have the following type typedef int traverseproc PyObject self visitproc visit void arg Part of the Stable ABI Traversal function for a container object Implementations must call the visit function for each object directly contained by self with the parameters to visit being the contained object and the arg value passed to the handler The visit function must not be called with a NULL object argument If visit returns a non zero value that value should be returned immediately To simplify writing tp_traverse handlers a Py_VISIT macro is provided In order to use this macro the tp_traverse implementation must name its arguments exactly visit and arg void Py_VISIT PyObject o If o is not NULL call the visit callback with arguments o and arg If visit returns a non zero value then return it Using this macro tp_traverse handlers look like static int my_traverse Noddy self visitproc visit void arg Py_VISIT self foo Py_VISIT self bar return 0 The tp_clear handler must be of the inquiry type or NULL if the object is immutable typedef int inquiry PyObject self Part of the Stable ABI Drop references that may have created reference cycles Immutable objects do not have to define this method since they can never directly create reference cycles Note that the object must still be valid after calling this method don t just call Py_DECREF on a reference The collector will call this method if it detects that this object is involved in a reference cycle Controlling the Garbage Collector State The C API provides the following functions for controlling garbage collection runs Py_ssize_t PyGC_Collect void Part of the Stable ABI Perform a full garbage collection if the garbage collector is enabled Note that gc collect runs it unconditionally Returns the number of collected unreachable objects which cannot be collected If the garbage collector is disabled or already collecting returns 0 immediately Errors during garbage collection are passed to sys unraisablehook This function does not raise exceptions int PyGC_Enable void Part of the Stable ABI since version 3 10 Enable the garbage collector similar to gc enable Returns the previous state 0 for disabled and 1 for enabled New in version 3 10 int PyGC_Disable void Part of the Stable ABI since version 3 10 Disable the garbage collector similar to gc disable Returns the previous state 0 for disabled and 1 for enabled New in version 3 10 int PyGC_IsEnabled void Part of the Stable ABI since version 3 10 Query the state of the garbage collector similar to gc isenabled Returns the current state 0 for disabled and 1 for enabled New in version 3 10 Querying Garbage Collector State The C API provides the following interface for querying information about the garbage collector void PyUnstable_GC_VisitObjects gcvisitobjects_t callback void arg This is Unstable API It may change with,en
570,out warning in minor releases Run supplied callback on all live GC capable objects arg is passed through to all invocations of callback Warning If new objects are de allocated by the callback it is undefined if they will be visited Garbage collection is disabled during operation Explicitly running a collection in the callback may lead to undefined behaviour e g visiting the same objects multiple times or not at all New in version 3 12 typedef int gcvisitobjects_t PyObject object void arg Type of the visitor function to be passed to PyUnstable_GC_VisitObjects arg is the same as the arg passed to PyUnstable_GC_VisitObjects Return 0 to continue iteration return 1 to stop iteration Other return values are reserved for now so behavior on returning anything else is undefined New in version 3 12,en
571,trace Trace or track Python statement execution Source code Lib trace py The trace module allows you to trace program execution generate annotated statement coverage listings print caller callee relationships and list functions executed during a program run It can be used in another program or from the command line See also Coverage py A popular third party coverage tool that provides HTML output along with advanced features such as branch coverage Command Line Usage The trace module can be invoked from the command line It can be as simple as python m trace count C somefile py The above will execute somefile py and generate annotated listings of all Python modules imported during the execution into the current directory help Display usage and exit version Display the version of the module and exit New in version 3 8 Added module option that allows to run an executable module Main options At least one of the following options must be specified when invoking trace The listfuncs option is mutually exclusive with the trace and count options When listfuncs is provided neither count nor trace are accepted and vice versa c count Produce a set of annotated listing files upon program completion that shows how many times each statement was executed See also coverdir file and no report below t trace Display lines as they are executed l listfuncs Display the functions executed by running the program r report Produce an annotated list from an earlier program run that used the count and file option This does not execute any code T trackcalls Display the calling relationships exposed by running the program Modifiers f file file Name of a file to accumulate counts over several tracing runs Should be used with the count option C coverdir dir Directory where the report files go The coverage report for package module is written to file dir package module cover m missing When generating annotated listings mark lines which were not executed with s summary When using count or report write a brief summary to stdout for each file processed R no report Do not generate annotated listings This is useful if you intend to make several runs with count and then produce a single set of annotated listings at the end g timing Prefix each line with the time since the program started Only used while tracing Filters These options may be repeated multiple times ignore module mod Ignore each of the given module names and its submodules if it is a package The argument can be a list of names separated by a comma ignore dir dir Ignore all modules and packages in the named directory and subdirectories The argument can be a list of directories separated by os pathsep Programmatic Interface class trace Trace count 1 trace 1 countfuncs 0 countcallers 0 ignoremods ignoredirs infile None outfile None timing False Create an object to trace execution of a single statement or expression All parameters are optional count enables counting of line numbers trace enables line execution tracing countfuncs enables listing of the functions called during the run countcallers enables call relationship tracking ignoremods is a list of modules or packages to ignore ignoredirs is a list of directories whose modules or packages should be ignored infile is the name of the file from which to read stored count information outfile is the name of the file in which to write updated count information timing enables a timestamp relative to when tracing was started to be displayed run cmd Execute the command and gather statistics from the execution with the current tracing parameters cmd must be a string or code object suitable for passing into exec runctx cmd globals None locals None Execute the command and gather statistics from the execution with the current tracing parameters in the defined global and local environments If not defined globals and locals default to empty dictionaries runfunc func args kwds Call func with the given arguments under control of the Trace object with the current tracing parameters results Return a CoverageResults object that contains the cumulative results of al,en
572,l previous calls to run runctx and runfunc for the given Trace instance Does not reset the accumulated trace results class trace CoverageResults A container for coverage results created by Trace results Should not be created directly by the user update other Merge in data from another CoverageResults object write_results show_missing True summary False coverdir None Write coverage results Set show_missing to show lines that had no hits Set summary to include in the output the coverage summary per module coverdir specifies the directory into which the coverage result files will be output If None the results for each source file are placed in its directory A simple example demonstrating the use of the programmatic interface import sys import trace create a Trace object telling it what to ignore and whether to do tracing or line counting or both tracer trace Trace ignoredirs sys prefix sys exec_prefix trace 0 count 1 run the new command using the given tracer tracer run main make a report placing output in the current directory r tracer results r write_results show_missing True coverdir,en
573,What s New in Python 2 3 Author A M Kuchling This article explains the new features in Python 2 3 Python 2 3 was released on July 29 2003 The main themes for Python 2 3 are polishing some of the features added in 2 2 adding various small but useful enhancements to the core language and expanding the standard library The new object model introduced in the previous version has benefited from 18 months of bugfixes and from optimization efforts that have improved the performance of new style classes A few new built in functions have been added such as sum and enumerate The in operator can now be used for substring searches e g ab in abc returns True Some of the many new library features include Boolean set heap and date time data types the ability to import modules from ZIP format archives metadata support for the long awaited Python catalog an updated version of IDLE and modules for logging messages wrapping text parsing CSV files processing command line options using BerkeleyDB databases the list of new and enhanced modules is lengthy This article doesn t attempt to provide a complete specification of the new features but instead provides a convenient overview For full details you should refer to the documentation for Python 2 3 such as the Python Library Reference and the Python Reference Manual If you want to understand the complete implementation and design rationale refer to the PEP for a particular new feature PEP 218 A Standard Set Datatype The new sets module contains an implementation of a set datatype The Set class is for mutable sets sets that can have members added and removed The ImmutableSet class is for sets that can t be modified and instances of ImmutableSet can therefore be used as dictionary keys Sets are built on top of dictionaries so the elements within a set must be hashable Here s a simple example import sets S sets Set 1 2 3 S Set 1 2 3 1 in S True 0 in S False S add 5 S remove 3 S Set 1 2 5 The union and intersection of sets can be computed with the union and intersection methods an alternative notation uses the bitwise operators and Mutable sets also have in place versions of these methods union_update and intersection_update S1 sets Set 1 2 3 S2 sets Set 4 5 6 S1 union S2 Set 1 2 3 4 5 6 S1 S2 Alternative notation Set 1 2 3 4 5 6 S1 intersection S2 Set S1 S2 Alternative notation Set S1 union_update S2 S1 Set 1 2 3 4 5 6 It s also possible to take the symmetric difference of two sets This is the set of all elements in the union that aren t in the intersection Another way of putting it is that the symmetric difference contains all elements that are in exactly one set Again there s an alternative notation and an in place version with the ungainly name symmetric_difference_update S1 sets Set 1 2 3 4 S2 sets Set 3 4 5 6 S1 symmetric_difference S2 Set 1 2 5 6 S1 S2 Set 1 2 5 6 There are also issubset and issuperset methods for checking whether one set is a subset or superset of another S1 sets Set 1 2 3 S2 sets Set 2 3 S2 issubset S1 True S1 issubset S2 False S1 issuperset S2 True See also PEP 218 Adding a Built In Set Object Type PEP written by Greg V Wilson Implemented by Greg V Wilson Alex Martelli and GvR PEP 255 Simple Generators In Python 2 2 generators were added as an optional feature to be enabled by a from __future__ import generators directive In 2 3 generators no longer need to be specially enabled and are now always present this means that yield is now always a keyword The rest of this section is a copy of the description of generators from the What s New in Python 2 2 document if you read it back when Python 2 2 came out you can skip the rest of this section You re doubtless familiar with how function calls work in Python or C When you call a function it gets a private namespace where its local variables are created When the function reaches a return statement the local variables are destroyed and the resulting value is returned to the caller A later call to the same function will get a fresh new set of local variables But what if the local variables weren t thrown away on exiting a funct,en
574,ion What if you could later resume the function where it left off This is what generators provide they can be thought of as resumable functions Here s the simplest example of a generator function def generate_ints N for i in range N yield i A new keyword yield was introduced for generators Any function containing a yield statement is a generator function this is detected by Python s bytecode compiler which compiles the function specially as a result When you call a generator function it doesn t return a single value instead it returns a generator object that supports the iterator protocol On executing the yield statement the generator outputs the value of i similar to a return statement The big difference between yield and a return statement is that on reaching a yield the generator s state of execution is suspended and local variables are preserved On the next call to the generator s next method the function will resume executing immediately after the yield statement For complicated reasons the yield statement isn t allowed inside the try block of a try finally statement read PEP 255 for a full explanation of the interaction between yield and exceptions Here s a sample usage of the generate_ints generator gen generate_ints 3 gen generator object at 0x8117f90 gen next 0 gen next 1 gen next 2 gen next Traceback most recent call last File stdin line 1 in File stdin line 2 in generate_ints StopIteration You could equally write for i in generate_ints 5 or a b c generate_ints 3 Inside a generator function the return statement can only be used without a value and signals the end of the procession of values afterwards the generator cannot return any further values return with a value such as return 5 is a syntax error inside a generator function The end of the generator s results can also be indicated by raising StopIteration manually or by just letting the flow of execution fall off the bottom of the function You could achieve the effect of generators manually by writing your own class and storing all the local variables of the generator as instance variables For example returning a list of integers could be done by setting self count to 0 and having the next method increment self count and return it However for a moderately complicated generator writing a corresponding class would be much messier Lib test test_generators py contains a number of more interesting examples The simplest one implements an in order traversal of a tree using generators recursively A recursive generator that generates Tree leaves in in order def inorder t if t for x in inorder t left yield x yield t label for x in inorder t right yield x Two other examples in Lib test test_generators py produce solutions for the N Queens problem placing N queens on an NxN chess board so that no queen threatens another and the Knight s Tour a route that takes a knight to every square of an NxN chessboard without visiting any square twice The idea of generators comes from other programming languages especially Icon https www2 cs arizona edu icon where the idea of generators is central In Icon every expression and function call behaves like a generator One example from An Overview of the Icon Programming Language at https www2 cs arizona edu icon docs ipd266 htm gives an idea of what this looks like sentence Store it in the neighboring harbor if i find or sentence 5 then write i In Icon the find function returns the indexes at which the substring or is found 3 23 33 In the if statement i is first assigned a value of 3 but 3 is less than 5 so the comparison fails and Icon retries it with the second value of 23 23 is greater than 5 so the comparison now succeeds and the code prints the value 23 to the screen Python doesn t go nearly as far as Icon in adopting generators as a central concept Generators are considered part of the core Python language but learning or using them isn t compulsory if they don t solve any problems that you have feel free to ignore them One novel feature of Python s interface as compared to Icon s is that a generator s state is represented as a c,en
575,oncrete object the iterator that can be passed around to other functions or stored in a data structure See also PEP 255 Simple Generators Written by Neil Schemenauer Tim Peters Magnus Lie Hetland Implemented mostly by Neil Schemenauer and Tim Peters with other fixes from the Python Labs crew PEP 263 Source Code Encodings Python source files can now be declared as being in different character set encodings Encodings are declared by including a specially formatted comment in the first or second line of the source file For example a UTF 8 file can be declared with usr bin env python coding UTF 8 Without such an encoding declaration the default encoding used is 7 bit ASCII Executing or importing modules that contain string literals with 8 bit characters and have no encoding declaration will result in a DeprecationWarning being signalled by Python 2 3 in 2 4 this will be a syntax error The encoding declaration only affects Unicode string literals which will be converted to Unicode using the specified encoding Note that Python identifiers are still restricted to ASCII characters so you can t have variable names that use characters outside of the usual alphanumerics See also PEP 263 Defining Python Source Code Encodings Written by Marc André Lemburg and Martin von Löwis implemented by Suzuki Hisao and Martin von Löwis PEP 273 Importing Modules from ZIP Archives The new zipimport module adds support for importing modules from a ZIP format archive You don t need to import the module explicitly it will be automatically imported if a ZIP archive s filename is added to sys path For example amk nyman src python unzip l tmp example zip Archive tmp example zip Length Date Time Name 8467 11 26 02 22 30 jwzthreading py 8467 1 file amk nyman src python python Python 2 3 1 Aug 1 2003 19 54 32 import sys sys path insert 0 tmp example zip Add zip file to front of path import jwzthreading jwzthreading __file__ tmp example zip jwzthreading py An entry in sys path can now be the filename of a ZIP archive The ZIP archive can contain any kind of files but only files named py pyc or pyo can be imported If an archive only contains py files Python will not attempt to modify the archive by adding the corresponding pyc file meaning that if a ZIP archive doesn t contain pyc files importing may be rather slow A path within the archive can also be specified to only import from a subdirectory for example the path tmp example zip lib would only import from the lib subdirectory within the archive See also PEP 273 Import Modules from Zip Archives Written by James C Ahlstrom who also provided an implementation Python 2 3 follows the specification in PEP 273 but uses an implementation written by Just van Rossum that uses the import hooks described in PEP 302 See section PEP 302 New Import Hooks for a description of the new import hooks PEP 277 Unicode file name support for Windows NT On Windows NT 2000 and XP the system stores file names as Unicode strings Traditionally Python has represented file names as byte strings which is inadequate because it renders some file names inaccessible Python now allows using arbitrary Unicode strings within the limitations of the file system for all functions that expect file names most notably the open built in function If a Unicode string is passed to os listdir Python now returns a list of Unicode strings A new function os getcwdu returns the current directory as a Unicode string Byte strings still work as file names and on Windows Python will transparently convert them to Unicode using the mbcs encoding Other systems also allow Unicode strings as file names but convert them to byte strings before passing them to the system which can cause a UnicodeError to be raised Applications can test whether arbitrary Unicode strings are supported as file names by checking os path supports_unicode_filenames a Boolean value Under MacOS os listdir may now return Unicode filenames See also PEP 277 Unicode file name support for Windows NT Written by Neil Hodgson implemented by Neil Hodgson Martin von Löwis and Mark Hammond PEP 278 Univers,en
576,al Newline Support The three major operating systems used today are Microsoft Windows Apple s Macintosh OS and the various Unix derivatives A minor irritation of cross platform work is that these three platforms all use different characters to mark the ends of lines in text files Unix uses the linefeed ASCII character 10 MacOS uses the carriage return ASCII character 13 and Windows uses a two character sequence of a carriage return plus a newline Python s file objects can now support end of line conventions other than the one followed by the platform on which Python is running Opening a file with the mode U or rU will open a file for reading in universal newlines mode All three line ending conventions will be translated to a n in the strings returned by the various file methods such as read and readline Universal newline support is also used when importing modules and when executing a file with the execfile function This means that Python modules can be shared between all three operating systems without needing to convert the line endings This feature can be disabled when compiling Python by specifying the without universal newlines switch when running Python s configure script See also PEP 278 Universal Newline Support Written and implemented by Jack Jansen PEP 279 enumerate A new built in function enumerate will make certain loops a bit clearer enumerate thing where thing is either an iterator or a sequence returns an iterator that will return 0 thing 0 1 thing 1 2 thing 2 and so forth A common idiom to change every element of a list looks like this for i in range len L item L i compute some result based on item L i result This can be rewritten using enumerate as for i item in enumerate L compute some result based on item L i result See also PEP 279 The enumerate built in function Written and implemented by Raymond D Hettinger PEP 282 The logging Package A standard package for writing logs logging has been added to Python 2 3 It provides a powerful and flexible mechanism for generating logging output which can then be filtered and processed in various ways A configuration file written in a standard format can be used to control the logging behavior of a program Python includes handlers that will write log records to standard error or to a file or socket send them to the system log or even e mail them to a particular address of course it s also possible to write your own handler classes The Logger class is the primary class Most application code will deal with one or more Logger objects each one used by a particular subsystem of the application Each Logger is identified by a name and names are organized into a hierarchy using as the component separator For example you might have Logger instances named server server auth and server network The latter two instances are below server in the hierarchy This means that if you turn up the verbosity for server or direct server messages to a different handler the changes will also apply to records logged to server auth and server network There s also a root Logger that s the parent of all other loggers For simple uses the logging package contains some convenience functions that always use the root log import logging logging debug Debugging information logging info Informational message logging warning Warning config file s not found server conf logging error Error occurred logging critical Critical error shutting down This produces the following output WARNING root Warning config file server conf not found ERROR root Error occurred CRITICAL root Critical error shutting down In the default configuration informational and debugging messages are suppressed and the output is sent to standard error You can enable the display of informational and debugging messages by calling the setLevel method on the root logger Notice the warning call s use of string formatting operators all of the functions for logging messages take the arguments msg arg1 arg2 and log the string resulting from msg arg1 arg2 There s also an exception function that records the most recent traceback Any of the other f,en
577,unctions will also record the traceback if you specify a true value for the keyword argument exc_info def f try 1 0 except logging exception Problem recorded f This produces the following output ERROR root Problem recorded Traceback most recent call last File t py line 6 in f 1 0 ZeroDivisionError integer division or modulo by zero Slightly more advanced programs will use a logger other than the root logger The getLogger name function is used to get a particular log creating it if it doesn t exist yet getLogger None returns the root logger log logging getLogger server log info Listening on port i port log critical Disk full Log records are usually propagated up the hierarchy so a message logged to server auth is also seen by server and root but a Logger can prevent this by setting its propagate attribute to False There are more classes provided by the logging package that can be customized When a Logger instance is told to log a message it creates a LogRecord instance that is sent to any number of different Handler instances Loggers and handlers can also have an attached list of filters and each filter can cause the LogRecord to be ignored or can modify the record before passing it along When they re finally output LogRecord instances are converted to text by a Formatter class All of these classes can be replaced by your own specially written classes With all of these features the logging package should provide enough flexibility for even the most complicated applications This is only an incomplete overview of its features so please see the package s reference documentation for all of the details Reading PEP 282 will also be helpful See also PEP 282 A Logging System Written by Vinay Sajip and Trent Mick implemented by Vinay Sajip PEP 285 A Boolean Type A Boolean type was added to Python 2 3 Two new constants were added to the __builtin__ module True and False True and False constants were added to the built ins in Python 2 2 1 but the 2 2 1 versions are simply set to integer values of 1 and 0 and aren t a different type The type object for this new type is named bool the constructor for it takes any Python value and converts it to True or False bool 1 True bool 0 False bool False bool 1 True Most of the standard library modules and built in functions have been changed to return Booleans obj hasattr obj append True isinstance obj list True isinstance obj tuple False Python s Booleans were added with the primary goal of making code clearer For example if you re reading a function and encounter the statement return 1 you might wonder whether the 1 represents a Boolean truth value an index or a coefficient that multiplies some other quantity If the statement is return True however the meaning of the return value is quite clear Python s Booleans were not added for the sake of strict type checking A very strict language such as Pascal would also prevent you performing arithmetic with Booleans and would require that the expression in an if statement always evaluate to a Boolean result Python is not this strict and never will be as PEP 285 explicitly says This means you can still use any expression in an if statement even ones that evaluate to a list or tuple or some random object The Boolean type is a subclass of the int class so that arithmetic using a Boolean still works True 1 2 False 1 1 False 75 0 True 75 75 To sum up True and False in a sentence they re alternative ways to spell the integer values 1 and 0 with the single difference that str and repr return the strings True and False instead of 1 and 0 See also PEP 285 Adding a bool type Written and implemented by GvR PEP 293 Codec Error Handling Callbacks When encoding a Unicode string into a byte string unencodable characters may be encountered So far Python has allowed specifying the error processing as either strict raising UnicodeError ignore skipping the character or replace using a question mark in the output string with strict being the default behavior It may be desirable to specify alternative processing of such errors such as inserting an XML character reference,en
578, or HTML entity reference into the converted string Python now has a flexible framework to add different processing strategies New error handlers can be added with codecs register_error and codecs then can access the error handler with codecs lookup_error An equivalent C API has been added for codecs written in C The error handler gets the necessary state information such as the string being converted the position in the string where the error was detected and the target encoding The handler can then either raise an exception or return a replacement string Two additional error handlers have been implemented using this framework backslashreplace uses Python backslash quoting to represent unencodable characters and xmlcharrefreplace emits XML character references See also PEP 293 Codec Error Handling Callbacks Written and implemented by Walter Dörwald PEP 301 Package Index and Metadata for Distutils Support for the long requested Python catalog makes its first appearance in 2 3 The heart of the catalog is the new Distutils register command Running python setup py register will collect the metadata describing a package such as its name version maintainer description c and send it to a central catalog server The resulting catalog is available from https pypi org To make the catalog a bit more useful a new optional classifiers keyword argument has been added to the Distutils setup function A list of Trove style strings can be supplied to help classify the software Here s an example setup py with classifiers written to be compatible with older versions of the Distutils from distutils import core kw name Quixote version 0 5 1 description A highly Pythonic Web application framework if hasattr core setup_keywords and classifiers in core setup_keywords kw classifiers Topic Internet WWW HTTP Dynamic Content Environment No Input Output Daemon Intended Audience Developers core setup kw The full list of classifiers can be obtained by running python setup py register list classifiers See also PEP 301 Package Index and Metadata for Distutils Written and implemented by Richard Jones PEP 302 New Import Hooks While it s been possible to write custom import hooks ever since the ihooks module was introduced in Python 1 3 no one has ever been really happy with it because writing new import hooks is difficult and messy There have been various proposed alternatives such as the imputil and iu modules but none of them has ever gained much acceptance and none of them were easily usable from C code PEP 302 borrows ideas from its predecessors especially from Gordon McMillan s iu module Three new items are added to the sys module sys path_hooks is a list of callable objects most often they ll be classes Each callable takes a string containing a path and either returns an importer object that will handle imports from this path or raises an ImportError exception if it can t handle this path sys path_importer_cache caches importer objects for each path so sys path_hooks will only need to be traversed once for each path sys meta_path is a list of importer objects that will be traversed before sys path is checked This list is initially empty but user code can add objects to it Additional built in and frozen modules can be imported by an object added to this list Importer objects must have a single method find_module fullname path None fullname will be a module or package name e g string or distutils core find_module must return a loader object that has a single method load_module fullname that creates and returns the corresponding module object Pseudo code for Python s new import logic therefore looks something like this simplified a bit see PEP 302 for the full details for mp in sys meta_path loader mp fullname if loader is not None module loader load_module fullname for path in sys path for hook in sys path_hooks try importer hook path except ImportError ImportError so try the other path hooks pass else loader importer find_module fullname module loader load_module fullname Not found raise ImportError See also PEP 302 New Import Hooks Written by Just va,en
579,n Rossum and Paul Moore Implemented by Just van Rossum PEP 305 Comma separated Files Comma separated files are a format frequently used for exporting data from databases and spreadsheets Python 2 3 adds a parser for comma separated files Comma separated format is deceptively simple at first glance Costs 150 200 3 95 Read a line and call line split what could be simpler But toss in string data that can contain commas and things get more complicated Costs 150 200 3 95 Includes taxes shipping and sundry items A big ugly regular expression can parse this but using the new csv package is much simpler import csv input open datafile rb reader csv reader input for line in reader print line The reader function takes a number of different options The field separator isn t limited to the comma and can be changed to any character and so can the quoting and line ending characters Different dialects of comma separated files can be defined and registered currently there are two dialects both used by Microsoft Excel A separate csv writer class will generate comma separated files from a succession of tuples or lists quoting strings that contain the delimiter See also PEP 305 CSV File API Written and implemented by Kevin Altis Dave Cole Andrew McNamara Skip Montanaro Cliff Wells PEP 307 Pickle Enhancements The pickle and cPickle modules received some attention during the 2 3 development cycle In 2 2 new style classes could be pickled without difficulty but they weren t pickled very compactly PEP 307 quotes a trivial example where a new style class results in a pickled string three times longer than that for a classic class The solution was to invent a new pickle protocol The pickle dumps function has supported a text or binary flag for a long time In 2 3 this flag is redefined from a Boolean to an integer 0 is the old text mode pickle format 1 is the old binary format and now 2 is a new 2 3 specific format A new constant pickle HIGHEST_PROTOCOL can be used to select the fanciest protocol available Unpickling is no longer considered a safe operation 2 2 s pickle provided hooks for trying to prevent unsafe classes from being unpickled specifically a __safe_for_unpickling__ attribute but none of this code was ever audited and therefore it s all been ripped out in 2 3 You should not unpickle untrusted data in any version of Python To reduce the pickling overhead for new style classes a new interface for customizing pickling was added using three special methods __getstate__ __setstate__ and __getnewargs__ Consult PEP 307 for the full semantics of these methods As a way to compress pickles yet further it s now possible to use integer codes instead of long strings to identify pickled classes The Python Software Foundation will maintain a list of standardized codes there s also a range of codes for private use Currently no codes have been specified See also PEP 307 Extensions to the pickle protocol Written and implemented by Guido van Rossum and Tim Peters Extended Slices Ever since Python 1 4 the slicing syntax has supported an optional third step or stride argument For example these are all legal Python syntax L 1 10 2 L 1 1 L 1 This was added to Python at the request of the developers of Numerical Python which uses the third argument extensively However Python s built in list tuple and string sequence types have never supported this feature raising a TypeError if you tried it Michael Hudson contributed a patch to fix this shortcoming For example you can now easily extract the elements of a list that have even indexes L range 10 L 2 0 2 4 6 8 Negative values also work to make a copy of the same list in reverse order L 1 9 8 7 6 5 4 3 2 1 0 This also works for tuples arrays and strings s abcd s 2 ac s 1 dcba If you have a mutable sequence such as a list or an array you can assign to or delete an extended slice but there are some differences between assignment to extended and regular slices Assignment to a regular slice can be used to change the length of the sequence a range 3 a 0 1 2 a 1 3 4 5 6 a 0 4 5 6 Extended slices aren t this flexible W,en
580,hen assigning to an extended slice the list on the right hand side of the statement must contain the same number of items as the slice it is replacing a range 4 a 0 1 2 3 a 2 0 2 a 2 0 1 a 0 1 1 3 a 2 0 1 2 Traceback most recent call last File stdin line 1 in ValueError attempt to assign sequence of size 3 to extended slice of size 2 Deletion is more straightforward a range 4 a 0 1 2 3 a 2 0 2 del a 2 a 1 3 One can also now pass slice objects to the __getitem__ methods of the built in sequences range 10 __getitem__ slice 0 5 2 0 2 4 Or use slice objects directly in subscripts range 10 slice 0 5 2 0 2 4 To simplify implementing sequences that support extended slicing slice objects now have a method indices length which given the length of a sequence returns a start stop step tuple that can be passed directly to range indices handles omitted and out of bounds indices in a manner consistent with regular slices and this innocuous phrase hides a welter of confusing details The method is intended to be used like this class FakeSeq def calc_item self i def __getitem__ self item if isinstance item slice indices item indices len self return FakeSeq self calc_item i for i in range indices else return self calc_item i From this example you can also see that the built in slice object is now the type object for the slice type and is no longer a function This is consistent with Python 2 2 where int str etc underwent the same change Other Language Changes Here are all of the changes that Python 2 3 makes to the core Python language The yield statement is now always a keyword as described in section PEP 255 Simple Generators of this document A new built in function enumerate was added as described in section PEP 279 enumerate of this document Two new constants True and False were added along with the built in bool type as described in section PEP 285 A Boolean Type of this document The int type constructor will now return a long integer instead of raising an OverflowError when a string or floating point number is too large to fit into an integer This can lead to the paradoxical result that isinstance int expression int is false but that seems unlikely to cause problems in practice Built in types now support the extended slicing syntax as described in section Extended Slices of this document A new built in function sum iterable start 0 adds up the numeric items in the iterable object and returns their sum sum only accepts numbers meaning that you can t use it to concatenate a bunch of strings Contributed by Alex Martelli list insert pos value used to insert value at the front of the list when pos was negative The behaviour has now been changed to be consistent with slice indexing so when pos is 1 the value will be inserted before the last element and so forth list index value which searches for value within the list and returns its index now takes optional start and stop arguments to limit the search to only part of the list Dictionaries have a new method pop key default that returns the value corresponding to key and removes that key value pair from the dictionary If the requested key isn t present in the dictionary default is returned if it s specified and KeyError raised if it isn t d 1 2 d 1 2 d pop 4 Traceback most recent call last File stdin line 1 in KeyError 4 d pop 1 2 d pop 1 Traceback most recent call last File stdin line 1 in KeyError pop dictionary is empty d There s also a new class method dict fromkeys iterable value that creates a dictionary with keys taken from the supplied iterator iterable and all values set to value defaulting to None Patches contributed by Raymond Hettinger Also the dict constructor now accepts keyword arguments to simplify creating small dictionaries dict red 1 blue 2 green 3 black 4 blue 2 black 4 green 3 red 1 Contributed by Just van Rossum The assert statement no longer checks the __debug__ flag so you can no longer disable assertions by assigning to __debug__ Running Python with the O switch will still generate code that doesn t execute any assertions Most type objects are now callable so you ca,en
581,n use them to create new objects such as functions classes and modules This means that the new module can be deprecated in a future Python version because you can now use the type objects available in the types module For example you can create a new module object with the following code import types m types ModuleType abc docstring m module abc built in m __doc__ docstring A new warning PendingDeprecationWarning was added to indicate features which are in the process of being deprecated The warning will not be printed by default To check for use of features that will be deprecated in the future supply Walways PendingDeprecationWarning on the command line or use warnings filterwarnings The process of deprecating string based exceptions as in raise Error occurred has begun Raising a string will now trigger PendingDeprecationWarning Using None as a variable name will now result in a SyntaxWarning warning In a future version of Python None may finally become a keyword The xreadlines method of file objects introduced in Python 2 1 is no longer necessary because files now behave as their own iterator xreadlines was originally introduced as a faster way to loop over all the lines in a file but now you can simply write for line in file_obj File objects also have a new read only encoding attribute that gives the encoding used by the file Unicode strings written to the file will be automatically converted to bytes using the given encoding The method resolution order used by new style classes has changed though you ll only notice the difference if you have a really complicated inheritance hierarchy Classic classes are unaffected by this change Python 2 2 originally used a topological sort of a class s ancestors but 2 3 now uses the C3 algorithm as described in the paper A Monotonic Superclass Linearization for Dylan To understand the motivation for this change read Michele Simionato s article Python 2 3 Method Resolution Order or read the thread on python dev starting with the message at https mail python org pipermail python dev 2002 October 029035 html Samuele Pedroni first pointed out the problem and also implemented the fix by coding the C3 algorithm Python runs multithreaded programs by switching between threads after executing N bytecodes The default value for N has been increased from 10 to 100 bytecodes speeding up single threaded applications by reducing the switching overhead Some multithreaded applications may suffer slower response time but that s easily fixed by setting the limit back to a lower number using sys setcheckinterval N The limit can be retrieved with the new sys getcheckinterval function One minor but far reaching change is that the names of extension types defined by the modules included with Python now contain the module and a in front of the type name For example in Python 2 2 if you created a socket and printed its __class__ you d get this output s socket socket s __class__ type socket In 2 3 you get this s __class__ type _socket socket One of the noted incompatibilities between old and new style classes has been removed you can now assign to the __name__ and __bases__ attributes of new style classes There are some restrictions on what can be assigned to __bases__ along the lines of those relating to assigning to an instance s __class__ attribute String Changes The in operator now works differently for strings Previously when evaluating X in Y where X and Y are strings X could only be a single character That s now changed X can be a string of any length and X in Y will return True if X is a substring of Y If X is the empty string the result is always True ab in abcd True ad in abcd False in abcd True Note that this doesn t tell you where the substring starts if you need that information use the find string method The strip lstrip and rstrip string methods now have an optional argument for specifying the characters to strip The default is still to remove all whitespace characters abc strip abc abc strip abc abc n strip abc n u u4000 u4001abc u4000 strip u u4000 u u4001abc Suggested by Simon Brunning and,en
582, implemented by Walter Dörwald The startswith and endswith string methods now accept negative numbers for the start and end parameters Another new string method is zfill originally a function in the string module zfill pads a numeric string with zeros on the left until it s the specified width Note that the operator is still more flexible and powerful than zfill 45 zfill 4 0045 12345 zfill 4 12345 goofy zfill 6 0goofy Contributed by Walter Dörwald A new type object basestring has been added Both 8 bit strings and Unicode strings inherit from this type so isinstance obj basestring will return True for either kind of string It s a completely abstract type so you can t create basestring instances Interned strings are no longer immortal and will now be garbage collected in the usual way when the only reference to them is from the internal dictionary of interned strings Implemented by Oren Tirosh Optimizations The creation of new style class instances has been made much faster they re now faster than classic classes The sort method of list objects has been extensively rewritten by Tim Peters and the implementation is significantly faster Multiplication of large long integers is now much faster thanks to an implementation of Karatsuba multiplication an algorithm that scales better than the O n 2 required for the grade school multiplication algorithm Original patch by Christopher A Craig and significantly reworked by Tim Peters The SET_LINENO opcode is now gone This may provide a small speed increase depending on your compiler s idiosyncrasies See section Other Changes and Fixes for a longer explanation Removed by Michael Hudson xrange objects now have their own iterator making for i in xrange n slightly faster than for i in range n Patch by Raymond Hettinger A number of small rearrangements have been made in various hotspots to improve performance such as inlining a function or removing some code Implemented mostly by GvR but lots of people have contributed single changes The net result of the 2 3 optimizations is that Python 2 3 runs the pystone benchmark around 25 faster than Python 2 2 New Improved and Deprecated Modules As usual Python s standard library received a number of enhancements and bug fixes Here s a partial list of the most notable changes sorted alphabetically by module name Consult the Misc NEWS file in the source tree for a more complete list of changes or look through the CVS logs for all the details The array module now supports arrays of Unicode characters using the u format character Arrays also now support using the assignment operator to add another array s contents and the assignment operator to repeat an array Contributed by Jason Orendorff The bsddb module has been replaced by version 4 1 6 of the PyBSDDB package providing a more complete interface to the transactional features of the BerkeleyDB library The old version of the module has been renamed to bsddb185 and is no longer built automatically you ll have to edit Modules Setup to enable it Note that the new bsddb package is intended to be compatible with the old module so be sure to file bugs if you discover any incompatibilities When upgrading to Python 2 3 if the new interpreter is compiled with a new version of the underlying BerkeleyDB library you will almost certainly have to convert your database files to the new version You can do this fairly easily with the new scripts db2pickle py and pickle2db py which you will find in the distribution s Tools scripts directory If you ve already been using the PyBSDDB package and importing it as bsddb3 you will have to change your import statements to import it as bsddb The new bz2 module is an interface to the bz2 data compression library bz2 compressed data is usually smaller than corresponding zlib compressed data Contributed by Gustavo Niemeyer A set of standard date time types has been added in the new datetime module See the following section for more details The Distutils Extension class now supports an extra constructor argument named depends for listing additional source files that an extension,en
583, depends on This lets Distutils recompile the module if any of the dependency files are modified For example if sampmodule c includes the header file sample h you would create the Extension object like this ext Extension samp sources sampmodule c depends sample h Modifying sample h would then cause the module to be recompiled Contributed by Jeremy Hylton Other minor changes to Distutils it now checks for the CC CFLAGS CPP LDFLAGS and CPPFLAGS environment variables using them to override the settings in Python s configuration contributed by Robert Weber Previously the doctest module would only search the docstrings of public methods and functions for test cases but it now also examines private ones as well The DocTestSuite function creates a unittest TestSuite object from a set of doctest tests The new gc get_referents object function returns a list of all the objects referenced by object The getopt module gained a new function gnu_getopt that supports the same arguments as the existing getopt function but uses GNU style scanning mode The existing getopt stops processing options as soon as a non option argument is encountered but in GNU style mode processing continues meaning that options and arguments can be mixed For example getopt getopt f filename output v f v f filename output v getopt gnu_getopt f filename output v f v f filename v output Contributed by Peter Åstrand The grp pwd and resource modules now return enhanced tuples import grp g grp getgrnam amk g gr_name g gr_gid amk 500 The gzip module can now handle files exceeding 2 GiB The new heapq module contains an implementation of a heap queue algorithm A heap is an array like data structure that keeps items in a partially sorted order such that for every index k heap k heap 2 k 1 and heap k heap 2 k 2 This makes it quick to remove the smallest item and inserting a new item while maintaining the heap property is O log n See https xlinux nist gov dads HTML priorityque html for more information about the priority queue data structure The heapq module provides heappush and heappop functions for adding and removing items while maintaining the heap property on top of some other mutable Python sequence type Here s an example that uses a Python list import heapq heap for item in 3 7 5 11 1 heapq heappush heap item heap 1 3 5 11 7 heapq heappop heap 1 heapq heappop heap 3 heap 5 7 11 Contributed by Kevin O Connor The IDLE integrated development environment has been updated using the code from the IDLEfork project https idlefork sourceforge net The most notable feature is that the code being developed is now executed in a subprocess meaning that there s no longer any need for manual reload operations IDLE s core code has been incorporated into the standard library as the idlelib package The imaplib module now supports IMAP over SSL Contributed by Piers Lauder and Tino Lange The itertools contains a number of useful functions for use with iterators inspired by various functions provided by the ML and Haskell languages For example itertools ifilter predicate iterator returns all elements in the iterator for which the function predicate returns True and itertools repeat obj N returns obj N times There are a number of other functions in the module see the package s reference documentation for details Contributed by Raymond Hettinger Two new functions in the math module degrees rads and radians degs convert between radians and degrees Other functions in the math module such as math sin and math cos have always required input values measured in radians Also an optional base argument was added to math log to make it easier to compute logarithms for bases other than e and 10 Contributed by Raymond Hettinger Several new POSIX functions getpgid killpg lchown loadavg major makedev minor and mknod were added to the posix module that underlies the os module Contributed by Gustavo Niemeyer Geert Jansen and Denis S Otkidach In the os module the stat family of functions can now report fractions of a second in a timestamp Such time stamps are represented as floats similar to the value ret,en
584,urned by time time During testing it was found that some applications will break if time stamps are floats For compatibility when using the tuple interface of the stat_result time stamps will be represented as integers When using named fields a feature first introduced in Python 2 2 time stamps are still represented as integers unless os stat_float_times is invoked to enable float return values os stat tmp st_mtime 1034791200 os stat_float_times True os stat tmp st_mtime 1034791200 6335014 In Python 2 4 the default will change to always returning floats Application developers should enable this feature only if all their libraries work properly when confronted with floating point time stamps or if they use the tuple API If used the feature should be activated on an application level instead of trying to enable it on a per use basis The optparse module contains a new parser for command line arguments that can convert option values to a particular Python type and will automatically generate a usage message See the following section for more details The old and never documented linuxaudiodev module has been deprecated and a new version named ossaudiodev has been added The module was renamed because the OSS sound drivers can be used on platforms other than Linux and the interface has also been tidied and brought up to date in various ways Contributed by Greg Ward and Nicholas FitzRoy Dale The new platform module contains a number of functions that try to determine various properties of the platform you re running on There are functions for getting the architecture CPU type the Windows OS version and even the Linux distribution version Contributed by Marc André Lemburg The parser objects provided by the pyexpat module can now optionally buffer character data resulting in fewer calls to your character data handler and therefore faster performance Setting the parser object s buffer_text attribute to True will enable buffering The sample population k function was added to the random module population is a sequence or xrange object containing the elements of a population and sample chooses k elements from the population without replacing chosen elements k can be any value up to len population For example days Mo Tu We Th Fr St Sn random sample days 3 Choose 3 elements St Sn Th random sample days 7 Choose 7 elements Tu Th Mo We St Fr Sn random sample days 7 Choose 7 again We Mo Sn Fr Tu St Th random sample days 8 Can t choose eight Traceback most recent call last File stdin line 1 in File random py line 414 in sample raise ValueError sample larger than population ValueError sample larger than population random sample xrange 1 10000 2 10 Choose ten odd nos under 10000 3407 3805 1505 7023 2401 2267 9733 3151 8083 9195 The random module now uses a new algorithm the Mersenne Twister implemented in C It s faster and more extensively studied than the previous algorithm All changes contributed by Raymond Hettinger The readline module also gained a number of new functions get_history_item get_current_history_length and redisplay The rexec and Bastion modules have been declared dead and attempts to import them will fail with a RuntimeError New style classes provide new ways to break out of the restricted execution environment provided by rexec and no one has interest in fixing them or time to do so If you have applications using rexec rewrite them to use something else Sticking with Python 2 2 or 2 1 will not make your applications any safer because there are known bugs in the rexec module in those versions To repeat if you re using rexec stop using it immediately The rotor module has been deprecated because the algorithm it uses for encryption is not believed to be secure If you need encryption use one of the several AES Python modules that are available separately The shutil module gained a move src dest function that recursively moves a file or directory to a new location Support for more advanced POSIX signal handling was added to the signal but then removed again as it proved impossible to make it work reliably across platforms The soc,en
585,ket module now supports timeouts You can call the settimeout t method on a socket object to set a timeout of t seconds Subsequent socket operations that take longer than t seconds to complete will abort and raise a socket timeout exception The original timeout implementation was by Tim O Malley Michael Gilfix integrated it into the Python socket module and shepherded it through a lengthy review After the code was checked in Guido van Rossum rewrote parts of it This is a good example of a collaborative development process in action On Windows the socket module now ships with Secure Sockets Layer SSL support The value of the C PYTHON_API_VERSION macro is now exposed at the Python level as sys api_version The current exception can be cleared by calling the new sys exc_clear function The new tarfile module allows reading from and writing to tar format archive files Contributed by Lars Gustäbel The new textwrap module contains functions for wrapping strings containing paragraphs of text The wrap text width function takes a string and returns a list containing the text split into lines of no more than the chosen width The fill text width function returns a single string reformatted to fit into lines no longer than the chosen width As you can guess fill is built on top of wrap For example import textwrap paragraph Not a whit we defy augury more text textwrap wrap paragraph 60 Not a whit we defy augury there s a special providence in the fall of a sparrow If it be now tis not to come if it print textwrap fill paragraph 35 Not a whit we defy augury there s a special providence in the fall of a sparrow If it be now tis not to come if it be not to come it will be now if it be not now yet it will come the readiness is all The module also contains a TextWrapper class that actually implements the text wrapping strategy Both the TextWrapper class and the wrap and fill functions support a number of additional keyword arguments for fine tuning the formatting consult the module s documentation for details Contributed by Greg Ward The thread and threading modules now have companion modules dummy_thread and dummy_threading that provide a do nothing implementation of the thread module s interface for platforms where threads are not supported The intention is to simplify thread aware modules ones that don t rely on threads to run by putting the following code at the top try import threading as _threading except ImportError import dummy_threading as _threading In this example _threading is used as the module name to make it clear that the module being used is not necessarily the actual threading module Code can call functions and use classes in _threading whether or not threads are supported avoiding an if statement and making the code slightly clearer This module will not magically make multithreaded code run without threads code that waits for another thread to return or to do something will simply hang forever The time module s strptime function has long been an annoyance because it uses the platform C library s strptime implementation and different platforms sometimes have odd bugs Brett Cannon contributed a portable implementation that s written in pure Python and should behave identically on all platforms The new timeit module helps measure how long snippets of Python code take to execute The timeit py file can be run directly from the command line or the module s Timer class can be imported and used directly Here s a short example that figures out whether it s faster to convert an 8 bit string to Unicode by appending an empty Unicode string to it or by using the unicode function import timeit timer1 timeit Timer unicode abc timer2 timeit Timer abc u Run three trials print timer1 repeat repeat 3 number 100000 print timer2 repeat repeat 3 number 100000 On my laptop this outputs 0 36831796169281006 0 37441694736480713 0 35304892063140869 0 17574405670166016 0 18193507194519043 0 17565798759460449 The Tix module has received various bug fixes and updates for the current version of the Tix package The Tkinter module now works with a thread e,en
586,nabled version of Tcl Tcl s threading model requires that widgets only be accessed from the thread in which they re created accesses from another thread can cause Tcl to panic For certain Tcl interfaces Tkinter will now automatically avoid this when a widget is accessed from a different thread by marshalling a command passing it to the correct thread and waiting for the results Other interfaces can t be handled automatically but Tkinter will now raise an exception on such an access so that you can at least find out about the problem See https mail python org pipermail python dev 2002 December 031107 html for a more detailed explanation of this change Implemented by Martin von Löwis Calling Tcl methods through _tkinter no longer returns only strings Instead if Tcl returns other objects those objects are converted to their Python equivalent if one exists or wrapped with a _tkinter Tcl_Obj object if no Python equivalent exists This behavior can be controlled through the wantobjects method of tkapp objects When using _tkinter through the Tkinter module as most Tkinter applications will this feature is always activated It should not cause compatibility problems since Tkinter would always convert string results to Python types where possible If any incompatibilities are found the old behavior can be restored by setting the wantobjects variable in the Tkinter module to false before creating the first tkapp object import Tkinter Tkinter wantobjects 0 Any breakage caused by this change should be reported as a bug The UserDict module has a new DictMixin class which defines all dictionary methods for classes that already have a minimum mapping interface This greatly simplifies writing classes that need to be substitutable for dictionaries such as the classes in the shelve module Adding the mix in as a superclass provides the full dictionary interface whenever the class defines __getitem__ __setitem__ __delitem__ and keys For example import UserDict class SeqDict UserDict DictMixin Dictionary lookalike implemented with lists def __init__ self self keylist self valuelist def __getitem__ self key try i self keylist index key except ValueError raise KeyError return self valuelist i def __setitem__ self key value try i self keylist index key self valuelist i value except ValueError self keylist append key self valuelist append value def __delitem__ self key try i self keylist index key except ValueError raise KeyError self keylist pop i self valuelist pop i def keys self return list self keylist s SeqDict dir s See that other dictionary methods are implemented __cmp__ __contains__ __delitem__ __doc__ __getitem__ __init__ __iter__ __len__ __module__ __repr__ __setitem__ clear get has_key items iteritems iterkeys itervalues keylist keys pop popitem setdefault update valuelist values Contributed by Raymond Hettinger The DOM implementation in xml dom minidom can now generate XML output in a particular encoding by providing an optional encoding argument to the toxml and toprettyxml methods of DOM nodes The xmlrpclib module now supports an XML RPC extension for handling nil data values such as Python s None Nil values are always supported on unmarshalling an XML RPC response To generate requests containing None you must supply a true value for the allow_none parameter when creating a Marshaller instance The new DocXMLRPCServer module allows writing self documenting XML RPC servers Run it in demo mode as a program to see it in action Pointing the web browser to the RPC server produces pydoc style documentation pointing xmlrpclib to the server allows invoking the actual methods Contributed by Brian Quinlan Support for internationalized domain names RFCs 3454 3490 3491 and 3492 has been added The idna encoding can be used to convert between a Unicode domain name and the ASCII compatible encoding ACE of that name u www Alliancefrançaise nu encode idna www xn alliancefranaise npb nu The socket module has also been extended to transparently convert Unicode hostnames to the ACE version before passing them to the C library Modules that deal with host,en
587,names such as httplib and ftplib also support Unicode host names httplib also sends HTTP Host headers using the ACE version of the domain name urllib supports Unicode URLs with non ASCII host names as long as the path part of the URL is ASCII only To implement this change the stringprep module the mkstringprep tool and the punycode encoding have been added Date Time Type Date and time types suitable for expressing timestamps were added as the datetime module The types don t support different calendars or many fancy features and just stick to the basics of representing time The three primary types are date representing a day month and year time consisting of hour minute and second and datetime which contains all the attributes of both date and time There s also a timedelta class representing differences between two points in time and time zone logic is implemented by classes inheriting from the abstract tzinfo class You can create instances of date and time by either supplying keyword arguments to the appropriate constructor e g datetime date year 1972 month 10 day 15 or by using one of a number of class methods For example the today class method returns the current local date Once created instances of the date time classes are all immutable There are a number of methods for producing formatted strings from objects import datetime now datetime datetime now now isoformat 2002 12 30T21 27 03 994956 now ctime Only available on date datetime Mon Dec 30 21 27 03 2002 now strftime Y d b 2002 30 Dec The replace method allows modifying one or more fields of a date or datetime instance returning a new instance d datetime datetime now d datetime datetime 2002 12 30 22 15 38 827738 d replace year 2001 hour 12 datetime datetime 2001 12 30 12 15 38 827738 Instances can be compared hashed and converted to strings the result is the same as that of isoformat date and datetime instances can be subtracted from each other and added to timedelta instances The largest missing feature is that there s no standard library support for parsing strings and getting back a date or datetime For more information refer to the module s reference documentation Contributed by Tim Peters The optparse Module The getopt module provides simple parsing of command line arguments The new optparse module originally named Optik provides more elaborate command line parsing that follows the Unix conventions automatically creates the output for help and can perform different actions for different options You start by creating an instance of OptionParser and telling it what your program s options are import sys from optparse import OptionParser op OptionParser op add_option i input action store type string dest input help set input filename op add_option l length action store type int dest length help set maximum length of output Parsing a command line is then done by calling the parse_args method options args op parse_args sys argv 1 print options print args This returns an object containing all of the option values and a list of strings containing the remaining arguments Invoking the script with the various arguments now works as you d expect it to Note that the length argument is automatically converted to an integer python opt py i data arg1 Values at 0x400cad4c input data length None arg1 python opt py input data length 4 Values at 0x400cad2c input data length 4 The help message is automatically generated for you python opt py help usage opt py options options h help show this help message and exit iINPUT input INPUT set input filename lLENGTH length LENGTH set maximum length of output See the module s documentation for more details Optik was written by Greg Ward with suggestions from the readers of the Getopt SIG Pymalloc A Specialized Object Allocator Pymalloc a specialized object allocator written by Vladimir Marangozov was a feature added to Python 2 1 Pymalloc is intended to be faster than the system malloc and to have less memory overhead for allocation patterns typical of Python programs The allocator uses C s malloc function to get large pools of memory an,en
588,d then fulfills smaller memory requests from these pools In 2 1 and 2 2 pymalloc was an experimental feature and wasn t enabled by default you had to explicitly enable it when compiling Python by providing the with pymalloc option to the configure script In 2 3 pymalloc has had further enhancements and is now enabled by default you ll have to supply without pymalloc to disable it This change is transparent to code written in Python however pymalloc may expose bugs in C extensions Authors of C extension modules should test their code with pymalloc enabled because some incorrect code may cause core dumps at runtime There s one particularly common error that causes problems There are a number of memory allocation functions in Python s C API that have previously just been aliases for the C library s malloc and free meaning that if you accidentally called mismatched functions the error wouldn t be noticeable When the object allocator is enabled these functions aren t aliases of malloc and free any more and calling the wrong function to free memory may get you a core dump For example if memory was allocated using PyObject_Malloc it has to be freed using PyObject_Free not free A few modules included with Python fell afoul of this and had to be fixed doubtless there are more third party modules that will have the same problem As part of this change the confusing multiple interfaces for allocating memory have been consolidated down into two API families Memory allocated with one family must not be manipulated with functions from the other family There is one family for allocating chunks of memory and another family of functions specifically for allocating Python objects To allocate and free an undistinguished chunk of memory use the raw memory family PyMem_Malloc PyMem_Realloc and PyMem_Free The object memory family is the interface to the pymalloc facility described above and is biased towards a large number of small allocations PyObject_Malloc PyObject_Realloc and PyObject_Free To allocate and free Python objects use the object family PyObject_New PyObject_NewVar and PyObject_Del Thanks to lots of work by Tim Peters pymalloc in 2 3 also provides debugging features to catch memory overwrites and doubled frees in both extension modules and in the interpreter itself To enable this support compile a debugging version of the Python interpreter by running configure with with pydebug To aid extension writers a header file Misc pymemcompat h is distributed with the source to Python 2 3 that allows Python extensions to use the 2 3 interfaces to memory allocation while compiling against any version of Python since 1 5 2 You would copy the file from Python s source distribution and bundle it with the source of your extension See also https hg python org cpython file default Objects obmalloc c For the full details of the pymalloc implementation see the comments at the top of the file Objects obmalloc c in the Python source code The above link points to the file within the python org SVN browser Build and C API Changes Changes to Python s build process and to the C API include The cycle detection implementation used by the garbage collection has proven to be stable so it s now been made mandatory You can no longer compile Python without it and the with cycle gc switch to configure has been removed Python can now optionally be built as a shared library libpython2 3 so by supplying enable shared when running Python s configure script Contributed by Ondrej Palkovsky The DL_EXPORT and DL_IMPORT macros are now deprecated Initialization functions for Python extension modules should now be declared using the new macro PyMODINIT_FUNC while the Python core will generally use the PyAPI_FUNC and PyAPI_DATA macros The interpreter can be compiled without any docstrings for the built in functions and modules by supplying without doc strings to the configure script This makes the Python executable about 10 smaller but will also mean that you can t get help for Python s built ins Contributed by Gustavo Niemeyer The PyArg_NoArgs macro is now deprecated and ,en
589,code that uses it should be changed For Python 2 2 and later the method definition table can specify the METH_NOARGS flag signalling that there are no arguments and the argument checking can then be removed If compatibility with pre 2 2 versions of Python is important the code could use PyArg_ParseTuple args instead but this will be slower than using METH_NOARGS PyArg_ParseTuple accepts new format characters for various sizes of unsigned integers B for unsigned char H for unsigned short int I for unsigned int and K for unsigned long long A new function PyObject_DelItemString mapping char key was added as shorthand for PyObject_DelItem mapping PyString_New key File objects now manage their internal string buffer differently increasing it exponentially when needed This results in the benchmark tests in Lib test test_bufio py speeding up considerably from 57 seconds to 1 7 seconds according to one measurement It s now possible to define class and static methods for a C extension type by setting either the METH_CLASS or METH_STATIC flags in a method s PyMethodDef structure Python now includes a copy of the Expat XML parser s source code removing any dependence on a system version or local installation of Expat If you dynamically allocate type objects in your extension you should be aware of a change in the rules relating to the __module__ and __name__ attributes In summary you will want to ensure the type s dictionary contains a __module__ key making the module name the part of the type name leading up to the final period will no longer have the desired effect For more detail read the API reference documentation or the source Port Specific Changes Support for a port to IBM s OS 2 using the EMX runtime environment was merged into the main Python source tree EMX is a POSIX emulation layer over the OS 2 system APIs The Python port for EMX tries to support all the POSIX like capability exposed by the EMX runtime and mostly succeeds fork and fcntl are restricted by the limitations of the underlying emulation layer The standard OS 2 port which uses IBM s Visual Age compiler also gained support for case sensitive import semantics as part of the integration of the EMX port into CVS Contributed by Andrew MacIntyre On MacOS most toolbox modules have been weaklinked to improve backward compatibility This means that modules will no longer fail to load if a single routine is missing on the current OS version Instead calling the missing routine will raise an exception Contributed by Jack Jansen The RPM spec files found in the Misc RPM directory in the Python source distribution were updated for 2 3 Contributed by Sean Reifschneider Other new platforms now supported by Python include AtheOS http www atheos cx GNU Hurd and OpenVMS Other Changes and Fixes As usual there were a bunch of other improvements and bugfixes scattered throughout the source tree A search through the CVS change logs finds there were 523 patches applied and 514 bugs fixed between Python 2 2 and 2 3 Both figures are likely to be underestimates Some of the more notable changes are If the PYTHONINSPECT environment variable is set the Python interpreter will enter the interactive prompt after running a Python program as if Python had been invoked with the i option The environment variable can be set before running the Python interpreter or it can be set by the Python program as part of its execution The regrtest py script now provides a way to allow all resources except foo A resource name passed to the u option can now be prefixed with a hyphen to mean remove this resource For example the option uall bsddb could be used to enable the use of all resources except bsddb The tools used to build the documentation now work under Cygwin as well as Unix The SET_LINENO opcode has been removed Back in the mists of time this opcode was needed to produce line numbers in tracebacks and support trace functions for e g pdb Since Python 1 5 the line numbers in tracebacks have been computed using a different mechanism that works with python O For Python 2 3 Michael Hudson implemented a si,en
590,milar scheme to determine when to call the trace function removing the need for SET_LINENO entirely It would be difficult to detect any resulting difference from Python code apart from a slight speed up when Python is run without O C extensions that access the f_lineno field of frame objects should instead call PyCode_Addr2Line f f_code f f_lasti This will have the added effect of making the code work as desired under python O in earlier versions of Python A nifty new feature is that trace functions can now assign to the f_lineno attribute of frame objects changing the line that will be executed next A jump command has been added to the pdb debugger taking advantage of this new feature Implemented by Richie Hindle Porting to Python 2 3 This section lists previously described changes that may require changes to your code yield is now always a keyword if it s used as a variable name in your code a different name must be chosen For strings X and Y X in Y now works if X is more than one character long The int type constructor will now return a long integer instead of raising an OverflowError when a string or floating point number is too large to fit into an integer If you have Unicode strings that contain 8 bit characters you must declare the file s encoding UTF 8 Latin 1 or whatever by adding a comment to the top of the file See section PEP 263 Source Code Encodings for more information Calling Tcl methods through _tkinter no longer returns only strings Instead if Tcl returns other objects those objects are converted to their Python equivalent if one exists or wrapped with a _tkinter Tcl_Obj object if no Python equivalent exists Large octal and hex literals such as 0xffffffff now trigger a FutureWarning Currently they re stored as 32 bit numbers and result in a negative value but in Python 2 4 they ll become positive long integers There are a few ways to fix this warning If you really need a positive number just add an L to the end of the literal If you re trying to get a 32 bit integer with low bits set and have previously used an expression such as 1 31 it s probably clearest to start with all bits set and clear the desired upper bits For example to clear just the top bit bit 31 you could write 0xffffffffL 1L 31 You can no longer disable assertions by assigning to __debug__ The Distutils setup function has gained various new keyword arguments such as depends Old versions of the Distutils will abort if passed unknown keywords A solution is to check for the presence of the new get_distutil_options function in your setup py and only uses the new keywords with a version of the Distutils that supports them from distutils import core kw sources foo c if hasattr core get_distutil_options kw depends foo h ext Extension kw Using None as a variable name will now result in a SyntaxWarning warning Names of extension types defined by the modules included with Python now contain the module and a in front of the type name Acknowledgements The author would like to thank the following people for offering suggestions corrections and assistance with various drafts of this article Jeff Bauer Simon Brunning Brett Cannon Michael Chermside Andrew Dalke Scott David Daniels Fred L Drake Jr David Fraser Kelly Gerber Raymond Hettinger Michael Hudson Chris Lambert Detlef Lannert Martin von Löwis Andrew MacIntyre Lalo Martins Chad Netzer Gustavo Niemeyer Neal Norwitz Hans Nowak Chris Reedy Francesco Ricciardi Vinay Sajip Neil Schemenauer Roman Suzi Jason Tishler Just van Rossum,en
591,compileall Byte compile Python libraries Source code Lib compileall py This module provides some utility functions to support installing Python libraries These functions compile Python source files in a directory tree This module can be used to create the cached byte code files at library installation time which makes them available for use even by users who don t have write permission to the library directories Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information Command line use This module can work as a script using python m compileall to compile Python sources directory file Positional arguments are files to compile or directories that contain source files traversed recursively If no argument is given behave as if the command line was l directories from sys path l Do not recurse into subdirectories only compile source code files directly contained in the named or implied directories f Force rebuild even if timestamps are up to date q Do not print the list of files compiled If passed once error messages will still be printed If passed twice qq all output is suppressed d destdir Directory prepended to the path to each file being compiled This will appear in compilation time tracebacks and is also compiled in to the byte code file where it will be used in tracebacks and other messages in cases where the source file does not exist at the time the byte code file is executed s strip_prefix p prepend_prefix Remove s or append p the given prefix of paths recorded in the pyc files Cannot be combined with d x regex regex is used to search the full path to each file considered for compilation and if the regex produces a match the file is skipped i list Read the file list and add each line that it contains to the list of files and directories to compile If list is read lines from stdin b Write the byte code files to their legacy locations and names which may overwrite byte code files created by another version of Python The default is to write files to their PEP 3147 locations and names which allows byte code files from multiple versions of Python to coexist r Control the maximum recursion level for subdirectories If this is given then l option will not be taken into account python m compileall directory r 0 is equivalent to python m compileall directory l j N Use N workers to compile the files within the given directory If 0 is used then the result of os cpu_count will be used invalidation mode timestamp checked hash unchecked hash Control how the generated byte code files are invalidated at runtime The timestamp value means that pyc files with the source timestamp and size embedded will be generated The checked hash and unchecked hash values cause hash based pycs to be generated Hash based pycs embed a hash of the source file contents rather than a timestamp See Cached bytecode invalidation for more information on how Python validates bytecode cache files at runtime The default is timestamp if the SOURCE_DATE_EPOCH environment variable is not set and checked hash if the SOURCE_DATE_EPOCH environment variable is set o level Compile with the given optimization level May be used multiple times to compile for multiple levels at a time for example compileall o 1 o 2 e dir Ignore symlinks pointing outside the given directory hardlink dupes If two pyc files with different optimization level have the same content use hard links to consolidate duplicate files Changed in version 3 2 Added the i b and h options Changed in version 3 5 Added the j r and qq options q option was changed to a multilevel value b will always produce a byte code file ending in pyc never pyo Changed in version 3 7 Added the invalidation mode option Changed in version 3 9 Added the s p e and hardlink dupes options Raised the default recursion limit from 10 to sys getrecursionlimit Added the possibility to specify the o option multiple times There is no command line option to control the optimization level used by the compile funct,en
592,ion because the Python interpreter itself already provides the option python O m compileall Similarly the compile function respects the sys pycache_prefix setting The generated bytecode cache will only be useful if compile is run with the same sys pycache_prefix if any that will be used at runtime Public functions compileall compile_dir dir maxlevels sys getrecursionlimit ddir None force False rx None quiet 0 legacy False optimize 1 workers 1 invalidation_mode None stripdir None prependdir None limit_sl_dest None hardlink_dupes False Recursively descend the directory tree named by dir compiling all py files along the way Return a true value if all the files compiled successfully and a false value otherwise The maxlevels parameter is used to limit the depth of the recursion it defaults to sys getrecursionlimit If ddir is given it is prepended to the path to each file being compiled for use in compilation time tracebacks and is also compiled in to the byte code file where it will be used in tracebacks and other messages in cases where the source file does not exist at the time the byte code file is executed If force is true modules are re compiled even if the timestamps are up to date If rx is given its search method is called on the complete path to each file considered for compilation and if it returns a true value the file is skipped This can be used to exclude files matching a regular expression given as a re Pattern object If quiet is False or 0 the default the filenames and other information are printed to standard out Set to 1 only errors are printed Set to 2 all output is suppressed If legacy is true byte code files are written to their legacy locations and names which may overwrite byte code files created by another version of Python The default is to write files to their PEP 3147 locations and names which allows byte code files from multiple versions of Python to coexist optimize specifies the optimization level for the compiler It is passed to the built in compile function Accepts also a sequence of optimization levels which lead to multiple compilations of one py file in one call The argument workers specifies how many workers are used to compile files in parallel The default is to not use multiple workers If the platform can t use multiple workers and workers argument is given then sequential compilation will be used as a fallback If workers is 0 the number of cores in the system is used If workers is lower than 0 a ValueError will be raised invalidation_mode should be a member of the py_compile PycInvalidationMode enum and controls how the generated pycs are invalidated at runtime The stripdir prependdir and limit_sl_dest arguments correspond to the s p and e options described above They may be specified as str or os PathLike If hardlink_dupes is true and two pyc files with different optimization level have the same content use hard links to consolidate duplicate files Changed in version 3 2 Added the legacy and optimize parameter Changed in version 3 5 Added the workers parameter Changed in version 3 5 quiet parameter was changed to a multilevel value Changed in version 3 5 The legacy parameter only writes out pyc files not pyo files no matter what the value of optimize is Changed in version 3 6 Accepts a path like object Changed in version 3 7 The invalidation_mode parameter was added Changed in version 3 7 2 The invalidation_mode parameter s default value is updated to None Changed in version 3 8 Setting workers to 0 now chooses the optimal number of cores Changed in version 3 9 Added stripdir prependdir limit_sl_dest and hardlink_dupes arguments Default value of maxlevels was changed from 10 to sys getrecursionlimit compileall compile_file fullname ddir None force False rx None quiet 0 legacy False optimize 1 invalidation_mode None stripdir None prependdir None limit_sl_dest None hardlink_dupes False Compile the file with path fullname Return a true value if the file compiled successfully and a false value otherwise If ddir is given it is prepended to the path to the file being compiled for use in compila,en
593,tion time tracebacks and is also compiled in to the byte code file where it will be used in tracebacks and other messages in cases where the source file does not exist at the time the byte code file is executed If rx is given its search method is passed the full path name to the file being compiled and if it returns a true value the file is not compiled and True is returned This can be used to exclude files matching a regular expression given as a re Pattern object If quiet is False or 0 the default the filenames and other information are printed to standard out Set to 1 only errors are printed Set to 2 all output is suppressed If legacy is true byte code files are written to their legacy locations and names which may overwrite byte code files created by another version of Python The default is to write files to their PEP 3147 locations and names which allows byte code files from multiple versions of Python to coexist optimize specifies the optimization level for the compiler It is passed to the built in compile function Accepts also a sequence of optimization levels which lead to multiple compilations of one py file in one call invalidation_mode should be a member of the py_compile PycInvalidationMode enum and controls how the generated pycs are invalidated at runtime The stripdir prependdir and limit_sl_dest arguments correspond to the s p and e options described above They may be specified as str or os PathLike If hardlink_dupes is true and two pyc files with different optimization level have the same content use hard links to consolidate duplicate files New in version 3 2 Changed in version 3 5 quiet parameter was changed to a multilevel value Changed in version 3 5 The legacy parameter only writes out pyc files not pyo files no matter what the value of optimize is Changed in version 3 7 The invalidation_mode parameter was added Changed in version 3 7 2 The invalidation_mode parameter s default value is updated to None Changed in version 3 9 Added stripdir prependdir limit_sl_dest and hardlink_dupes arguments compileall compile_path skip_curdir True maxlevels 0 force False quiet 0 legacy False optimize 1 invalidation_mode None Byte compile all the py files found along sys path Return a true value if all the files compiled successfully and a false value otherwise If skip_curdir is true the default the current directory is not included in the search All other parameters are passed to the compile_dir function Note that unlike the other compile functions maxlevels defaults to 0 Changed in version 3 2 Added the legacy and optimize parameter Changed in version 3 5 quiet parameter was changed to a multilevel value Changed in version 3 5 The legacy parameter only writes out pyc files not pyo files no matter what the value of optimize is Changed in version 3 7 The invalidation_mode parameter was added Changed in version 3 7 2 The invalidation_mode parameter s default value is updated to None To force a recompile of all the py files in the Lib subdirectory and all its subdirectories import compileall compileall compile_dir Lib force True Perform same compilation excluding files in svn directories import re compileall compile_dir Lib rx re compile r svn force True pathlib Path objects can also be used import pathlib compileall compile_dir pathlib Path Lib force True See also Module py_compile Byte compile a single source file,en
594,15 Floating Point Arithmetic Issues and Limitations Floating point numbers are represented in computer hardware as base 2 binary fractions For example the decimal fraction 0 625 has value 6 10 2 100 5 1000 and in the same way the binary fraction 0 101 has value 1 2 0 4 1 8 These two fractions have identical values the only real difference being that the first is written in base 10 fractional notation and the second in base 2 Unfortunately most decimal fractions cannot be represented exactly as binary fractions A consequence is that in general the decimal floating point numbers you enter are only approximated by the binary floating point numbers actually stored in the machine The problem is easier to understand at first in base 10 Consider the fraction 1 3 You can approximate that as a base 10 fraction 0 3 or better 0 33 or better 0 333 and so on No matter how many digits you re willing to write down the result will never be exactly 1 3 but will be an increasingly better approximation of 1 3 In the same way no matter how many base 2 digits you re willing to use the decimal value 0 1 cannot be represented exactly as a base 2 fraction In base 2 1 10 is the infinitely repeating fraction 0 0001100110011001100110011001100110011001100110011 Stop at any finite number of bits and you get an approximation On most machines today floats are approximated using a binary fraction with the numerator using the first 53 bits starting with the most significant bit and with the denominator as a power of two In the case of 1 10 the binary fraction is 3602879701896397 2 55 which is close to but not exactly equal to the true value of 1 10 Many users are not aware of the approximation because of the way values are displayed Python only prints a decimal approximation to the true decimal value of the binary approximation stored by the machine On most machines if Python were to print the true decimal value of the binary approximation stored for 0 1 it would have to display 0 1 0 1000000000000000055511151231257827021181583404541015625 That is more digits than most people find useful so Python keeps the number of digits manageable by displaying a rounded value instead 1 10 0 1 Just remember even though the printed result looks like the exact value of 1 10 the actual stored value is the nearest representable binary fraction Interestingly there are many different decimal numbers that share the same nearest approximate binary fraction For example the numbers 0 1 and 0 10000000000000001 and 0 1000000000000000055511151231257827021181583404541015625 are all approximated by 3602879701896397 2 55 Since all of these decimal values share the same approximation any one of them could be displayed while still preserving the invariant eval repr x x Historically the Python prompt and built in repr function would choose the one with 17 significant digits 0 10000000000000001 Starting with Python 3 1 Python on most systems is now able to choose the shortest of these and simply display 0 1 Note that this is in the very nature of binary floating point this is not a bug in Python and it is not a bug in your code either You ll see the same kind of thing in all languages that support your hardware s floating point arithmetic although some languages may not display the difference by default or in all output modes For more pleasant output you may wish to use string formatting to produce a limited number of significant digits format math pi 12g give 12 significant digits 3 14159265359 format math pi 2f give 2 digits after the point 3 14 repr math pi 3 141592653589793 It s important to realize that this is in a real sense an illusion you re simply rounding the display of the true machine value One illusion may beget another For example since 0 1 is not exactly 1 10 summing three values of 0 1 may not yield exactly 0 3 either 0 1 0 1 0 1 0 3 False Also since the 0 1 cannot get any closer to the exact value of 1 10 and 0 3 cannot get any closer to the exact value of 3 10 then pre rounding with round function cannot help round 0 1 1 round 0 1 1 round 0 1 1 round 0 3 1 False Thou,en
595,gh the numbers cannot be made closer to their intended exact values the math isclose function can be useful for comparing inexact values math isclose 0 1 0 1 0 1 0 3 True Alternatively the round function can be used to compare rough approximations round math pi ndigits 2 round 22 7 ndigits 2 True Binary floating point arithmetic holds many surprises like this The problem with 0 1 is explained in precise detail below in the Representation Error section See Examples of Floating Point Problems for a pleasant summary of how binary floating point works and the kinds of problems commonly encountered in practice Also see The Perils of Floating Point for a more complete account of other common surprises As that says near the end there are no easy answers Still don t be unduly wary of floating point The errors in Python float operations are inherited from the floating point hardware and on most machines are on the order of no more than 1 part in 2 53 per operation That s more than adequate for most tasks but you do need to keep in mind that it s not decimal arithmetic and that every float operation can suffer a new rounding error While pathological cases do exist for most casual use of floating point arithmetic you ll see the result you expect in the end if you simply round the display of your final results to the number of decimal digits you expect str usually suffices and for finer control see the str format method s format specifiers in Format String Syntax For use cases which require exact decimal representation try using the decimal module which implements decimal arithmetic suitable for accounting applications and high precision applications Another form of exact arithmetic is supported by the fractions module which implements arithmetic based on rational numbers so the numbers like 1 3 can be represented exactly If you are a heavy user of floating point operations you should take a look at the NumPy package and many other packages for mathematical and statistical operations supplied by the SciPy project See https scipy org Python provides tools that may help on those rare occasions when you really do want to know the exact value of a float The float as_integer_ratio method expresses the value of a float as a fraction x 3 14159 x as_integer_ratio 3537115888337719 1125899906842624 Since the ratio is exact it can be used to losslessly recreate the original value x 3537115888337719 1125899906842624 True The float hex method expresses a float in hexadecimal base 16 again giving the exact value stored by your computer x hex 0x1 921f9f01b866ep 1 This precise hexadecimal representation can be used to reconstruct the float value exactly x float fromhex 0x1 921f9f01b866ep 1 True Since the representation is exact it is useful for reliably porting values across different versions of Python platform independence and exchanging data with other languages that support the same format such as Java and C99 Another helpful tool is the sum function which helps mitigate loss of precision during summation It uses extended precision for intermediate rounding steps as values are added onto a running total That can make a difference in overall accuracy so that the errors do not accumulate to the point where they affect the final total 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 1 0 False sum 0 1 10 1 0 True The math fsum goes further and tracks all of the lost digits as values are added onto a running total so that the result has only a single rounding This is slower than sum but will be more accurate in uncommon cases where large magnitude inputs mostly cancel each other out leaving a final sum near zero arr 0 10430216751806065 266310978 67179024 143401161448607 16 143401161400469 7 266262841 31058735 0 003244936839808227 float sum map Fraction arr Exact summation with single rounding 8 042173697819788e 13 math fsum arr Single rounding 8 042173697819788e 13 sum arr Multiple roundings in extended precision 8 042178034628478e 13 total 0 0 for x in arr total x Multiple roundings in standard precision total Straight addition has no correct digits 0 00515,en
596,75902860057365 15 1 Representation Error This section explains the 0 1 example in detail and shows how you can perform an exact analysis of cases like this yourself Basic familiarity with binary floating point representation is assumed Representation error refers to the fact that some most actually decimal fractions cannot be represented exactly as binary base 2 fractions This is the chief reason why Python or Perl C C Java Fortran and many others often won t display the exact decimal number you expect Why is that 1 10 is not exactly representable as a binary fraction Since at least 2000 almost all machines use IEEE 754 binary floating point arithmetic and almost all platforms map Python floats to IEEE 754 binary64 double precision values IEEE 754 binary64 values contain 53 bits of precision so on input the computer strives to convert 0 1 to the closest fraction it can of the form J 2 N where J is an integer containing exactly 53 bits Rewriting 1 10 J 2 N as J 2 N 10 and recalling that J has exactly 53 bits is 2 52 but 2 53 the best value for N is 56 2 52 2 56 10 2 53 True That is 56 is the only value for N that leaves J with exactly 53 bits The best possible value for J is then that quotient rounded q r divmod 2 56 10 r 6 Since the remainder is more than half of 10 the best approximation is obtained by rounding up q 1 7205759403792794 Therefore the best possible approximation to 1 10 in IEEE 754 double precision is 7205759403792794 2 56 Dividing both the numerator and denominator by two reduces the fraction to 3602879701896397 2 55 Note that since we rounded up this is actually a little bit larger than 1 10 if we had not rounded up the quotient would have been a little bit smaller than 1 10 But in no case can it be exactly 1 10 So the computer never sees 1 10 what it sees is the exact fraction given above the best IEEE 754 double approximation it can get 0 1 2 55 3602879701896397 0 If we multiply that fraction by 10 55 we can see the value out to 55 decimal digits 3602879701896397 10 55 2 55 1000000000000000055511151231257827021181583404541015625 meaning that the exact number stored in the computer is equal to the decimal value 0 1000000000000000055511151231257827021181583404541015625 Instead of displaying the full decimal value many languages including older versions of Python round the result to 17 significant digits format 0 1 17f 0 10000000000000001 The fractions and decimal modules make these calculations easy from decimal import Decimal from fractions import Fraction Fraction from_float 0 1 Fraction 3602879701896397 36028797018963968 0 1 as_integer_ratio 3602879701896397 36028797018963968 Decimal from_float 0 1 Decimal 0 1000000000000000055511151231257827021181583404541015625 format Decimal from_float 0 1 17 0 10000000000000001,en
597,Numeric and Mathematical Modules The modules described in this chapter provide numeric and math related functions and data types The numbers module defines an abstract hierarchy of numeric types The math and cmath modules contain various mathematical functions for floating point and complex numbers The decimal module supports exact representations of decimal numbers using arbitrary precision arithmetic The following modules are documented in this chapter numbers Numeric abstract base classes The numeric tower Notes for type implementors Adding More Numeric ABCs Implementing the arithmetic operations math Mathematical functions Number theoretic and representation functions Power and logarithmic functions Trigonometric functions Angular conversion Hyperbolic functions Special functions Constants cmath Mathematical functions for complex numbers Conversions to and from polar coordinates Power and logarithmic functions Trigonometric functions Hyperbolic functions Classification functions Constants decimal Decimal fixed point and floating point arithmetic Quick start Tutorial Decimal objects Logical operands Context objects Constants Rounding modes Signals Floating Point Notes Mitigating round off error with increased precision Special values Working with threads Recipes Decimal FAQ fractions Rational numbers random Generate pseudo random numbers Bookkeeping functions Functions for bytes Functions for integers Functions for sequences Discrete distributions Real valued distributions Alternative Generator Notes on Reproducibility Examples Recipes statistics Mathematical statistics functions Averages and measures of central location Measures of spread Statistics for relations between two inputs Function details Exceptions NormalDist objects NormalDist Examples and Recipes Classic probability problems Monte Carlo inputs for simulations Approximating binomial distributions Naive bayesian classifier Kernel density estimation,en
598,zoneinfo IANA time zone support New in version 3 9 Source code Lib zoneinfo The zoneinfo module provides a concrete time zone implementation to support the IANA time zone database as originally specified in PEP 615 By default zoneinfo uses the system s time zone data if available if no system time zone data is available the library will fall back to using the first party tzdata package available on PyPI See also Module datetime Provides the time and datetime types with which the ZoneInfo class is designed to be used Package tzdata First party package maintained by the CPython core developers to supply time zone data via PyPI Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information Using ZoneInfo ZoneInfo is a concrete implementation of the datetime tzinfo abstract base class and is intended to be attached to tzinfo either via the constructor the datetime replace method or datetime astimezone from zoneinfo import ZoneInfo from datetime import datetime timedelta dt datetime 2020 10 31 12 tzinfo ZoneInfo America Los_Angeles print dt 2020 10 31 12 00 00 07 00 dt tzname PDT Datetimes constructed in this way are compatible with datetime arithmetic and handle daylight saving time transitions with no further intervention dt_add dt timedelta days 1 print dt_add 2020 11 01 12 00 00 08 00 dt_add tzname PST These time zones also support the fold attribute introduced in PEP 495 During offset transitions which induce ambiguous times such as a daylight saving time to standard time transition the offset from before the transition is used when fold 0 and the offset after the transition is used when fold 1 for example dt datetime 2020 11 1 1 tzinfo ZoneInfo America Los_Angeles print dt 2020 11 01 01 00 00 07 00 print dt replace fold 1 2020 11 01 01 00 00 08 00 When converting from another time zone the fold will be set to the correct value from datetime import timezone LOS_ANGELES ZoneInfo America Los_Angeles dt_utc datetime 2020 11 1 8 tzinfo timezone utc Before the PDT PST transition print dt_utc astimezone LOS_ANGELES 2020 11 01 01 00 00 07 00 After the PDT PST transition print dt_utc timedelta hours 1 astimezone LOS_ANGELES 2020 11 01 01 00 00 08 00 Data sources The zoneinfo module does not directly provide time zone data and instead pulls time zone information from the system time zone database or the first party PyPI package tzdata if available Some systems including notably Windows systems do not have an IANA database available and so for projects targeting cross platform compatibility that require time zone data it is recommended to declare a dependency on tzdata If neither system data nor tzdata are available all calls to ZoneInfo will raise ZoneInfoNotFoundError Configuring the data sources When ZoneInfo key is called the constructor first searches the directories specified in TZPATH for a file matching key and on failure looks for a match in the tzdata package This behavior can be configured in three ways 1 The default TZPATH when not otherwise specified can be configured at compile time 2 TZPATH can be configured using an environment variable 3 At runtime the search path can be manipulated using the reset_tzpath function Compile time configuration The default TZPATH includes several common deployment locations for the time zone database except on Windows where there are no well known locations for time zone data On POSIX systems downstream distributors and those building Python from source who know where their system time zone data is deployed may change the default time zone path by specifying the compile time option TZPATH or more likely the configure flag with tzpath which should be a string delimited by os pathsep On all platforms the configured value is available as the TZPATH key in sysconfig get_config_var Environment configuration When initializing TZPATH either at import time or whenever reset_tzpath is called with no arguments the zoneinfo module will use the environment variable PYTHONT,en
599,ZPATH if it exists to set the search path PYTHONTZPATH This is an os pathsep separated string containing the time zone search path to use It must consist of only absolute rather than relative paths Relative components specified in PYTHONTZPATH will not be used but otherwise the behavior when a relative path is specified is implementation defined CPython will raise InvalidTZPathWarning but other implementations are free to silently ignore the erroneous component or raise an exception To set the system to ignore the system data and use the tzdata package instead set PYTHONTZPATH Runtime configuration The TZ search path can also be configured at runtime using the reset_tzpath function This is generally not an advisable operation though it is reasonable to use it in test functions that require the use of a specific time zone path or require disabling access to the system time zones The ZoneInfo class class zoneinfo ZoneInfo key A concrete datetime tzinfo subclass that represents an IANA time zone specified by the string key Calls to the primary constructor will always return objects that compare identically put another way barring cache invalidation via ZoneInfo clear_cache for all values of key the following assertion will always be true a ZoneInfo key b ZoneInfo key assert a is b key must be in the form of a relative normalized POSIX path with no up level references The constructor will raise ValueError if a non conforming key is passed If no file matching key is found the constructor will raise ZoneInfoNotFoundError The ZoneInfo class has two alternate constructors classmethod ZoneInfo from_file fobj key None Constructs a ZoneInfo object from a file like object returning bytes e g a file opened in binary mode or an io BytesIO object Unlike the primary constructor this always constructs a new object The key parameter sets the name of the zone for the purposes of __str__ and __repr__ Objects created via this constructor cannot be pickled see pickling classmethod ZoneInfo no_cache key An alternate constructor that bypasses the constructor s cache It is identical to the primary constructor but returns a new object on each call This is most likely to be useful for testing or demonstration purposes but it can also be used to create a system with a different cache invalidation strategy Objects created via this constructor will also bypass the cache of a deserializing process when unpickled Caution Using this constructor may change the semantics of your datetimes in surprising ways only use it if you know that you need to The following class methods are also available classmethod ZoneInfo clear_cache only_keys None A method for invalidating the cache on the ZoneInfo class If no arguments are passed all caches are invalidated and the next call to the primary constructor for each key will return a new instance If an iterable of key names is passed to the only_keys parameter only the specified keys will be removed from the cache Keys passed to only_keys but not found in the cache are ignored Warning Invoking this function may change the semantics of datetimes using ZoneInfo in surprising ways this modifies module state and thus may have wide ranging effects Only use it if you know that you need to The class has one attribute ZoneInfo key This is a read only attribute that returns the value of key passed to the constructor which should be a lookup key in the IANA time zone database e g America New_York Europe Paris or Asia Tokyo For zones constructed from file without specifying a key parameter this will be set to None Note Although it is a somewhat common practice to expose these to end users these values are designed to be primary keys for representing the relevant zones and not necessarily user facing elements Projects like CLDR the Unicode Common Locale Data Repository can be used to get more user friendly strings from these keys String representations The string representation returned when calling str on a ZoneInfo object defaults to using the ZoneInfo key attribute see the note on usage in the attribute documentation zone Zone,en
600,Info Pacific Kwajalein str zone Pacific Kwajalein dt datetime 2020 4 1 3 15 tzinfo zone f dt isoformat dt tzinfo 2020 04 01T03 15 00 12 00 Pacific Kwajalein For objects constructed from a file without specifying a key parameter str falls back to calling repr ZoneInfo s repr is implementation defined and not necessarily stable between versions but it is guaranteed not to be a valid ZoneInfo key Pickle serialization Rather than serializing all transition data ZoneInfo objects are serialized by key and ZoneInfo objects constructed from files even those with a value for key specified cannot be pickled The behavior of a ZoneInfo file depends on how it was constructed 1 ZoneInfo key When constructed with the primary constructor a ZoneInfo object is serialized by key and when deserialized the deserializing process uses the primary and thus it is expected that these are expected to be the same object as other references to the same time zone For example if europe_berlin_pkl is a string containing a pickle constructed from ZoneInfo Europe Berlin one would expect the following behavior a ZoneInfo Europe Berlin b pickle loads europe_berlin_pkl a is b True 2 ZoneInfo no_cache key When constructed from the cache bypassing constructor the ZoneInfo object is also serialized by key but when deserialized the deserializing process uses the cache bypassing constructor If europe_berlin_pkl_nc is a string containing a pickle constructed from ZoneInfo no_cache Europe Berlin one would expect the following behavior a ZoneInfo Europe Berlin b pickle loads europe_berlin_pkl_nc a is b False 3 ZoneInfo from_file fobj key None When constructed from a file the ZoneInfo object raises an exception on pickling If an end user wants to pickle a ZoneInfo constructed from a file it is recommended that they use a wrapper type or a custom serialization function either serializing by key or storing the contents of the file object and serializing that This method of serialization requires that the time zone data for the required key be available on both the serializing and deserializing side similar to the way that references to classes and functions are expected to exist in both the serializing and deserializing environments It also means that no guarantees are made about the consistency of results when unpickling a ZoneInfo pickled in an environment with a different version of the time zone data Functions zoneinfo available_timezones Get a set containing all the valid keys for IANA time zones available anywhere on the time zone path This is recalculated on every call to the function This function only includes canonical zone names and does not include special zones such as those under the posix and right directories or the posixrules zone Caution This function may open a large number of files as the best way to determine if a file on the time zone path is a valid time zone is to read the magic string at the beginning Note These values are not designed to be exposed to end users for user facing elements applications should use something like CLDR the Unicode Common Locale Data Repository to get more user friendly strings See also the cautionary note on ZoneInfo key zoneinfo reset_tzpath to None Sets or resets the time zone search path TZPATH for the module When called with no arguments TZPATH is set to the default value Calling reset_tzpath will not invalidate the ZoneInfo cache and so calls to the primary ZoneInfo constructor will only use the new TZPATH in the case of a cache miss The to parameter must be a sequence of strings or os PathLike and not a string all of which must be absolute paths ValueError will be raised if something other than an absolute path is passed Globals zoneinfo TZPATH A read only sequence representing the time zone search path when constructing a ZoneInfo from a key the key is joined to each entry in the TZPATH and the first file found is used TZPATH may contain only absolute paths never relative paths regardless of how it is configured The object that zoneinfo TZPATH points to may change in response to a call to reset_tzpath so it i,en
601,s recommended to use zoneinfo TZPATH rather than importing TZPATH from zoneinfo or assigning a long lived variable to zoneinfo TZPATH For more information on configuring the time zone search path see Configuring the data sources Exceptions and warnings exception zoneinfo ZoneInfoNotFoundError Raised when construction of a ZoneInfo object fails because the specified key could not be found on the system This is a subclass of KeyError exception zoneinfo InvalidTZPathWarning Raised when PYTHONTZPATH contains an invalid component that will be filtered out such as a relative path,en
602,decimal Decimal fixed point and floating point arithmetic Source code Lib decimal py The decimal module provides support for fast correctly rounded decimal floating point arithmetic It offers several advantages over the float datatype Decimal is based on a floating point model which was designed with people in mind and necessarily has a paramount guiding principle computers must provide an arithmetic that works in the same way as the arithmetic that people learn at school excerpt from the decimal arithmetic specification Decimal numbers can be represented exactly In contrast numbers like 1 1 and 2 2 do not have exact representations in binary floating point End users typically would not expect 1 1 2 2 to display as 3 3000000000000003 as it does with binary floating point The exactness carries over into arithmetic In decimal floating point 0 1 0 1 0 1 0 3 is exactly equal to zero In binary floating point the result is 5 5511151231257827e 017 While near to zero the differences prevent reliable equality testing and differences can accumulate For this reason decimal is preferred in accounting applications which have strict equality invariants The decimal module incorporates a notion of significant places so that 1 30 1 20 is 2 50 The trailing zero is kept to indicate significance This is the customary presentation for monetary applications For multiplication the schoolbook approach uses all the figures in the multiplicands For instance 1 3 1 2 gives 1 56 while 1 30 1 20 gives 1 5600 Unlike hardware based binary floating point the decimal module has a user alterable precision defaulting to 28 places which can be as large as needed for a given problem from decimal import getcontext prec 6 Decimal 1 Decimal 7 Decimal 0 142857 getcontext prec 28 Decimal 1 Decimal 7 Decimal 0 1428571428571428571428571429 Both binary and decimal floating point are implemented in terms of published standards While the built in float type exposes only a modest portion of its capabilities the decimal module exposes all required parts of the standard When needed the programmer has full control over rounding and signal handling This includes an option to enforce exact arithmetic by using exceptions to block any inexact operations The decimal module was designed to support without prejudice both exact unrounded decimal arithmetic sometimes called fixed point arithmetic and rounded floating point arithmetic excerpt from the decimal arithmetic specification The module design is centered around three concepts the decimal number the context for arithmetic and signals A decimal number is immutable It has a sign coefficient digits and an exponent To preserve significance the coefficient digits do not truncate trailing zeros Decimals also include special values such as Infinity Infinity and NaN The standard also differentiates 0 from 0 The context for arithmetic is an environment specifying precision rounding rules limits on exponents flags indicating the results of operations and trap enablers which determine whether signals are treated as exceptions Rounding options include ROUND_CEILING ROUND_DOWN ROUND_FLOOR ROUND_HALF_DOWN ROUND_HALF_EVEN ROUND_HALF_UP ROUND_UP and ROUND_05UP Signals are groups of exceptional conditions arising during the course of computation Depending on the needs of the application signals may be ignored considered as informational or treated as exceptions The signals in the decimal module are Clamped InvalidOperation DivisionByZero Inexact Rounded Subnormal Overflow Underflow and FloatOperation For each signal there is a flag and a trap enabler When a signal is encountered its flag is set to one then if the trap enabler is set to one an exception is raised Flags are sticky so the user needs to reset them before monitoring a calculation See also IBM s General Decimal Arithmetic Specification The General Decimal Arithmetic Specification Quick start Tutorial The usual start to using decimals is importing the module viewing the current context with getcontext and if necessary setting new values for precision rounding or enabled traps from,en
603, decimal import getcontext Context prec 28 rounding ROUND_HALF_EVEN Emin 999999 Emax 999999 capitals 1 clamp 0 flags traps Overflow DivisionByZero InvalidOperation getcontext prec 7 Set a new precision Decimal instances can be constructed from integers strings floats or tuples Construction from an integer or a float performs an exact conversion of the value of that integer or float Decimal numbers include special values such as NaN which stands for Not a number positive and negative Infinity and 0 getcontext prec 28 Decimal 10 Decimal 10 Decimal 3 14 Decimal 3 14 Decimal 3 14 Decimal 3 140000000000000124344978758017532527446746826171875 Decimal 0 3 1 4 2 Decimal 3 14 Decimal str 2 0 0 5 Decimal 1 4142135623730951 Decimal 2 Decimal 0 5 Decimal 1 414213562373095048801688724 Decimal NaN Decimal NaN Decimal Infinity Decimal Infinity If the FloatOperation signal is trapped accidental mixing of decimals and floats in constructors or ordering comparisons raises an exception c getcontext c traps FloatOperation True Decimal 3 14 Traceback most recent call last File stdin line 1 in module decimal FloatOperation class decimal FloatOperation Decimal 3 5 3 7 Traceback most recent call last File stdin line 1 in module decimal FloatOperation class decimal FloatOperation Decimal 3 5 3 5 True New in version 3 3 The significance of a new Decimal is determined solely by the number of digits input Context precision and rounding only come into play during arithmetic operations getcontext prec 6 Decimal 3 0 Decimal 3 0 Decimal 3 1415926535 Decimal 3 1415926535 Decimal 3 1415926535 Decimal 2 7182818285 Decimal 5 85987 getcontext rounding ROUND_UP Decimal 3 1415926535 Decimal 2 7182818285 Decimal 5 85988 If the internal limits of the C version are exceeded constructing a decimal raises InvalidOperation Decimal 1e9999999999999999999 Traceback most recent call last File stdin line 1 in module decimal InvalidOperation class decimal InvalidOperation Changed in version 3 3 Decimals interact well with much of the rest of Python Here is a small decimal floating point flying circus data list map Decimal 1 34 1 87 3 45 2 35 1 00 0 03 9 25 split max data Decimal 9 25 min data Decimal 0 03 sorted data Decimal 0 03 Decimal 1 00 Decimal 1 34 Decimal 1 87 Decimal 2 35 Decimal 3 45 Decimal 9 25 sum data Decimal 19 29 a b c data 3 str a 1 34 float a 1 34 round a 1 Decimal 1 3 int a 1 a 5 Decimal 6 70 a b Decimal 2 5058 c a Decimal 0 77 And some mathematical functions are also available to Decimal getcontext prec 28 Decimal 2 sqrt Decimal 1 414213562373095048801688724 Decimal 1 exp Decimal 2 718281828459045235360287471 Decimal 10 ln Decimal 2 302585092994045684017991455 Decimal 10 log10 Decimal 1 The quantize method rounds a number to a fixed exponent This method is useful for monetary applications that often round results to a fixed number of places Decimal 7 325 quantize Decimal 01 rounding ROUND_DOWN Decimal 7 32 Decimal 7 325 quantize Decimal 1 rounding ROUND_UP Decimal 8 As shown above the getcontext function accesses the current context and allows the settings to be changed This approach meets the needs of most applications For more advanced work it may be useful to create alternate contexts using the Context constructor To make an alternate active use the setcontext function In accordance with the standard the decimal module provides two ready to use standard contexts BasicContext and ExtendedContext The former is especially useful for debugging because many of the traps are enabled myothercontext Context prec 60 rounding ROUND_HALF_DOWN setcontext myothercontext Decimal 1 Decimal 7 Decimal 0 142857142857142857142857142857142857142857142857142857142857 ExtendedContext Context prec 9 rounding ROUND_HALF_EVEN Emin 999999 Emax 999999 capitals 1 clamp 0 flags traps setcontext ExtendedContext Decimal 1 Decimal 7 Decimal 0 142857143 Decimal 42 Decimal 0 Decimal Infinity setcontext BasicContext Decimal 42 Decimal 0 Traceback most recent call last File pyshell 143 line 1 in toplevel Decimal 42 Decimal 0 DivisionByZero x 0 Contexts also have signal flags for moni,en
604,toring exceptional conditions encountered during computations The flags remain set until explicitly cleared so it is best to clear the flags before each set of monitored computations by using the clear_flags method setcontext ExtendedContext getcontext clear_flags Decimal 355 Decimal 113 Decimal 3 14159292 getcontext Context prec 9 rounding ROUND_HALF_EVEN Emin 999999 Emax 999999 capitals 1 clamp 0 flags Inexact Rounded traps The flags entry shows that the rational approximation to pi was rounded digits beyond the context precision were thrown away and that the result is inexact some of the discarded digits were non zero Individual traps are set using the dictionary in the traps attribute of a context setcontext ExtendedContext Decimal 1 Decimal 0 Decimal Infinity getcontext traps DivisionByZero 1 Decimal 1 Decimal 0 Traceback most recent call last File pyshell 112 line 1 in toplevel Decimal 1 Decimal 0 DivisionByZero x 0 Most programs adjust the current context only once at the beginning of the program And in many applications data is converted to Decimal with a single cast inside a loop With context set and decimals created the bulk of the program manipulates the data no differently than with other Python numeric types Decimal objects class decimal Decimal value 0 context None Construct a new Decimal object based from value value can be an integer string tuple float or another Decimal object If no value is given returns Decimal 0 If value is a string it should conform to the decimal numeric string syntax after leading and trailing whitespace characters as well as underscores throughout are removed sign digit 0 1 2 3 4 5 6 7 8 9 indicator e E digits digit digit decimal part digits digits digits exponent part indicator sign digits infinity Infinity Inf nan NaN digits sNaN digits numeric value decimal part exponent part infinity numeric string sign numeric value sign nan Other Unicode decimal digits are also permitted where digit appears above These include decimal digits from various other alphabets for example Arabic Indic and Devanāgarī digits along with the fullwidth digits uff10 through uff19 If value is a tuple it should have three components a sign 0 for positive or 1 for negative a tuple of digits and an integer exponent For example Decimal 0 1 4 1 4 3 returns Decimal 1 414 If value is a float the binary floating point value is losslessly converted to its exact decimal equivalent This conversion can often require 53 or more digits of precision For example Decimal float 1 1 converts to Decimal 1 100000000000000088817841970012523233890533447265625 The context precision does not affect how many digits are stored That is determined exclusively by the number of digits in value For example Decimal 3 00000 records all five zeros even if the context precision is only three The purpose of the context argument is determining what to do if value is a malformed string If the context traps InvalidOperation an exception is raised otherwise the constructor returns a new Decimal with the value of NaN Once constructed Decimal objects are immutable Changed in version 3 2 The argument to the constructor is now permitted to be a float instance Changed in version 3 3 float arguments raise an exception if the FloatOperation trap is set By default the trap is off Changed in version 3 6 Underscores are allowed for grouping as with integral and floating point literals in code Decimal floating point objects share many properties with the other built in numeric types such as float and int All of the usual math operations and special methods apply Likewise decimal objects can be copied pickled printed used as dictionary keys used as set elements compared sorted and coerced to another type such as float or int There are some small differences between arithmetic on Decimal objects and arithmetic on integers and floats When the remainder operator is applied to Decimal objects the sign of the result is the sign of the dividend rather than the sign of the divisor 7 4 1 Decimal 7 Decimal 4 Decimal 3 The integer division operator behaves analogousl,en
605,y returning the integer part of the true quotient truncating towards zero rather than its floor so as to preserve the usual identity x x y y x y 7 4 2 Decimal 7 Decimal 4 Decimal 1 The and operators implement the remainder and divide integer operations respectively as described in the specification Decimal objects cannot generally be combined with floats or instances of fractions Fraction in arithmetic operations an attempt to add a Decimal to a float for example will raise a TypeError However it is possible to use Python s comparison operators to compare a Decimal instance x with another number y This avoids confusing results when doing equality comparisons between numbers of different types Changed in version 3 2 Mixed type comparisons between Decimal instances and other numeric types are now fully supported In addition to the standard numeric properties decimal floating point objects also have a number of specialized methods adjusted Return the adjusted exponent after shifting out the coefficient s rightmost digits until only the lead digit remains Decimal 321e 5 adjusted returns seven Used for determining the position of the most significant digit with respect to the decimal point as_integer_ratio Return a pair n d of integers that represent the given Decimal instance as a fraction in lowest terms and with a positive denominator Decimal 3 14 as_integer_ratio 157 50 The conversion is exact Raise OverflowError on infinities and ValueError on NaNs New in version 3 6 as_tuple Return a named tuple representation of the number DecimalTuple sign digits exponent canonical Return the canonical encoding of the argument Currently the encoding of a Decimal instance is always canonical so this operation returns its argument unchanged compare other context None Compare the values of two Decimal instances compare returns a Decimal instance and if either operand is a NaN then the result is a NaN a or b is a NaN Decimal NaN a b Decimal 1 a b Decimal 0 a b Decimal 1 compare_signal other context None This operation is identical to the compare method except that all NaNs signal That is if neither operand is a signaling NaN then any quiet NaN operand is treated as though it were a signaling NaN compare_total other context None Compare two operands using their abstract representation rather than their numerical value Similar to the compare method but the result gives a total ordering on Decimal instances Two Decimal instances with the same numeric value but different representations compare unequal in this ordering Decimal 12 0 compare_total Decimal 12 Decimal 1 Quiet and signaling NaNs are also included in the total ordering The result of this function is Decimal 0 if both operands have the same representation Decimal 1 if the first operand is lower in the total order than the second and Decimal 1 if the first operand is higher in the total order than the second operand See the specification for details of the total order This operation is unaffected by context and is quiet no flags are changed and no rounding is performed As an exception the C version may raise InvalidOperation if the second operand cannot be converted exactly compare_total_mag other context None Compare two operands using their abstract representation rather than their value as in compare_total but ignoring the sign of each operand x compare_total_mag y is equivalent to x copy_abs compare_total y copy_abs This operation is unaffected by context and is quiet no flags are changed and no rounding is performed As an exception the C version may raise InvalidOperation if the second operand cannot be converted exactly conjugate Just returns self this method is only to comply with the Decimal Specification copy_abs Return the absolute value of the argument This operation is unaffected by the context and is quiet no flags are changed and no rounding is performed copy_negate Return the negation of the argument This operation is unaffected by the context and is quiet no flags are changed and no rounding is performed copy_sign other context None Return a copy of the first operand ,en
606,with the sign set to be the same as the sign of the second operand For example Decimal 2 3 copy_sign Decimal 1 5 Decimal 2 3 This operation is unaffected by context and is quiet no flags are changed and no rounding is performed As an exception the C version may raise InvalidOperation if the second operand cannot be converted exactly exp context None Return the value of the natural exponential function e x at the given number The result is correctly rounded using the ROUND_HALF_EVEN rounding mode Decimal 1 exp Decimal 2 718281828459045235360287471 Decimal 321 exp Decimal 2 561702493119680037517373933E 139 classmethod from_float f Alternative constructor that only accepts instances of float or int Note Decimal from_float 0 1 is not the same as Decimal 0 1 Since 0 1 is not exactly representable in binary floating point the value is stored as the nearest representable value which is 0x1 999999999999ap 4 That equivalent value in decimal is 0 1000000000000000055511151231257827021181583404541015625 Note From Python 3 2 onwards a Decimal instance can also be constructed directly from a float Decimal from_float 0 1 Decimal 0 1000000000000000055511151231257827021181583404541015625 Decimal from_float float nan Decimal NaN Decimal from_float float inf Decimal Infinity Decimal from_float float inf Decimal Infinity New in version 3 1 fma other third context None Fused multiply add Return self other third with no rounding of the intermediate product self other Decimal 2 fma 3 5 Decimal 11 is_canonical Return True if the argument is canonical and False otherwise Currently a Decimal instance is always canonical so this operation always returns True is_finite Return True if the argument is a finite number and False if the argument is an infinity or a NaN is_infinite Return True if the argument is either positive or negative infinity and False otherwise is_nan Return True if the argument is a quiet or signaling NaN and False otherwise is_normal context None Return True if the argument is a normal finite number Return False if the argument is zero subnormal infinite or a NaN is_qnan Return True if the argument is a quiet NaN and False otherwise is_signed Return True if the argument has a negative sign and False otherwise Note that zeros and NaNs can both carry signs is_snan Return True if the argument is a signaling NaN and False otherwise is_subnormal context None Return True if the argument is subnormal and False otherwise is_zero Return True if the argument is a positive or negative zero and False otherwise ln context None Return the natural base e logarithm of the operand The result is correctly rounded using the ROUND_HALF_EVEN rounding mode log10 context None Return the base ten logarithm of the operand The result is correctly rounded using the ROUND_HALF_EVEN rounding mode logb context None For a nonzero number return the adjusted exponent of its operand as a Decimal instance If the operand is a zero then Decimal Infinity is returned and the DivisionByZero flag is raised If the operand is an infinity then Decimal Infinity is returned logical_and other context None logical_and is a logical operation which takes two logical operands see Logical operands The result is the digit wise and of the two operands logical_invert context None logical_invert is a logical operation The result is the digit wise inversion of the operand logical_or other context None logical_or is a logical operation which takes two logical operands see Logical operands The result is the digit wise or of the two operands logical_xor other context None logical_xor is a logical operation which takes two logical operands see Logical operands The result is the digit wise exclusive or of the two operands max other context None Like max self other except that the context rounding rule is applied before returning and that NaN values are either signaled or ignored depending on the context and whether they are signaling or quiet max_mag other context None Similar to the max method but the comparison is done using the absolute values of the operands min other context None Like,en
607, min self other except that the context rounding rule is applied before returning and that NaN values are either signaled or ignored depending on the context and whether they are signaling or quiet min_mag other context None Similar to the min method but the comparison is done using the absolute values of the operands next_minus context None Return the largest number representable in the given context or in the current thread s context if no context is given that is smaller than the given operand next_plus context None Return the smallest number representable in the given context or in the current thread s context if no context is given that is larger than the given operand next_toward other context None If the two operands are unequal return the number closest to the first operand in the direction of the second operand If both operands are numerically equal return a copy of the first operand with the sign set to be the same as the sign of the second operand normalize context None Used for producing canonical values of an equivalence class within either the current context or the specified context This has the same semantics as the unary plus operation except that if the final result is finite it is reduced to its simplest form with all trailing zeros removed and its sign preserved That is while the coefficient is non zero and a multiple of ten the coefficient is divided by ten and the exponent is incremented by 1 Otherwise the coefficient is zero the exponent is set to 0 In all cases the sign is unchanged For example Decimal 32 100 and Decimal 0 321000e 2 both normalize to the equivalent value Decimal 32 1 Note that rounding is applied before reducing to simplest form In the latest versions of the specification this operation is also known as reduce number_class context None Return a string describing the class of the operand The returned value is one of the following ten strings Infinity indicating that the operand is negative infinity Normal indicating that the operand is a negative normal number Subnormal indicating that the operand is negative and subnormal Zero indicating that the operand is a negative zero Zero indicating that the operand is a positive zero Subnormal indicating that the operand is positive and subnormal Normal indicating that the operand is a positive normal number Infinity indicating that the operand is positive infinity NaN indicating that the operand is a quiet NaN Not a Number sNaN indicating that the operand is a signaling NaN quantize exp rounding None context None Return a value equal to the first operand after rounding and having the exponent of the second operand Decimal 1 41421356 quantize Decimal 1 000 Decimal 1 414 Unlike other operations if the length of the coefficient after the quantize operation would be greater than precision then an InvalidOperation is signaled This guarantees that unless there is an error condition the quantized exponent is always equal to that of the right hand operand Also unlike other operations quantize never signals Underflow even if the result is subnormal and inexact If the exponent of the second operand is larger than that of the first then rounding may be necessary In this case the rounding mode is determined by the rounding argument if given else by the given context argument if neither argument is given the rounding mode of the current thread s context is used An error is returned whenever the resulting exponent is greater than Emax or less than Etiny radix Return Decimal 10 the radix base in which the Decimal class does all its arithmetic Included for compatibility with the specification remainder_near other context None Return the remainder from dividing self by other This differs from self other in that the sign of the remainder is chosen so as to minimize its absolute value More precisely the return value is self n other where n is the integer nearest to the exact value of self other and if two integers are equally near then the even one is chosen If the result is zero then its sign will be the sign of self Decimal 18 remainder_near Decimal 10 Dec,en
608,imal 2 Decimal 25 remainder_near Decimal 10 Decimal 5 Decimal 35 remainder_near Decimal 10 Decimal 5 rotate other context None Return the result of rotating the digits of the first operand by an amount specified by the second operand The second operand must be an integer in the range precision through precision The absolute value of the second operand gives the number of places to rotate If the second operand is positive then rotation is to the left otherwise rotation is to the right The coefficient of the first operand is padded on the left with zeros to length precision if necessary The sign and exponent of the first operand are unchanged same_quantum other context None Test whether self and other have the same exponent or whether both are NaN This operation is unaffected by context and is quiet no flags are changed and no rounding is performed As an exception the C version may raise InvalidOperation if the second operand cannot be converted exactly scaleb other context None Return the first operand with exponent adjusted by the second Equivalently return the first operand multiplied by 10 other The second operand must be an integer shift other context None Return the result of shifting the digits of the first operand by an amount specified by the second operand The second operand must be an integer in the range precision through precision The absolute value of the second operand gives the number of places to shift If the second operand is positive then the shift is to the left otherwise the shift is to the right Digits shifted into the coefficient are zeros The sign and exponent of the first operand are unchanged sqrt context None Return the square root of the argument to full precision to_eng_string context None Convert to a string using engineering notation if an exponent is needed Engineering notation has an exponent which is a multiple of 3 This can leave up to 3 digits to the left of the decimal place and may require the addition of either one or two trailing zeros For example this converts Decimal 123E 1 to Decimal 1 23E 3 to_integral rounding None context None Identical to the to_integral_value method The to_integral name has been kept for compatibility with older versions to_integral_exact rounding None context None Round to the nearest integer signaling Inexact or Rounded as appropriate if rounding occurs The rounding mode is determined by the rounding parameter if given else by the given context If neither parameter is given then the rounding mode of the current context is used to_integral_value rounding None context None Round to the nearest integer without signaling Inexact or Rounded If given applies rounding otherwise uses the rounding method in either the supplied context or the current context Logical operands The logical_and logical_invert logical_or and logical_xor methods expect their arguments to be logical operands A logical operand is a Decimal instance whose exponent and sign are both zero and whose digits are all either 0 or 1 Context objects Contexts are environments for arithmetic operations They govern precision set rules for rounding determine which signals are treated as exceptions and limit the range for exponents Each thread has its own current context which is accessed or changed using the getcontext and setcontext functions decimal getcontext Return the current context for the active thread decimal setcontext c Set the current context for the active thread to c You can also use the with statement and the localcontext function to temporarily change the active context decimal localcontext ctx None kwargs Return a context manager that will set the current context for the active thread to a copy of ctx on entry to the with statement and restore the previous context when exiting the with statement If no context is specified a copy of the current context is used The kwargs argument is used to set the attributes of the new context For example the following code sets the current decimal precision to 42 places performs a calculation and then automatically restores the previous context from deci,en
609,mal import localcontext with localcontext as ctx ctx prec 42 Perform a high precision calculation s calculate_something s s Round the final result back to the default precision Using keyword arguments the code would be the following from decimal import localcontext with localcontext prec 42 as ctx s calculate_something s s Raises TypeError if kwargs supplies an attribute that Context doesn t support Raises either TypeError or ValueError if kwargs supplies an invalid value for an attribute Changed in version 3 11 localcontext now supports setting context attributes through the use of keyword arguments New contexts can also be created using the Context constructor described below In addition the module provides three pre made contexts class decimal BasicContext This is a standard context defined by the General Decimal Arithmetic Specification Precision is set to nine Rounding is set to ROUND_HALF_UP All flags are cleared All traps are enabled treated as exceptions except Inexact Rounded and Subnormal Because many of the traps are enabled this context is useful for debugging class decimal ExtendedContext This is a standard context defined by the General Decimal Arithmetic Specification Precision is set to nine Rounding is set to ROUND_HALF_EVEN All flags are cleared No traps are enabled so that exceptions are not raised during computations Because the traps are disabled this context is useful for applications that prefer to have result value of NaN or Infinity instead of raising exceptions This allows an application to complete a run in the presence of conditions that would otherwise halt the program class decimal DefaultContext This context is used by the Context constructor as a prototype for new contexts Changing a field such a precision has the effect of changing the default for new contexts created by the Context constructor This context is most useful in multi threaded environments Changing one of the fields before threads are started has the effect of setting system wide defaults Changing the fields after threads have started is not recommended as it would require thread synchronization to prevent race conditions In single threaded environments it is preferable to not use this context at all Instead simply create contexts explicitly as described below The default values are Context prec 28 Context rounding ROUND_HALF_EVEN and enabled traps for Overflow InvalidOperation and DivisionByZero In addition to the three supplied contexts new contexts can be created with the Context constructor class decimal Context prec None rounding None Emin None Emax None capitals None clamp None flags None traps None Creates a new context If a field is not specified or is None the default values are copied from the DefaultContext If the flags field is not specified or is None all flags are cleared prec is an integer in the range 1 MAX_PREC that sets the precision for arithmetic operations in the context The rounding option is one of the constants listed in the section Rounding Modes The traps and flags fields list any signals to be set Generally new contexts should only set traps and leave the flags clear The Emin and Emax fields are integers specifying the outer limits allowable for exponents Emin must be in the range MIN_EMIN 0 Emax in the range 0 MAX_EMAX The capitals field is either 0 or 1 the default If set to 1 exponents are printed with a capital E otherwise a lowercase e is used Decimal 6 02e 23 The clamp field is either 0 the default or 1 If set to 1 the exponent e of a Decimal instance representable in this context is strictly limited to the range Emin prec 1 e Emax prec 1 If clamp is 0 then a weaker condition holds the adjusted exponent of the Decimal instance is at most Emax When clamp is 1 a large normal number will where possible have its exponent reduced and a corresponding number of zeros added to its coefficient in order to fit the exponent constraints this preserves the value of the number but loses information about significant trailing zeros For example Context prec 6 Emax 999 clamp 1 create_decimal 1 23e999 Decimal 1,en
610, 23000E 999 A clamp value of 1 allows compatibility with the fixed width decimal interchange formats specified in IEEE 754 The Context class defines several general purpose methods as well as a large number of methods for doing arithmetic directly in a given context In addition for each of the Decimal methods described above with the exception of the adjusted and as_tuple methods there is a corresponding Context method For example for a Context instance C and Decimal instance x C exp x is equivalent to x exp context C Each Context method accepts a Python integer an instance of int anywhere that a Decimal instance is accepted clear_flags Resets all of the flags to 0 clear_traps Resets all of the traps to 0 New in version 3 3 copy Return a duplicate of the context copy_decimal num Return a copy of the Decimal instance num create_decimal num Creates a new Decimal instance from num but using self as context Unlike the Decimal constructor the context precision rounding method flags and traps are applied to the conversion This is useful because constants are often given to a greater precision than is needed by the application Another benefit is that rounding immediately eliminates unintended effects from digits beyond the current precision In the following example using unrounded inputs means that adding zero to a sum can change the result getcontext prec 3 Decimal 3 4445 Decimal 1 0023 Decimal 4 45 Decimal 3 4445 Decimal 0 Decimal 1 0023 Decimal 4 44 This method implements the to number operation of the IBM specification If the argument is a string no leading or trailing whitespace or underscores are permitted create_decimal_from_float f Creates a new Decimal instance from a float f but rounding using self as the context Unlike the Decimal from_float class method the context precision rounding method flags and traps are applied to the conversion context Context prec 5 rounding ROUND_DOWN context create_decimal_from_float math pi Decimal 3 1415 context Context prec 5 traps Inexact context create_decimal_from_float math pi Traceback most recent call last decimal Inexact None New in version 3 1 Etiny Returns a value equal to Emin prec 1 which is the minimum exponent value for subnormal results When underflow occurs the exponent is set to Etiny Etop Returns a value equal to Emax prec 1 The usual approach to working with decimals is to create Decimal instances and then apply arithmetic operations which take place within the current context for the active thread An alternative approach is to use context methods for calculating within a specific context The methods are similar to those for the Decimal class and are only briefly recounted here abs x Returns the absolute value of x add x y Return the sum of x and y canonical x Returns the same Decimal object x compare x y Compares x and y numerically compare_signal x y Compares the values of the two operands numerically compare_total x y Compares two operands using their abstract representation compare_total_mag x y Compares two operands using their abstract representation ignoring sign copy_abs x Returns a copy of x with the sign set to 0 copy_negate x Returns a copy of x with the sign inverted copy_sign x y Copies the sign from y to x divide x y Return x divided by y divide_int x y Return x divided by y truncated to an integer divmod x y Divides two numbers and returns the integer part of the result exp x Returns e x fma x y z Returns x multiplied by y plus z is_canonical x Returns True if x is canonical otherwise returns False is_finite x Returns True if x is finite otherwise returns False is_infinite x Returns True if x is infinite otherwise returns False is_nan x Returns True if x is a qNaN or sNaN otherwise returns False is_normal x Returns True if x is a normal number otherwise returns False is_qnan x Returns True if x is a quiet NaN otherwise returns False is_signed x Returns True if x is negative otherwise returns False is_snan x Returns True if x is a signaling NaN otherwise returns False is_subnormal x Returns True if x is subnormal otherwise returns False is_zero x Returns,en
611, True if x is a zero otherwise returns False ln x Returns the natural base e logarithm of x log10 x Returns the base 10 logarithm of x logb x Returns the exponent of the magnitude of the operand s MSD logical_and x y Applies the logical operation and between each operand s digits logical_invert x Invert all the digits in x logical_or x y Applies the logical operation or between each operand s digits logical_xor x y Applies the logical operation xor between each operand s digits max x y Compares two values numerically and returns the maximum max_mag x y Compares the values numerically with their sign ignored min x y Compares two values numerically and returns the minimum min_mag x y Compares the values numerically with their sign ignored minus x Minus corresponds to the unary prefix minus operator in Python multiply x y Return the product of x and y next_minus x Returns the largest representable number smaller than x next_plus x Returns the smallest representable number larger than x next_toward x y Returns the number closest to x in direction towards y normalize x Reduces x to its simplest form number_class x Returns an indication of the class of x plus x Plus corresponds to the unary prefix plus operator in Python This operation applies the context precision and rounding so it is not an identity operation power x y modulo None Return x to the power of y reduced modulo modulo if given With two arguments compute x y If x is negative then y must be integral The result will be inexact unless y is integral and the result is finite and can be expressed exactly in precision digits The rounding mode of the context is used Results are always correctly rounded in the Python version Decimal 0 Decimal 0 results in InvalidOperation and if InvalidOperation is not trapped then results in Decimal NaN Changed in version 3 3 The C module computes power in terms of the correctly rounded exp and ln functions The result is well defined but only almost always correctly rounded With three arguments compute x y modulo For the three argument form the following restrictions on the arguments hold all three arguments must be integral y must be nonnegative at least one of x or y must be nonzero modulo must be nonzero and have at most precision digits The value resulting from Context power x y modulo is equal to the value that would be obtained by computing x y modulo with unbounded precision but is computed more efficiently The exponent of the result is zero regardless of the exponents of x y and modulo The result is always exact quantize x y Returns a value equal to x rounded having the exponent of y radix Just returns 10 as this is Decimal remainder x y Returns the remainder from integer division The sign of the result if non zero is the same as that of the original dividend remainder_near x y Returns x y n where n is the integer nearest the exact value of x y if the result is 0 then its sign will be the sign of x rotate x y Returns a rotated copy of x y times same_quantum x y Returns True if the two operands have the same exponent scaleb x y Returns the first operand after adding the second value its exp shift x y Returns a shifted copy of x y times sqrt x Square root of a non negative number to context precision subtract x y Return the difference between x and y to_eng_string x Convert to a string using engineering notation if an exponent is needed Engineering notation has an exponent which is a multiple of 3 This can leave up to 3 digits to the left of the decimal place and may require the addition of either one or two trailing zeros to_integral_exact x Rounds to an integer to_sci_string x Converts a number to a string using scientific notation Constants The constants in this section are only relevant for the C module They are also included in the pure Python version for compatibility 32 bit 64 bit decimal MAX_PREC 425000000 999999999999999999 decimal MAX_EMAX 425000000 999999999999999999 decimal MIN_EMIN 425000000 999999999999999999 decimal MIN_ETINY 849999999 1999999999999999997 decimal HAVE_THREADS The value is True Deprecated because Pytho,en
612,n now always has threads Deprecated since version 3 9 decimal HAVE_CONTEXTVAR The default value is True If Python is configured using the without decimal contextvar option the C version uses a thread local rather than a coroutine local context and the value is False This is slightly faster in some nested context scenarios New in version 3 8 3 Rounding modes decimal ROUND_CEILING Round towards Infinity decimal ROUND_DOWN Round towards zero decimal ROUND_FLOOR Round towards Infinity decimal ROUND_HALF_DOWN Round to nearest with ties going towards zero decimal ROUND_HALF_EVEN Round to nearest with ties going to nearest even integer decimal ROUND_HALF_UP Round to nearest with ties going away from zero decimal ROUND_UP Round away from zero decimal ROUND_05UP Round away from zero if last digit after rounding towards zero would have been 0 or 5 otherwise round towards zero Signals Signals represent conditions that arise during computation Each corresponds to one context flag and one context trap enabler The context flag is set whenever the condition is encountered After the computation flags may be checked for informational purposes for instance to determine whether a computation was exact After checking the flags be sure to clear all flags before starting the next computation If the context s trap enabler is set for the signal then the condition causes a Python exception to be raised For example if the DivisionByZero trap is set then a DivisionByZero exception is raised upon encountering the condition class decimal Clamped Altered an exponent to fit representation constraints Typically clamping occurs when an exponent falls outside the context s Emin and Emax limits If possible the exponent is reduced to fit by adding zeros to the coefficient class decimal DecimalException Base class for other signals and a subclass of ArithmeticError class decimal DivisionByZero Signals the division of a non infinite number by zero Can occur with division modulo division or when raising a number to a negative power If this signal is not trapped returns Infinity or Infinity with the sign determined by the inputs to the calculation class decimal Inexact Indicates that rounding occurred and the result is not exact Signals when non zero digits were discarded during rounding The rounded result is returned The signal flag or trap is used to detect when results are inexact class decimal InvalidOperation An invalid operation was performed Indicates that an operation was requested that does not make sense If not trapped returns NaN Possible causes include Infinity Infinity 0 Infinity Infinity Infinity x 0 Infinity x sqrt x and x 0 0 0 x non integer x Infinity class decimal Overflow Numerical overflow Indicates the exponent is larger than Context Emax after rounding has occurred If not trapped the result depends on the rounding mode either pulling inward to the largest representable finite number or rounding outward to Infinity In either case Inexact and Rounded are also signaled class decimal Rounded Rounding occurred though possibly no information was lost Signaled whenever rounding discards digits even if those digits are zero such as rounding 5 00 to 5 0 If not trapped returns the result unchanged This signal is used to detect loss of significant digits class decimal Subnormal Exponent was lower than Emin prior to rounding Occurs when an operation result is subnormal the exponent is too small If not trapped returns the result unchanged class decimal Underflow Numerical underflow with result rounded to zero Occurs when a subnormal result is pushed to zero by rounding Inexact and Subnormal are also signaled class decimal FloatOperation Enable stricter semantics for mixing floats and Decimals If the signal is not trapped default mixing floats and Decimals is permitted in the Decimal constructor create_decimal and all comparison operators Both conversion and comparisons are exact Any occurrence of a mixed operation is silently recorded by setting FloatOperation in the context flags Explicit conversions with from_float or create_decimal_from_float do no,en
613,t set the flag Otherwise the signal is trapped only equality comparisons and explicit conversions are silent All other mixed operations raise FloatOperation The following table summarizes the hierarchy of signals exceptions ArithmeticError exceptions Exception DecimalException Clamped DivisionByZero DecimalException exceptions ZeroDivisionError Inexact Overflow Inexact Rounded Underflow Inexact Rounded Subnormal InvalidOperation Rounded Subnormal FloatOperation DecimalException exceptions TypeError Floating Point Notes Mitigating round off error with increased precision The use of decimal floating point eliminates decimal representation error making it possible to represent 0 1 exactly however some operations can still incur round off error when non zero digits exceed the fixed precision The effects of round off error can be amplified by the addition or subtraction of nearly offsetting quantities resulting in loss of significance Knuth provides two instructive examples where rounded floating point arithmetic with insufficient precision causes the breakdown of the associative and distributive properties of addition Examples from Seminumerical Algorithms Section 4 2 2 from decimal import Decimal getcontext getcontext prec 8 u v w Decimal 11111113 Decimal 11111111 Decimal 7 51111111 u v w Decimal 9 5111111 u v w Decimal 10 u v w Decimal 20000 Decimal 6 Decimal 6 0000003 u v u w Decimal 0 01 u v w Decimal 0 0060000 The decimal module makes it possible to restore the identities by expanding the precision sufficiently to avoid loss of significance getcontext prec 20 u v w Decimal 11111113 Decimal 11111111 Decimal 7 51111111 u v w Decimal 9 51111111 u v w Decimal 9 51111111 u v w Decimal 20000 Decimal 6 Decimal 6 0000003 u v u w Decimal 0 0060000 u v w Decimal 0 0060000 Special values The number system for the decimal module provides special values including NaN sNaN Infinity Infinity and two zeros 0 and 0 Infinities can be constructed directly with Decimal Infinity Also they can arise from dividing by zero when the DivisionByZero signal is not trapped Likewise when the Overflow signal is not trapped infinity can result from rounding beyond the limits of the largest representable number The infinities are signed affine and can be used in arithmetic operations where they get treated as very large indeterminate numbers For instance adding a constant to infinity gives another infinite result Some operations are indeterminate and return NaN or if the InvalidOperation signal is trapped raise an exception For example 0 0 returns NaN which means not a number This variety of NaN is quiet and once created will flow through other computations always resulting in another NaN This behavior can be useful for a series of computations that occasionally have missing inputs it allows the calculation to proceed while flagging specific results as invalid A variant is sNaN which signals rather than remaining quiet after every operation This is a useful return value when an invalid result needs to interrupt a calculation for special handling The behavior of Python s comparison operators can be a little surprising where a NaN is involved A test for equality where one of the operands is a quiet or signaling NaN always returns False even when doing Decimal NaN Decimal NaN while a test for inequality always returns True An attempt to compare two Decimals using any of the or operators will raise the InvalidOperation signal if either operand is a NaN and return False if this signal is not trapped Note that the General Decimal Arithmetic specification does not specify the behavior of direct comparisons these rules for comparisons involving a NaN were taken from the IEEE 854 standard see Table 3 in section 5 7 To ensure strict standards compliance use the compare and compare_signal methods instead The signed zeros can result from calculations that underflow They keep the sign that would have resulted if the calculation had been carried out to greater precision Since their magnitude is zero both positive and negative zeros are treated as equal and their sig,en
614,n is informational In addition to the two signed zeros which are distinct yet equal there are various representations of zero with differing precisions yet equivalent in value This takes a bit of getting used to For an eye accustomed to normalized floating point representations it is not immediately obvious that the following calculation returns a value equal to zero 1 Decimal Infinity Decimal 0E 1000026 Working with threads The getcontext function accesses a different Context object for each thread Having separate thread contexts means that threads may make changes such as getcontext prec 10 without interfering with other threads Likewise the setcontext function automatically assigns its target to the current thread If setcontext has not been called before getcontext then getcontext will automatically create a new context for use in the current thread The new context is copied from a prototype context called DefaultContext To control the defaults so that each thread will use the same values throughout the application directly modify the DefaultContext object This should be done before any threads are started so that there won t be a race condition between threads calling getcontext For example Set applicationwide defaults for all threads about to be launched DefaultContext prec 12 DefaultContext rounding ROUND_DOWN DefaultContext traps ExtendedContext traps copy DefaultContext traps InvalidOperation 1 setcontext DefaultContext Afterwards the threads can be started t1 start t2 start t3 start Recipes Here are a few recipes that serve as utility functions and that demonstrate ways to work with the Decimal class def moneyfmt value places 2 curr sep dp pos neg trailneg Convert Decimal to a money formatted string places required number of places after the decimal point curr optional currency symbol before the sign may be blank sep optional grouping separator comma period space or blank dp decimal point indicator comma or period only specify as blank when places is zero pos optional sign for positive numbers space or blank neg optional sign for negative numbers space or blank trailneg optional trailing minus indicator space or blank d Decimal 1234567 8901 moneyfmt d curr 1 234 567 89 moneyfmt d places 0 sep dp neg trailneg 1 234 568 moneyfmt d curr neg trailneg 1 234 567 89 moneyfmt Decimal 123456789 sep 123 456 789 00 moneyfmt Decimal 0 02 neg trailneg 0 02 q Decimal 10 places 2 places 0 01 sign digits exp value quantize q as_tuple result digits list map str digits build next result append digits pop if sign build trailneg for i in range places build next if digits else 0 if places build dp if not digits build 0 i 0 while digits build next i 1 if i 3 and digits i 0 build sep build curr build neg if sign else pos return join reversed result def pi Compute Pi to the current precision print pi 3 141592653589793238462643383 getcontext prec 2 extra digits for intermediate steps three Decimal 3 substitute three 3 0 for regular floats lasts t s n na d da 0 three 3 1 0 0 24 while s lasts lasts s n na n na na 8 d da d da da 32 t t n d s t getcontext prec 2 return s unary plus applies the new precision def exp x Return e raised to the power of x Result type matches input type print exp Decimal 1 2 718281828459045235360287471 print exp Decimal 2 7 389056098930650227230427461 print exp 2 0 7 38905609893 print exp 2 0j 7 38905609893 0j getcontext prec 2 i lasts s fact num 0 0 1 1 1 while s lasts lasts s i 1 fact i num x s num fact getcontext prec 2 return s def cos x Return the cosine of x as measured in radians The Taylor series approximation works best for a small value of x For larger values first compute x x 2 pi print cos Decimal 0 5 0 8775825618903727161162815826 print cos 0 5 0 87758256189 print cos 0 5 0j 0 87758256189 0j getcontext prec 2 i lasts s fact num sign 0 0 1 1 1 1 while s lasts lasts s i 2 fact i i 1 num x x sign 1 s num fact sign getcontext prec 2 return s def sin x Return the sine of x as measured in radians The Taylor series approximation works best for a small value of x For larger values first compute x x 2 pi prin,en
615,t sin Decimal 0 5 0 4794255386042030002732879352 print sin 0 5 0 479425538604 print sin 0 5 0j 0 479425538604 0j getcontext prec 2 i lasts s fact num sign 1 0 x 1 x 1 while s lasts lasts s i 2 fact i i 1 num x x sign 1 s num fact sign getcontext prec 2 return s Decimal FAQ Q It is cumbersome to type decimal Decimal 1234 5 Is there a way to minimize typing when using the interactive interpreter A Some users abbreviate the constructor to just a single letter D decimal Decimal D 1 23 D 3 45 Decimal 4 68 Q In a fixed point application with two decimal places some inputs have many places and need to be rounded Others are not supposed to have excess digits and need to be validated What methods should be used A The quantize method rounds to a fixed number of decimal places If the Inexact trap is set it is also useful for validation TWOPLACES Decimal 10 2 same as Decimal 0 01 Round to two places Decimal 3 214 quantize TWOPLACES Decimal 3 21 Validate that a number does not exceed two places Decimal 3 21 quantize TWOPLACES context Context traps Inexact Decimal 3 21 Decimal 3 214 quantize TWOPLACES context Context traps Inexact Traceback most recent call last Inexact None Q Once I have valid two place inputs how do I maintain that invariant throughout an application A Some operations like addition subtraction and multiplication by an integer will automatically preserve fixed point Others operations like division and non integer multiplication will change the number of decimal places and need to be followed up with a quantize step a Decimal 102 72 Initial fixed point values b Decimal 3 17 a b Addition preserves fixed point Decimal 105 89 a b Decimal 99 55 a 42 So does integer multiplication Decimal 4314 24 a b quantize TWOPLACES Must quantize non integer multiplication Decimal 325 62 b a quantize TWOPLACES And quantize division Decimal 0 03 In developing fixed point applications it is convenient to define functions to handle the quantize step def mul x y fp TWOPLACES return x y quantize fp def div x y fp TWOPLACES return x y quantize fp mul a b Automatically preserve fixed point Decimal 325 62 div b a Decimal 0 03 Q There are many ways to express the same value The numbers 200 200 000 2E2 and 02E 4 all have the same value at various precisions Is there a way to transform them to a single recognizable canonical value A The normalize method maps all equivalent values to a single representative values map Decimal 200 200 000 2E2 02E 4 split v normalize for v in values Decimal 2E 2 Decimal 2E 2 Decimal 2E 2 Decimal 2E 2 Q When does rounding occur in a computation A It occurs after the computation The philosophy of the decimal specification is that numbers are considered exact and are created independent of the current context They can even have greater precision than current context Computations process with those exact inputs and then rounding or other context operations is applied to the result of the computation getcontext prec 5 pi Decimal 3 1415926535 More than 5 digits pi All digits are retained Decimal 3 1415926535 pi 0 Rounded after an addition Decimal 3 1416 pi Decimal 0 00005 Subtract unrounded numbers then round Decimal 3 1415 pi 0 Decimal 0 00005 Intermediate values are rounded Decimal 3 1416 Q Some decimal values always print with exponential notation Is there a way to get a non exponential representation A For some values exponential notation is the only way to express the number of significant places in the coefficient For example expressing 5 0E 3 as 5000 keeps the value constant but cannot show the original s two place significance If an application does not care about tracking significance it is easy to remove the exponent and trailing zeroes losing significance but keeping the value unchanged def remove_exponent d return d quantize Decimal 1 if d d to_integral else d normalize remove_exponent Decimal 5E 3 Decimal 5000 Q Is there a way to convert a regular float to a Decimal A Yes any binary floating point number can be exactly expressed as a Decimal though an exact conversion may take more precision than intuition wou,en
616,ld suggest Decimal math pi Decimal 3 141592653589793115997963468544185161590576171875 Q Within a complex calculation how can I make sure that I haven t gotten a spurious result because of insufficient precision or rounding anomalies A The decimal module makes it easy to test results A best practice is to re run calculations using greater precision and with various rounding modes Widely differing results indicate insufficient precision rounding mode issues ill conditioned inputs or a numerically unstable algorithm Q I noticed that context precision is applied to the results of operations but not to the inputs Is there anything to watch out for when mixing values of different precisions A Yes The principle is that all values are considered to be exact and so is the arithmetic on those values Only the results are rounded The advantage for inputs is that what you type is what you get A disadvantage is that the results can look odd if you forget that the inputs haven t been rounded getcontext prec 3 Decimal 3 104 Decimal 2 104 Decimal 5 21 Decimal 3 104 Decimal 0 000 Decimal 2 104 Decimal 5 20 The solution is either to increase precision or to force rounding of inputs using the unary plus operation getcontext prec 3 Decimal 1 23456789 unary plus triggers rounding Decimal 1 23 Alternatively inputs can be rounded upon creation using the Context create_decimal method Context prec 5 rounding ROUND_DOWN create_decimal 1 2345678 Decimal 1 2345 Q Is the CPython implementation fast for large numbers A Yes In the CPython and PyPy3 implementations the C CFFI versions of the decimal module integrate the high speed libmpdec library for arbitrary precision correctly rounded decimal floating point arithmetic 1 libmpdec uses Karatsuba multiplication for medium sized numbers and the Number Theoretic Transform for very large numbers The context must be adapted for exact arbitrary precision arithmetic Emin and Emax should always be set to the maximum values clamp should always be 0 the default Setting prec requires some care The easiest approach for trying out bignum arithmetic is to use the maximum value for prec as well 2 setcontext Context prec MAX_PREC Emax MAX_EMAX Emin MIN_EMIN x Decimal 2 256 x 128 Decimal 904625697166532776746648320380374280103671755200316906558262375061821325312 For inexact results MAX_PREC is far too large on 64 bit platforms and the available memory will be insufficient Decimal 1 3 Traceback most recent call last File stdin line 1 in module MemoryError On systems with overallocation e g Linux a more sophisticated approach is to adjust prec to the amount of available RAM Suppose that you have 8GB of RAM and expect 10 simultaneous operands using a maximum of 500MB each import sys Maximum number of digits for a single operand using 500MB in 8 byte words with 19 digits per word 4 byte and 9 digits for the 32 bit build maxdigits 19 500 1024 2 8 Check that this works c Context prec maxdigits Emax MAX_EMAX Emin MIN_EMIN c traps Inexact True setcontext c Fill the available precision with nines x Decimal 0 logical_invert 9 sys getsizeof x 524288112 x 2 Traceback most recent call last File stdin line 1 in module decimal Inexact class decimal Inexact In general and especially on systems without overallocation it is recommended to estimate even tighter bounds and set the Inexact trap if all calculations are expected to be exact 1 New in version 3 3 2 Changed in version 3 9 This approach now works for all exact results except for non integer powers,en
617,Code Objects Code objects are a low level detail of the CPython implementation Each one represents a chunk of executable code that hasn t yet been bound into a function type PyCodeObject The C structure of the objects used to describe code objects The fields of this type are subject to change at any time PyTypeObject PyCode_Type This is an instance of PyTypeObject representing the Python code object int PyCode_Check PyObject co Return true if co is a code object This function always succeeds Py_ssize_t PyCode_GetNumFree PyCodeObject co Return the number of free variables in a code object int PyCode_GetFirstFree PyCodeObject co Return the position of the first free variable in a code object PyCodeObject PyUnstable_Code_New int argcount int kwonlyargcount int nlocals int stacksize int flags PyObject code PyObject consts PyObject names PyObject varnames PyObject freevars PyObject cellvars PyObject filename PyObject name PyObject qualname int firstlineno PyObject linetable PyObject exceptiontable This is Unstable API It may change without warning in minor releases Return a new code object If you need a dummy code object to create a frame use PyCode_NewEmpty instead Since the definition of the bytecode changes often calling PyUnstable_Code_New directly can bind you to a precise Python version The many arguments of this function are inter dependent in complex ways meaning that subtle changes to values are likely to result in incorrect execution or VM crashes Use this function only with extreme care Changed in version 3 11 Added qualname and exceptiontable parameters Changed in version 3 12 Renamed from PyCode_New as part of Unstable C API The old name is deprecated but will remain available until the signature changes again PyCodeObject PyUnstable_Code_NewWithPosOnlyArgs int argcount int posonlyargcount int kwonlyargcount int nlocals int stacksize int flags PyObject code PyObject consts PyObject names PyObject varnames PyObject freevars PyObject cellvars PyObject filename PyObject name PyObject qualname int firstlineno PyObject linetable PyObject exceptiontable This is Unstable API It may change without warning in minor releases Similar to PyUnstable_Code_New but with an extra posonlyargcount for positional only arguments The same caveats that apply to PyUnstable_Code_New also apply to this function New in version 3 8 as PyCode_NewWithPosOnlyArgs Changed in version 3 11 Added qualname and exceptiontable parameters Changed in version 3 12 Renamed to PyUnstable_Code_NewWithPosOnlyArgs The old name is deprecated but will remain available until the signature changes again PyCodeObject PyCode_NewEmpty const char filename const char funcname int firstlineno Return value New reference Return a new empty code object with the specified filename function name and first line number The resulting code object will raise an Exception if executed int PyCode_Addr2Line PyCodeObject co int byte_offset Return the line number of the instruction that occurs on or before byte_offset and ends after it If you just need the line number of a frame use PyFrame_GetLineNumber instead For efficiently iterating over the line numbers in a code object use the API described in PEP 626 int PyCode_Addr2Location PyObject co int byte_offset int start_line int start_column int end_line int end_column Sets the passed int pointers to the source code line and column numbers for the instruction at byte_offset Sets the value to 0 when information is not available for any particular element Returns 1 if the function succeeds and 0 otherwise New in version 3 11 PyObject PyCode_GetCode PyCodeObject co Equivalent to the Python code getattr co co_code Returns a strong reference to a PyBytesObject representing the bytecode in a code object On error NULL is returned and an exception is raised This PyBytesObject may be created on demand by the interpreter and does not necessarily represent the bytecode actually executed by CPython The primary use case for this function is debuggers and profilers New in version 3 11 PyObject PyCode_GetVarnames PyCodeObject co Equivalent to the P,en
618,ython code getattr co co_varnames Returns a new reference to a PyTupleObject containing the names of the local variables On error NULL is returned and an exception is raised New in version 3 11 PyObject PyCode_GetCellvars PyCodeObject co Equivalent to the Python code getattr co co_cellvars Returns a new reference to a PyTupleObject containing the names of the local variables that are referenced by nested functions On error NULL is returned and an exception is raised New in version 3 11 PyObject PyCode_GetFreevars PyCodeObject co Equivalent to the Python code getattr co co_freevars Returns a new reference to a PyTupleObject containing the names of the free variables On error NULL is returned and an exception is raised New in version 3 11 int PyCode_AddWatcher PyCode_WatchCallback callback Register callback as a code object watcher for the current interpreter Return an ID which may be passed to PyCode_ClearWatcher In case of error e g no more watcher IDs available return 1 and set an exception New in version 3 12 int PyCode_ClearWatcher int watcher_id Clear watcher identified by watcher_id previously returned from PyCode_AddWatcher for the current interpreter Return 0 on success or 1 and set an exception on error e g if the given watcher_id was never registered New in version 3 12 type PyCodeEvent Enumeration of possible code object watcher events PY_CODE_EVENT_CREATE PY_CODE_EVENT_DESTROY New in version 3 12 typedef int PyCode_WatchCallback PyCodeEvent event PyCodeObject co Type of a code object watcher callback function If event is PY_CODE_EVENT_CREATE then the callback is invoked after co has been fully initialized Otherwise the callback is invoked before the destruction of co takes place so the prior state of co can be inspected If event is PY_CODE_EVENT_DESTROY taking a reference in the callback to the about to be destroyed code object will resurrect it and prevent it from being freed at this time When the resurrected object is destroyed later any watcher callbacks active at that time will be called again Users of this API should not rely on internal runtime implementation details Such details may include but are not limited to the exact order and timing of creation and destruction of code objects While changes in these details may result in differences observable by watchers including whether a callback is invoked or not it does not change the semantics of the Python code being executed If the callback sets an exception it must return 1 this exception will be printed as an unraisable exception using PyErr_WriteUnraisable Otherwise it should return 0 There may already be a pending exception set on entry to the callback In this case the callback should return 0 with the same exception still set This means the callback may not call any other API that can set an exception unless it saves and clears the exception state first and restores it before returning New in version 3 12 Extra information To support low level extensions to frame evaluation such as external just in time compilers it is possible to attach arbitrary extra data to code objects These functions are part of the unstable C API tier this functionality is a CPython implementation detail and the API may change without deprecation warnings Py_ssize_t PyUnstable_Eval_RequestCodeExtraIndex freefunc free This is Unstable API It may change without warning in minor releases Return a new an opaque index value used to adding data to code objects You generally call this function once per interpreter and use the result with PyCode_GetExtra and PyCode_SetExtra to manipulate data on individual code objects If free is not NULL when a code object is deallocated free will be called on non NULL data stored under the new index Use Py_DecRef when storing PyObject New in version 3 6 as _PyEval_RequestCodeExtraIndex Changed in version 3 12 Renamed to PyUnstable_Eval_RequestCodeExtraIndex The old private name is deprecated but will be available until the API changes int PyUnstable_Code_GetExtra PyObject code Py_ssize_t index void extra This is Unstable API It may change without wa,en
619,rning in minor releases Set extra to the extra data stored under the given index Return 0 on success Set an exception and return 1 on failure If no data was set under the index set extra to NULL and return 0 without setting an exception New in version 3 6 as _PyCode_GetExtra Changed in version 3 12 Renamed to PyUnstable_Code_GetExtra The old private name is deprecated but will be available until the API changes int PyUnstable_Code_SetExtra PyObject code Py_ssize_t index void extra This is Unstable API It may change without warning in minor releases Set the extra data stored under the given index to extra Return 0 on success Set an exception and return 1 on failure New in version 3 6 as _PyCode_SetExtra Changed in version 3 12 Renamed to PyUnstable_Code_SetExtra The old private name is deprecated but will be available until the API changes,en
620,Tuple Objects type PyTupleObject This subtype of PyObject represents a Python tuple object PyTypeObject PyTuple_Type Part of the Stable ABI This instance of PyTypeObject represents the Python tuple type it is the same object as tuple in the Python layer int PyTuple_Check PyObject p Return true if p is a tuple object or an instance of a subtype of the tuple type This function always succeeds int PyTuple_CheckExact PyObject p Return true if p is a tuple object but not an instance of a subtype of the tuple type This function always succeeds PyObject PyTuple_New Py_ssize_t len Return value New reference Part of the Stable ABI Return a new tuple object of size len or NULL on failure PyObject PyTuple_Pack Py_ssize_t n Return value New reference Part of the Stable ABI Return a new tuple object of size n or NULL on failure The tuple values are initialized to the subsequent n C arguments pointing to Python objects PyTuple_Pack 2 a b is equivalent to Py_BuildValue OO a b Py_ssize_t PyTuple_Size PyObject p Part of the Stable ABI Take a pointer to a tuple object and return the size of that tuple Py_ssize_t PyTuple_GET_SIZE PyObject p Return the size of the tuple p which must be non NULL and point to a tuple no error checking is performed PyObject PyTuple_GetItem PyObject p Py_ssize_t pos Return value Borrowed reference Part of the Stable ABI Return the object at position pos in the tuple pointed to by p If pos is negative or out of bounds return NULL and set an IndexError exception PyObject PyTuple_GET_ITEM PyObject p Py_ssize_t pos Return value Borrowed reference Like PyTuple_GetItem but does no checking of its arguments PyObject PyTuple_GetSlice PyObject p Py_ssize_t low Py_ssize_t high Return value New reference Part of the Stable ABI Return the slice of the tuple pointed to by p between low and high or NULL on failure This is the equivalent of the Python expression p low high Indexing from the end of the tuple is not supported int PyTuple_SetItem PyObject p Py_ssize_t pos PyObject o Part of the Stable ABI Insert a reference to object o at position pos of the tuple pointed to by p Return 0 on success If pos is out of bounds return 1 and set an IndexError exception Note This function steals a reference to o and discards a reference to an item already in the tuple at the affected position void PyTuple_SET_ITEM PyObject p Py_ssize_t pos PyObject o Like PyTuple_SetItem but does no error checking and should only be used to fill in brand new tuples Note This function steals a reference to o and unlike PyTuple_SetItem does not discard a reference to any item that is being replaced any reference in the tuple at position pos will be leaked int _PyTuple_Resize PyObject p Py_ssize_t newsize Can be used to resize a tuple newsize will be the new length of the tuple Because tuples are supposed to be immutable this should only be used if there is only one reference to the object Do not use this if the tuple may already be known to some other part of the code The tuple will always grow or shrink at the end Think of this as destroying the old tuple and creating a new one only more efficiently Returns 0 on success Client code should never assume that the resulting value of p will be the same as before calling this function If the object referenced by p is replaced the original p is destroyed On failure returns 1 and sets p to NULL and raises MemoryError or SystemError Struct Sequence Objects Struct sequence objects are the C equivalent of namedtuple objects i e a sequence whose items can also be accessed through attributes To create a struct sequence you first have to create a specific struct sequence type PyTypeObject PyStructSequence_NewType PyStructSequence_Desc desc Return value New reference Part of the Stable ABI Create a new struct sequence type from the data in desc described below Instances of the resulting type can be created with PyStructSequence_New void PyStructSequence_InitType PyTypeObject type PyStructSequence_Desc desc Initializes a struct sequence type type from desc in place int PyStructSequence_InitType2 PyTypeObject type PyStr,en
621,uctSequence_Desc desc The same as PyStructSequence_InitType but returns 0 on success and 1 on failure New in version 3 4 type PyStructSequence_Desc Part of the Stable ABI including all members Contains the meta information of a struct sequence type to create const char name Name of the struct sequence type const char doc Pointer to docstring for the type or NULL to omit PyStructSequence_Field fields Pointer to NULL terminated array with field names of the new type int n_in_sequence Number of fields visible to the Python side if used as tuple type PyStructSequence_Field Part of the Stable ABI including all members Describes a field of a struct sequence As a struct sequence is modeled as a tuple all fields are typed as PyObject The index in the fields array of the PyStructSequence_Desc determines which field of the struct sequence is described const char name Name for the field or NULL to end the list of named fields set to PyStructSequence_UnnamedField to leave unnamed const char doc Field docstring or NULL to omit const char const PyStructSequence_UnnamedField Part of the Stable ABI since version 3 11 Special value for a field name to leave it unnamed Changed in version 3 9 The type was changed from char PyObject PyStructSequence_New PyTypeObject type Return value New reference Part of the Stable ABI Creates an instance of type which must have been created with PyStructSequence_NewType PyObject PyStructSequence_GetItem PyObject p Py_ssize_t pos Return value Borrowed reference Part of the Stable ABI Return the object at position pos in the struct sequence pointed to by p No bounds checking is performed PyObject PyStructSequence_GET_ITEM PyObject p Py_ssize_t pos Return value Borrowed reference Macro equivalent of PyStructSequence_GetItem void PyStructSequence_SetItem PyObject p Py_ssize_t pos PyObject o Part of the Stable ABI Sets the field at index pos of the struct sequence p to value o Like PyTuple_SET_ITEM this should only be used to fill in brand new instances Note This function steals a reference to o void PyStructSequence_SET_ITEM PyObject p Py_ssize_t pos PyObject o Similar to PyStructSequence_SetItem but implemented as a static inlined function Note This function steals a reference to o,en
622,fcntl The fcntl and ioctl system calls This module performs file and I O control on file descriptors It is an interface to the fcntl and ioctl Unix routines See the fcntl 2 and ioctl 2 Unix manual pages for full details Availability Unix not Emscripten not WASI All functions in this module take a file descriptor fd as their first argument This can be an integer file descriptor such as returned by sys stdin fileno or an io IOBase object such as sys stdin itself which provides a fileno that returns a genuine file descriptor Changed in version 3 3 Operations in this module used to raise an IOError where they now raise an OSError Changed in version 3 8 The fcntl module now contains F_ADD_SEALS F_GET_SEALS and F_SEAL_ constants for sealing of os memfd_create file descriptors Changed in version 3 9 On macOS the fcntl module exposes the F_GETPATH constant which obtains the path of a file from a file descriptor On Linux 3 15 the fcntl module exposes the F_OFD_GETLK F_OFD_SETLK and F_OFD_SETLKW constants which are used when working with open file description locks Changed in version 3 10 On Linux 2 6 11 the fcntl module exposes the F_GETPIPE_SZ and F_SETPIPE_SZ constants which allow to check and modify a pipe s size respectively Changed in version 3 11 On FreeBSD the fcntl module exposes the F_DUP2FD and F_DUP2FD_CLOEXEC constants which allow to duplicate a file descriptor the latter setting FD_CLOEXEC flag in addition Changed in version 3 12 On Linux 4 5 the fcntl module exposes the FICLONE and FICLONERANGE constants which allow to share some data of one file with another file by reflinking on some filesystems e g btrfs OCFS2 and XFS This behavior is commonly referred to as copy on write The module defines the following functions fcntl fcntl fd cmd arg 0 Perform the operation cmd on file descriptor fd file objects providing a fileno method are accepted as well The values used for cmd are operating system dependent and are available as constants in the fcntl module using the same names as used in the relevant C header files The argument arg can either be an integer value or a bytes object With an integer value the return value of this function is the integer return value of the C fcntl call When the argument is bytes it represents a binary structure e g created by struct pack The binary data is copied to a buffer whose address is passed to the C fcntl call The return value after a successful call is the contents of the buffer converted to a bytes object The length of the returned object will be the same as the length of the arg argument This is limited to 1024 bytes If the information returned in the buffer by the operating system is larger than 1024 bytes this is most likely to result in a segmentation violation or a more subtle data corruption If the fcntl call fails an OSError is raised Raises an auditing event fcntl fcntl with arguments fd cmd arg fcntl ioctl fd request arg 0 mutate_flag True This function is identical to the fcntl function except that the argument handling is even more complicated The request parameter is limited to values that can fit in 32 bits Additional constants of interest for use as the request argument can be found in the termios module under the same names as used in the relevant C header files The parameter arg can be one of an integer an object supporting the read only buffer interface like bytes or an object supporting the read write buffer interface like bytearray In all but the last case behaviour is as for the fcntl function If a mutable buffer is passed then the behaviour is determined by the value of the mutate_flag parameter If it is false the buffer s mutability is ignored and behaviour is as for a read only buffer except that the 1024 byte limit mentioned above is avoided so long as the buffer you pass is at least as long as what the operating system wants to put there things should work If mutate_flag is true the default then the buffer is in effect passed to the underlying ioctl system call the latter s return code is passed back to the calling Python and the buffer s new contents refle,en
623,ct the action of the ioctl This is a slight simplification because if the supplied buffer is less than 1024 bytes long it is first copied into a static buffer 1024 bytes long which is then passed to ioctl and copied back into the supplied buffer If the ioctl call fails an OSError exception is raised An example import array fcntl struct termios os os getpgrp 13341 struct unpack h fcntl ioctl 0 termios TIOCGPGRP 0 13341 buf array array h 0 fcntl ioctl 0 termios TIOCGPGRP buf 1 0 buf array h 13341 Raises an auditing event fcntl ioctl with arguments fd request arg fcntl flock fd operation Perform the lock operation operation on file descriptor fd file objects providing a fileno method are accepted as well See the Unix manual flock 2 for details On some systems this function is emulated using fcntl If the flock call fails an OSError exception is raised Raises an auditing event fcntl flock with arguments fd operation fcntl lockf fd cmd len 0 start 0 whence 0 This is essentially a wrapper around the fcntl locking calls fd is the file descriptor file objects providing a fileno method are accepted as well of the file to lock or unlock and cmd is one of the following values fcntl LOCK_UN Release an existing lock fcntl LOCK_SH Acquire a shared lock fcntl LOCK_EX Acquire an exclusive lock fcntl LOCK_NB Bitwise OR with any of the other three LOCK_ constants to make the request non blocking If LOCK_NB is used and the lock cannot be acquired an OSError will be raised and the exception will have an errno attribute set to EACCES or EAGAIN depending on the operating system for portability check for both values On at least some systems LOCK_EX can only be used if the file descriptor refers to a file opened for writing len is the number of bytes to lock start is the byte offset at which the lock starts relative to whence and whence is as with io IOBase seek specifically 0 relative to the start of the file os SEEK_SET 1 relative to the current buffer position os SEEK_CUR 2 relative to the end of the file os SEEK_END The default for start is 0 which means to start at the beginning of the file The default for len is 0 which means to lock to the end of the file The default for whence is also 0 Raises an auditing event fcntl lockf with arguments fd cmd len start whence Examples all on a SVR4 compliant system import struct fcntl os f open rv fcntl fcntl f fcntl F_SETFL os O_NDELAY lockdata struct pack hhllhh fcntl F_WRLCK 0 0 0 0 0 rv fcntl fcntl f fcntl F_SETLKW lockdata Note that in the first example the return value variable rv will hold an integer value in the second example it will hold a bytes object The structure lay out for the lockdata variable is system dependent therefore using the flock call may be better See also Module os If the locking flags O_SHLOCK and O_EXLOCK are present in the os module on BSD only the os open function provides an alternative to the lockf and flock functions,en
624,Development Tools The modules described in this chapter help you write software For example the pydoc module takes a module and generates documentation based on the module s contents The doctest and unittest modules contains frameworks for writing unit tests that automatically exercise code and verify that the expected output is produced 2to3 can translate Python 2 x source code into valid Python 3 x code The list of modules described in this chapter is typing Support for type hints Relevant PEPs Type aliases NewType Annotating callable objects Generics Annotating tuples The type of class objects User defined generic types The Any type Nominal vs structural subtyping Module contents Special typing primitives Special types Special forms Building generic types and type aliases Other special directives Protocols ABCs for working with IO Functions and decorators Introspection helpers Constant Deprecated aliases Aliases to built in types Aliases to types in collections Aliases to other concrete types Aliases to container ABCs in collections abc Aliases to asynchronous ABCs in collections abc Aliases to other ABCs in collections abc Aliases to contextlib ABCs Deprecation Timeline of Major Features pydoc Documentation generator and online help system Python Development Mode Effects of the Python Development Mode ResourceWarning Example Bad file descriptor error example doctest Test interactive Python examples Simple Usage Checking Examples in Docstrings Simple Usage Checking Examples in a Text File How It Works Which Docstrings Are Examined How are Docstring Examples Recognized What s the Execution Context What About Exceptions Option Flags Directives Warnings Basic API Unittest API Advanced API DocTest Objects Example Objects DocTestFinder objects DocTestParser objects DocTestRunner objects OutputChecker objects Debugging Soapbox unittest Unit testing framework Basic example Command Line Interface Command line options Test Discovery Organizing test code Re using old test code Skipping tests and expected failures Distinguishing test iterations using subtests Classes and functions Test cases Grouping tests Loading and running tests load_tests Protocol Class and Module Fixtures setUpClass and tearDownClass setUpModule and tearDownModule Signal Handling unittest mock mock object library Quick Guide The Mock Class Calling Deleting Attributes Mock names and the name attribute Attaching Mocks as Attributes The patchers patch patch object patch dict patch multiple patch methods start and stop patch builtins TEST_PREFIX Nesting Patch Decorators Where to patch Patching Descriptors and Proxy Objects MagicMock and magic method support Mocking Magic Methods Magic Mock Helpers sentinel DEFAULT call create_autospec ANY FILTER_DIR mock_open Autospeccing Sealing mocks unittest mock getting started Using Mock Mock Patching Methods Mock for Method Calls on an Object Mocking Classes Naming your mocks Tracking all Calls Setting Return Values and Attributes Raising exceptions with mocks Side effect functions and iterables Mocking asynchronous iterators Mocking asynchronous context manager Creating a Mock from an Existing Object Using side_effect to return per file content Patch Decorators Further Examples Mocking chained calls Partial mocking Mocking a Generator Method Applying the same patch to every test method Mocking Unbound Methods Checking multiple calls with mock Coping with mutable arguments Nesting Patches Mocking a dictionary with MagicMock Mock subclasses and their attributes Mocking imports with patch dict Tracking order of calls and less verbose call assertions More complex argument matching 2to3 Automated Python 2 to 3 code translation Using 2to3 Fixers lib2to3 2to3 s library test Regression tests package for Python Writing Unit Tests for the test package Running tests using the command line interface test support Utilities for the Python test suite test support socket_helper Utilities for socket tests test support script_helper Utilities for the Python execution tests test support bytecode_helper Support tools for testing correct byt,en
625,ecode generation test support threading_helper Utilities for threading tests test support os_helper Utilities for os tests test support import_helper Utilities for import tests test support warnings_helper Utilities for warnings tests,en
626,aifc Read and write AIFF and AIFC files Source code Lib aifc py Deprecated since version 3 11 will be removed in version 3 13 The aifc module is deprecated see PEP 594 for details This module provides support for reading and writing AIFF and AIFF C files AIFF is Audio Interchange File Format a format for storing digital audio samples in a file AIFF C is a newer version of the format that includes the ability to compress the audio data Audio files have a number of parameters that describe the audio data The sampling rate or frame rate is the number of times per second the sound is sampled The number of channels indicate if the audio is mono stereo or quadro Each frame consists of one sample per channel The sample size is the size in bytes of each sample Thus a frame consists of nchannels samplesize bytes and a second s worth of audio consists of nchannels samplesize framerate bytes For example CD quality audio has a sample size of two bytes 16 bits uses two channels stereo and has a frame rate of 44 100 frames second This gives a frame size of 4 bytes 2 2 and a second s worth occupies 2 2 44100 bytes 176 400 bytes Module aifc defines the following function aifc open file mode None Open an AIFF or AIFF C file and return an object instance with methods that are described below The argument file is either a string naming a file or a file object mode must be r or rb when the file must be opened for reading or w or wb when the file must be opened for writing If omitted file mode is used if it exists otherwise rb is used When used for writing the file object should be seekable unless you know ahead of time how many samples you are going to write in total and use writeframesraw and setnframes The open function may be used in a with statement When the with block completes the close method is called Changed in version 3 4 Support for the with statement was added Objects returned by open when a file is opened for reading have the following methods aifc getnchannels Return the number of audio channels 1 for mono 2 for stereo aifc getsampwidth Return the size in bytes of individual samples aifc getframerate Return the sampling rate number of audio frames per second aifc getnframes Return the number of audio frames in the file aifc getcomptype Return a bytes array of length 4 describing the type of compression used in the audio file For AIFF files the returned value is b NONE aifc getcompname Return a bytes array convertible to a human readable description of the type of compression used in the audio file For AIFF files the returned value is b not compressed aifc getparams Returns a namedtuple nchannels sampwidth framerate nframes comptype compname equivalent to output of the get methods aifc getmarkers Return a list of markers in the audio file A marker consists of a tuple of three elements The first is the mark ID an integer the second is the mark position in frames from the beginning of the data an integer the third is the name of the mark a string aifc getmark id Return the tuple as described in getmarkers for the mark with the given id aifc readframes nframes Read and return the next nframes frames from the audio file The returned data is a string containing for each frame the uncompressed samples of all channels aifc rewind Rewind the read pointer The next readframes will start from the beginning aifc setpos pos Seek to the specified frame number aifc tell Return the current frame number aifc close Close the AIFF file After calling this method the object can no longer be used Objects returned by open when a file is opened for writing have all the above methods except for readframes and setpos In addition the following methods exist The get methods can only be called after the corresponding set methods have been called Before the first writeframes or writeframesraw all parameters except for the number of frames must be filled in aifc aiff Create an AIFF file The default is that an AIFF C file is created unless the name of the file ends in aiff in which case the default is an AIFF file aifc aifc Create an AIFF C file The default i,en
627,s that an AIFF C file is created unless the name of the file ends in aiff in which case the default is an AIFF file aifc setnchannels nchannels Specify the number of channels in the audio file aifc setsampwidth width Specify the size in bytes of audio samples aifc setframerate rate Specify the sampling frequency in frames per second aifc setnframes nframes Specify the number of frames that are to be written to the audio file If this parameter is not set or not set correctly the file needs to support seeking aifc setcomptype type name Specify the compression type If not specified the audio data will not be compressed In AIFF files compression is not possible The name parameter should be a human readable description of the compression type as a bytes array the type parameter should be a bytes array of length 4 Currently the following compression types are supported b NONE b ULAW b ALAW b G722 aifc setparams nchannels sampwidth framerate comptype compname Set all the above parameters at once The argument is a tuple consisting of the various parameters This means that it is possible to use the result of a getparams call as argument to setparams aifc setmark id pos name Add a mark with the given id larger than 0 and the given name at the given position This method can be called at any time before close aifc tell Return the current write position in the output file Useful in combination with setmark aifc writeframes data Write data to the output file This method can only be called after the audio file parameters have been set Changed in version 3 4 Any bytes like object is now accepted aifc writeframesraw data Like writeframes except that the header of the audio file is not updated Changed in version 3 4 Any bytes like object is now accepted aifc close Close the AIFF file The header of the file is updated to reflect the actual size of the audio data After calling this method the object can no longer be used,en
628,Argument Clinic How To Note The Argument Clinic How TO has been moved to the Python Developer s Guide,en
629,winreg Windows registry access These functions expose the Windows registry API to Python Instead of using an integer as the registry handle a handle object is used to ensure that the handles are closed correctly even if the programmer neglects to explicitly close them Changed in version 3 3 Several functions in this module used to raise a WindowsError which is now an alias of OSError Functions This module offers the following functions winreg CloseKey hkey Closes a previously opened registry key The hkey argument specifies a previously opened key Note If hkey is not closed using this method or via hkey Close it is closed when the hkey object is destroyed by Python winreg ConnectRegistry computer_name key Establishes a connection to a predefined registry handle on another computer and returns a handle object computer_name is the name of the remote computer of the form r computername If None the local computer is used key is the predefined handle to connect to The return value is the handle of the opened key If the function fails an OSError exception is raised Raises an auditing event winreg ConnectRegistry with arguments computer_name key Changed in version 3 3 See above winreg CreateKey key sub_key Creates or opens the specified key returning a handle object key is an already open key or one of the predefined HKEY_ constants sub_key is a string that names the key this method opens or creates If key is one of the predefined keys sub_key may be None In that case the handle returned is the same key handle passed in to the function If the key already exists this function opens the existing key The return value is the handle of the opened key If the function fails an OSError exception is raised Raises an auditing event winreg CreateKey with arguments key sub_key access Raises an auditing event winreg OpenKey result with argument key Changed in version 3 3 See above winreg CreateKeyEx key sub_key reserved 0 access KEY_WRITE Creates or opens the specified key returning a handle object key is an already open key or one of the predefined HKEY_ constants sub_key is a string that names the key this method opens or creates reserved is a reserved integer and must be zero The default is zero access is an integer that specifies an access mask that describes the desired security access for the key Default is KEY_WRITE See Access Rights for other allowed values If key is one of the predefined keys sub_key may be None In that case the handle returned is the same key handle passed in to the function If the key already exists this function opens the existing key The return value is the handle of the opened key If the function fails an OSError exception is raised Raises an auditing event winreg CreateKey with arguments key sub_key access Raises an auditing event winreg OpenKey result with argument key New in version 3 2 Changed in version 3 3 See above winreg DeleteKey key sub_key Deletes the specified key key is an already open key or one of the predefined HKEY_ constants sub_key is a string that must be a subkey of the key identified by the key parameter This value must not be None and the key may not have subkeys This method can not delete keys with subkeys If the method succeeds the entire key including all of its values is removed If the method fails an OSError exception is raised Raises an auditing event winreg DeleteKey with arguments key sub_key access Changed in version 3 3 See above winreg DeleteKeyEx key sub_key access KEY_WOW64_64KEY reserved 0 Deletes the specified key key is an already open key or one of the predefined HKEY_ constants sub_key is a string that must be a subkey of the key identified by the key parameter This value must not be None and the key may not have subkeys reserved is a reserved integer and must be zero The default is zero access is an integer that specifies an access mask that describes the desired security access for the key Default is KEY_WOW64_64KEY On 32 bit Windows the WOW64 constants are ignored See Access Rights for other allowed values This method can not delete keys with subkeys If the method suc,en
630,ceeds the entire key including all of its values is removed If the method fails an OSError exception is raised On unsupported Windows versions NotImplementedError is raised Raises an auditing event winreg DeleteKey with arguments key sub_key access New in version 3 2 Changed in version 3 3 See above winreg DeleteValue key value Removes a named value from a registry key key is an already open key or one of the predefined HKEY_ constants value is a string that identifies the value to remove Raises an auditing event winreg DeleteValue with arguments key value winreg EnumKey key index Enumerates subkeys of an open registry key returning a string key is an already open key or one of the predefined HKEY_ constants index is an integer that identifies the index of the key to retrieve The function retrieves the name of one subkey each time it is called It is typically called repeatedly until an OSError exception is raised indicating no more values are available Raises an auditing event winreg EnumKey with arguments key index Changed in version 3 3 See above winreg EnumValue key index Enumerates values of an open registry key returning a tuple key is an already open key or one of the predefined HKEY_ constants index is an integer that identifies the index of the value to retrieve The function retrieves the name of one subkey each time it is called It is typically called repeatedly until an OSError exception is raised indicating no more values The result is a tuple of 3 items Index Meaning 0 A string that identifies the value name 1 An object that holds the value data and whose type depends on the underlying registry type 2 An integer that identifies the type of the value data see table in docs for SetValueEx Raises an auditing event winreg EnumValue with arguments key index Changed in version 3 3 See above winreg ExpandEnvironmentStrings str Expands environment variable placeholders NAME in strings like REG_EXPAND_SZ ExpandEnvironmentStrings windir C Windows Raises an auditing event winreg ExpandEnvironmentStrings with argument str winreg FlushKey key Writes all the attributes of a key to the registry key is an already open key or one of the predefined HKEY_ constants It is not necessary to call FlushKey to change a key Registry changes are flushed to disk by the registry using its lazy flusher Registry changes are also flushed to disk at system shutdown Unlike CloseKey the FlushKey method returns only when all the data has been written to the registry An application should only call FlushKey if it requires absolute certainty that registry changes are on disk Note If you don t know whether a FlushKey call is required it probably isn t winreg LoadKey key sub_key file_name Creates a subkey under the specified key and stores registration information from a specified file into that subkey key is a handle returned by ConnectRegistry or one of the constants HKEY_USERS or HKEY_LOCAL_MACHINE sub_key is a string that identifies the subkey to load file_name is the name of the file to load registry data from This file must have been created with the SaveKey function Under the file allocation table FAT file system the filename may not have an extension A call to LoadKey fails if the calling process does not have the SE_RESTORE_PRIVILEGE privilege Note that privileges are different from permissions see the RegLoadKey documentation for more details If key is a handle returned by ConnectRegistry then the path specified in file_name is relative to the remote computer Raises an auditing event winreg LoadKey with arguments key sub_key file_name winreg OpenKey key sub_key reserved 0 access KEY_READ winreg OpenKeyEx key sub_key reserved 0 access KEY_READ Opens the specified key returning a handle object key is an already open key or one of the predefined HKEY_ constants sub_key is a string that identifies the sub_key to open reserved is a reserved integer and must be zero The default is zero access is an integer that specifies an access mask that describes the desired security access for the key Default is KEY_READ See Access Rights for other allowed,en
631, values The result is a new handle to the specified key If the function fails OSError is raised Raises an auditing event winreg OpenKey with arguments key sub_key access Raises an auditing event winreg OpenKey result with argument key Changed in version 3 2 Allow the use of named arguments Changed in version 3 3 See above winreg QueryInfoKey key Returns information about a key as a tuple key is an already open key or one of the predefined HKEY_ constants The result is a tuple of 3 items Index Meaning 0 An integer giving the number of sub keys this key has 1 An integer giving the number of values this key has 2 An integer giving when the key was last modified if available as 100 s of nanoseconds since Jan 1 1601 Raises an auditing event winreg QueryInfoKey with argument key winreg QueryValue key sub_key Retrieves the unnamed value for a key as a string key is an already open key or one of the predefined HKEY_ constants sub_key is a string that holds the name of the subkey with which the value is associated If this parameter is None or empty the function retrieves the value set by the SetValue method for the key identified by key Values in the registry have name type and data components This method retrieves the data for a key s first value that has a NULL name But the underlying API call doesn t return the type so always use QueryValueEx if possible Raises an auditing event winreg QueryValue with arguments key sub_key value_name winreg QueryValueEx key value_name Retrieves the type and data for a specified value name associated with an open registry key key is an already open key or one of the predefined HKEY_ constants value_name is a string indicating the value to query The result is a tuple of 2 items Index Meaning 0 The value of the registry item 1 An integer giving the registry type for this value see table in docs for SetValueEx Raises an auditing event winreg QueryValue with arguments key sub_key value_name winreg SaveKey key file_name Saves the specified key and all its subkeys to the specified file key is an already open key or one of the predefined HKEY_ constants file_name is the name of the file to save registry data to This file cannot already exist If this filename includes an extension it cannot be used on file allocation table FAT file systems by the LoadKey method If key represents a key on a remote computer the path described by file_name is relative to the remote computer The caller of this method must possess the SeBackupPrivilege security privilege Note that privileges are different than permissions see the Conflicts Between User Rights and Permissions documentation for more details This function passes NULL for security_attributes to the API Raises an auditing event winreg SaveKey with arguments key file_name winreg SetValue key sub_key type value Associates a value with a specified key key is an already open key or one of the predefined HKEY_ constants sub_key is a string that names the subkey with which the value is associated type is an integer that specifies the type of the data Currently this must be REG_SZ meaning only strings are supported Use the SetValueEx function for support for other data types value is a string that specifies the new value If the key specified by the sub_key parameter does not exist the SetValue function creates it Value lengths are limited by available memory Long values more than 2048 bytes should be stored as files with the filenames stored in the configuration registry This helps the registry perform efficiently The key identified by the key parameter must have been opened with KEY_SET_VALUE access Raises an auditing event winreg SetValue with arguments key sub_key type value winreg SetValueEx key value_name reserved type value Stores data in the value field of an open registry key key is an already open key or one of the predefined HKEY_ constants value_name is a string that names the subkey with which the value is associated reserved can be anything zero is always passed to the API type is an integer that specifies the type of the data See Value Types for the avail,en
632,able types value is a string that specifies the new value This method can also set additional value and type information for the specified key The key identified by the key parameter must have been opened with KEY_SET_VALUE access To open the key use the CreateKey or OpenKey methods Value lengths are limited by available memory Long values more than 2048 bytes should be stored as files with the filenames stored in the configuration registry This helps the registry perform efficiently Raises an auditing event winreg SetValue with arguments key sub_key type value winreg DisableReflectionKey key Disables registry reflection for 32 bit processes running on a 64 bit operating system key is an already open key or one of the predefined HKEY_ constants Will generally raise NotImplementedError if executed on a 32 bit operating system If the key is not on the reflection list the function succeeds but has no effect Disabling reflection for a key does not affect reflection of any subkeys Raises an auditing event winreg DisableReflectionKey with argument key winreg EnableReflectionKey key Restores registry reflection for the specified disabled key key is an already open key or one of the predefined HKEY_ constants Will generally raise NotImplementedError if executed on a 32 bit operating system Restoring reflection for a key does not affect reflection of any subkeys Raises an auditing event winreg EnableReflectionKey with argument key winreg QueryReflectionKey key Determines the reflection state for the specified key key is an already open key or one of the predefined HKEY_ constants Returns True if reflection is disabled Will generally raise NotImplementedError if executed on a 32 bit operating system Raises an auditing event winreg QueryReflectionKey with argument key Constants The following constants are defined for use in many winreg functions HKEY_ Constants winreg HKEY_CLASSES_ROOT Registry entries subordinate to this key define types or classes of documents and the properties associated with those types Shell and COM applications use the information stored under this key winreg HKEY_CURRENT_USER Registry entries subordinate to this key define the preferences of the current user These preferences include the settings of environment variables data about program groups colors printers network connections and application preferences winreg HKEY_LOCAL_MACHINE Registry entries subordinate to this key define the physical state of the computer including data about the bus type system memory and installed hardware and software winreg HKEY_USERS Registry entries subordinate to this key define the default user configuration for new users on the local computer and the user configuration for the current user winreg HKEY_PERFORMANCE_DATA Registry entries subordinate to this key allow you to access performance data The data is not actually stored in the registry the registry functions cause the system to collect the data from its source winreg HKEY_CURRENT_CONFIG Contains information about the current hardware profile of the local computer system winreg HKEY_DYN_DATA This key is not used in versions of Windows after 98 Access Rights For more information see Registry Key Security and Access winreg KEY_ALL_ACCESS Combines the STANDARD_RIGHTS_REQUIRED KEY_QUERY_VALUE KEY_SET_VALUE KEY_CREATE_SUB_KEY KEY_ENUMERATE_SUB_KEYS KEY_NOTIFY and KEY_CREATE_LINK access rights winreg KEY_WRITE Combines the STANDARD_RIGHTS_WRITE KEY_SET_VALUE and KEY_CREATE_SUB_KEY access rights winreg KEY_READ Combines the STANDARD_RIGHTS_READ KEY_QUERY_VALUE KEY_ENUMERATE_SUB_KEYS and KEY_NOTIFY values winreg KEY_EXECUTE Equivalent to KEY_READ winreg KEY_QUERY_VALUE Required to query the values of a registry key winreg KEY_SET_VALUE Required to create delete or set a registry value winreg KEY_CREATE_SUB_KEY Required to create a subkey of a registry key winreg KEY_ENUMERATE_SUB_KEYS Required to enumerate the subkeys of a registry key winreg KEY_NOTIFY Required to request change notifications for a registry key or for subkeys of a registry key winreg KEY_CREATE_LINK Reserv,en
633,ed for system use 64 bit Specific For more information see Accessing an Alternate Registry View winreg KEY_WOW64_64KEY Indicates that an application on 64 bit Windows should operate on the 64 bit registry view On 32 bit Windows this constant is ignored winreg KEY_WOW64_32KEY Indicates that an application on 64 bit Windows should operate on the 32 bit registry view On 32 bit Windows this constant is ignored Value Types For more information see Registry Value Types winreg REG_BINARY Binary data in any form winreg REG_DWORD 32 bit number winreg REG_DWORD_LITTLE_ENDIAN A 32 bit number in little endian format Equivalent to REG_DWORD winreg REG_DWORD_BIG_ENDIAN A 32 bit number in big endian format winreg REG_EXPAND_SZ Null terminated string containing references to environment variables PATH winreg REG_LINK A Unicode symbolic link winreg REG_MULTI_SZ A sequence of null terminated strings terminated by two null characters Python handles this termination automatically winreg REG_NONE No defined value type winreg REG_QWORD A 64 bit number New in version 3 6 winreg REG_QWORD_LITTLE_ENDIAN A 64 bit number in little endian format Equivalent to REG_QWORD New in version 3 6 winreg REG_RESOURCE_LIST A device driver resource list winreg REG_FULL_RESOURCE_DESCRIPTOR A hardware setting winreg REG_RESOURCE_REQUIREMENTS_LIST A hardware resource list winreg REG_SZ A null terminated string Registry Handle Objects This object wraps a Windows HKEY object automatically closing it when the object is destroyed To guarantee cleanup you can call either the Close method on the object or the CloseKey function All registry functions in this module return one of these objects All registry functions in this module which accept a handle object also accept an integer however use of the handle object is encouraged Handle objects provide semantics for __bool__ thus if handle print Yes will print Yes if the handle is currently valid has not been closed or detached The object also support comparison semantics so handle objects will compare true if they both reference the same underlying Windows handle value Handle objects can be converted to an integer e g using the built in int function in which case the underlying Windows handle value is returned You can also use the Detach method to return the integer handle and also disconnect the Windows handle from the handle object PyHKEY Close Closes the underlying Windows handle If the handle is already closed no error is raised PyHKEY Detach Detaches the Windows handle from the handle object The result is an integer that holds the value of the handle before it is detached If the handle is already detached or closed this will return zero After calling this function the handle is effectively invalidated but the handle is not closed You would call this function when you need the underlying Win32 handle to exist beyond the lifetime of the handle object Raises an auditing event winreg PyHKEY Detach with argument key PyHKEY __enter__ PyHKEY __exit__ exc_info The HKEY object implements __enter__ and __exit__ and thus supports the context protocol for the with statement with OpenKey HKEY_LOCAL_MACHINE foo as key work with key will automatically close key when control leaves the with block,en
634,curses ascii Utilities for ASCII characters Source code Lib curses ascii py The curses ascii module supplies name constants for ASCII characters and functions to test membership in various ASCII character classes The constants supplied are names for control characters as follows Name Meaning curses ascii N UL curses ascii S Start of heading console interrupt OH curses ascii S Start of text TX curses ascii E End of text TX curses ascii E End of transmission OT curses ascii E Enquiry goes with ACK flow control NQ curses ascii A Acknowledgement CK curses ascii B Bell EL curses ascii BS Backspace curses ascii T Tab AB curses ascii HT Alias for TAB Horizontal tab curses ascii LF Line feed curses ascii NL Alias for LF New line curses ascii VT Vertical tab curses ascii FF Form feed curses ascii CR Carriage return curses ascii SO Shift out begin alternate character set curses ascii SI Shift in resume default character set curses ascii D Data link escape LE curses ascii D XON for flow control C1 curses ascii D Device control 2 block mode flow control C2 curses ascii D XOFF for flow control C3 curses ascii D Device control 4 C4 curses ascii N Negative acknowledgement AK curses ascii S Synchronous idle YN curses ascii E End transmission block TB curses ascii C Cancel AN curses ascii EM End of medium curses ascii S Substitute UB curses ascii E Escape SC curses ascii FS File separator curses ascii GS Group separator curses ascii RS Record separator block mode terminator curses ascii US Unit separator curses ascii SP Space curses ascii D Delete EL Note that many of these have little practical significance in modern usage The mnemonics derive from teleprinter conventions that predate digital computers The module supplies the following functions patterned on those in the standard C library curses ascii isalnum c Checks for an ASCII alphanumeric character it is equivalent to isalpha c or isdigit c curses ascii isalpha c Checks for an ASCII alphabetic character it is equivalent to isupper c or islower c curses ascii isascii c Checks for a character value that fits in the 7 bit ASCII set curses ascii isblank c Checks for an ASCII whitespace character space or horizontal tab curses ascii iscntrl c Checks for an ASCII control character in the range 0x00 to 0x1f or 0x7f curses ascii isdigit c Checks for an ASCII decimal digit 0 through 9 This is equivalent to c in string digits curses ascii isgraph c Checks for ASCII any printable character except space curses ascii islower c Checks for an ASCII lower case character curses ascii isprint c Checks for any ASCII printable character including space curses ascii ispunct c Checks for any printable ASCII character which is not a space or an alphanumeric character curses ascii isspace c Checks for ASCII white space characters space line feed carriage return form feed horizontal tab vertical tab curses ascii isupper c Checks for an ASCII uppercase letter curses ascii isxdigit c Checks for an ASCII hexadecimal digit This is equivalent to c in string hexdigits curses ascii isctrl c Checks for an ASCII control character ordinal values 0 to 31 curses ascii ismeta c Checks for a non ASCII character ordinal values 0x80 and above These functions accept either integers or single character strings when the argument is a string it is first converted using the built in function ord Note that all these functions check ordinal bit values derived from the character of the string you pass in they do not actually know anything about the host machine s character encoding The following two functions take either a single character string or integer byte value they return a value of the same type curses ascii ascii c Return the ASCII value corresponding to the low 7 bits of c curses ascii ctrl c Return the control character corresponding to the given character the character bit value is bitwise anded with 0x1f curses ascii alt c Return the 8 bit character corresponding to the given ASCII character the character bit value is bitwise ored with 0x80 The following function takes either a single character string or integer va,en
635,lue it returns a string curses ascii unctrl c Return a string representation of the ASCII character c If c is printable this string is the character itself If the character is a control character 0x00 0x1f the string consists of a caret followed by the corresponding uppercase letter If the character is an ASCII delete 0x7f the string is If the character has its meta bit 0x80 set the meta bit is stripped the preceding rules applied and prepended to the result curses ascii controlnames A 33 element string array that contains the ASCII mnemonics for the thirty two ASCII control characters from 0 NUL to 0x1f US in order plus the mnemonic SP for the space character,en
636,py_compile Compile Python source files Source code Lib py_compile py The py_compile module provides a function to generate a byte code file from a source file and another function used when the module source file is invoked as a script Though not often needed this function can be useful when installing modules for shared use especially if some of the users may not have permission to write the byte code cache files in the directory containing the source code exception py_compile PyCompileError Exception raised when an error occurs while attempting to compile the file py_compile compile file cfile None dfile None doraise False optimize 1 invalidation_mode PycInvalidationMode TIMESTAMP quiet 0 Compile a source file to byte code and write out the byte code cache file The source code is loaded from the file named file The byte code is written to cfile which defaults to the PEP 3147 PEP 488 path ending in pyc For example if file is foo bar baz py cfile will default to foo bar __pycache__ baz cpython 32 pyc for Python 3 2 If dfile is specified it is used instead of file as the name of the source file from which source lines are obtained for display in exception tracebacks If doraise is true a PyCompileError is raised when an error is encountered while compiling file If doraise is false the default an error string is written to sys stderr but no exception is raised This function returns the path to byte compiled file i e whatever cfile value was used The doraise and quiet arguments determine how errors are handled while compiling file If quiet is 0 or 1 and doraise is false the default behaviour is enabled an error string is written to sys stderr and the function returns None instead of a path If doraise is true a PyCompileError is raised instead However if quiet is 2 no message is written and doraise has no effect If the path that cfile becomes either explicitly specified or computed is a symlink or non regular file FileExistsError will be raised This is to act as a warning that import will turn those paths into regular files if it is allowed to write byte compiled files to those paths This is a side effect of import using file renaming to place the final byte compiled file into place to prevent concurrent file writing issues optimize controls the optimization level and is passed to the built in compile function The default of 1 selects the optimization level of the current interpreter invalidation_mode should be a member of the PycInvalidationMode enum and controls how the generated bytecode cache is invalidated at runtime The default is PycInvalidationMode CHECKED_HASH if the SOURCE_DATE_EPOCH environment variable is set otherwise the default is PycInvalidationMode TIMESTAMP Changed in version 3 2 Changed default value of cfile to be PEP 3147 compliant Previous default was file c o if optimization was enabled Also added the optimize parameter Changed in version 3 4 Changed code to use importlib for the byte code cache file writing This means file creation writing semantics now match what importlib does e g permissions write and move semantics etc Also added the caveat that FileExistsError is raised if cfile is a symlink or non regular file Changed in version 3 7 The invalidation_mode parameter was added as specified in PEP 552 If the SOURCE_DATE_EPOCH environment variable is set invalidation_mode will be forced to PycInvalidationMode CHECKED_HASH Changed in version 3 7 2 The SOURCE_DATE_EPOCH environment variable no longer overrides the value of the invalidation_mode argument and determines its default value instead Changed in version 3 8 The quiet parameter was added class py_compile PycInvalidationMode A enumeration of possible methods the interpreter can use to determine whether a bytecode file is up to date with a source file The pyc file indicates the desired invalidation mode in its header See Cached bytecode invalidation for more information on how Python invalidates pyc files at runtime New in version 3 7 TIMESTAMP The pyc file includes the timestamp and size of the source file which Python will compare against the me,en
637,tadata of the source file at runtime to determine if the pyc file needs to be regenerated CHECKED_HASH The pyc file includes a hash of the source file content which Python will compare against the source at runtime to determine if the pyc file needs to be regenerated UNCHECKED_HASH Like CHECKED_HASH the pyc file includes a hash of the source file content However Python will at runtime assume the pyc file is up to date and not validate the pyc against the source file at all This option is useful when the pycs are kept up to date by some system external to Python like a build system Command Line Interface This module can be invoked as a script to compile several source files The files named in filenames are compiled and the resulting bytecode is cached in the normal manner This program does not search a directory structure to locate source files it only compiles files named explicitly The exit status is nonzero if one of the files could not be compiled file fileN Positional arguments are files to compile If is the only parameter the list of files is taken from standard input q quiet Suppress errors output Changed in version 3 2 Added support for Changed in version 3 10 Added support for q See also Module compileall Utilities to compile all Python source files in a directory tree,en
638,wsgiref WSGI Utilities and Reference Implementation Source code Lib wsgiref The Web Server Gateway Interface WSGI is a standard interface between web server software and web applications written in Python Having a standard interface makes it easy to use an application that supports WSGI with a number of different web servers Only authors of web servers and programming frameworks need to know every detail and corner case of the WSGI design You don t need to understand every detail of WSGI just to install a WSGI application or to write a web application using an existing framework wsgiref is a reference implementation of the WSGI specification that can be used to add WSGI support to a web server or framework It provides utilities for manipulating WSGI environment variables and response headers base classes for implementing WSGI servers a demo HTTP server that serves WSGI applications types for static type checking and a validation tool that checks WSGI servers and applications for conformance to the WSGI specification PEP 3333 See wsgi readthedocs io for more information about WSGI and links to tutorials and other resources wsgiref util WSGI environment utilities This module provides a variety of utility functions for working with WSGI environments A WSGI environment is a dictionary containing HTTP request variables as described in PEP 3333 All of the functions taking an environ parameter expect a WSGI compliant dictionary to be supplied please see PEP 3333 for a detailed specification and WSGIEnvironment for a type alias that can be used in type annotations wsgiref util guess_scheme environ Return a guess for whether wsgi url_scheme should be http or https by checking for a HTTPS environment variable in the environ dictionary The return value is a string This function is useful when creating a gateway that wraps CGI or a CGI like protocol such as FastCGI Typically servers providing such protocols will include a HTTPS variable with a value of 1 yes or on when a request is received via SSL So this function returns https if such a value is found and http otherwise wsgiref util request_uri environ include_query True Return the full request URI optionally including the query string using the algorithm found in the URL Reconstruction section of PEP 3333 If include_query is false the query string is not included in the resulting URI wsgiref util application_uri environ Similar to request_uri except that the PATH_INFO and QUERY_STRING variables are ignored The result is the base URI of the application object addressed by the request wsgiref util shift_path_info environ Shift a single name from PATH_INFO to SCRIPT_NAME and return the name The environ dictionary is modified in place use a copy if you need to keep the original PATH_INFO or SCRIPT_NAME intact If there are no remaining path segments in PATH_INFO None is returned Typically this routine is used to process each portion of a request URI path for example to treat the path as a series of dictionary keys This routine modifies the passed in environment to make it suitable for invoking another WSGI application that is located at the target URI For example if there is a WSGI application at foo and the request URI path is foo bar baz and the WSGI application at foo calls shift_path_info it will receive the string bar and the environment will be updated to be suitable for passing to a WSGI application at foo bar That is SCRIPT_NAME will change from foo to foo bar and PATH_INFO will change from bar baz to baz When PATH_INFO is just a this routine returns an empty string and appends a trailing slash to SCRIPT_NAME even though empty path segments are normally ignored and SCRIPT_NAME doesn t normally end in a slash This is intentional behavior to ensure that an application can tell the difference between URIs ending in x from ones ending in x when using this routine to do object traversal wsgiref util setup_testing_defaults environ Update environ with trivial defaults for testing purposes This routine adds various parameters required for WSGI including HTTP_HOST SERVER_NAME SERVER_PO,en
639,RT REQUEST_METHOD SCRIPT_NAME PATH_INFO and all of the PEP 3333 defined wsgi variables It only supplies default values and does not replace any existing settings for these variables This routine is intended to make it easier for unit tests of WSGI servers and applications to set up dummy environments It should NOT be used by actual WSGI servers or applications since the data is fake Example usage from wsgiref util import setup_testing_defaults from wsgiref simple_server import make_server A relatively simple WSGI application It s going to print out the environment dictionary after being updated by setup_testing_defaults def simple_app environ start_response setup_testing_defaults environ status 200 OK headers Content type text plain charset utf 8 start_response status headers ret s s n key value encode utf 8 for key value in environ items return ret with make_server 8000 simple_app as httpd print Serving on port 8000 httpd serve_forever In addition to the environment functions above the wsgiref util module also provides these miscellaneous utilities wsgiref util is_hop_by_hop header_name Return True if header_name is an HTTP 1 1 Hop by Hop header as defined by RFC 2616 class wsgiref util FileWrapper filelike blksize 8192 A concrete implementation of the wsgiref types FileWrapper protocol used to convert a file like object to an iterator The resulting objects are iterable s As the object is iterated over the optional blksize parameter will be repeatedly passed to the filelike object s read method to obtain bytestrings to yield When read returns an empty bytestring iteration is ended and is not resumable If filelike has a close method the returned object will also have a close method and it will invoke the filelike object s close method when called Example usage from io import StringIO from wsgiref util import FileWrapper We re using a StringIO buffer for as the file like object filelike StringIO This is an example file like object 10 wrapper FileWrapper filelike blksize 5 for chunk in wrapper print chunk Changed in version 3 11 Support for __getitem__ method has been removed wsgiref headers WSGI response header tools This module provides a single class Headers for convenient manipulation of WSGI response headers using a mapping like interface class wsgiref headers Headers headers Create a mapping like object wrapping headers which must be a list of header name value tuples as described in PEP 3333 The default value of headers is an empty list Headers objects support typical mapping operations including __getitem__ get __setitem__ setdefault __delitem__ and __contains__ For each of these methods the key is the header name treated case insensitively and the value is the first value associated with that header name Setting a header deletes any existing values for that header then adds a new value at the end of the wrapped header list Headers existing order is generally maintained with new headers added to the end of the wrapped list Unlike a dictionary Headers objects do not raise an error when you try to get or delete a key that isn t in the wrapped header list Getting a nonexistent header just returns None and deleting a nonexistent header does nothing Headers objects also support keys values and items methods The lists returned by keys and items can include the same key more than once if there is a multi valued header The len of a Headers object is the same as the length of its items which is the same as the length of the wrapped header list In fact the items method just returns a copy of the wrapped header list Calling bytes on a Headers object returns a formatted bytestring suitable for transmission as HTTP response headers Each header is placed on a line with its value separated by a colon and a space Each line is terminated by a carriage return and line feed and the bytestring is terminated with a blank line In addition to their mapping interface and formatting features Headers objects also have the following methods for querying and adding multi valued headers and for adding headers with MIME parameters get_all name ,en
640,Return a list of all the values for the named header The returned list will be sorted in the order they appeared in the original header list or were added to this instance and may contain duplicates Any fields deleted and re inserted are always appended to the header list If no fields exist with the given name returns an empty list add_header name value _params Add a possibly multi valued header with optional MIME parameters specified via keyword arguments name is the header field to add Keyword arguments can be used to set MIME parameters for the header field Each parameter must be a string or None Underscores in parameter names are converted to dashes since dashes are illegal in Python identifiers but many MIME parameter names include dashes If the parameter value is a string it is added to the header value parameters in the form name value If it is None only the parameter name is added This is used for MIME parameters without a value Example usage h add_header content disposition attachment filename bud gif The above will add a header that looks like this Content Disposition attachment filename bud gif Changed in version 3 5 headers parameter is optional wsgiref simple_server a simple WSGI HTTP server This module implements a simple HTTP server based on http server that serves WSGI applications Each server instance serves a single WSGI application on a given host and port If you want to serve multiple applications on a single host and port you should create a WSGI application that parses PATH_INFO to select which application to invoke for each request E g using the shift_path_info function from wsgiref util wsgiref simple_server make_server host port app server_class WSGIServer handler_class WSGIRequestHandler Create a new WSGI server listening on host and port accepting connections for app The return value is an instance of the supplied server_class and will process requests using the specified handler_class app must be a WSGI application object as defined by PEP 3333 Example usage from wsgiref simple_server import make_server demo_app with make_server 8000 demo_app as httpd print Serving HTTP on port 8000 Respond to requests until process is killed httpd serve_forever Alternative serve one request then exit httpd handle_request wsgiref simple_server demo_app environ start_response This function is a small but complete WSGI application that returns a text page containing the message Hello world and a list of the key value pairs provided in the environ parameter It s useful for verifying that a WSGI server such as wsgiref simple_server is able to run a simple WSGI application correctly class wsgiref simple_server WSGIServer server_address RequestHandlerClass Create a WSGIServer instance server_address should be a host port tuple and RequestHandlerClass should be the subclass of http server BaseHTTPRequestHandler that will be used to process requests You do not normally need to call this constructor as the make_server function can handle all the details for you WSGIServer is a subclass of http server HTTPServer so all of its methods such as serve_forever and handle_request are available WSGIServer also provides these WSGI specific methods set_app application Sets the callable application as the WSGI application that will receive requests get_app Returns the currently set application callable Normally however you do not need to use these additional methods as set_app is normally called by make_server and the get_app exists mainly for the benefit of request handler instances class wsgiref simple_server WSGIRequestHandler request client_address server Create an HTTP handler for the given request i e a socket client_address a host port tuple and server WSGIServer instance You do not need to create instances of this class directly they are automatically created as needed by WSGIServer objects You can however subclass this class and supply it as a handler_class to the make_server function Some possibly relevant methods for overriding in subclasses get_environ Return a WSGIEnvironment dictionary for a request The default impl,en
641,ementation copies the contents of the WSGIServer object s base_environ dictionary attribute and then adds various headers derived from the HTTP request Each call to this method should return a new dictionary containing all of the relevant CGI environment variables as specified in PEP 3333 get_stderr Return the object that should be used as the wsgi errors stream The default implementation just returns sys stderr handle Process the HTTP request The default implementation creates a handler instance using a wsgiref handlers class to implement the actual WSGI application interface wsgiref validate WSGI conformance checker When creating new WSGI application objects frameworks servers or middleware it can be useful to validate the new code s conformance using wsgiref validate This module provides a function that creates WSGI application objects that validate communications between a WSGI server or gateway and a WSGI application object to check both sides for protocol conformance Note that this utility does not guarantee complete PEP 3333 compliance an absence of errors from this module does not necessarily mean that errors do not exist However if this module does produce an error then it is virtually certain that either the server or application is not 100 compliant This module is based on the paste lint module from Ian Bicking s Python Paste library wsgiref validate validator application Wrap application and return a new WSGI application object The returned application will forward all requests to the original application and will check that both the application and the server invoking it are conforming to the WSGI specification and to RFC 2616 Any detected nonconformance results in an AssertionError being raised note however that how these errors are handled is server dependent For example wsgiref simple_server and other servers based on wsgiref handlers that don t override the error handling methods to do something else will simply output a message that an error has occurred and dump the traceback to sys stderr or some other error stream This wrapper may also generate output using the warnings module to indicate behaviors that are questionable but which may not actually be prohibited by PEP 3333 Unless they are suppressed using Python command line options or the warnings API any such warnings will be written to sys stderr not wsgi errors unless they happen to be the same object Example usage from wsgiref validate import validator from wsgiref simple_server import make_server Our callable object which is intentionally not compliant to the standard so the validator is going to break def simple_app environ start_response status 200 OK HTTP Status headers Content type text plain HTTP Headers start_response status headers This is going to break because we need to return a list and the validator is going to inform us return b Hello World This is the application wrapped in a validator validator_app validator simple_app with make_server 8000 validator_app as httpd print Listening on port 8000 httpd serve_forever wsgiref handlers server gateway base classes This module provides base handler classes for implementing WSGI servers and gateways These base classes handle most of the work of communicating with a WSGI application as long as they are given a CGI like environment along with input output and error streams class wsgiref handlers CGIHandler CGI based invocation via sys stdin sys stdout sys stderr and os environ This is useful when you have a WSGI application and want to run it as a CGI script Simply invoke CGIHandler run app where app is the WSGI application object you wish to invoke This class is a subclass of BaseCGIHandler that sets wsgi run_once to true wsgi multithread to false and wsgi multiprocess to true and always uses sys and os to obtain the necessary CGI streams and environment class wsgiref handlers IISCGIHandler A specialized alternative to CGIHandler for use when deploying on Microsoft s IIS web server without having set the config allowPathInfo option IIS 7 or metabase allowPathInfoForScriptMappings IIS 7 By def,en
642,ault IIS gives a PATH_INFO that duplicates the SCRIPT_NAME at the front causing problems for WSGI applications that wish to implement routing This handler strips any such duplicated path IIS can be configured to pass the correct PATH_INFO but this causes another bug where PATH_TRANSLATED is wrong Luckily this variable is rarely used and is not guaranteed by WSGI On IIS 7 though the setting can only be made on a vhost level affecting all other script mappings many of which break when exposed to the PATH_TRANSLATED bug For this reason IIS 7 is almost never deployed with the fix Even IIS7 rarely uses it because there is still no UI for it There is no way for CGI code to tell whether the option was set so a separate handler class is provided It is used in the same way as CGIHandler i e by calling IISCGIHandler run app where app is the WSGI application object you wish to invoke New in version 3 2 class wsgiref handlers BaseCGIHandler stdin stdout stderr environ multithread True multiprocess False Similar to CGIHandler but instead of using the sys and os modules the CGI environment and I O streams are specified explicitly The multithread and multiprocess values are used to set the wsgi multithread and wsgi multiprocess flags for any applications run by the handler instance This class is a subclass of SimpleHandler intended for use with software other than HTTP origin servers If you are writing a gateway protocol implementation such as CGI FastCGI SCGI etc that uses a Status header to send an HTTP status you probably want to subclass this instead of SimpleHandler class wsgiref handlers SimpleHandler stdin stdout stderr environ multithread True multiprocess False Similar to BaseCGIHandler but designed for use with HTTP origin servers If you are writing an HTTP server implementation you will probably want to subclass this instead of BaseCGIHandler This class is a subclass of BaseHandler It overrides the __init__ get_stdin get_stderr add_cgi_vars _write and _flush methods to support explicitly setting the environment and streams via the constructor The supplied environment and streams are stored in the stdin stdout stderr and environ attributes The write method of stdout should write each chunk in full like io BufferedIOBase class wsgiref handlers BaseHandler This is an abstract base class for running WSGI applications Each instance will handle a single HTTP request although in principle you could create a subclass that was reusable for multiple requests BaseHandler instances have only one method intended for external use run app Run the specified WSGI application app All of the other BaseHandler methods are invoked by this method in the process of running the application and thus exist primarily to allow customizing the process The following methods MUST be overridden in a subclass _write data Buffer the bytes data for transmission to the client It s okay if this method actually transmits the data BaseHandler just separates write and flush operations for greater efficiency when the underlying system actually has such a distinction _flush Force buffered data to be transmitted to the client It s okay if this method is a no op i e if _write actually sends the data get_stdin Return an object compatible with InputStream suitable for use as the wsgi input of the request currently being processed get_stderr Return an object compatible with ErrorStream suitable for use as the wsgi errors of the request currently being processed add_cgi_vars Insert CGI variables for the current request into the environ attribute Here are some other methods and attributes you may wish to override This list is only a summary however and does not include every method that can be overridden You should consult the docstrings and source code for additional information before attempting to create a customized BaseHandler subclass Attributes and methods for customizing the WSGI environment wsgi_multithread The value to be used for the wsgi multithread environment variable It defaults to true in BaseHandler but may have a different default or be set by the constru,en
643,ctor in the other subclasses wsgi_multiprocess The value to be used for the wsgi multiprocess environment variable It defaults to true in BaseHandler but may have a different default or be set by the constructor in the other subclasses wsgi_run_once The value to be used for the wsgi run_once environment variable It defaults to false in BaseHandler but CGIHandler sets it to true by default os_environ The default environment variables to be included in every request s WSGI environment By default this is a copy of os environ at the time that wsgiref handlers was imported but subclasses can either create their own at the class or instance level Note that the dictionary should be considered read only since the default value is shared between multiple classes and instances server_software If the origin_server attribute is set this attribute s value is used to set the default SERVER_SOFTWARE WSGI environment variable and also to set a default Server header in HTTP responses It is ignored for handlers such as BaseCGIHandler and CGIHandler that are not HTTP origin servers Changed in version 3 3 The term Python is replaced with implementation specific term like CPython Jython etc get_scheme Return the URL scheme being used for the current request The default implementation uses the guess_scheme function from wsgiref util to guess whether the scheme should be http or https based on the current request s environ variables setup_environ Set the environ attribute to a fully populated WSGI environment The default implementation uses all of the above methods and attributes plus the get_stdin get_stderr and add_cgi_vars methods and the wsgi_file_wrapper attribute It also inserts a SERVER_SOFTWARE key if not present as long as the origin_server attribute is a true value and the server_software attribute is set Methods and attributes for customizing exception handling log_exception exc_info Log the exc_info tuple in the server log exc_info is a type value traceback tuple The default implementation simply writes the traceback to the request s wsgi errors stream and flushes it Subclasses can override this method to change the format or retarget the output mail the traceback to an administrator or whatever other action may be deemed suitable traceback_limit The maximum number of frames to include in tracebacks output by the default log_exception method If None all frames are included error_output environ start_response This method is a WSGI application to generate an error page for the user It is only invoked if an error occurs before headers are sent to the client This method can access the current error using sys exception and should pass that information to start_response when calling it as described in the Error Handling section of PEP 3333 The default implementation just uses the error_status error_headers and error_body attributes to generate an output page Subclasses can override this to produce more dynamic error output Note however that it s not recommended from a security perspective to spit out diagnostics to any old user ideally you should have to do something special to enable diagnostic output which is why the default implementation doesn t include any error_status The HTTP status used for error responses This should be a status string as defined in PEP 3333 it defaults to a 500 code and message error_headers The HTTP headers used for error responses This should be a list of WSGI response headers name value tuples as described in PEP 3333 The default list just sets the content type to text plain error_body The error response body This should be an HTTP response body bytestring It defaults to the plain text A server error occurred Please contact the administrator Methods and attributes for PEP 3333 s Optional Platform Specific File Handling feature wsgi_file_wrapper A wsgi file_wrapper factory compatible with wsgiref types FileWrapper or None The default value of this attribute is the wsgiref util FileWrapper class sendfile Override to implement platform specific file transmission This method is called only if the application s r,en
644,eturn value is an instance of the class specified by the wsgi_file_wrapper attribute It should return a true value if it was able to successfully transmit the file so that the default transmission code will not be executed The default implementation of this method just returns a false value Miscellaneous methods and attributes origin_server This attribute should be set to a true value if the handler s _write and _flush are being used to communicate directly to the client rather than via a CGI like gateway protocol that wants the HTTP status in a special Status header This attribute s default value is true in BaseHandler but false in BaseCGIHandler and CGIHandler http_version If origin_server is true this string attribute is used to set the HTTP version of the response set to the client It defaults to 1 0 wsgiref handlers read_environ Transcode CGI variables from os environ to PEP 3333 bytes in unicode strings returning a new dictionary This function is used by CGIHandler and IISCGIHandler in place of directly using os environ which is not necessarily WSGI compliant on all platforms and web servers using Python 3 specifically ones where the OS s actual environment is Unicode i e Windows or ones where the environment is bytes but the system encoding used by Python to decode it is anything other than ISO 8859 1 e g Unix systems using UTF 8 If you are implementing a CGI based handler of your own you probably want to use this routine instead of just copying values out of os environ directly New in version 3 2 wsgiref types WSGI types for static type checking This module provides various types for static type checking as described in PEP 3333 New in version 3 11 class wsgiref types StartResponse A typing Protocol describing start_response callables PEP 3333 wsgiref types WSGIEnvironment A type alias describing a WSGI environment dictionary wsgiref types WSGIApplication A type alias describing a WSGI application callable class wsgiref types InputStream A typing Protocol describing a WSGI Input Stream class wsgiref types ErrorStream A typing Protocol describing a WSGI Error Stream class wsgiref types FileWrapper A typing Protocol describing a file wrapper See wsgiref util FileWrapper for a concrete implementation of this protocol Examples This is a working Hello World WSGI application Every WSGI application must have an application object a callable object that accepts two arguments For that purpose we re going to use a function note that you re not limited to a function you can use a class for example The first argument passed to the function is a dictionary containing CGI style environment variables and the second variable is the callable object from wsgiref simple_server import make_server def hello_world_app environ start_response status 200 OK HTTP Status headers Content type text plain charset utf 8 HTTP Headers start_response status headers The returned object is going to be printed return b Hello World with make_server 8000 hello_world_app as httpd print Serving on port 8000 Serve until process is killed httpd serve_forever Example of a WSGI application serving the current directory accept optional directory and port number default 8000 on the command line Small wsgiref based web server Takes a path to serve from and an optional port number defaults to 8000 then tries to serve files MIME types are guessed from the file names 404 errors are raised if the file is not found import mimetypes import os import sys from wsgiref import simple_server util def app environ respond Get the file name and MIME type fn os path join path environ PATH_INFO 1 if not in fn split os path sep 1 fn os path join fn index html mime_type mimetypes guess_type fn 0 Return 200 OK if file exists otherwise 404 Not Found if os path exists fn respond 200 OK Content Type mime_type return util FileWrapper open fn rb else respond 404 Not Found Content Type text plain return b not found if __name__ __main__ Get the path and port from command line arguments path sys argv 1 if len sys argv 1 else os getcwd port int sys argv 2 if len sys argv 2 else 8000 Make,en
645, and start the server until control c httpd simple_server make_server port app print f Serving path on port port control C to stop try httpd serve_forever except KeyboardInterrupt print Shutting down httpd server_close,en
646,nntplib NNTP protocol client Source code Lib nntplib py Deprecated since version 3 11 The nntplib module is deprecated see PEP 594 for details This module defines the class NNTP which implements the client side of the Network News Transfer Protocol It can be used to implement a news reader or poster or automated news processors It is compatible with RFC 3977 as well as the older RFC 977 and RFC 2980 Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information Here are two small examples of how it can be used To list some statistics about a newsgroup and print the subjects of the last 10 articles s nntplib NNTP news gmane io resp count first last name s group gmane comp python committers print Group name has count articles range first to last Group gmane comp python committers has 1096 articles range 1 to 1096 resp overviews s over last 9 last for id over in overviews print id nntplib decode_header over subject 1087 Re Commit privileges for Łukasz Langa 1088 Re 3 2 alpha 2 freeze 1089 Re 3 2 alpha 2 freeze 1090 Re Commit privileges for Łukasz Langa 1091 Re Commit privileges for Łukasz Langa 1092 Updated ssh key 1093 Re Updated ssh key 1094 Re Updated ssh key 1095 Hello fellow committers 1096 Re Hello fellow committers s quit 205 Bye To post an article from a binary file this assumes that the article has valid headers and that you have right to post on the particular newsgroup s nntplib NNTP news gmane io f open article txt rb s post f 240 Article posted successfully s quit 205 Bye The module itself defines the following classes class nntplib NNTP host port 119 user None password None readermode None usenetrc False timeout Return a new NNTP object representing a connection to the NNTP server running on host host listening at port port An optional timeout can be specified for the socket connection If the optional user and password are provided or if suitable credentials are present in netrc and the optional flag usenetrc is true the AUTHINFO USER and AUTHINFO PASS commands are used to identify and authenticate the user to the server If the optional flag readermode is true then a mode reader command is sent before authentication is performed Reader mode is sometimes necessary if you are connecting to an NNTP server on the local machine and intend to call reader specific commands such as group If you get unexpected NNTPPermanentError s you might need to set readermode The NNTP class supports the with statement to unconditionally consume OSError exceptions and to close the NNTP connection when done e g from nntplib import NNTP with NNTP news gmane io as n n group gmane comp python committers 211 1755 1 1755 gmane comp python committers 1755 1 1755 gmane comp python committers Raises an auditing event nntplib connect with arguments self host port All commands will raise an auditing event nntplib putline with arguments self and line where line is the bytes about to be sent to the remote host Changed in version 3 2 usenetrc is now False by default Changed in version 3 3 Support for the with statement was added Changed in version 3 9 If the timeout parameter is set to be zero it will raise a ValueError to prevent the creation of a non blocking socket class nntplib NNTP_SSL host port 563 user None password None ssl_context None readermode None usenetrc False timeout Return a new NNTP_SSL object representing an encrypted connection to the NNTP server running on host host listening at port port NNTP_SSL objects have the same methods as NNTP objects If port is omitted port 563 NNTPS is used ssl_context is also optional and is a SSLContext object Please read Security considerations for best practices All other parameters behave the same as for NNTP Note that SSL on 563 is discouraged per RFC 4642 in favor of STARTTLS as described below However some servers only support the former Raises an auditing event nntplib connect with arguments self host port All commands will raise an auditing event nntplib putline wit,en
647,h arguments self and line where line is the bytes about to be sent to the remote host New in version 3 2 Changed in version 3 4 The class now supports hostname check with ssl SSLContext check_hostname and Server Name Indication see ssl HAS_SNI Changed in version 3 9 If the timeout parameter is set to be zero it will raise a ValueError to prevent the creation of a non blocking socket exception nntplib NNTPError Derived from the standard exception Exception this is the base class for all exceptions raised by the nntplib module Instances of this class have the following attribute response The response of the server if available as a str object exception nntplib NNTPReplyError Exception raised when an unexpected reply is received from the server exception nntplib NNTPTemporaryError Exception raised when a response code in the range 400 499 is received exception nntplib NNTPPermanentError Exception raised when a response code in the range 500 599 is received exception nntplib NNTPProtocolError Exception raised when a reply is received from the server that does not begin with a digit in the range 1 5 exception nntplib NNTPDataError Exception raised when there is some error in the response data NNTP Objects When connected NNTP and NNTP_SSL objects support the following methods and attributes Attributes NNTP nntp_version An integer representing the version of the NNTP protocol supported by the server In practice this should be 2 for servers advertising RFC 3977 compliance and 1 for others New in version 3 2 NNTP nntp_implementation A string describing the software name and version of the NNTP server or None if not advertised by the server New in version 3 2 Methods The response that is returned as the first item in the return tuple of almost all methods is the server s response a string beginning with a three digit code If the server s response indicates an error the method raises one of the above exceptions Many of the following methods take an optional keyword only argument file When the file argument is supplied it must be either a file object opened for binary writing or the name of an on disk file to be written to The method will then write any data returned by the server except for the response line and the terminating dot to the file any list of lines tuples or objects that the method normally returns will be empty Changed in version 3 2 Many of the following methods have been reworked and fixed which makes them incompatible with their 3 1 counterparts NNTP quit Send a QUIT command and close the connection Once this method has been called no other methods of the NNTP object should be called NNTP getwelcome Return the welcome message sent by the server in reply to the initial connection This message sometimes contains disclaimers or help information that may be relevant to the user NNTP getcapabilities Return the RFC 3977 capabilities advertised by the server as a dict instance mapping capability names to possibly empty lists of values On legacy servers which don t understand the CAPABILITIES command an empty dictionary is returned instead s NNTP news gmane io POST in s getcapabilities True New in version 3 2 NNTP login user None password None usenetrc True Send AUTHINFO commands with the user name and password If user and password are None and usenetrc is true credentials from netrc will be used if possible Unless intentionally delayed login is normally performed during the NNTP object initialization and separately calling this function is unnecessary To force authentication to be delayed you must not set user or password when creating the object and must set usenetrc to False New in version 3 2 NNTP starttls context None Send a STARTTLS command This will enable encryption on the NNTP connection The context argument is optional and should be a ssl SSLContext object Please read Security considerations for best practices Note that this may not be done after authentication information has been transmitted and authentication occurs by default if possible during a NNTP object initialization See NNTP login for information on su,en
648,ppressing this behavior New in version 3 2 Changed in version 3 4 The method now supports hostname check with ssl SSLContext check_hostname and Server Name Indication see ssl HAS_SNI NNTP newgroups date file None Send a NEWGROUPS command The date argument should be a datetime date or datetime datetime object Return a pair response groups where groups is a list representing the groups that are new since the given date If file is supplied though then groups will be empty from datetime import date timedelta resp groups s newgroups date today timedelta days 3 len groups 85 groups 0 GroupInfo group gmane network tor devel last 4 first 1 flag m NNTP newnews group date file None Send a NEWNEWS command Here group is a group name or and date has the same meaning as for newgroups Return a pair response articles where articles is a list of message ids This command is frequently disabled by NNTP server administrators NNTP list group_pattern None file None Send a LIST or LIST ACTIVE command Return a pair response list where list is a list of tuples representing all the groups available from this NNTP server optionally matching the pattern string group_pattern Each tuple has the form group last first flag where group is a group name last and first are the last and first article numbers and flag usually takes one of these values y Local postings and articles from peers are allowed m The group is moderated and all postings must be approved n No local postings are allowed only articles from peers j Articles from peers are filed in the junk group instead x No local postings and articles from peers are ignored foo bar Articles are filed in the foo bar group instead If flag has another value then the status of the newsgroup should be considered unknown This command can return very large results especially if group_pattern is not specified It is best to cache the results offline unless you really need to refresh them Changed in version 3 2 group_pattern was added NNTP descriptions grouppattern Send a LIST NEWSGROUPS command where grouppattern is a wildmat string as specified in RFC 3977 it s essentially the same as DOS or UNIX shell wildcard strings Return a pair response descriptions where descriptions is a dictionary mapping group names to textual descriptions resp descs s descriptions gmane comp python len descs 295 descs popitem gmane comp python bio general BioPython discussion list Moderated NNTP description group Get a description for a single group group If more than one group matches if group is a real wildmat string return the first match If no group matches return an empty string This elides the response code from the server If the response code is needed use descriptions NNTP group name Send a GROUP command where name is the group name The group is selected as the current group if it exists Return a tuple response count first last name where count is the estimated number of articles in the group first is the first article number in the group last is the last article number in the group and name is the group name NNTP over message_spec file None Send an OVER command or an XOVER command on legacy servers message_spec can be either a string representing a message id or a first last tuple of numbers indicating a range of articles in the current group or a first None tuple indicating a range of articles starting from first to the last article in the current group or None to select the current article in the current group Return a pair response overviews overviews is a list of article_number overview tuples one for each article selected by message_spec Each overview is a dictionary with the same number of items but this number depends on the server These items are either message headers the key is then the lower cased header name or metadata items the key is then the metadata name prepended with The following items are guaranteed to be present by the NNTP specification the subject from date message id and references headers the bytes metadata the number of bytes in the entire raw article including headers and body the lines metadata th,en
649,e number of lines in the article body The value of each item is either a string or None if not present It is advisable to use the decode_header function on header values when they may contain non ASCII characters _ _ first last _ s group gmane comp python devel resp overviews s over last last art_num over overviews 0 art_num 117216 list over keys xref from lines bytes references date message id subject over from UTF 8 B Ik1hcnRpbiB2LiBMw7Z3aXMi martin v loewis de nntplib decode_header over from Martin v Löwis martin v loewis de New in version 3 2 NNTP help file None Send a HELP command Return a pair response list where list is a list of help strings NNTP stat message_spec None Send a STAT command where message_spec is either a message id enclosed in and or an article number in the current group If message_spec is omitted or None the current article in the current group is considered Return a triple response number id where number is the article number and id is the message id _ _ first last _ s group gmane comp python devel resp number message_id s stat first number message_id 9099 20030112190404 GE29873 epoch metaslash com NNTP next Send a NEXT command Return as for stat NNTP last Send a LAST command Return as for stat NNTP article message_spec None file None Send an ARTICLE command where message_spec has the same meaning as for stat Return a tuple response info where info is a namedtuple with three attributes number message_id and lines in that order number is the article number in the group or 0 if the information is not available message_id the message id as a string and lines a list of lines without terminating newlines comprising the raw message including headers and body resp info s article 20030112190404 GE29873 epoch metaslash com info number 0 info message_id 20030112190404 GE29873 epoch metaslash com len info lines 65 info lines 0 b Path main gmane org not for mail info lines 1 b From Neal Norwitz neal metaslash com info lines 3 b There is a patch for 2 3 as well as 2 2 b b Neal NNTP head message_spec None file None Same as article but sends a HEAD command The lines returned or written to file will only contain the message headers not the body NNTP body message_spec None file None Same as article but sends a BODY command The lines returned or written to file will only contain the message body not the headers NNTP post data Post an article using the POST command The data argument is either a file object opened for binary reading or any iterable of bytes objects representing raw lines of the article to be posted It should represent a well formed news article including the required headers The post method automatically escapes lines beginning with and appends the termination line If the method succeeds the server s response is returned If the server refuses posting a NNTPReplyError is raised NNTP ihave message_id data Send an IHAVE command message_id is the id of the message to send to the server enclosed in and The data parameter and the return value are the same as for post NNTP date Return a pair response date date is a datetime object containing the current date and time of the server NNTP slave Send a SLAVE command Return the server s response NNTP set_debuglevel level Set the instance s debugging level This controls the amount of debugging output printed The default 0 produces no debugging output A value of 1 produces a moderate amount of debugging output generally a single line per request or response A value of 2 or higher produces the maximum amount of debugging output logging each line sent and received on the connection including message text The following are optional NNTP extensions defined in RFC 2980 Some of them have been superseded by newer commands in RFC 3977 NNTP xhdr hdr str file None Send an XHDR command The hdr argument is a header keyword e g subject The str argument should have the form first last where first and last are the first and last article numbers to search Return a pair response list where list is a list of pairs id text where id is an article number as a string and text is the ,en
650,text of the requested header for that article If the file parameter is supplied then the output of the XHDR command is stored in a file If file is a string then the method will open a file with that name write to it then close it If file is a file object then it will start calling write on it to store the lines of the command output If file is supplied then the returned list is an empty list NNTP xover start end file None Send an XOVER command start and end are article numbers delimiting the range of articles to select The return value is the same of for over It is recommended to use over instead since it will automatically use the newer OVER command if available Utility functions The module also defines the following utility function nntplib decode_header header_str Decode a header value un escaping any escaped non ASCII characters header_str must be a str object The unescaped value is returned Using this function is recommended to display some headers in a human readable form decode_header Some subject Some subject decode_header ISO 8859 15 Q D E9buter_en_Python Débuter en Python decode_header Re UTF 8 B cHJvYmzDqG1lIGRlIG1hdHJpY2U Re problème de matrice,en
651,Floating Point Objects type PyFloatObject This subtype of PyObject represents a Python floating point object PyTypeObject PyFloat_Type Part of the Stable ABI This instance of PyTypeObject represents the Python floating point type This is the same object as float in the Python layer int PyFloat_Check PyObject p Return true if its argument is a PyFloatObject or a subtype of PyFloatObject This function always succeeds int PyFloat_CheckExact PyObject p Return true if its argument is a PyFloatObject but not a subtype of PyFloatObject This function always succeeds PyObject PyFloat_FromString PyObject str Return value New reference Part of the Stable ABI Create a PyFloatObject object based on the string value in str or NULL on failure PyObject PyFloat_FromDouble double v Return value New reference Part of the Stable ABI Create a PyFloatObject object from v or NULL on failure double PyFloat_AsDouble PyObject pyfloat Part of the Stable ABI Return a C double representation of the contents of pyfloat If pyfloat is not a Python floating point object but has a __float__ method this method will first be called to convert pyfloat into a float If __float__ is not defined then it falls back to __index__ This method returns 1 0 upon failure so one should call PyErr_Occurred to check for errors Changed in version 3 8 Use __index__ if available double PyFloat_AS_DOUBLE PyObject pyfloat Return a C double representation of the contents of pyfloat but without error checking PyObject PyFloat_GetInfo void Return value New reference Part of the Stable ABI Return a structseq instance which contains information about the precision minimum and maximum values of a float It s a thin wrapper around the header file float h double PyFloat_GetMax Part of the Stable ABI Return the maximum representable finite float DBL_MAX as C double double PyFloat_GetMin Part of the Stable ABI Return the minimum normalized positive float DBL_MIN as C double Pack and Unpack functions The pack and unpack functions provide an efficient platform independent way to store floating point values as byte strings The Pack routines produce a bytes string from a C double and the Unpack routines produce a C double from such a bytes string The suffix 2 4 or 8 specifies the number of bytes in the bytes string On platforms that appear to use IEEE 754 formats these functions work by copying bits On other platforms the 2 byte format is identical to the IEEE 754 binary16 half precision format the 4 byte format 32 bit is identical to the IEEE 754 binary32 single precision format and the 8 byte format to the IEEE 754 binary64 double precision format although the packing of INFs and NaNs if such things exist on the platform isn t handled correctly and attempting to unpack a bytes string containing an IEEE INF or NaN will raise an exception On non IEEE platforms with more precision or larger dynamic range than IEEE 754 supports not all values can be packed on non IEEE platforms with less precision or smaller dynamic range not all values can be unpacked What happens in such cases is partly accidental alas New in version 3 11 Pack functions The pack routines write 2 4 or 8 bytes starting at p le is an int argument non zero if you want the bytes string in little endian format exponent last at p 1 p 3 or p 6 p 7 zero if you want big endian format exponent first at p The PY_BIG_ENDIAN constant can be used to use the native endian it is equal to 1 on big endian processor or 0 on little endian processor Return value 0 if all is OK 1 if error and an exception is set most likely OverflowError There are two problems on non IEEE platforms What this does is undefined if x is a NaN or infinity 0 0 and 0 0 produce the same bytes string int PyFloat_Pack2 double x unsigned char p int le Pack a C double as the IEEE 754 binary16 half precision format int PyFloat_Pack4 double x unsigned char p int le Pack a C double as the IEEE 754 binary32 single precision format int PyFloat_Pack8 double x unsigned char p int le Pack a C double as the IEEE 754 binary64 double precision format Unpack functions The unpack routine,en
652,s read 2 4 or 8 bytes starting at p le is an int argument non zero if the bytes string is in little endian format exponent last at p 1 p 3 or p 6 and p 7 zero if big endian exponent first at p The PY_BIG_ENDIAN constant can be used to use the native endian it is equal to 1 on big endian processor or 0 on little endian processor Return value The unpacked double On error this is 1 0 and PyErr_Occurred is true and an exception is set most likely OverflowError Note that on a non IEEE platform this will refuse to unpack a bytes string that represents a NaN or infinity double PyFloat_Unpack2 const unsigned char p int le Unpack the IEEE 754 binary16 half precision format as a C double double PyFloat_Unpack4 const unsigned char p int le Unpack the IEEE 754 binary32 single precision format as a C double double PyFloat_Unpack8 const unsigned char p int le Unpack the IEEE 754 binary64 double precision format as a C double,en
653,email encoders Encoders Source code Lib email encoders py This module is part of the legacy Compat32 email API In the new API the functionality is provided by the cte parameter of the set_content method This module is deprecated in Python 3 The functions provided here should not be called explicitly since the MIMEText class sets the content type and CTE header using the _subtype and _charset values passed during the instantiation of that class The remaining text in this section is the original documentation of the module When creating Message objects from scratch you often need to encode the payloads for transport through compliant mail servers This is especially true for image and text type messages containing binary data The email package provides some convenient encoders in its encoders module These encoders are actually used by the MIMEAudio and MIMEImage class constructors to provide default encodings All encoder functions take exactly one argument the message object to encode They usually extract the payload encode it and reset the payload to this newly encoded value They should also set the Content Transfer Encoding header as appropriate Note that these functions are not meaningful for a multipart message They must be applied to individual subparts instead and will raise a TypeError if passed a message whose type is multipart Here are the encoding functions provided email encoders encode_quopri msg Encodes the payload into quoted printable form and sets the Content Transfer Encoding header to quoted printable 1 This is a good encoding to use when most of your payload is normal printable data but contains a few unprintable characters email encoders encode_base64 msg Encodes the payload into base64 form and sets the Content Transfer Encoding header to base64 This is a good encoding to use when most of your payload is unprintable data since it is a more compact form than quoted printable The drawback of base64 encoding is that it renders the text non human readable email encoders encode_7or8bit msg This doesn t actually modify the message s payload but it does set the Content Transfer Encoding header to either 7bit or 8bit as appropriate based on the payload data email encoders encode_noop msg This does nothing it doesn t even set the Content Transfer Encoding header Footnotes 1 Note that encoding with encode_quopri also encodes all tabs and space characters in the data,en
654,sunau Read and write Sun AU files Source code Lib sunau py Deprecated since version 3 11 will be removed in version 3 13 The sunau module is deprecated see PEP 594 for details The sunau module provides a convenient interface to the Sun AU sound format Note that this module is interface compatible with the modules aifc and wave An audio file consists of a header followed by the data The fields of the header are Field Contents magic word The four bytes snd header size Size of the header including info in bytes data size Physical size of the data in bytes encoding Indicates how the audio samples are encoded sample rate The sampling rate of channels The number of channels in the samples info ASCII string giving a description of the audio file padded with null bytes Apart from the info field all header fields are 4 bytes in size They are all 32 bit unsigned integers encoded in big endian byte order The sunau module defines the following functions sunau open file mode If file is a string open the file by that name otherwise treat it as a seekable file like object mode can be any of r Read only mode w Write only mode Note that it does not allow read write files A mode of r returns an AU_read object while a mode of w or wb returns an AU_write object The sunau module defines the following exception exception sunau Error An error raised when something is impossible because of Sun AU specs or implementation deficiency The sunau module defines the following data items sunau AUDIO_FILE_MAGIC An integer every valid Sun AU file begins with stored in big endian form This is the string snd interpreted as an integer sunau AUDIO_FILE_ENCODING_MULAW_8 sunau AUDIO_FILE_ENCODING_LINEAR_8 sunau AUDIO_FILE_ENCODING_LINEAR_16 sunau AUDIO_FILE_ENCODING_LINEAR_24 sunau AUDIO_FILE_ENCODING_LINEAR_32 sunau AUDIO_FILE_ENCODING_ALAW_8 Values of the encoding field from the AU header which are supported by this module sunau AUDIO_FILE_ENCODING_FLOAT sunau AUDIO_FILE_ENCODING_DOUBLE sunau AUDIO_FILE_ENCODING_ADPCM_G721 sunau AUDIO_FILE_ENCODING_ADPCM_G722 sunau AUDIO_FILE_ENCODING_ADPCM_G723_3 sunau AUDIO_FILE_ENCODING_ADPCM_G723_5 Additional known values of the encoding field from the AU header but which are not supported by this module AU_read Objects AU_read objects as returned by open above have the following methods AU_read close Close the stream and make the instance unusable This is called automatically on deletion AU_read getnchannels Returns number of audio channels 1 for mono 2 for stereo AU_read getsampwidth Returns sample width in bytes AU_read getframerate Returns sampling frequency AU_read getnframes Returns number of audio frames AU_read getcomptype Returns compression type Supported compression types are ULAW ALAW and NONE AU_read getcompname Human readable version of getcomptype The supported types have the respective names CCITT G 711 u law CCITT G 711 A law and not compressed AU_read getparams Returns a namedtuple nchannels sampwidth framerate nframes comptype compname equivalent to output of the get methods AU_read readframes n Reads and returns at most n frames of audio as a bytes object The data will be returned in linear format If the original data is in u LAW format it will be converted AU_read rewind Rewind the file pointer to the beginning of the audio stream The following two methods define a term position which is compatible between them and is otherwise implementation dependent AU_read setpos pos Set the file pointer to the specified position Only values returned from tell should be used for pos AU_read tell Return current file pointer position Note that the returned value has nothing to do with the actual position in the file The following two functions are defined for compatibility with the aifc and don t do anything interesting AU_read getmarkers Returns None AU_read getmark id Raise an error AU_write Objects AU_write objects as returned by open above have the following methods AU_write setnchannels n Set the number of channels AU_write setsampwidth n Set the sample width in bytes Changed in version 3 4 Added support for 2,en
655,4 bit samples AU_write setframerate n Set the frame rate AU_write setnframes n Set the number of frames This can be later changed when and if more frames are written AU_write setcomptype type name Set the compression type and description Only NONE and ULAW are supported on output AU_write setparams tuple The tuple should be nchannels sampwidth framerate nframes comptype compname with values valid for the set methods Set all parameters AU_write tell Return current position in the file with the same disclaimer for the AU_read tell and AU_read setpos methods AU_write writeframesraw data Write audio frames without correcting nframes Changed in version 3 4 Any bytes like object is now accepted AU_write writeframes data Write audio frames and make sure nframes is correct Changed in version 3 4 Any bytes like object is now accepted AU_write close Make sure nframes is correct and close the file This method is called upon deletion Note that it is invalid to set any parameters after calling writeframes or writeframesraw,en
656,quopri Encode and decode MIME quoted printable data Source code Lib quopri py This module performs quoted printable transport encoding and decoding as defined in RFC 1521 MIME Multipurpose Internet Mail Extensions Part One Mechanisms for Specifying and Describing the Format of Internet Message Bodies The quoted printable encoding is designed for data where there are relatively few nonprintable characters the base64 encoding scheme available via the base64 module is more compact if there are many such characters as when sending a graphics file quopri decode input output header False Decode the contents of the input file and write the resulting decoded binary data to the output file input and output must be binary file objects If the optional argument header is present and true underscore will be decoded as space This is used to decode Q encoded headers as described in RFC 1522 MIME Multipurpose Internet Mail Extensions Part Two Message Header Extensions for Non ASCII Text quopri encode input output quotetabs header False Encode the contents of the input file and write the resulting quoted printable data to the output file input and output must be binary file objects quotetabs a non optional flag which controls whether to encode embedded spaces and tabs when true it encodes such embedded whitespace and when false it leaves them unencoded Note that spaces and tabs appearing at the end of lines are always encoded as per RFC 1521 header is a flag which controls if spaces are encoded as underscores as per RFC 1522 quopri decodestring s header False Like decode except that it accepts a source bytes and returns the corresponding decoded bytes quopri encodestring s quotetabs False header False Like encode except that it accepts a source bytes and returns the corresponding encoded bytes By default it sends a False value to quotetabs parameter of the encode function See also Module base64 Encode and decode MIME base64 data,en
657,atexit Exit handlers The atexit module defines functions to register and unregister cleanup functions Functions thus registered are automatically executed upon normal interpreter termination atexit runs these functions in the reverse order in which they were registered if you register A B and C at interpreter termination time they will be run in the order C B A Note The functions registered via this module are not called when the program is killed by a signal not handled by Python when a Python fatal internal error is detected or when os _exit is called Note The effect of registering or unregistering functions from within a cleanup function is undefined Changed in version 3 7 When used with C API subinterpreters registered functions are local to the interpreter they were registered in atexit register func args kwargs Register func as a function to be executed at termination Any optional arguments that are to be passed to func must be passed as arguments to register It is possible to register the same function and arguments more than once At normal program termination for instance if sys exit is called or the main module s execution completes all functions registered are called in last in first out order The assumption is that lower level modules will normally be imported before higher level modules and thus must be cleaned up later If an exception is raised during execution of the exit handlers a traceback is printed unless SystemExit is raised and the exception information is saved After all exit handlers have had a chance to run the last exception to be raised is re raised This function returns func which makes it possible to use it as a decorator Warning Starting new threads or calling os fork from a registered function can lead to race condition between the main Python runtime thread freeing thread states while internal threading routines or the new process try to use that state This can lead to crashes rather than clean shutdown Changed in version 3 12 Attempts to start a new thread or os fork a new process in a registered function now leads to RuntimeError atexit unregister func Remove func from the list of functions to be run at interpreter shutdown unregister silently does nothing if func was not previously registered If func has been registered more than once every occurrence of that function in the atexit call stack will be removed Equality comparisons are used internally during unregistration so function references do not need to have matching identities See also Module readline Useful example of atexit to read and write readline history files atexit Example The following simple example demonstrates how a module can initialize a counter from a file when it is imported and save the counter s updated value automatically when the program terminates without relying on the application making an explicit call into this module at termination try with open counterfile as infile _count int infile read except FileNotFoundError _count 0 def incrcounter n global _count _count _count n def savecounter with open counterfile w as outfile outfile write d _count import atexit atexit register savecounter Positional and keyword arguments may also be passed to register to be passed along to the registered function when it is called def goodbye name adjective print Goodbye s it was s to meet you name adjective import atexit atexit register goodbye Donny nice or atexit register goodbye adjective nice name Donny Usage as a decorator import atexit atexit register def goodbye print You are now leaving the Python sector This only works with functions that can be called without arguments,en
658,Socket Programming HOWTO Author Gordon McMillan Abstract Sockets are used nearly everywhere but are one of the most severely misunderstood technologies around This is a 10 000 foot overview of sockets It s not really a tutorial you ll still have work to do in getting things operational It doesn t cover the fine points and there are a lot of them but I hope it will give you enough background to begin using them decently Sockets I m only going to talk about INET i e IPv4 sockets but they account for at least 99 of the sockets in use And I ll only talk about STREAM i e TCP sockets unless you really know what you re doing in which case this HOWTO isn t for you you ll get better behavior and performance from a STREAM socket than anything else I will try to clear up the mystery of what a socket is as well as some hints on how to work with blocking and non blocking sockets But I ll start by talking about blocking sockets You ll need to know how they work before dealing with non blocking sockets Part of the trouble with understanding these things is that socket can mean a number of subtly different things depending on context So first let s make a distinction between a client socket an endpoint of a conversation and a server socket which is more like a switchboard operator The client application your browser for example uses client sockets exclusively the web server it s talking to uses both server sockets and client sockets History Of the various forms of IPC Inter Process Communication sockets are by far the most popular On any given platform there are likely to be other forms of IPC that are faster but for cross platform communication sockets are about the only game in town They were invented in Berkeley as part of the BSD flavor of Unix They spread like wildfire with the internet With good reason the combination of sockets with INET makes talking to arbitrary machines around the world unbelievably easy at least compared to other schemes Creating a Socket Roughly speaking when you clicked on the link that brought you to this page your browser did something like the following create an INET STREAMing socket s socket socket socket AF_INET socket SOCK_STREAM now connect to the web server on port 80 the normal http port s connect www python org 80 When the connect completes the socket s can be used to send in a request for the text of the page The same socket will read the reply and then be destroyed That s right destroyed Client sockets are normally only used for one exchange or a small set of sequential exchanges What happens in the web server is a bit more complex First the web server creates a server socket create an INET STREAMing socket serversocket socket socket socket AF_INET socket SOCK_STREAM bind the socket to a public host and a well known port serversocket bind socket gethostname 80 become a server socket serversocket listen 5 A couple things to notice we used socket gethostname so that the socket would be visible to the outside world If we had used s bind localhost 80 or s bind 127 0 0 1 80 we would still have a server socket but one that was only visible within the same machine s bind 80 specifies that the socket is reachable by any address the machine happens to have A second thing to note low number ports are usually reserved for well known services HTTP SNMP etc If you re playing around use a nice high number 4 digits Finally the argument to listen tells the socket library that we want it to queue up as many as 5 connect requests the normal max before refusing outside connections If the rest of the code is written properly that should be plenty Now that we have a server socket listening on port 80 we can enter the mainloop of the web server while True accept connections from outside clientsocket address serversocket accept now do something with the clientsocket in this case we ll pretend this is a threaded server ct client_thread clientsocket ct run There s actually 3 general ways in which this loop could work dispatching a thread to handle clientsocket create a new process to handle clientsocket or restructure ,en
659,this app to use non blocking sockets and multiplex between our server socket and any active clientsocket s using select More about that later The important thing to understand now is this this is all a server socket does It doesn t send any data It doesn t receive any data It just produces client sockets Each clientsocket is created in response to some other client socket doing a connect to the host and port we re bound to As soon as we ve created that clientsocket we go back to listening for more connections The two clients are free to chat it up they are using some dynamically allocated port which will be recycled when the conversation ends IPC If you need fast IPC between two processes on one machine you should look into pipes or shared memory If you do decide to use AF_INET sockets bind the server socket to localhost On most platforms this will take a shortcut around a couple of layers of network code and be quite a bit faster See also The multiprocessing integrates cross platform IPC into a higher level API Using a Socket The first thing to note is that the web browser s client socket and the web server s client socket are identical beasts That is this is a peer to peer conversation Or to put it another way as the designer you will have to decide what the rules of etiquette are for a conversation Normally the connect ing socket starts the conversation by sending in a request or perhaps a signon But that s a design decision it s not a rule of sockets Now there are two sets of verbs to use for communication You can use send and recv or you can transform your client socket into a file like beast and use read and write The latter is the way Java presents its sockets I m not going to talk about it here except to warn you that you need to use flush on sockets These are buffered files and a common mistake is to write something and then read for a reply Without a flush in there you may wait forever for the reply because the request may still be in your output buffer Now we come to the major stumbling block of sockets send and recv operate on the network buffers They do not necessarily handle all the bytes you hand them or expect from them because their major focus is handling the network buffers In general they return when the associated network buffers have been filled send or emptied recv They then tell you how many bytes they handled It is your responsibility to call them again until your message has been completely dealt with When a recv returns 0 bytes it means the other side has closed or is in the process of closing the connection You will not receive any more data on this connection Ever You may be able to send data successfully I ll talk more about this later A protocol like HTTP uses a socket for only one transfer The client sends a request then reads a reply That s it The socket is discarded This means that a client can detect the end of the reply by receiving 0 bytes But if you plan to reuse your socket for further transfers you need to realize that there is no EOT End of Transfer on a socket I repeat if a socket send or recv returns after handling 0 bytes the connection has been broken If the connection has not been broken you may wait on a recv forever because the socket will not tell you that there s nothing more to read for now Now if you think about that a bit you ll come to realize a fundamental truth of sockets messages must either be fixed length yuck or be delimited shrug or indicate how long they are much better or end by shutting down the connection The choice is entirely yours but some ways are righter than others Assuming you don t want to end the connection the simplest solution is a fixed length message class MySocket demonstration class only coded for clarity not efficiency def __init__ self sock None if sock is None self sock socket socket socket AF_INET socket SOCK_STREAM else self sock sock def connect self host port self sock connect host port def mysend self msg totalsent 0 while totalsent MSGLEN sent self sock send msg totalsent if sent 0 raise RuntimeError socket connection broken totalsen,en
660,t totalsent sent def myreceive self chunks bytes_recd 0 while bytes_recd MSGLEN chunk self sock recv min MSGLEN bytes_recd 2048 if chunk b raise RuntimeError socket connection broken chunks append chunk bytes_recd bytes_recd len chunk return b join chunks The sending code here is usable for almost any messaging scheme in Python you send strings and you can use len to determine its length even if it has embedded 0 characters It s mostly the receiving code that gets more complex And in C it s not much worse except you can t use strlen if the message has embedded 0 s The easiest enhancement is to make the first character of the message an indicator of message type and have the type determine the length Now you have two recv s the first to get at least that first character so you can look up the length and the second in a loop to get the rest If you decide to go the delimited route you ll be receiving in some arbitrary chunk size 4096 or 8192 is frequently a good match for network buffer sizes and scanning what you ve received for a delimiter One complication to be aware of if your conversational protocol allows multiple messages to be sent back to back without some kind of reply and you pass recv an arbitrary chunk size you may end up reading the start of a following message You ll need to put that aside and hold onto it until it s needed Prefixing the message with its length say as 5 numeric characters gets more complex because believe it or not you may not get all 5 characters in one recv In playing around you ll get away with it but in high network loads your code will very quickly break unless you use two recv loops the first to determine the length the second to get the data part of the message Nasty This is also when you ll discover that send does not always manage to get rid of everything in one pass And despite having read this you will eventually get bit by it In the interests of space building your character and preserving my competitive position these enhancements are left as an exercise for the reader Lets move on to cleaning up Binary Data It is perfectly possible to send binary data over a socket The major problem is that not all machines use the same formats for binary data For example network byte order is big endian with the most significant byte first so a 16 bit integer with the value 1 would be the two hex bytes 00 01 However most common processors x86 AMD64 ARM RISC V are little endian with the least significant byte first that same 1 would be 01 00 Socket libraries have calls for converting 16 and 32 bit integers ntohl htonl ntohs htons where n means network and h means host s means short and l means long Where network order is host order these do nothing but where the machine is byte reversed these swap the bytes around appropriately In these days of 64 bit machines the ASCII representation of binary data is frequently smaller than the binary representation That s because a surprising amount of the time most integers have the value 0 or maybe 1 The string 0 would be two bytes while a full 64 bit integer would be 8 Of course this doesn t fit well with fixed length messages Decisions decisions Disconnecting Strictly speaking you re supposed to use shutdown on a socket before you close it The shutdown is an advisory to the socket at the other end Depending on the argument you pass it it can mean I m not going to send anymore but I ll still listen or I m not listening good riddance Most socket libraries however are so used to programmers neglecting to use this piece of etiquette that normally a close is the same as shutdown close So in most situations an explicit shutdown is not needed One way to use shutdown effectively is in an HTTP like exchange The client sends a request and then does a shutdown 1 This tells the server This client is done sending but can still receive The server can detect EOF by a receive of 0 bytes It can assume it has the complete request The server sends a reply If the send completes successfully then indeed the client was still receiving Python takes the automatic shutdown a step,en
661, further and says that when a socket is garbage collected it will automatically do a close if it s needed But relying on this is a very bad habit If your socket just disappears without doing a close the socket at the other end may hang indefinitely thinking you re just being slow Please close your sockets when you re done When Sockets Die Probably the worst thing about using blocking sockets is what happens when the other side comes down hard without doing a close Your socket is likely to hang TCP is a reliable protocol and it will wait a long long time before giving up on a connection If you re using threads the entire thread is essentially dead There s not much you can do about it As long as you aren t doing something dumb like holding a lock while doing a blocking read the thread isn t really consuming much in the way of resources Do not try to kill the thread part of the reason that threads are more efficient than processes is that they avoid the overhead associated with the automatic recycling of resources In other words if you do manage to kill the thread your whole process is likely to be screwed up Non blocking Sockets If you ve understood the preceding you already know most of what you need to know about the mechanics of using sockets You ll still use the same calls in much the same ways It s just that if you do it right your app will be almost inside out In Python you use socket setblocking False to make it non blocking In C it s more complex for one thing you ll need to choose between the BSD flavor O_NONBLOCK and the almost indistinguishable POSIX flavor O_NDELAY which is completely different from TCP_NODELAY but it s the exact same idea You do this after creating the socket but before using it Actually if you re nuts you can switch back and forth The major mechanical difference is that send recv connect and accept can return without having done anything You have of course a number of choices You can check return code and error codes and generally drive yourself crazy If you don t believe me try it sometime Your app will grow large buggy and suck CPU So let s skip the brain dead solutions and do it right Use select In C coding select is fairly complex In Python it s a piece of cake but it s close enough to the C version that if you understand select in Python you ll have little trouble with it in C ready_to_read ready_to_write in_error select select potential_readers potential_writers potential_errs timeout You pass select three lists the first contains all sockets that you might want to try reading the second all the sockets you might want to try writing to and the last normally left empty those that you want to check for errors You should note that a socket can go into more than one list The select call is blocking but you can give it a timeout This is generally a sensible thing to do give it a nice long timeout say a minute unless you have good reason to do otherwise In return you will get three lists They contain the sockets that are actually readable writable and in error Each of these lists is a subset possibly empty of the corresponding list you passed in If a socket is in the output readable list you can be as close to certain as we ever get in this business that a recv on that socket will return something Same idea for the writable list You ll be able to send something Maybe not all you want to but something is better than nothing Actually any reasonably healthy socket will return as writable it just means outbound network buffer space is available If you have a server socket put it in the potential_readers list If it comes out in the readable list your accept will almost certainly work If you have created a new socket to connect to someone else put it in the potential_writers list If it shows up in the writable list you have a decent chance that it has connected Actually select can be handy even with blocking sockets It s one way of determining whether you will block the socket returns as readable when there s something in the buffers However this still doesn t help with the problem of determining w,en
662,hether the other end is done or just busy with something else Portability alert On Unix select works both with the sockets and files Don t try this on Windows On Windows select works with sockets only Also note that in C many of the more advanced socket options are done differently on Windows In fact on Windows I usually use threads which work very very well with my sockets,en
663,pty Pseudo terminal utilities Source code Lib pty py The pty module defines operations for handling the pseudo terminal concept starting another process and being able to write to and read from its controlling terminal programmatically Availability Unix Pseudo terminal handling is highly platform dependent This code is mainly tested on Linux FreeBSD and macOS it is supposed to work on other POSIX platforms but it s not been thoroughly tested The pty module defines the following functions pty fork Fork Connect the child s controlling terminal to a pseudo terminal Return value is pid fd Note that the child gets pid 0 and the fd is invalid The parent s return value is the pid of the child and fd is a file descriptor connected to the child s controlling terminal and also to the child s standard input and output Warning On macOS the use of this function is unsafe when mixed with using higher level system APIs and that includes using urllib request pty openpty Open a new pseudo terminal pair using os openpty if possible or emulation code for generic Unix systems Return a pair of file descriptors master slave for the master and the slave end respectively pty spawn argv master_read stdin_read Spawn a process and connect its controlling terminal with the current process s standard io This is often used to baffle programs which insist on reading from the controlling terminal It is expected that the process spawned behind the pty will eventually terminate and when it does spawn will return A loop copies STDIN of the current process to the child and data received from the child to STDOUT of the current process It is not signaled to the child if STDIN of the current process closes down The functions master_read and stdin_read are passed a file descriptor which they should read from and they should always return a byte string In order to force spawn to return before the child process exits an empty byte array should be returned to signal end of file The default implementation for both functions will read and return up to 1024 bytes each time the function is called The master_read callback is passed the pseudoterminal s master file descriptor to read output from the child process and stdin_read is passed file descriptor 0 to read from the parent process s standard input Returning an empty byte string from either callback is interpreted as an end of file EOF condition and that callback will not be called after that If stdin_read signals EOF the controlling terminal can no longer communicate with the parent process OR the child process Unless the child process will quit without any input spawn will then loop forever If master_read signals EOF the same behavior results on linux at least Return the exit status value from os waitpid on the child process os waitstatus_to_exitcode can be used to convert the exit status into an exit code Raises an auditing event pty spawn with argument argv Changed in version 3 4 spawn now returns the status value from os waitpid on the child process Example The following program acts like the Unix command script 1 using a pseudo terminal to record all input and output of a terminal session in a typescript import argparse import os import pty import sys import time parser argparse ArgumentParser parser add_argument a dest append action store_true parser add_argument p dest use_python action store_true parser add_argument filename nargs default typescript options parser parse_args shell sys executable if options use_python else os environ get SHELL sh filename options filename mode ab if options append else wb with open filename mode as script def read fd data os read fd 1024 script write data return data print Script started file is filename script write Script started on s n time asctime encode pty spawn shell read script write Script done on s n time asctime encode print Script done file is filename,en
664,types Dynamic type creation and names for built in types Source code Lib types py This module defines utility functions to assist in dynamic creation of new types It also defines names for some object types that are used by the standard Python interpreter but not exposed as builtins like int or str are Finally it provides some additional type related utility classes and functions that are not fundamental enough to be builtins Dynamic Type Creation types new_class name bases kwds None exec_body None Creates a class object dynamically using the appropriate metaclass The first three arguments are the components that make up a class definition header the class name the base classes in order the keyword arguments such as metaclass The exec_body argument is a callback that is used to populate the freshly created class namespace It should accept the class namespace as its sole argument and update the namespace directly with the class contents If no callback is provided it has the same effect as passing in lambda ns None New in version 3 3 types prepare_class name bases kwds None Calculates the appropriate metaclass and creates the class namespace The arguments are the components that make up a class definition header the class name the base classes in order and the keyword arguments such as metaclass The return value is a 3 tuple metaclass namespace kwds metaclass is the appropriate metaclass namespace is the prepared class namespace and kwds is an updated copy of the passed in kwds argument with any metaclass entry removed If no kwds argument is passed in this will be an empty dict New in version 3 3 Changed in version 3 6 The default value for the namespace element of the returned tuple has changed Now an insertion order preserving mapping is used when the metaclass does not have a __prepare__ method See also Metaclasses Full details of the class creation process supported by these functions PEP 3115 Metaclasses in Python 3000 Introduced the __prepare__ namespace hook types resolve_bases bases Resolve MRO entries dynamically as specified by PEP 560 This function looks for items in bases that are not instances of type and returns a tuple where each such object that has an __mro_entries__ method is replaced with an unpacked result of calling this method If a bases item is an instance of type or it doesn t have an __mro_entries__ method then it is included in the return tuple unchanged New in version 3 7 types get_original_bases cls Return the tuple of objects originally given as the bases of cls before the __mro_entries__ method has been called on any bases following the mechanisms laid out in PEP 560 This is useful for introspecting Generics For classes that have an __orig_bases__ attribute this function returns the value of cls __orig_bases__ For classes without the __orig_bases__ attribute cls __bases__ is returned Examples from typing import TypeVar Generic NamedTuple TypedDict T TypeVar T class Foo Generic T class Bar Foo int float class Baz list str Eggs NamedTuple Eggs a int b str Spam TypedDict Spam a int b str assert Bar __bases__ Foo float assert get_original_bases Bar Foo int float assert Baz __bases__ list assert get_original_bases Baz list str assert Eggs __bases__ tuple assert get_original_bases Eggs NamedTuple assert Spam __bases__ dict assert get_original_bases Spam TypedDict assert int __bases__ object assert get_original_bases int object New in version 3 12 See also PEP 560 Core support for typing module and generic types Standard Interpreter Types This module provides names for many of the types that are required to implement a Python interpreter It deliberately avoids including some of the types that arise only incidentally during processing such as the listiterator type Typical use of these names is for isinstance or issubclass checks If you instantiate any of these types note that signatures may vary between Python versions Standard names are defined for the following types types NoneType The type of None New in version 3 10 types FunctionType types LambdaType The type of user defined functions and functio,en
665,ns created by lambda expressions Raises an auditing event function __new__ with argument code The audit event only occurs for direct instantiation of function objects and is not raised for normal compilation types GeneratorType The type of generator iterator objects created by generator functions types CoroutineType The type of coroutine objects created by async def functions New in version 3 5 types AsyncGeneratorType The type of asynchronous generator iterator objects created by asynchronous generator functions New in version 3 6 class types CodeType kwargs The type of code objects such as returned by compile Raises an auditing event code __new__ with arguments code filename name argcount posonlyargcount kwonlyargcount nlocals stacksize flags Note that the audited arguments may not match the names or positions required by the initializer The audit event only occurs for direct instantiation of code objects and is not raised for normal compilation types CellType The type for cell objects such objects are used as containers for a function s free variables New in version 3 8 types MethodType The type of methods of user defined class instances types BuiltinFunctionType types BuiltinMethodType The type of built in functions like len or sys exit and methods of built in classes Here the term built in means written in C types WrapperDescriptorType The type of methods of some built in data types and base classes such as object __init__ or object __lt__ New in version 3 7 types MethodWrapperType The type of bound methods of some built in data types and base classes For example it is the type of object __str__ New in version 3 7 types NotImplementedType The type of NotImplemented New in version 3 10 types MethodDescriptorType The type of methods of some built in data types such as str join New in version 3 7 types ClassMethodDescriptorType The type of unbound class methods of some built in data types such as dict __dict__ fromkeys New in version 3 7 class types ModuleType name doc None The type of modules The constructor takes the name of the module to be created and optionally its docstring Note Use importlib util module_from_spec to create a new module if you wish to set the various import controlled attributes __doc__ The docstring of the module Defaults to None __loader__ The loader which loaded the module Defaults to None This attribute is to match importlib machinery ModuleSpec loader as stored in the __spec__ object Note A future version of Python may stop setting this attribute by default To guard against this potential change preferably read from the __spec__ attribute instead or use getattr module __loader__ None if you explicitly need to use this attribute Changed in version 3 4 Defaults to None Previously the attribute was optional __name__ The name of the module Expected to match importlib machinery ModuleSpec name __package__ Which package a module belongs to If the module is top level i e not a part of any specific package then the attribute should be set to else it should be set to the name of the package which can be __name__ if the module is a package itself Defaults to None This attribute is to match importlib machinery ModuleSpec parent as stored in the __spec__ object Note A future version of Python may stop setting this attribute by default To guard against this potential change preferably read from the __spec__ attribute instead or use getattr module __package__ None if you explicitly need to use this attribute Changed in version 3 4 Defaults to None Previously the attribute was optional __spec__ A record of the module s import system related state Expected to be an instance of importlib machinery ModuleSpec New in version 3 4 types EllipsisType The type of Ellipsis New in version 3 10 class types GenericAlias t_origin t_args The type of parameterized generics such as list int t_origin should be a non parameterized generic class such as list tuple or dict t_args should be a tuple possibly of length 1 of types which parameterize t_origin from types import GenericAlias list int GenericAlias list int True dict ,en
666,str int GenericAlias dict str int True New in version 3 9 Changed in version 3 9 2 This type can now be subclassed See also Generic Alias Types In depth documentation on instances of types GenericAlias PEP 585 Type Hinting Generics In Standard Collections Introducing the types GenericAlias class class types UnionType The type of union type expressions New in version 3 10 class types TracebackType tb_next tb_frame tb_lasti tb_lineno The type of traceback objects such as found in sys exception __traceback__ See the language reference for details of the available attributes and operations and guidance on creating tracebacks dynamically types FrameType The type of frame objects such as found in tb tb_frame if tb is a traceback object types GetSetDescriptorType The type of objects defined in extension modules with PyGetSetDef such as FrameType f_locals or array array typecode This type is used as descriptor for object attributes it has the same purpose as the property type but for classes defined in extension modules types MemberDescriptorType The type of objects defined in extension modules with PyMemberDef such as datetime timedelta days This type is used as descriptor for simple C data members which use standard conversion functions it has the same purpose as the property type but for classes defined in extension modules In addition when a class is defined with a __slots__ attribute then for each slot an instance of MemberDescriptorType will be added as an attribute on the class This allows the slot to appear in the class s __dict__ CPython implementation detail In other implementations of Python this type may be identical to GetSetDescriptorType class types MappingProxyType mapping Read only proxy of a mapping It provides a dynamic view on the mapping s entries which means that when the mapping changes the view reflects these changes New in version 3 3 Changed in version 3 9 Updated to support the new union operator from PEP 584 which simply delegates to the underlying mapping key in proxy Return True if the underlying mapping has a key key else False proxy key Return the item of the underlying mapping with key key Raises a KeyError if key is not in the underlying mapping iter proxy Return an iterator over the keys of the underlying mapping This is a shortcut for iter proxy keys len proxy Return the number of items in the underlying mapping copy Return a shallow copy of the underlying mapping get key default Return the value for key if key is in the underlying mapping else default If default is not given it defaults to None so that this method never raises a KeyError items Return a new view of the underlying mapping s items key value pairs keys Return a new view of the underlying mapping s keys values Return a new view of the underlying mapping s values reversed proxy Return a reverse iterator over the keys of the underlying mapping New in version 3 9 hash proxy Return a hash of the underlying mapping New in version 3 12 Additional Utility Classes and Functions class types SimpleNamespace A simple object subclass that provides attribute access to its namespace as well as a meaningful repr Unlike object with SimpleNamespace you can add and remove attributes If a SimpleNamespace object is initialized with keyword arguments those are directly added to the underlying namespace The type is roughly equivalent to the following code class SimpleNamespace def __init__ self kwargs self __dict__ update kwargs def __repr__ self items f k v r for k v in self __dict__ items return format type self __name__ join items def __eq__ self other if isinstance self SimpleNamespace and isinstance other SimpleNamespace return self __dict__ other __dict__ return NotImplemented SimpleNamespace may be useful as a replacement for class NS pass However for a structured record type use namedtuple instead New in version 3 3 Changed in version 3 9 Attribute order in the repr changed from alphabetical to insertion like dict types DynamicClassAttribute fget None fset None fdel None doc None Route attribute access on a class to __getattr__ This is a descri,en
667,ptor used to define attributes that act differently when accessed through an instance and through a class Instance access remains normal but access to an attribute through a class will be routed to the class s __getattr__ method this is done by raising AttributeError This allows one to have properties active on an instance and have virtual attributes on the class with the same name see enum Enum for an example New in version 3 4 Coroutine Utility Functions types coroutine gen_func This function transforms a generator function into a coroutine function which returns a generator based coroutine The generator based coroutine is still a generator iterator but is also considered to be a coroutine object and is awaitable However it may not necessarily implement the __await__ method If gen_func is a generator function it will be modified in place If gen_func is not a generator function it will be wrapped If it returns an instance of collections abc Generator the instance will be wrapped in an awaitable proxy object All other types of objects will be returned as is New in version 3 5,en
668,High level API Index This page lists all high level async await enabled asyncio APIs Tasks Utilities to run asyncio programs create Tasks and await on multiple things with timeouts run Create event loop run a coroutine close the loop Runner A context manager that simplifies multiple async function calls Task Task object TaskGroup A context manager that holds a group of tasks Provides a convenient and reliable way to wait for all tasks in the group to finish create_task Start an asyncio Task then returns it current_task Return the current Task all_tasks Return all tasks that are not yet finished for an event loop await sleep Sleep for a number of seconds await gather Schedule and wait for things concurrently await wait_for Run with a timeout await shield Shield from cancellation await wait Monitor for completion timeout Run with a timeout Useful in cases when wait_for is not suitable to_thread Asynchronously run a function in a separate OS thread run_coroutine_threadsafe Schedule a coroutine from another OS thread for in as_completed Monitor for completion with a for loop Examples Using asyncio gather to run things in parallel Using asyncio wait_for to enforce a timeout Cancellation Using asyncio sleep See also the main Tasks documentation page Queues Queues should be used to distribute work amongst multiple asyncio Tasks implement connection pools and pub sub patterns Queue A FIFO queue PriorityQueue A priority queue LifoQueue A LIFO queue Examples Using asyncio Queue to distribute workload between several Tasks See also the Queues documentation page Subprocesses Utilities to spawn subprocesses and run shell commands await create_subprocess_exec Create a subprocess await create_subprocess_shell Run a shell command Examples Executing a shell command See also the subprocess APIs documentation Streams High level APIs to work with network IO await open_connection Establish a TCP connection await open_unix_connection Establish a Unix socket connection await start_server Start a TCP server await start_unix_server Start a Unix socket server StreamReader High level async await object to receive network data StreamWriter High level async await object to send network data Examples Example TCP client See also the streams APIs documentation Synchronization Threading like synchronization primitives that can be used in Tasks Lock A mutex lock Event An event object Condition A condition object Semaphore A semaphore BoundedSemaphore A bounded semaphore Barrier A barrier object Examples Using asyncio Event Using asyncio Barrier See also the documentation of asyncio synchronization primitives Exceptions asyncio CancelledError Raised when a Task is cancelled See also Task cancel asyncio BrokenBarrierError Raised when a Barrier is broken See also Barrier wait Examples Handling CancelledError to run code on cancellation request See also the full list of asyncio specific exceptions,en
669,zipfile Work with ZIP archives Source code Lib zipfile The ZIP file format is a common archive and compression standard This module provides tools to create read write append and list a ZIP file Any advanced use of this module will require an understanding of the format as defined in PKZIP Application Note This module does not currently handle multi disk ZIP files It can handle ZIP files that use the ZIP64 extensions that is ZIP files that are more than 4 GiB in size It supports decryption of encrypted files in ZIP archives but it currently cannot create an encrypted file Decryption is extremely slow as it is implemented in native Python rather than C The module defines the following items exception zipfile BadZipFile The error raised for bad ZIP files New in version 3 2 exception zipfile BadZipfile Alias of BadZipFile for compatibility with older Python versions Deprecated since version 3 2 exception zipfile LargeZipFile The error raised when a ZIP file would require ZIP64 functionality but that has not been enabled class zipfile ZipFile The class for reading and writing ZIP files See section ZipFile Objects for constructor details class zipfile Path Class that implements a subset of the interface provided by pathlib Path including the full importlib resources abc Traversable interface New in version 3 8 class zipfile PyZipFile Class for creating ZIP archives containing Python libraries class zipfile ZipInfo filename NoName date_time 1980 1 1 0 0 0 Class used to represent information about a member of an archive Instances of this class are returned by the getinfo and infolist methods of ZipFile objects Most users of the zipfile module will not need to create these but only use those created by this module filename should be the full name of the archive member and date_time should be a tuple containing six fields which describe the time of the last modification to the file the fields are described in section ZipInfo Objects zipfile is_zipfile filename Returns True if filename is a valid ZIP file based on its magic number otherwise returns False filename may be a file or file like object too Changed in version 3 1 Support for file and file like objects zipfile ZIP_STORED The numeric constant for an uncompressed archive member zipfile ZIP_DEFLATED The numeric constant for the usual ZIP compression method This requires the zlib module zipfile ZIP_BZIP2 The numeric constant for the BZIP2 compression method This requires the bz2 module New in version 3 3 zipfile ZIP_LZMA The numeric constant for the LZMA compression method This requires the lzma module New in version 3 3 Note The ZIP file format specification has included support for bzip2 compression since 2001 and for LZMA compression since 2006 However some tools including older Python releases do not support these compression methods and may either refuse to process the ZIP file altogether or fail to extract individual files See also PKZIP Application Note Documentation on the ZIP file format by Phil Katz the creator of the format and algorithms used Info ZIP Home Page Information about the Info ZIP project s ZIP archive programs and development libraries ZipFile Objects class zipfile ZipFile file mode r compression ZIP_STORED allowZip64 True compresslevel None strict_timestamps True metadata_encoding None Open a ZIP file where file can be a path to a file a string a file like object or a path like object The mode parameter should be r to read an existing file w to truncate and write a new file a to append to an existing file or x to exclusively create and write a new file If mode is x and file refers to an existing file a FileExistsError will be raised If mode is a and file refers to an existing ZIP file then additional files are added to it If file does not refer to a ZIP file then a new ZIP archive is appended to the file This is meant for adding a ZIP archive to another file such as python exe If mode is a and the file does not exist at all it is created If mode is r or a the file should be seekable compression is the ZIP compression method to use when writing the arc,en
670,hive and should be ZIP_STORED ZIP_DEFLATED ZIP_BZIP2 or ZIP_LZMA unrecognized values will cause NotImplementedError to be raised If ZIP_DEFLATED ZIP_BZIP2 or ZIP_LZMA is specified but the corresponding module zlib bz2 or lzma is not available RuntimeError is raised The default is ZIP_STORED If allowZip64 is True the default zipfile will create ZIP files that use the ZIP64 extensions when the zipfile is larger than 4 GiB If it is false zipfile will raise an exception when the ZIP file would require ZIP64 extensions The compresslevel parameter controls the compression level to use when writing files to the archive When using ZIP_STORED or ZIP_LZMA it has no effect When using ZIP_DEFLATED integers 0 through 9 are accepted see zlib for more information When using ZIP_BZIP2 integers 1 through 9 are accepted see bz2 for more information The strict_timestamps argument when set to False allows to zip files older than 1980 01 01 at the cost of setting the timestamp to 1980 01 01 Similar behavior occurs with files newer than 2107 12 31 the timestamp is also set to the limit When mode is r metadata_encoding may be set to the name of a codec which will be used to decode metadata such as the names of members and ZIP comments If the file is created with mode w x or a and then closed without adding any files to the archive the appropriate ZIP structures for an empty archive will be written to the file ZipFile is also a context manager and therefore supports the with statement In the example myzip is closed after the with statement s suite is finished even if an exception occurs with ZipFile spam zip w as myzip myzip write eggs txt Note metadata_encoding is an instance wide setting for the ZipFile It is not currently possible to set this on a per member basis This attribute is a workaround for legacy implementations which produce archives with names in the current locale encoding or code page mostly on Windows According to the ZIP standard the encoding of metadata may be specified to be either IBM code page default or UTF 8 by a flag in the archive header That flag takes precedence over metadata_encoding which is a Python specific extension Changed in version 3 2 Added the ability to use ZipFile as a context manager Changed in version 3 3 Added support for bzip2 and lzma compression Changed in version 3 4 ZIP64 extensions are enabled by default Changed in version 3 5 Added support for writing to unseekable streams Added support for the x mode Changed in version 3 6 Previously a plain RuntimeError was raised for unrecognized compression values Changed in version 3 6 2 The file parameter accepts a path like object Changed in version 3 7 Add the compresslevel parameter Changed in version 3 8 The strict_timestamps keyword only parameter Changed in version 3 11 Added support for specifying member name encoding for reading metadata in the zipfile s directory and file headers ZipFile close Close the archive file You must call close before exiting your program or essential records will not be written ZipFile getinfo name Return a ZipInfo object with information about the archive member name Calling getinfo for a name not currently contained in the archive will raise a KeyError ZipFile infolist Return a list containing a ZipInfo object for each member of the archive The objects are in the same order as their entries in the actual ZIP file on disk if an existing archive was opened ZipFile namelist Return a list of archive members by name ZipFile open name mode r pwd None force_zip64 False Access a member of the archive as a binary file like object name can be either the name of a file within the archive or a ZipInfo object The mode parameter if included must be r the default or w pwd is the password used to decrypt encrypted ZIP files as a bytes object open is also a context manager and therefore supports the with statement with ZipFile spam zip as myzip with myzip open eggs txt as myfile print myfile read With mode r the file like object ZipExtFile is read only and provides the following methods read readline readlines seek tell __iter__ __next_,en
671,_ These objects can operate independently of the ZipFile With mode w a writable file handle is returned which supports the write method While a writable file handle is open attempting to read or write other files in the ZIP file will raise a ValueError When writing a file if the file size is not known in advance but may exceed 2 GiB pass force_zip64 True to ensure that the header format is capable of supporting large files If the file size is known in advance construct a ZipInfo object with file_size set and use that as the name parameter Note The open read and extract methods can take a filename or a ZipInfo object You will appreciate this when trying to read a ZIP file that contains members with duplicate names Changed in version 3 6 Removed support of mode U Use io TextIOWrapper for reading compressed text files in universal newlines mode Changed in version 3 6 ZipFile open can now be used to write files into the archive with the mode w option Changed in version 3 6 Calling open on a closed ZipFile will raise a ValueError Previously a RuntimeError was raised ZipFile extract member path None pwd None Extract a member from the archive to the current working directory member must be its full name or a ZipInfo object Its file information is extracted as accurately as possible path specifies a different directory to extract to member can be a filename or a ZipInfo object pwd is the password used for encrypted files as a bytes object Returns the normalized path created a directory or new file Note If a member filename is an absolute path a drive UNC sharepoint and leading back slashes will be stripped e g foo bar becomes foo bar on Unix and C foo bar becomes foo bar on Windows And all components in a member filename will be removed e g foo ba r becomes foo ba r On Windows illegal characters and replaced by underscore _ Changed in version 3 6 Calling extract on a closed ZipFile will raise a ValueError Previously a RuntimeError was raised Changed in version 3 6 2 The path parameter accepts a path like object ZipFile extractall path None members None pwd None Extract all members from the archive to the current working directory path specifies a different directory to extract to members is optional and must be a subset of the list returned by namelist pwd is the password used for encrypted files as a bytes object Warning Never extract archives from untrusted sources without prior inspection It is possible that files are created outside of path e g members that have absolute filenames starting with or filenames with two dots This module attempts to prevent that See extract note Changed in version 3 6 Calling extractall on a closed ZipFile will raise a ValueError Previously a RuntimeError was raised Changed in version 3 6 2 The path parameter accepts a path like object ZipFile printdir Print a table of contents for the archive to sys stdout ZipFile setpassword pwd Set pwd a bytes object as default password to extract encrypted files ZipFile read name pwd None Return the bytes of the file name in the archive name is the name of the file in the archive or a ZipInfo object The archive must be open for read or append pwd is the password used for encrypted files as a bytes object and if specified overrides the default password set with setpassword Calling read on a ZipFile that uses a compression method other than ZIP_STORED ZIP_DEFLATED ZIP_BZIP2 or ZIP_LZMA will raise a NotImplementedError An error will also be raised if the corresponding compression module is not available Changed in version 3 6 Calling read on a closed ZipFile will raise a ValueError Previously a RuntimeError was raised ZipFile testzip Read all the files in the archive and check their CRC s and file headers Return the name of the first bad file or else return None Changed in version 3 6 Calling testzip on a closed ZipFile will raise a ValueError Previously a RuntimeError was raised ZipFile write filename arcname None compress_type None compresslevel None Write the file named filename to the archive giving it the archive name arcname by default this will be the sam,en
672,e as filename but without a drive letter and with leading path separators removed If given compress_type overrides the value given for the compression parameter to the constructor for the new entry Similarly compresslevel will override the constructor if given The archive must be open with mode w x or a Note The ZIP file standard historically did not specify a metadata encoding but strongly recommended CP437 the original IBM PC encoding for interoperability Recent versions allow use of UTF 8 only In this module UTF 8 will automatically be used to write the member names if they contain any non ASCII characters It is not possible to write member names in any encoding other than ASCII or UTF 8 Note Archive names should be relative to the archive root that is they should not start with a path separator Note If arcname or filename if arcname is not given contains a null byte the name of the file in the archive will be truncated at the null byte Note A leading slash in the filename may lead to the archive being impossible to open in some zip programs on Windows systems Changed in version 3 6 Calling write on a ZipFile created with mode r or a closed ZipFile will raise a ValueError Previously a RuntimeError was raised ZipFile writestr zinfo_or_arcname data compress_type None compresslevel None Write a file into the archive The contents is data which may be either a str or a bytes instance if it is a str it is encoded as UTF 8 first zinfo_or_arcname is either the file name it will be given in the archive or a ZipInfo instance If it s an instance at least the filename date and time must be given If it s a name the date and time is set to the current date and time The archive must be opened with mode w x or a If given compress_type overrides the value given for the compression parameter to the constructor for the new entry or in the zinfo_or_arcname if that is a ZipInfo instance Similarly compresslevel will override the constructor if given Note When passing a ZipInfo instance as the zinfo_or_arcname parameter the compression method used will be that specified in the compress_type member of the given ZipInfo instance By default the ZipInfo constructor sets this member to ZIP_STORED Changed in version 3 2 The compress_type argument Changed in version 3 6 Calling writestr on a ZipFile created with mode r or a closed ZipFile will raise a ValueError Previously a RuntimeError was raised ZipFile mkdir zinfo_or_directory mode 511 Create a directory inside the archive If zinfo_or_directory is a string a directory is created inside the archive with the mode that is specified in the mode argument If however zinfo_or_directory is a ZipInfo instance then the mode argument is ignored The archive must be opened with mode w x or a New in version 3 11 The following data attributes are also available ZipFile filename Name of the ZIP file ZipFile debug The level of debug output to use This may be set from 0 the default no output to 3 the most output Debugging information is written to sys stdout ZipFile comment The comment associated with the ZIP file as a bytes object If assigning a comment to a ZipFile instance created with mode w x or a it should be no longer than 65535 bytes Comments longer than this will be truncated Path Objects class zipfile Path root at Construct a Path object from a root zipfile which may be a ZipFile instance or file suitable for passing to the ZipFile constructor at specifies the location of this Path within the zipfile e g dir file txt dir or Defaults to the empty string indicating the root Path objects expose the following features of pathlib Path objects Path objects are traversable using the operator or joinpath Path name The final path component Path open mode r pwd Invoke ZipFile open on the current path Allows opening for read or write text or binary through supported modes r w rb wb Positional and keyword arguments are passed through to io TextIOWrapper when opened as text and ignored otherwise pwd is the pwd parameter to ZipFile open Changed in version 3 9 Added support for text and binary modes for open Default,en
673, mode is now text Changed in version 3 11 2 The encoding parameter can be supplied as a positional argument without causing a TypeError As it could in 3 9 Code needing to be compatible with unpatched 3 10 and 3 11 versions must pass all io TextIOWrapper arguments encoding included as keywords Path iterdir Enumerate the children of the current directory Path is_dir Return True if the current context references a directory Path is_file Return True if the current context references a file Path exists Return True if the current context references a file or directory in the zip file Path suffix The file extension of the final component New in version 3 11 Added Path suffix property Path stem The final path component without its suffix New in version 3 11 Added Path stem property Path suffixes A list of the path s file extensions New in version 3 11 Added Path suffixes property Path read_text Read the current file as unicode text Positional and keyword arguments are passed through to io TextIOWrapper except buffer which is implied by the context Changed in version 3 11 2 The encoding parameter can be supplied as a positional argument without causing a TypeError As it could in 3 9 Code needing to be compatible with unpatched 3 10 and 3 11 versions must pass all io TextIOWrapper arguments encoding included as keywords Path read_bytes Read the current file as bytes Path joinpath other Return a new Path object with each of the other arguments joined The following are equivalent Path joinpath child joinpath grandchild Path joinpath child grandchild Path child grandchild Changed in version 3 10 Prior to 3 10 joinpath was undocumented and accepted exactly one parameter The zipp project provides backports of the latest path object functionality to older Pythons Use zipp Path in place of zipfile Path for early access to changes PyZipFile Objects The PyZipFile constructor takes the same parameters as the ZipFile constructor and one additional parameter optimize class zipfile PyZipFile file mode r compression ZIP_STORED allowZip64 True optimize 1 Changed in version 3 2 Added the optimize parameter Changed in version 3 4 ZIP64 extensions are enabled by default Instances have one method in addition to those of ZipFile objects writepy pathname basename filterfunc None Search for files py and add the corresponding file to the archive If the optimize parameter to PyZipFile was not given or 1 the corresponding file is a pyc file compiling if necessary If the optimize parameter to PyZipFile was 0 1 or 2 only files with that optimization level see compile are added to the archive compiling if necessary If pathname is a file the filename must end with py and just the corresponding pyc file is added at the top level no path information If pathname is a file that does not end with py a RuntimeError will be raised If it is a directory and the directory is not a package directory then all the files pyc are added at the top level If the directory is a package directory then all pyc are added under the package name as a file path and if any subdirectories are package directories all of these are added recursively in sorted order basename is intended for internal use only filterfunc if given must be a function taking a single string argument It will be passed each path including each individual full file path before it is added to the archive If filterfunc returns a false value the path will not be added and if it is a directory its contents will be ignored For example if our test files are all either in test directories or start with the string test_ we can use a filterfunc to exclude them zf PyZipFile myprog zip def notests s fn os path basename s return not fn test or fn startswith test_ zf writepy myprog filterfunc notests The writepy method makes archives with file names like this string pyc Top level name test __init__ pyc Package directory test testall pyc Module test testall test bogus __init__ pyc Subpackage directory test bogus myfile pyc Submodule test bogus myfile Changed in version 3 4 Added the filterfunc parameter Changed in version 3 6 2,en
674, The pathname parameter accepts a path like object Changed in version 3 7 Recursion sorts directory entries ZipInfo Objects Instances of the ZipInfo class are returned by the getinfo and infolist methods of ZipFile objects Each object stores information about a single member of the ZIP archive There is one classmethod to make a ZipInfo instance for a filesystem file classmethod ZipInfo from_file filename arcname None strict_timestamps True Construct a ZipInfo instance for a file on the filesystem in preparation for adding it to a zip file filename should be the path to a file or directory on the filesystem If arcname is specified it is used as the name within the archive If arcname is not specified the name will be the same as filename but with any drive letter and leading path separators removed The strict_timestamps argument when set to False allows to zip files older than 1980 01 01 at the cost of setting the timestamp to 1980 01 01 Similar behavior occurs with files newer than 2107 12 31 the timestamp is also set to the limit New in version 3 6 Changed in version 3 6 2 The filename parameter accepts a path like object Changed in version 3 8 Added the strict_timestamps keyword only parameter Instances have the following methods and attributes ZipInfo is_dir Return True if this archive member is a directory This uses the entry s name directories should always end with New in version 3 6 ZipInfo filename Name of the file in the archive ZipInfo date_time The time and date of the last modification to the archive member This is a tuple of six values Index Value 0 Year 1980 1 Month one based 2 Day of month one based 3 Hours zero based 4 Minutes zero based 5 Seconds zero based Note The ZIP file format does not support timestamps before 1980 ZipInfo compress_type Type of compression for the archive member ZipInfo comment Comment for the individual archive member as a bytes object ZipInfo extra Expansion field data The PKZIP Application Note contains some comments on the internal structure of the data contained in this bytes object ZipInfo create_system System which created ZIP archive ZipInfo create_version PKZIP version which created ZIP archive ZipInfo extract_version PKZIP version needed to extract archive ZipInfo reserved Must be zero ZipInfo flag_bits ZIP flag bits ZipInfo volume Volume number of file header ZipInfo internal_attr Internal attributes ZipInfo external_attr External file attributes ZipInfo header_offset Byte offset to the file header ZipInfo CRC CRC 32 of the uncompressed file ZipInfo compress_size Size of the compressed data ZipInfo file_size Size of the uncompressed file Command Line Interface The zipfile module provides a simple command line interface to interact with ZIP archives If you want to create a new ZIP archive specify its name after the c option and then list the filename s that should be included python m zipfile c monty zip spam txt eggs txt Passing a directory is also acceptable python m zipfile c monty zip life of brian_1979 If you want to extract a ZIP archive into the specified directory use the e option python m zipfile e monty zip target dir For a list of the files in a ZIP archive use the l option python m zipfile l monty zip Command line options l zipfile list zipfile List files in a zipfile c zipfile source1 sourceN create zipfile source1 sourceN Create zipfile from source files e zipfile output_dir extract zipfile output_dir Extract zipfile into target directory t zipfile test zipfile Test whether the zipfile is valid or not metadata encoding encoding Specify encoding of member names for l e and t New in version 3 11 Decompression pitfalls The extraction in zipfile module might fail due to some pitfalls listed below From file itself Decompression may fail due to incorrect password CRC checksum ZIP format or unsupported compression method decryption File System limitations Exceeding limitations on different file systems can cause decompression failed Such as allowable characters in the directory entries length of the file name length of the pathname size of a single file and number o,en
675,f files etc Resources limitations The lack of memory or disk volume would lead to decompression failed For example decompression bombs aka ZIP bomb apply to zipfile library that can cause disk volume exhaustion Interruption Interruption during the decompression such as pressing control C or killing the decompression process may result in incomplete decompression of the archive Default behaviors of extraction Not knowing the default extraction behaviors can cause unexpected decompression results For example when extracting the same archive twice it overwrites files without asking,en
676,Logging HOWTO Author Vinay Sajip vinay_sajip at red dove dot com This page contains tutorial information For links to reference information and a logging cookbook please see Other resources Basic Logging Tutorial Logging is a means of tracking events that happen when some software runs The software s developer adds logging calls to their code to indicate that certain events have occurred An event is described by a descriptive message which can optionally contain variable data i e data that is potentially different for each occurrence of the event Events also have an importance which the developer ascribes to the event the importance can also be called the level or severity When to use logging You can access logging functionality by creating a logger via logger getLogger __name__ and then calling the logger s debug info warning error and critical methods To determine when to use logging and to see which logger methods to use when see the table below It states for each of a set of common tasks the best tool to use for that task Task you want to perform The best tool for the task Display console output for ordinary print usage of a command line script or program Report events that occur during A logger s info or debug normal operation of a program e g method for very detailed output for for status monitoring or fault diagnostic purposes investigation Issue a warning regarding a warnings warn in library code if particular runtime event the issue is avoidable and the client application should be modified to eliminate the warning A logger s warning method if there is nothing the client application can do about the situation but the event should still be noted Report an error regarding a Raise an exception particular runtime event Report suppression of an error A logger s error exception or without raising an exception e g critical method as appropriate for error handler in a long running the specific error and application server process domain The logger methods are named after the level or severity of the events they are used to track The standard levels and their applicability are described below in increasing order of severity Level When it s used DEBUG Detailed information typically of interest only when diagnosing problems INFO Confirmation that things are working as expected WARNING An indication that something unexpected happened or indicative of some problem in the near future e g disk space low The software is still working as expected ERROR Due to a more serious problem the software has not been able to perform some function CRITICAL A serious error indicating that the program itself may be unable to continue running The default level is WARNING which means that only events of this level and above will be tracked unless the logging package is configured to do otherwise Events that are tracked can be handled in different ways The simplest way of handling tracked events is to print them to the console Another common way is to write them to a disk file A simple example A very simple example is import logging logging warning Watch out will print a message to the console logging info I told you so will not print anything If you type these lines into a script and run it you ll see WARNING root Watch out printed out on the console The INFO message doesn t appear because the default level is WARNING The printed message includes the indication of the level and the description of the event provided in the logging call i e Watch out The actual output can be formatted quite flexibly if you need that formatting options will also be explained later Notice that in this example we use functions directly on the logging module like logging debug rather than creating a logger and calling functions on it These functions operation on the root logger but can be useful as they will call basicConfig for you if it has not been called yet like in this example In larger programs you ll usually want to control the logging configuration explicitly however so for that reason as well as others it s better to create loggers and call their methods L,en
677,ogging to a file A very common situation is that of recording logging events in a file so let s look at that next Be sure to try the following in a newly started Python interpreter and don t just continue from the session described above import logging logger logging getLogger __name__ logging basicConfig filename example log encoding utf 8 level logging DEBUG logger debug This message should go to the log file logger info So should this logger warning And this too logger error And non ASCII stuff too like Øresund and Malmö Changed in version 3 9 The encoding argument was added In earlier Python versions or if not specified the encoding used is the default value used by open While not shown in the above example an errors argument can also now be passed which determines how encoding errors are handled For available values and the default see the documentation for open And now if we open the file and look at what we have we should find the log messages DEBUG __main__ This message should go to the log file INFO __main__ So should this WARNING __main__ And this too ERROR __main__ And non ASCII stuff too like Øresund and Malmö This example also shows how you can set the logging level which acts as the threshold for tracking In this case because we set the threshold to DEBUG all of the messages were printed If you want to set the logging level from a command line option such as log INFO and you have the value of the parameter passed for log in some variable loglevel you can use getattr logging loglevel upper to get the value which you ll pass to basicConfig via the level argument You may want to error check any user input value perhaps as in the following example assuming loglevel is bound to the string value obtained from the command line argument Convert to upper case to allow the user to specify log DEBUG or log debug numeric_level getattr logging loglevel upper None if not isinstance numeric_level int raise ValueError Invalid log level s loglevel logging basicConfig level numeric_level The call to basicConfig should come before any calls to a logger s methods such as debug info etc Otherwise that logging event may not be handled in the desired manner If you run the above script several times the messages from successive runs are appended to the file example log If you want each run to start afresh not remembering the messages from earlier runs you can specify the filemode argument by changing the call in the above example to logging basicConfig filename example log filemode w level logging DEBUG The output will be the same as before but the log file is no longer appended to so the messages from earlier runs are lost Logging variable data To log variable data use a format string for the event description message and append the variable data as arguments For example import logging logging warning s before you s Look leap will display WARNING root Look before you leap As you can see merging of variable data into the event description message uses the old style of string formatting This is for backwards compatibility the logging package pre dates newer formatting options such as str format and string Template These newer formatting options are supported but exploring them is outside the scope of this tutorial see Using particular formatting styles throughout your application for more information Changing the format of displayed messages To change the format which is used to display messages you need to specify the format you want to use import logging logging basicConfig format levelname s message s level logging DEBUG logging debug This message should appear on the console logging info So should this logging warning And this too which would print DEBUG This message should appear on the console INFO So should this WARNING And this too Notice that the root which appeared in earlier examples has disappeared For a full set of things that can appear in format strings you can refer to the documentation for LogRecord attributes but for simple usage you just need the levelname severity message event description including variable dat,en
678,a and perhaps to display when the event occurred This is described in the next section Displaying the date time in messages To display the date and time of an event you would place asctime s in your format string import logging logging basicConfig format asctime s message s logging warning is when this event was logged which should print something like this 2010 12 12 11 41 42 612 is when this event was logged The default format for date time display shown above is like ISO8601 or RFC 3339 If you need more control over the formatting of the date time provide a datefmt argument to basicConfig as in this example import logging logging basicConfig format asctime s message s datefmt m d Y I M S p logging warning is when this event was logged which would display something like this 12 12 2010 11 46 36 AM is when this event was logged The format of the datefmt argument is the same as supported by time strftime Next Steps That concludes the basic tutorial It should be enough to get you up and running with logging There s a lot more that the logging package offers but to get the best out of it you ll need to invest a little more of your time in reading the following sections If you re ready for that grab some of your favourite beverage and carry on If your logging needs are simple then use the above examples to incorporate logging into your own scripts and if you run into problems or don t understand something please post a question on the comp lang python Usenet group available at https groups google com g comp lang python and you should receive help before too long Still here You can carry on reading the next few sections which provide a slightly more advanced in depth tutorial than the basic one above After that you can take a look at the Logging Cookbook Advanced Logging Tutorial The logging library takes a modular approach and offers several categories of components loggers handlers filters and formatters Loggers expose the interface that application code directly uses Handlers send the log records created by loggers to the appropriate destination Filters provide a finer grained facility for determining which log records to output Formatters specify the layout of log records in the final output Log event information is passed between loggers handlers filters and formatters in a LogRecord instance Logging is performed by calling methods on instances of the Logger class hereafter called loggers Each instance has a name and they are conceptually arranged in a namespace hierarchy using dots periods as separators For example a logger named scan is the parent of loggers scan text scan html and scan pdf Logger names can be anything you want and indicate the area of an application in which a logged message originates A good convention to use when naming loggers is to use a module level logger in each module which uses logging named as follows logger logging getLogger __name__ This means that logger names track the package module hierarchy and it s intuitively obvious where events are logged just from the logger name The root of the hierarchy of loggers is called the root logger That s the logger used by the functions debug info warning error and critical which just call the same named method of the root logger The functions and the methods have the same signatures The root logger s name is printed as root in the logged output It is of course possible to log messages to different destinations Support is included in the package for writing log messages to files HTTP GET POST locations email via SMTP generic sockets queues or OS specific logging mechanisms such as syslog or the Windows NT event log Destinations are served by handler classes You can create your own log destination class if you have special requirements not met by any of the built in handler classes By default no destination is set for any logging messages You can specify a destination such as console or file by using basicConfig as in the tutorial examples If you call the functions debug info warning error and critical they will check to see if no destination is set an,en
679,d if one is not set they will set a destination of the console sys stderr and a default format for the displayed message before delegating to the root logger to do the actual message output The default format set by basicConfig for messages is severity logger name message You can change this by passing a format string to basicConfig with the format keyword argument For all options regarding how a format string is constructed see Formatter Objects Logging Flow The flow of log event information in loggers and handlers is illustrated in the following diagram image Loggers Logger objects have a threefold job First they expose several methods to application code so that applications can log messages at runtime Second logger objects determine which log messages to act upon based upon severity the default filtering facility or filter objects Third logger objects pass along relevant log messages to all interested log handlers The most widely used methods on logger objects fall into two categories configuration and message sending These are the most common configuration methods Logger setLevel specifies the lowest severity log message a logger will handle where debug is the lowest built in severity level and critical is the highest built in severity For example if the severity level is INFO the logger will handle only INFO WARNING ERROR and CRITICAL messages and will ignore DEBUG messages Logger addHandler and Logger removeHandler add and remove handler objects from the logger object Handlers are covered in more detail in Handlers Logger addFilter and Logger removeFilter add and remove filter objects from the logger object Filters are covered in more detail in Filter Objects You don t need to always call these methods on every logger you create See the last two paragraphs in this section With the logger object configured the following methods create log messages Logger debug Logger info Logger warning Logger error and Logger critical all create log records with a message and a level that corresponds to their respective method names The message is actually a format string which may contain the standard string substitution syntax of s d f and so on The rest of their arguments is a list of objects that correspond with the substitution fields in the message With regard to kwargs the logging methods care only about a keyword of exc_info and use it to determine whether to log exception information Logger exception creates a log message similar to Logger error The difference is that Logger exception dumps a stack trace along with it Call this method only from an exception handler Logger log takes a log level as an explicit argument This is a little more verbose for logging messages than using the log level convenience methods listed above but this is how to log at custom log levels getLogger returns a reference to a logger instance with the specified name if it is provided or root if not The names are period separated hierarchical structures Multiple calls to getLogger with the same name will return a reference to the same logger object Loggers that are further down in the hierarchical list are children of loggers higher up in the list For example given a logger with a name of foo loggers with names of foo bar foo bar baz and foo bam are all descendants of foo Loggers have a concept of effective level If a level is not explicitly set on a logger the level of its parent is used instead as its effective level If the parent has no explicit level set its parent is examined and so on all ancestors are searched until an explicitly set level is found The root logger always has an explicit level set WARNING by default When deciding whether to process an event the effective level of the logger is used to determine whether the event is passed to the logger s handlers Child loggers propagate messages up to the handlers associated with their ancestor loggers Because of this it is unnecessary to define and configure handlers for all the loggers an application uses It is sufficient to configure handlers for a top level logger and create child loggers,en
680, as needed You can however turn off propagation by setting the propagate attribute of a logger to False Handlers Handler objects are responsible for dispatching the appropriate log messages based on the log messages severity to the handler s specified destination Logger objects can add zero or more handler objects to themselves with an addHandler method As an example scenario an application may want to send all log messages to a log file all log messages of error or higher to stdout and all messages of critical to an email address This scenario requires three individual handlers where each handler is responsible for sending messages of a specific severity to a specific location The standard library includes quite a few handler types see Useful Handlers the tutorials use mainly StreamHandler and FileHandler in its examples There are very few methods in a handler for application developers to concern themselves with The only handler methods that seem relevant for application developers who are using the built in handler objects that is not creating custom handlers are the following configuration methods The setLevel method just as in logger objects specifies the lowest severity that will be dispatched to the appropriate destination Why are there two setLevel methods The level set in the logger determines which severity of messages it will pass to its handlers The level set in each handler determines which messages that handler will send on setFormatter selects a Formatter object for this handler to use addFilter and removeFilter respectively configure and deconfigure filter objects on handlers Application code should not directly instantiate and use instances of Handler Instead the Handler class is a base class that defines the interface that all handlers should have and establishes some default behavior that child classes can use or override Formatters Formatter objects configure the final order structure and contents of the log message Unlike the base logging Handler class application code may instantiate formatter classes although you could likely subclass the formatter if your application needs special behavior The constructor takes three optional arguments a message format string a date format string and a style indicator logging Formatter __init__ fmt None datefmt None style If there is no message format string the default is to use the raw message If there is no date format string the default date format is Y m d H M S with the milliseconds tacked on at the end The style is one of or If one of these is not specified then will be used If the style is the message format string uses dictionary key s styled string substitution the possible keys are documented in LogRecord attributes If the style is the message format string is assumed to be compatible with str format using keyword arguments while if the style is then the message format string should conform to what is expected by string Template substitute Changed in version 3 2 Added the style parameter The following message format string will log the time in a human readable format the severity of the message and the contents of the message in that order asctime s levelname s message s Formatters use a user configurable function to convert the creation time of a record to a tuple By default time localtime is used to change this for a particular formatter instance set the converter attribute of the instance to a function with the same signature as time localtime or time gmtime To change it for all formatters for example if you want all logging times to be shown in GMT set the converter attribute in the Formatter class to time gmtime for GMT display Configuring Logging Programmers can configure logging in three ways 1 Creating loggers handlers and formatters explicitly using Python code that calls the configuration methods listed above 2 Creating a logging config file and reading it using the fileConfig function 3 Creating a dictionary of configuration information and passing it to the dictConfig function For the reference documentation on the last two options see Confi,en
681,guration functions The following example configures a very simple logger a console handler and a simple formatter using Python code import logging create logger logger logging getLogger simple_example logger setLevel logging DEBUG create console handler and set level to debug ch logging StreamHandler ch setLevel logging DEBUG create formatter formatter logging Formatter asctime s name s levelname s message s add formatter to ch ch setFormatter formatter add ch to logger logger addHandler ch application code logger debug debug message logger info info message logger warning warn message logger error error message logger critical critical message Running this module from the command line produces the following output python simple_logging_module py 2005 03 19 15 10 26 618 simple_example DEBUG debug message 2005 03 19 15 10 26 620 simple_example INFO info message 2005 03 19 15 10 26 695 simple_example WARNING warn message 2005 03 19 15 10 26 697 simple_example ERROR error message 2005 03 19 15 10 26 773 simple_example CRITICAL critical message The following Python module creates a logger handler and formatter nearly identical to those in the example listed above with the only difference being the names of the objects import logging import logging config logging config fileConfig logging conf create logger logger logging getLogger simpleExample application code logger debug debug message logger info info message logger warning warn message logger error error message logger critical critical message Here is the logging conf file loggers keys root simpleExample handlers keys consoleHandler formatters keys simpleFormatter logger_root level DEBUG handlers consoleHandler logger_simpleExample level DEBUG handlers consoleHandler qualname simpleExample propagate 0 handler_consoleHandler class StreamHandler level DEBUG formatter simpleFormatter args sys stdout formatter_simpleFormatter format asctime s name s levelname s message s The output is nearly identical to that of the non config file based example python simple_logging_config py 2005 03 19 15 38 55 977 simpleExample DEBUG debug message 2005 03 19 15 38 55 979 simpleExample INFO info message 2005 03 19 15 38 56 054 simpleExample WARNING warn message 2005 03 19 15 38 56 055 simpleExample ERROR error message 2005 03 19 15 38 56 130 simpleExample CRITICAL critical message You can see that the config file approach has a few advantages over the Python code approach mainly separation of configuration and code and the ability of noncoders to easily modify the logging properties Warning The fileConfig function takes a default parameter disable_existing_loggers which defaults to True for reasons of backward compatibility This may or may not be what you want since it will cause any non root loggers existing before the fileConfig call to be disabled unless they or an ancestor are explicitly named in the configuration Please refer to the reference documentation for more information and specify False for this parameter if you wish The dictionary passed to dictConfig can also specify a Boolean value with key disable_existing_loggers which if not specified explicitly in the dictionary also defaults to being interpreted as True This leads to the logger disabling behaviour described above which may not be what you want in which case provide the key explicitly with a value of False Note that the class names referenced in config files need to be either relative to the logging module or absolute values which can be resolved using normal import mechanisms Thus you could use either WatchedFileHandler relative to the logging module or mypackage mymodule MyHandler for a class defined in package mypackage and module mymodule where mypackage is available on the Python import path In Python 3 2 a new means of configuring logging has been introduced using dictionaries to hold configuration information This provides a superset of the functionality of the config file based approach outlined above and is the recommended configuration method for new applications and deployments Because a Python dictionary is,en
682, used to hold configuration information and since you can populate that dictionary using different means you have more options for configuration For example you can use a configuration file in JSON format or if you have access to YAML processing functionality a file in YAML format to populate the configuration dictionary Or of course you can construct the dictionary in Python code receive it in pickled form over a socket or use whatever approach makes sense for your application Here s an example of the same configuration as above in YAML format for the new dictionary based approach version 1 formatters simple format asctime s name s levelname s message s handlers console class logging StreamHandler level DEBUG formatter simple stream ext sys stdout loggers simpleExample level DEBUG handlers console propagate no root level DEBUG handlers console For more information about logging using a dictionary see Configuration functions What happens if no configuration is provided If no logging configuration is provided it is possible to have a situation where a logging event needs to be output but no handlers can be found to output the event The event is output using a handler of last resort stored in lastResort This internal handler is not associated with any logger and acts like a StreamHandler which writes the event description message to the current value of sys stderr therefore respecting any redirections which may be in effect No formatting is done on the message just the bare event description message is printed The handler s level is set to WARNING so all events at this and greater severities will be output Changed in version 3 2 For versions of Python prior to 3 2 the behaviour is as follows If raiseExceptions is False production mode the event is silently dropped If raiseExceptions is True development mode a message No handlers could be found for logger X Y Z is printed once To obtain the pre 3 2 behaviour lastResort can be set to None Configuring Logging for a Library When developing a library which uses logging you should take care to document how the library uses logging for example the names of loggers used Some consideration also needs to be given to its logging configuration If the using application does not use logging and library code makes logging calls then as described in the previous section events of severity WARNING and greater will be printed to sys stderr This is regarded as the best default behaviour If for some reason you don t want these messages printed in the absence of any logging configuration you can attach a do nothing handler to the top level logger for your library This avoids the message being printed since a handler will always be found for the library s events it just doesn t produce any output If the library user configures logging for application use presumably that configuration will add some handlers and if levels are suitably configured then logging calls made in library code will send output to those handlers as normal A do nothing handler is included in the logging package NullHandler since Python 3 1 An instance of this handler could be added to the top level logger of the logging namespace used by the library if you want to prevent your library s logged events being output to sys stderr in the absence of logging configuration If all logging by a library foo is done using loggers with names matching foo x foo x y etc then the code import logging logging getLogger foo addHandler logging NullHandler should have the desired effect If an organisation produces a number of libraries then the logger name specified can be orgname foo rather than just foo Note It is strongly advised that you do not log to the root logger in your library Instead use a logger with a unique and easily identifiable name such as the __name__ for your library s top level package or module Logging to the root logger will make it difficult or impossible for the application developer to configure the logging verbosity or handlers of your library as they wish Note It is strongly advised that you do not add any handlers ,en
683,other than NullHandler to your library s loggers This is because the configuration of handlers is the prerogative of the application developer who uses your library The application developer knows their target audience and what handlers are most appropriate for their application if you add handlers under the hood you might well interfere with their ability to carry out unit tests and deliver logs which suit their requirements Logging Levels The numeric values of logging levels are given in the following table These are primarily of interest if you want to define your own levels and need them to have specific values relative to the predefined levels If you define a level with the same numeric value it overwrites the predefined value the predefined name is lost Level Numeric value CRITICAL 50 ERROR 40 WARNING 30 INFO 20 DEBUG 10 NOTSET 0 Levels can also be associated with loggers being set either by the developer or through loading a saved logging configuration When a logging method is called on a logger the logger compares its own level with the level associated with the method call If the logger s level is higher than the method call s no logging message is actually generated This is the basic mechanism controlling the verbosity of logging output Logging messages are encoded as instances of the LogRecord class When a logger decides to actually log an event a LogRecord instance is created from the logging message Logging messages are subjected to a dispatch mechanism through the use of handlers which are instances of subclasses of the Handler class Handlers are responsible for ensuring that a logged message in the form of a LogRecord ends up in a particular location or set of locations which is useful for the target audience for that message such as end users support desk staff system administrators developers Handlers are passed LogRecord instances intended for particular destinations Each logger can have zero one or more handlers associated with it via the addHandler method of Logger In addition to any handlers directly associated with a logger all handlers associated with all ancestors of the logger are called to dispatch the message unless the propagate flag for a logger is set to a false value at which point the passing to ancestor handlers stops Just as for loggers handlers can have levels associated with them A handler s level acts as a filter in the same way as a logger s level does If a handler decides to actually dispatch an event the emit method is used to send the message to its destination Most user defined subclasses of Handler will need to override this emit Custom Levels Defining your own levels is possible but should not be necessary as the existing levels have been chosen on the basis of practical experience However if you are convinced that you need custom levels great care should be exercised when doing this and it is possibly a very bad idea to define custom levels if you are developing a library That s because if multiple library authors all define their own custom levels there is a chance that the logging output from such multiple libraries used together will be difficult for the using developer to control and or interpret because a given numeric value might mean different things for different libraries Useful Handlers In addition to the base Handler class many useful subclasses are provided 1 StreamHandler instances send messages to streams file like objects 2 FileHandler instances send messages to disk files 3 BaseRotatingHandler is the base class for handlers that rotate log files at a certain point It is not meant to be instantiated directly Instead use RotatingFileHandler or TimedRotatingFileHandler 4 RotatingFileHandler instances send messages to disk files with support for maximum log file sizes and log file rotation 5 TimedRotatingFileHandler instances send messages to disk files rotating the log file at certain timed intervals 6 SocketHandler instances send messages to TCP IP sockets Since 3 4 Unix domain sockets are also supported 7 DatagramHandler instances send messages to UDP sockets Si,en
684,nce 3 4 Unix domain sockets are also supported 8 SMTPHandler instances send messages to a designated email address 9 SysLogHandler instances send messages to a Unix syslog daemon possibly on a remote machine 10 NTEventLogHandler instances send messages to a Windows NT 2000 XP event log 11 MemoryHandler instances send messages to a buffer in memory which is flushed whenever specific criteria are met 12 HTTPHandler instances send messages to an HTTP server using either GET or POST semantics 13 WatchedFileHandler instances watch the file they are logging to If the file changes it is closed and reopened using the file name This handler is only useful on Unix like systems Windows does not support the underlying mechanism used 14 QueueHandler instances send messages to a queue such as those implemented in the queue or multiprocessing modules 15 NullHandler instances do nothing with error messages They are used by library developers who want to use logging but want to avoid the No handlers could be found for logger XXX message which can be displayed if the library user has not configured logging See Configuring Logging for a Library for more information New in version 3 1 The NullHandler class New in version 3 2 The QueueHandler class The NullHandler StreamHandler and FileHandler classes are defined in the core logging package The other handlers are defined in a sub module logging handlers There is also another sub module logging config for configuration functionality Logged messages are formatted for presentation through instances of the Formatter class They are initialized with a format string suitable for use with the operator and a dictionary For formatting multiple messages in a batch instances of BufferingFormatter can be used In addition to the format string which is applied to each message in the batch there is provision for header and trailer format strings When filtering based on logger level and or handler level is not enough instances of Filter can be added to both Logger and Handler instances through their addFilter method Before deciding to process a message further both loggers and handlers consult all their filters for permission If any filter returns a false value the message is not processed further The basic Filter functionality allows filtering by specific logger name If this feature is used messages sent to the named logger and its children are allowed through the filter and all others dropped Exceptions raised during logging The logging package is designed to swallow exceptions which occur while logging in production This is so that errors which occur while handling logging events such as logging misconfiguration network or other similar errors do not cause the application using logging to terminate prematurely SystemExit and KeyboardInterrupt exceptions are never swallowed Other exceptions which occur during the emit method of a Handler subclass are passed to its handleError method The default implementation of handleError in Handler checks to see if a module level variable raiseExceptions is set If set a traceback is printed to sys stderr If not set the exception is swallowed Note The default value of raiseExceptions is True This is because during development you typically want to be notified of any exceptions that occur It s advised that you set raiseExceptions to False for production usage Using arbitrary objects as messages In the preceding sections and examples it has been assumed that the message passed when logging the event is a string However this is not the only possibility You can pass an arbitrary object as a message and its __str__ method will be called when the logging system needs to convert it to a string representation In fact if you want to you can avoid computing a string representation altogether for example the SocketHandler emits an event by pickling it and sending it over the wire Optimization Formatting of message arguments is deferred until it cannot be avoided However computing the arguments passed to the logging method can also be expensive and you may want to avoid doing it if ,en
685,the logger will just throw away your event To decide what to do you can call the isEnabledFor method which takes a level argument and returns true if the event would be created by the Logger for that level of call You can write code like this if logger isEnabledFor logging DEBUG logger debug Message with s s expensive_func1 expensive_func2 so that if the logger s threshold is set above DEBUG the calls to expensive_func1 and expensive_func2 are never made Note In some cases isEnabledFor can itself be more expensive than you d like e g for deeply nested loggers where an explicit level is only set high up in the logger hierarchy In such cases or if you want to avoid calling a method in tight loops you can cache the result of a call to isEnabledFor in a local or instance variable and use that instead of calling the method each time Such a cached value would only need to be recomputed when the logging configuration changes dynamically while the application is running which is not all that common There are other optimizations which can be made for specific applications which need more precise control over what logging information is collected Here s a list of things you can do to avoid processing during logging which you don t need What you don t want to collect How to avoid collecting it Information about where calls were made from Set logging _srcfile to None This avoids calling sys _getframe which may help to speed up your code in environments like PyPy which can t speed up code that uses sys _getframe Threading information Set logging logThreads to False Current process ID os getpid Set logging logProcesses to False Current process name when using multiprocessing to Set logging logMultiprocessing to False manage multiple processes Current asyncio Task name when using asyncio Set logging logAsyncioTasks to False Also note that the core logging module only includes the basic handlers If you don t import logging handlers and logging config they won t take up any memory Other resources See also Module logging API reference for the logging module Module logging config Configuration API for the logging module Module logging handlers Useful handlers included with the logging module A logging cookbook,en
686,Python on Windows FAQ How do I run a Python program under Windows This is not necessarily a straightforward question If you are already familiar with running programs from the Windows command line then everything will seem obvious otherwise you might need a little more guidance Unless you use some sort of integrated development environment you will end up typing Windows commands into what is referred to as a Command prompt window Usually you can create such a window from your search bar by searching for cmd You should be able to recognize when you have started such a window because you will see a Windows command prompt which usually looks like this C The letter may be different and there might be other things after it so you might just as easily see something like D YourName Projects Python depending on how your computer has been set up and what else you have recently done with it Once you have started such a window you are well on the way to running Python programs You need to realize that your Python scripts have to be processed by another program called the Python interpreter The interpreter reads your script compiles it into bytecodes and then executes the bytecodes to run your program So how do you arrange for the interpreter to handle your Python First you need to make sure that your command window recognises the word py as an instruction to start the interpreter If you have opened a command window you should try entering the command py and hitting return C Users YourName py You should then see something like Python 3 6 4 v3 6 4 d48eceb Dec 19 2017 06 04 45 MSC v 1900 32 bit Intel on win32 Type help copyright credits or license for more information You have started the interpreter in interactive mode That means you can enter Python statements or expressions interactively and have them executed or evaluated while you wait This is one of Python s strongest features Check it by entering a few expressions of your choice and seeing the results print Hello Hello Hello 3 HelloHelloHello Many people use the interactive mode as a convenient yet highly programmable calculator When you want to end your interactive Python session call the exit function or hold the Ctrl key down while you enter a Z then hit the Enter key to get back to your Windows command prompt You may also find that you have a Start menu entry such as Start Programs Python 3 x Python command line that results in you seeing the prompt in a new window If so the window will disappear after you call the exit function or enter the Ctrl Z character Windows is running a single python command in the window and closes it when you terminate the interpreter Now that we know the py command is recognized you can give your Python script to it You ll have to give either an absolute or a relative path to the Python script Let s say your Python script is located in your desktop and is named hello py and your command prompt is nicely opened in your home directory so you re seeing something similar to C Users YourName So now you ll ask the py command to give your script to Python by typing py followed by your script path C Users YourName py Desktop hello py hello How do I make Python scripts executable On Windows the standard Python installer already associates the py extension with a file type Python File and gives that file type an open command that runs the interpreter D Program Files Python python exe 1 This is enough to make scripts executable from the command prompt as foo py If you d rather be able to execute the script by simple typing foo with no extension you need to add py to the PATHEXT environment variable Why does Python sometimes take so long to start Usually Python starts very quickly on Windows but occasionally there are bug reports that Python suddenly begins to take a long time to start up This is made even more puzzling because Python will work fine on other Windows systems which appear to be configured identically The problem may be caused by a misconfiguration of virus checking software on the problem machine Some virus scanners have been known to introdu,en
687,ce startup overhead of two orders of magnitude when the scanner is configured to monitor all reads from the filesystem Try checking the configuration of virus scanning software on your systems to ensure that they are indeed configured identically McAfee when configured to scan all file system read activity is a particular offender How do I make an executable from a Python script See How can I create a stand alone binary from a Python script for a list of tools that can be used to make executables Is a pyd file the same as a DLL Yes pyd files are dll s but there are a few differences If you have a DLL named foo pyd then it must have a function PyInit_foo You can then write Python import foo and Python will search for foo pyd as well as foo py foo pyc and if it finds it will attempt to call PyInit_foo to initialize it You do not link your exe with foo lib as that would cause Windows to require the DLL to be present Note that the search path for foo pyd is PYTHONPATH not the same as the path that Windows uses to search for foo dll Also foo pyd need not be present to run your program whereas if you linked your program with a dll the dll is required Of course foo pyd is required if you want to say import foo In a DLL linkage is declared in the source code with __declspec dllexport In a pyd linkage is defined in a list of available functions How can I embed Python into a Windows application Embedding the Python interpreter in a Windows app can be summarized as follows 1 Do not build Python into your exe file directly On Windows Python must be a DLL to handle importing modules that are themselves DLL s This is the first key undocumented fact Instead link to python NN dll it is typically installed in C Windows System NN is the Python version a number such as 33 for Python 3 3 You can link to Python in two different ways Load time linking means linking against python NN lib while run time linking means linking against python NN dll General note python NN lib is the so called import lib corresponding to python NN dll It merely defines symbols for the linker Run time linking greatly simplifies link options everything happens at run time Your code must load python NN dll using the Windows LoadLibraryEx routine The code must also use access routines and data in python NN dll that is Python s C API s using pointers obtained by the Windows GetProcAddress routine Macros can make using these pointers transparent to any C code that calls routines in Python s C API 2 If you use SWIG it is easy to create a Python extension module that will make the app s data and methods available to Python SWIG will handle just about all the grungy details for you The result is C code that you link into your exe file You do not have to create a DLL file and this also simplifies linking 3 SWIG will create an init function a C function whose name depends on the name of the extension module For example if the name of the module is leo the init function will be called initleo If you use SWIG shadow classes as you should the init function will be called initleoc This initializes a mostly hidden helper class used by the shadow class The reason you can link the C code in step 2 into your exe file is that calling the initialization function is equivalent to importing the module into Python This is the second key undocumented fact 4 In short you can use the following code to initialize the Python interpreter with your extension module include Python h Py_Initialize Initialize Python initmyAppc Initialize import the helper class PyRun_SimpleString import myApp Import the shadow class 5 There are two problems with Python s C API which will become apparent if you use a compiler other than MSVC the compiler used to build pythonNN dll Problem 1 The so called Very High Level functions that take FILE arguments will not work in a multi compiler environment because each compiler s notion of a struct FILE will be different From an implementation standpoint these are very low level functions Problem 2 SWIG generates the following code when generating wrappers to void function,en
688,s Py_INCREF Py_None _resultobj Py_None return _resultobj Alas Py_None is a macro that expands to a reference to a complex data structure called _Py_NoneStruct inside pythonNN dll Again this code will fail in a mult compiler environment Replace such code by return Py_BuildValue It may be possible to use SWIG s typemap command to make the change automatically though I have not been able to get this to work I m a complete SWIG newbie 6 Using a Python shell script to put up a Python interpreter window from inside your Windows app is not a good idea the resulting window will be independent of your app s windowing system Rather you or the wxPythonWindow class should create a native interpreter window It is easy to connect that window to the Python interpreter You can redirect Python s i o to _any_ object that supports read and write so all you need is a Python object defined in your extension module that contains read and write methods How do I keep editors from inserting tabs into my Python source The FAQ does not recommend using tabs and the Python style guide PEP 8 recommends 4 spaces for distributed Python code this is also the Emacs python mode default Under any editor mixing tabs and spaces is a bad idea MSVC is no different in this respect and is easily configured to use spaces Take Tools Options Tabs and for file type Default set Tab size and Indent size to 4 and select the Insert spaces radio button Python raises IndentationError or TabError if mixed tabs and spaces are causing problems in leading whitespace You may also run the tabnanny module to check a directory tree in batch mode How do I check for a keypress without blocking Use the msvcrt module This is a standard Windows specific extension module It defines a function kbhit which checks whether a keyboard hit is present and getch which gets one character without echoing it How do I solve the missing api ms win crt runtime l1 1 0 dll error This can occur on Python 3 5 and later when using Windows 8 1 or earlier without all updates having been installed First ensure your operating system is supported and is up to date and if that does not resolve the issue visit the Microsoft support page for guidance on manually installing the C Runtime update,en
689,__main__ Top level code environment In Python the special name __main__ is used for two important constructs 1 the name of the top level environment of the program which can be checked using the __name__ __main__ expression and 2 the __main__ py file in Python packages Both of these mechanisms are related to Python modules how users interact with them and how they interact with each other They are explained in detail below If you re new to Python modules see the tutorial section Modules for an introduction __name__ __main__ When a Python module or package is imported __name__ is set to the module s name Usually this is the name of the Python file itself without the py extension import configparser configparser __name__ configparser If the file is part of a package __name__ will also include the parent package s path from concurrent futures import process process __name__ concurrent futures process However if the module is executed in the top level code environment its __name__ is set to the string __main__ What is the top level code environment __main__ is the name of the environment where top level code is run Top level code is the first user specified Python module that starts running It s top level because it imports all other modules that the program needs Sometimes top level code is called an entry point to the application The top level code environment can be the scope of an interactive prompt __name__ __main__ the Python module passed to the Python interpreter as a file argument python helloworld py Hello world the Python module or package passed to the Python interpreter with the m argument python m tarfile usage tarfile py h v Python code read by the Python interpreter from standard input echo import this python The Zen of Python by Tim Peters Beautiful is better than ugly Explicit is better than implicit Python code passed to the Python interpreter with the c argument python c import this The Zen of Python by Tim Peters Beautiful is better than ugly Explicit is better than implicit In each of these situations the top level module s __name__ is set to __main__ As a result a module can discover whether or not it is running in the top level environment by checking its own __name__ which allows a common idiom for conditionally executing code when the module is not initialized from an import statement if __name__ __main__ Execute when the module is not initialized from an import statement See also For a more detailed look at how __name__ is set in all situations see the tutorial section Modules Idiomatic Usage Some modules contain code that is intended for script use only like parsing command line arguments or fetching data from standard input If a module like this was imported from a different module for example to unit test it the script code would unintentionally execute as well This is where using the if __name__ __main__ code block comes in handy Code within this block won t run unless the module is executed in the top level environment Putting as few statements as possible in the block below if __name__ __main__ can improve code clarity and correctness Most often a function named main encapsulates the program s primary behavior echo py import shlex import sys def echo phrase str None A dummy wrapper around print for demonstration purposes you can imagine that there is some valuable and reusable logic inside this function print phrase def main int Echo the input arguments to standard output phrase shlex join sys argv echo phrase return 0 if __name__ __main__ sys exit main next section explains the use of sys exit Note that if the module didn t encapsulate code inside the main function but instead put it directly within the if __name__ __main__ block the phrase variable would be global to the entire module This is error prone as other functions within the module could be unintentionally using the global variable instead of a local name A main function solves this problem Using a main function has the added benefit of the echo function itself being isolated and importable elsewhere When echo py is imported the ec,en
690,ho and main functions will be defined but neither of them will be called because __name__ __main__ Packaging Considerations main functions are often used to create command line tools by specifying them as entry points for console scripts When this is done pip inserts the function call into a template script where the return value of main is passed into sys exit For example sys exit main Since the call to main is wrapped in sys exit the expectation is that your function will return some value acceptable as an input to sys exit typically an integer or None which is implicitly returned if your function does not have a return statement By proactively following this convention ourselves our module will have the same behavior when run directly i e python echo py as it will have if we later package it as a console script entry point in a pip installable package In particular be careful about returning strings from your main function sys exit will interpret a string argument as a failure message so your program will have an exit code of 1 indicating failure and the string will be written to sys stderr The echo py example from earlier exemplifies using the sys exit main convention See also Python Packaging User Guide contains a collection of tutorials and references on how to distribute and install Python packages with modern tools __main__ py in Python Packages If you are not familiar with Python packages see section Packages of the tutorial Most commonly the __main__ py file is used to provide a command line interface for a package Consider the following hypothetical package bandclass bandclass __init__ py __main__ py student py __main__ py will be executed when the package itself is invoked directly from the command line using the m flag For example python m bandclass This command will cause __main__ py to run How you utilize this mechanism will depend on the nature of the package you are writing but in this hypothetical case it might make sense to allow the teacher to search for students bandclass __main__ py import sys from student import search_students student_name sys argv 1 if len sys argv 2 else print f Found student search_students student_name Note that from student import search_students is an example of a relative import This import style can be used when referencing modules within a package For more details see Intra package References in the Modules section of the tutorial Idiomatic Usage The content of __main__ py typically isn t fenced with an if __name__ __main__ block Instead those files are kept short and import functions to execute from other modules Those other modules can then be easily unit tested and are properly reusable If used an if __name__ __main__ block will still work as expected for a __main__ py file within a package because its __name__ attribute will include the package s path if imported import asyncio __main__ asyncio __main__ __name__ asyncio __main__ This won t work for __main__ py files in the root directory of a zip file though Hence for consistency minimal __main__ py like the venv one mentioned below are preferred See also See venv for an example of a package with a minimal __main__ py in the standard library It doesn t contain a if __name__ __main__ block You can invoke it with python m venv directory See runpy for more details on the m flag to the interpreter executable See zipapp for how to run applications packaged as zip files In this case Python looks for a __main__ py file in the root directory of the archive import __main__ Regardless of which module a Python program was started with other modules running within that same program can import the top level environment s scope namespace by importing the __main__ module This doesn t import a __main__ py file but rather whichever module that received the special name __main__ Here is an example module that consumes the __main__ namespace namely py import __main__ def did_user_define_their_name return my_name in dir __main__ def print_user_name if not did_user_define_their_name raise ValueError Define the variable my_name if __file__,en
691, in dir __main__ print __main__ my_name found in file __main__ __file__ else print __main__ my_name Example usage of this module could be as follows start py import sys from namely import print_user_name my_name Dinsdale def main try print_user_name except ValueError as ve return str ve if __name__ __main__ sys exit main Now if we started our program the result would look like this python start py Define the variable my_name The exit code of the program would be 1 indicating an error Uncommenting the line with my_name Dinsdale fixes the program and now it exits with status code 0 indicating success python start py Dinsdale found in file path to start py Note that importing __main__ doesn t cause any issues with unintentionally running top level code meant for script use which is put in the if __name__ __main__ block of the start module Why does this work Python inserts an empty __main__ module in sys modules at interpreter startup and populates it by running top level code In our example this is the start module which runs line by line and imports namely In turn namely imports __main__ which is really start That s an import cycle Fortunately since the partially populated __main__ module is present in sys modules Python passes that to namely See Special considerations for __main__ in the import system s reference for details on how this works The Python REPL is another example of a top level environment so anything defined in the REPL becomes part of the __main__ scope import namely namely did_user_define_their_name False namely print_user_name Traceback most recent call last ValueError Define the variable my_name my_name Jabberwocky namely did_user_define_their_name True namely print_user_name Jabberwocky Note that in this case the __main__ scope doesn t contain a __file__ attribute as it s interactive The __main__ scope is used in the implementation of pdb and rlcompleter,en
692,Python support for the Linux perf profiler author Pablo Galindo The Linux perf profiler is a very powerful tool that allows you to profile and obtain information about the performance of your application perf also has a very vibrant ecosystem of tools that aid with the analysis of the data that it produces The main problem with using the perf profiler with Python applications is that perf only gets information about native symbols that is the names of functions and procedures written in C This means that the names and file names of Python functions in your code will not appear in the output of perf Since Python 3 12 the interpreter can run in a special mode that allows Python functions to appear in the output of the perf profiler When this mode is enabled the interpreter will interpose a small piece of code compiled on the fly before the execution of every Python function and it will teach perf the relationship between this piece of code and the associated Python function using perf map files Note Support for the perf profiler is currently only available for Linux on select architectures Check the output of the configure build step or check the output of python m sysconfig grep HAVE_PERF_TRAMPOLINE to see if your system is supported For example consider the following script def foo n result 0 for _ in range n result 1 return result def bar n foo n def baz n bar n if __name__ __main__ baz 1000000 We can run perf to sample CPU stack traces at 9999 hertz perf record F 9999 g o perf data python my_script py Then we can use perf report to analyze the data perf report stdio n g Children Self Samples Command Shared Object Symbol 91 08 0 00 0 python exe python exe _start _start 90 71 __libc_start_main Py_BytesMain 56 88 pymain_run_python constprop 0 56 13 _PyRun_AnyFileObject _PyRun_SimpleFileObject 55 02 run_mod 54 65 PyEval_EvalCode _PyEval_EvalFrameDefault PyObject_Vectorcall _PyEval_Vector _PyEval_EvalFrameDefault PyObject_Vectorcall _PyEval_Vector _PyEval_EvalFrameDefault PyObject_Vectorcall _PyEval_Vector 51 67 _PyEval_EvalFrameDefault 11 52 _PyLong_Add 2 97 _PyObject_Malloc As you can see the Python functions are not shown in the output only _PyEval_EvalFrameDefault the function that evaluates the Python bytecode shows up Unfortunately that s not very useful because all Python functions use the same C function to evaluate bytecode so we cannot know which Python function corresponds to which bytecode evaluating function Instead if we run the same experiment with perf support enabled we get perf report stdio n g Children Self Samples Command Shared Object Symbol 90 58 0 36 1 python exe python exe _start _start 89 86 __libc_start_main Py_BytesMain 55 43 pymain_run_python constprop 0 54 71 _PyRun_AnyFileObject _PyRun_SimpleFileObject 53 62 run_mod 53 26 PyEval_EvalCode py module src script py _PyEval_EvalFrameDefault PyObject_Vectorcall _PyEval_Vector py baz src script py _PyEval_EvalFrameDefault PyObject_Vectorcall _PyEval_Vector py bar src script py _PyEval_EvalFrameDefault PyObject_Vectorcall _PyEval_Vector py foo src script py 51 81 _PyEval_EvalFrameDefault 13 77 _PyLong_Add 3 26 _PyObject_Malloc How to enable perf profiling support perf profiling support can be enabled either from the start using the environment variable PYTHONPERFSUPPORT or the X perf option or dynamically using sys activate_stack_trampoline and sys deactivate_stack_trampoline The sys functions take precedence over the X option the X option takes precedence over the environment variable Example using the environment variable PYTHONPERFSUPPORT 1 python script py perf report g i perf data Example using the X option python X perf script py perf report g i perf data Example using the sys APIs in file example py import sys sys activate_stack_trampoline perf do_profiled_stuff sys deactivate_stack_trampoline non_profiled_stuff then python example py perf report g i perf data How to obtain the best results For best results Python should be compiled with CFLAGS fno omit frame pointer mno omit leaf frame pointer as this allows profilers to unwind using only the f,en
693,rame pointer and not on DWARF debug information This is because as the code that is interposed to allow perf support is dynamically generated it doesn t have any DWARF debugging information available You can check if your system has been compiled with this flag by running python m sysconfig grep no omit frame pointer If you don t see any output it means that your interpreter has not been compiled with frame pointers and therefore it may not be able to show Python functions in the output of perf,en
694,Introduction The Python library contains several different kinds of components It contains data types that would normally be considered part of the core of a language such as numbers and lists For these types the Python language core defines the form of literals and places some constraints on their semantics but does not fully define the semantics On the other hand the language core does define syntactic properties like the spelling and priorities of operators The library also contains built in functions and exceptions objects that can be used by all Python code without the need of an import statement Some of these are defined by the core language but many are not essential for the core semantics and are only described here The bulk of the library however consists of a collection of modules There are many ways to dissect this collection Some modules are written in C and built in to the Python interpreter others are written in Python and imported in source form Some modules provide interfaces that are highly specific to Python like printing a stack trace some provide interfaces that are specific to particular operating systems such as access to specific hardware others provide interfaces that are specific to a particular application domain like the World Wide Web Some modules are available in all versions and ports of Python others are only available when the underlying system supports or requires them yet others are available only when a particular configuration option was chosen at the time when Python was compiled and installed This manual is organized from the inside out it first describes the built in functions data types and exceptions and finally the modules grouped in chapters of related modules This means that if you start reading this manual from the start and skip to the next chapter when you get bored you will get a reasonable overview of the available modules and application areas that are supported by the Python library Of course you don t have to read it like a novel you can also browse the table of contents in front of the manual or look for a specific function module or term in the index in the back And finally if you enjoy learning about random subjects you choose a random page number see module random and read a section or two Regardless of the order in which you read the sections of this manual it helps to start with chapter Built in Functions as the remainder of the manual assumes familiarity with this material Let the show begin Notes on availability An Availability Unix note means that this function is commonly found on Unix systems It does not make any claims about its existence on a specific operating system If not separately noted all functions that claim Availability Unix are supported on macOS which builds on a Unix core If an availability note contains both a minimum Kernel version and a minimum libc version then both conditions must hold For example a feature with note Availability Linux 3 17 with glibc 2 27 requires both Linux 3 17 or newer and glibc 2 27 or newer WebAssembly platforms The WebAssembly platforms wasm32 emscripten Emscripten and wasm32 wasi WASI provide a subset of POSIX APIs WebAssembly runtimes and browsers are sandboxed and have limited access to the host and external resources Any Python standard library module that uses processes threading networking signals or other forms of inter process communication IPC is either not available or may not work as on other Unix like systems File I O file system and Unix permission related functions are restricted too Emscripten does not permit blocking I O Other blocking operations like sleep block the browser event loop The properties and behavior of Python on WebAssembly platforms depend on the Emscripten SDK or WASI SDK version WASM runtimes browser NodeJS wasmtime and Python build time flags WebAssembly Emscripten and WASI are evolving standards some features like networking may be supported in the future For Python in the browser users should consider Pyodide or PyScript PyScript is built on top of Pyodide which itself is built on ,en
695,top of CPython and Emscripten Pyodide provides access to browsers JavaScript and DOM APIs as well as limited networking capabilities with JavaScript s XMLHttpRequest and Fetch APIs Process related APIs are not available or always fail with an error That includes APIs that spawn new processes fork execve wait for processes waitpid send signals kill or otherwise interact with processes The subprocess is importable but does not work The socket module is available but is limited and behaves differently from other platforms On Emscripten sockets are always non blocking and require additional JavaScript code and helpers on the server to proxy TCP through WebSockets see Emscripten Networking for more information WASI snapshot preview 1 only permits sockets from an existing file descriptor Some functions are stubs that either don t do anything and always return hardcoded values Functions related to file descriptors file permissions file ownership and links are limited and don t support some operations For example WASI does not permit symlinks with absolute file names,en
696,4 More Control Flow Tools As well as the while statement just introduced Python uses a few more that we will encounter in this chapter 4 1 if Statements Perhaps the most well known statement type is the if statement For example x int input Please enter an integer Please enter an integer 42 if x 0 x 0 print Negative changed to zero elif x 0 print Zero elif x 1 print Single else print More More There can be zero or more elif parts and the else part is optional The keyword elif is short for else if and is useful to avoid excessive indentation An if elif elif sequence is a substitute for the switch or case statements found in other languages If you re comparing the same value to several constants or checking for specific types or attributes you may also find the match statement useful For more details see match Statements 4 2 for Statements The for statement in Python differs a bit from what you may be used to in C or Pascal Rather than always iterating over an arithmetic progression of numbers like in Pascal or giving the user the ability to define both the iteration step and halting condition as C Python s for statement iterates over the items of any sequence a list or a string in the order that they appear in the sequence For example no pun intended Measure some strings words cat window defenestrate for w in words print w len w cat 3 window 6 defenestrate 12 Code that modifies a collection while iterating over that same collection can be tricky to get right Instead it is usually more straight forward to loop over a copy of the collection or to create a new collection Create a sample collection users Hans active Éléonore inactive 景太郎 active Strategy Iterate over a copy for user status in users copy items if status inactive del users user Strategy Create a new collection active_users for user status in users items if status active active_users user status 4 3 The range Function If you do need to iterate over a sequence of numbers the built in function range comes in handy It generates arithmetic progressions for i in range 5 print i 0 1 2 3 4 The given end point is never part of the generated sequence range 10 generates 10 values the legal indices for items of a sequence of length 10 It is possible to let the range start at another number or to specify a different increment even negative sometimes this is called the step list range 5 10 5 6 7 8 9 list range 0 10 3 0 3 6 9 list range 10 100 30 10 40 70 To iterate over the indices of a sequence you can combine range and len as follows a Mary had a little lamb for i in range len a print i a i 0 Mary 1 had 2 a 3 little 4 lamb In most such cases however it is convenient to use the enumerate function see Looping Techniques A strange thing happens if you just print a range range 10 range 0 10 In many ways the object returned by range behaves as if it is a list but in fact it isn t It is an object which returns the successive items of the desired sequence when you iterate over it but it doesn t really make the list thus saving space We say such an object is iterable that is suitable as a target for functions and constructs that expect something from which they can obtain successive items until the supply is exhausted We have seen that the for statement is such a construct while an example of a function that takes an iterable is sum sum range 4 0 1 2 3 6 Later we will see more functions that return iterables and take iterables as arguments In chapter Data Structures we will discuss in more detail about list 4 4 break and continue Statements and else Clauses on Loops The break statement breaks out of the innermost enclosing for or while loop A for or while loop can include an else clause In a for loop the else clause is executed after the loop reaches its final iteration In a while loop it s executed after the loop s condition becomes false In either kind of loop the else clause is not executed if the loop was terminated by a break This is exemplified in the following for loop which searches for prime numbers for n in range 2 10 for x in range 2 n if n x 0 print n equals x n x break ,en
697,else loop fell through without finding a factor print n is a prime number 2 is a prime number 3 is a prime number 4 equals 2 2 5 is a prime number 6 equals 2 3 7 is a prime number 8 equals 2 4 9 equals 3 3 Yes this is the correct code Look closely the else clause belongs to the for loop not the if statement When used with a loop the else clause has more in common with the else clause of a try statement than it does with that of if statements a try statement s else clause runs when no exception occurs and a loop s else clause runs when no break occurs For more on the try statement and exceptions see Handling Exceptions The continue statement also borrowed from C continues with the next iteration of the loop for num in range 2 10 if num 2 0 print Found an even number num continue print Found an odd number num Found an even number 2 Found an odd number 3 Found an even number 4 Found an odd number 5 Found an even number 6 Found an odd number 7 Found an even number 8 Found an odd number 9 4 5 pass Statements The pass statement does nothing It can be used when a statement is required syntactically but the program requires no action For example while True pass Busy wait for keyboard interrupt Ctrl C This is commonly used for creating minimal classes class MyEmptyClass pass Another place pass can be used is as a place holder for a function or conditional body when you are working on new code allowing you to keep thinking at a more abstract level The pass is silently ignored def initlog args pass Remember to implement this 4 6 match Statements A match statement takes an expression and compares its value to successive patterns given as one or more case blocks This is superficially similar to a switch statement in C Java or JavaScript and many other languages but it s more similar to pattern matching in languages like Rust or Haskell Only the first pattern that matches gets executed and it can also extract components sequence elements or object attributes from the value into variables The simplest form compares a subject value against one or more literals def http_error status match status case 400 return Bad request case 404 return Not found case 418 return I m a teapot case _ return Something s wrong with the internet Note the last block the variable name _ acts as a wildcard and never fails to match If no case matches none of the branches is executed You can combine several literals in a single pattern using or case 401 403 404 return Not allowed Patterns can look like unpacking assignments and can be used to bind variables point is an x y tuple match point case 0 0 print Origin case 0 y print f Y y case x 0 print f X x case x y print f X x Y y case _ raise ValueError Not a point Study that one carefully The first pattern has two literals and can be thought of as an extension of the literal pattern shown above But the next two patterns combine a literal and a variable and the variable binds a value from the subject point The fourth pattern captures two values which makes it conceptually similar to the unpacking assignment x y point If you are using classes to structure your data you can use the class name followed by an argument list resembling a constructor but with the ability to capture attributes into variables class Point def __init__ self x y self x x self y y def where_is point match point case Point x 0 y 0 print Origin case Point x 0 y y print f Y y case Point x x y 0 print f X x case Point print Somewhere else case _ print Not a point You can use positional parameters with some builtin classes that provide an ordering for their attributes e g dataclasses You can also define a specific position for attributes in patterns by setting the __match_args__ special attribute in your classes If it s set to x y the following patterns are all equivalent and all bind the y attribute to the var variable Point 1 var Point 1 y var Point x 1 y var Point y var x 1 A recommended way to read patterns is to look at them as an extended form of what you would put on the left of an assignment to understand which variables would be set to wha,en
698,t Only the standalone names like var above are assigned to by a match statement Dotted names like foo bar attribute names the x and y above or class names recognized by the next to them like Point above are never assigned to Patterns can be arbitrarily nested For example if we have a short list of Points with __match_args__ added we could match it like this class Point __match_args__ x y def __init__ self x y self x x self y y match points case print No points case Point 0 0 print The origin case Point x y print f Single point x y case Point 0 y1 Point 0 y2 print f Two on the Y axis at y1 y2 case _ print Something else We can add an if clause to a pattern known as a guard If the guard is false match goes on to try the next case block Note that value capture happens before the guard is evaluated match point case Point x y if x y print f Y X at x case Point x y print f Not on the diagonal Several other key features of this statement Like unpacking assignments tuple and list patterns have exactly the same meaning and actually match arbitrary sequences An important exception is that they don t match iterators or strings Sequence patterns support extended unpacking x y rest and x y rest work similar to unpacking assignments The name after may also be _ so x y _ matches a sequence of at least two items without binding the remaining items Mapping patterns bandwidth b latency l captures the bandwidth and latency values from a dictionary Unlike sequence patterns extra keys are ignored An unpacking like rest is also supported But _ would be redundant so it is not allowed Subpatterns may be captured using the as keyword case Point x1 y1 Point x2 y2 as p2 will capture the second element of the input as p2 as long as the input is a sequence of two points Most literals are compared by equality however the singletons True False and None are compared by identity Patterns may use named constants These must be dotted names to prevent them from being interpreted as capture variable from enum import Enum class Color Enum RED red GREEN green BLUE blue color Color input Enter your choice of red blue or green match color case Color RED print I see red case Color GREEN print Grass is green case Color BLUE print I m feeling the blues For a more detailed explanation and additional examples you can look into PEP 636 which is written in a tutorial format 4 7 Defining Functions We can create a function that writes the Fibonacci series to an arbitrary boundary def fib n write Fibonacci series up to n Print a Fibonacci series up to n a b 0 1 while a n print a end a b b a b print Now call the function we just defined fib 2000 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 The keyword def introduces a function definition It must be followed by the function name and the parenthesized list of formal parameters The statements that form the body of the function start at the next line and must be indented The first statement of the function body can optionally be a string literal this string literal is the function s documentation string or docstring More about docstrings can be found in the section Documentation Strings There are tools which use docstrings to automatically produce online or printed documentation or to let the user interactively browse through code it s good practice to include docstrings in code that you write so make a habit of it The execution of a function introduces a new symbol table used for the local variables of the function More precisely all variable assignments in a function store the value in the local symbol table whereas variable references first look in the local symbol table then in the local symbol tables of enclosing functions then in the global symbol table and finally in the table of built in names Thus global variables and variables of enclosing functions cannot be directly assigned a value within a function unless for global variables named in a global statement or for variables of enclosing functions named in a nonlocal statement although they may be referenced The actual parameters arguments to a function call,en
699, are introduced in the local symbol table of the called function when it is called thus arguments are passed using call by value where the value is always an object reference not the value of the object 1 When a function calls another function or calls itself recursively a new local symbol table is created for that call A function definition associates the function name with the function object in the current symbol table The interpreter recognizes the object pointed to by that name as a user defined function Other names can also point to that same function object and can also be used to access the function fib function fib at 10042ed0 f fib f 100 0 1 1 2 3 5 8 13 21 34 55 89 Coming from other languages you might object that fib is not a function but a procedure since it doesn t return a value In fact even functions without a return statement do return a value albeit a rather boring one This value is called None it s a built in name Writing the value None is normally suppressed by the interpreter if it would be the only value written You can see it if you really want to using print fib 0 print fib 0 None It is simple to write a function that returns a list of the numbers of the Fibonacci series instead of printing it def fib2 n return Fibonacci series up to n Return a list containing the Fibonacci series up to n result a b 0 1 while a n result append a see below a b b a b return result f100 fib2 100 call it f100 write the result 0 1 1 2 3 5 8 13 21 34 55 89 This example as usual demonstrates some new Python features The return statement returns with a value from a function return without an expression argument returns None Falling off the end of a function also returns None The statement result append a calls a method of the list object result A method is a function that belongs to an object and is named obj methodname where obj is some object this may be an expression and methodname is the name of a method that is defined by the object s type Different types define different methods Methods of different types may have the same name without causing ambiguity It is possible to define your own object types and methods using classes see Classes The method append shown in the example is defined for list objects it adds a new element at the end of the list In this example it is equivalent to result result a but more efficient 4 8 More on Defining Functions It is also possible to define functions with a variable number of arguments There are three forms which can be combined 4 8 1 Default Argument Values The most useful form is to specify a default value for one or more arguments This creates a function that can be called with fewer arguments than it is defined to allow For example def ask_ok prompt retries 4 reminder Please try again while True reply input prompt if reply in y ye yes return True if reply in n no nop nope return False retries retries 1 if retries 0 raise ValueError invalid user response print reminder This function can be called in several ways giving only the mandatory argument ask_ok Do you really want to quit giving one of the optional arguments ask_ok OK to overwrite the file 2 or even giving all arguments ask_ok OK to overwrite the file 2 Come on only yes or no This example also introduces the in keyword This tests whether or not a sequence contains a certain value The default values are evaluated at the point of function definition in the defining scope so that i 5 def f arg i print arg i 6 f will print 5 Important warning The default value is evaluated only once This makes a difference when the default is a mutable object such as a list dictionary or instances of most classes For example the following function accumulates the arguments passed to it on subsequent calls def f a L L append a return L print f 1 print f 2 print f 3 This will print 1 1 2 1 2 3 If you don t want the default to be shared between subsequent calls you can write the function like this instead def f a L None if L is None L L append a return L 4 8 2 Keyword Arguments Functions can also be called using keyword arguments of the form k,en
700,warg value For instance the following function def parrot voltage state a stiff action voom type Norwegian Blue print This parrot wouldn t action end print if you put voltage volts through it print Lovely plumage the type print It s state accepts one required argument voltage and three optional arguments state action and type This function can be called in any of the following ways parrot 1000 1 positional argument parrot voltage 1000 1 keyword argument parrot voltage 1000000 action VOOOOOM 2 keyword arguments parrot action VOOOOOM voltage 1000000 2 keyword arguments parrot a million bereft of life jump 3 positional arguments parrot a thousand state pushing up the daisies 1 positional 1 keyword but all the following calls would be invalid parrot required argument missing parrot voltage 5 0 dead non keyword argument after a keyword argument parrot 110 voltage 220 duplicate value for the same argument parrot actor John Cleese unknown keyword argument In a function call keyword arguments must follow positional arguments All the keyword arguments passed must match one of the arguments accepted by the function e g actor is not a valid argument for the parrot function and their order is not important This also includes non optional arguments e g parrot voltage 1000 is valid too No argument may receive a value more than once Here s an example that fails due to this restriction def function a pass function 0 a 0 Traceback most recent call last File stdin line 1 in module TypeError function got multiple values for argument a When a final formal parameter of the form name is present it receives a dictionary see Mapping Types dict containing all keyword arguments except for those corresponding to a formal parameter This may be combined with a formal parameter of the form name described in the next subsection which receives a tuple containing the positional arguments beyond the formal parameter list name must occur before name For example if we define a function like this def cheeseshop kind arguments keywords print Do you have any kind print I m sorry we re all out of kind for arg in arguments print arg print 40 for kw in keywords print kw keywords kw It could be called like this cheeseshop Limburger It s very runny sir It s really very VERY runny sir shopkeeper Michael Palin client John Cleese sketch Cheese Shop Sketch and of course it would print Do you have any Limburger I m sorry we re all out of Limburger It s very runny sir It s really very VERY runny sir shopkeeper Michael Palin client John Cleese sketch Cheese Shop Sketch Note that the order in which the keyword arguments are printed is guaranteed to match the order in which they were provided in the function call 4 8 3 Special parameters By default arguments may be passed to a Python function either by position or explicitly by keyword For readability and performance it makes sense to restrict the way arguments can be passed so that a developer need only look at the function definition to determine if items are passed by position by position or keyword or by keyword A function definition may look like def f pos1 pos2 pos_or_kwd kwd1 kwd2 Positional or keyword Keyword only Positional only where and are optional If used these symbols indicate the kind of parameter by how the arguments may be passed to the function positional only positional or keyword and keyword only Keyword parameters are also referred to as named parameters 4 8 3 1 Positional or Keyword Arguments If and are not present in the function definition arguments may be passed to a function by position or by keyword 4 8 3 2 Positional Only Parameters Looking at this in a bit more detail it is possible to mark certain parameters as positional only If positional only the parameters order matters and the parameters cannot be passed by keyword Positional only parameters are placed before a forward slash The is used to logically separate the positional only parameters from the rest of the parameters If there is no in the function definition there are no positional only parameters Parameters following the may be positi,en
701,onal or keyword or keyword only 4 8 3 3 Keyword Only Arguments To mark parameters as keyword only indicating the parameters must be passed by keyword argument place an in the arguments list just before the first keyword only parameter 4 8 3 4 Function Examples Consider the following example function definitions paying close attention to the markers and def standard_arg arg print arg def pos_only_arg arg print arg def kwd_only_arg arg print arg def combined_example pos_only standard kwd_only print pos_only standard kwd_only The first function definition standard_arg the most familiar form places no restrictions on the calling convention and arguments may be passed by position or keyword standard_arg 2 2 standard_arg arg 2 2 The second function pos_only_arg is restricted to only use positional parameters as there is a in the function definition pos_only_arg 1 1 pos_only_arg arg 1 Traceback most recent call last File stdin line 1 in module TypeError pos_only_arg got some positional only arguments passed as keyword arguments arg The third function kwd_only_args only allows keyword arguments as indicated by a in the function definition kwd_only_arg 3 Traceback most recent call last File stdin line 1 in module TypeError kwd_only_arg takes 0 positional arguments but 1 was given kwd_only_arg arg 3 3 And the last uses all three calling conventions in the same function definition combined_example 1 2 3 Traceback most recent call last File stdin line 1 in module TypeError combined_example takes 2 positional arguments but 3 were given combined_example 1 2 kwd_only 3 1 2 3 combined_example 1 standard 2 kwd_only 3 1 2 3 combined_example pos_only 1 standard 2 kwd_only 3 Traceback most recent call last File stdin line 1 in module TypeError combined_example got some positional only arguments passed as keyword arguments pos_only Finally consider this function definition which has a potential collision between the positional argument name and kwds which has name as a key def foo name kwds return name in kwds There is no possible call that will make it return True as the keyword name will always bind to the first parameter For example foo 1 name 2 Traceback most recent call last File stdin line 1 in module TypeError foo got multiple values for argument name But using positional only arguments it is possible since it allows name as a positional argument and name as a key in the keyword arguments def foo name kwds return name in kwds foo 1 name 2 True In other words the names of positional only parameters can be used in kwds without ambiguity 4 8 3 5 Recap The use case will determine which parameters to use in the function definition def f pos1 pos2 pos_or_kwd kwd1 kwd2 As guidance Use positional only if you want the name of the parameters to not be available to the user This is useful when parameter names have no real meaning if you want to enforce the order of the arguments when the function is called or if you need to take some positional parameters and arbitrary keywords Use keyword only when names have meaning and the function definition is more understandable by being explicit with names or you want to prevent users relying on the position of the argument being passed For an API use positional only to prevent breaking API changes if the parameter s name is modified in the future 4 8 4 Arbitrary Argument Lists Finally the least frequently used option is to specify that a function can be called with an arbitrary number of arguments These arguments will be wrapped up in a tuple see Tuples and Sequences Before the variable number of arguments zero or more normal arguments may occur def write_multiple_items file separator args file write separator join args Normally these variadic arguments will be last in the list of formal parameters because they scoop up all remaining input arguments that are passed to the function Any formal parameters which occur after the args parameter are keyword only arguments meaning that they can only be used as keywords rather than positional arguments def concat args sep return sep join args concat earth mars ve,en
702,nus earth mars venus concat earth mars venus sep earth mars venus 4 8 5 Unpacking Argument Lists The reverse situation occurs when the arguments are already in a list or tuple but need to be unpacked for a function call requiring separate positional arguments For instance the built in range function expects separate start and stop arguments If they are not available separately write the function call with the operator to unpack the arguments out of a list or tuple list range 3 6 normal call with separate arguments 3 4 5 args 3 6 list range args call with arguments unpacked from a list 3 4 5 In the same fashion dictionaries can deliver keyword arguments with the operator def parrot voltage state a stiff action voom print This parrot wouldn t action end print if you put voltage volts through it end print E s state d voltage four million state bleedin demised action VOOM parrot d This parrot wouldn t VOOM if you put four million volts through it E s bleedin demised 4 8 6 Lambda Expressions Small anonymous functions can be created with the lambda keyword This function returns the sum of its two arguments lambda a b a b Lambda functions can be used wherever function objects are required They are syntactically restricted to a single expression Semantically they are just syntactic sugar for a normal function definition Like nested function definitions lambda functions can reference variables from the containing scope def make_incrementor n return lambda x x n f make_incrementor 42 f 0 42 f 1 43 The above example uses a lambda expression to return a function Another use is to pass a small function as an argument pairs 1 one 2 two 3 three 4 four pairs sort key lambda pair pair 1 pairs 4 four 1 one 3 three 2 two 4 8 7 Documentation Strings Here are some conventions about the content and formatting of documentation strings The first line should always be a short concise summary of the object s purpose For brevity it should not explicitly state the object s name or type since these are available by other means except if the name happens to be a verb describing a function s operation This line should begin with a capital letter and end with a period If there are more lines in the documentation string the second line should be blank visually separating the summary from the rest of the description The following lines should be one or more paragraphs describing the object s calling conventions its side effects etc The Python parser does not strip indentation from multi line string literals in Python so tools that process documentation have to strip indentation if desired This is done using the following convention The first non blank line after the first line of the string determines the amount of indentation for the entire documentation string We can t use the first line since it is generally adjacent to the string s opening quotes so its indentation is not apparent in the string literal Whitespace equivalent to this indentation is then stripped from the start of all lines of the string Lines that are indented less should not occur but if they occur all their leading whitespace should be stripped Equivalence of whitespace should be tested after expansion of tabs to 8 spaces normally Here is an example of a multi line docstring def my_function Do nothing but document it No really it doesn t do anything pass print my_function __doc__ Do nothing but document it No really it doesn t do anything 4 8 8 Function Annotations Function annotations are completely optional metadata information about the types used by user defined functions see PEP 3107 and PEP 484 for more information Annotations are stored in the __annotations__ attribute of the function as a dictionary and have no effect on any other part of the function Parameter annotations are defined by a colon after the parameter name followed by an expression evaluating to the value of the annotation Return annotations are defined by a literal followed by an expression between the parameter list and the colon denoting the end of the def statement The following example has a required argume,en
703,nt an optional argument and the return value annotated def f ham str eggs str eggs str print Annotations f __annotations__ print Arguments ham eggs return ham and eggs f spam Annotations ham class str return class str eggs class str Arguments spam eggs spam and eggs 4 9 Intermezzo Coding Style Now that you are about to write longer more complex pieces of Python it is a good time to talk about coding style Most languages can be written or more concise formatted in different styles some are more readable than others Making it easy for others to read your code is always a good idea and adopting a nice coding style helps tremendously for that For Python PEP 8 has emerged as the style guide that most projects adhere to it promotes a very readable and eye pleasing coding style Every Python developer should read it at some point here are the most important points extracted for you Use 4 space indentation and no tabs 4 spaces are a good compromise between small indentation allows greater nesting depth and large indentation easier to read Tabs introduce confusion and are best left out Wrap lines so that they don t exceed 79 characters This helps users with small displays and makes it possible to have several code files side by side on larger displays Use blank lines to separate functions and classes and larger blocks of code inside functions When possible put comments on a line of their own Use docstrings Use spaces around operators and after commas but not directly inside bracketing constructs a f 1 2 g 3 4 Name your classes and functions consistently the convention is to use UpperCamelCase for classes and lowercase_with_underscores for functions and methods Always use self as the name for the first method argument see A First Look at Classes for more on classes and methods Don t use fancy encodings if your code is meant to be used in international environments Python s default UTF 8 or even plain ASCII work best in any case Likewise don t use non ASCII characters in identifiers if there is only the slightest chance people speaking a different language will read or maintain the code Footnotes 1 Actually call by object reference would be a better description since if a mutable object is passed the caller will see any changes the callee makes to it items inserted into a list,en
704,uuid UUID objects according to RFC 4122 Source code Lib uuid py This module provides immutable UUID objects the UUID class and the functions uuid1 uuid3 uuid4 uuid5 for generating version 1 3 4 and 5 UUIDs as specified in RFC 4122 If all you want is a unique ID you should probably call uuid1 or uuid4 Note that uuid1 may compromise privacy since it creates a UUID containing the computer s network address uuid4 creates a random UUID Depending on support from the underlying platform uuid1 may or may not return a safe UUID A safe UUID is one which is generated using synchronization methods that ensure no two processes can obtain the same UUID All instances of UUID have an is_safe attribute which relays any information about the UUID s safety using this enumeration class uuid SafeUUID New in version 3 7 safe The UUID was generated by the platform in a multiprocessing safe way unsafe The UUID was not generated in a multiprocessing safe way unknown The platform does not provide information on whether the UUID was generated safely or not class uuid UUID hex None bytes None bytes_le None fields None int None version None is_safe SafeUUID unknown Create a UUID from either a string of 32 hexadecimal digits a string of 16 bytes in big endian order as the bytes argument a string of 16 bytes in little endian order as the bytes_le argument a tuple of six integers 32 bit time_low 16 bit time_mid 16 bit time_hi_version 8 bit clock_seq_hi_variant 8 bit clock_seq_low 48 bit node as the fields argument or a single 128 bit integer as the int argument When a string of hex digits is given curly braces hyphens and a URN prefix are all optional For example these expressions all yield the same UUID UUID 12345678 1234 5678 1234 567812345678 UUID 12345678123456781234567812345678 UUID urn uuid 12345678 1234 5678 1234 567812345678 UUID bytes b x12 x34 x56 x78 4 UUID bytes_le b x78 x56 x34 x12 x34 x12 x78 x56 b x12 x34 x56 x78 x12 x34 x56 x78 UUID fields 0x12345678 0x1234 0x5678 0x12 0x34 0x567812345678 UUID int 0x12345678123456781234567812345678 Exactly one of hex bytes bytes_le fields or int must be given The version argument is optional if given the resulting UUID will have its variant and version number set according to RFC 4122 overriding bits in the given hex bytes bytes_le fields or int Comparison of UUID objects are made by way of comparing their UUID int attributes Comparison with a non UUID object raises a TypeError str uuid returns a string in the form 12345678 1234 5678 1234 567812345678 where the 32 hexadecimal digits represent the UUID UUID instances have these read only attributes UUID bytes The UUID as a 16 byte string containing the six integer fields in big endian byte order UUID bytes_le The UUID as a 16 byte string with time_low time_mid and time_hi_version in little endian byte order UUID fields A tuple of the six integer fields of the UUID which are also available as six individual attributes and two derived attributes Field Meaning UUID time_low The first 32 bits of the UUID UUID time_mid The next 16 bits of the UUID UUID time_hi_version The next 16 bits of the UUID UUID clock_seq_hi_variant The next 8 bits of the UUID UUID clock_seq_low The next 8 bits of the UUID UUID node The last 48 bits of the UUID UUID time The 60 bit timestamp UUID clock_seq The 14 bit sequence number UUID hex The UUID as a 32 character lowercase hexadecimal string UUID int The UUID as a 128 bit integer UUID urn The UUID as a URN as specified in RFC 4122 UUID variant The UUID variant which determines the internal layout of the UUID This will be one of the constants RESERVED_NCS RFC_4122 RESERVED_MICROSOFT or RESERVED_FUTURE UUID version The UUID version number 1 through 5 meaningful only when the variant is RFC_4122 UUID is_safe An enumeration of SafeUUID which indicates whether the platform generated the UUID in a multiprocessing safe way New in version 3 7 The uuid module defines the following functions uuid getnode Get the hardware address as a 48 bit positive integer The first time this runs it may launch a separate program which could be quite slow I,en
705,f all attempts to obtain the hardware address fail we choose a random 48 bit number with the multicast bit least significant bit of the first octet set to 1 as recommended in RFC 4122 Hardware address means the MAC address of a network interface On a machine with multiple network interfaces universally administered MAC addresses i e where the second least significant bit of the first octet is unset will be preferred over locally administered MAC addresses but with no other ordering guarantees Changed in version 3 7 Universally administered MAC addresses are preferred over locally administered MAC addresses since the former are guaranteed to be globally unique while the latter are not uuid uuid1 node None clock_seq None Generate a UUID from a host ID sequence number and the current time If node is not given getnode is used to obtain the hardware address If clock_seq is given it is used as the sequence number otherwise a random 14 bit sequence number is chosen uuid uuid3 namespace name Generate a UUID based on the MD5 hash of a namespace identifier which is a UUID and a name which is a bytes object or a string that will be encoded using UTF 8 uuid uuid4 Generate a random UUID uuid uuid5 namespace name Generate a UUID based on the SHA 1 hash of a namespace identifier which is a UUID and a name which is a bytes object or a string that will be encoded using UTF 8 The uuid module defines the following namespace identifiers for use with uuid3 or uuid5 uuid NAMESPACE_DNS When this namespace is specified the name string is a fully qualified domain name uuid NAMESPACE_URL When this namespace is specified the name string is a URL uuid NAMESPACE_OID When this namespace is specified the name string is an ISO OID uuid NAMESPACE_X500 When this namespace is specified the name string is an X 500 DN in DER or a text output format The uuid module defines the following constants for the possible values of the variant attribute uuid RESERVED_NCS Reserved for NCS compatibility uuid RFC_4122 Specifies the UUID layout given in RFC 4122 uuid RESERVED_MICROSOFT Reserved for Microsoft compatibility uuid RESERVED_FUTURE Reserved for future definition See also RFC 4122 A Universally Unique IDentifier UUID URN Namespace This specification defines a Uniform Resource Name namespace for UUIDs the internal format of UUIDs and methods of generating UUIDs Command Line Usage New in version 3 12 The uuid module can be executed as a script from the command line python m uuid h u uuid1 uuid3 uuid4 uuid5 n NAMESPACE N NAME The following options are accepted h help Show the help message and exit u uuid uuid uuid Specify the function name to use to generate the uuid By default uuid4 is used n namespace namespace namespace The namespace is a UUID or ns where ns is a well known predefined UUID addressed by namespace name Such as dns url oid and x500 Only required for uuid3 uuid5 functions N name name name The name used as part of generating the uuid Only required for uuid3 uuid5 functions Example Here are some examples of typical usage of the uuid module import uuid make a UUID based on the host ID and current time uuid uuid1 UUID a8098c1a f86e 11da bd1a 00112444be1e make a UUID using an MD5 hash of a namespace UUID and a name uuid uuid3 uuid NAMESPACE_DNS python org UUID 6fa459ea ee8a 3ca4 894e db77e160355e make a random UUID uuid uuid4 UUID 16fd2706 8baf 433b 82eb 8c7fada847da make a UUID using a SHA 1 hash of a namespace UUID and a name uuid uuid5 uuid NAMESPACE_DNS python org UUID 886313e1 3b8a 5372 9b90 0c9aee199e5d make a UUID from a string of hex digits braces and hyphens ignored x uuid UUID 00010203 0405 0607 0809 0a0b0c0d0e0f convert a UUID to a string of hex digits in standard form str x 00010203 0405 0607 0809 0a0b0c0d0e0f get the raw 16 bytes of the UUID x bytes b x00 x01 x02 x03 x04 x05 x06 x07 x08 t n x0b x0c r x0e x0f make a UUID from a 16 byte string uuid UUID bytes x bytes UUID 00010203 0405 0607 0809 0a0b0c0d0e0f Command Line Example Here are some examples of typical usage of the uuid command line interface generate a random uuid by default uuid4 ,en
706,is used python m uuid generate a uuid using uuid1 python m uuid u uuid1 generate a uuid using uuid5 python m uuid u uuid5 n url N example com,et
707,1 Extending Python with C or C It is quite easy to add new built in modules to Python if you know how to program in C Such extension modules can do two things that can t be done directly in Python they can implement new built in object types and they can call C library functions and system calls To support extensions the Python API Application Programmers Interface defines a set of functions macros and variables that provide access to most aspects of the Python run time system The Python API is incorporated in a C source file by including the header Python h The compilation of an extension module depends on its intended use as well as on your system setup details are given in later chapters Note The C extension interface is specific to CPython and extension modules do not work on other Python implementations In many cases it is possible to avoid writing C extensions and preserve portability to other implementations For example if your use case is calling C library functions or system calls you should consider using the ctypes module or the cffi library rather than writing custom C code These modules let you write Python code to interface with C code and are more portable between implementations of Python than writing and compiling a C extension module 1 1 A Simple Example Let s create an extension module called spam the favorite food of Monty Python fans and let s say we want to create a Python interface to the C library function system 1 This function takes a null terminated character string as argument and returns an integer We want this function to be callable from Python as follows import spam status spam system ls l Begin by creating a file spammodule c Historically if a module is called spam the C file containing its implementation is called spammodule c if the module name is very long like spammify the module name can be just spammify c The first two lines of our file can be define PY_SSIZE_T_CLEAN include Python h which pulls in the Python API you can add a comment describing the purpose of the module and a copyright notice if you like Note Since Python may define some pre processor definitions which affect the standard headers on some systems you must include Python h before any standard headers are included It is recommended to always define PY_SSIZE_T_CLEAN before including Python h See Extracting Parameters in Extension Functions for a description of this macro All user visible symbols defined by Python h have a prefix of Py or PY except those defined in standard header files For convenience and since they are used extensively by the Python interpreter Python h includes a few standard header files stdio h string h errno h and stdlib h If the latter header file does not exist on your system it declares the functions malloc free and realloc directly The next thing we add to our module file is the C function that will be called when the Python expression spam system string is evaluated we ll see shortly how it ends up being called static PyObject spam_system PyObject self PyObject args const char command int sts if PyArg_ParseTuple args s command return NULL sts system command return PyLong_FromLong sts There is a straightforward translation from the argument list in Python for example the single expression ls l to the arguments passed to the C function The C function always has two arguments conventionally named self and args The self argument points to the module object for module level functions for a method it would point to the object instance The args argument will be a pointer to a Python tuple object containing the arguments Each item of the tuple corresponds to an argument in the call s argument list The arguments are Python objects in order to do anything with them in our C function we have to convert them to C values The function PyArg_ParseTuple in the Python API checks the argument types and converts them to C values It uses a template string to determine the required types of the arguments as well as the types of the C variables into which to store the converted values More about this later PyArg_P,en
708,arseTuple returns true nonzero if all arguments have the right type and its components have been stored in the variables whose addresses are passed It returns false zero if an invalid argument list was passed In the latter case it also raises an appropriate exception so the calling function can return NULL immediately as we saw in the example 1 2 Intermezzo Errors and Exceptions An important convention throughout the Python interpreter is the following when a function fails it should set an exception condition and return an error value usually 1 or a NULL pointer Exception information is stored in three members of the interpreter s thread state These are NULL if there is no exception Otherwise they are the C equivalents of the members of the Python tuple returned by sys exc_info These are the exception type exception instance and a traceback object It is important to know about them to understand how errors are passed around The Python API defines a number of functions to set various types of exceptions The most common one is PyErr_SetString Its arguments are an exception object and a C string The exception object is usually a predefined object like PyExc_ZeroDivisionError The C string indicates the cause of the error and is converted to a Python string object and stored as the associated value of the exception Another useful function is PyErr_SetFromErrno which only takes an exception argument and constructs the associated value by inspection of the global variable errno The most general function is PyErr_SetObject which takes two object arguments the exception and its associated value You don t need to Py_INCREF the objects passed to any of these functions You can test non destructively whether an exception has been set with PyErr_Occurred This returns the current exception object or NULL if no exception has occurred You normally don t need to call PyErr_Occurred to see whether an error occurred in a function call since you should be able to tell from the return value When a function f that calls another function g detects that the latter fails f should itself return an error value usually NULL or 1 It should not call one of the PyErr_ functions one has already been called by g f s caller is then supposed to also return an error indication to its caller again without calling PyErr_ and so on the most detailed cause of the error was already reported by the function that first detected it Once the error reaches the Python interpreter s main loop this aborts the currently executing Python code and tries to find an exception handler specified by the Python programmer There are situations where a module can actually give a more detailed error message by calling another PyErr_ function and in such cases it is fine to do so As a general rule however this is not necessary and can cause information about the cause of the error to be lost most operations can fail for a variety of reasons To ignore an exception set by a function call that failed the exception condition must be cleared explicitly by calling PyErr_Clear The only time C code should call PyErr_Clear is if it doesn t want to pass the error on to the interpreter but wants to handle it completely by itself possibly by trying something else or pretending nothing went wrong Every failing malloc call must be turned into an exception the direct caller of malloc or realloc must call PyErr_NoMemory and return a failure indicator itself All the object creating functions for example PyLong_FromLong already do this so this note is only relevant to those who call malloc directly Also note that with the important exception of PyArg_ParseTuple and friends functions that return an integer status usually return a positive value or zero for success and 1 for failure like Unix system calls Finally be careful to clean up garbage by making Py_XDECREF or Py_DECREF calls for objects you have already created when you return an error indicator The choice of which exception to raise is entirely yours There are predeclared C objects corresponding to all built in Python exceptions such as PyExc,en
709,_ZeroDivisionError which you can use directly Of course you should choose exceptions wisely don t use PyExc_TypeError to mean that a file couldn t be opened that should probably be PyExc_OSError If something s wrong with the argument list the PyArg_ParseTuple function usually raises PyExc_TypeError If you have an argument whose value must be in a particular range or must satisfy other conditions PyExc_ValueError is appropriate You can also define a new exception that is unique to your module For this you usually declare a static object variable at the beginning of your file static PyObject SpamError and initialize it in your module s initialization function PyInit_spam with an exception object PyMODINIT_FUNC PyInit_spam void PyObject m m PyModule_Create spammodule if m NULL return NULL SpamError PyErr_NewException spam error NULL NULL Py_XINCREF SpamError if PyModule_AddObject m error SpamError 0 Py_XDECREF SpamError Py_CLEAR SpamError Py_DECREF m return NULL return m Note that the Python name for the exception object is spam error The PyErr_NewException function may create a class with the base class being Exception unless another class is passed in instead of NULL described in Built in Exceptions Note also that the SpamError variable retains a reference to the newly created exception class this is intentional Since the exception could be removed from the module by external code an owned reference to the class is needed to ensure that it will not be discarded causing SpamError to become a dangling pointer Should it become a dangling pointer C code which raises the exception could cause a core dump or other unintended side effects We discuss the use of PyMODINIT_FUNC as a function return type later in this sample The spam error exception can be raised in your extension module using a call to PyErr_SetString as shown below static PyObject spam_system PyObject self PyObject args const char command int sts if PyArg_ParseTuple args s command return NULL sts system command if sts 0 PyErr_SetString SpamError System command failed return NULL return PyLong_FromLong sts 1 3 Back to the Example Going back to our example function you should now be able to understand this statement if PyArg_ParseTuple args s command return NULL It returns NULL the error indicator for functions returning object pointers if an error is detected in the argument list relying on the exception set by PyArg_ParseTuple Otherwise the string value of the argument has been copied to the local variable command This is a pointer assignment and you are not supposed to modify the string to which it points so in Standard C the variable command should properly be declared as const char command The next statement is a call to the Unix function system passing it the string we just got from PyArg_ParseTuple sts system command Our spam system function must return the value of sts as a Python object This is done using the function PyLong_FromLong return PyLong_FromLong sts In this case it will return an integer object Yes even integers are objects on the heap in Python If you have a C function that returns no useful argument a function returning void the corresponding Python function must return None You need this idiom to do so which is implemented by the Py_RETURN_NONE macro Py_INCREF Py_None return Py_None Py_None is the C name for the special Python object None It is a genuine Python object rather than a NULL pointer which means error in most contexts as we have seen 1 4 The Module s Method Table and Initialization Function I promised to show how spam_system is called from Python programs First we need to list its name and address in a method table static PyMethodDef SpamMethods system spam_system METH_VARARGS Execute a shell command NULL NULL 0 NULL Sentinel Note the third entry METH_VARARGS This is a flag telling the interpreter the calling convention to be used for the C function It should normally always be METH_VARARGS or METH_VARARGS METH_KEYWORDS a value of 0 means that an obsolete variant of PyArg_ParseTuple is used When using only METH_VARARGS the function ,en
710,should expect the Python level parameters to be passed in as a tuple acceptable for parsing via PyArg_ParseTuple more information on this function is provided below The METH_KEYWORDS bit may be set in the third field if keyword arguments should be passed to the function In this case the C function should accept a third PyObject parameter which will be a dictionary of keywords Use PyArg_ParseTupleAndKeywords to parse the arguments to such a function The method table must be referenced in the module definition structure static struct PyModuleDef spammodule PyModuleDef_HEAD_INIT spam name of module spam_doc module documentation may be NULL 1 size of per interpreter state of the module or 1 if the module keeps state in global variables SpamMethods This structure in turn must be passed to the interpreter in the module s initialization function The initialization function must be named PyInit_name where name is the name of the module and should be the only non static item defined in the module file PyMODINIT_FUNC PyInit_spam void return PyModule_Create spammodule Note that PyMODINIT_FUNC declares the function as PyObject return type declares any special linkage declarations required by the platform and for C declares the function as extern C When the Python program imports module spam for the first time PyInit_spam is called See below for comments about embedding Python It calls PyModule_Create which returns a module object and inserts built in function objects into the newly created module based upon the table an array of PyMethodDef structures found in the module definition PyModule_Create returns a pointer to the module object that it creates It may abort with a fatal error for certain errors or return NULL if the module could not be initialized satisfactorily The init function must return the module object to its caller so that it then gets inserted into sys modules When embedding Python the PyInit_spam function is not called automatically unless there s an entry in the PyImport_Inittab table To add the module to the initialization table use PyImport_AppendInittab optionally followed by an import of the module int main int argc char argv wchar_t program Py_DecodeLocale argv 0 NULL if program NULL fprintf stderr Fatal error cannot decode argv 0 n exit 1 Add a built in module before Py_Initialize if PyImport_AppendInittab spam PyInit_spam 1 fprintf stderr Error could not extend in built modules table n exit 1 Pass argv 0 to the Python interpreter Py_SetProgramName program Initialize the Python interpreter Required If this step fails it will be a fatal error Py_Initialize Optionally import the module alternatively import can be deferred until the embedded script imports it PyObject pmodule PyImport_ImportModule spam if pmodule PyErr_Print fprintf stderr Error could not import module spam n PyMem_RawFree program return 0 Note Removing entries from sys modules or importing compiled modules into multiple interpreters within a process or following a fork without an intervening exec can create problems for some extension modules Extension module authors should exercise caution when initializing internal data structures A more substantial example module is included in the Python source distribution as Modules xxmodule c This file may be used as a template or simply read as an example Note Unlike our spam example xxmodule uses multi phase initialization new in Python 3 5 where a PyModuleDef structure is returned from PyInit_spam and creation of the module is left to the import machinery For details on multi phase initialization see PEP 489 1 5 Compilation and Linkage There are two more things to do before you can use your new extension compiling and linking it with the Python system If you use dynamic loading the details may depend on the style of dynamic loading your system uses see the chapters about building extension modules chapter Building C and C Extensions and additional information that pertains only to building on Windows chapter Building C and C Extensions on Windows for more information about this If you can t use dynami,en
711,c loading or if you want to make your module a permanent part of the Python interpreter you will have to change the configuration setup and rebuild the interpreter Luckily this is very simple on Unix just place your file spammodule c for example in the Modules directory of an unpacked source distribution add a line to the file Modules Setup local describing your file spam spammodule o and rebuild the interpreter by running make in the toplevel directory You can also run make in the Modules subdirectory but then you must first rebuild Makefile there by running make Makefile This is necessary each time you change the Setup file If your module requires additional libraries to link with these can be listed on the line in the configuration file as well for instance spam spammodule o lX11 1 6 Calling Python Functions from C So far we have concentrated on making C functions callable from Python The reverse is also useful calling Python functions from C This is especially the case for libraries that support so called callback functions If a C interface makes use of callbacks the equivalent Python often needs to provide a callback mechanism to the Python programmer the implementation will require calling the Python callback functions from a C callback Other uses are also imaginable Fortunately the Python interpreter is easily called recursively and there is a standard interface to call a Python function I won t dwell on how to call the Python parser with a particular string as input if you re interested have a look at the implementation of the c command line option in Modules main c from the Python source code Calling a Python function is easy First the Python program must somehow pass you the Python function object You should provide a function or some other interface to do this When this function is called save a pointer to the Python function object be careful to Py_INCREF it in a global variable or wherever you see fit For example the following function might be part of a module definition static PyObject my_callback NULL static PyObject my_set_callback PyObject dummy PyObject args PyObject result NULL PyObject temp if PyArg_ParseTuple args O set_callback temp if PyCallable_Check temp PyErr_SetString PyExc_TypeError parameter must be callable return NULL Py_XINCREF temp Add a reference to new callback Py_XDECREF my_callback Dispose of previous callback my_callback temp Remember new callback Boilerplate to return None Py_INCREF Py_None result Py_None return result This function must be registered with the interpreter using the METH_VARARGS flag this is described in section The Module s Method Table and Initialization Function The PyArg_ParseTuple function and its arguments are documented in section Extracting Parameters in Extension Functions The macros Py_XINCREF and Py_XDECREF increment decrement the reference count of an object and are safe in the presence of NULL pointers but note that temp will not be NULL in this context More info on them in section Reference Counts Later when it is time to call the function you call the C function PyObject_CallObject This function has two arguments both pointers to arbitrary Python objects the Python function and the argument list The argument list must always be a tuple object whose length is the number of arguments To call the Python function with no arguments pass in NULL or an empty tuple to call it with one argument pass a singleton tuple Py_BuildValue returns a tuple when its format string consists of zero or more format codes between parentheses For example int arg PyObject arglist PyObject result arg 123 Time to call the callback arglist Py_BuildValue i arg result PyObject_CallObject my_callback arglist Py_DECREF arglist PyObject_CallObject returns a Python object pointer this is the return value of the Python function PyObject_CallObject is reference count neutral with respect to its arguments In the example a new tuple was created to serve as the argument list which is Py_DECREF ed immediately after the PyObject_CallObject call The return value of PyObject_CallObject is new ei,en
712,ther it is a brand new object or it is an existing object whose reference count has been incremented So unless you want to save it in a global variable you should somehow Py_DECREF the result even especially if you are not interested in its value Before you do this however it is important to check that the return value isn t NULL If it is the Python function terminated by raising an exception If the C code that called PyObject_CallObject is called from Python it should now return an error indication to its Python caller so the interpreter can print a stack trace or the calling Python code can handle the exception If this is not possible or desirable the exception should be cleared by calling PyErr_Clear For example if result NULL return NULL Pass error back use result Py_DECREF result Depending on the desired interface to the Python callback function you may also have to provide an argument list to PyObject_CallObject In some cases the argument list is also provided by the Python program through the same interface that specified the callback function It can then be saved and used in the same manner as the function object In other cases you may have to construct a new tuple to pass as the argument list The simplest way to do this is to call Py_BuildValue For example if you want to pass an integral event code you might use the following code PyObject arglist arglist Py_BuildValue l eventcode result PyObject_CallObject my_callback arglist Py_DECREF arglist if result NULL return NULL Pass error back Here maybe use the result Py_DECREF result Note the placement of Py_DECREF arglist immediately after the call before the error check Also note that strictly speaking this code is not complete Py_BuildValue may run out of memory and this should be checked You may also call a function with keyword arguments by using PyObject_Call which supports arguments and keyword arguments As in the above example we use Py_BuildValue to construct the dictionary PyObject dict dict Py_BuildValue s i name val result PyObject_Call my_callback NULL dict Py_DECREF dict if result NULL return NULL Pass error back Here maybe use the result Py_DECREF result 1 7 Extracting Parameters in Extension Functions The PyArg_ParseTuple function is declared as follows int PyArg_ParseTuple PyObject arg const char format The arg argument must be a tuple object containing an argument list passed from Python to a C function The format argument must be a format string whose syntax is explained in Parsing arguments and building values in the Python C API Reference Manual The remaining arguments must be addresses of variables whose type is determined by the format string Note that while PyArg_ParseTuple checks that the Python arguments have the required types it cannot check the validity of the addresses of C variables passed to the call if you make mistakes there your code will probably crash or at least overwrite random bits in memory So be careful Note that any Python object references which are provided to the caller are borrowed references do not decrement their reference count Some example calls define PY_SSIZE_T_CLEAN Make s use Py_ssize_t rather than int include Python h int ok int i j long k l const char s Py_ssize_t size ok PyArg_ParseTuple args No arguments Python call f ok PyArg_ParseTuple args s s A string Possible Python call f whoops ok PyArg_ParseTuple args lls k l s Two longs and a string Possible Python call f 1 2 three ok PyArg_ParseTuple args ii s i j s size A pair of ints and a string whose size is also returned Possible Python call f 1 2 three const char file const char mode r int bufsize 0 ok PyArg_ParseTuple args s si file mode bufsize A string and optionally another string and an integer Possible Python calls f spam f spam w f spam wb 100000 int left top right bottom h v ok PyArg_ParseTuple args ii ii ii left top right bottom h v A rectangle and a point Possible Python call f 0 0 400 300 10 10 Py_complex c ok PyArg_ParseTuple args D myfunction c a complex also providing a function name for errors Possible Python call myfunction 1 2j 1 8 Keyword Par,en
713,ameters for Extension Functions The PyArg_ParseTupleAndKeywords function is declared as follows int PyArg_ParseTupleAndKeywords PyObject arg PyObject kwdict const char format char kwlist The arg and format parameters are identical to those of the PyArg_ParseTuple function The kwdict parameter is the dictionary of keywords received as the third parameter from the Python runtime The kwlist parameter is a NULL terminated list of strings which identify the parameters the names are matched with the type information from format from left to right On success PyArg_ParseTupleAndKeywords returns true otherwise it returns false and raises an appropriate exception Note Nested tuples cannot be parsed when using keyword arguments Keyword parameters passed in which are not present in the kwlist will cause TypeError to be raised Here is an example module which uses keywords based on an example by Geoff Philbrick philbrick hks com define PY_SSIZE_T_CLEAN Make s use Py_ssize_t rather than int include Python h static PyObject keywdarg_parrot PyObject self PyObject args PyObject keywds int voltage const char state a stiff const char action voom const char type Norwegian Blue static char kwlist voltage state action type NULL if PyArg_ParseTupleAndKeywords args keywds i sss kwlist voltage state action type return NULL printf This parrot wouldn t s if you put i Volts through it n action voltage printf Lovely plumage the s It s s n type state Py_RETURN_NONE static PyMethodDef keywdarg_methods The cast of the function is necessary since PyCFunction values only take two PyObject parameters and keywdarg_parrot takes three parrot PyCFunction void void keywdarg_parrot METH_VARARGS METH_KEYWORDS Print a lovely skit to standard output NULL NULL 0 NULL sentinel static struct PyModuleDef keywdargmodule PyModuleDef_HEAD_INIT keywdarg NULL 1 keywdarg_methods PyMODINIT_FUNC PyInit_keywdarg void return PyModule_Create keywdargmodule 1 9 Building Arbitrary Values This function is the counterpart to PyArg_ParseTuple It is declared as follows PyObject Py_BuildValue const char format It recognizes a set of format units similar to the ones recognized by PyArg_ParseTuple but the arguments which are input to the function not output must not be pointers just values It returns a new Python object suitable for returning from a C function called from Python One difference with PyArg_ParseTuple while the latter requires its first argument to be a tuple since Python argument lists are always represented as tuples internally Py_BuildValue does not always build a tuple It builds a tuple only if its format string contains two or more format units If the format string is empty it returns None if it contains exactly one format unit it returns whatever object is described by that format unit To force it to return a tuple of size 0 or one parenthesize the format string Examples to the left the call to the right the resulting Python value Py_BuildValue None Py_BuildValue i 123 123 Py_BuildValue iii 123 456 789 123 456 789 Py_BuildValue s hello hello Py_BuildValue y hello b hello Py_BuildValue ss hello world hello world Py_BuildValue s hello 4 hell Py_BuildValue y hello 4 b hell Py_BuildValue Py_BuildValue i 123 123 Py_BuildValue ii 123 456 123 456 Py_BuildValue i i 123 456 123 456 Py_BuildValue i i 123 456 123 456 Py_BuildValue s i s i abc 123 def 456 abc 123 def 456 Py_BuildValue ii ii ii 1 2 3 4 5 6 1 2 3 4 5 6 1 10 Reference Counts In languages like C or C the programmer is responsible for dynamic allocation and deallocation of memory on the heap In C this is done using the functions malloc and free In C the operators new and delete are used with essentially the same meaning and we ll restrict the following discussion to the C case Every block of memory allocated with malloc should eventually be returned to the pool of available memory by exactly one call to free It is important to call free at the right time If a block s address is forgotten but free is not called for it the memory it occupies cannot be reused until the program terminates This is called a memory leak On th,en
714,e other hand if a program calls free for a block and then continues to use the block it creates a conflict with re use of the block through another malloc call This is called using freed memory It has the same bad consequences as referencing uninitialized data core dumps wrong results mysterious crashes Common causes of memory leaks are unusual paths through the code For instance a function may allocate a block of memory do some calculation and then free the block again Now a change in the requirements for the function may add a test to the calculation that detects an error condition and can return prematurely from the function It s easy to forget to free the allocated memory block when taking this premature exit especially when it is added later to the code Such leaks once introduced often go undetected for a long time the error exit is taken only in a small fraction of all calls and most modern machines have plenty of virtual memory so the leak only becomes apparent in a long running process that uses the leaking function frequently Therefore it s important to prevent leaks from happening by having a coding convention or strategy that minimizes this kind of errors Since Python makes heavy use of malloc and free it needs a strategy to avoid memory leaks as well as the use of freed memory The chosen method is called reference counting The principle is simple every object contains a counter which is incremented when a reference to the object is stored somewhere and which is decremented when a reference to it is deleted When the counter reaches zero the last reference to the object has been deleted and the object is freed An alternative strategy is called automatic garbage collection Sometimes reference counting is also referred to as a garbage collection strategy hence my use of automatic to distinguish the two The big advantage of automatic garbage collection is that the user doesn t need to call free explicitly Another claimed advantage is an improvement in speed or memory usage this is no hard fact however The disadvantage is that for C there is no truly portable automatic garbage collector while reference counting can be implemented portably as long as the functions malloc and free are available which the C Standard guarantees Maybe some day a sufficiently portable automatic garbage collector will be available for C Until then we ll have to live with reference counts While Python uses the traditional reference counting implementation it also offers a cycle detector that works to detect reference cycles This allows applications to not worry about creating direct or indirect circular references these are the weakness of garbage collection implemented using only reference counting Reference cycles consist of objects which contain possibly indirect references to themselves so that each object in the cycle has a reference count which is non zero Typical reference counting implementations are not able to reclaim the memory belonging to any objects in a reference cycle or referenced from the objects in the cycle even though there are no further references to the cycle itself The cycle detector is able to detect garbage cycles and can reclaim them The gc module exposes a way to run the detector the collect function as well as configuration interfaces and the ability to disable the detector at runtime 1 10 1 Reference Counting in Python There are two macros Py_INCREF x and Py_DECREF x which handle the incrementing and decrementing of the reference count Py_DECREF also frees the object when the count reaches zero For flexibility it doesn t call free directly rather it makes a call through a function pointer in the object s type object For this purpose and others every object also contains a pointer to its type object The big question now remains when to use Py_INCREF x and Py_DECREF x Let s first introduce some terms Nobody owns an object however you can own a reference to an object An object s reference count is now defined as the number of owned references to it The owner of a reference is responsible for calling Py_DECREF wh,en
715,en the reference is no longer needed Ownership of a reference can be transferred There are three ways to dispose of an owned reference pass it on store it or call Py_DECREF Forgetting to dispose of an owned reference creates a memory leak It is also possible to borrow 2 a reference to an object The borrower of a reference should not call Py_DECREF The borrower must not hold on to the object longer than the owner from which it was borrowed Using a borrowed reference after the owner has disposed of it risks using freed memory and should be avoided completely 3 The advantage of borrowing over owning a reference is that you don t need to take care of disposing of the reference on all possible paths through the code in other words with a borrowed reference you don t run the risk of leaking when a premature exit is taken The disadvantage of borrowing over owning is that there are some subtle situations where in seemingly correct code a borrowed reference can be used after the owner from which it was borrowed has in fact disposed of it A borrowed reference can be changed into an owned reference by calling Py_INCREF This does not affect the status of the owner from which the reference was borrowed it creates a new owned reference and gives full owner responsibilities the new owner must dispose of the reference properly as well as the previous owner 1 10 2 Ownership Rules Whenever an object reference is passed into or out of a function it is part of the function s interface specification whether ownership is transferred with the reference or not Most functions that return a reference to an object pass on ownership with the reference In particular all functions whose function it is to create a new object such as PyLong_FromLong and Py_BuildValue pass ownership to the receiver Even if the object is not actually new you still receive ownership of a new reference to that object For instance PyLong_FromLong maintains a cache of popular values and can return a reference to a cached item Many functions that extract objects from other objects also transfer ownership with the reference for instance PyObject_GetAttrString The picture is less clear here however since a few common routines are exceptions PyTuple_GetItem PyList_GetItem PyDict_GetItem and PyDict_GetItemString all return references that you borrow from the tuple list or dictionary The function PyImport_AddModule also returns a borrowed reference even though it may actually create the object it returns this is possible because an owned reference to the object is stored in sys modules When you pass an object reference into another function in general the function borrows the reference from you if it needs to store it it will use Py_INCREF to become an independent owner There are exactly two important exceptions to this rule PyTuple_SetItem and PyList_SetItem These functions take over ownership of the item passed to them even if they fail Note that PyDict_SetItem and friends don t take over ownership they are normal When a C function is called from Python it borrows references to its arguments from the caller The caller owns a reference to the object so the borrowed reference s lifetime is guaranteed until the function returns Only when such a borrowed reference must be stored or passed on it must be turned into an owned reference by calling Py_INCREF The object reference returned from a C function that is called from Python must be an owned reference ownership is transferred from the function to its caller 1 10 3 Thin Ice There are a few situations where seemingly harmless use of a borrowed reference can lead to problems These all have to do with implicit invocations of the interpreter which can cause the owner of a reference to dispose of it The first and most important case to know about is using Py_DECREF on an unrelated object while borrowing a reference to a list item For instance void bug PyObject list PyObject item PyList_GetItem list 0 PyList_SetItem list 1 PyLong_FromLong 0L PyObject_Print item stdout 0 BUG This function first borrows a reference to list 0 then replaces ,en
716,list 1 with the value 0 and finally prints the borrowed reference Looks harmless right But it s not Let s follow the control flow into PyList_SetItem The list owns references to all its items so when item 1 is replaced it has to dispose of the original item 1 Now let s suppose the original item 1 was an instance of a user defined class and let s further suppose that the class defined a __del__ method If this class instance has a reference count of 1 disposing of it will call its __del__ method Since it is written in Python the __del__ method can execute arbitrary Python code Could it perhaps do something to invalidate the reference to item in bug You bet Assuming that the list passed into bug is accessible to the __del__ method it could execute a statement to the effect of del list 0 and assuming this was the last reference to that object it would free the memory associated with it thereby invalidating item The solution once you know the source of the problem is easy temporarily increment the reference count The correct version of the function reads void no_bug PyObject list PyObject item PyList_GetItem list 0 Py_INCREF item PyList_SetItem list 1 PyLong_FromLong 0L PyObject_Print item stdout 0 Py_DECREF item This is a true story An older version of Python contained variants of this bug and someone spent a considerable amount of time in a C debugger to figure out why his __del__ methods would fail The second case of problems with a borrowed reference is a variant involving threads Normally multiple threads in the Python interpreter can t get in each other s way because there is a global lock protecting Python s entire object space However it is possible to temporarily release this lock using the macro Py_BEGIN_ALLOW_THREADS and to re acquire it using Py_END_ALLOW_THREADS This is common around blocking I O calls to let other threads use the processor while waiting for the I O to complete Obviously the following function has the same problem as the previous one void bug PyObject list PyObject item PyList_GetItem list 0 Py_BEGIN_ALLOW_THREADS some blocking I O call Py_END_ALLOW_THREADS PyObject_Print item stdout 0 BUG 1 10 4 NULL Pointers In general functions that take object references as arguments do not expect you to pass them NULL pointers and will dump core or cause later core dumps if you do so Functions that return object references generally return NULL only to indicate that an exception occurred The reason for not testing for NULL arguments is that functions often pass the objects they receive on to other function if each function were to test for NULL there would be a lot of redundant tests and the code would run more slowly It is better to test for NULL only at the source when a pointer that may be NULL is received for example from malloc or from a function that may raise an exception The macros Py_INCREF and Py_DECREF do not check for NULL pointers however their variants Py_XINCREF and Py_XDECREF do The macros for checking for a particular object type Pytype_Check don t check for NULL pointers again there is much code that calls several of these in a row to test an object against various different expected types and this would generate redundant tests There are no variants with NULL checking The C function calling mechanism guarantees that the argument list passed to C functions args in the examples is never NULL in fact it guarantees that it is always a tuple 4 It is a severe error to ever let a NULL pointer escape to the Python user 1 11 Writing Extensions in C It is possible to write extension modules in C Some restrictions apply If the main program the Python interpreter is compiled and linked by the C compiler global or static objects with constructors cannot be used This is not a problem if the main program is linked by the C compiler Functions that will be called by the Python interpreter in particular module initialization functions have to be declared using extern C It is unnecessary to enclose the Python header files in extern C they use this form already if the symbol __cplusplus is defined all recent ,en
717,C compilers define this symbol 1 12 Providing a C API for an Extension Module Many extension modules just provide new functions and types to be used from Python but sometimes the code in an extension module can be useful for other extension modules For example an extension module could implement a type collection which works like lists without order Just like the standard Python list type has a C API which permits extension modules to create and manipulate lists this new collection type should have a set of C functions for direct manipulation from other extension modules At first sight this seems easy just write the functions without declaring them static of course provide an appropriate header file and document the C API And in fact this would work if all extension modules were always linked statically with the Python interpreter When modules are used as shared libraries however the symbols defined in one module may not be visible to another module The details of visibility depend on the operating system some systems use one global namespace for the Python interpreter and all extension modules Windows for example whereas others require an explicit list of imported symbols at module link time AIX is one example or offer a choice of different strategies most Unices And even if symbols are globally visible the module whose functions one wishes to call might not have been loaded yet Portability therefore requires not to make any assumptions about symbol visibility This means that all symbols in extension modules should be declared static except for the module s initialization function in order to avoid name clashes with other extension modules as discussed in section The Module s Method Table and Initialization Function And it means that symbols that should be accessible from other extension modules must be exported in a different way Python provides a special mechanism to pass C level information pointers from one extension module to another one Capsules A Capsule is a Python data type which stores a pointer void Capsules can only be created and accessed via their C API but they can be passed around like any other Python object In particular they can be assigned to a name in an extension module s namespace Other extension modules can then import this module retrieve the value of this name and then retrieve the pointer from the Capsule There are many ways in which Capsules can be used to export the C API of an extension module Each function could get its own Capsule or all C API pointers could be stored in an array whose address is published in a Capsule And the various tasks of storing and retrieving the pointers can be distributed in different ways between the module providing the code and the client modules Whichever method you choose it s important to name your Capsules properly The function PyCapsule_New takes a name parameter const char you re permitted to pass in a NULL name but we strongly encourage you to specify a name Properly named Capsules provide a degree of runtime type safety there is no feasible way to tell one unnamed Capsule from another In particular Capsules used to expose C APIs should be given a name following this convention modulename attributename The convenience function PyCapsule_Import makes it easy to load a C API provided via a Capsule but only if the Capsule s name matches this convention This behavior gives C API users a high degree of certainty that the Capsule they load contains the correct C API The following example demonstrates an approach that puts most of the burden on the writer of the exporting module which is appropriate for commonly used library modules It stores all C API pointers just one in the example in an array of void pointers which becomes the value of a Capsule The header file corresponding to the module provides a macro that takes care of importing the module and retrieving its C API pointers client modules only have to call this macro before accessing the C API The exporting module is a modification of the spam module from section A Simple Example The function spam syst,en
718,em does not call the C library function system directly but a function PySpam_System which would of course do something more complicated in reality such as adding spam to every command This function PySpam_System is also exported to other extension modules The function PySpam_System is a plain C function declared static like everything else static int PySpam_System const char command return system command The function spam_system is modified in a trivial way static PyObject spam_system PyObject self PyObject args const char command int sts if PyArg_ParseTuple args s command return NULL sts PySpam_System command return PyLong_FromLong sts In the beginning of the module right after the line include Python h two more lines must be added define SPAM_MODULE include spammodule h The define is used to tell the header file that it is being included in the exporting module not a client module Finally the module s initialization function must take care of initializing the C API pointer array PyMODINIT_FUNC PyInit_spam void PyObject m static void PySpam_API PySpam_API_pointers PyObject c_api_object m PyModule_Create spammodule if m NULL return NULL Initialize the C API pointer array PySpam_API PySpam_System_NUM void PySpam_System Create a Capsule containing the API pointer array s address c_api_object PyCapsule_New void PySpam_API spam _C_API NULL if PyModule_AddObject m _C_API c_api_object 0 Py_XDECREF c_api_object Py_DECREF m return NULL return m Note that PySpam_API is declared static otherwise the pointer array would disappear when PyInit_spam terminates The bulk of the work is in the header file spammodule h which looks like this ifndef Py_SPAMMODULE_H define Py_SPAMMODULE_H ifdef __cplusplus extern C endif Header file for spammodule C API functions define PySpam_System_NUM 0 define PySpam_System_RETURN int define PySpam_System_PROTO const char command Total number of C API pointers define PySpam_API_pointers 1 ifdef SPAM_MODULE This section is used when compiling spammodule c static PySpam_System_RETURN PySpam_System PySpam_System_PROTO else This section is used in modules that use spammodule s API static void PySpam_API define PySpam_System PySpam_System_RETURN PySpam_System_PROTO PySpam_API PySpam_System_NUM Return 1 on error 0 on success PyCapsule_Import will set an exception if there s an error static int import_spam void PySpam_API void PyCapsule_Import spam _C_API 0 return PySpam_API NULL 0 1 endif ifdef __cplusplus endif endif defined Py_SPAMMODULE_H All that a client module must do in order to have access to the function PySpam_System is to call the function or rather macro import_spam in its initialization function PyMODINIT_FUNC PyInit_client void PyObject m m PyModule_Create clientmodule if m NULL return NULL if import_spam 0 return NULL additional initialization can happen here return m The main disadvantage of this approach is that the file spammodule h is rather complicated However the basic structure is the same for each function that is exported so it has to be learned only once Finally it should be mentioned that Capsules offer additional functionality which is especially useful for memory allocation and deallocation of the pointer stored in a Capsule The details are described in the Python C API Reference Manual in the section Capsules and in the implementation of Capsules files Include pycapsule h and Objects pycapsule c in the Python source code distribution Footnotes 1 An interface for this function already exists in the standard module os it was chosen as a simple and straightforward example 2 The metaphor of borrowing a reference is not completely correct the owner still has a copy of the reference 3 Checking that the reference count is at least 1 does not work the reference count itself could be in freed memory and may thus be reused for another object 4 These guarantees don t hold when you use the old style calling convention this is still found in much existing code,en
719,Integer Objects All integers are implemented as long integer objects of arbitrary size On error most PyLong_As APIs return return type 1 which cannot be distinguished from a number Use PyErr_Occurred to disambiguate type PyLongObject Part of the Limited API as an opaque struct This subtype of PyObject represents a Python integer object PyTypeObject PyLong_Type Part of the Stable ABI This instance of PyTypeObject represents the Python integer type This is the same object as int in the Python layer int PyLong_Check PyObject p Return true if its argument is a PyLongObject or a subtype of PyLongObject This function always succeeds int PyLong_CheckExact PyObject p Return true if its argument is a PyLongObject but not a subtype of PyLongObject This function always succeeds PyObject PyLong_FromLong long v Return value New reference Part of the Stable ABI Return a new PyLongObject object from v or NULL on failure The current implementation keeps an array of integer objects for all integers between 5 and 256 When you create an int in that range you actually just get back a reference to the existing object PyObject PyLong_FromUnsignedLong unsigned long v Return value New reference Part of the Stable ABI Return a new PyLongObject object from a C unsigned long or NULL on failure PyObject PyLong_FromSsize_t Py_ssize_t v Return value New reference Part of the Stable ABI Return a new PyLongObject object from a C Py_ssize_t or NULL on failure PyObject PyLong_FromSize_t size_t v Return value New reference Part of the Stable ABI Return a new PyLongObject object from a C size_t or NULL on failure PyObject PyLong_FromLongLong long long v Return value New reference Part of the Stable ABI Return a new PyLongObject object from a C long long or NULL on failure PyObject PyLong_FromUnsignedLongLong unsigned long long v Return value New reference Part of the Stable ABI Return a new PyLongObject object from a C unsigned long long or NULL on failure PyObject PyLong_FromDouble double v Return value New reference Part of the Stable ABI Return a new PyLongObject object from the integer part of v or NULL on failure PyObject PyLong_FromString const char str char pend int base Return value New reference Part of the Stable ABI Return a new PyLongObject based on the string value in str which is interpreted according to the radix in base or NULL on failure If pend is non NULL pend will point to the end of str on success or to the first character that could not be processed on error If base is 0 str is interpreted using the Integer literals definition in this case leading zeros in a non zero decimal number raises a ValueError If base is not 0 it must be between 2 and 36 inclusive Leading and trailing whitespace and single underscores after a base specifier and between digits are ignored If there are no digits or str is not NULL terminated following the digits and trailing whitespace ValueError will be raised See also Python methods int to_bytes and int from_bytes to convert a PyLongObject to from an array of bytes in base 256 You can call those from C using PyObject_CallMethod PyObject PyLong_FromUnicodeObject PyObject u int base Return value New reference Convert a sequence of Unicode digits in the string u to a Python integer value New in version 3 3 PyObject PyLong_FromVoidPtr void p Return value New reference Part of the Stable ABI Create a Python integer from the pointer p The pointer value can be retrieved from the resulting value using PyLong_AsVoidPtr long PyLong_AsLong PyObject obj Part of the Stable ABI Return a C long representation of obj If obj is not an instance of PyLongObject first call its __index__ method if present to convert it to a PyLongObject Raise OverflowError if the value of obj is out of range for a long Returns 1 on error Use PyErr_Occurred to disambiguate Changed in version 3 8 Use __index__ if available Changed in version 3 10 This function will no longer use __int__ long PyLong_AsLongAndOverflow PyObject obj int overflow Part of the Stable ABI Return a C long representation of obj If obj is not an instance of PyLongObject first ,en
720,call its __index__ method if present to convert it to a PyLongObject If the value of obj is greater than LONG_MAX or less than LONG_MIN set overflow to 1 or 1 respectively and return 1 otherwise set overflow to 0 If any other exception occurs set overflow to 0 and return 1 as usual Returns 1 on error Use PyErr_Occurred to disambiguate Changed in version 3 8 Use __index__ if available Changed in version 3 10 This function will no longer use __int__ long long PyLong_AsLongLong PyObject obj Part of the Stable ABI Return a C long long representation of obj If obj is not an instance of PyLongObject first call its __index__ method if present to convert it to a PyLongObject Raise OverflowError if the value of obj is out of range for a long long Returns 1 on error Use PyErr_Occurred to disambiguate Changed in version 3 8 Use __index__ if available Changed in version 3 10 This function will no longer use __int__ long long PyLong_AsLongLongAndOverflow PyObject obj int overflow Part of the Stable ABI Return a C long long representation of obj If obj is not an instance of PyLongObject first call its __index__ method if present to convert it to a PyLongObject If the value of obj is greater than LLONG_MAX or less than LLONG_MIN set overflow to 1 or 1 respectively and return 1 otherwise set overflow to 0 If any other exception occurs set overflow to 0 and return 1 as usual Returns 1 on error Use PyErr_Occurred to disambiguate New in version 3 2 Changed in version 3 8 Use __index__ if available Changed in version 3 10 This function will no longer use __int__ Py_ssize_t PyLong_AsSsize_t PyObject pylong Part of the Stable ABI Return a C Py_ssize_t representation of pylong pylong must be an instance of PyLongObject Raise OverflowError if the value of pylong is out of range for a Py_ssize_t Returns 1 on error Use PyErr_Occurred to disambiguate unsigned long PyLong_AsUnsignedLong PyObject pylong Part of the Stable ABI Return a C unsigned long representation of pylong pylong must be an instance of PyLongObject Raise OverflowError if the value of pylong is out of range for a unsigned long Returns unsigned long 1 on error Use PyErr_Occurred to disambiguate size_t PyLong_AsSize_t PyObject pylong Part of the Stable ABI Return a C size_t representation of pylong pylong must be an instance of PyLongObject Raise OverflowError if the value of pylong is out of range for a size_t Returns size_t 1 on error Use PyErr_Occurred to disambiguate unsigned long long PyLong_AsUnsignedLongLong PyObject pylong Part of the Stable ABI Return a C unsigned long long representation of pylong pylong must be an instance of PyLongObject Raise OverflowError if the value of pylong is out of range for an unsigned long long Returns unsigned long long 1 on error Use PyErr_Occurred to disambiguate Changed in version 3 1 A negative pylong now raises OverflowError not TypeError unsigned long PyLong_AsUnsignedLongMask PyObject obj Part of the Stable ABI Return a C unsigned long representation of obj If obj is not an instance of PyLongObject first call its __index__ method if present to convert it to a PyLongObject If the value of obj is out of range for an unsigned long return the reduction of that value modulo ULONG_MAX 1 Returns unsigned long 1 on error Use PyErr_Occurred to disambiguate Changed in version 3 8 Use __index__ if available Changed in version 3 10 This function will no longer use __int__ unsigned long long PyLong_AsUnsignedLongLongMask PyObject obj Part of the Stable ABI Return a C unsigned long long representation of obj If obj is not an instance of PyLongObject first call its __index__ method if present to convert it to a PyLongObject If the value of obj is out of range for an unsigned long long return the reduction of that value modulo ULLONG_MAX 1 Returns unsigned long long 1 on error Use PyErr_Occurred to disambiguate Changed in version 3 8 Use __index__ if available Changed in version 3 10 This function will no longer use __int__ double PyLong_AsDouble PyObject pylong Part of the Stable ABI Return a C double representation of pylong pylong must be an instance,en
721, of PyLongObject Raise OverflowError if the value of pylong is out of range for a double Returns 1 0 on error Use PyErr_Occurred to disambiguate void PyLong_AsVoidPtr PyObject pylong Part of the Stable ABI Convert a Python integer pylong to a C void pointer If pylong cannot be converted an OverflowError will be raised This is only assured to produce a usable void pointer for values created with PyLong_FromVoidPtr Returns NULL on error Use PyErr_Occurred to disambiguate int PyUnstable_Long_IsCompact const PyLongObject op This is Unstable API It may change without warning in minor releases Return 1 if op is compact 0 otherwise This function makes it possible for performance critical code to implement a fast path for small integers For compact values use PyUnstable_Long_CompactValue for others fall back to a PyLong_As function or calling int to_bytes The speedup is expected to be negligible for most users Exactly what values are considered compact is an implementation detail and is subject to change Py_ssize_t PyUnstable_Long_CompactValue const PyLongObject op This is Unstable API It may change without warning in minor releases If op is compact as determined by PyUnstable_Long_IsCompact return its value Otherwise the return value is undefined,en
722,General Python FAQ General Information What is Python Python is an interpreted interactive object oriented programming language It incorporates modules exceptions dynamic typing very high level dynamic data types and classes It supports multiple programming paradigms beyond object oriented programming such as procedural and functional programming Python combines remarkable power with very clear syntax It has interfaces to many system calls and libraries as well as to various window systems and is extensible in C or C It is also usable as an extension language for applications that need a programmable interface Finally Python is portable it runs on many Unix variants including Linux and macOS and on Windows To find out more start with The Python Tutorial The Beginner s Guide to Python links to other introductory tutorials and resources for learning Python What is the Python Software Foundation The Python Software Foundation is an independent non profit organization that holds the copyright on Python versions 2 1 and newer The PSF s mission is to advance open source technology related to the Python programming language and to publicize the use of Python The PSF s home page is at https www python org psf Donations to the PSF are tax exempt in the US If you use Python and find it helpful please contribute via the PSF donation page Are there copyright restrictions on the use of Python You can do anything you want with the source as long as you leave the copyrights in and display those copyrights in any documentation about Python that you produce If you honor the copyright rules it s OK to use Python for commercial use to sell copies of Python in source or binary form modified or unmodified or to sell products that incorporate Python in some form We would still like to know about all commercial use of Python of course See the license page to find further explanations and the full text of the PSF License The Python logo is trademarked and in certain cases permission is required to use it Consult the Trademark Usage Policy for more information Why was Python created in the first place Here s a very brief summary of what started it all written by Guido van Rossum I had extensive experience with implementing an interpreted language in the ABC group at CWI and from working with this group I had learned a lot about language design This is the origin of many Python features including the use of indentation for statement grouping and the inclusion of very high level data types although the details are all different in Python I had a number of gripes about the ABC language but also liked many of its features It was impossible to extend the ABC language or its implementation to remedy my complaints in fact its lack of extensibility was one of its biggest problems I had some experience with using Modula 2 and talked with the designers of Modula 3 and read the Modula 3 report Modula 3 is the origin of the syntax and semantics used for exceptions and some other Python features I was working in the Amoeba distributed operating system group at CWI We needed a better way to do system administration than by writing either C programs or Bourne shell scripts since Amoeba had its own system call interface which wasn t easily accessible from the Bourne shell My experience with error handling in Amoeba made me acutely aware of the importance of exceptions as a programming language feature It occurred to me that a scripting language with a syntax like ABC but with access to the Amoeba system calls would fill the need I realized that it would be foolish to write an Amoeba specific language so I decided that I needed a language that was generally extensible During the 1989 Christmas holidays I had a lot of time on my hand so I decided to give it a try During the next year while still mostly working on it in my own time Python was used in the Amoeba project with increasing success and the feedback from colleagues made me add many early improvements In February 1991 after just over a year of development I decided to post to USENET The rest is in the Mis,en
723,c HISTORY file What is Python good for Python is a high level general purpose programming language that can be applied to many different classes of problems The language comes with a large standard library that covers areas such as string processing regular expressions Unicode calculating differences between files internet protocols HTTP FTP SMTP XML RPC POP IMAP software engineering unit testing logging profiling parsing Python code and operating system interfaces system calls filesystems TCP IP sockets Look at the table of contents for The Python Standard Library to get an idea of what s available A wide variety of third party extensions are also available Consult the Python Package Index to find packages of interest to you How does the Python version numbering scheme work Python versions are numbered A B C or A B A is the major version number it is only incremented for really major changes in the language B is the minor version number it is incremented for less earth shattering changes C is the micro version number it is incremented for each bugfix release Not all releases are bugfix releases In the run up to a new feature release a series of development releases are made denoted as alpha beta or release candidate Alphas are early releases in which interfaces aren t yet finalized it s not unexpected to see an interface change between two alpha releases Betas are more stable preserving existing interfaces but possibly adding new modules and release candidates are frozen making no changes except as needed to fix critical bugs Alpha beta and release candidate versions have an additional suffix The suffix for an alpha version is aN for some small number N The suffix for a beta version is bN for some small number N The suffix for a release candidate version is rcN for some small number N In other words all versions labeled 2 0aN precede the versions labeled 2 0bN which precede versions labeled 2 0rcN and those precede 2 0 You may also find version numbers with a suffix e g 2 2 These are unreleased versions built directly from the CPython development repository In practice after a final minor release is made the version is incremented to the next minor version which becomes the a0 version e g 2 4a0 See the Developer s Guide for more information about the development cycle and PEP 387 to learn more about Python s backward compatibility policy See also the documentation for sys version sys hexversion and sys version_info How do I obtain a copy of the Python source The latest Python source distribution is always available from python org at https www python org downloads The latest development sources can be obtained at https github com python cpython The source distribution is a gzipped tar file containing the complete C source Sphinx formatted documentation Python library modules example programs and several useful pieces of freely distributable software The source will compile and run out of the box on most UNIX platforms Consult the Getting Started section of the Python Developer s Guide for more information on getting the source code and compiling it How do I get documentation on Python The standard documentation for the current stable version of Python is available at https docs python org 3 PDF plain text and downloadable HTML versions are also available at https docs python org 3 download html The documentation is written in reStructuredText and processed by the Sphinx documentation tool The reStructuredText source for the documentation is part of the Python source distribution I ve never programmed before Is there a Python tutorial There are numerous tutorials and books available The standard documentation includes The Python Tutorial Consult the Beginner s Guide to find information for beginning Python programmers including lists of tutorials Is there a newsgroup or mailing list devoted to Python There is a newsgroup comp lang python and a mailing list python list The newsgroup and mailing list are gatewayed into each other if you can read news it s unnecessary to subscribe to the mailing list comp lang python is hig,en
724,h traffic receiving hundreds of postings every day and Usenet readers are often more able to cope with this volume Announcements of new software releases and events can be found in comp lang python announce a low traffic moderated list that receives about five postings per day It s available as the python announce mailing list More info about other mailing lists and newsgroups can be found at https www python org community lists How do I get a beta test version of Python Alpha and beta releases are available from https www python org downloads All releases are announced on the comp lang python and comp lang python announce newsgroups and on the Python home page at https www python org an RSS feed of news is available You can also access the development version of Python through Git See The Python Developer s Guide for details How do I submit bug reports and patches for Python To report a bug or submit a patch use the issue tracker at https github com python cpython issues For more information on how Python is developed consult the Python Developer s Guide Are there any published articles about Python that I can reference It s probably best to cite your favorite book about Python The very first article about Python was written in 1991 and is now quite outdated Guido van Rossum and Jelke de Boer Interactively Testing Remote Servers Using the Python Programming Language CWI Quarterly Volume 4 Issue 4 December 1991 Amsterdam pp 283 303 Are there any books on Python Yes there are many and more are being published See the python org wiki at https wiki python org moin PythonBooks for a list You can also search online bookstores for Python and filter out the Monty Python references or perhaps search for Python and language Where in the world is www python org located The Python project s infrastructure is located all over the world and is managed by the Python Infrastructure Team Details here Why is it called Python When he began implementing Python Guido van Rossum was also reading the published scripts from Monty Python s Flying Circus a BBC comedy series from the 1970s Van Rossum thought he needed a name that was short unique and slightly mysterious so he decided to call the language Python Do I have to like Monty Python s Flying Circus No but it helps Python in the real world How stable is Python Very stable New stable releases have been coming out roughly every 6 to 18 months since 1991 and this seems likely to continue As of version 3 9 Python will have a new feature release every 12 months PEP 602 The developers issue bugfix releases of older versions so the stability of existing releases gradually improves Bugfix releases indicated by a third component of the version number e g 3 5 3 3 6 2 are managed for stability only fixes for known problems are included in a bugfix release and it s guaranteed that interfaces will remain the same throughout a series of bugfix releases The latest stable releases can always be found on the Python download page There are two production ready versions of Python 2 x and 3 x The recommended version is 3 x which is supported by most widely used libraries Although 2 x is still widely used it is not maintained anymore How many people are using Python There are probably millions of users though it s difficult to obtain an exact count Python is available for free download so there are no sales figures and it s available from many different sites and packaged with many Linux distributions so download statistics don t tell the whole story either The comp lang python newsgroup is very active but not all Python users post to the group or even read it Have any significant projects been done in Python See https www python org about success for a list of projects that use Python Consulting the proceedings for past Python conferences will reveal contributions from many different companies and organizations High profile Python projects include the Mailman mailing list manager and the Zope application server Several Linux distributions most notably Red Hat have written part or all of their installer and s,en
725,ystem administration software in Python Companies that use Python internally include Google Yahoo and Lucasfilm Ltd What new developments are expected for Python in the future See https peps python org for the Python Enhancement Proposals PEPs PEPs are design documents describing a suggested new feature for Python providing a concise technical specification and a rationale Look for a PEP titled Python X Y Release Schedule where X Y is a version that hasn t been publicly released yet New development is discussed on the python dev mailing list Is it reasonable to propose incompatible changes to Python In general no There are already millions of lines of Python code around the world so any change in the language that invalidates more than a very small fraction of existing programs has to be frowned upon Even if you can provide a conversion program there s still the problem of updating all documentation many books have been written about Python and we don t want to invalidate them all at a single stroke Providing a gradual upgrade path is necessary if a feature has to be changed PEP 5 describes the procedure followed for introducing backward incompatible changes while minimizing disruption for users Is Python a good language for beginning programmers Yes It is still common to start students with a procedural and statically typed language such as Pascal C or a subset of C or Java Students may be better served by learning Python as their first language Python has a very simple and consistent syntax and a large standard library and most importantly using Python in a beginning programming course lets students concentrate on important programming skills such as problem decomposition and data type design With Python students can be quickly introduced to basic concepts such as loops and procedures They can probably even work with user defined objects in their very first course For a student who has never programmed before using a statically typed language seems unnatural It presents additional complexity that the student must master and slows the pace of the course The students are trying to learn to think like a computer decompose problems design consistent interfaces and encapsulate data While learning to use a statically typed language is important in the long term it is not necessarily the best topic to address in the students first programming course Many other aspects of Python make it a good first language Like Java Python has a large standard library so that students can be assigned programming projects very early in the course that do something Assignments aren t restricted to the standard four function calculator and check balancing programs By using the standard library students can gain the satisfaction of working on realistic applications as they learn the fundamentals of programming Using the standard library also teaches students about code reuse Third party modules such as PyGame are also helpful in extending the students reach Python s interactive interpreter enables students to test language features while they re programming They can keep a window with the interpreter running while they enter their program s source in another window If they can t remember the methods for a list they can do something like this L dir L __add__ __class__ __contains__ __delattr__ __delitem__ __dir__ __doc__ __eq__ __format__ __ge__ __getattribute__ __getitem__ __gt__ __hash__ __iadd__ __imul__ __init__ __iter__ __le__ __len__ __lt__ __mul__ __ne__ __new__ __reduce__ __reduce_ex__ __repr__ __reversed__ __rmul__ __setattr__ __setitem__ __sizeof__ __str__ __subclasshook__ append clear copy count extend index insert pop remove reverse sort d for d in dir L if __ not in d append clear copy count extend index insert pop remove reverse sort help L append Help on built in function append append L append object None append object to end L append 1 L 1 With the interpreter documentation is never far from the student as they are programming There are also good IDEs for Python IDLE is a cross platform IDE for Python that is written in Python usi,en
726,ng Tkinter Emacs users will be happy to know that there is a very good Python mode for Emacs All of these programming environments provide syntax highlighting auto indenting and access to the interactive interpreter while coding Consult the Python wiki for a full list of Python editing environments If you want to discuss Python s use in education you may be interested in joining the edu sig mailing list,en
727,xml dom pulldom Support for building partial DOM trees Source code Lib xml dom pulldom py The xml dom pulldom module provides a pull parser which can also be asked to produce DOM accessible fragments of the document where necessary The basic concept involves pulling events from a stream of incoming XML and processing them In contrast to SAX which also employs an event driven processing model together with callbacks the user of a pull parser is responsible for explicitly pulling events from the stream looping over those events until either processing is finished or an error condition occurs Warning The xml dom pulldom module is not secure against maliciously constructed data If you need to parse untrusted or unauthenticated data see XML vulnerabilities Changed in version 3 7 1 The SAX parser no longer processes general external entities by default to increase security by default To enable processing of external entities pass a custom parser instance in from xml dom pulldom import parse from xml sax import make_parser from xml sax handler import feature_external_ges parser make_parser parser setFeature feature_external_ges True parse filename parser parser Example from xml dom import pulldom doc pulldom parse sales_items xml for event node in doc if event pulldom START_ELEMENT and node tagName item if int node getAttribute price 50 doc expandNode node print node toxml event is a constant and can be one of START_ELEMENT END_ELEMENT COMMENT START_DOCUMENT END_DOCUMENT CHARACTERS PROCESSING_INSTRUCTION IGNORABLE_WHITESPACE node is an object of type xml dom minidom Document xml dom minidom Element or xml dom minidom Text Since the document is treated as a flat stream of events the document tree is implicitly traversed and the desired elements are found regardless of their depth in the tree In other words one does not need to consider hierarchical issues such as recursive searching of the document nodes although if the context of elements were important one would either need to maintain some context related state i e remembering where one is in the document at any given point or to make use of the DOMEventStream expandNode method and switch to DOM related processing class xml dom pulldom PullDom documentFactory None Subclass of xml sax handler ContentHandler class xml dom pulldom SAX2DOM documentFactory None Subclass of xml sax handler ContentHandler xml dom pulldom parse stream_or_string parser None bufsize None Return a DOMEventStream from the given input stream_or_string may be either a file name or a file like object parser if given must be an XMLReader object This function will change the document handler of the parser and activate namespace support other parser configuration like setting an entity resolver must have been done in advance If you have XML in a string you can use the parseString function instead xml dom pulldom parseString string parser None Return a DOMEventStream that represents the Unicode string xml dom pulldom default_bufsize Default value for the bufsize parameter to parse The value of this variable can be changed before calling parse and the new value will take effect DOMEventStream Objects class xml dom pulldom DOMEventStream stream parser bufsize Changed in version 3 11 Support for __getitem__ method has been removed getEvent Return a tuple containing event and the current node as xml dom minidom Document if event equals START_DOCUMENT xml dom minidom Element if event equals START_ELEMENT or END_ELEMENT or xml dom minidom Text if event equals CHARACTERS The current node does not contain information about its children unless expandNode is called expandNode node Expands all children of node into node Example from xml dom import pulldom xml html title Foo title p Some text div and more div p html doc pulldom parseString xml for event node in doc if event pulldom START_ELEMENT and node tagName p Following statement only prints p print node toxml doc expandNode node Following statement prints node with all its children p Some text div and more div p print node toxml reset,en
728,csv CSV File Reading and Writing Source code Lib csv py The so called CSV Comma Separated Values format is the most common import and export format for spreadsheets and databases CSV format was used for many years prior to attempts to describe the format in a standardized way in RFC 4180 The lack of a well defined standard means that subtle differences often exist in the data produced and consumed by different applications These differences can make it annoying to process CSV files from multiple sources Still while the delimiters and quoting characters vary the overall format is similar enough that it is possible to write a single module which can efficiently manipulate such data hiding the details of reading and writing the data from the programmer The csv module implements classes to read and write tabular data in CSV format It allows programmers to say write this data in the format preferred by Excel or read data from this file which was generated by Excel without knowing the precise details of the CSV format used by Excel Programmers can also describe the CSV formats understood by other applications or define their own special purpose CSV formats The csv module s reader and writer objects read and write sequences Programmers can also read and write data in dictionary form using the DictReader and DictWriter classes See also PEP 305 CSV File API The Python Enhancement Proposal which proposed this addition to Python Module Contents The csv module defines the following functions csv reader csvfile dialect excel fmtparams Return a reader object that will process lines from the given csvfile A csvfile must be an iterable of strings each in the reader s defined csv format A csvfile is most commonly a file like object or list If csvfile is a file object it should be opened with newline 1 An optional dialect parameter can be given which is used to define a set of parameters specific to a particular CSV dialect It may be an instance of a subclass of the Dialect class or one of the strings returned by the list_dialects function The other optional fmtparams keyword arguments can be given to override individual formatting parameters in the current dialect For full details about the dialect and formatting parameters see section Dialects and Formatting Parameters Each row read from the csv file is returned as a list of strings No automatic data type conversion is performed unless the QUOTE_NONNUMERIC format option is specified in which case unquoted fields are transformed into floats A short usage example import csv with open eggs csv newline as csvfile spamreader csv reader csvfile delimiter quotechar for row in spamreader print join row Spam Spam Spam Spam Spam Baked Beans Spam Lovely Spam Wonderful Spam csv writer csvfile dialect excel fmtparams Return a writer object responsible for converting the user s data into delimited strings on the given file like object csvfile can be any object with a write method If csvfile is a file object it should be opened with newline 1 An optional dialect parameter can be given which is used to define a set of parameters specific to a particular CSV dialect It may be an instance of a subclass of the Dialect class or one of the strings returned by the list_dialects function The other optional fmtparams keyword arguments can be given to override individual formatting parameters in the current dialect For full details about dialects and formatting parameters see the Dialects and Formatting Parameters section To make it as easy as possible to interface with modules which implement the DB API the value None is written as the empty string While this isn t a reversible transformation it makes it easier to dump SQL NULL data values to CSV files without preprocessing the data returned from a cursor fetch call All other non string data are stringified with str before being written A short usage example import csv with open eggs csv w newline as csvfile spamwriter csv writer csvfile delimiter quotechar quoting csv QUOTE_MINIMAL spamwriter writerow Spam 5 Baked Beans spamwriter writerow Spam Lovely Spam Wo,en
729,nderful Spam csv register_dialect name dialect fmtparams Associate dialect with name name must be a string The dialect can be specified either by passing a sub class of Dialect or by fmtparams keyword arguments or both with keyword arguments overriding parameters of the dialect For full details about dialects and formatting parameters see section Dialects and Formatting Parameters csv unregister_dialect name Delete the dialect associated with name from the dialect registry An Error is raised if name is not a registered dialect name csv get_dialect name Return the dialect associated with name An Error is raised if name is not a registered dialect name This function returns an immutable Dialect csv list_dialects Return the names of all registered dialects csv field_size_limit new_limit Returns the current maximum field size allowed by the parser If new_limit is given this becomes the new limit The csv module defines the following classes class csv DictReader f fieldnames None restkey None restval None dialect excel args kwds Create an object that operates like a regular reader but maps the information in each row to a dict whose keys are given by the optional fieldnames parameter The fieldnames parameter is a sequence If fieldnames is omitted the values in the first row of file f will be used as the fieldnames Regardless of how the fieldnames are determined the dictionary preserves their original ordering If a row has more fields than fieldnames the remaining data is put in a list and stored with the fieldname specified by restkey which defaults to None If a non blank row has fewer fields than fieldnames the missing values are filled in with the value of restval which defaults to None All other optional or keyword arguments are passed to the underlying reader instance If the argument passed to fieldnames is an iterator it will be coerced to a list Changed in version 3 6 Returned rows are now of type OrderedDict Changed in version 3 8 Returned rows are now of type dict A short usage example import csv with open names csv newline as csvfile reader csv DictReader csvfile for row in reader print row first_name row last_name Eric Idle John Cleese print row first_name John last_name Cleese class csv DictWriter f fieldnames restval extrasaction raise dialect excel args kwds Create an object which operates like a regular writer but maps dictionaries onto output rows The fieldnames parameter is a sequence of keys that identify the order in which values in the dictionary passed to the writerow method are written to file f The optional restval parameter specifies the value to be written if the dictionary is missing a key in fieldnames If the dictionary passed to the writerow method contains a key not found in fieldnames the optional extrasaction parameter indicates what action to take If it is set to raise the default value a ValueError is raised If it is set to ignore extra values in the dictionary are ignored Any other optional or keyword arguments are passed to the underlying writer instance Note that unlike the DictReader class the fieldnames parameter of the DictWriter class is not optional If the argument passed to fieldnames is an iterator it will be coerced to a list A short usage example import csv with open names csv w newline as csvfile fieldnames first_name last_name writer csv DictWriter csvfile fieldnames fieldnames writer writeheader writer writerow first_name Baked last_name Beans writer writerow first_name Lovely last_name Spam writer writerow first_name Wonderful last_name Spam class csv Dialect The Dialect class is a container class whose attributes contain information for how to handle doublequotes whitespace delimiters etc Due to the lack of a strict CSV specification different applications produce subtly different CSV data Dialect instances define how reader and writer instances behave All available Dialect names are returned by list_dialects and they can be registered with specific reader and writer classes through their initializer __init__ functions like this import csv with open students csv w newline as csv,en
730,file writer csv writer csvfile dialect unix class csv excel The excel class defines the usual properties of an Excel generated CSV file It is registered with the dialect name excel class csv excel_tab The excel_tab class defines the usual properties of an Excel generated TAB delimited file It is registered with the dialect name excel tab class csv unix_dialect The unix_dialect class defines the usual properties of a CSV file generated on UNIX systems i e using n as line terminator and quoting all fields It is registered with the dialect name unix New in version 3 2 class csv Sniffer The Sniffer class is used to deduce the format of a CSV file The Sniffer class provides two methods sniff sample delimiters None Analyze the given sample and return a Dialect subclass reflecting the parameters found If the optional delimiters parameter is given it is interpreted as a string containing possible valid delimiter characters has_header sample Analyze the sample text presumed to be in CSV format and return True if the first row appears to be a series of column headers Inspecting each column one of two key criteria will be considered to estimate if the sample contains a header the second through n th rows contain numeric values the second through n th rows contain strings where at least one value s length differs from that of the putative header of that column Twenty rows after the first row are sampled if more than half of columns rows meet the criteria True is returned Note This method is a rough heuristic and may produce both false positives and negatives An example for Sniffer use with open example csv newline as csvfile dialect csv Sniffer sniff csvfile read 1024 csvfile seek 0 reader csv reader csvfile dialect process CSV file contents here The csv module defines the following constants csv QUOTE_ALL Instructs writer objects to quote all fields csv QUOTE_MINIMAL Instructs writer objects to only quote those fields which contain special characters such as delimiter quotechar or any of the characters in lineterminator csv QUOTE_NONNUMERIC Instructs writer objects to quote all non numeric fields Instructs reader objects to convert all non quoted fields to type float csv QUOTE_NONE Instructs writer objects to never quote fields When the current delimiter occurs in output data it is preceded by the current escapechar character If escapechar is not set the writer will raise Error if any characters that require escaping are encountered Instructs reader objects to perform no special processing of quote characters csv QUOTE_NOTNULL Instructs writer objects to quote all fields which are not None This is similar to QUOTE_ALL except that if a field value is None an empty unquoted string is written Instructs reader objects to interpret an empty unquoted field as None and to otherwise behave as QUOTE_ALL New in version 3 12 csv QUOTE_STRINGS Instructs writer objects to always place quotes around fields which are strings This is similar to QUOTE_NONNUMERIC except that if a field value is None an empty unquoted string is written Instructs reader objects to interpret an empty unquoted string as None and to otherwise behave as QUOTE_NONNUMERIC New in version 3 12 The csv module defines the following exception exception csv Error Raised by any of the functions when an error is detected Dialects and Formatting Parameters To make it easier to specify the format of input and output records specific formatting parameters are grouped together into dialects A dialect is a subclass of the Dialect class containing various attributes describing the format of the CSV file When creating reader or writer objects the programmer can specify a string or a subclass of the Dialect class as the dialect parameter In addition to or instead of the dialect parameter the programmer can also specify individual formatting parameters which have the same names as the attributes defined below for the Dialect class Dialects support the following attributes Dialect delimiter A one character string used to separate fields It defaults to Dialect doublequote Controls how instanc,en
731,es of quotechar appearing inside a field should themselves be quoted When True the character is doubled When False the escapechar is used as a prefix to the quotechar It defaults to True On output if doublequote is False and no escapechar is set Error is raised if a quotechar is found in a field Dialect escapechar A one character string used by the writer to escape the delimiter if quoting is set to QUOTE_NONE and the quotechar if doublequote is False On reading the escapechar removes any special meaning from the following character It defaults to None which disables escaping Changed in version 3 11 An empty escapechar is not allowed Dialect lineterminator The string used to terminate lines produced by the writer It defaults to r n Note The reader is hard coded to recognise either r or n as end of line and ignores lineterminator This behavior may change in the future Dialect quotechar A one character string used to quote fields containing special characters such as the delimiter or quotechar or which contain new line characters It defaults to Changed in version 3 11 An empty quotechar is not allowed Dialect quoting Controls when quotes should be generated by the writer and recognised by the reader It can take on any of the QUOTE_ constants and defaults to QUOTE_MINIMAL Dialect skipinitialspace When True spaces immediately following the delimiter are ignored The default is False Dialect strict When True raise exception Error on bad CSV input The default is False Reader Objects Reader objects DictReader instances and objects returned by the reader function have the following public methods csvreader __next__ Return the next row of the reader s iterable object as a list if the object was returned from reader or a dict if it is a DictReader instance parsed according to the current Dialect Usually you should call this as next reader Reader objects have the following public attributes csvreader dialect A read only description of the dialect in use by the parser csvreader line_num The number of lines read from the source iterator This is not the same as the number of records returned as records can span multiple lines DictReader objects have the following public attribute DictReader fieldnames If not passed as a parameter when creating the object this attribute is initialized upon first access or when the first record is read from the file Writer Objects writer objects DictWriter instances and objects returned by the writer function have the following public methods A row must be an iterable of strings or numbers for writer objects and a dictionary mapping fieldnames to strings or numbers by passing them through str first for DictWriter objects Note that complex numbers are written out surrounded by parens This may cause some problems for other programs which read CSV files assuming they support complex numbers at all csvwriter writerow row Write the row parameter to the writer s file object formatted according to the current Dialect Return the return value of the call to the write method of the underlying file object Changed in version 3 5 Added support of arbitrary iterables csvwriter writerows rows Write all elements in rows an iterable of row objects as described above to the writer s file object formatted according to the current dialect Writer objects have the following public attribute csvwriter dialect A read only description of the dialect in use by the writer DictWriter objects have the following public method DictWriter writeheader Write a row with the field names as specified in the constructor to the writer s file object formatted according to the current dialect Return the return value of the csvwriter writerow call used internally New in version 3 2 Changed in version 3 8 writeheader now also returns the value returned by the csvwriter writerow method it uses internally Examples The simplest example of reading a CSV file import csv with open some csv newline as f reader csv reader f for row in reader print row Reading a file with an alternate format import csv with open passwd newline as f reader csv reader f del,en
732,imiter quoting csv QUOTE_NONE for row in reader print row The corresponding simplest possible writing example is import csv with open some csv w newline as f writer csv writer f writer writerows someiterable Since open is used to open a CSV file for reading the file will by default be decoded into unicode using the system default encoding see locale getencoding To decode a file using a different encoding use the encoding argument of open import csv with open some csv newline encoding utf 8 as f reader csv reader f for row in reader print row The same applies to writing in something other than the system default encoding specify the encoding argument when opening the output file Registering a new dialect import csv csv register_dialect unixpwd delimiter quoting csv QUOTE_NONE with open passwd newline as f reader csv reader f unixpwd A slightly more advanced use of the reader catching and reporting errors import csv sys filename some csv with open filename newline as f reader csv reader f try for row in reader print row except csv Error as e sys exit file line format filename reader line_num e And while the module doesn t directly support parsing strings it can easily be done import csv for row in csv reader one two three print row Footnotes 1 If newline is not specified newlines embedded inside quoted fields will not be interpreted correctly and on platforms that use r n linendings on write an extra r will be added It should always be safe to specify newline since the csv module does its own universal newline handling,en
733,Data marshalling support These routines allow C code to work with serialized objects using the same data format as the marshal module There are functions to write data into the serialization format and additional functions that can be used to read the data back Files used to store marshalled data must be opened in binary mode Numeric values are stored with the least significant byte first The module supports two versions of the data format version 0 is the historical version version 1 shares interned strings in the file and upon unmarshalling Version 2 uses a binary format for floating point numbers Py_MARSHAL_VERSION indicates the current file format currently 2 void PyMarshal_WriteLongToFile long value FILE file int version Marshal a long integer value to file This will only write the least significant 32 bits of value regardless of the size of the native long type version indicates the file format This function can fail in which case it sets the error indicator Use PyErr_Occurred to check for that void PyMarshal_WriteObjectToFile PyObject value FILE file int version Marshal a Python object value to file version indicates the file format This function can fail in which case it sets the error indicator Use PyErr_Occurred to check for that PyObject PyMarshal_WriteObjectToString PyObject value int version Return value New reference Return a bytes object containing the marshalled representation of value version indicates the file format The following functions allow marshalled values to be read back in long PyMarshal_ReadLongFromFile FILE file Return a C long from the data stream in a FILE opened for reading Only a 32 bit value can be read in using this function regardless of the native size of long On error sets the appropriate exception EOFError and returns 1 int PyMarshal_ReadShortFromFile FILE file Return a C short from the data stream in a FILE opened for reading Only a 16 bit value can be read in using this function regardless of the native size of short On error sets the appropriate exception EOFError and returns 1 PyObject PyMarshal_ReadObjectFromFile FILE file Return value New reference Return a Python object from the data stream in a FILE opened for reading On error sets the appropriate exception EOFError ValueError or TypeError and returns NULL PyObject PyMarshal_ReadLastObjectFromFile FILE file Return value New reference Return a Python object from the data stream in a FILE opened for reading Unlike PyMarshal_ReadObjectFromFile this function assumes that no further objects will be read from the file allowing it to aggressively load file data into memory so that the de serialization can operate from data in memory rather than reading a byte at a time from the file Only use these variant if you are certain that you won t be reading anything else from the file On error sets the appropriate exception EOFError ValueError or TypeError and returns NULL PyObject PyMarshal_ReadObjectFromString const char data Py_ssize_t len Return value New reference Return a Python object from the data stream in a byte buffer containing len bytes pointed to by data On error sets the appropriate exception EOFError ValueError or TypeError and returns NULL,en
734,Python Language Services Python provides a number of modules to assist in working with the Python language These modules support tokenizing parsing syntax analysis bytecode disassembly and various other facilities These modules include ast Abstract Syntax Trees Abstract Grammar Node classes Root nodes Literals Variables Expressions Subscripting Comprehensions Statements Imports Control flow Pattern matching Type parameters Function and class definitions Async and await ast Helpers Compiler Flags Command Line Usage symtable Access to the compiler s symbol tables Generating Symbol Tables Examining Symbol Tables token Constants used with Python parse trees keyword Testing for Python keywords tokenize Tokenizer for Python source Tokenizing Input Command Line Usage Examples tabnanny Detection of ambiguous indentation pyclbr Python module browser support Function Objects Class Objects py_compile Compile Python source files Command Line Interface compileall Byte compile Python libraries Command line use Public functions dis Disassembler for Python bytecode Command line interface Bytecode analysis Analysis functions Python Bytecode Instructions Opcode collections pickletools Tools for pickle developers Command line usage Command line options Programmatic Interface,en
735,imghdr Determine the type of an image Source code Lib imghdr py Deprecated since version 3 11 will be removed in version 3 13 The imghdr module is deprecated see PEP 594 for details and alternatives The imghdr module determines the type of image contained in a file or byte stream The imghdr module defines the following function imghdr what file h None Test the image data contained in the file named file and return a string describing the image type If h is provided the file argument is ignored and h is assumed to contain the byte stream to test Changed in version 3 6 Accepts a path like object The following image types are recognized as listed below with the return value from what Value Image format rgb SGI ImgLib Files gif GIF 87a and 89a Files pbm Portable Bitmap Files pgm Portable Graymap Files ppm Portable Pixmap Files tiff TIFF Files rast Sun Raster Files xbm X Bitmap Files jpeg JPEG data in JFIF or Exif formats bmp BMP files png Portable Network Graphics webp WebP files exr OpenEXR Files New in version 3 5 The exr and webp formats were added You can extend the list of file types imghdr can recognize by appending to this variable imghdr tests A list of functions performing the individual tests Each function takes two arguments the byte stream and an open file like object When what is called with a byte stream the file like object will be None The test function should return a string describing the image type if the test succeeded or None if it failed Example import imghdr imghdr what bass gif gif,en
736,Custom Python Interpreters The modules described in this chapter allow writing interfaces similar to Python s interactive interpreter If you want a Python interpreter that supports some special feature in addition to the Python language you should look at the code module The codeop module is lower level used to support compiling a possibly incomplete chunk of Python code The full list of modules described in this chapter is code Interpreter base classes Interactive Interpreter Objects Interactive Console Objects codeop Compile Python code,en
737,grp The group database This module provides access to the Unix group database It is available on all Unix versions Availability Unix not Emscripten not WASI Group database entries are reported as a tuple like object whose attributes correspond to the members of the group structure Attribute field below see grp h Index Attribute Meaning 0 gr_name the name of the group 1 gr_passwd the encrypted group password often empty 2 gr_gid the numerical group ID 3 gr_mem all the group member s user names The gid is an integer name and password are strings and the member list is a list of strings Note that most users are not explicitly listed as members of the group they are in according to the password database Check both databases to get complete membership information Also note that a gr_name that starts with a or is likely to be a YP NIS reference and may not be accessible via getgrnam or getgrgid It defines the following items grp getgrgid id Return the group database entry for the given numeric group ID KeyError is raised if the entry asked for cannot be found Changed in version 3 10 TypeError is raised for non integer arguments like floats or strings grp getgrnam name Return the group database entry for the given group name KeyError is raised if the entry asked for cannot be found grp getgrall Return a list of all available group entries in arbitrary order See also Module pwd An interface to the user database similar to this Module spwd An interface to the shadow password database similar to this,en
738,crypt Function to check Unix passwords Source code Lib crypt py Deprecated since version 3 11 will be removed in version 3 13 The crypt module is deprecated see PEP 594 for details and alternatives The hashlib module is a potential replacement for certain use cases The passlib package can replace all use cases of this module This module implements an interface to the crypt 3 routine which is a one way hash function based upon a modified DES algorithm see the Unix man page for further details Possible uses include storing hashed passwords so you can check passwords without storing the actual password or attempting to crack Unix passwords with a dictionary Notice that the behavior of this module depends on the actual implementation of the crypt 3 routine in the running system Therefore any extensions available on the current implementation will also be available on this module Availability Unix not VxWorks Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information Hashing Methods New in version 3 3 The crypt module defines the list of hashing methods not all methods are available on all platforms crypt METHOD_SHA512 A Modular Crypt Format method with 16 character salt and 86 character hash based on the SHA 512 hash function This is the strongest method crypt METHOD_SHA256 Another Modular Crypt Format method with 16 character salt and 43 character hash based on the SHA 256 hash function crypt METHOD_BLOWFISH Another Modular Crypt Format method with 22 character salt and 31 character hash based on the Blowfish cipher New in version 3 7 crypt METHOD_MD5 Another Modular Crypt Format method with 8 character salt and 22 character hash based on the MD5 hash function crypt METHOD_CRYPT The traditional method with a 2 character salt and 13 characters of hash This is the weakest method Module Attributes New in version 3 3 crypt methods A list of available password hashing algorithms as crypt METHOD_ objects This list is sorted from strongest to weakest Module Functions The crypt module defines the following functions crypt crypt word salt None word will usually be a user s password as typed at a prompt or in a graphical interface The optional salt is either a string as returned from mksalt one of the crypt METHOD_ values though not all may be available on all platforms or a full encrypted password including salt as returned by this function If salt is not provided the strongest method available in methods will be used Checking a password is usually done by passing the plain text password as word and the full results of a previous crypt call which should be the same as the results of this call salt either a random 2 or 16 character string possibly prefixed with digit to indicate the method which will be used to perturb the encryption algorithm The characters in salt must be in the set a zA Z0 9 with the exception of Modular Crypt Format which prefixes a digit Returns the hashed password as a string which will be composed of characters from the same alphabet as the salt Since a few crypt 3 extensions allow different values with different sizes in the salt it is recommended to use the full crypted password as salt when checking for a password Changed in version 3 3 Accept crypt METHOD_ values in addition to strings for salt crypt mksalt method None rounds None Return a randomly generated salt of the specified method If no method is given the strongest method available in methods is used The return value is a string suitable for passing as the salt argument to crypt rounds specifies the number of rounds for METHOD_SHA256 METHOD_SHA512 and METHOD_BLOWFISH For METHOD_SHA256 and METHOD_SHA512 it must be an integer between 1000 and 999_999_999 the default is 5000 For METHOD_BLOWFISH it must be a power of two between 16 2 4 and 2_147_483_648 2 31 the default is 4096 2 12 New in version 3 3 Changed in version 3 7 Added the rounds parameter Examples A simple example illustrating typical use a constant time compariso,en
739,n operation is needed to limit exposure to timing attacks hmac compare_digest is suitable for this purpose import pwd import crypt import getpass from hmac import compare_digest as compare_hash def login username input Python login cryptedpasswd pwd getpwnam username 1 if cryptedpasswd if cryptedpasswd x or cryptedpasswd raise ValueError no support for shadow passwords cleartext getpass getpass return compare_hash crypt crypt cleartext cryptedpasswd cryptedpasswd else return True To generate a hash of a password using the strongest available method and check it against the original import crypt from hmac import compare_digest as compare_hash hashed crypt crypt plaintext if not compare_hash hashed crypt crypt plaintext hashed raise ValueError hashed version doesn t validate against original,en
740,Concurrent Execution The modules described in this chapter provide support for concurrent execution of code The appropriate choice of tool will depend on the task to be executed CPU bound vs IO bound and preferred style of development event driven cooperative multitasking vs preemptive multitasking Here s an overview threading Thread based parallelism Thread Local Data Thread Objects Lock Objects RLock Objects Condition Objects Semaphore Objects Semaphore Example Event Objects Timer Objects Barrier Objects Using locks conditions and semaphores in the with statement multiprocessing Process based parallelism Introduction The Process class Contexts and start methods Exchanging objects between processes Synchronization between processes Sharing state between processes Using a pool of workers Reference Process and exceptions Pipes and Queues Miscellaneous Connection Objects Synchronization primitives Shared ctypes Objects The multiprocessing sharedctypes module Managers Customized managers Using a remote manager Proxy Objects Cleanup Process Pools Listeners and Clients Address Formats Authentication keys Logging The multiprocessing dummy module Programming guidelines All start methods The spawn and forkserver start methods Examples multiprocessing shared_memory Shared memory for direct access across processes The concurrent package concurrent futures Launching parallel tasks Executor Objects ThreadPoolExecutor ThreadPoolExecutor Example ProcessPoolExecutor ProcessPoolExecutor Example Future Objects Module Functions Exception classes subprocess Subprocess management Using the subprocess Module Frequently Used Arguments Popen Constructor Exceptions Security Considerations Popen Objects Windows Popen Helpers Windows Constants Older high level API Replacing Older Functions with the subprocess Module Replacing bin sh shell command substitution Replacing shell pipeline Replacing os system Replacing the os spawn family Replacing os popen os popen2 os popen3 Replacing functions from the popen2 module Legacy Shell Invocation Functions Notes Converting an argument sequence to a string on Windows Disabling use of vfork or posix_spawn sched Event scheduler Scheduler Objects queue A synchronized queue class Queue Objects SimpleQueue Objects contextvars Context Variables Context Variables Manual Context Management asyncio support The following are support modules for some of the above services _thread Low level threading API,en
741,unittest mock mock object library New in version 3 3 Source code Lib unittest mock py unittest mock is a library for testing in Python It allows you to replace parts of your system under test with mock objects and make assertions about how they have been used unittest mock provides a core Mock class removing the need to create a host of stubs throughout your test suite After performing an action you can make assertions about which methods attributes were used and arguments they were called with You can also specify return values and set needed attributes in the normal way Additionally mock provides a patch decorator that handles patching module and class level attributes within the scope of a test along with sentinel for creating unique objects See the quick guide for some examples of how to use Mock MagicMock and patch Mock is designed for use with unittest and is based on the action assertion pattern instead of record replay used by many mocking frameworks There is a backport of unittest mock for earlier versions of Python available as mock on PyPI Quick Guide Mock and MagicMock objects create all attributes and methods as you access them and store details of how they have been used You can configure them to specify return values or limit what attributes are available and then make assertions about how they have been used from unittest mock import MagicMock thing ProductionClass thing method MagicMock return_value 3 thing method 3 4 5 key value 3 thing method assert_called_with 3 4 5 key value side_effect allows you to perform side effects including raising an exception when a mock is called from unittest mock import Mock mock Mock side_effect KeyError foo mock Traceback most recent call last KeyError foo values a 1 b 2 c 3 def side_effect arg return values arg mock side_effect side_effect mock a mock b mock c 1 2 3 mock side_effect 5 4 3 2 1 mock mock mock 5 4 3 Mock has many other ways you can configure it and control its behaviour For example the spec argument configures the mock to take its specification from another object Attempting to access attributes or methods on the mock that don t exist on the spec will fail with an AttributeError The patch decorator context manager makes it easy to mock classes or objects in a module under test The object you specify will be replaced with a mock or other object during the test and restored when the test ends from unittest mock import patch patch module ClassName2 patch module ClassName1 def test MockClass1 MockClass2 module ClassName1 module ClassName2 assert MockClass1 is module ClassName1 assert MockClass2 is module ClassName2 assert MockClass1 called assert MockClass2 called test Note When you nest patch decorators the mocks are passed in to the decorated function in the same order they applied the normal Python order that decorators are applied This means from the bottom up so in the example above the mock for module ClassName1 is passed in first With patch it matters that you patch objects in the namespace where they are looked up This is normally straightforward but for a quick guide read where to patch As well as a decorator patch can be used as a context manager in a with statement with patch object ProductionClass method return_value None as mock_method thing ProductionClass thing method 1 2 3 mock_method assert_called_once_with 1 2 3 There is also patch dict for setting values in a dictionary just during a scope and restoring the dictionary to its original state when the test ends foo key value original foo copy with patch dict foo newkey newvalue clear True assert foo newkey newvalue assert foo original Mock supports the mocking of Python magic methods The easiest way of using magic methods is with the MagicMock class It allows you to do things like mock MagicMock mock __str__ return_value foobarbaz str mock foobarbaz mock __str__ assert_called_with Mock allows you to assign functions or other Mock instances to magic methods and they will be called appropriately The MagicMock class is just a Mock variant that has all of the magic methods pre created for you well,en
742, all the useful ones anyway The following is an example of using magic methods with the ordinary Mock class mock Mock mock __str__ Mock return_value wheeeeee str mock wheeeeee For ensuring that the mock objects in your tests have the same api as the objects they are replacing you can use auto speccing Auto speccing can be done through the autospec argument to patch or the create_autospec function Auto speccing creates mock objects that have the same attributes and methods as the objects they are replacing and any functions and methods including constructors have the same call signature as the real object This ensures that your mocks will fail in the same way as your production code if they are used incorrectly from unittest mock import create_autospec def function a b c pass mock_function create_autospec function return_value fishy mock_function 1 2 3 fishy mock_function assert_called_once_with 1 2 3 mock_function wrong arguments Traceback most recent call last TypeError lambda takes exactly 3 arguments 1 given create_autospec can also be used on classes where it copies the signature of the __init__ method and on callable objects where it copies the signature of the __call__ method The Mock Class Mock is a flexible mock object intended to replace the use of stubs and test doubles throughout your code Mocks are callable and create attributes as new mocks when you access them 1 Accessing the same attribute will always return the same mock Mocks record how you use them allowing you to make assertions about what your code has done to them MagicMock is a subclass of Mock with all the magic methods pre created and ready to use There are also non callable variants useful when you are mocking out objects that aren t callable NonCallableMock and NonCallableMagicMock The patch decorators makes it easy to temporarily replace classes in a particular module with a Mock object By default patch will create a MagicMock for you You can specify an alternative class of Mock using the new_callable argument to patch class unittest mock Mock spec None side_effect None return_value DEFAULT wraps None name None spec_set None unsafe False kwargs Create a new Mock object Mock takes several optional arguments that specify the behaviour of the Mock object spec This can be either a list of strings or an existing object a class or instance that acts as the specification for the mock object If you pass in an object then a list of strings is formed by calling dir on the object excluding unsupported magic attributes and methods Accessing any attribute not in this list will raise an AttributeError If spec is an object rather than a list of strings then __class__ returns the class of the spec object This allows mocks to pass isinstance tests spec_set A stricter variant of spec If used attempting to set or get an attribute on the mock that isn t on the object passed as spec_set will raise an AttributeError side_effect A function to be called whenever the Mock is called See the side_effect attribute Useful for raising exceptions or dynamically changing return values The function is called with the same arguments as the mock and unless it returns DEFAULT the return value of this function is used as the return value Alternatively side_effect can be an exception class or instance In this case the exception will be raised when the mock is called If side_effect is an iterable then each call to the mock will return the next value from the iterable A side_effect can be cleared by setting it to None return_value The value returned when the mock is called By default this is a new Mock created on first access See the return_value attribute unsafe By default accessing any attribute whose name starts with assert assret asert aseert or assrt will raise an AttributeError Passing unsafe True will allow access to these attributes New in version 3 5 wraps Item for the mock object to wrap If wraps is not None then calling the Mock will pass the call through to the wrapped object returning the real result Attribute access on the mock will return a Mock object that wraps the c,en
743,orresponding attribute of the wrapped object so attempting to access an attribute that doesn t exist will raise an AttributeError If the mock has an explicit return_value set then calls are not passed to the wrapped object and the return_value is returned instead name If the mock has a name then it will be used in the repr of the mock This can be useful for debugging The name is propagated to child mocks Mocks can also be called with arbitrary keyword arguments These will be used to set attributes on the mock after it is created See the configure_mock method for details assert_called Assert that the mock was called at least once mock Mock mock method Mock name mock method id mock method assert_called New in version 3 6 assert_called_once Assert that the mock was called exactly once mock Mock mock method Mock name mock method id mock method assert_called_once mock method Mock name mock method id mock method assert_called_once Traceback most recent call last AssertionError Expected method to have been called once Called 2 times New in version 3 6 assert_called_with args kwargs This method is a convenient way of asserting that the last call has been made in a particular way mock Mock mock method 1 2 3 test wow Mock name mock method id mock method assert_called_with 1 2 3 test wow assert_called_once_with args kwargs Assert that the mock was called exactly once and that call was with the specified arguments mock Mock return_value None mock foo bar baz mock assert_called_once_with foo bar baz mock other bar values mock assert_called_once_with other bar values Traceback most recent call last AssertionError Expected mock to be called once Called 2 times assert_any_call args kwargs assert the mock has been called with the specified arguments The assert passes if the mock has ever been called unlike assert_called_with and assert_called_once_with that only pass if the call is the most recent one and in the case of assert_called_once_with it must also be the only call mock Mock return_value None mock 1 2 arg thing mock some thing else mock assert_any_call 1 2 arg thing assert_has_calls calls any_order False assert the mock has been called with the specified calls The mock_calls list is checked for the calls If any_order is false then the calls must be sequential There can be extra calls before or after the specified calls If any_order is true then the calls can be in any order but they must all appear in mock_calls mock Mock return_value None mock 1 mock 2 mock 3 mock 4 calls call 2 call 3 mock assert_has_calls calls calls call 4 call 2 call 3 mock assert_has_calls calls any_order True assert_not_called Assert the mock was never called m Mock m hello assert_not_called obj m hello m hello assert_not_called Traceback most recent call last AssertionError Expected hello to not have been called Called 1 times New in version 3 5 reset_mock return_value False side_effect False The reset_mock method resets all the call attributes on a mock object mock Mock return_value None mock hello mock called True mock reset_mock mock called False Changed in version 3 6 Added two keyword only arguments to the reset_mock function This can be useful where you want to make a series of assertions that reuse the same object Note that reset_mock doesn t clear the return value side_effect or any child attributes you have set using normal assignment by default In case you want to reset return_value or side_effect then pass the corresponding parameter as True Child mocks and the return value mock if any are reset as well Note return_value and side_effect are keyword only arguments mock_add_spec spec spec_set False Add a spec to a mock spec can either be an object or a list of strings Only attributes on the spec can be fetched as attributes from the mock If spec_set is true then only attributes on the spec can be set attach_mock mock attribute Attach a mock as an attribute of this one replacing its name and parent Calls to the attached mock will be recorded in the method_calls and mock_calls attributes of this one configure_mock kwargs Set attributes on the mock ,en
744,through keyword arguments Attributes plus return values and side effects can be set on child mocks using standard dot notation and unpacking a dictionary in the method call mock Mock attrs method return_value 3 other side_effect KeyError mock configure_mock attrs mock method 3 mock other Traceback most recent call last KeyError The same thing can be achieved in the constructor call to mocks attrs method return_value 3 other side_effect KeyError mock Mock some_attribute eggs attrs mock some_attribute eggs mock method 3 mock other Traceback most recent call last KeyError configure_mock exists to make it easier to do configuration after the mock has been created __dir__ Mock objects limit the results of dir some_mock to useful results For mocks with a spec this includes all the permitted attributes for the mock See FILTER_DIR for what this filtering does and how to switch it off _get_child_mock kw Create the child mocks for attributes and return value By default child mocks will be the same type as the parent Subclasses of Mock may want to override this to customize the way child mocks are made For non callable mocks the callable variant will be used rather than any custom subclass called A boolean representing whether or not the mock object has been called mock Mock return_value None mock called False mock mock called True call_count An integer telling you how many times the mock object has been called mock Mock return_value None mock call_count 0 mock mock mock call_count 2 return_value Set this to configure the value returned by calling the mock mock Mock mock return_value fish mock fish The default return value is a mock object and you can configure it in the normal way mock Mock mock return_value attribute sentinel Attribute mock return_value Mock name mock id mock return_value assert_called_with return_value can also be set in the constructor mock Mock return_value 3 mock return_value 3 mock 3 side_effect This can either be a function to be called when the mock is called an iterable or an exception class or instance to be raised If you pass in a function it will be called with same arguments as the mock and unless the function returns the DEFAULT singleton the call to the mock will then return whatever the function returns If the function returns DEFAULT then the mock will return its normal value from the return_value If you pass in an iterable it is used to retrieve an iterator which must yield a value on every call This value can either be an exception instance to be raised or a value to be returned from the call to the mock DEFAULT handling is identical to the function case An example of a mock that raises an exception to test exception handling of an API mock Mock mock side_effect Exception Boom mock Traceback most recent call last Exception Boom Using side_effect to return a sequence of values mock Mock mock side_effect 3 2 1 mock mock mock 3 2 1 Using a callable mock Mock return_value 3 def side_effect args kwargs return DEFAULT mock side_effect side_effect mock 3 side_effect can be set in the constructor Here s an example that adds one to the value the mock is called with and returns it side_effect lambda value value 1 mock Mock side_effect side_effect mock 3 4 mock 8 7 Setting side_effect to None clears it m Mock side_effect KeyError return_value 3 m Traceback most recent call last KeyError m side_effect None m 3 call_args This is either None if the mock hasn t been called or the arguments that the mock was last called with This will be in the form of a tuple the first member which can also be accessed through the args property is any ordered arguments the mock was called with or an empty tuple and the second member which can also be accessed through the kwargs property is any keyword arguments or an empty dictionary mock Mock return_value None print mock call_args None mock mock call_args call mock call_args True mock 3 4 mock call_args call 3 4 mock call_args 3 4 True mock call_args args 3 4 mock call_args kwargs mock 3 4 5 key fish next w00t mock call_args call 3 4 5 key fish next w00t mock call_args args 3,en
745, 4 5 mock call_args kwargs key fish next w00t call_args along with members of the lists call_args_list method_calls and mock_calls are call objects These are tuples so they can be unpacked to get at the individual arguments and make more complex assertions See calls as tuples Changed in version 3 8 Added args and kwargs properties call_args_list This is a list of all the calls made to the mock object in sequence so the length of the list is the number of times it has been called Before any calls have been made it is an empty list The call object can be used for conveniently constructing lists of calls to compare with call_args_list mock Mock return_value None mock mock 3 4 mock key fish next w00t mock call_args_list call call 3 4 call key fish next w00t expected 3 4 key fish next w00t mock call_args_list expected True Members of call_args_list are call objects These can be unpacked as tuples to get at the individual arguments See calls as tuples method_calls As well as tracking calls to themselves mocks also track calls to methods and attributes and their methods and attributes mock Mock mock method Mock name mock method id mock property method attribute Mock name mock property method attribute id mock method_calls call method call property method attribute Members of method_calls are call objects These can be unpacked as tuples to get at the individual arguments See calls as tuples mock_calls mock_calls records all calls to the mock object its methods magic methods and return value mocks mock MagicMock result mock 1 2 3 mock first a 3 MagicMock name mock first id mock second MagicMock name mock second id int mock 1 result 1 MagicMock name mock id expected call 1 2 3 call first a 3 call second call __int__ call 1 mock mock_calls expected True Members of mock_calls are call objects These can be unpacked as tuples to get at the individual arguments See calls as tuples Note The way mock_calls are recorded means that where nested calls are made the parameters of ancestor calls are not recorded and so will always compare equal mock MagicMock mock top a 3 bottom MagicMock name mock top bottom id mock mock_calls call top a 3 call top bottom mock mock_calls 1 call top a 1 bottom True __class__ Normally the __class__ attribute of an object will return its type For a mock object with a spec __class__ returns the spec class instead This allows mock objects to pass isinstance tests for the object they are replacing masquerading as mock Mock spec 3 isinstance mock int True __class__ is assignable to this allows a mock to pass an isinstance check without forcing you to use a spec mock Mock mock __class__ dict isinstance mock dict True class unittest mock NonCallableMock spec None wraps None name None spec_set None kwargs A non callable version of Mock The constructor parameters have the same meaning of Mock with the exception of return_value and side_effect which have no meaning on a non callable mock Mock objects that use a class or an instance as a spec or spec_set are able to pass isinstance tests mock Mock spec SomeClass isinstance mock SomeClass True mock Mock spec_set SomeClass isinstance mock SomeClass True The Mock classes have support for mocking magic methods See magic methods for the full details The mock classes and the patch decorators all take arbitrary keyword arguments for configuration For the patch decorators the keywords are passed to the constructor of the mock being created The keyword arguments are for configuring attributes of the mock m MagicMock attribute 3 other fish m attribute 3 m other fish The return value and side effect of child mocks can be set in the same way using dotted notation As you can t use dotted names directly in a call you have to create a dictionary and unpack it using attrs method return_value 3 other side_effect KeyError mock Mock some_attribute eggs attrs mock some_attribute eggs mock method 3 mock other Traceback most recent call last KeyError A callable mock which was created with a spec or a spec_set will introspect the specification object s signature when matching calls to the mock ,en
746,Therefore it can match the actual call s arguments regardless of whether they were passed positionally or by name def f a b c pass mock Mock spec f mock 1 2 c 3 Mock name mock id 140161580456576 mock assert_called_with 1 2 3 mock assert_called_with a 1 b 2 c 3 This applies to assert_called_with assert_called_once_with assert_has_calls and assert_any_call When Autospeccing it will also apply to method calls on the mock object Changed in version 3 4 Added signature introspection on specced and autospecced mock objects class unittest mock PropertyMock args kwargs A mock intended to be used as a property or other descriptor on a class PropertyMock provides __get__ and __set__ methods so you can specify a return value when it is fetched Fetching a PropertyMock instance from an object calls the mock with no args Setting it calls the mock with the value being set class Foo property def foo self return something foo setter def foo self value pass with patch __main__ Foo foo new_callable PropertyMock as mock_foo mock_foo return_value mockity mock this_foo Foo print this_foo foo this_foo foo 6 mockity mock mock_foo mock_calls call call 6 Because of the way mock attributes are stored you can t directly attach a PropertyMock to a mock object Instead you can attach it to the mock type object m MagicMock p PropertyMock return_value 3 type m foo p m foo 3 p assert_called_once_with class unittest mock AsyncMock spec None side_effect None return_value DEFAULT wraps None name None spec_set None unsafe False kwargs An asynchronous version of MagicMock The AsyncMock object will behave so the object is recognized as an async function and the result of a call is an awaitable mock AsyncMock asyncio iscoroutinefunction mock True inspect isawaitable mock True The result of mock is an async function which will have the outcome of side_effect or return_value after it has been awaited if side_effect is a function the async function will return the result of that function if side_effect is an exception the async function will raise the exception if side_effect is an iterable the async function will return the next value of the iterable however if the sequence of result is exhausted StopAsyncIteration is raised immediately if side_effect is not defined the async function will return the value defined by return_value hence by default the async function returns a new AsyncMock object Setting the spec of a Mock or MagicMock to an async function will result in a coroutine object being returned after calling async def async_func pass mock MagicMock async_func mock MagicMock spec function id mock coroutine object AsyncMockMixin _mock_call at Setting the spec of a Mock MagicMock or AsyncMock to a class with asynchronous and synchronous functions will automatically detect the synchronous functions and set them as MagicMock if the parent mock is AsyncMock or MagicMock or Mock if the parent mock is Mock All asynchronous functions will be AsyncMock class ExampleClass def sync_foo pass async def async_foo pass a_mock AsyncMock ExampleClass a_mock sync_foo MagicMock name mock sync_foo id a_mock async_foo AsyncMock name mock async_foo id mock Mock ExampleClass mock sync_foo Mock name mock sync_foo id mock async_foo AsyncMock name mock async_foo id New in version 3 8 assert_awaited Assert that the mock was awaited at least once Note that this is separate from the object having been called the await keyword must be used mock AsyncMock async def main coroutine_mock await coroutine_mock coroutine_mock mock mock called True mock assert_awaited Traceback most recent call last AssertionError Expected mock to have been awaited asyncio run main coroutine_mock mock assert_awaited assert_awaited_once Assert that the mock was awaited exactly once mock AsyncMock async def main await mock asyncio run main mock assert_awaited_once asyncio run main mock method assert_awaited_once Traceback most recent call last AssertionError Expected mock to have been awaited once Awaited 2 times assert_awaited_with args kwargs Assert that the last await was with the specified arguments mock Asy,en
747,ncMock async def main args kwargs await mock args kwargs asyncio run main foo bar bar mock assert_awaited_with foo bar bar mock assert_awaited_with other Traceback most recent call last AssertionError expected call not found Expected mock other Actual mock foo bar bar assert_awaited_once_with args kwargs Assert that the mock was awaited exactly once and with the specified arguments mock AsyncMock async def main args kwargs await mock args kwargs asyncio run main foo bar bar mock assert_awaited_once_with foo bar bar asyncio run main foo bar bar mock assert_awaited_once_with foo bar bar Traceback most recent call last AssertionError Expected mock to have been awaited once Awaited 2 times assert_any_await args kwargs Assert the mock has ever been awaited with the specified arguments mock AsyncMock async def main args kwargs await mock args kwargs asyncio run main foo bar bar asyncio run main hello mock assert_any_await foo bar bar mock assert_any_await other Traceback most recent call last AssertionError mock other await not found assert_has_awaits calls any_order False Assert the mock has been awaited with the specified calls The await_args_list list is checked for the awaits If any_order is false then the awaits must be sequential There can be extra calls before or after the specified awaits If any_order is true then the awaits can be in any order but they must all appear in await_args_list mock AsyncMock async def main args kwargs await mock args kwargs calls call foo call bar mock assert_has_awaits calls Traceback most recent call last AssertionError Awaits not found Expected call foo call bar Actual asyncio run main foo asyncio run main bar mock assert_has_awaits calls assert_not_awaited Assert that the mock was never awaited mock AsyncMock mock assert_not_awaited reset_mock args kwargs See Mock reset_mock Also sets await_count to 0 await_args to None and clears the await_args_list await_count An integer keeping track of how many times the mock object has been awaited mock AsyncMock async def main await mock asyncio run main mock await_count 1 asyncio run main mock await_count 2 await_args This is either None if the mock hasn t been awaited or the arguments that the mock was last awaited with Functions the same as Mock call_args mock AsyncMock async def main args await mock args mock await_args asyncio run main foo mock await_args call foo asyncio run main bar mock await_args call bar await_args_list This is a list of all the awaits made to the mock object in sequence so the length of the list is the number of times it has been awaited Before any awaits have been made it is an empty list mock AsyncMock async def main args await mock args mock await_args_list asyncio run main foo mock await_args_list call foo asyncio run main bar mock await_args_list call foo call bar Calling Mock objects are callable The call will return the value set as the return_value attribute The default return value is a new Mock object it is created the first time the return value is accessed either explicitly or by calling the Mock but it is stored and the same one returned each time Calls made to the object will be recorded in the attributes like call_args and call_args_list If side_effect is set then it will be called after the call has been recorded so if side_effect raises an exception the call is still recorded The simplest way to make a mock raise an exception when called is to make side_effect an exception class or instance m MagicMock side_effect IndexError m 1 2 3 Traceback most recent call last IndexError m mock_calls call 1 2 3 m side_effect KeyError Bang m two three four Traceback most recent call last KeyError Bang m mock_calls call 1 2 3 call two three four If side_effect is a function then whatever that function returns is what calls to the mock return The side_effect function is called with the same arguments as the mock This allows you to vary the return value of the call dynamically based on the input def side_effect value return value 1 m MagicMock side_effect side_effect m 1 2 m 2 3 m mock_calls call 1 call 2 If you want the,en
748, mock to still return the default return value a new mock or any set return value then there are two ways of doing this Either return mock return_value from inside side_effect or return DEFAULT m MagicMock def side_effect args kwargs return m return_value m side_effect side_effect m return_value 3 m 3 def side_effect args kwargs return DEFAULT m side_effect side_effect m 3 To remove a side_effect and return to the default behaviour set the side_effect to None m MagicMock return_value 6 def side_effect args kwargs return 3 m side_effect side_effect m 3 m side_effect None m 6 The side_effect can also be any iterable object Repeated calls to the mock will return values from the iterable until the iterable is exhausted and a StopIteration is raised m MagicMock side_effect 1 2 3 m 1 m 2 m 3 m Traceback most recent call last StopIteration If any members of the iterable are exceptions they will be raised instead of returned iterable 33 ValueError 66 m MagicMock side_effect iterable m 33 m Traceback most recent call last ValueError m 66 Deleting Attributes Mock objects create attributes on demand This allows them to pretend to be objects of any type You may want a mock object to return False to a hasattr call or raise an AttributeError when an attribute is fetched You can do this by providing an object as a spec for a mock but that isn t always convenient You block attributes by deleting them Once deleted accessing an attribute will raise an AttributeError mock MagicMock hasattr mock m True del mock m hasattr mock m False del mock f mock f Traceback most recent call last AttributeError f Mock names and the name attribute Since name is an argument to the Mock constructor if you want your mock object to have a name attribute you can t just pass it in at creation time There are two alternatives One option is to use configure_mock mock MagicMock mock configure_mock name my_name mock name my_name A simpler option is to simply set the name attribute after mock creation mock MagicMock mock name foo Attaching Mocks as Attributes When you attach a mock as an attribute of another mock or as the return value it becomes a child of that mock Calls to the child are recorded in the method_calls and mock_calls attributes of the parent This is useful for configuring child mocks and then attaching them to the parent or for attaching mocks to a parent that records all calls to the children and allows you to make assertions about the order of calls between mocks parent MagicMock child1 MagicMock return_value None child2 MagicMock return_value None parent child1 child1 parent child2 child2 child1 1 child2 2 parent mock_calls call child1 1 call child2 2 The exception to this is if the mock has a name This allows you to prevent the parenting if for some reason you don t want it to happen mock MagicMock not_a_child MagicMock name not a child mock attribute not_a_child mock attribute MagicMock name not a child id mock mock_calls Mocks created for you by patch are automatically given names To attach mocks that have names to a parent you use the attach_mock method thing1 object thing2 object parent MagicMock with patch __main__ thing1 return_value None as child1 with patch __main__ thing2 return_value None as child2 parent attach_mock child1 child1 parent attach_mock child2 child2 child1 one child2 two parent mock_calls call child1 one call child2 two 1 The only exceptions are magic methods and attributes those that have leading and trailing double underscores Mock doesn t create these but instead raises an AttributeError This is because the interpreter will often implicitly request these methods and gets very confused to get a new Mock object when it expects a magic method If you need magic method support see magic methods The patchers The patch decorators are used for patching objects only within the scope of the function they decorate They automatically handle the unpatching for you even if exceptions are raised All of these functions can also be used in with statements or as class decorators patch Note The key is to do the patching in the right namesp,en
749,ace See the section where to patch unittest mock patch target new DEFAULT spec None create False spec_set None autospec None new_callable None kwargs patch acts as a function decorator class decorator or a context manager Inside the body of the function or with statement the target is patched with a new object When the function with statement exits the patch is undone If new is omitted then the target is replaced with an AsyncMock if the patched object is an async function or a MagicMock otherwise If patch is used as a decorator and new is omitted the created mock is passed in as an extra argument to the decorated function If patch is used as a context manager the created mock is returned by the context manager target should be a string in the form package module ClassName The target is imported and the specified object replaced with the new object so the target must be importable from the environment you are calling patch from The target is imported when the decorated function is executed not at decoration time The spec and spec_set keyword arguments are passed to the MagicMock if patch is creating one for you In addition you can pass spec True or spec_set True which causes patch to pass in the object being mocked as the spec spec_set object new_callable allows you to specify a different class or callable object that will be called to create the new object By default AsyncMock is used for async functions and MagicMock for the rest A more powerful form of spec is autospec If you set autospec True then the mock will be created with a spec from the object being replaced All attributes of the mock will also have the spec of the corresponding attribute of the object being replaced Methods and functions being mocked will have their arguments checked and will raise a TypeError if they are called with the wrong signature For mocks replacing a class their return value the instance will have the same spec as the class See the create_autospec function and Autospeccing Instead of autospec True you can pass autospec some_object to use an arbitrary object as the spec instead of the one being replaced By default patch will fail to replace attributes that don t exist If you pass in create True and the attribute doesn t exist patch will create the attribute for you when the patched function is called and delete it again after the patched function has exited This is useful for writing tests against attributes that your production code creates at runtime It is off by default because it can be dangerous With it switched on you can write passing tests against APIs that don t actually exist Note Changed in version 3 5 If you are patching builtins in a module then you don t need to pass create True it will be added by default Patch can be used as a TestCase class decorator It works by decorating each test method in the class This reduces the boilerplate code when your test methods share a common patchings set patch finds tests by looking for method names that start with patch TEST_PREFIX By default this is test which matches the way unittest finds tests You can specify an alternative prefix by setting patch TEST_PREFIX Patch can be used as a context manager with the with statement Here the patching applies to the indented block after the with statement If you use as then the patched object will be bound to the name after the as very useful if patch is creating a mock object for you patch takes arbitrary keyword arguments These will be passed to AsyncMock if the patched object is asynchronous to MagicMock otherwise or to new_callable if specified patch dict patch multiple and patch object are available for alternate use cases patch as function decorator creating the mock for you and passing it into the decorated function patch __main__ SomeClass def function normal_argument mock_class print mock_class is SomeClass function None True Patching a class replaces the class with a MagicMock instance If the class is instantiated in the code under test then it will be the return_value of the mock that will be used If the class is instantiated multiple,en
750, times you could use side_effect to return a new mock each time Alternatively you can set the return_value to be anything you want To configure return values on methods of instances on the patched class you must do this on the return_value For example class Class def method self pass with patch __main__ Class as MockClass instance MockClass return_value instance method return_value foo assert Class is instance assert Class method foo If you use spec or spec_set and patch is replacing a class then the return value of the created mock will have the same spec Original Class patcher patch __main__ Class spec True MockClass patcher start instance MockClass assert isinstance instance Original patcher stop The new_callable argument is useful where you want to use an alternative class to the default MagicMock for the created mock For example if you wanted a NonCallableMock to be used thing object with patch __main__ thing new_callable NonCallableMock as mock_thing assert thing is mock_thing thing Traceback most recent call last TypeError NonCallableMock object is not callable Another use case might be to replace an object with an io StringIO instance from io import StringIO def foo print Something patch sys stdout new_callable StringIO def test mock_stdout foo assert mock_stdout getvalue Something n test When patch is creating a mock for you it is common that the first thing you need to do is to configure the mock Some of that configuration can be done in the call to patch Any arbitrary keywords you pass into the call will be used to set attributes on the created mock patcher patch __main__ thing first one second two mock_thing patcher start mock_thing first one mock_thing second two As well as attributes on the created mock attributes like the return_value and side_effect of child mocks can also be configured These aren t syntactically valid to pass in directly as keyword arguments but a dictionary with these as keys can still be expanded into a patch call using config method return_value 3 other side_effect KeyError patcher patch __main__ thing config mock_thing patcher start mock_thing method 3 mock_thing other Traceback most recent call last KeyError By default attempting to patch a function in a module or a method or an attribute in a class that does not exist will fail with AttributeError patch sys non_existing_attribute 42 def test assert sys non_existing_attribute 42 test Traceback most recent call last AttributeError module sys built in does not have the attribute non_existing_attribute but adding create True in the call to patch will make the previous example work as expected patch sys non_existing_attribute 42 create True def test mock_stdout assert sys non_existing_attribute 42 test Changed in version 3 8 patch now returns an AsyncMock if the target is an async function patch object patch object target attribute new DEFAULT spec None create False spec_set None autospec None new_callable None kwargs patch the named member attribute on an object target with a mock object patch object can be used as a decorator class decorator or a context manager Arguments new spec create spec_set autospec and new_callable have the same meaning as for patch Like patch patch object takes arbitrary keyword arguments for configuring the mock object it creates When used as a class decorator patch object honours patch TEST_PREFIX for choosing which methods to wrap You can either call patch object with three arguments or two arguments The three argument form takes the object to be patched the attribute name and the object to replace the attribute with When calling with the two argument form you omit the replacement object and a mock is created for you and passed in as an extra argument to the decorated function patch object SomeClass class_method def test mock_method SomeClass class_method 3 mock_method assert_called_with 3 test spec create and the other arguments to patch object have the same meaning as they do for patch patch dict patch dict in_dict values clear False kwargs Patch a dictionary or dictionary like object and restore the dict,en
751,ionary to its original state after the test in_dict can be a dictionary or a mapping like container If it is a mapping then it must at least support getting setting and deleting items plus iterating over keys in_dict can also be a string specifying the name of the dictionary which will then be fetched by importing it values can be a dictionary of values to set in the dictionary values can also be an iterable of key value pairs If clear is true then the dictionary will be cleared before the new values are set patch dict can also be called with arbitrary keyword arguments to set values in the dictionary Changed in version 3 8 patch dict now returns the patched dictionary when used as a context manager patch dict can be used as a context manager decorator or class decorator foo patch dict foo newkey newvalue def test assert foo newkey newvalue test assert foo When used as a class decorator patch dict honours patch TEST_PREFIX default to test for choosing which methods to wrap import os import unittest from unittest mock import patch patch dict os environ newkey newvalue class TestSample unittest TestCase def test_sample self self assertEqual os environ newkey newvalue If you want to use a different prefix for your test you can inform the patchers of the different prefix by setting patch TEST_PREFIX For more details about how to change the value of see TEST_PREFIX patch dict can be used to add members to a dictionary or simply let a test change a dictionary and ensure the dictionary is restored when the test ends foo with patch dict foo newkey newvalue as patched_foo assert foo newkey newvalue assert patched_foo newkey newvalue You can add update or delete keys of foo or patched_foo it s the same dict patched_foo spam eggs assert foo assert patched_foo import os with patch dict os environ newkey newvalue print os environ newkey newvalue assert newkey not in os environ Keywords can be used in the patch dict call to set values in the dictionary mymodule MagicMock mymodule function return_value fish with patch dict sys modules mymodule mymodule import mymodule mymodule function some args fish patch dict can be used with dictionary like objects that aren t actually dictionaries At the very minimum they must support item getting setting deleting and either iteration or membership test This corresponds to the magic methods __getitem__ __setitem__ __delitem__ and either __iter__ or __contains__ class Container def __init__ self self values def __getitem__ self name return self values name def __setitem__ self name value self values name value def __delitem__ self name del self values name def __iter__ self return iter self values thing Container thing one 1 with patch dict thing one 2 two 3 assert thing one 2 assert thing two 3 assert thing one 1 assert list thing one patch multiple patch multiple target spec None create False spec_set None autospec None new_callable None kwargs Perform multiple patches in a single call It takes the object to be patched either as an object or a string to fetch the object by importing and keyword arguments for the patches with patch multiple settings FIRST_PATCH one SECOND_PATCH two Use DEFAULT as the value if you want patch multiple to create mocks for you In this case the created mocks are passed into a decorated function by keyword and a dictionary is returned when patch multiple is used as a context manager patch multiple can be used as a decorator class decorator or a context manager The arguments spec spec_set create autospec and new_callable have the same meaning as for patch These arguments will be applied to all patches done by patch multiple When used as a class decorator patch multiple honours patch TEST_PREFIX for choosing which methods to wrap If you want patch multiple to create mocks for you then you can use DEFAULT as the value If you use patch multiple as a decorator then the created mocks are passed into the decorated function by keyword thing object other object patch multiple __main__ thing DEFAULT other DEFAULT def test_function thing other assert isinstance thing MagicMock asse,en
752,rt isinstance other MagicMock test_function patch multiple can be nested with other patch decorators but put arguments passed by keyword after any of the standard arguments created by patch patch sys exit patch multiple __main__ thing DEFAULT other DEFAULT def test_function mock_exit other thing assert other in repr other assert thing in repr thing assert exit in repr mock_exit test_function If patch multiple is used as a context manager the value returned by the context manager is a dictionary where created mocks are keyed by name with patch multiple __main__ thing DEFAULT other DEFAULT as values assert other in repr values other assert thing in repr values thing assert values thing is thing assert values other is other patch methods start and stop All the patchers have start and stop methods These make it simpler to do patching in setUp methods or where you want to do multiple patches without nesting decorators or with statements To use them call patch patch object or patch dict as normal and keep a reference to the returned patcher object You can then call start to put the patch in place and stop to undo it If you are using patch to create a mock for you then it will be returned by the call to patcher start patcher patch package module ClassName from package import module original module ClassName new_mock patcher start assert module ClassName is not original assert module ClassName is new_mock patcher stop assert module ClassName is original assert module ClassName is not new_mock A typical use case for this might be for doing multiple patches in the setUp method of a TestCase class MyTest unittest TestCase def setUp self self patcher1 patch package module Class1 self patcher2 patch package module Class2 self MockClass1 self patcher1 start self MockClass2 self patcher2 start def tearDown self self patcher1 stop self patcher2 stop def test_something self assert package module Class1 is self MockClass1 assert package module Class2 is self MockClass2 MyTest test_something run Caution If you use this technique you must ensure that the patching is undone by calling stop This can be fiddlier than you might think because if an exception is raised in the setUp then tearDown is not called unittest TestCase addCleanup makes this easier class MyTest unittest TestCase def setUp self patcher patch package module Class self MockClass patcher start self addCleanup patcher stop def test_something self assert package module Class is self MockClass As an added bonus you no longer need to keep a reference to the patcher object It is also possible to stop all patches which have been started by using patch stopall patch stopall Stop all active patches Only stops patches started with start patch builtins You can patch any builtins within a module The following example patches builtin ord patch __main__ ord def test mock_ord mock_ord return_value 101 print ord c test 101 TEST_PREFIX All of the patchers can be used as class decorators When used in this way they wrap every test method on the class The patchers recognise methods that start with test as being test methods This is the same way that the unittest TestLoader finds test methods by default It is possible that you want to use a different prefix for your tests You can inform the patchers of the different prefix by setting patch TEST_PREFIX patch TEST_PREFIX foo value 3 patch __main__ value not three class Thing def foo_one self print value def foo_two self print value Thing foo_one not three Thing foo_two not three value 3 Nesting Patch Decorators If you want to perform multiple patches then you can simply stack up the decorators You can stack up multiple patch decorators using this pattern patch object SomeClass class_method patch object SomeClass static_method def test mock1 mock2 assert SomeClass static_method is mock1 assert SomeClass class_method is mock2 SomeClass static_method foo SomeClass class_method bar return mock1 mock2 mock1 mock2 test mock1 assert_called_once_with foo mock2 assert_called_once_with bar Note that the decorators are applied from the bottom upwards This is ,en
753,the standard way that Python applies decorators The order of the created mocks passed into your test function matches this order Where to patch patch works by temporarily changing the object that a name points to with another one There can be many names pointing to any individual object so for patching to work you must ensure that you patch the name used by the system under test The basic principle is that you patch where an object is looked up which is not necessarily the same place as where it is defined A couple of examples will help to clarify this Imagine we have a project that we want to test with the following structure a py Defines SomeClass b py from a import SomeClass some_function instantiates SomeClass Now we want to test some_function but we want to mock out SomeClass using patch The problem is that when we import module b which we will have to do then it imports SomeClass from module a If we use patch to mock out a SomeClass then it will have no effect on our test module b already has a reference to the real SomeClass and it looks like our patching had no effect The key is to patch out SomeClass where it is used or where it is looked up In this case some_function will actually look up SomeClass in module b where we have imported it The patching should look like patch b SomeClass However consider the alternative scenario where instead of from a import SomeClass module b does import a and some_function uses a SomeClass Both of these import forms are common In this case the class we want to patch is being looked up in the module and so we have to patch a SomeClass instead patch a SomeClass Patching Descriptors and Proxy Objects Both patch and patch object correctly patch and restore descriptors class methods static methods and properties You should patch these on the class rather than an instance They also work with some objects that proxy attribute access like the django settings object MagicMock and magic method support Mocking Magic Methods Mock supports mocking the Python protocol methods also known as magic methods This allows mock objects to replace containers or other objects that implement Python protocols Because magic methods are looked up differently from normal methods 2 this support has been specially implemented This means that only specific magic methods are supported The supported list includes almost all of them If there are any missing that you need please let us know You mock magic methods by setting the method you are interested in to a function or a mock instance If you are using a function then it must take self as the first argument 3 def __str__ self return fooble mock Mock mock __str__ __str__ str mock fooble mock Mock mock __str__ Mock mock __str__ return_value fooble str mock fooble mock Mock mock __iter__ Mock return_value iter list mock One use case for this is for mocking objects used as context managers in a with statement mock Mock mock __enter__ Mock return_value foo mock __exit__ Mock return_value False with mock as m assert m foo mock __enter__ assert_called_with mock __exit__ assert_called_with None None None Calls to magic methods do not appear in method_calls but they are recorded in mock_calls Note If you use the spec keyword argument to create a mock then attempting to set a magic method that isn t in the spec will raise an AttributeError The full list of supported magic methods is __hash__ __sizeof__ __repr__ and __str__ __dir__ __format__ and __subclasses__ __round__ __floor__ __trunc__ and __ceil__ Comparisons __lt__ __gt__ __le__ __ge__ __eq__ and __ne__ Container methods __getitem__ __setitem__ __delitem__ __contains__ __len__ __iter__ __reversed__ and __missing__ Context manager __enter__ __exit__ __aenter__ and __aexit__ Unary numeric methods __neg__ __pos__ and __invert__ The numeric methods including right hand and in place variants __add__ __sub__ __mul__ __matmul__ __truediv__ __floordiv__ __mod__ __divmod__ __lshift__ __rshift__ __and__ __xor__ __or__ and __pow__ Numeric conversion methods __complex__ __int__ __float__ and __index__ Descriptor methods __get__,en
754, __set__ and __delete__ Pickling __reduce__ __reduce_ex__ __getinitargs__ __getnewargs__ __getstate__ and __setstate__ File system path representation __fspath__ Asynchronous iteration methods __aiter__ and __anext__ Changed in version 3 8 Added support for os PathLike __fspath__ Changed in version 3 8 Added support for __aenter__ __aexit__ __aiter__ and __anext__ The following methods exist but are not supported as they are either in use by mock can t be set dynamically or can cause problems __getattr__ __setattr__ __init__ and __new__ __prepare__ __instancecheck__ __subclasscheck__ __del__ Magic Mock There are two MagicMock variants MagicMock and NonCallableMagicMock class unittest mock MagicMock args kw MagicMock is a subclass of Mock with default implementations of most of the magic methods You can use MagicMock without having to configure the magic methods yourself The constructor parameters have the same meaning as for Mock If you use the spec or spec_set arguments then only magic methods that exist in the spec will be created class unittest mock NonCallableMagicMock args kw A non callable version of MagicMock The constructor parameters have the same meaning as for MagicMock with the exception of return_value and side_effect which have no meaning on a non callable mock The magic methods are setup with MagicMock objects so you can configure them and use them in the usual way mock MagicMock mock 3 fish mock __setitem__ assert_called_with 3 fish mock __getitem__ return_value result mock 2 result By default many of the protocol methods are required to return objects of a specific type These methods are preconfigured with a default return value so that they can be used without you having to do anything if you aren t interested in the return value You can still set the return value manually if you want to change the default Methods and their defaults __lt__ NotImplemented __gt__ NotImplemented __le__ NotImplemented __ge__ NotImplemented __int__ 1 __contains__ False __len__ 0 __iter__ iter __exit__ False __aexit__ False __complex__ 1j __float__ 1 0 __bool__ True __index__ 1 __hash__ default hash for the mock __str__ default str for the mock __sizeof__ default sizeof for the mock For example mock MagicMock int mock 1 len mock 0 list mock object in mock False The two equality methods __eq__ and __ne__ are special They do the default equality comparison on identity using the side_effect attribute unless you change their return value to return something else MagicMock 3 False MagicMock 3 True mock MagicMock mock __eq__ return_value True mock 3 True The return value of MagicMock __iter__ can be any iterable object and isn t required to be an iterator mock MagicMock mock __iter__ return_value a b c list mock a b c list mock a b c If the return value is an iterator then iterating over it once will consume it and subsequent iterations will result in an empty list mock __iter__ return_value iter a b c list mock a b c list mock MagicMock has all of the supported magic methods configured except for some of the obscure and obsolete ones You can still set these up if you want Magic methods that are supported but not setup by default in MagicMock are __subclasses__ __dir__ __format__ __get__ __set__ and __delete__ __reversed__ and __missing__ __reduce__ __reduce_ex__ __getinitargs__ __getnewargs__ __getstate__ and __setstate__ __getformat__ 2 Magic methods should be looked up on the class rather than the instance Different versions of Python are inconsistent about applying this rule The supported protocol methods should work with all supported versions of Python 3 The function is basically hooked up to the class but each Mock instance is kept isolated from the others Helpers sentinel unittest mock sentinel The sentinel object provides a convenient way of providing unique objects for your tests Attributes are created on demand when you access them by name Accessing the same attribute will always return the same object The objects returned have a sensible repr so that test failure messages are readable Changed in version 3 7 The sentinel,en
755, attributes now preserve their identity when they are copied or pickled Sometimes when testing you need to test that a specific object is passed as an argument to another method or returned It can be common to create named sentinel objects to test this sentinel provides a convenient way of creating and testing the identity of objects like this In this example we monkey patch method to return sentinel some_object real ProductionClass real method Mock name method real method return_value sentinel some_object result real method assert result is sentinel some_object result sentinel some_object DEFAULT unittest mock DEFAULT The DEFAULT object is a pre created sentinel actually sentinel DEFAULT It can be used by side_effect functions to indicate that the normal return value should be used call unittest mock call args kwargs call is a helper object for making simpler assertions for comparing with call_args call_args_list mock_calls and method_calls call can also be used with assert_has_calls m MagicMock return_value None m 1 2 a foo b bar m m call_args_list call 1 2 a foo b bar call True call call_list For a call object that represents multiple calls call_list returns a list of all the intermediate calls as well as the final call call_list is particularly useful for making assertions on chained calls A chained call is multiple calls on a single line of code This results in multiple entries in mock_calls on a mock Manually constructing the sequence of calls can be tedious call_list can construct the sequence of calls from the same chained call m MagicMock m 1 method arg foo other bar 2 0 MagicMock name mock method other id kall call 1 method arg foo other bar 2 0 kall call_list call 1 call method arg foo call method other bar call method other 2 0 m mock_calls kall call_list True A call object is either a tuple of positional args keyword args or name positional args keyword args depending on how it was constructed When you construct them yourself this isn t particularly interesting but the call objects that are in the Mock call_args Mock call_args_list and Mock mock_calls attributes can be introspected to get at the individual arguments they contain The call objects in Mock call_args and Mock call_args_list are two tuples of positional args keyword args whereas the call objects in Mock mock_calls along with ones you construct yourself are three tuples of name positional args keyword args You can use their tupleness to pull out the individual arguments for more complex introspection and assertions The positional arguments are a tuple an empty tuple if there are no positional arguments and the keyword arguments are a dictionary m MagicMock return_value None m 1 2 3 arg one arg2 two kall m call_args kall args 1 2 3 kall kwargs arg one arg2 two kall args is kall 0 True kall kwargs is kall 1 True m MagicMock m foo 4 5 6 arg two arg2 three MagicMock name mock foo id kall m mock_calls 0 name args kwargs kall name foo args 4 5 6 kwargs arg two arg2 three name is m mock_calls 0 0 True create_autospec unittest mock create_autospec spec spec_set False instance False kwargs Create a mock object using another object as a spec Attributes on the mock will use the corresponding attribute on the spec object as their spec Functions or methods being mocked will have their arguments checked to ensure that they are called with the correct signature If spec_set is True then attempting to set attributes that don t exist on the spec object will raise an AttributeError If a class is used as a spec then the return value of the mock the instance of the class will have the same spec You can use a class as the spec for an instance object by passing instance True The returned mock will only be callable if instances of the mock are callable create_autospec also takes arbitrary keyword arguments that are passed to the constructor of the created mock See Autospeccing for examples of how to use auto speccing with create_autospec and the autospec argument to patch Changed in version 3 8 create_autospec now returns an AsyncMock if the target is an async function A,en
756,NY unittest mock ANY Sometimes you may need to make assertions about some of the arguments in a call to mock but either not care about some of the arguments or want to pull them individually out of call_args and make more complex assertions on them To ignore certain arguments you can pass in objects that compare equal to everything Calls to assert_called_with and assert_called_once_with will then succeed no matter what was passed in mock Mock return_value None mock foo bar object mock assert_called_once_with foo bar ANY ANY can also be used in comparisons with call lists like mock_calls m MagicMock return_value None m 1 m 1 2 m object m mock_calls call 1 call 1 2 ANY True ANY is not limited to comparisons with call objects and so can also be used in test assertions class TestStringMethods unittest TestCase def test_split self s hello world self assertEqual s split hello ANY FILTER_DIR unittest mock FILTER_DIR FILTER_DIR is a module level variable that controls the way mock objects respond to dir The default is True which uses the filtering described below to only show useful members If you dislike this filtering or need to switch it off for diagnostic purposes then set mock FILTER_DIR False With filtering on dir some_mock shows only useful attributes and will include any dynamically created attributes that wouldn t normally be shown If the mock was created with a spec or autospec of course then all the attributes from the original are shown even if they haven t been accessed yet dir Mock assert_any_call assert_called assert_called_once assert_called_once_with assert_called_with assert_has_calls assert_not_called attach_mock from urllib import request dir Mock spec request AbstractBasicAuthHandler AbstractDigestAuthHandler AbstractHTTPHandler BaseHandler Many of the not very useful private to Mock rather than the thing being mocked underscore and double underscore prefixed attributes have been filtered from the result of calling dir on a Mock If you dislike this behaviour you can switch it off by setting the module level switch FILTER_DIR from unittest import mock mock FILTER_DIR False dir mock Mock _NonCallableMock__get_return_value _NonCallableMock__get_side_effect _NonCallableMock__return_value_doc _NonCallableMock__set_return_value _NonCallableMock__set_side_effect __call__ __class__ Alternatively you can just use vars my_mock instance members and dir type my_mock type members to bypass the filtering irrespective of mock FILTER_DIR mock_open unittest mock mock_open mock None read_data None A helper function to create a mock to replace the use of open It works for open called directly or used as a context manager The mock argument is the mock object to configure If None the default then a MagicMock will be created for you with the API limited to methods or attributes available on standard file handles read_data is a string for the read readline and readlines methods of the file handle to return Calls to those methods will take data from read_data until it is depleted The mock of these methods is pretty simplistic every time the mock is called the read_data is rewound to the start If you need more control over the data that you are feeding to the tested code you will need to customize this mock for yourself When that is insufficient one of the in memory filesystem packages on PyPI can offer a realistic filesystem for testing Changed in version 3 4 Added readline and readlines support The mock of read changed to consume read_data rather than returning it on each call Changed in version 3 5 read_data is now reset on each call to the mock Changed in version 3 8 Added __iter__ to implementation so that iteration such as in for loops correctly consumes read_data Using open as a context manager is a great way to ensure your file handles are closed properly and is becoming common with open some path w as f f write something The issue is that even if you mock out the call to open it is the returned object that is used as a context manager and has __enter__ and __exit__ called Mocking context managers with a MagicMock is common ,en
757,enough and fiddly enough that a helper function is useful m mock_open with patch __main__ open m with open foo w as h h write some stuff m mock_calls call foo w call __enter__ call write some stuff call __exit__ None None None m assert_called_once_with foo w handle m handle write assert_called_once_with some stuff And for reading files with patch __main__ open mock_open read_data bibble as m with open foo as h result h read m assert_called_once_with foo assert result bibble Autospeccing Autospeccing is based on the existing spec feature of mock It limits the api of mocks to the api of an original object the spec but it is recursive implemented lazily so that attributes of mocks only have the same api as the attributes of the spec In addition mocked functions methods have the same call signature as the original so they raise a TypeError if they are called incorrectly Before I explain how auto speccing works here s why it is needed Mock is a very powerful and flexible object but it suffers from two flaws when used to mock out objects from a system under test One of these flaws is specific to the Mock api and the other is a more general problem with using mock objects First the problem specific to Mock Mock has two assert methods that are extremely handy assert_called_with and assert_called_once_with mock Mock name Thing return_value None mock 1 2 3 mock assert_called_once_with 1 2 3 mock 1 2 3 mock assert_called_once_with 1 2 3 Traceback most recent call last AssertionError Expected mock to be called once Called 2 times Because mocks auto create attributes on demand and allow you to call them with arbitrary arguments if you misspell one of these assert methods then your assertion is gone mock Mock name Thing return_value None mock 1 2 3 mock assret_called_once_with 4 5 6 Intentional typo Your tests can pass silently and incorrectly because of the typo The second issue is more general to mocking If you refactor some of your code rename members and so on any tests for code that is still using the old api but uses mocks instead of the real objects will still pass This means your tests can all pass even though your code is broken Note that this is another reason why you need integration tests as well as unit tests Testing everything in isolation is all fine and dandy but if you don t test how your units are wired together there is still lots of room for bugs that tests might have caught mock already provides a feature to help with this called speccing If you use a class or instance as the spec for a mock then you can only access attributes on the mock that exist on the real class from urllib import request mock Mock spec request Request mock assret_called_with Intentional typo Traceback most recent call last AttributeError Mock object has no attribute assret_called_with The spec only applies to the mock itself so we still have the same issue with any methods on the mock mock has_data mock Mock object at 0x mock has_data assret_called_with Intentional typo Auto speccing solves this problem You can either pass autospec True to patch patch object or use the create_autospec function to create a mock with a spec If you use the autospec True argument to patch then the object that is being replaced will be used as the spec object Because the speccing is done lazily the spec is created as attributes on the mock are accessed you can use it with very complex or deeply nested objects like modules that import modules that import modules without a big performance hit Here s an example of it in use from urllib import request patcher patch __main__ request autospec True mock_request patcher start request is mock_request True mock_request Request MagicMock name request Request spec Request id You can see that request Request has a spec request Request takes two arguments in the constructor one of which is self Here s what happens if we try to call it incorrectly req request Request Traceback most recent call last TypeError lambda takes at least 2 arguments 1 given The spec also applies to instantiated classes i e the return value of specced m,en
758,ocks req request Request foo req NonCallableMagicMock name request Request spec Request id Request objects are not callable so the return value of instantiating our mocked out request Request is a non callable mock With the spec in place any typos in our asserts will raise the correct error req add_header spam eggs MagicMock name request Request add_header id req add_header assret_called_with Intentional typo Traceback most recent call last AttributeError Mock object has no attribute assret_called_with req add_header assert_called_with spam eggs In many cases you will just be able to add autospec True to your existing patch calls and then be protected against bugs due to typos and api changes As well as using autospec through patch there is a create_autospec for creating autospecced mocks directly from urllib import request mock_request create_autospec request mock_request Request foo bar NonCallableMagicMock name mock Request spec Request id This isn t without caveats and limitations however which is why it is not the default behaviour In order to know what attributes are available on the spec object autospec has to introspect access attributes the spec As you traverse attributes on the mock a corresponding traversal of the original object is happening under the hood If any of your specced objects have properties or descriptors that can trigger code execution then you may not be able to use autospec On the other hand it is much better to design your objects so that introspection is safe 4 A more serious problem is that it is common for instance attributes to be created in the __init__ method and not to exist on the class at all autospec can t know about any dynamically created attributes and restricts the api to visible attributes class Something def __init__ self self a 33 with patch __main__ Something autospec True thing Something thing a Traceback most recent call last AttributeError Mock object has no attribute a There are a few different ways of resolving this problem The easiest but not necessarily the least annoying way is to simply set the required attributes on the mock after creation Just because autospec doesn t allow you to fetch attributes that don t exist on the spec it doesn t prevent you setting them with patch __main__ Something autospec True thing Something thing a 33 There is a more aggressive version of both spec and autospec that does prevent you setting non existent attributes This is useful if you want to ensure your code only sets valid attributes too but obviously it prevents this particular scenario with patch __main__ Something autospec True spec_set True thing Something thing a 33 Traceback most recent call last AttributeError Mock object has no attribute a Probably the best way of solving the problem is to add class attributes as default values for instance members initialised in __init__ Note that if you are only setting default attributes in __init__ then providing them via class attributes shared between instances of course is faster too e g class Something a 33 This brings up another issue It is relatively common to provide a default value of None for members that will later be an object of a different type None would be useless as a spec because it wouldn t let you access any attributes or methods on it As None is never going to be useful as a spec and probably indicates a member that will normally of some other type autospec doesn t use a spec for members that are set to None These will just be ordinary mocks well MagicMocks class Something member None mock create_autospec Something mock member foo bar baz MagicMock name mock member foo bar baz id If modifying your production classes to add defaults isn t to your liking then there are more options One of these is simply to use an instance as the spec rather than the class The other is to create a subclass of the production class and add the defaults to the subclass without affecting the production class Both of these require you to use an alternative object as the spec Thankfully patch supports this you can simply pass the alternative ,en
759,object as the autospec argument class Something def __init__ self self a 33 class SomethingForTest Something a 33 p patch __main__ Something autospec SomethingForTest mock p start mock a NonCallableMagicMock name Something a spec int id 4 This only applies to classes or already instantiated objects Calling a mocked class to create a mock instance does not create a real instance It is only attribute lookups along with calls to dir that are done Sealing mocks unittest mock seal mock Seal will disable the automatic creation of mocks when accessing an attribute of the mock being sealed or any of its attributes that are already mocks recursively If a mock instance with a name or a spec is assigned to an attribute it won t be considered in the sealing chain This allows one to prevent seal from fixing part of the mock object mock Mock mock submock attribute1 2 mock not_submock mock Mock name sample_name seal mock mock new_attribute This will raise AttributeError mock submock attribute2 This will raise AttributeError mock not_submock attribute2 This won t raise New in version 3 7,en
760,What s New in Python 2 4 Author A M Kuchling This article explains the new features in Python 2 4 1 released on March 30 2005 Python 2 4 is a medium sized release It doesn t introduce as many changes as the radical Python 2 2 but introduces more features than the conservative 2 3 release The most significant new language features are function decorators and generator expressions most other changes are to the standard library According to the CVS change logs there were 481 patches applied and 502 bugs fixed between Python 2 3 and 2 4 Both figures are likely to be underestimates This article doesn t attempt to provide a complete specification of every single new feature but instead provides a brief introduction to each feature For full details you should refer to the documentation for Python 2 4 such as the Python Library Reference and the Python Reference Manual Often you will be referred to the PEP for a particular new feature for explanations of the implementation and design rationale PEP 218 Built In Set Objects Python 2 3 introduced the sets module C implementations of set data types have now been added to the Python core as two new built in types set iterable and frozenset iterable They provide high speed operations for membership testing for eliminating duplicates from sequences and for mathematical operations like unions intersections differences and symmetric differences a set abracadabra form a set from a string z in a fast membership testing False a unique letters in a set a r b c d join a convert back into a string arbcd b set alacazam form a second set a b letters in a but not in b set r d b a b letters in either a or b set a c r d b m z l a b letters in both a and b set a c a b letters in a or b but not both set r d b m z l a add z add a new element a update wxy add multiple new elements a set a c b d r w y x z a remove x take one element out a set a c b d r w y z The frozenset type is an immutable version of set Since it is immutable and hashable it may be used as a dictionary key or as a member of another set The sets module remains in the standard library and may be useful if you wish to subclass the Set or ImmutableSet classes There are currently no plans to deprecate the module See also PEP 218 Adding a Built In Set Object Type Originally proposed by Greg Wilson and ultimately implemented by Raymond Hettinger PEP 237 Unifying Long Integers and Integers The lengthy transition process for this PEP begun in Python 2 2 takes another step forward in Python 2 4 In 2 3 certain integer operations that would behave differently after int long unification triggered FutureWarning warnings and returned values limited to 32 or 64 bits depending on your platform In 2 4 these expressions no longer produce a warning and instead produce a different result that s usually a long integer The problematic expressions are primarily left shifts and lengthy hexadecimal and octal constants For example 2 32 results in a warning in 2 3 evaluating to 0 on 32 bit platforms In Python 2 4 this expression now returns the correct answer 8589934592 See also PEP 237 Unifying Long Integers and Integers Original PEP written by Moshe Zadka and GvR The changes for 2 4 were implemented by Kalle Svensson PEP 289 Generator Expressions The iterator feature introduced in Python 2 2 and the itertools module make it easier to write programs that loop through large data sets without having the entire data set in memory at one time List comprehensions don t fit into this picture very well because they produce a Python list object containing all of the items This unavoidably pulls all of the objects into memory which can be a problem if your data set is very large When trying to write a functionally styled program it would be natural to write something like links link for link in get_all_links if not link followed for link in links instead of for link in get_all_links if link followed continue The first form is more concise and perhaps more readable but if you re dealing with a large number of link objects you d have to write the second form to avoid hav,en
761,ing all link objects in memory at the same time Generator expressions work similarly to list comprehensions but don t materialize the entire list instead they create a generator that will return elements one by one The above example could be written as links link for link in get_all_links if not link followed for link in links Generator expressions always have to be written inside parentheses as in the above example The parentheses signalling a function call also count so if you want to create an iterator that will be immediately passed to a function you could write print sum obj count for obj in list_all_objects Generator expressions differ from list comprehensions in various small ways Most notably the loop variable obj in the above example is not accessible outside of the generator expression List comprehensions leave the variable assigned to its last value future versions of Python will change this making list comprehensions match generator expressions in this respect See also PEP 289 Generator Expressions Proposed by Raymond Hettinger and implemented by Jiwon Seo with early efforts steered by Hye Shik Chang PEP 292 Simpler String Substitutions Some new classes in the standard library provide an alternative mechanism for substituting variables into strings this style of substitution may be better for applications where untrained users need to edit templates The usual way of substituting variables by name is the operator page i title s page 2 title The Best of Times 2 The Best of Times When writing the template string it can be easy to forget the i or s after the closing parenthesis This isn t a big problem if the template is in a Python module because you run the code get an Unsupported format character ValueError and fix the problem However consider an application such as Mailman where template strings or translations are being edited by users who aren t aware of the Python language The format string s syntax is complicated to explain to such users and if they make a mistake it s difficult to provide helpful feedback to them PEP 292 adds a Template class to the string module that uses to indicate a substitution import string t string Template page title t substitute page 2 title The Best of Times 2 The Best of Times If a key is missing from the dictionary the substitute method will raise a KeyError There s also a safe_substitute method that ignores missing keys t string Template page title t safe_substitute page 3 3 title See also PEP 292 Simpler String Substitutions Written and implemented by Barry Warsaw PEP 318 Decorators for Functions and Methods Python 2 2 extended Python s object model by adding static methods and class methods but it didn t extend Python s syntax to provide any new way of defining static or class methods Instead you had to write a def statement in the usual way and pass the resulting method to a staticmethod or classmethod function that would wrap up the function as a method of the new type Your code would look like this class C def meth cls meth classmethod meth Rebind name to wrapped up class method If the method was very long it would be easy to miss or forget the classmethod invocation after the function body The intention was always to add some syntax to make such definitions more readable but at the time of 2 2 s release a good syntax was not obvious Today a good syntax still isn t obvious but users are asking for easier access to the feature a new syntactic feature has been added to meet this need The new feature is called function decorators The name comes from the idea that classmethod staticmethod and friends are storing additional information on a function object they re decorating functions with more details The notation borrows from Java and uses the character as an indicator Using the new syntax the example above would be written class C classmethod def meth cls The classmethod is shorthand for the meth classmethod meth assignment More generally if you have the following A B C def f It s equivalent to the following pre decorator code def f f A B C f Decorators must come on the l,en
762,ine before a function definition one decorator per line and can t be on the same line as the def statement meaning that A def f is illegal You can only decorate function definitions either at the module level or inside a class you can t decorate class definitions A decorator is just a function that takes the function to be decorated as an argument and returns either the same function or some new object The return value of the decorator need not be callable though it typically is unless further decorators will be applied to the result It s easy to write your own decorators The following simple example just sets an attribute on the function object def deco func func attr decorated return func deco def f pass f function f at 0x402ef0d4 f attr decorated As a slightly more realistic example the following decorator checks that the supplied argument is an integer def require_int func def wrapper arg assert isinstance arg int return func arg return wrapper require_int def p1 arg print arg require_int def p2 arg print arg 2 An example in PEP 318 contains a fancier version of this idea that lets you both specify the required type and check the returned type Decorator functions can take arguments If arguments are supplied your decorator function is called with only those arguments and must return a new decorator function this function must take a single function and return a function as previously described In other words A B C args becomes def f _deco C args f A B _deco f Getting this right can be slightly brain bending but it s not too difficult A small related change makes the func_name attribute of functions writable This attribute is used to display function names in tracebacks so decorators should change the name of any new function that s constructed and returned See also PEP 318 Decorators for Functions Methods and Classes Written by Kevin D Smith Jim Jewett and Skip Montanaro Several people wrote patches implementing function decorators but the one that was actually checked in was patch 979728 written by Mark Russell https wiki python org moin PythonDecoratorLibrary This Wiki page contains several examples of decorators PEP 322 Reverse Iteration A new built in function reversed seq takes a sequence and returns an iterator that loops over the elements of the sequence in reverse order for i in reversed xrange 1 4 print i 3 2 1 Compared to extended slicing such as range 1 4 1 reversed is easier to read runs faster and uses substantially less memory Note that reversed only accepts sequences not arbitrary iterators If you want to reverse an iterator first convert it to a list with list input open etc passwd r for line in reversed list input print line root 0 0 System Administrator var root bin tcsh See also PEP 322 Reverse Iteration Written and implemented by Raymond Hettinger PEP 324 New subprocess Module The standard library provides a number of ways to execute a subprocess offering different features and different levels of complexity os system command is easy to use but slow it runs a shell process which executes the command and dangerous you have to be careful about escaping the shell s metacharacters The popen2 module offers classes that can capture standard output and standard error from the subprocess but the naming is confusing The subprocess module cleans this up providing a unified interface that offers all the features you might need Instead of popen2 s collection of classes subprocess contains a single class called subprocess Popen whose constructor supports a number of different keyword arguments class Popen args bufsize 0 executable None stdin None stdout None stderr None preexec_fn None close_fds False shell False cwd None env None universal_newlines False startupinfo None creationflags 0 args is commonly a sequence of strings that will be the arguments to the program executed as the subprocess If the shell argument is true args can be a string which will then be passed on to the shell for interpretation just as os system does stdin stdout and stderr specify what the subprocess s input output and error streams w,en
763,ill be You can provide a file object or a file descriptor or you can use the constant subprocess PIPE to create a pipe between the subprocess and the parent The constructor has a number of handy options close_fds requests that all file descriptors be closed before running the subprocess cwd specifies the working directory in which the subprocess will be executed defaulting to whatever the parent s working directory is env is a dictionary specifying environment variables preexec_fn is a function that gets called before the child is started universal_newlines opens the child s input and output using Python s universal newlines feature Once you ve created the Popen instance you can call its wait method to pause until the subprocess has exited poll to check if it s exited without pausing or communicate data to send the string data to the subprocess s standard input communicate data then reads any data that the subprocess has sent to its standard output or standard error returning a tuple stdout_data stderr_data call is a shortcut that passes its arguments along to the Popen constructor waits for the command to complete and returns the status code of the subprocess It can serve as a safer analog to os system sts subprocess call dpkg i tmp new package deb if sts 0 Success else dpkg returned an error The command is invoked without use of the shell If you really do want to use the shell you can add shell True as a keyword argument and provide a string instead of a sequence sts subprocess call dpkg i tmp new package deb shell True The PEP takes various examples of shell and Python code and shows how they d be translated into Python code that uses subprocess Reading this section of the PEP is highly recommended See also PEP 324 subprocess New process module Written and implemented by Peter Åstrand with assistance from Fredrik Lundh and others PEP 327 Decimal Data Type Python has always supported floating point FP numbers based on the underlying C double type as a data type However while most programming languages provide a floating point type many people even programmers are unaware that floating point numbers don t represent certain decimal fractions accurately The new Decimal type can represent these fractions accurately up to a user specified precision limit Why is Decimal needed The limitations arise from the representation used for floating point numbers FP numbers are made up of three components The sign which is positive or negative The mantissa which is a single digit binary number followed by a fractional part For example 1 01 in base 2 notation is 1 0 2 1 4 or 1 25 in decimal notation The exponent which tells where the decimal point is located in the number represented For example the number 1 25 has positive sign a mantissa value of 1 01 in binary and an exponent of 0 the decimal point doesn t need to be shifted The number 5 has the same sign and mantissa but the exponent is 2 because the mantissa is multiplied by 4 2 to the power of the exponent 2 1 25 4 equals 5 Modern systems usually provide floating point support that conforms to a standard called IEEE 754 C s double type is usually implemented as a 64 bit IEEE 754 number which uses 52 bits of space for the mantissa This means that numbers can only be specified to 52 bits of precision If you re trying to represent numbers whose expansion repeats endlessly the expansion is cut off after 52 bits Unfortunately most software needs to produce output in base 10 and common fractions in base 10 are often repeating decimals in binary For example 1 1 decimal is binary 1 0001100110011 1 1 16 1 32 1 256 plus an infinite number of additional terms IEEE 754 has to chop off that infinitely repeated decimal after 52 digits so the representation is slightly inaccurate Sometimes you can see this inaccuracy when the number is printed 1 1 1 1000000000000001 The inaccuracy isn t always visible when you print the number because the FP to decimal string conversion is provided by the C library and most C libraries try to produce sensible output Even if it s not displayed however the inaccu,en
764,racy is still there and subsequent operations can magnify the error For many applications this doesn t matter If I m plotting points and displaying them on my monitor the difference between 1 1 and 1 1000000000000001 is too small to be visible Reports often limit output to a certain number of decimal places and if you round the number to two or three or even eight decimal places the error is never apparent However for applications where it does matter it s a lot of work to implement your own custom arithmetic routines Hence the Decimal type was created The Decimal type A new module decimal was added to Python s standard library It contains two classes Decimal and Context Decimal instances represent numbers and Context instances are used to wrap up various settings such as the precision and default rounding mode Decimal instances are immutable like regular Python integers and FP numbers once it s been created you can t change the value an instance represents Decimal instances can be created from integers or strings import decimal decimal Decimal 1972 Decimal 1972 decimal Decimal 1 1 Decimal 1 1 You can also provide tuples containing the sign the mantissa represented as a tuple of decimal digits and the exponent decimal Decimal 1 1 4 7 5 2 Decimal 14 75 Cautionary note the sign bit is a Boolean value so 0 is positive and 1 is negative Converting from floating point numbers poses a bit of a problem should the FP number representing 1 1 turn into the decimal number for exactly 1 1 or for 1 1 plus whatever inaccuracies are introduced The decision was to dodge the issue and leave such a conversion out of the API Instead you should convert the floating point number into a string using the desired precision and pass the string to the Decimal constructor f 1 1 decimal Decimal str f Decimal 1 1 decimal Decimal 12f f Decimal 1 100000000000 Once you have Decimal instances you can perform the usual mathematical operations on them One limitation exponentiation requires an integer exponent a decimal Decimal 35 72 b decimal Decimal 1 73 a b Decimal 37 45 a b Decimal 33 99 a b Decimal 61 7956 a b Decimal 20 64739884393063583815028902 a 2 Decimal 1275 9184 a b Traceback most recent call last decimal InvalidOperation x non integer You can combine Decimal instances with integers but not with floating point numbers a 4 Decimal 39 72 a 4 5 Traceback most recent call last TypeError You can interact Decimal only with int long or Decimal data types Decimal numbers can be used with the math and cmath modules but note that they ll be immediately converted to floating point numbers before the operation is performed resulting in a possible loss of precision and accuracy You ll also get back a regular floating point number and not a Decimal import math cmath d decimal Decimal 123456789012 345 math sqrt d 351364 18288201344 cmath sqrt d 351364 18288201344j Decimal instances have a sqrt method that returns a Decimal but if you need other things such as trigonometric functions you ll have to implement them d sqrt Decimal 351364 1828820134592177245001 The Context type Instances of the Context class encapsulate several settings for decimal operations prec is the precision the number of decimal places rounding specifies the rounding mode The decimal module has constants for the various possibilities ROUND_DOWN ROUND_CEILING ROUND_HALF_EVEN and various others traps is a dictionary specifying what happens on encountering certain error conditions either an exception is raised or a value is returned Some examples of error conditions are division by zero loss of precision and overflow There s a thread local default context available by calling getcontext you can change the properties of this context to alter the default precision rounding or trap handling The following example shows the effect of changing the precision of the default context decimal getcontext prec 28 decimal Decimal 1 decimal Decimal 7 Decimal 0 1428571428571428571428571429 decimal getcontext prec 9 decimal Decimal 1 decimal Decimal 7 Decimal 0 142857143 The default action for error conditions,en
765, is selectable the module can either return a special value such as infinity or not a number or exceptions can be raised decimal Decimal 1 decimal Decimal 0 Traceback most recent call last decimal DivisionByZero x 0 decimal getcontext traps decimal DivisionByZero False decimal Decimal 1 decimal Decimal 0 Decimal Infinity The Context instance also has various methods for formatting numbers such as to_eng_string and to_sci_string For more information see the documentation for the decimal module which includes a quick start tutorial and a reference See also PEP 327 Decimal Data Type Written by Facundo Batista and implemented by Facundo Batista Eric Price Raymond Hettinger Aahz and Tim Peters http www lahey com float htm The article uses Fortran code to illustrate many of the problems that floating point inaccuracy can cause http speleotrove com decimal A description of a decimal based representation This representation is being proposed as a standard and underlies the new Python decimal type Much of this material was written by Mike Cowlishaw designer of the Rexx language PEP 328 Multi line Imports One language change is a small syntactic tweak aimed at making it easier to import many names from a module In a from module import names statement names is a sequence of names separated by commas If the sequence is very long you can either write multiple imports from the same module or you can use backslashes to escape the line endings like this from SimpleXMLRPCServer import SimpleXMLRPCServer SimpleXMLRPCRequestHandler CGIXMLRPCRequestHandler resolve_dotted_attribute The syntactic change in Python 2 4 simply allows putting the names within parentheses Python ignores newlines within a parenthesized expression so the backslashes are no longer needed from SimpleXMLRPCServer import SimpleXMLRPCServer SimpleXMLRPCRequestHandler CGIXMLRPCRequestHandler resolve_dotted_attribute The PEP also proposes that all import statements be absolute imports with a leading character to indicate a relative import This part of the PEP was not implemented for Python 2 4 but was completed for Python 2 5 See also PEP 328 Imports Multi Line and Absolute Relative Written by Aahz Multi line imports were implemented by Dima Dorfman PEP 331 Locale Independent Float String Conversions The locale modules lets Python software select various conversions and display conventions that are localized to a particular country or language However the module was careful to not change the numeric locale because various functions in Python s implementation required that the numeric locale remain set to the C locale Often this was because the code was using the C library s atof function Not setting the numeric locale caused trouble for extensions that used third party C libraries however because they wouldn t have the correct locale set The motivating example was GTK whose user interface widgets weren t displaying numbers in the current locale The solution described in the PEP is to add three new functions to the Python API that perform ASCII only conversions ignoring the locale setting PyOS_ascii_strtod str ptr and PyOS_ascii_atof str ptr both convert a string to a C double PyOS_ascii_formatd buffer buf_len format d converts a double to an ASCII string The code for these functions came from the GLib library https developer old gnome org glib 2 26 whose developers kindly relicensed the relevant functions and donated them to the Python Software Foundation The locale module can now change the numeric locale letting extensions such as GTK produce the correct results See also PEP 331 Locale Independent Float String Conversions Written by Christian R Reis and implemented by Gustavo Carneiro Other Language Changes Here are all of the changes that Python 2 4 makes to the core Python language Decorators for functions and methods were added PEP 318 Built in set and frozenset types were added PEP 218 Other new built ins include the reversed seq function PEP 322 Generator expressions were added PEP 289 Certain numeric expressions no longer return values restricted to 32 or 64 bits P,en
766,EP 237 You can now put parentheses around the list of names in a from module import names statement PEP 328 The dict update method now accepts the same argument forms as the dict constructor This includes any mapping any iterable of key value pairs and keyword arguments Contributed by Raymond Hettinger The string methods ljust rjust and center now take an optional argument for specifying a fill character other than a space Contributed by Raymond Hettinger Strings also gained an rsplit method that works like the split method but splits from the end of the string Contributed by Sean Reifschneider www python org split 1 www python org www python org rsplit 1 www python org Three keyword parameters cmp key and reverse were added to the sort method of lists These parameters make some common usages of sort simpler All of these parameters are optional For the cmp parameter the value should be a comparison function that takes two parameters and returns 1 0 or 1 depending on how the parameters compare This function will then be used to sort the list Previously this was the only parameter that could be provided to sort key should be a single parameter function that takes a list element and returns a comparison key for the element The list is then sorted using the comparison keys The following example sorts a list case insensitively L A b c D L sort Case sensitive sort L A D b c Using key parameter to sort list L sort key lambda x x lower L A b c D Old fashioned way L sort cmp lambda x y cmp x lower y lower L A b c D The last example which uses the cmp parameter is the old way to perform a case insensitive sort It works but is slower than using a key parameter Using key calls lower method once for each element in the list while using cmp will call it twice for each comparison so using key saves on invocations of the lower method For simple key functions and comparison functions it is often possible to avoid a lambda expression by using an unbound method instead For example the above case insensitive sort is best written as L sort key str lower L A b c D Finally the reverse parameter takes a Boolean value If the value is true the list will be sorted into reverse order Instead of L sort L reverse you can now write L sort reverse True The results of sorting are now guaranteed to be stable This means that two entries with equal keys will be returned in the same order as they were input For example you can sort a list of people by name and then sort the list by age resulting in a list sorted by age where people with the same age are in name sorted order All changes to sort contributed by Raymond Hettinger There is a new built in function sorted iterable that works like the in place list sort method but can be used in expressions The differences are the input may be any iterable a newly formed copy is sorted leaving the original intact and the expression returns the new sorted copy L 9 7 8 3 2 4 1 6 5 10 i for i in sorted L usable in a list comprehension 11 12 13 14 15 16 17 18 19 L original is left unchanged 9 7 8 3 2 4 1 6 5 sorted Monty Python any iterable may be an input M P h n n o o t t y y List the contents of a dict sorted by key values colormap dict red 1 blue 2 green 3 black 4 yellow 5 for k v in sorted colormap iteritems print k v black 4 blue 2 green 3 red 1 yellow 5 Contributed by Raymond Hettinger Integer operations will no longer trigger an OverflowWarning The OverflowWarning warning will disappear in Python 2 5 The interpreter gained a new switch m that takes a name searches for the corresponding module on sys path and runs the module as a script For example you can now run the Python profiler with python m profile Contributed by Nick Coghlan The eval expr globals locals and execfile filename globals locals functions and the exec statement now accept any mapping type for the locals parameter Previously this had to be a regular Python dictionary Contributed by Raymond Hettinger The zip built in function and itertools izip now return an empty list if called with no arguments Previously they raised a TypeError exception This,en
767, makes them more suitable for use with variable length argument lists def transpose array return zip array transpose 1 2 3 4 5 6 1 4 2 5 3 6 transpose Contributed by Raymond Hettinger Encountering a failure while importing a module no longer leaves a partially initialized module object in sys modules The incomplete module object left behind would fool further imports of the same module into succeeding leading to confusing errors Fixed by Tim Peters None is now a constant code that binds a new value to the name None is now a syntax error Contributed by Raymond Hettinger Optimizations The inner loops for list and tuple slicing were optimized and now run about one third faster The inner loops for dictionaries were also optimized resulting in performance boosts for keys values items iterkeys itervalues and iteritems Contributed by Raymond Hettinger The machinery for growing and shrinking lists was optimized for speed and for space efficiency Appending and popping from lists now runs faster due to more efficient code paths and less frequent use of the underlying system realloc List comprehensions also benefit list extend was also optimized and no longer converts its argument into a temporary list before extending the base list Contributed by Raymond Hettinger list tuple map filter and zip now run several times faster with non sequence arguments that supply a __len__ method Contributed by Raymond Hettinger The methods list __getitem__ dict __getitem__ and dict __contains__ are now implemented as method_descriptor objects rather than wrapper_descriptor objects This form of access doubles their performance and makes them more suitable for use as arguments to functionals map mydict __getitem__ keylist Contributed by Raymond Hettinger Added a new opcode LIST_APPEND that simplifies the generated bytecode for list comprehensions and speeds them up by about a third Contributed by Raymond Hettinger The peephole bytecode optimizer has been improved to produce shorter faster bytecode remarkably the resulting bytecode is more readable Enhanced by Raymond Hettinger String concatenations in statements of the form s s abc and s abc are now performed more efficiently in certain circumstances This optimization won t be present in other Python implementations such as Jython so you shouldn t rely on it using the join method of strings is still recommended when you want to efficiently glue a large number of strings together Contributed by Armin Rigo The net result of the 2 4 optimizations is that Python 2 4 runs the pystone benchmark around 5 faster than Python 2 3 and 35 faster than Python 2 2 pystone is not a particularly good benchmark but it s the most commonly used measurement of Python s performance Your own applications may show greater or smaller benefits from Python 2 4 New Improved and Deprecated Modules As usual Python s standard library received a number of enhancements and bug fixes Here s a partial list of the most notable changes sorted alphabetically by module name Consult the Misc NEWS file in the source tree for a more complete list of changes or look through the CVS logs for all the details The asyncore module s loop function now has a count parameter that lets you perform a limited number of passes through the polling loop The default is still to loop forever The base64 module now has more complete RFC 3548 support for Base64 Base32 and Base16 encoding and decoding including optional case folding and optional alternative alphabets Contributed by Barry Warsaw The bisect module now has an underlying C implementation for improved performance Contributed by Dmitry Vasiliev The CJKCodecs collections of East Asian codecs maintained by Hye Shik Chang was integrated into 2 4 The new encodings are Chinese PRC gb2312 gbk gb18030 big5hkscs hz Chinese ROC big5 cp950 Japanese cp932 euc jis 2004 euc jp euc jisx0213 iso 2022 jp iso 2022 jp 1 iso 2022 jp 2 iso 2022 jp 3 iso 2022 jp ext iso 2022 jp 2004 shift jis shift jisx0213 shift jis 2004 Korean cp949 euc kr johab iso 2022 kr Some other new encodings were added HP Roman8 ISO_8859 11 ISO_8,en
768,859 16 PCTP 154 and TIS 620 The UTF 8 and UTF 16 codecs now cope better with receiving partial input Previously the StreamReader class would try to read more data making it impossible to resume decoding from the stream The read method will now return as much data as it can and future calls will resume decoding where previous ones left off Implemented by Walter Dörwald There is a new collections module for various specialized collection datatypes Currently it contains just one type deque a double ended queue that supports efficiently adding and removing elements from either end from collections import deque d deque ghi make a new deque with three items d append j add a new entry to the right side d appendleft f add a new entry to the left side d show the representation of the deque deque f g h i j d pop return and remove the rightmost item j d popleft return and remove the leftmost item f list d list the contents of the deque g h i h in d search the deque True Several modules such as the Queue and threading modules now take advantage of collections deque for improved performance Contributed by Raymond Hettinger The ConfigParser classes have been enhanced slightly The read method now returns a list of the files that were successfully parsed and the set method raises TypeError if passed a value argument that isn t a string Contributed by John Belmonte and David Goodger The curses module now supports the ncurses extension use_default_colors On platforms where the terminal supports transparency this makes it possible to use a transparent background Contributed by Jörg Lehmann The difflib module now includes an HtmlDiff class that creates an HTML table showing a side by side comparison of two versions of a text Contributed by Dan Gass The email package was updated to version 3 0 which dropped various deprecated APIs and removes support for Python versions earlier than 2 3 The 3 0 version of the package uses a new incremental parser for MIME messages available in the email FeedParser module The new parser doesn t require reading the entire message into memory and doesn t raise exceptions if a message is malformed instead it records any problems in the defect attribute of the message Developed by Anthony Baxter Barry Warsaw Thomas Wouters and others The heapq module has been converted to C The resulting tenfold improvement in speed makes the module suitable for handling high volumes of data In addition the module has two new functions nlargest and nsmallest that use heaps to find the N largest or smallest values in a dataset without the expense of a full sort Contributed by Raymond Hettinger The httplib module now contains constants for HTTP status codes defined in various HTTP related RFC documents Constants have names such as OK CREATED CONTINUE and MOVED_PERMANENTLY use pydoc to get a full list Contributed by Andrew Eland The imaplib module now supports IMAP s THREAD command contributed by Yves Dionne and new deleteacl and myrights methods contributed by Arnaud Mazin The itertools module gained a groupby iterable func function iterable is something that can be iterated over to return a stream of elements and the optional func parameter is a function that takes an element and returns a key value if omitted the key is simply the element itself groupby then groups the elements into subsequences which have matching values of the key and returns a series of 2 tuples containing the key value and an iterator over the subsequence Here s an example to make this clearer The key function simply returns whether a number is even or odd so the result of groupby is to return consecutive runs of odd or even numbers import itertools L 2 4 6 7 8 9 11 12 14 for key_val it in itertools groupby L lambda x x 2 print key_val list it 0 2 4 6 1 7 0 8 1 9 11 0 12 14 groupby is typically used with sorted input The logic for groupby is similar to the Unix uniq filter which makes it handy for eliminating counting or identifying duplicate elements word abracadabra letters sorted word Turn string into a sorted list of letters letters a a a a a b b c d r r ,en
769,for k g in itertools groupby letters print k list g a a a a a a b b b c c d d r r r List unique letters k for k g in groupby letters a b c d r Count letter occurrences k len list g for k g in groupby letters a 5 b 2 c 1 d 1 r 2 Contributed by Hye Shik Chang itertools also gained a function named tee iterator N that returns N independent iterators that replicate iterator If N is omitted the default is 2 L 1 2 3 i1 i2 itertools tee L i1 i2 itertools tee object at 0x402c2080 itertools tee object at 0x402c2090 list i1 Run the first iterator to exhaustion 1 2 3 list i2 Run the second iterator to exhaustion 1 2 3 Note that tee has to keep copies of the values returned by the iterator in the worst case it may need to keep all of them This should therefore be used carefully if the leading iterator can run far ahead of the trailing iterator in a long stream of inputs If the separation is large then you might as well use list instead When the iterators track closely with one another tee is ideal Possible applications include bookmarking windowing or lookahead iterators Contributed by Raymond Hettinger A number of functions were added to the locale module such as bind_textdomain_codeset to specify a particular encoding and a family of l gettext functions that return messages in the chosen encoding Contributed by Gustavo Niemeyer Some keyword arguments were added to the logging package s basicConfig function to simplify log configuration The default behavior is to log messages to standard error but various keyword arguments can be specified to log to a particular file change the logging format or set the logging level For example import logging logging basicConfig filename var log application log level 0 Log all messages format levelname process thread message Other additions to the logging package include a log level msg convenience method as well as a TimedRotatingFileHandler class that rotates its log files at a timed interval The module already had RotatingFileHandler which rotated logs once the file exceeded a certain size Both classes derive from a new BaseRotatingHandler class that can be used to implement other rotating handlers Changes implemented by Vinay Sajip The marshal module now shares interned strings on unpacking a data structure This may shrink the size of certain pickle strings but the primary effect is to make pyc files significantly smaller Contributed by Martin von Löwis The nntplib module s NNTP class gained description and descriptions methods to retrieve newsgroup descriptions for a single group or for a range of groups Contributed by Jürgen A Erhard Two new functions were added to the operator module attrgetter attr and itemgetter index Both functions return callables that take a single argument and return the corresponding attribute or item these callables make excellent data extractors when used with map or sorted For example L c 2 d 1 a 4 b 3 map operator itemgetter 0 L c d a b map operator itemgetter 1 L 2 1 4 3 sorted L key operator itemgetter 1 Sort list by second tuple item d 1 c 2 b 3 a 4 Contributed by Raymond Hettinger The optparse module was updated in various ways The module now passes its messages through gettext gettext making it possible to internationalize Optik s help and error messages Help messages for options can now include the string default which will be replaced by the option s default value Contributed by Greg Ward The long term plan is to deprecate the rfc822 module in some future Python release in favor of the email package To this end the email Utils formatdate function has been changed to make it usable as a replacement for rfc822 formatdate You may want to write new e mail processing code with this in mind Change implemented by Anthony Baxter A new urandom n function was added to the os module returning a string containing n bytes of random data This function provides access to platform specific sources of randomness such as dev urandom on Linux or the Windows CryptoAPI Contributed by Trevor Perrin Another new function os path lexists path returns true if the file specified by ,en
770,path exists whether or not it s a symbolic link This differs from the existing os path exists path function which returns false if path is a symlink that points to a destination that doesn t exist Contributed by Beni Cherniavsky A new getsid function was added to the posix module that underlies the os module Contributed by J Raynor The poplib module now supports POP over SSL Contributed by Hector Urtubia The profile module can now profile C extension functions Contributed by Nick Bastin The random module has a new method called getrandbits N that returns a long integer N bits in length The existing randrange method now uses getrandbits where appropriate making generation of arbitrarily large random numbers more efficient Contributed by Raymond Hettinger The regular expression language accepted by the re module was extended with simple conditional expressions written as group A B group is either a numeric group ID or a group name defined with P group earlier in the expression If the specified group matched the regular expression pattern A will be tested against the string if the group didn t match the pattern B will be used instead Contributed by Gustavo Niemeyer The re module is also no longer recursive thanks to a massive amount of work by Gustavo Niemeyer In a recursive regular expression engine certain patterns result in a large amount of C stack space being consumed and it was possible to overflow the stack For example if you matched a 30000 byte string of a characters against the expression a b one stack frame was consumed per character Python 2 3 tried to check for stack overflow and raise a RuntimeError exception but certain patterns could sidestep the checking and if you were unlucky Python could segfault Python 2 4 s regular expression engine can match this pattern without problems The signal module now performs tighter error checking on the parameters to the signal signal function For example you can t set a handler on the SIGKILL signal previous versions of Python would quietly accept this but 2 4 will raise a RuntimeError exception Two new functions were added to the socket module socketpair returns a pair of connected sockets and getservbyport port looks up the service name for a given port number Contributed by Dave Cole and Barry Warsaw The sys exitfunc function has been deprecated Code should be using the existing atexit module which correctly handles calling multiple exit functions Eventually sys exitfunc will become a purely internal interface accessed only by atexit The tarfile module now generates GNU format tar files by default Contributed by Lars Gustäbel The threading module now has an elegantly simple way to support thread local data The module contains a local class whose attribute values are local to different threads import threading data threading local data number 42 data url www python org 80 Other threads can assign and retrieve their own values for the number and url attributes You can subclass local to initialize attributes or to add methods Contributed by Jim Fulton The timeit module now automatically disables periodic garbage collection during the timing loop This change makes consecutive timings more comparable Contributed by Raymond Hettinger The weakref module now supports a wider variety of objects including Python functions class instances sets frozensets deques arrays files sockets and regular expression pattern objects Contributed by Raymond Hettinger The xmlrpclib module now supports a multi call extension for transmitting multiple XML RPC calls in a single HTTP operation Contributed by Brian Quinlan The mpz rotor and xreadlines modules have been removed cookielib The cookielib library supports client side handling for HTTP cookies mirroring the Cookie module s server side cookie support Cookies are stored in cookie jars the library transparently stores cookies offered by the web server in the cookie jar and fetches the cookie from the jar when connecting to the server As in web browsers policy objects control whether cookies are accepted or not In order to store cookies across ,en
771,sessions two implementations of cookie jars are provided one that stores cookies in the Netscape format so applications can use the Mozilla or Lynx cookie files and one that stores cookies in the same format as the Perl libwww library urllib2 has been changed to interact with cookielib HTTPCookieProcessor manages a cookie jar that is used when accessing URLs This module was contributed by John J Lee doctest The doctest module underwent considerable refactoring thanks to Edward Loper and Tim Peters Testing can still be as simple as running doctest testmod but the refactorings allow customizing the module s operation in various ways The new DocTestFinder class extracts the tests from a given object s docstrings def f x y f 2 2 4 f 3 2 6 return x y finder doctest DocTestFinder Get list of DocTest instances tests finder find f The new DocTestRunner class then runs individual tests and can produce a summary of the results runner doctest DocTestRunner for t in tests tried failed runner run t runner summarize verbose 1 The above example produces the following output 1 items passed all tests 2 tests in f 2 tests in 1 items 2 passed and 0 failed Test passed DocTestRunner uses an instance of the OutputChecker class to compare the expected output with the actual output This class takes a number of different flags that customize its behaviour ambitious users can also write a completely new subclass of OutputChecker The default output checker provides a number of handy features For example with the doctest ELLIPSIS option flag an ellipsis in the expected output matches any substring making it easier to accommodate outputs that vary in minor ways def o n o 1 __main__ C instance at 0x Another special string BLANKLINE matches a blank line def p n p 1 BLANKLINE Another new capability is producing a diff style display of the output by specifying the doctest REPORT_UDIFF unified diffs doctest REPORT_CDIFF context diffs or doctest REPORT_NDIFF delta style option flags For example def g n g 4 here is a lengthy L here is a rather lengthy list of words split for word in L n print word Running the above function s tests with doctest REPORT_UDIFF specified you get the following output File t py line 15 in g Failed example g 4 Differences unified diff with expected actual 2 3 2 3 is a lengthy rather Build and C API Changes Some of the changes to Python s build process and to the C API are Three new convenience macros were added for common return values from extension functions Py_RETURN_NONE Py_RETURN_TRUE and Py_RETURN_FALSE Contributed by Brett Cannon Another new macro Py_CLEAR decreases the reference count of obj and sets obj to the null pointer Contributed by Jim Fulton A new function PyTuple_Pack N obj1 obj2 objN constructs tuples from a variable length argument list of Python objects Contributed by Raymond Hettinger A new function PyDict_Contains d k implements fast dictionary lookups without masking exceptions raised during the look up process Contributed by Raymond Hettinger The Py_IS_NAN X macro returns 1 if its float or double argument X is a NaN Contributed by Tim Peters C code can avoid unnecessary locking by using the new PyEval_ThreadsInitialized function to tell if any thread operations have been performed If this function returns false no lock operations are needed Contributed by Nick Coghlan A new function PyArg_VaParseTupleAndKeywords is the same as PyArg_ParseTupleAndKeywords but takes a va_list instead of a number of arguments Contributed by Greg Chapman A new method flag METH_COEXIST allows a function defined in slots to co exist with a PyCFunction having the same name This can halve the access time for a method such as set __contains__ Contributed by Raymond Hettinger Python can now be built with additional profiling for the interpreter itself intended as an aid to people developing the Python core Providing enable profiling to the configure script will let you profile the interpreter with gprof and providing the with tsc switch enables profiling using the Pentium s Time Stamp Counter register Note that the with tsc switch i,en
772,s slightly misnamed because the profiling feature also works on the PowerPC platform though that processor architecture doesn t call that register the TSC register Contributed by Jeremy Hylton The tracebackobject type has been renamed to PyTracebackObject Port Specific Changes The Windows port now builds under MSVC 7 1 as well as version 6 Contributed by Martin von Löwis Porting to Python 2 4 This section lists previously described changes that may require changes to your code Left shifts and hexadecimal octal constants that are too large no longer trigger a FutureWarning and return a value limited to 32 or 64 bits instead they return a long integer Integer operations will no longer trigger an OverflowWarning The OverflowWarning warning will disappear in Python 2 5 The zip built in function and itertools izip now return an empty list instead of raising a TypeError exception if called with no arguments You can no longer compare the date and datetime instances provided by the datetime module Two instances of different classes will now always be unequal and relative comparisons will raise a TypeError dircache listdir now passes exceptions to the caller instead of returning empty lists LexicalHandler startDTD used to receive the public and system IDs in the wrong order This has been corrected applications relying on the wrong order need to be fixed fcntl ioctl now warns if the mutate argument is omitted and relevant The tarfile module now generates GNU format tar files by default Encountering a failure while importing a module no longer leaves a partially initialized module object in sys modules None is now a constant code that binds a new value to the name None is now a syntax error The signals signal function now raises a RuntimeError exception for certain illegal values previously these errors would pass silently For example you can no longer set a handler on the SIGKILL signal Acknowledgements The author would like to thank the following people for offering suggestions corrections and assistance with various drafts of this article Koray Can Hye Shik Chang Michael Dyck Raymond Hettinger Brian Hurt Hamish Lawson Fredrik Lundh Sean Reifschneider Sadruddin Rejeb,en
773,abc Abstract Base Classes Source code Lib abc py This module provides the infrastructure for defining abstract base classes ABCs in Python as outlined in PEP 3119 see the PEP for why this was added to Python See also PEP 3141 and the numbers module regarding a type hierarchy for numbers based on ABCs The collections module has some concrete classes that derive from ABCs these can of course be further derived In addition the collections abc submodule has some ABCs that can be used to test whether a class or instance provides a particular interface for example if it is hashable or if it is a mapping This module provides the metaclass ABCMeta for defining ABCs and a helper class ABC to alternatively define ABCs through inheritance class abc ABC A helper class that has ABCMeta as its metaclass With this class an abstract base class can be created by simply deriving from ABC avoiding sometimes confusing metaclass usage for example from abc import ABC class MyABC ABC pass Note that the type of ABC is still ABCMeta therefore inheriting from ABC requires the usual precautions regarding metaclass usage as multiple inheritance may lead to metaclass conflicts One may also define an abstract base class by passing the metaclass keyword and using ABCMeta directly for example from abc import ABCMeta class MyABC metaclass ABCMeta pass New in version 3 4 class abc ABCMeta Metaclass for defining Abstract Base Classes ABCs Use this metaclass to create an ABC An ABC can be subclassed directly and then acts as a mix in class You can also register unrelated concrete classes even built in classes and unrelated ABCs as virtual subclasses these and their descendants will be considered subclasses of the registering ABC by the built in issubclass function but the registering ABC won t show up in their MRO Method Resolution Order nor will method implementations defined by the registering ABC be callable not even via super 1 Classes created with a metaclass of ABCMeta have the following method register subclass Register subclass as a virtual subclass of this ABC For example from abc import ABC class MyABC ABC pass MyABC register tuple assert issubclass tuple MyABC assert isinstance MyABC Changed in version 3 3 Returns the registered subclass to allow usage as a class decorator Changed in version 3 4 To detect calls to register you can use the get_cache_token function You can also override this method in an abstract base class __subclasshook__ subclass Must be defined as a class method Check whether subclass is considered a subclass of this ABC This means that you can customize the behavior of issubclass further without the need to call register on every class you want to consider a subclass of the ABC This class method is called from the __subclasscheck__ method of the ABC This method should return True False or NotImplemented If it returns True the subclass is considered a subclass of this ABC If it returns False the subclass is not considered a subclass of this ABC even if it would normally be one If it returns NotImplemented the subclass check is continued with the usual mechanism For a demonstration of these concepts look at this example ABC definition class Foo def __getitem__ self index def __len__ self def get_iterator self return iter self class MyIterable ABC abstractmethod def __iter__ self while False yield None def get_iterator self return self __iter__ classmethod def __subclasshook__ cls C if cls is MyIterable if any __iter__ in B __dict__ for B in C __mro__ return True return NotImplemented MyIterable register Foo The ABC MyIterable defines the standard iterable method __iter__ as an abstract method The implementation given here can still be called from subclasses The get_iterator method is also part of the MyIterable abstract base class but it does not have to be overridden in non abstract derived classes The __subclasshook__ class method defined here says that any class that has an __iter__ method in its __dict__ or in that of one of its base classes accessed via the __mro__ list is considered a MyIterable too Finally the last line ,en
774,makes Foo a virtual subclass of MyIterable even though it does not define an __iter__ method it uses the old style iterable protocol defined in terms of __len__ and __getitem__ Note that this will not make get_iterator available as a method of Foo so it is provided separately The abc module also provides the following decorator abc abstractmethod A decorator indicating abstract methods Using this decorator requires that the class s metaclass is ABCMeta or is derived from it A class that has a metaclass derived from ABCMeta cannot be instantiated unless all of its abstract methods and properties are overridden The abstract methods can be called using any of the normal super call mechanisms abstractmethod may be used to declare abstract methods for properties and descriptors Dynamically adding abstract methods to a class or attempting to modify the abstraction status of a method or class once it is created are only supported using the update_abstractmethods function The abstractmethod only affects subclasses derived using regular inheritance virtual subclasses registered with the ABC s register method are not affected When abstractmethod is applied in combination with other method descriptors it should be applied as the innermost decorator as shown in the following usage examples class C ABC abstractmethod def my_abstract_method self arg1 classmethod abstractmethod def my_abstract_classmethod cls arg2 staticmethod abstractmethod def my_abstract_staticmethod arg3 property abstractmethod def my_abstract_property self my_abstract_property setter abstractmethod def my_abstract_property self val abstractmethod def _get_x self abstractmethod def _set_x self val x property _get_x _set_x In order to correctly interoperate with the abstract base class machinery the descriptor must identify itself as abstract using __isabstractmethod__ In general this attribute should be True if any of the methods used to compose the descriptor are abstract For example Python s built in property does the equivalent of class Descriptor property def __isabstractmethod__ self return any getattr f __isabstractmethod__ False for f in self _fget self _fset self _fdel Note Unlike Java abstract methods these abstract methods may have an implementation This implementation can be called via the super mechanism from the class that overrides it This could be useful as an end point for a super call in a framework that uses cooperative multiple inheritance The abc module also supports the following legacy decorators abc abstractclassmethod New in version 3 2 Deprecated since version 3 3 It is now possible to use classmethod with abstractmethod making this decorator redundant A subclass of the built in classmethod indicating an abstract classmethod Otherwise it is similar to abstractmethod This special case is deprecated as the classmethod decorator is now correctly identified as abstract when applied to an abstract method class C ABC classmethod abstractmethod def my_abstract_classmethod cls arg abc abstractstaticmethod New in version 3 2 Deprecated since version 3 3 It is now possible to use staticmethod with abstractmethod making this decorator redundant A subclass of the built in staticmethod indicating an abstract staticmethod Otherwise it is similar to abstractmethod This special case is deprecated as the staticmethod decorator is now correctly identified as abstract when applied to an abstract method class C ABC staticmethod abstractmethod def my_abstract_staticmethod arg abc abstractproperty Deprecated since version 3 3 It is now possible to use property property getter property setter and property deleter with abstractmethod making this decorator redundant A subclass of the built in property indicating an abstract property This special case is deprecated as the property decorator is now correctly identified as abstract when applied to an abstract method class C ABC property abstractmethod def my_abstract_property self The above example defines a read only property you can also define a read write abstract property by appropriately marking one or more of t,en
775,he underlying methods as abstract class C ABC property def x self x setter abstractmethod def x self val If only some components are abstract only those components need to be updated to create a concrete property in a subclass class D C C x setter def x self val The abc module also provides the following functions abc get_cache_token Returns the current abstract base class cache token The token is an opaque object that supports equality testing identifying the current version of the abstract base class cache for virtual subclasses The token changes with every call to ABCMeta register on any ABC New in version 3 4 abc update_abstractmethods cls A function to recalculate an abstract class s abstraction status This function should be called if a class s abstract methods have been implemented or changed after it was created Usually this function should be called from within a class decorator Returns cls to allow usage as a class decorator If cls is not an instance of ABCMeta does nothing Note This function assumes that cls s superclasses are already updated It does not update any subclasses New in version 3 10 Footnotes 1 C programmers should note that Python s virtual base class concept is not the same as C s,en
776,_thread Low level threading API This module provides low level primitives for working with multiple threads also called light weight processes or tasks multiple threads of control sharing their global data space For synchronization simple locks also called mutexes or binary semaphores are provided The threading module provides an easier to use and higher level threading API built on top of this module Changed in version 3 7 This module used to be optional it is now always available This module defines the following constants and functions exception _thread error Raised on thread specific errors Changed in version 3 3 This is now a synonym of the built in RuntimeError _thread LockType This is the type of lock objects _thread start_new_thread function args kwargs Start a new thread and return its identifier The thread executes the function function with the argument list args which must be a tuple The optional kwargs argument specifies a dictionary of keyword arguments When the function returns the thread silently exits When the function terminates with an unhandled exception sys unraisablehook is called to handle the exception The object attribute of the hook argument is function By default a stack trace is printed and then the thread exits but other threads continue to run When the function raises a SystemExit exception it is silently ignored Raises an auditing event _thread start_new_thread with arguments function args kwargs Changed in version 3 8 sys unraisablehook is now used to handle unhandled exceptions _thread interrupt_main signum signal SIGINT Simulate the effect of a signal arriving in the main thread A thread can use this function to interrupt the main thread though there is no guarantee that the interruption will happen immediately If given signum is the number of the signal to simulate If signum is not given signal SIGINT is simulated If the given signal isn t handled by Python it was set to signal SIG_DFL or signal SIG_IGN this function does nothing Changed in version 3 10 The signum argument is added to customize the signal number Note This does not emit the corresponding signal but schedules a call to the associated handler if it exists If you want to truly emit the signal use signal raise_signal _thread exit Raise the SystemExit exception When not caught this will cause the thread to exit silently _thread allocate_lock Return a new lock object Methods of locks are described below The lock is initially unlocked _thread get_ident Return the thread identifier of the current thread This is a nonzero integer Its value has no direct meaning it is intended as a magic cookie to be used e g to index a dictionary of thread specific data Thread identifiers may be recycled when a thread exits and another thread is created _thread get_native_id Return the native integral Thread ID of the current thread assigned by the kernel This is a non negative integer Its value may be used to uniquely identify this particular thread system wide until the thread terminates after which the value may be recycled by the OS Availability Windows FreeBSD Linux macOS OpenBSD NetBSD AIX DragonFlyBSD New in version 3 8 _thread stack_size size Return the thread stack size used when creating new threads The optional size argument specifies the stack size to be used for subsequently created threads and must be 0 use platform or configured default or a positive integer value of at least 32 768 32 KiB If size is not specified 0 is used If changing the thread stack size is unsupported a RuntimeError is raised If the specified stack size is invalid a ValueError is raised and the stack size is unmodified 32 KiB is currently the minimum supported stack size value to guarantee sufficient stack space for the interpreter itself Note that some platforms may have particular restrictions on values for the stack size such as requiring a minimum stack size 32 KiB or requiring allocation in multiples of the system memory page size platform documentation should be referred to for more information 4 KiB pages are common using multiples of 4096 for the stack ,en
777,size is the suggested approach in the absence of more specific information Availability Windows pthreads Unix platforms with POSIX threads support _thread TIMEOUT_MAX The maximum value allowed for the timeout parameter of Lock acquire Specifying a timeout greater than this value will raise an OverflowError New in version 3 2 Lock objects have the following methods lock acquire blocking True timeout 1 Without any optional argument this method acquires the lock unconditionally if necessary waiting until it is released by another thread only one thread at a time can acquire a lock that s their reason for existence If the blocking argument is present the action depends on its value if it is False the lock is only acquired if it can be acquired immediately without waiting while if it is True the lock is acquired unconditionally as above If the floating point timeout argument is present and positive it specifies the maximum wait time in seconds before returning A negative timeout argument specifies an unbounded wait You cannot specify a timeout if blocking is False The return value is True if the lock is acquired successfully False if not Changed in version 3 2 The timeout parameter is new Changed in version 3 2 Lock acquires can now be interrupted by signals on POSIX lock release Releases the lock The lock must have been acquired earlier but not necessarily by the same thread lock locked Return the status of the lock True if it has been acquired by some thread False if not In addition to these methods lock objects can also be used via the with statement e g import _thread a_lock _thread allocate_lock with a_lock print a_lock is locked while this executes Caveats Threads interact strangely with interrupts the KeyboardInterrupt exception will be received by an arbitrary thread When the signal module is available interrupts always go to the main thread Calling sys exit or raising the SystemExit exception is equivalent to calling _thread exit It is not possible to interrupt the acquire method on a lock the KeyboardInterrupt exception will happen after the lock has been acquired When the main thread exits it is system defined whether the other threads survive On most systems they are killed without executing try finally clauses or executing object destructors When the main thread exits it does not do any of its usual cleanup except that try finally clauses are honored and the standard I O files are not flushed,en
778,select Waiting for I O completion This module provides access to the select and poll functions available in most operating systems devpoll available on Solaris and derivatives epoll available on Linux 2 5 and kqueue available on most BSD Note that on Windows it only works for sockets on other operating systems it also works for other file types in particular on Unix it works on pipes It cannot be used on regular files to determine whether a file has grown since it was last read Note The selectors module allows high level and efficient I O multiplexing built upon the select module primitives Users are encouraged to use the selectors module instead unless they want precise control over the OS level primitives used Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information The module defines the following exception select error A deprecated alias of OSError Changed in version 3 3 Following PEP 3151 this class was made an alias of OSError select devpoll Only supported on Solaris and derivatives Returns a dev poll polling object see section dev poll Polling Objects below for the methods supported by devpoll objects devpoll objects are linked to the number of file descriptors allowed at the time of instantiation If your program reduces this value devpoll will fail If your program increases this value devpoll may return an incomplete list of active file descriptors The new file descriptor is non inheritable New in version 3 3 Changed in version 3 4 The new file descriptor is now non inheritable select epoll sizehint 1 flags 0 Only supported on Linux 2 5 44 and newer Return an edge polling object which can be used as Edge or Level Triggered interface for I O events sizehint informs epoll about the expected number of events to be registered It must be positive or 1 to use the default It is only used on older systems where epoll_create1 is not available otherwise it has no effect though its value is still checked flags is deprecated and completely ignored However when supplied its value must be 0 or select EPOLL_CLOEXEC otherwise OSError is raised See the Edge and Level Trigger Polling epoll Objects section below for the methods supported by epolling objects epoll objects support the context management protocol when used in a with statement the new file descriptor is automatically closed at the end of the block The new file descriptor is non inheritable Changed in version 3 3 Added the flags parameter Changed in version 3 4 Support for the with statement was added The new file descriptor is now non inheritable Deprecated since version 3 4 The flags parameter select EPOLL_CLOEXEC is used by default now Use os set_inheritable to make the file descriptor inheritable select poll Not supported by all operating systems Returns a polling object which supports registering and unregistering file descriptors and then polling them for I O events see section Polling Objects below for the methods supported by polling objects select kqueue Only supported on BSD Returns a kernel queue object see section Kqueue Objects below for the methods supported by kqueue objects The new file descriptor is non inheritable Changed in version 3 4 The new file descriptor is now non inheritable select kevent ident filter KQ_FILTER_READ flags KQ_EV_ADD fflags 0 data 0 udata 0 Only supported on BSD Returns a kernel event object see section Kevent Objects below for the methods supported by kevent objects select select rlist wlist xlist timeout This is a straightforward interface to the Unix select system call The first three arguments are iterables of waitable objects either integers representing file descriptors or objects with a parameterless method named fileno returning such an integer rlist wait until ready for reading wlist wait until ready for writing xlist wait for an exceptional condition see the manual page for what your system considers such a condition Empty iterables are allowed but acceptance of three empty iterables is pla,en
779,tform dependent It is known to work on Unix but not on Windows The optional timeout argument specifies a time out as a floating point number in seconds When the timeout argument is omitted the function blocks until at least one file descriptor is ready A time out value of zero specifies a poll and never blocks The return value is a triple of lists of objects that are ready subsets of the first three arguments When the time out is reached without a file descriptor becoming ready three empty lists are returned Among the acceptable object types in the iterables are Python file objects e g sys stdin or objects returned by open or os popen socket objects returned by socket socket You may also define a wrapper class yourself as long as it has an appropriate fileno method that really returns a file descriptor not just a random integer Note File objects on Windows are not acceptable but sockets are On Windows the underlying select function is provided by the WinSock library and does not handle file descriptors that don t originate from WinSock Changed in version 3 5 The function is now retried with a recomputed timeout when interrupted by a signal except if the signal handler raises an exception see PEP 475 for the rationale instead of raising InterruptedError select PIPE_BUF The minimum number of bytes which can be written without blocking to a pipe when the pipe has been reported as ready for writing by select poll or another interface in this module This doesn t apply to other kind of file like objects such as sockets This value is guaranteed by POSIX to be at least 512 Availability Unix New in version 3 2 dev poll Polling Objects Solaris and derivatives have dev poll While select is O highest file descriptor and poll is O number of file descriptors dev poll is O active file descriptors dev poll behaviour is very close to the standard poll object devpoll close Close the file descriptor of the polling object New in version 3 4 devpoll closed True if the polling object is closed New in version 3 4 devpoll fileno Return the file descriptor number of the polling object New in version 3 4 devpoll register fd eventmask Register a file descriptor with the polling object Future calls to the poll method will then check whether the file descriptor has any pending I O events fd can be either an integer or an object with a fileno method that returns an integer File objects implement fileno so they can also be used as the argument eventmask is an optional bitmask describing the type of events you want to check for The constants are the same that with poll object The default value is a combination of the constants POLLIN POLLPRI and POLLOUT Warning Registering a file descriptor that s already registered is not an error but the result is undefined The appropriate action is to unregister or modify it first This is an important difference compared with poll devpoll modify fd eventmask This method does an unregister followed by a register It is a bit more efficient that doing the same explicitly devpoll unregister fd Remove a file descriptor being tracked by a polling object Just like the register method fd can be an integer or an object with a fileno method that returns an integer Attempting to remove a file descriptor that was never registered is safely ignored devpoll poll timeout Polls the set of registered file descriptors and returns a possibly empty list containing fd event 2 tuples for the descriptors that have events or errors to report fd is the file descriptor and event is a bitmask with bits set for the reported events for that descriptor POLLIN for waiting input POLLOUT to indicate that the descriptor can be written to and so forth An empty list indicates that the call timed out and no file descriptors had any events to report If timeout is given it specifies the length of time in milliseconds which the system will wait for events before returning If timeout is omitted 1 or None the call will block until there is an event for this poll object Changed in version 3 5 The function is now retried with a recomputed timeout when interru,en
780,pted by a signal except if the signal handler raises an exception see PEP 475 for the rationale instead of raising InterruptedError Edge and Level Trigger Polling epoll Objects https linux die net man 4 epoll eventmask Constant Meaning EPOLLIN Available for read EPOLLOUT Available for write EPOLLPRI Urgent data for read EPOLLERR Error condition happened on the assoc fd EPOLLHUP Hang up happened on the assoc fd EPOLLET Set Edge Trigger behavior the default is Level Trigger behavior EPOLLONESHOT Set one shot behavior After one event is pulled out the fd is internally disabled EPOLLEXCLUSIVE Wake only one epoll object when the associated fd has an event The default if this flag is not set is to wake all epoll objects polling on a fd EPOLLRDHUP Stream socket peer closed connection or shut down writing half of connection EPOLLRDNORM Equivalent to EPOLLIN EPOLLRDBAND Priority data band can be read EPOLLWRNORM Equivalent to EPOLLOUT EPOLLWRBAND Priority data may be written EPOLLMSG Ignored New in version 3 6 EPOLLEXCLUSIVE was added It s only supported by Linux Kernel 4 5 or later epoll close Close the control file descriptor of the epoll object epoll closed True if the epoll object is closed epoll fileno Return the file descriptor number of the control fd epoll fromfd fd Create an epoll object from a given file descriptor epoll register fd eventmask Register a fd descriptor with the epoll object epoll modify fd eventmask Modify a registered file descriptor epoll unregister fd Remove a registered file descriptor from the epoll object Changed in version 3 9 The method no longer ignores the EBADF error epoll poll timeout None maxevents 1 Wait for events timeout in seconds float Changed in version 3 5 The function is now retried with a recomputed timeout when interrupted by a signal except if the signal handler raises an exception see PEP 475 for the rationale instead of raising InterruptedError Polling Objects The poll system call supported on most Unix systems provides better scalability for network servers that service many many clients at the same time poll scales better because the system call only requires listing the file descriptors of interest while select builds a bitmap turns on bits for the fds of interest and then afterward the whole bitmap has to be linearly scanned again select is O highest file descriptor while poll is O number of file descriptors poll register fd eventmask Register a file descriptor with the polling object Future calls to the poll method will then check whether the file descriptor has any pending I O events fd can be either an integer or an object with a fileno method that returns an integer File objects implement fileno so they can also be used as the argument eventmask is an optional bitmask describing the type of events you want to check for and can be a combination of the constants POLLIN POLLPRI and POLLOUT described in the table below If not specified the default value used will check for all 3 types of events Constant Meaning POLLIN There is data to read POLLPRI There is urgent data to read POLLOUT Ready for output writing will not block POLLERR Error condition of some sort POLLHUP Hung up POLLRDHUP Stream socket peer closed connection or shut down writing half of connection POLLNVAL Invalid request descriptor not open Registering a file descriptor that s already registered is not an error and has the same effect as registering the descriptor exactly once poll modify fd eventmask Modifies an already registered fd This has the same effect as register fd eventmask Attempting to modify a file descriptor that was never registered causes an OSError exception with errno ENOENT to be raised poll unregister fd Remove a file descriptor being tracked by a polling object Just like the register method fd can be an integer or an object with a fileno method that returns an integer Attempting to remove a file descriptor that was never registered causes a KeyError exception to be raised poll poll timeout Polls the set of registered file descriptors and returns a possibly empty list containing fd event 2 tu,en
781,ples for the descriptors that have events or errors to report fd is the file descriptor and event is a bitmask with bits set for the reported events for that descriptor POLLIN for waiting input POLLOUT to indicate that the descriptor can be written to and so forth An empty list indicates that the call timed out and no file descriptors had any events to report If timeout is given it specifies the length of time in milliseconds which the system will wait for events before returning If timeout is omitted negative or None the call will block until there is an event for this poll object Changed in version 3 5 The function is now retried with a recomputed timeout when interrupted by a signal except if the signal handler raises an exception see PEP 475 for the rationale instead of raising InterruptedError Kqueue Objects kqueue close Close the control file descriptor of the kqueue object kqueue closed True if the kqueue object is closed kqueue fileno Return the file descriptor number of the control fd kqueue fromfd fd Create a kqueue object from a given file descriptor kqueue control changelist max_events timeout eventlist Low level interface to kevent changelist must be an iterable of kevent objects or None max_events must be 0 or a positive integer timeout in seconds floats possible the default is None to wait forever Changed in version 3 5 The function is now retried with a recomputed timeout when interrupted by a signal except if the signal handler raises an exception see PEP 475 for the rationale instead of raising InterruptedError Kevent Objects https man freebsd org cgi man cgi query kqueue sektion 2 kevent ident Value used to identify the event The interpretation depends on the filter but it s usually the file descriptor In the constructor ident can either be an int or an object with a fileno method kevent stores the integer internally kevent filter Name of the kernel filter Constant Meaning KQ_FILTER_READ Takes a descriptor and returns whenever there is data available to read KQ_FILTER_WRITE Takes a descriptor and returns whenever there is data available to write KQ_FILTER_AIO AIO requests KQ_FILTER_VNODE Returns when one or more of the requested events watched in fflag occurs KQ_FILTER_PROC Watch for events on a process id KQ_FILTER_NETDEV Watch for events on a network device not available on macOS KQ_FILTER_SIGNAL Returns whenever the watched signal is delivered to the process KQ_FILTER_TIMER Establishes an arbitrary timer kevent flags Filter action Constant Meaning KQ_EV_ADD Adds or modifies an event KQ_EV_DELETE Removes an event from the queue KQ_EV_ENABLE Permitscontrol to returns the event KQ_EV_DISABLE Disablesevent KQ_EV_ONESHOT Removes event after first occurrence KQ_EV_CLEAR Reset the state after an event is retrieved KQ_EV_SYSFLAGS internal event KQ_EV_FLAG1 internal event KQ_EV_EOF Filter specific EOF condition KQ_EV_ERROR See return values kevent fflags Filter specific flags KQ_FILTER_READ and KQ_FILTER_WRITE filter flags Constant Meaning KQ_NOTE_LOWAT low water mark of a socket buffer KQ_FILTER_VNODE filter flags Constant Meaning KQ_NOTE_DELETE unlink was called KQ_NOTE_WRITE a write occurred KQ_NOTE_EXTEND the file was extended KQ_NOTE_ATTRIB an attribute was changed KQ_NOTE_LINK the link count has changed KQ_NOTE_RENAME the file was renamed KQ_NOTE_REVOKE access to the file was revoked KQ_FILTER_PROC filter flags Constant Meaning KQ_NOTE_EXIT the process has exited KQ_NOTE_FORK the process has called fork KQ_NOTE_EXEC the process has executed a new process KQ_NOTE_PCTRLMASK internal filter flag KQ_NOTE_PDATAMASK internal filter flag KQ_NOTE_TRACK follow a process across fork KQ_NOTE_CHILD returned on the child process for NOTE_TRACK KQ_NOTE_TRACKERR unable to attach to a child KQ_FILTER_NETDEV filter flags not available on macOS Constant Meaning KQ_NOTE_LINKUP link is up KQ_NOTE_LINKDOWN link is down KQ_NOTE_LINKINV link state is invalid kevent data Filter specific data kevent udata User defined value,en
782,hmac Keyed Hashing for Message Authentication Source code Lib hmac py This module implements the HMAC algorithm as described by RFC 2104 hmac new key msg None digestmod Return a new hmac object key is a bytes or bytearray object giving the secret key If msg is present the method call update msg is made digestmod is the digest name digest constructor or module for the HMAC object to use It may be any name suitable to hashlib new Despite its argument position it is required Changed in version 3 4 Parameter key can be a bytes or bytearray object Parameter msg can be of any type supported by hashlib Parameter digestmod can be the name of a hash algorithm Changed in version 3 8 The digestmod argument is now required Pass it as a keyword argument to avoid awkwardness when you do not have an initial msg hmac digest key msg digest Return digest of msg for given secret key and digest The function is equivalent to HMAC key msg digest digest but uses an optimized C or inline implementation which is faster for messages that fit into memory The parameters key msg and digest have the same meaning as in new CPython implementation detail the optimized C implementation is only used when digest is a string and name of a digest algorithm which is supported by OpenSSL New in version 3 7 An HMAC object has the following methods HMAC update msg Update the hmac object with msg Repeated calls are equivalent to a single call with the concatenation of all the arguments m update a m update b is equivalent to m update a b Changed in version 3 4 Parameter msg can be of any type supported by hashlib HMAC digest Return the digest of the bytes passed to the update method so far This bytes object will be the same length as the digest_size of the digest given to the constructor It may contain non ASCII bytes including NUL bytes Warning When comparing the output of digest to an externally supplied digest during a verification routine it is recommended to use the compare_digest function instead of the operator to reduce the vulnerability to timing attacks HMAC hexdigest Like digest except the digest is returned as a string twice the length containing only hexadecimal digits This may be used to exchange the value safely in email or other non binary environments Warning When comparing the output of hexdigest to an externally supplied digest during a verification routine it is recommended to use the compare_digest function instead of the operator to reduce the vulnerability to timing attacks HMAC copy Return a copy clone of the hmac object This can be used to efficiently compute the digests of strings that share a common initial substring A hash object has the following attributes HMAC digest_size The size of the resulting HMAC digest in bytes HMAC block_size The internal block size of the hash algorithm in bytes New in version 3 4 HMAC name The canonical name of this HMAC always lowercase e g hmac md5 New in version 3 4 Changed in version 3 10 Removed the undocumented attributes HMAC digest_cons HMAC inner and HMAC outer This module also provides the following helper function hmac compare_digest a b Return a b This function uses an approach designed to prevent timing analysis by avoiding content based short circuiting behaviour making it appropriate for cryptography a and b must both be of the same type either str ASCII only as e g returned by HMAC hexdigest or a bytes like object Note If a and b are of different lengths or if an error occurs a timing attack could theoretically reveal information about the types and lengths of a and b but not their values New in version 3 3 Changed in version 3 10 The function uses OpenSSL s CRYPTO_memcmp internally when available See also Module hashlib The Python module providing secure hash functions,en
783,smtplib SMTP protocol client Source code Lib smtplib py The smtplib module defines an SMTP client session object that can be used to send mail to any internet machine with an SMTP or ESMTP listener daemon For details of SMTP and ESMTP operation consult RFC 821 Simple Mail Transfer Protocol and RFC 1869 SMTP Service Extensions Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information class smtplib SMTP host port 0 local_hostname None timeout source_address None An SMTP instance encapsulates an SMTP connection It has methods that support a full repertoire of SMTP and ESMTP operations If the optional host and port parameters are given the SMTP connect method is called with those parameters during initialization If specified local_hostname is used as the FQDN of the local host in the HELO EHLO command Otherwise the local hostname is found using socket getfqdn If the connect call returns anything other than a success code an SMTPConnectError is raised The optional timeout parameter specifies a timeout in seconds for blocking operations like the connection attempt if not specified the global default timeout setting will be used If the timeout expires TimeoutError is raised The optional source_address parameter allows binding to some specific source address in a machine with multiple network interfaces and or to some specific source TCP port It takes a 2 tuple host port for the socket to bind to as its source address before connecting If omitted or if host or port are and or 0 respectively the OS default behavior will be used For normal use you should only require the initialization connect sendmail and SMTP quit methods An example is included below The SMTP class supports the with statement When used like this the SMTP QUIT command is issued automatically when the with statement exits E g from smtplib import SMTP with SMTP domain org as smtp smtp noop 250 b Ok All commands will raise an auditing event smtplib SMTP send with arguments self and data where data is the bytes about to be sent to the remote host Changed in version 3 3 Support for the with statement was added Changed in version 3 3 source_address argument was added New in version 3 5 The SMTPUTF8 extension RFC 6531 is now supported Changed in version 3 9 If the timeout parameter is set to be zero it will raise a ValueError to prevent the creation of a non blocking socket class smtplib SMTP_SSL host port 0 local_hostname None timeout context None source_address None An SMTP_SSL instance behaves exactly the same as instances of SMTP SMTP_SSL should be used for situations where SSL is required from the beginning of the connection and using starttls is not appropriate If host is not specified the local host is used If port is zero the standard SMTP over SSL port 465 is used The optional arguments local_hostname timeout and source_address have the same meaning as they do in the SMTP class context also optional can contain a SSLContext and allows configuring various aspects of the secure connection Please read Security considerations for best practices Changed in version 3 3 context was added Changed in version 3 3 The source_address argument was added Changed in version 3 4 The class now supports hostname check with ssl SSLContext check_hostname and Server Name Indication see ssl HAS_SNI Changed in version 3 9 If the timeout parameter is set to be zero it will raise a ValueError to prevent the creation of a non blocking socket Changed in version 3 12 The deprecated keyfile and certfile parameters have been removed class smtplib LMTP host port LMTP_PORT local_hostname None source_address None timeout The LMTP protocol which is very similar to ESMTP is heavily based on the standard SMTP client It s common to use Unix sockets for LMTP so our connect method must support that as well as a regular host port server The optional arguments local_hostname and source_address have the same meaning as they do in the SMTP class To specify a Unix socket you ,en
784,must use an absolute path for host starting with a Authentication is supported using the regular SMTP mechanism When using a Unix socket LMTP generally don t support or require any authentication but your mileage might vary Changed in version 3 9 The optional timeout parameter was added A nice selection of exceptions is defined as well exception smtplib SMTPException Subclass of OSError that is the base exception class for all the other exceptions provided by this module Changed in version 3 4 SMTPException became subclass of OSError exception smtplib SMTPServerDisconnected This exception is raised when the server unexpectedly disconnects or when an attempt is made to use the SMTP instance before connecting it to a server exception smtplib SMTPResponseException Base class for all exceptions that include an SMTP error code These exceptions are generated in some instances when the SMTP server returns an error code The error code is stored in the smtp_code attribute of the error and the smtp_error attribute is set to the error message exception smtplib SMTPSenderRefused Sender address refused In addition to the attributes set by on all SMTPResponseException exceptions this sets sender to the string that the SMTP server refused exception smtplib SMTPRecipientsRefused All recipient addresses refused The errors for each recipient are accessible through the attribute recipients which is a dictionary of exactly the same sort as SMTP sendmail returns exception smtplib SMTPDataError The SMTP server refused to accept the message data exception smtplib SMTPConnectError Error occurred during establishment of a connection with the server exception smtplib SMTPHeloError The server refused our HELO message exception smtplib SMTPNotSupportedError The command or option attempted is not supported by the server New in version 3 5 exception smtplib SMTPAuthenticationError SMTP authentication went wrong Most probably the server didn t accept the username password combination provided See also RFC 821 Simple Mail Transfer Protocol Protocol definition for SMTP This document covers the model operating procedure and protocol details for SMTP RFC 1869 SMTP Service Extensions Definition of the ESMTP extensions for SMTP This describes a framework for extending SMTP with new commands supporting dynamic discovery of the commands provided by the server and defines a few additional commands SMTP Objects An SMTP instance has the following methods SMTP set_debuglevel level Set the debug output level A value of 1 or True for level results in debug messages for connection and for all messages sent to and received from the server A value of 2 for level results in these messages being timestamped Changed in version 3 5 Added debuglevel 2 SMTP docmd cmd args Send a command cmd to the server The optional argument args is simply concatenated to the command separated by a space This returns a 2 tuple composed of a numeric response code and the actual response line multiline responses are joined into one long line In normal operation it should not be necessary to call this method explicitly It is used to implement other methods and may be useful for testing private extensions If the connection to the server is lost while waiting for the reply SMTPServerDisconnected will be raised SMTP connect host localhost port 0 Connect to a host on a given port The defaults are to connect to the local host at the standard SMTP port 25 If the hostname ends with a colon followed by a number that suffix will be stripped off and the number interpreted as the port number to use This method is automatically invoked by the constructor if a host is specified during instantiation Returns a 2 tuple of the response code and message sent by the server in its connection response Raises an auditing event smtplib connect with arguments self host port SMTP helo name Identify yourself to the SMTP server using HELO The hostname argument defaults to the fully qualified domain name of the local host The message returned by the server is stored as the helo_resp attribute of the object In normal ope,en
785,ration it should not be necessary to call this method explicitly It will be implicitly called by the sendmail when necessary SMTP ehlo name Identify yourself to an ESMTP server using EHLO The hostname argument defaults to the fully qualified domain name of the local host Examine the response for ESMTP option and store them for use by has_extn Also sets several informational attributes the message returned by the server is stored as the ehlo_resp attribute does_esmtp is set to True or False depending on whether the server supports ESMTP and esmtp_features will be a dictionary containing the names of the SMTP service extensions this server supports and their parameters if any Unless you wish to use has_extn before sending mail it should not be necessary to call this method explicitly It will be implicitly called by sendmail when necessary SMTP ehlo_or_helo_if_needed This method calls ehlo and or helo if there has been no previous EHLO or HELO command this session It tries ESMTP EHLO first SMTPHeloError The server didn t reply properly to the HELO greeting SMTP has_extn name Return True if name is in the set of SMTP service extensions returned by the server False otherwise Case is ignored SMTP verify address Check the validity of an address on this server using SMTP VRFY Returns a tuple consisting of code 250 and a full RFC 822 address including human name if the user address is valid Otherwise returns an SMTP error code of 400 or greater and an error string Note Many sites disable SMTP VRFY in order to foil spammers SMTP login user password initial_response_ok True Log in on an SMTP server that requires authentication The arguments are the username and the password to authenticate with If there has been no previous EHLO or HELO command this session this method tries ESMTP EHLO first This method will return normally if the authentication was successful or may raise the following exceptions SMTPHeloError The server didn t reply properly to the HELO greeting SMTPAuthenticationError The server didn t accept the username password combination SMTPNotSupportedError The AUTH command is not supported by the server SMTPException No suitable authentication method was found Each of the authentication methods supported by smtplib are tried in turn if they are advertised as supported by the server See auth for a list of supported authentication methods initial_response_ok is passed through to auth Optional keyword argument initial_response_ok specifies whether for authentication methods that support it an initial response as specified in RFC 4954 can be sent along with the AUTH command rather than requiring a challenge response Changed in version 3 5 SMTPNotSupportedError may be raised and the initial_response_ok parameter was added SMTP auth mechanism authobject initial_response_ok True Issue an SMTP AUTH command for the specified authentication mechanism and handle the challenge response via authobject mechanism specifies which authentication mechanism is to be used as argument to the AUTH command the valid values are those listed in the auth element of esmtp_features authobject must be a callable object taking an optional single argument data authobject challenge None If optional keyword argument initial_response_ok is true authobject will be called first with no argument It can return the RFC 4954 initial response ASCII str which will be encoded and sent with the AUTH command as below If the authobject does not support an initial response e g because it requires a challenge it should return None when called with challenge None If initial_response_ok is false then authobject will not be called first with None If the initial response check returns None or if initial_response_ok is false authobject will be called to process the server s challenge response the challenge argument it is passed will be a bytes It should return ASCII str data that will be base64 encoded and sent to the server The SMTP class provides authobjects for the CRAM MD5 PLAIN and LOGIN mechanisms they are named SMTP auth_cram_md5 SMTP auth_plain and SMTP auth_login ,en
786,respectively They all require that the user and password properties of the SMTP instance are set to appropriate values User code does not normally need to call auth directly but can instead call the login method which will try each of the above mechanisms in turn in the order listed auth is exposed to facilitate the implementation of authentication methods not or not yet supported directly by smtplib New in version 3 5 SMTP starttls context None Put the SMTP connection in TLS Transport Layer Security mode All SMTP commands that follow will be encrypted You should then call ehlo again If keyfile and certfile are provided they are used to create an ssl SSLContext Optional context parameter is an ssl SSLContext object This is an alternative to using a keyfile and a certfile and if specified both keyfile and certfile should be None If there has been no previous EHLO or HELO command this session this method tries ESMTP EHLO first Changed in version 3 12 The deprecated keyfile and certfile parameters have been removed SMTPHeloError The server didn t reply properly to the HELO greeting SMTPNotSupportedError The server does not support the STARTTLS extension RuntimeError SSL TLS support is not available to your Python interpreter Changed in version 3 3 context was added Changed in version 3 4 The method now supports hostname check with SSLContext check_hostname and Server Name Indicator see HAS_SNI Changed in version 3 5 The error raised for lack of STARTTLS support is now the SMTPNotSupportedError subclass instead of the base SMTPException SMTP sendmail from_addr to_addrs msg mail_options rcpt_options Send mail The required arguments are an RFC 822 from address string a list of RFC 822 to address strings a bare string will be treated as a list with 1 address and a message string The caller may pass a list of ESMTP options such as 8bitmime to be used in MAIL FROM commands as mail_options ESMTP options such as DSN commands that should be used with all RCPT commands can be passed as rcpt_options If you need to use different ESMTP options to different recipients you have to use the low level methods such as mail rcpt and data to send the message Note The from_addr and to_addrs parameters are used to construct the message envelope used by the transport agents sendmail does not modify the message headers in any way msg may be a string containing characters in the ASCII range or a byte string A string is encoded to bytes using the ascii codec and lone r and n characters are converted to r n characters A byte string is not modified If there has been no previous EHLO or HELO command this session this method tries ESMTP EHLO first If the server does ESMTP message size and each of the specified options will be passed to it if the option is in the feature set the server advertises If EHLO fails HELO will be tried and ESMTP options suppressed This method will return normally if the mail is accepted for at least one recipient Otherwise it will raise an exception That is if this method does not raise an exception then someone should get your mail If this method does not raise an exception it returns a dictionary with one entry for each recipient that was refused Each entry contains a tuple of the SMTP error code and the accompanying error message sent by the server If SMTPUTF8 is included in mail_options and the server supports it from_addr and to_addrs may contain non ASCII characters This method may raise the following exceptions SMTPRecipientsRefused All recipients were refused Nobody got the mail The recipients attribute of the exception object is a dictionary with information about the refused recipients like the one returned when at least one recipient was accepted SMTPHeloError The server didn t reply properly to the HELO greeting SMTPSenderRefused The server didn t accept the from_addr SMTPDataError The server replied with an unexpected error code other than a refusal of a recipient SMTPNotSupportedError SMTPUTF8 was given in the mail_options but is not supported by the server Unless otherwise noted the connection will be open even af,en
787,ter an exception is raised Changed in version 3 2 msg may be a byte string Changed in version 3 5 SMTPUTF8 support added and SMTPNotSupportedError may be raised if SMTPUTF8 is specified but the server does not support it SMTP send_message msg from_addr None to_addrs None mail_options rcpt_options This is a convenience method for calling sendmail with the message represented by an email message Message object The arguments have the same meaning as for sendmail except that msg is a Message object If from_addr is None or to_addrs is None send_message fills those arguments with addresses extracted from the headers of msg as specified in RFC 5322 from_addr is set to the Sender field if it is present and otherwise to the From field to_addrs combines the values if any of the To Cc and Bcc fields from msg If exactly one set of Resent headers appear in the message the regular headers are ignored and the Resent headers are used instead If the message contains more than one set of Resent headers a ValueError is raised since there is no way to unambiguously detect the most recent set of Resent headers send_message serializes msg using BytesGenerator with r n as the linesep and calls sendmail to transmit the resulting message Regardless of the values of from_addr and to_addrs send_message does not transmit any Bcc or Resent Bcc headers that may appear in msg If any of the addresses in from_addr and to_addrs contain non ASCII characters and the server does not advertise SMTPUTF8 support an SMTPNotSupported error is raised Otherwise the Message is serialized with a clone of its policy with the utf8 attribute set to True and SMTPUTF8 and BODY 8BITMIME are added to mail_options New in version 3 2 New in version 3 5 Support for internationalized addresses SMTPUTF8 SMTP quit Terminate the SMTP session and close the connection Return the result of the SMTP QUIT command Low level methods corresponding to the standard SMTP ESMTP commands HELP RSET NOOP MAIL RCPT and DATA are also supported Normally these do not need to be called directly so they are not documented here For details consult the module code SMTP Example This example prompts the user for addresses needed in the message envelope To and From addresses and the message to be delivered Note that the headers to be included with the message must be included in the message as entered this example doesn t do any processing of the RFC 822 headers In particular the To and From addresses must be included in the message headers explicitly import smtplib def prompt prompt return input prompt strip fromaddr prompt From toaddrs prompt To split print Enter message end with D Unix or Z Windows Add the From and To headers at the start msg From s r nTo s r n r n fromaddr join toaddrs while True try line input except EOFError break if not line break msg msg line print Message length is len msg server smtplib SMTP localhost server set_debuglevel 1 server sendmail fromaddr toaddrs msg server quit Note In general you will want to use the email package s features to construct an email message which you can then send via send_message see email Examples,en
788,zipapp Manage executable Python zip archives New in version 3 5 Source code Lib zipapp py This module provides tools to manage the creation of zip files containing Python code which can be executed directly by the Python interpreter The module provides both a Command Line Interface and a Python API Basic Example The following example shows how the Command Line Interface can be used to create an executable archive from a directory containing Python code When run the archive will execute the main function from the module myapp in the archive python m zipapp myapp m myapp main python myapp pyz output from myapp Command Line Interface When called as a program from the command line the following form is used python m zipapp source options If source is a directory this will create an archive from the contents of source If source is a file it should be an archive and it will be copied to the target archive or the contents of its shebang line will be displayed if the info option is specified The following options are understood o output output output Write the output to a file named output If this option is not specified the output filename will be the same as the input source with the extension pyz added If an explicit filename is given it is used as is so a pyz extension should be included if required An output filename must be specified if the source is an archive and in that case output must not be the same as source p interpreter python interpreter Add a line to the archive specifying interpreter as the command to run Also on POSIX make the archive executable The default is to write no line and not make the file executable m mainfn main mainfn Write a __main__ py file to the archive that executes mainfn The mainfn argument should have the form pkg mod fn where pkg mod is a package module in the archive and fn is a callable in the given module The __main__ py file will execute that callable main cannot be specified when copying an archive c compress Compress files with the deflate method reducing the size of the output file By default files are stored uncompressed in the archive compress has no effect when copying an archive New in version 3 7 info Display the interpreter embedded in the archive for diagnostic purposes In this case any other options are ignored and SOURCE must be an archive not a directory h help Print a short usage message and exit Python API The module defines two convenience functions zipapp create_archive source target None interpreter None main None filter None compressed False Create an application archive from source The source can be any of the following The name of a directory or a path like object referring to a directory in which case a new application archive will be created from the content of that directory The name of an existing application archive file or a path like object referring to such a file in which case the file is copied to the target modifying it to reflect the value given for the interpreter argument The file name should include the pyz extension if required A file object open for reading in bytes mode The content of the file should be an application archive and the file object is assumed to be positioned at the start of the archive The target argument determines where the resulting archive will be written If it is the name of a file or a path like object the archive will be written to that file If it is an open file object the archive will be written to that file object which must be open for writing in bytes mode If the target is omitted or None the source must be a directory and the target will be a file with the same name as the source with a pyz extension added The interpreter argument specifies the name of the Python interpreter with which the archive will be executed It is written as a shebang line at the start of the archive On POSIX this will be interpreted by the OS and on Windows it will be handled by the Python launcher Omitting the interpreter results in no shebang line being written If an interpreter is specified and the target is a filename the executable bit of th,en
789,e target file will be set The main argument specifies the name of a callable which will be used as the main program for the archive It can only be specified if the source is a directory and the source does not already contain a __main__ py file The main argument should take the form pkg module callable and the archive will be run by importing pkg module and executing the given callable with no arguments It is an error to omit main if the source is a directory and does not contain a __main__ py file as otherwise the resulting archive would not be executable The optional filter argument specifies a callback function that is passed a Path object representing the path to the file being added relative to the source directory It should return True if the file is to be added The optional compressed argument determines whether files are compressed If set to True files in the archive are compressed with the deflate method otherwise files are stored uncompressed This argument has no effect when copying an existing archive If a file object is specified for source or target it is the caller s responsibility to close it after calling create_archive When copying an existing archive file objects supplied only need read and readline or write methods When creating an archive from a directory if the target is a file object it will be passed to the zipfile ZipFile class and must supply the methods needed by that class Changed in version 3 7 Added the filter and compressed parameters zipapp get_interpreter archive Return the interpreter specified in the line at the start of the archive If there is no line return None The archive argument can be a filename or a file like object open for reading in bytes mode It is assumed to be at the start of the archive Examples Pack up a directory into an archive and run it python m zipapp myapp python myapp pyz output from myapp The same can be done using the create_archive function import zipapp zipapp create_archive myapp myapp pyz To make the application directly executable on POSIX specify an interpreter to use python m zipapp myapp p usr bin env python myapp pyz output from myapp To replace the shebang line on an existing archive create a modified archive using the create_archive function import zipapp zipapp create_archive old_archive pyz new_archive pyz usr bin python3 To update the file in place do the replacement in memory using a BytesIO object and then overwrite the source afterwards Note that there is a risk when overwriting a file in place that an error will result in the loss of the original file This code does not protect against such errors but production code should do so Also this method will only work if the archive fits in memory import zipapp import io temp io BytesIO zipapp create_archive myapp pyz temp usr bin python2 with open myapp pyz wb as f f write temp getvalue Specifying the Interpreter Note that if you specify an interpreter and then distribute your application archive you need to ensure that the interpreter used is portable The Python launcher for Windows supports most common forms of POSIX line but there are other issues to consider If you use usr bin env python or other forms of the python command such as usr bin python you need to consider that your users may have either Python 2 or Python 3 as their default and write your code to work under both versions If you use an explicit version for example usr bin env python3 your application will not work for users who do not have that version This may be what you want if you have not made your code Python 2 compatible There is no way to say python X Y or later so be careful of using an exact version like usr bin env python3 4 as you will need to change your shebang line for users of Python 3 5 for example Typically you should use an usr bin env python2 or usr bin env python3 depending on whether your code is written for Python 2 or 3 Creating Standalone Applications with zipapp Using the zipapp module it is possible to create self contained Python programs which can be distributed to end users who only need to have a suitable ,en
790,version of Python installed on their system The key to doing this is to bundle all of the application s dependencies into the archive along with the application code The steps to create a standalone archive are as follows 1 Create your application in a directory as normal so you have a myapp directory containing a __main__ py file and any supporting application code 2 Install all of your application s dependencies into the myapp directory using pip python m pip install r requirements txt target myapp this assumes you have your project requirements in a requirements txt file if not you can just list the dependencies manually on the pip command line 3 Package the application using python m zipapp p interpreter myapp This will produce a standalone executable which can be run on any machine with the appropriate interpreter available See Specifying the Interpreter for details It can be shipped to users as a single file On Unix the myapp pyz file is executable as it stands You can rename the file to remove the pyz extension if you prefer a plain command name On Windows the myapp pyz w file is executable by virtue of the fact that the Python interpreter registers the pyz and pyzw file extensions when installed Caveats If your application depends on a package that includes a C extension that package cannot be run from a zip file this is an OS limitation as executable code must be present in the filesystem for the OS loader to load it In this case you can exclude that dependency from the zipfile and either require your users to have it installed or ship it alongside your zipfile and add code to your __main__ py to include the directory containing the unzipped module in sys path In this case you will need to make sure to ship appropriate binaries for your target architecture s and potentially pick the correct version to add to sys path at runtime based on the user s machine The Python Zip Application Archive Format Python has been able to execute zip files which contain a __main__ py file since version 2 6 In order to be executed by Python an application archive simply has to be a standard zip file containing a __main__ py file which will be run as the entry point for the application As usual for any Python script the parent of the script in this case the zip file will be placed on sys path and thus further modules can be imported from the zip file The zip file format allows arbitrary data to be prepended to a zip file The zip application format uses this ability to prepend a standard POSIX shebang line to the file path to interpreter Formally the Python zip application format is therefore 1 An optional shebang line containing the characters b followed by an interpreter name and then a newline b n character The interpreter name can be anything acceptable to the OS shebang processing or the Python launcher on Windows The interpreter should be encoded in UTF 8 on Windows and in sys getfilesystemencoding on POSIX 2 Standard zipfile data as generated by the zipfile module The zipfile content must include a file called __main__ py which must be in the root of the zipfile i e it cannot be in a subdirectory The zipfile data can be compressed or uncompressed If an application archive has a shebang line it may have the executable bit set on POSIX systems to allow it to be executed directly There is no requirement that the tools in this module are used to create application archives the module is a convenience but archives in the above format created by any means are acceptable to Python,en
791,importlib The implementation of import New in version 3 1 Source code Lib importlib __init__ py Introduction The purpose of the importlib package is three fold One is to provide the implementation of the import statement and thus by extension the __import__ function in Python source code This provides an implementation of import which is portable to any Python interpreter This also provides an implementation which is easier to comprehend than one implemented in a programming language other than Python Two the components to implement import are exposed in this package making it easier for users to create their own custom objects known generically as an importer to participate in the import process Three the package contains modules exposing additional functionality for managing aspects of Python packages importlib metadata presents access to metadata from third party distributions importlib resources provides routines for accessing non code resources from Python packages See also The import statement The language reference for the import statement Packages specification Original specification of packages Some semantics have changed since the writing of this document e g redirecting based on None in sys modules The __import__ function The import statement is syntactic sugar for this function The initialization of the sys path module search path The initialization of sys path PEP 235 Import on Case Insensitive Platforms PEP 263 Defining Python Source Code Encodings PEP 302 New Import Hooks PEP 328 Imports Multi Line and Absolute Relative PEP 366 Main module explicit relative imports PEP 420 Implicit namespace packages PEP 451 A ModuleSpec Type for the Import System PEP 488 Elimination of PYO files PEP 489 Multi phase extension module initialization PEP 552 Deterministic pycs PEP 3120 Using UTF 8 as the Default Source Encoding PEP 3147 PYC Repository Directories Functions importlib __import__ name globals None locals None fromlist level 0 An implementation of the built in __import__ function Note Programmatic importing of modules should use import_module instead of this function importlib import_module name package None Import a module The name argument specifies what module to import in absolute or relative terms e g either pkg mod or mod If the name is specified in relative terms then the package argument must be set to the name of the package which is to act as the anchor for resolving the package name e g import_module mod pkg subpkg will import pkg mod The import_module function acts as a simplifying wrapper around importlib __import__ This means all semantics of the function are derived from importlib __import__ The most important difference between these two functions is that import_module returns the specified package or module e g pkg mod while __import__ returns the top level package or module e g pkg If you are dynamically importing a module that was created since the interpreter began execution e g created a Python source file you may need to call invalidate_caches in order for the new module to be noticed by the import system Changed in version 3 3 Parent packages are automatically imported importlib invalidate_caches Invalidate the internal caches of finders stored at sys meta_path If a finder implements invalidate_caches then it will be called to perform the invalidation This function should be called if any modules are created installed while your program is running to guarantee all finders will notice the new module s existence New in version 3 3 Changed in version 3 10 Namespace packages created installed in a different sys path location after the same namespace was already imported are noticed importlib reload module Reload a previously imported module The argument must be a module object so it must have been successfully imported before This is useful if you have edited the module source file using an external editor and want to try out the new version without leaving the Python interpreter The return value is the module object which can be different if re importing causes a different object to be placed ,en
792,in sys modules When reload is executed Python module s code is recompiled and the module level code re executed defining a new set of objects which are bound to names in the module s dictionary by reusing the loader which originally loaded the module The init function of extension modules is not called a second time As with all other objects in Python the old objects are only reclaimed after their reference counts drop to zero The names in the module namespace are updated to point to any new or changed objects Other references to the old objects such as names external to the module are not rebound to refer to the new objects and must be updated in each namespace where they occur if that is desired There are a number of other caveats When a module is reloaded its dictionary containing the module s global variables is retained Redefinitions of names will override the old definitions so this is generally not a problem If the new version of a module does not define a name that was defined by the old version the old definition remains This feature can be used to the module s advantage if it maintains a global table or cache of objects with a try statement it can test for the table s presence and skip its initialization if desired try cache except NameError cache It is generally not very useful to reload built in or dynamically loaded modules Reloading sys __main__ builtins and other key modules is not recommended In many cases extension modules are not designed to be initialized more than once and may fail in arbitrary ways when reloaded If a module imports objects from another module using from import calling reload for the other module does not redefine the objects imported from it one way around this is to re execute the from statement another is to use import and qualified names module name instead If a module instantiates instances of a class reloading the module that defines the class does not affect the method definitions of the instances they continue to use the old class definition The same is true for derived classes New in version 3 4 Changed in version 3 7 ModuleNotFoundError is raised when the module being reloaded lacks a ModuleSpec importlib abc Abstract base classes related to import Source code Lib importlib abc py The importlib abc module contains all of the core abstract base classes used by import Some subclasses of the core abstract base classes are also provided to help in implementing the core ABCs ABC hierarchy object MetaPathFinder PathEntryFinder Loader ResourceLoader InspectLoader ExecutionLoader FileLoader SourceLoader class importlib abc MetaPathFinder An abstract base class representing a meta path finder New in version 3 3 Changed in version 3 10 No longer a subclass of Finder find_spec fullname path target None An abstract method for finding a spec for the specified module If this is a top level import path will be None Otherwise this is a search for a subpackage or module and path will be the value of __path__ from the parent package If a spec cannot be found None is returned When passed in target is a module object that the finder may use to make a more educated guess about what spec to return importlib util spec_from_loader may be useful for implementing concrete MetaPathFinders New in version 3 4 invalidate_caches An optional method which when called should invalidate any internal cache used by the finder Used by importlib invalidate_caches when invalidating the caches of all finders on sys meta_path Changed in version 3 4 Returns None when called instead of NotImplemented class importlib abc PathEntryFinder An abstract base class representing a path entry finder Though it bears some similarities to MetaPathFinder PathEntryFinder is meant for use only within the path based import subsystem provided by importlib machinery PathFinder New in version 3 3 Changed in version 3 10 No longer a subclass of Finder find_spec fullname target None An abstract method for finding a spec for the specified module The finder will search for the module only within the path entry to which it is assigned If a s,en
793,pec cannot be found None is returned When passed in target is a module object that the finder may use to make a more educated guess about what spec to return importlib util spec_from_loader may be useful for implementing concrete PathEntryFinders New in version 3 4 invalidate_caches An optional method which when called should invalidate any internal cache used by the finder Used by importlib machinery PathFinder invalidate_caches when invalidating the caches of all cached finders class importlib abc Loader An abstract base class for a loader See PEP 302 for the exact definition for a loader Loaders that wish to support resource reading should implement a get_resource_reader method as specified by importlib resources abc ResourceReader Changed in version 3 7 Introduced the optional get_resource_reader method create_module spec A method that returns the module object to use when importing a module This method may return None indicating that default module creation semantics should take place New in version 3 4 Changed in version 3 6 This method is no longer optional when exec_module is defined exec_module module An abstract method that executes the module in its own namespace when a module is imported or reloaded The module should already be initialized when exec_module is called When this method exists create_module must be defined New in version 3 4 Changed in version 3 6 create_module must also be defined load_module fullname A legacy method for loading a module If the module cannot be loaded ImportError is raised otherwise the loaded module is returned If the requested module already exists in sys modules that module should be used and reloaded Otherwise the loader should create a new module and insert it into sys modules before any loading begins to prevent recursion from the import If the loader inserted a module and the load fails it must be removed by the loader from sys modules modules already in sys modules before the loader began execution should be left alone The loader should set several attributes on the module note that some of these attributes can change when a module is reloaded __name__ The module s fully qualified name It is __main__ for an executed module __file__ The location the loader used to load the module For example for modules loaded from a py file this is the filename It is not set on all modules e g built in modules __cached__ The filename of a compiled version of the module s code It is not set on all modules e g built in modules __path__ The list of locations where the package s submodules will be found Most of the time this is a single directory The import system passes this attribute to __import__ and to finders in the same way as sys path but just for the package It is not set on non package modules so it can be used as an indicator that the module is a package __package__ The fully qualified name of the package the module is in or the empty string for a top level module If the module is a package then this is the same as __name__ __loader__ The loader used to load the module When exec_module is available then backwards compatible functionality is provided Changed in version 3 4 Raise ImportError when called instead of NotImplementedError Functionality provided when exec_module is available Deprecated since version 3 4 The recommended API for loading a module is exec_module and create_module Loaders should implement it instead of load_module The import machinery takes care of all the other responsibilities of load_module when exec_module is implemented class importlib abc ResourceLoader An abstract base class for a loader which implements the optional PEP 302 protocol for loading arbitrary resources from the storage back end Deprecated since version 3 7 This ABC is deprecated in favour of supporting resource loading through importlib resources abc ResourceReader abstractmethod get_data path An abstract method to return the bytes for the data located at path Loaders that have a file like storage back end that allows storing arbitrary data can implement this abstract method to give direct a,en
794,ccess to the data stored OSError is to be raised if the path cannot be found The path is expected to be constructed using a module s __file__ attribute or an item from a package s __path__ Changed in version 3 4 Raises OSError instead of NotImplementedError class importlib abc InspectLoader An abstract base class for a loader which implements the optional PEP 302 protocol for loaders that inspect modules get_code fullname Return the code object for a module or None if the module does not have a code object as would be the case for example for a built in module Raise an ImportError if loader cannot find the requested module Note While the method has a default implementation it is suggested that it be overridden if possible for performance Changed in version 3 4 No longer abstract and a concrete implementation is provided abstractmethod get_source fullname An abstract method to return the source of a module It is returned as a text string using universal newlines translating all recognized line separators into n characters Returns None if no source is available e g a built in module Raises ImportError if the loader cannot find the module specified Changed in version 3 4 Raises ImportError instead of NotImplementedError is_package fullname An optional method to return a true value if the module is a package a false value otherwise ImportError is raised if the loader cannot find the module Changed in version 3 4 Raises ImportError instead of NotImplementedError static source_to_code data path string Create a code object from Python source The data argument can be whatever the compile function supports i e string or bytes The path argument should be the path to where the source code originated from which can be an abstract concept e g location in a zip file With the subsequent code object one can execute it in a module by running exec code module __dict__ New in version 3 4 Changed in version 3 5 Made the method static exec_module module Implementation of Loader exec_module New in version 3 4 load_module fullname Implementation of Loader load_module Deprecated since version 3 4 use exec_module instead class importlib abc ExecutionLoader An abstract base class which inherits from InspectLoader that when implemented helps a module to be executed as a script The ABC represents an optional PEP 302 protocol abstractmethod get_filename fullname An abstract method that is to return the value of __file__ for the specified module If no path is available ImportError is raised If source code is available then the method should return the path to the source file regardless of whether a bytecode was used to load the module Changed in version 3 4 Raises ImportError instead of NotImplementedError class importlib abc FileLoader fullname path An abstract base class which inherits from ResourceLoader and ExecutionLoader providing concrete implementations of ResourceLoader get_data and ExecutionLoader get_filename The fullname argument is a fully resolved name of the module the loader is to handle The path argument is the path to the file for the module New in version 3 3 name The name of the module the loader can handle path Path to the file of the module load_module fullname Calls super s load_module Deprecated since version 3 4 Use Loader exec_module instead abstractmethod get_filename fullname Returns path abstractmethod get_data path Reads path as a binary file and returns the bytes from it class importlib abc SourceLoader An abstract base class for implementing source and optionally bytecode file loading The class inherits from both ResourceLoader and ExecutionLoader requiring the implementation of ResourceLoader get_data ExecutionLoader get_filename Should only return the path to the source file sourceless loading is not supported The abstract methods defined by this class are to add optional bytecode file support Not implementing these optional methods or causing them to raise NotImplementedError causes the loader to only work with source code Implementing the methods allows the loader to work with source and bytecode files it does not ,en
795,allow for sourceless loading where only bytecode is provided Bytecode files are an optimization to speed up loading by removing the parsing step of Python s compiler and so no bytecode specific API is exposed path_stats path Optional abstract method which returns a dict containing metadata about the specified path Supported dictionary keys are mtime mandatory an integer or floating point number representing the modification time of the source code size optional the size in bytes of the source code Any other keys in the dictionary are ignored to allow for future extensions If the path cannot be handled OSError is raised New in version 3 3 Changed in version 3 4 Raise OSError instead of NotImplementedError path_mtime path Optional abstract method which returns the modification time for the specified path Deprecated since version 3 3 This method is deprecated in favour of path_stats You don t have to implement it but it is still available for compatibility purposes Raise OSError if the path cannot be handled Changed in version 3 4 Raise OSError instead of NotImplementedError set_data path data Optional abstract method which writes the specified bytes to a file path Any intermediate directories which do not exist are to be created automatically When writing to the path fails because the path is read only errno EACCES PermissionError do not propagate the exception Changed in version 3 4 No longer raises NotImplementedError when called get_code fullname Concrete implementation of InspectLoader get_code exec_module module Concrete implementation of Loader exec_module New in version 3 4 load_module fullname Concrete implementation of Loader load_module Deprecated since version 3 4 Use exec_module instead get_source fullname Concrete implementation of InspectLoader get_source is_package fullname Concrete implementation of InspectLoader is_package A module is determined to be a package if its file path as provided by ExecutionLoader get_filename is a file named __init__ when the file extension is removed and the module name itself does not end in __init__ class importlib abc ResourceReader Superseded by TraversableResources An abstract base class to provide the ability to read resources From the perspective of this ABC a resource is a binary artifact that is shipped within a package Typically this is something like a data file that lives next to the __init__ py file of the package The purpose of this class is to help abstract out the accessing of such data files so that it does not matter if the package and its data file s are stored in a e g zip file versus on the file system For any of methods of this class a resource argument is expected to be a path like object which represents conceptually just a file name This means that no subdirectory paths should be included in the resource argument This is because the location of the package the reader is for acts as the directory Hence the metaphor for directories and file names is packages and resources respectively This is also why instances of this class are expected to directly correlate to a specific package instead of potentially representing multiple packages or a module Loaders that wish to support resource reading are expected to provide a method called get_resource_reader fullname which returns an object implementing this ABC s interface If the module specified by fullname is not a package this method should return None An object compatible with this ABC should only be returned when the specified module is a package New in version 3 7 Deprecated since version 3 12 will be removed in version 3 14 Use importlib resources abc TraversableResources instead abstractmethod open_resource resource Returns an opened file like object for binary reading of the resource If the resource cannot be found FileNotFoundError is raised abstractmethod resource_path resource Returns the file system path to the resource If the resource does not concretely exist on the file system raise FileNotFoundError abstractmethod is_resource name Returns True if the named name is considered a resource FileNotFo,en
796,undError is raised if name does not exist abstractmethod contents Returns an iterable of strings over the contents of the package Do note that it is not required that all names returned by the iterator be actual resources e g it is acceptable to return names for which is_resource would be false Allowing non resource names to be returned is to allow for situations where how a package and its resources are stored are known a priori and the non resource names would be useful For instance returning subdirectory names is allowed so that when it is known that the package and resources are stored on the file system then those subdirectory names can be used directly The abstract method returns an iterable of no items class importlib abc Traversable An object with a subset of pathlib Path methods suitable for traversing directories and opening files For a representation of the object on the file system use importlib resources as_file New in version 3 9 Deprecated since version 3 12 will be removed in version 3 14 Use importlib resources abc Traversable instead name Abstract The base name of this object without any parent references abstractmethod iterdir Yield Traversable objects in self abstractmethod is_dir Return True if self is a directory abstractmethod is_file Return True if self is a file abstractmethod joinpath child Return Traversable child in self abstractmethod __truediv__ child Return Traversable child in self abstractmethod open mode r args kwargs mode may be r or rb to open as text or binary Return a handle suitable for reading same as pathlib Path open When opening as text accepts encoding parameters such as those accepted by io TextIOWrapper read_bytes Read contents of self as bytes read_text encoding None Read contents of self as text class importlib abc TraversableResources An abstract base class for resource readers capable of serving the importlib resources files interface Subclasses importlib resources abc ResourceReader and provides concrete implementations of the importlib resources abc ResourceReader s abstract methods Therefore any loader supplying importlib abc TraversableResources also supplies ResourceReader Loaders that wish to support resource reading are expected to implement this interface New in version 3 9 Deprecated since version 3 12 will be removed in version 3 14 Use importlib resources abc TraversableResources instead abstractmethod files Returns a importlib resources abc Traversable object for the loaded package importlib machinery Importers and path hooks Source code Lib importlib machinery py This module contains the various objects that help import find and load modules importlib machinery SOURCE_SUFFIXES A list of strings representing the recognized file suffixes for source modules New in version 3 3 importlib machinery DEBUG_BYTECODE_SUFFIXES A list of strings representing the file suffixes for non optimized bytecode modules New in version 3 3 Deprecated since version 3 5 Use BYTECODE_SUFFIXES instead importlib machinery OPTIMIZED_BYTECODE_SUFFIXES A list of strings representing the file suffixes for optimized bytecode modules New in version 3 3 Deprecated since version 3 5 Use BYTECODE_SUFFIXES instead importlib machinery BYTECODE_SUFFIXES A list of strings representing the recognized file suffixes for bytecode modules including the leading dot New in version 3 3 Changed in version 3 5 The value is no longer dependent on __debug__ importlib machinery EXTENSION_SUFFIXES A list of strings representing the recognized file suffixes for extension modules New in version 3 3 importlib machinery all_suffixes Returns a combined list of strings representing all file suffixes for modules recognized by the standard import machinery This is a helper for code which simply needs to know if a filesystem path potentially refers to a module without needing any details on the kind of module for example inspect getmodulename New in version 3 3 class importlib machinery BuiltinImporter An importer for built in modules All known built in modules are listed in sys builtin_module_names This class implements ,en
797,the importlib abc MetaPathFinder and importlib abc InspectLoader ABCs Only class methods are defined by this class to alleviate the need for instantiation Changed in version 3 5 As part of PEP 489 the builtin importer now implements Loader create_module and Loader exec_module class importlib machinery FrozenImporter An importer for frozen modules This class implements the importlib abc MetaPathFinder and importlib abc InspectLoader ABCs Only class methods are defined by this class to alleviate the need for instantiation Changed in version 3 4 Gained create_module and exec_module methods class importlib machinery WindowsRegistryFinder Finder for modules declared in the Windows registry This class implements the importlib abc MetaPathFinder ABC Only class methods are defined by this class to alleviate the need for instantiation New in version 3 3 Deprecated since version 3 6 Use site configuration instead Future versions of Python may not enable this finder by default class importlib machinery PathFinder A Finder for sys path and package __path__ attributes This class implements the importlib abc MetaPathFinder ABC Only class methods are defined by this class to alleviate the need for instantiation classmethod find_spec fullname path None target None Class method that attempts to find a spec for the module specified by fullname on sys path or if defined on path For each path entry that is searched sys path_importer_cache is checked If a non false object is found then it is used as the path entry finder to look for the module being searched for If no entry is found in sys path_importer_cache then sys path_hooks is searched for a finder for the path entry and if found is stored in sys path_importer_cache along with being queried about the module If no finder is ever found then None is both stored in the cache and returned New in version 3 4 Changed in version 3 5 If the current working directory represented by an empty string is no longer valid then None is returned but no value is cached in sys path_importer_cache classmethod invalidate_caches Calls importlib abc PathEntryFinder invalidate_caches on all finders stored in sys path_importer_cache that define the method Otherwise entries in sys path_importer_cache set to None are deleted Changed in version 3 7 Entries of None in sys path_importer_cache are deleted Changed in version 3 4 Calls objects in sys path_hooks with the current working directory for i e the empty string class importlib machinery FileFinder path loader_details A concrete implementation of importlib abc PathEntryFinder which caches results from the file system The path argument is the directory for which the finder is in charge of searching The loader_details argument is a variable number of 2 item tuples each containing a loader and a sequence of file suffixes the loader recognizes The loaders are expected to be callables which accept two arguments of the module s name and the path to the file found The finder will cache the directory contents as necessary making stat calls for each module search to verify the cache is not outdated Because cache staleness relies upon the granularity of the operating system s state information of the file system there is a potential race condition of searching for a module creating a new file and then searching for the module the new file represents If the operations happen fast enough to fit within the granularity of stat calls then the module search will fail To prevent this from happening when you create a module dynamically make sure to call importlib invalidate_caches New in version 3 3 path The path the finder will search in find_spec fullname target None Attempt to find the spec to handle fullname within path New in version 3 4 invalidate_caches Clear out the internal cache classmethod path_hook loader_details A class method which returns a closure for use on sys path_hooks An instance of FileFinder is returned by the closure using the path argument given to the closure directly and loader_details indirectly If the argument to the closure is not an existing directo,en
798,ry ImportError is raised class importlib machinery SourceFileLoader fullname path A concrete implementation of importlib abc SourceLoader by subclassing importlib abc FileLoader and providing some concrete implementations of other methods New in version 3 3 name The name of the module that this loader will handle path The path to the source file is_package fullname Return True if path appears to be for a package path_stats path Concrete implementation of importlib abc SourceLoader path_stats set_data path data Concrete implementation of importlib abc SourceLoader set_data load_module name None Concrete implementation of importlib abc Loader load_module where specifying the name of the module to load is optional Deprecated since version 3 6 Use importlib abc Loader exec_module instead class importlib machinery SourcelessFileLoader fullname path A concrete implementation of importlib abc FileLoader which can import bytecode files i e no source code files exist Please note that direct use of bytecode files and thus not source code files inhibits your modules from being usable by all Python implementations or new versions of Python which change the bytecode format New in version 3 3 name The name of the module the loader will handle path The path to the bytecode file is_package fullname Determines if the module is a package based on path get_code fullname Returns the code object for name created from path get_source fullname Returns None as bytecode files have no source when this loader is used load_module name None Concrete implementation of importlib abc Loader load_module where specifying the name of the module to load is optional Deprecated since version 3 6 Use importlib abc Loader exec_module instead class importlib machinery ExtensionFileLoader fullname path A concrete implementation of importlib abc ExecutionLoader for extension modules The fullname argument specifies the name of the module the loader is to support The path argument is the path to the extension module s file Note that by default importing an extension module will fail in subinterpreters if it doesn t implement multi phase init see PEP 489 even if it would otherwise import successfully New in version 3 3 Changed in version 3 12 Multi phase init is now required for use in subinterpreters name Name of the module the loader supports path Path to the extension module create_module spec Creates the module object from the given specification in accordance with PEP 489 New in version 3 5 exec_module module Initializes the given module object in accordance with PEP 489 New in version 3 5 is_package fullname Returns True if the file path points to a package s __init__ module based on EXTENSION_SUFFIXES get_code fullname Returns None as extension modules lack a code object get_source fullname Returns None as extension modules do not have source code get_filename fullname Returns path New in version 3 4 class importlib machinery NamespaceLoader name path path_finder A concrete implementation of importlib abc InspectLoader for namespace packages This is an alias for a private class and is only made public for introspecting the __loader__ attribute on namespace packages from importlib machinery import NamespaceLoader import my_namespace isinstance my_namespace __loader__ NamespaceLoader True import importlib abc isinstance my_namespace __loader__ importlib abc Loader True New in version 3 11 class importlib machinery ModuleSpec name loader origin None loader_state None is_package None A specification for a module s import system related state This is typically exposed as the module s __spec__ attribute In the descriptions below the names in parentheses give the corresponding attribute available directly on the module object e g module __spec__ origin module __file__ Note however that while the values are usually equivalent they can differ since there is no synchronization between the two objects For example it is possible to update the module s __file__ at runtime and this will not be automatically reflected in the module s __spec__ origin and vice versa New in ve,en
799,rsion 3 4 name __name__ The module s fully qualified name The finder should always set this attribute to a non empty string loader __loader__ The loader used to load the module The finder should always set this attribute origin __file__ The location the loader should use to load the module For example for modules loaded from a py file this is the filename The finder should always set this attribute to a meaningful value for the loader to use In the uncommon case that there is not one like for namespace packages it should be set to None submodule_search_locations __path__ The list of locations where the package s submodules will be found Most of the time this is a single directory The finder should set this attribute to a list even an empty one to indicate to the import system that the module is a package It should be set to None for non package modules It is set automatically later to a special object for namespace packages loader_state The finder may set this attribute to an object containing additional module specific data to use when loading the module Otherwise it should be set to None cached __cached__ The filename of a compiled version of the module s code The finder should always set this attribute but it may be None for modules that do not need compiled code stored parent __package__ Read only The fully qualified name of the package the module is in or the empty string for a top level module If the module is a package then this is the same as name has_location True if the spec s origin refers to a loadable location False otherwise This value impacts how origin is interpreted and how the module s __file__ is populated importlib util Utility code for importers Source code Lib importlib util py This module contains the various objects that help in the construction of an importer importlib util MAGIC_NUMBER The bytes which represent the bytecode version number If you need help with loading writing bytecode then consider importlib abc SourceLoader New in version 3 4 importlib util cache_from_source path debug_override None optimization None Return the PEP 3147 PEP 488 path to the byte compiled file associated with the source path For example if path is foo bar baz py the return value would be foo bar __pycache__ baz cpython 32 pyc for Python 3 2 The cpython 32 string comes from the current magic tag see get_tag if sys implementation cache_tag is not defined then NotImplementedError will be raised The optimization parameter is used to specify the optimization level of the bytecode file An empty string represents no optimization so foo bar baz py with an optimization of will result in a bytecode path of foo bar __pycache__ baz cpython 32 pyc None causes the interpreter s optimization level to be used Any other value s string representation is used so foo bar baz py with an optimization of 2 will lead to the bytecode path of foo bar __pycache__ baz cpython 32 opt 2 pyc The string representation of optimization can only be alphanumeric else ValueError is raised The debug_override parameter is deprecated and can be used to override the system s value for __debug__ A True value is the equivalent of setting optimization to the empty string A False value is the same as setting optimization to 1 If both debug_override an optimization are not None then TypeError is raised New in version 3 4 Changed in version 3 5 The optimization parameter was added and the debug_override parameter was deprecated Changed in version 3 6 Accepts a path like object importlib util source_from_cache path Given the path to a PEP 3147 file name return the associated source code file path For example if path is foo bar __pycache__ baz cpython 32 pyc the returned path would be foo bar baz py path need not exist however if it does not conform to PEP 3147 or PEP 488 format a ValueError is raised If sys implementation cache_tag is not defined NotImplementedError is raised New in version 3 4 Changed in version 3 6 Accepts a path like object importlib util decode_source source_bytes Decode the given bytes representing source code and return it as a string wi,en
800,th universal newlines as required by importlib abc InspectLoader get_source New in version 3 4 importlib util resolve_name name package Resolve a relative module name to an absolute one If name has no leading dots then name is simply returned This allows for usage such as importlib util resolve_name sys __spec__ parent without doing a check to see if the package argument is needed ImportError is raised if name is a relative module name but package is a false value e g None or the empty string ImportError is also raised if a relative name would escape its containing package e g requesting bacon from within the spam package New in version 3 3 Changed in version 3 9 To improve consistency with import statements raise ImportError instead of ValueError for invalid relative import attempts importlib util find_spec name package None Find the spec for a module optionally relative to the specified package name If the module is in sys modules then sys modules name __spec__ is returned unless the spec would be None or is not set in which case ValueError is raised Otherwise a search using sys meta_path is done None is returned if no spec is found If name is for a submodule contains a dot the parent module is automatically imported name and package work the same as for import_module New in version 3 4 Changed in version 3 7 Raises ModuleNotFoundError instead of AttributeError if package is in fact not a package i e lacks a __path__ attribute importlib util module_from_spec spec Create a new module based on spec and spec loader create_module If spec loader create_module does not return None then any pre existing attributes will not be reset Also no AttributeError will be raised if triggered while accessing spec or setting an attribute on the module This function is preferred over using types ModuleType to create a new module as spec is used to set as many import controlled attributes on the module as possible New in version 3 5 importlib util spec_from_loader name loader origin None is_package None A factory function for creating a ModuleSpec instance based on a loader The parameters have the same meaning as they do for ModuleSpec The function uses available loader APIs such as InspectLoader is_package to fill in any missing information on the spec New in version 3 4 importlib util spec_from_file_location name location loader None submodule_search_locations None A factory function for creating a ModuleSpec instance based on the path to a file Missing information will be filled in on the spec by making use of loader APIs and by the implication that the module will be file based New in version 3 4 Changed in version 3 6 Accepts a path like object importlib util source_hash source_bytes Return the hash of source_bytes as bytes A hash based pyc file embeds the source_hash of the corresponding source file s contents in its header New in version 3 7 importlib util _incompatible_extension_module_restrictions disable_check A context manager that can temporarily skip the compatibility check for extension modules By default the check is enabled and will fail when a single phase init module is imported in a subinterpreter It will also fail for a multi phase init module that doesn t explicitly support a per interpreter GIL when imported in an interpreter with its own GIL Note that this function is meant to accommodate an unusual case one which is likely to eventually go away There s is a pretty good chance this is not what you were looking for You can get the same effect as this function by implementing the basic interface of multi phase init PEP 489 and lying about support for multiple interpreters or per interpreter GIL Warning Using this function to disable the check can lead to unexpected behavior and even crashes It should only be used during extension module development New in version 3 12 class importlib util LazyLoader loader A class which postpones the execution of the loader of a module until the module has an attribute accessed This class only works with loaders that define exec_module as control over what module type is used for the m,en
801,odule is required For those same reasons the loader s create_module method must return None or a type for which its __class__ attribute can be mutated along with not using slots Finally modules which substitute the object placed into sys modules will not work as there is no way to properly replace the module references throughout the interpreter safely ValueError is raised if such a substitution is detected Note For projects where startup time is critical this class allows for potentially minimizing the cost of loading a module if it is never used For projects where startup time is not essential then use of this class is heavily discouraged due to error messages created during loading being postponed and thus occurring out of context New in version 3 5 Changed in version 3 6 Began calling create_module removing the compatibility warning for importlib machinery BuiltinImporter and importlib machinery ExtensionFileLoader classmethod factory loader A class method which returns a callable that creates a lazy loader This is meant to be used in situations where the loader is passed by class instead of by instance suffixes importlib machinery SOURCE_SUFFIXES loader importlib machinery SourceFileLoader lazy_loader importlib util LazyLoader factory loader finder importlib machinery FileFinder path lazy_loader suffixes Examples Importing programmatically To programmatically import a module use importlib import_module import importlib itertools importlib import_module itertools Checking if a module can be imported If you need to find out if a module can be imported without actually doing the import then you should use importlib util find_spec Note that if name is a submodule contains a dot importlib util find_spec will import the parent module import importlib util import sys For illustrative purposes name itertools if name in sys modules print f name r already in sys modules elif spec importlib util find_spec name is not None If you chose to perform the actual import module importlib util module_from_spec spec sys modules name module spec loader exec_module module print f name r has been imported else print f can t find the name r module Importing a source file directly To import a Python source file directly use the following recipe import importlib util import sys For illustrative purposes import tokenize file_path tokenize __file__ module_name tokenize __name__ spec importlib util spec_from_file_location module_name file_path module importlib util module_from_spec spec sys modules module_name module spec loader exec_module module Implementing lazy imports The example below shows how to implement lazy imports import importlib util import sys def lazy_import name spec importlib util find_spec name loader importlib util LazyLoader spec loader spec loader loader module importlib util module_from_spec spec sys modules name module loader exec_module module return module lazy_typing lazy_import typing lazy_typing is a real module object but it is not loaded in memory yet lazy_typing TYPE_CHECKING False Setting up an importer For deep customizations of import you typically want to implement an importer This means managing both the finder and loader side of things For finders there are two flavours to choose from depending on your needs a meta path finder or a path entry finder The former is what you would put on sys meta_path while the latter is what you create using a path entry hook on sys path_hooks which works with sys path entries to potentially create a finder This example will show you how to register your own importers so that import will use them for creating an importer for yourself read the documentation for the appropriate classes defined within this package import importlib machinery import sys For illustrative purposes only SpamMetaPathFinder importlib machinery PathFinder SpamPathEntryFinder importlib machinery FileFinder loader_details importlib machinery SourceFileLoader importlib machinery SOURCE_SUFFIXES Setting up a meta path finder Make sure to put the finder in the proper location in the list in terms of priority ,en
802,sys meta_path append SpamMetaPathFinder Setting up a path entry finder Make sure to put the path hook in the proper location in the list in terms of priority sys path_hooks append SpamPathEntryFinder path_hook loader_details Approximating importlib import_module Import itself is implemented in Python code making it possible to expose most of the import machinery through importlib The following helps illustrate the various APIs that importlib exposes by providing an approximate implementation of importlib import_module import importlib util import sys def import_module name package None An approximate implementation of import absolute_name importlib util resolve_name name package try return sys modules absolute_name except KeyError pass path None if in absolute_name parent_name _ child_name absolute_name rpartition parent_module import_module parent_name path parent_module __spec__ submodule_search_locations for finder in sys meta_path spec finder find_spec absolute_name path if spec is not None break else msg f No module named absolute_name r raise ModuleNotFoundError msg name absolute_name module importlib util module_from_spec spec sys modules absolute_name module spec loader exec_module module if path is not None setattr parent_module child_name module return module,en
803,Built in Exceptions In Python all exceptions must be instances of a class that derives from BaseException In a try statement with an except clause that mentions a particular class that clause also handles any exception classes derived from that class but not exception classes from which it is derived Two exception classes that are not related via subclassing are never equivalent even if they have the same name The built in exceptions listed in this chapter can be generated by the interpreter or built in functions Except where mentioned they have an associated value indicating the detailed cause of the error This may be a string or a tuple of several items of information e g an error code and a string explaining the code The associated value is usually passed as arguments to the exception class s constructor User code can raise built in exceptions This can be used to test an exception handler or to report an error condition just like the situation in which the interpreter raises the same exception but beware that there is nothing to prevent user code from raising an inappropriate error The built in exception classes can be subclassed to define new exceptions programmers are encouraged to derive new exceptions from the Exception class or one of its subclasses and not from BaseException More information on defining exceptions is available in the Python Tutorial under User defined Exceptions Exception context Three attributes on exception objects provide information about the context in which the exception was raised BaseException __context__ BaseException __cause__ BaseException __suppress_context__ When raising a new exception while another exception is already being handled the new exception s __context__ attribute is automatically set to the handled exception An exception may be handled when an except or finally clause or a with statement is used This implicit exception context can be supplemented with an explicit cause by using from with raise raise new_exc from original_exc The expression following from must be an exception or None It will be set as __cause__ on the raised exception Setting __cause__ also implicitly sets the __suppress_context__ attribute to True so that using raise new_exc from None effectively replaces the old exception with the new one for display purposes e g converting KeyError to AttributeError while leaving the old exception available in __context__ for introspection when debugging The default traceback display code shows these chained exceptions in addition to the traceback for the exception itself An explicitly chained exception in __cause__ is always shown when present An implicitly chained exception in __context__ is shown only if __cause__ is None and __suppress_context__ is false In either case the exception itself is always shown after any chained exceptions so that the final line of the traceback always shows the last exception that was raised Inheriting from built in exceptions User code can create subclasses that inherit from an exception type It s recommended to only subclass one exception type at a time to avoid any possible conflicts between how the bases handle the args attribute as well as due to possible memory layout incompatibilities CPython implementation detail Most built in exceptions are implemented in C for efficiency see Objects exceptions c Some have custom memory layouts which makes it impossible to create a subclass that inherits from multiple exception types The memory layout of a type is an implementation detail and might change between Python versions leading to new conflicts in the future Therefore it s recommended to avoid subclassing multiple exception types altogether Base classes The following exceptions are used mostly as base classes for other exceptions exception BaseException The base class for all built in exceptions It is not meant to be directly inherited by user defined classes for that use Exception If str is called on an instance of this class the representation of the argument s to the instance are returned or the empty string when there were no argu,en
804,ments args The tuple of arguments given to the exception constructor Some built in exceptions like OSError expect a certain number of arguments and assign a special meaning to the elements of this tuple while others are usually called only with a single string giving an error message with_traceback tb This method sets tb as the new traceback for the exception and returns the exception object It was more commonly used before the exception chaining features of PEP 3134 became available The following example shows how we can convert an instance of SomeException into an instance of OtherException while preserving the traceback Once raised the current frame is pushed onto the traceback of the OtherException as would have happened to the traceback of the original SomeException had we allowed it to propagate to the caller try except SomeException tb sys exception __traceback__ raise OtherException with_traceback tb __traceback__ A writable field that holds the traceback object associated with this exception See also The raise statement add_note note Add the string note to the exception s notes which appear in the standard traceback after the exception string A TypeError is raised if note is not a string New in version 3 11 __notes__ A list of the notes of this exception which were added with add_note This attribute is created when add_note is called New in version 3 11 exception Exception All built in non system exiting exceptions are derived from this class All user defined exceptions should also be derived from this class exception ArithmeticError The base class for those built in exceptions that are raised for various arithmetic errors OverflowError ZeroDivisionError FloatingPointError exception BufferError Raised when a buffer related operation cannot be performed exception LookupError The base class for the exceptions that are raised when a key or index used on a mapping or sequence is invalid IndexError KeyError This can be raised directly by codecs lookup Concrete exceptions The following exceptions are the exceptions that are usually raised exception AssertionError Raised when an assert statement fails exception AttributeError Raised when an attribute reference see Attribute references or assignment fails When an object does not support attribute references or attribute assignments at all TypeError is raised The name and obj attributes can be set using keyword only arguments to the constructor When set they represent the name of the attribute that was attempted to be accessed and the object that was accessed for said attribute respectively Changed in version 3 10 Added the name and obj attributes exception EOFError Raised when the input function hits an end of file condition EOF without reading any data N B the io IOBase read and io IOBase readline methods return an empty string when they hit EOF exception FloatingPointError Not currently used exception GeneratorExit Raised when a generator or coroutine is closed see generator close and coroutine close It directly inherits from BaseException instead of Exception since it is technically not an error exception ImportError Raised when the import statement has troubles trying to load a module Also raised when the from list in from import has a name that cannot be found The optional name and path keyword only arguments set the corresponding attributes name The name of the module that was attempted to be imported path The path to any file which triggered the exception Changed in version 3 3 Added the name and path attributes exception ModuleNotFoundError A subclass of ImportError which is raised by import when a module could not be located It is also raised when None is found in sys modules New in version 3 6 exception IndexError Raised when a sequence subscript is out of range Slice indices are silently truncated to fall in the allowed range if an index is not an integer TypeError is raised exception KeyError Raised when a mapping dictionary key is not found in the set of existing keys exception KeyboardInterrupt Raised when the user hits the interrupt key normally Control C,en
805, or Delete During execution a check for interrupts is made regularly The exception inherits from BaseException so as to not be accidentally caught by code that catches Exception and thus prevent the interpreter from exiting Note Catching a KeyboardInterrupt requires special consideration Because it can be raised at unpredictable points it may in some circumstances leave the running program in an inconsistent state It is generally best to allow KeyboardInterrupt to end the program as quickly as possible or avoid raising it entirely See Note on Signal Handlers and Exceptions exception MemoryError Raised when an operation runs out of memory but the situation may still be rescued by deleting some objects The associated value is a string indicating what kind of internal operation ran out of memory Note that because of the underlying memory management architecture C s malloc function the interpreter may not always be able to completely recover from this situation it nevertheless raises an exception so that a stack traceback can be printed in case a run away program was the cause exception NameError Raised when a local or global name is not found This applies only to unqualified names The associated value is an error message that includes the name that could not be found The name attribute can be set using a keyword only argument to the constructor When set it represent the name of the variable that was attempted to be accessed Changed in version 3 10 Added the name attribute exception NotImplementedError This exception is derived from RuntimeError In user defined base classes abstract methods should raise this exception when they require derived classes to override the method or while the class is being developed to indicate that the real implementation still needs to be added Note It should not be used to indicate that an operator or method is not meant to be supported at all in that case either leave the operator method undefined or if a subclass set it to None Note NotImplementedError and NotImplemented are not interchangeable even though they have similar names and purposes See NotImplemented for details on when to use it exception OSError arg exception OSError errno strerror filename winerror filename2 This exception is raised when a system function returns a system related error including I O failures such as file not found or disk full not for illegal argument types or other incidental errors The second form of the constructor sets the corresponding attributes described below The attributes default to None if not specified For backwards compatibility if three arguments are passed the args attribute contains only a 2 tuple of the first two constructor arguments The constructor often actually returns a subclass of OSError as described in OS exceptions below The particular subclass depends on the final errno value This behaviour only occurs when constructing OSError directly or via an alias and is not inherited when subclassing errno A numeric error code from the C variable errno winerror Under Windows this gives you the native Windows error code The errno attribute is then an approximate translation in POSIX terms of that native error code Under Windows if the winerror constructor argument is an integer the errno attribute is determined from the Windows error code and the errno argument is ignored On other platforms the winerror argument is ignored and the winerror attribute does not exist strerror The corresponding error message as provided by the operating system It is formatted by the C functions perror under POSIX and FormatMessage under Windows filename filename2 For exceptions that involve a file system path such as open or os unlink filename is the file name passed to the function For functions that involve two file system paths such as os rename filename2 corresponds to the second file name passed to the function Changed in version 3 3 EnvironmentError IOError WindowsError socket error select error and mmap error have been merged into OSError and the constructor may return a subclass Changed in version 3 4 The fil,en
806,ename attribute is now the original file name passed to the function instead of the name encoded to or decoded from the filesystem encoding and error handler Also the filename2 constructor argument and attribute was added exception OverflowError Raised when the result of an arithmetic operation is too large to be represented This cannot occur for integers which would rather raise MemoryError than give up However for historical reasons OverflowError is sometimes raised for integers that are outside a required range Because of the lack of standardization of floating point exception handling in C most floating point operations are not checked exception RecursionError This exception is derived from RuntimeError It is raised when the interpreter detects that the maximum recursion depth see sys getrecursionlimit is exceeded New in version 3 5 Previously a plain RuntimeError was raised exception ReferenceError This exception is raised when a weak reference proxy created by the weakref proxy function is used to access an attribute of the referent after it has been garbage collected For more information on weak references see the weakref module exception RuntimeError Raised when an error is detected that doesn t fall in any of the other categories The associated value is a string indicating what precisely went wrong exception StopIteration Raised by built in function next and an iterator s __next__ method to signal that there are no further items produced by the iterator value The exception object has a single attribute value which is given as an argument when constructing the exception and defaults to None When a generator or coroutine function returns a new StopIteration instance is raised and the value returned by the function is used as the value parameter to the constructor of the exception If a generator code directly or indirectly raises StopIteration it is converted into a RuntimeError retaining the StopIteration as the new exception s cause Changed in version 3 3 Added value attribute and the ability for generator functions to use it to return a value Changed in version 3 5 Introduced the RuntimeError transformation via from __future__ import generator_stop see PEP 479 Changed in version 3 7 Enable PEP 479 for all code by default a StopIteration error raised in a generator is transformed into a RuntimeError exception StopAsyncIteration Must be raised by __anext__ method of an asynchronous iterator object to stop the iteration New in version 3 5 exception SyntaxError message details Raised when the parser encounters a syntax error This may occur in an import statement in a call to the built in functions compile exec or eval or when reading the initial script or standard input also interactively The str of the exception instance returns only the error message Details is a tuple whose members are also available as separate attributes filename The name of the file the syntax error occurred in lineno Which line number in the file the error occurred in This is 1 indexed the first line in the file has a lineno of 1 offset The column in the line where the error occurred This is 1 indexed the first character in the line has an offset of 1 text The source code text involved in the error end_lineno Which line number in the file the error occurred ends in This is 1 indexed the first line in the file has a lineno of 1 end_offset The column in the end line where the error occurred finishes This is 1 indexed the first character in the line has an offset of 1 For errors in f string fields the message is prefixed by f string and the offsets are offsets in a text constructed from the replacement expression For example compiling f Bad a b field results in this args attribute f string 1 2 a b n 1 5 Changed in version 3 10 Added the end_lineno and end_offset attributes exception IndentationError Base class for syntax errors related to incorrect indentation This is a subclass of SyntaxError exception TabError Raised when indentation contains an inconsistent use of tabs and spaces This is a subclass of IndentationError exception SystemError Ra,en
807,ised when the interpreter finds an internal error but the situation does not look so serious to cause it to abandon all hope The associated value is a string indicating what went wrong in low level terms You should report this to the author or maintainer of your Python interpreter Be sure to report the version of the Python interpreter sys version it is also printed at the start of an interactive Python session the exact error message the exception s associated value and if possible the source of the program that triggered the error exception SystemExit This exception is raised by the sys exit function It inherits from BaseException instead of Exception so that it is not accidentally caught by code that catches Exception This allows the exception to properly propagate up and cause the interpreter to exit When it is not handled the Python interpreter exits no stack traceback is printed The constructor accepts the same optional argument passed to sys exit If the value is an integer it specifies the system exit status passed to C s exit function if it is None the exit status is zero if it has another type such as a string the object s value is printed and the exit status is one A call to sys exit is translated into an exception so that clean up handlers finally clauses of try statements can be executed and so that a debugger can execute a script without running the risk of losing control The os _exit function can be used if it is absolutely positively necessary to exit immediately for example in the child process after a call to os fork code The exit status or error message that is passed to the constructor Defaults to None exception TypeError Raised when an operation or function is applied to an object of inappropriate type The associated value is a string giving details about the type mismatch This exception may be raised by user code to indicate that an attempted operation on an object is not supported and is not meant to be If an object is meant to support a given operation but has not yet provided an implementation NotImplementedError is the proper exception to raise Passing arguments of the wrong type e g passing a list when an int is expected should result in a TypeError but passing arguments with the wrong value e g a number outside expected boundaries should result in a ValueError exception UnboundLocalError Raised when a reference is made to a local variable in a function or method but no value has been bound to that variable This is a subclass of NameError exception UnicodeError Raised when a Unicode related encoding or decoding error occurs It is a subclass of ValueError UnicodeError has attributes that describe the encoding or decoding error For example err object err start err end gives the particular invalid input that the codec failed on encoding The name of the encoding that raised the error reason A string describing the specific codec error object The object the codec was attempting to encode or decode start The first index of invalid data in object end The index after the last invalid data in object exception UnicodeEncodeError Raised when a Unicode related error occurs during encoding It is a subclass of UnicodeError exception UnicodeDecodeError Raised when a Unicode related error occurs during decoding It is a subclass of UnicodeError exception UnicodeTranslateError Raised when a Unicode related error occurs during translating It is a subclass of UnicodeError exception ValueError Raised when an operation or function receives an argument that has the right type but an inappropriate value and the situation is not described by a more precise exception such as IndexError exception ZeroDivisionError Raised when the second argument of a division or modulo operation is zero The associated value is a string indicating the type of the operands and the operation The following exceptions are kept for compatibility with previous versions starting from Python 3 3 they are aliases of OSError exception EnvironmentError exception IOError exception WindowsError Only available on Windows OS exceptions The following exce,en
808,ptions are subclasses of OSError they get raised depending on the system error code exception BlockingIOError Raised when an operation would block on an object e g socket set for non blocking operation Corresponds to errno EAGAIN EALREADY EWOULDBLOCK and EINPROGRESS In addition to those of OSError BlockingIOError can have one more attribute characters_written An integer containing the number of characters written to the stream before it blocked This attribute is available when using the buffered I O classes from the io module exception ChildProcessError Raised when an operation on a child process failed Corresponds to errno ECHILD exception ConnectionError A base class for connection related issues Subclasses are BrokenPipeError ConnectionAbortedError ConnectionRefusedError and ConnectionResetError exception BrokenPipeError A subclass of ConnectionError raised when trying to write on a pipe while the other end has been closed or trying to write on a socket which has been shutdown for writing Corresponds to errno EPIPE and ESHUTDOWN exception ConnectionAbortedError A subclass of ConnectionError raised when a connection attempt is aborted by the peer Corresponds to errno ECONNABORTED exception ConnectionRefusedError A subclass of ConnectionError raised when a connection attempt is refused by the peer Corresponds to errno ECONNREFUSED exception ConnectionResetError A subclass of ConnectionError raised when a connection is reset by the peer Corresponds to errno ECONNRESET exception FileExistsError Raised when trying to create a file or directory which already exists Corresponds to errno EEXIST exception FileNotFoundError Raised when a file or directory is requested but doesn t exist Corresponds to errno ENOENT exception InterruptedError Raised when a system call is interrupted by an incoming signal Corresponds to errno EINTR Changed in version 3 5 Python now retries system calls when a syscall is interrupted by a signal except if the signal handler raises an exception see PEP 475 for the rationale instead of raising InterruptedError exception IsADirectoryError Raised when a file operation such as os remove is requested on a directory Corresponds to errno EISDIR exception NotADirectoryError Raised when a directory operation such as os listdir is requested on something which is not a directory On most POSIX platforms it may also be raised if an operation attempts to open or traverse a non directory file as if it were a directory Corresponds to errno ENOTDIR exception PermissionError Raised when trying to run an operation without the adequate access rights for example filesystem permissions Corresponds to errno EACCES EPERM and ENOTCAPABLE Changed in version 3 11 1 WASI s ENOTCAPABLE is now mapped to PermissionError exception ProcessLookupError Raised when a given process doesn t exist Corresponds to errno ESRCH exception TimeoutError Raised when a system function timed out at the system level Corresponds to errno ETIMEDOUT New in version 3 3 All the above OSError subclasses were added See also PEP 3151 Reworking the OS and IO exception hierarchy Warnings The following exceptions are used as warning categories see the Warning Categories documentation for more details exception Warning Base class for warning categories exception UserWarning Base class for warnings generated by user code exception DeprecationWarning Base class for warnings about deprecated features when those warnings are intended for other Python developers Ignored by the default warning filters except in the __main__ module PEP 565 Enabling the Python Development Mode shows this warning The deprecation policy is described in PEP 387 exception PendingDeprecationWarning Base class for warnings about features which are obsolete and expected to be deprecated in the future but are not deprecated at the moment This class is rarely used as emitting a warning about a possible upcoming deprecation is unusual and DeprecationWarning is preferred for already active deprecations Ignored by the default warning filters Enabling the Python Development Mode shows this warning T,en
809,he deprecation policy is described in PEP 387 exception SyntaxWarning Base class for warnings about dubious syntax exception RuntimeWarning Base class for warnings about dubious runtime behavior exception FutureWarning Base class for warnings about deprecated features when those warnings are intended for end users of applications that are written in Python exception ImportWarning Base class for warnings about probable mistakes in module imports Ignored by the default warning filters Enabling the Python Development Mode shows this warning exception UnicodeWarning Base class for warnings related to Unicode exception EncodingWarning Base class for warnings related to encodings See Opt in EncodingWarning for details New in version 3 10 exception BytesWarning Base class for warnings related to bytes and bytearray exception ResourceWarning Base class for warnings related to resource usage Ignored by the default warning filters Enabling the Python Development Mode shows this warning New in version 3 2 Exception groups The following are used when it is necessary to raise multiple unrelated exceptions They are part of the exception hierarchy so they can be handled with except like all other exceptions In addition they are recognised by except which matches their subgroups based on the types of the contained exceptions exception ExceptionGroup msg excs exception BaseExceptionGroup msg excs Both of these exception types wrap the exceptions in the sequence excs The msg parameter must be a string The difference between the two classes is that BaseExceptionGroup extends BaseException and it can wrap any exception while ExceptionGroup extends Exception and it can only wrap subclasses of Exception This design is so that except Exception catches an ExceptionGroup but not BaseExceptionGroup The BaseExceptionGroup constructor returns an ExceptionGroup rather than a BaseExceptionGroup if all contained exceptions are Exception instances so it can be used to make the selection automatic The ExceptionGroup constructor on the other hand raises a TypeError if any contained exception is not an Exception subclass message The msg argument to the constructor This is a read only attribute exceptions A tuple of the exceptions in the excs sequence given to the constructor This is a read only attribute subgroup condition Returns an exception group that contains only the exceptions from the current group that match condition or None if the result is empty The condition can be either a function that accepts an exception and returns true for those that should be in the subgroup or it can be an exception type or a tuple of exception types which is used to check for a match using the same check that is used in an except clause The nesting structure of the current exception is preserved in the result as are the values of its message __traceback__ __cause__ __context__ and __notes__ fields Empty nested groups are omitted from the result The condition is checked for all exceptions in the nested exception group including the top level and any nested exception groups If the condition is true for such an exception group it is included in the result in full split condition Like subgroup but returns the pair match rest where match is subgroup condition and rest is the remaining non matching part derive excs Returns an exception group with the same message but which wraps the exceptions in excs This method is used by subgroup and split A subclass needs to override it in order to make subgroup and split return instances of the subclass rather than ExceptionGroup subgroup and split copy the __traceback__ __cause__ __context__ and __notes__ fields from the original exception group to the one returned by derive so these fields do not need to be updated by derive class MyGroup ExceptionGroup def derive self excs return MyGroup self message excs e MyGroup eg ValueError 1 TypeError 2 e add_note a note e __context__ Exception context e __cause__ Exception cause try raise e except Exception as e exc e match rest exc split ValueError exc exc __context__ exc __cause__ exc __not,en
810,es__ MyGroup eg ValueError 1 TypeError 2 Exception context Exception cause a note match match __context__ match __cause__ match __notes__ MyGroup eg ValueError 1 Exception context Exception cause a note rest rest __context__ rest __cause__ rest __notes__ MyGroup eg TypeError 2 Exception context Exception cause a note exc __traceback__ is match __traceback__ is rest __traceback__ True Note that BaseExceptionGroup defines __new__ so subclasses that need a different constructor signature need to override that rather than __init__ For example the following defines an exception group subclass which accepts an exit_code and and constructs the group s message from it class Errors ExceptionGroup def __new__ cls errors exit_code self super __new__ Errors f exit code exit_code errors self exit_code exit_code return self def derive self excs return Errors excs self exit_code Like ExceptionGroup any subclass of BaseExceptionGroup which is also a subclass of Exception can only wrap instances of Exception New in version 3 11 Exception hierarchy The class hierarchy for built in exceptions is BaseException BaseExceptionGroup GeneratorExit KeyboardInterrupt SystemExit Exception ArithmeticError FloatingPointError OverflowError ZeroDivisionError AssertionError AttributeError BufferError EOFError ExceptionGroup BaseExceptionGroup ImportError ModuleNotFoundError LookupError IndexError KeyError MemoryError NameError UnboundLocalError OSError BlockingIOError ChildProcessError ConnectionError BrokenPipeError ConnectionAbortedError ConnectionRefusedError ConnectionResetError FileExistsError FileNotFoundError InterruptedError IsADirectoryError NotADirectoryError PermissionError ProcessLookupError TimeoutError ReferenceError RuntimeError NotImplementedError RecursionError StopAsyncIteration StopIteration SyntaxError IndentationError TabError SystemError TypeError ValueError UnicodeError UnicodeDecodeError UnicodeEncodeError UnicodeTranslateError Warning BytesWarning DeprecationWarning EncodingWarning FutureWarning ImportWarning PendingDeprecationWarning ResourceWarning RuntimeWarning SyntaxWarning UnicodeWarning UserWarning,en
811,tempfile Generate temporary files and directories Source code Lib tempfile py This module creates temporary files and directories It works on all supported platforms TemporaryFile NamedTemporaryFile TemporaryDirectory and SpooledTemporaryFile are high level interfaces which provide automatic cleanup and can be used as context managers mkstemp and mkdtemp are lower level functions which require manual cleanup All the user callable functions and constructors take additional arguments which allow direct control over the location and name of temporary files and directories Files names used by this module include a string of random characters which allows those files to be securely created in shared temporary directories To maintain backward compatibility the argument order is somewhat odd it is recommended to use keyword arguments for clarity The module defines the following user callable items tempfile TemporaryFile mode w b buffering 1 encoding None newline None suffix None prefix None dir None errors None Return a file like object that can be used as a temporary storage area The file is created securely using the same rules as mkstemp It will be destroyed as soon as it is closed including an implicit close when the object is garbage collected Under Unix the directory entry for the file is either not created at all or is removed immediately after the file is created Other platforms do not support this your code should not rely on a temporary file created using this function having or not having a visible name in the file system The resulting object can be used as a context manager see Examples On completion of the context or destruction of the file object the temporary file will be removed from the filesystem The mode parameter defaults to w b so that the file created can be read and written without being closed Binary mode is used so that it behaves consistently on all platforms without regard for the data that is stored buffering encoding errors and newline are interpreted as for open The dir prefix and suffix parameters have the same meaning and defaults as with mkstemp The returned object is a true file object on POSIX platforms On other platforms it is a file like object whose file attribute is the underlying true file object The os O_TMPFILE flag is used if it is available and works Linux specific requires Linux kernel 3 11 or later On platforms that are neither Posix nor Cygwin TemporaryFile is an alias for NamedTemporaryFile Raises an auditing event tempfile mkstemp with argument fullpath Changed in version 3 5 The os O_TMPFILE flag is now used if available Changed in version 3 8 Added errors parameter tempfile NamedTemporaryFile mode w b buffering 1 encoding None newline None suffix None prefix None dir None delete True errors None delete_on_close True This function operates exactly as TemporaryFile does except the following differences This function returns a file that is guaranteed to have a visible name in the file system To manage the named file it extends the parameters of TemporaryFile with delete and delete_on_close parameters that determine whether and how the named file should be automatically deleted The returned object is always a file like object whose file attribute is the underlying true file object This file like object can be used in a with statement just like a normal file The name of the temporary file can be retrieved from the name attribute of the returned file like object On Unix unlike with the TemporaryFile the directory entry does not get unlinked immediately after the file creation If delete is true the default and delete_on_close is true the default the file is deleted as soon as it is closed If delete is true and delete_on_close is false the file is deleted on context manager exit only or else when the file like object is finalized Deletion is not always guaranteed in this case see object __del__ If delete is false the value of delete_on_close is ignored Therefore to use the name of the temporary file to reopen the file after closing it either make sure not to delete the file upon closur,en
812,e set the delete parameter to be false or in case the temporary file is created in a with statement set the delete_on_close parameter to be false The latter approach is recommended as it provides assistance in automatic cleaning of the temporary file upon the context manager exit Opening the temporary file again by its name while it is still open works as follows On POSIX the file can always be opened again On Windows make sure that at least one of the following conditions are fulfilled delete is false additional open shares delete access e g by calling os open with the flag O_TEMPORARY delete is true but delete_on_close is false Note that in this case the additional opens that do not share delete access e g created via builtin open must be closed before exiting the context manager else the os unlink call on context manager exit will fail with a PermissionError On Windows if delete_on_close is false and the file is created in a directory for which the user lacks delete access then the os unlink call on exit of the context manager will fail with a PermissionError This cannot happen when delete_on_close is true because delete access is requested by the open which fails immediately if the requested access is not granted On POSIX only a process that is terminated abruptly with SIGKILL cannot automatically delete any NamedTemporaryFiles it created Raises an auditing event tempfile mkstemp with argument fullpath Changed in version 3 8 Added errors parameter Changed in version 3 12 Added delete_on_close parameter class tempfile SpooledTemporaryFile max_size 0 mode w b buffering 1 encoding None newline None suffix None prefix None dir None errors None This class operates exactly as TemporaryFile does except that data is spooled in memory until the file size exceeds max_size or until the file s fileno method is called at which point the contents are written to disk and operation proceeds as with TemporaryFile rollover The resulting file has one additional method rollover which causes the file to roll over to an on disk file regardless of its size The returned object is a file like object whose _file attribute is either an io BytesIO or io TextIOWrapper object depending on whether binary or text mode was specified or a true file object depending on whether rollover has been called This file like object can be used in a with statement just like a normal file Changed in version 3 3 the truncate method now accepts a size argument Changed in version 3 8 Added errors parameter Changed in version 3 11 Fully implements the io BufferedIOBase and io TextIOBase abstract base classes depending on whether binary or text mode was specified class tempfile TemporaryDirectory suffix None prefix None dir None ignore_cleanup_errors False delete True This class securely creates a temporary directory using the same rules as mkdtemp The resulting object can be used as a context manager see Examples On completion of the context or destruction of the temporary directory object the newly created temporary directory and all its contents are removed from the filesystem name The directory name can be retrieved from the name attribute of the returned object When the returned object is used as a context manager the name will be assigned to the target of the as clause in the with statement if there is one cleanup The directory can be explicitly cleaned up by calling the cleanup method If ignore_cleanup_errors is true any unhandled exceptions during explicit or implicit cleanup such as a PermissionError removing open files on Windows will be ignored and the remaining removable items deleted on a best effort basis Otherwise errors will be raised in whatever context cleanup occurs the cleanup call exiting the context manager when the object is garbage collected or during interpreter shutdown The delete parameter can be used to disable cleanup of the directory tree upon exiting the context While it may seem unusual for a context manager to disable the action taken when exiting the context it can be useful during debugging or when you need your cleanup behavior to ,en
813,be conditional based on other logic Raises an auditing event tempfile mkdtemp with argument fullpath New in version 3 2 Changed in version 3 10 Added ignore_cleanup_errors parameter Changed in version 3 12 Added the delete parameter tempfile mkstemp suffix None prefix None dir None text False Creates a temporary file in the most secure manner possible There are no race conditions in the file s creation assuming that the platform properly implements the os O_EXCL flag for os open The file is readable and writable only by the creating user ID If the platform uses permission bits to indicate whether a file is executable the file is executable by no one The file descriptor is not inherited by child processes Unlike TemporaryFile the user of mkstemp is responsible for deleting the temporary file when done with it If suffix is not None the file name will end with that suffix otherwise there will be no suffix mkstemp does not put a dot between the file name and the suffix if you need one put it at the beginning of suffix If prefix is not None the file name will begin with that prefix otherwise a default prefix is used The default is the return value of gettempprefix or gettempprefixb as appropriate If dir is not None the file will be created in that directory otherwise a default directory is used The default directory is chosen from a platform dependent list but the user of the application can control the directory location by setting the TMPDIR TEMP or TMP environment variables There is thus no guarantee that the generated filename will have any nice properties such as not requiring quoting when passed to external commands via os popen If any of suffix prefix and dir are not None they must be the same type If they are bytes the returned name will be bytes instead of str If you want to force a bytes return value with otherwise default behavior pass suffix b If text is specified and true the file is opened in text mode Otherwise the default the file is opened in binary mode mkstemp returns a tuple containing an OS level handle to an open file as would be returned by os open and the absolute pathname of that file in that order Raises an auditing event tempfile mkstemp with argument fullpath Changed in version 3 5 suffix prefix and dir may now be supplied in bytes in order to obtain a bytes return value Prior to this only str was allowed suffix and prefix now accept and default to None to cause an appropriate default value to be used Changed in version 3 6 The dir parameter now accepts a path like object tempfile mkdtemp suffix None prefix None dir None Creates a temporary directory in the most secure manner possible There are no race conditions in the directory s creation The directory is readable writable and searchable only by the creating user ID The user of mkdtemp is responsible for deleting the temporary directory and its contents when done with it The prefix suffix and dir arguments are the same as for mkstemp mkdtemp returns the absolute pathname of the new directory Raises an auditing event tempfile mkdtemp with argument fullpath Changed in version 3 5 suffix prefix and dir may now be supplied in bytes in order to obtain a bytes return value Prior to this only str was allowed suffix and prefix now accept and default to None to cause an appropriate default value to be used Changed in version 3 6 The dir parameter now accepts a path like object Changed in version 3 12 mkdtemp now always returns an absolute path even if dir is relative tempfile gettempdir Return the name of the directory used for temporary files This defines the default value for the dir argument to all functions in this module Python searches a standard list of directories to find one which the calling user can create files in The list is 1 The directory named by the TMPDIR environment variable 2 The directory named by the TEMP environment variable 3 The directory named by the TMP environment variable 4 A platform specific location On Windows the directories C TEMP C TMP TEMP and TMP in that order On all other platforms the directories tmp var tmp and usr ,en
814,tmp in that order 5 As a last resort the current working directory The result of this search is cached see the description of tempdir below Changed in version 3 10 Always returns a str Previously it would return any tempdir value regardless of type so long as it was not None tempfile gettempdirb Same as gettempdir but the return value is in bytes New in version 3 5 tempfile gettempprefix Return the filename prefix used to create temporary files This does not contain the directory component tempfile gettempprefixb Same as gettempprefix but the return value is in bytes New in version 3 5 The module uses a global variable to store the name of the directory used for temporary files returned by gettempdir It can be set directly to override the selection process but this is discouraged All functions in this module take a dir argument which can be used to specify the directory This is the recommended approach that does not surprise other unsuspecting code by changing global API behavior tempfile tempdir When set to a value other than None this variable defines the default value for the dir argument to the functions defined in this module including its type bytes or str It cannot be a path like object If tempdir is None the default at any call to any of the above functions except gettempprefix it is initialized following the algorithm described in gettempdir Note Beware that if you set tempdir to a bytes value there is a nasty side effect The global default return type of mkstemp and mkdtemp changes to bytes when no explicit prefix suffix or dir arguments of type str are supplied Please do not write code expecting or depending on this This awkward behavior is maintained for compatibility with the historical implementation Examples Here are some examples of typical usage of the tempfile module import tempfile create a temporary file and write some data to it fp tempfile TemporaryFile fp write b Hello world read data from file fp seek 0 fp read b Hello world close the file it will be removed fp close create a temporary file using a context manager with tempfile TemporaryFile as fp fp write b Hello world fp seek 0 fp read b Hello world file is now closed and removed create a temporary file using a context manager close the file use the name to open the file again with tempfile NamedTemporaryFile delete_on_close False as fp fp write b Hello world fp close the file is closed but not removed open the file again by using its name with open fp name mode rb as f f read b Hello world file is now removed create a temporary directory using the context manager with tempfile TemporaryDirectory as tmpdirname print created temporary directory tmpdirname directory and contents have been removed Deprecated functions and variables A historical way to create temporary files was to first generate a file name with the mktemp function and then create a file using this name Unfortunately this is not secure because a different process may create a file with this name in the time between the call to mktemp and the subsequent attempt to create the file by the first process The solution is to combine the two steps and create the file immediately This approach is used by mkstemp and the other functions described above tempfile mktemp suffix prefix tmp dir None Deprecated since version 2 3 Use mkstemp instead Return an absolute pathname of a file that did not exist at the time the call is made The prefix suffix and dir arguments are similar to those of mkstemp except that bytes file names suffix None and prefix None are not supported Warning Use of this function may introduce a security hole in your program By the time you get around to doing anything with the file name it returns someone else may have beaten you to the punch mktemp usage can be replaced easily with NamedTemporaryFile passing it the delete False parameter f NamedTemporaryFile delete False f name tmp tmptjujjt f write b Hello World n 13 f close os unlink f name os path exists f name False,en
815,Software Packaging and Distribution These libraries help you with publishing and installing Python software While these modules are designed to work in conjunction with the Python Package Index they can also be used with a local index server or without any index server at all ensurepip Bootstrapping the pip installer Command line interface Module API venv Creation of virtual environments Creating virtual environments How venvs work API An example of extending EnvBuilder zipapp Manage executable Python zip archives Basic Example Command Line Interface Python API Examples Specifying the Interpreter Creating Standalone Applications with zipapp Caveats The Python Zip Application Archive Format,en
816,filecmp File and Directory Comparisons Source code Lib filecmp py The filecmp module defines functions to compare files and directories with various optional time correctness trade offs For comparing files see also the difflib module The filecmp module defines the following functions filecmp cmp f1 f2 shallow True Compare the files named f1 and f2 returning True if they seem equal False otherwise If shallow is true and the os stat signatures file type size and modification time of both files are identical the files are taken to be equal Otherwise the files are treated as different if their sizes or contents differ Note that no external programs are called from this function giving it portability and efficiency This function uses a cache for past comparisons and the results with cache entries invalidated if the os stat information for the file changes The entire cache may be cleared using clear_cache filecmp cmpfiles dir1 dir2 common shallow True Compare the files in the two directories dir1 and dir2 whose names are given by common Returns three lists of file names match mismatch errors match contains the list of files that match mismatch contains the names of those that don t and errors lists the names of files which could not be compared Files are listed in errors if they don t exist in one of the directories the user lacks permission to read them or if the comparison could not be done for some other reason The shallow parameter has the same meaning and default value as for filecmp cmp For example cmpfiles a b c d e will compare a c with b c and a d e with b d e c and d e will each be in one of the three returned lists filecmp clear_cache Clear the filecmp cache This may be useful if a file is compared so quickly after it is modified that it is within the mtime resolution of the underlying filesystem New in version 3 4 The dircmp class class filecmp dircmp a b ignore None hide None Construct a new directory comparison object to compare the directories a and b ignore is a list of names to ignore and defaults to filecmp DEFAULT_IGNORES hide is a list of names to hide and defaults to os curdir os pardir The dircmp class compares files by doing shallow comparisons as described for filecmp cmp The dircmp class provides the following methods report Print to sys stdout a comparison between a and b report_partial_closure Print a comparison between a and b and common immediate subdirectories report_full_closure Print a comparison between a and b and common subdirectories recursively The dircmp class offers a number of interesting attributes that may be used to get various bits of information about the directory trees being compared Note that via __getattr__ hooks all attributes are computed lazily so there is no speed penalty if only those attributes which are lightweight to compute are used left The directory a right The directory b left_list Files and subdirectories in a filtered by hide and ignore right_list Files and subdirectories in b filtered by hide and ignore common Files and subdirectories in both a and b left_only Files and subdirectories only in a right_only Files and subdirectories only in b common_dirs Subdirectories in both a and b common_files Files in both a and b common_funny Names in both a and b such that the type differs between the directories or names for which os stat reports an error same_files Files which are identical in both a and b using the class s file comparison operator diff_files Files which are in both a and b whose contents differ according to the class s file comparison operator funny_files Files which are in both a and b but could not be compared subdirs A dictionary mapping names in common_dirs to dircmp instances or MyDirCmp instances if this instance is of type MyDirCmp a subclass of dircmp Changed in version 3 10 Previously entries were always dircmp instances Now entries are the same type as self if self is a subclass of dircmp filecmp DEFAULT_IGNORES New in version 3 4 List of directories ignored by dircmp by default Here is a simplified example of using the subdirs attribute to search,en
817, recursively through two directories to show common different files from filecmp import dircmp def print_diff_files dcmp for name in dcmp diff_files print diff_file s found in s and s name dcmp left dcmp right for sub_dcmp in dcmp subdirs values print_diff_files sub_dcmp dcmp dircmp dir1 dir2 print_diff_files dcmp,en
818,tkinter font Tkinter font wrapper Source code Lib tkinter font py The tkinter font module provides the Font class for creating and using named fonts The different font weights and slants are tkinter font NORMAL tkinter font BOLD tkinter font ITALIC tkinter font ROMAN class tkinter font Font root None font None name None exists False options The Font class represents a named font Font instances are given unique names and can be specified by their family size and style configuration Named fonts are Tk s method of creating and identifying fonts as a single object rather than specifying a font by its attributes with each occurrence arguments font font specifier tuple family size options name unique font name exists self points to existing named font if true additional keyword options ignored if font is specified family font family i e Courier Times size font size If size is positive it is interpreted as size in points If size is a negative number its absolute value is treated as size in pixels weight font emphasis NORMAL BOLD slant ROMAN ITALIC underline font underlining 0 none 1 underline overstrike font strikeout 0 none 1 strikeout actual option None displayof None Return the attributes of the font cget option Retrieve an attribute of the font config options Modify attributes of the font copy Return new instance of the current font measure text displayof None Return amount of space the text would occupy on the specified display when formatted in the current font If no display is specified then the main application window is assumed metrics options kw Return font specific data Options include ascent distance between baseline and highest point that a character of the font can occupy descent distance between baseline and lowest point that a character of the font can occupy linespace minimum vertical separation necessary between any two characters of the font that ensures no vertical overlap between lines fixed 1 if font is fixed width else 0 tkinter font families root None displayof None Return the different font families tkinter font names root None Return the names of defined fonts tkinter font nametofont name root None Return a Font representation of a tk named font Changed in version 3 10 The root parameter was added,en
819,uu Encode and decode uuencode files Source code Lib uu py Deprecated since version 3 11 will be removed in version 3 13 The uu module is deprecated see PEP 594 for details base64 is a modern alternative This module encodes and decodes files in uuencode format allowing arbitrary binary data to be transferred over ASCII only connections Wherever a file argument is expected the methods accept a file like object For backwards compatibility a string containing a pathname is also accepted and the corresponding file will be opened for reading and writing the pathname is understood to mean the standard input or output However this interface is deprecated it s better for the caller to open the file itself and be sure that when required the mode is rb or wb on Windows This code was contributed by Lance Ellinghouse and modified by Jack Jansen The uu module defines the following functions uu encode in_file out_file name None mode None backtick False Uuencode file in_file into file out_file The uuencoded file will have the header specifying name and mode as the defaults for the results of decoding the file The default defaults are taken from in_file or and 0o666 respectively If backtick is true zeros are represented by instead of spaces Changed in version 3 7 Added the backtick parameter uu decode in_file out_file None mode None quiet False This call decodes uuencoded file in_file placing the result on file out_file If out_file is a pathname mode is used to set the permission bits if the file must be created Defaults for out_file and mode are taken from the uuencode header However if the file specified in the header already exists a uu Error is raised decode may print a warning to standard error if the input was produced by an incorrect uuencoder and Python could recover from that error Setting quiet to a true value silences this warning exception uu Error Subclass of Exception this can be raised by uu decode under various situations such as described above but also including a badly formatted header or truncated input file See also Module binascii Support module containing ASCII to binary and binary to ASCII conversions,en
820,Python Initialization Configuration New in version 3 8 Python can be initialized with Py_InitializeFromConfig and the PyConfig structure It can be preinitialized with Py_PreInitialize and the PyPreConfig structure There are two kinds of configuration The Python Configuration can be used to build a customized Python which behaves as the regular Python For example environment variables and command line arguments are used to configure Python The Isolated Configuration can be used to embed Python into an application It isolates Python from the system For example environment variables are ignored the LC_CTYPE locale is left unchanged and no signal handler is registered The Py_RunMain function can be used to write a customized Python program See also Initialization Finalization and Threads See also PEP 587 Python Initialization Configuration Example Example of customized Python always running in isolated mode int main int argc char argv PyStatus status PyConfig config PyConfig_InitPythonConfig config config isolated 1 Decode command line arguments Implicitly preinitialize Python in isolated mode status PyConfig_SetBytesArgv config argc argv if PyStatus_Exception status goto exception status Py_InitializeFromConfig config if PyStatus_Exception status goto exception PyConfig_Clear config return Py_RunMain exception PyConfig_Clear config if PyStatus_IsExit status return status exitcode Display the error message and exit the process with non zero exit code Py_ExitStatusException status PyWideStringList type PyWideStringList List of wchar_t strings If length is non zero items must be non NULL and all strings must be non NULL Methods PyStatus PyWideStringList_Append PyWideStringList list const wchar_t item Append item to list Python must be preinitialized to call this function PyStatus PyWideStringList_Insert PyWideStringList list Py_ssize_t index const wchar_t item Insert item into list at index If index is greater than or equal to list length append item to list index must be greater than or equal to 0 Python must be preinitialized to call this function Structure fields Py_ssize_t length List length wchar_t items List items PyStatus type PyStatus Structure to store an initialization function status success error or exit For an error it can store the C function name which created the error Structure fields int exitcode Exit code Argument passed to exit const char err_msg Error message const char func Name of the function which created an error can be NULL Functions to create a status PyStatus PyStatus_Ok void Success PyStatus PyStatus_Error const char err_msg Initialization error with a message err_msg must not be NULL PyStatus PyStatus_NoMemory void Memory allocation failure out of memory PyStatus PyStatus_Exit int exitcode Exit Python with the specified exit code Functions to handle a status int PyStatus_Exception PyStatus status Is the status an error or an exit If true the exception must be handled by calling Py_ExitStatusException for example int PyStatus_IsError PyStatus status Is the result an error int PyStatus_IsExit PyStatus status Is the result an exit void Py_ExitStatusException PyStatus status Call exit exitcode if status is an exit Print the error message and exit with a non zero exit code if status is an error Must only be called if PyStatus_Exception status is non zero Note Internally Python uses macros which set PyStatus func whereas functions to create a status set func to NULL Example PyStatus alloc void ptr size_t size ptr PyMem_RawMalloc size if ptr NULL return PyStatus_NoMemory return PyStatus_Ok int main int argc char argv void ptr PyStatus status alloc ptr 16 if PyStatus_Exception status Py_ExitStatusException status PyMem_Free ptr return 0 PyPreConfig type PyPreConfig Structure used to preinitialize Python Function to initialize a preconfiguration void PyPreConfig_InitPythonConfig PyPreConfig preconfig Initialize the preconfiguration with Python Configuration void PyPreConfig_InitIsolatedConfig PyPreConfig preconfig Initialize the preconfiguration with Isolated Configuration Structure fields int allocator N,en
821,ame of the Python memory allocators PYMEM_ALLOCATOR_NOT_SET 0 don t change memory allocators use defaults PYMEM_ALLOCATOR_DEFAULT 1 default memory allocators PYMEM_ALLOCATOR_DEBUG 2 default memory allocators with debug hooks PYMEM_ALLOCATOR_MALLOC 3 use malloc of the C library PYMEM_ALLOCATOR_MALLOC_DEBUG 4 force usage of malloc with debug hooks PYMEM_ALLOCATOR_PYMALLOC 5 Python pymalloc memory allocator PYMEM_ALLOCATOR_PYMALLOC_DEBUG 6 Python pymalloc memory allocator with debug hooks PYMEM_ALLOCATOR_PYMALLOC and PYMEM_ALLOCATOR_PYMALLOC_DEBUG are not supported if Python is configured using without pymalloc See Memory Management Default PYMEM_ALLOCATOR_NOT_SET int configure_locale Set the LC_CTYPE locale to the user preferred locale If equals to 0 set coerce_c_locale and coerce_c_locale_warn members to 0 See the locale encoding Default 1 in Python config 0 in isolated config int coerce_c_locale If equals to 2 coerce the C locale If equals to 1 read the LC_CTYPE locale to decide if it should be coerced See the locale encoding Default 1 in Python config 0 in isolated config int coerce_c_locale_warn If non zero emit a warning if the C locale is coerced Default 1 in Python config 0 in isolated config int dev_mode Python Development Mode see PyConfig dev_mode Default 1 in Python mode 0 in isolated mode int isolated Isolated mode see PyConfig isolated Default 0 in Python mode 1 in isolated mode int legacy_windows_fs_encoding If non zero Set PyPreConfig utf8_mode to 0 Set PyConfig filesystem_encoding to mbcs Set PyConfig filesystem_errors to replace Initialized the from PYTHONLEGACYWINDOWSFSENCODING environment variable value Only available on Windows ifdef MS_WINDOWS macro can be used for Windows specific code Default 0 int parse_argv If non zero Py_PreInitializeFromArgs and Py_PreInitializeFromBytesArgs parse their argv argument the same way the regular Python parses command line arguments see Command Line Arguments Default 1 in Python config 0 in isolated config int use_environment Use environment variables See PyConfig use_environment Default 1 in Python config and 0 in isolated config int utf8_mode If non zero enable the Python UTF 8 Mode Set to 0 or 1 by the X utf8 command line option and the PYTHONUTF8 environment variable Also set to 1 if the LC_CTYPE locale is C or POSIX Default 1 in Python config and 0 in isolated config Preinitialize Python with PyPreConfig The preinitialization of Python Set the Python memory allocators PyPreConfig allocator Configure the LC_CTYPE locale locale encoding Set the Python UTF 8 Mode PyPreConfig utf8_mode The current preconfiguration PyPreConfig type is stored in _PyRuntime preconfig Functions to preinitialize Python PyStatus Py_PreInitialize const PyPreConfig preconfig Preinitialize Python from preconfig preconfiguration preconfig must not be NULL PyStatus Py_PreInitializeFromBytesArgs const PyPreConfig preconfig int argc char const argv Preinitialize Python from preconfig preconfiguration Parse argv command line arguments bytes strings if parse_argv of preconfig is non zero preconfig must not be NULL PyStatus Py_PreInitializeFromArgs const PyPreConfig preconfig int argc wchar_t const argv Preinitialize Python from preconfig preconfiguration Parse argv command line arguments wide strings if parse_argv of preconfig is non zero preconfig must not be NULL The caller is responsible to handle exceptions error or exit using PyStatus_Exception and Py_ExitStatusException For Python Configuration PyPreConfig_InitPythonConfig if Python is initialized with command line arguments the command line arguments must also be passed to preinitialize Python since they have an effect on the pre configuration like encodings For example the X utf8 command line option enables the Python UTF 8 Mode PyMem_SetAllocator can be called after Py_PreInitialize and before Py_InitializeFromConfig to install a custom memory allocator It can be called before Py_PreInitialize if PyPreConfig allocator is set to PYMEM_ALLOCATOR_NOT_SET Python memory allocation functions like PyMem_RawMalloc must not be used before the Pytho,en
822,n preinitialization whereas calling directly malloc and free is always safe Py_DecodeLocale must not be called before the Python preinitialization Example using the preinitialization to enable the Python UTF 8 Mode PyStatus status PyPreConfig preconfig PyPreConfig_InitPythonConfig preconfig preconfig utf8_mode 1 status Py_PreInitialize preconfig if PyStatus_Exception status Py_ExitStatusException status at this point Python speaks UTF 8 Py_Initialize use Python API here Py_Finalize PyConfig type PyConfig Structure containing most parameters to configure Python When done the PyConfig_Clear function must be used to release the configuration memory Structure methods void PyConfig_InitPythonConfig PyConfig config Initialize configuration with the Python Configuration void PyConfig_InitIsolatedConfig PyConfig config Initialize configuration with the Isolated Configuration PyStatus PyConfig_SetString PyConfig config wchar_t const config_str const wchar_t str Copy the wide character string str into config_str Preinitialize Python if needed PyStatus PyConfig_SetBytesString PyConfig config wchar_t const config_str const char str Decode str using Py_DecodeLocale and set the result into config_str Preinitialize Python if needed PyStatus PyConfig_SetArgv PyConfig config int argc wchar_t const argv Set command line arguments argv member of config from the argv list of wide character strings Preinitialize Python if needed PyStatus PyConfig_SetBytesArgv PyConfig config int argc char const argv Set command line arguments argv member of config from the argv list of bytes strings Decode bytes using Py_DecodeLocale Preinitialize Python if needed PyStatus PyConfig_SetWideStringList PyConfig config PyWideStringList list Py_ssize_t length wchar_t items Set the list of wide strings list to length and items Preinitialize Python if needed PyStatus PyConfig_Read PyConfig config Read all Python configuration Fields which are already initialized are left unchanged Fields for path configuration are no longer calculated or modified when calling this function as of Python 3 11 The PyConfig_Read function only parses PyConfig argv arguments once PyConfig parse_argv is set to 2 after arguments are parsed Since Python arguments are strippped from PyConfig argv parsing arguments twice would parse the application options as Python options Preinitialize Python if needed Changed in version 3 10 The PyConfig argv arguments are now only parsed once PyConfig parse_argv is set to 2 after arguments are parsed and arguments are only parsed if PyConfig parse_argv equals 1 Changed in version 3 11 PyConfig_Read no longer calculates all paths and so fields listed under Python Path Configuration may no longer be updated until Py_InitializeFromConfig is called void PyConfig_Clear PyConfig config Release configuration memory Most PyConfig methods preinitialize Python if needed In that case the Python preinitialization configuration PyPreConfig in based on the PyConfig If configuration fields which are in common with PyPreConfig are tuned they must be set before calling a PyConfig method PyConfig dev_mode PyConfig isolated PyConfig parse_argv PyConfig use_environment Moreover if PyConfig_SetArgv or PyConfig_SetBytesArgv is used this method must be called before other methods since the preinitialization configuration depends on command line arguments if parse_argv is non zero The caller of these methods is responsible to handle exceptions error or exit using PyStatus_Exception and Py_ExitStatusException Structure fields PyWideStringList argv Command line arguments sys argv Set parse_argv to 1 to parse argv the same way the regular Python parses Python command line arguments and then to strip Python arguments from argv If argv is empty an empty string is added to ensure that sys argv always exists and is never empty Default NULL See also the orig_argv member int safe_path If equals to zero Py_RunMain prepends a potentially unsafe path to sys path at startup If argv 0 is equal to L m python m module prepend the current working directory If running a script python script py pr,en
823,epend the script s directory If it s a symbolic link resolve symbolic links Otherwise python c code and python prepend an empty string which means the current working directory Set to 1 by the P command line option and the PYTHONSAFEPATH environment variable Default 0 in Python config 1 in isolated config New in version 3 11 wchar_t base_exec_prefix sys base_exec_prefix Default NULL Part of the Python Path Configuration output wchar_t base_executable Python base executable sys _base_executable Set by the __PYVENV_LAUNCHER__ environment variable Set from PyConfig executable if NULL Default NULL Part of the Python Path Configuration output wchar_t base_prefix sys base_prefix Default NULL Part of the Python Path Configuration output int buffered_stdio If equals to 0 and configure_c_stdio is non zero disable buffering on the C streams stdout and stderr Set to 0 by the u command line option and the PYTHONUNBUFFERED environment variable stdin is always opened in buffered mode Default 1 int bytes_warning If equals to 1 issue a warning when comparing bytes or bytearray with str or comparing bytes with int If equal or greater to 2 raise a BytesWarning exception in these cases Incremented by the b command line option Default 0 int warn_default_encoding If non zero emit a EncodingWarning warning when io TextIOWrapper uses its default encoding See Opt in EncodingWarning for details Default 0 New in version 3 10 int code_debug_ranges If equals to 0 disables the inclusion of the end line and column mappings in code objects Also disables traceback printing carets to specific error locations Set to 0 by the PYTHONNODEBUGRANGES environment variable and by the X no_debug_ranges command line option Default 1 New in version 3 11 wchar_t check_hash_pycs_mode Control the validation behavior of hash based pyc files value of the check hash based pycs command line option Valid values L always Hash the source file for invalidation regardless of value of the check_source flag L never Assume that hash based pycs always are valid L default The check_source flag in hash based pycs determines invalidation Default L default See also PEP 552 Deterministic pycs int configure_c_stdio If non zero configure C standard streams On Windows set the binary mode O_BINARY on stdin stdout and stderr If buffered_stdio equals zero disable buffering of stdin stdout and stderr streams If interactive is non zero enable stream buffering on stdin and stdout only stdout on Windows Default 1 in Python config 0 in isolated config int dev_mode If non zero enable the Python Development Mode Set to 1 by the X dev option and the PYTHONDEVMODE environment variable Default 1 in Python mode 0 in isolated mode int dump_refs Dump Python references If non zero dump all objects which are still alive at exit Set to 1 by the PYTHONDUMPREFS environment variable Need a special build of Python with the Py_TRACE_REFS macro defined see the configure with trace refs option Default 0 wchar_t exec_prefix The site specific directory prefix where the platform dependent Python files are installed sys exec_prefix Default NULL Part of the Python Path Configuration output wchar_t executable The absolute path of the executable binary for the Python interpreter sys executable Default NULL Part of the Python Path Configuration output int faulthandler Enable faulthandler If non zero call faulthandler enable at startup Set to 1 by X faulthandler and the PYTHONFAULTHANDLER environment variable Default 1 in Python mode 0 in isolated mode wchar_t filesystem_encoding Filesystem encoding sys getfilesystemencoding On macOS Android and VxWorks use utf 8 by default On Windows use utf 8 by default or mbcs if legacy_windows_fs_encoding of PyPreConfig is non zero Default encoding on other platforms utf 8 if PyPreConfig utf8_mode is non zero ascii if Python detects that nl_langinfo CODESET announces the ASCII encoding whereas the mbstowcs function decodes from a different encoding usually Latin1 utf 8 if nl_langinfo CODESET returns an empty string Otherwise use the locale encoding nl_langinfo CODESET result At Python ,en
824,startup the encoding name is normalized to the Python codec name For example ANSI_X3 4 1968 is replaced with ascii See also the filesystem_errors member wchar_t filesystem_errors Filesystem error handler sys getfilesystemencodeerrors On Windows use surrogatepass by default or replace if legacy_windows_fs_encoding of PyPreConfig is non zero On other platforms use surrogateescape by default Supported error handlers strict surrogateescape surrogatepass only supported with the UTF 8 encoding See also the filesystem_encoding member unsigned long hash_seed int use_hash_seed Randomized hash function seed If use_hash_seed is zero a seed is chosen randomly at Python startup and hash_seed is ignored Set by the PYTHONHASHSEED environment variable Default use_hash_seed value 1 in Python mode 0 in isolated mode wchar_t home Python home directory If Py_SetPythonHome has been called use its argument if it is not NULL Set by the PYTHONHOME environment variable Default NULL Part of the Python Path Configuration input int import_time If non zero profile import time Set the 1 by the X importtime option and the PYTHONPROFILEIMPORTTIME environment variable Default 0 int inspect Enter interactive mode after executing a script or a command If greater than 0 enable inspect when a script is passed as first argument or the c option is used enter interactive mode after executing the script or the command even when sys stdin does not appear to be a terminal Incremented by the i command line option Set to 1 if the PYTHONINSPECT environment variable is non empty Default 0 int install_signal_handlers Install Python signal handlers Default 1 in Python mode 0 in isolated mode int interactive If greater than 0 enable the interactive mode REPL Incremented by the i command line option Default 0 int int_max_str_digits Configures the integer string conversion length limitation An initial value of 1 means the value will be taken from the command line or environment or otherwise default to 4300 sys int_info default_max_str_digits A value of 0 disables the limitation Values greater than zero but less than 640 sys int_info str_digits_check_threshold are unsupported and will produce an error Configured by the X int_max_str_digits command line flag or the PYTHONINTMAXSTRDIGITS environment variable Default 1 in Python mode 4300 sys int_info default_max_str_digits in isolated mode New in version 3 12 int isolated If greater than 0 enable isolated mode Set safe_path to 1 don t prepend a potentially unsafe path to sys path at Python startup such as the current directory the script s directory or an empty string Set use_environment to 0 ignore PYTHON environment variables Set user_site_directory to 0 don t add the user site directory to sys path Python REPL doesn t import readline nor enable default readline configuration on interactive prompts Set to 1 by the I command line option Default 0 in Python mode 1 in isolated mode See also the Isolated Configuration and PyPreConfig isolated int legacy_windows_stdio If non zero use io FileIO instead of io _WindowsConsoleIO for sys stdin sys stdout and sys stderr Set to 1 if the PYTHONLEGACYWINDOWSSTDIO environment variable is set to a non empty string Only available on Windows ifdef MS_WINDOWS macro can be used for Windows specific code Default 0 See also the PEP 528 Change Windows console encoding to UTF 8 int malloc_stats If non zero dump statistics on Python pymalloc memory allocator at exit Set to 1 by the PYTHONMALLOCSTATS environment variable The option is ignored if Python is configured using the without pymalloc option Default 0 wchar_t platlibdir Platform library directory name sys platlibdir Set by the PYTHONPLATLIBDIR environment variable Default value of the PLATLIBDIR macro which is set by the configure with platlibdir option default lib or DLLs on Windows Part of the Python Path Configuration input New in version 3 9 Changed in version 3 11 This macro is now used on Windows to locate the standard library extension modules typically under DLLs However for compatibility note that this value is ignored for any non ,en
825,standard layouts including in tree builds and virtual environments wchar_t pythonpath_env Module search paths sys path as a string separated by DELIM os pathsep Set by the PYTHONPATH environment variable Default NULL Part of the Python Path Configuration input PyWideStringList module_search_paths int module_search_paths_set Module search paths sys path If module_search_paths_set is equal to 0 Py_InitializeFromConfig will replace module_search_paths and sets module_search_paths_set to 1 Default empty list module_search_paths and 0 module_search_paths_set Part of the Python Path Configuration output int optimization_level Compilation optimization level 0 Peephole optimizer set __debug__ to True 1 Level 0 remove assertions set __debug__ to False 2 Level 1 strip docstrings Incremented by the O command line option Set to the PYTHONOPTIMIZE environment variable value Default 0 PyWideStringList orig_argv The list of the original command line arguments passed to the Python executable sys orig_argv If orig_argv list is empty and argv is not a list only containing an empty string PyConfig_Read copies argv into orig_argv before modifying argv if parse_argv is non zero See also the argv member and the Py_GetArgcArgv function Default empty list New in version 3 10 int parse_argv Parse command line arguments If equals to 1 parse argv the same way the regular Python parses command line arguments and strip Python arguments from argv The PyConfig_Read function only parses PyConfig argv arguments once PyConfig parse_argv is set to 2 after arguments are parsed Since Python arguments are strippped from PyConfig argv parsing arguments twice would parse the application options as Python options Default 1 in Python mode 0 in isolated mode Changed in version 3 10 The PyConfig argv arguments are now only parsed if PyConfig parse_argv equals to 1 int parser_debug Parser debug mode If greater than 0 turn on parser debugging output for expert only depending on compilation options Incremented by the d command line option Set to the PYTHONDEBUG environment variable value Need a debug build of Python the Py_DEBUG macro must be defined Default 0 int pathconfig_warnings If non zero calculation of path configuration is allowed to log warnings into stderr If equals to 0 suppress these warnings Default 1 in Python mode 0 in isolated mode Part of the Python Path Configuration input Changed in version 3 11 Now also applies on Windows wchar_t prefix The site specific directory prefix where the platform independent Python files are installed sys prefix Default NULL Part of the Python Path Configuration output wchar_t program_name Program name used to initialize executable and in early error messages during Python initialization If Py_SetProgramName has been called use its argument On macOS use PYTHONEXECUTABLE environment variable if set If the WITH_NEXT_FRAMEWORK macro is defined use __PYVENV_LAUNCHER__ environment variable if set Use argv 0 of argv if available and non empty Otherwise use L python on Windows or L python3 on other platforms Default NULL Part of the Python Path Configuration input wchar_t pycache_prefix Directory where cached pyc files are written sys pycache_prefix Set by the X pycache_prefix PATH command line option and the PYTHONPYCACHEPREFIX environment variable If NULL sys pycache_prefix is set to None Default NULL int quiet Quiet mode If greater than 0 don t display the copyright and version at Python startup in interactive mode Incremented by the q command line option Default 0 wchar_t run_command Value of the c command line option Used by Py_RunMain Default NULL wchar_t run_filename Filename passed on the command line trailing command line argument without c or m It is used by the Py_RunMain function For example it is set to script py by the python3 script py arg command line See also the PyConfig skip_source_first_line option Default NULL wchar_t run_module Value of the m command line option Used by Py_RunMain Default NULL int show_ref_count Show total reference count at exit excluding immortal objects Set to 1 by X showrefcount comma,en
826,nd line option Need a debug build of Python the Py_REF_DEBUG macro must be defined Default 0 int site_import Import the site module at startup If equal to zero disable the import of the module site and the site dependent manipulations of sys path that it entails Also disable these manipulations if the site module is explicitly imported later call site main if you want them to be triggered Set to 0 by the S command line option sys flags no_site is set to the inverted value of site_import Default 1 int skip_source_first_line If non zero skip the first line of the PyConfig run_filename source It allows the usage of non Unix forms of cmd This is intended for a DOS specific hack only Set to 1 by the x command line option Default 0 wchar_t stdio_encoding wchar_t stdio_errors Encoding and encoding errors of sys stdin sys stdout and sys stderr but sys stderr always uses backslashreplace error handler If Py_SetStandardStreamEncoding has been called use its error and errors arguments if they are not NULL Use the PYTHONIOENCODING environment variable if it is non empty Default encoding UTF 8 if PyPreConfig utf8_mode is non zero Otherwise use the locale encoding Default error handler On Windows use surrogateescape surrogateescape if PyPreConfig utf8_mode is non zero or if the LC_CTYPE locale is C or POSIX strict otherwise int tracemalloc Enable tracemalloc If non zero call tracemalloc start at startup Set by X tracemalloc N command line option and by the PYTHONTRACEMALLOC environment variable Default 1 in Python mode 0 in isolated mode int perf_profiling Enable compatibility mode with the perf profiler If non zero initialize the perf trampoline See Python support for the Linux perf profiler for more information Set by X perf command line option and by the PYTHONPERFSUPPORT environment variable Default 1 New in version 3 12 int use_environment Use environment variables If equals to zero ignore the environment variables Set to 0 by the E environment variable Default 1 in Python config and 0 in isolated config int user_site_directory If non zero add the user site directory to sys path Set to 0 by the s and I command line options Set to 0 by the PYTHONNOUSERSITE environment variable Default 1 in Python mode 0 in isolated mode int verbose Verbose mode If greater than 0 print a message each time a module is imported showing the place filename or built in module from which it is loaded If greater than or equal to 2 print a message for each file that is checked for when searching for a module Also provides information on module cleanup at exit Incremented by the v command line option Set by the PYTHONVERBOSE environment variable value Default 0 PyWideStringList warnoptions Options of the warnings module to build warnings filters lowest to highest priority sys warnoptions The warnings module adds sys warnoptions in the reverse order the last PyConfig warnoptions item becomes the first item of warnings filters which is checked first highest priority The W command line options adds its value to warnoptions it can be used multiple times The PYTHONWARNINGS environment variable can also be used to add warning options Multiple options can be specified separated by commas Default empty list int write_bytecode If equal to 0 Python won t try to write pyc files on the import of source modules Set to 0 by the B command line option and the PYTHONDONTWRITEBYTECODE environment variable sys dont_write_bytecode is initialized to the inverted value of write_bytecode Default 1 PyWideStringList xoptions Values of the X command line options sys _xoptions Default empty list If parse_argv is non zero argv arguments are parsed the same way the regular Python parses command line arguments and Python arguments are stripped from argv The xoptions options are parsed to set other options see the X command line option Changed in version 3 9 The show_alloc_count field has been removed Initialization with PyConfig Function to initialize Python PyStatus Py_InitializeFromConfig const PyConfig config Initialize Python from config configuration The caller is responsible to ha,en
827,ndle exceptions error or exit using PyStatus_Exception and Py_ExitStatusException If PyImport_FrozenModules PyImport_AppendInittab or PyImport_ExtendInittab are used they must be set or called after Python preinitialization and before the Python initialization If Python is initialized multiple times PyImport_AppendInittab or PyImport_ExtendInittab must be called before each Python initialization The current configuration PyConfig type is stored in PyInterpreterState config Example setting the program name void init_python void PyStatus status PyConfig config PyConfig_InitPythonConfig config Set the program name Implicitly preinitialize Python status PyConfig_SetString config config program_name L path to my_program if PyStatus_Exception status goto exception status Py_InitializeFromConfig config if PyStatus_Exception status goto exception PyConfig_Clear config return exception PyConfig_Clear config Py_ExitStatusException status More complete example modifying the default configuration read the configuration and then override some parameters Note that since 3 11 many parameters are not calculated until initialization and so values cannot be read from the configuration structure Any values set before initialize is called will be left unchanged by initialization PyStatus init_python const char program_name PyStatus status PyConfig config PyConfig_InitPythonConfig config Set the program name before reading the configuration decode byte string from the locale encoding Implicitly preinitialize Python status PyConfig_SetBytesString config config program_name program_name if PyStatus_Exception status goto done Read all configuration at once status PyConfig_Read config if PyStatus_Exception status goto done Specify sys path explicitly If you want to modify the default set of paths finish initialization first and then use PySys_GetObject path config module_search_paths_set 1 status PyWideStringList_Append config module_search_paths L path to stdlib if PyStatus_Exception status goto done status PyWideStringList_Append config module_search_paths L path to more modules if PyStatus_Exception status goto done Override executable computed by PyConfig_Read status PyConfig_SetString config config executable L path to my_executable if PyStatus_Exception status goto done status Py_InitializeFromConfig config done PyConfig_Clear config return status Isolated Configuration PyPreConfig_InitIsolatedConfig and PyConfig_InitIsolatedConfig functions create a configuration to isolate Python from the system For example to embed Python into an application This configuration ignores global configuration variables environment variables command line arguments PyConfig argv is not parsed and user site directory The C standard streams ex stdout and the LC_CTYPE locale are left unchanged Signal handlers are not installed Configuration files are still used with this configuration to determine paths that are unspecified Ensure PyConfig home is specified to avoid computing the default path configuration Python Configuration PyPreConfig_InitPythonConfig and PyConfig_InitPythonConfig functions create a configuration to build a customized Python which behaves as the regular Python Environments variables and command line arguments are used to configure Python whereas global configuration variables are ignored This function enables C locale coercion PEP 538 and Python UTF 8 Mode PEP 540 depending on the LC_CTYPE locale PYTHONUTF8 and PYTHONCOERCECLOCALE environment variables Python Path Configuration PyConfig contains multiple fields for the path configuration Path configuration inputs PyConfig home PyConfig platlibdir PyConfig pathconfig_warnings PyConfig program_name PyConfig pythonpath_env current working directory to get absolute paths PATH environment variable to get the program full path from PyConfig program_name __PYVENV_LAUNCHER__ environment variable Windows only Application paths in the registry under SoftwarePythonPythonCoreX YPythonPath of HKEY_CURRENT_USER and HKEY_LOCAL_MACHINE where X Y is the Python version Path configuration output fields PyConfi,en
828,g base_exec_prefix PyConfig base_executable PyConfig base_prefix PyConfig exec_prefix PyConfig executable PyConfig module_search_paths_set PyConfig module_search_paths PyConfig prefix If at least one output field is not set Python calculates the path configuration to fill unset fields If module_search_paths_set is equal to 0 module_search_paths is overridden and module_search_paths_set is set to 1 It is possible to completely ignore the function calculating the default path configuration by setting explicitly all path configuration output fields listed above A string is considered as set even if it is non empty module_search_paths is considered as set if module_search_paths_set is set to 1 In this case module_search_paths will be used without modification Set pathconfig_warnings to 0 to suppress warnings when calculating the path configuration Unix only Windows does not log any warning If base_prefix or base_exec_prefix fields are not set they inherit their value from prefix and exec_prefix respectively Py_RunMain and Py_Main modify sys path If run_filename is set and is a directory which contains a __main__ py script prepend run_filename to sys path If isolated is zero If run_module is set prepend the current directory to sys path Do nothing if the current directory cannot be read If run_filename is set prepend the directory of the filename to sys path Otherwise prepend an empty string to sys path If site_import is non zero sys path can be modified by the site module If user_site_directory is non zero and the user s site package directory exists the site module appends the user s site package directory to sys path The following configuration files are used by the path configuration pyvenv cfg _pth file ex python _pth pybuilddir txt Unix only If a _pth file is present Set isolated to 1 Set use_environment to 0 Set site_import to 0 Set safe_path to 1 The __PYVENV_LAUNCHER__ environment variable is used to set PyConfig base_executable Py_RunMain int Py_RunMain void Execute the command PyConfig run_command the script PyConfig run_filename or the module PyConfig run_module specified on the command line or in the configuration By default and when if i option is used run the REPL Finally finalizes Python and returns an exit status that can be passed to the exit function See Python Configuration for an example of customized Python always running in isolated mode using Py_RunMain Py_GetArgcArgv void Py_GetArgcArgv int argc wchar_t argv Get the original command line arguments before Python modified them See also PyConfig orig_argv member Multi Phase Initialization Private Provisional API This section is a private provisional API introducing multi phase initialization the core feature of PEP 432 Core initialization phase bare minimum Python Builtin types Builtin exceptions Builtin and frozen modules The sys module is only partially initialized ex sys path doesn t exist yet Main initialization phase Python is fully initialized Install and configure importlib Apply the Path Configuration Install signal handlers Finish sys module initialization ex create sys stdout and sys path Enable optional features like faulthandler and tracemalloc Import the site module etc Private provisional API PyConfig _init_main if set to 0 Py_InitializeFromConfig stops at the Core initialization phase PyStatus _Py_InitializeMain void Move to the Main initialization phase finish the Python initialization No module is imported during the Core phase and the importlib module is not configured the Path Configuration is only applied during the Main phase It may allow to customize Python in Python to override or tune the Path Configuration maybe install a custom sys meta_path importer or an import hook etc It may become possible to calculate the Path Configuration in Python after the Core phase and before the Main phase which is one of the PEP 432 motivation The Core phase is not properly defined what should be and what should not be available at this phase is not specified yet The API is marked as private and provisional the API can be modified or even be remove,en
829,d anytime until a proper public API is designed Example running Python code between Core and Main initialization phases void init_python void PyStatus status PyConfig config PyConfig_InitPythonConfig config config _init_main 0 customize config configuration status Py_InitializeFromConfig config PyConfig_Clear config if PyStatus_Exception status Py_ExitStatusException status Use sys stderr because sys stdout is only created by _Py_InitializeMain int res PyRun_SimpleString import sys print Run Python code before _Py_InitializeMain file sys stderr if res 0 exit 1 put more configuration code here status _Py_InitializeMain if PyStatus_Exception status Py_ExitStatusException status,en
830,Functional Programming HOWTO Author A M Kuchling Release 0 32 In this document we ll take a tour of Python s features suitable for implementing programs in a functional style After an introduction to the concepts of functional programming we ll look at language features such as iterator s and generator s and relevant library modules such as itertools and functools Introduction This section explains the basic concept of functional programming if you re just interested in learning about Python language features skip to the next section on Iterators Programming languages support decomposing problems in several different ways Most programming languages are procedural programs are lists of instructions that tell the computer what to do with the program s input C Pascal and even Unix shells are procedural languages In declarative languages you write a specification that describes the problem to be solved and the language implementation figures out how to perform the computation efficiently SQL is the declarative language you re most likely to be familiar with a SQL query describes the data set you want to retrieve and the SQL engine decides whether to scan tables or use indexes which subclauses should be performed first etc Object oriented programs manipulate collections of objects Objects have internal state and support methods that query or modify this internal state in some way Smalltalk and Java are object oriented languages C and Python are languages that support object oriented programming but don t force the use of object oriented features Functional programming decomposes a problem into a set of functions Ideally functions only take inputs and produce outputs and don t have any internal state that affects the output produced for a given input Well known functional languages include the ML family Standard ML OCaml and other variants and Haskell The designers of some computer languages choose to emphasize one particular approach to programming This often makes it difficult to write programs that use a different approach Other languages are multi paradigm languages that support several different approaches Lisp C and Python are multi paradigm you can write programs or libraries that are largely procedural object oriented or functional in all of these languages In a large program different sections might be written using different approaches the GUI might be object oriented while the processing logic is procedural or functional for example In a functional program input flows through a set of functions Each function operates on its input and produces some output Functional style discourages functions with side effects that modify internal state or make other changes that aren t visible in the function s return value Functions that have no side effects at all are called purely functional Avoiding side effects means not using data structures that get updated as a program runs every function s output must only depend on its input Some languages are very strict about purity and don t even have assignment statements such as a 3 or c a b but it s difficult to avoid all side effects such as printing to the screen or writing to a disk file Another example is a call to the print or time sleep function neither of which returns a useful value Both are called only for their side effects of sending some text to the screen or pausing execution for a second Python programs written in functional style usually won t go to the extreme of avoiding all I O or all assignments instead they ll provide a functional appearing interface but will use non functional features internally For example the implementation of a function will still use assignments to local variables but won t modify global variables or have other side effects Functional programming can be considered the opposite of object oriented programming Objects are little capsules containing some internal state along with a collection of method calls that let you modify this state and programs consist of making the right set of state changes Functional programming wants to avoid state c,en
831,hanges as much as possible and works with data flowing between functions In Python you might combine the two approaches by writing functions that take and return instances representing objects in your application e mail messages transactions etc Functional design may seem like an odd constraint to work under Why should you avoid objects and side effects There are theoretical and practical advantages to the functional style Formal provability Modularity Composability Ease of debugging and testing Formal provability A theoretical benefit is that it s easier to construct a mathematical proof that a functional program is correct For a long time researchers have been interested in finding ways to mathematically prove programs correct This is different from testing a program on numerous inputs and concluding that its output is usually correct or reading a program s source code and concluding that the code looks right the goal is instead a rigorous proof that a program produces the right result for all possible inputs The technique used to prove programs correct is to write down invariants properties of the input data and of the program s variables that are always true For each line of code you then show that if invariants X and Y are true before the line is executed the slightly different invariants X and Y are true after the line is executed This continues until you reach the end of the program at which point the invariants should match the desired conditions on the program s output Functional programming s avoidance of assignments arose because assignments are difficult to handle with this technique assignments can break invariants that were true before the assignment without producing any new invariants that can be propagated onward Unfortunately proving programs correct is largely impractical and not relevant to Python software Even trivial programs require proofs that are several pages long the proof of correctness for a moderately complicated program would be enormous and few or none of the programs you use daily the Python interpreter your XML parser your web browser could be proven correct Even if you wrote down or generated a proof there would then be the question of verifying the proof maybe there s an error in it and you wrongly believe you ve proved the program correct Modularity A more practical benefit of functional programming is that it forces you to break apart your problem into small pieces Programs are more modular as a result It s easier to specify and write a small function that does one thing than a large function that performs a complicated transformation Small functions are also easier to read and to check for errors Ease of debugging and testing Testing and debugging a functional style program is easier Debugging is simplified because functions are generally small and clearly specified When a program doesn t work each function is an interface point where you can check that the data are correct You can look at the intermediate inputs and outputs to quickly isolate the function that s responsible for a bug Testing is easier because each function is a potential subject for a unit test Functions don t depend on system state that needs to be replicated before running a test instead you only have to synthesize the right input and then check that the output matches expectations Composability As you work on a functional style program you ll write a number of functions with varying inputs and outputs Some of these functions will be unavoidably specialized to a particular application but others will be useful in a wide variety of programs For example a function that takes a directory path and returns all the XML files in the directory or a function that takes a filename and returns its contents can be applied to many different situations Over time you ll form a personal library of utilities Often you ll assemble new programs by arranging existing functions in a new configuration and writing a few functions specialized for the current task Iterators I ll start by looking at a Python language feature that s an imp,en
832,ortant foundation for writing functional style programs iterators An iterator is an object representing a stream of data this object returns the data one element at a time A Python iterator must support a method called __next__ that takes no arguments and always returns the next element of the stream If there are no more elements in the stream __next__ must raise the StopIteration exception Iterators don t have to be finite though it s perfectly reasonable to write an iterator that produces an infinite stream of data The built in iter function takes an arbitrary object and tries to return an iterator that will return the object s contents or elements raising TypeError if the object doesn t support iteration Several of Python s built in data types support iteration the most common being lists and dictionaries An object is called iterable if you can get an iterator for it You can experiment with the iteration interface manually L 1 2 3 it iter L it iterator object at it __next__ same as next it 1 next it 2 next it 3 next it Traceback most recent call last File stdin line 1 in module StopIteration Python expects iterable objects in several different contexts the most important being the for statement In the statement for X in Y Y must be an iterator or some object for which iter can create an iterator These two statements are equivalent for i in iter obj print i for i in obj print i Iterators can be materialized as lists or tuples by using the list or tuple constructor functions L 1 2 3 iterator iter L t tuple iterator t 1 2 3 Sequence unpacking also supports iterators if you know an iterator will return N elements you can unpack them into an N tuple L 1 2 3 iterator iter L a b c iterator a b c 1 2 3 Built in functions such as max and min can take a single iterator argument and will return the largest or smallest element The in and not in operators also support iterators X in iterator is true if X is found in the stream returned by the iterator You ll run into obvious problems if the iterator is infinite max min will never return and if the element X never appears in the stream the in and not in operators won t return either Note that you can only go forward in an iterator there s no way to get the previous element reset the iterator or make a copy of it Iterator objects can optionally provide these additional capabilities but the iterator protocol only specifies the __next__ method Functions may therefore consume all of the iterator s output and if you need to do something different with the same stream you ll have to create a new iterator Data Types That Support Iterators We ve already seen how lists and tuples support iterators In fact any Python sequence type such as strings will automatically support creation of an iterator Calling iter on a dictionary returns an iterator that will loop over the dictionary s keys m Jan 1 Feb 2 Mar 3 Apr 4 May 5 Jun 6 Jul 7 Aug 8 Sep 9 Oct 10 Nov 11 Dec 12 for key in m print key m key Jan 1 Feb 2 Mar 3 Apr 4 May 5 Jun 6 Jul 7 Aug 8 Sep 9 Oct 10 Nov 11 Dec 12 Note that starting with Python 3 7 dictionary iteration order is guaranteed to be the same as the insertion order In earlier versions the behaviour was unspecified and could vary between implementations Applying iter to a dictionary always loops over the keys but dictionaries have methods that return other iterators If you want to iterate over values or key value pairs you can explicitly call the values or items methods to get an appropriate iterator The dict constructor can accept an iterator that returns a finite stream of key value tuples L Italy Rome France Paris US Washington DC dict iter L Italy Rome France Paris US Washington DC Files also support iteration by calling the readline method until there are no more lines in the file This means you can read each line of a file like this for line in file do something for each line Sets can take their contents from an iterable and let you iterate over the set s elements S 2 3 5 7 11 13 for i in S print i 2 3 5 7 11 13 Generator expressions and list comprehensions Two common operatio,en
833,ns on an iterator s output are 1 performing some operation for every element 2 selecting a subset of elements that meet some condition For example given a list of strings you might want to strip off trailing whitespace from each line or extract all the strings containing a given substring List comprehensions and generator expressions short form listcomps and genexps are a concise notation for such operations borrowed from the functional programming language Haskell https www haskell org You can strip all the whitespace from a stream of strings with the following code line_list line 1 n line 2 n n Generator expression returns iterator stripped_iter line strip for line in line_list List comprehension returns list stripped_list line strip for line in line_list You can select only certain elements by adding an if condition stripped_list line strip for line in line_list if line With a list comprehension you get back a Python list stripped_list is a list containing the resulting lines not an iterator Generator expressions return an iterator that computes the values as necessary not needing to materialize all the values at once This means that list comprehensions aren t useful if you re working with iterators that return an infinite stream or a very large amount of data Generator expressions are preferable in these situations Generator expressions are surrounded by parentheses and list comprehensions are surrounded by square brackets Generator expressions have the form expression for expr in sequence1 if condition1 for expr2 in sequence2 if condition2 for expr3 in sequence3 if condition3 for exprN in sequenceN if conditionN Again for a list comprehension only the outside brackets are different square brackets instead of parentheses The elements of the generated output will be the successive values of expression The if clauses are all optional if present expression is only evaluated and added to the result when condition is true Generator expressions always have to be written inside parentheses but the parentheses signalling a function call also count If you want to create an iterator that will be immediately passed to a function you can write obj_total sum obj count for obj in list_all_objects The for in clauses contain the sequences to be iterated over The sequences do not have to be the same length because they are iterated over from left to right not in parallel For each element in sequence1 sequence2 is looped over from the beginning sequence3 is then looped over for each resulting pair of elements from sequence1 and sequence2 To put it another way a list comprehension or generator expression is equivalent to the following Python code for expr1 in sequence1 if not condition1 continue Skip this element for expr2 in sequence2 if not condition2 continue Skip this element for exprN in sequenceN if not conditionN continue Skip this element Output the value of the expression This means that when there are multiple for in clauses but no if clauses the length of the resulting output will be equal to the product of the lengths of all the sequences If you have two lists of length 3 the output list is 9 elements long seq1 abc seq2 1 2 3 x y for x in seq1 for y in seq2 a 1 a 2 a 3 b 1 b 2 b 3 c 1 c 2 c 3 To avoid introducing an ambiguity into Python s grammar if expression is creating a tuple it must be surrounded with parentheses The first list comprehension below is a syntax error while the second one is correct Syntax error x y for x in seq1 for y in seq2 Correct x y for x in seq1 for y in seq2 Generators Generators are a special class of functions that simplify the task of writing iterators Regular functions compute a value and return it but generators return an iterator that returns a stream of values You re doubtless familiar with how regular function calls work in Python or C When you call a function it gets a private namespace where its local variables are created When the function reaches a return statement the local variables are destroyed and the value is returned to the caller A later call to the same function creates a new,en
834, private namespace and a fresh set of local variables But what if the local variables weren t thrown away on exiting a function What if you could later resume the function where it left off This is what generators provide they can be thought of as resumable functions Here s the simplest example of a generator function def generate_ints N for i in range N yield i Any function containing a yield keyword is a generator function this is detected by Python s bytecode compiler which compiles the function specially as a result When you call a generator function it doesn t return a single value instead it returns a generator object that supports the iterator protocol On executing the yield expression the generator outputs the value of i similar to a return statement The big difference between yield and a return statement is that on reaching a yield the generator s state of execution is suspended and local variables are preserved On the next call to the generator s __next__ method the function will resume executing Here s a sample usage of the generate_ints generator gen generate_ints 3 gen generator object generate_ints at next gen 0 next gen 1 next gen 2 next gen Traceback most recent call last File stdin line 1 in module File stdin line 2 in generate_ints StopIteration You could equally write for i in generate_ints 5 or a b c generate_ints 3 Inside a generator function return value causes StopIteration value to be raised from the __next__ method Once this happens or the bottom of the function is reached the procession of values ends and the generator cannot yield any further values You could achieve the effect of generators manually by writing your own class and storing all the local variables of the generator as instance variables For example returning a list of integers could be done by setting self count to 0 and having the __next__ method increment self count and return it However for a moderately complicated generator writing a corresponding class can be much messier The test suite included with Python s library Lib test test_generators py contains a number of more interesting examples Here s one generator that implements an in order traversal of a tree using generators recursively A recursive generator that generates Tree leaves in in order def inorder t if t for x in inorder t left yield x yield t label for x in inorder t right yield x Two other examples in test_generators py produce solutions for the N Queens problem placing N queens on an NxN chess board so that no queen threatens another and the Knight s Tour finding a route that takes a knight to every square of an NxN chessboard without visiting any square twice Passing values into a generator In Python 2 4 and earlier generators only produced output Once a generator s code was invoked to create an iterator there was no way to pass any new information into the function when its execution is resumed You could hack together this ability by making the generator look at a global variable or by passing in some mutable object that callers then modify but these approaches are messy In Python 2 5 there s a simple way to pass values into a generator yield became an expression returning a value that can be assigned to a variable or otherwise operated on val yield i I recommend that you always put parentheses around a yield expression when you re doing something with the returned value as in the above example The parentheses aren t always necessary but it s easier to always add them instead of having to remember when they re needed PEP 342 explains the exact rules which are that a yield expression must always be parenthesized except when it occurs at the top level expression on the right hand side of an assignment This means you can write val yield i but have to use parentheses when there s an operation as in val yield i 12 Values are sent into a generator by calling its send value method This method resumes the generator s code and the yield expression returns the specified value If the regular __next__ method is called the yield returns None Here s a simple counter that inc,en
835,rements by 1 and allows changing the value of the internal counter def counter maximum i 0 while i maximum val yield i If value provided change counter if val is not None i val else i 1 And here s an example of changing the counter it counter 10 next it 0 next it 1 it send 8 8 next it 9 next it Traceback most recent call last File t py line 15 in module it next StopIteration Because yield will often be returning None you should always check for this case Don t just use its value in expressions unless you re sure that the send method will be the only method used to resume your generator function In addition to send there are two other methods on generators throw value is used to raise an exception inside the generator the exception is raised by the yield expression where the generator s execution is paused close raises a GeneratorExit exception inside the generator to terminate the iteration On receiving this exception the generator s code must either raise GeneratorExit or StopIteration catching the exception and doing anything else is illegal and will trigger a RuntimeError close will also be called by Python s garbage collector when the generator is garbage collected If you need to run cleanup code when a GeneratorExit occurs I suggest using a try finally suite instead of catching GeneratorExit The cumulative effect of these changes is to turn generators from one way producers of information into both producers and consumers Generators also become coroutines a more generalized form of subroutines Subroutines are entered at one point and exited at another point the top of the function and a return statement but coroutines can be entered exited and resumed at many different points the yield statements Built in functions Let s look in more detail at built in functions often used with iterators Two of Python s built in functions map and filter duplicate the features of generator expressions map f iterA iterB returns an iterator over the sequence f iterA 0 iterB 0 f iterA 1 iterB 1 f iterA 2 iterB 2 def upper s return s upper list map upper sentence fragment SENTENCE FRAGMENT upper s for s in sentence fragment SENTENCE FRAGMENT You can of course achieve the same effect with a list comprehension filter predicate iter returns an iterator over all the sequence elements that meet a certain condition and is similarly duplicated by list comprehensions A predicate is a function that returns the truth value of some condition for use with filter the predicate must take a single value def is_even x return x 2 0 list filter is_even range 10 0 2 4 6 8 This can also be written as a list comprehension list x for x in range 10 if is_even x 0 2 4 6 8 enumerate iter start 0 counts off the elements in the iterable returning 2 tuples containing the count from start and each element for item in enumerate subject verb object print item 0 subject 1 verb 2 object enumerate is often used when looping through a list and recording the indexes at which certain conditions are met f open data txt r for i line in enumerate f if line strip print Blank line at line i i sorted iterable key None reverse False collects all the elements of the iterable into a list sorts the list and returns the sorted result The key and reverse arguments are passed through to the constructed list s sort method import random Generate 8 random numbers between 0 10000 rand_list random sample range 10000 8 rand_list 769 7953 9828 6431 8442 9878 6213 2207 sorted rand_list 769 2207 6213 6431 7953 8442 9828 9878 sorted rand_list reverse True 9878 9828 8442 7953 6431 6213 2207 769 For a more detailed discussion of sorting see the Sorting Techniques The any iter and all iter built ins look at the truth values of an iterable s contents any returns True if any element in the iterable is a true value and all returns True if all of the elements are true values any 0 1 0 True any 0 0 0 False any 1 1 1 True all 0 1 0 False all 0 0 0 False all 1 1 1 True zip iterA iterB takes one element from each iterable and returns them in a tuple zip a b c 1 2 3 a 1 b 2 c 3 It doesn t construct an in mem,en
836,ory list and exhaust all the input iterators before returning instead tuples are constructed and returned only if they re requested The technical term for this behaviour is lazy evaluation This iterator is intended to be used with iterables that are all of the same length If the iterables are of different lengths the resulting stream will be the same length as the shortest iterable zip a b 1 2 3 a 1 b 2 You should avoid doing this though because an element may be taken from the longer iterators and discarded This means you can t go on to use the iterators further because you risk skipping a discarded element The itertools module The itertools module contains a number of commonly used iterators as well as functions for combining several iterators This section will introduce the module s contents by showing small examples The module s functions fall into a few broad classes Functions that create a new iterator based on an existing iterator Functions for treating an iterator s elements as function arguments Functions for selecting portions of an iterator s output A function for grouping an iterator s output Creating new iterators itertools count start step returns an infinite stream of evenly spaced values You can optionally supply the starting number which defaults to 0 and the interval between numbers which defaults to 1 itertools count 0 1 2 3 4 5 6 7 8 9 itertools count 10 10 11 12 13 14 15 16 17 18 19 itertools count 10 5 10 15 20 25 30 35 40 45 50 55 itertools cycle iter saves a copy of the contents of a provided iterable and returns a new iterator that returns its elements from first to last The new iterator will repeat these elements infinitely itertools cycle 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 itertools repeat elem n returns the provided element n times or returns the element endlessly if n is not provided itertools repeat abc abc abc abc abc abc abc abc abc abc abc itertools repeat abc 5 abc abc abc abc abc itertools chain iterA iterB takes an arbitrary number of iterables as input and returns all the elements of the first iterator then all the elements of the second and so on until all of the iterables have been exhausted itertools chain a b c 1 2 3 a b c 1 2 3 itertools islice iter start stop step returns a stream that s a slice of the iterator With a single stop argument it will return the first stop elements If you supply a starting index you ll get stop start elements and if you supply a value for step elements will be skipped accordingly Unlike Python s string and list slicing you can t use negative values for start stop or step itertools islice range 10 8 0 1 2 3 4 5 6 7 itertools islice range 10 2 8 2 3 4 5 6 7 itertools islice range 10 2 8 2 2 4 6 itertools tee iter n replicates an iterator it returns n independent iterators that will all return the contents of the source iterator If you don t supply a value for n the default is 2 Replicating iterators requires saving some of the contents of the source iterator so this can consume significant memory if the iterator is large and one of the new iterators is consumed more than the others itertools tee itertools count iterA iterB where iterA 0 1 2 3 4 5 6 7 8 9 and iterB 0 1 2 3 4 5 6 7 8 9 Calling functions on elements The operator module contains a set of functions corresponding to Python s operators Some examples are operator add a b adds two values operator ne a b same as a b and operator attrgetter id returns a callable that fetches the id attribute itertools starmap func iter assumes that the iterable will return a stream of tuples and calls func using these tuples as the arguments itertools starmap os path join bin python usr bin java usr bin perl usr bin ruby bin python usr bin java usr bin perl usr bin ruby Selecting elements Another group of functions chooses a subset of an iterator s elements based on a predicate itertools filterfalse predicate iter is the opposite of filter returning all elements for which the predicate returns false itertools filterfalse is_even itertools count 1 3 5 7 9 11 13 15 itertools takewhile predicate iter returns elements for,en
837, as long as the predicate returns true Once the predicate returns false the iterator will signal the end of its results def less_than_10 x return x 10 itertools takewhile less_than_10 itertools count 0 1 2 3 4 5 6 7 8 9 itertools takewhile is_even itertools count 0 itertools dropwhile predicate iter discards elements while the predicate returns true and then returns the rest of the iterable s results itertools dropwhile less_than_10 itertools count 10 11 12 13 14 15 16 17 18 19 itertools dropwhile is_even itertools count 1 2 3 4 5 6 7 8 9 10 itertools compress data selectors takes two iterators and returns only those elements of data for which the corresponding element of selectors is true stopping whenever either one is exhausted itertools compress 1 2 3 4 5 True True False False True 1 2 5 Combinatoric functions The itertools combinations iterable r returns an iterator giving all possible r tuple combinations of the elements contained in iterable itertools combinations 1 2 3 4 5 2 1 2 1 3 1 4 1 5 2 3 2 4 2 5 3 4 3 5 4 5 itertools combinations 1 2 3 4 5 3 1 2 3 1 2 4 1 2 5 1 3 4 1 3 5 1 4 5 2 3 4 2 3 5 2 4 5 3 4 5 The elements within each tuple remain in the same order as iterable returned them For example the number 1 is always before 2 3 4 or 5 in the examples above A similar function itertools permutations iterable r None removes this constraint on the order returning all possible arrangements of length r itertools permutations 1 2 3 4 5 2 1 2 1 3 1 4 1 5 2 1 2 3 2 4 2 5 3 1 3 2 3 4 3 5 4 1 4 2 4 3 4 5 5 1 5 2 5 3 5 4 itertools permutations 1 2 3 4 5 1 2 3 4 5 1 2 3 5 4 1 2 4 3 5 5 4 3 2 1 If you don t supply a value for r the length of the iterable is used meaning that all the elements are permuted Note that these functions produce all of the possible combinations by position and don t require that the contents of iterable are unique itertools permutations aba 3 a b a a a b b a a b a a a a b a b a The identical tuple a a b occurs twice but the two a strings came from different positions The itertools combinations_with_replacement iterable r function relaxes a different constraint elements can be repeated within a single tuple Conceptually an element is selected for the first position of each tuple and then is replaced before the second element is selected itertools combinations_with_replacement 1 2 3 4 5 2 1 1 1 2 1 3 1 4 1 5 2 2 2 3 2 4 2 5 3 3 3 4 3 5 4 4 4 5 5 5 Grouping elements The last function I ll discuss itertools groupby iter key_func None is the most complicated key_func elem is a function that can compute a key value for each element returned by the iterable If you don t supply a key function the key is simply each element itself groupby collects all the consecutive elements from the underlying iterable that have the same key value and returns a stream of 2 tuples containing a key value and an iterator for the elements with that key city_list Decatur AL Huntsville AL Selma AL Anchorage AK Nome AK Flagstaff AZ Phoenix AZ Tucson AZ def get_state city_state return city_state 1 itertools groupby city_list get_state AL iterator 1 AK iterator 2 AZ iterator 3 where iterator 1 Decatur AL Huntsville AL Selma AL iterator 2 Anchorage AK Nome AK iterator 3 Flagstaff AZ Phoenix AZ Tucson AZ groupby assumes that the underlying iterable s contents will already be sorted based on the key Note that the returned iterators also use the underlying iterable so you have to consume the results of iterator 1 before requesting iterator 2 and its corresponding key The functools module The functools module contains some higher order functions A higher order function takes one or more functions as input and returns a new function The most useful tool in this module is the functools partial function For programs written in a functional style you ll sometimes want to construct variants of existing functions that have some of the parameters filled in Consider a Python function f a b c you may wish to create a new function g b c that s equivalent to f 1 b c you re filling in a value for one of f s parameters This is called partial func,en
838,tion application The constructor for partial takes the arguments function arg1 arg2 kwarg1 value1 kwarg2 value2 The resulting object is callable so you can just call it to invoke function with the filled in arguments Here s a small but realistic example import functools def log message subsystem Write the contents of message to the specified subsystem print s s subsystem message server_log functools partial log subsystem server server_log Unable to open socket functools reduce func iter initial_value cumulatively performs an operation on all the iterable s elements and therefore can t be applied to infinite iterables func must be a function that takes two elements and returns a single value functools reduce takes the first two elements A and B returned by the iterator and calculates func A B It then requests the third element C calculates func func A B C combines this result with the fourth element returned and continues until the iterable is exhausted If the iterable returns no values at all a TypeError exception is raised If the initial value is supplied it s used as a starting point and func initial_value A is the first calculation import operator functools functools reduce operator concat A BB C ABBC functools reduce operator concat Traceback most recent call last TypeError reduce of empty sequence with no initial value functools reduce operator mul 1 2 3 1 6 functools reduce operator mul 1 1 If you use operator add with functools reduce you ll add up all the elements of the iterable This case is so common that there s a special built in called sum to compute it import functools operator functools reduce operator add 1 2 3 4 0 10 sum 1 2 3 4 10 sum 0 For many uses of functools reduce though it can be clearer to just write the obvious for loop import functools Instead of product functools reduce operator mul 1 2 3 1 You can write product 1 for i in 1 2 3 product i A related function is itertools accumulate iterable func operator add It performs the same calculation but instead of returning only the final result accumulate returns an iterator that also yields each partial result itertools accumulate 1 2 3 4 5 1 3 6 10 15 itertools accumulate 1 2 3 4 5 operator mul 1 2 6 24 120 The operator module The operator module was mentioned earlier It contains a set of functions corresponding to Python s operators These functions are often useful in functional style code because they save you from writing trivial functions that perform a single operation Some of the functions in this module are Math operations add sub mul floordiv abs Logical operations not_ truth Bitwise operations and_ or_ invert Comparisons eq ne lt le gt and ge Object identity is_ is_not Consult the operator module s documentation for a complete list Small functions and the lambda expression When writing functional style programs you ll often need little functions that act as predicates or that combine elements in some way If there s a Python built in or a module function that s suitable you don t need to define a new function at all stripped_lines line strip for line in lines existing_files filter os path exists file_list If the function you need doesn t exist you need to write it One way to write small functions is to use the lambda expression lambda takes a number of parameters and an expression combining these parameters and creates an anonymous function that returns the value of the expression adder lambda x y x y print_assign lambda name value name str value An alternative is to just use the def statement and define a function in the usual way def adder x y return x y def print_assign name value return name str value Which alternative is preferable That s a style question my usual course is to avoid using lambda One reason for my preference is that lambda is quite limited in the functions it can define The result has to be computable as a single expression which means you can t have multiway if elif else comparisons or try except statements If you try to do too much in a lambda statement you ll end up with an overly complicated expression that s hard to,en
839, read Quick what s the following code doing import functools total functools reduce lambda a b 0 a 1 b 1 items 1 You can figure it out but it takes time to disentangle the expression to figure out what s going on Using a short nested def statements makes things a little bit better import functools def combine a b return 0 a 1 b 1 total functools reduce combine items 1 But it would be best of all if I had simply used a for loop total 0 for a b in items total b Or the sum built in and a generator expression total sum b for a b in items Many uses of functools reduce are clearer when written as for loops Fredrik Lundh once suggested the following set of rules for refactoring uses of lambda 1 Write a lambda function 2 Write a comment explaining what the heck that lambda does 3 Study the comment for a while and think of a name that captures the essence of the comment 4 Convert the lambda to a def statement using that name 5 Remove the comment I really like these rules but you re free to disagree about whether this lambda free style is better Revision History and Acknowledgements The author would like to thank the following people for offering suggestions corrections and assistance with various drafts of this article Ian Bicking Nick Coghlan Nick Efford Raymond Hettinger Jim Jewett Mike Krell Leandro Lameiro Jussi Salmela Collin Winter Blake Winton Version 0 1 posted June 30 2006 Version 0 11 posted July 1 2006 Typo fixes Version 0 2 posted July 10 2006 Merged genexp and listcomp sections into one Typo fixes Version 0 21 Added more references suggested on the tutor mailing list Version 0 30 Adds a section on the functional module written by Collin Winter adds short section on the operator module a few other edits References General Structure and Interpretation of Computer Programs by Harold Abelson and Gerald Jay Sussman with Julie Sussman The book can be found at https mitpress mit edu sicp In this classic textbook of computer science chapters 2 and 3 discuss the use of sequences and streams to organize the data flow inside a program The book uses Scheme for its examples but many of the design approaches described in these chapters are applicable to functional style Python code https www defmacro org ramblings fp html A general introduction to functional programming that uses Java examples and has a lengthy historical introduction https en wikipedia org wiki Functional_programming General Wikipedia entry describing functional programming https en wikipedia org wiki Coroutine Entry for coroutines https en wikipedia org wiki Partial_application Entry for the concept of partial function application https en wikipedia org wiki Currying Entry for the concept of currying Python specific https gnosis cx TPiP The first chapter of David Mertz s book Text Processing in Python discusses functional programming for text processing in the section titled Utilizing Higher Order Functions in Text Processing Mertz also wrote a 3 part series of articles on functional programming for IBM s DeveloperWorks site see part 1 part 2 and part 3 Python documentation Documentation for the itertools module Documentation for the functools module Documentation for the operator module PEP 289 Generator Expressions PEP 342 Coroutines via Enhanced Generators describes the new generator features in Python 2 5,en
840,email parser Parsing email messages Source code Lib email parser py Message object structures can be created in one of two ways they can be created from whole cloth by creating an EmailMessage object adding headers using the dictionary interface and adding payload s using set_content and related methods or they can be created by parsing a serialized representation of the email message The email package provides a standard parser that understands most email document structures including MIME documents You can pass the parser a bytes string or file object and the parser will return to you the root EmailMessage instance of the object structure For simple non MIME messages the payload of this root object will likely be a string containing the text of the message For MIME messages the root object will return True from its is_multipart method and the subparts can be accessed via the payload manipulation methods such as get_body iter_parts and walk There are actually two parser interfaces available for use the Parser API and the incremental FeedParser API The Parser API is most useful if you have the entire text of the message in memory or if the entire message lives in a file on the file system FeedParser is more appropriate when you are reading the message from a stream which might block waiting for more input such as reading an email message from a socket The FeedParser can consume and parse the message incrementally and only returns the root object when you close the parser Note that the parser can be extended in limited ways and of course you can implement your own parser completely from scratch All of the logic that connects the email package s bundled parser and the EmailMessage class is embodied in the Policy class so a custom parser can create message object trees any way it finds necessary by implementing custom versions of the appropriate Policy methods FeedParser API The BytesFeedParser imported from the email feedparser module provides an API that is conducive to incremental parsing of email messages such as would be necessary when reading the text of an email message from a source that can block such as a socket The BytesFeedParser can of course be used to parse an email message fully contained in a bytes like object string or file but the BytesParser API may be more convenient for such use cases The semantics and results of the two parser APIs are identical The BytesFeedParser s API is simple you create an instance feed it a bunch of bytes until there s no more to feed it then close the parser to retrieve the root message object The BytesFeedParser is extremely accurate when parsing standards compliant messages and it does a very good job of parsing non compliant messages providing information about how a message was deemed broken It will populate a message object s defects attribute with a list of any problems it found in a message See the email errors module for the list of defects that it can find Here is the API for the BytesFeedParser class email parser BytesFeedParser _factory None policy policy compat32 Create a BytesFeedParser instance Optional _factory is a no argument callable if not specified use the message_factory from the policy Call _factory whenever a new message object is needed If policy is specified use the rules it specifies to update the representation of the message If policy is not set use the compat32 policy which maintains backward compatibility with the Python 3 2 version of the email package and provides Message as the default factory All other policies provide EmailMessage as the default _factory For more information on what else policy controls see the policy documentation Note The policy keyword should always be specified The default will change to email policy default in a future version of Python New in version 3 2 Changed in version 3 3 Added the policy keyword Changed in version 3 6 _factory defaults to the policy message_factory feed data Feed the parser some more data data should be a bytes like object containing one or more lines The lines can be partial and the parser will st,en
841,itch such partial lines together properly The lines can have any of the three common line endings carriage return newline or carriage return and newline they can even be mixed close Complete the parsing of all previously fed data and return the root message object It is undefined what happens if feed is called after this method has been called class email parser FeedParser _factory None policy policy compat32 Works like BytesFeedParser except that the input to the feed method must be a string This is of limited utility since the only way for such a message to be valid is for it to contain only ASCII text or if utf8 is True no binary attachments Changed in version 3 3 Added the policy keyword Parser API The BytesParser class imported from the email parser module provides an API that can be used to parse a message when the complete contents of the message are available in a bytes like object or file The email parser module also provides Parser for parsing strings and header only parsers BytesHeaderParser and HeaderParser which can be used if you re only interested in the headers of the message BytesHeaderParser and HeaderParser can be much faster in these situations since they do not attempt to parse the message body instead setting the payload to the raw body class email parser BytesParser _class None policy policy compat32 Create a BytesParser instance The _class and policy arguments have the same meaning and semantics as the _factory and policy arguments of BytesFeedParser Note The policy keyword should always be specified The default will change to email policy default in a future version of Python Changed in version 3 3 Removed the strict argument that was deprecated in 2 4 Added the policy keyword Changed in version 3 6 _class defaults to the policy message_factory parse fp headersonly False Read all the data from the binary file like object fp parse the resulting bytes and return the message object fp must support both the readline and the read methods The bytes contained in fp must be formatted as a block of RFC 5322 or if utf8 is True RFC 6532 style headers and header continuation lines optionally preceded by an envelope header The header block is terminated either by the end of the data or by a blank line Following the header block is the body of the message which may contain MIME encoded subparts including subparts with a Content Transfer Encoding of 8bit Optional headersonly is a flag specifying whether to stop parsing after reading the headers or not The default is False meaning it parses the entire contents of the file parsebytes bytes headersonly False Similar to the parse method except it takes a bytes like object instead of a file like object Calling this method on a bytes like object is equivalent to wrapping bytes in a BytesIO instance first and calling parse Optional headersonly is as with the parse method New in version 3 2 class email parser BytesHeaderParser _class None policy policy compat32 Exactly like BytesParser except that headersonly defaults to True New in version 3 3 class email parser Parser _class None policy policy compat32 This class is parallel to BytesParser but handles string input Changed in version 3 3 Removed the strict argument Added the policy keyword Changed in version 3 6 _class defaults to the policy message_factory parse fp headersonly False Read all the data from the text mode file like object fp parse the resulting text and return the root message object fp must support both the readline and the read methods on file like objects Other than the text mode requirement this method operates like BytesParser parse parsestr text headersonly False Similar to the parse method except it takes a string object instead of a file like object Calling this method on a string is equivalent to wrapping text in a StringIO instance first and calling parse Optional headersonly is as with the parse method class email parser HeaderParser _class None policy policy compat32 Exactly like Parser except that headersonly defaults to True Since creating a message object structure from a string or a file,en
842, object is such a common task four functions are provided as a convenience They are available in the top level email package namespace email message_from_bytes s _class None policy policy compat32 Return a message object structure from a bytes like object This is equivalent to BytesParser parsebytes s Optional _class and policy are interpreted as with the BytesParser class constructor New in version 3 2 Changed in version 3 3 Removed the strict argument Added the policy keyword email message_from_binary_file fp _class None policy policy compat32 Return a message object structure tree from an open binary file object This is equivalent to BytesParser parse fp _class and policy are interpreted as with the BytesParser class constructor New in version 3 2 Changed in version 3 3 Removed the strict argument Added the policy keyword email message_from_string s _class None policy policy compat32 Return a message object structure from a string This is equivalent to Parser parsestr s _class and policy are interpreted as with the Parser class constructor Changed in version 3 3 Removed the strict argument Added the policy keyword email message_from_file fp _class None policy policy compat32 Return a message object structure tree from an open file object This is equivalent to Parser parse fp _class and policy are interpreted as with the Parser class constructor Changed in version 3 3 Removed the strict argument Added the policy keyword Changed in version 3 6 _class defaults to the policy message_factory Here s an example of how you might use message_from_bytes at an interactive Python prompt import email msg email message_from_bytes myBytes Additional notes Here are some notes on the parsing semantics Most non multipart type messages are parsed as a single message object with a string payload These objects will return False for is_multipart and iter_parts will yield an empty list All multipart type messages will be parsed as a container message object with a list of sub message objects for their payload The outer container message will return True for is_multipart and iter_parts will yield a list of subparts Most messages with a content type of message such as message delivery status and message rfc822 will also be parsed as container object containing a list payload of length 1 Their is_multipart method will return True The single element yielded by iter_parts will be a sub message object Some non standards compliant messages may not be internally consistent about their multipart edness Such messages may have a Content Type header of type multipart but their is_multipart method may return False If such messages were parsed with the FeedParser they will have an instance of the MultipartInvariantViolationDefect class in their defects attribute list See email errors for details,en
843,multiprocessing Process based parallelism Source code Lib multiprocessing Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information Introduction multiprocessing is a package that supports spawning processes using an API similar to the threading module The multiprocessing package offers both local and remote concurrency effectively side stepping the Global Interpreter Lock by using subprocesses instead of threads Due to this the multiprocessing module allows the programmer to fully leverage multiple processors on a given machine It runs on both POSIX and Windows The multiprocessing module also introduces APIs which do not have analogs in the threading module A prime example of this is the Pool object which offers a convenient means of parallelizing the execution of a function across multiple input values distributing the input data across processes data parallelism The following example demonstrates the common practice of defining such functions in a module so that child processes can successfully import that module This basic example of data parallelism using Pool from multiprocessing import Pool def f x return x x if __name__ __main__ with Pool 5 as p print p map f 1 2 3 will print to standard output 1 4 9 See also concurrent futures ProcessPoolExecutor offers a higher level interface to push tasks to a background process without blocking execution of the calling process Compared to using the Pool interface directly the concurrent futures API more readily allows the submission of work to the underlying process pool to be separated from waiting for the results The Process class In multiprocessing processes are spawned by creating a Process object and then calling its start method Process follows the API of threading Thread A trivial example of a multiprocess program is from multiprocessing import Process def f name print hello name if __name__ __main__ p Process target f args bob p start p join To show the individual process IDs involved here is an expanded example from multiprocessing import Process import os def info title print title print module name __name__ print parent process os getppid print process id os getpid def f name info function f print hello name if __name__ __main__ info main line p Process target f args bob p start p join For an explanation of why the if __name__ __main__ part is necessary see Programming guidelines Contexts and start methods Depending on the platform multiprocessing supports three ways to start a process These start methods are spawn The parent process starts a fresh Python interpreter process The child process will only inherit those resources necessary to run the process object s run method In particular unnecessary file descriptors and handles from the parent process will not be inherited Starting a process using this method is rather slow compared to using fork or forkserver Available on POSIX and Windows platforms The default on Windows and macOS fork The parent process uses os fork to fork the Python interpreter The child process when it begins is effectively identical to the parent process All resources of the parent are inherited by the child process Note that safely forking a multithreaded process is problematic Available on POSIX systems Currently the default on POSIX except macOS Note The default start method will change away from fork in Python 3 14 Code that requires fork should explicitly specify that via get_context or set_start_method Changed in version 3 12 If Python is able to detect that your process has multiple threads the os fork function that this start method calls internally will raise a DeprecationWarning Use a different start method See the os fork documentation for further explanation forkserver When the program starts and selects the forkserver start method a server process is spawned From then on whenever a new process is needed the parent process connects to the server and requests that it fork a new process The fork server ,en
844,process is single threaded unless system libraries or preloaded imports spawn threads as a side effect so it is generally safe for it to use os fork No unnecessary resources are inherited Available on POSIX platforms which support passing file descriptors over Unix pipes such as Linux Changed in version 3 4 spawn added on all POSIX platforms and forkserver added for some POSIX platforms Child processes no longer inherit all of the parents inheritable handles on Windows Changed in version 3 8 On macOS the spawn start method is now the default The fork start method should be considered unsafe as it can lead to crashes of the subprocess as macOS system libraries may start threads See bpo 33725 On POSIX using the spawn or forkserver start methods will also start a resource tracker process which tracks the unlinked named system resources such as named semaphores or SharedMemory objects created by processes of the program When all processes have exited the resource tracker unlinks any remaining tracked object Usually there should be none but if a process was killed by a signal there may be some leaked resources Neither leaked semaphores nor shared memory segments will be automatically unlinked until the next reboot This is problematic for both objects because the system allows only a limited number of named semaphores and shared memory segments occupy some space in the main memory To select a start method you use the set_start_method in the if __name__ __main__ clause of the main module For example import multiprocessing as mp def foo q q put hello if __name__ __main__ mp set_start_method spawn q mp Queue p mp Process target foo args q p start print q get p join set_start_method should not be used more than once in the program Alternatively you can use get_context to obtain a context object Context objects have the same API as the multiprocessing module and allow one to use multiple start methods in the same program import multiprocessing as mp def foo q q put hello if __name__ __main__ ctx mp get_context spawn q ctx Queue p ctx Process target foo args q p start print q get p join Note that objects related to one context may not be compatible with processes for a different context In particular locks created using the fork context cannot be passed to processes started using the spawn or forkserver start methods A library which wants to use a particular start method should probably use get_context to avoid interfering with the choice of the library user Warning The spawn and forkserver start methods generally cannot be used with frozen executables i e binaries produced by packages like PyInstaller and cx_Freeze on POSIX systems The fork start method may work if code does not use threads Exchanging objects between processes multiprocessing supports two types of communication channel between processes Queues The Queue class is a near clone of queue Queue For example from multiprocessing import Process Queue def f q q put 42 None hello if __name__ __main__ q Queue p Process target f args q p start print q get prints 42 None hello p join Queues are thread and process safe Pipes The Pipe function returns a pair of connection objects connected by a pipe which by default is duplex two way For example from multiprocessing import Process Pipe def f conn conn send 42 None hello conn close if __name__ __main__ parent_conn child_conn Pipe p Process target f args child_conn p start print parent_conn recv prints 42 None hello p join The two connection objects returned by Pipe represent the two ends of the pipe Each connection object has send and recv methods among others Note that data in a pipe may become corrupted if two processes or threads try to read from or write to the same end of the pipe at the same time Of course there is no risk of corruption from processes using different ends of the pipe at the same time Synchronization between processes multiprocessing contains equivalents of all the synchronization primitives from threading For instance one can use a lock to ensure that only one process prints to standard output at a time from,en
845, multiprocessing import Process Lock def f l i l acquire try print hello world i finally l release if __name__ __main__ lock Lock for num in range 10 Process target f args lock num start Without using the lock output from the different processes is liable to get all mixed up Sharing state between processes As mentioned above when doing concurrent programming it is usually best to avoid using shared state as far as possible This is particularly true when using multiple processes However if you really do need to use some shared data then multiprocessing provides a couple of ways of doing so Shared memory Data can be stored in a shared memory map using Value or Array For example the following code from multiprocessing import Process Value Array def f n a n value 3 1415927 for i in range len a a i a i if __name__ __main__ num Value d 0 0 arr Array i range 10 p Process target f args num arr p start p join print num value print arr will print 3 1415927 0 1 2 3 4 5 6 7 8 9 The d and i arguments used when creating num and arr are typecodes of the kind used by the array module d indicates a double precision float and i indicates a signed integer These shared objects will be process and thread safe For more flexibility in using shared memory one can use the multiprocessing sharedctypes module which supports the creation of arbitrary ctypes objects allocated from shared memory Server process A manager object returned by Manager controls a server process which holds Python objects and allows other processes to manipulate them using proxies A manager returned by Manager will support types list dict Namespace Lock RLock Semaphore BoundedSemaphore Condition Event Barrier Queue Value and Array For example from multiprocessing import Process Manager def f d l d 1 1 d 2 2 d 0 25 None l reverse if __name__ __main__ with Manager as manager d manager dict l manager list range 10 p Process target f args d l p start p join print d print l will print 0 25 None 1 1 2 2 9 8 7 6 5 4 3 2 1 0 Server process managers are more flexible than using shared memory objects because they can be made to support arbitrary object types Also a single manager can be shared by processes on different computers over a network They are however slower than using shared memory Using a pool of workers The Pool class represents a pool of worker processes It has methods which allows tasks to be offloaded to the worker processes in a few different ways For example from multiprocessing import Pool TimeoutError import time import os def f x return x x if __name__ __main__ start 4 worker processes with Pool processes 4 as pool print 0 1 4 81 print pool map f range 10 print same numbers in arbitrary order for i in pool imap_unordered f range 10 print i evaluate f 20 asynchronously res pool apply_async f 20 runs in only one process print res get timeout 1 prints 400 evaluate os getpid asynchronously res pool apply_async os getpid runs in only one process print res get timeout 1 prints the PID of that process launching multiple evaluations asynchronously may use more processes multiple_results pool apply_async os getpid for i in range 4 print res get timeout 1 for res in multiple_results make a single worker sleep for 10 seconds res pool apply_async time sleep 10 try print res get timeout 1 except TimeoutError print We lacked patience and got a multiprocessing TimeoutError print For the moment the pool remains available for more work exiting the with block has stopped the pool print Now the pool is closed and no longer available Note that the methods of a pool should only ever be used by the process which created it Note Functionality within this package requires that the __main__ module be importable by the children This is covered in Programming guidelines however it is worth pointing out here This means that some examples such as the multiprocessing pool Pool examples will not work in the interactive interpreter For example from multiprocessing import Pool p Pool 5 def f x return x x with p p map f 1 2 3 Process PoolWorker 1 Process PoolWorker 2 Process PoolWorker 3 Traceback,en
846, most recent call last Traceback most recent call last Traceback most recent call last AttributeError Can t get attribute f on module __main__ class _frozen_importlib BuiltinImporter AttributeError Can t get attribute f on module __main__ class _frozen_importlib BuiltinImporter AttributeError Can t get attribute f on module __main__ class _frozen_importlib BuiltinImporter If you try this it will actually output three full tracebacks interleaved in a semi random fashion and then you may have to stop the parent process somehow Reference The multiprocessing package mostly replicates the API of the threading module Process and exceptions class multiprocessing Process group None target None name None args kwargs daemon None Process objects represent activity that is run in a separate process The Process class has equivalents of all the methods of threading Thread The constructor should always be called with keyword arguments group should always be None it exists solely for compatibility with threading Thread target is the callable object to be invoked by the run method It defaults to None meaning nothing is called name is the process name see name for more details args is the argument tuple for the target invocation kwargs is a dictionary of keyword arguments for the target invocation If provided the keyword only daemon argument sets the process daemon flag to True or False If None the default this flag will be inherited from the creating process By default no arguments are passed to target The args argument which defaults to can be used to specify a list or tuple of the arguments to pass to target If a subclass overrides the constructor it must make sure it invokes the base class constructor Process __init__ before doing anything else to the process Changed in version 3 3 Added the daemon parameter run Method representing the process s activity You may override this method in a subclass The standard run method invokes the callable object passed to the object s constructor as the target argument if any with sequential and keyword arguments taken from the args and kwargs arguments respectively Using a list or tuple as the args argument passed to Process achieves the same effect Example from multiprocessing import Process p Process target print args 1 p run 1 p Process target print args 1 p run 1 start Start the process s activity This must be called at most once per process object It arranges for the object s run method to be invoked in a separate process join timeout If the optional argument timeout is None the default the method blocks until the process whose join method is called terminates If timeout is a positive number it blocks at most timeout seconds Note that the method returns None if its process terminates or if the method times out Check the process s exitcode to determine if it terminated A process can be joined many times A process cannot join itself because this would cause a deadlock It is an error to attempt to join a process before it has been started name The process s name The name is a string used for identification purposes only It has no semantics Multiple processes may be given the same name The initial name is set by the constructor If no explicit name is provided to the constructor a name of the form Process N_1 N_2 N_k is constructed where each N_k is the N th child of its parent is_alive Return whether the process is alive Roughly a process object is alive from the moment the start method returns until the child process terminates daemon The process s daemon flag a Boolean value This must be set before start is called The initial value is inherited from the creating process When a process exits it attempts to terminate all of its daemonic child processes Note that a daemonic process is not allowed to create child processes Otherwise a daemonic process would leave its children orphaned if it gets terminated when its parent process exits Additionally these are not Unix daemons or services they are normal processes that will be terminated and not joined if non daemonic processes have exited In addition,en
847, to the threading Thread API Process objects also support the following attributes and methods pid Return the process ID Before the process is spawned this will be None exitcode The child s exit code This will be None if the process has not yet terminated If the child s run method returned normally the exit code will be 0 If it terminated via sys exit with an integer argument N the exit code will be N If the child terminated due to an exception not caught within run the exit code will be 1 If it was terminated by signal N the exit code will be the negative value N authkey The process s authentication key a byte string When multiprocessing is initialized the main process is assigned a random string using os urandom When a Process object is created it will inherit the authentication key of its parent process although this may be changed by setting authkey to another byte string See Authentication keys sentinel A numeric handle of a system object which will become ready when the process ends You can use this value if you want to wait on several events at once using multiprocessing connection wait Otherwise calling join is simpler On Windows this is an OS handle usable with the WaitForSingleObject and WaitForMultipleObjects family of API calls On POSIX this is a file descriptor usable with primitives from the select module New in version 3 3 terminate Terminate the process On POSIX this is done using the SIGTERM signal on Windows TerminateProcess is used Note that exit handlers and finally clauses etc will not be executed Note that descendant processes of the process will not be terminated they will simply become orphaned Warning If this method is used when the associated process is using a pipe or queue then the pipe or queue is liable to become corrupted and may become unusable by other process Similarly if the process has acquired a lock or semaphore etc then terminating it is liable to cause other processes to deadlock kill Same as terminate but using the SIGKILL signal on POSIX New in version 3 7 close Close the Process object releasing all resources associated with it ValueError is raised if the underlying process is still running Once close returns successfully most other methods and attributes of the Process object will raise ValueError New in version 3 7 Note that the start join is_alive terminate and exitcode methods should only be called by the process that created the process object Example usage of some of the methods of Process import multiprocessing time signal mp_context multiprocessing get_context spawn p mp_context Process target time sleep args 1000 print p p is_alive Process initial False p start print p p is_alive Process started True p terminate time sleep 0 1 print p p is_alive Process stopped exitcode SIGTERM False p exitcode signal SIGTERM True exception multiprocessing ProcessError The base class of all multiprocessing exceptions exception multiprocessing BufferTooShort Exception raised by Connection recv_bytes_into when the supplied buffer object is too small for the message read If e is an instance of BufferTooShort then e args 0 will give the message as a byte string exception multiprocessing AuthenticationError Raised when there is an authentication error exception multiprocessing TimeoutError Raised by methods with a timeout when the timeout expires Pipes and Queues When using multiple processes one generally uses message passing for communication between processes and avoids having to use any synchronization primitives like locks For passing messages one can use Pipe for a connection between two processes or a queue which allows multiple producers and consumers The Queue SimpleQueue and JoinableQueue types are multi producer multi consumer FIFO first in first out queues modelled on the queue Queue class in the standard library They differ in that Queue lacks the task_done and join methods introduced into Python 2 5 s queue Queue class If you use JoinableQueue then you must call JoinableQueue task_done for each task removed from the queue or else the semaphore used to count the number of unfini,en
848,shed tasks may eventually overflow raising an exception Note that one can also create a shared queue by using a manager object see Managers Note multiprocessing uses the usual queue Empty and queue Full exceptions to signal a timeout They are not available in the multiprocessing namespace so you need to import them from queue Note When an object is put on a queue the object is pickled and a background thread later flushes the pickled data to an underlying pipe This has some consequences which are a little surprising but should not cause any practical difficulties if they really bother you then you can instead use a queue created with a manager 1 After putting an object on an empty queue there may be an infinitesimal delay before the queue s empty method returns False and get_nowait can return without raising queue Empty 2 If multiple processes are enqueuing objects it is possible for the objects to be received at the other end out of order However objects enqueued by the same process will always be in the expected order with respect to each other Warning If a process is killed using Process terminate or os kill while it is trying to use a Queue then the data in the queue is likely to become corrupted This may cause any other process to get an exception when it tries to use the queue later on Warning As mentioned above if a child process has put items on a queue and it has not used JoinableQueue cancel_join_thread then that process will not terminate until all buffered items have been flushed to the pipe This means that if you try joining that process you may get a deadlock unless you are sure that all items which have been put on the queue have been consumed Similarly if the child process is non daemonic then the parent process may hang on exit when it tries to join all its non daemonic children Note that a queue created using a manager does not have this issue See Programming guidelines For an example of the usage of queues for interprocess communication see Examples multiprocessing Pipe duplex Returns a pair conn1 conn2 of Connection objects representing the ends of a pipe If duplex is True the default then the pipe is bidirectional If duplex is False then the pipe is unidirectional conn1 can only be used for receiving messages and conn2 can only be used for sending messages class multiprocessing Queue maxsize Returns a process shared queue implemented using a pipe and a few locks semaphores When a process first puts an item on the queue a feeder thread is started which transfers objects from a buffer into the pipe The usual queue Empty and queue Full exceptions from the standard library s queue module are raised to signal timeouts Queue implements all the methods of queue Queue except for task_done and join qsize Return the approximate size of the queue Because of multithreading multiprocessing semantics this number is not reliable Note that this may raise NotImplementedError on platforms like macOS where sem_getvalue is not implemented empty Return True if the queue is empty False otherwise Because of multithreading multiprocessing semantics this is not reliable full Return True if the queue is full False otherwise Because of multithreading multiprocessing semantics this is not reliable put obj block timeout Put obj into the queue If the optional argument block is True the default and timeout is None the default block if necessary until a free slot is available If timeout is a positive number it blocks at most timeout seconds and raises the queue Full exception if no free slot was available within that time Otherwise block is False put an item on the queue if a free slot is immediately available else raise the queue Full exception timeout is ignored in that case Changed in version 3 8 If the queue is closed ValueError is raised instead of AssertionError put_nowait obj Equivalent to put obj False get block timeout Remove and return an item from the queue If optional args block is True the default and timeout is None the default block if necessary until an item is available If timeout is a positive number it blocks at ,en
849,most timeout seconds and raises the queue Empty exception if no item was available within that time Otherwise block is False return an item if one is immediately available else raise the queue Empty exception timeout is ignored in that case Changed in version 3 8 If the queue is closed ValueError is raised instead of OSError get_nowait Equivalent to get False multiprocessing Queue has a few additional methods not found in queue Queue These methods are usually unnecessary for most code close Indicate that no more data will be put on this queue by the current process The background thread will quit once it has flushed all buffered data to the pipe This is called automatically when the queue is garbage collected join_thread Join the background thread This can only be used after close has been called It blocks until the background thread exits ensuring that all data in the buffer has been flushed to the pipe By default if a process is not the creator of the queue then on exit it will attempt to join the queue s background thread The process can call cancel_join_thread to make join_thread do nothing cancel_join_thread Prevent join_thread from blocking In particular this prevents the background thread from being joined automatically when the process exits see join_thread A better name for this method might be allow_exit_without_flush It is likely to cause enqueued data to be lost and you almost certainly will not need to use it It is really only there if you need the current process to exit immediately without waiting to flush enqueued data to the underlying pipe and you don t care about lost data Note This class s functionality requires a functioning shared semaphore implementation on the host operating system Without one the functionality in this class will be disabled and attempts to instantiate a Queue will result in an ImportError See bpo 3770 for additional information The same holds true for any of the specialized queue types listed below class multiprocessing SimpleQueue It is a simplified Queue type very close to a locked Pipe close Close the queue release internal resources A queue must not be used anymore after it is closed For example get put and empty methods must no longer be called New in version 3 9 empty Return True if the queue is empty False otherwise get Remove and return an item from the queue put item Put item into the queue class multiprocessing JoinableQueue maxsize JoinableQueue a Queue subclass is a queue which additionally has task_done and join methods task_done Indicate that a formerly enqueued task is complete Used by queue consumers For each get used to fetch a task a subsequent call to task_done tells the queue that the processing on the task is complete If a join is currently blocking it will resume when all items have been processed meaning that a task_done call was received for every item that had been put into the queue Raises a ValueError if called more times than there were items placed in the queue join Block until all items in the queue have been gotten and processed The count of unfinished tasks goes up whenever an item is added to the queue The count goes down whenever a consumer calls task_done to indicate that the item was retrieved and all work on it is complete When the count of unfinished tasks drops to zero join unblocks Miscellaneous multiprocessing active_children Return list of all live children of the current process Calling this has the side effect of joining any processes which have already finished multiprocessing cpu_count Return the number of CPUs in the system This number is not equivalent to the number of CPUs the current process can use The number of usable CPUs can be obtained with len os sched_getaffinity 0 When the number of CPUs cannot be determined a NotImplementedError is raised See also os cpu_count multiprocessing current_process Return the Process object corresponding to the current process An analogue of threading current_thread multiprocessing parent_process Return the Process object corresponding to the parent process of the current_process For the main pr,en
850,ocess parent_process will be None New in version 3 8 multiprocessing freeze_support Add support for when a program which uses multiprocessing has been frozen to produce a Windows executable Has been tested with py2exe PyInstaller and cx_Freeze One needs to call this function straight after the if __name__ __main__ line of the main module For example from multiprocessing import Process freeze_support def f print hello world if __name__ __main__ freeze_support Process target f start If the freeze_support line is omitted then trying to run the frozen executable will raise RuntimeError Calling freeze_support has no effect when invoked on any operating system other than Windows In addition if the module is being run normally by the Python interpreter on Windows the program has not been frozen then freeze_support has no effect multiprocessing get_all_start_methods Returns a list of the supported start methods the first of which is the default The possible start methods are fork spawn and forkserver Not all platforms support all methods See Contexts and start methods New in version 3 4 multiprocessing get_context method None Return a context object which has the same attributes as the multiprocessing module If method is None then the default context is returned Otherwise method should be fork spawn forkserver ValueError is raised if the specified start method is not available See Contexts and start methods New in version 3 4 multiprocessing get_start_method allow_none False Return the name of start method used for starting processes If the start method has not been fixed and allow_none is false then the start method is fixed to the default and the name is returned If the start method has not been fixed and allow_none is true then None is returned The return value can be fork spawn forkserver or None See Contexts and start methods New in version 3 4 Changed in version 3 8 On macOS the spawn start method is now the default The fork start method should be considered unsafe as it can lead to crashes of the subprocess See bpo 33725 multiprocessing set_executable executable Set the path of the Python interpreter to use when starting a child process By default sys executable is used Embedders will probably need to do some thing like set_executable os path join sys exec_prefix pythonw exe before they can create child processes Changed in version 3 4 Now supported on POSIX when the spawn start method is used Changed in version 3 11 Accepts a path like object multiprocessing set_forkserver_preload module_names Set a list of module names for the forkserver main process to attempt to import so that their already imported state is inherited by forked processes Any ImportError when doing so is silently ignored This can be used as a performance enhancement to avoid repeated work in every process For this to work it must be called before the forkserver process has been launched before creating a Pool or starting a Process Only meaningful when using the forkserver start method See Contexts and start methods New in version 3 4 multiprocessing set_start_method method force False Set the method which should be used to start child processes The method argument can be fork spawn or forkserver Raises RuntimeError if the start method has already been set and force is not True If method is None and force is True then the start method is set to None If method is None and force is False then the context is set to the default context Note that this should be called at most once and it should be protected inside the if __name__ __main__ clause of the main module See Contexts and start methods New in version 3 4 Note multiprocessing contains no analogues of threading active_count threading enumerate threading settrace threading setprofile threading Timer or threading local Connection Objects Connection objects allow the sending and receiving of picklable objects or strings They can be thought of as message oriented connected sockets Connection objects are usually created using Pipe see also Listeners and Clients class multiprocessing connection Connection s,en
851,end obj Send an object to the other end of the connection which should be read using recv The object must be picklable Very large pickles approximately 32 MiB though it depends on the OS may raise a ValueError exception recv Return an object sent from the other end of the connection using send Blocks until there is something to receive Raises EOFError if there is nothing left to receive and the other end was closed fileno Return the file descriptor or handle used by the connection close Close the connection This is called automatically when the connection is garbage collected poll timeout Return whether there is any data available to be read If timeout is not specified then it will return immediately If timeout is a number then this specifies the maximum time in seconds to block If timeout is None then an infinite timeout is used Note that multiple connection objects may be polled at once by using multiprocessing connection wait send_bytes buffer offset size Send byte data from a bytes like object as a complete message If offset is given then data is read from that position in buffer If size is given then that many bytes will be read from buffer Very large buffers approximately 32 MiB though it depends on the OS may raise a ValueError exception recv_bytes maxlength Return a complete message of byte data sent from the other end of the connection as a string Blocks until there is something to receive Raises EOFError if there is nothing left to receive and the other end has closed If maxlength is specified and the message is longer than maxlength then OSError is raised and the connection will no longer be readable Changed in version 3 3 This function used to raise IOError which is now an alias of OSError recv_bytes_into buffer offset Read into buffer a complete message of byte data sent from the other end of the connection and return the number of bytes in the message Blocks until there is something to receive Raises EOFError if there is nothing left to receive and the other end was closed buffer must be a writable bytes like object If offset is given then the message will be written into the buffer from that position Offset must be a non negative integer less than the length of buffer in bytes If the buffer is too short then a BufferTooShort exception is raised and the complete message is available as e args 0 where e is the exception instance Changed in version 3 3 Connection objects themselves can now be transferred between processes using Connection send and Connection recv Connection objects also now support the context management protocol see Context Manager Types __enter__ returns the connection object and __exit__ calls close For example from multiprocessing import Pipe a b Pipe a send 1 hello None b recv 1 hello None b send_bytes b thank you a recv_bytes b thank you import array arr1 array array i range 5 arr2 array array i 0 10 a send_bytes arr1 count b recv_bytes_into arr2 assert count len arr1 arr1 itemsize arr2 array i 0 1 2 3 4 0 0 0 0 0 Warning The Connection recv method automatically unpickles the data it receives which can be a security risk unless you can trust the process which sent the message Therefore unless the connection object was produced using Pipe you should only use the recv and send methods after performing some sort of authentication See Authentication keys Warning If a process is killed while it is trying to read or write to a pipe then the data in the pipe is likely to become corrupted because it may become impossible to be sure where the message boundaries lie Synchronization primitives Generally synchronization primitives are not as necessary in a multiprocess program as they are in a multithreaded program See the documentation for threading module Note that one can also create synchronization primitives by using a manager object see Managers class multiprocessing Barrier parties action timeout A barrier object a clone of threading Barrier New in version 3 3 class multiprocessing BoundedSemaphore value A bounded semaphore object a close analog of threading BoundedSemaphore A solitary diffe,en
852,rence from its close analog exists its acquire method s first argument is named block as is consistent with Lock acquire Note On macOS this is indistinguishable from Semaphore because sem_getvalue is not implemented on that platform class multiprocessing Condition lock A condition variable an alias for threading Condition If lock is specified then it should be a Lock or RLock object from multiprocessing Changed in version 3 3 The wait_for method was added class multiprocessing Event A clone of threading Event class multiprocessing Lock A non recursive lock object a close analog of threading Lock Once a process or thread has acquired a lock subsequent attempts to acquire it from any process or thread will block until it is released any process or thread may release it The concepts and behaviors of threading Lock as it applies to threads are replicated here in multiprocessing Lock as it applies to either processes or threads except as noted Note that Lock is actually a factory function which returns an instance of multiprocessing synchronize Lock initialized with a default context Lock supports the context manager protocol and thus may be used in with statements acquire block True timeout None Acquire a lock blocking or non blocking With the block argument set to True the default the method call will block until the lock is in an unlocked state then set it to locked and return True Note that the name of this first argument differs from that in threading Lock acquire With the block argument set to False the method call does not block If the lock is currently in a locked state return False otherwise set the lock to a locked state and return True When invoked with a positive floating point value for timeout block for at most the number of seconds specified by timeout as long as the lock can not be acquired Invocations with a negative value for timeout are equivalent to a timeout of zero Invocations with a timeout value of None the default set the timeout period to infinite Note that the treatment of negative or None values for timeout differs from the implemented behavior in threading Lock acquire The timeout argument has no practical implications if the block argument is set to False and is thus ignored Returns True if the lock has been acquired or False if the timeout period has elapsed release Release a lock This can be called from any process or thread not only the process or thread which originally acquired the lock Behavior is the same as in threading Lock release except that when invoked on an unlocked lock a ValueError is raised class multiprocessing RLock A recursive lock object a close analog of threading RLock A recursive lock must be released by the process or thread that acquired it Once a process or thread has acquired a recursive lock the same process or thread may acquire it again without blocking that process or thread must release it once for each time it has been acquired Note that RLock is actually a factory function which returns an instance of multiprocessing synchronize RLock initialized with a default context RLock supports the context manager protocol and thus may be used in with statements acquire block True timeout None Acquire a lock blocking or non blocking When invoked with the block argument set to True block until the lock is in an unlocked state not owned by any process or thread unless the lock is already owned by the current process or thread The current process or thread then takes ownership of the lock if it does not already have ownership and the recursion level inside the lock increments by one resulting in a return value of True Note that there are several differences in this first argument s behavior compared to the implementation of threading RLock acquire starting with the name of the argument itself When invoked with the block argument set to False do not block If the lock has already been acquired and thus is owned by another process or thread the current process or thread does not take ownership and the recursion level within the lock is not changed resulting in a return value of ,en
853,False If the lock is in an unlocked state the current process or thread takes ownership and the recursion level is incremented resulting in a return value of True Use and behaviors of the timeout argument are the same as in Lock acquire Note that some of these behaviors of timeout differ from the implemented behaviors in threading RLock acquire release Release a lock decrementing the recursion level If after the decrement the recursion level is zero reset the lock to unlocked not owned by any process or thread and if any other processes or threads are blocked waiting for the lock to become unlocked allow exactly one of them to proceed If after the decrement the recursion level is still nonzero the lock remains locked and owned by the calling process or thread Only call this method when the calling process or thread owns the lock An AssertionError is raised if this method is called by a process or thread other than the owner or if the lock is in an unlocked unowned state Note that the type of exception raised in this situation differs from the implemented behavior in threading RLock release class multiprocessing Semaphore value A semaphore object a close analog of threading Semaphore A solitary difference from its close analog exists its acquire method s first argument is named block as is consistent with Lock acquire Note On macOS sem_timedwait is unsupported so calling acquire with a timeout will emulate that function s behavior using a sleeping loop Note If the SIGINT signal generated by Ctrl C arrives while the main thread is blocked by a call to BoundedSemaphore acquire Lock acquire RLock acquire Semaphore acquire Condition acquire or Condition wait then the call will be immediately interrupted and KeyboardInterrupt will be raised This differs from the behaviour of threading where SIGINT will be ignored while the equivalent blocking calls are in progress Note Some of this package s functionality requires a functioning shared semaphore implementation on the host operating system Without one the multiprocessing synchronize module will be disabled and attempts to import it will result in an ImportError See bpo 3770 for additional information Shared ctypes Objects It is possible to create shared objects using shared memory which can be inherited by child processes multiprocessing Value typecode_or_type args lock True Return a ctypes object allocated from shared memory By default the return value is actually a synchronized wrapper for the object The object itself can be accessed via the value attribute of a Value typecode_or_type determines the type of the returned object it is either a ctypes type or a one character typecode of the kind used by the array module args is passed on to the constructor for the type If lock is True the default then a new recursive lock object is created to synchronize access to the value If lock is a Lock or RLock object then that will be used to synchronize access to the value If lock is False then access to the returned object will not be automatically protected by a lock so it will not necessarily be process safe Operations like which involve a read and write are not atomic So if for instance you want to atomically increment a shared value it is insufficient to just do counter value 1 Assuming the associated lock is recursive which it is by default you can instead do with counter get_lock counter value 1 Note that lock is a keyword only argument multiprocessing Array typecode_or_type size_or_initializer lock True Return a ctypes array allocated from shared memory By default the return value is actually a synchronized wrapper for the array typecode_or_type determines the type of the elements of the returned array it is either a ctypes type or a one character typecode of the kind used by the array module If size_or_initializer is an integer then it determines the length of the array and the array will be initially zeroed Otherwise size_or_initializer is a sequence which is used to initialize the array and whose length determines the length of the array If lock is True the default then a new l,en
854,ock object is created to synchronize access to the value If lock is a Lock or RLock object then that will be used to synchronize access to the value If lock is False then access to the returned object will not be automatically protected by a lock so it will not necessarily be process safe Note that lock is a keyword only argument Note that an array of ctypes c_char has value and raw attributes which allow one to use it to store and retrieve strings The multiprocessing sharedctypes module The multiprocessing sharedctypes module provides functions for allocating ctypes objects from shared memory which can be inherited by child processes Note Although it is possible to store a pointer in shared memory remember that this will refer to a location in the address space of a specific process However the pointer is quite likely to be invalid in the context of a second process and trying to dereference the pointer from the second process may cause a crash multiprocessing sharedctypes RawArray typecode_or_type size_or_initializer Return a ctypes array allocated from shared memory typecode_or_type determines the type of the elements of the returned array it is either a ctypes type or a one character typecode of the kind used by the array module If size_or_initializer is an integer then it determines the length of the array and the array will be initially zeroed Otherwise size_or_initializer is a sequence which is used to initialize the array and whose length determines the length of the array Note that setting and getting an element is potentially non atomic use Array instead to make sure that access is automatically synchronized using a lock multiprocessing sharedctypes RawValue typecode_or_type args Return a ctypes object allocated from shared memory typecode_or_type determines the type of the returned object it is either a ctypes type or a one character typecode of the kind used by the array module args is passed on to the constructor for the type Note that setting and getting the value is potentially non atomic use Value instead to make sure that access is automatically synchronized using a lock Note that an array of ctypes c_char has value and raw attributes which allow one to use it to store and retrieve strings see documentation for ctypes multiprocessing sharedctypes Array typecode_or_type size_or_initializer lock True The same as RawArray except that depending on the value of lock a process safe synchronization wrapper may be returned instead of a raw ctypes array If lock is True the default then a new lock object is created to synchronize access to the value If lock is a Lock or RLock object then that will be used to synchronize access to the value If lock is False then access to the returned object will not be automatically protected by a lock so it will not necessarily be process safe Note that lock is a keyword only argument multiprocessing sharedctypes Value typecode_or_type args lock True The same as RawValue except that depending on the value of lock a process safe synchronization wrapper may be returned instead of a raw ctypes object If lock is True the default then a new lock object is created to synchronize access to the value If lock is a Lock or RLock object then that will be used to synchronize access to the value If lock is False then access to the returned object will not be automatically protected by a lock so it will not necessarily be process safe Note that lock is a keyword only argument multiprocessing sharedctypes copy obj Return a ctypes object allocated from shared memory which is a copy of the ctypes object obj multiprocessing sharedctypes synchronized obj lock Return a process safe wrapper object for a ctypes object which uses lock to synchronize access If lock is None the default then a multiprocessing RLock object is created automatically A synchronized wrapper will have two methods in addition to those of the object it wraps get_obj returns the wrapped object and get_lock returns the lock object used for synchronization Note that accessing the ctypes object through the wrapper can be a lot slower,en
855, than accessing the raw ctypes object Changed in version 3 5 Synchronized objects support the context manager protocol The table below compares the syntax for creating shared ctypes objects from shared memory with the normal ctypes syntax In the table MyStruct is some subclass of ctypes Structure ctypes sharedctypes using type sharedctypes using typecode c_double 2 4 RawValue c_double 2 4 RawValue d 2 4 MyStruct 4 6 RawValue MyStruct 4 6 c_short 7 RawArray c_short 7 RawArray h 7 c_int 3 9 2 8 RawArray c_int 9 2 8 RawArray i 9 2 8 Below is an example where a number of ctypes objects are modified by a child process from multiprocessing import Process Lock from multiprocessing sharedctypes import Value Array from ctypes import Structure c_double class Point Structure _fields_ x c_double y c_double def modify n x s A n value 2 x value 2 s value s value upper for a in A a x 2 a y 2 if __name__ __main__ lock Lock n Value i 7 x Value c_double 1 0 3 0 lock False s Array c b hello world lock lock A Array Point 1 875 6 25 5 75 2 0 2 375 9 5 lock lock p Process target modify args n x s A p start p join print n value print x value print s value print a x a y for a in A The results printed are 49 0 1111111111111111 HELLO WORLD 3 515625 39 0625 33 0625 4 0 5 640625 90 25 Managers Managers provide a way to create data which can be shared between different processes including sharing over a network between processes running on different machines A manager object controls a server process which manages shared objects Other processes can access the shared objects by using proxies multiprocessing Manager Returns a started SyncManager object which can be used for sharing objects between processes The returned manager object corresponds to a spawned child process and has methods which will create shared objects and return corresponding proxies Manager processes will be shutdown as soon as they are garbage collected or their parent process exits The manager classes are defined in the multiprocessing managers module class multiprocessing managers BaseManager address None authkey None serializer pickle ctx None shutdown_timeout 1 0 Create a BaseManager object Once created one should call start or get_server serve_forever to ensure that the manager object refers to a started manager process address is the address on which the manager process listens for new connections If address is None then an arbitrary one is chosen authkey is the authentication key which will be used to check the validity of incoming connections to the server process If authkey is None then current_process authkey is used Otherwise authkey is used and it must be a byte string serializer must be pickle use pickle serialization or xmlrpclib use xmlrpc client serialization ctx is a context object or None use the current context See the get_context function shutdown_timeout is a timeout in seconds used to wait until the process used by the manager completes in the shutdown method If the shutdown times out the process is terminated If terminating the process also times out the process is killed Changed in version 3 11 Added the shutdown_timeout parameter start initializer initargs Start a subprocess to start the manager If initializer is not None then the subprocess will call initializer initargs when it starts get_server Returns a Server object which represents the actual server under the control of the Manager The Server object supports the serve_forever method from multiprocessing managers import BaseManager manager BaseManager address 50000 authkey b abc server manager get_server server serve_forever Server additionally has an address attribute connect Connect a local manager object to a remote manager process from multiprocessing managers import BaseManager m BaseManager address 127 0 0 1 50000 authkey b abc m connect shutdown Stop the process used by the manager This is only available if start has been used to start the server process This can be called multiple times register typeid callable proxytype exposed method_to_typeid create_method A classmethod which can be used f,en
856,or registering a type or callable with the manager class typeid is a type identifier which is used to identify a particular type of shared object This must be a string callable is a callable used for creating objects for this type identifier If a manager instance will be connected to the server using the connect method or if the create_method argument is False then this can be left as None proxytype is a subclass of BaseProxy which is used to create proxies for shared objects with this typeid If None then a proxy class is created automatically exposed is used to specify a sequence of method names which proxies for this typeid should be allowed to access using BaseProxy _callmethod If exposed is None then proxytype _exposed_ is used instead if it exists In the case where no exposed list is specified all public methods of the shared object will be accessible Here a public method means any attribute which has a __call__ method and whose name does not begin with _ method_to_typeid is a mapping used to specify the return type of those exposed methods which should return a proxy It maps method names to typeid strings If method_to_typeid is None then proxytype _method_to_typeid_ is used instead if it exists If a method s name is not a key of this mapping or if the mapping is None then the object returned by the method will be copied by value create_method determines whether a method should be created with name typeid which can be used to tell the server process to create a new shared object and return a proxy for it By default it is True BaseManager instances also have one read only property address The address used by the manager Changed in version 3 3 Manager objects support the context management protocol see Context Manager Types __enter__ starts the server process if it has not already started and then returns the manager object __exit__ calls shutdown In previous versions __enter__ did not start the manager s server process if it was not already started class multiprocessing managers SyncManager A subclass of BaseManager which can be used for the synchronization of processes Objects of this type are returned by multiprocessing Manager Its methods create and return Proxy Objects for a number of commonly used data types to be synchronized across processes This notably includes shared lists and dictionaries Barrier parties action timeout Create a shared threading Barrier object and return a proxy for it New in version 3 3 BoundedSemaphore value Create a shared threading BoundedSemaphore object and return a proxy for it Condition lock Create a shared threading Condition object and return a proxy for it If lock is supplied then it should be a proxy for a threading Lock or threading RLock object Changed in version 3 3 The wait_for method was added Event Create a shared threading Event object and return a proxy for it Lock Create a shared threading Lock object and return a proxy for it Namespace Create a shared Namespace object and return a proxy for it Queue maxsize Create a shared queue Queue object and return a proxy for it RLock Create a shared threading RLock object and return a proxy for it Semaphore value Create a shared threading Semaphore object and return a proxy for it Array typecode sequence Create an array and return a proxy for it Value typecode value Create an object with a writable value attribute and return a proxy for it dict dict mapping dict sequence Create a shared dict object and return a proxy for it list list sequence Create a shared list object and return a proxy for it Changed in version 3 6 Shared objects are capable of being nested For example a shared container object such as a shared list can contain other shared objects which will all be managed and synchronized by the SyncManager class multiprocessing managers Namespace A type that can register with SyncManager A namespace object has no public methods but does have writable attributes Its representation shows the values of its attributes However when using a proxy for a namespace object an attribute beginning with _ will be an attribute of the pro,en
857,xy and not an attribute of the referent mp_context multiprocessing get_context spawn manager mp_context Manager Global manager Namespace Global x 10 Global y hello Global _z 12 3 this is an attribute of the proxy print Global Namespace x 10 y hello Customized managers To create one s own manager one creates a subclass of BaseManager and uses the register classmethod to register new types or callables with the manager class For example from multiprocessing managers import BaseManager class MathsClass def add self x y return x y def mul self x y return x y class MyManager BaseManager pass MyManager register Maths MathsClass if __name__ __main__ with MyManager as manager maths manager Maths print maths add 4 3 prints 7 print maths mul 7 8 prints 56 Using a remote manager It is possible to run a manager server on one machine and have clients use it from other machines assuming that the firewalls involved allow it Running the following commands creates a server for a single shared queue which remote clients can access from multiprocessing managers import BaseManager from queue import Queue queue Queue class QueueManager BaseManager pass QueueManager register get_queue callable lambda queue m QueueManager address 50000 authkey b abracadabra s m get_server s serve_forever One client can access the server as follows from multiprocessing managers import BaseManager class QueueManager BaseManager pass QueueManager register get_queue m QueueManager address foo bar org 50000 authkey b abracadabra m connect queue m get_queue queue put hello Another client can also use it from multiprocessing managers import BaseManager class QueueManager BaseManager pass QueueManager register get_queue m QueueManager address foo bar org 50000 authkey b abracadabra m connect queue m get_queue queue get hello Local processes can also access that queue using the code from above on the client to access it remotely from multiprocessing import Process Queue from multiprocessing managers import BaseManager class Worker Process def __init__ self q self q q super __init__ def run self self q put local hello queue Queue w Worker queue w start class QueueManager BaseManager pass QueueManager register get_queue callable lambda queue m QueueManager address 50000 authkey b abracadabra s m get_server s serve_forever Proxy Objects A proxy is an object which refers to a shared object which lives presumably in a different process The shared object is said to be the referent of the proxy Multiple proxy objects may have the same referent A proxy object has methods which invoke corresponding methods of its referent although not every method of the referent will necessarily be available through the proxy In this way a proxy can be used just like its referent can mp_context multiprocessing get_context spawn manager mp_context Manager l manager list i i for i in range 10 print l 0 1 4 9 16 25 36 49 64 81 print repr l ListProxy object typeid list at 0x l 4 16 l 2 5 4 9 16 Notice that applying str to a proxy will return the representation of the referent whereas applying repr will return the representation of the proxy An important feature of proxy objects is that they are picklable so they can be passed between processes As such a referent can contain Proxy Objects This permits nesting of these managed lists dicts and other Proxy Objects a manager list b manager list a append b referent of a now contains referent of b print a b ListProxy object typeid list at b append hello print a 0 b hello hello Similarly dict and list proxies may be nested inside one another l_outer manager list manager dict for i in range 2 d_first_inner l_outer 0 d_first_inner a 1 d_first_inner b 2 l_outer 1 c 3 l_outer 1 z 26 print l_outer 0 a 1 b 2 print l_outer 1 c 3 z 26 If standard non proxy list or dict objects are contained in a referent modifications to those mutable values will not be propagated through the manager because the proxy has no way of knowing when the values contained within are modified However storing a value in a container proxy which triggers a __setitem__ on the proxy object do,en
858,es propagate through the manager and so to effectively modify such an item one could re assign the modified value to the container proxy create a list proxy and append a mutable object a dictionary lproxy manager list lproxy append now mutate the dictionary d lproxy 0 d a 1 d b 2 at this point the changes to d are not yet synced but by updating the dictionary the proxy is notified of the change lproxy 0 d This approach is perhaps less convenient than employing nested Proxy Objects for most use cases but also demonstrates a level of control over the synchronization Note The proxy types in multiprocessing do nothing to support comparisons by value So for instance we have manager list 1 2 3 1 2 3 False One should just use a copy of the referent instead when making comparisons class multiprocessing managers BaseProxy Proxy objects are instances of subclasses of BaseProxy _callmethod methodname args kwds Call and return the result of a method of the proxy s referent If proxy is a proxy whose referent is obj then the expression proxy _callmethod methodname args kwds will evaluate the expression getattr obj methodname args kwds in the manager s process The returned value will be a copy of the result of the call or a proxy to a new shared object see documentation for the method_to_typeid argument of BaseManager register If an exception is raised by the call then is re raised by _callmethod If some other exception is raised in the manager s process then this is converted into a RemoteError exception and is raised by _callmethod Note in particular that an exception will be raised if methodname has not been exposed An example of the usage of _callmethod l manager list range 10 l _callmethod __len__ 10 l _callmethod __getitem__ slice 2 7 equivalent to l 2 7 2 3 4 5 6 l _callmethod __getitem__ 20 equivalent to l 20 Traceback most recent call last IndexError list index out of range _getvalue Return a copy of the referent If the referent is unpicklable then this will raise an exception __repr__ Return a representation of the proxy object __str__ Return the representation of the referent Cleanup A proxy object uses a weakref callback so that when it gets garbage collected it deregisters itself from the manager which owns its referent A shared object gets deleted from the manager process when there are no longer any proxies referring to it Process Pools One can create a pool of processes which will carry out tasks submitted to it with the Pool class class multiprocessing pool Pool processes initializer initargs maxtasksperchild context A process pool object which controls a pool of worker processes to which jobs can be submitted It supports asynchronous results with timeouts and callbacks and has a parallel map implementation processes is the number of worker processes to use If processes is None then the number returned by os cpu_count is used If initializer is not None then each worker process will call initializer initargs when it starts maxtasksperchild is the number of tasks a worker process can complete before it will exit and be replaced with a fresh worker process to enable unused resources to be freed The default maxtasksperchild is None which means worker processes will live as long as the pool context can be used to specify the context used for starting the worker processes Usually a pool is created using the function multiprocessing Pool or the Pool method of a context object In both cases context is set appropriately Note that the methods of the pool object should only be called by the process which created the pool Warning multiprocessing pool objects have internal resources that need to be properly managed like any other resource by using the pool as a context manager or by calling close and terminate manually Failure to do this can lead to the process hanging on finalization Note that it is not correct to rely on the garbage collector to destroy the pool as CPython does not assure that the finalizer of the pool will be called see object __del__ for more information Changed in version 3 2 Added the maxtasksperchild paramet,en
859,er Changed in version 3 4 Added the context parameter Note Worker processes within a Pool typically live for the complete duration of the Pool s work queue A frequent pattern found in other systems such as Apache mod_wsgi etc to free resources held by workers is to allow a worker within a pool to complete only a set amount of work before being exiting being cleaned up and a new process spawned to replace the old one The maxtasksperchild argument to the Pool exposes this ability to the end user apply func args kwds Call func with arguments args and keyword arguments kwds It blocks until the result is ready Given this blocks apply_async is better suited for performing work in parallel Additionally func is only executed in one of the workers of the pool apply_async func args kwds callback error_callback A variant of the apply method which returns a AsyncResult object If callback is specified then it should be a callable which accepts a single argument When the result becomes ready callback is applied to it that is unless the call failed in which case the error_callback is applied instead If error_callback is specified then it should be a callable which accepts a single argument If the target function fails then the error_callback is called with the exception instance Callbacks should complete immediately since otherwise the thread which handles the results will get blocked map func iterable chunksize A parallel equivalent of the map built in function it supports only one iterable argument though for multiple iterables see starmap It blocks until the result is ready This method chops the iterable into a number of chunks which it submits to the process pool as separate tasks The approximate size of these chunks can be specified by setting chunksize to a positive integer Note that it may cause high memory usage for very long iterables Consider using imap or imap_unordered with explicit chunksize option for better efficiency map_async func iterable chunksize callback error_callback A variant of the map method which returns a AsyncResult object If callback is specified then it should be a callable which accepts a single argument When the result becomes ready callback is applied to it that is unless the call failed in which case the error_callback is applied instead If error_callback is specified then it should be a callable which accepts a single argument If the target function fails then the error_callback is called with the exception instance Callbacks should complete immediately since otherwise the thread which handles the results will get blocked imap func iterable chunksize A lazier version of map The chunksize argument is the same as the one used by the map method For very long iterables using a large value for chunksize can make the job complete much faster than using the default value of 1 Also if chunksize is 1 then the next method of the iterator returned by the imap method has an optional timeout parameter next timeout will raise multiprocessing TimeoutError if the result cannot be returned within timeout seconds imap_unordered func iterable chunksize The same as imap except that the ordering of the results from the returned iterator should be considered arbitrary Only when there is only one worker process is the order guaranteed to be correct starmap func iterable chunksize Like map except that the elements of the iterable are expected to be iterables that are unpacked as arguments Hence an iterable of 1 2 3 4 results in func 1 2 func 3 4 New in version 3 3 starmap_async func iterable chunksize callback error_callback A combination of starmap and map_async that iterates over iterable of iterables and calls func with the iterables unpacked Returns a result object New in version 3 3 close Prevents any more tasks from being submitted to the pool Once all the tasks have been completed the worker processes will exit terminate Stops the worker processes immediately without completing outstanding work When the pool object is garbage collected terminate will be called immediately join Wait for the worker processes to exit On,en
860,e must call close or terminate before using join Changed in version 3 3 Pool objects now support the context management protocol see Context Manager Types __enter__ returns the pool object and __exit__ calls terminate class multiprocessing pool AsyncResult The class of the result returned by Pool apply_async and Pool map_async get timeout Return the result when it arrives If timeout is not None and the result does not arrive within timeout seconds then multiprocessing TimeoutError is raised If the remote call raised an exception then that exception will be reraised by get wait timeout Wait until the result is available or until timeout seconds pass ready Return whether the call has completed successful Return whether the call completed without raising an exception Will raise ValueError if the result is not ready Changed in version 3 7 If the result is not ready ValueError is raised instead of AssertionError The following example demonstrates the use of a pool from multiprocessing import Pool import time def f x return x x if __name__ __main__ with Pool processes 4 as pool start 4 worker processes result pool apply_async f 10 evaluate f 10 asynchronously in a single process print result get timeout 1 prints 100 unless your computer is very slow print pool map f range 10 prints 0 1 4 81 it pool imap f range 10 print next it prints 0 print next it prints 1 print it next timeout 1 prints 4 unless your computer is very slow result pool apply_async time sleep 10 print result get timeout 1 raises multiprocessing TimeoutError Listeners and Clients Usually message passing between processes is done using queues or by using Connection objects returned by Pipe However the multiprocessing connection module allows some extra flexibility It basically gives a high level message oriented API for dealing with sockets or Windows named pipes It also has support for digest authentication using the hmac module and for polling multiple connections at the same time multiprocessing connection deliver_challenge connection authkey Send a randomly generated message to the other end of the connection and wait for a reply If the reply matches the digest of the message using authkey as the key then a welcome message is sent to the other end of the connection Otherwise AuthenticationError is raised multiprocessing connection answer_challenge connection authkey Receive a message calculate the digest of the message using authkey as the key and then send the digest back If a welcome message is not received then AuthenticationError is raised multiprocessing connection Client address family authkey Attempt to set up a connection to the listener which is using address address returning a Connection The type of the connection is determined by family argument but this can generally be omitted since it can usually be inferred from the format of address See Address Formats If authkey is given and not None it should be a byte string and will be used as the secret key for an HMAC based authentication challenge No authentication is done if authkey is None AuthenticationError is raised if authentication fails See Authentication keys class multiprocessing connection Listener address family backlog authkey A wrapper for a bound socket or Windows named pipe which is listening for connections address is the address to be used by the bound socket or named pipe of the listener object Note If an address of 0 0 0 0 is used the address will not be a connectable end point on Windows If you require a connectable end point you should use 127 0 0 1 family is the type of socket or named pipe to use This can be one of the strings AF_INET for a TCP socket AF_UNIX for a Unix domain socket or AF_PIPE for a Windows named pipe Of these only the first is guaranteed to be available If family is None then the family is inferred from the format of address If address is also None then a default is chosen This default is the family which is assumed to be the fastest available See Address Formats Note that if family is AF_UNIX and address is None then the socket will be created in a private t,en
861,emporary directory created using tempfile mkstemp If the listener object uses a socket then backlog 1 by default is passed to the listen method of the socket once it has been bound If authkey is given and not None it should be a byte string and will be used as the secret key for an HMAC based authentication challenge No authentication is done if authkey is None AuthenticationError is raised if authentication fails See Authentication keys accept Accept a connection on the bound socket or named pipe of the listener object and return a Connection object If authentication is attempted and fails then AuthenticationError is raised close Close the bound socket or named pipe of the listener object This is called automatically when the listener is garbage collected However it is advisable to call it explicitly Listener objects have the following read only properties address The address which is being used by the Listener object last_accepted The address from which the last accepted connection came If this is unavailable then it is None Changed in version 3 3 Listener objects now support the context management protocol see Context Manager Types __enter__ returns the listener object and __exit__ calls close multiprocessing connection wait object_list timeout None Wait till an object in object_list is ready Returns the list of those objects in object_list which are ready If timeout is a float then the call blocks for at most that many seconds If timeout is None then it will block for an unlimited period A negative timeout is equivalent to a zero timeout For both POSIX and Windows an object can appear in object_list if it is a readable Connection object a connected and readable socket socket object or the sentinel attribute of a Process object A connection or socket object is ready when there is data available to be read from it or the other end has been closed POSIX wait object_list timeout almost equivalent select select object_list timeout The difference is that if select select is interrupted by a signal it can raise OSError with an error number of EINTR whereas wait will not Windows An item in object_list must either be an integer handle which is waitable according to the definition used by the documentation of the Win32 function WaitForMultipleObjects or it can be an object with a fileno method which returns a socket handle or pipe handle Note that pipe handles and socket handles are not waitable handles New in version 3 3 Examples The following server code creates a listener which uses secret password as an authentication key It then waits for a connection and sends some data to the client from multiprocessing connection import Listener from array import array address localhost 6000 family is deduced to be AF_INET with Listener address authkey b secret password as listener with listener accept as conn print connection accepted from listener last_accepted conn send 2 25 None junk float conn send_bytes b hello conn send_bytes array i 42 1729 The following code connects to the server and receives some data from the server from multiprocessing connection import Client from array import array address localhost 6000 with Client address authkey b secret password as conn print conn recv 2 25 None junk float print conn recv_bytes hello arr array i 0 0 0 0 0 print conn recv_bytes_into arr 8 print arr array i 42 1729 0 0 0 The following code uses wait to wait for messages from multiple processes at once import time random from multiprocessing import Process Pipe current_process from multiprocessing connection import wait def foo w for i in range 10 w send i current_process name w close if __name__ __main__ readers for i in range 4 r w Pipe duplex False readers append r p Process target foo args w p start We close the writable end of the pipe now to be sure that p is the only process which owns a handle for it This ensures that when p closes its handle for the writable end wait will promptly report the readable end as being ready w close while readers for r in wait readers try msg r recv except EOFError readers remove r else print msg Add,en
862,ress Formats An AF_INET address is a tuple of the form hostname port where hostname is a string and port is an integer An AF_UNIX address is a string representing a filename on the filesystem An AF_PIPE address is a string of the form r pipe PipeName To use Client to connect to a named pipe on a remote computer called ServerName one should use an address of the form r ServerName pipe PipeName instead Note that any string beginning with two backslashes is assumed by default to be an AF_PIPE address rather than an AF_UNIX address Authentication keys When one uses Connection recv the data received is automatically unpickled Unfortunately unpickling data from an untrusted source is a security risk Therefore Listener and Client use the hmac module to provide digest authentication An authentication key is a byte string which can be thought of as a password once a connection is established both ends will demand proof that the other knows the authentication key Demonstrating that both ends are using the same key does not involve sending the key over the connection If authentication is requested but no authentication key is specified then the return value of current_process authkey is used see Process This value will be automatically inherited by any Process object that the current process creates This means that by default all processes of a multi process program will share a single authentication key which can be used when setting up connections between themselves Suitable authentication keys can also be generated by using os urandom Logging Some support for logging is available Note however that the logging package does not use process shared locks so it is possible depending on the handler type for messages from different processes to get mixed up multiprocessing get_logger Returns the logger used by multiprocessing If necessary a new one will be created When first created the logger has level logging NOTSET and no default handler Messages sent to this logger will not by default propagate to the root logger Note that on Windows child processes will only inherit the level of the parent process s logger any other customization of the logger will not be inherited multiprocessing log_to_stderr level None This function performs a call to get_logger but in addition to returning the logger created by get_logger it adds a handler which sends output to sys stderr using format levelname s processName s message s You can modify levelname of the logger by passing a level argument Below is an example session with logging turned on import multiprocessing logging logger multiprocessing log_to_stderr logger setLevel logging INFO logger warning doomed WARNING MainProcess doomed m multiprocessing Manager INFO SyncManager child process calling self run INFO SyncManager created temp directory pymp INFO SyncManager manager serving at listener del m INFO MainProcess sending shutdown message to manager INFO SyncManager manager exiting with exitcode 0 For a full table of logging levels see the logging module The multiprocessing dummy module multiprocessing dummy replicates the API of multiprocessing but is no more than a wrapper around the threading module In particular the Pool function provided by multiprocessing dummy returns an instance of ThreadPool which is a subclass of Pool that supports all the same method calls but uses a pool of worker threads rather than worker processes class multiprocessing pool ThreadPool processes initializer initargs A thread pool object which controls a pool of worker threads to which jobs can be submitted ThreadPool instances are fully interface compatible with Pool instances and their resources must also be properly managed either by using the pool as a context manager or by calling close and terminate manually processes is the number of worker threads to use If processes is None then the number returned by os cpu_count is used If initializer is not None then each worker process will call initializer initargs when it starts Unlike Pool maxtasksperchild and context cannot be provided Note A ThreadPool shares the s,en
863,ame interface as Pool which is designed around a pool of processes and predates the introduction of the concurrent futures module As such it inherits some operations that don t make sense for a pool backed by threads and it has its own type for representing the status of asynchronous jobs AsyncResult that is not understood by any other libraries Users should generally prefer to use concurrent futures ThreadPoolExecutor which has a simpler interface that was designed around threads from the start and which returns concurrent futures Future instances that are compatible with many other libraries including asyncio Programming guidelines There are certain guidelines and idioms which should be adhered to when using multiprocessing All start methods The following applies to all start methods Avoid shared state As far as possible one should try to avoid shifting large amounts of data between processes It is probably best to stick to using queues or pipes for communication between processes rather than using the lower level synchronization primitives Picklability Ensure that the arguments to the methods of proxies are picklable Thread safety of proxies Do not use a proxy object from more than one thread unless you protect it with a lock There is never a problem with different processes using the same proxy Joining zombie processes On POSIX when a process finishes but has not been joined it becomes a zombie There should never be very many because each time a new process starts or active_children is called all completed processes which have not yet been joined will be joined Also calling a finished process s Process is_alive will join the process Even so it is probably good practice to explicitly join all the processes that you start Better to inherit than pickle unpickle When using the spawn or forkserver start methods many types from multiprocessing need to be picklable so that child processes can use them However one should generally avoid sending shared objects to other processes using pipes or queues Instead you should arrange the program so that a process which needs access to a shared resource created elsewhere can inherit it from an ancestor process Avoid terminating processes Using the Process terminate method to stop a process is liable to cause any shared resources such as locks semaphores pipes and queues currently being used by the process to become broken or unavailable to other processes Therefore it is probably best to only consider using Process terminate on processes which never use any shared resources Joining processes that use queues Bear in mind that a process that has put items in a queue will wait before terminating until all the buffered items are fed by the feeder thread to the underlying pipe The child process can call the Queue cancel_join_thread method of the queue to avoid this behaviour This means that whenever you use a queue you need to make sure that all items which have been put on the queue will eventually be removed before the process is joined Otherwise you cannot be sure that processes which have put items on the queue will terminate Remember also that non daemonic processes will be joined automatically An example which will deadlock is the following from multiprocessing import Process Queue def f q q put X 1000000 if __name__ __main__ queue Queue p Process target f args queue p start p join this deadlocks obj queue get A fix here would be to swap the last two lines or simply remove the p join line Explicitly pass resources to child processes On POSIX using the fork start method a child process can make use of a shared resource created in a parent process using a global resource However it is better to pass the object as an argument to the constructor for the child process Apart from making the code potentially compatible with Windows and the other start methods this also ensures that as long as the child process is still alive the object will not be garbage collected in the parent process This might be important if some resource is freed when the object is garbage collected in the parent pro,en
864,cess So for instance from multiprocessing import Process Lock def f do something using lock if __name__ __main__ lock Lock for i in range 10 Process target f start should be rewritten as from multiprocessing import Process Lock def f l do something using l if __name__ __main__ lock Lock for i in range 10 Process target f args lock start Beware of replacing sys stdin with a file like object multiprocessing originally unconditionally called os close sys stdin fileno in the multiprocessing Process _bootstrap method this resulted in issues with processes in processes This has been changed to sys stdin close sys stdin open os open os devnull os O_RDONLY closefd False Which solves the fundamental issue of processes colliding with each other resulting in a bad file descriptor error but introduces a potential danger to applications which replace sys stdin with a file like object with output buffering This danger is that if multiple processes call close on this file like object it could result in the same data being flushed to the object multiple times resulting in corruption If you write a file like object and implement your own caching you can make it fork safe by storing the pid whenever you append to the cache and discarding the cache when the pid changes For example property def cache self pid os getpid if pid self _pid self _pid pid self _cache return self _cache For more information see bpo 5155 bpo 5313 and bpo 5331 The spawn and forkserver start methods There are a few extra restrictions which don t apply to the fork start method More picklability Ensure that all arguments to Process __init__ are picklable Also if you subclass Process then make sure that instances will be picklable when the Process start method is called Global variables Bear in mind that if code run in a child process tries to access a global variable then the value it sees if any may not be the same as the value in the parent process at the time that Process start was called However global variables which are just module level constants cause no problems Safe importing of main module Make sure that the main module can be safely imported by a new Python interpreter without causing unintended side effects such as starting a new process For example using the spawn or forkserver start method running the following module would fail with a RuntimeError from multiprocessing import Process def foo print hello p Process target foo p start Instead one should protect the entry point of the program by using if __name__ __main__ as follows from multiprocessing import Process freeze_support set_start_method def foo print hello if __name__ __main__ freeze_support set_start_method spawn p Process target foo p start The freeze_support line can be omitted if the program will be run normally instead of frozen This allows the newly spawned Python interpreter to safely import the module and then run the module s foo function Similar restrictions apply if a pool or manager is created in the main module Examples Demonstration of how to create and use customized managers and proxies from multiprocessing import freeze_support from multiprocessing managers import BaseManager BaseProxy import operator class Foo def f self print you called Foo f def g self print you called Foo g def _h self print you called Foo _h A simple generator function def baz for i in range 10 yield i i Proxy type for generator objects class GeneratorProxy BaseProxy _exposed_ __next__ def __iter__ self return self def __next__ self return self _callmethod __next__ Function to return the operator module def get_operator_module return operator class MyManager BaseManager pass register the Foo class make f and g accessible via proxy MyManager register Foo1 Foo register the Foo class make g and _h accessible via proxy MyManager register Foo2 Foo exposed g _h register the generator function baz use GeneratorProxy to make proxies MyManager register baz baz proxytype GeneratorProxy register get_operator_module make public functions accessible via proxy MyManager register operator get_operator_module def test mana,en
865,ger MyManager manager start print 20 f1 manager Foo1 f1 f f1 g assert not hasattr f1 _h assert sorted f1 _exposed_ sorted f g print 20 f2 manager Foo2 f2 g f2 _h assert not hasattr f2 f assert sorted f2 _exposed_ sorted g _h print 20 it manager baz for i in it print d i end print print 20 op manager operator print op add 23 45 op add 23 45 print op pow 2 94 op pow 2 94 print op _exposed_ op _exposed_ if __name__ __main__ freeze_support test Using Pool import multiprocessing import time import random import sys Functions used by test code def calculate func args result func args return s says that s s s multiprocessing current_process name func __name__ args result def calculatestar args return calculate args def mul a b time sleep 0 5 random random return a b def plus a b time sleep 0 5 random random return a b def f x return 1 0 x 5 0 def pow3 x return x 3 def noop x pass Test code def test PROCESSES 4 print Creating pool with d processes n PROCESSES with multiprocessing Pool PROCESSES as pool Tests TASKS mul i 7 for i in range 10 plus i 8 for i in range 10 results pool apply_async calculate t for t in TASKS imap_it pool imap calculatestar TASKS imap_unordered_it pool imap_unordered calculatestar TASKS print Ordered results using pool apply_async for r in results print t r get print print Ordered results using pool imap for x in imap_it print t x print print Unordered results using pool imap_unordered for x in imap_unordered_it print t x print print Ordered results using pool map will block till complete for x in pool map calculatestar TASKS print t x print Test error handling print Testing error handling try print pool apply f 5 except ZeroDivisionError print tGot ZeroDivisionError as expected from pool apply else raise AssertionError expected ZeroDivisionError try print pool map f list range 10 except ZeroDivisionError print tGot ZeroDivisionError as expected from pool map else raise AssertionError expected ZeroDivisionError try print list pool imap f list range 10 except ZeroDivisionError print tGot ZeroDivisionError as expected from list pool imap else raise AssertionError expected ZeroDivisionError it pool imap f list range 10 for i in range 10 try x next it except ZeroDivisionError if i 5 pass except StopIteration break else if i 5 raise AssertionError expected ZeroDivisionError assert i 9 print tGot ZeroDivisionError as expected from IMapIterator next print Testing timeouts print Testing ApplyResult get with timeout end res pool apply_async calculate TASKS 0 while 1 sys stdout flush try sys stdout write n t s res get 0 02 break except multiprocessing TimeoutError sys stdout write print print print Testing IMapIterator next with timeout end it pool imap calculatestar TASKS while 1 sys stdout flush try sys stdout write n t s it next 0 02 except StopIteration break except multiprocessing TimeoutError sys stdout write print print if __name__ __main__ multiprocessing freeze_support test An example showing how to use queues to feed tasks to a collection of worker processes and collect the results import time import random from multiprocessing import Process Queue current_process freeze_support Function run by worker processes def worker input output for func args in iter input get STOP result calculate func args output put result Function used to calculate result def calculate func args result func args return s says that s s s current_process name func __name__ args result Functions referenced by tasks def mul a b time sleep 0 5 random random return a b def plus a b time sleep 0 5 random random return a b def test NUMBER_OF_PROCESSES 4 TASKS1 mul i 7 for i in range 20 TASKS2 plus i 8 for i in range 10 Create queues task_queue Queue done_queue Queue Submit tasks for task in TASKS1 task_queue put task Start worker processes for i in range NUMBER_OF_PROCESSES Process target worker args task_queue done_queue start Get and print results print Unordered results for i in range len TASKS1 print t done_queue get Add more tasks using put for task in TASKS2 task_queue put task Get and print some more results for i in range len T,en
866,ASKS2 print t done_queue get Tell child processes to stop for i in range NUMBER_OF_PROCESSES task_queue put STOP if __name__ __main__ freeze_support test,fr
867,Policies An event loop policy is a global object used to get and set the current event loop as well as create new event loops The default policy can be replaced with built in alternatives to use different event loop implementations or substituted by a custom policy that can override these behaviors The policy object gets and sets a separate event loop per context This is per thread by default though custom policies could define context differently Custom event loop policies can control the behavior of get_event_loop set_event_loop and new_event_loop Policy objects should implement the APIs defined in the AbstractEventLoopPolicy abstract base class Getting and Setting the Policy The following functions can be used to get and set the policy for the current process asyncio get_event_loop_policy Return the current process wide policy asyncio set_event_loop_policy policy Set the current process wide policy to policy If policy is set to None the default policy is restored Policy Objects The abstract event loop policy base class is defined as follows class asyncio AbstractEventLoopPolicy An abstract base class for asyncio policies get_event_loop Get the event loop for the current context Return an event loop object implementing the AbstractEventLoop interface This method should never return None Changed in version 3 6 set_event_loop loop Set the event loop for the current context to loop new_event_loop Create and return a new event loop object This method should never return None get_child_watcher Get a child process watcher object Return a watcher object implementing the AbstractChildWatcher interface This function is Unix specific Deprecated since version 3 12 set_child_watcher watcher Set the current child process watcher to watcher This function is Unix specific Deprecated since version 3 12 asyncio ships with the following built in policies class asyncio DefaultEventLoopPolicy The default asyncio policy Uses SelectorEventLoop on Unix and ProactorEventLoop on Windows There is no need to install the default policy manually asyncio is configured to use the default policy automatically Changed in version 3 8 On Windows ProactorEventLoop is now used by default Deprecated since version 3 12 The get_event_loop method of the default asyncio policy now emits a DeprecationWarning if there is no current event loop set and it decides to create one In some future Python release this will become an error class asyncio WindowsSelectorEventLoopPolicy An alternative event loop policy that uses the SelectorEventLoop event loop implementation Availability Windows class asyncio WindowsProactorEventLoopPolicy An alternative event loop policy that uses the ProactorEventLoop event loop implementation Availability Windows Process Watchers A process watcher allows customization of how an event loop monitors child processes on Unix Specifically the event loop needs to know when a child process has exited In asyncio child processes are created with create_subprocess_exec and loop subprocess_exec functions asyncio defines the AbstractChildWatcher abstract base class which child watchers should implement and has four different implementations ThreadedChildWatcher configured to be used by default MultiLoopChildWatcher SafeChildWatcher and FastChildWatcher See also the Subprocess and Threads section The following two functions can be used to customize the child process watcher implementation used by the asyncio event loop asyncio get_child_watcher Return the current child watcher for the current policy Deprecated since version 3 12 asyncio set_child_watcher watcher Set the current child watcher to watcher for the current policy watcher must implement methods defined in the AbstractChildWatcher base class Deprecated since version 3 12 Note Third party event loops implementations might not support custom child watchers For such event loops using set_child_watcher might be prohibited or have no effect class asyncio AbstractChildWatcher add_child_handler pid callback args Register a new child handler Arrange for callback pid returncode args to be called whe,en
868,n a process with PID equal to pid terminates Specifying another callback for the same process replaces the previous handler The callback callable must be thread safe remove_child_handler pid Removes the handler for process with PID equal to pid The function returns True if the handler was successfully removed False if there was nothing to remove attach_loop loop Attach the watcher to an event loop If the watcher was previously attached to an event loop then it is first detached before attaching to the new loop Note loop may be None is_active Return True if the watcher is ready to use Spawning a subprocess with inactive current child watcher raises RuntimeError New in version 3 8 close Close the watcher This method has to be called to ensure that underlying resources are cleaned up Deprecated since version 3 12 class asyncio ThreadedChildWatcher This implementation starts a new waiting thread for every subprocess spawn It works reliably even when the asyncio event loop is run in a non main OS thread There is no noticeable overhead when handling a big number of children O 1 each time a child terminates but starting a thread per process requires extra memory This watcher is used by default New in version 3 8 class asyncio MultiLoopChildWatcher This implementation registers a SIGCHLD signal handler on instantiation That can break third party code that installs a custom handler for SIGCHLD signal The watcher avoids disrupting other code spawning processes by polling every process explicitly on a SIGCHLD signal There is no limitation for running subprocesses from different threads once the watcher is installed The solution is safe but it has a significant overhead when handling a big number of processes O n each time a SIGCHLD is received New in version 3 8 Deprecated since version 3 12 class asyncio SafeChildWatcher This implementation uses active event loop from the main thread to handle SIGCHLD signal If the main thread has no running event loop another thread cannot spawn a subprocess RuntimeError is raised The watcher avoids disrupting other code spawning processes by polling every process explicitly on a SIGCHLD signal This solution is as safe as MultiLoopChildWatcher and has the same O n complexity but requires a running event loop in the main thread to work Deprecated since version 3 12 class asyncio FastChildWatcher This implementation reaps every terminated processes by calling os waitpid 1 directly possibly breaking other code spawning processes and waiting for their termination There is no noticeable overhead when handling a big number of children O 1 each time a child terminates This solution requires a running event loop in the main thread to work as SafeChildWatcher Deprecated since version 3 12 class asyncio PidfdChildWatcher This implementation polls process file descriptors pidfds to await child process termination In some respects PidfdChildWatcher is a Goldilocks child watcher implementation It doesn t require signals or threads doesn t interfere with any processes launched outside the event loop and scales linearly with the number of subprocesses launched by the event loop The main disadvantage is that pidfds are specific to Linux and only work on recent 5 3 kernels New in version 3 9 Custom Policies To implement a new event loop policy it is recommended to subclass DefaultEventLoopPolicy and override the methods for which custom behavior is wanted e g class MyEventLoopPolicy asyncio DefaultEventLoopPolicy def get_event_loop self Get the event loop This may be None or an instance of EventLoop loop super get_event_loop Do something with loop return loop asyncio set_event_loop_policy MyEventLoopPolicy,en
869,What s New in Python 2 0 Author A M Kuchling and Moshe Zadka Introduction A new release of Python version 2 0 was released on October 16 2000 This article covers the exciting new features in 2 0 highlights some other useful changes and points out a few incompatible changes that may require rewriting code Python s development never completely stops between releases and a steady flow of bug fixes and improvements are always being submitted A host of minor fixes a few optimizations additional docstrings and better error messages went into 2 0 to list them all would be impossible but they re certainly significant Consult the publicly available CVS logs if you want to see the full list This progress is due to the five developers working for PythonLabs are now getting paid to spend their days fixing bugs and also due to the improved communication resulting from moving to SourceForge What About Python 1 6 Python 1 6 can be thought of as the Contractual Obligations Python release After the core development team left CNRI in May 2000 CNRI requested that a 1 6 release be created containing all the work on Python that had been performed at CNRI Python 1 6 therefore represents the state of the CVS tree as of May 2000 with the most significant new feature being Unicode support Development continued after May of course so the 1 6 tree received a few fixes to ensure that it s forward compatible with Python 2 0 1 6 is therefore part of Python s evolution and not a side branch So should you take much interest in Python 1 6 Probably not The 1 6final and 2 0beta1 releases were made on the same day September 5 2000 the plan being to finalize Python 2 0 within a month or so If you have applications to maintain there seems little point in breaking things by moving to 1 6 fixing them and then having another round of breakage within a month by moving to 2 0 you re better off just going straight to 2 0 Most of the really interesting features described in this document are only in 2 0 because a lot of work was done between May and September New Development Process The most important change in Python 2 0 may not be to the code at all but to how Python is developed in May 2000 the Python developers began using the tools made available by SourceForge for storing source code tracking bug reports and managing the queue of patch submissions To report bugs or submit patches for Python 2 0 use the bug tracking and patch manager tools available from Python s project page located at https sourceforge net projects python The most important of the services now hosted at SourceForge is the Python CVS tree the version controlled repository containing the source code for Python Previously there were roughly 7 or so people who had write access to the CVS tree and all patches had to be inspected and checked in by one of the people on this short list Obviously this wasn t very scalable By moving the CVS tree to SourceForge it became possible to grant write access to more people as of September 2000 there were 27 people able to check in changes a fourfold increase This makes possible large scale changes that wouldn t be attempted if they d have to be filtered through the small group of core developers For example one day Peter Schneider Kamp took it into his head to drop K R C compatibility and convert the C source for Python to ANSI C After getting approval on the python dev mailing list he launched into a flurry of checkins that lasted about a week other developers joined in to help and the job was done If there were only 5 people with write access probably that task would have been viewed as nice but not worth the time and effort needed and it would never have gotten done The shift to using SourceForge s services has resulted in a remarkable increase in the speed of development Patches now get submitted commented on revised by people other than the original submitter and bounced back and forth between people until the patch is deemed worth checking in Bugs are tracked in one central location and can be assigned to a specific person for fixing and we can count th,en
870,e number of open bugs to measure progress This didn t come without a cost developers now have more e mail to deal with more mailing lists to follow and special tools had to be written for the new environment For example SourceForge sends default patch and bug notification e mail messages that are completely unhelpful so Ka Ping Yee wrote an HTML screen scraper that sends more useful messages The ease of adding code caused a few initial growing pains such as code was checked in before it was ready or without getting clear agreement from the developer group The approval process that has emerged is somewhat similar to that used by the Apache group Developers can vote 1 0 0 or 1 on a patch 1 and 1 denote acceptance or rejection while 0 and 0 mean the developer is mostly indifferent to the change though with a slight positive or negative slant The most significant change from the Apache model is that the voting is essentially advisory letting Guido van Rossum who has Benevolent Dictator For Life status know what the general opinion is He can still ignore the result of a vote and approve or reject a change even if the community disagrees with him Producing an actual patch is the last step in adding a new feature and is usually easy compared to the earlier task of coming up with a good design Discussions of new features can often explode into lengthy mailing list threads making the discussion hard to follow and no one can read every posting to python dev Therefore a relatively formal process has been set up to write Python Enhancement Proposals PEPs modelled on the internet RFC process PEPs are draft documents that describe a proposed new feature and are continually revised until the community reaches a consensus either accepting or rejecting the proposal Quoting from the introduction to PEP 1 PEP Purpose and Guidelines PEP stands for Python Enhancement Proposal A PEP is a design document providing information to the Python community or describing a new feature for Python The PEP should provide a concise technical specification of the feature and a rationale for the feature We intend PEPs to be the primary mechanisms for proposing new features for collecting community input on an issue and for documenting the design decisions that have gone into Python The PEP author is responsible for building consensus within the community and documenting dissenting opinions Read the rest of PEP 1 for the details of the PEP editorial process style and format PEPs are kept in the Python CVS tree on SourceForge though they re not part of the Python 2 0 distribution and are also available in HTML form from https peps python org As of September 2000 there are 25 PEPs ranging from PEP 201 Lockstep Iteration to PEP 225 Elementwise Objectwise Operators Unicode The largest new feature in Python 2 0 is a new fundamental data type Unicode strings Unicode uses 16 bit numbers to represent characters instead of the 8 bit number used by ASCII meaning that 65 536 distinct characters can be supported The final interface for Unicode support was arrived at through countless often stormy discussions on the python dev mailing list and mostly implemented by Marc André Lemburg based on a Unicode string type implementation by Fredrik Lundh A detailed explanation of the interface was written up as PEP 100 Python Unicode Integration This article will simply cover the most significant points about the Unicode interfaces In Python source code Unicode strings are written as u string Arbitrary Unicode characters can be written using a new escape sequence u HHHH where HHHH is a 4 digit hexadecimal number from 0000 to FFFF The existing x HH escape sequence can also be used and octal escapes can be used for characters up to U 01FF which is represented by 777 Unicode strings just like regular strings are an immutable sequence type They can be indexed and sliced but not modified in place Unicode strings have an encode encoding method that returns an 8 bit string in the desired encoding Encodings are named by strings such as ascii utf 8 iso 8859 1 or whatever A codec API is de,en
871,fined for implementing and registering new encodings that are then available throughout a Python program If an encoding isn t specified the default encoding is usually 7 bit ASCII though it can be changed for your Python installation by calling the sys setdefaultencoding encoding function in a customized version of site py Combining 8 bit and Unicode strings always coerces to Unicode using the default ASCII encoding the result of a u bc is u abc New built in functions have been added and existing built ins modified to support Unicode unichr ch returns a Unicode string 1 character long containing the character ch ord u where u is a 1 character regular or Unicode string returns the number of the character as an integer unicode string encoding errors creates a Unicode string from an 8 bit string encoding is a string naming the encoding to use The errors parameter specifies the treatment of characters that are invalid for the current encoding passing strict as the value causes an exception to be raised on any encoding error while ignore causes errors to be silently ignored and replace uses U FFFD the official replacement character in case of any problems The exec statement and various built ins such as eval getattr and setattr will also accept Unicode strings as well as regular strings It s possible that the process of fixing this missed some built ins if you find a built in function that accepts strings but doesn t accept Unicode strings at all please report it as a bug A new module unicodedata provides an interface to Unicode character properties For example unicodedata category u A returns the 2 character string Lu the L denoting it s a letter and u meaning that it s uppercase unicodedata bidirectional u u0660 returns AN meaning that U 0660 is an Arabic number The codecs module contains functions to look up existing encodings and register new ones Unless you want to implement a new encoding you ll most often use the codecs lookup encoding function which returns a 4 element tuple encode_func decode_func stream_reader stream_writer encode_func is a function that takes a Unicode string and returns a 2 tuple string length string is an 8 bit string containing a portion perhaps all of the Unicode string converted into the given encoding and length tells you how much of the Unicode string was converted decode_func is the opposite of encode_func taking an 8 bit string and returning a 2 tuple ustring length consisting of the resulting Unicode string ustring and the integer length telling how much of the 8 bit string was consumed stream_reader is a class that supports decoding input from a stream stream_reader file_obj returns an object that supports the read readline and readlines methods These methods will all translate from the given encoding and return Unicode strings stream_writer similarly is a class that supports encoding output to a stream stream_writer file_obj returns an object that supports the write and writelines methods These methods expect Unicode strings translating them to the given encoding on output For example the following code writes a Unicode string into a file encoding it as UTF 8 import codecs unistr u u0660 u2000ab UTF8_encode UTF8_decode UTF8_streamreader UTF8_streamwriter codecs lookup UTF 8 output UTF8_streamwriter open tmp output wb output write unistr output close The following code would then read UTF 8 input from the file input UTF8_streamreader open tmp output rb print repr input read input close Unicode aware regular expressions are available through the re module which has a new underlying implementation called SRE written by Fredrik Lundh of Secret Labs AB A U command line option was added which causes the Python compiler to interpret all string literals as Unicode string literals This is intended to be used in testing and future proofing your Python code since some future version of Python may drop support for 8 bit strings and provide only Unicode strings List Comprehensions Lists are a workhorse data type in Python and many programs manipulate a list at some point Two common operations on lis,en
872,ts are to loop over them and either pick out the elements that meet a certain criterion or apply some function to each element For example given a list of strings you might want to pull out all the strings containing a given substring or strip off trailing whitespace from each line The existing map and filter functions can be used for this purpose but they require a function as one of their arguments This is fine if there s an existing built in function that can be passed directly but if there isn t you have to create a little function to do the required work and Python s scoping rules make the result ugly if the little function needs additional information Take the first example in the previous paragraph finding all the strings in the list containing a given substring You could write the following to do it Given the list L make a list of all strings containing the substring S sublist filter lambda s substring S string find s substring 1 L Because of Python s scoping rules a default argument is used so that the anonymous function created by the lambda expression knows what substring is being searched for List comprehensions make this cleaner sublist s for s in L if string find s S 1 List comprehensions have the form expression for expr in sequence1 for expr2 in sequence2 for exprN in sequenceN if condition The for in clauses contain the sequences to be iterated over The sequences do not have to be the same length because they are not iterated over in parallel but from left to right this is explained more clearly in the following paragraphs The elements of the generated list will be the successive values of expression The final if clause is optional if present expression is only evaluated and added to the result if condition is true To make the semantics very clear a list comprehension is equivalent to the following Python code for expr1 in sequence1 for expr2 in sequence2 for exprN in sequenceN if condition Append the value of the expression to the resulting list This means that when there are multiple for in clauses the resulting list will be equal to the product of the lengths of all the sequences If you have two lists of length 3 the output list is 9 elements long seq1 abc seq2 1 2 3 x y for x in seq1 for y in seq2 a 1 a 2 a 3 b 1 b 2 b 3 c 1 c 2 c 3 To avoid introducing an ambiguity into Python s grammar if expression is creating a tuple it must be surrounded with parentheses The first list comprehension below is a syntax error while the second one is correct Syntax error x y for x in seq1 for y in seq2 Correct x y for x in seq1 for y in seq2 The idea of list comprehensions originally comes from the functional programming language Haskell https www haskell org Greg Ewing argued most effectively for adding them to Python and wrote the initial list comprehension patch which was then discussed for a seemingly endless time on the python dev mailing list and kept up to date by Skip Montanaro Augmented Assignment Augmented assignment operators another long requested feature have been added to Python 2 0 Augmented assignment operators include and so forth For example the statement a 2 increments the value of the variable a by 2 equivalent to the slightly lengthier a a 2 The full list of supported assignment operators is and Python classes can override the augmented assignment operators by defining methods named __iadd__ __isub__ etc For example the following Number class stores a number and supports using to create a new instance with an incremented value class Number def __init__ self value self value value def __iadd__ self increment return Number self value increment n Number 5 n 3 print n value The __iadd__ special method is called with the value of the increment and should return a new instance with an appropriately modified value this return value is bound as the new value of the variable on the left hand side Augmented assignment operators were first introduced in the C programming language and most C derived languages such as awk C Java Perl and PHP also support them The augmented assignment patch was implemented by,en
873, Thomas Wouters String Methods Until now string manipulation functionality was in the string module which was usually a front end for the strop module written in C The addition of Unicode posed a difficulty for the strop module because the functions would all need to be rewritten in order to accept either 8 bit or Unicode strings For functions such as string replace which takes 3 string arguments that means eight possible permutations and correspondingly complicated code Instead Python 2 0 pushes the problem onto the string type making string manipulation functionality available through methods on both 8 bit strings and Unicode strings andrew capitalize Andrew hostname replace os linux hlinuxtname moshe find sh 2 One thing that hasn t changed a noteworthy April Fools joke notwithstanding is that Python strings are immutable Thus the string methods return new strings and do not modify the string on which they operate The old string module is still around for backwards compatibility but it mostly acts as a front end to the new string methods Two methods which have no parallel in pre 2 0 versions although they did exist in JPython for quite some time are startswith and endswith s startswith t is equivalent to s len t t while s endswith t is equivalent to s len t t One other method which deserves special mention is join The join method of a string receives one parameter a sequence of strings and is equivalent to the string join function from the old string module with the arguments reversed In other words s join seq is equivalent to the old string join seq s Garbage Collection of Cycles The C implementation of Python uses reference counting to implement garbage collection Every Python object maintains a count of the number of references pointing to itself and adjusts the count as references are created or destroyed Once the reference count reaches zero the object is no longer accessible since you need to have a reference to an object to access it and if the count is zero no references exist any longer Reference counting has some pleasant properties it s easy to understand and implement and the resulting implementation is portable fairly fast and reacts well with other libraries that implement their own memory handling schemes The major problem with reference counting is that it sometimes doesn t realise that objects are no longer accessible resulting in a memory leak This happens when there are cycles of references Consider the simplest possible cycle a class instance which has a reference to itself instance SomeClass instance myself instance After the above two lines of code have been executed the reference count of instance is 2 one reference is from the variable named instance and the other is from the myself attribute of the instance If the next line of code is del instance what happens The reference count of instance is decreased by 1 so it has a reference count of 1 the reference in the myself attribute still exists Yet the instance is no longer accessible through Python code and it could be deleted Several objects can participate in a cycle if they have references to each other causing all of the objects to be leaked Python 2 0 fixes this problem by periodically executing a cycle detection algorithm which looks for inaccessible cycles and deletes the objects involved A new gc module provides functions to perform a garbage collection obtain debugging statistics and tuning the collector s parameters Running the cycle detection algorithm takes some time and therefore will result in some additional overhead It is hoped that after we ve gotten experience with the cycle collection from using 2 0 Python 2 1 will be able to minimize the overhead with careful tuning It s not yet obvious how much performance is lost because benchmarking this is tricky and depends crucially on how often the program creates and destroys objects The detection of cycles can be disabled when Python is compiled if you can t afford even a tiny speed penalty or suspect that the cycle collection is buggy by specifying the without cycle gc switch when ru,en
874,nning the configure script Several people tackled this problem and contributed to a solution An early implementation of the cycle detection approach was written by Toby Kelsey The current algorithm was suggested by Eric Tiedemann during a visit to CNRI and Guido van Rossum and Neil Schemenauer wrote two different implementations which were later integrated by Neil Lots of other people offered suggestions along the way the March 2000 archives of the python dev mailing list contain most of the relevant discussion especially in the threads titled Reference cycle collection for Python and Finalization again Other Core Changes Various minor changes have been made to Python s syntax and built in functions None of the changes are very far reaching but they re handy conveniences Minor Language Changes A new syntax makes it more convenient to call a given function with a tuple of arguments and or a dictionary of keyword arguments In Python 1 5 and earlier you d use the apply built in function apply f args kw calls the function f with the argument tuple args and the keyword arguments in the dictionary kw apply is the same in 2 0 but thanks to a patch from Greg Ewing f args kw is a shorter and clearer way to achieve the same effect This syntax is symmetrical with the syntax for defining functions def f args kw args is a tuple of positional args kw is a dictionary of keyword args The print statement can now have its output directed to a file like object by following the print with file similar to the redirection operator in Unix shells Previously you d either have to use the write method of the file like object which lacks the convenience and simplicity of print or you could assign a new value to sys stdout and then restore the old value For sending output to standard error it s much easier to write this print sys stderr Warning action field not supplied Modules can now be renamed on importing them using the syntax import module as name or from module import name as othername The patch was submitted by Thomas Wouters A new format style is available when using the operator r will insert the repr of its argument This was also added from symmetry considerations this time for symmetry with the existing s format style which inserts the str of its argument For example r s abc abc returns a string containing abc abc Previously there was no way to implement a class that overrode Python s built in in operator and implemented a custom version obj in seq returns true if obj is present in the sequence seq Python computes this by simply trying every index of the sequence until either obj is found or an IndexError is encountered Moshe Zadka contributed a patch which adds a __contains__ magic method for providing a custom implementation for in Additionally new built in objects written in C can define what in means for them via a new slot in the sequence protocol Earlier versions of Python used a recursive algorithm for deleting objects Deeply nested data structures could cause the interpreter to fill up the C stack and crash Christian Tismer rewrote the deletion logic to fix this problem On a related note comparing recursive objects recursed infinitely and crashed Jeremy Hylton rewrote the code to no longer crash producing a useful result instead For example after this code a b a append a b append b The comparison a b returns true because the two recursive data structures are isomorphic See the thread trashcan and PR 7 in the April 2000 archives of the python dev mailing list for the discussion leading up to this implementation and some useful relevant links Note that comparisons can now also raise exceptions In earlier versions of Python a comparison operation such as cmp a b would always produce an answer even if a user defined __cmp__ method encountered an error since the resulting exception would simply be silently swallowed Work has been done on porting Python to 64 bit Windows on the Itanium processor mostly by Trent Mick of ActiveState Confusingly sys platform is still win32 on Win64 because it seems that for ease of porting MS Visual C tre,en
875,ats code as 32 bit on Itanium PythonWin also supports Windows CE see the Python CE page at https pythonce sourceforge net for more information Another new platform is Darwin MacOS X initial support for it is in Python 2 0 Dynamic loading works if you specify configure with dyld with suffix x Consult the README in the Python source distribution for more instructions An attempt has been made to alleviate one of Python s warts the often confusing NameError exception when code refers to a local variable before the variable has been assigned a value For example the following code raises an exception on the print statement in both 1 5 2 and 2 0 in 1 5 2 a NameError exception is raised while 2 0 raises a new UnboundLocalError exception UnboundLocalError is a subclass of NameError so any existing code that expects NameError to be raised should still work def f print i i i i 1 f Two new exceptions TabError and IndentationError have been introduced They re both subclasses of SyntaxError and are raised when Python code is found to be improperly indented Changes to Built in Functions A new built in zip seq1 seq2 has been added zip returns a list of tuples where each tuple contains the i th element from each of the argument sequences The difference between zip and map None seq1 seq2 is that map pads the sequences with None if the sequences aren t all of the same length while zip truncates the returned list to the length of the shortest argument sequence The int and long functions now accept an optional base parameter when the first argument is a string int 123 10 returns 123 while int 123 16 returns 291 int 123 16 raises a TypeError exception with the message can t convert non string with explicit base A new variable holding more detailed version information has been added to the sys module sys version_info is a tuple major minor micro level serial For example in a hypothetical 2 0 1beta1 sys version_info would be 2 0 1 beta 1 level is a string such as alpha beta or final for a final release Dictionaries have an odd new method setdefault key default which behaves similarly to the existing get method However if the key is missing setdefault both returns the value of default as get would do and also inserts it into the dictionary as the value for key Thus the following lines of code if dict has_key key return dict key else dict key return dict key can be reduced to a single return dict setdefault key statement The interpreter sets a maximum recursion depth in order to catch runaway recursion before filling the C stack and causing a core dump or GPF Previously this limit was fixed when you compiled Python but in 2 0 the maximum recursion depth can be read and modified using sys getrecursionlimit and sys setrecursionlimit The default value is 1000 and a rough maximum value for a given platform can be found by running a new script Misc find_recursionlimit py Porting to 2 0 New Python releases try hard to be compatible with previous releases and the record has been pretty good However some changes are considered useful enough usually because they fix initial design decisions that turned out to be actively mistaken that breaking backward compatibility can t always be avoided This section lists the changes in Python 2 0 that may cause old Python code to break The change which will probably break the most code is tightening up the arguments accepted by some methods Some methods would take multiple arguments and treat them as a tuple particularly various list methods such as append and insert In earlier versions of Python if L is a list L append 1 2 appends the tuple 1 2 to the list In Python 2 0 this causes a TypeError exception to be raised with the message append requires exactly 1 argument 2 given The fix is to simply add an extra set of parentheses to pass both values as a tuple L append 1 2 The earlier versions of these methods were more forgiving because they used an old function in Python s C interface to parse their arguments 2 0 modernizes them to use PyArg_ParseTuple the current argument parsing function which provides more helpful ,en
876,error messages and treats multi argument calls as errors If you absolutely must use 2 0 but can t fix your code you can edit Objects listobject c and define the preprocessor symbol NO_STRICT_LIST_APPEND to preserve the old behaviour this isn t recommended Some of the functions in the socket module are still forgiving in this way For example socket connect hostname 25 is the correct form passing a tuple representing an IP address but socket connect hostname 25 also works socket connect_ex and socket bind are similarly easy going 2 0alpha1 tightened these functions up but because the documentation actually used the erroneous multiple argument form many people wrote code which would break with the stricter checking GvR backed out the changes in the face of public reaction so for the socket module the documentation was fixed and the multiple argument form is simply marked as deprecated it will be tightened up again in a future Python version The x escape in string literals now takes exactly 2 hex digits Previously it would consume all the hex digits following the x and take the lowest 8 bits of the result so x123456 was equivalent to x56 The AttributeError and NameError exceptions have a more friendly error message whose text will be something like Spam instance has no attribute eggs or name eggs is not defined Previously the error message was just the missing attribute name eggs and code written to take advantage of this fact will break in 2 0 Some work has been done to make integers and long integers a bit more interchangeable In 1 5 2 large file support was added for Solaris to allow reading files larger than 2 GiB this made the tell method of file objects return a long integer instead of a regular integer Some code would subtract two file offsets and attempt to use the result to multiply a sequence or slice a string but this raised a TypeError In 2 0 long integers can be used to multiply or slice a sequence and it ll behave as you d intuitively expect it to 3L abc produces abcabcabc and 0 1 2 3 2L 4L produces 2 3 Long integers can also be used in various contexts where previously only integers were accepted such as in the seek method of file objects and in the formats supported by the operator d i x etc For example d 2L 64 will produce the string 18446744073709551616 The subtlest long integer change of all is that the str of a long integer no longer has a trailing L character though repr still includes it The L annoyed many people who wanted to print long integers that looked just like regular integers since they had to go out of their way to chop off the character This is no longer a problem in 2 0 but code which does str longval 1 and assumes the L is there will now lose the final digit Taking the repr of a float now uses a different formatting precision than str repr uses 17g format string for C s sprintf while str uses 12g as before The effect is that repr may occasionally show more decimal places than str for certain numbers For example the number 8 1 can t be represented exactly in binary so repr 8 1 is 8 0999999999999996 while str 8 1 is 8 1 The X command line option which turned all standard exceptions into strings instead of classes has been removed the standard exceptions will now always be classes The exceptions module containing the standard exceptions was translated from Python to a built in C module written by Barry Warsaw and Fredrik Lundh Extending Embedding Changes Some of the changes are under the covers and will only be apparent to people writing C extension modules or embedding a Python interpreter in a larger application If you aren t dealing with Python s C API you can safely skip this section The version number of the Python C API was incremented so C extensions compiled for 1 5 2 must be recompiled in order to work with 2 0 On Windows it s not possible for Python 2 0 to import a third party extension built for Python 1 5 x due to how Windows DLLs work so Python will raise an exception and the import will fail Users of Jim Fulton s ExtensionClass module will be pleased to find out that hooks have b,en
877,een added so that ExtensionClasses are now supported by isinstance and issubclass This means you no longer have to remember to write code such as if type obj myExtensionClass but can use the more natural if isinstance obj myExtensionClass The Python importdl c file which was a mass of ifdefs to support dynamic loading on many different platforms was cleaned up and reorganised by Greg Stein importdl c is now quite small and platform specific code has been moved into a bunch of Python dynload_ c files Another cleanup there were also a number of my h files in the Include directory that held various portability hacks they ve been merged into a single file Include pyport h Vladimir Marangozov s long awaited malloc restructuring was completed to make it easy to have the Python interpreter use a custom allocator instead of C s standard malloc For documentation read the comments in Include pymem h and Include objimpl h For the lengthy discussions during which the interface was hammered out see the web archives of the patches and python dev lists at python org Recent versions of the GUSI development environment for MacOS support POSIX threads Therefore Python s POSIX threading support now works on the Macintosh Threading support using the user space GNU pth library was also contributed Threading support on Windows was enhanced too Windows supports thread locks that use kernel objects only in case of contention in the common case when there s no contention they use simpler functions which are an order of magnitude faster A threaded version of Python 1 5 2 on NT is twice as slow as an unthreaded version with the 2 0 changes the difference is only 10 These improvements were contributed by Yakov Markovitch Python 2 0 s source now uses only ANSI C prototypes so compiling Python now requires an ANSI C compiler and can no longer be done using a compiler that only supports K R C Previously the Python virtual machine used 16 bit numbers in its bytecode limiting the size of source files In particular this affected the maximum size of literal lists and dictionaries in Python source occasionally people who are generating Python code would run into this limit A patch by Charles G Waldman raises the limit from 2 16 to 2 32 Three new convenience functions intended for adding constants to a module s dictionary at module initialization time were added PyModule_AddObject PyModule_AddIntConstant and PyModule_AddStringConstant Each of these functions takes a module object a null terminated C string containing the name to be added and a third argument for the value to be assigned to the name This third argument is respectively a Python object a C long or a C string A wrapper API was added for Unix style signal handlers PyOS_getsig gets a signal handler and PyOS_setsig will set a new handler Distutils Making Modules Easy to Install Before Python 2 0 installing modules was a tedious affair there was no way to figure out automatically where Python is installed or what compiler options to use for extension modules Software authors had to go through an arduous ritual of editing Makefiles and configuration files which only really work on Unix and leave Windows and MacOS unsupported Python users faced wildly differing installation instructions which varied between different extension packages which made administering a Python installation something of a chore The SIG for distribution utilities shepherded by Greg Ward has created the Distutils a system to make package installation much easier They form the distutils package a new part of Python s standard library In the best case installing a Python module from source will require the same steps first you simply mean unpack the tarball or zip archive and the run python setup py install The platform will be automatically detected the compiler will be recognized C extension modules will be compiled and the distribution installed into the proper directory Optional command line arguments provide more control over the installation process the distutils package offers many places to override defaults separating th,en
878,e build from the install building or installing in non default directories and more In order to use the Distutils you need to write a setup py script For the simple case when the software contains only py files a minimal setup py can be just a few lines long from distutils core import setup setup name foo version 1 0 py_modules module1 module2 The setup py file isn t much more complicated if the software consists of a few packages from distutils core import setup setup name foo version 1 0 packages package package subpackage A C extension can be the most complicated case here s an example taken from the PyXML package from distutils core import setup Extension expat_extension Extension xml parsers pyexpat define_macros XML_NS None include_dirs extensions expat xmltok extensions expat xmlparse sources extensions pyexpat c extensions expat xmltok xmltok c extensions expat xmltok xmlrole c setup name PyXML version 0 5 4 ext_modules expat_extension The Distutils can also take care of creating source and binary distributions The sdist command run by python setup py sdist builds a source distribution such as foo 1 0 tar gz Adding new commands isn t difficult bdist_rpm and bdist_wininst commands have already been contributed to create an RPM distribution and a Windows installer for the software respectively Commands to create other distribution formats such as Debian packages and Solaris pkg files are in various stages of development All this is documented in a new manual Distributing Python Modules that joins the basic set of Python documentation XML Modules Python 1 5 2 included a simple XML parser in the form of the xmllib module contributed by Sjoerd Mullender Since 1 5 2 s release two different interfaces for processing XML have become common SAX2 version 2 of the Simple API for XML provides an event driven interface with some similarities to xmllib and the DOM Document Object Model provides a tree based interface transforming an XML document into a tree of nodes that can be traversed and modified Python 2 0 includes a SAX2 interface and a stripped down DOM interface as part of the xml package Here we will give a brief overview of these new interfaces consult the Python documentation or the source code for complete details The Python XML SIG is also working on improved documentation SAX2 Support SAX defines an event driven interface for parsing XML To use SAX you must write a SAX handler class Handler classes inherit from various classes provided by SAX and override various methods that will then be called by the XML parser For example the startElement and endElement methods are called for every starting and end tag encountered by the parser the characters method is called for every chunk of character data and so forth The advantage of the event driven approach is that the whole document doesn t have to be resident in memory at any one time which matters if you are processing really huge documents However writing the SAX handler class can get very complicated if you re trying to modify the document structure in some elaborate way For example this little example program defines a handler that prints a message for every starting and ending tag and then parses the file hamlet xml using it from xml import sax class SimpleHandler sax ContentHandler def startElement self name attrs print Start of element name attrs keys def endElement self name print End of element name Create a parser object parser sax make_parser Tell it what handler to use handler SimpleHandler parser setContentHandler handler Parse a file parser parse hamlet xml For more information consult the Python documentation or the XML HOWTO at https pyxml sourceforge net topics howto xml howto html DOM Support The Document Object Model is a tree based representation for an XML document A top level Document instance is the root of the tree and has a single child which is the top level Element instance This Element has children nodes representing character data and any sub elements which may have further children of their own and so forth Using the DOM you can traverse ,en
879,the resulting tree any way you like access element and attribute values insert and delete nodes and convert the tree back into XML The DOM is useful for modifying XML documents because you can create a DOM tree modify it by adding new nodes or rearranging subtrees and then produce a new XML document as output You can also construct a DOM tree manually and convert it to XML which can be a more flexible way of producing XML output than simply writing tag1 tag1 to a file The DOM implementation included with Python lives in the xml dom minidom module It s a lightweight implementation of the Level 1 DOM with support for XML namespaces The parse and parseString convenience functions are provided for generating a DOM tree from xml dom import minidom doc minidom parse hamlet xml doc is a Document instance Document like all the other DOM classes such as Element and Text is a subclass of the Node base class All the nodes in a DOM tree therefore support certain common methods such as toxml which returns a string containing the XML representation of the node and its children Each class also has special methods of its own for example Element and Document instances have a method to find all child elements with a given tag name Continuing from the previous 2 line example perslist doc getElementsByTagName PERSONA print perslist 0 toxml print perslist 1 toxml For the Hamlet XML file the above few lines output PERSONA CLAUDIUS king of Denmark PERSONA PERSONA HAMLET son to the late and nephew to the present king PERSONA The root element of the document is available as doc documentElement and its children can be easily modified by deleting adding or removing nodes root doc documentElement Remove the first child root removeChild root childNodes 0 Move the new first child to the end root appendChild root childNodes 0 Insert the new first child originally the third child before the 20th child root insertBefore root childNodes 0 root childNodes 20 Again I will refer you to the Python documentation for a complete listing of the different Node classes and their various methods Relationship to PyXML The XML Special Interest Group has been working on XML related Python code for a while Its code distribution called PyXML is available from the SIG s web pages at https www python org community sigs current xml sig The PyXML distribution also used the package name xml If you ve written programs that used PyXML you re probably wondering about its compatibility with the 2 0 xml package The answer is that Python 2 0 s xml package isn t compatible with PyXML but can be made compatible by installing a recent version PyXML Many applications can get by with the XML support that is included with Python 2 0 but more complicated applications will require that the full PyXML package will be installed When installed PyXML versions 0 6 0 or greater will replace the xml package shipped with Python and will be a strict superset of the standard package adding a bunch of additional features Some of the additional features in PyXML include 4DOM a full DOM implementation from FourThought Inc The xmlproc validating parser written by Lars Marius Garshol The sgmlop parser accelerator module written by Fredrik Lundh Module changes Lots of improvements and bugfixes were made to Python s extensive standard library some of the affected modules include readline ConfigParser cgi calendar posix readline xmllib aifc chunk wave random shelve and nntplib Consult the CVS logs for the exact patch by patch details Brian Gallew contributed OpenSSL support for the socket module OpenSSL is an implementation of the Secure Socket Layer which encrypts the data being sent over a socket When compiling Python you can edit Modules Setup to include SSL support which adds an additional function to the socket module socket ssl socket keyfile certfile which takes a socket object and returns an SSL socket The httplib and urllib modules were also changed to support https URLs though no one has implemented FTP or SMTP over SSL The httplib module has been rewritten by Greg Stein to support HTTP 1 1 Backw,en
880,ard compatibility with the 1 5 version of httplib is provided though using HTTP 1 1 features such as pipelining will require rewriting code to use a different set of interfaces The Tkinter module now supports Tcl Tk version 8 1 8 2 or 8 3 and support for the older 7 x versions has been dropped The Tkinter module now supports displaying Unicode strings in Tk widgets Also Fredrik Lundh contributed an optimization which makes operations like create_line and create_polygon much faster especially when using lots of coordinates The curses module has been greatly extended starting from Oliver Andrich s enhanced version to provide many additional functions from ncurses and SYSV curses such as colour alternative character set support pads and mouse support This means the module is no longer compatible with operating systems that only have BSD curses but there don t seem to be any currently maintained OSes that fall into this category As mentioned in the earlier discussion of 2 0 s Unicode support the underlying implementation of the regular expressions provided by the re module has been changed SRE a new regular expression engine written by Fredrik Lundh and partially funded by Hewlett Packard supports matching against both 8 bit strings and Unicode strings New modules A number of new modules were added We ll simply list them with brief descriptions consult the 2 0 documentation for the details of a particular module atexit For registering functions to be called before the Python interpreter exits Code that currently sets sys exitfunc directly should be changed to use the atexit module instead importing atexit and calling atexit register with the function to be called on exit Contributed by Skip Montanaro codecs encodings unicodedata Added as part of the new Unicode support filecmp Supersedes the old cmp cmpcache and dircmp modules which have now become deprecated Contributed by Gordon MacMillan and Moshe Zadka gettext This module provides internationalization I18N and localization L10N support for Python programs by providing an interface to the GNU gettext message catalog library Integrated by Barry Warsaw from separate contributions by Martin von Löwis Peter Funk and James Henstridge linuxaudiodev Support for the dev audio device on Linux a twin to the existing sunaudiodev module Contributed by Peter Bosch with fixes by Jeremy Hylton mmap An interface to memory mapped files on both Windows and Unix A file s contents can be mapped directly into memory at which point it behaves like a mutable string so its contents can be read and modified They can even be passed to functions that expect ordinary strings such as the re module Contributed by Sam Rushing with some extensions by A M Kuchling pyexpat An interface to the Expat XML parser Contributed by Paul Prescod robotparser Parse a robots txt file which is used for writing web spiders that politely avoid certain areas of a web site The parser accepts the contents of a robots txt file builds a set of rules from it and can then answer questions about the fetchability of a given URL Contributed by Skip Montanaro tabnanny A module script to check Python source code for ambiguous indentation Contributed by Tim Peters UserString A base class useful for deriving objects that behave like strings webbrowser A module that provides a platform independent way to launch a web browser on a specific URL For each platform various browsers are tried in a specific order The user can alter which browser is launched by setting the BROWSER environment variable Originally inspired by Eric S Raymond s patch to urllib which added similar functionality but the final module comes from code originally implemented by Fred Drake as Tools idle BrowserControl py and adapted for the standard library by Fred _winreg An interface to the Windows registry _winreg is an adaptation of functions that have been part of PythonWin since 1995 but has now been added to the core distribution and enhanced to support Unicode _winreg was written by Bill Tutt and Mark Hammond zipfile A module for reading and writing ZIP format a,en
881,rchives These are archives produced by PKZIP on DOS Windows or zip on Unix not to be confused with gzip format files which are supported by the gzip module Contributed by James C Ahlstrom imputil A module that provides a simpler way for writing customized import hooks in comparison to the existing ihooks module Implemented by Greg Stein with much discussion on python dev along the way IDLE Improvements IDLE is the official Python cross platform IDE written using Tkinter Python 2 0 includes IDLE 0 6 which adds a number of new features and improvements A partial list UI improvements and optimizations especially in the area of syntax highlighting and auto indentation The class browser now shows more information such as the top level functions in a module Tab width is now a user settable option When opening an existing Python file IDLE automatically detects the indentation conventions and adapts There is now support for calling browsers on various platforms used to open the Python documentation in a browser IDLE now has a command line which is largely similar to the vanilla Python interpreter Call tips were added in many places IDLE can now be installed as a package In the editor window there is now a line column bar at the bottom Three new keystroke commands Check module Alt F5 Import module F5 and Run script Ctrl F5 Deleted and Deprecated Modules A few modules have been dropped because they re obsolete or because there are now better ways to do the same thing The stdwin module is gone it was for a platform independent windowing toolkit that s no longer developed A number of modules have been moved to the lib old subdirectory cmp cmpcache dircmp dump find grep packmail poly util whatsound zmod If you have code which relies on a module that s been moved to lib old you can simply add that directory to sys path to get them back but you re encouraged to update any code that uses these modules Acknowledgements The authors would like to thank the following people for offering suggestions on various drafts of this article David Bolen Mark Hammond Gregg Hauser Jeremy Hylton Fredrik Lundh Detlef Lannert Aahz Maruch Skip Montanaro Vladimir Marangozov Tobias Polzin Guido van Rossum Neil Schemenauer and Russ Schmidt,en
882,Python Frequently Asked Questions General Python FAQ Programming FAQ Design and History FAQ Library and Extension FAQ Extending Embedding FAQ Python on Windows FAQ Graphic User Interface FAQ Why is Python Installed on my Computer FAQ,en
883,Built in Types The following sections describe the standard types that are built into the interpreter The principal built in types are numerics sequences mappings classes instances and exceptions Some collection classes are mutable The methods that add subtract or rearrange their members in place and don t return a specific item never return the collection instance itself but None Some operations are supported by several object types in particular practically all objects can be compared for equality tested for truth value and converted to a string with the repr function or the slightly different str function The latter function is implicitly used when an object is written by the print function Truth Value Testing Any object can be tested for truth value for use in an if or while condition or as operand of the Boolean operations below By default an object is considered true unless its class defines either a __bool__ method that returns False or a __len__ method that returns zero when called with the object 1 Here are most of the built in objects considered false constants defined to be false None and False zero of any numeric type 0 0 0 0j Decimal 0 Fraction 0 1 empty sequences and collections set range 0 Operations and built in functions that have a Boolean result always return 0 or False for false and 1 or True for true unless otherwise stated Important exception the Boolean operations or and and always return one of their operands Boolean Operations and or not These are the Boolean operations ordered by ascending priority Operation Result Notes x or y if x is true then x else 1 y x and y if x is false then x else 2 y not x if x is false then True 3 else False Notes 1 This is a short circuit operator so it only evaluates the second argument if the first one is false 2 This is a short circuit operator so it only evaluates the second argument if the first one is true 3 not has a lower priority than non Boolean operators so not a b is interpreted as not a b and a not b is a syntax error Comparisons There are eight comparison operations in Python They all have the same priority which is higher than that of the Boolean operations Comparisons can be chained arbitrarily for example x y z is equivalent to x y and y z except that y is evaluated only once but in both cases z is not evaluated at all when x y is found to be false This table summarizes the comparison operations Operation Meaning strictly less than less than or equal strictly greater than greater than or equal equal not equal is object identity is not negated object identity Objects of different types except different numeric types never compare equal The operator is always defined but for some object types for example class objects is equivalent to is The and operators are only defined where they make sense for example they raise a TypeError exception when one of the arguments is a complex number Non identical instances of a class normally compare as non equal unless the class defines the __eq__ method Instances of a class cannot be ordered with respect to other instances of the same class or other types of object unless the class defines enough of the methods __lt__ __le__ __gt__ and __ge__ in general __lt__ and __eq__ are sufficient if you want the conventional meanings of the comparison operators The behavior of the is and is not operators cannot be customized also they can be applied to any two objects and never raise an exception Two more operations with the same syntactic priority in and not in are supported by types that are iterable or implement the __contains__ method Numeric Types int float complex There are three distinct numeric types integers floating point numbers and complex numbers In addition Booleans are a subtype of integers Integers have unlimited precision Floating point numbers are usually implemented using double in C information about the precision and internal representation of floating point numbers for the machine on which your program is running is available in sys float_info Complex numbers have a real and imaginary part which are each a,en
884, floating point number To extract these parts from a complex number z use z real and z imag The standard library includes the additional numeric types fractions Fraction for rationals and decimal Decimal for floating point numbers with user definable precision Numbers are created by numeric literals or as the result of built in functions and operators Unadorned integer literals including hex octal and binary numbers yield integers Numeric literals containing a decimal point or an exponent sign yield floating point numbers Appending j or J to a numeric literal yields an imaginary number a complex number with a zero real part which you can add to an integer or float to get a complex number with real and imaginary parts Python fully supports mixed arithmetic when a binary arithmetic operator has operands of different numeric types the operand with the narrower type is widened to that of the other where integer is narrower than floating point which is narrower than complex A comparison between numbers of different types behaves as though the exact values of those numbers were being compared 2 The constructors int float and complex can be used to produce numbers of a specific type All numeric types except complex support the following operations for priorities of the operations see Operator precedence Operation Result Notes Full documentation x y sum of x and y x y difference of x and y x y product of x and y x y quotient of x and y x y floored quotient of x and y 1 2 x y remainder of x y 2 x x negated x x unchanged abs x absolute value or magnitude of abs x int x x converted to integer 3 6 int float x x converted to floating point 4 6 float complex re im a complex number with real part 6 complex re imaginary part im im defaults to zero c conjugate conjugate of the complex number c divmod x y the pair x y x y 2 divmod pow x y x to the power y 5 pow x y x to the power y 5 Notes 1 Also referred to as integer division For operands of type int the result has type int For operands of type float the result has type float In general the result is a whole integer though the result s type is not necessarily int The result is always rounded towards minus infinity 1 2 is 0 1 2 is 1 1 2 is 1 and 1 2 is 0 2 Not for complex numbers Instead convert to floats using abs if appropriate 3 Conversion from float to int truncates discarding the fractional part See functions math floor and math ceil for alternative conversions 4 float also accepts the strings nan and inf with an optional prefix or for Not a Number NaN and positive or negative infinity 5 Python defines pow 0 0 and 0 0 to be 1 as is common for programming languages 6 The numeric literals accepted include the digits 0 to 9 or any Unicode equivalent code points with the Nd property See the Unicode Standard for a complete list of code points with the Nd property All numbers Real types int and float also include the following operations Operation Result math trunc x x truncated to Integral round x n x rounded to n digits rounding half to even If n is omitted it defaults to 0 math floor x the greatest Integral x math ceil x the least Integral x For additional numeric operations see the math and cmath modules Bitwise Operations on Integer Types Bitwise operations only make sense for integers The result of bitwise operations is calculated as though carried out in two s complement with an infinite number of sign bits The priorities of the binary bitwise operations are all lower than the numeric operations and higher than the comparisons the unary operation has the same priority as the other unary numeric operations and This table lists the bitwise operations sorted in ascending priority Operation Result Notes x y bitwise or of x and y 4 x y bitwise exclusive or of x 4 and y x y bitwise and of x and y 4 x n x shifted left by n bits 1 2 x n x shifted right by n bits 1 3 x the bits of x inverted Notes 1 Negative shift counts are illegal and cause a ValueError to be raised 2 A left shift by n bits is equivalent to multiplication by pow 2 n 3 A right shift by n bits is equivalent to floor divisio,en
885,n by pow 2 n 4 Performing these calculations with at least one extra sign extension bit in a finite two s complement representation a working bit width of 1 max x bit_length y bit_length or more is sufficient to get the same result as if there were an infinite number of sign bits Additional Methods on Integer Types The int type implements the numbers Integral abstract base class In addition it provides a few more methods int bit_length Return the number of bits necessary to represent an integer in binary excluding the sign and leading zeros n 37 bin n 0b100101 n bit_length 6 More precisely if x is nonzero then x bit_length is the unique positive integer k such that 2 k 1 abs x 2 k Equivalently when abs x is small enough to have a correctly rounded logarithm then k 1 int log abs x 2 If x is zero then x bit_length returns 0 Equivalent to def bit_length self s bin self binary representation bin 37 0b100101 s s lstrip 0b remove leading zeros and minus sign return len s len 100101 6 New in version 3 1 int bit_count Return the number of ones in the binary representation of the absolute value of the integer This is also known as the population count Example n 19 bin n 0b10011 n bit_count 3 n bit_count 3 Equivalent to def bit_count self return bin self count 1 New in version 3 10 int to_bytes length 1 byteorder big signed False Return an array of bytes representing an integer 1024 to_bytes 2 byteorder big b x04 x00 1024 to_bytes 10 byteorder big b x00 x00 x00 x00 x00 x00 x00 x00 x04 x00 1024 to_bytes 10 byteorder big signed True b xff xff xff xff xff xff xff xff xfc x00 x 1000 x to_bytes x bit_length 7 8 byteorder little b xe8 x03 The integer is represented using length bytes and defaults to 1 An OverflowError is raised if the integer is not representable with the given number of bytes The byteorder argument determines the byte order used to represent the integer and defaults to big If byteorder is big the most significant byte is at the beginning of the byte array If byteorder is little the most significant byte is at the end of the byte array The signed argument determines whether two s complement is used to represent the integer If signed is False and a negative integer is given an OverflowError is raised The default value for signed is False The default values can be used to conveniently turn an integer into a single byte object 65 to_bytes b A However when using the default arguments don t try to convert a value greater than 255 or you ll get an OverflowError Equivalent to def to_bytes n length 1 byteorder big signed False if byteorder little order range length elif byteorder big order reversed range length else raise ValueError byteorder must be either little or big return bytes n i 8 0xff for i in order New in version 3 2 Changed in version 3 11 Added default argument values for length and byteorder classmethod int from_bytes bytes byteorder big signed False Return the integer represented by the given array of bytes int from_bytes b x00 x10 byteorder big 16 int from_bytes b x00 x10 byteorder little 4096 int from_bytes b xfc x00 byteorder big signed True 1024 int from_bytes b xfc x00 byteorder big signed False 64512 int from_bytes 255 0 0 byteorder big 16711680 The argument bytes must either be a bytes like object or an iterable producing bytes The byteorder argument determines the byte order used to represent the integer and defaults to big If byteorder is big the most significant byte is at the beginning of the byte array If byteorder is little the most significant byte is at the end of the byte array To request the native byte order of the host system use sys byteorder as the byte order value The signed argument indicates whether two s complement is used to represent the integer Equivalent to def from_bytes bytes byteorder big signed False if byteorder little little_ordered list bytes elif byteorder big little_ordered list reversed bytes else raise ValueError byteorder must be either little or big n sum b i 8 for i b in enumerate little_ordered if signed and little_ordered and little_ordered 1 0x80 n 1 8 len little_orde,en
886,red return n New in version 3 2 Changed in version 3 11 Added default argument value for byteorder int as_integer_ratio Return a pair of integers whose ratio is equal to the original integer and has a positive denominator The integer ratio of integers whole numbers is always the integer as the numerator and 1 as the denominator New in version 3 8 int is_integer Returns True Exists for duck type compatibility with float is_integer New in version 3 12 Additional Methods on Float The float type implements the numbers Real abstract base class float also has the following additional methods float as_integer_ratio Return a pair of integers whose ratio is exactly equal to the original float The ratio is in lowest terms and has a positive denominator Raises OverflowError on infinities and a ValueError on NaNs float is_integer Return True if the float instance is finite with integral value and False otherwise 2 0 is_integer True 3 2 is_integer False Two methods support conversion to and from hexadecimal strings Since Python s floats are stored internally as binary numbers converting a float to or from a decimal string usually involves a small rounding error In contrast hexadecimal strings allow exact representation and specification of floating point numbers This can be useful when debugging and in numerical work float hex Return a representation of a floating point number as a hexadecimal string For finite floating point numbers this representation will always include a leading 0x and a trailing p and exponent classmethod float fromhex s Class method to return the float represented by a hexadecimal string s The string s may have leading and trailing whitespace Note that float hex is an instance method while float fromhex is a class method A hexadecimal string takes the form sign 0x integer fraction p exponent where the optional sign may by either or integer and fraction are strings of hexadecimal digits and exponent is a decimal integer with an optional leading sign Case is not significant and there must be at least one hexadecimal digit in either the integer or the fraction This syntax is similar to the syntax specified in section 6 4 4 2 of the C99 standard and also to the syntax used in Java 1 5 onwards In particular the output of float hex is usable as a hexadecimal floating point literal in C or Java code and hexadecimal strings produced by C s a format character or Java s Double toHexString are accepted by float fromhex Note that the exponent is written in decimal rather than hexadecimal and that it gives the power of 2 by which to multiply the coefficient For example the hexadecimal string 0x3 a7p10 represents the floating point number 3 10 16 7 16 2 2 0 10 or 3740 0 float fromhex 0x3 a7p10 3740 0 Applying the reverse conversion to 3740 0 gives a different hexadecimal string representing the same number float hex 3740 0 0x1 d380000000000p 11 Hashing of numeric types For numbers x and y possibly of different types it s a requirement that hash x hash y whenever x y see the __hash__ method documentation for more details For ease of implementation and efficiency across a variety of numeric types including int float decimal Decimal and fractions Fraction Python s hash for numeric types is based on a single mathematical function that s defined for any rational number and hence applies to all instances of int and fractions Fraction and all finite instances of float and decimal Decimal Essentially this function is given by reduction modulo P for a fixed prime P The value of P is made available to Python as the modulus attribute of sys hash_info CPython implementation detail Currently the prime used is P 2 31 1 on machines with 32 bit C longs and P 2 61 1 on machines with 64 bit C longs Here are the rules in detail If x m n is a nonnegative rational number and n is not divisible by P define hash x as m invmod n P P where invmod n P gives the inverse of n modulo P If x m n is a nonnegative rational number and n is divisible by P but m is not then n has no inverse modulo P and the rule above doesn t apply in this case define hash x ,en
887,to be the constant value sys hash_info inf If x m n is a negative rational number define hash x as hash x If the resulting hash is 1 replace it with 2 The particular values sys hash_info inf and sys hash_info inf are used as hash values for positive infinity or negative infinity respectively For a complex number z the hash values of the real and imaginary parts are combined by computing hash z real sys hash_info imag hash z imag reduced modulo 2 sys hash_info width so that it lies in range 2 sys hash_info width 1 2 sys hash_info width 1 Again if the result is 1 it s replaced with 2 To clarify the above rules here s some example Python code equivalent to the built in hash for computing the hash of a rational number float or complex import sys math def hash_fraction m n Compute the hash of a rational number m n Assumes m and n are integers with n positive Equivalent to hash fractions Fraction m n P sys hash_info modulus Remove common factors of P Unnecessary if m and n already coprime while m P n P 0 m n m P n P if n P 0 hash_value sys hash_info inf else Fermat s Little Theorem pow n P 1 P is 1 so pow n P 2 P gives the inverse of n modulo P hash_value abs m P pow n P 2 P P if m 0 hash_value hash_value if hash_value 1 hash_value 2 return hash_value def hash_float x Compute the hash of a float x if math isnan x return object __hash__ x elif math isinf x return sys hash_info inf if x 0 else sys hash_info inf else return hash_fraction x as_integer_ratio def hash_complex z Compute the hash of a complex number z hash_value hash_float z real sys hash_info imag hash_float z imag do a signed reduction modulo 2 sys hash_info width M 2 sys hash_info width 1 hash_value hash_value M 1 hash_value M if hash_value 1 hash_value 2 return hash_value Boolean Type bool Booleans represent truth values The bool type has exactly two constant instances True and False The built in function bool converts any value to a boolean if the value can be interpreted as a truth value see section Truth Value Testing above For logical operations use the boolean operators and or and not When applying the bitwise operators to two booleans they return a bool equivalent to the logical operations and or xor However the logical operators and or and should be preferred over and Deprecated since version 3 12 The use of the bitwise inversion operator is deprecated and will raise an error in Python 3 14 bool is a subclass of int see Numeric Types int float complex In many numeric contexts False and True behave like the integers 0 and 1 respectively However relying on this is discouraged explicitly convert using int instead Iterator Types Python supports a concept of iteration over containers This is implemented using two distinct methods these are used to allow user defined classes to support iteration Sequences described below in more detail always support the iteration methods One method needs to be defined for container objects to provide iterable support container __iter__ Return an iterator object The object is required to support the iterator protocol described below If a container supports different types of iteration additional methods can be provided to specifically request iterators for those iteration types An example of an object supporting multiple forms of iteration would be a tree structure which supports both breadth first and depth first traversal This method corresponds to the tp_iter slot of the type structure for Python objects in the Python C API The iterator objects themselves are required to support the following two methods which together form the iterator protocol iterator __iter__ Return the iterator object itself This is required to allow both containers and iterators to be used with the for and in statements This method corresponds to the tp_iter slot of the type structure for Python objects in the Python C API iterator __next__ Return the next item from the iterator If there are no further items raise the StopIteration exception This method corresponds to the tp_iternext slot of the type structure for Python objects in the Python C API Pytho,en
888,n defines several iterator objects to support iteration over general and specific sequence types dictionaries and other more specialized forms The specific types are not important beyond their implementation of the iterator protocol Once an iterator s __next__ method raises StopIteration it must continue to do so on subsequent calls Implementations that do not obey this property are deemed broken Generator Types Python s generator s provide a convenient way to implement the iterator protocol If a container object s __iter__ method is implemented as a generator it will automatically return an iterator object technically a generator object supplying the __iter__ and __next__ methods More information about generators can be found in the documentation for the yield expression Sequence Types list tuple range There are three basic sequence types lists tuples and range objects Additional sequence types tailored for processing of binary data and text strings are described in dedicated sections Common Sequence Operations The operations in the following table are supported by most sequence types both mutable and immutable The collections abc Sequence ABC is provided to make it easier to correctly implement these operations on custom sequence types This table lists the sequence operations sorted in ascending priority In the table s and t are sequences of the same type n i j and k are integers and x is an arbitrary object that meets any type and value restrictions imposed by s The in and not in operations have the same priorities as the comparison operations The concatenation and repetition operations have the same priority as the corresponding numeric operations 3 Operation Result Notes x in s True if an item of s is 1 equal to x else False x not in s False if an item of s is 1 equal to x else True s t the concatenation of s and t 6 7 s n or n s equivalent to adding s to 2 7 itself n times s i i th item of s origin 0 3 s i j slice of s from i to j 3 4 s i j k slice of s from i to j 3 5 with step k len s length of s min s smallest item of s max s largest item of s s index x i j index of the first occurrence of 8 x in s at or after index i and before index j s count x total number of occurrences of x in s Sequences of the same type also support comparisons In particular tuples and lists are compared lexicographically by comparing corresponding elements This means that to compare equal every element must compare equal and the two sequences must be of the same type and have the same length For full details see Comparisons in the language reference Forward and reversed iterators over mutable sequences access values using an index That index will continue to march forward or backward even if the underlying sequence is mutated The iterator terminates only when an IndexError or a StopIteration is encountered or when the index drops below zero Notes 1 While the in and not in operations are used only for simple containment testing in the general case some specialised sequences such as str bytes and bytearray also use them for subsequence testing gg in eggs True 2 Values of n less than 0 are treated as 0 which yields an empty sequence of the same type as s Note that items in the sequence s are not copied they are referenced multiple times This often haunts new Python programmers consider lists 3 lists lists 0 append 3 lists 3 3 3 What has happened is that is a one element list containing an empty list so all three elements of 3 are references to this single empty list Modifying any of the elements of lists modifies this single list You can create a list of different lists this way lists for i in range 3 lists 0 append 3 lists 1 append 5 lists 2 append 7 lists 3 5 7 Further explanation is available in the FAQ entry How do I create a multidimensional list 3 If i or j is negative the index is relative to the end of sequence s len s i or len s j is substituted But note that 0 is still 0 4 The slice of s from i to j is defined as the sequence of items with index k such that i k j If i or j is greater than len s use len s If i is omitted or None us,en
889,e 0 If j is omitted or None use len s If i is greater than or equal to j the slice is empty 5 The slice of s from i to j with step k is defined as the sequence of items with index x i n k such that 0 n j i k In other words the indices are i i k i 2 k i 3 k and so on stopping when j is reached but never including j When k is positive i and j are reduced to len s if they are greater When k is negative i and j are reduced to len s 1 if they are greater If i or j are omitted or None they become end values which end depends on the sign of k Note k cannot be zero If k is None it is treated like 1 6 Concatenating immutable sequences always results in a new object This means that building up a sequence by repeated concatenation will have a quadratic runtime cost in the total sequence length To get a linear runtime cost you must switch to one of the alternatives below if concatenating str objects you can build a list and use str join at the end or else write to an io StringIO instance and retrieve its value when complete if concatenating bytes objects you can similarly use bytes join or io BytesIO or you can do in place concatenation with a bytearray object bytearray objects are mutable and have an efficient overallocation mechanism if concatenating tuple objects extend a list instead for other types investigate the relevant class documentation 7 Some sequence types such as range only support item sequences that follow specific patterns and hence don t support sequence concatenation or repetition 8 index raises ValueError when x is not found in s Not all implementations support passing the additional arguments i and j These arguments allow efficient searching of subsections of the sequence Passing the extra arguments is roughly equivalent to using s i j index x only without copying any data and with the returned index being relative to the start of the sequence rather than the start of the slice Immutable Sequence Types The only operation that immutable sequence types generally implement that is not also implemented by mutable sequence types is support for the hash built in This support allows immutable sequences such as tuple instances to be used as dict keys and stored in set and frozenset instances Attempting to hash an immutable sequence that contains unhashable values will result in TypeError Mutable Sequence Types The operations in the following table are defined on mutable sequence types The collections abc MutableSequence ABC is provided to make it easier to correctly implement these operations on custom sequence types In the table s is an instance of a mutable sequence type t is any iterable object and x is an arbitrary object that meets any type and value restrictions imposed by s for example bytearray only accepts integers that meet the value restriction 0 x 255 Operation Result Notes s i x item i of s is replaced by x s i j t slice of s from i to j is replaced by the contents of the iterable t del s i j same as s i j s i j k t the elements of s i j k are 1 replaced by those of t del s i j k removes the elements of s i j k from the list s append x appends x to the end of the sequence same as s len s len s x s clear removes all items from s same 5 as del s s copy creates a shallow copy of s 5 same as s s extend t or s t extends s with the contents of t for the most part the same as s len s len s t s n updates s with its contents 6 repeated n times s insert i x inserts x into s at the index given by i same as s i i x s pop or s pop i retrieves the item at i and 2 also removes it from s s remove x remove the first item from s 3 where s i is equal to x s reverse reverses the items of s in 4 place Notes 1 t must have the same length as the slice it is replacing 2 The optional argument i defaults to 1 so that by default the last item is removed and returned 3 remove raises ValueError when x is not found in s 4 The reverse method modifies the sequence in place for economy of space when reversing a large sequence To remind users that it operates by side effect it does not return the reversed sequence 5 clear and copy are inclu,en
890,ded for consistency with the interfaces of mutable containers that don t support slicing operations such as dict and set copy is not part of the collections abc MutableSequence ABC but most concrete mutable sequence classes provide it New in version 3 3 clear and copy methods 6 The value n is an integer or an object implementing __index__ Zero and negative values of n clear the sequence Items in the sequence are not copied they are referenced multiple times as explained for s n under Common Sequence Operations Lists Lists are mutable sequences typically used to store collections of homogeneous items where the precise degree of similarity will vary by application class list iterable Lists may be constructed in several ways Using a pair of square brackets to denote the empty list Using square brackets separating items with commas a a b c Using a list comprehension x for x in iterable Using the type constructor list or list iterable The constructor builds a list whose items are the same and in the same order as iterable s items iterable may be either a sequence a container that supports iteration or an iterator object If iterable is already a list a copy is made and returned similar to iterable For example list abc returns a b c and list 1 2 3 returns 1 2 3 If no argument is given the constructor creates a new empty list Many other operations also produce lists including the sorted built in Lists implement all of the common and mutable sequence operations Lists also provide the following additional method sort key None reverse False This method sorts the list in place using only comparisons between items Exceptions are not suppressed if any comparison operations fail the entire sort operation will fail and the list will likely be left in a partially modified state sort accepts two arguments that can only be passed by keyword keyword only arguments key specifies a function of one argument that is used to extract a comparison key from each list element for example key str lower The key corresponding to each item in the list is calculated once and then used for the entire sorting process The default value of None means that list items are sorted directly without calculating a separate key value The functools cmp_to_key utility is available to convert a 2 x style cmp function to a key function reverse is a boolean value If set to True then the list elements are sorted as if each comparison were reversed This method modifies the sequence in place for economy of space when sorting a large sequence To remind users that it operates by side effect it does not return the sorted sequence use sorted to explicitly request a new sorted list instance The sort method is guaranteed to be stable A sort is stable if it guarantees not to change the relative order of elements that compare equal this is helpful for sorting in multiple passes for example sort by department then by salary grade For sorting examples and a brief sorting tutorial see Sorting Techniques CPython implementation detail While a list is being sorted the effect of attempting to mutate or even inspect the list is undefined The C implementation of Python makes the list appear empty for the duration and raises ValueError if it can detect that the list has been mutated during a sort Tuples Tuples are immutable sequences typically used to store collections of heterogeneous data such as the 2 tuples produced by the enumerate built in Tuples are also used for cases where an immutable sequence of homogeneous data is needed such as allowing storage in a set or dict instance class tuple iterable Tuples may be constructed in a number of ways Using a pair of parentheses to denote the empty tuple Using a trailing comma for a singleton tuple a or a Separating items with commas a b c or a b c Using the tuple built in tuple or tuple iterable The constructor builds a tuple whose items are the same and in the same order as iterable s items iterable may be either a sequence a container that supports iteration or an iterator object If iterable is already a tuple it is returned unchanged For ex,en
891,ample tuple abc returns a b c and tuple 1 2 3 returns 1 2 3 If no argument is given the constructor creates a new empty tuple Note that it is actually the comma which makes a tuple not the parentheses The parentheses are optional except in the empty tuple case or when they are needed to avoid syntactic ambiguity For example f a b c is a function call with three arguments while f a b c is a function call with a 3 tuple as the sole argument Tuples implement all of the common sequence operations For heterogeneous collections of data where access by name is clearer than access by index collections namedtuple may be a more appropriate choice than a simple tuple object Ranges The range type represents an immutable sequence of numbers and is commonly used for looping a specific number of times in for loops class range stop class range start stop step The arguments to the range constructor must be integers either built in int or any object that implements the __index__ special method If the step argument is omitted it defaults to 1 If the start argument is omitted it defaults to 0 If step is zero ValueError is raised For a positive step the contents of a range r are determined by the formula r i start step i where i 0 and r i stop For a negative step the contents of the range are still determined by the formula r i start step i but the constraints are i 0 and r i stop A range object will be empty if r 0 does not meet the value constraint Ranges do support negative indices but these are interpreted as indexing from the end of the sequence determined by the positive indices Ranges containing absolute values larger than sys maxsize are permitted but some features such as len may raise OverflowError Range examples list range 10 0 1 2 3 4 5 6 7 8 9 list range 1 11 1 2 3 4 5 6 7 8 9 10 list range 0 30 5 0 5 10 15 20 25 list range 0 10 3 0 3 6 9 list range 0 10 1 0 1 2 3 4 5 6 7 8 9 list range 0 list range 1 0 Ranges implement all of the common sequence operations except concatenation and repetition due to the fact that range objects can only represent sequences that follow a strict pattern and repetition and concatenation will usually violate that pattern start The value of the start parameter or 0 if the parameter was not supplied stop The value of the stop parameter step The value of the step parameter or 1 if the parameter was not supplied The advantage of the range type over a regular list or tuple is that a range object will always take the same small amount of memory no matter the size of the range it represents as it only stores the start stop and step values calculating individual items and subranges as needed Range objects implement the collections abc Sequence ABC and provide features such as containment tests element index lookup slicing and support for negative indices see Sequence Types list tuple range r range 0 20 2 r range 0 20 2 11 in r False 10 in r True r index 10 5 r 5 10 r 5 range 0 10 2 r 1 18 Testing range objects for equality with and compares them as sequences That is two range objects are considered equal if they represent the same sequence of values Note that two range objects that compare equal might have different start stop and step attributes for example range 0 range 2 1 3 or range 0 3 2 range 0 4 2 Changed in version 3 2 Implement the Sequence ABC Support slicing and negative indices Test int objects for membership in constant time instead of iterating through all items Changed in version 3 3 Define and to compare range objects based on the sequence of values they define instead of comparing based on object identity Added the start stop and step attributes See also The linspace recipe shows how to implement a lazy version of range suitable for floating point applications Text Sequence Type str Textual data in Python is handled with str objects or strings Strings are immutable sequences of Unicode code points String literals are written in a variety of ways Single quotes allows embedded double quotes Double quotes allows embedded single quotes Triple quoted Three single quotes Three double quotes Triple,en
892, quoted strings may span multiple lines all associated whitespace will be included in the string literal String literals that are part of a single expression and have only whitespace between them will be implicitly converted to a single string literal That is spam eggs spam eggs See String and Bytes literals for more about the various forms of string literal including supported escape sequences and the r raw prefix that disables most escape sequence processing Strings may also be created from other objects using the str constructor Since there is no separate character type indexing a string produces strings of length 1 That is for a non empty string s s 0 s 0 1 There is also no mutable string type but str join or io StringIO can be used to efficiently construct strings from multiple fragments Changed in version 3 3 For backwards compatibility with the Python 2 series the u prefix is once again permitted on string literals It has no effect on the meaning of string literals and cannot be combined with the r prefix class str object class str object b encoding utf 8 errors strict Return a string version of object If object is not provided returns the empty string Otherwise the behavior of str depends on whether encoding or errors is given as follows If neither encoding nor errors is given str object returns type object __str__ object which is the informal or nicely printable string representation of object For string objects this is the string itself If object does not have a __str__ method then str falls back to returning repr object If at least one of encoding or errors is given object should be a bytes like object e g bytes or bytearray In this case if object is a bytes or bytearray object then str bytes encoding errors is equivalent to bytes decode encoding errors Otherwise the bytes object underlying the buffer object is obtained before calling bytes decode See Binary Sequence Types bytes bytearray memoryview and Buffer Protocol for information on buffer objects Passing a bytes object to str without the encoding or errors arguments falls under the first case of returning the informal string representation see also the b command line option to Python For example str b Zoot b Zoot For more information on the str class and its methods see Text Sequence Type str and the String Methods section below To output formatted strings see the f strings and Format String Syntax sections In addition see the Text Processing Services section String Methods Strings implement all of the common sequence operations along with the additional methods described below Strings also support two styles of string formatting one providing a large degree of flexibility and customization see str format Format String Syntax and Custom String Formatting and the other based on C printf style formatting that handles a narrower range of types and is slightly harder to use correctly but is often faster for the cases it can handle printf style String Formatting The Text Processing Services section of the standard library covers a number of other modules that provide various text related utilities including regular expression support in the re module str capitalize Return a copy of the string with its first character capitalized and the rest lowercased Changed in version 3 8 The first character is now put into titlecase rather than uppercase This means that characters like digraphs will only have their first letter capitalized instead of the full character str casefold Return a casefolded copy of the string Casefolded strings may be used for caseless matching Casefolding is similar to lowercasing but more aggressive because it is intended to remove all case distinctions in a string For example the German lowercase letter ß is equivalent to ss Since it is already lowercase lower would do nothing to ß casefold converts it to ss The casefolding algorithm is described in section 3 13 Default Case Folding of the Unicode Standard New in version 3 3 str center width fillchar Return centered in a string of length width Padding is done using the specified fillchar def,en
893,ault is an ASCII space The original string is returned if width is less than or equal to len s str count sub start end Return the number of non overlapping occurrences of substring sub in the range start end Optional arguments start and end are interpreted as in slice notation If sub is empty returns the number of empty strings between characters which is the length of the string plus one str encode encoding utf 8 errors strict Return the string encoded to bytes encoding defaults to utf 8 see Standard Encodings for possible values errors controls how encoding errors are handled If strict the default a UnicodeError exception is raised Other possible values are ignore replace xmlcharrefreplace backslashreplace and any other name registered via codecs register_error See Error Handlers for details For performance reasons the value of errors is not checked for validity unless an encoding error actually occurs Python Development Mode is enabled or a debug build is used Changed in version 3 1 Added support for keyword arguments Changed in version 3 9 The value of the errors argument is now checked in Python Development Mode and in debug mode str endswith suffix start end Return True if the string ends with the specified suffix otherwise return False suffix can also be a tuple of suffixes to look for With optional start test beginning at that position With optional end stop comparing at that position str expandtabs tabsize 8 Return a copy of the string where all tab characters are replaced by one or more spaces depending on the current column and the given tab size Tab positions occur every tabsize characters default is 8 giving tab positions at columns 0 8 16 and so on To expand the string the current column is set to zero and the string is examined character by character If the character is a tab t one or more space characters are inserted in the result until the current column is equal to the next tab position The tab character itself is not copied If the character is a newline n or return r it is copied and the current column is reset to zero Any other character is copied unchanged and the current column is incremented by one regardless of how the character is represented when printed 01 t012 t0123 t01234 expandtabs 01 012 0123 01234 01 t012 t0123 t01234 expandtabs 4 01 012 0123 01234 str find sub start end Return the lowest index in the string where substring sub is found within the slice s start end Optional arguments start and end are interpreted as in slice notation Return 1 if sub is not found Note The find method should be used only if you need to know the position of sub To check if sub is a substring or not use the in operator Py in Python True str format args kwargs Perform a string formatting operation The string on which this method is called can contain literal text or replacement fields delimited by braces Each replacement field contains either the numeric index of a positional argument or the name of a keyword argument Returns a copy of the string where each replacement field is replaced with the string value of the corresponding argument The sum of 1 2 is 0 format 1 2 The sum of 1 2 is 3 See Format String Syntax for a description of the various formatting options that can be specified in format strings Note When formatting a number int float complex decimal Decimal and subclasses with the n type ex n format 1234 the function temporarily sets the LC_CTYPE locale to the LC_NUMERIC locale to decode decimal_point and thousands_sep fields of localeconv if they are non ASCII or longer than 1 byte and the LC_NUMERIC locale is different than the LC_CTYPE locale This temporary change affects other threads Changed in version 3 7 When formatting a number with the n type the function sets temporarily the LC_CTYPE locale to the LC_NUMERIC locale in some cases str format_map mapping Similar to str format mapping except that mapping is used directly and not copied to a dict This is useful if for example mapping is a dict subclass class Default dict def __missing__ self key return key name was born in country format_map Defau,en
894,lt name Guido Guido was born in country New in version 3 2 str index sub start end Like find but raise ValueError when the substring is not found str isalnum Return True if all characters in the string are alphanumeric and there is at least one character False otherwise A character c is alphanumeric if one of the following returns True c isalpha c isdecimal c isdigit or c isnumeric str isalpha Return True if all characters in the string are alphabetic and there is at least one character False otherwise Alphabetic characters are those characters defined in the Unicode character database as Letter i e those with general category property being one of Lm Lt Lu Ll or Lo Note that this is different from the Alphabetic property defined in the section 4 10 Letters Alphabetic and Ideographic of the Unicode Standard str isascii Return True if the string is empty or all characters in the string are ASCII False otherwise ASCII characters have code points in the range U 0000 U 007F New in version 3 7 str isdecimal Return True if all characters in the string are decimal characters and there is at least one character False otherwise Decimal characters are those that can be used to form numbers in base 10 e g U 0660 ARABIC INDIC DIGIT ZERO Formally a decimal character is a character in the Unicode General Category Nd str isdigit Return True if all characters in the string are digits and there is at least one character False otherwise Digits include decimal characters and digits that need special handling such as the compatibility superscript digits This covers digits which cannot be used to form numbers in base 10 like the Kharosthi numbers Formally a digit is a character that has the property value Numeric_Type Digit or Numeric_Type Decimal str isidentifier Return True if the string is a valid identifier according to the language definition section Identifiers and keywords keyword iskeyword can be used to test whether string s is a reserved identifier such as def and class Example from keyword import iskeyword hello isidentifier iskeyword hello True False def isidentifier iskeyword def True True str islower Return True if all cased characters 4 in the string are lowercase and there is at least one cased character False otherwise str isnumeric Return True if all characters in the string are numeric characters and there is at least one character False otherwise Numeric characters include digit characters and all characters that have the Unicode numeric value property e g U 2155 VULGAR FRACTION ONE FIFTH Formally numeric characters are those with the property value Numeric_Type Digit Numeric_Type Decimal or Numeric_Type Numeric str isprintable Return True if all characters in the string are printable or the string is empty False otherwise Nonprintable characters are those characters defined in the Unicode character database as Other or Separator excepting the ASCII space 0x20 which is considered printable Note that printable characters in this context are those which should not be escaped when repr is invoked on a string It has no bearing on the handling of strings written to sys stdout or sys stderr str isspace Return True if there are only whitespace characters in the string and there is at least one character False otherwise A character is whitespace if in the Unicode character database see unicodedata either its general category is Zs Separator space or its bidirectional class is one of WS B or S str istitle Return True if the string is a titlecased string and there is at least one character for example uppercase characters may only follow uncased characters and lowercase characters only cased ones Return False otherwise str isupper Return True if all cased characters 4 in the string are uppercase and there is at least one cased character False otherwise BANANA isupper True banana isupper False baNana isupper False isupper False str join iterable Return a string which is the concatenation of the strings in iterable A TypeError will be raised if there are any non string values in iterable including bytes objects The separator between ,en
895,elements is the string providing this method str ljust width fillchar Return the string left justified in a string of length width Padding is done using the specified fillchar default is an ASCII space The original string is returned if width is less than or equal to len s str lower Return a copy of the string with all the cased characters 4 converted to lowercase The lowercasing algorithm used is described in section 3 13 Default Case Folding of the Unicode Standard str lstrip chars Return a copy of the string with leading characters removed The chars argument is a string specifying the set of characters to be removed If omitted or None the chars argument defaults to removing whitespace The chars argument is not a prefix rather all combinations of its values are stripped spacious lstrip spacious www example com lstrip cmowz example com See str removeprefix for a method that will remove a single prefix string rather than all of a set of characters For example Arthur three lstrip Arthur ee Arthur three removeprefix Arthur three static str maketrans x y z This static method returns a translation table usable for str translate If there is only one argument it must be a dictionary mapping Unicode ordinals integers or characters strings of length 1 to Unicode ordinals strings of arbitrary lengths or None Character keys will then be converted to ordinals If there are two arguments they must be strings of equal length and in the resulting dictionary each character in x will be mapped to the character at the same position in y If there is a third argument it must be a string whose characters will be mapped to None in the result str partition sep Split the string at the first occurrence of sep and return a 3 tuple containing the part before the separator the separator itself and the part after the separator If the separator is not found return a 3 tuple containing the string itself followed by two empty strings str removeprefix prefix If the string starts with the prefix string return string len prefix Otherwise return a copy of the original string TestHook removeprefix Test Hook BaseTestCase removeprefix Test BaseTestCase New in version 3 9 str removesuffix suffix If the string ends with the suffix string and that suffix is not empty return string len suffix Otherwise return a copy of the original string MiscTests removesuffix Tests Misc TmpDirMixin removesuffix Tests TmpDirMixin New in version 3 9 str replace old new count Return a copy of the string with all occurrences of substring old replaced by new If the optional argument count is given only the first count occurrences are replaced str rfind sub start end Return the highest index in the string where substring sub is found such that sub is contained within s start end Optional arguments start and end are interpreted as in slice notation Return 1 on failure str rindex sub start end Like rfind but raises ValueError when the substring sub is not found str rjust width fillchar Return the string right justified in a string of length width Padding is done using the specified fillchar default is an ASCII space The original string is returned if width is less than or equal to len s str rpartition sep Split the string at the last occurrence of sep and return a 3 tuple containing the part before the separator the separator itself and the part after the separator If the separator is not found return a 3 tuple containing two empty strings followed by the string itself str rsplit sep None maxsplit 1 Return a list of the words in the string using sep as the delimiter string If maxsplit is given at most maxsplit splits are done the rightmost ones If sep is not specified or None any whitespace string is a separator Except for splitting from the right rsplit behaves like split which is described in detail below str rstrip chars Return a copy of the string with trailing characters removed The chars argument is a string specifying the set of characters to be removed If omitted or None the chars argument defaults to removing whitespace The chars argument is not a suffix rather all combination,en
896,s of its values are stripped spacious rstrip spacious mississippi rstrip ipz mississ See str removesuffix for a method that will remove a single suffix string rather than all of a set of characters For example Monty Python rstrip Python M Monty Python removesuffix Python Monty str split sep None maxsplit 1 Return a list of the words in the string using sep as the delimiter string If maxsplit is given at most maxsplit splits are done thus the list will have at most maxsplit 1 elements If maxsplit is not specified or 1 then there is no limit on the number of splits all possible splits are made If sep is given consecutive delimiters are not grouped together and are deemed to delimit empty strings for example 1 2 split returns 1 2 The sep argument may consist of multiple characters for example 1 2 3 split returns 1 2 3 Splitting an empty string with a specified separator returns For example 1 2 3 split 1 2 3 1 2 3 split maxsplit 1 1 2 3 1 2 3 split 1 2 3 If sep is not specified or is None a different splitting algorithm is applied runs of consecutive whitespace are regarded as a single separator and the result will contain no empty strings at the start or end if the string has leading or trailing whitespace Consequently splitting an empty string or a string consisting of just whitespace with a None separator returns For example 1 2 3 split 1 2 3 1 2 3 split maxsplit 1 1 2 3 1 2 3 split 1 2 3 str splitlines keepends False Return a list of the lines in the string breaking at line boundaries Line breaks are not included in the resulting list unless keepends is given and true This method splits on the following line boundaries In particular the boundaries are a superset of universal newlines Representation Description n Line Feed r Carriage Return r n Carriage Return Line Feed v or x0b Line Tabulation f or x0c Form Feed x1c File Separator x1d Group Separator x1e Record Separator x85 Next Line C1 Control Code u2028 Line Separator u2029 Paragraph Separator Changed in version 3 2 v and f added to list of line boundaries For example ab c n nde fg rkl r n splitlines ab c de fg kl ab c n nde fg rkl r n splitlines keepends True ab c n n de fg r kl r n Unlike split when a delimiter string sep is given this method returns an empty list for the empty string and a terminal line break does not result in an extra line splitlines One line n splitlines One line For comparison split n gives split n Two lines n split n Two lines str startswith prefix start end Return True if string starts with the prefix otherwise return False prefix can also be a tuple of prefixes to look for With optional start test string beginning at that position With optional end stop comparing string at that position str strip chars Return a copy of the string with the leading and trailing characters removed The chars argument is a string specifying the set of characters to be removed If omitted or None the chars argument defaults to removing whitespace The chars argument is not a prefix or suffix rather all combinations of its values are stripped spacious strip spacious www example com strip cmowz example The outermost leading and trailing chars argument values are stripped from the string Characters are removed from the leading end until reaching a string character that is not contained in the set of characters in chars A similar action takes place on the trailing end For example comment_string Section 3 2 1 Issue 32 comment_string strip Section 3 2 1 Issue 32 str swapcase Return a copy of the string with uppercase characters converted to lowercase and vice versa Note that it is not necessarily true that s swapcase swapcase s str title Return a titlecased version of the string where words start with an uppercase character and the remaining characters are lowercase For example Hello world title Hello World The algorithm uses a simple language independent definition of a word as groups of consecutive letters The definition works in many contexts but it means that apostrophes in contractions and possessives form word boundaries which may not be the desired result they re b,en
897,ill s friends from the UK title They Re Bill S Friends From The Uk The string capwords function does not have this problem as it splits words on spaces only Alternatively a workaround for apostrophes can be constructed using regular expressions import re def titlecase s return re sub r A Za z A Za z lambda mo mo group 0 capitalize s titlecase they re bill s friends They re Bill s Friends str translate table Return a copy of the string in which each character has been mapped through the given translation table The table must be an object that implements indexing via __getitem__ typically a mapping or sequence When indexed by a Unicode ordinal an integer the table object can do any of the following return a Unicode ordinal or a string to map the character to one or more other characters return None to delete the character from the return string or raise a LookupError exception to map the character to itself You can use str maketrans to create a translation map from character to character mappings in different formats See also the codecs module for a more flexible approach to custom character mappings str upper Return a copy of the string with all the cased characters 4 converted to uppercase Note that s upper isupper might be False if s contains uncased characters or if the Unicode category of the resulting character s is not Lu Letter uppercase but e g Lt Letter titlecase The uppercasing algorithm used is described in section 3 13 Default Case Folding of the Unicode Standard str zfill width Return a copy of the string left filled with ASCII 0 digits to make a string of length width A leading sign prefix is handled by inserting the padding after the sign character rather than before The original string is returned if width is less than or equal to len s For example 42 zfill 5 00042 42 zfill 5 0042 printf style String Formatting Note The formatting operations described here exhibit a variety of quirks that lead to a number of common errors such as failing to display tuples and dictionaries correctly Using the newer formatted string literals the str format interface or template strings may help avoid these errors Each of these alternatives provides their own trade offs and benefits of simplicity flexibility and or extensibility String objects have one unique built in operation the operator modulo This is also known as the string formatting or interpolation operator Given format values where format is a string conversion specifications in format are replaced with zero or more elements of values The effect is similar to using the sprintf in the C language If format requires a single argument values may be a single non tuple object 5 Otherwise values must be a tuple with exactly the number of items specified by the format string or a single mapping object for example a dictionary A conversion specifier contains two or more characters and has the following components which must occur in this order 1 The character which marks the start of the specifier 2 Mapping key optional consisting of a parenthesised sequence of characters for example somename 3 Conversion flags optional which affect the result of some conversion types 4 Minimum field width optional If specified as an asterisk the actual width is read from the next element of the tuple in values and the object to convert comes after the minimum field width and optional precision 5 Precision optional given as a dot followed by the precision If specified as an asterisk the actual precision is read from the next element of the tuple in values and the value to convert comes after the precision 6 Length modifier optional 7 Conversion type When the right argument is a dictionary or other mapping type then the formats in the string must include a parenthesised mapping key into that dictionary inserted immediately after the character The mapping key selects the value to be formatted from the mapping For example print language s has number 03d quote types language Python number 2 Python has 002 quote types In this case no specifiers may occur in a format since they require a sequentia,en
898,l parameter list The conversion flag characters are Flag Meaning The value conversion will use the alternate form where defined below 0 The conversion will be zero padded for numeric values The converted value is left adjusted overrides the 0 conversion if both are given a space A blank should be left before a positive number or empty string produced by a signed conversion A sign character or will precede the conversion overrides a space flag A length modifier h l or L may be present but is ignored as it is not necessary for Python so e g ld is identical to d The conversion types are Conversion Meaning Notes d Signed integer decimal i Signed integer decimal o Signed octal value 1 u Obsolete type it is identical to d 6 x Signed hexadecimal lowercase 2 X Signed hexadecimal uppercase 2 e Floating point exponential format lowercase 3 E Floating point exponential format uppercase 3 f Floating point decimal format 3 F Floating point decimal format 3 g Floating point format Uses lowercase exponential 4 format if exponent is less than 4 or not less than precision decimal format otherwise G Floating point format Uses uppercase exponential 4 format if exponent is less than 4 or not less than precision decimal format otherwise c Single character accepts integer or single character string r String converts any Python object using repr 5 s String converts any Python object using str 5 a String converts any Python object using ascii 5 No argument is converted results in a character in the result Notes 1 The alternate form causes a leading octal specifier 0o to be inserted before the first digit 2 The alternate form causes a leading 0x or 0X depending on whether the x or X format was used to be inserted before the first digit 3 The alternate form causes the result to always contain a decimal point even if no digits follow it The precision determines the number of digits after the decimal point and defaults to 6 4 The alternate form causes the result to always contain a decimal point and trailing zeroes are not removed as they would otherwise be The precision determines the number of significant digits before and after the decimal point and defaults to 6 5 If precision is N the output is truncated to N characters 6 See PEP 237 Since Python strings have an explicit length s conversions do not assume that 0 is the end of the string Changed in version 3 1 f conversions for numbers whose absolute value is over 1e50 are no longer replaced by g conversions Binary Sequence Types bytes bytearray memoryview The core built in types for manipulating binary data are bytes and bytearray They are supported by memoryview which uses the buffer protocol to access the memory of other binary objects without needing to make a copy The array module supports efficient storage of basic data types like 32 bit integers and IEEE754 double precision floating values Bytes Objects Bytes objects are immutable sequences of single bytes Since many major binary protocols are based on the ASCII text encoding bytes objects offer several methods that are only valid when working with ASCII compatible data and are closely related to string objects in a variety of other ways class bytes source encoding errors Firstly the syntax for bytes literals is largely the same as that for string literals except that a b prefix is added Single quotes b still allows embedded double quotes Double quotes b still allows embedded single quotes Triple quoted b 3 single quotes b 3 double quotes Only ASCII characters are permitted in bytes literals regardless of the declared source code encoding Any binary values over 127 must be entered into bytes literals using the appropriate escape sequence As with string literals bytes literals may also use a r prefix to disable processing of escape sequences See String and Bytes literals for more about the various forms of bytes literal including supported escape sequences While bytes literals and representations are based on ASCII text bytes objects actually behave like immutable sequences of integers with each value in the sequence restricted such that ,en
899,0 x 256 attempts to violate this restriction will trigger ValueError This is done deliberately to emphasise that while many binary formats include ASCII based elements and can be usefully manipulated with some text oriented algorithms this is not generally the case for arbitrary binary data blindly applying text processing algorithms to binary data formats that are not ASCII compatible will usually lead to data corruption In addition to the literal forms bytes objects can be created in a number of other ways A zero filled bytes object of a specified length bytes 10 From an iterable of integers bytes range 20 Copying existing binary data via the buffer protocol bytes obj Also see the bytes built in Since 2 hexadecimal digits correspond precisely to a single byte hexadecimal numbers are a commonly used format for describing binary data Accordingly the bytes type has an additional class method to read data in that format classmethod fromhex string This bytes class method returns a bytes object decoding the given string object The string must contain two hexadecimal digits per byte with ASCII whitespace being ignored bytes fromhex 2Ef0 F1f2 b xf0 xf1 xf2 Changed in version 3 7 bytes fromhex now skips all ASCII whitespace in the string not just spaces A reverse conversion function exists to transform a bytes object into its hexadecimal representation hex sep bytes_per_sep Return a string object containing two hexadecimal digits for each byte in the instance b xf0 xf1 xf2 hex f0f1f2 If you want to make the hex string easier to read you can specify a single character separator sep parameter to include in the output By default this separator will be included between each byte A second optional bytes_per_sep parameter controls the spacing Positive values calculate the separator position from the right negative values from the left value b xf0 xf1 xf2 value hex f0 f1 f2 value hex _ 2 f0_f1f2 b UUDDLRLRAB hex 4 55554444 4c524c52 4142 New in version 3 5 Changed in version 3 8 bytes hex now supports optional sep and bytes_per_sep parameters to insert separators between bytes in the hex output Since bytes objects are sequences of integers akin to a tuple for a bytes object b b 0 will be an integer while b 0 1 will be a bytes object of length 1 This contrasts with text strings where both indexing and slicing will produce a string of length 1 The representation of bytes objects uses the literal format b since it is often more useful than e g bytes 46 46 46 You can always convert a bytes object into a list of integers using list b Bytearray Objects bytearray objects are a mutable counterpart to bytes objects class bytearray source encoding errors There is no dedicated literal syntax for bytearray objects instead they are always created by calling the constructor Creating an empty instance bytearray Creating a zero filled instance with a given length bytearray 10 From an iterable of integers bytearray range 20 Copying existing binary data via the buffer protocol bytearray b Hi As bytearray objects are mutable they support the mutable sequence operations in addition to the common bytes and bytearray operations described in Bytes and Bytearray Operations Also see the bytearray built in Since 2 hexadecimal digits correspond precisely to a single byte hexadecimal numbers are a commonly used format for describing binary data Accordingly the bytearray type has an additional class method to read data in that format classmethod fromhex string This bytearray class method returns bytearray object decoding the given string object The string must contain two hexadecimal digits per byte with ASCII whitespace being ignored bytearray fromhex 2Ef0 F1f2 bytearray b xf0 xf1 xf2 Changed in version 3 7 bytearray fromhex now skips all ASCII whitespace in the string not just spaces A reverse conversion function exists to transform a bytearray object into its hexadecimal representation hex sep bytes_per_sep Return a string object containing two hexadecimal digits for each byte in the instance bytearray b xf0 xf1 xf2 hex f0f1f2 New in version 3 5 Changed in vers,en
900,ion 3 8 Similar to bytes hex bytearray hex now supports optional sep and bytes_per_sep parameters to insert separators between bytes in the hex output Since bytearray objects are sequences of integers akin to a list for a bytearray object b b 0 will be an integer while b 0 1 will be a bytearray object of length 1 This contrasts with text strings where both indexing and slicing will produce a string of length 1 The representation of bytearray objects uses the bytes literal format bytearray b since it is often more useful than e g bytearray 46 46 46 You can always convert a bytearray object into a list of integers using list b Bytes and Bytearray Operations Both bytes and bytearray objects support the common sequence operations They interoperate not just with operands of the same type but with any bytes like object Due to this flexibility they can be freely mixed in operations without causing errors However the return type of the result may depend on the order of operands Note The methods on bytes and bytearray objects don t accept strings as their arguments just as the methods on strings don t accept bytes as their arguments For example you have to write a abc b a replace a f and a b abc b a replace b a b f Some bytes and bytearray operations assume the use of ASCII compatible binary formats and hence should be avoided when working with arbitrary binary data These restrictions are covered below Note Using these ASCII based operations to manipulate binary data that is not stored in an ASCII based format may lead to data corruption The following methods on bytes and bytearray objects can be used with arbitrary binary data bytes count sub start end bytearray count sub start end Return the number of non overlapping occurrences of subsequence sub in the range start end Optional arguments start and end are interpreted as in slice notation The subsequence to search for may be any bytes like object or an integer in the range 0 to 255 If sub is empty returns the number of empty slices between characters which is the length of the bytes object plus one Changed in version 3 3 Also accept an integer in the range 0 to 255 as the subsequence bytes removeprefix prefix bytearray removeprefix prefix If the binary data starts with the prefix string return bytes len prefix Otherwise return a copy of the original binary data b TestHook removeprefix b Test b Hook b BaseTestCase removeprefix b Test b BaseTestCase The prefix may be any bytes like object Note The bytearray version of this method does not operate in place it always produces a new object even if no changes were made New in version 3 9 bytes removesuffix suffix bytearray removesuffix suffix If the binary data ends with the suffix string and that suffix is not empty return bytes len suffix Otherwise return a copy of the original binary data b MiscTests removesuffix b Tests b Misc b TmpDirMixin removesuffix b Tests b TmpDirMixin The suffix may be any bytes like object Note The bytearray version of this method does not operate in place it always produces a new object even if no changes were made New in version 3 9 bytes decode encoding utf 8 errors strict bytearray decode encoding utf 8 errors strict Return the bytes decoded to a str encoding defaults to utf 8 see Standard Encodings for possible values errors controls how decoding errors are handled If strict the default a UnicodeError exception is raised Other possible values are ignore replace and any other name registered via codecs register_error See Error Handlers for details For performance reasons the value of errors is not checked for validity unless a decoding error actually occurs Python Development Mode is enabled or a debug build is used Note Passing the encoding argument to str allows decoding any bytes like object directly without needing to make a temporary bytes or bytearray object Changed in version 3 1 Added support for keyword arguments Changed in version 3 9 The value of the errors argument is now checked in Python Development Mode and in debug mode bytes endswith suffix start end bytearray endswith suffix start en,en
901,d Return True if the binary data ends with the specified suffix otherwise return False suffix can also be a tuple of suffixes to look for With optional start test beginning at that position With optional end stop comparing at that position The suffix es to search for may be any bytes like object bytes find sub start end bytearray find sub start end Return the lowest index in the data where the subsequence sub is found such that sub is contained in the slice s start end Optional arguments start and end are interpreted as in slice notation Return 1 if sub is not found The subsequence to search for may be any bytes like object or an integer in the range 0 to 255 Note The find method should be used only if you need to know the position of sub To check if sub is a substring or not use the in operator b Py in b Python True Changed in version 3 3 Also accept an integer in the range 0 to 255 as the subsequence bytes index sub start end bytearray index sub start end Like find but raise ValueError when the subsequence is not found The subsequence to search for may be any bytes like object or an integer in the range 0 to 255 Changed in version 3 3 Also accept an integer in the range 0 to 255 as the subsequence bytes join iterable bytearray join iterable Return a bytes or bytearray object which is the concatenation of the binary data sequences in iterable A TypeError will be raised if there are any values in iterable that are not bytes like objects including str objects The separator between elements is the contents of the bytes or bytearray object providing this method static bytes maketrans from to static bytearray maketrans from to This static method returns a translation table usable for bytes translate that will map each character in from into the character at the same position in to from and to must both be bytes like objects and have the same length New in version 3 1 bytes partition sep bytearray partition sep Split the sequence at the first occurrence of sep and return a 3 tuple containing the part before the separator the separator itself or its bytearray copy and the part after the separator If the separator is not found return a 3 tuple containing a copy of the original sequence followed by two empty bytes or bytearray objects The separator to search for may be any bytes like object bytes replace old new count bytearray replace old new count Return a copy of the sequence with all occurrences of subsequence old replaced by new If the optional argument count is given only the first count occurrences are replaced The subsequence to search for and its replacement may be any bytes like object Note The bytearray version of this method does not operate in place it always produces a new object even if no changes were made bytes rfind sub start end bytearray rfind sub start end Return the highest index in the sequence where the subsequence sub is found such that sub is contained within s start end Optional arguments start and end are interpreted as in slice notation Return 1 on failure The subsequence to search for may be any bytes like object or an integer in the range 0 to 255 Changed in version 3 3 Also accept an integer in the range 0 to 255 as the subsequence bytes rindex sub start end bytearray rindex sub start end Like rfind but raises ValueError when the subsequence sub is not found The subsequence to search for may be any bytes like object or an integer in the range 0 to 255 Changed in version 3 3 Also accept an integer in the range 0 to 255 as the subsequence bytes rpartition sep bytearray rpartition sep Split the sequence at the last occurrence of sep and return a 3 tuple containing the part before the separator the separator itself or its bytearray copy and the part after the separator If the separator is not found return a 3 tuple containing two empty bytes or bytearray objects followed by a copy of the original sequence The separator to search for may be any bytes like object bytes startswith prefix start end bytearray startswith prefix start end Return True if the binary data starts with the specified prefix otherw,en
902,ise return False prefix can also be a tuple of prefixes to look for With optional start test beginning at that position With optional end stop comparing at that position The prefix es to search for may be any bytes like object bytes translate table delete b bytearray translate table delete b Return a copy of the bytes or bytearray object where all bytes occurring in the optional argument delete are removed and the remaining bytes have been mapped through the given translation table which must be a bytes object of length 256 You can use the bytes maketrans method to create a translation table Set the table argument to None for translations that only delete characters b read this short text translate None b aeiou b rd ths shrt txt Changed in version 3 6 delete is now supported as a keyword argument The following methods on bytes and bytearray objects have default behaviours that assume the use of ASCII compatible binary formats but can still be used with arbitrary binary data by passing appropriate arguments Note that all of the bytearray methods in this section do not operate in place and instead produce new objects bytes center width fillbyte bytearray center width fillbyte Return a copy of the object centered in a sequence of length width Padding is done using the specified fillbyte default is an ASCII space For bytes objects the original sequence is returned if width is less than or equal to len s Note The bytearray version of this method does not operate in place it always produces a new object even if no changes were made bytes ljust width fillbyte bytearray ljust width fillbyte Return a copy of the object left justified in a sequence of length width Padding is done using the specified fillbyte default is an ASCII space For bytes objects the original sequence is returned if width is less than or equal to len s Note The bytearray version of this method does not operate in place it always produces a new object even if no changes were made bytes lstrip chars bytearray lstrip chars Return a copy of the sequence with specified leading bytes removed The chars argument is a binary sequence specifying the set of byte values to be removed the name refers to the fact this method is usually used with ASCII characters If omitted or None the chars argument defaults to removing ASCII whitespace The chars argument is not a prefix rather all combinations of its values are stripped b spacious lstrip b spacious b www example com lstrip b cmowz b example com The binary sequence of byte values to remove may be any bytes like object See removeprefix for a method that will remove a single prefix string rather than all of a set of characters For example b Arthur three lstrip b Arthur b ee b Arthur three removeprefix b Arthur b three Note The bytearray version of this method does not operate in place it always produces a new object even if no changes were made bytes rjust width fillbyte bytearray rjust width fillbyte Return a copy of the object right justified in a sequence of length width Padding is done using the specified fillbyte default is an ASCII space For bytes objects the original sequence is returned if width is less than or equal to len s Note The bytearray version of this method does not operate in place it always produces a new object even if no changes were made bytes rsplit sep None maxsplit 1 bytearray rsplit sep None maxsplit 1 Split the binary sequence into subsequences of the same type using sep as the delimiter string If maxsplit is given at most maxsplit splits are done the rightmost ones If sep is not specified or None any subsequence consisting solely of ASCII whitespace is a separator Except for splitting from the right rsplit behaves like split which is described in detail below bytes rstrip chars bytearray rstrip chars Return a copy of the sequence with specified trailing bytes removed The chars argument is a binary sequence specifying the set of byte values to be removed the name refers to the fact this method is usually used with ASCII characters If omitted or None the chars argument defaults to removing ASCII wh,en
903,itespace The chars argument is not a suffix rather all combinations of its values are stripped b spacious rstrip b spacious b mississippi rstrip b ipz b mississ The binary sequence of byte values to remove may be any bytes like object See removesuffix for a method that will remove a single suffix string rather than all of a set of characters For example b Monty Python rstrip b Python b M b Monty Python removesuffix b Python b Monty Note The bytearray version of this method does not operate in place it always produces a new object even if no changes were made bytes split sep None maxsplit 1 bytearray split sep None maxsplit 1 Split the binary sequence into subsequences of the same type using sep as the delimiter string If maxsplit is given and non negative at most maxsplit splits are done thus the list will have at most maxsplit 1 elements If maxsplit is not specified or is 1 then there is no limit on the number of splits all possible splits are made If sep is given consecutive delimiters are not grouped together and are deemed to delimit empty subsequences for example b 1 2 split b returns b 1 b b 2 The sep argument may consist of a multibyte sequence for example b 1 2 3 split b returns b 1 b 2 b 3 Splitting an empty sequence with a specified separator returns b or bytearray b depending on the type of object being split The sep argument may be any bytes like object For example b 1 2 3 split b b 1 b 2 b 3 b 1 2 3 split b maxsplit 1 b 1 b 2 3 b 1 2 3 split b b 1 b 2 b b 3 b If sep is not specified or is None a different splitting algorithm is applied runs of consecutive ASCII whitespace are regarded as a single separator and the result will contain no empty strings at the start or end if the sequence has leading or trailing whitespace Consequently splitting an empty sequence or a sequence consisting solely of ASCII whitespace without a specified separator returns For example b 1 2 3 split b 1 b 2 b 3 b 1 2 3 split maxsplit 1 b 1 b 2 3 b 1 2 3 split b 1 b 2 b 3 bytes strip chars bytearray strip chars Return a copy of the sequence with specified leading and trailing bytes removed The chars argument is a binary sequence specifying the set of byte values to be removed the name refers to the fact this method is usually used with ASCII characters If omitted or None the chars argument defaults to removing ASCII whitespace The chars argument is not a prefix or suffix rather all combinations of its values are stripped b spacious strip b spacious b www example com strip b cmowz b example The binary sequence of byte values to remove may be any bytes like object Note The bytearray version of this method does not operate in place it always produces a new object even if no changes were made The following methods on bytes and bytearray objects assume the use of ASCII compatible binary formats and should not be applied to arbitrary binary data Note that all of the bytearray methods in this section do not operate in place and instead produce new objects bytes capitalize bytearray capitalize Return a copy of the sequence with each byte interpreted as an ASCII character and the first byte capitalized and the rest lowercased Non ASCII byte values are passed through unchanged Note The bytearray version of this method does not operate in place it always produces a new object even if no changes were made bytes expandtabs tabsize 8 bytearray expandtabs tabsize 8 Return a copy of the sequence where all ASCII tab characters are replaced by one or more ASCII spaces depending on the current column and the given tab size Tab positions occur every tabsize bytes default is 8 giving tab positions at columns 0 8 16 and so on To expand the sequence the current column is set to zero and the sequence is examined byte by byte If the byte is an ASCII tab character b t one or more space characters are inserted in the result until the current column is equal to the next tab position The tab character itself is not copied If the current byte is an ASCII newline b n or carriage return b r it is copied and the current column is reset to zero Any other byte value is,en
904, copied unchanged and the current column is incremented by one regardless of how the byte value is represented when printed b 01 t012 t0123 t01234 expandtabs b 01 012 0123 01234 b 01 t012 t0123 t01234 expandtabs 4 b 01 012 0123 01234 Note The bytearray version of this method does not operate in place it always produces a new object even if no changes were made bytes isalnum bytearray isalnum Return True if all bytes in the sequence are alphabetical ASCII characters or ASCII decimal digits and the sequence is not empty False otherwise Alphabetic ASCII characters are those byte values in the sequence b abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ ASCII decimal digits are those byte values in the sequence b 0123456789 For example b ABCabc1 isalnum True b ABC abc1 isalnum False bytes isalpha bytearray isalpha Return True if all bytes in the sequence are alphabetic ASCII characters and the sequence is not empty False otherwise Alphabetic ASCII characters are those byte values in the sequence b abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ For example b ABCabc isalpha True b ABCabc1 isalpha False bytes isascii bytearray isascii Return True if the sequence is empty or all bytes in the sequence are ASCII False otherwise ASCII bytes are in the range 0 0x7F New in version 3 7 bytes isdigit bytearray isdigit Return True if all bytes in the sequence are ASCII decimal digits and the sequence is not empty False otherwise ASCII decimal digits are those byte values in the sequence b 0123456789 For example b 1234 isdigit True b 1 23 isdigit False bytes islower bytearray islower Return True if there is at least one lowercase ASCII character in the sequence and no uppercase ASCII characters False otherwise For example b hello world islower True b Hello world islower False Lowercase ASCII characters are those byte values in the sequence b abcdefghijklmnopqrstuvwxyz Uppercase ASCII characters are those byte values in the sequence b ABCDEFGHIJKLMNOPQRSTUVWXYZ bytes isspace bytearray isspace Return True if all bytes in the sequence are ASCII whitespace and the sequence is not empty False otherwise ASCII whitespace characters are those byte values in the sequence b t n r x0b f space tab newline carriage return vertical tab form feed bytes istitle bytearray istitle Return True if the sequence is ASCII titlecase and the sequence is not empty False otherwise See bytes title for more details on the definition of titlecase For example b Hello World istitle True b Hello world istitle False bytes isupper bytearray isupper Return True if there is at least one uppercase alphabetic ASCII character in the sequence and no lowercase ASCII characters False otherwise For example b HELLO WORLD isupper True b Hello world isupper False Lowercase ASCII characters are those byte values in the sequence b abcdefghijklmnopqrstuvwxyz Uppercase ASCII characters are those byte values in the sequence b ABCDEFGHIJKLMNOPQRSTUVWXYZ bytes lower bytearray lower Return a copy of the sequence with all the uppercase ASCII characters converted to their corresponding lowercase counterpart For example b Hello World lower b hello world Lowercase ASCII characters are those byte values in the sequence b abcdefghijklmnopqrstuvwxyz Uppercase ASCII characters are those byte values in the sequence b ABCDEFGHIJKLMNOPQRSTUVWXYZ Note The bytearray version of this method does not operate in place it always produces a new object even if no changes were made bytes splitlines keepends False bytearray splitlines keepends False Return a list of the lines in the binary sequence breaking at ASCII line boundaries This method uses the universal newlines approach to splitting lines Line breaks are not included in the resulting list unless keepends is given and true For example b ab c n nde fg rkl r n splitlines b ab c b b de fg b kl b ab c n nde fg rkl r n splitlines keepends True b ab c n b n b de fg r b kl r n Unlike split when a delimiter string sep is given this method returns an empty list for the empty string and a terminal line break does not result in an extra line b split b n b ,en
905,Two lines n split b n b b Two lines b b splitlines b One line n splitlines b One line bytes swapcase bytearray swapcase Return a copy of the sequence with all the lowercase ASCII characters converted to their corresponding uppercase counterpart and vice versa For example b Hello World swapcase b hELLO wORLD Lowercase ASCII characters are those byte values in the sequence b abcdefghijklmnopqrstuvwxyz Uppercase ASCII characters are those byte values in the sequence b ABCDEFGHIJKLMNOPQRSTUVWXYZ Unlike str swapcase it is always the case that bin swapcase swapcase bin for the binary versions Case conversions are symmetrical in ASCII even though that is not generally true for arbitrary Unicode code points Note The bytearray version of this method does not operate in place it always produces a new object even if no changes were made bytes title bytearray title Return a titlecased version of the binary sequence where words start with an uppercase ASCII character and the remaining characters are lowercase Uncased byte values are left unmodified For example b Hello world title b Hello World Lowercase ASCII characters are those byte values in the sequence b abcdefghijklmnopqrstuvwxyz Uppercase ASCII characters are those byte values in the sequence b ABCDEFGHIJKLMNOPQRSTUVWXYZ All other byte values are uncased The algorithm uses a simple language independent definition of a word as groups of consecutive letters The definition works in many contexts but it means that apostrophes in contractions and possessives form word boundaries which may not be the desired result b they re bill s friends from the UK title b They Re Bill S Friends From The Uk A workaround for apostrophes can be constructed using regular expressions import re def titlecase s return re sub rb A Za z A Za z lambda mo mo group 0 0 1 upper mo group 0 1 lower s titlecase b they re bill s friends b They re Bill s Friends Note The bytearray version of this method does not operate in place it always produces a new object even if no changes were made bytes upper bytearray upper Return a copy of the sequence with all the lowercase ASCII characters converted to their corresponding uppercase counterpart For example b Hello World upper b HELLO WORLD Lowercase ASCII characters are those byte values in the sequence b abcdefghijklmnopqrstuvwxyz Uppercase ASCII characters are those byte values in the sequence b ABCDEFGHIJKLMNOPQRSTUVWXYZ Note The bytearray version of this method does not operate in place it always produces a new object even if no changes were made bytes zfill width bytearray zfill width Return a copy of the sequence left filled with ASCII b 0 digits to make a sequence of length width A leading sign prefix b b is handled by inserting the padding after the sign character rather than before For bytes objects the original sequence is returned if width is less than or equal to len seq For example b 42 zfill 5 b 00042 b 42 zfill 5 b 0042 Note The bytearray version of this method does not operate in place it always produces a new object even if no changes were made printf style Bytes Formatting Note The formatting operations described here exhibit a variety of quirks that lead to a number of common errors such as failing to display tuples and dictionaries correctly If the value being printed may be a tuple or dictionary wrap it in a tuple Bytes objects bytes bytearray have one unique built in operation the operator modulo This is also known as the bytes formatting or interpolation operator Given format values where format is a bytes object conversion specifications in format are replaced with zero or more elements of values The effect is similar to using the sprintf in the C language If format requires a single argument values may be a single non tuple object 5 Otherwise values must be a tuple with exactly the number of items specified by the format bytes object or a single mapping object for example a dictionary A conversion specifier contains two or more characters and has the following components which must occur in this order 1 The character which marks the start of th,en
906,e specifier 2 Mapping key optional consisting of a parenthesised sequence of characters for example somename 3 Conversion flags optional which affect the result of some conversion types 4 Minimum field width optional If specified as an asterisk the actual width is read from the next element of the tuple in values and the object to convert comes after the minimum field width and optional precision 5 Precision optional given as a dot followed by the precision If specified as an asterisk the actual precision is read from the next element of the tuple in values and the value to convert comes after the precision 6 Length modifier optional 7 Conversion type When the right argument is a dictionary or other mapping type then the formats in the bytes object must include a parenthesised mapping key into that dictionary inserted immediately after the character The mapping key selects the value to be formatted from the mapping For example print b language s has number 03d quote types b language b Python b number 2 b Python has 002 quote types In this case no specifiers may occur in a format since they require a sequential parameter list The conversion flag characters are Flag Meaning The value conversion will use the alternate form where defined below 0 The conversion will be zero padded for numeric values The converted value is left adjusted overrides the 0 conversion if both are given a space A blank should be left before a positive number or empty string produced by a signed conversion A sign character or will precede the conversion overrides a space flag A length modifier h l or L may be present but is ignored as it is not necessary for Python so e g ld is identical to d The conversion types are Conversion Meaning Notes d Signed integer decimal i Signed integer decimal o Signed octal value 1 u Obsolete type it is identical to d 8 x Signed hexadecimal lowercase 2 X Signed hexadecimal uppercase 2 e Floating point exponential format lowercase 3 E Floating point exponential format uppercase 3 f Floating point decimal format 3 F Floating point decimal format 3 g Floating point format Uses lowercase exponential 4 format if exponent is less than 4 or not less than precision decimal format otherwise G Floating point format Uses uppercase exponential 4 format if exponent is less than 4 or not less than precision decimal format otherwise c Single byte accepts integer or single byte objects b Bytes any object that follows the buffer protocol or 5 has __bytes__ s s is an alias for b and should only be used 6 for Python2 3 code bases a Bytes converts any Python object using 5 repr obj encode ascii backslashreplace r r is an alias for a and should only be used 7 for Python2 3 code bases No argument is converted results in a character in the result Notes 1 The alternate form causes a leading octal specifier 0o to be inserted before the first digit 2 The alternate form causes a leading 0x or 0X depending on whether the x or X format was used to be inserted before the first digit 3 The alternate form causes the result to always contain a decimal point even if no digits follow it The precision determines the number of digits after the decimal point and defaults to 6 4 The alternate form causes the result to always contain a decimal point and trailing zeroes are not removed as they would otherwise be The precision determines the number of significant digits before and after the decimal point and defaults to 6 5 If precision is N the output is truncated to N characters 6 b s is deprecated but will not be removed during the 3 x series 7 b r is deprecated but will not be removed during the 3 x series 8 See PEP 237 Note The bytearray version of this method does not operate in place it always produces a new object even if no changes were made See also PEP 461 Adding formatting to bytes and bytearray New in version 3 5 Memory Views memoryview objects allow Python code to access the internal data of an object that supports the buffer protocol without copying class memoryview object Create a memoryview that references object object must support the buffer,en
907, protocol Built in objects that support the buffer protocol include bytes and bytearray A memoryview has the notion of an element which is the atomic memory unit handled by the originating object For many simple types such as bytes and bytearray an element is a single byte but other types such as array array may have bigger elements len view is equal to the length of tolist which is the nested list representation of the view If view ndim 1 this is equal to the number of elements in the view Changed in version 3 12 If view ndim 0 len view now raises TypeError instead of returning 1 The itemsize attribute will give you the number of bytes in a single element A memoryview supports slicing and indexing to expose its data One dimensional slicing will result in a subview v memoryview b abcefg v 1 98 v 1 103 v 1 4 memory at 0x7f3ddc9f4350 bytes v 1 4 b bce If format is one of the native format specifiers from the struct module indexing with an integer or a tuple of integers is also supported and returns a single element with the correct type One dimensional memoryviews can be indexed with an integer or a one integer tuple Multi dimensional memoryviews can be indexed with tuples of exactly ndim integers where ndim is the number of dimensions Zero dimensional memoryviews can be indexed with the empty tuple Here is an example with a non byte format import array a array array l 11111111 22222222 33333333 44444444 m memoryview a m 0 11111111 m 1 44444444 m 2 tolist 11111111 33333333 If the underlying object is writable the memoryview supports one dimensional slice assignment Resizing is not allowed data bytearray b abcefg v memoryview data v readonly False v 0 ord b z data bytearray b zbcefg v 1 4 b 123 data bytearray b z123fg v 2 3 b spam Traceback most recent call last File stdin line 1 in module ValueError memoryview assignment lvalue and rvalue have different structures v 2 6 b spam data bytearray b z1spam One dimensional memoryviews of hashable read only types with formats B b or c are also hashable The hash is defined as hash m hash m tobytes v memoryview b abcefg hash v hash b abcefg True hash v 2 4 hash b ce True hash v 2 hash b abcefg 2 True Changed in version 3 3 One dimensional memoryviews can now be sliced One dimensional memoryviews with formats B b or c are now hashable Changed in version 3 4 memoryview is now registered automatically with collections abc Sequence Changed in version 3 5 memoryviews can now be indexed with tuple of integers memoryview has several methods __eq__ exporter A memoryview and a PEP 3118 exporter are equal if their shapes are equivalent and if all corresponding values are equal when the operands respective format codes are interpreted using struct syntax For the subset of struct format strings currently supported by tolist v and w are equal if v tolist w tolist import array a array array I 1 2 3 4 5 b array array d 1 0 2 0 3 0 4 0 5 0 c array array b 5 3 1 x memoryview a y memoryview b x a y b True x tolist a tolist y tolist b tolist True z y 2 z c True z tolist c tolist True If either format string is not supported by the struct module then the objects will always compare as unequal even if the format strings and buffer contents are identical from ctypes import BigEndianStructure c_long class BEPoint BigEndianStructure _fields_ x c_long y c_long point BEPoint 100 200 a memoryview point b memoryview point a point False a b False Note that as with floating point numbers v is w does not imply v w for memoryview objects Changed in version 3 3 Previous versions compared the raw memory disregarding the item format and the logical array structure tobytes order C Return the data in the buffer as a bytestring This is equivalent to calling the bytes constructor on the memoryview m memoryview b abc m tobytes b abc bytes m b abc For non contiguous arrays the result is equal to the flattened list representation with all elements converted to bytes tobytes supports all format strings including those that are not in struct module syntax New in version 3 8 order can be C F A When order is C or F the data of ,en
908,the original array is converted to C or Fortran order For contiguous views A returns an exact copy of the physical memory In particular in memory Fortran order is preserved For non contiguous views the data is converted to C first order None is the same as order C hex sep bytes_per_sep Return a string object containing two hexadecimal digits for each byte in the buffer m memoryview b abc m hex 616263 New in version 3 5 Changed in version 3 8 Similar to bytes hex memoryview hex now supports optional sep and bytes_per_sep parameters to insert separators between bytes in the hex output tolist Return the data in the buffer as a list of elements memoryview b abc tolist 97 98 99 import array a array array d 1 1 2 2 3 3 m memoryview a m tolist 1 1 2 2 3 3 Changed in version 3 3 tolist now supports all single character native formats in struct module syntax as well as multi dimensional representations toreadonly Return a readonly version of the memoryview object The original memoryview object is unchanged m memoryview bytearray b abc mm m toreadonly mm tolist 97 98 99 mm 0 42 Traceback most recent call last File stdin line 1 in module TypeError cannot modify read only memory m 0 43 mm tolist 43 98 99 New in version 3 8 release Release the underlying buffer exposed by the memoryview object Many objects take special actions when a view is held on them for example a bytearray would temporarily forbid resizing therefore calling release is handy to remove these restrictions and free any dangling resources as soon as possible After this method has been called any further operation on the view raises a ValueError except release itself which can be called multiple times m memoryview b abc m release m 0 Traceback most recent call last File stdin line 1 in module ValueError operation forbidden on released memoryview object The context management protocol can be used for a similar effect using the with statement with memoryview b abc as m m 0 97 m 0 Traceback most recent call last File stdin line 1 in module ValueError operation forbidden on released memoryview object New in version 3 2 cast format shape Cast a memoryview to a new format or shape shape defaults to byte_length new_itemsize which means that the result view will be one dimensional The return value is a new memoryview but the buffer itself is not copied Supported casts are 1D C contiguous and C contiguous 1D The destination format is restricted to a single element native format in struct syntax One of the formats must be a byte format B b or c The byte length of the result must be the same as the original length Note that all byte lengths may depend on the operating system Cast 1D long to 1D unsigned bytes import array a array array l 1 2 3 x memoryview a x format l x itemsize 8 len x 3 x nbytes 24 y x cast B y format B y itemsize 1 len y 24 y nbytes 24 Cast 1D unsigned bytes to 1D char b bytearray b zyz x memoryview b x 0 b a Traceback most recent call last TypeError memoryview invalid type for format B y x cast c y 0 b a b bytearray b ayz Cast 1D bytes to 3D ints to 1D signed char import struct buf struct pack i 12 list range 12 x memoryview buf y x cast i shape 2 2 3 y tolist 0 1 2 3 4 5 6 7 8 9 10 11 y format i y itemsize 4 len y 2 y nbytes 48 z y cast b z format b z itemsize 1 len z 48 z nbytes 48 Cast 1D unsigned long to 2D unsigned long buf struct pack L 6 list range 6 x memoryview buf y x cast L shape 2 3 len y 2 y nbytes 48 y tolist 0 1 2 3 4 5 New in version 3 3 Changed in version 3 5 The source format is no longer restricted when casting to a byte view There are also several readonly attributes available obj The underlying object of the memoryview b bytearray b xyz m memoryview b m obj is b True New in version 3 3 nbytes nbytes product shape itemsize len m tobytes This is the amount of space in bytes that the array would use in a contiguous representation It is not necessarily equal to len m import array a array array i 1 2 3 4 5 m memoryview a len m 5 m nbytes 20 y m 2 len y 3 y nbytes 12 len y tobytes 12 Multi dimensional arrays import struct buf struct pack d 12 ,en
909,1 5 x for x in range 12 x memoryview buf y x cast d shape 3 4 y tolist 0 0 1 5 3 0 4 5 6 0 7 5 9 0 10 5 12 0 13 5 15 0 16 5 len y 3 y nbytes 96 New in version 3 3 readonly A bool indicating whether the memory is read only format A string containing the format in struct module style for each element in the view A memoryview can be created from exporters with arbitrary format strings but some methods e g tolist are restricted to native single element formats Changed in version 3 3 format B is now handled according to the struct module syntax This means that memoryview b abc 0 b abc 0 97 itemsize The size in bytes of each element of the memoryview import array struct m memoryview array array H 32000 32001 32002 m itemsize 2 m 0 32000 struct calcsize H m itemsize True ndim An integer indicating how many dimensions of a multi dimensional array the memory represents shape A tuple of integers the length of ndim giving the shape of the memory as an N dimensional array Changed in version 3 3 An empty tuple instead of None when ndim 0 strides A tuple of integers the length of ndim giving the size in bytes to access each element for each dimension of the array Changed in version 3 3 An empty tuple instead of None when ndim 0 suboffsets Used internally for PIL style arrays The value is informational only c_contiguous A bool indicating whether the memory is C contiguous New in version 3 3 f_contiguous A bool indicating whether the memory is Fortran contiguous New in version 3 3 contiguous A bool indicating whether the memory is contiguous New in version 3 3 Set Types set frozenset A set object is an unordered collection of distinct hashable objects Common uses include membership testing removing duplicates from a sequence and computing mathematical operations such as intersection union difference and symmetric difference For other containers see the built in dict list and tuple classes and the collections module Like other collections sets support x in set len set and for x in set Being an unordered collection sets do not record element position or order of insertion Accordingly sets do not support indexing slicing or other sequence like behavior There are currently two built in set types set and frozenset The set type is mutable the contents can be changed using methods like add and remove Since it is mutable it has no hash value and cannot be used as either a dictionary key or as an element of another set The frozenset type is immutable and hashable its contents cannot be altered after it is created it can therefore be used as a dictionary key or as an element of another set Non empty sets not frozensets can be created by placing a comma separated list of elements within braces for example jack sjoerd in addition to the set constructor The constructors for both classes work the same class set iterable class frozenset iterable Return a new set or frozenset object whose elements are taken from iterable The elements of a set must be hashable To represent sets of sets the inner sets must be frozenset objects If iterable is not specified a new empty set is returned Sets can be created by several means Use a comma separated list of elements within braces jack sjoerd Use a set comprehension c for c in abracadabra if c not in abc Use the type constructor set set foobar set a b foo Instances of set and frozenset provide the following operations len s Return the number of elements in set s cardinality of s x in s Test x for membership in s x not in s Test x for non membership in s isdisjoint other Return True if the set has no elements in common with other Sets are disjoint if and only if their intersection is the empty set issubset other set other Test whether every element in the set is in other set other Test whether the set is a proper subset of other that is set other and set other issuperset other set other Test whether every element in other is in the set set other Test whether the set is a proper superset of other that is set other and set other union others set other Return a new set with elements from the set and all others interse,en
910,ction others set other Return a new set with elements common to the set and all others difference others set other Return a new set with elements in the set that are not in the others symmetric_difference other set other Return a new set with elements in either the set or other but not both copy Return a shallow copy of the set Note the non operator versions of union intersection difference symmetric_difference issubset and issuperset methods will accept any iterable as an argument In contrast their operator based counterparts require their arguments to be sets This precludes error prone constructions like set abc cbs in favor of the more readable set abc intersection cbs Both set and frozenset support set to set comparisons Two sets are equal if and only if every element of each set is contained in the other each is a subset of the other A set is less than another set if and only if the first set is a proper subset of the second set is a subset but is not equal A set is greater than another set if and only if the first set is a proper superset of the second set is a superset but is not equal Instances of set are compared to instances of frozenset based on their members For example set abc frozenset abc returns True and so does set abc in set frozenset abc The subset and equality comparisons do not generalize to a total ordering function For example any two nonempty disjoint sets are not equal and are not subsets of each other so all of the following return False a b a b or a b Since sets only define partial ordering subset relationships the output of the list sort method is undefined for lists of sets Set elements like dictionary keys must be hashable Binary operations that mix set instances with frozenset return the type of the first operand For example frozenset ab set bc returns an instance of frozenset The following table lists operations available for set that do not apply to immutable instances of frozenset update others set other Update the set adding elements from all others intersection_update others set other Update the set keeping only elements found in it and all others difference_update others set other Update the set removing elements found in others symmetric_difference_update other set other Update the set keeping only elements found in either set but not in both add elem Add element elem to the set remove elem Remove element elem from the set Raises KeyError if elem is not contained in the set discard elem Remove element elem from the set if it is present pop Remove and return an arbitrary element from the set Raises KeyError if the set is empty clear Remove all elements from the set Note the non operator versions of the update intersection_update difference_update and symmetric_difference_update methods will accept any iterable as an argument Note the elem argument to the __contains__ remove and discard methods may be a set To support searching for an equivalent frozenset a temporary one is created from elem Mapping Types dict A mapping object maps hashable values to arbitrary objects Mappings are mutable objects There is currently only one standard mapping type the dictionary For other containers see the built in list set and tuple classes and the collections module A dictionary s keys are almost arbitrary values Values that are not hashable that is values containing lists dictionaries or other mutable types that are compared by value rather than by object identity may not be used as keys Values that compare equal such as 1 1 0 and True can be used interchangeably to index the same dictionary entry class dict kwargs class dict mapping kwargs class dict iterable kwargs Return a new dictionary initialized from an optional positional argument and a possibly empty set of keyword arguments Dictionaries can be created by several means Use a comma separated list of key value pairs within braces jack 4098 sjoerd 4127 or 4098 jack 4127 sjoerd Use a dict comprehension x x 2 for x in range 10 Use the type constructor dict dict foo 100 bar 200 dict foo 100 bar 200 If no positional argument is given an empty dicti,en
911,onary is created If a positional argument is given and it is a mapping object a dictionary is created with the same key value pairs as the mapping object Otherwise the positional argument must be an iterable object Each item in the iterable must itself be an iterable with exactly two objects The first object of each item becomes a key in the new dictionary and the second object the corresponding value If a key occurs more than once the last value for that key becomes the corresponding value in the new dictionary If keyword arguments are given the keyword arguments and their values are added to the dictionary created from the positional argument If a key being added is already present the value from the keyword argument replaces the value from the positional argument To illustrate the following examples all return a dictionary equal to one 1 two 2 three 3 a dict one 1 two 2 three 3 b one 1 two 2 three 3 c dict zip one two three 1 2 3 d dict two 2 one 1 three 3 e dict three 3 one 1 two 2 f dict one 1 three 3 two 2 a b c d e f True Providing keyword arguments as in the first example only works for keys that are valid Python identifiers Otherwise any valid keys can be used These are the operations that dictionaries support and therefore custom mapping types should support too list d Return a list of all the keys used in the dictionary d len d Return the number of items in the dictionary d d key Return the item of d with key key Raises a KeyError if key is not in the map If a subclass of dict defines a method __missing__ and key is not present the d key operation calls that method with the key key as argument The d key operation then returns or raises whatever is returned or raised by the __missing__ key call No other operations or methods invoke __missing__ If __missing__ is not defined KeyError is raised __missing__ must be a method it cannot be an instance variable class Counter dict def __missing__ self key return 0 c Counter c red 0 c red 1 c red 1 The example above shows part of the implementation of collections Counter A different __missing__ method is used by collections defaultdict d key value Set d key to value del d key Remove d key from d Raises a KeyError if key is not in the map key in d Return True if d has a key key else False key not in d Equivalent to not key in d iter d Return an iterator over the keys of the dictionary This is a shortcut for iter d keys clear Remove all items from the dictionary copy Return a shallow copy of the dictionary classmethod fromkeys iterable value Create a new dictionary with keys from iterable and values set to value fromkeys is a class method that returns a new dictionary value defaults to None All of the values refer to just a single instance so it generally doesn t make sense for value to be a mutable object such as an empty list To get distinct values use a dict comprehension instead get key default Return the value for key if key is in the dictionary else default If default is not given it defaults to None so that this method never raises a KeyError items Return a new view of the dictionary s items key value pairs See the documentation of view objects keys Return a new view of the dictionary s keys See the documentation of view objects pop key default If key is in the dictionary remove it and return its value else return default If default is not given and key is not in the dictionary a KeyError is raised popitem Remove and return a key value pair from the dictionary Pairs are returned in LIFO last in first out order popitem is useful to destructively iterate over a dictionary as often used in set algorithms If the dictionary is empty calling popitem raises a KeyError Changed in version 3 7 LIFO order is now guaranteed In prior versions popitem would return an arbitrary key value pair reversed d Return a reverse iterator over the keys of the dictionary This is a shortcut for reversed d keys New in version 3 8 setdefault key default If key is in the dictionary return its value If not insert key with a value of default and return default default defaults to None update other,en
912, Update the dictionary with the key value pairs from other overwriting existing keys Return None update accepts either another dictionary object or an iterable of key value pairs as tuples or other iterables of length two If keyword arguments are specified the dictionary is then updated with those key value pairs d update red 1 blue 2 values Return a new view of the dictionary s values See the documentation of view objects An equality comparison between one dict values view and another will always return False This also applies when comparing dict values to itself d a 1 d values d values False d other Create a new dictionary with the merged keys and values of d and other which must both be dictionaries The values of other take priority when d and other share keys New in version 3 9 d other Update the dictionary d with keys and values from other which may be either a mapping or an iterable of key value pairs The values of other take priority when d and other share keys New in version 3 9 Dictionaries compare equal if and only if they have the same key value pairs regardless of ordering Order comparisons raise TypeError Dictionaries preserve insertion order Note that updating a key does not affect the order Keys added after deletion are inserted at the end d one 1 two 2 three 3 four 4 d one 1 two 2 three 3 four 4 list d one two three four list d values 1 2 3 4 d one 42 d one 42 two 2 three 3 four 4 del d two d two None d one 42 three 3 four 4 two None Changed in version 3 7 Dictionary order is guaranteed to be insertion order This behavior was an implementation detail of CPython from 3 6 Dictionaries and dictionary views are reversible d one 1 two 2 three 3 four 4 d one 1 two 2 three 3 four 4 list reversed d four three two one list reversed d values 4 3 2 1 list reversed d items four 4 three 3 two 2 one 1 Changed in version 3 8 Dictionaries are now reversible See also types MappingProxyType can be used to create a read only view of a dict Dictionary view objects The objects returned by dict keys dict values and dict items are view objects They provide a dynamic view on the dictionary s entries which means that when the dictionary changes the view reflects these changes Dictionary views can be iterated over to yield their respective data and support membership tests len dictview Return the number of entries in the dictionary iter dictview Return an iterator over the keys values or items represented as tuples of key value in the dictionary Keys and values are iterated over in insertion order This allows the creation of value key pairs using zip pairs zip d values d keys Another way to create the same list is pairs v k for k v in d items Iterating views while adding or deleting entries in the dictionary may raise a RuntimeError or fail to iterate over all entries Changed in version 3 7 Dictionary order is guaranteed to be insertion order x in dictview Return True if x is in the underlying dictionary s keys values or items in the latter case x should be a key value tuple reversed dictview Return a reverse iterator over the keys values or items of the dictionary The view will be iterated in reverse order of the insertion Changed in version 3 8 Dictionary views are now reversible dictview mapping Return a types MappingProxyType that wraps the original dictionary to which the view refers New in version 3 10 Keys views are set like since their entries are unique and hashable Items views also have set like operations since the key value pairs are unique and the keys are hashable If all values in an items view are hashable as well then the items view can interoperate with other sets Values views are not treated as set like since the entries are generally not unique For set like views all of the operations defined for the abstract base class collections abc Set are available for example or While using set operators set like views accept any iterable as the other operand unlike sets which only accept sets as the input An example of dictionary view usage dishes eggs 2 sausage 1 bacon 1 spam 500 keys dishes keys values dishes values ite,en
913,ration n 0 for val in values n val print n 504 keys and values are iterated over in the same order insertion order list keys eggs sausage bacon spam list values 2 1 1 500 view objects are dynamic and reflect dict changes del dishes eggs del dishes sausage list keys bacon spam set operations keys eggs bacon salad bacon keys sausage juice juice sausage bacon spam True keys juice juice juice bacon spam juice True get back a read only proxy for the original dictionary values mapping mappingproxy bacon 1 spam 500 values mapping spam 500 Context Manager Types Python s with statement supports the concept of a runtime context defined by a context manager This is implemented using a pair of methods that allow user defined classes to define a runtime context that is entered before the statement body is executed and exited when the statement ends contextmanager __enter__ Enter the runtime context and return either this object or another object related to the runtime context The value returned by this method is bound to the identifier in the as clause of with statements using this context manager An example of a context manager that returns itself is a file object File objects return themselves from __enter__ to allow open to be used as the context expression in a with statement An example of a context manager that returns a related object is the one returned by decimal localcontext These managers set the active decimal context to a copy of the original decimal context and then return the copy This allows changes to be made to the current decimal context in the body of the with statement without affecting code outside the with statement contextmanager __exit__ exc_type exc_val exc_tb Exit the runtime context and return a Boolean flag indicating if any exception that occurred should be suppressed If an exception occurred while executing the body of the with statement the arguments contain the exception type value and traceback information Otherwise all three arguments are None Returning a true value from this method will cause the with statement to suppress the exception and continue execution with the statement immediately following the with statement Otherwise the exception continues propagating after this method has finished executing Exceptions that occur during execution of this method will replace any exception that occurred in the body of the with statement The exception passed in should never be reraised explicitly instead this method should return a false value to indicate that the method completed successfully and does not want to suppress the raised exception This allows context management code to easily detect whether or not an __exit__ method has actually failed Python defines several context managers to support easy thread synchronisation prompt closure of files or other objects and simpler manipulation of the active decimal arithmetic context The specific types are not treated specially beyond their implementation of the context management protocol See the contextlib module for some examples Python s generator s and the contextlib contextmanager decorator provide a convenient way to implement these protocols If a generator function is decorated with the contextlib contextmanager decorator it will return a context manager implementing the necessary __enter__ and __exit__ methods rather than the iterator produced by an undecorated generator function Note that there is no specific slot for any of these methods in the type structure for Python objects in the Python C API Extension types wanting to define these methods must provide them as a normal Python accessible method Compared to the overhead of setting up the runtime context the overhead of a single class dictionary lookup is negligible Type Annotation Types Generic Alias Union The core built in types for type annotations are Generic Alias and Union Generic Alias Type GenericAlias objects are generally created by subscripting a class They are most often used with container classes such as list or dict For example list int is a GenericAlias object created by subscripti,en
914,ng the list class with the argument int GenericAlias objects are intended primarily for use with type annotations Note It is generally only possible to subscript a class if the class implements the special method __class_getitem__ A GenericAlias object acts as a proxy for a generic type implementing parameterized generics For a container class the argument s supplied to a subscription of the class may indicate the type s of the elements an object contains For example set bytes can be used in type annotations to signify a set in which all the elements are of type bytes For a class which defines __class_getitem__ but is not a container the argument s supplied to a subscription of the class will often indicate the return type s of one or more methods defined on an object For example regular expressions can be used on both the str data type and the bytes data type If x re search foo foo x will be a re Match object where the return values of x group 0 and x 0 will both be of type str We can represent this kind of object in type annotations with the GenericAlias re Match str If y re search b bar b bar note the b for bytes y will also be an instance of re Match but the return values of y group 0 and y 0 will both be of type bytes In type annotations we would represent this variety of re Match objects with re Match bytes GenericAlias objects are instances of the class types GenericAlias which can also be used to create GenericAlias objects directly T X Y Creates a GenericAlias representing a type T parameterized by types X Y and more depending on the T used For example a function expecting a list containing float elements def average values list float float return sum values len values Another example for mapping objects using a dict which is a generic type expecting two type parameters representing the key type and the value type In this example the function expects a dict with keys of type str and values of type int def send_post_request url str body dict str int None The builtin functions isinstance and issubclass do not accept GenericAlias types for their second argument isinstance 1 2 list str Traceback most recent call last File stdin line 1 in module TypeError isinstance argument 2 cannot be a parameterized generic The Python runtime does not enforce type annotations This extends to generic types and their type parameters When creating a container object from a GenericAlias the elements in the container are not checked against their type For example the following code is discouraged but will run without errors t list str t 1 2 3 1 2 3 Furthermore parameterized generics erase type parameters during object creation t list str type t class types GenericAlias l t type l class list Calling repr or str on a generic shows the parameterized type repr list int list int str list int list int The __getitem__ method of generic containers will raise an exception to disallow mistakes like dict str str dict str str Traceback most recent call last TypeError dict str is not a generic class However such expressions are valid when type variables are used The index must have as many elements as there are type variable items in the GenericAlias object s __args__ from typing import TypeVar Y TypeVar Y dict str Y int dict str int Standard Generic Classes The following standard library classes support parameterized generics This list is non exhaustive tuple list dict set frozenset type collections deque collections defaultdict collections OrderedDict collections Counter collections ChainMap collections abc Awaitable collections abc Coroutine collections abc AsyncIterable collections abc AsyncIterator collections abc AsyncGenerator collections abc Iterable collections abc Iterator collections abc Generator collections abc Reversible collections abc Container collections abc Collection collections abc Callable collections abc Set collections abc MutableSet collections abc Mapping collections abc MutableMapping collections abc Sequence collections abc MutableSequence collections abc ByteString collections abc MappingView collections abc KeysView co,en
915,llections abc ItemsView collections abc ValuesView contextlib AbstractContextManager contextlib AbstractAsyncContextManager dataclasses Field functools cached_property functools partialmethod os PathLike queue LifoQueue queue Queue queue PriorityQueue queue SimpleQueue re Pattern re Match shelve BsdDbShelf shelve DbfilenameShelf shelve Shelf types MappingProxyType weakref WeakKeyDictionary weakref WeakMethod weakref WeakSet weakref WeakValueDictionary Special Attributes of GenericAlias objects All parameterized generics implement special read only attributes genericalias __origin__ This attribute points at the non parameterized generic class list int __origin__ class list genericalias __args__ This attribute is a tuple possibly of length 1 of generic types passed to the original __class_getitem__ of the generic class dict str list int __args__ class str list int genericalias __parameters__ This attribute is a lazily computed tuple possibly empty of unique type variables found in __args__ from typing import TypeVar T TypeVar T list T __parameters__ T Note A GenericAlias object with typing ParamSpec parameters may not have correct __parameters__ after substitution because typing ParamSpec is intended primarily for static type checking genericalias __unpacked__ A boolean that is true if the alias has been unpacked using the operator see TypeVarTuple New in version 3 11 See also PEP 484 Type Hints Introducing Python s framework for type annotations PEP 585 Type Hinting Generics In Standard Collections Introducing the ability to natively parameterize standard library classes provided they implement the special class method __class_getitem__ Generics user defined generics and typing Generic Documentation on how to implement generic classes that can be parameterized at runtime and understood by static type checkers New in version 3 9 Union Type A union object holds the value of the bitwise or operation on multiple type objects These types are intended primarily for type annotations The union type expression enables cleaner type hinting syntax compared to typing Union X Y Defines a union object which holds types X Y and so forth X Y means either X or Y It is equivalent to typing Union X Y For example the following function expects an argument of type int or float def square number int float int float return number 2 Note The operand cannot be used at runtime to define unions where one or more members is a forward reference For example int Foo where Foo is a reference to a class not yet defined will fail at runtime For unions which include forward references present the whole expression as a string e g int Foo union_object other Union objects can be tested for equality with other union objects Details Unions of unions are flattened int str float int str float Redundant types are removed int str int int str When comparing unions the order is ignored int str str int It is compatible with typing Union int str typing Union int str Optional types can be spelled as a union with None str None typing Optional str isinstance obj union_object issubclass obj union_object Calls to isinstance and issubclass are also supported with a union object isinstance int str True However parameterized generics in union objects cannot be checked isinstance 1 int list int short circuit evaluation True isinstance 1 int list int Traceback most recent call last TypeError isinstance argument 2 cannot be a parameterized generic The user exposed type for the union object can be accessed from types UnionType and used for isinstance checks An object cannot be instantiated from the type import types isinstance int str types UnionType True types UnionType Traceback most recent call last File stdin line 1 in module TypeError cannot create types UnionType instances Note The __or__ method for type objects was added to support the syntax X Y If a metaclass implements __or__ the Union may override it class M type def __or__ self other return Hello class C metaclass M pass C int Hello int C int C See also PEP 604 PEP proposing the X Y syntax and the Union type New in ver,en
916,sion 3 10 Other Built in Types The interpreter supports several other kinds of objects Most of these support only one or two operations Modules The only special operation on a module is attribute access m name where m is a module and name accesses a name defined in m s symbol table Module attributes can be assigned to Note that the import statement is not strictly speaking an operation on a module object import foo does not require a module object named foo to exist rather it requires an external definition for a module named foo somewhere A special attribute of every module is __dict__ This is the dictionary containing the module s symbol table Modifying this dictionary will actually change the module s symbol table but direct assignment to the __dict__ attribute is not possible you can write m __dict__ a 1 which defines m a to be 1 but you can t write m __dict__ Modifying __dict__ directly is not recommended Modules built into the interpreter are written like this module sys built in If loaded from a file they are written as module os from usr local lib pythonX Y os pyc Classes and Class Instances See Objects values and types and Class definitions for these Functions Function objects are created by function definitions The only operation on a function object is to call it func argument list There are really two flavors of function objects built in functions and user defined functions Both support the same operation to call the function but the implementation is different hence the different object types See Function definitions for more information Methods Methods are functions that are called using the attribute notation There are two flavors built in methods such as append on lists and class instance method Built in methods are described with the types that support them If you access a method a function defined in a class namespace through an instance you get a special object a bound method also called instance method object When called it will add the self argument to the argument list Bound methods have two special read only attributes m __self__ is the object on which the method operates and m __func__ is the function implementing the method Calling m arg 1 arg 2 arg n is completely equivalent to calling m __func__ m __self__ arg 1 arg 2 arg n Like function objects bound method objects support getting arbitrary attributes However since method attributes are actually stored on the underlying function object method __func__ setting method attributes on bound methods is disallowed Attempting to set an attribute on a method results in an AttributeError being raised In order to set a method attribute you need to explicitly set it on the underlying function object class C def method self pass c C c method whoami my name is method can t set on the method Traceback most recent call last File stdin line 1 in module AttributeError method object has no attribute whoami c method __func__ whoami my name is method c method whoami my name is method See Instance methods for more information Code Objects Code objects are used by the implementation to represent pseudo compiled executable Python code such as a function body They differ from function objects because they don t contain a reference to their global execution environment Code objects are returned by the built in compile function and can be extracted from function objects through their __code__ attribute See also the code module Accessing __code__ raises an auditing event object __getattr__ with arguments obj and __code__ A code object can be executed or evaluated by passing it instead of a source string to the exec or eval built in functions See The standard type hierarchy for more information Type Objects Type objects represent the various object types An object s type is accessed by the built in function type There are no special operations on types The standard module types defines names for all standard built in types Types are written like this class int The Null Object This object is returned by functions that don t explicitly return a value It supports no special ,en
917,operations There is exactly one null object named None a built in name type None produces the same singleton It is written as None The Ellipsis Object This object is commonly used by slicing see Slicings It supports no special operations There is exactly one ellipsis object named Ellipsis a built in name type Ellipsis produces the Ellipsis singleton It is written as Ellipsis or The NotImplemented Object This object is returned from comparisons and binary operations when they are asked to operate on types they don t support See Comparisons for more information There is exactly one NotImplemented object type NotImplemented produces the singleton instance It is written as NotImplemented Internal Objects See The standard type hierarchy for this information It describes stack frame objects traceback objects and slice objects Special Attributes The implementation adds a few special read only attributes to several object types where they are relevant Some of these are not reported by the dir built in function object __dict__ A dictionary or other mapping object used to store an object s writable attributes instance __class__ The class to which a class instance belongs class __bases__ The tuple of base classes of a class object definition __name__ The name of the class function method descriptor or generator instance definition __qualname__ The qualified name of the class function method descriptor or generator instance New in version 3 3 definition __type_params__ The type parameters of generic classes functions and type aliases New in version 3 12 class __mro__ This attribute is a tuple of classes that are considered when looking for base classes during method resolution class mro This method can be overridden by a metaclass to customize the method resolution order for its instances It is called at class instantiation and its result is stored in __mro__ class __subclasses__ Each class keeps a list of weak references to its immediate subclasses This method returns a list of all those references still alive The list is in definition order Example int __subclasses__ class bool enum IntEnum flag IntFlag class re _constants _NamedIntConstant Integer string conversion length limitation CPython has a global limit for converting between int and str to mitigate denial of service attacks This limit only applies to decimal or other non power of two number bases Hexadecimal octal and binary conversions are unlimited The limit can be configured The int type in CPython is an arbitrary length number stored in binary form commonly known as a bignum There exists no algorithm that can convert a string to a binary integer or a binary integer to a string in linear time unless the base is a power of 2 Even the best known algorithms for base 10 have sub quadratic complexity Converting a large value such as int 1 500_000 can take over a second on a fast CPU Limiting conversion size offers a practical way to avoid CVE 2020 10735 The limit is applied to the number of digit characters in the input or output string when a non linear conversion algorithm would be involved Underscores and the sign are not counted towards the limit When an operation would exceed the limit a ValueError is raised import sys sys set_int_max_str_digits 4300 Illustrative this is the default _ int 2 5432 Traceback most recent call last ValueError Exceeds the limit 4300 digits for integer string conversion value has 5432 digits use sys set_int_max_str_digits to increase the limit i int 2 4300 len str i 4300 i_squared i i len str i_squared Traceback most recent call last ValueError Exceeds the limit 4300 digits for integer string conversion use sys set_int_max_str_digits to increase the limit len hex i_squared 7144 assert int hex i_squared base 16 i i Hexadecimal is unlimited The default limit is 4300 digits as provided in sys int_info default_max_str_digits The lowest limit that can be configured is 640 digits as provided in sys int_info str_digits_check_threshold Verification import sys assert sys int_info default_max_str_digits 4300 sys int_info assert sys int_info str_digits_c,en
918,heck_threshold 640 sys int_info msg int 578966293710682886880994035146873798396722250538762761564 9252925514383915483333812743580549779436104706260696366600 571186405732 to_bytes 53 big New in version 3 11 Affected APIs The limitation only applies to potentially slow conversions between int and str or bytes int string with default base 10 int string base for all bases that are not a power of 2 str integer repr integer any other string conversion to base 10 for example f integer format integer or b d integer The limitations do not apply to functions with a linear algorithm int string base with base 2 4 8 16 or 32 int from_bytes and int to_bytes hex oct bin Format Specification Mini Language for hex octal and binary numbers str to float str to decimal Decimal Configuring the limit Before Python starts up you can use an environment variable or an interpreter command line flag to configure the limit PYTHONINTMAXSTRDIGITS e g PYTHONINTMAXSTRDIGITS 640 python3 to set the limit to 640 or PYTHONINTMAXSTRDIGITS 0 python3 to disable the limitation X int_max_str_digits e g python3 X int_max_str_digits 640 sys flags int_max_str_digits contains the value of PYTHONINTMAXSTRDIGITS or X int_max_str_digits If both the env var and the X option are set the X option takes precedence A value of 1 indicates that both were unset thus a value of sys int_info default_max_str_digits was used during initialization From code you can inspect the current limit and set a new one using these sys APIs sys get_int_max_str_digits and sys set_int_max_str_digits are a getter and setter for the interpreter wide limit Subinterpreters have their own limit Information about the default and minimum can be found in sys int_info sys int_info default_max_str_digits is the compiled in default limit sys int_info str_digits_check_threshold is the lowest accepted value for the limit other than 0 which disables it New in version 3 11 Caution Setting a low limit can lead to problems While rare code exists that contains integer constants in decimal in their source that exceed the minimum threshold A consequence of setting the limit is that Python source code containing decimal integer literals longer than the limit will encounter an error during parsing usually at startup time or import time or even at installation time anytime an up to date pyc does not already exist for the code A workaround for source that contains such large constants is to convert them to 0x hexadecimal form as it has no limit Test your application thoroughly if you use a low limit Ensure your tests run with the limit set early via the environment or flag so that it applies during startup and even during any installation step that may invoke Python to precompile py sources to pyc files Recommended configuration The default sys int_info default_max_str_digits is expected to be reasonable for most applications If your application requires a different limit set it from your main entry point using Python version agnostic code as these APIs were added in security patch releases in versions before 3 12 Example import sys if hasattr sys set_int_max_str_digits upper_bound 68000 lower_bound 4004 current_limit sys get_int_max_str_digits if current_limit 0 or current_limit upper_bound sys set_int_max_str_digits upper_bound elif current_limit lower_bound sys set_int_max_str_digits lower_bound If you need to disable it entirely set it to 0 Footnotes 1 Additional information on these special methods may be found in the Python Reference Manual Basic customization 2 As a consequence the list 1 2 is considered equal to 1 0 2 0 and similarly for tuples 3 They must have since the parser can t tell the type of the operands 4 Cased characters are those with general category property being one of Lu Letter uppercase Ll Letter lowercase or Lt Letter titlecase 5 To format only a tuple you should therefore provide a singleton tuple whose only element is the tuple to be formatted,en
919,test Regression tests package for Python Note The test package is meant for internal use by Python only It is documented for the benefit of the core developers of Python Any use of this package outside of Python s standard library is discouraged as code mentioned here can change or be removed without notice between releases of Python The test package contains all regression tests for Python as well as the modules test support and test regrtest test support is used to enhance your tests while test regrtest drives the testing suite Each module in the test package whose name starts with test_ is a testing suite for a specific module or feature All new tests should be written using the unittest or doctest module Some older tests are written using a traditional testing style that compares output printed to sys stdout this style of test is considered deprecated See also Module unittest Writing PyUnit regression tests Module doctest Tests embedded in documentation strings Writing Unit Tests for the test package It is preferred that tests that use the unittest module follow a few guidelines One is to name the test module by starting it with test_ and end it with the name of the module being tested The test methods in the test module should start with test_ and end with a description of what the method is testing This is needed so that the methods are recognized by the test driver as test methods Also no documentation string for the method should be included A comment such as Tests function returns only True or False should be used to provide documentation for test methods This is done because documentation strings get printed out if they exist and thus what test is being run is not stated A basic boilerplate is often used import unittest from test import support class MyTestCase1 unittest TestCase Only use setUp and tearDown if necessary def setUp self code to execute in preparation for tests def tearDown self code to execute to clean up after tests def test_feature_one self Test feature one testing code def test_feature_two self Test feature two testing code more test methods class MyTestCase2 unittest TestCase same structure as MyTestCase1 more test classes if __name__ __main__ unittest main This code pattern allows the testing suite to be run by test regrtest on its own as a script that supports the unittest CLI or via the python m unittest CLI The goal for regression testing is to try to break code This leads to a few guidelines to be followed The testing suite should exercise all classes functions and constants This includes not just the external API that is to be presented to the outside world but also private code Whitebox testing examining the code being tested when the tests are being written is preferred Blackbox testing testing only the published user interface is not complete enough to make sure all boundary and edge cases are tested Make sure all possible values are tested including invalid ones This makes sure that not only all valid values are acceptable but also that improper values are handled correctly Exhaust as many code paths as possible Test where branching occurs and thus tailor input to make sure as many different paths through the code are taken Add an explicit test for any bugs discovered for the tested code This will make sure that the error does not crop up again if the code is changed in the future Make sure to clean up after your tests such as close and remove all temporary files If a test is dependent on a specific condition of the operating system then verify the condition already exists before attempting the test Import as few modules as possible and do it as soon as possible This minimizes external dependencies of tests and also minimizes possible anomalous behavior from side effects of importing a module Try to maximize code reuse On occasion tests will vary by something as small as what type of input is used Minimize code duplication by subclassing a basic test class with a class that specifies the input class TestFuncAcceptsSequencesMixin func mySuperWhammyFunction def test_func self self fun,en
920,c self arg class AcceptLists TestFuncAcceptsSequencesMixin unittest TestCase arg 1 2 3 class AcceptStrings TestFuncAcceptsSequencesMixin unittest TestCase arg abc class AcceptTuples TestFuncAcceptsSequencesMixin unittest TestCase arg 1 2 3 When using this pattern remember that all classes that inherit from unittest TestCase are run as tests The TestFuncAcceptsSequencesMixin class in the example above does not have any data and so can t be run by itself thus it does not inherit from unittest TestCase See also Test Driven Development A book by Kent Beck on writing tests before code Running tests using the command line interface The test package can be run as a script to drive Python s regression test suite thanks to the m option python m test Under the hood it uses test regrtest the call python m test regrtest used in previous Python versions still works Running the script by itself automatically starts running all regression tests in the test package It does this by finding all modules in the package whose name starts with test_ importing them and executing the function test_main if present or loading the tests via unittest TestLoader loadTestsFromModule if test_main does not exist The names of tests to execute may also be passed to the script Specifying a single regression test python m test test_spam will minimize output and only print whether the test passed or failed Running test directly allows what resources are available for tests to use to be set You do this by using the u command line option Specifying all as the value for the u option enables all possible resources python m test uall If all but one resource is desired a more common case a comma separated list of resources that are not desired may be listed after all The command python m test uall audio largefile will run test with all resources except the audio and largefile resources For a list of all resources and more command line options run python m test h Some other ways to execute the regression tests depend on what platform the tests are being executed on On Unix you can run make test at the top level directory where Python was built On Windows executing rt bat from your PCbuild directory will run all regression tests test support Utilities for the Python test suite The test support module provides support for Python s regression test suite Note test support is not a public module It is documented here to help Python developers write tests The API of this module is subject to change without backwards compatibility concerns between releases This module defines the following exceptions exception test support TestFailed Exception to be raised when a test fails This is deprecated in favor of unittest based tests and unittest TestCase s assertion methods exception test support ResourceDenied Subclass of unittest SkipTest Raised when a resource such as a network connection is not available Raised by the requires function The test support module defines the following constants test support verbose True when verbose output is enabled Should be checked when more detailed information is desired about a running test verbose is set by test regrtest test support is_jython True if the running interpreter is Jython test support is_android True if the system is Android test support unix_shell Path for shell if not on Windows otherwise None test support LOOPBACK_TIMEOUT Timeout in seconds for tests using a network server listening on the network local loopback interface like 127 0 0 1 The timeout is long enough to prevent test failure it takes into account that the client and the server can run in different threads or even different processes The timeout should be long enough for connect recv and send methods of socket socket Its default value is 5 seconds See also INTERNET_TIMEOUT test support INTERNET_TIMEOUT Timeout in seconds for network requests going to the internet The timeout is short enough to prevent a test to wait for too long if the internet request is blocked for whatever reason Usually a timeout using INTERNET_TIMEOUT should not mark a test as failed but sk,en
921,ip the test instead see transient_internet Its default value is 1 minute See also LOOPBACK_TIMEOUT test support SHORT_TIMEOUT Timeout in seconds to mark a test as failed if the test takes too long The timeout value depends on the regrtest timeout command line option If a test using SHORT_TIMEOUT starts to fail randomly on slow buildbots use LONG_TIMEOUT instead Its default value is 30 seconds test support LONG_TIMEOUT Timeout in seconds to detect when a test hangs It is long enough to reduce the risk of test failure on the slowest Python buildbots It should not be used to mark a test as failed if the test takes too long The timeout value depends on the regrtest timeout command line option Its default value is 5 minutes See also LOOPBACK_TIMEOUT INTERNET_TIMEOUT and SHORT_TIMEOUT test support PGO Set when tests can be skipped when they are not useful for PGO test support PIPE_MAX_SIZE A constant that is likely larger than the underlying OS pipe buffer size to make writes blocking test support Py_DEBUG True if Python was built with the Py_DEBUG macro defined that is if Python was built in debug mode New in version 3 12 test support SOCK_MAX_SIZE A constant that is likely larger than the underlying OS socket buffer size to make writes blocking test support TEST_SUPPORT_DIR Set to the top level directory that contains test support test support TEST_HOME_DIR Set to the top level directory for the test package test support TEST_DATA_DIR Set to the data directory within the test package test support MAX_Py_ssize_t Set to sys maxsize for big memory tests test support max_memuse Set by set_memlimit as the memory limit for big memory tests Limited by MAX_Py_ssize_t test support real_max_memuse Set by set_memlimit as the memory limit for big memory tests Not limited by MAX_Py_ssize_t test support MISSING_C_DOCSTRINGS Set to True if Python is built without docstrings the WITH_DOC_STRINGS macro is not defined See the configure without doc strings option See also the HAVE_DOCSTRINGS variable test support HAVE_DOCSTRINGS Set to True if function docstrings are available See the python OO option which strips docstrings of functions implemented in Python See also the MISSING_C_DOCSTRINGS variable test support TEST_HTTP_URL Define the URL of a dedicated HTTP server for the network tests test support ALWAYS_EQ Object that is equal to anything Used to test mixed type comparison test support NEVER_EQ Object that is not equal to anything even to ALWAYS_EQ Used to test mixed type comparison test support LARGEST Object that is greater than anything except itself Used to test mixed type comparison test support SMALLEST Object that is less than anything except itself Used to test mixed type comparison The test support module defines the following functions test support busy_retry timeout err_msg None error True Run the loop body until break stops the loop After timeout seconds raise an AssertionError if error is true or just stop the loop if error is false Example for _ in support busy_retry support SHORT_TIMEOUT if check break Example of error False usage for _ in support busy_retry support SHORT_TIMEOUT error False if check break else raise RuntimeError my custom error test support sleeping_retry timeout err_msg None init_delay 0 010 max_delay 1 0 error True Wait strategy that applies exponential backoff Run the loop body until break stops the loop Sleep at each loop iteration but not at the first iteration The sleep delay is doubled at each iteration up to max_delay seconds See busy_retry documentation for the parameters usage Example raising an exception after SHORT_TIMEOUT seconds for _ in support sleeping_retry support SHORT_TIMEOUT if check break Example of error False usage for _ in support sleeping_retry support SHORT_TIMEOUT error False if check break else raise RuntimeError my custom error test support is_resource_enabled resource Return True if resource is enabled and available The list of available resources is only set when test regrtest is executing the tests test support python_is_optimized Return True if Python was not built with ,en
922,O0 or Og test support with_pymalloc Return _testcapi WITH_PYMALLOC test support requires resource msg None Raise ResourceDenied if resource is not available msg is the argument to ResourceDenied if it is raised Always returns True if called by a function whose __name__ is __main__ Used when tests are executed by test regrtest test support sortdict dict Return a repr of dict with keys sorted test support findfile filename subdir None Return the path to the file named filename If no match is found filename is returned This does not equal a failure since it could be the path to the file Setting subdir indicates a relative path to use to find the file rather than looking directly in the path directories test support get_pagesize Get size of a page in bytes New in version 3 12 test support setswitchinterval interval Set the sys setswitchinterval to the given interval Defines a minimum interval for Android systems to prevent the system from hanging test support check_impl_detail guards Use this check to guard CPython s implementation specific tests or to run them only on the implementations guarded by the arguments This function returns True or False depending on the host platform Example usage check_impl_detail Only on CPython default check_impl_detail jython True Only on Jython check_impl_detail cpython False Everywhere except CPython test support set_memlimit limit Set the values for max_memuse and real_max_memuse for big memory tests test support record_original_stdout stdout Store the value from stdout It is meant to hold the stdout at the time the regrtest began test support get_original_stdout Return the original stdout set by record_original_stdout or sys stdout if it s not set test support args_from_interpreter_flags Return a list of command line arguments reproducing the current settings in sys flags and sys warnoptions test support optim_args_from_interpreter_flags Return a list of command line arguments reproducing the current optimization settings in sys flags test support captured_stdin test support captured_stdout test support captured_stderr A context managers that temporarily replaces the named stream with io StringIO object Example use with output streams with captured_stdout as stdout captured_stderr as stderr print hello print error file sys stderr assert stdout getvalue hello n assert stderr getvalue error n Example use with input stream with captured_stdin as stdin stdin write hello n stdin seek 0 call test code that consumes from sys stdin captured input self assertEqual captured hello test support disable_faulthandler A context manager that temporary disables faulthandler test support gc_collect Force as many objects as possible to be collected This is needed because timely deallocation is not guaranteed by the garbage collector This means that __del__ methods may be called later than expected and weakrefs may remain alive for longer than expected test support disable_gc A context manager that disables the garbage collector on entry On exit the garbage collector is restored to its prior state test support swap_attr obj attr new_val Context manager to swap out an attribute with a new object Usage with swap_attr obj attr 5 This will set obj attr to 5 for the duration of the with block restoring the old value at the end of the block If attr doesn t exist on obj it will be created and then deleted at the end of the block The old value or None if it doesn t exist will be assigned to the target of the as clause if there is one test support swap_item obj attr new_val Context manager to swap out an item with a new object Usage with swap_item obj item 5 This will set obj item to 5 for the duration of the with block restoring the old value at the end of the block If item doesn t exist on obj it will be created and then deleted at the end of the block The old value or None if it doesn t exist will be assigned to the target of the as clause if there is one test support flush_std_streams Call the flush method on sys stdout and then on sys stderr It can be used to make sure that the logs order is consistent before wr,en
923,iting into stderr New in version 3 11 test support print_warning msg Print a warning into sys __stderr__ Format the message as f Warning msg If msg is made of multiple lines add Warning prefix to each line New in version 3 9 test support wait_process pid exitcode timeout None Wait until process pid completes and check that the process exit code is exitcode Raise an AssertionError if the process exit code is not equal to exitcode If the process runs longer than timeout seconds SHORT_TIMEOUT by default kill the process and raise an AssertionError The timeout feature is not available on Windows New in version 3 9 test support calcobjsize fmt Return the size of the PyObject whose structure members are defined by fmt The returned value includes the size of the Python object header and alignment test support calcvobjsize fmt Return the size of the PyVarObject whose structure members are defined by fmt The returned value includes the size of the Python object header and alignment test support checksizeof test o size For testcase test assert that the sys getsizeof for o plus the GC header size equals size test support anticipate_failure condition A decorator to conditionally mark tests with unittest expectedFailure Any use of this decorator should have an associated comment identifying the relevant tracker issue test support system_must_validate_cert f A decorator that skips the decorated test on TLS certification validation failures test support run_with_locale catstr locales A decorator for running a function in a different locale correctly resetting it after it has finished catstr is the locale category as a string for example LC_ALL The locales passed will be tried sequentially and the first valid locale will be used test support run_with_tz tz A decorator for running a function in a specific timezone correctly resetting it after it has finished test support requires_freebsd_version min_version Decorator for the minimum version when running test on FreeBSD If the FreeBSD version is less than the minimum the test is skipped test support requires_linux_version min_version Decorator for the minimum version when running test on Linux If the Linux version is less than the minimum the test is skipped test support requires_mac_version min_version Decorator for the minimum version when running test on macOS If the macOS version is less than the minimum the test is skipped test support requires_IEEE_754 Decorator for skipping tests on non IEEE 754 platforms test support requires_zlib Decorator for skipping tests if zlib doesn t exist test support requires_gzip Decorator for skipping tests if gzip doesn t exist test support requires_bz2 Decorator for skipping tests if bz2 doesn t exist test support requires_lzma Decorator for skipping tests if lzma doesn t exist test support requires_resource resource Decorator for skipping tests if resource is not available test support requires_docstrings Decorator for only running the test if HAVE_DOCSTRINGS test support requires_limited_api Decorator for only running the test if Limited C API is available test support cpython_only Decorator for tests only applicable to CPython test support impl_detail msg None guards Decorator for invoking check_impl_detail on guards If that returns False then uses msg as the reason for skipping the test test support no_tracing Decorator to temporarily turn off tracing for the duration of the test test support refcount_test Decorator for tests which involve reference counting The decorator does not run the test if it is not run by CPython Any trace function is unset for the duration of the test to prevent unexpected refcounts caused by the trace function test support bigmemtest size memuse dry_run True Decorator for bigmem tests size is a requested size for the test in arbitrary test interpreted units memuse is the number of bytes per unit for the test or a good estimate of it For example a test that needs two byte buffers of 4 GiB each could be decorated with bigmemtest size _4G memuse 2 The size argument is normally passed to the decorated test method as an extr,en
924,a argument If dry_run is True the value passed to the test method may be less than the requested value If dry_run is False it means the test doesn t support dummy runs when M is not specified test support bigaddrspacetest Decorator for tests that fill the address space test support check_syntax_error testcase statement errtext lineno None offset None Test for syntax errors in statement by attempting to compile statement testcase is the unittest instance for the test errtext is the regular expression which should match the string representation of the raised SyntaxError If lineno is not None compares to the line of the exception If offset is not None compares to the offset of the exception test support open_urlresource url args kw Open url If open fails raises TestFailed test support reap_children Use this at the end of test_main whenever sub processes are started This will help ensure that no extra children zombies stick around to hog resources and create problems when looking for refleaks test support get_attribute obj name Get an attribute raising unittest SkipTest if AttributeError is raised test support catch_unraisable_exception Context manager catching unraisable exception using sys unraisablehook Storing the exception value cm unraisable exc_value creates a reference cycle The reference cycle is broken explicitly when the context manager exits Storing the object cm unraisable object can resurrect it if it is set to an object which is being finalized Exiting the context manager clears the stored object Usage with support catch_unraisable_exception as cm code creating an unraisable exception check the unraisable exception use cm unraisable cm unraisable attribute no longer exists at this point to break a reference cycle New in version 3 8 test support load_package_tests pkg_dir loader standard_tests pattern Generic implementation of the unittest load_tests protocol for use in test packages pkg_dir is the root directory of the package loader standard_tests and pattern are the arguments expected by load_tests In simple cases the test package s __init__ py can be the following import os from test support import load_package_tests def load_tests args return load_package_tests os path dirname __file__ args test support detect_api_mismatch ref_api other_api ignore Returns the set of attributes functions or methods of ref_api not found on other_api except for a defined list of items to be ignored in this check specified in ignore By default this skips private attributes beginning with _ but includes all magic methods i e those starting and ending in __ New in version 3 5 test support patch test_instance object_to_patch attr_name new_value Override object_to_patch attr_name with new_value Also add cleanup procedure to test_instance to restore object_to_patch for attr_name The attr_name should be a valid attribute for object_to_patch test support run_in_subinterp code Run code in subinterpreter Raise unittest SkipTest if tracemalloc is enabled test support check_free_after_iterating test iter cls args Assert instances of cls are deallocated after iterating test support missing_compiler_executable cmd_names Check for the existence of the compiler executables whose names are listed in cmd_names or all the compiler executables when cmd_names is empty and return the first missing executable or None when none is found missing test support check__all__ test_case module name_of_module None extra not_exported Assert that the __all__ variable of module contains all public names The module s public names its API are detected automatically based on whether they match the public name convention and were defined in module The name_of_module argument can specify as a string or tuple thereof what module s an API could be defined in order to be detected as a public API One case for this is when module imports part of its public API from other modules possibly a C backend like csv and its _csv The extra argument can be a set of names that wouldn t otherwise be automatically detected as public like objects without a proper __module__ attribut,en
925,e If provided it will be added to the automatically detected ones The not_exported argument can be a set of names that must not be treated as part of the public API even though their names indicate otherwise Example use import bar import foo import unittest from test import support class MiscTestCase unittest TestCase def test__all__ self support check__all__ self foo class OtherTestCase unittest TestCase def test__all__ self extra BAR_CONST FOO_CONST not_exported baz Undocumented name bar imports part of its API from _bar support check__all__ self bar bar _bar extra extra not_exported not_exported New in version 3 6 test support skip_if_broken_multiprocessing_synchronize Skip tests if the multiprocessing synchronize module is missing if there is no available semaphore implementation or if creating a lock raises an OSError New in version 3 10 test support check_disallow_instantiation test_case tp args kwds Assert that type tp cannot be instantiated using args and kwds New in version 3 10 test support adjust_int_max_str_digits max_digits This function returns a context manager that will change the global sys set_int_max_str_digits setting for the duration of the context to allow execution of test code that needs a different limit on the number of digits when converting between an integer and string New in version 3 11 The test support module defines the following classes class test support SuppressCrashReport A context manager used to try to prevent crash dialog popups on tests that are expected to crash a subprocess On Windows it disables Windows Error Reporting dialogs using SetErrorMode On UNIX resource setrlimit is used to set resource RLIMIT_CORE s soft limit to 0 to prevent coredump file creation On both platforms the old value is restored by __exit__ class test support SaveSignals Class to save and restore signal handlers registered by the Python signal handler save self Save the signal handlers to a dictionary mapping signal numbers to the current signal handler restore self Set the signal numbers from the save dictionary to the saved handler class test support Matcher matches self d kwargs Try to match a single dict with the supplied arguments match_value self k dv v Try to match a single stored value dv with a supplied value v test support socket_helper Utilities for socket tests The test support socket_helper module provides support for socket tests New in version 3 9 test support socket_helper IPV6_ENABLED Set to True if IPv6 is enabled on this host False otherwise test support socket_helper find_unused_port family socket AF_INET socktype socket SOCK_STREAM Returns an unused port that should be suitable for binding This is achieved by creating a temporary socket with the same family and type as the sock parameter default is AF_INET SOCK_STREAM and binding it to the specified host address defaults to 0 0 0 0 with the port set to 0 eliciting an unused ephemeral port from the OS The temporary socket is then closed and deleted and the ephemeral port is returned Either this method or bind_port should be used for any tests where a server socket needs to be bound to a particular port for the duration of the test Which one to use depends on whether the calling code is creating a Python socket or if an unused port needs to be provided in a constructor or passed to an external program i e the accept argument to openssl s s_server mode Always prefer bind_port over find_unused_port where possible Using a hard coded port is discouraged since it can make multiple instances of the test impossible to run simultaneously which is a problem for buildbots test support socket_helper bind_port sock host HOST Bind the socket to a free port and return the port number Relies on ephemeral ports in order to ensure we are using an unbound port This is important as many tests may be running simultaneously especially in a buildbot environment This method raises an exception if the sock family is AF_INET and sock type is SOCK_STREAM and the socket has SO_REUSEADDR or SO_REUSEPORT set on it Tests should never set these socket options for TCP,en
926, IP sockets The only case for setting these options is testing multicasting via multiple UDP sockets Additionally if the SO_EXCLUSIVEADDRUSE socket option is available i e on Windows it will be set on the socket This will prevent anyone else from binding to our host port for the duration of the test test support socket_helper bind_unix_socket sock addr Bind a Unix socket raising unittest SkipTest if PermissionError is raised test support socket_helper skip_unless_bind_unix_socket A decorator for running tests that require a functional bind for Unix sockets test support socket_helper transient_internet resource_name timeout 30 0 errnos A context manager that raises ResourceDenied when various issues with the internet connection manifest themselves as exceptions test support script_helper Utilities for the Python execution tests The test support script_helper module provides support for Python s script execution tests test support script_helper interpreter_requires_environment Return True if sys executable interpreter requires environment variables in order to be able to run at all This is designed to be used with unittest skipIf to annotate tests that need to use an assert_python function to launch an isolated mode I or no environment mode E sub interpreter process A normal build test does not run into this situation but it can happen when trying to run the standard library test suite from an interpreter that doesn t have an obvious home with Python s current home finding logic Setting PYTHONHOME is one way to get most of the testsuite to run in that situation PYTHONPATH or PYTHONUSERSITE are other common environment variables that might impact whether or not the interpreter can start test support script_helper run_python_until_end args env_vars Set up the environment based on env_vars for running the interpreter in a subprocess The values can include __isolated __cleanenv __cwd and TERM Changed in version 3 9 The function no longer strips whitespaces from stderr test support script_helper assert_python_ok args env_vars Assert that running the interpreter with args and optional environment variables env_vars succeeds rc 0 and return a return code stdout stderr tuple If the __cleanenv keyword only parameter is set env_vars is used as a fresh environment Python is started in isolated mode command line option I except if the __isolated keyword only parameter is set to False Changed in version 3 9 The function no longer strips whitespaces from stderr test support script_helper assert_python_failure args env_vars Assert that running the interpreter with args and optional environment variables env_vars fails rc 0 and return a return code stdout stderr tuple See assert_python_ok for more options Changed in version 3 9 The function no longer strips whitespaces from stderr test support script_helper spawn_python args stdout subprocess PIPE stderr subprocess STDOUT kw Run a Python subprocess with the given arguments kw is extra keyword args to pass to subprocess Popen Returns a subprocess Popen object test support script_helper kill_python p Run the given subprocess Popen process until completion and return stdout test support script_helper make_script script_dir script_basename source omit_suffix False Create script containing source in path script_dir and script_basename If omit_suffix is False append py to the name Return the full script path test support script_helper make_zip_script zip_dir zip_basename script_name name_in_zip None Create zip file at zip_dir and zip_basename with extension zip which contains the files in script_name name_in_zip is the archive name Return a tuple containing full path full path of archive name test support script_helper make_pkg pkg_dir init_source Create a directory named pkg_dir containing an __init__ file with init_source as its contents test support script_helper make_zip_pkg zip_dir zip_basename pkg_name script_basename source depth 1 compiled False Create a zip package directory with a path of zip_dir and zip_basename containing an empty __init__ file and a file script_basename containing ,en
927,the source If compiled is True both source files will be compiled and added to the zip package Return a tuple of the full zip path and the archive name for the zip file test support bytecode_helper Support tools for testing correct bytecode generation The test support bytecode_helper module provides support for testing and inspecting bytecode generation New in version 3 9 The module defines the following class class test support bytecode_helper BytecodeTestCase unittest TestCase This class has custom assertion methods for inspecting bytecode BytecodeTestCase get_disassembly_as_string co Return the disassembly of co as string BytecodeTestCase assertInBytecode x opname argval _UNSPECIFIED Return instr if opname is found otherwise throws AssertionError BytecodeTestCase assertNotInBytecode x opname argval _UNSPECIFIED Throws AssertionError if opname is found test support threading_helper Utilities for threading tests The test support threading_helper module provides support for threading tests New in version 3 10 test support threading_helper join_thread thread timeout None Join a thread within timeout Raise an AssertionError if thread is still alive after timeout seconds test support threading_helper reap_threads Decorator to ensure the threads are cleaned up even if the test fails test support threading_helper start_threads threads unlock None Context manager to start threads which is a sequence of threads unlock is a function called after the threads are started even if an exception was raised an example would be threading Event set start_threads will attempt to join the started threads upon exit test support threading_helper threading_cleanup original_values Cleanup up threads not specified in original_values Designed to emit a warning if a test leaves running threads in the background test support threading_helper threading_setup Return current thread count and copy of dangling threads test support threading_helper wait_threads_exit timeout None Context manager to wait until all threads created in the with statement exit test support threading_helper catch_threading_exception Context manager catching threading Thread exception using threading excepthook Attributes set when an exception is caught exc_type exc_value exc_traceback thread See threading excepthook documentation These attributes are deleted at the context manager exit Usage with threading_helper catch_threading_exception as cm code spawning a thread which raises an exception check the thread exception use cm attributes exc_type exc_value exc_traceback thread exc_type exc_value exc_traceback thread attributes of cm no longer exists at this point to avoid reference cycles New in version 3 8 test support os_helper Utilities for os tests The test support os_helper module provides support for os tests New in version 3 10 test support os_helper FS_NONASCII A non ASCII character encodable by os fsencode test support os_helper SAVEDCWD Set to os getcwd test support os_helper TESTFN Set to a name that is safe to use as the name of a temporary file Any temporary file that is created should be closed and unlinked removed test support os_helper TESTFN_NONASCII Set to a filename containing the FS_NONASCII character if it exists This guarantees that if the filename exists it can be encoded and decoded with the default filesystem encoding This allows tests that require a non ASCII filename to be easily skipped on platforms where they can t work test support os_helper TESTFN_UNENCODABLE Set to a filename str type that should not be able to be encoded by file system encoding in strict mode It may be None if it s not possible to generate such a filename test support os_helper TESTFN_UNDECODABLE Set to a filename bytes type that should not be able to be decoded by file system encoding in strict mode It may be None if it s not possible to generate such a filename test support os_helper TESTFN_UNICODE Set to a non ASCII name for a temporary file class test support os_helper EnvironmentVarGuard Class used to temporarily set or unset environment variables Instances can be used as a,en
928, context manager and have a complete dictionary interface for querying modifying the underlying os environ After exit from the context manager all changes to environment variables done through this instance will be rolled back Changed in version 3 1 Added dictionary interface class test support os_helper FakePath path Simple path like object It implements the __fspath__ method which just returns the path argument If path is an exception it will be raised in __fspath__ EnvironmentVarGuard set envvar value Temporarily set the environment variable envvar to the value of value EnvironmentVarGuard unset envvar Temporarily unset the environment variable envvar test support os_helper can_symlink Return True if the OS supports symbolic links False otherwise test support os_helper can_xattr Return True if the OS supports xattr False otherwise test support os_helper change_cwd path quiet False A context manager that temporarily changes the current working directory to path and yields the directory If quiet is False the context manager raises an exception on error Otherwise it issues only a warning and keeps the current working directory the same test support os_helper create_empty_file filename Create an empty file with filename If it already exists truncate it test support os_helper fd_count Count the number of open file descriptors test support os_helper fs_is_case_insensitive directory Return True if the file system for directory is case insensitive test support os_helper make_bad_fd Create an invalid file descriptor by opening and closing a temporary file and returning its descriptor test support os_helper rmdir filename Call os rmdir on filename On Windows platforms this is wrapped with a wait loop that checks for the existence of the file which is needed due to antivirus programs that can hold files open and prevent deletion test support os_helper rmtree path Call shutil rmtree on path or call os lstat and os rmdir to remove a path and its contents As with rmdir on Windows platforms this is wrapped with a wait loop that checks for the existence of the files test support os_helper skip_unless_symlink A decorator for running tests that require support for symbolic links test support os_helper skip_unless_xattr A decorator for running tests that require support for xattr test support os_helper temp_cwd name tempcwd quiet False A context manager that temporarily creates a new directory and changes the current working directory CWD The context manager creates a temporary directory in the current directory with name name before temporarily changing the current working directory If name is None the temporary directory is created using tempfile mkdtemp If quiet is False and it is not possible to create or change the CWD an error is raised Otherwise only a warning is raised and the original CWD is used test support os_helper temp_dir path None quiet False A context manager that creates a temporary directory at path and yields the directory If path is None the temporary directory is created using tempfile mkdtemp If quiet is False the context manager raises an exception on error Otherwise if path is specified and cannot be created only a warning is issued test support os_helper temp_umask umask A context manager that temporarily sets the process umask test support os_helper unlink filename Call os unlink on filename As with rmdir on Windows platforms this is wrapped with a wait loop that checks for the existence of the file test support import_helper Utilities for import tests The test support import_helper module provides support for import tests New in version 3 10 test support import_helper forget module_name Remove the module named module_name from sys modules and delete any byte compiled files of the module test support import_helper import_fresh_module name fresh blocked deprecated False This function imports and returns a fresh copy of the named Python module by removing the named module from sys modules before doing the import Note that unlike reload the original module is not affected by this operation fresh is an iterable of,en
929, additional module names that are also removed from the sys modules cache before doing the import blocked is an iterable of module names that are replaced with None in the module cache during the import to ensure that attempts to import them raise ImportError The named module and any modules named in the fresh and blocked parameters are saved before starting the import and then reinserted into sys modules when the fresh import is complete Module and package deprecation messages are suppressed during this import if deprecated is True This function will raise ImportError if the named module cannot be imported Example use Get copies of the warnings module for testing without affecting the version being used by the rest of the test suite One copy uses the C implementation the other is forced to use the pure Python fallback implementation py_warnings import_fresh_module warnings blocked _warnings c_warnings import_fresh_module warnings fresh _warnings New in version 3 1 test support import_helper import_module name deprecated False required_on This function imports and returns the named module Unlike a normal import this function raises unittest SkipTest if the module cannot be imported Module and package deprecation messages are suppressed during this import if deprecated is True If a module is required on a platform but optional for others set required_on to an iterable of platform prefixes which will be compared against sys platform New in version 3 1 test support import_helper modules_setup Return a copy of sys modules test support import_helper modules_cleanup oldmodules Remove modules except for oldmodules and encodings in order to preserve internal cache test support import_helper unload name Delete name from sys modules test support import_helper make_legacy_pyc source Move a PEP 3147 PEP 488 pyc file to its legacy pyc location and return the file system path to the legacy pyc file The source value is the file system path to the source file It does not need to exist however the PEP 3147 488 pyc file must exist class test support import_helper CleanImport module_names A context manager to force import to return a new module reference This is useful for testing module level behaviors such as the emission of a DeprecationWarning on import Example usage with CleanImport foo importlib import_module foo New reference class test support import_helper DirsOnSysPath paths A context manager to temporarily add directories to sys path This makes a copy of sys path appends any directories given as positional arguments then reverts sys path to the copied settings when the context ends Note that all sys path modifications in the body of the context manager including replacement of the object will be reverted at the end of the block test support warnings_helper Utilities for warnings tests The test support warnings_helper module provides support for warnings tests New in version 3 10 test support warnings_helper ignore_warnings category Suppress warnings that are instances of category which must be Warning or a subclass Roughly equivalent to warnings catch_warnings with warnings simplefilter ignore category category For example warning_helper ignore_warnings category DeprecationWarning def test_suppress_warning do something New in version 3 8 test support warnings_helper check_no_resource_warning testcase Context manager to check that no ResourceWarning was raised You must remove the object which may emit ResourceWarning before the end of the context manager test support warnings_helper check_syntax_warning testcase statement errtext lineno 1 offset None Test for syntax warning in statement by attempting to compile statement Test also that the SyntaxWarning is emitted only once and that it will be converted to a SyntaxError when turned into error testcase is the unittest instance for the test errtext is the regular expression which should match the string representation of the emitted SyntaxWarning and raised SyntaxError If lineno is not None compares to the line of the warning and exception If offset is not None compares to the offs,en
930,et of the exception New in version 3 8 test support warnings_helper check_warnings filters quiet True A convenience wrapper for warnings catch_warnings that makes it easier to test that a warning was correctly raised It is approximately equivalent to calling warnings catch_warnings record True with warnings simplefilter set to always and with the option to automatically validate the results that are recorded check_warnings accepts 2 tuples of the form message regexp WarningCategory as positional arguments If one or more filters are provided or if the optional keyword argument quiet is False it checks to make sure the warnings are as expected each specified filter must match at least one of the warnings raised by the enclosed code or the test fails and if any warnings are raised that do not match any of the specified filters the test fails To disable the first of these checks set quiet to True If no arguments are specified it defaults to check_warnings Warning quiet True In this case all warnings are caught and no errors are raised On entry to the context manager a WarningRecorder instance is returned The underlying warnings list from catch_warnings is available via the recorder object s warnings attribute As a convenience the attributes of the object representing the most recent warning can also be accessed directly through the recorder object see example below If no warning has been raised then any of the attributes that would otherwise be expected on an object representing a warning will return None The recorder object also has a reset method which clears the warnings list The context manager is designed to be used like this with check_warnings assertion is always true SyntaxWarning UserWarning exec assert False Hey warnings warn UserWarning Hide me In this case if either warning was not raised or some other warning was raised check_warnings would raise an error When a test needs to look more deeply into the warnings rather than just checking whether or not they occurred code like this can be used with check_warnings quiet True as w warnings warn foo assert str w args 0 foo warnings warn bar assert str w args 0 bar assert str w warnings 0 args 0 foo assert str w warnings 1 args 0 bar w reset assert len w warnings 0 Here all warnings will be caught and the test code tests the captured warnings directly Changed in version 3 2 New optional arguments filters and quiet class test support warnings_helper WarningsRecorder Class used to record warnings for unit tests See documentation of check_warnings above for more details,en
931,1 Whetting Your Appetite If you do much work on computers eventually you find that there s some task you d like to automate For example you may wish to perform a search and replace over a large number of text files or rename and rearrange a bunch of photo files in a complicated way Perhaps you d like to write a small custom database or a specialized GUI application or a simple game If you re a professional software developer you may have to work with several C C Java libraries but find the usual write compile test re compile cycle is too slow Perhaps you re writing a test suite for such a library and find writing the testing code a tedious task Or maybe you ve written a program that could use an extension language and you don t want to design and implement a whole new language for your application Python is just the language for you You could write a Unix shell script or Windows batch files for some of these tasks but shell scripts are best at moving around files and changing text data not well suited for GUI applications or games You could write a C C Java program but it can take a lot of development time to get even a first draft program Python is simpler to use available on Windows macOS and Unix operating systems and will help you get the job done more quickly Python is simple to use but it is a real programming language offering much more structure and support for large programs than shell scripts or batch files can offer On the other hand Python also offers much more error checking than C and being a very high level language it has high level data types built in such as flexible arrays and dictionaries Because of its more general data types Python is applicable to a much larger problem domain than Awk or even Perl yet many things are at least as easy in Python as in those languages Python allows you to split your program into modules that can be reused in other Python programs It comes with a large collection of standard modules that you can use as the basis of your programs or as examples to start learning to program in Python Some of these modules provide things like file I O system calls sockets and even interfaces to graphical user interface toolkits like Tk Python is an interpreted language which can save you considerable time during program development because no compilation and linking is necessary The interpreter can be used interactively which makes it easy to experiment with features of the language to write throw away programs or to test functions during bottom up program development It is also a handy desk calculator Python enables programs to be written compactly and readably Programs written in Python are typically much shorter than equivalent C C or Java programs for several reasons the high level data types allow you to express complex operations in a single statement statement grouping is done by indentation instead of beginning and ending brackets no variable or argument declarations are necessary Python is extensible if you know how to program in C it is easy to add a new built in function or module to the interpreter either to perform critical operations at maximum speed or to link Python programs to libraries that may only be available in binary form such as a vendor specific graphics library Once you are really hooked you can link the Python interpreter into an application written in C and use it as an extension or command language for that application By the way the language is named after the BBC show Monty Python s Flying Circus and has nothing to do with reptiles Making references to Monty Python skits in documentation is not only allowed it is encouraged Now that you are all excited about Python you ll want to examine it in some more detail Since the best way to learn a language is to use it the tutorial invites you to play with the Python interpreter as you read In the next chapter the mechanics of using the interpreter are explained This is rather mundane information but essential for trying out the examples shown later The rest of the tutorial introduces various features of the Python ,en
932,language and system through examples beginning with simple expressions statements and data types through functions and modules and finally touching upon advanced concepts like exceptions and user defined classes,en
933,Internet Protocols and Support The modules described in this chapter implement internet protocols and support for related technology They are all implemented in Python Most of these modules require the presence of the system dependent module socket which is currently supported on most popular platforms Here is an overview webbrowser Convenient web browser controller Browser Controller Objects wsgiref WSGI Utilities and Reference Implementation wsgiref util WSGI environment utilities wsgiref headers WSGI response header tools wsgiref simple_server a simple WSGI HTTP server wsgiref validate WSGI conformance checker wsgiref handlers server gateway base classes wsgiref types WSGI types for static type checking Examples urllib URL handling modules urllib request Extensible library for opening URLs Request Objects OpenerDirector Objects BaseHandler Objects HTTPRedirectHandler Objects HTTPCookieProcessor Objects ProxyHandler Objects HTTPPasswordMgr Objects HTTPPasswordMgrWithPriorAuth Objects AbstractBasicAuthHandler Objects HTTPBasicAuthHandler Objects ProxyBasicAuthHandler Objects AbstractDigestAuthHandler Objects HTTPDigestAuthHandler Objects ProxyDigestAuthHandler Objects HTTPHandler Objects HTTPSHandler Objects FileHandler Objects DataHandler Objects FTPHandler Objects CacheFTPHandler Objects UnknownHandler Objects HTTPErrorProcessor Objects Examples Legacy interface urllib request Restrictions urllib response Response classes used by urllib urllib parse Parse URLs into components URL Parsing URL parsing security Parsing ASCII Encoded Bytes Structured Parse Results URL Quoting urllib error Exception classes raised by urllib request urllib robotparser Parser for robots txt http HTTP modules HTTP status codes HTTP status category HTTP methods http client HTTP protocol client HTTPConnection Objects HTTPResponse Objects Examples HTTPMessage Objects ftplib FTP protocol client Reference FTP objects FTP_TLS objects Module variables poplib POP3 protocol client POP3 Objects POP3 Example imaplib IMAP4 protocol client IMAP4 Objects IMAP4 Example smtplib SMTP protocol client SMTP Objects SMTP Example uuid UUID objects according to RFC 4122 Command Line Usage Example Command Line Example socketserver A framework for network servers Server Creation Notes Server Objects Request Handler Objects Examples socketserver TCPServer Example socketserver UDPServer Example Asynchronous Mixins http server HTTP servers Security Considerations http cookies HTTP state management Cookie Objects Morsel Objects Example http cookiejar Cookie handling for HTTP clients CookieJar and FileCookieJar Objects FileCookieJar subclasses and co operation with web browsers CookiePolicy Objects DefaultCookiePolicy Objects Cookie Objects Examples xmlrpc XMLRPC server and client modules xmlrpc client XML RPC client access ServerProxy Objects DateTime Objects Binary Objects Fault Objects ProtocolError Objects MultiCall Objects Convenience Functions Example of Client Usage Example of Client and Server Usage xmlrpc server Basic XML RPC servers SimpleXMLRPCServer Objects SimpleXMLRPCServer Example CGIXMLRPCRequestHandler Documenting XMLRPC server DocXMLRPCServer Objects DocCGIXMLRPCRequestHandler ipaddress IPv4 IPv6 manipulation library Convenience factory functions IP Addresses Address objects Conversion to Strings and Integers Operators Comparison operators Arithmetic operators IP Network definitions Prefix net mask and host mask Network objects Operators Logical operators Iteration Networks as containers of addresses Interface objects Operators Logical operators Other Module Level Functions Custom Exceptions,en
934,16 Appendix 16 1 Interactive Mode 16 1 1 Error Handling When an error occurs the interpreter prints an error message and a stack trace In interactive mode it then returns to the primary prompt when input came from a file it exits with a nonzero exit status after printing the stack trace Exceptions handled by an except clause in a try statement are not errors in this context Some errors are unconditionally fatal and cause an exit with a nonzero exit status this applies to internal inconsistencies and some cases of running out of memory All error messages are written to the standard error stream normal output from executed commands is written to standard output Typing the interrupt character usually Control C or Delete to the primary or secondary prompt cancels the input and returns to the primary prompt 1 Typing an interrupt while a command is executing raises the KeyboardInterrupt exception which may be handled by a try statement 16 1 2 Executable Python Scripts On BSD ish Unix systems Python scripts can be made directly executable like shell scripts by putting the line usr bin env python3 5 assuming that the interpreter is on the user s PATH at the beginning of the script and giving the file an executable mode The must be the first two characters of the file On some platforms this first line must end with a Unix style line ending n not a Windows r n line ending Note that the hash or pound character is used to start a comment in Python The script can be given an executable mode or permission using the chmod command chmod x myscript py On Windows systems there is no notion of an executable mode The Python installer automatically associates py files with python exe so that a double click on a Python file will run it as a script The extension can also be pyw in that case the console window that normally appears is suppressed 16 1 3 The Interactive Startup File When you use Python interactively it is frequently handy to have some standard commands executed every time the interpreter is started You can do this by setting an environment variable named PYTHONSTARTUP to the name of a file containing your start up commands This is similar to the profile feature of the Unix shells This file is only read in interactive sessions not when Python reads commands from a script and not when dev tty is given as the explicit source of commands which otherwise behaves like an interactive session It is executed in the same namespace where interactive commands are executed so that objects that it defines or imports can be used without qualification in the interactive session You can also change the prompts sys ps1 and sys ps2 in this file If you want to read an additional start up file from the current directory you can program this in the global start up file using code like if os path isfile pythonrc py exec open pythonrc py read If you want to use the startup file in a script you must do this explicitly in the script import os filename os environ get PYTHONSTARTUP if filename and os path isfile filename with open filename as fobj startup_file fobj read exec startup_file 16 1 4 The Customization Modules Python provides two hooks to let you customize it sitecustomize and usercustomize To see how it works you need first to find the location of your user site packages directory Start Python and run this code import site site getusersitepackages home user local lib python3 5 site packages Now you can create a file named usercustomize py in that directory and put anything you want in it It will affect every invocation of Python unless it is started with the s option to disable the automatic import sitecustomize works in the same way but is typically created by an administrator of the computer in the global site packages directory and is imported before usercustomize See the documentation of the site module for more details Footnotes 1 A problem with the GNU Readline package may prevent this,en
935,hashlib Secure hashes and message digests Source code Lib hashlib py This module implements a common interface to many different secure hash and message digest algorithms Included are the FIPS secure hash algorithms SHA1 SHA224 SHA256 SHA384 SHA512 defined in the FIPS 180 4 standard the SHA 3 series defined in the FIPS 202 standard as well as RSA s MD5 algorithm defined in internet RFC 1321 The terms secure hash and message digest are interchangeable Older algorithms were called message digests The modern term is secure hash Note If you want the adler32 or crc32 hash functions they are available in the zlib module Hash algorithms There is one constructor method named for each type of hash All return a hash object with the same simple interface For example use sha256 to create a SHA 256 hash object You can now feed this object with bytes like objects normally bytes using the update method At any point you can ask it for the digest of the concatenation of the data fed to it so far using the digest or hexdigest methods To allow multithreading the Python GIL is released while computing a hash supplied more than 2047 bytes of data at once in its constructor or update method Constructors for hash algorithms that are always present in this module are sha1 sha224 sha256 sha384 sha512 sha3_224 sha3_256 sha3_384 sha3_512 shake_128 shake_256 blake2b and blake2s md5 is normally available as well though it may be missing or blocked if you are using a rare FIPS compliant build of Python These correspond to algorithms_guaranteed Additional algorithms may also be available if your Python distribution s hashlib was linked against a build of OpenSSL that provides others Others are not guaranteed available on all installations and will only be accessible by name via new See algorithms_available Warning Some algorithms have known hash collision weaknesses including MD5 and SHA1 Refer to Attacks on cryptographic hash algorithms and the hashlib seealso section at the end of this document New in version 3 6 SHA3 Keccak and SHAKE constructors sha3_224 sha3_256 sha3_384 sha3_512 shake_128 shake_256 were added blake2b and blake2s were added Changed in version 3 9 All hashlib constructors take a keyword only argument usedforsecurity with default value True A false value allows the use of insecure and blocked hashing algorithms in restricted environments False indicates that the hashing algorithm is not used in a security context e g as a non cryptographic one way compression function Changed in version 3 9 Hashlib now uses SHA3 and SHAKE from OpenSSL if it provides it Changed in version 3 12 For any of the MD5 SHA1 SHA2 or SHA3 algorithms that the linked OpenSSL does not provide we fall back to a verified implementation from the HACL project Usage To obtain the digest of the byte string b Nobody inspects the spammish repetition import hashlib m hashlib sha256 m update b Nobody inspects m update b the spammish repetition m digest b x03 x1e xdd Ae x15 x93 xc5 xfe x00o xa5u 7 xfd xdf xf7 xbcN x84 xa6 xaf x0c x95 x0fK x94 x06 m hexdigest 031edd7d41651593c5fe5c006fa5752b37fddff7bc4e843aa6af0c950f4b9406 More condensed hashlib sha256 b Nobody inspects the spammish repetition hexdigest 031edd7d41651593c5fe5c006fa5752b37fddff7bc4e843aa6af0c950f4b9406 Constructors hashlib new name data usedforsecurity True Is a generic constructor that takes the string name of the desired algorithm as its first parameter It also exists to allow access to the above listed hashes as well as any other algorithms that your OpenSSL library may offer Using new with an algorithm name h hashlib new sha256 h update b Nobody inspects the spammish repetition h hexdigest 031edd7d41651593c5fe5c006fa5752b37fddff7bc4e843aa6af0c950f4b9406 hashlib md5 data usedforsecurity True hashlib sha1 data usedforsecurity True hashlib sha224 data usedforsecurity True hashlib sha256 data usedforsecurity True hashlib sha384 data usedforsecurity True hashlib sha512 data usedforsecurity True hashlib sha3_224 data usedforsecurity True hashlib sha3_256 data usedforsecurity True hashlib sha3_384 data usedfors,en
936,ecurity True hashlib sha3_512 data usedforsecurity True Named constructors such as these are faster than passing an algorithm name to new Attributes Hashlib provides the following constant module attributes hashlib algorithms_guaranteed A set containing the names of the hash algorithms guaranteed to be supported by this module on all platforms Note that md5 is in this list despite some upstream vendors offering an odd FIPS compliant Python build that excludes it New in version 3 2 hashlib algorithms_available A set containing the names of the hash algorithms that are available in the running Python interpreter These names will be recognized when passed to new algorithms_guaranteed will always be a subset The same algorithm may appear multiple times in this set under different names thanks to OpenSSL New in version 3 2 Hash Objects The following values are provided as constant attributes of the hash objects returned by the constructors hash digest_size The size of the resulting hash in bytes hash block_size The internal block size of the hash algorithm in bytes A hash object has the following attributes hash name The canonical name of this hash always lowercase and always suitable as a parameter to new to create another hash of this type Changed in version 3 4 The name attribute has been present in CPython since its inception but until Python 3 4 was not formally specified so may not exist on some platforms A hash object has the following methods hash update data Update the hash object with the bytes like object Repeated calls are equivalent to a single call with the concatenation of all the arguments m update a m update b is equivalent to m update a b hash digest Return the digest of the data passed to the update method so far This is a bytes object of size digest_size which may contain bytes in the whole range from 0 to 255 hash hexdigest Like digest except the digest is returned as a string object of double length containing only hexadecimal digits This may be used to exchange the value safely in email or other non binary environments hash copy Return a copy clone of the hash object This can be used to efficiently compute the digests of data sharing a common initial substring SHAKE variable length digests hashlib shake_128 data usedforsecurity True hashlib shake_256 data usedforsecurity True The shake_128 and shake_256 algorithms provide variable length digests with length_in_bits 2 up to 128 or 256 bits of security As such their digest methods require a length Maximum length is not limited by the SHAKE algorithm shake digest length Return the digest of the data passed to the update method so far This is a bytes object of size length which may contain bytes in the whole range from 0 to 255 shake hexdigest length Like digest except the digest is returned as a string object of double length containing only hexadecimal digits This may be used to exchange the value in email or other non binary environments Example use h hashlib shake_256 b Nobody inspects the spammish repetition h hexdigest 20 44709d6fcb83d92a76dcb0b668c98e1b1d3dafe7 File hashing The hashlib module provides a helper function for efficient hashing of a file or file like object hashlib file_digest fileobj digest Return a digest object that has been updated with contents of file object fileobj must be a file like object opened for reading in binary mode It accepts file objects from builtin open BytesIO instances SocketIO objects from socket socket makefile and similar The function may bypass Python s I O and use the file descriptor from fileno directly fileobj must be assumed to be in an unknown state after this function returns or raises It is up to the caller to close fileobj digest must either be a hash algorithm name as a str a hash constructor or a callable that returns a hash object Example import io hashlib hmac with open hashlib __file__ rb as f digest hashlib file_digest f sha256 digest hexdigest buf io BytesIO b somedata mac1 hmac HMAC b key digestmod hashlib sha512 digest hashlib file_digest buf lambda mac1 digest is mac1 True mac2 hmac HMAC b key ,en
937,b somedata digestmod hashlib sha512 mac1 digest mac2 digest True New in version 3 11 Key derivation Key derivation and key stretching algorithms are designed for secure password hashing Naive algorithms such as sha1 password are not resistant against brute force attacks A good password hashing function must be tunable slow and include a salt hashlib pbkdf2_hmac hash_name password salt iterations dklen None The function provides PKCS 5 password based key derivation function 2 It uses HMAC as pseudorandom function The string hash_name is the desired name of the hash digest algorithm for HMAC e g sha1 or sha256 password and salt are interpreted as buffers of bytes Applications and libraries should limit password to a sensible length e g 1024 salt should be about 16 or more bytes from a proper source e g os urandom The number of iterations should be chosen based on the hash algorithm and computing power As of 2022 hundreds of thousands of iterations of SHA 256 are suggested For rationale as to why and how to choose what is best for your application read Appendix A 2 2 of NIST SP 800 132 The answers on the stackexchange pbkdf2 iterations question explain in detail dklen is the length of the derived key If dklen is None then the digest size of the hash algorithm hash_name is used e g 64 for SHA 512 from hashlib import pbkdf2_hmac our_app_iters 500_000 Application specific read above dk pbkdf2_hmac sha256 b password b bad salt 2 our_app_iters dk hex 15530bba69924174860db778f2c6f8104d3aaf9d26241840c8c4a641c8d000a9 Function only available when Python is compiled with OpenSSL New in version 3 4 Changed in version 3 12 Function now only available when Python is built with OpenSSL The slow pure Python implementation has been removed hashlib scrypt password salt n r p maxmem 0 dklen 64 The function provides scrypt password based key derivation function as defined in RFC 7914 password and salt must be bytes like objects Applications and libraries should limit password to a sensible length e g 1024 salt should be about 16 or more bytes from a proper source e g os urandom n is the CPU Memory cost factor r the block size p parallelization factor and maxmem limits memory OpenSSL 1 1 0 defaults to 32 MiB dklen is the length of the derived key New in version 3 6 BLAKE2 BLAKE2 is a cryptographic hash function defined in RFC 7693 that comes in two flavors BLAKE2b optimized for 64 bit platforms and produces digests of any size between 1 and 64 bytes BLAKE2s optimized for 8 to 32 bit platforms and produces digests of any size between 1 and 32 bytes BLAKE2 supports keyed mode a faster and simpler replacement for HMAC salted hashing personalization and tree hashing Hash objects from this module follow the API of standard library s hashlib objects Creating hash objects New hash objects are created by calling constructor functions hashlib blake2b data b digest_size 64 key b salt b person b fanout 1 depth 1 leaf_size 0 node_offset 0 node_depth 0 inner_size 0 last_node False usedforsecurity True hashlib blake2s data b digest_size 32 key b salt b person b fanout 1 depth 1 leaf_size 0 node_offset 0 node_depth 0 inner_size 0 last_node False usedforsecurity True These functions return the corresponding hash objects for calculating BLAKE2b or BLAKE2s They optionally take these general parameters data initial chunk of data to hash which must be bytes like object It can be passed only as positional argument digest_size size of output digest in bytes key key for keyed hashing up to 64 bytes for BLAKE2b up to 32 bytes for BLAKE2s salt salt for randomized hashing up to 16 bytes for BLAKE2b up to 8 bytes for BLAKE2s person personalization string up to 16 bytes for BLAKE2b up to 8 bytes for BLAKE2s The following table shows limits for general parameters in bytes Hash digest_size len key len salt len person BLAKE2b 64 64 16 16 BLAKE2s 32 32 8 8 Note BLAKE2 specification defines constant lengths for salt and personalization parameters however for convenience this implementation accepts byte strings of any size up to the specified length If the length of the parame,en
938,ter is less than specified it is padded with zeros thus for example b salt and b salt x00 is the same value This is not the case for key These sizes are available as module constants described below Constructor functions also accept the following tree hashing parameters fanout fanout 0 to 255 0 if unlimited 1 in sequential mode depth maximal depth of tree 1 to 255 255 if unlimited 1 in sequential mode leaf_size maximal byte length of leaf 0 to 2 32 1 0 if unlimited or in sequential mode node_offset node offset 0 to 2 64 1 for BLAKE2b 0 to 2 48 1 for BLAKE2s 0 for the first leftmost leaf or in sequential mode node_depth node depth 0 to 255 0 for leaves or in sequential mode inner_size inner digest size 0 to 64 for BLAKE2b 0 to 32 for BLAKE2s 0 in sequential mode last_node boolean indicating whether the processed node is the last one False for sequential mode image Explanation of tree mode parameters image See section 2 10 in BLAKE2 specification for comprehensive review of tree hashing Constants blake2b SALT_SIZE blake2s SALT_SIZE Salt length maximum length accepted by constructors blake2b PERSON_SIZE blake2s PERSON_SIZE Personalization string length maximum length accepted by constructors blake2b MAX_KEY_SIZE blake2s MAX_KEY_SIZE Maximum key size blake2b MAX_DIGEST_SIZE blake2s MAX_DIGEST_SIZE Maximum digest size that the hash function can output Examples Simple hashing To calculate hash of some data you should first construct a hash object by calling the appropriate constructor function blake2b or blake2s then update it with the data by calling update on the object and finally get the digest out of the object by calling digest or hexdigest for hex encoded string from hashlib import blake2b h blake2b h update b Hello world h hexdigest 6ff843ba685842aa82031d3f53c48b66326df7639a63d128974c5c14f31a0f33343a8c65551134ed1ae0f2b0dd2bb495dc81039e3eeb0aa1bb0388bbeac29183 As a shortcut you can pass the first chunk of data to update directly to the constructor as the positional argument from hashlib import blake2b blake2b b Hello world hexdigest 6ff843ba685842aa82031d3f53c48b66326df7639a63d128974c5c14f31a0f33343a8c65551134ed1ae0f2b0dd2bb495dc81039e3eeb0aa1bb0388bbeac29183 You can call hash update as many times as you need to iteratively update the hash from hashlib import blake2b items b Hello b b world h blake2b for item in items h update item h hexdigest 6ff843ba685842aa82031d3f53c48b66326df7639a63d128974c5c14f31a0f33343a8c65551134ed1ae0f2b0dd2bb495dc81039e3eeb0aa1bb0388bbeac29183 Using different digest sizes BLAKE2 has configurable size of digests up to 64 bytes for BLAKE2b and up to 32 bytes for BLAKE2s For example to replace SHA 1 with BLAKE2b without changing the size of output we can tell BLAKE2b to produce 20 byte digests from hashlib import blake2b h blake2b digest_size 20 h update b Replacing SHA1 with the more secure function h hexdigest d24f26cf8de66472d58d4e1b1774b4c9158b1f4c h digest_size 20 len h digest 20 Hash objects with different digest sizes have completely different outputs shorter hashes are not prefixes of longer hashes BLAKE2b and BLAKE2s produce different outputs even if the output length is the same from hashlib import blake2b blake2s blake2b digest_size 10 hexdigest 6fa1d8fcfd719046d762 blake2b digest_size 11 hexdigest eb6ec15daf9546254f0809 blake2s digest_size 10 hexdigest 1bf21a98c78a1c376ae9 blake2s digest_size 11 hexdigest 567004bf96e4a25773ebf4 Keyed hashing Keyed hashing can be used for authentication as a faster and simpler replacement for Hash based message authentication code HMAC BLAKE2 can be securely used in prefix MAC mode thanks to the indifferentiability property inherited from BLAKE This example shows how to get a hex encoded 128 bit authentication code for message b message data with key b pseudorandom key from hashlib import blake2b h blake2b key b pseudorandom key digest_size 16 h update b message data h hexdigest 3d363ff7401e02026f4a4687d4863ced As a practical example a web application can symmetrically sign cookies sent to users and later verify them to make sure they weren t tampered ,en
939,with from hashlib import blake2b from hmac import compare_digest SECRET_KEY b pseudorandomly generated server secret key AUTH_SIZE 16 def sign cookie h blake2b digest_size AUTH_SIZE key SECRET_KEY h update cookie return h hexdigest encode utf 8 def verify cookie sig good_sig sign cookie return compare_digest good_sig sig cookie b user alice sig sign cookie print 0 1 format cookie decode utf 8 sig user alice b 43b3c982cf697e0c5ab22172d1ca7421 verify cookie sig True verify b user bob sig False verify cookie b 0102030405060708090a0b0c0d0e0f00 False Even though there s a native keyed hashing mode BLAKE2 can of course be used in HMAC construction with hmac module import hmac hashlib m hmac new b secret key digestmod hashlib blake2s m update b message m hexdigest e3c8102868d28b5ff85fc35dda07329970d1a01e273c37481326fe0c861c8142 Randomized hashing By setting salt parameter users can introduce randomization to the hash function Randomized hashing is useful for protecting against collision attacks on the hash function used in digital signatures Randomized hashing is designed for situations where one party the message preparer generates all or part of a message to be signed by a second party the message signer If the message preparer is able to find cryptographic hash function collisions i e two messages producing the same hash value then they might prepare meaningful versions of the message that would produce the same hash value and digital signature but with different results e g transferring 1 000 000 to an account rather than 10 Cryptographic hash functions have been designed with collision resistance as a major goal but the current concentration on attacking cryptographic hash functions may result in a given cryptographic hash function providing less collision resistance than expected Randomized hashing offers the signer additional protection by reducing the likelihood that a preparer can generate two or more messages that ultimately yield the same hash value during the digital signature generation process even if it is practical to find collisions for the hash function However the use of randomized hashing may reduce the amount of security provided by a digital signature when all portions of the message are prepared by the signer NIST SP 800 106 Randomized Hashing for Digital Signatures In BLAKE2 the salt is processed as a one time input to the hash function during initialization rather than as an input to each compression function Warning Salted hashing or just hashing with BLAKE2 or any other general purpose cryptographic hash function such as SHA 256 is not suitable for hashing passwords See BLAKE2 FAQ for more information import os from hashlib import blake2b msg b some message Calculate the first hash with a random salt salt1 os urandom blake2b SALT_SIZE h1 blake2b salt salt1 h1 update msg Calculate the second hash with a different random salt salt2 os urandom blake2b SALT_SIZE h2 blake2b salt salt2 h2 update msg The digests are different h1 digest h2 digest True Personalization Sometimes it is useful to force hash function to produce different digests for the same input for different purposes Quoting the authors of the Skein hash function We recommend that all application designers seriously consider doing this we have seen many protocols where a hash that is computed in one part of the protocol can be used in an entirely different part because two hash computations were done on similar or related data and the attacker can force the application to make the hash inputs the same Personalizing each hash function used in the protocol summarily stops this type of attack The Skein Hash Function Family p 21 BLAKE2 can be personalized by passing bytes to the person argument from hashlib import blake2b FILES_HASH_PERSON b MyApp Files Hash BLOCK_HASH_PERSON b MyApp Block Hash h blake2b digest_size 32 person FILES_HASH_PERSON h update b the same content h hexdigest 20d9cd024d4fb086aae819a1432dd2466de12947831b75c5a30cf2676095d3b4 h blake2b digest_size 32 person BLOCK_HASH_PERSON h update b the same content h hexdigest cf68fb5761b9c,en
940,44e7878bfb2c4c9aea52264a80b75005e65619778de59f383a3 Personalization together with the keyed mode can also be used to derive different keys from a single one from hashlib import blake2s from base64 import b64decode b64encode orig_key b64decode b Rm5EPJai72qcK3RGBpW3vPNfZy5OZothY kHY6h21KM enc_key blake2s key orig_key person b kEncrypt digest mac_key blake2s key orig_key person b kMAC digest print b64encode enc_key decode utf 8 rbPb15S Z9t agffno5wuhB77VbRi6F9Iv2qIxU7WHw print b64encode mac_key decode utf 8 G9GtHFE1YluXY1zWPlYk1e nWfu0WSEb0KRcjhDeP o Tree mode Here s an example of hashing a minimal tree with two leaf nodes 10 00 01 This example uses 64 byte internal digests and returns the 32 byte final digest from hashlib import blake2b FANOUT 2 DEPTH 2 LEAF_SIZE 4096 INNER_SIZE 64 buf bytearray 6000 Left leaf h00 blake2b buf 0 LEAF_SIZE fanout FANOUT depth DEPTH leaf_size LEAF_SIZE inner_size INNER_SIZE node_offset 0 node_depth 0 last_node False Right leaf h01 blake2b buf LEAF_SIZE fanout FANOUT depth DEPTH leaf_size LEAF_SIZE inner_size INNER_SIZE node_offset 1 node_depth 0 last_node True Root node h10 blake2b digest_size 32 fanout FANOUT depth DEPTH leaf_size LEAF_SIZE inner_size INNER_SIZE node_offset 0 node_depth 1 last_node True h10 update h00 digest h10 update h01 digest h10 hexdigest 3ad2a9b37c6070e374c7a8c508fe20ca86b6ed54e286e93a0318e95e881db5aa Credits BLAKE2 was designed by Jean Philippe Aumasson Samuel Neves Zooko Wilcox O Hearn and Christian Winnerlein based on SHA 3 finalist BLAKE created by Jean Philippe Aumasson Luca Henzen Willi Meier and Raphael C W Phan It uses core algorithm from ChaCha cipher designed by Daniel J Bernstein The stdlib implementation is based on pyblake2 module It was written by Dmitry Chestnykh based on C implementation written by Samuel Neves The documentation was copied from pyblake2 and written by Dmitry Chestnykh The C code was partly rewritten for Python by Christian Heimes The following public domain dedication applies for both C hash function implementation extension code and this documentation To the extent possible under law the author s have dedicated all copyright and related and neighboring rights to this software to the public domain worldwide This software is distributed without any warranty You should have received a copy of the CC0 Public Domain Dedication along with this software If not see https creativecommons org publicdomain zero 1 0 The following people have helped with development or contributed their changes to the project and the public domain according to the Creative Commons Public Domain Dedication 1 0 Universal Alexandr Sokolovskiy See also Module hmac A module to generate message authentication codes using hashes Module base64 Another way to encode binary hashes for non binary environments https nvlpubs nist gov nistpubs fips nist fips 180 4 pdf The FIPS 180 4 publication on Secure Hash Algorithms https csrc nist gov publications detail fips 202 final The FIPS 202 publication on the SHA 3 Standard https www blake2 net Official BLAKE2 website https en wikipedia org wiki Cryptographic_hash_function Wikipedia article with information on which algorithms have known issues and what that means regarding their use https www ietf org rfc rfc8018 txt PKCS 5 Password Based Cryptography Specification Version 2 1 https nvlpubs nist gov nistpubs Legacy SP nistspecialpublication8 00 132 pdf NIST Recommendation for Password Based Key Derivation,en
941,Type Objects type PyTypeObject Part of the Limited API as an opaque struct The C structure of the objects used to describe built in types PyTypeObject PyType_Type Part of the Stable ABI This is the type object for type objects it is the same object as type in the Python layer int PyType_Check PyObject o Return non zero if the object o is a type object including instances of types derived from the standard type object Return 0 in all other cases This function always succeeds int PyType_CheckExact PyObject o Return non zero if the object o is a type object but not a subtype of the standard type object Return 0 in all other cases This function always succeeds unsigned int PyType_ClearCache Part of the Stable ABI Clear the internal lookup cache Return the current version tag unsigned long PyType_GetFlags PyTypeObject type Part of the Stable ABI Return the tp_flags member of type This function is primarily meant for use with Py_LIMITED_API the individual flag bits are guaranteed to be stable across Python releases but access to tp_flags itself is not part of the limited API New in version 3 2 Changed in version 3 4 The return type is now unsigned long rather than long PyObject PyType_GetDict PyTypeObject type Return the type object s internal namespace which is otherwise only exposed via a read only proxy cls __dict__ This is a replacement for accessing tp_dict directly The returned dictionary must be treated as read only This function is meant for specific embedding and language binding cases where direct access to the dict is necessary and indirect access e g via the proxy or PyObject_GetAttr isn t adequate Extension modules should continue to use tp_dict directly or indirectly when setting up their own types New in version 3 12 void PyType_Modified PyTypeObject type Part of the Stable ABI Invalidate the internal lookup cache for the type and all of its subtypes This function must be called after any manual modification of the attributes or base classes of the type int PyType_AddWatcher PyType_WatchCallback callback Register callback as a type watcher Return a non negative integer ID which must be passed to future calls to PyType_Watch In case of error e g no more watcher IDs available return 1 and set an exception New in version 3 12 int PyType_ClearWatcher int watcher_id Clear watcher identified by watcher_id previously returned from PyType_AddWatcher Return 0 on success 1 on error e g if watcher_id was never registered An extension should never call PyType_ClearWatcher with a watcher_id that was not returned to it by a previous call to PyType_AddWatcher New in version 3 12 int PyType_Watch int watcher_id PyObject type Mark type as watched The callback granted watcher_id by PyType_AddWatcher will be called whenever PyType_Modified reports a change to type The callback may be called only once for a series of consecutive modifications to type if _PyType_Lookup is not called on type between the modifications this is an implementation detail and subject to change An extension should never call PyType_Watch with a watcher_id that was not returned to it by a previous call to PyType_AddWatcher New in version 3 12 typedef int PyType_WatchCallback PyObject type Type of a type watcher callback function The callback must not modify type or cause PyType_Modified to be called on type or any type in its MRO violating this rule could cause infinite recursion New in version 3 12 int PyType_HasFeature PyTypeObject o int feature Return non zero if the type object o sets the feature feature Type features are denoted by single bit flags int PyType_IS_GC PyTypeObject o Return true if the type object includes support for the cycle detector this tests the type flag Py_TPFLAGS_HAVE_GC int PyType_IsSubtype PyTypeObject a PyTypeObject b Part of the Stable ABI Return true if a is a subtype of b This function only checks for actual subtypes which means that __subclasscheck__ is not called on b Call PyObject_IsSubclass to do the same check that issubclass would do PyObject PyType_GenericAlloc PyTypeObject type Py_ssize_t nitems Return value New refer,en
942,ence Part of the Stable ABI Generic handler for the tp_alloc slot of a type object Use Python s default memory allocation mechanism to allocate a new instance and initialize all its contents to NULL PyObject PyType_GenericNew PyTypeObject type PyObject args PyObject kwds Return value New reference Part of the Stable ABI Generic handler for the tp_new slot of a type object Create a new instance using the type s tp_alloc slot int PyType_Ready PyTypeObject type Part of the Stable ABI Finalize a type object This should be called on all type objects to finish their initialization This function is responsible for adding inherited slots from a type s base class Return 0 on success or return 1 and sets an exception on error Note If some of the base classes implements the GC protocol and the provided type does not include the Py_TPFLAGS_HAVE_GC in its flags then the GC protocol will be automatically implemented from its parents On the contrary if the type being created does include Py_TPFLAGS_HAVE_GC in its flags then it must implement the GC protocol itself by at least implementing the tp_traverse handle PyObject PyType_GetName PyTypeObject type Return value New reference Part of the Stable ABI since version 3 11 Return the type s name Equivalent to getting the type s __name__ attribute New in version 3 11 PyObject PyType_GetQualName PyTypeObject type Return value New reference Part of the Stable ABI since version 3 11 Return the type s qualified name Equivalent to getting the type s __qualname__ attribute New in version 3 11 void PyType_GetSlot PyTypeObject type int slot Part of the Stable ABI since version 3 4 Return the function pointer stored in the given slot If the result is NULL this indicates that either the slot is NULL or that the function was called with invalid parameters Callers will typically cast the result pointer into the appropriate function type See PyType_Slot slot for possible values of the slot argument New in version 3 4 Changed in version 3 10 PyType_GetSlot can now accept all types Previously it was limited to heap types PyObject PyType_GetModule PyTypeObject type Part of the Stable ABI since version 3 10 Return the module object associated with the given type when the type was created using PyType_FromModuleAndSpec If no module is associated with the given type sets TypeError and returns NULL This function is usually used to get the module in which a method is defined Note that in such a method PyType_GetModule Py_TYPE self may not return the intended result Py_TYPE self may be a subclass of the intended class and subclasses are not necessarily defined in the same module as their superclass See PyCMethod to get the class that defines the method See PyType_GetModuleByDef for cases when PyCMethod cannot be used New in version 3 9 void PyType_GetModuleState PyTypeObject type Part of the Stable ABI since version 3 10 Return the state of the module object associated with the given type This is a shortcut for calling PyModule_GetState on the result of PyType_GetModule If no module is associated with the given type sets TypeError and returns NULL If the type has an associated module but its state is NULL returns NULL without setting an exception New in version 3 9 PyObject PyType_GetModuleByDef PyTypeObject type struct PyModuleDef def Find the first superclass whose module was created from the given PyModuleDef def and return that module If no module is found raises a TypeError and returns NULL This function is intended to be used together with PyModule_GetState to get module state from slot methods such as tp_init or nb_add and other places where a method s defining class cannot be passed using the PyCMethod calling convention New in version 3 11 int PyUnstable_Type_AssignVersionTag PyTypeObject type This is Unstable API It may change without warning in minor releases Attempt to assign a version tag to the given type Returns 1 if the type already had a valid version tag or a new one was assigned or 0 if a new tag could not be assigned New in version 3 12 Creating Heap Allocated Types The following functions a,en
943,nd structs are used to create heap types PyObject PyType_FromMetaclass PyTypeObject metaclass PyObject module PyType_Spec spec PyObject bases Part of the Stable ABI since version 3 12 Create and return a heap type from the spec see Py_TPFLAGS_HEAPTYPE The metaclass metaclass is used to construct the resulting type object When metaclass is NULL the metaclass is derived from bases or Py_tp_base s slots if bases is NULL see below Metaclasses that override tp_new are not supported except if tp_new is NULL For backwards compatibility other PyType_From functions allow such metaclasses They ignore tp_new which may result in incomplete initialization This is deprecated and in Python 3 14 such metaclasses will not be supported The bases argument can be used to specify base classes it can either be only one class or a tuple of classes If bases is NULL the Py_tp_bases slot is used instead If that also is NULL the Py_tp_base slot is used instead If that also is NULL the new type derives from object The module argument can be used to record the module in which the new class is defined It must be a module object or NULL If not NULL the module is associated with the new type and can later be retrieved with PyType_GetModule The associated module is not inherited by subclasses it must be specified for each class individually This function calls PyType_Ready on the new type Note that this function does not fully match the behavior of calling type or using the class statement With user provided base types or metaclasses prefer calling type or the metaclass over PyType_From functions Specifically __new__ is not called on the new class and it must be set to type __new__ __init__ is not called on the new class __init_subclass__ is not called on any bases __set_name__ is not called on new descriptors New in version 3 12 PyObject PyType_FromModuleAndSpec PyObject module PyType_Spec spec PyObject bases Return value New reference Part of the Stable ABI since version 3 10 Equivalent to PyType_FromMetaclass NULL module spec bases New in version 3 9 Changed in version 3 10 The function now accepts a single class as the bases argument and NULL as the tp_doc slot Changed in version 3 12 The function now finds and uses a metaclass corresponding to the provided base classes Previously only type instances were returned The tp_new of the metaclass is ignored which may result in incomplete initialization Creating classes whose metaclass overrides tp_new is deprecated and in Python 3 14 it will be no longer allowed PyObject PyType_FromSpecWithBases PyType_Spec spec PyObject bases Return value New reference Part of the Stable ABI since version 3 3 Equivalent to PyType_FromMetaclass NULL NULL spec bases New in version 3 3 Changed in version 3 12 The function now finds and uses a metaclass corresponding to the provided base classes Previously only type instances were returned The tp_new of the metaclass is ignored which may result in incomplete initialization Creating classes whose metaclass overrides tp_new is deprecated and in Python 3 14 it will be no longer allowed PyObject PyType_FromSpec PyType_Spec spec Return value New reference Part of the Stable ABI Equivalent to PyType_FromMetaclass NULL NULL spec NULL Changed in version 3 12 The function now finds and uses a metaclass corresponding to the base classes provided in Py_tp_base s slots Previously only type instances were returned The tp_new of the metaclass is ignored which may result in incomplete initialization Creating classes whose metaclass overrides tp_new is deprecated and in Python 3 14 it will be no longer allowed type PyType_Spec Part of the Stable ABI including all members Structure defining a type s behavior const char name Name of the type used to set PyTypeObject tp_name int basicsize If positive specifies the size of the instance in bytes It is used to set PyTypeObject tp_basicsize If zero specifies that tp_basicsize should be inherited If negative the absolute value specifies how much space instances of the class need in addition to the superclass Use PyObject_GetTypeData to get a point,en
944,er to subclass specific memory reserved this way Changed in version 3 12 Previously this field could not be negative int itemsize Size of one element of a variable size type in bytes Used to set PyTypeObject tp_itemsize See tp_itemsize documentation for caveats If zero tp_itemsize is inherited Extending arbitrary variable sized classes is dangerous since some types use a fixed offset for variable sized memory which can then overlap fixed sized memory used by a subclass To help prevent mistakes inheriting itemsize is only possible in the following situations The base is not variable sized its tp_itemsize The requested PyType_Spec basicsize is positive suggesting that the memory layout of the base class is known The requested PyType_Spec basicsize is zero suggesting that the subclass does not access the instance s memory directly With the Py_TPFLAGS_ITEMS_AT_END flag unsigned int flags Type flags used to set PyTypeObject tp_flags If the Py_TPFLAGS_HEAPTYPE flag is not set PyType_FromSpecWithBases sets it automatically PyType_Slot slots Array of PyType_Slot structures Terminated by the special slot value 0 NULL Each slot ID should be specified at most once type PyType_Slot Part of the Stable ABI including all members Structure defining optional functionality of a type containing a slot ID and a value pointer int slot A slot ID Slot IDs are named like the field names of the structures PyTypeObject PyNumberMethods PySequenceMethods PyMappingMethods and PyAsyncMethods with an added Py_ prefix For example use Py_tp_dealloc to set PyTypeObject tp_dealloc Py_nb_add to set PyNumberMethods nb_add Py_sq_length to set PySequenceMethods sq_length The following offset fields cannot be set using PyType_Slot tp_weaklistoffset use Py_TPFLAGS_MANAGED_WEAKREF instead if possible tp_dictoffset use Py_TPFLAGS_MANAGED_DICT instead if possible tp_vectorcall_offset use __vectorcalloffset__ in PyMemberDef If it is not possible to switch to a MANAGED flag for example for vectorcall or to support Python older than 3 12 specify the offset in Py_tp_members See PyMemberDef documentation for details The following fields cannot be set at all when creating a heap type tp_vectorcall use tp_new and or tp_init Internal fields tp_dict tp_mro tp_cache tp_subclasses and tp_weaklist Setting Py_tp_bases or Py_tp_base may be problematic on some platforms To avoid issues use the bases argument of PyType_FromSpecWithBases instead Changed in version 3 9 Slots in PyBufferProcs may be set in the unlimited API Changed in version 3 11 bf_getbuffer and bf_releasebuffer are now available under the limited API void pfunc The desired value of the slot In most cases this is a pointer to a function Slots other than Py_tp_doc may not be NULL,en
945,queue A synchronized queue class Source code Lib queue py The queue module implements multi producer multi consumer queues It is especially useful in threaded programming when information must be exchanged safely between multiple threads The Queue class in this module implements all the required locking semantics The module implements three types of queue which differ only in the order in which the entries are retrieved In a FIFO first in first out queue the first tasks added are the first retrieved In a LIFO last in first out queue the most recently added entry is the first retrieved operating like a stack With a priority queue the entries are kept sorted using the heapq module and the lowest valued entry is retrieved first Internally those three types of queues use locks to temporarily block competing threads however they are not designed to handle reentrancy within a thread In addition the module implements a simple FIFO first in first out queue type SimpleQueue whose specific implementation provides additional guarantees in exchange for the smaller functionality The queue module defines the following classes and exceptions class queue Queue maxsize 0 Constructor for a FIFO first in first out queue maxsize is an integer that sets the upperbound limit on the number of items that can be placed in the queue Insertion will block once this size has been reached until queue items are consumed If maxsize is less than or equal to zero the queue size is infinite class queue LifoQueue maxsize 0 Constructor for a LIFO last in first out queue maxsize is an integer that sets the upperbound limit on the number of items that can be placed in the queue Insertion will block once this size has been reached until queue items are consumed If maxsize is less than or equal to zero the queue size is infinite class queue PriorityQueue maxsize 0 Constructor for a priority queue maxsize is an integer that sets the upperbound limit on the number of items that can be placed in the queue Insertion will block once this size has been reached until queue items are consumed If maxsize is less than or equal to zero the queue size is infinite The lowest valued entries are retrieved first the lowest valued entry is the one that would be returned by min entries A typical pattern for entries is a tuple in the form priority_number data If the data elements are not comparable the data can be wrapped in a class that ignores the data item and only compares the priority number from dataclasses import dataclass field from typing import Any dataclass order True class PrioritizedItem priority int item Any field compare False class queue SimpleQueue Constructor for an unbounded FIFO first in first out queue Simple queues lack advanced functionality such as task tracking New in version 3 7 exception queue Empty Exception raised when non blocking get or get_nowait is called on a Queue object which is empty exception queue Full Exception raised when non blocking put or put_nowait is called on a Queue object which is full Queue Objects Queue objects Queue LifoQueue or PriorityQueue provide the public methods described below Queue qsize Return the approximate size of the queue Note qsize 0 doesn t guarantee that a subsequent get will not block nor will qsize maxsize guarantee that put will not block Queue empty Return True if the queue is empty False otherwise If empty returns True it doesn t guarantee that a subsequent call to put will not block Similarly if empty returns False it doesn t guarantee that a subsequent call to get will not block Queue full Return True if the queue is full False otherwise If full returns True it doesn t guarantee that a subsequent call to get will not block Similarly if full returns False it doesn t guarantee that a subsequent call to put will not block Queue put item block True timeout None Put item into the queue If optional args block is true and timeout is None the default block if necessary until a free slot is available If timeout is a positive number it blocks at most timeout seconds and raises the Full exception if no free slot wa,en
946,s available within that time Otherwise block is false put an item on the queue if a free slot is immediately available else raise the Full exception timeout is ignored in that case Queue put_nowait item Equivalent to put item block False Queue get block True timeout None Remove and return an item from the queue If optional args block is true and timeout is None the default block if necessary until an item is available If timeout is a positive number it blocks at most timeout seconds and raises the Empty exception if no item was available within that time Otherwise block is false return an item if one is immediately available else raise the Empty exception timeout is ignored in that case Prior to 3 0 on POSIX systems and for all versions on Windows if block is true and timeout is None this operation goes into an uninterruptible wait on an underlying lock This means that no exceptions can occur and in particular a SIGINT will not trigger a KeyboardInterrupt Queue get_nowait Equivalent to get False Two methods are offered to support tracking whether enqueued tasks have been fully processed by daemon consumer threads Queue task_done Indicate that a formerly enqueued task is complete Used by queue consumer threads For each get used to fetch a task a subsequent call to task_done tells the queue that the processing on the task is complete If a join is currently blocking it will resume when all items have been processed meaning that a task_done call was received for every item that had been put into the queue Raises a ValueError if called more times than there were items placed in the queue Queue join Blocks until all items in the queue have been gotten and processed The count of unfinished tasks goes up whenever an item is added to the queue The count goes down whenever a consumer thread calls task_done to indicate that the item was retrieved and all work on it is complete When the count of unfinished tasks drops to zero join unblocks Example of how to wait for enqueued tasks to be completed import threading import queue q queue Queue def worker while True item q get print f Working on item print f Finished item q task_done Turn on the worker thread threading Thread target worker daemon True start Send thirty task requests to the worker for item in range 30 q put item Block until all tasks are done q join print All work completed SimpleQueue Objects SimpleQueue objects provide the public methods described below SimpleQueue qsize Return the approximate size of the queue Note qsize 0 doesn t guarantee that a subsequent get will not block SimpleQueue empty Return True if the queue is empty False otherwise If empty returns False it doesn t guarantee that a subsequent call to get will not block SimpleQueue put item block True timeout None Put item into the queue The method never blocks and always succeeds except for potential low level errors such as failure to allocate memory The optional args block and timeout are ignored and only provided for compatibility with Queue put CPython implementation detail This method has a C implementation which is reentrant That is a put or get call can be interrupted by another put call in the same thread without deadlocking or corrupting internal state inside the queue This makes it appropriate for use in destructors such as __del__ methods or weakref callbacks SimpleQueue put_nowait item Equivalent to put item block False provided for compatibility with Queue put_nowait SimpleQueue get block True timeout None Remove and return an item from the queue If optional args block is true and timeout is None the default block if necessary until an item is available If timeout is a positive number it blocks at most timeout seconds and raises the Empty exception if no item was available within that time Otherwise block is false return an item if one is immediately available else raise the Empty exception timeout is ignored in that case SimpleQueue get_nowait Equivalent to get False See also Class multiprocessing Queue A queue class for use in a multi processing rather than multi threading context collections,en
947, deque is an alternative implementation of unbounded queues with fast atomic append and popleft operations that do not require locking and also support indexing,en
948,3 Data model 3 1 Objects values and types Objects are Python s abstraction for data All data in a Python program is represented by objects or by relations between objects In a sense and in conformance to Von Neumann s model of a stored program computer code is also represented by objects Every object has an identity a type and a value An object s identity never changes once it has been created you may think of it as the object s address in memory The is operator compares the identity of two objects the id function returns an integer representing its identity CPython implementation detail For CPython id x is the memory address where x is stored An object s type determines the operations that the object supports e g does it have a length and also defines the possible values for objects of that type The type function returns an object s type which is an object itself Like its identity an object s type is also unchangeable 1 The value of some objects can change Objects whose value can change are said to be mutable objects whose value is unchangeable once they are created are called immutable The value of an immutable container object that contains a reference to a mutable object can change when the latter s value is changed however the container is still considered immutable because the collection of objects it contains cannot be changed So immutability is not strictly the same as having an unchangeable value it is more subtle An object s mutability is determined by its type for instance numbers strings and tuples are immutable while dictionaries and lists are mutable Objects are never explicitly destroyed however when they become unreachable they may be garbage collected An implementation is allowed to postpone garbage collection or omit it altogether it is a matter of implementation quality how garbage collection is implemented as long as no objects are collected that are still reachable CPython implementation detail CPython currently uses a reference counting scheme with optional delayed detection of cyclically linked garbage which collects most objects as soon as they become unreachable but is not guaranteed to collect garbage containing circular references See the documentation of the gc module for information on controlling the collection of cyclic garbage Other implementations act differently and CPython may change Do not depend on immediate finalization of objects when they become unreachable so you should always close files explicitly Note that the use of the implementation s tracing or debugging facilities may keep objects alive that would normally be collectable Also note that catching an exception with a try except statement may keep objects alive Some objects contain references to external resources such as open files or windows It is understood that these resources are freed when the object is garbage collected but since garbage collection is not guaranteed to happen such objects also provide an explicit way to release the external resource usually a close method Programs are strongly recommended to explicitly close such objects The try finally statement and the with statement provide convenient ways to do this Some objects contain references to other objects these are called containers Examples of containers are tuples lists and dictionaries The references are part of a container s value In most cases when we talk about the value of a container we imply the values not the identities of the contained objects however when we talk about the mutability of a container only the identities of the immediately contained objects are implied So if an immutable container like a tuple contains a reference to a mutable object its value changes if that mutable object is changed Types affect almost all aspects of object behavior Even the importance of object identity is affected in some sense for immutable types operations that compute new values may actually return a reference to any existing object with the same type and value while for mutable objects this is not allowed E g after a 1 b 1 a and b may or may not refer to th,en
949,e same object with the value one depending on the implementation but after c d c and d are guaranteed to refer to two different unique newly created empty lists Note that c d assigns the same object to both c and d 3 2 The standard type hierarchy Below is a list of the types that are built into Python Extension modules written in C Java or other languages depending on the implementation can define additional types Future versions of Python may add types to the type hierarchy e g rational numbers efficiently stored arrays of integers etc although such additions will often be provided via the standard library instead Some of the type descriptions below contain a paragraph listing special attributes These are attributes that provide access to the implementation and are not intended for general use Their definition may change in the future 3 2 1 None This type has a single value There is a single object with this value This object is accessed through the built in name None It is used to signify the absence of a value in many situations e g it is returned from functions that don t explicitly return anything Its truth value is false 3 2 2 NotImplemented This type has a single value There is a single object with this value This object is accessed through the built in name NotImplemented Numeric methods and rich comparison methods should return this value if they do not implement the operation for the operands provided The interpreter will then try the reflected operation or some other fallback depending on the operator It should not be evaluated in a boolean context See Implementing the arithmetic operations for more details Changed in version 3 9 Evaluating NotImplemented in a boolean context is deprecated While it currently evaluates as true it will emit a DeprecationWarning It will raise a TypeError in a future version of Python 3 2 3 Ellipsis This type has a single value There is a single object with this value This object is accessed through the literal or the built in name Ellipsis Its truth value is true 3 2 4 numbers Number These are created by numeric literals and returned as results by arithmetic operators and arithmetic built in functions Numeric objects are immutable once created their value never changes Python numbers are of course strongly related to mathematical numbers but subject to the limitations of numerical representation in computers The string representations of the numeric classes computed by __repr__ and __str__ have the following properties They are valid numeric literals which when passed to their class constructor produce an object having the value of the original numeric The representation is in base 10 when possible Leading zeros possibly excepting a single zero before a decimal point are not shown Trailing zeros possibly excepting a single zero after a decimal point are not shown A sign is shown only when the number is negative Python distinguishes between integers floating point numbers and complex numbers 3 2 4 1 numbers Integral These represent elements from the mathematical set of integers positive and negative Note The rules for integer representation are intended to give the most meaningful interpretation of shift and mask operations involving negative integers There are two types of integers Integers int These represent numbers in an unlimited range subject to available virtual memory only For the purpose of shift and mask operations a binary representation is assumed and negative numbers are represented in a variant of 2 s complement which gives the illusion of an infinite string of sign bits extending to the left Booleans bool These represent the truth values False and True The two objects representing the values False and True are the only Boolean objects The Boolean type is a subtype of the integer type and Boolean values behave like the values 0 and 1 respectively in almost all contexts the exception being that when converted to a string the strings False or True are returned respectively 3 2 4 2 numbers Real float These represent machine level double precision floating point numbers ,en
950,You are at the mercy of the underlying machine architecture and C or Java implementation for the accepted range and handling of overflow Python does not support single precision floating point numbers the savings in processor and memory usage that are usually the reason for using these are dwarfed by the overhead of using objects in Python so there is no reason to complicate the language with two kinds of floating point numbers 3 2 4 3 numbers Complex complex These represent complex numbers as a pair of machine level double precision floating point numbers The same caveats apply as for floating point numbers The real and imaginary parts of a complex number z can be retrieved through the read only attributes z real and z imag 3 2 5 Sequences These represent finite ordered sets indexed by non negative numbers The built in function len returns the number of items of a sequence When the length of a sequence is n the index set contains the numbers 0 1 n 1 Item i of sequence a is selected by a i Sequences also support slicing a i j selects all items with index k such that i k j When used as an expression a slice is a sequence of the same type This implies that the index set is renumbered so that it starts at 0 Some sequences also support extended slicing with a third step parameter a i j k selects all items of a with index x where x i n k n 0 and i x j Sequences are distinguished according to their mutability 3 2 5 1 Immutable sequences An object of an immutable sequence type cannot change once it is created If the object contains references to other objects these other objects may be mutable and may be changed however the collection of objects directly referenced by an immutable object cannot change The following types are immutable sequences Strings A string is a sequence of values that represent Unicode code points All the code points in the range U 0000 U 10FFFF can be represented in a string Python doesn t have a char type instead every code point in the string is represented as a string object with length 1 The built in function ord converts a code point from its string form to an integer in the range 0 10FFFF chr converts an integer in the range 0 10FFFF to the corresponding length 1 string object str encode can be used to convert a str to bytes using the given text encoding and bytes decode can be used to achieve the opposite Tuples The items of a tuple are arbitrary Python objects Tuples of two or more items are formed by comma separated lists of expressions A tuple of one item a singleton can be formed by affixing a comma to an expression an expression by itself does not create a tuple since parentheses must be usable for grouping of expressions An empty tuple can be formed by an empty pair of parentheses Bytes A bytes object is an immutable array The items are 8 bit bytes represented by integers in the range 0 x 256 Bytes literals like b abc and the built in bytes constructor can be used to create bytes objects Also bytes objects can be decoded to strings via the decode method 3 2 5 2 Mutable sequences Mutable sequences can be changed after they are created The subscription and slicing notations can be used as the target of assignment and del delete statements Note The collections and array module provide additional examples of mutable sequence types There are currently two intrinsic mutable sequence types Lists The items of a list are arbitrary Python objects Lists are formed by placing a comma separated list of expressions in square brackets Note that there are no special cases needed to form lists of length 0 or 1 Byte Arrays A bytearray object is a mutable array They are created by the built in bytearray constructor Aside from being mutable and hence unhashable byte arrays otherwise provide the same interface and functionality as immutable bytes objects 3 2 6 Set types These represent unordered finite sets of unique immutable objects As such they cannot be indexed by any subscript However they can be iterated over and the built in function len returns the number of items in a set Common uses for sets are fast me,en
951,mbership testing removing duplicates from a sequence and computing mathematical operations such as intersection union difference and symmetric difference For set elements the same immutability rules apply as for dictionary keys Note that numeric types obey the normal rules for numeric comparison if two numbers compare equal e g 1 and 1 0 only one of them can be contained in a set There are currently two intrinsic set types Sets These represent a mutable set They are created by the built in set constructor and can be modified afterwards by several methods such as add Frozen sets These represent an immutable set They are created by the built in frozenset constructor As a frozenset is immutable and hashable it can be used again as an element of another set or as a dictionary key 3 2 7 Mappings These represent finite sets of objects indexed by arbitrary index sets The subscript notation a k selects the item indexed by k from the mapping a this can be used in expressions and as the target of assignments or del statements The built in function len returns the number of items in a mapping There is currently a single intrinsic mapping type 3 2 7 1 Dictionaries These represent finite sets of objects indexed by nearly arbitrary values The only types of values not acceptable as keys are values containing lists or dictionaries or other mutable types that are compared by value rather than by object identity the reason being that the efficient implementation of dictionaries requires a key s hash value to remain constant Numeric types used for keys obey the normal rules for numeric comparison if two numbers compare equal e g 1 and 1 0 then they can be used interchangeably to index the same dictionary entry Dictionaries preserve insertion order meaning that keys will be produced in the same order they were added sequentially over the dictionary Replacing an existing key does not change the order however removing a key and re inserting it will add it to the end instead of keeping its old place Dictionaries are mutable they can be created by the notation see section Dictionary displays The extension modules dbm ndbm and dbm gnu provide additional examples of mapping types as does the collections module Changed in version 3 7 Dictionaries did not preserve insertion order in versions of Python before 3 6 In CPython 3 6 insertion order was preserved but it was considered an implementation detail at that time rather than a language guarantee 3 2 8 Callable types These are the types to which the function call operation see section Calls can be applied 3 2 8 1 User defined functions A user defined function object is created by a function definition see section Function definitions It should be called with an argument list containing the same number of items as the function s formal parameter list 3 2 8 1 1 Special read only attributes Attribute Meaning function __globals__ A reference to the dictionary that holds the function s global variables the global namespace of the module in which the function was defined function __closure__ None or a tuple of cells that contain bindings for the function s free variables A cell object has the attribute cell_contents This can be used to get the value of the cell as well as set the value 3 2 8 1 2 Special writable attributes Most of these attributes check the type of the assigned value Attribute Meaning function __doc__ The function s documentation string or None if unavailable Not inherited by subclasses function __name__ The function s name See also __name__ attributes function __qualname__ The function s qualified name See also __qualname__ attributes New in version 3 3 function __module__ The name of the module the function was defined in or None if unavailable function __defaults__ A tuple containing default parameter values for those parameters that have defaults or None if no parameters have a default value function __code__ The code object representing the compiled function body function __dict__ The namespace supporting arbitrary function attributes See also __dict__ attributes function __annotat,en
952,ions__ A dictionary containing annotations of parameters The keys of the dictionary are the parameter names and return for the return annotation if provided See also Annotations Best Practices function __kwdefaults__ A dictionary containing defaults for keyword only parameters function __type_params__ A tuple containing the type parameters of a generic function New in version 3 12 Function objects also support getting and setting arbitrary attributes which can be used for example to attach metadata to functions Regular attribute dot notation is used to get and set such attributes CPython implementation detail CPython s current implementation only supports function attributes on user defined functions Function attributes on built in functions may be supported in the future Additional information about a function s definition can be retrieved from its code object accessible via the __code__ attribute 3 2 8 2 Instance methods An instance method object combines a class a class instance and any callable object normally a user defined function Special read only attributes method __self__ Refers to the class instance object to which the method is bound method __func__ Refers to the original function object method __doc__ The method s documentation same as method __func__ __doc__ A string if the original function had a docstring else None method __name__ The name of the method same as method __func__ __name__ method __module__ The name of the module the method was defined in or None if unavailable Methods also support accessing but not setting the arbitrary function attributes on the underlying function object User defined method objects may be created when getting an attribute of a class perhaps via an instance of that class if that attribute is a user defined function object or a classmethod object When an instance method object is created by retrieving a user defined function object from a class via one of its instances its __self__ attribute is the instance and the method object is said to be bound The new method s __func__ attribute is the original function object When an instance method object is created by retrieving a classmethod object from a class or instance its __self__ attribute is the class itself and its __func__ attribute is the function object underlying the class method When an instance method object is called the underlying function __func__ is called inserting the class instance __self__ in front of the argument list For instance when C is a class which contains a definition for a function f and x is an instance of C calling x f 1 is equivalent to calling C f x 1 When an instance method object is derived from a classmethod object the class instance stored in __self__ will actually be the class itself so that calling either x f 1 or C f 1 is equivalent to calling f C 1 where f is the underlying function Note that the transformation from function object to instance method object happens each time the attribute is retrieved from the instance In some cases a fruitful optimization is to assign the attribute to a local variable and call that local variable Also notice that this transformation only happens for user defined functions other callable objects and all non callable objects are retrieved without transformation It is also important to note that user defined functions which are attributes of a class instance are not converted to bound methods this only happens when the function is an attribute of the class 3 2 8 3 Generator functions A function or method which uses the yield statement see section The yield statement is called a generator function Such a function when called always returns an iterator object which can be used to execute the body of the function calling the iterator s iterator __next__ method will cause the function to execute until it provides a value using the yield statement When the function executes a return statement or falls off the end a StopIteration exception is raised and the iterator will have reached the end of the set of values to be returned 3 2 8 4 Coroutine functions A functio,en
953,n or method which is defined using async def is called a coroutine function Such a function when called returns a coroutine object It may contain await expressions as well as async with and async for statements See also the Coroutine Objects section 3 2 8 5 Asynchronous generator functions A function or method which is defined using async def and which uses the yield statement is called a asynchronous generator function Such a function when called returns an asynchronous iterator object which can be used in an async for statement to execute the body of the function Calling the asynchronous iterator s aiterator __anext__ method will return an awaitable which when awaited will execute until it provides a value using the yield expression When the function executes an empty return statement or falls off the end a StopAsyncIteration exception is raised and the asynchronous iterator will have reached the end of the set of values to be yielded 3 2 8 6 Built in functions A built in function object is a wrapper around a C function Examples of built in functions are len and math sin math is a standard built in module The number and type of the arguments are determined by the C function Special read only attributes __doc__ is the function s documentation string or None if unavailable See function __doc__ __name__ is the function s name See function __name__ __self__ is set to None but see the next item __module__ is the name of the module the function was defined in or None if unavailable See function __module__ 3 2 8 7 Built in methods This is really a different disguise of a built in function this time containing an object passed to the C function as an implicit extra argument An example of a built in method is alist append assuming alist is a list object In this case the special read only attribute __self__ is set to the object denoted by alist The attribute has the same semantics as it does with other instance methods 3 2 8 8 Classes Classes are callable These objects normally act as factories for new instances of themselves but variations are possible for class types that override __new__ The arguments of the call are passed to __new__ and in the typical case to __init__ to initialize the new instance 3 2 8 9 Class Instances Instances of arbitrary classes can be made callable by defining a __call__ method in their class 3 2 9 Modules Modules are a basic organizational unit of Python code and are created by the import system as invoked either by the import statement or by calling functions such as importlib import_module and built in __import__ A module object has a namespace implemented by a dictionary object this is the dictionary referenced by the __globals__ attribute of functions defined in the module Attribute references are translated to lookups in this dictionary e g m x is equivalent to m __dict__ x A module object does not contain the code object used to initialize the module since it isn t needed once the initialization is done Attribute assignment updates the module s namespace dictionary e g m x 1 is equivalent to m __dict__ x 1 Predefined writable attributes __name__ The module s name __doc__ The module s documentation string or None if unavailable __file__ The pathname of the file from which the module was loaded if it was loaded from a file The __file__ attribute may be missing for certain types of modules such as C modules that are statically linked into the interpreter For extension modules loaded dynamically from a shared library it s the pathname of the shared library file __annotations__ A dictionary containing variable annotations collected during module body execution For best practices on working with __annotations__ please see Annotations Best Practices Special read only attribute __dict__ is the module s namespace as a dictionary object CPython implementation detail Because of the way CPython clears module dictionaries the module dictionary will be cleared when the module falls out of scope even if the dictionary still has live references To avoid this copy the dictionary or keep the module around whil,en
954,e using its dictionary directly 3 2 10 Custom classes Custom class types are typically created by class definitions see section Class definitions A class has a namespace implemented by a dictionary object Class attribute references are translated to lookups in this dictionary e g C x is translated to C __dict__ x although there are a number of hooks which allow for other means of locating attributes When the attribute name is not found there the attribute search continues in the base classes This search of the base classes uses the C3 method resolution order which behaves correctly even in the presence of diamond inheritance structures where there are multiple inheritance paths leading back to a common ancestor Additional details on the C3 MRO used by Python can be found in the documentation accompanying the 2 3 release at https www python org download releases 2 3 mro When a class attribute reference for class C say would yield a class method object it is transformed into an instance method object whose __self__ attribute is C When it would yield a staticmethod object it is transformed into the object wrapped by the static method object See section Implementing Descriptors for another way in which attributes retrieved from a class may differ from those actually contained in its __dict__ Class attribute assignments update the class s dictionary never the dictionary of a base class A class object can be called see above to yield a class instance see below Special attributes __name__ The class name __module__ The name of the module in which the class was defined __dict__ The dictionary containing the class s namespace __bases__ A tuple containing the base classes in the order of their occurrence in the base class list __doc__ The class s documentation string or None if undefined __annotations__ A dictionary containing variable annotations collected during class body execution For best practices on working with __annotations__ please see Annotations Best Practices __type_params__ A tuple containing the type parameters of a generic class 3 2 11 Class instances A class instance is created by calling a class object see above A class instance has a namespace implemented as a dictionary which is the first place in which attribute references are searched When an attribute is not found there and the instance s class has an attribute by that name the search continues with the class attributes If a class attribute is found that is a user defined function object it is transformed into an instance method object whose __self__ attribute is the instance Static method and class method objects are also transformed see above under Classes See section Implementing Descriptors for another way in which attributes of a class retrieved via its instances may differ from the objects actually stored in the class s __dict__ If no class attribute is found and the object s class has a __getattr__ method that is called to satisfy the lookup Attribute assignments and deletions update the instance s dictionary never a class s dictionary If the class has a __setattr__ or __delattr__ method this is called instead of updating the instance dictionary directly Class instances can pretend to be numbers sequences or mappings if they have methods with certain special names See section Special method names Special attributes __dict__ is the attribute dictionary __class__ is the instance s class 3 2 12 I O objects also known as file objects A file object represents an open file Various shortcuts are available to create file objects the open built in function and also os popen os fdopen and the makefile method of socket objects and perhaps by other functions or methods provided by extension modules The objects sys stdin sys stdout and sys stderr are initialized to file objects corresponding to the interpreter s standard input output and error streams they are all open in text mode and therefore follow the interface defined by the io TextIOBase abstract class 3 2 13 Internal types A few types used internally by the interpreter are exposed to the user Their definiti,en
955,ons may change with future versions of the interpreter but they are mentioned here for completeness 3 2 13 1 Code objects Code objects represent byte compiled executable Python code or bytecode The difference between a code object and a function object is that the function object contains an explicit reference to the function s globals the module in which it was defined while a code object contains no context also the default argument values are stored in the function object not in the code object because they represent values calculated at run time Unlike function objects code objects are immutable and contain no references directly or indirectly to mutable objects 3 2 13 1 1 Special read only attributes codeobject co_name The function name codeobject co_qualname The fully qualified function name New in version 3 11 codeobject co_argcount The total number of positional parameters including positional only parameters and parameters with default values that the function has codeobject co_posonlyargcount The number of positional only parameters including arguments with default values that the function has codeobject co_kwonlyargcount The number of keyword only parameters including arguments with default values that the function has codeobject co_nlocals The number of local variables used by the function including parameters codeobject co_varnames A tuple containing the names of the local variables in the function starting with the parameter names codeobject co_cellvars A tuple containing the names of local variables that are referenced by nested functions inside the function codeobject co_freevars A tuple containing the names of free variables in the function codeobject co_code A string representing the sequence of bytecode instructions in the function codeobject co_consts A tuple containing the literals used by the bytecode in the function codeobject co_names A tuple containing the names used by the bytecode in the function codeobject co_filename The name of the file from which the code was compiled codeobject co_firstlineno The line number of the first line of the function codeobject co_lnotab A string encoding the mapping from bytecode offsets to line numbers For details see the source code of the interpreter Deprecated since version 3 12 This attribute of code objects is deprecated and may be removed in Python 3 14 codeobject co_stacksize The required stack size of the code object codeobject co_flags An integer encoding a number of flags for the interpreter The following flag bits are defined for co_flags bit 0x04 is set if the function uses the arguments syntax to accept an arbitrary number of positional arguments bit 0x08 is set if the function uses the keywords syntax to accept arbitrary keyword arguments bit 0x20 is set if the function is a generator See Code Objects Bit Flags for details on the semantics of each flags that might be present Future feature declarations from __future__ import division also use bits in co_flags to indicate whether a code object was compiled with a particular feature enabled bit 0x2000 is set if the function was compiled with future division enabled bits 0x10 and 0x1000 were used in earlier versions of Python Other bits in co_flags are reserved for internal use If a code object represents a function the first item in co_consts is the documentation string of the function or None if undefined 3 2 13 1 2 Methods on code objects codeobject co_positions Returns an iterable over the source code positions of each bytecode instruction in the code object The iterator returns tuple s containing the start_line end_line start_column end_column The i th tuple corresponds to the position of the source code that compiled to the i th instruction Column information is 0 indexed utf 8 byte offsets on the given source line This positional information can be missing A non exhaustive lists of cases where this may happen Running the interpreter with X no_debug_ranges Loading a pyc file compiled while using X no_debug_ranges Position tuples corresponding to artificial instructions Line and column numbers tha,en
956,t can t be represented due to implementation specific limitations When this occurs some or all of the tuple elements can be None New in version 3 11 Note This feature requires storing column positions in code objects which may result in a small increase of disk usage of compiled Python files or interpreter memory usage To avoid storing the extra information and or deactivate printing the extra traceback information the X no_debug_ranges command line flag or the PYTHONNODEBUGRANGES environment variable can be used codeobject co_lines Returns an iterator that yields information about successive ranges of bytecode s Each item yielded is a start end lineno tuple start an int represents the offset inclusive of the start of the bytecode range end an int represents the offset exclusive of the end of the bytecode range lineno is an int representing the line number of the bytecode range or None if the bytecodes in the given range have no line number The items yielded will have the following properties The first range yielded will have a start of 0 The start end ranges will be non decreasing and consecutive That is for any pair of tuple s the start of the second will be equal to the end of the first No range will be backwards end start for all triples The last tuple yielded will have end equal to the size of the bytecode Zero width ranges where start end are allowed Zero width ranges are used for lines that are present in the source code but have been eliminated by the bytecode compiler New in version 3 10 See also PEP 626 Precise line numbers for debugging and other tools The PEP that introduced the co_lines method codeobject replace kwargs Return a copy of the code object with new values for the specified fields New in version 3 8 3 2 13 2 Frame objects Frame objects represent execution frames They may occur in traceback objects and are also passed to registered trace functions 3 2 13 2 1 Special read only attributes frame f_back Points to the previous stack frame towards the caller or None if this is the bottom stack frame frame f_code The code object being executed in this frame Accessing this attribute raises an auditing event object __getattr__ with arguments obj and f_code frame f_locals The dictionary used by the frame to look up local variables frame f_globals The dictionary used by the frame to look up global variables frame f_builtins The dictionary used by the frame to look up built in intrinsic names frame f_lasti The precise instruction of the frame object this is an index into the bytecode string of the code object 3 2 13 2 2 Special writable attributes frame f_trace If not None this is a function called for various events during code execution this is used by debuggers Normally an event is triggered for each new source line see f_trace_lines frame f_trace_lines Set this attribute to False to disable triggering a tracing event for each source line frame f_trace_opcodes Set this attribute to True to allow per opcode events to be requested Note that this may lead to undefined interpreter behaviour if exceptions raised by the trace function escape to the function being traced frame f_lineno The current line number of the frame writing to this from within a trace function jumps to the given line only for the bottom most frame A debugger can implement a Jump command aka Set Next Statement by writing to this attribute 3 2 13 2 3 Frame object methods Frame objects support one method frame clear This method clears all references to local variables held by the frame Also if the frame belonged to a generator the generator is finalized This helps break reference cycles involving frame objects for example when catching an exception and storing its traceback for later use RuntimeError is raised if the frame is currently executing New in version 3 4 3 2 13 3 Traceback objects Traceback objects represent the stack trace of an exception A traceback object is implicitly created when an exception occurs and may also be explicitly created by calling types TracebackType Changed in version 3 7 Traceback objects can now be explicitly ins,en
957,tantiated from Python code For implicitly created tracebacks when the search for an exception handler unwinds the execution stack at each unwound level a traceback object is inserted in front of the current traceback When an exception handler is entered the stack trace is made available to the program See section The try statement It is accessible as the third item of the tuple returned by sys exc_info and as the __traceback__ attribute of the caught exception When the program contains no suitable handler the stack trace is written nicely formatted to the standard error stream if the interpreter is interactive it is also made available to the user as sys last_traceback For explicitly created tracebacks it is up to the creator of the traceback to determine how the tb_next attributes should be linked to form a full stack trace Special read only attributes traceback tb_frame Points to the execution frame of the current level Accessing this attribute raises an auditing event object __getattr__ with arguments obj and tb_frame traceback tb_lineno Gives the line number where the exception occurred traceback tb_lasti Indicates the precise instruction The line number and last instruction in the traceback may differ from the line number of its frame object if the exception occurred in a try statement with no matching except clause or with a finally clause traceback tb_next The special writable attribute tb_next is the next level in the stack trace towards the frame where the exception occurred or None if there is no next level Changed in version 3 7 This attribute is now writable 3 2 13 4 Slice objects Slice objects are used to represent slices for __getitem__ methods They are also created by the built in slice function Special read only attributes start is the lower bound stop is the upper bound step is the step value each is None if omitted These attributes can have any type Slice objects support one method slice indices self length This method takes a single integer argument length and computes information about the slice that the slice object would describe if applied to a sequence of length items It returns a tuple of three integers respectively these are the start and stop indices and the step or stride length of the slice Missing or out of bounds indices are handled in a manner consistent with regular slices 3 2 13 5 Static method objects Static method objects provide a way of defeating the transformation of function objects to method objects described above A static method object is a wrapper around any other object usually a user defined method object When a static method object is retrieved from a class or a class instance the object actually returned is the wrapped object which is not subject to any further transformation Static method objects are also callable Static method objects are created by the built in staticmethod constructor 3 2 13 6 Class method objects A class method object like a static method object is a wrapper around another object that alters the way in which that object is retrieved from classes and class instances The behaviour of class method objects upon such retrieval is described above under instance methods Class method objects are created by the built in classmethod constructor 3 3 Special method names A class can implement certain operations that are invoked by special syntax such as arithmetic operations or subscripting and slicing by defining methods with special names This is Python s approach to operator overloading allowing classes to define their own behavior with respect to language operators For instance if a class defines a method named __getitem__ and x is an instance of this class then x i is roughly equivalent to type x __getitem__ x i Except where mentioned attempts to execute an operation raise an exception when no appropriate method is defined typically AttributeError or TypeError Setting a special method to None indicates that the corresponding operation is not available For example if a class sets __iter__ to None the class is not iterable so calling iter on its instances will ,en
958,raise a TypeError without falling back to __getitem__ 2 When implementing a class that emulates any built in type it is important that the emulation only be implemented to the degree that it makes sense for the object being modelled For example some sequences may work well with retrieval of individual elements but extracting a slice may not make sense One example of this is the NodeList interface in the W3C s Document Object Model 3 3 1 Basic customization object __new__ cls Called to create a new instance of class cls __new__ is a static method special cased so you need not declare it as such that takes the class of which an instance was requested as its first argument The remaining arguments are those passed to the object constructor expression the call to the class The return value of __new__ should be the new object instance usually an instance of cls Typical implementations create a new instance of the class by invoking the superclass s __new__ method using super __new__ cls with appropriate arguments and then modifying the newly created instance as necessary before returning it If __new__ is invoked during object construction and it returns an instance of cls then the new instance s __init__ method will be invoked like __init__ self where self is the new instance and the remaining arguments are the same as were passed to the object constructor If __new__ does not return an instance of cls then the new instance s __init__ method will not be invoked __new__ is intended mainly to allow subclasses of immutable types like int str or tuple to customize instance creation It is also commonly overridden in custom metaclasses in order to customize class creation object __init__ self Called after the instance has been created by __new__ but before it is returned to the caller The arguments are those passed to the class constructor expression If a base class has an __init__ method the derived class s __init__ method if any must explicitly call it to ensure proper initialization of the base class part of the instance for example super __init__ args Because __new__ and __init__ work together in constructing objects __new__ to create it and __init__ to customize it no non None value may be returned by __init__ doing so will cause a TypeError to be raised at runtime object __del__ self Called when the instance is about to be destroyed This is also called a finalizer or improperly a destructor If a base class has a __del__ method the derived class s __del__ method if any must explicitly call it to ensure proper deletion of the base class part of the instance It is possible though not recommended for the __del__ method to postpone destruction of the instance by creating a new reference to it This is called object resurrection It is implementation dependent whether __del__ is called a second time when a resurrected object is about to be destroyed the current CPython implementation only calls it once It is not guaranteed that __del__ methods are called for objects that still exist when the interpreter exits Note del x doesn t directly call x __del__ the former decrements the reference count for x by one and the latter is only called when x s reference count reaches zero CPython implementation detail It is possible for a reference cycle to prevent the reference count of an object from going to zero In this case the cycle will be later detected and deleted by the cyclic garbage collector A common cause of reference cycles is when an exception has been caught in a local variable The frame s locals then reference the exception which references its own traceback which references the locals of all frames caught in the traceback See also Documentation for the gc module Warning Due to the precarious circumstances under which __del__ methods are invoked exceptions that occur during their execution are ignored and a warning is printed to sys stderr instead In particular __del__ can be invoked when arbitrary code is being executed including from any arbitrary thread If __del__ needs to take a lock or invoke any other blocking resource it may dea,en
959,dlock as the resource may already be taken by the code that gets interrupted to execute __del__ __del__ can be executed during interpreter shutdown As a consequence the global variables it needs to access including other modules may already have been deleted or set to None Python guarantees that globals whose name begins with a single underscore are deleted from their module before other globals are deleted if no other references to such globals exist this may help in assuring that imported modules are still available at the time when the __del__ method is called object __repr__ self Called by the repr built in function to compute the official string representation of an object If at all possible this should look like a valid Python expression that could be used to recreate an object with the same value given an appropriate environment If this is not possible a string of the form some useful description should be returned The return value must be a string object If a class defines __repr__ but not __str__ then __repr__ is also used when an informal string representation of instances of that class is required This is typically used for debugging so it is important that the representation is information rich and unambiguous object __str__ self Called by str object and the built in functions format and print to compute the informal or nicely printable string representation of an object The return value must be a string object This method differs from object __repr__ in that there is no expectation that __str__ return a valid Python expression a more convenient or concise representation can be used The default implementation defined by the built in type object calls object __repr__ object __bytes__ self Called by bytes to compute a byte string representation of an object This should return a bytes object object __format__ self format_spec Called by the format built in function and by extension evaluation of formatted string literals and the str format method to produce a formatted string representation of an object The format_spec argument is a string that contains a description of the formatting options desired The interpretation of the format_spec argument is up to the type implementing __format__ however most classes will either delegate formatting to one of the built in types or use a similar formatting option syntax See Format Specification Mini Language for a description of the standard formatting syntax The return value must be a string object Changed in version 3 4 The __format__ method of object itself raises a TypeError if passed any non empty string Changed in version 3 7 object __format__ x is now equivalent to str x rather than format str x object __lt__ self other object __le__ self other object __eq__ self other object __ne__ self other object __gt__ self other object __ge__ self other These are the so called rich comparison methods The correspondence between operator symbols and method names is as follows x y calls x __lt__ y x y calls x __le__ y x y calls x __eq__ y x y calls x __ne__ y x y calls x __gt__ y and x y calls x __ge__ y A rich comparison method may return the singleton NotImplemented if it does not implement the operation for a given pair of arguments By convention False and True are returned for a successful comparison However these methods can return any value so if the comparison operator is used in a Boolean context e g in the condition of an if statement Python will call bool on the value to determine if the result is true or false By default object implements __eq__ by using is returning NotImplemented in the case of a false comparison True if x is y else NotImplemented For __ne__ by default it delegates to __eq__ and inverts the result unless it is NotImplemented There are no other implied relationships among the comparison operators or default implementations for example the truth of x y or x y does not imply x y To automatically generate ordering operations from a single root operation see functools total_ordering See the paragraph on __hash__ for some important notes on creating hashabl,en
960,e objects which support custom comparison operations and are usable as dictionary keys There are no swapped argument versions of these methods to be used when the left argument does not support the operation but the right argument does rather __lt__ and __gt__ are each other s reflection __le__ and __ge__ are each other s reflection and __eq__ and __ne__ are their own reflection If the operands are of different types and the right operand s type is a direct or indirect subclass of the left operand s type the reflected method of the right operand has priority otherwise the left operand s method has priority Virtual subclassing is not considered When no appropriate method returns any value other than NotImplemented the and operators will fall back to is and is not respectively object __hash__ self Called by built in function hash and for operations on members of hashed collections including set frozenset and dict The __hash__ method should return an integer The only required property is that objects which compare equal have the same hash value it is advised to mix together the hash values of the components of the object that also play a part in comparison of objects by packing them into a tuple and hashing the tuple Example def __hash__ self return hash self name self nick self color Note hash truncates the value returned from an object s custom __hash__ method to the size of a Py_ssize_t This is typically 8 bytes on 64 bit builds and 4 bytes on 32 bit builds If an object s __hash__ must interoperate on builds of different bit sizes be sure to check the width on all supported builds An easy way to do this is with python c import sys print sys hash_info width If a class does not define an __eq__ method it should not define a __hash__ operation either if it defines __eq__ but not __hash__ its instances will not be usable as items in hashable collections If a class defines mutable objects and implements an __eq__ method it should not implement __hash__ since the implementation of hashable collections requires that a key s hash value is immutable if the object s hash value changes it will be in the wrong hash bucket User defined classes have __eq__ and __hash__ methods by default with them all objects compare unequal except with themselves and x __hash__ returns an appropriate value such that x y implies both that x is y and hash x hash y A class that overrides __eq__ and does not define __hash__ will have its __hash__ implicitly set to None When the __hash__ method of a class is None instances of the class will raise an appropriate TypeError when a program attempts to retrieve their hash value and will also be correctly identified as unhashable when checking isinstance obj collections abc Hashable If a class that overrides __eq__ needs to retain the implementation of __hash__ from a parent class the interpreter must be told this explicitly by setting __hash__ ParentClass __hash__ If a class that does not override __eq__ wishes to suppress hash support it should include __hash__ None in the class definition A class which defines its own __hash__ that explicitly raises a TypeError would be incorrectly identified as hashable by an isinstance obj collections abc Hashable call Note By default the __hash__ values of str and bytes objects are salted with an unpredictable random value Although they remain constant within an individual Python process they are not predictable between repeated invocations of Python This is intended to provide protection against a denial of service caused by carefully chosen inputs that exploit the worst case performance of a dict insertion O n 2 complexity See http ocert org advisories ocert 2011 003 html for details Changing hash values affects the iteration order of sets Python has never made guarantees about this ordering and it typically varies between 32 bit and 64 bit builds See also PYTHONHASHSEED Changed in version 3 3 Hash randomization is enabled by default object __bool__ self Called to implement truth value testing and the built in operation bool should return False or True When this method ,en
961,is not defined __len__ is called if it is defined and the object is considered true if its result is nonzero If a class defines neither __len__ nor __bool__ all its instances are considered true 3 3 2 Customizing attribute access The following methods can be defined to customize the meaning of attribute access use of assignment to or deletion of x name for class instances object __getattr__ self name Called when the default attribute access fails with an AttributeError either __getattribute__ raises an AttributeError because name is not an instance attribute or an attribute in the class tree for self or __get__ of a name property raises AttributeError This method should either return the computed attribute value or raise an AttributeError exception Note that if the attribute is found through the normal mechanism __getattr__ is not called This is an intentional asymmetry between __getattr__ and __setattr__ This is done both for efficiency reasons and because otherwise __getattr__ would have no way to access other attributes of the instance Note that at least for instance variables you can fake total control by not inserting any values in the instance attribute dictionary but instead inserting them in another object See the __getattribute__ method below for a way to actually get total control over attribute access object __getattribute__ self name Called unconditionally to implement attribute accesses for instances of the class If the class also defines __getattr__ the latter will not be called unless __getattribute__ either calls it explicitly or raises an AttributeError This method should return the computed attribute value or raise an AttributeError exception In order to avoid infinite recursion in this method its implementation should always call the base class method with the same name to access any attributes it needs for example object __getattribute__ self name Note This method may still be bypassed when looking up special methods as the result of implicit invocation via language syntax or built in functions See Special method lookup For certain sensitive attribute accesses raises an auditing event object __getattr__ with arguments obj and name object __setattr__ self name value Called when an attribute assignment is attempted This is called instead of the normal mechanism i e store the value in the instance dictionary name is the attribute name value is the value to be assigned to it If __setattr__ wants to assign to an instance attribute it should call the base class method with the same name for example object __setattr__ self name value For certain sensitive attribute assignments raises an auditing event object __setattr__ with arguments obj name value object __delattr__ self name Like __setattr__ but for attribute deletion instead of assignment This should only be implemented if del obj name is meaningful for the object For certain sensitive attribute deletions raises an auditing event object __delattr__ with arguments obj and name object __dir__ self Called when dir is called on the object An iterable must be returned dir converts the returned iterable to a list and sorts it 3 3 2 1 Customizing module attribute access Special names __getattr__ and __dir__ can be also used to customize access to module attributes The __getattr__ function at the module level should accept one argument which is the name of an attribute and return the computed value or raise an AttributeError If an attribute is not found on a module object through the normal lookup i e object __getattribute__ then __getattr__ is searched in the module __dict__ before raising an AttributeError If found it is called with the attribute name and the result is returned The __dir__ function should accept no arguments and return an iterable of strings that represents the names accessible on module If present this function overrides the standard dir search on a module For a more fine grained customization of the module behavior setting attributes properties etc one can set the __class__ attribute of a module object to a subclass of types ModuleType For e,en
962,xample import sys from types import ModuleType class VerboseModule ModuleType def __repr__ self return f Verbose self __name__ def __setattr__ self attr value print f Setting attr super __setattr__ attr value sys modules __name__ __class__ VerboseModule Note Defining module __getattr__ and setting module __class__ only affect lookups made using the attribute access syntax directly accessing the module globals whether by code within the module or via a reference to the module s globals dictionary is unaffected Changed in version 3 5 __class__ module attribute is now writable New in version 3 7 __getattr__ and __dir__ module attributes See also PEP 562 Module __getattr__ and __dir__ Describes the __getattr__ and __dir__ functions on modules 3 3 2 2 Implementing Descriptors The following methods only apply when an instance of the class containing the method a so called descriptor class appears in an owner class the descriptor must be in either the owner s class dictionary or in the class dictionary for one of its parents In the examples below the attribute refers to the attribute whose name is the key of the property in the owner class __dict__ object __get__ self instance owner None Called to get the attribute of the owner class class attribute access or of an instance of that class instance attribute access The optional owner argument is the owner class while instance is the instance that the attribute was accessed through or None when the attribute is accessed through the owner This method should return the computed attribute value or raise an AttributeError exception PEP 252 specifies that __get__ is callable with one or two arguments Python s own built in descriptors support this specification however it is likely that some third party tools have descriptors that require both arguments Python s own __getattribute__ implementation always passes in both arguments whether they are required or not object __set__ self instance value Called to set the attribute on an instance instance of the owner class to a new value value Note adding __set__ or __delete__ changes the kind of descriptor to a data descriptor See Invoking Descriptors for more details object __delete__ self instance Called to delete the attribute on an instance instance of the owner class Instances of descriptors may also have the __objclass__ attribute present object __objclass__ The attribute __objclass__ is interpreted by the inspect module as specifying the class where this object was defined setting this appropriately can assist in runtime introspection of dynamic class attributes For callables it may indicate that an instance of the given type or a subclass is expected or required as the first positional argument for example CPython sets this attribute for unbound methods that are implemented in C 3 3 2 3 Invoking Descriptors In general a descriptor is an object attribute with binding behavior one whose attribute access has been overridden by methods in the descriptor protocol __get__ __set__ and __delete__ If any of those methods are defined for an object it is said to be a descriptor The default behavior for attribute access is to get set or delete the attribute from an object s dictionary For instance a x has a lookup chain starting with a __dict__ x then type a __dict__ x and continuing through the base classes of type a excluding metaclasses However if the looked up value is an object defining one of the descriptor methods then Python may override the default behavior and invoke the descriptor method instead Where this occurs in the precedence chain depends on which descriptor methods were defined and how they were called The starting point for descriptor invocation is a binding a x How the arguments are assembled depends on a Direct Call The simplest and least common call is when user code directly invokes a descriptor method x __get__ a Instance Binding If binding to an object instance a x is transformed into the call type a __dict__ x __get__ a type a Class Binding If binding to a class A x is transformed into the call A __dict__ x __get__ None A,en
963, Super Binding A dotted lookup such as super A a x searches a __class__ __mro__ for a base class B following A and then returns B __dict__ x __get__ a A If not a descriptor x is returned unchanged For instance bindings the precedence of descriptor invocation depends on which descriptor methods are defined A descriptor can define any combination of __get__ __set__ and __delete__ If it does not define __get__ then accessing the attribute will return the descriptor object itself unless there is a value in the object s instance dictionary If the descriptor defines __set__ and or __delete__ it is a data descriptor if it defines neither it is a non data descriptor Normally data descriptors define both __get__ and __set__ while non data descriptors have just the __get__ method Data descriptors with __get__ and __set__ and or __delete__ defined always override a redefinition in an instance dictionary In contrast non data descriptors can be overridden by instances Python methods including those decorated with staticmethod and classmethod are implemented as non data descriptors Accordingly instances can redefine and override methods This allows individual instances to acquire behaviors that differ from other instances of the same class The property function is implemented as a data descriptor Accordingly instances cannot override the behavior of a property 3 3 2 4 __slots__ __slots__ allow us to explicitly declare data members like properties and deny the creation of __dict__ and __weakref__ unless explicitly declared in __slots__ or available in a parent The space saved over using __dict__ can be significant Attribute lookup speed can be significantly improved as well object __slots__ This class variable can be assigned a string iterable or sequence of strings with variable names used by instances __slots__ reserves space for the declared variables and prevents the automatic creation of __dict__ and __weakref__ for each instance Notes on using __slots__ When inheriting from a class without __slots__ the __dict__ and __weakref__ attribute of the instances will always be accessible Without a __dict__ variable instances cannot be assigned new variables not listed in the __slots__ definition Attempts to assign to an unlisted variable name raises AttributeError If dynamic assignment of new variables is desired then add __dict__ to the sequence of strings in the __slots__ declaration Without a __weakref__ variable for each instance classes defining __slots__ do not support weak references to its instances If weak reference support is needed then add __weakref__ to the sequence of strings in the __slots__ declaration __slots__ are implemented at the class level by creating descriptors for each variable name As a result class attributes cannot be used to set default values for instance variables defined by __slots__ otherwise the class attribute would overwrite the descriptor assignment The action of a __slots__ declaration is not limited to the class where it is defined __slots__ declared in parents are available in child classes However child subclasses will get a __dict__ and __weakref__ unless they also define __slots__ which should only contain names of any additional slots If a class defines a slot also defined in a base class the instance variable defined by the base class slot is inaccessible except by retrieving its descriptor directly from the base class This renders the meaning of the program undefined In the future a check may be added to prevent this TypeError will be raised if nonempty __slots__ are defined for a class derived from a variable length built in type such as int bytes and tuple Any non string iterable may be assigned to __slots__ If a dictionary is used to assign __slots__ the dictionary keys will be used as the slot names The values of the dictionary can be used to provide per attribute docstrings that will be recognised by inspect getdoc and displayed in the output of help __class__ assignment works only if both classes have the same __slots__ Multiple inheritance with multiple slotted parent classes can be u,en
964,sed but only one parent is allowed to have attributes created by slots the other bases must have empty slot layouts violations raise TypeError If an iterator is used for __slots__ then a descriptor is created for each of the iterator s values However the __slots__ attribute will be an empty iterator 3 3 3 Customizing class creation Whenever a class inherits from another class __init_subclass__ is called on the parent class This way it is possible to write classes which change the behavior of subclasses This is closely related to class decorators but where class decorators only affect the specific class they re applied to __init_subclass__ solely applies to future subclasses of the class defining the method classmethod object __init_subclass__ cls This method is called whenever the containing class is subclassed cls is then the new subclass If defined as a normal instance method this method is implicitly converted to a class method Keyword arguments which are given to a new class are passed to the parent class s __init_subclass__ For compatibility with other classes using __init_subclass__ one should take out the needed keyword arguments and pass the others over to the base class as in class Philosopher def __init_subclass__ cls default_name kwargs super __init_subclass__ kwargs cls default_name default_name class AustralianPhilosopher Philosopher default_name Bruce pass The default implementation object __init_subclass__ does nothing but raises an error if it is called with any arguments Note The metaclass hint metaclass is consumed by the rest of the type machinery and is never passed to __init_subclass__ implementations The actual metaclass rather than the explicit hint can be accessed as type cls New in version 3 6 When a class is created type __new__ scans the class variables and makes callbacks to those with a __set_name__ hook object __set_name__ self owner name Automatically called at the time the owning class owner is created The object has been assigned to name in that class class A x C Automatically calls x __set_name__ A x If the class variable is assigned after the class is created __set_name__ will not be called automatically If needed __set_name__ can be called directly class A pass c C A x c The hook is not called c __set_name__ A x Manually invoke the hook See Creating the class object for more details New in version 3 6 3 3 3 1 Metaclasses By default classes are constructed using type The class body is executed in a new namespace and the class name is bound locally to the result of type name bases namespace The class creation process can be customized by passing the metaclass keyword argument in the class definition line or by inheriting from an existing class that included such an argument In the following example both MyClass and MySubclass are instances of Meta class Meta type pass class MyClass metaclass Meta pass class MySubclass MyClass pass Any other keyword arguments that are specified in the class definition are passed through to all metaclass operations described below When a class definition is executed the following steps occur MRO entries are resolved the appropriate metaclass is determined the class namespace is prepared the class body is executed the class object is created 3 3 3 2 Resolving MRO entries object __mro_entries__ self bases If a base that appears in a class definition is not an instance of type then an __mro_entries__ method is searched on the base If an __mro_entries__ method is found the base is substituted with the result of a call to __mro_entries__ when creating the class The method is called with the original bases tuple passed to the bases parameter and must return a tuple of classes that will be used instead of the base The returned tuple may be empty in these cases the original base is ignored See also types resolve_bases Dynamically resolve bases that are not instances of type types get_original_bases Retrieve a class s original bases prior to modifications by __mro_entries__ PEP 560 Core support for typing module and generic types 3 3 3 3 Determining the appropriate,en
965, metaclass The appropriate metaclass for a class definition is determined as follows if no bases and no explicit metaclass are given then type is used if an explicit metaclass is given and it is not an instance of type then it is used directly as the metaclass if an instance of type is given as the explicit metaclass or bases are defined then the most derived metaclass is used The most derived metaclass is selected from the explicitly specified metaclass if any and the metaclasses i e type cls of all specified base classes The most derived metaclass is one which is a subtype of all of these candidate metaclasses If none of the candidate metaclasses meets that criterion then the class definition will fail with TypeError 3 3 3 4 Preparing the class namespace Once the appropriate metaclass has been identified then the class namespace is prepared If the metaclass has a __prepare__ attribute it is called as namespace metaclass __prepare__ name bases kwds where the additional keyword arguments if any come from the class definition The __prepare__ method should be implemented as a classmethod The namespace returned by __prepare__ is passed in to __new__ but when the final class object is created the namespace is copied into a new dict If the metaclass has no __prepare__ attribute then the class namespace is initialised as an empty ordered mapping See also PEP 3115 Metaclasses in Python 3000 Introduced the __prepare__ namespace hook 3 3 3 5 Executing the class body The class body is executed approximately as exec body globals namespace The key difference from a normal call to exec is that lexical scoping allows the class body including any methods to reference names from the current and outer scopes when the class definition occurs inside a function However even when the class definition occurs inside the function methods defined inside the class still cannot see names defined at the class scope Class variables must be accessed through the first parameter of instance or class methods or through the implicit lexically scoped __class__ reference described in the next section 3 3 3 6 Creating the class object Once the class namespace has been populated by executing the class body the class object is created by calling metaclass name bases namespace kwds the additional keywords passed here are the same as those passed to __prepare__ This class object is the one that will be referenced by the zero argument form of super __class__ is an implicit closure reference created by the compiler if any methods in a class body refer to either __class__ or super This allows the zero argument form of super to correctly identify the class being defined based on lexical scoping while the class or instance that was used to make the current call is identified based on the first argument passed to the method CPython implementation detail In CPython 3 6 and later the __class__ cell is passed to the metaclass as a __classcell__ entry in the class namespace If present this must be propagated up to the type __new__ call in order for the class to be initialised correctly Failing to do so will result in a RuntimeError in Python 3 8 When using the default metaclass type or any metaclass that ultimately calls type __new__ the following additional customization steps are invoked after creating the class object 1 The type __new__ method collects all of the attributes in the class namespace that define a __set_name__ method 2 Those __set_name__ methods are called with the class being defined and the assigned name of that particular attribute 3 The __init_subclass__ hook is called on the immediate parent of the new class in its method resolution order After the class object is created it is passed to the class decorators included in the class definition if any and the resulting object is bound in the local namespace as the defined class When a new class is created by type __new__ the object provided as the namespace parameter is copied to a new ordered mapping and the original object is discarded The new copy is wrapped in a read only proxy which becomes the __di,en
966,ct__ attribute of the class object See also PEP 3135 New super Describes the implicit __class__ closure reference 3 3 3 7 Uses for metaclasses The potential uses for metaclasses are boundless Some ideas that have been explored include enum logging interface checking automatic delegation automatic property creation proxies frameworks and automatic resource locking synchronization 3 3 4 Customizing instance and subclass checks The following methods are used to override the default behavior of the isinstance and issubclass built in functions In particular the metaclass abc ABCMeta implements these methods in order to allow the addition of Abstract Base Classes ABCs as virtual base classes to any class or type including built in types including other ABCs class __instancecheck__ self instance Return true if instance should be considered a direct or indirect instance of class If defined called to implement isinstance instance class class __subclasscheck__ self subclass Return true if subclass should be considered a direct or indirect subclass of class If defined called to implement issubclass subclass class Note that these methods are looked up on the type metaclass of a class They cannot be defined as class methods in the actual class This is consistent with the lookup of special methods that are called on instances only in this case the instance is itself a class See also PEP 3119 Introducing Abstract Base Classes Includes the specification for customizing isinstance and issubclass behavior through __instancecheck__ and __subclasscheck__ with motivation for this functionality in the context of adding Abstract Base Classes see the abc module to the language 3 3 5 Emulating generic types When using type annotations it is often useful to parameterize a generic type using Python s square brackets notation For example the annotation list int might be used to signify a list in which all the elements are of type int See also PEP 484 Type Hints Introducing Python s framework for type annotations Generic Alias Types Documentation for objects representing parameterized generic classes Generics user defined generics and typing Generic Documentation on how to implement generic classes that can be parameterized at runtime and understood by static type checkers A class can generally only be parameterized if it defines the special class method __class_getitem__ classmethod object __class_getitem__ cls key Return an object representing the specialization of a generic class by type arguments found in key When defined on a class __class_getitem__ is automatically a class method As such there is no need for it to be decorated with classmethod when it is defined 3 3 5 1 The purpose of __class_getitem__ The purpose of __class_getitem__ is to allow runtime parameterization of standard library generic classes in order to more easily apply type hints to these classes To implement custom generic classes that can be parameterized at runtime and understood by static type checkers users should either inherit from a standard library class that already implements __class_getitem__ or inherit from typing Generic which has its own implementation of __class_getitem__ Custom implementations of __class_getitem__ on classes defined outside of the standard library may not be understood by third party type checkers such as mypy Using __class_getitem__ on any class for purposes other than type hinting is discouraged 3 3 5 2 __class_getitem__ versus __getitem__ Usually the subscription of an object using square brackets will call the __getitem__ instance method defined on the object s class However if the object being subscribed is itself a class the class method __class_getitem__ may be called instead __class_getitem__ should return a GenericAlias object if it is properly defined Presented with the expression obj x the Python interpreter follows something like the following process to decide whether __getitem__ or __class_getitem__ should be called from inspect import isclass def subscribe obj x Return the result of the expression obj x class_of_obj type obj If ,en
967,the class of obj defines __getitem__ call class_of_obj __getitem__ obj x if hasattr class_of_obj __getitem__ return class_of_obj __getitem__ obj x Else if obj is a class and defines __class_getitem__ call obj __class_getitem__ x elif isclass obj and hasattr obj __class_getitem__ return obj __class_getitem__ x Else raise an exception else raise TypeError f class_of_obj __name__ object is not subscriptable In Python all classes are themselves instances of other classes The class of a class is known as that class s metaclass and most classes have the type class as their metaclass type does not define __getitem__ meaning that expressions such as list int dict str float and tuple str bytes all result in __class_getitem__ being called list has class type as its metaclass like most classes type list class type type dict type list type tuple type str type bytes True list int calls list __class_getitem__ int list int list int list __class_getitem__ returns a GenericAlias object type list int class types GenericAlias However if a class has a custom metaclass that defines __getitem__ subscribing the class may result in different behaviour An example of this can be found in the enum module from enum import Enum class Menu Enum A breakfast menu SPAM spam BACON bacon Enum classes have a custom metaclass type Menu class enum EnumMeta EnumMeta defines __getitem__ so __class_getitem__ is not called and the result is not a GenericAlias object Menu SPAM Menu SPAM spam type Menu SPAM enum Menu See also PEP 560 Core Support for typing module and generic types Introducing __class_getitem__ and outlining when a subscription results in __class_getitem__ being called instead of __getitem__ 3 3 6 Emulating callable objects object __call__ self args Called when the instance is called as a function if this method is defined x arg1 arg2 roughly translates to type x __call__ x arg1 3 3 7 Emulating container types The following methods can be defined to implement container objects Containers usually are sequences such as lists or tuples or mappings like dictionaries but can represent other containers as well The first set of methods is used either to emulate a sequence or to emulate a mapping the difference is that for a sequence the allowable keys should be the integers k for which 0 k N where N is the length of the sequence or slice objects which define a range of items It is also recommended that mappings provide the methods keys values items get clear setdefault pop popitem copy and update behaving similar to those for Python s standard dictionary objects The collections abc module provides a MutableMapping abstract base class to help create those methods from a base set of __getitem__ __setitem__ __delitem__ and keys Mutable sequences should provide methods append count index extend insert pop remove reverse and sort like Python standard list objects Finally sequence types should implement addition meaning concatenation and multiplication meaning repetition by defining the methods __add__ __radd__ __iadd__ __mul__ __rmul__ and __imul__ described below they should not define other numerical operators It is recommended that both mappings and sequences implement the __contains__ method to allow efficient use of the in operator for mappings in should search the mapping s keys for sequences it should search through the values It is further recommended that both mappings and sequences implement the __iter__ method to allow efficient iteration through the container for mappings __iter__ should iterate through the object s keys for sequences it should iterate through the values object __len__ self Called to implement the built in function len Should return the length of the object an integer 0 Also an object that doesn t define a __bool__ method and whose __len__ method returns zero is considered to be false in a Boolean context CPython implementation detail In CPython the length is required to be at most sys maxsize If the length is larger than sys maxsize some features such as len may raise OverflowError To prevent raising OverflowError by truth value ,en
968,testing an object must define a __bool__ method object __length_hint__ self Called to implement operator length_hint Should return an estimated length for the object which may be greater or less than the actual length The length must be an integer 0 The return value may also be NotImplemented which is treated the same as if the __length_hint__ method didn t exist at all This method is purely an optimization and is never required for correctness New in version 3 4 Note Slicing is done exclusively with the following three methods A call like a 1 2 b is translated to a slice 1 2 None b and so forth Missing slice items are always filled in with None object __getitem__ self key Called to implement evaluation of self key For sequence types the accepted keys should be integers Optionally they may support slice objects as well Negative index support is also optional If key is of an inappropriate type TypeError may be raised if key is a value outside the set of indexes for the sequence after any special interpretation of negative values IndexError should be raised For mapping types if key is missing not in the container KeyError should be raised Note for loops expect that an IndexError will be raised for illegal indexes to allow proper detection of the end of the sequence Note When subscripting a class the special class method __class_getitem__ may be called instead of __getitem__ See __class_getitem__ versus __getitem__ for more details object __setitem__ self key value Called to implement assignment to self key Same note as for __getitem__ This should only be implemented for mappings if the objects support changes to the values for keys or if new keys can be added or for sequences if elements can be replaced The same exceptions should be raised for improper key values as for the __getitem__ method object __delitem__ self key Called to implement deletion of self key Same note as for __getitem__ This should only be implemented for mappings if the objects support removal of keys or for sequences if elements can be removed from the sequence The same exceptions should be raised for improper key values as for the __getitem__ method object __missing__ self key Called by dict __getitem__ to implement self key for dict subclasses when key is not in the dictionary object __iter__ self This method is called when an iterator is required for a container This method should return a new iterator object that can iterate over all the objects in the container For mappings it should iterate over the keys of the container object __reversed__ self Called if present by the reversed built in to implement reverse iteration It should return a new iterator object that iterates over all the objects in the container in reverse order If the __reversed__ method is not provided the reversed built in will fall back to using the sequence protocol __len__ and __getitem__ Objects that support the sequence protocol should only provide __reversed__ if they can provide an implementation that is more efficient than the one provided by reversed The membership test operators in and not in are normally implemented as an iteration through a container However container objects can supply the following special method with a more efficient implementation which also does not require the object be iterable object __contains__ self item Called to implement membership test operators Should return true if item is in self false otherwise For mapping objects this should consider the keys of the mapping rather than the values or the key item pairs For objects that don t define __contains__ the membership test first tries iteration via __iter__ then the old sequence iteration protocol via __getitem__ see this section in the language reference 3 3 8 Emulating numeric types The following methods can be defined to emulate numeric objects Methods corresponding to operations that are not supported by the particular kind of number implemented e g bitwise operations for non integral numbers should be left undefined object __add__ self other object __sub__ self other object __mul__ self ot,en
969,her object __matmul__ self other object __truediv__ self other object __floordiv__ self other object __mod__ self other object __divmod__ self other object __pow__ self other modulo object __lshift__ self other object __rshift__ self other object __and__ self other object __xor__ self other object __or__ self other These methods are called to implement the binary arithmetic operations divmod pow For instance to evaluate the expression x y where x is an instance of a class that has an __add__ method type x __add__ x y is called The __divmod__ method should be the equivalent to using __floordiv__ and __mod__ it should not be related to __truediv__ Note that __pow__ should be defined to accept an optional third argument if the ternary version of the built in pow function is to be supported If one of those methods does not support the operation with the supplied arguments it should return NotImplemented object __radd__ self other object __rsub__ self other object __rmul__ self other object __rmatmul__ self other object __rtruediv__ self other object __rfloordiv__ self other object __rmod__ self other object __rdivmod__ self other object __rpow__ self other modulo object __rlshift__ self other object __rrshift__ self other object __rand__ self other object __rxor__ self other object __ror__ self other These methods are called to implement the binary arithmetic operations divmod pow with reflected swapped operands These functions are only called if the left operand does not support the corresponding operation 3 and the operands are of different types 4 For instance to evaluate the expression x y where y is an instance of a class that has an __rsub__ method type y __rsub__ y x is called if type x __sub__ x y returns NotImplemented Note that ternary pow will not try calling __rpow__ the coercion rules would become too complicated Note If the right operand s type is a subclass of the left operand s type and that subclass provides a different implementation of the reflected method for the operation this method will be called before the left operand s non reflected method This behavior allows subclasses to override their ancestors operations object __iadd__ self other object __isub__ self other object __imul__ self other object __imatmul__ self other object __itruediv__ self other object __ifloordiv__ self other object __imod__ self other object __ipow__ self other modulo object __ilshift__ self other object __irshift__ self other object __iand__ self other object __ixor__ self other object __ior__ self other These methods are called to implement the augmented arithmetic assignments These methods should attempt to do the operation in place modifying self and return the result which could be but does not have to be self If a specific method is not defined or if that method returns NotImplemented the augmented assignment falls back to the normal methods For instance if x is an instance of a class with an __iadd__ method x y is equivalent to x x __iadd__ y If __iadd__ does not exist or if x __iadd__ y returns NotImplemented x __add__ y and y __radd__ x are considered as with the evaluation of x y In certain situations augmented assignment can result in unexpected errors see Why does a_tuple i item raise an exception when the addition works but this behavior is in fact part of the data model object __neg__ self object __pos__ self object __abs__ self object __invert__ self Called to implement the unary arithmetic operations abs and object __complex__ self object __int__ self object __float__ self Called to implement the built in functions complex int and float Should return a value of the appropriate type object __index__ self Called to implement operator index and whenever Python needs to losslessly convert the numeric object to an integer object such as in slicing or in the built in bin hex and oct functions Presence of this method indicates that the numeric object is an integer type Must return an integer If __int__ __float__ and __complex__ are not defined then corresponding built in functions int float and complex fall back to __i,en
970,ndex__ object __round__ self ndigits object __trunc__ self object __floor__ self object __ceil__ self Called to implement the built in function round and math functions trunc floor and ceil Unless ndigits is passed to __round__ all these methods should return the value of the object truncated to an Integral typically an int The built in function int falls back to __trunc__ if neither __int__ nor __index__ is defined Changed in version 3 11 The delegation of int to __trunc__ is deprecated 3 3 9 With Statement Context Managers A context manager is an object that defines the runtime context to be established when executing a with statement The context manager handles the entry into and the exit from the desired runtime context for the execution of the block of code Context managers are normally invoked using the with statement described in section The with statement but can also be used by directly invoking their methods Typical uses of context managers include saving and restoring various kinds of global state locking and unlocking resources closing opened files etc For more information on context managers see Context Manager Types object __enter__ self Enter the runtime context related to this object The with statement will bind this method s return value to the target s specified in the as clause of the statement if any object __exit__ self exc_type exc_value traceback Exit the runtime context related to this object The parameters describe the exception that caused the context to be exited If the context was exited without an exception all three arguments will be None If an exception is supplied and the method wishes to suppress the exception i e prevent it from being propagated it should return a true value Otherwise the exception will be processed normally upon exit from this method Note that __exit__ methods should not reraise the passed in exception this is the caller s responsibility See also PEP 343 The with statement The specification background and examples for the Python with statement 3 3 10 Customizing positional arguments in class pattern matching When using a class name in a pattern positional arguments in the pattern are not allowed by default i e case MyClass x y is typically invalid without special support in MyClass To be able to use that kind of pattern the class needs to define a __match_args__ attribute object __match_args__ This class variable can be assigned a tuple of strings When this class is used in a class pattern with positional arguments each positional argument will be converted into a keyword argument using the corresponding value in __match_args__ as the keyword The absence of this attribute is equivalent to setting it to For example if MyClass __match_args__ is left center right that means that case MyClass x y is equivalent to case MyClass left x center y Note that the number of arguments in the pattern must be smaller than or equal to the number of elements in __match_args__ if it is larger the pattern match attempt will raise a TypeError New in version 3 10 See also PEP 634 Structural Pattern Matching The specification for the Python match statement 3 3 11 Emulating buffer types The buffer protocol provides a way for Python objects to expose efficient access to a low level memory array This protocol is implemented by builtin types such as bytes and memoryview and third party libraries may define additional buffer types While buffer types are usually implemented in C it is also possible to implement the protocol in Python object __buffer__ self flags Called when a buffer is requested from self for example by the memoryview constructor The flags argument is an integer representing the kind of buffer requested affecting for example whether the returned buffer is read only or writable inspect BufferFlags provides a convenient way to interpret the flags The method must return a memoryview object object __release_buffer__ self buffer Called when a buffer is no longer needed The buffer argument is a memoryview object that was previously returned by __buffer__ The method must release any resou,en
971,rces associated with the buffer This method should return None Buffer objects that do not need to perform any cleanup are not required to implement this method New in version 3 12 See also PEP 688 Making the buffer protocol accessible in Python Introduces the Python __buffer__ and __release_buffer__ methods collections abc Buffer ABC for buffer types 3 3 12 Special method lookup For custom classes implicit invocations of special methods are only guaranteed to work correctly if defined on an object s type not in the object s instance dictionary That behaviour is the reason why the following code raises an exception class C pass c C c __len__ lambda 5 len c Traceback most recent call last File stdin line 1 in module TypeError object of type C has no len The rationale behind this behaviour lies with a number of special methods such as __hash__ and __repr__ that are implemented by all objects including type objects If the implicit lookup of these methods used the conventional lookup process they would fail when invoked on the type object itself 1 __hash__ hash 1 True int __hash__ hash int Traceback most recent call last File stdin line 1 in module TypeError descriptor __hash__ of int object needs an argument Incorrectly attempting to invoke an unbound method of a class in this way is sometimes referred to as metaclass confusion and is avoided by bypassing the instance when looking up special methods type 1 __hash__ 1 hash 1 True type int __hash__ int hash int True In addition to bypassing any instance attributes in the interest of correctness implicit special method lookup generally also bypasses the __getattribute__ method even of the object s metaclass class Meta type def __getattribute__ args print Metaclass getattribute invoked return type __getattribute__ args class C object metaclass Meta def __len__ self return 10 def __getattribute__ args print Class getattribute invoked return object __getattribute__ args c C c __len__ Explicit lookup via instance Class getattribute invoked 10 type c __len__ c Explicit lookup via type Metaclass getattribute invoked 10 len c Implicit lookup 10 Bypassing the __getattribute__ machinery in this fashion provides significant scope for speed optimisations within the interpreter at the cost of some flexibility in the handling of special methods the special method must be set on the class object itself in order to be consistently invoked by the interpreter 3 4 Coroutines 3 4 1 Awaitable Objects An awaitable object generally implements an __await__ method Coroutine objects returned from async def functions are awaitable Note The generator iterator objects returned from generators decorated with types coroutine are also awaitable but they do not implement __await__ object __await__ self Must return an iterator Should be used to implement awaitable objects For instance asyncio Future implements this method to be compatible with the await expression Note The language doesn t place any restriction on the type or value of the objects yielded by the iterator returned by __await__ as this is specific to the implementation of the asynchronous execution framework e g asyncio that will be managing the awaitable object New in version 3 5 See also PEP 492 for additional information about awaitable objects 3 4 2 Coroutine Objects Coroutine objects are awaitable objects A coroutine s execution can be controlled by calling __await__ and iterating over the result When the coroutine has finished executing and returns the iterator raises StopIteration and the exception s value attribute holds the return value If the coroutine raises an exception it is propagated by the iterator Coroutines should not directly raise unhandled StopIteration exceptions Coroutines also have the methods listed below which are analogous to those of generators see Generator iterator methods However unlike generators coroutines do not directly support iteration Changed in version 3 5 2 It is a RuntimeError to await on a coroutine more than once coroutine send value Starts or resumes execution of the coroutine If value is None this is e,en
972,quivalent to advancing the iterator returned by __await__ If value is not None this method delegates to the send method of the iterator that caused the coroutine to suspend The result return value StopIteration or other exception is the same as when iterating over the __await__ return value described above coroutine throw value coroutine throw type value traceback Raises the specified exception in the coroutine This method delegates to the throw method of the iterator that caused the coroutine to suspend if it has such a method Otherwise the exception is raised at the suspension point The result return value StopIteration or other exception is the same as when iterating over the __await__ return value described above If the exception is not caught in the coroutine it propagates back to the caller Changed in version 3 12 The second signature type value traceback is deprecated and may be removed in a future version of Python coroutine close Causes the coroutine to clean itself up and exit If the coroutine is suspended this method first delegates to the close method of the iterator that caused the coroutine to suspend if it has such a method Then it raises GeneratorExit at the suspension point causing the coroutine to immediately clean itself up Finally the coroutine is marked as having finished executing even if it was never started Coroutine objects are automatically closed using the above process when they are about to be destroyed 3 4 3 Asynchronous Iterators An asynchronous iterator can call asynchronous code in its __anext__ method Asynchronous iterators can be used in an async for statement object __aiter__ self Must return an asynchronous iterator object object __anext__ self Must return an awaitable resulting in a next value of the iterator Should raise a StopAsyncIteration error when the iteration is over An example of an asynchronous iterable object class Reader async def readline self def __aiter__ self return self async def __anext__ self val await self readline if val b raise StopAsyncIteration return val New in version 3 5 Changed in version 3 7 Prior to Python 3 7 __aiter__ could return an awaitable that would resolve to an asynchronous iterator Starting with Python 3 7 __aiter__ must return an asynchronous iterator object Returning anything else will result in a TypeError error 3 4 4 Asynchronous Context Managers An asynchronous context manager is a context manager that is able to suspend execution in its __aenter__ and __aexit__ methods Asynchronous context managers can be used in an async with statement object __aenter__ self Semantically similar to __enter__ the only difference being that it must return an awaitable object __aexit__ self exc_type exc_value traceback Semantically similar to __exit__ the only difference being that it must return an awaitable An example of an asynchronous context manager class class AsyncContextManager async def __aenter__ self await log entering context async def __aexit__ self exc_type exc tb await log exiting context New in version 3 5 Footnotes 1 It is possible in some cases to change an object s type under certain controlled conditions It generally isn t a good idea though since it can lead to some very strange behaviour if it is handled incorrectly 2 The __hash__ __iter__ __reversed__ and __contains__ methods have special handling for this others will still raise a TypeError but may do so by relying on the behavior that None is not callable 3 Does not support here means that the class has no such method or the method returns NotImplemented Do not set the method to None if you want to force fallback to the right operand s reflected method that will instead have the opposite effect of explicitly blocking such fallback 4 For operands of the same type it is assumed that if the non reflected method such as __add__ fails then the overall operation is not supported which is why the reflected method is not called,en
973,Internet Data Handling This chapter describes modules which support handling data formats commonly used on the internet email An email and MIME handling package email message Representing an email message email parser Parsing email messages FeedParser API Parser API Additional notes email generator Generating MIME documents email policy Policy Objects email errors Exception and Defect classes email headerregistry Custom Header Objects email contentmanager Managing MIME Content Content Manager Instances email Examples email message Message Representing an email message using the compat32 API email mime Creating email and MIME objects from scratch email header Internationalized headers email charset Representing character sets email encoders Encoders email utils Miscellaneous utilities email iterators Iterators json JSON encoder and decoder Basic Usage Encoders and Decoders Exceptions Standard Compliance and Interoperability Character Encodings Infinite and NaN Number Values Repeated Names Within an Object Top level Non Object Non Array Values Implementation Limitations Command Line Interface Command line options mailbox Manipulate mailboxes in various formats Mailbox objects Maildir objects mbox objects MH objects Babyl objects MMDF objects Message objects MaildirMessage objects mboxMessage objects MHMessage objects BabylMessage objects MMDFMessage objects Exceptions Examples mimetypes Map filenames to MIME types MimeTypes Objects base64 Base16 Base32 Base64 Base85 Data Encodings Security Considerations binascii Convert between binary and ASCII quopri Encode and decode MIME quoted printable data,en
974,pickletools Tools for pickle developers Source code Lib pickletools py This module contains various constants relating to the intimate details of the pickle module some lengthy comments about the implementation and a few useful functions for analyzing pickled data The contents of this module are useful for Python core developers who are working on the pickle ordinary users of the pickle module probably won t find the pickletools module relevant Command line usage New in version 3 2 When invoked from the command line python m pickletools will disassemble the contents of one or more pickle files Note that if you want to see the Python object stored in the pickle rather than the details of pickle format you may want to use m pickle instead However when the pickle file that you want to examine comes from an untrusted source m pickletools is a safer option because it does not execute pickle bytecode For example with a tuple 1 2 pickled in file x pickle python m pickle x pickle 1 2 python m pickletools x pickle 0 x80 PROTO 3 2 K BININT1 1 4 K BININT1 2 6 x86 TUPLE2 7 q BINPUT 0 9 STOP highest protocol among opcodes 2 Command line options a annotate Annotate each line with a short opcode description o output file Name of a file where the output should be written l indentlevel num The number of blanks by which to indent a new MARK level m memo When multiple objects are disassembled preserve memo between disassemblies p preamble preamble When more than one pickle file are specified print given preamble before each disassembly Programmatic Interface pickletools dis pickle out None memo None indentlevel 4 annotate 0 Outputs a symbolic disassembly of the pickle to the file like object out defaulting to sys stdout pickle can be a string or a file like object memo can be a Python dictionary that will be used as the pickle s memo it can be used to perform disassemblies across multiple pickles created by the same pickler Successive levels indicated by MARK opcodes in the stream are indented by indentlevel spaces If a nonzero value is given to annotate each opcode in the output is annotated with a short description The value of annotate is used as a hint for the column where annotation should start Changed in version 3 2 Added the annotate parameter pickletools genops pickle Provides an iterator over all of the opcodes in a pickle returning a sequence of opcode arg pos triples opcode is an instance of an OpcodeInfo class arg is the decoded value as a Python object of the opcode s argument pos is the position at which this opcode is located pickle can be a string or a file like object pickletools optimize picklestring Returns a new equivalent pickle string after eliminating unused PUT opcodes The optimized pickle is shorter takes less transmission time requires less storage space and unpickles more efficiently,en
975,What s New In Python 3 12 Editor Adam Turner This article explains the new features in Python 3 12 compared to 3 11 Python 3 12 was released on October 2 2023 For full details see the changelog See also PEP 693 Python 3 12 Release Schedule Summary Release highlights Python 3 12 is the latest stable release of the Python programming language with a mix of changes to the language and the standard library The library changes focus on cleaning up deprecated APIs usability and correctness Of note the distutils package has been removed from the standard library Filesystem support in os and pathlib has seen a number of improvements and several modules have better performance The language changes focus on usability as f strings have had many limitations removed and Did you mean suggestions continue to improve The new type parameter syntax and type statement improve ergonomics for using generic types and type aliases with static type checkers This article doesn t attempt to provide a complete specification of all new features but instead gives a convenient overview For full details you should refer to the documentation such as the Library Reference and Language Reference If you want to understand the complete implementation and design rationale for a change refer to the PEP for a particular new feature but note that PEPs usually are not kept up to date once a feature has been fully implemented New syntax features PEP 695 type parameter syntax and the type statement New grammar features PEP 701 f strings in the grammar Interpreter improvements PEP 684 a unique per interpreter GIL PEP 669 low impact monitoring Improved Did you mean suggestions for NameError ImportError and SyntaxError exceptions Python data model improvements PEP 688 using the buffer protocol from Python Significant improvements in the standard library The pathlib Path class now supports subclassing The os module received several improvements for Windows support A command line interface has been added to the sqlite3 module isinstance checks against runtime checkable protocols enjoy a speed up of between two and 20 times The asyncio package has had a number of performance improvements with some benchmarks showing a 75 speed up A command line interface has been added to the uuid module Due to the changes in PEP 701 producing tokens via the tokenize module is up to 64 faster Security improvements Replace the builtin hashlib implementations of SHA1 SHA3 SHA2 384 SHA2 512 and MD5 with formally verified code from the HACL project These builtin implementations remain as fallbacks that are only used when OpenSSL does not provide them C API improvements PEP 697 unstable C API tier PEP 683 immortal objects CPython implementation improvements PEP 709 comprehension inlining CPython support for the Linux perf profiler Implement stack overflow protection on supported platforms New typing features PEP 692 using TypedDict to annotate kwargs PEP 698 typing override decorator Important deprecations removals or restrictions PEP 623 Remove wstr from Unicode objects in Python s C API reducing the size of every str object by at least 8 bytes PEP 632 Remove the distutils package See the migration guide for advice replacing the APIs it provided The third party Setuptools package continues to provide distutils if you still require it in Python 3 12 and beyond gh 95299 Do not pre install setuptools in virtual environments created with venv This means that distutils setuptools pkg_resources and easy_install will no longer available by default to access these run pip install setuptools in the activated virtual environment The asynchat asyncore and imp modules have been removed along with several unittest TestCase method aliases New Features PEP 695 Type Parameter Syntax Generic classes and functions under PEP 484 were declared using a verbose syntax that left the scope of type parameters unclear and required explicit declarations of variance PEP 695 introduces a new more compact and explicit way to create generic classes and functions def max T args Iterable T T class list T def __getitem__ s,en
976,elf index int T def append self element T None In addition the PEP introduces a new way to declare type aliases using the type statement which creates an instance of TypeAliasType type Point tuple float float Type aliases can also be generic type Point T tuple T T The new syntax allows declaring TypeVarTuple and ParamSpec parameters as well as TypeVar parameters with bounds or constraints type IntFunc P Callable P int ParamSpec type LabeledTuple Ts tuple str Ts TypeVarTuple type HashableSequence T Hashable Sequence T TypeVar with bound type IntOrStrSequence T int str Sequence T TypeVar with constraints The value of type aliases and the bound and constraints of type variables created through this syntax are evaluated only on demand see lazy evaluation This means type aliases are able to refer to other types defined later in the file Type parameters declared through a type parameter list are visible within the scope of the declaration and any nested scopes but not in the outer scope For example they can be used in the type annotations for the methods of a generic class or in the class body However they cannot be used in the module scope after the class is defined See Type parameter lists for a detailed description of the runtime semantics of type parameters In order to support these scoping semantics a new kind of scope is introduced the annotation scope Annotation scopes behave for the most part like function scopes but interact differently with enclosing class scopes In Python 3 13 annotations will also be evaluated in annotation scopes See PEP 695 for more details PEP written by Eric Traut Implementation by Jelle Zijlstra Eric Traut and others in gh 103764 PEP 701 Syntactic formalization of f strings PEP 701 lifts some restrictions on the usage of f strings Expression components inside f strings can now be any valid Python expression including strings reusing the same quote as the containing f string multi line expressions comments backslashes and unicode escape sequences Let s cover these in detail Quote reuse in Python 3 11 reusing the same quotes as the enclosing f string raises a SyntaxError forcing the user to either use other available quotes like using double quotes or triple quotes if the f string uses single quotes In Python 3 12 you can now do things like this songs Take me back to Eden Alkaline Ascensionism f This is the playlist join songs This is the playlist Take me back to Eden Alkaline Ascensionism Note that before this change there was no explicit limit in how f strings can be nested but the fact that string quotes cannot be reused inside the expression component of f strings made it impossible to nest f strings arbitrarily In fact this is the most nested f string that could be written f f f f 1 1 2 As now f strings can contain any valid Python expression inside expression components it is now possible to nest f strings arbitrarily f f f f f f 1 1 2 Multi line expressions and comments In Python 3 11 f string expressions must be defined in a single line even if the expression within the f string could normally span multiple lines like literal lists being defined over multiple lines making them harder to read In Python 3 12 you can now define f strings spanning multiple lines and add inline comments f This is the playlist join Take me back to Eden My my those eyes like fire Alkaline Not acid nor alkaline Ascensionism Take to the broken skies at last This is the playlist Take me back to Eden Alkaline Ascensionism Backslashes and unicode characters before Python 3 12 f string expressions couldn t contain any character This also affected unicode escape sequences such as N snowman as these contain the N part that previously could not be part of expression components of f strings Now you can define expressions like this print f This is the playlist n join songs This is the playlist Take me back to Eden Alkaline Ascensionism print f This is the playlist N BLACK HEART SUIT join songs This is the playlist Take me back to Eden Alkaline Ascensionism See PEP 701 for more details As a positive side effect of how this,en
977, feature has been implemented by parsing f strings with the PEG parser now error messages for f strings are more precise and include the exact location of the error For example in Python 3 11 the following f string raises a SyntaxError my_string f x z y f 1 1 File stdin line 1 x z y SyntaxError f string invalid syntax Perhaps you forgot a comma but the error message doesn t include the exact location of the error within the line and also has the expression artificially surrounded by parentheses In Python 3 12 as f strings are parsed with the PEG parser error messages can be more precise and show the entire line my_string f x z y f 1 1 File stdin line 1 my_string f x z y f 1 1 SyntaxError invalid syntax Perhaps you forgot a comma Contributed by Pablo Galindo Batuhan Taskaya Lysandros Nikolaou Cristián Maureira Fredes and Marta Gómez in gh 102856 PEP written by Pablo Galindo Batuhan Taskaya Lysandros Nikolaou and Marta Gómez PEP 684 A Per Interpreter GIL PEP 684 introduces a per interpreter GIL so that sub interpreters may now be created with a unique GIL per interpreter This allows Python programs to take full advantage of multiple CPU cores This is currently only available through the C API though a Python API is anticipated for 3 13 Use the new Py_NewInterpreterFromConfig function to create an interpreter with its own GIL PyInterpreterConfig config check_multi_interp_extensions 1 gil PyInterpreterConfig_OWN_GIL PyThreadState tstate NULL PyStatus status Py_NewInterpreterFromConfig tstate config if PyStatus_Exception status return 1 The new interpreter is now active in the current thread For further examples how to use the C API for sub interpreters with a per interpreter GIL see Modules _xxsubinterpretersmodule c Contributed by Eric Snow in gh 104210 etc PEP 669 Low impact monitoring for CPython PEP 669 defines a new API for profilers debuggers and other tools to monitor events in CPython It covers a wide range of events including calls returns lines exceptions jumps and more This means that you only pay for what you use providing support for near zero overhead debuggers and coverage tools See sys monitoring for details Contributed by Mark Shannon in gh 103082 PEP 688 Making the buffer protocol accessible in Python PEP 688 introduces a way to use the buffer protocol from Python code Classes that implement the __buffer__ method are now usable as buffer types The new collections abc Buffer ABC provides a standard way to represent buffer objects for example in type annotations The new inspect BufferFlags enum represents the flags that can be used to customize buffer creation Contributed by Jelle Zijlstra in gh 102500 PEP 709 Comprehension inlining Dictionary list and set comprehensions are now inlined rather than creating a new single use function object for each execution of the comprehension This speeds up execution of a comprehension by up to two times See PEP 709 for further details Comprehension iteration variables remain isolated and don t overwrite a variable of the same name in the outer scope nor are they visible after the comprehension Inlining does result in a few visible behavior changes There is no longer a separate frame for the comprehension in tracebacks and tracing profiling no longer shows the comprehension as a function call The symtable module will no longer produce child symbol tables for each comprehension instead the comprehension s locals will be included in the parent function s symbol table Calling locals inside a comprehension now includes variables from outside the comprehension and no longer includes the synthetic 0 variable for the comprehension argument A comprehension iterating directly over locals e g k for k in locals may see RuntimeError dictionary changed size during iteration when run under tracing e g code coverage measurement This is the same behavior already seen in e g for k in locals To avoid the error first create a list of keys to iterate over keys list locals k for k in keys Contributed by Carl Meyer and Vladimir Matveev in PEP 709 Improved Error Messages Modules from the standar,en
978,d library are now potentially suggested as part of the error messages displayed by the interpreter when a NameError is raised to the top level Contributed by Pablo Galindo in gh 98254 sys version_info Traceback most recent call last File stdin line 1 in module NameError name sys is not defined Did you forget to import sys Improve the error suggestion for NameError exceptions for instances Now if a NameError is raised in a method and the instance has an attribute that s exactly equal to the name in the exception the suggestion will include self NAME instead of the closest match in the method scope Contributed by Pablo Galindo in gh 99139 class A def __init__ self self blech 1 def foo self somethin blech A foo Traceback most recent call last File stdin line 1 somethin blech NameError name blech is not defined Did you mean self blech Improve the SyntaxError error message when the user types import x from y instead of from y import x Contributed by Pablo Galindo in gh 98931 import a y z from b y z Traceback most recent call last File stdin line 1 import a y z from b y z SyntaxError Did you mean to use from import instead ImportError exceptions raised from failed from module import name statements now include suggestions for the value of name based on the available names in module Contributed by Pablo Galindo in gh 91058 from collections import chainmap Traceback most recent call last File stdin line 1 in module ImportError cannot import name chainmap from collections Did you mean ChainMap New Features Related to Type Hints This section covers major changes affecting type hints and the typing module PEP 692 Using TypedDict for more precise kwargs typing Typing kwargs in a function signature as introduced by PEP 484 allowed for valid annotations only in cases where all of the kwargs were of the same type PEP 692 specifies a more precise way of typing kwargs by relying on typed dictionaries from typing import TypedDict Unpack class Movie TypedDict name str year int def foo kwargs Unpack Movie See PEP 692 for more details Contributed by Franek Magiera in gh 103629 PEP 698 Override Decorator for Static Typing A new decorator typing override has been added to the typing module It indicates to type checkers that the method is intended to override a method in a superclass This allows type checkers to catch mistakes where a method that is intended to override something in a base class does not in fact do so Example from typing import override class Base def get_color self str return blue class GoodChild Base override ok overrides Base get_color def get_color self str return yellow class BadChild Base override type checker error does not override Base get_color def get_colour self str return red See PEP 698 for more details Contributed by Steven Troxler in gh 101561 Other Language Changes The parser now raises SyntaxError when parsing source code containing null bytes Contributed by Pablo Galindo in gh 96670 A backslash character pair that is not a valid escape sequence now generates a SyntaxWarning instead of DeprecationWarning For example re compile d d now emits a SyntaxWarning d is an invalid escape sequence use raw strings for regular expression re compile r d d In a future Python version SyntaxError will eventually be raised instead of SyntaxWarning Contributed by Victor Stinner in gh 98401 Octal escapes with value larger than 0o377 ex 477 deprecated in Python 3 11 now produce a SyntaxWarning instead of DeprecationWarning In a future Python version they will be eventually a SyntaxError Contributed by Victor Stinner in gh 98401 Variables used in the target part of comprehensions that are not stored to can now be used in assignment expressions For example in b 1 for a b prop in some_iter the assignment to b is now allowed Note that assigning to variables stored to in the target part of comprehensions like a is still disallowed as per PEP 572 Contributed by Nikita Sobolev in gh 100581 Exceptions raised in a class or type s __set_name__ method are no longer wrapped by a RuntimeError Context information is added to the exception as a,en
979, PEP 678 note Contributed by Irit Katriel in gh 77757 When a try except construct handles the entire ExceptionGroup and raises one other exception that exception is no longer wrapped in an ExceptionGroup Also changed in version 3 11 4 Contributed by Irit Katriel in gh 103590 The Garbage Collector now runs only on the eval breaker mechanism of the Python bytecode evaluation loop instead of object allocations The GC can also run when PyErr_CheckSignals is called so C extensions that need to run for a long time without executing any Python code also have a chance to execute the GC periodically Contributed by Pablo Galindo in gh 97922 All builtin and extension callables expecting boolean parameters now accept arguments of any type instead of just bool and int Contributed by Serhiy Storchaka in gh 60203 memoryview now supports the half float type the e format code Contributed by Donghee Na and Antoine Pitrou in gh 90751 slice objects are now hashable allowing them to be used as dict keys and set items Contributed by Will Bradshaw Furkan Onder and Raymond Hettinger in gh 101264 sum now uses Neumaier summation to improve accuracy and commutativity when summing floats or mixed ints and floats Contributed by Raymond Hettinger in gh 100425 ast parse now raises SyntaxError instead of ValueError when parsing source code containing null bytes Contributed by Pablo Galindo in gh 96670 The extraction methods in tarfile and shutil unpack_archive have a new a filter argument that allows limiting tar features than may be surprising or dangerous such as creating files outside the destination directory See tarfile extraction filters for details In Python 3 14 the default will switch to data Contributed by Petr Viktorin in PEP 706 types MappingProxyType instances are now hashable if the underlying mapping is hashable Contributed by Serhiy Storchaka in gh 87995 Add support for the perf profiler through the new environment variable PYTHONPERFSUPPORT and command line option X perf as well as the new sys activate_stack_trampoline sys deactivate_stack_trampoline and sys is_stack_trampoline_active functions Design by Pablo Galindo Contributed by Pablo Galindo and Christian Heimes with contributions from Gregory P Smith Google and Mark Shannon in gh 96123 New Modules None Improved Modules array The array array class now supports subscripting making it a generic type Contributed by Jelle Zijlstra in gh 98658 asyncio The performance of writing to sockets in asyncio has been significantly improved asyncio now avoids unnecessary copying when writing to sockets and uses sendmsg if the platform supports it Contributed by Kumar Aditya in gh 91166 Add asyncio eager_task_factory and asyncio create_eager_task_factory functions to allow opting an event loop in to eager task execution making some use cases 2x to 5x faster Contributed by Jacob Bower Itamar Oren in gh 102853 gh 104140 and gh 104138 On Linux asyncio uses asyncio PidfdChildWatcher by default if os pidfd_open is available and functional instead of asyncio ThreadedChildWatcher Contributed by Kumar Aditya in gh 98024 The event loop now uses the best available child watcher for each platform asyncio PidfdChildWatcher if supported and asyncio ThreadedChildWatcher otherwise so manually configuring a child watcher is not recommended Contributed by Kumar Aditya in gh 94597 Add loop_factory parameter to asyncio run to allow specifying a custom event loop factory Contributed by Kumar Aditya in gh 99388 Add C implementation of asyncio current_task for 4x 6x speedup Contributed by Itamar Oren and Pranav Thulasiram Bhat in gh 100344 asyncio iscoroutine now returns False for generators as asyncio does not support legacy generator based coroutines Contributed by Kumar Aditya in gh 102748 asyncio wait and asyncio as_completed now accepts generators yielding tasks Contributed by Kumar Aditya in gh 78530 calendar Add enums calendar Month and calendar Day defining months of the year and days of the week Contributed by Prince Roshan in gh 103636 csv Add csv QUOTE_NOTNULL and csv QUOTE_STRINGS flags to provide finer gr,en
980,ained control of None and empty strings by csv writer objects dis Pseudo instruction opcodes which are used by the compiler but do not appear in executable bytecode are now exposed in the dis module HAVE_ARGUMENT is still relevant to real opcodes but it is not useful for pseudo instructions Use the new dis hasarg collection instead Contributed by Irit Katriel in gh 94216 Add the dis hasexc collection to signify instructions that set an exception handler Contributed by Irit Katriel in gh 94216 fractions Objects of type fractions Fraction now support float style formatting Contributed by Mark Dickinson in gh 100161 importlib resources importlib resources as_file now supports resource directories Contributed by Jason R Coombs in gh 97930 Rename first parameter of importlib resources files to anchor Contributed by Jason R Coombs in gh 100598 inspect Add inspect markcoroutinefunction to mark sync functions that return a coroutine for use with inspect iscoroutinefunction Contributed Carlton Gibson in gh 99247 Add inspect getasyncgenstate and inspect getasyncgenlocals for determining the current state of asynchronous generators Contributed by Thomas Krennwallner in gh 79940 The performance of inspect getattr_static has been considerably improved Most calls to the function should be at least 2x faster than they were in Python 3 11 and some may be 6x faster or more Contributed by Alex Waygood in gh 103193 itertools Add itertools batched for collecting into even sized tuples where the last batch may be shorter than the rest Contributed by Raymond Hettinger in gh 98363 math Add math sumprod for computing a sum of products Contributed by Raymond Hettinger in gh 100485 Extend math nextafter to include a steps argument for moving up or down multiple steps at a time By Matthias Goergens Mark Dickinson and Raymond Hettinger in gh 94906 os Add os PIDFD_NONBLOCK to open a file descriptor for a process with os pidfd_open in non blocking mode Contributed by Kumar Aditya in gh 93312 os DirEntry now includes an os DirEntry is_junction method to check if the entry is a junction Contributed by Charles Machalow in gh 99547 Add os listdrives os listvolumes and os listmounts functions on Windows for enumerating drives volumes and mount points Contributed by Steve Dower in gh 102519 os stat and os lstat are now more accurate on Windows The st_birthtime field will now be filled with the creation time of the file and st_ctime is deprecated but still contains the creation time but in the future will return the last metadata change for consistency with other platforms st_dev may be up to 64 bits and st_ino up to 128 bits depending on your file system and st_rdev is always set to zero rather than incorrect values Both functions may be significantly faster on newer releases of Windows Contributed by Steve Dower in gh 99726 os path Add os path isjunction to check if a given path is a junction Contributed by Charles Machalow in gh 99547 Add os path splitroot to split a path into a triad drive root tail Contributed by Barney Gale in gh 101000 pathlib Add support for subclassing pathlib PurePath and pathlib Path plus their Posix and Windows specific variants Subclasses may override the pathlib PurePath with_segments method to pass information between path instances Add pathlib Path walk for walking the directory trees and generating all file or directory names within them similar to os walk Contributed by Stanislav Zmiev in gh 90385 Add walk_up optional parameter to pathlib PurePath relative_to to allow the insertion of entries in the result this behavior is more consistent with os path relpath Contributed by Domenico Ragusa in gh 84538 Add pathlib Path is_junction as a proxy to os path isjunction Contributed by Charles Machalow in gh 99547 Add case_sensitive optional parameter to pathlib Path glob pathlib Path rglob and pathlib PurePath match for matching the path s case sensitivity allowing for more precise control over the matching process pdb Add convenience variables to hold values temporarily for debug session and provide quick access to values like th,en
981,e current frame or the return value Contributed by Tian Gao in gh 103693 random Add random binomialvariate Contributed by Raymond Hettinger in gh 81620 Add a default of lambd 1 0 to random expovariate Contributed by Raymond Hettinger in gh 100234 shutil shutil make_archive now passes the root_dir argument to custom archivers which support it In this case it no longer temporarily changes the current working directory of the process to root_dir to perform archiving Contributed by Serhiy Storchaka in gh 74696 shutil rmtree now accepts a new argument onexc which is an error handler like onerror but which expects an exception instance rather than a typ val tb triplet onerror is deprecated Contributed by Irit Katriel in gh 102828 shutil which now consults the PATHEXT environment variable to find matches within PATH on Windows even when the given cmd includes a directory component Contributed by Charles Machalow in gh 103179 shutil which will call NeedCurrentDirectoryForExePathW when querying for executables on Windows to determine if the current working directory should be prepended to the search path Contributed by Charles Machalow in gh 103179 shutil which will return a path matching the cmd with a component from PATHEXT prior to a direct match elsewhere in the search path on Windows Contributed by Charles Machalow in gh 103179 sqlite3 Add a command line interface Contributed by Erlend E Aasland in gh 77617 Add the sqlite3 Connection autocommit attribute to sqlite3 Connection and the autocommit parameter to sqlite3 connect to control PEP 249 compliant transaction handling Contributed by Erlend E Aasland in gh 83638 Add entrypoint keyword only parameter to sqlite3 Connection load_extension for overriding the SQLite extension entry point Contributed by Erlend E Aasland in gh 103015 Add sqlite3 Connection getconfig and sqlite3 Connection setconfig to sqlite3 Connection to make configuration changes to a database connection Contributed by Erlend E Aasland in gh 103489 statistics Extend statistics correlation to include as a ranked method for computing the Spearman correlation of ranked data Contributed by Raymond Hettinger in gh 95861 sys Add the sys monitoring namespace to expose the new PEP 669 monitoring API Contributed by Mark Shannon in gh 103082 Add sys activate_stack_trampoline and sys deactivate_stack_trampoline for activating and deactivating stack profiler trampolines and sys is_stack_trampoline_active for querying if stack profiler trampolines are active Contributed by Pablo Galindo and Christian Heimes with contributions from Gregory P Smith Google and Mark Shannon in gh 96123 Add sys last_exc which holds the last unhandled exception that was raised for post mortem debugging use cases Deprecate the three fields that have the same information in its legacy form sys last_type sys last_value and sys last_traceback Contributed by Irit Katriel in gh 102778 sys _current_exceptions now returns a mapping from thread id to an exception instance rather than to a typ exc tb tuple Contributed by Irit Katriel in gh 103176 sys setrecursionlimit and sys getrecursionlimit The recursion limit now applies only to Python code Builtin functions do not use the recursion limit but are protected by a different mechanism that prevents recursion from causing a virtual machine crash tempfile The tempfile NamedTemporaryFile function has a new optional parameter delete_on_close Contributed by Evgeny Zorin in gh 58451 tempfile mkdtemp now always returns an absolute path even if the argument provided to the dir parameter is a relative path threading Add threading settrace_all_threads and threading setprofile_all_threads that allow to set tracing and profiling functions in all running threads in addition to the calling one Contributed by Pablo Galindo in gh 93503 tkinter tkinter Canvas coords now flattens its arguments It now accepts not only coordinates as separate arguments x1 y1 x2 y2 and a sequence of coordinates x1 y1 x2 y2 but also coordinates grouped in pairs x1 y1 x2 y2 and x1 y1 x2 y2 like create_ methods Contributed by Serhiy Storchaka i,en
982,n gh 94473 tokenize The tokenize module includes the changes introduced in PEP 701 Contributed by Marta Gómez Macías and Pablo Galindo in gh 102856 See Porting to Python 3 12 for more information on the changes to the tokenize module types Add types get_original_bases to allow for further introspection of User defined generic types when subclassed Contributed by James Hilton Balfe and Alex Waygood in gh 101827 typing isinstance checks against runtime checkable protocols now use inspect getattr_static rather than hasattr to lookup whether attributes exist This means that descriptors and __getattr__ methods are no longer unexpectedly evaluated during isinstance checks against runtime checkable protocols However it may also mean that some objects which used to be considered instances of a runtime checkable protocol may no longer be considered instances of that protocol on Python 3 12 and vice versa Most users are unlikely to be affected by this change Contributed by Alex Waygood in gh 102433 The members of a runtime checkable protocol are now considered frozen at runtime as soon as the class has been created Monkey patching attributes onto a runtime checkable protocol will still work but will have no impact on isinstance checks comparing objects to the protocol For example from typing import Protocol runtime_checkable runtime_checkable class HasX Protocol x 1 class Foo f Foo isinstance f HasX False f x 1 isinstance f HasX True HasX y 2 isinstance f HasX unchanged even though HasX now also has a y attribute True This change was made in order to speed up isinstance checks against runtime checkable protocols The performance profile of isinstance checks against runtime checkable protocols has changed significantly Most isinstance checks against protocols with only a few members should be at least 2x faster than in 3 11 and some may be 20x faster or more However isinstance checks against protocols with fourteen or more members may be slower than in Python 3 11 Contributed by Alex Waygood in gh 74690 and gh 103193 All typing TypedDict and typing NamedTuple classes now have the __orig_bases__ attribute Contributed by Adrian Garcia Badaracco in gh 103699 Add frozen_default parameter to typing dataclass_transform Contributed by Erik De Bonte in gh 99957 unicodedata The Unicode database has been updated to version 15 0 0 Contributed by Benjamin Peterson in gh 96734 unittest Add a durations command line option showing the N slowest test cases python3 m unittest durations 3 lib tests test_threading Slowest test durations 1 210s test_timeout Lib test test_threading BarrierTests 1 003s test_default_timeout Lib test test_threading BarrierTests 0 518s test_timeout Lib test test_threading EventTests 0 000 durations hidden Use v to show these durations Ran 158 tests in 9 869s OK skipped 3 Contributed by Giampaolo Rodola in gh 48330 uuid Add a command line interface Contributed by Adam Chhina in gh 88597 Optimizations Remove wstr and wstr_length members from Unicode objects It reduces object size by 8 or 16 bytes on 64bit platform PEP 623 Contributed by Inada Naoki in gh 92536 Add experimental support for using the BOLT binary optimizer in the build process which improves performance by 1 5 Contributed by Kevin Modzelewski in gh 90536 and tuned by Donghee Na in gh 101525 Speed up the regular expression substitution functions re sub and re subn and corresponding re Pattern methods for replacement strings containing group references by 2 3 times Contributed by Serhiy Storchaka in gh 91524 Speed up asyncio Task creation by deferring expensive string formatting Contributed by Itamar Oren in gh 103793 The tokenize tokenize and tokenize generate_tokens functions are up to 64 faster as a side effect of the changes required to cover PEP 701 in the tokenize module Contributed by Marta Gómez Macías and Pablo Galindo in gh 102856 Speed up super method calls and attribute loads via the new LOAD_SUPER_ATTR instruction Contributed by Carl Meyer and Vladimir Matveev in gh 103497 CPython bytecode changes Remove the LOAD_METHOD instruction It has been merged ,en
983,into LOAD_ATTR LOAD_ATTR will now behave like the old LOAD_METHOD instruction if the low bit of its oparg is set Contributed by Ken Jin in gh 93429 Remove the JUMP_IF_FALSE_OR_POP and JUMP_IF_TRUE_OR_POP instructions Contributed by Irit Katriel in gh 102859 Remove the PRECALL instruction Contributed by Mark Shannon in gh 92925 Add the BINARY_SLICE and STORE_SLICE instructions Contributed by Mark Shannon in gh 94163 Add the CALL_INTRINSIC_1 instructions Contributed by Mark Shannon in gh 99005 Add the CALL_INTRINSIC_2 instruction Contributed by Irit Katriel in gh 101799 Add the CLEANUP_THROW instruction Contributed by Brandt Bucher in gh 90997 Add the END_SEND instruction Contributed by Mark Shannon in gh 103082 Add the LOAD_FAST_AND_CLEAR instruction as part of the implementation of PEP 709 Contributed by Carl Meyer in gh 101441 Add the LOAD_FAST_CHECK instruction Contributed by Dennis Sweeney in gh 93143 Add the LOAD_FROM_DICT_OR_DEREF LOAD_FROM_DICT_OR_GLOBALS and LOAD_LOCALS opcodes as part of the implementation of PEP 695 Remove the LOAD_CLASSDEREF opcode which can be replaced with LOAD_LOCALS plus LOAD_FROM_DICT_OR_DEREF Contributed by Jelle Zijlstra in gh 103764 Add the LOAD_SUPER_ATTR instruction Contributed by Carl Meyer and Vladimir Matveev in gh 103497 Add the RETURN_CONST instruction Contributed by Wenyang Wang in gh 101632 Demos and Tools Remove the Tools demo directory which contained old demo scripts A copy can be found in the old demos project Contributed by Victor Stinner in gh 97681 Remove outdated example scripts of the Tools scripts directory A copy can be found in the old demos project Contributed by Victor Stinner in gh 97669 Deprecated argparse The type choices and metavar parameters of argparse BooleanOptionalAction are deprecated and will be removed in 3 14 Contributed by Nikita Sobolev in gh 92248 ast The following ast features have been deprecated in documentation since Python 3 8 now cause a DeprecationWarning to be emitted at runtime when they are accessed or used and will be removed in Python 3 14 ast Num ast Str ast Bytes ast NameConstant ast Ellipsis Use ast Constant instead Contributed by Serhiy Storchaka in gh 90953 asyncio The child watcher classes asyncio MultiLoopChildWatcher asyncio FastChildWatcher asyncio AbstractChildWatcher and asyncio SafeChildWatcher are deprecated and will be removed in Python 3 14 Contributed by Kumar Aditya in gh 94597 asyncio set_child_watcher asyncio get_child_watcher asyncio AbstractEventLoopPolicy set_child_watcher and asyncio AbstractEventLoopPolicy get_child_watcher are deprecated and will be removed in Python 3 14 Contributed by Kumar Aditya in gh 94597 The get_event_loop method of the default event loop policy now emits a DeprecationWarning if there is no current event loop set and it decides to create one Contributed by Serhiy Storchaka and Guido van Rossum in gh 100160 calendar calendar January and calendar February constants are deprecated and replaced by calendar JANUARY and calendar FEBRUARY Contributed by Prince Roshan in gh 103636 collections abc Deprecated collections abc ByteString Prefer Sequence or collections abc Buffer For use in typing prefer a union like bytes bytearray or collections abc Buffer Contributed by Shantanu Jain in gh 91896 datetime datetime datetime s utcnow and utcfromtimestamp are deprecated and will be removed in a future version Instead use timezone aware objects to represent datetimes in UTC respectively call now and fromtimestamp with the tz parameter set to datetime UTC Contributed by Paul Ganssle in gh 103857 email Deprecate the isdst parameter in email utils localtime Contributed by Alan Williams in gh 72346 importlib abc Deprecated the following classes scheduled for removal in Python 3 14 importlib abc ResourceReader importlib abc Traversable importlib abc TraversableResources Use importlib resources abc classes instead importlib resources abc Traversable importlib resources abc TraversableResources Contributed by Jason R Coombs and Hugo van Kemenade in gh 93963 itertools Deprecate the support for copy deepcopy an,en
984,d pickle operations which is undocumented inefficient historically buggy and inconsistent This will be removed in 3 14 for a significant reduction in code volume and maintenance burden Contributed by Raymond Hettinger in gh 101588 multiprocessing In Python 3 14 the default multiprocessing start method will change to a safer one on Linux BSDs and other non macOS POSIX platforms where fork is currently the default gh 84559 Adding a runtime warning about this was deemed too disruptive as the majority of code is not expected to care Use the get_context or set_start_method APIs to explicitly specify when your code requires fork See contexts and start methods pkgutil pkgutil find_loader and pkgutil get_loader are deprecated and will be removed in Python 3 14 use importlib util find_spec instead Contributed by Nikita Sobolev in gh 97850 pty The module has two undocumented master_open and slave_open functions that have been deprecated since Python 2 but only gained a proper DeprecationWarning in 3 12 Remove them in 3 14 Contributed by Soumendra Ganguly and Gregory P Smith in gh 85984 os The st_ctime fields return by os stat and os lstat on Windows are deprecated In a future release they will contain the last metadata change time consistent with other platforms For now they still contain the creation time which is also available in the new st_birthtime field Contributed by Steve Dower in gh 99726 On POSIX platforms os fork can now raise a DeprecationWarning when it can detect being called from a multithreaded process There has always been a fundamental incompatibility with the POSIX platform when doing so Even if such code appeared to work We added the warning to to raise awareness as issues encounted by code doing this are becoming more frequent See the os fork documentation for more details along with this discussion on fork being incompatible with threads for why we re now surfacing this longstanding platform compatibility problem to developers When this warning appears due to usage of multiprocessing or concurrent futures the fix is to use a different multiprocessing start method such as spawn or forkserver shutil The onerror argument of shutil rmtree is deprecated use onexc instead Contributed by Irit Katriel in gh 102828 sqlite3 default adapters and converters are now deprecated Instead use the Adapter and converter recipes and tailor them to your needs Contributed by Erlend E Aasland in gh 90016 In execute DeprecationWarning is now emitted when named placeholders are used together with parameters supplied as a sequence instead of as a dict Starting from Python 3 14 using named placeholders with parameters supplied as a sequence will raise a ProgrammingError Contributed by Erlend E Aasland in gh 101698 sys The sys last_type sys last_value and sys last_traceback fields are deprecated Use sys last_exc instead Contributed by Irit Katriel in gh 102778 tarfile Extracting tar archives without specifying filter is deprecated until Python 3 14 when data filter will become the default See Extraction filters for details typing typing Hashable and typing Sized aliases for collections abc Hashable and collections abc Sized respectively are deprecated gh 94309 typing ByteString deprecated since Python 3 9 now causes a DeprecationWarning to be emitted when it is used Contributed by Alex Waygood in gh 91896 xml etree ElementTree The module now emits DeprecationWarning when testing the truth value of an xml etree ElementTree Element Before the Python implementation emitted FutureWarning and the C implementation emitted nothing Contributed by Jacob Walls in gh 83122 The 3 arg signatures type value traceback of coroutine throw generator throw and async generator throw are deprecated and may be removed in a future version of Python Use the single arg versions of these functions instead Contributed by Ofey Chan in gh 89874 DeprecationWarning is now raised when __package__ on a module differs from __spec__ parent previously it was ImportWarning Contributed by Brett Cannon in gh 65961 Setting __package__ or __cached__ on a module is deprecated a,en
985,nd will cease to be set or taken into consideration by the import system in Python 3 14 Contributed by Brett Cannon in gh 65961 The bitwise inversion operator on bool is deprecated It will throw an error in Python 3 14 Use not for logical negation of bools instead In the rare case that you really need the bitwise inversion of the underlying int convert to int explicitly int x Contributed by Tim Hoffmann in gh 103487 Accessing co_lnotab on code objects was deprecated in Python 3 10 via PEP 626 but it only got a proper DeprecationWarning in 3 12 therefore it will be removed in 3 14 Contributed by Nikita Sobolev in gh 101866 Pending Removal in Python 3 13 The following modules and APIs have been deprecated in earlier Python releases and will be removed in Python 3 13 Modules see PEP 594 aifc audioop cgi cgitb chunk crypt imghdr mailcap msilib nis nntplib ossaudiodev pipes sndhdr spwd sunau telnetlib uu xdrlib Other modules lib2to3 and the 2to3 program gh 84540 APIs configparser LegacyInterpolation gh 90765 locale resetlocale gh 90817 turtle RawTurtle settiltangle gh 50096 unittest findTestCases gh 50096 unittest getTestCaseNames gh 50096 unittest makeSuite gh 50096 unittest TestProgram usageExit gh 67048 webbrowser MacOSX gh 86421 classmethod descriptor chaining gh 89519 importlib resources deprecated methods contents is_resource open_binary open_text path read_binary read_text Use importlib resources files instead Refer to importlib resources Migrating from Legacy gh 106531 Pending Removal in Python 3 14 The following APIs have been deprecated and will be removed in Python 3 14 argparse The type choices and metavar parameters of argparse BooleanOptionalAction ast ast Num ast Str ast Bytes ast NameConstant ast Ellipsis asyncio asyncio MultiLoopChildWatcher asyncio FastChildWatcher asyncio AbstractChildWatcher asyncio SafeChildWatcher asyncio set_child_watcher asyncio get_child_watcher asyncio AbstractEventLoopPolicy set_child_watcher asyncio AbstractEventLoopPolicy get_child_watcher collections abc collections abc ByteString email the isdst parameter in email utils localtime importlib abc importlib abc ResourceReader importlib abc Traversable importlib abc TraversableResources itertools Support for copy deepcopy and pickle operations pkgutil pkgutil find_loader pkgutil get_loader pty pty master_open pty slave_open shutil The onerror argument of shutil rmtree typing typing ByteString xml etree ElementTree Testing the truth value of an xml etree ElementTree Element The __package__ and __cached__ attributes on module objects The co_lnotab attribute of code objects Pending Removal in Python 3 15 The following APIs have been deprecated and will be removed in Python 3 15 APIs locale getdefaultlocale gh 90817 Pending Removal in Future Versions The following APIs were deprecated in earlier Python versions and will be removed although there is currently no date scheduled for their removal array s u format code gh 57281 typing Text gh 92332 Currently Python accepts numeric literals immediately followed by keywords for example 0in x 1or x 0if 1else 2 It allows confusing and ambiguous expressions like 0x1for x in y which can be interpreted as 0x1 for x in y or 0x1f or x in y A syntax warning is raised if the numeric literal is immediately followed by one of keywords and else for if in is and or In a future release it will be changed to a syntax error gh 87999 Removed asynchat and asyncore These two modules have been removed according to the schedule in PEP 594 having been deprecated in Python 3 6 Use asyncio instead Contributed by Nikita Sobolev in gh 96580 configparser Several names deprecated in the configparser way back in 3 2 have been removed per gh 89336 configparser ParsingError no longer has a filename attribute or argument Use the source attribute and argument instead configparser no longer has a SafeConfigParser class Use the shorter ConfigParser name instead configparser ConfigParser no longer has a readfp method Use read_file instead distutils Remove the distutils package It was deprecated in Python 3 10 by PEP 632 Deprecat,en
986,e distutils module For projects still using distutils and cannot be updated to something else the setuptools project can be installed it still provides distutils Contributed by Victor Stinner in gh 92584 ensurepip Remove the bundled setuptools wheel from ensurepip and stop installing setuptools in environments created by venv pip 22 1 does not require setuptools to be installed in the environment setuptools based and distutils based packages can still be used with pip install since pip will provide setuptools in the build environment it uses for building a package easy_install pkg_resources setuptools and distutils are no longer provided by default in environments created with venv or bootstrapped with ensurepip since they are part of the setuptools package For projects relying on these at runtime the setuptools project should be declared as a dependency and installed separately typically using pip Contributed by Pradyun Gedam in gh 95299 enum Remove enum s EnumMeta __getattr__ which is no longer needed for enum attribute access Contributed by Ethan Furman in gh 95083 ftplib Remove ftplib s FTP_TLS ssl_version class attribute use the context parameter instead Contributed by Victor Stinner in gh 94172 gzip Remove the filename attribute of gzip s gzip GzipFile deprecated since Python 2 6 use the name attribute instead In write mode the filename attribute added gz file extension if it was not present Contributed by Victor Stinner in gh 94196 hashlib Remove the pure Python implementation of hashlib s hashlib pbkdf2_hmac deprecated in Python 3 10 Python 3 10 and newer requires OpenSSL 1 1 1 PEP 644 this OpenSSL version provides a C implementation of pbkdf2_hmac which is faster Contributed by Victor Stinner in gh 94199 importlib Many previously deprecated cleanups in importlib have now been completed References to and support for module_repr has been removed Contributed by Barry Warsaw in gh 97850 importlib util set_package importlib util set_loader and importlib util module_for_loader have all been removed Contributed by Brett Cannon and Nikita Sobolev in gh 65961 and gh 97850 Support for find_loader and find_module APIs have been removed Contributed by Barry Warsaw in gh 98040 importlib abc Finder pkgutil ImpImporter and pkgutil ImpLoader have been removed Contributed by Barry Warsaw in gh 98040 imp The imp module has been removed Contributed by Barry Warsaw in gh 98040 To migrate consult the following correspondence table imp importlib imp NullImporter Insert None into sys path_importer_cache imp cache_from_source importlib util cache_from_source imp find_module importlib util find_spec imp get_magic importlib util MAGIC_NUMBER imp get_suffixes importlib machinery SOURCE_SUFFIXES importlib machinery EXTENSION_SUFFIXES and importlib machinery BYTECODE_SUFFIXES imp get_tag sys implementation cache_tag imp load_module importlib import_module imp new_module name types ModuleType name imp reload importlib reload imp source_from_cache importlib util source_from_cache imp load_source See below Replace imp load_source with import importlib util import importlib machinery def load_source modname filename loader importlib machinery SourceFileLoader modname filename spec importlib util spec_from_file_location modname filename loader loader module importlib util module_from_spec spec The module is always executed and not cached in sys modules Uncomment the following line to cache the module sys modules module __name__ module loader exec_module module return module Remove imp functions and attributes with no replacements Undocumented functions imp init_builtin imp load_compiled imp load_dynamic imp load_package imp lock_held imp acquire_lock imp release_lock the locking scheme has changed in Python 3 3 to per module locks imp find_module constants SEARCH_ERROR PY_SOURCE PY_COMPILED C_EXTENSION PY_RESOURCE PKG_DIRECTORY C_BUILTIN PY_FROZEN PY_CODERESOURCE IMP_HOOK io Remove io s io OpenWrapper and _pyio OpenWrapper deprecated in Python 3 10 just use open instead The open io open function is a built in function Since Python 3 10 _pyio ope,en
987,n is also a static method Contributed by Victor Stinner in gh 94169 locale Remove locale s locale format function deprecated in Python 3 7 use locale format_string instead Contributed by Victor Stinner in gh 94226 smtpd The smtpd module has been removed according to the schedule in PEP 594 having been deprecated in Python 3 4 7 and 3 5 4 Use aiosmtpd PyPI module or any other asyncio based server instead Contributed by Oleg Iarygin in gh 93243 sqlite3 The following undocumented sqlite3 features deprecated in Python 3 10 are now removed sqlite3 enable_shared_cache sqlite3 OptimizedUnicode If a shared cache must be used open the database in URI mode using the cache shared query parameter The sqlite3 OptimizedUnicode text factory has been an alias for str since Python 3 3 Code that previously set the text factory to OptimizedUnicode can either use str explicitly or rely on the default value which is also str Contributed by Erlend E Aasland in gh 92548 ssl Remove ssl s ssl RAND_pseudo_bytes function deprecated in Python 3 6 use os urandom or ssl RAND_bytes instead Contributed by Victor Stinner in gh 94199 Remove the ssl match_hostname function It was deprecated in Python 3 7 OpenSSL performs hostname matching since Python 3 7 Python no longer uses the ssl match_hostname function Contributed by Victor Stinner in gh 94199 Remove the ssl wrap_socket function deprecated in Python 3 7 instead create a ssl SSLContext object and call its ssl SSLContext wrap_socket method Any package that still uses ssl wrap_socket is broken and insecure The function neither sends a SNI TLS extension nor validates server hostname Code is subject to CWE 295 Improper Certificate Validation Contributed by Victor Stinner in gh 94199 unittest Remove many long deprecated unittest features A number of TestCase method aliases Deprecated alias Method Name Deprecated in failUnless assertTrue 3 1 failIf assertFalse 3 1 failUnlessEqual assertEqual 3 1 failIfEqual assertNotEqual 3 1 failUnlessAlmostEqual assertAlmostEqual 3 1 failIfAlmostEqual assertNotAlmostEqual 3 1 failUnlessRaises assertRaises 3 1 assert_ assertTrue 3 2 assertEquals assertEqual 3 2 assertNotEquals assertNotEqual 3 2 assertAlmostEquals assertAlmostEqual 3 2 assertNotAlmostEquals assertNotAlmostEqual 3 2 assertRegexpMatches assertRegex 3 2 assertRaisesRegexp assertRaisesRegex 3 2 assertNotRegexpMatches assertNotRegex 3 5 You can use https github com isidentical teyit to automatically modernise your unit tests Undocumented and broken TestCase method assertDictContainsSubset deprecated in Python 3 2 Undocumented TestLoader loadTestsFromModule parameter use_load_tests deprecated and ignored since Python 3 2 An alias of the TextTestResult class _TextTestResult deprecated in Python 3 2 Contributed by Serhiy Storchaka in gh 89325 webbrowser Remove support for obsolete browsers from webbrowser The removed browsers include Grail Mosaic Netscape Galeon Skipstone Iceape Firebird and Firefox versions 35 and below gh 102871 xml etree ElementTree Remove the ElementTree Element copy method of the pure Python implementation deprecated in Python 3 10 use the copy copy function instead The C implementation of xml etree ElementTree has no copy method only a __copy__ method Contributed by Victor Stinner in gh 94383 zipimport Remove zipimport s find_loader and find_module methods deprecated in Python 3 10 use the find_spec method instead See PEP 451 for the rationale Contributed by Victor Stinner in gh 94379 Others Remove the suspicious rule from the documentation Makefile and Doc tools rstlint py both in favor of sphinx lint Contributed by Julien Palard in gh 98179 Remove the keyfile and certfile parameters from the ftplib imaplib poplib and smtplib modules and the key_file cert_file and check_hostname parameters from the http client module all deprecated since Python 3 6 Use the context parameter ssl_context in imaplib instead Contributed by Victor Stinner in gh 94172 Remove Jython compatibility hacks from several stdlib modules and tests Contributed by Nikita Sobolev in gh 99482 Remove _use_broken_old_ctypes_st,en
988,ructure_semantics_ flag from ctypes module Contributed by Nikita Sobolev in gh 99285 Porting to Python 3 12 This section lists previously described changes and other bugfixes that may require changes to your code Changes in the Python API More strict rules are now applied for numerical group references and group names in regular expressions Only sequence of ASCII digits is now accepted as a numerical reference The group name in bytes patterns and replacement strings can now only contain ASCII letters and digits and underscore Contributed by Serhiy Storchaka in gh 91760 Remove randrange functionality deprecated since Python 3 10 Formerly randrange 10 0 losslessly converted to randrange 10 Now it raises a TypeError Also the exception raised for non integer values such as randrange 10 5 or randrange 10 has been changed from ValueError to TypeError This also prevents bugs where randrange 1e25 would silently select from a larger range than randrange 10 25 Originally suggested by Serhiy Storchaka gh 86388 argparse ArgumentParser changed encoding and error handler for reading arguments from file e g fromfile_prefix_chars option from default text encoding e g locale getpreferredencoding False to filesystem encoding and error handler Argument files should be encoded in UTF 8 instead of ANSI Codepage on Windows Remove the asyncore based smtpd module deprecated in Python 3 4 7 and 3 5 4 A recommended replacement is the asyncio based aiosmtpd PyPI module shlex split Passing None for s argument now raises an exception rather than reading sys stdin The feature was deprecated in Python 3 9 Contributed by Victor Stinner in gh 94352 The os module no longer accepts bytes like paths like bytearray and memoryview types only the exact bytes type is accepted for bytes strings Contributed by Victor Stinner in gh 98393 syslog openlog and syslog closelog now fail if used in subinterpreters syslog syslog may still be used in subinterpreters but now only if syslog openlog has already been called in the main interpreter These new restrictions do not apply to the main interpreter so only a very small set of users might be affected This change helps with interpreter isolation Furthermore syslog is a wrapper around process global resources which are best managed from the main interpreter Contributed by Donghee Na in gh 99127 The undocumented locking behavior of cached_property is removed because it locked across all instances of the class leading to high lock contention This means that a cached property getter function could now run more than once for a single instance if two threads race For most simple cached properties e g those that are idempotent and simply calculate a value based on other attributes of the instance this will be fine If synchronization is needed implement locking within the cached property getter function or around multi threaded access points sys _current_exceptions now returns a mapping from thread id to an exception instance rather than to a typ exc tb tuple Contributed by Irit Katriel in gh 103176 When extracting tar files using tarfile or shutil unpack_archive pass the filter argument to limit features that may be surprising or dangerous See Extraction filters for details The output of the tokenize tokenize and tokenize generate_tokens functions is now changed due to the changes introduced in PEP 701 This means that STRING tokens are not emitted any more for f strings and the tokens described in PEP 701 are now produced instead FSTRING_START FSTRING_MIDDLE and FSTRING_END are now emitted for f string string parts in addition to the appropriate tokens for the tokenization in the expression components For example for the f string f start 1 1 end the old version of the tokenizer emitted 1 0 1 18 STRING f start 1 1 end while the new version emits 1 0 1 2 FSTRING_START f 1 2 1 8 FSTRING_MIDDLE start 1 8 1 9 OP 1 9 1 10 NUMBER 1 1 10 1 11 OP 1 11 1 12 NUMBER 1 1 12 1 13 OP 1 13 1 17 FSTRING_MIDDLE end 1 17 1 18 FSTRING_END Additionally there may be some minor behavioral changes as a consequence of the changes required to support P,en
989,EP 701 Some of these changes include The type attribute of the tokens emitted when tokenizing some invalid Python characters such as has changed from ERRORTOKEN to OP Incomplete single line strings now also raise tokenize TokenError as incomplete multiline strings do Some incomplete or invalid Python code now raises tokenize TokenError instead of returning arbitrary ERRORTOKEN tokens when tokenizing it Mixing tabs and spaces as indentation in the same file is not supported anymore and will raise a TabError The threading module now expects the _thread module to have an _is_main_interpreter attribute It is a function with no arguments that returns True if the current interpreter is the main interpreter Any library or application that provides a custom _thread module should provide _is_main_interpreter See gh 112826 Build Changes Python no longer uses setup py to build shared C extension modules Build parameters like headers and libraries are detected in configure script Extensions are built by Makefile Most extensions use pkg config and fall back to manual detection Contributed by Christian Heimes in gh 93939 va_start with two parameters like va_start args format is now required to build Python va_start is no longer called with a single parameter Contributed by Kumar Aditya in gh 93207 CPython now uses the ThinLTO option as the default link time optimization policy if the Clang compiler accepts the flag Contributed by Donghee Na in gh 89536 Add COMPILEALL_OPTS variable in Makefile to override compileall options default j0 in make install Also merged the 3 compileall commands into a single command to build pyc files for all optimization levels 0 1 2 at once Contributed by Victor Stinner in gh 99289 Add platform triplets for 64 bit LoongArch loongarch64 linux gnusf loongarch64 linux gnuf32 loongarch64 linux gnu Contributed by Zhang Na in gh 90656 PYTHON_FOR_REGEN now require Python 3 10 or newer Autoconf 2 71 and aclocal 1 16 4 is now required to regenerate configure Contributed by Christian Heimes in gh 89886 Windows builds and macOS installers from python org now use OpenSSL 3 0 C API Changes New Features PEP 697 Introduce the Unstable C API tier intended for low level tools like debuggers and JIT compilers This API may change in each minor release of CPython without deprecation warnings Its contents are marked by the PyUnstable_ prefix in names Code object constructors PyUnstable_Code_New renamed from PyCode_New PyUnstable_Code_NewWithPosOnlyArgs renamed from PyCode_NewWithPosOnlyArgs Extra storage for code objects PEP 523 PyUnstable_Eval_RequestCodeExtraIndex renamed from _PyEval_RequestCodeExtraIndex PyUnstable_Code_GetExtra renamed from _PyCode_GetExtra PyUnstable_Code_SetExtra renamed from _PyCode_SetExtra The original names will continue to be available until the respective API changes Contributed by Petr Viktorin in gh 101101 PEP 697 Add an API for extending types whose instance memory layout is opaque PyType_Spec basicsize can be zero or negative to specify inheriting or extending the base class size PyObject_GetTypeData and PyType_GetTypeDataSize added to allow access to subclass specific instance data Py_TPFLAGS_ITEMS_AT_END and PyObject_GetItemData added to allow safely extending certain variable sized types including PyType_Type Py_RELATIVE_OFFSET added to allow defining members in terms of a subclass specific struct Contributed by Petr Viktorin in gh 103509 Add the new limited C API function PyType_FromMetaclass which generalizes the existing PyType_FromModuleAndSpec using an additional metaclass argument Contributed by Wenzel Jakob in gh 93012 API for creating objects that can be called using the vectorcall protocol was added to the Limited API Py_TPFLAGS_HAVE_VECTORCALL PyVectorcall_NARGS PyVectorcall_Call vectorcallfunc The Py_TPFLAGS_HAVE_VECTORCALL flag is now removed from a class when the class s __call__ method is reassigned This makes vectorcall safe to use with mutable types i e heap types without the immutable flag Py_TPFLAGS_IMMUTABLETYPE Mutable types that do not override tp_call now inherit the Py,en
990,_TPFLAGS_HAVE_VECTORCALL flag Contributed by Petr Viktorin in gh 93274 The Py_TPFLAGS_MANAGED_DICT and Py_TPFLAGS_MANAGED_WEAKREF flags have been added This allows extensions classes to support object __dict__ and weakrefs with less bookkeeping using less memory and with faster access API for performing calls using the vectorcall protocol was added to the Limited API PyObject_Vectorcall PyObject_VectorcallMethod PY_VECTORCALL_ARGUMENTS_OFFSET This means that both the incoming and outgoing ends of the vector call protocol are now available in the Limited API Contributed by Wenzel Jakob in gh 98586 Add two new public functions PyEval_SetProfileAllThreads and PyEval_SetTraceAllThreads that allow to set tracing and profiling functions in all running threads in addition to the calling one Contributed by Pablo Galindo in gh 93503 Add new function PyFunction_SetVectorcall to the C API which sets the vectorcall field of a given PyFunctionObject Contributed by Andrew Frost in gh 92257 The C API now permits registering callbacks via PyDict_AddWatcher PyDict_Watch and related APIs to be called whenever a dictionary is modified This is intended for use by optimizing interpreters JIT compilers or debuggers Contributed by Carl Meyer in gh 91052 Add PyType_AddWatcher and PyType_Watch API to register callbacks to receive notification on changes to a type Contributed by Carl Meyer in gh 91051 Add PyCode_AddWatcher and PyCode_ClearWatcher APIs to register callbacks to receive notification on creation and destruction of code objects Contributed by Itamar Oren in gh 91054 Add PyFrame_GetVar and PyFrame_GetVarString functions to get a frame variable by its name Contributed by Victor Stinner in gh 91248 Add PyErr_GetRaisedException and PyErr_SetRaisedException for saving and restoring the current exception These functions return and accept a single exception object rather than the triple arguments of the now deprecated PyErr_Fetch and PyErr_Restore This is less error prone and a bit more efficient Contributed by Mark Shannon in gh 101578 Add _PyErr_ChainExceptions1 which takes an exception instance to replace the legacy API _PyErr_ChainExceptions which is now deprecated Contributed by Mark Shannon in gh 101578 Add PyException_GetArgs and PyException_SetArgs as convenience functions for retrieving and modifying the args passed to the exception s constructor Contributed by Mark Shannon in gh 101578 Add PyErr_DisplayException which takes an exception instance to replace the legacy api PyErr_Display Contributed by Irit Katriel in gh 102755 PEP 683 Introduce Immortal Objects which allows objects to bypass reference counts and related changes to the C API _Py_IMMORTAL_REFCNT The reference count that defines an object as immortal _Py_IsImmortal Checks if an object has the immortal reference count PyObject_HEAD_INIT This will now initialize reference count to _Py_IMMORTAL_REFCNT when used with Py_BUILD_CORE SSTATE_INTERNED_IMMORTAL An identifier for interned unicode objects that are immortal SSTATE_INTERNED_IMMORTAL_STATIC An identifier for interned unicode objects that are immortal and static sys getunicodeinternedsize This returns the total number of unicode objects that have been interned This is now needed for refleak py to correctly track reference counts and allocated blocks Contributed by Eddie Elizondo in gh 84436 PEP 684 Add the new Py_NewInterpreterFromConfig function and PyInterpreterConfig which may be used to create sub interpreters with their own GILs See PEP 684 A Per Interpreter GIL for more info Contributed by Eric Snow in gh 104110 In the limited C API version 3 12 Py_INCREF and Py_DECREF functions are now implemented as opaque function calls to hide implementation details Contributed by Victor Stinner in gh 105387 Porting to Python 3 12 Legacy Unicode APIs based on Py_UNICODE representation has been removed Please migrate to APIs based on UTF 8 or wchar_t Argument parsing functions like PyArg_ParseTuple doesn t support Py_UNICODE based format e g u Z anymore Please migrate to other formats for Unicode like s z es and U tp_weaklist ,en
991,for all static builtin types is always NULL This is an internal only field on PyTypeObject but we re pointing out the change in case someone happens to be accessing the field directly anyway To avoid breakage consider using the existing public C API instead or if necessary the internal only _PyObject_GET_WEAKREFS_LISTPTR macro This internal only PyTypeObject tp_subclasses may now not be a valid object pointer Its type was changed to void to reflect this We mention this in case someone happens to be accessing the internal only field directly To get a list of subclasses call the Python method __subclasses__ using PyObject_CallMethod for example Add support of more formatting options left aligning octals uppercase hexadecimals intmax_t ptrdiff_t wchar_t C strings variable width and precision in PyUnicode_FromFormat and PyUnicode_FromFormatV Contributed by Serhiy Storchaka in gh 98836 An unrecognized format character in PyUnicode_FromFormat and PyUnicode_FromFormatV now sets a SystemError In previous versions it caused all the rest of the format string to be copied as is to the result string and any extra arguments discarded Contributed by Serhiy Storchaka in gh 95781 Fix wrong sign placement in PyUnicode_FromFormat and PyUnicode_FromFormatV Contributed by Philip Georgi in gh 95504 Extension classes wanting to add a __dict__ or weak reference slot should use Py_TPFLAGS_MANAGED_DICT and Py_TPFLAGS_MANAGED_WEAKREF instead of tp_dictoffset and tp_weaklistoffset respectively The use of tp_dictoffset and tp_weaklistoffset is still supported but does not fully support multiple inheritance gh 95589 and performance may be worse Classes declaring Py_TPFLAGS_MANAGED_DICT should call _PyObject_VisitManagedDict and _PyObject_ClearManagedDict to traverse and clear their instance s dictionaries To clear weakrefs call PyObject_ClearWeakRefs as before The PyUnicode_FSDecoder function no longer accepts bytes like paths like bytearray and memoryview types only the exact bytes type is accepted for bytes strings Contributed by Victor Stinner in gh 98393 The Py_CLEAR Py_SETREF and Py_XSETREF macros now only evaluate their arguments once If an argument has side effects these side effects are no longer duplicated Contributed by Victor Stinner in gh 98724 The interpreter s error indicator is now always normalized This means that PyErr_SetObject PyErr_SetString and the other functions that set the error indicator now normalize the exception before storing it Contributed by Mark Shannon in gh 101578 _Py_RefTotal is no longer authoritative and only kept around for ABI compatibility Note that it is an internal global and only available on debug builds If you happen to be using it then you ll need to start using _Py_GetGlobalRefTotal The following functions now select an appropriate metaclass for the newly created type PyType_FromSpec PyType_FromSpecWithBases PyType_FromModuleAndSpec Creating classes whose metaclass overrides tp_new is deprecated and in Python 3 14 it will be disallowed Note that these functions ignore tp_new of the metaclass possibly allowing incomplete initialization Note that PyType_FromMetaclass added in Python 3 12 already disallows creating classes whose metaclass overrides tp_new __new__ in Python Since tp_new overrides almost everything PyType_From functions do the two are incompatible with each other The existing behavior ignoring the metaclass for several steps of type creation is unsafe in general since meta classes assume that tp_new was called There is no simple general workaround One of the following may work for you If you control the metaclass avoid using tp_new in it If initialization can be skipped it can be done in tp_init instead If the metaclass doesn t need to be instantiated from Python set its tp_new to NULL using the Py_TPFLAGS_DISALLOW_INSTANTIATION flag This makes it acceptable for PyType_From functions Avoid PyType_From functions if you don t need C specific features slots or setting the instance size create types by calling the metaclass If you know the tp_new can be skipped safely filter the deprecation war,en
992,ning out using warnings catch_warnings from Python PyOS_InputHook and PyOS_ReadlineFunctionPointer are no longer called in subinterpreters This is because clients generally rely on process wide global state since these callbacks have no way of recovering extension module state This also avoids situations where extensions may find themselves running in a subinterpreter that they don t support or haven t yet been loaded in See gh 104668 for more info PyLongObject has had its internals changed for better performance Although the internals of PyLongObject are private they are used by some extension modules The internal fields should no longer be accessed directly instead the API functions beginning PyLong_ should be used instead Two new unstable API functions are provided for efficient access to the value of PyLongObject s which fit into a single machine word PyUnstable_Long_IsCompact PyUnstable_Long_CompactValue Custom allocators set via PyMem_SetAllocator are now required to be thread safe regardless of memory domain Allocators that don t have their own state including hooks are not affected If your custom allocator is not already thread safe and you need guidance then please create a new GitHub issue and CC ericsnowcurrently Deprecated In accordance with PEP 699 the ma_version_tag field in PyDictObject is deprecated for extension modules Accessing this field will generate a compiler warning at compile time This field will be removed in Python 3 14 Contributed by Ramvikrams and Kumar Aditya in gh 101193 PEP by Ken Jin Deprecate global configuration variable Py_DebugFlag use PyConfig parser_debug Py_VerboseFlag use PyConfig verbose Py_QuietFlag use PyConfig quiet Py_InteractiveFlag use PyConfig interactive Py_InspectFlag use PyConfig inspect Py_OptimizeFlag use PyConfig optimization_level Py_NoSiteFlag use PyConfig site_import Py_BytesWarningFlag use PyConfig bytes_warning Py_FrozenFlag use PyConfig pathconfig_warnings Py_IgnoreEnvironmentFlag use PyConfig use_environment Py_DontWriteBytecodeFlag use PyConfig write_bytecode Py_NoUserSiteDirectory use PyConfig user_site_directory Py_UnbufferedStdioFlag use PyConfig buffered_stdio Py_HashRandomizationFlag use PyConfig use_hash_seed and PyConfig hash_seed Py_IsolatedFlag use PyConfig isolated Py_LegacyWindowsFSEncodingFlag use PyPreConfig legacy_windows_fs_encoding Py_LegacyWindowsStdioFlag use PyConfig legacy_windows_stdio Py_FileSystemDefaultEncoding use PyConfig filesystem_encoding Py_HasFileSystemDefaultEncoding use PyConfig filesystem_encoding Py_FileSystemDefaultEncodeErrors use PyConfig filesystem_errors Py_UTF8Mode use PyPreConfig utf8_mode see Py_PreInitialize The Py_InitializeFromConfig API should be used with PyConfig instead Contributed by Victor Stinner in gh 77782 Creating immutable types with mutable bases is deprecated and will be disabled in Python 3 14 gh 95388 The structmember h header is deprecated though it continues to be available and there are no plans to remove it Its contents are now available just by including Python h with a Py prefix added if it was missing PyMemberDef PyMember_GetOne and PyMember_SetOne Type macros like Py_T_INT Py_T_DOUBLE etc previously T_INT T_DOUBLE etc The flags Py_READONLY previously READONLY and Py_AUDIT_READ previously all uppercase Several items are not exposed from Python h T_OBJECT use Py_T_OBJECT_EX T_NONE previously undocumented and pretty quirky The macro WRITE_RESTRICTED which does nothing The macros RESTRICTED and READ_RESTRICTED equivalents of Py_AUDIT_READ In some configurations stddef h is not included from Python h It should be included manually when using offsetof The deprecated header continues to provide its original contents under the original names Your old code can stay unchanged unless the extra include and non namespaced macros bother you greatly Contributed in gh 47146 by Petr Viktorin based on earlier work by Alexander Belopolsky and Matthias Braun PyErr_Fetch and PyErr_Restore are deprecated Use PyErr_GetRaisedException and PyErr_SetRaisedException instead Contributed by Mark Shannon in gh 101578 PyE,en
993,rr_Display is deprecated Use PyErr_DisplayException instead Contributed by Irit Katriel in gh 102755 _PyErr_ChainExceptions is deprecated Use _PyErr_ChainExceptions1 instead Contributed by Irit Katriel in gh 102192 Using PyType_FromSpec PyType_FromSpecWithBases or PyType_FromModuleAndSpec to create a class whose metaclass overrides tp_new is deprecated Call the metaclass instead Pending Removal in Python 3 14 The ma_version_tag field in PyDictObject for extension modules PEP 699 gh 101193 Global configuration variables Py_DebugFlag use PyConfig parser_debug Py_VerboseFlag use PyConfig verbose Py_QuietFlag use PyConfig quiet Py_InteractiveFlag use PyConfig interactive Py_InspectFlag use PyConfig inspect Py_OptimizeFlag use PyConfig optimization_level Py_NoSiteFlag use PyConfig site_import Py_BytesWarningFlag use PyConfig bytes_warning Py_FrozenFlag use PyConfig pathconfig_warnings Py_IgnoreEnvironmentFlag use PyConfig use_environment Py_DontWriteBytecodeFlag use PyConfig write_bytecode Py_NoUserSiteDirectory use PyConfig user_site_directory Py_UnbufferedStdioFlag use PyConfig buffered_stdio Py_HashRandomizationFlag use PyConfig use_hash_seed and PyConfig hash_seed Py_IsolatedFlag use PyConfig isolated Py_LegacyWindowsFSEncodingFlag use PyPreConfig legacy_windows_fs_encoding Py_LegacyWindowsStdioFlag use PyConfig legacy_windows_stdio Py_FileSystemDefaultEncoding use PyConfig filesystem_encoding Py_HasFileSystemDefaultEncoding use PyConfig filesystem_encoding Py_FileSystemDefaultEncodeErrors use PyConfig filesystem_errors Py_UTF8Mode use PyPreConfig utf8_mode see Py_PreInitialize The Py_InitializeFromConfig API should be used with PyConfig instead Creating immutable types with mutable bases gh 95388 Pending Removal in Python 3 15 PyImport_ImportModuleNoBlock use PyImport_ImportModule Py_UNICODE_WIDE type use wchar_t Py_UNICODE type use wchar_t Python initialization functions PySys_ResetWarnOptions clear sys warnoptions and warnings filters Py_GetExecPrefix get sys exec_prefix Py_GetPath get sys path Py_GetPrefix get sys prefix Py_GetProgramFullPath get sys executable Py_GetProgramName get sys executable Py_GetPythonHome get PyConfig home or the PYTHONHOME environment variable Pending Removal in Future Versions The following APIs are deprecated and will be removed although there is currently no date scheduled for their removal Py_TPFLAGS_HAVE_FINALIZE unneeded since Python 3 8 PyErr_Fetch use PyErr_GetRaisedException PyErr_NormalizeException use PyErr_GetRaisedException PyErr_Restore use PyErr_SetRaisedException PyModule_GetFilename use PyModule_GetFilenameObject PyOS_AfterFork use PyOS_AfterFork_Child PySlice_GetIndicesEx use PySlice_Unpack and PySlice_AdjustIndices PyUnicode_AsDecodedObject use PyCodec_Decode PyUnicode_AsDecodedUnicode use PyCodec_Decode PyUnicode_AsEncodedObject use PyCodec_Encode PyUnicode_AsEncodedUnicode use PyCodec_Encode PyUnicode_READY unneeded since Python 3 12 PyErr_Display use PyErr_DisplayException _PyErr_ChainExceptions use _PyErr_ChainExceptions1 PyBytesObject ob_shash member call PyObject_Hash instead PyDictObject ma_version_tag member Thread Local Storage TLS API PyThread_create_key use PyThread_tss_alloc PyThread_delete_key use PyThread_tss_free PyThread_set_key_value use PyThread_tss_set PyThread_get_key_value use PyThread_tss_get PyThread_delete_key_value use PyThread_tss_delete PyThread_ReInitTLS unneeded since Python 3 7 Removed Remove the token h header file There was never any public tokenizer C API The token h header file was only designed to be used by Python internals Contributed by Victor Stinner in gh 92651 Legacy Unicode APIs have been removed See PEP 623 for detail PyUnicode_WCHAR_KIND PyUnicode_AS_UNICODE PyUnicode_AsUnicode PyUnicode_AsUnicodeAndSize PyUnicode_AS_DATA PyUnicode_FromUnicode PyUnicode_GET_SIZE PyUnicode_GetSize PyUnicode_GET_DATA_SIZE Remove the PyUnicode_InternImmortal function macro Contributed by Victor Stinner in gh 85858,en
994,readline GNU readline interface The readline module defines a number of functions to facilitate completion and reading writing of history files from the Python interpreter This module can be used directly or via the rlcompleter module which supports completion of Python identifiers at the interactive prompt Settings made using this module affect the behaviour of both the interpreter s interactive prompt and the prompts offered by the built in input function Readline keybindings may be configured via an initialization file typically inputrc in your home directory See Readline Init File in the GNU Readline manual for information about the format and allowable constructs of that file and the capabilities of the Readline library in general Note The underlying Readline library API may be implemented by the libedit library instead of GNU readline On macOS the readline module detects which library is being used at run time The configuration file for libedit is different from that of GNU readline If you programmatically load configuration strings you can check for the text libedit in readline __doc__ to differentiate between GNU readline and libedit If you use editline libedit readline emulation on macOS the initialization file located in your home directory is named editrc For example the following content in editrc will turn ON vi keybindings and TAB completion python bind v python bind I rl_complete Init file The following functions relate to the init file and user configuration readline parse_and_bind string Execute the init line provided in the string argument This calls rl_parse_and_bind in the underlying library readline read_init_file filename Execute a readline initialization file The default filename is the last filename used This calls rl_read_init_file in the underlying library Line buffer The following functions operate on the line buffer readline get_line_buffer Return the current contents of the line buffer rl_line_buffer in the underlying library readline insert_text string Insert text into the line buffer at the cursor position This calls rl_insert_text in the underlying library but ignores the return value readline redisplay Change what s displayed on the screen to reflect the current contents of the line buffer This calls rl_redisplay in the underlying library History file The following functions operate on a history file readline read_history_file filename Load a readline history file and append it to the history list The default filename is history This calls read_history in the underlying library readline write_history_file filename Save the history list to a readline history file overwriting any existing file The default filename is history This calls write_history in the underlying library readline append_history_file nelements filename Append the last nelements items of history to a file The default filename is history The file must already exist This calls append_history in the underlying library This function only exists if Python was compiled for a version of the library that supports it New in version 3 5 readline get_history_length readline set_history_length length Set or return the desired number of lines to save in the history file The write_history_file function uses this value to truncate the history file by calling history_truncate_file in the underlying library Negative values imply unlimited history file size History list The following functions operate on a global history list readline clear_history Clear the current history This calls clear_history in the underlying library The Python function only exists if Python was compiled for a version of the library that supports it readline get_current_history_length Return the number of items currently in the history This is different from get_history_length which returns the maximum number of lines that will be written to a history file readline get_history_item index Return the current contents of history item at index The item index is one based This calls history_get in the underlying library readline remove_history_item pos Remove history ite,en
995,m specified by its position from the history The position is zero based This calls remove_history in the underlying library readline replace_history_item pos line Replace history item specified by its position with line The position is zero based This calls replace_history_entry in the underlying library readline add_history line Append line to the history buffer as if it was the last line typed This calls add_history in the underlying library readline set_auto_history enabled Enable or disable automatic calls to add_history when reading input via readline The enabled argument should be a Boolean value that when true enables auto history and that when false disables auto history New in version 3 6 CPython implementation detail Auto history is enabled by default and changes to this do not persist across multiple sessions Startup hooks readline set_startup_hook function Set or remove the function invoked by the rl_startup_hook callback of the underlying library If function is specified it will be used as the new hook function if omitted or None any function already installed is removed The hook is called with no arguments just before readline prints the first prompt readline set_pre_input_hook function Set or remove the function invoked by the rl_pre_input_hook callback of the underlying library If function is specified it will be used as the new hook function if omitted or None any function already installed is removed The hook is called with no arguments after the first prompt has been printed and just before readline starts reading input characters This function only exists if Python was compiled for a version of the library that supports it Completion The following functions relate to implementing a custom word completion function This is typically operated by the Tab key and can suggest and automatically complete a word being typed By default Readline is set up to be used by rlcompleter to complete Python identifiers for the interactive interpreter If the readline module is to be used with a custom completer a different set of word delimiters should be set readline set_completer function Set or remove the completer function If function is specified it will be used as the new completer function if omitted or None any completer function already installed is removed The completer function is called as function text state for state in 0 1 2 until it returns a non string value It should return the next possible completion starting with text The installed completer function is invoked by the entry_func callback passed to rl_completion_matches in the underlying library The text string comes from the first parameter to the rl_attempted_completion_function callback of the underlying library readline get_completer Get the completer function or None if no completer function has been set readline get_completion_type Get the type of completion being attempted This returns the rl_completion_type variable in the underlying library as an integer readline get_begidx readline get_endidx Get the beginning or ending index of the completion scope These indexes are the start and end arguments passed to the rl_attempted_completion_function callback of the underlying library The values may be different in the same input editing scenario based on the underlying C readline implementation Ex libedit is known to behave differently than libreadline readline set_completer_delims string readline get_completer_delims Set or get the word delimiters for completion These determine the start of the word to be considered for completion the completion scope These functions access the rl_completer_word_break_characters variable in the underlying library readline set_completion_display_matches_hook function Set or remove the completion display function If function is specified it will be used as the new completion display function if omitted or None any completion display function already installed is removed This sets or clears the rl_completion_display_matches_hook callback in the underlying library The completion display function is called as function su,en
996,bstitution matches longest_match_length once each time matches need to be displayed Example The following example demonstrates how to use the readline module s history reading and writing functions to automatically load and save a history file named python_history from the user s home directory The code below would normally be executed automatically during interactive sessions from the user s PYTHONSTARTUP file import atexit import os import readline histfile os path join os path expanduser python_history try readline read_history_file histfile default history len is 1 infinite which may grow unruly readline set_history_length 1000 except FileNotFoundError pass atexit register readline write_history_file histfile This code is actually automatically run when Python is run in interactive mode see Readline configuration The following example achieves the same goal but supports concurrent interactive sessions by only appending the new history import atexit import os import readline histfile os path join os path expanduser python_history try readline read_history_file histfile h_len readline get_current_history_length except FileNotFoundError open histfile wb close h_len 0 def save prev_h_len histfile new_h_len readline get_current_history_length readline set_history_length 1000 readline append_history_file new_h_len prev_h_len histfile atexit register save h_len histfile The following example extends the code InteractiveConsole class to support history save restore import atexit import code import os import readline class HistoryConsole code InteractiveConsole def __init__ self locals None filename console histfile os path expanduser console history code InteractiveConsole __init__ self locals filename self init_history histfile def init_history self histfile readline parse_and_bind tab complete if hasattr readline read_history_file try readline read_history_file histfile except FileNotFoundError pass atexit register self save_history histfile def save_history self histfile readline set_history_length 1000 readline write_history_file histfile,en
997,Utilities The functions in this chapter perform various utility tasks ranging from helping C code be more portable across platforms using Python modules from C and parsing function arguments and constructing Python values from C values Operating System Utilities System Functions Process Control Importing Modules Data marshalling support Parsing arguments and building values Parsing arguments Strings and buffers Numbers Other objects API Functions Building values String conversion and formatting PyHash API Reflection Codec registry and support functions Codec lookup API Registry API for Unicode encoding error handlers Support for Perf Maps,en
998,email Examples Here are a few examples of how to use the email package to read write and send simple email messages as well as more complex MIME messages First let s see how to create and send a simple text message both the text content and the addresses may contain unicode characters Import smtplib for the actual sending function import smtplib Import the email modules we ll need from email message import EmailMessage Open the plain text file whose name is in textfile for reading with open textfile as fp Create a text plain message msg EmailMessage msg set_content fp read me the sender s email address you the recipient s email address msg Subject f The contents of textfile msg From me msg To you Send the message via our own SMTP server s smtplib SMTP localhost s send_message msg s quit Parsing RFC 822 headers can easily be done by the using the classes from the parser module Import the email modules we ll need from email parser import BytesParser from email parser import Parser from email policy import default If the e mail headers are in a file uncomment these two lines with open messagefile rb as fp headers BytesParser policy default parse fp Or for parsing headers in a string this is an uncommon operation use headers Parser policy default parsestr From Foo Bar user example com n To someone_else example com n Subject Test message n n Body would go here n Now the header items can be accessed as a dictionary print To format headers to print From format headers from print Subject format headers subject You can also access the parts of the addresses print Recipient username format headers to addresses 0 username print Sender name format headers from addresses 0 display_name Here s an example of how to send a MIME message containing a bunch of family pictures that may be residing in a directory Import smtplib for the actual sending function import smtplib Here are the email package modules we ll need from email message import EmailMessage Create the container email message msg EmailMessage msg Subject Our family reunion me the sender s email address family the list of all recipients email addresses msg From me msg To join family msg preamble You will not see this in a MIME aware mail reader n Open the files in binary mode You can also omit the subtype if you want MIMEImage to guess it for file in pngfiles with open file rb as fp img_data fp read msg add_attachment img_data maintype image subtype png Send the email via our own SMTP server with smtplib SMTP localhost as s s send_message msg Here s an example of how to send the entire contents of a directory as an email message 1 usr bin env python3 Send the contents of a directory as a MIME message import os import smtplib For guessing MIME type based on file name extension import mimetypes from argparse import ArgumentParser from email message import EmailMessage from email policy import SMTP def main parser ArgumentParser description Send the contents of a directory as a MIME message Unless the o option is given the email is sent by forwarding to your local SMTP server which then does the normal delivery process Your local machine must be running an SMTP server parser add_argument d directory help Mail the contents of the specified directory otherwise use the current directory Only the regular files in the directory are sent and we don t recurse to subdirectories parser add_argument o output metavar FILE help Print the composed message to FILE instead of sending the message to the SMTP server parser add_argument s sender required True help The value of the From header required parser add_argument r recipient required True action append metavar RECIPIENT default dest recipients help A To header value at least one required args parser parse_args directory args directory if not directory directory Create the message msg EmailMessage msg Subject f Contents of directory os path abspath directory msg To join args recipients msg From args sender msg preamble You will not see this in a MIME aware mail reader n for filename in os listdir directory path os path join directory filena,en
999,me if not os path isfile path continue Guess the content type based on the file s extension Encoding will be ignored although we should check for simple things like gzip d or compressed files ctype encoding mimetypes guess_type path if ctype is None or encoding is not None No guess could be made or the file is encoded compressed so use a generic bag of bits type ctype application octet stream maintype subtype ctype split 1 with open path rb as fp msg add_attachment fp read maintype maintype subtype subtype filename filename Now send or store the message if args output with open args output wb as fp fp write msg as_bytes policy SMTP else with smtplib SMTP localhost as s s send_message msg if __name__ __main__ main Here s an example of how to unpack a MIME message like the one above into a directory of files usr bin env python3 Unpack a MIME message into a directory of files import os import email import mimetypes from email policy import default from argparse import ArgumentParser def main parser ArgumentParser description Unpack a MIME message into a directory of files parser add_argument d directory required True help Unpack the MIME message into the named directory which will be created if it doesn t already exist parser add_argument msgfile args parser parse_args with open args msgfile rb as fp msg email message_from_binary_file fp policy default try os mkdir args directory except FileExistsError pass counter 1 for part in msg walk multipart are just containers if part get_content_maintype multipart continue Applications should really sanitize the given filename so that an email message can t be used to overwrite important files filename part get_filename if not filename ext mimetypes guess_extension part get_content_type if not ext Use a generic bag of bits extension ext bin filename f part counter 03d ext counter 1 with open os path join args directory filename wb as fp fp write part get_payload decode True if __name__ __main__ main Here s an example of how to create an HTML message with an alternative plain text version To make things a bit more interesting we include a related image in the html part and we save a copy of what we are going to send to disk as well as sending it usr bin env python3 import smtplib from email message import EmailMessage from email headerregistry import Address from email utils import make_msgid Create the base text message msg EmailMessage msg Subject Ayons asperges pour le déjeuner msg From Address Pepé Le Pew pepe example com msg To Address Penelope Pussycat penelope example com Address Fabrette Pussycat fabrette example com msg set_content Salut Cela ressemble à un excellent recipie 1 déjeuner 1 http www yummly com recipe Roasted Asparagus Epicurious 203718 Pepé Add the html version This converts the message into a multipart alternative container with the original text message as the first part and the new html message as the second part asparagus_cid make_msgid msg add_alternative html head head body p Salut p p Cela ressemble à un excellent a href http www yummly com recipe Roasted Asparagus Epicurious 203718 recipie a déjeuner p img src cid asparagus_cid body html format asparagus_cid asparagus_cid 1 1 subtype html note that we needed to peel the off the msgid for use in the html Now add the related image to the html part with open roasted asparagus jpg rb as img msg get_payload 1 add_related img read image jpeg cid asparagus_cid Make a local copy of what we are going to send with open outgoing msg wb as f f write bytes msg Send the message via local SMTP server with smtplib SMTP localhost as s s send_message msg If we were sent the message from the last example here is one way we could process it import os import sys import tempfile import mimetypes import webbrowser Import the email modules we ll need from email import policy from email parser import BytesParser def magic_html_parser html_text partfiles Return safety sanitized html linked to partfiles Rewrite the href cid attributes to point to the filenames in partfiles Though not trivial this should be possible using html par,en
1000,ser raise NotImplementedError Add the magic needed In a real program you d get the filename from the arguments with open outgoing msg rb as fp msg BytesParser policy policy default parse fp Now the header items can be accessed as a dictionary and any non ASCII will be converted to unicode print To msg to print From msg from print Subject msg subject If we want to print a preview of the message content we can extract whatever the least formatted payload is and print the first three lines Of course if the message has no plain text part printing the first three lines of html is probably useless but this is just a conceptual example simplest msg get_body preferencelist plain html print print join simplest get_content splitlines keepends True 3 ans input View full message if ans lower 0 n sys exit We can extract the richest alternative in order to display it richest msg get_body partfiles if richest content type maintype text if richest content type subtype plain for line in richest get_content splitlines print line sys exit elif richest content type subtype html body richest else print Don t know how to display format richest get_content_type sys exit elif richest content type content_type multipart related body richest get_body preferencelist html for part in richest iter_attachments fn part get_filename if fn extension os path splitext part get_filename 1 else extension mimetypes guess_extension part get_content_type with tempfile NamedTemporaryFile suffix extension delete False as f f write part get_content again strip the to go from email form of cid to html form partfiles part content id 1 1 f name else print Don t know how to display format richest get_content_type sys exit with tempfile NamedTemporaryFile mode w delete False as f f write magic_html_parser body get_content partfiles webbrowser open f name os remove f name for fn in partfiles values os remove fn Of course there are lots of email messages that could break this simple minded program but it will handle the most common ones Up to the prompt the output from the above is To Penelope Pussycat penelope example com Fabrette Pussycat fabrette example com From Pepé Le Pew pepe example com Subject Ayons asperges pour le déjeuner Salut Cela ressemble à un excellent recipie 1 déjeuner Footnotes 1 Thanks to Matthew Dixon Cowles for the original inspiration and examples,en
1001,tkinter messagebox Tkinter message prompts Source code Lib tkinter messagebox py The tkinter messagebox module provides a template base class as well as a variety of convenience methods for commonly used configurations The message boxes are modal and will return a subset of True False None OK CANCEL YES NO based on the user s selection Common message box styles and layouts include but are not limited to image class tkinter messagebox Message master None options Create a message window with an application specified message an icon and a set of buttons Each of the buttons in the message window is identified by a unique symbolic name see the type options The following options are supported command Specifies the function to invoke when the user closes the dialog The name of the button clicked by the user to close the dialog is passed as argument This is only available on macOS default Gives the symbolic name of the default button for this message window OK CANCEL and so on If this option is not specified the first button in the dialog will be made the default detail Specifies an auxiliary message to the main message given by the message option The message detail will be presented beneath the main message and where supported by the OS in a less emphasized font than the main message icon Specifies an icon to display If this option is not specified then the INFO icon will be displayed message Specifies the message to display in this message box The default value is an empty string parent Makes the specified window the logical parent of the message box The message box is displayed on top of its parent window title Specifies a string to display as the title of the message box This option is ignored on macOS where platform guidelines forbid the use of a title on this kind of dialog type Arranges for a predefined set of buttons to be displayed show options Display a message window and wait for the user to select one of the buttons Then return the symbolic name of the selected button Keyword arguments can override options specified in the constructor Information message box tkinter messagebox showinfo title None message None options Creates and displays an information message box with the specified title and message Warning message boxes tkinter messagebox showwarning title None message None options Creates and displays a warning message box with the specified title and message tkinter messagebox showerror title None message None options Creates and displays an error message box with the specified title and message Question message boxes tkinter messagebox askquestion title None message None type YESNO options Ask a question By default shows buttons YES and NO Returns the symbolic name of the selected button tkinter messagebox askokcancel title None message None options Ask if operation should proceed Shows buttons OK and CANCEL Returns True if the answer is ok and False otherwise tkinter messagebox askretrycancel title None message None options Ask if operation should be retried Shows buttons RETRY and CANCEL Return True if the answer is yes and False otherwise tkinter messagebox askyesno title None message None options Ask a question Shows buttons YES and NO Returns True if the answer is yes and False otherwise tkinter messagebox askyesnocancel title None message None options Ask a question Shows buttons YES NO and CANCEL Return True if the answer is yes None if cancelled and False otherwise Symbolic names of buttons tkinter messagebox ABORT abort tkinter messagebox RETRY retry tkinter messagebox IGNORE ignore tkinter messagebox OK ok tkinter messagebox CANCEL cancel tkinter messagebox YES yes tkinter messagebox NO no Predefined sets of buttons tkinter messagebox ABORTRETRYIGNORE abortretryignore Displays three buttons whose symbolic names are ABORT RETRY and IGNORE tkinter messagebox OK ok Displays one button whose symbolic name is OK tkinter messagebox OKCANCEL okcancel Displays two buttons whose symbolic names are OK and CANCEL tkinter messagebox RETRYCANCEL retrycancel Displays two buttons whose symbolic names are RETRY and CA,en
1002,NCEL tkinter messagebox YESNO yesno Displays two buttons whose symbolic names are YES and NO tkinter messagebox YESNOCANCEL yesnocancel Displays three buttons whose symbolic names are YES NO and CANCEL Icon images tkinter messagebox ERROR error tkinter messagebox INFO info tkinter messagebox QUESTION question tkinter messagebox WARNING warning,en
1003,PyHash API See also the PyTypeObject tp_hash member type Py_hash_t Hash value type signed integer New in version 3 2 type Py_uhash_t Hash value type unsigned integer New in version 3 2 type PyHash_FuncDef Hash function definition used by PyHash_GetFuncDef const char name Hash function name UTF 8 encoded string const int hash_bits Internal size of the hash value in bits const int seed_bits Size of seed input in bits New in version 3 4 PyHash_FuncDef PyHash_GetFuncDef void Get the hash function definition See also PEP 456 Secure and interchangeable hash algorithm New in version 3 4,en
1004,Synchronization Primitives Source code Lib asyncio locks py asyncio synchronization primitives are designed to be similar to those of the threading module with two important caveats asyncio primitives are not thread safe therefore they should not be used for OS thread synchronization use threading for that methods of these synchronization primitives do not accept the timeout argument use the asyncio wait_for function to perform operations with timeouts asyncio has the following basic synchronization primitives Lock Event Condition Semaphore BoundedSemaphore Barrier Lock class asyncio Lock Implements a mutex lock for asyncio tasks Not thread safe An asyncio lock can be used to guarantee exclusive access to a shared resource The preferred way to use a Lock is an async with statement lock asyncio Lock later async with lock access shared state which is equivalent to lock asyncio Lock later await lock acquire try access shared state finally lock release Changed in version 3 10 Removed the loop parameter coroutine acquire Acquire the lock This method waits until the lock is unlocked sets it to locked and returns True When more than one coroutine is blocked in acquire waiting for the lock to be unlocked only one coroutine eventually proceeds Acquiring a lock is fair the coroutine that proceeds will be the first coroutine that started waiting on the lock release Release the lock When the lock is locked reset it to unlocked and return If the lock is unlocked a RuntimeError is raised locked Return True if the lock is locked Event class asyncio Event An event object Not thread safe An asyncio event can be used to notify multiple asyncio tasks that some event has happened An Event object manages an internal flag that can be set to true with the set method and reset to false with the clear method The wait method blocks until the flag is set to true The flag is set to false initially Changed in version 3 10 Removed the loop parameter Example async def waiter event print waiting for it await event wait print got it async def main Create an Event object event asyncio Event Spawn a Task to wait until event is set waiter_task asyncio create_task waiter event Sleep for 1 second and set the event await asyncio sleep 1 event set Wait until the waiter task is finished await waiter_task asyncio run main coroutine wait Wait until the event is set If the event is set return True immediately Otherwise block until another task calls set set Set the event All tasks waiting for event to be set will be immediately awakened clear Clear unset the event Tasks awaiting on wait will now block until the set method is called again is_set Return True if the event is set Condition class asyncio Condition lock None A Condition object Not thread safe An asyncio condition primitive can be used by a task to wait for some event to happen and then get exclusive access to a shared resource In essence a Condition object combines the functionality of an Event and a Lock It is possible to have multiple Condition objects share one Lock which allows coordinating exclusive access to a shared resource between different tasks interested in particular states of that shared resource The optional lock argument must be a Lock object or None In the latter case a new Lock object is created automatically Changed in version 3 10 Removed the loop parameter The preferred way to use a Condition is an async with statement cond asyncio Condition later async with cond await cond wait which is equivalent to cond asyncio Condition later await cond acquire try await cond wait finally cond release coroutine acquire Acquire the underlying lock This method waits until the underlying lock is unlocked sets it to locked and returns True notify n 1 Wake up at most n tasks 1 by default waiting on this condition The method is no op if no tasks are waiting The lock must be acquired before this method is called and released shortly after If called with an unlocked lock a RuntimeError error is raised locked Return True if the underlying lock is acquired notify_all Wake up all tasks waiting on this cond,en
1005,ition This method acts like notify but wakes up all waiting tasks The lock must be acquired before this method is called and released shortly after If called with an unlocked lock a RuntimeError error is raised release Release the underlying lock When invoked on an unlocked lock a RuntimeError is raised coroutine wait Wait until notified If the calling task has not acquired the lock when this method is called a RuntimeError is raised This method releases the underlying lock and then blocks until it is awakened by a notify or notify_all call Once awakened the Condition re acquires its lock and this method returns True coroutine wait_for predicate Wait until a predicate becomes true The predicate must be a callable which result will be interpreted as a boolean value The final value is the return value Semaphore class asyncio Semaphore value 1 A Semaphore object Not thread safe A semaphore manages an internal counter which is decremented by each acquire call and incremented by each release call The counter can never go below zero when acquire finds that it is zero it blocks waiting until some task calls release The optional value argument gives the initial value for the internal counter 1 by default If the given value is less than 0 a ValueError is raised Changed in version 3 10 Removed the loop parameter The preferred way to use a Semaphore is an async with statement sem asyncio Semaphore 10 later async with sem work with shared resource which is equivalent to sem asyncio Semaphore 10 later await sem acquire try work with shared resource finally sem release coroutine acquire Acquire a semaphore If the internal counter is greater than zero decrement it by one and return True immediately If it is zero wait until a release is called and return True locked Returns True if semaphore can not be acquired immediately release Release a semaphore incrementing the internal counter by one Can wake up a task waiting to acquire the semaphore Unlike BoundedSemaphore Semaphore allows making more release calls than acquire calls BoundedSemaphore class asyncio BoundedSemaphore value 1 A bounded semaphore object Not thread safe Bounded Semaphore is a version of Semaphore that raises a ValueError in release if it increases the internal counter above the initial value Changed in version 3 10 Removed the loop parameter Barrier class asyncio Barrier parties A barrier object Not thread safe A barrier is a simple synchronization primitive that allows to block until parties number of tasks are waiting on it Tasks can wait on the wait method and would be blocked until the specified number of tasks end up waiting on wait At that point all of the waiting tasks would unblock simultaneously async with can be used as an alternative to awaiting on wait The barrier can be reused any number of times Example async def example_barrier barrier with 3 parties b asyncio Barrier 3 create 2 new waiting tasks asyncio create_task b wait asyncio create_task b wait await asyncio sleep 0 print b The third wait call passes the barrier await b wait print b print barrier passed await asyncio sleep 0 print b asyncio run example_barrier Result of this example is asyncio locks Barrier object at 0x filling waiters 2 3 asyncio locks Barrier object at 0x draining waiters 0 3 barrier passed asyncio locks Barrier object at 0x filling waiters 0 3 New in version 3 11 coroutine wait Pass the barrier When all the tasks party to the barrier have called this function they are all unblocked simultaneously When a waiting or blocked task in the barrier is cancelled this task exits the barrier which stays in the same state If the state of the barrier is filling the number of waiting task decreases by 1 The return value is an integer in the range of 0 to parties 1 different for each task This can be used to select a task to do some special housekeeping e g async with barrier as position if position 0 Only one task prints this print End of draining phase This method may raise a BrokenBarrierError exception if the barrier is broken or reset while a task is waiting It could raise a CancelledEr,en
1006,ror if a task is cancelled coroutine reset Return the barrier to the default empty state Any tasks waiting on it will receive the BrokenBarrierError exception If a barrier is broken it may be better to just leave it and create a new one coroutine abort Put the barrier into a broken state This causes any active or future calls to wait to fail with the BrokenBarrierError Use this for example if one of the tasks needs to abort to avoid infinite waiting tasks parties The number of tasks required to pass the barrier n_waiting The number of tasks currently waiting in the barrier while filling broken A boolean that is True if the barrier is in the broken state exception asyncio BrokenBarrierError This exception a subclass of RuntimeError is raised when the Barrier object is reset or broken Changed in version 3 9 Acquiring a lock using await lock or yield from lock and or with statement with await lock with yield from lock was removed Use async with lock instead,en
1007,zlib Compression compatible with gzip For applications that require data compression the functions in this module allow compression and decompression using the zlib library The zlib library has its own home page at https www zlib net There are known incompatibilities between the Python module and versions of the zlib library earlier than 1 1 3 1 1 3 has a security vulnerability so we recommend using 1 1 4 or later zlib s functions have many options and often need to be used in a particular order This documentation doesn t attempt to cover all of the permutations consult the zlib manual at http www zlib net manual html for authoritative information For reading and writing gz files see the gzip module The available exception and functions in this module are exception zlib error Exception raised on compression and decompression errors zlib adler32 data value Computes an Adler 32 checksum of data An Adler 32 checksum is almost as reliable as a CRC32 but can be computed much more quickly The result is an unsigned 32 bit integer If value is present it is used as the starting value of the checksum otherwise a default value of 1 is used Passing in value allows computing a running checksum over the concatenation of several inputs The algorithm is not cryptographically strong and should not be used for authentication or digital signatures Since the algorithm is designed for use as a checksum algorithm it is not suitable for use as a general hash algorithm Changed in version 3 0 The result is always unsigned zlib compress data level 1 wbits MAX_WBITS Compresses the bytes in data returning a bytes object containing compressed data level is an integer from 0 to 9 or 1 controlling the level of compression 1 Z_BEST_SPEED is fastest and produces the least compression 9 Z_BEST_COMPRESSION is slowest and produces the most 0 Z_NO_COMPRESSION is no compression The default value is 1 Z_DEFAULT_COMPRESSION Z_DEFAULT_COMPRESSION represents a default compromise between speed and compression currently equivalent to level 6 The wbits argument controls the size of the history buffer or the window size used when compressing data and whether a header and trailer is included in the output It can take several ranges of values defaulting to 15 MAX_WBITS 9 to 15 The base two logarithm of the window size which therefore ranges between 512 and 32768 Larger values produce better compression at the expense of greater memory usage The resulting output will include a zlib specific header and trailer 9 to 15 Uses the absolute value of wbits as the window size logarithm while producing a raw output stream with no header or trailing checksum 25 to 31 16 9 to 15 Uses the low 4 bits of the value as the window size logarithm while including a basic gzip header and trailing checksum in the output Raises the error exception if any error occurs Changed in version 3 6 level can now be used as a keyword parameter Changed in version 3 11 The wbits parameter is now available to set window bits and compression type zlib compressobj level 1 method DEFLATED wbits MAX_WBITS memLevel DEF_MEM_LEVEL strategy Z_DEFAULT_STRATEGY zdict Returns a compression object to be used for compressing data streams that won t fit into memory at once level is the compression level an integer from 0 to 9 or 1 A value of 1 Z_BEST_SPEED is fastest and produces the least compression while a value of 9 Z_BEST_COMPRESSION is slowest and produces the most 0 Z_NO_COMPRESSION is no compression The default value is 1 Z_DEFAULT_COMPRESSION Z_DEFAULT_COMPRESSION represents a default compromise between speed and compression currently equivalent to level 6 method is the compression algorithm Currently the only supported value is DEFLATED The wbits parameter controls the size of the history buffer or the window size and what header and trailer format will be used It has the same meaning as described for compress The memLevel argument controls the amount of memory used for the internal compression state Valid values range from 1 to 9 Higher values use more memory but are faster and produce smaller output strat,en
1008,egy is used to tune the compression algorithm Possible values are Z_DEFAULT_STRATEGY Z_FILTERED Z_HUFFMAN_ONLY Z_RLE zlib 1 2 0 1 and Z_FIXED zlib 1 2 2 2 zdict is a predefined compression dictionary This is a sequence of bytes such as a bytes object containing subsequences that are expected to occur frequently in the data that is to be compressed Those subsequences that are expected to be most common should come at the end of the dictionary Changed in version 3 3 Added the zdict parameter and keyword argument support zlib crc32 data value Computes a CRC Cyclic Redundancy Check checksum of data The result is an unsigned 32 bit integer If value is present it is used as the starting value of the checksum otherwise a default value of 0 is used Passing in value allows computing a running checksum over the concatenation of several inputs The algorithm is not cryptographically strong and should not be used for authentication or digital signatures Since the algorithm is designed for use as a checksum algorithm it is not suitable for use as a general hash algorithm Changed in version 3 0 The result is always unsigned zlib decompress data wbits MAX_WBITS bufsize DEF_BUF_SIZE Decompresses the bytes in data returning a bytes object containing the uncompressed data The wbits parameter depends on the format of data and is discussed further below If bufsize is given it is used as the initial size of the output buffer Raises the error exception if any error occurs The wbits parameter controls the size of the history buffer or window size and what header and trailer format is expected It is similar to the parameter for compressobj but accepts more ranges of values 8 to 15 The base two logarithm of the window size The input must include a zlib header and trailer 0 Automatically determine the window size from the zlib header Only supported since zlib 1 2 3 5 8 to 15 Uses the absolute value of wbits as the window size logarithm The input must be a raw stream with no header or trailer 24 to 31 16 8 to 15 Uses the low 4 bits of the value as the window size logarithm The input must include a gzip header and trailer 40 to 47 32 8 to 15 Uses the low 4 bits of the value as the window size logarithm and automatically accepts either the zlib or gzip format When decompressing a stream the window size must not be smaller than the size originally used to compress the stream using a too small value may result in an error exception The default wbits value corresponds to the largest window size and requires a zlib header and trailer to be included bufsize is the initial size of the buffer used to hold decompressed data If more space is required the buffer size will be increased as needed so you don t have to get this value exactly right tuning it will only save a few calls to malloc Changed in version 3 6 wbits and bufsize can be used as keyword arguments zlib decompressobj wbits MAX_WBITS zdict Returns a decompression object to be used for decompressing data streams that won t fit into memory at once The wbits parameter controls the size of the history buffer or the window size and what header and trailer format is expected It has the same meaning as described for decompress The zdict parameter specifies a predefined compression dictionary If provided this must be the same dictionary as was used by the compressor that produced the data that is to be decompressed Note If zdict is a mutable object such as a bytearray you must not modify its contents between the call to decompressobj and the first call to the decompressor s decompress method Changed in version 3 3 Added the zdict parameter Compression objects support the following methods Compress compress data Compress data returning a bytes object containing compressed data for at least part of the data in data This data should be concatenated to the output produced by any preceding calls to the compress method Some input may be kept in internal buffers for later processing Compress flush mode All pending input is processed and a bytes object containing the remaining compressed output is returned mode c,en
1009,an be selected from the constants Z_NO_FLUSH Z_PARTIAL_FLUSH Z_SYNC_FLUSH Z_FULL_FLUSH Z_BLOCK zlib 1 2 3 4 or Z_FINISH defaulting to Z_FINISH Except Z_FINISH all constants allow compressing further bytestrings of data while Z_FINISH finishes the compressed stream and prevents compressing any more data After calling flush with mode set to Z_FINISH the compress method cannot be called again the only realistic action is to delete the object Compress copy Returns a copy of the compression object This can be used to efficiently compress a set of data that share a common initial prefix Changed in version 3 8 Added copy copy and copy deepcopy support to compression objects Decompression objects support the following methods and attributes Decompress unused_data A bytes object which contains any bytes past the end of the compressed data That is this remains b until the last byte that contains compression data is available If the whole bytestring turned out to contain compressed data this is b an empty bytes object Decompress unconsumed_tail A bytes object that contains any data that was not consumed by the last decompress call because it exceeded the limit for the uncompressed data buffer This data has not yet been seen by the zlib machinery so you must feed it possibly with further data concatenated to it back to a subsequent decompress method call in order to get correct output Decompress eof A boolean indicating whether the end of the compressed data stream has been reached This makes it possible to distinguish between a properly formed compressed stream and an incomplete or truncated one New in version 3 3 Decompress decompress data max_length 0 Decompress data returning a bytes object containing the uncompressed data corresponding to at least part of the data in string This data should be concatenated to the output produced by any preceding calls to the decompress method Some of the input data may be preserved in internal buffers for later processing If the optional parameter max_length is non zero then the return value will be no longer than max_length This may mean that not all of the compressed input can be processed and unconsumed data will be stored in the attribute unconsumed_tail This bytestring must be passed to a subsequent call to decompress if decompression is to continue If max_length is zero then the whole input is decompressed and unconsumed_tail is empty Changed in version 3 6 max_length can be used as a keyword argument Decompress flush length All pending input is processed and a bytes object containing the remaining uncompressed output is returned After calling flush the decompress method cannot be called again the only realistic action is to delete the object The optional parameter length sets the initial size of the output buffer Decompress copy Returns a copy of the decompression object This can be used to save the state of the decompressor midway through the data stream in order to speed up random seeks into the stream at a future point Changed in version 3 8 Added copy copy and copy deepcopy support to decompression objects Information about the version of the zlib library in use is available through the following constants zlib ZLIB_VERSION The version string of the zlib library that was used for building the module This may be different from the zlib library actually used at runtime which is available as ZLIB_RUNTIME_VERSION zlib ZLIB_RUNTIME_VERSION The version string of the zlib library actually loaded by the interpreter New in version 3 3 See also Module gzip Reading and writing gzip format files http www zlib net The zlib library home page http www zlib net manual html The zlib manual explains the semantics and usage of the library s many functions,en
1010,pprint Data pretty printer Source code Lib pprint py The pprint module provides a capability to pretty print arbitrary Python data structures in a form which can be used as input to the interpreter If the formatted structures include objects which are not fundamental Python types the representation may not be loadable This may be the case if objects such as files sockets or classes are included as well as many other objects which are not representable as Python literals The formatted representation keeps objects on a single line if it can and breaks them onto multiple lines if they don t fit within the allowed width Construct PrettyPrinter objects explicitly if you need to adjust the width constraint Dictionaries are sorted by key before the display is computed Changed in version 3 9 Added support for pretty printing types SimpleNamespace Changed in version 3 10 Added support for pretty printing dataclasses dataclass Functions pprint pp object args sort_dicts False kwargs Prints the formatted representation of object followed by a newline If sort_dicts is false the default dictionaries will be displayed with their keys in insertion order otherwise the dict keys will be sorted args and kwargs will be passed to pprint as formatting parameters New in version 3 8 pprint pprint object stream None indent 1 width 80 depth None compact False sort_dicts True underscore_numbers False Prints the formatted representation of object on stream followed by a newline If stream is None sys stdout is used This may be used in the interactive interpreter instead of the print function for inspecting values you can even reassign print pprint pprint for use within a scope The configuration parameters stream indent width depth compact sort_dicts and underscore_numbers are passed to the PrettyPrinter constructor and their meanings are as described in its documentation below import pprint stuff spam eggs lumberjack knights ni stuff insert 0 stuff pprint pprint stuff Recursion on list with id spam eggs lumberjack knights ni pprint pformat object indent 1 width 80 depth None compact False sort_dicts True underscore_numbers False Return the formatted representation of object as a string indent width depth compact sort_dicts and underscore_numbers are passed to the PrettyPrinter constructor as formatting parameters and their meanings are as described in its documentation below pprint isreadable object Determine if the formatted representation of object is readable or can be used to reconstruct the value using eval This always returns False for recursive objects pprint isreadable stuff False pprint isrecursive object Determine if object requires a recursive representation This function is subject to the same limitations as noted in saferepr below and may raise an RecursionError if it fails to detect a recursive object pprint saferepr object Return a string representation of object protected against recursion in some common data structures namely instances of dict list and tuple or subclasses whose __repr__ has not been overridden If the representation of object exposes a recursive entry the recursive reference will be represented as Recursion on typename with id number The representation is not otherwise formatted pprint saferepr stuff Recursion on list with id spam eggs lumberjack knights ni PrettyPrinter Objects This module defines one class class pprint PrettyPrinter indent 1 width 80 depth None stream None compact False sort_dicts True underscore_numbers False Construct a PrettyPrinter instance This constructor understands several keyword parameters stream default sys stdout is a file like object to which the output will be written by calling its write method If both stream and sys stdout are None then pprint silently returns Other values configure the manner in which nesting of complex data structures is displayed indent default 1 specifies the amount of indentation added for each nesting level depth controls the number of nesting levels which may be printed if the data structure being printed is too deep the next contained level is replaced by By,en
1011, default there is no constraint on the depth of the objects being formatted width default 80 specifies the desired maximum number of characters per line in the output If a structure cannot be formatted within the width constraint a best effort will be made compact impacts the way that long sequences lists tuples sets etc are formatted If compact is false the default then each item of a sequence will be formatted on a separate line If compact is true as many items as will fit within the width will be formatted on each output line If sort_dicts is true the default dictionaries will be formatted with their keys sorted otherwise they will display in insertion order If underscore_numbers is true integers will be formatted with the _ character for a thousands separator otherwise underscores are not displayed the default Changed in version 3 4 Added the compact parameter Changed in version 3 8 Added the sort_dicts parameter Changed in version 3 10 Added the underscore_numbers parameter Changed in version 3 11 No longer attempts to write to sys stdout if it is None import pprint stuff spam eggs lumberjack knights ni stuff insert 0 stuff pp pprint PrettyPrinter indent 4 pp pprint stuff spam eggs lumberjack knights ni spam eggs lumberjack knights ni pp pprint PrettyPrinter width 41 compact True pp pprint stuff spam eggs lumberjack knights ni spam eggs lumberjack knights ni tup spam eggs lumberjack knights ni dead parrot fresh fruit pp pprint PrettyPrinter depth 6 pp pprint tup spam eggs lumberjack knights ni dead PrettyPrinter instances have the following methods PrettyPrinter pformat object Return the formatted representation of object This takes into account the options passed to the PrettyPrinter constructor PrettyPrinter pprint object Print the formatted representation of object on the configured stream followed by a newline The following methods provide the implementations for the corresponding functions of the same names Using these methods on an instance is slightly more efficient since new PrettyPrinter objects don t need to be created PrettyPrinter isreadable object Determine if the formatted representation of the object is readable or can be used to reconstruct the value using eval Note that this returns False for recursive objects If the depth parameter of the PrettyPrinter is set and the object is deeper than allowed this returns False PrettyPrinter isrecursive object Determine if the object requires a recursive representation This method is provided as a hook to allow subclasses to modify the way objects are converted to strings The default implementation uses the internals of the saferepr implementation PrettyPrinter format object context maxlevels level Returns three values the formatted version of object as a string a flag indicating whether the result is readable and a flag indicating whether recursion was detected The first argument is the object to be presented The second is a dictionary which contains the id of objects that are part of the current presentation context direct and indirect containers for object that are affecting the presentation as the keys if an object needs to be presented which is already represented in context the third return value should be True Recursive calls to the format method should add additional entries for containers to this dictionary The third argument maxlevels gives the requested limit to recursion this will be 0 if there is no requested limit This argument should be passed unmodified to recursive calls The fourth argument level gives the current level recursive calls should be passed a value less than that of the current call Example To demonstrate several uses of the pprint function and its parameters let s fetch information about a project from PyPI import json import pprint from urllib request import urlopen with urlopen https pypi org pypi sampleproject json as resp project_info json load resp info In its basic form pprint shows the whole object pprint pprint project_info author The Python Packaging Authority author_email pypa dev googlegroups com bugtrack_url None classi,en
1012,fiers Development Status 3 Alpha Intended Audience Developers License OSI Approved MIT License Programming Language Python 2 Programming Language Python 2 6 Programming Language Python 2 7 Programming Language Python 3 Programming Language Python 3 2 Programming Language Python 3 3 Programming Language Python 3 4 Topic Software Development Build Tools description A sample Python project n n n This is the description file for the project n n The file should use UTF 8 encoding and be written using ReStructured Text It n will be used to generate the project webpage on PyPI and should be written for n that purpose n n Typical contents for this file would include an overview of the project basic n usage examples etc Generally including the project changelog in here is not n a good idea although a simple What s New section for the most recent version n may be appropriate description_content_type None docs_url None download_url UNKNOWN downloads last_day 1 last_month 1 last_week 1 home_page https github com pypa sampleproject keywords sample setuptools development license MIT maintainer None maintainer_email None name sampleproject package_url https pypi org project sampleproject platform UNKNOWN project_url https pypi org project sampleproject project_urls Download UNKNOWN Homepage https github com pypa sampleproject release_url https pypi org project sampleproject 1 2 0 requires_dist None requires_python None summary A sample Python project version 1 2 0 The result can be limited to a certain depth ellipsis is used for deeper contents pprint pprint project_info depth 1 author The Python Packaging Authority author_email pypa dev googlegroups com bugtrack_url None classifiers description A sample Python project n n n This is the description file for the project n n The file should use UTF 8 encoding and be written using ReStructured Text It n will be used to generate the project webpage on PyPI and should be written for n that purpose n n Typical contents for this file would include an overview of the project basic n usage examples etc Generally including the project changelog in here is not n a good idea although a simple What s New section for the most recent version n may be appropriate description_content_type None docs_url None download_url UNKNOWN downloads home_page https github com pypa sampleproject keywords sample setuptools development license MIT maintainer None maintainer_email None name sampleproject package_url https pypi org project sampleproject platform UNKNOWN project_url https pypi org project sampleproject project_urls release_url https pypi org project sampleproject 1 2 0 requires_dist None requires_python None summary A sample Python project version 1 2 0 Additionally maximum character width can be suggested If a long object cannot be split the specified width will be exceeded pprint pprint project_info depth 1 width 60 author The Python Packaging Authority author_email pypa dev googlegroups com bugtrack_url None classifiers description A sample Python project n n n This is the description file for the project n n The file should use UTF 8 encoding and be written using ReStructured Text It n will be used to generate the project webpage on PyPI and should be written for n that purpose n n Typical contents for this file would include an overview of the project basic n usage examples etc Generally including the project changelog in here is not n a good idea although a simple What s New section for the most recent version n may be appropriate description_content_type None docs_url None download_url UNKNOWN downloads home_page https github com pypa sampleproject keywords sample setuptools development license MIT maintainer None maintainer_email None name sampleproject package_url https pypi org project sampleproject platform UNKNOWN project_url https pypi org project sampleproject project_urls release_url https pypi org project sampleproject 1 2 0 requires_dist None requires_python None summary A sample Python project version 1 2 0,en
1013,Object Protocol PyObject Py_NotImplemented The NotImplemented singleton used to signal that an operation is not implemented for the given type combination Py_RETURN_NOTIMPLEMENTED Properly handle returning Py_NotImplemented from within a C function that is create a new strong reference to NotImplemented and return it Py_PRINT_RAW Flag to be used with multiple functions that print the object like PyObject_Print and PyFile_WriteObject If passed these function would use the str of the object instead of the repr int PyObject_Print PyObject o FILE fp int flags Print an object o on file fp Returns 1 on error The flags argument is used to enable certain printing options The only option currently supported is Py_PRINT_RAW if given the str of the object is written instead of the repr int PyObject_HasAttr PyObject o PyObject attr_name Part of the Stable ABI Returns 1 if o has the attribute attr_name and 0 otherwise This is equivalent to the Python expression hasattr o attr_name This function always succeeds Note Exceptions that occur when this calls __getattr__ and __getattribute__ methods are silently ignored For proper error handling use PyObject_GetAttr instead int PyObject_HasAttrString PyObject o const char attr_name Part of the Stable ABI This is the same as PyObject_HasAttr but attr_name is specified as a const char UTF 8 encoded bytes string rather than a PyObject Note Exceptions that occur when this calls __getattr__ and __getattribute__ methods or while creating the temporary str object are silently ignored For proper error handling use PyObject_GetAttrString instead PyObject PyObject_GetAttr PyObject o PyObject attr_name Return value New reference Part of the Stable ABI Retrieve an attribute named attr_name from object o Returns the attribute value on success or NULL on failure This is the equivalent of the Python expression o attr_name PyObject PyObject_GetAttrString PyObject o const char attr_name Return value New reference Part of the Stable ABI This is the same as PyObject_GetAttr but attr_name is specified as a const char UTF 8 encoded bytes string rather than a PyObject PyObject PyObject_GenericGetAttr PyObject o PyObject name Return value New reference Part of the Stable ABI Generic attribute getter function that is meant to be put into a type object s tp_getattro slot It looks for a descriptor in the dictionary of classes in the object s MRO as well as an attribute in the object s __dict__ if present As outlined in Implementing Descriptors data descriptors take preference over instance attributes while non data descriptors don t Otherwise an AttributeError is raised int PyObject_SetAttr PyObject o PyObject attr_name PyObject v Part of the Stable ABI Set the value of the attribute named attr_name for object o to the value v Raise an exception and return 1 on failure return 0 on success This is the equivalent of the Python statement o attr_name v If v is NULL the attribute is deleted This behaviour is deprecated in favour of using PyObject_DelAttr but there are currently no plans to remove it int PyObject_SetAttrString PyObject o const char attr_name PyObject v Part of the Stable ABI This is the same as PyObject_SetAttr but attr_name is specified as a const char UTF 8 encoded bytes string rather than a PyObject If v is NULL the attribute is deleted but this feature is deprecated in favour of using PyObject_DelAttrString int PyObject_GenericSetAttr PyObject o PyObject name PyObject value Part of the Stable ABI Generic attribute setter and deleter function that is meant to be put into a type object s tp_setattro slot It looks for a data descriptor in the dictionary of classes in the object s MRO and if found it takes preference over setting or deleting the attribute in the instance dictionary Otherwise the attribute is set or deleted in the object s __dict__ if present On success 0 is returned otherwise an AttributeError is raised and 1 is returned int PyObject_DelAttr PyObject o PyObject attr_name Delete attribute named attr_name for object o Returns 1 on failure This is the equivalent of the Python statement del o,en
1014, attr_name int PyObject_DelAttrString PyObject o const char attr_name This is the same as PyObject_DelAttr but attr_name is specified as a const char UTF 8 encoded bytes string rather than a PyObject PyObject PyObject_GenericGetDict PyObject o void context Return value New reference Part of the Stable ABI since version 3 10 A generic implementation for the getter of a __dict__ descriptor It creates the dictionary if necessary This function may also be called to get the __dict__ of the object o Pass NULL for context when calling it Since this function may need to allocate memory for the dictionary it may be more efficient to call PyObject_GetAttr when accessing an attribute on the object On failure returns NULL with an exception set New in version 3 3 int PyObject_GenericSetDict PyObject o PyObject value void context Part of the Stable ABI since version 3 7 A generic implementation for the setter of a __dict__ descriptor This implementation does not allow the dictionary to be deleted New in version 3 3 PyObject _PyObject_GetDictPtr PyObject obj Return a pointer to __dict__ of the object obj If there is no __dict__ return NULL without setting an exception This function may need to allocate memory for the dictionary so it may be more efficient to call PyObject_GetAttr when accessing an attribute on the object PyObject PyObject_RichCompare PyObject o1 PyObject o2 int opid Return value New reference Part of the Stable ABI Compare the values of o1 and o2 using the operation specified by opid which must be one of Py_LT Py_LE Py_EQ Py_NE Py_GT or Py_GE corresponding to or respectively This is the equivalent of the Python expression o1 op o2 where op is the operator corresponding to opid Returns the value of the comparison on success or NULL on failure int PyObject_RichCompareBool PyObject o1 PyObject o2 int opid Part of the Stable ABI Compare the values of o1 and o2 using the operation specified by opid like PyObject_RichCompare but returns 1 on error 0 if the result is false 1 otherwise Note If o1 and o2 are the same object PyObject_RichCompareBool will always return 1 for Py_EQ and 0 for Py_NE PyObject PyObject_Format PyObject obj PyObject format_spec Part of the Stable ABI Format obj using format_spec This is equivalent to the Python expression format obj format_spec format_spec may be NULL In this case the call is equivalent to format obj Returns the formatted string on success NULL on failure PyObject PyObject_Repr PyObject o Return value New reference Part of the Stable ABI Compute a string representation of object o Returns the string representation on success NULL on failure This is the equivalent of the Python expression repr o Called by the repr built in function Changed in version 3 4 This function now includes a debug assertion to help ensure that it does not silently discard an active exception PyObject PyObject_ASCII PyObject o Return value New reference Part of the Stable ABI As PyObject_Repr compute a string representation of object o but escape the non ASCII characters in the string returned by PyObject_Repr with x u or U escapes This generates a string similar to that returned by PyObject_Repr in Python 2 Called by the ascii built in function PyObject PyObject_Str PyObject o Return value New reference Part of the Stable ABI Compute a string representation of object o Returns the string representation on success NULL on failure This is the equivalent of the Python expression str o Called by the str built in function and therefore by the print function Changed in version 3 4 This function now includes a debug assertion to help ensure that it does not silently discard an active exception PyObject PyObject_Bytes PyObject o Return value New reference Part of the Stable ABI Compute a bytes representation of object o NULL is returned on failure and a bytes object on success This is equivalent to the Python expression bytes o when o is not an integer Unlike bytes o a TypeError is raised when o is an integer instead of a zero initialized bytes object int PyObject_IsSubclass PyObject derived PyObject cls Part of the Stab,en
1015,le ABI Return 1 if the class derived is identical to or derived from the class cls otherwise return 0 In case of an error return 1 If cls is a tuple the check will be done against every entry in cls The result will be 1 when at least one of the checks returns 1 otherwise it will be 0 If cls has a __subclasscheck__ method it will be called to determine the subclass status as described in PEP 3119 Otherwise derived is a subclass of cls if it is a direct or indirect subclass i e contained in cls __mro__ Normally only class objects i e instances of type or a derived class are considered classes However objects can override this by having a __bases__ attribute which must be a tuple of base classes int PyObject_IsInstance PyObject inst PyObject cls Part of the Stable ABI Return 1 if inst is an instance of the class cls or a subclass of cls or 0 if not On error returns 1 and sets an exception If cls is a tuple the check will be done against every entry in cls The result will be 1 when at least one of the checks returns 1 otherwise it will be 0 If cls has a __instancecheck__ method it will be called to determine the subclass status as described in PEP 3119 Otherwise inst is an instance of cls if its class is a subclass of cls An instance inst can override what is considered its class by having a __class__ attribute An object cls can override if it is considered a class and what its base classes are by having a __bases__ attribute which must be a tuple of base classes Py_hash_t PyObject_Hash PyObject o Part of the Stable ABI Compute and return the hash value of an object o On failure return 1 This is the equivalent of the Python expression hash o Changed in version 3 2 The return type is now Py_hash_t This is a signed integer the same size as Py_ssize_t Py_hash_t PyObject_HashNotImplemented PyObject o Part of the Stable ABI Set a TypeError indicating that type o is not hashable and return 1 This function receives special treatment when stored in a tp_hash slot allowing a type to explicitly indicate to the interpreter that it is not hashable int PyObject_IsTrue PyObject o Part of the Stable ABI Returns 1 if the object o is considered to be true and 0 otherwise This is equivalent to the Python expression not not o On failure return 1 int PyObject_Not PyObject o Part of the Stable ABI Returns 0 if the object o is considered to be true and 1 otherwise This is equivalent to the Python expression not o On failure return 1 PyObject PyObject_Type PyObject o Return value New reference Part of the Stable ABI When o is non NULL returns a type object corresponding to the object type of object o On failure raises SystemError and returns NULL This is equivalent to the Python expression type o This function creates a new strong reference to the return value There s really no reason to use this function instead of the Py_TYPE function which returns a pointer of type PyTypeObject except when a new strong reference is needed int PyObject_TypeCheck PyObject o PyTypeObject type Return non zero if the object o is of type type or a subtype of type and 0 otherwise Both parameters must be non NULL Py_ssize_t PyObject_Size PyObject o Py_ssize_t PyObject_Length PyObject o Part of the Stable ABI Return the length of object o If the object o provides either the sequence and mapping protocols the sequence length is returned On error 1 is returned This is the equivalent to the Python expression len o Py_ssize_t PyObject_LengthHint PyObject o Py_ssize_t defaultvalue Return an estimated length for the object o First try to return its actual length then an estimate using __length_hint__ and finally return the default value On error return 1 This is the equivalent to the Python expression operator length_hint o defaultvalue New in version 3 4 PyObject PyObject_GetItem PyObject o PyObject key Return value New reference Part of the Stable ABI Return element of o corresponding to the object key or NULL on failure This is the equivalent of the Python expression o key int PyObject_SetItem PyObject o PyObject key PyObject v Part of the Stable ABI Map the object key to ,en
1016,the value v Raise an exception and return 1 on failure return 0 on success This is the equivalent of the Python statement o key v This function does not steal a reference to v int PyObject_DelItem PyObject o PyObject key Part of the Stable ABI Remove the mapping for the object key from the object o Return 1 on failure This is equivalent to the Python statement del o key PyObject PyObject_Dir PyObject o Return value New reference Part of the Stable ABI This is equivalent to the Python expression dir o returning a possibly empty list of strings appropriate for the object argument or NULL if there was an error If the argument is NULL this is like the Python dir returning the names of the current locals in this case if no execution frame is active then NULL is returned but PyErr_Occurred will return false PyObject PyObject_GetIter PyObject o Return value New reference Part of the Stable ABI This is equivalent to the Python expression iter o It returns a new iterator for the object argument or the object itself if the object is already an iterator Raises TypeError and returns NULL if the object cannot be iterated PyObject PyObject_GetAIter PyObject o Return value New reference Part of the Stable ABI since version 3 10 This is the equivalent to the Python expression aiter o Takes an AsyncIterable object and returns an AsyncIterator for it This is typically a new iterator but if the argument is an AsyncIterator this returns itself Raises TypeError and returns NULL if the object cannot be iterated New in version 3 10 void PyObject_GetTypeData PyObject o PyTypeObject cls Part of the Stable ABI since version 3 12 Get a pointer to subclass specific data reserved for cls The object o must be an instance of cls and cls must have been created using negative PyType_Spec basicsize Python does not check this On error set an exception and return NULL New in version 3 12 Py_ssize_t PyType_GetTypeDataSize PyTypeObject cls Part of the Stable ABI since version 3 12 Return the size of the instance memory space reserved for cls i e the size of the memory PyObject_GetTypeData returns This may be larger than requested using PyType_Spec basicsize it is safe to use this larger size e g with memset The type cls must have been created using negative PyType_Spec basicsize Python does not check this On error set an exception and return a negative value New in version 3 12 void PyObject_GetItemData PyObject o Get a pointer to per item data for a class with Py_TPFLAGS_ITEMS_AT_END On error set an exception and return NULL TypeError is raised if o does not have Py_TPFLAGS_ITEMS_AT_END set New in version 3 12,en
1017,Networking and Interprocess Communication The modules described in this chapter provide mechanisms for networking and inter processes communication Some modules only work for two processes that are on the same machine e g signal and mmap Other modules support networking protocols that two or more processes can use to communicate across machines The list of modules described in this chapter is asyncio Asynchronous I O socket Low level networking interface ssl TLS SSL wrapper for socket objects select Waiting for I O completion selectors High level I O multiplexing signal Set handlers for asynchronous events mmap Memory mapped file support,en
1018,tkinter tix Extension widgets for Tk Source code Lib tkinter tix py Deprecated since version 3 6 This Tk extension is unmaintained and should not be used in new code Use tkinter ttk instead The tkinter tix Tk Interface Extension module provides an additional rich set of widgets Although the standard Tk library has many useful widgets they are far from complete The tkinter tix library provides most of the commonly needed widgets that are missing from standard Tk HList ComboBox Control a k a SpinBox and an assortment of scrollable widgets tkinter tix also includes many more widgets that are generally useful in a wide range of applications NoteBook FileEntry PanedWindow etc there are more than 40 of them With all these new widgets you can introduce new interaction techniques into applications creating more useful and more intuitive user interfaces You can design your application by choosing the most appropriate widgets to match the special needs of your application and users See also Tix Homepage The home page for Tix This includes links to additional documentation and downloads Tix Man Pages On line version of the man pages and reference material Tix Programming Guide On line version of the programmer s reference material Tix Development Applications Tix applications for development of Tix and Tkinter programs Tide applications work under Tk or Tkinter and include TixInspect an inspector to remotely modify and debug Tix Tk Tkinter applications Using Tix class tkinter tix Tk screenName None baseName None className Tix Toplevel widget of Tix which represents mostly the main window of an application It has an associated Tcl interpreter Classes in the tkinter tix module subclasses the classes in the tkinter The former imports the latter so to use tkinter tix with Tkinter all you need to do is to import one module In general you can just import tkinter tix and replace the toplevel call to tkinter Tk with tix Tk from tkinter import tix from tkinter constants import root tix Tk To use tkinter tix you must have the Tix widgets installed usually alongside your installation of the Tk widgets To test your installation try the following from tkinter import tix root tix Tk root tk eval package require Tix Tix Widgets Tix introduces over 40 widget classes to the tkinter repertoire Basic Widgets class tkinter tix Balloon A Balloon that pops up over a widget to provide help When the user moves the cursor inside a widget to which a Balloon widget has been bound a small pop up window with a descriptive message will be shown on the screen class tkinter tix ButtonBox The ButtonBox widget creates a box of buttons such as is commonly used for Ok Cancel class tkinter tix ComboBox The ComboBox widget is similar to the combo box control in MS Windows The user can select a choice by either typing in the entry subwidget or selecting from the listbox subwidget class tkinter tix Control The Control widget is also known as the SpinBox widget The user can adjust the value by pressing the two arrow buttons or by entering the value directly into the entry The new value will be checked against the user defined upper and lower limits class tkinter tix LabelEntry The LabelEntry widget packages an entry widget and a label into one mega widget It can be used to simplify the creation of entry form type of interface class tkinter tix LabelFrame The LabelFrame widget packages a frame widget and a label into one mega widget To create widgets inside a LabelFrame widget one creates the new widgets relative to the frame subwidget and manage them inside the frame subwidget class tkinter tix Meter The Meter widget can be used to show the progress of a background job which may take a long time to execute class tkinter tix OptionMenu The OptionMenu creates a menu button of options class tkinter tix PopupMenu The PopupMenu widget can be used as a replacement of the tk_popup command The advantage of the Tix PopupMenu widget is it requires less application code to manipulate class tkinter tix Select The Select widget is a container of button subwidgets It can be used to pro,en
1019,vide radio box or check box style of selection options for the user class tkinter tix StdButtonBox The StdButtonBox widget is a group of standard buttons for Motif like dialog boxes File Selectors class tkinter tix DirList The DirList widget displays a list view of a directory its previous directories and its sub directories The user can choose one of the directories displayed in the list or change to another directory class tkinter tix DirTree The DirTree widget displays a tree view of a directory its previous directories and its sub directories The user can choose one of the directories displayed in the list or change to another directory class tkinter tix DirSelectDialog The DirSelectDialog widget presents the directories in the file system in a dialog window The user can use this dialog window to navigate through the file system to select the desired directory class tkinter tix DirSelectBox The DirSelectBox is similar to the standard Motif TM directory selection box It is generally used for the user to choose a directory DirSelectBox stores the directories mostly recently selected into a ComboBox widget so that they can be quickly selected again class tkinter tix ExFileSelectBox The ExFileSelectBox widget is usually embedded in a tixExFileSelectDialog widget It provides a convenient method for the user to select files The style of the ExFileSelectBox widget is very similar to the standard file dialog on MS Windows 3 1 class tkinter tix FileSelectBox The FileSelectBox is similar to the standard Motif TM file selection box It is generally used for the user to choose a file FileSelectBox stores the files mostly recently selected into a ComboBox widget so that they can be quickly selected again class tkinter tix FileEntry The FileEntry widget can be used to input a filename The user can type in the filename manually Alternatively the user can press the button widget that sits next to the entry which will bring up a file selection dialog Hierarchical ListBox class tkinter tix HList The HList widget can be used to display any data that have a hierarchical structure for example file system directory trees The list entries are indented and connected by branch lines according to their places in the hierarchy class tkinter tix CheckList The CheckList widget displays a list of items to be selected by the user CheckList acts similarly to the Tk checkbutton or radiobutton widgets except it is capable of handling many more items than checkbuttons or radiobuttons class tkinter tix Tree The Tree widget can be used to display hierarchical data in a tree form The user can adjust the view of the tree by opening or closing parts of the tree Tabular ListBox class tkinter tix TList The TList widget can be used to display data in a tabular format The list entries of a TList widget are similar to the entries in the Tk listbox widget The main differences are 1 the TList widget can display the list entries in a two dimensional format and 2 you can use graphical images as well as multiple colors and fonts for the list entries Manager Widgets class tkinter tix PanedWindow The PanedWindow widget allows the user to interactively manipulate the sizes of several panes The panes can be arranged either vertically or horizontally The user changes the sizes of the panes by dragging the resize handle between two panes class tkinter tix ListNoteBook The ListNoteBook widget is very similar to the TixNoteBook widget it can be used to display many windows in a limited space using a notebook metaphor The notebook is divided into a stack of pages windows At one time only one of these pages can be shown The user can navigate through these pages by choosing the name of the desired page in the hlist subwidget class tkinter tix NoteBook The NoteBook widget can be used to display many windows in a limited space using a notebook metaphor The notebook is divided into a stack of pages At one time only one of these pages can be shown The user can navigate through these pages by choosing the visual tabs at the top of the NoteBook widget Image Types The tkinter tix modu,en
1020,le adds pixmap capabilities to all tkinter tix and tkinter widgets to create color images from XPM files Compound image types can be used to create images that consists of multiple horizontal lines each line is composed of a series of items texts bitmaps images or spaces arranged from left to right For example a compound image can be used to display a bitmap and a text string simultaneously in a Tk Button widget Miscellaneous Widgets class tkinter tix InputOnly The InputOnly widgets are to accept inputs from the user which can be done with the bind command Unix only Form Geometry Manager In addition tkinter tix augments tkinter by providing class tkinter tix Form The Form geometry manager based on attachment rules for all Tk widgets Tix Commands class tkinter tix tixCommand The tix commands provide access to miscellaneous elements of Tix s internal state and the Tix application context Most of the information manipulated by these methods pertains to the application as a whole or to a screen or display rather than to a particular window To view the current settings the common usage is from tkinter import tix root tix Tk print root tix_configure tixCommand tix_configure cnf None kw Query or modify the configuration options of the Tix application context If no option is specified returns a dictionary all of the available options If option is specified with no value then the method returns a list describing the one named option this list will be identical to the corresponding sublist of the value returned if no option is specified If one or more option value pairs are specified then the method modifies the given option s to have the given value s in this case the method returns an empty string Option may be any of the configuration options tixCommand tix_cget option Returns the current value of the configuration option given by option Option may be any of the configuration options tixCommand tix_getbitmap name Locates a bitmap file of the name name xpm or name in one of the bitmap directories see the tix_addbitmapdir method By using tix_getbitmap you can avoid hard coding the pathnames of the bitmap files in your application When successful it returns the complete pathname of the bitmap file prefixed with the character The returned value can be used to configure the bitmap option of the Tk and Tix widgets tixCommand tix_addbitmapdir directory Tix maintains a list of directories under which the tix_getimage and tix_getbitmap methods will search for image files The standard bitmap directory is TIX_LIBRARY bitmaps The tix_addbitmapdir method adds directory into this list By using this method the image files of an applications can also be located using the tix_getimage or tix_getbitmap method tixCommand tix_filedialog dlgclass Returns the file selection dialog that may be shared among different calls from this application This method will create a file selection dialog widget when it is called the first time This dialog will be returned by all subsequent calls to tix_filedialog An optional dlgclass parameter can be passed as a string to specified what type of file selection dialog widget is desired Possible options are tix FileSelectDialog or tixExFileSelectDialog tixCommand tix_getimage self name Locates an image file of the name name xpm name xbm or name ppm in one of the bitmap directories see the tix_addbitmapdir method above If more than one file with the same name but different extensions exist then the image type is chosen according to the depth of the X display xbm images are chosen on monochrome displays and color images are chosen on color displays By using tix_getimage you can avoid hard coding the pathnames of the image files in your application When successful this method returns the name of the newly created image which can be used to configure the image option of the Tk and Tix widgets tixCommand tix_option_get name Gets the options maintained by the Tix scheme mechanism tixCommand tix_resetoptions newScheme newFontSet newScmPrio Resets the scheme and fontset of the Tix application to newScheme and newFontSet resp,en
1021,ectively This affects only those widgets created after this call Therefore it is best to call the resetoptions method before the creation of any widgets in a Tix application The optional parameter newScmPrio can be given to reset the priority level of the Tk options set by the Tix schemes Because of the way Tk handles the X option database after Tix has been has imported and inited it is not possible to reset the color schemes and font sets using the tix_config method Instead the tix_resetoptions method must be used,en
1022,10 Full Grammar specification This is the full Python grammar derived directly from the grammar used to generate the CPython parser see Grammar python gram The version here omits details related to code generation and error recovery The notation is a mixture of EBNF and PEG In particular followed by a symbol token or parenthesized group indicates a positive lookahead i e is required to match but not consumed while indicates a negative lookahead i e is required not to match We use the separator to mean PEG s ordered choice written as in traditional PEG grammars See PEP 617 for more details on the grammar s syntax PEG grammar for Python trailer void _PyPegen_parse Parser p Initialize keywords p keywords reserved_keywords p n_keyword_lists n_keyword_lists p soft_keywords soft_keywords Run parser void result NULL if p start_rule Py_file_input result file_rule p else if p start_rule Py_single_input result interactive_rule p else if p start_rule Py_eval_input result eval_rule p else if p start_rule Py_func_type_input result func_type_rule p return result START OF THE GRAMMAR General grammatical elements and rules Strings with double quotes denote SOFT KEYWORDS Strings with single quotes denote KEYWORDS Upper case names NAME denote tokens in the Grammar Tokens file Rule names starting with invalid_ are used for specialized syntax errors These rules are NOT used in the first pass of the parser Only if the first pass fails to parse a second pass including the invalid rules will be executed If the parser fails in the second phase with a generic syntax error the location of the generic failure of the first pass will be used this avoids reporting incorrect locations due to the invalid rules The order of the alternatives involving invalid rules matter like any rule in PEG Grammar Syntax see PEP 617 for more information rule_name expression Optionally a type can be included right after the rule name which specifies the return type of the C or Python function corresponding to the rule rule_name return_type expression If the return type is omitted then a void is returned in C and an Any in Python e1 e2 Match e1 then match e2 e1 e2 Match e1 or e2 The first alternative can also appear on the line after the rule name for formatting purposes In that case a must be used before the first alternative like so rule_name return_type first_alt second_alt e Match e allows also to use other operators in the group like e e or e Optionally match e e Match zero or more occurrences of e e Match one or more occurrences of e s e Match one or more occurrences of e separated by s The generated parse tree does not include the separator This is otherwise identical to e s e e Succeed if e can be parsed without consuming any input e Fail if e can be parsed without consuming any input Commit to the current alternative even if it fails to parse STARTING RULES file mod_ty a statements ENDMARKER _PyPegen_make_module p a interactive mod_ty a statement_newline _PyAST_Interactive a p arena eval mod_ty a expressions NEWLINE ENDMARKER _PyAST_Expression a p arena func_type mod_ty a type_expressions b expression NEWLINE ENDMARKER _PyAST_FunctionType a b p arena GENERAL STATEMENTS statements asdl_stmt_seq a statement asdl_stmt_seq _PyPegen_seq_flatten p a statement asdl_stmt_seq a compound_stmt asdl_stmt_seq _PyPegen_singleton_seq p a a asdl_stmt_seq simple_stmts a statement_newline asdl_stmt_seq a compound_stmt NEWLINE asdl_stmt_seq _PyPegen_singleton_seq p a simple_stmts NEWLINE asdl_stmt_seq _PyPegen_singleton_seq p CHECK stmt_ty _PyAST_Pass EXTRA ENDMARKER _PyPegen_interactive_exit p simple_stmts asdl_stmt_seq a simple_stmt NEWLINE asdl_stmt_seq _PyPegen_singleton_seq p a Not needed there for speedup a asdl_stmt_seq simple_stmt NEWLINE a NOTE assignment MUST precede expression else parsing a simple assignment will throw a SyntaxError simple_stmt stmt_ty memo assignment type type_alias e star_expressions _PyAST_Expr e EXTRA return return_stmt import from import_stmt raise raise_stmt pass _PyAST_Pass EXTRA del del_stmt yield yield_stmt assert assert_stmt break _PyAST_Bre,en
1023,ak EXTRA continue _PyAST_Continue EXTRA global global_stmt nonlocal nonlocal_stmt compound_stmt stmt_ty def ASYNC function_def if if_stmt class class_def with ASYNC with_stmt for ASYNC for_stmt try try_stmt while while_stmt match_stmt SIMPLE STATEMENTS NOTE annotated_rhs may start with yield yield_expr must start with yield assignment stmt_ty a NAME b expression c d annotated_rhs d CHECK_VERSION stmt_ty 6 Variable annotation syntax is _PyAST_AnnAssign CHECK expr_ty _PyPegen_set_expr_context p a Store b c 1 EXTRA a b single_target b single_subscript_attribute_target b expression c d annotated_rhs d CHECK_VERSION stmt_ty 6 Variable annotations syntax is _PyAST_AnnAssign a b c 0 EXTRA a asdl_expr_seq z star_targets z b yield_expr star_expressions tc TYPE_COMMENT _PyAST_Assign a b NEW_TYPE_COMMENT p tc EXTRA a single_target b augassign c yield_expr star_expressions _PyAST_AugAssign a b kind c EXTRA invalid_assignment annotated_rhs expr_ty yield_expr star_expressions augassign AugOperator _PyPegen_augoperator p Add _PyPegen_augoperator p Sub _PyPegen_augoperator p Mult CHECK_VERSION AugOperator 5 The operator is _PyPegen_augoperator p MatMult _PyPegen_augoperator p Div _PyPegen_augoperator p Mod _PyPegen_augoperator p BitAnd _PyPegen_augoperator p BitOr _PyPegen_augoperator p BitXor _PyPegen_augoperator p LShift _PyPegen_augoperator p RShift _PyPegen_augoperator p Pow _PyPegen_augoperator p FloorDiv return_stmt stmt_ty return a star_expressions _PyAST_Return a EXTRA raise_stmt stmt_ty raise a expression b from z expression z _PyAST_Raise a b EXTRA raise _PyAST_Raise NULL NULL EXTRA global_stmt stmt_ty global a asdl_expr_seq NAME _PyAST_Global CHECK asdl_identifier_seq _PyPegen_map_names_to_ids p a EXTRA nonlocal_stmt stmt_ty nonlocal a asdl_expr_seq NAME _PyAST_Nonlocal CHECK asdl_identifier_seq _PyPegen_map_names_to_ids p a EXTRA del_stmt stmt_ty del a del_targets NEWLINE _PyAST_Delete a EXTRA invalid_del_stmt yield_stmt stmt_ty y yield_expr _PyAST_Expr y EXTRA assert_stmt stmt_ty assert a expression b z expression z _PyAST_Assert a b EXTRA import_stmt stmt_ty invalid_import import_name import_from Import statements import_name stmt_ty import a dotted_as_names _PyAST_Import a EXTRA note below the is necessary because is tokenized as ELLIPSIS import_from stmt_ty from a b dotted_name import c import_from_targets _PyAST_ImportFrom b v Name id c _PyPegen_seq_count_dots a EXTRA from a import b import_from_targets _PyAST_ImportFrom NULL b _PyPegen_seq_count_dots a EXTRA import_from_targets asdl_alias_seq a import_from_as_names a import_from_as_names asdl_alias_seq _PyPegen_singleton_seq p CHECK alias_ty _PyPegen_alias_for_star p EXTRA invalid_import_from_targets import_from_as_names asdl_alias_seq a asdl_alias_seq import_from_as_name a import_from_as_name alias_ty a NAME b as z NAME z _PyAST_alias a v Name id b expr_ty b v Name id NULL EXTRA dotted_as_names asdl_alias_seq a asdl_alias_seq dotted_as_name a dotted_as_name alias_ty a dotted_name b as z NAME z _PyAST_alias a v Name id b expr_ty b v Name id NULL EXTRA dotted_name expr_ty a dotted_name b NAME _PyPegen_join_names_with_dot p a b NAME COMPOUND STATEMENTS Common elements block asdl_stmt_seq memo NEWLINE INDENT a statements DEDENT a simple_stmts invalid_block decorators asdl_expr_seq a asdl_expr_seq f named_expression NEWLINE f a Class definitions class_def stmt_ty a decorators b class_def_raw _PyPegen_class_def_decorators p a b class_def_raw class_def_raw stmt_ty invalid_class_def_raw class a NAME t type_params b z arguments z c block _PyAST_ClassDef a v Name id b expr_ty b v Call args NULL b expr_ty b v Call keywords NULL c NULL t EXTRA Function definitions function_def stmt_ty d decorators f function_def_raw _PyPegen_function_def_decorators p d f function_def_raw function_def_raw stmt_ty invalid_def_raw def n NAME t type_params params params a z expression z tc func_type_comment b block _PyAST_FunctionDef n v Name id params params CHECK arguments_ty _PyPegen_empty_arguments p b NULL a NEW_TYPE_COMMENT p tc t EXTRA ASYNC def n NAME t type_params params params a z expressio,en
1024,n z tc func_type_comment b block CHECK_VERSION stmt_ty 5 Async functions are _PyAST_AsyncFunctionDef n v Name id params params CHECK arguments_ty _PyPegen_empty_arguments p b NULL a NEW_TYPE_COMMENT p tc t EXTRA Function parameters params arguments_ty invalid_parameters parameters parameters arguments_ty a slash_no_default b asdl_arg_seq param_no_default c param_with_default d star_etc CHECK_VERSION arguments_ty 8 Positional only parameters are _PyPegen_make_arguments p a NULL b c d a slash_with_default b param_with_default c star_etc CHECK_VERSION arguments_ty 8 Positional only parameters are _PyPegen_make_arguments p NULL a NULL b c a asdl_arg_seq param_no_default b param_with_default c star_etc _PyPegen_make_arguments p NULL NULL a b c a param_with_default b star_etc _PyPegen_make_arguments p NULL NULL NULL a b a star_etc _PyPegen_make_arguments p NULL NULL NULL NULL a Some duplication here because we can t write which is because we don t support empty alternatives yet slash_no_default asdl_arg_seq a asdl_arg_seq param_no_default a a asdl_arg_seq param_no_default a slash_with_default SlashWithDefault a param_no_default b param_with_default _PyPegen_slash_with_default p asdl_arg_seq a b a param_no_default b param_with_default _PyPegen_slash_with_default p asdl_arg_seq a b star_etc StarEtc invalid_star_etc a param_no_default b param_maybe_default c kwds _PyPegen_star_etc p a b c a param_no_default_star_annotation b param_maybe_default c kwds _PyPegen_star_etc p a b c b param_maybe_default c kwds _PyPegen_star_etc p NULL b c a kwds _PyPegen_star_etc p NULL NULL a kwds arg_ty invalid_kwds a param_no_default a One parameter This includes a following comma and type comment There are three styles No default With default Maybe with default There are two alternative forms of each to deal with type comments Ends in a comma followed by an optional type comment No comma optional type comment must be followed by close paren The latter form is for a final parameter without trailing comma param_no_default arg_ty a param tc TYPE_COMMENT _PyPegen_add_type_comment_to_arg p a tc a param tc TYPE_COMMENT _PyPegen_add_type_comment_to_arg p a tc param_no_default_star_annotation arg_ty a param_star_annotation tc TYPE_COMMENT _PyPegen_add_type_comment_to_arg p a tc a param_star_annotation tc TYPE_COMMENT _PyPegen_add_type_comment_to_arg p a tc param_with_default NameDefaultPair a param c default tc TYPE_COMMENT _PyPegen_name_default_pair p a c tc a param c default tc TYPE_COMMENT _PyPegen_name_default_pair p a c tc param_maybe_default NameDefaultPair a param c default tc TYPE_COMMENT _PyPegen_name_default_pair p a c tc a param c default tc TYPE_COMMENT _PyPegen_name_default_pair p a c tc param arg_ty a NAME b annotation _PyAST_arg a v Name id b NULL EXTRA param_star_annotation arg_ty a NAME b star_annotation _PyAST_arg a v Name id b NULL EXTRA annotation expr_ty a expression a star_annotation expr_ty a star_expression a default expr_ty a expression a invalid_default If statement if_stmt stmt_ty invalid_if_stmt if a named_expression b block c elif_stmt _PyAST_If a b CHECK asdl_stmt_seq _PyPegen_singleton_seq p c EXTRA if a named_expression b block c else_block _PyAST_If a b c EXTRA elif_stmt stmt_ty invalid_elif_stmt elif a named_expression b block c elif_stmt _PyAST_If a b CHECK asdl_stmt_seq _PyPegen_singleton_seq p c EXTRA elif a named_expression b block c else_block _PyAST_If a b c EXTRA else_block asdl_stmt_seq invalid_else_stmt else b block b While statement while_stmt stmt_ty invalid_while_stmt while a named_expression b block c else_block _PyAST_While a b c EXTRA For statement for_stmt stmt_ty invalid_for_stmt for t star_targets in ex star_expressions tc TYPE_COMMENT b block el else_block _PyAST_For t ex b el NEW_TYPE_COMMENT p tc EXTRA ASYNC for t star_targets in ex star_expressions tc TYPE_COMMENT b block el else_block CHECK_VERSION stmt_ty 5 Async for loops are _PyAST_AsyncFor t ex b el NEW_TYPE_COMMENT p tc EXTRA invalid_for_target With statement with_stmt stmt_ty invalid_with_stmt_indent with a asdl_withitem_seq with_item b block ,en
1025,_PyAST_With a b NULL EXTRA with a asdl_withitem_seq with_item tc TYPE_COMMENT b block _PyAST_With a b NEW_TYPE_COMMENT p tc EXTRA ASYNC with a asdl_withitem_seq with_item b block CHECK_VERSION stmt_ty 5 Async with statements are _PyAST_AsyncWith a b NULL EXTRA ASYNC with a asdl_withitem_seq with_item tc TYPE_COMMENT b block CHECK_VERSION stmt_ty 5 Async with statements are _PyAST_AsyncWith a b NEW_TYPE_COMMENT p tc EXTRA invalid_with_stmt with_item withitem_ty e expression as t star_target _PyAST_withitem e t p arena invalid_with_item e expression _PyAST_withitem e NULL p arena Try statement try_stmt stmt_ty invalid_try_stmt try b block f finally_block _PyAST_Try b NULL NULL f EXTRA try b block ex asdl_excepthandler_seq except_block el else_block f finally_block _PyAST_Try b ex el f EXTRA try b block ex asdl_excepthandler_seq except_star_block el else_block f finally_block CHECK_VERSION stmt_ty 11 Exception groups are _PyAST_TryStar b ex el f EXTRA Except statement except_block excepthandler_ty invalid_except_stmt_indent except e expression t as z NAME z b block _PyAST_ExceptHandler e t expr_ty t v Name id NULL b EXTRA except b block _PyAST_ExceptHandler NULL NULL b EXTRA invalid_except_stmt except_star_block excepthandler_ty invalid_except_star_stmt_indent except e expression t as z NAME z b block _PyAST_ExceptHandler e t expr_ty t v Name id NULL b EXTRA invalid_except_stmt finally_block asdl_stmt_seq invalid_finally_stmt finally a block a Match statement match_stmt stmt_ty match subject subject_expr NEWLINE INDENT cases asdl_match_case_seq case_block DEDENT CHECK_VERSION stmt_ty 10 Pattern matching is _PyAST_Match subject cases EXTRA invalid_match_stmt subject_expr expr_ty value star_named_expression values star_named_expressions _PyAST_Tuple CHECK asdl_expr_seq _PyPegen_seq_insert_in_front p value values Load EXTRA named_expression case_block match_case_ty invalid_case_block case pattern patterns guard guard body block _PyAST_match_case pattern guard body p arena guard expr_ty if guard named_expression guard patterns pattern_ty patterns asdl_pattern_seq open_sequence_pattern _PyAST_MatchSequence patterns EXTRA pattern pattern pattern_ty as_pattern or_pattern as_pattern pattern_ty pattern or_pattern as target pattern_capture_target _PyAST_MatchAs pattern target v Name id EXTRA invalid_as_pattern or_pattern pattern_ty patterns asdl_pattern_seq closed_pattern asdl_seq_LEN patterns 1 asdl_seq_GET patterns 0 _PyAST_MatchOr patterns EXTRA closed_pattern pattern_ty memo literal_pattern capture_pattern wildcard_pattern value_pattern group_pattern sequence_pattern mapping_pattern class_pattern Literal patterns are used for equality and identity constraints literal_pattern pattern_ty value signed_number _PyAST_MatchValue value EXTRA value complex_number _PyAST_MatchValue value EXTRA value strings _PyAST_MatchValue value EXTRA None _PyAST_MatchSingleton Py_None EXTRA True _PyAST_MatchSingleton Py_True EXTRA False _PyAST_MatchSingleton Py_False EXTRA Literal expressions are used to restrict permitted mapping pattern keys literal_expr expr_ty signed_number complex_number strings None _PyAST_Constant Py_None NULL EXTRA True _PyAST_Constant Py_True NULL EXTRA False _PyAST_Constant Py_False NULL EXTRA complex_number expr_ty real signed_real_number imag imaginary_number _PyAST_BinOp real Add imag EXTRA real signed_real_number imag imaginary_number _PyAST_BinOp real Sub imag EXTRA signed_number expr_ty NUMBER number NUMBER _PyAST_UnaryOp USub number EXTRA signed_real_number expr_ty real_number real real_number _PyAST_UnaryOp USub real EXTRA real_number expr_ty real NUMBER _PyPegen_ensure_real p real imaginary_number expr_ty imag NUMBER _PyPegen_ensure_imaginary p imag capture_pattern pattern_ty target pattern_capture_target _PyAST_MatchAs NULL target v Name id EXTRA pattern_capture_target expr_ty _ name NAME _PyPegen_set_expr_context p name Store wildcard_pattern pattern_ty _ _PyAST_MatchAs NULL NULL EXTRA value_pattern pattern_ty attr attr _PyAST_MatchValue attr EXTRA attr expr_ty value name_or_attr attr NAME _PyAST_Attribute value at,en
1026,tr v Name id Load EXTRA name_or_attr expr_ty attr NAME group_pattern pattern_ty pattern pattern pattern sequence_pattern pattern_ty patterns maybe_sequence_pattern _PyAST_MatchSequence patterns EXTRA patterns open_sequence_pattern _PyAST_MatchSequence patterns EXTRA open_sequence_pattern asdl_seq pattern maybe_star_pattern patterns maybe_sequence_pattern _PyPegen_seq_insert_in_front p pattern patterns maybe_sequence_pattern asdl_seq patterns maybe_star_pattern patterns maybe_star_pattern pattern_ty star_pattern pattern star_pattern pattern_ty memo target pattern_capture_target _PyAST_MatchStar target v Name id EXTRA wildcard_pattern _PyAST_MatchStar NULL EXTRA mapping_pattern pattern_ty _PyAST_MatchMapping NULL NULL NULL EXTRA rest double_star_pattern _PyAST_MatchMapping NULL NULL rest v Name id EXTRA items items_pattern rest double_star_pattern _PyAST_MatchMapping CHECK asdl_expr_seq _PyPegen_get_pattern_keys p items CHECK asdl_pattern_seq _PyPegen_get_patterns p items rest v Name id EXTRA items items_pattern _PyAST_MatchMapping CHECK asdl_expr_seq _PyPegen_get_pattern_keys p items CHECK asdl_pattern_seq _PyPegen_get_patterns p items NULL EXTRA items_pattern asdl_seq key_value_pattern key_value_pattern KeyPatternPair key literal_expr attr pattern pattern _PyPegen_key_pattern_pair p key pattern double_star_pattern expr_ty target pattern_capture_target target class_pattern pattern_ty cls name_or_attr _PyAST_MatchClass cls NULL NULL NULL EXTRA cls name_or_attr patterns positional_patterns _PyAST_MatchClass cls patterns NULL NULL EXTRA cls name_or_attr keywords keyword_patterns _PyAST_MatchClass cls NULL CHECK asdl_identifier_seq _PyPegen_map_names_to_ids p CHECK asdl_expr_seq _PyPegen_get_pattern_keys p keywords CHECK asdl_pattern_seq _PyPegen_get_patterns p keywords EXTRA cls name_or_attr patterns positional_patterns keywords keyword_patterns _PyAST_MatchClass cls patterns CHECK asdl_identifier_seq _PyPegen_map_names_to_ids p CHECK asdl_expr_seq _PyPegen_get_pattern_keys p keywords CHECK asdl_pattern_seq _PyPegen_get_patterns p keywords EXTRA invalid_class_pattern positional_patterns asdl_pattern_seq args asdl_pattern_seq pattern args keyword_patterns asdl_seq keyword_pattern keyword_pattern KeyPatternPair arg NAME value pattern _PyPegen_key_pattern_pair p arg value Type statement type_alias stmt_ty type n NAME t type_params b expression CHECK_VERSION stmt_ty 12 Type statement is _PyAST_TypeAlias CHECK expr_ty _PyPegen_set_expr_context p n Store t b EXTRA Type parameter declaration type_params asdl_type_param_seq t type_param_seq CHECK_VERSION asdl_type_param_seq 12 Type parameter lists are t type_param_seq asdl_type_param_seq a asdl_type_param_seq type_param a type_param type_param_ty memo a NAME b type_param_bound _PyAST_TypeVar a v Name id b EXTRA a NAME colon e expression RAISE_SYNTAX_ERROR_STARTING_FROM colon e kind Tuple_kind cannot use constraints with TypeVarTuple cannot use bound with TypeVarTuple a NAME _PyAST_TypeVarTuple a v Name id EXTRA a NAME colon e expression RAISE_SYNTAX_ERROR_STARTING_FROM colon e kind Tuple_kind cannot use constraints with ParamSpec cannot use bound with ParamSpec a NAME _PyAST_ParamSpec a v Name id EXTRA type_param_bound expr_ty e expression e EXPRESSIONS expressions expr_ty a expression b c expression c _PyAST_Tuple CHECK asdl_expr_seq _PyPegen_seq_insert_in_front p a b Load EXTRA a expression _PyAST_Tuple CHECK asdl_expr_seq _PyPegen_singleton_seq p a Load EXTRA expression expression expr_ty memo invalid_expression invalid_legacy_expression a disjunction if b disjunction else c expression _PyAST_IfExp b a c EXTRA disjunction lambdef yield_expr expr_ty yield from a expression _PyAST_YieldFrom a EXTRA yield a star_expressions _PyAST_Yield a EXTRA star_expressions expr_ty a star_expression b c star_expression c _PyAST_Tuple CHECK asdl_expr_seq _PyPegen_seq_insert_in_front p a b Load EXTRA a star_expression _PyAST_Tuple CHECK asdl_expr_seq _PyPegen_singleton_seq p a Load EXTRA star_expression star_expression expr_ty memo a bitwise_or _PyAST_Starred a Load EXTRA expression star_named_exp,en
1027,ressions asdl_expr_seq a asdl_expr_seq star_named_expression a star_named_expression expr_ty a bitwise_or _PyAST_Starred a Load EXTRA named_expression assignment_expression expr_ty a NAME b expression CHECK_VERSION expr_ty 8 Assignment expressions are _PyAST_NamedExpr CHECK expr_ty _PyPegen_set_expr_context p a Store b EXTRA named_expression expr_ty assignment_expression invalid_named_expression expression disjunction expr_ty memo a conjunction b or c conjunction c _PyAST_BoolOp Or CHECK asdl_expr_seq _PyPegen_seq_insert_in_front p a b EXTRA conjunction conjunction expr_ty memo a inversion b and c inversion c _PyAST_BoolOp And CHECK asdl_expr_seq _PyPegen_seq_insert_in_front p a b EXTRA inversion inversion expr_ty memo not a inversion _PyAST_UnaryOp Not a EXTRA comparison Comparison operators comparison expr_ty a bitwise_or b compare_op_bitwise_or_pair _PyAST_Compare a CHECK asdl_int_seq _PyPegen_get_cmpops p b CHECK asdl_expr_seq _PyPegen_get_exprs p b EXTRA bitwise_or compare_op_bitwise_or_pair CmpopExprPair eq_bitwise_or noteq_bitwise_or lte_bitwise_or lt_bitwise_or gte_bitwise_or gt_bitwise_or notin_bitwise_or in_bitwise_or isnot_bitwise_or is_bitwise_or eq_bitwise_or CmpopExprPair a bitwise_or _PyPegen_cmpop_expr_pair p Eq a noteq_bitwise_or CmpopExprPair tok _PyPegen_check_barry_as_flufl p tok NULL tok a bitwise_or _PyPegen_cmpop_expr_pair p NotEq a lte_bitwise_or CmpopExprPair a bitwise_or _PyPegen_cmpop_expr_pair p LtE a lt_bitwise_or CmpopExprPair a bitwise_or _PyPegen_cmpop_expr_pair p Lt a gte_bitwise_or CmpopExprPair a bitwise_or _PyPegen_cmpop_expr_pair p GtE a gt_bitwise_or CmpopExprPair a bitwise_or _PyPegen_cmpop_expr_pair p Gt a notin_bitwise_or CmpopExprPair not in a bitwise_or _PyPegen_cmpop_expr_pair p NotIn a in_bitwise_or CmpopExprPair in a bitwise_or _PyPegen_cmpop_expr_pair p In a isnot_bitwise_or CmpopExprPair is not a bitwise_or _PyPegen_cmpop_expr_pair p IsNot a is_bitwise_or CmpopExprPair is a bitwise_or _PyPegen_cmpop_expr_pair p Is a Bitwise operators bitwise_or expr_ty a bitwise_or b bitwise_xor _PyAST_BinOp a BitOr b EXTRA bitwise_xor bitwise_xor expr_ty a bitwise_xor b bitwise_and _PyAST_BinOp a BitXor b EXTRA bitwise_and bitwise_and expr_ty a bitwise_and b shift_expr _PyAST_BinOp a BitAnd b EXTRA shift_expr shift_expr expr_ty a shift_expr b sum _PyAST_BinOp a LShift b EXTRA a shift_expr b sum _PyAST_BinOp a RShift b EXTRA sum Arithmetic operators sum expr_ty a sum b term _PyAST_BinOp a Add b EXTRA a sum b term _PyAST_BinOp a Sub b EXTRA term term expr_ty a term b factor _PyAST_BinOp a Mult b EXTRA a term b factor _PyAST_BinOp a Div b EXTRA a term b factor _PyAST_BinOp a FloorDiv b EXTRA a term b factor _PyAST_BinOp a Mod b EXTRA a term b factor CHECK_VERSION expr_ty 5 The operator is _PyAST_BinOp a MatMult b EXTRA factor factor expr_ty memo a factor _PyAST_UnaryOp UAdd a EXTRA a factor _PyAST_UnaryOp USub a EXTRA a factor _PyAST_UnaryOp Invert a EXTRA power power expr_ty a await_primary b factor _PyAST_BinOp a Pow b EXTRA await_primary Primary elements Primary elements are things like obj something something obj something obj something obj await_primary expr_ty memo AWAIT a primary CHECK_VERSION expr_ty 5 Await expressions are _PyAST_Await a EXTRA primary primary expr_ty a primary b NAME _PyAST_Attribute a b v Name id Load EXTRA a primary b genexp _PyAST_Call a CHECK asdl_expr_seq asdl_expr_seq _PyPegen_singleton_seq p b NULL EXTRA a primary b arguments _PyAST_Call a b expr_ty b v Call args NULL b expr_ty b v Call keywords NULL EXTRA a primary b slices _PyAST_Subscript a b Load EXTRA atom slices expr_ty a slice a a asdl_expr_seq slice starred_expression _PyAST_Tuple a Load EXTRA slice expr_ty a expression b expression c d expression d _PyAST_Slice a b c EXTRA a named_expression a atom expr_ty NAME True _PyAST_Constant Py_True NULL EXTRA False _PyAST_Constant Py_False NULL EXTRA None _PyAST_Constant Py_None NULL EXTRA STRING FSTRING_START strings NUMBER tuple group genexp list listcomp dict set dictcomp setcomp _PyAST_Constant Py_Ellipsis NULL EXTRA group expr_ty a yield_expr named_expres,en
1028,sion a invalid_group Lambda functions lambdef expr_ty lambda a lambda_params b expression _PyAST_Lambda a a CHECK arguments_ty _PyPegen_empty_arguments p b EXTRA lambda_params arguments_ty invalid_lambda_parameters lambda_parameters lambda_parameters etc duplicates parameters but without annotations or type comments and if there s no comma after a parameter we expect a colon not a close parenthesis For more see parameters above lambda_parameters arguments_ty a lambda_slash_no_default b asdl_arg_seq lambda_param_no_default c lambda_param_with_default d lambda_star_etc CHECK_VERSION arguments_ty 8 Positional only parameters are _PyPegen_make_arguments p a NULL b c d a lambda_slash_with_default b lambda_param_with_default c lambda_star_etc CHECK_VERSION arguments_ty 8 Positional only parameters are _PyPegen_make_arguments p NULL a NULL b c a asdl_arg_seq lambda_param_no_default b lambda_param_with_default c lambda_star_etc _PyPegen_make_arguments p NULL NULL a b c a lambda_param_with_default b lambda_star_etc _PyPegen_make_arguments p NULL NULL NULL a b a lambda_star_etc _PyPegen_make_arguments p NULL NULL NULL NULL a lambda_slash_no_default asdl_arg_seq a asdl_arg_seq lambda_param_no_default a a asdl_arg_seq lambda_param_no_default a lambda_slash_with_default SlashWithDefault a lambda_param_no_default b lambda_param_with_default _PyPegen_slash_with_default p asdl_arg_seq a b a lambda_param_no_default b lambda_param_with_default _PyPegen_slash_with_default p asdl_arg_seq a b lambda_star_etc StarEtc invalid_lambda_star_etc a lambda_param_no_default b lambda_param_maybe_default c lambda_kwds _PyPegen_star_etc p a b c b lambda_param_maybe_default c lambda_kwds _PyPegen_star_etc p NULL b c a lambda_kwds _PyPegen_star_etc p NULL NULL a lambda_kwds arg_ty invalid_lambda_kwds a lambda_param_no_default a lambda_param_no_default arg_ty a lambda_param a a lambda_param a lambda_param_with_default NameDefaultPair a lambda_param c default _PyPegen_name_default_pair p a c NULL a lambda_param c default _PyPegen_name_default_pair p a c NULL lambda_param_maybe_default NameDefaultPair a lambda_param c default _PyPegen_name_default_pair p a c NULL a lambda_param c default _PyPegen_name_default_pair p a c NULL lambda_param arg_ty a NAME _PyAST_arg a v Name id NULL NULL EXTRA LITERALS fstring_middle expr_ty fstring_replacement_field t FSTRING_MIDDLE _PyPegen_constant_from_token p t fstring_replacement_field expr_ty a yield_expr star_expressions debug_expr conversion fstring_conversion format fstring_full_format_spec rbrace _PyPegen_formatted_value p a debug_expr conversion format rbrace EXTRA invalid_replacement_field fstring_conversion ResultTokenWithMetadata conv_token conv NAME _PyPegen_check_fstring_conversion p conv_token conv fstring_full_format_spec ResultTokenWithMetadata colon spec fstring_format_spec _PyPegen_setup_full_format_spec p colon asdl_expr_seq spec EXTRA fstring_format_spec expr_ty t FSTRING_MIDDLE _PyPegen_decoded_constant_from_token p t fstring_replacement_field fstring expr_ty a FSTRING_START b fstring_middle c FSTRING_END _PyPegen_joined_str p a asdl_expr_seq b c string expr_ty s Token STRING _PyPegen_constant_from_string p s strings expr_ty memo a asdl_expr_seq fstring string _PyPegen_concatenate_strings p a EXTRA list expr_ty a star_named_expressions _PyAST_List a Load EXTRA tuple expr_ty a y star_named_expression z star_named_expressions _PyPegen_seq_insert_in_front p y z _PyAST_Tuple a Load EXTRA set expr_ty a star_named_expressions _PyAST_Set a EXTRA Dicts dict expr_ty a double_starred_kvpairs _PyAST_Dict CHECK asdl_expr_seq _PyPegen_get_keys p a CHECK asdl_expr_seq _PyPegen_get_values p a EXTRA invalid_double_starred_kvpairs double_starred_kvpairs asdl_seq a double_starred_kvpair a double_starred_kvpair KeyValuePair a bitwise_or _PyPegen_key_value_pair p NULL a kvpair kvpair KeyValuePair a expression b expression _PyPegen_key_value_pair p a b Comprehensions Generators for_if_clauses asdl_comprehension_seq a asdl_comprehension_seq for_if_clause a for_if_clause comprehension_ty ASYNC for a star_targets in b disjuncti,en
1029,on c asdl_expr_seq if z disjunction z CHECK_VERSION comprehension_ty 6 Async comprehensions are _PyAST_comprehension a b c 1 p arena for a star_targets in b disjunction c asdl_expr_seq if z disjunction z _PyAST_comprehension a b c 0 p arena invalid_for_target listcomp expr_ty a named_expression b for_if_clauses _PyAST_ListComp a b EXTRA invalid_comprehension setcomp expr_ty a named_expression b for_if_clauses _PyAST_SetComp a b EXTRA invalid_comprehension genexp expr_ty a assignment_expression expression b for_if_clauses _PyAST_GeneratorExp a b EXTRA invalid_comprehension dictcomp expr_ty a kvpair b for_if_clauses _PyAST_DictComp a key a value b EXTRA invalid_dict_comprehension FUNCTION CALL ARGUMENTS arguments expr_ty memo a args a invalid_arguments args expr_ty a asdl_expr_seq starred_expression assignment_expression expression b k kwargs k _PyPegen_collect_call_seqs p a b EXTRA a kwargs _PyAST_Call _PyPegen_dummy_name p CHECK_NULL_ALLOWED asdl_expr_seq _PyPegen_seq_extract_starred_exprs p a CHECK_NULL_ALLOWED asdl_keyword_seq _PyPegen_seq_delete_starred_exprs p a EXTRA kwargs asdl_seq a kwarg_or_starred b kwarg_or_double_starred _PyPegen_join_sequences p a b kwarg_or_starred kwarg_or_double_starred starred_expression expr_ty invalid_starred_expression a expression _PyAST_Starred a Load EXTRA kwarg_or_starred KeywordOrStarred invalid_kwarg a NAME b expression _PyPegen_keyword_or_starred p CHECK keyword_ty _PyAST_keyword a v Name id b EXTRA 1 a starred_expression _PyPegen_keyword_or_starred p a 0 kwarg_or_double_starred KeywordOrStarred invalid_kwarg a NAME b expression _PyPegen_keyword_or_starred p CHECK keyword_ty _PyAST_keyword a v Name id b EXTRA 1 a expression _PyPegen_keyword_or_starred p CHECK keyword_ty _PyAST_keyword NULL a EXTRA 1 ASSIGNMENT TARGETS Generic targets NOTE star_targets may contain bitwise_or targets may not star_targets expr_ty a star_target a a star_target b c star_target c _PyAST_Tuple CHECK asdl_expr_seq _PyPegen_seq_insert_in_front p a b Store EXTRA star_targets_list_seq asdl_expr_seq a asdl_expr_seq star_target a star_targets_tuple_seq asdl_expr_seq a star_target b c star_target c asdl_expr_seq _PyPegen_seq_insert_in_front p a b a star_target asdl_expr_seq _PyPegen_singleton_seq p a star_target expr_ty memo a star_target _PyAST_Starred CHECK expr_ty _PyPegen_set_expr_context p a Store Store EXTRA target_with_star_atom target_with_star_atom expr_ty memo a t_primary b NAME t_lookahead _PyAST_Attribute a b v Name id Store EXTRA a t_primary b slices t_lookahead _PyAST_Subscript a b Store EXTRA star_atom star_atom expr_ty a NAME _PyPegen_set_expr_context p a Store a target_with_star_atom _PyPegen_set_expr_context p a Store a star_targets_tuple_seq _PyAST_Tuple a Store EXTRA a star_targets_list_seq _PyAST_List a Store EXTRA single_target expr_ty single_subscript_attribute_target a NAME _PyPegen_set_expr_context p a Store a single_target a single_subscript_attribute_target expr_ty a t_primary b NAME t_lookahead _PyAST_Attribute a b v Name id Store EXTRA a t_primary b slices t_lookahead _PyAST_Subscript a b Store EXTRA t_primary expr_ty a t_primary b NAME t_lookahead _PyAST_Attribute a b v Name id Load EXTRA a t_primary b slices t_lookahead _PyAST_Subscript a b Load EXTRA a t_primary b genexp t_lookahead _PyAST_Call a CHECK asdl_expr_seq asdl_expr_seq _PyPegen_singleton_seq p b NULL EXTRA a t_primary b arguments t_lookahead _PyAST_Call a b expr_ty b v Call args NULL b expr_ty b v Call keywords NULL EXTRA a atom t_lookahead a t_lookahead Targets for del statements del_targets asdl_expr_seq a asdl_expr_seq del_target a del_target expr_ty memo a t_primary b NAME t_lookahead _PyAST_Attribute a b v Name id Del EXTRA a t_primary b slices t_lookahead _PyAST_Subscript a b Del EXTRA del_t_atom del_t_atom expr_ty a NAME _PyPegen_set_expr_context p a Del a del_target _PyPegen_set_expr_context p a Del a del_targets _PyAST_Tuple a Del EXTRA a del_targets _PyAST_List a Del EXTRA TYPING ELEMENTS type_expressions allow but ignore them type_expressions asdl_expr_seq a expression b expression c expression asdl_expr_s,en
1030,eq _PyPegen_seq_append_to_end p CHECK asdl_seq _PyPegen_seq_append_to_end p a b c a expression b expression asdl_expr_seq _PyPegen_seq_append_to_end p a b a expression b expression asdl_expr_seq _PyPegen_seq_append_to_end p a b a expression b expression asdl_expr_seq _PyPegen_seq_append_to_end p CHECK asdl_seq _PyPegen_singleton_seq p a b a expression asdl_expr_seq _PyPegen_singleton_seq p a a expression asdl_expr_seq _PyPegen_singleton_seq p a a asdl_expr_seq expression a func_type_comment Token NEWLINE t TYPE_COMMENT NEWLINE INDENT t Must be followed by indented block invalid_double_type_comments TYPE_COMMENT END OF THE GRAMMAR START OF INVALID RULES From here on there are rules for invalid syntax with specialised error messages invalid_arguments starred_expression assignment_expression expression kwargs kwargs b RAISE_SYNTAX_ERROR_KNOWN_LOCATION b iterable argument unpacking follows keyword argument unpacking a expression b for_if_clauses args expression for_if_clauses RAISE_SYNTAX_ERROR_KNOWN_RANGE a _PyPegen_get_last_comprehension_item PyPegen_last_item b comprehension_ty Generator expression must be parenthesized a NAME b expression for_if_clauses RAISE_SYNTAX_ERROR_KNOWN_RANGE a b invalid syntax Maybe you meant or instead of args a NAME b RAISE_SYNTAX_ERROR_KNOWN_RANGE a b expected argument value expression a args b for_if_clauses _PyPegen_nonparen_genexp_in_call p a b args a expression b for_if_clauses RAISE_SYNTAX_ERROR_KNOWN_RANGE a _PyPegen_get_last_comprehension_item PyPegen_last_item b comprehension_ty Generator expression must be parenthesized a args args _PyPegen_arguments_parsing_error p a invalid_kwarg a Token True False None b RAISE_SYNTAX_ERROR_KNOWN_RANGE a b cannot assign to s PyBytes_AS_STRING a bytes a NAME b expression for_if_clauses RAISE_SYNTAX_ERROR_KNOWN_RANGE a b invalid syntax Maybe you meant or instead of NAME a expression b RAISE_SYNTAX_ERROR_KNOWN_RANGE a b expression cannot contain assignment perhaps you meant a expression b expression RAISE_SYNTAX_ERROR_KNOWN_RANGE a b cannot assign to keyword argument unpacking IMPORTANT Note that the _without_invalid suffix causes the rule to not call invalid rules under it expression_without_invalid expr_ty a disjunction if b disjunction else c expression _PyAST_IfExp b a c EXTRA disjunction lambdef invalid_legacy_expression a NAME b star_expressions _PyPegen_check_legacy_stmt p a RAISE_SYNTAX_ERROR_KNOWN_RANGE a b Missing parentheses in call to U Did you mean U a v Name id a v Name id NULL invalid_expression NAME STRING is not matched so we don t show this error with some invalid string prefixes like kf dsfsdf Soft keywords need to also be ignored because they can be parsed as NAME NAME NAME STRING SOFT_KEYWORD a disjunction b expression_without_invalid _PyPegen_check_legacy_stmt p a NULL p tokens p mark 1 level 0 NULL RAISE_SYNTAX_ERROR_KNOWN_RANGE a b invalid syntax Perhaps you forgot a comma a disjunction if b disjunction else RAISE_SYNTAX_ERROR_KNOWN_RANGE a b expected else after if expression a lambda lambda_params b FSTRING_MIDDLE RAISE_SYNTAX_ERROR_KNOWN_RANGE a b f string lambda expressions are not allowed without parentheses invalid_named_expression memo a expression expression RAISE_SYNTAX_ERROR_KNOWN_LOCATION a cannot use assignment expressions with s _PyPegen_get_expr_name a a NAME b bitwise_or RAISE_SYNTAX_ERROR_KNOWN_RANGE a b invalid syntax Maybe you meant or instead of list tuple genexp True None False a bitwise_or b bitwise_or RAISE_SYNTAX_ERROR_KNOWN_LOCATION a cannot assign to s here Maybe you meant instead of _PyPegen_get_expr_name a invalid_assignment a invalid_ann_assign_target expression RAISE_SYNTAX_ERROR_KNOWN_LOCATION a only single target not s can be annotated _PyPegen_get_expr_name a a star_named_expression star_named_expressions expression RAISE_SYNTAX_ERROR_KNOWN_LOCATION a only single target not tuple can be annotated a expression expression RAISE_SYNTAX_ERROR_KNOWN_LOCATION a illegal target for annotation star_targets a star_expressions RAISE_SYNTAX_ERROR_INVALID_TARGET STAR_TARGETS a star_targets a yield_expr RAISE_S,en
1031,YNTAX_ERROR_KNOWN_LOCATION a assignment to yield expression not possible a star_expressions augassign yield_expr star_expressions RAISE_SYNTAX_ERROR_KNOWN_LOCATION a s is an illegal expression for augmented assignment _PyPegen_get_expr_name a invalid_ann_assign_target expr_ty list tuple a invalid_ann_assign_target a invalid_del_stmt del a star_expressions RAISE_SYNTAX_ERROR_INVALID_TARGET DEL_TARGETS a invalid_block NEWLINE INDENT RAISE_INDENTATION_ERROR expected an indented block invalid_comprehension a starred_expression for_if_clauses RAISE_SYNTAX_ERROR_KNOWN_LOCATION a iterable unpacking cannot be used in comprehension a star_named_expression b star_named_expressions for_if_clauses RAISE_SYNTAX_ERROR_KNOWN_RANGE a PyPegen_last_item b expr_ty did you forget parentheses around the comprehension target a star_named_expression b for_if_clauses RAISE_SYNTAX_ERROR_KNOWN_RANGE a b did you forget parentheses around the comprehension target invalid_dict_comprehension a bitwise_or for_if_clauses RAISE_SYNTAX_ERROR_KNOWN_LOCATION a dict unpacking cannot be used in dict comprehension invalid_parameters a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a at least one argument must precede slash_no_default slash_with_default param_maybe_default a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a may appear only once slash_no_default param_no_default invalid_parameters_helper a param_no_default RAISE_SYNTAX_ERROR_KNOWN_LOCATION a parameter without a default follows parameter with a default param_no_default a param_no_default b RAISE_SYNTAX_ERROR_KNOWN_RANGE a b Function parameters cannot be parenthesized slash_no_default slash_with_default param_maybe_default param_no_default param_maybe_default a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a must be ahead of param_maybe_default a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a expected comma between and invalid_default a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a expected default value expression invalid_star_etc a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a named arguments must follow bare TYPE_COMMENT RAISE_SYNTAX_ERROR bare has associated type comment param a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a var positional argument cannot have default value param_no_default param_maybe_default a param_no_default RAISE_SYNTAX_ERROR_KNOWN_LOCATION a argument may appear only once invalid_kwds param a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a var keyword argument cannot have default value param a param RAISE_SYNTAX_ERROR_KNOWN_LOCATION a arguments cannot follow var keyword argument param a Token RAISE_SYNTAX_ERROR_KNOWN_LOCATION a arguments cannot follow var keyword argument invalid_parameters_helper This is only there to avoid type errors a slash_with_default _PyPegen_singleton_seq p a param_with_default invalid_lambda_parameters a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a at least one argument must precede lambda_slash_no_default lambda_slash_with_default lambda_param_maybe_default a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a may appear only once lambda_slash_no_default lambda_param_no_default invalid_lambda_parameters_helper a lambda_param_no_default RAISE_SYNTAX_ERROR_KNOWN_LOCATION a parameter without a default follows parameter with a default lambda_param_no_default a lambda_param b RAISE_SYNTAX_ERROR_KNOWN_RANGE a b Lambda expression parameters cannot be parenthesized lambda_slash_no_default lambda_slash_with_default lambda_param_maybe_default lambda_param_no_default lambda_param_maybe_default a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a must be ahead of lambda_param_maybe_default a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a expected comma between and invalid_lambda_parameters_helper a lambda_slash_with_default _PyPegen_singleton_seq p a lambda_param_with_default invalid_lambda_star_etc RAISE_SYNTAX_ERROR named arguments must follow bare lambda_param a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a var positional argument cannot have default value lambda_param_no_default lambda_param_maybe_default a lambda_param_no_default RAISE_SYNTAX_ERROR_KNOWN_LOCATION a argument may appear only once invalid_lambda_kwds lambda_param a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a var keyword argument cannot have defau,en
1032,lt value lambda_param a lambda_param RAISE_SYNTAX_ERROR_KNOWN_LOCATION a arguments cannot follow var keyword argument lambda_param a Token RAISE_SYNTAX_ERROR_KNOWN_LOCATION a arguments cannot follow var keyword argument invalid_double_type_comments TYPE_COMMENT NEWLINE TYPE_COMMENT NEWLINE INDENT RAISE_SYNTAX_ERROR Cannot have two type comments on def invalid_with_item expression as a expression RAISE_SYNTAX_ERROR_INVALID_TARGET STAR_TARGETS a invalid_for_target ASYNC for a star_expressions RAISE_SYNTAX_ERROR_INVALID_TARGET FOR_TARGETS a invalid_group a starred_expression RAISE_SYNTAX_ERROR_KNOWN_LOCATION a cannot use starred expression here a expression RAISE_SYNTAX_ERROR_KNOWN_LOCATION a cannot use double starred expression here invalid_import a import dotted_name from dotted_name RAISE_SYNTAX_ERROR_STARTING_FROM a Did you mean to use from import instead invalid_import_from_targets import_from_as_names NEWLINE RAISE_SYNTAX_ERROR trailing comma not allowed without surrounding parentheses invalid_with_stmt ASYNC with expression as star_target NEWLINE RAISE_SYNTAX_ERROR expected ASYNC with expressions as star_target NEWLINE RAISE_SYNTAX_ERROR expected invalid_with_stmt_indent ASYNC a with expression as star_target NEWLINE INDENT RAISE_INDENTATION_ERROR expected an indented block after with statement on line d a lineno ASYNC a with expressions as star_target NEWLINE INDENT RAISE_INDENTATION_ERROR expected an indented block after with statement on line d a lineno invalid_try_stmt a try NEWLINE INDENT RAISE_INDENTATION_ERROR expected an indented block after try statement on line d a lineno try block except finally RAISE_SYNTAX_ERROR expected except or finally block try block except_block a except b expression as NAME RAISE_SYNTAX_ERROR_KNOWN_RANGE a b cannot have both except and except on the same try try block except_star_block a except expression as NAME RAISE_SYNTAX_ERROR_KNOWN_LOCATION a cannot have both except and except on the same try invalid_except_stmt except a expression expressions as NAME RAISE_SYNTAX_ERROR_STARTING_FROM a multiple exception types must be parenthesized a except expression as NAME NEWLINE RAISE_SYNTAX_ERROR expected a except NEWLINE RAISE_SYNTAX_ERROR expected a except NEWLINE RAISE_SYNTAX_ERROR expected one or more exception types invalid_finally_stmt a finally NEWLINE INDENT RAISE_INDENTATION_ERROR expected an indented block after finally statement on line d a lineno invalid_except_stmt_indent a except expression as NAME NEWLINE INDENT RAISE_INDENTATION_ERROR expected an indented block after except statement on line d a lineno a except NEWLINE INDENT RAISE_INDENTATION_ERROR expected an indented block after except statement on line d a lineno invalid_except_star_stmt_indent a except expression as NAME NEWLINE INDENT RAISE_INDENTATION_ERROR expected an indented block after except statement on line d a lineno invalid_match_stmt match subject_expr NEWLINE CHECK_VERSION void 10 Pattern matching is RAISE_SYNTAX_ERROR expected a match subject subject_expr NEWLINE INDENT RAISE_INDENTATION_ERROR expected an indented block after match statement on line d a lineno invalid_case_block case patterns guard NEWLINE RAISE_SYNTAX_ERROR expected a case patterns guard NEWLINE INDENT RAISE_INDENTATION_ERROR expected an indented block after case statement on line d a lineno invalid_as_pattern or_pattern as a _ RAISE_SYNTAX_ERROR_KNOWN_LOCATION a cannot use _ as a target or_pattern as NAME a expression RAISE_SYNTAX_ERROR_KNOWN_LOCATION a invalid pattern target invalid_class_pattern name_or_attr a invalid_class_argument_pattern RAISE_SYNTAX_ERROR_KNOWN_RANGE PyPegen_first_item a pattern_ty PyPegen_last_item a pattern_ty positional patterns follow keyword patterns invalid_class_argument_pattern asdl_pattern_seq positional_patterns keyword_patterns a positional_patterns a invalid_if_stmt if named_expression NEWLINE RAISE_SYNTAX_ERROR expected a if a named_expression NEWLINE INDENT RAISE_INDENTATION_ERROR expected an indented block after if statement on line d a lineno invalid_elif_stmt elif named_expression NEWLINE RAISE,en
1033,_SYNTAX_ERROR expected a elif named_expression NEWLINE INDENT RAISE_INDENTATION_ERROR expected an indented block after elif statement on line d a lineno invalid_else_stmt a else NEWLINE INDENT RAISE_INDENTATION_ERROR expected an indented block after else statement on line d a lineno invalid_while_stmt while named_expression NEWLINE RAISE_SYNTAX_ERROR expected a while named_expression NEWLINE INDENT RAISE_INDENTATION_ERROR expected an indented block after while statement on line d a lineno invalid_for_stmt ASYNC for star_targets in star_expressions NEWLINE RAISE_SYNTAX_ERROR expected ASYNC a for star_targets in star_expressions NEWLINE INDENT RAISE_INDENTATION_ERROR expected an indented block after for statement on line d a lineno invalid_def_raw ASYNC a def NAME type_params params expression NEWLINE INDENT RAISE_INDENTATION_ERROR expected an indented block after function definition on line d a lineno invalid_class_def_raw class NAME type_params arguments NEWLINE RAISE_SYNTAX_ERROR expected a class NAME type_params arguments NEWLINE INDENT RAISE_INDENTATION_ERROR expected an indented block after class definition on line d a lineno invalid_double_starred_kvpairs double_starred_kvpair invalid_kvpair expression a bitwise_or RAISE_SYNTAX_ERROR_STARTING_FROM a cannot use a starred expression in a dictionary value expression a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a expression expected after dictionary key and invalid_kvpair a expression RAISE_ERROR_KNOWN_LOCATION p PyExc_SyntaxError a lineno a end_col_offset 1 a end_lineno 1 expected after dictionary key expression a bitwise_or RAISE_SYNTAX_ERROR_STARTING_FROM a cannot use a starred expression in a dictionary value expression a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a expression expected after dictionary key and invalid_starred_expression a expression b expression RAISE_SYNTAX_ERROR_KNOWN_RANGE a b cannot assign to iterable argument unpacking invalid_replacement_field a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a f string valid expression required before a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a f string valid expression required before a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a f string valid expression required before a RAISE_SYNTAX_ERROR_KNOWN_LOCATION a f string valid expression required before yield_expr star_expressions RAISE_SYNTAX_ERROR_ON_NEXT_TOKEN f string expecting a valid expression after yield_expr star_expressions PyErr_Occurred NULL RAISE_SYNTAX_ERROR_ON_NEXT_TOKEN f string expecting or or or yield_expr star_expressions PyErr_Occurred NULL RAISE_SYNTAX_ERROR_ON_NEXT_TOKEN f string expecting or or yield_expr star_expressions invalid_conversion_character yield_expr star_expressions NAME PyErr_Occurred NULL RAISE_SYNTAX_ERROR_ON_NEXT_TOKEN f string expecting or yield_expr star_expressions NAME fstring_format_spec PyErr_Occurred NULL RAISE_SYNTAX_ERROR_ON_NEXT_TOKEN f string expecting or format specs yield_expr star_expressions NAME PyErr_Occurred NULL RAISE_SYNTAX_ERROR_ON_NEXT_TOKEN f string expecting invalid_conversion_character RAISE_SYNTAX_ERROR_ON_NEXT_TOKEN f string missing conversion character NAME RAISE_SYNTAX_ERROR_ON_NEXT_TOKEN f string invalid conversion character,en
1034,email generator Generating MIME documents Source code Lib email generator py One of the most common tasks is to generate the flat serialized version of the email message represented by a message object structure You will need to do this if you want to send your message via smtplib SMTP sendmail or the nntplib module or print the message on the console Taking a message object structure and producing a serialized representation is the job of the generator classes As with the email parser module you aren t limited to the functionality of the bundled generator you could write one from scratch yourself However the bundled generator knows how to generate most email in a standards compliant way should handle MIME and non MIME email messages just fine and is designed so that the bytes oriented parsing and generation operations are inverses assuming the same non transforming policy is used for both That is parsing the serialized byte stream via the BytesParser class and then regenerating the serialized byte stream using BytesGenerator should produce output identical to the input 1 On the other hand using the generator on an EmailMessage constructed by program may result in changes to the EmailMessage object as defaults are filled in The Generator class can be used to flatten a message into a text as opposed to binary serialized representation but since Unicode cannot represent binary data directly the message is of necessity transformed into something that contains only ASCII characters using the standard email RFC Content Transfer Encoding techniques for encoding email messages for transport over channels that are not 8 bit clean To accommodate reproducible processing of SMIME signed messages Generator disables header folding for message parts of type multipart signed and all subparts class email generator BytesGenerator outfp mangle_from_ None maxheaderlen None policy None Return a BytesGenerator object that will write any message provided to the flatten method or any surrogateescape encoded text provided to the write method to the file like object outfp outfp must support a write method that accepts binary data If optional mangle_from_ is True put a character in front of any line in the body that starts with the exact string From that is From followed by a space at the beginning of a line mangle_from_ defaults to the value of the mangle_from_ setting of the policy which is True for the compat32 policy and False for all others mangle_from_ is intended for use when messages are stored in Unix mbox format see mailbox and WHY THE CONTENT LENGTH FORMAT IS BAD If maxheaderlen is not None refold any header lines that are longer than maxheaderlen or if 0 do not rewrap any headers If manheaderlen is None the default wrap headers and other message lines according to the policy settings If policy is specified use that policy to control message generation If policy is None the default use the policy associated with the Message or EmailMessage object passed to flatten to control the message generation See email policy for details on what policy controls New in version 3 2 Changed in version 3 3 Added the policy keyword Changed in version 3 6 The default behavior of the mangle_from_ and maxheaderlen parameters is to follow the policy flatten msg unixfrom False linesep None Print the textual representation of the message object structure rooted at msg to the output file specified when the BytesGenerator instance was created If the policy option cte_type is 8bit the default copy any headers in the original parsed message that have not been modified to the output with any bytes with the high bit set reproduced as in the original and preserve the non ASCII Content Transfer Encoding of any body parts that have them If cte_type is 7bit convert the bytes with the high bit set as needed using an ASCII compatible Content Transfer Encoding That is transform parts with non ASCII Content Transfer Encoding Content Transfer Encoding 8bit to an ASCII compatible Content Transfer Encoding and encode RFC invalid non ASCII bytes in headers using the MIME unkn,en
1035,own 8bit character set thus rendering them RFC compliant If unixfrom is True print the envelope header delimiter used by the Unix mailbox format see mailbox before the first of the RFC 5322 headers of the root message object If the root object has no envelope header craft a standard one The default is False Note that for subparts no envelope header is ever printed If linesep is not None use it as the separator character between all the lines of the flattened message If linesep is None the default use the value specified in the policy clone fp Return an independent clone of this BytesGenerator instance with the exact same option settings and fp as the new outfp write s Encode s using the ASCII codec and the surrogateescape error handler and pass it to the write method of the outfp passed to the BytesGenerator s constructor As a convenience EmailMessage provides the methods as_bytes and bytes aMessage a k a __bytes__ which simplify the generation of a serialized binary representation of a message object For more detail see email message Because strings cannot represent binary data the Generator class must convert any binary data in any message it flattens to an ASCII compatible format by converting them to an ASCII compatible Content Transfer_Encoding Using the terminology of the email RFCs you can think of this as Generator serializing to an I O stream that is not 8 bit clean In other words most applications will want to be using BytesGenerator and not Generator class email generator Generator outfp mangle_from_ None maxheaderlen None policy None Return a Generator object that will write any message provided to the flatten method or any text provided to the write method to the file like object outfp outfp must support a write method that accepts string data If optional mangle_from_ is True put a character in front of any line in the body that starts with the exact string From that is From followed by a space at the beginning of a line mangle_from_ defaults to the value of the mangle_from_ setting of the policy which is True for the compat32 policy and False for all others mangle_from_ is intended for use when messages are stored in Unix mbox format see mailbox and WHY THE CONTENT LENGTH FORMAT IS BAD If maxheaderlen is not None refold any header lines that are longer than maxheaderlen or if 0 do not rewrap any headers If manheaderlen is None the default wrap headers and other message lines according to the policy settings If policy is specified use that policy to control message generation If policy is None the default use the policy associated with the Message or EmailMessage object passed to flatten to control the message generation See email policy for details on what policy controls Changed in version 3 3 Added the policy keyword Changed in version 3 6 The default behavior of the mangle_from_ and maxheaderlen parameters is to follow the policy flatten msg unixfrom False linesep None Print the textual representation of the message object structure rooted at msg to the output file specified when the Generator instance was created If the policy option cte_type is 8bit generate the message as if the option were set to 7bit This is required because strings cannot represent non ASCII bytes Convert any bytes with the high bit set as needed using an ASCII compatible Content Transfer Encoding That is transform parts with non ASCII Content Transfer Encoding Content Transfer Encoding 8bit to an ASCII compatible Content Transfer Encoding and encode RFC invalid non ASCII bytes in headers using the MIME unknown 8bit character set thus rendering them RFC compliant If unixfrom is True print the envelope header delimiter used by the Unix mailbox format see mailbox before the first of the RFC 5322 headers of the root message object If the root object has no envelope header craft a standard one The default is False Note that for subparts no envelope header is ever printed If linesep is not None use it as the separator character between all the lines of the flattened message If linesep is None the default use the value specified in the p,en
1036,olicy Changed in version 3 2 Added support for re encoding 8bit message bodies and the linesep argument clone fp Return an independent clone of this Generator instance with the exact same options and fp as the new outfp write s Write s to the write method of the outfp passed to the Generator s constructor This provides just enough file like API for Generator instances to be used in the print function As a convenience EmailMessage provides the methods as_string and str aMessage a k a __str__ which simplify the generation of a formatted string representation of a message object For more detail see email message The email generator module also provides a derived class DecodedGenerator which is like the Generator base class except that non text parts are not serialized but are instead represented in the output stream by a string derived from a template filled in with information about the part class email generator DecodedGenerator outfp mangle_from_ None maxheaderlen None fmt None policy None Act like Generator except that for any subpart of the message passed to Generator flatten if the subpart is of main type text print the decoded payload of the subpart and if the main type is not text instead of printing it fill in the string fmt using information from the part and print the resulting filled in string To fill in fmt execute fmt part_info where part_info is a dictionary composed of the following keys and values type Full MIME type of the non text part maintype Main MIME type of the non text part subtype Sub MIME type of the non text part filename Filename of the non text part description Description associated with the non text part encoding Content transfer encoding of the non text part If fmt is None use the following default fmt Non text type s part of message omitted filename filename s Optional _mangle_from_ and maxheaderlen are as with the Generator base class Footnotes 1 This statement assumes that you use the appropriate setting for unixfrom and that there are no email policy settings calling for automatic adjustments for example refold_source must be none which is not the default It is also not 100 true since if the message does not conform to the RFC standards occasionally information about the exact original text is lost during parsing error recovery It is a goal to fix these latter edge cases when possible,en
1037,unittest Unit testing framework Source code Lib unittest __init__ py If you are already familiar with the basic concepts of testing you might want to skip to the list of assert methods The unittest unit testing framework was originally inspired by JUnit and has a similar flavor as major unit testing frameworks in other languages It supports test automation sharing of setup and shutdown code for tests aggregation of tests into collections and independence of the tests from the reporting framework To achieve this unittest supports some important concepts in an object oriented way test fixture A test fixture represents the preparation needed to perform one or more tests and any associated cleanup actions This may involve for example creating temporary or proxy databases directories or starting a server process test case A test case is the individual unit of testing It checks for a specific response to a particular set of inputs unittest provides a base class TestCase which may be used to create new test cases test suite A test suite is a collection of test cases test suites or both It is used to aggregate tests that should be executed together test runner A test runner is a component which orchestrates the execution of tests and provides the outcome to the user The runner may use a graphical interface a textual interface or return a special value to indicate the results of executing the tests See also Module doctest Another test support module with a very different flavor Simple Smalltalk Testing With Patterns Kent Beck s original paper on testing frameworks using the pattern shared by unittest pytest Third party unittest framework with a lighter weight syntax for writing tests For example assert func 10 42 The Python Testing Tools Taxonomy An extensive list of Python testing tools including functional testing frameworks and mock object libraries Testing in Python Mailing List A special interest group for discussion of testing and testing tools in Python The script Tools unittestgui unittestgui py in the Python source distribution is a GUI tool for test discovery and execution This is intended largely for ease of use for those new to unit testing For production environments it is recommended that tests be driven by a continuous integration system such as Buildbot Jenkins GitHub Actions or AppVeyor Basic example The unittest module provides a rich set of tools for constructing and running tests This section demonstrates that a small subset of the tools suffice to meet the needs of most users Here is a short script to test three string methods import unittest class TestStringMethods unittest TestCase def test_upper self self assertEqual foo upper FOO def test_isupper self self assertTrue FOO isupper self assertFalse Foo isupper def test_split self s hello world self assertEqual s split hello world check that s split fails when the separator is not a string with self assertRaises TypeError s split 2 if __name__ __main__ unittest main A testcase is created by subclassing unittest TestCase The three individual tests are defined with methods whose names start with the letters test This naming convention informs the test runner about which methods represent tests The crux of each test is a call to assertEqual to check for an expected result assertTrue or assertFalse to verify a condition or assertRaises to verify that a specific exception gets raised These methods are used instead of the assert statement so the test runner can accumulate all test results and produce a report The setUp and tearDown methods allow you to define instructions that will be executed before and after each test method They are covered in more detail in the section Organizing test code The final block shows a simple way to run the tests unittest main provides a command line interface to the test script When run from the command line the above script produces an output that looks like this Ran 3 tests in 0 000s OK Passing the v option to your test script will instruct unittest main to enable a higher level of verbosity and produce the following output test_i,en
1038,supper __main__ TestStringMethods test_isupper ok test_split __main__ TestStringMethods test_split ok test_upper __main__ TestStringMethods test_upper ok Ran 3 tests in 0 001s OK The above examples show the most commonly used unittest features which are sufficient to meet many everyday testing needs The remainder of the documentation explores the full feature set from first principles Changed in version 3 11 The behavior of returning a value from a test method other than the default None value is now deprecated Command Line Interface The unittest module can be used from the command line to run tests from modules classes or even individual test methods python m unittest test_module1 test_module2 python m unittest test_module TestClass python m unittest test_module TestClass test_method You can pass in a list with any combination of module names and fully qualified class or method names Test modules can be specified by file path as well python m unittest tests test_something py This allows you to use the shell filename completion to specify the test module The file specified must still be importable as a module The path is converted to a module name by removing the py and converting path separators into If you want to execute a test file that isn t importable as a module you should execute the file directly instead You can run tests with more detail higher verbosity by passing in the v flag python m unittest v test_module When executed without arguments Test Discovery is started python m unittest For a list of all the command line options python m unittest h Changed in version 3 2 In earlier versions it was only possible to run individual test methods and not modules or classes Command line options unittest supports these command line options b buffer The standard output and standard error streams are buffered during the test run Output during a passing test is discarded Output is echoed normally on test fail or error and is added to the failure messages c catch Control C during the test run waits for the current test to end and then reports all the results so far A second Control C raises the normal KeyboardInterrupt exception See Signal Handling for the functions that provide this functionality f failfast Stop the test run on the first error or failure k Only run test methods and classes that match the pattern or substring This option may be used multiple times in which case all test cases that match any of the given patterns are included Patterns that contain a wildcard character are matched against the test name using fnmatch fnmatchcase otherwise simple case sensitive substring matching is used Patterns are matched against the fully qualified test method name as imported by the test loader For example k foo matches foo_tests SomeTest test_something bar_tests SomeTest test_foo but not bar_tests FooTest test_something locals Show local variables in tracebacks durations N Show the N slowest test cases N 0 for all New in version 3 2 The command line options b c and f were added New in version 3 5 The command line option locals New in version 3 7 The command line option k New in version 3 12 The command line option durations The command line can also be used for test discovery for running all of the tests in a project or just a subset Test Discovery New in version 3 2 Unittest supports simple test discovery In order to be compatible with test discovery all of the test files must be modules or packages importable from the top level directory of the project this means that their filenames must be valid identifiers Test discovery is implemented in TestLoader discover but can also be used from the command line The basic command line usage is cd project_directory python m unittest discover Note As a shortcut python m unittest is the equivalent of python m unittest discover If you want to pass arguments to test discovery the discover sub command must be used explicitly The discover sub command has the following options v verbose Verbose output s start directory directory Directory to start discovery default p pattern pattern Pat,en
1039,tern to match test files test py default t top level directory directory Top level directory of project defaults to start directory The s p and t options can be passed in as positional arguments in that order The following two command lines are equivalent python m unittest discover s project_directory p _test py python m unittest discover project_directory _test py As well as being a path it is possible to pass a package name for example myproject subpackage test as the start directory The package name you supply will then be imported and its location on the filesystem will be used as the start directory Caution Test discovery loads tests by importing them Once test discovery has found all the test files from the start directory you specify it turns the paths into package names to import For example foo bar baz py will be imported as foo bar baz If you have a package installed globally and attempt test discovery on a different copy of the package then the import could happen from the wrong place If this happens test discovery will warn you and exit If you supply the start directory as a package name rather than a path to a directory then discover assumes that whichever location it imports from is the location you intended so you will not get the warning Test modules and packages can customize test loading and discovery by through the load_tests protocol Changed in version 3 4 Test discovery supports namespace packages for the start directory Note that you need to specify the top level directory too e g python m unittest discover s root namespace t root Changed in version 3 11 unittest dropped the namespace packages support in Python 3 11 It has been broken since Python 3 7 Start directory and subdirectories containing tests must be regular package that have __init__ py file Directories containing start directory still can be a namespace package In this case you need to specify start directory as dotted package name and target directory explicitly For example proj current directory namespace mypkg __init__ py test_mypkg py python m unittest discover s namespace mypkg t Organizing test code The basic building blocks of unit testing are test cases single scenarios that must be set up and checked for correctness In unittest test cases are represented by unittest TestCase instances To make your own test cases you must write subclasses of TestCase or use FunctionTestCase The testing code of a TestCase instance should be entirely self contained such that it can be run either in isolation or in arbitrary combination with any number of other test cases The simplest TestCase subclass will simply implement a test method i e a method whose name starts with test in order to perform specific testing code import unittest class DefaultWidgetSizeTestCase unittest TestCase def test_default_widget_size self widget Widget The widget self assertEqual widget size 50 50 Note that in order to test something we use one of the assert methods provided by the TestCase base class If the test fails an exception will be raised with an explanatory message and unittest will identify the test case as a failure Any other exceptions will be treated as errors Tests can be numerous and their set up can be repetitive Luckily we can factor out set up code by implementing a method called setUp which the testing framework will automatically call for every single test we run import unittest class WidgetTestCase unittest TestCase def setUp self self widget Widget The widget def test_default_widget_size self self assertEqual self widget size 50 50 incorrect default size def test_widget_resize self self widget resize 100 150 self assertEqual self widget size 100 150 wrong size after resize Note The order in which the various tests will be run is determined by sorting the test method names with respect to the built in ordering for strings If the setUp method raises an exception while the test is running the framework will consider the test to have suffered an error and the test method will not be executed Similarly we can provide a tearDown method that tidies up afte,en
1040,r the test method has been run import unittest class WidgetTestCase unittest TestCase def setUp self self widget Widget The widget def tearDown self self widget dispose If setUp succeeded tearDown will be run whether the test method succeeded or not Such a working environment for the testing code is called a test fixture A new TestCase instance is created as a unique test fixture used to execute each individual test method Thus setUp tearDown and __init__ will be called once per test It is recommended that you use TestCase implementations to group tests together according to the features they test unittest provides a mechanism for this the test suite represented by unittest s TestSuite class In most cases calling unittest main will do the right thing and collect all the module s test cases for you and execute them However should you want to customize the building of your test suite you can do it yourself def suite suite unittest TestSuite suite addTest WidgetTestCase test_default_widget_size suite addTest WidgetTestCase test_widget_resize return suite if __name__ __main__ runner unittest TextTestRunner runner run suite You can place the definitions of test cases and test suites in the same modules as the code they are to test such as widget py but there are several advantages to placing the test code in a separate module such as test_widget py The test module can be run standalone from the command line The test code can more easily be separated from shipped code There is less temptation to change test code to fit the code it tests without a good reason Test code should be modified much less frequently than the code it tests Tested code can be refactored more easily Tests for modules written in C must be in separate modules anyway so why not be consistent If the testing strategy changes there is no need to change the source code Re using old test code Some users will find that they have existing test code that they would like to run from unittest without converting every old test function to a TestCase subclass For this reason unittest provides a FunctionTestCase class This subclass of TestCase can be used to wrap an existing test function Set up and tear down functions can also be provided Given the following test function def testSomething something makeSomething assert something name is not None one can create an equivalent test case instance as follows with optional set up and tear down methods testcase unittest FunctionTestCase testSomething setUp makeSomethingDB tearDown deleteSomethingDB Note Even though FunctionTestCase can be used to quickly convert an existing test base over to a unittest based system this approach is not recommended Taking the time to set up proper TestCase subclasses will make future test refactorings infinitely easier In some cases the existing tests may have been written using the doctest module If so doctest provides a DocTestSuite class that can automatically build unittest TestSuite instances from the existing doctest based tests Skipping tests and expected failures New in version 3 1 Unittest supports skipping individual test methods and even whole classes of tests In addition it supports marking a test as an expected failure a test that is broken and will fail but shouldn t be counted as a failure on a TestResult Skipping a test is simply a matter of using the skip decorator or one of its conditional variants calling TestCase skipTest within a setUp or test method or raising SkipTest directly Basic skipping looks like this class MyTestCase unittest TestCase unittest skip demonstrating skipping def test_nothing self self fail shouldn t happen unittest skipIf mylib __version__ 1 3 not supported in this library version def test_format self Tests that work for only a certain version of the library pass unittest skipUnless sys platform startswith win requires Windows def test_windows_support self windows specific testing code pass def test_maybe_skipped self if not external_resource_available self skipTest external resource not available test code that depends on the external resource pass T,en
1041,his is the output of running the example above in verbose mode test_format __main__ MyTestCase test_format skipped not supported in this library version test_nothing __main__ MyTestCase test_nothing skipped demonstrating skipping test_maybe_skipped __main__ MyTestCase test_maybe_skipped skipped external resource not available test_windows_support __main__ MyTestCase test_windows_support skipped requires Windows Ran 4 tests in 0 005s OK skipped 4 Classes can be skipped just like methods unittest skip showing class skipping class MySkippedTestCase unittest TestCase def test_not_run self pass TestCase setUp can also skip the test This is useful when a resource that needs to be set up is not available Expected failures use the expectedFailure decorator class ExpectedFailureTestCase unittest TestCase unittest expectedFailure def test_fail self self assertEqual 1 0 broken It s easy to roll your own skipping decorators by making a decorator that calls skip on the test when it wants it to be skipped This decorator skips the test unless the passed object has a certain attribute def skipUnlessHasattr obj attr if hasattr obj attr return lambda func func return unittest skip r doesn t have r format obj attr The following decorators and exception implement test skipping and expected failures unittest skip reason Unconditionally skip the decorated test reason should describe why the test is being skipped unittest skipIf condition reason Skip the decorated test if condition is true unittest skipUnless condition reason Skip the decorated test unless condition is true unittest expectedFailure Mark the test as an expected failure or error If the test fails or errors in the test function itself rather than in one of the test fixture methods then it will be considered a success If the test passes it will be considered a failure exception unittest SkipTest reason This exception is raised to skip a test Usually you can use TestCase skipTest or one of the skipping decorators instead of raising this directly Skipped tests will not have setUp or tearDown run around them Skipped classes will not have setUpClass or tearDownClass run Skipped modules will not have setUpModule or tearDownModule run Distinguishing test iterations using subtests New in version 3 4 When there are very small differences among your tests for instance some parameters unittest allows you to distinguish them inside the body of a test method using the subTest context manager For example the following test class NumbersTest unittest TestCase def test_even self Test that numbers between 0 and 5 are all even for i in range 0 6 with self subTest i i self assertEqual i 2 0 will produce the following output FAIL test_even __main__ NumbersTest test_even i 1 Test that numbers between 0 and 5 are all even Traceback most recent call last File subtests py line 11 in test_even self assertEqual i 2 0 AssertionError 1 0 FAIL test_even __main__ NumbersTest test_even i 3 Test that numbers between 0 and 5 are all even Traceback most recent call last File subtests py line 11 in test_even self assertEqual i 2 0 AssertionError 1 0 FAIL test_even __main__ NumbersTest test_even i 5 Test that numbers between 0 and 5 are all even Traceback most recent call last File subtests py line 11 in test_even self assertEqual i 2 0 AssertionError 1 0 Without using a subtest execution would stop after the first failure and the error would be less easy to diagnose because the value of i wouldn t be displayed FAIL test_even __main__ NumbersTest test_even Traceback most recent call last File subtests py line 32 in test_even self assertEqual i 2 0 AssertionError 1 0 Classes and functions This section describes in depth the API of unittest Test cases class unittest TestCase methodName runTest Instances of the TestCase class represent the logical test units in the unittest universe This class is intended to be used as a base class with specific tests being implemented by concrete subclasses This class implements the interface needed by the test runner to allow it to drive the tests and methods that the test code can ,en
1042,use to check for and report various kinds of failure Each instance of TestCase will run a single base method the method named methodName In most uses of TestCase you will neither change the methodName nor reimplement the default runTest method Changed in version 3 2 TestCase can be instantiated successfully without providing a methodName This makes it easier to experiment with TestCase from the interactive interpreter TestCase instances provide three groups of methods one group used to run the test another used by the test implementation to check conditions and report failures and some inquiry methods allowing information about the test itself to be gathered Methods in the first group running the test are setUp Method called to prepare the test fixture This is called immediately before calling the test method other than AssertionError or SkipTest any exception raised by this method will be considered an error rather than a test failure The default implementation does nothing tearDown Method called immediately after the test method has been called and the result recorded This is called even if the test method raised an exception so the implementation in subclasses may need to be particularly careful about checking internal state Any exception other than AssertionError or SkipTest raised by this method will be considered an additional error rather than a test failure thus increasing the total number of reported errors This method will only be called if the setUp succeeds regardless of the outcome of the test method The default implementation does nothing setUpClass A class method called before tests in an individual class are run setUpClass is called with the class as the only argument and must be decorated as a classmethod classmethod def setUpClass cls See Class and Module Fixtures for more details New in version 3 2 tearDownClass A class method called after tests in an individual class have run tearDownClass is called with the class as the only argument and must be decorated as a classmethod classmethod def tearDownClass cls See Class and Module Fixtures for more details New in version 3 2 run result None Run the test collecting the result into the TestResult object passed as result If result is omitted or None a temporary result object is created by calling the defaultTestResult method and used The result object is returned to run s caller The same effect may be had by simply calling the TestCase instance Changed in version 3 3 Previous versions of run did not return the result Neither did calling an instance skipTest reason Calling this during a test method or setUp skips the current test See Skipping tests and expected failures for more information New in version 3 1 subTest msg None params Return a context manager which executes the enclosed code block as a subtest msg and params are optional arbitrary values which are displayed whenever a subtest fails allowing you to identify them clearly A test case can contain any number of subtest declarations and they can be arbitrarily nested See Distinguishing test iterations using subtests for more information New in version 3 4 debug Run the test without collecting the result This allows exceptions raised by the test to be propagated to the caller and can be used to support running tests under a debugger The TestCase class provides several assert methods to check for and report failures The following table lists the most commonly used methods see the tables below for more assert methods Method Checks that New in assertEqual a b a b assertNotEqual a b a b assertTrue x bool x is True assertFalse x bool x is False assertIs a b a is b 3 1 assertIsNot a b a is not b 3 1 assertIsNone x x is None 3 1 assertIsNotNone x x is not None 3 1 assertIn a b a in b 3 1 assertNotIn a b a not in b 3 1 assertIsInstance a b isinstance a b 3 2 assertNotIsInstance a b not isinstance a b 3 2 All the assert methods accept a msg argument that if specified is used as the error message on failure see also longMessage Note that the msg keyword argument can be passed to assertRaises assertRaisesRegex a,en
1043,ssertWarns assertWarnsRegex only when they are used as a context manager assertEqual first second msg None Test that first and second are equal If the values do not compare equal the test will fail In addition if first and second are the exact same type and one of list tuple dict set frozenset or str or any type that a subclass registers with addTypeEqualityFunc the type specific equality function will be called in order to generate a more useful default error message see also the list of type specific methods Changed in version 3 1 Added the automatic calling of type specific equality function Changed in version 3 2 assertMultiLineEqual added as the default type equality function for comparing strings assertNotEqual first second msg None Test that first and second are not equal If the values do compare equal the test will fail assertTrue expr msg None assertFalse expr msg None Test that expr is true or false Note that this is equivalent to bool expr is True and not to expr is True use assertIs expr True for the latter This method should also be avoided when more specific methods are available e g assertEqual a b instead of assertTrue a b because they provide a better error message in case of failure assertIs first second msg None assertIsNot first second msg None Test that first and second are or are not the same object New in version 3 1 assertIsNone expr msg None assertIsNotNone expr msg None Test that expr is or is not None New in version 3 1 assertIn member container msg None assertNotIn member container msg None Test that member is or is not in container New in version 3 1 assertIsInstance obj cls msg None assertNotIsInstance obj cls msg None Test that obj is or is not an instance of cls which can be a class or a tuple of classes as supported by isinstance To check for the exact type use assertIs type obj cls New in version 3 2 It is also possible to check the production of exceptions warnings and log messages using the following methods Method Checks that New in assertRaises exc fun args kwds fun args kwds raises exc assertRaisesRegex exc r fun args kwds fun args kwds raises exc and 3 1 the message matches regex r assertWarns warn fun args kwds fun args kwds raises warn 3 2 assertWarnsRegex warn r fun args kwds fun args kwds raises warn and 3 2 the message matches regex r assertLogs logger level The with block logs on logger with 3 4 minimum level assertNoLogs logger level The with block does not log on 3 10 logger with minimum level assertRaises exception callable args kwds assertRaises exception msg None Test that an exception is raised when callable is called with any positional or keyword arguments that are also passed to assertRaises The test passes if exception is raised is an error if another exception is raised or fails if no exception is raised To catch any of a group of exceptions a tuple containing the exception classes may be passed as exception If only the exception and possibly the msg arguments are given return a context manager so that the code under test can be written inline rather than as a function with self assertRaises SomeException do_something When used as a context manager assertRaises accepts the additional keyword argument msg The context manager will store the caught exception object in its exception attribute This can be useful if the intention is to perform additional checks on the exception raised with self assertRaises SomeException as cm do_something the_exception cm exception self assertEqual the_exception error_code 3 Changed in version 3 1 Added the ability to use assertRaises as a context manager Changed in version 3 2 Added the exception attribute Changed in version 3 3 Added the msg keyword argument when used as a context manager assertRaisesRegex exception regex callable args kwds assertRaisesRegex exception regex msg None Like assertRaises but also tests that regex matches on the string representation of the raised exception regex may be a regular expression object or a string containing a regular expression suitable for use by re search Examples self assertRaisesRegex Valu,en
1044,eError invalid literal for XYZ int XYZ or with self assertRaisesRegex ValueError literal int XYZ New in version 3 1 Added under the name assertRaisesRegexp Changed in version 3 2 Renamed to assertRaisesRegex Changed in version 3 3 Added the msg keyword argument when used as a context manager assertWarns warning callable args kwds assertWarns warning msg None Test that a warning is triggered when callable is called with any positional or keyword arguments that are also passed to assertWarns The test passes if warning is triggered and fails if it isn t Any exception is an error To catch any of a group of warnings a tuple containing the warning classes may be passed as warnings If only the warning and possibly the msg arguments are given return a context manager so that the code under test can be written inline rather than as a function with self assertWarns SomeWarning do_something When used as a context manager assertWarns accepts the additional keyword argument msg The context manager will store the caught warning object in its warning attribute and the source line which triggered the warnings in the filename and lineno attributes This can be useful if the intention is to perform additional checks on the warning caught with self assertWarns SomeWarning as cm do_something self assertIn myfile py cm filename self assertEqual 320 cm lineno This method works regardless of the warning filters in place when it is called New in version 3 2 Changed in version 3 3 Added the msg keyword argument when used as a context manager assertWarnsRegex warning regex callable args kwds assertWarnsRegex warning regex msg None Like assertWarns but also tests that regex matches on the message of the triggered warning regex may be a regular expression object or a string containing a regular expression suitable for use by re search Example self assertWarnsRegex DeprecationWarning r legacy_function is deprecated legacy_function XYZ or with self assertWarnsRegex RuntimeWarning unsafe frobnicating frobnicate etc passwd New in version 3 2 Changed in version 3 3 Added the msg keyword argument when used as a context manager assertLogs logger None level None A context manager to test that at least one message is logged on the logger or one of its children with at least the given level If given logger should be a logging Logger object or a str giving the name of a logger The default is the root logger which will catch all messages that were not blocked by a non propagating descendent logger If given level should be either a numeric logging level or its string equivalent for example either ERROR or logging ERROR The default is logging INFO The test passes if at least one message emitted inside the with block matches the logger and level conditions otherwise it fails The object returned by the context manager is a recording helper which keeps tracks of the matching log messages It has two attributes records A list of logging LogRecord objects of the matching log messages output A list of str objects with the formatted output of matching messages Example with self assertLogs foo level INFO as cm logging getLogger foo info first message logging getLogger foo bar error second message self assertEqual cm output INFO foo first message ERROR foo bar second message New in version 3 4 assertNoLogs logger None level None A context manager to test that no messages are logged on the logger or one of its children with at least the given level If given logger should be a logging Logger object or a str giving the name of a logger The default is the root logger which will catch all messages If given level should be either a numeric logging level or its string equivalent for example either ERROR or logging ERROR The default is logging INFO Unlike assertLogs nothing will be returned by the context manager New in version 3 10 There are also other methods used to perform more specific checks such as Method Checks that New in assertAlmostEqual a b round a b 7 0 assertNotAlmostEqual a b round a b 7 0 assertGreater a b a b 3 1 assertGreaterEqual a b a b 3 1 assertLess a b a b 3,en
1045, 1 assertLessEqual a b a b 3 1 assertRegex s r r search s 3 1 assertNotRegex s r not r search s 3 2 assertCountEqual a b a and b have the same 3 2 elements in the same number regardless of their order assertAlmostEqual first second places 7 msg None delta None assertNotAlmostEqual first second places 7 msg None delta None Test that first and second are approximately or not approximately equal by computing the difference rounding to the given number of decimal places default 7 and comparing to zero Note that these methods round the values to the given number of decimal places i e like the round function and not significant digits If delta is supplied instead of places then the difference between first and second must be less or equal to or greater than delta Supplying both delta and places raises a TypeError Changed in version 3 2 assertAlmostEqual automatically considers almost equal objects that compare equal assertNotAlmostEqual automatically fails if the objects compare equal Added the delta keyword argument assertGreater first second msg None assertGreaterEqual first second msg None assertLess first second msg None assertLessEqual first second msg None Test that first is respectively or than second depending on the method name If not the test will fail self assertGreaterEqual 3 4 AssertionError 3 unexpectedly not greater than or equal to 4 New in version 3 1 assertRegex text regex msg None assertNotRegex text regex msg None Test that a regex search matches or does not match text In case of failure the error message will include the pattern and the text or the pattern and the part of text that unexpectedly matched regex may be a regular expression object or a string containing a regular expression suitable for use by re search New in version 3 1 Added under the name assertRegexpMatches Changed in version 3 2 The method assertRegexpMatches has been renamed to assertRegex New in version 3 2 assertNotRegex assertCountEqual first second msg None Test that sequence first contains the same elements as second regardless of their order When they don t an error message listing the differences between the sequences will be generated Duplicate elements are not ignored when comparing first and second It verifies whether each element has the same count in both sequences Equivalent to assertEqual Counter list first Counter list second but works with sequences of unhashable objects as well New in version 3 2 The assertEqual method dispatches the equality check for objects of the same type to different type specific methods These methods are already implemented for most of the built in types but it s also possible to register new methods using addTypeEqualityFunc addTypeEqualityFunc typeobj function Registers a type specific method called by assertEqual to check if two objects of exactly the same typeobj not subclasses compare equal function must take two positional arguments and a third msg None keyword argument just as assertEqual does It must raise self failureException msg when inequality between the first two parameters is detected possibly providing useful information and explaining the inequalities in details in the error message New in version 3 1 The list of type specific methods automatically used by assertEqual are summarized in the following table Note that it s usually not necessary to invoke these methods directly Method Used to compare New in assertMultiLineEqual a b strings 3 1 assertSequenceEqual a b sequences 3 1 assertListEqual a b lists 3 1 assertTupleEqual a b tuples 3 1 assertSetEqual a b sets or frozensets 3 1 assertDictEqual a b dicts 3 1 assertMultiLineEqual first second msg None Test that the multiline string first is equal to the string second When not equal a diff of the two strings highlighting the differences will be included in the error message This method is used by default when comparing strings with assertEqual New in version 3 1 assertSequenceEqual first second msg None seq_type None Tests that two sequences are equal If a seq_type is supplied both first and second must be instances of seq_type or ,en
1046,a failure will be raised If the sequences are different an error message is constructed that shows the difference between the two This method is not called directly by assertEqual but it s used to implement assertListEqual and assertTupleEqual New in version 3 1 assertListEqual first second msg None assertTupleEqual first second msg None Tests that two lists or tuples are equal If not an error message is constructed that shows only the differences between the two An error is also raised if either of the parameters are of the wrong type These methods are used by default when comparing lists or tuples with assertEqual New in version 3 1 assertSetEqual first second msg None Tests that two sets are equal If not an error message is constructed that lists the differences between the sets This method is used by default when comparing sets or frozensets with assertEqual Fails if either of first or second does not have a set difference method New in version 3 1 assertDictEqual first second msg None Test that two dictionaries are equal If not an error message is constructed that shows the differences in the dictionaries This method will be used by default to compare dictionaries in calls to assertEqual New in version 3 1 Finally the TestCase provides the following methods and attributes fail msg None Signals a test failure unconditionally with msg or None for the error message failureException This class attribute gives the exception raised by the test method If a test framework needs to use a specialized exception possibly to carry additional information it must subclass this exception in order to play fair with the framework The initial value of this attribute is AssertionError longMessage This class attribute determines what happens when a custom failure message is passed as the msg argument to an assertXYY call that fails True is the default value In this case the custom message is appended to the end of the standard failure message When set to False the custom message replaces the standard message The class setting can be overridden in individual test methods by assigning an instance attribute self longMessage to True or False before calling the assert methods The class setting gets reset before each test call New in version 3 1 maxDiff This attribute controls the maximum length of diffs output by assert methods that report diffs on failure It defaults to 80 8 characters Assert methods affected by this attribute are assertSequenceEqual including all the sequence comparison methods that delegate to it assertDictEqual and assertMultiLineEqual Setting maxDiff to None means that there is no maximum length of diffs New in version 3 2 Testing frameworks can use the following methods to collect information on the test countTestCases Return the number of tests represented by this test object For TestCase instances this will always be 1 defaultTestResult Return an instance of the test result class that should be used for this test case class if no other result instance is provided to the run method For TestCase instances this will always be an instance of TestResult subclasses of TestCase should override this as necessary id Return a string identifying the specific test case This is usually the full name of the test method including the module and class name shortDescription Returns a description of the test or None if no description has been provided The default implementation of this method returns the first line of the test method s docstring if available or None Changed in version 3 1 In 3 1 this was changed to add the test name to the short description even in the presence of a docstring This caused compatibility issues with unittest extensions and adding the test name was moved to the TextTestResult in Python 3 2 addCleanup function args kwargs Add a function to be called after tearDown to cleanup resources used during the test Functions will be called in reverse order to the order they are added LIFO last in first out They are called with any arguments and keyword arguments passed into addCleanup when they are added If setUp fa,en
1047,ils meaning that tearDown is not called then any cleanup functions added will still be called New in version 3 1 enterContext cm Enter the supplied context manager If successful also add its __exit__ method as a cleanup function by addCleanup and return the result of the __enter__ method New in version 3 11 doCleanups This method is called unconditionally after tearDown or after setUp if setUp raises an exception It is responsible for calling all the cleanup functions added by addCleanup If you need cleanup functions to be called prior to tearDown then you can call doCleanups yourself doCleanups pops methods off the stack of cleanup functions one at a time so it can be called at any time New in version 3 1 classmethod addClassCleanup function args kwargs Add a function to be called after tearDownClass to cleanup resources used during the test class Functions will be called in reverse order to the order they are added LIFO last in first out They are called with any arguments and keyword arguments passed into addClassCleanup when they are added If setUpClass fails meaning that tearDownClass is not called then any cleanup functions added will still be called New in version 3 8 classmethod enterClassContext cm Enter the supplied context manager If successful also add its __exit__ method as a cleanup function by addClassCleanup and return the result of the __enter__ method New in version 3 11 classmethod doClassCleanups This method is called unconditionally after tearDownClass or after setUpClass if setUpClass raises an exception It is responsible for calling all the cleanup functions added by addClassCleanup If you need cleanup functions to be called prior to tearDownClass then you can call doClassCleanups yourself doClassCleanups pops methods off the stack of cleanup functions one at a time so it can be called at any time New in version 3 8 class unittest IsolatedAsyncioTestCase methodName runTest This class provides an API similar to TestCase and also accepts coroutines as test functions New in version 3 8 coroutine asyncSetUp Method called to prepare the test fixture This is called after setUp This is called immediately before calling the test method other than AssertionError or SkipTest any exception raised by this method will be considered an error rather than a test failure The default implementation does nothing coroutine asyncTearDown Method called immediately after the test method has been called and the result recorded This is called before tearDown This is called even if the test method raised an exception so the implementation in subclasses may need to be particularly careful about checking internal state Any exception other than AssertionError or SkipTest raised by this method will be considered an additional error rather than a test failure thus increasing the total number of reported errors This method will only be called if the asyncSetUp succeeds regardless of the outcome of the test method The default implementation does nothing addAsyncCleanup function args kwargs This method accepts a coroutine that can be used as a cleanup function coroutine enterAsyncContext cm Enter the supplied asynchronous context manager If successful also add its __aexit__ method as a cleanup function by addAsyncCleanup and return the result of the __aenter__ method New in version 3 11 run result None Sets up a new event loop to run the test collecting the result into the TestResult object passed as result If result is omitted or None a temporary result object is created by calling the defaultTestResult method and used The result object is returned to run s caller At the end of the test all the tasks in the event loop are cancelled An example illustrating the order from unittest import IsolatedAsyncioTestCase events class Test IsolatedAsyncioTestCase def setUp self events append setUp async def asyncSetUp self self _async_connection await AsyncConnection events append asyncSetUp async def test_response self events append test_response response await self _async_connection get https example com self assertEqual response status_code ,en
1048,200 self addAsyncCleanup self on_cleanup def tearDown self events append tearDown async def asyncTearDown self await self _async_connection close events append asyncTearDown async def on_cleanup self events append cleanup if __name__ __main__ unittest main After running the test events would contain setUp asyncSetUp test_response asyncTearDown tearDown cleanup class unittest FunctionTestCase testFunc setUp None tearDown None description None This class implements the portion of the TestCase interface which allows the test runner to drive the test but does not provide the methods which test code can use to check and report errors This is used to create test cases using legacy test code allowing it to be integrated into a unittest based test framework Grouping tests class unittest TestSuite tests This class represents an aggregation of individual test cases and test suites The class presents the interface needed by the test runner to allow it to be run as any other test case Running a TestSuite instance is the same as iterating over the suite running each test individually If tests is given it must be an iterable of individual test cases or other test suites that will be used to build the suite initially Additional methods are provided to add test cases and suites to the collection later on TestSuite objects behave much like TestCase objects except they do not actually implement a test Instead they are used to aggregate tests into groups of tests that should be run together Some additional methods are available to add tests to TestSuite instances addTest test Add a TestCase or TestSuite to the suite addTests tests Add all the tests from an iterable of TestCase and TestSuite instances to this test suite This is equivalent to iterating over tests calling addTest for each element TestSuite shares the following methods with TestCase run result Run the tests associated with this suite collecting the result into the test result object passed as result Note that unlike TestCase run TestSuite run requires the result object to be passed in debug Run the tests associated with this suite without collecting the result This allows exceptions raised by the test to be propagated to the caller and can be used to support running tests under a debugger countTestCases Return the number of tests represented by this test object including all individual tests and sub suites __iter__ Tests grouped by a TestSuite are always accessed by iteration Subclasses can lazily provide tests by overriding __iter__ Note that this method may be called several times on a single suite for example when counting tests or comparing for equality so the tests returned by repeated iterations before TestSuite run must be the same for each call iteration After TestSuite run callers should not rely on the tests returned by this method unless the caller uses a subclass that overrides TestSuite _removeTestAtIndex to preserve test references Changed in version 3 2 In earlier versions the TestSuite accessed tests directly rather than through iteration so overriding __iter__ wasn t sufficient for providing tests Changed in version 3 4 In earlier versions the TestSuite held references to each TestCase after TestSuite run Subclasses can restore that behavior by overriding TestSuite _removeTestAtIndex In the typical usage of a TestSuite object the run method is invoked by a TestRunner rather than by the end user test harness Loading and running tests class unittest TestLoader The TestLoader class is used to create test suites from classes and modules Normally there is no need to create an instance of this class the unittest module provides an instance that can be shared as unittest defaultTestLoader Using a subclass or instance however allows customization of some configurable properties TestLoader objects have the following attributes errors A list of the non fatal errors encountered while loading tests Not reset by the loader at any point Fatal errors are signalled by the relevant method raising an exception to the caller Non fatal errors are also indicated by a synthetic tes,en
1049,t that will raise the original error when run New in version 3 5 TestLoader objects have the following methods loadTestsFromTestCase testCaseClass Return a suite of all test cases contained in the TestCase derived testCaseClass A test case instance is created for each method named by getTestCaseNames By default these are the method names beginning with test If getTestCaseNames returns no methods but the runTest method is implemented a single test case is created for that method instead loadTestsFromModule module pattern None Return a suite of all test cases contained in the given module This method searches module for classes derived from TestCase and creates an instance of the class for each test method defined for the class Note While using a hierarchy of TestCase derived classes can be convenient in sharing fixtures and helper functions defining test methods on base classes that are not intended to be instantiated directly does not play well with this method Doing so however can be useful when the fixtures are different and defined in subclasses If a module provides a load_tests function it will be called to load the tests This allows modules to customize test loading This is the load_tests protocol The pattern argument is passed as the third argument to load_tests Changed in version 3 2 Support for load_tests added Changed in version 3 5 Support for a keyword only argument pattern has been added Changed in version 3 12 The undocumented and unofficial use_load_tests parameter has been removed loadTestsFromName name module None Return a suite of all test cases given a string specifier The specifier name is a dotted name that may resolve either to a module a test case class a test method within a test case class a TestSuite instance or a callable object which returns a TestCase or TestSuite instance These checks are applied in the order listed here that is a method on a possible test case class will be picked up as a test method within a test case class rather than a callable object For example if you have a module SampleTests containing a TestCase derived class SampleTestCase with three test methods test_one test_two and test_three the specifier SampleTests SampleTestCase would cause this method to return a suite which will run all three test methods Using the specifier SampleTests SampleTestCase test_two would cause it to return a test suite which will run only the test_two test method The specifier can refer to modules and packages which have not been imported they will be imported as a side effect The method optionally resolves name relative to the given module Changed in version 3 5 If an ImportError or AttributeError occurs while traversing name then a synthetic test that raises that error when run will be returned These errors are included in the errors accumulated by self errors loadTestsFromNames names module None Similar to loadTestsFromName but takes a sequence of names rather than a single name The return value is a test suite which supports all the tests defined for each name getTestCaseNames testCaseClass Return a sorted sequence of method names found within testCaseClass this should be a subclass of TestCase discover start_dir pattern test py top_level_dir None Find all the test modules by recursing into subdirectories from the specified start directory and return a TestSuite object containing them Only test files that match pattern will be loaded Using shell style pattern matching Only module names that are importable i e are valid Python identifiers will be loaded All test modules must be importable from the top level of the project If the start directory is not the top level directory then the top level directory must be specified separately If importing a module fails for example due to a syntax error then this will be recorded as a single error and discovery will continue If the import failure is due to SkipTest being raised it will be recorded as a skip instead of an error If a package a directory containing a file named __init__ py is found the package will be checked for a load_tests function If t,en
1050,his exists then it will be called package load_tests loader tests pattern Test discovery takes care to ensure that a package is only checked for tests once during an invocation even if the load_tests function itself calls loader discover If load_tests exists then discovery does not recurse into the package load_tests is responsible for loading all tests in the package The pattern is deliberately not stored as a loader attribute so that packages can continue discovery themselves top_level_dir is stored so load_tests does not need to pass this argument in to loader discover start_dir can be a dotted module name as well as a directory New in version 3 2 Changed in version 3 4 Modules that raise SkipTest on import are recorded as skips not errors Changed in version 3 4 start_dir can be a namespace packages Changed in version 3 4 Paths are sorted before being imported so that execution order is the same even if the underlying file system s ordering is not dependent on file name Changed in version 3 5 Found packages are now checked for load_tests regardless of whether their path matches pattern because it is impossible for a package name to match the default pattern Changed in version 3 11 start_dir can not be a namespace packages It has been broken since Python 3 7 and Python 3 11 officially remove it The following attributes of a TestLoader can be configured either by subclassing or assignment on an instance testMethodPrefix String giving the prefix of method names which will be interpreted as test methods The default value is test This affects getTestCaseNames and all the loadTestsFrom methods sortTestMethodsUsing Function to be used to compare method names when sorting them in getTestCaseNames and all the loadTestsFrom methods suiteClass Callable object that constructs a test suite from a list of tests No methods on the resulting object are needed The default value is the TestSuite class This affects all the loadTestsFrom methods testNamePatterns List of Unix shell style wildcard test name patterns that test methods have to match to be included in test suites see k option If this attribute is not None the default all test methods to be included in test suites must match one of the patterns in this list Note that matches are always performed using fnmatch fnmatchcase so unlike patterns passed to the k option simple substring patterns will have to be converted using wildcards This affects all the loadTestsFrom methods New in version 3 7 class unittest TestResult This class is used to compile information about which tests have succeeded and which have failed A TestResult object stores the results of a set of tests The TestCase and TestSuite classes ensure that results are properly recorded test authors do not need to worry about recording the outcome of tests Testing frameworks built on top of unittest may want access to the TestResult object generated by running a set of tests for reporting purposes a TestResult instance is returned by the TestRunner run method for this purpose TestResult instances have the following attributes that will be of interest when inspecting the results of running a set of tests errors A list containing 2 tuples of TestCase instances and strings holding formatted tracebacks Each tuple represents a test which raised an unexpected exception failures A list containing 2 tuples of TestCase instances and strings holding formatted tracebacks Each tuple represents a test where a failure was explicitly signalled using the assert methods skipped A list containing 2 tuples of TestCase instances and strings holding the reason for skipping the test New in version 3 1 expectedFailures A list containing 2 tuples of TestCase instances and strings holding formatted tracebacks Each tuple represents an expected failure or error of the test case unexpectedSuccesses A list containing TestCase instances that were marked as expected failures but succeeded collectedDurations A list containing 2 tuples of test case names and floats representing the elapsed time of each test which was run New in version 3 12 shouldStop Set,en
1051, to True when the execution of tests should stop by stop testsRun The total number of tests run so far buffer If set to true sys stdout and sys stderr will be buffered in between startTest and stopTest being called Collected output will only be echoed onto the real sys stdout and sys stderr if the test fails or errors Any output is also attached to the failure error message New in version 3 2 failfast If set to true stop will be called on the first failure or error halting the test run New in version 3 2 tb_locals If set to true then local variables will be shown in tracebacks New in version 3 5 wasSuccessful Return True if all tests run so far have passed otherwise returns False Changed in version 3 4 Returns False if there were any unexpectedSuccesses from tests marked with the expectedFailure decorator stop This method can be called to signal that the set of tests being run should be aborted by setting the shouldStop attribute to True TestRunner objects should respect this flag and return without running any additional tests For example this feature is used by the TextTestRunner class to stop the test framework when the user signals an interrupt from the keyboard Interactive tools which provide TestRunner implementations can use this in a similar manner The following methods of the TestResult class are used to maintain the internal data structures and may be extended in subclasses to support additional reporting requirements This is particularly useful in building tools which support interactive reporting while tests are being run startTest test Called when the test case test is about to be run stopTest test Called after the test case test has been executed regardless of the outcome startTestRun Called once before any tests are executed New in version 3 1 stopTestRun Called once after all tests are executed New in version 3 1 addError test err Called when the test case test raises an unexpected exception err is a tuple of the form returned by sys exc_info type value traceback The default implementation appends a tuple test formatted_err to the instance s errors attribute where formatted_err is a formatted traceback derived from err addFailure test err Called when the test case test signals a failure err is a tuple of the form returned by sys exc_info type value traceback The default implementation appends a tuple test formatted_err to the instance s failures attribute where formatted_err is a formatted traceback derived from err addSuccess test Called when the test case test succeeds The default implementation does nothing addSkip test reason Called when the test case test is skipped reason is the reason the test gave for skipping The default implementation appends a tuple test reason to the instance s skipped attribute addExpectedFailure test err Called when the test case test fails or errors but was marked with the expectedFailure decorator The default implementation appends a tuple test formatted_err to the instance s expectedFailures attribute where formatted_err is a formatted traceback derived from err addUnexpectedSuccess test Called when the test case test was marked with the expectedFailure decorator but succeeded The default implementation appends the test to the instance s unexpectedSuccesses attribute addSubTest test subtest outcome Called when a subtest finishes test is the test case corresponding to the test method subtest is a custom TestCase instance describing the subtest If outcome is None the subtest succeeded Otherwise it failed with an exception where outcome is a tuple of the form returned by sys exc_info type value traceback The default implementation does nothing when the outcome is a success and records subtest failures as normal failures New in version 3 4 addDuration test elapsed Called when the test case finishes elapsed is the time represented in seconds and it includes the execution of cleanup functions New in version 3 12 class unittest TextTestResult stream descriptions verbosity durations None A concrete implementation of TestResult used by the TextTestRunner Subclasses should accept k,en
1052,wargs to ensure compatibility as the interface changes New in version 3 2 Changed in version 3 12 Added the durations keyword parameter unittest defaultTestLoader Instance of the TestLoader class intended to be shared If no customization of the TestLoader is needed this instance can be used instead of repeatedly creating new instances class unittest TextTestRunner stream None descriptions True verbosity 1 failfast False buffer False resultclass None warnings None tb_locals False durations None A basic test runner implementation that outputs results to a stream If stream is None the default sys stderr is used as the output stream This class has a few configurable parameters but is essentially very simple Graphical applications which run test suites should provide alternate implementations Such implementations should accept kwargs as the interface to construct runners changes when features are added to unittest By default this runner shows DeprecationWarning PendingDeprecationWarning ResourceWarning and ImportWarning even if they are ignored by default This behavior can be overridden using Python s Wd or Wa options see Warning control and leaving warnings to None Changed in version 3 2 Added the warnings parameter Changed in version 3 2 The default stream is set to sys stderr at instantiation time rather than import time Changed in version 3 5 Added the tb_locals parameter Changed in version 3 12 Added the durations parameter _makeResult This method returns the instance of TestResult used by run It is not intended to be called directly but can be overridden in subclasses to provide a custom TestResult _makeResult instantiates the class or callable passed in the TextTestRunner constructor as the resultclass argument It defaults to TextTestResult if no resultclass is provided The result class is instantiated with the following arguments stream descriptions verbosity run test This method is the main public interface to the TextTestRunner This method takes a TestSuite or TestCase instance A TestResult is created by calling _makeResult and the test s are run and the results printed to stdout unittest main module __main__ defaultTest None argv None testRunner None testLoader unittest defaultTestLoader exit True verbosity 1 failfast None catchbreak None buffer None warnings None A command line program that loads a set of tests from module and runs them this is primarily for making test modules conveniently executable The simplest use for this function is to include the following line at the end of a test script if __name__ __main__ unittest main You can run tests with more detailed information by passing in the verbosity argument if __name__ __main__ unittest main verbosity 2 The defaultTest argument is either the name of a single test or an iterable of test names to run if no test names are specified via argv If not specified or None and no test names are provided via argv all tests found in module are run The argv argument can be a list of options passed to the program with the first element being the program name If not specified or None the values of sys argv are used The testRunner argument can either be a test runner class or an already created instance of it By default main calls sys exit with an exit code indicating success 0 or failure 1 of the tests run An exit code of 5 indicates that no tests were run or skipped The testLoader argument has to be a TestLoader instance and defaults to defaultTestLoader main supports being used from the interactive interpreter by passing in the argument exit False This displays the result on standard output without calling sys exit from unittest import main main module test_module exit False The failfast catchbreak and buffer parameters have the same effect as the same name command line options The warnings argument specifies the warning filter that should be used while running the tests If it s not specified it will remain None if a W option is passed to python see Warning control otherwise it will be set to default Calling main actually returns an instance of the TestProgram class This,en
1053, stores the result of the tests run as the result attribute Changed in version 3 1 The exit parameter was added Changed in version 3 2 The verbosity failfast catchbreak buffer and warnings parameters were added Changed in version 3 4 The defaultTest parameter was changed to also accept an iterable of test names load_tests Protocol New in version 3 2 Modules or packages can customize how tests are loaded from them during normal test runs or test discovery by implementing a function called load_tests If a test module defines load_tests it will be called by TestLoader loadTestsFromModule with the following arguments load_tests loader standard_tests pattern where pattern is passed straight through from loadTestsFromModule It defaults to None It should return a TestSuite loader is the instance of TestLoader doing the loading standard_tests are the tests that would be loaded by default from the module It is common for test modules to only want to add or remove tests from the standard set of tests The third argument is used when loading packages as part of test discovery A typical load_tests function that loads tests from a specific set of TestCase classes may look like test_cases TestCase1 TestCase2 TestCase3 def load_tests loader tests pattern suite TestSuite for test_class in test_cases tests loader loadTestsFromTestCase test_class suite addTests tests return suite If discovery is started in a directory containing a package either from the command line or by calling TestLoader discover then the package __init__ py will be checked for load_tests If that function does not exist discovery will recurse into the package as though it were just another directory Otherwise discovery of the package s tests will be left up to load_tests which is called with the following arguments load_tests loader standard_tests pattern This should return a TestSuite representing all the tests from the package standard_tests will only contain tests collected from __init__ py Because the pattern is passed into load_tests the package is free to continue and potentially modify test discovery A do nothing load_tests function for a test package would look like def load_tests loader standard_tests pattern top level directory cached on loader instance this_dir os path dirname __file__ package_tests loader discover start_dir this_dir pattern pattern standard_tests addTests package_tests return standard_tests Changed in version 3 5 Discovery no longer checks package names for matching pattern due to the impossibility of package names matching the default pattern Class and Module Fixtures Class and module level fixtures are implemented in TestSuite When the test suite encounters a test from a new class then tearDownClass from the previous class if there is one is called followed by setUpClass from the new class Similarly if a test is from a different module from the previous test then tearDownModule from the previous module is run followed by setUpModule from the new module After all the tests have run the final tearDownClass and tearDownModule are run Note that shared fixtures do not play well with potential features like test parallelization and they break test isolation They should be used with care The default ordering of tests created by the unittest test loaders is to group all tests from the same modules and classes together This will lead to setUpClass setUpModule etc being called exactly once per class and module If you randomize the order so that tests from different modules and classes are adjacent to each other then these shared fixture functions may be called multiple times in a single test run Shared fixtures are not intended to work with suites with non standard ordering A BaseTestSuite still exists for frameworks that don t want to support shared fixtures If there are any exceptions raised during one of the shared fixture functions the test is reported as an error Because there is no corresponding test instance an _ErrorHolder object that has the same interface as a TestCase is created to represent the error If you are just using the standard u,en
1054,nittest test runner then this detail doesn t matter but if you are a framework author it may be relevant setUpClass and tearDownClass These must be implemented as class methods import unittest class Test unittest TestCase classmethod def setUpClass cls cls _connection createExpensiveConnectionObject classmethod def tearDownClass cls cls _connection destroy If you want the setUpClass and tearDownClass on base classes called then you must call up to them yourself The implementations in TestCase are empty If an exception is raised during a setUpClass then the tests in the class are not run and the tearDownClass is not run Skipped classes will not have setUpClass or tearDownClass run If the exception is a SkipTest exception then the class will be reported as having been skipped instead of as an error setUpModule and tearDownModule These should be implemented as functions def setUpModule createConnection def tearDownModule closeConnection If an exception is raised in a setUpModule then none of the tests in the module will be run and the tearDownModule will not be run If the exception is a SkipTest exception then the module will be reported as having been skipped instead of as an error To add cleanup code that must be run even in the case of an exception use addModuleCleanup unittest addModuleCleanup function args kwargs Add a function to be called after tearDownModule to cleanup resources used during the test class Functions will be called in reverse order to the order they are added LIFO last in first out They are called with any arguments and keyword arguments passed into addModuleCleanup when they are added If setUpModule fails meaning that tearDownModule is not called then any cleanup functions added will still be called New in version 3 8 classmethod unittest enterModuleContext cm Enter the supplied context manager If successful also add its __exit__ method as a cleanup function by addModuleCleanup and return the result of the __enter__ method New in version 3 11 unittest doModuleCleanups This function is called unconditionally after tearDownModule or after setUpModule if setUpModule raises an exception It is responsible for calling all the cleanup functions added by addModuleCleanup If you need cleanup functions to be called prior to tearDownModule then you can call doModuleCleanups yourself doModuleCleanups pops methods off the stack of cleanup functions one at a time so it can be called at any time New in version 3 8 Signal Handling New in version 3 2 The c catch command line option to unittest along with the catchbreak parameter to unittest main provide more friendly handling of control C during a test run With catch break behavior enabled control C will allow the currently running test to complete and the test run will then end and report all the results so far A second control c will raise a KeyboardInterrupt in the usual way The control c handling signal handler attempts to remain compatible with code or tests that install their own signal SIGINT handler If the unittest handler is called but isn t the installed signal SIGINT handler i e it has been replaced by the system under test and delegated to then it calls the default handler This will normally be the expected behavior by code that replaces an installed handler and delegates to it For individual tests that need unittest control c handling disabled the removeHandler decorator can be used There are a few utility functions for framework authors to enable control c handling functionality within test frameworks unittest installHandler Install the control c handler When a signal SIGINT is received usually in response to the user pressing control c all registered results have stop called unittest registerResult result Register a TestResult object for control c handling Registering a result stores a weak reference to it so it doesn t prevent the result from being garbage collected Registering a TestResult object has no side effects if control c handling is not enabled so test frameworks can unconditionally register all results they create independently of whether or,en
1055, not handling is enabled unittest removeResult result Remove a registered result Once a result has been removed then stop will no longer be called on that result object in response to a control c unittest removeHandler function None When called without arguments this function removes the control c handler if it has been installed This function can also be used as a test decorator to temporarily remove the handler while the test is being executed unittest removeHandler def test_signal_handling self,en
1056,tokenize Tokenizer for Python source Source code Lib tokenize py The tokenize module provides a lexical scanner for Python source code implemented in Python The scanner in this module returns comments as tokens as well making it useful for implementing pretty printers including colorizers for on screen displays To simplify token stream handling all operator and delimiter tokens and Ellipsis are returned using the generic OP token type The exact type can be determined by checking the exact_type property on the named tuple returned from tokenize tokenize Warning Note that the functions in this module are only designed to parse syntactically valid Python code code that does not raise when parsed using ast parse The behavior of the functions in this module is undefined when providing invalid Python code and it can change at any point Tokenizing Input The primary entry point is a generator tokenize tokenize readline The tokenize generator requires one argument readline which must be a callable object which provides the same interface as the io IOBase readline method of file objects Each call to the function should return one line of input as bytes The generator produces 5 tuples with these members the token type the token string a 2 tuple srow scol of ints specifying the row and column where the token begins in the source a 2 tuple erow ecol of ints specifying the row and column where the token ends in the source and the line on which the token was found The line passed the last tuple item is the physical line The 5 tuple is returned as a named tuple with the field names type string start end line The returned named tuple has an additional property named exact_type that contains the exact operator type for OP tokens For all other token types exact_type equals the named tuple type field Changed in version 3 1 Added support for named tuples Changed in version 3 3 Added support for exact_type tokenize determines the source encoding of the file by looking for a UTF 8 BOM or encoding cookie according to PEP 263 tokenize generate_tokens readline Tokenize a source reading unicode strings instead of bytes Like tokenize the readline argument is a callable returning a single line of input However generate_tokens expects readline to return a str object rather than bytes The result is an iterator yielding named tuples exactly like tokenize It does not yield an ENCODING token All constants from the token module are also exported from tokenize Another function is provided to reverse the tokenization process This is useful for creating tools that tokenize a script modify the token stream and write back the modified script tokenize untokenize iterable Converts tokens back into Python source code The iterable must return sequences with at least two elements the token type and the token string Any additional sequence elements are ignored The reconstructed script is returned as a single string The result is guaranteed to tokenize back to match the input so that the conversion is lossless and round trips are assured The guarantee applies only to the token type and token string as the spacing between tokens column positions may change It returns bytes encoded using the ENCODING token which is the first token sequence output by tokenize If there is no encoding token in the input it returns a str instead tokenize needs to detect the encoding of source files it tokenizes The function it uses to do this is available tokenize detect_encoding readline The detect_encoding function is used to detect the encoding that should be used to decode a Python source file It requires one argument readline in the same way as the tokenize generator It will call readline a maximum of twice and return the encoding used as a string and a list of any lines not decoded from bytes it has read in It detects the encoding from the presence of a UTF 8 BOM or an encoding cookie as specified in PEP 263 If both a BOM and a cookie are present but disagree a SyntaxError will be raised Note that if the BOM is found utf 8 sig will be returned as an encoding If no encoding is specifi,en
1057,ed then the default of utf 8 will be returned Use open to open Python source files it uses detect_encoding to detect the file encoding tokenize open filename Open a file in read only mode using the encoding detected by detect_encoding New in version 3 2 exception tokenize TokenError Raised when either a docstring or expression that may be split over several lines is not completed anywhere in the file for example Beginning of docstring or 1 2 3 Command Line Usage New in version 3 3 The tokenize module can be executed as a script from the command line It is as simple as python m tokenize e filename py The following options are accepted h help show this help message and exit e exact display token names using the exact type If filename py is specified its contents are tokenized to stdout Otherwise tokenization is performed on stdin Examples Example of a script rewriter that transforms float literals into Decimal objects from tokenize import tokenize untokenize NUMBER STRING NAME OP from io import BytesIO def decistmt s Substitute Decimals for floats in a string of statements from decimal import Decimal s print 21 3e 5 1234 81 7 decistmt s print Decimal 21 3e 5 Decimal 1234 Decimal 81 7 The format of the exponent is inherited from the platform C library Known cases are e 007 Windows and e 07 not Windows Since we re only showing 12 digits and the 13th isn t close to 5 the rest of the output should be platform independent exec s doctest ELLIPSIS 3 21716034272e 0 7 Output from calculations with Decimal should be identical across all platforms exec decistmt s 3 217160342717258261933904529E 7 result g tokenize BytesIO s encode utf 8 readline tokenize the string for toknum tokval _ _ _ in g if toknum NUMBER and in tokval replace NUMBER tokens result extend NAME Decimal OP STRING repr tokval OP else result append toknum tokval return untokenize result decode utf 8 Example of tokenizing from the command line The script def say_hello print Hello World say_hello will be tokenized to the following output where the first column is the range of the line column coordinates where the token is found the second column is the name of the token and the final column is the value of the token if any python m tokenize hello py 0 0 0 0 ENCODING utf 8 1 0 1 3 NAME def 1 4 1 13 NAME say_hello 1 13 1 14 OP 1 14 1 15 OP 1 15 1 16 OP 1 16 1 17 NEWLINE n 2 0 2 4 INDENT 2 4 2 9 NAME print 2 9 2 10 OP 2 10 2 25 STRING Hello World 2 25 2 26 OP 2 26 2 27 NEWLINE n 3 0 3 1 NL n 4 0 4 0 DEDENT 4 0 4 9 NAME say_hello 4 9 4 10 OP 4 10 4 11 OP 4 11 4 12 NEWLINE n 5 0 5 0 ENDMARKER The exact token type names can be displayed using the e option python m tokenize e hello py 0 0 0 0 ENCODING utf 8 1 0 1 3 NAME def 1 4 1 13 NAME say_hello 1 13 1 14 LPAR 1 14 1 15 RPAR 1 15 1 16 COLON 1 16 1 17 NEWLINE n 2 0 2 4 INDENT 2 4 2 9 NAME print 2 9 2 10 LPAR 2 10 2 25 STRING Hello World 2 25 2 26 RPAR 2 26 2 27 NEWLINE n 3 0 3 1 NL n 4 0 4 0 DEDENT 4 0 4 9 NAME say_hello 4 9 4 10 LPAR 4 10 4 11 RPAR 4 11 4 12 NEWLINE n 5 0 5 0 ENDMARKER Example of tokenizing a file programmatically reading unicode strings instead of bytes with generate_tokens import tokenize with tokenize open hello py as f tokens tokenize generate_tokens f readline for token in tokens print token Or reading bytes directly with tokenize import tokenize with open hello py rb as f tokens tokenize tokenize f readline for token in tokens print token,en
1058,pkgutil Package extension utility Source code Lib pkgutil py This module provides utilities for the import system in particular package support class pkgutil ModuleInfo module_finder name ispkg A namedtuple that holds a brief summary of a module s info New in version 3 6 pkgutil extend_path path name Extend the search path for the modules which comprise a package Intended use is to place the following code in a package s __init__ py from pkgutil import extend_path __path__ extend_path __path__ __name__ For each directory on sys path that has a subdirectory that matches the package name add the subdirectory to the package s __path__ This is useful if one wants to distribute different parts of a single logical package as multiple directories It also looks for pkg files beginning where matches the name argument This feature is similar to pth files see the site module for more information except that it doesn t special case lines starting with import A pkg file is trusted at face value apart from checking for duplicates all entries found in a pkg file are added to the path regardless of whether they exist on the filesystem This is a feature If the input path is not a list as is the case for frozen packages it is returned unchanged The input path is not modified an extended copy is returned Items are only appended to the copy at the end It is assumed that sys path is a sequence Items of sys path that are not strings referring to existing directories are ignored Unicode items on sys path that cause errors when used as filenames may cause this function to raise an exception in line with os path isdir behavior pkgutil find_loader fullname Retrieve a module loader for the given fullname This is a backwards compatibility wrapper around importlib util find_spec that converts most failures to ImportError and only returns the loader rather than the full importlib machinery ModuleSpec Changed in version 3 3 Updated to be based directly on importlib rather than relying on the package internal PEP 302 import emulation Changed in version 3 4 Updated to be based on PEP 451 Deprecated since version 3 12 will be removed in version 3 14 Use importlib util find_spec instead pkgutil get_importer path_item Retrieve a finder for the given path_item The returned finder is cached in sys path_importer_cache if it was newly created by a path hook The cache or part of it can be cleared manually if a rescan of sys path_hooks is necessary Changed in version 3 3 Updated to be based directly on importlib rather than relying on the package internal PEP 302 import emulation pkgutil get_loader module_or_name Get a loader object for module_or_name If the module or package is accessible via the normal import mechanism a wrapper around the relevant part of that machinery is returned Returns None if the module cannot be found or imported If the named module is not already imported its containing package if any is imported in order to establish the package __path__ Changed in version 3 3 Updated to be based directly on importlib rather than relying on the package internal PEP 302 import emulation Changed in version 3 4 Updated to be based on PEP 451 Deprecated since version 3 12 will be removed in version 3 14 Use importlib util find_spec instead pkgutil iter_importers fullname Yield finder objects for the given module name If fullname contains a the finders will be for the package containing fullname otherwise they will be all registered top level finders i e those on both sys meta_path and sys path_hooks If the named module is in a package that package is imported as a side effect of invoking this function If no module name is specified all top level finders are produced Changed in version 3 3 Updated to be based directly on importlib rather than relying on the package internal PEP 302 import emulation pkgutil iter_modules path None prefix Yields ModuleInfo for all submodules on path or if path is None all top level modules on sys path path should be either None or a list of paths to look for modules in prefix is a string to output on the front of every module,en
1059, name on output Note Only works for a finder which defines an iter_modules method This interface is non standard so the module also provides implementations for importlib machinery FileFinder and zipimport zipimporter Changed in version 3 3 Updated to be based directly on importlib rather than relying on the package internal PEP 302 import emulation pkgutil walk_packages path None prefix onerror None Yields ModuleInfo for all modules recursively on path or if path is None all accessible modules path should be either None or a list of paths to look for modules in prefix is a string to output on the front of every module name on output Note that this function must import all packages not all modules on the given path in order to access the __path__ attribute to find submodules onerror is a function which gets called with one argument the name of the package which was being imported if any exception occurs while trying to import a package If no onerror function is supplied ImportError s are caught and ignored while all other exceptions are propagated terminating the search Examples list all modules python can access walk_packages list all submodules of ctypes walk_packages ctypes __path__ ctypes __name__ Note Only works for a finder which defines an iter_modules method This interface is non standard so the module also provides implementations for importlib machinery FileFinder and zipimport zipimporter Changed in version 3 3 Updated to be based directly on importlib rather than relying on the package internal PEP 302 import emulation pkgutil get_data package resource Get a resource from a package This is a wrapper for the loader get_data API The package argument should be the name of a package in standard module format foo bar The resource argument should be in the form of a relative filename using as the path separator The parent directory name is not allowed and nor is a rooted name starting with a The function returns a binary string that is the contents of the specified resource For packages located in the filesystem which have already been imported this is the rough equivalent of d os path dirname sys modules package __file__ data open os path join d resource rb read If the package cannot be located or loaded or it uses a loader which does not support get_data then None is returned In particular the loader for namespace packages does not support get_data pkgutil resolve_name name Resolve a name to an object This functionality is used in numerous places in the standard library see bpo 12915 and equivalent functionality is also in widely used third party packages such as setuptools Django and Pyramid It is expected that name will be a string in one of the following formats where W is shorthand for a valid Python identifier and dot stands for a literal period in these pseudo regexes W W W W W W The first form is intended for backward compatibility only It assumes that some part of the dotted name is a package and the rest is an object somewhere within that package possibly nested inside other objects Because the place where the package stops and the object hierarchy starts can t be inferred by inspection repeated attempts to import must be done with this form In the second form the caller makes the division point clear through the provision of a single colon the dotted name to the left of the colon is a package to be imported and the dotted name to the right is the object hierarchy within that package Only one import is needed in this form If it ends with the colon then a module object is returned The function will return an object which might be a module or raise one of the following exceptions ValueError if name isn t in a recognised format ImportError if an import failed when it shouldn t have AttributeError If a failure occurred when traversing the object hierarchy within the imported package to get to the desired object New in version 3 9,en
1060,xmlrpc server Basic XML RPC servers Source code Lib xmlrpc server py The xmlrpc server module provides a basic server framework for XML RPC servers written in Python Servers can either be free standing using SimpleXMLRPCServer or embedded in a CGI environment using CGIXMLRPCRequestHandler Warning The xmlrpc server module is not secure against maliciously constructed data If you need to parse untrusted or unauthenticated data see XML vulnerabilities Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information class xmlrpc server SimpleXMLRPCServer addr requestHandler SimpleXMLRPCRequestHandler logRequests True allow_none False encoding None bind_and_activate True use_builtin_types False Create a new server instance This class provides methods for registration of functions that can be called by the XML RPC protocol The requestHandler parameter should be a factory for request handler instances it defaults to SimpleXMLRPCRequestHandler The addr and requestHandler parameters are passed to the socketserver TCPServer constructor If logRequests is true the default requests will be logged setting this parameter to false will turn off logging The allow_none and encoding parameters are passed on to xmlrpc client and control the XML RPC responses that will be returned from the server The bind_and_activate parameter controls whether server_bind and server_activate are called immediately by the constructor it defaults to true Setting it to false allows code to manipulate the allow_reuse_address class variable before the address is bound The use_builtin_types parameter is passed to the loads function and controls which types are processed when date times values or binary data are received it defaults to false Changed in version 3 3 The use_builtin_types flag was added class xmlrpc server CGIXMLRPCRequestHandler allow_none False encoding None use_builtin_types False Create a new instance to handle XML RPC requests in a CGI environment The allow_none and encoding parameters are passed on to xmlrpc client and control the XML RPC responses that will be returned from the server The use_builtin_types parameter is passed to the loads function and controls which types are processed when date times values or binary data are received it defaults to false Changed in version 3 3 The use_builtin_types flag was added class xmlrpc server SimpleXMLRPCRequestHandler Create a new request handler instance This request handler supports POST requests and modifies logging so that the logRequests parameter to the SimpleXMLRPCServer constructor parameter is honored SimpleXMLRPCServer Objects The SimpleXMLRPCServer class is based on socketserver TCPServer and provides a means of creating simple stand alone XML RPC servers SimpleXMLRPCServer register_function function None name None Register a function that can respond to XML RPC requests If name is given it will be the method name associated with function otherwise function __name__ will be used name is a string and may contain characters not legal in Python identifiers including the period character This method can also be used as a decorator When used as a decorator name can only be given as a keyword argument to register function under name If no name is given function __name__ will be used Changed in version 3 7 register_function can be used as a decorator SimpleXMLRPCServer register_instance instance allow_dotted_names False Register an object which is used to expose method names which have not been registered using register_function If instance contains a _dispatch method it is called with the requested method name and the parameters from the request Its API is def _dispatch self method params note that params does not represent a variable argument list If it calls an underlying function to perform its task that function is called as func params expanding the parameter list The return value from _dispatch is returned to the client as the result If instance does not have a _dispa,en
1061,tch method it is searched for an attribute matching the name of the requested method If the optional allow_dotted_names argument is true and the instance does not have a _dispatch method then if the requested method name contains periods each component of the method name is searched for individually with the effect that a simple hierarchical search is performed The value found from this search is then called with the parameters from the request and the return value is passed back to the client Warning Enabling the allow_dotted_names option allows intruders to access your module s global variables and may allow intruders to execute arbitrary code on your machine Only use this option on a secure closed network SimpleXMLRPCServer register_introspection_functions Registers the XML RPC introspection functions system listMethods system methodHelp and system methodSignature SimpleXMLRPCServer register_multicall_functions Registers the XML RPC multicall function system multicall SimpleXMLRPCRequestHandler rpc_paths An attribute value that must be a tuple listing valid path portions of the URL for receiving XML RPC requests Requests posted to other paths will result in a 404 no such page HTTP error If this tuple is empty all paths will be considered valid The default value is RPC2 SimpleXMLRPCServer Example Server code from xmlrpc server import SimpleXMLRPCServer from xmlrpc server import SimpleXMLRPCRequestHandler Restrict to a particular path class RequestHandler SimpleXMLRPCRequestHandler rpc_paths RPC2 Create server with SimpleXMLRPCServer localhost 8000 requestHandler RequestHandler as server server register_introspection_functions Register pow function this will use the value of pow __name__ as the name which is just pow server register_function pow Register a function under a different name def adder_function x y return x y server register_function adder_function add Register an instance all the methods of the instance are published as XML RPC methods in this case just mul class MyFuncs def mul self x y return x y server register_instance MyFuncs Run the server s main loop server serve_forever The following client code will call the methods made available by the preceding server import xmlrpc client s xmlrpc client ServerProxy http localhost 8000 print s pow 2 3 Returns 2 3 8 print s add 2 3 Returns 5 print s mul 5 2 Returns 5 2 10 Print list of available methods print s system listMethods register_function can also be used as a decorator The previous server example can register functions in a decorator way from xmlrpc server import SimpleXMLRPCServer from xmlrpc server import SimpleXMLRPCRequestHandler class RequestHandler SimpleXMLRPCRequestHandler rpc_paths RPC2 with SimpleXMLRPCServer localhost 8000 requestHandler RequestHandler as server server register_introspection_functions Register pow function this will use the value of pow __name__ as the name which is just pow server register_function pow Register a function under a different name using register_function as a decorator name can only be given as a keyword argument server register_function name add def adder_function x y return x y Register a function under function __name__ server register_function def mul x y return x y server serve_forever The following example included in the Lib xmlrpc server py module shows a server allowing dotted names and registering a multicall function Warning Enabling the allow_dotted_names option allows intruders to access your module s global variables and may allow intruders to execute arbitrary code on your machine Only use this example only within a secure closed network import datetime class ExampleService def getData self return 42 class currentTime staticmethod def getCurrentTime return datetime datetime now with SimpleXMLRPCServer localhost 8000 as server server register_function pow server register_function lambda x y x y add server register_instance ExampleService allow_dotted_names True server register_multicall_functions print Serving XML RPC on localhost port 8000 try server serve_forever except KeyboardInterrupt print n,en
1062,Keyboard interrupt received exiting sys exit 0 This ExampleService demo can be invoked from the command line python m xmlrpc server The client that interacts with the above server is included in Lib xmlrpc client py server ServerProxy http localhost 8000 try print server currentTime getCurrentTime except Error as v print ERROR v multi MultiCall server multi getData multi pow 2 9 multi add 1 2 try for response in multi print response except Error as v print ERROR v This client which interacts with the demo XMLRPC server can be invoked as python m xmlrpc client CGIXMLRPCRequestHandler The CGIXMLRPCRequestHandler class can be used to handle XML RPC requests sent to Python CGI scripts CGIXMLRPCRequestHandler register_function function None name None Register a function that can respond to XML RPC requests If name is given it will be the method name associated with function otherwise function __name__ will be used name is a string and may contain characters not legal in Python identifiers including the period character This method can also be used as a decorator When used as a decorator name can only be given as a keyword argument to register function under name If no name is given function __name__ will be used Changed in version 3 7 register_function can be used as a decorator CGIXMLRPCRequestHandler register_instance instance Register an object which is used to expose method names which have not been registered using register_function If instance contains a _dispatch method it is called with the requested method name and the parameters from the request the return value is returned to the client as the result If instance does not have a _dispatch method it is searched for an attribute matching the name of the requested method if the requested method name contains periods each component of the method name is searched for individually with the effect that a simple hierarchical search is performed The value found from this search is then called with the parameters from the request and the return value is passed back to the client CGIXMLRPCRequestHandler register_introspection_functions Register the XML RPC introspection functions system listMethods system methodHelp and system methodSignature CGIXMLRPCRequestHandler register_multicall_functions Register the XML RPC multicall function system multicall CGIXMLRPCRequestHandler handle_request request_text None Handle an XML RPC request If request_text is given it should be the POST data provided by the HTTP server otherwise the contents of stdin will be used Example class MyFuncs def mul self x y return x y handler CGIXMLRPCRequestHandler handler register_function pow handler register_function lambda x y x y add handler register_introspection_functions handler register_instance MyFuncs handler handle_request Documenting XMLRPC server These classes extend the above classes to serve HTML documentation in response to HTTP GET requests Servers can either be free standing using DocXMLRPCServer or embedded in a CGI environment using DocCGIXMLRPCRequestHandler class xmlrpc server DocXMLRPCServer addr requestHandler DocXMLRPCRequestHandler logRequests True allow_none False encoding None bind_and_activate True use_builtin_types True Create a new server instance All parameters have the same meaning as for SimpleXMLRPCServer requestHandler defaults to DocXMLRPCRequestHandler Changed in version 3 3 The use_builtin_types flag was added class xmlrpc server DocCGIXMLRPCRequestHandler Create a new instance to handle XML RPC requests in a CGI environment class xmlrpc server DocXMLRPCRequestHandler Create a new request handler instance This request handler supports XML RPC POST requests documentation GET requests and modifies logging so that the logRequests parameter to the DocXMLRPCServer constructor parameter is honored DocXMLRPCServer Objects The DocXMLRPCServer class is derived from SimpleXMLRPCServer and provides a means of creating self documenting stand alone XML RPC servers HTTP POST requests are handled as XML RPC method calls HTTP GET requests are handled by generating pydoc style HTML do,en
1063,cumentation This allows a server to provide its own web based documentation DocXMLRPCServer set_server_title server_title Set the title used in the generated HTML documentation This title will be used inside the HTML title element DocXMLRPCServer set_server_name server_name Set the name used in the generated HTML documentation This name will appear at the top of the generated documentation inside a h1 element DocXMLRPCServer set_server_documentation server_documentation Set the description used in the generated HTML documentation This description will appear as a paragraph below the server name in the documentation DocCGIXMLRPCRequestHandler The DocCGIXMLRPCRequestHandler class is derived from CGIXMLRPCRequestHandler and provides a means of creating self documenting XML RPC CGI scripts HTTP POST requests are handled as XML RPC method calls HTTP GET requests are handled by generating pydoc style HTML documentation This allows a server to provide its own web based documentation DocCGIXMLRPCRequestHandler set_server_title server_title Set the title used in the generated HTML documentation This title will be used inside the HTML title element DocCGIXMLRPCRequestHandler set_server_name server_name Set the name used in the generated HTML documentation This name will appear at the top of the generated documentation inside a h1 element DocCGIXMLRPCRequestHandler set_server_documentation server_documentation Set the description used in the generated HTML documentation This description will appear as a paragraph below the server name in the documentation,en
1064,difflib Helpers for computing deltas Source code Lib difflib py This module provides classes and functions for comparing sequences It can be used for example for comparing files and can produce information about file differences in various formats including HTML and context and unified diffs For comparing directories and files see also the filecmp module class difflib SequenceMatcher This is a flexible class for comparing pairs of sequences of any type so long as the sequence elements are hashable The basic algorithm predates and is a little fancier than an algorithm published in the late 1980 s by Ratcliff and Obershelp under the hyperbolic name gestalt pattern matching The idea is to find the longest contiguous matching subsequence that contains no junk elements these junk elements are ones that are uninteresting in some sense such as blank lines or whitespace Handling junk is an extension to the Ratcliff and Obershelp algorithm The same idea is then applied recursively to the pieces of the sequences to the left and to the right of the matching subsequence This does not yield minimal edit sequences but does tend to yield matches that look right to people Timing The basic Ratcliff Obershelp algorithm is cubic time in the worst case and quadratic time in the expected case SequenceMatcher is quadratic time for the worst case and has expected case behavior dependent in a complicated way on how many elements the sequences have in common best case time is linear Automatic junk heuristic SequenceMatcher supports a heuristic that automatically treats certain sequence items as junk The heuristic counts how many times each individual item appears in the sequence If an item s duplicates after the first one account for more than 1 of the sequence and the sequence is at least 200 items long this item is marked as popular and is treated as junk for the purpose of sequence matching This heuristic can be turned off by setting the autojunk argument to False when creating the SequenceMatcher Changed in version 3 2 Added the autojunk parameter class difflib Differ This is a class for comparing sequences of lines of text and producing human readable differences or deltas Differ uses SequenceMatcher both to compare sequences of lines and to compare sequences of characters within similar near matching lines Each line of a Differ delta begins with a two letter code Code Meaning line unique to sequence 1 line unique to sequence 2 line common to both sequences line not present in either input sequence Lines beginning with attempt to guide the eye to intraline differences and were not present in either input sequence These lines can be confusing if the sequences contain whitespace characters such as spaces tabs or line breaks class difflib HtmlDiff This class can be used to create an HTML table or a complete HTML file containing the table showing a side by side line by line comparison of text with inter line and intra line change highlights The table can be generated in either full or contextual difference mode The constructor for this class is __init__ tabsize 8 wrapcolumn None linejunk None charjunk IS_CHARACTER_JUNK Initializes instance of HtmlDiff tabsize is an optional keyword argument to specify tab stop spacing and defaults to 8 wrapcolumn is an optional keyword to specify column number where lines are broken and wrapped defaults to None where lines are not wrapped linejunk and charjunk are optional keyword arguments passed into ndiff used by HtmlDiff to generate the side by side HTML differences See ndiff documentation for argument default values and descriptions The following methods are public make_file fromlines tolines fromdesc todesc context False numlines 5 charset utf 8 Compares fromlines and tolines lists of strings and returns a string which is a complete HTML file containing a table showing line by line differences with inter line and intra line changes highlighted fromdesc and todesc are optional keyword arguments to specify from to file column header strings both default to an empty string context and numlines are both optio,en
1065,nal keyword arguments Set context to True when contextual differences are to be shown else the default is False to show the full files numlines defaults to 5 When context is True numlines controls the number of context lines which surround the difference highlights When context is False numlines controls the number of lines which are shown before a difference highlight when using the next hyperlinks setting to zero would cause the next hyperlinks to place the next difference highlight at the top of the browser without any leading context Note fromdesc and todesc are interpreted as unescaped HTML and should be properly escaped while receiving input from untrusted sources Changed in version 3 5 charset keyword only argument was added The default charset of HTML document changed from ISO 8859 1 to utf 8 make_table fromlines tolines fromdesc todesc context False numlines 5 Compares fromlines and tolines lists of strings and returns a string which is a complete HTML table showing line by line differences with inter line and intra line changes highlighted The arguments for this method are the same as those for the make_file method difflib context_diff a b fromfile tofile fromfiledate tofiledate n 3 lineterm n Compare a and b lists of strings return a delta a generator generating the delta lines in context diff format Context diffs are a compact way of showing just the lines that have changed plus a few lines of context The changes are shown in a before after style The number of context lines is set by n which defaults to three By default the diff control lines those with or are created with a trailing newline This is helpful so that inputs created from io IOBase readlines result in diffs that are suitable for use with io IOBase writelines since both the inputs and outputs have trailing newlines For inputs that do not have trailing newlines set the lineterm argument to so that the output will be uniformly newline free The context diff format normally has a header for filenames and modification times Any or all of these may be specified using strings for fromfile tofile fromfiledate and tofiledate The modification times are normally expressed in the ISO 8601 format If not specified the strings default to blanks import sys from difflib import s1 bacon n eggs n ham n guido n s2 python n eggy n hamster n guido n sys stdout writelines context_diff s1 s2 fromfile before py tofile after py before py after py 1 4 bacon eggs ham guido 1 4 python eggy hamster guido See A command line interface to difflib for a more detailed example difflib get_close_matches word possibilities n 3 cutoff 0 6 Return a list of the best good enough matches word is a sequence for which close matches are desired typically a string and possibilities is a list of sequences against which to match word typically a list of strings Optional argument n default 3 is the maximum number of close matches to return n must be greater than 0 Optional argument cutoff default 0 6 is a float in the range 0 1 Possibilities that don t score at least that similar to word are ignored The best no more than n matches among the possibilities are returned in a list sorted by similarity score most similar first get_close_matches appel ape apple peach puppy apple ape import keyword get_close_matches wheel keyword kwlist while get_close_matches pineapple keyword kwlist get_close_matches accept keyword kwlist except difflib ndiff a b linejunk None charjunk IS_CHARACTER_JUNK Compare a and b lists of strings return a Differ style delta a generator generating the delta lines Optional keyword parameters linejunk and charjunk are filtering functions or None linejunk A function that accepts a single string argument and returns true if the string is junk or false if not The default is None There is also a module level function IS_LINE_JUNK which filters out lines without visible characters except for at most one pound character however the underlying SequenceMatcher class does a dynamic analysis of which lines are so frequent as to constitute noise and this usually works better than using this f,en
1066,unction charjunk A function that accepts a character a string of length 1 and returns if the character is junk or false if not The default is module level function IS_CHARACTER_JUNK which filters out whitespace characters a blank or tab it s a bad idea to include newline in this diff ndiff one ntwo nthree n splitlines keepends True ore ntree nemu n splitlines keepends True print join diff end one ore two three tree emu difflib restore sequence which Return one of the two sequences that generated a delta Given a sequence produced by Differ compare or ndiff extract lines originating from file 1 or 2 parameter which stripping off line prefixes Example diff ndiff one ntwo nthree n splitlines keepends True ore ntree nemu n splitlines keepends True diff list diff materialize the generated delta into a list print join restore diff 1 end one two three print join restore diff 2 end ore tree emu difflib unified_diff a b fromfile tofile fromfiledate tofiledate n 3 lineterm n Compare a and b lists of strings return a delta a generator generating the delta lines in unified diff format Unified diffs are a compact way of showing just the lines that have changed plus a few lines of context The changes are shown in an inline style instead of separate before after blocks The number of context lines is set by n which defaults to three By default the diff control lines those with or are created with a trailing newline This is helpful so that inputs created from io IOBase readlines result in diffs that are suitable for use with io IOBase writelines since both the inputs and outputs have trailing newlines For inputs that do not have trailing newlines set the lineterm argument to so that the output will be uniformly newline free The unified diff format normally has a header for filenames and modification times Any or all of these may be specified using strings for fromfile tofile fromfiledate and tofiledate The modification times are normally expressed in the ISO 8601 format If not specified the strings default to blanks s1 bacon n eggs n ham n guido n s2 python n eggy n hamster n guido n sys stdout writelines unified_diff s1 s2 fromfile before py tofile after py before py after py 1 4 1 4 bacon eggs ham python eggy hamster guido See A command line interface to difflib for a more detailed example difflib diff_bytes dfunc a b fromfile b tofile b fromfiledate b tofiledate b n 3 lineterm b n Compare a and b lists of bytes objects using dfunc yield a sequence of delta lines also bytes in the format returned by dfunc dfunc must be a callable typically either unified_diff or context_diff Allows you to compare data with unknown or inconsistent encoding All inputs except n must be bytes objects not str Works by losslessly converting all inputs except n to str and calling dfunc a b fromfile tofile fromfiledate tofiledate n lineterm The output of dfunc is then converted back to bytes so the delta lines that you receive have the same unknown inconsistent encodings as a and b New in version 3 5 difflib IS_LINE_JUNK line Return True for ignorable lines The line line is ignorable if line is blank or contains a single otherwise it is not ignorable Used as a default for parameter linejunk in ndiff in older versions difflib IS_CHARACTER_JUNK ch Return True for ignorable characters The character ch is ignorable if ch is a space or tab otherwise it is not ignorable Used as a default for parameter charjunk in ndiff See also Pattern Matching The Gestalt Approach Discussion of a similar algorithm by John W Ratcliff and D E Metzener This was published in Dr Dobb s Journal in July 1988 SequenceMatcher Objects The SequenceMatcher class has this constructor class difflib SequenceMatcher isjunk None a b autojunk True Optional argument isjunk must be None the default or a one argument function that takes a sequence element and returns true if and only if the element is junk and should be ignored Passing None for isjunk is equivalent to passing lambda x False in other words no elements are ignored For example pass lambda x x in t if you re comparing lines as sequences of ,en
1067,characters and don t want to synch up on blanks or hard tabs The optional arguments a and b are sequences to be compared both default to empty strings The elements of both sequences must be hashable The optional argument autojunk can be used to disable the automatic junk heuristic Changed in version 3 2 Added the autojunk parameter SequenceMatcher objects get three data attributes bjunk is the set of elements of b for which isjunk is True bpopular is the set of non junk elements considered popular by the heuristic if it is not disabled b2j is a dict mapping the remaining elements of b to a list of positions where they occur All three are reset whenever b is reset with set_seqs or set_seq2 New in version 3 2 The bjunk and bpopular attributes SequenceMatcher objects have the following methods set_seqs a b Set the two sequences to be compared SequenceMatcher computes and caches detailed information about the second sequence so if you want to compare one sequence against many sequences use set_seq2 to set the commonly used sequence once and call set_seq1 repeatedly once for each of the other sequences set_seq1 a Set the first sequence to be compared The second sequence to be compared is not changed set_seq2 b Set the second sequence to be compared The first sequence to be compared is not changed find_longest_match alo 0 ahi None blo 0 bhi None Find longest matching block in a alo ahi and b blo bhi If isjunk was omitted or None find_longest_match returns i j k such that a i i k is equal to b j j k where alo i i k ahi and blo j j k bhi For all i j k meeting those conditions the additional conditions k k i i and if i i j j are also met In other words of all maximal matching blocks return one that starts earliest in a and of all those maximal matching blocks that start earliest in a return the one that starts earliest in b s SequenceMatcher None abcd abcd abcd s find_longest_match 0 5 0 9 Match a 0 b 4 size 5 If isjunk was provided first the longest matching block is determined as above but with the additional restriction that no junk element appears in the block Then that block is extended as far as possible by matching only junk elements on both sides So the resulting block never matches on junk except as identical junk happens to be adjacent to an interesting match Here s the same example as before but considering blanks to be junk That prevents abcd from matching the abcd at the tail end of the second sequence directly Instead only the abcd can match and matches the leftmost abcd in the second sequence s SequenceMatcher lambda x x abcd abcd abcd s find_longest_match 0 5 0 9 Match a 1 b 0 size 4 If no blocks match this returns alo blo 0 This method returns a named tuple Match a b size Changed in version 3 9 Added default arguments get_matching_blocks Return list of triples describing non overlapping matching subsequences Each triple is of the form i j n and means that a i i n b j j n The triples are monotonically increasing in i and j The last triple is a dummy and has the value len a len b 0 It is the only triple with n 0 If i j n and i j n are adjacent triples in the list and the second is not the last triple in the list then i n i or j n j in other words adjacent triples always describe non adjacent equal blocks s SequenceMatcher None abxcd abcd s get_matching_blocks Match a 0 b 0 size 2 Match a 3 b 2 size 2 Match a 5 b 4 size 0 get_opcodes Return list of 5 tuples describing how to turn a into b Each tuple is of the form tag i1 i2 j1 j2 The first tuple has i1 j1 0 and remaining tuples have i1 equal to the i2 from the preceding tuple and likewise j1 equal to the previous j2 The tag values are strings with these meanings Value Meaning replace a i1 i2 should be replaced by b j1 j2 delete a i1 i2 should be deleted Note that j1 j2 in this case insert b j1 j2 should be inserted at a i1 i1 Note that i1 i2 in this case equal a i1 i2 b j1 j2 the sub sequences are equal For example a qabxcd b abycdf s SequenceMatcher None a b for tag i1 i2 j1 j2 in s get_opcodes print 7 a b r 8 r format tag i1 i2 j1 j2 a i1 i2 b j1 j2 delete a 0 1 b,en
1068, 0 0 q equal a 1 3 b 0 2 ab ab replace a 3 4 b 2 3 x y equal a 4 6 b 3 5 cd cd insert a 6 6 b 5 6 f get_grouped_opcodes n 3 Return a generator of groups with up to n lines of context Starting with the groups returned by get_opcodes this method splits out smaller change clusters and eliminates intervening ranges which have no changes The groups are returned in the same format as get_opcodes ratio Return a measure of the sequences similarity as a float in the range 0 1 Where T is the total number of elements in both sequences and M is the number of matches this is 2 0 M T Note that this is 1 0 if the sequences are identical and 0 0 if they have nothing in common This is expensive to compute if get_matching_blocks or get_opcodes hasn t already been called in which case you may want to try quick_ratio or real_quick_ratio first to get an upper bound Note Caution The result of a ratio call may depend on the order of the arguments For instance SequenceMatcher None tide diet ratio 0 25 SequenceMatcher None diet tide ratio 0 5 quick_ratio Return an upper bound on ratio relatively quickly real_quick_ratio Return an upper bound on ratio very quickly The three methods that return the ratio of matching to total characters can give different results due to differing levels of approximation although quick_ratio and real_quick_ratio are always at least as large as ratio s SequenceMatcher None abcd bcde s ratio 0 75 s quick_ratio 0 75 s real_quick_ratio 1 0 SequenceMatcher Examples This example compares two strings considering blanks to be junk s SequenceMatcher lambda x x private Thread currentThread private volatile Thread currentThread ratio returns a float in 0 1 measuring the similarity of the sequences As a rule of thumb a ratio value over 0 6 means the sequences are close matches print round s ratio 3 0 866 If you re only interested in where the sequences match get_matching_blocks is handy for block in s get_matching_blocks print a d and b d match for d elements block a 0 and b 0 match for 8 elements a 8 and b 17 match for 21 elements a 29 and b 38 match for 0 elements Note that the last tuple returned by get_matching_blocks is always a dummy len a len b 0 and this is the only case in which the last tuple element number of elements matched is 0 If you want to know how to change the first sequence into the second use get_opcodes for opcode in s get_opcodes print 6s a d d b d d opcode equal a 0 8 b 0 8 insert a 8 8 b 8 17 equal a 8 29 b 17 38 See also The get_close_matches function in this module which shows how simple code building on SequenceMatcher can be used to do useful work Simple version control recipe for a small application built with SequenceMatcher Differ Objects Note that Differ generated deltas make no claim to be minimal diffs To the contrary minimal diffs are often counter intuitive because they synch up anywhere possible sometimes accidental matches 100 pages apart Restricting synch points to contiguous matches preserves some notion of locality at the occasional cost of producing a longer diff The Differ class has this constructor class difflib Differ linejunk None charjunk None Optional keyword parameters linejunk and charjunk are for filter functions or None linejunk A function that accepts a single string argument and returns true if the string is junk The default is None meaning that no line is considered junk charjunk A function that accepts a single character argument a string of length 1 and returns true if the character is junk The default is None meaning that no character is considered junk These junk filtering functions speed up matching to find differences and do not cause any differing lines or characters to be ignored Read the description of the find_longest_match method s isjunk parameter for an explanation Differ objects are used deltas generated via a single method compare a b Compare two sequences of lines and generate the delta a sequence of lines Each sequence must contain individual single line strings ending with newlines Such sequences can be obtained from the readlines method of file like obje,en
1069,cts The delta generated also consists of newline terminated strings ready to be printed as is via the writelines method of a file like object Differ Example This example compares two texts First we set up the texts sequences of individual single line strings ending with newlines such sequences can also be obtained from the readlines method of file like objects text1 1 Beautiful is better than ugly 2 Explicit is better than implicit 3 Simple is better than complex 4 Complex is better than complicated splitlines keepends True len text1 4 text1 0 1 n text2 1 Beautiful is better than ugly 3 Simple is better than complex 4 Complicated is better than complex 5 Flat is better than nested splitlines keepends True Next we instantiate a Differ object d Differ Note that when instantiating a Differ object we may pass functions to filter out line and character junk See the Differ constructor for details Finally we compare the two result list d compare text1 text2 result is a list of strings so let s pretty print it from pprint import pprint pprint result 1 Beautiful is better than ugly n 2 Explicit is better than implicit n 3 Simple is better than complex n 3 Simple is better than complex n n 4 Complex is better than complicated n n 4 Complicated is better than complex n n 5 Flat is better than nested n As a single multi line string it looks like this import sys sys stdout writelines result 1 Beautiful is better than ugly 2 Explicit is better than implicit 3 Simple is better than complex 3 Simple is better than complex 4 Complex is better than complicated 4 Complicated is better than complex 5 Flat is better than nested A command line interface to difflib This example shows how to use difflib to create a diff like utility Command line interface to difflib py providing diffs in four formats ndiff lists every line and highlights interline changes context highlights clusters of changes in a before after format unified highlights clusters of changes in an inline format html generates side by side comparison with change highlights import sys os difflib argparse from datetime import datetime timezone def file_mtime path t datetime fromtimestamp os stat path st_mtime timezone utc return t astimezone isoformat def main parser argparse ArgumentParser parser add_argument c action store_true default False help Produce a context format diff default parser add_argument u action store_true default False help Produce a unified format diff parser add_argument m action store_true default False help Produce HTML side by side diff can use c and l in conjunction parser add_argument n action store_true default False help Produce a ndiff format diff parser add_argument l lines type int default 3 help Set number of context lines default 3 parser add_argument fromfile parser add_argument tofile options parser parse_args n options lines fromfile options fromfile tofile options tofile fromdate file_mtime fromfile todate file_mtime tofile with open fromfile as ff fromlines ff readlines with open tofile as tf tolines tf readlines if options u diff difflib unified_diff fromlines tolines fromfile tofile fromdate todate n n elif options n diff difflib ndiff fromlines tolines elif options m diff difflib HtmlDiff make_file fromlines tolines fromfile tofile context options c numlines n else diff difflib context_diff fromlines tolines fromfile tofile fromdate todate n n sys stdout writelines diff if __name__ __main__ main ndiff example This example shows how to use difflib ndiff ndiff q file1 file2 or ndiff r1 r2 ndiff_output file1_or_file2 Print a human friendly file difference report to stdout Both inter and intra line differences are noted In the second form recreate file1 r1 or file2 r2 on stdout from an ndiff report on stdin In the first form if q quiet is not specified the first two lines of output are file1 file2 Each remaining line begins with a two letter code line unique to file1 line unique to file2 line common to both files line not present in either input file Lines beginning with attempt to guide the eye to intraline differences and were not present in e,en
1070,ither input file These lines can be confusing if the source files contain tab characters The first file can be recovered by retaining only lines that begin with or and deleting those 2 character prefixes use ndiff with r1 The second file can be recovered similarly but by retaining only and lines use ndiff with r2 or on Unix the second file can be recovered by piping the output through sed n s p __version__ 1 7 0 import difflib sys def fail msg out sys stderr write out msg n n out __doc__ return 0 open a file return the file object gripe and return 0 if it couldn t be opened def fopen fname try return open fname except IOError as detail return fail couldn t open fname str detail open two files spray the diff to stdout return false iff a problem def fcompare f1name f2name f1 fopen f1name f2 fopen f2name if not f1 or not f2 return 0 a f1 readlines f1 close b f2 readlines f2 close for line in difflib ndiff a b print line end return 1 crack args sys argv 1 is normal compare return false iff a problem def main args import getopt try opts args getopt getopt args qr except getopt error as detail return fail str detail noisy 1 qseen rseen 0 for opt val in opts if opt q qseen 1 noisy 0 elif opt r rseen 1 whichfile val if qseen and rseen return fail can t specify both q and r if rseen if args return fail no args allowed with r option if whichfile in 1 2 restore whichfile return 1 return fail r value must be 1 or 2 if len args 2 return fail need 2 filename args f1name f2name args if noisy print f1name print f2name return fcompare f1name f2name read ndiff output from stdin and print file1 which 1 or file2 which 2 to stdout def restore which restored difflib restore sys stdin readlines which sys stdout writelines restored if __name__ __main__ main sys argv 1,en
1071,threading Thread based parallelism Source code Lib threading py This module constructs higher level threading interfaces on top of the lower level _thread module Changed in version 3 7 This module used to be optional it is now always available See also concurrent futures ThreadPoolExecutor offers a higher level interface to push tasks to a background thread without blocking execution of the calling thread while still being able to retrieve their results when needed queue provides a thread safe interface for exchanging data between running threads asyncio offers an alternative approach to achieving task level concurrency without requiring the use of multiple operating system threads Note In the Python 2 x series this module contained camelCase names for some methods and functions These are deprecated as of Python 3 10 but they are still supported for compatibility with Python 2 5 and lower CPython implementation detail In CPython due to the Global Interpreter Lock only one thread can execute Python code at once even though certain performance oriented libraries might overcome this limitation If you want your application to make better use of the computational resources of multi core machines you are advised to use multiprocessing or concurrent futures ProcessPoolExecutor However threading is still an appropriate model if you want to run multiple I O bound tasks simultaneously Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information This module defines the following functions threading active_count Return the number of Thread objects currently alive The returned count is equal to the length of the list returned by enumerate The function activeCount is a deprecated alias for this function threading current_thread Return the current Thread object corresponding to the caller s thread of control If the caller s thread of control was not created through the threading module a dummy thread object with limited functionality is returned The function currentThread is a deprecated alias for this function threading excepthook args Handle uncaught exception raised by Thread run The args argument has the following attributes exc_type Exception type exc_value Exception value can be None exc_traceback Exception traceback can be None thread Thread which raised the exception can be None If exc_type is SystemExit the exception is silently ignored Otherwise the exception is printed out on sys stderr If this function raises an exception sys excepthook is called to handle it threading excepthook can be overridden to control how uncaught exceptions raised by Thread run are handled Storing exc_value using a custom hook can create a reference cycle It should be cleared explicitly to break the reference cycle when the exception is no longer needed Storing thread using a custom hook can resurrect it if it is set to an object which is being finalized Avoid storing thread after the custom hook completes to avoid resurrecting objects See also sys excepthook handles uncaught exceptions New in version 3 8 threading __excepthook__ Holds the original value of threading excepthook It is saved so that the original value can be restored in case they happen to get replaced with broken or alternative objects New in version 3 10 threading get_ident Return the thread identifier of the current thread This is a nonzero integer Its value has no direct meaning it is intended as a magic cookie to be used e g to index a dictionary of thread specific data Thread identifiers may be recycled when a thread exits and another thread is created New in version 3 3 threading get_native_id Return the native integral Thread ID of the current thread assigned by the kernel This is a non negative integer Its value may be used to uniquely identify this particular thread system wide until the thread terminates after which the value may be recycled by the OS Availability Windows FreeBSD Linux macOS OpenBSD NetBSD AIX DragonFlyBSD New in version 3 8 thread,en
1072,ing enumerate Return a list of all Thread objects currently active The list includes daemonic threads and dummy thread objects created by current_thread It excludes terminated threads and threads that have not yet been started However the main thread is always part of the result even when terminated threading main_thread Return the main Thread object In normal conditions the main thread is the thread from which the Python interpreter was started New in version 3 4 threading settrace func Set a trace function for all threads started from the threading module The func will be passed to sys settrace for each thread before its run method is called threading settrace_all_threads func Set a trace function for all threads started from the threading module and all Python threads that are currently executing The func will be passed to sys settrace for each thread before its run method is called New in version 3 12 threading gettrace Get the trace function as set by settrace New in version 3 10 threading setprofile func Set a profile function for all threads started from the threading module The func will be passed to sys setprofile for each thread before its run method is called threading setprofile_all_threads func Set a profile function for all threads started from the threading module and all Python threads that are currently executing The func will be passed to sys setprofile for each thread before its run method is called New in version 3 12 threading getprofile Get the profiler function as set by setprofile New in version 3 10 threading stack_size size Return the thread stack size used when creating new threads The optional size argument specifies the stack size to be used for subsequently created threads and must be 0 use platform or configured default or a positive integer value of at least 32 768 32 KiB If size is not specified 0 is used If changing the thread stack size is unsupported a RuntimeError is raised If the specified stack size is invalid a ValueError is raised and the stack size is unmodified 32 KiB is currently the minimum supported stack size value to guarantee sufficient stack space for the interpreter itself Note that some platforms may have particular restrictions on values for the stack size such as requiring a minimum stack size 32 KiB or requiring allocation in multiples of the system memory page size platform documentation should be referred to for more information 4 KiB pages are common using multiples of 4096 for the stack size is the suggested approach in the absence of more specific information Availability Windows pthreads Unix platforms with POSIX threads support This module also defines the following constant threading TIMEOUT_MAX The maximum value allowed for the timeout parameter of blocking functions Lock acquire RLock acquire Condition wait etc Specifying a timeout greater than this value will raise an OverflowError New in version 3 2 This module defines a number of classes which are detailed in the sections below The design of this module is loosely based on Java s threading model However where Java makes locks and condition variables basic behavior of every object they are separate objects in Python Python s Thread class supports a subset of the behavior of Java s Thread class currently there are no priorities no thread groups and threads cannot be destroyed stopped suspended resumed or interrupted The static methods of Java s Thread class when implemented are mapped to module level functions All of the methods described below are executed atomically Thread Local Data Thread local data is data whose values are thread specific To manage thread local data just create an instance of local or a subclass and store attributes on it mydata threading local mydata x 1 The instance s values will be different for separate threads class threading local A class that represents thread local data For more details and extensive examples see the documentation string of the _threading_local module Lib _threading_local py Thread Objects The Thread class represents an activity that is run in a separate threa,en
1073,d of control There are two ways to specify the activity by passing a callable object to the constructor or by overriding the run method in a subclass No other methods except for the constructor should be overridden in a subclass In other words only override the __init__ and run methods of this class Once a thread object is created its activity must be started by calling the thread s start method This invokes the run method in a separate thread of control Once the thread s activity is started the thread is considered alive It stops being alive when its run method terminates either normally or by raising an unhandled exception The is_alive method tests whether the thread is alive Other threads can call a thread s join method This blocks the calling thread until the thread whose join method is called is terminated A thread has a name The name can be passed to the constructor and read or changed through the name attribute If the run method raises an exception threading excepthook is called to handle it By default threading excepthook ignores silently SystemExit A thread can be flagged as a daemon thread The significance of this flag is that the entire Python program exits when only daemon threads are left The initial value is inherited from the creating thread The flag can be set through the daemon property or the daemon constructor argument Note Daemon threads are abruptly stopped at shutdown Their resources such as open files database transactions etc may not be released properly If you want your threads to stop gracefully make them non daemonic and use a suitable signalling mechanism such as an Event There is a main thread object this corresponds to the initial thread of control in the Python program It is not a daemon thread There is the possibility that dummy thread objects are created These are thread objects corresponding to alien threads which are threads of control started outside the threading module such as directly from C code Dummy thread objects have limited functionality they are always considered alive and daemonic and cannot be joined They are never deleted since it is impossible to detect the termination of alien threads class threading Thread group None target None name None args kwargs daemon None This constructor should always be called with keyword arguments Arguments are group should be None reserved for future extension when a ThreadGroup class is implemented target is the callable object to be invoked by the run method Defaults to None meaning nothing is called name is the thread name By default a unique name is constructed of the form Thread N where N is a small decimal number or Thread N target where target is target __name__ if the target argument is specified args is a list or tuple of arguments for the target invocation Defaults to kwargs is a dictionary of keyword arguments for the target invocation Defaults to If not None daemon explicitly sets whether the thread is daemonic If None the default the daemonic property is inherited from the current thread If the subclass overrides the constructor it must make sure to invoke the base class constructor Thread __init__ before doing anything else to the thread Changed in version 3 3 Added the daemon parameter Changed in version 3 10 Use the target name if name argument is omitted start Start the thread s activity It must be called at most once per thread object It arranges for the object s run method to be invoked in a separate thread of control This method will raise a RuntimeError if called more than once on the same thread object run Method representing the thread s activity You may override this method in a subclass The standard run method invokes the callable object passed to the object s constructor as the target argument if any with positional and keyword arguments taken from the args and kwargs arguments respectively Using list or tuple as the args argument which passed to the Thread could achieve the same effect Example from threading import Thread t Thread target print args 1 t run 1 t Thread target print args 1 t run 1 join timeout None Wa,en
1074,it until the thread terminates This blocks the calling thread until the thread whose join method is called terminates either normally or through an unhandled exception or until the optional timeout occurs When the timeout argument is present and not None it should be a floating point number specifying a timeout for the operation in seconds or fractions thereof As join always returns None you must call is_alive after join to decide whether a timeout happened if the thread is still alive the join call timed out When the timeout argument is not present or None the operation will block until the thread terminates A thread can be joined many times join raises a RuntimeError if an attempt is made to join the current thread as that would cause a deadlock It is also an error to join a thread before it has been started and attempts to do so raise the same exception name A string used for identification purposes only It has no semantics Multiple threads may be given the same name The initial name is set by the constructor getName setName Deprecated getter setter API for name use it directly as a property instead Deprecated since version 3 10 ident The thread identifier of this thread or None if the thread has not been started This is a nonzero integer See the get_ident function Thread identifiers may be recycled when a thread exits and another thread is created The identifier is available even after the thread has exited native_id The Thread ID TID of this thread as assigned by the OS kernel This is a non negative integer or None if the thread has not been started See the get_native_id function This value may be used to uniquely identify this particular thread system wide until the thread terminates after which the value may be recycled by the OS Note Similar to Process IDs Thread IDs are only valid guaranteed unique system wide from the time the thread is created until the thread has been terminated Availability Windows FreeBSD Linux macOS OpenBSD NetBSD AIX DragonFlyBSD New in version 3 8 is_alive Return whether the thread is alive This method returns True just before the run method starts until just after the run method terminates The module function enumerate returns a list of all alive threads daemon A boolean value indicating whether this thread is a daemon thread True or not False This must be set before start is called otherwise RuntimeError is raised Its initial value is inherited from the creating thread the main thread is not a daemon thread and therefore all threads created in the main thread default to daemon False The entire Python program exits when no alive non daemon threads are left isDaemon setDaemon Deprecated getter setter API for daemon use it directly as a property instead Deprecated since version 3 10 Lock Objects A primitive lock is a synchronization primitive that is not owned by a particular thread when locked In Python it is currently the lowest level synchronization primitive available implemented directly by the _thread extension module A primitive lock is in one of two states locked or unlocked It is created in the unlocked state It has two basic methods acquire and release When the state is unlocked acquire changes the state to locked and returns immediately When the state is locked acquire blocks until a call to release in another thread changes it to unlocked then the acquire call resets it to locked and returns The release method should only be called in the locked state it changes the state to unlocked and returns immediately If an attempt is made to release an unlocked lock a RuntimeError will be raised Locks also support the context management protocol When more than one thread is blocked in acquire waiting for the state to turn to unlocked only one thread proceeds when a release call resets the state to unlocked which one of the waiting threads proceeds is not defined and may vary across implementations All methods are executed atomically class threading Lock The class implementing primitive lock objects Once a thread has acquired a lock subsequent attempts to acquire it block until it is rel,en
1075,eased any thread may release it Note that Lock is actually a factory function which returns an instance of the most efficient version of the concrete Lock class that is supported by the platform acquire blocking True timeout 1 Acquire a lock blocking or non blocking When invoked with the blocking argument set to True the default block until the lock is unlocked then set it to locked and return True When invoked with the blocking argument set to False do not block If a call with blocking set to True would block return False immediately otherwise set the lock to locked and return True When invoked with the floating point timeout argument set to a positive value block for at most the number of seconds specified by timeout and as long as the lock cannot be acquired A timeout argument of 1 specifies an unbounded wait It is forbidden to specify a timeout when blocking is False The return value is True if the lock is acquired successfully False if not for example if the timeout expired Changed in version 3 2 The timeout parameter is new Changed in version 3 2 Lock acquisition can now be interrupted by signals on POSIX if the underlying threading implementation supports it release Release a lock This can be called from any thread not only the thread which has acquired the lock When the lock is locked reset it to unlocked and return If any other threads are blocked waiting for the lock to become unlocked allow exactly one of them to proceed When invoked on an unlocked lock a RuntimeError is raised There is no return value locked Return True if the lock is acquired RLock Objects A reentrant lock is a synchronization primitive that may be acquired multiple times by the same thread Internally it uses the concepts of owning thread and recursion level in addition to the locked unlocked state used by primitive locks In the locked state some thread owns the lock in the unlocked state no thread owns it To lock the lock a thread calls its acquire method this returns once the thread owns the lock To unlock the lock a thread calls its release method acquire release call pairs may be nested only the final release the release of the outermost pair resets the lock to unlocked and allows another thread blocked in acquire to proceed Reentrant locks also support the context management protocol class threading RLock This class implements reentrant lock objects A reentrant lock must be released by the thread that acquired it Once a thread has acquired a reentrant lock the same thread may acquire it again without blocking the thread must release it once for each time it has acquired it Note that RLock is actually a factory function which returns an instance of the most efficient version of the concrete RLock class that is supported by the platform acquire blocking True timeout 1 Acquire a lock blocking or non blocking When invoked without arguments if this thread already owns the lock increment the recursion level by one and return immediately Otherwise if another thread owns the lock block until the lock is unlocked Once the lock is unlocked not owned by any thread then grab ownership set the recursion level to one and return If more than one thread is blocked waiting until the lock is unlocked only one at a time will be able to grab ownership of the lock There is no return value in this case When invoked with the blocking argument set to True do the same thing as when called without arguments and return True When invoked with the blocking argument set to False do not block If a call without an argument would block return False immediately otherwise do the same thing as when called without arguments and return True When invoked with the floating point timeout argument set to a positive value block for at most the number of seconds specified by timeout and as long as the lock cannot be acquired Return True if the lock has been acquired False if the timeout has elapsed Changed in version 3 2 The timeout parameter is new release Release a lock decrementing the recursion level If after the decrement it is zero reset the lock to unlocked not owned by an,en
1076,y thread and if any other threads are blocked waiting for the lock to become unlocked allow exactly one of them to proceed If after the decrement the recursion level is still nonzero the lock remains locked and owned by the calling thread Only call this method when the calling thread owns the lock A RuntimeError is raised if this method is called when the lock is unlocked There is no return value Condition Objects A condition variable is always associated with some kind of lock this can be passed in or one will be created by default Passing one in is useful when several condition variables must share the same lock The lock is part of the condition object you don t have to track it separately A condition variable obeys the context management protocol using the with statement acquires the associated lock for the duration of the enclosed block The acquire and release methods also call the corresponding methods of the associated lock Other methods must be called with the associated lock held The wait method releases the lock and then blocks until another thread awakens it by calling notify or notify_all Once awakened wait re acquires the lock and returns It is also possible to specify a timeout The notify method wakes up one of the threads waiting for the condition variable if any are waiting The notify_all method wakes up all threads waiting for the condition variable Note the notify and notify_all methods don t release the lock this means that the thread or threads awakened will not return from their wait call immediately but only when the thread that called notify or notify_all finally relinquishes ownership of the lock The typical programming style using condition variables uses the lock to synchronize access to some shared state threads that are interested in a particular change of state call wait repeatedly until they see the desired state while threads that modify the state call notify or notify_all when they change the state in such a way that it could possibly be a desired state for one of the waiters For example the following code is a generic producer consumer situation with unlimited buffer capacity Consume one item with cv while not an_item_is_available cv wait get_an_available_item Produce one item with cv make_an_item_available cv notify The while loop checking for the application s condition is necessary because wait can return after an arbitrary long time and the condition which prompted the notify call may no longer hold true This is inherent to multi threaded programming The wait_for method can be used to automate the condition checking and eases the computation of timeouts Consume an item with cv cv wait_for an_item_is_available get_an_available_item To choose between notify and notify_all consider whether one state change can be interesting for only one or several waiting threads E g in a typical producer consumer situation adding one item to the buffer only needs to wake up one consumer thread class threading Condition lock None This class implements condition variable objects A condition variable allows one or more threads to wait until they are notified by another thread If the lock argument is given and not None it must be a Lock or RLock object and it is used as the underlying lock Otherwise a new RLock object is created and used as the underlying lock Changed in version 3 3 changed from a factory function to a class acquire args Acquire the underlying lock This method calls the corresponding method on the underlying lock the return value is whatever that method returns release Release the underlying lock This method calls the corresponding method on the underlying lock there is no return value wait timeout None Wait until notified or until a timeout occurs If the calling thread has not acquired the lock when this method is called a RuntimeError is raised This method releases the underlying lock and then blocks until it is awakened by a notify or notify_all call for the same condition variable in another thread or until the optional timeout occurs Once awakened or timed out it re acquires the lock a,en
1077,nd returns When the timeout argument is present and not None it should be a floating point number specifying a timeout for the operation in seconds or fractions thereof When the underlying lock is an RLock it is not released using its release method since this may not actually unlock the lock when it was acquired multiple times recursively Instead an internal interface of the RLock class is used which really unlocks it even when it has been recursively acquired several times Another internal interface is then used to restore the recursion level when the lock is reacquired The return value is True unless a given timeout expired in which case it is False Changed in version 3 2 Previously the method always returned None wait_for predicate timeout None Wait until a condition evaluates to true predicate should be a callable which result will be interpreted as a boolean value A timeout may be provided giving the maximum time to wait This utility method may call wait repeatedly until the predicate is satisfied or until a timeout occurs The return value is the last return value of the predicate and will evaluate to False if the method timed out Ignoring the timeout feature calling this method is roughly equivalent to writing while not predicate cv wait Therefore the same rules apply as with wait The lock must be held when called and is re acquired on return The predicate is evaluated with the lock held New in version 3 2 notify n 1 By default wake up one thread waiting on this condition if any If the calling thread has not acquired the lock when this method is called a RuntimeError is raised This method wakes up at most n of the threads waiting for the condition variable it is a no op if no threads are waiting The current implementation wakes up exactly n threads if at least n threads are waiting However it s not safe to rely on this behavior A future optimized implementation may occasionally wake up more than n threads Note an awakened thread does not actually return from its wait call until it can reacquire the lock Since notify does not release the lock its caller should notify_all Wake up all threads waiting on this condition This method acts like notify but wakes up all waiting threads instead of one If the calling thread has not acquired the lock when this method is called a RuntimeError is raised The method notifyAll is a deprecated alias for this method Semaphore Objects This is one of the oldest synchronization primitives in the history of computer science invented by the early Dutch computer scientist Edsger W Dijkstra he used the names P and V instead of acquire and release A semaphore manages an internal counter which is decremented by each acquire call and incremented by each release call The counter can never go below zero when acquire finds that it is zero it blocks waiting until some other thread calls release Semaphores also support the context management protocol class threading Semaphore value 1 This class implements semaphore objects A semaphore manages an atomic counter representing the number of release calls minus the number of acquire calls plus an initial value The acquire method blocks if necessary until it can return without making the counter negative If not given value defaults to 1 The optional argument gives the initial value for the internal counter it defaults to 1 If the value given is less than 0 ValueError is raised Changed in version 3 3 changed from a factory function to a class acquire blocking True timeout None Acquire a semaphore When invoked without arguments If the internal counter is larger than zero on entry decrement it by one and return True immediately If the internal counter is zero on entry block until awoken by a call to release Once awoken and the counter is greater than 0 decrement the counter by 1 and return True Exactly one thread will be awoken by each call to release The order in which threads are awoken should not be relied on When invoked with blocking set to False do not block If a call without an argument would block return False immediately otherwise do the same thing,en
1078, as when called without arguments and return True When invoked with a timeout other than None it will block for at most timeout seconds If acquire does not complete successfully in that interval return False Return True otherwise Changed in version 3 2 The timeout parameter is new release n 1 Release a semaphore incrementing the internal counter by n When it was zero on entry and other threads are waiting for it to become larger than zero again wake up n of those threads Changed in version 3 9 Added the n parameter to release multiple waiting threads at once class threading BoundedSemaphore value 1 Class implementing bounded semaphore objects A bounded semaphore checks to make sure its current value doesn t exceed its initial value If it does ValueError is raised In most situations semaphores are used to guard resources with limited capacity If the semaphore is released too many times it s a sign of a bug If not given value defaults to 1 Changed in version 3 3 changed from a factory function to a class Semaphore Example Semaphores are often used to guard resources with limited capacity for example a database server In any situation where the size of the resource is fixed you should use a bounded semaphore Before spawning any worker threads your main thread would initialize the semaphore maxconnections 5 pool_sema BoundedSemaphore value maxconnections Once spawned worker threads call the semaphore s acquire and release methods when they need to connect to the server with pool_sema conn connectdb try use connection finally conn close The use of a bounded semaphore reduces the chance that a programming error which causes the semaphore to be released more than it s acquired will go undetected Event Objects This is one of the simplest mechanisms for communication between threads one thread signals an event and other threads wait for it An event object manages an internal flag that can be set to true with the set method and reset to false with the clear method The wait method blocks until the flag is true class threading Event Class implementing event objects An event manages a flag that can be set to true with the set method and reset to false with the clear method The wait method blocks until the flag is true The flag is initially false Changed in version 3 3 changed from a factory function to a class is_set Return True if and only if the internal flag is true The method isSet is a deprecated alias for this method set Set the internal flag to true All threads waiting for it to become true are awakened Threads that call wait once the flag is true will not block at all clear Reset the internal flag to false Subsequently threads calling wait will block until set is called to set the internal flag to true again wait timeout None Block as long as the internal flag is false and the timeout if given has not expired The return value represents the reason that this blocking method returned True if returning because the internal flag is set to true or False if a timeout is given and the the internal flag did not become true within the given wait time When the timeout argument is present and not None it should be a floating point number specifying a timeout for the operation in seconds or fractions thereof Changed in version 3 1 Previously the method always returned None Timer Objects This class represents an action that should be run only after a certain amount of time has passed a timer Timer is a subclass of Thread and as such also functions as an example of creating custom threads Timers are started as with threads by calling their Timer start method The timer can be stopped before its action has begun by calling the cancel method The interval the timer will wait before executing its action may not be exactly the same as the interval specified by the user For example def hello print hello world t Timer 30 0 hello t start after 30 seconds hello world will be printed class threading Timer interval function args None kwargs None Create a timer that will run function with arguments args and keyword arguments kwargs after interval secon,en
1079,ds have passed If args is None the default then an empty list will be used If kwargs is None the default then an empty dict will be used Changed in version 3 3 changed from a factory function to a class cancel Stop the timer and cancel the execution of the timer s action This will only work if the timer is still in its waiting stage Barrier Objects New in version 3 2 This class provides a simple synchronization primitive for use by a fixed number of threads that need to wait for each other Each of the threads tries to pass the barrier by calling the wait method and will block until all of the threads have made their wait calls At this point the threads are released simultaneously The barrier can be reused any number of times for the same number of threads As an example here is a simple way to synchronize a client and server thread b Barrier 2 timeout 5 def server start_server b wait while True connection accept_connection process_server_connection connection def client b wait while True connection make_connection process_client_connection connection class threading Barrier parties action None timeout None Create a barrier object for parties number of threads An action when provided is a callable to be called by one of the threads when they are released timeout is the default timeout value if none is specified for the wait method wait timeout None Pass the barrier When all the threads party to the barrier have called this function they are all released simultaneously If a timeout is provided it is used in preference to any that was supplied to the class constructor The return value is an integer in the range 0 to parties 1 different for each thread This can be used to select a thread to do some special housekeeping e g i barrier wait if i 0 Only one thread needs to print this print passed the barrier If an action was provided to the constructor one of the threads will have called it prior to being released Should this call raise an error the barrier is put into the broken state If the call times out the barrier is put into the broken state This method may raise a BrokenBarrierError exception if the barrier is broken or reset while a thread is waiting reset Return the barrier to the default empty state Any threads waiting on it will receive the BrokenBarrierError exception Note that using this function may require some external synchronization if there are other threads whose state is unknown If a barrier is broken it may be better to just leave it and create a new one abort Put the barrier into a broken state This causes any active or future calls to wait to fail with the BrokenBarrierError Use this for example if one of the threads needs to abort to avoid deadlocking the application It may be preferable to simply create the barrier with a sensible timeout value to automatically guard against one of the threads going awry parties The number of threads required to pass the barrier n_waiting The number of threads currently waiting in the barrier broken A boolean that is True if the barrier is in the broken state exception threading BrokenBarrierError This exception a subclass of RuntimeError is raised when the Barrier object is reset or broken Using locks conditions and semaphores in the with statement All of the objects provided by this module that have acquire and release methods can be used as context managers for a with statement The acquire method will be called when the block is entered and release will be called when the block is exited Hence the following snippet with some_lock do something is equivalent to some_lock acquire try do something finally some_lock release Currently Lock RLock Condition Semaphore and BoundedSemaphore objects may be used as with statement context managers,en
1080,Dealing with Bugs Python is a mature programming language which has established a reputation for stability In order to maintain this reputation the developers would like to know of any deficiencies you find in Python It can be sometimes faster to fix bugs yourself and contribute patches to Python as it streamlines the process and involves less people Learn how to contribute Documentation bugs If you find a bug in this documentation or would like to propose an improvement please submit a bug report on the tracker If you have a suggestion on how to fix it include that as well You can also open a discussion item on our Documentation Discourse forum If you re short on time you can also email documentation bug reports to docs python org behavioral bugs can be sent to python list python org docs is a mailing list run by volunteers your request will be noticed though it may take a while to be processed See also Documentation bugs A list of documentation bugs that have been submitted to the Python issue tracker Issue Tracking Overview of the process involved in reporting an improvement on the tracker Helping with Documentation Comprehensive guide for individuals that are interested in contributing to Python documentation Documentation Translations A list of GitHub pages for documentation translation and their primary contacts Using the Python issue tracker Issue reports for Python itself should be submitted via the GitHub issues tracker https github com python cpython issues The GitHub issues tracker offers a web form which allows pertinent information to be entered and submitted to the developers The first step in filing a report is to determine whether the problem has already been reported The advantage in doing so aside from saving the developers time is that you learn what has been done to fix it it may be that the problem has already been fixed for the next release or additional information is needed in which case you are welcome to provide it if you can To do this search the tracker using the search box at the top of the page If the problem you re reporting is not already in the list log in to GitHub If you don t already have a GitHub account create a new account using the Sign up link It is not possible to submit a bug report anonymously Being now logged in you can submit an issue Click on the New issue button in the top bar to report a new issue The submission form has two fields Title and Comment For the Title field enter a very short description of the problem fewer than ten words is good In the Comment field describe the problem in detail including what you expected to happen and what did happen Be sure to include whether any extension modules were involved and what hardware and software platform you were using including version information as appropriate Each issue report will be reviewed by a developer who will determine what needs to be done to correct the problem You will receive an update each time an action is taken on the issue See also How to Report Bugs Effectively Article which goes into some detail about how to create a useful bug report This describes what kind of information is useful and why it is useful Bug Writing Guidelines Information about writing a good bug report Some of this is specific to the Mozilla project but describes general good practices Getting started contributing to Python yourself Beyond just reporting bugs that you find you are also welcome to submit patches to fix them You can find more information on how to get started patching Python in the Python Developer s Guide If you have questions the core mentorship mailing list is a friendly place to get answers to any and all questions pertaining to the process of fixing issues in Python,en
1081,io Core tools for working with streams Source code Lib io py Overview The io module provides Python s main facilities for dealing with various types of I O There are three main types of I O text I O binary I O and raw I O These are generic categories and various backing stores can be used for each of them A concrete object belonging to any of these categories is called a file object Other common terms are stream and file like object Independent of its category each concrete stream object will also have various capabilities it can be read only write only or read write It can also allow arbitrary random access seeking forwards or backwards to any location or only sequential access for example in the case of a socket or pipe All streams are careful about the type of data you give to them For example giving a str object to the write method of a binary stream will raise a TypeError So will giving a bytes object to the write method of a text stream Changed in version 3 3 Operations that used to raise IOError now raise OSError since IOError is now an alias of OSError Text I O Text I O expects and produces str objects This means that whenever the backing store is natively made of bytes such as in the case of a file encoding and decoding of data is made transparently as well as optional translation of platform specific newline characters The easiest way to create a text stream is with open optionally specifying an encoding f open myfile txt r encoding utf 8 In memory text streams are also available as StringIO objects f io StringIO some initial text data The text stream API is described in detail in the documentation of TextIOBase Binary I O Binary I O also called buffered I O expects bytes like objects and produces bytes objects No encoding decoding or newline translation is performed This category of streams can be used for all kinds of non text data and also when manual control over the handling of text data is desired The easiest way to create a binary stream is with open with b in the mode string f open myfile jpg rb In memory binary streams are also available as BytesIO objects f io BytesIO b some initial binary data x00 x01 The binary stream API is described in detail in the docs of BufferedIOBase Other library modules may provide additional ways to create text or binary streams See socket socket makefile for example Raw I O Raw I O also called unbuffered I O is generally used as a low level building block for binary and text streams it is rarely useful to directly manipulate a raw stream from user code Nevertheless you can create a raw stream by opening a file in binary mode with buffering disabled f open myfile jpg rb buffering 0 The raw stream API is described in detail in the docs of RawIOBase Text Encoding The default encoding of TextIOWrapper and open is locale specific locale getencoding However many developers forget to specify the encoding when opening text files encoded in UTF 8 e g JSON TOML Markdown etc since most Unix platforms use UTF 8 locale by default This causes bugs because the locale encoding is not UTF 8 for most Windows users For example May not work on Windows when non ASCII characters in the file with open README md as f long_description f read Accordingly it is highly recommended that you specify the encoding explicitly when opening text files If you want to use UTF 8 pass encoding utf 8 To use the current locale encoding encoding locale is supported since Python 3 10 See also Python UTF 8 Mode Python UTF 8 Mode can be used to change the default encoding to UTF 8 from locale specific encoding PEP 686 Python 3 15 will make Python UTF 8 Mode default Opt in EncodingWarning New in version 3 10 See PEP 597 for more details To find where the default locale encoding is used you can enable the X warn_default_encoding command line option or set the PYTHONWARNDEFAULTENCODING environment variable which will emit an EncodingWarning when the default encoding is used If you are providing an API that uses open or TextIOWrapper and passes encoding None as a parameter you can use text_encoding so that callers of th,en
1082,e API will emit an EncodingWarning if they don t pass an encoding However please consider using UTF 8 by default i e encoding utf 8 for new APIs High level Module Interface io DEFAULT_BUFFER_SIZE An int containing the default buffer size used by the module s buffered I O classes open uses the file s blksize as obtained by os stat if possible io open file mode r buffering 1 encoding None errors None newline None closefd True opener None This is an alias for the builtin open function This function raises an auditing event open with arguments path mode and flags The mode and flags arguments may have been modified or inferred from the original call io open_code path Opens the provided file with mode rb This function should be used when the intent is to treat the contents as executable code path should be a str and an absolute path The behavior of this function may be overridden by an earlier call to the PyFile_SetOpenCodeHook However assuming that path is a str and an absolute path open_code path should always behave the same as open path rb Overriding the behavior is intended for additional validation or preprocessing of the file New in version 3 8 io text_encoding encoding stacklevel 2 This is a helper function for callables that use open or TextIOWrapper and have an encoding None parameter This function returns encoding if it is not None Otherwise it returns locale or utf 8 depending on UTF 8 Mode This function emits an EncodingWarning if sys flags warn_default_encoding is true and encoding is None stacklevel specifies where the warning is emitted For example def read_text path encoding None encoding io text_encoding encoding stacklevel 2 with open path encoding as f return f read In this example an EncodingWarning is emitted for the caller of read_text See Text Encoding for more information New in version 3 10 Changed in version 3 11 text_encoding returns utf 8 when UTF 8 mode is enabled and encoding is None exception io BlockingIOError This is a compatibility alias for the builtin BlockingIOError exception exception io UnsupportedOperation An exception inheriting OSError and ValueError that is raised when an unsupported operation is called on a stream See also sys contains the standard IO streams sys stdin sys stdout and sys stderr Class hierarchy The implementation of I O streams is organized as a hierarchy of classes First abstract base classes ABCs which are used to specify the various categories of streams then concrete classes providing the standard stream implementations Note The abstract base classes also provide default implementations of some methods in order to help implementation of concrete stream classes For example BufferedIOBase provides unoptimized implementations of readinto and readline At the top of the I O hierarchy is the abstract base class IOBase It defines the basic interface to a stream Note however that there is no separation between reading and writing to streams implementations are allowed to raise UnsupportedOperation if they do not support a given operation The RawIOBase ABC extends IOBase It deals with the reading and writing of bytes to a stream FileIO subclasses RawIOBase to provide an interface to files in the machine s file system The BufferedIOBase ABC extends IOBase It deals with buffering on a raw binary stream RawIOBase Its subclasses BufferedWriter BufferedReader and BufferedRWPair buffer raw binary streams that are writable readable and both readable and writable respectively BufferedRandom provides a buffered interface to seekable streams Another BufferedIOBase subclass BytesIO is a stream of in memory bytes The TextIOBase ABC extends IOBase It deals with streams whose bytes represent text and handles encoding and decoding to and from strings TextIOWrapper which extends TextIOBase is a buffered text interface to a buffered raw stream BufferedIOBase Finally StringIO is an in memory stream for text Argument names are not part of the specification and only the arguments of open are intended to be used as keyword arguments The following table summarizes the ABCs provided by the io m,en
1083,odule ABC Inherits Stub Methods Mixin Methods and Properties IOBase fileno seek and close closed __enter__ __exit__ truncate flush isatty __iter__ __next__ readable readline readlines seekable tell writable and writelines RawIOBase IOBase readinto and write Inherited IOBase methods read and readall BufferedIOBase IOBase detach read Inherited IOBase methods readinto and read1 and write readinto1 TextIOBase IOBase detach read Inherited IOBase methods encoding errors readline and write and newlines I O Base Classes class io IOBase The abstract base class for all I O classes This class provides empty abstract implementations for many methods that derived classes can override selectively the default implementations represent a file that cannot be read written or seeked Even though IOBase does not declare read or write because their signatures will vary implementations and clients should consider those methods part of the interface Also implementations may raise a ValueError or UnsupportedOperation when operations they do not support are called The basic type used for binary data read from or written to a file is bytes Other bytes like objects are accepted as method arguments too Text I O classes work with str data Note that calling any method even inquiries on a closed stream is undefined Implementations may raise ValueError in this case IOBase and its subclasses supports the iterator protocol meaning that an IOBase object can be iterated over yielding the lines in a stream Lines are defined slightly differently depending on whether the stream is a binary stream yielding bytes or a text stream yielding character strings See readline below IOBase is also a context manager and therefore supports the with statement In this example file is closed after the with statement s suite is finished even if an exception occurs with open spam txt w as file file write Spam and eggs IOBase provides these data attributes and methods close Flush and close this stream This method has no effect if the file is already closed Once the file is closed any operation on the file e g reading or writing will raise a ValueError As a convenience it is allowed to call this method more than once only the first call however will have an effect closed True if the stream is closed fileno Return the underlying file descriptor an integer of the stream if it exists An OSError is raised if the IO object does not use a file descriptor flush Flush the write buffers of the stream if applicable This does nothing for read only and non blocking streams isatty Return True if the stream is interactive i e connected to a terminal tty device readable Return True if the stream can be read from If False read will raise OSError readline size 1 Read and return one line from the stream If size is specified at most size bytes will be read The line terminator is always b n for binary files for text files the newline argument to open can be used to select the line terminator s recognized readlines hint 1 Read and return a list of lines from the stream hint can be specified to control the number of lines read no more lines will be read if the total size in bytes characters of all lines so far exceeds hint hint values of 0 or less as well as None are treated as no hint Note that it s already possible to iterate on file objects using for line in file without calling file readlines seek offset whence os SEEK_SET Change the stream position to the given byte offset interpreted relative to the position indicated by whence and return the new absolute position Values for whence are os SEEK_SET or 0 start of the stream the default offset should be zero or positive os SEEK_CUR or 1 current stream position offset may be negative os SEEK_END or 2 end of the stream offset is usually negative New in version 3 1 The SEEK_ constants New in version 3 3 Some operating systems could support additional values like os SEEK_HOLE or os SEEK_DATA The valid values for a file could depend on it being open in text or binary mode seekable Return True if the stream supports random access If False seek tell and ,en
1084,truncate will raise OSError tell Return the current stream position truncate size None Resize the stream to the given size in bytes or the current position if size is not specified The current stream position isn t changed This resizing can extend or reduce the current file size In case of extension the contents of the new file area depend on the platform on most systems additional bytes are zero filled The new file size is returned Changed in version 3 5 Windows will now zero fill files when extending writable Return True if the stream supports writing If False write and truncate will raise OSError writelines lines Write a list of lines to the stream Line separators are not added so it is usual for each of the lines provided to have a line separator at the end __del__ Prepare for object destruction IOBase provides a default implementation of this method that calls the instance s close method class io RawIOBase Base class for raw binary streams It inherits from IOBase Raw binary streams typically provide low level access to an underlying OS device or API and do not try to encapsulate it in high level primitives this functionality is done at a higher level in buffered binary streams and text streams described later in this page RawIOBase provides these methods in addition to those from IOBase read size 1 Read up to size bytes from the object and return them As a convenience if size is unspecified or 1 all bytes until EOF are returned Otherwise only one system call is ever made Fewer than size bytes may be returned if the operating system call returns fewer than size bytes If 0 bytes are returned and size was not 0 this indicates end of file If the object is in non blocking mode and no bytes are available None is returned The default implementation defers to readall and readinto readall Read and return all the bytes from the stream until EOF using multiple calls to the stream if necessary readinto b Read bytes into a pre allocated writable bytes like object b and return the number of bytes read For example b might be a bytearray If the object is in non blocking mode and no bytes are available None is returned write b Write the given bytes like object b to the underlying raw stream and return the number of bytes written This can be less than the length of b in bytes depending on specifics of the underlying raw stream and especially if it is in non blocking mode None is returned if the raw stream is set not to block and no single byte could be readily written to it The caller may release or mutate b after this method returns so the implementation should only access b during the method call class io BufferedIOBase Base class for binary streams that support some kind of buffering It inherits from IOBase The main difference with RawIOBase is that methods read readinto and write will try respectively to read as much input as requested or to consume all given output at the expense of making perhaps more than one system call In addition those methods can raise BlockingIOError if the underlying raw stream is in non blocking mode and cannot take or give enough data unlike their RawIOBase counterparts they will never return None Besides the read method does not have a default implementation that defers to readinto A typical BufferedIOBase implementation should not inherit from a RawIOBase implementation but wrap one like BufferedWriter and BufferedReader do BufferedIOBase provides or overrides these data attributes and methods in addition to those from IOBase raw The underlying raw stream a RawIOBase instance that BufferedIOBase deals with This is not part of the BufferedIOBase API and may not exist on some implementations detach Separate the underlying raw stream from the buffer and return it After the raw stream has been detached the buffer is in an unusable state Some buffers like BytesIO do not have the concept of a single raw stream to return from this method They raise UnsupportedOperation New in version 3 1 read size 1 Read and return up to size bytes If the argument is omitted None or negative data is read and returned until ,en
1085,EOF is reached An empty bytes object is returned if the stream is already at EOF If the argument is positive and the underlying raw stream is not interactive multiple raw reads may be issued to satisfy the byte count unless EOF is reached first But for interactive raw streams at most one raw read will be issued and a short result does not imply that EOF is imminent A BlockingIOError is raised if the underlying raw stream is in non blocking mode and has no data available at the moment read1 size 1 Read and return up to size bytes with at most one call to the underlying raw stream s read or readinto method This can be useful if you are implementing your own buffering on top of a BufferedIOBase object If size is 1 the default an arbitrary number of bytes are returned more than zero unless EOF is reached readinto b Read bytes into a pre allocated writable bytes like object b and return the number of bytes read For example b might be a bytearray Like read multiple reads may be issued to the underlying raw stream unless the latter is interactive A BlockingIOError is raised if the underlying raw stream is in non blocking mode and has no data available at the moment readinto1 b Read bytes into a pre allocated writable bytes like object b using at most one call to the underlying raw stream s read or readinto method Return the number of bytes read A BlockingIOError is raised if the underlying raw stream is in non blocking mode and has no data available at the moment New in version 3 5 write b Write the given bytes like object b and return the number of bytes written always equal to the length of b in bytes since if the write fails an OSError will be raised Depending on the actual implementation these bytes may be readily written to the underlying stream or held in a buffer for performance and latency reasons When in non blocking mode a BlockingIOError is raised if the data needed to be written to the raw stream but it couldn t accept all the data without blocking The caller may release or mutate b after this method returns so the implementation should only access b during the method call Raw File I O class io FileIO name mode r closefd True opener None A raw binary stream representing an OS level file containing bytes data It inherits from RawIOBase The name can be one of two things a character string or bytes object representing the path to the file which will be opened In this case closefd must be True the default otherwise an error will be raised an integer representing the number of an existing OS level file descriptor to which the resulting FileIO object will give access When the FileIO object is closed this fd will be closed as well unless closefd is set to False The mode can be r w x or a for reading default writing exclusive creation or appending The file will be created if it doesn t exist when opened for writing or appending it will be truncated when opened for writing FileExistsError will be raised if it already exists when opened for creating Opening a file for creating implies writing so this mode behaves in a similar way to w Add a to the mode to allow simultaneous reading and writing The read when called with a positive argument readinto and write methods on this class will only make one system call A custom opener can be used by passing a callable as opener The underlying file descriptor for the file object is then obtained by calling opener with name flags opener must return an open file descriptor passing os open as opener results in functionality similar to passing None The newly created file is non inheritable See the open built in function for examples on using the opener parameter Changed in version 3 3 The opener parameter was added The x mode was added Changed in version 3 4 The file is now non inheritable FileIO provides these data attributes in addition to those from RawIOBase and IOBase mode The mode as given in the constructor name The file name This is the file descriptor of the file when no name is given in the constructor Buffered Streams Buffered I O streams provide a higher level interface to an I ,en
1086,O device than raw I O does class io BytesIO initial_bytes b A binary stream using an in memory bytes buffer It inherits from BufferedIOBase The buffer is discarded when the close method is called The optional argument initial_bytes is a bytes like object that contains initial data BytesIO provides or overrides these methods in addition to those from BufferedIOBase and IOBase getbuffer Return a readable and writable view over the contents of the buffer without copying them Also mutating the view will transparently update the contents of the buffer b io BytesIO b abcdef view b getbuffer view 2 4 b 56 b getvalue b ab56ef Note As long as the view exists the BytesIO object cannot be resized or closed New in version 3 2 getvalue Return bytes containing the entire contents of the buffer read1 size 1 In BytesIO this is the same as read Changed in version 3 7 The size argument is now optional readinto1 b In BytesIO this is the same as readinto New in version 3 5 class io BufferedReader raw buffer_size DEFAULT_BUFFER_SIZE A buffered binary stream providing higher level access to a readable non seekable RawIOBase raw binary stream It inherits from BufferedIOBase When reading data from this object a larger amount of data may be requested from the underlying raw stream and kept in an internal buffer The buffered data can then be returned directly on subsequent reads The constructor creates a BufferedReader for the given readable raw stream and buffer_size If buffer_size is omitted DEFAULT_BUFFER_SIZE is used BufferedReader provides or overrides these methods in addition to those from BufferedIOBase and IOBase peek size 0 Return bytes from the stream without advancing the position At most one single read on the raw stream is done to satisfy the call The number of bytes returned may be less or more than requested read size 1 Read and return size bytes or if size is not given or negative until EOF or if the read call would block in non blocking mode read1 size 1 Read and return up to size bytes with only one call on the raw stream If at least one byte is buffered only buffered bytes are returned Otherwise one raw stream read call is made Changed in version 3 7 The size argument is now optional class io BufferedWriter raw buffer_size DEFAULT_BUFFER_SIZE A buffered binary stream providing higher level access to a writeable non seekable RawIOBase raw binary stream It inherits from BufferedIOBase When writing to this object data is normally placed into an internal buffer The buffer will be written out to the underlying RawIOBase object under various conditions including when the buffer gets too small for all pending data when flush is called when a seek is requested for BufferedRandom objects when the BufferedWriter object is closed or destroyed The constructor creates a BufferedWriter for the given writeable raw stream If the buffer_size is not given it defaults to DEFAULT_BUFFER_SIZE BufferedWriter provides or overrides these methods in addition to those from BufferedIOBase and IOBase flush Force bytes held in the buffer into the raw stream A BlockingIOError should be raised if the raw stream blocks write b Write the bytes like object b and return the number of bytes written When in non blocking mode a BlockingIOError is raised if the buffer needs to be written out but the raw stream blocks class io BufferedRandom raw buffer_size DEFAULT_BUFFER_SIZE A buffered binary stream providing higher level access to a seekable RawIOBase raw binary stream It inherits from BufferedReader and BufferedWriter The constructor creates a reader and writer for a seekable raw stream given in the first argument If the buffer_size is omitted it defaults to DEFAULT_BUFFER_SIZE BufferedRandom is capable of anything BufferedReader or BufferedWriter can do In addition seek and tell are guaranteed to be implemented class io BufferedRWPair reader writer buffer_size DEFAULT_BUFFER_SIZE A buffered binary stream providing higher level access to two non seekable RawIOBase raw binary streams one readable the other writeable It inherits from BufferedIOBase reader and writ,en
1087,er are RawIOBase objects that are readable and writeable respectively If the buffer_size is omitted it defaults to DEFAULT_BUFFER_SIZE BufferedRWPair implements all of BufferedIOBase s methods except for detach which raises UnsupportedOperation Warning BufferedRWPair does not attempt to synchronize accesses to its underlying raw streams You should not pass it the same object as reader and writer use BufferedRandom instead Text I O class io TextIOBase Base class for text streams This class provides a character and line based interface to stream I O It inherits from IOBase TextIOBase provides or overrides these data attributes and methods in addition to those from IOBase encoding The name of the encoding used to decode the stream s bytes into strings and to encode strings into bytes errors The error setting of the decoder or encoder newlines A string a tuple of strings or None indicating the newlines translated so far Depending on the implementation and the initial constructor flags this may not be available buffer The underlying binary buffer a BufferedIOBase instance that TextIOBase deals with This is not part of the TextIOBase API and may not exist in some implementations detach Separate the underlying binary buffer from the TextIOBase and return it After the underlying buffer has been detached the TextIOBase is in an unusable state Some TextIOBase implementations like StringIO may not have the concept of an underlying buffer and calling this method will raise UnsupportedOperation New in version 3 1 read size 1 Read and return at most size characters from the stream as a single str If size is negative or None reads until EOF readline size 1 Read until newline or EOF and return a single str If the stream is already at EOF an empty string is returned If size is specified at most size characters will be read seek offset whence SEEK_SET Change the stream position to the given offset Behaviour depends on the whence parameter The default value for whence is SEEK_SET SEEK_SET or 0 seek from the start of the stream the default offset must either be a number returned by TextIOBase tell or zero Any other offset value produces undefined behaviour SEEK_CUR or 1 seek to the current position offset must be zero which is a no operation all other values are unsupported SEEK_END or 2 seek to the end of the stream offset must be zero all other values are unsupported Return the new absolute position as an opaque number New in version 3 1 The SEEK_ constants tell Return the current stream position as an opaque number The number does not usually represent a number of bytes in the underlying binary storage write s Write the string s to the stream and return the number of characters written class io TextIOWrapper buffer encoding None errors None newline None line_buffering False write_through False A buffered text stream providing higher level access to a BufferedIOBase buffered binary stream It inherits from TextIOBase encoding gives the name of the encoding that the stream will be decoded or encoded with It defaults to locale getencoding encoding locale can be used to specify the current locale s encoding explicitly See Text Encoding for more information errors is an optional string that specifies how encoding and decoding errors are to be handled Pass strict to raise a ValueError exception if there is an encoding error the default of None has the same effect or pass ignore to ignore errors Note that ignoring encoding errors can lead to data loss replace causes a replacement marker such as to be inserted where there is malformed data backslashreplace causes malformed data to be replaced by a backslashed escape sequence When writing xmlcharrefreplace replace with the appropriate XML character reference or namereplace replace with N escape sequences can be used Any other error handling name that has been registered with codecs register_error is also valid newline controls how line endings are handled It can be None n r and r n It works as follows When reading input from the stream if newline is None universal newlines mode is enabled Lines in,en
1088, the input can end in n r or r n and these are translated into n before being returned to the caller If newline is universal newlines mode is enabled but line endings are returned to the caller untranslated If newline has any of the other legal values input lines are only terminated by the given string and the line ending is returned to the caller untranslated When writing output to the stream if newline is None any n characters written are translated to the system default line separator os linesep If newline is or n no translation takes place If newline is any of the other legal values any n characters written are translated to the given string If line_buffering is True flush is implied when a call to write contains a newline character or a carriage return If write_through is True calls to write are guaranteed not to be buffered any data written on the TextIOWrapper object is immediately handled to its underlying binary buffer Changed in version 3 3 The write_through argument has been added Changed in version 3 3 The default encoding is now locale getpreferredencoding False instead of locale getpreferredencoding Don t change temporary the locale encoding using locale setlocale use the current locale encoding instead of the user preferred encoding Changed in version 3 10 The encoding argument now supports the locale dummy encoding name TextIOWrapper provides these data attributes and methods in addition to those from TextIOBase and IOBase line_buffering Whether line buffering is enabled write_through Whether writes are passed immediately to the underlying binary buffer New in version 3 7 reconfigure encoding None errors None newline None line_buffering None write_through None Reconfigure this text stream using new settings for encoding errors newline line_buffering and write_through Parameters not specified keep current settings except errors strict is used when encoding is specified but errors is not specified It is not possible to change the encoding or newline if some data has already been read from the stream On the other hand changing encoding after write is possible This method does an implicit stream flush before setting the new parameters New in version 3 7 Changed in version 3 11 The method supports encoding locale option seek cookie whence os SEEK_SET Set the stream position Return the new stream position as an int Four operations are supported given by the following argument combinations seek 0 SEEK_SET Rewind to the start of the stream seek cookie SEEK_SET Restore a previous position cookie must be a number returned by tell seek 0 SEEK_END Fast forward to the end of the stream seek 0 SEEK_CUR Leave the current stream position unchanged Any other argument combinations are invalid and may raise exceptions See also os SEEK_SET os SEEK_CUR and os SEEK_END tell Return the stream position as an opaque number The return value of tell can be given as input to seek to restore a previous stream position class io StringIO initial_value newline n A text stream using an in memory text buffer It inherits from TextIOBase The text buffer is discarded when the close method is called The initial value of the buffer can be set by providing initial_value If newline translation is enabled newlines will be encoded as if by write The stream is positioned at the start of the buffer which emulates opening an existing file in a w mode making it ready for an immediate write from the beginning or for a write that would overwrite the initial value To emulate opening a file in an a mode ready for appending use f seek 0 io SEEK_END to reposition the stream at the end of the buffer The newline argument works like that of TextIOWrapper except that when writing output to the stream if newline is None newlines are written as n on all platforms StringIO provides this method in addition to those from TextIOBase and IOBase getvalue Return a str containing the entire contents of the buffer Newlines are decoded as if by read although the stream position is not changed Example usage import io output io StringIO output write First line n print Second,en
1089, line file output Retrieve file contents this will be First line nSecond line n contents output getvalue Close object and discard memory buffer getvalue will now raise an exception output close class io IncrementalNewlineDecoder A helper codec that decodes newlines for universal newlines mode It inherits from codecs IncrementalDecoder Performance This section discusses the performance of the provided concrete I O implementations Binary I O By reading and writing only large chunks of data even when the user asks for a single byte buffered I O hides any inefficiency in calling and executing the operating system s unbuffered I O routines The gain depends on the OS and the kind of I O which is performed For example on some modern OSes such as Linux unbuffered disk I O can be as fast as buffered I O The bottom line however is that buffered I O offers predictable performance regardless of the platform and the backing device Therefore it is almost always preferable to use buffered I O rather than unbuffered I O for binary data Text I O Text I O over a binary storage such as a file is significantly slower than binary I O over the same storage because it requires conversions between unicode and binary data using a character codec This can become noticeable handling huge amounts of text data like large log files Also tell and seek are both quite slow due to the reconstruction algorithm used StringIO however is a native in memory unicode container and will exhibit similar speed to BytesIO Multi threading FileIO objects are thread safe to the extent that the operating system calls such as read 2 under Unix they wrap are thread safe too Binary buffered objects instances of BufferedReader BufferedWriter BufferedRandom and BufferedRWPair protect their internal structures using a lock it is therefore safe to call them from multiple threads at once TextIOWrapper objects are not thread safe Reentrancy Binary buffered objects instances of BufferedReader BufferedWriter BufferedRandom and BufferedRWPair are not reentrant While reentrant calls will not happen in normal situations they can arise from doing I O in a signal handler If a thread tries to re enter a buffered object which it is already accessing a RuntimeError is raised Note this doesn t prohibit a different thread from entering the buffered object The above implicitly extends to text files since the open function will wrap a buffered object inside a TextIOWrapper This includes standard streams and therefore affects the built in print function as well,en
1090,Iterator Objects Python provides two general purpose iterator objects The first a sequence iterator works with an arbitrary sequence supporting the __getitem__ method The second works with a callable object and a sentinel value calling the callable for each item in the sequence and ending the iteration when the sentinel value is returned PyTypeObject PySeqIter_Type Part of the Stable ABI Type object for iterator objects returned by PySeqIter_New and the one argument form of the iter built in function for built in sequence types int PySeqIter_Check PyObject op Return true if the type of op is PySeqIter_Type This function always succeeds PyObject PySeqIter_New PyObject seq Return value New reference Part of the Stable ABI Return an iterator that works with a general sequence object seq The iteration ends when the sequence raises IndexError for the subscripting operation PyTypeObject PyCallIter_Type Part of the Stable ABI Type object for iterator objects returned by PyCallIter_New and the two argument form of the iter built in function int PyCallIter_Check PyObject op Return true if the type of op is PyCallIter_Type This function always succeeds PyObject PyCallIter_New PyObject callable PyObject sentinel Return value New reference Part of the Stable ABI Return a new iterator The first parameter callable can be any Python callable object that can be called with no parameters each call to it should return the next item in the iteration When callable returns a value equal to sentinel the iteration will be terminated,en
1091,Number Protocol int PyNumber_Check PyObject o Part of the Stable ABI Returns 1 if the object o provides numeric protocols and false otherwise This function always succeeds Changed in version 3 8 Returns 1 if o is an index integer PyObject PyNumber_Add PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the result of adding o1 and o2 or NULL on failure This is the equivalent of the Python expression o1 o2 PyObject PyNumber_Subtract PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the result of subtracting o2 from o1 or NULL on failure This is the equivalent of the Python expression o1 o2 PyObject PyNumber_Multiply PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the result of multiplying o1 and o2 or NULL on failure This is the equivalent of the Python expression o1 o2 PyObject PyNumber_MatrixMultiply PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI since version 3 7 Returns the result of matrix multiplication on o1 and o2 or NULL on failure This is the equivalent of the Python expression o1 o2 New in version 3 5 PyObject PyNumber_FloorDivide PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Return the floor of o1 divided by o2 or NULL on failure This is the equivalent of the Python expression o1 o2 PyObject PyNumber_TrueDivide PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Return a reasonable approximation for the mathematical value of o1 divided by o2 or NULL on failure The return value is approximate because binary floating point numbers are approximate it is not possible to represent all real numbers in base two This function can return a floating point value when passed two integers This is the equivalent of the Python expression o1 o2 PyObject PyNumber_Remainder PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the remainder of dividing o1 by o2 or NULL on failure This is the equivalent of the Python expression o1 o2 PyObject PyNumber_Divmod PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI See the built in function divmod Returns NULL on failure This is the equivalent of the Python expression divmod o1 o2 PyObject PyNumber_Power PyObject o1 PyObject o2 PyObject o3 Return value New reference Part of the Stable ABI See the built in function pow Returns NULL on failure This is the equivalent of the Python expression pow o1 o2 o3 where o3 is optional If o3 is to be ignored pass Py_None in its place passing NULL for o3 would cause an illegal memory access PyObject PyNumber_Negative PyObject o Return value New reference Part of the Stable ABI Returns the negation of o on success or NULL on failure This is the equivalent of the Python expression o PyObject PyNumber_Positive PyObject o Return value New reference Part of the Stable ABI Returns o on success or NULL on failure This is the equivalent of the Python expression o PyObject PyNumber_Absolute PyObject o Return value New reference Part of the Stable ABI Returns the absolute value of o or NULL on failure This is the equivalent of the Python expression abs o PyObject PyNumber_Invert PyObject o Return value New reference Part of the Stable ABI Returns the bitwise negation of o on success or NULL on failure This is the equivalent of the Python expression o PyObject PyNumber_Lshift PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the result of left shifting o1 by o2 on success or NULL on failure This is the equivalent of the Python expression o1 o2 PyObject PyNumber_Rshift PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the result of right shifting o1 by o2 on success or NULL on failure This is the equivalent of the Python expression o1 o2 PyObject PyNumber_And PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the bitwise and of o1 and o2 on success and NULL on failure This is the equivalent of the Python expression o1 o2 PyObject PyNumber_Xor PyObjec,en
1092,t o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the bitwise exclusive or of o1 by o2 on success or NULL on failure This is the equivalent of the Python expression o1 o2 PyObject PyNumber_Or PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the bitwise or of o1 and o2 on success or NULL on failure This is the equivalent of the Python expression o1 o2 PyObject PyNumber_InPlaceAdd PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the result of adding o1 and o2 or NULL on failure The operation is done in place when o1 supports it This is the equivalent of the Python statement o1 o2 PyObject PyNumber_InPlaceSubtract PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the result of subtracting o2 from o1 or NULL on failure The operation is done in place when o1 supports it This is the equivalent of the Python statement o1 o2 PyObject PyNumber_InPlaceMultiply PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the result of multiplying o1 and o2 or NULL on failure The operation is done in place when o1 supports it This is the equivalent of the Python statement o1 o2 PyObject PyNumber_InPlaceMatrixMultiply PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI since version 3 7 Returns the result of matrix multiplication on o1 and o2 or NULL on failure The operation is done in place when o1 supports it This is the equivalent of the Python statement o1 o2 New in version 3 5 PyObject PyNumber_InPlaceFloorDivide PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the mathematical floor of dividing o1 by o2 or NULL on failure The operation is done in place when o1 supports it This is the equivalent of the Python statement o1 o2 PyObject PyNumber_InPlaceTrueDivide PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Return a reasonable approximation for the mathematical value of o1 divided by o2 or NULL on failure The return value is approximate because binary floating point numbers are approximate it is not possible to represent all real numbers in base two This function can return a floating point value when passed two integers The operation is done in place when o1 supports it This is the equivalent of the Python statement o1 o2 PyObject PyNumber_InPlaceRemainder PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the remainder of dividing o1 by o2 or NULL on failure The operation is done in place when o1 supports it This is the equivalent of the Python statement o1 o2 PyObject PyNumber_InPlacePower PyObject o1 PyObject o2 PyObject o3 Return value New reference Part of the Stable ABI See the built in function pow Returns NULL on failure The operation is done in place when o1 supports it This is the equivalent of the Python statement o1 o2 when o3 is Py_None or an in place variant of pow o1 o2 o3 otherwise If o3 is to be ignored pass Py_None in its place passing NULL for o3 would cause an illegal memory access PyObject PyNumber_InPlaceLshift PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the result of left shifting o1 by o2 on success or NULL on failure The operation is done in place when o1 supports it This is the equivalent of the Python statement o1 o2 PyObject PyNumber_InPlaceRshift PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the result of right shifting o1 by o2 on success or NULL on failure The operation is done in place when o1 supports it This is the equivalent of the Python statement o1 o2 PyObject PyNumber_InPlaceAnd PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the bitwise and of o1 and o2 on success and NULL on failure The operation is done in place when o1 supports it This is the equivalent of the Python statement o1 o2 PyObject PyNumber_InPlaceXor PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the bitwise exclusive or of o1 by o2 ,en
1093,on success or NULL on failure The operation is done in place when o1 supports it This is the equivalent of the Python statement o1 o2 PyObject PyNumber_InPlaceOr PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Returns the bitwise or of o1 and o2 on success or NULL on failure The operation is done in place when o1 supports it This is the equivalent of the Python statement o1 o2 PyObject PyNumber_Long PyObject o Return value New reference Part of the Stable ABI Returns the o converted to an integer object on success or NULL on failure This is the equivalent of the Python expression int o PyObject PyNumber_Float PyObject o Return value New reference Part of the Stable ABI Returns the o converted to a float object on success or NULL on failure This is the equivalent of the Python expression float o PyObject PyNumber_Index PyObject o Return value New reference Part of the Stable ABI Returns the o converted to a Python int on success or NULL with a TypeError exception raised on failure Changed in version 3 10 The result always has exact type int Previously the result could have been an instance of a subclass of int PyObject PyNumber_ToBase PyObject n int base Return value New reference Part of the Stable ABI Returns the integer n converted to base base as a string The base argument must be one of 2 8 10 or 16 For base 2 8 or 16 the returned string is prefixed with a base marker of 0b 0o or 0x respectively If n is not a Python int it is converted with PyNumber_Index first Py_ssize_t PyNumber_AsSsize_t PyObject o PyObject exc Part of the Stable ABI Returns o converted to a Py_ssize_t value if o can be interpreted as an integer If the call fails an exception is raised and 1 is returned If o can be converted to a Python int but the attempt to convert to a Py_ssize_t value would raise an OverflowError then the exc argument is the type of exception that will be raised usually IndexError or OverflowError If exc is NULL then the exception is cleared and the value is clipped to PY_SSIZE_T_MIN for a negative integer or PY_SSIZE_T_MAX for a positive integer int PyIndex_Check PyObject o Part of the Stable ABI since version 3 8 Returns 1 if o is an index integer has the nb_index slot of the tp_as_number structure filled in and 0 otherwise This function always succeeds,en
1094,os Miscellaneous operating system interfaces Source code Lib os py This module provides a portable way of using operating system dependent functionality If you just want to read or write a file see open if you want to manipulate paths see the os path module and if you want to read all the lines in all the files on the command line see the fileinput module For creating temporary files and directories see the tempfile module and for high level file and directory handling see the shutil module Notes on the availability of these functions The design of all built in operating system dependent modules of Python is such that as long as the same functionality is available it uses the same interface for example the function os stat path returns stat information about path in the same format which happens to have originated with the POSIX interface Extensions peculiar to a particular operating system are also available through the os module but using them is of course a threat to portability All functions accepting path or file names accept both bytes and string objects and result in an object of the same type if a path or file name is returned On VxWorks os popen os fork os execv and os spawn p are not supported On WebAssembly platforms wasm32 emscripten and wasm32 wasi large parts of the os module are not available or behave differently API related to processes e g fork execve signals e g kill wait and resources e g nice are not available Others like getuid and getpid are emulated or stubs Note All functions in this module raise OSError or subclasses thereof in the case of invalid or inaccessible file names and paths or other arguments that have the correct type but are not accepted by the operating system exception os error An alias for the built in OSError exception os name The name of the operating system dependent module imported The following names have currently been registered posix nt java See also sys platform has a finer granularity os uname gives system dependent version information The platform module provides detailed checks for the system s identity File Names Command Line Arguments and Environment Variables In Python file names command line arguments and environment variables are represented using the string type On some systems decoding these strings to and from bytes is necessary before passing them to the operating system Python uses the filesystem encoding and error handler to perform this conversion see sys getfilesystemencoding The filesystem encoding and error handler are configured at Python startup by the PyConfig_Read function see filesystem_encoding and filesystem_errors members of PyConfig Changed in version 3 1 On some systems conversion using the file system encoding may fail In this case Python uses the surrogateescape encoding error handler which means that undecodable bytes are replaced by a Unicode character U DC xx on decoding and these are again translated to the original byte on encoding The file system encoding must guarantee to successfully decode all bytes below 128 If the file system encoding fails to provide this guarantee API functions can raise UnicodeError See also the locale encoding Python UTF 8 Mode New in version 3 7 See PEP 540 for more details The Python UTF 8 Mode ignores the locale encoding and forces the usage of the UTF 8 encoding Use UTF 8 as the filesystem encoding sys getfilesystemencoding returns utf 8 locale getpreferredencoding returns utf 8 the do_setlocale argument has no effect sys stdin sys stdout and sys stderr all use UTF 8 as their text encoding with the surrogateescape error handler being enabled for sys stdin and sys stdout sys stderr continues to use backslashreplace as it does in the default locale aware mode On Unix os device_encoding returns utf 8 rather than the device encoding Note that the standard stream settings in UTF 8 mode can be overridden by PYTHONIOENCODING just as they can be in the default locale aware mode As a consequence of the changes in those lower level APIs other higher level APIs also exhibit different default behaviours Command line ar,en
1095,guments environment variables and filenames are decoded to text using the UTF 8 encoding os fsdecode and os fsencode use the UTF 8 encoding open io open and codecs open use the UTF 8 encoding by default However they still use the strict error handler by default so that attempting to open a binary file in text mode is likely to raise an exception rather than producing nonsense data The Python UTF 8 Mode is enabled if the LC_CTYPE locale is C or POSIX at Python startup see the PyConfig_Read function It can be enabled or disabled using the X utf8 command line option and the PYTHONUTF8 environment variable If the PYTHONUTF8 environment variable is not set at all then the interpreter defaults to using the current locale settings unless the current locale is identified as a legacy ASCII based locale as described for PYTHONCOERCECLOCALE and locale coercion is either disabled or fails In such legacy locales the interpreter will default to enabling UTF 8 mode unless explicitly instructed not to do so The Python UTF 8 Mode can only be enabled at the Python startup Its value can be read from sys flags utf8_mode See also the UTF 8 mode on Windows and the filesystem encoding and error handler See also PEP 686 Python 3 15 will make Python UTF 8 Mode default Process Parameters These functions and data items provide information and operate on the current process and user os ctermid Return the filename corresponding to the controlling terminal of the process Availability Unix not Emscripten not WASI os environ A mapping object where keys and values are strings that represent the process environment For example environ HOME is the pathname of your home directory on some platforms and is equivalent to getenv HOME in C This mapping is captured the first time the os module is imported typically during Python startup as part of processing site py Changes to the environment made after this time are not reflected in os environ except for changes made by modifying os environ directly This mapping may be used to modify the environment as well as query the environment putenv will be called automatically when the mapping is modified On Unix keys and values use sys getfilesystemencoding and surrogateescape error handler Use environb if you would like to use a different encoding On Windows the keys are converted to uppercase This also applies when getting setting or deleting an item For example environ monty python maps the key MONTY to the value python Note Calling putenv directly does not change os environ so it s better to modify os environ Note On some platforms including FreeBSD and macOS setting environ may cause memory leaks Refer to the system documentation for putenv You can delete items in this mapping to unset environment variables unsetenv will be called automatically when an item is deleted from os environ and when one of the pop or clear methods is called Changed in version 3 9 Updated to support PEP 584 s merge and update operators os environb Bytes version of environ a mapping object where both keys and values are bytes objects representing the process environment environ and environb are synchronized modifying environb updates environ and vice versa environb is only available if supports_bytes_environ is True New in version 3 2 Changed in version 3 9 Updated to support PEP 584 s merge and update operators os chdir path os fchdir fd os getcwd These functions are described in Files and Directories os fsencode filename Encode path like filename to the filesystem encoding and error handler return bytes unchanged fsdecode is the reverse function New in version 3 2 Changed in version 3 6 Support added to accept objects implementing the os PathLike interface os fsdecode filename Decode the path like filename from the filesystem encoding and error handler return str unchanged fsencode is the reverse function New in version 3 2 Changed in version 3 6 Support added to accept objects implementing the os PathLike interface os fspath path Return the file system representation of the path If str or bytes is passed in it is returned unchanged Other,en
1096,wise __fspath__ is called and its value is returned as long as it is a str or bytes object In all other cases TypeError is raised New in version 3 6 class os PathLike An abstract base class for objects representing a file system path e g pathlib PurePath New in version 3 6 abstractmethod __fspath__ Return the file system path representation of the object The method should only return a str or bytes object with the preference being for str os getenv key default None Return the value of the environment variable key as a string if it exists or default if it doesn t key is a string Note that since getenv uses os environ the mapping of getenv is similarly also captured on import and the function may not reflect future environment changes On Unix keys and values are decoded with sys getfilesystemencoding and surrogateescape error handler Use os getenvb if you would like to use a different encoding Availability Unix Windows os getenvb key default None Return the value of the environment variable key as bytes if it exists or default if it doesn t key must be bytes Note that since getenvb uses os environb the mapping of getenvb is similarly also captured on import and the function may not reflect future environment changes getenvb is only available if supports_bytes_environ is True Availability Unix New in version 3 2 os get_exec_path env None Returns the list of directories that will be searched for a named executable similar to a shell when launching a process env when specified should be an environment variable dictionary to lookup the PATH in By default when env is None environ is used New in version 3 2 os getegid Return the effective group id of the current process This corresponds to the set id bit on the file being executed in the current process Availability Unix not Emscripten not WASI os geteuid Return the current process s effective user id Availability Unix not Emscripten not WASI os getgid Return the real group id of the current process Availability Unix The function is a stub on Emscripten and WASI see WebAssembly platforms for more information os getgrouplist user group Return list of group ids that user belongs to If group is not in the list it is included typically group is specified as the group ID field from the password record for user because that group ID will otherwise be potentially omitted Availability Unix not Emscripten not WASI New in version 3 3 os getgroups Return list of supplemental group ids associated with the current process Availability Unix not Emscripten not WASI Note On macOS getgroups behavior differs somewhat from other Unix platforms If the Python interpreter was built with a deployment target of 10 5 or earlier getgroups returns the list of effective group ids associated with the current user process this list is limited to a system defined number of entries typically 16 and may be modified by calls to setgroups if suitably privileged If built with a deployment target greater than 10 5 getgroups returns the current group access list for the user associated with the effective user id of the process the group access list may change over the lifetime of the process it is not affected by calls to setgroups and its length is not limited to 16 The deployment target value MACOSX_DEPLOYMENT_TARGET can be obtained with sysconfig get_config_var os getlogin Return the name of the user logged in on the controlling terminal of the process For most purposes it is more useful to use getpass getuser since the latter checks the environment variables LOGNAME or USERNAME to find out who the user is and falls back to pwd getpwuid os getuid 0 to get the login name of the current real user id Availability Unix Windows not Emscripten not WASI os getpgid pid Return the process group id of the process with process id pid If pid is 0 the process group id of the current process is returned Availability Unix not Emscripten not WASI os getpgrp Return the id of the current process group Availability Unix not Emscripten not WASI os getpid Return the current process id The function is a stub on Emscripten and WASI see,en
1097, WebAssembly platforms for more information os getppid Return the parent s process id When the parent process has exited on Unix the id returned is the one of the init process 1 on Windows it is still the same id which may be already reused by another process Availability Unix Windows not Emscripten not WASI Changed in version 3 2 Added support for Windows os getpriority which who Get program scheduling priority The value which is one of PRIO_PROCESS PRIO_PGRP or PRIO_USER and who is interpreted relative to which a process identifier for PRIO_PROCESS process group identifier for PRIO_PGRP and a user ID for PRIO_USER A zero value for who denotes respectively the calling process the process group of the calling process or the real user ID of the calling process Availability Unix not Emscripten not WASI New in version 3 3 os PRIO_PROCESS os PRIO_PGRP os PRIO_USER Parameters for the getpriority and setpriority functions Availability Unix not Emscripten not WASI New in version 3 3 os PRIO_DARWIN_THREAD os PRIO_DARWIN_PROCESS os PRIO_DARWIN_BG os PRIO_DARWIN_NONUI Parameters for the getpriority and setpriority functions Availability macOS New in version 3 12 os getresuid Return a tuple ruid euid suid denoting the current process s real effective and saved user ids Availability Unix not Emscripten not WASI New in version 3 2 os getresgid Return a tuple rgid egid sgid denoting the current process s real effective and saved group ids Availability Unix not Emscripten not WASI New in version 3 2 os getuid Return the current process s real user id Availability Unix The function is a stub on Emscripten and WASI see WebAssembly platforms for more information os initgroups username gid Call the system initgroups to initialize the group access list with all of the groups of which the specified username is a member plus the specified group id Availability Unix not Emscripten not WASI New in version 3 2 os putenv key value Set the environment variable named key to the string value Such changes to the environment affect subprocesses started with os system popen or fork and execv Assignments to items in os environ are automatically translated into corresponding calls to putenv however calls to putenv don t update os environ so it is actually preferable to assign to items of os environ This also applies to getenv and getenvb which respectively use os environ and os environb in their implementations Note On some platforms including FreeBSD and macOS setting environ may cause memory leaks Refer to the system documentation for putenv Raises an auditing event os putenv with arguments key value Changed in version 3 9 The function is now always available os setegid egid Set the current process s effective group id Availability Unix not Emscripten not WASI os seteuid euid Set the current process s effective user id Availability Unix not Emscripten not WASI os setgid gid Set the current process group id Availability Unix not Emscripten not WASI os setgroups groups Set the list of supplemental group ids associated with the current process to groups groups must be a sequence and each element must be an integer identifying a group This operation is typically available only to the superuser Availability Unix not Emscripten not WASI Note On macOS the length of groups may not exceed the system defined maximum number of effective group ids typically 16 See the documentation for getgroups for cases where it may not return the same group list set by calling setgroups os setns fd nstype 0 Reassociate the current thread with a Linux namespace See the setns 2 and namespaces 7 man pages for more details If fd refers to a proc pid ns link setns reassociates the calling thread with the namespace associated with that link and nstype may be set to one of the CLONE_NEW constants to impose constraints on the operation 0 means no constraints Since Linux 5 8 fd may refer to a PID file descriptor obtained from pidfd_open In this case setns reassociates the calling thread into one or more of the same namespaces as the thread referred to by fd This is subject to any constr,en
1098,aints imposed by nstype which is a bit mask combining one or more of the CLONE_NEW constants e g setns fd os CLONE_NEWUTS os CLONE_NEWPID The caller s memberships in unspecified namespaces are left unchanged fd can be any object with a fileno method or a raw file descriptor This example reassociates the thread with the init process s network namespace fd os open proc 1 ns net os O_RDONLY os setns fd os CLONE_NEWNET os close fd Availability Linux 3 0 with glibc 2 14 New in version 3 12 See also The unshare function os setpgrp Call the system call setpgrp or setpgrp 0 0 depending on which version is implemented if any See the Unix manual for the semantics Availability Unix not Emscripten not WASI os setpgid pid pgrp Call the system call setpgid to set the process group id of the process with id pid to the process group with id pgrp See the Unix manual for the semantics Availability Unix not Emscripten not WASI os setpriority which who priority Set program scheduling priority The value which is one of PRIO_PROCESS PRIO_PGRP or PRIO_USER and who is interpreted relative to which a process identifier for PRIO_PROCESS process group identifier for PRIO_PGRP and a user ID for PRIO_USER A zero value for who denotes respectively the calling process the process group of the calling process or the real user ID of the calling process priority is a value in the range 20 to 19 The default priority is 0 lower priorities cause more favorable scheduling Availability Unix not Emscripten not WASI New in version 3 3 os setregid rgid egid Set the current process s real and effective group ids Availability Unix not Emscripten not WASI os setresgid rgid egid sgid Set the current process s real effective and saved group ids Availability Unix not Emscripten not WASI New in version 3 2 os setresuid ruid euid suid Set the current process s real effective and saved user ids Availability Unix not Emscripten not WASI New in version 3 2 os setreuid ruid euid Set the current process s real and effective user ids Availability Unix not Emscripten not WASI os getsid pid Call the system call getsid See the Unix manual for the semantics Availability Unix not Emscripten not WASI os setsid Call the system call setsid See the Unix manual for the semantics Availability Unix not Emscripten not WASI os setuid uid Set the current process s user id Availability Unix not Emscripten not WASI os strerror code Return the error message corresponding to the error code in code On platforms where strerror returns NULL when given an unknown error number ValueError is raised os supports_bytes_environ True if the native OS type of the environment is bytes eg False on Windows New in version 3 2 os umask mask Set the current numeric umask and return the previous umask The function is a stub on Emscripten and WASI see WebAssembly platforms for more information os uname Returns information identifying the current operating system The return value is an object with five attributes sysname operating system name nodename name of machine on network implementation defined release operating system release version operating system version machine hardware identifier For backwards compatibility this object is also iterable behaving like a five tuple containing sysname nodename release version and machine in that order Some systems truncate nodename to 8 characters or to the leading component a better way to get the hostname is socket gethostname or even socket gethostbyaddr socket gethostname Availability Unix Changed in version 3 3 Return type changed from a tuple to a tuple like object with named attributes os unsetenv key Unset delete the environment variable named key Such changes to the environment affect subprocesses started with os system popen or fork and execv Deletion of items in os environ is automatically translated into a corresponding call to unsetenv however calls to unsetenv don t update os environ so it is actually preferable to delete items of os environ Raises an auditing event os unsetenv with argument key Changed in version 3 9 The function is now always available and ,en
1099,is also available on Windows os unshare flags Disassociate parts of the process execution context and move them into a newly created namespace See the unshare 2 man page for more details The flags argument is a bit mask combining zero or more of the CLONE_ constants that specifies which parts of the execution context should be unshared from their existing associations and moved to a new namespace If the flags argument is 0 no changes are made to the calling process s execution context Availability Linux 2 6 16 New in version 3 12 See also The setns function Flags to the unshare function if the implementation supports them See unshare 2 in the Linux manual for their exact effect and availability os CLONE_FILES os CLONE_FS os CLONE_NEWCGROUP os CLONE_NEWIPC os CLONE_NEWNET os CLONE_NEWNS os CLONE_NEWPID os CLONE_NEWTIME os CLONE_NEWUSER os CLONE_NEWUTS os CLONE_SIGHAND os CLONE_SYSVSEM os CLONE_THREAD os CLONE_VM File Object Creation These functions create new file objects See also open for opening file descriptors os fdopen fd args kwargs Return an open file object connected to the file descriptor fd This is an alias of the open built in function and accepts the same arguments The only difference is that the first argument of fdopen must always be an integer File Descriptor Operations These functions operate on I O streams referenced using file descriptors File descriptors are small integers corresponding to a file that has been opened by the current process For example standard input is usually file descriptor 0 standard output is 1 and standard error is 2 Further files opened by a process will then be assigned 3 4 5 and so forth The name file descriptor is slightly deceptive on Unix platforms sockets and pipes are also referenced by file descriptors The fileno method can be used to obtain the file descriptor associated with a file object when required Note that using the file descriptor directly will bypass the file object methods ignoring aspects such as internal buffering of data os close fd Close file descriptor fd Note This function is intended for low level I O and must be applied to a file descriptor as returned by os open or pipe To close a file object returned by the built in function open or by popen or fdopen use its close method os closerange fd_low fd_high Close all file descriptors from fd_low inclusive to fd_high exclusive ignoring errors Equivalent to but much faster than for fd in range fd_low fd_high try os close fd except OSError pass os copy_file_range src dst count offset_src None offset_dst None Copy count bytes from file descriptor src starting from offset offset_src to file descriptor dst starting from offset offset_dst If offset_src is None then src is read from the current position respectively for offset_dst In Linux kernel older than 5 3 the files pointed by src and dst must reside in the same filesystem otherwise an OSError is raised with errno set to errno EXDEV This copy is done without the additional cost of transferring data from the kernel to user space and then back into the kernel Additionally some filesystems could implement extra optimizations such as the use of reflinks i e two or more inodes that share pointers to the same copy on write disk blocks supported file systems include btrfs and XFS and server side copy in the case of NFS The function copies bytes between two file descriptors Text options like the encoding and the line ending are ignored The return value is the amount of bytes copied This could be less than the amount requested Note On Linux os copy_file_range should not be used for copying a range of a pseudo file from a special filesystem like procfs and sysfs It will always copy no bytes and return 0 as if the file was empty because of a known Linux kernel issue Availability Linux 4 5 with glibc 2 27 New in version 3 8 os device_encoding fd Return a string describing the encoding of the device associated with fd if it is connected to a terminal else return None On Unix if the Python UTF 8 Mode is enabled return UTF 8 rather than the device encoding Changed in version 3,en
1100, 10 On Unix the function now implements the Python UTF 8 Mode os dup fd Return a duplicate of file descriptor fd The new file descriptor is non inheritable On Windows when duplicating a standard stream 0 stdin 1 stdout 2 stderr the new file descriptor is inheritable Availability not WASI Changed in version 3 4 The new file descriptor is now non inheritable os dup2 fd fd2 inheritable True Duplicate file descriptor fd to fd2 closing the latter first if necessary Return fd2 The new file descriptor is inheritable by default or non inheritable if inheritable is False Availability not WASI Changed in version 3 4 Add the optional inheritable parameter Changed in version 3 7 Return fd2 on success Previously None was always returned os fchmod fd mode Change the mode of the file given by fd to the numeric mode See the docs for chmod for possible values of mode As of Python 3 3 this is equivalent to os chmod fd mode Raises an auditing event os chmod with arguments path mode dir_fd Availability Unix The function is limited on Emscripten and WASI see WebAssembly platforms for more information os fchown fd uid gid Change the owner and group id of the file given by fd to the numeric uid and gid To leave one of the ids unchanged set it to 1 See chown As of Python 3 3 this is equivalent to os chown fd uid gid Raises an auditing event os chown with arguments path uid gid dir_fd Availability Unix The function is limited on Emscripten and WASI see WebAssembly platforms for more information os fdatasync fd Force write of file with filedescriptor fd to disk Does not force update of metadata Availability Unix Note This function is not available on MacOS os fpathconf fd name Return system configuration information relevant to an open file name specifies the configuration value to retrieve it may be a string which is the name of a defined system value these names are specified in a number of standards POSIX 1 Unix 95 Unix 98 and others Some platforms define additional names as well The names known to the host operating system are given in the pathconf_names dictionary For configuration variables not included in that mapping passing an integer for name is also accepted If name is a string and is not known ValueError is raised If a specific value for name is not supported by the host system even if it is included in pathconf_names an OSError is raised with errno EINVAL for the error number As of Python 3 3 this is equivalent to os pathconf fd name Availability Unix os fstat fd Get the status of the file descriptor fd Return a stat_result object As of Python 3 3 this is equivalent to os stat fd See also The stat function os fstatvfs fd Return information about the filesystem containing the file associated with file descriptor fd like statvfs As of Python 3 3 this is equivalent to os statvfs fd Availability Unix os fsync fd Force write of file with filedescriptor fd to disk On Unix this calls the native fsync function on Windows the MS _commit function If you re starting with a buffered Python file object f first do f flush and then do os fsync f fileno to ensure that all internal buffers associated with f are written to disk Availability Unix Windows os ftruncate fd length Truncate the file corresponding to file descriptor fd so that it is at most length bytes in size As of Python 3 3 this is equivalent to os truncate fd length Raises an auditing event os truncate with arguments fd length Availability Unix Windows Changed in version 3 5 Added support for Windows os get_blocking fd Get the blocking mode of the file descriptor False if the O_NONBLOCK flag is set True if the flag is cleared See also set_blocking and socket socket setblocking Availability Unix Windows The function is limited on Emscripten and WASI see WebAssembly platforms for more information On Windows this function is limited to pipes New in version 3 5 Changed in version 3 12 Added support for pipes on Windows os isatty fd Return True if the file descriptor fd is open and connected to a tty like device else False os lockf fd cmd len Apply test or remove a POSIX lock on an open file,en
1101, descriptor fd is an open file descriptor cmd specifies the command to use one of F_LOCK F_TLOCK F_ULOCK or F_TEST len specifies the section of the file to lock Raises an auditing event os lockf with arguments fd cmd len Availability Unix New in version 3 3 os F_LOCK os F_TLOCK os F_ULOCK os F_TEST Flags that specify what action lockf will take Availability Unix New in version 3 3 os login_tty fd Prepare the tty of which fd is a file descriptor for a new login session Make the calling process a session leader make the tty the controlling tty the stdin the stdout and the stderr of the calling process close fd Availability Unix not Emscripten not WASI New in version 3 11 os lseek fd pos whence Set the current position of file descriptor fd to position pos modified by whence and return the new position in bytes relative to the start of the file Valid values for whence are SEEK_SET or 0 set pos relative to the beginning of the file SEEK_CUR or 1 set pos relative to the current file position SEEK_END or 2 set pos relative to the end of the file SEEK_HOLE set pos to the next data location relative to pos SEEK_DATA set pos to the next data hole relative to pos Changed in version 3 3 Add support for SEEK_HOLE and SEEK_DATA os SEEK_SET os SEEK_CUR os SEEK_END Parameters to the lseek function and the seek method on file like objects for whence to adjust the file position indicator SEEK_SET Adjust the file position relative to the beginning of the file SEEK_CUR Adjust the file position relative to the current file position SEEK_END Adjust the file position relative to the end of the file Their values are 0 1 and 2 respectively os SEEK_HOLE os SEEK_DATA Parameters to the lseek function and the seek method on file like objects for seeking file data and holes on sparsely allocated files SEEK_DATA Adjust the file offset to the next location containing data relative to the seek position SEEK_HOLE Adjust the file offset to the next location containing a hole relative to the seek position A hole is defined as a sequence of zeros Note These operations only make sense for filesystems that support them Availability Linux 3 1 macOS Unix New in version 3 3 os open path flags mode 0o777 dir_fd None Open the file path and set various flags according to flags and possibly its mode according to mode When computing mode the current umask value is first masked out Return the file descriptor for the newly opened file The new file descriptor is non inheritable For a description of the flag and mode values see the C run time documentation flag constants like O_RDONLY and O_WRONLY are defined in the os module In particular on Windows adding O_BINARY is needed to open files in binary mode This function can support paths relative to directory descriptors with the dir_fd parameter Raises an auditing event open with arguments path mode flags Changed in version 3 4 The new file descriptor is now non inheritable Note This function is intended for low level I O For normal usage use the built in function open which returns a file object with read and write methods and many more To wrap a file descriptor in a file object use fdopen Changed in version 3 3 Added the dir_fd parameter Changed in version 3 5 If the system call is interrupted and the signal handler does not raise an exception the function now retries the system call instead of raising an InterruptedError exception see PEP 475 for the rationale Changed in version 3 6 Accepts a path like object The following constants are options for the flags parameter to the open function They can be combined using the bitwise OR operator Some of them are not available on all platforms For descriptions of their availability and use consult the open 2 manual page on Unix or the MSDN on Windows os O_RDONLY os O_WRONLY os O_RDWR os O_APPEND os O_CREAT os O_EXCL os O_TRUNC The above constants are available on Unix and Windows os O_DSYNC os O_RSYNC os O_SYNC os O_NDELAY os O_NONBLOCK os O_NOCTTY os O_CLOEXEC The above constants are only available on Unix Changed in version 3 3 Add O_CLOEXEC constant os O_BINARY os O_NOINHE,en
1102,RIT os O_SHORT_LIVED os O_TEMPORARY os O_RANDOM os O_SEQUENTIAL os O_TEXT The above constants are only available on Windows os O_EVTONLY os O_FSYNC os O_SYMLINK os O_NOFOLLOW_ANY The above constants are only available on macOS Changed in version 3 10 Add O_EVTONLY O_FSYNC O_SYMLINK and O_NOFOLLOW_ANY constants os O_ASYNC os O_DIRECT os O_DIRECTORY os O_NOFOLLOW os O_NOATIME os O_PATH os O_TMPFILE os O_SHLOCK os O_EXLOCK The above constants are extensions and not present if they are not defined by the C library Changed in version 3 4 Add O_PATH on systems that support it Add O_TMPFILE only available on Linux Kernel 3 11 or newer os openpty Open a new pseudo terminal pair Return a pair of file descriptors master slave for the pty and the tty respectively The new file descriptors are non inheritable For a slightly more portable approach use the pty module Availability Unix not Emscripten not WASI Changed in version 3 4 The new file descriptors are now non inheritable os pipe Create a pipe Return a pair of file descriptors r w usable for reading and writing respectively The new file descriptor is non inheritable Availability Unix Windows Changed in version 3 4 The new file descriptors are now non inheritable os pipe2 flags Create a pipe with flags set atomically flags can be constructed by ORing together one or more of these values O_NONBLOCK O_CLOEXEC Return a pair of file descriptors r w usable for reading and writing respectively Availability Unix not Emscripten not WASI New in version 3 3 os posix_fallocate fd offset len Ensures that enough disk space is allocated for the file specified by fd starting from offset and continuing for len bytes Availability Unix not Emscripten New in version 3 3 os posix_fadvise fd offset len advice Announces an intention to access data in a specific pattern thus allowing the kernel to make optimizations The advice applies to the region of the file specified by fd starting at offset and continuing for len bytes advice is one of POSIX_FADV_NORMAL POSIX_FADV_SEQUENTIAL POSIX_FADV_RANDOM POSIX_FADV_NOREUSE POSIX_FADV_WILLNEED or POSIX_FADV_DONTNEED Availability Unix New in version 3 3 os POSIX_FADV_NORMAL os POSIX_FADV_SEQUENTIAL os POSIX_FADV_RANDOM os POSIX_FADV_NOREUSE os POSIX_FADV_WILLNEED os POSIX_FADV_DONTNEED Flags that can be used in advice in posix_fadvise that specify the access pattern that is likely to be used Availability Unix New in version 3 3 os pread fd n offset Read at most n bytes from file descriptor fd at a position of offset leaving the file offset unchanged Return a bytestring containing the bytes read If the end of the file referred to by fd has been reached an empty bytes object is returned Availability Unix New in version 3 3 os preadv fd buffers offset flags 0 Read from a file descriptor fd at a position of offset into mutable bytes like objects buffers leaving the file offset unchanged Transfer data into each buffer until it is full and then move on to the next buffer in the sequence to hold the rest of the data The flags argument contains a bitwise OR of zero or more of the following flags RWF_HIPRI RWF_NOWAIT Return the total number of bytes actually read which can be less than the total capacity of all the objects The operating system may set a limit sysconf value SC_IOV_MAX on the number of buffers that can be used Combine the functionality of os readv and os pread Availability Linux 2 6 30 FreeBSD 6 0 OpenBSD 2 7 AIX 7 1 Using flags requires Linux 4 6 New in version 3 7 os RWF_NOWAIT Do not wait for data which is not immediately available If this flag is specified the system call will return instantly if it would have to read data from the backing storage or wait for a lock If some data was successfully read it will return the number of bytes read If no bytes were read it will return 1 and set errno to errno EAGAIN Availability Linux 4 14 New in version 3 7 os RWF_HIPRI High priority read write Allows block based filesystems to use polling of the device which provides lower latency but may use additional resources Currently on Linux this feature is usable only,en
1103, on a file descriptor opened using the O_DIRECT flag Availability Linux 4 6 New in version 3 7 os pwrite fd str offset Write the bytestring in str to file descriptor fd at position of offset leaving the file offset unchanged Return the number of bytes actually written Availability Unix New in version 3 3 os pwritev fd buffers offset flags 0 Write the buffers contents to file descriptor fd at a offset offset leaving the file offset unchanged buffers must be a sequence of bytes like objects Buffers are processed in array order Entire contents of the first buffer is written before proceeding to the second and so on The flags argument contains a bitwise OR of zero or more of the following flags RWF_DSYNC RWF_SYNC RWF_APPEND Return the total number of bytes actually written The operating system may set a limit sysconf value SC_IOV_MAX on the number of buffers that can be used Combine the functionality of os writev and os pwrite Availability Linux 2 6 30 FreeBSD 6 0 OpenBSD 2 7 AIX 7 1 Using flags requires Linux 4 6 New in version 3 7 os RWF_DSYNC Provide a per write equivalent of the O_DSYNC os open flag This flag effect applies only to the data range written by the system call Availability Linux 4 7 New in version 3 7 os RWF_SYNC Provide a per write equivalent of the O_SYNC os open flag This flag effect applies only to the data range written by the system call Availability Linux 4 7 New in version 3 7 os RWF_APPEND Provide a per write equivalent of the O_APPEND os open flag This flag is meaningful only for os pwritev and its effect applies only to the data range written by the system call The offset argument does not affect the write operation the data is always appended to the end of the file However if the offset argument is 1 the current file offset is updated Availability Linux 4 16 New in version 3 10 os read fd n Read at most n bytes from file descriptor fd Return a bytestring containing the bytes read If the end of the file referred to by fd has been reached an empty bytes object is returned Note This function is intended for low level I O and must be applied to a file descriptor as returned by os open or pipe To read a file object returned by the built in function open or by popen or fdopen or sys stdin use its read or readline methods Changed in version 3 5 If the system call is interrupted and the signal handler does not raise an exception the function now retries the system call instead of raising an InterruptedError exception see PEP 475 for the rationale os sendfile out_fd in_fd offset count os sendfile out_fd in_fd offset count headers trailers flags 0 Copy count bytes from file descriptor in_fd to file descriptor out_fd starting at offset Return the number of bytes sent When EOF is reached return 0 The first function notation is supported by all platforms that define sendfile On Linux if offset is given as None the bytes are read from the current position of in_fd and the position of in_fd is updated The second case may be used on macOS and FreeBSD where headers and trailers are arbitrary sequences of buffers that are written before and after the data from in_fd is written It returns the same as the first case On macOS and FreeBSD a value of 0 for count specifies to send until the end of in_fd is reached All platforms support sockets as out_fd file descriptor and some platforms allow other types e g regular file pipe as well Cross platform applications should not use headers trailers and flags arguments Availability Unix not Emscripten not WASI Note For a higher level wrapper of sendfile see socket socket sendfile New in version 3 3 Changed in version 3 9 Parameters out and in was renamed to out_fd and in_fd os SF_NODISKIO os SF_MNOWAIT os SF_SYNC Parameters to the sendfile function if the implementation supports them Availability Unix not Emscripten not WASI New in version 3 3 os SF_NOCACHE Parameter to the sendfile function if the implementation supports it The data won t be cached in the virtual memory and will be freed afterwards Availability Unix not Emscripten not WASI New in version 3 11 os set_blocking,en
1104, fd blocking Set the blocking mode of the specified file descriptor Set the O_NONBLOCK flag if blocking is False clear the flag otherwise See also get_blocking and socket socket setblocking Availability Unix Windows The function is limited on Emscripten and WASI see WebAssembly platforms for more information On Windows this function is limited to pipes New in version 3 5 Changed in version 3 12 Added support for pipes on Windows os splice src dst count offset_src None offset_dst None Transfer count bytes from file descriptor src starting from offset offset_src to file descriptor dst starting from offset offset_dst At least one of the file descriptors must refer to a pipe If offset_src is None then src is read from the current position respectively for offset_dst The offset associated to the file descriptor that refers to a pipe must be None The files pointed by src and dst must reside in the same filesystem otherwise an OSError is raised with errno set to errno EXDEV This copy is done without the additional cost of transferring data from the kernel to user space and then back into the kernel Additionally some filesystems could implement extra optimizations The copy is done as if both files are opened as binary Upon successful completion returns the number of bytes spliced to or from the pipe A return value of 0 means end of input If src refers to a pipe then this means that there was no data to transfer and it would not make sense to block because there are no writers connected to the write end of the pipe Availability Linux 2 6 17 with glibc 2 5 New in version 3 10 os SPLICE_F_MOVE os SPLICE_F_NONBLOCK os SPLICE_F_MORE New in version 3 10 os readv fd buffers Read from a file descriptor fd into a number of mutable bytes like objects buffers Transfer data into each buffer until it is full and then move on to the next buffer in the sequence to hold the rest of the data Return the total number of bytes actually read which can be less than the total capacity of all the objects The operating system may set a limit sysconf value SC_IOV_MAX on the number of buffers that can be used Availability Unix New in version 3 3 os tcgetpgrp fd Return the process group associated with the terminal given by fd an open file descriptor as returned by os open Availability Unix not WASI os tcsetpgrp fd pg Set the process group associated with the terminal given by fd an open file descriptor as returned by os open to pg Availability Unix not WASI os ttyname fd Return a string which specifies the terminal device associated with file descriptor fd If fd is not associated with a terminal device an exception is raised Availability Unix os write fd str Write the bytestring in str to file descriptor fd Return the number of bytes actually written Note This function is intended for low level I O and must be applied to a file descriptor as returned by os open or pipe To write a file object returned by the built in function open or by popen or fdopen or sys stdout or sys stderr use its write method Changed in version 3 5 If the system call is interrupted and the signal handler does not raise an exception the function now retries the system call instead of raising an InterruptedError exception see PEP 475 for the rationale os writev fd buffers Write the contents of buffers to file descriptor fd buffers must be a sequence of bytes like objects Buffers are processed in array order Entire contents of the first buffer is written before proceeding to the second and so on Returns the total number of bytes actually written The operating system may set a limit sysconf value SC_IOV_MAX on the number of buffers that can be used Availability Unix New in version 3 3 Querying the size of a terminal New in version 3 3 os get_terminal_size fd STDOUT_FILENO Return the size of the terminal window as columns lines tuple of type terminal_size The optional argument fd default STDOUT_FILENO or standard output specifies which file descriptor should be queried If the file descriptor is not connected to a terminal an OSError is raised shutil get_terminal_size is the high level f,en
1105,unction which should normally be used os get_terminal_size is the low level implementation Availability Unix Windows class os terminal_size A subclass of tuple holding columns lines of the terminal window size columns Width of the terminal window in characters lines Height of the terminal window in characters Inheritance of File Descriptors New in version 3 4 A file descriptor has an inheritable flag which indicates if the file descriptor can be inherited by child processes Since Python 3 4 file descriptors created by Python are non inheritable by default On UNIX non inheritable file descriptors are closed in child processes at the execution of a new program other file descriptors are inherited On Windows non inheritable handles and file descriptors are closed in child processes except for standard streams file descriptors 0 1 and 2 stdin stdout and stderr which are always inherited Using spawn functions all inheritable handles and all inheritable file descriptors are inherited Using the subprocess module all file descriptors except standard streams are closed and inheritable handles are only inherited if the close_fds parameter is False On WebAssembly platforms wasm32 emscripten and wasm32 wasi the file descriptor cannot be modified os get_inheritable fd Get the inheritable flag of the specified file descriptor a boolean os set_inheritable fd inheritable Set the inheritable flag of the specified file descriptor os get_handle_inheritable handle Get the inheritable flag of the specified handle a boolean Availability Windows os set_handle_inheritable handle inheritable Set the inheritable flag of the specified handle Availability Windows Files and Directories On some Unix platforms many of these functions support one or more of these features specifying a file descriptor Normally the path argument provided to functions in the os module must be a string specifying a file path However some functions now alternatively accept an open file descriptor for their path argument The function will then operate on the file referred to by the descriptor For POSIX systems Python will call the variant of the function prefixed with f e g call fchdir instead of chdir You can check whether or not path can be specified as a file descriptor for a particular function on your platform using os supports_fd If this functionality is unavailable using it will raise a NotImplementedError If the function also supports dir_fd or follow_symlinks arguments it s an error to specify one of those when supplying path as a file descriptor paths relative to directory descriptors If dir_fd is not None it should be a file descriptor referring to a directory and the path to operate on should be relative path will then be relative to that directory If the path is absolute dir_fd is ignored For POSIX systems Python will call the variant of the function with an at suffix and possibly prefixed with f e g call faccessat instead of access You can check whether or not dir_fd is supported for a particular function on your platform using os supports_dir_fd If it s unavailable using it will raise a NotImplementedError not following symlinks If follow_symlinks is False and the last element of the path to operate on is a symbolic link the function will operate on the symbolic link itself rather than the file pointed to by the link For POSIX systems Python will call the l variant of the function You can check whether or not follow_symlinks is supported for a particular function on your platform using os supports_follow_symlinks If it s unavailable using it will raise a NotImplementedError os access path mode dir_fd None effective_ids False follow_symlinks True Use the real uid gid to test for access to path Note that most operations will use the effective uid gid therefore this routine can be used in a suid sgid environment to test if the invoking user has the specified access to path mode should be F_OK to test the existence of path or it can be the inclusive OR of one or more of R_OK W_OK and X_OK to test permissions Return True if access is allowed False if not See the Un,en
1106,ix man page access 2 for more information This function can support specifying paths relative to directory descriptors and not following symlinks If effective_ids is True access will perform its access checks using the effective uid gid instead of the real uid gid effective_ids may not be supported on your platform you can check whether or not it is available using os supports_effective_ids If it is unavailable using it will raise a NotImplementedError Note Using access to check if a user is authorized to e g open a file before actually doing so using open creates a security hole because the user might exploit the short time interval between checking and opening the file to manipulate it It s preferable to use EAFP techniques For example if os access myfile os R_OK with open myfile as fp return fp read return some default data is better written as try fp open myfile except PermissionError return some default data else with fp return fp read Note I O operations may fail even when access indicates that they would succeed particularly for operations on network filesystems which may have permissions semantics beyond the usual POSIX permission bit model Changed in version 3 3 Added the dir_fd effective_ids and follow_symlinks parameters Changed in version 3 6 Accepts a path like object os F_OK os R_OK os W_OK os X_OK Values to pass as the mode parameter of access to test the existence readability writability and executability of path respectively os chdir path Change the current working directory to path This function can support specifying a file descriptor The descriptor must refer to an opened directory not an open file This function can raise OSError and subclasses such as FileNotFoundError PermissionError and NotADirectoryError Raises an auditing event os chdir with argument path Changed in version 3 3 Added support for specifying path as a file descriptor on some platforms Changed in version 3 6 Accepts a path like object os chflags path flags follow_symlinks True Set the flags of path to the numeric flags flags may take a combination bitwise OR of the following values as defined in the stat module stat UF_NODUMP stat UF_IMMUTABLE stat UF_APPEND stat UF_OPAQUE stat UF_NOUNLINK stat UF_COMPRESSED stat UF_HIDDEN stat SF_ARCHIVED stat SF_IMMUTABLE stat SF_APPEND stat SF_NOUNLINK stat SF_SNAPSHOT This function can support not following symlinks Raises an auditing event os chflags with arguments path flags Availability Unix not Emscripten not WASI Changed in version 3 3 Added the follow_symlinks parameter Changed in version 3 6 Accepts a path like object os chmod path mode dir_fd None follow_symlinks True Change the mode of path to the numeric mode mode may take one of the following values as defined in the stat module or bitwise ORed combinations of them stat S_ISUID stat S_ISGID stat S_ENFMT stat S_ISVTX stat S_IREAD stat S_IWRITE stat S_IEXEC stat S_IRWXU stat S_IRUSR stat S_IWUSR stat S_IXUSR stat S_IRWXG stat S_IRGRP stat S_IWGRP stat S_IXGRP stat S_IRWXO stat S_IROTH stat S_IWOTH stat S_IXOTH This function can support specifying a file descriptor paths relative to directory descriptors and not following symlinks Note Although Windows supports chmod you can only set the file s read only flag with it via the stat S_IWRITE and stat S_IREAD constants or a corresponding integer value All other bits are ignored The function is limited on Emscripten and WASI see WebAssembly platforms for more information Raises an auditing event os chmod with arguments path mode dir_fd New in version 3 3 Added support for specifying path as an open file descriptor and the dir_fd and follow_symlinks arguments Changed in version 3 6 Accepts a path like object os chown path uid gid dir_fd None follow_symlinks True Change the owner and group id of path to the numeric uid and gid To leave one of the ids unchanged set it to 1 This function can support specifying a file descriptor paths relative to directory descriptors and not following symlinks See shutil chown for a higher level function that accepts names in addition to numeric ids Raises an aud,en
1107,iting event os chown with arguments path uid gid dir_fd Availability Unix The function is limited on Emscripten and WASI see WebAssembly platforms for more information New in version 3 3 Added support for specifying path as an open file descriptor and the dir_fd and follow_symlinks arguments Changed in version 3 6 Supports a path like object os chroot path Change the root directory of the current process to path Availability Unix not Emscripten not WASI Changed in version 3 6 Accepts a path like object os fchdir fd Change the current working directory to the directory represented by the file descriptor fd The descriptor must refer to an opened directory not an open file As of Python 3 3 this is equivalent to os chdir fd Raises an auditing event os chdir with argument path Availability Unix os getcwd Return a string representing the current working directory os getcwdb Return a bytestring representing the current working directory Changed in version 3 8 The function now uses the UTF 8 encoding on Windows rather than the ANSI code page see PEP 529 for the rationale The function is no longer deprecated on Windows os lchflags path flags Set the flags of path to the numeric flags like chflags but do not follow symbolic links As of Python 3 3 this is equivalent to os chflags path flags follow_symlinks False Raises an auditing event os chflags with arguments path flags Availability Unix not Emscripten not WASI Changed in version 3 6 Accepts a path like object os lchmod path mode Change the mode of path to the numeric mode If path is a symlink this affects the symlink rather than the target See the docs for chmod for possible values of mode As of Python 3 3 this is equivalent to os chmod path mode follow_symlinks False lchmod is not part of POSIX but Unix implementations may have it if changing the mode of symbolic links is supported Raises an auditing event os chmod with arguments path mode dir_fd Availability Unix not Linux FreeBSD 1 3 NetBSD 1 3 not OpenBSD Changed in version 3 6 Accepts a path like object os lchown path uid gid Change the owner and group id of path to the numeric uid and gid This function will not follow symbolic links As of Python 3 3 this is equivalent to os chown path uid gid follow_symlinks False Raises an auditing event os chown with arguments path uid gid dir_fd Availability Unix Changed in version 3 6 Accepts a path like object os link src dst src_dir_fd None dst_dir_fd None follow_symlinks True Create a hard link pointing to src named dst This function can support specifying src_dir_fd and or dst_dir_fd to supply paths relative to directory descriptors and not following symlinks Raises an auditing event os link with arguments src dst src_dir_fd dst_dir_fd Availability Unix Windows not Emscripten Changed in version 3 2 Added Windows support Changed in version 3 3 Added the src_dir_fd dst_dir_fd and follow_symlinks parameters Changed in version 3 6 Accepts a path like object for src and dst os listdir path Return a list containing the names of the entries in the directory given by path The list is in arbitrary order and does not include the special entries and even if they are present in the directory If a file is removed from or added to the directory during the call of this function whether a name for that file be included is unspecified path may be a path like object If path is of type bytes directly or indirectly through the PathLike interface the filenames returned will also be of type bytes in all other circumstances they will be of type str This function can also support specifying a file descriptor the file descriptor must refer to a directory Raises an auditing event os listdir with argument path Note To encode str filenames to bytes use fsencode See also The scandir function returns directory entries along with file attribute information giving better performance for many common use cases Changed in version 3 2 The path parameter became optional New in version 3 3 Added support for specifying path as an open file descriptor Changed in version 3 6 Accepts a path like object os listdrives Retur,en
1108,n a list containing the names of drives on a Windows system A drive name typically looks like C Not every drive name will be associated with a volume and some may be inaccessible for a variety of reasons including permissions network connectivity or missing media This function does not test for access May raise OSError if an error occurs collecting the drive names Raises an auditing event os listdrives with no arguments Availability Windows New in version 3 12 os listmounts volume Return a list containing the mount points for a volume on a Windows system volume must be represented as a GUID path like those returned by os listvolumes Volumes may be mounted in multiple locations or not at all In the latter case the list will be empty Mount points that are not associated with a volume will not be returned by this function The mount points return by this function will be absolute paths and may be longer than the drive name Raises OSError if the volume is not recognized or if an error occurs collecting the paths Raises an auditing event os listmounts with argument volume Availability Windows New in version 3 12 os listvolumes Return a list containing the volumes in the system Volumes are typically represented as a GUID path that looks like Volume xxxxxxxx xxxx xxxx xxxx xxxxxxxxxxxx Files can usually be accessed through a GUID path permissions allowing However users are generally not familiar with them and so the recommended use of this function is to retrieve mount points using os listmounts May raise OSError if an error occurs collecting the volumes Raises an auditing event os listvolumes with no arguments Availability Windows New in version 3 12 os lstat path dir_fd None Perform the equivalent of an lstat system call on the given path Similar to stat but does not follow symbolic links Return a stat_result object On platforms that do not support symbolic links this is an alias for stat As of Python 3 3 this is equivalent to os stat path dir_fd dir_fd follow_symlinks False This function can also support paths relative to directory descriptors See also The stat function Changed in version 3 2 Added support for Windows 6 0 Vista symbolic links Changed in version 3 3 Added the dir_fd parameter Changed in version 3 6 Accepts a path like object Changed in version 3 8 On Windows now opens reparse points that represent another path name surrogates including symbolic links and directory junctions Other kinds of reparse points are resolved by the operating system as for stat os mkdir path mode 0o777 dir_fd None Create a directory named path with numeric mode mode If the directory already exists FileExistsError is raised If a parent directory in the path does not exist FileNotFoundError is raised On some systems mode is ignored Where it is used the current umask value is first masked out If bits other than the last 9 i e the last 3 digits of the octal representation of the mode are set their meaning is platform dependent On some platforms they are ignored and you should call chmod explicitly to set them This function can also support paths relative to directory descriptors It is also possible to create temporary directories see the tempfile module s tempfile mkdtemp function Raises an auditing event os mkdir with arguments path mode dir_fd Changed in version 3 3 Added the dir_fd parameter Changed in version 3 6 Accepts a path like object os makedirs name mode 0o777 exist_ok False Recursive directory creation function Like mkdir but makes all intermediate level directories needed to contain the leaf directory The mode parameter is passed to mkdir for creating the leaf directory see the mkdir description for how it is interpreted To set the file permission bits of any newly created parent directories you can set the umask before invoking makedirs The file permission bits of existing parent directories are not changed If exist_ok is False the default a FileExistsError is raised if the target directory already exists Note makedirs will become confused if the path elements to create include pardir eg on UNIX systems This function handles U,en
1109,NC paths correctly Raises an auditing event os mkdir with arguments path mode dir_fd Changed in version 3 2 Added the exist_ok parameter Changed in version 3 4 1 Before Python 3 4 1 if exist_ok was True and the directory existed makedirs would still raise an error if mode did not match the mode of the existing directory Since this behavior was impossible to implement safely it was removed in Python 3 4 1 See bpo 21082 Changed in version 3 6 Accepts a path like object Changed in version 3 7 The mode argument no longer affects the file permission bits of newly created intermediate level directories os mkfifo path mode 0o666 dir_fd None Create a FIFO a named pipe named path with numeric mode mode The current umask value is first masked out from the mode This function can also support paths relative to directory descriptors FIFOs are pipes that can be accessed like regular files FIFOs exist until they are deleted for example with os unlink Generally FIFOs are used as rendezvous between client and server type processes the server opens the FIFO for reading and the client opens it for writing Note that mkfifo doesn t open the FIFO it just creates the rendezvous point Availability Unix not Emscripten not WASI Changed in version 3 3 Added the dir_fd parameter Changed in version 3 6 Accepts a path like object os mknod path mode 0o600 device 0 dir_fd None Create a filesystem node file device special file or named pipe named path mode specifies both the permissions to use and the type of node to be created being combined bitwise OR with one of stat S_IFREG stat S_IFCHR stat S_IFBLK and stat S_IFIFO those constants are available in stat For stat S_IFCHR and stat S_IFBLK device defines the newly created device special file probably using os makedev otherwise it is ignored This function can also support paths relative to directory descriptors Availability Unix not Emscripten not WASI Changed in version 3 3 Added the dir_fd parameter Changed in version 3 6 Accepts a path like object os major device Extract the device major number from a raw device number usually the st_dev or st_rdev field from stat os minor device Extract the device minor number from a raw device number usually the st_dev or st_rdev field from stat os makedev major minor Compose a raw device number from the major and minor device numbers os pathconf path name Return system configuration information relevant to a named file name specifies the configuration value to retrieve it may be a string which is the name of a defined system value these names are specified in a number of standards POSIX 1 Unix 95 Unix 98 and others Some platforms define additional names as well The names known to the host operating system are given in the pathconf_names dictionary For configuration variables not included in that mapping passing an integer for name is also accepted If name is a string and is not known ValueError is raised If a specific value for name is not supported by the host system even if it is included in pathconf_names an OSError is raised with errno EINVAL for the error number This function can support specifying a file descriptor Availability Unix Changed in version 3 6 Accepts a path like object os pathconf_names Dictionary mapping names accepted by pathconf and fpathconf to the integer values defined for those names by the host operating system This can be used to determine the set of names known to the system Availability Unix os readlink path dir_fd None Return a string representing the path to which the symbolic link points The result may be either an absolute or relative pathname if it is relative it may be converted to an absolute pathname using os path join os path dirname path result If the path is a string object directly or indirectly through a PathLike interface the result will also be a string object and the call may raise a UnicodeDecodeError If the path is a bytes object direct or indirectly the result will be a bytes object This function can also support paths relative to directory descriptors When trying to resolve a path that may contain links use realpat,en
1110,h to properly handle recursion and platform differences Availability Unix Windows Changed in version 3 2 Added support for Windows 6 0 Vista symbolic links Changed in version 3 3 Added the dir_fd parameter Changed in version 3 6 Accepts a path like object on Unix Changed in version 3 8 Accepts a path like object and a bytes object on Windows Added support for directory junctions and changed to return the substitution path which typically includes prefix rather than the optional print name field that was previously returned os remove path dir_fd None Remove delete the file path If path is a directory an OSError is raised Use rmdir to remove directories If the file does not exist a FileNotFoundError is raised This function can support paths relative to directory descriptors On Windows attempting to remove a file that is in use causes an exception to be raised on Unix the directory entry is removed but the storage allocated to the file is not made available until the original file is no longer in use This function is semantically identical to unlink Raises an auditing event os remove with arguments path dir_fd Changed in version 3 3 Added the dir_fd parameter Changed in version 3 6 Accepts a path like object os removedirs name Remove directories recursively Works like rmdir except that if the leaf directory is successfully removed removedirs tries to successively remove every parent directory mentioned in path until an error is raised which is ignored because it generally means that a parent directory is not empty For example os removedirs foo bar baz will first remove the directory foo bar baz and then remove foo bar and foo if they are empty Raises OSError if the leaf directory could not be successfully removed Raises an auditing event os remove with arguments path dir_fd Changed in version 3 6 Accepts a path like object os rename src dst src_dir_fd None dst_dir_fd None Rename the file or directory src to dst If dst exists the operation will fail with an OSError subclass in a number of cases On Windows if dst exists a FileExistsError is always raised The operation may fail if src and dst are on different filesystems Use shutil move to support moves to a different filesystem On Unix if src is a file and dst is a directory or vice versa an IsADirectoryError or a NotADirectoryError will be raised respectively If both are directories and dst is empty dst will be silently replaced If dst is a non empty directory an OSError is raised If both are files dst will be replaced silently if the user has permission The operation may fail on some Unix flavors if src and dst are on different filesystems If successful the renaming will be an atomic operation this is a POSIX requirement This function can support specifying src_dir_fd and or dst_dir_fd to supply paths relative to directory descriptors If you want cross platform overwriting of the destination use replace Raises an auditing event os rename with arguments src dst src_dir_fd dst_dir_fd Changed in version 3 3 Added the src_dir_fd and dst_dir_fd parameters Changed in version 3 6 Accepts a path like object for src and dst os renames old new Recursive directory or file renaming function Works like rename except creation of any intermediate directories needed to make the new pathname good is attempted first After the rename directories corresponding to rightmost path segments of the old name will be pruned away using removedirs Note This function can fail with the new directory structure made if you lack permissions needed to remove the leaf directory or file Raises an auditing event os rename with arguments src dst src_dir_fd dst_dir_fd Changed in version 3 6 Accepts a path like object for old and new os replace src dst src_dir_fd None dst_dir_fd None Rename the file or directory src to dst If dst is a non empty directory OSError will be raised If dst exists and is a file it will be replaced silently if the user has permission The operation may fail if src and dst are on different filesystems If successful the renaming will be an atomic operation this is a POSIX requirement This fu,en
1111,nction can support specifying src_dir_fd and or dst_dir_fd to supply paths relative to directory descriptors Raises an auditing event os rename with arguments src dst src_dir_fd dst_dir_fd New in version 3 3 Changed in version 3 6 Accepts a path like object for src and dst os rmdir path dir_fd None Remove delete the directory path If the directory does not exist or is not empty a FileNotFoundError or an OSError is raised respectively In order to remove whole directory trees shutil rmtree can be used This function can support paths relative to directory descriptors Raises an auditing event os rmdir with arguments path dir_fd Changed in version 3 3 Added the dir_fd parameter Changed in version 3 6 Accepts a path like object os scandir path Return an iterator of os DirEntry objects corresponding to the entries in the directory given by path The entries are yielded in arbitrary order and the special entries and are not included If a file is removed from or added to the directory after creating the iterator whether an entry for that file be included is unspecified Using scandir instead of listdir can significantly increase the performance of code that also needs file type or file attribute information because os DirEntry objects expose this information if the operating system provides it when scanning a directory All os DirEntry methods may perform a system call but is_dir and is_file usually only require a system call for symbolic links os DirEntry stat always requires a system call on Unix but only requires one for symbolic links on Windows path may be a path like object If path is of type bytes directly or indirectly through the PathLike interface the type of the name and path attributes of each os DirEntry will be bytes in all other circumstances they will be of type str This function can also support specifying a file descriptor the file descriptor must refer to a directory Raises an auditing event os scandir with argument path The scandir iterator supports the context manager protocol and has the following method scandir close Close the iterator and free acquired resources This is called automatically when the iterator is exhausted or garbage collected or when an error happens during iterating However it is advisable to call it explicitly or use the with statement New in version 3 6 The following example shows a simple use of scandir to display all the files excluding directories in the given path that don t start with The entry is_file call will generally not make an additional system call with os scandir path as it for entry in it if not entry name startswith and entry is_file print entry name Note On Unix based systems scandir uses the system s opendir and readdir functions On Windows it uses the Win32 FindFirstFileW and FindNextFileW functions New in version 3 5 Changed in version 3 6 Added support for the context manager protocol and the close method If a scandir iterator is neither exhausted nor explicitly closed a ResourceWarning will be emitted in its destructor The function accepts a path like object Changed in version 3 7 Added support for file descriptors on Unix class os DirEntry Object yielded by scandir to expose the file path and other file attributes of a directory entry scandir will provide as much of this information as possible without making additional system calls When a stat or lstat system call is made the os DirEntry object will cache the result os DirEntry instances are not intended to be stored in long lived data structures if you know the file metadata has changed or if a long time has elapsed since calling scandir call os stat entry path to fetch up to date information Because the os DirEntry methods can make operating system calls they may also raise OSError If you need very fine grained control over errors you can catch OSError when calling one of the os DirEntry methods and handle as appropriate To be directly usable as a path like object os DirEntry implements the PathLike interface Attributes and methods on a os DirEntry instance are as follows name The entry s base filename relative to ,en
1112,the scandir path argument The name attribute will be bytes if the scandir path argument is of type bytes and str otherwise Use fsdecode to decode byte filenames path The entry s full path name equivalent to os path join scandir_path entry name where scandir_path is the scandir path argument The path is only absolute if the scandir path argument was absolute If the scandir path argument was a file descriptor the path attribute is the same as the name attribute The path attribute will be bytes if the scandir path argument is of type bytes and str otherwise Use fsdecode to decode byte filenames inode Return the inode number of the entry The result is cached on the os DirEntry object Use os stat entry path follow_symlinks False st_ino to fetch up to date information On the first uncached call a system call is required on Windows but not on Unix is_dir follow_symlinks True Return True if this entry is a directory or a symbolic link pointing to a directory return False if the entry is or points to any other kind of file or if it doesn t exist anymore If follow_symlinks is False return True only if this entry is a directory without following symlinks return False if the entry is any other kind of file or if it doesn t exist anymore The result is cached on the os DirEntry object with a separate cache for follow_symlinks True and False Call os stat along with stat S_ISDIR to fetch up to date information On the first uncached call no system call is required in most cases Specifically for non symlinks neither Windows or Unix require a system call except on certain Unix file systems such as network file systems that return dirent d_type DT_UNKNOWN If the entry is a symlink a system call will be required to follow the symlink unless follow_symlinks is False This method can raise OSError such as PermissionError but FileNotFoundError is caught and not raised is_file follow_symlinks True Return True if this entry is a file or a symbolic link pointing to a file return False if the entry is or points to a directory or other non file entry or if it doesn t exist anymore If follow_symlinks is False return True only if this entry is a file without following symlinks return False if the entry is a directory or other non file entry or if it doesn t exist anymore The result is cached on the os DirEntry object Caching system calls made and exceptions raised are as per is_dir is_symlink Return True if this entry is a symbolic link even if broken return False if the entry points to a directory or any kind of file or if it doesn t exist anymore The result is cached on the os DirEntry object Call os path islink to fetch up to date information On the first uncached call no system call is required in most cases Specifically neither Windows or Unix require a system call except on certain Unix file systems such as network file systems that return dirent d_type DT_UNKNOWN This method can raise OSError such as PermissionError but FileNotFoundError is caught and not raised is_junction Return True if this entry is a junction even if broken return False if the entry points to a regular directory any kind of file a symlink or if it doesn t exist anymore The result is cached on the os DirEntry object Call os path isjunction to fetch up to date information New in version 3 12 stat follow_symlinks True Return a stat_result object for this entry This method follows symbolic links by default to stat a symbolic link add the follow_symlinks False argument On Unix this method always requires a system call On Windows it only requires a system call if follow_symlinks is True and the entry is a reparse point for example a symbolic link or directory junction On Windows the st_ino st_dev and st_nlink attributes of the stat_result are always set to zero Call os stat to get these attributes The result is cached on the os DirEntry object with a separate cache for follow_symlinks True and False Call os stat to fetch up to date information Note that there is a nice correspondence between several attributes and methods of os DirEntry and of pathlib Path In particular the name a,en
1113,ttribute has the same meaning as do the is_dir is_file is_symlink is_junction and stat methods New in version 3 5 Changed in version 3 6 Added support for the PathLike interface Added support for bytes paths on Windows Changed in version 3 12 The st_ctime attribute of a stat result is deprecated on Windows The file creation time is properly available as st_birthtime and in the future st_ctime may be changed to return zero or the metadata change time if available os stat path dir_fd None follow_symlinks True Get the status of a file or a file descriptor Perform the equivalent of a stat system call on the given path path may be specified as either a string or bytes directly or indirectly through the PathLike interface or as an open file descriptor Return a stat_result object This function normally follows symlinks to stat a symlink add the argument follow_symlinks False or use lstat This function can support specifying a file descriptor and not following symlinks On Windows passing follow_symlinks False will disable following all name surrogate reparse points which includes symlinks and directory junctions Other types of reparse points that do not resemble links or that the operating system is unable to follow will be opened directly When following a chain of multiple links this may result in the original link being returned instead of the non link that prevented full traversal To obtain stat results for the final path in this case use the os path realpath function to resolve the path name as far as possible and call lstat on the result This does not apply to dangling symlinks or junction points which will raise the usual exceptions Example import os statinfo os stat somefile txt statinfo os stat_result st_mode 33188 st_ino 7876932 st_dev 234881026 st_nlink 1 st_uid 501 st_gid 501 st_size 264 st_atime 1297230295 st_mtime 1297230027 st_ctime 1297230027 statinfo st_size 264 See also fstat and lstat functions Changed in version 3 3 Added the dir_fd and follow_symlinks parameters specifying a file descriptor instead of a path Changed in version 3 6 Accepts a path like object Changed in version 3 8 On Windows all reparse points that can be resolved by the operating system are now followed and passing follow_symlinks False disables following all name surrogate reparse points If the operating system reaches a reparse point that it is not able to follow stat now returns the information for the original path as if follow_symlinks False had been specified instead of raising an error class os stat_result Object whose attributes correspond roughly to the members of the stat structure It is used for the result of os stat os fstat and os lstat Attributes st_mode File mode file type and file mode bits permissions st_ino Platform dependent but if non zero uniquely identifies the file for a given value of st_dev Typically the inode number on Unix the file index on Windows st_dev Identifier of the device on which this file resides st_nlink Number of hard links st_uid User identifier of the file owner st_gid Group identifier of the file owner st_size Size of the file in bytes if it is a regular file or a symbolic link The size of a symbolic link is the length of the pathname it contains without a terminating null byte Timestamps st_atime Time of most recent access expressed in seconds st_mtime Time of most recent content modification expressed in seconds st_ctime Time of most recent metadata change expressed in seconds Changed in version 3 12 st_ctime is deprecated on Windows Use st_birthtime for the file creation time In the future st_ctime will contain the time of the most recent metadata change as for other platforms st_atime_ns Time of most recent access expressed in nanoseconds as an integer New in version 3 3 st_mtime_ns Time of most recent content modification expressed in nanoseconds as an integer New in version 3 3 st_ctime_ns Time of most recent metadata change expressed in nanoseconds as an integer New in version 3 3 Changed in version 3 12 st_ctime_ns is deprecated on Windows Use st_birthtime_ns for the file creation time In the ,en
1114,future st_ctime will contain the time of the most recent metadata change as for other platforms st_birthtime Time of file creation expressed in seconds This attribute is not always available and may raise AttributeError Changed in version 3 12 st_birthtime is now available on Windows st_birthtime_ns Time of file creation expressed in nanoseconds as an integer This attribute is not always available and may raise AttributeError New in version 3 12 Note The exact meaning and resolution of the st_atime st_mtime st_ctime and st_birthtime attributes depend on the operating system and the file system For example on Windows systems using the FAT32 file systems st_mtime has 2 second resolution and st_atime has only 1 day resolution See your operating system documentation for details Similarly although st_atime_ns st_mtime_ns st_ctime_ns and st_birthtime_ns are always expressed in nanoseconds many systems do not provide nanosecond precision On systems that do provide nanosecond precision the floating point object used to store st_atime st_mtime st_ctime and st_birthtime cannot preserve all of it and as such will be slightly inexact If you need the exact timestamps you should always use st_atime_ns st_mtime_ns st_ctime_ns and st_birthtime_ns On some Unix systems such as Linux the following attributes may also be available st_blocks Number of 512 byte blocks allocated for file This may be smaller than st_size 512 when the file has holes st_blksize Preferred blocksize for efficient file system I O Writing to a file in smaller chunks may cause an inefficient read modify rewrite st_rdev Type of device if an inode device st_flags User defined flags for file On other Unix systems such as FreeBSD the following attributes may be available but may be only filled out if root tries to use them st_gen File generation number On Solaris and derivatives the following attributes may also be available st_fstype String that uniquely identifies the type of the filesystem that contains the file On macOS systems the following attributes may also be available st_rsize Real size of the file st_creator Creator of the file st_type File type On Windows systems the following attributes are also available st_file_attributes Windows file attributes dwFileAttributes member of the BY_HANDLE_FILE_INFORMATION structure returned by GetFileInformationByHandle See the FILE_ATTRIBUTE_ stat FILE_ATTRIBUTE_ARCHIVE constants in the stat module New in version 3 5 st_reparse_tag When st_file_attributes has the FILE_ATTRIBUTE_REPARSE_POINT set this field contains the tag identifying the type of reparse point See the IO_REPARSE_TAG_ constants in the stat module The standard module stat defines functions and constants that are useful for extracting information from a stat structure On Windows some items are filled with dummy values For backward compatibility a stat_result instance is also accessible as a tuple of at least 10 integers giving the most important and portable members of the stat structure in the order st_mode st_ino st_dev st_nlink st_uid st_gid st_size st_atime st_mtime st_ctime More items may be added at the end by some implementations For compatibility with older Python versions accessing stat_result as a tuple always returns integers Changed in version 3 5 Windows now returns the file index as st_ino when available Changed in version 3 7 Added the st_fstype member to Solaris derivatives Changed in version 3 8 Added the st_reparse_tag member on Windows Changed in version 3 8 On Windows the st_mode member now identifies special files as S_IFCHR S_IFIFO or S_IFBLK as appropriate Changed in version 3 12 On Windows st_ctime is deprecated Eventually it will contain the last metadata change time for consistency with other platforms but for now still contains creation time Use st_birthtime for the creation time On Windows st_ino may now be up to 128 bits depending on the file system Previously it would not be above 64 bits and larger file identifiers would be arbitrarily packed On Windows st_rdev no longer returns a value Previously it would contain the same as st_de,en
1115,v which was incorrect Added the st_birthtime member on Windows os statvfs path Perform a statvfs system call on the given path The return value is an object whose attributes describe the filesystem on the given path and correspond to the members of the statvfs structure namely f_bsize f_frsize f_blocks f_bfree f_bavail f_files f_ffree f_favail f_flag f_namemax f_fsid Two module level constants are defined for the f_flag attribute s bit flags if ST_RDONLY is set the filesystem is mounted read only and if ST_NOSUID is set the semantics of setuid setgid bits are disabled or not supported Additional module level constants are defined for GNU glibc based systems These are ST_NODEV disallow access to device special files ST_NOEXEC disallow program execution ST_SYNCHRONOUS writes are synced at once ST_MANDLOCK allow mandatory locks on an FS ST_WRITE write on file directory symlink ST_APPEND append only file ST_IMMUTABLE immutable file ST_NOATIME do not update access times ST_NODIRATIME do not update directory access times ST_RELATIME update atime relative to mtime ctime This function can support specifying a file descriptor Availability Unix Changed in version 3 2 The ST_RDONLY and ST_NOSUID constants were added Changed in version 3 3 Added support for specifying path as an open file descriptor Changed in version 3 4 The ST_NODEV ST_NOEXEC ST_SYNCHRONOUS ST_MANDLOCK ST_WRITE ST_APPEND ST_IMMUTABLE ST_NOATIME ST_NODIRATIME and ST_RELATIME constants were added Changed in version 3 6 Accepts a path like object Changed in version 3 7 Added the f_fsid attribute os supports_dir_fd A set object indicating which functions in the os module accept an open file descriptor for their dir_fd parameter Different platforms provide different features and the underlying functionality Python uses to implement the dir_fd parameter is not available on all platforms Python supports For consistency s sake functions that may support dir_fd always allow specifying the parameter but will throw an exception if the functionality is used when it s not locally available Specifying None for dir_fd is always supported on all platforms To check whether a particular function accepts an open file descriptor for its dir_fd parameter use the in operator on supports_dir_fd As an example this expression evaluates to True if os stat accepts open file descriptors for dir_fd on the local platform os stat in os supports_dir_fd Currently dir_fd parameters only work on Unix platforms none of them work on Windows New in version 3 3 os supports_effective_ids A set object indicating whether os access permits specifying True for its effective_ids parameter on the local platform Specifying False for effective_ids is always supported on all platforms If the local platform supports it the collection will contain os access otherwise it will be empty This expression evaluates to True if os access supports effective_ids True on the local platform os access in os supports_effective_ids Currently effective_ids is only supported on Unix platforms it does not work on Windows New in version 3 3 os supports_fd A set object indicating which functions in the os module permit specifying their path parameter as an open file descriptor on the local platform Different platforms provide different features and the underlying functionality Python uses to accept open file descriptors as path arguments is not available on all platforms Python supports To determine whether a particular function permits specifying an open file descriptor for its path parameter use the in operator on supports_fd As an example this expression evaluates to True if os chdir accepts open file descriptors for path on your local platform os chdir in os supports_fd New in version 3 3 os supports_follow_symlinks A set object indicating which functions in the os module accept False for their follow_symlinks parameter on the local platform Different platforms provide different features and the underlying functionality Python uses to implement follow_symlinks is not available on all platforms Python supports For consistency s sa,en
1116,ke functions that may support follow_symlinks always allow specifying the parameter but will throw an exception if the functionality is used when it s not locally available Specifying True for follow_symlinks is always supported on all platforms To check whether a particular function accepts False for its follow_symlinks parameter use the in operator on supports_follow_symlinks As an example this expression evaluates to True if you may specify follow_symlinks False when calling os stat on the local platform os stat in os supports_follow_symlinks New in version 3 3 os symlink src dst target_is_directory False dir_fd None Create a symbolic link pointing to src named dst On Windows a symlink represents either a file or a directory and does not morph to the target dynamically If the target is present the type of the symlink will be created to match Otherwise the symlink will be created as a directory if target_is_directory is True or a file symlink the default otherwise On non Windows platforms target_is_directory is ignored This function can support paths relative to directory descriptors Note On newer versions of Windows 10 unprivileged accounts can create symlinks if Developer Mode is enabled When Developer Mode is not available enabled the SeCreateSymbolicLinkPrivilege privilege is required or the process must be run as an administrator OSError is raised when the function is called by an unprivileged user Raises an auditing event os symlink with arguments src dst dir_fd Availability Unix Windows The function is limited on Emscripten and WASI see WebAssembly platforms for more information Changed in version 3 2 Added support for Windows 6 0 Vista symbolic links Changed in version 3 3 Added the dir_fd parameter and now allow target_is_directory on non Windows platforms Changed in version 3 6 Accepts a path like object for src and dst Changed in version 3 8 Added support for unelevated symlinks on Windows with Developer Mode os sync Force write of everything to disk Availability Unix New in version 3 3 os truncate path length Truncate the file corresponding to path so that it is at most length bytes in size This function can support specifying a file descriptor Raises an auditing event os truncate with arguments path length Availability Unix Windows New in version 3 3 Changed in version 3 5 Added support for Windows Changed in version 3 6 Accepts a path like object os unlink path dir_fd None Remove delete the file path This function is semantically identical to remove the unlink name is its traditional Unix name Please see the documentation for remove for further information Raises an auditing event os remove with arguments path dir_fd Changed in version 3 3 Added the dir_fd parameter Changed in version 3 6 Accepts a path like object os utime path times None ns dir_fd None follow_symlinks True Set the access and modified times of the file specified by path utime takes two optional parameters times and ns These specify the times set on path and are used as follows If ns is specified it must be a 2 tuple of the form atime_ns mtime_ns where each member is an int expressing nanoseconds If times is not None it must be a 2 tuple of the form atime mtime where each member is an int or float expressing seconds If times is None and ns is unspecified this is equivalent to specifying ns atime_ns mtime_ns where both times are the current time It is an error to specify tuples for both times and ns Note that the exact times you set here may not be returned by a subsequent stat call depending on the resolution with which your operating system records access and modification times see stat The best way to preserve exact times is to use the st_atime_ns and st_mtime_ns fields from the os stat result object with the ns parameter to utime This function can support specifying a file descriptor paths relative to directory descriptors and not following symlinks Raises an auditing event os utime with arguments path times ns dir_fd Changed in version 3 3 Added support for specifying path as an open file descriptor and the dir_fd follow_symlinks and ,en
1117,ns parameters Changed in version 3 6 Accepts a path like object os walk top topdown True onerror None followlinks False Generate the file names in a directory tree by walking the tree either top down or bottom up For each directory in the tree rooted at directory top including top itself it yields a 3 tuple dirpath dirnames filenames dirpath is a string the path to the directory dirnames is a list of the names of the subdirectories in dirpath including symlinks to directories and excluding and filenames is a list of the names of the non directory files in dirpath Note that the names in the lists contain no path components To get a full path which begins with top to a file or directory in dirpath do os path join dirpath name Whether or not the lists are sorted depends on the file system If a file is removed from or added to the dirpath directory during generating the lists whether a name for that file be included is unspecified If optional argument topdown is True or not specified the triple for a directory is generated before the triples for any of its subdirectories directories are generated top down If topdown is False the triple for a directory is generated after the triples for all of its subdirectories directories are generated bottom up No matter the value of topdown the list of subdirectories is retrieved before the tuples for the directory and its subdirectories are generated When topdown is True the caller can modify the dirnames list in place perhaps using del or slice assignment and walk will only recurse into the subdirectories whose names remain in dirnames this can be used to prune the search impose a specific order of visiting or even to inform walk about directories the caller creates or renames before it resumes walk again Modifying dirnames when topdown is False has no effect on the behavior of the walk because in bottom up mode the directories in dirnames are generated before dirpath itself is generated By default errors from the scandir call are ignored If optional argument onerror is specified it should be a function it will be called with one argument an OSError instance It can report the error to continue with the walk or raise the exception to abort the walk Note that the filename is available as the filename attribute of the exception object By default walk will not walk down into symbolic links that resolve to directories Set followlinks to True to visit directories pointed to by symlinks on systems that support them Note Be aware that setting followlinks to True can lead to infinite recursion if a link points to a parent directory of itself walk does not keep track of the directories it visited already Note If you pass a relative pathname don t change the current working directory between resumptions of walk walk never changes the current directory and assumes that its caller doesn t either This example displays the number of bytes taken by non directory files in each directory under the starting directory except that it doesn t look under any CVS subdirectory import os from os path import join getsize for root dirs files in os walk python Lib email print root consumes end print sum getsize join root name for name in files end print bytes in len files non directory files if CVS in dirs dirs remove CVS don t visit CVS directories In the next example simple implementation of shutil rmtree walking the tree bottom up is essential rmdir doesn t allow deleting a directory before the directory is empty Delete everything reachable from the directory named in top assuming there are no symbolic links CAUTION This is dangerous For example if top it could delete all your disk files import os for root dirs files in os walk top topdown False for name in files os remove os path join root name for name in dirs os rmdir os path join root name Raises an auditing event os walk with arguments top topdown onerror followlinks Changed in version 3 5 This function now calls os scandir instead of os listdir making it faster by reducing the number of calls to os stat Changed in version 3 6 Accepts a path like object os ,en
1118,fwalk top topdown True onerror None follow_symlinks False dir_fd None This behaves exactly like walk except that it yields a 4 tuple dirpath dirnames filenames dirfd and it supports dir_fd dirpath dirnames and filenames are identical to walk output and dirfd is a file descriptor referring to the directory dirpath This function always supports paths relative to directory descriptors and not following symlinks Note however that unlike other functions the fwalk default value for follow_symlinks is False Note Since fwalk yields file descriptors those are only valid until the next iteration step so you should duplicate them e g with dup if you want to keep them longer This example displays the number of bytes taken by non directory files in each directory under the starting directory except that it doesn t look under any CVS subdirectory import os for root dirs files rootfd in os fwalk python Lib email print root consumes end print sum os stat name dir_fd rootfd st_size for name in files end print bytes in len files non directory files if CVS in dirs dirs remove CVS don t visit CVS directories In the next example walking the tree bottom up is essential rmdir doesn t allow deleting a directory before the directory is empty Delete everything reachable from the directory named in top assuming there are no symbolic links CAUTION This is dangerous For example if top it could delete all your disk files import os for root dirs files rootfd in os fwalk top topdown False for name in files os unlink name dir_fd rootfd for name in dirs os rmdir name dir_fd rootfd Raises an auditing event os fwalk with arguments top topdown onerror follow_symlinks dir_fd Availability Unix New in version 3 3 Changed in version 3 6 Accepts a path like object Changed in version 3 7 Added support for bytes paths os memfd_create name flags os MFD_CLOEXEC Create an anonymous file and return a file descriptor that refers to it flags must be one of the os MFD_ constants available on the system or a bitwise ORed combination of them By default the new file descriptor is non inheritable The name supplied in name is used as a filename and will be displayed as the target of the corresponding symbolic link in the directory proc self fd The displayed name is always prefixed with memfd and serves only for debugging purposes Names do not affect the behavior of the file descriptor and as such multiple files can have the same name without any side effects Availability Linux 3 17 with glibc 2 27 New in version 3 8 os MFD_CLOEXEC os MFD_ALLOW_SEALING os MFD_HUGETLB os MFD_HUGE_SHIFT os MFD_HUGE_MASK os MFD_HUGE_64KB os MFD_HUGE_512KB os MFD_HUGE_1MB os MFD_HUGE_2MB os MFD_HUGE_8MB os MFD_HUGE_16MB os MFD_HUGE_32MB os MFD_HUGE_256MB os MFD_HUGE_512MB os MFD_HUGE_1GB os MFD_HUGE_2GB os MFD_HUGE_16GB These flags can be passed to memfd_create Availability Linux 3 17 with glibc 2 27 The MFD_HUGE flags are only available since Linux 4 14 New in version 3 8 os eventfd initval flags os EFD_CLOEXEC Create and return an event file descriptor The file descriptors supports raw read and write with a buffer size of 8 select poll and similar See man page eventfd 2 for more information By default the new file descriptor is non inheritable initval is the initial value of the event counter The initial value must be an 32 bit unsigned integer Please note that the initial value is limited to a 32 bit unsigned int although the event counter is an unsigned 64 bit integer with a maximum value of 2 64 2 flags can be constructed from EFD_CLOEXEC EFD_NONBLOCK and EFD_SEMAPHORE If EFD_SEMAPHORE is specified and the event counter is non zero eventfd_read returns 1 and decrements the counter by one If EFD_SEMAPHORE is not specified and the event counter is non zero eventfd_read returns the current event counter value and resets the counter to zero If the event counter is zero and EFD_NONBLOCK is not specified eventfd_read blocks eventfd_write increments the event counter Write blocks if the write operation would increment the counter to a value larger than 2 64 2 Example import os semaphore with start v,en
1119,alue 1 fd os eventfd 1 os EFD_SEMAPHORE os EFC_CLOEXEC try acquire semaphore v os eventfd_read fd try do_work finally release semaphore os eventfd_write fd v finally os close fd Availability Linux 2 6 27 with glibc 2 8 New in version 3 10 os eventfd_read fd Read value from an eventfd file descriptor and return a 64 bit unsigned int The function does not verify that fd is an eventfd Availability Linux 2 6 27 New in version 3 10 os eventfd_write fd value Add value to an eventfd file descriptor value must be a 64 bit unsigned int The function does not verify that fd is an eventfd Availability Linux 2 6 27 New in version 3 10 os EFD_CLOEXEC Set close on exec flag for new eventfd file descriptor Availability Linux 2 6 27 New in version 3 10 os EFD_NONBLOCK Set O_NONBLOCK status flag for new eventfd file descriptor Availability Linux 2 6 27 New in version 3 10 os EFD_SEMAPHORE Provide semaphore like semantics for reads from a eventfd file descriptor On read the internal counter is decremented by one Availability Linux 2 6 30 New in version 3 10 Linux extended attributes New in version 3 3 These functions are all available on Linux only os getxattr path attribute follow_symlinks True Return the value of the extended filesystem attribute attribute for path attribute can be bytes or str directly or indirectly through the PathLike interface If it is str it is encoded with the filesystem encoding This function can support specifying a file descriptor and not following symlinks Raises an auditing event os getxattr with arguments path attribute Changed in version 3 6 Accepts a path like object for path and attribute os listxattr path None follow_symlinks True Return a list of the extended filesystem attributes on path The attributes in the list are represented as strings decoded with the filesystem encoding If path is None listxattr will examine the current directory This function can support specifying a file descriptor and not following symlinks Raises an auditing event os listxattr with argument path Changed in version 3 6 Accepts a path like object os removexattr path attribute follow_symlinks True Removes the extended filesystem attribute attribute from path attribute should be bytes or str directly or indirectly through the PathLike interface If it is a string it is encoded with the filesystem encoding and error handler This function can support specifying a file descriptor and not following symlinks Raises an auditing event os removexattr with arguments path attribute Changed in version 3 6 Accepts a path like object for path and attribute os setxattr path attribute value flags 0 follow_symlinks True Set the extended filesystem attribute attribute on path to value attribute must be a bytes or str with no embedded NULs directly or indirectly through the PathLike interface If it is a str it is encoded with the filesystem encoding and error handler flags may be XATTR_REPLACE or XATTR_CREATE If XATTR_REPLACE is given and the attribute does not exist ENODATA will be raised If XATTR_CREATE is given and the attribute already exists the attribute will not be created and EEXISTS will be raised This function can support specifying a file descriptor and not following symlinks Note A bug in Linux kernel versions less than 2 6 39 caused the flags argument to be ignored on some filesystems Raises an auditing event os setxattr with arguments path attribute value flags Changed in version 3 6 Accepts a path like object for path and attribute os XATTR_SIZE_MAX The maximum size the value of an extended attribute can be Currently this is 64 KiB on Linux os XATTR_CREATE This is a possible value for the flags argument in setxattr It indicates the operation must create an attribute os XATTR_REPLACE This is a possible value for the flags argument in setxattr It indicates the operation must replace an existing attribute Process Management These functions may be used to create and manage processes The various exec functions take a list of arguments for the new program loaded into the process In each case the first of these arguments is passed to the ne,en
1120,w program as its own name rather than as an argument a user may have typed on a command line For the C programmer this is the argv 0 passed to a program s main For example os execv bin echo foo bar will only print bar on standard output foo will seem to be ignored os abort Generate a SIGABRT signal to the current process On Unix the default behavior is to produce a core dump on Windows the process immediately returns an exit code of 3 Be aware that calling this function will not call the Python signal handler registered for SIGABRT with signal signal os add_dll_directory path Add a path to the DLL search path This search path is used when resolving dependencies for imported extension modules the module itself is resolved through sys path and also by ctypes Remove the directory by calling close on the returned object or using it in a with statement See the Microsoft documentation for more information about how DLLs are loaded Raises an auditing event os add_dll_directory with argument path Availability Windows New in version 3 8 Previous versions of CPython would resolve DLLs using the default behavior for the current process This led to inconsistencies such as only sometimes searching PATH or the current working directory and OS functions such as AddDllDirectory having no effect In 3 8 the two primary ways DLLs are loaded now explicitly override the process wide behavior to ensure consistency See the porting notes for information on updating libraries os execl path arg0 arg1 os execle path arg0 arg1 env os execlp file arg0 arg1 os execlpe file arg0 arg1 env os execv path args os execve path args env os execvp file args os execvpe file args env These functions all execute a new program replacing the current process they do not return On Unix the new executable is loaded into the current process and will have the same process id as the caller Errors will be reported as OSError exceptions The current process is replaced immediately Open file objects and descriptors are not flushed so if there may be data buffered on these open files you should flush them using sys stdout flush or os fsync before calling an exec function The l and v variants of the exec functions differ in how command line arguments are passed The l variants are perhaps the easiest to work with if the number of parameters is fixed when the code is written the individual parameters simply become additional parameters to the execl functions The v variants are good when the number of parameters is variable with the arguments being passed in a list or tuple as the args parameter In either case the arguments to the child process should start with the name of the command being run but this is not enforced The variants which include a p near the end execlp execlpe execvp and execvpe will use the PATH environment variable to locate the program file When the environment is being replaced using one of the exec e variants discussed in the next paragraph the new environment is used as the source of the PATH variable The other variants execl execle execv and execve will not use the PATH variable to locate the executable path must contain an appropriate absolute or relative path Relative paths must include at least one slash even on Windows as plain names will not be resolved For execle execlpe execve and execvpe note that these all end in e the env parameter must be a mapping which is used to define the environment variables for the new process these are used instead of the current process environment the functions execl execlp execv and execvp all cause the new process to inherit the environment of the current process For execve on some platforms path may also be specified as an open file descriptor This functionality may not be supported on your platform you can check whether or not it is available using os supports_fd If it is unavailable using it will raise a NotImplementedError Raises an auditing event os exec with arguments path args env Availability Unix Windows not Emscripten not WASI Changed in version 3 3 Added support for specifying path as an open file descri,en
1121,ptor for execve Changed in version 3 6 Accepts a path like object os _exit n Exit the process with status n without calling cleanup handlers flushing stdio buffers etc Note The standard way to exit is sys exit n _exit should normally only be used in the child process after a fork The following exit codes are defined and can be used with _exit although they are not required These are typically used for system programs written in Python such as a mail server s external command delivery program Note Some of these may not be available on all Unix platforms since there is some variation These constants are defined where they are defined by the underlying platform os EX_OK Exit code that means no error occurred May be taken from the defined value of EXIT_SUCCESS on some platforms Generally has a value of zero Availability Unix Windows os EX_USAGE Exit code that means the command was used incorrectly such as when the wrong number of arguments are given Availability Unix not Emscripten not WASI os EX_DATAERR Exit code that means the input data was incorrect Availability Unix not Emscripten not WASI os EX_NOINPUT Exit code that means an input file did not exist or was not readable Availability Unix not Emscripten not WASI os EX_NOUSER Exit code that means a specified user did not exist Availability Unix not Emscripten not WASI os EX_NOHOST Exit code that means a specified host did not exist Availability Unix not Emscripten not WASI os EX_UNAVAILABLE Exit code that means that a required service is unavailable Availability Unix not Emscripten not WASI os EX_SOFTWARE Exit code that means an internal software error was detected Availability Unix not Emscripten not WASI os EX_OSERR Exit code that means an operating system error was detected such as the inability to fork or create a pipe Availability Unix not Emscripten not WASI os EX_OSFILE Exit code that means some system file did not exist could not be opened or had some other kind of error Availability Unix not Emscripten not WASI os EX_CANTCREAT Exit code that means a user specified output file could not be created Availability Unix not Emscripten not WASI os EX_IOERR Exit code that means that an error occurred while doing I O on some file Availability Unix not Emscripten not WASI os EX_TEMPFAIL Exit code that means a temporary failure occurred This indicates something that may not really be an error such as a network connection that couldn t be made during a retryable operation Availability Unix not Emscripten not WASI os EX_PROTOCOL Exit code that means that a protocol exchange was illegal invalid or not understood Availability Unix not Emscripten not WASI os EX_NOPERM Exit code that means that there were insufficient permissions to perform the operation but not intended for file system problems Availability Unix not Emscripten not WASI os EX_CONFIG Exit code that means that some kind of configuration error occurred Availability Unix not Emscripten not WASI os EX_NOTFOUND Exit code that means something like an entry was not found Availability Unix not Emscripten not WASI os fork Fork a child process Return 0 in the child and the child s process id in the parent If an error occurs OSError is raised Note that some platforms including FreeBSD 6 3 and Cygwin have known issues when using fork from a thread Raises an auditing event os fork with no arguments Warning If you use TLS sockets in an application calling fork see the warning in the ssl documentation Warning On macOS the use of this function is unsafe when mixed with using higher level system APIs and that includes using urllib request Changed in version 3 8 Calling fork in a subinterpreter is no longer supported RuntimeError is raised Changed in version 3 12 If Python is able to detect that your process has multiple threads os fork now raises a DeprecationWarning We chose to surface this as a warning when detectable to better inform developers of a design problem that the POSIX platform specifically notes as not supported Even in code that appears to work it has never been safe to mix threading with os fork on POSIX platforms,en
1122, The CPython runtime itself has always made API calls that are not safe for use in the child process when threads existed in the parent such as malloc and free Users of macOS or users of libc or malloc implementations other than those typically found in glibc to date are among those already more likely to experience deadlocks running such code See this discussion on fork being incompatible with threads for technical details of why we re surfacing this longstanding platform compatibility problem to developers Availability POSIX not Emscripten not WASI os forkpty Fork a child process using a new pseudo terminal as the child s controlling terminal Return a pair of pid fd where pid is 0 in the child the new child s process id in the parent and fd is the file descriptor of the master end of the pseudo terminal For a more portable approach use the pty module If an error occurs OSError is raised Raises an auditing event os forkpty with no arguments Warning On macOS the use of this function is unsafe when mixed with using higher level system APIs and that includes using urllib request Changed in version 3 8 Calling forkpty in a subinterpreter is no longer supported RuntimeError is raised Changed in version 3 12 If Python is able to detect that your process has multiple threads this now raises a DeprecationWarning See the longer explanation on os fork Availability Unix not Emscripten not WASI os kill pid sig Send signal sig to the process pid Constants for the specific signals available on the host platform are defined in the signal module Windows The signal CTRL_C_EVENT and signal CTRL_BREAK_EVENT signals are special signals which can only be sent to console processes which share a common console window e g some subprocesses Any other value for sig will cause the process to be unconditionally killed by the TerminateProcess API and the exit code will be set to sig The Windows version of kill additionally takes process handles to be killed See also signal pthread_kill Raises an auditing event os kill with arguments pid sig Availability Unix Windows not Emscripten not WASI Changed in version 3 2 Added Windows support os killpg pgid sig Send the signal sig to the process group pgid Raises an auditing event os killpg with arguments pgid sig Availability Unix not Emscripten not WASI os nice increment Add increment to the process s niceness Return the new niceness Availability Unix not Emscripten not WASI os pidfd_open pid flags 0 Return a file descriptor referring to the process pid with flags set This descriptor can be used to perform process management without races and signals See the pidfd_open 2 man page for more details Availability Linux 5 3 New in version 3 9 os PIDFD_NONBLOCK This flag indicates that the file descriptor will be non blocking If the process referred to by the file descriptor has not yet terminated then an attempt to wait on the file descriptor using waitid 2 will immediately return the error EAGAIN rather than blocking Availability Linux 5 10 New in version 3 12 os plock op Lock program segments into memory The value of op defined in sys lock h determines which segments are locked Availability Unix not Emscripten not WASI os popen cmd mode r buffering 1 Open a pipe to or from command cmd The return value is an open file object connected to the pipe which can be read or written depending on whether mode is r default or w The buffering argument have the same meaning as the corresponding argument to the built in open function The returned file object reads or writes text strings rather than bytes The close method returns None if the subprocess exited successfully or the subprocess s return code if there was an error On POSIX systems if the return code is positive it represents the return value of the process left shifted by one byte If the return code is negative the process was terminated by the signal given by the negated value of the return code For example the return value might be signal SIGKILL if the subprocess was killed On Windows systems the return value contains the signed integer return code from the c,en
1123,hild process On Unix waitstatus_to_exitcode can be used to convert the close method result exit status into an exit code if it is not None On Windows the close method result is directly the exit code or None This is implemented using subprocess Popen see that class s documentation for more powerful ways to manage and communicate with subprocesses Availability not Emscripten not WASI Note The Python UTF 8 Mode affects encodings used for cmd and pipe contents popen is a simple wrapper around subprocess Popen Use subprocess Popen or subprocess run to control options like encodings os posix_spawn path argv env file_actions None setpgroup None resetids False setsid False setsigmask setsigdef scheduler None Wraps the posix_spawn C library API for use from Python Most users should use subprocess run instead of posix_spawn The positional only arguments path args and env are similar to execve The path parameter is the path to the executable file The path should contain a directory Use posix_spawnp to pass an executable file without directory The file_actions argument may be a sequence of tuples describing actions to take on specific file descriptors in the child process between the C library implementation s fork and exec steps The first item in each tuple must be one of the three type indicator listed below describing the remaining tuple elements os POSIX_SPAWN_OPEN os POSIX_SPAWN_OPEN fd path flags mode Performs os dup2 os open path flags mode fd os POSIX_SPAWN_CLOSE os POSIX_SPAWN_CLOSE fd Performs os close fd os POSIX_SPAWN_DUP2 os POSIX_SPAWN_DUP2 fd new_fd Performs os dup2 fd new_fd These tuples correspond to the C library posix_spawn_file_actions_addopen posix_spawn_file_actions_addclose and posix_spawn_file_actions_adddup2 API calls used to prepare for the posix_spawn call itself The setpgroup argument will set the process group of the child to the value specified If the value specified is 0 the child s process group ID will be made the same as its process ID If the value of setpgroup is not set the child will inherit the parent s process group ID This argument corresponds to the C library POSIX_SPAWN_SETPGROUP flag If the resetids argument is True it will reset the effective UID and GID of the child to the real UID and GID of the parent process If the argument is False then the child retains the effective UID and GID of the parent In either case if the set user ID and set group ID permission bits are enabled on the executable file their effect will override the setting of the effective UID and GID This argument corresponds to the C library POSIX_SPAWN_RESETIDS flag If the setsid argument is True it will create a new session ID for posix_spawn setsid requires POSIX_SPAWN_SETSID or POSIX_SPAWN_SETSID_NP flag Otherwise NotImplementedError is raised The setsigmask argument will set the signal mask to the signal set specified If the parameter is not used then the child inherits the parent s signal mask This argument corresponds to the C library POSIX_SPAWN_SETSIGMASK flag The sigdef argument will reset the disposition of all signals in the set specified This argument corresponds to the C library POSIX_SPAWN_SETSIGDEF flag The scheduler argument must be a tuple containing the optional scheduler policy and an instance of sched_param with the scheduler parameters A value of None in the place of the scheduler policy indicates that is not being provided This argument is a combination of the C library POSIX_SPAWN_SETSCHEDPARAM and POSIX_SPAWN_SETSCHEDULER flags Raises an auditing event os posix_spawn with arguments path argv env New in version 3 8 Availability Unix not Emscripten not WASI os posix_spawnp path argv env file_actions None setpgroup None resetids False setsid False setsigmask setsigdef scheduler None Wraps the posix_spawnp C library API for use from Python Similar to posix_spawn except that the system searches for the executable file in the list of directories specified by the PATH environment variable in the same way as for execvp 3 Raises an auditing event os posix_spawn with arguments path argv env New in version 3 ,en
1124,8 Availability POSIX not Emscripten not WASI See posix_spawn documentation os register_at_fork before None after_in_parent None after_in_child None Register callables to be executed when a new child process is forked using os fork or similar process cloning APIs The parameters are optional and keyword only Each specifies a different call point before is a function called before forking a child process after_in_parent is a function called from the parent process after forking a child process after_in_child is a function called from the child process These calls are only made if control is expected to return to the Python interpreter A typical subprocess launch will not trigger them as the child is not going to re enter the interpreter Functions registered for execution before forking are called in reverse registration order Functions registered for execution after forking either in the parent or in the child are called in registration order Note that fork calls made by third party C code may not call those functions unless it explicitly calls PyOS_BeforeFork PyOS_AfterFork_Parent and PyOS_AfterFork_Child There is no way to unregister a function Availability Unix not Emscripten not WASI New in version 3 7 os spawnl mode path os spawnle mode path env os spawnlp mode file os spawnlpe mode file env os spawnv mode path args os spawnve mode path args env os spawnvp mode file args os spawnvpe mode file args env Execute the program path in a new process Note that the subprocess module provides more powerful facilities for spawning new processes and retrieving their results using that module is preferable to using these functions Check especially the Replacing Older Functions with the subprocess Module section If mode is P_NOWAIT this function returns the process id of the new process if mode is P_WAIT returns the process s exit code if it exits normally or signal where signal is the signal that killed the process On Windows the process id will actually be the process handle so can be used with the waitpid function Note on VxWorks this function doesn t return signal when the new process is killed Instead it raises OSError exception The l and v variants of the spawn functions differ in how command line arguments are passed The l variants are perhaps the easiest to work with if the number of parameters is fixed when the code is written the individual parameters simply become additional parameters to the spawnl functions The v variants are good when the number of parameters is variable with the arguments being passed in a list or tuple as the args parameter In either case the arguments to the child process must start with the name of the command being run The variants which include a second p near the end spawnlp spawnlpe spawnvp and spawnvpe will use the PATH environment variable to locate the program file When the environment is being replaced using one of the spawn e variants discussed in the next paragraph the new environment is used as the source of the PATH variable The other variants spawnl spawnle spawnv and spawnve will not use the PATH variable to locate the executable path must contain an appropriate absolute or relative path For spawnle spawnlpe spawnve and spawnvpe note that these all end in e the env parameter must be a mapping which is used to define the environment variables for the new process they are used instead of the current process environment the functions spawnl spawnlp spawnv and spawnvp all cause the new process to inherit the environment of the current process Note that keys and values in the env dictionary must be strings invalid keys or values will cause the function to fail with a return value of 127 As an example the following calls to spawnlp and spawnvpe are equivalent import os os spawnlp os P_WAIT cp cp index html dev null L cp index html dev null os spawnvpe os P_WAIT cp L os environ Raises an auditing event os spawn with arguments mode path args env Availability Unix Windows not Emscripten not WASI spawnlp spawnlpe spawnvp and spawnvpe are not available on Windows spawnle and spawnve are not thre,en
1125,ad safe on Windows we advise you to use the subprocess module instead Changed in version 3 6 Accepts a path like object os P_NOWAIT os P_NOWAITO Possible values for the mode parameter to the spawn family of functions If either of these values is given the spawn functions will return as soon as the new process has been created with the process id as the return value Availability Unix Windows os P_WAIT Possible value for the mode parameter to the spawn family of functions If this is given as mode the spawn functions will not return until the new process has run to completion and will return the exit code of the process the run is successful or signal if a signal kills the process Availability Unix Windows os P_DETACH os P_OVERLAY Possible values for the mode parameter to the spawn family of functions These are less portable than those listed above P_DETACH is similar to P_NOWAIT but the new process is detached from the console of the calling process If P_OVERLAY is used the current process will be replaced the spawn function will not return Availability Windows os startfile path operation arguments cwd show_cmd Start a file with its associated application When operation is not specified this acts like double clicking the file in Windows Explorer or giving the file name as an argument to the start command from the interactive command shell the file is opened with whatever application if any its extension is associated When another operation is given it must be a command verb that specifies what should be done with the file Common verbs documented by Microsoft are open print and edit to be used on files as well as explore and find to be used on directories When launching an application specify arguments to be passed as a single string This argument may have no effect when using this function to launch a document The default working directory is inherited but may be overridden by the cwd argument This should be an absolute path A relative path will be resolved against this argument Use show_cmd to override the default window style Whether this has any effect will depend on the application being launched Values are integers as supported by the Win32 ShellExecute function startfile returns as soon as the associated application is launched There is no option to wait for the application to close and no way to retrieve the application s exit status The path parameter is relative to the current directory or cwd If you want to use an absolute path make sure the first character is not a slash Use pathlib or the os path normpath function to ensure that paths are properly encoded for Win32 To reduce interpreter startup overhead the Win32 ShellExecute function is not resolved until this function is first called If the function cannot be resolved NotImplementedError will be raised Raises an auditing event os startfile with arguments path operation Raises an auditing event os startfile 2 with arguments path operation arguments cwd show_cmd Availability Windows Changed in version 3 10 Added the arguments cwd and show_cmd arguments and the os startfile 2 audit event os system command Execute the command a string in a subshell This is implemented by calling the Standard C function system and has the same limitations Changes to sys stdin etc are not reflected in the environment of the executed command If command generates any output it will be sent to the interpreter standard output stream The C standard does not specify the meaning of the return value of the C function so the return value of the Python function is system dependent On Unix the return value is the exit status of the process encoded in the format specified for wait On Windows the return value is that returned by the system shell after running command The shell is given by the Windows environment variable COMSPEC it is usually cmd exe which returns the exit status of the command run on systems using a non native shell consult your shell documentation The subprocess module provides more powerful facilities for spawning new processes and retrieving their results using that module ,en
1126,is preferable to using this function See the Replacing Older Functions with the subprocess Module section in the subprocess documentation for some helpful recipes On Unix waitstatus_to_exitcode can be used to convert the result exit status into an exit code On Windows the result is directly the exit code Raises an auditing event os system with argument command Availability Unix Windows not Emscripten not WASI os times Returns the current global process times The return value is an object with five attributes user user time system system time children_user user time of all child processes children_system system time of all child processes elapsed elapsed real time since a fixed point in the past For backwards compatibility this object also behaves like a five tuple containing user system children_user children_system and elapsed in that order See the Unix manual page times 2 and times 3 manual page on Unix or the GetProcessTimes MSDN on Windows On Windows only user and system are known the other attributes are zero Availability Unix Windows Changed in version 3 3 Return type changed from a tuple to a tuple like object with named attributes os wait Wait for completion of a child process and return a tuple containing its pid and exit status indication a 16 bit number whose low byte is the signal number that killed the process and whose high byte is the exit status if the signal number is zero the high bit of the low byte is set if a core file was produced If there are no children that could be waited for ChildProcessError is raised waitstatus_to_exitcode can be used to convert the exit status into an exit code Availability Unix not Emscripten not WASI See also The other wait functions documented below can be used to wait for the completion of a specific child process and have more options waitpid is the only one also available on Windows os waitid idtype id options Wait for the completion of a child process idtype can be P_PID P_PGID P_ALL or on Linux P_PIDFD The interpretation of id depends on it see their individual descriptions options is an OR combination of flags At least one of WEXITED WSTOPPED or WCONTINUED is required WNOHANG and WNOWAIT are additional optional flags The return value is an object representing the data contained in the siginfo_t structure with the following attributes si_pid process ID si_uid real user ID of the child si_signo always SIGCHLD si_status the exit status or signal number depending on si_code si_code see CLD_EXITED for possible values If WNOHANG is specified and there are no matching children in the requested state None is returned Otherwise if there are no matching children that could be waited for ChildProcessError is raised Availability Unix not Emscripten not WASI Note This function is not available on macOS New in version 3 3 os waitpid pid options The details of this function differ on Unix and Windows On Unix Wait for completion of a child process given by process id pid and return a tuple containing its process id and exit status indication encoded as for wait The semantics of the call are affected by the value of the integer options which should be 0 for normal operation If pid is greater than 0 waitpid requests status information for that specific process If pid is 0 the request is for the status of any child in the process group of the current process If pid is 1 the request pertains to any child of the current process If pid is less than 1 status is requested for any process in the process group pid the absolute value of pid options is an OR combination of flags If it contains WNOHANG and there are no matching children in the requested state 0 0 is returned Otherwise if there are no matching children that could be waited for ChildProcessError is raised Other options that can be used are WUNTRACED and WCONTINUED On Windows Wait for completion of a process given by process handle pid and return a tuple containing pid and its exit status shifted left by 8 bits shifting makes cross platform use of the function easier A pid less than or equal to 0 has no special meaning on Windows ,en
1127,and raises an exception The value of integer options has no effect pid can refer to any process whose id is known not necessarily a child process The spawn functions called with P_NOWAIT return suitable process handles waitstatus_to_exitcode can be used to convert the exit status into an exit code Availability Unix Windows not Emscripten not WASI Changed in version 3 5 If the system call is interrupted and the signal handler does not raise an exception the function now retries the system call instead of raising an InterruptedError exception see PEP 475 for the rationale os wait3 options Similar to waitpid except no process id argument is given and a 3 element tuple containing the child s process id exit status indication and resource usage information is returned Refer to resource getrusage for details on resource usage information The options argument is the same as that provided to waitpid and wait4 waitstatus_to_exitcode can be used to convert the exit status into an exitcode Availability Unix not Emscripten not WASI os wait4 pid options Similar to waitpid except a 3 element tuple containing the child s process id exit status indication and resource usage information is returned Refer to resource getrusage for details on resource usage information The arguments to wait4 are the same as those provided to waitpid waitstatus_to_exitcode can be used to convert the exit status into an exitcode Availability Unix not Emscripten not WASI os P_PID os P_PGID os P_ALL os P_PIDFD These are the possible values for idtype in waitid They affect how id is interpreted P_PID wait for the child whose PID is id P_PGID wait for any child whose progress group ID is id P_ALL wait for any child id is ignored P_PIDFD wait for the child identified by the file descriptor id a process file descriptor created with pidfd_open Availability Unix not Emscripten not WASI Note P_PIDFD is only available on Linux 5 4 New in version 3 3 New in version 3 9 The P_PIDFD constant os WCONTINUED This options flag for waitpid wait3 wait4 and waitid causes child processes to be reported if they have been continued from a job control stop since they were last reported Availability Unix not Emscripten not WASI os WEXITED This options flag for waitid causes child processes that have terminated to be reported The other wait functions always report children that have terminated so this option is not available for them Availability Unix not Emscripten not WASI New in version 3 3 os WSTOPPED This options flag for waitid causes child processes that have been stopped by the delivery of a signal to be reported This option is not available for the other wait functions Availability Unix not Emscripten not WASI New in version 3 3 os WUNTRACED This options flag for waitpid wait3 and wait4 causes child processes to also be reported if they have been stopped but their current state has not been reported since they were stopped This option is not available for waitid Availability Unix not Emscripten not WASI os WNOHANG This options flag causes waitpid wait3 wait4 and waitid to return right away if no child process status is available immediately Availability Unix not Emscripten not WASI os WNOWAIT This options flag causes waitid to leave the child in a waitable state so that a later wait call can be used to retrieve the child status information again This option is not available for the other wait functions Availability Unix not Emscripten not WASI os CLD_EXITED os CLD_KILLED os CLD_DUMPED os CLD_TRAPPED os CLD_STOPPED os CLD_CONTINUED These are the possible values for si_code in the result returned by waitid Availability Unix not Emscripten not WASI New in version 3 3 Changed in version 3 9 Added CLD_KILLED and CLD_STOPPED values os waitstatus_to_exitcode status Convert a wait status to an exit code On Unix If the process exited normally if WIFEXITED status is true return the process exit status return WEXITSTATUS status result greater than or equal to 0 If the process was terminated by a signal if WIFSIGNALED status is true return signum where signum is the number of the signal,en
1128, that caused the process to terminate return WTERMSIG status result less than 0 Otherwise raise a ValueError On Windows return status shifted right by 8 bits On Unix if the process is being traced or if waitpid was called with WUNTRACED option the caller must first check if WIFSTOPPED status is true This function must not be called if WIFSTOPPED status is true See also WIFEXITED WEXITSTATUS WIFSIGNALED WTERMSIG WIFSTOPPED WSTOPSIG functions Availability Unix Windows not Emscripten not WASI New in version 3 9 The following functions take a process status code as returned by system wait or waitpid as a parameter They may be used to determine the disposition of a process os WCOREDUMP status Return True if a core dump was generated for the process otherwise return False This function should be employed only if WIFSIGNALED is true Availability Unix not Emscripten not WASI os WIFCONTINUED status Return True if a stopped child has been resumed by delivery of SIGCONT if the process has been continued from a job control stop otherwise return False See WCONTINUED option Availability Unix not Emscripten not WASI os WIFSTOPPED status Return True if the process was stopped by delivery of a signal otherwise return False WIFSTOPPED only returns True if the waitpid call was done using WUNTRACED option or when the process is being traced see ptrace 2 Availability Unix not Emscripten not WASI os WIFSIGNALED status Return True if the process was terminated by a signal otherwise return False Availability Unix not Emscripten not WASI os WIFEXITED status Return True if the process exited terminated normally that is by calling exit or _exit or by returning from main otherwise return False Availability Unix not Emscripten not WASI os WEXITSTATUS status Return the process exit status This function should be employed only if WIFEXITED is true Availability Unix not Emscripten not WASI os WSTOPSIG status Return the signal which caused the process to stop This function should be employed only if WIFSTOPPED is true Availability Unix not Emscripten not WASI os WTERMSIG status Return the number of the signal that caused the process to terminate This function should be employed only if WIFSIGNALED is true Availability Unix not Emscripten not WASI Interface to the scheduler These functions control how a process is allocated CPU time by the operating system They are only available on some Unix platforms For more detailed information consult your Unix manpages New in version 3 3 The following scheduling policies are exposed if they are supported by the operating system os SCHED_OTHER The default scheduling policy os SCHED_BATCH Scheduling policy for CPU intensive processes that tries to preserve interactivity on the rest of the computer os SCHED_IDLE Scheduling policy for extremely low priority background tasks os SCHED_SPORADIC Scheduling policy for sporadic server programs os SCHED_FIFO A First In First Out scheduling policy os SCHED_RR A round robin scheduling policy os SCHED_RESET_ON_FORK This flag can be OR ed with any other scheduling policy When a process with this flag set forks its child s scheduling policy and priority are reset to the default class os sched_param sched_priority This class represents tunable scheduling parameters used in sched_setparam sched_setscheduler and sched_getparam It is immutable At the moment there is only one possible parameter sched_priority The scheduling priority for a scheduling policy os sched_get_priority_min policy Get the minimum priority value for policy policy is one of the scheduling policy constants above os sched_get_priority_max policy Get the maximum priority value for policy policy is one of the scheduling policy constants above os sched_setscheduler pid policy param Set the scheduling policy for the process with PID pid A pid of 0 means the calling process policy is one of the scheduling policy constants above param is a sched_param instance os sched_getscheduler pid Return the scheduling policy for the process with PID pid A pid of 0 means the calling process The result is one of the scheduling policy,en
1129, constants above os sched_setparam pid param Set the scheduling parameters for the process with PID pid A pid of 0 means the calling process param is a sched_param instance os sched_getparam pid Return the scheduling parameters as a sched_param instance for the process with PID pid A pid of 0 means the calling process os sched_rr_get_interval pid Return the round robin quantum in seconds for the process with PID pid A pid of 0 means the calling process os sched_yield Voluntarily relinquish the CPU os sched_setaffinity pid mask Restrict the process with PID pid or the current process if zero to a set of CPUs mask is an iterable of integers representing the set of CPUs to which the process should be restricted os sched_getaffinity pid Return the set of CPUs the process with PID pid is restricted to If pid is zero return the set of CPUs the calling thread of the current process is restricted to Miscellaneous System Information os confstr name Return string valued system configuration values name specifies the configuration value to retrieve it may be a string which is the name of a defined system value these names are specified in a number of standards POSIX Unix 95 Unix 98 and others Some platforms define additional names as well The names known to the host operating system are given as the keys of the confstr_names dictionary For configuration variables not included in that mapping passing an integer for name is also accepted If the configuration value specified by name isn t defined None is returned If name is a string and is not known ValueError is raised If a specific value for name is not supported by the host system even if it is included in confstr_names an OSError is raised with errno EINVAL for the error number Availability Unix os confstr_names Dictionary mapping names accepted by confstr to the integer values defined for those names by the host operating system This can be used to determine the set of names known to the system Availability Unix os cpu_count Return the number of logical CPUs in the system Returns None if undetermined This number is not equivalent to the number of logical CPUs the current process can use len os sched_getaffinity 0 gets the number of logical CPUs the calling thread of the current process is restricted to New in version 3 4 os getloadavg Return the number of processes in the system run queue averaged over the last 1 5 and 15 minutes or raises OSError if the load average was unobtainable Availability Unix os sysconf name Return integer valued system configuration values If the configuration value specified by name isn t defined 1 is returned The comments regarding the name parameter for confstr apply here as well the dictionary that provides information on the known names is given by sysconf_names Availability Unix os sysconf_names Dictionary mapping names accepted by sysconf to the integer values defined for those names by the host operating system This can be used to determine the set of names known to the system Availability Unix Changed in version 3 11 Add SC_MINSIGSTKSZ name The following data values are used to support path manipulation operations These are defined for all platforms Higher level operations on pathnames are defined in the os path module os curdir The constant string used by the operating system to refer to the current directory This is for Windows and POSIX Also available via os path os pardir The constant string used by the operating system to refer to the parent directory This is for Windows and POSIX Also available via os path os sep The character used by the operating system to separate pathname components This is for POSIX and for Windows Note that knowing this is not sufficient to be able to parse or concatenate pathnames use os path split and os path join but it is occasionally useful Also available via os path os altsep An alternative character used by the operating system to separate pathname components or None if only one separator character exists This is set to on Windows systems where sep is a backslash Also available via os path os extsep The chara,en
1130,cter which separates the base filename from the extension for example the in os py Also available via os path os pathsep The character conventionally used by the operating system to separate search path components as in PATH such as for POSIX or for Windows Also available via os path os defpath The default search path used by exec p and spawn p if the environment doesn t have a PATH key Also available via os path os linesep The string used to separate or rather terminate lines on the current platform This may be a single character such as n for POSIX or multiple characters for example r n for Windows Do not use os linesep as a line terminator when writing files opened in text mode the default use a single n instead on all platforms os devnull The file path of the null device For example dev null for POSIX nul for Windows Also available via os path os RTLD_LAZY os RTLD_NOW os RTLD_GLOBAL os RTLD_LOCAL os RTLD_NODELETE os RTLD_NOLOAD os RTLD_DEEPBIND Flags for use with the setdlopenflags and getdlopenflags functions See the Unix manual page dlopen 3 for what the different flags mean New in version 3 3 Random numbers os getrandom size flags 0 Get up to size random bytes The function can return less bytes than requested These bytes can be used to seed user space random number generators or for cryptographic purposes getrandom relies on entropy gathered from device drivers and other sources of environmental noise Unnecessarily reading large quantities of data will have a negative impact on other users of the dev random and dev urandom devices The flags argument is a bit mask that can contain zero or more of the following values ORed together os GRND_RANDOM and GRND_NONBLOCK See also the Linux getrandom manual page Availability Linux 3 17 New in version 3 6 os urandom size Return a bytestring of size random bytes suitable for cryptographic use This function returns random bytes from an OS specific randomness source The returned data should be unpredictable enough for cryptographic applications though its exact quality depends on the OS implementation On Linux if the getrandom syscall is available it is used in blocking mode block until the system urandom entropy pool is initialized 128 bits of entropy are collected by the kernel See the PEP 524 for the rationale On Linux the getrandom function can be used to get random bytes in non blocking mode using the GRND_NONBLOCK flag or to poll until the system urandom entropy pool is initialized On a Unix like system random bytes are read from the dev urandom device If the dev urandom device is not available or not readable the NotImplementedError exception is raised On Windows it will use BCryptGenRandom See also The secrets module provides higher level functions For an easy to use interface to the random number generator provided by your platform please see random SystemRandom Changed in version 3 5 On Linux 3 17 and newer the getrandom syscall is now used when available On OpenBSD 5 6 and newer the C getentropy function is now used These functions avoid the usage of an internal file descriptor Changed in version 3 5 2 On Linux if the getrandom syscall blocks the urandom entropy pool is not initialized yet fall back on reading dev urandom Changed in version 3 6 On Linux getrandom is now used in blocking mode to increase the security Changed in version 3 11 On Windows BCryptGenRandom is used instead of CryptGenRandom which is deprecated os GRND_NONBLOCK By default when reading from dev random getrandom blocks if no random bytes are available and when reading from dev urandom it blocks if the entropy pool has not yet been initialized If the GRND_NONBLOCK flag is set then getrandom does not block in these cases but instead immediately raises BlockingIOError New in version 3 6 os GRND_RANDOM If this bit is set then random bytes are drawn from the dev random pool instead of the dev urandom pool New in version 3 6,en
1131,tarfile Read and write tar archive files Source code Lib tarfile py The tarfile module makes it possible to read and write tar archives including those using gzip bz2 and lzma compression Use the zipfile module to read or write zip files or the higher level functions in shutil Some facts and figures reads and writes gzip bz2 and lzma compressed archives if the respective modules are available read write support for the POSIX 1 1988 ustar format read write support for the GNU tar format including longname and longlink extensions read only support for all variants of the sparse extension including restoration of sparse files read write support for the POSIX 1 2001 pax format handles directories regular files hardlinks symbolic links fifos character devices and block devices and is able to acquire and restore file information like timestamp access permissions and owner Changed in version 3 3 Added support for lzma compression Changed in version 3 12 Archives are extracted using a filter which makes it possible to either limit surprising dangerous features or to acknowledge that they are expected and the archive is fully trusted By default archives are fully trusted but this default is deprecated and slated to change in Python 3 14 tarfile open name None mode r fileobj None bufsize 10240 kwargs Return a TarFile object for the pathname name For detailed information on TarFile objects and the keyword arguments that are allowed see TarFile Objects mode has to be a string of the form filemode compression it defaults to r Here is a full list of mode combinations mode action r or r Open for reading with transparent compression recommended r Open for reading exclusively without compression r gz Open for reading with gzip compression r bz2 Open for reading with bzip2 compression r xz Open for reading with lzma compression x or x Create a tarfile exclusively without compression Raise a FileExistsError exception if it already exists x gz Create a tarfile with gzip compression Raise a FileExistsError exception if it already exists x bz2 Create a tarfile with bzip2 compression Raise a FileExistsError exception if it already exists x xz Create a tarfile with lzma compression Raise a FileExistsError exception if it already exists a or a Open for appending with no compression The file is created if it does not exist w or w Open for uncompressed writing w gz Open for gzip compressed writing w bz2 Open for bzip2 compressed writing w xz Open for lzma compressed writing Note that a gz a bz2 or a xz is not possible If mode is not suitable to open a certain compressed file for reading ReadError is raised Use mode r to avoid this If a compression method is not supported CompressionError is raised If fileobj is specified it is used as an alternative to a file object opened in binary mode for name It is supposed to be at position 0 For modes w gz x gz w gz w bz2 x bz2 w bz2 tarfile open accepts the keyword argument compresslevel default 9 to specify the compression level of the file For modes w xz and x xz tarfile open accepts the keyword argument preset to specify the compression level of the file For special purposes there is a second format for mode filemode compression tarfile open will return a TarFile object that processes its data as a stream of blocks No random seeking will be done on the file If given fileobj may be any object that has a read or write method depending on the mode that works with bytes bufsize specifies the blocksize and defaults to 20 512 bytes Use this variant in combination with e g sys stdin buffer a socket file object or a tape device However such a TarFile object is limited in that it does not allow random access see Examples The currently possible modes Mode Action r Open a stream of tar blocks for reading with transparent compression r Open a stream of uncompressed tar blocks for reading r gz Open a gzip compressed stream for reading r bz2 Open a bzip2 compressed stream for reading r xz Open an lzma compressed stream for reading w Open an uncompressed stream for writing w gz Open a gzip compressed stream for writing,en
1132, w bz2 Open a bzip2 compressed stream for writing w xz Open an lzma compressed stream for writing Changed in version 3 5 The x exclusive creation mode was added Changed in version 3 6 The name parameter accepts a path like object Changed in version 3 12 The compresslevel keyword argument also works for streams class tarfile TarFile Class for reading and writing tar archives Do not use this class directly use tarfile open instead See TarFile Objects tarfile is_tarfile name Return True if name is a tar archive file that the tarfile module can read name may be a str file or file like object Changed in version 3 9 Support for file and file like objects The tarfile module defines the following exceptions exception tarfile TarError Base class for all tarfile exceptions exception tarfile ReadError Is raised when a tar archive is opened that either cannot be handled by the tarfile module or is somehow invalid exception tarfile CompressionError Is raised when a compression method is not supported or when the data cannot be decoded properly exception tarfile StreamError Is raised for the limitations that are typical for stream like TarFile objects exception tarfile ExtractError Is raised for non fatal errors when using TarFile extract but only if TarFile errorlevel 2 exception tarfile HeaderError Is raised by TarInfo frombuf if the buffer it gets is invalid exception tarfile FilterError Base class for members refused by filters tarinfo Information about the member that the filter refused to extract as TarInfo exception tarfile AbsolutePathError Raised to refuse extracting a member with an absolute path exception tarfile OutsideDestinationError Raised to refuse extracting a member outside the destination directory exception tarfile SpecialFileError Raised to refuse extracting a special file e g a device or pipe exception tarfile AbsoluteLinkError Raised to refuse extracting a symbolic link with an absolute path exception tarfile LinkOutsideDestinationError Raised to refuse extracting a symbolic link pointing outside the destination directory The following constants are available at the module level tarfile ENCODING The default character encoding utf 8 on Windows the value returned by sys getfilesystemencoding otherwise tarfile REGTYPE tarfile AREGTYPE A regular file type tarfile LNKTYPE A link inside tarfile type tarfile SYMTYPE A symbolic link type tarfile CHRTYPE A character special device type tarfile BLKTYPE A block special device type tarfile DIRTYPE A directory type tarfile FIFOTYPE A FIFO special device type tarfile CONTTYPE A contiguous file type tarfile GNUTYPE_LONGNAME A GNU tar longname type tarfile GNUTYPE_LONGLINK A GNU tar longlink type tarfile GNUTYPE_SPARSE A GNU tar sparse file type Each of the following constants defines a tar archive format that the tarfile module is able to create See section Supported tar formats for details tarfile USTAR_FORMAT POSIX 1 1988 ustar format tarfile GNU_FORMAT GNU tar format tarfile PAX_FORMAT POSIX 1 2001 pax format tarfile DEFAULT_FORMAT The default format for creating archives This is currently PAX_FORMAT Changed in version 3 8 The default format for new archives was changed to PAX_FORMAT from GNU_FORMAT See also Module zipfile Documentation of the zipfile standard module Archiving operations Documentation of the higher level archiving facilities provided by the standard shutil module GNU tar manual Basic Tar Format Documentation for tar archive files including GNU tar extensions TarFile Objects The TarFile object provides an interface to a tar archive A tar archive is a sequence of blocks An archive member a stored file is made up of a header block followed by data blocks It is possible to store a file in a tar archive several times Each archive member is represented by a TarInfo object see TarInfo Objects for details A TarFile object can be used as a context manager in a with statement It will automatically be closed when the block is completed Please note that in the event of an exception an archive opened for writing will not be finalized only the internally used file object,en
1133, will be closed See the Examples section for a use case New in version 3 2 Added support for the context management protocol class tarfile TarFile name None mode r fileobj None format DEFAULT_FORMAT tarinfo TarInfo dereference False ignore_zeros False encoding ENCODING errors surrogateescape pax_headers None debug 0 errorlevel 1 All following arguments are optional and can be accessed as instance attributes as well name is the pathname of the archive name may be a path like object It can be omitted if fileobj is given In this case the file object s name attribute is used if it exists mode is either r to read from an existing archive a to append data to an existing file w to create a new file overwriting an existing one or x to create a new file only if it does not already exist If fileobj is given it is used for reading or writing data If it can be determined mode is overridden by fileobj s mode fileobj will be used from position 0 Note fileobj is not closed when TarFile is closed format controls the archive format for writing It must be one of the constants USTAR_FORMAT GNU_FORMAT or PAX_FORMAT that are defined at module level When reading format will be automatically detected even if different formats are present in a single archive The tarinfo argument can be used to replace the default TarInfo class with a different one If dereference is False add symbolic and hard links to the archive If it is True add the content of the target files to the archive This has no effect on systems that do not support symbolic links If ignore_zeros is False treat an empty block as the end of the archive If it is True skip empty and invalid blocks and try to get as many members as possible This is only useful for reading concatenated or damaged archives debug can be set from 0 no debug messages up to 3 all debug messages The messages are written to sys stderr errorlevel controls how extraction errors are handled see the corresponding attribute The encoding and errors arguments define the character encoding to be used for reading or writing the archive and how conversion errors are going to be handled The default settings will work for most users See section Unicode issues for in depth information The pax_headers argument is an optional dictionary of strings which will be added as a pax global header if format is PAX_FORMAT Changed in version 3 2 Use surrogateescape as the default for the errors argument Changed in version 3 5 The x exclusive creation mode was added Changed in version 3 6 The name parameter accepts a path like object classmethod TarFile open Alternative constructor The tarfile open function is actually a shortcut to this classmethod TarFile getmember name Return a TarInfo object for member name If name can not be found in the archive KeyError is raised Note If a member occurs more than once in the archive its last occurrence is assumed to be the most up to date version TarFile getmembers Return the members of the archive as a list of TarInfo objects The list has the same order as the members in the archive TarFile getnames Return the members as a list of their names It has the same order as the list returned by getmembers TarFile list verbose True members None Print a table of contents to sys stdout If verbose is False only the names of the members are printed If it is True output similar to that of ls l is produced If optional members is given it must be a subset of the list returned by getmembers Changed in version 3 5 Added the members parameter TarFile next Return the next member of the archive as a TarInfo object when TarFile is opened for reading Return None if there is no more available TarFile extractall path members None numeric_owner False filter None Extract all members from the archive to the current working directory or directory path If optional members is given it must be a subset of the list returned by getmembers Directory information like owner modification time and permissions are set after all members have been extracted This is done to work around two problems A directory s modification time is reset ,en
1134,each time a file is created in it And if a directory s permissions do not allow writing extracting files to it will fail If numeric_owner is True the uid and gid numbers from the tarfile are used to set the owner group for the extracted files Otherwise the named values from the tarfile are used The filter argument specifies how members are modified or rejected before extraction See Extraction filters for details It is recommended to set this explicitly depending on which tar features you need to support Warning Never extract archives from untrusted sources without prior inspection It is possible that files are created outside of path e g members that have absolute filenames starting with or filenames with two dots Set filter data to prevent the most dangerous security issues and read the Extraction filters section for details Changed in version 3 5 Added the numeric_owner parameter Changed in version 3 6 The path parameter accepts a path like object Changed in version 3 12 Added the filter parameter TarFile extract member path set_attrs True numeric_owner False filter None Extract a member from the archive to the current working directory using its full name Its file information is extracted as accurately as possible member may be a filename or a TarInfo object You can specify a different directory using path path may be a path like object File attributes owner mtime mode are set unless set_attrs is false The numeric_owner and filter arguments are the same as for extractall Note The extract method does not take care of several extraction issues In most cases you should consider using the extractall method Warning See the warning for extractall Set filter data to prevent the most dangerous security issues and read the Extraction filters section for details Changed in version 3 2 Added the set_attrs parameter Changed in version 3 5 Added the numeric_owner parameter Changed in version 3 6 The path parameter accepts a path like object Changed in version 3 12 Added the filter parameter TarFile extractfile member Extract a member from the archive as a file object member may be a filename or a TarInfo object If member is a regular file or a link an io BufferedReader object is returned For all other existing members None is returned If member does not appear in the archive KeyError is raised Changed in version 3 3 Return an io BufferedReader object TarFile errorlevel int If errorlevel is 0 errors are ignored when using TarFile extract and TarFile extractall Nevertheless they appear as error messages in the debug output when debug is greater than 0 If 1 the default all fatal errors are raised as OSError or FilterError exceptions If 2 all non fatal errors are raised as TarError exceptions as well Some exceptions e g ones caused by wrong argument types or data corruption are always raised Custom extraction filters should raise FilterError for fatal errors and ExtractError for non fatal ones Note that when an exception is raised the archive may be partially extracted It is the user s responsibility to clean up TarFile extraction_filter New in version 3 12 The extraction filter used as a default for the filter argument of extract and extractall The attribute may be None or a callable String names are not allowed for this attribute unlike the filter argument to extract If extraction_filter is None the default calling an extraction method without a filter argument will raise a DeprecationWarning and fall back to the fully_trusted filter whose dangerous behavior matches previous versions of Python In Python 3 14 leaving extraction_filter None will cause extraction methods to use the data filter by default The attribute may be set on instances or overridden in subclasses It also is possible to set it on the TarFile class itself to set a global default although since it affects all uses of tarfile it is best practice to only do so in top level applications or site configuration To set a global default this way a filter function needs to be wrapped in staticmethod to prevent injection of a self argument TarFile add name arcname None recurs,en
1135,ive True filter None Add the file name to the archive name may be any type of file directory fifo symbolic link etc If given arcname specifies an alternative name for the file in the archive Directories are added recursively by default This can be avoided by setting recursive to False Recursion adds entries in sorted order If filter is given it should be a function that takes a TarInfo object argument and returns the changed TarInfo object If it instead returns None the TarInfo object will be excluded from the archive See Examples for an example Changed in version 3 2 Added the filter parameter Changed in version 3 7 Recursion adds entries in sorted order TarFile addfile tarinfo fileobj None Add the TarInfo object tarinfo to the archive If fileobj is given it should be a binary file and tarinfo size bytes are read from it and added to the archive You can create TarInfo objects directly or by using gettarinfo TarFile gettarinfo name None arcname None fileobj None Create a TarInfo object from the result of os stat or equivalent on an existing file The file is either named by name or specified as a file object fileobj with a file descriptor name may be a path like object If given arcname specifies an alternative name for the file in the archive otherwise the name is taken from fileobj s name attribute or the name argument The name should be a text string You can modify some of the TarInfo s attributes before you add it using addfile If the file object is not an ordinary file object positioned at the beginning of the file attributes such as size may need modifying This is the case for objects such as GzipFile The name may also be modified in which case arcname could be a dummy string Changed in version 3 6 The name parameter accepts a path like object TarFile close Close the TarFile In write mode two finishing zero blocks are appended to the archive TarFile pax_headers dict A dictionary containing key value pairs of pax global headers TarInfo Objects A TarInfo object represents one member in a TarFile Aside from storing all required attributes of a file like file type size time permissions owner etc it provides some useful methods to determine its type It does not contain the file s data itself TarInfo objects are returned by TarFile s methods getmember getmembers and gettarinfo Modifying the objects returned by getmember or getmembers will affect all subsequent operations on the archive For cases where this is unwanted you can use copy copy or call the replace method to create a modified copy in one step Several attributes can be set to None to indicate that a piece of metadata is unused or unknown Different TarInfo methods handle None differently The extract or extractall methods will ignore the corresponding metadata leaving it set to a default addfile will fail list will print a placeholder string class tarfile TarInfo name Create a TarInfo object classmethod TarInfo frombuf buf encoding errors Create and return a TarInfo object from string buffer buf Raises HeaderError if the buffer is invalid classmethod TarInfo fromtarfile tarfile Read the next member from the TarFile object tarfile and return it as a TarInfo object TarInfo tobuf format DEFAULT_FORMAT encoding ENCODING errors surrogateescape Create a string buffer from a TarInfo object For information on the arguments see the constructor of the TarFile class Changed in version 3 2 Use surrogateescape as the default for the errors argument A TarInfo object has the following public data attributes TarInfo name str Name of the archive member TarInfo size int Size in bytes TarInfo mtime int float Time of last modification in seconds since the epoch as in os stat_result st_mtime Changed in version 3 12 Can be set to None for extract and extractall causing extraction to skip applying this attribute TarInfo mode int Permission bits as for os chmod Changed in version 3 12 Can be set to None for extract and extractall causing extraction to skip applying this attribute TarInfo type File type type is usually one of these constants REGTYPE AREGTYPE LNKTYPE SYMTYPE DIRTYPE FIFOTYP,en
1136,E CONTTYPE CHRTYPE BLKTYPE GNUTYPE_SPARSE To determine the type of a TarInfo object more conveniently use the is methods below TarInfo linkname str Name of the target file name which is only present in TarInfo objects of type LNKTYPE and SYMTYPE For symbolic links SYMTYPE the linkname is relative to the directory that contains the link For hard links LNKTYPE the linkname is relative to the root of the archive TarInfo uid int User ID of the user who originally stored this member Changed in version 3 12 Can be set to None for extract and extractall causing extraction to skip applying this attribute TarInfo gid int Group ID of the user who originally stored this member Changed in version 3 12 Can be set to None for extract and extractall causing extraction to skip applying this attribute TarInfo uname str User name Changed in version 3 12 Can be set to None for extract and extractall causing extraction to skip applying this attribute TarInfo gname str Group name Changed in version 3 12 Can be set to None for extract and extractall causing extraction to skip applying this attribute TarInfo chksum int Header checksum TarInfo devmajor int Device major number TarInfo devminor int Device minor number TarInfo offset int The tar header starts here TarInfo offset_data int The file s data starts here TarInfo sparse Sparse member information TarInfo pax_headers dict A dictionary containing key value pairs of an associated pax extended header TarInfo replace name mtime mode linkname uid gid uname gname deep True New in version 3 12 Return a new copy of the TarInfo object with the given attributes changed For example to return a TarInfo with the group name set to staff use new_tarinfo old_tarinfo replace gname staff By default a deep copy is made If deep is false the copy is shallow i e pax_headers and any custom attributes are shared with the original TarInfo object A TarInfo object also provides some convenient query methods TarInfo isfile Return True if the TarInfo object is a regular file TarInfo isreg Same as isfile TarInfo isdir Return True if it is a directory TarInfo issym Return True if it is a symbolic link TarInfo islnk Return True if it is a hard link TarInfo ischr Return True if it is a character device TarInfo isblk Return True if it is a block device TarInfo isfifo Return True if it is a FIFO TarInfo isdev Return True if it is one of character device block device or FIFO Extraction filters New in version 3 12 The tar format is designed to capture all details of a UNIX like filesystem which makes it very powerful Unfortunately the features make it easy to create tar files that have unintended and possibly malicious effects when extracted For example extracting a tar file can overwrite arbitrary files in various ways e g by using absolute paths path components or symlinks that affect later members In most cases the full functionality is not needed Therefore tarfile supports extraction filters a mechanism to limit functionality and thus mitigate some of the security issues See also PEP 706 Contains further motivation and rationale behind the design The filter argument to TarFile extract or extractall can be the string fully_trusted Honor all metadata as specified in the archive Should be used if the user trusts the archive completely or implements their own complex verification the string tar Honor most tar specific features i e features of UNIX like filesystems but block features that are very likely to be surprising or malicious See tar_filter for details the string data Ignore or block most features specific to UNIX like filesystems Intended for extracting cross platform data archives See data_filter for details None default Use TarFile extraction_filter If that is also None the default raise a DeprecationWarning and fall back to the fully_trusted filter whose dangerous behavior matches previous versions of Python In Python 3 14 the data filter will become the default instead It s possible to switch earlier see TarFile extraction_filter A callable which will be called for each extracted member with a TarInfo describing t,en
1137,he member and the destination path to where the archive is extracted i e the same path is used for all members filter member TarInfo path str TarInfo None The callable is called just before each member is extracted so it can take the current state of the disk into account It can return a TarInfo object which will be used instead of the metadata in the archive or return None in which case the member will be skipped or raise an exception to abort the operation or skip the member depending on errorlevel Note that when extraction is aborted extractall may leave the archive partially extracted It does not attempt to clean up Default named filters The pre defined named filters are available as functions so they can be reused in custom filters tarfile fully_trusted_filter member path Return member unchanged This implements the fully_trusted filter tarfile tar_filter member path Implements the tar filter Strip leading slashes and os sep from filenames Refuse to extract files with absolute paths in case the name is absolute even after stripping slashes e g C foo on Windows This raises AbsolutePathError Refuse to extract files whose absolute path after following symlinks would end up outside the destination This raises OutsideDestinationError Clear high mode bits setuid setgid sticky and group other write bits S_IWGRP S_IWOTH Return the modified TarInfo member tarfile data_filter member path Implements the data filter In addition to what tar_filter does Refuse to extract links hard or soft that link to absolute paths or ones that link outside the destination This raises AbsoluteLinkError or LinkOutsideDestinationError Note that such files are refused even on platforms that do not support symbolic links Refuse to extract device files including pipes This raises SpecialFileError For regular files including hard links Set the owner read and write permissions S_IRUSR S_IWUSR Remove the group other executable permission S_IXGRP S_IXOTH if the owner doesn t have it S_IXUSR For other files directories set mode to None so that extraction methods skip applying permission bits Set user and group info uid gid uname gname to None so that extraction methods skip setting it Return the modified TarInfo member Filter errors When a filter refuses to extract a file it will raise an appropriate exception a subclass of FilterError This will abort the extraction if TarFile errorlevel is 1 or more With errorlevel 0 the error will be logged and the member will be skipped but extraction will continue Hints for further verification Even with filter data tarfile is not suited for extracting untrusted files without prior inspection Among other issues the pre defined filters do not prevent denial of service attacks Users should do additional checks Here is an incomplete list of things to consider Extract to a new temporary directory to prevent e g exploiting pre existing links and to make it easier to clean up after a failed extraction When working with untrusted data use external e g OS level limits on disk memory and CPU usage Check filenames against an allow list of characters to filter out control characters confusables foreign path separators etc Check that filenames have expected extensions discouraging files that execute when you click on them or extension less files like Windows special device names Limit the number of extracted files total size of extracted data filename length including symlink length and size of individual files Check for files that would be shadowed on case insensitive filesystems Also note that Tar files may contain multiple versions of the same file Later ones are expected to overwrite any earlier ones This feature is crucial to allow updating tape archives but can be abused maliciously tarfile does not protect against issues with live data e g an attacker tinkering with the destination or source directory while extraction or archiving is in progress Supporting older Python versions Extraction filters were added to Python 3 12 but may be backported to older versions as security updates To check whether the feature is available ,en
1138,use e g hasattr tarfile data_filter rather than checking the Python version The following examples show how to support Python versions with and without the feature Note that setting extraction_filter will affect any subsequent operations Fully trusted archive my_tarfile extraction_filter lambda member path member my_tarfile extractall Use the data filter if available but revert to Python 3 11 behavior fully_trusted if this feature is not available my_tarfile extraction_filter getattr tarfile data_filter lambda member path member my_tarfile extractall Use the data filter fail if it is not available my_tarfile extractall filter tarfile data_filter or my_tarfile extraction_filter tarfile data_filter my_tarfile extractall Use the data filter warn if it is not available if hasattr tarfile data_filter my_tarfile extractall filter data else remove this when no longer needed warn_the_user Extracting may be unsafe consider updating Python my_tarfile extractall Stateful extraction filter example While tarfile s extraction methods take a simple filter callable custom filters may be more complex objects with an internal state It may be useful to write these as context managers to be used like this with StatefulFilter as filter_func tar extractall path filter filter_func Such a filter can be written as for example class StatefulFilter def __init__ self self file_count 0 def __enter__ self return self def __call__ self member path self file_count 1 return member def __exit__ self exc_info print f self file_count files extracted Command Line Interface New in version 3 4 The tarfile module provides a simple command line interface to interact with tar archives If you want to create a new tar archive specify its name after the c option and then list the filename s that should be included python m tarfile c monty tar spam txt eggs txt Passing a directory is also acceptable python m tarfile c monty tar life of brian_1979 If you want to extract a tar archive into the current directory use the e option python m tarfile e monty tar You can also extract a tar archive into a different directory by passing the directory s name python m tarfile e monty tar other dir For a list of the files in a tar archive use the l option python m tarfile l monty tar Command line options l tarfile list tarfile List files in a tarfile c tarfile source1 sourceN create tarfile source1 sourceN Create tarfile from source files e tarfile output_dir extract tarfile output_dir Extract tarfile into the current directory if output_dir is not specified t tarfile test tarfile Test whether the tarfile is valid or not v verbose Verbose output filter filtername Specifies the filter for extract See Extraction filters for details Only string names are accepted that is fully_trusted tar and data Examples How to extract an entire tar archive to the current working directory import tarfile tar tarfile open sample tar gz tar extractall filter data tar close How to extract a subset of a tar archive with TarFile extractall using a generator function instead of a list import os import tarfile def py_files members for tarinfo in members if os path splitext tarinfo name 1 py yield tarinfo tar tarfile open sample tar gz tar extractall members py_files tar tar close How to create an uncompressed tar archive from a list of filenames import tarfile tar tarfile open sample tar w for name in foo bar quux tar add name tar close The same example using the with statement import tarfile with tarfile open sample tar w as tar for name in foo bar quux tar add name How to read a gzip compressed tar archive and display some member information import tarfile tar tarfile open sample tar gz r gz for tarinfo in tar print tarinfo name is tarinfo size bytes in size and is end if tarinfo isreg print a regular file elif tarinfo isdir print a directory else print something else tar close How to create an archive and reset the user information using the filter parameter in TarFile add import tarfile def reset tarinfo tarinfo uid tarinfo gid 0 tarinfo uname tarinfo gname root return tarinfo tar tarfile open sample,en
1139, tar gz w gz tar add foo filter reset tar close Supported tar formats There are three tar formats that can be created with the tarfile module The POSIX 1 1988 ustar format USTAR_FORMAT It supports filenames up to a length of at best 256 characters and linknames up to 100 characters The maximum file size is 8 GiB This is an old and limited but widely supported format The GNU tar format GNU_FORMAT It supports long filenames and linknames files bigger than 8 GiB and sparse files It is the de facto standard on GNU Linux systems tarfile fully supports the GNU tar extensions for long names sparse file support is read only The POSIX 1 2001 pax format PAX_FORMAT It is the most flexible format with virtually no limits It supports long filenames and linknames large files and stores pathnames in a portable way Modern tar implementations including GNU tar bsdtar libarchive and star fully support extended pax features some old or unmaintained libraries may not but should treat pax archives as if they were in the universally supported ustar format It is the current default format for new archives It extends the existing ustar format with extra headers for information that cannot be stored otherwise There are two flavours of pax headers Extended headers only affect the subsequent file header global headers are valid for the complete archive and affect all following files All the data in a pax header is encoded in UTF 8 for portability reasons There are some more variants of the tar format which can be read but not created The ancient V7 format This is the first tar format from Unix Seventh Edition storing only regular files and directories Names must not be longer than 100 characters there is no user group name information Some archives have miscalculated header checksums in case of fields with non ASCII characters The SunOS tar extended format This format is a variant of the POSIX 1 2001 pax format but is not compatible Unicode issues The tar format was originally conceived to make backups on tape drives with the main focus on preserving file system information Nowadays tar archives are commonly used for file distribution and exchanging archives over networks One problem of the original format which is the basis of all other formats is that there is no concept of supporting different character encodings For example an ordinary tar archive created on a UTF 8 system cannot be read correctly on a Latin 1 system if it contains non ASCII characters Textual metadata like filenames linknames user group names will appear damaged Unfortunately there is no way to autodetect the encoding of an archive The pax format was designed to solve this problem It stores non ASCII metadata using the universal character encoding UTF 8 The details of character conversion in tarfile are controlled by the encoding and errors keyword arguments of the TarFile class encoding defines the character encoding to use for the metadata in the archive The default value is sys getfilesystemencoding or ascii as a fallback Depending on whether the archive is read or written the metadata must be either decoded or encoded If encoding is not set appropriately this conversion may fail The errors argument defines how characters are treated that cannot be converted Possible values are listed in section Error Handlers The default scheme is surrogateescape which Python also uses for its file system calls see File Names Command Line Arguments and Environment Variables For PAX_FORMAT archives the default encoding is generally not needed because all the metadata is stored using UTF 8 encoding is only used in the rare cases when binary pax headers are decoded or when strings with surrogate characters are stored,en
1140,stringprep Internet String Preparation Source code Lib stringprep py When identifying things such as host names in the internet it is often necessary to compare such identifications for equality Exactly how this comparison is executed may depend on the application domain e g whether it should be case insensitive or not It may be also necessary to restrict the possible identifications to allow only identifications consisting of printable characters RFC 3454 defines a procedure for preparing Unicode strings in internet protocols Before passing strings onto the wire they are processed with the preparation procedure after which they have a certain normalized form The RFC defines a set of tables which can be combined into profiles Each profile must define which tables it uses and what other optional parts of the stringprep procedure are part of the profile One example of a stringprep profile is nameprep which is used for internationalized domain names The module stringprep only exposes the tables from RFC 3454 As these tables would be very large to represent as dictionaries or lists the module uses the Unicode character database internally The module source code itself was generated using the mkstringprep py utility As a result these tables are exposed as functions not as data structures There are two kinds of tables in the RFC sets and mappings For a set stringprep provides the characteristic function i e a function that returns True if the parameter is part of the set For mappings it provides the mapping function given the key it returns the associated value Below is a list of all functions available in the module stringprep in_table_a1 code Determine whether code is in tableA 1 Unassigned code points in Unicode 3 2 stringprep in_table_b1 code Determine whether code is in tableB 1 Commonly mapped to nothing stringprep map_table_b2 code Return the mapped value for code according to tableB 2 Mapping for case folding used with NFKC stringprep map_table_b3 code Return the mapped value for code according to tableB 3 Mapping for case folding used with no normalization stringprep in_table_c11 code Determine whether code is in tableC 1 1 ASCII space characters stringprep in_table_c12 code Determine whether code is in tableC 1 2 Non ASCII space characters stringprep in_table_c11_c12 code Determine whether code is in tableC 1 Space characters union of C 1 1 and C 1 2 stringprep in_table_c21 code Determine whether code is in tableC 2 1 ASCII control characters stringprep in_table_c22 code Determine whether code is in tableC 2 2 Non ASCII control characters stringprep in_table_c21_c22 code Determine whether code is in tableC 2 Control characters union of C 2 1 and C 2 2 stringprep in_table_c3 code Determine whether code is in tableC 3 Private use stringprep in_table_c4 code Determine whether code is in tableC 4 Non character code points stringprep in_table_c5 code Determine whether code is in tableC 5 Surrogate codes stringprep in_table_c6 code Determine whether code is in tableC 6 Inappropriate for plain text stringprep in_table_c7 code Determine whether code is in tableC 7 Inappropriate for canonical representation stringprep in_table_c8 code Determine whether code is in tableC 8 Change display properties or are deprecated stringprep in_table_c9 code Determine whether code is in tableC 9 Tagging characters stringprep in_table_d1 code Determine whether code is in tableD 1 Characters with bidirectional property R or AL stringprep in_table_d2 code Determine whether code is in tableD 2 Characters with bidirectional property L,en
1141,Slice Objects PyTypeObject PySlice_Type Part of the Stable ABI The type object for slice objects This is the same as slice in the Python layer int PySlice_Check PyObject ob Return true if ob is a slice object ob must not be NULL This function always succeeds PyObject PySlice_New PyObject start PyObject stop PyObject step Return value New reference Part of the Stable ABI Return a new slice object with the given values The start stop and step parameters are used as the values of the slice object attributes of the same names Any of the values may be NULL in which case the None will be used for the corresponding attribute Return NULL if the new object could not be allocated int PySlice_GetIndices PyObject slice Py_ssize_t length Py_ssize_t start Py_ssize_t stop Py_ssize_t step Part of the Stable ABI Retrieve the start stop and step indices from the slice object slice assuming a sequence of length length Treats indices greater than length as errors Returns 0 on success and 1 on error with no exception set unless one of the indices was not None and failed to be converted to an integer in which case 1 is returned with an exception set You probably do not want to use this function Changed in version 3 2 The parameter type for the slice parameter was PySliceObject before int PySlice_GetIndicesEx PyObject slice Py_ssize_t length Py_ssize_t start Py_ssize_t stop Py_ssize_t step Py_ssize_t slicelength Part of the Stable ABI Usable replacement for PySlice_GetIndices Retrieve the start stop and step indices from the slice object slice assuming a sequence of length length and store the length of the slice in slicelength Out of bounds indices are clipped in a manner consistent with the handling of normal slices Returns 0 on success and 1 on error with exception set Note This function is considered not safe for resizable sequences Its invocation should be replaced by a combination of PySlice_Unpack and PySlice_AdjustIndices where if PySlice_GetIndicesEx slice length start stop step slicelength 0 return error is replaced by if PySlice_Unpack slice start stop step 0 return error slicelength PySlice_AdjustIndices length start stop step Changed in version 3 2 The parameter type for the slice parameter was PySliceObject before Changed in version 3 6 1 If Py_LIMITED_API is not set or set to the value between 0x03050400 and 0x03060000 not including or 0x03060100 or higher PySlice_GetIndicesEx is implemented as a macro using PySlice_Unpack and PySlice_AdjustIndices Arguments start stop and step are evaluated more than once Deprecated since version 3 6 1 If Py_LIMITED_API is set to the value less than 0x03050400 or between 0x03060000 and 0x03060100 not including PySlice_GetIndicesEx is a deprecated function int PySlice_Unpack PyObject slice Py_ssize_t start Py_ssize_t stop Py_ssize_t step Part of the Stable ABI since version 3 7 Extract the start stop and step data members from a slice object as C integers Silently reduce values larger than PY_SSIZE_T_MAX to PY_SSIZE_T_MAX silently boost the start and stop values less than PY_SSIZE_T_MIN to PY_SSIZE_T_MIN and silently boost the step values less than PY_SSIZE_T_MAX to PY_SSIZE_T_MAX Return 1 on error 0 on success New in version 3 6 1 Py_ssize_t PySlice_AdjustIndices Py_ssize_t length Py_ssize_t start Py_ssize_t stop Py_ssize_t step Part of the Stable ABI since version 3 7 Adjust start end slice indices assuming a sequence of the specified length Out of bounds indices are clipped in a manner consistent with the handling of normal slices Return the length of the slice Always successful Doesn t call Python code New in version 3 6 1 Ellipsis Object PyObject Py_Ellipsis The Python Ellipsis object This object has no methods Like Py_None it is an immortal singleton object Changed in version 3 12 Py_Ellipsis is immortal,en
1142,Unicode HOWTO Release 1 12 This HOWTO discusses Python s support for the Unicode specification for representing textual data and explains various problems that people commonly encounter when trying to work with Unicode Introduction to Unicode Definitions Today s programs need to be able to handle a wide variety of characters Applications are often internationalized to display messages and output in a variety of user selectable languages the same program might need to output an error message in English French Japanese Hebrew or Russian Web content can be written in any of these languages and can also include a variety of emoji symbols Python s string type uses the Unicode Standard for representing characters which lets Python programs work with all these different possible characters Unicode https www unicode org is a specification that aims to list every character used by human languages and give each character its own unique code The Unicode specifications are continually revised and updated to add new languages and symbols A character is the smallest possible component of a text A B C etc are all different characters So are È and Í Characters vary depending on the language or context you re talking about For example there s a character for Roman Numeral One Ⅰ that s separate from the uppercase letter I They ll usually look the same but these are two different characters that have different meanings The Unicode standard describes how characters are represented by code points A code point value is an integer in the range 0 to 0x10FFFF about 1 1 million values the actual number assigned is less than that In the standard and in this document a code point is written using the notation U 265E to mean the character with value 0x265e 9 822 in decimal The Unicode standard contains a lot of tables listing characters and their corresponding code points 0061 a LATIN SMALL LETTER A 0062 b LATIN SMALL LETTER B 0063 c LATIN SMALL LETTER C 007B LEFT CURLY BRACKET 2167 Ⅷ ROMAN NUMERAL EIGHT 2168 Ⅸ ROMAN NUMERAL NINE 265E BLACK CHESS KNIGHT 265F BLACK CHESS PAWN 1F600 GRINNING FACE 1F609 WINKING FACE Strictly these definitions imply that it s meaningless to say this is character U 265E U 265E is a code point which represents some particular character in this case it represents the character BLACK CHESS KNIGHT In informal contexts this distinction between code points and characters will sometimes be forgotten A character is represented on a screen or on paper by a set of graphical elements that s called a glyph The glyph for an uppercase A for example is two diagonal strokes and a horizontal stroke though the exact details will depend on the font being used Most Python code doesn t need to worry about glyphs figuring out the correct glyph to display is generally the job of a GUI toolkit or a terminal s font renderer Encodings To summarize the previous section a Unicode string is a sequence of code points which are numbers from 0 through 0x10FFFF 1 114 111 decimal This sequence of code points needs to be represented in memory as a set of code units and code units are then mapped to 8 bit bytes The rules for translating a Unicode string into a sequence of bytes are called a character encoding or just an encoding The first encoding you might think of is using 32 bit integers as the code unit and then using the CPU s representation of 32 bit integers In this representation the string Python might look like this P y t h o n 0x50 00 00 00 79 00 00 00 74 00 00 00 68 00 00 00 6f 00 00 00 6e 00 00 00 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 This representation is straightforward but using it presents a number of problems 1 It s not portable different processors order the bytes differently 2 It s very wasteful of space In most texts the majority of the code points are less than 127 or less than 255 so a lot of space is occupied by 0x00 bytes The above string takes 24 bytes compared to the 6 bytes needed for an ASCII representation Increased RAM usage doesn t matter too much desktop computers have gigabytes of RAM and strings a,en
1143,ren t usually that large but expanding our usage of disk and network bandwidth by a factor of 4 is intolerable 3 It s not compatible with existing C functions such as strlen so a new family of wide string functions would need to be used Therefore this encoding isn t used very much and people instead choose other encodings that are more efficient and convenient such as UTF 8 UTF 8 is one of the most commonly used encodings and Python often defaults to using it UTF stands for Unicode Transformation Format and the 8 means that 8 bit values are used in the encoding There are also UTF 16 and UTF 32 encodings but they are less frequently used than UTF 8 UTF 8 uses the following rules 1 If the code point is 128 it s represented by the corresponding byte value 2 If the code point is 128 it s turned into a sequence of two three or four bytes where each byte of the sequence is between 128 and 255 UTF 8 has several convenient properties 1 It can handle any Unicode code point 2 A Unicode string is turned into a sequence of bytes that contains embedded zero bytes only where they represent the null character U 0000 This means that UTF 8 strings can be processed by C functions such as strcpy and sent through protocols that can t handle zero bytes for anything other than end of string markers 3 A string of ASCII text is also valid UTF 8 text 4 UTF 8 is fairly compact the majority of commonly used characters can be represented with one or two bytes 5 If bytes are corrupted or lost it s possible to determine the start of the next UTF 8 encoded code point and resynchronize It s also unlikely that random 8 bit data will look like valid UTF 8 6 UTF 8 is a byte oriented encoding The encoding specifies that each character is represented by a specific sequence of one or more bytes This avoids the byte ordering issues that can occur with integer and word oriented encodings like UTF 16 and UTF 32 where the sequence of bytes varies depending on the hardware on which the string was encoded References The Unicode Consortium site has character charts a glossary and PDF versions of the Unicode specification Be prepared for some difficult reading A chronology of the origin and development of Unicode is also available on the site On the Computerphile Youtube channel Tom Scott briefly discusses the history of Unicode and UTF 8 9 minutes 36 seconds To help understand the standard Jukka Korpela has written an introductory guide to reading the Unicode character tables Another good introductory article was written by Joel Spolsky If this introduction didn t make things clear to you you should try reading this alternate article before continuing Wikipedia entries are often helpful see the entries for character encoding and UTF 8 for example Python s Unicode Support Now that you ve learned the rudiments of Unicode we can look at Python s Unicode features The String Type Since Python 3 0 the language s str type contains Unicode characters meaning any string created using unicode rocks unicode rocks or the triple quoted string syntax is stored as Unicode The default encoding for Python source code is UTF 8 so you can simply include a Unicode character in a string literal try with open tmp input txt r as f except OSError File not found error message print Fichier non trouvé Side note Python 3 also supports using Unicode characters in identifiers répertoire tmp records log with open répertoire w as f f write test n If you can t enter a particular character in your editor or want to keep the source code ASCII only for some reason you can also use escape sequences in string literals Depending on your system you may see the actual capital delta glyph instead of a u escape N GREEK CAPITAL LETTER DELTA Using the character name u0394 u0394 Using a 16 bit hex value u0394 U00000394 Using a 32 bit hex value u0394 In addition one can create a string using the decode method of bytes This method takes an encoding argument such as UTF 8 and optionally an errors argument The errors argument specifies the response when the input string can t be converted according to the encodin,en
1144,g s rules Legal values for this argument are strict raise a UnicodeDecodeError exception replace use U FFFD REPLACEMENT CHARACTER ignore just leave the character out of the Unicode result or backslashreplace inserts a xNN escape sequence The following examples show the differences b x80abc decode utf 8 strict Traceback most recent call last UnicodeDecodeError utf 8 codec can t decode byte 0x80 in position 0 invalid start byte b x80abc decode utf 8 replace ufffdabc b x80abc decode utf 8 backslashreplace x80abc b x80abc decode utf 8 ignore abc Encodings are specified as strings containing the encoding s name Python comes with roughly 100 different encodings see the Python Library Reference at Standard Encodings for a list Some encodings have multiple names for example latin 1 iso_8859_1 and 8859 are all synonyms for the same encoding One character Unicode strings can also be created with the chr built in function which takes integers and returns a Unicode string of length 1 that contains the corresponding code point The reverse operation is the built in ord function that takes a one character Unicode string and returns the code point value chr 57344 ue000 ord ue000 57344 Converting to Bytes The opposite method of bytes decode is str encode which returns a bytes representation of the Unicode string encoded in the requested encoding The errors parameter is the same as the parameter of the decode method but supports a few more possible handlers As well as strict ignore and replace which in this case inserts a question mark instead of the unencodable character there is also xmlcharrefreplace inserts an XML character reference backslashreplace inserts a uNNNN escape sequence and namereplace inserts a N escape sequence The following example shows the different results u chr 40960 abcd chr 1972 u encode utf 8 b xea x80 x80abcd xde xb4 u encode ascii Traceback most recent call last UnicodeEncodeError ascii codec can t encode character ua000 in position 0 ordinal not in range 128 u encode ascii ignore b abcd u encode ascii replace b abcd u encode ascii xmlcharrefreplace b 40960 abcd 1972 u encode ascii backslashreplace b ua000abcd u07b4 u encode ascii namereplace b N YI SYLLABLE IT abcd u07b4 The low level routines for registering and accessing the available encodings are found in the codecs module Implementing new encodings also requires understanding the codecs module However the encoding and decoding functions returned by this module are usually more low level than is comfortable and writing new encodings is a specialized task so the module won t be covered in this HOWTO Unicode Literals in Python Source Code In Python source code specific Unicode code points can be written using the u escape sequence which is followed by four hex digits giving the code point The U escape sequence is similar but expects eight hex digits not four s a xac u1234 u20ac U00008000 two digit hex escape four digit Unicode escape eight digit Unicode escape ord c for c in s 97 172 4660 8364 32768 Using escape sequences for code points greater than 127 is fine in small doses but becomes an annoyance if you re using many accented characters as you would in a program with messages in French or some other accent using language You can also assemble strings using the chr built in function but this is even more tedious Ideally you d want to be able to write literals in your language s natural encoding You could then edit Python source code with your favorite editor which would display the accented characters naturally and have the right characters used at runtime Python supports writing source code in UTF 8 by default but you can use almost any encoding if you declare the encoding being used This is done by including a special comment as either the first or second line of the source file usr bin env python coding latin 1 u abcdé print ord u 1 The syntax is inspired by Emacs s notation for specifying variables local to a file Emacs supports many different variables but Python only supports coding The symbols indicate to Emacs that the comment is special they hav,en
1145,e no significance to Python but are a convention Python looks for coding name or coding name in the comment If you don t include such a comment the default encoding used will be UTF 8 as already mentioned See also PEP 263 for more information Unicode Properties The Unicode specification includes a database of information about code points For each defined code point the information includes the character s name its category the numeric value if applicable for characters representing numeric concepts such as the Roman numerals fractions such as one third and four fifths etc There are also display related properties such as how to use the code point in bidirectional text The following program displays some information about several characters and prints the numeric value of one particular character import unicodedata u chr 233 chr 0x0bf2 chr 3972 chr 6000 chr 13231 for i c in enumerate u print i 04x ord c unicodedata category c end print unicodedata name c Get numeric value of second character print unicodedata numeric u 1 When run this prints 0 00e9 Ll LATIN SMALL LETTER E WITH ACUTE 1 0bf2 No TAMIL NUMBER ONE THOUSAND 2 0f84 Mn TIBETAN MARK HALANTA 3 1770 Lo TAGBANWA LETTER SA 4 33af So SQUARE RAD OVER S SQUARED 1000 0 The category codes are abbreviations describing the nature of the character These are grouped into categories such as Letter Number Punctuation or Symbol which in turn are broken up into subcategories To take the codes from the above output Ll means Letter lowercase No means Number other Mn is Mark nonspacing and So is Symbol other See the General Category Values section of the Unicode Character Database documentation for a list of category codes Comparing Strings Unicode adds some complication to comparing strings because the same set of characters can be represented by different sequences of code points For example a letter like ê can be represented as a single code point U 00EA or as U 0065 U 0302 which is the code point for e followed by a code point for COMBINING CIRCUMFLEX ACCENT These will produce the same output when printed but one is a string of length 1 and the other is of length 2 One tool for a case insensitive comparison is the casefold string method that converts a string to a case insensitive form following an algorithm described by the Unicode Standard This algorithm has special handling for characters such as the German letter ß code point U 00DF which becomes the pair of lowercase letters ss street Gürzenichstraße street casefold gürzenichstrasse A second tool is the unicodedata module s normalize function that converts strings to one of several normal forms where letters followed by a combining character are replaced with single characters normalize can be used to perform string comparisons that won t falsely report inequality if two strings use combining characters differently import unicodedata def compare_strs s1 s2 def NFD s return unicodedata normalize NFD s return NFD s1 NFD s2 single_char ê multiple_chars N LATIN SMALL LETTER E N COMBINING CIRCUMFLEX ACCENT print length of first string len single_char print length of second string len multiple_chars print compare_strs single_char multiple_chars When run this outputs python compare strs py length of first string 1 length of second string 2 True The first argument to the normalize function is a string giving the desired normalization form which can be one of NFC NFKC NFD and NFKD The Unicode Standard also specifies how to do caseless comparisons import unicodedata def compare_caseless s1 s2 def NFD s return unicodedata normalize NFD s return NFD NFD s1 casefold NFD NFD s2 casefold Example usage single_char ê multiple_chars N LATIN CAPITAL LETTER E N COMBINING CIRCUMFLEX ACCENT print compare_caseless single_char multiple_chars This will print True Why is NFD invoked twice Because there are a few characters that make casefold return a non normalized string so the result needs to be normalized again See section 3 13 of the Unicode Standard for a discussion and an example Unicode Regular Expressions The regular expressions supported by,en
1146, the re module can be provided either as bytes or strings Some of the special character sequences such as d and w have different meanings depending on whether the pattern is supplied as bytes or a string For example d will match the characters 0 9 in bytes but in strings will match any character that s in the Nd category The string in this example has the number 57 written in both Thai and Arabic numerals import re p re compile r d s Over u0e55 u0e57 57 flavours m p search s print repr m group When executed d will match the Thai numerals and print them out If you supply the re ASCII flag to compile d will match the substring 57 instead Similarly w matches a wide variety of Unicode characters but only a zA Z0 9_ in bytes or if re ASCII is supplied and s will match either Unicode whitespace characters or t n r f v References Some good alternative discussions of Python s Unicode support are Processing Text Files in Python 3 by Nick Coghlan Pragmatic Unicode a PyCon 2012 presentation by Ned Batchelder The str type is described in the Python library reference at Text Sequence Type str The documentation for the unicodedata module The documentation for the codecs module Marc André Lemburg gave a presentation titled Python and Unicode PDF slides at EuroPython 2002 The slides are an excellent overview of the design of Python 2 s Unicode features where the Unicode string type is called unicode and literals start with u Reading and Writing Unicode Data Once you ve written some code that works with Unicode data the next problem is input output How do you get Unicode strings into your program and how do you convert Unicode into a form suitable for storage or transmission It s possible that you may not need to do anything depending on your input sources and output destinations you should check whether the libraries used in your application support Unicode natively XML parsers often return Unicode data for example Many relational databases also support Unicode valued columns and can return Unicode values from an SQL query Unicode data is usually converted to a particular encoding before it gets written to disk or sent over a socket It s possible to do all the work yourself open a file read an 8 bit bytes object from it and convert the bytes with bytes decode encoding However the manual approach is not recommended One problem is the multi byte nature of encodings one Unicode character can be represented by several bytes If you want to read the file in arbitrary sized chunks say 1024 or 4096 bytes you need to write error handling code to catch the case where only part of the bytes encoding a single Unicode character are read at the end of a chunk One solution would be to read the entire file into memory and then perform the decoding but that prevents you from working with files that are extremely large if you need to read a 2 GiB file you need 2 GiB of RAM More really since for at least a moment you d need to have both the encoded string and its Unicode version in memory The solution would be to use the low level decoding interface to catch the case of partial coding sequences The work of implementing this has already been done for you the built in open function can return a file like object that assumes the file s contents are in a specified encoding and accepts Unicode parameters for methods such as read and write This works through open s encoding and errors parameters which are interpreted just like those in str encode and bytes decode Reading Unicode from a file is therefore simple with open unicode txt encoding utf 8 as f for line in f print repr line It s also possible to open files in update mode allowing both reading and writing with open test encoding utf 8 mode w as f f write u4500 blah blah blah n f seek 0 print repr f readline 1 The Unicode character U FEFF is used as a byte order mark BOM and is often written as the first character of a file in order to assist with autodetection of the file s byte ordering Some encodings such as UTF 16 expect a BOM to be present at the start of a file when such an encoding is used the BOM w,en
1147,ill be automatically written as the first character and will be silently dropped when the file is read There are variants of these encodings such as utf 16 le and utf 16 be for little endian and big endian encodings that specify one particular byte ordering and don t skip the BOM In some areas it is also convention to use a BOM at the start of UTF 8 encoded files the name is misleading since UTF 8 is not byte order dependent The mark simply announces that the file is encoded in UTF 8 For reading such files use the utf 8 sig codec to automatically skip the mark if present Unicode filenames Most of the operating systems in common use today support filenames that contain arbitrary Unicode characters Usually this is implemented by converting the Unicode string into some encoding that varies depending on the system Today Python is converging on using UTF 8 Python on MacOS has used UTF 8 for several versions and Python 3 6 switched to using UTF 8 on Windows as well On Unix systems there will only be a filesystem encoding if you ve set the LANG or LC_CTYPE environment variables if you haven t the default encoding is again UTF 8 The sys getfilesystemencoding function returns the encoding to use on your current system in case you want to do the encoding manually but there s not much reason to bother When opening a file for reading or writing you can usually just provide the Unicode string as the filename and it will be automatically converted to the right encoding for you filename filename u4500abc with open filename w as f f write blah n Functions in the os module such as os stat will also accept Unicode filenames The os listdir function returns filenames which raises an issue should it return the Unicode version of filenames or should it return bytes containing the encoded versions os listdir can do both depending on whether you provided the directory path as bytes or a Unicode string If you pass a Unicode string as the path filenames will be decoded using the filesystem s encoding and a list of Unicode strings will be returned while passing a byte path will return the filenames as bytes For example assuming the default filesystem encoding is UTF 8 running the following program fn filename u4500abc f open fn w f close import os print os listdir b print os listdir will produce the following output python listdir test py b filename xe4 x94 x80abc filename u4500abc The first list contains UTF 8 encoded filenames and the second list contains the Unicode versions Note that on most occasions you should can just stick with using Unicode with these APIs The bytes APIs should only be used on systems where undecodable file names can be present that s pretty much only Unix systems now Tips for Writing Unicode aware Programs This section provides some suggestions on writing software that deals with Unicode The most important tip is Software should only work with Unicode strings internally decoding the input data as soon as possible and encoding the output only at the end If you attempt to write processing functions that accept both Unicode and byte strings you will find your program vulnerable to bugs wherever you combine the two different kinds of strings There is no automatic encoding or decoding if you do e g str bytes a TypeError will be raised When using data coming from a web browser or some other untrusted source a common technique is to check for illegal characters in a string before using the string in a generated command line or storing it in a database If you re doing this be careful to check the decoded string not the encoded bytes data some encodings may have interesting properties such as not being bijective or not being fully ASCII compatible This is especially true if the input data also specifies the encoding since the attacker can then choose a clever way to hide malicious text in the encoded bytestream Converting Between File Encodings The StreamRecoder class can transparently convert between encodings taking a stream that returns data in encoding 1 and behaving like a stream returning data in encoding 2 For example if y,en
1148,ou have an input file f that s in Latin 1 you can wrap it with a StreamRecoder to return bytes encoded in UTF 8 new_f codecs StreamRecoder f en decoder used by read to encode its results and by write to decode its input codecs getencoder utf 8 codecs getdecoder utf 8 reader writer used to read and write to the stream codecs getreader latin 1 codecs getwriter latin 1 Files in an Unknown Encoding What can you do if you need to make a change to a file but don t know the file s encoding If you know the encoding is ASCII compatible and only want to examine or modify the ASCII parts you can open the file with the surrogateescape error handler with open fname r encoding ascii errors surrogateescape as f data f read make changes to the string data with open fname new w encoding ascii errors surrogateescape as f f write data The surrogateescape error handler will decode any non ASCII bytes as code points in a special range running from U DC80 to U DCFF These code points will then turn back into the same bytes when the surrogateescape error handler is used to encode the data and write it back out References One section of Mastering Python 3 Input Output a PyCon 2010 talk by David Beazley discusses text processing and binary data handling The PDF slides for Marc André Lemburg s presentation Writing Unicode aware Applications in Python discuss questions of character encodings as well as how to internationalize and localize an application These slides cover Python 2 x only The Guts of Unicode in Python is a PyCon 2013 talk by Benjamin Peterson that discusses the internal Unicode representation in Python 3 3 Acknowledgements The initial draft of this document was written by Andrew Kuchling It has since been revised further by Alexander Belopolsky Georg Brandl Andrew Kuchling and Ezio Melotti Thanks to the following people who have noted errors or offered suggestions on this article Éric Araujo Nicholas Bastin Nick Coghlan Marius Gedminas Kent Johnson Ken Krugler Marc André Lemburg Martin von Löwis Terry J Reedy Serhiy Storchaka Eryk Sun Chad Whitacre Graham Wideman,en
1149,linecache Random access to text lines Source code Lib linecache py The linecache module allows one to get any line from a Python source file while attempting to optimize internally using a cache the common case where many lines are read from a single file This is used by the traceback module to retrieve source lines for inclusion in the formatted traceback The tokenize open function is used to open files This function uses tokenize detect_encoding to get the encoding of the file in the absence of an encoding token the file encoding defaults to UTF 8 The linecache module defines the following functions linecache getline filename lineno module_globals None Get line lineno from file named filename This function will never raise an exception it will return on errors the terminating newline character will be included for lines that are found If a file named filename is not found the function first checks for a PEP 302 __loader__ in module_globals If there is such a loader and it defines a get_source method then that determines the source lines if get_source returns None then is returned Finally if filename is a relative filename it is looked up relative to the entries in the module search path sys path linecache clearcache Clear the cache Use this function if you no longer need lines from files previously read using getline linecache checkcache filename None Check the cache for validity Use this function if files in the cache may have changed on disk and you require the updated version If filename is omitted it will check all the entries in the cache linecache lazycache filename module_globals Capture enough detail about a non file based module to permit getting its lines later via getline even if module_globals is None in the later call This avoids doing I O until a line is actually needed without having to carry the module globals around indefinitely New in version 3 5 Example import linecache linecache getline linecache __file__ 8 import sys n,en
1150,pdb The Python Debugger Source code Lib pdb py The module pdb defines an interactive source code debugger for Python programs It supports setting conditional breakpoints and single stepping at the source line level inspection of stack frames source code listing and evaluation of arbitrary Python code in the context of any stack frame It also supports post mortem debugging and can be called under program control The debugger is extensible it is actually defined as the class Pdb This is currently undocumented but easily understood by reading the source The extension interface uses the modules bdb and cmd See also Module faulthandler Used to dump Python tracebacks explicitly on a fault after a timeout or on a user signal Module traceback Standard interface to extract format and print stack traces of Python programs The typical usage to break into the debugger is to insert import pdb pdb set_trace Or breakpoint at the location you want to break into the debugger and then run the program You can then step through the code following this statement and continue running without the debugger using the continue command Changed in version 3 7 The built in breakpoint when called with defaults can be used instead of import pdb pdb set_trace def double x breakpoint return x 2 val 3 print f val 2 is double val The debugger s prompt is Pdb which is the indicator that you are in debug mode 3 double return x 2 Pdb p x 3 Pdb continue 3 2 is 6 Changed in version 3 3 Tab completion via the readline module is available for commands and command arguments e g the current global and local names are offered as arguments of the p command You can also invoke pdb from the command line to debug other scripts For example python m pdb myscript py When invoked as a module pdb will automatically enter post mortem debugging if the program being debugged exits abnormally After post mortem debugging or after normal exit of the program pdb will restart the program Automatic restarting preserves pdb s state such as breakpoints and in most cases is more useful than quitting the debugger upon program s exit Changed in version 3 2 Added the c option to execute commands as if given in a pdbrc file see Debugger Commands Changed in version 3 7 Added the m option to execute modules similar to the way python m does As with a script the debugger will pause execution just before the first line of the module Typical usage to execute a statement under control of the debugger is import pdb def f x print 1 x pdb run f 2 string 1 module Pdb continue 0 5 The typical usage to inspect a crashed program is import pdb def f x print 1 x f 0 Traceback most recent call last File stdin line 1 in module File stdin line 2 in f ZeroDivisionError division by zero pdb pm stdin 2 f Pdb p x 0 Pdb The module defines the following functions each enters the debugger in a slightly different way pdb run statement globals None locals None Execute the statement given as a string or a code object under debugger control The debugger prompt appears before any code is executed you can set breakpoints and type continue or you can step through the statement using step or next all these commands are explained below The optional globals and locals arguments specify the environment in which the code is executed by default the dictionary of the module __main__ is used See the explanation of the built in exec or eval functions pdb runeval expression globals None locals None Evaluate the expression given as a string or a code object under debugger control When runeval returns it returns the value of the expression Otherwise this function is similar to run pdb runcall function args kwds Call the function a function or method object not a string with the given arguments When runcall returns it returns whatever the function call returned The debugger prompt appears as soon as the function is entered pdb set_trace header None Enter the debugger at the calling stack frame This is useful to hard code a breakpoint at a given point in a program even if the code is not otherwise being debugged e g when an assertion f,en
1151,ails If given header is printed to the console just before debugging begins Changed in version 3 7 The keyword only argument header pdb post_mortem traceback None Enter post mortem debugging of the given traceback object If no traceback is given it uses the one of the exception that is currently being handled an exception must be being handled if the default is to be used pdb pm Enter post mortem debugging of the traceback found in sys last_traceback The run functions and set_trace are aliases for instantiating the Pdb class and calling the method of the same name If you want to access further features you have to do this yourself class pdb Pdb completekey tab stdin None stdout None skip None nosigint False readrc True Pdb is the debugger class The completekey stdin and stdout arguments are passed to the underlying cmd Cmd class see the description there The skip argument if given must be an iterable of glob style module name patterns The debugger will not step into frames that originate in a module that matches one of these patterns 1 By default Pdb sets a handler for the SIGINT signal which is sent when the user presses Ctrl C on the console when you give a continue command This allows you to break into the debugger again by pressing Ctrl C If you want Pdb not to touch the SIGINT handler set nosigint to true The readrc argument defaults to true and controls whether Pdb will load pdbrc files from the filesystem Example call to enable tracing with skip import pdb pdb Pdb skip django set_trace Raises an auditing event pdb Pdb with no arguments Changed in version 3 1 Added the skip parameter Changed in version 3 2 Added the nosigint parameter Previously a SIGINT handler was never set by Pdb Changed in version 3 6 The readrc argument run statement globals None locals None runeval expression globals None locals None runcall function args kwds set_trace See the documentation for the functions explained above Debugger Commands The commands recognized by the debugger are listed below Most commands can be abbreviated to one or two letters as indicated e g h elp means that either h or help can be used to enter the help command but not he or hel nor H or Help or HELP Arguments to commands must be separated by whitespace spaces or tabs Optional arguments are enclosed in square brackets in the command syntax the square brackets must not be typed Alternatives in the command syntax are separated by a vertical bar Entering a blank line repeats the last command entered Exception if the last command was a list command the next 11 lines are listed Commands that the debugger doesn t recognize are assumed to be Python statements and are executed in the context of the program being debugged Python statements can also be prefixed with an exclamation point This is a powerful way to inspect the program being debugged it is even possible to change a variable or call a function When an exception occurs in such a statement the exception name is printed but the debugger s state is not changed The debugger supports aliases Aliases can have parameters which allows one a certain level of adaptability to the context under examination Multiple commands may be entered on a single line separated by A single is not used as it is the separator for multiple commands in a line that is passed to the Python parser No intelligence is applied to separating the commands the input is split at the first pair even if it is in the middle of a quoted string A workaround for strings with double semicolons is to use implicit string concatenation or To set a temporary global variable use a convenience variable A convenience variable is a variable whose name starts with For example foo 1 sets a global variable foo which you can use in the debugger session The convenience variables are cleared when the program resumes execution so it s less likely to interfere with your program compared to using normal variables like foo 1 There are three preset convenience variables _frame the current frame you are debugging _retval the return value if the frame is returning _exception the,en
1152, exception if the frame is raising an exception New in version 3 12 If a file pdbrc exists in the user s home directory or in the current directory it is read with utf 8 encoding and executed as if it had been typed at the debugger prompt This is particularly useful for aliases If both files exist the one in the home directory is read first and aliases defined there can be overridden by the local file Changed in version 3 2 pdbrc can now contain commands that continue debugging such as continue or next Previously these commands had no effect Changed in version 3 11 pdbrc is now read with utf 8 encoding Previously it was read with the system locale encoding h elp command Without argument print the list of available commands With a command as argument print help about that command help pdb displays the full documentation the docstring of the pdb module Since the command argument must be an identifier help exec must be entered to get help on the command w here Print a stack trace with the most recent frame at the bottom An arrow indicates the current frame which determines the context of most commands d own count Move the current frame count default one levels down in the stack trace to a newer frame u p count Move the current frame count default one levels up in the stack trace to an older frame b reak filename lineno function condition With a lineno argument set a break there in the current file With a function argument set a break at the first executable statement within that function The line number may be prefixed with a filename and a colon to specify a breakpoint in another file probably one that hasn t been loaded yet The file is searched on sys path Note that each breakpoint is assigned a number to which all the other breakpoint commands refer If a second argument is present it is an expression which must evaluate to true before the breakpoint is honored Without argument list all breaks including for each breakpoint the number of times that breakpoint has been hit the current ignore count and the associated condition if any tbreak filename lineno function condition Temporary breakpoint which is removed automatically when it is first hit The arguments are the same as for break cl ear filename lineno bpnumber With a filename lineno argument clear all the breakpoints at this line With a space separated list of breakpoint numbers clear those breakpoints Without argument clear all breaks but first ask confirmation disable bpnumber bpnumber Disable the breakpoints given as a space separated list of breakpoint numbers Disabling a breakpoint means it cannot cause the program to stop execution but unlike clearing a breakpoint it remains in the list of breakpoints and can be re enabled enable bpnumber bpnumber Enable the breakpoints specified ignore bpnumber count Set the ignore count for the given breakpoint number If count is omitted the ignore count is set to 0 A breakpoint becomes active when the ignore count is zero When non zero the count is decremented each time the breakpoint is reached and the breakpoint is not disabled and any associated condition evaluates to true condition bpnumber condition Set a new condition for the breakpoint an expression which must evaluate to true before the breakpoint is honored If condition is absent any existing condition is removed i e the breakpoint is made unconditional commands bpnumber Specify a list of commands for breakpoint number bpnumber The commands themselves appear on the following lines Type a line containing just end to terminate the commands An example Pdb commands 1 com p some_variable com end Pdb To remove all commands from a breakpoint type commands and follow it immediately with end that is give no commands With no bpnumber argument commands refers to the last breakpoint set You can use breakpoint commands to start your program up again Simply use the continue command or step or any other command that resumes execution Specifying any command resuming execution currently continue step next return jump quit and their abbreviations terminates the command list as if that,en
1153, command was immediately followed by end This is because any time you resume execution even with a simple next or step you may encounter another breakpoint which could have its own command list leading to ambiguities about which list to execute If you use the silent command in the command list the usual message about stopping at a breakpoint is not printed This may be desirable for breakpoints that are to print a specific message and then continue If none of the other commands print anything you see no sign that the breakpoint was reached s tep Execute the current line stop at the first possible occasion either in a function that is called or on the next line in the current function n ext Continue execution until the next line in the current function is reached or it returns The difference between next and step is that step stops inside a called function while next executes called functions at nearly full speed only stopping at the next line in the current function unt il lineno Without argument continue execution until the line with a number greater than the current one is reached With lineno continue execution until a line with a number greater or equal to lineno is reached In both cases also stop when the current frame returns Changed in version 3 2 Allow giving an explicit line number r eturn Continue execution until the current function returns c ont inue Continue execution only stop when a breakpoint is encountered j ump lineno Set the next line that will be executed Only available in the bottom most frame This lets you jump back and execute code again or jump forward to skip code that you don t want to run It should be noted that not all jumps are allowed for instance it is not possible to jump into the middle of a for loop or out of a finally clause l ist first last List source code for the current file Without arguments list 11 lines around the current line or continue the previous listing With as argument list 11 lines around the current line With one argument list 11 lines around at that line With two arguments list the given range if the second argument is less than the first it is interpreted as a count The current line in the current frame is indicated by If an exception is being debugged the line where the exception was originally raised or propagated is indicated by if it differs from the current line Changed in version 3 2 Added the marker ll longlist List all source code for the current function or frame Interesting lines are marked as for list New in version 3 2 a rgs Print the arguments of the current function and their current values p expression Evaluate expression in the current context and print its value Note print can also be used but is not a debugger command this executes the Python print function pp expression Like the p command except the value of expression is pretty printed using the pprint module whatis expression Print the type of expression source expression Try to get source code of expression and display it New in version 3 2 display expression Display the value of expression if it changed each time execution stops in the current frame Without expression list all display expressions for the current frame Note Display evaluates expression and compares to the result of the previous evaluation of expression so when the result is mutable display may not be able to pick up the changes Example lst breakpoint pass lst append 1 print lst Display won t realize lst has been changed because the result of evaluation is modified in place by lst append 1 before being compared example py 3 module pass Pdb display lst display lst Pdb n example py 4 module lst append 1 Pdb n example py 5 module print lst Pdb You can do some tricks with copy mechanism to make it work example py 3 module pass Pdb display lst display lst Pdb n example py 4 module lst append 1 Pdb n example py 5 module print lst display lst 1 old Pdb New in version 3 2 undisplay expression Do not display expression anymore in the current frame Without expression clear all display expressions for the current frame New in version 3 2 intera,en
1154,ct Start an interactive interpreter using the code module whose global namespace contains all the global and local names found in the current scope New in version 3 2 alias name command Create an alias called name that executes command The command must not be enclosed in quotes Replaceable parameters can be indicated by 1 2 and so on while is replaced by all the parameters If command is omitted the current alias for name is shown If no arguments are given all aliases are listed Aliases may be nested and can contain anything that can be legally typed at the pdb prompt Note that internal pdb commands can be overridden by aliases Such a command is then hidden until the alias is removed Aliasing is recursively applied to the first word of the command line all other words in the line are left alone As an example here are two useful aliases especially when placed in the pdbrc file Print instance variables usage pi classInst alias pi for k in 1 __dict__ keys print f 1 k 1 __dict__ k Print instance variables in self alias ps pi self unalias name Delete the specified alias name statement Execute the one line statement in the context of the current stack frame The exclamation point can be omitted unless the first word of the statement resembles a debugger command e g Pdb n 42 Pdb To set a global variable you can prefix the assignment command with a global statement on the same line e g Pdb global list_options list_options l Pdb run args restart args Restart the debugged Python program If args is supplied it is split with shlex and the result is used as the new sys argv History breakpoints actions and debugger options are preserved restart is an alias for run q uit Quit from the debugger The program being executed is aborted debug code Enter a recursive debugger that steps through code which is an arbitrary expression or statement to be executed in the current environment retval Print the return value for the last return of the current function Footnotes 1 Whether a frame is considered to originate in a certain module is determined by the __name__ in the frame globals,en
1155,urllib request Extensible library for opening URLs Source code Lib urllib request py The urllib request module defines functions and classes which help in opening URLs mostly HTTP in a complex world basic and digest authentication redirections cookies and more See also The Requests package is recommended for a higher level HTTP client interface Warning On macOS it is unsafe to use this module in programs using os fork because the getproxies implementation for macOS uses a higher level system API Set the environment variable no_proxy to to avoid this problem e g os environ no_proxy Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information The urllib request module defines the following functions urllib request urlopen url data None timeout cafile None capath None cadefault False context None Open url which can be either a string containing a valid properly encoded URL or a Request object data must be an object specifying additional data to be sent to the server or None if no such data is needed See Request for details urllib request module uses HTTP 1 1 and includes Connection close header in its HTTP requests The optional timeout parameter specifies a timeout in seconds for blocking operations like the connection attempt if not specified the global default timeout setting will be used This actually only works for HTTP HTTPS and FTP connections If context is specified it must be a ssl SSLContext instance describing the various SSL options See HTTPSConnection for more details The optional cafile and capath parameters specify a set of trusted CA certificates for HTTPS requests cafile should point to a single file containing a bundle of CA certificates whereas capath should point to a directory of hashed certificate files More information can be found in ssl SSLContext load_verify_locations The cadefault parameter is ignored This function always returns an object which can work as a context manager and has the properties url headers and status See urllib response addinfourl for more detail on these properties For HTTP and HTTPS URLs this function returns a http client HTTPResponse object slightly modified In addition to the three new methods above the msg attribute contains the same information as the reason attribute the reason phrase returned by server instead of the response headers as it is specified in the documentation for HTTPResponse For FTP file and data URLs and requests explicitly handled by legacy URLopener and FancyURLopener classes this function returns a urllib response addinfourl object Raises URLError on protocol errors Note that None may be returned if no handler handles the request though the default installed global OpenerDirector uses UnknownHandler to ensure this never happens In addition if proxy settings are detected for example when a _proxy environment variable like http_proxy is set ProxyHandler is default installed and makes sure the requests are handled through the proxy The legacy urllib urlopen function from Python 2 6 and earlier has been discontinued urllib request urlopen corresponds to the old urllib2 urlopen Proxy handling which was done by passing a dictionary parameter to urllib urlopen can be obtained by using ProxyHandler objects The default opener raises an auditing event urllib Request with arguments fullurl data headers method taken from the request object Changed in version 3 2 cafile and capath were added HTTPS virtual hosts are now supported if possible that is if ssl HAS_SNI is true data can be an iterable object Changed in version 3 3 cadefault was added Changed in version 3 4 3 context was added Changed in version 3 10 HTTPS connection now send an ALPN extension with protocol indicator http 1 1 when no context is given Custom context should set ALPN protocols with set_alpn_protocols Deprecated since version 3 6 cafile capath and cadefault are deprecated in favor of context Please use ssl SSLContext load_cert_chain instead or let ssl create_default_,en
1156,context select the system s trusted CA certificates for you urllib request install_opener opener Install an OpenerDirector instance as the default global opener Installing an opener is only necessary if you want urlopen to use that opener otherwise simply call OpenerDirector open instead of urlopen The code does not check for a real OpenerDirector and any class with the appropriate interface will work urllib request build_opener handler Return an OpenerDirector instance which chains the handlers in the order given handler s can be either instances of BaseHandler or subclasses of BaseHandler in which case it must be possible to call the constructor without any parameters Instances of the following classes will be in front of the handler s unless the handler s contain them instances of them or subclasses of them ProxyHandler if proxy settings are detected UnknownHandler HTTPHandler HTTPDefaultErrorHandler HTTPRedirectHandler FTPHandler FileHandler HTTPErrorProcessor If the Python installation has SSL support i e if the ssl module can be imported HTTPSHandler will also be added A BaseHandler subclass may also change its handler_order attribute to modify its position in the handlers list urllib request pathname2url path Convert the pathname path from the local syntax for a path to the form used in the path component of a URL This does not produce a complete URL The return value will already be quoted using the quote function urllib request url2pathname path Convert the path component path from a percent encoded URL to the local syntax for a path This does not accept a complete URL This function uses unquote to decode path urllib request getproxies This helper function returns a dictionary of scheme to proxy server URL mappings It scans the environment for variables named scheme _proxy in a case insensitive approach for all operating systems first and when it cannot find it looks for proxy information from System Configuration for macOS and Windows Systems Registry for Windows If both lowercase and uppercase environment variables exist and disagree lowercase is preferred Note If the environment variable REQUEST_METHOD is set which usually indicates your script is running in a CGI environment the environment variable HTTP_PROXY uppercase _PROXY will be ignored This is because that variable can be injected by a client using the Proxy HTTP header If you need to use an HTTP proxy in a CGI environment either use ProxyHandler explicitly or make sure the variable name is in lowercase or at least the _proxy suffix The following classes are provided class urllib request Request url data None headers origin_req_host None unverifiable False method None This class is an abstraction of a URL request url should be a string containing a valid properly encoded URL data must be an object specifying additional data to send to the server or None if no such data is needed Currently HTTP requests are the only ones that use data The supported object types include bytes file like objects and iterables of bytes like objects If no Content Length nor Transfer Encoding header field has been provided HTTPHandler will set these headers according to the type of data Content Length will be used to send bytes objects while Transfer Encoding chunked as specified in RFC 7230 Section 3 3 1 will be used to send files and other iterables For an HTTP POST request method data should be a buffer in the standard application x www form urlencoded format The urllib parse urlencode function takes a mapping or sequence of 2 tuples and returns an ASCII string in this format It should be encoded to bytes before being used as the data parameter headers should be a dictionary and will be treated as if add_header was called with each key and value as arguments This is often used to spoof the User Agent header value which is used by a browser to identify itself some HTTP servers only allow requests coming from common browsers as opposed to scripts For example Mozilla Firefox may identify itself as Mozilla 5 0 X11 U Linux i686 Gecko 20071127 Firefox 2 0 0 11 while urllib s def,en
1157,ault user agent string is Python urllib 2 6 on Python 2 6 All header keys are sent in camel case An appropriate Content Type header should be included if the data argument is present If this header has not been provided and data is not None Content Type application x www form urlencoded will be added as a default The next two arguments are only of interest for correct handling of third party HTTP cookies origin_req_host should be the request host of the origin transaction as defined by RFC 2965 It defaults to http cookiejar request_host self This is the host name or IP address of the original request that was initiated by the user For example if the request is for an image in an HTML document this should be the request host of the request for the page containing the image unverifiable should indicate whether the request is unverifiable as defined by RFC 2965 It defaults to False An unverifiable request is one whose URL the user did not have the option to approve For example if the request is for an image in an HTML document and the user had no option to approve the automatic fetching of the image this should be true method should be a string that indicates the HTTP request method that will be used e g HEAD If provided its value is stored in the method attribute and is used by get_method The default is GET if data is None or POST otherwise Subclasses may indicate a different default method by setting the method attribute in the class itself Note The request will not work as expected if the data object is unable to deliver its content more than once e g a file or an iterable that can produce the content only once and the request is retried for HTTP redirects or authentication The data is sent to the HTTP server right away after the headers There is no support for a 100 continue expectation in the library Changed in version 3 3 Request method argument is added to the Request class Changed in version 3 4 Default Request method may be indicated at the class level Changed in version 3 6 Do not raise an error if the Content Length has not been provided and data is neither None nor a bytes object Fall back to use chunked transfer encoding instead class urllib request OpenerDirector The OpenerDirector class opens URLs via BaseHandler s chained together It manages the chaining of handlers and recovery from errors class urllib request BaseHandler This is the base class for all registered handlers and handles only the simple mechanics of registration class urllib request HTTPDefaultErrorHandler A class which defines a default handler for HTTP error responses all responses are turned into HTTPError exceptions class urllib request HTTPRedirectHandler A class to handle redirections class urllib request HTTPCookieProcessor cookiejar None A class to handle HTTP Cookies class urllib request ProxyHandler proxies None Cause requests to go through a proxy If proxies is given it must be a dictionary mapping protocol names to URLs of proxies The default is to read the list of proxies from the environment variables protocol _proxy If no proxy environment variables are set then in a Windows environment proxy settings are obtained from the registry s Internet Settings section and in a macOS environment proxy information is retrieved from the System Configuration Framework To disable autodetected proxy pass an empty dictionary The no_proxy environment variable can be used to specify hosts which shouldn t be reached via proxy if set it should be a comma separated list of hostname suffixes optionally with port appended for example cern ch ncsa uiuc edu some host 8080 Note HTTP_PROXY will be ignored if a variable REQUEST_METHOD is set see the documentation on getproxies class urllib request HTTPPasswordMgr Keep a database of realm uri user password mappings class urllib request HTTPPasswordMgrWithDefaultRealm Keep a database of realm uri user password mappings A realm of None is considered a catch all realm which is searched if no other realm fits class urllib request HTTPPasswordMgrWithPriorAuth A variant of HTTPPasswordMgrWithDefaultRealm that also,en
1158, has a database of uri is_authenticated mappings Can be used by a BasicAuth handler to determine when to send authentication credentials immediately instead of waiting for a 401 response first New in version 3 5 class urllib request AbstractBasicAuthHandler password_mgr None This is a mixin class that helps with HTTP authentication both to the remote host and to a proxy password_mgr if given should be something that is compatible with HTTPPasswordMgr refer to section HTTPPasswordMgr Objects for information on the interface that must be supported If passwd_mgr also provides is_authenticated and update_authenticated methods see HTTPPasswordMgrWithPriorAuth Objects then the handler will use the is_authenticated result for a given URI to determine whether or not to send authentication credentials with the request If is_authenticated returns True for the URI credentials are sent If is_authenticated is False credentials are not sent and then if a 401 response is received the request is re sent with the authentication credentials If authentication succeeds update_authenticated is called to set is_authenticated True for the URI so that subsequent requests to the URI or any of its super URIs will automatically include the authentication credentials New in version 3 5 Added is_authenticated support class urllib request HTTPBasicAuthHandler password_mgr None Handle authentication with the remote host password_mgr if given should be something that is compatible with HTTPPasswordMgr refer to section HTTPPasswordMgr Objects for information on the interface that must be supported HTTPBasicAuthHandler will raise a ValueError when presented with a wrong Authentication scheme class urllib request ProxyBasicAuthHandler password_mgr None Handle authentication with the proxy password_mgr if given should be something that is compatible with HTTPPasswordMgr refer to section HTTPPasswordMgr Objects for information on the interface that must be supported class urllib request AbstractDigestAuthHandler password_mgr None This is a mixin class that helps with HTTP authentication both to the remote host and to a proxy password_mgr if given should be something that is compatible with HTTPPasswordMgr refer to section HTTPPasswordMgr Objects for information on the interface that must be supported class urllib request HTTPDigestAuthHandler password_mgr None Handle authentication with the remote host password_mgr if given should be something that is compatible with HTTPPasswordMgr refer to section HTTPPasswordMgr Objects for information on the interface that must be supported When both Digest Authentication Handler and Basic Authentication Handler are both added Digest Authentication is always tried first If the Digest Authentication returns a 40x response again it is sent to Basic Authentication handler to Handle This Handler method will raise a ValueError when presented with an authentication scheme other than Digest or Basic Changed in version 3 3 Raise ValueError on unsupported Authentication Scheme class urllib request ProxyDigestAuthHandler password_mgr None Handle authentication with the proxy password_mgr if given should be something that is compatible with HTTPPasswordMgr refer to section HTTPPasswordMgr Objects for information on the interface that must be supported class urllib request HTTPHandler A class to handle opening of HTTP URLs class urllib request HTTPSHandler debuglevel 0 context None check_hostname None A class to handle opening of HTTPS URLs context and check_hostname have the same meaning as in http client HTTPSConnection Changed in version 3 2 context and check_hostname were added class urllib request FileHandler Open local files class urllib request DataHandler Open data URLs New in version 3 4 class urllib request FTPHandler Open FTP URLs class urllib request CacheFTPHandler Open FTP URLs keeping a cache of open FTP connections to minimize delays class urllib request UnknownHandler A catch all class to handle unknown URLs class urllib request HTTPErrorProcessor Process HTTP error responses Request Objects The following methods d,en
1159,escribe Request s public interface and so all may be overridden in subclasses It also defines several public attributes that can be used by clients to inspect the parsed request Request full_url The original URL passed to the constructor Changed in version 3 4 Request full_url is a property with setter getter and a deleter Getting full_url returns the original request URL with the fragment if it was present Request type The URI scheme Request host The URI authority typically a host but may also contain a port separated by a colon Request origin_req_host The original host for the request without port Request selector The URI path If the Request uses a proxy then selector will be the full URL that is passed to the proxy Request data The entity body for the request or None if not specified Changed in version 3 4 Changing value of Request data now deletes Content Length header if it was previously set or calculated Request unverifiable boolean indicates whether the request is unverifiable as defined by RFC 2965 Request method The HTTP request method to use By default its value is None which means that get_method will do its normal computation of the method to be used Its value can be set thus overriding the default computation in get_method either by providing a default value by setting it at the class level in a Request subclass or by passing a value in to the Request constructor via the method argument New in version 3 3 Changed in version 3 4 A default value can now be set in subclasses previously it could only be set via the constructor argument Request get_method Return a string indicating the HTTP request method If Request method is not None return its value otherwise return GET if Request data is None or POST if it s not This is only meaningful for HTTP requests Changed in version 3 3 get_method now looks at the value of Request method Request add_header key val Add another header to the request Headers are currently ignored by all handlers except HTTP handlers where they are added to the list of headers sent to the server Note that there cannot be more than one header with the same name and later calls will overwrite previous calls in case the key collides Currently this is no loss of HTTP functionality since all headers which have meaning when used more than once have a header specific way of gaining the same functionality using only one header Note that headers added using this method are also added to redirected requests Request add_unredirected_header key header Add a header that will not be added to a redirected request Request has_header header Return whether the instance has the named header checks both regular and unredirected Request remove_header header Remove named header from the request instance both from regular and unredirected headers New in version 3 4 Request get_full_url Return the URL given in the constructor Changed in version 3 4 Returns Request full_url Request set_proxy host type Prepare the request by connecting to a proxy server The host and type will replace those of the instance and the instance s selector will be the original URL given in the constructor Request get_header header_name default None Return the value of the given header If the header is not present return the default value Request header_items Return a list of tuples header_name header_value of the Request headers Changed in version 3 4 The request methods add_data has_data get_data get_type get_host get_selector get_origin_req_host and is_unverifiable that were deprecated since 3 3 have been removed OpenerDirector Objects OpenerDirector instances have the following methods OpenerDirector add_handler handler handler should be an instance of BaseHandler The following methods are searched and added to the possible chains note that HTTP errors are a special case Note that in the following protocol should be replaced with the actual protocol to handle for example http_response would be the HTTP protocol response handler Also type should be replaced with the actual HTTP code for example http_error_404 would handle HTTP 404 errors,en
1160, protocol _open signal that the handler knows how to open protocol URLs See BaseHandler protocol _open for more information http_error_ type signal that the handler knows how to handle HTTP errors with HTTP error code type See BaseHandler http_error_ nnn for more information protocol _error signal that the handler knows how to handle errors from non http protocol protocol _request signal that the handler knows how to pre process protocol requests See BaseHandler protocol _request for more information protocol _response signal that the handler knows how to post process protocol responses See BaseHandler protocol _response for more information OpenerDirector open url data None timeout Open the given url which can be a request object or a string optionally passing the given data Arguments return values and exceptions raised are the same as those of urlopen which simply calls the open method on the currently installed global OpenerDirector The optional timeout parameter specifies a timeout in seconds for blocking operations like the connection attempt if not specified the global default timeout setting will be used The timeout feature actually works only for HTTP HTTPS and FTP connections OpenerDirector error proto args Handle an error of the given protocol This will call the registered error handlers for the given protocol with the given arguments which are protocol specific The HTTP protocol is a special case which uses the HTTP response code to determine the specific error handler refer to the http_error_ type methods of the handler classes Return values and exceptions raised are the same as those of urlopen OpenerDirector objects open URLs in three stages The order in which these methods are called within each stage is determined by sorting the handler instances 1 Every handler with a method named like protocol _request has that method called to pre process the request 2 Handlers with a method named like protocol _open are called to handle the request This stage ends when a handler either returns a non None value ie a response or raises an exception usually URLError Exceptions are allowed to propagate In fact the above algorithm is first tried for methods named default_open If all such methods return None the algorithm is repeated for methods named like protocol _open If all such methods return None the algorithm is repeated for methods named unknown_open Note that the implementation of these methods may involve calls of the parent OpenerDirector instance s open and error methods 3 Every handler with a method named like protocol _response has that method called to post process the response BaseHandler Objects BaseHandler objects provide a couple of methods that are directly useful and others that are meant to be used by derived classes These are intended for direct use BaseHandler add_parent director Add a director as parent BaseHandler close Remove any parents The following attribute and methods should only be used by classes derived from BaseHandler Note The convention has been adopted that subclasses defining protocol _request or protocol _response methods are named Processor all others are named Handler BaseHandler parent A valid OpenerDirector which can be used to open using a different protocol or handle errors BaseHandler default_open req This method is not defined in BaseHandler but subclasses should define it if they want to catch all URLs This method if implemented will be called by the parent OpenerDirector It should return a file like object as described in the return value of the open method of OpenerDirector or None It should raise URLError unless a truly exceptional thing happens for example MemoryError should not be mapped to URLError This method will be called before any protocol specific open method BaseHandler protocol _open req This method is not defined in BaseHandler but subclasses should define it if they want to handle URLs with the given protocol This method if defined will be called by the parent OpenerDirector Return values should be the same as for default_open BaseHandler unknown_open req Thi,en
1161,s method is not defined in BaseHandler but subclasses should define it if they want to catch all URLs with no specific registered handler to open it This method if implemented will be called by the parent OpenerDirector Return values should be the same as for default_open BaseHandler http_error_default req fp code msg hdrs This method is not defined in BaseHandler but subclasses should override it if they intend to provide a catch all for otherwise unhandled HTTP errors It will be called automatically by the OpenerDirector getting the error and should not normally be called in other circumstances req will be a Request object fp will be a file like object with the HTTP error body code will be the three digit code of the error msg will be the user visible explanation of the code and hdrs will be a mapping object with the headers of the error Return values and exceptions raised should be the same as those of urlopen BaseHandler http_error_ nnn req fp code msg hdrs nnn should be a three digit HTTP error code This method is also not defined in BaseHandler but will be called if it exists on an instance of a subclass when an HTTP error with code nnn occurs Subclasses should override this method to handle specific HTTP errors Arguments return values and exceptions raised should be the same as for http_error_default BaseHandler protocol _request req This method is not defined in BaseHandler but subclasses should define it if they want to pre process requests of the given protocol This method if defined will be called by the parent OpenerDirector req will be a Request object The return value should be a Request object BaseHandler protocol _response req response This method is not defined in BaseHandler but subclasses should define it if they want to post process responses of the given protocol This method if defined will be called by the parent OpenerDirector req will be a Request object response will be an object implementing the same interface as the return value of urlopen The return value should implement the same interface as the return value of urlopen HTTPRedirectHandler Objects Note Some HTTP redirections require action from this module s client code If this is the case HTTPError is raised See RFC 2616 for details of the precise meanings of the various redirection codes An HTTPError exception raised as a security consideration if the HTTPRedirectHandler is presented with a redirected URL which is not an HTTP HTTPS or FTP URL HTTPRedirectHandler redirect_request req fp code msg hdrs newurl Return a Request or None in response to a redirect This is called by the default implementations of the http_error_30 methods when a redirection is received from the server If a redirection should take place return a new Request to allow http_error_30 to perform the redirect to newurl Otherwise raise HTTPError if no other handler should try to handle this URL or return None if you can t but another handler might Note The default implementation of this method does not strictly follow RFC 2616 which says that 301 and 302 responses to POST requests must not be automatically redirected without confirmation by the user In reality browsers do allow automatic redirection of these responses changing the POST to a GET and the default implementation reproduces this behavior HTTPRedirectHandler http_error_301 req fp code msg hdrs Redirect to the Location or URI URL This method is called by the parent OpenerDirector when getting an HTTP moved permanently response HTTPRedirectHandler http_error_302 req fp code msg hdrs The same as http_error_301 but called for the found response HTTPRedirectHandler http_error_303 req fp code msg hdrs The same as http_error_301 but called for the see other response HTTPRedirectHandler http_error_307 req fp code msg hdrs The same as http_error_301 but called for the temporary redirect response It does not allow changing the request method from POST to GET HTTPRedirectHandler http_error_308 req fp code msg hdrs The same as http_error_301 but called for the permanent redirect response It does not allow changing the reques,en
1162,t method from POST to GET New in version 3 11 HTTPCookieProcessor Objects HTTPCookieProcessor instances have one attribute HTTPCookieProcessor cookiejar The http cookiejar CookieJar in which cookies are stored ProxyHandler Objects ProxyHandler protocol _open request The ProxyHandler will have a method protocol _open for every protocol which has a proxy in the proxies dictionary given in the constructor The method will modify requests to go through the proxy by calling request set_proxy and call the next handler in the chain to actually execute the protocol HTTPPasswordMgr Objects These methods are available on HTTPPasswordMgr and HTTPPasswordMgrWithDefaultRealm objects HTTPPasswordMgr add_password realm uri user passwd uri can be either a single URI or a sequence of URIs realm user and passwd must be strings This causes user passwd to be used as authentication tokens when authentication for realm and a super URI of any of the given URIs is given HTTPPasswordMgr find_user_password realm authuri Get user password for given realm and URI if any This method will return None None if there is no matching user password For HTTPPasswordMgrWithDefaultRealm objects the realm None will be searched if the given realm has no matching user password HTTPPasswordMgrWithPriorAuth Objects This password manager extends HTTPPasswordMgrWithDefaultRealm to support tracking URIs for which authentication credentials should always be sent HTTPPasswordMgrWithPriorAuth add_password realm uri user passwd is_authenticated False realm uri user passwd are as for HTTPPasswordMgr add_password is_authenticated sets the initial value of the is_authenticated flag for the given URI or list of URIs If is_authenticated is specified as True realm is ignored HTTPPasswordMgrWithPriorAuth find_user_password realm authuri Same as for HTTPPasswordMgrWithDefaultRealm objects HTTPPasswordMgrWithPriorAuth update_authenticated self uri is_authenticated False Update the is_authenticated flag for the given uri or list of URIs HTTPPasswordMgrWithPriorAuth is_authenticated self authuri Returns the current state of the is_authenticated flag for the given URI AbstractBasicAuthHandler Objects AbstractBasicAuthHandler http_error_auth_reqed authreq host req headers Handle an authentication request by getting a user password pair and re trying the request authreq should be the name of the header where the information about the realm is included in the request host specifies the URL and path to authenticate for req should be the failed Request object and headers should be the error headers host is either an authority e g python org or a URL containing an authority component e g http python org In either case the authority must not contain a userinfo component so python org and python org 80 are fine joe password python org is not HTTPBasicAuthHandler Objects HTTPBasicAuthHandler http_error_401 req fp code msg hdrs Retry the request with authentication information if available ProxyBasicAuthHandler Objects ProxyBasicAuthHandler http_error_407 req fp code msg hdrs Retry the request with authentication information if available AbstractDigestAuthHandler Objects AbstractDigestAuthHandler http_error_auth_reqed authreq host req headers authreq should be the name of the header where the information about the realm is included in the request host should be the host to authenticate to req should be the failed Request object and headers should be the error headers HTTPDigestAuthHandler Objects HTTPDigestAuthHandler http_error_401 req fp code msg hdrs Retry the request with authentication information if available ProxyDigestAuthHandler Objects ProxyDigestAuthHandler http_error_407 req fp code msg hdrs Retry the request with authentication information if available HTTPHandler Objects HTTPHandler http_open req Send an HTTP request which can be either GET or POST depending on req has_data HTTPSHandler Objects HTTPSHandler https_open req Send an HTTPS request which can be either GET or POST depending on req has_data FileHandler Objects FileHandler file_open req Open the file locally if there is ,en
1163,no host name or the host name is localhost Changed in version 3 2 This method is applicable only for local hostnames When a remote hostname is given an URLError is raised DataHandler Objects DataHandler data_open req Read a data URL This kind of URL contains the content encoded in the URL itself The data URL syntax is specified in RFC 2397 This implementation ignores white spaces in base64 encoded data URLs so the URL may be wrapped in whatever source file it comes from But even though some browsers don t mind about a missing padding at the end of a base64 encoded data URL this implementation will raise an ValueError in that case FTPHandler Objects FTPHandler ftp_open req Open the FTP file indicated by req The login is always done with empty username and password CacheFTPHandler Objects CacheFTPHandler objects are FTPHandler objects with the following additional methods CacheFTPHandler setTimeout t Set timeout of connections to t seconds CacheFTPHandler setMaxConns m Set maximum number of cached connections to m UnknownHandler Objects UnknownHandler unknown_open Raise a URLError exception HTTPErrorProcessor Objects HTTPErrorProcessor http_response request response Process HTTP error responses For 200 error codes the response object is returned immediately For non 200 error codes this simply passes the job on to the http_error_ type handler methods via OpenerDirector error Eventually HTTPDefaultErrorHandler will raise an HTTPError if no other handler handles the error HTTPErrorProcessor https_response request response Process HTTPS error responses The behavior is same as http_response Examples In addition to the examples below more examples are given in HOWTO Fetch Internet Resources Using The urllib Package This example gets the python org main page and displays the first 300 bytes of it import urllib request with urllib request urlopen http www python org as f print f read 300 b DOCTYPE html PUBLIC W3C DTD XHTML 1 0 Transitional EN http www w3 org TR xhtml1 DTD xhtml1 transitional dtd n n n html xmlns http www w3 org 1999 xhtml xml lang en lang en n n head n meta http equiv content type content text html charset utf 8 n title Python Programming Note that urlopen returns a bytes object This is because there is no way for urlopen to automatically determine the encoding of the byte stream it receives from the HTTP server In general a program will decode the returned bytes object to string once it determines or guesses the appropriate encoding The following W3C document https www w3 org International O charset lists the various ways in which an X HTML or an XML document could have specified its encoding information As the python org website uses utf 8 encoding as specified in its meta tag we will use the same for decoding the bytes object with urllib request urlopen http www python org as f print f read 100 decode utf 8 DOCTYPE html PUBLIC W3C DTD XHTML 1 0 Transitional EN http www w3 org TR xhtml1 DTD xhtm It is also possible to achieve the same result without using the context manager approach import urllib request f urllib request urlopen http www python org print f read 100 decode utf 8 DOCTYPE html PUBLIC W3C DTD XHTML 1 0 Transitional EN http www w3 org TR xhtml1 DTD xhtm In the following example we are sending a data stream to the stdin of a CGI and reading the data it returns to us Note that this example will only work when the Python installation supports SSL import urllib request req urllib request Request url https localhost cgi bin test cgi data b This data is passed to stdin of the CGI with urllib request urlopen req as f print f read decode utf 8 Got Data This data is passed to stdin of the CGI The code for the sample CGI used in the above example is usr bin env python import sys data sys stdin read print Content type text plain n nGot Data s data Here is an example of doing a PUT request using Request import urllib request DATA b some data req urllib request Request url http localhost 8080 data DATA method PUT with urllib request urlopen req as f pass print f status print f reason Use of Basic HTTP Authentica,en
1164,tion import urllib request Create an OpenerDirector with support for Basic HTTP Authentication auth_handler urllib request HTTPBasicAuthHandler auth_handler add_password realm PDQ Application uri https mahler 8092 site updates py user klem passwd kadidd ehopper opener urllib request build_opener auth_handler and install it globally so it can be used with urlopen urllib request install_opener opener urllib request urlopen http www example com login html build_opener provides many handlers by default including a ProxyHandler By default ProxyHandler uses the environment variables named scheme _proxy where scheme is the URL scheme involved For example the http_proxy environment variable is read to obtain the HTTP proxy s URL This example replaces the default ProxyHandler with one that uses programmatically supplied proxy URLs and adds proxy authorization support with ProxyBasicAuthHandler proxy_handler urllib request ProxyHandler http http www example com 3128 proxy_auth_handler urllib request ProxyBasicAuthHandler proxy_auth_handler add_password realm host username password opener urllib request build_opener proxy_handler proxy_auth_handler This time rather than install the OpenerDirector we use it directly opener open http www example com login html Adding HTTP headers Use the headers argument to the Request constructor or import urllib request req urllib request Request http www example com req add_header Referer http www python org Customize the default User Agent header value req add_header User Agent urllib example 0 1 Contact r urllib request urlopen req OpenerDirector automatically adds a User Agent header to every Request To change this import urllib request opener urllib request build_opener opener addheaders User agent Mozilla 5 0 opener open http www example com Also remember that a few standard headers Content Length Content Type and Host are added when the Request is passed to urlopen or OpenerDirector open Here is an example session that uses the GET method to retrieve a URL containing parameters import urllib request import urllib parse params urllib parse urlencode spam 1 eggs 2 bacon 0 url http www musi cal com cgi bin query s params with urllib request urlopen url as f print f read decode utf 8 The following example uses the POST method instead Note that params output from urlencode is encoded to bytes before it is sent to urlopen as data import urllib request import urllib parse data urllib parse urlencode spam 1 eggs 2 bacon 0 data data encode ascii with urllib request urlopen http requestb in xrbl82xr data as f print f read decode utf 8 The following example uses an explicitly specified HTTP proxy overriding environment settings import urllib request proxies http http proxy example com 8080 opener urllib request FancyURLopener proxies with opener open http www python org as f f read decode utf 8 The following example uses no proxies at all overriding environment settings import urllib request opener urllib request FancyURLopener with opener open http www python org as f f read decode utf 8 Legacy interface The following functions and classes are ported from the Python 2 module urllib as opposed to urllib2 They might become deprecated at some point in the future urllib request urlretrieve url filename None reporthook None data None Copy a network object denoted by a URL to a local file If the URL points to a local file the object will not be copied unless filename is supplied Return a tuple filename headers where filename is the local file name under which the object can be found and headers is whatever the info method of the object returned by urlopen returned for a remote object Exceptions are the same as for urlopen The second argument if present specifies the file location to copy to if absent the location will be a tempfile with a generated name The third argument if present is a callable that will be called once on establishment of the network connection and once after each block read thereafter The callable will be passed three arguments a count of blocks transferred so far a block size in bytes a,en
1165,nd the total size of the file The third argument may be 1 on older FTP servers which do not return a file size in response to a retrieval request The following example illustrates the most common usage scenario import urllib request local_filename headers urllib request urlretrieve http python org html open local_filename html close If the url uses the http scheme identifier the optional data argument may be given to specify a POST request normally the request type is GET The data argument must be a bytes object in standard application x www form urlencoded format see the urllib parse urlencode function urlretrieve will raise ContentTooShortError when it detects that the amount of data available was less than the expected amount which is the size reported by a Content Length header This can occur for example when the download is interrupted The Content Length is treated as a lower bound if there s more data to read urlretrieve reads more data but if less data is available it raises the exception You can still retrieve the downloaded data in this case it is stored in the content attribute of the exception instance If no Content Length header was supplied urlretrieve can not check the size of the data it has downloaded and just returns it In this case you just have to assume that the download was successful urllib request urlcleanup Cleans up temporary files that may have been left behind by previous calls to urlretrieve class urllib request URLopener proxies None x509 Deprecated since version 3 3 Base class for opening and reading URLs Unless you need to support opening objects using schemes other than http ftp or file you probably want to use FancyURLopener By default the URLopener class sends a User Agent header of urllib VVV where VVV is the urllib version number Applications can define their own User Agent header by subclassing URLopener or FancyURLopener and setting the class attribute version to an appropriate string value in the subclass definition The optional proxies parameter should be a dictionary mapping scheme names to proxy URLs where an empty dictionary turns proxies off completely Its default value is None in which case environmental proxy settings will be used if present as discussed in the definition of urlopen above Additional keyword parameters collected in x509 may be used for authentication of the client when using the https scheme The keywords key_file and cert_file are supported to provide an SSL key and certificate both are needed to support client authentication URLopener objects will raise an OSError exception if the server returns an error code open fullurl data None Open fullurl using the appropriate protocol This method sets up cache and proxy information then calls the appropriate open method with its input arguments If the scheme is not recognized open_unknown is called The data argument has the same meaning as the data argument of urlopen This method always quotes fullurl using quote open_unknown fullurl data None Overridable interface to open unknown URL types retrieve url filename None reporthook None data None Retrieves the contents of url and places it in filename The return value is a tuple consisting of a local filename and either an email message Message object containing the response headers for remote URLs or None for local URLs The caller must then open and read the contents of filename If filename is not given and the URL refers to a local file the input filename is returned If the URL is non local and filename is not given the filename is the output of tempfile mktemp with a suffix that matches the suffix of the last path component of the input URL If reporthook is given it must be a function accepting three numeric parameters A chunk number the maximum size chunks are read in and the total size of the download 1 if unknown It will be called once at the start and after each chunk of data is read from the network reporthook is ignored for local URLs If the url uses the http scheme identifier the optional data argument may be given to specify a POST request normally the request t,en
1166,ype is GET The data argument must in standard application x www form urlencoded format see the urllib parse urlencode function version Variable that specifies the user agent of the opener object To get urllib to tell servers that it is a particular user agent set this in a subclass as a class variable or in the constructor before calling the base constructor class urllib request FancyURLopener Deprecated since version 3 3 FancyURLopener subclasses URLopener providing default handling for the following HTTP response codes 301 302 303 307 and 401 For the 30x response codes listed above the Location header is used to fetch the actual URL For 401 response codes authentication required basic HTTP authentication is performed For the 30x response codes recursion is bounded by the value of the maxtries attribute which defaults to 10 For all other response codes the method http_error_default is called which you can override in subclasses to handle the error appropriately Note According to the letter of RFC 2616 301 and 302 responses to POST requests must not be automatically redirected without confirmation by the user In reality browsers do allow automatic redirection of these responses changing the POST to a GET and urllib reproduces this behaviour The parameters to the constructor are the same as those for URLopener Note When performing basic authentication a FancyURLopener instance calls its prompt_user_passwd method The default implementation asks the users for the required information on the controlling terminal A subclass may override this method to support more appropriate behavior if needed The FancyURLopener class offers one additional method that should be overloaded to provide the appropriate behavior prompt_user_passwd host realm Return information needed to authenticate the user at the given host in the specified security realm The return value should be a tuple user password which can be used for basic authentication The implementation prompts for this information on the terminal an application should override this method to use an appropriate interaction model in the local environment urllib request Restrictions Currently only the following protocols are supported HTTP versions 0 9 and 1 0 FTP local files and data URLs Changed in version 3 4 Added support for data URLs The caching feature of urlretrieve has been disabled until someone finds the time to hack proper processing of Expiration time headers There should be a function to query whether a particular URL is in the cache For backward compatibility if a URL appears to point to a local file but the file can t be opened the URL is re interpreted using the FTP protocol This can sometimes cause confusing error messages The urlopen and urlretrieve functions can cause arbitrarily long delays while waiting for a network connection to be set up This means that it is difficult to build an interactive web client using these functions without using threads The data returned by urlopen or urlretrieve is the raw data returned by the server This may be binary data such as an image plain text or for example HTML The HTTP protocol provides type information in the reply header which can be inspected by looking at the Content Type header If the returned data is HTML you can use the module html parser to parse it The code handling the FTP protocol cannot differentiate between a file and a directory This can lead to unexpected behavior when attempting to read a URL that points to a file that is not accessible If the URL ends in a it is assumed to refer to a directory and will be handled accordingly But if an attempt to read a file leads to a 550 error meaning the URL cannot be found or is not accessible often for permission reasons then the path is treated as a directory in order to handle the case when a directory is specified by a URL but the trailing has been left off This can cause misleading results when you try to fetch a file whose read permissions make it inaccessible the FTP code will try to read it fail with a 550 error and then perform a directory listing for the unrea,en
1167,dable file If fine grained control is needed consider using the ftplib module subclassing FancyURLopener or changing _urlopener to meet your needs urllib response Response classes used by urllib The urllib response module defines functions and classes which define a minimal file like interface including read and readline Functions defined by this module are used internally by the urllib request module The typical response object is a urllib response addinfourl instance class urllib response addinfourl url URL of the resource retrieved commonly used to determine if a redirect was followed headers Returns the headers of the response in the form of an EmailMessage instance status New in version 3 9 Status code returned by server geturl Deprecated since version 3 9 Deprecated in favor of url info Deprecated since version 3 9 Deprecated in favor of headers code Deprecated since version 3 9 Deprecated in favor of status getcode Deprecated since version 3 9 Deprecated in favor of status,en
1168,What s New In Python 3 0 Author Guido van Rossum This article explains the new features in Python 3 0 compared to 2 6 Python 3 0 also known as Python 3000 or Py3K is the first ever intentionally backwards incompatible Python release Python 3 0 was released on December 3 2008 There are more changes than in a typical release and more that are important for all Python users Nevertheless after digesting the changes you ll find that Python really hasn t changed all that much by and large we re mostly fixing well known annoyances and warts and removing a lot of old cruft This article doesn t attempt to provide a complete specification of all new features but instead tries to give a convenient overview For full details you should refer to the documentation for Python 3 0 and or the many PEPs referenced in the text If you want to understand the complete implementation and design rationale for a particular feature PEPs usually have more details than the regular documentation but note that PEPs usually are not kept up to date once a feature has been fully implemented Due to time constraints this document is not as complete as it should have been As always for a new release the Misc NEWS file in the source distribution contains a wealth of detailed information about every small thing that was changed Common Stumbling Blocks This section lists those few changes that are most likely to trip you up if you re used to Python 2 5 Print Is A Function The print statement has been replaced with a print function with keyword arguments to replace most of the special syntax of the old print statement PEP 3105 Examples Old print The answer is 2 2 New print The answer is 2 2 Old print x Trailing comma suppresses newline New print x end Appends a space instead of a newline Old print Prints a newline New print You must call the function Old print sys stderr fatal error New print fatal error file sys stderr Old print x y prints repr x y New print x y Not the same as print x y You can also customize the separator between items e g print There are 2 32 possibilities sep which produces There are 4294967296 possibilities Note The print function doesn t support the softspace feature of the old print statement For example in Python 2 x print A n B would write A nB n but in Python 3 0 print A n B writes A n B n Initially you ll be finding yourself typing the old print x a lot in interactive mode Time to retrain your fingers to type print x instead When using the 2to3 source to source conversion tool all print statements are automatically converted to print function calls so this is mostly a non issue for larger projects Views And Iterators Instead Of Lists Some well known APIs no longer return lists dict methods dict keys dict items and dict values return views instead of lists For example this no longer works k d keys k sort Use k sorted d instead this works in Python 2 5 too and is just as efficient Also the dict iterkeys dict iteritems and dict itervalues methods are no longer supported map and filter return iterators If you really need a list and the input sequences are all of equal length a quick fix is to wrap map in list e g list map but a better fix is often to use a list comprehension especially when the original code uses lambda or rewriting the code so it doesn t need a list at all Particularly tricky is map invoked for the side effects of the function the correct transformation is to use a regular for loop since creating a list would just be wasteful If the input sequences are not of equal length map will stop at the termination of the shortest of the sequences For full compatibility with map from Python 2 x also wrap the sequences in itertools zip_longest e g map func sequences becomes list map func itertools zip_longest sequences range now behaves like xrange used to behave except it works with values of arbitrary size The latter no longer exists zip now returns an iterator Ordering Comparisons Python 3 0 has simplified the rules for ordering comparisons The ordering comparison operators raise a TypeError exception when the operands don t ha,en
1169,ve a meaningful natural ordering Thus expressions like 1 0 None or len len are no longer valid and e g None None raises TypeError instead of returning False A corollary is that sorting a heterogeneous list no longer makes sense all the elements must be comparable to each other Note that this does not apply to the and operators objects of different incomparable types always compare unequal to each other builtin sorted and list sort no longer accept the cmp argument providing a comparison function Use the key argument instead N B the key and reverse arguments are now keyword only The cmp function should be treated as gone and the __cmp__ special method is no longer supported Use __lt__ for sorting __eq__ with __hash__ and other rich comparisons as needed If you really need the cmp functionality you could use the expression a b a b as the equivalent for cmp a b Integers PEP 237 Essentially long renamed to int That is there is only one built in integral type named int but it behaves mostly like the old long type PEP 238 An expression like 1 2 returns a float Use 1 2 to get the truncating behavior The latter syntax has existed for years at least since Python 2 2 The sys maxint constant was removed since there is no longer a limit to the value of integers However sys maxsize can be used as an integer larger than any practical list or string index It conforms to the implementation s natural integer size and is typically the same as sys maxint in previous releases on the same platform assuming the same build options The repr of a long integer doesn t include the trailing L anymore so code that unconditionally strips that character will chop off the last digit instead Use str instead Octal literals are no longer of the form 0720 use 0o720 instead Text Vs Data Instead Of Unicode Vs 8 bit Everything you thought you knew about binary data and Unicode has changed Python 3 0 uses the concepts of text and binary data instead of Unicode strings and 8 bit strings All text is Unicode however encoded Unicode is represented as binary data The type used to hold text is str the type used to hold data is bytes The biggest difference with the 2 x situation is that any attempt to mix text and data in Python 3 0 raises TypeError whereas if you were to mix Unicode and 8 bit strings in Python 2 x it would work if the 8 bit string happened to contain only 7 bit ASCII bytes but you would get UnicodeDecodeError if it contained non ASCII values This value specific behavior has caused numerous sad faces over the years As a consequence of this change in philosophy pretty much all code that uses Unicode encodings or binary data most likely has to change The change is for the better as in the 2 x world there were numerous bugs having to do with mixing encoded and unencoded text To be prepared in Python 2 x start using unicode for all unencoded text and str for binary or encoded data only Then the 2to3 tool will do most of the work for you You can no longer use u literals for Unicode text However you must use b literals for binary data As the str and bytes types cannot be mixed you must always explicitly convert between them Use str encode to go from str to bytes and bytes decode to go from bytes to str You can also use bytes s encoding and str b encoding respectively Like str the bytes type is immutable There is a separate mutable type to hold buffered binary data bytearray Nearly all APIs that accept bytes also accept bytearray The mutable API is based on collections MutableSequence All backslashes in raw string literals are interpreted literally This means that U and u escapes in raw strings are not treated specially For example r u20ac is a string of 6 characters in Python 3 0 whereas in 2 6 ur u20ac was the single euro character Of course this change only affects raw string literals the euro character is u20ac in Python 3 0 The built in basestring abstract type was removed Use str instead The str and bytes types don t have functionality enough in common to warrant a shared base class The 2to3 tool see below replaces every occurrence of basestring with ,en
1170,str Files opened as text files still the default mode for open always use an encoding to map between strings in memory and bytes on disk Binary files opened with a b in the mode argument always use bytes in memory This means that if a file is opened using an incorrect mode or encoding I O will likely fail loudly instead of silently producing incorrect data It also means that even Unix users will have to specify the correct mode text or binary when opening a file There is a platform dependent default encoding which on Unixy platforms can be set with the LANG environment variable and sometimes also with some other platform specific locale related environment variables In many cases but not all the system default is UTF 8 you should never count on this default Any application reading or writing more than pure ASCII text should probably have a way to override the encoding There is no longer any need for using the encoding aware streams in the codecs module The initial values of sys stdin sys stdout and sys stderr are now unicode only text files i e they are instances of io TextIOBase To read and write bytes data with these streams you need to use their io TextIOBase buffer attribute Filenames are passed to and returned from APIs as Unicode strings This can present platform specific problems because on some platforms filenames are arbitrary byte strings On the other hand on Windows filenames are natively stored as Unicode As a work around most APIs e g open and many functions in the os module that take filenames accept bytes objects as well as strings and a few APIs have a way to ask for a bytes return value Thus os listdir returns a list of bytes instances if the argument is a bytes instance and os getcwdb returns the current working directory as a bytes instance Note that when os listdir returns a list of strings filenames that cannot be decoded properly are omitted rather than raising UnicodeError Some system APIs like os environ and sys argv can also present problems when the bytes made available by the system is not interpretable using the default encoding Setting the LANG variable and rerunning the program is probably the best approach PEP 3138 The repr of a string no longer escapes non ASCII characters It still escapes control characters and code points with non printable status in the Unicode standard however PEP 3120 The default source encoding is now UTF 8 PEP 3131 Non ASCII letters are now allowed in identifiers However the standard library remains ASCII only with the exception of contributor names in comments The StringIO and cStringIO modules are gone Instead import the io module and use io StringIO or io BytesIO for text and data respectively See also the Unicode HOWTO which was updated for Python 3 0 Overview Of Syntax Changes This section gives a brief overview of every syntactic change in Python 3 0 New Syntax PEP 3107 Function argument and return value annotations This provides a standardized way of annotating a function s parameters and return value There are no semantics attached to such annotations except that they can be introspected at runtime using the __annotations__ attribute The intent is to encourage experimentation through metaclasses decorators or frameworks PEP 3102 Keyword only arguments Named parameters occurring after args in the parameter list must be specified using keyword syntax in the call You can also use a bare in the parameter list to indicate that you don t accept a variable length argument list but you do have keyword only arguments Keyword arguments are allowed after the list of base classes in a class definition This is used by the new convention for specifying a metaclass see next section but can be used for other purposes as well as long as the metaclass supports it PEP 3104 nonlocal statement Using nonlocal x you can now assign directly to a variable in an outer but non global scope nonlocal is a new reserved word PEP 3132 Extended Iterable Unpacking You can now write things like a b rest some_sequence And even rest a stuff The rest object is always a possibly empty list the ri,en
1171,ght hand side may be any iterable Example a rest b range 5 This sets a to 0 b to 4 and rest to 1 2 3 Dictionary comprehensions k v for k v in stuff means the same thing as dict stuff but is more flexible This is PEP 274 vindicated Set literals e g 1 2 Note that is an empty dictionary use set for an empty set Set comprehensions are also supported e g x for x in stuff means the same thing as set stuff but is more flexible New octal literals e g 0o720 already in 2 6 The old octal literals 0720 are gone New binary literals e g 0b1010 already in 2 6 and there is a new corresponding built in function bin Bytes literals are introduced with a leading b or B and there is a new corresponding built in function bytes Changed Syntax PEP 3109 and PEP 3134 new raise statement syntax raise expr from expr See below as and with are now reserved words Since 2 6 actually True False and None are reserved words 2 6 partially enforced the restrictions on None already Change from except exc var to except exc as var See PEP 3110 PEP 3115 New Metaclass Syntax Instead of class C __metaclass__ M you must now use class C metaclass M The module global __metaclass__ variable is no longer supported It was a crutch to make it easier to default to new style classes without deriving every class from object List comprehensions no longer support the syntactic form for var in item1 item2 Use for var in item1 item2 instead Also note that list comprehensions have different semantics they are closer to syntactic sugar for a generator expression inside a list constructor and in particular the loop control variables are no longer leaked into the surrounding scope The ellipsis can be used as an atomic expression anywhere Previously it was only allowed in slices Also it must now be spelled as Previously it could also be spelled as by a mere accident of the grammar Removed Syntax PEP 3113 Tuple parameter unpacking removed You can no longer write def foo a b c Use def foo a b_c b c b_c instead Removed backticks use repr instead Removed use instead Removed keyword exec is no longer a keyword it remains as a function Fortunately the function syntax was also accepted in 2 x Also note that exec no longer takes a stream argument instead of exec f you can use exec f read Integer literals no longer support a trailing l or L String literals no longer support a leading u or U The from module import syntax is only allowed at the module level no longer inside functions The only acceptable syntax for relative imports is from module import name All import forms not starting with are interpreted as absolute imports PEP 328 Classic classes are gone Changes Already Present In Python 2 6 Since many users presumably make the jump straight from Python 2 5 to Python 3 0 this section reminds the reader of new features that were originally designed for Python 3 0 but that were back ported to Python 2 6 The corresponding sections in What s New in Python 2 6 should be consulted for longer descriptions PEP 343 The with statement The with statement is now a standard feature and no longer needs to be imported from the __future__ Also check out Writing Context Managers and The contextlib module PEP 366 Explicit Relative Imports From a Main Module This enhances the usefulness of the m option when the referenced module lives in a package PEP 370 Per user site packages Directory PEP 371 The multiprocessing Package PEP 3101 Advanced String Formatting Note the 2 6 description mentions the format method for both 8 bit and Unicode strings In 3 0 only the str type text strings with Unicode support supports this method the bytes type does not The plan is to eventually make this the only API for string formatting and to start deprecating the operator in Python 3 1 PEP 3105 print As a Function This is now a standard feature and no longer needs to be imported from __future__ More details were given above PEP 3110 Exception Handling Changes The except exc as var syntax is now standard and except exc var is no longer supported Of course the as var part is still optional PEP 3112 Byte Literals The b string li,en
1172,teral notation and its variants like b b and br now produces a literal of type bytes PEP 3116 New I O Library The io module is now the standard way of doing file I O The built in open function is now an alias for io open and has additional keyword arguments encoding errors newline and closefd Also note that an invalid mode argument now raises ValueError not IOError The binary file object underlying a text file object can be accessed as f buffer but beware that the text object maintains a buffer of itself in order to speed up the encoding and decoding operations PEP 3118 Revised Buffer Protocol The old builtin buffer is now really gone the new builtin memoryview provides mostly similar functionality PEP 3119 Abstract Base Classes The abc module and the ABCs defined in the collections module plays a somewhat more prominent role in the language now and built in collection types like dict and list conform to the collections MutableMapping and collections MutableSequence ABCs respectively PEP 3127 Integer Literal Support and Syntax As mentioned above the new octal literal notation is the only one supported and binary literals have been added PEP 3129 Class Decorators PEP 3141 A Type Hierarchy for Numbers The numbers module is another new use of ABCs defining Python s numeric tower Also note the new fractions module which implements numbers Rational Library Changes Due to time constraints this document does not exhaustively cover the very extensive changes to the standard library PEP 3108 is the reference for the major changes to the library Here s a capsule review Many old modules were removed Some like gopherlib no longer used and md5 replaced by hashlib were already deprecated by PEP 4 Others were removed as a result of the removal of support for various platforms such as Irix BeOS and Mac OS 9 see PEP 11 Some modules were also selected for removal in Python 3 0 due to lack of use or because a better replacement exists See PEP 3108 for an exhaustive list The bsddb3 package was removed because its presence in the core standard library has proved over time to be a particular burden for the core developers due to testing instability and Berkeley DB s release schedule However the package is alive and well externally maintained at https www jcea es programacion pybsddb htm Some modules were renamed because their old name disobeyed PEP 8 or for various other reasons Here s the list Old Name New Name _winreg winreg ConfigParser configparser copy_reg copyreg Queue queue SocketServer socketserver markupbase _markupbase repr reprlib test test_support test support A common pattern in Python 2 x is to have one version of a module implemented in pure Python with an optional accelerated version implemented as a C extension for example pickle and cPickle This places the burden of importing the accelerated version and falling back on the pure Python version on each user of these modules In Python 3 0 the accelerated versions are considered implementation details of the pure Python versions Users should always import the standard version which attempts to import the accelerated version and falls back to the pure Python version The pickle cPickle pair received this treatment The profile module is on the list for 3 1 The StringIO module has been turned into a class in the io module Some related modules have been grouped into packages and usually the submodule names have been simplified The resulting new packages are dbm anydbm dbhash dbm dumbdbm gdbm whichdb html HTMLParser htmlentitydefs http httplib BaseHTTPServer CGIHTTPServer SimpleHTTPServer Cookie cookielib tkinter all Tkinter related modules except turtle The target audience of turtle doesn t really care about tkinter Also note that as of Python 2 6 the functionality of turtle has been greatly enhanced urllib urllib urllib2 urlparse robotparse xmlrpc xmlrpclib DocXMLRPCServer SimpleXMLRPCServer Some other changes to standard library modules not covered by PEP 3108 Killed sets Use the built in set class Cleanup of the sys module removed sys exitfunc sys exc_clear sys exc_type sys exc_va,en
1173,lue sys exc_traceback Note that sys last_type etc remain Cleanup of the array array type the read and write methods are gone use fromfile and tofile instead Also the c typecode for array is gone use either b for bytes or u for Unicode characters Cleanup of the operator module removed sequenceIncludes and isCallable Cleanup of the thread module acquire_lock and release_lock are gone use acquire and release instead Cleanup of the random module removed the jumpahead API The new module is gone The functions os tmpnam os tempnam and os tmpfile have been removed in favor of the tempfile module The tokenize module has been changed to work with bytes The main entry point is now tokenize tokenize instead of generate_tokens string letters and its friends string lowercase and string uppercase are gone Use string ascii_letters etc instead The reason for the removal is that string letters and friends had locale specific behavior which is a bad idea for such attractively named global constants Renamed module __builtin__ to builtins removing the underscores adding an s The __builtins__ variable found in most global namespaces is unchanged To modify a builtin you should use builtins not __builtins__ PEP 3101 A New Approach To String Formatting A new system for built in string formatting operations replaces the string formatting operator However the operator is still supported it will be deprecated in Python 3 1 and removed from the language at some later time Read PEP 3101 for the full scoop Changes To Exceptions The APIs for raising and catching exception have been cleaned up and new powerful features added PEP 352 All exceptions must be derived directly or indirectly from BaseException This is the root of the exception hierarchy This is not new as a recommendation but the requirement to inherit from BaseException is new Python 2 6 still allowed classic classes to be raised and placed no restriction on what you can catch As a consequence string exceptions are finally truly and utterly dead Almost all exceptions should actually derive from Exception BaseException should only be used as a base class for exceptions that should only be handled at the top level such as SystemExit or KeyboardInterrupt The recommended idiom for handling all exceptions except for this latter category is to use except Exception StandardError was removed Exceptions no longer behave as sequences Use the args attribute instead PEP 3109 Raising exceptions You must now use raise Exception args instead of raise Exception args Additionally you can no longer explicitly specify a traceback instead if you have to do this you can assign directly to the __traceback__ attribute see below PEP 3110 Catching exceptions You must now use except SomeException as variable instead of except SomeException variable Moreover the variable is explicitly deleted when the except block is left PEP 3134 Exception chaining There are two cases implicit chaining and explicit chaining Implicit chaining happens when an exception is raised in an except or finally handler block This usually happens due to a bug in the handler block we call this a secondary exception In this case the original exception that was being handled is saved as the __context__ attribute of the secondary exception Explicit chaining is invoked with this syntax raise SecondaryException from primary_exception where primary_exception is any expression that produces an exception object probably an exception that was previously caught In this case the primary exception is stored on the __cause__ attribute of the secondary exception The traceback printed when an unhandled exception occurs walks the chain of __cause__ and __context__ attributes and prints a separate traceback for each component of the chain with the primary exception at the top Java users may recognize this behavior PEP 3134 Exception objects now store their traceback as the __traceback__ attribute This means that an exception object now contains all the information pertaining to an exception and there are fewer reasons to use sys exc_info though the latter is not ,en
1174,removed A few exception messages are improved when Windows fails to load an extension module For example error code 193 is now 1 is not a valid Win32 application Strings now deal with non English locales Miscellaneous Other Changes Operators And Special Methods now returns the opposite of unless returns NotImplemented The concept of unbound methods has been removed from the language When referencing a method as a class attribute you now get a plain function object __getslice__ __setslice__ and __delslice__ were killed The syntax a i j now translates to a __getitem__ slice i j or __setitem__ or __delitem__ when used as an assignment or deletion target respectively PEP 3114 the standard next method has been renamed to __next__ The __oct__ and __hex__ special methods are removed oct and hex use __index__ now to convert the argument to an integer Removed support for __members__ and __methods__ The function attributes named func_X have been renamed to use the __X__ form freeing up these names in the function attribute namespace for user defined attributes To wit func_closure func_code func_defaults func_dict func_doc func_globals func_name were renamed to __closure__ __code__ __defaults__ __dict__ __doc__ __globals__ __name__ respectively __nonzero__ is now __bool__ Builtins PEP 3135 New super You can now invoke super without arguments and assuming this is in a regular instance method defined inside a class statement the right class and instance will automatically be chosen With arguments the behavior of super is unchanged PEP 3111 raw_input was renamed to input That is the new input function reads a line from sys stdin and returns it with the trailing newline stripped It raises EOFError if the input is terminated prematurely To get the old behavior of input use eval input A new built in function next was added to call the __next__ method on an object The round function rounding strategy and return type have changed Exact halfway cases are now rounded to the nearest even result instead of away from zero For example round 2 5 now returns 2 rather than 3 round x n now delegates to x __round__ n instead of always returning a float It generally returns an integer when called with a single argument and a value of the same type as x when called with two arguments Moved intern to sys intern Removed apply Instead of apply f args use f args Removed callable Instead of callable f you can use isinstance f collections Callable The operator isCallable function is also gone Removed coerce This function no longer serves a purpose now that classic classes are gone Removed execfile Instead of execfile fn use exec open fn read Removed the file type Use open There are now several different kinds of streams that open can return in the io module Removed reduce Use functools reduce if you really need it however 99 percent of the time an explicit for loop is more readable Removed reload Use imp reload Removed dict has_key use the in operator instead Build and C API Changes Due to time constraints here is a very incomplete list of changes to the C API Support for several platforms was dropped including but not limited to Mac OS 9 BeOS RISCOS Irix and Tru64 PEP 3118 New Buffer API PEP 3121 Extension Module Initialization Finalization PEP 3123 Making PyObject_HEAD conform to standard C No more C API support for restricted execution PyNumber_Coerce PyNumber_CoerceEx PyMember_Get and PyMember_Set C APIs are removed New C API PyImport_ImportModuleNoBlock works like PyImport_ImportModule but won t block on the import lock returning an error instead Renamed the boolean conversion C level slot and method nb_nonzero is now nb_bool Removed METH_OLDARGS and WITH_CYCLE_GC from the C API Performance The net result of the 3 0 generalizations is that Python 3 0 runs the pystone benchmark around 10 slower than Python 2 5 Most likely the biggest cause is the removal of special casing for small integers There s room for improvement but it will happen after 3 0 is released Porting To Python 3 0 For porting existing Python 2 5 or 2 6 source code to Python 3 0 the best ,en
1175,strategy is the following Prerequisite Start with excellent test coverage Port to Python 2 6 This should be no more work than the average port from Python 2 x to Python 2 x 1 Make sure all your tests pass Still using 2 6 Turn on the 3 command line switch This enables warnings about features that will be removed or change in 3 0 Run your test suite again and fix code that you get warnings about until there are no warnings left and all your tests still pass Run the 2to3 source to source translator over your source code tree See 2to3 Automated Python 2 to 3 code translation for more on this tool Run the result of the translation under Python 3 0 Manually fix up any remaining issues fixing problems until all tests pass again It is not recommended to try to write source code that runs unchanged under both Python 2 6 and 3 0 you d have to use a very contorted coding style e g avoiding print statements metaclasses and much more If you are maintaining a library that needs to support both Python 2 6 and Python 3 0 the best approach is to modify step 3 above by editing the 2 6 version of the source code and running the 2to3 translator again rather than editing the 3 0 version of the source code For porting C extensions to Python 3 0 please see Porting Extension Modules to Python 3,en
1176,rlcompleter Completion function for GNU readline Source code Lib rlcompleter py The rlcompleter module defines a completion function suitable to be passed to set_completer in the readline module When this module is imported on a Unix platform with the readline module available an instance of the Completer class is automatically created and its complete method is set as the readline completer The method provides completion of valid Python identifiers and keywords Example import rlcompleter import readline readline parse_and_bind tab complete readline TAB PRESSED readline __doc__ readline get_line_buffer readline read_init_file readline __file__ readline insert_text readline set_completer readline __name__ readline parse_and_bind readline The rlcompleter module is designed for use with Python s interactive mode Unless Python is run with the S option the module is automatically imported and configured see Readline configuration On platforms without readline the Completer class defined by this module can still be used for custom purposes class rlcompleter Completer Completer objects have the following method complete text state Return the next possible completion for text When called by the readline module this method is called successively with state 0 1 2 until the method returns None If called for text that doesn t include a period character it will complete from names currently defined in __main__ builtins and keywords as defined by the keyword module If called for a dotted name it will try to evaluate anything without obvious side effects functions will not be evaluated but it can generate calls to __getattr__ up to the last part and find matches for the rest via the dir function Any exception raised during the evaluation of the expression is caught silenced and None is returned,en
1177,What s New in Python The What s New in Python series of essays takes tours through the most important changes between major Python versions They are a must read for anyone wishing to stay up to date after a new release What s New In Python 3 12 Summary Release highlights New Features New Features Related to Type Hints Other Language Changes New Modules Improved Modules Optimizations CPython bytecode changes Demos and Tools Deprecated Removed Porting to Python 3 12 Build Changes C API Changes What s New In Python 3 11 Summary Release highlights New Features New Features Related to Type Hints Other Language Changes Other CPython Implementation Changes New Modules Improved Modules Optimizations Faster CPython CPython bytecode changes Deprecated Pending Removal in Python 3 12 Removed Porting to Python 3 11 Build Changes C API Changes Notable changes in 3 11 4 Notable changes in 3 11 5 What s New In Python 3 10 Summary Release highlights New Features New Features Related to Type Hints Other Language Changes New Modules Improved Modules Optimizations Deprecated Removed Porting to Python 3 10 CPython bytecode changes Build Changes C API Changes Notable security feature in 3 10 7 Notable security feature in 3 10 8 Notable changes in 3 10 12 What s New In Python 3 9 Summary Release highlights You should check for DeprecationWarning in your code New Features Other Language Changes New Modules Improved Modules Optimizations Deprecated Removed Porting to Python 3 9 Build Changes C API Changes Notable changes in Python 3 9 1 Notable changes in Python 3 9 2 Notable changes in Python 3 9 3 Notable changes in Python 3 9 5 Notable security feature in 3 9 14 Notable changes in 3 9 17 What s New In Python 3 8 Summary Release highlights New Features Other Language Changes New Modules Improved Modules Optimizations Build and C API Changes Deprecated API and Feature Removals Porting to Python 3 8 Notable changes in Python 3 8 1 Notable changes in Python 3 8 2 Notable changes in Python 3 8 3 Notable changes in Python 3 8 8 Notable changes in Python 3 8 9 Notable changes in Python 3 8 10 Notable changes in Python 3 8 10 Notable changes in Python 3 8 12 Notable security feature in 3 8 14 Notable changes in 3 8 17 What s New In Python 3 7 Summary Release Highlights New Features Other Language Changes New Modules Improved Modules C API Changes Build Changes Optimizations Other CPython Implementation Changes Deprecated Python Behavior Deprecated Python modules functions and methods Deprecated functions and types of the C API Platform Support Removals API and Feature Removals Module Removals Windows only Changes Porting to Python 3 7 Notable changes in Python 3 7 1 Notable changes in Python 3 7 2 Notable changes in Python 3 7 6 Notable changes in Python 3 7 10 Notable changes in Python 3 7 11 Notable security feature in 3 7 14 What s New In Python 3 6 Summary Release highlights New Features Other Language Changes New Modules Improved Modules Optimizations Build and C API Changes Other Improvements Deprecated Removed Porting to Python 3 6 Notable changes in Python 3 6 2 Notable changes in Python 3 6 4 Notable changes in Python 3 6 5 Notable changes in Python 3 6 7 Notable changes in Python 3 6 10 Notable changes in Python 3 6 13 Notable changes in Python 3 6 14 What s New In Python 3 5 Summary Release highlights New Features Other Language Changes New Modules Improved Modules Other module level changes Optimizations Build and C API Changes Deprecated Removed Porting to Python 3 5 Notable changes in Python 3 5 4 What s New In Python 3 4 Summary Release Highlights New Features New Modules Improved Modules CPython Implementation Changes Deprecated Removed Porting to Python 3 4 Changed in 3 4 3 What s New In Python 3 3 Summary Release highlights PEP 405 Virtual Environments PEP 420 Implicit Namespace Packages PEP 3118 New memoryview implementation and buffer protocol documentation PEP 393 Flexible String Representation PEP 397 Python Launcher for Windows PEP 3151 Reworking the OS and IO exception hierarchy PEP 380 Syntax for Delegating to a Subgenerator ,en
1178,PEP 409 Suppressing exception context PEP 414 Explicit Unicode literals PEP 3155 Qualified name for classes and functions PEP 412 Key Sharing Dictionary PEP 362 Function Signature Object PEP 421 Adding sys implementation Using importlib as the Implementation of Import Other Language Changes A Finer Grained Import Lock Builtin functions and types New Modules Improved Modules Optimizations Build and C API Changes Deprecated Porting to Python 3 3 What s New In Python 3 2 PEP 384 Defining a Stable ABI PEP 389 Argparse Command Line Parsing Module PEP 391 Dictionary Based Configuration for Logging PEP 3148 The concurrent futures module PEP 3147 PYC Repository Directories PEP 3149 ABI Version Tagged so Files PEP 3333 Python Web Server Gateway Interface v1 0 1 Other Language Changes New Improved and Deprecated Modules Multi threading Optimizations Unicode Codecs Documentation IDLE Code Repository Build and C API Changes Porting to Python 3 2 What s New In Python 3 1 PEP 372 Ordered Dictionaries PEP 378 Format Specifier for Thousands Separator Other Language Changes New Improved and Deprecated Modules Optimizations IDLE Build and C API Changes Porting to Python 3 1 What s New In Python 3 0 Common Stumbling Blocks Overview Of Syntax Changes Changes Already Present In Python 2 6 Library Changes PEP 3101 A New Approach To String Formatting Changes To Exceptions Miscellaneous Other Changes Build and C API Changes Performance Porting To Python 3 0 What s New in Python 2 7 The Future for Python 2 x Changes to the Handling of Deprecation Warnings Python 3 1 Features PEP 372 Adding an Ordered Dictionary to collections PEP 378 Format Specifier for Thousands Separator PEP 389 The argparse Module for Parsing Command Lines PEP 391 Dictionary Based Configuration For Logging PEP 3106 Dictionary Views PEP 3137 The memoryview Object Other Language Changes New and Improved Modules Build and C API Changes Other Changes and Fixes Porting to Python 2 7 New Features Added to Python 2 7 Maintenance Releases Acknowledgements What s New in Python 2 6 Python 3 0 Changes to the Development Process PEP 343 The with statement PEP 366 Explicit Relative Imports From a Main Module PEP 370 Per user site packages Directory PEP 371 The multiprocessing Package PEP 3101 Advanced String Formatting PEP 3105 print As a Function PEP 3110 Exception Handling Changes PEP 3112 Byte Literals PEP 3116 New I O Library PEP 3118 Revised Buffer Protocol PEP 3119 Abstract Base Classes PEP 3127 Integer Literal Support and Syntax PEP 3129 Class Decorators PEP 3141 A Type Hierarchy for Numbers Other Language Changes New and Improved Modules Deprecations and Removals Build and C API Changes Porting to Python 2 6 Acknowledgements What s New in Python 2 5 PEP 308 Conditional Expressions PEP 309 Partial Function Application PEP 314 Metadata for Python Software Packages v1 1 PEP 328 Absolute and Relative Imports PEP 338 Executing Modules as Scripts PEP 341 Unified try except finally PEP 342 New Generator Features PEP 343 The with statement PEP 352 Exceptions as New Style Classes PEP 353 Using ssize_t as the index type PEP 357 The __index__ method Other Language Changes New Improved and Removed Modules Build and C API Changes Porting to Python 2 5 Acknowledgements What s New in Python 2 4 PEP 218 Built In Set Objects PEP 237 Unifying Long Integers and Integers PEP 289 Generator Expressions PEP 292 Simpler String Substitutions PEP 318 Decorators for Functions and Methods PEP 322 Reverse Iteration PEP 324 New subprocess Module PEP 327 Decimal Data Type PEP 328 Multi line Imports PEP 331 Locale Independent Float String Conversions Other Language Changes New Improved and Deprecated Modules Build and C API Changes Porting to Python 2 4 Acknowledgements What s New in Python 2 3 PEP 218 A Standard Set Datatype PEP 255 Simple Generators PEP 263 Source Code Encodings PEP 273 Importing Modules from ZIP Archives PEP 277 Unicode file name support for Windows NT PEP 278 Universal Newline Support PEP 279 enumerate PEP 282 The logging Package PEP 285 A Boolean Type PEP 293 Codec Error Handling Callbacks,en
1179, PEP 301 Package Index and Metadata for Distutils PEP 302 New Import Hooks PEP 305 Comma separated Files PEP 307 Pickle Enhancements Extended Slices Other Language Changes New Improved and Deprecated Modules Pymalloc A Specialized Object Allocator Build and C API Changes Other Changes and Fixes Porting to Python 2 3 Acknowledgements What s New in Python 2 2 Introduction PEPs 252 and 253 Type and Class Changes PEP 234 Iterators PEP 255 Simple Generators PEP 237 Unifying Long Integers and Integers PEP 238 Changing the Division Operator Unicode Changes PEP 227 Nested Scopes New and Improved Modules Interpreter Changes and Fixes Other Changes and Fixes Acknowledgements What s New in Python 2 1 Introduction PEP 227 Nested Scopes PEP 236 __future__ Directives PEP 207 Rich Comparisons PEP 230 Warning Framework PEP 229 New Build System PEP 205 Weak References PEP 232 Function Attributes PEP 235 Importing Modules on Case Insensitive Platforms PEP 217 Interactive Display Hook PEP 208 New Coercion Model PEP 241 Metadata in Python Packages New and Improved Modules Other Changes and Fixes Acknowledgements What s New in Python 2 0 Introduction What About Python 1 6 New Development Process Unicode List Comprehensions Augmented Assignment String Methods Garbage Collection of Cycles Other Core Changes Porting to 2 0 Extending Embedding Changes Distutils Making Modules Easy to Install XML Modules Module changes New modules IDLE Improvements Deleted and Deprecated Modules Acknowledgements The Changelog is an HTML version of the file built from the contents of the Misc NEWS d directory tree which contains all nontrivial changes to Python for the current version Changelog Python next Python 3 12 2 final Python 3 12 1 final Python 3 12 0 final Python 3 12 0 release candidate 3 Python 3 12 0 release candidate 2 Python 3 12 0 release candidate 1 Python 3 12 0 beta 4 Python 3 12 0 beta 3 Python 3 12 0 beta 2 Python 3 12 0 beta 1 Python 3 12 0 alpha 7 Python 3 12 0 alpha 6 Python 3 12 0 alpha 5 Python 3 12 0 alpha 4 Python 3 12 0 alpha 3 Python 3 12 0 alpha 2 Python 3 12 0 alpha 1 Python 3 11 0 beta 1 Python 3 11 0 alpha 7 Python 3 11 0 alpha 6 Python 3 11 0 alpha 5 Python 3 11 0 alpha 4 Python 3 11 0 alpha 3 Python 3 11 0 alpha 2 Python 3 11 0 alpha 1 Python 3 10 0 beta 1 Python 3 10 0 alpha 7 Python 3 10 0 alpha 6 Python 3 10 0 alpha 5 Python 3 10 0 alpha 4 Python 3 10 0 alpha 3 Python 3 10 0 alpha 2 Python 3 10 0 alpha 1 Python 3 9 0 beta 1 Python 3 9 0 alpha 6 Python 3 9 0 alpha 5 Python 3 9 0 alpha 4 Python 3 9 0 alpha 3 Python 3 9 0 alpha 2 Python 3 9 0 alpha 1 Python 3 8 0 beta 1 Python 3 8 0 alpha 4 Python 3 8 0 alpha 3 Python 3 8 0 alpha 2 Python 3 8 0 alpha 1 Python 3 7 0 final Python 3 7 0 release candidate 1 Python 3 7 0 beta 5 Python 3 7 0 beta 4 Python 3 7 0 beta 3 Python 3 7 0 beta 2 Python 3 7 0 beta 1 Python 3 7 0 alpha 4 Python 3 7 0 alpha 3 Python 3 7 0 alpha 2 Python 3 7 0 alpha 1 Python 3 6 6 final Python 3 6 6 release candidate 1 Python 3 6 5 final Python 3 6 5 release candidate 1 Python 3 6 4 final Python 3 6 4 release candidate 1 Python 3 6 3 final Python 3 6 3 release candidate 1 Python 3 6 2 final Python 3 6 2 release candidate 2 Python 3 6 2 release candidate 1 Python 3 6 1 final Python 3 6 1 release candidate 1 Python 3 6 0 final Python 3 6 0 release candidate 2 Python 3 6 0 release candidate 1 Python 3 6 0 beta 4 Python 3 6 0 beta 3 Python 3 6 0 beta 2 Python 3 6 0 beta 1 Python 3 6 0 alpha 4 Python 3 6 0 alpha 3 Python 3 6 0 alpha 2 Python 3 6 0 alpha 1 Python 3 5 5 final Python 3 5 5 release candidate 1 Python 3 5 4 final Python 3 5 4 release candidate 1 Python 3 5 3 final Python 3 5 3 release candidate 1 Python 3 5 2 final Python 3 5 2 release candidate 1 Python 3 5 1 final Python 3 5 1 release candidate 1 Python 3 5 0 final Python 3 5 0 release candidate 4 Python 3 5 0 release candidate 3 Python 3 5 0 release candidate 2 Python 3 5 0 release candidate 1 Python 3 5 0 beta 4 Python 3 5 0 beta 3 Python 3 5 0 beta 2 Python 3 5 0 beta 1 Python 3 5 0 alpha 4 Python 3 5 0 alpha 3 Python 3 5 0 alpha 2 Python 3 5 0 alpha 1,en
1180,Importing Modules The modules described in this chapter provide new ways to import other Python modules and hooks for customizing the import process The full list of modules described in this chapter is zipimport Import modules from Zip archives zipimporter Objects Examples pkgutil Package extension utility modulefinder Find modules used by a script Example usage of ModuleFinder runpy Locating and executing Python modules importlib The implementation of import Introduction Functions importlib abc Abstract base classes related to import importlib machinery Importers and path hooks importlib util Utility code for importers Examples Importing programmatically Checking if a module can be imported Importing a source file directly Implementing lazy imports Setting up an importer Approximating importlib import_module importlib resources Package resource reading opening and access Deprecated functions importlib resources abc Abstract base classes for resources importlib metadata Accessing package metadata Overview Functional API Entry points Distribution metadata Distribution versions Distribution files Distribution requirements Mapping import to distribution packages Distributions Distribution Discovery Extending the search algorithm The initialization of the sys path module search path Virtual environments _pth files Embedded Python,en
1181,xdrlib Encode and decode XDR data Source code Lib xdrlib py Deprecated since version 3 11 will be removed in version 3 13 The xdrlib module is deprecated see PEP 594 for details The xdrlib module supports the External Data Representation Standard as described in RFC 1014 written by Sun Microsystems Inc June 1987 It supports most of the data types described in the RFC The xdrlib module defines two classes one for packing variables into XDR representation and another for unpacking from XDR representation There are also two exception classes class xdrlib Packer Packer is the class for packing data into XDR representation The Packer class is instantiated with no arguments class xdrlib Unpacker data Unpacker is the complementary class which unpacks XDR data values from a string buffer The input buffer is given as data See also RFC 1014 XDR External Data Representation Standard This RFC defined the encoding of data which was XDR at the time this module was originally written It has apparently been obsoleted by RFC 1832 RFC 1832 XDR External Data Representation Standard Newer RFC that provides a revised definition of XDR Packer Objects Packer instances have the following methods Packer get_buffer Returns the current pack buffer as a string Packer reset Resets the pack buffer to the empty string In general you can pack any of the most common XDR data types by calling the appropriate pack_type method Each method takes a single argument the value to pack The following simple data type packing methods are supported pack_uint pack_int pack_enum pack_bool pack_uhyper and pack_hyper Packer pack_float value Packs the single precision floating point number value Packer pack_double value Packs the double precision floating point number value The following methods support packing strings bytes and opaque data Packer pack_fstring n s Packs a fixed length string s n is the length of the string but it is not packed into the data buffer The string is padded with null bytes if necessary to guaranteed 4 byte alignment Packer pack_fopaque n data Packs a fixed length opaque data stream similarly to pack_fstring Packer pack_string s Packs a variable length string s The length of the string is first packed as an unsigned integer then the string data is packed with pack_fstring Packer pack_opaque data Packs a variable length opaque data string similarly to pack_string Packer pack_bytes bytes Packs a variable length byte stream similarly to pack_string The following methods support packing arrays and lists Packer pack_list list pack_item Packs a list of homogeneous items This method is useful for lists with an indeterminate size i e the size is not available until the entire list has been walked For each item in the list an unsigned integer 1 is packed first followed by the data value from the list pack_item is the function that is called to pack the individual item At the end of the list an unsigned integer 0 is packed For example to pack a list of integers the code might appear like this import xdrlib p xdrlib Packer p pack_list 1 2 3 p pack_int Packer pack_farray n array pack_item Packs a fixed length list array of homogeneous items n is the length of the list it is not packed into the buffer but a ValueError exception is raised if len array is not equal to n As above pack_item is the function used to pack each element Packer pack_array list pack_item Packs a variable length list of homogeneous items First the length of the list is packed as an unsigned integer then each element is packed as in pack_farray above Unpacker Objects The Unpacker class offers the following methods Unpacker reset data Resets the string buffer with the given data Unpacker get_position Returns the current unpack position in the data buffer Unpacker set_position position Sets the data buffer unpack position to position You should be careful about using get_position and set_position Unpacker get_buffer Returns the current unpack data buffer as a string Unpacker done Indicates unpack completion Raises an Error exception if all of the data has not been unpacked In addition ev,en
1182,ery data type that can be packed with a Packer can be unpacked with an Unpacker Unpacking methods are of the form unpack_type and take no arguments They return the unpacked object Unpacker unpack_float Unpacks a single precision floating point number Unpacker unpack_double Unpacks a double precision floating point number similarly to unpack_float In addition the following methods unpack strings bytes and opaque data Unpacker unpack_fstring n Unpacks and returns a fixed length string n is the number of characters expected Padding with null bytes to guaranteed 4 byte alignment is assumed Unpacker unpack_fopaque n Unpacks and returns a fixed length opaque data stream similarly to unpack_fstring Unpacker unpack_string Unpacks and returns a variable length string The length of the string is first unpacked as an unsigned integer then the string data is unpacked with unpack_fstring Unpacker unpack_opaque Unpacks and returns a variable length opaque data string similarly to unpack_string Unpacker unpack_bytes Unpacks and returns a variable length byte stream similarly to unpack_string The following methods support unpacking arrays and lists Unpacker unpack_list unpack_item Unpacks and returns a list of homogeneous items The list is unpacked one element at a time by first unpacking an unsigned integer flag If the flag is 1 then the item is unpacked and appended to the list A flag of 0 indicates the end of the list unpack_item is the function that is called to unpack the items Unpacker unpack_farray n unpack_item Unpacks and returns as a list a fixed length array of homogeneous items n is number of list elements to expect in the buffer As above unpack_item is the function used to unpack each element Unpacker unpack_array unpack_item Unpacks and returns a variable length list of homogeneous items First the length of the list is unpacked as an unsigned integer then each element is unpacked as in unpack_farray above Exceptions Exceptions in this module are coded as class instances exception xdrlib Error The base exception class Error has a single public attribute msg containing the description of the error exception xdrlib ConversionError Class derived from Error Contains no additional instance variables Here is an example of how you would catch one of these exceptions import xdrlib p xdrlib Packer try p pack_double 8 01 except xdrlib ConversionError as instance print packing the double failed instance msg,en
1183,Memory Management Overview Memory management in Python involves a private heap containing all Python objects and data structures The management of this private heap is ensured internally by the Python memory manager The Python memory manager has different components which deal with various dynamic storage management aspects like sharing segmentation preallocation or caching At the lowest level a raw memory allocator ensures that there is enough room in the private heap for storing all Python related data by interacting with the memory manager of the operating system On top of the raw memory allocator several object specific allocators operate on the same heap and implement distinct memory management policies adapted to the peculiarities of every object type For example integer objects are managed differently within the heap than strings tuples or dictionaries because integers imply different storage requirements and speed space tradeoffs The Python memory manager thus delegates some of the work to the object specific allocators but ensures that the latter operate within the bounds of the private heap It is important to understand that the management of the Python heap is performed by the interpreter itself and that the user has no control over it even if they regularly manipulate object pointers to memory blocks inside that heap The allocation of heap space for Python objects and other internal buffers is performed on demand by the Python memory manager through the Python C API functions listed in this document To avoid memory corruption extension writers should never try to operate on Python objects with the functions exported by the C library malloc calloc realloc and free This will result in mixed calls between the C allocator and the Python memory manager with fatal consequences because they implement different algorithms and operate on different heaps However one may safely allocate and release memory blocks with the C library allocator for individual purposes as shown in the following example PyObject res char buf char malloc BUFSIZ for I O if buf NULL return PyErr_NoMemory Do some I O operation involving buf res PyBytes_FromString buf free buf malloc ed return res In this example the memory request for the I O buffer is handled by the C library allocator The Python memory manager is involved only in the allocation of the bytes object returned as a result In most situations however it is recommended to allocate memory from the Python heap specifically because the latter is under control of the Python memory manager For example this is required when the interpreter is extended with new object types written in C Another reason for using the Python heap is the desire to inform the Python memory manager about the memory needs of the extension module Even when the requested memory is used exclusively for internal highly specific purposes delegating all memory requests to the Python memory manager causes the interpreter to have a more accurate image of its memory footprint as a whole Consequently under certain circumstances the Python memory manager may or may not trigger appropriate actions like garbage collection memory compaction or other preventive procedures Note that by using the C library allocator as shown in the previous example the allocated memory for the I O buffer escapes completely the Python memory manager See also The PYTHONMALLOC environment variable can be used to configure the memory allocators used by Python The PYTHONMALLOCSTATS environment variable can be used to print statistics of the pymalloc memory allocator every time a new pymalloc object arena is created and on shutdown Allocator Domains All allocating functions belong to one of three different domains see also PyMemAllocatorDomain These domains represent different allocation strategies and are optimized for different purposes The specific details on how every domain allocates memory or what internal functions each domain calls is considered an implementation detail but for debugging purposes a simplified table can be found at here There is n,en
1184,o hard requirement to use the memory returned by the allocation functions belonging to a given domain for only the purposes hinted by that domain although this is the recommended practice For example one could use the memory returned by PyMem_RawMalloc for allocating Python objects or the memory returned by PyObject_Malloc for allocating memory for buffers The three allocation domains are Raw domain intended for allocating memory for general purpose memory buffers where the allocation must go to the system allocator or where the allocator can operate without the GIL The memory is requested directly to the system Mem domain intended for allocating memory for Python buffers and general purpose memory buffers where the allocation must be performed with the GIL held The memory is taken from the Python private heap Object domain intended for allocating memory belonging to Python objects The memory is taken from the Python private heap When freeing memory previously allocated by the allocating functions belonging to a given domain the matching specific deallocating functions must be used For example PyMem_Free must be used to free memory allocated using PyMem_Malloc Raw Memory Interface The following function sets are wrappers to the system allocator These functions are thread safe the GIL does not need to be held The default raw memory allocator uses the following functions malloc calloc realloc and free call malloc 1 or calloc 1 1 when requesting zero bytes New in version 3 4 void PyMem_RawMalloc size_t n Allocates n bytes and returns a pointer of type void to the allocated memory or NULL if the request fails Requesting zero bytes returns a distinct non NULL pointer if possible as if PyMem_RawMalloc 1 had been called instead The memory will not have been initialized in any way void PyMem_RawCalloc size_t nelem size_t elsize Allocates nelem elements each whose size in bytes is elsize and returns a pointer of type void to the allocated memory or NULL if the request fails The memory is initialized to zeros Requesting zero elements or elements of size zero bytes returns a distinct non NULL pointer if possible as if PyMem_RawCalloc 1 1 had been called instead New in version 3 5 void PyMem_RawRealloc void p size_t n Resizes the memory block pointed to by p to n bytes The contents will be unchanged to the minimum of the old and the new sizes If p is NULL the call is equivalent to PyMem_RawMalloc n else if n is equal to zero the memory block is resized but is not freed and the returned pointer is non NULL Unless p is NULL it must have been returned by a previous call to PyMem_RawMalloc PyMem_RawRealloc or PyMem_RawCalloc If the request fails PyMem_RawRealloc returns NULL and p remains a valid pointer to the previous memory area void PyMem_RawFree void p Frees the memory block pointed to by p which must have been returned by a previous call to PyMem_RawMalloc PyMem_RawRealloc or PyMem_RawCalloc Otherwise or if PyMem_RawFree p has been called before undefined behavior occurs If p is NULL no operation is performed Memory Interface The following function sets modeled after the ANSI C standard but specifying behavior when requesting zero bytes are available for allocating and releasing memory from the Python heap The default memory allocator uses the pymalloc memory allocator Warning The GIL must be held when using these functions Changed in version 3 6 The default allocator is now pymalloc instead of system malloc void PyMem_Malloc size_t n Part of the Stable ABI Allocates n bytes and returns a pointer of type void to the allocated memory or NULL if the request fails Requesting zero bytes returns a distinct non NULL pointer if possible as if PyMem_Malloc 1 had been called instead The memory will not have been initialized in any way void PyMem_Calloc size_t nelem size_t elsize Part of the Stable ABI since version 3 7 Allocates nelem elements each whose size in bytes is elsize and returns a pointer of type void to the allocated memory or NULL if the request fails The memory is initialized to zeros Requesting zero elements or elements of s,en
1185,ize zero bytes returns a distinct non NULL pointer if possible as if PyMem_Calloc 1 1 had been called instead New in version 3 5 void PyMem_Realloc void p size_t n Part of the Stable ABI Resizes the memory block pointed to by p to n bytes The contents will be unchanged to the minimum of the old and the new sizes If p is NULL the call is equivalent to PyMem_Malloc n else if n is equal to zero the memory block is resized but is not freed and the returned pointer is non NULL Unless p is NULL it must have been returned by a previous call to PyMem_Malloc PyMem_Realloc or PyMem_Calloc If the request fails PyMem_Realloc returns NULL and p remains a valid pointer to the previous memory area void PyMem_Free void p Part of the Stable ABI Frees the memory block pointed to by p which must have been returned by a previous call to PyMem_Malloc PyMem_Realloc or PyMem_Calloc Otherwise or if PyMem_Free p has been called before undefined behavior occurs If p is NULL no operation is performed The following type oriented macros are provided for convenience Note that TYPE refers to any C type PyMem_New TYPE n Same as PyMem_Malloc but allocates n sizeof TYPE bytes of memory Returns a pointer cast to TYPE The memory will not have been initialized in any way PyMem_Resize p TYPE n Same as PyMem_Realloc but the memory block is resized to n sizeof TYPE bytes Returns a pointer cast to TYPE On return p will be a pointer to the new memory area or NULL in the event of failure This is a C preprocessor macro p is always reassigned Save the original value of p to avoid losing memory when handling errors void PyMem_Del void p Same as PyMem_Free In addition the following macro sets are provided for calling the Python memory allocator directly without involving the C API functions listed above However note that their use does not preserve binary compatibility across Python versions and is therefore deprecated in extension modules PyMem_MALLOC size PyMem_NEW type size PyMem_REALLOC ptr size PyMem_RESIZE ptr type size PyMem_FREE ptr PyMem_DEL ptr Object allocators The following function sets modeled after the ANSI C standard but specifying behavior when requesting zero bytes are available for allocating and releasing memory from the Python heap Note There is no guarantee that the memory returned by these allocators can be successfully cast to a Python object when intercepting the allocating functions in this domain by the methods described in the Customize Memory Allocators section The default object allocator uses the pymalloc memory allocator Warning The GIL must be held when using these functions void PyObject_Malloc size_t n Part of the Stable ABI Allocates n bytes and returns a pointer of type void to the allocated memory or NULL if the request fails Requesting zero bytes returns a distinct non NULL pointer if possible as if PyObject_Malloc 1 had been called instead The memory will not have been initialized in any way void PyObject_Calloc size_t nelem size_t elsize Part of the Stable ABI since version 3 7 Allocates nelem elements each whose size in bytes is elsize and returns a pointer of type void to the allocated memory or NULL if the request fails The memory is initialized to zeros Requesting zero elements or elements of size zero bytes returns a distinct non NULL pointer if possible as if PyObject_Calloc 1 1 had been called instead New in version 3 5 void PyObject_Realloc void p size_t n Part of the Stable ABI Resizes the memory block pointed to by p to n bytes The contents will be unchanged to the minimum of the old and the new sizes If p is NULL the call is equivalent to PyObject_Malloc n else if n is equal to zero the memory block is resized but is not freed and the returned pointer is non NULL Unless p is NULL it must have been returned by a previous call to PyObject_Malloc PyObject_Realloc or PyObject_Calloc If the request fails PyObject_Realloc returns NULL and p remains a valid pointer to the previous memory area void PyObject_Free void p Part of the Stable ABI Frees the memory block pointed to by p which must have been returned by a previous ,en
1186,call to PyObject_Malloc PyObject_Realloc or PyObject_Calloc Otherwise or if PyObject_Free p has been called before undefined behavior occurs If p is NULL no operation is performed Default Memory Allocators Default memory allocators Configuration Name PyMem_RawMalloc PyMem_Malloc PyObject_Malloc Release build pymalloc malloc pymalloc pymalloc Debug build pymalloc_debug malloc debug pymalloc debug pymalloc debug Release build without pymalloc malloc malloc malloc malloc Debug build without pymalloc malloc_debug malloc debug malloc debug malloc debug Legend Name value for PYTHONMALLOC environment variable malloc system allocators from the standard C library C functions malloc calloc realloc and free pymalloc pymalloc memory allocator debug with debug hooks on the Python memory allocators Debug build Python build in debug mode Customize Memory Allocators New in version 3 4 type PyMemAllocatorEx Structure used to describe a memory block allocator The structure has the following fields Field Meaning void ctx user context passed as first argument void malloc void ctx size_t size allocate a memory block void calloc void ctx size_t nelem size_t elsize allocate a memory block initialized with zeros void realloc void ctx void ptr size_t new_size allocate or resize a memory block void free void ctx void ptr free a memory block Changed in version 3 5 The PyMemAllocator structure was renamed to PyMemAllocatorEx and a new calloc field was added type PyMemAllocatorDomain Enum used to identify an allocator domain Domains PYMEM_DOMAIN_RAW Functions PyMem_RawMalloc PyMem_RawRealloc PyMem_RawCalloc PyMem_RawFree PYMEM_DOMAIN_MEM Functions PyMem_Malloc PyMem_Realloc PyMem_Calloc PyMem_Free PYMEM_DOMAIN_OBJ Functions PyObject_Malloc PyObject_Realloc PyObject_Calloc PyObject_Free void PyMem_GetAllocator PyMemAllocatorDomain domain PyMemAllocatorEx allocator Get the memory block allocator of the specified domain void PyMem_SetAllocator PyMemAllocatorDomain domain PyMemAllocatorEx allocator Set the memory block allocator of the specified domain The new allocator must return a distinct non NULL pointer when requesting zero bytes For the PYMEM_DOMAIN_RAW domain the allocator must be thread safe the GIL is not held when the allocator is called For the remaining domains the allocator must also be thread safe the allocator may be called in different interpreters that do not share a GIL If the new allocator is not a hook does not call the previous allocator the PyMem_SetupDebugHooks function must be called to reinstall the debug hooks on top on the new allocator See also PyPreConfig allocator and Preinitialize Python with PyPreConfig Warning PyMem_SetAllocator does have the following contract It can be called after Py_PreInitialize and before Py_InitializeFromConfig to install a custom memory allocator There are no restrictions over the installed allocator other than the ones imposed by the domain for instance the Raw Domain allows the allocator to be called without the GIL held See the section on allocator domains for more information If called after Python has finish initializing after Py_InitializeFromConfig has been called the allocator must wrap the existing allocator Substituting the current allocator for some other arbitrary one is not supported Changed in version 3 12 All allocators must be thread safe void PyMem_SetupDebugHooks void Setup debug hooks in the Python memory allocators to detect memory errors Debug hooks on the Python memory allocators When Python is built in debug mode the PyMem_SetupDebugHooks function is called at the Python preinitialization to setup debug hooks on Python memory allocators to detect memory errors The PYTHONMALLOC environment variable can be used to install debug hooks on a Python compiled in release mode ex PYTHONMALLOC debug The PyMem_SetupDebugHooks function can be used to set debug hooks after calling PyMem_SetAllocator These debug hooks fill dynamically allocated memory blocks with special recognizable bit patterns Newly allocated memory is filled with the byte 0xCD PYMEM_CLEANBYTE freed memory is filled ,en
1187,with the byte 0xDD PYMEM_DEADBYTE Memory blocks are surrounded by forbidden bytes filled with the byte 0xFD PYMEM_FORBIDDENBYTE Strings of these bytes are unlikely to be valid addresses floats or ASCII strings Runtime checks Detect API violations For example detect if PyObject_Free is called on a memory block allocated by PyMem_Malloc Detect write before the start of the buffer buffer underflow Detect write after the end of the buffer buffer overflow Check that the GIL is held when allocator functions of PYMEM_DOMAIN_OBJ ex PyObject_Malloc and PYMEM_DOMAIN_MEM ex PyMem_Malloc domains are called On error the debug hooks use the tracemalloc module to get the traceback where a memory block was allocated The traceback is only displayed if tracemalloc is tracing Python memory allocations and the memory block was traced Let S sizeof size_t 2 S bytes are added at each end of each block of N bytes requested The memory layout is like so where p represents the address returned by a malloc like or realloc like function p i j means the slice of bytes from p i inclusive up to p j exclusive note that the treatment of negative indices differs from a Python slice p 2 S S Number of bytes originally asked for This is a size_t big endian easier to read in a memory dump p S API identifier ASCII character r for PYMEM_DOMAIN_RAW m for PYMEM_DOMAIN_MEM o for PYMEM_DOMAIN_OBJ p S 1 0 Copies of PYMEM_FORBIDDENBYTE Used to catch under writes and reads p 0 N The requested memory filled with copies of PYMEM_CLEANBYTE used to catch reference to uninitialized memory When a realloc like function is called requesting a larger memory block the new excess bytes are also filled with PYMEM_CLEANBYTE When a free like function is called these are overwritten with PYMEM_DEADBYTE to catch reference to freed memory When a realloc like function is called requesting a smaller memory block the excess old bytes are also filled with PYMEM_DEADBYTE p N N S Copies of PYMEM_FORBIDDENBYTE Used to catch over writes and reads p N S N 2 S Only used if the PYMEM_DEBUG_SERIALNO macro is defined not defined by default A serial number incremented by 1 on each call to a malloc like or realloc like function Big endian size_t If bad memory is detected later the serial number gives an excellent way to set a breakpoint on the next run to capture the instant at which this block was passed out The static function bumpserialno in obmalloc c is the only place the serial number is incremented and exists so you can set such a breakpoint easily A realloc like or free like function first checks that the PYMEM_FORBIDDENBYTE bytes at each end are intact If they ve been altered diagnostic output is written to stderr and the program is aborted via Py_FatalError The other main failure mode is provoking a memory error when a program reads up one of the special bit patterns and tries to use it as an address If you get in a debugger then and look at the object you re likely to see that it s entirely filled with PYMEM_DEADBYTE meaning freed memory is getting used or PYMEM_CLEANBYTE meaning uninitialized memory is getting used Changed in version 3 6 The PyMem_SetupDebugHooks function now also works on Python compiled in release mode On error the debug hooks now use tracemalloc to get the traceback where a memory block was allocated The debug hooks now also check if the GIL is held when functions of PYMEM_DOMAIN_OBJ and PYMEM_DOMAIN_MEM domains are called Changed in version 3 8 Byte patterns 0xCB PYMEM_CLEANBYTE 0xDB PYMEM_DEADBYTE and 0xFB PYMEM_FORBIDDENBYTE have been replaced with 0xCD 0xDD and 0xFD to use the same values than Windows CRT debug malloc and free The pymalloc allocator Python has a pymalloc allocator optimized for small objects smaller or equal to 512 bytes with a short lifetime It uses memory mappings called arenas with a fixed size of either 256 KiB on 32 bit platforms or 1 MiB on 64 bit platforms It falls back to PyMem_RawMalloc and PyMem_RawRealloc for allocations larger than 512 bytes pymalloc is the default allocator of the PYMEM_DOMAIN_MEM ex PyMem_Malloc and PYMEM_DOMAIN_OBJ ,en
1188,ex PyObject_Malloc domains The arena allocator uses the following functions VirtualAlloc and VirtualFree on Windows mmap and munmap if available malloc and free otherwise This allocator is disabled if Python is configured with the without pymalloc option It can also be disabled at runtime using the PYTHONMALLOC environment variable ex PYTHONMALLOC malloc Customize pymalloc Arena Allocator New in version 3 4 type PyObjectArenaAllocator Structure used to describe an arena allocator The structure has three fields Field Meaning void ctx user context passed as first argument void alloc void ctx size_t size allocate an arena of size bytes void free void ctx void ptr size_t size free an arena void PyObject_GetArenaAllocator PyObjectArenaAllocator allocator Get the arena allocator void PyObject_SetArenaAllocator PyObjectArenaAllocator allocator Set the arena allocator tracemalloc C API New in version 3 7 int PyTraceMalloc_Track unsigned int domain uintptr_t ptr size_t size Track an allocated memory block in the tracemalloc module Return 0 on success return 1 on error failed to allocate memory to store the trace Return 2 if tracemalloc is disabled If memory block is already tracked update the existing trace int PyTraceMalloc_Untrack unsigned int domain uintptr_t ptr Untrack an allocated memory block in the tracemalloc module Do nothing if the block was not tracked Return 2 if tracemalloc is disabled otherwise return 0 Examples Here is the example from section Overview rewritten so that the I O buffer is allocated from the Python heap by using the first function set PyObject res char buf char PyMem_Malloc BUFSIZ for I O if buf NULL return PyErr_NoMemory Do some I O operation involving buf res PyBytes_FromString buf PyMem_Free buf allocated with PyMem_Malloc return res The same code using the type oriented function set PyObject res char buf PyMem_New char BUFSIZ for I O if buf NULL return PyErr_NoMemory Do some I O operation involving buf res PyBytes_FromString buf PyMem_Del buf allocated with PyMem_New return res Note that in the two examples above the buffer is always manipulated via functions belonging to the same set Indeed it is required to use the same memory API family for a given memory block so that the risk of mixing different allocators is reduced to a minimum The following code sequence contains two errors one of which is labeled as fatal because it mixes two different allocators operating on different heaps char buf1 PyMem_New char BUFSIZ char buf2 char malloc BUFSIZ char buf3 char PyMem_Malloc BUFSIZ PyMem_Del buf3 Wrong should be PyMem_Free free buf2 Right allocated via malloc free buf1 Fatal should be PyMem_Del In addition to the functions aimed at handling raw memory blocks from the Python heap objects in Python are allocated and released with PyObject_New PyObject_NewVar and PyObject_Del These will be explained in the next chapter on defining and implementing new object types in C,en
1189,Object Implementation Support This chapter describes the functions types and macros used when defining new object types Allocating Objects on the Heap Common Object Structures Base object types and macros Implementing functions and methods Accessing attributes of extension types Member flags Member types Defining Getters and Setters Type Objects Quick Reference tp slots sub slots slot typedefs PyTypeObject Definition PyObject Slots PyVarObject Slots PyTypeObject Slots Static Types Heap Types Number Object Structures Mapping Object Structures Sequence Object Structures Buffer Object Structures Async Object Structures Slot Type typedefs Examples Supporting Cyclic Garbage Collection Controlling the Garbage Collector State Querying Garbage Collector State,en
1190,Modules command line interface CLI The following modules have a command line interface ast asyncio base64 calendar code compileall cProfile see profile difflib dis doctest encodings rot_13 ensurepip filecmp fileinput ftplib gzip http server idlelib inspect json tool mimetypes pdb pickle pickletools platform poplib profile pstats py_compile pyclbr pydoc quopri runpy site sqlite3 sysconfig tabnanny tarfile this timeit tokenize trace turtledemo unittest uuid venv webbrowser zipapp zipfile See also the Python command line interface,en
1191,contextvars Context Variables This module provides APIs to manage store and access context local state The ContextVar class is used to declare and work with Context Variables The copy_context function and the Context class should be used to manage the current context in asynchronous frameworks Context managers that have state should use Context Variables instead of threading local to prevent their state from bleeding to other code unexpectedly when used in concurrent code See also PEP 567 for additional details New in version 3 7 Context Variables class contextvars ContextVar name default This class is used to declare a new Context Variable e g var ContextVar int ContextVar var default 42 The required name parameter is used for introspection and debug purposes The optional keyword only default parameter is returned by ContextVar get when no value for the variable is found in the current context Important Context Variables should be created at the top module level and never in closures Context objects hold strong references to context variables which prevents context variables from being properly garbage collected name The name of the variable This is a read only property New in version 3 7 1 get default Return a value for the context variable for the current context If there is no value for the variable in the current context the method will return the value of the default argument of the method if provided or return the default value for the context variable if it was created with one or raise a LookupError set value Call to set a new value for the context variable in the current context The required value argument is the new value for the context variable Returns a Token object that can be used to restore the variable to its previous value via the ContextVar reset method reset token Reset the context variable to the value it had before the ContextVar set that created the token was used For example var ContextVar var token var set new value code that uses var var get returns new value var reset token After the reset call the var has no value again so var get would raise a LookupError class contextvars Token Token objects are returned by the ContextVar set method They can be passed to the ContextVar reset method to revert the value of the variable to what it was before the corresponding set var A read only property Points to the ContextVar object that created the token old_value A read only property Set to the value the variable had before the ContextVar set method call that created the token It points to Token MISSING if the variable was not set before the call MISSING A marker object used by Token old_value Manual Context Management contextvars copy_context Returns a copy of the current Context object The following snippet gets a copy of the current context and prints all variables and their values that are set in it ctx Context copy_context print list ctx items The function has an O 1 complexity i e works equally fast for contexts with a few context variables and for contexts that have a lot of them class contextvars Context A mapping of ContextVars to their values Context creates an empty context with no values in it To get a copy of the current context use the copy_context function Every thread will have a different top level Context object This means that a ContextVar object behaves in a similar fashion to threading local when values are assigned in different threads Context implements the collections abc Mapping interface run callable args kwargs Execute callable args kwargs code in the context object the run method is called on Return the result of the execution or propagate an exception if one occurred Any changes to any context variables that callable makes will be contained in the context object var ContextVar var var set spam def main var was set to spam before calling copy_context and ctx run main so var get ctx var spam var set ham Now after setting var to ham var get ctx var ham ctx copy_context Any changes that the main function makes to var will be contained in ctx ctx run main The main function was run ,en
1192,in the ctx context so changes to var are contained in it ctx var ham However outside of ctx var is still set to spam var get spam The method raises a RuntimeError when called on the same context object from more than one OS thread or when called recursively copy Return a shallow copy of the context object var in context Return True if the context has a value for var set return False otherwise context var Return the value of the var ContextVar variable If the variable is not set in the context object a KeyError is raised get var default Return the value for var if var has the value in the context object Return default otherwise If default is not given return None iter context Return an iterator over the variables stored in the context object len proxy Return the number of variables set in the context object keys Return a list of all variables in the context object values Return a list of all variables values in the context object items Return a list of 2 tuples containing all variables and their values in the context object asyncio support Context variables are natively supported in asyncio and are ready to be used without any extra configuration For example here is a simple echo server that uses a context variable to make the address of a remote client available in the Task that handles that client import asyncio import contextvars client_addr_var contextvars ContextVar client_addr def render_goodbye The address of the currently handled client can be accessed without passing it explicitly to this function client_addr client_addr_var get return f Good bye client client_addr n encode async def handle_request reader writer addr writer transport get_extra_info socket getpeername client_addr_var set addr In any code that we call is now possible to get client s address by calling client_addr_var get while True line await reader readline print line if not line strip break writer write line writer write render_goodbye writer close async def main srv await asyncio start_server handle_request 127 0 0 1 8081 async with srv await srv serve_forever asyncio run main To test it you can use telnet telnet 127 0 0 1 8081,en
1193,Regular Expression HOWTO Author A M Kuchling amk amk ca Abstract This document is an introductory tutorial to using regular expressions in Python with the re module It provides a gentler introduction than the corresponding section in the Library Reference Introduction Regular expressions called REs or regexes or regex patterns are essentially a tiny highly specialized programming language embedded inside Python and made available through the re module Using this little language you specify the rules for the set of possible strings that you want to match this set might contain English sentences or e mail addresses or TeX commands or anything you like You can then ask questions such as Does this string match the pattern or Is there a match for the pattern anywhere in this string You can also use REs to modify a string or to split it apart in various ways Regular expression patterns are compiled into a series of bytecodes which are then executed by a matching engine written in C For advanced use it may be necessary to pay careful attention to how the engine will execute a given RE and write the RE in a certain way in order to produce bytecode that runs faster Optimization isn t covered in this document because it requires that you have a good understanding of the matching engine s internals The regular expression language is relatively small and restricted so not all possible string processing tasks can be done using regular expressions There are also tasks that can be done with regular expressions but the expressions turn out to be very complicated In these cases you may be better off writing Python code to do the processing while Python code will be slower than an elaborate regular expression it will also probably be more understandable Simple Patterns We ll start by learning about the simplest possible regular expressions Since regular expressions are used to operate on strings we ll begin with the most common task matching characters For a detailed explanation of the computer science underlying regular expressions deterministic and non deterministic finite automata you can refer to almost any textbook on writing compilers Matching Characters Most letters and characters will simply match themselves For example the regular expression test will match the string test exactly You can enable a case insensitive mode that would let this RE match Test or TEST as well more about this later There are exceptions to this rule some characters are special metacharacters and don t match themselves Instead they signal that some out of the ordinary thing should be matched or they affect other portions of the RE by repeating them or changing their meaning Much of this document is devoted to discussing various metacharacters and what they do Here s a complete list of the metacharacters their meanings will be discussed in the rest of this HOWTO The first metacharacters we ll look at are and They re used for specifying a character class which is a set of characters that you wish to match Characters can be listed individually or a range of characters can be indicated by giving two characters and separating them by a For example abc will match any of the characters a b or c this is the same as a c which uses a range to express the same set of characters If you wanted to match only lowercase letters your RE would be a z Metacharacters except are not active inside classes For example akm will match any of the characters a k m or is usually a metacharacter but inside a character class it s stripped of its special nature You can match the characters not listed within the class by complementing the set This is indicated by including a as the first character of the class For example 5 will match any character except 5 If the caret appears elsewhere in a character class it does not have special meaning For example 5 will match either a 5 or a Perhaps the most important metacharacter is the backslash As in Python string literals the backslash can be followed by various characters to signal various special sequences It s also used to escape all the met,en
1194,acharacters so you can still match them in patterns for example if you need to match a or you can precede them with a backslash to remove their special meaning or Some of the special sequences beginning with represent predefined sets of characters that are often useful such as the set of digits the set of letters or the set of anything that isn t whitespace Let s take an example w matches any alphanumeric character If the regex pattern is expressed in bytes this is equivalent to the class a zA Z0 9_ If the regex pattern is a string w will match all the characters marked as letters in the Unicode database provided by the unicodedata module You can use the more restricted definition of w in a string pattern by supplying the re ASCII flag when compiling the regular expression The following list of special sequences isn t complete For a complete list of sequences and expanded class definitions for Unicode string patterns see the last part of Regular Expression Syntax in the Standard Library reference In general the Unicode versions match any character that s in the appropriate category in the Unicode database d Matches any decimal digit this is equivalent to the class 0 9 D Matches any non digit character this is equivalent to the class 0 9 s Matches any whitespace character this is equivalent to the class t n r f v S Matches any non whitespace character this is equivalent to the class t n r f v w Matches any alphanumeric character this is equivalent to the class a zA Z0 9_ W Matches any non alphanumeric character this is equivalent to the class a zA Z0 9_ These sequences can be included inside a character class For example s is a character class that will match any whitespace character or or The final metacharacter in this section is It matches anything except a newline character and there s an alternate mode re DOTALL where it will match even a newline is often used where you want to match any character Repeating Things Being able to match varying sets of characters is the first thing regular expressions can do that isn t already possible with the methods available on strings However if that was the only additional capability of regexes they wouldn t be much of an advance Another capability is that you can specify that portions of the RE must be repeated a certain number of times The first metacharacter for repeating things that we ll look at is doesn t match the literal character instead it specifies that the previous character can be matched zero or more times instead of exactly once For example ca t will match ct 0 a characters cat 1 a caaat 3 a characters and so forth Repetitions such as are greedy when repeating a RE the matching engine will try to repeat it as many times as possible If later portions of the pattern don t match the matching engine will then back up and try again with fewer repetitions A step by step example will make this more obvious Let s consider the expression a bcd b This matches the letter a zero or more letters from the class bcd and finally ends with a b Now imagine matching this RE against the string abcbd Step Matched Explanation 1 a The a in the RE matches 2 abcbd The engine matches bcd going as far as it can which is to the end of the string 3 Failure The engine tries to match b but the current position is at the end of the string so it fails 4 abcb Back up so that bcd matches one less character 5 Failure Try b again but the current position is at the last character which is a d 6 abc Back up again so that bcd is only matching bc 6 abcb Try b again This time the character at the current position is b so it succeeds The end of the RE has now been reached and it has matched abcb This demonstrates how the matching engine goes as far as it can at first and if no match is found it will then progressively back up and retry the rest of the RE again and again It will back up until it has tried zero matches for bcd and if that subsequently fails the engine will conclude that the string doesn t match the RE at all Another repeating metacharacter is which matches one or more times Pay careful attenti,en
1195,on to the difference between and matches zero or more times so whatever s being repeated may not be present at all while requires at least one occurrence To use a similar example ca t will match cat 1 a caaat 3 a s but won t match ct There are two more repeating operators or quantifiers The question mark character matches either once or zero times you can think of it as marking something as being optional For example home brew matches either homebrew or home brew The most complicated quantifier is m n where m and n are decimal integers This quantifier means there must be at least m repetitions and at most n For example a 1 3 b will match a b a b and a b It won t match ab which has no slashes or a b which has four You can omit either m or n in that case a reasonable value is assumed for the missing value Omitting m is interpreted as a lower limit of 0 while omitting n results in an upper bound of infinity The simplest case m matches the preceding item exactly m times For example a 2 b will only match a b Readers of a reductionist bent may notice that the three other quantifiers can all be expressed using this notation 0 is the same as 1 is equivalent to and 0 1 is the same as It s better to use or when you can simply because they re shorter and easier to read Using Regular Expressions Now that we ve looked at some simple regular expressions how do we actually use them in Python The re module provides an interface to the regular expression engine allowing you to compile REs into objects and then perform matches with them Compiling Regular Expressions Regular expressions are compiled into pattern objects which have methods for various operations such as searching for pattern matches or performing string substitutions import re p re compile ab p re compile ab re compile also accepts an optional flags argument used to enable various special features and syntax variations We ll go over the available settings later but for now a single example will do p re compile ab re IGNORECASE The RE is passed to re compile as a string REs are handled as strings because regular expressions aren t part of the core Python language and no special syntax was created for expressing them There are applications that don t need REs at all so there s no need to bloat the language specification by including them Instead the re module is simply a C extension module included with Python just like the socket or zlib modules Putting REs in strings keeps the Python language simpler but has one disadvantage which is the topic of the next section The Backslash Plague As stated earlier regular expressions use the backslash character to indicate special forms or to allow special characters to be used without invoking their special meaning This conflicts with Python s usage of the same character for the same purpose in string literals Let s say you want to write a RE that matches the string section which might be found in a LaTeX file To figure out what to write in the program code start with the desired string to be matched Next you must escape any backslashes and other metacharacters by preceding them with a backslash resulting in the string section The resulting string that must be passed to re compile must be section However to express this as a Python string literal both backslashes must be escaped again Characters Stage section Text string to be matched section Escaped backslash for re compile section Escaped backslashes for a string literal In short to match a literal backslash one has to write as the RE string because the regular expression must be and each backslash must be expressed as inside a regular Python string literal In REs that feature backslashes repeatedly this leads to lots of repeated backslashes and makes the resulting strings difficult to understand The solution is to use Python s raw string notation for regular expressions backslashes are not handled in any special way in a string literal prefixed with r so r n is a two character string containing and n while n is a one character string containing a newline Regular expressions will oft,en
1196,en be written in Python code using this raw string notation In addition special escape sequences that are valid in regular expressions but not valid as Python string literals now result in a DeprecationWarning and will eventually become a SyntaxError which means the sequences will be invalid if raw string notation or escaping the backslashes isn t used Regular String Raw string ab r ab section r section w s 1 r w s 1 Performing Matches Once you have an object representing a compiled regular expression what do you do with it Pattern objects have several methods and attributes Only the most significant ones will be covered here consult the re docs for a complete listing Method Attribute Purpose match Determine if the RE matches at the beginning of the string search Scan through a string looking for any location where this RE matches findall Find all substrings where the RE matches and returns them as a list finditer Find all substrings where the RE matches and returns them as an iterator match and search return None if no match can be found If they re successful a match object instance is returned containing information about the match where it starts and ends the substring it matched and more You can learn about this by interactively experimenting with the re module This HOWTO uses the standard Python interpreter for its examples First run the Python interpreter import the re module and compile a RE import re p re compile a z p re compile a z Now you can try matching various strings against the RE a z An empty string shouldn t match at all since means one or more repetitions match should return None in this case which will cause the interpreter to print no output You can explicitly print the result of match to make this clear p match print p match None Now let s try it on a string that it should match such as tempo In this case match will return a match object so you should store the result in a variable for later use m p match tempo m re Match object span 0 5 match tempo Now you can query the match object for information about the matching string Match object instances also have several methods and attributes the most important ones are Method Attribute Purpose group Return the string matched by the RE start Return the starting position of the match end Return the ending position of the match span Return a tuple containing the start end positions of the match Trying these methods will soon clarify their meaning m group tempo m start m end 0 5 m span 0 5 group returns the substring that was matched by the RE start and end return the starting and ending index of the match span returns both start and end indexes in a single tuple Since the match method only checks if the RE matches at the start of a string start will always be zero However the search method of patterns scans through the string so the match may not start at zero in that case print p match message None m p search message print m re Match object span 4 11 match message m group message m span 4 11 In actual programs the most common style is to store the match object in a variable and then check if it was None This usually looks like p re compile m p match string goes here if m print Match found m group else print No match Two pattern methods return all of the matches for a pattern findall returns a list of matching strings p re compile r d p findall 12 drummers drumming 11 pipers piping 10 lords a leaping 12 11 10 The r prefix making the literal a raw string literal is needed in this example because escape sequences in a normal cooked string literal that are not recognized by Python as opposed to regular expressions now result in a DeprecationWarning and will eventually become a SyntaxError See The Backslash Plague findall has to create the entire list before it can be returned as the result The finditer method returns a sequence of match object instances as an iterator iterator p finditer 12 drummers drumming 11 10 iterator callable_iterator object at 0x for match in iterator print match span 0 2 22 24 29 31 Module Level Functions You don t have to create a pa,en
1197,ttern object and call its methods the re module also provides top level functions called match search findall sub and so forth These functions take the same arguments as the corresponding pattern method with the RE string added as the first argument and still return either None or a match object instance print re match r From s Fromage amk None re match r From s From amk Thu May 14 19 12 10 1998 re Match object span 0 5 match From Under the hood these functions simply create a pattern object for you and call the appropriate method on it They also store the compiled object in a cache so future calls using the same RE won t need to parse the pattern again and again Should you use these module level functions or should you get the pattern and call its methods yourself If you re accessing a regex within a loop pre compiling it will save a few function calls Outside of loops there s not much difference thanks to the internal cache Compilation Flags Compilation flags let you modify some aspects of how regular expressions work Flags are available in the re module under two names a long name such as IGNORECASE and a short one letter form such as I If you re familiar with Perl s pattern modifiers the one letter forms use the same letters the short form of re VERBOSE is re X for example Multiple flags can be specified by bitwise OR ing them re I re M sets both the I and M flags for example Here s a table of the available flags followed by a more detailed explanation of each one Flag Meaning ASCII A Makes several escapes like w b s and d match only on ASCII characters with the respective property DOTALL S Make match any character including newlines IGNORECASE I Do case insensitive matches LOCALE L Do a locale aware match MULTILINE M Multi line matching affecting and VERBOSE X for extended Enable verbose REs which can be organized more cleanly and understandably re I re IGNORECASE Perform case insensitive matching character class and literal strings will match letters by ignoring case For example A Z will match lowercase letters too Full Unicode matching also works unless the ASCII flag is used to disable non ASCII matches When the Unicode patterns a z or A Z are used in combination with the IGNORECASE flag they will match the 52 ASCII letters and 4 additional non ASCII letters İ U 0130 Latin capital letter I with dot above ı U 0131 Latin small letter dotless i ſ U 017F Latin small letter long s and K U 212A Kelvin sign Spam will match Spam spam spAM or ſpam the latter is matched only in Unicode mode This lowercasing doesn t take the current locale into account it will if you also set the LOCALE flag re L re LOCALE Make w W b B and case insensitive matching dependent on the current locale instead of the Unicode database Locales are a feature of the C library intended to help in writing programs that take account of language differences For example if you re processing encoded French text you d want to be able to write w to match words but w only matches the character class A Za z in bytes patterns it won t match bytes corresponding to é or ç If your system is configured properly and a French locale is selected certain C functions will tell the program that the byte corresponding to é should also be considered a letter Setting the LOCALE flag when compiling a regular expression will cause the resulting compiled object to use these C functions for w this is slower but also enables w to match French words as you d expect The use of this flag is discouraged in Python 3 as the locale mechanism is very unreliable it only handles one culture at a time and it only works with 8 bit locales Unicode matching is already enabled by default in Python 3 for Unicode str patterns and it is able to handle different locales languages re M re MULTILINE and haven t been explained yet they ll be introduced in section More Metacharacters Usually matches only at the beginning of the string and matches only at the end of the string and immediately before the newline if any at the end of the string When this flag is specified matches at the beginning of the ,en
1198,string and at the beginning of each line within the string immediately following each newline Similarly the metacharacter matches either at the end of the string and at the end of each line immediately preceding each newline re S re DOTALL Makes the special character match any character at all including a newline without this flag will match anything except a newline re A re ASCII Make w W b B s and S perform ASCII only matching instead of full Unicode matching This is only meaningful for Unicode patterns and is ignored for byte patterns re X re VERBOSE This flag allows you to write regular expressions that are more readable by granting you more flexibility in how you can format them When this flag has been specified whitespace within the RE string is ignored except when the whitespace is in a character class or preceded by an unescaped backslash this lets you organize and indent the RE more clearly This flag also lets you put comments within a RE that will be ignored by the engine comments are marked by a that s neither in a character class or preceded by an unescaped backslash For example here s a RE that uses re VERBOSE see how much easier it is to read charref re compile r Start of a numeric entity reference 0 0 7 Octal form 0 9 Decimal form x 0 9a fA F Hexadecimal form Trailing semicolon re VERBOSE Without the verbose setting the RE would look like this charref re compile 0 0 7 0 9 x 0 9a fA F In the above example Python s automatic concatenation of string literals has been used to break up the RE into smaller pieces but it s still more difficult to understand than the version using re VERBOSE More Pattern Power So far we ve only covered a part of the features of regular expressions In this section we ll cover some new metacharacters and how to use groups to retrieve portions of the text that was matched More Metacharacters There are some metacharacters that we haven t covered yet Most of them will be covered in this section Some of the remaining metacharacters to be discussed are zero width assertions They don t cause the engine to advance through the string instead they consume no characters at all and simply succeed or fail For example b is an assertion that the current position is located at a word boundary the position isn t changed by the b at all This means that zero width assertions should never be repeated because if they match once at a given location they can obviously be matched an infinite number of times Alternation or the or operator If A and B are regular expressions A B will match any string that matches either A or B has very low precedence in order to make it work reasonably when you re alternating multi character strings Crow Servo will match either Crow or Servo not Cro a w or an S and ervo To match a literal use or enclose it inside a character class as in Matches at the beginning of lines Unless the MULTILINE flag has been set this will only match at the beginning of the string In MULTILINE mode this also matches immediately after each newline within the string For example if you wish to match the word From only at the beginning of a line the RE to use is From print re search From From Here to Eternity re Match object span 0 4 match From print re search From Reciting From Memory None To match a literal use Matches at the end of a line which is defined as either the end of the string or any location followed by a newline character print re search block re Match object span 6 7 match print re search block None print re search block n re Match object span 6 7 match To match a literal use or enclose it inside a character class as in A Matches only at the start of the string When not in MULTILINE mode A and are effectively the same In MULTILINE mode they re different A still matches only at the beginning of the string but may match at any location inside the string that follows a newline character Z Matches only at the end of the string b Word boundary This is a zero width assertion that matches only at the beginning or end of a word A word is defined as a sequence of alphanumeric characters so the,en
1199, end of a word is indicated by whitespace or a non alphanumeric character The following example matches class only when it s a complete word it won t match when it s contained inside another word p re compile r bclass b print p search no class at all re Match object span 3 8 match class print p search the declassified algorithm None print p search one subclass is None There are two subtleties you should remember when using this special sequence First this is the worst collision between Python s string literals and regular expression sequences In Python s string literals b is the backspace character ASCII value 8 If you re not using raw strings then Python will convert the b to a backspace and your RE won t match as you expect it to The following example looks the same as our previous RE but omits the r in front of the RE string p re compile bclass b print p search no class at all None print p search b class b re Match object span 0 7 match x08class x08 Second inside a character class where there s no use for this assertion b represents the backspace character for compatibility with Python s string literals B Another zero width assertion this is the opposite of b only matching when the current position is not at a word boundary Grouping Frequently you need to obtain more information than just whether the RE matched or not Regular expressions are often used to dissect strings by writing a RE divided into several subgroups which match different components of interest For example an RFC 822 header line is divided into a header name and a value separated by a like this From author example com User Agent Thunderbird 1 5 0 9 X11 20061227 MIME Version 1 0 To editor example com This can be handled by writing a regular expression which matches an entire header line and has one group which matches the header name and another group which matches the header s value Groups are marked by the metacharacters and have much the same meaning as they do in mathematical expressions they group together the expressions contained inside them and you can repeat the contents of a group with a quantifier such as or m n For example ab will match zero or more repetitions of ab p re compile ab print p match ababababab span 0 10 Groups indicated with also capture the starting and ending index of the text that they match this can be retrieved by passing an argument to group start end and span Groups are numbered starting with 0 Group 0 is always present it s the whole RE so match object methods all have group 0 as their default argument Later we ll see how to express groups that don t capture the span of text that they match p re compile a b m p match ab m group ab m group 0 ab Subgroups are numbered from left to right from 1 upward Groups can be nested to determine the number just count the opening parenthesis characters going from left to right p re compile a b c d m p match abcd m group 0 abcd m group 1 abc m group 2 b group can be passed multiple group numbers at a time in which case it will return a tuple containing the corresponding values for those groups m group 2 1 2 b abc b The groups method returns a tuple containing the strings for all the subgroups from 1 up to however many there are m groups abc b Backreferences in a pattern allow you to specify that the contents of an earlier capturing group must also be found at the current location in the string For example 1 will succeed if the exact contents of group 1 can be found at the current position and fails otherwise Remember that Python s string literals also use a backslash followed by numbers to allow including arbitrary characters in a string so be sure to use a raw string when incorporating backreferences in a RE For example the following RE detects doubled words in a string p re compile r b w s 1 b p search Paris in the the spring group the the Backreferences like this aren t often useful for just searching through a string there are few text formats which repeat data in this way but you ll soon find out that they re very useful when performing string substitutions Non capturing and Name,en
1200,d Groups Elaborate REs may use many groups both to capture substrings of interest and to group and structure the RE itself In complex REs it becomes difficult to keep track of the group numbers There are two features which help with this problem Both of them use a common syntax for regular expression extensions so we ll look at that first Perl 5 is well known for its powerful additions to standard regular expressions For these new features the Perl developers couldn t choose new single keystroke metacharacters or new special sequences beginning with without making Perl s regular expressions confusingly different from standard REs If they chose as a new metacharacter for example old expressions would be assuming that was a regular character and wouldn t have escaped it by writing or The solution chosen by the Perl developers was to use as the extension syntax immediately after a parenthesis was a syntax error because the would have nothing to repeat so this didn t introduce any compatibility problems The characters immediately after the indicate what extension is being used so foo is one thing a positive lookahead assertion and foo is something else a non capturing group containing the subexpression foo Python supports several of Perl s extensions and adds an extension syntax to Perl s extension syntax If the first character after the question mark is a P you know that it s an extension that s specific to Python Now that we ve looked at the general extension syntax we can return to the features that simplify working with groups in complex REs Sometimes you ll want to use a group to denote a part of a regular expression but aren t interested in retrieving the group s contents You can make this fact explicit by using a non capturing group where you can replace the with any other regular expression m re match abc abc m groups c m re match abc abc m groups Except for the fact that you can t retrieve the contents of what the group matched a non capturing group behaves exactly the same as a capturing group you can put anything inside it repeat it with a repetition metacharacter such as and nest it within other groups capturing or non capturing is particularly useful when modifying an existing pattern since you can add new groups without changing how all the other groups are numbered It should be mentioned that there s no performance difference in searching between capturing and non capturing groups neither form is any faster than the other A more significant feature is named groups instead of referring to them by numbers groups can be referenced by a name The syntax for a named group is one of the Python specific extensions P name name is obviously the name of the group Named groups behave exactly like capturing groups and additionally associate a name with a group The match object methods that deal with capturing groups all accept either integers that refer to the group by number or strings that contain the desired group s name Named groups are still given numbers so you can retrieve information about a group in two ways p re compile r P word b w b m p search Lots of punctuation m group word Lots m group 1 Lots Additionally you can retrieve named groups as a dictionary with groupdict m re match r P first w P last w Jane Doe m groupdict first Jane last Doe Named groups are handy because they let you use easily remembered names instead of having to remember numbers Here s an example RE from the imaplib module InternalDate re compile r INTERNALDATE r P day 123 0 9 P mon A Z a z a z r P year 0 9 0 9 0 9 0 9 r P hour 0 9 0 9 P min 0 9 0 9 P sec 0 9 0 9 r P zonen P zoneh 0 9 0 9 P zonem 0 9 0 9 r It s obviously much easier to retrieve m group zonem instead of having to remember to retrieve group 9 The syntax for backreferences in an expression such as 1 refers to the number of the group There s naturally a variant that uses the group name instead of the number This is another Python extension P name indicates that the contents of the group called name should again be matched at the current point The regular expression for finding do,en
1201,ubled words b w s 1 b can also be written as b P word w s P word b p re compile r b P word w s P word b p search Paris in the the spring group the the Lookahead Assertions Another zero width assertion is the lookahead assertion Lookahead assertions are available in both positive and negative form and look like this Positive lookahead assertion This succeeds if the contained regular expression represented here by successfully matches at the current location and fails otherwise But once the contained expression has been tried the matching engine doesn t advance at all the rest of the pattern is tried right where the assertion started Negative lookahead assertion This is the opposite of the positive assertion it succeeds if the contained expression doesn t match at the current position in the string To make this concrete let s look at a case where a lookahead is useful Consider a simple pattern to match a filename and split it apart into a base name and an extension separated by a For example in news rc news is the base name and rc is the filename s extension The pattern to match this is quite simple Notice that the needs to be treated specially because it s a metacharacter so it s inside a character class to only match that specific character Also notice the trailing this is added to ensure that all the rest of the string must be included in the extension This regular expression matches foo bar and autoexec bat and sendmail cf and printers conf Now consider complicating the problem a bit what if you want to match filenames where the extension is not bat Some incorrect attempts b The first attempt above tries to exclude bat by requiring that the first character of the extension is not a b This is wrong because the pattern also doesn t match foo bar b a t The expression gets messier when you try to patch up the first solution by requiring one of the following cases to match the first character of the extension isn t b the second character isn t a or the third character isn t t This accepts foo bar and rejects autoexec bat but it requires a three letter extension and won t accept a filename with a two letter extension such as sendmail cf We ll complicate the pattern again in an effort to fix it b a t In the third attempt the second and third letters are all made optional in order to allow matching extensions shorter than three characters such as sendmail cf The pattern s getting really complicated now which makes it hard to read and understand Worse if the problem changes and you want to exclude both bat and exe as extensions the pattern would get even more complicated and confusing A negative lookahead cuts through all this confusion bat The negative lookahead means if the expression bat doesn t match at this point try the rest of the pattern if bat does match the whole pattern will fail The trailing is required to ensure that something like sample batch where the extension only starts with bat will be allowed The makes sure that the pattern works when there are multiple dots in the filename Excluding another filename extension is now easy simply add it as an alternative inside the assertion The following pattern excludes filenames that end in either bat or exe bat exe Modifying Strings Up to this point we ve simply performed searches against a static string Regular expressions are also commonly used to modify strings in various ways using the following pattern methods Method Attribute Purpose split Split the string into a list splitting it wherever the RE matches sub Find all substrings where the RE matches and replace them with a different string subn Does the same thing as sub but returns the new string and the number of replacements Splitting Strings The split method of a pattern splits a string apart wherever the RE matches returning a list of the pieces It s similar to the split method of strings but provides much more generality in the delimiters that you can split by string split only supports splitting by whitespace or by a fixed string As you d expect there s a module level re split function too split string maxspl,en
1202,it 0 Split string by the matches of the regular expression If capturing parentheses are used in the RE then their contents will also be returned as part of the resulting list If maxsplit is nonzero at most maxsplit splits are performed You can limit the number of splits made by passing a value for maxsplit When maxsplit is nonzero at most maxsplit splits will be made and the remainder of the string is returned as the final element of the list In the following example the delimiter is any sequence of non alphanumeric characters p re compile r W p split This is a test short and sweet of split This is a test short and sweet of split p split This is a test short and sweet of split 3 This is a test short and sweet of split Sometimes you re not only interested in what the text between delimiters is but also need to know what the delimiter was If capturing parentheses are used in the RE then their values are also returned as part of the list Compare the following calls p re compile r W p2 re compile r W p split This is a test This is a test p2 split This is a test This is a test The module level function re split adds the RE to be used as the first argument but is otherwise the same re split r W Words words words Words words words re split r W Words words words Words words words re split r W Words words words 1 Words words words Search and Replace Another common task is to find all the matches for a pattern and replace them with a different string The sub method takes a replacement value which can be either a string or a function and the string to be processed sub replacement string count 0 Returns the string obtained by replacing the leftmost non overlapping occurrences of the RE in string by the replacement replacement If the pattern isn t found string is returned unchanged The optional argument count is the maximum number of pattern occurrences to be replaced count must be a non negative integer The default value of 0 means to replace all occurrences Here s a simple example of using the sub method It replaces colour names with the word colour p re compile blue white red p sub colour blue socks and red shoes colour socks and colour shoes p sub colour blue socks and red shoes count 1 colour socks and red shoes The subn method does the same work but returns a 2 tuple containing the new string value and the number of replacements that were performed p re compile blue white red p subn colour blue socks and red shoes colour socks and colour shoes 2 p subn colour no colours at all no colours at all 0 Empty matches are replaced only when they re not adjacent to a previous empty match p re compile x p sub abxd a b d If replacement is a string any backslash escapes in it are processed That is n is converted to a single newline character r is converted to a carriage return and so forth Unknown escapes such as are left alone Backreferences such as 6 are replaced with the substring matched by the corresponding group in the RE This lets you incorporate portions of the original text in the resulting replacement string This example matches the word section followed by a string enclosed in and changes section to subsection p re compile section re VERBOSE p sub r subsection 1 section First section second subsection First subsection second There s also a syntax for referring to named groups as defined by the P name syntax g name will use the substring matched by the group named name and g number uses the corresponding group number g 2 is therefore equivalent to 2 but isn t ambiguous in a replacement string such as g 2 0 20 would be interpreted as a reference to group 20 not a reference to group 2 followed by the literal character 0 The following substitutions are all equivalent but use all three variations of the replacement string p re compile section P name re VERBOSE p sub r subsection 1 section First subsection First p sub r subsection g 1 section First subsection First p sub r subsection g name section First subsection First replacement can also be a function which gives you even more control If replacement is a function the function is c,en
1203,alled for every non overlapping occurrence of pattern On each call the function is passed a match object argument for the match and can use this information to compute the desired replacement string and return it In the following example the replacement function translates decimals into hexadecimal def hexrepl match Return the hex string for a decimal number value int match group return hex value p re compile r d p sub hexrepl Call 65490 for printing 49152 for user code Call 0xffd2 for printing 0xc000 for user code When using the module level re sub function the pattern is passed as the first argument The pattern may be provided as an object or as a string if you need to specify regular expression flags you must either use a pattern object as the first parameter or use embedded modifiers in the pattern string e g sub i b x bbbb BBBB returns x x Common Problems Regular expressions are a powerful tool for some applications but in some ways their behaviour isn t intuitive and at times they don t behave the way you may expect them to This section will point out some of the most common pitfalls Use String Methods Sometimes using the re module is a mistake If you re matching a fixed string or a single character class and you re not using any re features such as the IGNORECASE flag then the full power of regular expressions may not be required Strings have several methods for performing operations with fixed strings and they re usually much faster because the implementation is a single small C loop that s been optimized for the purpose instead of the large more generalized regular expression engine One example might be replacing a single fixed string with another one for example you might replace word with deed re sub seems like the function to use for this but consider the replace method Note that replace will also replace word inside words turning swordfish into sdeedfish but the naive RE word would have done that too To avoid performing the substitution on parts of words the pattern would have to be bword b in order to require that word have a word boundary on either side This takes the job beyond replace s abilities Another common task is deleting every occurrence of a single character from a string or replacing it with another single character You might do this with something like re sub n S but translate is capable of doing both tasks and will be faster than any regular expression operation can be In short before turning to the re module consider whether your problem can be solved with a faster and simpler string method match versus search The match function only checks if the RE matches at the beginning of the string while search will scan forward through the string for a match It s important to keep this distinction in mind Remember match will only report a successful match which will start at 0 if the match wouldn t start at zero match will not report it print re match super superstition span 0 5 print re match super insuperable None On the other hand search will scan forward through the string reporting the first match it finds print re search super superstition span 0 5 print re search super insuperable span 2 7 Sometimes you ll be tempted to keep using re match and just add to the front of your RE Resist this temptation and use re search instead The regular expression compiler does some analysis of REs in order to speed up the process of looking for a match One such analysis figures out what the first character of a match must be for example a pattern starting with Crow must match starting with a C The analysis lets the engine quickly scan through the string looking for the starting character only trying the full match if a C is found Adding defeats this optimization requiring scanning to the end of the string and then backtracking to find a match for the rest of the RE Use re search instead Greedy versus Non Greedy When repeating a regular expression as in a the resulting action is to consume as much of the pattern as possible This fact often bites you when you re trying to match a pair of balanced delimiters such ,en
1204,as the angle brackets surrounding an HTML tag The naive pattern for matching a single HTML tag doesn t work because of the greedy nature of s html head title Title title len s 32 print re match s span 0 32 print re match s group html head title Title title The RE matches the in html and the consumes the rest of the string There s still more left in the RE though and the can t match at the end of the string so the regular expression engine has to backtrack character by character until it finds a match for the The final match extends from the in html to the in title which isn t what you want In this case the solution is to use the non greedy quantifiers or m n which match as little text as possible In the above example the is tried immediately after the first matches and when it fails the engine advances a character at a time retrying the at every step This produces just the right result print re match s group html Note that parsing HTML or XML with regular expressions is painful Quick and dirty patterns will handle common cases but HTML and XML have special cases that will break the obvious regular expression by the time you ve written a regular expression that handles all of the possible cases the patterns will be very complicated Use an HTML or XML parser module for such tasks Using re VERBOSE By now you ve probably noticed that regular expressions are a very compact notation but they re not terribly readable REs of moderate complexity can become lengthy collections of backslashes parentheses and metacharacters making them difficult to read and understand For such REs specifying the re VERBOSE flag when compiling the regular expression can be helpful because it allows you to format the regular expression more clearly The re VERBOSE flag has several effects Whitespace in the regular expression that isn t inside a character class is ignored This means that an expression such as dog cat is equivalent to the less readable dog cat but a b will still match the characters a b or a space In addition you can also put comments inside a RE comments extend from a character to the next newline When used with triple quoted strings this enables REs to be formatted more neatly pat re compile r s Skip leading whitespace P header Header name s Whitespace and a colon P value The header s value used to lose the following trailing whitespace s Trailing whitespace to end of line re VERBOSE This is far more readable than pat re compile r s P header s P value s Feedback Regular expressions are a complicated topic Did this document help you understand them Were there parts that were unclear or Problems you encountered that weren t covered here If so please send suggestions for improvements to the author The most complete book on regular expressions is almost certainly Jeffrey Friedl s Mastering Regular Expressions published by O Reilly Unfortunately it exclusively concentrates on Perl and Java s flavours of regular expressions and doesn t contain any Python material at all so it won t be useful as a reference for programming in Python The first edition covered Python s now removed regex module which won t help you much Consider checking it out from your library,en
1205,Distributing Python Modules Note Information and guidance on distributing Python modules and packages has been moved to the Python Packaging User Guide and the tutorial on packaging Python projects,en
1206,zipimport Import modules from Zip archives Source code Lib zipimport py This module adds the ability to import Python modules py pyc and packages from ZIP format archives It is usually not needed to use the zipimport module explicitly it is automatically used by the built in import mechanism for sys path items that are paths to ZIP archives Typically sys path is a list of directory names as strings This module also allows an item of sys path to be a string naming a ZIP file archive The ZIP archive can contain a subdirectory structure to support package imports and a path within the archive can be specified to only import from a subdirectory For example the path example zip lib would only import from the lib subdirectory within the archive Any files may be present in the ZIP archive but importers are only invoked for py and pyc files ZIP import of dynamic modules pyd so is disallowed Note that if an archive only contains py files Python will not attempt to modify the archive by adding the corresponding pyc file meaning that if a ZIP archive doesn t contain pyc files importing may be rather slow Changed in version 3 8 Previously ZIP archives with an archive comment were not supported See also PKZIP Application Note Documentation on the ZIP file format by Phil Katz the creator of the format and algorithms used PEP 273 Import Modules from Zip Archives Written by James C Ahlstrom who also provided an implementation Python 2 3 follows the specification in PEP 273 but uses an implementation written by Just van Rossum that uses the import hooks described in PEP 302 importlib The implementation of the import machinery Package providing the relevant protocols for all importers to implement This module defines an exception exception zipimport ZipImportError Exception raised by zipimporter objects It s a subclass of ImportError so it can be caught as ImportError too zipimporter Objects zipimporter is the class for importing ZIP files class zipimport zipimporter archivepath Create a new zipimporter instance archivepath must be a path to a ZIP file or to a specific path within a ZIP file For example an archivepath of foo bar zip lib will look for modules in the lib directory inside the ZIP file foo bar zip provided that it exists ZipImportError is raised if archivepath doesn t point to a valid ZIP archive Changed in version 3 12 Methods find_loader and find_module deprecated in 3 10 are now removed Use find_spec instead create_module spec Implementation of importlib abc Loader create_module that returns None to explicitly request the default semantics New in version 3 10 exec_module module Implementation of importlib abc Loader exec_module New in version 3 10 find_spec fullname target None An implementation of importlib abc PathEntryFinder find_spec New in version 3 10 get_code fullname Return the code object for the specified module Raise ZipImportError if the module couldn t be imported get_data pathname Return the data associated with pathname Raise OSError if the file wasn t found Changed in version 3 3 IOError used to be raised it is now an alias of OSError get_filename fullname Return the value __file__ would be set to if the specified module was imported Raise ZipImportError if the module couldn t be imported New in version 3 1 get_source fullname Return the source code for the specified module Raise ZipImportError if the module couldn t be found return None if the archive does contain the module but has no source for it is_package fullname Return True if the module specified by fullname is a package Raise ZipImportError if the module couldn t be found load_module fullname Load the module specified by fullname fullname must be the fully qualified dotted module name Returns the imported module on success raises ZipImportError on failure Deprecated since version 3 10 Use exec_module instead invalidate_caches Clear out the internal cache of information about files found within the ZIP archive New in version 3 10 archive The file name of the importer s associated ZIP file without a possible subpath prefix The subpath within the ZIP,en
1207, file where modules are searched This is the empty string for zipimporter objects which point to the root of the ZIP file The archive and prefix attributes when combined with a slash equal the original archivepath argument given to the zipimporter constructor Examples Here is an example that imports a module from a ZIP archive note that the zipimport module is not explicitly used unzip l example zip Archive example zip Length Date Time Name 8467 11 26 02 22 30 jwzthreading py 8467 1 file python Python 2 3 1 Aug 1 2003 19 54 32 import sys sys path insert 0 example zip Add zip file to front of path import jwzthreading jwzthreading __file__ example zip jwzthreading py,en
1208,sysconfig Provide access to Python s configuration information New in version 3 2 Source code Lib sysconfig py The sysconfig module provides access to Python s configuration information like the list of installation paths and the configuration variables relevant for the current platform Configuration variables A Python distribution contains a Makefile and a pyconfig h header file that are necessary to build both the Python binary itself and third party C extensions compiled using setuptools sysconfig puts all variables found in these files in a dictionary that can be accessed using get_config_vars or get_config_var Notice that on Windows it s a much smaller set sysconfig get_config_vars args With no arguments return a dictionary of all configuration variables relevant for the current platform With arguments return a list of values that result from looking up each argument in the configuration variable dictionary For each argument if the value is not found return None sysconfig get_config_var name Return the value of a single variable name Equivalent to get_config_vars get name If name is not found return None Example of usage import sysconfig sysconfig get_config_var Py_ENABLE_SHARED 0 sysconfig get_config_var LIBDIR usr local lib sysconfig get_config_vars AR CXX ar g Installation paths Python uses an installation scheme that differs depending on the platform and on the installation options These schemes are stored in sysconfig under unique identifiers based on the value returned by os name The schemes are used by package installers to determine where to copy files to Python currently supports nine schemes posix_prefix scheme for POSIX platforms like Linux or macOS This is the default scheme used when Python or a component is installed posix_home scheme for POSIX platforms when the home option is used This scheme defines paths located under a specific home prefix posix_user scheme for POSIX platforms when the user option is used This scheme defines paths located under the user s home directory site USER_BASE posix_venv scheme for Python virtual environments on POSIX platforms by default it is the same as posix_prefix nt scheme for Windows This is the default scheme used when Python or a component is installed nt_user scheme for Windows when the user option is used nt_venv scheme for Python virtual environments on Windows by default it is the same as nt venv a scheme with values from either posix_venv or nt_venv depending on the platform Python runs on osx_framework_user scheme for macOS when the user option is used Each scheme is itself composed of a series of paths and each path has a unique identifier Python currently uses eight paths stdlib directory containing the standard Python library files that are not platform specific platstdlib directory containing the standard Python library files that are platform specific platlib directory for site specific platform specific files purelib directory for site specific non platform specific files pure Python include directory for non platform specific header files for the Python C API platinclude directory for platform specific header files for the Python C API scripts directory for script files data directory for data files User scheme This scheme is designed to be the most convenient solution for users that don t have write permission to the global site packages directory or don t want to install into it Files will be installed into subdirectories of site USER_BASE written as userbase hereafter This scheme installs pure Python modules and extension modules in the same location also known as site USER_SITE posix_user Path Installation directory stdlib userbase lib python X Y platstdlib userbase lib python X Y platlib userbase lib python X Y site packages purelib userbase lib python X Y site packages include userbase include python X Y scripts userbase bin data userbase nt_user Path Installation directory stdlib userbase Python XY platstdlib userbase Python XY platlib userbase Python XY site packages purelib userbase Python XY site packages include userbase Python XY Include s,en
1209,cripts userbase Python XY Scripts data userbase osx_framework_user Path Installation directory stdlib userbase lib python platstdlib userbase lib python platlib userbase lib python site packages purelib userbase lib python site packages include userbase include python X Y scripts userbase bin data userbase Home scheme The idea behind the home scheme is that you build and maintain a personal stash of Python modules This scheme s name is derived from the idea of a home directory on Unix since it s not unusual for a Unix user to make their home directory have a layout similar to usr or usr local This scheme can be used by anyone regardless of the operating system they are installing for posix_home Path Installation directory stdlib home lib python platstdlib home lib python platlib home lib python purelib home lib python include home include python platinclude home include python scripts home bin data home Prefix scheme The prefix scheme is useful when you wish to use one Python installation to perform the build install i e to run the setup script but install modules into the third party module directory of a different Python installation or something that looks like a different Python installation If this sounds a trifle unusual it is that s why the user and home schemes come before However there are at least two known cases where the prefix scheme will be useful First consider that many Linux distributions put Python in usr rather than the more traditional usr local This is entirely appropriate since in those cases Python is part of the system rather than a local add on However if you are installing Python modules from source you probably want them to go in usr local lib python2 X rather than usr lib python2 X Another possibility is a network filesystem where the name used to write to a remote directory is different from the name used to read it for example the Python interpreter accessed as usr local bin python might search for modules in usr local lib python2 X but those modules would have to be installed to say mnt server export lib python2 X posix_prefix Path Installation directory stdlib prefix lib python X Y platstdlib prefix lib python X Y platlib prefix lib python X Y site packages purelib prefix lib python X Y site packages include prefix include python X Y platinclude prefix include python X Y scripts prefix bin data prefix nt Path Installation directory stdlib prefix Lib platstdlib prefix Lib platlib prefix Lib site packages purelib prefix Lib site packages include prefix Include platinclude prefix Include scripts prefix Scripts data prefix Installation path functions sysconfig provides some functions to determine these installation paths sysconfig get_scheme_names Return a tuple containing all schemes currently supported in sysconfig sysconfig get_default_scheme Return the default scheme name for the current platform New in version 3 10 This function was previously named _get_default_scheme and considered an implementation detail Changed in version 3 11 When Python runs from a virtual environment the venv scheme is returned sysconfig get_preferred_scheme key Return a preferred scheme name for an installation layout specified by key key must be either prefix home or user The return value is a scheme name listed in get_scheme_names It can be passed to sysconfig functions that take a scheme argument such as get_paths New in version 3 10 Changed in version 3 11 When Python runs from a virtual environment and key prefix the venv scheme is returned sysconfig _get_preferred_schemes Return a dict containing preferred scheme names on the current platform Python implementers and redistributors may add their preferred schemes to the _INSTALL_SCHEMES module level global value and modify this function to return those scheme names to e g provide different schemes for system and language package managers to use so packages installed by either do not mix with those by the other End users should not use this function but get_default_scheme and get_preferred_scheme instead New in version 3 10 sysconfig get_path_names Return a t,en
1210,uple containing all path names currently supported in sysconfig sysconfig get_path name scheme vars expand Return an installation path corresponding to the path name from the install scheme named scheme name has to be a value from the list returned by get_path_names sysconfig stores installation paths corresponding to each path name for each platform with variables to be expanded For instance the stdlib path for the nt scheme is base Lib get_path will use the variables returned by get_config_vars to expand the path All variables have default values for each platform so one may call this function and get the default value If scheme is provided it must be a value from the list returned by get_scheme_names Otherwise the default scheme for the current platform is used If vars is provided it must be a dictionary of variables that will update the dictionary returned by get_config_vars If expand is set to False the path will not be expanded using the variables If name is not found raise a KeyError sysconfig get_paths scheme vars expand Return a dictionary containing all installation paths corresponding to an installation scheme See get_path for more information If scheme is not provided will use the default scheme for the current platform If vars is provided it must be a dictionary of variables that will update the dictionary used to expand the paths If expand is set to false the paths will not be expanded If scheme is not an existing scheme get_paths will raise a KeyError Other functions sysconfig get_python_version Return the MAJOR MINOR Python version number as a string Similar to d d sys version_info 2 sysconfig get_platform Return a string that identifies the current platform This is used mainly to distinguish platform specific build directories and platform specific built distributions Typically includes the OS name and version and the architecture as supplied by os uname although the exact information included depends on the OS e g on Linux the kernel version isn t particularly important Examples of returned values linux i586 linux alpha solaris 2 6 sun4u Windows will return one of win amd64 64bit Windows on AMD64 aka x86_64 Intel64 and EM64T win32 all others specifically sys platform is returned macOS can return macosx 10 6 ppc macosx 10 4 ppc64 macosx 10 3 i386 macosx 10 4 fat For other non POSIX platforms currently just returns sys platform sysconfig is_python_build Return True if the running Python interpreter was built from source and is being run from its built location and not from a location resulting from e g running make install or installing via a binary installer sysconfig parse_config_h fp vars Parse a config h style file fp is a file like object pointing to the config h like file A dictionary containing name value pairs is returned If an optional dictionary is passed in as the second argument it is used instead of a new dictionary and updated with the values read in the file sysconfig get_config_h_filename Return the path of pyconfig h sysconfig get_makefile_filename Return the path of Makefile Using sysconfig as a script You can use sysconfig as a script with Python s m option python m sysconfig Platform macosx 10 4 i386 Python version 3 2 Current installation scheme posix_prefix Paths data usr local include Users tarek Dev svn python org py3k Include platinclude platlib usr local lib python3 2 site packages platstdlib usr local lib python3 2 purelib usr local lib python3 2 site packages scripts usr local bin stdlib usr local lib python3 2 Variables AC_APPLE_UNIVERSAL_BUILD 0 AIX_GENUINE_CPLUSPLUS 0 AR ar ARFLAGS rc This call will print in the standard output the information returned by get_platform get_python_version get_path and get_config_vars,en
1211,5 Building C and C Extensions on Windows This chapter briefly explains how to create a Windows extension module for Python using Microsoft Visual C and follows with more detailed background information on how it works The explanatory material is useful for both the Windows programmer learning to build Python extensions and the Unix programmer interested in producing software which can be successfully built on both Unix and Windows Module authors are encouraged to use the distutils approach for building extension modules instead of the one described in this section You will still need the C compiler that was used to build Python typically Microsoft Visual C Note This chapter mentions a number of filenames that include an encoded Python version number These filenames are represented with the version number shown as XY in practice X will be the major version number and Y will be the minor version number of the Python release you re working with For example if you are using Python 2 2 1 XY will actually be 22 5 1 A Cookbook Approach There are two approaches to building extension modules on Windows just as there are on Unix use the setuptools package to control the build process or do things manually The setuptools approach works well for most extensions documentation on using setuptools to build and package extension modules is available in Building C and C Extensions with setuptools If you find you really need to do things manually it may be instructive to study the project file for the winsound standard library module 5 2 Differences Between Unix and Windows Unix and Windows use completely different paradigms for run time loading of code Before you try to build a module that can be dynamically loaded be aware of how your system works In Unix a shared object so file contains code to be used by the program and also the names of functions and data that it expects to find in the program When the file is joined to the program all references to those functions and data in the file s code are changed to point to the actual locations in the program where the functions and data are placed in memory This is basically a link operation In Windows a dynamic link library dll file has no dangling references Instead an access to functions or data goes through a lookup table So the DLL code does not have to be fixed up at runtime to refer to the program s memory instead the code already uses the DLL s lookup table and the lookup table is modified at runtime to point to the functions and data In Unix there is only one type of library file a which contains code from several object files o During the link step to create a shared object file so the linker may find that it doesn t know where an identifier is defined The linker will look for it in the object files in the libraries if it finds it it will include all the code from that object file In Windows there are two types of library a static library and an import library both called lib A static library is like a Unix a file it contains code to be included as necessary An import library is basically used only to reassure the linker that a certain identifier is legal and will be present in the program when the DLL is loaded So the linker uses the information from the import library to build the lookup table for using identifiers that are not included in the DLL When an application or a DLL is linked an import library may be generated which will need to be used for all future DLLs that depend on the symbols in the application or DLL Suppose you are building two dynamic load modules B and C which should share another block of code A On Unix you would not pass A a to the linker for B so and C so that would cause it to be included twice so that B and C would each have their own copy In Windows building A dll will also build A lib You do pass A lib to the linker for B and C A lib does not contain code it just contains information which will be used at runtime to access A s code In Windows using an import library is sort of like using import spam it gives you access to spam s names but does not cre,en
1212,ate a separate copy On Unix linking with a library is more like from spam import it does create a separate copy 5 3 Using DLLs in Practice Windows Python is built in Microsoft Visual C using other compilers may or may not work The rest of this section is MSVC specific When creating DLLs in Windows you must pass pythonXY lib to the linker To build two DLLs spam and ni which uses C functions found in spam you could use these commands cl LD I python include spam c libs pythonXY lib cl LD I python include ni c spam lib libs pythonXY lib The first command created three files spam obj spam dll and spam lib Spam dll does not contain any Python functions such as PyArg_ParseTuple but it does know how to find the Python code thanks to pythonXY lib The second command created ni dll and obj and lib which knows how to find the necessary functions from spam and also from the Python executable Not every identifier is exported to the lookup table If you want any other modules including Python to be able to see your identifiers you have to say _declspec dllexport as in void _declspec dllexport initspam void or PyObject _declspec dllexport NiGetSpamData void Developer Studio will throw in a lot of import libraries that you do not really need adding about 100K to your executable To get rid of them use the Project Settings dialog Link tab to specify ignore default libraries Add the correct msvcrt xx lib to the list of libraries,en
1213,importlib resources abc Abstract base classes for resources Source code Lib importlib resources abc py New in version 3 11 class importlib resources abc ResourceReader Superseded by TraversableResources An abstract base class to provide the ability to read resources From the perspective of this ABC a resource is a binary artifact that is shipped within a package Typically this is something like a data file that lives next to the __init__ py file of the package The purpose of this class is to help abstract out the accessing of such data files so that it does not matter if the package and its data file s are stored in a e g zip file versus on the file system For any of methods of this class a resource argument is expected to be a path like object which represents conceptually just a file name This means that no subdirectory paths should be included in the resource argument This is because the location of the package the reader is for acts as the directory Hence the metaphor for directories and file names is packages and resources respectively This is also why instances of this class are expected to directly correlate to a specific package instead of potentially representing multiple packages or a module Loaders that wish to support resource reading are expected to provide a method called get_resource_reader fullname which returns an object implementing this ABC s interface If the module specified by fullname is not a package this method should return None An object compatible with this ABC should only be returned when the specified module is a package Deprecated since version 3 12 will be removed in version 3 14 Use importlib resources abc TraversableResources instead abstractmethod open_resource resource Returns an opened file like object for binary reading of the resource If the resource cannot be found FileNotFoundError is raised abstractmethod resource_path resource Returns the file system path to the resource If the resource does not concretely exist on the file system raise FileNotFoundError abstractmethod is_resource name Returns True if the named name is considered a resource FileNotFoundError is raised if name does not exist abstractmethod contents Returns an iterable of strings over the contents of the package Do note that it is not required that all names returned by the iterator be actual resources e g it is acceptable to return names for which is_resource would be false Allowing non resource names to be returned is to allow for situations where how a package and its resources are stored are known a priori and the non resource names would be useful For instance returning subdirectory names is allowed so that when it is known that the package and resources are stored on the file system then those subdirectory names can be used directly The abstract method returns an iterable of no items class importlib resources abc Traversable An object with a subset of pathlib Path methods suitable for traversing directories and opening files For a representation of the object on the file system use importlib resources as_file name Abstract The base name of this object without any parent references abstractmethod iterdir Yield Traversable objects in self abstractmethod is_dir Return True if self is a directory abstractmethod is_file Return True if self is a file abstractmethod joinpath child Return Traversable child in self abstractmethod __truediv__ child Return Traversable child in self abstractmethod open mode r args kwargs mode may be r or rb to open as text or binary Return a handle suitable for reading same as pathlib Path open When opening as text accepts encoding parameters such as those accepted by io TextIOWrapper read_bytes Read contents of self as bytes read_text encoding None Read contents of self as text class importlib resources abc TraversableResources An abstract base class for resource readers capable of serving the importlib resources files interface Subclasses ResourceReader and provides concrete implementations of the ResourceReader s abstract methods Therefore any loader supplying TraversableResources als,en
1214,o supplies ResourceReader Loaders that wish to support resource reading are expected to implement this interface abstractmethod files Returns a importlib resources abc Traversable object for the loaded package,en
1215,What s New In Python 3 5 Editors Elvis Pranskevichus elvis magic io Yury Selivanov yury magic io This article explains the new features in Python 3 5 compared to 3 4 Python 3 5 was released on September 13 2015 See the changelog for a full list of changes See also PEP 478 Python 3 5 Release Schedule Summary Release highlights New syntax features PEP 492 coroutines with async and await syntax PEP 465 a new matrix multiplication operator a b PEP 448 additional unpacking generalizations New library modules typing PEP 484 Type Hints zipapp PEP 441 Improving Python ZIP Application Support New built in features bytes args bytearray args PEP 461 Adding formatting to bytes and bytearray New bytes hex bytearray hex and memoryview hex methods Contributed by Arnon Yaari in bpo 9951 memoryview now supports tuple indexing including multi dimensional Contributed by Antoine Pitrou in bpo 23632 Generators have a new gi_yieldfrom attribute which returns the object being iterated by yield from expressions Contributed by Benno Leslie and Yury Selivanov in bpo 24450 A new RecursionError exception is now raised when maximum recursion depth is reached Contributed by Georg Brandl in bpo 19235 CPython implementation improvements When the LC_TYPE locale is the POSIX locale C locale sys stdin and sys stdout now use the surrogateescape error handler instead of the strict error handler Contributed by Victor Stinner in bpo 19977 pyo files are no longer used and have been replaced by a more flexible scheme that includes the optimization level explicitly in pyc name See PEP 488 overview Builtin and extension modules are now initialized in a multi phase process which is similar to how Python modules are loaded See PEP 489 overview Significant improvements in the standard library collections OrderedDict is now implemented in C which makes it 4 to 100 times faster The ssl module gained support for Memory BIO which decouples SSL protocol handling from network IO The new os scandir function provides a better and significantly faster way of directory traversal functools lru_cache has been mostly reimplemented in C yielding much better performance The new subprocess run function provides a streamlined way to run subprocesses The traceback module has been significantly enhanced for improved performance and developer convenience Security improvements SSLv3 is now disabled throughout the standard library It can still be enabled by instantiating a ssl SSLContext manually See bpo 22638 for more details this change was backported to CPython 3 4 and 2 7 HTTP cookie parsing is now stricter in order to protect against potential injection attacks Contributed by Antoine Pitrou in bpo 22796 Windows improvements A new installer for Windows has replaced the old MSI See Using Python on Windows for more information Windows builds now use Microsoft Visual C 14 0 and extension modules should use the same Please read on for a comprehensive list of user facing changes including many other smaller improvements CPython optimizations deprecations and potential porting issues New Features PEP 492 Coroutines with async and await syntax PEP 492 greatly improves support for asynchronous programming in Python by adding awaitable objects coroutine functions asynchronous iteration and asynchronous context managers Coroutine functions are declared using the new async def syntax async def coro return spam Inside a coroutine function the new await expression can be used to suspend coroutine execution until the result is available Any object can be awaited as long as it implements the awaitable protocol by defining the __await__ method PEP 492 also adds async for statement for convenient iteration over asynchronous iterables An example of a rudimentary HTTP client written using the new syntax import asyncio async def http_get domain reader writer await asyncio open_connection domain 80 writer write b r n join b GET HTTP 1 1 b Host b domain encode latin 1 b Connection close b b async for line in reader print line writer close loop asyncio get_event_loop try loop run_until_complete http_get ex,en
1216,ample com finally loop close Similarly to asynchronous iteration there is a new syntax for asynchronous context managers The following script import asyncio async def coro name lock print coro waiting for lock format name async with lock print coro holding the lock format name await asyncio sleep 1 print coro releasing the lock format name loop asyncio get_event_loop lock asyncio Lock coros asyncio gather coro 1 lock coro 2 lock try loop run_until_complete coros finally loop close will output coro 2 waiting for lock coro 2 holding the lock coro 1 waiting for lock coro 2 releasing the lock coro 1 holding the lock coro 1 releasing the lock Note that both async for and async with can only be used inside a coroutine function declared with async def Coroutine functions are intended to be run inside a compatible event loop such as the asyncio loop Note Changed in version 3 5 2 Starting with CPython 3 5 2 __aiter__ can directly return asynchronous iterators Returning an awaitable object will result in a PendingDeprecationWarning See more details in the Asynchronous Iterators documentation section See also PEP 492 Coroutines with async and await syntax PEP written and implemented by Yury Selivanov PEP 465 A dedicated infix operator for matrix multiplication PEP 465 adds the infix operator for matrix multiplication Currently no builtin Python types implement the new operator however it can be implemented by defining __matmul__ __rmatmul__ and __imatmul__ for regular reflected and in place matrix multiplication The semantics of these methods is similar to that of methods defining other infix arithmetic operators Matrix multiplication is a notably common operation in many fields of mathematics science engineering and the addition of allows writing cleaner code S H beta r T inv H V H T H beta r instead of S dot dot H beta r T dot inv dot dot H V H T dot H beta r NumPy 1 10 has support for the new operator import numpy x numpy ones 3 x array 1 1 1 m numpy eye 3 m array 1 0 0 0 1 0 0 0 1 x m array 1 1 1 See also PEP 465 A dedicated infix operator for matrix multiplication PEP written by Nathaniel J Smith implemented by Benjamin Peterson PEP 448 Additional Unpacking Generalizations PEP 448 extends the allowed uses of the iterable unpacking operator and dictionary unpacking operator It is now possible to use an arbitrary number of unpackings in function calls print 1 2 3 4 5 1 2 3 4 5 def fn a b c d print a b c d fn a 1 c 3 b 2 d 4 1 2 3 4 Similarly tuple list set and dictionary displays allow multiple unpackings see Expression lists and Dictionary displays range 4 4 0 1 2 3 4 range 4 4 0 1 2 3 4 range 4 4 5 6 7 0 1 2 3 4 5 6 7 x 1 y 2 x 1 y 2 See also PEP 448 Additional Unpacking Generalizations PEP written by Joshua Landau implemented by Neil Girdhar Thomas Wouters and Joshua Landau PEP 461 percent formatting support for bytes and bytearray PEP 461 adds support for the interpolation operator to bytes and bytearray While interpolation is usually thought of as a string operation there are cases where interpolation on bytes or bytearrays makes sense and the work needed to make up for this missing functionality detracts from the overall readability of the code This issue is particularly important when dealing with wire format protocols which are often a mixture of binary and ASCII compatible text Examples b Hello b b World b Hello World b x i y f 1 2 5 b x 1 y 2 500000 Unicode is not allowed for b but it is accepted by a equivalent of repr obj encode ascii backslashreplace b Hello b World Traceback most recent call last File stdin line 1 in module TypeError b requires bytes or an object that implements __bytes__ not str b price a 10 b price 10 u20ac Note that s and r conversion types although supported should only be used in codebases that need compatibility with Python 2 See also PEP 461 Adding formatting to bytes and bytearray PEP written by Ethan Furman implemented by Neil Schemenauer and Ethan Furman PEP 484 Type Hints Function annotation syntax has been a Python feature since version 3 0 PEP 3107 however the semantics of annotations ,en
1217,has been left undefined Experience has shown that the majority of function annotation uses were to provide type hints to function parameters and return values It became evident that it would be beneficial for Python users if the standard library included the base definitions and tools for type annotations PEP 484 introduces a provisional module to provide these standard definitions and tools along with some conventions for situations where annotations are not available For example here is a simple function whose argument and return type are declared in the annotations def greeting name str str return Hello name While these annotations are available at runtime through the usual __annotations__ attribute no automatic type checking happens at runtime Instead it is assumed that a separate off line type checker e g mypy will be used for on demand source code analysis The type system supports unions generic types and a special type named Any which is consistent with i e assignable to and from all types See also typing module documentation PEP 484 Type Hints PEP written by Guido van Rossum Jukka Lehtosalo and Łukasz Langa implemented by Guido van Rossum PEP 483 The Theory of Type Hints PEP written by Guido van Rossum PEP 471 os scandir function a better and faster directory iterator PEP 471 adds a new directory iteration function os scandir to the standard library Additionally os walk is now implemented using scandir which makes it 3 to 5 times faster on POSIX systems and 7 to 20 times faster on Windows systems This is largely achieved by greatly reducing the number of calls to os stat required to walk a directory tree Additionally scandir returns an iterator as opposed to returning a list of file names which improves memory efficiency when iterating over very large directories The following example shows a simple use of os scandir to display all the files excluding directories in the given path that don t start with The entry is_file call will generally not make an additional system call for entry in os scandir path if not entry name startswith and entry is_file print entry name See also PEP 471 os scandir function a better and faster directory iterator PEP written and implemented by Ben Hoyt with the help of Victor Stinner PEP 475 Retry system calls failing with EINTR An errno EINTR error code is returned whenever a system call that is waiting for I O is interrupted by a signal Previously Python would raise InterruptedError in such cases This meant that when writing a Python application the developer had two choices 1 Ignore the InterruptedError 2 Handle the InterruptedError and attempt to restart the interrupted system call at every call site The first option makes an application fail intermittently The second option adds a large amount of boilerplate that makes the code nearly unreadable Compare print Hello World and while True try print Hello World break except InterruptedError continue PEP 475 implements automatic retry of system calls on EINTR This removes the burden of dealing with EINTR or InterruptedError in user code in most situations and makes Python programs including the standard library more robust Note that the system call is only retried if the signal handler does not raise an exception Below is a list of functions which are now retried when interrupted by a signal open and io open functions of the faulthandler module os functions fchdir fchmod fchown fdatasync fstat fstatvfs fsync ftruncate mkfifo mknod open posix_fadvise posix_fallocate pread pwrite read readv sendfile wait3 wait4 wait waitid waitpid write writev special cases os close and os dup2 now ignore EINTR errors the syscall is not retried see the PEP for the rationale select functions devpoll poll epoll poll kqueue control poll poll select methods of the socket class accept connect except for non blocking sockets recv recvfrom recvmsg send sendall sendmsg sendto signal sigtimedwait and signal sigwaitinfo time sleep See also PEP 475 Retry system calls failing with EINTR PEP and implementation written by Charles François Natali and Victor Stinner with,en
1218, the help of Antoine Pitrou the French connection PEP 479 Change StopIteration handling inside generators The interaction of generators and StopIteration in Python 3 4 and earlier was sometimes surprising and could conceal obscure bugs Previously StopIteration raised accidentally inside a generator function was interpreted as the end of the iteration by the loop construct driving the generator PEP 479 changes the behavior of generators when a StopIteration exception is raised inside a generator it is replaced with a RuntimeError before it exits the generator frame The main goal of this change is to ease debugging in the situation where an unguarded next call raises StopIteration and causes the iteration controlled by the generator to terminate silently This is particularly pernicious in combination with the yield from construct This is a backwards incompatible change so to enable the new behavior a __future__ import is necessary from __future__ import generator_stop def gen next iter yield next gen Traceback most recent call last File stdin line 2 in gen StopIteration The above exception was the direct cause of the following exception Traceback most recent call last File stdin line 1 in module RuntimeError generator raised StopIteration Without a __future__ import a PendingDeprecationWarning will be raised whenever a StopIteration exception is raised inside a generator See also PEP 479 Change StopIteration handling inside generators PEP written by Chris Angelico and Guido van Rossum Implemented by Chris Angelico Yury Selivanov and Nick Coghlan PEP 485 A function for testing approximate equality PEP 485 adds the math isclose and cmath isclose functions which tell whether two values are approximately equal or close to each other Whether or not two values are considered close is determined according to given absolute and relative tolerances Relative tolerance is the maximum allowed difference between isclose arguments relative to the larger absolute value import math a 5 0 b 4 99998 math isclose a b rel_tol 1e 5 True math isclose a b rel_tol 1e 6 False It is also possible to compare two values using absolute tolerance which must be a non negative value import math a 5 0 b 4 99998 math isclose a b abs_tol 0 00003 True math isclose a b abs_tol 0 00001 False See also PEP 485 A function for testing approximate equality PEP written by Christopher Barker implemented by Chris Barker and Tal Einat PEP 486 Make the Python Launcher aware of virtual environments PEP 486 makes the Windows launcher see PEP 397 aware of an active virtual environment When the default interpreter would be used and the VIRTUAL_ENV environment variable is set the interpreter in the virtual environment will be used See also PEP 486 Make the Python Launcher aware of virtual environments PEP written and implemented by Paul Moore PEP 488 Elimination of PYO files PEP 488 does away with the concept of pyo files This means that pyc files represent both unoptimized and optimized bytecode To prevent the need to constantly regenerate bytecode files pyc files now have an optional opt tag in their name when the bytecode is optimized This has the side effect of no more bytecode file name clashes when running under either O or OO Consequently bytecode files generated from O and OO may now exist simultaneously importlib util cache_from_source has an updated API to help with this change See also PEP 488 Elimination of PYO files PEP written and implemented by Brett Cannon PEP 489 Multi phase extension module initialization PEP 489 updates extension module initialization to take advantage of the two step module loading mechanism introduced by PEP 451 in Python 3 4 This change brings the import semantics of extension modules that opt in to using the new mechanism much closer to those of Python source and bytecode modules including the ability to use any valid identifier as a module name rather than being restricted to ASCII See also PEP 489 Multi phase extension module initialization PEP written by Petr Viktorin Stefan Behnel and Nick Coghlan implemented by Petr Viktorin Other,en
1219, Language Changes Some smaller changes made to the core Python language are Added the namereplace error handlers The backslashreplace error handlers now work with decoding and translating Contributed by Serhiy Storchaka in bpo 19676 and bpo 22286 The b option now affects comparisons of bytes with int Contributed by Serhiy Storchaka in bpo 23681 New Kazakh kz1048 and Tajik koi8_t codecs Contributed by Serhiy Storchaka in bpo 22682 and bpo 22681 Property docstrings are now writable This is especially useful for collections namedtuple docstrings Contributed by Berker Peksag in bpo 24064 Circular imports involving relative imports are now supported Contributed by Brett Cannon and Antoine Pitrou in bpo 17636 New Modules typing The new typing provisional module provides standard definitions and tools for function type annotations See Type Hints for more information zipapp The new zipapp module specified in PEP 441 provides an API and command line tool for creating executable Python Zip Applications which were introduced in Python 2 6 in bpo 1739468 but which were not well publicized either at the time or since With the new module bundling your application is as simple as putting all the files including a __main__ py file into a directory myapp and running python m zipapp myapp python myapp pyz The module implementation has been contributed by Paul Moore in bpo 23491 See also PEP 441 Improving Python ZIP Application Support Improved Modules argparse The ArgumentParser class now allows disabling abbreviated usage of long options by setting allow_abbrev to False Contributed by Jonathan Paugh Steven Bethard paul j3 and Daniel Eriksson in bpo 14910 asyncio Since the asyncio module is provisional all changes introduced in Python 3 5 have also been backported to Python 3 4 x Notable changes in the asyncio module since Python 3 4 0 New debugging APIs loop set_debug and loop get_debug methods Contributed by Victor Stinner The proactor event loop now supports SSL Contributed by Antoine Pitrou and Victor Stinner in bpo 22560 A new loop is_closed method to check if the event loop is closed Contributed by Victor Stinner in bpo 21326 A new loop create_task to conveniently create and schedule a new Task for a coroutine The create_task method is also used by all asyncio functions that wrap coroutines into tasks such as asyncio wait asyncio gather etc Contributed by Victor Stinner A new transport get_write_buffer_limits method to inquire for high and low water limits of the flow control Contributed by Victor Stinner The async function is deprecated in favor of ensure_future Contributed by Yury Selivanov New loop set_task_factory and loop get_task_factory methods to customize the task factory that loop create_task method uses Contributed by Yury Selivanov New Queue join and Queue task_done queue methods Contributed by Victor Stinner The JoinableQueue class was removed in favor of the asyncio Queue class Contributed by Victor Stinner Updates in 3 5 1 The ensure_future function and all functions that use it such as loop run_until_complete now accept all kinds of awaitable objects Contributed by Yury Selivanov New run_coroutine_threadsafe function to submit coroutines to event loops from other threads Contributed by Vincent Michel New Transport is_closing method to check if the transport is closing or closed Contributed by Yury Selivanov The loop create_server method can now accept a list of hosts Contributed by Yann Sionneau Updates in 3 5 2 New loop create_future method to create Future objects This allows alternative event loop implementations such as uvloop to provide a faster asyncio Future implementation Contributed by Yury Selivanov New loop get_exception_handler method to get the current exception handler Contributed by Yury Selivanov New StreamReader readuntil method to read data from the stream until a separator bytes sequence appears Contributed by Mark Korenberg The loop create_connection and loop create_server methods are optimized to avoid calling the system getaddrinfo function if the address is already resolved Contributed by A Jes,en
1220,se Jiryu Davis The loop sock_connect sock address no longer requires the address to be resolved prior to the call Contributed by A Jesse Jiryu Davis bz2 The BZ2Decompressor decompress method now accepts an optional max_length argument to limit the maximum size of decompressed data Contributed by Nikolaus Rath in bpo 15955 cgi The FieldStorage class now supports the context manager protocol Contributed by Berker Peksag in bpo 20289 cmath A new function isclose provides a way to test for approximate equality Contributed by Chris Barker and Tal Einat in bpo 24270 code The InteractiveInterpreter showtraceback method now prints the full chained traceback just like the interactive interpreter Contributed by Claudiu Popa in bpo 17442 collections The OrderedDict class is now implemented in C which makes it 4 to 100 times faster Contributed by Eric Snow in bpo 16991 OrderedDict items OrderedDict keys OrderedDict values views now support reversed iteration Contributed by Serhiy Storchaka in bpo 19505 The deque class now defines index insert and copy and supports the and operators This allows deques to be recognized as a MutableSequence and improves their substitutability for lists Contributed by Raymond Hettinger in bpo 23704 Docstrings produced by namedtuple can now be updated Point namedtuple Point x y Point __doc__ Cartesian coordinate Point x __doc__ abscissa Point y __doc__ ordinate Contributed by Berker Peksag in bpo 24064 The UserString class now implements the __getnewargs__ __rmod__ casefold format_map isprintable and maketrans methods to match the corresponding methods of str Contributed by Joe Jevnik in bpo 22189 collections abc The Sequence index method now accepts start and stop arguments to match the corresponding methods of tuple list etc Contributed by Devin Jeanpierre in bpo 23086 A new Generator abstract base class Contributed by Stefan Behnel in bpo 24018 New Awaitable Coroutine AsyncIterator and AsyncIterable abstract base classes Contributed by Yury Selivanov in bpo 24184 For earlier Python versions a backport of the new ABCs is available in an external PyPI package compileall A new compileall option j N allows running N workers simultaneously to perform parallel bytecode compilation The compile_dir function has a corresponding workers parameter Contributed by Claudiu Popa in bpo 16104 Another new option r allows controlling the maximum recursion level for subdirectories Contributed by Claudiu Popa in bpo 19628 The q command line option can now be specified more than once in which case all output including errors will be suppressed The corresponding quiet parameter in compile_dir compile_file and compile_path can now accept an integer value indicating the level of output suppression Contributed by Thomas Kluyver in bpo 21338 concurrent futures The Executor map method now accepts a chunksize argument to allow batching of tasks to improve performance when ProcessPoolExecutor is used Contributed by Dan O Reilly in bpo 11271 The number of workers in the ThreadPoolExecutor constructor is optional now The default value is 5 times the number of CPUs Contributed by Claudiu Popa in bpo 21527 configparser configparser now provides a way to customize the conversion of values by specifying a dictionary of converters in the ConfigParser constructor or by defining them as methods in ConfigParser subclasses Converters defined in a parser instance are inherited by its section proxies Example import configparser conv conv list lambda v e strip for e in v split if e strip cfg configparser ConfigParser converters conv cfg read_string s list a b c d e f g cfg get s list a b c d e f g cfg getlist s list a b c d e f g section cfg s section getlist list a b c d e f g Contributed by Łukasz Langa in bpo 18159 contextlib The new redirect_stderr context manager similar to redirect_stdout makes it easier for utility scripts to handle inflexible APIs that write their output to sys stderr and don t provide any options to redirect it import contextlib io logging f io StringIO with contextlib redirect_stderr f logging warning warning f getva,en
1221,lue WARNING root warning n Contributed by Berker Peksag in bpo 22389 csv The writerow method now supports arbitrary iterables not just sequences Contributed by Serhiy Storchaka in bpo 23171 curses The new update_lines_cols function updates the LINES and COLS module variables This is useful for detecting manual screen resizing Contributed by Arnon Yaari in bpo 4254 dbm dumb open always creates a new database when the flag has the value n Contributed by Claudiu Popa in bpo 18039 difflib The charset of HTML documents generated by HtmlDiff make_file can now be customized by using a new charset keyword only argument The default charset of HTML document changed from ISO 8859 1 to utf 8 Contributed by Berker Peksag in bpo 2052 The diff_bytes function can now compare lists of byte strings This fixes a regression from Python 2 Contributed by Terry J Reedy and Greg Ward in bpo 17445 distutils Both the build and build_ext commands now accept a j option to enable parallel building of extension modules Contributed by Antoine Pitrou in bpo 5309 The distutils module now supports xz compression and can be enabled by passing xztar as an argument to bdist format Contributed by Serhiy Storchaka in bpo 16314 doctest The DocTestSuite function returns an empty unittest TestSuite if module contains no docstrings instead of raising ValueError Contributed by Glenn Jones in bpo 15916 email A new policy option Policy mangle_from_ controls whether or not lines that start with From in email bodies are prefixed with a character by generators The default is True for compat32 and False for all other policies Contributed by Milan Oberkirch in bpo 20098 A new Message get_content_disposition method provides easy access to a canonical value for the Content Disposition header Contributed by Abhilash Raj in bpo 21083 A new policy option EmailPolicy utf8 can be set to True to encode email headers using the UTF 8 charset instead of using encoded words This allows Messages to be formatted according to RFC 6532 and used with an SMTP server that supports the RFC 6531 SMTPUTF8 extension Contributed by R David Murray in bpo 24211 The mime text MIMEText constructor now accepts a charset Charset instance Contributed by Claude Paroz and Berker Peksag in bpo 16324 enum The Enum callable has a new parameter start to specify the initial number of enum values if only names are provided Animal enum Enum Animal cat dog start 10 Animal cat Animal cat 10 Animal dog Animal dog 11 Contributed by Ethan Furman in bpo 21706 faulthandler The enable register dump_traceback and dump_traceback_later functions now accept file descriptors in addition to file like objects Contributed by Wei Wu in bpo 23566 functools Most of the lru_cache machinery is now implemented in C making it significantly faster Contributed by Matt Joiner Alexey Kachayev and Serhiy Storchaka in bpo 14373 glob The iglob and glob functions now support recursive search in subdirectories using the pattern Contributed by Serhiy Storchaka in bpo 13968 gzip The mode argument of the GzipFile constructor now accepts x to request exclusive creation Contributed by Tim Heaney in bpo 19222 heapq Element comparison in merge can now be customized by passing a key function in a new optional key keyword argument and a new optional reverse keyword argument can be used to reverse element comparison import heapq a 9 777 55555 b 88 6666 list heapq merge a b key len 9 88 777 6666 55555 list heapq merge reversed a reversed b key len reverse True 55555 6666 777 88 9 Contributed by Raymond Hettinger in bpo 13742 http A new HTTPStatus enum that defines a set of HTTP status codes reason phrases and long descriptions written in English Contributed by Demian Brecht in bpo 21793 http client HTTPConnection getresponse now raises a RemoteDisconnected exception when a remote server connection is closed unexpectedly Additionally if a ConnectionError of which RemoteDisconnected is a subclass is raised the client socket is now closed automatically and will reconnect on the next request import http client conn http client HTTPConnection www python org,en
1222, for retries in range 3 try conn request GET resp conn getresponse except http client RemoteDisconnected pass Contributed by Martin Panter in bpo 3566 idlelib and IDLE Since idlelib implements the IDLE shell and editor and is not intended for import by other programs it gets improvements with every release See Lib idlelib NEWS txt for a cumulative list of changes since 3 4 0 as well as changes made in future 3 5 x releases This file is also available from the IDLE Help About IDLE dialog imaplib The IMAP4 class now supports the context manager protocol When used in a with statement the IMAP4 LOGOUT command will be called automatically at the end of the block Contributed by Tarek Ziadé and Serhiy Storchaka in bpo 4972 The imaplib module now supports RFC 5161 ENABLE Extension and RFC 6855 UTF 8 Support via the IMAP4 enable method A new IMAP4 utf8_enabled attribute tracks whether or not RFC 6855 support is enabled Contributed by Milan Oberkirch R David Murray and Maciej Szulik in bpo 21800 The imaplib module now automatically encodes non ASCII string usernames and passwords using UTF 8 as recommended by the RFCs Contributed by Milan Oberkirch in bpo 21800 imghdr The what function now recognizes the OpenEXR format contributed by Martin Vignali and Claudiu Popa in bpo 20295 and the WebP format contributed by Fabrice Aneche and Claudiu Popa in bpo 20197 importlib The util LazyLoader class allows for lazy loading of modules in applications where startup time is important Contributed by Brett Cannon in bpo 17621 The abc InspectLoader source_to_code method is now a static method This makes it easier to initialize a module object with code compiled from a string by running exec code module __dict__ Contributed by Brett Cannon in bpo 21156 The new util module_from_spec function is now the preferred way to create a new module As opposed to creating a types ModuleType instance directly this new function will set the various import controlled attributes based on the passed in spec object Contributed by Brett Cannon in bpo 20383 inspect Both the Signature and Parameter classes are now picklable and hashable Contributed by Yury Selivanov in bpo 20726 and bpo 20334 A new BoundArguments apply_defaults method provides a way to set default values for missing arguments def foo a b ham args pass ba inspect signature foo bind spam ba apply_defaults ba arguments OrderedDict a spam b ham args Contributed by Yury Selivanov in bpo 24190 A new class method Signature from_callable makes subclassing of Signature easier Contributed by Yury Selivanov and Eric Snow in bpo 17373 The signature function now accepts a follow_wrapped optional keyword argument which when set to False disables automatic following of __wrapped__ links Contributed by Yury Selivanov in bpo 20691 A set of new functions to inspect coroutine functions and coroutine objects has been added iscoroutine iscoroutinefunction isawaitable getcoroutinelocals and getcoroutinestate Contributed by Yury Selivanov in bpo 24017 and bpo 24400 The stack trace getouterframes and getinnerframes functions now return a list of named tuples Contributed by Daniel Shahaf in bpo 16808 io A new BufferedIOBase readinto1 method that uses at most one call to the underlying raw stream s RawIOBase read or RawIOBase readinto methods Contributed by Nikolaus Rath in bpo 20578 ipaddress Both the IPv4Network and IPv6Network classes now accept an address netmask tuple argument so as to easily construct network objects from existing addresses import ipaddress ipaddress IPv4Network 127 0 0 0 8 IPv4Network 127 0 0 0 8 ipaddress IPv4Network 127 0 0 0 255 0 0 0 IPv4Network 127 0 0 0 8 Contributed by Peter Moody and Antoine Pitrou in bpo 16531 A new reverse_pointer attribute for the IPv4Network and IPv6Network classes returns the name of the reverse DNS PTR record import ipaddress addr ipaddress IPv4Address 127 0 0 1 addr reverse_pointer 1 0 0 127 in addr arpa addr6 ipaddress IPv6Address 1 addr6 reverse_pointer 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ip6 arpa Contributed by Leon Weber in bpo 20480 json,en
1223, The json tool command line interface now preserves the order of keys in JSON objects passed in input The new sort keys option can be used to sort the keys alphabetically Contributed by Berker Peksag in bpo 21650 JSON decoder now raises JSONDecodeError instead of ValueError to provide better context information about the error Contributed by Serhiy Storchaka in bpo 19361 linecache A new lazycache function can be used to capture information about a non file based module to permit getting its lines later via getline This avoids doing I O until a line is actually needed without having to carry the module globals around indefinitely Contributed by Robert Collins in bpo 17911 locale A new delocalize function can be used to convert a string into a normalized number string taking the LC_NUMERIC settings into account import locale locale setlocale locale LC_NUMERIC de_DE UTF 8 de_DE UTF 8 locale delocalize 1 234 56 1234 56 locale setlocale locale LC_NUMERIC en_US UTF 8 en_US UTF 8 locale delocalize 1 234 56 1234 56 Contributed by Cédric Krier in bpo 13918 logging All logging methods Logger log exception critical debug etc now accept exception instances as an exc_info argument in addition to boolean values and exception tuples import logging try 1 0 except ZeroDivisionError as ex logging error exception exc_info ex ERROR root exception Contributed by Yury Selivanov in bpo 20537 The handlers HTTPHandler class now accepts an optional ssl SSLContext instance to configure SSL settings used in an HTTP connection Contributed by Alex Gaynor in bpo 22788 The handlers QueueListener class now takes a respect_handler_level keyword argument which if set to True will pass messages to handlers taking handler levels into account Contributed by Vinay Sajip lzma The LZMADecompressor decompress method now accepts an optional max_length argument to limit the maximum size of decompressed data Contributed by Martin Panter in bpo 15955 math Two new constants have been added to the math module inf and nan Contributed by Mark Dickinson in bpo 23185 A new function isclose provides a way to test for approximate equality Contributed by Chris Barker and Tal Einat in bpo 24270 A new gcd function has been added The fractions gcd function is now deprecated Contributed by Mark Dickinson and Serhiy Storchaka in bpo 22486 multiprocessing sharedctypes synchronized objects now support the context manager protocol Contributed by Charles François Natali in bpo 21565 operator attrgetter itemgetter and methodcaller objects now support pickling Contributed by Josh Rosenberg and Serhiy Storchaka in bpo 22955 New matmul and imatmul functions to perform matrix multiplication Contributed by Benjamin Peterson in bpo 21176 os The new scandir function returning an iterator of DirEntry objects has been added If possible scandir extracts file attributes while scanning a directory removing the need to perform subsequent system calls to determine file type or attributes which may significantly improve performance Contributed by Ben Hoyt with the help of Victor Stinner in bpo 22524 On Windows a new stat_result st_file_attributes attribute is now available It corresponds to the dwFileAttributes member of the BY_HANDLE_FILE_INFORMATION structure returned by GetFileInformationByHandle Contributed by Ben Hoyt in bpo 21719 The urandom function now uses the getrandom syscall on Linux 3 17 or newer and getentropy on OpenBSD 5 6 and newer removing the need to use dev urandom and avoiding failures due to potential file descriptor exhaustion Contributed by Victor Stinner in bpo 22181 New get_blocking and set_blocking functions allow getting and setting a file descriptor s blocking mode O_NONBLOCK Contributed by Victor Stinner in bpo 22054 The truncate and ftruncate functions are now supported on Windows Contributed by Steve Dower in bpo 23668 There is a new os path commonpath function returning the longest common sub path of each passed pathname Unlike the os path commonprefix function it always returns a valid path os path commonprefix usr lib usr local lib usr l os path commonpath usr lib ,en
1224,usr local lib usr Contributed by Rafik Draoui and Serhiy Storchaka in bpo 10395 pathlib The new Path samefile method can be used to check whether the path points to the same file as another path which can be either another Path object or a string import pathlib p1 pathlib Path etc hosts p2 pathlib Path etc etc hosts p1 samefile p2 True Contributed by Vajrasky Kok and Antoine Pitrou in bpo 19775 The Path mkdir method now accepts a new optional exist_ok argument to match mkdir p and os makedirs functionality Contributed by Berker Peksag in bpo 21539 There is a new Path expanduser method to expand and user prefixes Contributed by Serhiy Storchaka and Claudiu Popa in bpo 19776 A new Path home class method can be used to get a Path instance representing the user s home directory Contributed by Victor Salgado and Mayank Tripathi in bpo 19777 New Path write_text Path read_text Path write_bytes Path read_bytes methods to simplify read write operations on files The following code snippet will create or rewrite existing file spam42 import pathlib p pathlib Path spam42 p expanduser write_text ham 3 Contributed by Christopher Welborn in bpo 20218 pickle Nested objects such as unbound methods or nested classes can now be pickled using pickle protocols older than protocol version 4 Protocol version 4 already supports these cases Contributed by Serhiy Storchaka in bpo 23611 poplib A new POP3 utf8 command enables RFC 6856 Internationalized Email support if a POP server supports it Contributed by Milan OberKirch in bpo 21804 re References and conditional references to groups with fixed length are now allowed in lookbehind assertions import re pat re compile r a b 1 c pat match aac _sre SRE_Match object span 0 3 match aac pat match bbc _sre SRE_Match object span 0 3 match bbc Contributed by Serhiy Storchaka in bpo 9179 The number of capturing groups in regular expressions is no longer limited to 100 Contributed by Serhiy Storchaka in bpo 22437 The sub and subn functions now replace unmatched groups with empty strings instead of raising an exception Contributed by Serhiy Storchaka in bpo 1519638 The re error exceptions have new attributes msg pattern pos lineno and colno that provide better context information about the error re compile x Traceback most recent call last sre_constants error multiple repeat at position 16 line 3 column 7 Contributed by Serhiy Storchaka in bpo 22578 readline A new append_history_file function can be used to append the specified number of trailing elements in history to the given file Contributed by Bruno Cauet in bpo 22940 selectors The new DevpollSelector supports efficient dev poll polling on Solaris Contributed by Giampaolo Rodola in bpo 18931 shutil The move function now accepts a copy_function argument allowing for example the copy function to be used instead of the default copy2 if there is a need to ignore file metadata when moving Contributed by Claudiu Popa in bpo 19840 The make_archive function now supports the xztar format Contributed by Serhiy Storchaka in bpo 5411 signal On Windows the set_wakeup_fd function now also supports socket handles Contributed by Victor Stinner in bpo 22018 Various SIG constants in the signal module have been converted into Enums This allows meaningful names to be printed during debugging instead of integer magic numbers Contributed by Giampaolo Rodola in bpo 21076 smtpd Both the SMTPServer and SMTPChannel classes now accept a decode_data keyword argument to determine if the DATA portion of the SMTP transaction is decoded using the utf 8 codec or is instead provided to the SMTPServer process_message method as a byte string The default is True for backward compatibility reasons but will change to False in Python 3 6 If decode_data is set to False the process_message method must be prepared to accept keyword arguments Contributed by Maciej Szulik in bpo 19662 The SMTPServer class now advertises the 8BITMIME extension RFC 6152 if decode_data has been set True If the client specifies BODY 8BITMIME on the MAIL command it is passed to SMTPServer process_message via the mail_op,en
1225,tions keyword Contributed by Milan Oberkirch and R David Murray in bpo 21795 The SMTPServer class now also supports the SMTPUTF8 extension RFC 6531 Internationalized Email If the client specified SMTPUTF8 BODY 8BITMIME on the MAIL command they are passed to SMTPServer process_message via the mail_options keyword It is the responsibility of the process_message method to correctly handle the SMTPUTF8 data Contributed by Milan Oberkirch in bpo 21725 It is now possible to provide directly or via name resolution IPv6 addresses in the SMTPServer constructor and have it successfully connect Contributed by Milan Oberkirch in bpo 14758 smtplib A new SMTP auth method provides a convenient way to implement custom authentication mechanisms Contributed by Milan Oberkirch in bpo 15014 The SMTP set_debuglevel method now accepts an additional debuglevel 2 which enables timestamps in debug messages Contributed by Gavin Chappell and Maciej Szulik in bpo 16914 Both the SMTP sendmail and SMTP send_message methods now support RFC 6531 SMTPUTF8 Contributed by Milan Oberkirch and R David Murray in bpo 22027 sndhdr The what and whathdr functions now return a namedtuple Contributed by Claudiu Popa in bpo 18615 socket Functions with timeouts now use a monotonic clock instead of a system clock Contributed by Victor Stinner in bpo 22043 A new socket sendfile method allows sending a file over a socket by using the high performance os sendfile function on UNIX resulting in uploads being from 2 to 3 times faster than when using plain socket send Contributed by Giampaolo Rodola in bpo 17552 The socket sendall method no longer resets the socket timeout every time bytes are received or sent The socket timeout is now the maximum total duration to send all data Contributed by Victor Stinner in bpo 23853 The backlog argument of the socket listen method is now optional By default it is set to SOMAXCONN or to 128 whichever is less Contributed by Charles François Natali in bpo 21455 ssl Memory BIO Support Contributed by Geert Jansen in bpo 21965 The new SSLObject class has been added to provide SSL protocol support for cases when the network I O capabilities of SSLSocket are not necessary or are suboptimal SSLObject represents an SSL protocol instance but does not implement any network I O methods and instead provides a memory buffer interface The new MemoryBIO class can be used to pass data between Python and an SSL protocol instance The memory BIO SSL support is primarily intended to be used in frameworks implementing asynchronous I O for which SSLSocket s readiness model select poll is inefficient A new SSLContext wrap_bio method can be used to create a new SSLObject instance Application Layer Protocol Negotiation Support Contributed by Benjamin Peterson in bpo 20188 Where OpenSSL support is present the ssl module now implements the Application Layer Protocol Negotiation TLS extension as described in RFC 7301 The new SSLContext set_alpn_protocols can be used to specify which protocols a socket should advertise during the TLS handshake The new SSLSocket selected_alpn_protocol returns the protocol that was selected during the TLS handshake The HAS_ALPN flag indicates whether ALPN support is present Other Changes There is a new SSLSocket version method to query the actual protocol version in use Contributed by Antoine Pitrou in bpo 20421 The SSLSocket class now implements a SSLSocket sendfile method Contributed by Giampaolo Rodola in bpo 17552 The SSLSocket send method now raises either the ssl SSLWantReadError or ssl SSLWantWriteError exception on a non blocking socket if the operation would block Previously it would return 0 Contributed by Nikolaus Rath in bpo 20951 The cert_time_to_seconds function now interprets the input time as UTC and not as local time per RFC 5280 Additionally the return value is always an int Contributed by Akira Li in bpo 19940 New SSLObject shared_ciphers and SSLSocket shared_ciphers methods return the list of ciphers sent by the client during the handshake Contributed by Benjamin Peterson in bpo 23186 The SSLSocket do_handshake SSL,en
1226,Socket read SSLSocket shutdown and SSLSocket write methods of the SSLSocket class no longer reset the socket timeout every time bytes are received or sent The socket timeout is now the maximum total duration of the method Contributed by Victor Stinner in bpo 23853 The match_hostname function now supports matching of IP addresses Contributed by Antoine Pitrou in bpo 23239 sqlite3 The Row class now fully supports the sequence protocol in particular reversed iteration and slice indexing Contributed by Claudiu Popa in bpo 10203 by Lucas Sinclair Jessica McKellar and Serhiy Storchaka in bpo 13583 subprocess The new run function has been added It runs the specified command and returns a CompletedProcess object which describes a finished process The new API is more consistent and is the recommended approach to invoking subprocesses in Python code that does not need to maintain compatibility with earlier Python versions Contributed by Thomas Kluyver in bpo 23342 Examples subprocess run ls l doesn t capture output CompletedProcess args ls l returncode 0 subprocess run exit 1 shell True check True Traceback most recent call last subprocess CalledProcessError Command exit 1 returned non zero exit status 1 subprocess run ls l dev null stdout subprocess PIPE CompletedProcess args ls l dev null returncode 0 stdout b crw rw rw 1 root root 1 3 Jan 23 16 23 dev null n sys A new set_coroutine_wrapper function allows setting a global hook that will be called whenever a coroutine object is created by an async def function A corresponding get_coroutine_wrapper can be used to obtain a currently set wrapper Both functions are provisional and are intended for debugging purposes only Contributed by Yury Selivanov in bpo 24017 A new is_finalizing function can be used to check if the Python interpreter is shutting down Contributed by Antoine Pitrou in bpo 22696 sysconfig The name of the user scripts directory on Windows now includes the first two components of the Python version Contributed by Paul Moore in bpo 23437 tarfile The mode argument of the open function now accepts x to request exclusive creation Contributed by Berker Peksag in bpo 21717 The TarFile extractall and TarFile extract methods now take a keyword argument numeric_owner If set to True the extracted files and directories will be owned by the numeric uid and gid from the tarfile If set to False the default and the behavior in versions prior to 3 5 they will be owned by the named user and group in the tarfile Contributed by Michael Vogt and Eric Smith in bpo 23193 The TarFile list now accepts an optional members keyword argument that can be set to a subset of the list returned by TarFile getmembers Contributed by Serhiy Storchaka in bpo 21549 threading Both the Lock acquire and RLock acquire methods now use a monotonic clock for timeout management Contributed by Victor Stinner in bpo 22043 time The monotonic function is now always available Contributed by Victor Stinner in bpo 22043 timeit A new command line option u or unit U can be used to specify the time unit for the timer output Supported options are usec msec or sec Contributed by Julian Gindi in bpo 18983 The timeit function has a new globals parameter for specifying the namespace in which the code will be running Contributed by Ben Roberts in bpo 2527 tkinter The tkinter _fix module used for setting up the Tcl Tk environment on Windows has been replaced by a private function in the _tkinter module which makes no permanent changes to environment variables Contributed by Zachary Ware in bpo 20035 traceback New walk_stack and walk_tb functions to conveniently traverse frame and traceback objects Contributed by Robert Collins in bpo 17911 New lightweight classes TracebackException StackSummary and FrameSummary Contributed by Robert Collins in bpo 17911 Both the print_tb and print_stack functions now support negative values for the limit argument Contributed by Dmitry Kazakov in bpo 22619 types A new coroutine function to transform generator and generator like objects into awaitables Contributed by Yury Selivanov in bpo 24017 A ,en
1227,new type called CoroutineType which is used for coroutine objects created by async def functions Contributed by Yury Selivanov in bpo 24400 unicodedata The unicodedata module now uses data from Unicode 8 0 0 unittest The TestLoader loadTestsFromModule method now accepts a keyword only argument pattern which is passed to load_tests as the third argument Found packages are now checked for load_tests regardless of whether their path matches pattern because it is impossible for a package name to match the default pattern Contributed by Robert Collins and Barry A Warsaw in bpo 16662 Unittest discovery errors now are exposed in the TestLoader errors attribute of the TestLoader instance Contributed by Robert Collins in bpo 19746 A new command line option locals to show local variables in tracebacks Contributed by Robert Collins in bpo 22936 unittest mock The Mock class has the following improvements The class constructor has a new unsafe parameter which causes mock objects to raise AttributeError on attribute names starting with assert Contributed by Kushal Das in bpo 21238 A new Mock assert_not_called method to check if the mock object was called Contributed by Kushal Das in bpo 21262 The MagicMock class now supports __truediv__ __divmod__ and __matmul__ operators Contributed by Johannes Baiter in bpo 20968 and Håkan Lövdahl in bpo 23581 and bpo 23568 It is no longer necessary to explicitly pass create True to the patch function when patching builtin names Contributed by Kushal Das in bpo 17660 urllib A new request HTTPPasswordMgrWithPriorAuth class allows HTTP Basic Authentication credentials to be managed so as to eliminate unnecessary 401 response handling or to unconditionally send credentials on the first request in order to communicate with servers that return a 404 response instead of a 401 if the Authorization header is not sent Contributed by Matej Cepl in bpo 19494 and Akshit Khurana in bpo 7159 A new quote_via argument for the parse urlencode function provides a way to control the encoding of query parts if needed Contributed by Samwyse and Arnon Yaari in bpo 13866 The request urlopen function accepts an ssl SSLContext object as a context argument which will be used for the HTTPS connection Contributed by Alex Gaynor in bpo 22366 The parse urljoin was updated to use the RFC 3986 semantics for the resolution of relative URLs rather than RFC 1808 and RFC 2396 Contributed by Demian Brecht and Senthil Kumaran in bpo 22118 wsgiref The headers argument of the headers Headers class constructor is now optional Contributed by Pablo Torres Navarrete and SilentGhost in bpo 5800 xmlrpc The client ServerProxy class now supports the context manager protocol Contributed by Claudiu Popa in bpo 20627 The client ServerProxy constructor now accepts an optional ssl SSLContext instance Contributed by Alex Gaynor in bpo 22960 xml sax SAX parsers now support a character stream of the xmlreader InputSource object Contributed by Serhiy Storchaka in bpo 2175 parseString now accepts a str instance Contributed by Serhiy Storchaka in bpo 10590 zipfile ZIP output can now be written to unseekable streams Contributed by Serhiy Storchaka in bpo 23252 The mode argument of ZipFile open method now accepts x to request exclusive creation Contributed by Serhiy Storchaka in bpo 21717 Other module level changes Many functions in the mmap ossaudiodev socket ssl and codecs modules now accept writable bytes like objects Contributed by Serhiy Storchaka in bpo 23001 Optimizations The os walk function has been sped up by 3 to 5 times on POSIX systems and by 7 to 20 times on Windows This was done using the new os scandir function which exposes file information from the underlying readdir or FindFirstFile FindNextFile system calls Contributed by Ben Hoyt with help from Victor Stinner in bpo 23605 Construction of bytes int filled by zero bytes is faster and uses less memory for large objects calloc is used instead of malloc to allocate memory for these objects Contributed by Victor Stinner in bpo 21233 Some operations on ipaddress IPv4Network and IPv6Network have ,en
1228,been massively sped up such as subnets supernet summarize_address_range collapse_addresses The speed up can range from 3 to 15 times Contributed by Antoine Pitrou Michel Albert and Markus in bpo 21486 bpo 21487 bpo 20826 bpo 23266 Pickling of ipaddress objects was optimized to produce significantly smaller output Contributed by Serhiy Storchaka in bpo 23133 Many operations on io BytesIO are now 50 to 100 faster Contributed by Serhiy Storchaka in bpo 15381 and David Wilson in bpo 22003 The marshal dumps function is now faster 65 85 with versions 3 and 4 20 25 with versions 0 to 2 on typical data and up to 5 times in best cases Contributed by Serhiy Storchaka in bpo 20416 and bpo 23344 The UTF 32 encoder is now 3 to 7 times faster Contributed by Serhiy Storchaka in bpo 15027 Regular expressions are now parsed up to 10 faster Contributed by Serhiy Storchaka in bpo 19380 The json dumps function was optimized to run with ensure_ascii False as fast as with ensure_ascii True Contributed by Naoki Inada in bpo 23206 The PyObject_IsInstance and PyObject_IsSubclass functions have been sped up in the common case that the second argument has type as its metaclass Contributed Georg Brandl by in bpo 22540 Method caching was slightly improved yielding up to 5 performance improvement in some benchmarks Contributed by Antoine Pitrou in bpo 22847 Objects from the random module now use 50 less memory on 64 bit builds Contributed by Serhiy Storchaka in bpo 23488 The property getter calls are up to 25 faster Contributed by Joe Jevnik in bpo 23910 Instantiation of fractions Fraction is now up to 30 faster Contributed by Stefan Behnel in bpo 22464 String methods find rfind split partition and the in string operator are now significantly faster for searching 1 character substrings Contributed by Serhiy Storchaka in bpo 23573 Build and C API Changes New calloc functions were added PyMem_RawCalloc PyMem_Calloc PyObject_Calloc Contributed by Victor Stinner in bpo 21233 New encoding decoding helper functions Py_DecodeLocale replaced _Py_char2wchar Py_EncodeLocale replaced _Py_wchar2char Contributed by Victor Stinner in bpo 18395 A new PyCodec_NameReplaceErrors function to replace the unicode encode error with N escapes Contributed by Serhiy Storchaka in bpo 19676 A new PyErr_FormatV function similar to PyErr_Format but accepts a va_list argument Contributed by Antoine Pitrou in bpo 18711 A new PyExc_RecursionError exception Contributed by Georg Brandl in bpo 19235 New PyModule_FromDefAndSpec PyModule_FromDefAndSpec2 and PyModule_ExecDef functions introduced by PEP 489 multi phase extension module initialization Contributed by Petr Viktorin in bpo 24268 New PyNumber_MatrixMultiply and PyNumber_InPlaceMatrixMultiply functions to perform matrix multiplication Contributed by Benjamin Peterson in bpo 21176 See also PEP 465 for details The PyTypeObject tp_finalize slot is now part of the stable ABI Windows builds now require Microsoft Visual C 14 0 which is available as part of Visual Studio 2015 Extension modules now include a platform information tag in their filename on some platforms the tag is optional and CPython will import extensions without it although if the tag is present and mismatched the extension won t be loaded On Linux extension module filenames end with cpython major minor m architecture os pyd major is the major number of the Python version for Python 3 5 this is 3 minor is the minor number of the Python version for Python 3 5 this is 5 architecture is the hardware architecture the extension module was built to run on It s most commonly either i386 for 32 bit Intel platforms or x86_64 for 64 bit Intel and AMD platforms os is always linux gnu except for extensions built to talk to the 32 bit ABI on 64 bit platforms in which case it is linux gnu32 and architecture will be x86_64 On Windows extension module filenames end with debug cp major minor platform pyd major is the major number of the Python version for Python 3 5 this is 3 minor is the minor number of the Python version for Python 3 5 this is 5 platform is the platform the extensio,en
1229,n module was built for either win32 for Win32 win_amd64 for Win64 win_ia64 for Windows Itanium 64 and win_arm for Windows on ARM If built in debug mode debug will be _d otherwise it will be blank On OS X platforms extension module filenames now end with darwin so On all other platforms extension module filenames are the same as they were with Python 3 4 Deprecated New Keywords async and await are not recommended to be used as variable class function or module names Introduced by PEP 492 in Python 3 5 they will become proper keywords in Python 3 7 Deprecated Python Behavior Raising the StopIteration exception inside a generator will now generate a silent PendingDeprecationWarning which will become a non silent deprecation warning in Python 3 6 and will trigger a RuntimeError in Python 3 7 See PEP 479 Change StopIteration handling inside generators for details Unsupported Operating Systems Windows XP is no longer supported by Microsoft thus per PEP 11 CPython 3 5 is no longer officially supported on this OS Deprecated Python modules functions and methods The formatter module has now graduated to full deprecation and is still slated for removal in Python 3 6 The asyncio async function is deprecated in favor of ensure_future The smtpd module has in the past always decoded the DATA portion of email messages using the utf 8 codec This can now be controlled by the new decode_data keyword to SMTPServer The default value is True but this default is deprecated Specify the decode_data keyword with an appropriate value to avoid the deprecation warning Directly assigning values to the key value and coded_value of http cookies Morsel objects is deprecated Use the set method instead In addition the undocumented LegalChars parameter of set is deprecated and is now ignored Passing a format string as keyword argument format_string to the format method of the string Formatter class has been deprecated Contributed by Serhiy Storchaka in bpo 23671 The platform dist and platform linux_distribution functions are now deprecated Linux distributions use too many different ways of describing themselves so the functionality is left to a package Contributed by Vajrasky Kok and Berker Peksag in bpo 1322 The previously undocumented from_function and from_builtin methods of inspect Signature are deprecated Use the new Signature from_callable method instead Contributed by Yury Selivanov in bpo 24248 The inspect getargspec function is deprecated and scheduled to be removed in Python 3 6 See bpo 20438 for details The inspect getfullargspec getcallargs and formatargspec functions are deprecated in favor of the inspect signature API Contributed by Yury Selivanov in bpo 20438 getargvalues and formatargvalues functions were inadvertently marked as deprecated with the release of Python 3 5 0 Use of re LOCALE flag with str patterns or re ASCII is now deprecated Contributed by Serhiy Storchaka in bpo 22407 Use of unrecognized special sequences consisting of and an ASCII letter in regular expression patterns and replacement patterns now raises a deprecation warning and will be forbidden in Python 3 6 Contributed by Serhiy Storchaka in bpo 23622 The undocumented and unofficial use_load_tests default argument of the unittest TestLoader loadTestsFromModule method now is deprecated and ignored Contributed by Robert Collins and Barry A Warsaw in bpo 16662 Removed API and Feature Removals The following obsolete and previously deprecated APIs and features have been removed The __version__ attribute has been dropped from the email package The email code hasn t been shipped separately from the stdlib for a long time and the __version__ string was not updated in the last few releases The internal Netrc class in the ftplib module was deprecated in 3 4 and has now been removed Contributed by Matt Chaput in bpo 6623 The concept of pyo files has been removed The JoinableQueue class in the provisional asyncio module was deprecated in 3 4 4 and is now removed Contributed by A Jesse Jiryu Davis in bpo 23464 Porting to Python 3 5 This section lists previously described changes and,en
1230, other bugfixes that may require changes to your code Changes in Python behavior Due to an oversight earlier Python versions erroneously accepted the following syntax f 1 for x in 1 args f 1 for x in 1 kwargs Python 3 5 now correctly raises a SyntaxError as generator expressions must be put in parentheses if not a sole argument to a function Changes in the Python API PEP 475 System calls are now retried when interrupted by a signal instead of raising InterruptedError if the Python signal handler does not raise an exception Before Python 3 5 a datetime time object was considered to be false if it represented midnight in UTC This behavior was considered obscure and error prone and has been removed in Python 3 5 See bpo 13936 for full details The ssl SSLSocket send method now raises either ssl SSLWantReadError or ssl SSLWantWriteError on a non blocking socket if the operation would block Previously it would return 0 Contributed by Nikolaus Rath in bpo 20951 The __name__ attribute of generators is now set from the function name instead of being set from the code name Use gen gi_code co_name to retrieve the code name Generators also have a new __qualname__ attribute the qualified name which is now used for the representation of a generator repr gen Contributed by Victor Stinner in bpo 21205 The deprecated strict mode and argument of HTMLParser HTMLParser error and the HTMLParserError exception have been removed Contributed by Ezio Melotti in bpo 15114 The convert_charrefs argument of HTMLParser is now True by default Contributed by Berker Peksag in bpo 21047 Although it is not formally part of the API it is worth noting for porting purposes ie fixing tests that error messages that were previously of the form sometype does not support the buffer protocol are now of the form a bytes like object is required not sometype Contributed by Ezio Melotti in bpo 16518 If the current directory is set to a directory that no longer exists then FileNotFoundError will no longer be raised and instead find_spec will return None without caching None in sys path_importer_cache which is different than the typical case bpo 22834 HTTP status code and messages from http client and http server were refactored into a common HTTPStatus enum The values in http client and http server remain available for backwards compatibility Contributed by Demian Brecht in bpo 21793 When an import loader defines importlib machinery Loader exec_module it is now expected to also define create_module raises a DeprecationWarning now will be an error in Python 3 6 If the loader inherits from importlib abc Loader then there is nothing to do else simply define create_module to return None Contributed by Brett Cannon in bpo 23014 The re split function always ignored empty pattern matches so the x pattern worked the same as x and the b pattern never worked Now re split raises a warning if the pattern could match an empty string For compatibility use patterns that never match an empty string e g x instead of x Patterns that could only match an empty string such as b now raise an error Contributed by Serhiy Storchaka in bpo 22818 The http cookies Morsel dict like interface has been made self consistent morsel comparison now takes the key and value into account copy now results in a Morsel instance rather than a dict and update will now raise an exception if any of the keys in the update dictionary are invalid In addition the undocumented LegalChars parameter of set is deprecated and is now ignored Contributed by Demian Brecht in bpo 2211 PEP 488 has removed pyo files from Python and introduced the optional opt tag in pyc file names The importlib util cache_from_source has gained an optimization parameter to help control the opt tag Because of this the debug_override parameter of the function is now deprecated pyo files are also no longer supported as a file argument to the Python interpreter and thus serve no purpose when distributed on their own i e sourceless code distribution Due to the fact that the magic number for bytecode has changed in Python 3 5 all old pyo files from p,en
1231,revious versions of Python are invalid regardless of this PEP The socket module now exports the CAN_RAW_FD_FRAMES constant on linux 3 6 and greater The ssl cert_time_to_seconds function now interprets the input time as UTC and not as local time per RFC 5280 Additionally the return value is always an int Contributed by Akira Li in bpo 19940 The pygettext py Tool now uses the standard NNNN format for timezones in the POT Creation Date header The smtplib module now uses sys stderr instead of the previous module level stderr variable for debug output If your test program depends on patching the module level variable to capture the debug output you will need to update it to capture sys stderr instead The str startswith and str endswith methods no longer return True when finding the empty string and the indexes are completely out of range Contributed by Serhiy Storchaka in bpo 24284 The inspect getdoc function now returns documentation strings inherited from base classes Documentation strings no longer need to be duplicated if the inherited documentation is appropriate To suppress an inherited string an empty string must be specified or the documentation may be filled in This change affects the output of the pydoc module and the help function Contributed by Serhiy Storchaka in bpo 15582 Nested functools partial calls are now flattened If you were relying on the previous behavior you can now either add an attribute to a functools partial object or you can create a subclass of functools partial Contributed by Alexander Belopolsky in bpo 7830 Changes in the C API The undocumented format member of the non public PyMemoryViewObject structure has been removed All extensions relying on the relevant parts in memoryobject h must be rebuilt The PyMemAllocator structure was renamed to PyMemAllocatorEx and a new calloc field was added Removed non documented macro PyObject_REPR which leaked references Use format character R in PyUnicode_FromFormat like functions to format the repr of the object Contributed by Serhiy Storchaka in bpo 22453 Because the lack of the __module__ attribute breaks pickling and introspection a deprecation warning is now raised for builtin types without the __module__ attribute This would be an AttributeError in the future Contributed by Serhiy Storchaka in bpo 20204 As part of the PEP 492 implementation the tp_reserved slot of PyTypeObject was replaced with a tp_as_async slot Refer to Coroutine Objects for new types structures and functions Notable changes in Python 3 5 4 New make regen all build target To simplify cross compilation and to ensure that CPython can reliably be compiled without requiring an existing version of Python to already be available the autotools based build system no longer attempts to implicitly recompile generated files based on file modification times Instead a new make regen all command has been added to force regeneration of these files when desired e g after an initial version of Python has already been built based on the pregenerated versions More selective regeneration targets are also defined see Makefile pre in for details Contributed by Victor Stinner in bpo 23404 New in version 3 5 4 Removal of make touch build target The make touch build target previously used to request implicit regeneration of generated files by updating their modification times has been removed It has been replaced by the new make regen all target Contributed by Victor Stinner in bpo 23404 Changed in version 3 5 4,en
1232,8 Compound statements Compound statements contain groups of other statements they affect or control the execution of those other statements in some way In general compound statements span multiple lines although in simple incarnations a whole compound statement may be contained in one line The if while and for statements implement traditional control flow constructs try specifies exception handlers and or cleanup code for a group of statements while the with statement allows the execution of initialization and finalization code around a block of code Function and class definitions are also syntactically compound statements A compound statement consists of one or more clauses A clause consists of a header and a suite The clause headers of a particular compound statement are all at the same indentation level Each clause header begins with a uniquely identifying keyword and ends with a colon A suite is a group of statements controlled by a clause A suite can be one or more semicolon separated simple statements on the same line as the header following the header s colon or it can be one or more indented statements on subsequent lines Only the latter form of a suite can contain nested compound statements the following is illegal mostly because it wouldn t be clear to which if clause a following else clause would belong if test1 if test2 print x Also note that the semicolon binds tighter than the colon in this context so that in the following example either all or none of the print calls are executed if x y z print x print y print z Summarizing compound_stmt if_stmt while_stmt for_stmt try_stmt with_stmt match_stmt funcdef classdef async_with_stmt async_for_stmt async_funcdef suite stmt_list NEWLINE NEWLINE INDENT statement DEDENT statement stmt_list NEWLINE compound_stmt stmt_list simple_stmt simple_stmt Note that statements always end in a NEWLINE possibly followed by a DEDENT Also note that optional continuation clauses always begin with a keyword that cannot start a statement thus there are no ambiguities the dangling else problem is solved in Python by requiring nested if statements to be indented The formatting of the grammar rules in the following sections places each clause on a separate line for clarity 8 1 The if statement The if statement is used for conditional execution if_stmt if assignment_expression suite elif assignment_expression suite else suite It selects exactly one of the suites by evaluating the expressions one by one until one is found to be true see section Boolean operations for the definition of true and false then that suite is executed and no other part of the if statement is executed or evaluated If all expressions are false the suite of the else clause if present is executed 8 2 The while statement The while statement is used for repeated execution as long as an expression is true while_stmt while assignment_expression suite else suite This repeatedly tests the expression and if it is true executes the first suite if the expression is false which may be the first time it is tested the suite of the else clause if present is executed and the loop terminates A break statement executed in the first suite terminates the loop without executing the else clause s suite A continue statement executed in the first suite skips the rest of the suite and goes back to testing the expression 8 3 The for statement The for statement is used to iterate over the elements of a sequence such as a string tuple or list or other iterable object for_stmt for target_list in starred_list suite else suite The starred_list expression is evaluated once it should yield an iterable object An iterator is created for that iterable The first item provided by the iterator is then assigned to the target list using the standard rules for assignments see Assignment statements and the suite is executed This repeats for each item provided by the iterator When the iterator is exhausted the suite in the else clause if present is executed and the loop terminates A break statement executed in the first suite terminates the loop without execu,en
1233,ting the else clause s suite A continue statement executed in the first suite skips the rest of the suite and continues with the next item or with the else clause if there is no next item The for loop makes assignments to the variables in the target list This overwrites all previous assignments to those variables including those made in the suite of the for loop for i in range 10 print i i 5 this will not affect the for loop because i will be overwritten with the next index in the range Names in the target list are not deleted when the loop is finished but if the sequence is empty they will not have been assigned to at all by the loop Hint the built in type range represents immutable arithmetic sequences of integers For instance iterating range 3 successively yields 0 1 and then 2 Changed in version 3 11 Starred elements are now allowed in the expression list 8 4 The try statement The try statement specifies exception handlers and or cleanup code for a group of statements try_stmt try1_stmt try2_stmt try3_stmt try1_stmt try suite except expression as identifier suite else suite finally suite try2_stmt try suite except expression as identifier suite else suite finally suite try3_stmt try suite finally suite Additional information on exceptions can be found in section Exceptions and information on using the raise statement to generate exceptions may be found in section The raise statement 8 4 1 except clause The except clause s specify one or more exception handlers When no exception occurs in the try clause no exception handler is executed When an exception occurs in the try suite a search for an exception handler is started This search inspects the except clauses in turn until one is found that matches the exception An expression less except clause if present must be last it matches any exception For an except clause with an expression that expression is evaluated and the clause matches the exception if the resulting object is compatible with the exception An object is compatible with an exception if the object is the class or a non virtual base class of the exception object or a tuple containing an item that is the class or a non virtual base class of the exception object If no except clause matches the exception the search for an exception handler continues in the surrounding code and on the invocation stack 1 If the evaluation of an expression in the header of an except clause raises an exception the original search for a handler is canceled and a search starts for the new exception in the surrounding code and on the call stack it is treated as if the entire try statement raised the exception When a matching except clause is found the exception is assigned to the target specified after the as keyword in that except clause if present and the except clause s suite is executed All except clauses must have an executable block When the end of this block is reached execution continues normally after the entire try statement This means that if two nested handlers exist for the same exception and the exception occurs in the try clause of the inner handler the outer handler will not handle the exception When an exception has been assigned using as target it is cleared at the end of the except clause This is as if except E as N foo was translated to except E as N try foo finally del N This means the exception must be assigned to a different name to be able to refer to it after the except clause Exceptions are cleared because with the traceback attached to them they form a reference cycle with the stack frame keeping all locals in that frame alive until the next garbage collection occurs Before an except clause s suite is executed the exception is stored in the sys module where it can be accessed from within the body of the except clause by calling sys exception When leaving an exception handler the exception stored in the sys module is reset to its previous value print sys exception None try raise TypeError except print repr sys exception try raise ValueError except print repr sys exception print repr sys exception TypeError Va,en
1234,lueError TypeError print sys exception None 8 4 2 except clause The except clause s are used for handling ExceptionGroup s The exception type for matching is interpreted as in the case of except but in the case of exception groups we can have partial matches when the type matches some of the exceptions in the group This means that multiple except clauses can execute each handling part of the exception group Each clause executes at most once and handles an exception group of all matching exceptions Each exception in the group is handled by at most one except clause the first that matches it try raise ExceptionGroup eg ValueError 1 TypeError 2 OSError 3 OSError 4 except TypeError as e print f caught type e with nested e exceptions except OSError as e print f caught type e with nested e exceptions caught class ExceptionGroup with nested TypeError 2 caught class ExceptionGroup with nested OSError 3 OSError 4 Exception Group Traceback most recent call last File stdin line 2 in module ExceptionGroup eg 1 ValueError 1 Any remaining exceptions that were not handled by any except clause are re raised at the end along with all exceptions that were raised from within the except clauses If this list contains more than one exception to reraise they are combined into an exception group If the raised exception is not an exception group and its type matches one of the except clauses it is caught and wrapped by an exception group with an empty message string try raise BlockingIOError except BlockingIOError as e print repr e ExceptionGroup BlockingIOError An except clause must have a matching type and this type cannot be a subclass of BaseExceptionGroup It is not possible to mix except and except in the same try break continue and return cannot appear in an except clause 8 4 3 else clause The optional else clause is executed if the control flow leaves the try suite no exception was raised and no return continue or break statement was executed Exceptions in the else clause are not handled by the preceding except clauses 8 4 4 finally clause If finally is present it specifies a cleanup handler The try clause is executed including any except and else clauses If an exception occurs in any of the clauses and is not handled the exception is temporarily saved The finally clause is executed If there is a saved exception it is re raised at the end of the finally clause If the finally clause raises another exception the saved exception is set as the context of the new exception If the finally clause executes a return break or continue statement the saved exception is discarded def f try 1 0 finally return 42 f 42 The exception information is not available to the program during execution of the finally clause When a return break or continue statement is executed in the try suite of a try finally statement the finally clause is also executed on the way out The return value of a function is determined by the last return statement executed Since the finally clause always executes a return statement executed in the finally clause will always be the last one executed def foo try return try finally return finally foo finally Changed in version 3 8 Prior to Python 3 8 a continue statement was illegal in the finally clause due to a problem with the implementation 8 5 The with statement The with statement is used to wrap the execution of a block with methods defined by a context manager see section With Statement Context Managers This allows common try except finally usage patterns to be encapsulated for convenient reuse with_stmt with with_stmt_contents with_stmt_contents suite with_stmt_contents with_item with_item with_item expression as target The execution of the with statement with one item proceeds as follows 1 The context expression the expression given in the with_item is evaluated to obtain a context manager 2 The context manager s __enter__ is loaded for later use 3 The context manager s __exit__ is loaded for later use 4 The context manager s __enter__ method is invoked 5 If a target was included in the with statement the return value from __ente,en
1235,r__ is assigned to it Note The with statement guarantees that if the __enter__ method returns without an error then __exit__ will always be called Thus if an error occurs during the assignment to the target list it will be treated the same as an error occurring within the suite would be See step 7 below 6 The suite is executed 7 The context manager s __exit__ method is invoked If an exception caused the suite to be exited its type value and traceback are passed as arguments to __exit__ Otherwise three None arguments are supplied If the suite was exited due to an exception and the return value from the __exit__ method was false the exception is reraised If the return value was true the exception is suppressed and execution continues with the statement following the with statement If the suite was exited for any reason other than an exception the return value from __exit__ is ignored and execution proceeds at the normal location for the kind of exit that was taken The following code with EXPRESSION as TARGET SUITE is semantically equivalent to manager EXPRESSION enter type manager __enter__ exit type manager __exit__ value enter manager hit_except False try TARGET value SUITE except hit_except True if not exit manager sys exc_info raise finally if not hit_except exit manager None None None With more than one item the context managers are processed as if multiple with statements were nested with A as a B as b SUITE is semantically equivalent to with A as a with B as b SUITE You can also write multi item context managers in multiple lines if the items are surrounded by parentheses For example with A as a B as b SUITE Changed in version 3 1 Support for multiple context expressions Changed in version 3 10 Support for using grouping parentheses to break the statement in multiple lines See also PEP 343 The with statement The specification background and examples for the Python with statement 8 6 The match statement New in version 3 10 The match statement is used for pattern matching Syntax match_stmt match subject_expr NEWLINE INDENT case_block DEDENT subject_expr star_named_expression star_named_expressions named_expression case_block case patterns guard block Note This section uses single quotes to denote soft keywords Pattern matching takes a pattern as input following case and a subject value following match The pattern which may contain subpatterns is matched against the subject value The outcomes are A match success or failure also termed a pattern success or failure Possible binding of matched values to a name The prerequisites for this are further discussed below The match and case keywords are soft keywords See also PEP 634 Structural Pattern Matching Specification PEP 636 Structural Pattern Matching Tutorial 8 6 1 Overview Here s an overview of the logical flow of a match statement 1 The subject expression subject_expr is evaluated and a resulting subject value obtained If the subject expression contains a comma a tuple is constructed using the standard rules 2 Each pattern in a case_block is attempted to match with the subject value The specific rules for success or failure are described below The match attempt can also bind some or all of the standalone names within the pattern The precise pattern binding rules vary per pattern type and are specified below Name bindings made during a successful pattern match outlive the executed block and can be used after the match statement Note During failed pattern matches some subpatterns may succeed Do not rely on bindings being made for a failed match Conversely do not rely on variables remaining unchanged after a failed match The exact behavior is dependent on implementation and may vary This is an intentional decision made to allow different implementations to add optimizations 3 If the pattern succeeds the corresponding guard if present is evaluated In this case all name bindings are guaranteed to have happened If the guard evaluates as true or is missing the block inside case_block is executed Otherwise the next case_block is attempted as described above If there are no fu,en
1236,rther case blocks the match statement is completed Note Users should generally never rely on a pattern being evaluated Depending on implementation the interpreter may cache values or use other optimizations which skip repeated evaluations A sample match statement flag False match 100 200 case 100 300 Mismatch 200 300 print Case 1 case 100 200 if flag Successful match but guard fails print Case 2 case 100 y Matches and binds y to 200 print f Case 3 y y case _ Pattern not attempted print Case 4 I match anything Case 3 y 200 In this case if flag is a guard Read more about that in the next section 8 6 2 Guards guard if named_expression A guard which is part of the case must succeed for code inside the case block to execute It takes the form if followed by an expression The logical flow of a case block with a guard follows 1 Check that the pattern in the case block succeeded If the pattern failed the guard is not evaluated and the next case block is checked 2 If the pattern succeeded evaluate the guard If the guard condition evaluates as true the case block is selected If the guard condition evaluates as false the case block is not selected If the guard raises an exception during evaluation the exception bubbles up Guards are allowed to have side effects as they are expressions Guard evaluation must proceed from the first to the last case block one at a time skipping case blocks whose pattern s don t all succeed I e guard evaluation must happen in order Guard evaluation must stop once a case block is selected 8 6 3 Irrefutable Case Blocks An irrefutable case block is a match all case block A match statement may have at most one irrefutable case block and it must be last A case block is considered irrefutable if it has no guard and its pattern is irrefutable A pattern is considered irrefutable if we can prove from its syntax alone that it will always succeed Only the following patterns are irrefutable AS Patterns whose left hand side is irrefutable OR Patterns containing at least one irrefutable pattern Capture Patterns Wildcard Patterns parenthesized irrefutable patterns 8 6 4 Patterns Note This section uses grammar notations beyond standard EBNF the notation SEP RULE is shorthand for RULE SEP RULE the notation RULE is shorthand for a negative lookahead assertion The top level syntax for patterns is patterns open_sequence_pattern pattern pattern as_pattern or_pattern closed_pattern literal_pattern capture_pattern wildcard_pattern value_pattern group_pattern sequence_pattern mapping_pattern class_pattern The descriptions below will include a description in simple terms of what a pattern does for illustration purposes credits to Raymond Hettinger for a document that inspired most of the descriptions Note that these descriptions are purely for illustration purposes and may not reflect the underlying implementation Furthermore they do not cover all valid forms 8 6 4 1 OR Patterns An OR pattern is two or more patterns separated by vertical bars Syntax or_pattern closed_pattern Only the final subpattern may be irrefutable and each subpattern must bind the same set of names to avoid ambiguity An OR pattern matches each of its subpatterns in turn to the subject value until one succeeds The OR pattern is then considered successful Otherwise if none of the subpatterns succeed the OR pattern fails In simple terms P1 P2 will try to match P1 if it fails it will try to match P2 succeeding immediately if any succeeds failing otherwise 8 6 4 2 AS Patterns An AS pattern matches an OR pattern on the left of the as keyword against a subject Syntax as_pattern or_pattern as capture_pattern If the OR pattern fails the AS pattern fails Otherwise the AS pattern binds the subject to the name on the right of the as keyword and succeeds capture_pattern cannot be a _ In simple terms P as NAME will match with P and on success it will set NAME subject 8 6 4 3 Literal Patterns A literal pattern corresponds to most literals in Python Syntax literal_pattern signed_number signed_number NUMBER signed_number NUMBER strings None True False signed_number NUMBER N,en
1237,UMBER The rule strings and the token NUMBER are defined in the standard Python grammar Triple quoted strings are supported Raw strings and byte strings are supported f strings are not supported The forms signed_number NUMBER and signed_number NUMBER are for expressing complex numbers they require a real number on the left and an imaginary number on the right E g 3 4j In simple terms LITERAL will succeed only if subject LITERAL For the singletons None True and False the is operator is used 8 6 4 4 Capture Patterns A capture pattern binds the subject value to a name Syntax capture_pattern _ NAME A single underscore _ is not a capture pattern this is what _ expresses It is instead treated as a wildcard_pattern In a given pattern a given name can only be bound once E g case x x is invalid while case x x is allowed Capture patterns always succeed The binding follows scoping rules established by the assignment expression operator in PEP 572 the name becomes a local variable in the closest containing function scope unless there s an applicable global or nonlocal statement In simple terms NAME will always succeed and it will set NAME subject 8 6 4 5 Wildcard Patterns A wildcard pattern always succeeds matches anything and binds no name Syntax wildcard_pattern _ _ is a soft keyword within any pattern but only within patterns It is an identifier as usual even within match subject expressions guard s and case blocks In simple terms _ will always succeed 8 6 4 6 Value Patterns A value pattern represents a named value in Python Syntax value_pattern attr attr name_or_attr NAME name_or_attr attr NAME The dotted name in the pattern is looked up using standard Python name resolution rules The pattern succeeds if the value found compares equal to the subject value using the equality operator In simple terms NAME1 NAME2 will succeed only if subject NAME1 NAME2 Note If the same value occurs multiple times in the same match statement the interpreter may cache the first value found and reuse it rather than repeat the same lookup This cache is strictly tied to a given execution of a given match statement 8 6 4 7 Group Patterns A group pattern allows users to add parentheses around patterns to emphasize the intended grouping Otherwise it has no additional syntax Syntax group_pattern pattern In simple terms P has the same effect as P 8 6 4 8 Sequence Patterns A sequence pattern contains several subpatterns to be matched against sequence elements The syntax is similar to the unpacking of a list or tuple sequence_pattern maybe_sequence_pattern open_sequence_pattern open_sequence_pattern maybe_star_pattern maybe_sequence_pattern maybe_sequence_pattern maybe_star_pattern maybe_star_pattern star_pattern pattern star_pattern capture_pattern wildcard_pattern There is no difference if parentheses or square brackets are used for sequence patterns i e vs Note A single pattern enclosed in parentheses without a trailing comma e g 3 4 is a group pattern While a single pattern enclosed in square brackets e g 3 4 is still a sequence pattern At most one star subpattern may be in a sequence pattern The star subpattern may occur in any position If no star subpattern is present the sequence pattern is a fixed length sequence pattern otherwise it is a variable length sequence pattern The following is the logical flow for matching a sequence pattern against a subject value 1 If the subject value is not a sequence 2 the sequence pattern fails 2 If the subject value is an instance of str bytes or bytearray the sequence pattern fails 3 The subsequent steps depend on whether the sequence pattern is fixed or variable length If the sequence pattern is fixed length 1 If the length of the subject sequence is not equal to the number of subpatterns the sequence pattern fails 2 Subpatterns in the sequence pattern are matched to their corresponding items in the subject sequence from left to right Matching stops as soon as a subpattern fails If all subpatterns succeed in matching their corresponding item the sequence pattern succeeds Otherwise if the sequence pattern is variable,en
1238, length 1 If the length of the subject sequence is less than the number of non star subpatterns the sequence pattern fails 2 The leading non star subpatterns are matched to their corresponding items as for fixed length sequences 3 If the previous step succeeds the star subpattern matches a list formed of the remaining subject items excluding the remaining items corresponding to non star subpatterns following the star subpattern 4 Remaining non star subpatterns are matched to their corresponding subject items as for a fixed length sequence Note The length of the subject sequence is obtained via len i e via the __len__ protocol This length may be cached by the interpreter in a similar manner as value patterns In simple terms P1 P2 P3 P N matches only if all the following happens check subject is a sequence len subject N P1 matches subject 0 note that this match can also bind names P2 matches subject 1 note that this match can also bind names and so on for the corresponding pattern element 8 6 4 9 Mapping Patterns A mapping pattern contains one or more key value patterns The syntax is similar to the construction of a dictionary Syntax mapping_pattern items_pattern items_pattern key_value_pattern key_value_pattern literal_pattern value_pattern pattern double_star_pattern double_star_pattern capture_pattern At most one double star pattern may be in a mapping pattern The double star pattern must be the last subpattern in the mapping pattern Duplicate keys in mapping patterns are disallowed Duplicate literal keys will raise a SyntaxError Two keys that otherwise have the same value will raise a ValueError at runtime The following is the logical flow for matching a mapping pattern against a subject value 1 If the subject value is not a mapping 3 the mapping pattern fails 2 If every key given in the mapping pattern is present in the subject mapping and the pattern for each key matches the corresponding item of the subject mapping the mapping pattern succeeds 3 If duplicate keys are detected in the mapping pattern the pattern is considered invalid A SyntaxError is raised for duplicate literal values or a ValueError for named keys of the same value Note Key value pairs are matched using the two argument form of the mapping subject s get method Matched key value pairs must already be present in the mapping and not created on the fly via __missing__ or __getitem__ In simple terms KEY1 P1 KEY2 P2 matches only if all the following happens check subject is a mapping KEY1 in subject P1 matches subject KEY1 and so on for the corresponding KEY pattern pair 8 6 4 10 Class Patterns A class pattern represents a class and its positional and keyword arguments if any Syntax class_pattern name_or_attr pattern_arguments pattern_arguments positional_patterns keyword_patterns keyword_patterns positional_patterns pattern keyword_patterns keyword_pattern keyword_pattern NAME pattern The same keyword should not be repeated in class patterns The following is the logical flow for matching a class pattern against a subject value 1 If name_or_attr is not an instance of the builtin type raise TypeError 2 If the subject value is not an instance of name_or_attr tested via isinstance the class pattern fails 3 If no pattern arguments are present the pattern succeeds Otherwise the subsequent steps depend on whether keyword or positional argument patterns are present For a number of built in types specified below a single positional subpattern is accepted which will match the entire subject for these types keyword patterns also work as for other types If only keyword patterns are present they are processed as follows one by one I The keyword is looked up as an attribute on the subject If this raises an exception other than AttributeError the exception bubbles up If this raises AttributeError the class pattern has failed Else the subpattern associated with the keyword pattern is matched against the subject s attribute value If this fails the class pattern fails if this succeeds the match proceeds to the next keyword II If all keyword patterns succeed the class patt,en
1239,ern succeeds If any positional patterns are present they are converted to keyword patterns using the __match_args__ attribute on the class name_or_attr before matching I The equivalent of getattr cls __match_args__ is called If this raises an exception the exception bubbles up If the returned value is not a tuple the conversion fails and TypeError is raised If there are more positional patterns than len cls __match_args__ TypeError is raised Otherwise positional pattern i is converted to a keyword pattern using __match_args__ i as the keyword __match_args__ i must be a string if not TypeError is raised If there are duplicate keywords TypeError is raised See also Customizing positional arguments in class pattern matching II Once all positional patterns have been converted to keyword patterns the match proceeds as if there were only keyword patterns For the following built in types the handling of positional subpatterns is different bool bytearray bytes dict float frozenset int list set str tuple These classes accept a single positional argument and the pattern there is matched against the whole object rather than an attribute For example int 0 1 matches the value 0 but not the value 0 0 In simple terms CLS P1 attr P2 matches only if the following happens isinstance subject CLS convert P1 to a keyword pattern using CLS __match_args__ For each keyword argument attr P2 hasattr subject attr P2 matches subject attr and so on for the corresponding keyword argument pattern pair See also PEP 634 Structural Pattern Matching Specification PEP 636 Structural Pattern Matching Tutorial 8 7 Function definitions A function definition defines a user defined function object see section The standard type hierarchy funcdef decorators def funcname type_params parameter_list expression suite decorators decorator decorator assignment_expression NEWLINE parameter_list defparameter defparameter parameter_list_no_posonly parameter_list_no_posonly parameter_list_no_posonly defparameter defparameter parameter_list_starargs parameter_list_starargs parameter_list_starargs parameter defparameter parameter parameter parameter identifier expression defparameter parameter expression funcname identifier A function definition is an executable statement Its execution binds the function name in the current local namespace to a function object a wrapper around the executable code for the function This function object contains a reference to the current global namespace as the global namespace to be used when the function is called The function definition does not execute the function body this gets executed only when the function is called 4 A function definition may be wrapped by one or more decorator expressions Decorator expressions are evaluated when the function is defined in the scope that contains the function definition The result must be a callable which is invoked with the function object as the only argument The returned value is bound to the function name instead of the function object Multiple decorators are applied in nested fashion For example the following code f1 arg f2 def func pass is roughly equivalent to def func pass func f1 arg f2 func except that the original function is not temporarily bound to the name func Changed in version 3 9 Functions may be decorated with any valid assignment_expression Previously the grammar was much more restrictive see PEP 614 for details A list of type parameters may be given in square brackets between the function s name and the opening parenthesis for its parameter list This indicates to static type checkers that the function is generic At runtime the type parameters can be retrieved from the function s __type_params__ attribute See Generic functions for more Changed in version 3 12 Type parameter lists are new in Python 3 12 When one or more parameters have the form parameter expression the function is said to have default parameter values For a parameter with a default value the corresponding argument may be omitted from a call in which case the parameter s default value is substituted If a parameter ha,en
1240,s a default value all following parameters up until the must also have a default value this is a syntactic restriction that is not expressed by the grammar Default parameter values are evaluated from left to right when the function definition is executed This means that the expression is evaluated once when the function is defined and that the same pre computed value is used for each call This is especially important to understand when a default parameter value is a mutable object such as a list or a dictionary if the function modifies the object e g by appending an item to a list the default parameter value is in effect modified This is generally not what was intended A way around this is to use None as the default and explicitly test for it in the body of the function e g def whats_on_the_telly penguin None if penguin is None penguin penguin append property of the zoo return penguin Function call semantics are described in more detail in section Calls A function call always assigns values to all parameters mentioned in the parameter list either from positional arguments from keyword arguments or from default values If the form identifier is present it is initialized to a tuple receiving any excess positional parameters defaulting to the empty tuple If the form identifier is present it is initialized to a new ordered mapping receiving any excess keyword arguments defaulting to a new empty mapping of the same type Parameters after or identifier are keyword only parameters and may only be passed by keyword arguments Parameters before are positional only parameters and may only be passed by positional arguments Changed in version 3 8 The function parameter syntax may be used to indicate positional only parameters See PEP 570 for details Parameters may have an annotation of the form expression following the parameter name Any parameter may have an annotation even those of the form identifier or identifier Functions may have return annotation of the form expression after the parameter list These annotations can be any valid Python expression The presence of annotations does not change the semantics of a function The annotation values are available as values of a dictionary keyed by the parameters names in the __annotations__ attribute of the function object If the annotations import from __future__ is used annotations are preserved as strings at runtime which enables postponed evaluation Otherwise they are evaluated when the function definition is executed In this case annotations may be evaluated in a different order than they appear in the source code It is also possible to create anonymous functions functions not bound to a name for immediate use in expressions This uses lambda expressions described in section Lambdas Note that the lambda expression is merely a shorthand for a simplified function definition a function defined in a def statement can be passed around or assigned to another name just like a function defined by a lambda expression The def form is actually more powerful since it allows the execution of multiple statements and annotations Programmer s note Functions are first class objects A def statement executed inside a function definition defines a local function that can be returned or passed around Free variables used in the nested function can access the local variables of the function containing the def See section Naming and binding for details See also PEP 3107 Function Annotations The original specification for function annotations PEP 484 Type Hints Definition of a standard meaning for annotations type hints PEP 526 Syntax for Variable Annotations Ability to type hint variable declarations including class variables and instance variables PEP 563 Postponed Evaluation of Annotations Support for forward references within annotations by preserving annotations in a string form at runtime instead of eager evaluation PEP 318 Decorators for Functions and Methods Function and method decorators were introduced Class decorators were introduced in PEP 3129 8 8 Class definitions A class definition defines a clas,en
1241,s object see section The standard type hierarchy classdef decorators class classname type_params inheritance suite inheritance argument_list classname identifier A class definition is an executable statement The inheritance list usually gives a list of base classes see Metaclasses for more advanced uses so each item in the list should evaluate to a class object which allows subclassing Classes without an inheritance list inherit by default from the base class object hence class Foo pass is equivalent to class Foo object pass The class s suite is then executed in a new execution frame see Naming and binding using a newly created local namespace and the original global namespace Usually the suite contains mostly function definitions When the class s suite finishes execution its execution frame is discarded but its local namespace is saved 5 A class object is then created using the inheritance list for the base classes and the saved local namespace for the attribute dictionary The class name is bound to this class object in the original local namespace The order in which attributes are defined in the class body is preserved in the new class s __dict__ Note that this is reliable only right after the class is created and only for classes that were defined using the definition syntax Class creation can be customized heavily using metaclasses Classes can also be decorated just like when decorating functions f1 arg f2 class Foo pass is roughly equivalent to class Foo pass Foo f1 arg f2 Foo The evaluation rules for the decorator expressions are the same as for function decorators The result is then bound to the class name Changed in version 3 9 Classes may be decorated with any valid assignment_expression Previously the grammar was much more restrictive see PEP 614 for details A list of type parameters may be given in square brackets immediately after the class s name This indicates to static type checkers that the class is generic At runtime the type parameters can be retrieved from the class s __type_params__ attribute See Generic classes for more Changed in version 3 12 Type parameter lists are new in Python 3 12 Programmer s note Variables defined in the class definition are class attributes they are shared by instances Instance attributes can be set in a method with self name value Both class and instance attributes are accessible through the notation self name and an instance attribute hides a class attribute with the same name when accessed in this way Class attributes can be used as defaults for instance attributes but using mutable values there can lead to unexpected results Descriptors can be used to create instance variables with different implementation details See also PEP 3115 Metaclasses in Python 3000 The proposal that changed the declaration of metaclasses to the current syntax and the semantics for how classes with metaclasses are constructed PEP 3129 Class Decorators The proposal that added class decorators Function and method decorators were introduced in PEP 318 8 9 Coroutines New in version 3 5 8 9 1 Coroutine function definition async_funcdef decorators async def funcname parameter_list expression suite Execution of Python coroutines can be suspended and resumed at many points see coroutine await expressions async for and async with can only be used in the body of a coroutine function Functions defined with async def syntax are always coroutine functions even if they do not contain await or async keywords It is a SyntaxError to use a yield from expression inside the body of a coroutine function An example of a coroutine function async def func param1 param2 do_stuff await some_coroutine Changed in version 3 7 await and async are now keywords previously they were only treated as such inside the body of a coroutine function 8 9 2 The async for statement async_for_stmt async for_stmt An asynchronous iterable provides an __aiter__ method that directly returns an asynchronous iterator which can call asynchronous code in its __anext__ method The async for statement allows convenient iteration over asynchronous it,en
1242,erables The following code async for TARGET in ITER SUITE else SUITE2 Is semantically equivalent to iter ITER iter type iter __aiter__ iter running True while running try TARGET await type iter __anext__ iter except StopAsyncIteration running False else SUITE else SUITE2 See also __aiter__ and __anext__ for details It is a SyntaxError to use an async for statement outside the body of a coroutine function 8 9 3 The async with statement async_with_stmt async with_stmt An asynchronous context manager is a context manager that is able to suspend execution in its enter and exit methods The following code async with EXPRESSION as TARGET SUITE is semantically equivalent to manager EXPRESSION aenter type manager __aenter__ aexit type manager __aexit__ value await aenter manager hit_except False try TARGET value SUITE except hit_except True if not await aexit manager sys exc_info raise finally if not hit_except await aexit manager None None None See also __aenter__ and __aexit__ for details It is a SyntaxError to use an async with statement outside the body of a coroutine function See also PEP 492 Coroutines with async and await syntax The proposal that made coroutines a proper standalone concept in Python and added supporting syntax 8 10 Type parameter lists New in version 3 12 type_params type_param type_param type_param typevar typevartuple paramspec typevar identifier expression typevartuple identifier paramspec identifier Functions including coroutines classes and type aliases may contain a type parameter list def max T args list T T async def amax T args list T T class Bag T def __iter__ self Iterator T def add self arg T None type ListOrSet T list T set T Semantically this indicates that the function class or type alias is generic over a type variable This information is primarily used by static type checkers and at runtime generic objects behave much like their non generic counterparts Type parameters are declared in square brackets immediately after the name of the function class or type alias The type parameters are accessible within the scope of the generic object but not elsewhere Thus after a declaration def func T pass the name T is not available in the module scope Below the semantics of generic objects are described with more precision The scope of type parameters is modeled with a special function technically an annotation scope that wraps the creation of the generic object Generic functions classes and type aliases have a __type_params__ attribute listing their type parameters Type parameters come in three kinds typing TypeVar introduced by a plain name e g T Semantically this represents a single type to a type checker typing TypeVarTuple introduced by a name prefixed with a single asterisk e g Ts Semantically this stands for a tuple of any number of types typing ParamSpec introduced by a name prefixed with two asterisks e g P Semantically this stands for the parameters of a callable typing TypeVar declarations can define bounds and constraints with a colon followed by an expression A single expression after the colon indicates a bound e g T int Semantically this means that the typing TypeVar can only represent types that are a subtype of this bound A parenthesized tuple of expressions after the colon indicates a set of constraints e g T str bytes Each member of the tuple should be a type again this is not enforced at runtime Constrained type variables can only take on one of the types in the list of constraints For typing TypeVar s declared using the type parameter list syntax the bound and constraints are not evaluated when the generic object is created but only when the value is explicitly accessed through the attributes __bound__ and __constraints__ To accomplish this the bounds or constraints are evaluated in a separate annotation scope typing TypeVarTuple s and typing ParamSpec s cannot have bounds or constraints The following example indicates the full set of allowed type parameter declarations def overly_generic SimpleTypeVar TypeVarWithBound int TypeVarWithConstraints str bytes SimpleTypeVarTuple Simple,en
1243,ParamSpec a SimpleTypeVar b TypeVarWithBound c Callable SimpleParamSpec TypeVarWithConstraints d SimpleTypeVarTuple 8 10 1 Generic functions Generic functions are declared as follows def func T arg T This syntax is equivalent to annotation def TYPE_PARAMS_OF_func T typing TypeVar T def func arg T func __type_params__ T return func func TYPE_PARAMS_OF_func Here annotation def indicates an annotation scope which is not actually bound to any name at runtime One other liberty is taken in the translation the syntax does not go through attribute access on the typing module but creates an instance of typing TypeVar directly The annotations of generic functions are evaluated within the annotation scope used for declaring the type parameters but the function s defaults and decorators are not The following example illustrates the scoping rules for these cases as well as for additional flavors of type parameters decorator def func T int Ts P args Ts arg Callable P T some_default Except for the lazy evaluation of the TypeVar bound this is equivalent to DEFAULT_OF_arg some_default annotation def TYPE_PARAMS_OF_func annotation def BOUND_OF_T return int In reality BOUND_OF_T is evaluated only on demand T typing TypeVar T bound BOUND_OF_T Ts typing TypeVarTuple Ts P typing ParamSpec P def func args Ts arg Callable P T DEFAULT_OF_arg func __type_params__ T Ts P return func func decorator TYPE_PARAMS_OF_func The capitalized names like DEFAULT_OF_arg are not actually bound at runtime 8 10 2 Generic classes Generic classes are declared as follows class Bag T This syntax is equivalent to annotation def TYPE_PARAMS_OF_Bag T typing TypeVar T class Bag typing Generic T __type_params__ T return Bag Bag TYPE_PARAMS_OF_Bag Here again annotation def not a real keyword indicates an annotation scope and the name TYPE_PARAMS_OF_Bag is not actually bound at runtime Generic classes implicitly inherit from typing Generic The base classes and keyword arguments of generic classes are evaluated within the type scope for the type parameters and decorators are evaluated outside that scope This is illustrated by this example decorator class Bag Base T arg T This is equivalent to annotation def TYPE_PARAMS_OF_Bag T typing TypeVar T class Bag Base T typing Generic T arg T __type_params__ T return Bag Bag decorator TYPE_PARAMS_OF_Bag 8 10 3 Generic type aliases The type statement can also be used to create a generic type alias type ListOrSet T list T set T Except for the lazy evaluation of the value this is equivalent to annotation def TYPE_PARAMS_OF_ListOrSet T typing TypeVar T annotation def VALUE_OF_ListOrSet return list T set T In reality the value is lazily evaluated return typing TypeAliasType ListOrSet VALUE_OF_ListOrSet type_params T ListOrSet TYPE_PARAMS_OF_ListOrSet Here annotation def not a real keyword indicates an annotation scope The capitalized names like TYPE_PARAMS_OF_ListOrSet are not actually bound at runtime Footnotes 1 The exception is propagated to the invocation stack unless there is a finally clause which happens to raise another exception That new exception causes the old one to be lost 2 In pattern matching a sequence is defined as one of the following a class that inherits from collections abc Sequence a Python class that has been registered as collections abc Sequence a builtin class that has its CPython Py_TPFLAGS_SEQUENCE bit set a class that inherits from any of the above The following standard library classes are sequences array array collections deque list memoryview range tuple Note Subject values of type str bytes and bytearray do not match sequence patterns 3 In pattern matching a mapping is defined as one of the following a class that inherits from collections abc Mapping a Python class that has been registered as collections abc Mapping a builtin class that has its CPython Py_TPFLAGS_MAPPING bit set a class that inherits from any of the above The standard library classes dict and types MappingProxyType are mappings 4 A string literal appearing as the first statement in the function body is transformed into the function s __do,en
1244,c__ attribute and therefore the function s docstring 5 A string literal appearing as the first statement in the class body is transformed into the namespace s __doc__ item and therefore the class s docstring,en
1245,http client HTTP protocol client Source code Lib http client py This module defines classes that implement the client side of the HTTP and HTTPS protocols It is normally not used directly the module urllib request uses it to handle URLs that use HTTP and HTTPS See also The Requests package is recommended for a higher level HTTP client interface Note HTTPS support is only available if Python was compiled with SSL support through the ssl module Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information The module provides the following classes class http client HTTPConnection host port None timeout source_address None blocksize 8192 An HTTPConnection instance represents one transaction with an HTTP server It should be instantiated by passing it a host and optional port number If no port number is passed the port is extracted from the host string if it has the form host port else the default HTTP port 80 is used If the optional timeout parameter is given blocking operations like connection attempts will timeout after that many seconds if it is not given the global default timeout setting is used The optional source_address parameter may be a tuple of a host port to use as the source address the HTTP connection is made from The optional blocksize parameter sets the buffer size in bytes for sending a file like message body For example the following calls all create instances that connect to the server at the same host and port h1 http client HTTPConnection www python org h2 http client HTTPConnection www python org 80 h3 http client HTTPConnection www python org 80 h4 http client HTTPConnection www python org 80 timeout 10 Changed in version 3 2 source_address was added Changed in version 3 4 The strict parameter was removed HTTP 0 9 style Simple Responses are no longer supported Changed in version 3 7 blocksize parameter was added class http client HTTPSConnection host port None timeout source_address None context None blocksize 8192 A subclass of HTTPConnection that uses SSL for communication with secure servers Default port is 443 If context is specified it must be a ssl SSLContext instance describing the various SSL options Please read Security considerations for more information on best practices Changed in version 3 2 source_address context and check_hostname were added Changed in version 3 2 This class now supports HTTPS virtual hosts if possible that is if ssl HAS_SNI is true Changed in version 3 4 The strict parameter was removed HTTP 0 9 style Simple Responses are no longer supported Changed in version 3 4 3 This class now performs all the necessary certificate and hostname checks by default To revert to the previous unverified behavior ssl _create_unverified_context can be passed to the context parameter Changed in version 3 8 This class now enables TLS 1 3 ssl SSLContext post_handshake_auth for the default context or when cert_file is passed with a custom context Changed in version 3 10 This class now sends an ALPN extension with protocol indicator http 1 1 when no context is given Custom context should set ALPN protocols with set_alpn_protocols Changed in version 3 12 The deprecated key_file cert_file and check_hostname parameters have been removed class http client HTTPResponse sock debuglevel 0 method None url None Class whose instances are returned upon successful connection Not instantiated directly by user Changed in version 3 4 The strict parameter was removed HTTP 0 9 style Simple Responses are no longer supported This module provides the following function http client parse_headers fp Parse the headers from a file pointer fp representing a HTTP request response The file has to be a BufferedIOBase reader i e not text and must provide a valid RFC 2822 style header This function returns an instance of http client HTTPMessage that holds the header fields but no payload the same as HTTPResponse msg and http server BaseHTTPRequestHandler headers After returning the file pointer fp is,en
1246, ready to read the HTTP body Note parse_headers does not parse the start line of a HTTP message it only parses the Name value lines The file has to be ready to read these field lines so the first line should already be consumed before calling the function The following exceptions are raised as appropriate exception http client HTTPException The base class of the other exceptions in this module It is a subclass of Exception exception http client NotConnected A subclass of HTTPException exception http client InvalidURL A subclass of HTTPException raised if a port is given and is either non numeric or empty exception http client UnknownProtocol A subclass of HTTPException exception http client UnknownTransferEncoding A subclass of HTTPException exception http client UnimplementedFileMode A subclass of HTTPException exception http client IncompleteRead A subclass of HTTPException exception http client ImproperConnectionState A subclass of HTTPException exception http client CannotSendRequest A subclass of ImproperConnectionState exception http client CannotSendHeader A subclass of ImproperConnectionState exception http client ResponseNotReady A subclass of ImproperConnectionState exception http client BadStatusLine A subclass of HTTPException Raised if a server responds with a HTTP status code that we don t understand exception http client LineTooLong A subclass of HTTPException Raised if an excessively long line is received in the HTTP protocol from the server exception http client RemoteDisconnected A subclass of ConnectionResetError and BadStatusLine Raised by HTTPConnection getresponse when the attempt to read the response results in no data read from the connection indicating that the remote end has closed the connection New in version 3 5 Previously BadStatusLine was raised The constants defined in this module are http client HTTP_PORT The default port for the HTTP protocol always 80 http client HTTPS_PORT The default port for the HTTPS protocol always 443 http client responses This dictionary maps the HTTP 1 1 status codes to the W3C names Example http client responses http client NOT_FOUND is Not Found See HTTP status codes for a list of HTTP status codes that are available in this module as constants HTTPConnection Objects HTTPConnection instances have the following methods HTTPConnection request method url body None headers encode_chunked False This will send a request to the server using the HTTP request method method and the request URI url The provided url must be an absolute path to conform with RFC 2616 5 1 2 unless connecting to an HTTP proxy server or using the OPTIONS or CONNECT methods If body is specified the specified data is sent after the headers are finished It may be a str a bytes like object an open file object or an iterable of bytes If body is a string it is encoded as ISO 8859 1 the default for HTTP If it is a bytes like object the bytes are sent as is If it is a file object the contents of the file is sent this file object should support at least the read method If the file object is an instance of io TextIOBase the data returned by the read method will be encoded as ISO 8859 1 otherwise the data returned by read is sent as is If body is an iterable the elements of the iterable are sent as is until the iterable is exhausted The headers argument should be a mapping of extra HTTP headers to send with the request A Host header must be provided to conform with RFC 2616 5 1 2 unless connecting to an HTTP proxy server or using the OPTIONS or CONNECT methods If headers contains neither Content Length nor Transfer Encoding but there is a request body one of those header fields will be added automatically If body is None the Content Length header is set to 0 for methods that expect a body PUT POST and PATCH If body is a string or a bytes like object that is not also a file the Content Length header is set to its length Any other type of body files and iterables in general will be chunk encoded and the Transfer Encoding header will automatically be set instead of Content Length The encode_chunked argument,en
1247, is only relevant if Transfer Encoding is specified in headers If encode_chunked is False the HTTPConnection object assumes that all encoding is handled by the calling code If it is True the body will be chunk encoded For example to perform a GET request to https docs python org 3 import http client host docs python org conn http client HTTPSConnection host conn request GET 3 headers Host host response conn getresponse print response status response reason 200 OK Note Chunked transfer encoding has been added to the HTTP protocol version 1 1 Unless the HTTP server is known to handle HTTP 1 1 the caller must either specify the Content Length or must pass a str or bytes like object that is not also a file as the body representation Changed in version 3 2 body can now be an iterable Changed in version 3 6 If neither Content Length nor Transfer Encoding are set in headers file and iterable body objects are now chunk encoded The encode_chunked argument was added No attempt is made to determine the Content Length for file objects HTTPConnection getresponse Should be called after a request is sent to get the response from the server Returns an HTTPResponse instance Note Note that you must have read the whole response before you can send a new request to the server Changed in version 3 5 If a ConnectionError or subclass is raised the HTTPConnection object will be ready to reconnect when a new request is sent HTTPConnection set_debuglevel level Set the debugging level The default debug level is 0 meaning no debugging output is printed Any value greater than 0 will cause all currently defined debug output to be printed to stdout The debuglevel is passed to any new HTTPResponse objects that are created New in version 3 1 HTTPConnection set_tunnel host port None headers None Set the host and the port for HTTP Connect Tunnelling This allows running the connection through a proxy server The host and port arguments specify the endpoint of the tunneled connection i e the address included in the CONNECT request not the address of the proxy server The headers argument should be a mapping of extra HTTP headers to send with the CONNECT request As HTTP 1 1 is used for HTTP CONNECT tunnelling request as per the RFC a HTTP Host header must be provided matching the authority form of the request target provided as the destination for the CONNECT request If a HTTP Host header is not provided via the headers argument one is generated and transmitted automatically For example to tunnel through a HTTPS proxy server running locally on port 8080 we would pass the address of the proxy to the HTTPSConnection constructor and the address of the host that we eventually want to reach to the set_tunnel method import http client conn http client HTTPSConnection localhost 8080 conn set_tunnel www python org conn request HEAD index html New in version 3 2 Changed in version 3 12 HTTP CONNECT tunnelling requests use protocol HTTP 1 1 upgraded from protocol HTTP 1 0 Host HTTP headers are mandatory for HTTP 1 1 so one will be automatically generated and transmitted if not provided in the headers argument HTTPConnection get_proxy_response_headers Returns a dictionary with the headers of the response received from the proxy server to the CONNECT request If the CONNECT request was not sent the method returns None New in version 3 12 HTTPConnection connect Connect to the server specified when the object was created By default this is called automatically when making a request if the client does not already have a connection Raises an auditing event http client connect with arguments self host port HTTPConnection close Close the connection to the server HTTPConnection blocksize Buffer size in bytes for sending a file like message body New in version 3 7 As an alternative to using the request method described above you can also send your request step by step by using the four functions below HTTPConnection putrequest method url skip_host False skip_accept_encoding False This should be the first call after the connection to the server has been made It sends a line to the ,en
1248,server consisting of the method string the url string and the HTTP version HTTP 1 1 To disable automatic sending of Host or Accept Encoding headers for example to accept additional content encodings specify skip_host or skip_accept_encoding with non False values HTTPConnection putheader header argument Send an RFC 822 style header to the server It sends a line to the server consisting of the header a colon and a space and the first argument If more arguments are given continuation lines are sent each consisting of a tab and an argument HTTPConnection endheaders message_body None encode_chunked False Send a blank line to the server signalling the end of the headers The optional message_body argument can be used to pass a message body associated with the request If encode_chunked is True the result of each iteration of message_body will be chunk encoded as specified in RFC 7230 Section 3 3 1 How the data is encoded is dependent on the type of message_body If message_body implements the buffer interface the encoding will result in a single chunk If message_body is a collections abc Iterable each iteration of message_body will result in a chunk If message_body is a file object each call to read will result in a chunk The method automatically signals the end of the chunk encoded data immediately after message_body Note Due to the chunked encoding specification empty chunks yielded by an iterator body will be ignored by the chunk encoder This is to avoid premature termination of the read of the request by the target server due to malformed encoding Changed in version 3 6 Added chunked encoding support and the encode_chunked parameter HTTPConnection send data Send data to the server This should be used directly only after the endheaders method has been called and before getresponse is called Raises an auditing event http client send with arguments self data HTTPResponse Objects An HTTPResponse instance wraps the HTTP response from the server It provides access to the request headers and the entity body The response is an iterable object and can be used in a with statement Changed in version 3 5 The io BufferedIOBase interface is now implemented and all of its reader operations are supported HTTPResponse read amt Reads and returns the response body or up to the next amt bytes HTTPResponse readinto b Reads up to the next len b bytes of the response body into the buffer b Returns the number of bytes read New in version 3 3 HTTPResponse getheader name default None Return the value of the header name or default if there is no header matching name If there is more than one header with the name name return all of the values joined by If default is any iterable other than a single string its elements are similarly returned joined by commas HTTPResponse getheaders Return a list of header value tuples HTTPResponse fileno Return the fileno of the underlying socket HTTPResponse msg A http client HTTPMessage instance containing the response headers http client HTTPMessage is a subclass of email message Message HTTPResponse version HTTP protocol version used by server 10 for HTTP 1 0 11 for HTTP 1 1 HTTPResponse url URL of the resource retrieved commonly used to determine if a redirect was followed HTTPResponse headers Headers of the response in the form of an email message EmailMessage instance HTTPResponse status Status code returned by server HTTPResponse reason Reason phrase returned by server HTTPResponse debuglevel A debugging hook If debuglevel is greater than zero messages will be printed to stdout as the response is read and parsed HTTPResponse closed Is True if the stream is closed HTTPResponse geturl Deprecated since version 3 9 Deprecated in favor of url HTTPResponse info Deprecated since version 3 9 Deprecated in favor of headers HTTPResponse getcode Deprecated since version 3 9 Deprecated in favor of status Examples Here is an example session that uses the GET method import http client conn http client HTTPSConnection www python org conn request GET r1 conn getresponse print r1 status r1 reason 200 OK data1 r1 read This will re,en
1249,turn entire content The following example demonstrates reading data in chunks conn request GET r1 conn getresponse while chunk r1 read 200 print repr chunk b doctype html n if Example of an invalid request conn http client HTTPSConnection docs python org conn request GET parrot spam r2 conn getresponse print r2 status r2 reason 404 Not Found data2 r2 read conn close Here is an example session that uses the HEAD method Note that the HEAD method never returns any data import http client conn http client HTTPSConnection www python org conn request HEAD res conn getresponse print res status res reason 200 OK data res read print len data 0 data b True Here is an example session that uses the POST method import http client urllib parse params urllib parse urlencode number 12524 type issue action show headers Content type application x www form urlencoded Accept text plain conn http client HTTPConnection bugs python org conn request POST params headers response conn getresponse print response status response reason 302 Found data response read data b Redirecting to a href https bugs python org issue12524 https bugs python org issue12524 a conn close Client side HTTP PUT requests are very similar to POST requests The difference lies only on the server side where HTTP servers will allow resources to be created via PUT requests It should be noted that custom HTTP methods are also handled in urllib request Request by setting the appropriate method attribute Here is an example session that uses the PUT method This creates an HTTP request with the content of BODY as the enclosed representation for the resource http localhost 8080 file import http client BODY filecontents conn http client HTTPConnection localhost 8080 conn request PUT file BODY response conn getresponse print response status response reason 200 OK HTTPMessage Objects class http client HTTPMessage email message Message An http client HTTPMessage instance holds the headers from an HTTP response It is implemented using the email message Message class,en
1250,The Very High Level Layer The functions in this chapter will let you execute Python source code given in a file or a buffer but they will not let you interact in a more detailed way with the interpreter Several of these functions accept a start symbol from the grammar as a parameter The available start symbols are Py_eval_input Py_file_input and Py_single_input These are described following the functions which accept them as parameters Note also that several of these functions take FILE parameters One particular issue which needs to be handled carefully is that the FILE structure for different C libraries can be different and incompatible Under Windows at least it is possible for dynamically linked extensions to actually use different libraries so care should be taken that FILE parameters are only passed to these functions if it is certain that they were created by the same library that the Python runtime is using int Py_Main int argc wchar_t argv Part of the Stable ABI The main program for the standard interpreter This is made available for programs which embed Python The argc and argv parameters should be prepared exactly as those which are passed to a C program s main function converted to wchar_t according to the user s locale It is important to note that the argument list may be modified but the contents of the strings pointed to by the argument list are not The return value will be 0 if the interpreter exits normally i e without an exception 1 if the interpreter exits due to an exception or 2 if the parameter list does not represent a valid Python command line Note that if an otherwise unhandled SystemExit is raised this function will not return 1 but exit the process as long as PyConfig inspect is zero int Py_BytesMain int argc char argv Part of the Stable ABI since version 3 8 Similar to Py_Main but argv is an array of bytes strings New in version 3 8 int PyRun_AnyFile FILE fp const char filename This is a simplified interface to PyRun_AnyFileExFlags below leaving closeit set to 0 and flags set to NULL int PyRun_AnyFileFlags FILE fp const char filename PyCompilerFlags flags This is a simplified interface to PyRun_AnyFileExFlags below leaving the closeit argument set to 0 int PyRun_AnyFileEx FILE fp const char filename int closeit This is a simplified interface to PyRun_AnyFileExFlags below leaving the flags argument set to NULL int PyRun_AnyFileExFlags FILE fp const char filename int closeit PyCompilerFlags flags If fp refers to a file associated with an interactive device console or terminal input or Unix pseudo terminal return the value of PyRun_InteractiveLoop otherwise return the result of PyRun_SimpleFile filename is decoded from the filesystem encoding sys getfilesystemencoding If filename is NULL this function uses as the filename If closeit is true the file is closed before PyRun_SimpleFileExFlags returns int PyRun_SimpleString const char command This is a simplified interface to PyRun_SimpleStringFlags below leaving the PyCompilerFlags argument set to NULL int PyRun_SimpleStringFlags const char command PyCompilerFlags flags Executes the Python source code from command in the __main__ module according to the flags argument If __main__ does not already exist it is created Returns 0 on success or 1 if an exception was raised If there was an error there is no way to get the exception information For the meaning of flags see below Note that if an otherwise unhandled SystemExit is raised this function will not return 1 but exit the process as long as PyConfig inspect is zero int PyRun_SimpleFile FILE fp const char filename This is a simplified interface to PyRun_SimpleFileExFlags below leaving closeit set to 0 and flags set to NULL int PyRun_SimpleFileEx FILE fp const char filename int closeit This is a simplified interface to PyRun_SimpleFileExFlags below leaving flags set to NULL int PyRun_SimpleFileExFlags FILE fp const char filename int closeit PyCompilerFlags flags Similar to PyRun_SimpleStringFlags but the Python source code is read from fp instead of an in memory string filename should be the name of th,en
1251,e file it is decoded from filesystem encoding and error handler If closeit is true the file is closed before PyRun_SimpleFileExFlags returns Note On Windows fp should be opened as binary mode e g fopen filename rb Otherwise Python may not handle script file with LF line ending correctly int PyRun_InteractiveOne FILE fp const char filename This is a simplified interface to PyRun_InteractiveOneFlags below leaving flags set to NULL int PyRun_InteractiveOneFlags FILE fp const char filename PyCompilerFlags flags Read and execute a single statement from a file associated with an interactive device according to the flags argument The user will be prompted using sys ps1 and sys ps2 filename is decoded from the filesystem encoding and error handler Returns 0 when the input was executed successfully 1 if there was an exception or an error code from the errcode h include file distributed as part of Python if there was a parse error Note that errcode h is not included by Python h so must be included specifically if needed int PyRun_InteractiveLoop FILE fp const char filename This is a simplified interface to PyRun_InteractiveLoopFlags below leaving flags set to NULL int PyRun_InteractiveLoopFlags FILE fp const char filename PyCompilerFlags flags Read and execute statements from a file associated with an interactive device until EOF is reached The user will be prompted using sys ps1 and sys ps2 filename is decoded from the filesystem encoding and error handler Returns 0 at EOF or a negative number upon failure int PyOS_InputHook void Part of the Stable ABI Can be set to point to a function with the prototype int func void The function will be called when Python s interpreter prompt is about to become idle and wait for user input from the terminal The return value is ignored Overriding this hook can be used to integrate the interpreter s prompt with other event loops as done in the Modules _tkinter c in the Python source code Changed in version 3 12 This function is only called from the main interpreter char PyOS_ReadlineFunctionPointer FILE FILE const char Can be set to point to a function with the prototype char func FILE stdin FILE stdout char prompt overriding the default function used to read a single line of input at the interpreter s prompt The function is expected to output the string prompt if it s not NULL and then read a line of input from the provided standard input file returning the resulting string For example The readline module sets this hook to provide line editing and tab completion features The result must be a string allocated by PyMem_RawMalloc or PyMem_RawRealloc or NULL if an error occurred Changed in version 3 4 The result must be allocated by PyMem_RawMalloc or PyMem_RawRealloc instead of being allocated by PyMem_Malloc or PyMem_Realloc Changed in version 3 12 This function is only called from the main interpreter PyObject PyRun_String const char str int start PyObject globals PyObject locals Return value New reference This is a simplified interface to PyRun_StringFlags below leaving flags set to NULL PyObject PyRun_StringFlags const char str int start PyObject globals PyObject locals PyCompilerFlags flags Return value New reference Execute Python source code from str in the context specified by the objects globals and locals with the compiler flags specified by flags globals must be a dictionary locals can be any object that implements the mapping protocol The parameter start specifies the start token that should be used to parse the source code Returns the result of executing the code as a Python object or NULL if an exception was raised PyObject PyRun_File FILE fp const char filename int start PyObject globals PyObject locals Return value New reference This is a simplified interface to PyRun_FileExFlags below leaving closeit set to 0 and flags set to NULL PyObject PyRun_FileEx FILE fp const char filename int start PyObject globals PyObject locals int closeit Return value New reference This is a simplified interface to PyRun_FileExFlags below leaving flags set to NULL PyObject PyRun_FileFlags FILE fp const ,en
1252,char filename int start PyObject globals PyObject locals PyCompilerFlags flags Return value New reference This is a simplified interface to PyRun_FileExFlags below leaving closeit set to 0 PyObject PyRun_FileExFlags FILE fp const char filename int start PyObject globals PyObject locals int closeit PyCompilerFlags flags Return value New reference Similar to PyRun_StringFlags but the Python source code is read from fp instead of an in memory string filename should be the name of the file it is decoded from the filesystem encoding and error handler If closeit is true the file is closed before PyRun_FileExFlags returns PyObject Py_CompileString const char str const char filename int start Return value New reference Part of the Stable ABI This is a simplified interface to Py_CompileStringFlags below leaving flags set to NULL PyObject Py_CompileStringFlags const char str const char filename int start PyCompilerFlags flags Return value New reference This is a simplified interface to Py_CompileStringExFlags below with optimize set to 1 PyObject Py_CompileStringObject const char str PyObject filename int start PyCompilerFlags flags int optimize Return value New reference Parse and compile the Python source code in str returning the resulting code object The start token is given by start this can be used to constrain the code which can be compiled and should be Py_eval_input Py_file_input or Py_single_input The filename specified by filename is used to construct the code object and may appear in tracebacks or SyntaxError exception messages This returns NULL if the code cannot be parsed or compiled The integer optimize specifies the optimization level of the compiler a value of 1 selects the optimization level of the interpreter as given by O options Explicit levels are 0 no optimization __debug__ is true 1 asserts are removed __debug__ is false or 2 docstrings are removed too New in version 3 4 PyObject Py_CompileStringExFlags const char str const char filename int start PyCompilerFlags flags int optimize Return value New reference Like Py_CompileStringObject but filename is a byte string decoded from the filesystem encoding and error handler New in version 3 2 PyObject PyEval_EvalCode PyObject co PyObject globals PyObject locals Return value New reference Part of the Stable ABI This is a simplified interface to PyEval_EvalCodeEx with just the code object and global and local variables The other arguments are set to NULL PyObject PyEval_EvalCodeEx PyObject co PyObject globals PyObject locals PyObject const args int argcount PyObject const kws int kwcount PyObject const defs int defcount PyObject kwdefs PyObject closure Return value New reference Part of the Stable ABI Evaluate a precompiled code object given a particular environment for its evaluation This environment consists of a dictionary of global variables a mapping object of local variables arrays of arguments keywords and defaults a dictionary of default values for keyword only arguments and a closure tuple of cells PyObject PyEval_EvalFrame PyFrameObject f Return value New reference Part of the Stable ABI Evaluate an execution frame This is a simplified interface to PyEval_EvalFrameEx for backward compatibility PyObject PyEval_EvalFrameEx PyFrameObject f int throwflag Return value New reference Part of the Stable ABI This is the main unvarnished function of Python interpretation The code object associated with the execution frame f is executed interpreting bytecode and executing calls as needed The additional throwflag parameter can mostly be ignored if true then it causes an exception to immediately be thrown this is used for the throw methods of generator objects Changed in version 3 4 This function now includes a debug assertion to help ensure that it does not silently discard an active exception int PyEval_MergeCompilerFlags PyCompilerFlags cf This function changes the flags of the current evaluation frame and returns true on success false on failure int Py_eval_input The start symbol from the Python grammar for isolated expressions for use with Py_CompileString int P,en
1253,y_file_input The start symbol from the Python grammar for sequences of statements as read from a file or other source for use with Py_CompileString This is the symbol to use when compiling arbitrarily long Python source code int Py_single_input The start symbol from the Python grammar for a single statement for use with Py_CompileString This is the symbol used for the interactive interpreter loop struct PyCompilerFlags This is the structure used to hold compiler flags In cases where code is only being compiled it is passed as int flags and in cases where code is being executed it is passed as PyCompilerFlags flags In this case from __future__ import can modify flags Whenever PyCompilerFlags flags is NULL cf_flags is treated as equal to 0 and any modification due to from __future__ import is discarded int cf_flags Compiler flags int cf_feature_version cf_feature_version is the minor Python version It should be initialized to PY_MINOR_VERSION The field is ignored by default it is used if and only if PyCF_ONLY_AST flag is set in cf_flags Changed in version 3 8 Added cf_feature_version field int CO_FUTURE_DIVISION This bit can be set in flags to cause division operator to be interpreted as true division according to PEP 238,en
1254,Python Documentation contents What s New in Python What s New In Python 3 12 Summary Release highlights New Features PEP 695 Type Parameter Syntax PEP 701 Syntactic formalization of f strings PEP 684 A Per Interpreter GIL PEP 669 Low impact monitoring for CPython PEP 688 Making the buffer protocol accessible in Python PEP 709 Comprehension inlining Improved Error Messages New Features Related to Type Hints PEP 692 Using TypedDict for more precise kwargs typing PEP 698 Override Decorator for Static Typing Other Language Changes New Modules Improved Modules array asyncio calendar csv dis fractions importlib resources inspect itertools math os os path pathlib pdb random shutil sqlite3 statistics sys tempfile threading tkinter tokenize types typing unicodedata unittest uuid Optimizations CPython bytecode changes Demos and Tools Deprecated Pending Removal in Python 3 13 Pending Removal in Python 3 14 Pending Removal in Python 3 15 Pending Removal in Future Versions Removed asynchat and asyncore configparser distutils ensurepip enum ftplib gzip hashlib importlib imp io locale smtpd sqlite3 ssl unittest webbrowser xml etree ElementTree zipimport Others Porting to Python 3 12 Changes in the Python API Build Changes C API Changes New Features Porting to Python 3 12 Deprecated Pending Removal in Python 3 14 Pending Removal in Python 3 15 Pending Removal in Future Versions Removed What s New In Python 3 11 Summary Release highlights New Features PEP 657 Fine grained error locations in tracebacks PEP 654 Exception Groups and except PEP 678 Exceptions can be enriched with notes Windows py exe launcher improvements New Features Related to Type Hints PEP 646 Variadic generics PEP 655 Marking individual TypedDict items as required or not required PEP 673 Self type PEP 675 Arbitrary literal string type PEP 681 Data class transforms PEP 563 may not be the future Other Language Changes Other CPython Implementation Changes New Modules Improved Modules asyncio contextlib dataclasses datetime enum fcntl fractions functools hashlib IDLE and idlelib inspect locale logging math operator os pathlib re shutil socket sqlite3 string sys sysconfig tempfile threading time tkinter traceback typing unicodedata unittest venv warnings zipfile Optimizations Faster CPython Faster Startup Frozen imports Static code objects Faster Runtime Cheaper lazy Python frames Inlined Python function calls PEP 659 Specializing Adaptive Interpreter Misc FAQ How should I write my code to utilize these speedups Will CPython 3 11 use more memory I don t see any speedups in my workload Why Is there a JIT compiler About CPython bytecode changes New opcodes Replaced opcodes Changed removed opcodes Deprecated Language Builtins Modules Standard Library Pending Removal in Python 3 12 Removed Porting to Python 3 11 Build Changes C API Changes New Features Porting to Python 3 11 Deprecated Pending Removal in Python 3 12 Removed Notable changes in 3 11 4 tarfile Notable changes in 3 11 5 OpenSSL What s New In Python 3 10 Summary Release highlights New Features Parenthesized context managers Better error messages SyntaxErrors IndentationErrors AttributeErrors NameErrors PEP 626 Precise line numbers for debugging and other tools PEP 634 Structural Pattern Matching Syntax and operations Declarative approach Simple pattern match to a literal Behavior without the wildcard Patterns with a literal and variable Patterns and classes Patterns with positional parameters Nested patterns Complex patterns and the wildcard Guard Other Key Features Optional EncodingWarning and encoding locale option New Features Related to Type Hints PEP 604 New Type Union Operator PEP 612 Parameter Specification Variables PEP 613 TypeAlias PEP 647 User Defined Type Guards Other Language Changes New Modules Improved Modules asyncio argparse array asynchat asyncore smtpd base64 bdb bisect codecs collections abc contextlib curses dataclasses __slots__ Keyword only fields distutils doctest encodings enum fileinput faulthandler gc glob hashlib hmac IDLE and idlelib importlib metadata inspect itertools linecache os os pa,en
1255,th pathlib platform pprint py_compile pyclbr shelve statistics site socket ssl sqlite3 sys _thread threading traceback types typing unittest urllib parse xml zipimport Optimizations Deprecated Removed Porting to Python 3 10 Changes in the Python syntax Changes in the Python API Changes in the C API CPython bytecode changes Build Changes C API Changes PEP 652 Maintaining the Stable ABI New Features Porting to Python 3 10 Deprecated Removed Notable security feature in 3 10 7 Notable security feature in 3 10 8 Notable changes in 3 10 12 tarfile What s New In Python 3 9 Summary Release highlights You should check for DeprecationWarning in your code New Features Dictionary Merge Update Operators New String Methods to Remove Prefixes and Suffixes Type Hinting Generics in Standard Collections New Parser Other Language Changes New Modules zoneinfo graphlib Improved Modules ast asyncio compileall concurrent futures curses datetime distutils fcntl ftplib gc hashlib http IDLE and idlelib imaplib importlib inspect ipaddress math multiprocessing nntplib os pathlib pdb poplib pprint pydoc random signal smtplib socket time sys tracemalloc typing unicodedata venv xml Optimizations Deprecated Removed Porting to Python 3 9 Changes in the Python API Changes in the C API CPython bytecode changes Build Changes C API Changes New Features Porting to Python 3 9 Removed Notable changes in Python 3 9 1 typing macOS 11 0 Big Sur and Apple Silicon Mac support Notable changes in Python 3 9 2 collections abc urllib parse Notable changes in Python 3 9 3 Notable changes in Python 3 9 5 urllib parse Notable security feature in 3 9 14 Notable changes in 3 9 17 tarfile What s New In Python 3 8 Summary Release highlights New Features Assignment expressions Positional only parameters Parallel filesystem cache for compiled bytecode files Debug build uses the same ABI as release build f strings support for self documenting expressions and debugging PEP 578 Python Runtime Audit Hooks PEP 587 Python Initialization Configuration PEP 590 Vectorcall a fast calling protocol for CPython Pickle protocol 5 with out of band data buffers Other Language Changes New Modules Improved Modules ast asyncio builtins collections cProfile csv curses ctypes datetime functools gc gettext gzip IDLE and idlelib inspect io itertools json tool logging math mmap multiprocessing os os path pathlib pickle plistlib pprint py_compile shlex shutil socket ssl statistics sys tarfile threading tokenize tkinter time typing unicodedata unittest venv weakref xml xmlrpc Optimizations Build and C API Changes Deprecated API and Feature Removals Porting to Python 3 8 Changes in Python behavior Changes in the Python API Changes in the C API CPython bytecode changes Demos and Tools Notable changes in Python 3 8 1 Notable changes in Python 3 8 2 Notable changes in Python 3 8 3 Notable changes in Python 3 8 8 Notable changes in Python 3 8 9 Notable changes in Python 3 8 10 macOS 11 0 Big Sur and Apple Silicon Mac support Notable changes in Python 3 8 10 urllib parse Notable changes in Python 3 8 12 Changes in the Python API Notable security feature in 3 8 14 Notable changes in 3 8 17 tarfile What s New In Python 3 7 Summary Release Highlights New Features PEP 563 Postponed Evaluation of Annotations PEP 538 Legacy C Locale Coercion PEP 540 Forced UTF 8 Runtime Mode PEP 553 Built in breakpoint PEP 539 New C API for Thread Local Storage PEP 562 Customization of Access to Module Attributes PEP 564 New Time Functions With Nanosecond Resolution PEP 565 Show DeprecationWarning in __main__ PEP 560 Core Support for typing module and Generic Types PEP 552 Hash based pyc Files PEP 545 Python Documentation Translations Python Development Mode X dev Other Language Changes New Modules contextvars dataclasses importlib resources Improved Modules argparse asyncio binascii calendar collections compileall concurrent futures contextlib cProfile crypt datetime dbm decimal dis distutils enum functools gc hmac http client http server idlelib and IDLE importlib io ipaddress itertools locale logging math mimetypes msilib multip,en
1256,rocessing os pathlib pdb py_compile pydoc queue re signal socket socketserver sqlite3 ssl string subprocess sys time tkinter tracemalloc types unicodedata unittest unittest mock urllib parse uu uuid warnings xml xml etree xmlrpc server zipapp zipfile C API Changes Build Changes Optimizations Other CPython Implementation Changes Deprecated Python Behavior Deprecated Python modules functions and methods aifc asyncio collections dbm enum gettext importlib locale macpath threading socket ssl sunau sys wave Deprecated functions and types of the C API Platform Support Removals API and Feature Removals Module Removals Windows only Changes Porting to Python 3 7 Changes in Python Behavior Changes in the Python API Changes in the C API CPython bytecode changes Windows only Changes Other CPython implementation changes Notable changes in Python 3 7 1 Notable changes in Python 3 7 2 Notable changes in Python 3 7 6 Notable changes in Python 3 7 10 Notable changes in Python 3 7 11 Notable security feature in 3 7 14 What s New In Python 3 6 Summary Release highlights New Features PEP 498 Formatted string literals PEP 526 Syntax for variable annotations PEP 515 Underscores in Numeric Literals PEP 525 Asynchronous Generators PEP 530 Asynchronous Comprehensions PEP 487 Simpler customization of class creation PEP 487 Descriptor Protocol Enhancements PEP 519 Adding a file system path protocol PEP 495 Local Time Disambiguation PEP 529 Change Windows filesystem encoding to UTF 8 PEP 528 Change Windows console encoding to UTF 8 PEP 520 Preserving Class Attribute Definition Order PEP 468 Preserving Keyword Argument Order New dict implementation PEP 523 Adding a frame evaluation API to CPython PYTHONMALLOC environment variable DTrace and SystemTap probing support Other Language Changes New Modules secrets Improved Modules array ast asyncio binascii cmath collections concurrent futures contextlib datetime decimal distutils email encodings enum faulthandler fileinput hashlib http client idlelib and IDLE importlib inspect json logging math multiprocessing os pathlib pdb pickle pickletools pydoc random re readline rlcompleter shlex site sqlite3 socket socketserver ssl statistics struct subprocess sys telnetlib time timeit tkinter traceback tracemalloc typing unicodedata unittest mock urllib request urllib robotparser venv warnings winreg winsound xmlrpc client zipfile zlib Optimizations Build and C API Changes Other Improvements Deprecated New Keywords Deprecated Python behavior Deprecated Python modules functions and methods asynchat asyncore dbm distutils grp importlib os re ssl tkinter venv xml Deprecated functions and types of the C API Deprecated Build Options Removed API and Feature Removals Porting to Python 3 6 Changes in python Command Behavior Changes in the Python API Changes in the C API CPython bytecode changes Notable changes in Python 3 6 2 New make regen all build target Removal of make touch build target Notable changes in Python 3 6 4 Notable changes in Python 3 6 5 Notable changes in Python 3 6 7 Notable changes in Python 3 6 10 Notable changes in Python 3 6 13 Notable changes in Python 3 6 14 What s New In Python 3 5 Summary Release highlights New Features PEP 492 Coroutines with async and await syntax PEP 465 A dedicated infix operator for matrix multiplication PEP 448 Additional Unpacking Generalizations PEP 461 percent formatting support for bytes and bytearray PEP 484 Type Hints PEP 471 os scandir function a better and faster directory iterator PEP 475 Retry system calls failing with EINTR PEP 479 Change StopIteration handling inside generators PEP 485 A function for testing approximate equality PEP 486 Make the Python Launcher aware of virtual environments PEP 488 Elimination of PYO files PEP 489 Multi phase extension module initialization Other Language Changes New Modules typing zipapp Improved Modules argparse asyncio bz2 cgi cmath code collections collections abc compileall concurrent futures configparser contextlib csv curses dbm difflib distutils doctest email enum faulthandler functools glob gzip heapq http http client,en
1257, idlelib and IDLE imaplib imghdr importlib inspect io ipaddress json linecache locale logging lzma math multiprocessing operator os pathlib pickle poplib re readline selectors shutil signal smtpd smtplib sndhdr socket ssl Memory BIO Support Application Layer Protocol Negotiation Support Other Changes sqlite3 subprocess sys sysconfig tarfile threading time timeit tkinter traceback types unicodedata unittest unittest mock urllib wsgiref xmlrpc xml sax zipfile Other module level changes Optimizations Build and C API Changes Deprecated New Keywords Deprecated Python Behavior Unsupported Operating Systems Deprecated Python modules functions and methods Removed API and Feature Removals Porting to Python 3 5 Changes in Python behavior Changes in the Python API Changes in the C API Notable changes in Python 3 5 4 New make regen all build target Removal of make touch build target What s New In Python 3 4 Summary Release Highlights New Features PEP 453 Explicit Bootstrapping of PIP in Python Installations Bootstrapping pip By Default Documentation Changes PEP 446 Newly Created File Descriptors Are Non Inheritable Improvements to Codec Handling PEP 451 A ModuleSpec Type for the Import System Other Language Changes New Modules asyncio ensurepip enum pathlib selectors statistics tracemalloc Improved Modules abc aifc argparse audioop base64 collections colorsys contextlib dbm dis doctest email filecmp functools gc glob hashlib hmac html http idlelib and IDLE importlib inspect ipaddress logging marshal mmap multiprocessing operator os pdb pickle plistlib poplib pprint pty pydoc re resource select shelve shutil smtpd smtplib socket sqlite3 ssl stat struct subprocess sunau sys tarfile textwrap threading traceback types urllib unittest venv wave weakref xml etree zipfile CPython Implementation Changes PEP 445 Customization of CPython Memory Allocators PEP 442 Safe Object Finalization PEP 456 Secure and Interchangeable Hash Algorithm PEP 436 Argument Clinic Other Build and C API Changes Other Improvements Significant Optimizations Deprecated Deprecations in the Python API Deprecated Features Removed Operating Systems No Longer Supported API and Feature Removals Code Cleanups Porting to Python 3 4 Changes in python Command Behavior Changes in the Python API Changes in the C API Changed in 3 4 3 PEP 476 Enabling certificate verification by default for stdlib http clients What s New In Python 3 3 Summary Release highlights PEP 405 Virtual Environments PEP 420 Implicit Namespace Packages PEP 3118 New memoryview implementation and buffer protocol documentation Features API changes PEP 393 Flexible String Representation Functionality Performance and resource usage PEP 397 Python Launcher for Windows PEP 3151 Reworking the OS and IO exception hierarchy PEP 380 Syntax for Delegating to a Subgenerator PEP 409 Suppressing exception context PEP 414 Explicit Unicode literals PEP 3155 Qualified name for classes and functions PEP 412 Key Sharing Dictionary PEP 362 Function Signature Object PEP 421 Adding sys implementation SimpleNamespace Using importlib as the Implementation of Import New APIs Visible Changes Other Language Changes A Finer Grained Import Lock Builtin functions and types New Modules faulthandler ipaddress lzma Improved Modules abc array base64 binascii bz2 codecs collections contextlib crypt curses datetime decimal Features API changes email Policy Framework Provisional Policy with New Header API Other API Changes ftplib functools gc hmac http html imaplib inspect io itertools logging math mmap multiprocessing nntplib os pdb pickle pydoc re sched select shlex shutil signal smtpd smtplib socket socketserver sqlite3 ssl stat struct subprocess sys tarfile tempfile textwrap threading time types unittest urllib webbrowser xml etree ElementTree zlib Optimizations Build and C API Changes Deprecated Unsupported Operating Systems Deprecated Python modules functions and methods Deprecated functions and types of the C API Deprecated features Porting to Python 3 3 Porting Python code Porting C code Building C extensions Command Line Switch Changes ,en
1258,What s New In Python 3 2 PEP 384 Defining a Stable ABI PEP 389 Argparse Command Line Parsing Module PEP 391 Dictionary Based Configuration for Logging PEP 3148 The concurrent futures module PEP 3147 PYC Repository Directories PEP 3149 ABI Version Tagged so Files PEP 3333 Python Web Server Gateway Interface v1 0 1 Other Language Changes New Improved and Deprecated Modules email elementtree functools itertools collections threading datetime and time math abc io reprlib logging csv contextlib decimal and fractions ftp popen select gzip and zipfile tarfile hashlib ast os shutil sqlite3 html socket ssl nntp certificates imaplib http client unittest random poplib asyncore tempfile inspect pydoc dis dbm ctypes site sysconfig pdb configparser urllib parse mailbox turtledemo Multi threading Optimizations Unicode Codecs Documentation IDLE Code Repository Build and C API Changes Porting to Python 3 2 What s New In Python 3 1 PEP 372 Ordered Dictionaries PEP 378 Format Specifier for Thousands Separator Other Language Changes New Improved and Deprecated Modules Optimizations IDLE Build and C API Changes Porting to Python 3 1 What s New In Python 3 0 Common Stumbling Blocks Print Is A Function Views And Iterators Instead Of Lists Ordering Comparisons Integers Text Vs Data Instead Of Unicode Vs 8 bit Overview Of Syntax Changes New Syntax Changed Syntax Removed Syntax Changes Already Present In Python 2 6 Library Changes PEP 3101 A New Approach To String Formatting Changes To Exceptions Miscellaneous Other Changes Operators And Special Methods Builtins Build and C API Changes Performance Porting To Python 3 0 What s New in Python 2 7 The Future for Python 2 x Changes to the Handling of Deprecation Warnings Python 3 1 Features PEP 372 Adding an Ordered Dictionary to collections PEP 378 Format Specifier for Thousands Separator PEP 389 The argparse Module for Parsing Command Lines PEP 391 Dictionary Based Configuration For Logging PEP 3106 Dictionary Views PEP 3137 The memoryview Object Other Language Changes Interpreter Changes Optimizations New and Improved Modules New module importlib New module sysconfig ttk Themed Widgets for Tk Updated module unittest Updated module ElementTree 1 3 Build and C API Changes Capsules Port Specific Changes Windows Port Specific Changes Mac OS X Port Specific Changes FreeBSD Other Changes and Fixes Porting to Python 2 7 New Features Added to Python 2 7 Maintenance Releases Two new environment variables for debug mode PEP 434 IDLE Enhancement Exception for All Branches PEP 466 Network Security Enhancements for Python 2 7 PEP 477 Backport ensurepip PEP 453 to Python 2 7 Bootstrapping pip By Default Documentation Changes PEP 476 Enabling certificate verification by default for stdlib http clients PEP 493 HTTPS verification migration tools for Python 2 7 New make regen all build target Removal of make touch build target Acknowledgements What s New in Python 2 6 Python 3 0 Changes to the Development Process New Issue Tracker Roundup New Documentation Format reStructuredText Using Sphinx PEP 343 The with statement Writing Context Managers The contextlib module PEP 366 Explicit Relative Imports From a Main Module PEP 370 Per user site packages Directory PEP 371 The multiprocessing Package PEP 3101 Advanced String Formatting PEP 3105 print As a Function PEP 3110 Exception Handling Changes PEP 3112 Byte Literals PEP 3116 New I O Library PEP 3118 Revised Buffer Protocol PEP 3119 Abstract Base Classes PEP 3127 Integer Literal Support and Syntax PEP 3129 Class Decorators PEP 3141 A Type Hierarchy for Numbers The fractions Module Other Language Changes Optimizations Interpreter Changes New and Improved Modules The ast module The future_builtins module The json module JavaScript Object Notation The plistlib module A Property List Parser ctypes Enhancements Improved SSL Support Deprecations and Removals Build and C API Changes Port Specific Changes Windows Port Specific Changes Mac OS X Port Specific Changes IRIX Porting to Python 2 6 Acknowledgements What s New in Python 2 5 PEP 308 Conditional Expressions PEP 309 Part,en
1259,ial Function Application PEP 314 Metadata for Python Software Packages v1 1 PEP 328 Absolute and Relative Imports PEP 338 Executing Modules as Scripts PEP 341 Unified try except finally PEP 342 New Generator Features PEP 343 The with statement Writing Context Managers The contextlib module PEP 352 Exceptions as New Style Classes PEP 353 Using ssize_t as the index type PEP 357 The __index__ method Other Language Changes Interactive Interpreter Changes Optimizations New Improved and Removed Modules The ctypes package The ElementTree package The hashlib package The sqlite3 package The wsgiref package Build and C API Changes Port Specific Changes Porting to Python 2 5 Acknowledgements What s New in Python 2 4 PEP 218 Built In Set Objects PEP 237 Unifying Long Integers and Integers PEP 289 Generator Expressions PEP 292 Simpler String Substitutions PEP 318 Decorators for Functions and Methods PEP 322 Reverse Iteration PEP 324 New subprocess Module PEP 327 Decimal Data Type Why is Decimal needed The Decimal type The Context type PEP 328 Multi line Imports PEP 331 Locale Independent Float String Conversions Other Language Changes Optimizations New Improved and Deprecated Modules cookielib doctest Build and C API Changes Port Specific Changes Porting to Python 2 4 Acknowledgements What s New in Python 2 3 PEP 218 A Standard Set Datatype PEP 255 Simple Generators PEP 263 Source Code Encodings PEP 273 Importing Modules from ZIP Archives PEP 277 Unicode file name support for Windows NT PEP 278 Universal Newline Support PEP 279 enumerate PEP 282 The logging Package PEP 285 A Boolean Type PEP 293 Codec Error Handling Callbacks PEP 301 Package Index and Metadata for Distutils PEP 302 New Import Hooks PEP 305 Comma separated Files PEP 307 Pickle Enhancements Extended Slices Other Language Changes String Changes Optimizations New Improved and Deprecated Modules Date Time Type The optparse Module Pymalloc A Specialized Object Allocator Build and C API Changes Port Specific Changes Other Changes and Fixes Porting to Python 2 3 Acknowledgements What s New in Python 2 2 Introduction PEPs 252 and 253 Type and Class Changes Old and New Classes Descriptors Multiple Inheritance The Diamond Rule Attribute Access Related Links PEP 234 Iterators PEP 255 Simple Generators PEP 237 Unifying Long Integers and Integers PEP 238 Changing the Division Operator Unicode Changes PEP 227 Nested Scopes New and Improved Modules Interpreter Changes and Fixes Other Changes and Fixes Acknowledgements What s New in Python 2 1 Introduction PEP 227 Nested Scopes PEP 236 __future__ Directives PEP 207 Rich Comparisons PEP 230 Warning Framework PEP 229 New Build System PEP 205 Weak References PEP 232 Function Attributes PEP 235 Importing Modules on Case Insensitive Platforms PEP 217 Interactive Display Hook PEP 208 New Coercion Model PEP 241 Metadata in Python Packages New and Improved Modules Other Changes and Fixes Acknowledgements What s New in Python 2 0 Introduction What About Python 1 6 New Development Process Unicode List Comprehensions Augmented Assignment String Methods Garbage Collection of Cycles Other Core Changes Minor Language Changes Changes to Built in Functions Porting to 2 0 Extending Embedding Changes Distutils Making Modules Easy to Install XML Modules SAX2 Support DOM Support Relationship to PyXML Module changes New modules IDLE Improvements Deleted and Deprecated Modules Acknowledgements Changelog Python next Security Core and Builtins Library Documentation Tests Build Windows IDLE Tools Demos Python 3 12 2 final Security Core and Builtins Library Documentation Tests Build Windows macOS IDLE Tools Demos Python 3 12 1 final Core and Builtins Library Documentation Tests Build Windows macOS IDLE C API Python 3 12 0 final Core and Builtins Library Documentation Windows macOS Tools Demos Python 3 12 0 release candidate 3 Core and Builtins Library Documentation Tests Build Python 3 12 0 release candidate 2 Security Core and Builtins Library Documentation Tests Build Windows macOS Tools Demos C API Python 3 12 0 release candidate 1 Security Core and Builti,en
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1262,Library IDLE Tests Documentation Tools Demos Python 3 5 0 alpha 4 Core and Builtins Library Build Tests Tools Demos C API Python 3 5 0 alpha 3 Core and Builtins Library Build Tests Tools Demos Python 3 5 0 alpha 2 Core and Builtins Library Build C API Windows Python 3 5 0 alpha 1 Core and Builtins Library IDLE Build C API Documentation Tests Tools Demos Windows The Python Tutorial 1 Whetting Your Appetite 2 Using the Python Interpreter 2 1 Invoking the Interpreter 2 1 1 Argument Passing 2 1 2 Interactive Mode 2 2 The Interpreter and Its Environment 2 2 1 Source Code Encoding 3 An Informal Introduction to Python 3 1 Using Python as a Calculator 3 1 1 Numbers 3 1 2 Text 3 1 3 Lists 3 2 First Steps Towards Programming 4 More Control Flow Tools 4 1 if Statements 4 2 for Statements 4 3 The range Function 4 4 break and continue Statements and else Clauses on Loops 4 5 pass Statements 4 6 match Statements 4 7 Defining Functions 4 8 More on Defining Functions 4 8 1 Default Argument Values 4 8 2 Keyword Arguments 4 8 3 Special parameters 4 8 3 1 Positional or Keyword Arguments 4 8 3 2 Positional Only Parameters 4 8 3 3 Keyword Only Arguments 4 8 3 4 Function Examples 4 8 3 5 Recap 4 8 4 Arbitrary Argument Lists 4 8 5 Unpacking Argument Lists 4 8 6 Lambda Expressions 4 8 7 Documentation Strings 4 8 8 Function Annotations 4 9 Intermezzo Coding Style 5 Data Structures 5 1 More on Lists 5 1 1 Using Lists as Stacks 5 1 2 Using Lists as Queues 5 1 3 List Comprehensions 5 1 4 Nested List Comprehensions 5 2 The del statement 5 3 Tuples and Sequences 5 4 Sets 5 5 Dictionaries 5 6 Looping Techniques 5 7 More on Conditions 5 8 Comparing Sequences and Other Types 6 Modules 6 1 More on Modules 6 1 1 Executing modules as scripts 6 1 2 The Module Search Path 6 1 3 Compiled Python files 6 2 Standard Modules 6 3 The dir Function 6 4 Packages 6 4 1 Importing From a Package 6 4 2 Intra package References 6 4 3 Packages in Multiple Directories 7 Input and Output 7 1 Fancier Output Formatting 7 1 1 Formatted String Literals 7 1 2 The String format Method 7 1 3 Manual String Formatting 7 1 4 Old string formatting 7 2 Reading and Writing Files 7 2 1 Methods of File Objects 7 2 2 Saving structured data with json 8 Errors and Exceptions 8 1 Syntax Errors 8 2 Exceptions 8 3 Handling Exceptions 8 4 Raising Exceptions 8 5 Exception Chaining 8 6 User defined Exceptions 8 7 Defining Clean up Actions 8 8 Predefined Clean up Actions 8 9 Raising and Handling Multiple Unrelated Exceptions 8 10 Enriching Exceptions with Notes 9 Classes 9 1 A Word About Names and Objects 9 2 Python Scopes and Namespaces 9 2 1 Scopes and Namespaces Example 9 3 A First Look at Classes 9 3 1 Class Definition Syntax 9 3 2 Class Objects 9 3 3 Instance Objects 9 3 4 Method Objects 9 3 5 Class and Instance Variables 9 4 Random Remarks 9 5 Inheritance 9 5 1 Multiple Inheritance 9 6 Private Variables 9 7 Odds and Ends 9 8 Iterators 9 9 Generators 9 10 Generator Expressions 10 Brief Tour of the Standard Library 10 1 Operating System Interface 10 2 File Wildcards 10 3 Command Line Arguments 10 4 Error Output Redirection and Program Termination 10 5 String Pattern Matching 10 6 Mathematics 10 7 Internet Access 10 8 Dates and Times 10 9 Data Compression 10 10 Performance Measurement 10 11 Quality Control 10 12 Batteries Included 11 Brief Tour of the Standard Library Part II 11 1 Output Formatting 11 2 Templating 11 3 Working with Binary Data Record Layouts 11 4 Multi threading 11 5 Logging 11 6 Weak References 11 7 Tools for Working with Lists 11 8 Decimal Floating Point Arithmetic 12 Virtual Environments and Packages 12 1 Introduction 12 2 Creating Virtual Environments 12 3 Managing Packages with pip 13 What Now 14 Interactive Input Editing and History Substitution 14 1 Tab Completion and History Editing 14 2 Alternatives to the Interactive Interpreter 15 Floating Point Arithmetic Issues and Limitations 15 1 Representation Error 16 Appendix 16 1 Interactive Mode 16 1 1 Error Handling 16 1 2 Executable Python Scripts 16 1 3 The Interactive Startup File 16 1 4 The Customization Modules Python Se,en
1263,tup and Usage 1 Command line and environment 1 1 Command line 1 1 1 Interface options 1 1 2 Generic options 1 1 3 Miscellaneous options 1 1 4 Options you shouldn t use 1 2 Environment variables 1 2 1 Debug mode variables 2 Using Python on Unix platforms 2 1 Getting and installing the latest version of Python 2 1 1 On Linux 2 1 2 On FreeBSD and OpenBSD 2 2 Building Python 2 3 Python related paths and files 2 4 Miscellaneous 2 5 Custom OpenSSL 3 Configure Python 3 1 Build Requirements 3 2 Generated files 3 2 1 configure script 3 3 Configure Options 3 3 1 General Options 3 3 2 WebAssembly Options 3 3 3 Install Options 3 3 4 Performance options 3 3 5 Python Debug Build 3 3 6 Debug options 3 3 7 Linker options 3 3 8 Libraries options 3 3 9 Security Options 3 3 10 macOS Options 3 3 11 Cross Compiling Options 3 4 Python Build System 3 4 1 Main files of the build system 3 4 2 Main build steps 3 4 3 Main Makefile targets 3 4 4 C extensions 3 5 Compiler and linker flags 3 5 1 Preprocessor flags 3 5 2 Compiler flags 3 5 3 Linker flags 4 Using Python on Windows 4 1 The full installer 4 1 1 Installation steps 4 1 2 Removing the MAX_PATH Limitation 4 1 3 Installing Without UI 4 1 4 Installing Without Downloading 4 1 5 Modifying an install 4 2 The Microsoft Store package 4 2 1 Known issues 4 2 1 1 Redirection of local data registry and temporary paths 4 3 The nuget org packages 4 4 The embeddable package 4 4 1 Python Application 4 4 2 Embedding Python 4 5 Alternative bundles 4 6 Configuring Python 4 6 1 Excursus Setting environment variables 4 6 2 Finding the Python executable 4 7 UTF 8 mode 4 8 Python Launcher for Windows 4 8 1 Getting started 4 8 1 1 From the command line 4 8 1 2 Virtual environments 4 8 1 3 From a script 4 8 1 4 From file associations 4 8 2 Shebang Lines 4 8 3 Arguments in shebang lines 4 8 4 Customization 4 8 4 1 Customization via INI files 4 8 4 2 Customizing default Python versions 4 8 5 Diagnostics 4 8 6 Dry Run 4 8 7 Install on demand 4 8 8 Return codes 4 9 Finding modules 4 10 Additional modules 4 10 1 PyWin32 4 10 2 cx_Freeze 4 11 Compiling Python on Windows 4 12 Other Platforms 5 Using Python on a Mac 5 1 Getting and Installing Python 5 1 1 How to run a Python script 5 1 2 Running scripts with a GUI 5 1 3 Configuration 5 2 The IDE 5 3 Installing Additional Python Packages 5 4 GUI Programming 5 5 Distributing Python Applications 5 6 Other Resources 6 Editors and IDEs The Python Language Reference 1 Introduction 1 1 Alternate Implementations 1 2 Notation 2 Lexical analysis 2 1 Line structure 2 1 1 Logical lines 2 1 2 Physical lines 2 1 3 Comments 2 1 4 Encoding declarations 2 1 5 Explicit line joining 2 1 6 Implicit line joining 2 1 7 Blank lines 2 1 8 Indentation 2 1 9 Whitespace between tokens 2 2 Other tokens 2 3 Identifiers and keywords 2 3 1 Keywords 2 3 2 Soft Keywords 2 3 3 Reserved classes of identifiers 2 4 Literals 2 4 1 String and Bytes literals 2 4 1 1 Escape sequences 2 4 2 String literal concatenation 2 4 3 f strings 2 4 4 Numeric literals 2 4 5 Integer literals 2 4 6 Floating point literals 2 4 7 Imaginary literals 2 5 Operators 2 6 Delimiters 3 Data model 3 1 Objects values and types 3 2 The standard type hierarchy 3 2 1 None 3 2 2 NotImplemented 3 2 3 Ellipsis 3 2 4 numbers Number 3 2 4 1 numbers Integral 3 2 4 2 numbers Real float 3 2 4 3 numbers Complex complex 3 2 5 Sequences 3 2 5 1 Immutable sequences 3 2 5 2 Mutable sequences 3 2 6 Set types 3 2 7 Mappings 3 2 7 1 Dictionaries 3 2 8 Callable types 3 2 8 1 User defined functions 3 2 8 1 1 Special read only attributes 3 2 8 1 2 Special writable attributes 3 2 8 2 Instance methods 3 2 8 3 Generator functions 3 2 8 4 Coroutine functions 3 2 8 5 Asynchronous generator functions 3 2 8 6 Built in functions 3 2 8 7 Built in methods 3 2 8 8 Classes 3 2 8 9 Class Instances 3 2 9 Modules 3 2 10 Custom classes 3 2 11 Class instances 3 2 12 I O objects also known as file objects 3 2 13 Internal types 3 2 13 1 Code objects 3 2 13 1 1 Special read only attributes 3 2 13 1 2 Methods on code objects 3 2 13 2 Frame objects 3 2 13 2 1 Special read only att,en
1264,ributes 3 2 13 2 2 Special writable attributes 3 2 13 2 3 Frame object methods 3 2 13 3 Traceback objects 3 2 13 4 Slice objects 3 2 13 5 Static method objects 3 2 13 6 Class method objects 3 3 Special method names 3 3 1 Basic customization 3 3 2 Customizing attribute access 3 3 2 1 Customizing module attribute access 3 3 2 2 Implementing Descriptors 3 3 2 3 Invoking Descriptors 3 3 2 4 __slots__ 3 3 3 Customizing class creation 3 3 3 1 Metaclasses 3 3 3 2 Resolving MRO entries 3 3 3 3 Determining the appropriate metaclass 3 3 3 4 Preparing the class namespace 3 3 3 5 Executing the class body 3 3 3 6 Creating the class object 3 3 3 7 Uses for metaclasses 3 3 4 Customizing instance and subclass checks 3 3 5 Emulating generic types 3 3 5 1 The purpose of __class_getitem__ 3 3 5 2 __class_getitem__ versus __getitem__ 3 3 6 Emulating callable objects 3 3 7 Emulating container types 3 3 8 Emulating numeric types 3 3 9 With Statement Context Managers 3 3 10 Customizing positional arguments in class pattern matching 3 3 11 Emulating buffer types 3 3 12 Special method lookup 3 4 Coroutines 3 4 1 Awaitable Objects 3 4 2 Coroutine Objects 3 4 3 Asynchronous Iterators 3 4 4 Asynchronous Context Managers 4 Execution model 4 1 Structure of a program 4 2 Naming and binding 4 2 1 Binding of names 4 2 2 Resolution of names 4 2 3 Annotation scopes 4 2 4 Lazy evaluation 4 2 5 Builtins and restricted execution 4 2 6 Interaction with dynamic features 4 3 Exceptions 5 The import system 5 1 importlib 5 2 Packages 5 2 1 Regular packages 5 2 2 Namespace packages 5 3 Searching 5 3 1 The module cache 5 3 2 Finders and loaders 5 3 3 Import hooks 5 3 4 The meta path 5 4 Loading 5 4 1 Loaders 5 4 2 Submodules 5 4 3 Module spec 5 4 4 Import related module attributes 5 4 5 module __path__ 5 4 6 Module reprs 5 4 7 Cached bytecode invalidation 5 5 The Path Based Finder 5 5 1 Path entry finders 5 5 2 Path entry finder protocol 5 6 Replacing the standard import system 5 7 Package Relative Imports 5 8 Special considerations for __main__ 5 8 1 __main__ __spec__ 5 9 References 6 Expressions 6 1 Arithmetic conversions 6 2 Atoms 6 2 1 Identifiers Names 6 2 2 Literals 6 2 3 Parenthesized forms 6 2 4 Displays for lists sets and dictionaries 6 2 5 List displays 6 2 6 Set displays 6 2 7 Dictionary displays 6 2 8 Generator expressions 6 2 9 Yield expressions 6 2 9 1 Generator iterator methods 6 2 9 2 Examples 6 2 9 3 Asynchronous generator functions 6 2 9 4 Asynchronous generator iterator methods 6 3 Primaries 6 3 1 Attribute references 6 3 2 Subscriptions 6 3 3 Slicings 6 3 4 Calls 6 4 Await expression 6 5 The power operator 6 6 Unary arithmetic and bitwise operations 6 7 Binary arithmetic operations 6 8 Shifting operations 6 9 Binary bitwise operations 6 10 Comparisons 6 10 1 Value comparisons 6 10 2 Membership test operations 6 10 3 Identity comparisons 6 11 Boolean operations 6 12 Assignment expressions 6 13 Conditional expressions 6 14 Lambdas 6 15 Expression lists 6 16 Evaluation order 6 17 Operator precedence 7 Simple statements 7 1 Expression statements 7 2 Assignment statements 7 2 1 Augmented assignment statements 7 2 2 Annotated assignment statements 7 3 The assert statement 7 4 The pass statement 7 5 The del statement 7 6 The return statement 7 7 The yield statement 7 8 The raise statement 7 9 The break statement 7 10 The continue statement 7 11 The import statement 7 11 1 Future statements 7 12 The global statement 7 13 The nonlocal statement 7 14 The type statement 8 Compound statements 8 1 The if statement 8 2 The while statement 8 3 The for statement 8 4 The try statement 8 4 1 except clause 8 4 2 except clause 8 4 3 else clause 8 4 4 finally clause 8 5 The with statement 8 6 The match statement 8 6 1 Overview 8 6 2 Guards 8 6 3 Irrefutable Case Blocks 8 6 4 Patterns 8 6 4 1 OR Patterns 8 6 4 2 AS Patterns 8 6 4 3 Literal Patterns 8 6 4 4 Capture Patterns 8 6 4 5 Wildcard Patterns 8 6 4 6 Value Patterns 8 6 4 7 Group Patterns 8 6 4 8 Sequence Patterns 8 6 4 9 Mapping Patterns 8 6 4 10 Class Patterns 8 7 Function definitions 8 8 Class definitions 8 9,en
1265, Coroutines 8 9 1 Coroutine function definition 8 9 2 The async for statement 8 9 3 The async with statement 8 10 Type parameter lists 8 10 1 Generic functions 8 10 2 Generic classes 8 10 3 Generic type aliases 9 Top level components 9 1 Complete Python programs 9 2 File input 9 3 Interactive input 9 4 Expression input 10 Full Grammar specification The Python Standard Library Introduction Notes on availability WebAssembly platforms Built in Functions Built in Constants Constants added by the site module Built in Types Truth Value Testing Boolean Operations and or not Comparisons Numeric Types int float complex Bitwise Operations on Integer Types Additional Methods on Integer Types Additional Methods on Float Hashing of numeric types Boolean Type bool Iterator Types Generator Types Sequence Types list tuple range Common Sequence Operations Immutable Sequence Types Mutable Sequence Types Lists Tuples Ranges Text Sequence Type str String Methods printf style String Formatting Binary Sequence Types bytes bytearray memoryview Bytes Objects Bytearray Objects Bytes and Bytearray Operations printf style Bytes Formatting Memory Views Set Types set frozenset Mapping Types dict Dictionary view objects Context Manager Types Type Annotation Types Generic Alias Union Generic Alias Type Standard Generic Classes Special Attributes of GenericAlias objects Union Type Other Built in Types Modules Classes and Class Instances Functions Methods Code Objects Type Objects The Null Object The Ellipsis Object The NotImplemented Object Internal Objects Special Attributes Integer string conversion length limitation Affected APIs Configuring the limit Recommended configuration Built in Exceptions Exception context Inheriting from built in exceptions Base classes Concrete exceptions OS exceptions Warnings Exception groups Exception hierarchy Text Processing Services string Common string operations String constants Custom String Formatting Format String Syntax Format Specification Mini Language Format examples Template strings Helper functions re Regular expression operations Regular Expression Syntax Module Contents Flags Functions Exceptions Regular Expression Objects Match Objects Regular Expression Examples Checking for a Pair Simulating scanf search vs match Making a Phonebook Text Munging Finding all Adverbs Finding all Adverbs and their Positions Raw String Notation Writing a Tokenizer difflib Helpers for computing deltas SequenceMatcher Objects SequenceMatcher Examples Differ Objects Differ Example A command line interface to difflib ndiff example textwrap Text wrapping and filling unicodedata Unicode Database stringprep Internet String Preparation readline GNU readline interface Init file Line buffer History file History list Startup hooks Completion Example rlcompleter Completion function for GNU readline Binary Data Services struct Interpret bytes as packed binary data Functions and Exceptions Format Strings Byte Order Size and Alignment Format Characters Examples Applications Native Formats Standard Formats Classes codecs Codec registry and base classes Codec Base Classes Error Handlers Stateless Encoding and Decoding Incremental Encoding and Decoding IncrementalEncoder Objects IncrementalDecoder Objects Stream Encoding and Decoding StreamWriter Objects StreamReader Objects StreamReaderWriter Objects StreamRecoder Objects Encodings and Unicode Standard Encodings Python Specific Encodings Text Encodings Binary Transforms Text Transforms encodings idna Internationalized Domain Names in Applications encodings mbcs Windows ANSI codepage encodings utf_8_sig UTF 8 codec with BOM signature Data Types datetime Basic date and time types Aware and Naive Objects Constants Available Types Common Properties Determining if an Object is Aware or Naive timedelta Objects Examples of usage timedelta date Objects Examples of Usage date datetime Objects Examples of Usage datetime time Objects Examples of Usage time tzinfo Objects timezone Objects strftime and strptime Behavior strftime and strptime Format Codes Technical Detail zoneinfo IANA time zone support,en
1266, Using ZoneInfo Data sources Configuring the data sources Compile time configuration Environment configuration Runtime configuration The ZoneInfo class String representations Pickle serialization Functions Globals Exceptions and warnings calendar General calendar related functions Command Line Usage collections Container datatypes ChainMap objects ChainMap Examples and Recipes Counter objects deque objects deque Recipes defaultdict objects defaultdict Examples namedtuple Factory Function for Tuples with Named Fields OrderedDict objects OrderedDict Examples and Recipes UserDict objects UserList objects UserString objects collections abc Abstract Base Classes for Containers Collections Abstract Base Classes Collections Abstract Base Classes Detailed Descriptions Examples and Recipes heapq Heap queue algorithm Basic Examples Priority Queue Implementation Notes Theory bisect Array bisection algorithm Performance Notes Searching Sorted Lists Examples array Efficient arrays of numeric values weakref Weak references Weak Reference Objects Example Finalizer Objects Comparing finalizers with __del__ methods types Dynamic type creation and names for built in types Dynamic Type Creation Standard Interpreter Types Additional Utility Classes and Functions Coroutine Utility Functions copy Shallow and deep copy operations pprint Data pretty printer Functions PrettyPrinter Objects Example reprlib Alternate repr implementation Repr Objects Subclassing Repr Objects enum Support for enumerations Module Contents Data Types Supported __dunder__ names Supported _sunder_ names Utilities and Decorators Notes graphlib Functionality to operate with graph like structures Exceptions Numeric and Mathematical Modules numbers Numeric abstract base classes The numeric tower Notes for type implementors Adding More Numeric ABCs Implementing the arithmetic operations math Mathematical functions Number theoretic and representation functions Power and logarithmic functions Trigonometric functions Angular conversion Hyperbolic functions Special functions Constants cmath Mathematical functions for complex numbers Conversions to and from polar coordinates Power and logarithmic functions Trigonometric functions Hyperbolic functions Classification functions Constants decimal Decimal fixed point and floating point arithmetic Quick start Tutorial Decimal objects Logical operands Context objects Constants Rounding modes Signals Floating Point Notes Mitigating round off error with increased precision Special values Working with threads Recipes Decimal FAQ fractions Rational numbers random Generate pseudo random numbers Bookkeeping functions Functions for bytes Functions for integers Functions for sequences Discrete distributions Real valued distributions Alternative Generator Notes on Reproducibility Examples Recipes statistics Mathematical statistics functions Averages and measures of central location Measures of spread Statistics for relations between two inputs Function details Exceptions NormalDist objects NormalDist Examples and Recipes Classic probability problems Monte Carlo inputs for simulations Approximating binomial distributions Naive bayesian classifier Kernel density estimation Functional Programming Modules itertools Functions creating iterators for efficient looping Itertool Functions Itertools Recipes functools Higher order functions and operations on callable objects partial Objects operator Standard operators as functions Mapping Operators to Functions In place Operators File and Directory Access pathlib Object oriented filesystem paths Basic use Pure paths General properties Operators Accessing individual parts Methods and properties Concrete paths Methods Correspondence to tools in the os module os path Common pathname manipulations fileinput Iterate over lines from multiple input streams stat Interpreting stat results filecmp File and Directory Comparisons The dircmp class tempfile Generate temporary files and directories Examples Deprecated functions and variables glob Unix style pathname pattern expansion fnmatch Unix filename pattern matchin,en
1267,g linecache Random access to text lines shutil High level file operations Directory and files operations Platform dependent efficient copy operations copytree example rmtree example Archiving operations Archiving example Archiving example with base_dir Querying the size of the output terminal Data Persistence pickle Python object serialization Relationship to other Python modules Comparison with marshal Comparison with json Data stream format Module Interface What can be pickled and unpickled Pickling Class Instances Persistence of External Objects Dispatch Tables Handling Stateful Objects Custom Reduction for Types Functions and Other Objects Out of band Buffers Provider API Consumer API Example Restricting Globals Performance Examples copyreg Register pickle support functions Example shelve Python object persistence Restrictions Example marshal Internal Python object serialization dbm Interfaces to Unix databases dbm gnu GNU database manager dbm ndbm New Database Manager dbm dumb Portable DBM implementation sqlite3 DB API 2 0 interface for SQLite databases Tutorial Reference Module functions Module constants Connection objects Cursor objects Row objects Blob objects PrepareProtocol objects Exceptions SQLite and Python types Default adapters and converters deprecated Command line interface How to guides How to use placeholders to bind values in SQL queries How to adapt custom Python types to SQLite values How to write adaptable objects How to register adapter callables How to convert SQLite values to custom Python types Adapter and converter recipes How to use connection shortcut methods How to use the connection context manager How to work with SQLite URIs How to create and use row factories How to handle non UTF 8 text encodings Explanation Transaction control Transaction control via the autocommit attribute Transaction control via the isolation_level attribute Data Compression and Archiving zlib Compression compatible with gzip gzip Support for gzip files Examples of usage Command Line Interface Command line options bz2 Support for bzip2 compression De compression of files Incremental de compression One shot de compression Examples of usage lzma Compression using the LZMA algorithm Reading and writing compressed files Compressing and decompressing data in memory Miscellaneous Specifying custom filter chains Examples zipfile Work with ZIP archives ZipFile Objects Path Objects PyZipFile Objects ZipInfo Objects Command Line Interface Command line options Decompression pitfalls From file itself File System limitations Resources limitations Interruption Default behaviors of extraction tarfile Read and write tar archive files TarFile Objects TarInfo Objects Extraction filters Default named filters Filter errors Hints for further verification Supporting older Python versions Stateful extraction filter example Command Line Interface Command line options Examples Supported tar formats Unicode issues File Formats csv CSV File Reading and Writing Module Contents Dialects and Formatting Parameters Reader Objects Writer Objects Examples configparser Configuration file parser Quick Start Supported Datatypes Fallback Values Supported INI File Structure Interpolation of values Mapping Protocol Access Customizing Parser Behaviour Legacy API Examples ConfigParser Objects RawConfigParser Objects Exceptions tomllib Parse TOML files Examples Conversion Table netrc netrc file processing netrc Objects plistlib Generate and parse Apple plist files Examples Cryptographic Services hashlib Secure hashes and message digests Hash algorithms Usage Constructors Attributes Hash Objects SHAKE variable length digests File hashing Key derivation BLAKE2 Creating hash objects Constants Examples Simple hashing Using different digest sizes Keyed hashing Randomized hashing Personalization Tree mode Credits hmac Keyed Hashing for Message Authentication secrets Generate secure random numbers for managing secrets Random numbers Generating tokens How many bytes should tokens use Other functions Recipes and best practices Generic Operating System Services os Mi,en
1268,scellaneous operating system interfaces File Names Command Line Arguments and Environment Variables Python UTF 8 Mode Process Parameters File Object Creation File Descriptor Operations Querying the size of a terminal Inheritance of File Descriptors Files and Directories Linux extended attributes Process Management Interface to the scheduler Miscellaneous System Information Random numbers io Core tools for working with streams Overview Text I O Binary I O Raw I O Text Encoding Opt in EncodingWarning High level Module Interface Class hierarchy I O Base Classes Raw File I O Buffered Streams Text I O Performance Binary I O Text I O Multi threading Reentrancy time Time access and conversions Functions Clock ID Constants Timezone Constants argparse Parser for command line options arguments and sub commands Core Functionality Quick Links for add_argument Example Creating a parser Adding arguments Parsing arguments ArgumentParser objects prog usage description epilog parents formatter_class prefix_chars fromfile_prefix_chars argument_default allow_abbrev conflict_handler add_help exit_on_error The add_argument method name or flags action nargs const default type choices required help metavar dest Action classes The parse_args method Option value syntax Invalid arguments Arguments containing Argument abbreviations prefix matching Beyond sys argv The Namespace object Other utilities Sub commands FileType objects Argument groups Mutual exclusion Parser defaults Printing help Partial parsing Customizing file parsing Exiting methods Intermixed parsing Upgrading optparse code Exceptions getopt C style parser for command line options logging Logging facility for Python Logger Objects Logging Levels Handler Objects Formatter Objects Filter Objects LogRecord Objects LogRecord attributes LoggerAdapter Objects Thread Safety Module Level Functions Module Level Attributes Integration with the warnings module logging config Logging configuration Configuration functions Security considerations Configuration dictionary schema Dictionary Schema Details Incremental Configuration Object connections User defined objects Handler configuration order Access to external objects Access to internal objects Import resolution and custom importers Configuring QueueHandler and QueueListener Configuration file format logging handlers Logging handlers StreamHandler FileHandler NullHandler WatchedFileHandler BaseRotatingHandler RotatingFileHandler TimedRotatingFileHandler SocketHandler DatagramHandler SysLogHandler NTEventLogHandler SMTPHandler MemoryHandler HTTPHandler QueueHandler QueueListener getpass Portable password input curses Terminal handling for character cell displays Functions Window Objects Constants curses textpad Text input widget for curses programs Textbox objects curses ascii Utilities for ASCII characters curses panel A panel stack extension for curses Functions Panel Objects platform Access to underlying platform s identifying data Cross Platform Java Platform Windows Platform macOS Platform Unix Platforms Linux Platforms errno Standard errno system symbols ctypes A foreign function library for Python ctypes tutorial Loading dynamic link libraries Accessing functions from loaded dlls Calling functions Fundamental data types Calling functions continued Calling variadic functions Calling functions with your own custom data types Specifying the required argument types function prototypes Return types Passing pointers or passing parameters by reference Structures and unions Structure union alignment and byte order Bit fields in structures and unions Arrays Pointers Type conversions Incomplete Types Callback functions Accessing values exported from dlls Surprises Variable sized data types ctypes reference Finding shared libraries Loading shared libraries Foreign functions Function prototypes Utility functions Data types Fundamental data types Structured data types Arrays and pointers Concurrent Execution threading Thread based parallelism Thread Local Data Thread Objects Lock Objects RLock Objects Condition Objects Semaphore Objects Semaphore Ex,en
1269,ample Event Objects Timer Objects Barrier Objects Using locks conditions and semaphores in the with statement multiprocessing Process based parallelism Introduction The Process class Contexts and start methods Exchanging objects between processes Synchronization between processes Sharing state between processes Using a pool of workers Reference Process and exceptions Pipes and Queues Miscellaneous Connection Objects Synchronization primitives Shared ctypes Objects The multiprocessing sharedctypes module Managers Customized managers Using a remote manager Proxy Objects Cleanup Process Pools Listeners and Clients Address Formats Authentication keys Logging The multiprocessing dummy module Programming guidelines All start methods The spawn and forkserver start methods Examples multiprocessing shared_memory Shared memory for direct access across processes The concurrent package concurrent futures Launching parallel tasks Executor Objects ThreadPoolExecutor ThreadPoolExecutor Example ProcessPoolExecutor ProcessPoolExecutor Example Future Objects Module Functions Exception classes subprocess Subprocess management Using the subprocess Module Frequently Used Arguments Popen Constructor Exceptions Security Considerations Popen Objects Windows Popen Helpers Windows Constants Older high level API Replacing Older Functions with the subprocess Module Replacing bin sh shell command substitution Replacing shell pipeline Replacing os system Replacing the os spawn family Replacing os popen os popen2 os popen3 Replacing functions from the popen2 module Legacy Shell Invocation Functions Notes Converting an argument sequence to a string on Windows Disabling use of vfork or posix_spawn sched Event scheduler Scheduler Objects queue A synchronized queue class Queue Objects SimpleQueue Objects contextvars Context Variables Context Variables Manual Context Management asyncio support _thread Low level threading API Networking and Interprocess Communication asyncio Asynchronous I O Runners Running an asyncio Program Runner context manager Handling Keyboard Interruption Coroutines and Tasks Coroutines Awaitables Creating Tasks Task Cancellation Task Groups Sleeping Running Tasks Concurrently Eager Task Factory Shielding From Cancellation Timeouts Waiting Primitives Running in Threads Scheduling From Other Threads Introspection Task Object Streams StreamReader StreamWriter Examples TCP echo client using streams TCP echo server using streams Get HTTP headers Register an open socket to wait for data using streams Synchronization Primitives Lock Event Condition Semaphore BoundedSemaphore Barrier Subprocesses Creating Subprocesses Constants Interacting with Subprocesses Subprocess and Threads Examples Queues Queue Priority Queue LIFO Queue Exceptions Examples Exceptions Event Loop Event Loop Methods Running and stopping the loop Scheduling callbacks Scheduling delayed callbacks Creating Futures and Tasks Opening network connections Creating network servers Transferring files TLS Upgrade Watching file descriptors Working with socket objects directly DNS Working with pipes Unix signals Executing code in thread or process pools Error Handling API Enabling debug mode Running Subprocesses Callback Handles Server Objects Event Loop Implementations Examples Hello World with call_soon Display the current date with call_later Watch a file descriptor for read events Set signal handlers for SIGINT and SIGTERM Futures Future Functions Future Object Transports and Protocols Transports Transports Hierarchy Base Transport Read only Transports Write only Transports Datagram Transports Subprocess Transports Protocols Base Protocols Base Protocol Streaming Protocols Buffered Streaming Protocols Datagram Protocols Subprocess Protocols Examples TCP Echo Server TCP Echo Client UDP Echo Server UDP Echo Client Connecting Existing Sockets loop subprocess_exec and SubprocessProtocol Policies Getting and Setting the Policy Policy Objects Process Watchers Custom Policies Platform Support All Platforms Windows Subprocess Support on Windows macOS Extending Writing a Custom Event Lo,en
1270,op Future and Task private constructors Task lifetime support High level API Index Tasks Queues Subprocesses Streams Synchronization Exceptions Low level API Index Obtaining the Event Loop Event Loop Methods Transports Protocols Event Loop Policies Developing with asyncio Debug Mode Concurrency and Multithreading Running Blocking Code Logging Detect never awaited coroutines Detect never retrieved exceptions socket Low level networking interface Socket families Module contents Exceptions Constants Functions Creating sockets Other functions Socket Objects Notes on socket timeouts Timeouts and the connect method Timeouts and the accept method Example ssl TLS SSL wrapper for socket objects Functions Constants and Exceptions Socket creation Context creation Exceptions Random generation Certificate handling Constants SSL Sockets SSL Contexts Certificates Certificate chains CA certificates Combined key and certificate Self signed certificates Examples Testing for SSL support Client side operation Server side operation Notes on non blocking sockets Memory BIO Support SSL session Security considerations Best defaults Manual settings Verifying certificates Protocol versions Cipher selection Multi processing TLS 1 3 select Waiting for I O completion dev poll Polling Objects Edge and Level Trigger Polling epoll Objects Polling Objects Kqueue Objects Kevent Objects selectors High level I O multiplexing Introduction Classes Examples signal Set handlers for asynchronous events General rules Execution of Python signal handlers Signals and threads Module contents Examples Note on SIGPIPE Note on Signal Handlers and Exceptions mmap Memory mapped file support MADV_ Constants MAP_ Constants Internet Data Handling email An email and MIME handling package email message Representing an email message email parser Parsing email messages FeedParser API Parser API Additional notes email generator Generating MIME documents email policy Policy Objects email errors Exception and Defect classes email headerregistry Custom Header Objects email contentmanager Managing MIME Content Content Manager Instances email Examples email message Message Representing an email message using the compat32 API email mime Creating email and MIME objects from scratch email header Internationalized headers email charset Representing character sets email encoders Encoders email utils Miscellaneous utilities email iterators Iterators json JSON encoder and decoder Basic Usage Encoders and Decoders Exceptions Standard Compliance and Interoperability Character Encodings Infinite and NaN Number Values Repeated Names Within an Object Top level Non Object Non Array Values Implementation Limitations Command Line Interface Command line options mailbox Manipulate mailboxes in various formats Mailbox objects Maildir objects mbox objects MH objects Babyl objects MMDF objects Message objects MaildirMessage objects mboxMessage objects MHMessage objects BabylMessage objects MMDFMessage objects Exceptions Examples mimetypes Map filenames to MIME types MimeTypes Objects base64 Base16 Base32 Base64 Base85 Data Encodings Security Considerations binascii Convert between binary and ASCII quopri Encode and decode MIME quoted printable data Structured Markup Processing Tools html HyperText Markup Language support html parser Simple HTML and XHTML parser Example HTML Parser Application HTMLParser Methods Examples html entities Definitions of HTML general entities XML Processing Modules XML vulnerabilities The defusedxml Package xml etree ElementTree The ElementTree XML API Tutorial XML tree and elements Parsing XML Pull API for non blocking parsing Finding interesting elements Modifying an XML File Building XML documents Parsing XML with Namespaces XPath support Example Supported XPath syntax Reference Functions XInclude support Example Reference Functions Element Objects ElementTree Objects QName Objects TreeBuilder Objects XMLParser Objects XMLPullParser Objects Exceptions xml dom The Document Object Model API Module Contents Objects in the DOM DOMImplementation Objects Node Objects NodeList Ob,en
1271,jects DocumentType Objects Document Objects Element Objects Attr Objects NamedNodeMap Objects Comment Objects Text and CDATASection Objects ProcessingInstruction Objects Exceptions Conformance Type Mapping Accessor Methods xml dom minidom Minimal DOM implementation DOM Objects DOM Example minidom and the DOM standard xml dom pulldom Support for building partial DOM trees DOMEventStream Objects xml sax Support for SAX2 parsers SAXException Objects xml sax handler Base classes for SAX handlers ContentHandler Objects DTDHandler Objects EntityResolver Objects ErrorHandler Objects LexicalHandler Objects xml sax saxutils SAX Utilities xml sax xmlreader Interface for XML parsers XMLReader Objects IncrementalParser Objects Locator Objects InputSource Objects The Attributes Interface The AttributesNS Interface xml parsers expat Fast XML parsing using Expat XMLParser Objects ExpatError Exceptions Example Content Model Descriptions Expat error constants Internet Protocols and Support webbrowser Convenient web browser controller Browser Controller Objects wsgiref WSGI Utilities and Reference Implementation wsgiref util WSGI environment utilities wsgiref headers WSGI response header tools wsgiref simple_server a simple WSGI HTTP server wsgiref validate WSGI conformance checker wsgiref handlers server gateway base classes wsgiref types WSGI types for static type checking Examples urllib URL handling modules urllib request Extensible library for opening URLs Request Objects OpenerDirector Objects BaseHandler Objects HTTPRedirectHandler Objects HTTPCookieProcessor Objects ProxyHandler Objects HTTPPasswordMgr Objects HTTPPasswordMgrWithPriorAuth Objects AbstractBasicAuthHandler Objects HTTPBasicAuthHandler Objects ProxyBasicAuthHandler Objects AbstractDigestAuthHandler Objects HTTPDigestAuthHandler Objects ProxyDigestAuthHandler Objects HTTPHandler Objects HTTPSHandler Objects FileHandler Objects DataHandler Objects FTPHandler Objects CacheFTPHandler Objects UnknownHandler Objects HTTPErrorProcessor Objects Examples Legacy interface urllib request Restrictions urllib response Response classes used by urllib urllib parse Parse URLs into components URL Parsing URL parsing security Parsing ASCII Encoded Bytes Structured Parse Results URL Quoting urllib error Exception classes raised by urllib request urllib robotparser Parser for robots txt http HTTP modules HTTP status codes HTTP status category HTTP methods http client HTTP protocol client HTTPConnection Objects HTTPResponse Objects Examples HTTPMessage Objects ftplib FTP protocol client Reference FTP objects FTP_TLS objects Module variables poplib POP3 protocol client POP3 Objects POP3 Example imaplib IMAP4 protocol client IMAP4 Objects IMAP4 Example smtplib SMTP protocol client SMTP Objects SMTP Example uuid UUID objects according to RFC 4122 Command Line Usage Example Command Line Example socketserver A framework for network servers Server Creation Notes Server Objects Request Handler Objects Examples socketserver TCPServer Example socketserver UDPServer Example Asynchronous Mixins http server HTTP servers Security Considerations http cookies HTTP state management Cookie Objects Morsel Objects Example http cookiejar Cookie handling for HTTP clients CookieJar and FileCookieJar Objects FileCookieJar subclasses and co operation with web browsers CookiePolicy Objects DefaultCookiePolicy Objects Cookie Objects Examples xmlrpc XMLRPC server and client modules xmlrpc client XML RPC client access ServerProxy Objects DateTime Objects Binary Objects Fault Objects ProtocolError Objects MultiCall Objects Convenience Functions Example of Client Usage Example of Client and Server Usage xmlrpc server Basic XML RPC servers SimpleXMLRPCServer Objects SimpleXMLRPCServer Example CGIXMLRPCRequestHandler Documenting XMLRPC server DocXMLRPCServer Objects DocCGIXMLRPCRequestHandler ipaddress IPv4 IPv6 manipulation library Convenience factory functions IP Addresses Address objects Conversion to Strings and Integers Operators Comparison operators Arithmetic operators IP Network definitions Prefix net mask and ,en
1272,host mask Network objects Operators Logical operators Iteration Networks as containers of addresses Interface objects Operators Logical operators Other Module Level Functions Custom Exceptions Multimedia Services wave Read and write WAV files Wave_read Objects Wave_write Objects colorsys Conversions between color systems Internationalization gettext Multilingual internationalization services GNU gettext API Class based API The NullTranslations class The GNUTranslations class Solaris message catalog support The Catalog constructor Internationalizing your programs and modules Localizing your module Localizing your application Changing languages on the fly Deferred translations Acknowledgements locale Internationalization services Background details hints tips and caveats For extension writers and programs that embed Python Access to message catalogs Program Frameworks turtle Turtle graphics Introduction Tutorial Starting a turtle environment Basic drawing Pen control The turtle s position Making algorithmic patterns How to Get started as quickly as possible Use the turtle module namespace Use turtle graphics in a script Use object oriented turtle graphics Turtle graphics reference Turtle methods Methods of TurtleScreen Screen Methods of RawTurtle Turtle and corresponding functions Turtle motion Tell Turtle s state Settings for measurement Pen control Drawing state Color control Filling More drawing control Turtle state Visibility Appearance Using events Special Turtle methods Compound shapes Methods of TurtleScreen Screen and corresponding functions Window control Animation control Using screen events Input methods Settings and special methods Methods specific to Screen not inherited from TurtleScreen Public classes Explanation Help and configuration How to use help Translation of docstrings into different languages How to configure Screen and Turtles turtledemo Demo scripts Changes since Python 2 6 Changes since Python 3 0 cmd Support for line oriented command interpreters Cmd Objects Cmd Example shlex Simple lexical analysis shlex Objects Parsing Rules Improved Compatibility with Shells Graphical User Interfaces with Tk tkinter Python interface to Tcl Tk Architecture Tkinter Modules Tkinter Life Preserver A Hello World Program Important Tk Concepts Understanding How Tkinter Wraps Tcl Tk How do I What option does Navigating the Tcl Tk Reference Manual Threading model Handy Reference Setting Options The Packer Packer Options Coupling Widget Variables The Window Manager Tk Option Data Types Bindings and Events The index Parameter Images File Handlers tkinter colorchooser Color choosing dialog tkinter font Tkinter font wrapper Tkinter Dialogs tkinter simpledialog Standard Tkinter input dialogs tkinter filedialog File selection dialogs Native Load Save Dialogs tkinter commondialog Dialog window templates tkinter messagebox Tkinter message prompts tkinter scrolledtext Scrolled Text Widget tkinter dnd Drag and drop support tkinter ttk Tk themed widgets Using Ttk Ttk Widgets Widget Standard Options Scrollable Widget Options Label Options Compatibility Options Widget States ttk Widget Combobox Options Virtual events ttk Combobox Spinbox Options Virtual events ttk Spinbox Notebook Options Tab Options Tab Identifiers Virtual Events ttk Notebook Progressbar Options ttk Progressbar Separator Options Sizegrip Platform specific notes Bugs Treeview Options Item Options Tag Options Column Identifiers Virtual Events ttk Treeview Ttk Styling Layouts tkinter tix Extension widgets for Tk Using Tix Tix Widgets Basic Widgets File Selectors Hierarchical ListBox Tabular ListBox Manager Widgets Image Types Miscellaneous Widgets Form Geometry Manager Tix Commands IDLE Menus File menu Shell and Editor Edit menu Shell and Editor Format menu Editor window only Run menu Editor window only Shell menu Shell window only Debug menu Shell window only Options menu Shell and Editor Window menu Shell and Editor Help menu Shell and Editor Context menus Editing and Navigation Editor windows Key bindings Automatic indentation Search and Replace Completions Callt,en
1273,ips Code Context Shell window Text colors Startup and Code Execution Command line usage Startup failure Running user code User output in Shell Developing tkinter applications Running without a subprocess Help and Preferences Help sources Setting preferences IDLE on macOS Extensions idlelib Development Tools typing Support for type hints Relevant PEPs Type aliases NewType Annotating callable objects Generics Annotating tuples The type of class objects User defined generic types The Any type Nominal vs structural subtyping Module contents Special typing primitives Special types Special forms Building generic types and type aliases Other special directives Protocols ABCs for working with IO Functions and decorators Introspection helpers Constant Deprecated aliases Aliases to built in types Aliases to types in collections Aliases to other concrete types Aliases to container ABCs in collections abc Aliases to asynchronous ABCs in collections abc Aliases to other ABCs in collections abc Aliases to contextlib ABCs Deprecation Timeline of Major Features pydoc Documentation generator and online help system Python Development Mode Effects of the Python Development Mode ResourceWarning Example Bad file descriptor error example doctest Test interactive Python examples Simple Usage Checking Examples in Docstrings Simple Usage Checking Examples in a Text File How It Works Which Docstrings Are Examined How are Docstring Examples Recognized What s the Execution Context What About Exceptions Option Flags Directives Warnings Basic API Unittest API Advanced API DocTest Objects Example Objects DocTestFinder objects DocTestParser objects DocTestRunner objects OutputChecker objects Debugging Soapbox unittest Unit testing framework Basic example Command Line Interface Command line options Test Discovery Organizing test code Re using old test code Skipping tests and expected failures Distinguishing test iterations using subtests Classes and functions Test cases Grouping tests Loading and running tests load_tests Protocol Class and Module Fixtures setUpClass and tearDownClass setUpModule and tearDownModule Signal Handling unittest mock mock object library Quick Guide The Mock Class Calling Deleting Attributes Mock names and the name attribute Attaching Mocks as Attributes The patchers patch patch object patch dict patch multiple patch methods start and stop patch builtins TEST_PREFIX Nesting Patch Decorators Where to patch Patching Descriptors and Proxy Objects MagicMock and magic method support Mocking Magic Methods Magic Mock Helpers sentinel DEFAULT call create_autospec ANY FILTER_DIR mock_open Autospeccing Sealing mocks unittest mock getting started Using Mock Mock Patching Methods Mock for Method Calls on an Object Mocking Classes Naming your mocks Tracking all Calls Setting Return Values and Attributes Raising exceptions with mocks Side effect functions and iterables Mocking asynchronous iterators Mocking asynchronous context manager Creating a Mock from an Existing Object Using side_effect to return per file content Patch Decorators Further Examples Mocking chained calls Partial mocking Mocking a Generator Method Applying the same patch to every test method Mocking Unbound Methods Checking multiple calls with mock Coping with mutable arguments Nesting Patches Mocking a dictionary with MagicMock Mock subclasses and their attributes Mocking imports with patch dict Tracking order of calls and less verbose call assertions More complex argument matching 2to3 Automated Python 2 to 3 code translation Using 2to3 Fixers lib2to3 2to3 s library test Regression tests package for Python Writing Unit Tests for the test package Running tests using the command line interface test support Utilities for the Python test suite test support socket_helper Utilities for socket tests test support script_helper Utilities for the Python execution tests test support bytecode_helper Support tools for testing correct bytecode generation test support threading_helper Utilities for threading tests test support os_helper Utilities for os tests test support import_helper,en
1274, Utilities for import tests test support warnings_helper Utilities for warnings tests Debugging and Profiling Audit events table bdb Debugger framework faulthandler Dump the Python traceback Dumping the traceback Fault handler state Dumping the tracebacks after a timeout Dumping the traceback on a user signal Issue with file descriptors Example pdb The Python Debugger Debugger Commands The Python Profilers Introduction to the profilers Instant User s Manual profile and cProfile Module Reference The Stats Class What Is Deterministic Profiling Limitations Calibration Using a custom timer timeit Measure execution time of small code snippets Basic Examples Python Interface Command Line Interface Examples trace Trace or track Python statement execution Command Line Usage Main options Modifiers Filters Programmatic Interface tracemalloc Trace memory allocations Examples Display the top 10 Compute differences Get the traceback of a memory block Pretty top Record the current and peak size of all traced memory blocks API Functions DomainFilter Filter Frame Snapshot Statistic StatisticDiff Trace Traceback Software Packaging and Distribution ensurepip Bootstrapping the pip installer Command line interface Module API venv Creation of virtual environments Creating virtual environments How venvs work API An example of extending EnvBuilder zipapp Manage executable Python zip archives Basic Example Command Line Interface Python API Examples Specifying the Interpreter Creating Standalone Applications with zipapp Caveats The Python Zip Application Archive Format Python Runtime Services sys System specific parameters and functions sys monitoring Execution event monitoring Tool identifiers Registering and using tools Events Local events Ancillary events Other events The STOP_ITERATION event Turning events on and off Setting events globally Per code object events Disabling events Registering callback functions Callback function arguments sysconfig Provide access to Python s configuration information Configuration variables Installation paths User scheme posix_user nt_user osx_framework_user Home scheme posix_home Prefix scheme posix_prefix nt Installation path functions Other functions Using sysconfig as a script builtins Built in objects __main__ Top level code environment __name__ __main__ What is the top level code environment Idiomatic Usage Packaging Considerations __main__ py in Python Packages Idiomatic Usage import __main__ warnings Warning control Warning Categories The Warnings Filter Describing Warning Filters Default Warning Filter Overriding the default filter Temporarily Suppressing Warnings Testing Warnings Updating Code For New Versions of Dependencies Available Functions Available Context Managers dataclasses Data Classes Module contents Post init processing Class variables Init only variables Frozen instances Inheritance Re ordering of keyword only parameters in __init__ Default factory functions Mutable default values Descriptor typed fields contextlib Utilities for with statement contexts Utilities Examples and Recipes Supporting a variable number of context managers Catching exceptions from __enter__ methods Cleaning up in an __enter__ implementation Replacing any use of try finally and flag variables Using a context manager as a function decorator Single use reusable and reentrant context managers Reentrant context managers Reusable context managers abc Abstract Base Classes atexit Exit handlers atexit Example traceback Print or retrieve a stack traceback TracebackException Objects StackSummary Objects FrameSummary Objects Traceback Examples __future__ Future statement definitions Module Contents gc Garbage Collector interface inspect Inspect live objects Types and members Retrieving source code Introspecting callables with the Signature object Classes and functions The interpreter stack Fetching attributes statically Current State of Generators Coroutines and Asynchronous Generators Code Objects Bit Flags Buffer flags Command Line Interface site Site specific configuration hook sitecustomize usercustomize Readline conf,en
1275,iguration Module contents Command Line Interface Custom Python Interpreters code Interpreter base classes Interactive Interpreter Objects Interactive Console Objects codeop Compile Python code Importing Modules zipimport Import modules from Zip archives zipimporter Objects Examples pkgutil Package extension utility modulefinder Find modules used by a script Example usage of ModuleFinder runpy Locating and executing Python modules importlib The implementation of import Introduction Functions importlib abc Abstract base classes related to import importlib machinery Importers and path hooks importlib util Utility code for importers Examples Importing programmatically Checking if a module can be imported Importing a source file directly Implementing lazy imports Setting up an importer Approximating importlib import_module importlib resources Package resource reading opening and access Deprecated functions importlib resources abc Abstract base classes for resources importlib metadata Accessing package metadata Overview Functional API Entry points Distribution metadata Distribution versions Distribution files Distribution requirements Mapping import to distribution packages Distributions Distribution Discovery Extending the search algorithm The initialization of the sys path module search path Virtual environments _pth files Embedded Python Python Language Services ast Abstract Syntax Trees Abstract Grammar Node classes Root nodes Literals Variables Expressions Subscripting Comprehensions Statements Imports Control flow Pattern matching Type parameters Function and class definitions Async and await ast Helpers Compiler Flags Command Line Usage symtable Access to the compiler s symbol tables Generating Symbol Tables Examining Symbol Tables token Constants used with Python parse trees keyword Testing for Python keywords tokenize Tokenizer for Python source Tokenizing Input Command Line Usage Examples tabnanny Detection of ambiguous indentation pyclbr Python module browser support Function Objects Class Objects py_compile Compile Python source files Command Line Interface compileall Byte compile Python libraries Command line use Public functions dis Disassembler for Python bytecode Command line interface Bytecode analysis Analysis functions Python Bytecode Instructions Opcode collections pickletools Tools for pickle developers Command line usage Command line options Programmatic Interface MS Windows Specific Services msvcrt Useful routines from the MS VC runtime File Operations Console I O Other Functions winreg Windows registry access Functions Constants HKEY_ Constants Access Rights 64 bit Specific Value Types Registry Handle Objects winsound Sound playing interface for Windows Unix Specific Services posix The most common POSIX system calls Large File Support Notable Module Contents pwd The password database grp The group database termios POSIX style tty control Example tty Terminal control functions pty Pseudo terminal utilities Example fcntl The fcntl and ioctl system calls resource Resource usage information Resource Limits Resource Usage syslog Unix syslog library routines Examples Simple example Modules command line interface CLI Superseded Modules aifc Read and write AIFF and AIFC files audioop Manipulate raw audio data cgi Common Gateway Interface support Introduction Using the cgi module Higher Level Interface Functions Caring about security Installing your CGI script on a Unix system Testing your CGI script Debugging CGI scripts Common problems and solutions cgitb Traceback manager for CGI scripts chunk Read IFF chunked data crypt Function to check Unix passwords Hashing Methods Module Attributes Module Functions Examples imghdr Determine the type of an image mailcap Mailcap file handling msilib Read and write Microsoft Installer files Database Objects View Objects Summary Information Objects Record Objects Errors CAB Objects Directory Objects Features GUI classes Precomputed tables nis Interface to Sun s NIS Yellow Pages nntplib NNTP protocol client NNTP Objects Attributes Methods Utility functions optparse Parser for,en
1276, command line options Background Terminology What are options for What are positional arguments for Tutorial Understanding option actions The store action Handling boolean flag options Other actions Default values Generating help Grouping Options Printing a version string How optparse handles errors Putting it all together Reference Guide Creating the parser Populating the parser Defining options Option attributes Standard option actions Standard option types Parsing arguments Querying and manipulating your option parser Conflicts between options Cleanup Other methods Option Callbacks Defining a callback option How callbacks are called Raising errors in a callback Callback example 1 trivial callback Callback example 2 check option order Callback example 3 check option order generalized Callback example 4 check arbitrary condition Callback example 5 fixed arguments Callback example 6 variable arguments Extending optparse Adding new types Adding new actions Exceptions ossaudiodev Access to OSS compatible audio devices Audio Device Objects Mixer Device Objects pipes Interface to shell pipelines Template Objects sndhdr Determine type of sound file spwd The shadow password database sunau Read and write Sun AU files AU_read Objects AU_write Objects telnetlib Telnet client Telnet Objects Telnet Example uu Encode and decode uuencode files xdrlib Encode and decode XDR data Packer Objects Unpacker Objects Exceptions Security Considerations Extending and Embedding the Python Interpreter Recommended third party tools Creating extensions without third party tools 1 Extending Python with C or C 1 1 A Simple Example 1 2 Intermezzo Errors and Exceptions 1 3 Back to the Example 1 4 The Module s Method Table and Initialization Function 1 5 Compilation and Linkage 1 6 Calling Python Functions from C 1 7 Extracting Parameters in Extension Functions 1 8 Keyword Parameters for Extension Functions 1 9 Building Arbitrary Values 1 10 Reference Counts 1 10 1 Reference Counting in Python 1 10 2 Ownership Rules 1 10 3 Thin Ice 1 10 4 NULL Pointers 1 11 Writing Extensions in C 1 12 Providing a C API for an Extension Module 2 Defining Extension Types Tutorial 2 1 The Basics 2 2 Adding data and methods to the Basic example 2 3 Providing finer control over data attributes 2 4 Supporting cyclic garbage collection 2 5 Subclassing other types 3 Defining Extension Types Assorted Topics 3 1 Finalization and De allocation 3 2 Object Presentation 3 3 Attribute Management 3 3 1 Generic Attribute Management 3 3 2 Type specific Attribute Management 3 4 Object Comparison 3 5 Abstract Protocol Support 3 6 Weak Reference Support 3 7 More Suggestions 4 Building C and C Extensions 4 1 Building C and C Extensions with setuptools 5 Building C and C Extensions on Windows 5 1 A Cookbook Approach 5 2 Differences Between Unix and Windows 5 3 Using DLLs in Practice Embedding the CPython runtime in a larger application 1 Embedding Python in Another Application 1 1 Very High Level Embedding 1 2 Beyond Very High Level Embedding An overview 1 3 Pure Embedding 1 4 Extending Embedded Python 1 5 Embedding Python in C 1 6 Compiling and Linking under Unix like systems Python C API Reference Manual Introduction Coding standards Include Files Useful macros Objects Types and Reference Counts Reference Counts Reference Count Details Types Exceptions Embedding Python Debugging Builds C API Stability Unstable C API Stable Application Binary Interface Limited C API Stable ABI Limited API Scope and Performance Limited API Caveats Platform Considerations Contents of Limited API The Very High Level Layer Reference Counting Exception Handling Printing and clearing Raising exceptions Issuing warnings Querying the error indicator Signal Handling Exception Classes Exception Objects Unicode Exception Objects Recursion Control Standard Exceptions Standard Warning Categories Utilities Operating System Utilities System Functions Process Control Importing Modules Data marshalling support Parsing arguments and building values Parsing arguments Strings and buffers Numbers Other objects API Functions Bui,en
1277,lding values String conversion and formatting PyHash API Reflection Codec registry and support functions Codec lookup API Registry API for Unicode encoding error handlers Support for Perf Maps Abstract Objects Layer Object Protocol Call Protocol The tp_call Protocol The Vectorcall Protocol Recursion Control Vectorcall Support API Object Calling API Call Support API Number Protocol Sequence Protocol Mapping Protocol Iterator Protocol Buffer Protocol Buffer structure Buffer request types request independent fields readonly format shape strides suboffsets contiguity requests compound requests Complex arrays NumPy style shape and strides PIL style shape strides and suboffsets Buffer related functions Old Buffer Protocol Concrete Objects Layer Fundamental Objects Type Objects Creating Heap Allocated Types The None Object Numeric Objects Integer Objects Boolean Objects Floating Point Objects Pack and Unpack functions Pack functions Unpack functions Complex Number Objects Complex Numbers as C Structures Complex Numbers as Python Objects Sequence Objects Bytes Objects Byte Array Objects Type check macros Direct API functions Macros Unicode Objects and Codecs Unicode Objects Unicode Type Unicode Character Properties Creating and accessing Unicode strings Locale Encoding File System Encoding wchar_t Support Built in Codecs Generic Codecs UTF 8 Codecs UTF 32 Codecs UTF 16 Codecs UTF 7 Codecs Unicode Escape Codecs Raw Unicode Escape Codecs Latin 1 Codecs ASCII Codecs Character Map Codecs MBCS codecs for Windows Methods Slots Methods and Slot Functions Tuple Objects Struct Sequence Objects List Objects Container Objects Dictionary Objects Set Objects Function Objects Function Objects Instance Method Objects Method Objects Cell Objects Code Objects Extra information Other Objects File Objects Module Objects Initializing C modules Single phase initialization Multi phase initialization Low level module creation functions Support functions Module lookup Iterator Objects Descriptor Objects Slice Objects Ellipsis Object MemoryView objects Weak Reference Objects Capsules Frame Objects Internal Frames Generator Objects Coroutine Objects Context Variables Objects DateTime Objects Objects for Type Hinting Initialization Finalization and Threads Before Python Initialization Global configuration variables Initializing and finalizing the interpreter Process wide parameters Thread State and the Global Interpreter Lock Releasing the GIL from extension code Non Python created threads Cautions about fork High level API Low level API Sub interpreter support A Per Interpreter GIL Bugs and caveats Asynchronous Notifications Profiling and Tracing Advanced Debugger Support Thread Local Storage Support Thread Specific Storage TSS API Dynamic Allocation Methods Thread Local Storage TLS API Python Initialization Configuration Example PyWideStringList PyStatus PyPreConfig Preinitialize Python with PyPreConfig PyConfig Initialization with PyConfig Isolated Configuration Python Configuration Python Path Configuration Py_RunMain Py_GetArgcArgv Multi Phase Initialization Private Provisional API Memory Management Overview Allocator Domains Raw Memory Interface Memory Interface Object allocators Default Memory Allocators Customize Memory Allocators Debug hooks on the Python memory allocators The pymalloc allocator Customize pymalloc Arena Allocator tracemalloc C API Examples Object Implementation Support Allocating Objects on the Heap Common Object Structures Base object types and macros Implementing functions and methods Accessing attributes of extension types Member flags Member types Defining Getters and Setters Type Objects Quick Reference tp slots sub slots slot typedefs PyTypeObject Definition PyObject Slots PyVarObject Slots PyTypeObject Slots Static Types Heap Types Number Object Structures Mapping Object Structures Sequence Object Structures Buffer Object Structures Async Object Structures Slot Type typedefs Examples Supporting Cyclic Garbage Collection Controlling the Garbage Collector State Querying Garbage Collector State API and ABI Versioning Installi,en
1278,ng Python Modules Key terms Basic usage How do I install pip in versions of Python prior to Python 3 4 install packages just for the current user install scientific Python packages work with multiple versions of Python installed in parallel Common installation issues Installing into the system Python on Linux Pip not installed Installing binary extensions Python HOWTOs Porting Extension Modules to Python 3 Curses Programming with Python What is curses The Python curses module Starting and ending a curses application Windows and Pads Displaying Text Attributes and Color User Input For More Information Descriptor Guide Primer Simple example A descriptor that returns a constant Dynamic lookups Managed attributes Customized names Closing thoughts Complete Practical Example Validator class Custom validators Practical application Technical Tutorial Abstract Definition and introduction Descriptor protocol Overview of descriptor invocation Invocation from an instance Invocation from a class Invocation from super Summary of invocation logic Automatic name notification ORM example Pure Python Equivalents Properties Functions and methods Kinds of methods Static methods Class methods Member objects and __slots__ Debugging C API extensions and CPython Internals with GDB Prerequisites Setup with Python built from source Setup for Python from a Linux distro Using the Debug build and Development mode Using the python gdb extension Pretty printers py list py up and py down py bt py print py locals Use with GDB commands Enum HOWTO Programmatic access to enumeration members and their attributes Duplicating enum members and values Ensuring unique enumeration values Using automatic values Iteration Comparisons Allowed members and attributes of enumerations Restricted Enum subclassing Dataclass support Pickling Functional API Derived Enumerations IntEnum StrEnum IntFlag Flag Others When to use __new__ vs __init__ Finer Points Supported __dunder__ names Supported _sunder_ names _Private__names Enum member type Creating members that are mixed with other data types Boolean value of Enum classes and members Enum classes with methods Combining members of Flag Flag and IntFlag minutia How are Enums and Flags different Enum Classes Flag Classes Enum Members aka instances Flag Members Enum Cookbook Omitting values Using auto Using object Using a descriptive string Using a custom __new__ OrderedEnum DuplicateFreeEnum Planet TimePeriod Subclassing EnumType Functional Programming HOWTO Introduction Formal provability Modularity Ease of debugging and testing Composability Iterators Data Types That Support Iterators Generator expressions and list comprehensions Generators Passing values into a generator Built in functions The itertools module Creating new iterators Calling functions on elements Selecting elements Combinatoric functions Grouping elements The functools module The operator module Small functions and the lambda expression Revision History and Acknowledgements References General Python specific Python documentation Logging HOWTO Basic Logging Tutorial When to use logging A simple example Logging to a file Logging variable data Changing the format of displayed messages Displaying the date time in messages Next Steps Advanced Logging Tutorial Logging Flow Loggers Handlers Formatters Configuring Logging What happens if no configuration is provided Configuring Logging for a Library Logging Levels Custom Levels Useful Handlers Exceptions raised during logging Using arbitrary objects as messages Optimization Other resources Logging Cookbook Using logging in multiple modules Logging from multiple threads Multiple handlers and formatters Logging to multiple destinations Custom handling of levels Configuration server example Dealing with handlers that block Sending and receiving logging events across a network Running a logging socket listener in production Adding contextual information to your logging output Using LoggerAdapters to impart contextual information Using objects other than dicts to pass contextual information Using Filters to impart conte,en
1279,xtual information Use of contextvars Imparting contextual information in handlers Logging to a single file from multiple processes Using concurrent futures ProcessPoolExecutor Deploying Web applications using Gunicorn and uWSGI Using file rotation Use of alternative formatting styles Customizing LogRecord Subclassing QueueHandler a ZeroMQ example Subclassing QueueListener a ZeroMQ example An example dictionary based configuration Using a rotator and namer to customize log rotation processing A more elaborate multiprocessing example Inserting a BOM into messages sent to a SysLogHandler Implementing structured logging Customizing handlers with dictConfig Using particular formatting styles throughout your application Using LogRecord factories Using custom message objects Configuring filters with dictConfig Customized exception formatting Speaking logging messages Buffering logging messages and outputting them conditionally Sending logging messages to email with buffering Formatting times using UTC GMT via configuration Using a context manager for selective logging A CLI application starter template A Qt GUI for logging Logging to syslog with RFC5424 support How to treat a logger like an output stream Patterns to avoid Opening the same log file multiple times Using loggers as attributes in a class or passing them as parameters Adding handlers other than NullHandler to a logger in a library Creating a lot of loggers Other resources Regular Expression HOWTO Introduction Simple Patterns Matching Characters Repeating Things Using Regular Expressions Compiling Regular Expressions The Backslash Plague Performing Matches Module Level Functions Compilation Flags More Pattern Power More Metacharacters Grouping Non capturing and Named Groups Lookahead Assertions Modifying Strings Splitting Strings Search and Replace Common Problems Use String Methods match versus search Greedy versus Non Greedy Using re VERBOSE Feedback Socket Programming HOWTO Sockets History Creating a Socket IPC Using a Socket Binary Data Disconnecting When Sockets Die Non blocking Sockets Sorting Techniques Sorting Basics Key Functions Operator Module Functions and Partial Function Evaluation Ascending and Descending Sort Stability and Complex Sorts Decorate Sort Undecorate Comparison Functions Odds and Ends Partial Sorts Unicode HOWTO Introduction to Unicode Definitions Encodings References Python s Unicode Support The String Type Converting to Bytes Unicode Literals in Python Source Code Unicode Properties Comparing Strings Unicode Regular Expressions References Reading and Writing Unicode Data Unicode filenames Tips for Writing Unicode aware Programs Converting Between File Encodings Files in an Unknown Encoding References Acknowledgements HOWTO Fetch Internet Resources Using The urllib Package Introduction Fetching URLs Data Headers Handling Exceptions URLError HTTPError Error Codes Wrapping it Up Number 1 Number 2 info and geturl Openers and Handlers Basic Authentication Proxies Sockets and Layers Footnotes Argparse Tutorial Concepts The basics Introducing Positional arguments Introducing Optional arguments Short options Combining Positional and Optional arguments Getting a little more advanced Specifying ambiguous arguments Conflicting options How to translate the argparse output Conclusion An introduction to the ipaddress module Creating Address Network Interface objects A Note on IP Versions IP Host Addresses Defining Networks Host Interfaces Inspecting Address Network Interface Objects Networks as lists of Addresses Comparisons Using IP Addresses with other modules Getting more detail when instance creation fails Instrumenting CPython with DTrace and SystemTap Enabling the static markers Static DTrace probes Static SystemTap markers Available static markers SystemTap Tapsets Examples Python support for the Linux perf profiler How to enable perf profiling support How to obtain the best results Annotations Best Practices Accessing The Annotations Dict Of An Object In Python 3 10 And Newer Accessing The Annotations Dict Of An Object In Python 3 9 And Older M,en
1280,anually Un Stringizing Stringized Annotations Best Practices For __annotations__ In Any Python Version __annotations__ Quirks Isolating Extension Modules Who should read this Background Enter Per Module State Isolated Module Objects Surprising Edge Cases Making Modules Safe with Multiple Interpreters Managing Global State Managing Per Module State Opt Out Limiting to One Module Object per Process Module State Access from Functions Heap Types Changing Static Types to Heap Types Defining Heap Types Garbage Collection Protocol tp_traverse in Python 3 8 and lower Delegating tp_traverse Defining tp_dealloc Not overriding tp_free Avoiding PyObject_New Module State Access from Classes Module State Access from Regular Methods Module State Access from Slot Methods Getters and Setters Lifetime of the Module State Open Issues Per Class Scope Lossless Conversion to Heap Types Python Frequently Asked Questions General Python FAQ General Information Python in the real world Programming FAQ General Questions Core Language Numbers and strings Performance Sequences Tuples Lists Objects Modules Design and History FAQ Why does Python use indentation for grouping of statements Why am I getting strange results with simple arithmetic operations Why are floating point calculations so inaccurate Why are Python strings immutable Why must self be used explicitly in method definitions and calls Why can t I use an assignment in an expression Why does Python use methods for some functionality e g list index but functions for other e g len list Why is join a string method instead of a list or tuple method How fast are exceptions Why isn t there a switch or case statement in Python Can t you emulate threads in the interpreter instead of relying on an OS specific thread implementation Why can t lambda expressions contain statements Can Python be compiled to machine code C or some other language How does Python manage memory Why doesn t CPython use a more traditional garbage collection scheme Why isn t all memory freed when CPython exits Why are there separate tuple and list data types How are lists implemented in CPython How are dictionaries implemented in CPython Why must dictionary keys be immutable Why doesn t list sort return the sorted list How do you specify and enforce an interface spec in Python Why is there no goto Why can t raw strings r strings end with a backslash Why doesn t Python have a with statement for attribute assignments Why don t generators support the with statement Why are colons required for the if while def class statements Why does Python allow commas at the end of lists and tuples Library and Extension FAQ General Library Questions Common tasks Threads Input and Output Network Internet Programming Databases Mathematics and Numerics Extending Embedding FAQ Can I create my own functions in C Can I create my own functions in C Writing C is hard are there any alternatives How can I execute arbitrary Python statements from C How can I evaluate an arbitrary Python expression from C How do I extract C values from a Python object How do I use Py_BuildValue to create a tuple of arbitrary length How do I call an object s method from C How do I catch the output from PyErr_Print or anything that prints to stdout stderr How do I access a module written in Python from C How do I interface to C objects from Python I added a module using the Setup file and the make fails why How do I debug an extension I want to compile a Python module on my Linux system but some files are missing Why How do I tell incomplete input from invalid input How do I find undefined g symbols __builtin_new or __pure_virtual Can I create an object class with some methods implemented in C and others in Python e g through inheritance Python on Windows FAQ How do I run a Python program under Windows How do I make Python scripts executable Why does Python sometimes take so long to start How do I make an executable from a Python script Is a pyd file the same as a DLL How can I embed Python into a Windows application How do I keep editors from inserting tabs into my Python,en
1281, source How do I check for a keypress without blocking How do I solve the missing api ms win crt runtime l1 1 0 dll error Graphic User Interface FAQ General GUI Questions What GUI toolkits exist for Python Tkinter questions Why is Python Installed on my Computer FAQ What is Python Why is Python installed on my machine Can I delete Python Glossary About these documents Contributors to the Python Documentation Dealing with Bugs Documentation bugs Using the Python issue tracker Getting started contributing to Python yourself Copyright History and License History of the software Terms and conditions for accessing or otherwise using Python PSF LICENSE AGREEMENT FOR PYTHON 3 12 2 BEOPEN COM LICENSE AGREEMENT FOR PYTHON 2 0 CNRI LICENSE AGREEMENT FOR PYTHON 1 6 1 CWI LICENSE AGREEMENT FOR PYTHON 0 9 0 THROUGH 1 2 ZERO CLAUSE BSD LICENSE FOR CODE IN THE PYTHON 3 12 2 DOCUMENTATION Licenses and Acknowledgements for Incorporated Software Mersenne Twister Sockets Asynchronous socket services Cookie management Execution tracing UUencode and UUdecode functions XML Remote Procedure Calls test_epoll Select kqueue SipHash24 strtod and dtoa OpenSSL expat libffi zlib cfuhash libmpdec W3C C14N test suite Audioop asyncio,en
1282,2 Using Python on Unix platforms 2 1 Getting and installing the latest version of Python 2 1 1 On Linux Python comes preinstalled on most Linux distributions and is available as a package on all others However there are certain features you might want to use that are not available on your distro s package You can easily compile the latest version of Python from source In the event that Python doesn t come preinstalled and isn t in the repositories as well you can easily make packages for your own distro Have a look at the following links See also https www debian org doc manuals maint guide first en html for Debian users https en opensuse org Portal Packaging for OpenSuse users https docs fedoraproject org en US package maintainers Packaging_Tutorial_GNU_Hello for Fedora users https slackbook org html package management making packages html for Slackware users 2 1 2 On FreeBSD and OpenBSD FreeBSD users to add the package use pkg install python3 OpenBSD users to add the package use pkg_add r python pkg_add ftp ftp openbsd org pub OpenBSD 4 2 packages insert your architecture here python version tgz For example i386 users get the 2 5 1 version of Python using pkg_add ftp ftp openbsd org pub OpenBSD 4 2 packages i386 python 2 5 1p2 tgz 2 2 Building Python If you want to compile CPython yourself first thing you should do is get the source You can download either the latest release s source or just grab a fresh clone If you want to contribute patches you will need a clone The build process consists of the usual commands configure make make install Configuration options and caveats for specific Unix platforms are extensively documented in the README rst file in the root of the Python source tree Warning make install can overwrite or masquerade the python3 binary make altinstall is therefore recommended instead of make install since it only installs exec_prefix bin python version 2 3 Python related paths and files These are subject to difference depending on local installation conventions prefix and exec_prefix are installation dependent and should be interpreted as for GNU software they may be the same For example on most Linux systems the default for both is usr File directory Meaning exec_prefix bin python3 Recommended location of the interpreter prefix lib python version Recommended locations of the directories exec_prefix lib python version containing the standard modules prefix include python version Recommended locations of the directories exec_prefix include python version containing the include files needed for developing Python extensions and embedding the interpreter 2 4 Miscellaneous To easily use Python scripts on Unix you need to make them executable e g with chmod x script and put an appropriate Shebang line at the top of the script A good choice is usually usr bin env python3 which searches for the Python interpreter in the whole PATH However some Unices may not have the env command so you may need to hardcode usr bin python3 as the interpreter path To use shell commands in your Python scripts look at the subprocess module 2 5 Custom OpenSSL 1 To use your vendor s OpenSSL configuration and system trust store locate the directory with openssl cnf file or symlink in etc On most distribution the file is either in etc ssl or etc pki tls The directory should also contain a cert pem file and or a certs directory find etc name openssl cnf printf h n etc ssl 2 Download build and install OpenSSL Make sure you use install_sw and not install The install_sw target does not override openssl cnf curl O https www openssl org source openssl VERSION tar gz tar xzf openssl VERSION pushd openssl VERSION config prefix usr local custom openssl libdir lib openssldir etc ssl make j1 depend make j8 make install_sw popd 3 Build Python with custom OpenSSL see the configure with openssl and with openssl rpath options pushd python 3 x x configure C with openssl usr local custom openssl with openssl rpath auto prefix usr local python 3 x x make j8 make altinstall Note Patch releases of OpenSSL have a backwards compatible ABI You don t need ,en
1283,to recompile Python to update OpenSSL It s sufficient to replace the custom OpenSSL installation with a newer version,en
1284,colorsys Conversions between color systems Source code Lib colorsys py The colorsys module defines bidirectional conversions of color values between colors expressed in the RGB Red Green Blue color space used in computer monitors and three other coordinate systems YIQ HLS Hue Lightness Saturation and HSV Hue Saturation Value Coordinates in all of these color spaces are floating point values In the YIQ space the Y coordinate is between 0 and 1 but the I and Q coordinates can be positive or negative In all other spaces the coordinates are all between 0 and 1 See also More information about color spaces can be found at https poynton ca ColorFAQ html and https www cambridgeincolour com tutorials color spaces htm The colorsys module defines the following functions colorsys rgb_to_yiq r g b Convert the color from RGB coordinates to YIQ coordinates colorsys yiq_to_rgb y i q Convert the color from YIQ coordinates to RGB coordinates colorsys rgb_to_hls r g b Convert the color from RGB coordinates to HLS coordinates colorsys hls_to_rgb h l s Convert the color from HLS coordinates to RGB coordinates colorsys rgb_to_hsv r g b Convert the color from RGB coordinates to HSV coordinates colorsys hsv_to_rgb h s v Convert the color from HSV coordinates to RGB coordinates Example import colorsys colorsys rgb_to_hsv 0 2 0 4 0 4 0 5 0 5 0 4 colorsys hsv_to_rgb 0 5 0 5 0 4 0 2 0 4 0 4,en
1285,tty Terminal control functions Source code Lib tty py The tty module defines functions for putting the tty into cbreak and raw modes Availability Unix Because it requires the termios module it will work only on Unix The tty module defines the following functions tty cfmakeraw mode Convert the tty attribute list mode which is a list like the one returned by termios tcgetattr to that of a tty in raw mode New in version 3 12 tty cfmakecbreak mode Convert the tty attribute list mode which is a list like the one returned by termios tcgetattr to that of a tty in cbreak mode This clears the ECHO and ICANON local mode flags in mode as well as setting the minimum input to 1 byte with no delay New in version 3 12 Changed in version 3 12 2 The ICRNL flag is no longer cleared This matches Linux and macOS stty cbreak behavior and what setcbreak historically did tty setraw fd when termios TCSAFLUSH Change the mode of the file descriptor fd to raw If when is omitted it defaults to termios TCSAFLUSH and is passed to termios tcsetattr The return value of termios tcgetattr is saved before setting fd to raw mode this value is returned Changed in version 3 12 The return value is now the original tty attributes instead of None tty setcbreak fd when termios TCSAFLUSH Change the mode of file descriptor fd to cbreak If when is omitted it defaults to termios TCSAFLUSH and is passed to termios tcsetattr The return value of termios tcgetattr is saved before setting fd to cbreak mode this value is returned This clears the ECHO and ICANON local mode flags as well as setting the minimum input to 1 byte with no delay Changed in version 3 12 The return value is now the original tty attributes instead of None Changed in version 3 12 2 The ICRNL flag is no longer cleared This restores the behavior of Python 3 11 and earlier as well as matching what Linux macOS BSDs describe in their stty 1 man pages regarding cbreak mode See also Module termios Low level terminal control interface,en
1286,IDLE Source code Lib idlelib IDLE is Python s Integrated Development and Learning Environment IDLE has the following features cross platform works mostly the same on Windows Unix and macOS Python shell window interactive interpreter with colorizing of code input output and error messages multi window text editor with multiple undo Python colorizing smart indent call tips auto completion and other features search within any window replace within editor windows and search through multiple files grep debugger with persistent breakpoints stepping and viewing of global and local namespaces configuration browsers and other dialogs Menus IDLE has two main window types the Shell window and the Editor window It is possible to have multiple editor windows simultaneously On Windows and Linux each has its own top menu Each menu documented below indicates which window type it is associated with Output windows such as used for Edit Find in Files are a subtype of editor window They currently have the same top menu but a different default title and context menu On macOS there is one application menu It dynamically changes according to the window currently selected It has an IDLE menu and some entries described below are moved around to conform to Apple guidelines File menu Shell and Editor New File Create a new file editing window Open Open an existing file with an Open dialog Open Module Open an existing module searches sys path Recent Files Open a list of recent files Click one to open it Module Browser Show functions classes and methods in the current Editor file in a tree structure In the shell open a module first Path Browser Show sys path directories modules functions classes and methods in a tree structure Save Save the current window to the associated file if there is one Windows that have been changed since being opened or last saved have a before and after the window title If there is no associated file do Save As instead Save As Save the current window with a Save As dialog The file saved becomes the new associated file for the window If your file namager is set to hide extensions the current extension will be omitted in the file name box If the new filename has no py and txt will be added for Python and text files except that on macOS Aqua py is added for all files Save Copy As Save the current window to different file without changing the associated file See Save As note above about filename extensions Print Window Print the current window to the default printer Close Window Close the current window if an unsaved editor ask to save if an unsaved Shell ask to quit execution Calling exit or close in the Shell window also closes Shell If this is the only window also exit IDLE Exit IDLE Close all windows and quit IDLE ask to save unsaved edit windows Edit menu Shell and Editor Undo Undo the last change to the current window A maximum of 1000 changes may be undone Redo Redo the last undone change to the current window Select All Select the entire contents of the current window Cut Copy selection into the system wide clipboard then delete the selection Copy Copy selection into the system wide clipboard Paste Insert contents of the system wide clipboard into the current window The clipboard functions are also available in context menus Find Open a search dialog with many options Find Again Repeat the last search if there is one Find Selection Search for the currently selected string if there is one Find in Files Open a file search dialog Put results in a new output window Replace Open a search and replace dialog Go to Line Move the cursor to the beginning of the line requested and make that line visible A request past the end of the file goes to the end Clear any selection and update the line and column status Show Completions Open a scrollable list allowing selection of existing names See Completions in the Editing and navigation section below Expand Word Expand a prefix you have typed to match a full word in the same window repeat to get a different expansion Show Call Tip After an unclosed parenthesis for a function open a smal,en
1287,l window with function parameter hints See Calltips in the Editing and navigation section below Show Surrounding Parens Highlight the surrounding parenthesis Format menu Editor window only Format Paragraph Reformat the current blank line delimited paragraph in comment block or multiline string or selected line in a string All lines in the paragraph will be formatted to less than N columns where N defaults to 72 Indent Region Shift selected lines right by the indent width default 4 spaces Dedent Region Shift selected lines left by the indent width default 4 spaces Comment Out Region Insert in front of selected lines Uncomment Region Remove leading or from selected lines Tabify Region Turn leading stretches of spaces into tabs Note We recommend using 4 space blocks to indent Python code Untabify Region Turn all tabs into the correct number of spaces Toggle Tabs Open a dialog to switch between indenting with spaces and tabs New Indent Width Open a dialog to change indent width The accepted default by the Python community is 4 spaces Strip Trailing Chitespace Remove trailing space and other whitespace characters after the last non whitespace character of a line by applying str rstrip to each line including lines within multiline strings Except for Shell windows remove extra newlines at the end of the file Run menu Editor window only Run Module Do Check Module If no error restart the shell to clean the environment then execute the module Output is displayed in the Shell window Note that output requires use of print or write When execution is complete the Shell retains focus and displays a prompt At this point one may interactively explore the result of execution This is similar to executing a file with python i file at a command line Run Customized Same as Run Module but run the module with customized settings Command Line Arguments extend sys argv as if passed on a command line The module can be run in the Shell without restarting Check Module Check the syntax of the module currently open in the Editor window If the module has not been saved IDLE will either prompt the user to save or autosave as selected in the General tab of the Idle Settings dialog If there is a syntax error the approximate location is indicated in the Editor window Python Shell Open or wake up the Python Shell window Shell menu Shell window only View Last Restart Scroll the shell window to the last Shell restart Restart Shell Restart the shell to clean the environment and reset display and exception handling Previous History Cycle through earlier commands in history which match the current entry Next History Cycle through later commands in history which match the current entry Interrupt Execution Stop a running program Debug menu Shell window only Go to File Line Look on the current line with the cursor and the line above for a filename and line number If found open the file if not already open and show the line Use this to view source lines referenced in an exception traceback and lines found by Find in Files Also available in the context menu of the Shell window and Output windows Debugger toggle When activated code entered in the Shell or run from an Editor will run under the debugger In the Editor breakpoints can be set with the context menu This feature is still incomplete and somewhat experimental Stack Viewer Show the stack traceback of the last exception in a tree widget with access to locals and globals Auto open Stack Viewer Toggle automatically opening the stack viewer on an unhandled exception Options menu Shell and Editor Configure IDLE Open a configuration dialog and change preferences for the following fonts indentation keybindings text color themes startup windows and size additional help sources and extensions On macOS open the configuration dialog by selecting Preferences in the application menu For more details see Setting preferences under Help and preferences Most configuration options apply to all windows or all future windows The option items below only apply to the active window Show Hide Code Context Editor Window only Open a pan,en
1288,e at the top of the edit window which shows the block context of the code which has scrolled above the top of the window See Code Context in the Editing and Navigation section below Show Hide Line Numbers Editor Window only Open a column to the left of the edit window which shows the number of each line of text The default is off which may be changed in the preferences see Setting preferences Zoom Restore Height Toggles the window between normal size and maximum height The initial size defaults to 40 lines by 80 chars unless changed on the General tab of the Configure IDLE dialog The maximum height for a screen is determined by momentarily maximizing a window the first time one is zoomed on the screen Changing screen settings may invalidate the saved height This toggle has no effect when a window is maximized Window menu Shell and Editor Lists the names of all open windows select one to bring it to the foreground deiconifying it if necessary Help menu Shell and Editor About IDLE Display version copyright license credits and more IDLE Help Display this IDLE document detailing the menu options basic editing and navigation and other tips Python Docs Access local Python documentation if installed or start a web browser and open docs python org showing the latest Python documentation Turtle Demo Run the turtledemo module with example Python code and turtle drawings Additional help sources may be added here with the Configure IDLE dialog under the General tab See the Help sources subsection below for more on Help menu choices Context menus Open a context menu by right clicking in a window Control click on macOS Context menus have the standard clipboard functions also on the Edit menu Cut Copy selection into the system wide clipboard then delete the selection Copy Copy selection into the system wide clipboard Paste Insert contents of the system wide clipboard into the current window Editor windows also have breakpoint functions Lines with a breakpoint set are specially marked Breakpoints only have an effect when running under the debugger Breakpoints for a file are saved in the user s idlerc directory Set Breakpoint Set a breakpoint on the current line Clear Breakpoint Clear the breakpoint on that line Shell and Output windows also have the following Go to file line Same as in Debug menu The Shell window also has an output squeezing facility explained in the Python Shell window subsection below Squeeze If the cursor is over an output line squeeze all the output between the code above and the prompt below down to a Squeezed text label Editing and Navigation Editor windows IDLE may open editor windows when it starts depending on settings and how you start IDLE Thereafter use the File menu There can be only one open editor window for a given file The title bar contains the name of the file the full path and the version of Python and IDLE running the window The status bar contains the line number Ln and column number Col Line numbers start with 1 column numbers with 0 IDLE assumes that files with a known py extension contain Python code and that other files do not Run Python code with the Run menu Key bindings The IDLE insertion cursor is a thin vertical bar between character positions When characters are entered the insertion cursor and everything to its right moves right one character and the new character is entered in the new space Several non character keys move the cursor and possibly delete characters Deletion does not puts text on the clipboard but IDLE has an undo list Wherever this doc discusses keys C refers to the Control key on Windows and Unix and the Command key on macOS And all such dicussions assume that the keys have not been re bound to something else Arrow keys move the cursor one character or line C LeftArrow and C RightArrow moves left or right one word Home and End go to the beginning or end of the line Page Up and Page Down go up or down one screen C Home and C End go to beginning or end of the file Backspace and Del or C d delete the previous or next character C Backspace and C Del delete one word left or r,en
1289,ight C k deletes kills everything to the right Standard keybindings like C c to copy and C v to paste may work Keybindings are selected in the Configure IDLE dialog Automatic indentation After a block opening statement the next line is indented by 4 spaces in the Python Shell window by one tab After certain keywords break return etc the next line is dedented In leading indentation Backspace deletes up to 4 spaces if they are there Tab inserts spaces in the Python Shell window one tab number depends on Indent width Currently tabs are restricted to four spaces due to Tcl Tk limitations See also the indent dedent region commands on the Format menu Search and Replace Any selection becomes a search target However only selections within a line work because searches are only performed within lines with the terminal newline removed If x Regular expression is checked the target is interpreted according to the Python re module Completions Completions are supplied when requested and available for module names attributes of classes or functions or filenames Each request method displays a completion box with existing names See tab completions below for an exception For any box change the name being completed and the item highlighted in the box by typing and deleting characters by hitting Up Down PageUp PageDown Home and End keys and by a single click within the box Close the box with Escape Enter and double Tab keys or clicks outside the box A double click within the box selects and closes One way to open a box is to type a key character and wait for a predefined interval This defaults to 2 seconds customize it in the settings dialog To prevent auto popups set the delay to a large number of milliseconds such as 100000000 For imported module names or class or function attributes type For filenames in the root directory type os sep or os altsep immediately after an opening quote On Windows one can specify a drive first Move into subdirectories by typing a directory name and a separator Instead of waiting or after a box is closed open a completion box immediately with Show Completions on the Edit menu The default hot key is C space If one types a prefix for the desired name before opening the box the first match or near miss is made visible The result is the same as if one enters a prefix after the box is displayed Show Completions after a quote completes filenames in the current directory instead of a root directory Hitting Tab after a prefix usually has the same effect as Show Completions With no prefix it indents However if there is only one match to the prefix that match is immediately added to the editor text without opening a box Invoking Show Completions or hitting Tab after a prefix outside of a string and without a preceding opens a box with keywords builtin names and available module level names When editing code in an editor as oppose to Shell increase the available module level names by running your code and not restarting the Shell thereafter This is especially useful after adding imports at the top of a file This also increases possible attribute completions Completion boxes initially exclude names beginning with _ or for modules not included in __all__ The hidden names can be accessed by typing _ after either before or after the box is opened Calltips A calltip is shown automatically when one types after the name of an accessible function A function name expression may include dots and subscripts A calltip remains until it is clicked the cursor is moved out of the argument area or is typed Whenever the cursor is in the argument part of a definition select Edit and Show Call Tip on the menu or enter its shortcut to display a calltip The calltip consists of the function s signature and docstring up to the latter s first blank line or the fifth non blank line Some builtin functions lack an accessible signature A or in the signature indicates that the preceding or following arguments are passed by position or name keyword only Details are subject to change In Shell the accessible functions depends on what modules have been im,en
1290,ported into the user process including those imported by Idle itself and which definitions have been run all since the last restart For example restart the Shell and enter itertools count A calltip appears because Idle imports itertools into the user process for its own use This could change Enter turtle write and nothing appears Idle does not itself import turtle The menu entry and shortcut also do nothing Enter import turtle Thereafter turtle write will display a calltip In an editor import statements have no effect until one runs the file One might want to run a file after writing import statements after adding function definitions or after opening an existing file Code Context Within an editor window containing Python code code context can be toggled in order to show or hide a pane at the top of the window When shown this pane freezes the opening lines for block code such as those beginning with class def or if keywords that would have otherwise scrolled out of view The size of the pane will be expanded and contracted as needed to show the all current levels of context up to the maximum number of lines defined in the Configure IDLE dialog which defaults to 15 If there are no current context lines and the feature is toggled on a single blank line will display Clicking on a line in the context pane will move that line to the top of the editor The text and background colors for the context pane can be configured under the Highlights tab in the Configure IDLE dialog Shell window In IDLE s Shell enter edit and recall complete statements Most consoles and terminals only work with a single physical line at a time Submit a single line statement for execution by hitting Return with the cursor anywhere on the line If a line is extended with Backslash the cursor must be on the last physical line Submit a multi line compound statement by entering a blank line after the statement When one pastes code into Shell it is not compiled and possibly executed until one hits Return as specified above One may edit pasted code first If one pastes more than one statement into Shell the result will be a SyntaxError when multiple statements are compiled as if they were one Lines containing RESTART mean that the user execution process has been re started This occurs when the user execution process has crashed when one requests a restart on the Shell menu or when one runs code in an editor window The editing features described in previous subsections work when entering code interactively IDLE s Shell window also responds to the following C c attempts to interrupt statement execution but may fail C d closes Shell if typed at a prompt Alt p and Alt n C p and C n on macOS retrieve to the current prompt the previous or next previously entered statement that matches anything already typed Return while the cursor is on any previous statement appends the latter to anything already typed at the prompt Text colors Idle defaults to black on white text but colors text with special meanings For the shell these are shell output shell error user output and user error For Python code at the shell prompt or in an editor these are keywords builtin class and function names names following class and def strings and comments For any text window these are the cursor when present found text when possible and selected text IDLE also highlights the soft keywords match case and _ in pattern matching statements However this highlighting is not perfect and will be incorrect in some rare cases including some _ s in case patterns Text coloring is done in the background so uncolorized text is occasionally visible To change the color scheme use the Configure IDLE dialog Highlighting tab The marking of debugger breakpoint lines in the editor and text in popups and dialogs is not user configurable Startup and Code Execution Upon startup with the s option IDLE will execute the file referenced by the environment variables IDLESTARTUP or PYTHONSTARTUP IDLE first checks for IDLESTARTUP if IDLESTARTUP is present the file referenced is run If IDLESTARTUP is not present IDLE checks fo,en
1291,r PYTHONSTARTUP Files referenced by these environment variables are convenient places to store functions that are used frequently from the IDLE shell or for executing import statements to import common modules In addition Tk also loads a startup file if it is present Note that the Tk file is loaded unconditionally This additional file is Idle py and is looked for in the user s home directory Statements in this file will be executed in the Tk namespace so this file is not useful for importing functions to be used from IDLE s Python shell Command line usage idle py c command d e h i r file s t title arg c command run command in the shell window d enable debugger and open shell window e open editor window h print help message with legal combinations and exit i open shell window r file run file in shell window s run IDLESTARTUP or PYTHONSTARTUP first in shell window t title set title of shell window run stdin in shell must be last option before args If there are arguments If c or r is used all arguments are placed in sys argv 1 and sys argv 0 is set to c or r No editor window is opened even if that is the default set in the Options dialog Otherwise arguments are files opened for editing and sys argv reflects the arguments passed to IDLE itself Startup failure IDLE uses a socket to communicate between the IDLE GUI process and the user code execution process A connection must be established whenever the Shell starts or restarts The latter is indicated by a divider line that says RESTART If the user process fails to connect to the GUI process it usually displays a Tk error box with a cannot connect message that directs the user here It then exits One specific connection failure on Unix systems results from misconfigured masquerading rules somewhere in a system s network setup When IDLE is started from a terminal one will see a message starting with Invalid host The valid value is 127 0 0 1 idlelib rpc LOCALHOST One can diagnose with tcpconnect irv 127 0 0 1 6543 in one terminal window and tcplisten same args in another A common cause of failure is a user written file with the same name as a standard library module such as random py and tkinter py When such a file is located in the same directory as a file that is about to be run IDLE cannot import the stdlib file The current fix is to rename the user file Though less common than in the past an antivirus or firewall program may stop the connection If the program cannot be taught to allow the connection then it must be turned off for IDLE to work It is safe to allow this internal connection because no data is visible on external ports A similar problem is a network mis configuration that blocks connections Python installation issues occasionally stop IDLE multiple versions can clash or a single installation might need admin access If one undo the clash or cannot or does not want to run as admin it might be easiest to completely remove Python and start over A zombie pythonw exe process could be a problem On Windows use Task Manager to check for one and stop it if there is Sometimes a restart initiated by a program crash or Keyboard Interrupt control C may fail to connect Dismissing the error box or using Restart Shell on the Shell menu may fix a temporary problem When IDLE first starts it attempts to read user configuration files in idlerc is one s home directory If there is a problem an error message should be displayed Leaving aside random disk glitches this can be prevented by never editing the files by hand Instead use the configuration dialog under Options Once there is an error in a user configuration file the best solution may be to delete it and start over with the settings dialog If IDLE quits with no message and it was not started from a console try starting it from a console or terminal python m idlelib and see if this results in an error message On Unix based systems with tcl tk older than 8 6 11 see About IDLE certain characters of certain fonts can cause a tk failure with a message to the terminal This can happen either if one starts IDLE to edit a file with such a c,en
1292,haracter or later when entering such a character If one cannot upgrade tcl tk then re configure IDLE to use a font that works better Running user code With rare exceptions the result of executing Python code with IDLE is intended to be the same as executing the same code by the default method directly with Python in a text mode system console or terminal window However the different interface and operation occasionally affect visible results For instance sys modules starts with more entries and threading active_count returns 2 instead of 1 By default IDLE runs user code in a separate OS process rather than in the user interface process that runs the shell and editor In the execution process it replaces sys stdin sys stdout and sys stderr with objects that get input from and send output to the Shell window The original values stored in sys __stdin__ sys __stdout__ and sys __stderr__ are not touched but may be None Sending print output from one process to a text widget in another is slower than printing to a system terminal in the same process This has the most effect when printing multiple arguments as the string for each argument each separator the newline are sent separately For development this is usually not a problem but if one wants to print faster in IDLE format and join together everything one wants displayed together and then print a single string Both format strings and str join can help combine fields and lines IDLE s standard stream replacements are not inherited by subprocesses created in the execution process whether directly by user code or by modules such as multiprocessing If such subprocess use input from sys stdin or print or write to sys stdout or sys stderr IDLE should be started in a command line window On Windows use python or py rather than pythonw or pyw The secondary subprocess will then be attached to that window for input and output If sys is reset by user code such as with importlib reload sys IDLE s changes are lost and input from the keyboard and output to the screen will not work correctly When Shell has the focus it controls the keyboard and screen This is normally transparent but functions that directly access the keyboard and screen will not work These include system specific functions that determine whether a key has been pressed and if so which The IDLE code running in the execution process adds frames to the call stack that would not be there otherwise IDLE wraps sys getrecursionlimit and sys setrecursionlimit to reduce the effect of the additional stack frames When user code raises SystemExit either directly or by calling sys exit IDLE returns to a Shell prompt instead of exiting User output in Shell When a program outputs text the result is determined by the corresponding output device When IDLE executes user code sys stdout and sys stderr are connected to the display area of IDLE s Shell Some of its features are inherited from the underlying Tk Text widget Others are programmed additions Where it matters Shell is designed for development rather than production runs For instance Shell never throws away output A program that sends unlimited output to Shell will eventually fill memory resulting in a memory error In contrast some system text windows only keep the last n lines of output A Windows console for instance keeps a user settable 1 to 9999 lines with 300 the default A Tk Text widget and hence IDLE s Shell displays characters codepoints in the BMP Basic Multilingual Plane subset of Unicode Which characters are displayed with a proper glyph and which with a replacement box depends on the operating system and installed fonts Tab characters cause the following text to begin after the next tab stop They occur every 8 characters Newline characters cause following text to appear on a new line Other control characters are ignored or displayed as a space box or something else depending on the operating system and font Moving the text cursor through such output with arrow keys may exhibit some surprising spacing behavior s a tb a x02 r bc nd Enter 22 chars len s 14 s Display repr s a tb ,en
1293,x07 x02 r x08c nd print s end Display s as is Result varies by OS and font Try it The repr function is used for interactive echo of expression values It returns an altered version of the input string in which control codes some BMP codepoints and all non BMP codepoints are replaced with escape codes As demonstrated above it allows one to identify the characters in a string regardless of how they are displayed Normal and error output are generally kept separate on separate lines from code input and each other They each get different highlight colors For SyntaxError tracebacks the normal marking where the error was detected is replaced by coloring the text with an error highlight When code run from a file causes other exceptions one may right click on a traceback line to jump to the corresponding line in an IDLE editor The file will be opened if necessary Shell has a special facility for squeezing output lines down to a Squeezed text label This is done automatically for output over N lines N 50 by default N can be changed in the PyShell section of the General page of the Settings dialog Output with fewer lines can be squeezed by right clicking on the output This can be useful lines long enough to slow down scrolling Squeezed output is expanded in place by double clicking the label It can also be sent to the clipboard or a separate view window by right clicking the label Developing tkinter applications IDLE is intentionally different from standard Python in order to facilitate development of tkinter programs Enter import tkinter as tk root tk Tk in standard Python and nothing appears Enter the same in IDLE and a tk window appears In standard Python one must also enter root update to see the window IDLE does the equivalent in the background about 20 times a second which is about every 50 milliseconds Next enter b tk Button root text button b pack Again nothing visibly changes in standard Python until one enters root update Most tkinter programs run root mainloop which usually does not return until the tk app is destroyed If the program is run with python i or from an IDLE editor a shell prompt does not appear until mainloop returns at which time there is nothing left to interact with When running a tkinter program from an IDLE editor one can comment out the mainloop call One then gets a shell prompt immediately and can interact with the live application One just has to remember to re enable the mainloop call when running in standard Python Running without a subprocess By default IDLE executes user code in a separate subprocess via a socket which uses the internal loopback interface This connection is not externally visible and no data is sent to or received from the internet If firewall software complains anyway you can ignore it If the attempt to make the socket connection fails Idle will notify you Such failures are sometimes transient but if persistent the problem may be either a firewall blocking the connection or misconfiguration of a particular system Until the problem is fixed one can run Idle with the n command line switch If IDLE is started with the n command line switch it will run in a single process and will not create the subprocess which runs the RPC Python execution server This can be useful if Python cannot create the subprocess or the RPC socket interface on your platform However in this mode user code is not isolated from IDLE itself Also the environment is not restarted when Run Run Module F5 is selected If your code has been modified you must reload the affected modules and re import any specific items e g from foo import baz if the changes are to take effect For these reasons it is preferable to run IDLE with the default subprocess if at all possible Deprecated since version 3 4 Help and Preferences Help sources Help menu entry IDLE Help displays a formatted html version of the IDLE chapter of the Library Reference The result in a read only tkinter text window is close to what one sees in a web browser Navigate through the text with a mousewheel the scrollbar or up and down arrow keys held down Or click ,en
1294,the TOC Table of Contents button and select a section header in the opened box Help menu entry Python Docs opens the extensive sources of help including tutorials available at docs python org x y where x y is the currently running Python version If your system has an off line copy of the docs this may be an installation option that will be opened instead Selected URLs can be added or removed from the help menu at any time using the General tab of the Configure IDLE dialog Setting preferences The font preferences highlighting keys and general preferences can be changed via Configure IDLE on the Option menu Non default user settings are saved in a idlerc directory in the user s home directory Problems caused by bad user configuration files are solved by editing or deleting one or more of the files in idlerc On the Font tab see the text sample for the effect of font face and size on multiple characters in multiple languages Edit the sample to add other characters of personal interest Use the sample to select monospaced fonts If particular characters have problems in Shell or an editor add them to the top of the sample and try changing first size and then font On the Highlights and Keys tab select a built in or custom color theme and key set To use a newer built in color theme or key set with older IDLEs save it as a new custom theme or key set and it well be accessible to older IDLEs IDLE on macOS Under System Preferences Dock one can set Prefer tabs when opening documents to Always This setting is not compatible with the tk tkinter GUI framework used by IDLE and it breaks a few IDLE features Extensions IDLE contains an extension facility Preferences for extensions can be changed with the Extensions tab of the preferences dialog See the beginning of config extensions def in the idlelib directory for further information The only current default extension is zzdummy an example also used for testing idlelib Source code Lib idlelib The Lib idlelib package implements the IDLE application See the rest of this page for how to use IDLE The files in idlelib are described in idlelib README txt Access it either in idlelib or click Help About IDLE on the IDLE menu This file also maps IDLE menu items to the code that implements the item Except for files listed under Startup the idlelib code is private in sense that feature changes can be backported see PEP 434,en
1295,What s New in Python 2 7 Author A M Kuchling amk at amk ca This article explains the new features in Python 2 7 Python 2 7 was released on July 3 2010 Numeric handling has been improved in many ways for both floating point numbers and for the Decimal class There are some useful additions to the standard library such as a greatly enhanced unittest module the argparse module for parsing command line options convenient OrderedDict and Counter classes in the collections module and many other improvements Python 2 7 is planned to be the last of the 2 x releases so we worked on making it a good release for the long term To help with porting to Python 3 several new features from the Python 3 x series have been included in 2 7 This article doesn t attempt to provide a complete specification of the new features but instead provides a convenient overview For full details you should refer to the documentation for Python 2 7 at https docs python org If you want to understand the rationale for the design and implementation refer to the PEP for a particular new feature or the issue on https bugs python org in which a change was discussed Whenever possible What s New in Python links to the bug patch item for each change The Future for Python 2 x Python 2 7 is the last major release in the 2 x series as the Python maintainers have shifted the focus of their new feature development efforts to the Python 3 x series This means that while Python 2 continues to receive bug fixes and to be updated to build correctly on new hardware and versions of supported operated systems there will be no new full feature releases for the language or standard library However while there is a large common subset between Python 2 7 and Python 3 and many of the changes involved in migrating to that common subset or directly to Python 3 can be safely automated some other changes notably those associated with Unicode handling may require careful consideration and preferably robust automated regression test suites to migrate effectively This means that Python 2 7 will remain in place for a long time providing a stable and supported base platform for production systems that have not yet been ported to Python 3 The full expected lifecycle of the Python 2 7 series is detailed in PEP 373 Some key consequences of the long term significance of 2 7 are As noted above the 2 7 release has a much longer period of maintenance when compared to earlier 2 x versions Python 2 7 is currently expected to remain supported by the core development team receiving security updates and other bug fixes until at least 2020 10 years after its initial release compared to the more typical support period of 18 24 months As the Python 2 7 standard library ages making effective use of the Python Package Index either directly or via a redistributor becomes more important for Python 2 users In addition to a wide variety of third party packages for various tasks the available packages include backports of new modules and features from the Python 3 standard library that are compatible with Python 2 as well as various tools and libraries that can make it easier to migrate to Python 3 The Python Packaging User Guide provides guidance on downloading and installing software from the Python Package Index While the preferred approach to enhancing Python 2 is now the publication of new packages on the Python Package Index this approach doesn t necessarily work in all cases especially those related to network security In exceptional cases that cannot be handled adequately by publishing new or updated packages on PyPI the Python Enhancement Proposal process may be used to make the case for adding new features directly to the Python 2 standard library Any such additions and the maintenance releases where they were added will be noted in the New Features Added to Python 2 7 Maintenance Releases section below For projects wishing to migrate from Python 2 to Python 3 or for library and framework developers wishing to support users on both Python 2 and Python 3 there are a variety of tools and guides available ,en
1296,to help decide on a suitable approach and manage some of the technical details involved The recommended starting point is the How to port Python 2 Code to Python 3 HOWTO guide Changes to the Handling of Deprecation Warnings For Python 2 7 a policy decision was made to silence warnings only of interest to developers by default DeprecationWarning and its descendants are now ignored unless otherwise requested preventing users from seeing warnings triggered by an application This change was also made in the branch that became Python 3 2 Discussed on stdlib sig and carried out in bpo 7319 In previous releases DeprecationWarning messages were enabled by default providing Python developers with a clear indication of where their code may break in a future major version of Python However there are increasingly many users of Python based applications who are not directly involved in the development of those applications DeprecationWarning messages are irrelevant to such users making them worry about an application that s actually working correctly and burdening application developers with responding to these concerns You can re enable display of DeprecationWarning messages by running Python with the Wdefault short form Wd switch or by setting the PYTHONWARNINGS environment variable to default or d before running Python Python code can also re enable them by calling warnings simplefilter default The unittest module also automatically reenables deprecation warnings when running tests Python 3 1 Features Much as Python 2 6 incorporated features from Python 3 0 version 2 7 incorporates some of the new features in Python 3 1 The 2 x series continues to provide tools for migrating to the 3 x series A partial list of 3 1 features that were backported to 2 7 The syntax for set literals 1 2 3 is a mutable set Dictionary and set comprehensions i i 2 for i in range 3 Multiple context managers in a single with statement A new version of the io library rewritten in C for performance The ordered dictionary type described in PEP 372 Adding an Ordered Dictionary to collections The new format specifier described in PEP 378 Format Specifier for Thousands Separator The memoryview object A small subset of the importlib module described below The repr of a float x is shorter in many cases it s now based on the shortest decimal string that s guaranteed to round back to x As in previous versions of Python it s guaranteed that float repr x recovers x Float to string and string to float conversions are correctly rounded The round function is also now correctly rounded The PyCapsule type used to provide a C API for extension modules The PyLong_AsLongAndOverflow C API function Other new Python3 mode warnings include operator isCallable and operator sequenceIncludes which are not supported in 3 x now trigger warnings The 3 switch now automatically enables the Qwarn switch that causes warnings about using classic division with integers and long integers PEP 372 Adding an Ordered Dictionary to collections Regular Python dictionaries iterate over key value pairs in arbitrary order Over the years a number of authors have written alternative implementations that remember the order that the keys were originally inserted Based on the experiences from those implementations 2 7 introduces a new OrderedDict class in the collections module The OrderedDict API provides the same interface as regular dictionaries but iterates over keys and values in a guaranteed order depending on when a key was first inserted from collections import OrderedDict d OrderedDict first 1 second 2 third 3 d items first 1 second 2 third 3 If a new entry overwrites an existing entry the original insertion position is left unchanged d second 4 d items first 1 second 4 third 3 Deleting an entry and reinserting it will move it to the end del d second d second 5 d items first 1 third 3 second 5 The popitem method has an optional last argument that defaults to True If last is true the most recently added key is returned and removed if it s false the oldest key is selected od OrderedDict x 0 for x in ,en
1297,range 20 od popitem 19 0 od popitem 18 0 od popitem last False 0 0 od popitem last False 1 0 Comparing two ordered dictionaries checks both the keys and values and requires that the insertion order was the same od1 OrderedDict first 1 second 2 third 3 od2 OrderedDict third 3 first 1 second 2 od1 od2 False Move third key to the end del od2 third od2 third 3 od1 od2 True Comparing an OrderedDict with a regular dictionary ignores the insertion order and just compares the keys and values How does the OrderedDict work It maintains a doubly linked list of keys appending new keys to the list as they re inserted A secondary dictionary maps keys to their corresponding list node so deletion doesn t have to traverse the entire linked list and therefore remains O 1 The standard library now supports use of ordered dictionaries in several modules The ConfigParser module uses them by default meaning that configuration files can now be read modified and then written back in their original order The _asdict method for collections namedtuple now returns an ordered dictionary with the values appearing in the same order as the underlying tuple indices The json module s JSONDecoder class constructor was extended with an object_pairs_hook parameter to allow OrderedDict instances to be built by the decoder Support was also added for third party tools like PyYAML See also PEP 372 Adding an ordered dictionary to collections PEP written by Armin Ronacher and Raymond Hettinger implemented by Raymond Hettinger PEP 378 Format Specifier for Thousands Separator To make program output more readable it can be useful to add separators to large numbers rendering them as 18 446 744 073 709 551 616 instead of 18446744073709551616 The fully general solution for doing this is the locale module which can use different separators in North America in Europe and different grouping sizes but locale is complicated to use and unsuitable for multi threaded applications where different threads are producing output for different locales Therefore a simple comma grouping mechanism has been added to the mini language used by the str format method When formatting a floating point number simply include a comma between the width and the precision 20 2f format 18446744073709551616 0 18 446 744 073 709 551 616 00 When formatting an integer include the comma after the width 20 d format 18446744073709551616 18 446 744 073 709 551 616 This mechanism is not adaptable at all commas are always used as the separator and the grouping is always into three digit groups The comma formatting mechanism isn t as general as the locale module but it s easier to use See also PEP 378 Format Specifier for Thousands Separator PEP written by Raymond Hettinger implemented by Eric Smith PEP 389 The argparse Module for Parsing Command Lines The argparse module for parsing command line arguments was added as a more powerful replacement for the optparse module This means Python now supports three different modules for parsing command line arguments getopt optparse and argparse The getopt module closely resembles the C library s getopt function so it remains useful if you re writing a Python prototype that will eventually be rewritten in C optparse becomes redundant but there are no plans to remove it because there are many scripts still using it and there s no automated way to update these scripts Making the argparse API consistent with optparse s interface was discussed but rejected as too messy and difficult In short if you re writing a new script and don t need to worry about compatibility with earlier versions of Python use argparse instead of optparse Here s an example import argparse parser argparse ArgumentParser description Command line example Add optional switches parser add_argument v action store_true dest is_verbose help produce verbose output parser add_argument o action store dest output metavar FILE help direct output to FILE instead of stdout parser add_argument C action store type int dest context metavar NUM default 0 help display NUM lines of added context Allow any number of addit,en
1298,ional arguments parser add_argument nargs action store dest inputs help input filenames default is stdin args parser parse_args print args __dict__ Unless you override it h and help switches are automatically added and produce neatly formatted output python exe argparse example py help usage argparse example py h v o FILE C NUM inputs inputs Command line example positional arguments inputs input filenames default is stdin optional arguments h help show this help message and exit v produce verbose output o FILE direct output to FILE instead of stdout C NUM display NUM lines of added context As with optparse the command line switches and arguments are returned as an object with attributes named by the dest parameters python exe argparse example py v output None is_verbose True context 0 inputs python exe argparse example py v o tmp output C 4 file1 file2 output tmp output is_verbose True context 4 inputs file1 file2 argparse has much fancier validation than optparse you can specify an exact number of arguments as an integer 0 or more arguments by passing 1 or more by passing or an optional argument with A top level parser can contain sub parsers to define subcommands that have different sets of switches as in svn commit svn checkout etc You can specify an argument s type as FileType which will automatically open files for you and understands that means standard input or output See also argparse documentation The documentation page of the argparse module Upgrading optparse code Part of the Python documentation describing how to convert code that uses optparse PEP 389 argparse New Command Line Parsing Module PEP written and implemented by Steven Bethard PEP 391 Dictionary Based Configuration For Logging The logging module is very flexible applications can define a tree of logging subsystems and each logger in this tree can filter out certain messages format them differently and direct messages to a varying number of handlers All this flexibility can require a lot of configuration You can write Python statements to create objects and set their properties but a complex set up requires verbose but boring code logging also supports a fileConfig function that parses a file but the file format doesn t support configuring filters and it s messier to generate programmatically Python 2 7 adds a dictConfig function that uses a dictionary to configure logging There are many ways to produce a dictionary from different sources construct one with code parse a file containing JSON or use a YAML parsing library if one is installed For more information see Configuration functions The following example configures two loggers the root logger and a logger named network Messages sent to the root logger will be sent to the system log using the syslog protocol and messages to the network logger will be written to a network log file that will be rotated once the log reaches 1MB import logging import logging config configdict version 1 Configuration schema in use must be 1 for now formatters standard format asctime s name 15s levelname 8s message s handlers netlog backupCount 10 class logging handlers RotatingFileHandler filename logs network log formatter standard level INFO maxBytes 1000000 syslog class logging handlers SysLogHandler formatter standard level ERROR Specify all the subordinate loggers loggers network handlers netlog Specify properties of the root logger root handlers syslog Set up configuration logging config dictConfig configdict As an example log two error messages logger logging getLogger logger error Database not found netlogger logging getLogger network netlogger error Connection failed Three smaller enhancements to the logging module all implemented by Vinay Sajip are The SysLogHandler class now supports syslogging over TCP The constructor has a socktype parameter giving the type of socket to use either socket SOCK_DGRAM for UDP or socket SOCK_STREAM for TCP The default protocol remains UDP Logger instances gained a getChild method that retrieves a descendant logger using a relative path For example once you retrieve a logger ,en
1299,by doing log getLogger app calling log getChild network listen is equivalent to getLogger app network listen The LoggerAdapter class gained an isEnabledFor method that takes a level and returns whether the underlying logger would process a message of that level of importance See also PEP 391 Dictionary Based Configuration For Logging PEP written and implemented by Vinay Sajip PEP 3106 Dictionary Views The dictionary methods keys values and items are different in Python 3 x They return an object called a view instead of a fully materialized list It s not possible to change the return values of keys values and items in Python 2 7 because too much code would break Instead the 3 x versions were added under the new names viewkeys viewvalues and viewitems d dict i 10 chr 65 i for i in range 26 d 0 A 130 N 10 B 140 O 20 250 Z d viewkeys dict_keys 0 130 10 140 20 150 30 250 Views can be iterated over but the key and item views also behave like sets The operator performs intersection and performs a union d1 dict i 10 chr 65 i for i in range 26 d2 dict i 5 i for i in range 1000 d1 viewkeys d2 viewkeys set 0 0 10 0 20 0 30 0 d1 viewkeys range 0 30 set 0 1 130 3 4 5 6 120 250 The view keeps track of the dictionary and its contents change as the dictionary is modified vk d viewkeys vk dict_keys 0 130 10 250 d 260 vk dict_keys 0 130 260 10 250 However note that you can t add or remove keys while you re iterating over the view for k in vk d k 2 k Traceback most recent call last File stdin line 1 in module RuntimeError dictionary changed size during iteration You can use the view methods in Python 2 x code and the 2to3 converter will change them to the standard keys values and items methods See also PEP 3106 Revamping dict keys values and items PEP written by Guido van Rossum Backported to 2 7 by Alexandre Vassalotti bpo 1967 PEP 3137 The memoryview Object The memoryview object provides a view of another object s memory content that matches the bytes type s interface import string m memoryview string letters m memory at 0x37f850 len m Returns length of underlying object 52 m 0 m 25 m 26 Indexing returns one byte a z A m2 m 0 26 Slicing returns another memoryview m2 memory at 0x37f080 The content of the view can be converted to a string of bytes or a list of integers m2 tobytes abcdefghijklmnopqrstuvwxyz m2 tolist 97 98 99 100 101 102 103 121 122 memoryview objects allow modifying the underlying object if it s a mutable object m2 0 75 Traceback most recent call last File stdin line 1 in module TypeError cannot modify read only memory b bytearray string letters Creating a mutable object b bytearray b abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ mb memoryview b mb 0 Assign to view changing the bytearray b 0 5 The bytearray has been changed bytearray b bcde See also PEP 3137 Immutable Bytes and Mutable Buffer PEP written by Guido van Rossum Implemented by Travis Oliphant Antoine Pitrou and others Backported to 2 7 by Antoine Pitrou bpo 2396 Other Language Changes Some smaller changes made to the core Python language are The syntax for set literals has been backported from Python 3 x Curly brackets are used to surround the contents of the resulting mutable set set literals are distinguished from dictionaries by not containing colons and values continues to represent an empty dictionary use set for an empty set 1 2 3 4 5 set 1 2 3 4 5 set empty set set empty dict Backported by Alexandre Vassalotti bpo 2335 Dictionary and set comprehensions are another feature backported from 3 x generalizing list generator comprehensions to use the literal syntax for sets and dictionaries x x x for x in range 6 0 0 1 1 2 4 3 9 4 16 5 25 a x for x in range 6 set a aa aaa aaaa aaaaa Backported by Alexandre Vassalotti bpo 2333 The with statement can now use multiple context managers in one statement Context managers are processed from left to right and each one is treated as beginning a new with statement This means that with A as a B as b suite of statements is equivalent to with A as a with B as b suite of statements The contextlib nested function prov,en
1300,ides a very similar function so it s no longer necessary and has been deprecated Proposed in https codereview appspot com 53094 implemented by Georg Brandl Conversions between floating point numbers and strings are now correctly rounded on most platforms These conversions occur in many different places str on floats and complex numbers the float and complex constructors numeric formatting serializing and deserializing floats and complex numbers using the marshal pickle and json modules parsing of float and imaginary literals in Python code and Decimal to float conversion Related to this the repr of a floating point number x now returns a result based on the shortest decimal string that s guaranteed to round back to x under correct rounding with round half to even rounding mode Previously it gave a string based on rounding x to 17 decimal digits The rounding library responsible for this improvement works on Windows and on Unix platforms using the gcc icc or suncc compilers There may be a small number of platforms where correct operation of this code cannot be guaranteed so the code is not used on such systems You can find out which code is being used by checking sys float_repr_style which will be short if the new code is in use and legacy if it isn t Implemented by Eric Smith and Mark Dickinson using David Gay s dtoa c library bpo 7117 Conversions from long integers and regular integers to floating point now round differently returning the floating point number closest to the number This doesn t matter for small integers that can be converted exactly but for large numbers that will unavoidably lose precision Python 2 7 now approximates more closely For example Python 2 6 computed the following n 295147905179352891391 float n 2 9514790517935283e 20 n long float n 65535L Python 2 7 s floating point result is larger but much closer to the true value n 295147905179352891391 float n 2 9514790517935289e 20 n long float n 1L Implemented by Mark Dickinson bpo 3166 Integer division is also more accurate in its rounding behaviours Also implemented by Mark Dickinson bpo 1811 Implicit coercion for complex numbers has been removed the interpreter will no longer ever attempt to call a __coerce__ method on complex objects Removed by Meador Inge and Mark Dickinson bpo 5211 The str format method now supports automatic numbering of the replacement fields This makes using str format more closely resemble using s formatting format 2009 04 Sunday 2009 4 Sunday day format 2009 4 day Sunday 2009 4 Sunday The auto numbering takes the fields from left to right so the first specifier will use the first argument to str format the next specifier will use the next argument and so on You can t mix auto numbering and explicit numbering either number all of your specifier fields or none of them but you can mix auto numbering and named fields as in the second example above Contributed by Eric Smith bpo 5237 Complex numbers now correctly support usage with format and default to being right aligned Specifying a precision or comma separation applies to both the real and imaginary parts of the number but a specified field width and alignment is applied to the whole of the resulting 1 5 3j output Contributed by Eric Smith bpo 1588 and bpo 7988 The F format code now always formats its output using uppercase characters so it will now produce INF and NAN Contributed by Eric Smith bpo 3382 A low level change the object __format__ method now triggers a PendingDeprecationWarning if it s passed a format string because the __format__ method for object converts the object to a string representation and formats that Previously the method silently applied the format string to the string representation but that could hide mistakes in Python code If you re supplying formatting information such as an alignment or precision presumably you re expecting the formatting to be applied in some object specific way Fixed by Eric Smith bpo 7994 The int and long types gained a bit_length method that returns the number of bits necessary to represent its argument in binary n 37 bin n 0,en
1301,b100101 n bit_length 6 n 2 123 1 n bit_length 123 n 1 bit_length 124 Contributed by Fredrik Johansson and Victor Stinner bpo 3439 The import statement will no longer try an absolute import if a relative import e g from os import sep fails This fixes a bug but could possibly break certain import statements that were only working by accident Fixed by Meador Inge bpo 7902 It s now possible for a subclass of the built in unicode type to override the __unicode__ method Implemented by Victor Stinner bpo 1583863 The bytearray type s translate method now accepts None as its first argument Fixed by Georg Brandl bpo 4759 When using classmethod and staticmethod to wrap methods as class or static methods the wrapper object now exposes the wrapped function as their __func__ attribute Contributed by Amaury Forgeot d Arc after a suggestion by George Sakkis bpo 5982 When a restricted set of attributes were set using __slots__ deleting an unset attribute would not raise AttributeError as you would expect Fixed by Benjamin Peterson bpo 7604 Two new encodings are now supported cp720 used primarily for Arabic text and cp858 a variant of CP 850 that adds the euro symbol CP720 contributed by Alexander Belchenko and Amaury Forgeot d Arc in bpo 1616979 CP858 contributed by Tim Hatch in bpo 8016 The file object will now set the filename attribute on the IOError exception when trying to open a directory on POSIX platforms noted by Jan Kaliszewski bpo 4764 and now explicitly checks for and forbids writing to read only file objects instead of trusting the C library to catch and report the error fixed by Stefan Krah bpo 5677 The Python tokenizer now translates line endings itself so the compile built in function now accepts code using any line ending convention Additionally it no longer requires that the code end in a newline Extra parentheses in function definitions are illegal in Python 3 x meaning that you get a syntax error from def f x pass In Python3 warning mode Python 2 7 will now warn about this odd usage Noted by James Lingard bpo 7362 It s now possible to create weak references to old style class objects New style classes were always weak referenceable Fixed by Antoine Pitrou bpo 8268 When a module object is garbage collected the module s dictionary is now only cleared if no one else is holding a reference to the dictionary bpo 7140 Interpreter Changes A new environment variable PYTHONWARNINGS allows controlling warnings It should be set to a string containing warning settings equivalent to those used with the W switch separated by commas Contributed by Brian Curtin bpo 7301 For example the following setting will print warnings every time they occur but turn warnings from the Cookie module into an error The exact syntax for setting an environment variable varies across operating systems and shells export PYTHONWARNINGS all error Cookie 0 Optimizations Several performance enhancements have been added A new opcode was added to perform the initial setup for with statements looking up the __enter__ and __exit__ methods Contributed by Benjamin Peterson The garbage collector now performs better for one common usage pattern when many objects are being allocated without deallocating any of them This would previously take quadratic time for garbage collection but now the number of full garbage collections is reduced as the number of objects on the heap grows The new logic only performs a full garbage collection pass when the middle generation has been collected 10 times and when the number of survivor objects from the middle generation exceeds 10 of the number of objects in the oldest generation Suggested by Martin von Löwis and implemented by Antoine Pitrou bpo 4074 The garbage collector tries to avoid tracking simple containers which can t be part of a cycle In Python 2 7 this is now true for tuples and dicts containing atomic types such as ints strings etc Transitively a dict containing tuples of atomic types won t be tracked either This helps reduce the cost of each garbage collection by decreasing the number of objects to be considered and tr,en
1302,aversed by the collector Contributed by Antoine Pitrou bpo 4688 Long integers are now stored internally either in base 2 15 or in base 2 30 the base being determined at build time Previously they were always stored in base 2 15 Using base 2 30 gives significant performance improvements on 64 bit machines but benchmark results on 32 bit machines have been mixed Therefore the default is to use base 2 30 on 64 bit machines and base 2 15 on 32 bit machines on Unix there s a new configure option enable big digits that can be used to override this default Apart from the performance improvements this change should be invisible to end users with one exception for testing and debugging purposes there s a new structseq sys long_info that provides information about the internal format giving the number of bits per digit and the size in bytes of the C type used to store each digit import sys sys long_info sys long_info bits_per_digit 30 sizeof_digit 4 Contributed by Mark Dickinson bpo 4258 Another set of changes made long objects a few bytes smaller 2 bytes smaller on 32 bit systems and 6 bytes on 64 bit Contributed by Mark Dickinson bpo 5260 The division algorithm for long integers has been made faster by tightening the inner loop doing shifts instead of multiplications and fixing an unnecessary extra iteration Various benchmarks show speedups of between 50 and 150 for long integer divisions and modulo operations Contributed by Mark Dickinson bpo 5512 Bitwise operations are also significantly faster initial patch by Gregory Smith bpo 1087418 The implementation of checks for the left side operand being a Python string and special cases it this results in a 1 3 performance increase for applications that frequently use with strings such as templating libraries Implemented by Collin Winter bpo 5176 List comprehensions with an if condition are compiled into faster bytecode Patch by Antoine Pitrou back ported to 2 7 by Jeffrey Yasskin bpo 4715 Converting an integer or long integer to a decimal string was made faster by special casing base 10 instead of using a generalized conversion function that supports arbitrary bases Patch by Gawain Bolton bpo 6713 The split replace rindex rpartition and rsplit methods of string like types strings Unicode strings and bytearray objects now use a fast reverse search algorithm instead of a character by character scan This is sometimes faster by a factor of 10 Added by Florent Xicluna bpo 7462 and bpo 7622 The pickle and cPickle modules now automatically intern the strings used for attribute names reducing memory usage of the objects resulting from unpickling Contributed by Jake McGuire bpo 5084 The cPickle module now special cases dictionaries nearly halving the time required to pickle them Contributed by Collin Winter bpo 5670 New and Improved Modules As in every release Python s standard library received a number of enhancements and bug fixes Here s a partial list of the most notable changes sorted alphabetically by module name Consult the Misc NEWS file in the source tree for a more complete list of changes or look through the Subversion logs for all the details The bdb module s base debugging class Bdb gained a feature for skipping modules The constructor now takes an iterable containing glob style patterns such as django the debugger will not step into stack frames from a module that matches one of these patterns Contributed by Maru Newby after a suggestion by Senthil Kumaran bpo 5142 The binascii module now supports the buffer API so it can be used with memoryview instances and other similar buffer objects Backported from 3 x by Florent Xicluna bpo 7703 Updated module the bsddb module has been updated from 4 7 2devel9 to version 4 8 4 of the pybsddb package The new version features better Python 3 x compatibility various bug fixes and adds several new BerkeleyDB flags and methods Updated by Jesús Cea Avión bpo 8156 The pybsddb changelog can be read at https hg jcea es pybsddb file tip ChangeLog The bz2 module s BZ2File now supports the context management protocol so you can write with bz2 BZ2File ,en
1303,as f Contributed by Hagen Fürstenau bpo 3860 New class the Counter class in the collections module is useful for tallying data Counter instances behave mostly like dictionaries but return zero for missing keys instead of raising a KeyError from collections import Counter c Counter for letter in here is a sample of english text c letter 1 c Counter 6 e 5 s 3 a 2 i 2 h 2 l 2 t 2 g 1 f 1 m 1 o 1 n 1 p 1 r 1 x 1 c e 5 c z 0 There are three additional Counter methods most_common returns the N most common elements and their counts elements returns an iterator over the contained elements repeating each element as many times as its count subtract takes an iterable and subtracts one for each element instead of adding if the argument is a dictionary or another Counter the counts are subtracted c most_common 5 6 e 5 s 3 a 2 i 2 c elements a a e e e e e g f i i h h m l l o n p s s s r t t x c e 5 c subtract very heavy on the letter e c e Count is now lower 1 Contributed by Raymond Hettinger bpo 1696199 New class OrderedDict is described in the earlier section PEP 372 Adding an Ordered Dictionary to collections New method The deque data type now has a count method that returns the number of contained elements equal to the supplied argument x and a reverse method that reverses the elements of the deque in place deque also exposes its maximum length as the read only maxlen attribute Both features added by Raymond Hettinger The namedtuple class now has an optional rename parameter If rename is true field names that are invalid because they ve been repeated or aren t legal Python identifiers will be renamed to legal names that are derived from the field s position within the list of fields from collections import namedtuple T namedtuple T field1 illegal for field2 rename True T _fields field1 _1 _2 field2 Added by Raymond Hettinger bpo 1818 Finally the Mapping abstract base class now returns NotImplemented if a mapping is compared to another type that isn t a Mapping Fixed by Daniel Stutzbach bpo 8729 Constructors for the parsing classes in the ConfigParser module now take an allow_no_value parameter defaulting to false if true options without values will be allowed For example import ConfigParser StringIO sample_config mysqld user mysql pid file var run mysqld mysqld pid skip bdb config ConfigParser RawConfigParser allow_no_value True config readfp StringIO StringIO sample_config config get mysqld user mysql print config get mysqld skip bdb None print config get mysqld unknown Traceback most recent call last NoOptionError No option unknown in section mysqld Contributed by Mats Kindahl bpo 7005 Deprecated function contextlib nested which allows handling more than one context manager with a single with statement has been deprecated because the with statement now supports multiple context managers The cookielib module now ignores cookies that have an invalid version field one that doesn t contain an integer value Fixed by John J Lee bpo 3924 The copy module s deepcopy function will now correctly copy bound instance methods Implemented by Robert Collins bpo 1515 The ctypes module now always converts None to a C NULL pointer for arguments declared as pointers Changed by Thomas Heller bpo 4606 The underlying libffi library has been updated to version 3 0 9 containing various fixes for different platforms Updated by Matthias Klose bpo 8142 New method the datetime module s timedelta class gained a total_seconds method that returns the number of seconds in the duration Contributed by Brian Quinlan bpo 5788 New method the Decimal class gained a from_float class method that performs an exact conversion of a floating point number to a Decimal This exact conversion strives for the closest decimal approximation to the floating point representation s value the resulting decimal value will therefore still include the inaccuracy if any For example Decimal from_float 0 1 returns Decimal 0 1000000000000000055511151231257827021181583404541015625 Implemented by Raymond Hettinger bpo 4796 Comparing instances of Decimal with floating point numbers now produce,en
1304,s sensible results based on the numeric values of the operands Previously such comparisons would fall back to Python s default rules for comparing objects which produced arbitrary results based on their type Note that you still cannot combine Decimal and floating point in other operations such as addition since you should be explicitly choosing how to convert between float and Decimal Fixed by Mark Dickinson bpo 2531 The constructor for Decimal now accepts floating point numbers added by Raymond Hettinger bpo 8257 and non European Unicode characters such as Arabic Indic digits contributed by Mark Dickinson bpo 6595 Most of the methods of the Context class now accept integers as well as Decimal instances the only exceptions are the canonical and is_canonical methods Patch by Juan José Conti bpo 7633 When using Decimal instances with a string s format method the default alignment was previously left alignment This has been changed to right alignment which is more sensible for numeric types Changed by Mark Dickinson bpo 6857 Comparisons involving a signaling NaN value or sNAN now signal InvalidOperation instead of silently returning a true or false value depending on the comparison operator Quiet NaN values or NaN are now hashable Fixed by Mark Dickinson bpo 7279 The difflib module now produces output that is more compatible with modern diff patch tools through one small change using a tab character instead of spaces as a separator in the header giving the filename Fixed by Anatoly Techtonik bpo 7585 The Distutils sdist command now always regenerates the MANIFEST file since even if the MANIFEST in or setup py files haven t been modified the user might have created some new files that should be included Fixed by Tarek Ziadé bpo 8688 The doctest module s IGNORE_EXCEPTION_DETAIL flag will now ignore the name of the module containing the exception being tested Patch by Lennart Regebro bpo 7490 The email module s Message class will now accept a Unicode valued payload automatically converting the payload to the encoding specified by output_charset Added by R David Murray bpo 1368247 The Fraction class now accepts a single float or Decimal instance or two rational numbers as arguments to its constructor Implemented by Mark Dickinson rationals added in bpo 5812 and float decimal in bpo 8294 Ordering comparisons between fractions and complex numbers now raise a TypeError This fixes an oversight making the Fraction match the other numeric types New class FTP_TLS in the ftplib module provides secure FTP connections using TLS encapsulation of authentication as well as subsequent control and data transfers Contributed by Giampaolo Rodola bpo 2054 The storbinary method for binary uploads can now restart uploads thanks to an added rest parameter patch by Pablo Mouzo bpo 6845 New class decorator total_ordering in the functools module takes a class that defines an __eq__ method and one of __lt__ __le__ __gt__ or __ge__ and generates the missing comparison methods Since the __cmp__ method is being deprecated in Python 3 x this decorator makes it easier to define ordered classes Added by Raymond Hettinger bpo 5479 New function cmp_to_key will take an old style comparison function that expects two arguments and return a new callable that can be used as the key parameter to functions such as sorted min and max etc The primary intended use is to help with making code compatible with Python 3 x Added by Raymond Hettinger New function the gc module s is_tracked returns true if a given instance is tracked by the garbage collector false otherwise Contributed by Antoine Pitrou bpo 4688 The gzip module s GzipFile now supports the context management protocol so you can write with gzip GzipFile as f contributed by Hagen Fürstenau bpo 3860 and it now implements the io BufferedIOBase ABC so you can wrap it with io BufferedReader for faster processing contributed by Nir Aides bpo 7471 It s also now possible to override the modification time recorded in a gzipped file by providing an optional timestamp to the constructor Contributed by Jacques Frechet bpo 4,en
1305,272 Files in gzip format can be padded with trailing zero bytes the gzip module will now consume these trailing bytes Fixed by Tadek Pietraszek and Brian Curtin bpo 2846 New attribute the hashlib module now has an algorithms attribute containing a tuple naming the supported algorithms In Python 2 7 hashlib algorithms contains md5 sha1 sha224 sha256 sha384 sha512 Contributed by Carl Chenet bpo 7418 The default HTTPResponse class used by the httplib module now supports buffering resulting in much faster reading of HTTP responses Contributed by Kristján Valur Jónsson bpo 4879 The HTTPConnection and HTTPSConnection classes now support a source_address parameter a host port 2 tuple giving the source address that will be used for the connection Contributed by Eldon Ziegler bpo 3972 The ihooks module now supports relative imports Note that ihooks is an older module for customizing imports superseded by the imputil module added in Python 2 0 Relative import support added by Neil Schemenauer The imaplib module now supports IPv6 addresses Contributed by Derek Morr bpo 1655 New function the inspect module s getcallargs takes a callable and its positional and keyword arguments and figures out which of the callable s parameters will receive each argument returning a dictionary mapping argument names to their values For example from inspect import getcallargs def f a b 1 pos named pass getcallargs f 1 2 3 a 1 b 2 pos 3 named getcallargs f a 2 x 4 a 2 b 1 pos named x 4 getcallargs f Traceback most recent call last TypeError f takes at least 1 argument 0 given Contributed by George Sakkis bpo 3135 Updated module The io library has been upgraded to the version shipped with Python 3 1 For 3 1 the I O library was entirely rewritten in C and is 2 to 20 times faster depending on the task being performed The original Python version was renamed to the _pyio module One minor resulting change the io TextIOBase class now has an errors attribute giving the error setting used for encoding and decoding errors one of strict replace ignore The io FileIO class now raises an OSError when passed an invalid file descriptor Implemented by Benjamin Peterson bpo 4991 The truncate method now preserves the file position previously it would change the file position to the end of the new file Fixed by Pascal Chambon bpo 6939 New function itertools compress data selectors takes two iterators Elements of data are returned if the corresponding value in selectors is true itertools compress ABCDEF 1 0 1 0 1 1 A C E F New function itertools combinations_with_replacement iter r returns all the possible r length combinations of elements from the iterable iter Unlike combinations individual elements can be repeated in the generated combinations itertools combinations_with_replacement abc 2 a a a b a c b b b c c c Note that elements are treated as unique depending on their position in the input not their actual values The itertools count function now has a step argument that allows incrementing by values other than 1 count also now allows keyword arguments and using non integer values such as floats or Decimal instances Implemented by Raymond Hettinger bpo 5032 itertools combinations and itertools product previously raised ValueError for values of r larger than the input iterable This was deemed a specification error so they now return an empty iterator Fixed by Raymond Hettinger bpo 4816 Updated module The json module was upgraded to version 2 0 9 of the simplejson package which includes a C extension that makes encoding and decoding faster Contributed by Bob Ippolito bpo 4136 To support the new collections OrderedDict type json load now has an optional object_pairs_hook parameter that will be called with any object literal that decodes to a list of pairs Contributed by Raymond Hettinger bpo 5381 The mailbox module s Maildir class now records the timestamp on the directories it reads and only re reads them if the modification time has subsequently changed This improves performance by avoiding unneeded directory scans Fixed by A M Kuchling and Antoine Pitrou bpo 1607951 b,en
1306,po 6896 New functions the math module gained erf and erfc for the error function and the complementary error function expm1 which computes e x 1 with more precision than using exp and subtracting 1 gamma for the Gamma function and lgamma for the natural log of the Gamma function Contributed by Mark Dickinson and nirinA raseliarison bpo 3366 The multiprocessing module s Manager classes can now be passed a callable that will be called whenever a subprocess is started along with a set of arguments that will be passed to the callable Contributed by lekma bpo 5585 The Pool class which controls a pool of worker processes now has an optional maxtasksperchild parameter Worker processes will perform the specified number of tasks and then exit causing the Pool to start a new worker This is useful if tasks may leak memory or other resources or if some tasks will cause the worker to become very large Contributed by Charles Cazabon bpo 6963 The nntplib module now supports IPv6 addresses Contributed by Derek Morr bpo 1664 New functions the os module wraps the following POSIX system calls getresgid and getresuid which return the real effective and saved GIDs and UIDs setresgid and setresuid which set real effective and saved GIDs and UIDs to new values initgroups which initialize the group access list for the current process GID UID functions contributed by Travis H bpo 6508 Support for initgroups added by Jean Paul Calderone bpo 7333 The os fork function now re initializes the import lock in the child process this fixes problems on Solaris when fork is called from a thread Fixed by Zsolt Cserna bpo 7242 In the os path module the normpath and abspath functions now preserve Unicode if their input path is a Unicode string the return value is also a Unicode string normpath fixed by Matt Giuca in bpo 5827 abspath fixed by Ezio Melotti in bpo 3426 The pydoc module now has help for the various symbols that Python uses You can now do help or help for example Contributed by David Laban bpo 4739 The re module s split sub and subn now accept an optional flags argument for consistency with the other functions in the module Added by Gregory P Smith New function run_path in the runpy module will execute the code at a provided path argument path can be the path of a Python source file example py a compiled bytecode file example pyc a directory package or a zip archive example zip If a directory or zip path is provided it will be added to the front of sys path and the module __main__ will be imported It s expected that the directory or zip contains a __main__ py if it doesn t some other __main__ py might be imported from a location later in sys path This makes more of the machinery of runpy available to scripts that want to mimic the way Python s command line processes an explicit path name Added by Nick Coghlan bpo 6816 New function in the shutil module make_archive takes a filename archive type zip or tar format and a directory path and creates an archive containing the directory s contents Added by Tarek Ziadé shutil s copyfile and copytree functions now raise a SpecialFileError exception when asked to copy a named pipe Previously the code would treat named pipes like a regular file by opening them for reading and this would block indefinitely Fixed by Antoine Pitrou bpo 3002 The signal module no longer re installs the signal handler unless this is truly necessary which fixes a bug that could make it impossible to catch the EINTR signal robustly Fixed by Charles Francois Natali bpo 8354 New functions in the site module three new functions return various site and user specific paths getsitepackages returns a list containing all global site packages directories getusersitepackages returns the path of the user s site packages directory and getuserbase returns the value of the USER_BASE environment variable giving the path to a directory that can be used to store data Contributed by Tarek Ziadé bpo 6693 The site module now reports exceptions occurring when the sitecustomize module is imported and will no longer catch and swallow the KeyboardInterrupt ,en
1307,exception Fixed by Victor Stinner bpo 3137 The create_connection function gained a source_address parameter a host port 2 tuple giving the source address that will be used for the connection Contributed by Eldon Ziegler bpo 3972 The recv_into and recvfrom_into methods will now write into objects that support the buffer API most usefully the bytearray and memoryview objects Implemented by Antoine Pitrou bpo 8104 The SocketServer module s TCPServer class now supports socket timeouts and disabling the Nagle algorithm The disable_nagle_algorithm class attribute defaults to False if overridden to be true new request connections will have the TCP_NODELAY option set to prevent buffering many small sends into a single TCP packet The timeout class attribute can hold a timeout in seconds that will be applied to the request socket if no request is received within that time handle_timeout will be called and handle_request will return Contributed by Kristján Valur Jónsson bpo 6192 and bpo 6267 Updated module the sqlite3 module has been updated to version 2 6 0 of the pysqlite package Version 2 6 0 includes a number of bugfixes and adds the ability to load SQLite extensions from shared libraries Call the enable_load_extension True method to enable extensions and then call load_extension to load a particular shared library Updated by Gerhard Häring The ssl module s SSLSocket objects now support the buffer API which fixed a test suite failure fix by Antoine Pitrou bpo 7133 and automatically set OpenSSL s SSL_MODE_AUTO_RETRY which will prevent an error code being returned from recv operations that trigger an SSL renegotiation fix by Antoine Pitrou bpo 8222 The wrap_socket constructor function now takes a ciphers argument that s a string listing the encryption algorithms to be allowed the format of the string is described in the OpenSSL documentation Added by Antoine Pitrou bpo 8322 Another change makes the extension load all of OpenSSL s ciphers and digest algorithms so that they re all available Some SSL certificates couldn t be verified reporting an unknown algorithm error Reported by Beda Kosata and fixed by Antoine Pitrou bpo 8484 The version of OpenSSL being used is now available as the module attributes ssl OPENSSL_VERSION a string ssl OPENSSL_VERSION_INFO a 5 tuple and ssl OPENSSL_VERSION_NUMBER an integer Added by Antoine Pitrou bpo 8321 The struct module will no longer silently ignore overflow errors when a value is too large for a particular integer format code one of bBhHiIlLqQ it now always raises a struct error exception Changed by Mark Dickinson bpo 1523 The pack function will also attempt to use __index__ to convert and pack non integers before trying the __int__ method or reporting an error Changed by Mark Dickinson bpo 8300 New function the subprocess module s check_output runs a command with a specified set of arguments and returns the command s output as a string when the command runs without error or raises a CalledProcessError exception otherwise subprocess check_output df h Filesystem Size Used Avail Capacity Mounted on n dev disk0s2 52G 49G 3 0G 94 n subprocess check_output df h bogus subprocess CalledProcessError Command df h bogus returned non zero exit status 1 Contributed by Gregory P Smith The subprocess module will now retry its internal system calls on receiving an EINTR signal Reported by several people final patch by Gregory P Smith in bpo 1068268 New function is_declared_global in the symtable module returns true for variables that are explicitly declared to be global false for ones that are implicitly global Contributed by Jeremy Hylton The syslog module will now use the value of sys argv 0 as the identifier instead of the previous default value of python Changed by Sean Reifschneider bpo 8451 The sys version_info value is now a named tuple with attributes named major minor micro releaselevel and serial Contributed by Ross Light bpo 4285 sys getwindowsversion also returns a named tuple with attributes named major minor build platform service_pack service_pack_major service_pack_minor suite_mask and produ,en
1308,ct_type Contributed by Brian Curtin bpo 7766 The tarfile module s default error handling has changed to no longer suppress fatal errors The default error level was previously 0 which meant that errors would only result in a message being written to the debug log but because the debug log is not activated by default these errors go unnoticed The default error level is now 1 which raises an exception if there s an error Changed by Lars Gustäbel bpo 7357 tarfile now supports filtering the TarInfo objects being added to a tar file When you call add you may supply an optional filter argument that s a callable The filter callable will be passed the TarInfo for every file being added and can modify and return it If the callable returns None the file will be excluded from the resulting archive This is more powerful than the existing exclude argument which has therefore been deprecated Added by Lars Gustäbel bpo 6856 The TarFile class also now supports the context management protocol Added by Lars Gustäbel bpo 7232 The wait method of the threading Event class now returns the internal flag on exit This means the method will usually return true because wait is supposed to block until the internal flag becomes true The return value will only be false if a timeout was provided and the operation timed out Contributed by Tim Lesher bpo 1674032 The Unicode database provided by the unicodedata module is now used internally to determine which characters are numeric whitespace or represent line breaks The database also includes information from the Unihan txt data file patch by Anders Chrigström and Amaury Forgeot d Arc bpo 1571184 and has been updated to version 5 2 0 updated by Florent Xicluna bpo 8024 The urlparse module s urlsplit now handles unknown URL schemes in a fashion compliant with RFC 3986 if the URL is of the form something the text before the is treated as the scheme even if it s a made up scheme that the module doesn t know about This change may break code that worked around the old behaviour For example Python 2 6 4 or 2 5 will return the following import urlparse urlparse urlsplit invented host filename query invented host filename query Python 2 7 and Python 2 6 5 will return import urlparse urlparse urlsplit invented host filename query invented host filename query Python 2 7 actually produces slightly different output since it returns a named tuple instead of a standard tuple The urlparse module also supports IPv6 literal addresses as defined by RFC 2732 contributed by Senthil Kumaran bpo 2987 urlparse urlparse http 1080 8 800 200C 417A foo ParseResult scheme http netloc 1080 8 800 200C 417A path foo params query fragment New class the WeakSet class in the weakref module is a set that only holds weak references to its elements elements will be removed once there are no references pointing to them Originally implemented in Python 3 x by Raymond Hettinger and backported to 2 7 by Michael Foord The xml etree ElementTree library no longer escapes ampersands and angle brackets when outputting an XML processing instruction which looks like xml stylesheet href style1 or comment which looks like comment Patch by Neil Muller bpo 2746 The XML RPC client and server provided by the xmlrpclib and SimpleXMLRPCServer modules have improved performance by supporting HTTP 1 1 keep alive and by optionally using gzip encoding to compress the XML being exchanged The gzip compression is controlled by the encode_threshold attribute of SimpleXMLRPCRequestHandler which contains a size in bytes responses larger than this will be compressed Contributed by Kristján Valur Jónsson bpo 6267 The zipfile module s ZipFile now supports the context management protocol so you can write with zipfile ZipFile as f Contributed by Brian Curtin bpo 5511 zipfile now also supports archiving empty directories and extracts them correctly Fixed by Kuba Wieczorek bpo 4710 Reading files out of an archive is faster and interleaving read and readline now works correctly Contributed by Nir Aides bpo 7610 The is_zipfile function now accepts a file object in addition to th,en
1309,e path names accepted in earlier versions Contributed by Gabriel Genellina bpo 4756 The writestr method now has an optional compress_type parameter that lets you override the default compression method specified in the ZipFile constructor Contributed by Ronald Oussoren bpo 6003 New module importlib Python 3 1 includes the importlib package a re implementation of the logic underlying Python s import statement importlib is useful for implementors of Python interpreters and to users who wish to write new importers that can participate in the import process Python 2 7 doesn t contain the complete importlib package but instead has a tiny subset that contains a single function import_module import_module name package None imports a module name is a string containing the module or package s name It s possible to do relative imports by providing a string that begins with a character such as utils errors For relative imports the package argument must be provided and is the name of the package that will be used as the anchor for the relative import import_module both inserts the imported module into sys modules and returns the module object Here are some examples from importlib import import_module anydbm import_module anydbm Standard absolute import anydbm module anydbm from p python Lib anydbm py Relative import file_util import_module file_util distutils command file_util module distutils file_util from python Lib distutils file_util pyc importlib was implemented by Brett Cannon and introduced in Python 3 1 New module sysconfig The sysconfig module has been pulled out of the Distutils package becoming a new top level module in its own right sysconfig provides functions for getting information about Python s build process compiler switches installation paths the platform name and whether Python is running from its source directory Some of the functions in the module are get_config_var returns variables from Python s Makefile and the pyconfig h file get_config_vars returns a dictionary containing all of the configuration variables get_path returns the configured path for a particular type of module the standard library site specific modules platform specific modules etc is_python_build returns true if you re running a binary from a Python source tree and false otherwise Consult the sysconfig documentation for more details and for a complete list of functions The Distutils package and sysconfig are now maintained by Tarek Ziadé who has also started a Distutils2 package source repository at https hg python org distutils2 for developing a next generation version of Distutils ttk Themed Widgets for Tk Tcl Tk 8 5 includes a set of themed widgets that re implement basic Tk widgets but have a more customizable appearance and can therefore more closely resemble the native platform s widgets This widget set was originally called Tile but was renamed to Ttk for themed Tk on being added to Tcl Tck release 8 5 To learn more read the ttk module documentation You may also wish to read the Tcl Tk manual page describing the Ttk theme engine available at https www tcl tk man tcl8 5 TkCmd ttk_intro html Some screenshots of the Python Ttk code in use are at https code google com archive p python ttk wikis Screenshots wiki The tkinter ttk module was written by Guilherme Polo and added in bpo 2983 An alternate version called Tile py written by Martin Franklin and maintained by Kevin Walzer was proposed for inclusion in bpo 2618 but the authors argued that Guilherme Polo s work was more comprehensive Updated module unittest The unittest module was greatly enhanced many new features were added Most of these features were implemented by Michael Foord unless otherwise noted The enhanced version of the module is downloadable separately for use with Python versions 2 4 to 2 6 packaged as the unittest2 package from https pypi org project unittest2 When used from the command line the module can automatically discover tests It s not as fancy as py test or nose but provides a simple way to run tests kept within a set of package directories For example the foll,en
1310,owing command will search the test subdirectory for any importable test files named test py python m unittest discover s test Consult the unittest module documentation for more details Developed in bpo 6001 The main function supports some other new options b or buffer will buffer the standard output and standard error streams during each test If the test passes any resulting output will be discarded on failure the buffered output will be displayed c or catch will cause the control C interrupt to be handled more gracefully Instead of interrupting the test process immediately the currently running test will be completed and then the partial results up to the interruption will be reported If you re impatient a second press of control C will cause an immediate interruption This control C handler tries to avoid causing problems when the code being tested or the tests being run have defined a signal handler of their own by noticing that a signal handler was already set and calling it If this doesn t work for you there s a removeHandler decorator that can be used to mark tests that should have the control C handling disabled f or failfast makes test execution stop immediately when a test fails instead of continuing to execute further tests Suggested by Cliff Dyer and implemented by Michael Foord bpo 8074 The progress messages now show x for expected failures and u for unexpected successes when run in verbose mode Contributed by Benjamin Peterson Test cases can raise the SkipTest exception to skip a test bpo 1034053 The error messages for assertEqual assertTrue and assertFalse failures now provide more information If you set the longMessage attribute of your TestCase classes to true both the standard error message and any additional message you provide will be printed for failures Added by Michael Foord bpo 5663 The assertRaises method now returns a context handler when called without providing a callable object to run For example you can write this with self assertRaises KeyError foo Implemented by Antoine Pitrou bpo 4444 Module and class level setup and teardown fixtures are now supported Modules can contain setUpModule and tearDownModule functions Classes can have setUpClass and tearDownClass methods that must be defined as class methods using classmethod or equivalent These functions and methods are invoked when the test runner switches to a test case in a different module or class The methods addCleanup and doCleanups were added addCleanup lets you add cleanup functions that will be called unconditionally after setUp if setUp fails otherwise after tearDown This allows for much simpler resource allocation and deallocation during tests bpo 5679 A number of new methods were added that provide more specialized tests Many of these methods were written by Google engineers for use in their test suites Gregory P Smith Michael Foord and GvR worked on merging them into Python s version of unittest assertIsNone and assertIsNotNone take one expression and verify that the result is or is not None assertIs and assertIsNot take two values and check whether the two values evaluate to the same object or not Added by Michael Foord bpo 2578 assertIsInstance and assertNotIsInstance check whether the resulting object is an instance of a particular class or of one of a tuple of classes Added by Georg Brandl bpo 7031 assertGreater assertGreaterEqual assertLess and assertLessEqual compare two quantities assertMultiLineEqual compares two strings and if they re not equal displays a helpful comparison that highlights the differences in the two strings This comparison is now used by default when Unicode strings are compared with assertEqual assertRegexpMatches and assertNotRegexpMatches checks whether the first argument is a string matching or not matching the regular expression provided as the second argument bpo 8038 assertRaisesRegexp checks whether a particular exception is raised and then also checks that the string representation of the exception matches the provided regular expression assertIn and assertNotIn tests whether first is or is not in,en
1311, second assertItemsEqual tests whether two provided sequences contain the same elements assertSetEqual compares whether two sets are equal and only reports the differences between the sets in case of error Similarly assertListEqual and assertTupleEqual compare the specified types and explain any differences without necessarily printing their full values these methods are now used by default when comparing lists and tuples using assertEqual More generally assertSequenceEqual compares two sequences and can optionally check whether both sequences are of a particular type assertDictEqual compares two dictionaries and reports the differences it s now used by default when you compare two dictionaries using assertEqual assertDictContainsSubset checks whether all of the key value pairs in first are found in second assertAlmostEqual and assertNotAlmostEqual test whether first and second are approximately equal This method can either round their difference to an optionally specified number of places the default is 7 and compare it to zero or require the difference to be smaller than a supplied delta value loadTestsFromName properly honors the suiteClass attribute of the TestLoader Fixed by Mark Roddy bpo 6866 A new hook lets you extend the assertEqual method to handle new data types The addTypeEqualityFunc method takes a type object and a function The function will be used when both of the objects being compared are of the specified type This function should compare the two objects and raise an exception if they don t match it s a good idea for the function to provide additional information about why the two objects aren t matching much as the new sequence comparison methods do unittest main now takes an optional exit argument If false main doesn t call sys exit allowing main to be used from the interactive interpreter Contributed by J Pablo Fernández bpo 3379 TestResult has new startTestRun and stopTestRun methods that are called immediately before and after a test run Contributed by Robert Collins bpo 5728 With all these changes the unittest py was becoming awkwardly large so the module was turned into a package and the code split into several files by Benjamin Peterson This doesn t affect how the module is imported or used See also https web archive org web 20210619163128 http www voidspace org uk python articles unittest2 shtml Describes the new features how to use them and the rationale for various design decisions By Michael Foord Updated module ElementTree 1 3 The version of the ElementTree library included with Python was updated to version 1 3 Some of the new features are The various parsing functions now take a parser keyword argument giving an XMLParser instance that will be used This makes it possible to override the file s internal encoding p ET XMLParser encoding utf 8 t ET XML root parser p Errors in parsing XML now raise a ParseError exception whose instances have a position attribute containing a line column tuple giving the location of the problem ElementTree s code for converting trees to a string has been significantly reworked making it roughly twice as fast in many cases The ElementTree write and Element write methods now have a method parameter that can be xml the default html or text HTML mode will output empty elements as empty empty instead of empty and text mode will skip over elements and only output the text chunks If you set the tag attribute of an element to None but leave its children in place the element will be omitted when the tree is written out so you don t need to do more extensive rearrangement to remove a single element Namespace handling has also been improved All xmlns whatever declarations are now output on the root element not scattered throughout the resulting XML You can set the default namespace for a tree by setting the default_namespace attribute and can register new prefixes with register_namespace In XML mode you can use the true false xml_declaration parameter to suppress the XML declaration New Element method extend appends the items from a sequence to the element s children Ele,en
1312,ments themselves behave like sequences so it s easy to move children from one element to another from xml etree import ElementTree as ET t ET XML list item 1 item item 2 item item 3 item list new ET XML root new extend t Outputs root item 1 item root print ET tostring new New Element method iter yields the children of the element as a generator It s also possible to write for child in elem to loop over an element s children The existing method getiterator is now deprecated as is getchildren which constructs and returns a list of children New Element method itertext yields all chunks of text that are descendants of the element For example t ET XML list item 1 item item 2 item item 3 item list Outputs n 1 2 3 n print list t itertext Deprecated using an element as a Boolean i e if elem would return true if the element had any children or false if there were no children This behaviour is confusing None is false but so is a childless element so it will now trigger a FutureWarning In your code you should be explicit write len elem 0 if you re interested in the number of children or elem is not None Fredrik Lundh develops ElementTree and produced the 1 3 version you can read his article describing 1 3 at https web archive org web 20 200703234532 http effbot org zone elementtree 13 intro htm Florent Xicluna updated the version included with Python after discussions on python dev and in bpo 6472 Build and C API Changes Changes to Python s build process and to the C API include The latest release of the GNU Debugger GDB 7 can be scripted using Python When you begin debugging an executable program P GDB will look for a file named P gdb py and automatically read it Dave Malcolm contributed a python gdb py that adds a number of commands useful when debugging Python itself For example py up and py down go up or down one Python stack frame which usually corresponds to several C stack frames py print prints the value of a Python variable and py bt prints the Python stack trace Added as a result of bpo 8032 If you use the gdbinit file provided with Python the pyo macro in the 2 7 version now works correctly when the thread being debugged doesn t hold the GIL the macro now acquires it before printing Contributed by Victor Stinner bpo 3632 Py_AddPendingCall is now thread safe letting any worker thread submit notifications to the main Python thread This is particularly useful for asynchronous IO operations Contributed by Kristján Valur Jónsson bpo 4293 New function PyCode_NewEmpty creates an empty code object only the filename function name and first line number are required This is useful for extension modules that are attempting to construct a more useful traceback stack Previously such extensions needed to call PyCode_New which had many more arguments Added by Jeffrey Yasskin New function PyErr_NewExceptionWithDoc creates a new exception class just as the existing PyErr_NewException does but takes an extra char argument containing the docstring for the new exception class Added by lekma on the Python bug tracker bpo 7033 New function PyFrame_GetLineNumber takes a frame object and returns the line number that the frame is currently executing Previously code would need to get the index of the bytecode instruction currently executing and then look up the line number corresponding to that address Added by Jeffrey Yasskin New functions PyLong_AsLongAndOverflow and PyLong_AsLongLongAndOverflow approximates a Python long integer as a C long or long long If the number is too large to fit into the output type an overflow flag is set and returned to the caller Contributed by Case Van Horsen bpo 7528 and bpo 7767 New function stemming from the rewrite of string to float conversion a new PyOS_string_to_double function was added The old PyOS_ascii_strtod and PyOS_ascii_atof functions are now deprecated New function PySys_SetArgvEx sets the value of sys argv and can optionally update sys path to include the directory containing the script named by sys argv 0 depending on the value of an updatepath parameter This function was added to close a security ,en
1313,hole for applications that embed Python The old function PySys_SetArgv would always update sys path and sometimes it would add the current directory This meant that if you ran an application embedding Python in a directory controlled by someone else attackers could put a Trojan horse module in the directory say a file named os py that your application would then import and run If you maintain a C C application that embeds Python check whether you re calling PySys_SetArgv and carefully consider whether the application should be using PySys_SetArgvEx with updatepath set to false Security issue reported as CVE 2008 5983 discussed in bpo 5753 and fixed by Antoine Pitrou New macros the Python header files now define the following macros Py_ISALNUM Py_ISALPHA Py_ISDIGIT Py_ISLOWER Py_ISSPACE Py_ISUPPER Py_ISXDIGIT Py_TOLOWER and Py_TOUPPER All of these functions are analogous to the C standard macros for classifying characters but ignore the current locale setting because in several places Python needs to analyze characters in a locale independent way Added by Eric Smith bpo 5793 Removed function PyEval_CallObject is now only available as a macro A function version was being kept around to preserve ABI linking compatibility but that was in 1997 it can certainly be deleted by now Removed by Antoine Pitrou bpo 8276 New format codes the PyString_FromFormat PyString_FromFormatV and PyErr_Format functions now accept lld and llu format codes for displaying C s long long types Contributed by Mark Dickinson bpo 7228 The complicated interaction between threads and process forking has been changed Previously the child process created by os fork might fail because the child is created with only a single thread running the thread performing the os fork If other threads were holding a lock such as Python s import lock when the fork was performed the lock would still be marked as held in the new process But in the child process nothing would ever release the lock since the other threads weren t replicated and the child process would no longer be able to perform imports Python 2 7 acquires the import lock before performing an os fork and will also clean up any locks created using the threading module C extension modules that have internal locks or that call fork themselves will not benefit from this clean up Fixed by Thomas Wouters bpo 1590864 The Py_Finalize function now calls the internal threading _shutdown function this prevents some exceptions from being raised when an interpreter shuts down Patch by Adam Olsen bpo 1722344 When using the PyMemberDef structure to define attributes of a type Python will no longer let you try to delete or set a T_STRING_INPLACE attribute Global symbols defined by the ctypes module are now prefixed with Py or with _ctypes Implemented by Thomas Heller bpo 3102 New configure option the with system expat switch allows building the pyexpat module to use the system Expat library Contributed by Arfrever Frehtes Taifersar Arahesis bpo 7609 New configure option the with valgrind option will now disable the pymalloc allocator which is difficult for the Valgrind memory error detector to analyze correctly Valgrind will therefore be better at detecting memory leaks and overruns Contributed by James Henstridge bpo 2422 New configure option you can now supply an empty string to with dbmliborder in order to disable all of the various DBM modules Added by Arfrever Frehtes Taifersar Arahesis bpo 6491 The configure script now checks for floating point rounding bugs on certain 32 bit Intel chips and defines a X87_DOUBLE_ROUNDING preprocessor definition No code currently uses this definition but it s available if anyone wishes to use it Added by Mark Dickinson bpo 2937 configure also now sets a LDCXXSHARED Makefile variable for supporting C linking Contributed by Arfrever Frehtes Taifersar Arahesis bpo 1222585 The build process now creates the necessary files for pkg config support Contributed by Clinton Roy bpo 3585 The build process now supports Subversion 1 7 Contributed by Arfrever Frehtes Taifersar Arahesis bpo 6094 Capsu,en
1314,les Python 3 1 adds a new C datatype PyCapsule for providing a C API to an extension module A capsule is essentially the holder of a C void pointer and is made available as a module attribute for example the socket module s API is exposed as socket CAPI and unicodedata exposes ucnhash_CAPI Other extensions can import the module access its dictionary to get the capsule object and then get the void pointer which will usually point to an array of pointers to the module s various API functions There is an existing data type already used for this PyCObject but it doesn t provide type safety Evil code written in pure Python could cause a segmentation fault by taking a PyCObject from module A and somehow substituting it for the PyCObject in module B Capsules know their own name and getting the pointer requires providing the name void vtable if PyCapsule_IsValid capsule mymodule CAPI PyErr_SetString PyExc_ValueError argument type invalid return NULL vtable PyCapsule_GetPointer capsule mymodule CAPI You are assured that vtable points to whatever you re expecting If a different capsule was passed in PyCapsule_IsValid would detect the mismatched name and return false Refer to Providing a C API for an Extension Module for more information on using these objects Python 2 7 now uses capsules internally to provide various extension module APIs but the PyCObject_AsVoidPtr was modified to handle capsules preserving compile time compatibility with the PyCObject interface Use of PyCObject_AsVoidPtr will signal a PendingDeprecationWarning which is silent by default Implemented in Python 3 1 and backported to 2 7 by Larry Hastings discussed in bpo 5630 Port Specific Changes Windows The msvcrt module now contains some constants from the crtassem h header file CRT_ASSEMBLY_VERSION VC_ASSEMBLY_PUBLICKEYTOKEN and LIBRARIES_ASSEMBLY_NAME_PREFIX Contributed by David Cournapeau bpo 4365 The _winreg module for accessing the registry now implements the CreateKeyEx and DeleteKeyEx functions extended versions of previously supported functions that take several extra arguments The DisableReflectionKey EnableReflectionKey and QueryReflectionKey were also tested and documented Implemented by Brian Curtin bpo 7347 The new _beginthreadex API is used to start threads and the native thread local storage functions are now used Contributed by Kristján Valur Jónsson bpo 3582 The os kill function now works on Windows The signal value can be the constants CTRL_C_EVENT CTRL_BREAK_EVENT or any integer The first two constants will send Control C and Control Break keystroke events to subprocesses any other value will use the TerminateProcess API Contributed by Miki Tebeka bpo 1220212 The os listdir function now correctly fails for an empty path Fixed by Hirokazu Yamamoto bpo 5913 The mimetypes module will now read the MIME database from the Windows registry when initializing Patch by Gabriel Genellina bpo 4969 Port Specific Changes Mac OS X The path Library Python 2 7 site packages is now appended to sys path in order to share added packages between the system installation and a user installed copy of the same version Changed by Ronald Oussoren bpo 4865 Changed in version 2 7 13 As of 2 7 13 this change was removed Library Python 2 7 site packages the site packages directory used by the Apple supplied system Python 2 7 is no longer appended to sys path for user installed Pythons such as from the python org installers As of macOS 10 12 Apple changed how the system site packages directory is configured which could cause installation of pip components like setuptools to fail Packages installed for the system Python will no longer be shared with user installed Pythons bpo 28440 Port Specific Changes FreeBSD FreeBSD 7 1 s SO_SETFIB constant used with the socket methods getsockopt setsockopt to select an alternate routing table is now available in the socket module Added by Kyle VanderBeek bpo 8235 Other Changes and Fixes Two benchmark scripts iobench and ccbench were added to the Tools directory iobench measures the speed of the built in file I O objects returned by open w,en
1315,hile performing various operations and ccbench is a concurrency benchmark that tries to measure computing throughput thread switching latency and IO processing bandwidth when performing several tasks using a varying number of threads The Tools i18n msgfmt py script now understands plural forms in po files Fixed by Martin von Löwis bpo 5464 When importing a module from a pyc or pyo file with an existing py counterpart the co_filename attributes of the resulting code objects are overwritten when the original filename is obsolete This can happen if the file has been renamed moved or is accessed through different paths Patch by Ziga Seilnacht and Jean Paul Calderone bpo 1180193 The regrtest py script now takes a randseed switch that takes an integer that will be used as the random seed for the r option that executes tests in random order The r option also reports the seed that was used Added by Collin Winter Another regrtest py switch is j which takes an integer specifying how many tests run in parallel This allows reducing the total runtime on multi core machines This option is compatible with several other options including the R switch which is known to produce long runtimes Added by Antoine Pitrou bpo 6152 This can also be used with a new F switch that runs selected tests in a loop until they fail Added by Antoine Pitrou bpo 7312 When executed as a script the py_compile py module now accepts as an argument which will read standard input for the list of filenames to be compiled Contributed by Piotr Ożarowski bpo 8233 Porting to Python 2 7 This section lists previously described changes and other bugfixes that may require changes to your code The range function processes its arguments more consistently it will now call __int__ on non float non integer arguments that are supplied to it Fixed by Alexander Belopolsky bpo 1533 The string format method changed the default precision used for floating point and complex numbers from 6 decimal places to 12 which matches the precision used by str Changed by Eric Smith bpo 5920 Because of an optimization for the with statement the special methods __enter__ and __exit__ must belong to the object s type and cannot be directly attached to the object s instance This affects new style classes derived from object and C extension types bpo 6101 Due to a bug in Python 2 6 the exc_value parameter to __exit__ methods was often the string representation of the exception not an instance This was fixed in 2 7 so exc_value will be an instance as expected Fixed by Florent Xicluna bpo 7853 When a restricted set of attributes were set using __slots__ deleting an unset attribute would not raise AttributeError as you would expect Fixed by Benjamin Peterson bpo 7604 In the standard library Operations with datetime instances that resulted in a year falling outside the supported range didn t always raise OverflowError Such errors are now checked more carefully and will now raise the exception Reported by Mark Leander patch by Anand B Pillai and Alexander Belopolsky bpo 7150 When using Decimal instances with a string s format method the default alignment was previously left alignment This has been changed to right alignment which might change the output of your programs Changed by Mark Dickinson bpo 6857 Comparisons involving a signaling NaN value or sNAN now signal InvalidOperation instead of silently returning a true or false value depending on the comparison operator Quiet NaN values or NaN are now hashable Fixed by Mark Dickinson bpo 7279 The xml etree ElementTree library no longer escapes ampersands and angle brackets when outputting an XML processing instruction which looks like xml stylesheet href style1 or comment which looks like comment Patch by Neil Muller bpo 2746 The readline method of StringIO objects now does nothing when a negative length is requested as other file like objects do bpo 7348 The syslog module will now use the value of sys argv 0 as the identifier instead of the previous default value of python Changed by Sean Reifschneider bpo 8451 The tarfile module s default error handling ,en
1316,has changed to no longer suppress fatal errors The default error level was previously 0 which meant that errors would only result in a message being written to the debug log but because the debug log is not activated by default these errors go unnoticed The default error level is now 1 which raises an exception if there s an error Changed by Lars Gustäbel bpo 7357 The urlparse module s urlsplit now handles unknown URL schemes in a fashion compliant with RFC 3986 if the URL is of the form something the text before the is treated as the scheme even if it s a made up scheme that the module doesn t know about This change may break code that worked around the old behaviour For example Python 2 6 4 or 2 5 will return the following import urlparse urlparse urlsplit invented host filename query invented host filename query Python 2 7 and Python 2 6 5 will return import urlparse urlparse urlsplit invented host filename query invented host filename query Python 2 7 actually produces slightly different output since it returns a named tuple instead of a standard tuple For C extensions C extensions that use integer format codes with the PyArg_Parse family of functions will now raise a TypeError exception instead of triggering a DeprecationWarning bpo 5080 Use the new PyOS_string_to_double function instead of the old PyOS_ascii_strtod and PyOS_ascii_atof functions which are now deprecated For applications that embed Python The PySys_SetArgvEx function was added letting applications close a security hole when the existing PySys_SetArgv function was used Check whether you re calling PySys_SetArgv and carefully consider whether the application should be using PySys_SetArgvEx with updatepath set to false New Features Added to Python 2 7 Maintenance Releases New features may be added to Python 2 7 maintenance releases when the situation genuinely calls for it Any such additions must go through the Python Enhancement Proposal process and make a compelling case for why they can t be adequately addressed by either adding the new feature solely to Python 3 or else by publishing it on the Python Package Index In addition to the specific proposals listed below there is a general exemption allowing new 3 warnings to be added in any Python 2 7 maintenance release Two new environment variables for debug mode In debug mode the xxx refs statistic is not written by default the PYTHONSHOWREFCOUNT environment variable now must also be set Contributed by Victor Stinner bpo 31733 When Python is compiled with COUNT_ALLOC defined allocation counts are no longer dumped by default anymore the PYTHONSHOWALLOCCOUNT environment variable must now also be set Moreover allocation counts are now dumped into stderr rather than stdout Contributed by Victor Stinner bpo 31692 New in version 2 7 15 PEP 434 IDLE Enhancement Exception for All Branches PEP 434 describes a general exemption for changes made to the IDLE development environment shipped along with Python This exemption makes it possible for the IDLE developers to provide a more consistent user experience across all supported versions of Python 2 and 3 For details of any IDLE changes refer to the NEWS file for the specific release PEP 466 Network Security Enhancements for Python 2 7 PEP 466 describes a number of network security enhancement proposals that have been approved for inclusion in Python 2 7 maintenance releases with the first of those changes appearing in the Python 2 7 7 release PEP 466 related features added in Python 2 7 7 hmac compare_digest was backported from Python 3 to make a timing attack resistant comparison operation available to Python 2 applications Contributed by Alex Gaynor bpo 21306 OpenSSL 1 0 1g was upgraded in the official Windows installers published on python org Contributed by Zachary Ware bpo 21462 PEP 466 related features added in Python 2 7 8 hashlib pbkdf2_hmac was backported from Python 3 to make a hashing algorithm suitable for secure password storage broadly available to Python 2 applications Contributed by Alex Gaynor bpo 21304 OpenSSL 1 0 1h was upgraded for the official,en
1317, Windows installers published on python org contributed by Zachary Ware in bpo 21671 for CVE 2014 0224 PEP 466 related features added in Python 2 7 9 Most of Python 3 4 s ssl module was backported This means ssl now supports Server Name Indication TLS1 x settings access to the platform certificate store the SSLContext class and other features Contributed by Alex Gaynor and David Reid bpo 21308 Refer to the Version added 2 7 9 notes in the module documentation for specific details os urandom was changed to cache a file descriptor to dev urandom instead of reopening dev urandom on every call Contributed by Alex Gaynor bpo 21305 hashlib algorithms_guaranteed and hashlib algorithms_available were backported from Python 3 to make it easier for Python 2 applications to select the strongest available hash algorithm Contributed by Alex Gaynor in bpo 21307 PEP 477 Backport ensurepip PEP 453 to Python 2 7 PEP 477 approves the inclusion of the PEP 453 ensurepip module and the improved documentation that was enabled by it in the Python 2 7 maintenance releases appearing first in the Python 2 7 9 release Bootstrapping pip By Default The new ensurepip module defined in PEP 453 provides a standard cross platform mechanism to bootstrap the pip installer into Python installations The version of pip included with Python 2 7 9 is pip 1 5 6 and future 2 7 x maintenance releases will update the bundled version to the latest version of pip that is available at the time of creating the release candidate By default the commands pip pipX and pipX Y will be installed on all platforms where X Y stands for the version of the Python installation along with the pip Python package and its dependencies For CPython source builds on POSIX systems the make install and make altinstall commands do not bootstrap pip by default This behaviour can be controlled through configure options and overridden through Makefile options On Windows and Mac OS X the CPython installers now default to installing pip along with CPython itself users may opt out of installing it during the installation process Window users will need to opt in to the automatic PATH modifications to have pip available from the command line by default otherwise it can still be accessed through the Python launcher for Windows as py m pip As discussed in the PEP platform packagers may choose not to install these commands by default as long as when invoked they provide clear and simple directions on how to install them on that platform usually using the system package manager Documentation Changes As part of this change the Installing Python Modules and Distributing Python Modules sections of the documentation have been completely redesigned as short getting started and FAQ documents Most packaging documentation has now been moved out to the Python Packaging Authority maintained Python Packaging User Guide and the documentation of the individual projects However as this migration is currently still incomplete the legacy versions of those guides remaining available as Building C and C Extensions with setuptools and Building C and C Extensions with setuptools See also PEP 453 Explicit bootstrapping of pip in Python installations PEP written by Donald Stufft and Nick Coghlan implemented by Donald Stufft Nick Coghlan Martin von Löwis and Ned Deily PEP 476 Enabling certificate verification by default for stdlib http clients PEP 476 updated httplib and modules which use it such as urllib2 and xmlrpclib to now verify that the server presents a certificate which is signed by a Certificate Authority in the platform trust store and whose hostname matches the hostname being requested by default significantly improving security for many applications This change was made in the Python 2 7 9 release For applications which require the old previous behavior they can pass an alternate context import urllib2 import ssl This disables all verification context ssl _create_unverified_context This allows using a specific certificate for the host which doesn t need to be in the trust store context ssl create_default_context,en
1318, cafile path to file crt urllib2 urlopen https invalid cert context context PEP 493 HTTPS verification migration tools for Python 2 7 PEP 493 provides additional migration tools to support a more incremental infrastructure upgrade process for environments containing applications and services relying on the historically permissive processing of server certificates when establishing client HTTPS connections These additions were made in the Python 2 7 12 release These tools are intended for use in cases where affected applications and services can t be modified to explicitly pass a more permissive SSL context when establishing the connection For applications and services which can t be modified at all the new PYTHONHTTPSVERIFY environment variable may be set to 0 to revert an entire Python process back to the default permissive behaviour of Python 2 7 8 and earlier For cases where the connection establishment code can t be modified but the overall application can be the new ssl _https_verify_certificates function can be used to adjust the default behaviour at runtime New make regen all build target To simplify cross compilation and to ensure that CPython can reliably be compiled without requiring an existing version of Python to already be available the autotools based build system no longer attempts to implicitly recompile generated files based on file modification times Instead a new make regen all command has been added to force regeneration of these files when desired e g after an initial version of Python has already been built based on the pregenerated versions More selective regeneration targets are also defined see Makefile pre in for details Contributed by Victor Stinner in bpo 23404 New in version 2 7 14 Removal of make touch build target The make touch build target previously used to request implicit regeneration of generated files by updating their modification times has been removed It has been replaced by the new make regen all target Contributed by Victor Stinner in bpo 23404 Changed in version 2 7 14 Acknowledgements The author would like to thank the following people for offering suggestions corrections and assistance with various drafts of this article Nick Coghlan Philip Jenvey Ryan Lovett R David Murray Hugh Secker Walker,en
1319,Importing Modules PyObject PyImport_ImportModule const char name Return value New reference Part of the Stable ABI This is a wrapper around PyImport_Import which takes a const char as an argument instead of a PyObject PyObject PyImport_ImportModuleNoBlock const char name Return value New reference Part of the Stable ABI This function is a deprecated alias of PyImport_ImportModule Changed in version 3 3 This function used to fail immediately when the import lock was held by another thread In Python 3 3 though the locking scheme switched to per module locks for most purposes so this function s special behaviour isn t needed anymore PyObject PyImport_ImportModuleEx const char name PyObject globals PyObject locals PyObject fromlist Return value New reference Import a module This is best described by referring to the built in Python function __import__ The return value is a new reference to the imported module or top level package or NULL with an exception set on failure Like for __import__ the return value when a submodule of a package was requested is normally the top level package unless a non empty fromlist was given Failing imports remove incomplete module objects like with PyImport_ImportModule PyObject PyImport_ImportModuleLevelObject PyObject name PyObject globals PyObject locals PyObject fromlist int level Return value New reference Part of the Stable ABI since version 3 7 Import a module This is best described by referring to the built in Python function __import__ as the standard __import__ function calls this function directly The return value is a new reference to the imported module or top level package or NULL with an exception set on failure Like for __import__ the return value when a submodule of a package was requested is normally the top level package unless a non empty fromlist was given New in version 3 3 PyObject PyImport_ImportModuleLevel const char name PyObject globals PyObject locals PyObject fromlist int level Return value New reference Part of the Stable ABI Similar to PyImport_ImportModuleLevelObject but the name is a UTF 8 encoded string instead of a Unicode object Changed in version 3 3 Negative values for level are no longer accepted PyObject PyImport_Import PyObject name Return value New reference Part of the Stable ABI This is a higher level interface that calls the current import hook function with an explicit level of 0 meaning absolute import It invokes the __import__ function from the __builtins__ of the current globals This means that the import is done using whatever import hooks are installed in the current environment This function always uses absolute imports PyObject PyImport_ReloadModule PyObject m Return value New reference Part of the Stable ABI Reload a module Return a new reference to the reloaded module or NULL with an exception set on failure the module still exists in this case PyObject PyImport_AddModuleObject PyObject name Return value Borrowed reference Part of the Stable ABI since version 3 7 Return the module object corresponding to a module name The name argument may be of the form package module First check the modules dictionary if there s one there and if not create a new one and insert it in the modules dictionary Return NULL with an exception set on failure Note This function does not load or import the module if the module wasn t already loaded you will get an empty module object Use PyImport_ImportModule or one of its variants to import a module Package structures implied by a dotted name for name are not created if not already present New in version 3 3 PyObject PyImport_AddModule const char name Return value Borrowed reference Part of the Stable ABI Similar to PyImport_AddModuleObject but the name is a UTF 8 encoded string instead of a Unicode object PyObject PyImport_ExecCodeModule const char name PyObject co Return value New reference Part of the Stable ABI Given a module name possibly of the form package module and a code object read from a Python bytecode file or obtained from the built in function compile load the module Return a new reference to the modu,en
1320,le object or NULL with an exception set if an error occurred name is removed from sys modules in error cases even if name was already in sys modules on entry to PyImport_ExecCodeModule Leaving incompletely initialized modules in sys modules is dangerous as imports of such modules have no way to know that the module object is an unknown and probably damaged with respect to the module author s intents state The module s __spec__ and __loader__ will be set if not set already with the appropriate values The spec s loader will be set to the module s __loader__ if set and to an instance of SourceFileLoader otherwise The module s __file__ attribute will be set to the code object s co_filename If applicable __cached__ will also be set This function will reload the module if it was already imported See PyImport_ReloadModule for the intended way to reload a module If name points to a dotted name of the form package module any package structures not already created will still not be created See also PyImport_ExecCodeModuleEx and PyImport_ExecCodeModuleWithPathnames Changed in version 3 12 The setting of __cached__ and __loader__ is deprecated See ModuleSpec for alternatives PyObject PyImport_ExecCodeModuleEx const char name PyObject co const char pathname Return value New reference Part of the Stable ABI Like PyImport_ExecCodeModule but the __file__ attribute of the module object is set to pathname if it is non NULL See also PyImport_ExecCodeModuleWithPathnames PyObject PyImport_ExecCodeModuleObject PyObject name PyObject co PyObject pathname PyObject cpathname Return value New reference Part of the Stable ABI since version 3 7 Like PyImport_ExecCodeModuleEx but the __cached__ attribute of the module object is set to cpathname if it is non NULL Of the three functions this is the preferred one to use New in version 3 3 Changed in version 3 12 Setting __cached__ is deprecated See ModuleSpec for alternatives PyObject PyImport_ExecCodeModuleWithPathnames const char name PyObject co const char pathname const char cpathname Return value New reference Part of the Stable ABI Like PyImport_ExecCodeModuleObject but name pathname and cpathname are UTF 8 encoded strings Attempts are also made to figure out what the value for pathname should be from cpathname if the former is set to NULL New in version 3 2 Changed in version 3 3 Uses imp source_from_cache in calculating the source path if only the bytecode path is provided Changed in version 3 12 No longer uses the removed imp module long PyImport_GetMagicNumber Part of the Stable ABI Return the magic number for Python bytecode files a k a pyc file The magic number should be present in the first four bytes of the bytecode file in little endian byte order Returns 1 on error Changed in version 3 3 Return value of 1 upon failure const char PyImport_GetMagicTag Part of the Stable ABI Return the magic tag string for PEP 3147 format Python bytecode file names Keep in mind that the value at sys implementation cache_tag is authoritative and should be used instead of this function New in version 3 2 PyObject PyImport_GetModuleDict Return value Borrowed reference Part of the Stable ABI Return the dictionary used for the module administration a k a sys modules Note that this is a per interpreter variable PyObject PyImport_GetModule PyObject name Return value New reference Part of the Stable ABI since version 3 8 Return the already imported module with the given name If the module has not been imported yet then returns NULL but does not set an error Returns NULL and sets an error if the lookup failed New in version 3 7 PyObject PyImport_GetImporter PyObject path Return value New reference Part of the Stable ABI Return a finder object for a sys path pkg __path__ item path possibly by fetching it from the sys path_importer_cache dict If it wasn t yet cached traverse sys path_hooks until a hook is found that can handle the path item Return None if no hook could this tells our caller that the path based finder could not find a finder for this path item Cache the result in sys path_importer_cache Return a new r,en
1321,eference to the finder object int PyImport_ImportFrozenModuleObject PyObject name Part of the Stable ABI since version 3 7 Load a frozen module named name Return 1 for success 0 if the module is not found and 1 with an exception set if the initialization failed To access the imported module on a successful load use PyImport_ImportModule Note the misnomer this function would reload the module if it was already imported New in version 3 3 Changed in version 3 4 The __file__ attribute is no longer set on the module int PyImport_ImportFrozenModule const char name Part of the Stable ABI Similar to PyImport_ImportFrozenModuleObject but the name is a UTF 8 encoded string instead of a Unicode object struct _frozen This is the structure type definition for frozen module descriptors as generated by the freeze utility see Tools freeze in the Python source distribution Its definition found in Include import h is struct _frozen const char name const unsigned char code int size bool is_package Changed in version 3 11 The new is_package field indicates whether the module is a package or not This replaces setting the size field to a negative value const struct _frozen PyImport_FrozenModules This pointer is initialized to point to an array of _frozen records terminated by one whose members are all NULL or zero When a frozen module is imported it is searched in this table Third party code could play tricks with this to provide a dynamically created collection of frozen modules int PyImport_AppendInittab const char name PyObject initfunc void Part of the Stable ABI Add a single module to the existing table of built in modules This is a convenience wrapper around PyImport_ExtendInittab returning 1 if the table could not be extended The new module can be imported by the name name and uses the function initfunc as the initialization function called on the first attempted import This should be called before Py_Initialize struct _inittab Structure describing a single entry in the list of built in modules Programs which embed Python may use an array of these structures in conjunction with PyImport_ExtendInittab to provide additional built in modules The structure consists of two members const char name The module name as an ASCII encoded string PyObject initfunc void Initialization function for a module built into the interpreter int PyImport_ExtendInittab struct _inittab newtab Add a collection of modules to the table of built in modules The newtab array must end with a sentinel entry which contains NULL for the name field failure to provide the sentinel value can result in a memory fault Returns 0 on success or 1 if insufficient memory could be allocated to extend the internal table In the event of failure no modules are added to the internal table This must be called before Py_Initialize If Python is initialized multiple times PyImport_AppendInittab or PyImport_ExtendInittab must be called before each Python initialization,en
1322,What s New In Python 3 4 Author R David Murray rdmurray bitdance com Editor This article explains the new features in Python 3 4 compared to 3 3 Python 3 4 was released on March 16 2014 For full details see the changelog See also PEP 429 Python 3 4 Release Schedule Summary Release Highlights New syntax features No new syntax features were added in Python 3 4 Other new features pip should always be available PEP 453 Newly created file descriptors are non inheritable PEP 446 command line option for isolated mode bpo 16499 improvements in the handling of codecs that are not text encodings multiple issues A ModuleSpec Type for the Import System PEP 451 Affects importer authors The marshal format has been made more compact and efficient bpo 16475 New library modules asyncio New provisional API for asynchronous IO PEP 3156 ensurepip Bootstrapping the pip installer PEP 453 enum Support for enumeration types PEP 435 pathlib Object oriented filesystem paths PEP 428 selectors High level and efficient I O multiplexing built upon the select module primitives part of PEP 3156 statistics A basic numerically stable statistics library PEP 450 tracemalloc Trace Python memory allocations PEP 454 Significantly improved library modules Single dispatch generic functions in functools PEP 443 New pickle protocol 4 PEP 3154 multiprocessing now has an option to avoid using os fork on Unix bpo 8713 email has a new submodule contentmanager and a new Message subclass EmailMessage that simplify MIME handling bpo 18891 The inspect and pydoc modules are now capable of correct introspection of a much wider variety of callable objects which improves the output of the Python help system The ipaddress module API has been declared stable Security improvements Secure and interchangeable hash algorithm PEP 456 Make newly created file descriptors non inheritable PEP 446 to avoid leaking file descriptors to child processes New command line option for isolated mode bpo 16499 multiprocessing now has an option to avoid using os fork on Unix spawn and forkserver are more secure because they avoid sharing data with child processes multiprocessing child processes on Windows no longer inherit all of the parent s inheritable handles only the necessary ones A new hashlib pbkdf2_hmac function provides the PKCS 5 password based key derivation function 2 TLSv1 1 and TLSv1 2 support for ssl Retrieving certificates from the Windows system cert store support for ssl Server side SNI Server Name Indication support for ssl The ssl SSLContext class has a lot of improvements All modules in the standard library that support SSL now support server certificate verification including hostname matching ssl match_hostname and CRLs Certificate Revocation lists see ssl SSLContext load_verify_locations CPython implementation improvements Safe object finalization PEP 442 Leveraging PEP 442 in most cases module globals are no longer set to None during finalization bpo 18214 Configurable memory allocators PEP 445 Argument Clinic PEP 436 Please read on for a comprehensive list of user facing changes including many other smaller improvements CPython optimizations deprecations and potential porting issues New Features PEP 453 Explicit Bootstrapping of PIP in Python Installations Bootstrapping pip By Default The new ensurepip module defined in PEP 453 provides a standard cross platform mechanism to bootstrap the pip installer into Python installations and virtual environments The version of pip included with Python 3 4 0 is pip 1 5 4 and future 3 4 x maintenance releases will update the bundled version to the latest version of pip that is available at the time of creating the release candidate By default the commands pipX and pipX Y will be installed on all platforms where X Y stands for the version of the Python installation along with the pip Python package and its dependencies On Windows and in virtual environments on all platforms the unversioned pip command will also be installed On other platforms the system wide unversioned pip command typically refers to the separately installed Python 2,en
1323, version The pyvenv command line utility and the venv module make use of the ensurepip module to make pip readily available in virtual environments When using the command line utility pip is installed by default while when using the venv module API installation of pip must be requested explicitly For CPython source builds on POSIX systems the make install and make altinstall commands bootstrap pip by default This behaviour can be controlled through configure options and overridden through Makefile options On Windows and Mac OS X the CPython installers now default to installing pip along with CPython itself users may opt out of installing it during the installation process Window users will need to opt in to the automatic PATH modifications to have pip available from the command line by default otherwise it can still be accessed through the Python launcher for Windows as py m pip As discussed in the PEP platform packagers may choose not to install these commands by default as long as when invoked they provide clear and simple directions on how to install them on that platform usually using the system package manager Note To avoid conflicts between parallel Python 2 and Python 3 installations only the versioned pip3 and pip3 4 commands are bootstrapped by default when ensurepip is invoked directly the default pip option is needed to also request the unversioned pip command pyvenv and the Windows installer ensure that the unqualified pip command is made available in those environments and pip can always be invoked via the m switch rather than directly to avoid ambiguity on systems with multiple Python installations Documentation Changes As part of this change the Installing Python Modules and Distributing Python Modules sections of the documentation have been completely redesigned as short getting started and FAQ documents Most packaging documentation has now been moved out to the Python Packaging Authority maintained Python Packaging User Guide and the documentation of the individual projects However as this migration is currently still incomplete the legacy versions of those guides remaining available as Building C and C Extensions with setuptools and Building C and C Extensions with setuptools See also PEP 453 Explicit bootstrapping of pip in Python installations PEP written by Donald Stufft and Nick Coghlan implemented by Donald Stufft Nick Coghlan Martin von Löwis and Ned Deily PEP 446 Newly Created File Descriptors Are Non Inheritable PEP 446 makes newly created file descriptors non inheritable In general this is the behavior an application will want when launching a new process having currently open files also open in the new process can lead to all sorts of hard to find bugs and potentially to security issues However there are occasions when inheritance is desired To support these cases the following new functions and methods are available os get_inheritable os set_inheritable os get_handle_inheritable os set_handle_inheritable socket socket get_inheritable socket socket set_inheritable See also PEP 446 Make newly created file descriptors non inheritable PEP written and implemented by Victor Stinner Improvements to Codec Handling Since it was first introduced the codecs module has always been intended to operate as a type neutral dynamic encoding and decoding system However its close coupling with the Python text model especially the type restricted convenience methods on the builtin str bytes and bytearray types has historically obscured that fact As a key step in clarifying the situation the codecs encode and codecs decode convenience functions are now properly documented in Python 2 7 3 3 and 3 4 These functions have existed in the codecs module and have been covered by the regression test suite since Python 2 4 but were previously only discoverable through runtime introspection Unlike the convenience methods on str bytes and bytearray the codecs convenience functions support arbitrary codecs in both Python 2 and Python 3 rather than being limited to Unicode text encodings in Python 3 or basestring basestring con,en
1324,versions in Python 2 In Python 3 4 the interpreter is able to identify the known non text encodings provided in the standard library and direct users towards these general purpose convenience functions when appropriate b abcdef decode hex Traceback most recent call last File stdin line 1 in module LookupError hex is not a text encoding use codecs decode to handle arbitrary codecs hello encode rot13 Traceback most recent call last File stdin line 1 in module LookupError rot13 is not a text encoding use codecs encode to handle arbitrary codecs open foo txt encoding hex Traceback most recent call last File stdin line 1 in module LookupError hex is not a text encoding use codecs open to handle arbitrary codecs In a related change whenever it is feasible without breaking backwards compatibility exceptions raised during encoding and decoding operations are wrapped in a chained exception of the same type that mentions the name of the codec responsible for producing the error import codecs codecs decode b abcdefgh hex Traceback most recent call last File usr lib python3 4 encodings hex_codec py line 20 in hex_decode return binascii a2b_hex input len input binascii Error Non hexadecimal digit found The above exception was the direct cause of the following exception Traceback most recent call last File stdin line 1 in module binascii Error decoding with hex codec failed Error Non hexadecimal digit found codecs encode hello bz2 Traceback most recent call last File usr lib python3 4 encodings bz2_codec py line 17 in bz2_encode return bz2 compress input len input File usr lib python3 4 bz2 py line 498 in compress return comp compress data comp flush TypeError str does not support the buffer interface The above exception was the direct cause of the following exception Traceback most recent call last File stdin line 1 in module TypeError encoding with bz2 codec failed TypeError str does not support the buffer interface Finally as the examples above show these improvements have permitted the restoration of the convenience aliases for the non Unicode codecs that were themselves restored in Python 3 2 This means that encoding binary data to and from its hexadecimal representation for example can now be written as from codecs import encode decode encode b hello hex b 68656c6c6f decode b 68656c6c6f hex b hello The binary and text transforms provided in the standard library are detailed in Binary Transforms and Text Transforms Contributed by Nick Coghlan in bpo 7475 bpo 17827 bpo 17828 and bpo 19619 PEP 451 A ModuleSpec Type for the Import System PEP 451 provides an encapsulation of the information about a module that the import machinery will use to load it that is a module specification This helps simplify both the import implementation and several import related APIs The change is also a stepping stone for several future import related improvements The public facing changes from the PEP are entirely backward compatible Furthermore they should be transparent to everyone but importer authors Key finder and loader methods have been deprecated but they will continue working New importers should use the new methods described in the PEP Existing importers should be updated to implement the new methods See the Deprecated section for a list of methods that should be replaced and their replacements Other Language Changes Some smaller changes made to the core Python language are Unicode database updated to UCD version 6 3 min and max now accept a default keyword only argument that can be used to specify the value they return if the iterable they are evaluating has no elements Contributed by Julian Berman in bpo 18111 Module objects are now weakly referenceable Module __file__ attributes and related values should now always contain absolute paths by default with the sole exception of __main__ __file__ when a script has been executed directly using a relative path Contributed by Brett Cannon in bpo 18416 All the UTF codecs except UTF 7 now reject surrogates during both encoding and decoding unless the surrogatepass error handler is used with the exce,en
1325,ption of the UTF 16 decoder which accepts valid surrogate pairs and the UTF 16 encoder which produces them while encoding non BMP characters Contributed by Victor Stinner Kang Hao Kenny Lu and Serhiy Storchaka in bpo 12892 New German EBCDIC codec cp273 Contributed by Michael Bierenfeld and Andrew Kuchling in bpo 1097797 New Ukrainian codec cp1125 Contributed by Serhiy Storchaka in bpo 19668 bytes join and bytearray join now accept arbitrary buffer objects as arguments Contributed by Antoine Pitrou in bpo 15958 The int constructor now accepts any object that has an __index__ method for its base argument Contributed by Mark Dickinson in bpo 16772 Frame objects now have a clear method that clears all references to local variables from the frame Contributed by Antoine Pitrou in bpo 17934 memoryview is now registered as a Sequence and supports the reversed builtin Contributed by Nick Coghlan and Claudiu Popa in bpo 18690 and bpo 19078 Signatures reported by help have been modified and improved in several cases as a result of the introduction of Argument Clinic and other changes to the inspect and pydoc modules __length_hint__ is now part of the formal language specification see PEP 424 Contributed by Armin Ronacher in bpo 16148 New Modules asyncio The new asyncio module defined in PEP 3156 provides a standard pluggable event loop model for Python providing solid asynchronous IO support in the standard library and making it easier for other event loop implementations to interoperate with the standard library and each other For Python 3 4 this module is considered a provisional API See also PEP 3156 Asynchronous IO Support Rebooted the asyncio Module PEP written and implementation led by Guido van Rossum ensurepip The new ensurepip module is the primary infrastructure for the PEP 453 implementation In the normal course of events end users will not need to interact with this module but it can be used to manually bootstrap pip if the automated bootstrapping into an installation or virtual environment was declined ensurepip includes a bundled copy of pip up to date as of the first release candidate of the release of CPython with which it ships this applies to both maintenance releases and feature releases ensurepip does not access the internet If the installation has internet access after ensurepip is run the bundled pip can be used to upgrade pip to a more recent release than the bundled one Note that such an upgraded version of pip is considered to be a separately installed package and will not be removed if Python is uninstalled The module is named ensure pip because if called when pip is already installed it does nothing It also has an upgrade option that will cause it to install the bundled copy of pip if the existing installed version of pip is older than the bundled copy enum The new enum module defined in PEP 435 provides a standard implementation of enumeration types allowing other modules such as socket to provide more informative error messages and better debugging support by replacing opaque integer constants with backwards compatible enumeration values See also PEP 435 Adding an Enum type to the Python standard library PEP written by Barry Warsaw Eli Bendersky and Ethan Furman implemented by Ethan Furman pathlib The new pathlib module offers classes representing filesystem paths with semantics appropriate for different operating systems Path classes are divided between pure paths which provide purely computational operations without I O and concrete paths which inherit from pure paths but also provide I O operations For Python 3 4 this module is considered a provisional API See also PEP 428 The pathlib module object oriented filesystem paths PEP written and implemented by Antoine Pitrou selectors The new selectors module created as part of implementing PEP 3156 allows high level and efficient I O multiplexing built upon the select module primitives statistics The new statistics module defined in PEP 450 offers some core statistics functionality directly in the standard library This module supports calculation of the m,en
1326,ean median mode variance and standard deviation of a data series See also PEP 450 Adding A Statistics Module To The Standard Library PEP written and implemented by Steven D Aprano tracemalloc The new tracemalloc module defined in PEP 454 is a debug tool to trace memory blocks allocated by Python It provides the following information Trace where an object was allocated Statistics on allocated memory blocks per filename and per line number total size number and average size of allocated memory blocks Compute the differences between two snapshots to detect memory leaks See also PEP 454 Add a new tracemalloc module to trace Python memory allocations PEP written and implemented by Victor Stinner Improved Modules abc New function abc get_cache_token can be used to know when to invalidate caches that are affected by changes in the object graph Contributed by Łukasz Langa in bpo 16832 New class ABC has ABCMeta as its meta class Using ABC as a base class has essentially the same effect as specifying metaclass abc ABCMeta but is simpler to type and easier to read Contributed by Bruno Dupuis in bpo 16049 aifc The getparams method now returns a namedtuple rather than a plain tuple Contributed by Claudiu Popa in bpo 17818 aifc open now supports the context management protocol when used in a with block the close method of the returned object will be called automatically at the end of the block Contributed by Serhiy Storchacha in bpo 16486 The writeframesraw and writeframes methods now accept any bytes like object Contributed by Serhiy Storchaka in bpo 8311 argparse The FileType class now accepts encoding and errors arguments which are passed through to open Contributed by Lucas Maystre in bpo 11175 audioop audioop now supports 24 bit samples Contributed by Serhiy Storchaka in bpo 12866 New byteswap function converts big endian samples to little endian and vice versa Contributed by Serhiy Storchaka in bpo 19641 All audioop functions now accept any bytes like object Strings are not accepted they didn t work before now they raise an error right away Contributed by Serhiy Storchaka in bpo 16685 base64 The encoding and decoding functions in base64 now accept any bytes like object in cases where it previously required a bytes or bytearray instance Contributed by Nick Coghlan in bpo 17839 New functions a85encode a85decode b85encode and b85decode provide the ability to encode and decode binary data from and to Ascii85 and the git mercurial Base85 formats respectively The a85 functions have options that can be used to make them compatible with the variants of the Ascii85 encoding including the Adobe variant Contributed by Martin Morrison the Mercurial project Serhiy Storchaka and Antoine Pitrou in bpo 17618 collections The ChainMap new_child method now accepts an m argument specifying the child map to add to the chain This allows an existing mapping and or a custom mapping type to be used for the child Contributed by Vinay Sajip in bpo 16613 colorsys The number of digits in the coefficients for the RGB YIQ conversions have been expanded so that they match the FCC NTSC versions The change in results should be less than 1 and may better match results found elsewhere Contributed by Brian Landers and Serhiy Storchaka in bpo 14323 contextlib The new contextlib suppress context manager helps to clarify the intent of code that deliberately suppresses exceptions from a single statement Contributed by Raymond Hettinger in bpo 15806 and Zero Piraeus in bpo 19266 The new contextlib redirect_stdout context manager makes it easier for utility scripts to handle inflexible APIs that write their output to sys stdout and don t provide any options to redirect it Using the context manager the sys stdout output can be redirected to any other stream or in conjunction with io StringIO to a string The latter can be especially useful for example to capture output from a function that was written to implement a command line interface It is recommended only for utility scripts because it affects the global state of sys stdout Contributed by Raymond Hettinger in bpo 158,en
1327,05 The contextlib documentation has also been updated to include a discussion of the differences between single use reusable and reentrant context managers dbm dbm open objects now support the context management protocol When used in a with statement the close method of the database object will be called automatically at the end of the block Contributed by Claudiu Popa and Nick Coghlan in bpo 19282 dis Functions show_code dis distb and disassemble now accept a keyword only file argument that controls where they write their output The dis module is now built around an Instruction class that provides object oriented access to the details of each individual bytecode operation A new method get_instructions provides an iterator that emits the Instruction stream for a given piece of Python code Thus it is now possible to write a program that inspects and manipulates a bytecode object in ways different from those provided by the dis module itself For example import dis for instr in dis get_instructions lambda x x 1 print instr opname LOAD_FAST LOAD_CONST BINARY_ADD RETURN_VALUE The various display tools in the dis module have been rewritten to use these new components In addition a new application friendly class Bytecode provides an object oriented API for inspecting bytecode in both in human readable form and for iterating over instructions The Bytecode constructor takes the same arguments that get_instruction does plus an optional current_offset and the resulting object can be iterated to produce Instruction objects But it also has a dis method equivalent to calling dis on the constructor argument but returned as a multi line string bytecode dis Bytecode lambda x x 1 current_offset 3 for instr in bytecode print format instr opname instr opcode LOAD_FAST 124 LOAD_CONST 100 BINARY_ADD 23 RETURN_VALUE 83 bytecode dis splitlines 1 0 LOAD_FAST 0 x 3 LOAD_CONST 1 1 6 BINARY_ADD 7 RETURN_VALUE Bytecode also has a class method from_traceback that provides the ability to manipulate a traceback that is print Bytecode from_traceback tb dis is equivalent to distb tb Contributed by Nick Coghlan Ryan Kelly and Thomas Kluyver in bpo 11816 and Claudiu Popa in bpo 17916 New function stack_effect computes the effect on the Python stack of a given opcode and argument information that is not otherwise available Contributed by Larry Hastings in bpo 19722 doctest A new option flag FAIL_FAST halts test running as soon as the first failure is detected Contributed by R David Murray and Daniel Urban in bpo 16522 The doctest command line interface now uses argparse and has two new options o and f o allows doctest options to be specified on the command line and f is a shorthand for o FAIL_FAST to parallel the similar option supported by the unittest CLI Contributed by R David Murray in bpo 11390 doctest will now find doctests in extension module __doc__ strings Contributed by Zachary Ware in bpo 3158 email as_string now accepts a policy argument to override the default policy of the message when generating a string representation of it This means that as_string can now be used in more circumstances instead of having to create and use a generator in order to pass formatting parameters to its flatten method Contributed by R David Murray in bpo 18600 New method as_bytes added to produce a bytes representation of the message in a fashion similar to how as_string produces a string representation It does not accept the maxheaderlen argument but does accept the unixfrom and policy arguments The Message __bytes__ method calls it meaning that bytes mymsg will now produce the intuitive result a bytes object containing the fully formatted message Contributed by R David Murray in bpo 18600 The Message set_param message now accepts a replace keyword argument When specified the associated header will be updated without changing its location in the list of headers For backward compatibility the default is False Contributed by R David Murray in bpo 18891 A pair of new subclasses of Message have been added EmailMessage and MIMEPart along with a new sub module contentman,en
1328,ager and a new policy attribute content_manager All documentation is currently in the new module which is being added as part of email s new provisional API These classes provide a number of new methods that make extracting content from and inserting content into email messages much easier For details see the contentmanager documentation and the email Examples These API additions complete the bulk of the work that was planned as part of the email6 project The currently provisional API is scheduled to become final in Python 3 5 possibly with a few minor additions in the area of error handling Contributed by R David Murray in bpo 18891 filecmp A new clear_cache function provides the ability to clear the filecmp comparison cache which uses os stat information to determine if the file has changed since the last compare This can be used for example if the file might have been changed and re checked in less time than the resolution of a particular filesystem s file modification time field Contributed by Mark Levitt in bpo 18149 New module attribute DEFAULT_IGNORES provides the list of directories that are used as the default value for the ignore parameter of the dircmp function Contributed by Eli Bendersky in bpo 15442 functools The new partialmethod descriptor brings partial argument application to descriptors just as partial provides for normal callables The new descriptor also makes it easier to get arbitrary callables including partial instances to behave like normal instance methods when included in a class definition Contributed by Alon Horev and Nick Coghlan in bpo 4331 The new singledispatch decorator brings support for single dispatch generic functions to the Python standard library Where object oriented programming focuses on grouping multiple operations on a common set of data into a class a generic function focuses on grouping multiple implementations of an operation that allows it to work with different kinds of data See also PEP 443 Single dispatch generic functions PEP written and implemented by Łukasz Langa total_ordering now supports a return value of NotImplemented from the underlying comparison function Contributed by Katie Miller in bpo 10042 A pure python version of the partial function is now in the stdlib in CPython it is overridden by the C accelerated version but it is available for other implementations to use Contributed by Brian Thorne in bpo 12428 gc New function get_stats returns a list of three per generation dictionaries containing the collections statistics since interpreter startup Contributed by Antoine Pitrou in bpo 16351 glob A new function escape provides a way to escape special characters in a filename so that they do not become part of the globbing expansion but are instead matched literally Contributed by Serhiy Storchaka in bpo 8402 hashlib A new hashlib pbkdf2_hmac function provides the PKCS 5 password based key derivation function 2 Contributed by Christian Heimes in bpo 18582 The name attribute of hashlib hash objects is now a formally supported interface It has always existed in CPython s hashlib although it did not return lower case names for all supported hashes but it was not a public interface and so some other Python implementations have not previously supported it Contributed by Jason R Coombs in bpo 18532 hmac hmac now accepts bytearray as well as bytes for the key argument to the new function and the msg parameter to both the new function and the update method now accepts any type supported by the hashlib module Contributed by Jonas Borgström in bpo 18240 The digestmod argument to the hmac new function may now be any hash digest name recognized by hashlib In addition the current behavior in which the value of digestmod defaults to MD5 is deprecated in a future version of Python there will be no default value Contributed by Christian Heimes in bpo 17276 With the addition of block_size and name attributes and the formal documentation of the digest_size attribute the hmac module now conforms fully to the PEP 247 API Contributed by Christian Heimes in bpo 18775 html New functio,en
1329,n unescape function converts HTML5 character references to the corresponding Unicode characters Contributed by Ezio Melotti in bpo 2927 HTMLParser accepts a new keyword argument convert_charrefs that when True automatically converts all character references For backward compatibility its value defaults to False but it will change to True in a future version of Python so you are invited to set it explicitly and update your code to use this new feature Contributed by Ezio Melotti in bpo 13633 The strict argument of HTMLParser is now deprecated Contributed by Ezio Melotti in bpo 15114 http send_error now accepts an optional additional explain parameter which can be used to provide an extended error description overriding the hardcoded default if there is one This extended error description will be formatted using the error_message_format attribute and sent as the body of the error response Contributed by Karl Cow in bpo 12921 The http server command line interface now has a b bind option that causes the server to listen on a specific address Contributed by Malte Swart in bpo 17764 idlelib and IDLE Since idlelib implements the IDLE shell and editor and is not intended for import by other programs it gets improvements with every release See Lib idlelib NEWS txt for a cumulative list of changes since 3 3 0 as well as changes made in future 3 4 x releases This file is also available from the IDLE Help About IDLE dialog importlib The InspectLoader ABC defines a new method source_to_code that accepts source data and a path and returns a code object The default implementation is equivalent to compile data path exec dont_inherit True Contributed by Eric Snow and Brett Cannon in bpo 15627 InspectLoader also now has a default implementation for the get_code method However it will normally be desirable to override the default implementation for performance reasons Contributed by Brett Cannon in bpo 18072 The reload function has been moved from imp to importlib as part of the imp module deprecation Contributed by Berker Peksag in bpo 18193 importlib util now has a MAGIC_NUMBER attribute providing access to the bytecode version number This replaces the get_magic function in the deprecated imp module Contributed by Brett Cannon in bpo 18192 New importlib util functions cache_from_source and source_from_cache replace the same named functions in the deprecated imp module Contributed by Brett Cannon in bpo 18194 The importlib bootstrap NamespaceLoader now conforms to the InspectLoader ABC which means that runpy and python m can now be used with namespace packages Contributed by Brett Cannon in bpo 18058 importlib util has a new function decode_source that decodes source from bytes using universal newline processing This is useful for implementing InspectLoader get_source methods importlib machinery ExtensionFileLoader now has a get_filename method This was inadvertently omitted in the original implementation Contributed by Eric Snow in bpo 19152 inspect The inspect module now offers a basic command line interface to quickly display source code and other information for modules classes and functions Contributed by Claudiu Popa and Nick Coghlan in bpo 18626 unwrap makes it easy to unravel wrapper function chains created by functools wraps and any other API that sets the __wrapped__ attribute on a wrapper function Contributed by Daniel Urban Aaron Iles and Nick Coghlan in bpo 13266 As part of the implementation of the new enum module the inspect module now has substantially better support for custom __dir__ methods and dynamic class attributes provided through metaclasses Contributed by Ethan Furman in bpo 18929 and bpo 19030 getfullargspec and getargspec now use the signature API This allows them to support a much broader range of callables including those with __signature__ attributes those with metadata provided by argument clinic functools partial objects and more Note that unlike signature these functions still ignore __wrapped__ attributes and report the already bound first argument for bound methods so it is still necessary to update yo,en
1330,ur code to use signature directly if those features are desired Contributed by Yury Selivanov in bpo 17481 signature now supports duck types of CPython functions which adds support for functions compiled with Cython Contributed by Stefan Behnel and Yury Selivanov in bpo 17159 ipaddress ipaddress was added to the standard library in Python 3 3 as a provisional API With the release of Python 3 4 this qualification has been removed ipaddress is now considered a stable API covered by the normal standard library requirements to maintain backwards compatibility A new is_global property is True if an address is globally routeable Contributed by Peter Moody in bpo 17400 logging The TimedRotatingFileHandler has a new atTime parameter that can be used to specify the time of day when rollover should happen Contributed by Ronald Oussoren in bpo 9556 SocketHandler and DatagramHandler now support Unix domain sockets by setting port to None Contributed by Vinay Sajip in commit ce46195b56a9 fileConfig now accepts a configparser RawConfigParser subclass instance for the fname parameter This facilitates using a configuration file when logging configuration is just a part of the overall application configuration or where the application modifies the configuration before passing it to fileConfig Contributed by Vinay Sajip in bpo 16110 Logging configuration data received from a socket via the logging config listen function can now be validated before being processed by supplying a verification function as the argument to the new verify keyword argument Contributed by Vinay Sajip in bpo 15452 marshal The default marshal version has been bumped to 3 The code implementing the new version restores the Python2 behavior of recording only one copy of interned strings and preserving the interning on deserialization and extends this one copy ability to any object type including handling recursive references This reduces both the size of pyc files and the amount of memory a module occupies in memory when it is loaded from a pyc or pyo file Contributed by Kristján Valur Jónsson in bpo 16475 with additional speedups by Antoine Pitrou in bpo 19219 mmap mmap objects are now weakly referenceable Contributed by Valerie Lambert in bpo 4885 multiprocessing On Unix two new start methods spawn and forkserver have been added for starting processes using multiprocessing These make the mixing of processes with threads more robust and the spawn method matches the semantics that multiprocessing has always used on Windows New function get_all_start_methods reports all start methods available on the platform get_start_method reports the current start method and set_start_method sets the start method Contributed by Richard Oudkerk in bpo 8713 multiprocessing also now has the concept of a context which determines how child processes are created New function get_context returns a context that uses a specified start method It has the same API as the multiprocessing module itself so you can use it to create Pool s and other objects that will operate within that context This allows a framework and an application or different parts of the same application to use multiprocessing without interfering with each other Contributed by Richard Oudkerk in bpo 18999 Except when using the old fork start method child processes no longer inherit unneeded handles file descriptors from their parents part of bpo 8713 multiprocessing now relies on runpy which implements the m switch to initialise __main__ appropriately in child processes when using the spawn or forkserver start methods This resolves some edge cases where combining multiprocessing the m command line switch and explicit relative imports could cause obscure failures in child processes Contributed by Nick Coghlan in bpo 19946 operator New function length_hint provides an implementation of the specification for how the __length_hint__ special method should be used as part of the PEP 424 formal specification of this language feature Contributed by Armin Ronacher in bpo 16148 There is now a pure python version of the operator modul,en
1331,e available for reference and for use by alternate implementations of Python Contributed by Zachary Ware in bpo 16694 os There are new functions to get and set the inheritable flag of a file descriptor os get_inheritable os set_inheritable or a Windows handle os get_handle_inheritable os set_handle_inheritable New function cpu_count reports the number of CPUs available on the platform on which Python is running or None if the count can t be determined The multiprocessing cpu_count function is now implemented in terms of this function Contributed by Trent Nelson Yogesh Chaudhari Victor Stinner and Charles François Natali in bpo 17914 os path samestat is now available on the Windows platform and the os path samefile implementation is now shared between Unix and Windows Contributed by Brian Curtin in bpo 11939 os path ismount now recognizes volumes mounted below a drive root on Windows Contributed by Tim Golden in bpo 9035 os open supports two new flags on platforms that provide them O_PATH un opened file descriptor and O_TMPFILE unnamed temporary file as of 3 4 0 release available only on Linux systems with a kernel version of 3 11 or newer that have uapi headers Contributed by Christian Heimes in bpo 18673 and Benjamin Peterson respectively pdb pdb has been enhanced to handle generators yield and yield from in a more useful fashion This is especially helpful when debugging asyncio based programs Contributed by Andrew Svetlov and Xavier de Gaye in bpo 16596 The print command has been removed from pdb restoring access to the Python print function from the pdb command line Python2 s pdb did not have a print command instead entering print executed the print statement In Python3 print was mistakenly made an alias for the pdb p command p however prints the repr of its argument not the str like the Python2 print command did Worse the Python3 pdb print command shadowed the Python3 print function making it inaccessible at the pdb prompt Contributed by Connor Osborn in bpo 18764 pickle pickle now supports but does not use by default a new pickle protocol protocol 4 This new protocol addresses a number of issues that were present in previous protocols such as the serialization of nested classes very large strings and containers and classes whose __new__ method takes keyword only arguments It also provides some efficiency improvements See also PEP 3154 Pickle protocol 4 PEP written by Antoine Pitrou and implemented by Alexandre Vassalotti plistlib plistlib now has an API that is similar to the standard pattern for stdlib serialization protocols with new load dump loads and dumps functions The older API is now deprecated In addition to the already supported XML plist format FMT_XML it also now supports the binary plist format FMT_BINARY Contributed by Ronald Oussoren and others in bpo 14455 poplib Two new methods have been added to poplib capa which returns the list of capabilities advertised by the POP server and stls which switches a clear text POP3 session into an encrypted POP3 session if the POP server supports it Contributed by Lorenzo Catucci in bpo 4473 pprint The pprint module s PrettyPrinter class and its pformat and pprint functions have a new option compact that controls how the output is formatted Currently setting compact to True means that sequences will be printed with as many sequence elements as will fit within width on each indented line Contributed by Serhiy Storchaka in bpo 19132 Long strings are now wrapped using Python s normal line continuation syntax Contributed by Antoine Pitrou in bpo 17150 pty pty spawn now returns the status value from os waitpid on the child process instead of None Contributed by Gregory P Smith pydoc The pydoc module is now based directly on the inspect signature introspection API allowing it to provide signature information for a wider variety of callable objects This change also means that __wrapped__ attributes are now taken into account when displaying help information Contributed by Larry Hastings in bpo 19674 The pydoc module no longer displays the self parameter for already bound ,en
1332,methods Instead it aims to always display the exact current signature of the supplied callable Contributed by Larry Hastings in bpo 20710 In addition to the changes that have been made to pydoc directly its handling of custom __dir__ methods and various descriptor behaviours has also been improved substantially by the underlying changes in the inspect module As the help builtin is based on pydoc the above changes also affect the behaviour of help re New fullmatch function and regex fullmatch method anchor the pattern at both ends of the string to match This provides a way to be explicit about the goal of the match which avoids a class of subtle bugs where characters get lost during code changes or the addition of alternatives to an existing regular expression Contributed by Matthew Barnett in bpo 16203 The repr of regex objects now includes the pattern and the flags the repr of match objects now includes the start end and the part of the string that matched Contributed by Hugo Lopes Tavares and Serhiy Storchaka in bpo 13592 and bpo 17087 resource New prlimit function available on Linux platforms with a kernel version of 2 6 36 or later and glibc of 2 13 or later provides the ability to query or set the resource limits for processes other than the one making the call Contributed by Christian Heimes in bpo 16595 On Linux kernel version 2 6 36 or later there are also some new Linux specific constants RLIMIT_MSGQUEUE RLIMIT_NICE RLIMIT_RTPRIO RLIMIT_RTTIME and RLIMIT_SIGPENDING Contributed by Christian Heimes in bpo 19324 On FreeBSD version 9 and later there some new FreeBSD specific constants RLIMIT_SBSIZE RLIMIT_SWAP and RLIMIT_NPTS Contributed by Claudiu Popa in bpo 19343 select epoll objects now support the context management protocol When used in a with statement the close method will be called automatically at the end of the block Contributed by Serhiy Storchaka in bpo 16488 devpoll objects now have fileno and close methods as well as a new attribute closed Contributed by Victor Stinner in bpo 18794 shelve Shelf instances may now be used in with statements and will be automatically closed at the end of the with block Contributed by Filip Gruszczyński in bpo 13896 shutil copyfile now raises a specific Error subclass SameFileError when the source and destination are the same file which allows an application to take appropriate action on this specific error Contributed by Atsuo Ishimoto and Hynek Schlawack in bpo 1492704 smtpd The SMTPServer and SMTPChannel classes now accept a map keyword argument which if specified is passed in to asynchat async_chat as its map argument This allows an application to avoid affecting the global socket map Contributed by Vinay Sajip in bpo 11959 smtplib SMTPException is now a subclass of OSError which allows both socket level errors and SMTP protocol level errors to be caught in one try except statement by code that only cares whether or not an error occurred Contributed by Ned Jackson Lovely in bpo 2118 socket The socket module now supports the CAN_BCM protocol on platforms that support it Contributed by Brian Thorne in bpo 15359 Socket objects have new methods to get or set their inheritable flag get_inheritable and set_inheritable The socket AF_ and socket SOCK_ constants are now enumeration values using the new enum module This allows meaningful names to be printed during debugging instead of integer magic numbers The AF_LINK constant is now available on BSD and OSX inet_pton and inet_ntop are now supported on Windows Contributed by Atsuo Ishimoto in bpo 7171 sqlite3 A new boolean parameter to the connect function uri can be used to indicate that the database parameter is a uri see the SQLite URI documentation Contributed by poq in bpo 13773 ssl PROTOCOL_TLSv1_1 and PROTOCOL_TLSv1_2 TLSv1 1 and TLSv1 2 support have been added support for these protocols is only available if Python is linked with OpenSSL 1 0 1 or later Contributed by Michele Orrù and Antoine Pitrou in bpo 16692 New function create_default_context provides a standard way to obtain an SSLContext whose settings are intende,en
1333,d to be a reasonable balance between compatibility and security These settings are more stringent than the defaults provided by the SSLContext constructor and may be adjusted in the future without prior deprecation if best practice security requirements change The new recommended best practice for using stdlib libraries that support SSL is to use create_default_context to obtain an SSLContext object modify it if needed and then pass it as the context argument of the appropriate stdlib API Contributed by Christian Heimes in bpo 19689 SSLContext method load_verify_locations accepts a new optional argument cadata which can be used to provide PEM or DER encoded certificates directly via strings or bytes respectively Contributed by Christian Heimes in bpo 18138 New function get_default_verify_paths returns a named tuple of the paths and environment variables that the set_default_verify_paths method uses to set OpenSSL s default cafile and capath This can be an aid in debugging default verification issues Contributed by Christian Heimes in bpo 18143 SSLContext has a new method cert_store_stats that reports the number of loaded X 509 certs X 509 CA certs and certificate revocation lists crl s as well as a get_ca_certs method that returns a list of the loaded CA certificates Contributed by Christian Heimes in bpo 18147 If OpenSSL 0 9 8 or later is available SSLContext has a new attribute verify_flags that can be used to control the certificate verification process by setting it to some combination of the new constants VERIFY_DEFAULT VERIFY_CRL_CHECK_LEAF VERIFY_CRL_CHECK_CHAIN or VERIFY_X509_STRICT OpenSSL does not do any CRL verification by default Contributed by Christien Heimes in bpo 8813 New SSLContext method load_default_certs loads a set of default certificate authority CA certificates from default locations which vary according to the platform It can be used to load both TLS web server authentication certificates purpose SERVER_AUTH for a client to use to verify a server and certificates for a server to use in verifying client certificates purpose CLIENT_AUTH Contributed by Christian Heimes in bpo 19292 Two new windows only functions enum_certificates and enum_crls provide the ability to retrieve certificates certificate information and CRLs from the Windows cert store Contributed by Christian Heimes in bpo 17134 Support for server side SNI Server Name Indication using the new ssl SSLContext set_servername_callback method Contributed by Daniel Black in bpo 8109 The dictionary returned by SSLSocket getpeercert contains additional X509v3 extension items crlDistributionPoints calIssuers and OCSP URIs Contributed by Christian Heimes in bpo 18379 stat The stat module is now backed by a C implementation in _stat A C implementation is required as most of the values aren t standardized and are platform dependent Contributed by Christian Heimes in bpo 11016 The module supports new ST_MODE flags S_IFDOOR S_IFPORT and S_IFWHT Contributed by Christian Hiemes in bpo 11016 struct New function iter_unpack and a new struct Struct iter_unpack method on compiled formats provide streamed unpacking of a buffer containing repeated instances of a given format of data Contributed by Antoine Pitrou in bpo 17804 subprocess check_output now accepts an input argument that can be used to provide the contents of stdin for the command that is run Contributed by Zack Weinberg in bpo 16624 getstatus and getstatusoutput now work on Windows This change was actually inadvertently made in 3 3 4 Contributed by Tim Golden in bpo 10197 sunau The getparams method now returns a namedtuple rather than a plain tuple Contributed by Claudiu Popa in bpo 18901 sunau open now supports the context management protocol when used in a with block the close method of the returned object will be called automatically at the end of the block Contributed by Serhiy Storchaka in bpo 18878 AU_write setsampwidth now supports 24 bit samples thus adding support for writing 24 sample using the module Contributed by Serhiy Storchaka in bpo 19261 The writeframesraw and writeframes metho,en
1334,ds now accept any bytes like object Contributed by Serhiy Storchaka in bpo 8311 sys New function sys getallocatedblocks returns the current number of blocks allocated by the interpreter In CPython with the default with pymalloc setting this is allocations made through the PyObject_Malloc API This can be useful for tracking memory leaks especially if automated via a test suite Contributed by Antoine Pitrou in bpo 13390 When the Python interpreter starts in interactive mode it checks for an __interactivehook__ attribute on the sys module If the attribute exists its value is called with no arguments just before interactive mode is started The check is made after the PYTHONSTARTUP file is read so it can be set there The site module sets it to a function that enables tab completion and history saving in python history if the platform supports readline If you do not want this new behavior you can override it in PYTHONSTARTUP sitecustomize or usercustomize by deleting this attribute from sys or setting it to some other callable Contributed by Éric Araujo and Antoine Pitrou in bpo 5845 tarfile The tarfile module now supports a simple Command Line Interface when called as a script directly or via m This can be used to create and extract tarfile archives Contributed by Berker Peksag in bpo 13477 textwrap The TextWrapper class has two new attributes constructor arguments max_lines which limits the number of lines in the output and placeholder which is a string that will appear at the end of the output if it has been truncated because of max_lines Building on these capabilities a new convenience function shorten collapses all of the whitespace in the input to single spaces and produces a single line of a given width that ends with the placeholder by default Contributed by Antoine Pitrou and Serhiy Storchaka in bpo 18585 and bpo 18725 threading The Thread object representing the main thread can be obtained from the new main_thread function In normal conditions this will be the thread from which the Python interpreter was started Contributed by Andrew Svetlov in bpo 18882 traceback A new traceback clear_frames function takes a traceback object and clears the local variables in all of the frames it references reducing the amount of memory consumed Contributed by Andrew Kuchling in bpo 1565525 types A new DynamicClassAttribute descriptor provides a way to define an attribute that acts normally when looked up through an instance object but which is routed to the class __getattr__ when looked up through the class This allows one to have properties active on a class and have virtual attributes on the class with the same name see Enum for an example Contributed by Ethan Furman in bpo 19030 urllib urllib request now supports data URLs via the DataHandler class Contributed by Mathias Panzenböck in bpo 16423 The http method that will be used by a Request class can now be specified by setting a method class attribute on the subclass Contributed by Jason R Coombs in bpo 18978 Request objects are now reusable if the full_url or data attributes are modified all relevant internal properties are updated This means for example that it is now possible to use the same Request object in more than one OpenerDirector open call with different data arguments or to modify a Request s url rather than recomputing it from scratch There is also a new remove_header method that can be used to remove headers from a Request Contributed by Alexey Kachayev in bpo 16464 Daniel Wozniak in bpo 17485 and Damien Brecht and Senthil Kumaran in bpo 17272 HTTPError objects now have a headers attribute that provides access to the HTTP response headers associated with the error Contributed by Berker Peksag in bpo 15701 unittest The TestCase class has a new method subTest that produces a context manager whose with block becomes a sub test This context manager allows a test method to dynamically generate subtests by say calling the subTest context manager inside a loop A single test method can thereby produce an indefinite number of separately identified and separately counted tes,en
1335,ts all of which will run even if one or more of them fail For example class NumbersTest unittest TestCase def test_even self for i in range 6 with self subTest i i self assertEqual i 2 0 will result in six subtests each identified in the unittest verbose output with a label consisting of the variable name i and a particular value for that variable i 0 i 1 etc See Distinguishing test iterations using subtests for the full version of this example Contributed by Antoine Pitrou in bpo 16997 unittest main now accepts an iterable of test names for defaultTest where previously it only accepted a single test name as a string Contributed by Jyrki Pulliainen in bpo 15132 If SkipTest is raised during test discovery that is at the module level in the test file it is now reported as a skip instead of an error Contributed by Zach Ware in bpo 16935 discover now sorts the discovered files to provide consistent test ordering Contributed by Martin Melin and Jeff Ramnani in bpo 16709 TestSuite now drops references to tests as soon as the test has been run if the test is successful On Python interpreters that do garbage collection this allows the tests to be garbage collected if nothing else is holding a reference to the test It is possible to override this behavior by creating a TestSuite subclass that defines a custom _removeTestAtIndex method Contributed by Tom Wardill Matt McClure and Andrew Svetlov in bpo 11798 A new test assertion context manager assertLogs will ensure that a given block of code emits a log message using the logging module By default the message can come from any logger and have a priority of INFO or higher but both the logger name and an alternative minimum logging level may be specified The object returned by the context manager can be queried for the LogRecord s and or formatted messages that were logged Contributed by Antoine Pitrou in bpo 18937 Test discovery now works with namespace packages Contributed by Claudiu Popa in bpo 17457 unittest mock objects now inspect their specification signatures when matching calls which means an argument can now be matched by either position or name instead of only by position Contributed by Antoine Pitrou in bpo 17015 mock_open objects now have readline and readlines methods Contributed by Toshio Kuratomi in bpo 17467 venv venv now includes activation scripts for the csh and fish shells Contributed by Andrew Svetlov in bpo 15417 EnvBuilder and the create convenience function take a new keyword argument with_pip which defaults to False that controls whether or not EnvBuilder ensures that pip is installed in the virtual environment Contributed by Nick Coghlan in bpo 19552 as part of the PEP 453 implementation wave The getparams method now returns a namedtuple rather than a plain tuple Contributed by Claudiu Popa in bpo 17487 wave open now supports the context management protocol Contributed by Claudiu Popa in bpo 17616 wave can now write output to unseekable files Contributed by David Jones Guilherme Polo and Serhiy Storchaka in bpo 5202 The writeframesraw and writeframes methods now accept any bytes like object Contributed by Serhiy Storchaka in bpo 8311 weakref New WeakMethod class simulates weak references to bound methods Contributed by Antoine Pitrou in bpo 14631 New finalize class makes it possible to register a callback to be invoked when an object is garbage collected without needing to carefully manage the lifecycle of the weak reference itself Contributed by Richard Oudkerk in bpo 15528 The callback if any associated with a ref is now exposed via the __callback__ attribute Contributed by Mark Dickinson in bpo 17643 xml etree A new parser XMLPullParser allows a non blocking applications to parse XML documents An example can be seen at Pull API for non blocking parsing Contributed by Antoine Pitrou in bpo 17741 The xml etree ElementTree tostring and tostringlist functions and the ElementTree write method now have a short_empty_elements keyword only parameter providing control over whether elements with no content are written in abbreviated tag or expanded tag tag form Co,en
1336,ntributed by Ariel Poliak and Serhiy Storchaka in bpo 14377 zipfile The writepy method of the PyZipFile class has a new filterfunc option that can be used to control which directories and files are added to the archive For example this could be used to exclude test files from the archive Contributed by Christian Tismer in bpo 19274 The allowZip64 parameter to ZipFile and PyZipfile is now True by default Contributed by William Mallard in bpo 17201 CPython Implementation Changes PEP 445 Customization of CPython Memory Allocators PEP 445 adds new C level interfaces to customize memory allocation in the CPython interpreter See also PEP 445 Add new APIs to customize Python memory allocators PEP written and implemented by Victor Stinner PEP 442 Safe Object Finalization PEP 442 removes the current limitations and quirks of object finalization in CPython With it objects with __del__ methods as well as generators with finally clauses can be finalized when they are part of a reference cycle As part of this change module globals are no longer forcibly set to None during interpreter shutdown in most cases instead relying on the normal operation of the cyclic garbage collector This avoids a whole class of interpreter shutdown time errors usually involving __del__ methods that have plagued Python since the cyclic GC was first introduced See also PEP 442 Safe object finalization PEP written and implemented by Antoine Pitrou PEP 456 Secure and Interchangeable Hash Algorithm PEP 456 follows up on earlier security fix work done on Python s hash algorithm to address certain DOS attacks to which public facing APIs backed by dictionary lookups may be subject See bpo 14621 for the start of the current round of improvements The PEP unifies CPython s hash code to make it easier for a packager to substitute a different hash algorithm and switches Python s default implementation to a SipHash implementation on platforms that have a 64 bit data type Any performance differences in comparison with the older FNV algorithm are trivial The PEP adds additional fields to the sys hash_info named tuple to describe the hash algorithm in use by the currently executing binary Otherwise the PEP does not alter any existing CPython APIs PEP 436 Argument Clinic Argument Clinic PEP 436 is now part of the CPython build process and can be used to simplify the process of defining and maintaining accurate signatures for builtins and standard library extension modules implemented in C Some standard library extension modules have been converted to use Argument Clinic in Python 3 4 and pydoc and inspect have been updated accordingly It is expected that signature metadata for programmatic introspection will be added to additional callables implemented in C as part of Python 3 4 maintenance releases Note The Argument Clinic PEP is not fully up to date with the state of the implementation This has been deemed acceptable by the release manager and core development team in this case as Argument Clinic will not be made available as a public API for third party use in Python 3 4 See also PEP 436 The Argument Clinic DSL PEP written and implemented by Larry Hastings Other Build and C API Changes The new PyType_GetSlot function has been added to the stable ABI allowing retrieval of function pointers from named type slots when using the limited API Contributed by Martin von Löwis in bpo 17162 The new Py_SetStandardStreamEncoding pre initialization API allows applications embedding the CPython interpreter to reliably force a particular encoding and error handler for the standard streams Contributed by Bastien Montagne and Nick Coghlan in bpo 16129 Most Python C APIs that don t mutate string arguments are now correctly marked as accepting const char rather than char Contributed by Serhiy Storchaka in bpo 1772673 A new shell version of python config can be used even when a python interpreter is not available for example in cross compilation scenarios PyUnicode_FromFormat now supports width and precision specifications for s A U V S and R Contributed by Ysj Ray and Victor Stinner in bpo,en
1337, 7330 New function PyStructSequence_InitType2 supplements the existing PyStructSequence_InitType function The difference is that it returns 0 on success and 1 on failure The CPython source can now be compiled using the address sanity checking features of recent versions of GCC and clang the false alarms in the small object allocator have been silenced Contributed by Dhiru Kholia in bpo 18596 The Windows build now uses Address Space Layout Randomization and Data Execution Prevention Contributed by Christian Heimes in bpo 16632 New function PyObject_LengthHint is the C API equivalent of operator length_hint Contributed by Armin Ronacher in bpo 16148 Other Improvements The python command has a new option I which causes it to run in isolated mode which means that sys path contains neither the script s directory nor the user s site packages directory and all PYTHON environment variables are ignored it implies both s and E Other restrictions may also be applied in the future with the goal being to isolate the execution of a script from the user s environment This is appropriate for example when Python is used to run a system script On most POSIX systems it can and should be used in the line of system scripts Contributed by Christian Heimes in bpo 16499 Tab completion is now enabled by default in the interactive interpreter on systems that support readline History is also enabled by default and is written to and read from the file python history Contributed by Antoine Pitrou and Éric Araujo in bpo 5845 Invoking the Python interpreter with version now outputs the version to standard output instead of standard error bpo 18338 Similar changes were made to argparse bpo 18920 and other modules that have script like invocation capabilities bpo 18922 The CPython Windows installer now adds py to the PATHEXT variable when extensions are registered allowing users to run a python script at the windows command prompt by just typing its name without the py extension Contributed by Paul Moore in bpo 18569 A new make target coverage report will build python run the test suite and generate an HTML coverage report for the C codebase using gcov and lcov The R option to the python regression test suite now also checks for memory allocation leaks using sys getallocatedblocks Contributed by Antoine Pitrou in bpo 13390 python m now works with namespace packages The stat module is now implemented in C which means it gets the values for its constants from the C header files instead of having the values hard coded in the python module as was previously the case Loading multiple python modules from a single OS module so dll now works correctly previously it silently returned the first python module in the file Contributed by Václav Šmilauer in bpo 16421 A new opcode LOAD_CLASSDEREF has been added to fix a bug in the loading of free variables in class bodies that could be triggered by certain uses of __prepare__ Contributed by Benjamin Peterson in bpo 17853 A number of MemoryError related crashes were identified and fixed by Victor Stinner using his PEP 445 based pyfailmalloc tool bpo 18408 bpo 18520 The pyvenv command now accepts a copies option to use copies rather than symlinks even on systems where symlinks are the default Contributed by Vinay Sajip in bpo 18807 The pyvenv command also accepts a without pip option to suppress the otherwise automatic bootstrapping of pip into the virtual environment Contributed by Nick Coghlan in bpo 19552 as part of the PEP 453 implementation The encoding name is now optional in the value set for the PYTHONIOENCODING environment variable This makes it possible to set just the error handler without changing the default encoding Contributed by Serhiy Storchaka in bpo 18818 The bz2 lzma and gzip module open functions now support x exclusive creation mode Contributed by Tim Heaney and Vajrasky Kok in bpo 19201 bpo 19222 and bpo 19223 Significant Optimizations The UTF 32 decoder is now 3x to 4x faster Contributed by Serhiy Storchaka in bpo 14625 The cost of hash collisions for sets is now reduced Each hash table probe now,en
1338, checks a series of consecutive adjacent key hash pairs before continuing to make random probes through the hash table This exploits cache locality to make collision resolution less expensive The collision resolution scheme can be described as a hybrid of linear probing and open addressing The number of additional linear probes defaults to nine This can be changed at compile time by defining LINEAR_PROBES to be any value Set LINEAR_PROBES 0 to turn off linear probing entirely Contributed by Raymond Hettinger in bpo 18771 The interpreter starts about 30 faster A couple of measures lead to the speedup The interpreter loads fewer modules on startup e g the re collections and locale modules and their dependencies are no longer imported by default The marshal module has been improved to load compiled Python code faster Contributed by Antoine Pitrou Christian Heimes and Victor Stinner in bpo 19219 bpo 19218 bpo 19209 bpo 19205 and bpo 9548 bz2 BZ2File is now as fast or faster than the Python2 version for most cases lzma LZMAFile has also been optimized Contributed by Serhiy Storchaka and Nadeem Vawda in bpo 16034 random getrandbits is 20 40 faster for small integers the most common use case Contributed by Serhiy Storchaka in bpo 16674 By taking advantage of the new storage format for strings pickling of strings is now significantly faster Contributed by Victor Stinner and Antoine Pitrou in bpo 15596 A performance issue in io FileIO readall has been solved This particularly affects Windows and significantly speeds up the case of piping significant amounts of data through subprocess Contributed by Richard Oudkerk in bpo 15758 html escape is now 10x faster Contributed by Matt Bryant in bpo 18020 On Windows the native VirtualAlloc is now used instead of the CRT malloc in obmalloc Artificial benchmarks show about a 3 memory savings os urandom now uses a lazily opened persistent file descriptor so as to avoid using many file descriptors when run in parallel from multiple threads Contributed by Antoine Pitrou in bpo 18756 Deprecated This section covers various APIs and other features that have been deprecated in Python 3 4 and will be removed in Python 3 5 or later In most but not all cases using the deprecated APIs will produce a DeprecationWarning when the interpreter is run with deprecation warnings enabled for example by using Wd Deprecations in the Python API As mentioned in PEP 451 A ModuleSpec Type for the Import System a number of importlib methods and functions are deprecated importlib find_loader is replaced by importlib util find_spec importlib machinery PathFinder find_module is replaced by importlib machinery PathFinder find_spec importlib abc MetaPathFinder find_module is replaced by importlib abc MetaPathFinder find_spec importlib abc PathEntryFinder find_loader and find_module are replaced by importlib abc PathEntryFinder find_spec all of the xxx Loader ABC load_module methods importlib abc Loader load_module importlib abc InspectLoader load_module importlib abc FileLoader load_module importlib abc SourceLoader load_module should no longer be implemented instead loaders should implement an exec_module method importlib abc Loader exec_module importlib abc InspectLoader exec_module importlib abc SourceLoader exec_module and let the import system take care of the rest and importlib abc Loader module_repr importlib util module_for_loader importlib util set_loader and importlib util set_package are no longer needed because their functions are now handled automatically by the import system The imp module is pending deprecation To keep compatibility with Python 2 3 code bases the module s removal is currently not scheduled The formatter module is pending deprecation and is slated for removal in Python 3 6 MD5 as the default digestmod for the hmac new function is deprecated Python 3 6 will require an explicit digest name or constructor as digestmod argument The internal Netrc class in the ftplib module has been documented as deprecated in its docstring for quite some time It now emits a DeprecationWarning and will be removed ,en
1339,completely in Python 3 5 The undocumented endtime argument to subprocess Popen wait should not have been exposed and is hopefully not in use it is deprecated and will mostly likely be removed in Python 3 5 The strict argument of HTMLParser is deprecated The plistlib readPlist writePlist readPlistFromBytes and writePlistToBytes functions are deprecated in favor of the corresponding new functions load dump loads and dumps Data is deprecated in favor of just using the bytes constructor The sysconfig key SO is deprecated it has been replaced by EXT_SUFFIX The U mode accepted by various open functions is deprecated In Python3 it does not do anything useful and should be replaced by appropriate uses of io TextIOWrapper if needed and its newline argument The parser argument of xml etree ElementTree iterparse has been deprecated as has the html argument of XMLParser To prepare for the removal of the latter all arguments to XMLParser should be passed by keyword Deprecated Features Running IDLE with the n flag no subprocess is deprecated However the feature will not be removed until bpo 18823 is resolved The site module adding a site python directory to sys path if it exists is deprecated bpo 19375 Removed Operating Systems No Longer Supported Support for the following operating systems has been removed from the source and build tools OS 2 bpo 16135 Windows 2000 changeset e52df05b496a Windows systems where COMSPEC points to command com bpo 14470 VMS bpo 16136 API and Feature Removals The following obsolete and previously deprecated APIs and features have been removed The unmaintained Misc TextMate and Misc vim directories have been removed see the devguide for suggestions on what to use instead The SO makefile macro is removed it was replaced by the SHLIB_SUFFIX and EXT_SUFFIX macros bpo 16754 The PyThreadState tick_counter field has been removed its value has been meaningless since Python 3 2 when the new GIL was introduced bpo 19199 PyLoader and PyPycLoader have been removed from importlib Contributed by Taras Lyapun in bpo 15641 The strict argument to HTTPConnection and HTTPSConnection has been removed HTTP 0 9 style Simple Responses are no longer supported The deprecated urllib request Request getter and setter methods add_data has_data get_data get_type get_host get_selector set_proxy get_origin_req_host and is_unverifiable have been removed use direct attribute access instead Support for loading the deprecated TYPE_INT64 has been removed from marshal Contributed by Dan Riti in bpo 15480 inspect Signature positional only parameters are now required to have a valid name object __format__ no longer accepts non empty format strings it now raises a TypeError instead Using a non empty string has been deprecated since Python 3 2 This change has been made to prevent a situation where previously working but incorrect code would start failing if an object gained a __format__ method which means that your code may now raise a TypeError if you are using an s format code with objects that do not have a __format__ method that handles it See bpo 7994 for background difflib SequenceMatcher isbjunk and difflib SequenceMatcher isbpopular were deprecated in 3 2 and have now been removed use x in sm bjunk and x in sm bpopular where sm is a SequenceMatcher object bpo 13248 Code Cleanups The unused and undocumented internal Scanner class has been removed from the pydoc module The private and effectively unused _gestalt module has been removed along with the private platform functions _mac_ver_lookup _mac_ver_gstalt and _bcd2str which would only have ever been called on badly broken OSX systems see bpo 18393 The hardcoded copies of certain stat constants that were included in the tarfile module namespace have been removed Porting to Python 3 4 This section lists previously described changes and other bugfixes that may require changes to your code Changes in python Command Behavior In a posix shell setting the PATH environment variable to an empty value is equivalent to not setting it at all However setting PYTHONPATH to an empty value was not equiv,en
1340,alent to not setting it at all setting PYTHONPATH to an empty value was equivalent to setting it to which leads to confusion when reasoning by analogy to how PATH works The behavior now conforms to the posix convention for PATH The X refs Y blocks output of a debug with pydebug build of the CPython interpreter is now off by default It can be re enabled using the X showrefcount option Contributed by Ezio Melotti in bpo 17323 The python command and most stdlib scripts as well as argparse now output version information to stdout instead of stderr for issue list see Other Improvements above Changes in the Python API The ABCs defined in importlib abc now either raise the appropriate exception or return a default value instead of raising NotImplementedError blindly This will only affect code calling super and falling through all the way to the ABCs For compatibility catch both NotImplementedError or the appropriate exception as needed The module type now initializes the __package__ and __loader__ attributes to None by default To determine if these attributes were set in a backwards compatible fashion use e g getattr module __loader__ None is not None bpo 17115 importlib util module_for_loader now sets __loader__ and __package__ unconditionally to properly support reloading If this is not desired then you will need to set these attributes manually You can use importlib util module_to_load for module management Import now resets relevant attributes e g __name__ __loader__ __package__ __file__ __cached__ unconditionally when reloading Note that this restores a pre 3 3 behavior in that it means a module is re found when re loaded bpo 19413 Frozen packages no longer set __path__ to a list containing the package name they now set it to an empty list The previous behavior could cause the import system to do the wrong thing on submodule imports if there was also a directory with the same name as the frozen package The correct way to determine if a module is a package or not is to use hasattr module __path__ bpo 18065 Frozen modules no longer define a __file__ attribute It s semantically incorrect for frozen modules to set the attribute as they are not loaded from any explicit location If you must know that a module comes from frozen code then you can see if the module s __spec__ location is set to frozen check if the loader is a subclass of importlib machinery FrozenImporter or if Python 2 compatibility is necessary you can use imp is_frozen py_compile compile now raises FileExistsError if the file path it would write to is a symlink or a non regular file This is to act as a warning that import will overwrite those files with a regular file regardless of what type of file path they were originally importlib abc SourceLoader get_source no longer raises ImportError when the source code being loaded triggers a SyntaxError or UnicodeDecodeError As ImportError is meant to be raised only when source code cannot be found but it should it was felt to be over reaching overloading of that meaning when the source code is found but improperly structured If you were catching ImportError before and wish to continue to ignore syntax or decoding issues catch all three exceptions now functools update_wrapper and functools wraps now correctly set the __wrapped__ attribute to the function being wrapped even if that function also had its __wrapped__ attribute set This means __wrapped__ attributes now correctly link a stack of decorated functions rather than every __wrapped__ attribute in the chain referring to the innermost function Introspection libraries that assumed the previous behaviour was intentional can use inspect unwrap to access the first function in the chain that has no __wrapped__ attribute inspect getfullargspec has been reimplemented on top of inspect signature and hence handles a much wider variety of callable objects than it did in the past It is expected that additional builtin and extension module callables will gain signature metadata over the course of the Python 3 4 series Code that assumes that inspect getfullargspec will fail on ,en
1341,non Python callables may need to be adjusted accordingly importlib machinery PathFinder now passes on the current working directory to objects in sys path_hooks for the empty string This results in sys path_importer_cache never containing thus iterating through sys path_importer_cache based on sys path will not find all keys A module s __file__ when imported in the current working directory will also now have an absolute path including when using m with the interpreter except for __main__ __file__ when a script has been executed directly using a relative path Contributed by Brett Cannon in bpo 18416 is specified on the command line bpo 18416 The removal of the strict argument to HTTPConnection and HTTPSConnection changes the meaning of the remaining arguments if you are specifying them positionally rather than by keyword If you ve been paying attention to deprecation warnings your code should already be specifying any additional arguments via keywords Strings between from __future__ import statements now always raise a SyntaxError Previously if there was no leading docstring an interstitial string would sometimes be ignored This brings CPython into compliance with the language spec Jython and PyPy already were bpo 17434 ssl SSLSocket getpeercert and ssl SSLSocket do_handshake now raise an OSError with ENOTCONN when the SSLSocket is not connected instead of the previous behavior of raising an AttributeError In addition getpeercert will raise a ValueError if the handshake has not yet been done base64 b32decode now raises a binascii Error when the input string contains non b32 alphabet characters instead of a TypeError This particular TypeError was missed when the other TypeError s were converted Contributed by Serhiy Storchaka in bpo 18011 Note this change was also inadvertently applied in Python 3 3 3 The file attribute is now automatically closed when the creating cgi FieldStorage instance is garbage collected If you were pulling the file object out separately from the cgi FieldStorage instance and not keeping the instance alive then you should either store the entire cgi FieldStorage instance or read the contents of the file before the cgi FieldStorage instance is garbage collected Calling read or write on a closed SSL socket now raises an informative ValueError rather than the previous more mysterious AttributeError bpo 9177 slice indices no longer produces an OverflowError for huge values As a consequence of this fix slice indices now raises a ValueError if given a negative length previously it returned nonsense values bpo 14794 The complex constructor unlike the cmath functions was incorrectly accepting float values if an object s __complex__ special method returned one This now raises a TypeError bpo 16290 The int constructor in 3 2 and 3 3 erroneously accepts float values for the base parameter It is unlikely anyone was doing this but if so it will now raise a TypeError bpo 16772 Defaults for keyword only arguments are now evaluated after defaults for regular keyword arguments instead of before Hopefully no one wrote any code that depends on the previous buggy behavior bpo 16967 Stale thread states are now cleared after fork This may cause some system resources to be released that previously were incorrectly kept perpetually alive for example database connections kept in thread local storage bpo 17094 Parameter names in __annotations__ dicts are now mangled properly similarly to __kwdefaults__ Contributed by Yury Selivanov in bpo 20625 hashlib hash name now always returns the identifier in lower case Previously some builtin hashes had uppercase names but now that it is a formal public interface the naming has been made consistent bpo 18532 Because unittest TestSuite now drops references to tests after they are run test harnesses that re use a TestSuite to re run a set of tests may fail Test suites should not be re used in this fashion since it means state is retained between test runs breaking the test isolation that unittest is designed to provide However if the lack of isolation is considered acceptable the old b,en
1342,ehavior can be restored by creating a TestSuite subclass that defines a _removeTestAtIndex method that does nothing see TestSuite __iter__ bpo 11798 unittest now uses argparse for command line parsing There are certain invalid command forms that used to work that are no longer allowed in theory this should not cause backward compatibility issues since the disallowed command forms didn t make any sense and are unlikely to be in use The re split re findall and re sub functions and the group and groups methods of match objects now always return a bytes object when the string to be matched is a bytes like object Previously the return type matched the input type so if your code was depending on the return value being say a bytearray you will need to change your code audioop functions now raise an error immediately if passed string input instead of failing randomly later on bpo 16685 The new convert_charrefs argument to HTMLParser currently defaults to False for backward compatibility but will eventually be changed to default to True It is recommended that you add this keyword with the appropriate value to any HTMLParser calls in your code bpo 13633 Since the digestmod argument to the hmac new function will in the future have no default all calls to hmac new should be changed to explicitly specify a digestmod bpo 17276 Calling sysconfig get_config_var with the SO key or looking SO up in the results of a call to sysconfig get_config_vars is deprecated This key should be replaced by EXT_SUFFIX or SHLIB_SUFFIX depending on the context bpo 19555 Any calls to open functions that specify U should be modified U is ineffective in Python3 and will eventually raise an error if used Depending on the function the equivalent of its old Python2 behavior can be achieved using either a newline argument or if necessary by wrapping the stream in TextIOWrapper to use its newline argument bpo 15204 If you use pyvenv in a script and desire that pip not be installed you must add without pip to your command invocation The default behavior of json dump and json dumps when an indent is specified has changed it no longer produces trailing spaces after the item separating commas at the ends of lines This will matter only if you have tests that are doing white space sensitive comparisons of such output bpo 16333 doctest now looks for doctests in extension module __doc__ strings so if your doctest test discovery includes extension modules that have things that look like doctests in them you may see test failures you ve never seen before when running your tests bpo 3158 The collections abc module has been slightly refactored as part of the Python startup improvements As a consequence of this it is no longer the case that importing collections automatically imports collections abc If your program depended on the undocumented implicit import you will need to add an explicit import collections abc bpo 20784 Changes in the C API PyEval_EvalFrameEx PyObject_Repr and PyObject_Str along with some other internal C APIs now include a debugging assertion that ensures they are not used in situations where they may silently discard a currently active exception In cases where discarding the active exception is expected and desired for example because it has already been saved locally with PyErr_Fetch or is being deliberately replaced with a different exception an explicit PyErr_Clear call will be needed to avoid triggering the assertion when invoking these operations directly or indirectly and running against a version of Python that is compiled with assertions enabled PyErr_SetImportError now sets TypeError when its msg argument is not set Previously only NULL was returned with no exception set The result of the PyOS_ReadlineFunctionPointer callback must now be a string allocated by PyMem_RawMalloc or PyMem_RawRealloc or NULL if an error occurred instead of a string allocated by PyMem_Malloc or PyMem_Realloc bpo 16742 PyThread_set_key_value now always set the value In Python 3 3 the function did nothing if the key already exists if the current value is a non NULL poin,en
1343,ter The f_tstate thread state field of the PyFrameObject structure has been removed to fix a bug see bpo 14432 for the rationale Changed in 3 4 3 PEP 476 Enabling certificate verification by default for stdlib http clients http client and modules which use it such as urllib request and xmlrpc client will now verify that the server presents a certificate which is signed by a CA in the platform trust store and whose hostname matches the hostname being requested by default significantly improving security for many applications For applications which require the old previous behavior they can pass an alternate context import urllib request import ssl This disables all verification context ssl _create_unverified_context This allows using a specific certificate for the host which doesn t need to be in the trust store context ssl create_default_context cafile path to file crt urllib request urlopen https invalid cert context context,en
1344,copy Shallow and deep copy operations Source code Lib copy py Assignment statements in Python do not copy objects they create bindings between a target and an object For collections that are mutable or contain mutable items a copy is sometimes needed so one can change one copy without changing the other This module provides generic shallow and deep copy operations explained below Interface summary copy copy x Return a shallow copy of x copy deepcopy x memo Return a deep copy of x exception copy Error Raised for module specific errors The difference between shallow and deep copying is only relevant for compound objects objects that contain other objects like lists or class instances A shallow copy constructs a new compound object and then to the extent possible inserts references into it to the objects found in the original A deep copy constructs a new compound object and then recursively inserts copies into it of the objects found in the original Two problems often exist with deep copy operations that don t exist with shallow copy operations Recursive objects compound objects that directly or indirectly contain a reference to themselves may cause a recursive loop Because deep copy copies everything it may copy too much such as data which is intended to be shared between copies The deepcopy function avoids these problems by keeping a memo dictionary of objects already copied during the current copying pass and letting user defined classes override the copying operation or the set of components copied This module does not copy types like module method stack trace stack frame file socket window or any similar types It does copy functions and classes shallow and deeply by returning the original object unchanged this is compatible with the way these are treated by the pickle module Shallow copies of dictionaries can be made using dict copy and of lists by assigning a slice of the entire list for example copied_list original_list Classes can use the same interfaces to control copying that they use to control pickling See the description of module pickle for information on these methods In fact the copy module uses the registered pickle functions from the copyreg module In order for a class to define its own copy implementation it can define special methods __copy__ and __deepcopy__ The former is called to implement the shallow copy operation no additional arguments are passed The latter is called to implement the deep copy operation it is passed one argument the memo dictionary If the __deepcopy__ implementation needs to make a deep copy of a component it should call the deepcopy function with the component as first argument and the memo dictionary as second argument The memo dictionary should be treated as an opaque object See also Module pickle Discussion of the special methods used to support object state retrieval and restoration,en
1345,Developing with asyncio Asynchronous programming is different from classic sequential programming This page lists common mistakes and traps and explains how to avoid them Debug Mode By default asyncio runs in production mode In order to ease the development asyncio has a debug mode There are several ways to enable asyncio debug mode Setting the PYTHONASYNCIODEBUG environment variable to 1 Using the Python Development Mode Passing debug True to asyncio run Calling loop set_debug In addition to enabling the debug mode consider also setting the log level of the asyncio logger to logging DEBUG for example the following snippet of code can be run at startup of the application logging basicConfig level logging DEBUG configuring the warnings module to display ResourceWarning warnings One way of doing that is by using the W default command line option When the debug mode is enabled asyncio checks for coroutines that were not awaited and logs them this mitigates the forgotten await pitfall Many non threadsafe asyncio APIs such as loop call_soon and loop call_at methods raise an exception if they are called from a wrong thread The execution time of the I O selector is logged if it takes too long to perform an I O operation Callbacks taking longer than 100 milliseconds are logged The loop slow_callback_duration attribute can be used to set the minimum execution duration in seconds that is considered slow Concurrency and Multithreading An event loop runs in a thread typically the main thread and executes all callbacks and Tasks in its thread While a Task is running in the event loop no other Tasks can run in the same thread When a Task executes an await expression the running Task gets suspended and the event loop executes the next Task To schedule a callback from another OS thread the loop call_soon_threadsafe method should be used Example loop call_soon_threadsafe callback args Almost all asyncio objects are not thread safe which is typically not a problem unless there is code that works with them from outside of a Task or a callback If there s a need for such code to call a low level asyncio API the loop call_soon_threadsafe method should be used e g loop call_soon_threadsafe fut cancel To schedule a coroutine object from a different OS thread the run_coroutine_threadsafe function should be used It returns a concurrent futures Future to access the result async def coro_func return await asyncio sleep 1 42 Later in another OS thread future asyncio run_coroutine_threadsafe coro_func loop Wait for the result result future result To handle signals the event loop must be run in the main thread The loop run_in_executor method can be used with a concurrent futures ThreadPoolExecutor to execute blocking code in a different OS thread without blocking the OS thread that the event loop runs in There is currently no way to schedule coroutines or callbacks directly from a different process such as one started with multiprocessing The Event Loop Methods section lists APIs that can read from pipes and watch file descriptors without blocking the event loop In addition asyncio s Subprocess APIs provide a way to start a process and communicate with it from the event loop Lastly the aforementioned loop run_in_executor method can also be used with a concurrent futures ProcessPoolExecutor to execute code in a different process Running Blocking Code Blocking CPU bound code should not be called directly For example if a function performs a CPU intensive calculation for 1 second all concurrent asyncio Tasks and IO operations would be delayed by 1 second An executor can be used to run a task in a different thread or even in a different process to avoid blocking the OS thread with the event loop See the loop run_in_executor method for more details Logging asyncio uses the logging module and all logging is performed via the asyncio logger The default log level is logging INFO which can be easily adjusted logging getLogger asyncio setLevel logging WARNING Network logging can block the event loop It is recommended to use a separate thread for handling logs o,en
1346,r use non blocking IO For example see Dealing with handlers that block Detect never awaited coroutines When a coroutine function is called but not awaited e g coro instead of await coro or the coroutine is not scheduled with asyncio create_task asyncio will emit a RuntimeWarning import asyncio async def test print never scheduled async def main test asyncio run main Output test py 7 RuntimeWarning coroutine test was never awaited test Output in debug mode test py 7 RuntimeWarning coroutine test was never awaited Coroutine created at most recent call last File t py line 9 in module asyncio run main debug True File t py line 7 in main test test The usual fix is to either await the coroutine or call the asyncio create_task function async def main await test Detect never retrieved exceptions If a Future set_exception is called but the Future object is never awaited on the exception would never be propagated to the user code In this case asyncio would emit a log message when the Future object is garbage collected Example of an unhandled exception import asyncio async def bug raise Exception not consumed async def main asyncio create_task bug asyncio run main Output Task exception was never retrieved future Task finished coro bug done defined at test py 3 exception Exception not consumed Traceback most recent call last File test py line 4 in bug raise Exception not consumed Exception not consumed Enable the debug mode to get the traceback where the task was created asyncio run main debug True Output in debug mode Task exception was never retrieved future Task finished coro bug done defined at test py 3 exception Exception not consumed created at asyncio tasks py 321 source_traceback Object created at most recent call last File t py line 9 in module asyncio run main debug True Traceback most recent call last File t py line 4 in bug raise Exception not consumed Exception not consumed,en
1347,builtins Built in objects This module provides direct access to all built in identifiers of Python for example builtins open is the full name for the built in function open See Built in Functions and Built in Constants for documentation This module is not normally accessed explicitly by most applications but can be useful in modules that provide objects with the same name as a built in value but in which the built in of that name is also needed For example in a module that wants to implement an open function that wraps the built in open this module can be used directly import builtins def open path f builtins open path r return UpperCaser f class UpperCaser Wrapper around a file that converts output to uppercase def __init__ self f self _f f def read self count 1 return self _f read count upper As an implementation detail most modules have the name __builtins__ made available as part of their globals The value of __builtins__ is normally either this module or the value of this module s __dict__ attribute Since this is an implementation detail it may not be used by alternate implementations of Python,en
1348,5 Data Structures This chapter describes some things you ve learned about already in more detail and adds some new things as well 5 1 More on Lists The list data type has some more methods Here are all of the methods of list objects list append x Add an item to the end of the list Equivalent to a len a x list extend iterable Extend the list by appending all the items from the iterable Equivalent to a len a iterable list insert i x Insert an item at a given position The first argument is the index of the element before which to insert so a insert 0 x inserts at the front of the list and a insert len a x is equivalent to a append x list remove x Remove the first item from the list whose value is equal to x It raises a ValueError if there is no such item list pop i Remove the item at the given position in the list and return it If no index is specified a pop removes and returns the last item in the list It raises an IndexError if the list is empty or the index is outside the list range list clear Remove all items from the list Equivalent to del a list index x start end Return zero based index in the list of the first item whose value is equal to x Raises a ValueError if there is no such item The optional arguments start and end are interpreted as in the slice notation and are used to limit the search to a particular subsequence of the list The returned index is computed relative to the beginning of the full sequence rather than the start argument list count x Return the number of times x appears in the list list sort key None reverse False Sort the items of the list in place the arguments can be used for sort customization see sorted for their explanation list reverse Reverse the elements of the list in place list copy Return a shallow copy of the list Equivalent to a An example that uses most of the list methods fruits orange apple pear banana kiwi apple banana fruits count apple 2 fruits count tangerine 0 fruits index banana 3 fruits index banana 4 Find next banana starting at position 4 6 fruits reverse fruits banana apple kiwi banana pear apple orange fruits append grape fruits banana apple kiwi banana pear apple orange grape fruits sort fruits apple apple banana banana grape kiwi orange pear fruits pop pear You might have noticed that methods like insert remove or sort that only modify the list have no return value printed they return the default None 1 This is a design principle for all mutable data structures in Python Another thing you might notice is that not all data can be sorted or compared For instance None hello 10 doesn t sort because integers can t be compared to strings and None can t be compared to other types Also there are some types that don t have a defined ordering relation For example 3 4j 5 7j isn t a valid comparison 5 1 1 Using Lists as Stacks The list methods make it very easy to use a list as a stack where the last element added is the first element retrieved last in first out To add an item to the top of the stack use append To retrieve an item from the top of the stack use pop without an explicit index For example stack 3 4 5 stack append 6 stack append 7 stack 3 4 5 6 7 stack pop 7 stack 3 4 5 6 stack pop 6 stack pop 5 stack 3 4 5 1 2 Using Lists as Queues It is also possible to use a list as a queue where the first element added is the first element retrieved first in first out however lists are not efficient for this purpose While appends and pops from the end of list are fast doing inserts or pops from the beginning of a list is slow because all of the other elements have to be shifted by one To implement a queue use collections deque which was designed to have fast appends and pops from both ends For example from collections import deque queue deque Eric John Michael queue append Terry Terry arrives queue append Graham Graham arrives queue popleft The first to arrive now leaves Eric queue popleft The second to arrive now leaves John queue Remaining queue in order of arrival deque Michael Terry Graham 5 1 3 List Comprehensions List comprehensions provide a concise way to create lists Commo,en
1349,n applications are to make new lists where each element is the result of some operations applied to each member of another sequence or iterable or to create a subsequence of those elements that satisfy a certain condition For example assume we want to create a list of squares like squares for x in range 10 squares append x 2 squares 0 1 4 9 16 25 36 49 64 81 Note that this creates or overwrites a variable named x that still exists after the loop completes We can calculate the list of squares without any side effects using squares list map lambda x x 2 range 10 or equivalently squares x 2 for x in range 10 which is more concise and readable A list comprehension consists of brackets containing an expression followed by a for clause then zero or more for or if clauses The result will be a new list resulting from evaluating the expression in the context of the for and if clauses which follow it For example this listcomp combines the elements of two lists if they are not equal x y for x in 1 2 3 for y in 3 1 4 if x y 1 3 1 4 2 3 2 1 2 4 3 1 3 4 and it s equivalent to combs for x in 1 2 3 for y in 3 1 4 if x y combs append x y combs 1 3 1 4 2 3 2 1 2 4 3 1 3 4 Note how the order of the for and if statements is the same in both these snippets If the expression is a tuple e g the x y in the previous example it must be parenthesized vec 4 2 0 2 4 create a new list with the values doubled x 2 for x in vec 8 4 0 4 8 filter the list to exclude negative numbers x for x in vec if x 0 0 2 4 apply a function to all the elements abs x for x in vec 4 2 0 2 4 call a method on each element freshfruit banana loganberry passion fruit weapon strip for weapon in freshfruit banana loganberry passion fruit create a list of 2 tuples like number square x x 2 for x in range 6 0 0 1 1 2 4 3 9 4 16 5 25 the tuple must be parenthesized otherwise an error is raised x x 2 for x in range 6 File stdin line 1 x x 2 for x in range 6 SyntaxError did you forget parentheses around the comprehension target flatten a list using a listcomp with two for vec 1 2 3 4 5 6 7 8 9 num for elem in vec for num in elem 1 2 3 4 5 6 7 8 9 List comprehensions can contain complex expressions and nested functions from math import pi str round pi i for i in range 1 6 3 1 3 14 3 142 3 1416 3 14159 5 1 4 Nested List Comprehensions The initial expression in a list comprehension can be any arbitrary expression including another list comprehension Consider the following example of a 3x4 matrix implemented as a list of 3 lists of length 4 matrix 1 2 3 4 5 6 7 8 9 10 11 12 The following list comprehension will transpose rows and columns row i for row in matrix for i in range 4 1 5 9 2 6 10 3 7 11 4 8 12 As we saw in the previous section the inner list comprehension is evaluated in the context of the for that follows it so this example is equivalent to transposed for i in range 4 transposed append row i for row in matrix transposed 1 5 9 2 6 10 3 7 11 4 8 12 which in turn is the same as transposed for i in range 4 the following 3 lines implement the nested listcomp transposed_row for row in matrix transposed_row append row i transposed append transposed_row transposed 1 5 9 2 6 10 3 7 11 4 8 12 In the real world you should prefer built in functions to complex flow statements The zip function would do a great job for this use case list zip matrix 1 5 9 2 6 10 3 7 11 4 8 12 See Unpacking Argument Lists for details on the asterisk in this line 5 2 The del statement There is a way to remove an item from a list given its index instead of its value the del statement This differs from the pop method which returns a value The del statement can also be used to remove slices from a list or clear the entire list which we did earlier by assignment of an empty list to the slice For example a 1 1 66 25 333 333 1234 5 del a 0 a 1 66 25 333 333 1234 5 del a 2 4 a 1 66 25 1234 5 del a a del can also be used to delete entire variables del a Referencing the name a hereafter is an error at least until another value is assigned to it We ll find other uses for del later 5 3 Tuples and Sequences We saw that li,en
1350,sts and strings have many common properties such as indexing and slicing operations They are two examples of sequence data types see Sequence Types list tuple range Since Python is an evolving language other sequence data types may be added There is also another standard sequence data type the tuple A tuple consists of a number of values separated by commas for instance t 12345 54321 hello t 0 12345 t 12345 54321 hello Tuples may be nested u t 1 2 3 4 5 u 12345 54321 hello 1 2 3 4 5 Tuples are immutable t 0 88888 Traceback most recent call last File stdin line 1 in module TypeError tuple object does not support item assignment but they can contain mutable objects v 1 2 3 3 2 1 v 1 2 3 3 2 1 As you see on output tuples are always enclosed in parentheses so that nested tuples are interpreted correctly they may be input with or without surrounding parentheses although often parentheses are necessary anyway if the tuple is part of a larger expression It is not possible to assign to the individual items of a tuple however it is possible to create tuples which contain mutable objects such as lists Though tuples may seem similar to lists they are often used in different situations and for different purposes Tuples are immutable and usually contain a heterogeneous sequence of elements that are accessed via unpacking see later in this section or indexing or even by attribute in the case of namedtuples Lists are mutable and their elements are usually homogeneous and are accessed by iterating over the list A special problem is the construction of tuples containing 0 or 1 items the syntax has some extra quirks to accommodate these Empty tuples are constructed by an empty pair of parentheses a tuple with one item is constructed by following a value with a comma it is not sufficient to enclose a single value in parentheses Ugly but effective For example empty singleton hello note trailing comma len empty 0 len singleton 1 singleton hello The statement t 12345 54321 hello is an example of tuple packing the values 12345 54321 and hello are packed together in a tuple The reverse operation is also possible x y z t This is called appropriately enough sequence unpacking and works for any sequence on the right hand side Sequence unpacking requires that there are as many variables on the left side of the equals sign as there are elements in the sequence Note that multiple assignment is really just a combination of tuple packing and sequence unpacking 5 4 Sets Python also includes a data type for sets A set is an unordered collection with no duplicate elements Basic uses include membership testing and eliminating duplicate entries Set objects also support mathematical operations like union intersection difference and symmetric difference Curly braces or the set function can be used to create sets Note to create an empty set you have to use set not the latter creates an empty dictionary a data structure that we discuss in the next section Here is a brief demonstration basket apple orange apple pear orange banana print basket show that duplicates have been removed orange banana pear apple orange in basket fast membership testing True crabgrass in basket False Demonstrate set operations on unique letters from two words a set abracadabra b set alacazam a unique letters in a a r b c d a b letters in a but not in b r d b a b letters in a or b or both a c r d b m z l a b letters in both a and b a c a b letters in a or b but not both r d b m z l Similarly to list comprehensions set comprehensions are also supported a x for x in abracadabra if x not in abc a r d 5 5 Dictionaries Another useful data type built into Python is the dictionary see Mapping Types dict Dictionaries are sometimes found in other languages as associative memories or associative arrays Unlike sequences which are indexed by a range of numbers dictionaries are indexed by keys which can be any immutable type strings and numbers can always be keys Tuples can be used as keys if they contain only strings numbers or tuples if a tuple contains any mutable object either directly or indirec,en
1351,tly it cannot be used as a key You can t use lists as keys since lists can be modified in place using index assignments slice assignments or methods like append and extend It is best to think of a dictionary as a set of key value pairs with the requirement that the keys are unique within one dictionary A pair of braces creates an empty dictionary Placing a comma separated list of key value pairs within the braces adds initial key value pairs to the dictionary this is also the way dictionaries are written on output The main operations on a dictionary are storing a value with some key and extracting the value given the key It is also possible to delete a key value pair with del If you store using a key that is already in use the old value associated with that key is forgotten It is an error to extract a value using a non existent key Performing list d on a dictionary returns a list of all the keys used in the dictionary in insertion order if you want it sorted just use sorted d instead To check whether a single key is in the dictionary use the in keyword Here is a small example using a dictionary tel jack 4098 sape 4139 tel guido 4127 tel jack 4098 sape 4139 guido 4127 tel jack 4098 del tel sape tel irv 4127 tel jack 4098 guido 4127 irv 4127 list tel jack guido irv sorted tel guido irv jack guido in tel True jack not in tel False The dict constructor builds dictionaries directly from sequences of key value pairs dict sape 4139 guido 4127 jack 4098 sape 4139 guido 4127 jack 4098 In addition dict comprehensions can be used to create dictionaries from arbitrary key and value expressions x x 2 for x in 2 4 6 2 4 4 16 6 36 When the keys are simple strings it is sometimes easier to specify pairs using keyword arguments dict sape 4139 guido 4127 jack 4098 sape 4139 guido 4127 jack 4098 5 6 Looping Techniques When looping through dictionaries the key and corresponding value can be retrieved at the same time using the items method knights gallahad the pure robin the brave for k v in knights items print k v gallahad the pure robin the brave When looping through a sequence the position index and corresponding value can be retrieved at the same time using the enumerate function for i v in enumerate tic tac toe print i v 0 tic 1 tac 2 toe To loop over two or more sequences at the same time the entries can be paired with the zip function questions name quest favorite color answers lancelot the holy grail blue for q a in zip questions answers print What is your 0 It is 1 format q a What is your name It is lancelot What is your quest It is the holy grail What is your favorite color It is blue To loop over a sequence in reverse first specify the sequence in a forward direction and then call the reversed function for i in reversed range 1 10 2 print i 9 7 5 3 1 To loop over a sequence in sorted order use the sorted function which returns a new sorted list while leaving the source unaltered basket apple orange apple pear orange banana for i in sorted basket print i apple apple banana orange orange pear Using set on a sequence eliminates duplicate elements The use of sorted in combination with set over a sequence is an idiomatic way to loop over unique elements of the sequence in sorted order basket apple orange apple pear orange banana for f in sorted set basket print f apple banana orange pear It is sometimes tempting to change a list while you are looping over it however it is often simpler and safer to create a new list instead import math raw_data 56 2 float NaN 51 7 55 3 52 5 float NaN 47 8 filtered_data for value in raw_data if not math isnan value filtered_data append value filtered_data 56 2 51 7 55 3 52 5 47 8 5 7 More on Conditions The conditions used in while and if statements can contain any operators not just comparisons The comparison operators in and not in are membership tests that determine whether a value is in or not in a container The operators is and is not compare whether two objects are really the same object All comparison operators have the same priority which is lower than that of all numerical operators Comparisons,en
1352, can be chained For example a b c tests whether a is less than b and moreover b equals c Comparisons may be combined using the Boolean operators and and or and the outcome of a comparison or of any other Boolean expression may be negated with not These have lower priorities than comparison operators between them not has the highest priority and or the lowest so that A and not B or C is equivalent to A and not B or C As always parentheses can be used to express the desired composition The Boolean operators and and or are so called short circuit operators their arguments are evaluated from left to right and evaluation stops as soon as the outcome is determined For example if A and C are true but B is false A and B and C does not evaluate the expression C When used as a general value and not as a Boolean the return value of a short circuit operator is the last evaluated argument It is possible to assign the result of a comparison or other Boolean expression to a variable For example string1 string2 string3 Trondheim Hammer Dance non_null string1 or string2 or string3 non_null Trondheim Note that in Python unlike C assignment inside expressions must be done explicitly with the walrus operator This avoids a common class of problems encountered in C programs typing in an expression when was intended 5 8 Comparing Sequences and Other Types Sequence objects typically may be compared to other objects with the same sequence type The comparison uses lexicographical ordering first the first two items are compared and if they differ this determines the outcome of the comparison if they are equal the next two items are compared and so on until either sequence is exhausted If two items to be compared are themselves sequences of the same type the lexicographical comparison is carried out recursively If all items of two sequences compare equal the sequences are considered equal If one sequence is an initial sub sequence of the other the shorter sequence is the smaller lesser one Lexicographical ordering for strings uses the Unicode code point number to order individual characters Some examples of comparisons between sequences of the same type 1 2 3 1 2 4 1 2 3 1 2 4 ABC C Pascal Python 1 2 3 4 1 2 4 1 2 1 2 1 1 2 3 1 0 2 0 3 0 1 2 aa ab 1 2 abc a 4 Note that comparing objects of different types with or is legal provided that the objects have appropriate comparison methods For example mixed numeric types are compared according to their numeric value so 0 equals 0 0 etc Otherwise rather than providing an arbitrary ordering the interpreter will raise a TypeError exception Footnotes 1 Other languages may return the mutated object which allows method chaining such as d insert a remove b sort,en
1353,socket Low level networking interface Source code Lib socket py This module provides access to the BSD socket interface It is available on all modern Unix systems Windows MacOS and probably additional platforms Note Some behavior may be platform dependent since calls are made to the operating system socket APIs Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information The Python interface is a straightforward transliteration of the Unix system call and library interface for sockets to Python s object oriented style the socket function returns a socket object whose methods implement the various socket system calls Parameter types are somewhat higher level than in the C interface as with read and write operations on Python files buffer allocation on receive operations is automatic and buffer length is implicit on send operations See also Module socketserver Classes that simplify writing network servers Module ssl A TLS SSL wrapper for socket objects Socket families Depending on the system and the build options various socket families are supported by this module The address format required by a particular socket object is automatically selected based on the address family specified when the socket object was created Socket addresses are represented as follows The address of an AF_UNIX socket bound to a file system node is represented as a string using the file system encoding and the surrogateescape error handler see PEP 383 An address in Linux s abstract namespace is returned as a bytes like object with an initial null byte note that sockets in this namespace can communicate with normal file system sockets so programs intended to run on Linux may need to deal with both types of address A string or bytes like object can be used for either type of address when passing it as an argument Changed in version 3 3 Previously AF_UNIX socket paths were assumed to use UTF 8 encoding Changed in version 3 5 Writable bytes like object is now accepted A pair host port is used for the AF_INET address family where host is a string representing either a hostname in internet domain notation like daring cwi nl or an IPv4 address like 100 50 200 5 and port is an integer For IPv4 addresses two special forms are accepted instead of a host address represents INADDR_ANY which is used to bind to all interfaces and the string broadcast represents INADDR_BROADCAST This behavior is not compatible with IPv6 therefore you may want to avoid these if you intend to support IPv6 with your Python programs For AF_INET6 address family a four tuple host port flowinfo scope_id is used where flowinfo and scope_id represent the sin6_flowinfo and sin6_scope_id members in struct sockaddr_in6 in C For socket module methods flowinfo and scope_id can be omitted just for backward compatibility Note however omission of scope_id can cause problems in manipulating scoped IPv6 addresses Changed in version 3 7 For multicast addresses with scope_id meaningful address may not contain scope_id or zone id part This information is superfluous and may be safely omitted recommended AF_NETLINK sockets are represented as pairs pid groups Linux only support for TIPC is available using the AF_TIPC address family TIPC is an open non IP based networked protocol designed for use in clustered computer environments Addresses are represented by a tuple and the fields depend on the address type The general tuple form is addr_type v1 v2 v3 scope where addr_type is one of TIPC_ADDR_NAMESEQ TIPC_ADDR_NAME or TIPC_ADDR_ID scope is one of TIPC_ZONE_SCOPE TIPC_CLUSTER_SCOPE and TIPC_NODE_SCOPE If addr_type is TIPC_ADDR_NAME then v1 is the server type v2 is the port identifier and v3 should be 0 If addr_type is TIPC_ADDR_NAMESEQ then v1 is the server type v2 is the lower port number and v3 is the upper port number If addr_type is TIPC_ADDR_ID then v1 is the node v2 is the reference and v3 should be set to 0 A tuple interface is used for the AF_CAN address family where i,en
1354,nterface is a string representing a network interface name like can0 The network interface name can be used to receive packets from all network interfaces of this family CAN_ISOTP protocol require a tuple interface rx_addr tx_addr where both additional parameters are unsigned long integer that represent a CAN identifier standard or extended CAN_J1939 protocol require a tuple interface name pgn addr where additional parameters are 64 bit unsigned integer representing the ECU name a 32 bit unsigned integer representing the Parameter Group Number PGN and an 8 bit integer representing the address A string or a tuple id unit is used for the SYSPROTO_CONTROL protocol of the PF_SYSTEM family The string is the name of a kernel control using a dynamically assigned ID The tuple can be used if ID and unit number of the kernel control are known or if a registered ID is used New in version 3 3 AF_BLUETOOTH supports the following protocols and address formats BTPROTO_L2CAP accepts bdaddr psm where bdaddr is the Bluetooth address as a string and psm is an integer BTPROTO_RFCOMM accepts bdaddr channel where bdaddr is the Bluetooth address as a string and channel is an integer BTPROTO_HCI accepts device_id where device_id is either an integer or a string with the Bluetooth address of the interface This depends on your OS NetBSD and DragonFlyBSD expect a Bluetooth address while everything else expects an integer Changed in version 3 2 NetBSD and DragonFlyBSD support added BTPROTO_SCO accepts bdaddr where bdaddr is a bytes object containing the Bluetooth address in a string format ex b 12 23 34 45 56 67 This protocol is not supported under FreeBSD AF_ALG is a Linux only socket based interface to Kernel cryptography An algorithm socket is configured with a tuple of two to four elements type name feat mask where type is the algorithm type as string e g aead hash skcipher or rng name is the algorithm name and operation mode as string e g sha256 hmac sha256 cbc aes or drbg_nopr_ctr_aes256 feat and mask are unsigned 32bit integers Availability Linux 2 6 38 Some algorithm types require more recent Kernels New in version 3 6 AF_VSOCK allows communication between virtual machines and their hosts The sockets are represented as a CID port tuple where the context ID or CID and port are integers Availability Linux 3 9 See vsock 7 New in version 3 7 AF_PACKET is a low level interface directly to network devices The addresses are represented by the tuple ifname proto pkttype hatype addr where ifname String specifying the device name proto The Ethernet protocol number May be ETH_P_ALL to capture all protocols one of the ETHERTYPE_ constants or any other Ethernet protocol number pkttype Optional integer specifying the packet type PACKET_HOST the default Packet addressed to the local host PACKET_BROADCAST Physical layer broadcast packet PACKET_MULTICAST Packet sent to a physical layer multicast address PACKET_OTHERHOST Packet to some other host that has been caught by a device driver in promiscuous mode PACKET_OUTGOING Packet originating from the local host that is looped back to a packet socket hatype Optional integer specifying the ARP hardware address type addr Optional bytes like object specifying the hardware physical address whose interpretation depends on the device Availability Linux 2 2 AF_QIPCRTR is a Linux only socket based interface for communicating with services running on co processors in Qualcomm platforms The address family is represented as a node port tuple where the node and port are non negative integers Availability Linux 4 7 New in version 3 8 IPPROTO_UDPLITE is a variant of UDP which allows you to specify what portion of a packet is covered with the checksum It adds two socket options that you can change self setsockopt IPPROTO_UDPLITE UDPLITE_SEND_CSCOV length will change what portion of outgoing packets are covered by the checksum and self setsockopt IPPROTO_UDPLITE UDPLITE_RECV_CSCOV length will filter out packets which cover too little of their data In both cases length should be in range 8 2 16 8 Such a socket should be constru,en
1355,cted with socket AF_INET SOCK_DGRAM IPPROTO_UDPLITE for IPv4 or socket AF_INET6 SOCK_DGRAM IPPROTO_UDPLITE for IPv6 Availability Linux 2 6 20 FreeBSD 10 1 New in version 3 9 AF_HYPERV is a Windows only socket based interface for communicating with Hyper V hosts and guests The address family is represented as a vm_id service_id tuple where the vm_id and service_id are UUID strings The vm_id is the virtual machine identifier or a set of known VMID values if the target is not a specific virtual machine Known VMID constants defined on socket are HV_GUID_ZERO HV_GUID_BROADCAST HV_GUID_WILDCARD Used to bind on itself and accept connections from all partitions HV_GUID_CHILDREN Used to bind on itself and accept connection from child partitions HV_GUID_LOOPBACK Used as a target to itself HV_GUID_PARENT When used as a bind accepts connection from the parent partition When used as an address target it will connect to the parent partition The service_id is the service identifier of the registered service New in version 3 12 If you use a hostname in the host portion of IPv4 v6 socket address the program may show a nondeterministic behavior as Python uses the first address returned from the DNS resolution The socket address will be resolved differently into an actual IPv4 v6 address depending on the results from DNS resolution and or the host configuration For deterministic behavior use a numeric address in host portion All errors raise exceptions The normal exceptions for invalid argument types and out of memory conditions can be raised Errors related to socket or address semantics raise OSError or one of its subclasses Non blocking mode is supported through setblocking A generalization of this based on timeouts is supported through settimeout Module contents The module socket exports the following elements Exceptions exception socket error A deprecated alias of OSError Changed in version 3 3 Following PEP 3151 this class was made an alias of OSError exception socket herror A subclass of OSError this exception is raised for address related errors i e for functions that use h_errno in the POSIX C API including gethostbyname_ex and gethostbyaddr The accompanying value is a pair h_errno string representing an error returned by a library call h_errno is a numeric value while string represents the description of h_errno as returned by the hstrerror C function Changed in version 3 3 This class was made a subclass of OSError exception socket gaierror A subclass of OSError this exception is raised for address related errors by getaddrinfo and getnameinfo The accompanying value is a pair error string representing an error returned by a library call string represents the description of error as returned by the gai_strerror C function The numeric error value will match one of the EAI_ constants defined in this module Changed in version 3 3 This class was made a subclass of OSError exception socket timeout A deprecated alias of TimeoutError A subclass of OSError this exception is raised when a timeout occurs on a socket which has had timeouts enabled via a prior call to settimeout or implicitly through setdefaulttimeout The accompanying value is a string whose value is currently always timed out Changed in version 3 3 This class was made a subclass of OSError Changed in version 3 10 This class was made an alias of TimeoutError Constants The AF_ and SOCK_ constants are now AddressFamily and SocketKind IntEnum collections New in version 3 4 socket AF_UNIX socket AF_INET socket AF_INET6 These constants represent the address and protocol families used for the first argument to socket If the AF_UNIX constant is not defined then this protocol is unsupported More constants may be available depending on the system socket AF_UNSPEC AF_UNSPEC means that getaddrinfo should return socket addresses for any address family either IPv4 IPv6 or any other that can be used socket SOCK_STREAM socket SOCK_DGRAM socket SOCK_RAW socket SOCK_RDM socket SOCK_SEQPACKET These constants represent the socket types used for the second argument to socket More constants may be,en
1356, available depending on the system Only SOCK_STREAM and SOCK_DGRAM appear to be generally useful socket SOCK_CLOEXEC socket SOCK_NONBLOCK These two constants if defined can be combined with the socket types and allow you to set some flags atomically thus avoiding possible race conditions and the need for separate calls See also Secure File Descriptor Handling for a more thorough explanation Availability Linux 2 6 27 New in version 3 2 SO_ socket SOMAXCONN MSG_ SOL_ SCM_ IPPROTO_ IPPORT_ INADDR_ IP_ IPV6_ EAI_ AI_ NI_ TCP_ Many constants of these forms documented in the Unix documentation on sockets and or the IP protocol are also defined in the socket module They are generally used in arguments to the setsockopt and getsockopt methods of socket objects In most cases only those symbols that are defined in the Unix header files are defined for a few symbols default values are provided Changed in version 3 6 SO_DOMAIN SO_PROTOCOL SO_PEERSEC SO_PASSSEC TCP_USER_TIMEOUT TCP_CONGESTION were added Changed in version 3 6 5 On Windows TCP_FASTOPEN TCP_KEEPCNT appear if run time Windows supports Changed in version 3 7 TCP_NOTSENT_LOWAT was added On Windows TCP_KEEPIDLE TCP_KEEPINTVL appear if run time Windows supports Changed in version 3 10 IP_RECVTOS was added Added TCP_KEEPALIVE On MacOS this constant can be used in the same way that TCP_KEEPIDLE is used on Linux Changed in version 3 11 Added TCP_CONNECTION_INFO On MacOS this constant can be used in the same way that TCP_INFO is used on Linux and BSD Changed in version 3 12 Added SO_RTABLE and SO_USER_COOKIE On OpenBSD and FreeBSD respectively those constants can be used in the same way that SO_MARK is used on Linux Also added missing TCP socket options from Linux TCP_MD5SIG TCP_THIN_LINEAR_TIMEOUTS TCP_THIN_DUPACK TCP_REPAIR TCP_REPAIR_QUEUE TCP_QUEUE_SEQ TCP_REPAIR_OPTIONS TCP_TIMESTAMP TCP_CC_INFO TCP_SAVE_SYN TCP_SAVED_SYN TCP_REPAIR_WINDOW TCP_FASTOPEN_CONNECT TCP_ULP TCP_MD5SIG_EXT TCP_FASTOPEN_KEY TCP_FASTOPEN_NO_COOKIE TCP_ZEROCOPY_RECEIVE TCP_INQ TCP_TX_DELAY Added IP_PKTINFO IP_UNBLOCK_SOURCE IP_BLOCK_SOURCE IP_ADD_SOURCE_MEMBERSHIP IP_DROP_SOURCE_MEMBERSHIP socket AF_CAN socket PF_CAN SOL_CAN_ CAN_ Many constants of these forms documented in the Linux documentation are also defined in the socket module Availability Linux 2 6 25 NetBSD 8 New in version 3 3 Changed in version 3 11 NetBSD support was added socket CAN_BCM CAN_BCM_ CAN_BCM in the CAN protocol family is the broadcast manager BCM protocol Broadcast manager constants documented in the Linux documentation are also defined in the socket module Availability Linux 2 6 25 Note The CAN_BCM_CAN_FD_FRAME flag is only available on Linux 4 8 New in version 3 4 socket CAN_RAW_FD_FRAMES Enables CAN FD support in a CAN_RAW socket This is disabled by default This allows your application to send both CAN and CAN FD frames however you must accept both CAN and CAN FD frames when reading from the socket This constant is documented in the Linux documentation Availability Linux 3 6 New in version 3 5 socket CAN_RAW_JOIN_FILTERS Joins the applied CAN filters such that only CAN frames that match all given CAN filters are passed to user space This constant is documented in the Linux documentation Availability Linux 4 1 New in version 3 9 socket CAN_ISOTP CAN_ISOTP in the CAN protocol family is the ISO TP ISO 15765 2 protocol ISO TP constants documented in the Linux documentation Availability Linux 2 6 25 New in version 3 7 socket CAN_J1939 CAN_J1939 in the CAN protocol family is the SAE J1939 protocol J1939 constants documented in the Linux documentation Availability Linux 5 4 New in version 3 9 socket AF_DIVERT socket PF_DIVERT These two constants documented in the FreeBSD divert 4 manual page are also defined in the socket module Availability FreeBSD 14 0 New in version 3 12 socket AF_PACKET socket PF_PACKET PACKET_ Many constants of these forms documented in the Linux documentation are also defined in the socket module Availability Linux 2 2 socket ETH_P_ALL ETH_P_ALL can be used in the socket constructor as proto for the AF_PA,en
1357,CKET family in order to capture every packet regardless of protocol For more information see the packet 7 manpage Availability Linux New in version 3 12 socket AF_RDS socket PF_RDS socket SOL_RDS RDS_ Many constants of these forms documented in the Linux documentation are also defined in the socket module Availability Linux 2 6 30 New in version 3 3 socket SIO_RCVALL socket SIO_KEEPALIVE_VALS socket SIO_LOOPBACK_FAST_PATH RCVALL_ Constants for Windows WSAIoctl The constants are used as arguments to the ioctl method of socket objects Changed in version 3 6 SIO_LOOPBACK_FAST_PATH was added TIPC_ TIPC related constants matching the ones exported by the C socket API See the TIPC documentation for more information socket AF_ALG socket SOL_ALG ALG_ Constants for Linux Kernel cryptography Availability Linux 2 6 38 New in version 3 6 socket AF_VSOCK socket IOCTL_VM_SOCKETS_GET_LOCAL_CID VMADDR SO_VM Constants for Linux host guest communication Availability Linux 4 8 New in version 3 7 socket AF_LINK Availability BSD macOS New in version 3 4 socket has_ipv6 This constant contains a boolean value which indicates if IPv6 is supported on this platform socket BDADDR_ANY socket BDADDR_LOCAL These are string constants containing Bluetooth addresses with special meanings For example BDADDR_ANY can be used to indicate any address when specifying the binding socket with BTPROTO_RFCOMM socket HCI_FILTER socket HCI_TIME_STAMP socket HCI_DATA_DIR For use with BTPROTO_HCI HCI_FILTER is not available for NetBSD or DragonFlyBSD HCI_TIME_STAMP and HCI_DATA_DIR are not available for FreeBSD NetBSD or DragonFlyBSD socket AF_QIPCRTR Constant for Qualcomm s IPC router protocol used to communicate with service providing remote processors Availability Linux 4 7 socket SCM_CREDS2 socket LOCAL_CREDS socket LOCAL_CREDS_PERSISTENT LOCAL_CREDS and LOCAL_CREDS_PERSISTENT can be used with SOCK_DGRAM SOCK_STREAM sockets equivalent to Linux DragonFlyBSD SO_PASSCRED while LOCAL_CREDS sends the credentials at first read LOCAL_CREDS_PERSISTENT sends for each read SCM_CREDS2 must be then used for the latter for the message type New in version 3 11 Availability FreeBSD socket SO_INCOMING_CPU Constant to optimize CPU locality to be used in conjunction with SO_REUSEPORT New in version 3 11 Availability Linux 3 9 socket AF_HYPERV socket HV_PROTOCOL_RAW socket HVSOCKET_CONNECT_TIMEOUT socket HVSOCKET_CONNECT_TIMEOUT_MAX socket HVSOCKET_CONNECTED_SUSPEND socket HVSOCKET_ADDRESS_FLAG_PASSTHRU socket HV_GUID_ZERO socket HV_GUID_WILDCARD socket HV_GUID_BROADCAST socket HV_GUID_CHILDREN socket HV_GUID_LOOPBACK socket HV_GUID_PARENT Constants for Windows Hyper V sockets for host guest communications Availability Windows New in version 3 12 socket ETHERTYPE_ARP socket ETHERTYPE_IP socket ETHERTYPE_IPV6 socket ETHERTYPE_VLAN IEEE 802 3 protocol number constants Availability Linux FreeBSD macOS New in version 3 12 Functions Creating sockets The following functions all create socket objects class socket socket family AF_INET type SOCK_STREAM proto 0 fileno None Create a new socket using the given address family socket type and protocol number The address family should be AF_INET the default AF_INET6 AF_UNIX AF_CAN AF_PACKET or AF_RDS The socket type should be SOCK_STREAM the default SOCK_DGRAM SOCK_RAW or perhaps one of the other SOCK_ constants The protocol number is usually zero and may be omitted or in the case where the address family is AF_CAN the protocol should be one of CAN_RAW CAN_BCM CAN_ISOTP or CAN_J1939 If fileno is specified the values for family type and proto are auto detected from the specified file descriptor Auto detection can be overruled by calling the function with explicit family type or proto arguments This only affects how Python represents e g the return value of socket getpeername but not the actual OS resource Unlike socket fromfd fileno will return the same socket and not a duplicate This may help close a detached socket using socket close The newly created socket is non inheritable Raises an auditing event socket __new__ with arguments self family t,en
1358,ype protocol Changed in version 3 3 The AF_CAN family was added The AF_RDS family was added Changed in version 3 4 The CAN_BCM protocol was added Changed in version 3 4 The returned socket is now non inheritable Changed in version 3 7 The CAN_ISOTP protocol was added Changed in version 3 7 When SOCK_NONBLOCK or SOCK_CLOEXEC bit flags are applied to type they are cleared and socket type will not reflect them They are still passed to the underlying system socket call Therefore sock socket socket socket AF_INET socket SOCK_STREAM socket SOCK_NONBLOCK will still create a non blocking socket on OSes that support SOCK_NONBLOCK but sock type will be set to socket SOCK_STREAM Changed in version 3 9 The CAN_J1939 protocol was added Changed in version 3 10 The IPPROTO_MPTCP protocol was added socket socketpair family type proto Build a pair of connected socket objects using the given address family socket type and protocol number Address family socket type and protocol number are as for the socket function above The default family is AF_UNIX if defined on the platform otherwise the default is AF_INET The newly created sockets are non inheritable Changed in version 3 2 The returned socket objects now support the whole socket API rather than a subset Changed in version 3 4 The returned sockets are now non inheritable Changed in version 3 5 Windows support added socket create_connection address timeout GLOBAL_DEFAULT source_address None all_errors False Connect to a TCP service listening on the internet address a 2 tuple host port and return the socket object This is a higher level function than socket connect if host is a non numeric hostname it will try to resolve it for both AF_INET and AF_INET6 and then try to connect to all possible addresses in turn until a connection succeeds This makes it easy to write clients that are compatible to both IPv4 and IPv6 Passing the optional timeout parameter will set the timeout on the socket instance before attempting to connect If no timeout is supplied the global default timeout setting returned by getdefaulttimeout is used If supplied source_address must be a 2 tuple host port for the socket to bind to as its source address before connecting If host or port are or 0 respectively the OS default behavior will be used When a connection cannot be created an exception is raised By default it is the exception from the last address in the list If all_errors is True it is an ExceptionGroup containing the errors of all attempts Changed in version 3 2 source_address was added Changed in version 3 11 all_errors was added socket create_server address family AF_INET backlog None reuse_port False dualstack_ipv6 False Convenience function which creates a TCP socket bound to address a 2 tuple host port and returns the socket object family should be either AF_INET or AF_INET6 backlog is the queue size passed to socket listen if not specified a default reasonable value is chosen reuse_port dictates whether to set the SO_REUSEPORT socket option If dualstack_ipv6 is true and the platform supports it the socket will be able to accept both IPv4 and IPv6 connections else it will raise ValueError Most POSIX platforms and Windows are supposed to support this functionality When this functionality is enabled the address returned by socket getpeername when an IPv4 connection occurs will be an IPv6 address represented as an IPv4 mapped IPv6 address If dualstack_ipv6 is false it will explicitly disable this functionality on platforms that enable it by default e g Linux This parameter can be used in conjunction with has_dualstack_ipv6 import socket addr 8080 all interfaces port 8080 if socket has_dualstack_ipv6 s socket create_server addr family socket AF_INET6 dualstack_ipv6 True else s socket create_server addr Note On POSIX platforms the SO_REUSEADDR socket option is set in order to immediately reuse previous sockets which were bound on the same address and remained in TIME_WAIT state New in version 3 8 socket has_dualstack_ipv6 Return True if the platform supports creating a TCP socket which can handle both IPv4 and ,en
1359,IPv6 connections New in version 3 8 socket fromfd fd family type proto 0 Duplicate the file descriptor fd an integer as returned by a file object s fileno method and build a socket object from the result Address family socket type and protocol number are as for the socket function above The file descriptor should refer to a socket but this is not checked subsequent operations on the object may fail if the file descriptor is invalid This function is rarely needed but can be used to get or set socket options on a socket passed to a program as standard input or output such as a server started by the Unix inet daemon The socket is assumed to be in blocking mode The newly created socket is non inheritable Changed in version 3 4 The returned socket is now non inheritable socket fromshare data Instantiate a socket from data obtained from the socket share method The socket is assumed to be in blocking mode Availability Windows New in version 3 3 socket SocketType This is a Python type object that represents the socket object type It is the same as type socket Other functions The socket module also offers various network related services socket close fd Close a socket file descriptor This is like os close but for sockets On some platforms most noticeable Windows os close does not work for socket file descriptors New in version 3 7 socket getaddrinfo host port family 0 type 0 proto 0 flags 0 Translate the host port argument into a sequence of 5 tuples that contain all the necessary arguments for creating a socket connected to that service host is a domain name a string representation of an IPv4 v6 address or None port is a string service name such as http a numeric port number or None By passing None as the value of host and port you can pass NULL to the underlying C API The family type and proto arguments can be optionally specified in order to narrow the list of addresses returned Passing zero as a value for each of these arguments selects the full range of results The flags argument can be one or several of the AI_ constants and will influence how results are computed and returned For example AI_NUMERICHOST will disable domain name resolution and will raise an error if host is a domain name The function returns a list of 5 tuples with the following structure family type proto canonname sockaddr In these tuples family type proto are all integers and are meant to be passed to the socket function canonname will be a string representing the canonical name of the host if AI_CANONNAME is part of the flags argument else canonname will be empty sockaddr is a tuple describing a socket address whose format depends on the returned family a address port 2 tuple for AF_INET a address port flowinfo scope_id 4 tuple for AF_INET6 and is meant to be passed to the socket connect method Raises an auditing event socket getaddrinfo with arguments host port family type protocol The following example fetches address information for a hypothetical TCP connection to example org on port 80 results may differ on your system if IPv6 isn t enabled socket getaddrinfo example org 80 proto socket IPPROTO_TCP socket AF_INET6 socket SOCK_STREAM 6 2606 2800 220 1 248 1893 25c8 1946 80 0 0 socket AF_INET socket SOCK_STREAM 6 93 184 216 34 80 Changed in version 3 2 parameters can now be passed using keyword arguments Changed in version 3 7 for IPv6 multicast addresses string representing an address will not contain scope_id part socket getfqdn name Return a fully qualified domain name for name If name is omitted or empty it is interpreted as the local host To find the fully qualified name the hostname returned by gethostbyaddr is checked followed by aliases for the host if available The first name which includes a period is selected In case no fully qualified domain name is available and name was provided it is returned unchanged If name was empty or equal to 0 0 0 0 the hostname from gethostname is returned socket gethostbyname hostname Translate a host name to IPv4 address format The IPv4 address is returned as a string such as 100 50 200 5 If the host name is a,en
1360,n IPv4 address itself it is returned unchanged See gethostbyname_ex for a more complete interface gethostbyname does not support IPv6 name resolution and getaddrinfo should be used instead for IPv4 v6 dual stack support Raises an auditing event socket gethostbyname with argument hostname Availability not WASI socket gethostbyname_ex hostname Translate a host name to IPv4 address format extended interface Return a 3 tuple hostname aliaslist ipaddrlist where hostname is the host s primary host name aliaslist is a possibly empty list of alternative host names for the same address and ipaddrlist is a list of IPv4 addresses for the same interface on the same host often but not always a single address gethostbyname_ex does not support IPv6 name resolution and getaddrinfo should be used instead for IPv4 v6 dual stack support Raises an auditing event socket gethostbyname with argument hostname Availability not WASI socket gethostname Return a string containing the hostname of the machine where the Python interpreter is currently executing Raises an auditing event socket gethostname with no arguments Note gethostname doesn t always return the fully qualified domain name use getfqdn for that Availability not WASI socket gethostbyaddr ip_address Return a 3 tuple hostname aliaslist ipaddrlist where hostname is the primary host name responding to the given ip_address aliaslist is a possibly empty list of alternative host names for the same address and ipaddrlist is a list of IPv4 v6 addresses for the same interface on the same host most likely containing only a single address To find the fully qualified domain name use the function getfqdn gethostbyaddr supports both IPv4 and IPv6 Raises an auditing event socket gethostbyaddr with argument ip_address Availability not WASI socket getnameinfo sockaddr flags Translate a socket address sockaddr into a 2 tuple host port Depending on the settings of flags the result can contain a fully qualified domain name or numeric address representation in host Similarly port can contain a string port name or a numeric port number For IPv6 addresses scope_id is appended to the host part if sockaddr contains meaningful scope_id Usually this happens for multicast addresses For more information about flags you can consult getnameinfo 3 Raises an auditing event socket getnameinfo with argument sockaddr Availability not WASI socket getprotobyname protocolname Translate an internet protocol name for example icmp to a constant suitable for passing as the optional third argument to the socket function This is usually only needed for sockets opened in raw mode SOCK_RAW for the normal socket modes the correct protocol is chosen automatically if the protocol is omitted or zero Availability not WASI socket getservbyname servicename protocolname Translate an internet service name and protocol name to a port number for that service The optional protocol name if given should be tcp or udp otherwise any protocol will match Raises an auditing event socket getservbyname with arguments servicename protocolname Availability not WASI socket getservbyport port protocolname Translate an internet port number and protocol name to a service name for that service The optional protocol name if given should be tcp or udp otherwise any protocol will match Raises an auditing event socket getservbyport with arguments port protocolname Availability not WASI socket ntohl x Convert 32 bit positive integers from network to host byte order On machines where the host byte order is the same as network byte order this is a no op otherwise it performs a 4 byte swap operation socket ntohs x Convert 16 bit positive integers from network to host byte order On machines where the host byte order is the same as network byte order this is a no op otherwise it performs a 2 byte swap operation Changed in version 3 10 Raises OverflowError if x does not fit in a 16 bit unsigned integer socket htonl x Convert 32 bit positive integers from host to network byte order On machines where the host byte order is the same as network byte order this is a no op ot,en
1361,herwise it performs a 4 byte swap operation socket htons x Convert 16 bit positive integers from host to network byte order On machines where the host byte order is the same as network byte order this is a no op otherwise it performs a 2 byte swap operation Changed in version 3 10 Raises OverflowError if x does not fit in a 16 bit unsigned integer socket inet_aton ip_string Convert an IPv4 address from dotted quad string format for example 123 45 67 89 to 32 bit packed binary format as a bytes object four characters in length This is useful when conversing with a program that uses the standard C library and needs objects of type in_addr which is the C type for the 32 bit packed binary this function returns inet_aton also accepts strings with less than three dots see the Unix manual page inet 3 for details If the IPv4 address string passed to this function is invalid OSError will be raised Note that exactly what is valid depends on the underlying C implementation of inet_aton inet_aton does not support IPv6 and inet_pton should be used instead for IPv4 v6 dual stack support socket inet_ntoa packed_ip Convert a 32 bit packed IPv4 address a bytes like object four bytes in length to its standard dotted quad string representation for example 123 45 67 89 This is useful when conversing with a program that uses the standard C library and needs objects of type in_addr which is the C type for the 32 bit packed binary data this function takes as an argument If the byte sequence passed to this function is not exactly 4 bytes in length OSError will be raised inet_ntoa does not support IPv6 and inet_ntop should be used instead for IPv4 v6 dual stack support Changed in version 3 5 Writable bytes like object is now accepted socket inet_pton address_family ip_string Convert an IP address from its family specific string format to a packed binary format inet_pton is useful when a library or network protocol calls for an object of type in_addr similar to inet_aton or in6_addr Supported values for address_family are currently AF_INET and AF_INET6 If the IP address string ip_string is invalid OSError will be raised Note that exactly what is valid depends on both the value of address_family and the underlying implementation of inet_pton Availability Unix Windows Changed in version 3 4 Windows support added socket inet_ntop address_family packed_ip Convert a packed IP address a bytes like object of some number of bytes to its standard family specific string representation for example 7 10 0 5 or 5aef 2b 8 inet_ntop is useful when a library or network protocol returns an object of type in_addr similar to inet_ntoa or in6_addr Supported values for address_family are currently AF_INET and AF_INET6 If the bytes object packed_ip is not the correct length for the specified address family ValueError will be raised OSError is raised for errors from the call to inet_ntop Availability Unix Windows Changed in version 3 4 Windows support added Changed in version 3 5 Writable bytes like object is now accepted socket CMSG_LEN length Return the total length without trailing padding of an ancillary data item with associated data of the given length This value can often be used as the buffer size for recvmsg to receive a single item of ancillary data but RFC 3542 requires portable applications to use CMSG_SPACE and thus include space for padding even when the item will be the last in the buffer Raises OverflowError if length is outside the permissible range of values Availability Unix not Emscripten not WASI Most Unix platforms New in version 3 3 socket CMSG_SPACE length Return the buffer size needed for recvmsg to receive an ancillary data item with associated data of the given length along with any trailing padding The buffer space needed to receive multiple items is the sum of the CMSG_SPACE values for their associated data lengths Raises OverflowError if length is outside the permissible range of values Note that some systems might support ancillary data without providing this function Also note that setting the buffer size using the results of this functi,en
1362,on may not precisely limit the amount of ancillary data that can be received since additional data may be able to fit into the padding area Availability Unix not Emscripten not WASI most Unix platforms New in version 3 3 socket getdefaulttimeout Return the default timeout in seconds float for new socket objects A value of None indicates that new socket objects have no timeout When the socket module is first imported the default is None socket setdefaulttimeout timeout Set the default timeout in seconds float for new socket objects When the socket module is first imported the default is None See settimeout for possible values and their respective meanings socket sethostname name Set the machine s hostname to name This will raise an OSError if you don t have enough rights Raises an auditing event socket sethostname with argument name Availability Unix New in version 3 3 socket if_nameindex Return a list of network interface information index int name string tuples OSError if the system call fails Availability Unix Windows not Emscripten not WASI New in version 3 3 Changed in version 3 8 Windows support was added Note On Windows network interfaces have different names in different contexts all names are examples UUID FB605B73 AAC2 49A6 9A2F 25416AEA0573 name ethernet_32770 friendly name vEthernet nat description Hyper V Virtual Ethernet Adapter This function returns names of the second form from the list ethernet_32770 in this example case socket if_nametoindex if_name Return a network interface index number corresponding to an interface name OSError if no interface with the given name exists Availability Unix Windows not Emscripten not WASI New in version 3 3 Changed in version 3 8 Windows support was added See also Interface name is a name as documented in if_nameindex socket if_indextoname if_index Return a network interface name corresponding to an interface index number OSError if no interface with the given index exists Availability Unix Windows not Emscripten not WASI New in version 3 3 Changed in version 3 8 Windows support was added See also Interface name is a name as documented in if_nameindex socket send_fds sock buffers fds flags address Send the list of file descriptors fds over an AF_UNIX socket sock The fds parameter is a sequence of file descriptors Consult sendmsg for the documentation of these parameters Availability Unix Windows not Emscripten not WASI Unix platforms supporting sendmsg and SCM_RIGHTS mechanism New in version 3 9 socket recv_fds sock bufsize maxfds flags Receive up to maxfds file descriptors from an AF_UNIX socket sock Return msg list fds flags addr Consult recvmsg for the documentation of these parameters Availability Unix Windows not Emscripten not WASI Unix platforms supporting sendmsg and SCM_RIGHTS mechanism New in version 3 9 Note Any truncated integers at the end of the list of file descriptors Socket Objects Socket objects have the following methods Except for makefile these correspond to Unix system calls applicable to sockets Changed in version 3 2 Support for the context manager protocol was added Exiting the context manager is equivalent to calling close socket accept Accept a connection The socket must be bound to an address and listening for connections The return value is a pair conn address where conn is a new socket object usable to send and receive data on the connection and address is the address bound to the socket on the other end of the connection The newly created socket is non inheritable Changed in version 3 4 The socket is now non inheritable Changed in version 3 5 If the system call is interrupted and the signal handler does not raise an exception the method now retries the system call instead of raising an InterruptedError exception see PEP 475 for the rationale socket bind address Bind the socket to address The socket must not already be bound The format of address depends on the address family see above Raises an auditing event socket bind with arguments self address Availability not WASI socket close Mark the socket closed The underlying system resource e g ,en
1363,a file descriptor is also closed when all file objects from makefile are closed Once that happens all future operations on the socket object will fail The remote end will receive no more data after queued data is flushed Sockets are automatically closed when they are garbage collected but it is recommended to close them explicitly or to use a with statement around them Changed in version 3 6 OSError is now raised if an error occurs when the underlying close call is made Note close releases the resource associated with a connection but does not necessarily close the connection immediately If you want to close the connection in a timely fashion call shutdown before close socket connect address Connect to a remote socket at address The format of address depends on the address family see above If the connection is interrupted by a signal the method waits until the connection completes or raise a TimeoutError on timeout if the signal handler doesn t raise an exception and the socket is blocking or has a timeout For non blocking sockets the method raises an InterruptedError exception if the connection is interrupted by a signal or the exception raised by the signal handler Raises an auditing event socket connect with arguments self address Changed in version 3 5 The method now waits until the connection completes instead of raising an InterruptedError exception if the connection is interrupted by a signal the signal handler doesn t raise an exception and the socket is blocking or has a timeout see the PEP 475 for the rationale Availability not WASI socket connect_ex address Like connect address but return an error indicator instead of raising an exception for errors returned by the C level connect call other problems such as host not found can still raise exceptions The error indicator is 0 if the operation succeeded otherwise the value of the errno variable This is useful to support for example asynchronous connects Raises an auditing event socket connect with arguments self address Availability not WASI socket detach Put the socket object into closed state without actually closing the underlying file descriptor The file descriptor is returned and can be reused for other purposes New in version 3 2 socket dup Duplicate the socket The newly created socket is non inheritable Changed in version 3 4 The socket is now non inheritable Availability not WASI socket fileno Return the socket s file descriptor a small integer or 1 on failure This is useful with select select Under Windows the small integer returned by this method cannot be used where a file descriptor can be used such as os fdopen Unix does not have this limitation socket get_inheritable Get the inheritable flag of the socket s file descriptor or socket s handle True if the socket can be inherited in child processes False if it cannot New in version 3 4 socket getpeername Return the remote address to which the socket is connected This is useful to find out the port number of a remote IPv4 v6 socket for instance The format of the address returned depends on the address family see above On some systems this function is not supported socket getsockname Return the socket s own address This is useful to find out the port number of an IPv4 v6 socket for instance The format of the address returned depends on the address family see above socket getsockopt level optname buflen Return the value of the given socket option see the Unix man page getsockopt 2 The needed symbolic constants SO_ etc are defined in this module If buflen is absent an integer option is assumed and its integer value is returned by the function If buflen is present it specifies the maximum length of the buffer used to receive the option in and this buffer is returned as a bytes object It is up to the caller to decode the contents of the buffer see the optional built in module struct for a way to decode C structures encoded as byte strings Availability not WASI socket getblocking Return True if socket is in blocking mode False if in non blocking This is equivalent to checking socket gettimeout 0 New in versio,en
1364,n 3 7 socket gettimeout Return the timeout in seconds float associated with socket operations or None if no timeout is set This reflects the last call to setblocking or settimeout socket ioctl control option Platform Windows The ioctl method is a limited interface to the WSAIoctl system interface Please refer to the Win32 documentation for more information On other platforms the generic fcntl fcntl and fcntl ioctl functions may be used they accept a socket object as their first argument Currently only the following control codes are supported SIO_RCVALL SIO_KEEPALIVE_VALS and SIO_LOOPBACK_FAST_PATH Changed in version 3 6 SIO_LOOPBACK_FAST_PATH was added socket listen backlog Enable a server to accept connections If backlog is specified it must be at least 0 if it is lower it is set to 0 it specifies the number of unaccepted connections that the system will allow before refusing new connections If not specified a default reasonable value is chosen Availability not WASI Changed in version 3 5 The backlog parameter is now optional socket makefile mode r buffering None encoding None errors None newline None Return a file object associated with the socket The exact returned type depends on the arguments given to makefile These arguments are interpreted the same way as by the built in open function except the only supported mode values are r default w and b The socket must be in blocking mode it can have a timeout but the file object s internal buffer may end up in an inconsistent state if a timeout occurs Closing the file object returned by makefile won t close the original socket unless all other file objects have been closed and socket close has been called on the socket object Note On Windows the file like object created by makefile cannot be used where a file object with a file descriptor is expected such as the stream arguments of subprocess Popen socket recv bufsize flags Receive data from the socket The return value is a bytes object representing the data received The maximum amount of data to be received at once is specified by bufsize A returned empty bytes object indicates that the client has disconnected See the Unix manual page recv 2 for the meaning of the optional argument flags it defaults to zero Note For best match with hardware and network realities the value of bufsize should be a relatively small power of 2 for example 4096 Changed in version 3 5 If the system call is interrupted and the signal handler does not raise an exception the method now retries the system call instead of raising an InterruptedError exception see PEP 475 for the rationale socket recvfrom bufsize flags Receive data from the socket The return value is a pair bytes address where bytes is a bytes object representing the data received and address is the address of the socket sending the data See the Unix manual page recv 2 for the meaning of the optional argument flags it defaults to zero The format of address depends on the address family see above Changed in version 3 5 If the system call is interrupted and the signal handler does not raise an exception the method now retries the system call instead of raising an InterruptedError exception see PEP 475 for the rationale Changed in version 3 7 For multicast IPv6 address first item of address does not contain scope_id part anymore In order to get full IPv6 address use getnameinfo socket recvmsg bufsize ancbufsize flags Receive normal data up to bufsize bytes and ancillary data from the socket The ancbufsize argument sets the size in bytes of the internal buffer used to receive the ancillary data it defaults to 0 meaning that no ancillary data will be received Appropriate buffer sizes for ancillary data can be calculated using CMSG_SPACE or CMSG_LEN and items which do not fit into the buffer might be truncated or discarded The flags argument defaults to 0 and has the same meaning as for recv The return value is a 4 tuple data ancdata msg_flags address The data item is a bytes object holding the non ancillary data received The ancdata item is a list of zero or more tuples cmsg_level cmsg_ty,en
1365,pe cmsg_data representing the ancillary data control messages received cmsg_level and cmsg_type are integers specifying the protocol level and protocol specific type respectively and cmsg_data is a bytes object holding the associated data The msg_flags item is the bitwise OR of various flags indicating conditions on the received message see your system documentation for details If the receiving socket is unconnected address is the address of the sending socket if available otherwise its value is unspecified On some systems sendmsg and recvmsg can be used to pass file descriptors between processes over an AF_UNIX socket When this facility is used it is often restricted to SOCK_STREAM sockets recvmsg will return in its ancillary data items of the form socket SOL_SOCKET socket SCM_RIGHTS fds where fds is a bytes object representing the new file descriptors as a binary array of the native C int type If recvmsg raises an exception after the system call returns it will first attempt to close any file descriptors received via this mechanism Some systems do not indicate the truncated length of ancillary data items which have been only partially received If an item appears to extend beyond the end of the buffer recvmsg will issue a RuntimeWarning and will return the part of it which is inside the buffer provided it has not been truncated before the start of its associated data On systems which support the SCM_RIGHTS mechanism the following function will receive up to maxfds file descriptors returning the message data and a list containing the descriptors while ignoring unexpected conditions such as unrelated control messages being received See also sendmsg import socket array def recv_fds sock msglen maxfds fds array array i Array of ints msg ancdata flags addr sock recvmsg msglen socket CMSG_LEN maxfds fds itemsize for cmsg_level cmsg_type cmsg_data in ancdata if cmsg_level socket SOL_SOCKET and cmsg_type socket SCM_RIGHTS Append data ignoring any truncated integers at the end fds frombytes cmsg_data len cmsg_data len cmsg_data fds itemsize return msg list fds Availability Unix Most Unix platforms New in version 3 3 Changed in version 3 5 If the system call is interrupted and the signal handler does not raise an exception the method now retries the system call instead of raising an InterruptedError exception see PEP 475 for the rationale socket recvmsg_into buffers ancbufsize flags Receive normal data and ancillary data from the socket behaving as recvmsg would but scatter the non ancillary data into a series of buffers instead of returning a new bytes object The buffers argument must be an iterable of objects that export writable buffers e g bytearray objects these will be filled with successive chunks of the non ancillary data until it has all been written or there are no more buffers The operating system may set a limit sysconf value SC_IOV_MAX on the number of buffers that can be used The ancbufsize and flags arguments have the same meaning as for recvmsg The return value is a 4 tuple nbytes ancdata msg_flags address where nbytes is the total number of bytes of non ancillary data written into the buffers and ancdata msg_flags and address are the same as for recvmsg Example import socket s1 s2 socket socketpair b1 bytearray b b2 bytearray b 0123456789 b3 bytearray b s1 send b Mary had a little lamb 22 s2 recvmsg_into b1 memoryview b2 2 9 b3 22 0 None b1 b2 b3 bytearray b Mary bytearray b 01 had a 9 bytearray b little lamb Availability Unix Most Unix platforms New in version 3 3 socket recvfrom_into buffer nbytes flags Receive data from the socket writing it into buffer instead of creating a new bytestring The return value is a pair nbytes address where nbytes is the number of bytes received and address is the address of the socket sending the data See the Unix manual page recv 2 for the meaning of the optional argument flags it defaults to zero The format of address depends on the address family see above socket recv_into buffer nbytes flags Receive up to nbytes bytes from the socket storing the data into a buffer rather than,en
1366, creating a new bytestring If nbytes is not specified or 0 receive up to the size available in the given buffer Returns the number of bytes received See the Unix manual page recv 2 for the meaning of the optional argument flags it defaults to zero socket send bytes flags Send data to the socket The socket must be connected to a remote socket The optional flags argument has the same meaning as for recv above Returns the number of bytes sent Applications are responsible for checking that all data has been sent if only some of the data was transmitted the application needs to attempt delivery of the remaining data For further information on this topic consult the Socket Programming HOWTO Changed in version 3 5 If the system call is interrupted and the signal handler does not raise an exception the method now retries the system call instead of raising an InterruptedError exception see PEP 475 for the rationale socket sendall bytes flags Send data to the socket The socket must be connected to a remote socket The optional flags argument has the same meaning as for recv above Unlike send this method continues to send data from bytes until either all data has been sent or an error occurs None is returned on success On error an exception is raised and there is no way to determine how much data if any was successfully sent Changed in version 3 5 The socket timeout is no longer reset each time data is sent successfully The socket timeout is now the maximum total duration to send all data Changed in version 3 5 If the system call is interrupted and the signal handler does not raise an exception the method now retries the system call instead of raising an InterruptedError exception see PEP 475 for the rationale socket sendto bytes address socket sendto bytes flags address Send data to the socket The socket should not be connected to a remote socket since the destination socket is specified by address The optional flags argument has the same meaning as for recv above Return the number of bytes sent The format of address depends on the address family see above Raises an auditing event socket sendto with arguments self address Changed in version 3 5 If the system call is interrupted and the signal handler does not raise an exception the method now retries the system call instead of raising an InterruptedError exception see PEP 475 for the rationale socket sendmsg buffers ancdata flags address Send normal and ancillary data to the socket gathering the non ancillary data from a series of buffers and concatenating it into a single message The buffers argument specifies the non ancillary data as an iterable of bytes like objects e g bytes objects the operating system may set a limit sysconf value SC_IOV_MAX on the number of buffers that can be used The ancdata argument specifies the ancillary data control messages as an iterable of zero or more tuples cmsg_level cmsg_type cmsg_data where cmsg_level and cmsg_type are integers specifying the protocol level and protocol specific type respectively and cmsg_data is a bytes like object holding the associated data Note that some systems in particular systems without CMSG_SPACE might support sending only one control message per call The flags argument defaults to 0 and has the same meaning as for send If address is supplied and not None it sets a destination address for the message The return value is the number of bytes of non ancillary data sent The following function sends the list of file descriptors fds over an AF_UNIX socket on systems which support the SCM_RIGHTS mechanism See also recvmsg import socket array def send_fds sock msg fds return sock sendmsg msg socket SOL_SOCKET socket SCM_RIGHTS array array i fds Availability Unix not WASI Most Unix platforms Raises an auditing event socket sendmsg with arguments self address New in version 3 3 Changed in version 3 5 If the system call is interrupted and the signal handler does not raise an exception the method now retries the system call instead of raising an InterruptedError exception see PEP 475 for the rationale socket sendmsg_afalg msg op,en
1367, iv assoclen flags Specialized version of sendmsg for AF_ALG socket Set mode IV AEAD associated data length and flags for AF_ALG socket Availability Linux 2 6 38 New in version 3 6 socket sendfile file offset 0 count None Send a file until EOF is reached by using high performance os sendfile and return the total number of bytes which were sent file must be a regular file object opened in binary mode If os sendfile is not available e g Windows or file is not a regular file send will be used instead offset tells from where to start reading the file If specified count is the total number of bytes to transmit as opposed to sending the file until EOF is reached File position is updated on return or also in case of error in which case file tell can be used to figure out the number of bytes which were sent The socket must be of SOCK_STREAM type Non blocking sockets are not supported New in version 3 5 socket set_inheritable inheritable Set the inheritable flag of the socket s file descriptor or socket s handle New in version 3 4 socket setblocking flag Set blocking or non blocking mode of the socket if flag is false the socket is set to non blocking else to blocking mode This method is a shorthand for certain settimeout calls sock setblocking True is equivalent to sock settimeout None sock setblocking False is equivalent to sock settimeout 0 0 Changed in version 3 7 The method no longer applies SOCK_NONBLOCK flag on socket type socket settimeout value Set a timeout on blocking socket operations The value argument can be a nonnegative floating point number expressing seconds or None If a non zero value is given subsequent socket operations will raise a timeout exception if the timeout period value has elapsed before the operation has completed If zero is given the socket is put in non blocking mode If None is given the socket is put in blocking mode For further information please consult the notes on socket timeouts Changed in version 3 7 The method no longer toggles SOCK_NONBLOCK flag on socket type socket setsockopt level optname value int socket setsockopt level optname value buffer socket setsockopt level optname None optlen int Set the value of the given socket option see the Unix manual page setsockopt 2 The needed symbolic constants are defined in this module SO_ etc socket unix constants The value can be an integer None or a bytes like object representing a buffer In the later case it is up to the caller to ensure that the bytestring contains the proper bits see the optional built in module struct for a way to encode C structures as bytestrings When value is set to None optlen argument is required It s equivalent to call setsockopt C function with optval NULL and optlen optlen Changed in version 3 5 Writable bytes like object is now accepted Changed in version 3 6 setsockopt level optname None optlen int form added Availability not WASI socket shutdown how Shut down one or both halves of the connection If how is SHUT_RD further receives are disallowed If how is SHUT_WR further sends are disallowed If how is SHUT_RDWR further sends and receives are disallowed Availability not WASI socket share process_id Duplicate a socket and prepare it for sharing with a target process The target process must be provided with process_id The resulting bytes object can then be passed to the target process using some form of interprocess communication and the socket can be recreated there using fromshare Once this method has been called it is safe to close the socket since the operating system has already duplicated it for the target process Availability Windows New in version 3 3 Note that there are no methods read or write use recv and send without flags argument instead Socket objects also have these read only attributes that correspond to the values given to the socket constructor socket family The socket family socket type The socket type socket proto The socket protocol Notes on socket timeouts A socket object can be in one of three modes blocking non blocking or timeout Sockets are by default always created in blocking mode but this,en
1368, can be changed by calling setdefaulttimeout In blocking mode operations block until complete or the system returns an error such as connection timed out In non blocking mode operations fail with an error that is unfortunately system dependent if they cannot be completed immediately functions from the select module can be used to know when and whether a socket is available for reading or writing In timeout mode operations fail if they cannot be completed within the timeout specified for the socket they raise a timeout exception or if the system returns an error Note At the operating system level sockets in timeout mode are internally set in non blocking mode Also the blocking and timeout modes are shared between file descriptors and socket objects that refer to the same network endpoint This implementation detail can have visible consequences if e g you decide to use the fileno of a socket Timeouts and the connect method The connect operation is also subject to the timeout setting and in general it is recommended to call settimeout before calling connect or pass a timeout parameter to create_connection However the system network stack may also return a connection timeout error of its own regardless of any Python socket timeout setting Timeouts and the accept method If getdefaulttimeout is not None sockets returned by the accept method inherit that timeout Otherwise the behaviour depends on settings of the listening socket if the listening socket is in blocking mode or in timeout mode the socket returned by accept is in blocking mode if the listening socket is in non blocking mode whether the socket returned by accept is in blocking or non blocking mode is operating system dependent If you want to ensure cross platform behaviour it is recommended you manually override this setting Example Here are four minimal example programs using the TCP IP protocol a server that echoes all data that it receives back servicing only one client and a client using it Note that a server must perform the sequence socket bind listen accept possibly repeating the accept to service more than one client while a client only needs the sequence socket connect Also note that the server does not sendall recv on the socket it is listening on but on the new socket returned by accept The first two examples support IPv4 only Echo server program import socket HOST Symbolic name meaning all available interfaces PORT 50007 Arbitrary non privileged port with socket socket socket AF_INET socket SOCK_STREAM as s s bind HOST PORT s listen 1 conn addr s accept with conn print Connected by addr while True data conn recv 1024 if not data break conn sendall data Echo client program import socket HOST daring cwi nl The remote host PORT 50007 The same port as used by the server with socket socket socket AF_INET socket SOCK_STREAM as s s connect HOST PORT s sendall b Hello world data s recv 1024 print Received repr data The next two examples are identical to the above two but support both IPv4 and IPv6 The server side will listen to the first address family available it should listen to both instead On most of IPv6 ready systems IPv6 will take precedence and the server may not accept IPv4 traffic The client side will try to connect to all the addresses returned as a result of the name resolution and sends traffic to the first one connected successfully Echo server program import socket import sys HOST None Symbolic name meaning all available interfaces PORT 50007 Arbitrary non privileged port s None for res in socket getaddrinfo HOST PORT socket AF_UNSPEC socket SOCK_STREAM 0 socket AI_PASSIVE af socktype proto canonname sa res try s socket socket af socktype proto except OSError as msg s None continue try s bind sa s listen 1 except OSError as msg s close s None continue break if s is None print could not open socket sys exit 1 conn addr s accept with conn print Connected by addr while True data conn recv 1024 if not data break conn send data Echo client program import socket import sys HOST daring cwi nl The remote host PORT 50007 The same port as used by the serve,en
1369,r s None for res in socket getaddrinfo HOST PORT socket AF_UNSPEC socket SOCK_STREAM af socktype proto canonname sa res try s socket socket af socktype proto except OSError as msg s None continue try s connect sa except OSError as msg s close s None continue break if s is None print could not open socket sys exit 1 with s s sendall b Hello world data s recv 1024 print Received repr data The next example shows how to write a very simple network sniffer with raw sockets on Windows The example requires administrator privileges to modify the interface import socket the public network interface HOST socket gethostbyname socket gethostname create a raw socket and bind it to the public interface s socket socket socket AF_INET socket SOCK_RAW socket IPPROTO_IP s bind HOST 0 Include IP headers s setsockopt socket IPPROTO_IP socket IP_HDRINCL 1 receive all packets s ioctl socket SIO_RCVALL socket RCVALL_ON receive a packet print s recvfrom 65565 disabled promiscuous mode s ioctl socket SIO_RCVALL socket RCVALL_OFF The next example shows how to use the socket interface to communicate to a CAN network using the raw socket protocol To use CAN with the broadcast manager protocol instead open a socket with socket socket socket AF_CAN socket SOCK_DGRAM socket CAN_BCM After binding CAN_RAW or connecting CAN_BCM the socket you can use the socket send and socket recv operations and their counterparts on the socket object as usual This last example might require special privileges import socket import struct CAN frame packing unpacking see struct can_frame in linux can h can_frame_fmt IB3x8s can_frame_size struct calcsize can_frame_fmt def build_can_frame can_id data can_dlc len data data data ljust 8 b x00 return struct pack can_frame_fmt can_id can_dlc data def dissect_can_frame frame can_id can_dlc data struct unpack can_frame_fmt frame return can_id can_dlc data can_dlc create a raw socket and bind it to the vcan0 interface s socket socket socket AF_CAN socket SOCK_RAW socket CAN_RAW s bind vcan0 while True cf addr s recvfrom can_frame_size print Received can_id x can_dlc x data s dissect_can_frame cf try s send cf except OSError print Error sending CAN frame try s send build_can_frame 0x01 b x01 x02 x03 except OSError print Error sending CAN frame Running an example several times with too small delay between executions could lead to this error OSError Errno 98 Address already in use This is because the previous execution has left the socket in a TIME_WAIT state and can t be immediately reused There is a socket flag to set in order to prevent this socket SO_REUSEADDR s socket socket socket AF_INET socket SOCK_STREAM s setsockopt socket SOL_SOCKET socket SO_REUSEADDR 1 s bind HOST PORT the SO_REUSEADDR flag tells the kernel to reuse a local socket in TIME_WAIT state without waiting for its natural timeout to expire See also For an introduction to socket programming in C see the following papers An Introductory 4 3BSD Interprocess Communication Tutorial by Stuart Sechrest An Advanced 4 3BSD Interprocess Communication Tutorial by Samuel J Leffler et al both in the UNIX Programmer s Manual Supplementary Documents 1 sections PS1 7 and PS1 8 The platform specific reference material for the various socket related system calls are also a valuable source of information on the details of socket semantics For Unix refer to the manual pages for Windows see the WinSock or Winsock 2 specification For IPv6 ready APIs readers may want to refer to RFC 3493 titled Basic Socket Interface Extensions for IPv6,en
1370,Extending Embedding FAQ Can I create my own functions in C Yes you can create built in modules containing functions variables exceptions and even new types in C This is explained in the document Extending and Embedding the Python Interpreter Most intermediate or advanced Python books will also cover this topic Can I create my own functions in C Yes using the C compatibility features found in C Place extern C around the Python include files and put extern C before each function that is going to be called by the Python interpreter Global or static C objects with constructors are probably not a good idea Writing C is hard are there any alternatives There are a number of alternatives to writing your own C extensions depending on what you re trying to do Cython and its relative Pyrex are compilers that accept a slightly modified form of Python and generate the corresponding C code Cython and Pyrex make it possible to write an extension without having to learn Python s C API If you need to interface to some C or C library for which no Python extension currently exists you can try wrapping the library s data types and functions with a tool such as SWIG SIP CXX Boost or Weave are also alternatives for wrapping C libraries How can I execute arbitrary Python statements from C The highest level function to do this is PyRun_SimpleString which takes a single string argument to be executed in the context of the module __main__ and returns 0 for success and 1 when an exception occurred including SyntaxError If you want more control use PyRun_String see the source for PyRun_SimpleString in Python pythonrun c How can I evaluate an arbitrary Python expression from C Call the function PyRun_String from the previous question with the start symbol Py_eval_input it parses an expression evaluates it and returns its value How do I extract C values from a Python object That depends on the object s type If it s a tuple PyTuple_Size returns its length and PyTuple_GetItem returns the item at a specified index Lists have similar functions PyList_Size and PyList_GetItem For bytes PyBytes_Size returns its length and PyBytes_AsStringAndSize provides a pointer to its value and its length Note that Python bytes objects may contain null bytes so C s strlen should not be used To test the type of an object first make sure it isn t NULL and then use PyBytes_Check PyTuple_Check PyList_Check etc There is also a high level API to Python objects which is provided by the so called abstract interface read Include abstract h for further details It allows interfacing with any kind of Python sequence using calls like PySequence_Length PySequence_GetItem etc as well as many other useful protocols such as numbers PyNumber_Index et al and mappings in the PyMapping APIs How do I use Py_BuildValue to create a tuple of arbitrary length You can t Use PyTuple_Pack instead How do I call an object s method from C The PyObject_CallMethod function can be used to call an arbitrary method of an object The parameters are the object the name of the method to call a format string like that used with Py_BuildValue and the argument values PyObject PyObject_CallMethod PyObject object const char method_name const char arg_format This works for any object that has methods whether built in or user defined You are responsible for eventually Py_DECREF ing the return value To call e g a file object s seek method with arguments 10 0 assuming the file object pointer is f res PyObject_CallMethod f seek ii 10 0 if res NULL an exception occurred else Py_DECREF res Note that since PyObject_CallObject always wants a tuple for the argument list to call a function without arguments pass for the format and to call a function with one argument surround the argument in parentheses e g i How do I catch the output from PyErr_Print or anything that prints to stdout stderr In Python code define an object that supports the write method Assign this object to sys stdout and sys stderr Call print_error or just allow the standard traceback mechanism to work Then the output will go wherever your write method sends,en
1371, it The easiest way to do this is to use the io StringIO class import io sys sys stdout io StringIO print foo print hello world sys stderr write sys stdout getvalue foo hello world A custom object to do the same would look like this import io sys class StdoutCatcher io TextIOBase def __init__ self self data def write self stuff self data append stuff import sys sys stdout StdoutCatcher print foo print hello world sys stderr write join sys stdout data foo hello world How do I access a module written in Python from C You can get a pointer to the module object as follows module PyImport_ImportModule modulename If the module hasn t been imported yet i e it is not yet present in sys modules this initializes the module otherwise it simply returns the value of sys modules modulename Note that it doesn t enter the module into any namespace it only ensures it has been initialized and is stored in sys modules You can then access the module s attributes i e any name defined in the module as follows attr PyObject_GetAttrString module attrname Calling PyObject_SetAttrString to assign to variables in the module also works How do I interface to C objects from Python Depending on your requirements there are many approaches To do this manually begin by reading the Extending and Embedding document Realize that for the Python run time system there isn t a whole lot of difference between C and C so the strategy of building a new Python type around a C structure pointer type will also work for C objects For C libraries see Writing C is hard are there any alternatives I added a module using the Setup file and the make fails why Setup must end in a newline if there is no newline there the build process fails Fixing this requires some ugly shell script hackery and this bug is so minor that it doesn t seem worth the effort How do I debug an extension When using GDB with dynamically loaded extensions you can t set a breakpoint in your extension until your extension is loaded In your gdbinit file or interactively add the command br _PyImport_LoadDynamicModule Then when you run GDB gdb local bin python gdb run myscript py gdb continue repeat until your extension is loaded gdb finish so that your extension is loaded gdb br myfunction c 50 gdb continue I want to compile a Python module on my Linux system but some files are missing Why Most packaged versions of Python don t include the usr lib python2 x config directory which contains various files required for compiling Python extensions For Red Hat install the python devel RPM to get the necessary files For Debian run apt get install python dev How do I tell incomplete input from invalid input Sometimes you want to emulate the Python interactive interpreter s behavior where it gives you a continuation prompt when the input is incomplete e g you typed the start of an if statement or you didn t close your parentheses or triple string quotes but it gives you a syntax error message immediately when the input is invalid In Python you can use the codeop module which approximates the parser s behavior sufficiently IDLE uses this for example The easiest way to do it in C is to call PyRun_InteractiveLoop perhaps in a separate thread and let the Python interpreter handle the input for you You can also set the PyOS_ReadlineFunctionPointer to point at your custom input function See Modules readline c and Parser myreadline c for more hints How do I find undefined g symbols __builtin_new or __pure_virtual To dynamically load g extension modules you must recompile Python relink it using g change LINKCC in the Python Modules Makefile and link your extension module using g e g g shared o mymodule so mymodule o Can I create an object class with some methods implemented in C and others in Python e g through inheritance Yes you can inherit from built in classes such as int list dict etc The Boost Python Library BPL https www boost org libs python doc index html provides a way of doing this from C i e you can inherit from an extension class written in C using the BPL,en
1372,tkinter colorchooser Color choosing dialog Source code Lib tkinter colorchooser py The tkinter colorchooser module provides the Chooser class as an interface to the native color picker dialog Chooser implements a modal color choosing dialog window The Chooser class inherits from the Dialog class class tkinter colorchooser Chooser master None options tkinter colorchooser askcolor color None options Create a color choosing dialog A call to this method will show the window wait for the user to make a selection and return the selected color or None to the caller See also Module tkinter commondialog Tkinter standard dialog module,en
1373,What s New In Python 3 6 Editors Elvis Pranskevichus elvis magic io Yury Selivanov yury magic io This article explains the new features in Python 3 6 compared to 3 5 Python 3 6 was released on December 23 2016 See the changelog for a full list of changes See also PEP 494 Python 3 6 Release Schedule Summary Release highlights New syntax features PEP 498 formatted string literals PEP 515 underscores in numeric literals PEP 526 syntax for variable annotations PEP 525 asynchronous generators PEP 530 asynchronous comprehensions New library modules secrets PEP 506 Adding A Secrets Module To The Standard Library CPython implementation improvements The dict type has been reimplemented to use a more compact representation based on a proposal by Raymond Hettinger and similar to the PyPy dict implementation This resulted in dictionaries using 20 to 25 less memory when compared to Python 3 5 Customization of class creation has been simplified with the new protocol The class attribute definition order is now preserved The order of elements in kwargs now corresponds to the order in which keyword arguments were passed to the function DTrace and SystemTap probing support has been added The new PYTHONMALLOC environment variable can now be used to debug the interpreter memory allocation and access errors Significant improvements in the standard library The asyncio module has received new features significant usability and performance improvements and a fair amount of bug fixes Starting with Python 3 6 the asyncio module is no longer provisional and its API is considered stable A new file system path protocol has been implemented to support path like objects All standard library functions operating on paths have been updated to work with the new protocol The datetime module has gained support for Local Time Disambiguation The typing module received a number of improvements The tracemalloc module has been significantly reworked and is now used to provide better output for ResourceWarning as well as provide better diagnostics for memory allocation errors See the PYTHONMALLOC section for more information Security improvements The new secrets module has been added to simplify the generation of cryptographically strong pseudo random numbers suitable for managing secrets such as account authentication tokens and similar On Linux os urandom now blocks until the system urandom entropy pool is initialized to increase the security See the PEP 524 for the rationale The hashlib and ssl modules now support OpenSSL 1 1 0 The default settings and feature set of the ssl module have been improved The hashlib module received support for the BLAKE2 SHA 3 and SHAKE hash algorithms and the scrypt key derivation function Windows improvements PEP 528 and PEP 529 Windows filesystem and console encoding changed to UTF 8 The py exe launcher when used interactively no longer prefers Python 2 over Python 3 when the user doesn t specify a version via command line arguments or a config file Handling of shebang lines remains unchanged python refers to Python 2 in that case python exe and pythonw exe have been marked as long path aware which means that the 260 character path limit may no longer apply See removing the MAX_PATH limitation for details A _pth file can be added to force isolated mode and fully specify all search paths to avoid registry and environment lookup See the documentation for more information A python36 zip file now works as a landmark to infer PYTHONHOME See the documentation for more information New Features PEP 498 Formatted string literals PEP 498 introduces a new kind of string literals f strings or formatted string literals Formatted string literals are prefixed with f and are similar to the format strings accepted by str format They contain replacement fields surrounded by curly braces The replacement fields are expressions which are evaluated at run time and then formatted using the format protocol name Fred f He said his name is name He said his name is Fred width 10 precision 4 value decimal Decimal 12 34567 f result value width precision ne,en
1374,sted fields result 12 35 See also PEP 498 Literal String Interpolation PEP written and implemented by Eric V Smith Feature documentation PEP 526 Syntax for variable annotations PEP 484 introduced the standard for type annotations of function parameters a k a type hints This PEP adds syntax to Python for annotating the types of variables including class variables and instance variables primes List int captain str Note no initial value class Starship stats Dict str int Just as for function annotations the Python interpreter does not attach any particular meaning to variable annotations and only stores them in the __annotations__ attribute of a class or module In contrast to variable declarations in statically typed languages the goal of annotation syntax is to provide an easy way to specify structured type metadata for third party tools and libraries via the abstract syntax tree and the __annotations__ attribute See also PEP 526 Syntax for variable annotations PEP written by Ryan Gonzalez Philip House Ivan Levkivskyi Lisa Roach and Guido van Rossum Implemented by Ivan Levkivskyi Tools that use or will use the new syntax mypy pytype PyCharm etc PEP 515 Underscores in Numeric Literals PEP 515 adds the ability to use underscores in numeric literals for improved readability For example 1_000_000_000_000_000 1000000000000000 0x_FF_FF_FF_FF 4294967295 Single underscores are allowed between digits and after any base specifier Leading trailing or multiple underscores in a row are not allowed The string formatting language also now has support for the _ option to signal the use of an underscore for a thousands separator for floating point presentation types and for integer presentation type d For integer presentation types b o x and X underscores will be inserted every 4 digits _ format 1000000 1_000_000 _x format 0xFFFFFFFF ffff_ffff See also PEP 515 Underscores in Numeric Literals PEP written by Georg Brandl and Serhiy Storchaka PEP 525 Asynchronous Generators PEP 492 introduced support for native coroutines and async await syntax to Python 3 5 A notable limitation of the Python 3 5 implementation is that it was not possible to use await and yield in the same function body In Python 3 6 this restriction has been lifted making it possible to define asynchronous generators async def ticker delay to Yield numbers from 0 to to every delay seconds for i in range to yield i await asyncio sleep delay The new syntax allows for faster and more concise code See also PEP 525 Asynchronous Generators PEP written and implemented by Yury Selivanov PEP 530 Asynchronous Comprehensions PEP 530 adds support for using async for in list set dict comprehensions and generator expressions result i async for i in aiter if i 2 Additionally await expressions are supported in all kinds of comprehensions result await fun for fun in funcs if await condition See also PEP 530 Asynchronous Comprehensions PEP written and implemented by Yury Selivanov PEP 487 Simpler customization of class creation It is now possible to customize subclass creation without using a metaclass The new __init_subclass__ classmethod will be called on the base class whenever a new subclass is created class PluginBase subclasses def __init_subclass__ cls kwargs super __init_subclass__ kwargs cls subclasses append cls class Plugin1 PluginBase pass class Plugin2 PluginBase pass In order to allow zero argument super calls to work correctly from __init_subclass__ implementations custom metaclasses must ensure that the new __classcell__ namespace entry is propagated to type __new__ as described in Creating the class object See also PEP 487 Simpler customization of class creation PEP written and implemented by Martin Teichmann Feature documentation PEP 487 Descriptor Protocol Enhancements PEP 487 extends the descriptor protocol to include the new optional __set_name__ method Whenever a new class is defined the new method will be called on all descriptors included in the definition providing them with a reference to the class being defined and the name given to the descriptor within the class na,en
1375,mespace In other words instances of descriptors can now know the attribute name of the descriptor in the owner class class IntField def __get__ self instance owner return instance __dict__ self name def __set__ self instance value if not isinstance value int raise ValueError f expecting integer in self name instance __dict__ self name value this is the new initializer def __set_name__ self owner name self name name class Model int_field IntField See also PEP 487 Simpler customization of class creation PEP written and implemented by Martin Teichmann Feature documentation PEP 519 Adding a file system path protocol File system paths have historically been represented as str or bytes objects This has led to people who write code which operate on file system paths to assume that such objects are only one of those two types an int representing a file descriptor does not count as that is not a file path Unfortunately that assumption prevents alternative object representations of file system paths like pathlib from working with pre existing code including Python s standard library To fix this situation a new interface represented by os PathLike has been defined By implementing the __fspath__ method an object signals that it represents a path An object can then provide a low level representation of a file system path as a str or bytes object This means an object is considered path like if it implements os PathLike or is a str or bytes object which represents a file system path Code can use os fspath os fsdecode or os fsencode to explicitly get a str and or bytes representation of a path like object The built in open function has been updated to accept os PathLike objects as have all relevant functions in the os and os path modules and most other functions and classes in the standard library The os DirEntry class and relevant classes in pathlib have also been updated to implement os PathLike The hope is that updating the fundamental functions for operating on file system paths will lead to third party code to implicitly support all path like objects without any code changes or at least very minimal ones e g calling os fspath at the beginning of code before operating on a path like object Here are some examples of how the new interface allows for pathlib Path to be used more easily and transparently with pre existing code import pathlib with open pathlib Path README as f contents f read import os path os path splitext pathlib Path some_file txt some_file txt os path join a b pathlib Path c a b c import os os fspath pathlib Path some_file txt some_file txt Implemented by Brett Cannon Ethan Furman Dusty Phillips and Jelle Zijlstra See also PEP 519 Adding a file system path protocol PEP written by Brett Cannon and Koos Zevenhoven PEP 495 Local Time Disambiguation In most world locations there have been and will be times when local clocks are moved back In those times intervals are introduced in which local clocks show the same time twice in the same day In these situations the information displayed on a local clock or stored in a Python datetime instance is insufficient to identify a particular moment in time PEP 495 adds the new fold attribute to instances of datetime datetime and datetime time classes to differentiate between two moments in time for which local times are the same u0 datetime 2016 11 6 4 tzinfo timezone utc for i in range 4 u u0 i HOUR t u astimezone Eastern print u time UTC t time t tzname t fold 04 00 00 UTC 00 00 00 EDT 0 05 00 00 UTC 01 00 00 EDT 0 06 00 00 UTC 01 00 00 EST 1 07 00 00 UTC 02 00 00 EST 0 The values of the fold attribute have the value 0 for all instances except those that represent the second chronologically moment in time in an ambiguous case See also PEP 495 Local Time Disambiguation PEP written by Alexander Belopolsky and Tim Peters implementation by Alexander Belopolsky PEP 529 Change Windows filesystem encoding to UTF 8 Representing filesystem paths is best performed with str Unicode rather than bytes However there are some situations where using bytes is sufficient and correct Prior to Pytho,en
1376,n 3 6 data loss could result when using bytes paths on Windows With this change using bytes to represent paths is now supported on Windows provided those bytes are encoded with the encoding returned by sys getfilesystemencoding which now defaults to utf 8 Applications that do not use str to represent paths should use os fsencode and os fsdecode to ensure their bytes are correctly encoded To revert to the previous behaviour set PYTHONLEGACYWINDOWSFSENCODING or call sys _enablelegacywindowsfsencoding See PEP 529 for more information and discussion of code modifications that may be required PEP 528 Change Windows console encoding to UTF 8 The default console on Windows will now accept all Unicode characters and provide correctly read str objects to Python code sys stdin sys stdout and sys stderr now default to utf 8 encoding This change only applies when using an interactive console and not when redirecting files or pipes To revert to the previous behaviour for interactive console use set PYTHONLEGACYWINDOWSSTDIO See also PEP 528 Change Windows console encoding to UTF 8 PEP written and implemented by Steve Dower PEP 520 Preserving Class Attribute Definition Order Attributes in a class definition body have a natural ordering the same order in which the names appear in the source This order is now preserved in the new class s __dict__ attribute Also the effective default class execution namespace returned from type __prepare__ is now an insertion order preserving mapping See also PEP 520 Preserving Class Attribute Definition Order PEP written and implemented by Eric Snow PEP 468 Preserving Keyword Argument Order kwargs in a function signature is now guaranteed to be an insertion order preserving mapping See also PEP 468 Preserving Keyword Argument Order PEP written and implemented by Eric Snow New dict implementation The dict type now uses a compact representation based on a proposal by Raymond Hettinger which was first implemented by PyPy The memory usage of the new dict is between 20 and 25 smaller compared to Python 3 5 The order preserving aspect of this new implementation is considered an implementation detail and should not be relied upon this may change in the future but it is desired to have this new dict implementation in the language for a few releases before changing the language spec to mandate order preserving semantics for all current and future Python implementations this also helps preserve backwards compatibility with older versions of the language where random iteration order is still in effect e g Python 3 5 Contributed by INADA Naoki in bpo 27350 Idea originally suggested by Raymond Hettinger PEP 523 Adding a frame evaluation API to CPython While Python provides extensive support to customize how code executes one place it has not done so is in the evaluation of frame objects If you wanted some way to intercept frame evaluation in Python there really wasn t any way without directly manipulating function pointers for defined functions PEP 523 changes this by providing an API to make frame evaluation pluggable at the C level This will allow for tools such as debuggers and JITs to intercept frame evaluation before the execution of Python code begins This enables the use of alternative evaluation implementations for Python code tracking frame evaluation etc This API is not part of the limited C API and is marked as private to signal that usage of this API is expected to be limited and only applicable to very select low level use cases Semantics of the API will change with Python as necessary See also PEP 523 Adding a frame evaluation API to CPython PEP written by Brett Cannon and Dino Viehland PYTHONMALLOC environment variable The new PYTHONMALLOC environment variable allows setting the Python memory allocators and installing debug hooks It is now possible to install debug hooks on Python memory allocators on Python compiled in release mode using PYTHONMALLOC debug Effects of debug hooks Newly allocated memory is filled with the byte 0xCB Freed memory is filled with the byte 0xDB Detect violations of the Pytho,en
1377,n memory allocator API For example PyObject_Free called on a memory block allocated by PyMem_Malloc Detect writes before the start of a buffer buffer underflows Detect writes after the end of a buffer buffer overflows Check that the GIL is held when allocator functions of PYMEM_DOMAIN_OBJ ex PyObject_Malloc and PYMEM_DOMAIN_MEM ex PyMem_Malloc domains are called Checking if the GIL is held is also a new feature of Python 3 6 See the PyMem_SetupDebugHooks function for debug hooks on Python memory allocators It is now also possible to force the usage of the malloc allocator of the C library for all Python memory allocations using PYTHONMALLOC malloc This is helpful when using external memory debuggers like Valgrind on a Python compiled in release mode On error the debug hooks on Python memory allocators now use the tracemalloc module to get the traceback where a memory block was allocated Example of fatal error on buffer overflow using python3 6 X tracemalloc 5 store 5 frames in traces Debug memory block at address p 0x7fbcd41666f8 API o 4 bytes originally requested The 7 pad bytes at p 7 are FORBIDDENBYTE as expected The 8 pad bytes at tail 0x7fbcd41666fc are not all FORBIDDENBYTE 0xfb at tail 0 0x02 OUCH at tail 1 0xfb at tail 2 0xfb at tail 3 0xfb at tail 4 0xfb at tail 5 0xfb at tail 6 0xfb at tail 7 0xfb The block was made by call 1233329 to debug malloc realloc Data at p 1a 2b 30 00 Memory block allocated at most recent call first File test test_bytes py line 323 File unittest case py line 600 File unittest case py line 648 File unittest suite py line 122 File unittest suite py line 84 Fatal Python error bad trailing pad byte Current thread 0x00007fbcdbd32700 most recent call first File test test_bytes py line 323 in test_hex File unittest case py line 600 in run File unittest case py line 648 in __call__ File unittest suite py line 122 in run File unittest suite py line 84 in __call__ File unittest suite py line 122 in run File unittest suite py line 84 in __call__ Contributed by Victor Stinner in bpo 26516 and bpo 26564 DTrace and SystemTap probing support Python can now be built with dtrace which enables static markers for the following events in the interpreter function call return garbage collection started finished line of code executed This can be used to instrument running interpreters in production without the need to recompile specific debug builds or providing application specific profiling debugging code More details in Instrumenting CPython with DTrace and SystemTap The current implementation is tested on Linux and macOS Additional markers may be added in the future Contributed by Łukasz Langa in bpo 21590 based on patches by Jesús Cea Avión David Malcolm and Nikhil Benesch Other Language Changes Some smaller changes made to the core Python language are A global or nonlocal statement must now textually appear before the first use of the affected name in the same scope Previously this was a SyntaxWarning It is now possible to set a special method to None to indicate that the corresponding operation is not available For example if a class sets __iter__ to None the class is not iterable Contributed by Andrew Barnert and Ivan Levkivskyi in bpo 25958 Long sequences of repeated traceback lines are now abbreviated as Previous line repeated count more times see traceback for an example Contributed by Emanuel Barry in bpo 26823 Import now raises the new exception ModuleNotFoundError subclass of ImportError when it cannot find a module Code that currently checks for ImportError in try except will still work Contributed by Eric Snow in bpo 15767 Class methods relying on zero argument super will now work correctly when called from metaclass methods during class creation Contributed by Martin Teichmann in bpo 23722 New Modules secrets The main purpose of the new secrets module is to provide an obvious way to reliably generate cryptographically strong pseudo random values suitable for managing secrets such as account authentication tokens and similar Warning Note that the pseudo random generators in the random module ,en
1378,should NOT be used for security purposes Use secrets on Python 3 6 and os urandom on Python 3 5 and earlier See also PEP 506 Adding A Secrets Module To The Standard Library PEP written and implemented by Steven D Aprano Improved Modules array Exhausted iterators of array array will now stay exhausted even if the iterated array is extended This is consistent with the behavior of other mutable sequences Contributed by Serhiy Storchaka in bpo 26492 ast The new ast Constant AST node has been added It can be used by external AST optimizers for the purposes of constant folding Contributed by Victor Stinner in bpo 26146 asyncio Starting with Python 3 6 the asyncio module is no longer provisional and its API is considered stable Notable changes in the asyncio module since Python 3 5 0 all backported to 3 5 x due to the provisional status The get_event_loop function has been changed to always return the currently running loop when called from coroutines and callbacks Contributed by Yury Selivanov in bpo 28613 The ensure_future function and all functions that use it such as loop run_until_complete now accept all kinds of awaitable objects Contributed by Yury Selivanov New run_coroutine_threadsafe function to submit coroutines to event loops from other threads Contributed by Vincent Michel New Transport is_closing method to check if the transport is closing or closed Contributed by Yury Selivanov The loop create_server method can now accept a list of hosts Contributed by Yann Sionneau New loop create_future method to create Future objects This allows alternative event loop implementations such as uvloop to provide a faster asyncio Future implementation Contributed by Yury Selivanov in bpo 27041 New loop get_exception_handler method to get the current exception handler Contributed by Yury Selivanov in bpo 27040 New StreamReader readuntil method to read data from the stream until a separator bytes sequence appears Contributed by Mark Korenberg The performance of StreamReader readexactly has been improved Contributed by Mark Korenberg in bpo 28370 The loop getaddrinfo method is optimized to avoid calling the system getaddrinfo function if the address is already resolved Contributed by A Jesse Jiryu Davis The loop stop method has been changed to stop the loop immediately after the current iteration Any new callbacks scheduled as a result of the last iteration will be discarded Contributed by Guido van Rossum in bpo 25593 Future set_exception will now raise TypeError when passed an instance of the StopIteration exception Contributed by Chris Angelico in bpo 26221 New loop connect_accepted_socket method to be used by servers that accept connections outside of asyncio but that use asyncio to handle them Contributed by Jim Fulton in bpo 27392 TCP_NODELAY flag is now set for all TCP transports by default Contributed by Yury Selivanov in bpo 27456 New loop shutdown_asyncgens to properly close pending asynchronous generators before closing the loop Contributed by Yury Selivanov in bpo 28003 Future and Task classes now have an optimized C implementation which makes asyncio code up to 30 faster Contributed by Yury Selivanov and INADA Naoki in bpo 26081 and bpo 28544 binascii The b2a_base64 function now accepts an optional newline keyword argument to control whether the newline character is appended to the return value Contributed by Victor Stinner in bpo 25357 cmath The new cmath tau τ constant has been added Contributed by Lisa Roach in bpo 12345 see PEP 628 for details New constants cmath inf and cmath nan to match math inf and math nan and also cmath infj and cmath nanj to match the format used by complex repr Contributed by Mark Dickinson in bpo 23229 collections The new Collection abstract base class has been added to represent sized iterable container classes Contributed by Ivan Levkivskyi docs by Neil Girdhar in bpo 27598 The new Reversible abstract base class represents iterable classes that also provide the __reversed__ method Contributed by Ivan Levkivskyi in bpo 25987 The new AsyncGenerator abstract base class represents asynchronous,en
1379, generators Contributed by Yury Selivanov in bpo 28720 The namedtuple function now accepts an optional keyword argument module which when specified is used for the __module__ attribute of the returned named tuple class Contributed by Raymond Hettinger in bpo 17941 The verbose and rename arguments for namedtuple are now keyword only Contributed by Raymond Hettinger in bpo 25628 Recursive collections deque instances can now be pickled Contributed by Serhiy Storchaka in bpo 26482 concurrent futures The ThreadPoolExecutor class constructor now accepts an optional thread_name_prefix argument to make it possible to customize the names of the threads created by the pool Contributed by Gregory P Smith in bpo 27664 contextlib The contextlib AbstractContextManager class has been added to provide an abstract base class for context managers It provides a sensible default implementation for __enter__ which returns self and leaves __exit__ an abstract method A matching class has been added to the typing module as typing ContextManager Contributed by Brett Cannon in bpo 25609 datetime The datetime and time classes have the new fold attribute used to disambiguate local time when necessary Many functions in the datetime have been updated to support local time disambiguation See Local Time Disambiguation section for more information Contributed by Alexander Belopolsky in bpo 24773 The datetime strftime and date strftime methods now support ISO 8601 date directives G u and V Contributed by Ashley Anderson in bpo 12006 The datetime isoformat function now accepts an optional timespec argument that specifies the number of additional components of the time value to include Contributed by Alessandro Cucci and Alexander Belopolsky in bpo 19475 The datetime combine now accepts an optional tzinfo argument Contributed by Alexander Belopolsky in bpo 27661 decimal New Decimal as_integer_ratio method that returns a pair n d of integers that represent the given Decimal instance as a fraction in lowest terms and with a positive denominator Decimal 3 14 as_integer_ratio 157 50 Contributed by Stefan Krah amd Mark Dickinson in bpo 25928 distutils The default_format attribute has been removed from distutils command sdist sdist and the formats attribute defaults to gztar Although not anticipated any code relying on the presence of default_format may need to be adapted See bpo 27819 for more details email The new email API enabled via the policy keyword to various constructors is no longer provisional The email documentation has been reorganized and rewritten to focus on the new API while retaining the old documentation for the legacy API Contributed by R David Murray in bpo 24277 The email mime classes now all accept an optional policy keyword Contributed by Berker Peksag in bpo 27331 The DecodedGenerator now supports the policy keyword There is a new policy attribute message_factory that controls what class is used by default when the parser creates new message objects For the email policy compat32 policy this is Message for the new policies it is EmailMessage Contributed by R David Murray in bpo 20476 encodings On Windows added the oem encoding to use CP_OEMCP and the ansi alias for the existing mbcs encoding which uses the CP_ACP code page Contributed by Steve Dower in bpo 27959 enum Two new enumeration base classes have been added to the enum module Flag and IntFlags Both are used to define constants that can be combined using the bitwise operators Contributed by Ethan Furman in bpo 23591 Many standard library modules have been updated to use the IntFlags class for their constants The new enum auto value can be used to assign values to enum members automatically from enum import Enum auto class Color Enum red auto blue auto green auto list Color Color red 1 Color blue 2 Color green 3 faulthandler On Windows the faulthandler module now installs a handler for Windows exceptions see faulthandler enable Contributed by Victor Stinner in bpo 23848 fileinput hook_encoded now supports the errors argument Contributed by Joseph Hackman in bpo 25788 hashlib hashlib,en
1380, supports OpenSSL 1 1 0 The minimum recommend version is 1 0 2 Contributed by Christian Heimes in bpo 26470 BLAKE2 hash functions were added to the module blake2b and blake2s are always available and support the full feature set of BLAKE2 Contributed by Christian Heimes in bpo 26798 based on code by Dmitry Chestnykh and Samuel Neves Documentation written by Dmitry Chestnykh The SHA 3 hash functions sha3_224 sha3_256 sha3_384 sha3_512 and SHAKE hash functions shake_128 and shake_256 were added Contributed by Christian Heimes in bpo 16113 Keccak Code Package by Guido Bertoni Joan Daemen Michaël Peeters Gilles Van Assche and Ronny Van Keer The password based key derivation function scrypt is now available with OpenSSL 1 1 0 and newer Contributed by Christian Heimes in bpo 27928 http client HTTPConnection request and endheaders both now support chunked encoding request bodies Contributed by Demian Brecht and Rolf Krahl in bpo 12319 idlelib and IDLE The idlelib package is being modernized and refactored to make IDLE look and work better and to make the code easier to understand test and improve Part of making IDLE look better especially on Linux and Mac is using ttk widgets mostly in the dialogs As a result IDLE no longer runs with tcl tk 8 4 It now requires tcl tk 8 5 or 8 6 We recommend running the latest release of either Modernizing includes renaming and consolidation of idlelib modules The renaming of files with partial uppercase names is similar to the renaming of for instance Tkinter and TkFont to tkinter and tkinter font in 3 0 As a result imports of idlelib files that worked in 3 5 will usually not work in 3 6 At least a module name change will be needed see idlelib README txt sometimes more Name changes contributed by Al Swiegart and Terry Reedy in bpo 24225 Most idlelib patches since have been and will be part of the process In compensation the eventual result with be that some idlelib classes will be easier to use with better APIs and docstrings explaining them Additional useful information will be added to idlelib when available New in 3 6 2 Multiple fixes for autocompletion Contributed by Louie Lu in bpo 15786 New in 3 6 3 Module Browser on the File menu formerly called Class Browser now displays nested functions and classes in addition to top level functions and classes Contributed by Guilherme Polo Cheryl Sabella and Terry Jan Reedy in bpo 1612262 The IDLE features formerly implemented as extensions have been reimplemented as normal features Their settings have been moved from the Extensions tab to other dialog tabs Contributed by Charles Wohlganger and Terry Jan Reedy in bpo 27099 The Settings dialog Options Configure IDLE has been partly rewritten to improve both appearance and function Contributed by Cheryl Sabella and Terry Jan Reedy in multiple issues New in 3 6 4 The font sample now includes a selection of non Latin characters so that users can better see the effect of selecting a particular font Contributed by Terry Jan Reedy in bpo 13802 The sample can be edited to include other characters Contributed by Serhiy Storchaka in bpo 31860 New in 3 6 6 Editor code context option revised Box displays all context lines up to maxlines Clicking on a context line jumps the editor to that line Context colors for custom themes is added to Highlights tab of Settings dialog Contributed by Cheryl Sabella and Terry Jan Reedy in bpo 33642 bpo 33768 and bpo 33679 On Windows a new API call tells Windows that tk scales for DPI On Windows 8 1 or 10 with DPI compatibility properties of the Python binary unchanged and a monitor resolution greater than 96 DPI this should make text and lines sharper It should otherwise have no effect Contributed by Terry Jan Reedy in bpo 33656 New in 3 6 7 Output over N lines 50 by default is squeezed down to a button N can be changed in the PyShell section of the General page of the Settings dialog Fewer but possibly extra long lines can be squeezed by right clicking on the output Squeezed output can be expanded in place by double clicking the button or into the clipboard or a separate window ,en
1381,by right clicking the button Contributed by Tal Einat in bpo 1529353 importlib Import now raises the new exception ModuleNotFoundError subclass of ImportError when it cannot find a module Code that current checks for ImportError in try except will still work Contributed by Eric Snow in bpo 15767 importlib util LazyLoader now calls create_module on the wrapped loader removing the restriction that importlib machinery BuiltinImporter and importlib machinery ExtensionFileLoader couldn t be used with importlib util LazyLoader importlib util cache_from_source importlib util source_from_cache and importlib util spec_from_file_location now accept a path like object inspect The inspect signature function now reports the implicit 0 parameters generated by the compiler for comprehension and generator expression scopes as if they were positional only parameters called implicit0 Contributed by Jelle Zijlstra in bpo 19611 To reduce code churn when upgrading from Python 2 7 and the legacy inspect getargspec API the previously documented deprecation of inspect getfullargspec has been reversed While this function is convenient for single source Python 2 3 code bases the richer inspect signature interface remains the recommended approach for new code Contributed by Nick Coghlan in bpo 27172 json json load and json loads now support binary input Encoded JSON should be represented using either UTF 8 UTF 16 or UTF 32 Contributed by Serhiy Storchaka in bpo 17909 logging The new WatchedFileHandler reopenIfNeeded method has been added to add the ability to check if the log file needs to be reopened Contributed by Marian Horban in bpo 24884 math The tau τ constant has been added to the math and cmath modules Contributed by Lisa Roach in bpo 12345 see PEP 628 for details multiprocessing Proxy Objects returned by multiprocessing Manager can now be nested Contributed by Davin Potts in bpo 6766 os See the summary of PEP 519 for details on how the os and os path modules now support path like objects scandir now supports bytes paths on Windows A new close method allows explicitly closing a scandir iterator The scandir iterator now supports the context manager protocol If a scandir iterator is neither exhausted nor explicitly closed a ResourceWarning will be emitted in its destructor Contributed by Serhiy Storchaka in bpo 25994 On Linux os urandom now blocks until the system urandom entropy pool is initialized to increase the security See the PEP 524 for the rationale The Linux getrandom syscall get random bytes is now exposed as the new os getrandom function Contributed by Victor Stinner part of the PEP 524 pathlib pathlib now supports path like objects Contributed by Brett Cannon in bpo 27186 See the summary of PEP 519 for details pdb The Pdb class constructor has a new optional readrc argument to control whether pdbrc files should be read pickle Objects that need __new__ called with keyword arguments can now be pickled using pickle protocols older than protocol version 4 Protocol version 4 already supports this case Contributed by Serhiy Storchaka in bpo 24164 pickletools pickletools dis now outputs the implicit memo index for the MEMOIZE opcode Contributed by Serhiy Storchaka in bpo 25382 pydoc The pydoc module has learned to respect the MANPAGER environment variable Contributed by Matthias Klose in bpo 8637 help and pydoc can now list named tuple fields in the order they were defined rather than alphabetically Contributed by Raymond Hettinger in bpo 24879 random The new choices function returns a list of elements of specified size from the given population with optional weights Contributed by Raymond Hettinger in bpo 18844 re Added support of modifier spans in regular expressions Examples i p ython matches python and Python but not PYTHON i g i v r matches GvR and gvr but not GVR Contributed by Serhiy Storchaka in bpo 433028 Match object groups can be accessed by __getitem__ which is equivalent to group So mo name is now equivalent to mo group name Contributed by Eric Smith in bpo 24454 Match objects now support index like objects as group indices,en
1382, Contributed by Jeroen Demeyer and Xiang Zhang in bpo 27177 readline Added set_auto_history to enable or disable automatic addition of input to the history list Contributed by Tyler Crompton in bpo 26870 rlcompleter Private and special attribute names now are omitted unless the prefix starts with underscores A space or a colon is added after some completed keywords Contributed by Serhiy Storchaka in bpo 25011 and bpo 25209 shlex The shlex has much improved shell compatibility through the new punctuation_chars argument to control which characters are treated as punctuation Contributed by Vinay Sajip in bpo 1521950 site When specifying paths to add to sys path in a pth file you may now specify file paths on top of directories e g zip files Contributed by Wolfgang Langner in bpo 26587 sqlite3 sqlite3 Cursor lastrowid now supports the REPLACE statement Contributed by Alex LordThorsen in bpo 16864 socket The ioctl function now supports the SIO_LOOPBACK_FAST_PATH control code Contributed by Daniel Stokes in bpo 26536 The getsockopt constants SO_DOMAIN SO_PROTOCOL SO_PEERSEC and SO_PASSSEC are now supported Contributed by Christian Heimes in bpo 26907 The setsockopt now supports the setsockopt level optname None optlen int form Contributed by Christian Heimes in bpo 27744 The socket module now supports the address family AF_ALG to interface with Linux Kernel crypto API ALG_ SOL_ALG and sendmsg_afalg were added Contributed by Christian Heimes in bpo 27744 with support from Victor Stinner New Linux constants TCP_USER_TIMEOUT and TCP_CONGESTION were added Contributed by Omar Sandoval bpo 26273 socketserver Servers based on the socketserver module including those defined in http server xmlrpc server and wsgiref simple_server now support the context manager protocol Contributed by Aviv Palivoda in bpo 26404 The wfile attribute of StreamRequestHandler classes now implements the io BufferedIOBase writable interface In particular calling write is now guaranteed to send the data in full Contributed by Martin Panter in bpo 26721 ssl ssl supports OpenSSL 1 1 0 The minimum recommend version is 1 0 2 Contributed by Christian Heimes in bpo 26470 3DES has been removed from the default cipher suites and ChaCha20 Poly1305 cipher suites have been added Contributed by Christian Heimes in bpo 27850 and bpo 27766 SSLContext has better default configuration for options and ciphers Contributed by Christian Heimes in bpo 28043 SSL session can be copied from one client side connection to another with the new SSLSession class TLS session resumption can speed up the initial handshake reduce latency and improve performance Contributed by Christian Heimes in bpo 19500 based on a draft by Alex Warhawk The new get_ciphers method can be used to get a list of enabled ciphers in order of cipher priority All constants and flags have been converted to IntEnum and IntFlags Contributed by Christian Heimes in bpo 28025 Server and client side specific TLS protocols for SSLContext were added Contributed by Christian Heimes in bpo 28085 Added ssl SSLContext post_handshake_auth to enable and ssl SSLSocket verify_client_post_handshake to initiate TLS 1 3 post handshake authentication Contributed by Christian Heimes in gh 78851 statistics A new harmonic_mean function has been added Contributed by Steven D Aprano in bpo 27181 struct struct now supports IEEE 754 half precision floats via the e format specifier Contributed by Eli Stevens Mark Dickinson in bpo 11734 subprocess subprocess Popen destructor now emits a ResourceWarning warning if the child process is still running Use the context manager protocol with proc or explicitly call the wait method to read the exit status of the child process Contributed by Victor Stinner in bpo 26741 The subprocess Popen constructor and all functions that pass arguments through to it now accept encoding and errors arguments Specifying either of these will enable text mode for the stdin stdout and stderr streams Contributed by Steve Dower in bpo 6135 sys The new getfilesystemencodeerrors function returns the name of the error mode used t,en
1383,o convert between Unicode filenames and bytes filenames Contributed by Steve Dower in bpo 27781 On Windows the return value of the getwindowsversion function now includes the platform_version field which contains the accurate major version minor version and build number of the current operating system rather than the version that is being emulated for the process Contributed by Steve Dower in bpo 27932 telnetlib Telnet is now a context manager contributed by Stéphane Wirtel in bpo 25485 time The struct_time attributes tm_gmtoff and tm_zone are now available on all platforms timeit The new Timer autorange convenience method has been added to call Timer timeit repeatedly so that the total run time is greater or equal to 200 milliseconds Contributed by Steven D Aprano in bpo 6422 timeit now warns when there is substantial 4x variance between best and worst times Contributed by Serhiy Storchaka in bpo 23552 tkinter Added methods trace_add trace_remove and trace_info in the tkinter Variable class They replace old methods trace_variable trace trace_vdelete and trace_vinfo that use obsolete Tcl commands and might not work in future versions of Tcl Contributed by Serhiy Storchaka in bpo 22115 traceback Both the traceback module and the interpreter s builtin exception display now abbreviate long sequences of repeated lines in tracebacks as shown in the following example def f f f Traceback most recent call last File stdin line 1 in module File stdin line 1 in f File stdin line 1 in f File stdin line 1 in f Previous line repeated 995 more times RecursionError maximum recursion depth exceeded Contributed by Emanuel Barry in bpo 26823 tracemalloc The tracemalloc module now supports tracing memory allocations in multiple different address spaces The new DomainFilter filter class has been added to filter block traces by their address space domain Contributed by Victor Stinner in bpo 26588 typing Since the typing module is provisional all changes introduced in Python 3 6 have also been backported to Python 3 5 x The typing module has a much improved support for generic type aliases For example Dict str Tuple S T is now a valid type annotation Contributed by Guido van Rossum in Github 195 The typing ContextManager class has been added for representing contextlib AbstractContextManager Contributed by Brett Cannon in bpo 25609 The typing Collection class has been added for representing collections abc Collection Contributed by Ivan Levkivskyi in bpo 27598 The typing ClassVar type construct has been added to mark class variables As introduced in PEP 526 a variable annotation wrapped in ClassVar indicates that a given attribute is intended to be used as a class variable and should not be set on instances of that class Contributed by Ivan Levkivskyi in Github 280 A new TYPE_CHECKING constant that is assumed to be True by the static type checkers but is False at runtime Contributed by Guido van Rossum in Github 230 A new NewType helper function has been added to create lightweight distinct types for annotations from typing import NewType UserId NewType UserId int some_id UserId 524313 The static type checker will treat the new type as if it were a subclass of the original type Contributed by Ivan Levkivskyi in Github 189 unicodedata The unicodedata module now uses data from Unicode 9 0 0 Contributed by Benjamin Peterson unittest mock The Mock class has the following improvements Two new methods Mock assert_called and Mock assert_called_once to check if the mock object was called Contributed by Amit Saha in bpo 26323 The Mock reset_mock method now has two optional keyword only arguments return_value and side_effect Contributed by Kushal Das in bpo 21271 urllib request If a HTTP request has a file or iterable body other than a bytes object but no Content Length header rather than throwing an error AbstractHTTPHandler now falls back to use chunked transfer encoding Contributed by Demian Brecht and Rolf Krahl in bpo 12319 urllib robotparser RobotFileParser now supports the Crawl delay and Request rate extensions Contributed by Nikolay Bogoychev i,en
1384,n bpo 16099 venv venv accepts a new parameter prompt This parameter provides an alternative prefix for the virtual environment Proposed by Łukasz Balcerzak and ported to 3 6 by Stéphane Wirtel in bpo 22829 warnings A new optional source parameter has been added to the warnings warn_explicit function the destroyed object which emitted a ResourceWarning A source attribute has also been added to warnings WarningMessage contributed by Victor Stinner in bpo 26568 and bpo 26567 When a ResourceWarning warning is logged the tracemalloc module is now used to try to retrieve the traceback where the destroyed object was allocated Example with the script example py import warnings def func return open __file__ f func f None Output of the command python3 6 Wd X tracemalloc 5 example py example py 7 ResourceWarning unclosed file _io TextIOWrapper name example py mode r encoding UTF 8 f None Object allocated at most recent call first File example py lineno 4 return open __file__ File example py lineno 6 f func The Object allocated at traceback is new and is only displayed if tracemalloc is tracing Python memory allocations and if the warnings module was already imported winreg Added the 64 bit integer type REG_QWORD Contributed by Clement Rouault in bpo 23026 winsound Allowed keyword arguments to be passed to Beep MessageBeep and PlaySound bpo 27982 xmlrpc client The xmlrpc client module now supports unmarshalling additional data types used by the Apache XML RPC implementation for numerics and None Contributed by Serhiy Storchaka in bpo 26885 zipfile A new ZipInfo from_file class method allows making a ZipInfo instance from a filesystem file A new ZipInfo is_dir method can be used to check if the ZipInfo instance represents a directory Contributed by Thomas Kluyver in bpo 26039 The ZipFile open method can now be used to write data into a ZIP file as well as for extracting data Contributed by Thomas Kluyver in bpo 26039 zlib The compress and decompress functions now accept keyword arguments Contributed by Aviv Palivoda in bpo 26243 and Xiang Zhang in bpo 16764 respectively Optimizations The Python interpreter now uses a 16 bit wordcode instead of bytecode which made a number of opcode optimizations possible Contributed by Demur Rumed with input and reviews from Serhiy Storchaka and Victor Stinner in bpo 26647 and bpo 28050 The asyncio Future class now has an optimized C implementation Contributed by Yury Selivanov and INADA Naoki in bpo 26081 The asyncio Task class now has an optimized C implementation Contributed by Yury Selivanov in bpo 28544 Various implementation improvements in the typing module such as caching of generic types allow up to 30 times performance improvements and reduced memory footprint The ASCII decoder is now up to 60 times as fast for error handlers surrogateescape ignore and replace Contributed by Victor Stinner in bpo 24870 The ASCII and the Latin1 encoders are now up to 3 times as fast for the error handler surrogateescape Contributed by Victor Stinner in bpo 25227 The UTF 8 encoder is now up to 75 times as fast for error handlers ignore replace surrogateescape surrogatepass Contributed by Victor Stinner in bpo 25267 The UTF 8 decoder is now up to 15 times as fast for error handlers ignore replace and surrogateescape Contributed by Victor Stinner in bpo 25301 bytes args is now up to 2 times faster Contributed by Victor Stinner in bpo 25349 bytearray args is now between 2 5 and 5 times faster Contributed by Victor Stinner in bpo 25399 Optimize bytes fromhex and bytearray fromhex they are now between 2x and 3 5x faster Contributed by Victor Stinner in bpo 25401 Optimize bytes replace b b and bytearray replace b b up to 80 faster Contributed by Josh Snider in bpo 26574 Allocator functions of the PyMem_Malloc domain PYMEM_DOMAIN_MEM now use the pymalloc memory allocator instead of malloc function of the C library The pymalloc allocator is optimized for objects smaller or equal to 512 bytes with a short lifetime and use malloc for larger memory blocks Contributed by Victor Stinner in bpo 26249 pickle load and pickle,en
1385, loads are now up to 10 faster when deserializing many small objects Contributed by Victor Stinner in bpo 27056 Passing keyword arguments to a function has an overhead in comparison with passing positional arguments Now in extension functions implemented with using Argument Clinic this overhead is significantly decreased Contributed by Serhiy Storchaka in bpo 27574 Optimized glob and iglob functions in the glob module they are now about 3 6 times faster Contributed by Serhiy Storchaka in bpo 25596 Optimized globbing in pathlib by using os scandir it is now about 1 5 4 times faster Contributed by Serhiy Storchaka in bpo 26032 xml etree ElementTree parsing iteration and deepcopy performance has been significantly improved Contributed by Serhiy Storchaka in bpo 25638 bpo 25873 and bpo 25869 Creation of fractions Fraction instances from floats and decimals is now 2 to 3 times faster Contributed by Serhiy Storchaka in bpo 25971 Build and C API Changes Python now requires some C99 support in the toolchain to build Most notably Python now uses standard integer types and macros in place of custom macros like PY_LONG_LONG For more information see PEP 7 and bpo 17884 Cross compiling CPython with the Android NDK and the Android API level set to 21 Android 5 0 Lollipop or greater runs successfully While Android is not yet a supported platform the Python test suite runs on the Android emulator with only about 16 tests failures See the Android meta issue bpo 26865 The enable optimizations configure flag has been added Turning it on will activate expensive optimizations like PGO Original patch by Alecsandru Patrascu of Intel in bpo 26359 The GIL must now be held when allocator functions of PYMEM_DOMAIN_OBJ ex PyObject_Malloc and PYMEM_DOMAIN_MEM ex PyMem_Malloc domains are called New Py_FinalizeEx API which indicates if flushing buffered data failed Contributed by Martin Panter in bpo 5319 PyArg_ParseTupleAndKeywords now supports positional only parameters Positional only parameters are defined by empty names Contributed by Serhiy Storchaka in bpo 26282 PyTraceback_Print method now abbreviates long sequences of repeated lines as Previous line repeated count more times Contributed by Emanuel Barry in bpo 26823 The new PyErr_SetImportErrorSubclass function allows for specifying a subclass of ImportError to raise Contributed by Eric Snow in bpo 15767 The new PyErr_ResourceWarning function can be used to generate a ResourceWarning providing the source of the resource allocation Contributed by Victor Stinner in bpo 26567 The new PyOS_FSPath function returns the file system representation of a path like object Contributed by Brett Cannon in bpo 27186 The PyUnicode_FSConverter and PyUnicode_FSDecoder functions will now accept path like objects Other Improvements When version short form V is supplied twice Python prints sys version for detailed information python VV Python 3 6 0b4 3 6 223967b49e49 Nov 21 2016 20 55 04 GCC 4 2 1 Compatible Apple LLVM 8 0 0 clang 800 0 42 1 Deprecated New Keywords async and await are not recommended to be used as variable class function or module names Introduced by PEP 492 in Python 3 5 they will become proper keywords in Python 3 7 Starting in Python 3 6 the use of async or await as names will generate a DeprecationWarning Deprecated Python behavior Raising the StopIteration exception inside a generator will now generate a DeprecationWarning and will trigger a RuntimeError in Python 3 7 See PEP 479 Change StopIteration handling inside generators for details The __aiter__ method is now expected to return an asynchronous iterator directly instead of returning an awaitable as previously Doing the former will trigger a DeprecationWarning Backward compatibility will be removed in Python 3 7 Contributed by Yury Selivanov in bpo 27243 A backslash character pair that is not a valid escape sequence now generates a DeprecationWarning Although this will eventually become a SyntaxError that will not be for several Python releases Contributed by Emanuel Barry in bpo 27364 When performing a relative import falling back on _,en
1386,_name__ and __path__ from the calling module when __spec__ or __package__ are not defined now raises an ImportWarning Contributed by Rose Ames in bpo 25791 Deprecated Python modules functions and methods asynchat The asynchat has been deprecated in favor of asyncio Contributed by Mariatta in bpo 25002 asyncore The asyncore has been deprecated in favor of asyncio Contributed by Mariatta in bpo 25002 dbm Unlike other dbm implementations the dbm dumb module creates databases with the rw mode and allows modifying the database opened with the r mode This behavior is now deprecated and will be removed in 3 8 Contributed by Serhiy Storchaka in bpo 21708 distutils The undocumented extra_path argument to the distutils Distribution constructor is now considered deprecated and will raise a warning if set Support for this parameter will be removed in a future Python release See bpo 27919 for details grp The support of non integer arguments in getgrgid has been deprecated Contributed by Serhiy Storchaka in bpo 26129 importlib The importlib machinery SourceFileLoader load_module and importlib machinery SourcelessFileLoader load_module methods are now deprecated They were the only remaining implementations of importlib abc Loader load_module in importlib that had not been deprecated in previous versions of Python in favour of importlib abc Loader exec_module The importlib machinery WindowsRegistryFinder class is now deprecated As of 3 6 0 it is still added to sys meta_path by default on Windows but this may change in future releases os Undocumented support of general bytes like objects as paths in os functions compile and similar functions is now deprecated Contributed by Serhiy Storchaka in bpo 25791 and bpo 26754 re Support for inline flags letters in the middle of the regular expression has been deprecated and will be removed in a future Python version Flags at the start of a regular expression are still allowed Contributed by Serhiy Storchaka in bpo 22493 ssl OpenSSL 0 9 8 1 0 0 and 1 0 1 are deprecated and no longer supported In the future the ssl module will require at least OpenSSL 1 0 2 or 1 1 0 SSL related arguments like certfile keyfile and check_hostname in ftplib http client imaplib poplib and smtplib have been deprecated in favor of context Contributed by Christian Heimes in bpo 28022 A couple of protocols and functions of the ssl module are now deprecated Some features will no longer be available in future versions of OpenSSL Other features are deprecated in favor of a different API Contributed by Christian Heimes in bpo 28022 and bpo 26470 tkinter The tkinter tix module is now deprecated tkinter users should use tkinter ttk instead venv The pyvenv script has been deprecated in favour of python3 m venv This prevents confusion as to what Python interpreter pyvenv is connected to and thus what Python interpreter will be used by the virtual environment Contributed by Brett Cannon in bpo 25154 xml As mitigation against DTD and external entity retrieval the xml dom minidom and xml sax modules no longer process external entities by default Contributed by Christian Heimes in gh 61441 Deprecated functions and types of the C API Undocumented functions PyUnicode_AsEncodedObject PyUnicode_AsDecodedObject PyUnicode_AsEncodedUnicode and PyUnicode_AsDecodedUnicode are deprecated now Use the generic codec based API instead Deprecated Build Options The with system ffi configure flag is now on by default on non macOS UNIX platforms It may be disabled by using without system ffi but using the flag is deprecated and will not be accepted in Python 3 7 macOS is unaffected by this change Note that many OS distributors already use the with system ffi flag when building their system Python Removed API and Feature Removals Unknown escapes consisting of and an ASCII letter in regular expressions will now cause an error In replacement templates for re sub they are still allowed but deprecated The re LOCALE flag can now only be used with binary patterns inspect getmoduleinfo was removed was deprecated since CPython 3 3 inspect getmodulename should b,en
1387,e used for obtaining the module name for a given path Contributed by Yury Selivanov in bpo 13248 traceback Ignore class and traceback usage traceback modname traceback fullmodname traceback find_lines_from_code traceback find_lines traceback find_strings traceback find_executable_lines methods were removed from the traceback module They were undocumented methods deprecated since Python 3 2 and equivalent functionality is available from private methods The tk_menuBar and tk_bindForTraversal dummy methods in tkinter widget classes were removed corresponding Tk commands were obsolete since Tk 4 0 The open method of the zipfile ZipFile class no longer supports the U mode was deprecated since Python 3 4 Use io TextIOWrapper for reading compressed text files in universal newlines mode The undocumented IN CDROM DLFCN TYPES CDIO and STROPTS modules have been removed They had been available in the platform specific Lib plat directories but were chronically out of date inconsistently available across platforms and unmaintained The script that created these modules is still available in the source distribution at Tools scripts h2py py The deprecated asynchat fifo class has been removed Porting to Python 3 6 This section lists previously described changes and other bugfixes that may require changes to your code Changes in python Command Behavior The output of a special Python build with defined COUNT_ALLOCS SHOW_ALLOC_COUNT or SHOW_TRACK_COUNT macros is now off by default It can be re enabled using the X showalloccount option It now outputs to stderr instead of stdout Contributed by Serhiy Storchaka in bpo 23034 Changes in the Python API open will no longer allow combining the U mode flag with Contributed by Jeff Balogh and John O Connor in bpo 2091 sqlite3 no longer implicitly commits an open transaction before DDL statements On Linux os urandom now blocks until the system urandom entropy pool is initialized to increase the security When importlib abc Loader exec_module is defined importlib abc Loader create_module must also be defined PyErr_SetImportError now sets TypeError when its msg argument is not set Previously only NULL was returned The format of the co_lnotab attribute of code objects changed to support a negative line number delta By default Python does not emit bytecode with a negative line number delta Functions using frame f_lineno PyFrame_GetLineNumber or PyCode_Addr2Line are not affected Functions directly decoding co_lnotab should be updated to use a signed 8 bit integer type for the line number delta but this is only required to support applications using a negative line number delta See Objects lnotab_notes txt for the co_lnotab format and how to decode it and see the PEP 511 for the rationale The functions in the compileall module now return booleans instead of 1 or 0 to represent success or failure respectively Thanks to booleans being a subclass of integers this should only be an issue if you were doing identity checks for 1 or 0 See bpo 25768 Reading the port attribute of urllib parse urlsplit and urlparse results now raises ValueError for out of range values rather than returning None See bpo 20059 The imp module now raises a DeprecationWarning instead of PendingDeprecationWarning The following modules have had missing APIs added to their __all__ attributes to match the documented APIs calendar cgi csv ElementTree enum fileinput ftplib logging mailbox mimetypes optparse plistlib smtpd subprocess tarfile threading and wave This means they will export new symbols when import is used Contributed by Joel Taddei and Jacek Kołodziej in bpo 23883 When performing a relative import if __package__ does not compare equal to __spec__ parent then ImportWarning is raised Contributed by Brett Cannon in bpo 25791 When a relative import is performed and no parent package is known then ImportError will be raised Previously SystemError could be raised Contributed by Brett Cannon in bpo 18018 Servers based on the socketserver module including those defined in http server xmlrpc server and wsgiref simple_server now only catch exc,en
1388,eptions derived from Exception Therefore if a request handler raises an exception like SystemExit or KeyboardInterrupt handle_error is no longer called and the exception will stop a single threaded server Contributed by Martin Panter in bpo 23430 spwd getspnam now raises a PermissionError instead of KeyError if the user doesn t have privileges The socket socket close method now raises an exception if an error e g EBADF was reported by the underlying system call Contributed by Martin Panter in bpo 26685 The decode_data argument for the smtpd SMTPChannel and smtpd SMTPServer constructors is now False by default This means that the argument passed to process_message is now a bytes object by default and process_message will be passed keyword arguments Code that has already been updated in accordance with the deprecation warning generated by 3 5 will not be affected All optional arguments of the dump dumps load and loads functions and JSONEncoder and JSONDecoder class constructors in the json module are now keyword only Contributed by Serhiy Storchaka in bpo 18726 Subclasses of type which don t override type __new__ may no longer use the one argument form to get the type of an object As part of PEP 487 the handling of keyword arguments passed to type other than the metaclass hint metaclass is now consistently delegated to object __init_subclass__ This means that type __new__ and type __init__ both now accept arbitrary keyword arguments but object __init_subclass__ which is called from type __new__ will reject them by default Custom metaclasses accepting additional keyword arguments will need to adjust their calls to type __new__ whether direct or via super accordingly In distutils command sdist sdist the default_format attribute has been removed and is no longer honored Instead the gzipped tarfile format is the default on all platforms and no platform specific selection is made In environments where distributions are built on Windows and zip distributions are required configure the project with a setup cfg file containing the following sdist formats zip This behavior has also been backported to earlier Python versions by Setuptools 26 0 0 In the urllib request module and the http client HTTPConnection request method if no Content Length header field has been specified and the request body is a file object it is now sent with HTTP 1 1 chunked encoding If a file object has to be sent to a HTTP 1 0 server the Content Length value now has to be specified by the caller Contributed by Demian Brecht and Rolf Krahl with tweaks from Martin Panter in bpo 12319 The DictReader now returns rows of type OrderedDict Contributed by Steve Holden in bpo 27842 The crypt METHOD_CRYPT will no longer be added to crypt methods if unsupported by the platform Contributed by Victor Stinner in bpo 25287 The verbose and rename arguments for namedtuple are now keyword only Contributed by Raymond Hettinger in bpo 25628 On Linux ctypes util find_library now looks in LD_LIBRARY_PATH for shared libraries Contributed by Vinay Sajip in bpo 9998 The imaplib IMAP4 class now handles flags containing the character in messages sent from the server to improve real world compatibility Contributed by Lita Cho in bpo 21815 The mmap write function now returns the number of bytes written like other write methods Contributed by Jakub Stasiak in bpo 26335 The pkgutil iter_modules and pkgutil walk_packages functions now return ModuleInfo named tuples Contributed by Ramchandra Apte in bpo 17211 re sub now raises an error for invalid numerical group references in replacement templates even if the pattern is not found in the string The error message for invalid group references now includes the group index and the position of the reference Contributed by SilentGhost Serhiy Storchaka in bpo 25953 zipfile ZipFile will now raise NotImplementedError for unrecognized compression values Previously a plain RuntimeError was raised Additionally calling ZipFile methods on a closed ZipFile or calling the write method on a ZipFile created with mode r will raise a ValueError Previously a R,en
1389,untimeError was raised in those scenarios when custom metaclasses are combined with zero argument super or direct references from methods to the implicit __class__ closure variable the implicit __classcell__ namespace entry must now be passed up to type __new__ for initialisation Failing to do so will result in a DeprecationWarning in Python 3 6 and a RuntimeError in Python 3 8 With the introduction of ModuleNotFoundError import system consumers may start expecting import system replacements to raise that more specific exception when appropriate rather than the less specific ImportError To provide future compatibility with such consumers implementors of alternative import systems that completely replace __import__ will need to update their implementations to raise the new subclass when a module can t be found at all Implementors of compliant plugins to the default import system shouldn t need to make any changes as the default import system will raise the new subclass when appropriate Changes in the C API The PyMem_Malloc allocator family now uses the pymalloc allocator rather than the system malloc Applications calling PyMem_Malloc without holding the GIL can now crash Set the PYTHONMALLOC environment variable to debug to validate the usage of memory allocators in your application See bpo 26249 Py_Exit and the main interpreter now override the exit status with 120 if flushing buffered data failed See bpo 5319 CPython bytecode changes There have been several major changes to the bytecode in Python 3 6 The Python interpreter now uses a 16 bit wordcode instead of bytecode Contributed by Demur Rumed with input and reviews from Serhiy Storchaka and Victor Stinner in bpo 26647 and bpo 28050 The new FORMAT_VALUE and BUILD_STRING opcodes as part of the formatted string literal implementation Contributed by Eric Smith in bpo 25483 and Serhiy Storchaka in bpo 27078 The new BUILD_CONST_KEY_MAP opcode to optimize the creation of dictionaries with constant keys Contributed by Serhiy Storchaka in bpo 27140 The function call opcodes have been heavily reworked for better performance and simpler implementation The MAKE_FUNCTION CALL_FUNCTION CALL_FUNCTION_KW and BUILD_MAP_UNPACK_WITH_CALL opcodes have been modified the new CALL_FUNCTION_EX and BUILD_TUPLE_UNPACK_WITH_CALL have been added and CALL_FUNCTION_VAR CALL_FUNCTION_VAR_KW and MAKE_CLOSURE opcodes have been removed Contributed by Demur Rumed in bpo 27095 and Serhiy Storchaka in bpo 27213 bpo 28257 The new SETUP_ANNOTATIONS and STORE_ANNOTATION opcodes have been added to support the new variable annotation syntax Contributed by Ivan Levkivskyi in bpo 27985 Notable changes in Python 3 6 2 New make regen all build target To simplify cross compilation and to ensure that CPython can reliably be compiled without requiring an existing version of Python to already be available the autotools based build system no longer attempts to implicitly recompile generated files based on file modification times Instead a new make regen all command has been added to force regeneration of these files when desired e g after an initial version of Python has already been built based on the pregenerated versions More selective regeneration targets are also defined see Makefile pre in for details Contributed by Victor Stinner in bpo 23404 New in version 3 6 2 Removal of make touch build target The make touch build target previously used to request implicit regeneration of generated files by updating their modification times has been removed It has been replaced by the new make regen all target Contributed by Victor Stinner in bpo 23404 Changed in version 3 6 2 Notable changes in Python 3 6 4 The PyExc_RecursionErrorInst singleton that was part of the public API has been removed as its members being never cleared may cause a segfault during finalization of the interpreter Contributed by Xavier de Gaye in bpo 22898 and bpo 30697 Notable changes in Python 3 6 5 The locale localeconv function now sets temporarily the LC_CTYPE locale to the LC_NUMERIC locale in some cases Contributed by Victor Stinner in bpo 31,en
1390,900 Notable changes in Python 3 6 7 xml dom minidom and xml sax modules no longer process external entities by default See also gh 61441 In 3 6 7 the tokenize module now implicitly emits a NEWLINE token when provided with input that does not have a trailing new line This behavior now matches what the C tokenizer does internally Contributed by Ammar Askar in bpo 33899 Notable changes in Python 3 6 10 Due to significant security concerns the reuse_address parameter of asyncio loop create_datagram_endpoint is no longer supported This is because of the behavior of the socket option SO_REUSEADDR in UDP For more details see the documentation for loop create_datagram_endpoint Contributed by Kyle Stanley Antoine Pitrou and Yury Selivanov in bpo 37228 Notable changes in Python 3 6 13 Earlier Python versions allowed using both and as query parameter separators in urllib parse parse_qs and urllib parse parse_qsl Due to security concerns and to conform with newer W3C recommendations this has been changed to allow only a single separator key with as the default This change also affects cgi parse and cgi parse_multipart as they use the affected functions internally For more details please see their respective documentation Contributed by Adam Goldschmidt Senthil Kumaran and Ken Jin in bpo 42967 Notable changes in Python 3 6 14 A security fix alters the ftplib FTP behavior to not trust the IPv4 address sent from the remote server when setting up a passive data channel We reuse the ftp server IP address instead For unusual code requiring the old behavior set a trust_server_pasv_ipv4_address attribute on your FTP instance to True See gh 87451 The presence of newline or tab characters in parts of a URL allows for some forms of attacks Following the WHATWG specification that updates RFC 3986 ASCII newline n r and tab t characters are stripped from the URL by the parser urllib parse preventing such attacks The removal characters are controlled by a new module level variable urllib parse _UNSAFE_URL_BYTES_TO_REMOVE See gh 88048,en
1391,operator Standard operators as functions Source code Lib operator py The operator module exports a set of efficient functions corresponding to the intrinsic operators of Python For example operator add x y is equivalent to the expression x y Many function names are those used for special methods without the double underscores For backward compatibility many of these have a variant with the double underscores kept The variants without the double underscores are preferred for clarity The functions fall into categories that perform object comparisons logical operations mathematical operations and sequence operations The object comparison functions are useful for all objects and are named after the rich comparison operators they support operator lt a b operator le a b operator eq a b operator ne a b operator ge a b operator gt a b operator __lt__ a b operator __le__ a b operator __eq__ a b operator __ne__ a b operator __ge__ a b operator __gt__ a b Perform rich comparisons between a and b Specifically lt a b is equivalent to a b le a b is equivalent to a b eq a b is equivalent to a b ne a b is equivalent to a b gt a b is equivalent to a b and ge a b is equivalent to a b Note that these functions can return any value which may or may not be interpretable as a Boolean value See Comparisons for more information about rich comparisons The logical operations are also generally applicable to all objects and support truth tests identity tests and boolean operations operator not_ obj operator __not__ obj Return the outcome of not obj Note that there is no __not__ method for object instances only the interpreter core defines this operation The result is affected by the __bool__ and __len__ methods operator truth obj Return True if obj is true and False otherwise This is equivalent to using the bool constructor operator is_ a b Return a is b Tests object identity operator is_not a b Return a is not b Tests object identity The mathematical and bitwise operations are the most numerous operator abs obj operator __abs__ obj Return the absolute value of obj operator add a b operator __add__ a b Return a b for a and b numbers operator and_ a b operator __and__ a b Return the bitwise and of a and b operator floordiv a b operator __floordiv__ a b Return a b operator index a operator __index__ a Return a converted to an integer Equivalent to a __index__ Changed in version 3 10 The result always has exact type int Previously the result could have been an instance of a subclass of int operator inv obj operator invert obj operator __inv__ obj operator __invert__ obj Return the bitwise inverse of the number obj This is equivalent to obj operator lshift a b operator __lshift__ a b Return a shifted left by b operator mod a b operator __mod__ a b Return a b operator mul a b operator __mul__ a b Return a b for a and b numbers operator matmul a b operator __matmul__ a b Return a b New in version 3 5 operator neg obj operator __neg__ obj Return obj negated obj operator or_ a b operator __or__ a b Return the bitwise or of a and b operator pos obj operator __pos__ obj Return obj positive obj operator pow a b operator __pow__ a b Return a b for a and b numbers operator rshift a b operator __rshift__ a b Return a shifted right by b operator sub a b operator __sub__ a b Return a b operator truediv a b operator __truediv__ a b Return a b where 2 3 is 66 rather than 0 This is also known as true division operator xor a b operator __xor__ a b Return the bitwise exclusive or of a and b Operations which work with sequences some of them with mappings too include operator concat a b operator __concat__ a b Return a b for a and b sequences operator contains a b operator __contains__ a b Return the outcome of the test b in a Note the reversed operands operator countOf a b Return the number of occurrences of b in a operator delitem a b operator __delitem__ a b Remove the value of a at index b operator getitem a b operator __getitem__ a b Return the value of a at index b operator indexOf a b Return the index of the first of occurrence of b in a operator setitem a b c op,en
1392,erator __setitem__ a b c Set the value of a at index b to c operator length_hint obj default 0 Return an estimated length for the object obj First try to return its actual length then an estimate using object __length_hint__ and finally return the default value New in version 3 4 The following operation works with callables operator call obj args kwargs operator __call__ obj args kwargs Return obj args kwargs New in version 3 11 The operator module also defines tools for generalized attribute and item lookups These are useful for making fast field extractors as arguments for map sorted itertools groupby or other functions that expect a function argument operator attrgetter attr operator attrgetter attrs Return a callable object that fetches attr from its operand If more than one attribute is requested returns a tuple of attributes The attribute names can also contain dots For example After f attrgetter name the call f b returns b name After f attrgetter name date the call f b returns b name b date After f attrgetter name first name last the call f b returns b name first b name last Equivalent to def attrgetter items if any not isinstance item str for item in items raise TypeError attribute name must be a string if len items 1 attr items 0 def g obj return resolve_attr obj attr else def g obj return tuple resolve_attr obj attr for attr in items return g def resolve_attr obj attr for name in attr split obj getattr obj name return obj operator itemgetter item operator itemgetter items Return a callable object that fetches item from its operand using the operand s __getitem__ method If multiple items are specified returns a tuple of lookup values For example After f itemgetter 2 the call f r returns r 2 After g itemgetter 2 5 3 the call g r returns r 2 r 5 r 3 Equivalent to def itemgetter items if len items 1 item items 0 def g obj return obj item else def g obj return tuple obj item for item in items return g The items can be any type accepted by the operand s __getitem__ method Dictionaries accept any hashable value Lists tuples and strings accept an index or a slice itemgetter 1 ABCDEFG B itemgetter 1 3 5 ABCDEFG B D F itemgetter slice 2 None ABCDEFG CDEFG soldier dict rank captain name dotterbart itemgetter rank soldier captain Example of using itemgetter to retrieve specific fields from a tuple record inventory apple 3 banana 2 pear 5 orange 1 getcount itemgetter 1 list map getcount inventory 3 2 5 1 sorted inventory key getcount orange 1 banana 2 apple 3 pear 5 operator methodcaller name args kwargs Return a callable object that calls the method name on its operand If additional arguments and or keyword arguments are given they will be given to the method as well For example After f methodcaller name the call f b returns b name After f methodcaller name foo bar 1 the call f b returns b name foo bar 1 Equivalent to def methodcaller name args kwargs def caller obj return getattr obj name args kwargs return caller Mapping Operators to Functions This table shows how abstract operations correspond to operator symbols in the Python syntax and the functions in the operator module Operation Syntax Function Addition a b add a b Concatenation seq1 seq2 concat seq1 seq2 Containment Test obj in seq contains seq obj Division a b truediv a b Division a b floordiv a b Bitwise And a b and_ a b Bitwise Exclusive Or a b xor a b Bitwise Inversion a invert a Bitwise Or a b or_ a b Exponentiation a b pow a b Identity a is b is_ a b Identity a is not b is_not a b Indexed Assignment obj k v setitem obj k v Indexed Deletion del obj k delitem obj k Indexing obj k getitem obj k Left Shift a b lshift a b Modulo a b mod a b Multiplication a b mul a b Matrix Multiplication a b matmul a b Negation Arithmetic a neg a Negation Logical not a not_ a Positive a pos a Right Shift a b rshift a b Slice Assignment seq i j values setitem seq slice i j values Slice Deletion del seq i j delitem seq slice i j Slicing seq i j getitem seq slice i j String Formatting s obj mod s obj Subtraction a b sub a b Truth Test obj truth obj Ordering a b lt a b Ordering a b ,en
1393,le a b Equality a b eq a b Difference a b ne a b Ordering a b ge a b Ordering a b gt a b In place Operators Many operations have an in place version Listed below are functions providing a more primitive access to in place operators than the usual syntax does for example the statement x y is equivalent to x operator iadd x y Another way to put it is to say that z operator iadd x y is equivalent to the compound statement z x z y In those examples note that when an in place method is called the computation and assignment are performed in two separate steps The in place functions listed below only do the first step calling the in place method The second step assignment is not handled For immutable targets such as strings numbers and tuples the updated value is computed but not assigned back to the input variable a hello iadd a world hello world a hello For mutable targets such as lists and dictionaries the in place method will perform the update so no subsequent assignment is necessary s h e l l o iadd s w o r l d h e l l o w o r l d s h e l l o w o r l d operator iadd a b operator __iadd__ a b a iadd a b is equivalent to a b operator iand a b operator __iand__ a b a iand a b is equivalent to a b operator iconcat a b operator __iconcat__ a b a iconcat a b is equivalent to a b for a and b sequences operator ifloordiv a b operator __ifloordiv__ a b a ifloordiv a b is equivalent to a b operator ilshift a b operator __ilshift__ a b a ilshift a b is equivalent to a b operator imod a b operator __imod__ a b a imod a b is equivalent to a b operator imul a b operator __imul__ a b a imul a b is equivalent to a b operator imatmul a b operator __imatmul__ a b a imatmul a b is equivalent to a b New in version 3 5 operator ior a b operator __ior__ a b a ior a b is equivalent to a b operator ipow a b operator __ipow__ a b a ipow a b is equivalent to a b operator irshift a b operator __irshift__ a b a irshift a b is equivalent to a b operator isub a b operator __isub__ a b a isub a b is equivalent to a b operator itruediv a b operator __itruediv__ a b a itruediv a b is equivalent to a b operator ixor a b operator __ixor__ a b a ixor a b is equivalent to a b,en
1394,12 Virtual Environments and Packages 12 1 Introduction Python applications will often use packages and modules that don t come as part of the standard library Applications will sometimes need a specific version of a library because the application may require that a particular bug has been fixed or the application may be written using an obsolete version of the library s interface This means it may not be possible for one Python installation to meet the requirements of every application If application A needs version 1 0 of a particular module but application B needs version 2 0 then the requirements are in conflict and installing either version 1 0 or 2 0 will leave one application unable to run The solution for this problem is to create a virtual environment a self contained directory tree that contains a Python installation for a particular version of Python plus a number of additional packages Different applications can then use different virtual environments To resolve the earlier example of conflicting requirements application A can have its own virtual environment with version 1 0 installed while application B has another virtual environment with version 2 0 If application B requires a library be upgraded to version 3 0 this will not affect application A s environment 12 2 Creating Virtual Environments The module used to create and manage virtual environments is called venv venv will usually install the most recent version of Python that you have available If you have multiple versions of Python on your system you can select a specific Python version by running python3 or whichever version you want To create a virtual environment decide upon a directory where you want to place it and run the venv module as a script with the directory path python m venv tutorial env This will create the tutorial env directory if it doesn t exist and also create directories inside it containing a copy of the Python interpreter and various supporting files A common directory location for a virtual environment is venv This name keeps the directory typically hidden in your shell and thus out of the way while giving it a name that explains why the directory exists It also prevents clashing with env environment variable definition files that some tooling supports Once you ve created a virtual environment you may activate it On Windows run tutorial env Scripts activate On Unix or MacOS run source tutorial env bin activate This script is written for the bash shell If you use the csh or fish shells there are alternate activate csh and activate fish scripts you should use instead Activating the virtual environment will change your shell s prompt to show what virtual environment you re using and modify the environment so that running python will get you that particular version and installation of Python For example source envs tutorial env bin activate tutorial env python Python 3 5 1 default May 6 2016 10 59 36 import sys sys path usr local lib python35 zip envs tutorial env lib python3 5 site packages To deactivate a virtual environment type deactivate into the terminal 12 3 Managing Packages with pip You can install upgrade and remove packages using a program called pip By default pip will install packages from the Python Package Index You can browse the Python Package Index by going to it in your web browser pip has a number of subcommands install uninstall freeze etc Consult the Installing Python Modules guide for complete documentation for pip You can install the latest version of a package by specifying a package s name tutorial env python m pip install novas Collecting novas Downloading novas 3 1 1 3 tar gz 136kB Installing collected packages novas Running setup py install for novas Successfully installed novas 3 1 1 3 You can also install a specific version of a package by giving the package name followed by and the version number tutorial env python m pip install requests 2 6 0 Collecting requests 2 6 0 Using cached requests 2 6 0 py2 py3 none any whl Installing collected packages requests Successfully installed requests 2 6 0 If yo,en
1395,u re run this command pip will notice that the requested version is already installed and do nothing You can supply a different version number to get that version or you can run python m pip install upgrade to upgrade the package to the latest version tutorial env python m pip install upgrade requests Collecting requests Installing collected packages requests Found existing installation requests 2 6 0 Uninstalling requests 2 6 0 Successfully uninstalled requests 2 6 0 Successfully installed requests 2 7 0 python m pip uninstall followed by one or more package names will remove the packages from the virtual environment python m pip show will display information about a particular package tutorial env python m pip show requests Metadata Version 2 0 Name requests Version 2 7 0 Summary Python HTTP for Humans Home page http python requests org Author Kenneth Reitz Author email me kennethreitz com License Apache 2 0 Location Users akuchling envs tutorial env lib python3 4 site packages Requires python m pip list will display all of the packages installed in the virtual environment tutorial env python m pip list novas 3 1 1 3 numpy 1 9 2 pip 7 0 3 requests 2 7 0 setuptools 16 0 python m pip freeze will produce a similar list of the installed packages but the output uses the format that python m pip install expects A common convention is to put this list in a requirements txt file tutorial env python m pip freeze requirements txt tutorial env cat requirements txt novas 3 1 1 3 numpy 1 9 2 requests 2 7 0 The requirements txt can then be committed to version control and shipped as part of an application Users can then install all the necessary packages with install r tutorial env python m pip install r requirements txt Collecting novas 3 1 1 3 from r requirements txt line 1 Collecting numpy 1 9 2 from r requirements txt line 2 Collecting requests 2 7 0 from r requirements txt line 3 Installing collected packages novas numpy requests Running setup py install for novas Successfully installed novas 3 1 1 3 numpy 1 9 2 requests 2 7 0 pip has many more options Consult the Installing Python Modules guide for complete documentation for pip When you ve written a package and want to make it available on the Python Package Index consult the Python packaging user guide,en
1396,History and License History of the software Python was created in the early 1990s by Guido van Rossum at Stichting Mathematisch Centrum CWI see https www cwi nl in the Netherlands as a successor of a language called ABC Guido remains Python s principal author although it includes many contributions from others In 1995 Guido continued his work on Python at the Corporation for National Research Initiatives CNRI see https www cnri reston va us in Reston Virginia where he released several versions of the software In May 2000 Guido and the Python core development team moved to BeOpen com to form the BeOpen PythonLabs team In October of the same year the PythonLabs team moved to Digital Creations now Zope Corporation see https www zope org In 2001 the Python Software Foundation PSF see https www python org psf was formed a non profit organization created specifically to own Python related Intellectual Property Zope Corporation is a sponsoring member of the PSF All Python releases are Open Source see https opensource org for the Open Source Definition Historically most but not all Python releases have also been GPL compatible the table below summarizes the various releases Release Derived from Year Owner GPL compatible 0 9 0 thru 1 2 n a 1991 1995 CWI yes 1 3 thru 1 5 2 1 2 1995 1999 CNRI yes 1 6 1 5 2 2000 CNRI no 2 0 1 6 2000 BeOpen com no 1 6 1 1 6 2001 CNRI no 2 1 2 0 1 6 1 2001 PSF no 2 0 1 2 0 1 6 1 2001 PSF yes 2 1 1 2 1 2 0 1 2001 PSF yes 2 1 2 2 1 1 2002 PSF yes 2 1 3 2 1 2 2002 PSF yes 2 2 and above 2 1 1 2001 now PSF yes Note GPL compatible doesn t mean that we re distributing Python under the GPL All Python licenses unlike the GPL let you distribute a modified version without making your changes open source The GPL compatible licenses make it possible to combine Python with other software that is released under the GPL the others don t Thanks to the many outside volunteers who have worked under Guido s direction to make these releases possible Terms and conditions for accessing or otherwise using Python Python software and documentation are licensed under the PSF License Agreement Starting with Python 3 8 6 examples recipes and other code in the documentation are dual licensed under the PSF License Agreement and the Zero Clause BSD license Some software incorporated into Python is under different licenses The licenses are listed with code falling under that license See Licenses and Acknowledgements for Incorporated Software for an incomplete list of these licenses PSF LICENSE AGREEMENT FOR PYTHON 3 12 2 1 This LICENSE AGREEMENT is between the Python Software Foundation PSF and the Individual or Organization Licensee accessing and otherwise using Python 3 12 2 software in source or binary form and its associated documentation 2 Subject to the terms and conditions of this License Agreement PSF hereby grants Licensee a nonexclusive royalty free world wide license to reproduce analyze test perform and or display publicly prepare derivative works distribute and otherwise use Python 3 12 2 alone or in any derivative version provided however that PSF s License Agreement and PSF s notice of copyright i e Copyright 2001 2023 Python Software Foundation All Rights Reserved are retained in Python 3 12 2 alone or in any derivative version prepared by Licensee 3 In the event Licensee prepares a derivative work that is based on or incorporates Python 3 12 2 or any part thereof and wants to make the derivative work available to others as provided herein then Licensee hereby agrees to include in any such work a brief summary of the changes made to Python 3 12 2 4 PSF is making Python 3 12 2 available to Licensee on an AS IS basis PSF MAKES NO REPRESENTATIONS OR WARRANTIES EXPRESS OR IMPLIED BY WAY OF EXAMPLE BUT NOT LIMITATION PSF MAKES NO AND DISCLAIMS ANY REPRESENTATION OR WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR THAT THE USE OF PYTHON 3 12 2 WILL NOT INFRINGE ANY THIRD PARTY RIGHTS 5 PSF SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF PYTHON 3 12 2 FOR ANY INCIDENTAL SPECIAL OR CONSEQUENTIAL DAMA,en
1397,GES OR LOSS AS A RESULT OF MODIFYING DISTRIBUTING OR OTHERWISE USING PYTHON 3 12 2 OR ANY DERIVATIVE THEREOF EVEN IF ADVISED OF THE POSSIBILITY THEREOF 6 This License Agreement will automatically terminate upon a material breach of its terms and conditions 7 Nothing in this License Agreement shall be deemed to create any relationship of agency partnership or joint venture between PSF and Licensee This License Agreement does not grant permission to use PSF trademarks or trade name in a trademark sense to endorse or promote products or services of Licensee or any third party 8 By copying installing or otherwise using Python 3 12 2 Licensee agrees to be bound by the terms and conditions of this License Agreement BEOPEN COM LICENSE AGREEMENT FOR PYTHON 2 0 BEOPEN PYTHON OPEN SOURCE LICENSE AGREEMENT VERSION 1 1 This LICENSE AGREEMENT is between BeOpen com BeOpen having an office at 160 Saratoga Avenue Santa Clara CA 95051 and the Individual or Organization Licensee accessing and otherwise using this software in source or binary form and its associated documentation the Software 2 Subject to the terms and conditions of this BeOpen Python License Agreement BeOpen hereby grants Licensee a non exclusive royalty free world wide license to reproduce analyze test perform and or display publicly prepare derivative works distribute and otherwise use the Software alone or in any derivative version provided however that the BeOpen Python License is retained in the Software alone or in any derivative version prepared by Licensee 3 BeOpen is making the Software available to Licensee on an AS IS basis BEOPEN MAKES NO REPRESENTATIONS OR WARRANTIES EXPRESS OR IMPLIED BY WAY OF EXAMPLE BUT NOT LIMITATION BEOPEN MAKES NO AND DISCLAIMS ANY REPRESENTATION OR WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR THAT THE USE OF THE SOFTWARE WILL NOT INFRINGE ANY THIRD PARTY RIGHTS 4 BEOPEN SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF THE SOFTWARE FOR ANY INCIDENTAL SPECIAL OR CONSEQUENTIAL DAMAGES OR LOSS AS A RESULT OF USING MODIFYING OR DISTRIBUTING THE SOFTWARE OR ANY DERIVATIVE THEREOF EVEN IF ADVISED OF THE POSSIBILITY THEREOF 5 This License Agreement will automatically terminate upon a material breach of its terms and conditions 6 This License Agreement shall be governed by and interpreted in all respects by the law of the State of California excluding conflict of law provisions Nothing in this License Agreement shall be deemed to create any relationship of agency partnership or joint venture between BeOpen and Licensee This License Agreement does not grant permission to use BeOpen trademarks or trade names in a trademark sense to endorse or promote products or services of Licensee or any third party As an exception the BeOpen Python logos available at http www pythonlabs com logos html may be used according to the permissions granted on that web page 7 By copying installing or otherwise using the software Licensee agrees to be bound by the terms and conditions of this License Agreement CNRI LICENSE AGREEMENT FOR PYTHON 1 6 1 1 This LICENSE AGREEMENT is between the Corporation for National Research Initiatives having an office at 1895 Preston White Drive Reston VA 20191 CNRI and the Individual or Organization Licensee accessing and otherwise using Python 1 6 1 software in source or binary form and its associated documentation 2 Subject to the terms and conditions of this License Agreement CNRI hereby grants Licensee a nonexclusive royalty free world wide license to reproduce analyze test perform and or display publicly prepare derivative works distribute and otherwise use Python 1 6 1 alone or in any derivative version provided however that CNRI s License Agreement and CNRI s notice of copyright i e Copyright 1995 2001 Corporation for National Research Initiatives All Rights Reserved are retained in Python 1 6 1 alone or in any derivative version prepared by Licensee Alternately in lieu of CNRI s License Agreement Licensee may substitute the following text omitting the quotes Python 1 6 1 is made available subject t,en
1398,o the terms and conditions in CNRI s License Agreement This Agreement together with Python 1 6 1 may be located on the internet using the following unique persistent identifier known as a handle 1895 22 1013 This Agreement may also be obtained from a proxy server on the internet using the following URL http hdl handle net 1895 22 1013 3 In the event Licensee prepares a derivative work that is based on or incorporates Python 1 6 1 or any part thereof and wants to make the derivative work available to others as provided herein then Licensee hereby agrees to include in any such work a brief summary of the changes made to Python 1 6 1 4 CNRI is making Python 1 6 1 available to Licensee on an AS IS basis CNRI MAKES NO REPRESENTATIONS OR WARRANTIES EXPRESS OR IMPLIED BY WAY OF EXAMPLE BUT NOT LIMITATION CNRI MAKES NO AND DISCLAIMS ANY REPRESENTATION OR WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR THAT THE USE OF PYTHON 1 6 1 WILL NOT INFRINGE ANY THIRD PARTY RIGHTS 5 CNRI SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF PYTHON 1 6 1 FOR ANY INCIDENTAL SPECIAL OR CONSEQUENTIAL DAMAGES OR LOSS AS A RESULT OF MODIFYING DISTRIBUTING OR OTHERWISE USING PYTHON 1 6 1 OR ANY DERIVATIVE THEREOF EVEN IF ADVISED OF THE POSSIBILITY THEREOF 6 This License Agreement will automatically terminate upon a material breach of its terms and conditions 7 This License Agreement shall be governed by the federal intellectual property law of the United States including without limitation the federal copyright law and to the extent such U S federal law does not apply by the law of the Commonwealth of Virginia excluding Virginia s conflict of law provisions Notwithstanding the foregoing with regard to derivative works based on Python 1 6 1 that incorporate non separable material that was previously distributed under the GNU General Public License GPL the law of the Commonwealth of Virginia shall govern this License Agreement only as to issues arising under or with respect to Paragraphs 4 5 and 7 of this License Agreement Nothing in this License Agreement shall be deemed to create any relationship of agency partnership or joint venture between CNRI and Licensee This License Agreement does not grant permission to use CNRI trademarks or trade name in a trademark sense to endorse or promote products or services of Licensee or any third party 8 By clicking on the ACCEPT button where indicated or by copying installing or otherwise using Python 1 6 1 Licensee agrees to be bound by the terms and conditions of this License Agreement CWI LICENSE AGREEMENT FOR PYTHON 0 9 0 THROUGH 1 2 Copyright 1991 1995 Stichting Mathematisch Centrum Amsterdam The Netherlands All rights reserved Permission to use copy modify and distribute this software and its documentation for any purpose and without fee is hereby granted provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation and that the name of Stichting Mathematisch Centrum or CWI not be used in advertising or publicity pertaining to distribution of the software without specific written prior permission STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE FOR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE DATA OR PROFITS WHETHER IN AN ACTION OF CONTRACT NEGLIGENCE OR OTHER TORTIOUS ACTION ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE ZERO CLAUSE BSD LICENSE FOR CODE IN THE PYTHON 3 12 2 DOCUMENTATION Permission to use copy modify and or distribute this software for any purpose with or without fee is hereby granted THE SOFTWARE IS PROVIDED AS IS AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL DIRECT INDIRECT OR CONSEQUENTIAL,en
1399, DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE DATA OR PROFITS WHETHER IN AN ACTION OF CONTRACT NEGLIGENCE OR OTHER TORTIOUS ACTION ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE Licenses and Acknowledgements for Incorporated Software This section is an incomplete but growing list of licenses and acknowledgements for third party software incorporated in the Python distribution Mersenne Twister The _random C extension underlying the random module includes code based on a download from http www math sci hiroshima u ac jp m mat MT MT2002 emt19937ar html The following are the verbatim comments from the original code A C program for MT19937 with initialization improved 2002 1 26 Coded by Takuji Nishimura and Makoto Matsumoto Before using initialize the state by using init_genrand seed or init_by_array init_key key_length Copyright C 1997 2002 Makoto Matsumoto and Takuji Nishimura All rights reserved Redistribution and use in source and binary forms with or without modification are permitted provided that the following conditions are met 1 Redistributions of source code must retain the above copyright notice this list of conditions and the following disclaimer 2 Redistributions in binary form must reproduce the above copyright notice this list of conditions and the following disclaimer in the documentation and or other materials provided with the distribution 3 The names of its contributors may not be used to endorse or promote products derived from this software without specific prior written permission THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS AS IS AND ANY EXPRESS OR IMPLIED WARRANTIES INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT INDIRECT INCIDENTAL SPECIAL EXEMPLARY OR CONSEQUENTIAL DAMAGES INCLUDING BUT NOT LIMITED TO PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES LOSS OF USE DATA OR PROFITS OR BUSINESS INTERRUPTION HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY WHETHER IN CONTRACT STRICT LIABILITY OR TORT INCLUDING NEGLIGENCE OR OTHERWISE ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE Any feedback is very welcome http www math sci hiroshima u ac jp m mat MT emt html email m mat math sci hiroshima u ac jp remove space Sockets The socket module uses the functions getaddrinfo and getnameinfo which are coded in separate source files from the WIDE Project https www wide ad jp Copyright C 1995 1996 1997 and 1998 WIDE Project All rights reserved Redistribution and use in source and binary forms with or without modification are permitted provided that the following conditions are met 1 Redistributions of source code must retain the above copyright notice this list of conditions and the following disclaimer 2 Redistributions in binary form must reproduce the above copyright notice this list of conditions and the following disclaimer in the documentation and or other materials provided with the distribution 3 Neither the name of the project nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS AS IS AND ANY EXPRESS OR IMPLIED WARRANTIES INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT INDIRECT INCIDENTAL SPECIAL EXEMPLARY OR CONSEQUENTIAL DAMAGES INCLUDING BUT NOT LIMITED TO PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES LOSS OF USE DATA OR PROFITS OR BUSINESS INTERRUPTION HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY WHETHER IN CONTRACT STRICT LIABILITY OR TORT INCLUDING NEGLIGENCE OR OTHERWISE ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE Asynchronous socket services The test support asynchat and test support asynco,en
1400,re modules contain the following notice Copyright 1996 by Sam Rushing All Rights Reserved Permission to use copy modify and distribute this software and its documentation for any purpose and without fee is hereby granted provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation and that the name of Sam Rushing not be used in advertising or publicity pertaining to distribution of the software without specific written prior permission SAM RUSHING DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS IN NO EVENT SHALL SAM RUSHING BE LIABLE FOR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE DATA OR PROFITS WHETHER IN AN ACTION OF CONTRACT NEGLIGENCE OR OTHER TORTIOUS ACTION ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE Cookie management The http cookies module contains the following notice Copyright 2000 by Timothy O Malley timo alum mit edu All Rights Reserved Permission to use copy modify and distribute this software and its documentation for any purpose and without fee is hereby granted provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation and that the name of Timothy O Malley not be used in advertising or publicity pertaining to distribution of the software without specific written prior permission Timothy O Malley DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS IN NO EVENT SHALL Timothy O Malley BE LIABLE FOR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE DATA OR PROFITS WHETHER IN AN ACTION OF CONTRACT NEGLIGENCE OR OTHER TORTIOUS ACTION ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE Execution tracing The trace module contains the following notice portions copyright 2001 Autonomous Zones Industries Inc all rights err reserved and offered to the public under the terms of the Python 2 2 license Author Zooko O Whielacronx http zooko com mailto zooko zooko com Copyright 2000 Mojam Media Inc all rights reserved Author Skip Montanaro Copyright 1999 Bioreason Inc all rights reserved Author Andrew Dalke Copyright 1995 1997 Automatrix Inc all rights reserved Author Skip Montanaro Copyright 1991 1995 Stichting Mathematisch Centrum all rights reserved Permission to use copy modify and distribute this Python software and its associated documentation for any purpose without fee is hereby granted provided that the above copyright notice appears in all copies and that both that copyright notice and this permission notice appear in supporting documentation and that the name of neither Automatrix Bioreason or Mojam Media be used in advertising or publicity pertaining to distribution of the software without specific written prior permission UUencode and UUdecode functions The uu module contains the following notice Copyright 1994 by Lance Ellinghouse Cathedral City California Republic United States of America All Rights Reserved Permission to use copy modify and distribute this software and its documentation for any purpose and without fee is hereby granted provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation and that the name of Lance Ellinghouse not be used in advertising or publicity pertaining to distribution of the software without specific written prior permission LANCE ELLINGHOUSE DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS IN NO EVENT SHALL LANCE ELLINGHOUSE CENTRUM BE LIABLE FOR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE DATA OR PROFITS WHETHER IN AN ACTION OF CONTRACT NEGLIGENCE OR OTHER TORTIOUS ,en
1401,ACTION ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE Modified by Jack Jansen CWI July 1995 Use binascii module to do the actual line by line conversion between ascii and binary This results in a 1000 fold speedup The C version is still 5 times faster though Arguments more compliant with Python standard XML Remote Procedure Calls The xmlrpc client module contains the following notice The XML RPC client interface is Copyright c 1999 2002 by Secret Labs AB Copyright c 1999 2002 by Fredrik Lundh By obtaining using and or copying this software and or its associated documentation you agree that you have read understood and will comply with the following terms and conditions Permission to use copy modify and distribute this software and its associated documentation for any purpose and without fee is hereby granted provided that the above copyright notice appears in all copies and that both that copyright notice and this permission notice appear in supporting documentation and that the name of Secret Labs AB or the author not be used in advertising or publicity pertaining to distribution of the software without specific written prior permission SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT ABILITY AND FITNESS IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR BE LIABLE FOR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE DATA OR PROFITS WHETHER IN AN ACTION OF CONTRACT NEGLIGENCE OR OTHER TORTIOUS ACTION ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE test_epoll The test test_epoll module contains the following notice Copyright c 2001 2006 Twisted Matrix Laboratories Permission is hereby granted free of charge to any person obtaining a copy of this software and associated documentation files the Software to deal in the Software without restriction including without limitation the rights to use copy modify merge publish distribute sublicense and or sell copies of the Software and to permit persons to whom the Software is furnished to do so subject to the following conditions The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software THE SOFTWARE IS PROVIDED AS IS WITHOUT WARRANTY OF ANY KIND EXPRESS OR IMPLIED INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM DAMAGES OR OTHER LIABILITY WHETHER IN AN ACTION OF CONTRACT TORT OR OTHERWISE ARISING FROM OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE Select kqueue The select module contains the following notice for the kqueue interface Copyright c 2000 Doug White 2006 James Knight 2007 Christian Heimes All rights reserved Redistribution and use in source and binary forms with or without modification are permitted provided that the following conditions are met 1 Redistributions of source code must retain the above copyright notice this list of conditions and the following disclaimer 2 Redistributions in binary form must reproduce the above copyright notice this list of conditions and the following disclaimer in the documentation and or other materials provided with the distribution THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS AS IS AND ANY EXPRESS OR IMPLIED WARRANTIES INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT INDIRECT INCIDENTAL SPECIAL EXEMPLARY OR CONSEQUENTIAL DAMAGES INCLUDING BUT NOT LIMITED TO PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES LOSS OF USE DATA OR PROFITS OR BUSINESS INTERRUPTION HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY WHETHER IN CONTRACT STRICT LIABILITY OR TORT INCLUDING NEGLIGENCE OR OTHERWISE ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE EVEN IF ADVISED OF THE POSSIBI,en
1402,LITY OF SUCH DAMAGE SipHash24 The file Python pyhash c contains Marek Majkowski implementation of Dan Bernstein s SipHash24 algorithm It contains the following note MIT License Copyright c 2013 Marek Majkowski marek popcount org Permission is hereby granted free of charge to any person obtaining a copy of this software and associated documentation files the Software to deal in the Software without restriction including without limitation the rights to use copy modify merge publish distribute sublicense and or sell copies of the Software and to permit persons to whom the Software is furnished to do so subject to the following conditions The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software MIT License Original location https github com majek csiphash Solution inspired by code from Samuel Neves supercop crypto_auth siphash24 little djb supercop crypto_auth siphash24 little2 Jean Philippe Aumasson https 131002 net siphash siphash24 c strtod and dtoa The file Python dtoa c which supplies C functions dtoa and strtod for conversion of C doubles to and from strings is derived from the file of the same name by David M Gay currently available from https web archive org web 20220517033456 http www netlib org fp dtoa c The original file as retrieved on March 16 2009 contains the following copyright and licensing notice The author of this software is David M Gay Copyright c 1991 2000 2001 by Lucent Technologies Permission to use copy modify and distribute this software for any purpose without fee is hereby granted provided that this entire notice is included in all copies of any software which is or includes a copy or modification of this software and in all copies of the supporting documentation for such software THIS SOFTWARE IS BEING PROVIDED AS IS WITHOUT ANY EXPRESS OR IMPLIED WARRANTY IN PARTICULAR NEITHER THE AUTHOR NOR LUCENT MAKES ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE OpenSSL The modules hashlib posix ssl crypt use the OpenSSL library for added performance if made available by the operating system Additionally the Windows and macOS installers for Python may include a copy of the OpenSSL libraries so we include a copy of the OpenSSL license here For the OpenSSL 3 0 release and later releases derived from that the Apache License v2 applies Apache License Version 2 0 January 2004 https www apache org licenses TERMS AND CONDITIONS FOR USE REPRODUCTION AND DISTRIBUTION 1 Definitions License shall mean the terms and conditions for use reproduction and distribution as defined by Sections 1 through 9 of this document Licensor shall mean the copyright owner or entity authorized by the copyright owner that is granting the License Legal Entity shall mean the union of the acting entity and all other entities that control are controlled by or are under common control with that entity For the purposes of this definition control means i the power direct or indirect to cause the direction or management of such entity whether by contract or otherwise or ii ownership of fifty percent 50 or more of the outstanding shares or iii beneficial ownership of such entity You or Your shall mean an individual or Legal Entity exercising permissions granted by this License Source form shall mean the preferred form for making modifications including but not limited to software source code documentation source and configuration files Object form shall mean any form resulting from mechanical transformation or translation of a Source form including but not limited to compiled object code generated documentation and conversions to other media types Work shall mean the work of authorship whether in Source or Object form made available under the License as indicated by a copyright notice that is included in or attached to the work an example is provided in the Appendix below Derivative Works shall mean any work whether in Source or Object form that is based on or derived from the Work and for whic,en
1403,h the editorial revisions annotations elaborations or other modifications represent as a whole an original work of authorship For the purposes of this License Derivative Works shall not include works that remain separable from or merely link or bind by name to the interfaces of the Work and Derivative Works thereof Contribution shall mean any work of authorship including the original version of the Work and any modifications or additions to that Work or Derivative Works thereof that is intentionally submitted to Licensor for inclusion in the Work by the copyright owner or by an individual or Legal Entity authorized to submit on behalf of the copyright owner For the purposes of this definition submitted means any form of electronic verbal or written communication sent to the Licensor or its representatives including but not limited to communication on electronic mailing lists source code control systems and issue tracking systems that are managed by or on behalf of the Licensor for the purpose of discussing and improving the Work but excluding communication that is conspicuously marked or otherwise designated in writing by the copyright owner as Not a Contribution Contributor shall mean Licensor and any individual or Legal Entity on behalf of whom a Contribution has been received by Licensor and subsequently incorporated within the Work 2 Grant of Copyright License Subject to the terms and conditions of this License each Contributor hereby grants to You a perpetual worldwide non exclusive no charge royalty free irrevocable copyright license to reproduce prepare Derivative Works of publicly display publicly perform sublicense and distribute the Work and such Derivative Works in Source or Object form 3 Grant of Patent License Subject to the terms and conditions of this License each Contributor hereby grants to You a perpetual worldwide non exclusive no charge royalty free irrevocable except as stated in this section patent license to make have made use offer to sell sell import and otherwise transfer the Work where such license applies only to those patent claims licensable by such Contributor that are necessarily infringed by their Contribution s alone or by combination of their Contribution s with the Work to which such Contribution s was submitted If You institute patent litigation against any entity including a cross claim or counterclaim in a lawsuit alleging that the Work or a Contribution incorporated within the Work constitutes direct or contributory patent infringement then any patent licenses granted to You under this License for that Work shall terminate as of the date such litigation is filed 4 Redistribution You may reproduce and distribute copies of the Work or Derivative Works thereof in any medium with or without modifications and in Source or Object form provided that You meet the following conditions a You must give any other recipients of the Work or Derivative Works a copy of this License and b You must cause any modified files to carry prominent notices stating that You changed the files and c You must retain in the Source form of any Derivative Works that You distribute all copyright patent trademark and attribution notices from the Source form of the Work excluding those notices that do not pertain to any part of the Derivative Works and d If the Work includes a NOTICE text file as part of its distribution then any Derivative Works that You distribute must include a readable copy of the attribution notices contained within such NOTICE file excluding those notices that do not pertain to any part of the Derivative Works in at least one of the following places within a NOTICE text file distributed as part of the Derivative Works within the Source form or documentation if provided along with the Derivative Works or within a display generated by the Derivative Works if and wherever such third party notices normally appear The contents of the NOTICE file are for informational purposes only and do not modify the License You may add Your own attribution notices within Derivative Works that You distribute alon,en
1404,gside or as an addendum to the NOTICE text from the Work provided that such additional attribution notices cannot be construed as modifying the License You may add Your own copyright statement to Your modifications and may provide additional or different license terms and conditions for use reproduction or distribution of Your modifications or for any such Derivative Works as a whole provided Your use reproduction and distribution of the Work otherwise complies with the conditions stated in this License 5 Submission of Contributions Unless You explicitly state otherwise any Contribution intentionally submitted for inclusion in the Work by You to the Licensor shall be under the terms and conditions of this License without any additional terms or conditions Notwithstanding the above nothing herein shall supersede or modify the terms of any separate license agreement you may have executed with Licensor regarding such Contributions 6 Trademarks This License does not grant permission to use the trade names trademarks service marks or product names of the Licensor except as required for reasonable and customary use in describing the origin of the Work and reproducing the content of the NOTICE file 7 Disclaimer of Warranty Unless required by applicable law or agreed to in writing Licensor provides the Work and each Contributor provides its Contributions on an AS IS BASIS WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND either express or implied including without limitation any warranties or conditions of TITLE NON INFRINGEMENT MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE You are solely responsible for determining the appropriateness of using or redistributing the Work and assume any risks associated with Your exercise of permissions under this License 8 Limitation of Liability In no event and under no legal theory whether in tort including negligence contract or otherwise unless required by applicable law such as deliberate and grossly negligent acts or agreed to in writing shall any Contributor be liable to You for damages including any direct indirect special incidental or consequential damages of any character arising as a result of this License or out of the use or inability to use the Work including but not limited to damages for loss of goodwill work stoppage computer failure or malfunction or any and all other commercial damages or losses even if such Contributor has been advised of the possibility of such damages 9 Accepting Warranty or Additional Liability While redistributing the Work or Derivative Works thereof You may choose to offer and charge a fee for acceptance of support warranty indemnity or other liability obligations and or rights consistent with this License However in accepting such obligations You may act only on Your own behalf and on Your sole responsibility not on behalf of any other Contributor and only if You agree to indemnify defend and hold each Contributor harmless for any liability incurred by or claims asserted against such Contributor by reason of your accepting any such warranty or additional liability END OF TERMS AND CONDITIONS expat The pyexpat extension is built using an included copy of the expat sources unless the build is configured with system expat Copyright c 1998 1999 2000 Thai Open Source Software Center Ltd and Clark Cooper Permission is hereby granted free of charge to any person obtaining a copy of this software and associated documentation files the Software to deal in the Software without restriction including without limitation the rights to use copy modify merge publish distribute sublicense and or sell copies of the Software and to permit persons to whom the Software is furnished to do so subject to the following conditions The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software THE SOFTWARE IS PROVIDED AS IS WITHOUT WARRANTY OF ANY KIND EXPRESS OR IMPLIED INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT IN NO EVENT SHALL THE AUTHORS O,en
1405,R COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM DAMAGES OR OTHER LIABILITY WHETHER IN AN ACTION OF CONTRACT TORT OR OTHERWISE ARISING FROM OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE libffi The _ctypes C extension underlying the ctypes module is built using an included copy of the libffi sources unless the build is configured with system libffi Copyright c 1996 2008 Red Hat Inc and others Permission is hereby granted free of charge to any person obtaining a copy of this software and associated documentation files the Software to deal in the Software without restriction including without limitation the rights to use copy modify merge publish distribute sublicense and or sell copies of the Software and to permit persons to whom the Software is furnished to do so subject to the following conditions The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software THE SOFTWARE IS PROVIDED AS IS WITHOUT WARRANTY OF ANY KIND EXPRESS OR IMPLIED INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM DAMAGES OR OTHER LIABILITY WHETHER IN AN ACTION OF CONTRACT TORT OR OTHERWISE ARISING FROM OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE zlib The zlib extension is built using an included copy of the zlib sources if the zlib version found on the system is too old to be used for the build Copyright C 1995 2011 Jean loup Gailly and Mark Adler This software is provided as is without any express or implied warranty In no event will the authors be held liable for any damages arising from the use of this software Permission is granted to anyone to use this software for any purpose including commercial applications and to alter it and redistribute it freely subject to the following restrictions 1 The origin of this software must not be misrepresented you must not claim that you wrote the original software If you use this software in a product an acknowledgment in the product documentation would be appreciated but is not required 2 Altered source versions must be plainly marked as such and must not be misrepresented as being the original software 3 This notice may not be removed or altered from any source distribution Jean loup Gailly Mark Adler jloup gzip org madler alumni caltech edu cfuhash The implementation of the hash table used by the tracemalloc is based on the cfuhash project Copyright c 2005 Don Owens All rights reserved This code is released under the BSD license Redistribution and use in source and binary forms with or without modification are permitted provided that the following conditions are met Redistributions of source code must retain the above copyright notice this list of conditions and the following disclaimer Redistributions in binary form must reproduce the above copyright notice this list of conditions and the following disclaimer in the documentation and or other materials provided with the distribution Neither the name of the author nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS AS IS AND ANY EXPRESS OR IMPLIED WARRANTIES INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT INDIRECT INCIDENTAL SPECIAL EXEMPLARY OR CONSEQUENTIAL DAMAGES INCLUDING BUT NOT LIMITED TO PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES LOSS OF USE DATA OR PROFITS OR BUSINESS INTERRUPTION HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY WHETHER IN CONTRACT STRICT LIABILITY OR TORT INCLUDING NEGLIGENCE OR OTHERWISE ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE libmpdec The _decimal C extension underlying the decim,en
1406,al module is built using an included copy of the libmpdec library unless the build is configured with system libmpdec Copyright c 2008 2020 Stefan Krah All rights reserved Redistribution and use in source and binary forms with or without modification are permitted provided that the following conditions are met 1 Redistributions of source code must retain the above copyright notice this list of conditions and the following disclaimer 2 Redistributions in binary form must reproduce the above copyright notice this list of conditions and the following disclaimer in the documentation and or other materials provided with the distribution THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS AS IS AND ANY EXPRESS OR IMPLIED WARRANTIES INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT INDIRECT INCIDENTAL SPECIAL EXEMPLARY OR CONSEQUENTIAL DAMAGES INCLUDING BUT NOT LIMITED TO PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES LOSS OF USE DATA OR PROFITS OR BUSINESS INTERRUPTION HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY WHETHER IN CONTRACT STRICT LIABILITY OR TORT INCLUDING NEGLIGENCE OR OTHERWISE ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE W3C C14N test suite The C14N 2 0 test suite in the test package Lib test xmltestdata c14n 20 was retrieved from the W3C website at https www w3 org TR xml c14n2 testcases and is distributed under the 3 clause BSD license Copyright c 2013 W3C R MIT ERCIM Keio Beihang All Rights Reserved Redistribution and use in source and binary forms with or without modification are permitted provided that the following conditions are met Redistributions of works must retain the original copyright notice this list of conditions and the following disclaimer Redistributions in binary form must reproduce the original copyright notice this list of conditions and the following disclaimer in the documentation and or other materials provided with the distribution Neither the name of the W3C nor the names of its contributors may be used to endorse or promote products derived from this work without specific prior written permission THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS AS IS AND ANY EXPRESS OR IMPLIED WARRANTIES INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT INDIRECT INCIDENTAL SPECIAL EXEMPLARY OR CONSEQUENTIAL DAMAGES INCLUDING BUT NOT LIMITED TO PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES LOSS OF USE DATA OR PROFITS OR BUSINESS INTERRUPTION HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY WHETHER IN CONTRACT STRICT LIABILITY OR TORT INCLUDING NEGLIGENCE OR OTHERWISE ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE Audioop The audioop module uses the code base in g771 c file of the SoX project https sourceforge net projects sox files sox 12 17 7 sox 1 2 17 7 tar gz This source code is a product of Sun Microsystems Inc and is provided for unrestricted use Users may copy or modify this source code without charge SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING THE WARRANTIES OF DESIGN MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE OR ARISING FROM A COURSE OF DEALING USAGE OR TRADE PRACTICE Sun source code is provided with no support and without any obligation on the part of Sun Microsystems Inc to assist in its use correction modification or enhancement SUN MICROSYSTEMS INC SHALL HAVE NO LIABILITY WITH RESPECT TO THE INFRINGEMENT OF COPYRIGHTS TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE OR ANY PART THEREOF In no event will Sun Microsystems Inc be liable for any lost revenue or profits or other special indirect and consequential damages even if Sun has been advised of the possibility of such damages Sun Microsystems Inc 2550 Garcia Avenue Mountain View Californ,en
1407,ia 94043 asyncio Parts of the asyncio module are incorporated from uvloop 0 16 which is distributed under the MIT license Copyright c 2015 2021 MagicStack Inc http magic io Permission is hereby granted free of charge to any person obtaining a copy of this software and associated documentation files the Software to deal in the Software without restriction including without limitation the rights to use copy modify merge publish distribute sublicense and or sell copies of the Software and to permit persons to whom the Software is furnished to do so subject to the following conditions The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software THE SOFTWARE IS PROVIDED AS IS WITHOUT WARRANTY OF ANY KIND EXPRESS OR IMPLIED INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM DAMAGES OR OTHER LIABILITY WHETHER IN AN ACTION OF CONTRACT TORT OR OTHERWISE ARISING FROM OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE,en
1408,glob Unix style pathname pattern expansion Source code Lib glob py The glob module finds all the pathnames matching a specified pattern according to the rules used by the Unix shell although results are returned in arbitrary order No tilde expansion is done but and character ranges expressed with will be correctly matched This is done by using the os scandir and fnmatch fnmatch functions in concert and not by actually invoking a subshell Note that files beginning with a dot can only be matched by patterns that also start with a dot unlike fnmatch fnmatch or pathlib Path glob For tilde and shell variable expansion use os path expanduser and os path expandvars For a literal match wrap the meta characters in brackets For example matches the character See also The pathlib module offers high level path objects glob glob pathname root_dir None dir_fd None recursive False include_hidden False Return a possibly empty list of path names that match pathname which must be a string containing a path specification pathname can be either absolute like usr src Python 1 5 Makefile or relative like Tools gif and can contain shell style wildcards Broken symlinks are included in the results as in the shell Whether or not the results are sorted depends on the file system If a file that satisfies conditions is removed or added during the call of this function whether a path name for that file will be included is unspecified If root_dir is not None it should be a path like object specifying the root directory for searching It has the same effect on glob as changing the current directory before calling it If pathname is relative the result will contain paths relative to root_dir This function can support paths relative to directory descriptors with the dir_fd parameter If recursive is true the pattern will match any files and zero or more directories subdirectories and symbolic links to directories If the pattern is followed by an os sep or os altsep then files will not match If include_hidden is true pattern will match hidden directories Raises an auditing event glob glob with arguments pathname recursive Raises an auditing event glob glob 2 with arguments pathname recursive root_dir dir_fd Note Using the pattern in large directory trees may consume an inordinate amount of time Changed in version 3 5 Support for recursive globs using Changed in version 3 10 Added the root_dir and dir_fd parameters Changed in version 3 11 Added the include_hidden parameter glob iglob pathname root_dir None dir_fd None recursive False include_hidden False Return an iterator which yields the same values as glob without actually storing them all simultaneously Raises an auditing event glob glob with arguments pathname recursive Raises an auditing event glob glob 2 with arguments pathname recursive root_dir dir_fd Changed in version 3 5 Support for recursive globs using Changed in version 3 10 Added the root_dir and dir_fd parameters Changed in version 3 11 Added the include_hidden parameter glob escape pathname Escape all special characters and This is useful if you want to match an arbitrary literal string that may have special characters in it Special characters in drive UNC sharepoints are not escaped e g on Windows escape c Quo vadis txt returns c Quo vadis txt New in version 3 4 For example consider a directory containing the following files 1 gif 2 txt card gif and a subdirectory sub which contains only the file 3 txt glob will produce the following results Notice how any leading components of the path are preserved import glob glob glob 0 9 1 gif 2 txt glob glob gif 1 gif card gif glob glob gif 1 gif glob glob txt recursive True 2 txt sub 3 txt glob glob recursive True sub If the directory contains files starting with they won t be matched by default For example consider a directory containing card gif and card gif import glob glob glob gif card gif glob glob c card gif See also Module fnmatch Shell style filename not path expansion,en
1409,Text Processing Services The modules described in this chapter provide a wide range of string manipulation operations and other text processing services The codecs module described under Binary Data Services is also highly relevant to text processing In addition see the documentation for Python s built in string type in Text Sequence Type str string Common string operations String constants Custom String Formatting Format String Syntax Format Specification Mini Language Format examples Template strings Helper functions re Regular expression operations Regular Expression Syntax Module Contents Flags Functions Exceptions Regular Expression Objects Match Objects Regular Expression Examples Checking for a Pair Simulating scanf search vs match Making a Phonebook Text Munging Finding all Adverbs Finding all Adverbs and their Positions Raw String Notation Writing a Tokenizer difflib Helpers for computing deltas SequenceMatcher Objects SequenceMatcher Examples Differ Objects Differ Example A command line interface to difflib ndiff example textwrap Text wrapping and filling unicodedata Unicode Database stringprep Internet String Preparation readline GNU readline interface Init file Line buffer History file History list Startup hooks Completion Example rlcompleter Completion function for GNU readline,en
1410,email message Representing an email message Source code Lib email message py New in version 3 6 1 The central class in the email package is the EmailMessage class imported from the email message module It is the base class for the email object model EmailMessage provides the core functionality for setting and querying header fields for accessing message bodies and for creating or modifying structured messages An email message consists of headers and a payload which is also referred to as the content Headers are RFC 5322 or RFC 6532 style field names and values where the field name and value are separated by a colon The colon is not part of either the field name or the field value The payload may be a simple text message or a binary object or a structured sequence of sub messages each with their own set of headers and their own payload The latter type of payload is indicated by the message having a MIME type such as multipart or message rfc822 The conceptual model provided by an EmailMessage object is that of an ordered dictionary of headers coupled with a payload that represents the RFC 5322 body of the message which might be a list of sub EmailMessage objects In addition to the normal dictionary methods for accessing the header names and values there are methods for accessing specialized information from the headers for example the MIME content type for operating on the payload for generating a serialized version of the message and for recursively walking over the object tree The EmailMessage dictionary like interface is indexed by the header names which must be ASCII values The values of the dictionary are strings with some extra methods Headers are stored and returned in case preserving form but field names are matched case insensitively The keys are ordered but unlike a real dict there can be duplicates Addtional methods are provided for working with headers that have duplicate keys The payload is either a string or bytes object in the case of simple message objects or a list of EmailMessage objects for MIME container documents such as multipart and message rfc822 message objects class email message EmailMessage policy default If policy is specified use the rules it specifies to update and serialize the representation of the message If policy is not set use the default policy which follows the rules of the email RFCs except for line endings instead of the RFC mandated r n it uses the Python standard n line endings For more information see the policy documentation as_string unixfrom False maxheaderlen None policy None Return the entire message flattened as a string When optional unixfrom is true the envelope header is included in the returned string unixfrom defaults to False For backward compatibility with the base Message class maxheaderlen is accepted but defaults to None which means that by default the line length is controlled by the max_line_length of the policy The policy argument may be used to override the default policy obtained from the message instance This can be used to control some of the formatting produced by the method since the specified policy will be passed to the Generator Flattening the message may trigger changes to the EmailMessage if defaults need to be filled in to complete the transformation to a string for example MIME boundaries may be generated or modified Note that this method is provided as a convenience and may not be the most useful way to serialize messages in your application especially if you are dealing with multiple messages See email generator Generator for a more flexible API for serializing messages Note also that this method is restricted to producing messages serialized as 7 bit clean when utf8 is False which is the default Changed in version 3 6 the default behavior when maxheaderlen is not specified was changed from defaulting to 0 to defaulting to the value of max_line_length from the policy __str__ Equivalent to as_string policy self policy clone utf8 True Allows str msg to produce a string containing the serialized message in a readable format Changed in version 3 4 th,en
1411,e method was changed to use utf8 True thus producing an RFC 6531 like message representation instead of being a direct alias for as_string as_bytes unixfrom False policy None Return the entire message flattened as a bytes object When optional unixfrom is true the envelope header is included in the returned string unixfrom defaults to False The policy argument may be used to override the default policy obtained from the message instance This can be used to control some of the formatting produced by the method since the specified policy will be passed to the BytesGenerator Flattening the message may trigger changes to the EmailMessage if defaults need to be filled in to complete the transformation to a string for example MIME boundaries may be generated or modified Note that this method is provided as a convenience and may not be the most useful way to serialize messages in your application especially if you are dealing with multiple messages See email generator BytesGenerator for a more flexible API for serializing messages __bytes__ Equivalent to as_bytes Allows bytes msg to produce a bytes object containing the serialized message is_multipart Return True if the message s payload is a list of sub EmailMessage objects otherwise return False When is_multipart returns False the payload should be a string object which might be a CTE encoded binary payload Note that is_multipart returning True does not necessarily mean that msg get_content_maintype multipart will return the True For example is_multipart will return True when the EmailMessage is of type message rfc822 set_unixfrom unixfrom Set the message s envelope header to unixfrom which should be a string See mboxMessage for a brief description of this header get_unixfrom Return the message s envelope header Defaults to None if the envelope header was never set The following methods implement the mapping like interface for accessing the message s headers Note that there are some semantic differences between these methods and a normal mapping i e dictionary interface For example in a dictionary there are no duplicate keys but here there may be duplicate message headers Also in dictionaries there is no guaranteed order to the keys returned by keys but in an EmailMessage object headers are always returned in the order they appeared in the original message or in which they were added to the message later Any header deleted and then re added is always appended to the end of the header list These semantic differences are intentional and are biased toward convenience in the most common use cases Note that in all cases any envelope header present in the message is not included in the mapping interface __len__ Return the total number of headers including duplicates __contains__ name Return True if the message object has a field named name Matching is done without regard to case and name does not include the trailing colon Used for the in operator For example if message id in myMessage print Message ID myMessage message id __getitem__ name Return the value of the named header field name does not include the colon field separator If the header is missing None is returned a KeyError is never raised Note that if the named field appears more than once in the message s headers exactly which of those field values will be returned is undefined Use the get_all method to get the values of all the extant headers named name Using the standard non compat32 policies the returned value is an instance of a subclass of email headerregistry BaseHeader __setitem__ name val Add a header to the message with field name name and value val The field is appended to the end of the message s existing headers Note that this does not overwrite or delete any existing header with the same name If you want to ensure that the new header is the only one present in the message with field name name delete the field first e g del msg subject msg subject Python roolz If the policy defines certain headers to be unique as the standard policies do this method may raise a ValueError when an attempt is made to assign a valu,en
1412,e to such a header when one already exists This behavior is intentional for consistency s sake but do not depend on it as we may choose to make such assignments do an automatic deletion of the existing header in the future __delitem__ name Delete all occurrences of the field with name name from the message s headers No exception is raised if the named field isn t present in the headers keys Return a list of all the message s header field names values Return a list of all the message s field values items Return a list of 2 tuples containing all the message s field headers and values get name failobj None Return the value of the named header field This is identical to __getitem__ except that optional failobj is returned if the named header is missing failobj defaults to None Here are some additional useful header related methods get_all name failobj None Return a list of all the values for the field named name If there are no such named headers in the message failobj is returned defaults to None add_header _name _value _params Extended header setting This method is similar to __setitem__ except that additional header parameters can be provided as keyword arguments _name is the header field to add and _value is the primary value for the header For each item in the keyword argument dictionary _params the key is taken as the parameter name with underscores converted to dashes since dashes are illegal in Python identifiers Normally the parameter will be added as key value unless the value is None in which case only the key will be added If the value contains non ASCII characters the charset and language may be explicitly controlled by specifying the value as a three tuple in the format CHARSET LANGUAGE VALUE where CHARSET is a string naming the charset to be used to encode the value LANGUAGE can usually be set to None or the empty string see RFC 2231 for other possibilities and VALUE is the string value containing non ASCII code points If a three tuple is not passed and the value contains non ASCII characters it is automatically encoded in RFC 2231 format using a CHARSET of utf 8 and a LANGUAGE of None Here is an example msg add_header Content Disposition attachment filename bud gif This will add a header that looks like Content Disposition attachment filename bud gif An example of the extended interface with non ASCII characters msg add_header Content Disposition attachment filename iso 8859 1 Fußballer ppt replace_header _name _value Replace a header Replace the first header found in the message that matches _name retaining header order and field name case of the original header If no matching header is found raise a KeyError get_content_type Return the message s content type coerced to lower case of the form maintype subtype If there is no Content Type header in the message return the value returned by get_default_type If the Content Type header is invalid return text plain According to RFC 2045 messages always have a default type get_content_type will always return a value RFC 2045 defines a message s default type to be text plain unless it appears inside a multipart digest container in which case it would be message rfc822 If the Content Type header has an invalid type specification RFC 2045 mandates that the default type be text plain get_content_maintype Return the message s main content type This is the maintype part of the string returned by get_content_type get_content_subtype Return the message s sub content type This is the subtype part of the string returned by get_content_type get_default_type Return the default content type Most messages have a default content type of text plain except for messages that are subparts of multipart digest containers Such subparts have a default content type of message rfc822 set_default_type ctype Set the default content type ctype should either be text plain or message rfc822 although this is not enforced The default content type is not stored in the Content Type header so it only affects the return value of the get_content_type methods when no Content Type header is present in th,en
1413,e message set_param param value header Content Type requote True charset None language replace False Set a parameter in the Content Type header If the parameter already exists in the header replace its value with value When header is Content Type the default and the header does not yet exist in the message add it set its value to text plain and append the new parameter value Optional header specifies an alternative header to Content Type If the value contains non ASCII characters the charset and language may be explicitly specified using the optional charset and language parameters Optional language specifies the RFC 2231 language defaulting to the empty string Both charset and language should be strings The default is to use the utf8 charset and None for the language If replace is False the default the header is moved to the end of the list of headers If replace is True the header will be updated in place Use of the requote parameter with EmailMessage objects is deprecated Note that existing parameter values of headers may be accessed through the params attribute of the header value for example msg Content Type params charset Changed in version 3 4 replace keyword was added del_param param header content type requote True Remove the given parameter completely from the Content Type header The header will be re written in place without the parameter or its value Optional header specifies an alternative to Content Type Use of the requote parameter with EmailMessage objects is deprecated get_filename failobj None Return the value of the filename parameter of the Content Disposition header of the message If the header does not have a filename parameter this method falls back to looking for the name parameter on the Content Type header If neither is found or the header is missing then failobj is returned The returned string will always be unquoted as per email utils unquote get_boundary failobj None Return the value of the boundary parameter of the Content Type header of the message or failobj if either the header is missing or has no boundary parameter The returned string will always be unquoted as per email utils unquote set_boundary boundary Set the boundary parameter of the Content Type header to boundary set_boundary will always quote boundary if necessary A HeaderParseError is raised if the message object has no Content Type header Note that using this method is subtly different from deleting the old Content Type header and adding a new one with the new boundary via add_header because set_boundary preserves the order of the Content Type header in the list of headers get_content_charset failobj None Return the charset parameter of the Content Type header coerced to lower case If there is no Content Type header or if that header has no charset parameter failobj is returned get_charsets failobj None Return a list containing the character set names in the message If the message is a multipart then the list will contain one element for each subpart in the payload otherwise it will be a list of length 1 Each item in the list will be a string which is the value of the charset parameter in the Content Type header for the represented subpart If the subpart has no Content Type header no charset parameter or is not of the text main MIME type then that item in the returned list will be failobj is_attachment Return True if there is a Content Disposition header and its case insensitive value is attachment False otherwise Changed in version 3 4 2 is_attachment is now a method instead of a property for consistency with is_multipart get_content_disposition Return the lowercased value without parameters of the message s Content Disposition header if it has one or None The possible values for this method are inline attachment or None if the message follows RFC 2183 New in version 3 5 The following methods relate to interrogating and manipulating the content payload of the message walk The walk method is an all purpose generator which can be used to iterate over all the parts and subparts of a message object tree in depth first traversal o,en
1414,rder You will typically use walk as the iterator in a for loop each iteration returns the next subpart Here s an example that prints the MIME type of every part of a multipart message structure for part in msg walk print part get_content_type multipart report text plain message delivery status text plain text plain message rfc822 text plain walk iterates over the subparts of any part where is_multipart returns True even though msg get_content_maintype multipart may return False We can see this in our example by making use of the _structure debug helper function from email iterators import _structure for part in msg walk print part get_content_maintype multipart part is_multipart True True False False False True False False False False False True False False _structure msg multipart report text plain message delivery status text plain text plain message rfc822 text plain Here the message parts are not multiparts but they do contain subparts is_multipart returns True and walk descends into the subparts get_body preferencelist related html plain Return the MIME part that is the best candidate to be the body of the message preferencelist must be a sequence of strings from the set related html and plain and indicates the order of preference for the content type of the part returned Start looking for candidate matches with the object on which the get_body method is called If related is not included in preferencelist consider the root part or subpart of the root part of any related encountered as a candidate if the sub part matches a preference When encountering a multipart related check the start parameter and if a part with a matching Content ID is found consider only it when looking for candidate matches Otherwise consider only the first default root part of the multipart related If a part has a Content Disposition header only consider the part a candidate match if the value of the header is inline If none of the candidates matches any of the preferences in preferencelist return None Notes 1 For most applications the only preferencelist combinations that really make sense are plain html plain and the default related html plain 2 Because matching starts with the object on which get_body is called calling get_body on a multipart related will return the object itself unless preferencelist has a non default value 3 Messages or message parts that do not specify a Content Type or whose Content Type header is invalid will be treated as if they are of type text plain which may occasionally cause get_body to return unexpected results iter_attachments Return an iterator over all of the immediate sub parts of the message that are not candidate body parts That is skip the first occurrence of each of text plain text html multipart related or multipart alternative unless they are explicitly marked as attachments via Content Disposition attachment and return all remaining parts When applied directly to a multipart related return an iterator over the all the related parts except the root part ie the part pointed to by the start parameter or the first part if there is no start parameter or the start parameter doesn t match the Content ID of any of the parts When applied directly to a multipart alternative or a non multipart return an empty iterator iter_parts Return an iterator over all of the immediate sub parts of the message which will be empty for a non multipart See also walk get_content args content_manager None kw Call the get_content method of the content_manager passing self as the message object and passing along any other arguments or keywords as additional arguments If content_manager is not specified use the content_manager specified by the current policy set_content args content_manager None kw Call the set_content method of the content_manager passing self as the message object and passing along any other arguments or keywords as additional arguments If content_manager is not specified use the content_manager specified by the current policy make_related boundary None Convert a non multipart message into a multipart related mes,en
1415,sage moving any existing Content headers and payload into a new first part of the multipart If boundary is specified use it as the boundary string in the multipart otherwise leave the boundary to be automatically created when it is needed for example when the message is serialized make_alternative boundary None Convert a non multipart or a multipart related into a multipart alternative moving any existing Content headers and payload into a new first part of the multipart If boundary is specified use it as the boundary string in the multipart otherwise leave the boundary to be automatically created when it is needed for example when the message is serialized make_mixed boundary None Convert a non multipart a multipart related or a multipart alternative into a multipart mixed moving any existing Content headers and payload into a new first part of the multipart If boundary is specified use it as the boundary string in the multipart otherwise leave the boundary to be automatically created when it is needed for example when the message is serialized add_related args content_manager None kw If the message is a multipart related create a new message object pass all of the arguments to its set_content method and attach it to the multipart If the message is a non multipart call make_related and then proceed as above If the message is any other type of multipart raise a TypeError If content_manager is not specified use the content_manager specified by the current policy If the added part has no Content Disposition header add one with the value inline add_alternative args content_manager None kw If the message is a multipart alternative create a new message object pass all of the arguments to its set_content method and attach it to the multipart If the message is a non multipart or multipart related call make_alternative and then proceed as above If the message is any other type of multipart raise a TypeError If content_manager is not specified use the content_manager specified by the current policy add_attachment args content_manager None kw If the message is a multipart mixed create a new message object pass all of the arguments to its set_content method and attach it to the multipart If the message is a non multipart multipart related or multipart alternative call make_mixed and then proceed as above If content_manager is not specified use the content_manager specified by the current policy If the added part has no Content Disposition header add one with the value attachment This method can be used both for explicit attachments Content Disposition attachment and inline attachments Content Disposition inline by passing appropriate options to the content_manager clear Remove the payload and all of the headers clear_content Remove the payload and all of the Content headers leaving all other headers intact and in their original order EmailMessage objects have the following instance attributes preamble The format of a MIME document allows for some text between the blank line following the headers and the first multipart boundary string Normally this text is never visible in a MIME aware mail reader because it falls outside the standard MIME armor However when viewing the raw text of the message or when viewing the message in a non MIME aware reader this text can become visible The preamble attribute contains this leading extra armor text for MIME documents When the Parser discovers some text after the headers but before the first boundary string it assigns this text to the message s preamble attribute When the Generator is writing out the plain text representation of a MIME message and it finds the message has a preamble attribute it will write this text in the area between the headers and the first boundary See email parser and email generator for details Note that if the message object has no preamble the preamble attribute will be None epilogue The epilogue attribute acts the same way as the preamble attribute except that it contains text that appears between the last boundary and the end of the message As with the preamble if th,en
1416,ere is no epilog text this attribute will be None defects The defects attribute contains a list of all the problems found when parsing this message See email errors for a detailed description of the possible parsing defects class email message MIMEPart policy default This class represents a subpart of a MIME message It is identical to EmailMessage except that no MIME Version headers are added when set_content is called since sub parts do not need their own MIME Version headers Footnotes 1 Originally added in 3 4 as a provisional module Docs for legacy message class moved to email message Message Representing an email message using the compat32 API,en
1417,logging Logging facility for Python Source code Lib logging __init__ py Important This page contains the API reference information For tutorial information and discussion of more advanced topics see Basic Tutorial Advanced Tutorial Logging Cookbook This module defines functions and classes which implement a flexible event logging system for applications and libraries The key benefit of having the logging API provided by a standard library module is that all Python modules can participate in logging so your application log can include your own messages integrated with messages from third party modules Here s a simple example of idiomatic usage myapp py import logging import mylib logger logging getLogger __name__ def main logging basicConfig filename myapp log level logging INFO logger info Started mylib do_something logger info Finished if __name__ __main__ main mylib py import logging logger logging getLogger __name__ def do_something logger info Doing something If you run myapp py you should see this in myapp log INFO __main__ Started INFO mylib Doing something INFO __main__ Finished The key features of this idiomatic usage is that the majority of code is simply creating a module level logger with getLogger __name__ and using that logger to do any needed logging This is concise while allowing downstream code fine grained control if needed Logged messages to the module level logger get forwarded up to handlers of loggers in higher level modules all the way up to the root logger for this reason this approach is known as hierarchical logging For logging to be useful it needs to be configured setting the levels and destinations for each logger potentially changing how specific modules log often based on command line arguments or application configuration In most cases like the one above only the root logger needs to be so configured since all the lower level loggers at module level eventually forward their messages to its handlers basicConfig provides a quick way to configure the root logger that handles many use cases The module provides a lot of functionality and flexibility If you are unfamiliar with logging the best way to get to grips with it is to view the tutorials see the links above and on the right The basic classes defined by the module together with their functions are listed below Loggers expose the interface that application code directly uses Handlers send the log records created by loggers to the appropriate destination Filters provide a finer grained facility for determining which log records to output Formatters specify the layout of log records in the final output Logger Objects Loggers have the following attributes and methods Note that Loggers should NEVER be instantiated directly but always through the module level function logging getLogger name Multiple calls to getLogger with the same name will always return a reference to the same Logger object The name is potentially a period separated hierarchical value like foo bar baz though it could also be just plain foo for example Loggers that are further down in the hierarchical list are children of loggers higher up in the list For example given a logger with a name of foo loggers with names of foo bar foo bar baz and foo bam are all descendants of foo The logger name hierarchy is analogous to the Python package hierarchy and identical to it if you organise your loggers on a per module basis using the recommended construction logging getLogger __name__ That s because in a module __name__ is the module s name in the Python package namespace class logging Logger name This is the logger s name and is the value that was passed to getLogger to obtain the logger Note This attribute should be treated as read only level The threshold of this logger as set by the setLevel method Note Do not set this attribute directly always use setLevel which has checks for the level passed to it parent The parent logger of this logger It may change based on later instantiation of loggers which are higher up in the namespace hierarchy Note This value should be treated as read on,en
1418,ly propagate If this attribute evaluates to true events logged to this logger will be passed to the handlers of higher level ancestor loggers in addition to any handlers attached to this logger Messages are passed directly to the ancestor loggers handlers neither the level nor filters of the ancestor loggers in question are considered If this evaluates to false logging messages are not passed to the handlers of ancestor loggers Spelling it out with an example If the propagate attribute of the logger named A B C evaluates to true any event logged to A B C via a method call such as logging getLogger A B C error will subject to passing that logger s level and filter settings be passed in turn to any handlers attached to loggers named A B A and the root logger after first being passed to any handlers attached to A B C If any logger in the chain A B C A B A has its propagate attribute set to false then that is the last logger whose handlers are offered the event to handle and propagation stops at that point The constructor sets this attribute to True Note If you attach a handler to a logger and one or more of its ancestors it may emit the same record multiple times In general you should not need to attach a handler to more than one logger if you just attach it to the appropriate logger which is highest in the logger hierarchy then it will see all events logged by all descendant loggers provided that their propagate setting is left set to True A common scenario is to attach handlers only to the root logger and to let propagation take care of the rest handlers The list of handlers directly attached to this logger instance Note This attribute should be treated as read only it is normally changed via the addHandler and removeHandler methods which use locks to ensure thread safe operation disabled This attribute disables handling of any events It is set to False in the initializer and only changed by logging configuration code Note This attribute should be treated as read only setLevel level Sets the threshold for this logger to level Logging messages which are less severe than level will be ignored logging messages which have severity level or higher will be emitted by whichever handler or handlers service this logger unless a handler s level has been set to a higher severity level than level When a logger is created the level is set to NOTSET which causes all messages to be processed when the logger is the root logger or delegation to the parent when the logger is a non root logger Note that the root logger is created with level WARNING The term delegation to the parent means that if a logger has a level of NOTSET its chain of ancestor loggers is traversed until either an ancestor with a level other than NOTSET is found or the root is reached If an ancestor is found with a level other than NOTSET then that ancestor s level is treated as the effective level of the logger where the ancestor search began and is used to determine how a logging event is handled If the root is reached and it has a level of NOTSET then all messages will be processed Otherwise the root s level will be used as the effective level See Logging Levels for a list of levels Changed in version 3 2 The level parameter now accepts a string representation of the level such as INFO as an alternative to the integer constants such as INFO Note however that levels are internally stored as integers and methods such as e g getEffectiveLevel and isEnabledFor will return expect to be passed integers isEnabledFor level Indicates if a message of severity level would be processed by this logger This method checks first the module level level set by logging disable level and then the logger s effective level as determined by getEffectiveLevel getEffectiveLevel Indicates the effective level for this logger If a value other than NOTSET has been set using setLevel it is returned Otherwise the hierarchy is traversed towards the root until a value other than NOTSET is found and that value is returned The value returned is an integer typically one of logging DEBUG logging INFO etc,en
1419, getChild suffix Returns a logger which is a descendant to this logger as determined by the suffix Thus logging getLogger abc getChild def ghi would return the same logger as would be returned by logging getLogger abc def ghi This is a convenience method useful when the parent logger is named using e g __name__ rather than a literal string New in version 3 2 getChildren Returns a set of loggers which are immediate children of this logger So for example logging getLogger getChildren might return a set containing loggers named foo and bar but a logger named foo bar wouldn t be included in the set Likewise logging getLogger foo getChildren might return a set including a logger named foo bar but it wouldn t include one named foo bar baz New in version 3 12 debug msg args kwargs Logs a message with level DEBUG on this logger The msg is the message format string and the args are the arguments which are merged into msg using the string formatting operator Note that this means that you can use keywords in the format string together with a single dictionary argument No formatting operation is performed on msg when no args are supplied There are four keyword arguments in kwargs which are inspected exc_info stack_info stacklevel and extra If exc_info does not evaluate as false it causes exception information to be added to the logging message If an exception tuple in the format returned by sys exc_info or an exception instance is provided it is used otherwise sys exc_info is called to get the exception information The second optional keyword argument is stack_info which defaults to False If true stack information is added to the logging message including the actual logging call Note that this is not the same stack information as that displayed through specifying exc_info The former is stack frames from the bottom of the stack up to the logging call in the current thread whereas the latter is information about stack frames which have been unwound following an exception while searching for exception handlers You can specify stack_info independently of exc_info e g to just show how you got to a certain point in your code even when no exceptions were raised The stack frames are printed following a header line which says Stack most recent call last This mimics the Traceback most recent call last which is used when displaying exception frames The third optional keyword argument is stacklevel which defaults to 1 If greater than 1 the corresponding number of stack frames are skipped when computing the line number and function name set in the LogRecord created for the logging event This can be used in logging helpers so that the function name filename and line number recorded are not the information for the helper function method but rather its caller The name of this parameter mirrors the equivalent one in the warnings module The fourth keyword argument is extra which can be used to pass a dictionary which is used to populate the __dict__ of the LogRecord created for the logging event with user defined attributes These custom attributes can then be used as you like For example they could be incorporated into logged messages For example FORMAT asctime s clientip 15s user 8s message s logging basicConfig format FORMAT d clientip 192 168 0 1 user fbloggs logger logging getLogger tcpserver logger warning Protocol problem s connection reset extra d would print something like 2006 02 08 22 20 02 165 192 168 0 1 fbloggs Protocol problem connection reset The keys in the dictionary passed in extra should not clash with the keys used by the logging system See the section on LogRecord attributes for more information on which keys are used by the logging system If you choose to use these attributes in logged messages you need to exercise some care In the above example for instance the Formatter has been set up with a format string which expects clientip and user in the attribute dictionary of the LogRecord If these are missing the message will not be logged because a string formatting exception will occur So in this case you always need to pass the ex,en
1420,tra dictionary with these keys While this might be annoying this feature is intended for use in specialized circumstances such as multi threaded servers where the same code executes in many contexts and interesting conditions which arise are dependent on this context such as remote client IP address and authenticated user name in the above example In such circumstances it is likely that specialized Formatter s would be used with particular Handler s If no handler is attached to this logger or any of its ancestors taking into account the relevant Logger propagate attributes the message will be sent to the handler set on lastResort Changed in version 3 2 The stack_info parameter was added Changed in version 3 5 The exc_info parameter can now accept exception instances Changed in version 3 8 The stacklevel parameter was added info msg args kwargs Logs a message with level INFO on this logger The arguments are interpreted as for debug warning msg args kwargs Logs a message with level WARNING on this logger The arguments are interpreted as for debug Note There is an obsolete method warn which is functionally identical to warning As warn is deprecated please do not use it use warning instead error msg args kwargs Logs a message with level ERROR on this logger The arguments are interpreted as for debug critical msg args kwargs Logs a message with level CRITICAL on this logger The arguments are interpreted as for debug log level msg args kwargs Logs a message with integer level level on this logger The other arguments are interpreted as for debug exception msg args kwargs Logs a message with level ERROR on this logger The arguments are interpreted as for debug Exception info is added to the logging message This method should only be called from an exception handler addFilter filter Adds the specified filter filter to this logger removeFilter filter Removes the specified filter filter from this logger filter record Apply this logger s filters to the record and return True if the record is to be processed The filters are consulted in turn until one of them returns a false value If none of them return a false value the record will be processed passed to handlers If one returns a false value no further processing of the record occurs addHandler hdlr Adds the specified handler hdlr to this logger removeHandler hdlr Removes the specified handler hdlr from this logger findCaller stack_info False stacklevel 1 Finds the caller s source filename and line number Returns the filename line number function name and stack information as a 4 element tuple The stack information is returned as None unless stack_info is True The stacklevel parameter is passed from code calling the debug and other APIs If greater than 1 the excess is used to skip stack frames before determining the values to be returned This will generally be useful when calling logging APIs from helper wrapper code so that the information in the event log refers not to the helper wrapper code but to the code that calls it handle record Handles a record by passing it to all handlers associated with this logger and its ancestors until a false value of propagate is found This method is used for unpickled records received from a socket as well as those created locally Logger level filtering is applied using filter makeRecord name level fn lno msg args exc_info func None extra None sinfo None This is a factory method which can be overridden in subclasses to create specialized LogRecord instances hasHandlers Checks to see if this logger has any handlers configured This is done by looking for handlers in this logger and its parents in the logger hierarchy Returns True if a handler was found else False The method stops searching up the hierarchy whenever a logger with the propagate attribute set to false is found that will be the last logger which is checked for the existence of handlers New in version 3 2 Changed in version 3 7 Loggers can now be pickled and unpickled Logging Levels The numeric values of logging levels are given in the following table These are primarily of interest if y,en
1421,ou want to define your own levels and need them to have specific values relative to the predefined levels If you define a level with the same numeric value it overwrites the predefined value the predefined name is lost Level Numeric value What it means When to use it logging NOTSET 0 When set on a logger indicates that ancestor loggers are to be consulted to determine the effective level If that still resolves to NOTSET then all events are logged When set on a handler all events are handled logging DEBUG 10 Detailed information typically only of interest to a developer trying to diagnose a problem logging INFO 20 Confirmation that things are working as expected logging WARNING 30 An indication that something unexpected happened or that a problem might occur in the near future e g disk space low The software is still working as expected logging ERROR 40 Due to a more serious problem the software has not been able to perform some function logging CRITICAL 50 A serious error indicating that the program itself may be unable to continue running Handler Objects Handlers have the following attributes and methods Note that Handler is never instantiated directly this class acts as a base for more useful subclasses However the __init__ method in subclasses needs to call Handler __init__ class logging Handler __init__ level NOTSET Initializes the Handler instance by setting its level setting the list of filters to the empty list and creating a lock using createLock for serializing access to an I O mechanism createLock Initializes a thread lock which can be used to serialize access to underlying I O functionality which may not be threadsafe acquire Acquires the thread lock created with createLock release Releases the thread lock acquired with acquire setLevel level Sets the threshold for this handler to level Logging messages which are less severe than level will be ignored When a handler is created the level is set to NOTSET which causes all messages to be processed See Logging Levels for a list of levels Changed in version 3 2 The level parameter now accepts a string representation of the level such as INFO as an alternative to the integer constants such as INFO setFormatter fmt Sets the Formatter for this handler to fmt addFilter filter Adds the specified filter filter to this handler removeFilter filter Removes the specified filter filter from this handler filter record Apply this handler s filters to the record and return True if the record is to be processed The filters are consulted in turn until one of them returns a false value If none of them return a false value the record will be emitted If one returns a false value the handler will not emit the record flush Ensure all logging output has been flushed This version does nothing and is intended to be implemented by subclasses close Tidy up any resources used by the handler This version does no output but removes the handler from an internal list of handlers which is closed when shutdown is called Subclasses should ensure that this gets called from overridden close methods handle record Conditionally emits the specified logging record depending on filters which may have been added to the handler Wraps the actual emission of the record with acquisition release of the I O thread lock handleError record This method should be called from handlers when an exception is encountered during an emit call If the module level attribute raiseExceptions is False exceptions get silently ignored This is what is mostly wanted for a logging system most users will not care about errors in the logging system they are more interested in application errors You could however replace this with a custom handler if you wish The specified record is the one which was being processed when the exception occurred The default value of raiseExceptions is True as that is more useful during development format record Do formatting for a record if a formatter is set use it Otherwise use the default formatter for the module emit record Do whatever it takes to actually log the specified logging record This versio,en
1422,n is intended to be implemented by subclasses and so raises a NotImplementedError Warning This method is called after a handler level lock is acquired which is released after this method returns When you override this method note that you should be careful when calling anything that invokes other parts of the logging API which might do locking because that might result in a deadlock Specifically Logging configuration APIs acquire the module level lock and then individual handler level locks as those handlers are configured Many logging APIs lock the module level lock If such an API is called from this method it could cause a deadlock if a configuration call is made on another thread because that thread will try to acquire the module level lock before the handler level lock whereas this thread tries to acquire the module level lock after the handler level lock because in this method the handler level lock has already been acquired For a list of handlers included as standard see logging handlers Formatter Objects class logging Formatter fmt None datefmt None style validate True defaults None Responsible for converting a LogRecord to an output string to be interpreted by a human or external system Parameters fmt str A format string in the given style for the logged output as a whole The possible mapping keys are drawn from the LogRecord object s LogRecord attributes If not specified message s is used which is just the logged message datefmt str A format string in the given style for the date time portion of the logged output If not specified the default described in formatTime is used style str Can be one of or and determines how the format string will be merged with its data using one of printf style String Formatting str format or string Template This only applies to fmt and datefmt e g message s versus message not to the actual log messages passed to the logging methods However there are other ways to use and formatting for log messages validate bool If True the default incorrect or mismatched fmt and style will raise a ValueError for example logging Formatter asctime s message s style defaults dict str Any A dictionary with default values to use in custom fields For example logging Formatter ip s message s defaults ip None Changed in version 3 2 Added the style parameter Changed in version 3 8 Added the validate parameter Changed in version 3 10 Added the defaults parameter format record The record s attribute dictionary is used as the operand to a string formatting operation Returns the resulting string Before formatting the dictionary a couple of preparatory steps are carried out The message attribute of the record is computed using msg args If the formatting string contains asctime formatTime is called to format the event time If there is exception information it is formatted using formatException and appended to the message Note that the formatted exception information is cached in attribute exc_text This is useful because the exception information can be pickled and sent across the wire but you should be careful if you have more than one Formatter subclass which customizes the formatting of exception information In this case you will have to clear the cached value by setting the exc_text attribute to None after a formatter has done its formatting so that the next formatter to handle the event doesn t use the cached value but recalculates it afresh If stack information is available it s appended after the exception information using formatStack to transform it if necessary formatTime record datefmt None This method should be called from format by a formatter which wants to make use of a formatted time This method can be overridden in formatters to provide for any specific requirement but the basic behavior is as follows if datefmt a string is specified it is used with time strftime to format the creation time of the record Otherwise the format Y m d H M S uuu is used where the uuu part is a millisecond value and the other letters are as per the time strftime documentation An example time in this format is 2003 01 23,en
1423, 00 29 50 411 The resulting string is returned This function uses a user configurable function to convert the creation time to a tuple By default time localtime is used to change this for a particular formatter instance set the converter attribute to a function with the same signature as time localtime or time gmtime To change it for all formatters for example if you want all logging times to be shown in GMT set the converter attribute in the Formatter class Changed in version 3 3 Previously the default format was hard coded as in this example 2010 09 06 22 38 15 292 where the part before the comma is handled by a strptime format string Y m d H M S and the part after the comma is a millisecond value Because strptime does not have a format placeholder for milliseconds the millisecond value is appended using another format string s 03d and both of these format strings have been hardcoded into this method With the change these strings are defined as class level attributes which can be overridden at the instance level when desired The names of the attributes are default_time_format for the strptime format string and default_msec_format for appending the millisecond value Changed in version 3 9 The default_msec_format can be None formatException exc_info Formats the specified exception information a standard exception tuple as returned by sys exc_info as a string This default implementation just uses traceback print_exception The resulting string is returned formatStack stack_info Formats the specified stack information a string as returned by traceback print_stack but with the last newline removed as a string This default implementation just returns the input value class logging BufferingFormatter linefmt None A base formatter class suitable for subclassing when you want to format a number of records You can pass a Formatter instance which you want to use to format each line that corresponds to a single record If not specified the default formatter which just outputs the event message is used as the line formatter formatHeader records Return a header for a list of records The base implementation just returns the empty string You will need to override this method if you want specific behaviour e g to show the count of records a title or a separator line formatFooter records Return a footer for a list of records The base implementation just returns the empty string You will need to override this method if you want specific behaviour e g to show the count of records or a separator line format records Return formatted text for a list of records The base implementation just returns the empty string if there are no records otherwise it returns the concatenation of the header each record formatted with the line formatter and the footer Filter Objects Filters can be used by Handlers and Loggers for more sophisticated filtering than is provided by levels The base filter class only allows events which are below a certain point in the logger hierarchy For example a filter initialized with A B will allow events logged by loggers A B A B C A B C D A B D etc but not A BB B A B etc If initialized with the empty string all events are passed class logging Filter name Returns an instance of the Filter class If name is specified it names a logger which together with its children will have its events allowed through the filter If name is the empty string allows every event filter record Is the specified record to be logged Returns false for no true for yes Filters can either modify log records in place or return a completely different record instance which will replace the original log record in any future processing of the event Note that filters attached to handlers are consulted before an event is emitted by the handler whereas filters attached to loggers are consulted whenever an event is logged using debug info etc before sending an event to handlers This means that events which have been generated by descendant loggers will not be filtered by a logger s filter setting unless the filter has also been applied to those descendant loggers You,en
1424, don t actually need to subclass Filter you can pass any instance which has a filter method with the same semantics Changed in version 3 2 You don t need to create specialized Filter classes or use other classes with a filter method you can use a function or other callable as a filter The filtering logic will check to see if the filter object has a filter attribute if it does it s assumed to be a Filter and its filter method is called Otherwise it s assumed to be a callable and called with the record as the single parameter The returned value should conform to that returned by filter Changed in version 3 12 You can now return a LogRecord instance from filters to replace the log record rather than modifying it in place This allows filters attached to a Handler to modify the log record before it is emitted without having side effects on other handlers Although filters are used primarily to filter records based on more sophisticated criteria than levels they get to see every record which is processed by the handler or logger they re attached to this can be useful if you want to do things like counting how many records were processed by a particular logger or handler or adding changing or removing attributes in the LogRecord being processed Obviously changing the LogRecord needs to be done with some care but it does allow the injection of contextual information into logs see Using Filters to impart contextual information LogRecord Objects LogRecord instances are created automatically by the Logger every time something is logged and can be created manually via makeLogRecord for example from a pickled event received over the wire class logging LogRecord name level pathname lineno msg args exc_info func None sinfo None Contains all the information pertinent to the event being logged The primary information is passed in msg and args which are combined using msg args to create the message attribute of the record Parameters name str The name of the logger used to log the event represented by this LogRecord Note that the logger name in the LogRecord will always have this value even though it may be emitted by a handler attached to a different ancestor logger level int The numeric level of the logging event such as 10 for DEBUG 20 for INFO etc Note that this is converted to two attributes of the LogRecord levelno for the numeric value and levelname for the corresponding level name pathname str The full string path of the source file where the logging call was made lineno int The line number in the source file where the logging call was made msg Any The event description message which can be a format string with placeholders for variable data or an arbitrary object see Using arbitrary objects as messages args tuple dict str Any Variable data to merge into the msg argument to obtain the event description exc_info tuple type BaseException BaseException types TracebackType None An exception tuple with the current exception information as returned by sys exc_info or None if no exception information is available func str None The name of the function or method from which the logging call was invoked sinfo str None A text string representing stack information from the base of the stack in the current thread up to the logging call getMessage Returns the message for this LogRecord instance after merging any user supplied arguments with the message If the user supplied message argument to the logging call is not a string str is called on it to convert it to a string This allows use of user defined classes as messages whose __str__ method can return the actual format string to be used Changed in version 3 2 The creation of a LogRecord has been made more configurable by providing a factory which is used to create the record The factory can be set using getLogRecordFactory and setLogRecordFactory see this for the factory s signature This functionality can be used to inject your own values into a LogRecord at creation time You can use the following pattern old_factory logging getLogRecordFactory def record_factory args kwargs record old_factory a,en
1425,rgs kwargs record custom_attribute 0xdecafbad return record logging setLogRecordFactory record_factory With this pattern multiple factories could be chained and as long as they don t overwrite each other s attributes or unintentionally overwrite the standard attributes listed above there should be no surprises LogRecord attributes The LogRecord has a number of attributes most of which are derived from the parameters to the constructor Note that the names do not always correspond exactly between the LogRecord constructor parameters and the LogRecord attributes These attributes can be used to merge data from the record into the format string The following table lists in alphabetical order the attribute names their meanings and the corresponding placeholder in a style format string If you are using formatting str format you can use attrname as the placeholder in the format string If you are using formatting string Template use the form attrname In both cases of course replace attrname with the actual attribute name you want to use In the case of formatting you can specify formatting flags by placing them after the attribute name separated from it with a colon For example a placeholder of msecs 03 0f would format a millisecond value of 4 as 004 Refer to the str format documentation for full details on the options available to you Attribute name Format Description args You shouldn t need to The tuple of arguments merged into msg to format this yourself produce message or a dict whose values are used for the merge when there is only one argument and it is a dictionary asctime asctime s Human readable time when the LogRecord was created By default this is of the form 2003 07 08 16 49 45 896 the numbers after the comma are millisecond portion of the time created created f Time when the LogRecord was created as returned by time time exc_info You shouldn t need to Exception tuple à la sys exc_info or if no format this yourself exception has occurred None filename filename s Filename portion of pathname funcName funcName s Name of function containing the logging call levelname levelname s Text logging level for the message DEBUG INFO WARNING ERROR CRITICAL levelno levelno s Numeric logging level for the message DEBUG INFO WARNING ERROR CRITICAL lineno lineno d Source line number where the logging call was issued if available message message s The logged message computed as msg args This is set when Formatter format is invoked module module s Module name portion of filename msecs msecs d Millisecond portion of the time when the LogRecord was created msg You shouldn t need to The format string passed in the original format this yourself logging call Merged with args to produce message or an arbitrary object see Using arbitrary objects as messages name name s Name of the logger used to log the call pathname pathname s Full pathname of the source file where the logging call was issued if available process process d Process ID if available processName processName s Process name if available relativeCreated relativeCreated d Time in milliseconds when the LogRecord was created relative to the time the logging module was loaded stack_info You shouldn t need to Stack frame information where available from format this yourself the bottom of the stack in the current thread up to and including the stack frame of the logging call which resulted in the creation of this record thread thread d Thread ID if available threadName threadName s Thread name if available taskName taskName s asyncio Task name if available Changed in version 3 1 processName was added Changed in version 3 12 taskName was added LoggerAdapter Objects LoggerAdapter instances are used to conveniently pass contextual information into logging calls For a usage example see the section on adding contextual information to your logging output class logging LoggerAdapter logger extra Returns an instance of LoggerAdapter initialized with an underlying Logger instance and a dict like object process msg kwargs Modifies the message and or keyword arguments passed to a logging call in orde,en
1426,r to insert contextual information This implementation takes the object passed as extra to the constructor and adds it to kwargs using key extra The return value is a msg kwargs tuple which has the possibly modified versions of the arguments passed in manager Delegates to the underlying manager on logger _log Delegates to the underlying _log method on logger In addition to the above LoggerAdapter supports the following methods of Logger debug info warning error exception critical log isEnabledFor getEffectiveLevel setLevel and hasHandlers These methods have the same signatures as their counterparts in Logger so you can use the two types of instances interchangeably Changed in version 3 2 The isEnabledFor getEffectiveLevel setLevel and hasHandlers methods were added to LoggerAdapter These methods delegate to the underlying logger Changed in version 3 6 Attribute manager and method _log were added which delegate to the underlying logger and allow adapters to be nested Thread Safety The logging module is intended to be thread safe without any special work needing to be done by its clients It achieves this though using threading locks there is one lock to serialize access to the module s shared data and each handler also creates a lock to serialize access to its underlying I O If you are implementing asynchronous signal handlers using the signal module you may not be able to use logging from within such handlers This is because lock implementations in the threading module are not always re entrant and so cannot be invoked from such signal handlers Module Level Functions In addition to the classes described above there are a number of module level functions logging getLogger name None Return a logger with the specified name or if name is None return a logger which is the root logger of the hierarchy If specified the name is typically a dot separated hierarchical name like a a b or a b c d Choice of these names is entirely up to the developer who is using logging All calls to this function with a given name return the same logger instance This means that logger instances never need to be passed between different parts of an application logging getLoggerClass Return either the standard Logger class or the last class passed to setLoggerClass This function may be called from within a new class definition to ensure that installing a customized Logger class will not undo customizations already applied by other code For example class MyLogger logging getLoggerClass override behaviour here logging getLogRecordFactory Return a callable which is used to create a LogRecord New in version 3 2 This function has been provided along with setLogRecordFactory to allow developers more control over how the LogRecord representing a logging event is constructed See setLogRecordFactory for more information about the how the factory is called logging debug msg args kwargs This is a convenience function that calls Logger debug on the root logger The handling of the arguments is in every way identical to what is described in that method The only difference is that if the root logger has no handlers then basicConfig is called prior to calling debug on the root logger For very short scripts or quick demonstrations of logging facilities debug and the other module level functions may be convenient However most programs will want to carefully and explicitly control the logging configuration and should therefore prefer creating a module level logger and calling Logger debug or other level specific methods on it as described at the beginnning of this documentation logging info msg args kwargs Logs a message with level INFO on the root logger The arguments and behavior are otherwise the same as for debug logging warning msg args kwargs Logs a message with level WARNING on the root logger The arguments and behavior are otherwise the same as for debug Note There is an obsolete function warn which is functionally identical to warning As warn is deprecated please do not use it use warning instead logging error msg args kwargs Logs a message with level ERROR on t,en
1427,he root logger The arguments and behavior are otherwise the same as for debug logging critical msg args kwargs Logs a message with level CRITICAL on the root logger The arguments and behavior are otherwise the same as for debug logging exception msg args kwargs Logs a message with level ERROR on the root logger The arguments and behavior are otherwise the same as for debug Exception info is added to the logging message This function should only be called from an exception handler logging log level msg args kwargs Logs a message with level level on the root logger The arguments and behavior are otherwise the same as for debug logging disable level CRITICAL Provides an overriding level level for all loggers which takes precedence over the logger s own level When the need arises to temporarily throttle logging output down across the whole application this function can be useful Its effect is to disable all logging calls of severity level and below so that if you call it with a value of INFO then all INFO and DEBUG events would be discarded whereas those of severity WARNING and above would be processed according to the logger s effective level If logging disable logging NOTSET is called it effectively removes this overriding level so that logging output again depends on the effective levels of individual loggers Note that if you have defined any custom logging level higher than CRITICAL this is not recommended you won t be able to rely on the default value for the level parameter but will have to explicitly supply a suitable value Changed in version 3 7 The level parameter was defaulted to level CRITICAL See bpo 28524 for more information about this change logging addLevelName level levelName Associates level level with text levelName in an internal dictionary which is used to map numeric levels to a textual representation for example when a Formatter formats a message This function can also be used to define your own levels The only constraints are that all levels used must be registered using this function levels should be positive integers and they should increase in increasing order of severity Note If you are thinking of defining your own levels please see the section on Custom Levels logging getLevelNamesMapping Returns a mapping from level names to their corresponding logging levels For example the string CRITICAL maps to CRITICAL The returned mapping is copied from an internal mapping on each call to this function New in version 3 11 logging getLevelName level Returns the textual or numeric representation of logging level level If level is one of the predefined levels CRITICAL ERROR WARNING INFO or DEBUG then you get the corresponding string If you have associated levels with names using addLevelName then the name you have associated with level is returned If a numeric value corresponding to one of the defined levels is passed in the corresponding string representation is returned The level parameter also accepts a string representation of the level such as INFO In such cases this functions returns the corresponding numeric value of the level If no matching numeric or string value is passed in the string Level s level is returned Note Levels are internally integers as they need to be compared in the logging logic This function is used to convert between an integer level and the level name displayed in the formatted log output by means of the levelname s format specifier see LogRecord attributes and vice versa Changed in version 3 4 In Python versions earlier than 3 4 this function could also be passed a text level and would return the corresponding numeric value of the level This undocumented behaviour was considered a mistake and was removed in Python 3 4 but reinstated in 3 4 2 due to retain backward compatibility logging getHandlerByName name Returns a handler with the specified name or None if there is no handler with that name New in version 3 12 logging getHandlerNames Returns an immutable set of all known handler names New in version 3 12 logging makeLogRecord attrdict Creates and returns a new LogRecord insta,en
1428,nce whose attributes are defined by attrdict This function is useful for taking a pickled LogRecord attribute dictionary sent over a socket and reconstituting it as a LogRecord instance at the receiving end logging basicConfig kwargs Does basic configuration for the logging system by creating a StreamHandler with a default Formatter and adding it to the root logger The functions debug info warning error and critical will call basicConfig automatically if no handlers are defined for the root logger This function does nothing if the root logger already has handlers configured unless the keyword argument force is set to True Note This function should be called from the main thread before other threads are started In versions of Python prior to 2 7 1 and 3 2 if this function is called from multiple threads it is possible in rare circumstances that a handler will be added to the root logger more than once leading to unexpected results such as messages being duplicated in the log The following keyword arguments are supported Format Description filename Specifies that a FileHandler be created using the specified filename rather than a StreamHandler filemode If filename is specified open the file in this mode Defaults to a format Use the specified format string for the handler Defaults to attributes levelname name and message separated by colons datefmt Use the specified date time format as accepted by time strftime style If format is specified use this style for the format string One of or for printf style str format or string Template respectively Defaults to level Set the root logger level to the specified level stream Use the specified stream to initialize the StreamHandler Note that this argument is incompatible with filename if both are present a ValueError is raised handlers If specified this should be an iterable of already created handlers to add to the root logger Any handlers which don t already have a formatter set will be assigned the default formatter created in this function Note that this argument is incompatible with filename or stream if both are present a ValueError is raised force If this keyword argument is specified as true any existing handlers attached to the root logger are removed and closed before carrying out the configuration as specified by the other arguments encoding If this keyword argument is specified along with filename its value is used when the FileHandler is created and thus used when opening the output file errors If this keyword argument is specified along with filename its value is used when the FileHandler is created and thus used when opening the output file If not specified the value backslashreplace is used Note that if None is specified it will be passed as such to open which means that it will be treated the same as passing errors Changed in version 3 2 The style argument was added Changed in version 3 3 The handlers argument was added Additional checks were added to catch situations where incompatible arguments are specified e g handlers together with stream or filename or stream together with filename Changed in version 3 8 The force argument was added Changed in version 3 9 The encoding and errors arguments were added logging shutdown Informs the logging system to perform an orderly shutdown by flushing and closing all handlers This should be called at application exit and no further use of the logging system should be made after this call When the logging module is imported it registers this function as an exit handler see atexit so normally there s no need to do that manually logging setLoggerClass klass Tells the logging system to use the class klass when instantiating a logger The class should define __init__ such that only a name argument is required and the __init__ should call Logger __init__ This function is typically called before any loggers are instantiated by applications which need to use custom logger behavior After this call as at any other time do not instantiate loggers directly using the subclass continue to use the logging getLogger API to get your loggers log,en
1429,ging setLogRecordFactory factory Set a callable which is used to create a LogRecord Parameters factory The factory callable to be used to instantiate a log record New in version 3 2 This function has been provided along with getLogRecordFactory to allow developers more control over how the LogRecord representing a logging event is constructed The factory has the following signature factory name level fn lno msg args exc_info func None sinfo None kwargs name The logger name level The logging level numeric fn The full pathname of the file where the logging call was made lno The line number in the file where the logging call was made msg The logging message args The arguments for the logging message exc_info An exception tuple or None func The name of the function or method which invoked the logging call sinfo A stack traceback such as is provided by traceback print_stack showing the call hierarchy kwargs Additional keyword arguments Module Level Attributes logging lastResort A handler of last resort is available through this attribute This is a StreamHandler writing to sys stderr with a level of WARNING and is used to handle logging events in the absence of any logging configuration The end result is to just print the message to sys stderr This replaces the earlier error message saying that no handlers could be found for logger XYZ If you need the earlier behaviour for some reason lastResort can be set to None New in version 3 2 logging raiseExceptions Used to see if exceptions during handling should be propagated Default True If raiseExceptions is False exceptions get silently ignored This is what is mostly wanted for a logging system most users will not care about errors in the logging system they are more interested in application errors Integration with the warnings module The captureWarnings function can be used to integrate logging with the warnings module logging captureWarnings capture This function is used to turn the capture of warnings by logging on and off If capture is True warnings issued by the warnings module will be redirected to the logging system Specifically a warning will be formatted using warnings formatwarning and the resulting string logged to a logger named py warnings with a severity of WARNING If capture is False the redirection of warnings to the logging system will stop and warnings will be redirected to their original destinations i e those in effect before captureWarnings True was called See also Module logging config Configuration API for the logging module Module logging handlers Useful handlers included with the logging module PEP 282 A Logging System The proposal which described this feature for inclusion in the Python standard library Original Python logging package This is the original source for the logging package The version of the package available from this site is suitable for use with Python 1 5 2 2 1 x and 2 2 x which do not include the logging package in the standard library,en
1430,gzip Support for gzip files Source code Lib gzip py This module provides a simple interface to compress and decompress files just like the GNU programs gzip and gunzip would The data compression is provided by the zlib module The gzip module provides the GzipFile class as well as the open compress and decompress convenience functions The GzipFile class reads and writes gzip format files automatically compressing or decompressing the data so that it looks like an ordinary file object Note that additional file formats which can be decompressed by the gzip and gunzip programs such as those produced by compress and pack are not supported by this module The module defines the following items gzip open filename mode rb compresslevel 9 encoding None errors None newline None Open a gzip compressed file in binary or text mode returning a file object The filename argument can be an actual filename a str or bytes object or an existing file object to read from or write to The mode argument can be any of r rb a ab w wb x or xb for binary mode or rt at wt or xt for text mode The default is rb The compresslevel argument is an integer from 0 to 9 as for the GzipFile constructor For binary mode this function is equivalent to the GzipFile constructor GzipFile filename mode compresslevel In this case the encoding errors and newline arguments must not be provided For text mode a GzipFile object is created and wrapped in an io TextIOWrapper instance with the specified encoding error handling behavior and line ending s Changed in version 3 3 Added support for filename being a file object support for text mode and the encoding errors and newline arguments Changed in version 3 4 Added support for the x xb and xt modes Changed in version 3 6 Accepts a path like object exception gzip BadGzipFile An exception raised for invalid gzip files It inherits from OSError EOFError and zlib error can also be raised for invalid gzip files New in version 3 8 class gzip GzipFile filename None mode None compresslevel 9 fileobj None mtime None Constructor for the GzipFile class which simulates most of the methods of a file object with the exception of the truncate method At least one of fileobj and filename must be given a non trivial value The new class instance is based on fileobj which can be a regular file an io BytesIO object or any other object which simulates a file It defaults to None in which case filename is opened to provide a file object When fileobj is not None the filename argument is only used to be included in the gzip file header which may include the original filename of the uncompressed file It defaults to the filename of fileobj if discernible otherwise it defaults to the empty string and in this case the original filename is not included in the header The mode argument can be any of r rb a ab w wb x or xb depending on whether the file will be read or written The default is the mode of fileobj if discernible otherwise the default is rb In future Python releases the mode of fileobj will not be used It is better to always specify mode for writing Note that the file is always opened in binary mode To open a compressed file in text mode use open or wrap your GzipFile with an io TextIOWrapper The compresslevel argument is an integer from 0 to 9 controlling the level of compression 1 is fastest and produces the least compression and 9 is slowest and produces the most compression 0 is no compression The default is 9 The mtime argument is an optional numeric timestamp to be written to the last modification time field in the stream when compressing It should only be provided in compression mode If omitted or None the current time is used See the mtime attribute for more details Calling a GzipFile object s close method does not close fileobj since you might wish to append more material after the compressed data This also allows you to pass an io BytesIO object opened for writing as fileobj and retrieve the resulting memory buffer using the io BytesIO object s getvalue method GzipFile supports the io BufferedIOBase interface including iteration and the ,en
1431,with statement Only the truncate method isn t implemented GzipFile also provides the following method and attribute peek n Read n uncompressed bytes without advancing the file position At most one single read on the compressed stream is done to satisfy the call The number of bytes returned may be more or less than requested Note While calling peek does not change the file position of the GzipFile it may change the position of the underlying file object e g if the GzipFile was constructed with the fileobj parameter New in version 3 2 mtime When decompressing the value of the last modification time field in the most recently read header may be read from this attribute as an integer The initial value before reading any headers is None All gzip compressed streams are required to contain this timestamp field Some programs such as gunzip make use of the timestamp The format is the same as the return value of time time and the st_mtime attribute of the object returned by os stat name The path to the gzip file on disk as a str or bytes Equivalent to the output of os fspath on the original input path with no other normalization resolution or expansion Changed in version 3 1 Support for the with statement was added along with the mtime constructor argument and mtime attribute Changed in version 3 2 Support for zero padded and unseekable files was added Changed in version 3 3 The io BufferedIOBase read1 method is now implemented Changed in version 3 4 Added support for the x and xb modes Changed in version 3 5 Added support for writing arbitrary bytes like objects The read method now accepts an argument of None Changed in version 3 6 Accepts a path like object Changed in version 3 12 Remove the filename attribute use the name attribute instead Deprecated since version 3 9 Opening GzipFile for writing without specifying the mode argument is deprecated gzip compress data compresslevel 9 mtime None Compress the data returning a bytes object containing the compressed data compresslevel and mtime have the same meaning as in the GzipFile constructor above When mtime is set to 0 this function is equivalent to zlib compress with wbits set to 31 The zlib function is faster New in version 3 2 Changed in version 3 8 Added the mtime parameter for reproducible output Changed in version 3 11 Speed is improved by compressing all data at once instead of in a streamed fashion Calls with mtime set to 0 are delegated to zlib compress for better speed gzip decompress data Decompress the data returning a bytes object containing the uncompressed data This function is capable of decompressing multi member gzip data multiple gzip blocks concatenated together When the data is certain to contain only one member the zlib decompress function with wbits set to 31 is faster New in version 3 2 Changed in version 3 11 Speed is improved by decompressing members at once in memory instead of in a streamed fashion Examples of usage Example of how to read a compressed file import gzip with gzip open home joe file txt gz rb as f file_content f read Example of how to create a compressed GZIP file import gzip content b Lots of content here with gzip open home joe file txt gz wb as f f write content Example of how to GZIP compress an existing file import gzip import shutil with open home joe file txt rb as f_in with gzip open home joe file txt gz wb as f_out shutil copyfileobj f_in f_out Example of how to GZIP compress a binary string import gzip s_in b Lots of content here s_out gzip compress s_in See also Module zlib The basic data compression module needed to support the gzip file format Command Line Interface The gzip module provides a simple command line interface to compress or decompress files Once executed the gzip module keeps the input file s Changed in version 3 8 Add a new command line interface with a usage By default when you will execute the CLI the default compression level is 6 Command line options file If file is not specified read from sys stdin fast Indicates the fastest compression method less compression best Indicates the slowest compression method ,en
1432,best compression d decompress Decompress the given file h help Show the help message,en
1433,What s New in Python 2 5 Author A M Kuchling This article explains the new features in Python 2 5 The final release of Python 2 5 is scheduled for August 2006 PEP 356 describes the planned release schedule Python 2 5 was released on September 19 2006 The changes in Python 2 5 are an interesting mix of language and library improvements The library enhancements will be more important to Python s user community I think because several widely useful packages were added New modules include ElementTree for XML processing xml etree the SQLite database module sqlite and the ctypes module for calling C functions The language changes are of middling significance Some pleasant new features were added but most of them aren t features that you ll use every day Conditional expressions were finally added to the language using a novel syntax see section PEP 308 Conditional Expressions The new with statement will make writing cleanup code easier section PEP 343 The with statement Values can now be passed into generators section PEP 342 New Generator Features Imports are now visible as either absolute or relative section PEP 328 Absolute and Relative Imports Some corner cases of exception handling are handled better section PEP 341 Unified try except finally All these improvements are worthwhile but they re improvements to one specific language feature or another none of them are broad modifications to Python s semantics As well as the language and library additions other improvements and bugfixes were made throughout the source tree A search through the SVN change logs finds there were 353 patches applied and 458 bugs fixed between Python 2 4 and 2 5 Both figures are likely to be underestimates This article doesn t try to be a complete specification of the new features instead changes are briefly introduced using helpful examples For full details you should always refer to the documentation for Python 2 5 at https docs python org If you want to understand the complete implementation and design rationale refer to the PEP for a particular new feature Comments suggestions and error reports for this document are welcome please e mail them to the author or open a bug in the Python bug tracker PEP 308 Conditional Expressions For a long time people have been requesting a way to write conditional expressions which are expressions that return value A or value B depending on whether a Boolean value is true or false A conditional expression lets you write a single assignment statement that has the same effect as the following if condition x true_value else x false_value There have been endless tedious discussions of syntax on both python dev and comp lang python A vote was even held that found the majority of voters wanted conditional expressions in some form but there was no syntax that was preferred by a clear majority Candidates included C s cond true_v false_v if cond then true_v else false_v and 16 other variations Guido van Rossum eventually chose a surprising syntax x true_value if condition else false_value Evaluation is still lazy as in existing Boolean expressions so the order of evaluation jumps around a bit The condition expression in the middle is evaluated first and the true_value expression is evaluated only if the condition was true Similarly the false_value expression is only evaluated when the condition is false This syntax may seem strange and backwards why does the condition go in the middle of the expression and not in the front as in C s c x y The decision was checked by applying the new syntax to the modules in the standard library and seeing how the resulting code read In many cases where a conditional expression is used one value seems to be the common case and one value is an exceptional case used only on rarer occasions when the condition isn t met The conditional syntax makes this pattern a bit more obvious contents doc n if doc else I read the above statement as meaning here contents is usually assigned a value of doc n sometimes doc is empty in which special case an empty string is returned I doubt I will use condition,en
1434,al expressions very often where there isn t a clear common and uncommon case There was some discussion of whether the language should require surrounding conditional expressions with parentheses The decision was made to not require parentheses in the Python language s grammar but as a matter of style I think you should always use them Consider these two statements First version no parens level 1 if logging else 0 Second version with parens level 1 if logging else 0 In the first version I think a reader s eye might group the statement into level 1 if logging else 0 and think that the condition decides whether the assignment to level is performed The second version reads better in my opinion because it makes it clear that the assignment is always performed and the choice is being made between two values Another reason for including the brackets a few odd combinations of list comprehensions and lambdas could look like incorrect conditional expressions See PEP 308 for some examples If you put parentheses around your conditional expressions you won t run into this case See also PEP 308 Conditional Expressions PEP written by Guido van Rossum and Raymond D Hettinger implemented by Thomas Wouters PEP 309 Partial Function Application The functools module is intended to contain tools for functional style programming One useful tool in this module is the partial function For programs written in a functional style you ll sometimes want to construct variants of existing functions that have some of the parameters filled in Consider a Python function f a b c you could create a new function g b c that was equivalent to f 1 b c This is called partial function application partial takes the arguments function arg1 arg2 kwarg1 value1 kwarg2 value2 The resulting object is callable so you can just call it to invoke function with the filled in arguments Here s a small but realistic example import functools def log message subsystem Write the contents of message to the specified subsystem print s s subsystem message server_log functools partial log subsystem server server_log Unable to open socket Here s another example from a program that uses PyGTK Here a context sensitive pop up menu is being constructed dynamically The callback provided for the menu option is a partially applied version of the open_item method where the first argument has been provided class Application def open_item self path def init self open_func functools partial self open_item item_path popup_menu append Open open_func 1 Another function in the functools module is the update_wrapper wrapper wrapped function that helps you write well behaved decorators update_wrapper copies the name module and docstring attribute to a wrapper function so that tracebacks inside the wrapped function are easier to understand For example you might write def my_decorator f def wrapper args kwds print Calling decorated function return f args kwds functools update_wrapper wrapper f return wrapper wraps is a decorator that can be used inside your own decorators to copy the wrapped function s information An alternate version of the previous example would be def my_decorator f functools wraps f def wrapper args kwds print Calling decorated function return f args kwds return wrapper See also PEP 309 Partial Function Application PEP proposed and written by Peter Harris implemented by Hye Shik Chang and Nick Coghlan with adaptations by Raymond Hettinger PEP 314 Metadata for Python Software Packages v1 1 Some simple dependency support was added to Distutils The setup function now has requires provides and obsoletes keyword parameters When you build a source distribution using the sdist command the dependency information will be recorded in the PKG INFO file Another new keyword parameter is download_url which should be set to a URL for the package s source code This means it s now possible to look up an entry in the package index determine the dependencies for a package and download the required packages VERSION 1 0 setup name PyPackage version VERSION requires numarray zlib 1 1 4 obsoletes OldPackag,en
1435,e download_url http www example com pypackage dist pkg s tar gz VERSION Another new enhancement to the Python package index at https pypi org is storing source and binary archives for a package The new upload Distutils command will upload a package to the repository Before a package can be uploaded you must be able to build a distribution using the sdist Distutils command Once that works you can run python setup py upload to add your package to the PyPI archive Optionally you can GPG sign the package by supplying the sign and identity options Package uploading was implemented by Martin von Löwis and Richard Jones See also PEP 314 Metadata for Python Software Packages v1 1 PEP proposed and written by A M Kuchling Richard Jones and Fred Drake implemented by Richard Jones and Fred Drake PEP 328 Absolute and Relative Imports The simpler part of PEP 328 was implemented in Python 2 4 parentheses could now be used to enclose the names imported from a module using the from import statement making it easier to import many different names The more complicated part has been implemented in Python 2 5 importing a module can be specified to use absolute or package relative imports The plan is to move toward making absolute imports the default in future versions of Python Let s say you have a package directory like this pkg pkg __init__ py pkg main py pkg string py This defines a package named pkg containing the pkg main and pkg string submodules Consider the code in the main py module What happens if it executes the statement import string In Python 2 4 and earlier it will first look in the package s directory to perform a relative import finds pkg string py imports the contents of that file as the pkg string module and that module is bound to the name string in the pkg main module s namespace That s fine if pkg string was what you wanted But what if you wanted Python s standard string module There s no clean way to ignore pkg string and look for the standard module generally you had to look at the contents of sys modules which is slightly unclean Holger Krekel s py std package provides a tidier way to perform imports from the standard library import py py std string join but that package isn t available on all Python installations Reading code which relies on relative imports is also less clear because a reader may be confused about which module string or pkg string is intended to be used Python users soon learned not to duplicate the names of standard library modules in the names of their packages submodules but you can t protect against having your submodule s name being used for a new module added in a future version of Python In Python 2 5 you can switch import s behaviour to absolute imports using a from __future__ import absolute_import directive This absolute import behaviour will become the default in a future version probably Python 2 7 Once absolute imports are the default import string will always find the standard library s version It s suggested that users should begin using absolute imports as much as possible so it s preferable to begin writing from pkg import string in your code Relative imports are still possible by adding a leading period to the module name when using the from import form Import names from pkg string from string import name1 name2 Import pkg string from import string This imports the string module relative to the current package so in pkg main this will import name1 and name2 from pkg string Additional leading periods perform the relative import starting from the parent of the current package For example code in the A B C module can do from import D Imports A B D from import E Imports A E from F import G Imports A F G Leading periods cannot be used with the import modname form of the import statement only the from import form See also PEP 328 Imports Multi Line and Absolute Relative PEP written by Aahz implemented by Thomas Wouters https pylib readthedocs io The py library by Holger Krekel which contains the py std package PEP 338 Executing Modules as Scripts The m switch added in Python 2 4 to exec,en
1436,ute a module as a script gained a few more abilities Instead of being implemented in C code inside the Python interpreter the switch now uses an implementation in a new module runpy The runpy module implements a more sophisticated import mechanism so that it s now possible to run modules in a package such as pychecker checker The module also supports alternative import mechanisms such as the zipimport module This means you can add a zip archive s path to sys path and then use the m switch to execute code from the archive See also PEP 338 Executing modules as scripts PEP written and implemented by Nick Coghlan PEP 341 Unified try except finally Until Python 2 5 the try statement came in two flavours You could use a finally block to ensure that code is always executed or one or more except blocks to catch specific exceptions You couldn t combine both except blocks and a finally block because generating the right bytecode for the combined version was complicated and it wasn t clear what the semantics of the combined statement should be Guido van Rossum spent some time working with Java which does support the equivalent of combining except blocks and a finally block and this clarified what the statement should mean In Python 2 5 you can now write try block 1 except Exception1 handler 1 except Exception2 handler 2 else else block finally final block The code in block 1 is executed If the code raises an exception the various except blocks are tested if the exception is of class Exception1 handler 1 is executed otherwise if it s of class Exception2 handler 2 is executed and so forth If no exception is raised the else block is executed No matter what happened previously the final block is executed once the code block is complete and any raised exceptions handled Even if there s an error in an exception handler or the else block and a new exception is raised the code in the final block is still run See also PEP 341 Unifying try except and try finally PEP written by Georg Brandl implementation by Thomas Lee PEP 342 New Generator Features Python 2 5 adds a simple way to pass values into a generator As introduced in Python 2 3 generators only produce output once a generator s code was invoked to create an iterator there was no way to pass any new information into the function when its execution is resumed Sometimes the ability to pass in some information would be useful Hackish solutions to this include making the generator s code look at a global variable and then changing the global variable s value or passing in some mutable object that callers then modify To refresh your memory of basic generators here s a simple example def counter maximum i 0 while i maximum yield i i 1 When you call counter 10 the result is an iterator that returns the values from 0 up to 9 On encountering the yield statement the iterator returns the provided value and suspends the function s execution preserving the local variables Execution resumes on the following call to the iterator s next method picking up after the yield statement In Python 2 3 yield was a statement it didn t return any value In 2 5 yield is now an expression returning a value that can be assigned to a variable or otherwise operated on val yield i I recommend that you always put parentheses around a yield expression when you re doing something with the returned value as in the above example The parentheses aren t always necessary but it s easier to always add them instead of having to remember when they re needed PEP 342 explains the exact rules which are that a yield expression must always be parenthesized except when it occurs at the top level expression on the right hand side of an assignment This means you can write val yield i but have to use parentheses when there s an operation as in val yield i 12 Values are sent into a generator by calling its send value method The generator s code is then resumed and the yield expression returns the specified value If the regular next method is called the yield returns None Here s the previous example modified to allow changing the value of t,en
1437,he internal counter def counter maximum i 0 while i maximum val yield i If value provided change counter if val is not None i val else i 1 And here s an example of changing the counter it counter 10 print it next 0 print it next 1 print it send 8 8 print it next 9 print it next Traceback most recent call last File t py line 15 in print it next StopIteration yield will usually return None so you should always check for this case Don t just use its value in expressions unless you re sure that the send method will be the only method used to resume your generator function In addition to send there are two other new methods on generators throw type value None traceback None is used to raise an exception inside the generator the exception is raised by the yield expression where the generator s execution is paused close raises a new GeneratorExit exception inside the generator to terminate the iteration On receiving this exception the generator s code must either raise GeneratorExit or StopIteration Catching the GeneratorExit exception and returning a value is illegal and will trigger a RuntimeError if the function raises some other exception that exception is propagated to the caller close will also be called by Python s garbage collector when the generator is garbage collected If you need to run cleanup code when a GeneratorExit occurs I suggest using a try finally suite instead of catching GeneratorExit The cumulative effect of these changes is to turn generators from one way producers of information into both producers and consumers Generators also become coroutines a more generalized form of subroutines Subroutines are entered at one point and exited at another point the top of the function and a return statement but coroutines can be entered exited and resumed at many different points the yield statements We ll have to figure out patterns for using coroutines effectively in Python The addition of the close method has one side effect that isn t obvious close is called when a generator is garbage collected so this means the generator s code gets one last chance to run before the generator is destroyed This last chance means that try finally statements in generators can now be guaranteed to work the finally clause will now always get a chance to run The syntactic restriction that you couldn t mix yield statements with a try finally suite has therefore been removed This seems like a minor bit of language trivia but using generators and try finally is actually necessary in order to implement the with statement described by PEP 343 I ll look at this new statement in the following section Another even more esoteric effect of this change previously the gi_frame attribute of a generator was always a frame object It s now possible for gi_frame to be None once the generator has been exhausted See also PEP 342 Coroutines via Enhanced Generators PEP written by Guido van Rossum and Phillip J Eby implemented by Phillip J Eby Includes examples of some fancier uses of generators as coroutines Earlier versions of these features were proposed in PEP 288 by Raymond Hettinger and PEP 325 by Samuele Pedroni https en wikipedia org wiki Coroutine The Wikipedia entry for coroutines https web archive org web 20160321211320 http www sidhe org da n blog archives 000178 html An explanation of coroutines from a Perl point of view written by Dan Sugalski PEP 343 The with statement The with statement clarifies code that previously would use try finally blocks to ensure that clean up code is executed In this section I ll discuss the statement as it will commonly be used In the next section I ll examine the implementation details and show how to write objects for use with this statement The with statement is a new control flow structure whose basic structure is with expression as variable with block The expression is evaluated and it should result in an object that supports the context management protocol that is has __enter__ and __exit__ methods The object s __enter__ is called before with block is executed and therefore can run set up code It also may ,en
1438,return a value that is bound to the name variable if given Note carefully that variable is not assigned the result of expression After execution of the with block is finished the object s __exit__ method is called even if the block raised an exception and can therefore run clean up code To enable the statement in Python 2 5 you need to add the following directive to your module from __future__ import with_statement The statement will always be enabled in Python 2 6 Some standard Python objects now support the context management protocol and can be used with the with statement File objects are one example with open etc passwd r as f for line in f print line more processing code After this statement has executed the file object in f will have been automatically closed even if the for loop raised an exception part way through the block Note In this case f is the same object created by open because __enter__ returns self The threading module s locks and condition variables also support the with statement lock threading Lock with lock Critical section of code The lock is acquired before the block is executed and always released once the block is complete The new localcontext function in the decimal module makes it easy to save and restore the current decimal context which encapsulates the desired precision and rounding characteristics for computations from decimal import Decimal Context localcontext Displays with default precision of 28 digits v Decimal 578 print v sqrt with localcontext Context prec 16 All code in this block uses a precision of 16 digits The original context is restored on exiting the block print v sqrt Writing Context Managers Under the hood the with statement is fairly complicated Most people will only use with in company with existing objects and don t need to know these details so you can skip the rest of this section if you like Authors of new objects will need to understand the details of the underlying implementation and should keep reading A high level explanation of the context management protocol is The expression is evaluated and should result in an object called a context manager The context manager must have __enter__ and __exit__ methods The context manager s __enter__ method is called The value returned is assigned to VAR If no as VAR clause is present the value is simply discarded The code in BLOCK is executed If BLOCK raises an exception the __exit__ type value traceback is called with the exception details the same values returned by sys exc_info The method s return value controls whether the exception is re raised any false value re raises the exception and True will result in suppressing it You ll only rarely want to suppress the exception because if you do the author of the code containing the with statement will never realize anything went wrong If BLOCK didn t raise an exception the __exit__ method is still called but type value and traceback are all None Let s think through an example I won t present detailed code but will only sketch the methods necessary for a database that supports transactions For people unfamiliar with database terminology a set of changes to the database are grouped into a transaction Transactions can be either committed meaning that all the changes are written into the database or rolled back meaning that the changes are all discarded and the database is unchanged See any database textbook for more information Let s assume there s an object representing a database connection Our goal will be to let the user write code like this db_connection DatabaseConnection with db_connection as cursor cursor execute insert into cursor execute delete from more operations The transaction should be committed if the code in the block runs flawlessly or rolled back if there s an exception Here s the basic interface for DatabaseConnection that I ll assume class DatabaseConnection Database interface def cursor self Returns a cursor object and starts a new transaction def commit self Commits current transaction def rollback self Rolls back current transaction The __enter__ method i,en
1439,s pretty easy having only to start a new transaction For this application the resulting cursor object would be a useful result so the method will return it The user can then add as cursor to their with statement to bind the cursor to a variable name class DatabaseConnection def __enter__ self Code to start a new transaction cursor self cursor return cursor The __exit__ method is the most complicated because it s where most of the work has to be done The method has to check if an exception occurred If there was no exception the transaction is committed The transaction is rolled back if there was an exception In the code below execution will just fall off the end of the function returning the default value of None None is false so the exception will be re raised automatically If you wished you could be more explicit and add a return statement at the marked location class DatabaseConnection def __exit__ self type value tb if tb is None No exception so commit self commit else Exception occurred so rollback self rollback return False The contextlib module The new contextlib module provides some functions and a decorator that are useful for writing objects for use with the with statement The decorator is called contextmanager and lets you write a single generator function instead of defining a new class The generator should yield exactly one value The code up to the yield will be executed as the __enter__ method and the value yielded will be the method s return value that will get bound to the variable in the with statement s as clause if any The code after the yield will be executed in the __exit__ method Any exception raised in the block will be raised by the yield statement Our database example from the previous section could be written using this decorator as from contextlib import contextmanager contextmanager def db_transaction connection cursor connection cursor try yield cursor except connection rollback raise else connection commit db DatabaseConnection with db_transaction db as cursor The contextlib module also has a nested mgr1 mgr2 function that combines a number of context managers so you don t need to write nested with statements In this example the single with statement both starts a database transaction and acquires a thread lock lock threading Lock with nested db_transaction db lock as cursor locked Finally the closing object function returns object so that it can be bound to a variable and calls object close at the end of the block import urllib sys from contextlib import closing with closing urllib urlopen http www yahoo com as f for line in f sys stdout write line See also PEP 343 The with statement PEP written by Guido van Rossum and Nick Coghlan implemented by Mike Bland Guido van Rossum and Neal Norwitz The PEP shows the code generated for a with statement which can be helpful in learning how the statement works The documentation for the contextlib module PEP 352 Exceptions as New Style Classes Exception classes can now be new style classes not just classic classes and the built in Exception class and all the standard built in exceptions NameError ValueError etc are now new style classes The inheritance hierarchy for exceptions has been rearranged a bit In 2 5 the inheritance relationships are BaseException New in Python 2 5 KeyboardInterrupt SystemExit Exception all other current built in exceptions This rearrangement was done because people often want to catch all exceptions that indicate program errors KeyboardInterrupt and SystemExit aren t errors though and usually represent an explicit action such as the user hitting Control C or code calling sys exit A bare except will catch all exceptions so you commonly need to list KeyboardInterrupt and SystemExit in order to re raise them The usual pattern is try except KeyboardInterrupt SystemExit raise except Log error Continue running program In Python 2 5 you can now write except Exception to achieve the same result catching all the exceptions that usually indicate errors but leaving KeyboardInterrupt and SystemExit alone As in previous versions a bare exc,en
1440,ept still catches all exceptions The goal for Python 3 0 is to require any class raised as an exception to derive from BaseException or some descendant of BaseException and future releases in the Python 2 x series may begin to enforce this constraint Therefore I suggest you begin making all your exception classes derive from Exception now It s been suggested that the bare except form should be removed in Python 3 0 but Guido van Rossum hasn t decided whether to do this or not Raising of strings as exceptions as in the statement raise Error occurred is deprecated in Python 2 5 and will trigger a warning The aim is to be able to remove the string exception feature in a few releases See also PEP 352 Required Superclass for Exceptions PEP written by Brett Cannon and Guido van Rossum implemented by Brett Cannon PEP 353 Using ssize_t as the index type A wide ranging change to Python s C API using a new Py_ssize_t type definition instead of int will permit the interpreter to handle more data on 64 bit platforms This change doesn t affect Python s capacity on 32 bit platforms Various pieces of the Python interpreter used C s int type to store sizes or counts for example the number of items in a list or tuple were stored in an int The C compilers for most 64 bit platforms still define int as a 32 bit type so that meant that lists could only hold up to 2 31 1 2147483647 items There are actually a few different programming models that 64 bit C compilers can use see https unix org version2 whatsnew lp64_wp html for a discussion but the most commonly available model leaves int as 32 bits A limit of 2147483647 items doesn t really matter on a 32 bit platform because you ll run out of memory before hitting the length limit Each list item requires space for a pointer which is 4 bytes plus space for a PyObject representing the item 2147483647 4 is already more bytes than a 32 bit address space can contain It s possible to address that much memory on a 64 bit platform however The pointers for a list that size would only require 16 GiB of space so it s not unreasonable that Python programmers might construct lists that large Therefore the Python interpreter had to be changed to use some type other than int and this will be a 64 bit type on 64 bit platforms The change will cause incompatibilities on 64 bit machines so it was deemed worth making the transition now while the number of 64 bit users is still relatively small In 5 or 10 years we may all be on 64 bit machines and the transition would be more painful then This change most strongly affects authors of C extension modules Python strings and container types such as lists and tuples now use Py_ssize_t to store their size Functions such as PyList_Size now return Py_ssize_t Code in extension modules may therefore need to have some variables changed to Py_ssize_t The PyArg_ParseTuple and Py_BuildValue functions have a new conversion code n for Py_ssize_t PyArg_ParseTuple s s and t still output int by default but you can define the macro PY_SSIZE_T_CLEAN before including Python h to make them return Py_ssize_t PEP 353 has a section on conversion guidelines that extension authors should read to learn about supporting 64 bit platforms See also PEP 353 Using ssize_t as the index type PEP written and implemented by Martin von Löwis PEP 357 The __index__ method The NumPy developers had a problem that could only be solved by adding a new special method __index__ When using slice notation as in start stop step the values of the start stop and step indexes must all be either integers or long integers NumPy defines a variety of specialized integer types corresponding to unsigned and signed integers of 8 16 32 and 64 bits but there was no way to signal that these types could be used as slice indexes Slicing can t just use the existing __int__ method because that method is also used to implement coercion to integers If slicing used __int__ floating point numbers would also become legal slice indexes and that s clearly an undesirable behaviour Instead a new special method called __index__ was added It,en
1441, takes no arguments and returns an integer giving the slice index to use For example class C def __index__ self return self value The return value must be either a Python integer or long integer The interpreter will check that the type returned is correct and raises a TypeError if this requirement isn t met A corresponding nb_index slot was added to the C level PyNumberMethods structure to let C extensions implement this protocol PyNumber_Index obj can be used in extension code to call the __index__ function and retrieve its result See also PEP 357 Allowing Any Object to be Used for Slicing PEP written and implemented by Travis Oliphant Other Language Changes Here are all of the changes that Python 2 5 makes to the core Python language The dict type has a new hook for letting subclasses provide a default value when a key isn t contained in the dictionary When a key isn t found the dictionary s __missing__ key method will be called This hook is used to implement the new defaultdict class in the collections module The following example defines a dictionary that returns zero for any missing key class zerodict dict def __missing__ self key return 0 d zerodict 1 1 2 2 print d 1 d 2 Prints 1 2 print d 3 d 4 Prints 0 0 Both 8 bit and Unicode strings have new partition sep and rpartition sep methods that simplify a common use case The find S method is often used to get an index which is then used to slice the string and obtain the pieces that are before and after the separator partition sep condenses this pattern into a single method call that returns a 3 tuple containing the substring before the separator the separator itself and the substring after the separator If the separator isn t found the first element of the tuple is the entire string and the other two elements are empty rpartition sep also returns a 3 tuple but starts searching from the end of the string the r stands for reverse Some examples http www python org partition http www python org file usr share doc index html partition file usr share doc index html u Subject a quick question partition u Subject u u a quick question www python org rpartition www python org www python org rpartition www python org Implemented by Fredrik Lundh following a suggestion by Raymond Hettinger The startswith and endswith methods of string types now accept tuples of strings to check for def is_image_file filename return filename endswith gif jpg tiff Implemented by Georg Brandl following a suggestion by Tom Lynn The min and max built in functions gained a key keyword parameter analogous to the key argument for sort This parameter supplies a function that takes a single argument and is called for every value in the list min max will return the element with the smallest largest return value from this function For example to find the longest string in a list you can do L medium longest short Prints longest print max L key len Prints short because lexicographically short has the largest value print max L Contributed by Steven Bethard and Raymond Hettinger Two new built in functions any and all evaluate whether an iterator contains any true or false values any returns True if any value returned by the iterator is true otherwise it will return False all returns True only if all of the values returned by the iterator evaluate as true Suggested by Guido van Rossum and implemented by Raymond Hettinger The result of a class s __hash__ method can now be either a long integer or a regular integer If a long integer is returned the hash of that value is taken In earlier versions the hash value was required to be a regular integer but in 2 5 the id built in was changed to always return non negative numbers and users often seem to use id self in __hash__ methods though this is discouraged ASCII is now the default encoding for modules It s now a syntax error if a module contains string literals with 8 bit characters but doesn t have an encoding declaration In Python 2 4 this triggered a warning not a syntax error See PEP 263 for how to declare a module s encoding for example you might add a line like ,en
1442,this near the top of the source file coding latin1 A new warning UnicodeWarning is triggered when you attempt to compare a Unicode string and an 8 bit string that can t be converted to Unicode using the default ASCII encoding The result of the comparison is false chr 128 unichr 128 Can t convert chr 128 to Unicode __main__ 1 UnicodeWarning Unicode equal comparison failed to convert both arguments to Unicode interpreting them as being unequal False chr 127 unichr 127 chr 127 can be converted True Previously this would raise a UnicodeDecodeError exception but in 2 5 this could result in puzzling problems when accessing a dictionary If you looked up unichr 128 and chr 128 was being used as a key you d get a UnicodeDecodeError exception Other changes in 2 5 resulted in this exception being raised instead of suppressed by the code in dictobject c that implements dictionaries Raising an exception for such a comparison is strictly correct but the change might have broken code so instead UnicodeWarning was introduced Implemented by Marc André Lemburg One error that Python programmers sometimes make is forgetting to include an __init__ py module in a package directory Debugging this mistake can be confusing and usually requires running Python with the v switch to log all the paths searched In Python 2 5 a new ImportWarning warning is triggered when an import would have picked up a directory as a package but no __init__ py was found This warning is silently ignored by default provide the Wd option when running the Python executable to display the warning message Implemented by Thomas Wouters The list of base classes in a class definition can now be empty As an example this is now legal class C pass Implemented by Brett Cannon Interactive Interpreter Changes In the interactive interpreter quit and exit have long been strings so that new users get a somewhat helpful message when they try to quit quit Use Ctrl D i e EOF to exit In Python 2 5 quit and exit are now objects that still produce string representations of themselves but are also callable Newbies who try quit or exit will now exit the interpreter as they expect Implemented by Georg Brandl The Python executable now accepts the standard long options help and version on Windows it also accepts the option for displaying a help message Implemented by Georg Brandl Optimizations Several of the optimizations were developed at the NeedForSpeed sprint an event held in Reykjavik Iceland from May 21 28 2006 The sprint focused on speed enhancements to the CPython implementation and was funded by EWT LLC with local support from CCP Games Those optimizations added at this sprint are specially marked in the following list When they were introduced in Python 2 4 the built in set and frozenset types were built on top of Python s dictionary type In 2 5 the internal data structure has been customized for implementing sets and as a result sets will use a third less memory and are somewhat faster Implemented by Raymond Hettinger The speed of some Unicode operations such as finding substrings string splitting and character map encoding and decoding has been improved Substring search and splitting improvements were added by Fredrik Lundh and Andrew Dalke at the NeedForSpeed sprint Character maps were improved by Walter Dörwald and Martin von Löwis The long str base function is now faster on long digit strings because fewer intermediate results are calculated The peak is for strings of around 800 1000 digits where the function is 6 times faster Contributed by Alan McIntyre and committed at the NeedForSpeed sprint It s now illegal to mix iterating over a file with for line in file and calling the file object s read readline readlines methods Iteration uses an internal buffer and the read methods don t use that buffer Instead they would return the data following the buffer causing the data to appear out of order Mixing iteration and these methods will now trigger a ValueError from the read method Implemented by Thomas Wouters The struct module now compiles structure format strings into an internal rep,en
1443,resentation and caches this representation yielding a 20 speedup Contributed by Bob Ippolito at the NeedForSpeed sprint The re module got a 1 or 2 speedup by switching to Python s allocator functions instead of the system s malloc and free Contributed by Jack Diederich at the NeedForSpeed sprint The code generator s peephole optimizer now performs simple constant folding in expressions If you write something like a 2 3 the code generator will do the arithmetic and produce code corresponding to a 5 Proposed and implemented by Raymond Hettinger Function calls are now faster because code objects now keep the most recently finished frame a zombie frame in an internal field of the code object reusing it the next time the code object is invoked Original patch by Michael Hudson modified by Armin Rigo and Richard Jones committed at the NeedForSpeed sprint Frame objects are also slightly smaller which may improve cache locality and reduce memory usage a bit Contributed by Neal Norwitz Python s built in exceptions are now new style classes a change that speeds up instantiation considerably Exception handling in Python 2 5 is therefore about 30 faster than in 2 4 Contributed by Richard Jones Georg Brandl and Sean Reifschneider at the NeedForSpeed sprint Importing now caches the paths tried recording whether they exist or not so that the interpreter makes fewer open and stat calls on startup Contributed by Martin von Löwis and Georg Brandl New Improved and Removed Modules The standard library received many enhancements and bug fixes in Python 2 5 Here s a partial list of the most notable changes sorted alphabetically by module name Consult the Misc NEWS file in the source tree for a more complete list of changes or look through the SVN logs for all the details The audioop module now supports the a LAW encoding and the code for u LAW encoding has been improved Contributed by Lars Immisch The codecs module gained support for incremental codecs The codec lookup function now returns a CodecInfo instance instead of a tuple CodecInfo instances behave like a 4 tuple to preserve backward compatibility but also have the attributes encode decode incrementalencoder incrementaldecoder streamwriter and streamreader Incremental codecs can receive input and produce output in multiple chunks the output is the same as if the entire input was fed to the non incremental codec See the codecs module documentation for details Designed and implemented by Walter Dörwald The collections module gained a new type defaultdict that subclasses the standard dict type The new type mostly behaves like a dictionary but constructs a default value when a key isn t present automatically adding it to the dictionary for the requested key value The first argument to defaultdict s constructor is a factory function that gets called whenever a key is requested but not found This factory function receives no arguments so you can use built in type constructors such as list or int For example you can make an index of words based on their initial letter like this words Nel mezzo del cammin di nostra vita mi ritrovai per una selva oscura che la diritta via era smarrita lower split index defaultdict list for w in words init_letter w 0 index init_letter append w Printing index results in the following output defaultdict type list c cammin che e era d del di diritta m mezzo mi l la o oscura n nel nostra p per s selva smarrita r ritrovai u una v vita via Contributed by Guido van Rossum The deque double ended queue type supplied by the collections module now has a remove value method that removes the first occurrence of value in the queue raising ValueError if the value isn t found Contributed by Raymond Hettinger New module The contextlib module contains helper functions for use with the new with statement See section The contextlib module for more about this module New module The cProfile module is a C implementation of the existing profile module that has much lower overhead The module s interface is the same as profile you run cProfile run main to profile a function can save profi,en
1444,le data to a file etc It s not yet known if the Hotshot profiler which is also written in C but doesn t match the profile module s interface will continue to be maintained in future versions of Python Contributed by Armin Rigo Also the pstats module for analyzing the data measured by the profiler now supports directing the output to any file object by supplying a stream argument to the Stats constructor Contributed by Skip Montanaro The csv module which parses files in comma separated value format received several enhancements and a number of bugfixes You can now set the maximum size in bytes of a field by calling the csv field_size_limit new_limit function omitting the new_limit argument will return the currently set limit The reader class now has a line_num attribute that counts the number of physical lines read from the source records can span multiple physical lines so line_num is not the same as the number of records read The CSV parser is now stricter about multi line quoted fields Previously if a line ended within a quoted field without a terminating newline character a newline would be inserted into the returned field This behavior caused problems when reading files that contained carriage return characters within fields so the code was changed to return the field without inserting newlines As a consequence if newlines embedded within fields are important the input should be split into lines in a manner that preserves the newline characters Contributed by Skip Montanaro and Andrew McNamara The datetime class in the datetime module now has a strptime string format method for parsing date strings contributed by Josh Spoerri It uses the same format characters as time strptime and time strftime from datetime import datetime ts datetime strptime 10 13 15 2006 03 07 H M S Y m d The SequenceMatcher get_matching_blocks method in the difflib module now guarantees to return a minimal list of blocks describing matching subsequences Previously the algorithm would occasionally break a block of matching elements into two list entries Enhancement by Tim Peters The doctest module gained a SKIP option that keeps an example from being executed at all This is intended for code snippets that are usage examples intended for the reader and aren t actually test cases An encoding parameter was added to the testfile function and the DocFileSuite class to specify the file s encoding This makes it easier to use non ASCII characters in tests contained within a docstring Contributed by Bjorn Tillenius The email package has been updated to version 4 0 Contributed by Barry Warsaw The fileinput module was made more flexible Unicode filenames are now supported and a mode parameter that defaults to r was added to the input function to allow opening files in binary or universal newlines mode Another new parameter openhook lets you use a function other than open to open the input files Once you re iterating over the set of files the FileInput object s new fileno returns the file descriptor for the currently opened file Contributed by Georg Brandl In the gc module the new get_count function returns a 3 tuple containing the current collection counts for the three GC generations This is accounting information for the garbage collector when these counts reach a specified threshold a garbage collection sweep will be made The existing gc collect function now takes an optional generation argument of 0 1 or 2 to specify which generation to collect Contributed by Barry Warsaw The nsmallest and nlargest functions in the heapq module now support a key keyword parameter similar to the one provided by the min max functions and the sort methods For example import heapq L short medium longest longer still heapq nsmallest 2 L Return two lowest elements lexicographically longer still longest heapq nsmallest 2 L key len Return two shortest elements short medium Contributed by Raymond Hettinger The itertools islice function now accepts None for the start and step arguments This makes it more compatible with the attributes of slice objects so that you can now write th,en
1445,e following s slice 5 Create slice object itertools islice iterable s start s stop s step Contributed by Raymond Hettinger The format function in the locale module has been modified and two new functions were added format_string and currency The format function s val parameter could previously be a string as long as no more than one char specifier appeared now the parameter must be exactly one char specifier with no surrounding text An optional monetary parameter was also added which if True will use the locale s rules for formatting currency in placing a separator between groups of three digits To format strings with multiple char specifiers use the new format_string function that works like format but also supports mixing char specifiers with arbitrary text A new currency function was also added that formats a number according to the current locale s settings Contributed by Georg Brandl The mailbox module underwent a massive rewrite to add the capability to modify mailboxes in addition to reading them A new set of classes that include mbox MH and Maildir are used to read mailboxes and have an add message method to add messages remove key to remove messages and lock unlock to lock unlock the mailbox The following example converts a maildir format mailbox into an mbox format one import mailbox factory None uses email Message Message as the class representing individual messages src mailbox Maildir maildir factory None dest mailbox mbox tmp mbox for msg in src dest add msg Contributed by Gregory K Johnson Funding was provided by Google s 2005 Summer of Code New module the msilib module allows creating Microsoft Installer msi files and CAB files Some support for reading the msi database is also included Contributed by Martin von Löwis The nis module now supports accessing domains other than the system default domain by supplying a domain argument to the nis match and nis maps functions Contributed by Ben Bell The operator module s itemgetter and attrgetter functions now support multiple fields A call such as operator attrgetter a b will return a function that retrieves the a and b attributes Combining this new feature with the sort method s key parameter lets you easily sort lists using multiple fields Contributed by Raymond Hettinger The optparse module was updated to version 1 5 1 of the Optik library The OptionParser class gained an epilog attribute a string that will be printed after the help message and a destroy method to break reference cycles created by the object Contributed by Greg Ward The os module underwent several changes The stat_float_times variable now defaults to true meaning that os stat will now return time values as floats This doesn t necessarily mean that os stat will return times that are precise to fractions of a second not all systems support such precision Constants named os SEEK_SET os SEEK_CUR and os SEEK_END have been added these are the parameters to the os lseek function Two new constants for locking are os O_SHLOCK and os O_EXLOCK Two new functions wait3 and wait4 were added They re similar the waitpid function which waits for a child process to exit and returns a tuple of the process ID and its exit status but wait3 and wait4 return additional information wait3 doesn t take a process ID as input so it waits for any child process to exit and returns a 3 tuple of process id exit status resource usage as returned from the resource getrusage function wait4 pid does take a process ID Contributed by Chad J Schroeder On FreeBSD the os stat function now returns times with nanosecond resolution and the returned object now has st_gen and st_birthtime The st_flags attribute is also available if the platform supports it Contributed by Antti Louko and Diego Pettenò The Python debugger provided by the pdb module can now store lists of commands to execute when a breakpoint is reached and execution stops Once breakpoint 1 has been created enter commands 1 and enter a series of commands to be executed finishing the list with end The command list can include commands that resume execution such as continue o,en
1446,r next Contributed by Grégoire Dooms The pickle and cPickle modules no longer accept a return value of None from the __reduce__ method the method must return a tuple of arguments instead The ability to return None was deprecated in Python 2 4 so this completes the removal of the feature The pkgutil module containing various utility functions for finding packages was enhanced to support PEP 302 s import hooks and now also works for packages stored in ZIP format archives Contributed by Phillip J Eby The pybench benchmark suite by Marc André Lemburg is now included in the Tools pybench directory The pybench suite is an improvement on the commonly used pystone py program because pybench provides a more detailed measurement of the interpreter s speed It times particular operations such as function calls tuple slicing method lookups and numeric operations instead of performing many different operations and reducing the result to a single number as pystone py does The pyexpat module now uses version 2 0 of the Expat parser Contributed by Trent Mick The Queue class provided by the Queue module gained two new methods join blocks until all items in the queue have been retrieved and all processing work on the items have been completed Worker threads call the other new method task_done to signal that processing for an item has been completed Contributed by Raymond Hettinger The old regex and regsub modules which have been deprecated ever since Python 2 0 have finally been deleted Other deleted modules statcache tzparse whrandom Also deleted the lib old directory which includes ancient modules such as dircmp and ni was removed lib old wasn t on the default sys path so unless your programs explicitly added the directory to sys path this removal shouldn t affect your code The rlcompleter module is no longer dependent on importing the readline module and therefore now works on non Unix platforms Patch from Robert Kiendl The SimpleXMLRPCServer and DocXMLRPCServer classes now have a rpc_paths attribute that constrains XML RPC operations to a limited set of URL paths the default is to allow only and RPC2 Setting rpc_paths to None or an empty tuple disables this path checking The socket module now supports AF_NETLINK sockets on Linux thanks to a patch from Philippe Biondi Netlink sockets are a Linux specific mechanism for communications between a user space process and kernel code an introductory article about them is at https www linuxjournal com article 7356 In Python code netlink addresses are represented as a tuple of 2 integers pid group_mask Two new methods on socket objects recv_into buffer and recvfrom_into buffer store the received data in an object that supports the buffer protocol instead of returning the data as a string This means you can put the data directly into an array or a memory mapped file Socket objects also gained getfamily gettype and getproto accessor methods to retrieve the family type and protocol values for the socket New module the spwd module provides functions for accessing the shadow password database on systems that support shadow passwords The struct is now faster because it compiles format strings into Struct objects with pack and unpack methods This is similar to how the re module lets you create compiled regular expression objects You can still use the module level pack and unpack functions they ll create Struct objects and cache them Or you can use Struct instances directly s struct Struct ih3s data s pack 1972 187 abc year number name s unpack data You can also pack and unpack data to and from buffer objects directly using the pack_into buffer offset v1 v2 and unpack_from buffer offset methods This lets you store data directly into an array or a memory mapped file Struct objects were implemented by Bob Ippolito at the NeedForSpeed sprint Support for buffer objects was added by Martin Blais also at the NeedForSpeed sprint The Python developers switched from CVS to Subversion during the 2 5 development process Information about the exact build version is available as the sys subversion variable a 3 tuple,en
1447, of interpreter name branch name revision range For example at the time of writing my copy of 2 5 was reporting CPython trunk 45313 45315 This information is also available to C extensions via the Py_GetBuildInfo function that returns a string of build information like this trunk 45355 45356M Apr 13 2006 07 42 19 Contributed by Barry Warsaw Another new function sys _current_frames returns the current stack frames for all running threads as a dictionary mapping thread identifiers to the topmost stack frame currently active in that thread at the time the function is called Contributed by Tim Peters The TarFile class in the tarfile module now has an extractall method that extracts all members from the archive into the current working directory It s also possible to set a different directory as the extraction target and to unpack only a subset of the archive s members The compression used for a tarfile opened in stream mode can now be autodetected using the mode r Contributed by Lars Gustäbel The threading module now lets you set the stack size used when new threads are created The stack_size size function returns the currently configured stack size and supplying the optional size parameter sets a new value Not all platforms support changing the stack size but Windows POSIX threading and OS 2 all do Contributed by Andrew MacIntyre The unicodedata module has been updated to use version 4 1 0 of the Unicode character database Version 3 2 0 is required by some specifications so it s still available as unicodedata ucd_3_2_0 New module the uuid module generates universally unique identifiers UUIDs according to RFC 4122 The RFC defines several different UUID versions that are generated from a starting string from system properties or purely randomly This module contains a UUID class and functions named uuid1 uuid3 uuid4 and uuid5 to generate different versions of UUID Version 2 UUIDs are not specified in RFC 4122 and are not supported by this module import uuid make a UUID based on the host ID and current time uuid uuid1 UUID a8098c1a f86e 11da bd1a 00112444be1e make a UUID using an MD5 hash of a namespace UUID and a name uuid uuid3 uuid NAMESPACE_DNS python org UUID 6fa459ea ee8a 3ca4 894e db77e160355e make a random UUID uuid uuid4 UUID 16fd2706 8baf 433b 82eb 8c7fada847da make a UUID using a SHA 1 hash of a namespace UUID and a name uuid uuid5 uuid NAMESPACE_DNS python org UUID 886313e1 3b8a 5372 9b90 0c9aee199e5d Contributed by Ka Ping Yee The weakref module s WeakKeyDictionary and WeakValueDictionary types gained new methods for iterating over the weak references contained in the dictionary iterkeyrefs and keyrefs methods were added to WeakKeyDictionary and itervaluerefs and valuerefs were added to WeakValueDictionary Contributed by Fred L Drake Jr The webbrowser module received a number of enhancements It s now usable as a script with python m webbrowser taking a URL as the argument there are a number of switches to control the behaviour n for a new browser window t for a new tab New module level functions open_new and open_new_tab were added to support this The module s open function supports an additional feature an autoraise parameter that signals whether to raise the open window when possible A number of additional browsers were added to the supported list such as Firefox Opera Konqueror and elinks Contributed by Oleg Broytmann and Georg Brandl The xmlrpclib module now supports returning datetime objects for the XML RPC date type Supply use_datetime True to the loads function or the Unmarshaller class to enable this feature Contributed by Skip Montanaro The zipfile module now supports the ZIP64 version of the format meaning that a zip archive can now be larger than 4 GiB and can contain individual files larger than 4 GiB Contributed by Ronald Oussoren The zlib module s Compress and Decompress objects now support a copy method that makes a copy of the object s internal state and returns a new Compress or Decompress object Contributed by Chris AtLee The ctypes package The ctypes package written by Thomas Heller has been add,en
1448,ed to the standard library ctypes lets you call arbitrary functions in shared libraries or DLLs Long time users may remember the dl module which provides functions for loading shared libraries and calling functions in them The ctypes package is much fancier To load a shared library or DLL you must create an instance of the CDLL class and provide the name or path of the shared library or DLL Once that s done you can call arbitrary functions by accessing them as attributes of the CDLL object import ctypes libc ctypes CDLL libc so 6 result libc printf Line of output n Type constructors for the various C types are provided c_int c_float c_double c_char_p equivalent to char and so forth Unlike Python s types the C versions are all mutable you can assign to their value attribute to change the wrapped value Python integers and strings will be automatically converted to the corresponding C types but for other types you must call the correct type constructor And I mean must getting it wrong will often result in the interpreter crashing with a segmentation fault You shouldn t use c_char_p with a Python string when the C function will be modifying the memory area because Python strings are supposed to be immutable breaking this rule will cause puzzling bugs When you need a modifiable memory area use create_string_buffer s this is a string buf ctypes create_string_buffer s libc strfry buf C functions are assumed to return integers but you can set the restype attribute of the function object to change this libc atof 2 71828 1783957616 libc atof restype ctypes c_double libc atof 2 71828 2 71828 ctypes also provides a wrapper for Python s C API as the ctypes pythonapi object This object does not release the global interpreter lock before calling a function because the lock must be held when calling into the interpreter s code There s a py_object type constructor that will create a PyObject pointer A simple usage import ctypes d ctypes pythonapi PyObject_SetItem ctypes py_object d ctypes py_object abc ctypes py_object 1 d is now abc 1 Don t forget to use py_object if it s omitted you end up with a segmentation fault ctypes has been around for a while but people still write and distribution hand coded extension modules because you can t rely on ctypes being present Perhaps developers will begin to write Python wrappers atop a library accessed through ctypes instead of extension modules now that ctypes is included with core Python See also https web archive org web 20180410025338 http starship python n et crew theller ctypes The pre stdlib ctypes web page with a tutorial reference and FAQ The documentation for the ctypes module The ElementTree package A subset of Fredrik Lundh s ElementTree library for processing XML has been added to the standard library as xml etree The available modules are ElementTree ElementPath and ElementInclude from ElementTree 1 2 6 The cElementTree accelerator module is also included The rest of this section will provide a brief overview of using ElementTree Full documentation for ElementTree is available at https web archive org web 20201124024954 http effbot org zone element index htm ElementTree represents an XML document as a tree of element nodes The text content of the document is stored as the text and tail attributes of This is one of the major differences between ElementTree and the Document Object Model in the DOM there are many different types of node including TextNode The most commonly used parsing function is parse that takes either a string assumed to contain a filename or a file like object and returns an ElementTree instance from xml etree import ElementTree as ET tree ET parse ex 1 xml feed urllib urlopen http planet python org rss10 xml tree ET parse feed Once you have an ElementTree instance you can call its getroot method to get the root Element node There s also an XML function that takes a string literal and returns an Element node not an ElementTree This function provides a tidy way to incorporate XML fragments approaching the convenience of an XML literal svg ET XML svg width 10px versio,en
1449,n 1 0 svg svg set height 320px svg append elem1 Each XML element supports some dictionary like and some list like access methods Dictionary like operations are used to access attribute values and list like operations are used to access child nodes Operation Result elem n Returns n th child element elem m n Returns list of m th through n th child elements len elem Returns number of child elements list elem Returns list of child elements elem append elem2 Adds elem2 as a child elem insert index elem2 Inserts elem2 at the specified location del elem n Deletes n th child element elem keys Returns list of attribute names elem get name Returns value of attribute name elem set name value Sets new value for attribute name elem attrib Retrieves the dictionary containing attributes del elem attrib name Deletes attribute name Comments and processing instructions are also represented as Element nodes To check if a node is a comment or processing instructions if elem tag is ET Comment elif elem tag is ET ProcessingInstruction To generate XML output you should call the ElementTree write method Like parse it can take either a string or a file like object Encoding is US ASCII tree write output xml Encoding is UTF 8 f open output xml w tree write f encoding utf 8 Caution the default encoding used for output is ASCII For general XML work where an element s name may contain arbitrary Unicode characters ASCII isn t a very useful encoding because it will raise an exception if an element s name contains any characters with values greater than 127 Therefore it s best to specify a different encoding such as UTF 8 that can handle any Unicode character This section is only a partial description of the ElementTree interfaces Please read the package s official documentation for more details See also https web archive org web 20201124024954 http effbot org zone element index htm Official documentation for ElementTree The hashlib package A new hashlib module written by Gregory P Smith has been added to replace the md5 and sha modules hashlib adds support for additional secure hashes SHA 224 SHA 256 SHA 384 and SHA 512 When available the module uses OpenSSL for fast platform optimized implementations of algorithms The old md5 and sha modules still exist as wrappers around hashlib to preserve backwards compatibility The new module s interface is very close to that of the old modules but not identical The most significant difference is that the constructor functions for creating new hashing objects are named differently Old versions h md5 md5 h md5 new New version h hashlib md5 Old versions h sha sha h sha new New version h hashlib sha1 Hash that weren t previously available h hashlib sha224 h hashlib sha256 h hashlib sha384 h hashlib sha512 Alternative form h hashlib new md5 Provide algorithm as a string Once a hash object has been created its methods are the same as before update string hashes the specified string into the current digest state digest and hexdigest return the digest value as a binary string or a string of hex digits and copy returns a new hashing object with the same digest state See also The documentation for the hashlib module The sqlite3 package The pysqlite module https www pysqlite org a wrapper for the SQLite embedded database has been added to the standard library under the package name sqlite3 SQLite is a C library that provides a lightweight disk based database that doesn t require a separate server process and allows accessing the database using a nonstandard variant of the SQL query language Some applications can use SQLite for internal data storage It s also possible to prototype an application using SQLite and then port the code to a larger database such as PostgreSQL or Oracle pysqlite was written by Gerhard Häring and provides a SQL interface compliant with the DB API 2 0 specification described by PEP 249 If you re compiling the Python source yourself note that the source tree doesn t include the SQLite code only the wrapper module You ll need to have the SQLite libraries and headers installed before compiling Python an,en
1450,d the build process will compile the module when the necessary headers are available To use the module you must first create a Connection object that represents the database Here the data will be stored in the tmp example file conn sqlite3 connect tmp example You can also supply the special name memory to create a database in RAM Once you have a Connection you can create a Cursor object and call its execute method to perform SQL commands c conn cursor Create table c execute create table stocks date text trans text symbol text qty real price real Insert a row of data c execute insert into stocks values 2006 01 05 BUY RHAT 100 35 14 Usually your SQL operations will need to use values from Python variables You shouldn t assemble your query using Python s string operations because doing so is insecure it makes your program vulnerable to an SQL injection attack Instead use the DB API s parameter substitution Put as a placeholder wherever you want to use a value and then provide a tuple of values as the second argument to the cursor s execute method Other database modules may use a different placeholder such as s or 1 For example Never do this insecure symbol IBM c execute where symbol s symbol Do this instead t symbol c execute select from stocks where symbol t Larger example for t in 2006 03 28 BUY IBM 1000 45 00 2006 04 05 BUY MSOFT 1000 72 00 2006 04 06 SELL IBM 500 53 00 c execute insert into stocks values t To retrieve data after executing a SELECT statement you can either treat the cursor as an iterator call the cursor s fetchone method to retrieve a single matching row or call fetchall to get a list of the matching rows This example uses the iterator form c conn cursor c execute select from stocks order by price for row in c print row u 2006 01 05 u BUY u RHAT 100 35 140000000000001 u 2006 03 28 u BUY u IBM 1000 45 0 u 2006 04 06 u SELL u IBM 500 53 0 u 2006 04 05 u BUY u MSOFT 1000 72 0 For more information about the SQL dialect supported by SQLite see https www sqlite org See also https www pysqlite org The pysqlite web page https www sqlite org The SQLite web page the documentation describes the syntax and the available data types for the supported SQL dialect The documentation for the sqlite3 module PEP 249 Database API Specification 2 0 PEP written by Marc André Lemburg The wsgiref package The Web Server Gateway Interface WSGI v1 0 defines a standard interface between web servers and Python web applications and is described in PEP 333 The wsgiref package is a reference implementation of the WSGI specification The package includes a basic HTTP server that will run a WSGI application this server is useful for debugging but isn t intended for production use Setting up a server takes only a few lines of code from wsgiref import simple_server wsgi_app host port 8000 httpd simple_server make_server host port wsgi_app httpd serve_forever See also https web archive org web 20160331090247 http wsgi readthedocs org en latest A central web site for WSGI related resources PEP 333 Python Web Server Gateway Interface v1 0 PEP written by Phillip J Eby Build and C API Changes Changes to Python s build process and to the C API include The Python source tree was converted from CVS to Subversion in a complex migration procedure that was supervised and flawlessly carried out by Martin von Löwis The procedure was developed as PEP 347 Coverity a company that markets a source code analysis tool called Prevent provided the results of their examination of the Python source code The analysis found about 60 bugs that were quickly fixed Many of the bugs were refcounting problems often occurring in error handling code See https scan coverity com for the statistics The largest change to the C API came from PEP 353 which modifies the interpreter to use a Py_ssize_t type definition instead of int See the earlier section PEP 353 Using ssize_t as the index type for a discussion of this change The design of the bytecode compiler has changed a great deal no longer generating bytecode by traversing the parse tree Instead the parse tree is converted t,en
1451,o an abstract syntax tree or AST and it is the abstract syntax tree that s traversed to produce the bytecode It s possible for Python code to obtain AST objects by using the compile built in and specifying _ast PyCF_ONLY_AST as the value of the flags parameter from _ast import PyCF_ONLY_AST ast compile a 0 for i in range 10 a i string exec PyCF_ONLY_AST assignment ast body 0 for_loop ast body 1 No official documentation has been written for the AST code yet but PEP 339 discusses the design To start learning about the code read the definition of the various AST nodes in Parser Python asdl A Python script reads this file and generates a set of C structure definitions in Include Python ast h The PyParser_ASTFromString and PyParser_ASTFromFile defined in Include pythonrun h take Python source as input and return the root of an AST representing the contents This AST can then be turned into a code object by PyAST_Compile For more information read the source code and then ask questions on python dev The AST code was developed under Jeremy Hylton s management and implemented by in alphabetical order Brett Cannon Nick Coghlan Grant Edwards John Ehresman Kurt Kaiser Neal Norwitz Tim Peters Armin Rigo and Neil Schemenauer plus the participants in a number of AST sprints at conferences such as PyCon Evan Jones s patch to obmalloc first described in a talk at PyCon DC 2005 was applied Python 2 4 allocated small objects in 256K sized arenas but never freed arenas With this patch Python will free arenas when they re empty The net effect is that on some platforms when you allocate many objects Python s memory usage may actually drop when you delete them and the memory may be returned to the operating system Implemented by Evan Jones and reworked by Tim Peters Note that this change means extension modules must be more careful when allocating memory Python s API has many different functions for allocating memory that are grouped into families For example PyMem_Malloc PyMem_Realloc and PyMem_Free are one family that allocates raw memory while PyObject_Malloc PyObject_Realloc and PyObject_Free are another family that s supposed to be used for creating Python objects Previously these different families all reduced to the platform s malloc and free functions This meant it didn t matter if you got things wrong and allocated memory with the PyMem function but freed it with the PyObject function With 2 5 s changes to obmalloc these families now do different things and mismatches will probably result in a segfault You should carefully test your C extension modules with Python 2 5 The built in set types now have an official C API Call PySet_New and PyFrozenSet_New to create a new set PySet_Add and PySet_Discard to add and remove elements and PySet_Contains and PySet_Size to examine the set s state Contributed by Raymond Hettinger C code can now obtain information about the exact revision of the Python interpreter by calling the Py_GetBuildInfo function that returns a string of build information like this trunk 45355 45356M Apr 13 2006 07 42 19 Contributed by Barry Warsaw Two new macros can be used to indicate C functions that are local to the current file so that a faster calling convention can be used Py_LOCAL type declares the function as returning a value of the specified type and uses a fast calling qualifier Py_LOCAL_INLINE type does the same thing and also requests the function be inlined If macro PY_LOCAL_AGGRESSIVE is defined before python h is included a set of more aggressive optimizations are enabled for the module you should benchmark the results to find out if these optimizations actually make the code faster Contributed by Fredrik Lundh at the NeedForSpeed sprint PyErr_NewException name base dict can now accept a tuple of base classes as its base argument Contributed by Georg Brandl The PyErr_Warn function for issuing warnings is now deprecated in favour of PyErr_WarnEx category message stacklevel which lets you specify the number of stack frames separating this function and the caller A stacklevel of 1 is the function calling PyErr_,en
1452,WarnEx 2 is the function above that and so forth Added by Neal Norwitz The CPython interpreter is still written in C but the code can now be compiled with a C compiler without errors Implemented by Anthony Baxter Martin von Löwis Skip Montanaro The PyRange_New function was removed It was never documented never used in the core code and had dangerously lax error checking In the unlikely case that your extensions were using it you can replace it by something like the following range PyObject_CallFunction PyObject PyRange_Type lll start stop step Port Specific Changes MacOS X 10 3 and higher dynamic loading of modules now uses the dlopen function instead of MacOS specific functions MacOS X an enable universalsdk switch was added to the configure script that compiles the interpreter as a universal binary able to run on both PowerPC and Intel processors Contributed by Ronald Oussoren bpo 2573 Windows dll is no longer supported as a filename extension for extension modules pyd is now the only filename extension that will be searched for Porting to Python 2 5 This section lists previously described changes that may require changes to your code ASCII is now the default encoding for modules It s now a syntax error if a module contains string literals with 8 bit characters but doesn t have an encoding declaration In Python 2 4 this triggered a warning not a syntax error Previously the gi_frame attribute of a generator was always a frame object Because of the PEP 342 changes described in section PEP 342 New Generator Features it s now possible for gi_frame to be None A new warning UnicodeWarning is triggered when you attempt to compare a Unicode string and an 8 bit string that can t be converted to Unicode using the default ASCII encoding Previously such comparisons would raise a UnicodeDecodeError exception Library the csv module is now stricter about multi line quoted fields If your files contain newlines embedded within fields the input should be split into lines in a manner which preserves the newline characters Library the locale module s format function s would previously accept any string as long as no more than one char specifier appeared In Python 2 5 the argument must be exactly one char specifier with no surrounding text Library The pickle and cPickle modules no longer accept a return value of None from the __reduce__ method the method must return a tuple of arguments instead The modules also no longer accept the deprecated bin keyword parameter Library The SimpleXMLRPCServer and DocXMLRPCServer classes now have a rpc_paths attribute that constrains XML RPC operations to a limited set of URL paths the default is to allow only and RPC2 Setting rpc_paths to None or an empty tuple disables this path checking C API Many functions now use Py_ssize_t instead of int to allow processing more data on 64 bit machines Extension code may need to make the same change to avoid warnings and to support 64 bit machines See the earlier section PEP 353 Using ssize_t as the index type for a discussion of this change C API The obmalloc changes mean that you must be careful to not mix usage of the PyMem_ and PyObject_ families of functions Memory allocated with one family s _Malloc must be freed with the corresponding family s _Free function Acknowledgements The author would like to thank the following people for offering suggestions corrections and assistance with various drafts of this article Georg Brandl Nick Coghlan Phillip J Eby Lars Gustäbel Raymond Hettinger Ralf W Grosse Kunstleve Kent Johnson Iain Lowe Martin von Löwis Fredrik Lundh Andrew McNamara Skip Montanaro Gustavo Niemeyer Paul Prescod James Pryor Mike Rovner Scott Weikart Barry Warsaw Thomas Wouters,en
1453,email iterators Iterators Source code Lib email iterators py Iterating over a message object tree is fairly easy with the Message walk method The email iterators module provides some useful higher level iterations over message object trees email iterators body_line_iterator msg decode False This iterates over all the payloads in all the subparts of msg returning the string payloads line by line It skips over all the subpart headers and it skips over any subpart with a payload that isn t a Python string This is somewhat equivalent to reading the flat text representation of the message from a file using readline skipping over all the intervening headers Optional decode is passed through to Message get_payload email iterators typed_subpart_iterator msg maintype text subtype None This iterates over all the subparts of msg returning only those subparts that match the MIME type specified by maintype and subtype Note that subtype is optional if omitted then subpart MIME type matching is done only with the main type maintype is optional too it defaults to text Thus by default typed_subpart_iterator returns each subpart that has a MIME type of text The following function has been added as a useful debugging tool It should not be considered part of the supported public interface for the package email iterators _structure msg fp None level 0 include_default False Prints an indented representation of the content types of the message object structure For example msg email message_from_file somefile _structure msg multipart mixed text plain text plain multipart digest message rfc822 text plain message rfc822 text plain message rfc822 text plain message rfc822 text plain message rfc822 text plain text plain Optional fp is a file like object to print the output to It must be suitable for Python s print function level is used internally include_default if true prints the default type as well,en
1454,winsound Sound playing interface for Windows The winsound module provides access to the basic sound playing machinery provided by Windows platforms It includes functions and several constants winsound Beep frequency duration Beep the PC s speaker The frequency parameter specifies frequency in hertz of the sound and must be in the range 37 through 32 767 The duration parameter specifies the number of milliseconds the sound should last If the system is not able to beep the speaker RuntimeError is raised winsound PlaySound sound flags Call the underlying PlaySound function from the Platform API The sound parameter may be a filename a system sound alias audio data as a bytes like object or None Its interpretation depends on the value of flags which can be a bitwise ORed combination of the constants described below If the sound parameter is None any currently playing waveform sound is stopped If the system indicates an error RuntimeError is raised winsound MessageBeep type MB_OK Call the underlying MessageBeep function from the Platform API This plays a sound as specified in the registry The type argument specifies which sound to play possible values are 1 MB_ICONASTERISK MB_ICONEXCLAMATION MB_ICONHAND MB_ICONQUESTION and MB_OK all described below The value 1 produces a simple beep this is the final fallback if a sound cannot be played otherwise If the system indicates an error RuntimeError is raised winsound SND_FILENAME The sound parameter is the name of a WAV file Do not use with SND_ALIAS winsound SND_ALIAS The sound parameter is a sound association name from the registry If the registry contains no such name play the system default sound unless SND_NODEFAULT is also specified If no default sound is registered raise RuntimeError Do not use with SND_FILENAME All Win32 systems support at least the following most systems support many more PlaySound name Corresponding Control Panel Sound name SystemAsterisk Asterisk SystemExclamation Exclamation SystemExit Exit Windows SystemHand Critical Stop SystemQuestion Question For example import winsound Play Windows exit sound winsound PlaySound SystemExit winsound SND_ALIAS Probably play Windows default sound if any is registered because probably isn t the registered name of any sound winsound PlaySound winsound SND_ALIAS winsound SND_LOOP Play the sound repeatedly The SND_ASYNC flag must also be used to avoid blocking Cannot be used with SND_MEMORY winsound SND_MEMORY The sound parameter to PlaySound is a memory image of a WAV file as a bytes like object Note This module does not support playing from a memory image asynchronously so a combination of this flag and SND_ASYNC will raise RuntimeError winsound SND_PURGE Stop playing all instances of the specified sound Note This flag is not supported on modern Windows platforms winsound SND_ASYNC Return immediately allowing sounds to play asynchronously winsound SND_NODEFAULT If the specified sound cannot be found do not play the system default sound winsound SND_NOSTOP Do not interrupt sounds currently playing winsound SND_NOWAIT Return immediately if the sound driver is busy Note This flag is not supported on modern Windows platforms winsound MB_ICONASTERISK Play the SystemDefault sound winsound MB_ICONEXCLAMATION Play the SystemExclamation sound winsound MB_ICONHAND Play the SystemHand sound winsound MB_ICONQUESTION Play the SystemQuestion sound winsound MB_OK Play the SystemDefault sound,en
1455,http cookies HTTP state management Source code Lib http cookies py The http cookies module defines classes for abstracting the concept of cookies an HTTP state management mechanism It supports both simple string only cookies and provides an abstraction for having any serializable data type as cookie value The module formerly strictly applied the parsing rules described in the RFC 2109 and RFC 2068 specifications It has since been discovered that MSIE 3 0x didn t follow the character rules outlined in those specs many current day browsers and servers have also relaxed parsing rules when it comes to cookie handling As a result this module now uses parsing rules that are a bit less strict than they once were The character set string ascii_letters string digits and _ denote the set of valid characters allowed by this module in a cookie name as key Changed in version 3 3 Allowed as a valid cookie name character Note On encountering an invalid cookie CookieError is raised so if your cookie data comes from a browser you should always prepare for invalid data and catch CookieError on parsing exception http cookies CookieError Exception failing because of RFC 2109 invalidity incorrect attributes incorrect Set Cookie header etc class http cookies BaseCookie input This class is a dictionary like object whose keys are strings and whose values are Morsel instances Note that upon setting a key to a value the value is first converted to a Morsel containing the key and the value If input is given it is passed to the load method class http cookies SimpleCookie input This class derives from BaseCookie and overrides value_decode and value_encode SimpleCookie supports strings as cookie values When setting the value SimpleCookie calls the builtin str to convert the value to a string Values received from HTTP are kept as strings See also Module http cookiejar HTTP cookie handling for web clients The http cookiejar and http cookies modules do not depend on each other RFC 2109 HTTP State Management Mechanism This is the state management specification implemented by this module Cookie Objects BaseCookie value_decode val Return a tuple real_value coded_value from a string representation real_value can be any type This method does no decoding in BaseCookie it exists so it can be overridden BaseCookie value_encode val Return a tuple real_value coded_value val can be any type but coded_value will always be converted to a string This method does no encoding in BaseCookie it exists so it can be overridden In general it should be the case that value_encode and value_decode are inverses on the range of value_decode BaseCookie output attrs None header Set Cookie sep r n Return a string representation suitable to be sent as HTTP headers attrs and header are sent to each Morsel s output method sep is used to join the headers together and is by default the combination r n CRLF BaseCookie js_output attrs None Return an embeddable JavaScript snippet which if run on a browser which supports JavaScript will act the same as if the HTTP headers was sent The meaning for attrs is the same as in output BaseCookie load rawdata If rawdata is a string parse it as an HTTP_COOKIE and add the values found there as Morsel s If it is a dictionary it is equivalent to for k v in rawdata items cookie k v Morsel Objects class http cookies Morsel Abstract a key value pair which has some RFC 2109 attributes Morsels are dictionary like objects whose set of keys is constant the valid RFC 2109 attributes which are expires path comment domain max age secure version httponly samesite The attribute httponly specifies that the cookie is only transferred in HTTP requests and is not accessible through JavaScript This is intended to mitigate some forms of cross site scripting The attribute samesite specifies that the browser is not allowed to send the cookie along with cross site requests This helps to mitigate CSRF attacks Valid values for this attribute are Strict and Lax The keys are case insensitive and their default value is Changed in version 3 5 __eq__ now takes key and value into a,en
1456,ccount Changed in version 3 7 Attributes key value and coded_value are read only Use set for setting them Changed in version 3 8 Added support for the samesite attribute Morsel value The value of the cookie Morsel coded_value The encoded value of the cookie this is what should be sent Morsel key The name of the cookie Morsel set key value coded_value Set the key value and coded_value attributes Morsel isReservedKey K Whether K is a member of the set of keys of a Morsel Morsel output attrs None header Set Cookie Return a string representation of the Morsel suitable to be sent as an HTTP header By default all the attributes are included unless attrs is given in which case it should be a list of attributes to use header is by default Set Cookie Morsel js_output attrs None Return an embeddable JavaScript snippet which if run on a browser which supports JavaScript will act the same as if the HTTP header was sent The meaning for attrs is the same as in output Morsel OutputString attrs None Return a string representing the Morsel without any surrounding HTTP or JavaScript The meaning for attrs is the same as in output Morsel update values Update the values in the Morsel dictionary with the values in the dictionary values Raise an error if any of the keys in the values dict is not a valid RFC 2109 attribute Changed in version 3 5 an error is raised for invalid keys Morsel copy value Return a shallow copy of the Morsel object Changed in version 3 5 return a Morsel object instead of a dict Morsel setdefault key value None Raise an error if key is not a valid RFC 2109 attribute otherwise behave the same as dict setdefault Example The following example demonstrates how to use the http cookies module from http import cookies C cookies SimpleCookie C fig newton C sugar wafer print C generate HTTP headers Set Cookie fig newton Set Cookie sugar wafer print C output same thing Set Cookie fig newton Set Cookie sugar wafer C cookies SimpleCookie C rocky road C rocky path cookie print C output header Cookie Cookie rocky road Path cookie print C output attrs header Cookie Cookie rocky road C cookies SimpleCookie C load chips ahoy vienna finger load from a string HTTP header print C Set Cookie chips ahoy Set Cookie vienna finger C cookies SimpleCookie C load keebler E everybody L Loves fudge 012 print C Set Cookie keebler E everybody L Loves fudge 012 C cookies SimpleCookie C oreo doublestuff C oreo path print C Set Cookie oreo doublestuff Path C cookies SimpleCookie C twix none for you C twix value none for you C cookies SimpleCookie C number 7 equivalent to C number str 7 C string seven C number value 7 C string value seven print C Set Cookie number 7 Set Cookie string seven,en
1457,modulefinder Find modules used by a script Source code Lib modulefinder py This module provides a ModuleFinder class that can be used to determine the set of modules imported by a script modulefinder py can also be run as a script giving the filename of a Python script as its argument after which a report of the imported modules will be printed modulefinder AddPackagePath pkg_name path Record that the package named pkg_name can be found in the specified path modulefinder ReplacePackage oldname newname Allows specifying that the module named oldname is in fact the package named newname class modulefinder ModuleFinder path None debug 0 excludes replace_paths This class provides run_script and report methods to determine the set of modules imported by a script path can be a list of directories to search for modules if not specified sys path is used debug sets the debugging level higher values make the class print debugging messages about what it s doing excludes is a list of module names to exclude from the analysis replace_paths is a list of oldpath newpath tuples that will be replaced in module paths report Print a report to standard output that lists the modules imported by the script and their paths as well as modules that are missing or seem to be missing run_script pathname Analyze the contents of the pathname file which must contain Python code modules A dictionary mapping module names to modules See Example usage of ModuleFinder Example usage of ModuleFinder The script that is going to get analyzed later on bacon py import re itertools try import baconhameggs except ImportError pass try import guido python ham except ImportError pass The script that will output the report of bacon py from modulefinder import ModuleFinder finder ModuleFinder finder run_script bacon py print Loaded modules for name mod in finder modules items print s name end print join list mod globalnames keys 3 print 50 print Modules not imported print n join finder badmodules keys Sample output may vary depending on the architecture Loaded modules _types copyreg _inverted_registry _slotnames __all__ re _compiler isstring _sre _optimize_unicode _sre re _constants REPEAT_ONE makedict AT_END_LINE sys re __module__ finditer _expand itertools __main__ re itertools baconhameggs re _parser _PATTERNENDERS SRE_FLAG_UNICODE array types __module__ IntType TypeType Modules not imported guido python ham baconhameggs,en
1458,Instance Method Objects An instance method is a wrapper for a PyCFunction and the new way to bind a PyCFunction to a class object It replaces the former call PyMethod_New func NULL class PyTypeObject PyInstanceMethod_Type This instance of PyTypeObject represents the Python instance method type It is not exposed to Python programs int PyInstanceMethod_Check PyObject o Return true if o is an instance method object has type PyInstanceMethod_Type The parameter must not be NULL This function always succeeds PyObject PyInstanceMethod_New PyObject func Return value New reference Return a new instance method object with func being any callable object func is the function that will be called when the instance method is called PyObject PyInstanceMethod_Function PyObject im Return value Borrowed reference Return the function object associated with the instance method im PyObject PyInstanceMethod_GET_FUNCTION PyObject im Return value Borrowed reference Macro version of PyInstanceMethod_Function which avoids error checking Method Objects Methods are bound function objects Methods are always bound to an instance of a user defined class Unbound methods methods bound to a class object are no longer available PyTypeObject PyMethod_Type This instance of PyTypeObject represents the Python method type This is exposed to Python programs as types MethodType int PyMethod_Check PyObject o Return true if o is a method object has type PyMethod_Type The parameter must not be NULL This function always succeeds PyObject PyMethod_New PyObject func PyObject self Return value New reference Return a new method object with func being any callable object and self the instance the method should be bound func is the function that will be called when the method is called self must not be NULL PyObject PyMethod_Function PyObject meth Return value Borrowed reference Return the function object associated with the method meth PyObject PyMethod_GET_FUNCTION PyObject meth Return value Borrowed reference Macro version of PyMethod_Function which avoids error checking PyObject PyMethod_Self PyObject meth Return value Borrowed reference Return the instance associated with the method meth PyObject PyMethod_GET_SELF PyObject meth Return value Borrowed reference Macro version of PyMethod_Self which avoids error checking,en
1459,6 Expressions This chapter explains the meaning of the elements of expressions in Python Syntax Notes In this and the following chapters extended BNF notation will be used to describe syntax not lexical analysis When one alternative of a syntax rule has the form name othername and no semantics are given the semantics of this form of name are the same as for othername 6 1 Arithmetic conversions When a description of an arithmetic operator below uses the phrase the numeric arguments are converted to a common type this means that the operator implementation for built in types works as follows If either argument is a complex number the other is converted to complex otherwise if either argument is a floating point number the other is converted to floating point otherwise both must be integers and no conversion is necessary Some additional rules apply for certain operators e g a string as a left argument to the operator Extensions must define their own conversion behavior 6 2 Atoms Atoms are the most basic elements of expressions The simplest atoms are identifiers or literals Forms enclosed in parentheses brackets or braces are also categorized syntactically as atoms The syntax for atoms is atom identifier literal enclosure enclosure parenth_form list_display dict_display set_display generator_expression yield_atom 6 2 1 Identifiers Names An identifier occurring as an atom is a name See section Identifiers and keywords for lexical definition and section Naming and binding for documentation of naming and binding When the name is bound to an object evaluation of the atom yields that object When a name is not bound an attempt to evaluate it raises a NameError exception Private name mangling When an identifier that textually occurs in a class definition begins with two or more underscore characters and does not end in two or more underscores it is considered a private name of that class Private names are transformed to a longer form before code is generated for them The transformation inserts the class name with leading underscores removed and a single underscore inserted in front of the name For example the identifier __spam occurring in a class named Ham will be transformed to _Ham__spam This transformation is independent of the syntactical context in which the identifier is used If the transformed name is extremely long longer than 255 characters implementation defined truncation may happen If the class name consists only of underscores no transformation is done 6 2 2 Literals Python supports string and bytes literals and various numeric literals literal stringliteral bytesliteral integer floatnumber imagnumber Evaluation of a literal yields an object of the given type string bytes integer floating point number complex number with the given value The value may be approximated in the case of floating point and imaginary complex literals See section Literals for details All literals correspond to immutable data types and hence the object s identity is less important than its value Multiple evaluations of literals with the same value either the same occurrence in the program text or a different occurrence may obtain the same object or a different object with the same value 6 2 3 Parenthesized forms A parenthesized form is an optional expression list enclosed in parentheses parenth_form starred_expression A parenthesized expression list yields whatever that expression list yields if the list contains at least one comma it yields a tuple otherwise it yields the single expression that makes up the expression list An empty pair of parentheses yields an empty tuple object Since tuples are immutable the same rules as for literals apply i e two occurrences of the empty tuple may or may not yield the same object Note that tuples are not formed by the parentheses but rather by use of the comma The exception is the empty tuple for which parentheses are required allowing unparenthesized nothing in expressions would cause ambiguities and allow common typos to pass uncaught 6 2 4 Displays for lists sets and dictionaries For constructing a list,en
1460, a set or a dictionary Python provides special syntax called displays each of them in two flavors either the container contents are listed explicitly or they are computed via a set of looping and filtering instructions called a comprehension Common syntax elements for comprehensions are comprehension assignment_expression comp_for comp_for async for target_list in or_test comp_iter comp_iter comp_for comp_if comp_if if or_test comp_iter The comprehension consists of a single expression followed by at least one for clause and zero or more for or if clauses In this case the elements of the new container are those that would be produced by considering each of the for or if clauses a block nesting from left to right and evaluating the expression to produce an element each time the innermost block is reached However aside from the iterable expression in the leftmost for clause the comprehension is executed in a separate implicitly nested scope This ensures that names assigned to in the target list don t leak into the enclosing scope The iterable expression in the leftmost for clause is evaluated directly in the enclosing scope and then passed as an argument to the implicitly nested scope Subsequent for clauses and any filter condition in the leftmost for clause cannot be evaluated in the enclosing scope as they may depend on the values obtained from the leftmost iterable For example x y for x in range 10 for y in range x x 10 To ensure the comprehension always results in a container of the appropriate type yield and yield from expressions are prohibited in the implicitly nested scope Since Python 3 6 in an async def function an async for clause may be used to iterate over a asynchronous iterator A comprehension in an async def function may consist of either a for or async for clause following the leading expression may contain additional for or async for clauses and may also use await expressions If a comprehension contains either async for clauses or await expressions or other asynchronous comprehensions it is called an asynchronous comprehension An asynchronous comprehension may suspend the execution of the coroutine function in which it appears See also PEP 530 New in version 3 6 Asynchronous comprehensions were introduced Changed in version 3 8 yield and yield from prohibited in the implicitly nested scope Changed in version 3 11 Asynchronous comprehensions are now allowed inside comprehensions in asynchronous functions Outer comprehensions implicitly become asynchronous 6 2 5 List displays A list display is a possibly empty series of expressions enclosed in square brackets list_display starred_list comprehension A list display yields a new list object the contents being specified by either a list of expressions or a comprehension When a comma separated list of expressions is supplied its elements are evaluated from left to right and placed into the list object in that order When a comprehension is supplied the list is constructed from the elements resulting from the comprehension 6 2 6 Set displays A set display is denoted by curly braces and distinguishable from dictionary displays by the lack of colons separating keys and values set_display starred_list comprehension A set display yields a new mutable set object the contents being specified by either a sequence of expressions or a comprehension When a comma separated list of expressions is supplied its elements are evaluated from left to right and added to the set object When a comprehension is supplied the set is constructed from the elements resulting from the comprehension An empty set cannot be constructed with this literal constructs an empty dictionary 6 2 7 Dictionary displays A dictionary display is a possibly empty series of dict items key value pairs enclosed in curly braces dict_display dict_item_list dict_comprehension dict_item_list dict_item dict_item dict_item expression expression or_expr dict_comprehension expression expression comp_for A dictionary display yields a new dictionary object If a comma separated sequence of dict items is given they are eva,en
1461,luated from left to right to define the entries of the dictionary each key object is used as a key into the dictionary to store the corresponding value This means that you can specify the same key multiple times in the dict item list and the final dictionary s value for that key will be the last one given A double asterisk denotes dictionary unpacking Its operand must be a mapping Each mapping item is added to the new dictionary Later values replace values already set by earlier dict items and earlier dictionary unpackings New in version 3 5 Unpacking into dictionary displays originally proposed by PEP 448 A dict comprehension in contrast to list and set comprehensions needs two expressions separated with a colon followed by the usual for and if clauses When the comprehension is run the resulting key and value elements are inserted in the new dictionary in the order they are produced Restrictions on the types of the key values are listed earlier in section The standard type hierarchy To summarize the key type should be hashable which excludes all mutable objects Clashes between duplicate keys are not detected the last value textually rightmost in the display stored for a given key value prevails Changed in version 3 8 Prior to Python 3 8 in dict comprehensions the evaluation order of key and value was not well defined In CPython the value was evaluated before the key Starting with 3 8 the key is evaluated before the value as proposed by PEP 572 6 2 8 Generator expressions A generator expression is a compact generator notation in parentheses generator_expression expression comp_for A generator expression yields a new generator object Its syntax is the same as for comprehensions except that it is enclosed in parentheses instead of brackets or curly braces Variables used in the generator expression are evaluated lazily when the __next__ method is called for the generator object in the same fashion as normal generators However the iterable expression in the leftmost for clause is immediately evaluated so that an error produced by it will be emitted at the point where the generator expression is defined rather than at the point where the first value is retrieved Subsequent for clauses and any filter condition in the leftmost for clause cannot be evaluated in the enclosing scope as they may depend on the values obtained from the leftmost iterable For example x y for x in range 10 for y in range x x 10 The parentheses can be omitted on calls with only one argument See section Calls for details To avoid interfering with the expected operation of the generator expression itself yield and yield from expressions are prohibited in the implicitly defined generator If a generator expression contains either async for clauses or await expressions it is called an asynchronous generator expression An asynchronous generator expression returns a new asynchronous generator object which is an asynchronous iterator see Asynchronous Iterators New in version 3 6 Asynchronous generator expressions were introduced Changed in version 3 7 Prior to Python 3 7 asynchronous generator expressions could only appear in async def coroutines Starting with 3 7 any function can use asynchronous generator expressions Changed in version 3 8 yield and yield from prohibited in the implicitly nested scope 6 2 9 Yield expressions yield_atom yield_expression yield_from yield from expression yield_expression yield expression_list yield_from The yield expression is used when defining a generator function or an asynchronous generator function and thus can only be used in the body of a function definition Using a yield expression in a function s body causes that function to be a generator function and using it in an async def function s body causes that coroutine function to be an asynchronous generator function For example def gen defines a generator function yield 123 async def agen defines an asynchronous generator function yield 123 Due to their side effects on the containing scope yield expressions are not permitted as part of the implicitly defined scopes used to ,en
1462,implement comprehensions and generator expressions Changed in version 3 8 Yield expressions prohibited in the implicitly nested scopes used to implement comprehensions and generator expressions Generator functions are described below while asynchronous generator functions are described separately in section Asynchronous generator functions When a generator function is called it returns an iterator known as a generator That generator then controls the execution of the generator function The execution starts when one of the generator s methods is called At that time the execution proceeds to the first yield expression where it is suspended again returning the value of expression_list to the generator s caller or None if expression_list is omitted By suspended we mean that all local state is retained including the current bindings of local variables the instruction pointer the internal evaluation stack and the state of any exception handling When the execution is resumed by calling one of the generator s methods the function can proceed exactly as if the yield expression were just another external call The value of the yield expression after resuming depends on the method which resumed the execution If __next__ is used typically via either a for or the next builtin then the result is None Otherwise if send is used then the result will be the value passed in to that method All of this makes generator functions quite similar to coroutines they yield multiple times they have more than one entry point and their execution can be suspended The only difference is that a generator function cannot control where the execution should continue after it yields the control is always transferred to the generator s caller Yield expressions are allowed anywhere in a try construct If the generator is not resumed before it is finalized by reaching a zero reference count or by being garbage collected the generator iterator s close method will be called allowing any pending finally clauses to execute When yield from expr is used the supplied expression must be an iterable The values produced by iterating that iterable are passed directly to the caller of the current generator s methods Any values passed in with send and any exceptions passed in with throw are passed to the underlying iterator if it has the appropriate methods If this is not the case then send will raise AttributeError or TypeError while throw will just raise the passed in exception immediately When the underlying iterator is complete the value attribute of the raised StopIteration instance becomes the value of the yield expression It can be either set explicitly when raising StopIteration or automatically when the subiterator is a generator by returning a value from the subgenerator Changed in version 3 3 Added yield from expr to delegate control flow to a subiterator The parentheses may be omitted when the yield expression is the sole expression on the right hand side of an assignment statement See also PEP 255 Simple Generators The proposal for adding generators and the yield statement to Python PEP 342 Coroutines via Enhanced Generators The proposal to enhance the API and syntax of generators making them usable as simple coroutines PEP 380 Syntax for Delegating to a Subgenerator The proposal to introduce the yield_from syntax making delegation to subgenerators easy PEP 525 Asynchronous Generators The proposal that expanded on PEP 492 by adding generator capabilities to coroutine functions 6 2 9 1 Generator iterator methods This subsection describes the methods of a generator iterator They can be used to control the execution of a generator function Note that calling any of the generator methods below when the generator is already executing raises a ValueError exception generator __next__ Starts the execution of a generator function or resumes it at the last executed yield expression When a generator function is resumed with a __next__ method the current yield expression always evaluates to None The execution then continues to the next yield expression where the generator is ,en
1463,suspended again and the value of the expression_list is returned to __next__ s caller If the generator exits without yielding another value a StopIteration exception is raised This method is normally called implicitly e g by a for loop or by the built in next function generator send value Resumes the execution and sends a value into the generator function The value argument becomes the result of the current yield expression The send method returns the next value yielded by the generator or raises StopIteration if the generator exits without yielding another value When send is called to start the generator it must be called with None as the argument because there is no yield expression that could receive the value generator throw value generator throw type value traceback Raises an exception at the point where the generator was paused and returns the next value yielded by the generator function If the generator exits without yielding another value a StopIteration exception is raised If the generator function does not catch the passed in exception or raises a different exception then that exception propagates to the caller In typical use this is called with a single exception instance similar to the way the raise keyword is used For backwards compatibility however the second signature is supported following a convention from older versions of Python The type argument should be an exception class and value should be an exception instance If the value is not provided the type constructor is called to get an instance If traceback is provided it is set on the exception otherwise any existing __traceback__ attribute stored in value may be cleared Changed in version 3 12 The second signature type value traceback is deprecated and may be removed in a future version of Python generator close Raises a GeneratorExit at the point where the generator function was paused If the generator function then exits gracefully is already closed or raises GeneratorExit by not catching the exception close returns to its caller If the generator yields a value a RuntimeError is raised If the generator raises any other exception it is propagated to the caller close does nothing if the generator has already exited due to an exception or normal exit 6 2 9 2 Examples Here is a simple example that demonstrates the behavior of generators and generator functions def echo value None print Execution starts when next is called for the first time try while True try value yield value except Exception as e value e finally print Don t forget to clean up when close is called generator echo 1 print next generator Execution starts when next is called for the first time 1 print next generator None print generator send 2 2 generator throw TypeError spam TypeError spam generator close Don t forget to clean up when close is called For examples using yield from see PEP 380 Syntax for Delegating to a Subgenerator in What s New in Python 6 2 9 3 Asynchronous generator functions The presence of a yield expression in a function or method defined using async def further defines the function as an asynchronous generator function When an asynchronous generator function is called it returns an asynchronous iterator known as an asynchronous generator object That object then controls the execution of the generator function An asynchronous generator object is typically used in an async for statement in a coroutine function analogously to how a generator object would be used in a for statement Calling one of the asynchronous generator s methods returns an awaitable object and the execution starts when this object is awaited on At that time the execution proceeds to the first yield expression where it is suspended again returning the value of expression_list to the awaiting coroutine As with a generator suspension means that all local state is retained including the current bindings of local variables the instruction pointer the internal evaluation stack and the state of any exception handling When the execution is resumed by awaiting on the next object returned by the asynchronous ,en
1464,generator s methods the function can proceed exactly as if the yield expression were just another external call The value of the yield expression after resuming depends on the method which resumed the execution If __anext__ is used then the result is None Otherwise if asend is used then the result will be the value passed in to that method If an asynchronous generator happens to exit early by break the caller task being cancelled or other exceptions the generator s async cleanup code will run and possibly raise exceptions or access context variables in an unexpected context perhaps after the lifetime of tasks it depends or during the event loop shutdown when the async generator garbage collection hook is called To prevent this the caller must explicitly close the async generator by calling aclose method to finalize the generator and ultimately detach it from the event loop In an asynchronous generator function yield expressions are allowed anywhere in a try construct However if an asynchronous generator is not resumed before it is finalized by reaching a zero reference count or by being garbage collected then a yield expression within a try construct could result in a failure to execute pending finally clauses In this case it is the responsibility of the event loop or scheduler running the asynchronous generator to call the asynchronous generator iterator s aclose method and run the resulting coroutine object thus allowing any pending finally clauses to execute To take care of finalization upon event loop termination an event loop should define a finalizer function which takes an asynchronous generator iterator and presumably calls aclose and executes the coroutine This finalizer may be registered by calling sys set_asyncgen_hooks When first iterated over an asynchronous generator iterator will store the registered finalizer to be called upon finalization For a reference example of a finalizer method see the implementation of asyncio Loop shutdown_asyncgens in Lib asyncio base_events py The expression yield from expr is a syntax error when used in an asynchronous generator function 6 2 9 4 Asynchronous generator iterator methods This subsection describes the methods of an asynchronous generator iterator which are used to control the execution of a generator function coroutine agen __anext__ Returns an awaitable which when run starts to execute the asynchronous generator or resumes it at the last executed yield expression When an asynchronous generator function is resumed with an __anext__ method the current yield expression always evaluates to None in the returned awaitable which when run will continue to the next yield expression The value of the expression_list of the yield expression is the value of the StopIteration exception raised by the completing coroutine If the asynchronous generator exits without yielding another value the awaitable instead raises a StopAsyncIteration exception signalling that the asynchronous iteration has completed This method is normally called implicitly by a async for loop coroutine agen asend value Returns an awaitable which when run resumes the execution of the asynchronous generator As with the send method for a generator this sends a value into the asynchronous generator function and the value argument becomes the result of the current yield expression The awaitable returned by the asend method will return the next value yielded by the generator as the value of the raised StopIteration or raises StopAsyncIteration if the asynchronous generator exits without yielding another value When asend is called to start the asynchronous generator it must be called with None as the argument because there is no yield expression that could receive the value coroutine agen athrow value coroutine agen athrow type value traceback Returns an awaitable that raises an exception of type type at the point where the asynchronous generator was paused and returns the next value yielded by the generator function as the value of the raised StopIteration exception If the asynchronous generator exits without yiel,en
1465,ding another value a StopAsyncIteration exception is raised by the awaitable If the generator function does not catch the passed in exception or raises a different exception then when the awaitable is run that exception propagates to the caller of the awaitable Changed in version 3 12 The second signature type value traceback is deprecated and may be removed in a future version of Python coroutine agen aclose Returns an awaitable that when run will throw a GeneratorExit into the asynchronous generator function at the point where it was paused If the asynchronous generator function then exits gracefully is already closed or raises GeneratorExit by not catching the exception then the returned awaitable will raise a StopIteration exception Any further awaitables returned by subsequent calls to the asynchronous generator will raise a StopAsyncIteration exception If the asynchronous generator yields a value a RuntimeError is raised by the awaitable If the asynchronous generator raises any other exception it is propagated to the caller of the awaitable If the asynchronous generator has already exited due to an exception or normal exit then further calls to aclose will return an awaitable that does nothing 6 3 Primaries Primaries represent the most tightly bound operations of the language Their syntax is primary atom attributeref subscription slicing call 6 3 1 Attribute references An attribute reference is a primary followed by a period and a name attributeref primary identifier The primary must evaluate to an object of a type that supports attribute references which most objects do This object is then asked to produce the attribute whose name is the identifier The type and value produced is determined by the object Multiple evaluations of the same attribute reference may yield different objects This production can be customized by overriding the __getattribute__ method or the __getattr__ method The __getattribute__ method is called first and either returns a value or raises AttributeError if the attribute is not available If an AttributeError is raised and the object has a __getattr__ method that method is called as a fallback 6 3 2 Subscriptions The subscription of an instance of a container class will generally select an element from the container The subscription of a generic class will generally return a GenericAlias object subscription primary expression_list When an object is subscripted the interpreter will evaluate the primary and the expression list The primary must evaluate to an object that supports subscription An object may support subscription through defining one or both of __getitem__ and __class_getitem__ When the primary is subscripted the evaluated result of the expression list will be passed to one of these methods For more details on when __class_getitem__ is called instead of __getitem__ see __class_getitem__ versus __getitem__ If the expression list contains at least one comma it will evaluate to a tuple containing the items of the expression list Otherwise the expression list will evaluate to the value of the list s sole member For built in objects there are two types of objects that support subscription via __getitem__ 1 Mappings If the primary is a mapping the expression list must evaluate to an object whose value is one of the keys of the mapping and the subscription selects the value in the mapping that corresponds to that key An example of a builtin mapping class is the dict class 2 Sequences If the primary is a sequence the expression list must evaluate to an int or a slice as discussed in the following section Examples of builtin sequence classes include the str list and tuple classes The formal syntax makes no special provision for negative indices in sequences However built in sequences all provide a __getitem__ method that interprets negative indices by adding the length of the sequence to the index so that for example x 1 selects the last item of x The resulting value must be a nonnegative integer less than the number of items in the sequence and the subscription selects the item whose index,en
1466, is that value counting from zero Since the support for negative indices and slicing occurs in the object s __getitem__ method subclasses overriding this method will need to explicitly add that support A string is a special kind of sequence whose items are characters A character is not a separate data type but a string of exactly one character 6 3 3 Slicings A slicing selects a range of items in a sequence object e g a string tuple or list Slicings may be used as expressions or as targets in assignment or del statements The syntax for a slicing slicing primary slice_list slice_list slice_item slice_item slice_item expression proper_slice proper_slice lower_bound upper_bound stride lower_bound expression upper_bound expression stride expression There is ambiguity in the formal syntax here anything that looks like an expression list also looks like a slice list so any subscription can be interpreted as a slicing Rather than further complicating the syntax this is disambiguated by defining that in this case the interpretation as a subscription takes priority over the interpretation as a slicing this is the case if the slice list contains no proper slice The semantics for a slicing are as follows The primary is indexed using the same __getitem__ method as normal subscription with a key that is constructed from the slice list as follows If the slice list contains at least one comma the key is a tuple containing the conversion of the slice items otherwise the conversion of the lone slice item is the key The conversion of a slice item that is an expression is that expression The conversion of a proper slice is a slice object see section The standard type hierarchy whose start stop and step attributes are the values of the expressions given as lower bound upper bound and stride respectively substituting None for missing expressions 6 3 4 Calls A call calls a callable object e g a function with a possibly empty series of arguments call primary argument_list comprehension argument_list positional_arguments starred_and_keywords keywords_arguments starred_and_keywords keywords_arguments keywords_arguments positional_arguments positional_item positional_item positional_item assignment_expression expression starred_and_keywords expression keyword_item expression keyword_item keywords_arguments keyword_item expression keyword_item expression keyword_item identifier expression An optional trailing comma may be present after the positional and keyword arguments but does not affect the semantics The primary must evaluate to a callable object user defined functions built in functions methods of built in objects class objects methods of class instances and all objects having a __call__ method are callable All argument expressions are evaluated before the call is attempted Please refer to section Function definitions for the syntax of formal parameter lists If keyword arguments are present they are first converted to positional arguments as follows First a list of unfilled slots is created for the formal parameters If there are N positional arguments they are placed in the first N slots Next for each keyword argument the identifier is used to determine the corresponding slot if the identifier is the same as the first formal parameter name the first slot is used and so on If the slot is already filled a TypeError exception is raised Otherwise the argument is placed in the slot filling it even if the expression is None it fills the slot When all arguments have been processed the slots that are still unfilled are filled with the corresponding default value from the function definition Default values are calculated once when the function is defined thus a mutable object such as a list or dictionary used as default value will be shared by all calls that don t specify an argument value for the corresponding slot this should usually be avoided If there are any unfilled slots for which no default value is specified a TypeError exception is raised Otherwise the list of filled slots is used as the argument list for the call CPython implementation deta,en
1467,il An implementation may provide built in functions whose positional parameters do not have names even if they are named for the purpose of documentation and which therefore cannot be supplied by keyword In CPython this is the case for functions implemented in C that use PyArg_ParseTuple to parse their arguments If there are more positional arguments than there are formal parameter slots a TypeError exception is raised unless a formal parameter using the syntax identifier is present in this case that formal parameter receives a tuple containing the excess positional arguments or an empty tuple if there were no excess positional arguments If any keyword argument does not correspond to a formal parameter name a TypeError exception is raised unless a formal parameter using the syntax identifier is present in this case that formal parameter receives a dictionary containing the excess keyword arguments using the keywords as keys and the argument values as corresponding values or a new empty dictionary if there were no excess keyword arguments If the syntax expression appears in the function call expression must evaluate to an iterable Elements from these iterables are treated as if they were additional positional arguments For the call f x1 x2 y x3 x4 if y evaluates to a sequence y1 yM this is equivalent to a call with M 4 positional arguments x1 x2 y1 yM x3 x4 A consequence of this is that although the expression syntax may appear after explicit keyword arguments it is processed before the keyword arguments and any expression arguments see below So def f a b print a b f b 1 2 2 1 f a 1 2 Traceback most recent call last File stdin line 1 in module TypeError f got multiple values for keyword argument a f 1 2 1 2 It is unusual for both keyword arguments and the expression syntax to be used in the same call so in practice this confusion does not often arise If the syntax expression appears in the function call expression must evaluate to a mapping the contents of which are treated as additional keyword arguments If a parameter matching a key has already been given a value by an explicit keyword argument or from another unpacking a TypeError exception is raised When expression is used each key in this mapping must be a string Each value from the mapping is assigned to the first formal parameter eligible for keyword assignment whose name is equal to the key A key need not be a Python identifier e g max temp F is acceptable although it will not match any formal parameter that could be declared If there is no match to a formal parameter the key value pair is collected by the parameter if there is one or if there is not a TypeError exception is raised Formal parameters using the syntax identifier or identifier cannot be used as positional argument slots or as keyword argument names Changed in version 3 5 Function calls accept any number of and unpackings positional arguments may follow iterable unpackings and keyword arguments may follow dictionary unpackings Originally proposed by PEP 448 A call always returns some value possibly None unless it raises an exception How this value is computed depends on the type of the callable object If it is a user defined function The code block for the function is executed passing it the argument list The first thing the code block will do is bind the formal parameters to the arguments this is described in section Function definitions When the code block executes a return statement this specifies the return value of the function call a built in function or method The result is up to the interpreter see Built in Functions for the descriptions of built in functions and methods a class object A new instance of that class is returned a class instance method The corresponding user defined function is called with an argument list that is one longer than the argument list of the call the instance becomes the first argument a class instance The class must define a __call__ method the effect is then the same as if that method was called 6 4 Await expression Suspend the execution of coroutine on an awaitabl,en
1468,e object Can only be used inside a coroutine function await_expr await primary New in version 3 5 6 5 The power operator The power operator binds more tightly than unary operators on its left it binds less tightly than unary operators on its right The syntax is power await_expr primary u_expr Thus in an unparenthesized sequence of power and unary operators the operators are evaluated from right to left this does not constrain the evaluation order for the operands 1 2 results in 1 The power operator has the same semantics as the built in pow function when called with two arguments it yields its left argument raised to the power of its right argument The numeric arguments are first converted to a common type and the result is of that type For int operands the result has the same type as the operands unless the second argument is negative in that case all arguments are converted to float and a float result is delivered For example 10 2 returns 100 but 10 2 returns 0 01 Raising 0 0 to a negative power results in a ZeroDivisionError Raising a negative number to a fractional power results in a complex number In earlier versions it raised a ValueError This operation can be customized using the special __pow__ method 6 6 Unary arithmetic and bitwise operations All unary arithmetic and bitwise operations have the same priority u_expr power u_expr u_expr u_expr The unary minus operator yields the negation of its numeric argument the operation can be overridden with the __neg__ special method The unary plus operator yields its numeric argument unchanged the operation can be overridden with the __pos__ special method The unary invert operator yields the bitwise inversion of its integer argument The bitwise inversion of x is defined as x 1 It only applies to integral numbers or to custom objects that override the __invert__ special method In all three cases if the argument does not have the proper type a TypeError exception is raised 6 7 Binary arithmetic operations The binary arithmetic operations have the conventional priority levels Note that some of these operations also apply to certain non numeric types Apart from the power operator there are only two levels one for multiplicative operators and one for additive operators m_expr u_expr m_expr u_expr m_expr m_expr m_expr u_expr m_expr u_expr m_expr u_expr a_expr m_expr a_expr m_expr a_expr m_expr The multiplication operator yields the product of its arguments The arguments must either both be numbers or one argument must be an integer and the other must be a sequence In the former case the numbers are converted to a common type and then multiplied together In the latter case sequence repetition is performed a negative repetition factor yields an empty sequence This operation can be customized using the special __mul__ and __rmul__ methods The at operator is intended to be used for matrix multiplication No builtin Python types implement this operator New in version 3 5 The division and floor division operators yield the quotient of their arguments The numeric arguments are first converted to a common type Division of integers yields a float while floor division of integers results in an integer the result is that of mathematical division with the floor function applied to the result Division by zero raises the ZeroDivisionError exception This operation can be customized using the special __truediv__ and __floordiv__ methods The modulo operator yields the remainder from the division of the first argument by the second The numeric arguments are first converted to a common type A zero right argument raises the ZeroDivisionError exception The arguments may be floating point numbers e g 3 14 0 7 equals 0 34 since 3 14 equals 4 0 7 0 34 The modulo operator always yields a result with the same sign as its second operand or zero the absolute value of the result is strictly smaller than the absolute value of the second operand 1 The floor division and modulo operators are connected by the following identity x x y y x y Floor division and modulo are also connected with the built in function,en
1469, divmod divmod x y x y x y 2 In addition to performing the modulo operation on numbers the operator is also overloaded by string objects to perform old style string formatting also known as interpolation The syntax for string formatting is described in the Python Library Reference section printf style String Formatting The modulo operation can be customized using the special __mod__ method The floor division operator the modulo operator and the divmod function are not defined for complex numbers Instead convert to a floating point number using the abs function if appropriate The addition operator yields the sum of its arguments The arguments must either both be numbers or both be sequences of the same type In the former case the numbers are converted to a common type and then added together In the latter case the sequences are concatenated This operation can be customized using the special __add__ and __radd__ methods The subtraction operator yields the difference of its arguments The numeric arguments are first converted to a common type This operation can be customized using the special __sub__ method 6 8 Shifting operations The shifting operations have lower priority than the arithmetic operations shift_expr a_expr shift_expr a_expr These operators accept integers as arguments They shift the first argument to the left or right by the number of bits given by the second argument This operation can be customized using the special __lshift__ and __rshift__ methods A right shift by n bits is defined as floor division by pow 2 n A left shift by n bits is defined as multiplication with pow 2 n 6 9 Binary bitwise operations Each of the three bitwise operations has a different priority level and_expr shift_expr and_expr shift_expr xor_expr and_expr xor_expr and_expr or_expr xor_expr or_expr xor_expr The operator yields the bitwise AND of its arguments which must be integers or one of them must be a custom object overriding __and__ or __rand__ special methods The operator yields the bitwise XOR exclusive OR of its arguments which must be integers or one of them must be a custom object overriding __xor__ or __rxor__ special methods The operator yields the bitwise inclusive OR of its arguments which must be integers or one of them must be a custom object overriding __or__ or __ror__ special methods 6 10 Comparisons Unlike C all comparison operations in Python have the same priority which is lower than that of any arithmetic shifting or bitwise operation Also unlike C expressions like a b c have the interpretation that is conventional in mathematics comparison or_expr comp_operator or_expr comp_operator is not not in Comparisons yield boolean values True or False Custom rich comparison methods may return non boolean values In this case Python will call bool on such value in boolean contexts Comparisons can be chained arbitrarily e g x y z is equivalent to x y and y z except that y is evaluated only once but in both cases z is not evaluated at all when x y is found to be false Formally if a b c y z are expressions and op1 op2 opN are comparison operators then a op1 b op2 c y opN z is equivalent to a op1 b and b op2 c and y opN z except that each expression is evaluated at most once Note that a op1 b op2 c doesn t imply any kind of comparison between a and c so that e g x y z is perfectly legal though perhaps not pretty 6 10 1 Value comparisons The operators and compare the values of two objects The objects do not need to have the same type Chapter Objects values and types states that objects have a value in addition to type and identity The value of an object is a rather abstract notion in Python For example there is no canonical access method for an object s value Also there is no requirement that the value of an object should be constructed in a particular way e g comprised of all its data attributes Comparison operators implement a particular notion of what the value of an object is One can think of them as defining the value of an object indirectly by means of their comparison implementation Because all types are direct or indi,en
1470,rect subtypes of object they inherit the default comparison behavior from object Types can customize their comparison behavior by implementing rich comparison methods like __lt__ described in Basic customization The default behavior for equality comparison and is based on the identity of the objects Hence equality comparison of instances with the same identity results in equality and equality comparison of instances with different identities results in inequality A motivation for this default behavior is the desire that all objects should be reflexive i e x is y implies x y A default order comparison and is not provided an attempt raises TypeError A motivation for this default behavior is the lack of a similar invariant as for equality The behavior of the default equality comparison that instances with different identities are always unequal may be in contrast to what types will need that have a sensible definition of object value and value based equality Such types will need to customize their comparison behavior and in fact a number of built in types have done that The following list describes the comparison behavior of the most important built in types Numbers of built in numeric types Numeric Types int float complex and of the standard library types fractions Fraction and decimal Decimal can be compared within and across their types with the restriction that complex numbers do not support order comparison Within the limits of the types involved they compare mathematically algorithmically correct without loss of precision The not a number values float NaN and decimal Decimal NaN are special Any ordered comparison of a number to a not a number value is false A counter intuitive implication is that not a number values are not equal to themselves For example if x float NaN 3 x x 3 and x x are all false while x x is true This behavior is compliant with IEEE 754 None and NotImplemented are singletons PEP 8 advises that comparisons for singletons should always be done with is or is not never the equality operators Binary sequences instances of bytes or bytearray can be compared within and across their types They compare lexicographically using the numeric values of their elements Strings instances of str compare lexicographically using the numerical Unicode code points the result of the built in function ord of their characters 3 Strings and binary sequences cannot be directly compared Sequences instances of tuple list or range can be compared only within each of their types with the restriction that ranges do not support order comparison Equality comparison across these types results in inequality and ordering comparison across these types raises TypeError Sequences compare lexicographically using comparison of corresponding elements The built in containers typically assume identical objects are equal to themselves That lets them bypass equality tests for identical objects to improve performance and to maintain their internal invariants Lexicographical comparison between built in collections works as follows For two collections to compare equal they must be of the same type have the same length and each pair of corresponding elements must compare equal for example 1 2 1 2 is false because the type is not the same Collections that support order comparison are ordered the same as their first unequal elements for example 1 2 x 1 2 y has the same value as x y If a corresponding element does not exist the shorter collection is ordered first for example 1 2 1 2 3 is true Mappings instances of dict compare equal if and only if they have equal key value pairs Equality comparison of the keys and values enforces reflexivity Order comparisons and raise TypeError Sets instances of set or frozenset can be compared within and across their types They define order comparison operators to mean subset and superset tests Those relations do not define total orderings for example the two sets 1 2 and 2 3 are not equal nor subsets of one another nor supersets of one another Accordingly sets are not appropriate arguments for functions which depe,en
1471,nd on total ordering for example min max and sorted produce undefined results given a list of sets as inputs Comparison of sets enforces reflexivity of its elements Most other built in types have no comparison methods implemented so they inherit the default comparison behavior User defined classes that customize their comparison behavior should follow some consistency rules if possible Equality comparison should be reflexive In other words identical objects should compare equal x is y implies x y Comparison should be symmetric In other words the following expressions should have the same result x y and y x x y and y x x y and y x x y and y x Comparison should be transitive The following non exhaustive examples illustrate that x y and y z implies x z x y and y z implies x z Inverse comparison should result in the boolean negation In other words the following expressions should have the same result x y and not x y x y and not x y for total ordering x y and not x y for total ordering The last two expressions apply to totally ordered collections e g to sequences but not to sets or mappings See also the total_ordering decorator The hash result should be consistent with equality Objects that are equal should either have the same hash value or be marked as unhashable Python does not enforce these consistency rules In fact the not a number values are an example for not following these rules 6 10 2 Membership test operations The operators in and not in test for membership x in s evaluates to True if x is a member of s and False otherwise x not in s returns the negation of x in s All built in sequences and set types support this as well as dictionary for which in tests whether the dictionary has a given key For container types such as list tuple set frozenset dict or collections deque the expression x in y is equivalent to any x is e or x e for e in y For the string and bytes types x in y is True if and only if x is a substring of y An equivalent test is y find x 1 Empty strings are always considered to be a substring of any other string so in abc will return True For user defined classes which define the __contains__ method x in y returns True if y __contains__ x returns a true value and False otherwise For user defined classes which do not define __contains__ but do define __iter__ x in y is True if some value z for which the expression x is z or x z is true is produced while iterating over y If an exception is raised during the iteration it is as if in raised that exception Lastly the old style iteration protocol is tried if a class defines __getitem__ x in y is True if and only if there is a non negative integer index i such that x is y i or x y i and no lower integer index raises the IndexError exception If any other exception is raised it is as if in raised that exception The operator not in is defined to have the inverse truth value of in 6 10 3 Identity comparisons The operators is and is not test for an object s identity x is y is true if and only if x and y are the same object An Object s identity is determined using the id function x is not y yields the inverse truth value 4 6 11 Boolean operations or_test and_test or_test or and_test and_test not_test and_test and not_test not_test comparison not not_test In the context of Boolean operations and also when expressions are used by control flow statements the following values are interpreted as false False None numeric zero of all types and empty strings and containers including strings tuples lists dictionaries sets and frozensets All other values are interpreted as true User defined objects can customize their truth value by providing a __bool__ method The operator not yields True if its argument is false False otherwise The expression x and y first evaluates x if x is false its value is returned otherwise y is evaluated and the resulting value is returned The expression x or y first evaluates x if x is true its value is returned otherwise y is evaluated and the resulting value is returned Note that neither and nor or restrict the value and type they return to False and,en
1472, True but rather return the last evaluated argument This is sometimes useful e g if s is a string that should be replaced by a default value if it is empty the expression s or foo yields the desired value Because not has to create a new value it returns a boolean value regardless of the type of its argument for example not foo produces False rather than 6 12 Assignment expressions assignment_expression identifier expression An assignment expression sometimes also called a named expression or walrus assigns an expression to an identifier while also returning the value of the expression One common use case is when handling matched regular expressions if matching pattern search data do_something matching Or when processing a file stream in chunks while chunk file read 9000 process chunk Assignment expressions must be surrounded by parentheses when used as expression statements and when used as sub expressions in slicing conditional lambda keyword argument and comprehension if expressions and in assert with and assignment statements In all other places where they can be used parentheses are not required including in if and while statements New in version 3 8 See PEP 572 for more details about assignment expressions 6 13 Conditional expressions conditional_expression or_test if or_test else expression expression conditional_expression lambda_expr Conditional expressions sometimes called a ternary operator have the lowest priority of all Python operations The expression x if C else y first evaluates the condition C rather than x If C is true x is evaluated and its value is returned otherwise y is evaluated and its value is returned See PEP 308 for more details about conditional expressions 6 14 Lambdas lambda_expr lambda parameter_list expression Lambda expressions sometimes called lambda forms are used to create anonymous functions The expression lambda parameters expression yields a function object The unnamed object behaves like a function object defined with def lambda parameters return expression See section Function definitions for the syntax of parameter lists Note that functions created with lambda expressions cannot contain statements or annotations 6 15 Expression lists expression_list expression expression starred_list starred_item starred_item starred_expression expression starred_item starred_item starred_item assignment_expression or_expr Except when part of a list or set display an expression list containing at least one comma yields a tuple The length of the tuple is the number of expressions in the list The expressions are evaluated from left to right An asterisk denotes iterable unpacking Its operand must be an iterable The iterable is expanded into a sequence of items which are included in the new tuple list or set at the site of the unpacking New in version 3 5 Iterable unpacking in expression lists originally proposed by PEP 448 A trailing comma is required only to create a one item tuple such as 1 it is optional in all other cases A single expression without a trailing comma doesn t create a tuple but rather yields the value of that expression To create an empty tuple use an empty pair of parentheses 6 16 Evaluation order Python evaluates expressions from left to right Notice that while evaluating an assignment the right hand side is evaluated before the left hand side In the following lines expressions will be evaluated in the arithmetic order of their suffixes expr1 expr2 expr3 expr4 expr1 expr2 expr3 expr4 expr1 expr2 expr3 expr4 expr1 expr2 expr3 expr4 expr1 expr2 expr3 expr4 expr5 expr3 expr4 expr1 expr2 6 17 Operator precedence The following table summarizes the operator precedence in Python from highest precedence most binding to lowest precedence least binding Operators in the same box have the same precedence Unless the syntax is explicitly given operators are binary Operators in the same box group left to right except for exponentiation and conditional expressions which group from right to left Note that comparisons membership tests and identity tests all have the same precedence and have a left,en
1473, to right chaining feature as described in the Comparisons section Operator Description expressions expressions key Binding or parenthesized expression value expressions list display dictionary display set display x index x index index Subscription slicing call x arguments x attribute attribute reference await x Await expression Exponentiation 5 x x x Positive negative bitwise NOT Multiplication matrix multiplication division floor division remainder 6 Addition and subtraction Shifts Bitwise AND Bitwise XOR Bitwise OR in not in is is not Comparisons including membership tests and identity tests not x Boolean NOT and Boolean AND or Boolean OR if else Conditional expression lambda Lambda expression Assignment expression Footnotes 1 While abs x y abs y is true mathematically for floats it may not be true numerically due to roundoff For example and assuming a platform on which a Python float is an IEEE 754 double precision number in order that 1e 100 1e100 have the same sign as 1e100 the computed result is 1e 100 1e100 which is numerically exactly equal to 1e100 The function math fmod returns a result whose sign matches the sign of the first argument instead and so returns 1e 100 in this case Which approach is more appropriate depends on the application 2 If x is very close to an exact integer multiple of y it s possible for x y to be one larger than x x y y due to rounding In such cases Python returns the latter result in order to preserve that divmod x y 0 y x y be very close to x 3 The Unicode standard distinguishes between code points e g U 0041 and abstract characters e g LATIN CAPITAL LETTER A While most abstract characters in Unicode are only represented using one code point there is a number of abstract characters that can in addition be represented using a sequence of more than one code point For example the abstract character LATIN CAPITAL LETTER C WITH CEDILLA can be represented as a single precomposed character at code position U 00C7 or as a sequence of a base character at code position U 0043 LATIN CAPITAL LETTER C followed by a combining character at code position U 0327 COMBINING CEDILLA The comparison operators on strings compare at the level of Unicode code points This may be counter intuitive to humans For example u00C7 u0043 u0327 is False even though both strings represent the same abstract character LATIN CAPITAL LETTER C WITH CEDILLA To compare strings at the level of abstract characters that is in a way intuitive to humans use unicodedata normalize 4 Due to automatic garbage collection free lists and the dynamic nature of descriptors you may notice seemingly unusual behaviour in certain uses of the is operator like those involving comparisons between instance methods or constants Check their documentation for more info 5 The power operator binds less tightly than an arithmetic or bitwise unary operator on its right that is 2 1 is 0 5 6 The operator is also used for string formatting the same precedence applies,en
1474,1 Command line and environment The CPython interpreter scans the command line and the environment for various settings CPython implementation detail Other implementations command line schemes may differ See Alternate Implementations for further resources 1 1 Command line When invoking Python you may specify any of these options python bBdEhiIOqsSuvVWx c command m module name script args The most common use case is of course a simple invocation of a script python myscript py 1 1 1 Interface options The interpreter interface resembles that of the UNIX shell but provides some additional methods of invocation When called with standard input connected to a tty device it prompts for commands and executes them until an EOF an end of file character you can produce that with Ctrl D on UNIX or Ctrl Z Enter on Windows is read When called with a file name argument or with a file as standard input it reads and executes a script from that file When called with a directory name argument it reads and executes an appropriately named script from that directory When called with c command it executes the Python statement s given as command Here command may contain multiple statements separated by newlines Leading whitespace is significant in Python statements When called with m module name the given module is located on the Python module path and executed as a script In non interactive mode the entire input is parsed before it is executed An interface option terminates the list of options consumed by the interpreter all consecutive arguments will end up in sys argv note that the first element subscript zero sys argv 0 is a string reflecting the program s source c command Execute the Python code in command command can be one or more statements separated by newlines with significant leading whitespace as in normal module code If this option is given the first element of sys argv will be c and the current directory will be added to the start of sys path allowing modules in that directory to be imported as top level modules Raises an auditing event cpython run_command with argument command m module name Search sys path for the named module and execute its contents as the __main__ module Since the argument is a module name you must not give a file extension py The module name should be a valid absolute Python module name but the implementation may not always enforce this e g it may allow you to use a name that includes a hyphen Package names including namespace packages are also permitted When a package name is supplied instead of a normal module the interpreter will execute pkg __main__ as the main module This behaviour is deliberately similar to the handling of directories and zipfiles that are passed to the interpreter as the script argument Note This option cannot be used with built in modules and extension modules written in C since they do not have Python module files However it can still be used for precompiled modules even if the original source file is not available If this option is given the first element of sys argv will be the full path to the module file while the module file is being located the first element will be set to m As with the c option the current directory will be added to the start of sys path I option can be used to run the script in isolated mode where sys path contains neither the current directory nor the user s site packages directory All PYTHON environment variables are ignored too Many standard library modules contain code that is invoked on their execution as a script An example is the timeit module python m timeit s setup here benchmarked code here python m timeit h for details Raises an auditing event cpython run_module with argument module name See also runpy run_module Equivalent functionality directly available to Python code PEP 338 Executing modules as scripts Changed in version 3 1 Supply the package name to run a __main__ submodule Changed in version 3 4 namespace packages are also supported Read commands from standard input sys stdin If standard input is a terminal i is implied If this option is give,en
1475,n the first element of sys argv will be and the current directory will be added to the start of sys path Raises an auditing event cpython run_stdin with no arguments script Execute the Python code contained in script which must be a filesystem path absolute or relative referring to either a Python file a directory containing a __main__ py file or a zipfile containing a __main__ py file If this option is given the first element of sys argv will be the script name as given on the command line If the script name refers directly to a Python file the directory containing that file is added to the start of sys path and the file is executed as the __main__ module If the script name refers to a directory or zipfile the script name is added to the start of sys path and the __main__ py file in that location is executed as the __main__ module I option can be used to run the script in isolated mode where sys path contains neither the script s directory nor the user s site packages directory All PYTHON environment variables are ignored too Raises an auditing event cpython run_file with argument filename See also runpy run_path Equivalent functionality directly available to Python code If no interface option is given i is implied sys argv 0 is an empty string and the current directory will be added to the start of sys path Also tab completion and history editing is automatically enabled if available on your platform see Readline configuration See also Invoking the Interpreter Changed in version 3 4 Automatic enabling of tab completion and history editing 1 1 2 Generic options h help Print a short description of all command line options and corresponding environment variables and exit help env Print a short description of Python specific environment variables and exit New in version 3 11 help xoptions Print a description of implementation specific X options and exit New in version 3 11 help all Print complete usage information and exit New in version 3 11 V version Print the Python version number and exit Example output could be Python 3 8 0b2 When given twice print more information about the build like Python 3 8 0b2 3 8 0c076caaa8 Apr 20 2019 21 55 00 GCC 6 2 0 20161005 New in version 3 6 The VV option 1 1 3 Miscellaneous options b Issue a warning when converting bytes or bytearray to str without specifying encoding or comparing bytes or bytearray with str or bytes with int Issue an error when the option is given twice bb Changed in version 3 5 Affects also comparisons of bytes with int B If given Python won t try to write pyc files on the import of source modules See also PYTHONDONTWRITEBYTECODE check hash based pycs default always never Control the validation behavior of hash based pyc files See Cached bytecode invalidation When set to default checked and unchecked hash based bytecode cache files are validated according to their default semantics When set to always all hash based pyc files whether checked or unchecked are validated against their corresponding source file When set to never hash based pyc files are not validated against their corresponding source files The semantics of timestamp based pyc files are unaffected by this option d Turn on parser debugging output for expert only See also the PYTHONDEBUG environment variable This option requires a debug build of Python otherwise it s ignored E Ignore all PYTHON environment variables e g PYTHONPATH and PYTHONHOME that might be set See also the P and I isolated options i When a script is passed as first argument or the c option is used enter interactive mode after executing the script or the command even when sys stdin does not appear to be a terminal The PYTHONSTARTUP file is not read This can be useful to inspect global variables or a stack trace when a script raises an exception See also PYTHONINSPECT I Run Python in isolated mode This also implies E P and s options In isolated mode sys path contains neither the script s directory nor the user s site packages directory All PYTHON environment variables are ignored too Further restrictions may be imposed to prevent the user ,en
1476,from injecting malicious code New in version 3 4 O Remove assert statements and any code conditional on the value of __debug__ Augment the filename for compiled bytecode files by adding opt 1 before the pyc extension see PEP 488 See also PYTHONOPTIMIZE Changed in version 3 5 Modify pyc filenames according to PEP 488 OO Do O and also discard docstrings Augment the filename for compiled bytecode files by adding opt 2 before the pyc extension see PEP 488 Changed in version 3 5 Modify pyc filenames according to PEP 488 P Don t prepend a potentially unsafe path to sys path python m module command line Don t prepend the current working directory python script py command line Don t prepend the script s directory If it s a symbolic link resolve symbolic links python c code and python REPL command lines Don t prepend an empty string which means the current working directory See also the PYTHONSAFEPATH environment variable and E and I isolated options New in version 3 11 q Don t display the copyright and version messages even in interactive mode New in version 3 2 R Turn on hash randomization This option only has an effect if the PYTHONHASHSEED environment variable is set to 0 since hash randomization is enabled by default On previous versions of Python this option turns on hash randomization so that the __hash__ values of str and bytes objects are salted with an unpredictable random value Although they remain constant within an individual Python process they are not predictable between repeated invocations of Python Hash randomization is intended to provide protection against a denial of service caused by carefully chosen inputs that exploit the worst case performance of a dict construction O n 2 complexity See http ocert org advisories ocert 2011 003 html for details PYTHONHASHSEED allows you to set a fixed value for the hash seed secret New in version 3 2 3 Changed in version 3 7 The option is no longer ignored s Don t add the user site packages directory to sys path See also PYTHONNOUSERSITE See also PEP 370 Per user site packages directory S Disable the import of the module site and the site dependent manipulations of sys path that it entails Also disable these manipulations if site is explicitly imported later call site main if you want them to be triggered u Force the stdout and stderr streams to be unbuffered This option has no effect on the stdin stream See also PYTHONUNBUFFERED Changed in version 3 7 The text layer of the stdout and stderr streams now is unbuffered v Print a message each time a module is initialized showing the place filename or built in module from which it is loaded When given twice vv print a message for each file that is checked for when searching for a module Also provides information on module cleanup at exit Changed in version 3 10 The site module reports the site specific paths and pth files being processed See also PYTHONVERBOSE W arg Warning control Python s warning machinery by default prints warning messages to sys stderr The simplest settings apply a particular action unconditionally to all warnings emitted by a process even those that are otherwise ignored by default Wdefault Warn once per call location Werror Convert to exceptions Walways Warn every time Wmodule Warn once per calling module Wonce Warn once per Python process Wignore Never warn The action names can be abbreviated as desired and the interpreter will resolve them to the appropriate action name For example Wi is the same as Wignore The full form of argument is action message category module lineno Empty fields match all values trailing empty fields may be omitted For example W ignore DeprecationWarning ignores all DeprecationWarning warnings The action field is as explained above but only applies to warnings that match the remaining fields The message field must match the whole warning message this match is case insensitive The category field matches the warning category ex DeprecationWarning This must be a class name the match test whether the actual warning category of the message is a subclass of the specified warning categ,en
1477,ory The module field matches the fully qualified module name this match is case sensitive The lineno field matches the line number where zero matches all line numbers and is thus equivalent to an omitted line number Multiple W options can be given when a warning matches more than one option the action for the last matching option is performed Invalid W options are ignored though a warning message is printed about invalid options when the first warning is issued Warnings can also be controlled using the PYTHONWARNINGS environment variable and from within a Python program using the warnings module For example the warnings filterwarnings function can be used to use a regular expression on the warning message See The Warnings Filter and Describing Warning Filters for more details x Skip the first line of the source allowing use of non Unix forms of cmd This is intended for a DOS specific hack only X Reserved for various implementation specific options CPython currently defines the following possible values X faulthandler to enable faulthandler See also PYTHONFAULTHANDLER X showrefcount to output the total reference count and number of used memory blocks when the program finishes or after each statement in the interactive interpreter This only works on debug builds X tracemalloc to start tracing Python memory allocations using the tracemalloc module By default only the most recent frame is stored in a traceback of a trace Use X tracemalloc NFRAME to start tracing with a traceback limit of NFRAME frames See tracemalloc start and PYTHONTRACEMALLOC for more information X int_max_str_digits configures the integer string conversion length limitation See also PYTHONINTMAXSTRDIGITS X importtime to show how long each import takes It shows module name cumulative time including nested imports and self time excluding nested imports Note that its output may be broken in multi threaded application Typical usage is python3 X importtime c import asyncio See also PYTHONPROFILEIMPORTTIME X dev enable Python Development Mode introducing additional runtime checks that are too expensive to be enabled by default See also PYTHONDEVMODE X utf8 enables the Python UTF 8 Mode X utf8 0 explicitly disables Python UTF 8 Mode even when it would otherwise activate automatically See also PYTHONUTF8 X pycache_prefix PATH enables writing pyc files to a parallel tree rooted at the given directory instead of to the code tree See also PYTHONPYCACHEPREFIX X warn_default_encoding issues a EncodingWarning when the locale specific default encoding is used for opening files See also PYTHONWARNDEFAULTENCODING X no_debug_ranges disables the inclusion of the tables mapping extra location information end line start column offset and end column offset to every instruction in code objects This is useful when smaller code objects and pyc files are desired as well as suppressing the extra visual location indicators when the interpreter displays tracebacks See also PYTHONNODEBUGRANGES X frozen_modules determines whether or not frozen modules are ignored by the import machinery A value of on means they get imported and off means they are ignored The default is on if this is an installed Python the normal case If it s under development running from the source tree then the default is off Note that the importlib_bootstrap and importlib_bootstrap_external frozen modules are always used even if this flag is set to off X perf enables support for the Linux perf profiler When this option is provided the perf profiler will be able to report Python calls This option is only available on some platforms and will do nothing if is not supported on the current system The default value is off See also PYTHONPERFSUPPORT and Python support for the Linux perf profiler It also allows passing arbitrary values and retrieving them through the sys _xoptions dictionary New in version 3 2 Changed in version 3 3 Added the X faulthandler option Changed in version 3 4 Added the X showrefcount and X tracemalloc options Changed in version 3 6 Added the X showalloccount option Changed in version 3 7 Added t,en
1478,he X importtime X dev and X utf8 options Changed in version 3 8 Added the X pycache_prefix option The X dev option now logs close exceptions in io IOBase destructor Changed in version 3 9 Using X dev option check encoding and errors arguments on string encoding and decoding operations The X showalloccount option has been removed Changed in version 3 10 Added the X warn_default_encoding option Removed the X oldparser option Changed in version 3 11 Added the X no_debug_ranges X frozen_modules and X int_max_str_digits options Changed in version 3 12 Added the X perf option 1 1 4 Options you shouldn t use J Reserved for use by Jython 1 2 Environment variables These environment variables influence Python s behavior they are processed before the command line switches other than E or I It is customary that command line switches override environmental variables where there is a conflict PYTHONHOME Change the location of the standard Python libraries By default the libraries are searched in prefix lib python version and exec_prefix lib python version where prefix and exec_prefix are installation dependent directories both defaulting to usr local When PYTHONHOME is set to a single directory its value replaces both prefix and exec_prefix To specify different values for these set PYTHONHOME to prefix exec_prefix PYTHONPATH Augment the default search path for module files The format is the same as the shell s PATH one or more directory pathnames separated by os pathsep e g colons on Unix or semicolons on Windows Non existent directories are silently ignored In addition to normal directories individual PYTHONPATH entries may refer to zipfiles containing pure Python modules in either source or compiled form Extension modules cannot be imported from zipfiles The default search path is installation dependent but generally begins with prefix lib python version see PYTHONHOME above It is always appended to PYTHONPATH An additional directory will be inserted in the search path in front of PYTHONPATH as described above under Interface options The search path can be manipulated from within a Python program as the variable sys path PYTHONSAFEPATH If this is set to a non empty string don t prepend a potentially unsafe path to sys path see the P option for details New in version 3 11 PYTHONPLATLIBDIR If this is set to a non empty string it overrides the sys platlibdir value New in version 3 9 PYTHONSTARTUP If this is the name of a readable file the Python commands in that file are executed before the first prompt is displayed in interactive mode The file is executed in the same namespace where interactive commands are executed so that objects defined or imported in it can be used without qualification in the interactive session You can also change the prompts sys ps1 and sys ps2 and the hook sys __interactivehook__ in this file Raises an auditing event cpython run_startup with the filename as the argument when called on startup PYTHONOPTIMIZE If this is set to a non empty string it is equivalent to specifying the O option If set to an integer it is equivalent to specifying O multiple times PYTHONBREAKPOINT If this is set it names a callable using dotted path notation The module containing the callable will be imported and then the callable will be run by the default implementation of sys breakpointhook which itself is called by built in breakpoint If not set or set to the empty string it is equivalent to the value pdb set_trace Setting this to the string 0 causes the default implementation of sys breakpointhook to do nothing but return immediately New in version 3 7 PYTHONDEBUG If this is set to a non empty string it is equivalent to specifying the d option If set to an integer it is equivalent to specifying d multiple times This environment variable requires a debug build of Python otherwise it s ignored PYTHONINSPECT If this is set to a non empty string it is equivalent to specifying the i option This variable can also be modified by Python code using os environ to force inspect mode on program termination PYTHONUNBUFFERED If this is set to a ,en
1479,non empty string it is equivalent to specifying the u option PYTHONVERBOSE If this is set to a non empty string it is equivalent to specifying the v option If set to an integer it is equivalent to specifying v multiple times PYTHONCASEOK If this is set Python ignores case in import statements This only works on Windows and macOS PYTHONDONTWRITEBYTECODE If this is set to a non empty string Python won t try to write pyc files on the import of source modules This is equivalent to specifying the B option PYTHONPYCACHEPREFIX If this is set Python will write pyc files in a mirror directory tree at this path instead of in __pycache__ directories within the source tree This is equivalent to specifying the X pycache_prefix PATH option New in version 3 8 PYTHONHASHSEED If this variable is not set or set to random a random value is used to seed the hashes of str and bytes objects If PYTHONHASHSEED is set to an integer value it is used as a fixed seed for generating the hash of the types covered by the hash randomization Its purpose is to allow repeatable hashing such as for selftests for the interpreter itself or to allow a cluster of python processes to share hash values The integer must be a decimal number in the range 0 4294967295 Specifying the value 0 will disable hash randomization New in version 3 2 3 PYTHONINTMAXSTRDIGITS If this variable is set to an integer it is used to configure the interpreter s global integer string conversion length limitation New in version 3 11 PYTHONIOENCODING If this is set before running the interpreter it overrides the encoding used for stdin stdout stderr in the syntax encodingname errorhandler Both the encodingname and the errorhandler parts are optional and have the same meaning as in str encode For stderr the errorhandler part is ignored the handler will always be backslashreplace Changed in version 3 4 The encodingname part is now optional Changed in version 3 6 On Windows the encoding specified by this variable is ignored for interactive console buffers unless PYTHONLEGACYWINDOWSSTDIO is also specified Files and pipes redirected through the standard streams are not affected PYTHONNOUSERSITE If this is set Python won t add the user site packages directory to sys path See also PEP 370 Per user site packages directory PYTHONUSERBASE Defines the user base directory which is used to compute the path of the user site packages directory and installation paths for python m pip install user See also PEP 370 Per user site packages directory PYTHONEXECUTABLE If this environment variable is set sys argv 0 will be set to its value instead of the value got through the C runtime Only works on macOS PYTHONWARNINGS This is equivalent to the W option If set to a comma separated string it is equivalent to specifying W multiple times with filters later in the list taking precedence over those earlier in the list The simplest settings apply a particular action unconditionally to all warnings emitted by a process even those that are otherwise ignored by default PYTHONWARNINGS default Warn once per call location PYTHONWARNINGS error Convert to exceptions PYTHONWARNINGS always Warn every time PYTHONWARNINGS module Warn once per calling module PYTHONWARNINGS once Warn once per Python process PYTHONWARNINGS ignore Never warn See The Warnings Filter and Describing Warning Filters for more details PYTHONFAULTHANDLER If this environment variable is set to a non empty string faulthandler enable is called at startup install a handler for SIGSEGV SIGFPE SIGABRT SIGBUS and SIGILL signals to dump the Python traceback This is equivalent to X faulthandler option New in version 3 3 PYTHONTRACEMALLOC If this environment variable is set to a non empty string start tracing Python memory allocations using the tracemalloc module The value of the variable is the maximum number of frames stored in a traceback of a trace For example PYTHONTRACEMALLOC 1 stores only the most recent frame See the tracemalloc start function for more information This is equivalent to setting the X tracemalloc option New in version 3 4 PYTHONPROFILEIMPORT,en
1480,TIME If this environment variable is set to a non empty string Python will show how long each import takes This is equivalent to setting the X importtime option New in version 3 7 PYTHONASYNCIODEBUG If this environment variable is set to a non empty string enable the debug mode of the asyncio module New in version 3 4 PYTHONMALLOC Set the Python memory allocators and or install debug hooks Set the family of memory allocators used by Python default use the default memory allocators malloc use the malloc function of the C library for all domains PYMEM_DOMAIN_RAW PYMEM_DOMAIN_MEM PYMEM_DOMAIN_OBJ pymalloc use the pymalloc allocator for PYMEM_DOMAIN_MEM and PYMEM_DOMAIN_OBJ domains and use the malloc function for the PYMEM_DOMAIN_RAW domain Install debug hooks debug install debug hooks on top of the default memory allocators malloc_debug same as malloc but also install debug hooks pymalloc_debug same as pymalloc but also install debug hooks New in version 3 6 Changed in version 3 7 Added the default allocator PYTHONMALLOCSTATS If set to a non empty string Python will print statistics of the pymalloc memory allocator every time a new pymalloc object arena is created and on shutdown This variable is ignored if the PYTHONMALLOC environment variable is used to force the malloc allocator of the C library or if Python is configured without pymalloc support Changed in version 3 6 This variable can now also be used on Python compiled in release mode It now has no effect if set to an empty string PYTHONLEGACYWINDOWSFSENCODING If set to a non empty string the default filesystem encoding and error handler mode will revert to their pre 3 6 values of mbcs and replace respectively Otherwise the new defaults utf 8 and surrogatepass are used This may also be enabled at runtime with sys _enablelegacywindowsfsencoding Availability Windows New in version 3 6 See PEP 529 for more details PYTHONLEGACYWINDOWSSTDIO If set to a non empty string does not use the new console reader and writer This means that Unicode characters will be encoded according to the active console code page rather than using utf 8 This variable is ignored if the standard streams are redirected to files or pipes rather than referring to console buffers Availability Windows New in version 3 6 PYTHONCOERCECLOCALE If set to the value 0 causes the main Python command line application to skip coercing the legacy ASCII based C and POSIX locales to a more capable UTF 8 based alternative If this variable is not set or is set to a value other than 0 the LC_ALL locale override environment variable is also not set and the current locale reported for the LC_CTYPE category is either the default C locale or else the explicitly ASCII based POSIX locale then the Python CLI will attempt to configure the following locales for the LC_CTYPE category in the order listed before loading the interpreter runtime C UTF 8 C utf8 UTF 8 If setting one of these locale categories succeeds then the LC_CTYPE environment variable will also be set accordingly in the current process environment before the Python runtime is initialized This ensures that in addition to being seen by both the interpreter itself and other locale aware components running in the same process such as the GNU readline library the updated setting is also seen in subprocesses regardless of whether or not those processes are running a Python interpreter as well as in operations that query the environment rather than the current C locale such as Python s own locale getdefaultlocale Configuring one of these locales either explicitly or via the above implicit locale coercion automatically enables the surrogateescape error handler for sys stdin and sys stdout sys stderr continues to use backslashreplace as it does in any other locale This stream handling behavior can be overridden using PYTHONIOENCODING as usual For debugging purposes setting PYTHONCOERCECLOCALE warn will cause Python to emit warning messages on stderr if either the locale coercion activates or else if a locale that would have triggered coercion is still active when the Pyth,en
1481,on runtime is initialized Also note that even when locale coercion is disabled or when it fails to find a suitable target locale PYTHONUTF8 will still activate by default in legacy ASCII based locales Both features must be disabled in order to force the interpreter to use ASCII instead of UTF 8 for system interfaces Availability Unix New in version 3 7 See PEP 538 for more details PYTHONDEVMODE If this environment variable is set to a non empty string enable Python Development Mode introducing additional runtime checks that are too expensive to be enabled by default This is equivalent to setting the X dev option New in version 3 7 PYTHONUTF8 If set to 1 enable the Python UTF 8 Mode If set to 0 disable the Python UTF 8 Mode Setting any other non empty string causes an error during interpreter initialisation New in version 3 7 PYTHONWARNDEFAULTENCODING If this environment variable is set to a non empty string issue a EncodingWarning when the locale specific default encoding is used See Opt in EncodingWarning for details New in version 3 10 PYTHONNODEBUGRANGES If this variable is set it disables the inclusion of the tables mapping extra location information end line start column offset and end column offset to every instruction in code objects This is useful when smaller code objects and pyc files are desired as well as suppressing the extra visual location indicators when the interpreter displays tracebacks New in version 3 11 PYTHONPERFSUPPORT If this variable is set to a nonzero value it enables support for the Linux perf profiler so Python calls can be detected by it If set to 0 disable Linux perf profiler support See also the X perf command line option and Python support for the Linux perf profiler New in version 3 12 1 2 1 Debug mode variables PYTHONDUMPREFS If set Python will dump objects and reference counts still alive after shutting down the interpreter Need Python configured with the with trace refs build option PYTHONDUMPREFSFILE FILENAME If set Python will dump objects and reference counts still alive after shutting down the interpreter into a file called FILENAME Need Python configured with the with trace refs build option New in version 3 11,en
1482,Debugging C API extensions and CPython Internals with GDB This document explains how the Python GDB extension python gdb py can be used with the GDB debugger to debug CPython extensions and the CPython interpreter itself When debugging low level problems such as crashes or deadlocks a low level debugger such as GDB is useful to diagnose and correct the issue By default GDB or any of its front ends doesn t support high level information specific to the CPython interpreter The python gdb py extension adds CPython interpreter information to GDB The extension helps introspect the stack of currently executing Python functions Given a Python object represented by a PyObject pointer the extension surfaces the type and value of the object Developers who are working on CPython extensions or tinkering with parts of CPython that are written in C can use this document to learn how to use the python gdb py extension with GDB Note This document assumes that you are familiar with the basics of GDB and the CPython C API It consolidates guidance from the devguide and the Python wiki Prerequisites You need to have GDB 7 or later For earlier versions of GDB see Misc gdbinit in the sources of Python 3 11 or earlier GDB compatible debugging information for Python and any extension you are debugging The python gdb py extension The extension is built with Python but might be distributed separately or not at all Below we include tips for a few common systems as examples Note that even if the instructions match your system they might be outdated Setup with Python built from source When you build CPython from source debugging information should be available and the build should add a python gdb py file to the root directory of your repository To activate support you must add the directory containing python gdb py to GDB s auto load safe path If you haven t done this recent versions of GDB will print out a warning with instructions on how to do this Note If you do not see instructions for your version of GDB put this in your configuration file gdbinit or config gdb gdbinit add auto load safe path path to cpython You can also add multiple paths separated by Setup for Python from a Linux distro Most Linux systems provide debug information for the system Python in a package called python debuginfo python dbg or similar For example Fedora sudo dnf install gdb sudo dnf debuginfo install python3 Ubuntu sudo apt install gdb python3 dbg On several recent Linux systems GDB can download debugging symbols automatically using debuginfod However this will not install the python gdb py extension you generally do need to install the debug info package separately Using the Debug build and Development mode For easier debugging you might want to Use a debug build of Python When building from source use configure with pydebug On Linux distros install and run a package like python debug or python dbg if available Use the runtime development mode X dev Both enable extra assertions and disable some optimizations Sometimes this hides the bug you are trying to find but in most cases they make the process easier Using the python gdb extension When the extension is loaded it provides two main features pretty printers for Python values and additional commands Pretty printers This is what a GDB backtrace looks like truncated when this extension is enabled 0 0x000000000041a6b1 in PyObject_Malloc nbytes Cannot access memory at address 0x7fffff7fefe8 at Objects obmalloc c 748 1 0x000000000041b7c0 in _PyObject_DebugMallocApi id 111 o nbytes 24 at Objects obmalloc c 1445 2 0x000000000041b717 in _PyObject_DebugMalloc nbytes 24 at Objects obmalloc c 1412 3 0x000000000044060a in _PyUnicode_New length 11 at Objects unicodeobject c 346 4 0x00000000004466aa in PyUnicodeUCS2_DecodeUTF8Stateful s 0x5c2b8d __lltrace__ size 11 errors 0x0 consumed 0x0 at Objects unicodeobject c 2531 5 0x0000000000446647 in PyUnicodeUCS2_DecodeUTF8 s 0x5c2b8d __lltrace__ size 11 errors 0x0 at Objects unicodeobject c 2495 6 0x0000000000440d1b in PyUnicodeUCS2_FromStringAndSize u 0x5c2b8d __lltrace__ size 11 a,en
1483,t Objects unicodeobject c 551 7 0x0000000000440d94 in PyUnicodeUCS2_FromString u 0x5c2b8d __lltrace__ at Objects unicodeobject c 569 8 0x0000000000584abd in PyDict_GetItemString v Yuck type at remote 0xad4730 __builtins__ module at remote 0x7ffff7fd5ee8 __file__ Lib test crashers nasty_eq_vs_dict py __package__ None y Yuck i 0 at remote 0xaacd80 dict 0 0 1 1 2 2 3 3 __cached__ None __name__ __main__ z Yuck i 0 at remote 0xaace60 __doc__ None key 0x5c2b8d __lltrace__ at Objects dictobject c 2171 Notice how the dictionary argument to PyDict_GetItemString is displayed as its repr rather than an opaque PyObject pointer The extension works by supplying a custom printing routine for values of type PyObject If you need to access lower level details of an object then cast the value to a pointer of the appropriate type For example gdb p globals 1 __builtins__ module at remote 0x7ffff7fb1868 __name__ __main__ ctypes module at remote 0x7ffff7f14360 __doc__ None __package__ None gdb p PyDictObject globals 2 ob_refcnt 3 ob_type 0x3dbdf85820 ma_fill 5 ma_used 5 ma_mask 7 ma_table 0x63d0f8 ma_lookup 0x3dbdc7ea70 lookdict_string ma_smalltable me_hash 7065186196740147912 me_key __builtins__ me_value module at remote 0x7ffff7fb1868 me_hash 368181376027291943 me_key __name__ me_value __main__ me_hash 0 me_key 0x0 me_value 0x0 me_hash 0 me_key 0x0 me_value 0x0 me_hash 9177857982131165996 me_key ctypes me_value module at remote 0x7ffff7f14360 me_hash 8518757509529533123 me_key __doc__ me_value None me_hash 0 me_key 0x0 me_value 0x0 me_hash 6614918939584953775 me_key __package__ me_value None Note that the pretty printers do not actually call repr For basic types they try to match its result closely An area that can be confusing is that the custom printer for some types look a lot like GDB s built in printer for standard types For example the pretty printer for a Python int PyLongObject gives a representation that is not distinguishable from one of a regular machine level integer gdb p some_machine_integer 3 42 gdb p some_python_integer 4 42 The internal structure can be revealed with a cast to PyLongObject gdb p PyLongObject some_python_integer 5 ob_base ob_base ob_refcnt 8 ob_type 0x3dad39f5e0 ob_size 1 ob_digit 42 A similar confusion can arise with the str type where the output looks a lot like gdb s built in printer for char gdb p ptr_to_python_str 6 __builtins__ The pretty printer for str instances defaults to using single quotes as does Python s repr for strings whereas the standard printer for char values uses double quotes and contains a hexadecimal address gdb p ptr_to_char_star 7 0x6d72c0 hello world Again the implementation details can be revealed with a cast to PyUnicodeObject gdb p PyUnicodeObject 6 8 ob_base ob_refcnt 33 ob_type 0x3dad3a95a0 length 12 str 0x7ffff2128500 hash 7065186196740147912 state 1 defenc 0x0 py list The extension adds a py list command which lists the Python source code if any for the current frame in the selected thread The current line is marked with a gdb py list 901 if options profile 902 options profile False 903 profile_me 904 return 905 906 u UI 907 if not u quit 908 try 909 gtk main 910 except KeyboardInterrupt 911 properly quit on a keyboard interrupt Use py list START to list at a different line number within the Python source and py list START END to list a specific range of lines within the Python source py up and py down The py up and py down commands are analogous to GDB s regular up and down commands but try to move at the level of CPython frames rather than C frames GDB is not always able to read the relevant frame information depending on the optimization level with which CPython was compiled Internally the commands look for C frames that are executing the default frame evaluation function that is the core bytecode interpreter loop within CPython and look up the value of the related PyFrameObject They emit the frame number at the C level within the thread For example gdb py up 37 Frame 0x9420b04 for file usr lib python2 6 site packages gnome_sudoku main py line 906 in start_game u UI gdb py,en
1484, up 40 Frame 0x948e82c for file usr lib python2 6 site packages gnome_sudoku gnome_sudoku py line 22 in start_game main module at remote 0xb771b7f4 main start_game gdb py up Unable to find an older python frame so we re at the top of the Python stack The frame numbers correspond to those displayed by GDB s standard backtrace command The command skips C frames which are not executing Python code Going back down gdb py down 37 Frame 0x9420b04 for file usr lib python2 6 site packages gnome_sudoku main py line 906 in start_game u UI gdb py down 34 unable to read python frame information gdb py down 23 unable to read python frame information gdb py down 19 unable to read python frame information gdb py down 14 Frame 0x99262ac for file usr lib python2 6 site packages gnome_sudoku game_selector py line 201 in run_swallowed_dialog self NewOrSavedGameSelector new_game_model gtk ListStore at remote 0x98fab44 puzzle None saved_games gsd auto_fills 0 tracking trackers notes saved_at 1270084485 game 7 8 0 0 0 0 0 5 6 0 0 9 0 8 0 1 0 0 0 4 6 0 0 0 0 7 0 6 5 0 0 0 4 7 9 2 0 0 0 9 0 1 0 0 0 3 9 7 6 0 0 0 1 8 0 6 0 0 0 0 2 8 0 0 0 5 0 4 0 6 0 0 2 1 0 0 0 0 0 4 5 n7 8 0 0 0 0 0 5 6 0 0 9 0 8 0 1 0 0 0 4 6 0 0 0 0 7 0 6 5 1 8 3 4 7 9 2 0 0 0 9 0 1 0 0 0 3 9 7 6 0 0 0 1 8 0 6 0 0 0 0 2 8 0 0 0 5 0 4 0 6 0 0 2 1 0 0 0 0 0 4 5 gsd impossible_hints 0 timer __absolute_start_time__ float at remote 0x984b474 gsd hints 0 timer active_time float at remote 0x984b494 timer total_time float at remote 0x984b464 dialog gtk Dialog at remote 0x98faaa4 saved_game_model gtk ListStore at remote 0x98fad24 sudoku_maker SudokuMaker terminated False played batch_siz truncated swallower run_dialog self dialog gdb py down 11 Frame 0x9aead74 for file usr lib python2 6 site packages gnome_sudoku dialog_swallower py line 48 in run_dialog self SwappableArea running gtk Dialog at remote 0x98faaa4 main_page 0 at remote 0x98fa6e4 d gtk Dialog at remote 0x98faaa4 gtk main gdb py down 8 unable to read python frame information gdb py down Unable to find a newer python frame and we re at the bottom of the Python stack Note that in Python 3 12 and newer the same C stack frame can be used for multiple Python stack frames This means that py up and py down may move multiple Python frames at once For example gdb py up 6 Frame 0x7ffff7fb62b0 for file tmp rec py line 5 in recursive_function n 0 time sleep 5 6 Frame 0x7ffff7fb6240 for file tmp rec py line 7 in recursive_function n 1 recursive_function n 1 6 Frame 0x7ffff7fb61d0 for file tmp rec py line 7 in recursive_function n 2 recursive_function n 1 6 Frame 0x7ffff7fb6160 for file tmp rec py line 7 in recursive_function n 3 recursive_function n 1 6 Frame 0x7ffff7fb60f0 for file tmp rec py line 7 in recursive_function n 4 recursive_function n 1 6 Frame 0x7ffff7fb6080 for file tmp rec py line 7 in recursive_function n 5 recursive_function n 1 6 Frame 0x7ffff7fb6020 for file tmp rec py line 9 in module recursive_function 5 gdb py up Unable to find an older python frame py bt The py bt command attempts to display a Python level backtrace of the current thread For example gdb py bt 8 unable to read python frame information 11 Frame 0x9aead74 for file usr lib python2 6 site packages gnome_sudoku dialog_swallower py line 48 in run_dialog self SwappableArea running gtk Dialog at remote 0x98faaa4 main_page 0 at remote 0x98fa6e4 d gtk Dialog at remote 0x98faaa4 gtk main 14 Frame 0x99262ac for file usr lib python2 6 site packages gnome_sudoku game_selector py line 201 in run_swallowed_dialog self NewOrSavedGameSelector new_game_model gtk ListStore at remote 0x98fab44 puzzle None saved_games gsd auto_fills 0 tracking trackers notes saved_at 1270084485 game 7 8 0 0 0 0 0 5 6 0 0 9 0 8 0 1 0 0 0 4 6 0 0 0 0 7 0 6 5 0 0 0 4 7 9 2 0 0 0 9 0 1 0 0 0 3 9 7 6 0 0 0 1 8 0 6 0 0 0 0 2 8 0 0 0 5 0 4 0 6 0 0 2 1 0 0 0 0 0 4 5 n7 8 0 0 0 0 0 5 6 0 0 9 0 8 0 1 0 0 0 4 6 0 0 0 0 7 0 6 5 1 8 3 4 7 9 2 0 0 0 9 0 1 0 0 0 3 9 7 6 0 0 0 1 8 0 6 0 0 0 0 2 8 0 0 0 5 0 4 0 6 0 0 2 1 0 0 0 0 0 4 5 gsd impossible_hints 0 timer __absolute_start_time__ float at remot,en
1485,e 0x984b474 gsd hints 0 timer active_time float at remote 0x984b494 timer total_time float at remote 0x984b464 dialog gtk Dialog at remote 0x98faaa4 saved_game_model gtk ListStore at remote 0x98fad24 sudoku_maker SudokuMaker terminated False played batch_siz truncated swallower run_dialog self dialog 19 unable to read python frame information 23 unable to read python frame information 34 unable to read python frame information 37 Frame 0x9420b04 for file usr lib python2 6 site packages gnome_sudoku main py line 906 in start_game u UI 40 Frame 0x948e82c for file usr lib python2 6 site packages gnome_sudoku gnome_sudoku py line 22 in start_game main module at remote 0xb771b7f4 main start_game The frame numbers correspond to those displayed by GDB s standard backtrace command py print The py print command looks up a Python name and tries to print it It looks in locals within the current thread then globals then finally builtins gdb py print self local self SwappableArea running gtk Dialog at remote 0x98faaa4 main_page 0 at remote 0x98fa6e4 gdb py print __name__ global __name__ gnome_sudoku dialog_swallower gdb py print len builtin len built in function len gdb py print scarlet_pimpernel scarlet_pimpernel not found If the current C frame corresponds to multiple Python frames py print only considers the first one py locals The py locals command looks up all Python locals within the current Python frame in the selected thread and prints their representations gdb py locals self SwappableArea running gtk Dialog at remote 0x98faaa4 main_page 0 at remote 0x98fa6e4 d gtk Dialog at remote 0x98faaa4 If the current C frame corresponds to multiple Python frames locals from all of them will be shown gdb py locals Locals for recursive_function n 0 Locals for recursive_function n 1 Locals for recursive_function n 2 Locals for recursive_function n 3 Locals for recursive_function n 4 Locals for recursive_function n 5 Locals for module Use with GDB commands The extension commands complement GDB s built in commands For example you can use a frame numbers shown by py bt with the frame command to go a specific frame within the selected thread like this gdb py bt output snipped 68 Frame 0xaa4560 for file Lib test regrtest py line 1548 in module main gdb frame 68 68 0x00000000004cd1e6 in PyEval_EvalFrameEx f Frame 0xaa4560 for file Lib test regrtest py line 1548 in module throwflag 0 at Python ceval c 2665 2665 x call_function sp oparg gdb py list 1543 Run the tests in a context manager that temporary changes the CWD to a 1544 temporary and writable directory If it s not possible to create or 1545 change the CWD the original CWD will be used The original CWD is 1546 available from test_support SAVEDCWD 1547 with test_support temp_cwd TESTCWD quiet True 1548 main The info threads command will give you a list of the threads within the process and you can use the thread command to select a different one gdb info threads 105 Thread 0x7fffefa18710 LWP 10260 sem_wait at nptl sysdeps unix sysv linux x86_64 sem_wait S 86 104 Thread 0x7fffdf5fe710 LWP 10259 sem_wait at nptl sysdeps unix sysv linux x86_64 sem_wait S 86 1 Thread 0x7ffff7fe2700 LWP 10145 0x00000038e46d73e3 in select at sysdeps unix syscall template S 82 You can use thread apply all COMMAND or t a a COMMAND for short to run a command on all threads With py bt this lets you see what every thread is doing at the Python level gdb t a a py bt Thread 105 Thread 0x7fffefa18710 LWP 10260 5 Frame 0x7fffd00019d0 for file home david coding python svn Lib threading py line 155 in _acquire_restore self _RLock _Verbose__verbose False _RLock__owner 140737354016512 _RLock__block thread lock at remote 0x858770 _RLock__count 1 at remote 0xd7ff40 count_owner 1 140737213728528 count 1 owner 140737213728528 self __block acquire 8 Frame 0x7fffac001640 for file home david coding python svn Lib threading py line 269 in wait self _Condition _Condition__lock _RLock _Verbose__verbose False _RLock__owner 140737354016512 _RLock__block thread lock at remote 0x858770 _RLock__count 1 at remote 0xd7ff40 acquire instancemeth,en
1486,od at remote 0xd80260 _is_owned instancemethod at remote 0xd80160 _release_save instancemethod at remote 0xd803e0 release instancemethod at remote 0xd802e0 _acquire_restore instancemethod at remote 0xd7ee60 _Verbose__verbose False _Condition__waiters at remote 0xd7fd10 timeout None waiter thread lock at remote 0x858a90 saved_state 1 140737213728528 self _acquire_restore saved_state 12 Frame 0x7fffb8001a10 for file home david coding python svn Lib test lock_tests py line 348 in f cond wait 16 Frame 0x7fffb8001c40 for file home david coding python svn Lib test lock_tests py line 37 in task tid 140737213728528 f Thread 104 Thread 0x7fffdf5fe710 LWP 10259 5 Frame 0x7fffe4001580 for file home david coding python svn Lib threading py line 155 in _acquire_restore self _RLock _Verbose__verbose False _RLock__owner 140737354016512 _RLock__block thread lock at remote 0x858770 _RLock__count 1 at remote 0xd7ff40 count_owner 1 140736940992272 count 1 owner 140736940992272 self __block acquire 8 Frame 0x7fffc8002090 for file home david coding python svn Lib threading py line 269 in wait self _Condition _Condition__lock _RLock _Verbose__verbose False _RLock__owner 140737354016512 _RLock__block thread lock at remote 0x858770 _RLock__count 1 at remote 0xd7ff40 acquire instancemethod at remote 0xd80260 _is_owned instancemethod at remote 0xd80160 _release_save instancemethod at remote 0xd803e0 release instancemethod at remote 0xd802e0 _acquire_restore instancemethod at remote 0xd7ee60 _Verbose__verbose False _Condition__waiters at remote 0xd7fd10 timeout None waiter thread lock at remote 0x858860 saved_state 1 140736940992272 self _acquire_restore saved_state 12 Frame 0x7fffac001c90 for file home david coding python svn Lib test lock_tests py line 348 in f cond wait 16 Frame 0x7fffac0011c0 for file home david coding python svn Lib test lock_tests py line 37 in task tid 140736940992272 f Thread 1 Thread 0x7ffff7fe2700 LWP 10145 5 Frame 0xcb5380 for file home david coding python svn Lib test lock_tests py line 16 in _wait time sleep 0 01 8 Frame 0x7fffd00024a0 for file home david coding python svn Lib test lock_tests py line 378 in _check_notify self ConditionTests _testMethodName test_notify _resultForDoCleanups TestResult _original_stdout cStringIO StringO at remote 0xc191e0 skipped _mirrorOutput False testsRun 39 buffer False _original_stderr file at remote 0x7ffff7fc6340 _stdout_buffer cStringIO StringO at remote 0xc9c7f8 _stderr_buffer cStringIO StringO at remote 0xc9c790 _moduleSetUpFailed False expectedFailures errors _previousTestClass type at remote 0x928310 unexpectedSuccesses failures shouldStop False failfast False at remote 0xc185a0 _threads 0 _cleanups _type_equality_funcs type at remote 0x7eba00 instancemethod at remote 0xd750e0 type at remote 0x7e7820 instancemethod at remote 0xd75160 type at remote 0x7e30e0 instancemethod at remote 0xd75060 type at remote 0x7e7d20 instancemethod at remote 0xd751e0 type at remote 0x7f19e0 truncated _wait,en
1487,webbrowser Convenient web browser controller Source code Lib webbrowser py The webbrowser module provides a high level interface to allow displaying web based documents to users Under most circumstances simply calling the open function from this module will do the right thing Under Unix graphical browsers are preferred under X11 but text mode browsers will be used if graphical browsers are not available or an X11 display isn t available If text mode browsers are used the calling process will block until the user exits the browser If the environment variable BROWSER exists it is interpreted as the os pathsep separated list of browsers to try ahead of the platform defaults When the value of a list part contains the string s then it is interpreted as a literal browser command line to be used with the argument URL substituted for s if the part does not contain s it is simply interpreted as the name of the browser to launch 1 For non Unix platforms or when a remote browser is available on Unix the controlling process will not wait for the user to finish with the browser but allow the remote browser to maintain its own windows on the display If remote browsers are not available on Unix the controlling process will launch a new browser and wait The script webbrowser can be used as a command line interface for the module It accepts a URL as the argument It accepts the following optional parameters n opens the URL in a new browser window if possible t opens the URL in a new browser page tab The options are naturally mutually exclusive Usage example python m webbrowser t https www python org Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information The following exception is defined exception webbrowser Error Exception raised when a browser control error occurs The following functions are defined webbrowser open url new 0 autoraise True Display url using the default browser If new is 0 the url is opened in the same browser window if possible If new is 1 a new browser window is opened if possible If new is 2 a new browser page tab is opened if possible If autoraise is True the window is raised if possible note that under many window managers this will occur regardless of the setting of this variable Note that on some platforms trying to open a filename using this function may work and start the operating system s associated program However this is neither supported nor portable Raises an auditing event webbrowser open with argument url webbrowser open_new url Open url in a new window of the default browser if possible otherwise open url in the only browser window webbrowser open_new_tab url Open url in a new page tab of the default browser if possible otherwise equivalent to open_new webbrowser get using None Return a controller object for the browser type using If using is None return a controller for a default browser appropriate to the caller s environment webbrowser register name constructor instance None preferred False Register the browser type name Once a browser type is registered the get function can return a controller for that browser type If instance is not provided or is None constructor will be called without parameters to create an instance when needed If instance is provided constructor will never be called and may be None Setting preferred to True makes this browser a preferred result for a get call with no argument Otherwise this entry point is only useful if you plan to either set the BROWSER variable or call get with a nonempty argument matching the name of a handler you declare Changed in version 3 7 preferred keyword only parameter was added A number of browser types are predefined This table gives the type names that may be passed to the get function and the corresponding instantiations for the controller classes all defined in this module Type Name Class Name Notes mozilla Mozilla mozilla firefox Mozilla mozilla epiphany Epiphany epiphany kfmclient Konqueror 1 konqueror Konqueror,en
1488, 1 kfm Konqueror 1 opera Opera links GenericBrowser links elinks Elinks elinks lynx GenericBrowser lynx w3m GenericBrowser w3m windows default WindowsDefault 2 macosx MacOSXOSAScript default 3 safari MacOSXOSAScript safari 3 google chrome Chrome google chrome chrome Chrome chrome chromium Chromium chromium chromium browser Chromium chromium browser Notes 1 Konqueror is the file manager for the KDE desktop environment for Unix and only makes sense to use if KDE is running Some way of reliably detecting KDE would be nice the KDEDIR variable is not sufficient Note also that the name kfm is used even when using the konqueror command with KDE 2 the implementation selects the best strategy for running Konqueror 2 Only on Windows platforms 3 Only on macOS platform New in version 3 3 Support for Chrome Chromium has been added Changed in version 3 12 Support for several obsolete browsers has been removed Removed browsers include Grail Mosaic Netscape Galeon Skipstone Iceape and Firefox versions 35 and below Deprecated since version 3 11 will be removed in version 3 13 MacOSX is deprecated use MacOSXOSAScript instead Here are some simple examples url https docs python org Open URL in a new tab if a browser window is already open webbrowser open_new_tab url Open URL in new window raising the window if possible webbrowser open_new url Browser Controller Objects Browser controllers provide these methods which parallel three of the module level convenience functions webbrowser name System dependent name for the browser controller open url new 0 autoraise True Display url using the browser handled by this controller If new is 1 a new browser window is opened if possible If new is 2 a new browser page tab is opened if possible controller open_new url Open url in a new window of the browser handled by this controller if possible otherwise open url in the only browser window Alias open_new controller open_new_tab url Open url in a new page tab of the browser handled by this controller if possible otherwise equivalent to open_new Footnotes 1 Executables named here without a full path will be searched in the directories given in the PATH environment variable,en
1489,fileinput Iterate over lines from multiple input streams Source code Lib fileinput py This module implements a helper class and functions to quickly write a loop over standard input or a list of files If you just want to read or write one file see open The typical use is import fileinput for line in fileinput input encoding utf 8 process line This iterates over the lines of all files listed in sys argv 1 defaulting to sys stdin if the list is empty If a filename is it is also replaced by sys stdin and the optional arguments mode and openhook are ignored To specify an alternative list of filenames pass it as the first argument to input A single file name is also allowed All files are opened in text mode by default but you can override this by specifying the mode parameter in the call to input or FileInput If an I O error occurs during opening or reading a file OSError is raised Changed in version 3 3 IOError used to be raised it is now an alias of OSError If sys stdin is used more than once the second and further use will return no lines except perhaps for interactive use or if it has been explicitly reset e g using sys stdin seek 0 Empty files are opened and immediately closed the only time their presence in the list of filenames is noticeable at all is when the last file opened is empty Lines are returned with any newlines intact which means that the last line in a file may not have one You can control how files are opened by providing an opening hook via the openhook parameter to fileinput input or FileInput The hook must be a function that takes two arguments filename and mode and returns an accordingly opened file like object If encoding and or errors are specified they will be passed to the hook as additional keyword arguments This module provides a hook_compressed to support compressed files The following function is the primary interface of this module fileinput input files None inplace False backup mode r openhook None encoding None errors None Create an instance of the FileInput class The instance will be used as global state for the functions of this module and is also returned to use during iteration The parameters to this function will be passed along to the constructor of the FileInput class The FileInput instance can be used as a context manager in the with statement In this example input is closed after the with statement is exited even if an exception occurs with fileinput input files spam txt eggs txt encoding utf 8 as f for line in f process line Changed in version 3 2 Can be used as a context manager Changed in version 3 8 The keyword parameters mode and openhook are now keyword only Changed in version 3 10 The keyword only parameter encoding and errors are added The following functions use the global state created by fileinput input if there is no active state RuntimeError is raised fileinput filename Return the name of the file currently being read Before the first line has been read returns None fileinput fileno Return the integer file descriptor for the current file When no file is opened before the first line and between files returns 1 fileinput lineno Return the cumulative line number of the line that has just been read Before the first line has been read returns 0 After the last line of the last file has been read returns the line number of that line fileinput filelineno Return the line number in the current file Before the first line has been read returns 0 After the last line of the last file has been read returns the line number of that line within the file fileinput isfirstline Return True if the line just read is the first line of its file otherwise return False fileinput isstdin Return True if the last line was read from sys stdin otherwise return False fileinput nextfile Close the current file so that the next iteration will read the first line from the next file if any lines not read from the file will not count towards the cumulative line count The filename is not changed until after the first line of the next file has been read Before the first line has been read this function has no ,en
1490,effect it cannot be used to skip the first file After the last line of the last file has been read this function has no effect fileinput close Close the sequence The class which implements the sequence behavior provided by the module is available for subclassing as well class fileinput FileInput files None inplace False backup mode r openhook None encoding None errors None Class FileInput is the implementation its methods filename fileno lineno filelineno isfirstline isstdin nextfile and close correspond to the functions of the same name in the module In addition it is iterable and has a readline method which returns the next input line The sequence must be accessed in strictly sequential order random access and readline cannot be mixed With mode you can specify which file mode will be passed to open It must be one of r and rb The openhook when given must be a function that takes two arguments filename and mode and returns an accordingly opened file like object You cannot use inplace and openhook together You can specify encoding and errors that is passed to open or openhook A FileInput instance can be used as a context manager in the with statement In this example input is closed after the with statement is exited even if an exception occurs with FileInput files spam txt eggs txt as input process input Changed in version 3 2 Can be used as a context manager Changed in version 3 8 The keyword parameter mode and openhook are now keyword only Changed in version 3 10 The keyword only parameter encoding and errors are added Changed in version 3 11 The rU and U modes and the __getitem__ method have been removed Optional in place filtering if the keyword argument inplace True is passed to fileinput input or to the FileInput constructor the file is moved to a backup file and standard output is directed to the input file if a file of the same name as the backup file already exists it will be replaced silently This makes it possible to write a filter that rewrites its input file in place If the backup parameter is given typically as backup some extension it specifies the extension for the backup file and the backup file remains around by default the extension is bak and it is deleted when the output file is closed In place filtering is disabled when standard input is read The two following opening hooks are provided by this module fileinput hook_compressed filename mode encoding None errors None Transparently opens files compressed with gzip and bzip2 recognized by the extensions gz and bz2 using the gzip and bz2 modules If the filename extension is not gz or bz2 the file is opened normally ie using open without any decompression The encoding and errors values are passed to io TextIOWrapper for compressed files and open for normal files Usage example fi fileinput FileInput openhook fileinput hook_compressed encoding utf 8 Changed in version 3 10 The keyword only parameter encoding and errors are added fileinput hook_encoded encoding errors None Returns a hook which opens each file with open using the given encoding and errors to read the file Usage example fi fileinput FileInput openhook fileinput hook_encoded utf 8 surrogateescape Changed in version 3 6 Added the optional errors parameter Deprecated since version 3 10 This function is deprecated since fileinput input and FileInput now have encoding and errors parameters,en
1491,Byte Array Objects type PyByteArrayObject This subtype of PyObject represents a Python bytearray object PyTypeObject PyByteArray_Type Part of the Stable ABI This instance of PyTypeObject represents the Python bytearray type it is the same object as bytearray in the Python layer Type check macros int PyByteArray_Check PyObject o Return true if the object o is a bytearray object or an instance of a subtype of the bytearray type This function always succeeds int PyByteArray_CheckExact PyObject o Return true if the object o is a bytearray object but not an instance of a subtype of the bytearray type This function always succeeds Direct API functions PyObject PyByteArray_FromObject PyObject o Return value New reference Part of the Stable ABI Return a new bytearray object from any object o that implements the buffer protocol PyObject PyByteArray_FromStringAndSize const char string Py_ssize_t len Return value New reference Part of the Stable ABI Create a new bytearray object from string and its length len On failure NULL is returned PyObject PyByteArray_Concat PyObject a PyObject b Return value New reference Part of the Stable ABI Concat bytearrays a and b and return a new bytearray with the result Py_ssize_t PyByteArray_Size PyObject bytearray Part of the Stable ABI Return the size of bytearray after checking for a NULL pointer char PyByteArray_AsString PyObject bytearray Part of the Stable ABI Return the contents of bytearray as a char array after checking for a NULL pointer The returned array always has an extra null byte appended int PyByteArray_Resize PyObject bytearray Py_ssize_t len Part of the Stable ABI Resize the internal buffer of bytearray to len Macros These macros trade safety for speed and they don t check pointers char PyByteArray_AS_STRING PyObject bytearray Similar to PyByteArray_AsString but without error checking Py_ssize_t PyByteArray_GET_SIZE PyObject bytearray Similar to PyByteArray_Size but without error checking,en
1492,Changelog Python next Release date XXXX XX XX Security gh 115398 Allow controlling Expat 2 6 0 reparse deferral CVE 2023 52425 by adding five new methods xml etree ElementTree XMLParser flush xml etree ElementTree XMLPullParser flush xml parsers expat xmlparser GetReparseDeferralEnabled xml parsers expat xmlparser SetReparseDeferralEnabled xml sax expatreader ExpatParser flush gh 115399 Update bundled libexpat to 2 6 0 gh 115243 Fix possible crashes in collections deque index when the deque is concurrently modified gh 114572 ssl SSLContext cert_store_stats and ssl SSLContext get_ca_certs now correctly lock access to the certificate store when the ssl SSLContext is shared across multiple threads Core and Builtins gh 116604 Respect the status of the garbage collector when indirect calls are made via PyErr_CheckSignals and the evaluation breaker Patch by Pablo Galindo gh 116626 Ensure INSTRUMENTED_CALL_FUNCTION_EX always emits CALL gh 116296 Fix possible refleak in object __reduce__ internal error handling gh 116034 Fix location of the error on a failed assertion gh 115823 Properly calculate error ranges in the parser when raising SyntaxError exceptions caused by invalid byte sequences Patch by Pablo Galindo gh 112087 For an empty reverse iterator for list will be reduced to reversed Patch by Donghee Na gh 115154 Fix a bug that was causing the tokenize untokenize function to handle unicode named literals incorrectly Patch by Pablo Galindo gh 114828 Fix compilation crashes in uncommon code examples using super inside a comprehension in a class body gh 115011 Setters for members with an unsigned integer type now support the same range of valid values for objects that has a __index__ method as for int gh 112215 Change the C recursion limits to more closely reflect the underlying platform limits gh 96497 Fix incorrect resolution of mangled class variables used in assignment expressions in comprehensions Library gh 116600 Fix repr for global Flag members gh 116401 Fix blocking os fwalk and shutil rmtree on opening named pipe gh 116143 Fix a race in pydoc _start_server eliminating a window in which _start_server can return a thread that is serving but without a docserver set gh 116325 typing raise SyntaxError instead of AttributeError on forward references as empty strings gh 115978 Disable preadv readv pwritev and writev on WASI Under wasmtime for WASI 0 2 these functions don t pass test_posix https github com bytecodealliance wasmtime issues 7830 gh 88352 Fix the computation of the next rollover time in the logging TimedRotatingFileHandler handler computeRollover now always returns a timestamp larger than the specified time and works correctly during the DST change doRollover no longer overwrite the already rolled over file saving from data loss when run at midnight or during repeated time at the DST change gh 87115 Set __main__ __spec__ to None when running a script with pdb gh 76511 Fix UnicodeEncodeError in email Message as_string that results when a message that claims to be in the ascii character set actually has non ascii characters Non ascii characters are now replaced with the U FFFD replacement character like in the replace error handler gh 116040 Enum fix by value calls when second value is falsey e g Cardinal 1 0 gh 115881 Fix issue where ast parse would incorrectly flag conditional context managers such as with x if y else z as invalid syntax if feature_version 3 8 was passed This reverts changes to the grammar made as part of gh 94949 gh 115886 Fix silent truncation of the name with an embedded null character in multiprocessing shared_memory SharedMemory gh 115809 Improve algorithm for computing which rolled over log files to delete in logging TimedRotatingFileHandler It is now reliable for handlers without namer and with arbitrary deterministic namer that leaves the datetime part in the file name unmodified gh 74668 urllib parse functions parse_qs and parse_qsl now support bytes arguments containing raw and percent encoded non ASCII data gh 67044 csv writer now always quotes or escapes r and n regardless of linete,en
1493,rminator value gh 115712 csv writer now quotes empty fields if delimiter is a space and skipinitialspace is true and raises exception if quoting is not possible gh 112364 Fixed ast unparse to handle format_spec with or Patched by Frank Hoffmann gh 111358 Fix a bug in asyncio BaseEventLoop shutdown_default_executor to ensure the timeout passed to the coroutine behaves as expected gh 115618 Fix improper decreasing the reference count for None argument in property methods getter setter and deleter gh 115570 A DeprecationWarning is no longer omitted on access to the __doc__ attributes of the deprecated typing io and typing re pseudo modules gh 112006 Fix inspect unwrap for types with the __wrapper__ data descriptor gh 101293 Support callables with the __call__ method and types with __new__ and __init__ methods set to class methods static methods bound methods partial functions and other types of methods and descriptors in inspect Signature from_callable gh 115392 Fix a bug in doctest where incorrect line numbers would be reported for decorated functions gh 114563 Fix several format bugs when using the C implementation of Decimal memory leak in some rare cases when using the z format option coerce negative 0 incorrect output when applying the z format option to type F fixed point with capital NAN INF incorrect output when applying the format option alternate form gh 115197 urllib request no longer resolves the hostname before checking it against the system s proxy bypass list on macOS and Windows gh 115165 Most exceptions are now ignored when attempting to set the __orig_class__ attribute on objects returned when calling typing generic aliases including generic aliases created using typing Annotated Previously only AttributeError was ignored Patch by Dave Shawley gh 115133 Fix tests for XMLPullParser with Expat 2 6 0 gh 115059 io BufferedRandom read1 now flushes the underlying write buffer gh 79382 Trailing no longer allows to match files and non existing paths in recursive glob gh 114071 Support tuple subclasses using auto for enum member value gh 114763 Protect modules loaded with importlib util LazyLoader from race conditions when multiple threads try to access attributes before the loading is complete gh 97959 Fix rendering class methods bound methods method and function aliases in pydoc Class methods no longer have method of builtins type instance note Corresponding notes are now added for class and unbound methods Method and function aliases now have references to the module or the class where the origin was defined if it differs from the current Bound methods are now listed in the static methods section Methods of builtin classes are now supported as well as methods of Python classes gh 112281 Allow creating union of types for typing Annotated with unhashable metadata gh 111775 Fix importlib resources simple ResourceHandle open for text mode added missed stream argument gh 90095 Make pdbrc and c work with any valid pdb commands gh 107155 Fix incorrect output of help x where x is a lambda function which has an __annotations__ dictionary attribute with a return key gh 60346 Fix ArgumentParser inconsistent with parse_known_args gh 100985 Update HTTPSConnection to consistently wrap IPv6 Addresses when using a proxy gh 100884 email fix misfolding of comma in address lists over multiple lines in combination with unicode encoding gh 95782 Fix io BufferedReader tell io BufferedReader seek _pyio BufferedReader tell io BufferedRandom tell io BufferedRandom seek and _pyio BufferedRandom tell being able to return negative offsets gh 96310 Fix a traceback in argparse when all options in a mutually exclusive group are suppressed gh 93205 Fixed a bug in logging handlers TimedRotatingFileHandler where multiple rotating handler instances pointing to files with the same name but different extensions would conflict and not delete the correct files bpo 44865 Add missing call to localization function in argparse bpo 43952 Fix multiprocessing connection Listener accept to accept empty bytes as authkey Not accepting empty bytes as key causes,en
1494, it to hang indefinitely bpo 42125 linecache get module name from __spec__ if available This allows getting source code for the __main__ module when a custom loader is used bpo 33775 Add default and version help text for localization in argparse Documentation gh 115399 Document CVE 2023 52425 of Expat 2 6 0 under XML vulnerabilities gh 115233 Fix an example for LoggerAdapter in the Logging Cookbook Tests gh 115979 Update test_importlib so that it passes under WASI SDK 21 gh 116307 Added import helper isolated_modules as CleanImport does not remove modules imported during the context Use it in importlib resources tests to avoid leaving mod around to impede importlib metadata tests gh 115596 Fix ProgramPriorityTests in test_os permanently changing the process priority Build gh 116313 Get WASI builds to work under wasmtime 18 w WASI 0 2 preview2 primitives gh 116117 Backport libb2 s PR 42 to fix compiling CPython on 32 bit Windows with clang cl gh 115167 Avoid vendoring vcruntime140_threads dll when building with Visual Studio 2022 version 17 8 Windows gh 115554 The installer now has more strict rules about updating the Python Launcher for Windows In general most users only have a single launcher installed and will see no difference When multiple launchers have been installed the option to install the launcher is disabled until all but one have been removed Downgrading the launcher which was never allowed is now more obviously blocked gh 115543 Python Launcher for Windows can now detect Python 3 13 when installed from the Microsoft Store and will install Python 3 12 by default when PYLAUNCHER_ALLOW_INSTALL is set gh 115049 Fixes py exe launcher failing when run as users without user profiles gh 115009 Update Windows installer to use SQLite 3 45 1 IDLE gh 88516 On macOS show a proxy icon in the title bar of editor windows to match platform behaviour Tools Demos gh 113516 Don t set LDSHARED when building for WASI Python 3 12 2 final Release date 2024 02 06 Security gh 113659 Skip pth files with names starting with a dot or hidden file attribute Core and Builtins gh 114887 Changed socket type validation in create_datagram_endpoint to accept all non stream sockets This fixes a regression in compatibility with raw sockets gh 114388 Fix a RuntimeWarning emitted when assign an integer like value that is not an instance of int to an attribute that corresponds to a C struct member of type T_UINT and T_ULONG Fix a double RuntimeWarning emitted when assign a negative integer value to an attribute that corresponds to a C struct member of type T_UINT gh 113703 Fix a regression in the codeop module that was causing it to incorrectly identify incomplete f strings Patch by Pablo Galindo gh 89811 Check for a valid tp_version_tag before performing bytecode specializations that rely on this value being usable gh 113602 Fix an error that was causing the parser to try to overwrite existing errors and crashing in the process Patch by Pablo Galindo gh 113297 Fix segfault in the compiler on with statement with 19 context managers gh 106905 Use per AST parser state rather than global state to track recursion depth within the AST parser to prevent potential race condition due to simultaneous parsing The issue primarily showed up in 3 11 by multithreaded users of ast parse In 3 12 a change to when garbage collection can be triggered prevented the race condition from occurring gh 112943 Correctly compute end column offsets for multiline tokens in the tokenize module Patch by Pablo Galindo gh 112716 Fix SystemError in the import statement and in __reduce__ methods of builtin types when __builtins__ is not a dict gh 94606 Fix UnicodeEncodeError when email message get_payload reads a message with a Unicode surrogate character and the message content is not well formed for surrogateescape encoding Patch by Sidney Markowitz Library gh 114965 Update bundled pip to 24 0 gh 114959 tarfile no longer ignores errors when trying to extract a directory on top of a file gh 109475 Fix support of explicit option value in argparse e g option gh 110190 Fix ctypes struc,en
1495,ts with array on Windows ARM64 platform by setting MAX_STRUCT_SIZE to 32 in stgdict Patch by Diego Russo gh 113280 Fix a leak of open socket in rare cases when error occurred in ssl SSLSocket creation gh 77749 email policy EmailPolicy fold now always encodes non ASCII characters in headers if utf8 is false gh 114492 Make the result of termios tcgetattr reproducible on Alpine Linux Previously it could leave a random garbage in some fields gh 113267 Revert changes in gh 106584 which made calls of TestResult methods startTest and stopTest unbalanced gh 75128 Ignore an OSError in asyncio BaseEventLoop create_server when IPv6 is available but the interface cannot actually support it gh 114257 Dismiss the FileNotFound error in ctypes util find_library and just return None on Linux gh 114328 The tty setcbreak and new tty cfmakecbreak no longer clears the terminal input ICRLF flag This fixes a regression introduced in 3 12 that no longer matched how OSes define cbreak mode in their stty 1 manual pages gh 101438 Avoid reference cycle in ElementTree iterparse The iterator returned by ElementTree iterparse may hold on to a file descriptor The reference cycle prevented prompt clean up of the file descriptor if the returned iterator was not exhausted gh 104522 OSError raised when run a subprocess now only has filename attribute set to cwd if the error was caused by a failed attempt to change the current directory gh 114149 Enum correctly handle tuple subclasses in custom __new__ gh 109534 Fix a reference leak in asyncio selector_events BaseSelectorEventLoop when SSL handshakes fail Patch contributed by Jamie Phan gh 114077 Fix possible OverflowError in socket socket sendfile when pass count larger than 2 GiB on 32 bit platform gh 114014 Fixed a bug in fractions Fraction where an invalid string using d in the decimals part creates a different error compared to other invalid letters characters Patch by Jeremiah Gabriel Pascual gh 113951 Fix the behavior of tag_unbind methods of tkinter Text and tkinter Canvas classes with three arguments Previously widget tag_unbind tag sequence funcid destroyed the current binding for sequence leaving sequence unbound and deleted the funcid command Now it removes only funcid from the binding for sequence keeping other commands and deletes the funcid command It leaves sequence unbound only if funcid was the last bound command gh 113877 Fix tkinter method winfo_pathname on 64 bit Windows gh 113661 unittest runner Don t exit 5 if tests were skipped The intention of exiting 5 was to detect issues where the test suite wasn t discovered at all If we skipped tests it was correctly discovered gh 113781 Silence unraisable AttributeError when warnings are emitted during Python finalization gh 112932 Restore the ability for zipfile to extractall from zip files with a directory entry in them as is commonly added to zips by some wiki or bug tracker data exporters gh 113594 Fix UnicodeEncodeError in email when re fold lines that contain unknown 8bit encoded part followed by non unknown 8bit encoded part gh 113538 In asyncio StreamReaderProtocol connection_made there is callback that logs an error if the task wrapping the connected callback fails This callback would itself fail if the task was cancelled Prevent this by checking whether the task was cancelled first If so close the transport but don t log an error gh 85567 Fix resource warnings for unclosed files in pickle and pickletools command line interfaces gh 101225 Increase the backlog for multiprocessing connection Listener objects created by multiprocessing manager and multiprocessing resource_sharer to significantly reduce the risk of getting a connection refused error when creating a multiprocessing connection Connection to them gh 113543 Make sure that webbrowser MacOSXOSAScript sends webbrowser open audit event gh 113028 When a second reference to a string appears in the input to pickle and the Python implementation is in use we are guaranteed that a single copy gets pickled and a single object is shared when reloaded Previously in protocol 0 when a strin,en
1496,g contained certain characters e g newline it resulted in duplicate objects gh 113421 Fix multiprocessing logger for filename s gh 111784 Fix segfaults in the _elementtree module Fix first segfault during deallocation of _elementtree XMLParser instances by keeping strong reference to pyexpat module in module state for capsule lifetime Fix second segfault which happens in the same deallocation process by keeping strong reference to _elementtree module in XMLParser structure for _elementtree module lifetime gh 113407 Fix import of unittest mock when CPython is built without docstrings gh 113320 Fix regression in Python 3 12 where Protocol classes that were not marked as runtime checkable would be unnecessarily introspected potentially causing exceptions to be raised if the protocol had problematic members Patch by Alex Waygood gh 113358 Fix rendering tracebacks for exceptions with a broken __getattr__ gh 113214 Fix an AttributeError during asyncio SSL protocol aborts in SSL over SSL scenarios gh 113246 Update bundled pip to 23 3 2 gh 113199 Make http client HTTPResponse read1 and http client HTTPResponse readline close IO after reading all data when content length is known Patch by Illia Volochii gh 113188 Fix shutil copymode and shutil copystat on Windows Previously they worked differenly if dst is a symbolic link they modified the permission bits of dst itself rather than the file it points to if follow_symlinks is true or src is not a symbolic link and did not modify the permission bits if follow_symlinks is false and src is a symbolic link gh 61648 Detect line numbers of properties in doctests gh 112559 signal signal and signal getsignal no longer call repr on callable handlers asyncio run and asyncio Runner run no longer call repr on the task results Patch by Yilei Yang gh 110190 Fix ctypes structs with array on PPC64LE platform by setting MAX_STRUCT_SIZE to 64 in stgdict Patch by Diego Russo gh 79429 Ignore FileNotFoundError when remove a temporary directory in the multiprocessing finalizer gh 81194 Fix a crash in socket if_indextoname with specific value UINT_MAX Fix an integer overflow in socket if_indextoname on 64 bit non Windows platforms gh 112343 Improve handling of pdb convenience variables to avoid replacing string contents gh 111615 Fix a regression caused by a fix to gh 93162 whereby you couldn t configure a QueueHandler without specifying handlers gh 111049 Fix crash during garbage collection of the io BytesIO buffer object gh 110345 Show the Tcl Tk patchlevel rather than version in tkinter _test gh 109858 Protect zipfile from quoted overlap zipbomb It now raises BadZipFile when try to read an entry that overlaps with other entry or central directory gh 114440 On Windows closing the connection writer when cleaning up a broken multiprocessing Queue queue is now done for all queues rather than only in concurrent futures manager thread This can prevent a deadlock when a multiprocessing worker process terminates without cleaning up This completes the backport of patches by Victor Stinner and Serhiy Storchaka gh 38807 Fix race condition in trace Instead of checking if a directory exists and creating it directly call os makedirs with the kwarg exist_ok True gh 75705 Set unixfrom envelope in mailbox mbox and mailbox MMDF gh 106233 Fix stacklevel in InvalidTZPathWarning during zoneinfo module import gh 105102 Allow ctypes Union to be nested in ctypes Structure when the system endianness is the opposite of the classes gh 104282 Fix null pointer dereference in lzma _decode_filter_properties due to improper handling of BCJ filters with properties of zero length Patch by Radislav Chugunov gh 102512 When os fork is called from a foreign thread aka _DummyThread the type of the thread in a child process is changed to _MainThread Also changed its name and daemonic status it can be now joined bpo 35928 io TextIOWrapper now correctly handles the decoding buffer after read and write bpo 26791 shutil move now moves a symlink into a directory when that directory is the target of the symlink This provides the same behavior as ,en
1497,the mv shell command The previous behavior raised an exception Patch by Jeffrey Kintscher bpo 36959 Fix some error messages for invalid ISO format string combinations in strptime that referred to directives not contained in the format string Patch by Gordon P Hemsley bpo 18060 Fixed a class inheritance issue that can cause segfaults when deriving two or more levels of subclasses from a base class of Structure or Union Documentation gh 110746 Improved markup for valid options values for methods ttk treeview column and ttk treeview heading and for Layouts gh 95649 Document that the asyncio module contains code taken from v0 16 0 of the uvloop project as well as the required MIT licensing information Tests gh 109980 Fix test_tarfile_vs_tar in test_shutil for macOS where system tar can include more information in the archive than shutil make_archive gh 105089 Fix test test_zipfile test_core TestWithDirectory test_ create_directory_with_write test in AIX by doing a bitwise AND of 0xFFFF on mode so that it will be in sync with zinfo external_attr bpo 40648 Test modes that file can get with chmod on Windows Build gh 112305 Fixed the check clean src step performed on out of tree builds to detect errant srcdir Python frozen_modules h files and recommend appropriate source tree cleanup steps to get a working build again gh 112867 Fix the build for the case that WITH_PYMALLOC_RADIX_TREE 0 set bpo 11102 The os major os makedev and os minor functions are now available on HP UX v3 bpo 36351 Do not set ipv6type when cross compiling Windows gh 109991 Update Windows build to use OpenSSL 3 0 13 gh 111239 Update Windows builds to use zlib v1 3 1 gh 100107 The py exe launcher will no longer attempt to run the Microsoft Store redirector when launching a script containing a usr bin env shebang gh 114096 Process privileges that are activated for creating directory junctions are now restored afterwards avoiding behaviour changes in other parts of the program gh 111877 os stat calls were returning incorrect time values for files that could not be accessed directly gh 113009 multiprocessing On Windows fix a race condition in Process terminate no longer set the returncode attribute to always call WaitForSingleObject in Process wait Previously sometimes the process was still running after TerminateProcess even if GetExitCodeProcess is not STILL_ACTIVE Patch by Victor Stinner gh 87868 Correctly sort and remove duplicate environment variables in _winapi CreateProcess bpo 37308 Fix mojibake in mmap mmap when using a non ASCII tagname argument on Windows macOS gh 115009 Update macOS installer to use SQLite 3 45 1 gh 109991 Update macOS installer to use OpenSSL 3 0 13 gh 110459 Running configure with openssl rpath X Y Z no longer fails to detect OpenSSL on macOS gh 74573 Document that dbm ndbm can silently corrupt DBM files on updates when exceeding undocumented platform limits and can crash segmentation fault when reading such a corrupted file FB8919203 gh 65701 The freeze tool doesn t work with framework builds of Python Document this and bail out early when running the tool with such a build gh 108269 Set CFBundleAllowMixedLocalizations to true in the Info plist for the framework embedded Python app and IDLE app with framework installs on macOS This allows applications to pick up the user s preferred locale when that s different from english gh 102362 Make sure the result of sysconfig get_plaform includes at least a major and minor versions even if MACOSX_DEPLOYMENT_TARGET is set to only a major version during build to match the format expected by pip gh 110017 Disable a signal handling stress test on macOS due to a bug in macOS FB13453490 gh 110820 Make sure the preprocessor definitions for ALIGNOF_MAX_ALIGN_T SIZEOF_LONG_DOUBLE and HAVE_GCC_ASM_FOR_X64 are correct for Universal 2 builds on macOS IDLE gh 96905 In idlelib code stop redefining built ins dict and object gh 72284 Improve the lists of features editor key bindings and shell key bingings in the IDLE doc gh 113903 Fix rare failure of test test_idle in test_configdialog gh 113729 Fix the Hel,en
1498,p IDLE Doc menu bug in 3 11 7 and 3 12 1 gh 113269 Fix test_editor hang on macOS Catalina gh 112898 Fix processing unsaved files when quitting IDLE on macOS gh 103820 Revise IDLE bindings so that events from mouse button 4 5 on non X11 windowing systems i e Win32 and Aqua are not mistaken for scrolling bpo 13586 Enter the selected text when opening the Replace dialog Tools Demos gh 109991 Update GitHub CI workflows to use OpenSSL 3 0 13 and multissltests to use 1 1 1w 3 0 13 3 1 5 and 3 2 1 gh 115015 Fix a bug in Argument Clinic that generated incorrect code for methods with no parameters that use the METH_METHOD METH_FASTCALL METH_KEYWORDS calling convention Only the positional parameter count was checked any keyword argument passed would be silently accepted Python 3 12 1 final Release date 2023 12 07 Core and Builtins gh 112125 Fix None __ne__ None returning NotImplemented instead of False gh 112625 Fixes a bug where a bytearray object could be cleared while iterating over an argument in the bytearray join method that could result in reading memory after it was freed gh 105967 Workaround a bug in Apple s macOS platform zlib library where zlib crc32 and binascii crc32 could produce incorrect results on multi gigabyte inputs Including when using zipfile on zips containing large data gh 112356 Stopped erroneously deleting a LOAD_NULL bytecode instruction when optimized twice gh 111058 Change coro cr_frame gen gi_frame to return None after the coroutine generator has been closed This fixes a bug where getcoroutinestate and getgeneratorstate return the wrong state for a closed coroutine generator gh 112388 Fix an error that was causing the parser to try to overwrite tokenizer errors Patch by pablo Galindo gh 112387 Fix error positions for decoded strings with backwards tokenize errors Patch by Pablo Galindo gh 112367 Avoid undefined behaviour when using the perf trampolines by not freeing the code arenas until shutdown Patch by Pablo Galindo gh 112243 Don t include comments in f string debug expressions Patch by Pablo Galindo gh 112266 Change docstrings of __dict__ and __weakref__ gh 111654 Fix runtime crash when some error happens in opcode LOAD_FROM_DICT_OR_DEREF gh 109181 Speed up Traceback object creation by lazily compute the line number Patch by Pablo Galindo gh 102388 Fix a bug where iso2022_jp_3 and iso2022_jp_2004 codecs read out of bounds gh 111366 Fix an issue in the codeop that was causing SyntaxError exceptions raised in the presence of invalid syntax to not contain precise error messages Patch by Pablo Galindo gh 111380 Fix a bug that was causing SyntaxWarning to appear twice when parsing if invalid syntax is encountered later Patch by Pablo galindo gh 94438 Fix a regression that prevented jumping across is None and is not None when debugging Patch by Savannah Ostrowski gh 110938 Fix error messages for indented blocks with functions and classes with generic type parameters Patch by Pablo Galindo gh 109894 Fixed crash due to improperly initialized static MemoryError in subinterpreter gh 110782 Fix crash when typing TypeVar is constructed with a keyword argument Patch by Jelle Zijlstra gh 110696 Fix incorrect error message for invalid argument unpacking Patch by Pablo Galindo gh 110543 Fix regression in Python 3 12 where types CodeType replace would produce a broken code object if called on a module or class code object that contains a comprehension Patch by Jelle Zijlstra gh 110514 Add PY_THROW to sys setprofile events gh 110455 Guard assert tstate thread_id 0 with ifndef HAVE_PTHREAD_STUBS This allows for for pydebug builds to work under WASI which currently lacks thread support gh 110259 Correctly identify the format spec in f strings with single or triple quotes that have multiple lines in the expression part and include a formatting spec Patch by Pablo Galindo gh 110237 Fix missing error checks for calls to PyList_Append in _PyEval_MatchClass gh 109889 Fix the compiler s redundant NOP detection algorithm to skip over NOPs with no line number when looking for the next instruction s lineno gh 109853 sys path,en
1499, 0 is now set correctly for subinterpreters gh 105716 Subinterpreters now correctly handle the case where they have threads running in the background Before such threads would interfere with cleaning up and destroying them as well as prevent running another script gh 109793 The main thread no longer exits prematurely when a subinterpreter is cleaned up during runtime finalization The bug was a problem particularly because when triggered the Python process would always return with a 0 exitcode even if it failed gh 109596 Fix some tokens in the grammar that were incorrectly marked as soft keywords Also fix some repeated rule names and ensure that repeated rules are not allowed Patch by Pablo Galindo gh 109351 Fix crash when compiling an invalid AST involving a named walrus expression gh 109216 Fix possible memory leak in BUILD_MAP gh 109207 Fix a SystemError in __repr__ of symtable entry object gh 109179 Fix bug where the C traceback display drops notes from SyntaxError gh 109052 Use the base opcode when comparing code objects to avoid interference from instrumentation gh 88943 Improve syntax error for non ASCII character that follows a numerical literal It now points on the invalid non ASCII character not on the valid numerical literal gh 106931 Statically allocated string objects are now interned globally instead of per interpreter This fixes a situation where such a string would only be interned in a single interpreter Normal string objects are unaffected Library gh 79325 Fix an infinite recursion error in tempfile TemporaryDirectory cleanup on Windows gh 112645 Remove deprecation error on passing onerror to shutil rmtree gh 112618 Fix a caching bug relating to typing Annotated Annotated str True is no longer identical to Annotated str 1 gh 112334 Fixed a performance regression in 3 12 s subprocess on Linux where it would no longer use the fast path vfork system call when it should have due to a logic bug instead always falling back to the safe but slower fork Also fixed a related 3 12 security regression If a value of extra_groups was passed to subprocess Popen or related APIs the underlying setgroups 0 NULL system call to clear the groups list would not be made in the child process prior to exec This has been assigned CVE 2023 6507 This was identified via code inspection in the process of fixing the first bug gh 110190 Fix ctypes structs with array on Arm platform by setting MAX_STRUCT_SIZE to 32 in stgdict Patch by Diego Russo gh 112578 Fix a spurious RuntimeWarning when executing the zipfile module gh 112509 Fix edge cases that could cause a key to be present in both the __required_keys__ and __optional_keys__ attributes of a typing TypedDict Patch by Jelle Zijlstra gh 112414 Fix regression in Python 3 12 where calling repr on a module that had been imported using a custom loader could fail with AttributeError Patch by Alex Waygood gh 112358 Revert change to struct Struct initialization that broke some cases of subclassing gh 94722 Fix bug where comparison between instances of DocTest fails if one of them has None as its lineno gh 112105 Make readline set_completer_delims work with libedit gh 111942 Fix SystemError in the TextIOWrapper constructor with non encodable errors argument in non debug mode gh 109538 Issue warning message instead of having RuntimeError be displayed when event loop has already been closed at StreamWriter __del__ gh 111942 Fix crashes in io TextIOWrapper reconfigure when pass invalid arguments e g non string encoding gh 111460 curses restore wide character support including curses unget_wch and get_wch on macOS which was unavailable due to a regression in Python 3 12 gh 103791 contextlib suppress now supports suppressing exceptions raised as part of a BaseExceptionGroup in addition to the recent support for ExceptionGroup gh 111804 Remove posix fallocate under WASI as the underlying posix_fallocate is not available in WASI preview2 gh 111841 Fix truncating arguments on an embedded null character in os putenv and os unsetenv on Windows gh 111541 Fix doctest for SyntaxError not builtin subclass,en
1500,es gh 110894 Call loop exception handler for exceptions in client_connected_cb of asyncio start_server so that applications can handle it Patch by Kumar Aditya gh 111531 Fix reference leaks in bind_class and bind_all methods of tkinter widgets gh 111356 Added io text_encoding io DEFAULT_BUFFER_SIZE and io IncrementalNewlineDecoder to io __all__ gh 111342 Fixed typo in math sumprod gh 68166 Remove mention of not supported vsapi element type in tkinter ttk Style element_create Add tests for element_create and other ttk Style methods Add examples for element_create in the documentation gh 75666 Fix the behavior of tkinter widget s unbind method with two arguments Previously widget unbind sequence funcid destroyed the current binding for sequence leaving sequence unbound and deleted the funcid command Now it removes only funcid from the binding for sequence keeping other commands and deletes the funcid command It leaves sequence unbound only if funcid was the last bound command gh 79033 Another attempt at fixing asyncio Server wait_closed It now blocks until both conditions are true the server is closed and there are no more active connections This means that in some cases where in 3 12 0 this function would incorrectly have returned immediately it will now block in particular when there are no active connections but the server hasn t been closed yet gh 111295 Fix time not checking for errors when initializing gh 111253 Add error checking during _socket module init gh 111251 Fix _blake2 not checking for errors when initializing gh 111174 Fix crash in io BytesIO getbuffer called repeatedly for empty BytesIO gh 111187 Postpone removal version for locale getdefaultlocale to Python 3 15 gh 111159 Fix doctest output comparison for exceptions with notes gh 110910 Fix invalid state handling in asyncio TaskGroup and asyncio Timeout They now raise proper RuntimeError if they are improperly used and are left in consistent state after this gh 111092 Make turtledemo run without default root enabled gh 110488 Fix a couple of issues in pathlib PurePath with_name a single dot was incorrectly considered a valid name and in PureWindowsPath a name with an NTFS alternate data stream like a b was incorrectly considered invalid gh 110392 Fix tty setraw and tty setcbreak previously they returned partially modified list of the original tty attributes tty cfmakeraw and tty cfmakecbreak now make a copy of the list of special characters before modifying it gh 110590 Fix a bug in _sre compile where TypeError would be overwritten by OverflowError when the code argument was a list of non ints gh 65052 Prevent pdb from crashing when trying to display undisplayable objects gh 110519 Deprecation warning about non integer number in gettext now alwais refers to the line in the user code where gettext function or method is used Previously it could refer to a line in gettext code gh 110395 Ensure that select kqueue objects correctly appear as closed in forked children to prevent operations on an invalid file descriptor gh 110378 contextmanager and asynccontextmanager context managers now close an invalid underlying generator object that yields more then one value gh 110365 Fix termios tcsetattr bug that was overwritting existing errors during parsing integers from term list gh 109653 Fix a Python 3 12 regression in the import time of random Patch by Alex Waygood gh 110196 Add __reduce__ method to IPv6Address in order to keep scope_id gh 110036 On Windows multiprocessing Popen terminate now catchs PermissionError and get the process exit code If the process is still running raise again the PermissionError Otherwise the process terminated as expected store its exit code Patch by Victor Stinner gh 110038 Fixed an issue that caused KqueueSelector select to not return all the ready events in some cases when a file descriptor is registered for both read and write gh 109631 re functions such as re findall re split re search and re sub which perform short repeated matches can now be interrupted by user gh 109747 Improve errors for unsupported look behind patterns Now ,en
1501,re error is raised instead of OverflowError or RuntimeError for too large width of look behind pattern gh 109818 Fix reprlib recursive_repr not copying __type_params__ from decorated function gh 109047 concurrent futures The executor manager thread now catches exceptions when adding an item to the call queue During Python finalization creating a new thread can now raise RuntimeError Catch the exception and call terminate_broken in this case Patch by Victor Stinner gh 109782 Ensure the signature of os path isdir is identical on all platforms Patch by Amin Alaee gh 109590 shutil which will prefer files with an extension in PATHEXT if the given mode includes os X_OK on win32 If no PATHEXT match is found a file without an extension in PATHEXT can be returned This change will have shutil which act more similarly to previous behavior in Python 3 11 gh 109786 Fix possible reference leaks and crash when re enter the __next__ method of itertools pairwise gh 109593 Avoid deadlocking on a reentrant call to the multiprocessing resource tracker Such a reentrant call though unlikely can happen if a GC pass invokes the finalizer for a multiprocessing object such as SemLock gh 109613 Fix os stat and os DirEntry stat check for exceptions Previously on Python built in debug mode these functions could trigger a fatal Python error and abort the process when a function succeeded with an exception set Patch by Victor Stinner gh 109375 The pdb alias command now prevents registering aliases without arguments gh 107219 Fix a race condition in concurrent futures When a process in the process pool was terminated abruptly while the future was running or pending close the connection write end If the call queue is blocked on sending bytes to a worker process closing the connection write end interrupts the send so the queue can be closed Patch by Victor Stinner gh 50644 Attempts to pickle or create a shallow or deep copy of codecs streams now raise a TypeError Previously copying failed with a RecursionError while pickling produced wrong results that eventually caused unpickling to fail with a RecursionError gh 108987 Fix _thread start_new_thread race condition If a thread is created during Python finalization the newly spawned thread now exits immediately instead of trying to access freed memory and lead to a crash Patch by Victor Stinner gh 108791 Improved error handling in pdb command line interface making it produce more concise error messages gh 105829 Fix concurrent futures ProcessPoolExecutor deadlock gh 106584 Fix exit code for unittest if all tests are skipped Patch by Egor Eliseev gh 102956 Fix returning of empty byte strings after seek in zipfile module gh 84867 unittest TestLoader no longer loads test cases from exact unittest TestCase and unittest FunctionTestCase classes gh 91133 Fix a bug in tempfile TemporaryDirectory cleanup which now no longer dereferences symlinks when working around file system permission errors gh 73561 Omit the interface scope from an IPv6 address when used as Host header by http client gh 86826 zipinfo now supports the full range of values in the TZ string determined by RFC 8536 and detects all invalid formats Both Python and C implementations now raise exceptions of the same type on invalid data bpo 43153 On Windows tempfile TemporaryDirectory previously masked a PermissionError with NotADirectoryError during directory cleanup It now correctly raises PermissionError if errors are not ignored Patch by Andrei Kulakov and Ken Jin bpo 35332 The shutil rmtree function now ignores errors when calling os close when ignore_errors is True and os close no longer retried after error bpo 41422 Fixed memory leaks of pickle Pickler and pickle Unpickler involving cyclic references via the internal memo mapping bpo 40262 The ssl SSLSocket recv_into method no longer requires the buffer argument to implement __len__ and supports buffers with arbitrary item size Documentation gh 111699 Relocate smtpd deprecation notice to its own section rather than under locale in What s New in Python 3 12 document gh 108826 dis module command li,en
1502,ne interface is now mentioned in documentation Tests gh 112769 The tests now correctly compare zlib version when zlib ZLIB_RUNTIME_VERSION contains non integer suffixes For example zlib ng defines the version as 1 3 0 zlib ng gh 110367 Make regrtest verbose3 option compatible with huntrleaks jN options The python m test j1 R 3 3 verbose3 command now works as expected Patch by Victor Stinner gh 111165 Remove no longer used functions run_unittest and run_doctest from the test support module gh 110932 Fix regrtest if the SOURCE_DATE_EPOCH environment variable is defined use the variable value as the random seed Patch by Victor Stinner gh 110995 test_gdb Fix detection of gdb built without Python scripting support Patch by Victor Stinner gh 110918 Test case matching patterns specified by options match ignore matchfile and ignorefile are now tested in the order of specification and the last match determines whether the test case be run or ignored gh 110647 Fix test_stress_modifying_handlers of test_signal Patch by Victor Stinner gh 103053 Fix test_tools test_freeze on FreeBSD run make distclean instead of make clean in the copied source directory to remove also the python program Patch by Victor Stinner gh 110167 Fix a deadlock in test_socket when server fails with a timeout but the client is still running in its thread Don t hold a lock to call cleanup functions in doCleanups One of the cleanup function waits until the client completes whereas the client could deadlock if it called addCleanup in such situation Patch by Victor Stinner gh 110388 Add tests for tty gh 81002 Add tests for termios gh 110267 Add tests for pickling and copying PyStructSequence objects Patched by Xuehai Pan gh 110031 Skip test_threading tests using thread fork if Python is built with Address Sanitizer ASAN Patch by Victor Stinner gh 110088 Fix test_asyncio timeouts don t measure the maximum duration a test should not measure a CI performance Only measure the minimum duration when a task has a timeout or delay Add CLOCK_RES to test_asyncio utils Patch by Victor Stinner gh 109974 Fix race conditions in test_threading lock tests Wait until a condition is met rather than using time sleep with a hardcoded number of seconds Patch by Victor Stinner gh 110033 Fix test_interprocess_signal of test_signal Make sure that the subprocess Popen object is deleted before the test raising an exception in a signal handler Otherwise Popen __del__ can get the exception which is logged as Exception ignored in and the test fails Patch by Victor Stinner gh 109594 Fix test_timeout of test_concurrent_futures test_wait Remove the future which may or may not complete depending if it takes longer than the timeout ot not Keep the second future which does not complete before wait timeout Patch by Victor Stinner gh 109972 Split test_gdb py file into a test_gdb package made of multiple tests so tests can now be run in parallel Patch by Victor Stinner gh 103053 Skip test_freeze_simple_script of test_tools test_freeze if Python is built with configure enable optimizations which means with Profile Guided Optimization PGO it just makes the test too slow The freeze tool is tested by many other CIs with other faster compiler flags Patch by Victor Stinner gh 109580 Skip test_perf_profiler if Python is built with ASAN MSAN or UBSAN sanitizer Python does crash randomly in this test on such build Patch by Victor Stinner gh 104736 Fix test_gdb on Python built with LLVM clang 16 on Linux ppc64le ex Fedora 38 Search patterns in gdb bt command output to detect when gdb fails to retrieve the traceback For example skip a test if Backtrace stopped frame did not save the PC is found Patch by Victor Stinner gh 108927 Fixed order dependence in running tests in the same process when a test that has submodules e g test_importlib follows a test that imports its submodule e g test_importlib util and precedes a test e g test_unittest or test_compileall that uses that submodule Build gh 112088 Add Tools build regen configure sh script to regenerate the configure with an Ubuntu container image The quay io tira,en
1503,n cpython_autoconf 271 container image tiran cpython_autoconf is no longer used Patch by Victor Stinner gh 111046 For wasi threads memory is now exported to fix compatibility issues with some wasm runtimes gh 103053 make check clean src now also checks if the python program is found in the source directory fail with an error if it does exist Patch by Victor Stinner gh 109191 Fix compile error when building with recent versions of libedit Windows gh 111856 Fixes fstat on file systems that do not support file ID requests This includes FAT32 and exFAT gh 111293 Fix os DirEntry inode dropping higher 64 bits of a file id on some filesystems on Windows gh 110913 WindowsConsoleIO now correctly chunks large buffers without splitting up UTF 8 sequences gh 110437 Allows overriding the source of VC redistributables so that releases can be guaranteed to never downgrade between updates gh 109286 Update Windows installer to use SQLite 3 43 1 macOS gh 109981 Use dev fd on macOS to determine the number of open files in test support os_helper fd_count to avoid a crash with guarded file descriptors when probing for open files gh 110950 Update macOS installer to include an upstream Tcl Tk fix for the Secure coding is not enabled for restorable state warning encountered in Tkinter on macOS 14 Sonoma gh 111015 Ensure that IDLE app and Python Launcher app are installed with appropriate permissions on macOS builds gh 109286 Update macOS installer to use SQLite 3 43 1 gh 71383 Update macOS installer to include an upstream Tcl Tk fix for the ttk ThemeChanged error encountered in Tkinter gh 92603 Update macOS installer to include a fix accepted by upstream Tcl Tk for a crash encountered after the first tkinter Tk instance is destroyed IDLE bpo 35668 Add docstrings to the IDLE debugger module Fix two bugs initialize Idb botframe should be in Bdb in Idb in_rpc_code check whether prev_frame is None before trying to use it Greatly expand test_debugger C API gh 106560 Fix redundant declarations in the public C API Declare PyBool_Type and PyLong_Type only once Patch by Victor Stinner gh 112438 Fix support of format units es et es and et in nested tuples in PyArg_ParseTuple like functions gh 109521 PyImport_GetImporter now sets RuntimeError if it fails to get sys path_hooks or sys path_importer_cache or they are not list and dict correspondingly Previously it could return NULL without setting error in obscure cases crash or raise SystemError if these attributes have wrong type Python 3 12 0 final Release date 2023 10 02 Core and Builtins gh 109823 Fix bug where compiler does not adjust labels when removing an empty basic block which is a jump target gh 109719 Fix missing jump target labels when compiler reorders cold warm blocks gh 109627 Fix bug where the compiler does not assign a new jump target label to a duplicated small exit block Library gh 110045 Update the symtable module to support the new scopes introduced by PEP 695 Documentation gh 109209 The minimum Sphinx version required for the documentation is now 4 2 Windows gh 109991 Update Windows build to use OpenSSL 3 0 11 macOS gh 109991 Update macOS installer to use OpenSSL 3 0 11 Tools Demos gh 109991 Update GitHub CI workflows to use OpenSSL 3 0 11 and multissltests to use 1 1 1w 3 0 11 and 3 1 3 Python 3 12 0 release candidate 3 Release date 2023 09 18 Core and Builtins gh 109496 On a Python built in debug mode Py_DECREF now calls _Py_NegativeRefcount if the object is a dangling pointer to deallocated memory memory filled with 0xDD dead byte by the debug hook on memory allocators The fix is to check the reference count before checking for _Py_IsImmortal Patch by Victor Stinner gh 109371 Deopted instructions correctly for tool initialization and modified the incorrect assertion in instrumentation when a previous tool already sets INSTRUCTION events gh 105658 Fix bug where the line trace of an except block ending with a conditional includes an excess event with the line of the conditional expression gh 109219 Fix compiling type param scopes that use a name which is also free in an inner scope g,en
1504,h 109341 Fix crash when compiling an invalid AST involving a ast TypeAlias gh 109195 Fix source location for the LOAD_ instruction preceding a LOAD_SUPER_ATTR to load the super global or shadowing variable so that it encompasses only the name super and not the following parentheses gh 109118 Disallow nested scopes lambdas generator expressions and comprehensions within PEP 695 annotation scopes that are nested within classes gh 109114 Relax the detection of the error message for invalid lambdas inside f strings to not search for arbitrary replacement fields to avoid false positives Patch by Pablo Galindo gh 109118 Fix interpreter crash when a NameError is raised inside the type parameters of a generic class gh 108976 Fix crash that occurs after de instrumenting a code object in a monitoring callback gh 108732 Make iteration variables of module and class scoped comprehensions visible to pdb and other tools that use frame f_locals again gh 108959 Fix caret placement for error locations for subscript and binary operations that involve non semantic parentheses and spaces Patch by Pablo Galindo Library gh 108682 Enum require names or type to create an empty enum using the functional syntax gh 108843 Fix an issue in ast unparse when unparsing f strings containing many quote types Documentation gh 102823 Document the return type of x y when x and y have type float Tests gh 109396 Fix test_socket test_hmac_sha1 in FIPS mode Use a longer key FIPS mode requires at least of at least 112 bits The previous key was only 32 bits Patch by Victor Stinner gh 104736 Fix test_gdb on Python built with LLVM clang 16 on Linux ppc64le ex Fedora 38 Search patterns in gdb bt command output to detect when gdb fails to retrieve the traceback For example skip a test if Backtrace stopped frame did not save the PC is found Patch by Victor Stinner gh 109237 Fix test_site test_underpth_basic when the working directory contains at least one non ASCII character encode the _pth file to UTF 8 and enable the UTF 8 Mode to use UTF 8 for the child process stdout Patch by Victor Stinner gh 109230 Fix test_pyexpat test_exception it can now be run from a directory different than Python source code directory Before the test failed in this case Skip the test if Modules pyexpat c source is not available Skip also the test on Python implementations other than CPython Patch by Victor Stinner gh 109015 Fix test_asyncio test_imaplib and test_socket tests on FreeBSD if the TCP blackhole is enabled sysctl net inet tcp blackhole Skip the few tests which failed with ETIMEDOUT which such non standard configuration Currently the FreeBSD GCP image enables TCP and UDP blackhole sysctl net inet tcp blackhole 2 and sysctl net inet udp blackhole 1 Patch by Victor Stinner gh 91960 Skip test_gdb if gdb is unable to retrieve Python frame objects if a frame is optimized out When Python is built with clang Og gdb can fail to retrive the frame parameter of _PyEval_EvalFrameDefault In this case tests like py_bt are likely to fail Without getting access to Python frames python gdb py is mostly clueless on retrieving the Python traceback Moreover test_gdb is no longer skipped on macOS if Python is built with Clang Patch by Victor Stinner gh 108962 Skip test_tempfile test_flags if chflags fails with OSError Errno 45 Operation not supported ex on FreeBSD 13 Patch by Victor Stinner gh 108851 Fix test_tomllib recursion tests for WASI buildbots reduce the recursion limit and compute the maximum nested array dict depending on the current available recursion limit Patch by Victor Stinner gh 108851 Add get_recursion_available and get_recursion_depth functions to the test support module Patch by Victor Stinner gh 108834 Add fail rerun option option to regrtest if a test failed when then passed when rerun in verbose mode exit the process with exit code 2 error instead of exit code 0 success Patch by Victor Stinner gh 108834 Rename regrtest verbose2 option w to rerun Keep verbose2 as a deprecated alias Patch by Victor Stinner gh 108834 When regrtest reruns failed tests in verbose mode python m test r,en
1505,erun tests are now rerun in fresh worker processes rather than being executed in the main process If a test does crash or is killed by a timeout the main process can detect and handle the killed worker process Tests are rerun in parallel if the jN option is used to run tests in parallel Patch by Victor Stinner gh 103186 Suppress and assert expected RuntimeWarnings in test_sys_settrace py Build gh 108740 Fix a race condition in make regen all The deepfreeze c source and files generated by Argument Clinic are now generated or updated before generating global objects Previously some identifiers may miss depending on the order in which these files were generated Patch by Victor Stinner Python 3 12 0 release candidate 2 Release date 2023 09 05 Security gh 108310 Fixed an issue where instances of ssl SSLSocket were vulnerable to a bypass of the TLS handshake and included protections like certificate verification and treating sent unencrypted data as if it were post handshake TLS encrypted data Security issue reported as CVE 2023 40217 by Aapo Oksman Patch by Gregory P Smith gh 107774 PEP 669 specifies that sys monitoring register_callback will generate an audit event Pre releases of Python 3 12 did not generate the audit event This is now fixed Core and Builtins gh 108520 Fix multiprocessing synchronize SemLock __setstate__ to properly initialize multiprocessing synchronize SemLock _is_fork_ctx This fixes a regression when passing a SemLock accross nested processes Rename multiprocessing synchronize SemLock is_fork_ctx to multiprocessing synchronize SemLock _is_fork_ctx to avoid exposing it as public API gh 108654 Restore locals shadowed by an inlined comprehension if the comprehension raises an exception gh 108487 Change an assert that would cause a spurious crash in a devious case that should only trigger deoptimization gh 106176 Use a WeakValueDictionary to track the lists containing the modules each thread is currently importing This helps avoid a reference leak from keeping the list around longer than necessary Weakrefs are used as GC can t interrupt the cleanup gh 107901 Fix missing line number on JUMP_BACKWARD at the end of a for loop gh 108390 Raise an exception when setting a non local event RAISE EXCEPTION_HANDLED etc in sys monitoring set_local_events Fixes crash when tracing in recursive calls to Python classes gh 91051 Fix abort segfault when using all eight type watcher slots on platforms where char is signed by default gh 107724 In pre release versions of 3 12 up to rc1 the sys monitoring callback function for the PY_THROW event was missing the third exception argument That is now fixed gh 107080 Trace refs builds with trace refs were crashing when used with isolated subinterpreters The problematic global state has been isolated to each interpreter Other fixing the crashes this change does not affect users gh 77377 Ensure that multiprocessing synchronization objects created in a fork context are not sent to a different process created in a spawn context This changes a segfault into an actionable RuntimeError in the parent process Library gh 108469 ast unparse now supports new f string syntax introduced in Python 3 12 Note that the f string quotes are reselected for simplicity under the new syntax Patch by Steven Sun gh 108682 Enum raise TypeError if super __new__ is called from a custom __new__ gh 108295 Fix crashes related to use of weakrefs on typing TypeVar gh 64662 Fix support for virtual tables in sqlite3 Connection iterdump Patch by Aviv Palivoda gh 108111 Fix a regression introduced in gh 101251 for 3 12 resulting in an incorrect offset calculation in gzip GzipFile seek gh 105736 Harmonized the pure Python version of OrderedDict with the C version Now both versions set up their internal state in __new__ Formerly the pure Python version did the set up in __init__ gh 108083 Fix bugs in the constructor of sqlite3 Connection and sqlite3 Connection close where exceptions could be leaked Patch by Erlend E Aasland gh 107963 Fix multiprocessing set_forkserver_preload to check the given list of modules names Patch,en
1506, by Donghee Na gh 106242 Fixes os path normpath to handle embedded null characters without truncating the path gh 107913 Fix possible losses of errno and winerror values in OSError exceptions if they were cleared or modified by the cleanup code before creating the exception object gh 107845 tarfile data_filter now takes the location of symlinks into account when determining their target so it will no longer reject some valid tarballs with LinkOutsideDestinationError gh 107805 Fix signatures of module level generated functions in turtle gh 107715 Fix doctest DocTestFinder find in presence of class names with special characters Patch by Gertjan van Zwieten gh 100814 Passing a callable object as an option value to a Tkinter image now raises the expected TclError instead of an AttributeError gh 106684 Close asyncio StreamWriter when it is not closed by application leading to memory leaks Patch by Kumar Aditya gh 107396 tarfiles Fixed use before assignment of self exception for gzip decompression gh 106052 re module fix the matching of possessive quantifiers in the case of a subpattern containing backtracking gh 100061 Fix a bug that causes wrong matches for regular expressions with possessive qualifier gh 99203 Restore following CPython 3 10 5 behavior of shutil make_archive do not create an empty archive if root_dir is not a directory and in that case raise FileNotFoundError or NotADirectoryError regardless of format choice Beyond the brought back behavior the function may now also raise these exceptions in dry_run mode Documentation gh 105052 Update timeit doc to specify that time in seconds is just the default Tests gh 89392 Removed support of test_main function in tests They now always use normal unittest test runner gh 108388 Convert test_concurrent_futures to a package of 7 sub tests Patch by Victor Stinner gh 108388 Split test_multiprocessing_fork test_multiprocessing_forkserver and test_multiprocessing_spawn into test packages Each package is made of 4 sub tests processes threads manager and misc It allows running more tests in parallel and so reduce the total test duration Patch by Victor Stinner gh 105776 Fix test_cppext when the C compiler command std c11 option remove std options from the compiler command Patch by Victor Stinner gh 107178 Add the C API test for functions in the Mapping Protocol the Sequence Protocol and some functions in the Object Protocol Build gh 63760 Fix Solaris build no longer redefine the gethostname function Solaris defines the function since 2005 Patch by Victor Stinner original patch by Jakub Kulík gh 107814 When calling find_python bat with q it did not properly silence the output of nuget That is now fixed Windows gh 107565 Update Windows build to use OpenSSL 3 0 10 gh 106242 Fixes realpath to behave consistently when passed a path containing an embedded null character on Windows In strict mode it now raises OSError instead of the unexpected ValueError and in non strict mode will make the path absolute gh 106844 Fix integer overflow and truncating by the null character in _winapi LCMapStringEx which affects ntpath normcase macOS gh 107565 Update macOS installer to use OpenSSL 3 0 10 Tools Demos gh 107565 Update multissltests and GitHub CI workflows to use OpenSSL 1 1 1v 3 0 10 and 3 1 2 gh 95065 Argument Clinic now supports overriding automatically generated signature by using directive text_signature C API gh 107916 C API functions PyErr_SetFromErrnoWithFilename PyErr_SetExcFromWindowsErrWithFilename and PyErr_SetFromWindowsErrWithFilename save now the error code before calling PyUnicode_DecodeFSDefault gh 107915 Such C API functions as PyErr_SetString PyErr_Format PyErr_SetFromErrnoWithFilename and many others no longer crash or ignore errors if it failed to format the error message or decode the filename Instead they keep a corresponding error gh 107810 Improve DeprecationWarning for uses of PyType_Spec with metaclasses that have custom tp_new Python 3 12 0 release candidate 1 Release date 2023 08 05 Security gh 102988 Reverted the email utils security improvement change released i,en
1507,n 3 12beta4 that unintentionally caused email utils getaddresses to fail to parse email addresses with a comma in the quoted name field See gh 106669 gh 102509 Start initializing ob_digit during creation of PyLongObject objects Patch by Illia Volochii Core and Builtins gh 107263 Increase C recursion limit for functions other than the main interpreter from 800 to 1500 This should allow functions like list __repr__ and json dumps to handle all the inputs that they could prior to 3 12 gh 104432 Fix potential unaligned memory access on C APIs involving returned sequences of char pointers within the grp and socket modules These were revealed using a fsaniziter alignment build on ARM macOS Patch by Christopher Chavez gh 106898 Add the exception as the third argument to PY_UNIND callbacks in sys monitoring This makes the PY_UNWIND callback consistent with the other exception hanlding callbacks gh 106895 Raise a ValueError when a monitoring callback funtion returns DISABLE for events that cannot be disabled locally gh 106897 Add a RERAISE event to sys monitoring which occurs when an exception is reraised either explicitly by a plain raise statement or implicitly in an except or finally block gh 104621 Unsupported modules now always fail to be imported gh 106917 Fix classmethod style super method calls i e where the second argument to super or the implied second argument drawn from self cls in the case of zero arg super is a type when the target of the call is not a classmethod gh 105699 Python no longer crashes due an infrequent race when initialzing per interpreter interned strings The crash would manifest when the interpreter was finalized gh 105699 Python no longer crashes due to an infrequent race in setting Py_FileSystemDefaultEncoding and Py_FileSystemDefaultEncodeErrors both deprecated when simultaneously initializing two isolated subinterpreters Now they are only set during runtime initialization gh 106092 Fix a segmentation fault caused by a use after free bug in frame_dealloc when the trashcan delays the deallocation of a PyFrameObject gh 106719 No longer suppress arbitrary errors in the __annotations__ getter and setter in the type and module types gh 106723 Propagate frozen_modules to multiprocessing spawned process interpreters gh 105235 Prevent out of bounds memory access during mmap find calls Library gh 107077 Seems that in some conditions OpenSSL will return SSL_ERROR_SYSCALL instead of SSL_ERROR_SSL when a certification verification has failed but the error parameters will still contain ERR_LIB_SSL and SSL_R_CERTIFICATE_VERIFY_FAILED We are now detecting this situation and raising the appropiate ssl SSLCertVerificationError Patch by Pablo Galindo gh 107576 Fix types get_original_bases to only return __orig_bases__ if it is present on cls directly Patch by James Hilton Balfe gh 46376 Prevent memory leak and use after free when using pointers to pointers with ctypes gh 62519 Make gettext pgettext search plural definitions when translation is not found gh 83006 Document behavior of shutil disk_usage for non mounted filesystems on Unix gh 106186 Do not report MultipartInvariantViolationDefect defect when the email parser Parser class is used to parse emails with headersonly True gh 105002 Fix invalid result from PurePath relative_to method when attempting to walk a segment in other with walk_up enabled A ValueError exception is now raised in this case gh 106831 Fix potential missing NULL check of d2i_SSL_SESSION result in _ssl c gh 106774 Update the bundled copy of pip to version 23 2 1 gh 106752 Fixed several bugs in zipfile Path including in Path match Windows separators are no longer honored and never were meant to be Fixed name suffix suffixes stem operations when no filename is present and the Path is not at the root of the zipfile Reworked glob for performance and more correct matching behavior gh 106602 Add __copy__ and __deepcopy__ in enum gh 106530 Revert a change to colorsys rgb_to_hls that caused division by zero for certain almost white inputs Patch by Terry Jan Reedy gh 106403 Instances of typing TypeV,en
1508,ar typing ParamSpec typing ParamSpecArgs typing ParamSpecKwargs and typing TypeVarTuple once again support weak references fixing a regression introduced in Python 3 12 0 beta 1 Patch by Jelle Zijlstra gh 106350 Detect possible memory allocation failure in the libtommath function mp_init used by the _tkinter module gh 106263 Fix crash when calling repr with a manually constructed SignalDict object Patch by Charlie Zhao gh 105626 Change the default return value of http client HTTPConnection get_proxy_response_headers to be None and not bpo 18319 Ensure gettext msg retrieve translations even if a plural form exists In other words gettext msg ngettext msg 1 Documentation gh 107305 Add documentation for PyInterpreterConfig and Py_NewInterpreterFromConfig Also clarify some of the nearby docs relative to per interpreter GIL gh 107008 Document the curses module variables LINES and COLS gh 106948 Add a number of standard external names to nitpick_ignore gh 54738 Add documentation on how to localize the argparse module Tests gh 107237 test_logging Fix test_udp_reconnection by increasing the timeout from 100 ms to 5 minutes LONG_TIMEOUT Patch by Victor Stinner gh 106714 test_capi Fix test_no_FatalError_infinite_loop to no longer write a coredump by using test support SuppressCrashReport Patch by Victor Stinner gh 104090 Avoid creating a reference to the test object in collectedDurations gh 106752 Moved tests for zipfile Path into Lib test test_zipfile _path Made zipfile _path a package Build gh 106881 Check for linux limits h before including it in Modules posixmodule c gh 106962 Detect MPI compilers in configure gh 101538 Add experimental wasi threads support Patch by Takashi Yamamoto Windows gh 99079 Update Windows build to use OpenSSL 3 0 9 macOS gh 99079 Update macOS installer to use OpenSSL 3 0 9 Tools Demos gh 106970 Fix bugs in the Argument Clinic destination name clear command the destination buffers would never be cleared and the destination directive parser would simply continue to the fault handler after processing the command Patch by Erlend E Aasland gh 103186 freeze now fetches CONFIG_ARGS from the original CPython instance the Makefile uses to call utility scripts Patch by Ijtaba Hussain C API gh 107226 PyModule_AddObjectRef is now only available in the limited API version 3 10 or later Python 3 12 0 beta 4 Release date 2023 07 11 Security gh 102988 CVE 2023 27043 Prevent email utils parseaddr and email utils getaddresses from returning the realname portion of an invalid RFC2822 email header in the email address portion of the 2 tuple returned after being parsed by email _parseaddr AddressList Core and Builtins gh 106396 When the format specification of an f string expression is empty the parser now generates an empty ast JoinedStr node for it instead of an one element ast JoinedStr with an empty string ast Constant gh 106145 Make end_lineno and end_col_offset required on type_param ast nodes gh 105979 Fix crash in _imp get_frozen_object due to improper exception handling gh 98931 Ensure custom SyntaxError error messages are raised for invalid imports with multiple targets Patch by Pablo Galindo gh 105908 Fixed bug where gh 99111 breaks future import barry_as_FLUFL in the Python REPL gh 105340 Include the comprehension iteration variable in locals inside a module or class scope comprehension gh 105486 Change the repr of ParamSpec list of args in types GenericAlias gh 101006 Improve error handling when read marshal data Library gh 106524 Fix crash in _sre template with templates containing invalid group indices gh 106510 Improve debug output for atomic groups in regular expressions gh 106503 Fix ref cycle in asyncio _SelectorSocketTransport by removing _write_ready in close gh 105497 Fix flag mask inversion when unnamed flags exist gh 90876 Prevent multiprocessing spawn from failing to import in environments where sys executable is None This regressed in 3 11 with the addition of support for path like objects in multiprocessing gh 106292 Check for an instance dict cached value in the __get__ method of functools cache,en
1509,d_property This better matches the pre 3 12 behavior and improves compatibility for users subclassing functools cached_property and adding a __set__ method gh 106330 Fix incorrect matching of empty paths in pathlib PurePath match This bug was introduced in Python 3 12 0 beta 1 gh 102541 Make pydoc doc catch bad module ImportError when output stream is not None gh 106152 Added PY_THROW event hook for cProfile for generators gh 106075 Added asyncio taskgroups __all__ to asyncio __all__ for export in star imports gh 105987 Fix crash due to improper reference counting in asyncio eager task factory internal routines gh 105974 Fix bug where a typing Protocol class that had one or more non callable members would raise TypeError when issubclass was called against it even if it defined a custom __subclasshook__ method The behaviour in Python 3 11 and lower which has now been restored was not to raise TypeError in these situations if a custom __subclasshook__ method was defined Patch by Alex Waygood gh 96145 Reverted addition of json AttrDict gh 105497 Fix flag inversion when alias mask members exist gh 104554 Add RTSPS scheme support in urllib parse gh 94777 Fix hanging multiprocessing ProcessPoolExecutor when a child process crashes while data is being written in the call queue Documentation gh 106232 Make timeit doc command lines compatible with Windows by using double quotes for arguments This works on linux and macOS also Tests gh 101634 When running the Python test suite with jN option if a worker stdout cannot be decoded from the locale encoding report a failed testn so the exitcode is non zero Patch by Victor Stinner Build gh 106118 Fix compilation for platforms without O_CLOEXEC The issue was introduced with Python 3 12b1 in gh 103295 Patch by Erlend Aasland gh 104692 Include commoninstall as a prerequisite for bininstall This ensures that commoninstall is completed before bininstall is started when parallel builds are used make j install and so the python3 symlink is only installed after all standard library modules are installed Tools Demos gh 106359 Argument Clinic now explicitly forbids kwarg splats in function calls used as annotations C API gh 105227 The new PyType_GetDict provides the dictionary for the given type object that is normally exposed by cls __dict__ Normally it s sufficient to use tp_dict but for the static builtin types tp_dict is now always NULL PyType_GetDict provides the correct dict object instead Python 3 12 0 beta 3 Release date 2023 06 19 Core and Builtins gh 105840 Fix possible crashes when specializing function calls with too many __defaults__ gh 105831 Fix an f string bug where using a debug expression the sign that appears in the last line of a file results to the debug buffer that holds the expression text being one character too small gh 105800 Correctly issue SyntaxWarning in f strings if invalid sequences are used Patch by Pablo Galindo gh 105587 The runtime can t guarantee that immortal objects will not be mutated by Extensions Thus this modifies _PyStaticObject_CheckRefcnt to warn instead of asserting gh 105564 Don t include artificil newlines in the line attribute of tokens in the APIs of the tokenize module Patch by Pablo Galindo gh 105549 Tokenize separately NUMBER and NAME tokens that are not ambiguous Patch by Pablo Galindo gh 105588 Fix an issue that could result in crashes when compiling malformed ast nodes gh 105375 Fix bugs in the builtins module where exceptions could end up being overwritten gh 105375 Fix bug in the compiler where an exception could end up being overwritten gh 105375 Improve error handling in PyUnicode_BuildEncodingMap where an exception could end up being overwritten gh 105435 Fix spurious newline character if file ends on a comment without a newline Patch by Pablo Galindo gh 105390 Correctly raise tokenize TokenError exceptions instead of SyntaxError for tokenize errors such as incomplete input Patch by Pablo Galindo gh 104812 The pending call machinery now works for all interpreters not just the main interpreter and runs in all threads not just the main t,en
1510,hread Some calls are still only done in the main thread ergo in the main interpreter This change does not affect signal handling nor the existing public C API Py_AddPendingCall which both still only target the main thread The new functionality is meant strictly for internal use for now since consequences of its use are not well understood yet outside some very restricted cases This change brings the capability in line with the intention when the state was made per interpreter several years ago Library gh 105808 Fix a regression introduced in gh 101251 for 3 12 causing gzip GzipFile flush to not flush the compressor nor pass along the zip_mode argument gh 104799 Enable ast unparse to unparse function and class definitions created without the new type_params field from PEP 695 Patch by Jelle Zijlstra gh 105745 Fix webbrowser Konqueror open method gh 105375 Fix a bug in _Unpickler_SetInputStream where an exception could end up being overwritten in case of failure gh 105375 Fix bugs in sys where exceptions could end up being overwritten because of deferred error handling gh 105605 Harden pyexpat error handling during module initialisation to prevent exceptions from possibly being overwritten and objects from being dereferenced twice gh 105375 Fix bug in decimal where an exception could end up being overwritten gh 105375 Fix bugs in _datetime where exceptions could be overwritten in case of module initialisation failure gh 105375 Fix bugs in _ssl initialisation which could lead to leaked references and overwritten exceptions gh 105375 Fix a bug in array array where an exception could end up being overwritten gh 105375 Fix bugs in _ctypes where exceptions could end up being overwritten gh 105375 Fix a bug in the posix module where an exception could be overwritten gh 105375 Fix bugs in _elementtree where exceptions could be overwritten gh 105375 Fix bugs in zoneinfo where exceptions could be overwritten gh 105375 Fix bugs in errno where exceptions could be overwritten gh 105375 Fix bugs in pickle where exceptions could be overwritten gh 105375 Fix a bug in sqlite3 where an exception could be overwritten in the collation callback gh 105332 Revert pickling method from by name back to by value gh 104310 In the beta 1 release we added a utility function for extension module authors to use when testing their module for support in multiple interpreters or under a per interpreter GIL The name of that function has changed from allowing_all_extensions to _incompatible_extension_module_restrictions The default for the disable_check argument has change from True to False to better match the new function name gh 104996 Improve performance of pathlib PurePath initialisation by deferring joining of paths when multiple arguments are given gh 102541 Hide traceback in help prompt when import failed Tests gh 105084 When the Python build is configured with wheel pkg dir tests requiring the setuptools and wheel wheels will search for the wheels in WHEEL_PKG_DIR Windows gh 105436 Ensure that an empty environment block is terminated by two null characters as is required by Windows C API gh 105375 Fix a bug in PyErr_WarnExplicit where an exception could end up being overwritten if the API failed internally gh 105603 We ve renamed the new in 3 12 PyInterpreterConfig own_gil to PyInterpreterConfig gil and changed the meaning of the value from bool to an integer with supported values of PyInterpreterConfig_DEFAULT_GIL PyInterpreterConfig_SHARED_GIL and PyInterpreterConfig_OWN_GIL The default is shared gh 105387 In the limited C API version 3 12 Py_INCREF and Py_DECREF functions are now implemented as opaque function calls to hide implementation details Patch by Victor Stinner gh 103968 PyType_FromMetaclass now allows metaclasses with tp_new set to NULL Python 3 12 0 beta 2 Release date 2023 06 06 Security gh 103142 The version of OpenSSL used in our binary builds has been upgraded to 1 1 1u to address several CVEs gh 99108 Refresh our new HACL built in hashlib code from upstream Built in SHA2 should be faster and an issue with SHA3 on 32 bit platforms ,en
1511,is fixed Core and Builtins gh 105259 Don t include newline character for trailing NEWLINE tokens emitted in the tokenize module Patch by Pablo Galindo gh 105324 Fix the main function of the tokenize module when reading from sys stdin Patch by Pablo Galindo gh 98963 Restore the ability for a subclass of property to define __slots__ or otherwise be dict less by ignoring failures to set a docstring on such a class This behavior had regressed in 3 12beta1 An AttributeError where there had not previously been one was disruptive to existing code gh 105194 Do not escape with backslashes f string format specifiers Patch by Pablo Galindo gh 105162 Fixed bug in generator close throw where an inner iterator would be ignored when the outer iterator was instrumented gh 105164 Ensure annotations are set up correctly if the only annotation in a block is within a match block Patch by Jelle Zijlstra gh 104799 Attributes of ast nodes that are lists now default to the empty list if omitted This means that some code that previously raised TypeError when the AST node was used will now proceed with the empty list instead Patch by Jelle Zijlstra gh 105035 Fix super calls on types with custom tp_getattro implementation e g meta types gh 105017 Show CRLF lines in the tokenize string attribute in both NL and NEWLINE tokens Patch by Marta Gómez gh 105013 Fix handling of multiline parenthesized lambdas in inspect getsource Patch by Pablo Galindo gh 105017 Do not include an additional final NL token when parsing files having CRLF lines Patch by Marta Gómez gh 104976 Ensure that trailing DEDENT tokenize TokenInfo objects emitted by the tokenize module are reported as in Python 3 11 Patch by Pablo Galindo gh 104972 Ensure that the line attribute in tokenize TokenInfo objects in the tokenize module are always correct Patch by Pablo Galindo gh 104955 Fix signature for the new __release_buffer__ slot Patch by Jelle Zijlstra gh 104690 Starting new threads and process creation through os fork during interpreter shutdown such as from atexit handlers is no longer supported It can lead to race condition between the main Python runtime thread freeing thread states while internal threading routines are trying to allocate and use the state of just created threads Or forked children trying to use the mid shutdown runtime and thread state in the child process gh 104879 Fix crash when accessing the __module__ attribute of type aliases defined outside a module Patch by Jelle Zijlstra gh 104825 Tokens emitted by the tokenize module do not include an implicit n character in the line attribute anymore Patch by Pablo Galindo Library gh 105280 Fix bug where isinstance collections abc Mapping could evaluate to True if garbage collection happened at the wrong time The bug was caused by changes to the implementation of typing Protocol in Python 3 12 gh 105239 Fix longstanding bug where issubclass object typing Protocol would evaluate to True in some edge cases Patch by Alex Waygood gh 105080 Fixed inconsistent signature on derived classes for inspect signature gh 105144 Fix a recent regression in the typing module The regression meant that doing class Foo X typing Protocol where X was a class that had abc ABCMeta as its metaclass would then cause subsequent isinstance 1 X calls to erroneously raise TypeError Patch by Alex Waygood gh 105113 Improve performance of pathlib PurePath match by compiling an re Pattern object for the entire pattern gh 101588 Deprecate undocumented copy deepcopy pickle support for itertools gh 103631 Fix pathlib PurePosixPath pathlib PureWindowsPath not converting path separators to restore 3 11 compatible behavior gh 104947 Make comparisons between pathlib PureWindowsPath objects consistent across Windows and Posix to match 3 11 behavior gh 104935 Fix bugs with the interaction between typing runtime_checkable and typing Generic that were introduced by the PEP 695 implementation Patch by Jelle Zijlstra gh 104874 Document the __name__ and __supertype__ attributes of typing NewType Patch by Jelle Zijlstra gh 104799 Adjust the location of the see PEP 6,en
1512,95 type_params field on ast ClassDef ast AsyncFunctionDef and ast FunctionDef to better preserve backward compatibility Patch by Jelle Zijlstra gh 104797 Allow typing Protocol classes to inherit from collections abc Buffer Patch by Jelle Zijlstra gh 104372 On Linux where subprocess can use the vfork syscall for faster spawning prevent the parent process from blocking other threads by dropping the GIL while it waits for the vfork ed child process exec outcome This prevents spawning a binary from a slow filesystem from blocking the rest of the application gh 99108 We now release the GIL around built in hashlib computations of reasonable size for the SHA families and MD5 hash functions matching what our OpenSSL backed hash computations already does gh 104399 Prepare the _tkinter module for building with Tcl 9 0 and future libtommath by replacing usage of deprecated functions mp_to_unsigned_bin_n and mp_unsigned_bin_size when necessary gh 102024 Reduce calls of _idle_semaphore release in concurrent futures thread _worker Documentation gh 89455 Add missing documentation for the max_group_depth and max_group_width parameters and the exceptions attribute of the traceback TracebackException class gh 89412 Add missing documentation for the end_lineno and end_offset attributes of the traceback TracebackException class gh 104943 Remove mentions of old Python versions in typing NamedTuple Build gh 90005 Fix a regression in configure where we could end up unintentionally linking with libbsd gh 89886 Autoconf 2 71 and aclocal 1 16 4 is now required to regenerate configure Windows gh 105146 Updated the links at the end of the installer to point to Discourse rather than the mailing lists gh 103646 When installed from the Microsoft Store pip no longer defaults to per user installs However as the install directory is unwritable it should automatically decide to do a per user install anyway This should resolve issues when pip is passed an option that conflicts with user gh 88745 Improve performance of shutil copy2 by using the operating system s CopyFile2 function This may result in subtle changes to metadata copied along with some files bringing them in line with normal OS behavior gh 104820 Fixes stat and related functions on file systems that do not support file ID requests This includes FAT32 and exFAT gh 104803 Add os path isdevdrive to detect whether a path is on a Windows Dev Drive Returns False on platforms that do not support Dev Drive and is absent on non Windows platforms macOS gh 103142 Update macOS installer to use OpenSSL 1 1 1u IDLE gh 104719 Remove IDLE s modification of tokenize tabsize and test other uses of tokenize data and methods C API gh 105115 PyTypeObject tp_bases and tp_mro for builtin static types are now shared by all interpreters whereas in 3 12 beta1 they were stored on PyInterpreterState Also note that now the tuples are immortal objects gh 105071 Add PyUnstable_Exc_PrepReraiseStar to the unstable C api to expose the implementation of except gh 104668 Don t call PyOS_InputHook or PyOS_ReadlineFunctionPointer in subinterpreters since it s generally difficult to avoid using global state in their registered callbacks This also avoids situations where extensions may find themselves running in a subinterpreter they don t support or haven t yet been loaded in Python 3 12 0 beta 1 Release date 2023 05 22 Security gh 99889 Fixed a security in flaw in uu decode that could allow for directory traversal based on the input if no out_file was specified gh 104049 Do not expose the local on disk location in directory indexes produced by http client SimpleHTTPRequestHandler gh 99108 Upgrade built in hashlib SHA3 implementation to a verified implementation from the HACL project Used when OpenSSL is not present or lacks SHA3 gh 102153 urllib parse urlsplit now strips leading C0 control and space characters following the specification for URLs defined by WHATWG in response to CVE 2023 24329 Patch by Illia Volochii Core and Builtins gh 102856 Implement PEP 701 changes in the tokenize module Patch by Marta Gómez Macías and Pablo ,en
1513,Galindo Salgado gh 104615 Fix wrong ordering of assignments in code like a a x y Contributed by Carl Meyer gh 104572 Improve syntax error message for invalid constructs in PEP 695 contexts and in annotations when from __future__ import annotations is active gh 104482 Fix three error handling bugs in ast c s validation of pattern matching statements gh 102818 Do not add a frame to the traceback in the sys setprofile and sys settrace trampoline functions This ensures that frames are not duplicated if an exception is raised in the callback function and ensures that frames are not omitted if a C callback is used and that does not add the frame gh 104405 Fix an issue where some bytecode instructions could ignore PEP 523 when inlining calls gh 103082 Change behavior of sys monitoring events LINE events in sys monitoring Line events now occur when a new line is reached dynamically instead of using a static approximation as before This makes the behavior very similar to that of line events in sys settrace This should ease porting of tools from 3 11 to 3 12 gh 104263 Fix float nan to produce a quiet NaN on platforms like MIPS where the meaning of the signalling quiet bit is inverted from its usual meaning Also introduce a new macro Py_INFINITY matching C99 s INFINITY and refactor internals to rely on C99 s NAN and INFINITY macros instead of hard coding bit patterns for infinities and NaNs Thanks Sebastian Berg gh 99113 Multi phase init extension modules may now indicate that they support running in subinterpreters that have their own GIL This is done by using Py_MOD_PER_INTERPRETER_GIL_SUPPORTED as the value for the Py_mod_multiple_interpreters module def slot Otherwise the module by default cannot be imported in such subinterpreters This does not affect the main interpreter or subinterpreters that do not have their own GIL In addition to the isolation that multi phase init already normally requires support for per interpreter GIL involves one additional constraint thread safety If the module has external linked dependencies and those libraries have any state that isn t thread safe then the module must do the additional work to add thread safety This should be an uncommon case gh 99113 The GIL is now optionally per interpreter This is the fundamental change for PEP 684 This is all made possible by virtue of the isolated state of each interpreter in the process The behavior of the main interpreter remains unchanged Likewise interpreters created using Py_NewInterpreter are not affected To get an interpreter with its own GIL call Py_NewInterpreterFromConfig gh 104108 Multi phase init extension modules may now indicate whether or not they actually support multiple interpreters By default such modules are expected to support use in multiple interpreters In the uncommon case that one does not it may use the new Py_mod_multiple_interpreters module def slot A value of 0 means the module does not support them 1 means it does The default is 1 gh 104142 Fix an issue where list or tuple repetition could fail to respect PEP 683 gh 104078 Improve the performance of PyObject_HasAttrString gh 104066 Improve the performance of hasattr for module objects with a missing attribute gh 104028 Reduce object creation while calling callback function from gc Patch by Donghee Na gh 104018 Disallow the z format specifier in format of bytes objects gh 102213 Fix performance loss when accessing an object s attributes with __getattr__ defined gh 103895 Improve handling of edge cases in showing Exception __notes__ Ensures that the messages always end with a newline and that string bytes are not exploded over multiple lines Patch by Carey Metcalfe gh 103907 Don t modify the refcounts of known immortal objects True False and None in the main interpreter loop gh 103899 Provide a helpful hint in the TypeError message when accidentally calling a module object that has a callable attribute of the same name such as dis dis or datetime datetime gh 103845 Remove both line and instruction instrumentation before adding new ones for monitoring to avoid newly added instrume,en
1514,ntation being removed immediately gh 103763 Implement PEP 695 adding syntactic support for generic classes generic functions and type aliases A new type X syntax is added for type aliases which resolves at runtime to an instance of the new class typing TypeAliasType The value is lazily evaluated and is accessible through the __value__ attribute This is implemented as a new AST node ast TypeAlias New syntax class X T def func T is added for defining generic functions and classes This is implemented as a new type_params attribute on the AST nodes for classes and functions This node holds instances of the new AST classes ast TypeVar ast ParamSpec and ast TypeVarTuple typing TypeVar typing ParamSpec typing ParamSpecArgs typing ParamSpecKwargs typing TypeVarTuple and typing Generic are now implemented in C rather than Python There are new bytecode instructions LOAD_LOCALS LOAD_CLASSDICT_OR_GLOBAL and LOAD_CLASSDICT_OR_DEREF to support correct resolution of names in class namespaces Patch by Eric Traut Larry Hastings and Jelle Zijlstra gh 103801 Adds three minor linting fixes to the wasm module caught that were caught by ruff gh 103793 Optimized asyncio Task creation by deferring expensive string formatting task name generation from Task creation to the first time get_name is called This makes asyncio benchmarks up to 5 faster gh 102310 Change the error range for invalid bytes literals gh 103590 Do not wrap a single exception raised from a try except construct in an ExceptionGroup gh 103650 Change the perf map format to remove the 0x prefix from the addresses gh 102856 Implement the required C tokenizer changes for PEP 701 Patch by Pablo Galindo Salgado Lysandros Nikolaou Batuhan Taskaya Marta Gómez Macías and sunmy2019 gh 100530 Clarify the error message raised when the called part of a class pattern isn t actually a class gh 101517 Fix bug in line numbers of instructions emitted for except gh 103492 Clarify SyntaxWarning with literal is comparison by specifying which literal is problematic since comparisons using is with e g None and bool literals are idiomatic gh 87729 Add LOAD_SUPER_ATTR and a specialization for super method to speed up super method and super attr This makes super method roughly 2 3x faster and brings it within 20 of the performance of a simple method call Patch by Vladimir Matveev and Carl Meyer gh 103488 Change the internal offset distinguishing yield and return target addresses so that the instruction pointer is correct for exception handling and other stack unwinding gh 82012 The bitwise inversion operator on bool is deprecated It returns the bitwise inversion of the underlying int representation such that bool True True which can be confusing Use not for logical negation of bools In the rare case that you really need the bitwise inversion of the underlying int convert to int explicitly int x gh 77757 Exceptions raised in a typeobject s __set_name__ method are no longer wrapped by a RuntimeError Context information is added to the exception as a PEP 678 note gh 103333 AttributeError now retains the name attribute when pickled and unpickled gh 103242 Migrate set_ecdh_curve method not to use deprecated OpenSSL APIs Patch by Donghee Na gh 103323 We ve replaced our use of _PyRuntime tstate_current with a thread local variable This is a fairly low level implementation detail and there should be no change in behavior gh 84436 The implementation of PEP 683 which adds Immortal Objects by using a fixed reference count that skips reference counting to make objects truly immutable gh 102700 Allow built in modules to be submodules This allows submodules to be statically linked into a CPython binary gh 103082 Implement PEP 669 Low Impact Monitoring for CPython gh 88691 Reduce the number of inline CACHE entries for CALL gh 102500 Make the buffer protocol accessible in Python code using the new __buffer__ and __release_buffer__ magic methods See PEP 688 for details Patch by Jelle Zijlstra gh 97933 PEP 709 inline list dict and set comprehensions to improve performance and reduce bytecode size gh 99184 Bypass instance ,en
1515,attribute access of __name__ in repr of weakref ref gh 98003 Complex function calls are now faster and consume no C stack space bpo 39610 len for 0 dimensional memoryview objects such as memoryview ctypes c_uint8 42 now raises a TypeError Previously this returned 1 which was not consistent with mem_0d 0 raising an IndexError bpo 31821 Fix pause_reading to work when called from connection_made in asyncio Library gh 104600 functools update_wrapper now sets the __type_params__ attribute added by PEP 695 gh 104340 When an asyncio pipe protocol loses its connection due to an error and the caller doesn t await wait_closed on the corresponding StreamWriter don t log a warning about an exception that was never retrieved After all according to the StreamWriter close docs the wait_closed call is optional not mandatory gh 104555 Fix issue where an issubclass check comparing a class X against a runtime checkable protocol Y with non callable members would not cause TypeError to be raised if an isinstance call had previously been made comparing an instance of X to Y This issue was present in edge cases on Python 3 11 but became more prominent in 3 12 due to some unrelated changes that were made to runtime checkable protocols Patch by Alex Waygood gh 104372 Refactored the _posixsubprocess internals to avoid Python C API usage between fork and exec when marking pass_fds file descriptors inheritable gh 104484 Added case_sensitive argument to pathlib PurePath match gh 75367 Fix data descriptor detection in inspect getattr_static gh 104536 Fix a race condition in the internal multiprocessing process cleanup logic that could manifest as an unintended AttributeError when calling process close gh 103857 Update datetime deprecations stracktrace to point to the calling line gh 101520 Move the core functionality of the tracemalloc module in the Python folder leaving just the module wrapper in Modules gh 104392 Remove undocumented and unused _paramspec_tvars attribute from some classes in typing gh 102613 Fix issue where pathlib Path glob raised RecursionError when walking deep directory trees gh 103000 Improve performance of dataclasses asdict for the common case where dict_factory is dict Patch by David C Ellis gh 104301 Allow leading whitespace in disambiguated statements in pdb gh 104139 Teach urllib parse unsplit to retain the when assembling itms services action generate bugs style Apple Platform Deployment URLs gh 104307 socket getnameinfo now releases the GIL while contacting the DNS server gh 104310 Users may now use importlib util allowing_all_extensions a context manager to temporarily disable the strict compatibility checks for importing extension modules in subinterpreters gh 87695 Fix issue where pathlib Path glob raised OSError when it encountered a symlink to an overly long path gh 104265 Prevent possible crash by disallowing instantiation of the _csv Reader and _csv Writer types The regression was introduced in 3 10 0a4 with PR 23224 bpo 14935 Patch by Radislav Chugunov gh 102613 Improve performance of pathlib Path glob when expanding recursive wildcards by merging adjacent wildcards and de duplicating results only when necessary gh 65772 Remove unneeded comments and code in turtle py gh 90208 Fixed issue where pathlib Path glob returned incomplete results when it encountered a PermissionError This method now suppresses all OSError exceptions except those raised from calling is_dir on the top level path gh 104144 Optimize asyncio TaskGroup when using asyncio eager_task_factory Skip scheduling a done callback if a TaskGroup task completes eagerly gh 104144 Optimize asyncio gather when using asyncio eager_task_factory to complete eagerly if all fututres completed eagerly Avoid scheduling done callbacks for futures that complete eagerly gh 104114 Fix issue where pathlib Path glob returns paths using the case of non wildcard segments for corresponding path segments rather than the real filesystem case gh 104104 Improve performance of pathlib Path glob by using re IGNORECASE to implement case insensitive matching gh 104102 Improve per,en
1516,formance of pathlib Path glob when evaluating patterns that contain segments gh 103822 Update the return type of weekday to the newly added Day attribute gh 103629 Update the repr of typing Unpack according to PEP 692 gh 103963 Make dis display the names of the args for CALL_INTRINSIC_ gh 104035 Do not ignore user defined __getstate__ and __setstate__ methods for slotted frozen dataclasses gh 103987 In mmap fix several bugs that could lead to access to memory mapped files after they have been invalidated gh 103977 Improve import time of platform module gh 88773 Added turtle teleport to the turtle module to move a turtle to a new point without tracing a line visible or invisible Patch by Liam Gersten gh 103935 Use io open_code for files to be executed instead of raw open gh 68968 Fixed garbled output of assertEqual when an input lacks final newline gh 100370 Fix potential OverflowError in sqlite3 Connection blobopen for 32 bit builds Patch by Erlend E Aasland gh 102628 Substitute CTRL D with CTRL Z in sqlite3 CLI banner when running on Windows gh 103636 Module level attributes January and February are deprecated from calendar gh 103583 Isolate _multibytecodec and codecs extension modules Patches by Erlend E Aasland gh 103848 Add checks to ensure that bracketed hosts found by urllib parse urlsplit are of IPv6 or IPvFuture format gh 103872 Update the bundled copy of pip to version 23 1 2 gh 99944 Make dis display the value of oparg of KW_NAMES gh 74940 The C UTF 8 locale is no longer converted to en_US UTF 8 enabling the use of UTF 8 encoding on systems which have no locales installed gh 103861 Fix zipfile Zipfile creating invalid zip files when force_zip64 was used to add files to them Patch by Carey Metcalfe gh 103857 Deprecated datetime datetime utcnow and datetime datetime utcfromtimestamp Patch by Paul Ganssle gh 103839 Avoid compilation error due to tommath h not being found when building Tkinter against Tcl 8 7 built with bundled libtommath gh 103791 contextlib suppress now supports suppressing exceptions raised as part of an ExceptionGroup If other exceptions exist on the group they are re raised in a group that does not contain the suppressed exceptions gh 90750 Use datetime datetime fromisocalendar in the implementation of datetime datetime strptime which should now accept only valid ISO dates Patch by Paul Ganssle gh 103685 Prepare tkinter Menu index for Tk 8 7 so that it does not raise TclError expected integer but got when it should return None gh 81403 urllib request CacheFTPHandler no longer raises URLError if a cached FTP instance is reused ftplib s endtransfer method calls voidresp to drain the connection to handle FTP instance reuse properly gh 103699 Add __orig_bases__ to non generic TypedDicts call based TypedDicts and call based NamedTuples Other TypedDicts and NamedTuples already had the attribute gh 103693 Add convenience variable feature to pdb gh 92248 Deprecate type choices and metavar parameters of argparse BooleanOptionalAction gh 89415 Add socket constants for source specific multicast Patch by Reese Hyde gh 103673 socketserver gains ForkingUnixStreamServer and ForkingUnixDatagramServer classes Patch by Jay Berry gh 103636 Added Enum for months and days in the calendar module gh 84976 Create a new Lib _pydatetime py file that defines the Python version of the datetime module and make datetime import the contents of the new library only if the C implementation is missing Currently the full Python implementation is defined and then deleted if the C implementation is not available slowing down import datetime unnecessarily gh 103596 Attributes methods are no longer shadowed by same named enum members although they may be shadowed by enum property s gh 103584 Updated importlib metadata with changes from importlib_metadata 5 2 through 6 5 0 including Support installed files txt for Distribution files when present PackageMetadata now stipulates an additional get method allowing for easy querying of metadata keys that may not be present packages_distributions now honors packages and modules with Python,en
1517, modules that not py sources e g pyc so Expand protocol for PackageMetadata get_all to match the upstream implementation of email message Message get_all in python typeshed 9620 Deprecated use of Distribution without defining abstract methods Deprecated expectation that PackageMetadata __getitem__ will return None for missing keys In the future it will raise a KeyError gh 103578 Fixed a bug where pdb crashes when reading source file with different encoding by replacing io open with io open_code The new method would also call into the hook set by PyFile_SetOpenCodeHook gh 103556 Now creating inspect Signature objects with positional only parameter with a default followed by a positional or keyword parameter without one is impossible gh 103559 Update the bundled copy of pip to version 23 1 1 gh 103548 Improve performance of pathlib Path absolute and cwd by joining paths only when necessary Also improve performance of pathlib PurePath is_absolute on Posix by skipping path parsing and normalization gh 103538 Remove _tkinter module code guarded by definition of the TK_AQUA macro which was only needed for Tk 8 4 7 or earlier and was never actually defined by any build system or documented for manual use gh 103533 Update cProfile to use PEP 669 API gh 103525 Fix misleading exception message when mixed str and bytes arguments are supplied to pathlib PurePath and Path gh 103489 Add getconfig and setconfig to Connection to make configuration changes to a database connection Patch by Erlend E Aasland gh 103365 Set default Flag boundary to STRICT and fix bitwise operations gh 103472 Avoid a potential ResourceWarning in http client HTTPConnection by closing the proxy tunnel s CONNECT response explicitly gh 103462 Fixed an issue with using writelines in asyncio to send very large payloads that exceed the amount of data that can be written in one call to socket socket send or socket socket sendmsg resulting in the remaining buffer being left unwritten gh 103449 Fix a bug in doc string generation in dataclasses dataclass gh 103092 Isolate _collections apply PEP 687 Patch by Erlend E Aasland gh 103357 Added support for logging Formatter defaults parameter to logging config dictConfig and logging config fileConfig Patch by Bar Harel gh 103092 Adapt the winreg extension module to PEP 687 gh 74690 The performance of isinstance checks against runtime checkable protocols has been considerably improved for protocols that only have a few members To achieve this improvement several internal implementation details of the typing module have been refactored including typing _ProtocolMeta __instancecheck__ typing _is_callable_members_only and typing _get_protocol_attrs Patches by Alex Waygood gh 74690 The members of a runtime checkable protocol are now considered frozen at runtime as soon as the class has been created See What s new in Python 3 12 for more details gh 103256 Fixed a bug that caused hmac to raise an exception when the requested hash algorithm was not available in OpenSSL despite being available separately as part of hashlib itself It now falls back properly to the built in This could happen when for example your OpenSSL does not include SHA3 support and you want to compute hmac digest b K b M sha3_256 gh 102778 Support sys last_exc in idlelib gh 103285 Improve performance of ast get_source_segment gh 103225 Fix a bug in pdb when displaying line numbers of module level source code gh 103092 Adapt the msvcrt extension module to PEP 687 gh 103092 Adapt the winsound extension module to PEP 687 gh 93910 Remove deprecation of enum memmber member access gh 102978 Fixes unittest mock patch not enforcing function signatures for methods decorated with classmethod or staticmethod when patch is called with autospec True gh 103092 Isolate _socket apply PEP 687 Patch by Erlend E Aasland gh 100479 Add pathlib PurePath with_segments which creates a path object from arguments This method is called whenever a derivative path is created such as from pathlib PurePath parent Subclasses may override this method to share information between path objects gh ,en
1518,103220 Fix issue where os path join added a slash when joining onto an incomplete UNC drive with a trailing slash on Windows gh 103204 Fixes http server accepting HTTP requests with HTTP version numbers preceded by or or with digit separating _ characters The length of the version numbers is also constrained gh 75586 Fix various Windows specific issues with shutil which gh 103193 Improve performance of inspect getattr_static Patch by Alex Waygood gh 103176 sys _current_exceptions now returns a mapping from thread id to an exception instance rather than to a typ exc tb tuple gh 103143 Polish the help messages and docstrings of pdb gh 103015 Add entrypoint keyword only parameter to sqlite3 Connection load_extension for overriding the SQLite extension entry point Patch by Erlend E Aasland gh 103000 Improve performance of dataclasses astuple and dataclasses asdict in cases where the contents are common Python types gh 102953 The extraction methods in tarfile and shutil unpack_archive have a new a filter argument that allows limiting tar features than may be surprising or dangerous such as creating files outside the destination directory See Extraction filters for details gh 97696 Implemented an eager task factory in asyncio When used as a task factory on an event loop it performs eager execution of coroutines Coroutines that are able to complete synchronously e g return or raise without blocking are returned immediately as a finished task and the task is never scheduled to the event loop If the coroutine blocks the pending task is scheduled and returned gh 81079 Add case_sensitive keyword only argument to pathlib Path glob and rglob gh 101819 Isolate the io extension module by applying PEP 687 Patch by Kumar Aditya Victor Stinner and Erlend E Aasland gh 91896 Deprecate collections abc ByteString gh 101362 Speed up pathlib Path construction by omitting the path anchor from the internal list of path parts gh 102114 Functions in the dis module that accept a source code string as argument now print a more concise traceback when the string contains a syntax or indentation error gh 62432 The unittest runner will now exit with status code 5 if no tests were run It is common for test runner misconfiguration to fail to find any tests this should be an error gh 78079 Fix incorrect normalization of UNC device path roots and partial UNC share path roots in pathlib PurePath Pathlib no longer appends a trailing slash to such paths gh 85984 Add tty cfmakeraw and tty cfmakecbreak to tty and modernize the behavior of tty setraw and tty setcbreak to use POSIX 1 2017 Chapter 11 General Terminal Interface flag masks by default gh 101688 Implement types get_original_bases to provide further introspection for types gh 101640 argparse ArgumentParser now catches errors when writing messages such as when sys stderr is None Patch by Oleg Iarygin gh 83861 Fix datetime astimezone method return value when invoked on a naive datetime instance that represents local time falling in a timezone transition gap PEP 495 requires that instances with fold 1 produce earlier times than those with fold 0 in this case gh 89550 Decrease execution time of some gzip file writes by 15 by adding more appropriate buffering gh 95299 Remove the bundled setuptools wheel from ensurepip and stop installing setuptools in environments created by venv gh 99353 Respect the http client HTTPConnection debuglevel flag in urllib request AbstractHTTPHandler when its constructor parameter debuglevel is not set And do the same for HTTPS gh 98040 Remove the long deprecated imp module gh 97850 Deprecate pkgutil find_loader and pkgutil get_loader in favor of importlib util find_spec gh 94473 Flatten arguments in tkinter Canvas coords It now accepts not only x1 y1 x2 y2 and x1 y1 x2 y2 but also x1 y1 x2 y2 and x1 y1 x2 y2 gh 98040 Remove more deprecated importlib APIs find_loader find_module importlib abc Finder pkgutil ImpImporter pkgutil ImpLoader gh 96522 Fix potential deadlock in pty spawn gh 96534 Support divert 4 added in FreeBSD 14 gh 87474 Fix potential file descriptor leaks in subpro,en
1519,cess Popen gh 94906 Support multiple steps in math nextafter Patch by Shantanu Jain and Matthias Gorgens gh 51574 Make tempfile mkdtemp return absolute paths when its dir parameter is relative gh 94518 Convert private _posixsubprocess fork_exec to use Argument Clinic gh 92184 When creating zip files using zipfile os altsep if not None will always be treated as a path separator even when it is not Patch by Carey Metcalfe bpo 46797 Deprecation warnings are now emitted for ast Num ast Bytes ast Str ast NameConstant and ast Ellipsis These have been documented as deprecated since Python 3 8 and will be removed in Python 3 14 bpo 44844 Enables webbrowser to detect and launch Microsoft Edge browser bpo 45606 Fixed the bug in pathlib Path glob previously a dangling symlink would not be found by this method when the pattern is an exact match but would be found when the pattern contains a wildcard or the recursive wildcard With this change a dangling symlink will be found in both cases bpo 23041 Add QUOTE_STRINGS and QUOTE_NOTNULL to the suite of csv module quoting styles bpo 24964 Added http client HTTPConnection get_proxy_response_headers that provides access to the HTTP headers on a proxy server response to the CONNECT request bpo 17258 multiprocessing now supports stronger HMAC algorithms for inter process connection authentication rather than only HMAC MD5 bpo 39744 Make asyncio subprocess Process communicate close the subprocess s stdin even when called with input None bpo 22708 http client CONNECT method tunnel improvements Use HTTP 1 1 protocol send a matching Host header with CONNECT if one is not provided convert IDN domain names to Punycode Patch by Michael Handler Documentation gh 67056 Document that the effect of registering or unregistering an atexit cleanup function from within a registered cleanup function is undefined gh 103629 Mention the new way of typing kwargs with Unpack and TypedDict introduced in PEP 692 gh 48241 Clarifying documentation about the url parameter to urllib request urlopen and urllib request Request needing to be encoded properly gh 86094 Add support for Unicode Path Extra Field in ZipFile Patch by Yeojin Kim and Andrea Giudiceandrea gh 99202 Fix extension type from documentation for compiling in C 20 mode Tests gh 104494 Update test_pack_configure_in and test_place_configure_in for changes to error message formatting in Tk 8 7 gh 104461 Run test_configure_screen on X11 only since the DISPLAY environment variable and screen option for toplevels are not useful on Tk for Win32 or Aqua gh 86275 Added property based tests to the zoneinfo tests along with stubs for the hypothesis interface Patch by Paul Ganssle gh 103329 Regression tests for the behaviour of unittest mock PropertyMock were added gh 102795 fix use of poll in test_epoll s test_control_and_wait gh 75729 Fix the os spawn tests failing on Windows when the working directory or interpreter path contains spaces Build gh 101282 BOLT optimization is now applied to the libpython shared library if building a shared library BOLT instrumentation and application settings can now be influenced via the BOLT_INSTRUMENT_FLAGS and BOLT_APPLY_FLAGS configure variables gh 99017 PYTHON_FOR_REGEN now require Python 3 10 or newer gh 104490 Define PHONY virtual make targets consistently and properly gh 104106 Add gcc fallback of mkfifoat mknodat for macOS Patch by Donghee Na gh 103532 The TKINTER_PROTECT_LOADTK macro is no longer defined or used in the _tkinter module It was previously only defined when building against Tk 8 4 13 and older but Tk older than 8 5 12 has been unsupported since gh 91152 gh 99069 Extended workaround defining static_assert when missing from the libc headers to all clang and gcc builds In particular this fixes building on macOS 10 10 gh 100220 Changed the default value of the SHELL Makefile variable from bin sh to bin sh e to ensure that complex recipes correctly fail after an error Previously make install could fail to install some files and yet return a successful result gh 90656 Add platform triplets for 64 bit LoongArch loonga,en
1520,rch64 linux gnusf loongarch64 linux gnuf32 loongarch64 linux gnu Patch by Zhang Na Windows gh 104623 Update Windows installer to use SQLite 3 42 0 gh 82814 Fix a potential Errno 13 Permission denied when using shutil copystat within Windows Subsystem for Linux WSL on a mounted filesystem by adding errno EACCES to the list of ignored errors within the internal implementation gh 103088 Fix virtual environment activate script having incorrect line endings for Cygwin gh 103088 Fixes venvs not working in bash on Windows across different disks gh 102997 Update Windows installer to use SQLite 3 41 2 gh 88013 Fixed a bug where TypeError was raised when calling ntpath realpath with a bytes parameter in some cases macOS gh 99834 Update macOS installer to Tcl Tk 8 6 13 gh 104623 Update macOS installer to SQLite 3 42 0 gh 103545 Add os PRIO_DARWIN_THREAD os PRIO_DARWIN_PROCESS os PRIO_DARWIN_BG and os PRIO_DARWIN_NONUI These can be used with os setpriority to run the process at a lower priority and make use of the efficiency cores on Apple Silicon systems gh 104180 Support reading SOCKS proxy configuration from macOS System Configuration Patch by Sam Schott gh 60436 update curses textbox to additionally handle backspace using the curses ascii DEL key press gh 102997 Update macOS installer to SQLite 3 41 2 IDLE gh 104499 Fix completions for Tk Aqua 8 7 currently blank gh 104496 About prints both tcl and tk versions if different expected someday gh 88496 Fix IDLE test hang on macOS Tools Demos gh 104389 Argument Clinic C converters now accept the unused keyword for wrapping a parameter with Py_UNUSED Patch by Erlend E Aasland C API gh 101291 Added unstable C API for extracting the value of compact integers PyUnstable_Long_IsCompact and PyUnstable_Long_CompactValue gh 104109 We ve added Py_NewInterpreterFromConfig and PyInterpreterConfig to the public C API but not the stable ABI not yet at least The new function may be used to create a new interpreter with various features configured The function was added to support PEP 684 per interpreter GIL gh 103968 PyType_FromSpec and its variants now allow creating classes whose metaclass overrides tp_new The tp_new is ignored This behavior is deprecated and will be disallowed in 3 14 The new PyType_FromMetaclass already disallows it gh 103743 Add PyUnstable_Object_GC_NewWithExtraData function that can be used to allocate additional memory after an object for data not managed by Python gh 103295 Introduced PyUnstable_WritePerfMapEntry PyUnstable_PerfMapState_Init and PyUnstable_PerfMapState_Fini These allow extension modules JIT compilers in particular to write to perf map files in a thread safe manner The Python support for the Linux perf profiler also uses these APIs to write entries in the perf map file gh 103509 Added C API for extending types whose instance memory layout is opaque PyType_Spec basicsize can now be zero or negative PyObject_GetTypeData can be used to get subclass specific data and Py_TPFLAGS_ITEMS_AT_END can be used to safely extend variable size objects See PEP 697 for details gh 103091 Add a new C API function to eagerly assign a version tag to a PyTypeObject PyUnstable_Type_AssignVersionTag gh 101408 PyObject_GC_Resize should calculate preheader size if needed Patch by Donghee Na gh 98836 Add support of more formatting options left aligning octals uppercase hexadecimals intmax_t ptrdiff_t wchar_t C strings variable width and precision in PyUnicode_FromFormat and PyUnicode_FromFormatV gh 96803 Add unstable C API functions to get the code object lasti and line number from the internal _PyInterpreterFrame in the limited API The functions are PyCodeObject PyUnstable_InterpreterFrame_GetCode struct _PyInterpreterFrame frame int PyUnstable_InterpreterFrame_GetLasti struct _PyInterpreterFrame frame int PyUnstable_InterpreterFrame_GetLine struct _PyInterpreterFrame frame Python 3 12 0 alpha 7 Release date 2023 04 04 Core and Builtins gh 102192 Deprecated _PyErr_ChainExceptions in favour of _PyErr_ChainExceptions1 gh 89987 Reduce the number of inline CACHE entries for BINARY_SUBSC,en
1521,R gh 102859 Removed JUMP_IF_FALSE_OR_POP and JUMP_IF_TRUE_OR_POP instructions gh 101975 Fixed stacktop value on tracing entries to avoid corruption on garbage collection gh 102778 Add sys last_exc and deprecate sys last_type sys last_value and sys last_traceback which hold the same information in its legacy form gh 100982 Replace all occurrences of COMPARE_AND_BRANCH with COMPARE_OP gh 102701 Fix overflow when creating very large dict gh 102755 Add PyErr_DisplayException which takes just an exception instance to replace the legacy PyErr_Display which takes the typ exc tb triplet gh 102594 Add note to exception raised in PyErr_SetObject when normalization fails gh 90997 Shrink the number of inline CACHE entries used by LOAD_GLOBAL gh 102491 Improve import time of platform by removing IronPython version parsing The IronPython version parsing was not functional see https github com IronLanguages ironpython3 issues 1667 gh 101291 Rearrage bits in first field after header of PyLongObject Bits 0 and 1 1 sign I e 0 for positive numbers 1 for zero and 2 for negative numbers Bit 2 reserved probably for the immortal bit Bits 3 the unsigned size This makes a few operations slightly more efficient and will enable a more compact and faster 2s complement representation of most ints in future gh 102397 Fix segfault from race condition in signal handling during garbage collection Patch by Kumar Aditya gh 102406 codecs encoding decoding errors now get the context information which operation and which codecs attached as PEP 678 notes instead of through chaining a new instance of the exception gh 102281 Fix potential nullptr dereference and use of uninitialized memory in fileutils Patch by Max Bachmann gh 102300 Reuse operands with refcount of 1 in float specializations of BINARY_OP gh 102213 Fix performance loss when accessing an object s attributes with __getattr__ defined gh 102255 Improve build support for the Xbox Patch by Max Bachmann gh 102027 Fix SSE2 and SSE3 detection in _blake2 internal module Patch by Max Bachmann gh 101865 Deprecate co_lnotab in code objects schedule it for removal in Python 3 14 bpo 1635741 Adapt _pickle to PEP 687 Patch by Mohamed Koubaa and Erlend Aasland Library gh 103085 Pure python locale getencoding will not warn deprecation gh 103068 It s no longer possible to register conditional breakpoints in Pdb that raise SyntaxError Patch by Tian Gao gh 102549 Don t ignore exceptions in member type creation gh 103056 Ensure final _generate_next_value_ is a staticmethod gh 103046 Display current line label correctly in dis when show_caches is False and lasti points to a CACHE entry gh 102433 isinstance checks against runtime checkable protocols now use inspect getattr_static rather than hasattr to lookup whether attributes exist This means that descriptors and __getattr__ methods are no longer unexpectedly evaluated during isinstance checks against runtime checkable protocols However it may also mean that some objects which used to be considered instances of a runtime checkable protocol may no longer be considered instances of that protocol on Python 3 12 and vice versa Most users are unlikely to be affected by this change Patch by Alex Waygood gh 103023 It s no longer possible to register expressions to display in Pdb that raise SyntaxError Patch by Tian Gao gh 102947 Improve traceback when dataclasses fields is called on a non dataclass Patch by Alex Waygood gh 102780 The asyncio Timeout context manager now works reliably even when performing cleanup due to task cancellation Previously it could raise a CancelledError instead of an TimeoutError in such cases gh 102871 Remove support for obsolete browsers from webbrowser Removed browsers include Grail Mosaic Netscape Galeon Skipstone Iceape Firebird and Firefox versions 35 and below gh 102839 Improve performance of math log arguments handling by removing the argument clinic gh 102828 Add the onexc arg to shutil rmtree which is like onerror but expects an exception instance rather than an exc_info tuple Deprecate onerror gh 88965 typing Fix a bug relating to substi,en
1522,tution in custom classes generic over a ParamSpec Previously if the ParamSpec was substituted with a parameters list that itself contained a TypeVar the TypeVar in the parameters list could not be subsequently substituted This is now fixed Patch by Nikita Sobolev gh 76846 Fix issue where __new__ and __init__ methods of pathlib PurePath and Path subclasses were not called in some circumstances gh 78530 asyncio wait now accepts generators yielding tasks Patch by Kumar Aditya gh 102748 asyncio iscoroutine now returns False for generators as asyncio does not support legacy generator based coroutines Patch by Kumar Aditya gh 102670 Optimized fmean correlation covariance and linear_regression using the new math sumprod function gh 102615 Typing Improve the repr of generic aliases for classes generic over a ParamSpec Use square brackets to represent a parameter list gh 100112 asyncio Task get_coro now always returns a coroutine when wrapping an awaitable object Patch by Kumar Aditya gh 102578 Speed up setting or deleting mutable attributes on non dataclass subclasses of frozen dataclasses Due to the implementation of __setattr__ and __delattr__ for frozen dataclasses this previously had a time complexity of O n It now has a time complexity of O 1 gh 102519 Add os listdrives os listvolumes and os listmounts functions on Windows for enumerating drives volumes and mount points gh 74468 Attribute name of the extracted tarfile file object now holds filename of itself rather than of the archive it is contained in Patch by Oleg Iarygin gh 102378 Private helper method inspect _signature_strip_non_python_syntax will no longer strip from the input string gh 79940 Add inspect getasyncgenstate and inspect getasyncgenlocals Patch by Thomas Krennwallner gh 102103 Add module argument to dataclasses make_dataclass and make classes produced by it pickleable gh 102069 Fix __weakref__ descriptor generation for custom dataclasses gh 102038 Skip a stat in site if we have already found a pyvenv cfg gh 98886 Fix issues when defining dataclasses that have fields with specific underscore names that aren t clearly reserved by dataclasses gh 101673 Fix a pdb bug where ll clears the changes to local variables gh 101313 Added h and help arguments to the webbrowser CLI gh 100372 ssl SSLContext load_verify_locations no longer incorrectly accepts some cases of trailing data when parsing DER gh 89727 Fix pathlib Path walk RecursionError on deep directory trees by rewriting it using iteration instead of recursion gh 100131 Added an optional delete keyword argument to tempfile TemporaryDirectory gh 48330 Added durations command line option showing the N slowest test cases unittest TextTestRunner and unittest TextTestResult constructors accept a new durations keyword argument Subclasses should take this into account or accept kwargs Added unittest TestResult addDuration method and unittest TestResult collectedDurations attribute Contributed by Giampaolo Rodola gh 98169 Fix dataclasses astuple crash when collections defaultdict is present in the attributes gh 96931 Fix incorrect results from ssl SSLSocket shared_ciphers gh 95495 When built against OpenSSL 3 0 the ssl module had a bug where it reported unauthenticated EOFs i e without close_notify as a clean TLS level EOF It now raises SSLEOFError matching the behavior in previous versions of OpenSSL The options attribute on SSLContext also no longer includes OP_IGNORE_UNEXPECTED_EOF by default This option may be set to specify the previous OpenSSL 3 0 behavior gh 94684 Now uuid uuid3 and uuid uuid5 functions support bytes objects as their name argument gh 94440 Fix a concurrent futures process bug where ProcessPoolExecutor shutdown could hang after a future has been quickly submitted and canceled gh 72346 Added deprecation warning to isdst parameter of email utils localtime bpo 36305 Fix handling of Windows filenames that resemble drives such as a b in pathlib Documentation gh 103112 Add docstring to http client HTTPResponse read to fix pydoc output Tests gh 102980 Improve test coverage on pdb gh 102537 Adjust the,en
1523, error handling strategy in test_zoneinfo TzPathTest python_tzpath_context Patch by Paul Ganssle gh 101377 Improved test_locale_calendar_formatweekday of calendar Build gh 102973 Add a dev container along with accompanying Dockerfile for development purposes gh 102711 Fix Wstrict prototypes compiler warnings Windows gh 102690 Update webbrowser to fall back to Microsoft Edge instead of Internet Explorer gh 99726 Improves correctness of stat results for Windows and uses faster API when available Tools Demos gh 102809 Misc gdbinit was removed C API gh 102013 Add a new unstable C API function for iterating over GC able objects using a callback PyUnstable_VisitObjects Python 3 12 0 alpha 6 Release date 2023 03 07 Security gh 99108 Replace builtin hashlib implementations of MD5 and SHA1 with verified ones from the HACL project gh 101727 Updated the OpenSSL version used in Windows and macOS binary release builds to 1 1 1t to address CVE 2023 0286 CVE 2022 4303 and CVE 2022 4303 per the OpenSSL 2023 02 07 security advisory gh 99108 Replace the builtin hashlib implementations of SHA2 384 and SHA2 512 originally from LibTomCrypt with formally verified side channel resistant code from the HACL project The builtins remain a fallback only used when OpenSSL does not provide them gh 101283 subprocess Popen now uses a safer approach to find cmd exe when launching with shell True Patch by Eryk Sun based on a patch by Oleg Iarygin Core and Builtins gh 102493 Fix regression in semantics of normalisation in PyErr_SetObject gh 102416 Do not memoize incorrectly automatically generated loop rules in the parser Patch by Pablo Galindo gh 102356 Fix a bug that caused a crash when deallocating deeply nested filter objects Patch by Marta Gómez Macías gh 102336 Cleanup Windows 7 specific special handling Patch by Max Bachmann gh 102250 Fixed a segfault occurring when the interpreter calls a __bool__ method that raises gh 102126 Fix deadlock at shutdown when clearing thread states if any finalizer tries to acquire the runtime head lock Patch by Kumar Aditya gh 102027 Use GetCurrentProcessId on Windows when getpid is unavailable Patch by Max Bachmann gh 102056 Fix error handling bugs in interpreter s exception printing code which could cause a crash on infinite recursion gh 100982 Restrict the scope of the FOR_ITER_RANGE instruction to the scope of the original FOR_ITER instruction to allow instrumentation gh 101967 Fix possible segfault in positional_only_passed_as_keyword function when new list created gh 101952 Fix possible segfault in BUILD_SET opcode when new set created gh 74895 socket getaddrinfo no longer raises OverflowError for int port values outside of the C long range Out of range values are left up to the underlying string based C library API to report A socket gaierror SAI_SERVICE may occur instead or no error at all as not all platform C libraries generate an error gh 101799 Add CALL_INTRINSIC_2 and use it instead of PREP_RERAISE_STAR gh 101857 Fix xattr support detection on Linux systems by widening the check to linux not just glibc This fixes support for musl gh 84783 Make the slice object hashable Patch by Will Bradshaw and Furkan Onder gh 87849 Change the SEND instruction to leave the receiver on the stack This allows the specialized form of SEND to skip the chain of C calls and jump directly to the RESUME in the generator or coroutine gh 101765 Fix SystemError segmentation fault in iter __reduce__ when internal access of builtins __dict__ keys mutates the iter object gh 101430 Update tracemalloc to handle presize of object properly Patch by Donghee Na gh 101696 Invalidate type version tag in _PyStaticType_Dealloc for static types avoiding bug where a false cache hit could crash the interpreter Patch by Kumar Aditya gh 101632 Adds a new RETURN_CONST instruction gh 100719 Remove gi_code field from generator and coroutine and async generator objects as it is redundant The frame already includes a reference to the code object gh 98627 When an interpreter is configured to check and only then importing an extension module will now fail ,en
1524,when the extension does not support multiple interpreters i e doesn t implement PEP 489 multi phase init This does not apply to the main interpreter nor to subinterpreters created with Py_NewInterpreter Library gh 102302 Micro optimise hashing of inspect Parameter reducing the time it takes to hash an instance by around 40 gh 101979 Fix a bug where parentheses in the metavar argument to argparse ArgumentParser add_argument were dropped Patch by Yeojin Kim gh 91038 platform platform now has boolean default arguments gh 81652 Add mmap MAP_ALIGNED_SUPER FreeBSD and mmap MAP_CONCEAL OpenBSD constants to mmap Patch by Yeojin Kim gh 102179 Fix os dup2 error message for negative fds gh 101961 For the binary mode fileinput hookcompressed doesn t set the encoding value even if the value is None Patch by Gihwan Kim gh 101936 The default value of fp becomes io BytesIO if HTTPError is initialized without a designated fp parameter Patch by Long Vo gh 101566 In zipfile sync Path with zipp 3 14 including fix for extractall on the underlying zipfile after being wrapped in Path gh 97930 Apply changes from importlib_resources 5 12 including fix for MultiplexedPath to support directories in multiple namespaces python importlib_resources 265 gh 101997 Upgrade pip wheel bundled with ensurepip pip 23 0 1 gh 99108 The built in extension modules for hashlib SHA2 algorithms used when OpenSSL does not provide them now live in a single internal _sha2 module instead of separate _sha256 and _sha512 modules gh 101892 Callable iterators no longer raise SystemError when the callable object exhausts the iterator but forgets to either return a sentinel value or raise StopIteration gh 87634 Remove locking behavior from functools cached_property gh 97786 Fix potential undefined behaviour in corner cases of floating point to time conversions gh 101517 Fixed bug where bdb looks up the source line with linecache with a lineno None which causes it to fail with an unhandled exception gh 101773 Optimize fractions Fraction for small components The private argument _normalize of the fractions Fraction constructor has been removed gh 101693 In sqlite3 Cursor execute DeprecationWarning is now emitted when named placeholders are used together with parameters supplied as a sequence instead of as a dict Starting from Python 3 14 using named placeholders with parameters supplied as a sequence will raise a ProgrammingError Patch by Erlend E Aasland gh 101446 Change repr of collections OrderedDict to use regular dictionary formating instead of pairs of keys and values gh 101362 Speed up pathlib PurePath construction by handling arguments more uniformly When a pathlib Path argument is supplied we use its string representation rather than joining its parts with os path join gh 101362 Speed up pathlib PurePath construction by calling os path join only when two or more arguments are given gh 101362 Speed up pathlib Path construction by running the path flavour compatibility check only when pathlib is imported gh 85984 Refactored the implementation of pty fork to use os login_tty A DeprecationWarning is now raised by pty master_open and pty slave_open They were undocumented and deprecated long long ago in the docstring in favor of pty openpty gh 101561 Add a new decorator typing override See PEP 698 for details Patch by Steven Troxler gh 63301 Set exit code when tabnanny CLI exits on error gh 101360 Fix anchor matching in pathlib PureWindowsPath match Path and pattern anchors are now matched with fnmatch just like other path parts This allows patterns such as Users to be matched gh 101277 Remove global state from itertools module PEP 687 Patches by Erlend E Aasland gh 100809 Fix handling of drive relative paths like C and C foo in pathlib Path absolute This method now uses the OS API to retrieve the correct current working directory for the drive gh 99138 Apply PEP 687 to zoneinfo Patch by Erlend E Aasland gh 96764 asyncio wait_for now uses asyncio timeout as its underlying implementation Patch by Kumar Aditya gh 88233 Correctly preserve extra fields in zipfile regardless of t,en
1525,heir ordering relative to a zip64 extra bpo 23224 Fix segfaults when creating lzma LZMADecompressor and bz2 BZ2Decompressor objects without calling __init__ and fix leakage of locks and internal buffers when calling the __init__ methods of lzma LZMADecompressor lzma LZMACompressor bz2 BZ2Compressor and bz2 BZ2Decompressor objects multiple times Documentation gh 85417 Update cmath documentation to clarify behaviour on branch cuts gh 97725 Fix asyncio Task print_stack description for file None Patch by Oleg Iarygin Tests gh 102019 Fix deadlock on shutdown if test_current_ exception frames fails Patch by Jacob Bower gh 85984 Utilize new winsize functions from termios in pty tests gh 89792 test_tools now copies up to 10x less source data to a temporary directory during the freeze test by ignoring git metadata and other artifacts It also limits its python build parallelism based on os cpu_count instead of hard coding it as 8 cores Build gh 99942 On Android in a static build python config in embed mode no longer incorrectly reports a library to link to gh 99942 On Android python pc now correctly reports the library to link to the same as python config sh gh 100221 Fix creating install directories in make sharedinstall if they exist outside DESTDIR already gh 96821 Explicitly mark C extension modules that need defined signed integer overflow and add a configure option with strict overflow Patch by Matthias Görgens and Shantanu Jain Windows gh 102344 Implement winreg QueryValue using QueryValueEx and winreg SetValue using SetValueEx Patch by Max Bachmann gh 101881 Handle read and write operations on non blocking pipes properly on Windows gh 101881 Add support for the os get_blocking and os set_blocking functions on Windows gh 101849 Ensures installer will correctly upgrade existing py exe launcher installs gh 101763 Updates copy of libffi bundled with Windows installs to 3 4 4 gh 101759 Update Windows installer to SQLite 3 40 1 gh 101614 Correctly handle extensions built against debug binaries that reference python3_d dll gh 101196 The functions os path isdir os path isfile os path islink and os path exists are now 13 to 28 faster on Windows by making fewer Win32 API calls macOS gh 101759 Update macOS installer to SQLite 3 40 1 C API gh 101907 Removes use of non standard C extension in public header files gh 99293 Document that the Py_TPFLAGS_VALID_VERSION_TAG is an internal feature should not be used and will be removed gh 101578 Add PyErr_GetRaisedException and PyErr_SetRaisedException for saving and restoring the current exception These functions return and accept a single exception object rather than the triple arguments of the now deprecated PyErr_Fetch and PyErr_Restore This is less error prone and a bit more efficient Add PyException_GetArgs and PyException_SetArgs as convenience functions for retrieving and modifying the args passed to the exception s constructor gh 91744 Introduced the Unstable C API tier marking APi that is allowed to change in minor releases without a deprecation period See PEP 689 for details Python 3 12 0 alpha 5 Release date 2023 02 07 Security gh 99108 Replace the builtin hashlib implementations of SHA2 224 and SHA2 256 originally from LibTomCrypt with formally verified side channel resistant code from the HACL project The builtins remain a fallback only used when OpenSSL does not provide them Core and Builtins gh 92173 Fix the defs and kwdefs arguments to PyEval_EvalCodeEx and a reference leak in that function gh 59956 The GILState API is now partially compatible with subinterpreters Previously PyThreadState_GET and PyGILState_GetThisThreadState would get out of sync causing inconsistent behavior and crashes gh 101400 Fix wrong lineno in exception message on continue or break which are not in a loop Patch by Donghee Na gh 101372 Fix is_normalized to properly handle the UCD 3 2 0 cases Patch by Donghee Na gh 101266 Fix sys getsizeof reporting for int subclasses gh 101291 Refactor the PyLongObject struct into a normal Python object header and a PyLongValue struct gh 101046 Fix a possible memory lea,en
1526,k in the parser when raising MemoryError Patch by Pablo Galindo gh 101037 Fix potential memory underallocation issue for instances of int subclasses with value zero gh 100762 Record the virtual exception block depth in the oparg of YIELD_VALUE Use this to avoid the expensive throw when closing generators and coroutines that can be closed trivially gh 100982 Adds a new COMPARE_AND_BRANCH instruction This is a bit more efficient when performing a comparison immediately followed by a branch and restores the design intent of PEP 659 that specializations are local to a single instruction gh 100942 Fixed segfault in property getter setter deleter that occurred when a property subclass overrode the __new__ method to return a non property instance gh 100923 Remove the mask cache entry for the COMPARE_OP instruction and embed the mask into the oparg gh 100892 Fix race while iterating over thread states in clearing threading local Patch by Kumar Aditya gh 91351 Fix a case where re entrant imports could corrupt the import deadlock detection code and cause a KeyError to be raised out of importlib _bootstrap In addition to the straightforward cases this could also happen when garbage collection leads to a warning being emitted as happens when it collects an open socket or file gh 100726 Optimize construction of range object for medium size integers gh 100712 Added option to build cpython with specialization disabled by setting ENABLE_SPECIALIZATION False in opcode followed by make regen all bpo 32780 Inter field padding is now inserted into the PEP3118 format strings obtained from ctypes Structure objects reflecting their true representation in memory Library gh 101541 Enum fix psuedo flag creation gh 101570 Upgrade pip wheel bundled with ensurepip pip 23 0 gh 101323 Fix a bug where errors where not thrown by zlib _ZlibDecompressor if encountered during decompressing gh 101317 Add ssl_shutdown_timeout parameter for asyncio StreamWriter start_tls gh 101326 Fix regression when passing None as second or third argument to FutureIter throw gh 92123 Adapt the _elementtree extension module to multi phase init PEP 489 Patches by Erlend E Aasland gh 100795 Avoid potential unexpected freeaddrinfo call double free in socket when when a libc getaddrinfo implementation leaves garbage in an output pointer when returning an error Original patch by Sergey G Brester gh 101143 Remove unused references to TimerHandle in asyncio base_events BaseEventLoop _add_callback gh 101144 Make zipfile Path open and zipfile Path read_text also accept encoding as a positional argument This was the behavior in Python 3 9 and earlier 3 10 introduced a regression where supplying it as a positional argument would lead to a TypeError gh 94518 Group related variables of _posixsubprocess module are renamed to stress that supplimentary group affinity is added to a fork not replace the inherited ones Patch by Oleg Iarygin gh 101015 Fix typing get_type_hints on tuple and tuple It must not drop the Unpack part gh 101000 Add os path splitroot which splits a path into a 3 item tuple drive root tail This new function is used by pathlib to improve the performance of path construction by up to a third gh 100573 Fix a Windows asyncio bug with named pipes where a client doing os stat on the pipe would cause an error in the server that disabled serving future requests gh 39615 warnings warn now has the ability to skip stack frames based on code filename prefix rather than only a numeric stacklevel via the new skip_file_prefixes keyword argument gh 100750 pass encoding kwarg to subprocess in platform gh 100160 Emit a deprecation warning in asyncio DefaultEventLoopPolicy get_event_loop if there is no current event loop set and it decides to create one gh 96290 Fix handling of partial and invalid UNC drives in ntpath splitdrive and in ntpath normpath on non Windows systems Paths such as server and are now considered by splitdrive to contain only a drive and consequently are not modified by normpath on non Windows systems The behaviour of normpath on Windows systems is unaffected as nativ,en
1527,e OS APIs are used Patch by Eryk Sun with contributions by Barney Gale gh 99952 Fix a reference undercounting issue in ctypes Structure with from_param results larger than a C pointer gh 67790 Add float style formatting support for fractions Fraction instances gh 99266 Preserve more detailed error messages in ctypes gh 86682 Ensure runtime created collections have the correct module name using the newly added internal sys _getframemodulename gh 88597 uuid now has a command line interface Try python m uuid h gh 60580 ctypes wintypes BYTE definition changed from c_byte to c_ubyte to match Windows SDK Patch by Anatoly Techtonik and Oleg Iarygin gh 94518 _posixsubprocess now initializes all UID and GID variables using a reserved 1 value instead of a separate flag Patch by Oleg Iarygin bpo 38941 The xml etree ElementTree module now emits DeprecationWarning when testing the truth value of an xml etree ElementTree Element Before the Python implementation emitted FutureWarning and the C implementation emitted nothing bpo 40077 Convert elementtree types to heap types Patch by Erlend E Aasland bpo 29847 Fix a bug where pathlib Path accepted and ignored keyword arguments Patch provided by Yurii Karabas gh 77772 ctypes CDLL ctypes OleDLL ctypes WinDLL and ctypes PyDLL now accept path like objects as their name argument Patch by Robert Hoelzl Documentation gh 88324 Reword subprocess to emphasize default behavior of stdin stdout and stderr arguments Remove inaccurate statement about child file handle inheritance Tests gh 101334 test_tarfile has been updated to pass when run as a high UID Build gh 101282 Update BOLT configration not to use depreacted usage of split functions Patch by Donghee Na gh 101522 Allow overriding Windows dependencies versions and paths using MSBuild properties gh 77532 Minor fixes to allow building with PlatformToolset ClangCL on Windows gh 101152 In accordance with PEP 699 the ma_version_tag field in PyDictObject is deprecated for extension modules Accessing this field will generate a compiler warning at compile time This field will be removed in Python 3 14 gh 100340 Allows Wno int conversion for wasm sdk 17 and onwards thus enables building WASI builds once against the latest sdk gh 101060 Conditionally add fno reorder blocks and partition in configure Effectively fixes enable bolt when using Clang as this appears to be a GCC only flag gh 98705 __bool__ is defined in AIX system header files which breaks the build in AIX so undefine it gh 98636 Fix a regression in detecting gdbm_compat library for the _gdbm module build gh 96305 _aix_support now uses a simple code to get platform details rather than the now non existent _bootsubprocess during bootstrap Windows gh 101543 Ensure the install path in the registry is only used when the standard library hasn t been located in any other way gh 101467 The py exe launcher now correctly filters when only a single runtime is installed It also correctly handles prefix matches on tags so that 3 1 does not match 3 11 but would still match 3 1 32 gh 99834 Updates bundled copy of Tcl Tk to 8 6 13 0 gh 101135 Restore ability to launch older 32 bit versions from the py exe launcher when both 32 bit and 64 bit installs of the same version are available gh 82052 Fixed an issue where writing more than 32K of Unicode output to the console screen in one go can result in mojibake gh 100320 Ensures the PythonPath registry key from an install is used when launching from a different copy of Python that relies on an existing install to provide a copy of its modules and standard library gh 100247 Restores support for the py exe launcher finding shebang commands in its configuration file using the full command name Python 3 12 0 alpha 4 Release date 2023 01 10 Core and Builtins gh 100776 Fix misleading default value in input s __text_signature__ gh 99005 Remove UNARY_POSITIVE ASYNC_GEN_WRAP and LIST_TO_TUPLE replacing them with intrinsics gh 99005 Add new CALL_INTRINSIC_1 instruction Remove IMPORT_STAR PRINT_EXPR and STOPITERATION_ERROR replacing them with the CALL_INTRINSIC_1 instruction,en
1528, gh 100288 Remove the LOAD_ATTR_METHOD_WITH_DICT specialized instruction Stats show it is not useful gh 100720 Added _PyFrame_NumSlotsForCodeObject which returns the number of slots needed in a frame for a given code object gh 100719 Removed the co_nplaincellvars field from the code object as it is redundant gh 100637 Fix int __sizeof__ calculation to include the 1 element ob_digit array for 0 and False gh 100649 Update the native_thread_id field of PyThreadState after fork gh 100126 Fix an issue where incomplete frames could be briefly visible to C code while other frames are being torn down possibly resulting in corruption or hard crashes of the interpreter while running finalizers gh 87447 Fix SyntaxError on comprehension rebind checking with names that are not actually redefined Now reassigning b in b 1 for a b prop in some_iter is allowed Reassigning a is still disallowed as per PEP 572 gh 100268 Add int is_integer to improve duck type compatibility between int and float gh 100425 Improve the accuracy of sum with compensated summation gh 100374 Fix incorrect result and delay in socket getfqdn Patch by Dominic Socular gh 100357 Convert vars dir next getattr and iter to argument clinic gh 100117 Improve the output of codeobject co_lines by emitting only one entry for each line range gh 90043 Handle NaNs when specializing COMPARE_OP for float values gh 100222 Redefine the _Py_CODEUNIT typedef as a union to describe its layout to the C compiler avoiding type punning and improving clarity gh 99955 Internal compiler functions in compile c now consistently return 1 on error and 0 on success gh 100188 The BINARY_SUBSCR_LIST_INT and BINARY_SUBSCR_TUPLE_INT instructions are no longer used for negative integers because those instructions always miss when encountering negative integers gh 99110 Initialize frame previous in frameobject c to fix a segmentation fault when accessing frames created by PyFrame_New gh 94155 Improved the hashing algorithm for code objects mitigating some hash collisions gh 99540 None now hashes to a constant value This is not a requirements change gh 100143 When built with enable pystats stats collection is now off by default To enable it early at startup pass the Xpystats flag Stats are now always dumped even if switched off gh 100146 Improve BUILD_LIST opcode so that it works similarly to the BUILD_TUPLE opcode by stealing references from the stack rather than repeatedly using stack operations to set list elements Implementation details are in a new private API _PyList_FromArraySteal gh 100110 Specialize FOR_ITER for tuples gh 100050 Honor existing errors obtained when searching for mismatching parentheses in the tokenizer Patch by Pablo Galindo gh 92216 Improve the performance of hasattr for type objects with a missing attribute gh 99582 Freeze zipimport module into _bootstrap_python gh 99554 Pack debugging location tables more efficiently during bytecode compilation gh 98522 Add an internal version number to code objects to give better versioning of inner functions and comprehensions and thus better specialization of those functions This change is invisible to both Python and C extensions gh 94603 Improve performance of list pop for small lists gh 89051 Add ssl OP_LEGACY_SERVER_CONNECT bpo 32782 ctypes arrays of length 0 now report a correct itemsize when a memoryview is constructed from them rather than always giving a value of 0 Library gh 100833 Speed up math fsum by removing defensive volatile qualifiers gh 100805 Modify random choice implementation to once again work with NumPy arrays gh 100813 Add socket IP_PKTINFO constant gh 100792 Make email message Message __contains__ twice as fast gh 91851 Microoptimizations for fractions Fraction __round__ fractions Fraction __ceil__ and fractions Fraction __floor__ gh 90104 Avoid RecursionError on repr if a dataclass field definition has a cyclic reference gh 100689 Fix crash in pyexpat by statically allocating PyExpat_CAPI capsule gh 100740 Fix unittest mock Mock not respecting the spec for attribute names prefixed with assert gh 91219 Change SimpleH,en
1529,TTPRequestHandler to support subclassing to provide a different set of index file names instead of using __init__ parameters gh 100690 Mock objects which are not unsafe will now raise an AttributeError when accessing an attribute that matches the name of an assertion but without the prefix assert_ e g accessing called_once instead of assert_called_once This is in addition to this already happening for accessing attributes with prefixes assert assret asert aseert and assrt gh 89727 Simplify and optimize os walk by using isinstance checks to check the top of the stack gh 100485 Add math sumprod to compute the sum of products gh 86508 Fix asyncio open_connection to skip binding to local addresses of different family Patch by Kumar Aditya gh 97930 importlib resources files now accepts a module as an anchor instead of only accepting packages If a module is passed resources are resolved adjacent to that module in the same package or at the package root The parameter was renamed from package to anchor with a compatibility shim for those passing by keyword Additionally the new anchor parameter is now optional and will default to the caller s module gh 100585 Fixed a bug where importlib resources as_file was leaving file pointers open gh 100562 Improve performance of pathlib Path absolute by nearly 2x This comes at the cost of a performance regression in pathlib Path cwd which is generally used less frequently in user code gh 100519 Small simplification of http cookiejar eff_request_host that improves readability and better matches the RFC wording gh 100287 Fix the interaction of unittest mock seal with unittest mock AsyncMock gh 100488 Add Fraction is_integer to check whether a fractions Fraction is an integer This improves duck type compatibility with float and int gh 100474 http server now checks that an index page is actually a regular file before trying to serve it This avoids issues with directories named index html gh 100363 Speed up asyncio get_running_loop by removing redundant getpid checks Patch by Kumar Aditya gh 78878 Fix crash when creating an instance of _ctypes CField gh 100348 Fix ref cycle in asyncio _SelectorSocketTransport by removing _read_ready_cb in close gh 100344 Provide C implementation for asyncio current_task for a 4x 6x speedup gh 100272 Fix JSON serialization of OrderedDict It now preserves the order of keys gh 83076 Instantiation of Mock and AsyncMock is now 3 8x faster gh 100234 Set a default value of 1 0 for the lambd parameter in random expovariate gh 100228 A DeprecationWarning may be raised when os fork or os forkpty is called from multi threaded processes Forking with threads is unsafe and can cause deadlocks crashes and subtle problems Lack of a warning does not indicate that the fork call was actually safe as Python may not be aware of all threads gh 100039 Improve signatures for enums and flags gh 100133 Fix regression in asyncio where a subprocess would sometimes lose data received from pipe bpo 44592 Fixes inconsistent handling of case sensitivity of extrasaction arg in csv DictWriter gh 100098 Fix tuple subclasses being cast to tuple when used as enum values gh 85432 Rename the fmt parameter of the pure Python implementation of datetime time strftime to format Rename the t parameter of datetime datetime fromtimestamp to timestamp These changes mean the parameter names in the pure Python implementation now match the parameter names in the C implementation Patch by Alex Waygood gh 98778 Update HTTPError to be initialized properly even if the fp is None Patch by Donghee Na gh 99925 Unify error messages in JSON serialization between json dumps float nan allow_nan False and json dumps float nan allow_nan False indent SOMETHING Now both include the representation of the value that could not be serialized gh 89727 Fix issue with os walk where a RecursionError would occur on deep directory structures by adjusting the implementation of os walk to be iterative instead of recursive gh 94943 Add Dataclass support to the Enum __repr__ When inheriting from a dataclass only show the field names in the ,en
1530,value section of the member repr and not the dataclass class name gh 83035 Fix inspect getsource handling of decorator calls with nested parentheses gh 99576 Fix save method for LWPCookieJar and MozillaCookieJar saved file was not truncated on repeated save gh 94912 Add inspect markcoroutinefunction decorator which manually marks a function as a coroutine for the benefit of iscoroutinefunction gh 99509 Add PEP 585 support for multiprocessing queues Queue gh 99482 Remove Jython partial compatibility code from several stdlib modules gh 99433 Fix doctest failure on types MethodWrapperType in modules gh 85267 Several improvements to inspect signature s handling of __text_signature Fixes a case where inspect signature dropped parameters Fixes a case where inspect signature raised tokenize TokenError Allows inspect signature to understand defaults involving binary operations of constants inspect signature is documented as only raising TypeError or ValueError but sometimes raised RuntimeError These cases now raise ValueError Removed a dead code path gh 91166 asyncio is optimized to avoid excessive copying when writing to socket and use sendmsg if the platform supports it Patch by Kumar Aditya gh 98030 Add missing TCP socket options from Linux TCP_MD5SIG TCP_THIN_LINEAR_TIMEOUTS TCP_THIN_DUPACK TCP_REPAIR TCP_REPAIR_QUEUE TCP_QUEUE_SEQ TCP_REPAIR_OPTIONS TCP_TIMESTAMP TCP_CC_INFO TCP_SAVE_SYN TCP_SAVED_SYN TCP_REPAIR_WINDOW TCP_FASTOPEN_CONNECT TCP_ULP TCP_MD5SIG_EXT TCP_FASTOPEN_KEY TCP_FASTOPEN_NO_COOKIE TCP_ZEROCOPY_RECEIVE TCP_INQ TCP_TX_DELAY gh 88500 Reduced the memory usage of urllib parse unquote and urllib parse unquote_to_bytes on large values gh 96127 inspect signature was raising TypeError on call with mock objects Now it correctly returns args kwargs as infered signature gh 95882 Fix a 3 11 regression in asynccontextmanager which caused it to propagate exceptions with incorrect tracebacks and fix a 3 11 regression in contextmanager which caused it to propagate exceptions with incorrect tracebacks for StopIteration gh 78707 Deprecate passing more than one positional argument to pathlib PurePath relative_to and is_relative_to gh 92122 Fix reStructuredText syntax errors in docstrings in the enum module gh 91851 Optimize the Fraction arithmetics for small components bpo 24132 Make pathlib PurePath and Path subclassable private to start Previously attempting to instantiate a subclass resulted in an AttributeError being raised Patch by Barney Gale bpo 40447 Accept os PathLike such as pathlib Path in the stripdir arguments of compileall compile_file and compileall compile_dir bpo 36880 Fix a reference counting issue when a ctypes callback with return type py_object returns None which could cause crashes Documentation gh 100616 Document existing attr parameter to curses window vline function in curses gh 100472 Remove claim in documentation that the stripdir prependdir and limit_sl_dest parameters of compileall compile_dir and compileall compile_file could be bytes bpo 25377 Clarify use of octal format of mode argument in help os chmod as well as help os fchmod Tests gh 100454 Start running SSL tests with OpenSSL 3 1 0 beta1 gh 100086 The Python test runner libregrtest now logs Python build information like debug vs release build or LTO and PGO optimizations Patch by Victor Stinner gh 93018 Make two tests forgiving towards host system libexpat with backported security fixes applied Build gh 100540 Removed the with system ffi configure option libffi must now always be supplied by the system on all non Windows platforms The option has had no effect on non Darwin platforms for several releases and in 3 11 only had the non obvious effect of invoking pkg config to find libffi and never setting DUSING_APPLE_OS_LIBFFI Now on Darwin platforms configure will first check for the OS libffi and then fall back to the same processing as other platforms if it is not found gh 88267 Avoid exporting Python symbols in linked Windows applications when the core is built as static bpo 41916 Allow override of ac_cv_cxx_thread so that cross compil,en
1531,ed python can set pthread for CXX Windows gh 100180 Update Windows installer to OpenSSL 1 1 1s gh 99191 Use _MSVC_LANG 202002L instead of less precise _MSC_VER 1929 to more accurately test for C 20 support in PC _wmimodule cpp gh 79218 Define MS_WIN64 for Mingw w64 64bit fix cython compilation failure gh 99941 Ensure that asyncio Protocol data_received receives an immutable bytes object as documented instead of bytearray bpo 43984 winreg SetValueEx now leaves the target value untouched in the case of conversion errors Previously 1 would be written in case of such errors bpo 34816 hasattr ctypes windll nonexistant now returns False instead of raising OSError macOS gh 100180 Update macOS installer to OpenSSL 1 1 1s gh 100540 Removed obsolete dlfcn h shim from the _ctypes extension module which has not been necessary since Mac OS X 10 2 Tools Demos bpo 45256 Fix a bug that caused an AttributeError to be raised in python gdb py when py locals is used without a frame gh 100342 Add missing NULL check for possible allocation failure in args parsing in Argument Clinic C API gh 99947 Raising SystemError on import will now have its cause be set to the original unexpected exception gh 99240 In argument parsing after deallocating newly allocated memory reset its pointer to NULL gh 98724 The Py_CLEAR Py_SETREF and Py_XSETREF macros now only evaluate their arguments once If an argument has side effects these side effects are no longer duplicated Patch by Victor Stinner Python 3 12 0 alpha 3 Release date 2022 12 06 Security gh 100001 python m http server no longer allows terminal control characters sent within a garbage request to be printed to the stderr server log This is done by changing the http server BaseHTTPRequestHandler log_message method to replace control characters with a x HH hex escape before printing gh 87604 Avoid publishing list of active per interpreter audit hooks via the gc module Core and Builtins gh 99891 Fix a bug in the tokenizer that could cause infinite recursion when showing syntax warnings that happen in the first line of the source Patch by Pablo Galindo gh 91054 Add PyCode_AddWatcher and PyCode_ClearWatcher APIs to register callbacks to receive notification on creation and destruction of code objects gh 99729 Fix an issue that could cause frames to be visible to Python code as they are being torn down possibly leading to memory corruption or hard crashes of the interpreter gh 99708 Fix bug where compiler crashes on an if expression with an empty body block gh 99578 Fix a reference bug in _imp create_builtin after the creation of the first sub interpreter for modules builtins and sys Patch by Victor Stinner gh 99581 Fixed a bug that was causing a buffer overflow if the tokenizer copies a line missing the newline caracter from a file that is as long as the available tokenizer buffer Patch by Pablo galindo gh 99553 Fix bug where an ExceptionGroup subclass can wrap a BaseException gh 99547 Add a function to os path to check if a path is a junction isjunction Add similar functionality to pathlib Path as is_junction gh 99370 Fix zip path for venv created from a non installed python on POSIX platforms gh 99377 Add audit events for thread creation and clear operations gh 98686 Remove the BINARY_OP_GENERIC and COMPARE_OP_GENERIC specializations gh 99298 Remove the remaining error paths for attribute specializations and refuse to specialize attribute accesses on types that haven t had PyType_Ready called on them yet gh 99127 Allow some features of syslog to the main interpreter only Patch by Donghee Na gh 91053 Optimizing interpreters and JIT compilers may need to invalidate internal metadata when functions are modified This change adds the ability to provide a callback that will be invoked each time a function is created modified or destroyed gh 90994 Improve error messages when there s a syntax error with call arguments The following three cases are covered No value is assigned to a named argument eg foo a A value is assigned to a star argument eg foo args 0 A value is assigned to a double star keyword argument eg,en
1532, foo kwarg a 0 bpo 45026 Optimize the range object iterator It is now smaller faster iteration of ranges containing large numbers Smaller pickles faster unpickling bpo 31718 Raise ValueError instead of SystemError when methods of uninitialized io IncrementalNewlineDecoder objects are called Patch by Oren Milman bpo 38031 Fix a possible assertion failure in io FileIO when the opener returns an invalid file descriptor Library gh 100001 Also escape s in the http server BaseHTTPRequestHandler log_message so that it is technically possible to parse the line and reconstruct what the original data was Without this a xHH is ambiguious as to if it is a hex replacement we put in or the characters r x came through in the original request line gh 99957 Add frozen_default parameter to typing dataclass_transform gh 79033 Fix asyncio Server wait_closed to actually do what the docs promise wait for all existing connections to complete after closing the server gh 51524 Fix bug when calling trace CoverageResults with valid infile gh 99645 Fix a bug in handling class cleanups in unittest TestCase Now addClassCleanup uses separate lists for different TestCase subclasses and doClassCleanups only cleans up the particular class gh 99508 Fix TypeError in Lib importlib _bootstrap_external py while calling _imp source_hash gh 66285 Fix asyncio to not share event loop and signal wakeupfd in forked processes Patch by Kumar Aditya gh 97001 Release the GIL when calling termios APIs to avoid blocking threads gh 92647 Use final status of an enum to determine lookup or creation branch of functional API gh 99388 Add loop_factory parameter to asyncio run to allow specifying a custom event loop factory Patch by Kumar Aditya gh 99341 Fix ast increment_lineno to also cover ast TypeIgnore when changing line numbers gh 99382 Check the number of arguments in substitution in user generics containing a TypeVarTuple and one or more TypeVar gh 99379 Fix substitution of ParamSpec followed by TypeVarTuple in generic aliases gh 99344 Fix substitution of TypeVarTuple and ParamSpec together in user generics gh 99284 Remove _use_broken_old_ctypes_structure_semantics_ old untested and undocumented hack from ctypes gh 99201 Fix IndexError when initializing the config variables on Windows if HAVE_DYNAMIC_LOADING is not set gh 99240 Fix double free bug in Argument Clinic str_converter by extracting memory clean up to a new post_parsing section gh 64490 Fix refcount error when arguments are packed to tuple in Argument Clinic gh 99029 pathlib PurePath relative_to now treats naked Windows drive paths as relative This brings its behaviour in line with other parts of pathlib gh 98253 The implementation of the typing module is now more resilient to reference leaks in binary extension modules Previously a reference leak in a typed C API based extension module could leak internals of the typing module which could in turn introduce leaks in essentially any other package with typed function signatures Although the typing package is not the original source of the problem such non local dependences exacerbate debugging of large scale projects and the implementation was therefore changed to reduce harm by providing better isolation gh 98458 Fix infinite loop in unittest when a self referencing chained exception is raised gh 93453 asyncio get_event_loop and many other asyncio functions like asyncio ensure_future asyncio shield or asyncio gather and also the get_event_loop method of asyncio BaseDefaultEventLoopPolicy now raise a RuntimeError if called when there is no running event loop and the current event loop was not set Previously they implicitly created and set a new current event loop DeprecationWarning is no longer emitted if there is no running event loop but the current event loop was set gh 97966 On uname_result restored expectation that _fields and _asdict would include all six properties including processor gh 98248 Provide informative error messages in struct pack when its integral arguments are not in range gh 98108 zipfile Path is now pickleable if its initialization parame,en
1533,ters were pickleable e g for file system paths gh 98098 Created packages from zipfile and test_zipfile modules separating zipfile Path functionality gh 82836 Fix is_private properties in the ipaddress module Previously non private networks 0 0 0 0 0 would return True from this method now they correctly return False gh 96828 Add an OP_ENABLE_KTLS option for enabling the use of the kernel TLS kTLS Patch by Illia Volochii gh 88863 To avoid apparent memory leaks when asyncio open_connection raises break reference cycles generated by local exception and future instances which has exception instance as its member var Patch by Dong Uk Kang gh 91078 TarFile next now returns None when called on an empty tarfile bpo 47220 Document the optional callback parameter of WeakMethod Patch by Géry Ogam bpo 44817 Ignore WinError 53 ERROR_BAD_NETPATH 65 ERROR_NETWORK_ACCESS_DENIED and 161 ERROR_BAD_PATHNAME when using ntpath realpath bpo 41260 Rename the fmt parameter of the pure Python implementation of datetime date strftime to format bpo 15999 All built in functions now accept arguments of any type instead of just bool and int for boolean parameters Documentation gh 99931 Use sphinxext opengraph to generate OpenGraph metadata gh 89682 Reworded docstring of the default __contains__ to clarify that it returns a bool gh 88330 Improved the description of what a resource is in importlib resources docs gh 92892 Document that calling variadic functions with ctypes requires special care on macOS arm64 and possibly other platforms bpo 41825 Restructured the documentation for the os wait family of functions and improved the docs for os waitid with more explanation of the possible argument constants Tests gh 99892 Skip test_normalization of test_unicodedata if it fails to download NormalizationTest txt file from pythontest net Patch by Victor Stinner gh 99934 Correct test_marsh on 32 bit x86 test_deterministic sets was failing gh 99741 We ve implemented multi phase init PEP 489 630 687 for the internal for testing _xxsubinterpreters module gh 99659 Optional big memory tests in test_sqlite3 now catch the correct sqlite DataError exception type in case of too large strings and or blobs passed gh 99593 Cover the Unicode C API with tests gh 96002 Add functional test for Argument Clinic Build gh 99086 Fix Wimplicit int Wstrict prototypes and Wimplicit function declaration compiler warnings in configure checks gh 99337 Fix a compilation issue with GCC 12 on macOS gh 99289 Add a COMPILEALL_OPTS variable in Makefile to override compileall options default j0 in make install Also merged the compileall commands into a single command building pyc files for the all optimization levels 0 1 2 at once Patch by Victor Stinner gh 98872 Fix a possible fd leak in Programs _freeze_module c introduced in Python 3 11 gh 88226 Always define TARGET_ labels in Python ceval c even if USE_COMPUTED_GOTOS is disabled This allows breakpoints to be set at those labels in for instance gdb Windows gh 99345 Use faster initialization functions to detect install location for Windows Store package gh 98629 Fix initialization of sys version and sys _git on Windows gh 99442 Fix handling in Python Launcher for Windows when argv 0 does not include a file extension bpo 40882 Fix a memory leak in multiprocessing shared_memory SharedMemory on Windows macOS gh 87235 On macOS python3 dev fd 9 9 path to script py failed for any script longer than a couple of bytes gh 98940 Fix Mac Extras install py file filter bug Tools Demos gh 64490 Argument Clinic varargs bugfixes Fix out of bounds error in _PyArg_UnpackKeywordsWithVararg Fix incorrect check which allowed more than one varargs in clinic py Fix miscalculation of noptargs in generated code Do not generate noptargs when there is a vararg argument and no optional argument C API gh 98680 PyBUF_ constants were marked as part of Limited API of Python 3 11 These were available in 3 11 0 with Py_LIMITED_API defined for 3 11 and are necessary to use the buffer API gh 99612 Fix PyUnicode_DecodeUTF8Stateful for ASCII only data consumed was not set gh 471,en
1534,46 The structmember h header is deprecated Its non deprecated contents are now available just by including Python h with a Py_ prefix added if it was missing Deprecated contents are T_OBJECT T_NONE and no op flags Patch by Petr Viktorin based on earlier work by Alexander Belopolsky and Matthias Braun Python 3 12 0 alpha 2 Release date 2022 11 14 Security gh 98433 The IDNA codec decoder used on DNS hostnames by socket or asyncio related name resolution functions no longer involves a quadratic algorithm This prevents a potential CPU denial of service if an out of spec excessive length hostname involving bidirectional characters were decoded Some protocols such as urllib http 3 xx redirects potentially allow for an attacker to supply such a name Individual labels within an IDNA encoded DNS name will now raise an error early during IDNA decoding if they are longer than 1024 unicode characters given that each decoded DNS label must be 63 or fewer characters and the entire decoded DNS name is limited to 255 Only an application presenting a hostname or label consisting primarily of RFC 3454 section 3 1 Nothing characters to be removed would run into of this new limit See also RFC 5894 section 6 and RFC 3491 gh 98739 Update bundled libexpat to 2 5 0 Core and Builtins gh 81057 The docs clearly say that PyImport_Inittab PyImport_AppendInittab and PyImport_ExtendInittab should not be used after Py_Initialize has been called We now enforce this for the two functions Additionally the runtime now uses an internal copy of PyImport_Inittab to guard against modification gh 99298 Fix an issue that could potentially cause incorrect error handling for some bytecode instructions gh 99254 The compiler now removes all unused constants from code objects except the first one which may be a docstring gh 99205 Fix an issue that prevented PyThreadState and PyInterpreterState memory from being freed properly gh 81057 The 18 global C variables holding the state of the allocators have been moved to _PyRuntimeState This is a strictly internal change with no change in behavior gh 99181 Fix failure in except with unhashable exceptions gh 99204 Fix calculation of sys _base_executable when inside a POSIX virtual environment using copies of the python binary when the base installation does not provide the executable name used by the venv Calculation will fall back to alternative names python MAJOR python MAJOR MINOR gh 96055 Update faulthandler to emit an error message with the proper unexpected signal number Patch by Donghee Na gh 99153 Fix location of SyntaxError for a try block with both except and except gh 98686 Merge the adaptive opcode logic into each instruction s unquickened variant and merge the logic in EXTENDED_ARG_QUICK into EXTENDED_ARG With these changes the quickening that happens at code object creation is now only responsible for initializing warmup counters and inserting superinstructions gh 99103 Fix the error reporting positions of specialized traceback anchors when the source line contains Unicode characters gh 99139 Improve the error suggestion for NameError exceptions for instances Now if a NameError is raised in a method and the instance has an attribute that s exactly equal to the name in the exception the suggestion will include self NAME instead of the closest match in the method scope Patch by Pablo Galindo gh 98401 Octal escapes with value larger than 0o377 ex 477 deprecated in Python 3 11 now produce a SyntaxWarning instead of DeprecationWarning In a future Python version they will be eventually a SyntaxError Patch by Victor Stinner gh 98401 A backslash character pair that is not a valid escape sequence now generates a SyntaxWarning instead of DeprecationWarning For example re compile d d now emits a SyntaxWarning d is an invalid escape sequence use raw strings for regular expression re compile r d d In a future Python version SyntaxError will eventually be raised instead of SyntaxWarning Patch by Victor Stinner gh 96793 Handle StopIteration and StopAsyncIteration raised in generator or coroutines in the bytecode rather than i,en
1535,n wrapping C code gh 98931 Improve the SyntaxError error message when the user types import x from y instead of from y import x Patch by Pablo Galindo gh 98852 Fix subscription of type aliases containing bare generic types or types like TypeVar for example tuple A T int and tuple TypeVar T int where A is a generic type and T is a type variable gh 98925 Lower the recursion depth for marshal on WASI to support in development wasmtime 2 0 gh 98783 Fix multiple crashes in debug mode when str subclasses are used instead of str itself gh 98811 Use complete source locations to simplify detection of __future__ imports which are not at the beginning of the file Also corrects the offset in the exception raised in one case which was off by one and impeded highlighting gh 96793 Add specialization of FOR_ITER for generators Saves multiple layers of dispatch and checking to get from the FOR_ITER instruction in the caller to the RESUME in the generator gh 98762 Fix source locations of match sub patterns gh 98586 Added the methods PyObject_Vectorcall and PyObject_VectorcallMethod to the Limited API along with the auxiliary macro constant PY_VECTORCALL_ARGUMENTS_OFFSET The availability of these functions enables more efficient PEP 590 vector calls from binary extension modules that avoid argument boxing unboxing overheads gh 99257 Fix an issue where member descriptors such as those for __slots__ could behave incorrectly or crash instead of raising a TypeError when accessed via an instance of an invalid type gh 93143 Rather than changing co_code the interpreter will now display a RuntimeWarning and assign None to any fast locals that are left unbound after jumps or del statements executed while tracing gh 96421 When calling into Python code from C code through PyEval_EvalFrameEx or a related C API function a shim frame in inserted into the call stack This occurs in the _PyEval_EvalFrameDefault function The extra frame should be invisible to all Python and most C extensions but out of process profilers and debuggers need to be aware of it These shim frames can be detected by checking frame owner FRAME_OWNED_BY_CSTACK Extensions implementing their own interpreters using PEP 523 need to be aware of this shim frame and the changes to the semantics of RETURN_VALUE YIELD_VALUE and RETURN_GENERATOR which now clear the frame gh 98415 Fix detection of MAC addresses for uuid on certain OSs Patch by Chaim Sanders gh 98686 Quicken all code objects and specialize adaptive bytecode instructions more aggressively gh 92119 Print exception class name instead of its string representation when raising errors from ctypes calls gh 91058 ImportError raised from failed from module import name now include suggestions for the value of name based on the available names in module Patch by Pablo Galindo gh 96793 The FOR_ITER now leaves the iterator on the stack on termination of the loop This is to assist specialization of loops for generators gh 90716 Add _pylong py module It includes asymptotically faster algorithms that can be used for operations on integers with many digits It is used by longobject c to speed up some operations gh 95389 Expose ETH_P_ALL and some of the ETHERTYPE_ constants in socket Patch by Noam Cohen gh 93696 Allow pdb to locate source for frozen modules in the standard library Library gh 99418 Fix bug in urllib parse urlparse that causes URL schemes that begin with a digit a plus sign or a minus sign to be parsed incorrectly gh 94597 Deprecate asyncio AbstractChildWatcher to be removed in Python 3 14 Patch by Kumar Aditya gh 99305 Improve performance of secrets token_hex gh 74044 Fixed bug where inspect signature reported incorrect arguments for decorated methods gh 99275 Fix SystemError in ctypes when exception was not set during __initsubclass__ gh 99277 Remove older version of _SSLProtocolTransport get_write_buffer_limits in asyncio sslproto gh 99248 fix negative numbers failing in verify gh 99155 Fix statistics NormalDist pickle with 0 and 1 protocols gh 93464 enum auto is now correctly activated when combined with other assignment values,en
1536, E g ONE auto some text will now evaluate as 1 some text gh 99134 Update the bundled copy of pip to version 22 3 1 gh 92584 Remove the distutils package It was deprecated in Python 3 10 by PEP 632 Deprecate distutils module For projects still using distutils and cannot be updated to something else the setuptools project can be installed it still provides distutils Patch by Victor Stinner gh 98999 Now _pyio is consistent with _io in raising ValueError when executing methods over closed buffers gh 83004 Clean up refleak on failed module initialisation in _zoneinfo gh 83004 Clean up refleaks on failed module initialisation in _pickle gh 83004 Clean up refleak on failed module initialisation in _io gh 98897 Fix memory leak in math dist when both points don t have the same dimension Patch by Kumar Aditya gh 98878 Use the frame bound builtins when offering a name suggestion in traceback to prevent crashing when __builtins__ is not a dict gh 98139 In importlib _bootstrap enhance namespace package repr to module x namespace from path gh 90352 Fix _SelectorDatagramTransport to inherit from DatagramTransport in asyncio Patch by Kumar Aditya gh 98793 Fix argument typechecks in _overlapped WSAConnect and _overlapped Overlapped WSASendTo functions gh 98744 Prevent crashing in traceback when retrieving the byte offset for some source files that contain certain unicode characters gh 98740 Fix internal error in the re module which in very rare circumstances prevented compilation of a regular expression containing a conditional expression without the else branch gh 98703 Fix asyncio StreamWriter drain to call protocol connection_lost callback only once on Windows gh 98624 Add a mutex to unittest mock NonCallableMock to protect concurrent access to mock attributes gh 98658 The array array class now supports subscripting making it a generic type gh 98284 Improved TypeError message for undefined abstract methods of a abc ABC instance The names of the missing methods are surrounded by single quotes to highlight them gh 96151 Allow BUILTINS to be a valid field name for frozen dataclasses gh 98086 Make sure patch dict can be applied on async functions gh 72719 Remove modules asyncore and asynchat which were deprecated by PEP 594 gh 96192 Fix handling of bytes path like objects in os ismount gh 94172 ftplib Remove the FTP_TLS ssl_version class attribute use the context parameter instead Patch by Victor Stinner gh 94172 Remove the keyfile and certfile parameters from the ftplib imaplib poplib and smtplib modules and the key_file cert_file and check_hostname parameters from the http client module all deprecated since Python 3 6 Use the context parameter ssl_context in imaplib instead Patch by Victor Stinner gh 83638 Add the autocommit attribute to sqlite3 Connection and the autocommit parameter to sqlite3 connect to control PEP 249 compliant transaction handling Patch by Erlend E Aasland gh 92452 Fixed a race condition that could cause sysconfig get_config_var to incorrectly return None in multi threaded programs gh 91803 Fix an error when using a method of objects mocked with unittest mock create_autospec after it was sealed with unittest mock seal function bpo 38523 shutil copytree now applies the ignore_dangling_symlinks argument recursively bpo 40358 Add walk_up argument in pathlib PurePath relative_to bpo 36267 Fix IndexError in argparse ArgumentParser when a store_true action is given an explicit argument Documentation gh 98832 Changes wording of docstring for pathlib Path iterdir gh 97966 Update uname docs to clarify the special nature of the platform attribute and to indicate when it became late bound Tests gh 98903 The Python test suite now fails wit exit code 4 if no tests ran It should help detecting typos in test names and test methods gh 98713 Fix a bug in the typing tests where a test relying on CPython specific implementation details was not decorated with cpython_only and was not skipped on other implementations gh 87390 Add tests for star unpacking with PEP 646 and some other miscellaneous PEP 646 tests gh 96853 Added explicit co,en
1537,verage of Py_Initialize and hence Py_InitializeEx back to the embedding tests all other embedding tests migrated to Py_InitializeFromConfig in Python 3 11 bpo 34272 Some C API tests were moved into the new Lib test test_capi directory Build gh 99086 Fix Wimplicit int compiler warning in configure check for PTHREAD_SCOPE_SYSTEM gh 99016 Fix build with PYTHON_FOR_REGEN python3 8 gh 97731 Specify the full path to the source location for make docclean needed for cross builds gh 98949 Drop unused build dependency on readelf gh 98989 Use python3 11 if available for regeneration and freezing gh 98831 Add new tooling in Tools cases_generator to generate the interpreter switch statement from a list of opcode definitions This only affects adding modifying or removing instruction definitions The instruction definitions now live in Python bytecodes c in the form of a custom DSL under development The tooling reads this file and writes Python generated_cases c h which is then included by Python ceval c to provide most of the cases of the main interpreter switch gh 98817 Remove PCbuild lib pyproj it s not used for anything is only a minor convenience for Visual Studio users who probably mostly don t even know about it and it takes a lot of maintenance effort to keep updated gh 98776 Fix make regen test levenshtein for out of tree builds gh 98707 Don t use vendored libmpdec headers if with system libmpdec is passed to configure Don t use vendored libexpat headers if with system expat is passed to configure Windows gh 98689 Update Windows builds to zlib v1 2 13 v1 2 12 has CVE 2022 37434 but the vulnerable inflateGetHeader API is not used by Python gh 98790 Assumes that a missing DLLs directory means that standard extension modules are in the executable s directory gh 98745 Update py exe launcher to install 3 11 by default and 3 12 on request gh 98692 Fix the Python Launcher for Windows ignoring unrecognized shebang lines instead of treating them as local paths gh 94328 Update Windows installer to use SQLite 3 39 4 macOS gh 94328 Update macOS installer to SQLite 3 39 4 C API gh 98724 The Py_CLEAR Py_SETREF and Py_XSETREF macros now only evaluate their argument once If the argument has side effects these side effects are no longer duplicated Patch by Victor Stinner gh 98978 Fix use after free in Py_SetPythonHome NULL Py_SetProgramName NULL and _Py_SetProgramFullPath NULL function calls Issue reported by Benedikt Reinartz Patch by Victor Stinner gh 98410 Add getbufferproc and releasebufferproc to the stable API gh 98610 Some configurable capabilities of sub interpreters have changed They always allow subprocesses subprocess now whereas before subprocesses could be optionally disallowed for a sub interpreter Instead os exec can now be disallowed Disallowing daemon threads is now supported Disallowing all threads is still allowed but is never done by default Note that the optional restrictions are only available through _Py_NewInterpreterFromConfig which isn t a public API They do not affect the main interpreter nor Py_NewInterpreter gh 98608 A _PyInterpreterConfig has been added and _Py_NewInterpreter has been renamed to _Py_NewInterpreterFromConfig The isolated_subinterpreters argument is now a granular config that captures the previous behavior Note that this is all private API gh 96853 Py_InitializeEx now correctly calls PyConfig_Clear after initializing the interpreter the omission didn t cause a memory leak only because none of the dynamically allocated config fields are populated by the wrapper function gh 91248 Add PyFrame_GetVar and PyFrame_GetVarString functions to get a frame variable by its name Patch by Victor Stinner Python 3 12 0 alpha 1 Release date 2022 10 25 Security gh 97616 Fix multiplying a list by an integer list int detect the integer overflow when the new allocated length is close to the maximum size Issue reported by Jordan Limor Patch by Victor Stinner gh 97514 On Linux the multiprocessing module returns to using filesystem backed unix domain sockets for communication with the forkserver process instead of the Linux,en
1538, abstract socket namespace Only code that chooses to use the forkserver start method is affected Abstract sockets have no permissions and could allow any user on the system in the same network namespace often the whole system to inject code into the multiprocessing forkserver process This was a potential privilege escalation Filesystem based socket permissions restrict this to the forkserver process user as was the default in Python 3 8 and earlier This prevents Linux CVE 2022 42919 gh 87389 http server Fix an open redirection vulnerability in the HTTP server when an URI path starts with Vulnerability discovered and initial fix proposed by Hamza Avvan gh 79096 LWPCookieJar and MozillaCookieJar create files with file mode 600 instead of 644 Microsoft Windows is not affected gh 92888 Fix memoryview use after free when accessing the backing buffer in certain cases gh 68966 The deprecated mailcap module now refuses to inject unsafe text filenames MIME types parameters into shell commands Instead of using such text it will warn and act as if a match was not found or for test commands as if the test failed Core and Builtins gh 98374 Suppress ImportError for invalid query for help command Patch by Donghee Na gh 98461 Fix source location in bytecode for list set and dict comprehensions as well as generator expressions gh 98354 Added unicode check for name attribute of spec argument passed in _imp create_builtin function gh 98398 Fix source location of assert bytecodes gh 98390 Fix location of sub expressions of boolean expressions by reducing their scope to that of the sub expression gh 98254 Modules from the standard library are now potentially suggested as part of the error messages displayed by the interpreter when an NameError is raised to the top level Patch by Pablo Galindo gh 97997 Add running column offset to the tokenizer state to avoid calculating AST column information with pointer arithmetic gh 97973 Modify the tokenizer to return all necessary information the parser needs to set location information in the AST nodes so that the parser does not have to calculate those doing pointer arithmetic gh 96078 os sched_yield now release the GIL while calling sched_yield 2 Patch by Donghee Na gh 97955 Migrate zoneinfo to Argument Clinic gh 97912 The compiler now avoids quadratic behavior when finding which instructions should use the LOAD_FAST_CHECK opcode gh 97002 Fix an issue where several frame objects could be backed by the same interpreter frame possibly leading to corrupted memory and hard crashes of the interpreter gh 97943 Bugfix PyFunction_GetAnnotations should return a borrowed reference It was returning a new reference gh 97922 The Garbage Collector now runs only on the eval breaker mechanism of the Python bytecode evaluation loop instead on object allocations The GC can also run when PyErr_CheckSignals is called so C extensions that need to run for a long time without executing any Python code also have a chance to execute the GC periodically gh 65961 When __package__ is different than __spec__ parent raise a DeprecationWarning instead of ImportWarning Also remove importlib util set_package which was scheduled for removal gh 97850 Long deprecated module_repr should now be completely eradicated gh 86298 In cases where warnings warn_explicit consults the module s loader an DeprecationWarning is issued when m __loader__ differs from m __spec__ loader gh 97779 Ensure that all Python frame objects are backed by complete frames gh 91052 Add API for subscribing to modification events on selected dictionaries gh 97752 Fix possible data corruption or crashes when accessing the f_back member of newly created generator or coroutine frames gh 97591 Fixed a missing incref decref pair in Exception __setstate__ Patch by Ofey Chan gh 97670 Remove the sys getdxp function and the Tools scripts analyze_dxp py script DXP stands for dynamic execution pairs They were related to DYNAMIC_EXECUTION_PROFILE and DXPAIRS macros which have been removed in Python 3 11 Python can now be built with configure enable pystats to gather statistics on,en
1539, Python opcodes Patch by Victor Stinner gh 94526 Fix the Python path configuration used to initialized sys path at Python startup Paths are no longer encoded to UTF 8 strict to avoid encoding errors if it contains surrogate characters bytes paths are decoded with the surrogateescape error handler Patch by Victor Stinner gh 96670 The parser now raises SyntaxError when parsing source code containing null bytes Patch by Pablo Galindo gh 96975 Fix a crash occurring when PyEval_GetFrame is called while the topmost Python frame is in a partially initialized state gh 96848 Fix command line parsing reject X int_max_str_digits option with no value invalid when the PYTHONINTMAXSTRDIGITS environment variable is set to a valid limit Patch by Victor Stinner gh 95921 Fix overly broad source position information for chained comparisons used as branching conditions gh 96821 Fix undefined behaviour in audioop c gh 96821 Fix undefined behaviour in _testcapimodule c gh 95778 When ValueError is raised if an integer is larger than the limit mention the sys set_int_max_str_digits function in the error message Patch by Victor Stinner gh 96387 At Python exit sometimes a thread holding the GIL can wait forever for a thread usually a daemon thread which requested to drop the GIL whereas the thread already exited To fix the race condition the thread which requested the GIL drop now resets its request before exiting Issue discovered and analyzed by Mingliang ZHAO Patch by Victor Stinner gh 96864 Fix a possible assertion failure fatal error or SystemError if a line tracing event raises an exception while opcode tracing is enabled gh 95778 The PyLong_FromString function was refactored to make it more maintainable and extensible gh 96678 Fix undefined behaviour in C code of null pointer arithmetic gh 96754 Make sure that all frame objects created are created from valid interpreter frames Prevents the possibility of invalid frames in backtraces and signal handlers gh 90997 Improve the performance of reading and writing inline bytecode caches on some platforms gh 96751 Remove dead code from CALL_FUNCTION_EX opcode gh 90751 memoryview now supports half floats Patch by Donghee Na and Antoine Pitrou gh 96678 Fix case of undefined behavior in ceval c gh 64373 Convert _functools to argument clinic gh 96641 Do not expose KeyWrapper in _functools gh 96636 Ensure that tracing sys setrace is turned on immediately In pre release versions of 3 11 some tracing events might have been lost when turning on tracing in a __del__ method or interrupt gh 96572 Fix use after free in trace refs build mode Patch by Kumar Aditya gh 96611 When loading a file with invalid UTF 8 inside a multi line string a correct SyntaxError is emitted gh 96612 Make sure that incomplete frames do not show up in tracemalloc traces gh 90230 Fix compiler warnings and test failures when building with enable pystats gh 96587 Correctly raise SyntaxError on exception groups PEP 654 on python versions prior to 3 11 gh 96569 Remove two cases of undefined behavoir by adding NULL checks gh 96582 Fix possible NULL pointer dereference in _PyThread_CurrentFrames Patch by Kumar Aditya gh 91079 Separate Python recursion checking from C recursion checking which reduces the chance of C stack overflow and allows the recursion limit to be increased safely gh 93911 Fix an issue that could prevent LOAD_ATTR from specializing properly when accessing properties gh 96348 Emit a DeprecationWarning when throw throw or athrow are called with more than one argument gh 95196 Disable incorrect pickling of the C implemented classmethod descriptors gh 96364 Fix text signatures of list __getitem__ and dict __getitem__ gh 96352 Fix AttributeError missing name and obj attributes in object __getattribute__ Patch by Philip Georgi gh 93554 Change the jump opcodes so that all conditional jumps are forward jumps Backward jumps are converted by the assembler into a conditional forward jump whose target is the fallthrough block and with a reversed condition followed by an unconditional backward jump For example POP_JUMP_IF_TRUE BACKWARD,en
1540,_TARGET becomes POP_JUMP_IF_FALSE NEXT_BLOCK JUMP BACKWARD_TARGET All the directed conditional jump opcodes were removed POP_JUMP_FORWARD_IF_TRUE POP_JUMP_BACKWARD_IF_TRUE POP_JUMP_FORWARD_IF_FALSE POP_JUMP_BACKWARD_IF_FALSE POP_JUMP_FORWARD_IF_NONE POP_JUMP_BACKWARD_IF_NONE POP_JUMP_FORWARD_IF_NOT_NONE POP_JUMP_BACKWARD_IF_NOT_NONE The corresponding opcodes without direction are no longer pseudo instructions and they implement the forward conditional jumps gh 96268 Loading a file with invalid UTF 8 will now report the broken character at the correct location gh 96237 The internal field _PyInterpreterFrame f_func is renamed to _PyInterpreterFrame f_funcobj and may be any object The f_globals and f_builtin fields may hold junk values It is safest to treat the _PyInterpreterFrame struct as opaque gh 96187 Fixed a bug that caused _PyCode_GetExtra to return garbage for negative indexes Patch by Pablo Galindo gh 96143 Add a new X perf Python command line option as well as sys activate_stack_trampoline and sys deactivate_stack_trampoline function in the sys module that allows to set unset the interpreter in a way that the Linux perf profiler can detect Python calls The new sys is_stack_trampoline_active function allows to query the state of the perf trampoline Design by Pablo Galindo Patch by Pablo Galindo and Christian Heimes with contributions from Gregory P Smith Google and Mark Shannon gh 96071 Fix a deadlock in PyGILState_Ensure when allocating new thread state Patch by Kumar Aditya gh 96046 PyType_Ready now initializes ht_cached_keys and performs additional checks to ensure that type objects are properly configured This avoids crashes in 3rd party packages that don t use regular API to create new types gh 96005 On WASI ENOTCAPABLE is now mapped to PermissionError The errno modules exposes the new error number getpath py now ignores PermissionError when it cannot open landmark files pybuilddir txt and pyenv cfg gh 93678 Added test a harness for direct unit tests of the compiler s optimization stage The _testinternalcapi optimize_cfg function runs the optimiser on a sequence of instructions The CfgOptimizationTestCase class in test support has utilities for invoking the optimizer and checking the output gh 95245 Reduces the size of a simple Python object from 8 to 6 words by moving the weakreflist pointer into the pre header directly before the object s dict values pointer gh 90997 Compile virtual try except blocks to handle exceptions raised during close or throw calls through a suspended frame gh 95977 Optimized calling __get__ with vectorcall Patch by Kumar Aditya gh 91210 Improve error message when a parameter without a default value follows one with a default value and show the same message even when the non default default sequence is preceded by positional only parameters gh 95922 Fixed bug where the compiler s eliminate_empty_basic_blocks function ignores the last block of the code unit gh 95818 Skip over incomplete frames in PyThreadState_GetFrame gh 95876 Fix format string in _PyPegen_raise_error_known_location that can lead to memory corruption on some 64bit systems The function was building a tuple with i int instead of n Py_ssize_t for Py_ssize_t arguments gh 95605 Fix misleading contents of error message when converting an all whitespace string to float gh 95150 Update code object hashing and equality to consider all debugging and exception handling tables This fixes an issue where certain non identical code objects could be deduplicated during compilation gh 91146 Reduce allocation size of list from str split and str rsplit Patch by Donghee Na and Inada Naoki gh 87092 Create a jump target label abstraction in the compiler so that the compiler s codegen stage does not work directly with basic blocks This prepares the code for changes to the underlying CFG generation mechanism gh 95355 _PyPegen_Parser_New now properly detects token memory allocation errors Patch by Honglin Zhu gh 90081 Run Python code in tracer profiler function at full speed Fixes slowdown in earlier versions of 3 11 gh 95324 Emit a warning i,en
1541,n debug mode if an object does not call PyObject_GC_UnTrack before deallocation Patch by Pablo Galindo gh 95245 Merge managed dict and values pointer into a single tagged pointer to save one word in the pre header gh 93678 Add cfg_builder struct and refactor the relevant code so that a cfg can be constructed without an instance of the compiler struct gh 95185 Prevented crashes in the AST constructor when compiling some absurdly long expressions like 0 1000000 RecursionError is now raised instead Patch by Pablo Galindo gh 93351 ast AST node positions are now validated when provided to compile and other related functions If invalid positions are detected a ValueError will be raised gh 94438 Fix an issue that caused extended opcode arguments and some conditional pops to be ignored when calculating valid jump targets for assignments to the f_lineno attribute of frame objects In some cases this could cause inconsistent internal state resulting in a hard crash of the interpreter gh 95060 Undocumented PyCode_Addr2Location function now properly returns when addrq argument is less than zero gh 95113 Replace all EXTENDED_ARG_QUICK instructions with basic EXTENDED_ARG instructions in unquickened code Consumers of non adaptive bytecode should be able to handle extended arguments the same way they were handled in CPython 3 10 and older gh 91409 Fix incorrect source location info caused by certain optimizations in the bytecode compiler gh 95023 Implement os setns and os unshare for Linux Patch by Noam Cohen gh 94036 Fix incorrect source location info for some multi line attribute accesses and method calls gh 94938 Fix error detection in some builtin functions when keyword argument name is an instance of a str subclass with overloaded __eq__ and __hash__ Previously it could cause SystemError or other undesired behavior gh 94996 ast parse will no longer parse function definitions with positional only params when passed feature_version less than 3 8 Patch by Shantanu Jain gh 94739 Allow jumping within out of and across exception handlers in the debugger gh 94949 ast parse will no longer parse parenthesized context managers when passed feature_version less than 3 9 Patch by Shantanu Jain gh 94947 ast parse will no longer parse assignment expressions when passed feature_version less than 3 8 Patch by Shantanu Jain gh 91256 Ensures the program name is known for help text during interpreter startup gh 94869 Fix the column offsets for some expressions in multi line f strings ast nodes Patch by Pablo Galindo gh 94893 Fix an issue where frame object manipulations could corrupt inline bytecode caches gh 94822 Fix an issue where lookups of metaclass descriptors may be ignored when an identically named attribute also exists on the class itself gh 91153 Fix an issue where a bytearray item assignment could crash if it s resized by the new value s __index__ method gh 90699 Fix reference counting bug in bool __repr__ Patch by Kumar Aditya gh 94694 Fix an issue that could cause code with multi line method lookups to have misleading or incorrect column offset information In some cases when compiling a hand built AST this could have resulted in a hard crash of the interpreter gh 93252 Fix an issue that caused internal frames to outlive failed Python function calls possibly resulting in memory leaks or hard interpreter crashes gh 94215 Fix an issue where exceptions raised by line tracing events would cause frames to be left in an invalid state possibly resulting in a hard crash of the interpreter gh 92228 Disable the compiler s inline small exit blocks optimization for exit blocks that are associated with source code lines This fixes a bug where the debugger cannot tell where an exception handler ends and the following code block begins gh 94485 Line number of a module s RESUME instruction is set to 0 as specified in PEP 626 gh 94438 Account for instructions that can push NULL to the stack when setting line number in a frame Prevents some unlikely crashes gh 91719 Reload opcode when raising unknown opcode error in the interpreter main loop for C compilers,en
1542, to generate dispatching code independently gh 94329 Compile and run code with unpacking of extremely large sequences 1000s of elements Such code failed to compile It now compiles and runs correctly gh 94360 Fixed a tokenizer crash when reading encoded files with syntax errors from stdin with non utf 8 encoded text Patch by Pablo Galindo gh 88116 Fix an issue when reading line numbers from code objects if the encoded line numbers are close to INT_MIN Patch by Pablo Galindo gh 94262 Don t create frame objects for incomplete frames Prevents the creation of generators and closures from being observable to Python and C extensions restoring the behavior of 3 10 and earlier gh 94192 Fix error for dictionary literals with invalid expression as value gh 87995 types MappingProxyType instances are now hashable if the underlying mapping is hashable gh 93883 Revise the display strategy of traceback enhanced error locations The indicators are only shown when the location doesn t span the whole line gh 94163 Add BINARY_SLICE and STORE_SLICE instructions for more efficient handling and better specialization of slicing operations where the slice is explicit in the source code gh 94021 Fix unreachable code warning in Python specialize c gh 93911 Specialize LOAD_ATTR for objects with custom __getattribute__ gh 93955 Improve performance of attribute lookups on objects with custom __getattribute__ and __getattr__ Patch by Ken Jin gh 93911 Specialize LOAD_ATTR for property attributes gh 93678 Refactor compiler optimisation code so that it no longer needs the struct assembler and struct compiler passed around Instead each function takes the CFG and other data that it actually needs This will make it possible to test this code directly gh 93841 When built with enable pystats sys _stats_on sys _stats_off sys _stats_clear and sys _stats_dump functions have been added to enable gathering stats for parts of programs gh 93516 Store offset of first traceable instruction in code object to avoid having to recompute it for each instruction when tracing gh 93516 Lazily create a table mapping bytecode offsets to line numbers to speed up calculation of line numbers when tracing gh 89828 types GenericAlias no longer relays the __class__ attribute For example isinstance list int type no longer returns True gh 93678 Refactor the compiler to reduce boilerplate and repetition gh 93671 Fix some exponential backtrace case happening with deeply nested sequence patterns in match statements Patch by Pablo Galindo gh 93662 Make sure that the end column offsets are correct in multi line method calls Previously the end column could precede the column offset gh 93461 importlib invalidate_caches now drops entries from sys path_importer_cache with a relative path as name This solves a caching issue when a process changes its current working directory FileFinder no longer inserts a dot in the path e g egg spam is now egg spam gh 93621 Change order of bytecode instructions emitted for with and async with to reduce the number of entries in the exception table gh 93533 Reduce the size of the inline cache for LOAD_METHOD by 2 bytes gh 93444 Removed redundant fields from the compiler s basicblock struct b_nofallthrough b_exit b_return They can be easily calculated from the opcode of the last instruction of the block gh 93429 LOAD_METHOD instruction has been removed It was merged back into LOAD_ATTR gh 93418 Fixed an assert where an f string has an equal sign following an expression but there s no trailing brace For example f i gh 93382 Cache the result of PyCode_GetCode function to restore the O 1 lookup of the co_code attribute gh 93359 Ensure that custom ast nodes without explicit end positions can be compiled Patch by Pablo Galindo gh 93356 Code for exception handlers is emitted at the end of the code unit s bytecode This avoids one jump when no exception is raised gh 93354 Use exponential backoff for specialization counters in the interpreter Can reduce the number of failed specializations significantly and avoid slowdown for those parts of a program that are not suitable ,en
1543,for specialization gh 93283 Improve error message for invalid syntax of conversion character in f string expressions gh 93345 Fix a crash in substitution of a TypeVar in nested generic alias after TypeVarTuple gh 93223 When a bytecode instruction jumps to an unconditional jump instruction the first instruction can often be optimized to target the unconditional jump s target directly For tracing reasons this would previously only occur if both instructions have the same line number This also now occurs if the unconditional jump is artificial i e if it has no associated line number gh 84694 The experimental isolated subinterpreters configure option and EXPERIMENTAL_ISOLATED_SUBINTERPRETERS macro have been removed gh 91924 Fix __lltrace__ debug feature if the stdout encoding is not UTF 8 Patch by Victor Stinner gh 93040 Wraps unused parameters in Objects obmalloc c with Py_UNUSED gh 93143 Avoid NULL checks for uninitialized local variables by determining at compile time which variables must be initialized gh 93061 Backward jumps after async for loops are no longer given dubious line numbers gh 93065 Fix contextvars HAMT implementation to handle iteration over deep trees The bug was discovered and fixed by Eli Libman See MagicStack immutables 84 for more details gh 93012 Added the new function PyType_FromMetaclass which generalizes the existing PyType_FromModuleAndSpec using an additional metaclass argument This is useful for language binding tools where it can be used to intercept type related operations like subclassing or static attribute access by specifying a metaclass with custom slots Importantly PyType_FromMetaclass is available in the Limited API which provides a path towards migrating more binding tools onto the Stable ABI gh 93021 Fix the __text_signature__ for __get__ methods implemented in C Patch by Jelle Zijlstra gh 89914 The operand of the YIELD_VALUE instruction is set to the stack depth This is done to help frame handling on yield and may assist debuggers gh 92955 Fix memory leak in code object s lines and positions iterators as they were not finalized at exit Patch by Kumar Aditya gh 92930 Fixed a crash in _pickle c from mutating collections during __reduce__ or persistent_id gh 90690 The PRECALL instruction has been removed It offered only a small advantage for specialization and is not needed in the vast majority of cases gh 92914 Always round the allocated size for lists up to the nearest even number gh 92858 Improve error message for some suites with syntax error before gh 90473 Decrease default recursion limit on WASI to address limited call stack size gh 92804 Fix memory leak in memoryview iterator as it was not finalized at exit Patch by Kumar Aditya gh 92777 Specialize LOAD_METHOD for objects with lazy dictionaries Patch by Ken Jin gh 92658 Add support for connecting and binding to Hyper V sockets on Windows Hyper V hosts and guests gh 92236 Remove spurious LINE event when starting a generator or coroutine visible tracing functions implemented in C gh 91102 _warnings warn_explicit is ported to Argument Clinic gh 92619 Make the compiler duplicate an exit block only if none of its instructions have a lineno previously only the first instruction in the block was checked leading to unnecessarily duplicated blocks gh 88750 The deprecated debug build only PYTHONTHREADDEBUG environment variable no longer does anything gh 92261 Fix hang when trying to iterate over a typing Union gh 91432 Specialized the FOR_ITER opcode using the PEP 659 machinery gh 91399 Removed duplicate 0 0 0 0 0 0 entry in Objects unicodetype_db h gh 91578 Updates the error message for abstract class bpo 47091 Improve performance of repetition of list and tuple by using memcpy to copy data and performing the reference increments in one step bpo 46142 Make help output shorter by moving some info to the new help env and help xoptions command line options Also add help all option to print complete usage bpo 42316 Document some places where an assignment expression needs parentheses Library gh 89237 Fix hang on Windows in subprocess wait_c,en
1544,losed in asyncio with ProactorEventLoop Patch by Kumar Aditya gh 97928 tkinter Text count raises now an exception for options starting with instead of silently ignoring them gh 98393 The os module no longer accepts bytes like paths like bytearray and memoryview types only the exact bytes type is accepted for bytes strings Patch by Victor Stinner gh 98363 Added itertools batched to batch data into lists of a given length with the last list possibly being shorter than the others gh 98331 Update the bundled copies of pip and setuptools to versions 22 3 and 65 5 0 respectively gh 98307 A createSocket method was added to SysLogHandler gh 96035 Fix bug in urllib parse urlparse that causes certain port numbers containing whitespace underscores plus and minus signs or non ASCII digits to be incorrectly accepted gh 98257 Make sys setprofile and sys settrace functions reentrant They can no long fail with RuntimeError Cannot install a trace function while another trace function is being installed Patch by Victor Stinner gh 98251 Allow venv to pass along PYTHON variables to ensurepip and pip when they do not impact path resolution gh 94597 Deprecated asyncio AbstractEventLoopPolicy get_child_watcher and asyncio AbstractEventLoopPolicy set_child_watcher methods to be removed in Python 3 14 Patch by Kumar Aditya gh 98178 On macOS fix a crash in syslog syslog in multi threaded applications On macOS the libc syslog function is not thread safe so syslog syslog no longer releases the GIL to call it Patch by Victor Stinner gh 44098 Release the GIL when creating mmap mmap objects on Unix gh 87730 Wrap network errors consistently in urllib FTP support so the test suite doesn t fail when a network is available but the public internet is not reachable gh 94597 The child watcher classes MultiLoopChildWatcher FastChildWatcher and SafeChildWatcher are deprecated and will be removed in Python 3 14 Patch by Kumar Aditya gh 98023 Change default child watcher to PidfdChildWatcher on Linux systems which supports it Patch by Kumar Aditya gh 90985 Earlier in 3 11 we deprecated asyncio Task cancel message We realized we were too harsh and have undeprecated it gh 65961 Do not rely solely on __cached__ on modules code will also support __spec__ cached gh 97646 Replace deprecated application javascript with text javascript in mimetypes See RFC 9239 Patch by Noam Cohen gh 97930 Apply changes from importlib_resources 5 8 and 5 9 Traversable joinpath provides a concrete implementation as_file now supports directories of resources gh 97850 Remove deprecated importlib util set_loader and importlib util module_for_loader from importlib util gh 97837 Change deprecate warning message in unittest from It is deprecated to return a value None to It is deprecated to return a value that is not None from a test case gh 97825 Fixes AttributeError when subprocess check_output is used with argument input None and either of the arguments encoding or errors are used gh 97008 NameError and AttributeError spelling suggestions provided since gh 82711 are now also emitted by the pure Python traceback module Tests for those suggestions now exercise both implementations to ensure they are equivalent Patch by Carl Friedrich Bolz Tereick and Łukasz Langa gh 97799 dataclass now uses inspect get_annotations to examine the annotations on class objects gh 97781 Removed deprecated interfaces in importlib metadata entry points accessed as dictionary implicit dictionary construction of sequence of EntryPoint objects mutablility of EntryPoints result access of entry point by index entry_points now has a simpler more straightforward API returning EntryPoints gh 96827 Avoid spurious tracebacks from asyncio when default executor cleanup is delayed until after the event loop is closed e g as the result of a keyboard interrupt gh 95534 gzip GzipFile read reads 10 faster gh 97592 Avoid a crash in the C version of asyncio Future remove_done_callback when an evil argument is passed gh 97639 Remove tokenize NL check from tabnanny gh 97545 Make Semaphore run faster gh 73588 Fix generation of the defau,en
1545,lt name of tkinter Checkbutton Previously checkbuttons in different parent widgets could have the same short name and share the same state if arguments name and variable are not specified Now they are globally unique gh 96865 fix Flag to use boundary CONFORM This restores previous Flag behavior of allowing flags with non sequential values to be combined e g class Skip Flag TWO 2 EIGHT 8 Skip TWO Skip EIGHT Skip TWO EIGHT 10 gh 97005 Update bundled libexpat to 2 4 9 gh 85760 Fix race condition in asyncio where process_exited called before the pipe_data_received leading to inconsistent output Patch by Kumar Aditya gh 96704 Pass the correct contextvars Context when a asyncio exception handler is called on behalf of a task or callback handle This adds a new Task method get_context and also a new Handle method with the same name If this method is not found on a task object perhaps because it is a third party library that does not yet provide this method the context prevailing at the time the exception handler is called is used gh 96819 Fixed check in multiprocessing resource_tracker that guarantees that the length of a write to a pipe is not greater than PIPE_BUF gh 95865 Reduce urllib parse quote_from_bytes memory use on large values Contributed by Dennis Sweeney gh 96741 Corrected type annotation for dataclass attribute pstats FunctionProfile ncalls to be str gh 96734 Update unicodedata database to Unicode 15 0 0 gh 96735 Fix undefined behaviour in struct unpack gh 46412 Improve performance of bool db for large ndb gdb databases Previously this would call len db which would iterate over all keys the answer empty or not is known after the first key gh 96652 Fix the faulthandler implementation of faulthandler register signal chain True if the sigaction function is not available don t call the previous signal handler if it s NULL Patch by Victor Stinner gh 68163 Correct conversion of numbers Rational s to float gh 96538 Speed up bisect bisect functions by taking advantage of type stability gh 96465 Fraction hashes are now cached gh 96079 In typing fix missing field name and incorrect __module__ in _AnnotatedAlias gh 96415 Remove types _cell_factory from module namespace gh 95987 Fix repr of Any subclasses gh 96388 Work around missing socket functions in socket s __repr__ gh 96385 Fix TypeVarTuple __typing_prepare_subst__ TypeError was not raised when using more than one TypeVarTuple like T V in type alias substitutions gh 96142 Add match_args kw_only slots and weakref_slot to _DataclassParams gh 96073 In inspect fix overeager replacement of typing in formatting annotations gh 89258 Added a getChildren method to logging Logger to get the immediate child loggers of a logger gh 96346 Use double caching for compiled RE patterns gh 96349 Fixed a minor performance regression in threading Event __init__ gh 90467 Fix asyncio streams StreamReaderProtocol to keep a strong reference to the created task so that it s not garbage collected gh 96172 Fix a bug in unicodedata east_asian_width used to return the wrong value for unassigned characters and for yet unassigned but reserved characters gh 96159 Fix a performance regression in logging TimedRotatingFileHandler Only check for special files when the rollover time has passed gh 96175 Fix unused localName parameter in the Attr class in xml dom minidom gh 96145 Add AttrDict to JSON module for use with object_hook gh 96052 Fix handling compiler warnings SyntaxWarning and DeprecationWarning in codeop compile_command when checking for incomplete input Previously it emitted warnings and raised a SyntaxError Now it always returns None for incomplete input without emitting any warnings gh 96125 Fix incorrect condition that causes sys thread_info name to be wrong on pthread platforms gh 96019 Fix a bug in the makeunicodedata py script leading to about 13 KiB of space saving in the unicodedata module specifically the character decomposition data gh 95463 Remove an incompatible change from bpo 28080 that caused a regression that ignored the utf8 in ZipInfo flag_bits Patch by Pablo Galindo gh 69142 Ad,en
1546,d z strftime format code generates tzoffset with colons as separator see strftime and strptime Behavior gh 95899 Fix asyncio Runner to call asyncio set_event_loop only once to avoid calling attach_loop multiple times on child watchers Patch by Kumar Aditya gh 95736 Fix unittest IsolatedAsyncioTestCase to set event loop before calling setup functions Patch by Kumar Aditya gh 95865 Speed up urllib parse quote_from_bytes by replacing a list comprehension with map gh 95861 Add support for computing Spearman s correlation coefficient to the existing statistics correlation function gh 95804 Fix logging shutdown handler so it respects MemoryHandler flushOnClose gh 95704 When a task catches asyncio CancelledError and raises some other error the other error should generally not silently be suppressed gh 95149 The HTTPStatus enum offers a couple of properties to indicate the HTTP status category e g HTTPStatus OK is_success gh 95609 Update bundled pip to 22 2 2 gh 95289 Fix asyncio TaskGroup to propagate exception when asyncio CancelledError was replaced with another exception by a context manger Patch by Kumar Aditya and Guido van Rossum gh 94909 Fix incorrect joining of relative Windows paths with drives in pathlib PurePath initializer gh 95385 Faster json dumps when sorting of keys is not requested default gh 83901 Improve Signature bind error message for missing keyword only arguments gh 95339 Update bundled pip to 22 2 1 gh 95045 Fix GC crash when deallocating _lsprof Profiler by untracking it before calling any callbacks Patch by Kumar Aditya gh 95231 Fail gracefully if EPERM or ENOSYS is raised when loading crypt methods This may happen when trying to load MD5 on a Linux kernel with FIPS Federal Information Processing Standard enabled gh 95097 Fix asyncio run for asyncio Task implementations without uncancel method Patch by Kumar Aditya gh 95087 Fix IndexError in parsing invalid date in the email module gh 95199 Upgrade bundled setuptools to 63 2 0 gh 95194 Upgrade bundled pip to 22 2 gh 93899 Fix check for existence of os EFD_CLOEXEC os EFD_NONBLOCK and os EFD_SEMAPHORE flags on older kernel versions where these flags are not present Patch by Kumar Aditya gh 95166 Fix concurrent futures Executor map to cancel the currently waiting on future on an error e g TimeoutError or KeyboardInterrupt gh 95132 Fix a sqlite3 regression where args and kwds were incorrectly relayed from connect to the Connection factory The regression was introduced in 3 11a1 with PR 24421 gh 85128 Patch by Erlend E Aasland gh 93157 Fix fileinput module didn t support errors option when inplace is true gh 91212 Fixed flickering of the turtle window when the tracer is turned off Patch by Shin myoung serp gh 95077 Add deprecation warning for enum member member access e g Color RED BLUE Remove EnumMeta __getattr__ gh 95109 Ensure that timeouts scheduled with asyncio Timeout that have already expired are delivered promptly gh 95105 wsgiref types InputStream __iter__ should return Iterator bytes not Iterable bytes Patch by Shantanu Jain gh 95066 Replaced assert with exception in ast parse when feature_version has an invalid major version Patch by Shantanu Jain gh 77617 Add sqlite3 command line interface Patch by Erlend Aasland gh 95005 Replace _PyAccu with _PyUnicodeWriter in JSON encoder and StringIO and remove the _PyAccu implementation gh 90085 Remove c clock and t time CLI options of timeit The options had been deprecated since Python 3 3 and the functionality was removed in Python 3 7 Patch by Shantanu Jain gh 94857 Fix refleak in _io TextIOWrapper reconfigure Patch by Kumar Aditya gh 94821 Fix binding of unix socket to empty address on Linux to use an available address from the abstract namespace instead of 0 gh 94736 Fix crash when deallocating an instance of a subclass of _multiprocessing SemLock Patch by Kumar Aditya gh 81620 Add random binomialvariate gh 74116 Allow asyncio StreamWriter drain to be awaited concurrently by multiple tasks Patch by Kumar Aditya gh 87822 When called with capture_locals True the traceback module functions swallow excepti,en
1547,ons raised from calls to repr on local variables of frames This is in order to prioritize the original exception over rendering errors An indication of the failure is printed in place of the missing value Patch by Simon Martin Schroeder gh 88050 Fix asyncio subprocess transport to kill process cleanly when process is blocked and avoid RuntimeError when loop is closed Patch by Kumar Aditya gh 94637 SSLContext set_default_verify_paths now releases the GIL around SSL_CTX_set_default_verify_paths call The function call performs I O and CPU intensive work gh 94309 Deprecate aliases typing Hashable and typing Sized gh 92546 An undocumented python m pprint benchmark is moved into pprint suite of pyperformance Patch by Oleg Iarygin gh 94607 Fix subclassing complex generics with type variables in typing Previously an error message saying Some type variables are not listed in Generic was shown typing no longer populates __parameters__ with the __parameters__ of a Python class gh 94619 Remove the long deprecated module_repr from importlib gh 93910 The ability to access the other values of an enum on an enum e g Color RED BLUE has been restored in order to fix a performance regression gh 93896 Fix asyncio run and unittest IsolatedAsyncioTestCase to always the set event loop as it was done in Python 3 10 and earlier Patch by Kumar Aditya gh 94343 Allow setting the attributes of reprlib Repr during object initialization gh 94382 Port static types of _multiprocessing module to heap types Patch by Kumar Aditya gh 78724 Fix crash in struct Struct when it was not completely initialized by initializing it in __new__ Patch by Kumar Aditya gh 94510 Re entrant calls to sys setprofile and sys settrace now raise RuntimeError Patch by Pablo Galindo gh 92336 Fix bug where linecache getline fails on bad files with UnicodeDecodeError or SyntaxError It now returns an empty string as per the documentation gh 94398 Once a asyncio TaskGroup has started shutting down i e at least one task has failed and the task group has started cancelling the remaining tasks it should not be possible to add new tasks to the task group gh 94383 xml etree Remove the ElementTree Element copy method of the pure Python implementation deprecated in Python 3 10 use the copy copy function instead The C implementation of xml etree has no copy method only a __copy__ method Patch by Victor Stinner gh 94379 zipimport Remove find_loader and find_module methods deprecated in Python 3 10 use the find_spec method instead See PEP 451 for the rationale Patch by Victor Stinner gh 94352 shlex split Passing None for s argument now raises an exception rather than reading sys stdin The feature was deprecated in Python 3 9 Patch by Victor Stinner gh 94318 Strip trailing spaces in pydoc text output gh 89988 Fix memory leak in pickle Pickler when looking up dispatch_table Patch by Kumar Aditya gh 90016 Deprecate sqlite3 default adapters and converters Patch by Erlend E Aasland gh 94254 Fixed types of struct module to be immutable Patch by Kumar Aditya gh 93259 Now raise ValueError when None or an empty string are passed to Distribution from_name and other callers gh 74696 shutil make_archive now passes the root_dir argument to custom archivers which support it gh 94216 The dis module now has the opcodes for pseudo instructions those which are used by the compiler during code generation but then removed or replaced by real opcodes before the final bytecode is emitted gh 93096 Removed undocumented python m codecs Use python m unittest test test_codecs EncodedFileTest instead gh 94207 Made _struct Struct GC tracked in order to fix a reference leak in the _struct module gh 93096 Removed undocumented t argument of python m base64 Use python m unittest test test_base64 LegacyBase64TestCase test_encodebytes instead gh 94226 Remove the locale format function deprecated in Python 3 7 use locale format_string instead Patch by Victor Stinner gh 94199 Remove the ssl match_hostname function The ssl match_hostname was deprecated in Python 3 7 OpenSSL performs hostname matching since Python 3 7 Python no lon,en
1548,ger uses the ssl match_hostname function Patch by Victor Stinner gh 94214 Document the context object used in the venv EnvBuilder class and add the new environment s library path to it gh 94199 Remove the ssl wrap_socket function deprecated in Python 3 7 instead create a ssl SSLContext object and call its ssl SSLContext wrap_socket method Any package that still uses ssl wrap_socket is broken and insecure The function neither sends a SNI TLS extension nor validates server hostname Code is subject to CWE 295 Improper Certificate Validation Patch by Victor Stinner gh 94199 Remove the ssl RAND_pseudo_bytes function deprecated in Python 3 6 use os urandom or ssl RAND_bytes instead Patch by Victor Stinner gh 94199 hashlib Remove the pure Python implementation of hashlib pbkdf2_hmac deprecated in Python 3 10 Python 3 10 and newer requires OpenSSL 1 1 1 PEP 644 this OpenSSL version provides a C implementation of pbkdf2_hmac which is faster Patch by Victor Stinner gh 94196 gzip Remove the filename attribute of gzip GzipFile deprecated since Python 2 6 use the name attribute instead In write mode the filename attribute added gz file extension if it was not present Patch by Victor Stinner gh 94182 run the asyncio PidfdChildWatcher on the running loop this allows event loops to run subprocesses when there is no default event loop running on the main thread gh 94169 Remove io OpenWrapper and _pyio OpenWrapper deprecated in Python 3 10 just use open instead The open io open function is a built in function Since Python 3 10 _pyio open is also a static method Patch by Victor Stinner gh 91742 Fix pdb crash after jump caused by a null pointer dereference Patch by Kumar Aditya gh 94101 Manual instantiation of ssl SSLSession objects is no longer allowed as it lead to misconfigured instances that crashed the interpreter when attributes where accessed on them gh 84753 inspect iscoroutinefunction inspect isgeneratorfunction and inspect isasyncgenfunction now properly return True for duck typed function like objects like instances of unittest mock AsyncMock This makes inspect iscoroutinefunction consistent with the behavior of asyncio iscoroutinefunction Patch by Mehdi ABAAKOUK gh 94028 Fix a regression in the sqlite3 where statement objects were not properly cleared and reset after use in cursor iters The regression was introduced by PR 27884 in Python 3 11a1 Patch by Erlend E Aasland gh 93973 Add keyword argument all_errors to asyncio create_connection so that multiple connection errors can be raised as an ExceptionGroup gh 93963 Officially deprecate from importlib abc classes moved to importlib resources abc gh 93858 Prevent error when activating venv in nested fish instances gh 93820 Pickle enum Flag by name gh 93847 Fix repr of enum of generic aliases gh 91404 Revert the re memory leak when a match is terminated by a signal or memory allocation failure as the implemented fix caused a major performance regression gh 83499 Fix double closing of file description in tempfile gh 93820 Fixed a regression when copy copy ing enum Flag with multiple flag members gh 79512 Fixed names and __module__ value of weakref classes ReferenceType ProxyType CallableProxyType It makes them pickleable gh 91389 Fix an issue where dis utilities could report missing or incorrect position information in the presence of CACHE entries gh 93626 Set __future__ annotations to have a None mandatoryRelease to indicate that it is currently TBD gh 90473 Emscripten and WASI have no home directory and cannot provide PEP 370 user site directory gh 90494 copy copy and copy deepcopy now always raise a TypeError if __reduce__ returns a tuple with length 6 instead of silently ignore the 6th item or produce incorrect result gh 90549 Fix a multiprocessing bug where a global named resource such as a semaphore could leak when a child process is spawned as opposed to forked gh 93521 Fixed a case where dataclasses would try to add __weakref__ into the __slots__ for a dataclass that specified weakref_slot True when it was already defined in one of its bases This resulted in a TypeError up,en
1549,on the new class being created gh 79579 sqlite3 now correctly detects DML queries with leading comments Patch by Erlend E Aasland gh 93421 Update sqlite3 Cursor rowcount when a DML statement has run to completion This fixes the row count for SQL queries like UPDATE RETURNING Patch by Erlend E Aasland gh 93475 Expose FICLONE and FICLONERANGE constants in fcntl Patch by Illia Volochii gh 93370 Deprecate sqlite3 version and sqlite3 version_info gh 91810 Suppress writing an XML declaration in open files in ElementTree write with encoding unicode and xml_declaration None gh 91162 Support splitting of unpacked arbitrary length tuple over TypeVar and TypeVarTuple parameters For example A T Ts tuple int A int tuple int A Ts T tuple int A tuple int int gh 93353 Fix the importlib resources as_file context manager to remove the temporary file if destroyed late during Python finalization keep a local reference to the os remove function Patch by Victor Stinner gh 83658 Make multiprocessing Pool raise an exception if maxtasksperchild is not None or a positive int gh 93312 Add os PIDFD_NONBLOCK flag to open a file descriptor for a process with os pidfd_open in non blocking mode Patch by Kumar Aditya gh 88123 Implement Enum __contains__ that returns True or False to replace the deprecated behaviour that would sometimes raise a TypeError gh 93297 Make asyncio task groups prevent child tasks from being GCed gh 85308 Changed argparse ArgumentParser to use filesystem encoding and error handler instead of default text encoding to read arguments from file e g fromfile_prefix_chars option This change affects Windows argument file should be encoded with UTF 8 instead of ANSI Codepage gh 93156 Accessing the pathlib PurePath parents sequence of an absolute path using negative index values produced incorrect results gh 93162 Add the ability for logging config dictConfig to usefully configure QueueHandler and QueueListener as a pair and add logging getHandlerByName and logging getHandlerNames APIs to allow access to handlers by name gh 93243 The smtpd module was removed per the schedule in PEP 594 gh 92886 Replace assert statements with raise AssertionError in BaseHandler so that the tested behaviour is maintained running with optimizations O gh 90155 Fix broken asyncio Semaphore when acquire is cancelled gh 90817 The locale resetlocale function is deprecated and will be removed in Python 3 13 Use locale setlocale locale LC_ALL instead Patch by Victor Stinner gh 91513 Added taskName attribute to logging module for use with asyncio tasks gh 74696 shutil make_archive no longer temporarily changes the current working directory during creation of standard zip or tar archives gh 92728 The re template function and the corresponding re TEMPLATE and re T flags are restored after they were removed in 3 11 0b1 but they are now deprecated so they might be removed from Python 3 13 gh 93033 Search in some strings platform dependent i e U 0xFFFF U 0x0100 on Windows or U 0xFFFFFFFF U 0x00010000 on Linux 64 bit are now up to 10 times faster gh 89973 Fix re error raised in fnmatch if the pattern contains a character range with upper bound lower than lower bound e g c a Now such ranges are interpreted as empty ranges gh 93044 No longer convert the database argument of sqlite3 connect to bytes before passing it to the factory gh 93010 In a very special case the email package tried to append the nonexistent InvalidHeaderError to the defect list It should have been InvalidHeaderDefect gh 92986 Fix ast unparse when ImportFrom level is None gh 92932 Now dis and get_instructions handle operand values for instructions prefixed by EXTENDED_ARG_QUICK Patch by Sam Gross and Donghee Na gh 92675 Fix venv ensure_directories to accept pathlib Path arguments in addition to str paths Patch by David Foster gh 87901 Removed the encoding argument from os popen that was added in 3 11b1 gh 91922 Fix function sqlite connect and the sqlite Connection constructor on non UTF 8 locales Also they now support bytes paths non decodable with the current FS encoding gh 92869 Added c_time_t to cty,en
1550,pes which has the same size as the time_t type in C gh 92839 Fixed crash resulting from calling bisect insort or bisect insort_left with the key argument not equal to None gh 90473 subprocess now fails early on Emscripten and WASI platforms to work around missing os pipe on WASI gh 89325 Removed many old deprecated unittest features TestCase method aliases undocumented and broken TestCase method assertDictContainsSubset undocumented TestLoader loadTestsFromModule parameter use_load_tests and an underscored alias of the TextTestResult class gh 92734 Allow multi element reprs emitted by reprlib to be pretty printed using configurable indentation gh 92671 Fixed ast unparse for empty tuples in the assignment target context gh 91581 utcfromtimestamp no longer attempts to resolve fold in the pure Python implementation since the fold is never 1 in UTC In addition to being slightly faster in the common case this also prevents some errors when the timestamp is close to datetime min Patch by Paul Ganssle gh 86388 Removed randrange functionality deprecated since Python 3 10 Formerly randrange 10 0 losslessly converted to randrange 10 Now it raises a TypeError Also the exception raised for non integral values such as randrange 10 5 or randrange 10 has been changed from ValueError to TypeError gh 90385 Add pathlib Path walk as an alternative to os walk gh 92550 Fix pathlib Path rglob for empty pattern gh 92591 Allow logging filters to return a logging LogRecord instance so that filters attached to logging Handler s can enrich records without side effects on other handlers gh 92445 Fix a bug in argparse where nargs would raise an error instead of returning an empty list when 0 arguments were supplied if choice was also defined in parser add_argument gh 92547 Remove undocumented sqlite3 features deprecated in Python 3 10 sqlite3 enable_shared_cache sqlite3 OptimizedUnicode Patch by Erlend E Aasland gh 92530 Fix an issue that occurred after interrupting threading Condition notify gh 92531 The statistics median_grouped function now always return a float Formerly it did not convert the input type when for sequences of length one gh 84131 The pathlib Path deprecated method link_to has been removed Use 3 10 s hardlink_to method instead as its semantics are consistent with that of symlink_to gh 89336 Removed configparser module APIs the SafeConfigParser class alias the ParsingError filename property and parameter and the ConfigParser readfp method all of which were deprecated since Python 3 2 gh 92391 Add __class_getitem__ to csv DictReader and csv DictWriter allowing them to be parameterized at runtime Patch by Marc Mueller gh 91968 Add SO_RTABLE and SO_USER_COOKIE constants to socket gh 91810 ElementTree method write and function tostring now use the text file s encoding UTF 8 if not available instead of locale encoding in XML declaration when encoding unicode is specified gh 81790 os path splitdrive now understands DOS device paths with UNC links beginning UNC Contributed by Barney Gale gh 91760 Apply more strict rules for numerical group references and group names in regular expressions Only sequence of ASCII digits is now accepted as a numerical reference The group name in bytes patterns and replacement strings can now only contain ASCII letters and digits and underscore gh 90622 Worker processes for concurrent futures ProcessPoolExecutor are no longer spawned on demand a feature added in 3 9 when the multiprocessing context start method is fork as that can lead to deadlocks in the child processes due to a fork happening while threads are running gh 91577 Move imports in SharedMemory methods to module level so that they can be executed late in python finalization gh 91581 Remove an unhandled error case in the C implementation of calls to datetime fromtimestamp with no time zone i e getting a local time from an epoch timestamp This should have no user facing effect other than giving a possibly more accurate error message when called with timestamps that fall on 10000 01 01 in the local time Patch by Paul Ganssle gh 91539 Improve performa,en
1551,nce of urllib request getproxies_environment when there are many environment variables gh 91524 Speed up the regular expression substitution functions re sub and re subn and corresponding re Pattern methods for replacement strings containing group references by 2 3 times gh 91447 Fix findtext in the xml module to only give an empty string when the text attribute is set to None gh 91456 Deprecate current default auto behavior In 3 13 the default will be for for auto to always return the largest member value incremented by 1 and to raise if incompatible value types are used bpo 47231 Fixed an issue with inconsistent trailing slashes in tarfile longname directories bpo 39064 zipfile ZipFile now raises zipfile BadZipFile instead of ValueError when reading a corrupt zip file in which the central directory offset is negative bpo 41287 Fix handling of the doc argument in subclasses of property gh 90005 ctypes dependency libffi is now detected with pkg config bpo 32547 The constructors for DictWriter and DictReader now coerce the fieldnames argument to a list if it is an iterator bpo 35540 Fix dataclasses asdict crash when collections defaultdict is present in the attributes bpo 47063 Add an index_pages parameter to support using non default index page names bpo 47025 Drop support for bytes on sys path bpo 46951 Order the contents of zipapp archives to make builds more reproducible bpo 42777 Implement pathlib Path is_mount for Windows paths bpo 46755 In QueueHandler clear stack_info from LogRecord to prevent stack trace from being written twice bpo 45393 Fix the formatting for await x and not x in the operator precedence table when using the help system bpo 46642 Improve error message when trying to subclass an instance of typing TypeVar typing ParamSpec typing TypeVarTuple etc Based on patch by Gregory Beauregard bpo 46364 Restrict use of sockets instead of pipes for stdin of subprocesses created by asyncio to AIX platform only bpo 28249 Set doctest DocTest lineno to None when object does not have __doc__ bpo 46197 Fix ensurepip environment isolation for subprocess running pip bpo 45924 Fix asyncio incorrect traceback when future s exception is raised multiple times Patch by Kumar Aditya bpo 45046 Add support of context managers in unittest methods enterContext and enterClassContext of class TestCase method enterAsyncContext of class IsolatedAsyncioTestCase and function unittest enterModuleContext bpo 44173 Enable fast seeking of uncompressed unencrypted zipfile ZipExtFile bpo 42627 Fix incorrect parsing of Windows registry proxy settings bpo 42047 Add threading get_native_id support for DragonFly BSD Patch by David Carlier bpo 14243 The tempfile NamedTemporaryFile function has a new optional parameter delete_on_close bpo 41246 Give the same callback function for when the overlapped operation is done to the functions recv recv_into recvfrom sendto send and sendfile inside IocpProactor bpo 39264 Fixed collections UserDict get to not call __missing__ when a value is not found This matches the behavior of dict Patch by Bar Harel bpo 38693 importlib now uses f strings internally instead of str format bpo 38267 Add timeout parameter to asyncio loop shutdown_default_executor The default value is None which means the executor will be given an unlimited amount of time When called from asyncio Runner or asyncio run the default timeout is 5 minutes bpo 34828 sqlite3 Connection iterdump now handles databases that use AUTOINCREMENT in one or more tables bpo 32990 Support reading wave files with the WAVE_FORMAT_EXTENSIBLE format in the wave module bpo 26253 Allow adjustable compression level for tarfile streams in tarfile open Documentation gh 85525 Remove extra row gh 86404 Deprecated tools make suspicious and rstlint py are now removed They have been replaced by spinx lint gh 97741 Fix in c domain ref target syntax via a conf py patch so it works as intended to disable ref target resolution gh 96432 Fraction literals now support whitespace around the forward slash Fraction 2 3 gh 96098 Improve discoverability of the higher level concurren,en
1552,t futures module by providing clearer links from the lower level threading and multiprocessing modules gh 95957 What s New 3 11 now has instructions for how to provide compiler and linker flags for Tcl Tk and OpenSSL on RHEL 7 and CentOS 7 gh 95588 Clarified the conflicting advice given in the ast documentation about ast literal_eval being safe for use on untrusted input while at the same time warning that it can crash the process The latter statement is true and is deemed unfixable without a large amount of work unsuitable for a bugfix So we keep the warning and no longer claim that literal_eval is safe gh 91207 Fix stylesheet not working in Windows CHM htmlhelp docs and add warning that they are deprecated Contributed by C A M Gerlach gh 95454 Replaced incorrectly written true false values in documentiation Patch by Robert O Shea gh 95451 Update library documentation with availability information on WebAssembly platforms wasm32 emscripten and wasm32 wasi gh 95415 Use consistent syntax for platform availability The directive now supports a content body and emits a warning when it encounters an unknown platform gh 94321 Document the PEP 246 style protocol type sqlite3 PrepareProtocol gh 86128 Document a limitation in ThreadPoolExecutor where its exit handler is executed before any handlers in atexit gh 61162 Clarify sqlite3 behavior when How to use the connection context manager gh 87260 Align sqlite3 argument specs with the actual implementation gh 86986 The minimum Sphinx version required to build the documentation is now 3 2 gh 88831 Augmented documentation of asyncio create_task Clarified the need to keep strong references to tasks and added a code snippet detailing how to do this gh 86438 Clarify that W and PYTHONWARNINGS are matched literally and case insensitively rather than as regular expressions in warnings gh 93031 Update tutorial introduction output to use 3 10 SyntaxError invalid range gh 92240 Added release dates for What s New in Python 3 X for 3 0 3 1 3 2 3 8 and 3 10 bpo 47161 Document that pathlib PurePath does not collapse initial double slashes because they denote UNC paths bpo 40838 Document that inspect getdoc inspect getmodule and inspect getsourcefile might return None bpo 43689 The Differ documentation now also mentions other whitespace characters which make it harder to understand the diff output bpo 38056 Overhaul the Error Handlers documentation in codecs bpo 13553 Document tkinter Tk args Tests gh 95027 On Windows when the Python test suite is run with the jN option the ANSI code page is now used as the encoding for the stdout temporary file rather than using UTF 8 which can lead to decoding errors Patch by Victor Stinner gh 96624 Fixed the failure of repeated runs of test test_unittest caused by side effects in test_dotted_but_module_not_loaded gh 95243 Mitigate the inherent race condition from using find_unused_port in testSockName by trying to find an unused port a few times before failing Patch by Ross Burton gh 95573 Lib test test_asyncio test_ssl py exposed a bug in the macOS kernel where intense concurrent load on non blocking sockets occasionally causes errno ENOBUFS No buffer space available to be emitted FB11063974 filed with Apple in the mean time as a workaround buffer size used in tests on macOS is decreased to avoid intermittent failures Patch by Fantix King gh 95280 Fix problem with test_ssl test_get_ciphers on systems that require perfect forward secrecy PFS ciphers gh 95212 Make multiprocessing test case test_shared_memory_recreate parallel safe gh 95218 Move tests for importlib resources into test_importlib resources gh 93963 Updated tests to use preferred location for importlib resources ABCs gh 94675 Add a regression test for re exponentional slowdown when using rjsmin gh 91330 Added more tests for dataclasses to cover behavior with data descriptor based fields gh 94208 test_ssl is now checking for supported TLS version and protocols in more tests gh 94315 Tests now check for DAC override capability instead of relying on os geteuid gh 54781 Rename test_tk to test_tkinter a,en
1553,nd rename test_ttk_guionly to test_ttk Patch by Victor Stinner gh 93839 Move Lib ctypes test to Lib test test_ctypes Patch by Victor Stinner gh 93951 In test_bdb StateTestCase test_skip avoid including auxiliary importers gh 93957 Provide nicer error reporting from subprocesses in test_venv EnsurePipTest test_with_pip gh 93884 Add test cases for PyNumber_ToBase that take a large number or a non int object as parameter gh 93852 test_asyncio test_logging test_socket and test_socketserver now create AF_UNIX domains in the current directory to no longer fail with OSError AF_UNIX path too long if the temporary directory the TMPDIR environment variable is too long Patch by Victor Stinner gh 93353 regrtest now checks if a test leaks temporary files or directories if run with jN option Patch by Victor Stinner gh 84461 run_tests py now handles cross compiling env vars correctly and pass HOSTRUNNER to regression tests gh 93616 test_modulefinder now creates a temporary directory in ModuleFinderTest setUp instead of module scope gh 93575 Fix issue with test_unicode test_raiseMemError The test case now use test support calcobjsize to calculate size of PyUnicode structs sys getsizeof may return different size when string has UTF 8 memory gh 90473 WASI does not have a chmod 2 syscall os chmod is now a dummy function on WASI Skip all tests that depend on working os chmod gh 90473 Skip tests on WASI that require symlinks with absolute paths gh 57539 Increase calendar test coverage for calendar LocaleTextCalendar formatweekday gh 90473 Skip symlink tests on WASI wasmtime uses openat2 2 with RESOLVE_BENEATH flag which prevents symlinks with absolute paths gh 89858 Fix test_embed for out of tree builds Patch by Kumar Aditya gh 92886 Fixing tests that fail when running with optimizations O in test_imaplib py gh 92886 Fixing tests that fail when running with optimizations O in test_zipimport py gh 92886 Fixing tests that fail when running with optimizations O in test_py_compile py gh 92886 Fixing tests that fail when running with optimizations O in test_sys_settrace py gh 92886 Fixing tests that fail when running with optimizations O in _test_multiprocessing py gh 92670 Skip test_shutil TestCopy test_copyfile_nonexistent_dir test on AIX as the test uses a trailing slash to force the OS consider the path as a directory but on AIX the trailing slash has no effect and is considered as a file gh 92514 Remove unused test support BasicTestRunner Patch by Jelle Zijlstra bpo 47016 Create a GitHub Actions workflow for verifying bundled pip and setuptools Patch by Illia Volochii and Adam Turner Build gh 96761 Fix the build process of clang compiler for _bootstrap_python if LTO optimization is applied Patch by Matthias Görgens and Donghee Na gh 96883 wasm32 emscripten builds for browsers now include concurrent futures for asyncio and unittest mock gh 85936 CPython now uses the ThinLTO option as the default policy if the Clang compiler accepts the flag Patch by Donghee Na gh 96729 Ensure that Windows releases built with Tools msi buildrelease bat are upgradable to and from official Python releases gh 96269 Shared module targets now depend on new MODULE_DEPS variable which includes EXPORTSYMS This fixes a build order issue on unsupported AIX platform gh 84461 wasm32 emscripten platform no longer builds resource module getresuid getresgid and their setters The APIs are stubs and not functional gh 95973 Add a new with dsymutil configure option to link debug information in macOS Patch by Pablo Galindo gh 90536 Use the BOLT post link optimizer to improve performance particularly on medium to large applications gh 93744 Remove the configure with cxx main build option it didn t work for many years Remove the MAINCC variable from configure and Makefile Patch by Victor Stinner gh 94801 Fix a regression in configure script that caused some header checks to ignore custom CPPFLAGS The regression was introduced in gh 94802 gh 95145 wasm32 wasi builds no longer depend on WASIX s pthread stubs Python now has its own stubbed pthread API gh 95174 Python now detects missi,en
1554,ng dup function in WASI and works around some missing errno select and socket constants gh 95174 Python now skips missing socket functions and methods on WASI WASI can only create sockets from existing fd accept and has no netdb gh 95085 Platforms wasm32 unknown emscripten and wasm32 unknown wasi have been promoted to PEP 11 tier 3 platform support gh 94847 Fixed _decimal module build issue on GCC when compiling with LTO and pydebug Debug builds no longer force inlining of functions gh 94841 Fix the possible performance regression of PyObject_Free compiled with MSVC version 1932 gh 94801 configure now uses custom flags like ZLIB_CFLAGS and ZLIB_LIBS when searching for headers and libraries gh 94773 deepfreeze py now supports code object with frozensets that contain incompatible unsortable types gh 94682 Build and test with OpenSSL 1 1 1q gh 90005 Dependencies of readline and curses module are now detected in configure script with pkg config Only ncurses ncursesw are detected automatically The old curses library is not configured automatically Workaround for missing termcap or tinfo library has been removed gh 90005 Fix building _ctypes extension without pkg config gh 90005 _dbm module dependencies are now detected by configure gh 94404 makesetup now works around an issue with sed on macOS and uses correct CFLAGS for object files that end up in a shared extension Module CFLAGS are used before PY_STDMODULE_CFLAGS to avoid clashes with system headers gh 93939 C extension modules are now built by configure and make instead of distutils and setup py gh 93939 The 2to3 idle and pydoc scripts are now generated and installed by Makefile instead of setup py gh 94280 Updated pegen regeneration script on Windows to find and use Python 3 9 or higher Prior to this pegen regeneration already required 3 9 or higher but the script may have used lower versions of Python gh 93584 Address race condition in Makefile when installing a PGO build All test and install targets now depend on all target gh 93491 configure now detects and reports PEP 11 support tiers gh 69093 Fix Modules Setup stdlib in rule for _sqlite3 extension gh 93207 va_start with two parameters like va_start args format is now required to build Python va_start is no longer called with a single parameter Patch by Kumar Aditya gh 93202 Python now always use the zu and zd printf formats to format a size_t or Py_ssize_t number Building Python 3 12 requires a C11 compiler so these printf formats are now always supported Patch by Victor Stinner gh 90473 Disable pymalloc and increase stack size on wasm32 wasi bpo 34449 Drop invalid compiler switch fPIC for HP aCC on HP UX Patch by Michael Osipov Windows gh 98360 Fixes multiprocessing spawning child processes on Windows from a virtual environment to ensure that child processes that also use multiprocessing to spawn more children will recognize that they are in a virtual environment gh 98414 Fix py exe launcher handling of V company option when default preferences have been set in environment variables or configuration files gh 97728 Fix possible crashes caused by the use of uninitialized variables when pass invalid arguments in os system on Windows and in Windows specific modules like winreg gh 90989 Made Python Launcher for Windows install per user by default unless an all users install already exists and clarify some text in the installer gh 97649 The Tools directory is no longer installed on Windows gh 96965 Update libffi to 3 4 3 gh 96577 Fixes a potential buffer overrun in msilib gh 96559 Fixes the Windows launcher not using the compatible interpretation of default tags found in configuration files when no tag was passed to the command gh 94781 Fix pcbuild proj to clean previous instances of output files in Python deepfreeze and Python frozen_modules directories on Windows Patch by Charlie Zhao gh 89545 Updates platform code getting the Windows version to use native Windows Management Instrumentation WMI queries to determine OS version type and architecture gh 95733 Make certain requirements of the Windows Store package optional,en
1555, to allow installing on earlier updates of Windows gh 95656 Enable the enable_load_extension sqlite3 API gh 95587 Fixes some issues where the Windows installer would incorrectly detect certain features of an existing install when upgrading gh 94399 Restores the behaviour of Python Launcher for Windows for usr bin env shebang lines which will now search PATH for an executable matching the given command If none is found the usual search process is used gh 95445 Fixes the unsuccessful removal of the HTML document directory when uninstalling with Windows msi gh 95359 Fix Python Launcher for Windows handling of py ini commands it was incorrectly expecting a py_ prefix on keys and crashes when reading per user configuration file gh 95285 Fix Python Launcher for Windows handling of command lines where it is only passed a short executable name gh 90844 Allow virtual environments to correctly launch when they have spaces in the path gh 94772 Fix incorrect handling of shebang lines in py exe launcher gh 94018 zipfile will now remove trailing spaces from path components when extracting files on Windows gh 93824 Drag and drop of files onto Python files in Windows Explorer has been enabled for Windows ARM64 gh 43414 os get_terminal_size now attempts to read the size from any provided handle rather than only supporting file descriptors 0 1 and 2 gh 92817 Ensures that py exe will prefer an active virtual environment over default tags specified with environment variables or through a py ini file gh 92984 Explicitly disable incremental linking for non Debug builds gh 92841 asyncio no longer throws RuntimeError Event loop is closed on interpreter exit after asynchronous socket activity Patch by Oleg Iarygin bpo 46907 Update Windows installer to use SQLite 3 38 4 gh 91061 Accept os PathLike for the argument to winsound PlaySound bpo 42658 Support native Windows case insensitive path comparisons by using LCMapStringEx instead of str lower in ntpath normcase Add LCMapStringEx to the _winapi module bpo 38704 Prevent installation on unsupported Windows versions macOS gh 97897 The macOS 13 SDK includes support for the mkfifoat and mknodat system calls Using the dir_fd option with either os mkfifo or os mknod could result in a segfault if cpython is built with the macOS 13 SDK but run on an earlier version of macOS Prevent this by adding runtime support for detection of these system calls weaklinking as is done for other newer syscalls on macOS IDLE gh 97527 Fix a bug in the previous bugfix that caused IDLE to not start when run with 3 10 8 3 12 0a1 and at least Microsoft Python 3 10 2288 0 installed without the Lib test package 3 11 0 was never affected gh 65802 Document handling of extensions in Save As dialogs gh 95191 Include prompts when saving Shell interactive input and output gh 95511 Fix the Shell context menu copy with prompts bug of copying an extra line when one selects whole lines gh 95471 In the Edit menu move Select All and add a new separator gh 95411 Enable using IDLE s module browser with pyw files gh 89610 Add pyi as a recognized extension for IDLE on macOS This allows opening stub files by double clicking on them in the Finder Tools Demos gh 68686 Remove ptags and eptags scripts gh 97681 Remove the Tools demo directory which contained old demo scripts A copy can be found in the old demos project Patch by Victor Stinner gh 97669 Remove outdated example scripts of the Tools scripts directory A copy can be found in the old demos project Patch by Victor Stinner gh 95853 The wasm_build py script now pre builds Emscripten ports checks for broken EMSDK versions and warns about pkg config env vars gh 95853 The new tool Tools wasm wasm_builder py automates configure compile and test steps for building CPython on WebAssembly platforms gh 95731 Fix handling of module docstrings in Tools i18n pygettext py gh 93939 Add script Tools scripts check_modules py to check and validate builtin and shared extension modules The script also handles Modules Setup and will eventually replace setup py gh 94538 Fix Argument Clinic output to custom file ,en
1556,destinations Patch by Erlend E Aasland gh 94430 Allow parameters named module and self with custom C names in Argument Clinic Patch by Erlend E Aasland gh 86087 The Tools scripts parseentities py script used to parse HTML4 entities has been removed C API gh 98393 The PyUnicode_FSDecoder function no longer accepts bytes like paths like bytearray and memoryview types only the exact bytes type is accepted for bytes strings Patch by Victor Stinner gh 91051 Add PyType_Watch and related APIs to allow callbacks on PyType_Modified gh 95756 Lazily create and cache co_ attributes for better performance for code getters gh 96512 Configuration for the integer string conversion length limitation now lives in the PyConfig C API struct gh 95589 Extensions classes that set tp_dictoffset and tp_weaklistoffset lose the support for multiple inheritance but are now safe Extension classes should use Py_TPFLAGS_MANAGED_DICT and Py_TPFLAGS_MANAGED_WEAKREF instead gh 95781 An unrecognized format character in PyUnicode_FromFormat and PyUnicode_FromFormatV now sets a SystemError In previous versions it caused all the rest of the format string to be copied as is to the result string and any extra arguments discarded gh 92678 Restore the 3 10 behavior for multiple inheritance of C extension classes that store their dictionary at the end of the struct gh 92678 Support C extensions using managed dictionaries by setting the Py_TPFLAGS_MANAGED_DICT flag gh 93274 API for implementing vectorcall Py_TPFLAGS_HAVE_VECTORCALL PyVectorcall_NARGS and PyVectorcall_Call was added to the limited API and stable ABI gh 95504 Fix sign placement when specifying width or precision in PyUnicode_FromFormat and PyUnicode_FromFormatV Patch by Philip Georgi gh 93012 The Py_TPFLAGS_HAVE_VECTORCALL flag is now removed from a class when the class s __call__ method is reassigned This makes vectorcall safe to use with mutable types i e heap types without the immutable flag Mutable types that do not override tp_call now inherit the Py_TPFLAGS_HAVE_VECTORCALL flag gh 95388 Creating immutable types with mutable bases is deprecated and is planned to be disabled in Python 3 14 gh 92678 Adds unstable C API functions _PyObject_VisitManagedDict and _PyObject_ClearManagedDict to allow C extensions to allow the VM to manage their object s dictionaries gh 94936 Added PyCode_GetVarnames PyCode_GetCellvars and PyCode_GetFreevars for accessing co_varnames co_cellvars and co_freevars respectively via the C API gh 94930 Fix SystemError raised when PyArg_ParseTupleAndKeywords is used with in but without PY_SSIZE_T_CLEAN defined gh 94731 Python again uses C style casts for most casting operations when compiled with C This may trigger compiler warnings if they are enabled with e g Wold style cast or Wzero as null pointer constant options for g gh 93937 The following frame functions and type are now directly available with include Python h it s no longer needed to add include frameobject h PyFrame_Check PyFrame_GetBack PyFrame_GetBuiltins PyFrame_GetGenerator PyFrame_GetGlobals PyFrame_GetLasti PyFrame_GetLocals PyFrame_Type Patch by Victor Stinner gh 91321 Fix the compatibility of the Python C API with C older than C 11 Patch by Victor Stinner gh 91731 Avoid defining the static_assert when compiling with C 11 where this is a keyword and redefining it can lead to undefined behavior Patch by Pablo Galindo gh 89546 PyType_FromMetaclass and other PyType_From functions now check that offsets and the base class s tp_basicsize fit in the new class s tp_basicsize gh 93503 Add two new public functions to the public C API PyEval_SetProfileAllThreads and PyEval_SetTraceAllThreads that allow to set tracing and profiling functions in all running threads in addition to the calling one Also two analogous functions to the threading module threading setprofile_all_threads and threading settrace_all_threads that allow to do the same from Python Patch by Pablo Galindo gh 93442 Add C overloads for _Py_CAST_impl to handle 0 NULL This will allow C extensions that pass 0 or NULL to macros using _Py_CAST to continue to ,en
1557,compile gh 93466 Slot IDs in PyType_Spec may not be repeated The documentation was updated to mention this For some cases of repeated slots PyType_FromSpec and related functions will now raise an exception gh 92898 Fix C compiler warnings when casting function arguments to PyObject Patch by Serge Guelton gh 93103 Deprecate global configuration variables like Py_IgnoreEnvironmentFlag in the documentation the Py_InitializeFromConfig API should be instead Patch by Victor Stinner gh 77782 Deprecate global configuration variable like Py_IgnoreEnvironmentFlag the Py_InitializeFromConfig API should be instead Patch by Victor Stinner gh 92913 Ensures changes to PyConfig module_search_paths are ignored unless PyConfig module_search_paths_set is set gh 92781 Avoid mixing declarations and code in the C API to fix the compiler warning ISO C90 forbids mixed declarations and code Werror declaration after statement Patch by Victor Stinner gh 92651 Remove the token h header file There was never any public tokenizer C API The token h header file was only designed to be used by Python internals Patch by Victor Stinner gh 92536 Remove legacy Unicode APIs based on Py_UNICODE gh 85858 Remove the PyUnicode_InternImmortal function and the SSTATE_INTERNED_IMMORTAL macro Patch by Victor Stinner gh 92193 Add new function PyFunction_SetVectorcall to the C API which sets the vectorcall field of a given PyFunctionObject Warning extensions using this API must preserve the behavior of the unaltered function gh 59121 Fixed an assert that prevented PyRun_InteractiveOne from providing tracebacks when parsing from the provided FD bpo 45383 The PyType_FromSpec API will now find and use a metaclass based on the provided bases An error will be raised if there is a metaclass conflict Python 3 11 0 beta 1 Release date 2022 05 06 Security gh 57684 Add the P command line option and the PYTHONSAFEPATH environment variable to not prepend a potentially unsafe path to sys path Patch by Victor Stinner Core and Builtins gh 89519 Chaining classmethod descriptors introduced in bpo 19072 is deprecated It can no longer be used to wrap other descriptors such as property The core design of this feature was flawed and it caused a number of downstream problems gh 92345 pymain_run_python now imports readline and rlcompleter before sys path is extended to include the current working directory of an interactive interpreter Non interactive interpreters are not affected bpo 43857 Improve the AttributeError message when deleting a missing attribute Patch by Géry Ogam gh 92245 Make sure that PEP 523 is respected in all cases In 3 11a7 specialization may have prevented Python to Python calls respecting PEP 523 gh 92203 Add a closure keyword only parameter to exec It can only be specified when exec ing a code object that uses free variables When specified it must be a tuple with exactly the number of cell variables referenced by the code object closure has a default value of None and it must be None if the code object doesn t refer to any free variables gh 91173 Disable frozen modules in debug builds Patch by Kumar Aditya gh 92114 Improve error message when subscript a type with __class_getitem__ set to None gh 92112 Fix crash triggered by an evil custom mro on a metaclass gh 92063 The PRECALL_METHOD_DESCRIPTOR_FAST_WITH_KEYWORDS instruction now ensures methods are called only on objects of the correct type gh 92031 Deoptimize statically allocated code objects during Py_FINALIZE so that future _PyCode_Quicken calls always start with unquickened code gh 92036 Fix a crash in subinterpreters related to the garbage collector When a subinterpreter is deleted untrack all objects tracked by its GC To prevent a crash in deallocator functions expecting objects to be tracked by the GC leak a strong reference to these objects on purpose so they are never deleted and their deallocator functions are not called Patch by Victor Stinner gh 92032 The interpreter can now autocomplete soft keywords as of now match case and _ wildcard pattern from PEP 634 gh 87999 The warning emitted by the Python parser,en
1558, for a numeric literal immediately followed by keyword has been changed from deprecation warning to syntax warning gh 91869 Fix an issue where specialized opcodes with extended arguments could produce incorrect tracing output or lead to assertion failures gh 91603 Speed up types UnionType instantiation Based on patch provided by Yurii Karabas gh 89373 If Python is built in debug mode Python now ensures that deallocator functions leave the current exception unchanged Patch by Victor Stinner gh 91632 Fix a minor memory leak at exit release the memory of the generic_alias_iterator type Patch by Donghee Na gh 81548 Octal escapes with value larger than 0o377 now produce a DeprecationWarning In a future Python version they will be a SyntaxWarning and eventually a SyntaxError bpo 43950 Use a single compact table for line starts ends and column offsets Reduces memory consumption for location info by half gh 91102 Use Argument Clinic for EncodingMap Patch by Oleg Iarygin gh 91636 Fixed a crash in a garbage collection edge case in which a PyFunction_Type tp_clear function could leave a python function object in an inconsistent state gh 91603 Speed up isinstance and issubclass checks for types UnionType Patch by Yurii Karabas gh 91625 Fixed a bug in which adaptive opcodes ignored any preceding EXTENDED_ARG s on specialization failure gh 78607 The LLTRACE special build now looks for the name __lltrace__ defined in module globals rather than the name __ltrace__ which had been introduced as a typo gh 91576 Speed up iteration of ascii strings by 50 Patch by Kumar Aditya gh 89279 Improve interpreter performance on Windows by inlining a few specific macros gh 91502 Add a new _PyFrame_IsEntryFrame API function to check if a PyFrameObject is an entry frame Patch by Pablo Galindo gh 91266 Refactor the bytearray strip methods strip lstrip and rstrip to use a common implementation gh 91479 Replaced the __note__ field of BaseException added in an earlier version of 3 11 with the final design of PEP 678 Namely BaseException gets an add_note method and its __notes__ field is created when necessary gh 46055 Speed up right shift of negative integers by removing unnecessary creation of temporaries Original patch by Xinhang Xu reworked by Mark Dickinson gh 91462 Make the interpreter s low level tracing lltrace feature output more readable by displaying opcode names rather than just numbers and by displaying stack contents before each opcode gh 89455 Fixed an uninitialized bool value in the traceback printing code path that was introduced by the initial bpo 45292 exception groups work gh 91421 Fix a potential integer overflow in _Py_DecodeUTF8Ex gh 91428 Add static const char const _PyOpcode_OpName 256 to opcode h for debug builds to assist in debugging the Python interpreter It is now more convenient to make various forms of debugging output more human readable by including opcode names rather than just the corresponding decimal digits bpo 47120 Make POP_JUMP_IF_TRUE POP_JUMP_IF_FALSE POP_JUMP_IF_NONE and POP_JUMP_IF_NOT_NONE virtual mapping to new relative jump opcodes bpo 45317 Add internal documentation explaining design of new for 3 11 frame stack bpo 47197 ctypes used to mishandle void return types so that for instance a function declared like ctypes CFUNCTYPE None ctypes c_int would be called with signature int f int instead of void f int Wasm targets require function pointers to be called with the correct signatures so this led to crashes The problem is now fixed bpo 47120 Make opcodes JUMP_IF_TRUE_OR_POP and JUMP_IF_FALSE_OR_POP relative rather than absolute bpo 47177 Replace the f_lasti member of the internal _PyInterpreterFrame structure with a prev_instr pointer which reduces overhead in the main interpreter loop The f_lasti attribute of Python layer frame objects is preserved for backward compatibility bpo 46961 Integer mod remainder operations including the three argument form of pow now consistently return ints from the global small integer cache when applicable bpo 46962 Classes and functions that unconditionally declared their docstr,en
1559,ings ignoring the without doc strings compilation flag no longer do so The classes affected are ctypes UnionType pickle PickleBuffer testcapi RecursingInfinitelyError and types GenericAlias The functions affected are 24 methods in ctypes Patch by Oleg Iarygin bpo 46942 Use Argument Clinic for the types MethodType constructor Patch by Oleg Iarygin bpo 46764 Fix wrapping bound methods with classmethod bpo 43464 Optimize set intersection for non set arguments bpo 46721 Optimize set issuperset for non set argument bpo 46509 Add type specialized versions of the Py_DECREF and use them for float int str bool and None to avoid pointer chasing at runtime where types are known at C compile time bpo 46045 Do not use POSIX semaphores on NetBSD bpo 36819 Fix crashes in built in encoders with error handlers that return position less or equal than the starting position of non encodable characters bpo 34093 marshal dumps uses FLAG_REF for all interned strings This makes output more deterministic and helps reproducible build bpo 26579 Added object __getstate__ which provides the default implementation of the __getstate__ method Copying and pickling instances of subclasses of builtin types bytearray set frozenset collections OrderedDict collections deque weakref WeakSet and datetime tzinfo now copies and pickles instance attributes implemented as slots Library gh 87901 Add the encoding parameter to os popen gh 90997 Fix an issue where dis utilities may interpret populated inline cache entries as valid instructions gh 92332 Deprecate typing Text removal of the class is currently not planned Patch by Alex Waygood Deprecate nested classes in enum definitions becoming members in 3 13 they will be normal classes add member and nonmember functions to allow control over results now gh 92356 Fixed a performance regression in ctypes function calls gh 90997 Show the actual named values stored in inline caches when show_caches True is passed to dis utilities gh 92301 Prefer close_range to iterating over procfs for file descriptor closing in subprocess for better performance gh 67248 Sort the miscellaneous topics in Cmd do_help gh 92210 Port socket __init__ to Argument Clinic Patch by Cinder gh 80010 Add support for generalized ISO 8601 parsing to datetime datetime fromisoformat datetime date fromisoformat and datetime time fromisoformat Patch by Paul Ganssle gh 92118 Fix a 3 11 regression in contextmanager which caused it to propagate exceptions with incorrect tracebacks gh 90887 Adding COPYFILE_STAT COPYFILE_ACL and COPYFILE_XATTR constants for os fcopyfile available in macOs gh 91215 For dataclass add weakref_slot Default is False If True and if slots True add a slot named __weakref__ which will allow instances to be weakref d Contributed by Eric V Smith gh 85984 New function os login_tty for Unix gh 92128 Add __class_getitem__ to logging LoggerAdapter and logging StreamHandler allowing them to be parameterized at runtime Patch by Alex Waygood gh 92049 Forbid pickling constants re _constants SUCCESS etc Previously pickling did not fail but the result could not be unpickled gh 92062 inspect Parameter now raises ValueError if name is a keyword in addition to the existing check that it is an identifier gh 87390 Add an __unpacked__ attribute to types GenericAlias Patch by Jelle Zijlstra gh 88089 Add support for generic typing NamedTuple gh 91996 New http HTTPMethod enum to represent all the available HTTP request methods in a convenient way gh 91984 Modified test strings in test_argparse py to not contain trailing spaces before end of line gh 91952 Add encoding locale support to TextIOWrapper reconfigure gh 91954 Add encoding and errors arguments to subprocess getoutput and subprocess getstatusoutput bpo 47029 Always close the read end of the pipe used by multiprocessing Queue after the last write of buffered data to the write end of the pipe to avoid BrokenPipeError at garbage collection and at multiprocessing Queue close calls Patch by Géry Ogam gh 91928 Add datetime UTC alias for datetime timezone utc Patch by Kabir Kwatra gh 68966 The mailcap modu,en
1560,le is now deprecated and will be removed in Python 3 13 See PEP 594 for the rationale and the mimetypes module for an alternative Patch by Victor Stinner gh 91401 Provide a way to disable subprocess use of vfork just in case it is ever needed and document the existing mechanism for posix_spawn gh 64783 Fix signal NSIG value on FreeBSD to accept signal numbers greater than 32 like signal SIGRTMIN and signal SIGRTMAX Patch by Victor Stinner gh 91910 Add missing f prefix to f strings in error messages from the multiprocessing and asyncio modules gh 91860 Add typing dataclass_transform implementing PEP 681 Patch by Jelle Zijlstra gh 91832 Add required attribute to argparse Action repr output gh 91827 In the tkinter module add method info_patchlevel which returns the exact version of the Tcl library as a named tuple similar to sys version_info gh 84461 Add enable wasm pthreads to enable pthreads support for WASM builds Emscripten node no longer has threading enabled by default Include additional file systems gh 91821 Fix unstable test_from_tuple test in test_decimal py gh 91217 Deprecate the xdrlib module gh 91217 Deprecate the uu module gh 91760 More strict rules will be applied for numerical group references and group names in regular expressions For now a deprecation warning is emitted for group references and group names which will be errors in future Python versions gh 84461 Add provisional sys _emscripten_info named tuple with build time and run time information about Emscripten platform gh 90623 signal raise_signal and os kill now check immediately for pending signals Patch by Victor Stinner gh 91734 Fix OSS audio support on Solaris gh 90633 Include the passed value in the exception thrown by typing assert_never Patch by Jelle Zijlstra gh 91700 Compilation of regular expression containing a conditional expression group now raises an appropriate re error if the group number refers to not defined group Previously an internal RuntimeError was raised gh 91231 Add an optional keyword shutdown_timeout parameter to the multiprocessing BaseManager constructor Kill the process if terminate takes longer than the timeout Patch by Victor Stinner gh 91621 Fix typing get_type_hints for collections abc Callable Patch by Shantanu Jain gh 90568 Parsing N escapes of Unicode Named Character Sequences in a regular expression raises now re error instead of TypeError gh 91670 Remove deprecated SO config variable in sysconfig gh 91217 Deprecate the telnetlib module gh 91217 Deprecate the sunau module gh 91217 Deprecate the spwd module gh 91217 Deprecate the sndhdr module as well as inline needed functionality for email mime MIMEAudio gh 91616 re module fix fullmatch mismatch when using Atomic Grouping or Possessive Quantifiers gh 91217 Deprecate the pipes module gh 91217 Deprecate the ossaudiodev module bpo 47256 re module limit the maximum capturing group to 1 073 741 823 in 64 bit build this increases the depth of backtracking gh 91217 Deprecate the nis module gh 91595 Fix the comparison of character and integer inside Tools gdb libpython write_repr Patch by Yu Liu gh 74166 Add option to raise all errors from create_connection in an ExceptionGroup when it fails to create a connection The default remains to raise only the last error that had occurred when multiple addresses were tried gh 91487 Optimize asyncio UDP speed over 100 times faster when transferring a large file gh 91575 Update case insensitive matching in the re module to the latest Unicode version gh 90622 In concurrent futures process ProcessPoolExecutor disallow the fork multiprocessing start method when the new max_tasks_per_child feature is used as the mix of threads fork can hang the child processes Default to using the safe spawn start method in that circumstance if no mp_context was supplied gh 89022 In sqlite3 SQLITE_MISUSE result codes are now mapped to InterfaceError instead of ProgrammingError Also more accurate exceptions are raised when binding parameters fail Patch by Erlend E Aasland gh 91526 Stop calling os device_encoding file fileno in TextIOWrapper It was comp,en
1561,lex never documented and didn t work for most cases Patch by Inada Naoki gh 88116 Change the frame related functions in the inspect module to return a regular object that is backwards compatible with the old tuple like interface that include the extended PEP 657 position information end line number column and end column The affected functions are inspect getframeinfo inspect getouterframes inspect getinnerframes inspect stack and inspect trace Patch by Pablo Galindo gh 69093 Add indexing and slicing support to sqlite3 Blob Patch by Aviv Palivoda and Erlend E Aasland gh 69093 Add context manager support to sqlite3 Blob Patch by Aviv Palivoda and Erlend E Aasland gh 91217 Deprecate nntplib gh 91217 Deprecate msilib gh 91404 Improve the performance of re matching by using computed gotos or threaded code on supported platforms and removing expensive pointer indirections gh 91217 Deprecate the imghdr module gh 91217 Deprecate the crypt module gh 91276 Make space for longer opcodes in dis output bpo 47000 Make TextIOWrapper uses locale encoding when encoding locale is specified even in UTF 8 mode gh 91230 warnings catch_warnings now accepts arguments for warnings simplefilter providing a more concise way to locally ignore warnings or convert them to errors gh 91217 Deprecate the chunk module Add the TCP_CONNECTION_INFO option available on macOS to socket bpo 47260 Fix os closerange potentially being a no op in a Linux seccomp sandbox bpo 47087 Implement typing Required and typing NotRequired PEP 655 Patch by David Foster and Jelle Zijlstra bpo 47061 Deprecate cgi and cgitb bpo 47061 Deprecate audioop bpo 47000 Add locale getencoding to get the current locale encoding It is similar to locale getpreferredencoding False but ignores the Python UTF 8 Mode bpo 42012 Add wsgiref types containing WSGI specific types for static type checking bpo 47227 Suppress expression chaining for more re parsing errors bpo 47211 Remove undocumented and never working function re template and flag re TEMPLATE This was later reverted in 3 11 0b2 and deprecated instead bpo 47135 decimal localcontext now accepts context attributes via keyword arguments bpo 43323 Fix errors in the email module if the charset itself contains undecodable unencodable characters bpo 46841 Disassembly of quickened code bpo 46681 Forward gzip compress compresslevel to zlib bpo 45100 Add typing get_overloads and typing clear_overloads Patch by Jelle Zijlstra bpo 44807 typing Protocol no longer silently replaces __init__ methods defined on subclasses Patch by Adrian Garcia Badaracco bpo 46787 Fix concurrent futures ProcessPoolExecutor exception memory leak bpo 46720 Add support for path like objects to multiprocessing set_executable for Windows to be on a par with Unix like systems Patch by Géry Ogam bpo 46696 Add SO_INCOMING_CPU constant to socket bpo 46053 Fix OSS audio support on NetBSD bpo 45639 image avif and image webp were added to mimetypes bpo 46285 Add command line option p protocol to module http server which specifies the HTTP version to which the server is conformant HTTP 1 1 conformant servers can now be run from the command line interface of module http server Patch by Géry Ogam bpo 44791 Accept ellipsis as the last argument of typing Concatenate bpo 46547 Remove variables leaking into pydoc Helper class namespace bpo 46415 Fix ipaddress ip_ address interface network raising TypeError instead of ValueError if given invalid tuple as address parameter bpo 46075 CookieJar with DefaultCookiePolicy now can process cookies from localhost with domain localhost explicitly specified in Set Cookie header bpo 45995 Add a z option to the string formatting specification that coerces negative zero floating point values to positive zero after rounding to the format precision Contributed by John Belmonte bpo 26175 Fully implement the io BufferedIOBase or io TextIOBase interface for tempfile SpooledTemporaryFile objects This lets them work correctly with higher level layers like compression modules Patch by Carey Metcalfe bpo 45138 Fix a regression in the sqlite3 trace callback wh,en
1562,ere bound parameters were not expanded in the passed statement string The regression was introduced in Python 3 10 by bpo 40318 Patch by Erlend E Aasland bpo 44863 Allow TypedDict subclasses to also include Generic as a base class in class based syntax Thereby allowing the user to define a generic TypedDict just like a user defined generic but with TypedDict semantics bpo 44587 Fix BooleanOptionalAction to not automatically add a default string If a default string is desired use a formatter to add it bpo 43827 All positional or keyword parameters to ABCMeta __new__ are now positional only to avoid conflicts with keyword arguments to be passed to __init_subclass__ bpo 43218 Prevent creation of a venv whose path contains the PATH separator This could affect the usage of the activate script Patch by Dustin Rodrigues bpo 38435 Add a process_group parameter to subprocess Popen to help move more things off of the unsafe preexec_fn parameter bpo 42066 Fix cookies getting sorted in CookieJar __iter__ which is an extra behavior and not mentioned in RFC 2965 or Netscape cookie protocol Now the cookies in CookieJar follows the order of the Set Cookie header Patch by Iman Kermani bpo 40617 Add create_window_function to sqlite3 Connection for creating aggregate window functions Patch by Erlend E Aasland bpo 40676 Convert csv to use Argument Clinic for csv field_size_limit csv get_dialect csv unregister_dialect and csv list_dialects bpo 39716 Raise an ArgumentError when the same subparser name is added twice to an argparse ArgumentParser This is consistent with the default behavior when the same option string is added twice to an ArgumentParser bpo 36073 Raise ProgrammingError instead of segfaulting on recursive usage of cursors in sqlite3 converters Patch by Sergey Fedoseev bpo 34975 Adds a start_tls method to StreamWriter which upgrades the connection with TLS using the given SSLContext bpo 22276 Path methods glob and rglob return only directories if pattern ends with a pathname components separator or sep Patch by Eisuke Kawashima bpo 24905 Add blobopen to sqlite3 Connection sqlite3 Blob allows incremental I O operations on blobs Patch by Aviv Palivoda and Erlend E Aasland Documentation gh 91888 Add a new gh role to the documentation to link to GitHub issues gh 91783 Document security issues concerning the use of the function shutil unpack_archive gh 91547 Remove Undocumented modules page gh 91298 In importlib resources abc refined the documentation of the Traversable Protocol applying changes from importlib_resources 5 7 1 bpo 44347 Clarify the meaning of dirs_exist_ok a kwarg of shutil copytree bpo 36329 Remove make C Doc serve in favour of make C Doc htmlview bpo 47189 Add a What s New in Python 3 11 entry for the Faster CPython project Documentation by Ken Jin and Kumar Aditya bpo 38668 Update the introduction to documentation for os path to remove warnings that became irrelevant after the implementations of PEP 383 and PEP 529 bpo 47115 The documentation now lists which members of C structs are part of the Limited API Stable ABI bpo 46962 All docstrings in code snippets are now wrapped into PyDoc_STR to follow the guideline of PEP 7 s Documentation Strings paragraph Patch by Oleg Iarygin bpo 26792 Improve the docstrings of runpy run_module and runpy run_path Original patch by Andrew Brezovsky Tests gh 92169 Use warnings_helper import_deprecated to import deprecated modules uniformly in tests Patch by Hugo van Kemenade gh 84461 When multiprocessing is enabled libregrtest can now use a Python executable other than sys executable via the python flag gh 91904 Fix initialization of PYTHONREGRTEST_UNICODE_GUARD which prevented running regression tests on non UTF 8 locale gh 91752 Added requires_zlib to test test_tools test_freeze TestFreeze gh 91607 Fix test_concurrent_futures to test the correct multiprocessing start method context in several cases where the test logic mixed this up bpo 40280 Threading tests are now skipped on WASM targets without pthread support bpo 47109 Test for ctypes macholib dyld ctypes macholib dylib and cty,en
1563,pes macholib framework are brought from manual pre unittest times to ctypes test location and structure Patch by Oleg Iarygin bpo 29890 Add tests for ipaddress IPv4Interface and ipaddress IPv6Interface construction with tuple arguments Original patch and tests by louisom Build gh 89452 gdbm compat is now preferred over ndbm if both are available on the system This allows avoiding the problematic ndbm h on macOS gh 91731 Python is now built with std c11 compiler option rather than std c99 Patch by Victor Stinner bpo 47152 Add script and make target for generating sre_constants h bpo 47103 Windows PGInstrument builds now copy a required DLL into the output directory making it easier to run the profile stage of a PGO build Windows bpo 46907 Update Windows installer to use SQLite 3 38 3 bpo 47239 Fixed list and list paths output for Python Launcher for Windows when used in an active virtual environment bpo 46907 Update Windows installer to use SQLite 3 38 2 bpo 46785 Fix race condition between os stat and unlinking a file on Windows by using errors codes returned by FindFirstFileW when appropriate in win32_xstat_impl bpo 40859 Update Windows build to use xz 5 2 5 macOS bpo 46907 Update macOS installer to SQLite 3 38 4 Tools Demos gh 91583 Fix regression in the code generated by Argument Clinic for functions with the defining_class parameter gh 91575 Add script Tools scripts generate_re_casefix py and the make target regen re for generating additional data for case insensitive matching according to the current Unicode version gh 91551 Remove the ancient Pynche color editor It has moved to https gitlab com warsaw pynche C API gh 88279 Deprecate the C functions PySys_SetArgv PySys_SetArgvEx PySys_SetPath Patch by Victor Stinner gh 92154 Added the PyCode_GetCode function This function does the equivalent of the Python code getattr code_object co_code gh 92173 Fix the closure argument to PyEval_EvalCodeEx gh 91320 Fix C compiler warnings about old style cast g Wold style cast in the Python C API Use C reinterpret_cast and static_cast casts when the Python C API is used in C Patch by Victor Stinner gh 80527 Mark functions as deprecated by PEP 623 PyUnicode_AS_DATA PyUnicode_AS_UNICODE PyUnicode_GET_DATA_SIZE PyUnicode_GET_SIZE Patch by Victor Stinner gh 91768 Py_REFCNT Py_TYPE Py_SIZE and Py_IS_TYPE functions argument type is now PyObject rather than const PyObject Patch by Victor Stinner gh 91020 Add PyBytes_Type tp_alloc to initialize PyBytesObject ob_shash for bytes subclasses bpo 40421 Add PyFrame_GetLasti C API function to access frame object s f_lasti attribute safely from C code bpo 35134 Remove the Include code h header file C extensions should only include the main Python h header file Patch by Victor Stinner bpo 47169 PyOS_CheckStack is now exported in the Stable ABI on Windows bpo 47169 PyThread_get_thread_native_id is excluded from the stable ABI on platforms where it doesn t exist like Solaris bpo 46343 Added PyErr_GetHandledException and PyErr_SetHandledException as simpler alternatives to PyErr_GetExcInfo and PyErr_SetExcInfo They are included in the stable ABI Python 3 11 0 alpha 7 Release date 2022 04 05 Core and Builtins bpo 47212 Raise IndentationError instead of SyntaxError for a bare except with no following indent Improve SyntaxError locations for an un parenthesized generator used as arguments Patch by Matthieu Dartiailh bpo 47186 Replace JUMP_IF_NOT_EG_MATCH by CHECK_EG_MATCH jump bpo 47176 Emscripten builds cannot handle signals in the usual way due to platform limitations Python can now handle signals To use set Module Py_EmscriptenSignalBuffer to be a single byte SharedArrayBuffer and set Py_EMSCRIPTEN_SIGNAL_HANDLING to 1 Writing a number into the SharedArrayBuffer will cause the corresponding signal to be raised into the Python thread bpo 47186 Replace JUMP_IF_NOT_EXC_MATCH by CHECK_EXC_MATCH jump bpo 47120 Replace the absolute jump opcode JUMP_NO_INTERRUPT by the relative JUMP_BACKWARD_NO_INTERRUPT bpo 46841 Avoid unnecessary allocations when comparing code objects bpo 47182 Fix a crash when using a n,en
1564,amed unicode character like N digit nine after the main interpreter has been initialized a second time bpo 47162 WebAssembly cannot deal with bad function pointer casts different count or types of arguments Python can now use call trampolines to mitigate the problem Define PY_CALL_TRAMPOLINE to enable call trampolines bpo 46775 Some Windows system error codes 10000 are now mapped into the correct errno and may now raise a subclass of OSError Patch by Donghee Na bpo 47129 Improve error messages in f string syntax errors concerning empty expressions bpo 47117 Fix a crash if we fail to decode characters in interactive mode if the tokenizer buffers are uninitialized Patch by Pablo Galindo bpo 47127 Speed up calls to c functions with keyword arguments by 25 with specialization Patch by Kumar Aditya bpo 47120 Replaced JUMP_ABSOLUTE by the relative jump JUMP_BACKWARD bpo 42197 PyFrame_FastToLocalsWithError and PyFrame_LocalsToFast are no longer called during profiling nor tracing C code can access the f_locals attribute of PyFrameObject by calling PyFrame_GetLocals bpo 47070 Improve performance of array_inplace_repeat by reducing the number of invocations of memcpy Refactor the repeat and inplace repeat methods of array bytes bytearray and unicodeobject to use the common _PyBytes_Repeat bpo 47053 Reduce de optimization in the specialized BINARY_OP_INPLACE_ADD_UNICODE opcode bpo 47045 Remove the f_state field from the _PyInterpreterFrame struct Add the owner field to the _PyInterpreterFrame struct to make ownership explicit to simplify clearing and deallocing frames and generators bpo 46968 Check for the existence of the sys auxv h header in faulthandler to avoid compilation problems in systems where this header doesn t exist Patch by Pablo Galindo bpo 46329 Use low bit of LOAD_GLOBAL to indicate whether to push a NULL before the global Helps streamline the call sequence a bit bpo 46841 Quicken bytecode in place by storing it as part of the corresponding PyCodeObject bpo 47012 Speed up iteration of bytes and bytearray by 30 Patch by Kumar Aditya bpo 47009 Improved the performance of list append and list comprehensions by optimizing for the common case where no resize is needed Patch by Dennis Sweeney bpo 47005 Improve performance of bytearray_repeat and bytearray_irepeat by reducing the number of invocations of memcpy bpo 46829 Deprecate passing a message into asyncio Future cancel and asyncio Task cancel bpo 46993 Speed up bytearray creation from list and tuple by 40 Patch by Kumar Aditya bpo 39829 Removed the __len__ call when initializing a list and moved initializing to list_extend Patch by Jeremiah Pascual bpo 46944 Speed up throwing exception in generator with METH_FASTCALL calling convention Patch by Kumar Aditya bpo 46841 Modify STORE_SUBSCR to use an inline cache entry rather than its oparg as an adaptive counter bpo 46841 Use inline caching for PRECALL and CALL and remove the internal machinery for managing the now unused non inline caches bpo 46881 Statically allocate and initialize the latin1 characters bpo 46838 Improve syntax errors for incorrect function definitions Patch by Pablo Galindo bpo 43721 Fix docstrings of getter setter and deleter to clarify that they create a new copy of the property bpo 43224 Make grammar changes required for PEP 646 Library bpo 47208 Allow vendors to override CTYPES_MAX_ARGCOUNT bpo 23689 re module fix memory leak when a match is terminated by a signal or memory allocation failure Patch by Ma Lin bpo 47167 Allow overriding a future compliance check in asyncio Task bpo 47151 When subprocess tries to use vfork it now falls back to fork if vfork returns an error This allows use in situations where vfork isn t allowed by the OS kernel bpo 47152 Convert the re module into a package Deprecate modules sre_compile sre_constants and sre_parse bpo 4833 Add ZipFile mkdir bpo 27929 Fix asyncio loop sock_connect to only resolve names for socket AF_INET or socket AF_INET6 families Resolution may not make sense for other families like socket AF_BLUETOOTH and socket AF_UNIX bpo 14265 Adds the fully ,en
1565,qualified test name to unittest output bpo 47061 Deprecate the aifc module bpo 39622 Handle Ctrl C in asyncio programs to interrupt the main task bpo 47101 hashlib algorithms_available now lists only algorithms that are provided by activated crypto providers on OpenSSL 3 0 Legacy algorithms are not listed unless the legacy provider has been loaded into the default OSSL context bpo 47099 All URLError exception messages raised in urllib request URLopener now contain a colon between ftp error and the rest of the message Previously open_ftp missed the colon Patch by Oleg Iarygin bpo 47099 Exception chaining is changed from Exception with_traceback sys exc_info to PEP 3134 Patch by Oleg Iarygin bpo 47095 hashlib s internal _blake2 module now prefers libb2 from https www blake2 net over Python s vendored copy of blake2 bpo 47098 The Keccak Code Package for hashlib s internal _sha3 module has been replaced with tiny_sha3 The module is used as fallback when Python is built without OpenSSL bpo 47088 Implement typing LiteralString part of PEP 675 Patch by Jelle Zijlstra bpo 42885 Optimize re search re split re findall re finditer and re sub for regular expressions starting with A or bpo 23691 Protect the re finditer iterator from re entering bpo 47067 Optimize calling GenericAlias objects by using PEP 590 vectorcall and by replacing PyObject_SetAttrString with PyObject_SetAttr bpo 28080 Add the metadata_encoding parameter in the zipfile ZipFile constructor and the metadata encoding option in the zipfile CLI to allow reading zipfiles using non standard codecs to encode the filenames within the archive bpo 47000 Make io text_encoding returns utf 8 when UTF 8 mode is enabled bpo 42369 Fix thread safety of zipfile _SharedFile tell to avoid a zipfile BadZipFile Bad CRC 32 for file exception when reading a ZipFile from multiple threads bpo 38256 Fix binascii crc32 when it is compiled to use zlib c crc32 to work properly on inputs 4 GiB in length instead of returning the wrong result The workaround prior to this was to always feed the function data in increments smaller than 4GiB or to just call the zlib module function We also have binascii crc32 release the GIL when computing on larger inputs as zlib crc32 and hashlib do This also boosts performance on Windows as it now uses the zlib crc32 implementation for binascii crc32 for a 2 3x speedup That the stdlib has a crc32 API in two modules is a known historical oddity This moves us closer to a single implementation behind them bpo 47066 Global inline flags e g i can now only be used at the start of the regular expressions Using them not at the start of expression was deprecated since Python 3 6 bpo 39394 A warning about inline flags not at the start of the regular expression now contains the position of the flag bpo 433030 Add support of atomic grouping and possessive quantifiers m n in regular expressions bpo 47062 Implement asyncio Runner context manager bpo 46382 dataclass slots True now correctly omits slots already defined in base classes Patch by Arie Bovenberg bpo 47057 Use FASTCALL convention for FutureIter throw bpo 47061 Deprecate the various modules listed by PEP 594 aifc asynchat asyncore audioop cgi cgitb chunk crypt imghdr msilib nntplib nis ossaudiodev pipes smtpd sndhdr spwd sunau telnetlib uu xdrlib bpo 34790 Remove passing coroutine objects to asyncio wait bpo 47039 Normalize repr of asyncio future and task objects bpo 2604 Fix bug where doctests using globals would fail when run multiple times bpo 45150 Add hashlib file_digest helper for efficient hashing of file object bpo 34861 Made cumtime the default sorting key for cProfile bpo 45997 Fix asyncio Semaphore re aquiring FIFO order bpo 47022 The asynchat asyncore and smtpd modules have been deprecated since at least Python 3 6 Their documentation and deprecation warnings and have now been updated to note they will removed in Python 3 12 PEP 594 bpo 43253 Fix a crash when closing transports where the underlying socket handle is already invalid on the Proactor event loop bpo 40280 select select now passes NULL to select,en
1566, for each empty fdset bpo 47004 Apply bugfixes from importlib_metadata 4 11 3 including bugfix for EntryPoint extras which was returning match objects and not the extras strings bpo 46998 Allow subclassing of typing Any Patch by Shantanu Jain bpo 46995 Deprecate missing asyncio Task set_name for third party task implementations schedule making it mandatory in Python 3 13 bpo 46994 Accept explicit contextvars Context in asyncio create_task and asyncio loop create_task bpo 46981 typing get_args typing Tuple now returns instead of bpo 46968 Add os sysconf_names SC_MINSIGSTKSZ bpo 46985 Upgrade pip wheel bundled with ensurepip pip 22 0 4 bpo 46968 faulthandler On Linux 5 14 and newer dynamically determine size of signal handler stack size CPython allocates using getauxval AT_MINSIGSTKSZ This changes allows for Python extension s request to Linux kernel to use AMX_TILE instruction set on Sapphire Rapids Xeon processor to succeed unblocking use of the ISA in frameworks bpo 46917 The math nan value is now always available Patch by Victor Stinner bpo 46955 Expose asyncio base_events Server as asyncio Server Patch by Stefan Zabka bpo 23325 The signal module no longer assumes that SIG_IGN and SIG_DFL are small int singletons bpo 46932 Update bundled libexpat to 2 4 7 bpo 46933 The pwd module is now optional os path expanduser returns the path when the pwd module is not available bpo 40059 PEP 680 the tomllib module Adds support for parsing TOML bpo 464471 asyncio timeout and asyncio timeout_at context managers added Patch by Tin Tvrtković and Andrew Svetlov bpo 46805 Added raw datagram socket functions for asyncio sock_sendto sock_recvfrom and sock_recvfrom_into bpo 46644 No longer require valid typeforms to be callable This allows typing Annotated to wrap typing ParamSpecArgs and dataclasses InitVar Patch by Gregory Beauregard bpo 46581 Brings ParamSpec propagation for GenericAlias in line with Concatenate and others bpo 45413 Define posix_venv and nt_venv sysconfig installation schemes to be used for bootstrapping new virtual environments Add venv sysconfig installation scheme to get the appropriate one of the above The schemes are identical to the pre existing posix_prefix and nt install schemes The venv module now uses the venv scheme to create new virtual environments instead of hardcoding the paths depending only on the platform Downstream Python distributors customizing the posix_prefix or nt install scheme in a way that is not compatible with the install scheme used in virtual environments are encouraged not to customize the venv schemes When Python itself runs in a virtual environment sysconfig get_default_scheme and sysconfig get_preferred_scheme with key prefix returns venv bpo 43224 Implement support for PEP 646 in typing py bpo 43224 Allow unpacking types GenericAlias objects e g tuple int str bpo 46557 Warnings captured by the logging module are now logged without a format string to prevent systems that group logs by the msg argument from grouping captured warnings together bpo 41370 typing get_type_hints now supports evaluating strings as forward references in PEP 585 generic aliases bpo 46607 Add DeprecationWarning to LegacyInterpolation deprecated in the docstring since Python 3 2 Will be removed in Python 3 13 Use BasicInterpolation or ExtendedInterpolation instead bpo 26120 pydoc now excludes __future__ imports from the module s data items bpo 46480 Add typing assert_type Patch by Jelle Zijlstra bpo 46421 Fix a unittest issue where if the command was invoked as python m unittest and the filename s began with a dot a ValueError is returned bpo 46245 Add optional parameter dir_fd in shutil rmtree bpo 22859 usageExit is marked deprecated to be removed in 3 13 bpo 46170 Improve the error message when you try to subclass an instance of typing NewType bpo 40296 Fix supporting generic aliases in pydoc bpo 20392 Fix inconsistency with uppercase file extensions in MimeTypes guess_type Patch by Kumar Aditya bpo 46030 Add LOCAL_CREDS LOCAL_CREDS_PERSISTENT and SCM_CREDS2 FreeBSD constants to the socket module bpo 44439 Fix,en
1567, write method of a member file in ZipFile when the input data is an object that supports the buffer protocol the file length may be wrong bpo 45171 Fix handling of the stacklevel argument to logging functions in the logging module so that it is consistent across all logging functions and as advertised similar to the stacklevel argument used in warn bpo 24959 Fix bug where unittest sometimes drops frames from tracebacks of exceptions raised in tests bpo 44859 Raise more accurate and PEP 249 compatible exceptions in sqlite3 Raise InterfaceError instead of ProgrammingError for SQLITE_MISUSE errors Don t overwrite BufferError with ValueError when conversion to BLOB fails Raise ProgrammingError instead of Warning if user tries to execute more than one SQL statement Raise ProgrammingError instead of ValueError if an SQL query contains null characters bpo 44493 Add missing terminated NUL in sockaddr_un s length This was potentially observable when using non abstract AF_UNIX datagram sockets to processes written in another programming language bpo 41930 Add serialize and deserialize support to sqlite3 Patch by Erlend E Aasland bpo 33178 Added ctypes BigEndianUnion and ctypes LittleEndianUnion classes as originally documented in the library docs but not yet implemented bpo 43352 Add an Barrier object in synchronization primitives of asyncio Lib in order to be consistant with Barrier from threading and multiprocessing libs bpo 35859 re module fix a few bugs about capturing group In rare cases capturing group gets an incorrect string Patch by Ma Lin Documentation bpo 45099 Document internal asyncio API bpo 47126 Update PEP URLs to PEP 676 s new canonical form bpo 47040 Clarified the old Python versions compatiblity note of binascii crc32 zlib adler32 zlib crc32 functions bpo 46033 Clarify for statement execution in its doc bpo 45790 Adjust inaccurate phrasing in Defining Extension Types Tutorial about the ob_base field and the macros used to access its contents bpo 42340 Document that in some circumstances KeyboardInterrupt may cause the code to enter an inconsistent state Provided a sample workaround to avoid it if needed bpo 41233 Link the errnos referenced in Doc library exceptions rst to their respective section in Doc library errno rst and vice versa Previously this was only done for EINTR and InterruptedError Patch by Yan yyyyyyyan Orestes Tests bpo 47205 Skip test for sched_getaffinity and sched_setaffinity error case on FreeBSD bpo 46126 Restore descriptions when running tests internally bpo 47104 Rewrite asyncio to_thread tests to use unittest IsolatedAsyncioTestCase bpo 40280 The test suite is now passing on the Emscripten platform All fork socket and subprocess based tests are skipped bpo 47037 Skip strftime 4Y feature test on Windows It can cause an assertion error in debug builds bpo 46587 Skip tests if platform s strftime does not support non portable glibc extensions bpo 47015 A test case for os sendfile is converted from deprecated asyncore see PEP 594 to asyncio Patch by Oleg Iarygin Build bpo 40280 Add configure option enable wasm dynamic linking to enable dlopen and MAIN_MODULE SIDE_MODULE on wasm32 emscripten bpo 46023 makesetup now detects and skips all duplicated module definitions The first entry wins bpo 40280 Add SOABI wasm32 emscripten for Emscripten and wasm32 wasi for WASI on 32bit WASM as well as wasm64 counter parts bpo 47032 Ensure Windows install builds fail correctly with a non zero exit code when part of the build fails bpo 47024 Update OpenSSL to 1 1 1n for macOS installers and all Windows builds bpo 46996 The tkinter package now requires Tcl Tk version 8 5 12 or newer bpo 46973 Add regen configure make target to regenerate configure script with Christian s container image quay io tiran cpython_autoconf 269 bpo 46917 Building Python now requires support of IEEE 754 floating point numbers Patch by Victor Stinner bpo 45774 configure now verifies that all SQLite C APIs needed for the sqlite3 extension module are found Windows bpo 47194 Update zlib to v1 2 12 to resolve CVE 2018 25032 bpo 47171 Enable,en
1568,s installing the py exe launcher on Windows ARM64 bpo 46566 Upgraded Python Launcher for Windows to support a new V company tag argument for full PEP 514 support and to detect ARM64 installs The 64 suffix on arguments is deprecated but still selects any non 32 bit install Setting PYLAUNCHER_ALLOW_INSTALL and specifying a version that is not installed will attempt to install the requested version from the Microsoft Store bpo 47086 The installer for Windows now includes documentation as loose HTML files rather than a single compiled chm file bpo 46907 Update Windows installer to use SQLite 3 38 1 bpo 44549 Update bzip2 to 1 0 8 in Windows builds to mitigate CVE 2016 3189 and CVE 2019 12900 bpo 46948 Prevent CVE 2022 26488 by ensuring the Add to PATH option in the Windows installer uses the correct path when being repaired macOS bpo 46890 Fix a regression in the setting of sys _base_executable in framework builds and thereby fix a regression in venv virtual environments with such builds bpo 46907 Update macOS installer to SQLite 3 38 1 Tools Demos bpo 40280 Replace Emscripten s limited shell with Katie Bell s browser ui REPL from python wasm project C API bpo 40421 Add PyFrame_GetBuiltins PyFrame_GetGenerator and PyFrame_GetGlobals C API functions to access frame object attributes safely from C code bpo 46850 Move the private _PyFrameEvalFunction type and private _PyInterpreterState_GetEvalFrameFunc and _PyInterpreterState_SetEvalFrameFunc functions to the internal C API The _PyFrameEvalFunction callback function type now uses the _PyInterpreterFrame type which is part of the internal C API Patch by Victor Stinner bpo 46850 Move the private undocumented _PyEval_EvalFrameDefault function to the internal C API The function now uses the _PyInterpreterFrame type which is part of the internal C API Patch by Victor Stinner bpo 46850 Remove the private undocumented function _PyEval_CallTracing from the C API Call the public sys call_tracing function instead Patch by Victor Stinner bpo 46850 Remove the private undocumented function _PyEval_GetCoroutineOriginTrackingDepth from the C API Call the public sys get_coroutine_origin_tracking_depth function instead Patch by Victor Stinner bpo 46850 Remove the following private undocumented functions from the C API _PyEval_GetAsyncGenFirstiter _PyEval_GetAsyncGenFinalizer _PyEval_SetAsyncGenFirstiter _PyEval_SetAsyncGenFinalizer Call the public sys get_asyncgen_hooks and sys set_asyncgen_hooks functions instead Patch by Victor Stinner bpo 46987 Remove private functions _PySys_GetObjectId and _PySys_SetObjectId Patch by Donghee Na bpo 46906 Add new functions to pack and unpack C double serialize and deserialize PyFloat_Pack2 PyFloat_Pack4 PyFloat_Pack8 PyFloat_Unpack2 PyFloat_Unpack4 and PyFloat_Unpack8 Patch by Victor Stinner Python 3 11 0 alpha 6 Release date 2022 03 07 Core and Builtins bpo 46940 Avoid overriding AttributeError metadata information for nested attribute access calls Patch by Pablo Galindo bpo 46927 Include the type s name in the error message for subscripting non generic types bpo 46921 Support vectorcall for super Patch by Ken Jin bpo 46841 Fix incorrect handling of inline cache entries when specializing BINARY_OP bpo 46841 Use an oparg to simplify the construction of helpful error messages in GET_AWAITABLE bpo 46903 Make sure that str subclasses can be used as attribute names for instances with virtual dictionaries Fixes regression in 3 11alpha bpo 46841 Add more detailed specialization failure stats for COMPARE_OP followed by EXTENDED_ARG bpo 46891 Fix bug introduced during 3 11alpha where subclasses of types ModuleType with __slots__ were not initialized correctly resulting in an interpreter crash bpo 46841 Use inline caching for LOAD_ATTR LOAD_METHOD and STORE_ATTR bpo 46841 Use inline cache for BINARY_SUBSCR bpo 46841 Use inline caching for COMPARE_OP bpo 46864 Deprecate PyBytesObject ob_shash It will be removed in Python 3 13 bpo 46841 Use inline caching for UNPACK_SEQUENCE bpo 46845 Reduces dict size by removing hash value from hash table when all inserted keys are,en
1569, Unicode For example sys getsizeof dict fromkeys abcdefg becomes 272 bytes from 352 bytes on 64bit platform bpo 46841 Use inline cache for LOAD_GLOBAL bpo 46852 Rename the private undocumented float __set_format__ method to float __setformat__ to fix a typo introduced in Python 3 7 The method is only used by test_float Patch by Victor Stinner bpo 46852 Remove the undocumented private float __set_format__ method previously known as float __setformat__ in Python 3 7 Its docstring said You probably don t want to use this function It exists mainly to be used in Python s test suite Patch by Victor Stinner bpo 40116 Fix regression that dict update other may don t respect iterate order of other when other is key sharing dict bpo 46712 Share global string identifiers in deep frozen modules bpo 46430 Fix memory leak in interned strings of deep frozen modules bpo 46841 Store BINARY_OP caches inline using a new CACHE instruction bpo 45107 Specialize LOAD_METHOD for instances with a dict bpo 44337 Reduce the memory usage of specialized LOAD_ATTR and STORE_ATTR instructions bpo 46729 Add number of sub exceptions to BaseException __str__ bpo 45885 Don t un adapt COMPARE_OP when collecting specialization stats bpo 46329 Fix specialization stats gathering for PRECALL instructions bpo 46794 Bump up the libexpat version into 2 4 6 bpo 46823 Implement a specialized combined opcode LOAD_FAST__LOAD_ATTR_INSTANCE_VALUE Patch by Dennis Sweeney bpo 46820 Fix parsing a numeric literal immediately without spaces followed by not in keywords like in 1not in x Now the parser only emits a warning not a syntax error bpo 46329 Move KW_NAMES before PRECALL instruction in call sequence Change operand of CALL to match PRECALL for easier specialization bpo 46808 Remove the NEXT_BLOCK macro from compile c and make the compiler automatically generate implicit blocks when they are needed bpo 46329 Add PUSH_NULL instruction This is used as a prefix when evaluating a callable so that the stack has the same shape for methods and other calls PRECALL_FUNCTION and PRECALL_METHOD are merged into a single PRECALL instruction There is no change in semantics bpo 46762 Fix an assert failure in debug builds when a or is the last character in an f string that s missing a closing right brace bpo 46730 Message of AttributeError caused by getting setting or deleting a property without the corresponding function now mentions that the attribute is in fact a property and also specifies type of the class that it belongs to bpo 46724 Make sure that all backwards jumps use the JUMP_ABSOLUTE instruction rather than JUMP_FORWARD with an argument of 2 32 offset bpo 46732 Correct the docstring for the __bool__ method Patch by Jelle Zijlstra bpo 46072 Add more detailed specialization failure statistics for BINARY_OP bpo 46707 Avoid potential exponential backtracking when producing some syntax errors involving lots of brackets Patch by Pablo Galindo bpo 46323 ctypes now allocates memory on the stack instead of on the heap to pass arguments while calling a Python callback function Patch by Donghee Na bpo 45923 Add a quickened form of RESUME that skips quickening checks bpo 46702 Specialize UNPACK_SEQUENCE for tuple and list unpackings bpo 46072 Opcode pair stats are now gathered with enable pystats Defining DYNAMIC_EXECUTION_PROFILE or DXPAIRS no longer has any effect bpo 46675 Allow more than 16 items in a split dict before it is combined The limit is now 254 bpo 40479 Add a missing call to va_end in Modules _hashopenssl c bpo 46323 Use PyObject_Vectorcall while calling ctypes callback function Patch by Donghee Na bpo 46615 When iterating over sets internally in setobject c acquire strong references to the resulting items from the set This prevents crashes in corner cases of various set operations where the set gets mutated bpo 45828 The bytecode compiler now attempts to apply runtime stack manipulations at compile time whenever it is feasible to do so bpo 30496 Fixed a minor portability issue in the implementation of PyLong_FromLong and added a fast path for single digit integers to Py,en
1570,Long_FromLongLong Library bpo 25707 Fixed a file leak in xml etree ElementTree iterparse when the iterator is not exhausted Patch by Jacob Walls bpo 46877 Export unittest doModuleCleanups in unittest Patch by Kumar Aditya bpo 46848 For performance use the optimized string searching implementations from find and rfind for find and rfind bpo 46736 SimpleHTTPRequestHandler now uses HTML5 grammar Patch by Donghee Na bpo 44886 Inherit asyncio proactor datagram transport from asyncio DatagramTransport bpo 46827 Support UDP sockets in asyncio loop sock_connect for selector based event loops Patch by Thomas Grainger bpo 46811 Make test suite support Expat 2 4 5 bpo 46252 Raise TypeError if ssl SSLSocket is passed to transport based APIs bpo 46784 Fix libexpat symbols collisions with user dynamically loaded or statically linked libexpat in embedded Python bpo 46786 The HTML serialisation in xml etree ElementTree now writes embed source track and wbr as empty tags as defined in HTML 5 bpo 39327 shutil rmtree can now work with VirtualBox shared folders when running from the guest operating system bpo 45390 Propagate asyncio CancelledError message from inner task to outer awaiter bpo 46756 Fix a bug in urllib request HTTPPasswordMgr find_user_password and urllib request HTTPPasswordMgrWithPriorAuth is_authenticated which allowed to bypass authorization For example access to URI example org foobar was allowed if the user was authorized for URI example org foo bpo 46737 random gauss and random normalvariate now have default arguments bpo 46752 Add task groups to asyncio structured concurrency inspired by Trio s nurseries This also introduces a change to task cancellation where a cancelled task can t be cancelled again until it calls uncancel bpo 46724 Fix dis behavior on negative jump offsets bpo 46333 The __repr__ method of typing ForwardRef now includes the module parameter of typing ForwardRef when it is set bpo 46643 In typing get_type_hints support evaluating stringified ParamSpecArgs and ParamSpecKwargs annotations Patch by Gregory Beauregard bpo 45863 When the tarfile module creates a pax format archive it will put an integer representation of timestamps in the ustar header if possible for the benefit of older unarchivers in addition to the existing full precision timestamps in the pax extended header bpo 46066 Deprecate kwargs based syntax for typing TypedDict definitions It had confusing semantics when specifying totality and was largely unused Patch by Jingchen Ye bpo 46676 Make typing ParamSpec args and kwargs equal to themselves Patch by Gregory Beauregard bpo 46323 ctypes CFUNCTYPE and ctypes WINFUNCTYPE now fail to create the type if its _argtypes_ member contains too many arguments Previously the error was only raised when calling a function Patch by Victor Stinner bpo 46672 Fix NameError in asyncio gather when initial type check fails bpo 46659 The calendar LocaleTextCalendar and calendar LocaleHTMLCalendar classes now use locale getlocale instead of using locale getdefaultlocale if no locale is specified Patch by Victor Stinner bpo 46659 The locale getdefaultlocale function is deprecated and will be removed in Python 3 13 Use locale setlocale locale getpreferredencoding False and locale getlocale functions instead Patch by Victor Stinner bpo 46655 In typing get_type_hints support evaluating bare stringified TypeAlias annotations Patch by Gregory Beauregard bpo 45948 Fixed a discrepancy in the C implementation of the xml etree ElementTree module Now instantiating an xml etree ElementTree XMLParser with a target None keyword provides a default xml etree ElementTree TreeBuilder target as the Python implementation does bpo 46626 Expose Linux s IP_BIND_ADDRESS_NO_PORT option in socket bpo 46521 Fix a bug in the codeop module that was incorrectly identifying invalid code involving string quotes as valid code bpo 46571 Improve typing no_type_check Now it does not modify external classes and functions We also now correctly mark classmethods as not to be type checked bpo 46400 expat Update libexpat from 2 4 1 to 2 4 4 bpo 4655,en
1571,6 Deprecate undocumented support for using a pathlib Path object as a context manager bpo 46534 Implement PEP 673 typing Self Patch by James Hilton Balfe bpo 46522 Make various module __getattr__ AttributeErrors more closely match a typical AttributeError bpo 46475 Add typing Never and typing assert_never Patch by Jelle Zijlstra bpo 46333 The __eq__ and __hash__ methods of typing ForwardRef now honor the module parameter of typing ForwardRef Forward references from different modules are now differentiated bpo 46246 Add missing __slots__ to importlib metadata DeprecatedList Patch by Arie Bovenberg bpo 46232 The ssl module now handles certificates with bit strings in DN correctly bpo 46195 typing get_type_hints no longer adds Optional to parameters with None as a default This aligns to changes to PEP 484 in https github com python peps pull 689 bpo 31369 Add RegexFlag to re __all__ and documented it Add NOFLAG to indicate no flags being set bpo 45898 ctypes no longer defines ffi_type_ symbols in cfield c The symbols have been provided by libffi for over a decade bpo 44953 Calling operator itemgetter objects and operator attrgetter objects is now faster due to use of the vectorcall calling convention bpo 44289 Fix an issue with is_tarfile method when using fileobj argument position in the fileobj was advanced forward which made it unreadable with tarfile TarFile open bpo 44011 Reimplement SSL TLS support in asyncio borrow the implementation from uvloop library bpo 41086 Make the configparser ConfigParser constructor raise TypeError if the interpolation parameter is not of type configparser Interpolation bpo 29418 Implement inspect ismethodwrapper and fix inspect isroutine for cases where methodwrapper is given Patch by Hakan Çelik bpo 14156 argparse FileType now supports an argument of in binary mode returning the buffer attribute of sys stdin sys stdout as appropriate Modes including x and a are treated equivalently to w when argument is Patch contributed by Josh Rosenberg Documentation bpo 42238 Doc tools rstlint py has moved to its own repository and is now packaged on PyPI as sphinx lint Tests bpo 46913 Fix test_faulthandler test_sigfpe if Python is built with undefined behavior sanitizer UBSAN disable UBSAN on the faulthandler_sigfpe function Patch by Victor Stinner bpo 46760 Remove bytecode offsets from expected values in test test_dis module Reduces the obstacles to modifying the VM or compiler bpo 46708 Prevent default asyncio event loop policy modification warning after test_asyncio execution bpo 46678 The function make_legacy_pyc in Lib test support import_helper py no longer fails when PYTHONPYCACHEPREFIX is set to a directory on a different device from where tempfiles are stored bpo 46623 Skip test_pair and test_speech128 of test_zlib on s390x since they fail if zlib uses the s390x hardware accelerator Patch by Victor Stinner Build bpo 46860 Respect with suffix when building on case insensitive file systems bpo 46656 Building Python now requires a C11 compiler Optional C11 features are not required Patch by Victor Stinner bpo 46656 Building Python now requires support for floating point Not a Number NaN remove the Py_NO_NAN macro Patch by Victor Stinner bpo 46640 Building Python now requires a C99 math h header file providing a NAN constant or the __builtin_nan built in function Patch by Victor Stinner bpo 46608 Exclude marshalled frozen data if deep freezing to save 300 KB disk space This includes adding a new is_package field to _frozen Patch by Kumar Aditya bpo 40280 Fix wasm32 emscripten test failures and platform issues Disable syscalls that are not supported or don t work e g wait getrusage prlimit mkfifo mknod setres gu id setgroups Use fd_count to cound open fds Add more checks for subprocess and fork Add workarounds for missing _multiprocessing and failing socket accept Enable bzip2 Disable large file support Disable signal alarm bpo 46430 Intern strings in deep frozen modules Patch by Kumar Aditya Windows bpo 46744 The default all users install directory for ARM64 is now under the native Program Files ,en
1572,folder rather than Program Files Arm which is intended for ARM 32 bit files bpo 46567 Adds Tcl and Tk support for Windows ARM64 This also adds IDLE to the installation bpo 46638 Ensures registry virtualization is consistently disabled For 3 10 and earlier it remains enabled some registry writes are protected while for 3 11 and later it is disabled registry modifications affect all applications IDLE bpo 46630 Make query dialogs on Windows start with a cursor in the entry box bpo 45447 Apply IDLE syntax highlighting to pyi files Patch by Alex Waygood and Terry Jan Reedy C API bpo 46748 Python s public headers no longer import stdbool h leaving code that embedd extends Python free to define bool true and false bpo 46836 Move the PyFrameObject type definition struct _frame to the internal C API pycore_frame h header file Patch by Victor Stinner bpo 45459 Rename Include buffer h header file to Include pybuffer h to avoid conflits with projects having an existing buffer h header file Patch by Victor Stinner bpo 45412 Remove the HAVE_PY_SET_53BIT_PRECISION macro moved to the internal C API Patch by Victor Stinner bpo 46613 Added function PyType_GetModuleByDef which allows accesss to module state when a method s defining class is not available Python 3 11 0 alpha 5 Release date 2022 02 03 Core and Builtins bpo 45773 Remove two invalid peephole optimizations from the bytecode compiler bpo 46564 Do not create frame objects when creating super object Patch by Kumar Aditya bpo 45885 Added more fined grained specialization failure stats regarding the COMPARE_OP bytecode bpo 44977 The delegation of int to __trunc__ is now deprecated Calling int a when type a implements __trunc__ but not __int__ or __index__ now raises a DeprecationWarning bpo 46458 Reorder code emitted by the compiler for a try except block so that the else block s code immediately follows the try body without a jump This is more optimal for the happy path bpo 46527 Allow passing iterable as a keyword argument to enumerate again Patch by Jelle Zijlstra bpo 46528 Replace several stack manipulation instructions DUP_TOP DUP_TOP_TWO ROT_TWO ROT_THREE ROT_FOUR and ROT_N with new COPY and SWAP instructions bpo 46329 Use two or three bytecodes to implement most calls Calls without named arguments are implemented as a sequence of two instructions PRECALL CALL Calls with named arguments are implemented as a sequence of three instructions PRECALL KW_NAMES CALL There are two different PRECALL instructions PRECALL_FUNTION and PRECALL_METHOD The latter pairs with LOAD_METHOD This partition into pre call and call allows better specialization and thus better performance ultimately There is no change in semantics bpo 46503 Fix an assert when parsing some invalid N escape sequences in f strings bpo 46431 Improve error message on invalid calls to BaseExceptionGroup __new__ bpo 46476 Fix memory leak in code objects generated by deepfreeze Patch by Kumar Aditya bpo 46481 Speed up calls to weakref ref __call__ by using the PEP 590 vectorcall calling convention Patch by Donghee Na bpo 46417 Fix a race condition on setting a type __bases__ attribute the internal function add_subclass now gets the PyTypeObject tp_subclasses member after calling PyWeakref_NewRef which can trigger a garbage collection which can indirectly modify PyTypeObject tp_subclasses Patch by Victor Stinner bpo 46417 python X showrefcount now shows the total reference count after clearing and destroyed the main Python interpreter Previously it was shown before Patch by Victor Stinner bpo 43683 Add ASYNC_GEN_WRAP opcode to wrap the value to be yielded in async generators Removes the need to special case async generators in the YIELD_VALUE instruction bpo 46407 Optimize some modulo operations in Objects longobject c Patch by Jeremiah Vivian bpo 46409 Add new RETURN_GENERATOR bytecode to make generators Simplifies calling Python functions in the VM as they no longer any need to special case generator functions Also add JUMP_NO_INTERRUPT bytecode that acts like JUMP_ABSOLUTE but does not check for interrupts bpo 46406 The int,en
1573,eger division implementation has been optimized to better let the compiler understand its constraints It can be 20 faster on the amd64 platform when dividing an int by a value smaller than 2 30 bpo 46383 Fix invalid signature of _zoneinfo s module_free function to resolve a crash on wasm32 emscripten platform bpo 46361 Ensure that small integers created by int from_bytes and decimal Decimal are properly cached bpo 46161 Fix the class building error when the arguments are constants and CALL_FUNCTION_EX is used bpo 46028 Fixes calculation of sys _base_executable when inside a virtual environment that uses symlinks with different binary names than the base environment provides bpo 46091 Correctly calculate indentation levels for lines with whitespace character that are ended by line continuation characters Patch by Pablo Galindo bpo 30512 Add CAN Socket support for NetBSD bpo 46045 Do not use POSIX semaphores on NetBSD bpo 44024 Improve the TypeError message for non string second arguments passed to the built in functions getattr and hasattr Patch by Géry Ogam Library bpo 46624 Restore support for non integer arguments of random randrange and random randint bpo 46591 Make the IDLE doc URL on the About IDLE dialog clickable bpo 46565 Remove loop variables that are leaking into modules namespaces bpo 46553 In typing get_type_hints support evaluating bare stringified ClassVar annotations Patch by Gregory Beauregard bpo 46544 Don t leak x uspace intermediate vars in textwrap TextWrapper bpo 46487 Add the get_write_buffer_limits method to asyncio transports WriteTransport and to the SSL transport bpo 45173 Note the configparser deprecations will be removed in Python 3 12 bpo 45162 The deprecated unittest APIs removed in 3 11a1 have been temporarily restored to be removed in 3 12 while cleanups in external projects go in bpo 46539 In typing get_type_hints support evaluating stringified ClassVar and Final annotations inside Annotated Patch by Gregory Beauregard bpo 46510 Add missing test for types TracebackType and types FrameType Calculate them directly from the caught exception without calling sys exc_info bpo 46491 Allow typing Annotated to wrap typing Final and typing ClassVar Patch by Gregory Beauregard bpo 46483 Remove __class_getitem__ from pathlib PurePath as this class was not supposed to be generic bpo 46436 Fix command line option d directory in module http server which is ignored when combined with command line option cgi Patch by Géry Ogam bpo 41403 Make mock patch raise a TypeError with a relevant error message on invalid arg Previously it allowed a cryptic AttributeError to escape bpo 46474 In importlib metadata EntryPoint pattern avoid potential REDoS by limiting ambiguity in consecutive whitespace bpo 46474 Removed private method from importlib metadata Path Sync with importlib_metadata 4 10 0 bpo 46470 Remove unused branch from typing _remove_dups_flatten bpo 46469 asyncio generic classes now return types GenericAlias in __class_getitem__ instead of the same class bpo 41906 Support passing filter instances in the filters values of handlers and loggers in the dictionary passed to logging config dictConfig bpo 46422 Use dis Positions in dis Instruction instead of a regular tuple bpo 46434 pdb now gracefully handles help when __doc__ is missing for example when run with pregenerated optimized pyc files bpo 43869 Python uses the same time Epoch on all platforms Add an explicit unit test to ensure that it s the case Patch by Victor Stinner bpo 46414 Add typing reveal_type Patch by Jelle Zijlstra bpo 40280 subprocess now imports Windows specific imports when msvcrt module is available and POSIX specific imports on all other platforms This gives a clean exception when _posixsubprocess is not available e g Emscripten browser target bpo 40066 IntEnum IntFlag and StrEnum use the mixed in type for their str and format output bpo 46316 Optimize pathlib Path iterdir by removing an unnecessary check for special entries bpo 29688 Document pathlib Path absolute which has always existed bpo 43012 The pathlib module s obsolete and,en
1574, internal _Accessor class has been removed to prepare the terrain for upcoming enhancements to the module bpo 46258 Speed up math isqrt for small positive integers by replacing two division steps with a lookup table bpo 46242 Improve error message when creating a new enum Enum type subclassing an existing Enum with _member_names_ using enum Enum __call__ bpo 43118 Fix a bug in inspect signature that was causing it to fail on some subclasses of classes with a __text_signature__ referencing module globals Patch by Weipeng Hong bpo 26552 Fixed case where failing asyncio ensure_future did not close the coroutine Patch by Kumar Aditya bpo 21987 Fix an issue with tarfile TarFile getmember getting a directory name with a trailing slash bpo 46124 Update zoneinfo to rely on importlib resources traversable API bpo 46103 Now inspect getmembers only gets __bases__ attribute from class type Patch by Weipeng Hong bpo 46080 Fix exception in argparse help text generation if a argparse BooleanOptionalAction argument s default is argparse SUPPRESS and it has help specified Patch by Felix Fontein bpo 44791 Fix substitution of ParamSpec in Concatenate with different parameter expressions Substitution with a list of types returns now a tuple of types Substitution with Concatenate returns now a Concatenate with concatenated lists of arguments Documentation bpo 46463 Fixes escape4chm py script used when building the CHM documentation file Tests bpo 43478 Mocks can no longer be provided as the specs for other Mocks As a result an already mocked object cannot be passed to mock Mock This can uncover bugs in tests since these Mock derived Mocks will always pass certain tests e g isinstance and builtin assert functions e g assert_called_once_with will unconditionally pass bpo 46616 Ensures test_importlib test_windows cleans up registry keys after completion bpo 44359 test_ftplib now silently ignores socket errors to prevent logging unhandled threading exceptions Patch by Victor Stinner bpo 46600 Fix test_gdb test_pycfunction for Python built with clang Og Tolerate inlined functions in the gdb traceback Patch by Victor Stinner bpo 46542 Fix a Python crash in test_lib2to3 when using Python built in debug mode limit the recursion limit Patch by Victor Stinner bpo 46576 test_peg_generator now disables compiler optimization when testing compilation of its own C extensions to significantly speed up the testing on non debug builds of CPython bpo 46542 Fix test_json tests checking for RecursionError modify these tests to use support infinite_recursion Patch by Victor Stinner bpo 13886 Skip test_builtin PTY tests on non ASCII characters if the readline module is loaded The readline module changes input behavior but test_builtin is not intented to test the readline module Patch by Victor Stinner bpo 40280 Add test support requires_fork decorators to mark tests that require a working os fork bpo 40280 Add test support requires_subprocess decorator to mark tests which require working subprocess module or os spawn The wasm32 emscripten platform has no support for processes bpo 46126 Disable descriptions when running tests internally Build bpo 46602 Tidied up configure ac so that conftest c is truncated rather than appended This assists in the case where the rm of conftest c fails to happen between tests Downstream issues such as a clobbered SOABI can result bpo 46600 Fix the test checking if the C compiler supports Og option in the configure script to also use Og on clang which supports it Patch by Victor Stinner bpo 38472 Fix GCC detection in setup py when cross compiling The C compiler is now run with LC_ALL C Previously the detection failed with a German locale bpo 46513 configure no longer uses AC_C_CHAR_UNSIGNED macro and pyconfig h no longer defines reserved symbol __CHAR_UNSIGNED__ bpo 46471 Use global singletons for single byte bytes objects in deepfreeze bpo 46443 Deepfreeze now uses cached small integers as it saves some space for common small integers bpo 46429 Merge all deep frozen files into one for space savings Patch by Kumar Aditya bpo 45569 The,en
1575, build now defaults to using 30 bit digits for Python integers Previously either 15 bit or 30 bit digits would be selected depending on the platform 15 bit digits may still be selected using the enable big digits 15 option to the configure script or by defining PYLONG_BITS_IN_DIGIT in pyconfig h bpo 45925 Update Windows installer to use SQLite 3 37 2 bpo 43112 Detect musl libc as a separate SOABI tagged as linux musl Windows bpo 33125 The traditional EXE MSI based installer for Windows is now available for ARM64 bpo 46362 os path abspath C CON is now fixed to return CON not the same path The regression was true of all legacy DOS devices such as COM1 LPT1 or NUL bpo 44934 The installer now offers a command line only option to add the installation directory to the end of PATH instead of at the start macOS bpo 45925 Update macOS installer to SQLite 3 37 2 IDLE bpo 45296 Clarify close quit and exit in IDLE In the File menu Close and Exit are now Close Window the current one and Exit is now Exit IDLE by closing all windows In Shell quit and exit mean close Shell If there are no other windows this also exits IDLE C API bpo 40170 Remove the PyHeapType_GET_MEMBERS macro It was exposed in the public C API by mistake it must only be used by Python internally Use the PyTypeObject tp_members member instead Patch by Victor Stinner bpo 40170 Move _Py_GetAllocatedBlocks and _PyObject_DebugMallocStats private functions to the internal C API Patch by Victor Stinner bpo 46433 The internal function _PyType_GetModuleByDef now correctly handles inheritance patterns involving static types bpo 45459 Py_buffer and various Py_buffer related functions are now part of the limited API and stable ABI bpo 14916 Fixed bug in the tokenizer that prevented PyRun_InteractiveOne from parsing from the provided FD Python 3 11 0 alpha 4 Release date 2022 01 13 Core and Builtins bpo 46070 Py_EndInterpreter now explicitly untracks all objects currently tracked by the GC Previously if an object was used later by another interpreter calling PyObject_GC_UnTrack on the object crashed if the previous or the next object of the PyGC_Head structure became a dangling pointer Patch by Victor Stinner bpo 46347 Fix memory leak in PyEval_EvalCodeEx bpo 46339 Fix a crash in the parser when retrieving the error text for multi line f strings expressions that do not start in the first line of the string Patch by Pablo Galindo bpo 46331 Do not set line number of instruction storing doc string Fixes regression introduced in 3 11 alpha bpo 46314 Remove spurious call event when creating a lambda function that was accidentally introduced in 3 11a4 bpo 46289 ASDL declaration of FormattedValue has changed to reflect conversion field is not optional bpo 46297 Fixed an interpreter crash on bootup with multiple PythonPaths set in the Windows registry Patch by Derzsi Dániel bpo 46237 Fix the line number of tokenizer errors inside f strings Patch by Pablo Galindo bpo 46263 We always expect the use_frozen_modules config to be set now that getpath c was rewritten in pure Python and the logic improved bpo 46006 Fix a regression when a type method like __init__ is modified in a subinterpreter Fix a regression in _PyUnicode_EqualToASCIIId and type update_slot Revert the change which made the Unicode dictionary of interned strings compatible with subinterpreters the internal interned dictionary is shared again by all interpreters Patch by Victor Stinner bpo 45923 Add RESUME opcode This is a logical no op It is emitted by the compiler anywhere a Python function can be entered It is used by the interpreter to perform tracing and optimizer checks bpo 46208 Fix the regression of os path normpath A B not returning expected B but B bpo 46240 Correct the error message for unclosed parentheses when the tokenizer doesn t reach the end of the source when the error is reported Patch by Pablo Galindo bpo 46009 Remove the GEN_START opcode bpo 46235 Certain sequence multiplication operations like 0 1_000 are now faster due to reference counting optimizations Patch by Dennis Sweeney bpo 46221 PREP_RERAISE_STAR,en
1576, no longer pushes lasti to the stack bpo 46202 Remove POP_EXCEPT_AND_RERAISE and replace it by an equivalent sequence of other opcodes bpo 46085 Fix iterator cache mechanism of OrderedDict bpo 46055 Speed up shifting operation involving integers less than PyLong_BASE Patch by Xinhang Xu bpo 46110 Add a maximum recursion check to the PEG parser to avoid stack overflow Patch by Pablo Galindo bpo 46107 Fix bug where ExceptionGroup split and ExceptionGroup subgroup did not copy the exception group s __note__ field to the parts bpo 45711 The interpreter state s representation of handled exceptions a k a exc_info or _PyErr_StackItem now has only the exc_value field exc_type and exc_traceback have been removed as their values can be derived from exc_value bpo 44525 Replace the four call bytecode instructions which one pre call instruction and two call instructions Removes CALL_FUNCTION CALL_FUNCTION_KW CALL_METHOD and CALL_METHOD_KW Adds CALL_NO_KW and CALL_KW call instructions and PRECALL_METHOD prefix for pairing with LOAD_METHOD bpo 46039 Remove the YIELD_FROM instruction and replace it with the SEND instruction which performs the same operation but without the loop bpo 45635 The code called from _PyErr_Display was refactored to improve error handling It now exits immediately upon an unrecoverable error bpo 46054 Fix parser error when parsing non utf8 characters in source files Patch by Pablo Galindo bpo 46042 Improve the location of the caret in SyntaxError exceptions emitted by the symbol table Patch by Pablo Galindo bpo 46049 Ensure _pth files work as intended on platforms other than Windows bpo 46048 Fixes parsing of _pth files on startup so that single character paths are correctly read bpo 37971 Fix a bug where the line numbers given in a traceback when a decorator application raised an exception were wrong bpo 46031 Add POP_JUMP_IF_NOT_NONE and POP_JUMP_IF_NONE opcodes to speed up conditional jumps bpo 45654 Deepfreeze runpy patch by Kumar Aditya bpo 46025 Fix a crash in the atexit module involving functions that unregister themselves before raising exceptions Patch by Pablo Galindo bpo 46000 Improve compatibility of the curses module with NetBSD curses bpo 44525 Specialize the CALL_FUNCTION instruction for calls to builtin types with a single argument Speeds up range x list x and specifically type obj bpo 42918 Fix bug where the built in compile function did not always raise a SyntaxError when passed multiple statements in single mode Patch by Weipeng Hong bpo 45953 The main interpreter in _PyRuntimeState interpreters is now statically allocated as part of _PyRuntime Likewise for the initial thread state of each interpreter This means less allocation during runtime init as well as better memory locality for these key state objects bpo 45292 Complete the PEP 654 implementation add except bpo 43413 Revert changes in set __init__ Subclass of set needs to define a __init__ method if it defines a __new__ method with additional keyword parameters bpo 43931 Added the Py_Version constant which bears the same value as PY_VERSION_HEX Patch by Gabriele N Tornetta Library bpo 46342 The typing final decorator now sets the __final__ attribute on the decorated object to allow runtime introspection Patch by Jelle Zijlstra bpo 46328 Added the sys exception method which returns the active exception instance bpo 46307 Add string Template is_valid and string Template get_identifiers methods bpo 46306 Assume that types CodeType always has types CodeType co_firstlineno in doctest bpo 40479 Fix hashlib usedforsecurity option to work correctly with OpenSSL 3 0 0 in FIPS mode bpo 46070 Fix possible segfault when importing the asyncio module from different sub interpreters in parallel Patch by Erlend E Aasland bpo 46244 Removed __slots__ from typing ParamSpec and typing TypeVar They served no purpose Patch by Arie Bovenberg bpo 46278 Reflect context argument in AbstractEventLoop call_ methods Loop implementations already support it bpo 46269 Remove special casing of __new__ in enum Enum __dir__ bpo 46266 Improve day constants in calendar Now ,en
1577,all constants MONDAY SUNDAY are documented tested and added to __all__ bpo 46257 Optimized the mean variance and stdev functions in the statistics module If the input is an iterator it is consumed in a single pass rather than eating memory by conversion to a list The single pass algorithm is about twice as fast as the previous two pass code bpo 41011 Added two new variables to pyvenv cfg which is generated by venv module executable for the executable and command for the command line used to create the environment bpo 46239 Improve error message when importing asyncio windows_events on non Windows bpo 46238 Reuse _winapi constants in asyncio windows_events bpo 46222 Adding SF_NOCACHE sendfile constant for FreeBSD for the posixmodule bpo 37295 Add fast path for 0 k n 67 for math comb bpo 46176 Adding the MAP_STACK constant for the mmap module bpo 43424 Deprecate webbrowser MacOSXOSAScript _name and use name instead bpo 45321 Added missing error codes to module xml parsers expat errors bpo 46125 Refactor tests to test traversable API directly Includes changes from importlib 5 4 0 bpo 46118 Moved importlib resources and its related functionality to a package bpo 37578 Add include_hidden parameter to glob and iglob to match hidden files and directories when using special characters like and bpo 20369 concurrent futures wait no longer blocks forever when given duplicate Futures Patch by Kumar Aditya bpo 46105 Honor spec when generating requirement specs with urls and extras importlib_metadata 4 8 3 bpo 44893 EntryPoint objects are no longer tuples Recommended means to access is by attribute name group or accessor load Access by index is deprecated and will raise deprecation warning bpo 22815 Print unexpected successes together with failures and errors in summary in unittest TextTestResult bpo 22047 Calling add_argument_group on an argument group is deprecated Calling add_argument_group or add_mutually_exclusive_group on a mutually exclusive group is deprecated These features were never supported and do not always work correctly The functions exist on the API by accident through inheritance and will be removed in the future bpo 26952 argparse raises ValueError with clear message when trying to render usage for an empty mutually exclusive group Previously it raised a cryptic IndexError bpo 45615 Functions in the traceback module raise TypeError rather than AttributeError when an exception argument is not of type BaseException bpo 16594 Add allow allow_reuse_port flag in socketserver bpo 27718 Fix help for the signal module Some functions e g signal and getsignal were omitted bpo 46032 The registry method of functools singledispatch functions checks now the first argument or the first parameter annotation and raises a TypeError if it is not supported Previously unsupported types were ignored e g typing List int or caused an error at calling time e g list int bpo 46014 Add ability to use typing Union and types UnionType as dispatch argument to functools singledispatch Patch provided by Yurii Karabas bpo 27062 Add __all__ to inspect patch by Kumar Aditya bpo 46018 Ensure that math expm1 does not raise on underflow bpo 46016 Adding F_DUP2FD and F_DUP2FD_CLOEXEC constants from FreeBSD into the fcntl module bpo 45755 typing generic aliases now reveal the class attributes of the original generic class when passed to dir This was the behavior up to Python 3 6 but was changed in 3 7 3 9 bpo 45874 The empty query string consisting of no query arguments is now handled correctly in urllib parse parse_qsl This caused problems before when strict parsing was enabled bpo 44674 Change how dataclasses disallows mutable default values It used to use a list of known types list dict set Now it disallows unhashable objects to be defaults It s using unhashability as a proxy for mutability Patch by Eric V Smith idea by Raymond Hettinger bpo 23882 Remove namespace package PEP 420 support from unittest discovery It was introduced in Python 3 4 but has been broken since Python 3 7 bpo 25066 Added a __repr__ method to multiprocessing Event objects patch by,en
1578, Kumar Aditya bpo 45643 Added signal SIGSTKFLT on platforms where this signal is defined bpo 44092 Fetch across rollback no longer raises InterfaceError Instead we leave it to the SQLite library to handle these cases Patch by Erlend E Aasland bpo 42413 Replace concurrent futures TimeoutError and asyncio TimeoutError with builtin TimeoutError keep these names as deprecated aliases Documentation bpo 46196 Document method cmd Cmd columnize bpo 46120 State that is preferred for readability over Union in the typing docs bpo 46109 Extracted importlib resources and importlib resources abc documentation into separate files bpo 19737 Update the documentation for the globals function Tests bpo 46296 Add a test case for enum with _use_args_ True and _member_type_ object bpo 46205 Fix hang in runtest_mp due to race condition bpo 46263 Fix test_capi on FreeBSD 14 dev instruct jemalloc to not fill freed memory with junk byte bpo 46262 Cover ValueError path in tests for enum Flag _missing_ bpo 46150 Now fakename in test_pathlib PosixPathTest test_expanduser is checked to be non existent bpo 46129 Rewrite asyncio locks tests with unittest IsolatedAsyncioTestCase usage bpo 23819 Fixed asyncio tests in python optimized mode Patch by Kumar Aditya bpo 46114 Fix test case for OpenSSL 3 0 1 version OpenSSL 3 0 uses 0xMNN00PP0L Build bpo 44133 When Python is configured with without static libpython the Python static library libpython a is no longer built Patch by Victor Stinner bpo 44133 When Python is built without enable shared the python program is now linked to object files rather than being linked to the Python static library libpython a to make sure that all symbols are exported Previously the linker omitted some symbols like the Py_FrozenMain function Patch by Victor Stinner bpo 40280 The configure script has a new option with emscripten target to select browser or node as Emscripten build target bpo 46315 Added and fixed ifdef HAVE_FEATURE checks for functionality that is not available on WASI platform bpo 45723 Fixed a regression in configure check for select epoll bpo 46263 configure no longer sets MULTIARCH on FreeBSD platforms bpo 46106 Updated OpenSSL to 1 1 1m in Windows builds macOS installer builds and CI Patch by Kumar Aditya bpo 46088 Automatically detect or install bootstrap Python runtime when building from Visual Studio bpo 46072 Add a with pystats configure option to turn on internal statistics gathering bpo 40280 A new directory Tools wasm contains WebAssembly related helpers like config site override for wasm32 emscripten wasm assets generator to bundle the stdlib and a README bpo 46023 makesetup no longer builds extensions that have been marked as disabled This allows users to disable modules in Modules Setup local bpo 45949 Use pure Python freeze_module for all but importlib bootstrap files with freeze module configure option is no longer needed for cross builds Windows bpo 46217 Removed parameter that is unsupported on Windows 8 1 and early Windows 10 and may have caused build or runtime failures macOS bpo 40477 The Python Launcher app for macOS now properly launches scripts and if necessary the Terminal app when running on recent macOS releases C API bpo 46236 Fix a bug in PyFunction_GetAnnotations that caused it to return a tuple instead of a dict bpo 46140 PyBuffer_GetPointer PyBuffer_FromContiguous PyBuffer_ToContiguous and PyMemoryView_FromBuffer now take buffer info by const Py_buffer instead of Py_buffer as they do not need mutability PyBuffer_FromContiguous also now takes the source buffer as const void and similarly PyBuffer_GetPointer takes the strides as const Py_ssize_t bpo 45855 Document that the no_block argument to PyCapsule_Import is a no op now bpo 45855 Replaced deprecated usage of PyImport_ImportModuleNoBlock with PyImport_ImportModule in stdlib modules Patch by Kumar Aditya bpo 46007 The PyUnicode_CHECK_INTERNED macro has been excluded from the limited C API It was never usable there because it used internal structures which are not available in the limited C API Patch by Victor Stinner Python 3 1,en
1579,1 0 alpha 3 Release date 2021 12 08 Core and Builtins bpo 46009 Restore behavior from 3 9 and earlier when sending non None to newly started generator In 3 9 this did not affect the state of the generator In 3 10 0 and 3 10 1 gen_func send 0 is equivalent to gen_func throw TypeError which exhausts the generator In 3 10 2 onward the behavior has been reverted to that of 3 9 bpo 46004 Fix the SyntaxError location for errors involving for loops with invalid targets Patch by Pablo Galindo bpo 45711 _PyErr_ChainStackItem no longer normalizes exc_info including setting the traceback on the exception instance because exc_info is always normalized bpo 45607 The __note__ field was added to BaseException It is None by default but can be set to a string which is added to the exception s traceback bpo 45947 Place pointers to dict and values immediately before GC header This reduces number of dependent memory loads to access either dict or values from 3 to 1 bpo 45915 is_valid_fd now uses faster fcntl fd F_GETFD on Linux macOS and Windows bpo 44530 Reverts a change to the code __new__ audit event from an earlier prerelease bpo 42268 Fail the configure step if the selected compiler doesn t support memory sanitizer Patch by Pablo Galindo bpo 45711 The three values of exc_info are now always consistent with each other In particular the type and traceback fields are now derived from the exception instance This impacts the return values of sys exc_info and PyErr_GetExcInfo if the exception instance is modified while the exception is handled as well as PyErr_SetExcInfo which now ignores the type and traceback arguments provided to it bpo 45727 Refine the custom syntax error that suggests that a comma may be missing to trigger only when the expressions are detected between parentheses or brackets Patch by Pablo Galindo bpo 45885 Specialized the COMPARE_OP opcode using the PEP 659 machinery bpo 45786 Allocate space for the interpreter frame in the frame object to avoid an additional allocation when the frame object outlives the frame activation bpo 45614 Fix traceback display for exceptions with invalid module name bpo 45813 Fix crash when calling coro cr_frame clear after coroutine has been freed bpo 45811 Improve the tokenizer errors when encountering invisible control characters in the parser Patch by Pablo Galindo bpo 45848 Allow the parser to obtain error lines directly from encoded files Patch by Pablo Galindo bpo 45709 Restore behavior from 3 10 when tracing an exception raised within a with statement bpo 44525 Adds new COPY_FREE_VARS opcode to make copying of free variables from function to frame explicit Helps optimization of calls to Python function bpo 45829 Specialize BINARY_SUBSCR for classes with a __getitem__ method implemented in Python bpo 45826 Fixed a crash when calling with_traceback None on NameError This occurs internally in unittest TestCase assertRaises bpo 45822 Fixed a bug in the parser that was causing it to not respect PEP 263 coding cookies when no flags are provided Patch by Pablo Galindo bpo 45820 Fix a segfault when the parser fails without reading any input Patch by Pablo Galindo bpo 45636 Simplify the implementation of BINARY_OP by indexing into an array of function pointers rather than switching on the oparg bpo 42540 Fix crash when os fork is called with an active non default memory allocator bpo 45738 Fix computation of error location for invalid continuation characters in the parser Patch by Pablo Galindo bpo 45636 Remove an existing fast path for old style string formatting since it no longer appears to have any measurable impact bpo 45753 Make recursion checks a bit more efficient by tracking amount of calls left before overflow bpo 45773 Fix a compiler hang when attempting to optimize certain jump patterns bpo 45764 The parser now gives a better error message when leaving out the opening parenthesis after a def statement def f File stdin line 1 def f SyntaxError expected bpo 45609 Specialized the STORE_SUBSCR opcode using the PEP 659 machinery bpo 45636 Replace all numeric BINARY_ and INPLACE_ instruc,en
1580,tions with a single BINARY_OP implementation bpo 45582 Path calculation known as getpath has been reimplemented as a frozen Python module This should have no visible impact but may affect calculation of all paths referenced in sys and sysconfig bpo 45450 Improve the syntax error message for parenthesized arguments Patch by Pablo Galindo Library bpo 27946 Fix possible crash when getting an attribute of xml etree ElementTree Element simultaneously with replacing the attrib dict bpo 45711 Make asyncio normalize exceptions as soon as they are captured with PyErr_Fetch and before they are stored as an exc_info triplet This brings asyncio in line with the rest of the codebase where an exc_info triplet is always normalized bpo 23819 Replaced asserts with exceptions in asyncio patch by Kumar Aditya bpo 13236 unittest TextTestResult and unittest TextTestRunner flush now the output stream more often bpo 45917 Added math exp2 which returns 2 raised to the power of x bpo 37658 Fix issue when on certain conditions asyncio wait_for may allow a coroutine to complete successfully but fail to return the result potentially causing memory leaks or other issues bpo 45876 Improve the accuracy of stdev and pstdev in the statistics module When the inputs are floats or fractions the output is a correctly rounded float bpo 44649 Handle dataclass slots True with a field that has default a default value but for which init False bpo 45803 Added missing kw_only parameter to dataclasses make_dataclass bpo 45837 The turtle RawTurtle settiltangle is deprecated since Python 3 1 it now emits a deprecation warning and will be removed in Python 3 13 Use turtle RawTurtle tiltangle instead turtle RawTurtle tiltangle was earlier incorrectly marked as deprecated its docstring has been corrected Patch by Hugo van Kemenade bpo 45831 faulthandler can now write ASCII only strings like filenames and function names with a single write syscall when dumping a traceback It reduces the risk of getting an unreadable dump when two threads or two processes dump a traceback to the same file like stderr at the same time Patch by Victor Stinner bpo 45828 sqlite C callbacks now use unraisable exceptions if callback tracebacks are enabled Patch by Erlend E Aasland bpo 41735 Fix thread lock in zlib Decompress flush method before PyObject_GetBuffer bpo 45235 Reverted an argparse bugfix that caused regression in the handling of default arguments for subparsers This prevented leaf level arguments from taking precedence over root level arguments bpo 45754 Fix a regression in Python 3 11a1 and 3 11a2 where sqlite3 incorrectly would use SQLITE_LIMIT_LENGTH when checking SQL statement lengths Now SQLITE_LIMIT_SQL_LENGTH is used Patch by Erlend E Aasland bpo 45766 Added proportional option to statistics linear_regression bpo 45765 In importlib metadata fix distribution discovery for an empty path bpo 45757 Fix bug where dis produced an incorrect oparg when EXTENDED_ARG is followed by an opcode that does not use its argument bpo 45644 In place JSON file formatting using python3 m json tool infile infile now works correctly previously it left the file empty Patch by Chris Wesseling bpo 45703 When a namespace package is imported before another module from the same namespace is created installed in a different sys path location while the program is running calling the importlib invalidate_caches function will now also guarantee the new module is noticed bpo 45535 Improve output of dir with Enums bpo 45664 Fix types resolve_bases and types new_class for types GenericAlias instance as a base bpo 45663 Fix dataclasses is_dataclass for dataclasses which are subclasses of types GenericAlias bpo 45662 Fix the repr of dataclasses InitVar with a type alias to the built in class e g InitVar list int bpo 43137 Launch GNOME web browsers via gio tool instead of obsolete gvfs open bpo 45429 On Windows time sleep now uses a waitable timer which supports high resolution timers Patch by Donghee Na and Eryk Sun bpo 37295 Optimize math comb and math perm bpo 45514 Deprecated legacy functions in importlib res,en
1581,ources bpo 45507 Add tests for truncated missing trailers in gzip decompress implementation bpo 45359 Implement PEP 585 for graphlib TopologicalSorter bpo 44733 Add max_tasks_per_child to concurrent futures ProcessPoolExecutor This allows users to specify the maximum number of tasks a single process should execute before the process needs to be restarted bpo 28806 Improve netrc library netrc file no longer needs to contain all tokens And if the login name is anonymous security check is no longer need bpo 43498 Avoid a possible RuntimeError dictionary changed size during iteration when adjusting the process count of ProcessPoolExecutor bpo 42158 Add MIME types for N quads N triples Notation3 and TriG to mimetypes bpo 30533 Add inspect getmembers_static it return all members without triggering dynamic lookup via the descriptor protocol Patch by Weipeng Hong Documentation bpo 42238 make C Doc suspicious will be removed soon in favor of make C Doc check mark it as deprecated bpo 45840 Improve cross references in the documentation for the data model bpo 45640 Properly marked up grammar tokens in the documentation are now clickable and take you to the definition of a given piece of grammar Patch by Arthur Milchior bpo 45788 Link doc for sys prefix to sysconfig doc on installation paths bpo 45772 socket socket documentation is corrected to a class from a function bpo 45392 Update the docstring of the type built in to remove a redundant line and to mention keyword arguments for the constructor bpo 45250 Update the documentation to note that CPython does not consistently require iterators to define __iter__ bpo 25381 In the extending chapter of the extending doc update a paragraph about the global variables containing exception information bpo 43905 Expanded astuple and asdict docs warning about deepcopy being applied and providing a workaround Tests bpo 45695 Out of tree builds with a read only source directory are now tested by CI bpo 19460 Add new Test for Lib email mime nonmultipart py MIMENonMultipart bpo 45835 Fix race condition in test_queue tests with multiple feeder threads bpo 45783 The test for the freeze tool now handles file moves and deletions bpo 45745 Remove the findleaks command line option of regrtest use the fail env changed option instead Since Python 3 7 it was a deprecated alias to the fail env changed option bpo 45701 Add tests with tuple type with functools lru_cache to test_functools Build bpo 44035 CI now verifies that autoconf files have been regenerated with a current and unpatched autoconf package bpo 45950 The build system now uses a _bootstrap_python interpreter for freezing and deepfreezing again To speed up build process the build tools _bootstrap_python and _freeze_module are no longer build with LTO bpo 45881 The configure script now accepts with build python and with freeze module options to make cross compiling easier bpo 40280 Emscripten platform now uses wasm suffix by default bpo 40280 Disable unusable core extension modules on WASM Emscripten targets bpo 40280 configure now checks for socket shutdown function The check makes it possible to disable SYS_shutdown with ac_cv_func_shutdown no in CONFIG_SITE bpo 40280 configure now checks for functions fork1 getegid geteuid getgid getppid getuid opendir pipe system wait ttyname bpo 33393 Update config guess to 2021 06 03 and config sub to 2021 08 14 Makefile now has an update config target to make updating more convenient bpo 45866 make regen all now produces the same output when run from a directory other than the source tree when building Python out of the source tree pegen now strips directory of the generated by pygen from FILENAME header Patch by Victor Stinner bpo 40280 configure now accepts machine wasm32 or wasm64 and OS wasi or emscripten for cross building e g wasm32 unknown emscripten wasm32 wasi or wasm32 unknown wasi bpo 41498 Python now compiles on platforms without sigset_t Several functions in signal are not available when sigset_t is missing Based on patch by Roman Yurchak for pyodide bpo 45881 setup py now uses CC from environm,en
1582,ent first to discover multiarch and cross compile paths bpo 45886 The _freeze_module program path can now be overridden on the command line e g make FREEZE_MODULE x86_64 Program _freeze_module bpo 45873 Get rid of the _bootstrap_python build step The deepfreeze py script is now run using PYTHON_FOR_REGEN which can be Python 3 7 or newer on Windows 3 8 or newer bpo 45847 Port builtin hashlib extensions to PY_STDLIB_MOD macro and addext bpo 45723 Add autoconf helpers for saving and restoring environment variables SAVE_ENV Save CFLAGS LDFLAGS LIBS and CPPFLAGS RESTORE_ENV Restore CFLAGS LDFLAGS LIBS and CPPFLAGS WITH_SAVE_ENV SCRIPT Run SCRIPT wrapped with SAVE_ENV and RESTORE_ENV Patch by Erlend E Aasland bpo 45573 Mandatory core modules that are required to bootstrap Python are now in Modules Setup bootstrap bpo 45573 configure now creates Modules Setup stdlib with conditionally enabled disabled extension module lines The file is not used yet bpo 45573 configure now uses a unified format to set state compiler flags and linker flags in Makefile The new macro PY_STDLIB_MOD sets three variables that are consumed by Modules Setup and setup py bpo 45816 Python now supports building with Visual Studio 2022 MSVC v143 VS Version 17 0 Patch by Jeremiah Vivian bpo 45800 Settings for pyexpat C extension are now detected by configure The bundled expat library is built in Makefile bpo 45798 Settings for decimal internal C extension are now detected by configure The bundled libmpdec library is built in Makefile bpo 45723 configure has a new option with pkg config to disable or require pkg config bpo 45774 The build dependencies for sqlite3 are now detected by configure and pkg config Patch by Erlend E Aasland bpo 45763 The build dependencies for zlib bz2 and lzma are now detected by configure bpo 45747 gdbm and dbm build dependencies are now detected by configure bpo 45743 On macOS the build system no longer passes search_paths_first to the linker The flag has been the default since Xcode 4 macOS 10 6 bpo 45723 configure ac is now compatible with autoconf 2 71 Deprecated checks STDC_HEADERS and AC_HEADER_TIME have been removed bpo 45723 configure now prints a warning when pkg config is missing bpo 45731 configure enable loadable sqlite extensions is now handled by new PY_SQLITE_ENABLE_LOAD_EXTENSION macro instead of logic in setup py bpo 45723 configure ac now uses custom helper macros and AC_CACHE_CHECK to simplify and speed up configure runs bpo 45696 Skip the marshal step for frozen modules by generating C code that produces a set of ready to use code objects This speeds up startup time by another 10 or more bpo 45561 Run smelly py tool from srcdir Windows bpo 46105 Fixed calculation of sys path in a venv on Windows bpo 45901 When installed through the Microsoft Store and set as the default app for py files command line arguments will now be passed to Python when invoking a script without explicitly launching Python that is script py args rather than python script py args bpo 45616 Fix Python Launcher s ability to distinguish between versions 3 1 and 3 10 when either one is explicitly requested Previously 3 1 would be used if 3 10 was requested but not installed and 3 10 would be used if 3 1 was requested but 3 10 was installed bpo 45850 Implement changes to build with deep frozen modules on Windows Note that we now require Python 3 10 as the bootstrap or host Python bpo 45732 Updates bundled Tcl Tk to 8 6 12 bpo 45720 Internal reference to shlwapi dll was dropped to help improve startup time This DLL will no longer be loaded at the start of every Python process macOS bpo 45732 Update python org macOS installer to use Tcl Tk 8 6 12 C API bpo 39026 Fix Python h to build C extensions with Xcode remove a relative include from Include cpython pystate h Python 3 11 0 alpha 2 Release date 2021 11 05 Core and Builtins bpo 45716 Improve the SyntaxError message when using True None or False as keywords in a function call Patch by Pablo Galindo bpo 45688 sys stdlib_module_names now contains the macOS specific module _scproxy bpo 45379 Clarify,en
1583, ImportError message when we try to explicitly import a frozen module but frozen modules are disabled bpo 44525 Specialize simple calls to Python functions no starargs keyowrd dict or closure bpo 45530 Cases of sorting using tuples as keys may now be significantly faster in some cases Patch by Tim Peters The order of the result may differ from earlier releases if the tuple elements don t define a total ordering see Value comparisons for information on total ordering It s generally true that the result of sorting simply isn t well defined in the absence of a total ordering on list elements bpo 45526 In obmalloc set ADDRESS_BITS to not ignore any bits ignored 16 before That is safer in the case that the kernel gives user space virtual addresses that span a range greater than 48 bits bpo 30570 Fixed a crash in issubclass from infinite recursion when searching pathological __bases__ tuples bpo 45521 Fix a bug in the obmalloc radix tree code On 64 bit machines the bug causes the tree to hold 46 bits of virtual addresses rather than the intended 48 bits bpo 45494 Fix parser crash when reporting errors involving invalid continuation characters Patch by Pablo Galindo bpo 45445 Python now fails to initialize if it finds an invalid X option in the command line Patch by Pablo Galindo bpo 45340 Object attributes are held in an array instead of a dictionary An object s dictionary are created lazily only when needed Reduces the memory consumption of a typical Python object by about 30 Patch by Mark Shannon bpo 45408 Fix a crash in the parser when reporting tokenizer errors that occur at the same time unclosed parentheses are detected Patch by Pablo Galindo bpo 29410 Add SipHash13 for string hash algorithm and use it by default bpo 45385 Fix reference leak from descr_check Patch by Donghee Na bpo 45367 Specialized the BINARY_MULTIPLY opcode to BINARY_MULTIPLY_INT and BINARY_MULTIPLY_FLOAT using the PEP 659 machinery bpo 21736 Frozen stdlib modules now have __file__ to the py file they would otherwise be loaded from if possible For packages __path__ now has the correct entry instead of being an empty list which allows unfrozen submodules to be imported These are set only if the stdlib directory is known when the runtime is initialized Note that the file at __file__ is not guaranteed to exist None of this affects non stdlib frozen modules nor for now frozen modules imported using PyImport_ImportFrozenModule Also at the moment co_filename is not updated for the module bpo 45020 For frozen stdlib modules record the original module name as module __spec__ loader_state origname If the value is different than module __spec__ name then the module was defined as an alias in Tools scripts freeze_modules py If it is None then the module comes from a source file outside the stdlib bpo 45324 In FrozenImporter find_spec we now preserve the information needed in exec_module to load the module This change mostly impacts internal details rather than changing the importer s behavior bpo 45292 Implement PEP 654 Add ExceptionGroup and BaseExceptionGroup Update traceback display code bpo 40116 Change to the implementation of split dictionaries Classes where the instances differ either in the exact set of attributes or in the order in which those attributes are set can still share keys This should have no observable effect on users of Python or the C API Patch by Mark Shannon bpo 44050 Extensions that indicate they use global state by setting m_size to 1 can again be used in multiple interpreters This reverts to behavior of Python 3 8 bpo 44525 Setup initial specialization infrastructure for the CALL_FUNCTION opcode Implemented initial specializations for C function calls CALL_FUNCTION_BUILTIN_O for METH_O flag CALL_FUNCTION_BUILTIN_FAST for METH_FASTCALL flag without keywords CALL_FUNCTION_LEN for len o CALL_FUNCTION_ISINSTANCE for isinstance o t bpo 44511 Improve the generated bytecode for class and mapping patterns bpo 43706 Speed up calls to enumerate by using the PEP 590 vectorcall calling convention Patch by Donghee Na Library bpo 45679 Fix caching of,en
1584, multi value typing Literal Literal True 2 is no longer equal to Literal 1 2 bpo 42064 Convert sqlite3 to multi phase initialisation PEP 489 Patches by Erlend E Aasland bpo 45438 Fix typing Signature string representation for generic builtin types bpo 45613 sqlite3 now sets sqlite3 threadsafety based on the default threading mode the underlying SQLite library has been compiled with Patch by Erlend E Aasland bpo 45574 Fix warning about print_escape being unused bpo 45581 sqlite3 connect now correctly raises MemoryError if the underlying SQLite API signals memory error Patch by Erlend E Aasland bpo 45557 pprint pprint now handles underscore_numbers correctly Previously it was always setting it to False bpo 44019 Add operator call to operator __all__ Patch by Kreusada bpo 42174 shutil get_terminal_size now falls back to sane values if the column or line count are 0 bpo 35673 Improve the introspectability of the __loader__ attribute for namespace packages importlib machinery NamespaceLoader is now public and implements the importlib abc InspectLoader interface _NamespaceLoader is kept for backward compatibility bpo 45515 Add references to zoneinfo in the datetime documentation mostly replacing outdated references to dateutil tz Change by Paul Ganssle bpo 45475 Reverted optimization of iterating gzip GzipFile bz2 BZ2File and lzma LZMAFile see bpo 43787 because it caused regression when user iterate them without having reference of them Patch by Inada Naoki bpo 45489 Update ForwardRef to support operator Patch by Donghee Na bpo 42222 Removed deprecated support for float arguments in randrange bpo 45428 Fix a regression in py_compile when reading filenames from standard input bpo 45467 Fix incremental decoder and stream reader in the raw unicode escape codec Previously they failed if the escape sequence was split bpo 45461 Fix incremental decoder and stream reader in the unicode escape codec Previously they failed if the escape sequence was split bpo 45239 Fixed email utils parsedate_tz crashing with UnboundLocalError on certain invalid input instead of returning None Patch by Ben Hoyt bpo 45417 Fix quadratic behaviour in the enum module Creation of enum classes with a lot of entries was quadratic bpo 45249 Fix the behaviour of traceback print_exc when displaying the caret when the end_offset in the exception is set to 0 Patch by Pablo Galindo bpo 45416 Fix use of asyncio Condition with explicit asyncio Lock objects which was a regression due to removal of explicit loop arguments Patch by Joongi Kim bpo 20028 Empty escapechar quotechar is not allowed when initializing csv Dialect Patch by Vajrasky Kok and Donghee Na bpo 44904 Fix bug in the doctest module that caused it to fail if a docstring included an example with a classmethod property Patch by Alex Waygood bpo 45406 Make inspect getmodule catch FileNotFoundError raised by inspect getabsfile and return None to indicate that the module could not be determined bpo 45411 Add extensions for files containing subtitles srt vtt to the mimetypes py module bpo 10716 Migrated pydoc to HTML5 without changing the look of it Side effect is to update xmlrpc s ServerHTMLDoc which now uses the CSS too cgitb now relies less on pydoc as it can t use the CSS file bpo 27580 Add support of null characters in csv bpo 45262 Prevent use after free in asyncio Make sure the cached running loop holder gets cleared on dealloc to prevent use after free in get_running_loop bpo 45386 Make xmlrpc client more robust to C runtimes where the underlying C strftime function results in a ValueError when testing for year formatting options bpo 20028 Improve error message of csv Dialect when initializing Patch by Vajrasky Kok and Donghee Na bpo 45343 Update bundled pip to 21 2 4 and setuptools to 58 1 0 bpo 45328 Fixed http client HTTPConnection to work properly in OSs that don t support the TCP_NODELAY socket option bpo 45243 Add setlimit and getlimit to sqlite3 Connection for setting and getting SQLite limits by connection basis Patch by Erlend E Aasland bpo 45320 Removed from the inspect module the getargspec ,en
1585,function deprecated since Python 3 0 use inspect signature or inspect getfullargspec instead the formatargspec function deprecated since Python 3 5 use the inspect signature function and Signature object directly the undocumented Signature from_builtin and Signature from_function functions deprecated since Python 3 5 use the Signature from_callable method instead Patch by Hugo van Kemenade bpo 45192 Fix the tempfile _infer_return_type function so that the dir argument of the tempfile functions accepts an object implementing the os PathLike protocol Patch by Kyungmin Lee bpo 45160 When tracing a tkinter variable used by a ttk OptionMenu callbacks are no longer made twice bpo 25625 Added non parallel safe chdir context manager to change the current working directory and then restore it on exit Simple wrapper around chdir bpo 24139 Add support for SQLite extended result codes in sqlite3 Error Patch by Erlend E Aasland bpo 24444 Fixed an error raised in argparse help display when help for an option is set to 1 blank spaces or when choices arg is an empty container bpo 44547 Implement Fraction __int__ so that a fractions Fraction instance f passes an isinstance f typing SupportsInt check bpo 40321 Adds support for HTTP 308 redirects to urllib See RFC 7538 for details Patch by Jochem Schulenklopper bpo 41374 Ensure that socket TCP_ constants are exposed on Cygwin 3 1 6 and greater bpo 35970 Add help flag to the base64 module s command line interface Patch contributed by Robert Kuska Documentation bpo 45726 Improve documentation for functools singledispatch and functools singledispatchmethod bpo 45680 Amend the docs on GenericAlias objects to clarify that non container classes can also implement __class_getitem__ Patch contributed by Alex Waygood bpo 45618 Update Sphinx version used to build the documentation to 4 2 0 Patch by Maciej Olko bpo 45655 Add a new relevant PEPs section to the top of the documentation for the typing module Patch by Alex Waygood bpo 45604 Add level argument to multiprocessing log_to_stderr function docs bpo 45516 Add protocol description to the importlib abc TraversableResources documentation bpo 45464 Mention in the documentation of Built in Exceptions that inheriting from multiple exception types in a single subclass is not recommended due to possible memory layout incompatibility bpo 45449 Add note about PEP 585 in collections abc bpo 45516 Add protocol description to the importlib abc Traversable documentation bpo 20692 Add Programming FAQ entry explaining that int literal attribute access requires either a space after or parentheses around the literal Tests bpo 45678 Add tests for scenarios in which functools singledispatchmethod is stacked on top of a method that has already been wrapped by two other decorators Patch by Alex Waygood bpo 45578 Add tests for dis distb bpo 45678 Add tests to ensure that functools singledispatchmethod correctly wraps the attributes of the target function bpo 45668 PGO tests now pass when Python is built without test extension modules bpo 45577 Add subtests for all pickle protocols in test_zoneinfo bpo 45566 Fix test_frozen_pickle in test_dataclasses to check all pickle versions bpo 43592 test libregrtest now raises the soft resource limit for the maximum number of file descriptors when the default is too low for our test suite as was often the case on macOS bpo 39679 Add more test cases for functools singledispatchmethod when combined with classmethod or staticmethod bpo 45410 When libregrtest spawns a worker process stderr is now written into stdout to keep messages order Use a single pipe for stdout and stderr rather than two pipes Previously messages were out of order which made analysis of buildbot logs harder Patch by Victor Stinner bpo 45402 Fix test_tools test_sundry when Python is built out of tree fix how the freeze_modules py tool locates the _freeze_module program Patch by Victor Stinner bpo 45403 Fix test_sys test_stdlib_dir when Python is built outside the source tree compare normalized paths Patch by Victor Stinner bpo 45400 Fix test_name_error_suggesti,en
1586,ons_do_not_trigger_for_too_many_locals of test_exceptions if a directory name contains a1 like Python 3 11 0a1 use a stricter regular expression Patch by Victor Stinner bpo 10572 Rename sqlite3 tests from test_sqlite to test_sqlite3 and relocate them to Lib test test_sqlite3 Patch by Erlend E Aasland Build bpo 43158 setup py now uses values from configure script to build the _uuid extension module Configure now detects util linux s libuuid too bpo 45666 Fix warning of swprintf and s usage in _testembed c bpo 45548 Modules Setup and Modules makesetup have been improved The Setup file now contains working rules for all extensions Outdated comments have been removed Rules defined by makesetup track dependencies correctly bpo 45548 The math and cmath implementation now require a C99 compatible libm and no longer ship with workarounds for missing acosh asinh atanh expm1 and log1p functions bpo 45595 setup py and makesetup now track build dependencies on all Python header files and module specific header files bpo 45571 Modules Setup now use PY_CFLAGS_NODIST instead of PY_CFLAGS to compile shared modules bpo 45570 pyexpat and _elementtree no longer define obsolete macros HAVE_EXPAT_CONFIG_H and USE_PYEXPAT_CAPI XML_POOR_ENTROPY is now defined in expat_config h bpo 43974 setup py no longer defines Py_BUILD_CORE_MODULE Instead every module that uses the internal API defines the macro bpo 45548 Fill in missing entries in Modules Setup bpo 45532 Update sys version to use main as fallback information Patch by Jeong YunWon bpo 45536 The configure script now checks whether OpenSSL headers and libraries provide required APIs Most common APIs are verified The check detects outdated or missing OpenSSL Failures do not stop configure bpo 45221 Fixed regression in handling of LDFLAGS and CPPFLAGS options where argparse parse_known_args could interpret an option as one of the built in command line argument for example h for help bpo 45440 Building Python now requires a C99 math h header file providing the following functions copysign hypot isfinite isinf isnan round Patch by Victor Stinner bpo 45405 Prevent internal configure error when running configure with recent versions of non Apple clang Patch by David Bohman bpo 45433 Avoid linking libpython with libcrypt Windows bpo 43652 Update Tcl Tk to 8 6 11 actually this time The previous update incorrectly included 8 6 10 bpo 45337 venv now warns when the created environment may need to be accessed at a different path due to redirections links or junctions It also now correctly installs or upgrades components when the alternate path is required bpo 43851 Build SQLite SQLITE_OMIT_AUTOINIT on Windows Patch by Erlend E Aasland macOS bpo 44828 Avoid tkinter file dialog failure on macOS 12 Monterey when using the Tk 8 6 11 provided by python org macOS installers Patch by Marc Culler of the Tk project IDLE bpo 45495 Add context keywords case and match to completions list C API bpo 29103 PyType_FromSpec now copies the class name from the spec to a buffer owned by the class so the original can be safely deallocated Patch by Petr Viktorin bpo 45522 The internal freelists for frame float list dict async generators and context objects can now be disabled bpo 35134 Exclude PyWeakref_GET_OBJECT from the limited C API It never worked since the PyWeakReference structure is opaque in the limited C API bpo 35081 Move the interpreteridobject h header file from Include to Include internal It only provides private functions Patch by Victor Stinner bpo 35134 The non limited API files cellobject h classobject h context h funcobject h genobject h and longintrepr h have been moved to the Include cpython directory Moreover the eval h header file was removed These files must not be included directly as they are already included in Python h Include Files If they have been included directly consider including Python h instead Patch by Victor Stinner bpo 45474 The following items are no longer available when Py_LIMITED_API is defined PyMarshal_WriteLongToFile PyMarshal_WriteObjectToFile PyMarshal_ReadObjectFromString PyMa,en
1587,rshal_WriteObjectToString the Py_MARSHAL_VERSION macro These are not part of the limited API Patch by Victor Stinner bpo 45434 Remove the pystrhex h header file It only contains private functions C extensions should only include the main Python h header file Patch by Victor Stinner bpo 45440 Remove the Py_FORCE_DOUBLE macro It was used by the Py_IS_INFINITY macro Patch by Victor Stinner bpo 45434 Python h no longer includes the header files stdlib h stdio h errno h and string h when the Py_LIMITED_API macro is set to 0x030b0000 Python 3 11 or higher C extensions should explicitly include the header files after include Python h Patch by Victor Stinner bpo 41123 Remove Py_UNICODE_COPY and Py_UNICODE_FILL macros deprecated since Python 3 3 Use PyUnicode_CopyCharacters or memcpy wchar_t string and PyUnicode_Fill functions instead Patch by Victor Stinner bpo 45412 Remove the following math macros using the errno variable Py_ADJUST_ERANGE1 Py_ADJUST_ERANGE2 Py_OVERFLOWED Py_SET_ERANGE_IF_OVERFLOW Py_SET_ERRNO_ON_MATH_ERROR Patch by Victor Stinner bpo 45395 Custom frozen modules the array set to PyImport_FrozenModules are now treated as additions rather than replacing all the default frozen modules Frozen stdlib modules can still be disabled by setting the code field of the custom array entry to NULL bpo 43760 Add new PyThreadState_EnterTracing and PyThreadState_LeaveTracing functions to the limited C API to suspend and resume tracing and profiling Patch by Victor Stinner bpo 44220 PyStructSequence_UnnamedField is added to the Stable ABI Python 3 11 0 alpha 1 Release date 2021 10 05 Security bpo 42278 Replaced usage of tempfile mktemp with TemporaryDirectory to avoid a potential race condition bpo 44600 Fix incorrect line numbers while tracing some failed patterns in match statements Patch by Charles Burkland bpo 41180 Add auditing events to the marshal module and stop raising code __init__ events for every unmarshalled code object Directly instantiated code objects will continue to raise an event and audit event handlers should inspect or collect the raw marshal data This reduces a significant performance overhead when loading from pyc files bpo 44394 Update the vendored copy of libexpat to 2 4 1 from 2 2 8 to get the fix for the CVE 2013 0340 Billion Laughs vulnerability This copy is most used on Windows and macOS bpo 43124 Made the internal putcmd function in smtplib sanitize input for presence of r and n characters to avoid unlikely command injection bpo 44022 http client now avoids infinitely reading potential HTTP headers after a 100 Continue status response from the server Core and Builtins bpo 43760 The number of hardware branches per instruction dispatch is reduced from two to one by adding a special instruction for tracing Patch by Mark Shannon bpo 45061 Add a deallocator to the bool type to detect refcount bugs in C extensions which call Py_DECREF Py_True or Py_DECREF Py_False by mistake Detect also refcount bugs when the empty tuple singleton or the Unicode empty string singleton is destroyed by mistake Patch by Victor Stinner bpo 24076 sum was further optimised for summing up single digit integers bpo 45190 Update Unicode databases to Unicode 14 0 0 bpo 45167 Fix deepcopying of types GenericAlias objects bpo 45155 int to_bytes and int from_bytes now take a default value of big for the byteorder argument int to_bytes also takes a default value of 1 for the length argument bpo 44219 Release the GIL while performing isatty system calls on arbitrary file descriptors In particular this affects os isatty os device_encoding and io TextIOWrapper By extension io open in text mode is also affected This change solves a deadlock in os isatty Patch by Vincent Michel in bpo 44219 bpo 44959 Added fallback to extension modules with sl suffix on HP UX bpo 45121 Fix issue where Protocol __init__ raises RecursionError when it s called directly or via super Patch provided by Yurii Karabas bpo 44348 The deallocator function of the BaseException type now uses the trashcan mechanism to prevent stack overflow For example when a RecursionE,en
1588,rror instance is raised it can be linked to another RecursionError through the __context__ attribute or the __traceback__ attribute and then a chain of exceptions is created When the chain is destroyed nested deallocator function calls can crash with a stack overflow if the chain is too long compared to the available stack memory Patch by Victor Stinner bpo 45123 Fix PyAiter_Check to only check for the __anext__ presence not for __aiter__ Rename PyAiter_Check to PyAIter_Check PyObject_GetAiter PyObject_GetAIter bpo 1514420 Interpreter no longer attempts to open files with names in angle brackets like string or stdin when formatting an exception bpo 41031 Match C and Python code formatting of unprintable exceptions and exceptions in the __main__ module bpo 37330 open io open codecs open and fileinput FileInput no longer accept U universal newline in the file mode This flag was deprecated since Python 3 3 Patch by Victor Stinner bpo 45083 When the interpreter renders an exception its name now has a complete qualname Previously only the class name was concatenated to the module name which sometimes resulted in an incorrect full name being displayed This issue impacted only the C code exception rendering the traceback module was using qualname already bpo 34561 List sorting now uses the merge ordering strategy from Munro and Wild s powersort Unlike the former strategy this is provably near optimal in the entropy of the distribution of run lengths Most uses of list sort probably won t see a significant time difference but may see significant improvements in cases where the former strategy was exceptionally poor However as these are all fast linear time approximations to a problem that s inherently at best quadratic time to solve truly optimally it s also possible to contrive cases where the former strategy did better bpo 45056 Compiler now removes trailing unused constants from co_consts bpo 45020 Add a new command line option X frozen_modules on off to opt out of or into using optional frozen modules This defaults to on or off if it s running out of the source tree bpo 45012 In posix release GIL during stat lstat and fstatat syscalls made by os DirEntry stat Patch by Stanisław Skonieczny bpo 45018 Fixed pickling of range iterators that iterated for over 2 32 times bpo 45000 A SyntaxError is now raised when trying to delete __debug__ Patch by Donghee Na bpo 44963 Implement send and throw methods for anext_awaitable objects Patch by Pablo Galindo bpo 44962 Fix a race in WeakKeyDictionary WeakValueDictionary and WeakSet when two threads attempt to commit the last pending removal This fixes asyncio create_task and fixes a data loss in asyncio run where shutdown_asyncgens is not run bpo 24234 Implement the __bytes__ special method on the bytes type so a bytes object b passes an isinstance b typing SupportsBytes check bpo 24234 Implement the __complex__ special method on the complex type so a complex number z passes an isinstance z typing SupportsComplex check bpo 44954 Fixed a corner case bug where the result of float fromhex 0x 8p 1074 was rounded the wrong way bpo 44947 Refine the syntax error for trailing commas in import statements Patch by Pablo Galindo bpo 44945 Specialize the BINARY_ADD instruction using the PEP 659 machinery Adds five new instructions BINARY_ADD_ADAPTIVE BINARY_ADD_FLOAT BINARY_ADD_INT BINARY_ADD_UNICODE BINARY_ADD_UNICODE_INPLACE_FAST bpo 44929 Fix some edge cases of enum Flag string representation in the REPL Patch by Pablo Galindo bpo 44914 Class version tags are no longer recycled This means that a version tag serves as a unique identifier for the state of a class We rely on this for effective specialization of the LOAD_ATTR and other instructions bpo 44698 Restore behaviour of complex exponentiation with integer valued exponent of type float or complex bpo 44895 A debug variable PYTHONDUMPREFSFILE is added for creating a dump file which is generated by with trace refs Patch by Donghee Na bpo 44900 Add five superinstructions for PEP 659 quickening LOAD_FAST LOAD_FAST STORE_FAST LOAD_FAST LOAD_FAST LOA,en
1589,D_CONST LOAD_CONST LOAD_FAST STORE_FAST STORE_FAST bpo 44889 Initial implementation of adaptive specialization of LOAD_METHOD The following specialized forms were added LOAD_METHOD_CACHED LOAD_METHOD_MODULE LOAD_METHOD_CLASS bpo 44890 Specialization stats are always collected in debug builds bpo 44885 Correct the ast locations of f strings with format specs and repeated expressions Patch by Pablo Galindo bpo 44878 Remove the loop from the bytecode interpreter All instructions end with a DISPATCH macro so the loop is now redundant bpo 44878 Remove switch statement for interpreter loop when using computed gotos This makes sure that we only have one dispatch table in the interpreter bpo 44874 Deprecate the old trashcan macros Py_TRASHCAN_SAFE_BEGIN Py_TRASHCAN_SAFE_END They should be replaced by the new macros Py_TRASHCAN_BEGIN and Py_TRASHCAN_END bpo 44872 Use new trashcan macros Py_TRASHCAN_BEGIN END in frameobject c instead of the old ones Py_TRASHCAN_SAFE_BEGIN END bpo 33930 Fix segmentation fault with deep recursion when cleaning method objects Patch by Augusto Goulart and Pablo Galindo bpo 25782 Fix bug where PyErr_SetObject hangs when the current exception has a cycle in its context chain bpo 44856 Fix reference leaks in the error paths of update_bases and __build_class__ Patch by Pablo Galindo bpo 44826 Initial implementation of adaptive specialization of STORE_ATTR Three specialized forms of STORE_ATTR are added STORE_ATTR_SLOT STORE_ATTR_SPLIT_KEYS STORE_ATTR_WITH_HINT bpo 44838 Fixed a bug that was causing the parser to raise an incorrect custom SyntaxError for invalid if expressions Patch by Pablo Galindo bpo 44821 Create instance dictionaries __dict__ eagerly to improve regularity of object layout and assist specialization bpo 44792 Improve syntax errors for if expressions Patch by Miguel Brito bpo 34013 Generalize the invalid legacy statement custom error message like the one generated when print is called without parentheses to include more generic expressions Patch by Pablo Galindo bpo 44732 Rename types Union to types UnionType bpo 44725 Expose specialization stats in python via _opcode get_specialization_stats bpo 44717 Improve AttributeError on circular imports of submodules bpo 44698 Fix undefined behaviour in complex object exponentiation bpo 44653 Support typing types in parameter substitution in the union type bpo 44676 Add ability to serialise types Union objects Patch provided by Yurii Karabas bpo 44633 Parameter substitution of the union type with wrong types now raises TypeError instead of returning NotImplemented bpo 44661 Update property_descr_set to use vectorcall if possible Patch by Donghee Na bpo 44662 Add __module__ to types Union This also fixes types Union issues with typing Annotated Patch provided by Yurii Karabas bpo 44655 Include the name of the type in unset __slots__ attribute errors Patch by Pablo Galindo bpo 44655 Don t include a missing attribute with the same name as the failing one when offering suggestions for missing attributes Patch by Pablo Galindo bpo 44646 Fix the hash of the union type it no longer depends on the order of arguments bpo 44636 Collapse union of equal types E g the result of int int is now int Fix comparison of the union type with non hashable objects E g int str no longer raises a TypeError bpo 44611 On Windows os urandom uses BCryptGenRandom API instead of CryptGenRandom API which is deprecated from Microsoft Windows API Patch by Donghee Na bpo 44635 Convert None to type None in the union type constructor bpo 26280 Implement adaptive specialization for BINARY_SUBSCR Three specialized forms of BINARY_SUBSCR are added BINARY_SUBSCR_LIST_INT BINARY_SUBSCR_TUPLE_INT BINARY_SUBSCR_DICT bpo 44589 Mapping patterns in match statements with two or more equal literal keys will now raise a SyntaxError at compile time bpo 44606 Fix __instancecheck__ and __subclasscheck__ for the union type bpo 42073 The classmethod decorator can now wrap other classmethod like descriptors bpo 41972 Tuned the string searching algorithm of fastsearch h to have a shorter inner loop for ,en
1590,most cases bpo 44590 All necessary data for executing a Python function local variables stack etc is now kept in a per thread stack Frame objects are lazily allocated on demand This increases performance by about 7 on the standard benchmark suite Introspection and debugging are unaffected as frame objects are always available when needed Patch by Mark Shannon bpo 44584 The threading debug PYTHONTHREADDEBUG environment variable is deprecated in Python 3 10 and will be removed in Python 3 12 This feature requires a debug build of Python Patch by Victor Stinner bpo 43895 An obsolete internal cache of shared object file handles added in 1995 that attempted but did not guarantee that a so would not be dlopen ed twice to work around flaws in mid 1990s posix ish operating systems has been removed from dynload_shlib c bpo 44490 typing now searches for type parameters in types Union objects get_type_hints will also properly resolve annotations with nested types Union objects Patch provided by Yurii Karabas bpo 43950 Code objects can now provide the column information for instructions when available This is levaraged during traceback printing to show the expressions responsible for errors Contributed by Pablo Galindo Batuhan Taskaya and Ammar Askar as part of PEP 657 bpo 44562 Remove uses of PyObject_GC_Del in error path when initializing types GenericAlias bpo 41486 Fix a memory consumption and copying performance regression in earlier 3 10 beta releases if someone used an output buffer larger than 4GiB with zlib decompress on input data that expands that large bpo 43908 Heap types with the Py_TPFLAGS_IMMUTABLETYPE flag can now inherit the PEP 590 vectorcall protocol Previously this was only possible for static types Patch by Erlend E Aasland bpo 44553 Implement GC methods for types Union to break reference cycles and prevent memory leaks bpo 44490 Add __parameters__ attribute and __getitem__ operator to types Union Patch provided by Yurii Karabas bpo 44523 Remove the pass through for hash of weakref proxy objects to prevent unintended consequences when the original referred object dies while the proxy is part of a hashable object Patch by Pablo Galindo bpo 44483 Fix a crash in types Union objects when creating a union of an object with bad __module__ field bpo 44486 Modules will always have a dictionary even when created by types ModuleType __new__ bpo 44472 Fix ltrace functionality when exceptions are raised Patch by Pablo Galindo bpo 12022 A TypeError is now raised instead of an AttributeError in with and async with statements for objects which do not support the context manager or asynchronous context manager protocols correspondingly bpo 44297 Make sure that the line number is set when entering a comprehension scope Ensures that backtraces inclusing generator expressions show the correct line number bpo 44456 Improve the syntax error when mixing positional and keyword patterns Patch by Pablo Galindo bpo 44409 Fix error location information for tokenizer errors raised on initialization of the tokenizer Patch by Pablo Galindo bpo 44396 Fix a possible crash in the tokenizer when raising syntax errors for unclosed strings Patch by Pablo Galindo bpo 44376 Exact integer exponentiation like i 2 or pow i 2 with a small exponent is much faster due to reducing overhead in such cases bpo 44313 Directly imported objects and modules through import and from import statements don t generate LOAD_METHOD CALL_METHOD for directly accessed objects on their namespace They now use the regular LOAD_ATTR CALL_FUNCTION bpo 44338 Implement adaptive specialization for LOAD_GLOBAL Two specialized forms of LOAD_GLOBAL are added LOAD_GLOBAL_MODULE LOAD_GLOBAL_BUILTIN bpo 44368 Improve syntax errors for invalid as targets Patch by Pablo Galindo bpo 44349 Fix an edge case when displaying text from files with encoding in syntax errors Patch by Pablo Galindo bpo 44337 Initial implementation of adaptive specialization of LOAD_ATTR Four specialized forms of LOAD_ATTR are added LOAD_ATTR_SLOT LOAD_ATTR_SPLIT_KEYS LOAD_ATTR_WITH_HINT LOAD_ATTR_MODULE bpo 44335 ,en
1591,Fix a regression when identifying incorrect characters in syntax errors Patch by Pablo Galindo bpo 43693 Computation of the offsets of cell variables is done in the compiler instead of at runtime This reduces the overhead of handling cell and free variables especially in the case where a variable is both an argument and cell variable bpo 44317 Improve tokenizer error with improved locations Patch by Pablo Galindo bpo 44304 Fix a crash in the sqlite3 module that happened when the garbage collector clears sqlite Statement objects Patch by Pablo Galindo bpo 44305 Improve error message for try blocks without except or finally blocks Patch by Pablo Galindo bpo 43413 Constructors of subclasses of some builtin classes e g tuple list frozenset no longer accept arbitrary keyword arguments reverted in 3 11a4 Subclass of set can now define a __new__ method with additional keyword parameters without overriding also __init__ bpo 43667 Improve Unicode support in non UTF locales on Oracle Solaris This issue does not affect other Solaris systems bpo 43693 A new opcode MAKE_CELL has been added that effectively moves some of the work done on function entry into the compiler and into the eval loop In addition to creating the required cell objects the new opcode converts relevant arguments and other locals to cell variables on function entry bpo 44232 Fix a regression in type when a metaclass raises an exception The C function type_new must properly report the exception when a metaclass constructor raises an exception and the winner class is not the metaclass Patch by Victor Stinner bpo 44201 Avoid side effects of checking for specialized syntax errors in the REPL that was causing it to ask for extra tokens after a syntax error had been detected Patch by Pablo Galindo bpo 43693 PyCodeObject gained co_fastlocalnames and co_fastlocalkinds as the authoritative source of fast locals info Marshaled code objects have changed accordingly bpo 44184 Fix a crash at Python exit when a deallocator function removes the last strong reference to a heap type Patch by Victor Stinner bpo 44187 Implement quickening in the interpreter This offers no advantages as yet but is an enabler of future optimizations See PEP 659 for full explanation bpo 44180 The parser doesn t report generic syntax errors that happen in a position further away that the one it reached in the first pass Patch by Pablo Galindo bpo 44168 Fix error message in the parser involving keyword arguments with invalid expressions Patch by Pablo Galindo bpo 44156 String caches in compile c are now subinterpreter compatible bpo 44143 Fixed a crash in the parser that manifest when raising tokenizer errors when an existing exception was present Patch by Pablo Galindo bpo 44032 Move fast locals and other variables from the frame object to a per thread datastack bpo 44114 Fix incorrect dictkeys_reversed and dictitems_reversed function signatures in C code which broke webassembly builds bpo 44110 Improve str __getitem__ error message bpo 26110 Add CALL_METHOD_KW opcode to speed up method calls with keyword arguments Idea originated from PyPy A side effect is executing CALL_METHOD is now branchless in the evaluation loop bpo 28307 Compiler now optimizes simple C style formatting with literal format containing only format codes s r and a by converting them to f string expressions bpo 43149 Correct the syntax error message regarding multiple exception types to not refer to exception groups Patch by Pablo Galindo bpo 43822 The parser will prioritize tokenizer errors over custom syntax errors when raising exceptions Patch by Pablo Galindo bpo 40222 Zero cost exception handling Uses a lookup table to determine how to handle exceptions Removes SETUP_FINALLY and POP_TOP block instructions eliminating the runtime overhead of try statements Reduces the size of the frame object by about 60 Patch by Mark Shannon bpo 43918 Document the signature and default argument in the docstring of the new anext builtin bpo 43833 Emit a deprecation warning if the numeric literal is immediately followed by one of keywords and else,en
1592, for if in is or Raise a syntax error with more informative message if it is immediately followed by other keyword or identifier bpo 43879 Add native_thread_id to PyThreadState Patch by Gabriele N Tornetta bpo 43693 Compute cell offsets relative to locals in compiler Allows the interpreter to treats locals and cells a single array which is slightly more efficient Also make the LOAD_CLOSURE opcode an alias for LOAD_FAST Preserving LOAD_CLOSURE helps keep bytecode a bit more readable bpo 17792 More accurate error messages for access of unbound locals or free vars bpo 28146 Fix a confusing error message in str format bpo 11105 When compiling ast AST objects with recursive references through compile the interpreter doesn t crash anymore instead it raises a RecursionError bpo 39091 Fix crash when using passing a non exception to a generator s throw method Patch by Noah Oxer bpo 33346 Asynchronous comprehensions are now allowed inside comprehensions in asynchronous functions Outer comprehensions implicitly become asynchronous Library bpo 45371 Fix clang rpath issue in distutils The UnixCCompiler now uses correct clang option to add a runtime library directory rpath to a shared library bpo 45329 Fix freed memory access in pyexpat xmlparser when building it with an installed expat library 2 2 0 bpo 41710 On Unix if the sem_clockwait function is available in the C library glibc 2 30 and newer the threading Lock acquire method now uses the monotonic clock time CLOCK_MONOTONIC for the timeout rather than using the system clock time CLOCK_REALTIME to not be affected by system clock changes Patch by Victor Stinner bpo 1596321 Fix the threading _shutdown function when the threading module was imported first from a thread different than the main thread no longer log an error at Python exit bpo 45274 Fix a race condition in the Thread join method of the threading module If the function is interrupted by a signal and the signal handler raises an exception make sure that the thread remains in a consistent state to prevent a deadlock Patch by Victor Stinner bpo 21302 In Unix operating systems time sleep now uses the nanosleep function if clock_nanosleep is not available but nanosleep is available nanosleep allows to sleep with nanosecond precision bpo 21302 On Windows time sleep now uses a waitable timer which has a resolution of 100 nanoseconds 10 7 seconds Previously it had a resolution of 1 millisecond 10 3 seconds Patch by Benjamin Szőke and Victor Stinner bpo 45238 Fix unittest IsolatedAsyncioTestCase debug it runs now asynchronous methods and callbacks bpo 36674 unittest TestCase debug raises now a unittest SkipTest if the class or the test method are decorated with the skipping decorator bpo 45235 Fix an issue where argparse would not preserve values in a provided namespace when using a subparser with defaults bpo 45183 Have zipimport zipimporter find_spec not raise an exception when the underlying zip file has been deleted and the internal cache has been reset via invalidate_cache bpo 45234 Fixed a regression in copyfile copy copy2 raising FileNotFoundError when source is a directory which should raise IsADirectoryError bpo 45228 Fix stack buffer overflow in parsing J1939 network address bpo 45225 use map function instead of genexpr in capwords bpo 42135 Fix typo importlib find_loader is really slated for removal in Python 3 12 not 3 10 like the others in PR 25169 Patch by Hugo van Kemenade bpo 20524 Improves error messages on format operation for str float int and complex New format now shows the problematic pattern and the object type bpo 45168 Change dis dis output to omit op arg values that cannot be resolved due to co_consts co_names etc not being provided Previously the oparg itself was repeated in the value field which is not useful and can be confusing bpo 21302 In Unix operating systems time sleep now uses the clock_nanosleep function if available which allows to sleep for an interval specified with nanosecond precision bpo 45173 Remove from the configparser module the SafeConfigParser class the filename property of the Pa,en
1593,rsingError class the readfp method of the ConfigParser class deprecated since Python 3 2 Patch by Hugo van Kemenade bpo 44987 Pure ASCII strings are now normalized in constant time by unicodedata normalize Patch by Donghee Na bpo 35474 Calling mimetypes guess_all_extensions with strict False no longer affects the result of the following call with strict True Also mutating the returned list no longer affects the global state bpo 45166 typing get_type_hints now works with Final wrapped in ForwardRef bpo 45162 Remove many old deprecated unittest features fail and assert aliases of TestCase methods Broken from start TestCase method assertDictContainsSubset Ignored unittest TestLoader loadTestsFromModule TestLoader loadTestsFromModule parameter use_load_tests Old alias _TextTestResult of TextTestResult bpo 38371 Remove the deprecated split method of _tkinter TkappType Patch by Erlend E Aasland bpo 20499 Improve the speed and accuracy of statistics pvariance bpo 45132 Remove __getitem__ methods of xml dom pulldom DOMEventStream wsgiref util FileWrapper and fileinput FileInput deprecated since Python 3 9 Patch by Hugo van Kemenade bpo 45129 Due to significant security concerns the reuse_address parameter of asyncio loop create_datagram_endpoint disabled in Python 3 9 is now entirely removed This is because of the behavior of the socket option SO_REUSEADDR in UDP Patch by Hugo van Kemenade bpo 45124 The bdist_msi command deprecated in Python 3 9 is now removed Use bdist_wheel wheel packages instead Patch by Hugo van Kemenade bpo 30856 unittest TestResult methods addFailure addError addSkip and addSubTest are now called immediately after raising an exception in test or finishing a subtest Previously they were called only after finishing the test clean up bpo 45034 Changes how error is formatted for struct pack with H and h modes and too large small numbers Now it shows the actual numeric limits while previously it was showing arithmetic expressions bpo 25894 unittest now always reports skipped and failed subtests separately separate characters in default mode and separate lines in verbose mode Also the test description is now output for errors in test method class and module cleanups bpo 45081 Fix issue when dataclasses that inherit from typing Protocol subclasses have wrong __init__ Patch provided by Yurii Karabas bpo 45085 The binhex module deprecated in Python 3 9 is now removed The following binascii functions deprecated in Python 3 9 are now also removed a2b_hqx b2a_hqx rlecode_hqx rledecode_hqx The binascii crc_hqx function remains available Patch by Victor Stinner bpo 40360 The lib2to3 package is now deprecated and may not be able to parse Python 3 10 or newer See the PEP 617 New PEG parser for CPython Patch by Victor Stinner bpo 45075 Rename traceback StackSummary format_frame to traceback StackSummary format_frame_summary This method was added for 3 11 so it was not released yet Updated code and docs to better distinguish frame and FrameSummary bpo 31299 Add option to completely drop frames from a traceback by returning None from a format_frame override bpo 41620 run now always return a TestResult instance Previously it returned None if the test class or method was decorated with a skipping decorator bpo 45021 Fix a potential deadlock at shutdown of forked children when using concurrent futures module bpo 43913 Fix bugs in cleaning up classes and modules in unittest Functions registered with addModuleCleanup were not called unless the user defines tearDownModule in their test module Functions registered with addClassCleanup were not called if tearDownClass is set to None Buffering in TestResult did not work with functions registered with addClassCleanup and addModuleCleanup Errors in functions registered with addClassCleanup and addModuleCleanup were not handled correctly in buffered and debug modes Errors in setUpModule and functions registered with addModuleCleanup were reported in wrong order And several lesser bugs bpo 45030 Fix integer overflow in pickling and copying the range iterator bpo 45001 Made email date par,en
1594,sing more robust against malformed input namely a whitespace only Date header Patch by Wouter Bolsterlee bpo 45010 Remove support of special method __div__ in unittest mock It is not used in Python 3 bpo 39218 Improve accuracy of variance calculations by using x x instead of x 2 bpo 43613 Improve the speed of gzip compress and gzip decompress by compressing and decompressing at once in memory instead of in a streamed fashion bpo 37596 Ensure that set and frozenset objects are always marshalled reproducibly bpo 44019 A new function operator call has been added such that operator call obj args kwargs obj args kwargs bpo 42255 webbrowser MacOSX is deprecated and will be removed in Python 3 13 It is untested and undocumented and also not used by webbrowser itself Patch by Donghee Na bpo 44955 Method stopTestRun is now always called in pair with method startTestRun for TestResult objects implicitly created in run Previously it was not called for test methods and classes decorated with a skipping decorator bpo 39039 tarfile open raises ReadError when a zlib error occurs during file extraction bpo 44935 subprocess on Solaris now also uses os posix_spawn for better performance bpo 44911 IsolatedAsyncioTestCase will no longer throw an exception while cancelling leaked tasks Patch by Bar Harel bpo 41322 Added DeprecationWarning for tests and async tests that return a value None as this may indicate an improperly written test for example a test written as a generator function bpo 44524 Make exception message more useful when subclass from typing special form alias Patch provided by Yurii Karabas bpo 38956 argparse BooleanOptionalAction s default value is no longer printed twice when used with argparse ArgumentDefaultsHelpFormatter bpo 44860 Fix the posix_user scheme in sysconfig to not depend on sys platlibdir bpo 44859 Improve error handling in sqlite3 and raise more accurate exceptions MemoryError is now raised instead of sqlite3 Warning when memory is not enough for encoding a statement to UTF 8 in Connection __call__ and Cursor execute UnicodEncodeError is now raised instead of sqlite3 Warning when the statement contains surrogate characters in Connection __call__ and Cursor execute TypeError is now raised instead of ValueError for non string script argument in Cursor executescript ValueError is now raised for script containing the null character instead of truncating it in Cursor executescript Correctly handle exceptions raised when getting boolean value of the result of the progress handler Add many tests covering different corner cases bpo 44581 Upgrade bundled pip to 21 2 3 and setuptools to 57 4 0 bpo 44849 Fix the os set_inheritable function on FreeBSD 14 for file descriptor opened with the O_PATH flag ignore the EBADF error on ioctl fallback on the fcntl implementation Patch by Victor Stinner bpo 44605 The functools total_ordering decorator now works with metaclasses bpo 44524 Fixed an issue wherein the __name__ and __qualname__ attributes of subscribed specialforms could be None bpo 44839 MemoryError raised in user defined functions will now produce a MemoryError in sqlite3 OverflowError will now be converted to DataError Previously OperationalError was produced in these cases bpo 44822 sqlite3 user defined functions and aggregators returning strings with embedded NUL characters are no longer truncated Patch by Erlend E Aasland bpo 44801 Ensure that the ParamSpec variable in Callable can only be substituted with a parameters expression a list of types an ellipsis ParamSpec or Concatenate bpo 44806 Non protocol subclasses of typing Protocol ignore now the __init__ method inherited from protocol base classes bpo 27275 collections OrderedDict popitem and collections OrderedDict pop no longer call __getitem__ and __delitem__ methods of the OrderedDict subclasses bpo 44793 Fix checking the number of arguments when subscribe a generic type with ParamSpec parameter bpo 44784 In importlib metadata tests override warnings behavior under expected DeprecationWarnings importlib_metadata 4 6 3 bpo 44667 The tokenize tokenize doesn t,en
1595, incorrectly generate a NEWLINE token if the source doesn t end with a new line character but the last line is a comment as the function is already generating a NL token Patch by Pablo Galindo bpo 44771 Added importlib simple module implementing adapters from a low level resources reader interface to a TraversableResources interface Legacy API path contents is now supported entirely by the files API with a compatibility shim supplied for resource loaders without that functionality Feature parity with importlib_resources 5 2 bpo 44752 rcompleter does not call getattr on property objects to avoid the side effect of evaluating the corresponding method bpo 44747 Refactor usage of sys _getframe in typing module Patch provided by Yurii Karabas bpo 42378 Fixes the issue with log file being overwritten when logging FileHandler is used in atexit with filemode set to w Note this will cause the message in atexit not being logged if the log stream is already closed due to shutdown of logging bpo 44720 weakref proxy objects referencing non iterators now raise TypeError rather than dereferencing the null tp_iternext slot and crashing bpo 44704 The implementation of collections abc Set _hash now matches that of frozenset __hash__ bpo 44666 Fixed issue in compileall compile_file when sys stdout is redirected Patch by Stefan Hölzl bpo 44688 sqlite3 Connection create_collation now accepts non ASCII collation names Patch by Erlend E Aasland bpo 44690 Adopt binacii a2b_base64 s strict mode in base64 b64decode bpo 42854 Fixed a bug in the _ssl module that was throwing OverflowError when using _ssl _SSLSocket write and _ssl _SSLSocket read for a big value of the len parameter Patch by Pablo Galindo bpo 44686 Replace unittest mock _importer with pkgutil resolve_name bpo 44353 Make NewType __call__ faster by implementing it in C Patch provided by Yurii Karabas bpo 44682 Change the pdb commands directive to disallow setting commands for an invalid breakpoint and to display an appropriate error bpo 44353 Refactor typing NewType from function into callable class Patch provided by Yurii Karabas bpo 44678 Added a separate error message for discontinuous padding in binascii a2b_base64 strict mode bpo 44524 Add missing __name__ and __qualname__ attributes to typing module classes Patch provided by Yurii Karabas bpo 40897 Give priority to using the current class constructor in inspect signature Patch by Weipeng Hong bpo 44638 Add a reference to the zipp project and hint as to how to use it bpo 44648 Fixed wrong error being thrown by inspect getsource when examining a class in the interactive session Instead of TypeError it should be OSError with appropriate error message bpo 44608 Fix memory leak in _tkinter _flatten if it is called with a sequence or set but not list or tuple bpo 44594 Fix an edge case of ExitStack and AsyncExitStack exception chaining They will now match with block behavior when __context__ is explicitly set to None when the exception is in flight bpo 42799 In fnmatch the cache size for compiled regex patterns functools lru_cache was bumped up from 256 to 32768 affecting functions fnmatch fnmatch fnmatch fnmatchcase fnmatch filter bpo 41928 Update shutil copyfile to raise FileNotFoundError instead of confusing IsADirectoryError when a path ending with a os path sep does not exist shutil copy and shutil copy2 are also affected bpo 44569 Added the StackSummary format_frame function in traceback This allows users to customize the way individual lines are formatted in tracebacks without re implementing logic to handle recursive tracebacks bpo 44566 handle StopIteration subclass raised from contextlib contextmanager generator bpo 44558 Make the implementation consistency of indexOf between C and Python versions Patch by Donghee Na bpo 41249 Fixes TypedDict to work with typing get_type_hints and postponed evaluation of annotations across modules bpo 44554 Refactor argument processing in pdb main to simplify detection of errors in input loading and clarify behavior around module or script invocation bpo 34798 Break up paragraph about pprint,en
1596, PrettyPrinter construction parameters to make it easier to read bpo 44539 Added support for recognizing JPEG files without JFIF or Exif markers bpo 44461 Fix bug with pdb s handling of import error due to a package which does not have a __main__ module bpo 43625 Fix a bug in the detection of CSV file headers by csv Sniffer has_header and improve documentation of same bpo 44516 Update vendored pip to 21 1 3 bpo 42892 Fixed an exception thrown while parsing a malformed multipart email by email message EmailMessage bpo 44468 typing get_type_hints now finds annotations in classes and base classes with unexpected __module__ Previously it skipped those MRO elements bpo 44491 Allow clearing the sqlite3 authorizer callback by passing None to set_authorizer Patch by Erlend E Aasland bpo 43977 Set the proper Py_TPFLAGS_MAPPING and Py_TPFLAGS_SEQUENCE flags for subclasses created before a parent has been registered as a collections abc Mapping or collections abc Sequence bpo 44482 Fix very unlikely resource leak in glob in alternate Python implementations bpo 44466 The faulthandler module now detects if a fatal error occurs during a garbage collector collection Patch by Victor Stinner bpo 44471 A TypeError is now raised instead of an AttributeError in contextlib ExitStack enter_context and contextlib AsyncExitStack enter_async_context for objects which do not support the context manager or asynchronous context manager protocols correspondingly bpo 44404 tkinter s after method now supports callables without the __name__ attribute bpo 41546 Make pprint like the builtin print not attempt to write to stdout when it is None bpo 44458 BUFFER_BLOCK_SIZE is now declared static to avoid linking collisions when bz2 lmza or zlib are statically linked bpo 44464 Remove exception for flake8 in deprecated importlib metadata interfaces Sync with importlib_metadata 4 6 bpo 44446 Take into account that lineno might be None in traceback FrameSummary bpo 44439 Fix in bz2 BZ2File write lzma LZMAFile write methods when the input data is an object that supports the buffer protocol the file length may be wrong bpo 44434 _thread start_new_thread no longer calls PyThread_exit_thread explicitly at the thread exit the call was redundant On Linux with the glibc pthread_exit aborts the whole process if dlopen fails to open libgcc_s so file ex EMFILE error Patch by Victor Stinner bpo 42972 The _thread RLock type now fully implement the GC protocol add a traverse function and the Py_TPFLAGS_HAVE_GC flag Patch by Victor Stinner bpo 44422 The threading enumerate function now uses a reentrant lock to prevent a hang on reentrant call Patch by Victor Stinner bpo 38291 Importing typing io or typing re now prints a DeprecationWarning bpo 37880 argparse actions store_const and append_const each receive a default value of None when the const kwarg is not provided Previously this raised a TypeError bpo 44389 Fix deprecation of ssl OP_NO_TLSv1_3 bpo 27827 pathlib PureWindowsPath is_reserved now identifies a greater range of reserved filenames including those with trailing spaces or colons bpo 44395 Fix as_string to pass unixfrom properly Patch by Donghee Na bpo 34266 Handle exceptions from parsing the arg of pdb s run restart command bpo 44362 Improve ssl module s deprecation messages error reporting and documentation for deprecations bpo 44342 Enum Change pickling from by value to by name bpo 44356 Enum Allow multiple data type mixins if they are all the same bpo 44351 Restore back parse_makefile in distutils sysconfig because it behaves differently than the similar implementation in sysconfig bpo 35800 smtpd MailmanProxy is now removed as it is unusable without an external module mailman Patch by Donghee Na bpo 44357 Added a function that returns cube root of the given number math cbrt bpo 44339 Change math pow 0 0 math inf to return inf instead of raising ValueError This brings the special case handling of math pow into compliance with the IEEE 754 standard bpo 44242 Remove missing flag check from Enum creation and move into a verify decorator bpo 44246 In importlib met,en
1597,adata restore compatibility in the result from Distribution entry_points EntryPoints to honor expectations in older implementations and issuing deprecation warnings for these cases A EntryPoints objects are once again mutable allowing for sort and other list based mutation operations Avoid deprecation warnings by casting to a mutable sequence e g list dist entry_points sort B EntryPoints results once again allow for access by index To avoid deprecation warnings cast the result to a Sequence first e g tuple dist entry_points 0 bpo 44246 In importlib metadata entry_points de duplication of distributions no longer requires loading the full metadata for PathDistribution objects improving entry point loading performance by 10x bpo 43858 Added a function that returns a copy of a dict of logging levels logging getLevelNamesMapping bpo 44260 The random Random constructor no longer reads system entropy without need bpo 44254 On Mac give turtledemo button text a color that works on both light or dark background Programmers cannot control the latter bpo 44258 Support PEP 515 for Fraction s initialization from string bpo 44235 Remove deprecated functions in the gettext Patch by Donghee Na bpo 38693 Prefer f strings to format in importlib resources bpo 33693 Importlib metadata now prefers f strings to format bpo 44241 Incorporate minor tweaks from importlib_metadata 4 1 SimplePath protocol support for Metadata 2 2 bpo 43216 Remove the asyncio coroutine decorator enabling legacy generator based coroutines to be compatible with async await code remove asyncio coroutines CoroWrapper used for wrapping legacy coroutine objects in the debug mode The decorator has been deprecated since Python 3 8 and the removal was initially scheduled for Python 3 10 Patch by Illia Volochii bpo 44210 Make importlib metadata _meta PackageMetadata public bpo 43643 Declare readers MultiplexedPath name as a property per the spec bpo 27334 The sqlite3 context manager now performs a rollback thus releasing the database lock if commit failed Patch by Luca Citi and Erlend E Aasland bpo 4928 Documented existing behavior on POSIX NamedTemporaryFiles are not deleted when creating process is killed with SIGKILL bpo 44154 Optimize fractions Fraction pickling for large components bpo 33433 For IPv4 mapped IPv6 addresses RFC 4291 Section 2 5 5 2 the ipaddress IPv6Address is_private check is deferred to the mapped IPv4 address This solves a bug where public mapped IPv4 addresses were considered private by the IPv6 check bpo 44150 Add optional weights argument to statistics fmean bpo 44142 ast unparse will now drop the redundant parentheses when tuples used as assignment targets e g in for loops bpo 44145 hmac computations were not releasing the GIL while calling the OpenSSL HMAC_Update C API a new feature in 3 9 This unintentionally prevented parallel computation as other hashlib algorithms support bpo 44095 zipfile Path now supports zipfile Path stem zipfile Path suffixes and zipfile Path suffix attributes bpo 44077 It s now possible to receive the type of service ToS a k a differentiated services DS a k a differentiated services code point DSCP and explicit congestion notification ECN IP header fields with socket IP_RECVTOS bpo 37788 Fix a reference leak when a Thread object is never joined bpo 38908 Subclasses of typing Protocol which only have data variables declared will now raise a TypeError when checked with isinstance unless they are decorated with runtime_checkable Previously these checks passed silently Patch provided by Yurii Karabas bpo 44098 typing ParamSpec will no longer be found in the __parameters__ of most typing generics except in valid use locations specified by PEP 612 This prevents incorrect usage like typing List P int This change means incorrect usage which may have passed silently in 3 10 beta 1 and earlier will now error bpo 44089 Allow subclassing csv Error in 3 10 it was allowed in 3 9 and earlier but was disallowed in early versions of 3 10 bpo 44081 ast unparse now doesn t use redundant spaces to separate lambda and the if there are no parame,en
1598,ters bpo 44061 Fix regression in previous release when calling pkgutil iter_modules with a list of pathlib Path objects bpo 44059 Register the SerenityOS Browser in the webbrowser module bpo 36515 The hashlib module no longer does unaligned memory accesses when compiled for ARM platforms bpo 40465 Remove random module features deprecated in Python 3 9 bpo 44018 random seed no longer mutates bytearray inputs bpo 38352 Add IO BinaryIO TextIO Match and Pattern to typing __all__ Patch by Jelle Zijlstra bpo 44002 urllib parse now uses functool lru_cache for its internal URL splitting and quoting caches instead of rolling its own like its the 90s The undocumented internal urllib parse Quoted class API is now deprecated for removal in 3 14 bpo 43972 When http server SimpleHTTPRequestHandler sends a 301 Moved Permanently for a directory path not ending with add a Content Length 0 header This improves the behavior for certain clients bpo 28528 Fix a bug in pdb where checkline raises AttributeError if it is called after reset bpo 43853 Improved string handling for sqlite3 user defined functions and aggregates It is now possible to pass strings with embedded null characters to UDFs Conversion failures now correctly raise MemoryError Patch by Erlend E Aasland bpo 43666 AIX Lib _aix_support get_platform may fail in an AIX WPAR The fileset bos rte appears to have a builddate in both LPAR and WPAR so this fileset is queried rather than bos mp64 To prevent a similar situation no builddate in ODM a value 9988 sufficient for completing a build is provided Patch by M Felt bpo 43650 Fix MemoryError in shutil unpack_archive which fails inside shutil _unpack_zipfile on large files Patch by Igor Bolshakov bpo 43612 zlib compress now accepts a wbits parameter which allows users to compress data as a raw deflate block without zlib headers and trailers in one go Previously this required instantiating a zlib compressobj It also provides a faster alternative to gzip compress when wbits 31 is used bpo 43392 importlib _bootstrap _find_and_load now implements a two step check to avoid locking when modules have been already imported and are ready This improves performance of repeated calls to importlib import_module and importlib __import__ bpo 43318 Fix a bug where pdb does not always echo cleared breakpoints bpo 43234 Prohibit passing non concurrent futures ThreadPoolExecutor executors to loop set_default_executor following a deprecation in Python 3 8 Patch by Illia Volochii bpo 43232 Prohibit previously deprecated potentially disruptive operations on asyncio trsock TransportSocket Patch by Illia Volochii bpo 30077 Added support for Apple s aifc sowt pseudo compression bpo 42971 Add definition of errno EQFULL for platforms that define this constant such as macOS bpo 43086 Added a new optional strict_mode parameter to binascii a2b_base64 When scrict_mode is set to True the a2b_base64 function will accept only valid base64 content More details about what valid base64 content is can be found in the function s documentation bpo 43024 Improve the help signature of traceback print_exception traceback format_exception and traceback format_exception_only bpo 33809 Add the traceback TracebackException print method which prints the formatted exception information bpo 42862 sqlite3 now utilizes functools lru_cache to implement the connection statement cache As a small optimisation the default statement cache size has been increased from 100 to 128 Patch by Erlend E Aasland bpo 41818 Soumendra Ganguly add termios tcgetwinsize termios tcsetwinsize bpo 40497 subprocess check_output now raises ValueError when the invalid keyword argument check is passed by user code Previously such use would fail later with a TypeError Patch by Rémi Lapeyre bpo 37449 ensurepip now uses importlib resources files traversable APIs bpo 40956 Use Argument Clinic in sqlite3 Patches by Erlend E Aasland bpo 41730 DeprecationWarning is now raised when importing tkinter tix which has been deprecated in documentation since Python 3 6 bpo 20684 Remove unused _signature_get_bound_param function,en
1599, from inspect by Anthony Sottile bpo 41402 Fix email message EmailMessage set_content when called with binary data and 7bit content transfer encoding bpo 32695 The compresslevel and preset keyword arguments of tarfile open are now both documented and tested bpo 41137 Use utf 8 encoding while reading pdbrc files Patch by Srinivas Reddy Thatiparthy bpo 24391 Improved reprs of threading synchronization objects Semaphore BoundedSemaphore Event and Barrier bpo 5846 Deprecated the following unittest functions scheduled for removal in Python 3 13 findTestCases makeSuite getTestCaseNames Use TestLoader methods instead unittest TestLoader loadTestsFromModule unittest TestLoader loadTestsFromTestCase unittest TestLoader getTestCaseNames Patch by Erlend E Aasland bpo 40563 Support pathlike objects on dbm shelve Patch by Hakan Çelik and Henry Joseph Audéoud bpo 34990 Fixed a Y2k38 bug in the compileall module where it would fail to compile files with a modification time after the year 2038 bpo 39549 Whereas the code for reprlib Repr had previously used a hardcoded string value of this PR updates it to use of a fillvalue attribute whose value defaults to and can be reset in either individual reprlib Repr instances or in subclasses thereof bpo 37022 pdb now displays exceptions from repr with its p and pp commands bpo 38840 Fix test___all__ on platforms lacking a shared memory implementation bpo 39359 Add one missing check that the password is a bytes object for an encrypted zipfile bpo 38741 configparser using inside a section header will no longer cut the section name short at the bpo 38415 Added missing behavior to contextlib asynccontextmanager to match contextlib contextmanager so decorated functions can themselves be decorators bpo 30256 Pass multiprocessing BaseProxy argument manager_owned through AutoProxy bpo 27513 email utils getaddresses now accepts email header Header objects along with string values Patch by Zackery Spytz bpo 16379 Add SQLite error code and name to sqlite3 exceptions Patch by Aviv Palivoda Daniel Shahaf and Erlend E Aasland bpo 26228 pty spawn no longer hangs on FreeBSD macOS and Solaris bpo 33349 lib2to3 now recognizes async generators everywhere bpo 29298 Fix TypeError when required subparsers without dest do not receive arguments Patch by Anthony Sottile Documentation bpo 45216 Remove extra documentation listing methods in difflib It was rendering twice in pydoc and was outdated in some places bpo 45024 collections abc documentation has been expanded to explicitly cover how instance and subclass checks work with additional doctest examples and an exhaustive list of ABCs which test membership purely by presence of the right special method s Patch by Raymond Hettinger bpo 44957 Promote PEP 604 union syntax by using it where possible Also mention X Y more prominently in section about Union and mention X None at all in section about Optional bpo 16580 Added code equivalents for the int to_bytes and int from_bytes methods as well as tests ensuring that these code equivalents are valid bpo 44903 Removed the othergui rst file any references to it and the list of GUI frameworks in the FAQ In their place I ve added links to the Python Wiki page on GUI frameworks bpo 33479 Tkinter documentation has been greatly expanded with new Architecture and Threading model sections bpo 36700 base64 RFC references were updated to point to RFC 4648 a section was added to point users to the new security considerations section of the RFC bpo 44740 Replaced occurrences of uppercase Web and Internet with lowercase versions per the 2016 revised Associated Press Style Book bpo 44693 Update the definition of __future__ in the glossary by replacing the confusing word pseudo module with a more accurate description bpo 35183 Add typical examples to os path splitext docs bpo 30511 Clarify that shutil make_archive is not thread safe due to reliance on changing the current working directory bpo 44561 Update of three expired hyperlinks in Doc distributing index rst Project structure Building and packaging the project and Uploading the proje,en
1600,ct to the Python Packaging Index bpo 44651 Delete entry coercion in Doc glossary rst for its outdated definition bpo 42958 Updated the docstring and docs of filecmp cmp to be more accurate and less confusing especially in respect to shallow arg bpo 44631 Refactored the repr code of the _Environ os module bpo 44613 importlib metadata is no longer provisional bpo 44558 Match the docstring and python implementation of countOf to the behavior of its c implementation bpo 44544 List all kwargs for textwrap wrap textwrap fill and textwrap shorten Now there are nav links to attributes of TextWrap which makes navigation much easier while minimizing duplication in the documentation bpo 38062 Clarify that atexit uses equality comparisons internally bpo 40620 Convert examples in tutorial controlflow rst section 4 3 to be interpreter demo style bpo 43066 Added a warning to zipfile docs filename arg with a leading slash may cause archive to be un openable on Windows systems bpo 39452 Rewrote Doc library __main__ rst Broadened scope of the document to explicitly discuss and differentiate between __main__ py in packages versus the __name__ __main__ expression and the idioms that surround it bpo 13814 In the Design FAQ answer Why don t generators support the with statement bpo 27752 Documentation of csv Dialect is more descriptive bpo 44453 Fix documentation for the return type of sysconfig get_path bpo 44392 Added a new section in the C API documentation for types used in type hinting Documented Py_GenericAlias and Py_GenericAliasType bpo 38291 Mark typing io and typing re as deprecated since Python 3 8 in the documentation They were never properly supported by type checkers bpo 44322 Document that SyntaxError args have a details tuple and that details are adjusted for errors in f string field replacement expressions bpo 42392 Document the deprecation and removal of the loop parameter for many functions and classes in asyncio bpo 44195 Corrected references to TraversableResources in docs There is no TraversableReader bpo 41963 Document that ConfigParser strips off comments when reading configuration files bpo 44072 Correct where in the numeric ABC hierarchy support is added i e in numbers Complex not numbers Integral bpo 43558 Add the remark to dataclasses documentation that the __init__ of any base class has to be called in __post_init__ along with a code example bpo 44025 Clarify when _ in match statements is a keyword and when not bpo 41706 Fix docs about how methods like __add__ are invoked when evaluating operator expressions bpo 41621 Document that collections defaultdict parameter default_factory defaults to None and is positional only bpo 41576 document BaseException in favor of bare except bpo 21760 The description for __file__ fixed Patch by Furkan Onder bpo 39498 Add a Security Considerations index which links to standard library modules that have explicitly documented security considerations bpo 33479 Remove the unqualified claim that tkinter is threadsafe It has not been true for several years and likely never was An explanation of what is true may be added later after more discussion and possibly after patching _tkinter c Tests bpo 40173 Fix test support import_helper import_fresh_module bpo 45280 Add a test case for empty typing NamedTuple bpo 45269 Cover case when invalid markers type is supplied to c_make_encoder bpo 45128 Fix test_multiprocessing_fork failure due to test_logging and sys modules manipulation bpo 45209 Fix UserWarning resource_tracker warning in _test_mu ltiprocessing _TestSharedMemory test_shared_memory_cleaned_after_pr ocess_termination bpo 45185 Enables TestEnumerations test cases in test_ssl suite bpo 45195 Fix test_readline test_nonascii sometimes the newline character is not written at the end so don t expect it in the output Patch by Victor Stinner bpo 45156 Fixes infinite loop on unittest mock seal of mocks created by create_autospec bpo 45125 Improves pickling tests and docs of SharedMemory and SharableList objects bpo 44860 Update test_sysconfig test_user_similar for the posix_user scheme platl,en
1601,ib doesn t use sys platlibdir Patch by Victor Stinner bpo 45052 WithProcessesTestSharedMemory test_shared_memory_basics test was ignored because self assertEqual sms size sms2 size line was failing It is now removed and test is unskipped The main motivation for this line to be removed from the test is that the size of SharedMemory is not ever guaranteed to be the same It is decided by the platform bpo 44895 libregrtest now clears the type cache later to reduce the risk of false alarm when checking for reference leaks Previously the type cache was cleared too early and libregrtest raised a false alarm about reference leaks under very specific conditions Patch by Irit Katriel and Victor Stinner bpo 45042 Fixes that test classes decorated with hashlib_helper requires_hashdigest were skipped all the time bpo 25130 Add calls of gc collect in tests to support PyPy bpo 45011 Made tests relying on the _asyncio C extension module optional to allow running on alternative Python implementations Patch by Serhiy Storchaka bpo 44949 Fix auto history tests of test_readline sometimes the newline character is not written at the end so don t expect it in the output bpo 44891 Tests were added to clarify id is preserved when obj 1 is used on str and bytes objects Patch by Nikita Sobolev bpo 44852 Add ability to wholesale silence DeprecationWarnings while running the regression test suite bpo 40928 Notify users running test_decimal regression tests on macOS of potential harmless malloc can t allocate region messages spewed by test_decimal bpo 44734 Fixed floating point precision issue in turtle tests bpo 44708 Regression tests when run with w are now re running only the affected test methods instead of re running the entire test file bpo 42095 Added interop tests for Apple plists generate plist files with Python plistlib and parse with Apple plutil and the other way round bpo 44647 Added a permanent Unicode valued environment variable to regression tests to ensure they handle this use case in the future If your test environment breaks because of that report a bug to us and temporarily set PYTHONREGRTEST_UNICODE_GUARD 0 in your test environment bpo 44515 Adjust recently added contextlib tests to avoid assuming the use of a refcounted GC bpo 44287 Fix asyncio test_popen of test_windows_utils by using a longer timeout Use military grade battle tested test support SHORT_TIMEOUT timeout rather than a hardcoded timeout of 10 seconds it s 30 seconds by default but it is made longer on slow buildbots Patch by Victor Stinner bpo 44451 Reset DeprecationWarning filters in test test_importl ib test_metadata_api APITests test_entry_points_by_index to avoid StopIteration error if DeprecationWarnings are ignored bpo 44363 Account for address sanitizer in test_capi test_capi now passes when run GCC address sanitizer bpo 44364 Add non integral tests for math sqrt function bpo 43921 Fix test_ssl test_wrong_cert_tls13 use suppress_ragged_eofs False since read can raise ssl SSLEOFError on Windows Patch by Victor Stinner bpo 43921 Fix test_pha_required_nocert of test_ssl catch two more EOF cases when the recv method returns an empty string Patch by Victor Stinner bpo 44131 Add test_frozenmain to test_embed to test the Py_FrozenMain C function Patch by Victor Stinner bpo 31904 Ignore error string case in test_file_not_exists bpo 42083 Add test to check that PyStructSequence_NewType accepts a PyStructSequence_Desc with doc field set to NULL bpo 35753 Fix crash in doctest when doctest parses modules that include unwrappable functions by skipping those functions bpo 30256 Add test for nested queues when using multiprocessing shared objects AutoProxy Queue inside ListProxy and DictProxy Build bpo 45220 Avoid building with the Windows 11 SDK previews automatically This may be overridden by setting the DefaultWindowsSDKVersion environment variable before building bpo 45020 Freeze stdlib modules that are imported during startup This provides significant performance improvements to startup If necessary use the previously added X frozen_modules off commandline option to f,en
1602,orce importing the source modules bpo 45188 Windows builds now regenerate frozen modules as the first part of the build Previously the regeneration was later in the build which would require it to be restarted if any modules had changed bpo 45163 Fixes Haiku platform build bpo 45067 The ncurses function extended_color_content was introduced in 2017 https invisible island net ncurses NEWS html index t20170401 The ncurses devel package in CentOS 7 had a older version ncurses resulted in compilation error For compiling ncurses with extended color support we verify the version of the ncurses library 20170401 bpo 45019 Generate lines in relevant files for frozen modules Up until now each of the files had to be edited manually This change makes it easier to add to and modify the frozen modules bpo 44340 Add support for building with clang thin lto via with lto thin full Patch by Donghee Na and Brett Holman bpo 44535 Enable building using a Visual Studio 2022 install on Windows bpo 43298 Improved error message when building without a Windows SDK installed bpo 44381 The Windows build now accepts EnableControlFlowGuard set to guard to enable CFG bpo 41282 Fix broken make install that caused standard library extension modules to be unnecessarily and incorrectly rebuilt during the install phase of cpython Windows bpo 45375 Fixes an assertion failure due to searching for the standard library in unnormalised paths bpo 45022 Update Windows release to include libffi 3 4 2 bpo 45007 Update to OpenSSL 1 1 1l in Windows build bpo 44848 Upgrade Windows installer to use SQLite 3 36 0 bpo 44572 Avoid consuming standard input in the platform module bpo 44582 Accelerate speed of mimetypes initialization using a native implementation of the registry scan bpo 41299 Fix 16 milliseconds jitter when using timeouts in threading such as with threading Lock acquire or threading Condition wait bpo 42686 Build sqlite3 with math functions enabled Patch by Erlend E Aasland bpo 40263 This is a follow on bug from https bugs python org issue26903 Once that is applied we run into an off by one assertion problem The assert was not correct macOS bpo 45007 Update macOS installer builds to use OpenSSL 1 1 1l bpo 34602 When building CPython on macOS with configure with undefined behavior sanitizer with pydebug the stack size is now quadrupled to allow for the entire test suite to pass bpo 44848 Update macOS installer to use SQLite 3 36 0 bpo 44689 ctypes util find_library now works correctly on macOS 11 Big Sur even if Python is built on an older version of macOS Previously when built on older macOS systems find_library was not able to find macOS system libraries when running on Big Sur due to changes in how system libraries are stored bpo 41972 The framework build s user header path in sysconfig is changed to add a pythonX Y component to match distutils s behavior bpo 43109 Allow with lto configure option to work with Apple supplied Xcode or Command Line Tools bpo 34932 Add socket TCP_KEEPALIVE support for macOS Patch by Shane Harvey IDLE bpo 45296 On Windows change exit quit message to suggest Ctrl D which works instead of Ctrl Z Return which does not work in IDLE bpo 45193 Make completion boxes appear on Ubuntu again bpo 40128 Mostly fix completions on macOS when not using tcl tk 8 6 11 as with 3 9 The added update_idletask call should be harmless and possibly helpful otherwise bpo 33962 Move the indent space setting from the Font tab to the new Windows tab Patch by Mark Roseman and Terry Jan Reedy bpo 40468 Split the settings dialog General tab into Windows and Shell ED tabs Move help sources which extend the Help menu to the Extensions tab Make space for new options and shorten the dialog The latter makes the dialog better fit small screens bpo 41611 Avoid uncaught exceptions in AutoCompleteWindow winconfig_event bpo 41611 Fix IDLE sometimes freezing upon tab completion on macOS bpo 44010 Highlight the new match statement s soft keywords match case and _ However this highlighting is not perfect and will be incorrect in some rare cases including some _ s in ca,en
1603,se patterns bpo 44026 Include interpreter s typo fix suggestions in message line for NameErrors and AttributeErrors Patch by E Paine Tools Demos bpo 44786 Fix a warning in regular expression in the c analyzer script bpo 44967 pydoc now returns a non zero status code when a module cannot be found bpo 44978 Allow the Argument Clinic tool to handle __complex__ special methods bpo 43425 Removed the test2to3 demo project that demonstrated using lib2to3 to support Python 2 x and Python 3 x from a single source in a distutils package Patch by Donghee Na bpo 44074 Make patchcheck automatically detect the correct base branch name previously it was hardcoded to master bpo 20291 Added support for variadic positional parameters in Argument Clinic C API bpo 41710 The PyThread_acquire_lock_timed function now clamps the timeout if it is too large rather than aborting the process Patch by Victor Stinner bpo 44687 BufferedReader peek no longer raises ValueError when the entire file has already been buffered bpo 45116 Add the Py_ALWAYS_INLINE macro to ask the compiler to always inline a static inline function The compiler can ignore it and decides to not inline the function Patch by Victor Stinner bpo 45094 Add the Py_NO_INLINE macro to disable inlining on a function Patch by Victor Stinner bpo 45061 Add a deallocator to the bool type to detect refcount bugs in C extensions which call Py_DECREF Py_True or Py_DECREF Py_False by mistake Patch by Victor Stinner bpo 42035 Add a new PyType_GetQualName function to get type s qualified name bpo 41103 Reverts removal of the old buffer protocol because they are part of stable ABI bpo 44751 Remove crypt h include from the public Python h header bpo 42747 The Py_TPFLAGS_HAVE_VERSION_TAG type flag now does nothing The Py_TPFLAGS_HAVE_AM_SEND flag which was added in 3 10 is removed Both were unnecessary because it is not possible to have type objects with the relevant fields missing bpo 44530 Added the co_qualname to the PyCodeObject structure to propagate the qualified name from the compiler to code objects Patch by Gabriele N Tornetta bpo 44441 Py_RunMain now resets PyImport_Inittab to its initial value at exit It must be possible to call PyImport_AppendInittab or PyImport_ExtendInittab at each Python initialization Patch by Victor Stinner bpo 39947 Remove 4 private trashcan C API functions which were only kept for the backward compatibility of the stable ABI with Python 3 8 and older since the trashcan API was not usable with the limited C API on Python 3 8 and older The trashcan API was excluded from the limited C API in Python 3 9 Removed functions _PyTrash_deposit_object _PyTrash_destroy_chain _PyTrash_thread_deposit_object _PyTrash_thread_destroy_chain The trashcan C API was never usable with the limited C API since old trashcan macros accessed directly PyThreadState members like _tstate trash_delete_nesting whereas the PyThreadState structure is opaque in the limited C API Exclude also the PyTrash_UNWIND_LEVEL constant from the C API Patch by Victor Stinner bpo 40939 Removed documentation for the removed PyParser_ C API bpo 43795 The list in Contents of Limited API now shows the public name PyFrameObject rather than _frame The non existing entry _node no longer appears in the list bpo 44378 Py_IS_TYPE no longer uses Py_TYPE to avoid a compiler warning no longer cast const PyObject to PyObject Patch by Victor Stinner bpo 39573 Convert the Py_TYPE and Py_SIZE macros to static inline functions The Py_SET_TYPE and Py_SET_SIZE functions must now be used to set an object type and size Patch by Victor Stinner bpo 44263 The PyType_Ready function now raises an error if a type is defined with the Py_TPFLAGS_HAVE_GC flag set but has no traverse function PyTypeObject tp_traverse Patch by Victor Stinner bpo 43795 The undocumented function Py_FrozenMain is removed from the Limited API bpo 44113 Deprecate the following functions to configure the Python initialization PySys_AddWarnOptionUnicode PySys_AddWarnOption PySys_AddXOption PySys_HasWarnOptions Py_SetPath Py_SetProgramName Py_SetPythonHome Py_SetStanda,en
1604,rdStreamEncoding _Py_SetProgramFullPath Use the new PyConfig API of the Python Initialization Configuration instead PEP 587 bpo 44094 Remove PyErr_SetFromErrnoWithUnicodeFilename PyErr_SetFromWindowsErrWithUnicodeFilename and PyErr_SetExcFromWindowsErrWithUnicodeFilename They are not documented and have been deprecated since Python 3 3 bpo 43795 PyCodec_Unregister is now properly exported as a function in the Windows Stable ABI DLL bpo 44029 Remove deprecated Py_UNICODE APIs PyUnicode_Encode PyUnicode_EncodeUTF7 PyUnicode_EncodeUTF8 PyUnicode_EncodeUTF16 PyUnicode_EncodeUTF32 PyUnicode_EncodeLatin1 PyUnicode_EncodeMBCS PyUnicode_EncodeDecimal PyUnicode_EncodeRawUnicodeEscape PyUnicode_EncodeCharmap PyUnicode_EncodeUnicodeEscape PyUnicode_TransformDecimalToASCII PyUnicode_TranslateCharmap PyUnicodeEncodeError_Create PyUnicodeTranslateError_Create See PEP 393 and PEP 624 for reference bpo 42035 Add a new PyType_GetName function to get type s short name Python 3 10 0 beta 1 Release date 2021 05 03 Security bpo 43434 Creating sqlite3 Connection objects now also produces sqlite3 connect and sqlite3 connect handle auditing events Previously these events were only produced by sqlite3 connect calls Patch by Erlend E Aasland bpo 43998 The ssl module sets more secure cipher suites defaults Ciphers without forward secrecy and with SHA 1 MAC are disabled by default Security level 2 prohibits weak RSA DH and ECC keys with less than 112 bits of security SSLContext defaults to minimum protocol version TLS 1 2 Settings are based on Hynek Schlawack s research bpo 43882 The presence of newline or tab characters in parts of a URL could allow some forms of attacks Following the controlling specification for URLs defined by WHATWG urllib parse now removes ASCII newlines and tabs from URLs preventing such attacks bpo 43472 Ensures interpreter level audit hooks receive the cpython PyInterpreterState_New event when called through the _xxsubinterpreters module bpo 43362 Fix invalid free in _sha3 module The issue was introduced in 3 10 0a1 Python 3 9 and earlier are not affected bpo 43762 Add audit events for sqlite3 connect handle sqlite3 Connection enable_load_extension and sqlite3 Connection load_extension Patch by Erlend E Aasland bpo 43756 Add new audit event glob glob 2 to incorporate the new root_dir and dir_fd arguments added to glob glob and glob iglob bpo 36384 ipaddress module no longer accepts any leading zeros in IPv4 address strings Leading zeros are ambiguous and interpreted as octal notation by some libraries For example the legacy function socket inet_aton treats leading zeros as octal notation glibc implementation of modern inet_pton does not accept any leading zeros For a while the ipaddress module used to accept ambiguous leading zeros bpo 43075 Fix Regular Expression Denial of Service ReDoS vulnerability in urllib request AbstractBasicAuthHandler The ReDoS vulnerable regex has quadratic worst case complexity and it allows cause a denial of service when identifying crafted invalid RFCs This ReDoS issue is on the client side and needs remote attackers to control the HTTP server bpo 42800 Audit hooks are now fired for frame f_code traceback tb_frame and generator code frame attribute access bpo 37363 Add audit events to the http client module Core and Builtins bpo 43977 Prevent classes being both a sequence and a mapping when pattern matching bpo 43977 Use tp_flags on the class object to determine if the subject is a sequence or mapping when pattern matching Avoids the need to import collections abc when pattern matching bpo 43892 Restore proper validation of complex literal value patterns when parsing match blocks bpo 43933 Set frame f_lineno to the line number of the with kweyword when executing the call to __exit__ bpo 43933 If the current position in a frame has no line number then set the f_lineno attribute to None instead of 1 to conform to PEP 626 This should not normally be possible but might occur in some unusual circumstances bpo 43963 Importing the _signal module in a subinterpreter has no longer side effects bpo 4273,en
1605,9 The internal representation of line number tables is changed to not use sentinels and an explicit length parameter is added to the out of process API function PyLineTable_InitAddressRange This makes the handling of line number tables more robust in some circumstances bpo 43908 Make re types immutable Patch by Erlend E Aasland bpo 43908 Make the array array type immutable Patch by Erlend E Aasland bpo 43901 Change class and module objects to lazy create empty annotations dicts on demand The annotations dicts are stored in the object s __dict__ for backwards compatibility bpo 43892 Match patterns now use new dedicated AST nodes MatchValue MatchSingleton MatchSequence MatchStar MatchMapping MatchClass rather than reusing expression AST nodes MatchAs and MatchOr are now defined as pattern nodes rather than as expression nodes Patch by Nick Coghlan bpo 42725 Usage of await yield yield from and named expressions within an annotation is now forbidden when PEP 563 is activated bpo 43754 When performing structural pattern matching PEP 634 captured names are now left unbound until the entire pattern has matched successfully bpo 42737 Annotations for complex targets everything beside simple names no longer cause any runtime effects with from __future__ import annotations bpo 43914 SyntaxError exceptions raised by the interpreter will highlight the full error range of the expression that consistutes the syntax error itself instead of just where the problem is detected Patch by Pablo Galindo bpo 38605 Revert making from __future__ import annotations the default This follows the Steering Council decision to postpone PEP 563 changes to at least Python 3 11 See the original email for more information regarding the decision https mail python org archives list python dev python org thread CLVXXPQ2T2LQ5MP2Y53VVQFCXYWQJHKZ Patch by Pablo Galindo bpo 43475 Hashes of NaN values now depend on object identity Formerly they always hashed to 0 even though NaN values are not equal to one another Having the same hash for unequal values caused pile ups in hash tables bpo 43859 Improve the error message for IndentationError exceptions Patch by Pablo Galindo bpo 41323 Constant tuple folding in bytecode optimizer now reuses tuple in constant table bpo 43846 Data stack usage is much reduced for large literal and call expressions bpo 38530 When printing NameError raised by the interpreter PyErr_Display will offer suggestions of similar variable names in the function that the exception was raised from Patch by Pablo Galindo bpo 43823 Improve syntax errors for invalid dictionary literals Patch by Pablo Galindo bpo 43822 Improve syntax errors in the parser for missing commas between expressions Patch by Pablo Galindo bpo 43798 ast alias nodes now include source location metadata attributes e g lineno col_offset bpo 43797 Improve SyntaxError error messages for invalid comparisons Patch by Pablo Galindo bpo 43760 Move the flag for checking whether tracing is enabled to the C stack from the heap Should speed up dispatch in the interpreter bpo 43682 Static methods staticmethod and class methods classmethod now inherit the method attributes __module__ __name__ __qualname__ __doc__ __annotations__ and have a new __wrapped__ attribute Patch by Victor Stinner bpo 43751 Fixed a bug where anext ait default would erroneously return None bpo 42128 __match_args__ is no longer allowed to be a list bpo 43683 Add GEN_START opcode Marks start of generator including async or coroutine and handles sending values to a newly created generator or coroutine bpo 43105 Importlib now resolves relative paths when creating module spec objects from file locations bpo 43682 Static methods staticmethod are now callable as regular functions Patch by Victor Stinner bpo 42609 Prevented crashes in the AST validator and optimizer when compiling some absurdly long expressions like 0 1000000 RecursionError is now raised instead bpo 38530 When printing AttributeError PyErr_Display will offer suggestions of similar attribute names in the object that the exception was raised from Patch by Pablo ,en
1606,Galindo Library bpo 44015 In dataclass raise a TypeError if KW_ONLY is specified more than once bpo 25478 Added a total method to collections Counter to compute the sum of the counts bpo 43733 Change netrc netrc to use UTF 8 encoding before using locale encoding bpo 43979 Removed an unnecessary list comprehension before looping from urllib parse parse_qsl Patch by Christoph Zwerschke and Donghee Na bpo 43993 Update bundled pip to 21 1 1 bpo 43957 Enum Deprecate TypeError when non member is used in a containment check In 3 12 True or False will be returned instead and containment will return True if the value is either a member of that enum or one of its members value bpo 42904 For backwards compatibility with previous minor versions of Python if typing get_type_hints receives no namespace dictionary arguments typing get_type_hints will search through the global then local namespaces during evaluation of stringized type annotations string forward references inside a class bpo 43945 Enum Deprecate non standard mixin format behavior in 3 12 the enum member not the member s value will be used for format calls bpo 41139 Deprecate undocumented cgi log API bpo 43937 Fixed the turtle module working with non default root window bpo 43930 Update bundled pip to 21 1 and setuptools to 56 0 0 bpo 43907 Fix a bug in the pure Python pickle implementation when using protocol 5 where bytearray instances that occur several time in the pickled object graph would incorrectly unpickle into repeated copies of the bytearray object bpo 43926 In importlib metadata provide a uniform interface to Description allow for any field to be encoded with multiline values remove continuation lines from multiline values and add a json property for easy access to the PEP 566 JSON compatible form Sync with importlib_metadata 4 0 bpo 43920 OpenSSL 3 0 0 load_verify_locations now returns a consistent error message when cadata contains no valid certificate bpo 43607 urllib can now convert Windows paths with prefixes into URL paths bpo 43817 Add inspect get_annotations which safely computes the annotations defined on an object It works around the quirks of accessing the annotations from various types of objects and makes very few assumptions about the object passed in inspect get_annotations can also correctly un stringize stringized annotations inspect signature inspect from_callable and inspect from_function now call inspect get_annotations to retrieve annotations This means inspect signature and inspect from_callable can now un stringize stringized annotations too bpo 43284 platform win32_ver derives the windows version from sys getwindowsversion platform_version which in turn derives the version from kernel32 dll which can be of a different version than Windows itself Therefore change the platform win32_ver to determine the version using the platform module s _syscmd_ver private function to return an accurate version bpo 42854 The ssl module now uses SSL_read_ex and SSL_write_ex internally The functions support reading and writing of data larger than 2 GB Writing zero length data no longer fails with a protocol violation error bpo 42333 Port _ssl extension module to multiphase initialization bpo 43880 ssl now raises DeprecationWarning for OP_NO_SSL TLS options old TLS versions old protocols and other features that have been deprecated since Python 3 6 3 7 or OpenSSL 1 1 0 bpo 41559 PEP 612 is now implemented purely in Python builtin types GenericAlias objects no longer include typing ParamSpec in __parameters__ with the exception of collections abc Callable s GenericAlias This means previously invalid uses of ParamSpec such as list P which worked in earlier versions of Python 3 10 alpha will now raise TypeError during substitution bpo 43867 The multiprocessing Server class now explicitly catches SystemExit and closes the client connection in this case It happens when the Server serve_client method reaches the end of file EOF bpo 40443 Remove unused imports pyclbr no longer uses copy and typing no longer uses ast Patch by Victor Stinner bpo 43820 Remove an unn,en
1607,eeded copy of the namespace passed to dataclasses make_dataclass bpo 43787 Add __iter__ method to bz2 BZ2File gzip GzipFile and lzma LZMAFile It makes iterating them about 2x faster Patch by Inada Naoki bpo 43680 Deprecate io OpenWrapper and _pyio OpenWrapper use io open and _pyio open instead Until Python 3 9 _pyio open was not a static method and builtins open was set to OpenWrapper to not become a bound method when set to a class variable _io open is a built in function whereas _pyio open is a Python function In Python 3 10 _pyio open is now a static method and builtins open is now io open bpo 43680 The Python _pyio open function becomes a static method to behave as io open built in function don t become a bound method when stored as a class variable It becomes possible since static methods are now callable in Python 3 10 Moreover _pyio OpenWrapper becomes a simple alias to _pyio open Patch by Victor Stinner bpo 41515 Fix KeyError raised in typing get_type_hints due to synthetic modules that don t appear in sys modules bpo 43776 When subprocess Popen args are provided as a string or as pathlib Path the Popen instance repr now shows the right thing bpo 42248 Enum ensure exceptions raised in _missing__ are released bpo 43744 fix issue with enum member name matching the start of a private variable name bpo 43772 Fixed the return value of TypeVar __ror__ Patch by Jelle Zijlstra bpo 43764 Add match_args parameter to dataclass decorator to allow suppression of __match_args__ generation bpo 43799 OpenSSL 3 0 0 define OPENSSL_API_COMPAT 1 1 1 to suppress deprecation warnings Python requires OpenSSL 1 1 1 APIs bpo 43478 Mocks can no longer be used as the specs for other Mocks As a result an already mocked object cannot have an attribute mocked using autospec True or be the subject of a create_autospec call This can uncover bugs in tests since these Mock derived Mocks will always pass certain tests e g isinstance and builtin assert functions e g assert_called_once_with will unconditionally pass bpo 43794 Add ssl OP_IGNORE_UNEXPECTED_EOF constants OpenSSL 3 0 0 bpo 43785 Improve bz2 BZ2File performance by removing the RLock from BZ2File This makes BZ2File thread unsafe in the face of multiple simultaneous readers or writers just like its equivalent classes in gzip and lzma have always been Patch by Inada Naoki bpo 43789 OpenSSL 3 0 0 Don t call the password callback function a second time when first call has signaled an error condition bpo 43788 The header files for ssl error codes are now OpenSSL version specific Exceptions will now show correct reason and library codes The make_ssl_data py script has been rewritten to use OpenSSL s text file with error codes bpo 43766 Implement PEP 647 in the typing module by adding TypeGuard bpo 25264 os path realpath now accepts a strict keyword only argument When set to True OSError is raised if a path doesn t exist or a symlink loop is encountered bpo 43780 In importlib metadata incorporate changes from importlib_metadata 3 10 Add mtime based caching during distribution discovery Flagged use of dict result from entry_points as deprecated The P args and P kwargs attributes of typing ParamSpec are now instances of the new classes typing ParamSpecArgs and typing ParamSpecKwargs which enables a more useful repr Patch by Jelle Zijlstra bpo 43731 Add an encoding parameter logging fileConfig bpo 43712 Add encoding and errors parameters to fileinput input and fileinput FileInput bpo 38659 A simple_enum decorator is added to the enum module to convert a normal class into an Enum test_simple_enum added to test simple enums against a corresponding normal Enum Standard library modules updated to use simple_enum bpo 43764 Fix an issue where __match_args__ generation could fail for some dataclasses bpo 43752 Fix sqlite3 regression for zero sized blobs with converters where b was returned instead of None The regression was introduced by PR 24723 Patch by Erlend E Aasland bpo 43655 tkinter dialog windows are now recognized as dialogs by window managers on macOS and X Window bpo 43723 The following threadi,en
1608,ng methods are now deprecated and should be replaced currentThread threading current_thread activeCount threading active_count Condition notifyAll threading Condition notify_all Event isSet threading Event is_set Thread setName threading Thread name thread getName threading Thread name Thread isDaemon threading Thread daemon Thread setDaemon threading Thread daemon Patch by Jelle Zijlstra bpo 2135 Deprecate find_module and find_loader implementations in importlib and zipimport bpo 43534 turtle textinput and turtle numinput create now a transient window working on behalf of the canvas window bpo 43532 Add the ability to specify keyword only fields to dataclasses These fields will become keyword only arguments to the generated __init__ bpo 43522 Fix problem with hostname_checks_common_name OpenSSL does not copy hostflags from struct SSL_CTX to struct SSL bpo 8978 Improve error message for tarfile open when lzma bz2 are unavailable Patch by Anthony Sottile bpo 42967 Allow bytes separator argument in urllib parse parse_qs and urllib parse parse_qsl when parsing str query strings Previously this raised a TypeError bpo 43296 Improve sqlite3 error handling sqlite3_value_blob errors that set SQLITE_NOMEM now raise MemoryError Patch by Erlend E Aasland bpo 43312 New functions sysconfig get_preferred_scheme and sysconfig get_default_scheme are added to query a platform for its preferred user home and prefix default scheme names bpo 43265 Improve sqlite3 Connection backup error handling The error message for non existent target database names is now unknown database database name instead of SQL logic error Patch by Erlend E Aasland bpo 41282 Install schemes in distutils command install are now loaded from sysconfig bpo 41282 distutils sysconfig has been merged to sysconfig bpo 43176 Fixed processing of a dataclass that inherits from a frozen dataclass with no fields It is now correctly detected as an error bpo 43080 pprint now has support for dataclasses dataclass Patch by Lewis Gaul bpo 39950 Add pathlib Path hardlink_to method that supersedes link_to The new method has the same argument order as symlink_to bpo 42904 typing get_type_hints now checks the local namespace of a class when evaluating PEP 563 annotations inside said class bpo 42269 Add slots parameter to dataclasses dataclass decorator to automatically generate __slots__ for class Patch provided by Yurii Karabas bpo 39529 Deprecated use of asyncio get_event_loop without running event loop Emit deprecation warning for asyncio functions which implicitly create a Future or Task objects if there is no running event loop and no explicit loop argument is passed ensure_future wrap_future gather shield as_completed and constructors of Future Task StreamReader StreamReaderProtocol bpo 18369 Certificate and PrivateKey classes were added to the ssl module Certificates and keys can now be loaded from memory buffer too bpo 41486 Use a new output buffer management code for bz2 lzma zlib modules and add readall function to _compression DecompressReader class These bring some performance improvements Patch by Ma Lin bpo 31870 The ssl get_server_certificate function now has a timeout parameter bpo 41735 Fix thread locks in zlib module may go wrong in rare case Patch by Ma Lin bpo 36470 Fix dataclasses with InitVar s and replace Patch by Claudiu Popa bpo 40849 Expose X509_V_FLAG_PARTIAL_CHAIN ssl flag bpo 35114 ssl RAND_status now returns a boolean value as documented instead of 1 or 0 bpo 39906 pathlib Path stat and chmod now accept a follow_symlinks keyword only argument for consistency with corresponding functions in the os module bpo 39899 os path expanduser now refuses to guess Windows home directories if the basename of current user s home directory does not match their username pathlib Path expanduser and home now consistently raise RuntimeError exception when a home directory cannot be resolved Previously a KeyError exception could be raised on Windows when the USERNAME environment variable was unset bpo 36076 Added SNI support to ssl get_server_certificate bpo 38490 Covariance P,en
1609,earson s correlation and simple linear regression functionality was added to statistics module Patch by Tymoteusz Wołodźko bpo 33731 Provide a locale localize function which converts a normalized number string into a locale format bpo 32745 Fix a regression in the handling of ctypes ctypes c_wchar_p type embedded null characters would cause a ValueError to be raised Patch by Zackery Spytz Documentation bpo 43987 Add Annotations Best Practices document as a new HOWTO bpo 43977 Document the new Py_TPFLAGS_MAPPING and Py_TPFLAGS_SEQUENCE type flags bpo 43959 The documentation on the PyContextVar C API was clarified bpo 43938 Update dataclasses documentation to express that FrozenInstanceError is derived from AttributeError bpo 43778 Fix the Sphinx glossary_search extension create the _static sub directory if it doesn t exist bpo 43755 Update documentation to reflect that unparenthesized lambda expressions can no longer be the expression part in an if clause in comprehensions and generator expressions since Python 3 9 bpo 43739 Fixing the example code in Doc extending extending rst to declare and initialize the pmodule variable to be of the right type Tests bpo 43961 Fix test_logging test_namer_rotator_inheritance on Windows use os replace rather than os rename Patch by Victor Stinner bpo 43842 Fix a race condition in the SMTP test of test_logging Don t close a file descriptor socket from a different thread while asyncore loop is polling the file descriptor Patch by Victor Stinner bpo 43843 test libregrtest now marks a test as ENV_CHANGED altered the execution environment if a thread raises an exception but does not catch it It sets a hook on threading excepthook Use fail env changed option to mark the test as failed Patch by Victor Stinner bpo 43811 Tests multiple OpenSSL versions on GitHub Actions Use ccache to speed up testing bpo 43791 OpenSSL 3 0 0 Disable testing of legacy protocols TLS 1 0 and 1 1 Tests are failing with TLSV1_ALERT_INTERNAL_ERROR Build bpo 43567 Improved generated code refresh AST tokens opcodes keywords on Windows bpo 43669 Implement PEP 644 Python now requires OpenSSL 1 1 1 or newer Windows bpo 35306 Adds additional arguments to os startfile function bpo 43538 Avoid raising errors from pathlib Path exists when passed an invalid filename bpo 38822 Fixed os stat failing on inaccessible directories with a trailing slash rather than falling back to the parent directory s metadata This implicitly affected os path exists and os path isdir bpo 26227 Fixed decoding of host names in socket gethostbyaddr and socket gethostbyname_ex bpo 40432 Updated pegen regeneration script on Windows to find and use Python 3 8 or higher Prior to this pegen regeneration already required 3 8 or higher but the script may have used lower versions of Python bpo 43745 Actually updates Windows release to OpenSSL 1 1 1k Earlier releases were mislabelled and actually included 1 1 1i again bpo 43652 Update Tcl and Tk to 8 6 11 in Windows installer bpo 43492 Upgrade Windows installer to use SQLite 3 35 5 bpo 30555 Fix WindowsConsoleIO errors in the presence of fd redirection Patch by Segev Finer macOS bpo 42119 Fix check for macOS SDK paths when building Python Narrow search to match contents of SDKs namely only files in System Library System IOSSupport and usr other than usr local Previously anything under System was assumed to be in an SDK which causes problems with the new file system layout in 10 15 where user file systems may appear to be mounted under System Paths in Library were also incorrectly treated as SDK locations bpo 43568 Drop support for MACOSX_DEPLOYMENT_TARGET 10 3 bpo 44009 Provide python3 x intel64 executable to allow reliably forcing macOS universal2 framework builds to run under Rosetta 2 Intel 64 emulation on Apple Silicon Macs This can be useful for testing or when universal2 wheels are not yet available bpo 43851 Build SQLite with SQLITE_OMIT_AUTOINIT on macOS Patch by Erlend E Aasland bpo 43492 Update macOS installer to use SQLite 3 35 4 bpo 42235 Mac BuildScript build installer py will now use enable optimiz,en
1610,ations and with lto when building on macOS 10 15 or later IDLE bpo 37903 Add mouse actions to the shell sidebar Left click and optional drag selects one or more lines as with the editor line number sidebar Right click after selecting raises a context menu with copy with prompts This zips together prompts from the sidebar with lines from the selected text bpo 43981 Fix reference leak in test_sidebar and test_squeezer Patches by Terry Jan Reedy and Pablo Galindo bpo 37892 Indent IDLE Shell input with spaces instead of tabs bpo 43655 IDLE dialog windows are now recognized as dialogs by window managers on macOS and X Window bpo 37903 IDLE s shell now shows prompts in a separate side bar C API bpo 43916 Add a new Py_TPFLAGS_DISALLOW_INSTANTIATION type flag to disallow creating type instances Patch by Victor Stinner bpo 43774 Remove the now unused PYMALLOC_DEBUG macro Debug hooks on memory allocators are now installed by default if Python is built in debug mode if Py_DEBUG macro is defined Moreover they can now be used on Python build in release mode ex using PYTHONMALLOC debug environment variable bpo 43962 _PyInterpreterState_IDIncref now calls _PyInterpreterState_IDInitref and always increments id_refcount Previously calling _xxsubinterpreters get_current could create an id_refcount inconsistency when a _xxsubinterpreters InterpreterID object was deallocated Patch by Victor Stinner bpo 28254 Add new C API functions to control the state of the garbage collector PyGC_Enable PyGC_Disable PyGC_IsEnabled corresponding to the functions in the gc module bpo 43908 Introduce Py_TPFLAGS_IMMUTABLETYPE flag for immutable type objects and modify PyType_Ready to set it for static types Patch by Erlend E Aasland bpo 43795 PyMem_Calloc is now available in the limited C API Py_LIMITED_API bpo 43868 PyOS_ReadlineFunctionPointer is no longer exported by limited C API headers and by python3 dll on Windows Like any function that takes FILE it is not part of the stable ABI bpo 43795 Stable ABI and limited API definitions are generated from a central manifest PEP 652 bpo 43753 Add the Py_Is x y function to test if the x object is the y object the same as x is y in Python Add also the Py_IsNone Py_IsTrue Py_IsFalse functions to test if an object is respectively the None singleton the True singleton or the False singleton Patch by Victor Stinner Python 3 10 0 alpha 7 Release date 2021 04 05 Security bpo 42988 CVE 2021 3426 Remove the getfile feature of the pydoc module which could be abused to read arbitrary files on the disk directory traversal vulnerability Moreover even source code of Python modules can contain sensitive data like passwords Vulnerability reported by David Schwörer bpo 43285 ftplib no longer trusts the IP address value returned from the server in response to the PASV command by default This prevents a malicious FTP server from using the response to probe IPv4 address and port combinations on the client network Code that requires the former vulnerable behavior may set a trust_server_pasv_ipv4_address attribute on their ftplib FTP instances to True to re enable it bpo 43439 Add audit hooks for gc get_objects gc get_referrers and gc get_referents Patch by Pablo Galindo Core and Builtins bpo 27129 Update CPython bytecode magic number bpo 43672 Raise ImportWarning when calling find_loader bpo 43660 Fix crash that happens when replacing sys stderr with a callable that can remove the object while an exception is being printed Patch by Pablo Galindo bpo 27129 The bytecode interpreter uses instruction rather byte offsets internally This reduces the number of EXTENDED_ARG instructions needed and streamlines instruction dispatch a bit bpo 40645 Fix reference leak in the _hashopenssl extension Patch by Pablo Galindo bpo 42134 Calls to find_module by the import system now raise ImportWarning bpo 41064 Improve the syntax error for invalid usage of double starred elements in f strings Patch by Pablo Galindo bpo 43575 Speed up calls to map by using the PEP 590 vectorcall calling convention Patch by Donghee Na bpo 42137 The import system now pref,en
1611,ers using __spec__ for ModuleType __repr__ over module_repr bpo 43452 Added micro optimizations to _PyType_Lookup to improve cache lookup performance in the common case of cache hits bpo 43555 Report the column offset for SyntaxError for invalid line continuation characters Patch by Pablo Galindo bpo 43517 Fix misdetection of circular imports when using from pkg mod import attr which caused false positives in non trivial multi threaded code bpo 43497 Emit SyntaxWarnings for assertions with tuple constants this is a regression introduced in python3 7 bpo 39316 Tracing now has correct line numbers for attribute accesses when the attribute is on a different line from the object Improves debugging and profiling for multi line method chains bpo 35883 Python no longer fails at startup with a fatal error if a command line argument contains an invalid Unicode character The Py_DecodeLocale function now escapes byte sequences which would be decoded as Unicode characters outside the U 0000 U 10ffff range bpo 43410 Fix a bug that was causing the parser to crash when emitting syntax errors when reading input from stdin Patch by Pablo Galindo bpo 43406 Fix a possible race condition where PyErr_CheckSignals tries to execute a non Python signal handler bpo 42128 Add __match_args__ to struct sequence objects Patch by Pablo Galindo bpo 43390 CPython now sets the SA_ONSTACK flag in PyOS_setsig for the VM s default signal handlers This is friendlier to other in process code that an extension module or embedding use could pull in such as Golang s cgo where tiny thread stacks are the norm and sigaltstack has been used to provide for signal handlers This is a no op change for the vast majority of processes that don t use sigaltstack bpo 43287 Speed up calls to filter by using the PEP 590 vectorcall calling convention Patch by Donghee Na bpo 37448 Add a radix tree based memory map to track in use obmalloc arenas Use to replace the old implementation of address_in_range The radix tree approach makes it easy to increase pool sizes beyond the OS page size Boosting the pool and arena size allows obmalloc to handle a significantly higher percentage of requests from its ultra fast paths It also has the advantage of eliminating the memory unsanitary behavior of the previous address_in_range The old address_in_range was marked with the annotations _Py_NO_SANITIZE_ADDRESS _Py_NO_SANITIZE_THREAD and _Py_NO_SANITIZE_MEMORY Those annotations are no longer needed To disable the radix tree map set a preprocessor flag as follows DWITH_PYMALLOC_RADIX_TREE 0 Co authored by Tim Peters tim peters gmail com bpo 29988 Only handle asynchronous exceptions and requests to drop the GIL when returning from a call or on the back edges of loops Makes sure that __exit__ is always called in with statements even for interrupts Library bpo 43720 Document various stdlib deprecations in imp pkgutil and importlib util for removal in Python 3 12 bpo 43433 xmlrpc client ServerProxy no longer ignores query and fragment in the URL of the server bpo 31956 The index method of array array now has optional start and stop parameters bpo 40066 Enum adjust repr to show only enum and member name not value nor angle brackets and str to show only member name Update and improve documentation to match bpo 42136 Deprecate all module_repr methods found in importlib as their use is being phased out by Python 3 12 bpo 35930 Raising an exception raised in a future instance will create reference cycles bpo 41369 Finish updating the vendored libmpdec to version 2 5 1 Patch by Stefan Krah bpo 43422 Revert the _decimal C API which was added in bpo 41324 bpo 43577 Fix deadlock when using ssl SSLContext debug callback with ssl SSLContext sni_callback bpo 43571 It s now possible to create MPTCP sockets with IPPROTO_MPTCP bpo 43542 image heic and image heif were added to mimetypes bpo 40645 The hmac module now uses OpenSSL s HMAC implementation when digestmod argument is a hash name or builtin hash function bpo 43510 Implement PEP 597 Add EncodingWarning warning X warn_default_encoding option PYTHONWARNDEFA,en
1612,ULTENCODING environment variable and encoding locale argument value bpo 43521 ast unparse can now render NaNs and empty sets bpo 42914 pprint pprint gains a new boolean underscore_numbers optional argument to emit integers with thousands separated by an underscore character for improved readability for example 1_000_000 instead of 1000000 bpo 41361 rotate calls are now slightly faster due to faster argument parsing bpo 43423 subprocess communicate no longer raises an IndexError when there is an empty stdout or stderr IO buffer during a timeout on Windows bpo 27820 Fixed long standing bug of smtplib SMTP where doing AUTH LOGIN with initial_response_ok False will fail The cause is that SMTP auth_login _always_ returns a password if provided with a challenge string thus non compliant with the standard for AUTH LOGIN Also fixes bug with the test for smtpd bpo 43445 Add frozen modules to sys stdlib_module_names For example add _frozen_importlib and _frozen_importlib_external names bpo 43245 Add keyword arguments support to ChainMap new_child bpo 29982 Add optional parameter ignore_cleanup_errors to tempfile TemporaryDirectory and allow multiple cleanup attempts Contributed by C A M Gerlach bpo 43428 Include changes from importlib_metadata 3 7 Performance enhancements to distribution discovery entry_points only returns unique distributions Introduces new EntryPoints object for containing a set of entry points with convenience methods for selecting entry points by group or name entry_points now returns this object if selection parameters are supplied but continues to return a dict object for compatibility Users are encouraged to rely on the selection interface The dict object result is likely to be deprecated in the future Added packages_distributions function to return a mapping of packages to the distributions that provide them bpo 43332 Improves the networking efficiency of http client when using a proxy via set_tunnel Fewer small send calls are made during connection setup bpo 43420 Improve performance of fractions Fraction arithmetics for large components Contributed by Sergey B Kirpichev bpo 43356 Allow passing a signal number to _thread interrupt_main bpo 43399 Fix ElementTree extend not working on iterators when using the Python implementation bpo 43369 Improve sqlite3 error handling If sqlite3_column_text and sqlite3_column_blob set SQLITE_NOMEM MemoryError is now raised Patch by Erlend E Aasland bpo 43368 Fix a regression introduced in PR 24562 where an empty bytestring was fetched as None instead of b in sqlite3 Patch by Mariusz Felisiak bpo 41282 Fixed stacklevel of DeprecationWarning emitted from import distutils bpo 42129 importlib resources now honors namespace packages merging resources from each location in the namespace as introduced in importlib_resources 3 2 and including incidental changes through 5 0 3 bpo 43295 datetime datetime strptime now raises ValueError instead of IndexError when matching z with the z format specifier bpo 43125 Return empty string if base64mime body_encode receive empty bytes bpo 43084 curses window enclose returns now True or False as was documented instead of 1 or 0 bpo 42994 Add MIME types for opus AAC 3gpp and 3gpp2 bpo 14678 Add an invalidate_caches method to the zipimport zipimporter class to support importlib invalidate_caches Patch by Desmond Cheong bpo 42782 Fail fast in shutil move to avoid creating destination directories on failure bpo 40066 Enum s repr and str have changed repr is now EnumClass MemberName and str is MemberName Additionally stdlib Enum s whose contents are available as module attributes such as RegexFlag IGNORECASE have their repr as module name e g re IGNORECASE bpo 26053 Fixed bug where the pdb interactive run command echoed the args from the shell command line even if those have been overridden at the pdb prompt bpo 24160 Fixed bug where breakpoints did not persist across multiple debugger sessions in pdb s interactive mode bpo 40701 When the tempfile tempdir global variable is set to a value of type bytes it is now handled consistently Previously exc,en
1613,eptions could be raised from some tempfile APIs when the directory did not already exist in this situation Also ensures that the tempfile gettempdir and tempfile gettempdirb functions always return str and bytes respectively bpo 39342 Expose X509_V_FLAG_ALLOW_PROXY_CERTS as VERIFY_ALLOW_PROXY_CERTS to allow proxy certificate validation as explained in https www openssl org docs man1 1 1 man7 proxy certificates html bpo 31861 Add builtins aiter and builtins anext Patch by Joshua Bronson jab Daniel Pope lordmauve and Justin Wang justin39 Documentation bpo 43199 Answer Why is there no goto in the Design and History FAQ bpo 43407 Clarified that a result from time monotonic time perf_counter time process_time or time thread_time can be compared with the result from any following call to the same function not just the next immediate call bpo 43354 Fix type documentation for Fault faultCode the type has to be int instead of str bpo 41933 Clarified wording of s n in the Common Sequence Operations Tests bpo 37945 Fix test_getsetlocale_issue1813 of test_locale skip the test if setlocale fails Patch by Victor Stinner bpo 41561 Add workaround for Ubuntu s custom OpenSSL security level policy Build bpo 43179 Introduce and correctly use ALIGNOF_X in place of SIZEOF_X for alignment related code in optimized string routines Patch by Jessica Clarke bpo 43631 Update macOS Windows and CI to OpenSSL 1 1 1k bpo 43617 Improve configure ac Check for presence of autoconf archive package and remove our copies of M4 macros bpo 43466 The configure script now supports with openssl rpath option bpo 43372 Use _freeze_importlib to generate code for the __hello__ module This approach ensures the code matches the interpreter version Previously PYTHON_FOR_REGEN was used to generate the code which might be wrong The marshal format for code objects has changed with bpo 42246 commit 877df851 Update the code and the expected code sizes in ctypes test_frozentable Windows bpo 43440 Build sqlite3 with the R Tree module enabled Patch by Erlend E Aasland IDLE bpo 42225 Document that IDLE can fail on Unix either from misconfigured IP masquerade rules or failure displaying complex colored non ascii characters C API bpo 43688 The limited C API is now supported if Python is built in debug mode if the Py_DEBUG macro is defined In the limited C API the Py_INCREF and Py_DECREF functions are now implemented as opaque function calls rather than accessing directly the PyObject ob_refcnt member if Python is built in debug mode and the Py_LIMITED_API macro targets Python 3 10 or newer It became possible to support the limited C API in debug mode because the PyObject structure is the same in release and debug mode since Python 3 8 see bpo 36465 The limited C API is still not supported in the with trace refs special build Py_TRACE_REFS macro Patch by Victor Stinner bpo 43244 Remove the pyarena h header file with functions PyArena_New PyArena_Free PyArena_Malloc PyArena_AddPyObject These functions were undocumented excluded from the limited C API and were only used internally by the compiler Patch by Victor Stinner bpo 43244 Remove the compiler and parser functions using struct _mod type because the public AST C API was removed PyAST_Compile PyAST_CompileEx PyAST_CompileObject PyFuture_FromAST PyFuture_FromASTObject PyParser_ASTFromFile PyParser_ASTFromFileObject PyParser_ASTFromFilename PyParser_ASTFromString PyParser_ASTFromStringObject These functions were undocumented and excluded from the limited C API Patch by Victor Stinner bpo 43244 Remove ast h asdl h and Python ast h header files These functions were undocumented and excluded from the limited C API Most names defined by these header files were not prefixed by Py and so could create names conflicts For example Python ast h defined a Yield macro which was conflict with the Yield name used by the Windows winbase h header Use the Python ast module instead Patch by Victor Stinner bpo 43541 Fix a PyEval_EvalCodeEx regression fix reference counting on builtins Patch by Victor Stinner bpo 43244 Remove the symtable h header fi,en
1614,le and the undocumented functions PyST_GetScope PySymtable_Build PySymtable_BuildObject PySymtable_Free Py_SymtableString Py_SymtableStringObject The Py_SymtableString function was part the stable ABI by mistake but it could not be used because the symtable h header file was excluded from the limited C API The Python symtable module remains available and is unchanged Patch by Victor Stinner bpo 43244 Remove the PyAST_Validate function It is no longer possible to build a AST object mod_ty type with the public C API The function was already excluded from the limited C API PEP 384 Patch by Victor Stinner Python 3 10 0 alpha 6 Release date 2021 03 01 Security bpo 42967 Fix web cache poisoning vulnerability by defaulting the query args separator to and allowing the user to choose a custom separator Core and Builtins bpo 43321 Fix SystemError raised when PyArg_Parse is used with but without PY_SSIZE_T_CLEAN defined bpo 36346 PyArg_Parse functions now emits DeprecationWarning when u or Z format is used See PEP 623 for detail bpo 43277 Add a new PySet_CheckExact function to the C API to check if an object is an instance of set but not an instance of a subtype Patch by Pablo Galindo bpo 42990 The types FunctionType constructor now inherits the current builtins if the globals dictionary has no __builtins__ key rather than using None None as builtins same behavior as eval and exec functions Defining a function with def function in Python is not affected globals cannot be overridden with this syntax it also inherits the current builtins Patch by Victor Stinner bpo 42990 Functions have a new __builtins__ attribute which is used to look for builtin symbols when a function is executed instead of looking into __globals__ __builtins__ Patch by Mark Shannon and Victor Stinner bpo 43149 Improve the error message in the parser for exception groups without parentheses Patch by Pablo Galindo bpo 43121 Fixed an incorrect SyntaxError message for missing comma in literals Patch by Pablo Galindo bpo 42819 readline Explicitly disable bracketed paste in the interactive interpreter even if it s set in the inputrc is enabled by default eg GNU Readline 8 1 or a user calls readline read_init_file The Python REPL has not implemented bracketed paste support Also bracketed mode writes the x1b 2004h escape sequence into stdout which causes test failures in applications that don t support it It can still be explicitly enabled by calling readline parse_and_bind set enable bracketed paste on Patch by Dustin Rodrigues bpo 42808 Simple calls to type object are now faster due to the vectorcall calling convention Patch by Dennis Sweeney bpo 42217 Make the compiler merges same co_code and co_linetable objects in a module like already did for co_consts bpo 41972 Substring search functions such as str1 in str2 and str2 find str1 now sometimes use the Two Way string comparison algorithm to avoid quadratic behavior on long strings bpo 42128 Implement PEP 634 structural pattern matching Patch by Brandt Bucher bpo 40692 In the concurrent futures ProcessPoolExecutor validate that multiprocess synchronize is available on a given platform and rely on that check in the concurrent futures test suite so we can run tests that are unrelated to ProcessPoolExecutor on those platforms bpo 38302 If object __ipow__ returns NotImplemented the operator will correctly fall back to object __pow__ and object __rpow__ as expected Library bpo 43316 The python m gzip command line application now properly fails when detecting an unsupported extension It exits with a non zero exit code and prints an error message to stderr bpo 43317 Set the chunk size for the gzip module main function to io DEFAULT_BUFFER_SIZE This is slightly faster than the 1024 bytes constant that was used previously bpo 43146 Handle None in single arg versions of print_exception and format_exception bpo 43260 Fix TextIOWrapper can not flush internal buffer forever after very large text is written bpo 43258 Prevent needless allocation of sqlite3 aggregate function context when no rows match an aggregate query Patch by Erle,en
1615,nd E Aasland bpo 43251 Improve sqlite3 error handling sqlite3_column_name failures now result in MemoryError Patch by Erlend E Aasland bpo 40956 Fix segfault in sqlite3 Connection backup if no argument was provided The regression was introduced by PR 23838 Patch by Erlend E Aasland bpo 43172 The readline module now passes its tests when built directly against libedit Existing irreconcilable API differences remain in readline get_begidx and readline get_endidx behavior based on libreadline vs libedit use bpo 43163 Fix a bug in codeop that was causing it to not ask for more input when multi line snippets have unclosed parentheses Patch by Pablo Galindo bpo 43162 deprecate unsupported ability to access enum members as attributes of other enum members bpo 43146 Fix recent regression in None argument handling in traceback module functions bpo 43102 The namedtuple __new__ method had its __builtins__ set to None instead of an actual dictionary This created problems for introspection tools bpo 43106 Added O_EVTONLY O_FSYNC O_SYMLINK and O_NOFOLLOW_ANY for macOS Patch by Donghee Na bpo 42960 Adds resource RLIMIT_KQUEUES constant from FreeBSD to the resource module bpo 42151 Make the pure Python implementation of xml etree ElementTree behave the same as the C implementation _elementree regarding default attribute values by not setting specified_attributes 1 bpo 29753 In ctypes now packed bitfields are calculated properly and the first item of packed bitfields is now shrank correctly Documentation bpo 27646 Clarify that yield from expr works with any iterable not just iterators bpo 36346 Update some deprecated unicode APIs which are documented as will be removed in 4 0 to 3 12 See PEP 623 for detail Tests bpo 43288 Fix test_importlib to correctly skip Unicode file tests if the filesystem does not support them Build bpo 43174 Windows build now uses utf 8 compiler option bpo 43103 Add a new configure without static libpython option to not build the libpythonMAJOR MINOR a static library and not install the python o object file bpo 13501 The configure script can now use libedit instead of readline with the command line option with readline editline bpo 42603 Make configure script use pkg config to detect the location of Tcl Tk headers and libraries used to build tkinter On macOS a Tcl Tk configuration provided by pkg config will be preferred over Tcl Tk frameworks installed in System Library Frameworks If both exist and the latter is preferred the appropriate with tcltk configuration options need to be explicitly set bpo 39448 Add the regen frozen makefile target that regenerates the code for the frozen __hello__ module Windows bpo 43155 PyCMethod_New is now present in python3 lib macOS bpo 41837 Update macOS installer build to use OpenSSL 1 1 1j IDLE bpo 43283 Document why printing to IDLE s Shell is often slower than printing to a system terminal and that it can be made faster by pre formatting a single string before printing C API bpo 43278 Always put compiler and system information on the first line of the REPL welcome message bpo 43270 Remove the private _PyErr_OCCURRED macro use the public PyErr_Occurred function instead bpo 35134 Move odictobject h parser_interface h picklebufobject h pydebug h and pyfpe h into the cpython directory They must not be included directly as they are already included by Python h Include Files bpo 35134 Move pyarena h pyctype h and pytime h into the cpython directory They must not be included directly as they are already included by Python h Include Files bpo 40170 PyExceptionClass_Name is now always declared as a function in order to hide implementation details The macro accessed PyTypeObject tp_name directly Patch by Erlend E Aasland bpo 43239 The PyCFunction_New function is now exported in the ABI when compiled with fvisibility hidden bpo 40170 PyIter_Check is now always declared as a function in order to hide implementation details The macro accessed PyTypeObject tp_iternext directly Patch by Erlend E Aasland bpo 40170 Convert PyDescr_IsData macro to a function to hide implementation details The m,en
1616,acro accessed PyTypeObject tp_descr_set directly Patch by Erlend E Aasland bpo 43181 Convert PyObject_TypeCheck macro to a static inline function Patch by Erlend E Aasland Python 3 10 0 alpha 5 Release date 2021 02 02 Security bpo 42938 Avoid static buffers when computing the repr of ctypes c_double and ctypes c_longdouble values Core and Builtins bpo 42990 Refactor the PyEval_ family of functions An new function _PyEval_Vector is added to simplify calls to Python from C _PyEval_EvalCodeWithName is removed PyEval_EvalCodeEx is retained as part of the API but is not used internally bpo 38631 Replace Py_FatalError calls in the compiler with regular SystemError exceptions Patch by Victor Stinner bpo 42997 Improve error message for missing before blocks Patch by Pablo Galindo bpo 43017 Improve error message in the parser when using un parenthesised tuples in comprehensions Patch by Pablo Galindo bpo 42986 Fix parser crash when reporting syntax errors in f string with newlines Patch by Pablo Galindo bpo 40176 Syntax errors for unterminated string literals now point to the start of the string instead of reporting EOF EOL bpo 42927 The inline cache for LOAD_ATTR now also optimizes access to attributes defined by __slots__ This makes reading such attribute up to 30 faster bpo 42864 Improve error messages in the parser when parentheses are not closed Patch by Pablo Galindo bpo 42924 Fix bytearray repetition incorrectly copying data from the start of the buffer even if the data is offset within the buffer e g after reassigning a slice at the start of the bytearray to a shorter byte string bpo 42882 Fix the _PyUnicode_FromId function _Py_IDENTIFIER var API when Py_Initialize Py_Finalize is called multiple times preserve _PyRuntime unicode_ids next_index value bpo 42827 Fix a crash when working out the error line of a SyntaxError in some multi line expressions bpo 42823 frame f_lineno is correct even if frame f_trace is set to True bpo 37324 Remove deprecated aliases to Collections Abstract Base Classes from the collections module bpo 41994 Fixed possible leak in import when sys modules is not a dict bpo 27772 In string formatting preceding the width field by 0 no longer affects the default alignment for strings Library bpo 43108 Fixed a reference leak in the curses module Patch by Pablo Galindo bpo 43077 Update the bundled pip to 21 0 1 and setuptools to 52 0 0 bpo 41282 Deprecate distutils in documentation and add warning on import bpo 43014 Improve performance of tokenize by 20 30 Patch by Anthony Sottile bpo 42323 Fix math nextafter for NaN on AIX bpo 42955 Add sys stdlib_module_names containing the list of the standard library module names Patch by Victor Stinner bpo 42944 Fix random Random sample when counts argument is not None bpo 42934 Use TracebackException s new compact param in TestResult to reduce time and memory consumed by traceback formatting bpo 42931 Add randbytes to random __all__ bpo 38250 Enum Flags consisting of a single bit are now considered canonical and will be the only flags returned from listing and iterating over a Flag class or a Flag member Multi bit flags are considered aliases they will be returned from lookups and operations that result in their value Iteration for both Flag and Flag members is in definition order bpo 42877 Added the compact parameter to the constructor of traceback TracebackException to reduce time and memory for use cases that only need to call TracebackException format and TracebackException format_exception_only bpo 42923 The Py_FatalError function and the faulthandler module now dump the list of extension modules on a fatal error bpo 42848 Removed recursion from TracebackException to allow it to handle long exception chains bpo 42901 Enum move member creation from EnumMeta __new__ to _proto_member __set_name__ allowing members to be created and visible in __init_subclass__ bpo 42780 Fix os set_inheritable for O_PATH file descriptors on Linux bpo 42866 Fix a reference leak in the getcodec function of CJK codecs Patch by Victor Stinner bpo 42846 Convert the 6 CJK codec extension ,en
1617,modules _codecs_cn _codecs_hk _codecs_iso2022 _codecs_jp _codecs_kr and _codecs_tw to the multiphase initialization API PEP 489 Patch by Victor Stinner bpo 42851 remove __init_subclass__ support for Enum members bpo 42834 Make internal caches of the _json module compatible with subinterpreters bpo 41748 Fix HTMLParser parsing rules for element attributes containing commas with spaces Patch by Karl Dubost bpo 40810 Require SQLite 3 7 15 or newer Patch by Erlend E Aasland bpo 1635741 Convert the _multibytecodec extension module CJK codecs to multi phase initialization PEP 489 Patch by Erlend E Aasland bpo 42802 The distutils bdist_wininst command deprecated in Python 3 8 has been removed The distutils bdist_wheel command is now recommended to distribute binary packages on Windows bpo 24464 The undocumented built in function sqlite3 enable_shared_cache is now deprecated scheduled for removal in Python 3 12 Its use is strongly discouraged by the SQLite3 documentation Patch by Erlend E Aasland bpo 42384 Make pdb populate sys path 0 exactly the same as regular python execution bpo 42383 Fix pdb previously pdb would fail to restart the debugging target if it was specified using a relative path and the current directory changed bpo 42005 Fix CLI of cProfile and profile to catch BrokenPipeError bpo 41604 Don t decrement the reference count of the previous user_ptr when set_panel_userptr fails bpo 41149 Allow executing callables that have a boolean value of False when passed to Threading thread as the target Patch contributed by Barney Stratford bpo 38307 Add an end_lineno attribute to the Class and Function objects that appear in the tree returned by pyclbr functions This and the existing lineno attribute define the extent of class and def statements Patch by Aviral Srivastava bpo 39273 The BUTTON5_ constants are now exposed in the curses module if available bpo 33289 Correct call to tkinter colorchooser to return RGB triplet of ints instead of floats Patch by Cheryl Sabella Documentation bpo 40304 Fix doc for type name bases dict Patch by Boris Verkhovskiy and Éric Araujo bpo 42811 Updated importlib util resolve_name doc to use __spec__ parent instead of __package__ Thanks Yair Frid Tests bpo 40823 Use unittest TestLoader loadTestsFromTestCase instead of unittest makeSuite in sqlite3 tests Patch by Erlend E Aasland bpo 40810 In sqlite3 fix CheckTraceCallbackContent for SQLite pre 3 7 15 Build bpo 43031 Pass timeout TESTTIMEOUT option to the default profile task python m test pgo command bpo 36143 make regen all now also runs regen keyword Patch by Victor Stinner bpo 42874 Removed the grep q and E flags in the tzpath validation section of the configure script to better accommodate users of some platforms specifically Solaris 10 bpo 31904 Add library search path by wr cc in add_cross_compiling_paths for VxWorks bpo 42856 Add with wheel pkg dir PATH option to the configure script If specified the ensurepip module looks for setuptools and pip wheel packages in this directory if both are present these wheel packages are used instead of ensurepip bundled wheel packages Some Linux distribution packaging policies recommend against bundling dependencies For example Fedora installs wheel packages in the usr share python wheels directory and don t install the ensurepip _bundled package Windows bpo 41837 Updated Windows installer to include OpenSSL 1 1 1i bpo 42584 Upgrade Windows installer to use SQLite 3 34 0 macOS bpo 42504 Ensure that the value of sysconfig get_config_var MACOSX_DEPLOYMENT_TARGET is always a string even in when the value is parsable as an integer IDLE bpo 43008 Make IDLE invoke sys excepthook in normal 2 process mode Patch by Ken Hilton bpo 33065 Fix problem debugging user classes with __repr__ method bpo 23544 Disable Debug Stack Viewer when user code is running or Debugger is active to prevent hang or crash Patch by Zackery Spytz bpo 32631 Finish zzdummy example extension module make menu entries work add docstrings and tests with 100 coverage C API bpo 42979 When Python is built in debug mode with C assertions callin,en
1618,g a type slot like sq_length __len__ in Python now fails with a fatal error if the slot succeeded with an exception set or failed with no exception set The error message contains the slot the type name and the current exception if an exception is set Patch by Victor Stinner bpo 43030 Fixed a compiler warning in Py_UNICODE_ISSPACE on platforms with signed wchar_t Python 3 10 0 alpha 4 Release date 2021 01 04 Core and Builtins bpo 42814 Fix undefined behavior in Objects genericaliasobject c bpo 42806 Fix the column offsets for f strings ast nodes surrounded by parentheses and for nodes that spawn multiple lines Patch by Pablo Galindo bpo 40631 Fix regression where a single parenthesized starred expression was a valid assignment target bpo 27794 Improve the error message for failed writes deletes to property objects When possible the attribute name is now shown Patch provided by Yurii Karabas bpo 42745 Make the type attribute lookup cache per interpreter Patch by Victor Stinner bpo 42246 Jumps to jumps are not eliminated when it would break PEP 626 bpo 42246 Make sure that the f_lasti and f_lineno attributes of a frame are set correctly when an exception is raised or re raised Required for PEP 626 bpo 32381 The coding cookie ex coding latin1 is now ignored in the command passed to the c command line option Patch by Victor Stinner bpo 30858 Improve error location in expressions that contain assignments Patch by Pablo Galindo and Lysandros Nikolaou bpo 42615 Remove jump commands made redundant by the deletion of unreachable bytecode blocks bpo 42639 Make the atexit module state per interpreter It is now safe have more than one atexit module instance Patch by Donghee Na and Victor Stinner bpo 32381 Fix encoding name when running a pyc file on Windows PyRun_SimpleFileExFlags now uses the correct encoding to decode the filename bpo 42195 The __args__ of the parameterized generics for typing Callable and collections abc Callable are now consistent The __args__ for collections abc Callable are now flattened while typing Callable s have not changed To allow this change types GenericAlias can now be subclassed and collections abc Callable s __class_getitem__ will now return a subclass of types GenericAlias Tests for typing were also updated to not subclass things like Callable T as that is not a valid base class Finally both Callable s no longer validate their argtypes in Callable argtypes resulttype to prepare for PEP 612 Patch by Ken Jin bpo 40137 Convert functools module to use PyType_FromModuleAndSpec bpo 40077 Convert array to use heap types and establish module state for these bpo 42008 Fix _random Random seeding bpo 1635741 Port the pyexpat extension module to multi phase initialization PEP 489 bpo 40521 Make the Unicode dictionary of interned strings compatible with subinterpreters Patch by Victor Stinner bpo 39465 Make _PyUnicode_FromId function compatible with subinterpreters Each interpreter now has an array of identifier objects interned strings decoded from UTF 8 Patch by Victor Stinner Library bpo 42257 Handle empty string in variable executable in platform libc_ver bpo 42772 randrange now raises a TypeError when step is specified without a stop argument Formerly it silently ignored the step argument bpo 42759 Fixed equality comparison of tkinter Variable and tkinter font Font Objects which belong to different Tcl interpreters are now always different even if they have the same name bpo 42756 Configure LMTP Unix domain socket to use socket global default timeout when a timeout is not explicitly provided bpo 23328 Allow character in username password fields on _PROXY envars bpo 42740 typing get_args and typing get_origin now support PEP 604 union types and PEP 612 additions to Callable bpo 42655 subprocess extra_groups is now correctly passed into setgroups system call bpo 42727 EnumMeta __prepare__ now accepts kwds to properly support __init_subclass__ bpo 38308 Add optional weights to statistics harmonic_mean bpo 42721 When simple query dialogs tkinter simpledialog message boxes tkinter messagebox or color choose dial,en
1619,og tkinter colorchooser are created without arguments master and parent and the default root window is not yet created and NoDefaultRoot was not called a new temporal hidden root window will be created automatically It will not be set as the default root window and will be destroyed right after closing the dialog window It will help to use these simple dialog windows in programs which do not need other GUI bpo 25246 Optimized collections deque remove bpo 35728 Added a root parameter to tkinter font nametofont bpo 15303 tkinter supports now widgets with boolean value False bpo 42681 Fixed range checks for color and pair numbers in curses bpo 42685 Improved placing of simple query windows in Tkinter such as tkinter simpledialog askinteger They are now centered at the center of the parent window if it is specified and shown otherwise at the center of the screen bpo 9694 Argparse help no longer uses the confusing phrase optional arguments It uses options instead bpo 1635741 Port the _thread extension module to the multiphase initialization API PEP 489 and convert its static types to heap types bpo 37961 Fix crash in tracemalloc Traceback __repr__ regressed in Python 3 9 bpo 42630 tkinter functions and constructors which need a default root window raise now RuntimeError with descriptive message instead of obscure AttributeError or NameError if it is not created yet or cannot be created automatically bpo 42639 atexit _run_exitfuncs now logs callback exceptions using sys unraisablehook rather than logging them directly into sys stderr and raise the last exception bpo 42644 logging disable will now validate the types and value of its parameter It also now accepts strings representing the levels as does loging setLevel instead of only the numerical values bpo 42639 At Python exit if a callback registered with atexit register fails its exception is now logged Previously only some exceptions were logged and the last exception was always silently ignored bpo 36541 Fixed lib2to3 pgen2 to be able to parse PEP 570 positional only argument syntax bpo 42382 In importlib metadata EntryPoint objects now expose a dist object referencing the Distribution when constructed from a Distribution Add support for package discovery under package normalization rules The object returned by metadata now has a formally defined protocol called PackageMetadata with declared support for the get_all method Synced with importlib_metadata 3 3 bpo 41877 A check is added against misspellings of autospect auto_spec and set_spec being passed as arguments to patch patch object and create_autospec bpo 39717 tarfile update nested exception raising to use from None or from e bpo 41877 AttributeError for suspected misspellings of assertions on mocks are now pointing out that the cause are misspelled assertions and also what to do if the misspelling is actually an intended attribute name The unittest mock document is also updated to reflect the current set of recognised misspellings bpo 41559 Implemented PEP 612 added ParamSpec and Concatenate to typing Patch by Ken Jin bpo 42385 StrEnum fix _generate_next_value_ to return a str bpo 31904 Define THREAD_STACK_SIZE for VxWorks bpo 34750 Enum _EnumDict update is now supported bpo 42517 Enum private names do not become members do not generate errors they remain normal attributes bpo 42678 Enum call __init_subclass__ after members have been added bpo 28964 ast literal_eval adds line number information if available in error message for malformed nodes bpo 42470 random sample no longer warns on a sequence which is also a set bpo 31904 posixpath expanduser returns the input path unchanged if user home directory is None on VxWorks bpo 42388 Fix subprocess check_output input None behavior when text True to be consistent with that of the documentation and universal_newlines True bpo 34463 Fixed discrepancy between traceback and the interpreter in formatting of SyntaxError with lineno not set traceback was changed to match interpreter bpo 42393 Raise OverflowError instead of silent truncation in socket ntohs and socket htons Silen,en
1620,t truncation was deprecated in Python 3 7 Patch by Erlend E Aasland bpo 42222 Harmonized random randrange argument handling to match range The integer test and conversion in randrange now uses operator index Non integer arguments to randrange are deprecated The ValueError is deprecated in favor of a TypeError It now runs a little faster than before Contributed by Raymond Hettinger and Serhiy Storchaka bpo 42163 Restore compatibility for uname_result around deepcopy and _replace bpo 42090 zipfile Path joinpath now accepts arbitrary arguments same as pathlib Path joinpath bpo 1635741 Port the _csv module to the multi phase initialization API PEP 489 bpo 42059 typing TypedDict types created using the alternative call style syntax now correctly respect the total keyword argument when setting their __required_keys__ and __optional_keys__ class attributes bpo 41960 Add globalns and localns parameters to the inspect signature and inspect Signature from_callable bpo 41907 fix format behavior for IntFlag bpo 41891 Ensure asyncio wait_for waits for task completion bpo 24792 Fixed bug where zipimporter sometimes reports an incorrect cause of import errors bpo 31904 Fix site and sysconfig modules for VxWorks RTOS which has no home directories bpo 41462 Add os set_blocking support for VxWorks RTOS bpo 40219 Lowered tkinter ttk LabeledScale dummy widget to prevent hiding part of the content label bpo 37193 Fixed memory leak in socketserver ThreadingMixIn introduced in Python 3 7 bpo 39068 Fix initialization race condition in a85encode and b85encode in base64 Patch by Brandon Stansbury Documentation bpo 17140 Add documentation for the multiprocessing pool ThreadPool class bpo 34398 Prominently feature listings from the glossary in documentation search results Patch by Ammar Askar Tests bpo 42794 Update test_nntplib to use official group name of news aioe org for testing Patch by Donghee Na bpo 31904 Skip some asyncio tests on VxWorks bpo 42641 Enhance test_select test_select it now takes 500 milliseconds rather than 10 seconds Use Python rather than a shell to make the test more portable bpo 31904 Skip some tests in _test_all_chown_common on VxWorks bpo 42199 Fix bytecode helper assertNotInBytecode bpo 41443 Add more attribute checking in test_posix py bpo 31904 Disable os popen and impacted tests on VxWorks bpo 41439 Port test_ssl and test_uuid to VxWorks RTOS Build bpo 42692 Fix __builtin_available check on older compilers Patch by Joshua Root bpo 27640 Added disable test modules option to the configure script don t build nor install test modules Patch by Xavier de Gaye Thomas Petazzoni and Peixing Xin bpo 42604 Now all platforms use a value for the EXT_SUFFIX build variable derived from SOABI for instance in freeBSD EXT_SUFFIX is now cpython 310d so instead of so Previously only Linux Mac and VxWorks were using a value for EXT_SUFFIX that included SOABI bpo 42598 Fix implicit function declarations in configure which could have resulted in incorrect configuration checks Patch contributed by Joshua Root bpo 31904 Enable libpython3 so for VxWorks bpo 29076 Add fish shell support to macOS installer macOS bpo 42361 Update macOS installer build to use Tcl Tk 8 6 11 rc2 expected to be final release bpo 41837 Update macOS installer build to use OpenSSL 1 1 1i bpo 42584 Update macOS installer to use SQLite 3 34 0 Tools Demos bpo 42726 Fixed Python 3 compatibility issue with gdb libpython py handling of attribute dictionaries bpo 42613 Fix freeze py tool to use the prope config and library directories Patch by Victor Stinner C API bpo 42591 Export the Py_FrozenMain function fix a Python 3 9 0 regression Python 3 9 uses fvisibility hidden and the function was not exported explicitly and so not exported bpo 32381 Remove the private _Py_fopen function which is no longer needed Use _Py_wfopen or _Py_fopen_obj instead Patch by Victor Stinner bpo 1635741 Port resource extension module to module state bpo 42111 Update the xxlimited module to be a better example of how to use the limited C API bpo 40052 Fix an alignment build warning error in functio,en
1621,n PyVectorcall_Function Patch by Andreas Schneider Antoine Pitrou and Petr Viktorin Python 3 10 0 alpha 3 Release date 2020 12 07 Security bpo 40791 Add volatile to the accumulator variable in hmac compare_digest making constant time defeating optimizations less likely Core and Builtins bpo 42576 types GenericAlias will now raise a TypeError when attempting to initialize with a keyword argument Previously this would cause the interpreter to crash if the interpreter was compiled with debug symbols This does not affect interpreters compiled for release Patch by Ken Jin bpo 42536 Several built in and standard library types now ensure that their internal result tuples are always tracked by the garbage collector collections OrderedDict items dict items enumerate functools reduce itertools combinations itertools combinations_with_replacement itertools permutations itertools product itertools zip_longest zip Previously they could have become untracked by a prior garbage collection Patch by Brandt Bucher bpo 42500 Improve handling of exceptions near recursion limit Converts a number of Fatal Errors in RecursionErrors bpo 42246 PEP 626 After a return the f_lineno attribute of a frame is always the last line executed bpo 42435 Speed up comparison of bytes objects with non bytes objects when option b is specified Speed up comparison of bytarray objects with non buffer object bpo 1635741 Port the _warnings extension module to the multi phase initialization API PEP 489 Patch by Victor Stinner bpo 41686 On Windows the SIGINT event _PyOS_SigintEvent is now created even if Python is configured to not install signal handlers if PyConfig install_signal_handlers equals to 0 or Py_InitializeEx 0 bpo 42381 Allow assignment expressions in set literals and set comprehensions as per PEP 572 Patch by Pablo Galindo bpo 42202 Change function parameters annotations internal representation to tuple of strings Patch provided by Yurii Karabas bpo 42374 Fix a regression introduced by the new parser where an unparenthesized walrus operator was not allowed within generator expressions bpo 42316 Allow an unparenthesized walrus in subscript indexes bpo 42349 Make sure that the compiler front end produces a well formed control flow graph Be be more aggressive in the compiler back end as it is now safe to do so bpo 42296 On Windows fix a regression in signal handling which prevented to interrupt a program using CTRL C The signal handler can be run in a thread different than the Python thread in which case the test deciding if the thread can handle signals is wrong bpo 42332 types GenericAlias objects can now be the targets of weakrefs bpo 42282 Optimise constant subexpressions that appear as part of named expressions previously the AST optimiser did not descend into named expressions Patch by Nick Coghlan bpo 42266 Fixed a bug with the LOAD_ATTR opcode cache that was not respecting monkey patching a class level attribute to make it a descriptor Patch by Pablo Galindo bpo 40077 Convert queue to use heap types bpo 42246 Improved accuracy of line tracing events and f_lineno attribute of Frame objects See PEP 626 for details bpo 40077 Convert mmap to use heap types bpo 42233 Allow GenericAlias objects to use union type expressions This allows expressions like list int dict float str where previously a TypeError would have been thrown This also fixes union type expressions not de duplicating GenericAlias objects Contributed by Ken Jin in bpo 42233 bpo 26131 The import system triggers a ImportWarning when it falls back to using load_module Library bpo 5054 CGIHTTPRequestHandler run_cgi HTTP_ACCEPT improperly parsed Replace the special purpose getallmatchingheaders with generic get_all method and add relevant tests Original Patch by Martin Panter Modified by Senthil Kumaran bpo 42562 Fix issue when dis failed to parse function that has no line numbers Patch provided by Yurii Karabas bpo 17735 inspect findsource now raises OSError instead of IndexError when co_lineno of a code object is greater than the file length This can happen for example when a file is edited a,en
1622,fter it was imported PR by Irit Katriel bpo 42116 Fix handling of trailing comments by inspect getsource bpo 42532 Remove unexpected call of __bool__ when passing a spec_arg argument to a Mock bpo 38200 Added itertools pairwise bpo 41818 Fix test_master_read so that it succeeds on all platforms that either raise OSError or return b upon reading from master bpo 42487 ChainMap __iter__ no longer calls __getitem__ on underlying maps bpo 42482 TracebackException no longer holds a reference to the exception s traceback object Consequently instances of TracebackException for equivalent but non equal exceptions now compare as equal bpo 41818 Make test_openpty avoid unexpected success due to number of rows and or number of columns being 0 bpo 42392 Remove loop parameter from asyncio subprocess and asyncio tasks functions Patch provided by Yurii Karabas bpo 42392 Remove loop parameter from asyncio open_connection and asyncio start_server functions Patch provided by Yurii Karabas bpo 28468 Add platform freedesktop_os_release function to parse freedesktop org os release files bpo 42299 Removed the formatter module which was deprecated in Python 3 4 It is somewhat obsolete little used and not tested It was originally scheduled to be removed in Python 3 6 but such removals were delayed until after Python 2 7 EOL Existing users should copy whatever classes they use into their code Patch by Donghee Na and and Terry J Reedy bpo 26131 Deprecate zipimport zipimporter load_module in favour of exec_module bpo 41818 Updated tests for the pty library test_basic has been changed to test_openpty this additionally checks if slave termios and slave winsize are being set properly by pty openpty In order to add support for FreeBSD NetBSD OpenBSD and Darwin this also adds test_master_read which demonstrates that pty spawn should not depend on an OSError to exit from its copy loop bpo 42392 Remove loop parameter from __init__ in all asyncio locks and asyncio Queue classes Patch provided by Yurii Karabas bpo 15450 Make filecmp dircmp respect subclassing Now the filecmp dircmp subdirs behaves as expected when subclassing dircmp bpo 42413 The exception socket timeout is now an alias of TimeoutError bpo 31904 Support signal module on VxWorks bpo 42406 We fixed an issue in pickle whichmodule in which importing multiprocessing could change the how pickle identifies which module an object belongs to potentially breaking the unpickling of those objects bpo 42403 Simplify the importlib external bootstrap code importlib _bootstrap_external now uses regular imports to import builtin modules When it is imported the builtin __import__ function is already fully working and so can be used to import builtin modules like sys Patch by Victor Stinner bpo 1635741 Convert _sre module types to heap types PEP 384 Patch by Erlend E Aasland bpo 42375 subprocess module update for DragonFlyBSD support bpo 41713 Port the _signal extension module to the multi phase initialization API PEP 489 Patch by Victor Stinner and Mohamed Koubaa bpo 37205 time time time perf_counter and time monotonic functions can no longer fail with a Python fatal error instead raise a regular Python exception on failure bpo 42328 Fixed tkinter ttk Style map The function accepts now the representation of the default state as empty sequence as returned by Style map The structure of the result is now the same on all platform and does not depend on the value of wantobjects bpo 42345 Fix various issues with typing Literal parameter handling flatten deduplicate use type to cache key Patch provided by Yurii Karabas bpo 37205 time perf_counter on Windows and time monotonic on macOS are now system wide Previously they used an offset computed at startup to reduce the precision loss caused by the float type Use time perf_counter_ns and time monotonic_ns added in Python 3 7 to avoid this precision loss bpo 42318 Fixed support of non BMP characters in tkinter on macOS bpo 42350 Fix the threading Thread class at fork do nothing if the thread is already stopped ex fork called at Python exit Previously an error was logg,en
1623,ed in the child process bpo 42333 Port _ssl extension module to heap types bpo 42014 The onerror callback from shutil rmtree now receives correct function when os open fails bpo 42237 Fix os sendfile on illumos bpo 42308 Add threading __excepthook__ to allow retrieving the original value of threading excepthook in case it is set to a broken or a different value Patch by Mario Corchero bpo 42131 Implement PEP 451 spec methods on zipimport zipimporter find_spec create_module and exec_module This also allows for the documented deprecation of find_loader find_module and load_module bpo 41877 Mock objects which are not unsafe will now raise an AttributeError if an attribute with the prefix asert aseert or assrt is accessed in addition to this already happening for the prefixes assert or assret bpo 42264 sqlite3 OptimizedUnicode has been undocumented and obsolete since Python 3 3 when it was made an alias to str It is now deprecated scheduled for removal in Python 3 12 bpo 42251 Added threading gettrace and threading getprofile to retrieve the functions set by threading settrace and threading setprofile respectively Patch by Mario Corchero bpo 42249 Fixed writing binary Plist files larger than 4 GiB bpo 42236 On Unix the os device_encoding function now returns UTF 8 rather than the device encoding if the Python UTF 8 Mode is enabled bpo 41754 webbrowser Ignore NotADirectoryError when calling xdg settings bpo 42183 Fix a stack overflow error for asyncio Task or Future repr The overflow occurs under some circumstances when a Task or Future recursively returns itself bpo 42140 Improve asyncio wait function to create the futures set just one time bpo 42133 Update various modules in the stdlib to fall back on __spec__ loader when __loader__ isn t defined on a module bpo 26131 The load_module methods found in importlib now trigger a DeprecationWarning bpo 39825 Windows Change sysconfig get_config_var EXT_SUFFIX to the expected full platform_tag extension format Previously it was hard coded to pyd now it is compatible with distutils sysconfig and will result in something like cp38 win_amd64 pyd This brings windows into conformance with the other platforms bpo 26389 The traceback format_exception traceback format_exception_only and traceback print_exception functions can now take an exception object as a positional only argument bpo 41889 Enum fix regression involving inheriting a multiply inherited enum bpo 41861 Convert sqlite3 to use heap types PEP 384 Patch by Erlend E Aasland bpo 40624 Added support for the XPath operator in xml etree bpo 28850 Fix pprint PrettyPrinter format overrides being ignored for contents of small containers The pprint _safe_repr function was removed bpo 41625 Expose the splice as os splice in the os module Patch by Pablo Galindo bpo 34215 Clarify the error message for asyncio IncompleteReadError when expected is None bpo 41543 Add async context manager support for contextlib nullcontext bpo 21041 pathlib PurePath parents now supports negative indexing Patch contributed by Yaroslav Pankovych bpo 41332 Added missing connect_accepted_socket method to asyncio AbstractEventLoop bpo 12800 Extracting a symlink from a tarball should succeed and overwrite the symlink if it already exists The fix is to remove the existing file or symlink before extraction Based on patch by Chris AtLee Jeffrey Kintscher and Senthil Kumaran bpo 40968 urllib request and http client now send http 1 1 ALPN extension during TLS handshake when no custom context is supplied bpo 41001 Add os eventfd to provide a low level interface for Linux s event notification file descriptor bpo 40816 Add AsyncContextDecorator to contextlib to support async context manager as a decorator bpo 40550 Fix time of check time of action issue in subprocess Popen send_signal bpo 39411 Add an is_async identifier to pyclbr s Function objects Patch by Batuhan Taskaya bpo 35498 Add slice support to pathlib PurePath parents Documentation bpo 42238 Tentative to deprecate make suspicious by first removing it from the CI and documentation builds but keeping it around fo,en
1624,r manual uses bpo 42153 Fix the URL for the IMAP protocol documents bpo 41028 Language and version switchers previously maintained in every cpython branches are now handled by docsbuild script Tests bpo 41473 Re enable test_gdb on gdb 9 2 and newer https bugzilla redhat com show_bug cgi id 1866884 bug is fixed in gdb 10 1 bpo 42553 Fix test_asyncio test_call_later race condition don t measure asyncio performance in the call_later unit test The test failed randomly on the CI bpo 31904 Fix test_netrc on VxWorks create temporary directories using temp_cwd bpo 31904 skip test_getaddrinfo_ipv6_scopeid_symbolic and test_getnameinfo_ipv6_scopeid_symbolic on VxWorks bpo 31904 skip test_test of test_mailcap on VxWorks bpo 31904 add shell requirement for test_pipes bpo 31904 skip some tests related to fifo on VxWorks bpo 31904 Fix test_doctest py failures for VxWorks bpo 40754 Include _testinternalcapi module in Windows installer for test suite bpo 41561 test_ssl skip test_min_max_version_mismatch when TLS 1 0 is not available bpo 31904 Fix os module failures for VxWorks RTOS bpo 31904 Fix fifo test cases for VxWorks RTOS Build bpo 31904 remove libnet dependency from detect_socket for VxWorks bpo 42398 Fix a race condition in make regen all when make jN option is used to run jobs in parallel The clinic py script now only use atomic write to write files Moveover generated files are now left unchanged if the content does not change to not change the file modification time bpo 41617 Fix building pycore_bitutils h internal header on old clang version without __builtin_bswap16 ex Xcode 4 6 3 on Mac OS X 10 7 Patch by Joshua Root and Victor Stinner bpo 38823 It is no longer possible to build the _ctypes extension module without wchar_t type remove CTYPES_UNICODE macro Anyway the wchar_t type is required to build Python Patch by Victor Stinner bpo 42087 Support was removed for AIX 5 3 and below See bpo 40680 bpo 40998 Addressed three compiler warnings found by undefined behavior sanitizer ubsan Windows bpo 42120 Remove macro definition of copysign to _copysign in headers bpo 38506 The Windows launcher now properly handles Python 3 10 when listing installed Python versions macOS bpo 42504 Fix build on macOS Big Sur when MACOSX_DEPLOYMENT_TARGET 11 bpo 41116 Ensure distutils unixxcompiler find_library_file can find system provided libraries on macOS 11 bpo 41100 Add support for macOS 11 and Apple Silicon systems It is now possible to build Universal 2 binaries using enable universalsdk with universal archs universal2 Binaries build on later macOS versions can be deployed back to older versions tested up to macOS 10 9 when using the correct deployment target This is tested using Xcode 11 and later bpo 42232 Added Darwin specific madvise options to mmap module bpo 38443 The enable universalsdk and with universal archs options for the configure script now check that the specified architectures can be used IDLE bpo 42508 Keep IDLE running on macOS Remove obsolete workaround that prevented running files with shortcuts when using new universal2 installers built on macOS 11 bpo 42426 Fix reporting offset of the RE error in searchengine bpo 42415 Get docstrings for IDLE calltips more often by using inspect getdoc Tools Demos bpo 42212 The smelly py script now also checks the Python dynamic library and extension modules not only the Python static library Make also the script more verbose explain what it does bpo 36310 Allow Tools i18n pygettext py to detect calls to gettext in f strings C API bpo 42423 The PyType_FromSpecWithBases and PyType_FromModuleAndSpec functions now accept a single class as the bases argument bpo 1635741 Port select extension module to multiphase initialization PEP 489 bpo 1635741 Port _posixsubprocess extension module to multiphase initialization PEP 489 bpo 1635741 Port _posixshmem extension module to multiphase initialization PEP 489 bpo 1635741 Port _struct extension module to multiphase initialization PEP 489 bpo 1635741 Port spwd extension module to multiphase initialization PEP 489 bpo 1635741 Port gc extension module,en
1625, to multiphase initialization PEP 489 bpo 1635741 Port _queue extension module to multiphase initialization PEP 489 bpo 39573 Convert Py_TYPE and Py_SIZE back to macros to allow using them as an l value Many third party C extension modules rely on the ability of using Py_TYPE and Py_SIZE to set an object type and size Py_TYPE obj type and Py_SIZE obj size bpo 1635741 Port symtable extension module to multiphase initialization PEP 489 bpo 1635741 Port grp and pwd extension modules to multiphase initialization PEP 489 bpo 1635741 Port _random extension module to multiphase initialization PEP 489 bpo 1635741 Port _hashlib extension module to multiphase initialization PEP 489 bpo 41713 Removed the undocumented PyOS_InitInterrupts function Initializing Python already implicitly installs signal handlers see PyConfig install_signal_handlers Patch by Victor Stinner bpo 40170 The Py_TRASHCAN_BEGIN macro no longer accesses PyTypeObject attributes but now can get the condition by calling the new private _PyTrash_cond function which hides implementation details bpo 42260 Py_GetPath Py_GetPrefix Py_GetExecPrefix Py_GetProgramFullPath Py_GetPythonHome and Py_GetProgramName functions now return NULL if called before Py_Initialize before Python is initialized Use the new Python Initialization Configuration API to get the Python Path Configuration Patch by Victor Stinner bpo 42260 The PyConfig_Read function now only parses PyConfig argv arguments once PyConfig parse_argv is set to 2 after arguments are parsed Since Python arguments are strippped from PyConfig argv parsing arguments twice would parse the application options as Python options bpo 42262 Added Py_NewRef and Py_XNewRef functions to increment the reference count of an object and return the object Patch by Victor Stinner bpo 42260 When Py_Initialize is called twice the second call now updates more sys attributes for the configuration rather than only sys argv Patch by Victor Stinner bpo 41832 The PyType_FromModuleAndSpec function now accepts NULL tp_doc slot bpo 1635741 Added PyModule_AddObjectRef function similar to PyModule_AddObject but don t steal a reference to the value on success Patch by Victor Stinner bpo 42171 The METH_FASTCALL calling convention is added to the limited API The functions PyModule_AddType PyType_FromModuleAndSpec PyType_GetModule and PyType_GetModuleState are added to the limited API on Windows bpo 42085 Add dedicated entry to PyAsyncMethods for sending values bpo 41073 PyType_GetSlot can now accept static types bpo 30459 PyList_SET_ITEM PyTuple_SET_ITEM and PyCell_SET macros can no longer be used as l value or r value For example x PyList_SET_ITEM a b c and PyList_SET_ITEM a b c x now fail with a compiler error It prevents bugs like if PyList_SET_ITEM a b c 0 test Patch by Zackery Spytz and Victor Stinner Python 3 10 0 alpha 2 Release date 2020 11 03 Security bpo 42103 Prevented potential DoS attack via CPU and RAM exhaustion when processing malformed Apple Property List files in binary format bpo 42051 The plistlib module no longer accepts entity declarations in XML plist files to avoid XML vulnerabilities This should not affect users as entity declarations are not used in regular plist files Core and Builtins bpo 42236 If the nl_langinfo CODESET function returns an empty string Python now uses UTF 8 as the filesystem encoding Patch by Victor Stinner bpo 42218 Fixed a bug in the PEG parser that was causing crashes in debug mode Now errors are checked in left recursive rules to avoid cases where such errors do not get handled in time and appear as long distance crashes in other places bpo 42214 Fixed a possible crash in the PEG parser when checking for the token in the barry_as_flufl rule Patch by Pablo Galindo bpo 42206 Propagate and raise the errors caused by PyAST_Validate in the parser bpo 41796 The ast module internal state is now per interpreter Patch by Victor Stinner bpo 42143 Fix handling of errors during creation of PyFunctionObject which resulted in operations on uninitialized memory Patch by Yonatan Goldschmidt bpo 41659 Fix a bug in the p,en
1626,arser where a curly brace following a primary didn t fail immediately This led to invalid expressions like a b to throw a SyntaxError with a wrong offset or invalid expressions ending with a curly brace like a to not fail immediately in the REPL bpo 42150 Fix possible buffer overflow in the new parser when checking for continuation lines Patch by Pablo Galindo bpo 42123 Run the parser two times On the first run disable all the rules that only generate better error messages to gain performance If there s a parse failure run the parser a second time with those enabled bpo 42093 The LOAD_ATTR instruction now uses new per opcode cache mechanism and it is about 36 faster now Patch by Pablo Galindo and Yury Selivanov bpo 42030 Support for the legacy AIX specific shared library loading support has been removed All versions of AIX since 4 3 have supported and defaulted to using the common Unix mechanism instead bpo 41984 The garbage collector now tracks all user defined classes Patch by Brandt Bucher bpo 41993 Fixed potential issues with removing not completely initialized module from sys modules when import fails bpo 41979 Star unpacking is now allowed for with item s targets in the PEG parser bpo 41974 Removed special methods __int__ __float__ __floordiv__ __mod__ __divmod__ __rfloordiv__ __rmod__ and __rdivmod__ of the complex class They always raised a TypeError bpo 41902 Micro optimization when compute sq_item and mp_subscript of range Patch by Donghee Na bpo 41894 When loading a native module and a load failure occurs prevent a possible UnicodeDecodeError when not running in a UTF 8 locale by decoding the load error message using the current locale s encoding bpo 41902 Micro optimization for range index if step is 1 Patch by Donghee Na bpo 41435 Add sys _current_exceptions function to retrieve a dictionary mapping each thread s identifier to the topmost exception currently active in that thread at the time the function is called bpo 38605 Enable from __future__ import annotations PEP 563 by default The values found in __annotations__ dicts are now strings e g x int instead of x int Library bpo 35455 On Solaris thread_time is now implemented with gethrvtime because clock_gettime CLOCK_THREAD_CPUTIME_ID is not always available Patch by Jakub Kulik bpo 42233 The repr of typing types containing Generic Alias Types previously did not show the parameterized types in the GenericAlias They have now been changed to do so bpo 29566 binhex binhex consistently writes macOS 9 line endings bpo 26789 The logging FileHandler class now keeps a reference to the builtin open function to be able to open or reopen the file during Python finalization Fix errors like NameError name open is not defined Patch by Victor Stinner bpo 42157 Removed the unicodedata ucnhash_CAPI attribute which was an internal PyCapsule object The related private _PyUnicode_Name_CAPI structure was moved to the internal C API Patch by Victor Stinner bpo 42157 Convert the unicodedata extension module to the multiphase initialization API PEP 489 and convert the unicodedata UCD static type to a heap type Patch by Mohamed Koubaa and Victor Stinner bpo 42146 Fix memory leak in subprocess Popen in case an uid gid specified in user group extra_groups overflows uid_t gid_t bpo 42103 InvalidFileException and RecursionError are now the only errors caused by loading malformed binary Plist file previously ValueError and TypeError could be raised in some specific cases bpo 41490 In importlib resources path method is more aggressive about releasing handles to zipfile objects early enabling use cases like certifi to leave the context open but delete the underlying zip file bpo 41052 Pickling heap types implemented in C with protocols 0 and 1 raises now an error instead of producing incorrect data bpo 42089 In importlib metadata PackageNotFoundError make reference to the package metadata being missing to improve the user experience bpo 41491 plistlib fix parsing XML plists with hexadecimal integer values bpo 42065 Fix an incorrectly formatted error from _codecs charmap_decode when calle,en
1627,d with a mapped value outside the range of valid Unicode code points PR by Max Bernstein bpo 41966 Fix pickling pure Python datetime time subclasses Patch by Dean Inwood bpo 19270 sched scheduler cancel will now cancel the correct event if two events with same priority are scheduled for the same time Patch by Bar Harel bpo 28660 textwrap wrap now attempts to break long words after hyphens when break_long_words True and break_on_hyphens True bpo 35823 Use vfork instead of fork for subprocess Popen on Linux to improve performance in cases where it is deemed safe bpo 42043 Add support for zipfile Path inheritance zipfile Path is_file now returns False for non existent names zipfile Path objects now expose a filename attribute and rely on that to resolve name and parent when the Path object is at the root of the zipfile bpo 42021 Fix possible ref leaks in sqlite3 module init bpo 39101 Fixed tests using IsolatedAsyncioTestCase from hanging on BaseExceptions bpo 41976 Fixed a bug that was causing ctypes util find_library to return None when triying to locate a library in an environment when gcc 9 is available and ldconfig is not Patch by Pablo Galindo bpo 41943 Fix bug where TestCase assertLogs doesn t correctly filter messages by level bpo 41923 Implement PEP 613 introducing typing TypeAlias annotation bpo 41905 A new function in abc update_abstractmethods to re calculate an abstract class s abstract status In addition dataclass has been changed to call this function bpo 23706 Added newline parameter to pathlib Path write_text bpo 41876 Tkinter font class repr uses font name bpo 41831 str for the type attribute of the tkinter Event object always returns now the numeric code returned by Tk instead of the name of the event type bpo 39337 encodings normalize_encoding now ignores non ASCII characters bpo 41747 Ensure all methods that generated from dataclasses dataclass objects now have the proper __qualname__ attribute referring to the class they belong to Patch by Batuhan Taskaya bpo 30681 Handle exceptions caused by unparsable date headers when using email default policy Patch by Tim Bell Georges Toth bpo 41586 Add F_SETPIPE_SZ and F_GETPIPE_SZ to fcntl module Allow setting pipesize on subprocess Popen bpo 41229 Add contextlib aclosing for deterministic cleanup of async generators which is analogous to contextlib closing for non async generators Patch by Joongi Kim and John Belmonte bpo 16396 Allow ctypes wintypes to be imported on non Windows systems bpo 4356 Add a key function to the bisect module bpo 40592 shutil which now ignores empty entries in PATHEXT instead of treating them as a match bpo 40492 Fix outfile for cProfile profile not writing the output file in the original directory when the program being profiled changes the working directory PR by Anthony Sottile bpo 34204 The shelve module now uses pickle DEFAULT_PROTOCOL by default instead of pickle protocol 3 bpo 27321 Fixed KeyError exception when flattening an email to a string attempts to replace a non existent Content Transfer Encoding header bpo 38976 The http cookiejar module now supports the parsing of cookies in CURL style cookiejar files through MozillaCookieJar on all platforms Previously such cookie entries would be silently ignored when loading a cookiejar with such entries Additionally the HTTP Only attribute is persisted in the object and will be correctly written to file if the MozillaCookieJar object is subsequently dumped Documentation bpo 42061 Document __format__ functionality for IP addresses bpo 41910 Document the default implementation of object __eq__ bpo 42010 Clarify that subscription expressions are also valid for certain classes and types in the standard library and for user defined classes and types if the classmethod __class_getitem__ is provided bpo 41805 Documented generic alias type and types GenericAlias Also added an entry in glossary for generic types bpo 39693 Fix tarfile s extractfile documentation bpo 39416 Document some restrictions on the default string representations of numeric classes Tests bpo 41739 Fix test_logging test_r,en
1628,ace_between_set_target_and_flush the test now waits until all threads complete to avoid leaking running threads bpo 41970 Avoid a test failure in test_lib2to3 if the module has already imported at the time the test executes Patch by Pablo Galindo bpo 41944 Tests for CJK codecs no longer call eval on content received via HTTP bpo 41306 Fixed a failure in test_tk test_widgets ScaleTest happening when executing the test with Tk 8 6 10 Build bpo 38980 Add fno semantic interposition to both the compile and link line when building with enable optimizations Patch by Victor Stinner and Pablo Galindo Windows bpo 38439 Updates the icons for IDLE in the Windows Store package bpo 38252 Use 8 byte step to detect ASCII sequence in 64 bit Windows build bpo 39107 Update Tcl and Tk to 8 6 10 in Windows installer bpo 41557 Update Windows installer to use SQLite 3 33 0 bpo 38324 Avoid Unicode errors when accessing certain locale data on Windows macOS bpo 41471 Ignore invalid prefix lengths in system proxy excludes IDLE bpo 33987 Mostly finish using ttk widgets mainly for editor settings and searches Some patches by Mark Roseman bpo 40511 Typing opening and closing parentheses inside the parentheses of a function call will no longer cause unnecessary flashing off and on of an existing open call tip e g when typed in a string literal bpo 38439 Add a 256 256 pixel IDLE icon to the Windows ico file Created by Andrew Clover Remove the low color gif variations from the ico file C API bpo 42157 The private _PyUnicode_Name_CAPI structure of the PyCapsule API unicodedata ucnhash_CAPI has been moved to the internal C API Patch by Victor Stinner bpo 42015 Fix potential crash in deallocating method objects when dynamically allocated PyMethodDef s lifetime is managed through the self argument of a PyCFunction bpo 40423 The subprocess module and os closerange will now use the close_range low high flags syscall when it is available for more efficient closing of ranges of descriptors bpo 41845 PyObject_GenericGetDict is available again in the limited API when targeting 3 10 or later bpo 40422 Add _Py_closerange function to provide performant closing of a range of file descriptors bpo 41986 Py_FileSystemDefaultEncodeErrors and Py_UTF8Mode are available again in limited API bpo 41756 Add PyIter_Send function to allow sending value into generator coroutine iterator without raising StopIteration exception to signal return bpo 41784 Added PyUnicode_AsUTF8AndSize to the limited C API Python 3 10 0 alpha 1 Release date 2020 10 05 Security bpo 41304 Fixes python3x _pth being ignored on Windows caused by the fix for bpo 29778 CVE 2020 15801 bpo 41162 Audit hooks are now cleared later during finalization to avoid missing events bpo 29778 Ensure python3 dll is loaded from correct locations when Python is embedded CVE 2020 15523 bpo 41004 The __hash__ methods of ipaddress IPv4Interface and ipaddress IPv6Interface incorrectly generated constant hash values of 32 and 128 respectively This resulted in always causing hash collisions The fix uses hash to generate hash values for the tuple of address mask length network address bpo 39603 Prevent http header injection by rejecting control characters in http client putrequest Core and Builtins bpo 41909 Fixed stack overflow in issubclass and isinstance when getting the __bases__ attribute leads to infinite recursion bpo 41922 Speed up calls to reversed by using the PEP 590 vectorcall calling convention Patch by Donghee Na bpo 41873 Calls to float are now faster due to the vectorcall calling convention Patch by Dennis Sweeney bpo 41870 Speed up calls to bool by using the PEP 590 vectorcall calling convention Patch by Donghee Na bpo 1635741 Port the _bisect module to the multi phase initialization API PEP 489 bpo 39934 Correctly count control blocks in except in compiler Ensures that a syntax error rather a fatal error occurs for deeply nested named exception handlers bpo 41780 Fix __dir__ of types GenericAlias Patch by Batuhan Taskaya bpo 1635741 Port the _lsprof extension module to multi phase initialization PEP 489 bpo 1635,en
1629,741 Port the cmath extension module to multi phase initialization PEP 489 bpo 1635741 Port the _scproxy extension module to multi phase initialization PEP 489 bpo 1635741 Port the termios extension module to multi phase initialization PEP 489 bpo 1635741 Convert the _sha256 extension module types to heap types bpo 41690 Fix a possible stack overflow in the parser when parsing functions and classes with a huge amount of arguments Patch by Pablo Galindo bpo 1635741 Port the _overlapped extension module to multi phase initialization PEP 489 bpo 1635741 Port the _curses_panel extension module to multi phase initialization PEP 489 bpo 1635741 Port the _opcode extension module to multi phase initialization PEP 489 bpo 41681 Fixes the wrong error description in the error raised by using 2 in format string in f string and str format bpo 41675 The implementation of signal siginterrupt now uses sigaction if it is available in the system instead of the deprecated siginterrupt Patch by Pablo Galindo bpo 41670 Prevent line trace being skipped on platforms not compiled with USE_COMPUTED_GOTOS Fixes issue where some lines nested within a try except block were not being traced on Windows bpo 41654 Fix a crash that occurred when destroying subclasses of MemoryError Patch by Pablo Galindo bpo 1635741 Port the zlib extension module to multi phase initialization PEP 489 bpo 41631 The _ast module uses again a global state Using a module state per module instance is causing subtle practical problems For example the Mercurial project replaces the __import__ function to implement lazy import whereas Python expected that import _ast always return a fully initialized _ast module bpo 40077 Convert _operator to use PyType_FromSpec bpo 1653741 Port _sha3 to multi phase init Convert static types to heap types bpo 1635741 Port the _blake2 extension module to the multi phase initialization API PEP 489 bpo 41533 Free the stack allocated in va_build_stack if do_mkstack fails and the stack is not a small_stack bpo 41531 Fix a bug that was dropping keys when compiling dict literals with more than 0xFFFF elements Patch by Pablo Galindo bpo 41525 The output of python help contains now only ASCII characters bpo 1635741 Port the _sha1 _sha512 and _md5 extension modules to multi phase initialization API PEP 489 bpo 41431 Optimize dict_merge for copying dict e g dict d and update d bpo 41428 Implement PEP 604 This supports int str etc in place of Union str int bpo 41340 Removed fallback implementation for strdup bpo 38156 Handle interrupts that come after EOF correctly in PyOS_StdioReadline bpo 41342 round with integer argument is now faster 9 60 bpo 41334 Constructors str bytes and bytearray are now faster around 30 40 for small objects bpo 41295 Resolve a regression in CPython 3 8 4 where defining __setattr__ in a multi inheritance setup and calling up the hierarchy chain could fail if builtins extension types were involved in the base types bpo 41323 Bytecode optimizations are performed directly on the control flow graph This will result in slightly more compact code objects in some circumstances bpo 41247 Always cache the running loop holder when running asyncio set_running_loop bpo 41252 Fix incorrect refcounting in _ssl c s _servername_callback bpo 1635741 Port multiprocessing to multi phase initialization bpo 1635741 Port winapi to multiphase initialization bpo 41215 Use non NULL default values in the PEG parser keyword list to overcome a bug that was preventing Python from being properly compiled when using the XLC compiler Patch by Pablo Galindo bpo 41218 Python 3 8 3 had a regression where compiling with ast PyCF_ALLOW_TOP_LEVEL_AWAIT would aggressively mark list comprehension with CO_COROUTINE Now only list comprehension making use of async await will tagged as so bpo 1635741 Port faulthandler to multiphase initialization bpo 1635741 Port sha256 to multiphase initialization bpo 41175 Guard against a NULL pointer dereference within bytearrayobject triggered by the bytearray bytearray operation bpo 41100 add arm64 to the allowable Mac OS arches in mpdec,en
1630,imal h bpo 41094 Fix decoding errors with audit when open files with non ASCII names on non UTF 8 locale bpo 39960 The hackcheck that prevents sneaking around a type s __setattr__ by calling the superclass method was rewritten to allow C implemented heap types bpo 41084 Prefix the error message with f string when parsing an f string expression which throws a SyntaxError bpo 40521 Empty frozensets are no longer singletons bpo 41076 Pre feed the parser with the location of the f string expression not the f string itself which allows us to skip the shifting of the AST node locations after the parsing is completed bpo 41056 Fixes a reference to deallocated stack space during startup when constructing sys path involving a relative symlink when code was supplied via c discovered via Coverity bpo 41061 Fix incorrect expressions and asserts in hashtable code and tests bpo 41052 Opt out serialization deserialization for _random Random bpo 40939 Rename PyPegen functions to PyParser so that we can remove the old set of PyParser functions that were using the old parser but keep everything backwards compatible bpo 35975 Stefan Behnel reported that cf_feature_version is used even when PyCF_ONLY_AST is not set This is against the intention and against the documented behavior so it s been fixed bpo 40939 Remove the remaining files from the old parser and the symbol module bpo 40077 Convert _bz2 to use PyType_FromSpec bpo 41006 The encodings latin_1 module is no longer imported at startup Now it is only imported when it is the filesystem encoding or the stdio encoding bpo 40636 zip now supports PEP 618 s strict parameter which raises a ValueError if the arguments are exhausted at different lengths Patch by Brandt Bucher bpo 1635741 Port _gdbm to multiphase initialization bpo 40985 Fix a bug that caused the SyntaxError text to be empty when a file ends with a line ending in a line continuation character i e backslash The error text should contain the text of the last line bpo 40958 Fix a possible buffer overflow in the PEG parser when gathering information for emitting syntax errors Patch by Pablo Galindo bpo 1635741 Port _dbm to multiphase initialization bpo 40957 Fix refleak in _Py_fopen_obj when PySys_Audit fails bpo 40950 Add a state to the nis module PEP 3121 and apply the multiphase initialization Patch by Donghee Na bpo 40947 The Python Path Configuration now takes PyConfig platlibdir in account bpo 40939 Remove the old parser the parser module and all associated support code command line options and environment variables Patch by Pablo Galindo bpo 40847 Fix a bug where a line with only a line continuation character is not considered a blank line at tokenizer level In such cases more than a single NEWLINE token was emitted The old parser was working around the issue but the new parser threw a SyntaxError for valid input due to this For example an empty line following a line continuation character was interpreted as a SyntaxError bpo 40890 Each dictionary view now has a mapping attribute that provides a types MappingProxyType wrapping the original dictionary Patch contributed by Dennis Sweeney bpo 40889 Improved the performance of symmetric difference operations on dictionary item views Patch by Dennis Sweeney bpo 40904 Fix possible segfault in the new PEG parser when parsing f string containing yield statements with no value f yield Patch by Pablo Galindo bpo 40903 Fixed a possible segfault in the new PEG parser when producing error messages for invalid assignments of the form p p Patch by Pablo Galindo bpo 40880 Fix invalid memory read in the new parser when checking newlines in string literals Patch by Pablo Galindo bpo 40883 Fix memory leak in when parsing f strings in the new parser Patch by Pablo Galindo bpo 40870 Raise ValueError when validating custom AST s where the constants True False and None are used within a ast Name node bpo 40854 Allow overriding sys platlibdir via a new PYTHONPLATLIBDIR environment variable bpo 40826 Fix GIL usage in PyOS_Readline lock the GIL to set an exception and pass the Python thread state whe,en
1631,n checking if there is a pending signal bpo 1635741 Port fcntl to multiphase initialization bpo 19468 Delete unnecessary instance check in importlib reload Patch by Furkan Önder bpo 40824 Unexpected errors in calling the __iter__ method are no longer masked by TypeError in the in operator and functions contains indexOf and countOf of the operator module bpo 40792 Attributes start stop and step of the range object now always has exact type int Previously they could have been an instance of a subclass of int bpo 40780 Fix a corner case where g style string formatting of a float failed to remove trailing zeros bpo 38964 When there s a SyntaxError in the expression part of an fstring the filename attribute of the SyntaxError gets correctly set to the name of the file the fstring resides in bpo 40750 Support the d debug flag in the new PEG parser Patch by Pablo Galindo bpo 40217 Instances of types created with PyType_FromSpecWithBases will no longer automatically visit their class object when traversing references in the garbage collector The user is expected to manually visit the object s class Patch by Pablo Galindo bpo 39573 Py_TYPE is changed to the inline static function Patch by Donghee Na bpo 40696 Fix a hang that can arise after generator throw due to a cycle in the exception context chain bpo 40521 Each interpreter now its has own free lists singletons and caches Free lists float tuple list dict frame context asynchronous generator MemoryError Singletons empty tuple empty bytes string empty Unicode string single byte character single Unicode latin1 character Slice cache They are no longer shared by all interpreters bpo 40679 Certain TypeError messages about missing or extra arguments now include the function s qualified name Patch by Dennis Sweeney bpo 29590 Make the stack trace correct after calling generator throw on a generator that has yielded from a yield from bpo 4022 Improve performance of generators by not raising internal StopIteration bpo 1635741 Port mmap to multiphase initialization bpo 1635741 Port _lzma to multiphase initialization bpo 37999 Builtin and extension functions that take integer arguments no longer accept Decimal s Fraction s and other objects that can be converted to integers only with a loss e g that have the __int__ method but do not have the __index__ method bpo 29882 Add int bit_count counting the number of ones in the binary representation of an integer Patch by Niklas Fiekas bpo 36982 Use ncurses extended color functions when available to support terminals with 256 colors and add the new function curses has_extended_color_support to indicate whether extended color support is provided by the underlying ncurses library bpo 19569 Add the private macros _Py_COMP_DIAG_PUSH _Py_COMP_DIAG_IGNORE_DEPR_DECLS and _Py_COMP_DIAG_POP bpo 26680 The int type now supports the x is_integer method for compatibility with float Library bpo 41900 C14N 2 0 serialisation in xml etree ElementTree failed for unprefixed attributes when a default namespace was defined bpo 41887 Strip leading spaces and tabs on ast literal_eval Also document stripping of spaces and tabs for eval bpo 41773 Note in documentation that random choices doesn t support non finite weights raise ValueError when given non finite weights bpo 41840 Fix a bug in the symtable module that was causing module scope global variables to not be reported as both local and global Patch by Pablo Galindo bpo 41842 Add codecs unregister function to unregister a codec search function bpo 40564 In zipfile Path mutate the passed ZipFile object type instead of making a copy Prevents issues when both the local copy and the caller s copy attempt to close the same file handle bpo 40670 More reliable validation of statements in timeit Timer It now accepts empty statements only whitespaces and comments and rejects misindentent statements bpo 41833 The threading Thread constructor now uses the target name if the target argument is specified but the name argument is omitted bpo 41817 fix tkinter EventType Enum so all members are strings and none are tuples bpo 418,en
1632,10 types EllipsisType types NotImplementedType and types NoneType have been reintroduced providing a new set of types readily interpretable by static type checkers bpo 41815 Fix SQLite3 segfault when backing up closed database Patch contributed by Peter David McCormick bpo 41816 StrEnum added it ensures that all members are already strings or string candidates bpo 41517 fix bug allowing Enums to be extended via multiple inheritance bpo 39587 use the correct mix in data type when constructing Enums bpo 41792 Add is_typeddict function to typing py to check if a type is a TypedDict class Previously there was no way to check that without using private API See the relevant issue in python typing bpo 41789 Honor object overrides in Enum class creation specifically __str__ __repr__ __format__ and __reduce_ex__ bpo 32218 enum Flag and enum IntFlag members are now iterable bpo 39651 Fix a race condition in the call_soon_threadsafe method of asyncio ProactorEventLoop do nothing if the self pipe socket has been closed bpo 1635741 Port the mashal extension module to the multi phase initialization API PEP 489 bpo 1635741 Port the _string extension module to the multi phase initialization API PEP 489 bpo 41732 Added an iterator to memoryview bpo 41720 Fixed turtle Vec2D __rmul__ for arguments which are not int or float bpo 41696 Fix handling of debug mode in asyncio run This allows setting PYTHONASYNCIODEBUG or X dev to enable asyncio debug mode when using asyncio run bpo 41687 Fix implementation of sendfile to be compatible with Solaris bpo 41662 No longer override exceptions raised in __len__ of a sequence of parameters in sqlite3 with ProgrammingError bpo 39010 Restarting a ProactorEventLoop on Windows no longer logs spurious ConnectionResetErrors bpo 41638 ProgrammingError message for absent parameter in sqlite3 contains now the name of the parameter instead of its index when parameters are supplied as a dict bpo 41662 Fixed crash when mutate list of parameters during iteration in sqlite3 bpo 41513 Improved the accuracy of math hypot Internally each step is computed with extra precision so that the result is now almost always correctly rounded bpo 41609 The pdb whatis command correctly reports instance methods as Method rather than Function bpo 39994 Fixed pprint s handling of dict subclasses that override __repr__ bpo 32751 When cancelling the task due to a timeout asyncio wait_for will now wait until the cancellation is complete also in the case when timeout is 0 like it does with positive timeouts bpo 37658 asyncio wait_for now properly handles races between cancellation of itself and the completion of the wrapped awaitable bpo 40782 Change the method asyncio AbstractEventLoop run_in_executor to not be a coroutine bpo 41520 Fix codeop regression that prevented turning compile warnings into errors bpo 41528 turtle uses math module functions to convert degrees to radians and vice versa and to calculate vector norm bpo 41513 Minor algorithmic improvement to math hypot and math dist giving small gains in speed and accuracy bpo 41503 Fixed a race between setTarget and flush in logging handlers MemoryHandler bpo 41497 Fix potential UnicodeDecodeError in dis module bpo 41467 On Windows fix asyncio recv_into return value when the socket pipe is closed BrokenPipeError return 0 rather than an empty byte string b bpo 41425 Make tkinter doc example runnable bpo 41421 Make an algebraic simplification to random paretovariate It now is slightly less subject to round off error and is slightly faster Inputs that used to cause ZeroDivisionError now cause an OverflowError instead bpo 41440 Add os cpu_count support for VxWorks RTOS bpo 41316 Fix the tarfile module to write only basename of TAR file to GZIP compression header bpo 41384 Raise TclError instead of TypeError when an unknown option is passed to tkinter OptionMenu bpo 41317 Use add_done_callback in asyncio loop sock_accept to unsubscribe reader early on cancellation bpo 41364 Reduce import overhead of uuid bpo 35328 Set the environment variable VIRTUAL_ENV_PROMPT at venv activation bpo 4,en
1633,1341 Recursive evaluation of typing ForwardRef in get_type_hints bpo 41344 Prevent creating shared_memory SharedMemory objects with size 0 bpo 41333 collections OrderedDict pop is now 2 times faster bpo 41288 Unpickling invalid NEWOBJ_EX opcode with the C implementation raises now UnpicklingError instead of crashing bpo 39017 Avoid infinite loop when reading specially crafted TAR files using the tarfile module CVE 2019 20907 bpo 41273 Speed up any transport using _ProactorReadPipeTransport by calling recv_into instead of recv thus not creating a new buffer for each recv call in the transport s read loop bpo 41235 Fix the error handling in ssl SSLContext load_dh_params bpo 41207 In distutils spawn restore expectation that DistutilsExecError is raised when the command is not found bpo 29727 Register array array as a MutableSequence Patch by Pablo Galindo bpo 39168 Remove the __new__ method of typing Generic bpo 41194 Fix a crash in the _ast module it can no longer be loaded more than once It now uses a global state rather than a module state bpo 41195 Add read only ssl SSLContext security_level attribute to retrieve the context s security level bpo 41193 The write_history atexit function of the readline completer now ignores any OSError to ignore error if the filesystem is read only instead of only ignoring FileNotFoundError and PermissionError bpo 41182 selector use DefaultSelector based upon implementation bpo 41161 The decimal module now requires libmpdec 2 5 0 Users of with system libmpdec should update their system library bpo 40874 The decimal module now requires libmpdec 2 5 0 bpo 41138 Fixed the trace module CLI for Python source files with non UTF 8 encoding bpo 31082 Use the term iterable in the docstring for functools reduce bpo 40521 Remove freelist from collections deque bpo 31938 Fix default value signatures of several functions in the select module by Anthony Sottile bpo 41068 Fixed reading files with non ASCII names from ZIP archive directly after writing them bpo 41058 pdb find_function now correctly determines the source file encoding bpo 41056 Invalid file descriptor values are now prevented from being passed to os fpathconf discovered by Coverity bpo 41056 Fix a NULL pointer dereference within the ssl module during a MemoryError in the keylog callback discovered by Coverity bpo 41056 Fixed an instance where a MemoryError within the zoneinfo module might not be reported or not reported at its source found by Coverity bpo 41048 mimetypes read_mime_types function reads the rule file using UTF 8 encoding not the locale encoding Patch by Srinivas Reddy Thatiparthy bpo 41043 Fixed the use of glob in the stdlib literal part of the path is now always correctly escaped bpo 41025 Fixed an issue preventing the C implementation of zoneinfo ZoneInfo from being subclassed bpo 35018 Add the xml sax handler LexicalHandler class that is present in other SAX XML implementations bpo 41002 Improve performance of HTTPResponse read with a given amount Patch by Bruce Merry bpo 40448 ensurepip now disables the use of pip cache when installing the bundled versions of pip and setuptools Patch by Krzysztof Konopko bpo 40967 Removed asyncio Task current_task and asyncio Task all_tasks Patch contributed by Rémi Lapeyre bpo 40924 Ensure importlib resources path returns an extant path for the SourceFileLoader s resource reader Avoids the regression identified in master while a long term solution is devised bpo 40955 Fix a minor memory leak in subprocess module when extra_groups was specified bpo 40855 The standard deviation and variance functions in the statistics module were ignoring their mu and xbar arguments bpo 40939 Use the new PEG parser when generating the stdlib keyword module bpo 23427 Add sys orig_argv attribute the list of the original command line arguments passed to the Python executable bpo 33689 Ignore empty or whitespace only lines in pth files This matches the documentated behavior Before empty lines caused the site packages dir to appear multiple times in sys path By Ido Michael contributors Malcolm Smith and Tal E,en
1634,inat bpo 40884 Added a defaults parameter to logging Formatter to allow specifying default values for custom fields Patch by Asaf Alon and Bar Harel bpo 40876 Clarify error message in the csv module bpo 39791 Refresh importlib metadata from importlib_metadata 1 6 1 bpo 40807 Stop codeop _maybe_compile used by code InteractiveInterpreter and IDLE from emitting each warning three times bpo 32604 Fix reference leak in the select module when the module is imported in a subinterpreter bpo 39791 Built in loaders SourceFileLoader and ZipImporter now supply TraversableResources implementations for ResourceReader and the fallback function has been removed bpo 39314 rlcompleter Completer and the standard Python shell now close the parenthesis for functions that take no arguments Patch contributed by Rémi Lapeyre bpo 17005 The topological sort functionality that was introduced initially in the functools module has been moved to a new graphlib module to better accommodate the new tools and keep the original scope of the functools module Patch by Pablo Galindo bpo 40834 Fix truncate when sending str object with_xxsubinterpreters channel_send bpo 40755 Add rich comparisons to collections Counter bpo 26407 Unexpected errors in calling the __iter__ method are no longer masked by TypeError in csv reader csv writer writerow and csv writer writerows bpo 39384 Fixed email contentmanager to allow set_content to set a null string bpo 40744 The sqlite3 module uses SQLite API functions that require SQLite v3 7 3 or higher This patch removes support for older SQLite versions and explicitly requires SQLite 3 7 3 both at build compile and runtime Patch by Sergey Fedoseev and Erlend E Aasland bpo 40777 Initialize PyDateTime_IsoCalendarDateType tp_base at run time to avoid errors on some compilers bpo 38488 Update ensurepip to install pip 20 1 1 and setuptools 47 1 0 bpo 40792 The result of operator index now always has exact type int Previously the result could have been an instance of a subclass of int bpo 40767 webbrowser now properly finds the default browser in pure Wayland systems by checking the WAYLAND_DISPLAY environment variable Patch contributed by Jérémy Attali bpo 40791 hashlib compare_digest uses OpenSSL s CRYPTO_memcmp function when OpenSSL is available bpo 40795 ctypes module If ctypes fails to convert the result of a callback or if a ctypes callback function raises an exception sys unraisablehook is now called with an exception set Previously the error was logged into stderr by PyErr_Print bpo 16995 Add base64 b32hexencode and base64 b32hexdecode to support the Base32 Encoding with Extended Hex Alphabet bpo 30008 Fix ssl code to be compatible with OpenSSL 1 1 x builds that use no deprecated and api 1 1 0 bpo 30064 Fix asyncio loop sock_ race condition issue bpo 40759 Deprecate the symbol module bpo 40756 The second argument extra of LoggerAdapter __init__ now defaults to None bpo 37129 Add a new os RWF_APPEND flag for os pwritev bpo 40737 Fix possible reference leak for sqlite3 initialization bpo 40726 Handle cases where the end_lineno is None on ast increment_lineno bpo 40698 distutils upload creates SHA2 256 and Blake2b 256 digests MD5 digests is skipped if platform blocks MD5 bpo 40695 hashlib no longer falls back to builtin hash implementations when OpenSSL provides a hash digest and the algorithm is blocked by security policy bpo 9216 hashlib new passed usedforsecurity to OpenSSL EVP constructor _hashlib new test_hashlib and test_smtplib handle strict security policy better bpo 40614 ast parse will not parse self documenting expressions in f strings when passed feature_version is less than 3 8 bpo 40626 Add h5 file extension as MIME Type application x hdf5 as per HDF Group recommendation for HDF5 formatted data files Patch contributed by Mark Schwab bpo 25920 On macOS when building Python for macOS 10 4 and older which wasn t the case for python org macOS installer socket getaddrinfo no longer uses an internal lock to prevent race conditions when calling getaddrinfo which is thread safe since macOS 10 5 Python 3 9 requires macO,en
1635,S 10 6 or newer The internal lock caused random hang on fork when another thread was calling socket getaddrinfo The lock was also used on FreeBSD older than 5 3 OpenBSD older than 201311 and NetBSD older than 4 bpo 40671 Prepare _hashlib for PEP 489 and use PyModule_AddType bpo 32309 Added a new coroutine asyncio to_thread It is mainly used for running IO bound functions in a separate thread to avoid blocking the event loop and essentially works as a high level version of run_in_executor that can directly take keyword arguments bpo 36543 Restored the deprecated xml etree cElementTree module bpo 40611 MAP_POPULATE constant has now been added to the list of exported mmap module flags bpo 39881 PEP 554 for use in the test suite Patch By Joannah Nanjekye bpo 13097 ctypes now raises an ArgumentError when a callback is invoked with more than 1024 arguments bpo 39385 A new test assertion context manager unittest assertNoLogs will ensure a given block of code emits no log messages using the logging module Contributed by Kit Yan Choi bpo 23082 Updated the error message and docs of PurePath relative_to to better reflect the function behaviour bpo 40318 Use SQLite3 trace v2 API if it is available bpo 40105 ZipFile truncates files to avoid corruption when a shorter comment is provided in append a mode Patch by Jan Mazur bpo 40084 Fix Enum __dir__ dir Enum member now includes attributes as well as methods bpo 31122 ssl wrap_socket now raises ssl SSLEOFError rather than OSError when peer closes connection during TLS negotiation bpo 39728 fix default _missing_ so a duplicate ValueError is not set as the __context__ of the original ValueError bpo 39244 Fixed multiprocessing context get_all_start_methods to properly return the default method first on macOS bpo 39040 Fix parsing of invalid mime headers parameters by collapsing whitespace between encoded words in a bare quote string bpo 38731 Add quiet option to command line interface of py_compile Patch by Gregory Schevchenko bpo 35714 struct error is now raised if there is a null character in a struct format string bpo 38144 Added the root_dir and dir_fd parameters in glob glob bpo 26543 Fix IMAP4 noop when debug mode is enabled ex imaplib Debug 3 bpo 12178 csv writer now correctly escapes escapechar when input contains escapechar Patch by Catalin Iacob Berker Peksag and Itay Elbirt bpo 36290 AST nodes are now raising TypeError on conflicting keyword arguments Patch contributed by Rémi Lapeyre bpo 33944 Added site py site packages tracing in verbose mode bpo 35078 Refactor formatweekday formatmonthname methods in LocaleHTMLCalendar and LocaleTextCalendar classes in calendar module to call the base class methods This enables customizable CSS classes for LocaleHTMLCalendar Patch by Srinivas Reddy Thatiparthy bpo 29620 assertWarns no longer raises a RuntimeException when accessing a module s __warningregistry__ causes importation of a new module or when a new module is imported in another thread Patch by Kernc bpo 31844 Remove ParserBase error method from the private and undocumented _markupbase module html parser HTMLParser is the only subclass of ParserBase and its error implementation was deprecated in Python 3 4 and removed in Python 3 5 bpo 34226 Fix cgi parse_multipart without content_length Patch by Roger Duran bpo 33660 Fix pathlib PosixPath to resolve a relative path located on the root directory properly bpo 28557 Improve the error message for a misbehaving rawio readinto bpo 26680 The d is_integer method is added to the Decimal type for compatibility with other number types bpo 26680 The x is_integer method is incorporated into the abstract types of the numeric tower Real Rational and Integral with appropriate default implementations Documentation bpo 41428 Add documentation for PEP 604 Allow writing union types as X Y bpo 41774 In Programming FAQ Sequences Tuples Lists section add How do you remove multiple items from a list bpo 35293 Fix RemovedInSphinx40Warning when building the documentation Patch by Donghee Na bpo 37149 Change Shipman tkinter doc link from archive org to TkD,en
1636,ocs The doc has been removed from the NMT server The new link responds much faster and includes a short explanatory note bpo 41726 Update the refcounts info of PyType_FromModuleAndSpec bpo 41624 Fix the signature of typing Coroutine bpo 40204 Enable Sphinx 3 2 c_allow_pre_v3 option and disable c_warn_on_allowed_pre_v3 option to make the documentation compatible with Sphinx 2 and Sphinx 3 bpo 41045 Add documentation for debug feature of f strings bpo 41314 Changed the release when from __future__ import annotations becomes the default from 4 0 to 3 10 following a change in PEP 563 bpo 40979 Refactored typing rst arranging more than 70 classes functions and decorators into new sub sections bpo 40552 Fix in tutorial section 4 2 Code snippet is now correct bpo 39883 Make code examples and recipes in the Python documentation be licensed under the more permissive BSD0 license in addition to the existing Python 2 0 license bpo 37703 Updated Documentation to comprehensively elaborate on the behaviour of gather cancel Tests bpo 41939 Fix test_site test_license_exists_at_url call urllib request urlcleanup to reset the global urllib request _opener Patch by Victor Stinner bpo 41731 Make test_cmd_line_script pass with option vv bpo 41602 Add tests for SIGINT handling in the runpy module bpo 41521 test support Rename blacklist parameter of check__all__ to not_exported bpo 41477 Make ctypes optional in test_genericalias bpo 41085 Fix integer overflow in the array array index method on 64 bit Windows for index larger than 2 31 bpo 41069 test support TESTFN and the current directory for tests when run via test regrtest contain now non ascii characters if possible bpo 38377 On Linux skip tests using multiprocessing if the current user cannot create a file in dev shm directory Add the skip_if_broken_multiprocessing_synchronize function to the test support module bpo 41009 Fix use of support require_ linux mac freebsd _version decorators as class decorator bpo 41003 Fix test_copyreg when numpy is installed test pickletester now saves restores warnings filters when importing numpy to ignore filters installed by numpy bpo 40964 Disable remote imaplib tests host cyrus andrew cmu edu is blocking incoming connections bpo 40927 Fix test_binhex when run twice it now uses import_fresh_module to ensure that it raises DeprecationWarning each time bpo 17258 Skip some multiprocessing tests when MD5 hash digest is blocked bpo 31904 Increase LOOPBACK_TIMEOUT to 10 for VxWorks RTOS bpo 38169 Increase code coverage for SharedMemory and ShareableList bpo 34401 Make test_gdb properly run on HP UX Patch by Michael Osipov Build bpo 38249 Update Py_UNREACHABLE to use __builtin_unreachable if only the compiler is able to use it Patch by Donghee Na bpo 41617 Fix pycore_bitutils h header file to support old clang versions __builtin_bswap16 is not available in LLVM clang 3 0 bpo 40204 Pin Sphinx version to 2 3 1 in Doc Makefile bpo 36020 The C99 functions snprintf and vsnprintf are now required to build Python bpo 40684 make install now uses the PLATLIBDIR variable for the destination lib dynload directory when configure with platlibdir is used bpo 40683 Fixed an issue where the zoneinfo module and its tests were not included when Python is installed with make Windows bpo 41744 Fixes automatic import of props file when using the Nuget package bpo 41627 The user site directory for 32 bit now includes a 32 suffix to distinguish it from the 64 bit interpreter s directory bpo 41526 Fixed layout of final page of the installer by removing the special thanks to Mark Hammond with his permission bpo 41492 Fixes the description that appears in UAC prompts bpo 40948 Improve post install message to direct people to the py command bpo 41412 The installer will now fail to install on Windows 7 and Windows 8 Further the UCRT dependency is now always downloaded on demand bpo 40741 Update Windows release to include SQLite 3 32 3 bpo 41142 msilib now supports creating CAB files with non ASCII file path and adding files with non ASCII file path to them bpo 41074 Fixed support of non ,en
1637,ASCII names in functions msilib OpenDatabase and msilib init_database and non ASCII SQL in method msilib Database OpenView bpo 41039 Stable ABI redirection DLL python3 dll now uses pragma comment linker for re exporting bpo 40164 Updates Windows OpenSSL to 1 1 1g bpo 39631 Changes the registered MIME type for py files on Windows to text x python instead of text plain bpo 40677 Manually define IO_REPARSE_TAG_APPEXECLINK in case some old Windows SDK doesn t have it bpo 37556 Extend py exe help to mention overrides via venv shebang environmental variables ini files macOS bpo 41557 Update macOS installer to use SQLite 3 33 0 bpo 39580 Avoid opening Finder window if running installer from the command line Patch contributed by Rick Heil bpo 41100 Fix configure error when building on macOS 11 Note that the current Python release was released shortly after the first developer preview of macOS 11 Big Sur there are other known issues with building and running on the developer preview Big Sur is expected to be fully supported in a future bugfix release of Python 3 8 x and with 3 9 0 bpo 40741 Update macOS installer to use SQLite 3 32 3 bpo 41005 fixed an XDG settings issue not allowing macos to open browser in webbrowser py bpo 40741 Update macOS installer to use SQLite 3 32 2 IDLE bpo 41775 Use IDLE Shell as shell title bpo 35764 Rewrite the Calltips doc section bpo 40181 In calltips stop reminding that marks the end of positional only arguments bpo 41468 Improve IDLE run crash error message which users should never see bpo 41373 Save files loaded with no line ending as when blank or different line endings by setting its line ending to the system default Fix regression in 3 8 4 and 3 9 0b4 bpo 41300 Save files with non ascii chars Fix regression released in 3 9 0b4 and 3 8 4 bpo 37765 Add keywords to module name completion list Rewrite Completions section of IDLE doc bpo 41152 The encoding of stdin stdout and stderr in IDLE is now always UTF 8 bpo 41144 Make Open Module open a special module such as os path bpo 39885 Make context menu Cut and Copy work again when right clicking within a selection bpo 40723 Make test_idle pass when run after import C API bpo 41936 Removed undocumented macros Py_ALLOW_RECURSION and Py_END_ALLOW_RECURSION and the recursion_critical field of the PyInterpreterState structure bpo 41692 The PyUnicode_InternImmortal function is now deprecated and will be removed in Python 3 12 use PyUnicode_InternInPlace instead Patch by Victor Stinner bpo 41842 Add PyCodec_Unregister function to unregister a codec search function bpo 41834 Remove the _Py_CheckRecursionLimit variable it has been replaced by ceval recursion_limit of the PyInterpreterState structure Patch by Victor Stinner bpo 41689 Types created with PyType_FromSpec now make any signature in their tp_doc slot accessible from __text_signature__ bpo 41524 Fix bug in PyOS_mystrnicmp and PyOS_mystricmp that incremented pointers beyond the end of a string bpo 41324 Add a minimal decimal capsule API The API supports fast conversions between Decimals up to 38 digits and their triple representation as a C struct bpo 30155 Add PyDateTime_DATE_GET_TZINFO and PyDateTime_TIME_GET_TZINFO macros for accessing the tzinfo attributes of datetime datetime and datetime time objects bpo 40170 Revert PyType_HasFeature change it reads again directly the PyTypeObject tp_flags member when the limited C API is not used rather than always calling PyType_GetFlags which hides implementation details bpo 41123 Remove PyUnicode_AsUnicodeCopy bpo 41123 Removed PyLong_FromUnicode bpo 41123 Removed PyUnicode_GetMax bpo 41123 Removed Py_UNICODE_str functions manipulating Py_UNICODE strings bpo 41103 PyObject_AsCharBuffer PyObject_AsReadBuffer PyObject_CheckReadBuffer and PyObject_AsWriteBuffer are removed Please migrate to new buffer protocol PyObject_GetBuffer and PyBuffer_Release bpo 36346 Raises DeprecationWarning for PyUnicode_FromUnicode NULL size and PyUnicode_FromStringAndSize NULL size with size 0 bpo 36346 Mark Py_UNICODE_COPY Py_UNICODE_FILL PyUnicode_WSTR_LENGTH PyUnicode_FromUni,en
1638,code PyUnicode_AsUnicode and PyUnicode_AsUnicodeAndSize as deprecated in C Remove Py_UNICODE_MATCH which was deprecated and broken since Python 3 3 bpo 40989 The PyObject_INIT and PyObject_INIT_VAR macros become aliases to respectively PyObject_Init and PyObject_InitVar functions bpo 36020 On Windows include pyerrors h no longer defines snprintf and vsnprintf macros bpo 40943 The PY_SSIZE_T_CLEAN macro must now be defined to use PyArg_ParseTuple and Py_BuildValue formats which use es et s u y z U and Z See Parsing arguments and building values and the PEP 353 bpo 40910 Export explicitly the Py_GetArgcArgv function to the C API and document the function Previously it was exported implicitly which no longer works since Python is built with fvisibility hidden bpo 40724 Allow defining buffer slots in type specs bpo 40679 Fix a _PyEval_EvalCode crash if qualname argument is NULL bpo 40839 Calling PyDict_GetItem without GIL held had been allowed for historical reason It is no longer allowed bpo 40826 PyOS_InterruptOccurred now fails with a fatal error if it is called with the GIL released bpo 40792 The result of PyNumber_Index now always has exact type int Previously the result could have been an instance of a subclass of int bpo 39573 Convert Py_REFCNT and Py_SIZE macros to static inline functions They cannot be used as l value anymore use Py_SET_REFCNT and Py_SET_SIZE to set an object reference count and size This change is backward incompatible on purpose to prepare the C API for an opaque PyObject structure bpo 40703 The PyType_FromSpec functions no longer overwrite the type s __module__ attribute if it is set via Py_tp_members or Py_tp_getset bpo 39583 Remove superfluous extern C declarations from Include cpython h Python 3 9 0 beta 1 Release date 2020 05 19 Security bpo 40501 uuid no longer uses ctypes to load libuuid or rpcrt4 dll at runtime Core and Builtins bpo 40663 Correctly generate annotations where parentheses are omitted but required e g Type str int other bpo 40596 Fixed str isidentifier for non canonicalized strings containing non BMP characters on Windows bpo 40593 Improved syntax errors for invalid characters in source code bpo 40585 Fixed a bug when using codeop compile_command that was causing exceptions to be swallowed with the new parser Patch by Pablo Galindo bpo 40566 Apply PEP 573 to abc bpo 40502 Initialize n n_col_offset Patch by Joannah Nanjekye bpo 40527 Fix command line argument parsing no longer write errors multiple times into stderr bpo 1635741 Port errno to multiphase initialization PEP 489 bpo 40523 Add pass throughs for hash and reversed to weakref proxy objects Patch by Pablo Galindo bpo 1635741 Port syslog to multiphase initialization PEP 489 bpo 40246 Reporting a specialised error message for invalid string prefixes which was introduced in bpo 40246 is being reverted due to backwards compatibility concerns for strings that immediately follow a reserved keyword without whitespace between them Constructs like bg d00 if clear else fca were failing to parse which is not an acceptable breakage on such short notice bpo 40417 Fix imp module deprecation warning when PyImport_ReloadModule is called Patch by Robert Rouhani bpo 40408 Fixed support of nested type variables in GenericAlias e g list list T bpo 1635741 Port _stat module to multiphase initialization PEP 489 bpo 29587 Enable implicit exception chaining when calling generator throw bpo 40328 Add tools for generating mappings headers for CJKCodecs bpo 40228 Setting frame f_lineno is now robust w r t changes in the source to bytecode compiler bpo 38880 Added the ability to list interpreters associated with channel ends in the internal subinterpreters module bpo 37986 Improve performance of PyLong_FromDouble for values that fit into long Library bpo 40662 Fixed ast get_source_segment for ast nodes that have incomplete location information Patch by Irit Katriel bpo 40665 Convert bisect to use Argument Clinic bpo 40536 Added the available_timezones function to the zoneinfo module Patch by Paul Ganssle bpo 40645 The hmac HMAC exposes internal i,en
1639,mplementation details The attributes digest_cons inner and outer are deprecated and will be removed in the future bpo 40645 The internal module _hashlib wraps and exposes OpenSSL s HMAC API The new code will be used in Python 3 10 after the internal implementation details of the pure Python HMAC module are no longer part of the public API bpo 40637 Builtin hash modules can now be disabled or selectively enabled with configure with builtin hashlib hashes sha3 blake1 or without builtin hashlib hashes bpo 37630 The hashlib module can now use SHA3 hashes and SHAKE XOF from OpenSSL when available bpo 40479 The hashlib now compiles with OpenSSL 3 0 0 alpha2 bpo 40257 Revert changes to inspect getdoc bpo 40607 When cancelling a task due to timeout asyncio wait_for will now propagate the exception if an error happens during cancellation Patch by Roman Skurikhin bpo 40612 Fix edge cases in SyntaxError formatting If the offset is 0 no caret is printed If the offset is line length the caret is printed pointing just after the last character bpo 40597 If text content lines are longer than policy max_line_length always use a content encoding to make sure they are wrapped bpo 40571 Added functools cache as a simpler more discoverable way to access the unbounded cache variant of lru_cache maxsize None bpo 40503 PEP 615 the zoneinfo module Adds support for the IANA time zone database bpo 40397 Removed attributes __args__ and __parameters__ from special generic aliases like typing List not subscripted bpo 40549 Convert posixmodule c posix or nt module to the multiphase initialization PEP 489 bpo 31033 Add a msg argument to Future cancel and Task cancel bpo 40541 Added an optional counts parameter to random sample bpo 40515 The ssl and hashlib modules now actively check that OpenSSL is build with thread support Python 3 7 0 made thread support mandatory and no longer works safely with a no thread builds bpo 31033 When a asyncio Task is cancelled the exception traceback now chains all the way back to where the task was first interrupted bpo 40504 functools lru_cache objects can now be the targets of weakrefs bpo 40559 Fix possible memory leak in the C implementation of asyncio Task bpo 40480 fnmatch fnmatch could take exponential time in the presence of multiple pattern characters This was repaired by generating more elaborate regular expressions to avoid futile backtracking bpo 40495 compileall is now able to use hardlinks to prevent duplicates in a case when pyc files for different optimization levels have the same content bpo 40457 The ssl module now support OpenSSL builds without TLS 1 0 and 1 1 methods bpo 40355 Improve error reporting in ast literal_eval in the presence of malformed ast Dict nodes instead of silently ignoring any non conforming elements Patch by Curtis Bucher bpo 40465 Deprecated the optional random argument to random shuffle bpo 40459 platform win32_ver now produces correct ptype strings instead of empty strings bpo 39435 The first argument of pickle loads is now positional only bpo 39305 Update nntplib to merge nntplib NNTP and nntplib _NNTPBase Patch by Donghee Na bpo 32494 Update dbm gnu to use gdbm_count if possible when calling len Patch by Donghee Na bpo 40453 Add isolated True keyword only parameter to _xxsubinterpreters create An isolated subinterpreter cannot spawn threads spawn a child process or call os fork bpo 40286 Remove _random Random randbytes the C implementation of randbytes Implement the method in Python to ease subclassing randbytes now directly reuses getrandbits bpo 40394 Added default arguments to difflib SequenceMatcher find_longest_match bpo 39995 Fix a race condition in concurrent futures _ThreadWakeup access to _ThreadWakeup is now protected with the shutdown lock bpo 30966 Process shutdown wait True of concurrent futures now closes explicitly the result queue bpo 30966 Add a new close method to the SimpleQueue class to explicitly close the queue bpo 39966 Revert bpo 25597 unittest mock MagicMock with wraps set uses default return values for magic methods bpo 39791 Added files function to ,en
1640,importlib resources with support for subdirectories in package data matching backport in importlib_resources 1 5 bpo 40375 imaplib IMAP4 unselect is added Patch by Donghee Na bpo 40389 repr now returns typing Optional T when called for typing Union of two types one of which is NoneType bpo 40291 Add support for CAN_J1939 sockets available on Linux 5 4 bpo 40273 types MappingProxyType is now reversible bpo 39075 The repr for types SimpleNamespace is now insertion ordered rather than alphabetical bpo 40192 On AIX thread_time is now implemented with thread_cputime which has nanosecond resolution rather than clock_gettime CLOCK_THREAD_CPUTIME_ID which has a resolution of 10 milliseconds Patch by Batuhan Taskaya bpo 40025 Raise TypeError when _generate_next_value_ is defined after members Patch by Ethan Onstott bpo 39058 In the argparse module the repr for Namespace and other argument holders now displayed in the order attributes were added Formerly it displayed in alphabetical order even though argument order is preserved the user visible parts of the module bpo 24416 The isocalendar methods of datetime date and datetime datetime now return a named tuple instead of a tuple Documentation bpo 34790 Add version of removal for explicit passing of coros to asyncio wait s documentation bpo 40561 Provide docstrings for webbrowser open functions bpo 40499 Mention that asyncio wait requires a non empty set of awaitables bpo 39705 Tutorial example for sorted in the Loop Techniques section is given a better explanation Also a new example is included to explain sorted s basic behavior bpo 39435 Fix an incorrect signature for pickle loads in the docs Tests bpo 40055 distutils tests now saves restores warnings filters to leave them unchanged Importing tests imports docutils which imports pkg_resources which adds a warnings filter bpo 40436 test_gdb and test pythoninfo now check gdb command exit code Build bpo 40653 Move _dirnameW out of HAVE_SYMLINK to fix a potential compiling issue bpo 40514 Add with experimental isolated subinterpreters build option to configure better isolate subinterpreters experimental build mode Windows bpo 40650 Include winsock2 h in pytime c for timeval bpo 40458 Increase reserved stack space to prevent overflow crash on Windows bpo 39148 Add IPv6 support to asyncio datagram endpoints in ProactorEventLoop Change the raised exception for unknown address families to ValueError as it s not coming from Windows API macOS bpo 34956 When building Python on macOS from source _tkinter now links with non system Tcl and Tk frameworks if they are installed in Library Frameworks as had been the case on older releases of macOS If a macOS SDK is explicitly configured by using enable universalsdk or isysroot only the SDK itself is searched The default behavior can still be overridden with with tcltk includes and with tcltk libs bpo 35569 Expose RFC 3542 IPv6 socket options Tools Demos bpo 40479 Update multissltest helper to test with latest OpenSSL 1 0 2 1 1 0 1 1 1 and 3 0 0 alpha bpo 40431 Fix a syntax typo in turtledemo that now raises a SyntaxError bpo 40163 Fix multissltest tool OpenSSL has changed download URL for old releases The multissltest tool now tries to download from current and old download URLs C API bpo 39465 Remove the _PyUnicode_ClearStaticStrings function from the C API bpo 38787 Add PyCFunction_CheckExact macro for exact type checks now that we allow subtypes of PyCFunction as well as PyCMethod_CheckExact and PyCMethod_Check for the new PyCMethod subtype bpo 40545 Declare _PyErr_GetTopmostException with PyAPI_FUNC to properly export the function in the C API The function remains private _Py prefix bpo 40412 Nullify inittab_copy during finalization preventing future interpreter initializations in an embedded situation from crashing Patch by Gregory Szorc bpo 40429 The PyThreadState_GetFrame function now returns a strong reference to the frame bpo 40428 Remove the following functions from the C API Call PyGC_Collect explicitly to free all free lists PyAsyncGen_ClearFreeLists PyContext_ClearFreeList PyDict_Clea,en
1641,rFreeList PyFloat_ClearFreeList PyFrame_ClearFreeList PyList_ClearFreeList PySet_ClearFreeList PyTuple_ClearFreeList bpo 40421 New PyFrame_GetBack function get the frame next outer frame bpo 40421 New PyFrame_GetCode function return a borrowed reference to the frame code bpo 40217 Ensure that instances of types created with PyType_FromSpecWithBases will visit its class object when traversing references in the garbage collector implemented as an extension of the provided tp_traverse Patch by Pablo Galindo bpo 38787 Module C state is now accessible from C defined heap type methods PEP 573 Patch by Marcel Plch and Petr Viktorin Python 3 9 0 alpha 6 Release date 2020 04 27 Security bpo 40121 Fixes audit events raised on creating a new socket bpo 39073 Disallow CR or LF in email headerregistry Address arguments to guard against header injection attacks bpo 39503 CVE 2020 8492 The AbstractBasicAuthHandler class of the urllib request module uses an inefficient regular expression which can be exploited by an attacker to cause a denial of service Fix the regex to prevent the catastrophic backtracking Vulnerability reported by Ben Caller and Matt Schwager Core and Builtins bpo 40313 Improve the performance of bytes hex bpo 40334 Switch to a new parser based on PEG For more details see PEP 617 To temporarily switch back to the old parser use X oldparser or PYTHONOLDPARSER 1 In Python 3 10 we will remove the old parser completely including the parser module already deprecated and anything that depends on it bpo 40267 Fix the tokenizer to display the correct error message when there is a SyntaxError on the last input character and no newline follows It used to be unexpected EOF while parsing while it should be invalid syntax bpo 39522 Correctly unparse explicit u prefix for strings when postponed evaluation for annotations activated Patch by Batuhan Taskaya bpo 40246 Report a specialized error message invalid string prefix when the tokenizer encounters a string with an invalid prefix bpo 40082 Fix the signal handler it now always uses the main interpreter rather than trying to get the current Python thread state bpo 37388 str encode and str decode no longer check the encoding and errors in development mode or in debug mode during Python finalization The codecs machinery can no longer work on very late calls to str encode and str decode bpo 40077 Fix possible refleaks in _json memo of PyScannerObject should be traversed bpo 37207 Speed up calls to dict by using the PEP 590 vectorcall calling convention bpo 40141 Add column and line information to ast keyword nodes Patch by Pablo Galindo bpo 1635741 Port resource to multiphase initialization PEP 489 bpo 1635741 Port math to multiphase initialization PEP 489 bpo 1635741 Port _uuid module to multiphase initialization PEP 489 bpo 40077 Convert json module to use PyType_FromSpec bpo 40067 Improve the error message for multiple star expressions in an assignment Patch by Furkan Onder bpo 1635741 Port _functools module to multiphase initialization PEP 489 Patch by Paulo Henrique Silva bpo 1635741 Port operator module to multiphase initialization PEP 489 Patch by Paulo Henrique Silva bpo 20526 Fix PyThreadState_Clear PyThreadState frame is a borrowed reference not a strong reference PyThreadState_Clear must not call Py_CLEAR tstate frame bpo 1635741 Port time module to multiphase initialization PEP 489 Patch by Paulo Henrique Silva bpo 1635741 Port _weakref extension module to multiphase initialization PEP 489 bpo 40020 Fix a leak and subsequent crash in parsetok c caused by realloc misuse on a rare codepath bpo 39939 Added str removeprefix and str removesuffix methods and corresponding bytes bytearray and collections UserString methods to remove affixes from a string if present See PEP 616 for a full description Patch by Dennis Sweeney bpo 39481 Implement PEP 585 This supports list int tuple str etc bpo 32894 Support unparsing of infinity numbers in postponed annotations Patch by Batuhan Taşkaya bpo 37207 Speed up calls to list by using the PEP 590 vectorcall calling convention Patch by Mark ,en
1642,Shannon Library bpo 40398 typing get_args now always returns an empty tuple for special generic aliases bpo 40396 Functions typing get_origin typing get_args and typing get_type_hints support now generic aliases like list int bpo 38061 Optimize the subprocess module on FreeBSD using closefrom A single close fd syscall is cheap but when sysconf _SC_OPEN_MAX is high the loop calling close fd on each file descriptor can take several milliseconds The workaround on FreeBSD to improve performance was to load and mount the fdescfs kernel module but this is not enabled by default Initial patch by Ed Maste emaste Conrad Meyer cem Kyle Evans kevans and Kubilay Kocak koobs https bugs freebsd org bugzilla show_bug cgi id 242274 bpo 38061 On FreeBSD os closerange fd_low fd_high now calls closefrom fd_low if fd_high is greater than or equal to sysconf _SC_OPEN_MAX Initial patch by Ed Maste emaste Conrad Meyer cem Kyle Evans kevans and Kubilay Kocak koobs https bugs freebsd org bugzilla show_bug cgi id 242274 bpo 40360 The lib2to3 module is pending deprecation due to PEP 617 bpo 40138 Fix the Windows implementation of os waitpid for exit code larger than INT_MAX 8 The exit status is now interpreted as an unsigned number bpo 39942 Set __main__ as the default module name when __name__ is missing in typing TypeVar Patch by Weipeng Hong bpo 40275 The logging package is now imported lazily in unittest only when the assertLogs assertion is used bpo 40275 The asyncio package is now imported lazily in unittest only when the IsolatedAsyncioTestCase class is used bpo 40330 In ShareableList __setitem__ check the size of a new string item after encoding it to utf 8 not before bpo 40148 Added pathlib Path with_stem to create a new Path with the stem replaced bpo 40325 Deprecated support for set objects in random sample bpo 40257 Improved help for the typing module Docstrings are now shown for all special forms and special generic aliases like Union and List Using help with generic alias like List int will show the help for the correspondent concrete type list in this case bpo 40257 inspect getdoc no longer returns docstring inherited from the type of the object or from parent class if it is a class if it is not defined in the object itself In pydoc the documentation string is now shown not only for class function method etc but for any object that has its own __doc__ attribute bpo 40287 Fixed SpooledTemporaryFile seek to return the position bpo 40290 Added zscore to statistics NormalDist bpo 40282 Allow random getrandbits 0 to succeed and to return 0 bpo 40286 Add random randbytes function and random Random randbytes method to generate random bytes bpo 40277 collections namedtuple now provides a human readable repr for its field accessors bpo 40270 The included copy of sqlite3 on Windows is now compiled with the json extension This allows the use of functions such as json_object bpo 29255 Wait in KqueueSelector select when no fds are registered bpo 40260 Ensure modulefinder uses io open_code and respects coding comments bpo 40234 Allow again to spawn daemon threads in subinterpreters revert change which denied them bpo 39207 Workers in ProcessPoolExecutor are now spawned on demand only when there are no available idle workers to reuse This optimizes startup overhead and reduces the amount of lost CPU time to idle workers Patch by Kyle Stanley bpo 40091 Fix a hang at fork in the logging module the new private _at_fork_reinit method is now used to reinitialize locks at fork in the child process bpo 40149 Implement traverse and clear slots in _abc _abc_data type bpo 40208 Remove deprecated symtable SymbolTable has_exec bpo 40196 Fix a bug in the symtable module that was causing incorrectly report global variables as local Patch by Pablo Galindo bpo 40190 Add support for _SC_AIX_REALMEM to posix sysconf bpo 40182 Removed the _field_types attribute of the typing NamedTuple class bpo 36517 Multiple inheritance with typing NamedTuple now raises an error instead of silently ignoring other types bpo 40126 Fixed reverting multiple patches in unittest mock Pa,en
1643,tcher s __exit__ is now never called if its __enter__ is failed Returning true from __exit__ silences now the exception bpo 40094 CGIHTTPRequestHandler of http server now logs the CGI script exit code rather than the CGI script exit status of os waitpid For example if the script is killed by signal 11 it now logs CGI script exit code 11 bpo 40108 Improve the error message when triying to import a module using runpy and incorrently use the py extension at the end of the module name Patch by Pablo Galindo bpo 40094 Add os waitstatus_to_exitcode function convert a wait status to an exit code bpo 40089 Fix threading _after_fork if fork was not called by a thread spawned by threading Thread threading _after_fork now creates a _MainThread instance for _main_thread instead of a _DummyThread instance bpo 40089 Add a private _at_fork_reinit method to _thread Lock _thread RLock threading RLock and threading Condition classes reinitialize the lock at fork in the child process reset the lock to the unlocked state Rename also the private _reset_internal_locks method of threading Event to _at_fork_reinit bpo 25780 Expose CAN_RAW_JOIN_FILTERS in the socket module bpo 39503 AbstractBasicAuthHandler of urllib request now parses all WWW Authenticate HTTP headers and accepts multiple challenges per header use the realm of the first Basic challenge bpo 39812 Removed daemon threads from concurrent futures by adding an internal threading _register_atexit which calls registered functions prior to joining all non daemon threads This allows for compatibility with subinterpreters which don t support daemon threads bpo 40050 Fix importlib _bootstrap_external avoid creating a new winreg builtin module if it s already available in sys modules and remove redundant imports bpo 40014 Fix os getgrouplist if getgrouplist function fails because the group list is too small retry with a larger group list On failure the glibc implementation of getgrouplist sets ngroups to the total number of groups For other implementations double the group list size bpo 40017 Add time CLOCK_TAI constant if the operating system support it bpo 40016 In re docstring clarify the relationship between inline and argument compile flags bpo 39953 Update internal table of OpenSSL error codes in the ssl module bpo 36144 Added PEP 584 operators to weakref WeakValueDictionary bpo 36144 Added PEP 584 operators to weakref WeakKeyDictionary bpo 38891 Fix linear runtime behaviour of the __getitem__ and __setitem__ methods in multiprocessing shared_memory ShareableList This avoids quadratic performance when iterating a ShareableList Patch by Thomas Krennwallner bpo 39682 Remove undocumented support for closing a pathlib Path object via its context manager The context manager magic methods remain but they are now a no op making Path objects immutable bpo 36144 Added PEP 584 operators and to collections ChainMap bpo 39011 Normalization of line endings in ElementTree attributes was removed as line endings which were replaced by entity numbers should be preserved in original form bpo 38410 Properly handle sys audit failures in sys set_asyncgen_hooks bpo 36541 lib2to3 now recognizes named assignment expressions the walrus operator bpo 35967 In platform delay the invocation of uname p until the processor attribute is requested bpo 35113 inspect getsource now returns correct source code for inner class with same name as module level class Decorators are also returned as part of source of the class Patch by Karthikeyan Singaravelan bpo 33262 Deprecate passing None as an argument for shlex split s s parameter Patch by Zackery Spytz bpo 31758 Prevent crashes when using an uninitialized _elementtree XMLParser object Patch by Oren Milman Documentation bpo 27635 The pickle documentation incorrectly claimed that __new__ isn t called by default when unpickling bpo 39879 Updated Data model docs to include dict insertion order preservation Patch by Furkan Onder and Samy Lahfa bpo 38387 Document PyDoc_STRVAR macro in the C API reference bpo 13743 Some methods within xml dom minidom Element class are now bett,en
1644,er documented Tests bpo 31904 Set expected default encoding in test_c_locale_coercion py for VxWorks RTOS bpo 40162 Update Travis CI configuration to OpenSSL 1 1 1f bpo 40146 Update OpenSSL to 1 1 1f in Azure Pipelines bpo 40094 Add test support wait_process function bpo 40003 test bisect_cmd now copies Python command line options like O or W Moreover emit a warning if test bisect_cmd is used with w verbose2 option bpo 39380 Add the encoding in ftplib FTP and ftplib FTP_TLS to the constructor as keyword only and change the default from latin 1 to utf 8 to follow RFC 2640 bpo 39793 Use the same domain when testing make_msgid Patch by Batuhan Taskaya bpo 1812 Fix newline handling in doctest testfile when loading from a package whose loader has a get_data method Patch by Peter Donis Build bpo 38360 Support single argument form of macOS isysroot flag bpo 40158 Fix CPython MSBuild Properties in NuGet Package build native python props bpo 38527 Fix configure check on Solaris for float word ordering sometimes the correct grep command was not being used Patch by Arnon Yaari Windows bpo 40164 Updates Windows to OpenSSL 1 1 1f bpo 8901 Ignore the Windows registry when the E option is used macOS bpo 38329 python org macOS installers now update the Current version symlink of Library Frameworks Python framework Versions for 3 9 installs Previously Current was only updated for Python 2 x installs This should make it easier to embed Python 3 into other macOS applications bpo 40164 Update macOS installer builds to use OpenSSL 1 1 1g IDLE bpo 38439 Add a 256 256 pixel IDLE icon to support more modern environments Created by Andrew Clover Delete the unused macOS idle icns icon file bpo 38689 IDLE will no longer freeze when inspect signature fails when fetching a calltip Tools Demos bpo 40385 Removed the checkpyc py tool Please see compileall without force mode as a potential alternative bpo 40179 Fixed translation of elif in Argument Clinic bpo 40094 Fix which py script exit code it now uses os waitstatus_to_exitcode to convert os system exit status into an exit code C API bpo 40241 Move the PyGC_Head structure to the internal C API bpo 40170 Convert PyObject_IS_GC macro to a function to hide implementation details bpo 40241 Add the functions PyObject_GC_IsTracked and PyObject_GC_IsFinalized to the public API to allow to query if Python objects are being currently tracked or have been already finalized by the garbage collector respectively Patch by Pablo Galindo bpo 40170 The PyObject_NEW macro becomes an alias to the PyObject_New macro and the PyObject_NEW_VAR macro becomes an alias to the PyObject_NewVar macro to hide implementation details They no longer access directly the PyTypeObject tp_basicsize member bpo 40170 PyType_HasFeature now always calls PyType_GetFlags to hide implementation details Previously it accessed directly the PyTypeObject tp_flags member when the limited C API was not used bpo 40170 Convert the PyObject_GET_WEAKREFS_LISTPTR macro to a function to hide implementation details the macro accessed directly to the PyTypeObject tp_weaklistoffset member bpo 40170 Convert PyObject_CheckBuffer macro to a function to hide implementation details the macro accessed directly the PyTypeObject tp_as_buffer member bpo 40170 Always declare PyIndex_Check as an opaque function to hide implementation details remove PyIndex_Check macro The macro accessed directly the PyTypeObject tp_as_number member bpo 39947 Add PyThreadState_GetID function get the unique identifier of a Python thread state Python 3 9 0 alpha 5 Release date 2020 03 23 Security bpo 38576 Disallow control characters in hostnames in http client addressing CVE 2019 18348 Such potentially malicious header injection URLs now cause a InvalidURL to be raised Core and Builtins bpo 40010 Optimize pending calls in multithreaded applications If a thread different than the main thread schedules a pending call Py_AddPendingCall the bytecode evaluation loop is no longer interrupted at each bytecode instruction to check for pending calls which cannot be executed Only the main thread,en
1645, can execute pending calls Previously the bytecode evaluation loop was interrupted at each instruction until the main thread executes pending calls bpo 1635741 Port _weakref extension module to multiphase initialization PEP 489 bpo 1635741 Port _collections module to multiphase initialization PEP 489 bpo 40010 Optimize signal handling in multithreaded applications If a thread different than the main thread gets a signal the bytecode evaluation loop is no longer interrupted at each bytecode instruction to check for pending signals which cannot be handled Only the main thread of the main interpreter can handle signals Previously the bytecode evaluation loop was interrupted at each instruction until the main thread handles signals bpo 39984 If Py_AddPendingCall is called in a subinterpreter the function is now scheduled to be called from the subinterpreter rather than being called from the main interpreter Each subinterpreter now has its own list of scheduled calls bpo 1635741 Port _heapq module to multiphase initialization bpo 1635741 Port itertools module to multiphase initialization PEP 489 bpo 37207 Speed up calls to frozenset by using the PEP 590 vectorcall calling convention Patch by Donghee Na bpo 39984 subinterpreters Move _PyRuntimeState ceval tracing_possible to PyInterpreterState ceval tracing_possible each interpreter now has its own variable bpo 37207 Speed up calls to set by using the PEP 590 vectorcall calling convention Patch by Donghee Na bpo 1635741 Port _statistics module to multiphase initialization PEP 489 bpo 39968 Use inline function to replace extension modules get_module_state macros bpo 39965 Correctly raise SyntaxError if await is used inside non async functions and PyCF_ALLOW_TOP_LEVEL_AWAIT is set like in the asyncio REPL Patch by Pablo Galindo bpo 39562 Allow executing asynchronous comprehensions on the top level when the PyCF_ALLOW_TOP_LEVEL_AWAIT flag is given Patch by Batuhan Taskaya bpo 37207 Speed up calls to tuple by using the PEP 590 vectorcall calling convention Patch by Donghee Na bpo 38373 Changed list overallocation strategy It no longer overallocates if the new size is closer to overallocated size than to the old size and adds padding bpo 39926 Update Unicode database to Unicode version 13 0 0 bpo 19466 Clear the frames of daemon threads earlier during the Python shutdown to call objects destructors So unclosed file resource warnings are now emitted for daemon threads in a more reliable way bpo 38894 Fix a bug that was causing incomplete results when calling pathlib Path glob in the presence of symlinks that point to files where the user does not have read access Patch by Pablo Galindo and Matt Wozniski bpo 39877 Fix PyEval_RestoreThread random crash at exit with daemon threads It now accesses the _PyRuntime variable directly instead of using tstate interp runtime since tstate can be a dangling pointer after Py_Finalize has been called Moreover the daemon thread now exits before trying to take the GIL bpo 39871 Fix a possible SystemError in math atan2 copysign remainder when the first argument cannot be converted to a float Patch by Zackery Spytz bpo 39776 Fix race condition where threads created by PyGILState_Ensure could get a duplicate id This affects consumers of tstate id like the contextvar caching machinery which could return invalid cached objects under heavy thread load observed in embedded scenarios bpo 39778 Fixed a crash due to incorrect handling of weak references in collections OrderedDict classes Patch by Pablo Galindo bpo 1635741 Port audioop extension module to multiphase initialization PEP 489 bpo 39702 Relax decorator grammar restrictions to allow any valid expression PEP 614 bpo 38091 Tweak import deadlock detection code to not deadlock itself bpo 1635741 Port _locale extension module to multiphase initialization PEP 489 bpo 39087 Optimize PyUnicode_AsUTF8 and PyUnicode_AsUTF8AndSize slightly when they need to create internal UTF 8 cache bpo 39520 Fix unparsing of ext slices with no items foo Patch by Batuhan Taskaya bpo 39220 Do not optimize annotations if from ,en
1646,__future__ import annotations is used Patch by Pablo Galindo bpo 35712 Using NotImplemented in a boolean context has been deprecated Patch contributed by Josh Rosenberg bpo 22490 Don t leak environment variable __PYVENV_LAUNCHER__ into the interpreter session on macOS Library bpo 39830 Add zipfile Path to __all__ in the zipfile module bpo 40000 Improved error messages for validation of ast Constant nodes Patch by Batuhan Taskaya bpo 39999 __module__ of the AST node classes is now set to ast instead of _ast Added docstrings for dummy AST node classes and deprecated attributes bpo 39991 uuid getnode now skips IPv6 addresses with the same string length than a MAC address 17 characters only use MAC addresses bpo 39988 Deprecated ast AugLoad and ast AugStore node classes because they are no longer used bpo 39656 Ensure bin python3 is always present in virtual environments on POSIX platforms by Anthony Sottile bpo 39969 Deprecated ast Param node class because it s no longer used Patch by Batuhan Taskaya bpo 39360 Ensure all workers exit when finalizing a multiprocessing Pool implicitly via the module finalization handlers of multiprocessing This fixes a deadlock situation that can be experienced when the Pool is not properly finalized via the context manager or a call to multiprocessing Pool terminate Patch by Batuhan Taskaya and Pablo Galindo bpo 35370 sys settrace sys setprofile and _lsprof Profiler enable now properly report PySys_Audit error if sys setprofile or sys settrace audit event is denied bpo 39936 AIX Fix _aix_support module when the subprocess is not available when building Python from scratch It now uses new private _bootsubprocess module rather than having two implementations depending if subprocess is available or not So _aix_support aix_platform result is now the same if subprocess is available or not bpo 36144 collections OrderedDict now implements and PEP 584 bpo 39652 The column name found in sqlite3 Cursor description is now truncated on the first only if the PARSE_COLNAMES option is set bpo 39915 Ensure unittest mock AsyncMock await_args_list has call objects in the order of awaited arguments instead of using unittest mock Mock call_args which has the last value of the call Patch by Karthikeyan Singaravelan bpo 36144 Updated os environ and os environb to support PEP 584 s merge and update operators bpo 38662 The ensurepip module now invokes pip via the runpy module Hence it is no longer tightly coupled with the internal API of the bundled pip version allowing easier updates to a newer pip version both internally and for distributors bpo 38075 Fix the random Random seed method when a bool is passed as the seed bpo 39916 More reliable use of os scandir in Path glob It no longer emits a ResourceWarning when interrupted bpo 39850 multiprocessing now supports abstract socket addresses if abstract sockets are supported in the running platform When creating arbitrary addresses like when default constructing multiprocessing connection Listener objects abstract sockets are preferred to avoid the case when the temporary file generated address is too large for an AF_UNIX socket address Patch by Pablo Galindo bpo 36287 ast dump no longer outputs optional fields and attributes with default values The default values for optional fields and attributes of AST nodes are now set as class attributes e g Constant kind is set to None bpo 39889 Fixed ast unparse for extended slices containing a single element e g a i j Remove redundant tuples when index with a tuple e g a i j bpo 39828 Fix json tool to catch BrokenPipeError Patch by Donghee Na bpo 13487 Avoid a possible RuntimeError dictionary changed size during iteration from inspect getmodule when it tried to loop through sys modules bpo 39674 Revert bpo 37330 open no longer accept U in file mode The U mode of open is kept in Python 3 9 to ease transition from Python 2 7 but will be removed in Python 3 10 bpo 28577 The hosts method on 32 bit prefix length IPv4Networks and 128 bit prefix IPv6Networks now returns a list containing the single Address instead of an empty list ,en
1647,bpo 39826 Add getConnection method to logging HTTPHandler to enable custom connections bpo 39763 Reimplement distutils spawn spawn function with the subprocess module bpo 39794 Add without decimal contextvar build option This enables a thread local rather than a coroutine local context bpo 36144 collections defaultdict now implements PEP 584 bpo 39517 Fix runpy run_path when using pathlike objects bpo 39775 Change inspect Signature parameters back to collections OrderedDict This was changed to dict in Python 3 9 0a4 bpo 39678 Refactor queue_manager in concurrent futures ProcessPoolExecutor to make it easier to maintain bpo 39764 Fix AttributeError when calling get_stack on a PyAsyncGenObject Task bpo 39769 The compileall compile_dir function s ddir parameter and the compileall command line flag d no longer write the wrong pathname to the generated pyc file for submodules beneath the root of the directory tree being compiled This fixes a regression introduced with Python 3 5 bpo 36144 types MappingProxyType objects now support the merge operator from PEP 584 bpo 38691 The importlib module now ignores the PYTHONCASEOK environment variable when the E or I command line options are being used bpo 39719 Remove tempfile SpooledTemporaryFile softspace as files no longer have the softspace attribute in Python 3 Patch by Shantanu bpo 39667 Improve pathlib Path compatibility on zipfile Path and correct performance degradation as found in zipp 3 0 bpo 39638 Keep ASDL signatures in the docstrings for AST nodes Patch by Batuhan Taskaya bpo 39639 Deprecated ast Suite node class because it s no longer used Patch by Batuhan Taskaya bpo 39609 Add thread_name_prefix to default asyncio executor bpo 39548 Fix handling of header in urllib request AbstractDigestAuthHandler when the optional qop parameter is not present bpo 39509 HTTP status codes 103 EARLY_HINTS and 425 TOO_EARLY are added to http HTTPStatus Patch by Donghee Na bpo 39507 Adding HTTP status 418 I m a Teapot to HTTPStatus in http library Patch by Ross Rhodes bpo 39495 Remove default value from attrs parameter of xml etree ElementTree TreeBuilder start for consistency between Python and C implementations bpo 38971 Open issue in the BPO indicated a desire to make the implementation of codecs open at parity with io open which implements a try except to assure file stream gets closed before an exception is raised bpo 38641 Added starred expressions support to return and yield statements for lib2to3 Patch by Vlad Emelianov bpo 37534 When using minidom module to generate XML documents the ability to add Standalone Document Declaration is added All the changes are made to generate a document in compliance with Extensible Markup Language XML 1 0 Fifth Edition W3C Recommendation available here https www w3 org TR xml sec prolog dtd bpo 34788 Add support for scoped IPv6 addresses to ipaddress Patch by Oleksandr Pavliuk bpo 34822 Simplified AST for subscription Simple indices are now represented by their value extended slices are represented as tuples ast classes Index and ExtSlice are considered deprecated and will be removed in future Python versions In the meantime Index value now returns a value itself ExtSlice slices returns Tuple slices Load Documentation bpo 39868 Updated the Language Reference for PEP 572 bpo 13790 Change string to specification in format doc bpo 17422 The language reference no longer restricts default class namespaces to dicts only bpo 39530 Fix misleading documentation about mixed type numeric comparisons bpo 39718 Update token documentation to reflect additions in Python 3 8 bpo 39677 Changed operand name of MAKE_FUNCTION from argc to flags for module dis Tests bpo 40019 test_gdb now skips tests if it detects that gdb failed to read debug information because the Python binary is optimized bpo 27807 test_site test_startup_imports is now skipped if a path of sys path contains a pth file bpo 26067 Do not fail test_shutil test_chown test when uid or gid of user cannot be resolved to a name bpo 39855 test_subprocess test_user now skips the test on an user name if the,en
1648, user name doesn t exist For example skip the test if the user nobody doesn t exist on Linux Build bpo 39761 Fix build with DTrace but without additional DFLAGS bpo 39763 setup py now uses a basic implementation of the subprocess module if the subprocess module is not available before required C extension modules are built bpo 1294959 Add with platlibdir option to the configure script name of the platform specific library directory stored in the new sys platlibdir attribute It is used to build the path of platform specific extension modules and the path of the standard library It is equal to lib on most platforms On Fedora and SuSE it is equal to lib64 on 64 bit platforms Patch by Jan Matějek Matěj Cepl Charalampos Stratakis and Victor Stinner Windows bpo 39930 Ensures the required vcruntime140 dll is included in install packages bpo 39847 Avoid hang when computer is hibernated whilst waiting for a mutex for lock related objects from threading around 49 day uptime bpo 38597 distutils will no longer statically link vcruntime140 dll when a redistributable version is unavailable All future releases of CPython will include a copy of this DLL to ensure distributed extensions can continue to load bpo 38380 Update Windows builds to use SQLite 3 31 1 bpo 39789 Update Windows release build machines to Visual Studio 2019 MSVC 14 2 bpo 34803 Package for nuget org now includes repository reference and bundled icon image macOS bpo 38380 Update macOS builds to use SQLite 3 31 1 IDLE bpo 27115 For Go to Line use a Query box subclass with IDLE standard behavior and improved error checking bpo 39885 Since clicking to get an IDLE context menu moves the cursor any text selection should be and now is cleared bpo 39852 Edit Go to line now clears any selection preventing accidental deletion It also updates Ln and Col on the status bar bpo 39781 Selecting code context lines no longer causes a jump Tools Demos bpo 36184 Port python gdb py to FreeBSD python gdb py now checks for take_gil function name to check if a frame tries to acquire the GIL instead of checking for pthread_cond_timedwait which is specific to Linux and can be a different condition than the GIL bpo 38080 Added support to fix getproxies in the lib2to3 fixes fix_urllib module Patch by José Roberto Meza Cabrera C API bpo 40024 Add PyModule_AddType helper function add a type to a module Patch by Donghee Na bpo 39946 Remove _PyRuntime getframe hook and remove _PyThreadState_GetFrame macro which was an alias to _PyRuntime getframe They were only exposed by the internal C API Remove also PyThreadFrameGetter type bpo 39947 Add PyThreadState_GetFrame function get the current frame of a Python thread state bpo 37207 Add _PyArg_NoKwnames helper function Patch by Donghee Na bpo 39947 Add PyThreadState_GetInterpreter get the interpreter of a Python thread state bpo 39947 Add PyInterpreterState_Get function to the limited C API bpo 35370 If PySys_Audit fails in PyEval_SetProfile or PyEval_SetTrace log the error as an unraisable exception bpo 39947 Move the static inline function flavor of Py_EnterRecursiveCall and Py_LeaveRecursiveCall to the internal C API they access PyThreadState attributes The limited C API provides regular functions which hide implementation details bpo 39947 Py_TRASHCAN_BEGIN_CONDITION and Py_TRASHCAN_END macro no longer access PyThreadState attributes but call new private _PyTrash_begin and _PyTrash_end functions which hide implementation details bpo 39884 PyDescr_NewMethod and PyCFunction_NewEx now include the method name in the SystemError bad call flags error message to ease debug bpo 39877 Deprecated PyEval_InitThreads and PyEval_ThreadsInitialized Calling PyEval_InitThreads now does nothing bpo 38249 Py_UNREACHABLE is now implemented with __builtin_unreachable and analogs in release mode bpo 38643 PyNumber_ToBase now raises a SystemError instead of crashing when called with invalid base bpo 39882 The Py_FatalError function is replaced with a macro which logs automatically the name of the current function unless the Py_LIMITED_API macro is defined bpo 39824 Exten,en
1649,sion modules m_traverse m_clear and m_free functions of PyModuleDef are no longer called if the module state was requested but is not allocated yet This is the case immediately after the module is created and before the module is executed Py_mod_exec function More precisely these functions are not called if m_size is greater than 0 and the module state as returned by PyModule_GetState is NULL Extension modules without module state m_size 0 are not affected bpo 38913 Fixed segfault in Py_BuildValue called with a format containing and undefined PY_SSIZE_T_CLEAN whwn an exception is set bpo 38500 Add a private API to get and set the frame evaluation function add _PyInterpreterState_GetEvalFrameFunc and _PyInterpreterState_SetEvalFrameFunc C functions The _PyFrameEvalFunction function type now takes a tstate parameter Python 3 9 0 alpha 4 Release date 2020 02 25 Security bpo 39184 Add audit events to functions in fcntl msvcrt os resource shutil signal and syslog bpo 39401 Avoid unsafe DLL load at startup on Windows 7 and earlier bpo 39184 Add audit events to command execution functions in os and pty modules Core and Builtins bpo 39382 Fix a use after free in the single inheritance path of issubclass when the __bases__ of an object has a single reference and so does its first item Patch by Yonatan Goldschmidt bpo 39573 Update clinic tool to use Py_IS_TYPE Patch by Donghee Na bpo 39619 Enable use of os chroot on HP UX systems bpo 39573 Add Py_IS_TYPE static inline function to check whether the object o type is type bpo 39606 Fix regression caused by fix for bpo 39386 that prevented calling aclose on an async generator that had already been closed or exhausted bpo 39579 Change the ending column offset of Attribute nodes constructed in ast_for_dotted_name to point at the end of the current node and not at the end of the last NAME node bpo 1635741 Port _crypt extension module to multiphase initialization PEP 489 bpo 1635741 Port _contextvars extension module to multiphase initialization PEP 489 bpo 39510 Fix segfault in readinto method on closed BufferedReader bpo 39502 Fix time localtime on 64 bit AIX to support years before 1902 and after 2038 Patch by M Felt bpo 39492 Fix a reference cycle in the C Pickler that was preventing the garbage collection of deleted pickled objects bpo 39453 Fixed a possible crash in list __contains__ when a list is changed during comparing items Patch by Donghee Na bpo 39434 floor division of float operation now has a better performance Also the message of ZeroDivisionError for this operation is updated Patch by Donghee Na bpo 1635741 Port _codecs extension module to multiphase initialization PEP 489 bpo 1635741 Port _bz2 extension module to multiphase initialization PEP 489 bpo 1635741 Port _abc extension module to multiphase initialization PEP 489 bpo 39320 Replace two complex bytecodes for building dicts with two simpler ones The new bytecodes DICT_MERGE and DICT_UPDATE have been added The old bytecodes BUILD_MAP_UNPACK and BUILD_MAP_UNPACK_WITH_CALL have been removed bpo 39219 Syntax errors raised in the tokenizer now always set correct text and offset attributes bpo 36051 Drop the GIL during large bytes join operations Patch by Bruce Merry bpo 38960 Fix DTrace build issues on FreeBSD Patch by David Carlier bpo 37207 Speed up calls to range by about 30 by using the PEP 590 vectorcall calling convention Patch by Mark Shannon bpo 36144 dict and collections UserDict objects now support PEP 584 s merge and update operators Patch by Brandt Bucher bpo 32856 Optimized the idiom for assignment a temporary variable in comprehensions Now for y in expr in comprehensions is as fast as a simple assignment y expr Library bpo 30566 Fix IndexError when trying to decode an invalid string with punycode codec bpo 39649 Remove obsolete check for __args__ in bdb Bdb format_stack_entry bpo 39648 Expanded math gcd and math lcm to handle multiple arguments bpo 39681 Fix a regression where the C pickle module wouldn t allow unpickling from a file like object that doesn t expose a readinto method bpo 35950 Raise io Unsup,en
1650,portedOperation in io BufferedReader truncate when it is called on a read only io BufferedReader instance bpo 39479 Add math lcm function least common multiple bpo 39674 Revert Do not expose abstract collection classes in the collections module change bpo 25988 Aliases to ABC like collections Mapping are kept in Python 3 9 to ease transition from Python 2 7 but will be removed in Python 3 10 bpo 39104 Fix hanging ProcessPoolExcutor on shutdown wait False when a task has failed pickling bpo 39627 Fixed TypedDict totality check for inherited keys bpo 39474 Fixed starting position of AST for expressions like a b a b and a b bpo 21016 The pydoc and trace modules now use the sysconfig module to get the path to the Python standard library to support uncommon installation path like usr lib64 python3 9 on Fedora Patch by Jan Matějek bpo 39590 Collections deque now holds strong references during deque __contains__ and deque count fixing crashes bpo 39586 The distutils bdist_msi command is deprecated in Python 3 9 use bdist_wheel wheel packages instead bpo 39595 Improved performance of zipfile Path for files with a large number of entries Also improved performance and fixed minor issue as published with importlib_metadata 1 5 bpo 39350 Fix regression in fractions Fraction if the numerator and or the denominator is an int subclass The math gcd function is now used to normalize the numerator and denominator math gcd always return a int type Previously the GCD type depended on numerator and denominator bpo 39567 Added audit for os walk os fwalk pathlib Path glob and pathlib Path rglob bpo 39559 Remove unused undocumented argument getters from uuid getnode bpo 38149 sys audit is now called only once per call of glob glob and glob iglob bpo 39546 Fix a regression in ArgumentParser where allow_abbrev False was ignored for long options that used a prefix character other than bpo 39450 Striped whitespace from docstring before returning it from unittest case shortDescription bpo 12915 A new function resolve_name has been added to the pkgutil module This resolves a string of the form a b c d or a b c d to an object In the example a b is a package module and c d is an object within that package module reached via recursive attribute access bpo 39353 The binascii crc_hqx function is no longer deprecated bpo 39493 Mark typing IO closed as a property bpo 39491 Add typing Annotated and include_extras parameter to typing get_type_hints as part of PEP 593 Patch by Till Varoquaux documentation by Till Varoquaux and Konstantin Kashin bpo 39485 Fix a bug in unittest mock create_autospec that would complain about the wrong number of arguments for custom descriptors defined in an extension module returning functions bpo 38932 Mock fully resets child objects on reset_mock Patch by Vegard Stikbakke bpo 39082 Allow AsyncMock to correctly patch static class methods bpo 39432 Implement PEP 489 algorithm for non ascii PyInit_ symbol names in distutils to make it export the correct init symbol also on Windows bpo 18819 Omit devmajor and devminor fields for non device files in tarfile archives enabling bit for bit compatibility with GNU tar 1 bpo 39349 Added a new cancel_futures parameter to concurrent futures Executor shutdown that cancels all pending futures which have not started running instead of waiting for them to complete before shutting down the executor bpo 39274 bool fraction Fraction now returns a boolean even if numerator 0 does not return a boolean ex numpy number bpo 34793 Remove support for with await asyncio lock and with yield from asyncio lock The same is correct for asyncio Condition and asyncio Semaphore bpo 25597 Ensure if wraps is supplied to unittest mock MagicMock it is used to calculate return values for the magic methods instead of using the default return values Patch by Karthikeyan Singaravelan bpo 36350 inspect Signature parameters and inspect BoundArguments arguments are now dicts instead of OrderedDicts Patch contributed by Rémi Lapeyre bpo 35727 Fix sys exit and sys exit None exit code propagation when used in multiprocessing P,en
1651,rocess bpo 32173 Add lazycache function to __all__ Use dict clear to clear the cache Refactoring getline function and checkcache function Documentation bpo 17422 The language reference now specifies restrictions on class namespaces Adapted from a patch by Ethan Furman bpo 39572 Updated documentation of total flag of TypedDict bpo 39654 In pyclbr doc update class to module where appropriate and add readmodule comment Patch by Hakan Çelik bpo 39153 Clarify refcounting semantics for the following functions PyObject_SetItem PyMapping_SetItemString PyDict_SetItem PyDict_SetItemString bpo 39392 Explain that when filling with turtle overlap regions may be left unfilled bpo 39369 Update mmap readline method description The fact that the readline method does update the file position should not be ignored since this might give the impression for the programmer that it doesn t update it bpo 9056 Include subsection in TOC for PDF version of docs Tests bpo 38325 Skip tests on non BMP characters of test_winconsoleio bpo 39502 Skip test_zipfile test_add_file_after_2107 if time localtime fails with OverflowError It is the case on AIX 6 1 for example Build bpo 39489 Remove COUNT_ALLOCS special build Windows bpo 39553 Delete unused code related to SxS manifests bpo 39439 Honor the Python path when a virtualenv is active on Windows bpo 39393 Improve the error message when attempting to load a DLL with unresolved dependencies bpo 38883 home and expanduser on Windows now prefer USERPROFILE and no longer use HOME which is not normally set for regular user accounts This makes them again behave like os path expanduser which was changed to ignore HOME in 3 8 see bpo 36264 bpo 39185 The build bat script has additional options for very quiet output q and very verbose output vv IDLE bpo 39663 Add tests for pyparse find_good_parse_start bpo 39600 In the font configuration window remove duplicated font names bpo 30780 Add remaining configdialog tests for buttons and highlights and keys tabs bpo 39388 IDLE Settings Cancel button now cancels pending changes bpo 38792 Close an IDLE shell calltip if a KeyboardInterrupt or shell restart occurs Patch by Zackery Spytz C API bpo 35081 Move the bytes_methods h header file to the internal C API as pycore_bytes_methods h it only contains private symbols prefixed by _Py except of the PyDoc_STRVAR_shared macro bpo 35081 Move the dtoa h header file to the internal C API as pycore_dtoa h it only contains private functions prefixed by _Py The math and cmath modules must now be compiled with the Py_BUILD_CORE macro defined bpo 39573 Add Py_SET_SIZE function to set the size of an object bpo 39500 PyUnicode_IsIdentifier does not call Py_FatalError anymore if the string is not ready bpo 39573 Add Py_SET_TYPE function to set the type of an object bpo 39573 Add a Py_SET_REFCNT function to set the reference counter of an object bpo 39542 Convert PyType_HasFeature PyType_Check and PyType_CheckExact macros to static inline functions bpo 39542 In the limited C API PyObject_INIT and PyObject_INIT_VAR are now defined as aliases to PyObject_Init and PyObject_InitVar to make their implementation opaque It avoids to leak implementation details in the limited C API Exclude the following functions from the limited C API _Py_NewReference _Py_ForgetReference _PyTraceMalloc_NewReference and _Py_GetRefTotal bpo 39542 Exclude trashcan mechanism from the limited C API it requires access to PyTypeObject and PyThreadState structure fields whereas these structures are opaque in the limited C API bpo 39511 The PyThreadState_Clear function now calls the PyThreadState on_delete callback Previously that happened in PyThreadState_Delete bpo 38076 Fix to clear the interpreter state only after clearing module globals to guarantee module state access from C Extensions during runtime destruction bpo 39245 The Vectorcall API PEP 590 was made public adding the functions PyObject_Vectorcall PyObject_VectorcallMethod PyVectorcall_Function PyObject_CallOneArg PyObject_CallMethodNoArgs PyObject_CallMethodOneArg PyObject_FastCallDict and the flag Py_TPFLAGS,en
1652,_HAVE_VECTORCALL Python 3 9 0 alpha 3 Release date 2020 01 24 Core and Builtins bpo 39427 Document all possibilities for the X options in the command line help section Patch by Pablo Galindo bpo 39421 Fix possible crashes when operating with the functions in the heapq module and custom comparison operators bpo 39386 Prevent double awaiting of async iterator bpo 17005 Add functools TopologicalSorter to the functools module to offers functionality to perform topological sorting of graphs Patch by Pablo Galindo Tim Peters and Larry Hastings bpo 39320 Replace four complex bytecodes for building sequences with three simpler ones The following four bytecodes have been removed BUILD_LIST_UNPACK BUILD_TUPLE_UNPACK BUILD_SET_UNPACK BUILD_TUPLE_UNPACK_WITH_CALL The following three bytecodes have been added LIST_TO_TUPLE LIST_EXTEND SET_UPDATE bpo 39336 Import loaders which publish immutable module objects can now publish immutable packages in addition to individual modules bpo 39322 Added a new function gc is_finalized to check if an object has been finalized by the garbage collector Patch by Pablo Galindo bpo 39048 Improve the displayed error message when incorrect types are passed to async with statements by looking up the __aenter__ special method before the __aexit__ special method when entering an asynchronous context manager Patch by Géry Ogam bpo 39235 Fix AST end location for lone generator expression in function call e g f i for i in a bpo 39209 Correctly handle multi line tokens in interactive mode Patch by Pablo Galindo bpo 1635741 Port _json extension module to multiphase initialization PEP 489 bpo 39216 Fix constant folding optimization for positional only arguments by Anthony Sottile bpo 39215 Fix SystemError when nested function has annotation on positional only argument by Anthony Sottile bpo 39200 Correct the error message when calling the min or max with no arguments Patch by Donghee Na bpo 39200 Correct the error message when trying to construct range objects with no arguments Patch by Pablo Galindo bpo 39166 Fix incorrect line execution reporting in trace functions when tracing the last iteration of asynchronous for loops Patch by Pablo Galindo bpo 39114 Fix incorrect line execution reporting in trace functions when tracing exception handlers with name binding Patch by Pablo Galindo bpo 39156 Split the COMPARE_OP bytecode instruction into four distinct instructions COMPARE_OP for rich comparisons IS_OP for is and is not tests CONTAINS_OP for in and is not tests JUMP_IF_NOT_EXC_MATCH for checking exceptions in try except statements This improves the clarity of the interpreter and should provide a modest speedup bpo 38588 Fix possible crashes in dict and list when calling PyObject_RichCompareBool bpo 13601 By default sys stderr is line buffered now even if stderr is redirected to a file You can still make sys stderr unbuffered by passing the u command line option or setting the PYTHONUNBUFFERED environment variable Contributed by Jendrik Seipp in bpo 13601 bpo 38610 Fix possible crashes in several list methods by holding strong references to list elements when calling PyObject_RichCompareBool bpo 32021 Include brotli br encoding in mimetypes encodings_map Library bpo 39430 Fixed race condition in lazy imports in tarfile bpo 39413 The os unsetenv function is now also available on Windows bpo 39390 Fixed a regression with the ignore callback of shutil copytree The argument types are now str and List str again bpo 39395 The os putenv and os unsetenv functions are now always available bpo 39406 If setenv C function is available os putenv is now implemented with setenv instead of putenv so Python doesn t have to handle the environment variable memory bpo 39396 Fix math nextafter 0 0 0 0 on AIX 7 1 bpo 29435 Allow tarfile is_tarfile to be used with file and file like objects like zipfile is_zipfile Patch by William Woodruff bpo 39377 Removed encoding option from json loads It has been deprecated since Python 3 1 bpo 39389 Write accurate compression level metadata in gzip archives rather than always signaling maximum co,en
1653,mpression bpo 39366 The previously deprecated xpath and xgtitle methods of nntplib NNTP have been removed bpo 39357 Remove the buffering parameter of bz2 BZ2File Since Python 3 0 it was ignored and using it was emitting DeprecationWarning Pass an open file object to control how the file is opened The compresslevel parameter becomes keyword only bpo 39353 Deprecate binhex4 and hexbin4 standards Deprecate the binhex module and the following binascii functions b2a_hqx a2b_hqx rlecode_hqx rledecode_hqx crc_hqx bpo 39351 Remove base64 encodestring and base64 decodestring aliases deprecated since Python 3 1 use base64 encodebytes and base64 decodebytes instead bpo 39350 Remove fractions gcd function deprecated since Python 3 5 bpo 22486 use math gcd instead bpo 39329 LMTP constructor now has an optional timeout parameter Patch by Donghee Na bpo 39313 Add a new exec_function option exec function in the CLI to RefactoringTool for making exec a function Patch by Batuhan Taskaya bpo 39259 FTP_TLS and FTP_TLS now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non blocking socket Patch by Donghee Na bpo 39259 SMTP and SMTP_SSL now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non blocking socket Patch by Donghee Na bpo 39310 Add math ulp return the value of the least significant bit of a float bpo 39297 Improved performance of importlib metadata distribution discovery and resilients to inaccessible sys path entries importlib_metadata v1 4 0 bpo 39259 NNTP and NNTP_SSL now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non blocking socket Patch by Donghee Na bpo 38901 When you specify prompt or equivalently python m venv prompt the basename of the current directory is used to set the created venv s prompt when it s activated bpo 39288 Add math nextafter return the next floating point value after x towards y bpo 39259 POP3 and POP3_SSL now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non blocking socket Patch by Donghee Na bpo 39242 Updated the Gmane domain from news gmane org to news gmane io which is used for examples of NNTP news reader server and nntplib tests bpo 35292 Proxy the SimpleHTTPRequestHandler guess_type to mimetypes guess_type so the mimetypes init is called lazily to avoid unnecessary costs when http server module is imported bpo 39239 The select epoll unregister method no longer ignores the EBADF error bpo 38907 In http server script restore binding to IPv4 on Windows bpo 39152 Fix ttk Scale configure name to return configuration tuple for name or all options Giovanni Lombardo contributed part of the patch bpo 39198 If an exception were to be thrown in Logger isEnabledFor say by asyncio timeouts or stopit the logging global lock may not be released appropriately resulting in deadlock This change wraps that block of code with try finally to ensure the lock is released bpo 39191 Perform a check for running loop before starting a new task in loop run_until_complete to fail fast it prevents the side effect of new task spawning before exception raising bpo 38871 Correctly parenthesize filter based statements that contain lambda expressions in lib2to3 Patch by Donghee Na bpo 39142 A change was made to logging config dictConfig to avoid converting instances of named tuples to ConvertingTuple It s assumed that named tuples are too specialised to be treated like ordinary tuples if a user of named tuples requires ConvertingTuple functionality they will have to implement that themselves in their named tuple class bpo 39158 ast literal_eval now supports empty sets bpo 39129 Fix import path for asyncio TimeoutError bpo 39057 urllib request proxy_bypass_environment now ignores leading dots and no longer ignores a trailing newline bpo 39056 Fixed handling invalid warning category in the W option No longer import the re module if it is not needed bpo 39055 base64 b64decode with validate True raises now a binascii Error if the,en
1654, input ends with a single n bpo 21600 Fix mock patch stopall to stop active patches that were created with mock patch dict bpo 39019 Implement dummy __class_getitem__ for tempfile SpooledTemporaryFile bpo 39019 Implement dummy __class_getitem__ for subprocess Popen subprocess CompletedProcess bpo 38914 Adjusted the wording of the warning issued by distutils check command when the author and maintainer fields are supplied but no corresponding e mail field author_email or maintainer_email is found The wording now reflects the fact that these fields are suggested but not required Patch by Juergen Gmach bpo 38878 Fixed __subclasshook__ of os PathLike to return a correct result upon inheritance Patch by Bar Harel bpo 38615 IMAP4 and IMAP4_SSL now have an optional timeout parameter for their constructors Also the open method now has an optional timeout parameter with this change The overridden methods of IMAP4_SSL and IMAP4_stream were applied to this change Patch by Donghee Na bpo 35182 Fixed Popen communicate subsequent call crash when the child process has already closed any piped standard stream but still continues to be running Patch by Andriy Maletsky bpo 38630 On Unix subprocess Popen send_signal now polls the process status Polling reduces the risk of sending a signal to the wrong process if the process completed the subprocess Popen returncode attribute is still None and the pid has been reassigned recycled to a new different process bpo 38536 Removes trailing space in formatted currency with international True and a locale with symbol following value E g locale currency 12 34 international True returned 12 34 EUR instead of 12 34 EUR bpo 38473 Use signature from inner mock for autospecced methods attached with unittest mock attach_mock Patch by Karthikeyan Singaravelan bpo 38361 Fixed an issue where ident could include a leading path separator when syslog openlog was called without arguments bpo 38293 Add copy copy and copy deepcopy support to property objects bpo 37958 Added the pstats Stats get_profile_dict method to return the profile data as a StatsProfile instance bpo 28367 Termios magic constants for the following baud rates B500000 B576000 B921600 B1000000 B1152000 B1500000 B2000000 B2500000 B3000000 B3500000 B4000000 Patch by Andrey Smirnov Documentation bpo 39381 Mention in docs that asyncio get_event_loop implicitly creates new event loop only if called from the main thread bpo 38918 Add an entry for __module__ in the function method sections of the inspect docs Types and members table bpo 3530 In the ast module documentation fix a misleading NodeTransformer example and add advice on when to use the fix_missing_locations function Build bpo 39395 On non Windows platforms the setenv and unsetenv functions are now required to build Python bpo 39160 Updated the documentation in configure help to show default values reference documentation where required and add additional explanation where needed bpo 39144 The ctags and etags build targets both include Modules _ctypes and Python standard library source files IDLE bpo 39050 Make IDLE Settings dialog Help button work again bpo 34118 Tag memoryview range and tuple as classes the same as list etcetera in the library manual built in functions list bpo 32989 Add tests for editor newline_and_indent_event method Remove dead code from pyparse find_good_parse_start method C API bpo 39372 Clean header files of interfaces defined but with no implementation The public API symbols being removed are _PyBytes_InsertThousandsGroupingLocale _PyBytes_InsertThousandsGrouping _Py_InitializeFromArgs _Py_InitializeFromWideArgs _PyFloat_Repr _PyFloat_Digits _PyFloat_DigitsInit PyFrame_ExtendStack _PyAIterWrapper_Type PyNullImporter_Type PyCmpWrapper_Type PySortWrapper_Type PyNoArgsFunction bpo 39164 Add a private _PyErr_GetExcInfo function to retrieve exception information of the specified Python thread state Python 3 9 0 alpha 2 Release date 2019 12 18 Security bpo 38945 Newline characters have been escaped when performing uu encoding to prevent them from overflowing into to content ,en
1655,section of the encoded file This prevents malicious or accidental modification of data during the decoding process bpo 37228 Due to significant security concerns the reuse_address parameter of asyncio loop create_datagram_endpoint is no longer supported This is because of the behavior of SO_REUSEADDR in UDP For more details see the documentation for loop create_datagram_endpoint Contributed by Kyle Stanley Antoine Pitrou and Yury Selivanov in bpo 37228 bpo 38804 Fixes a ReDoS vulnerability in http cookiejar Patch by Ben Caller Core and Builtins bpo 39028 Slightly improve the speed of keyword argument parsing with many kwargs by strengthening the assumption that kwargs are interned strings bpo 39080 Fix the value of end_col_offset for Starred Expression AST nodes when they are among the elements in the args attribute of Call AST nodes bpo 39031 When parsing an elif node lineno and col_offset of the node now point to the elif keyword and not to its condition making it consistent with the if node Patch by Lysandros Nikolaou bpo 20443 In Python 3 9 0a1 sys argv 0 was made an absolute path if a filename was specified on the command line Revert this change since most users expect sys argv to be unmodified bpo 39008 PySys_Audit now requires Py_ssize_t to be used for size arguments in the format string regardless of whether PY_SSIZE_T_CLEAN was defined at include time bpo 38673 In REPL mode don t switch to PS2 if the line starts with comment or whitespace Based on work by Batuhan Taşkaya bpo 38922 Calling replace on a code object now raises the code __new__ audit event bpo 38920 Add audit hooks for when sys excepthook and sys unraisablehook are invoked bpo 38892 Improve documentation for audit events table and functions bpo 38852 Set the thread stack size to 8 Mb for debug builds on android platforms bpo 38858 Each Python subinterpreter now has its own small integer singletons numbers in 5 257 range It is no longer possible to change the number of small integers at build time by overriding NSMALLNEGINTS and NSMALLPOSINTS macros macros should now be modified manually in pycore_pystate h header file bpo 36854 The garbage collector state becomes per interpreter PyInterpreterState gc rather than being global _PyRuntimeState gc bpo 38835 The PyFPE_START_PROTECT and PyFPE_END_PROTECT macros are empty they have been doing nothing for the last year so stop using them bpo 38328 Sped up the creation time of constant list and set displays Patch by Brandt Bucher bpo 38707 MainThread native_id is now correctly reset in child processes spawned using multiprocessing Process instead of retaining the parent s value bpo 38629 Added __floor__ and __ceil__ methods to float object Patch by Batuhan Taşkaya bpo 27145 int int and int int operators can now return small integer singletons Patch by hongweipeng bpo 38021 Provide a platform tag for AIX that is sufficient for PEP425 binary distribution identification Patch by Michael Felt bpo 35409 Ignore GeneratorExit exceptions when throwing an exception into the aclose coroutine of an asynchronous generator bpo 33387 Removed WITH_CLEANUP_START WITH_CLEANUP_FINISH BEGIN_FINALLY END_FINALLY CALL_FINALLY and POP_FINALLY bytecodes Replaced with RERAISE and WITH_EXCEPT_START bytecodes The compiler now generates different code for exceptional and non exceptional branches for with and try except statements For try finally statements the finally block is replicated for each exit from the try body Library bpo 39033 Fix NameError in zipimport Patch by Karthikeyan Singaravelan bpo 39022 Update importlib metadata to include improvements from importlib_metadata 1 3 including better serialization of EntryPoints and improved documentation for custom finders bpo 39006 Fix asyncio when the ssl module is missing only check for ssl SSLSocket instance if the ssl module is available bpo 38708 Fix a potential IndexError in email parser when parsing an empty msg id bpo 38698 Add a new InvalidMessageID token to email parser to represent invalid Message ID headers Also add defects when there is remaining value after parsing the h,en
1656,eader bpo 38994 Implement __class_getitem__ for os PathLike pathlib Path bpo 38979 Return class from ContextVar __class_getitem__ to simplify subclassing bpo 38978 Implement __class_getitem__ on asyncio objects Future Task Queue Patch by Batuhan Taskaya bpo 38916 array array Remove tostring and fromstring methods They were aliases to tobytes and frombytes deprecated since Python 3 2 bpo 38986 Make repr of C accelerated TaskWakeupMethWrapper the same as of pure Python version bpo 38982 Fix asyncio PidfdChildWatcher handle waitpid error If waitpid is called elsewhere waitpid call fails with ChildProcessError use return code 255 in this case and log a warning It ensures that the pidfd file descriptor is closed if this error occurs bpo 38529 Drop too noisy asyncio warning about deletion of a stream without explicit close call bpo 27413 Added ability to pass through ensure_ascii options to json dumps in the json tool command line interface bpo 38634 The readline module now detects if Python is linked to libedit at runtime on all platforms Previously the check was only done on macOS bpo 33684 Fix json tool failed to read a JSON file with non ASCII characters when locale encoding is not UTF 8 bpo 38698 Prevent UnboundLocalError to pop up in parse_message_id parse_message_id was improperly using a token defined inside an exception handler which was raising UnboundLocalError on parsing an invalid value Patch by Claudiu Popa bpo 38927 Use python m pip instead of pip to upgrade dependencies in venv bpo 26730 Fix SpooledTemporaryFile rollover might corrupt the file when it is in text mode Patch by Serhiy Storchaka bpo 38881 random choices now raises a ValueError when all the weights are zero bpo 38876 Raise pickle UnpicklingError when loading an item from memo for invalid input The previous code was raising a KeyError for both the Python and C implementation This was caused by the specified index of an invalid input which did not exist in the memo structure where the pickle stores what objects it has seen The malformed input would have caused either a BINGET or LONG_BINGET load from the memo leading to a KeyError as the determined index was bogus Patch by Claudiu Popa bpo 38688 Calling func shutil copytree to copy a directory tree from one directory to another subdirectory resulted in an endless loop and a RecursionError A fix was added to consume an iterator and create the list of the entries to be copied avoiding the recursion for newly created directories Patch by Bruno P Kinoshita bpo 38863 Improve is_cgi function in http server which enables processing the case that cgi directory is a child of another directory other than root bpo 37838 typing get_type_hints properly handles functions decorated with functools wraps bpo 38870 Expose ast unparse as a function of the ast module that can be used to unparse an ast AST object and produce a string with code that would produce an equivalent ast AST object when parsed Patch by Pablo Galindo and Batuhan Taskaya bpo 38859 AsyncMock now returns StopAsyncIteration on the exhaustion of a side_effects iterable Since PEP 479 its Impossible to raise a StopIteration exception from a coroutine bpo 38857 AsyncMock fix for return values that are awaitable types This also covers side_effect iterable values that happened to be awaitable and wraps callables that return an awaitable type Before these awaitables were being awaited instead of being returned as is bpo 38834 typing TypedDict subclasses now track which keys are optional using the __required_keys__ and __optional_keys__ attributes to enable runtime validation by downstream projects Patch by Zac Hatfield Dodds bpo 38821 Fix unhandled exceptions in argparse when internationalizing error messages for arguments with nargs set to special non integer values Patch by Federico Bond bpo 38820 Make Python compatible with OpenSSL 3 0 0 ssl SSLSocket getpeercert no longer returns IPv6 addresses with a trailing new line bpo 38811 Fix an unhandled exception in pathlib when os link is missing Patch by Toke Høiland Jørgensen bpo 38686 Added support for mult,en
1657,iple qop values in urllib request AbstractDigestAuthHandler bpo 38712 Add the Linux specific signal pidfd_send_signal function which allows sending a signal to a process identified by a file descriptor rather than a pid bpo 38348 Add i and indent indentation level and no type comments type comments command line options to ast parsing tool bpo 37523 Change zipfile ZipExtFile to raise ValueError when trying to access the underlying file object after it has been closed This new behavior is consistent with how accessing closed files is handled in other parts of Python bpo 38045 Improve the performance of enum _decompose in enum Patch by hongweipeng bpo 36820 Break cycle generated when saving an exception in socket py codeop py and dyld py as they keep alive not only the exception but user objects through the __traceback__ attribute Patch by Mario Corchero bpo 36406 Handle namespace packages in doctest Patch by Karthikeyan Singaravelan bpo 34776 Fix dataclasses to support forward references in type annotations bpo 20928 ElementTree supports recursive XInclude processing Patch by Stefan Behnel bpo 29636 Add whitespace options for formatting JSON with the json tool CLI The following mutually exclusive options are now supported indent for setting the indent level in spaces tab for indenting with tabs no indent for suppressing newlines and compact for suppressing all whitespace The default behavior remains the same as indent 4 Documentation bpo 38928 Correct when venv s upgrade_dependencies and upgrade deps are added bpo 38899 Update documentation to state that to activate virtual environments under fish one should use source not as documented at https fishshell com docs current cmds source html bpo 22377 Improves documentation of the values that datetime datetime strptime accepts for Z Patch by Karl Dubost Tests bpo 38546 Fix test_ressources_gced_in_workers of test_concurrent_futures explicitly stop the manager to prevent leaking a child process running in the background after the test completes bpo 38546 Multiprocessing and concurrent futures tests now stop the resource tracker process when tests complete bpo 38614 Replace hardcoded timeout constants in tests with new test support constants LOOPBACK_TIMEOUT INTERNET_TIMEOUT SHORT_TIMEOUT and LONG_TIMEOUT It becomes easier to adjust these four timeout constants for all tests at once rather than having to adjust every single test file bpo 38547 Fix test_pty if the process is the session leader closing the master file descriptor raises a SIGHUP signal simply ignore SIGHUP when running the tests bpo 38992 Fix a test for math fsum that was failing due to constant folding bpo 38991 test support run_python_until_end assert_python_ok and assert_python_failure functions no longer strip whitespaces from stderr Remove test support strip_python_stderr function bpo 38965 Fix test_faulthandler on GCC 10 Use the volatile keyword in faulthandler _stack_overflow to prevent tail call optimization on any compiler rather than relying on compiler specific pragma bpo 38875 test_capi trashcan tests now require the test cpu resource bpo 38841 Skip asyncio test_create_datagram_endpoint_existing_sock_unix on platforms lacking a functional bind for named unix domain sockets bpo 38692 Skip the test_posix test_pidfd_open test if os pidfd_open fails with a PermissionError This situation can happen in a Linux sandbox using a syscall whitelist which doesn t allow the pidfd_open syscall yet bpo 38839 Fix some unused functions in tests Patch by Adam Johnson bpo 38669 Raise TypeError when passing target as a string with unittest mock patch object bpo 37957 test regrtest now can receive a list of test patterns to ignore using the i ignore argument or a file with a list of patterns to ignore using the ignore file argument Patch by Pablo Galindo Build bpo 37404 asyncio now raises TyperError when calling incompatible methods with an ssl SSLSocket socket Patch by Ido Michael bpo 36500 Added an optional regen project to the Visual Studio solution that will regenerate all grammar tokens and opcodes Windows bpo 39007 Ad,en
1658,d auditing events to functions in winreg bpo 33125 Add support for building and releasing Windows ARM64 packages macOS bpo 37931 Fixed a crash on OSX dynamic builds that occurred when re initializing the posix module after a Py_Finalize if the environment had changed since the previous import posix Patch by Benoît Hudson IDLE bpo 38944 Escape key now closes IDLE completion windows Patch by Johnny Najera bpo 38943 Fix IDLE autocomplete windows not always appearing on some systems Patch by Johnny Najera bpo 38862 Strip Trailing Whitespace on the Format menu removes extra newlines at the end of non shell files bpo 38636 Fix IDLE Format menu tab toggle and file indent width These functions default shortcuts Alt T and Alt U were mistakenly disabled in 3 7 5 and 3 8 0 C API bpo 38896 Remove PyUnicode_ClearFreeList function the Unicode free list has been removed in Python 3 3 bpo 37340 Remove PyMethod_ClearFreeList and PyCFunction_ClearFreeList functions the free lists of bound method objects have been removed bpo 38835 Exclude PyFPE_START_PROTECT and PyFPE_END_PROTECT macros of pyfpe h from Py_LIMITED_API stable API Python 3 9 0 alpha 1 Release date 2019 11 19 Security bpo 38722 runpy now uses io open_code to open code files Patch by Jason Killen bpo 38622 Add additional audit events for the ctypes module bpo 38418 Fixes audit event for os system to be named os system bpo 38243 Escape the server title of xmlrpc server DocXMLRPCServer when rendering the document page as HTML Contributed by Donghee Na in bpo 38243 bpo 38174 Update vendorized expat library version to 2 2 8 which resolves CVE 2019 15903 bpo 37764 Fixes email _header_value_parser get_unstructured going into an infinite loop for a specific case in which the email header does not have trailing whitespace and the case in which it contains an invalid encoded word Patch by Ashwin Ramaswami bpo 37461 Fix an infinite loop when parsing specially crafted email headers Patch by Abhilash Raj bpo 37363 Adds audit events for the range of supported run commands see Command line and environment bpo 37463 ssl match_hostname no longer accepts IPv4 addresses with additional text after the address and only quad dotted notation without trailing whitespaces Some inet_aton implementations ignore whitespace and all data after whitespace e g 127 0 0 1 whatever bpo 37363 Adds audit events for ensurepip ftplib glob imaplib nntplib pdb poplib shutil smtplib sqlite3 subprocess telnetlib tempfile and webbrowser as well as os listdir os scandir and breakpoint bpo 37364 io open_code is now used when reading pth files bpo 34631 Updated OpenSSL to 1 1 1c in Windows installer bpo 34155 Fix parsing of invalid email addresses with more than one e g a b c com to not return the part before 2nd as valid email address Patch by maxking jpic Core and Builtins bpo 38631 Replace Py_FatalError call with a regular RuntimeError exception in float __getformat__ bpo 38639 Optimized math floor math ceil and math trunc for floats bpo 38640 Fixed a bug in the compiler that was causing to raise in the presence of break statements and continue statements inside always false while loops Patch by Pablo Galindo bpo 38613 Optimized some set operations e g and of dict_keys d keys other was slower than set d other but they are almost same performance for now bpo 28029 replace s n now returns s instead of an empty string for all non zero n There are similar changes for bytes and bytearray objects bpo 38535 Fixed line numbers and column offsets for AST nodes for calls without arguments in decorators bpo 38525 Fix a segmentation fault when using reverse iterators of empty dict objects Patch by Donghee Na and Inada Naoki bpo 38465 bytearray array and mmap objects allow now to export more than 2 31 buffers at a time bpo 38469 Fixed a bug where the scope of named expressions was not being resolved correctly in the presence of the global keyword Patch by Pablo Galindo bpo 38437 Activate the GC_DEBUG macro for debug builds of the interpreter when Py_DEBUG is set Patch by Pablo Galindo bpo 38379 When the garbage collector makes a co,en
1659,llection in which some objects resurrect they are reachable from outside the isolated cycles after the finalizers have been executed do not block the collection of all objects that are still unreachable Patch by Pablo Galindo and Tim Peters bpo 38379 When cyclic garbage collection gc runs finalizers that resurrect unreachable objects the current gc run ends without collecting any cyclic trash However the statistics reported by collect and get_stats claimed that all cyclic trash found was collected and that the resurrected objects were collected Changed the stats to report that none were collected bpo 38392 In debug mode PyObject_GC_Track now calls tp_traverse of the object type to ensure that the object is valid test that objects visited by tp_traverse are valid bpo 38210 Remove unnecessary intersection and update set operation in dictview with empty set Contributed by Donghee Na in bpo 38210 bpo 38402 Check the error from the system s underlying crypt or crypt_r bpo 37474 On FreeBSD Python no longer calls fedisableexcept at startup to control the floating point control mode The call became useless since FreeBSD 6 it became the default mode bpo 38006 Fix a bug due to the interaction of weakrefs and the cyclic garbage collector We must clear any weakrefs in garbage in order to prevent their callbacks from executing and causing a crash bpo 38317 Fix warnings options priority PyConfig warnoptions has the highest priority as stated in the PEP 587 bpo 38310 Predict BUILD_MAP_UNPACK_WITH_CALL CALL_FUNCTION_EX opcode pairs in the main interpreter loop Patch by Brandt Bucher bpo 36871 Improve error handling for the assert_has_calls and assert_has_awaits methods of mocks Fixed a bug where any errors encountered while binding the expected calls to the mock s spec were silently swallowed leading to misleading error output bpo 11410 Better control over symbol visibility is provided through use of the visibility attributes available in gcc 4 0 provided in a uniform way across POSIX and Windows The POSIX build files have been updated to compile with fvisibility hidden minimising exported symbols bpo 38219 Optimized the dict constructor and the update method for the case when the argument is a dict bpo 38236 Python now dumps path configuration if it fails to import the Python codecs of the filesystem and stdio encodings bpo 38013 Allow to call async_generator_athrow throw even for non started async generator helper It fixes annoying warning at the end of asyncio run call bpo 38124 Fix an off by one error in PyState_AddModule that could cause out of bounds memory access bpo 38116 The select module is now PEP 384 compliant and no longer has static state bpo 38113 ast module updated to PEP 384 and all statics removed bpo 38076 The struct module is now PEP 384 compatible bpo 38075 The random module is now PEP 384 compatible bpo 38074 zlib module made PEP 384 compatible bpo 38073 Make pwd extension module PEP 384 compatible bpo 38072 grp module made PEP 384 compatible bpo 38069 Make _posixsubprocess PEP 384 compatible bpo 38071 Make termios extension module PEP 384 compatible bpo 38005 Fixed comparing and creating of InterpreterID and ChannelID bpo 36946 Fix possible signed integer overflow when handling slices Patch by hongweipeng bpo 37994 Fixed silencing arbitrary errors if an attribute lookup fails in several sites Only AttributeError should be silenced bpo 8425 Optimize set difference_update for the case when the other set is much larger than the base set Suggested by Evgeny Kapun with code contributed by Michele Orrù bpo 37966 The implementation of is_normalized has been greatly sped up on strings that aren t normalized by implementing the full normalization quick check algorithm from the Unicode standard bpo 37947 Adjust correctly the recursion level in the symtable generation for named expressions Patch by Pablo Galindo bpo 37812 The CHECK_SMALL_INT macro used inside Object longobject c has been replaced with an explicit return at each call site bpo 37751 Fix codecs lookup to normalize the encoding name the same way than encodings n,en
1660,ormalize_encoding except that codecs lookup also converts the name to lower case bpo 37830 Fixed compilation of break and continue in the finally block when the corresponding try block contains return with a non constant value bpo 20490 Improve import error message for partially initialized module on circular from imports by Anthony Sottile bpo 37840 Fix handling of negative indices in sq_item of bytearray Patch by Sergey Fedoseev bpo 37802 Slightly improve performance of PyLong_FromUnsignedLong PyLong_FromUnsignedLongLong and PyLong_FromSize_t Patch by Sergey Fedoseev bpo 37409 Ensure explicit relative imports from interactive sessions and scripts having no parent package always raise ImportError rather than treating the current module as the package Patch by Ben Lewis bpo 32912 Reverted bpo 32912 emitting SyntaxWarning instead of DeprecationWarning for invalid escape sequences in string and bytes literals bpo 37757 PEP 572 As described in the PEP assignment expressions now raise SyntaxError when their interaction with comprehension scoping results in an ambiguous target scope The TargetScopeError subclass originally proposed by the PEP has been removed in favour of just raising regular syntax errors for the disallowed cases bpo 36279 Fix potential use of uninitialized memory in os wait3 bpo 36311 Decoding bytes objects larger than 2GiB is faster and no longer fails when a multibyte characters spans a chunk boundary bpo 34880 The assert statement now works properly if the AssertionError exception is being shadowed Patch by Zackery Spytz bpo 37340 Removed object cache free_list for bound method objects Temporary bound method objects are less used than before thanks to the LOAD_METHOD opcode and the _PyObject_VectorcallMethod C API bpo 37648 Fixed minor inconsistency in list __contains__ tuple __contains__ and a few other places The collection s item is now always at the left and the needle is on the right of bpo 37444 Update differing exception between builtins __import__ and importlib __import__ bpo 37619 When adding a wrapper descriptor from one class to a different class for example setting __add__ str __add__ on an int subclass an exception is correctly raised when the operator is called bpo 37593 Swap the positions of the posonlyargs and args parameters in the constructor of ast parameters nodes bpo 37543 Optimized pymalloc for non PGO build bpo 37537 Compute allocated pymalloc blocks inside _Py_GetAllocatedBlocks This slows down _Py_GetAllocatedBlocks but gives a small speedup to _PyObject_Malloc and _PyObject_Free bpo 37467 Fix sys excepthook and PyErr_Display if a filename is a bytes string For example for a SyntaxError exception where the filename attribute is a bytes string bpo 37433 Fix SyntaxError indicator printing too many spaces for multi line strings by Anthony Sottile bpo 37417 bytearray extend now correctly handles errors that arise during iteration Patch by Brandt Bucher bpo 37414 The undocumented sys callstats function has been removed Since Python 3 7 it was deprecated and always returned None It required a special build option CALL_PROFILE which was already removed in Python 3 7 bpo 37392 Remove sys getcheckinterval and sys setcheckinterval functions They were deprecated since Python 3 2 Use sys getswitchinterval and sys setswitchinterval instead Remove also check_interval field of the PyInterpreterState structure bpo 37388 In development mode and in debug build encoding and errors arguments are now checked on string encoding and decoding operations Examples open str encode and bytes decode By default for best performances the errors argument is only checked at the first encoding decoding error and the encoding argument is sometimes ignored for empty strings bpo 37348 Optimized decoding short ASCII string with UTF 8 and ascii codecs b foo decode is about 15 faster Patch by Inada Naoki bpo 24214 Improved support of the surrogatepass error handler in the UTF 8 and UTF 16 incremental decoders bpo 37330 open io open codecs open and fileinput FileInput no longer accept U universal newline in the file mod,en
1661,e This flag was deprecated since Python 3 3 bpo 35224 Reverse evaluation order of key value in dict comprehensions as proposed in PEP 572 I e in k v for k will be evaluated before v bpo 37316 Fix the PySys_Audit call in mmap mmap bpo 37300 Remove an unnecessary Py_XINCREF in classobject c bpo 37269 Fix a bug in the peephole optimizer that was not treating correctly constant conditions with binary operators Patch by Pablo Galindo bpo 20443 Python now gets the absolute path of the script filename specified on the command line ex python3 script py the __file__ attribute of the __main__ module and sys path 0 become an absolute path rather than a relative path bpo 37257 Python s small object allocator obmalloc c now allows no more than one empty arena to remain available for immediate reuse without returning it to the OS This prevents thrashing in simple loops where an arena could be created and destroyed anew on each iteration bpo 37231 The dispatching of type slots to special methods for example calling __mul__ when doing x y has been made faster bpo 36974 Implemented separate vectorcall functions for every calling convention of builtin functions and methods This improves performance for calls bpo 37213 Handle correctly negative line offsets in the peephole optimizer Patch by Pablo Galindo bpo 37219 Remove erroneous optimization for empty set differences bpo 15913 Implement PyBuffer_SizeFromFormat function previously documented but not implemented call struct calcsize Patch by Joannah Nanjekye bpo 36922 Slot functions optimize any callable with Py_TPFLAGS_METHOD_DESCRIPTOR instead of only instances of function bpo 36974 The slot tp_vectorcall_offset is inherited unconditionally to support super __call__ when the base class uses vectorcall bpo 37160 threading get_native_id now also supports NetBSD bpo 37077 Add threading get_native_id support for AIX Patch by M Felt bpo 36781 sum has been optimized for boolean values bpo 34556 Add upgrade deps to venv module Patch by Cooper Ry Lees bpo 20523 pdb Pdb supports pdbrc in Windows 7 Patch by Tim Hopper and Dan Lidral Porter bpo 35551 Updated encodings Removed the tis260 encoding which was an alias for the nonexistent tactis codec Added mac_centeuro as an alias for the mac_latin2 encoding bpo 19072 The classmethod decorator can now wrap other descriptors such as property objects Adapted from a patch written by Graham Dumpleton bpo 27575 Improve speed of dictview intersection by directly using set intersection logic Patch by David Su bpo 30773 Prohibit parallel running of aclose asend athrow Fix ag_running to reflect the actual running status of the AG Library bpo 36589 The curses update_lines_cols function now returns None instead of 1 on success bpo 38807 Update TypeError messages for os path join to include os PathLike objects as acceptable input types bpo 38724 Add a repr for subprocess Popen objects Patch by Andrey Doroschenko bpo 38786 pydoc now recognizes and parses HTTPS URLs Patch by python273 bpo 38785 Prevent asyncio from crashing if parent __init__ is not called from a constructor of object derived from asyncio Future bpo 38723 pdb now uses io open_code to trigger auditing events bpo 27805 Allow opening pipes and other non seekable files in append mode with open bpo 38438 Simplify the argparse usage message for nargs bpo 38761 WeakSet is now registered as a collections abc MutableSet bpo 38716 logging change RotatingHandler namer and rotator to class level attributes This stops __init__ from setting them to None in the case where a subclass defines them with eponymous methods bpo 38713 Add os P_PIDFD constant which may be passed to os waitid to wait on a Linux process file descriptor bpo 38692 Add asyncio PidfdChildWatcher a Linux specific child watcher implementation that polls process file descriptors bpo 38692 Expose the Linux pidfd_open syscall as os pidfd_open bpo 38602 Added constants F_OFD_GETLK F_OFD_SETLK and F_OFD_SETLKW to the fcntl module Patch by Donghee Na bpo 38334 Fixed seeking backward on an encrypted zipfile ZipExtFile bpo 38312 Add curses get_escdelay ,en
1662,curses set_escdelay curses get_tabsize and curses set_tabsize functions by Anthony Sottile bpo 38586 Now fileConfig correctly sets the name of handlers loaded bpo 38565 Add new cache_parameters method for functools lru_cache to better support pickling bpo 34679 asynci ProactorEventLoop close now only calls signal set_wakeup_fd in the main thread bpo 31202 The case the result of pathlib WindowsPath glob matches now the case of the pattern for literal parts bpo 36321 Remove misspelled attribute The 3 8 changelog noted that this would be removed in 3 9 bpo 38521 Fixed erroneous equality comparison in statistics NormalDist bpo 38493 Added CLD_KILLED and CLD_STOPPED for si_code Patch by Donghee Na bpo 38478 Fixed a bug in inspect signature bind that was causing it to fail when handling a keyword argument with same name as positional only parameter Patch by Pablo Galindo bpo 33604 Fixed hmac new and hmac HMAC to raise TypeError instead of ValueError when the digestmod parameter now required in 3 8 is omitted Also clarified the hmac module documentation and docstrings bpo 38378 Parameters out and in of os sendfile was renamed to out_fd and in_fd bpo 38417 Added support for setting the umask in the child process to the subprocess module on POSIX systems bpo 38449 Revert PR 15522 which introduces a regression in mimetypes guess_type due to improper handling of filenames as urls bpo 38431 Fix __repr__ method for dataclasses InitVar to support typing objects patch by Samuel Colvin bpo 38109 Add missing stat S_IFDOOR stat S_IFPORT stat S_IFWHT stat S_ISDOOR stat S_ISPORT and stat S_ISWHT values to the Python implementation of stat bpo 38422 Clarify docstrings of pathlib suffix es bpo 38405 Nested subclasses of typing NamedTuple are now pickleable bpo 38332 Prevent KeyError thrown by _encoded_words decode when given an encoded word with invalid content type encoding from propagating all the way to email message get bpo 38371 Deprecated the split method in _tkinter TkappType in favour of the splitlist method which has more consistent and predicable behavior bpo 38341 Add smtplib SMTPNotSupportedError to the smtplib exported names bpo 38319 sendfile used in socket and shutil modules was raising OverflowError for files 2GiB on 32 bit architectures patch by Giampaolo Rodola bpo 38242 Revert the new asyncio Streams API bpo 13153 OS native encoding is now used for converting between Python strings and Tcl objects This allows to display copy and paste to clipboard emoji and other non BMP characters Converting strings from Tcl to Python and back now never fails except MemoryError bpo 38019 Correctly handle pause resume reading of closed asyncio unix pipe bpo 38163 Child mocks will now detect their type as either synchronous or asynchronous asynchronous child mocks will be AsyncMocks and synchronous child mocks will be either MagicMock or Mock depending on their parent type bpo 38161 Removes _AwaitEvent from AsyncMock bpo 38216 Allow the rare code that wants to send invalid http requests from the http client library a way to do so The fixes for bpo 30458 led to breakage for some projects that were relying on this ability to test their own behavior in the face of bad requests bpo 28286 Deprecate opening GzipFile for writing implicitly Always specify the mode argument for writing bpo 38108 Any synchronous magic methods on an AsyncMock now return a MagicMock Any asynchronous magic methods on a MagicMock now return an AsyncMock bpo 38265 Update the length parameter of os pread to accept Py_ssize_t instead of int bpo 38112 compileall has a higher default recursion limit and new command line arguments for path manipulation symlinks handling and multiple optimization levels bpo 38248 asyncio Fix inconsistent immediate Task cancellation bpo 38237 The arguments for the builtin pow function are more descriptive They can now also be passed in as keywords bpo 34002 Improve efficiency in parts of email package by changing while pop to a for loop using isdisjoint instead of set intersections bpo 38191 Constructors of NamedTuple and TypedDict types now acce,en
1663,pt arbitrary keyword argument names including cls self typename _typename fields and _fields bpo 38155 Add __all__ to datetime Patch by Tahia Khan bpo 38185 Fixed case insensitive string comparison in sqlite3 Row indexing bpo 38136 Changes AsyncMock call count and await count to be two different counters Now await count only counts when a coroutine has been awaited not when it has been called and vice versa Update the documentation around this bpo 37828 Fix default mock name in unittest mock Mock assert_called exceptions Patch by Abraham Toriz Cruz bpo 38175 Fix a memory leak in comparison of sqlite3 Row objects bpo 33936 _hashlib no longer calls obsolete OpenSSL initialization function with OpenSSL 1 1 0 bpo 34706 Preserve subclassing in inspect Signature from_callable bpo 38153 Names of hashing algorithms from OpenSSL are now normalized to follow Python s naming conventions For example OpenSSL uses sha3 512 instead of sha3_512 or blake2b512 instead of blake2b bpo 38115 Fix a bug in dis findlinestarts where it would return invalid bytecode offsets Document that a code object s co_lnotab can contain invalid bytecode offsets bpo 38148 Add slots to asyncio transport classes which can reduce memory usage bpo 38142 The _hashlib OpenSSL wrapper extension module is now PEP 384 compliant bpo 9216 hashlib constructors now support usedforsecurity flag to signal that a hashing algorithm is not used in a security context bpo 36991 Fixes a potential incorrect AttributeError exception escaping ZipFile extract in some unsupported input error situations bpo 38134 Remove obsolete copy of PBKDF2_HMAC_fast All supported OpenSSL versions contain a fast implementation bpo 38132 The OpenSSL hashlib wrapper uses a simpler implementation Several Macros and pointless caches are gone The hash name now comes from OpenSSL s EVP The algorithm name stays the same except it is now always lower case bpo 38008 Fix parent class check in protocols to correctly identify the module that provides a builtin protocol instead of assuming they all come from the collections abc module bpo 34037 For asyncio add a new coroutine loop shutdown_default_executor The new coroutine provides an API to schedule an executor shutdown that waits on the threadpool to finish closing Also asyncio run has been updated to utilize the new coroutine Patch by Kyle Stanley bpo 37405 Fixed regression bug for socket getsockname for non CAN_ISOTP AF_CAN address family sockets by returning a 1 tuple instead of string bpo 38121 Update parameter names on functions in importlib metadata matching the changes in the 0 22 release of importlib_metadata bpo 38110 The os closewalk implementation now uses the libc fdwalk API on platforms where it is available bpo 38093 Fixes AsyncMock so it doesn t crash when used with AsyncContextManagers or AsyncIterators bpo 37488 Add warning to datetime utctimetuple datetime utcnow and datetime utcfromtimestamp bpo 35640 Allow passing a path like object as directory argument to the http server SimpleHTTPRequestHandler class Patch by Géry Ogam bpo 38086 Update importlib metadata with changes from importlib_metadata 0 21 bpo 37251 Remove __code__ check in AsyncMock that incorrectly evaluated function specs as async objects but failed to evaluate classes with __await__ but no __code__ attribute defined as async objects bpo 38037 Fix reference counters in the signal module bpo 38066 Hide internal asyncio Stream methods feed_eof feed_data set_exception and set_transport bpo 38059 inspect py now uses sys exit instead of exit bpo 38049 Added command line interface for the ast module bpo 37953 In typing improved the __hash__ and __eq__ methods for ForwardReferences bpo 38026 Fixed inspect getattr_static used isinstance while it should avoid dynamic lookup bpo 35923 Update importlib machinery BuiltinImporter to use loader _ORIGIN instead of a hardcoded value Patch by Donghee Na bpo 38010 In importlib metadata sync with importlib_metadata 0 20 clarifying behavior of files and fixing issue where only one requirement was returned for requires on dist info packages bpo 380,en
1664,06 weakref WeakValueDictionary defines a local remove function used as callback for weak references This function was created with a closure Modify the implementation to avoid the closure bpo 37995 Added the indent option to ast dump which allows it to produce a multiline indented output bpo 34410 Fixed a crash in the tee iterator when re enter it RuntimeError is now raised in this case bpo 37140 Fix a ctypes regression of Python 3 8 When a ctypes Structure is passed by copy to a function ctypes internals created a temporary object which had the side effect of calling the structure finalizer __del__ twice The Python semantics requires a finalizer to be called exactly once Fix ctypes internals to no longer call the finalizer twice bpo 37587 _json scanstring is now up to 3x faster when there are many backslash escaped characters in the JSON string bpo 37834 Prevent shutil rmtree exception when built on non Windows system without fd system call support like older versions of macOS bpo 10978 Semaphores and BoundedSemaphores can now release more than one waiting thread at a time bpo 37972 Subscripts to the unittest mock call objects now receive the same chaining mechanism as any other custom attributes so that the following usage no longer raises a TypeError call foo __getitem__ bar Patch by blhsing bpo 37965 Fix C compiler warning caused by distutils ccompiler CCompiler has_function bpo 37964 Add F_GETPATH command to fcntl bpo 37960 repr of buffered and text streams now silences only expected exceptions when get the value of name and mode attributes bpo 37961 Add a total_nframe field to the traces collected by the tracemalloc module This field indicates the original number of frames before it was truncated bpo 37951 Most features of the subprocess module now work again in subinterpreters Only preexec_fn is restricted in subinterpreters bpo 36205 Fix the rusage implementation of time process_time to correctly report the sum of the system and user CPU time bpo 37950 Fix ast dump when call with incompletely initialized node bpo 34679 Restores instantiation of Windows IOCP event loops from the non main thread bpo 36917 Add default implementation of the ast NodeVisitor visit_Constant method which emits a deprecation warning and calls corresponding methods visit_Num visit_Str etc bpo 37798 Update test_statistics py to verify that the statistics module works well for both C and Python implementations Patch by Donghee Na bpo 26589 Added a new status code to the http module 451 UNAVAILABLE_FOR_LEGAL_REASONS bpo 37915 Fix a segmentation fault that appeared when comparing instances of datetime timezone and datetime tzinfo objects Patch by Pablo Galindo bpo 32554 Deprecate having random seed call hash on arbitrary types bpo 9938 Add optional keyword argument exit_on_error for ArgumentParser bpo 37851 The faulthandler module no longer allocates its alternative stack at Python startup Now the stack is only allocated at the first faulthandler usage bpo 32793 Fix a duplicated debug message when smtplib SMTP connect is called bpo 37885 venv Don t generate unset variable warning on deactivate bpo 37868 Fix dataclasses is_dataclass when given an instance that never raises AttributeError in __getattr__ That is an object that returns something for __dataclass_fields__ even if it s not a dataclass bpo 37811 Fix socket module s socket connect address function being unable to establish connection in case of interrupted system call The problem was observed on all OSes which poll 2 system call can take only non negative integers and 1 as a timeout value bpo 37863 Optimizations for Fraction __hash__ suggested by Tim Peters bpo 21131 Fix faulthandler register chain True stack faulthandler now allocates a dedicated stack of SIGSTKSZ 2 bytes instead of just SIGSTKSZ bytes Calling the previous signal handler in faulthandler signal handler uses more than SIGSTKSZ bytes of stack memory on some platforms bpo 37798 Add C fastpath for statistics NormalDist inv_cdf Patch by Donghee Na bpo 37804 Remove the deprecated method threading Thread isAlive Patch by Dong,en
1665,hee Na bpo 37819 Add Fraction as_integer_ratio to match the corresponding methods in bool int float and decimal bpo 14465 Add an xml etree ElementTree indent function for pretty printing XML trees Contributed by Stefan Behnel bpo 37810 Fix difflib hint in diff output when dealing with tabs Patch by Anthony Sottile bpo 37772 In zipfile Path when adding implicit dirs ensure that ancestral directories are added and that duplicates are excluded bpo 18578 Renamed and documented test bytecode_helper as test support bytecode_helper Patch by Joannah Nanjekye bpo 37785 Fix xgettext warnings in argparse bpo 34488 writelines method of io BytesIO is now slightly faster when many small lines are passed Patch by Sergey Fedoseev bpo 37449 ensurepip now uses importlib resources read_binary to read data instead of pkgutil get_data Patch by Joannah Nanjekye bpo 28292 Mark calendar py helper functions as being private The follows PEP 8 guidance to maintain the style conventions in the module and it addresses a known case of user confusion bpo 18049 Add definition of THREAD_STACK_SIZE for AIX in Python thread_pthread h The default thread stacksize caused crashes with the default recursion limit Patch by M Felt bpo 37742 The logging getLogger API now returns the root logger when passed the name root whereas previously it returned a non root logger named root This could affect cases where user code explicitly wants a non root logger named root or instantiates a logger using logging getLogger __name__ in some top level module called root py bpo 37738 Fix the implementation of curses addch str color_pair pass the color pair to setcchar instead of always passing 0 as the color pair bpo 37723 Fix performance regression on regular expression parsing with huge character sets Patch by Yann Vaginay bpo 35943 The function PyImport_GetModule now ensures any module it returns is fully initialized Patch by Joannah Nanjekye bpo 32178 Fix IndexError in email package when trying to parse invalid address fields starting with bpo 37268 The parser module is deprecated and will be removed in future versions of Python bpo 11953 Completing WSA error codes in socket bpo 37685 Fixed comparisons of datetime timedelta and datetime timezone bpo 37697 Synchronize importlib metadata with importlib_metadata 0 19 improving handling of EGG INFO files and fixing a crash when entry point names contained colons bpo 37695 Correct curses unget_wch error message Patch by Anthony Sottile bpo 37689 Add is_relative_to in PurePath to determine whether or not one path is relative to another bpo 29553 Fixed argparse ArgumentParser format_usage for mutually exclusive groups Patch by Andrew Nester bpo 37691 Let math dist accept coordinates as sequences or iterables rather than just tuples bpo 37685 Fixed __eq__ __lt__ etc implementations in some classes They now return NotImplemented for unsupported type of the other operand This allows the other operand to play role for example the equality comparison with ANY will return True bpo 37354 Make Activate ps1 Powershell script static to allow for signing it bpo 37664 Update wheels bundled with ensurepip pip 19 2 3 and setuptools 41 2 0 bpo 37663 Bring consistency to venv shell activation scripts by always using __VENV_PROMPT__ bpo 37642 Allowed the pure Python implementation of datetime timezone to represent sub minute offsets close to minimum and maximum boundaries specifically in the ranges 23 59 24 00 and 23 59 24 00 Patch by Ngalim Siregar bpo 36161 In posix use ttyname_r instead of ttyname for thread safety bpo 36324 Make internal attributes for statistics NormalDist private bpo 37555 Fix NonCallableMock _call_matcher returning tuple instead of _Call object when self _spec_signature exists Patch by Elizabeth Uselton bpo 29446 Make from tkinter import import only the expected objects bpo 16970 Adding a value error when an invalid value in passed to nargs Patch by Robert Leenders bpo 34443 Exceptions from enum now use the __qualname of the enum class in the exception message instead of the __name__ bpo 37491 Fix IndexError when parsing e,en
1666,mail headers with unexpectedly ending bare quoted string value Patch by Abhilash Raj bpo 37587 Make json loads faster for long strings Patch by Marco Paolini bpo 18378 Recognize UTF 8 as a valid value for LC_CTYPE in locale _parse_localename bpo 37579 Return NotImplemented in Python implementation of __eq__ for timedelta and time when the other object being compared is not of the same type to match C implementation Patch by Karthikeyan Singaravelan bpo 21478 Record calls to parent when autospecced object is attached to a mock using unittest mock attach_mock Patch by Karthikeyan Singaravelan bpo 37531 python3 m test jN timeout TIMEOUT now kills a worker process if it runs longer than TIMEOUT seconds bpo 37482 Fix serialization of display name in originator or destination address fields with both encoded words and special chars bpo 36993 Improve error reporting for corrupt zip files with bad zip64 extra data Patch by Daniel Hillier bpo 37502 pickle loads no longer raises TypeError when the buffers argument is set to None bpo 37520 Correct behavior for zipfile Path parent when the path object identifies a subdirectory bpo 18374 Fix the col_offset attribute of nested ast BinOp instances which had a too large value in some situations bpo 37424 Fixes a possible hang when using a timeout on subprocess run while capturing output If the child process spawned its own children or otherwise connected its stdout or stderr handles with another process we could hang after the timeout was reached and our child was killed when attempting to read final output from the pipes bpo 37421 Fix multiprocessing util get_temp_dir finalizer clear also the tempdir configuration of the current process so next call to get_temp_dir will create a new temporary directory rather than reusing the removed temporary directory bpo 37481 The distutils bdist_wininst command is deprecated in Python 3 8 use bdist_wheel wheel packages instead bpo 37479 When Enum __str__ is overridden in a derived class the override will be used by Enum __format__ regardless of whether mixin classes are present bpo 37440 http client now enables TLS 1 3 post handshake authentication for default context or if a cert_file is passed to HTTPSConnection bpo 37437 Update vendorized expat version to 2 2 7 bpo 37428 SSLContext post_handshake_auth True no longer sets SSL_VERIFY_POST_HANDSHAKE verify flag for client connections Although the option is documented as ignored for clients OpenSSL implicitly enables cert chain validation when the flag is set bpo 37420 os sched_setaffinity now correctly handles errors that arise during iteration over its mask argument Patch by Brandt Bucher bpo 37412 The os getcwdb function now uses the UTF 8 encoding on Windows rather than the ANSI code page see PEP 529 for the rationale The function is no longer deprecated on Windows bpo 37406 The sqlite3 module now raises TypeError rather than ValueError if operation argument type is not str execute executemany and calling a connection bpo 29412 Fix IndexError in parsing a header value ending unexpectedly Patch by Abhilash Raj bpo 36546 The dist argument for statistics quantiles is now positional only The current name doesn t reflect that the argument can be either a dataset or a distribution Marking the parameter as positional avoids confusion and makes it possible to change the name later bpo 37394 Fix a bug that was causing the queue module to fail if the accelerator module was not available Patch by Pablo Galindo bpo 37376 pprint now has support for types SimpleNamespace Patch by Carl Bordum Hansen bpo 26967 An ArgumentParser with allow_abbrev False no longer disables grouping of short flags such as vv but only disables abbreviation of long flags as documented Patch by Zac Hatfield Dodds bpo 37212 unittest mock call now preserves the order of keyword arguments in repr output Patch by Karthikeyan Singaravelan bpo 37372 Fix error unpickling datetime time objects from Python 2 with seconds 24 Patch by Justin Blanchard bpo 37345 Add formal support for UDPLITE sockets Support was present before but it is now easie,en
1667,r to detect support with hasattr socket IPPROTO_UDPLITE and there are constants defined for each of the values needed socket IPPROTO_UDPLITE UDPLITE_SEND_CSCOV and UDPLITE_RECV_CSCOV Patch by Gabe Appleton bpo 37358 Optimized functools partial by using vectorcall bpo 37347 sqlite3 Connection create_aggregate sqlite3 Connection create_function sqlite3 Connection set_authorizer sqlite3 Connection set_progress_handler sqlite3 Connection set_trace_callback methods lead to segfaults if some of these methods are called twice with an equal object but not the same Now callbacks are stored more carefully Patch by Aleksandr Balezin bpo 37163 The obj argument of dataclasses replace is positional only now bpo 37085 Add the optional Linux SocketCAN Broadcast Manager constants used as flags to configure the BCM behaviour in the socket module Patch by Karl Ding bpo 37328 HTMLParser unescape is removed It was undocumented and deprecated since Python 3 4 bpo 37305 Add webmanifest application manifest json to list of recognized file types and content type headers bpo 37320 aifc openfp alias to aifc open sunau openfp alias to sunau open and wave openfp alias to wave open have been removed They were deprecated since Python 3 7 bpo 37315 Deprecated accepting floats with integral value like 5 0 in math factorial bpo 37312 _dummy_thread and dummy_threading modules have been removed These modules were deprecated since Python 3 7 which requires threading support bpo 33972 Email with single part but content type set to multipart doesn t raise AttributeError anymore bpo 37280 Use threadpool for reading from file for sendfile fallback mode bpo 37279 Fix asyncio sendfile support when sendfile sends extra data in fallback mode bpo 19865 ctypes create_unicode_buffer now also supports non BMP characters on platforms with 16 bit wchar_t for example Windows and AIX bpo 37266 In a subinterpreter spawning a daemon thread now raises an exception Daemon threads were never supported in subinterpreters Previously the subinterpreter finalization crashed with a Python fatal error if a daemon thread was still running bpo 37210 Allow pure Python implementation of pickle to work even when the C _pickle module is unavailable bpo 21872 Fix lzma module decompresses data incompletely When decompressing a FORMAT_ALONE format file and it doesn t have the end marker sometimes the last one to dozens bytes can t be output Patch by Ma Lin bpo 35922 Fix RobotFileParser crawl_delay and RobotFileParser request_rate to return None rather than raise AttributeError when no relevant rule is defined in the robots txt file Patch by Rémi Lapeyre bpo 35766 Change the format of feature_version to be a major minor tuple bpo 36607 Eliminate RuntimeError raised by asyncio all_tasks if internal tasks weak set is changed by another thread during iteration bpo 18748 _pyio IOBase destructor now does nothing if getting the closed attribute fails to better mimic _io IOBase finalizer bpo 36402 Fix a race condition at Python shutdown when waiting for threads Wait until the Python thread state of all non daemon threads get deleted join all non daemon threads rather than just wait until non daemon Python threads complete bpo 37206 Default values which cannot be represented as Python objects no longer improperly represented as None in function signatures bpo 37111 Added encoding and errors keyword parameters to logging basicConfig bpo 12144 Ensure cookies with expires attribute are handled in CookieJar make_cookies bpo 34886 Fix an unintended ValueError from subprocess run when checking for conflicting input and stdin or capture_output and stdout or stderr args when they were explicitly provided but with None values within a passed in kwargs dict rather than as passed directly by name Patch contributed by Rémi Lapeyre bpo 37173 The exception message for inspect getfile now correctly reports the passed class rather than the builtins module bpo 37178 Give math perm a one argument form that means the same as math factorial bpo 37178 For math perm n k let k default to n giving the same result as factoria,en
1668,l bpo 37165 Converted _collections _count_elements to use the Argument Clinic bpo 34767 Do not always create a collections deque in asyncio Lock bpo 37158 Speed up statistics fmean by switching from a function to a generator bpo 34282 Remove Enum _convert method deprecated in 3 8 bpo 37150 argparse _ActionsContainer add_argument now throws error if someone accidentally pass FileType class object instead of instance of FileType as type argument bpo 28724 The socket module now has the socket send_fds and socket recv fds methods Contributed by Joannah Nanjekye Shinya Okano and Victor Stinner bpo 35621 Support running asyncio subprocesses when execution event loop in a thread on UNIX bpo 36520 Lengthy email headers with UTF 8 characters are now properly encoded when they are folded Patch by Jeffrey Kintscher bpo 30835 Fixed a bug in email parsing where a message with invalid bytes in content transfer encoding of a multipart message can cause an AttributeError Patch by Andrew Donnellan bpo 31163 pathlib Path instance s rename and replace methods now return the new Path instance bpo 25068 urllib request ProxyHandler now lowercases the keys of the passed dictionary bpo 26185 Fix repr on empty ZipInfo object Patch by Mickaël Schoentgen bpo 21315 Email headers containing RFC2047 encoded words are parsed despite the missing whitespace and a defect registered Also missing trailing whitespace after encoded words is now registered as a defect bpo 31904 Port test_datetime to VxWorks skip zoneinfo tests on VxWorks bpo 35805 Add parser for Message ID header and add it to default HeaderRegistry This should prevent folding of Message ID using RFC 2048 encoded words bpo 36871 Ensure method signature is used instead of constructor signature of a class while asserting mock object against method calls Patch by Karthikeyan Singaravelan bpo 35070 posix getgrouplist now works correctly when the user belongs to NGROUPS_MAX supplemental groups Patch by Jeffrey Kintscher bpo 31783 Fix race condition in ThreadPoolExecutor when worker threads are created during interpreter shutdown bpo 36582 Fix UserString encode to correctly return bytes rather than a UserString instance bpo 32424 Deprecate xml etree ElementTree Element copy in favor of copy copy Patch by Gordon P Hemsley bpo 36564 Fix infinite loop in email header folding logic that would be triggered when an email policy s max_line_length is not long enough to include the required markup and any values in the message Patch by Paul Ganssle bpo 36543 Removed methods Element getchildren Element getiterator and ElementTree getiterator and the xml etree cElementTree module bpo 36409 Remove the old plistlib API deprecated in Python 3 4 bpo 36302 distutils sorts source file lists so that Extension so files build more reproducibly by default bpo 36250 Ignore ValueError from signal with interaction in non main thread bpo 36046 Added user group and extra_groups parameters to the subprocess Popen constructor Patch by Patrick McLean bpo 32627 Fix compile error when _uuid headers conflicting included bpo 35800 Deprecate smtpd MailmanProxy ready for future removal bpo 35168 shlex shlex punctuation_chars is now a read only property bpo 8538 Add support for boolean actions like foo and no foo to argparse Patch contributed by Rémi Lapeyre bpo 20504 Fixes a bug in cgi module when a multipart form data request has no Content Length header bpo 25988 The abstract base classes in collections abc no longer are exposed in the regular collections module bpo 11122 Distutils won t check for rpmbuild in specified paths only bpo 34775 Division handling of PurePath now returns NotImplemented instead of raising a TypeError when passed something other than an instance of str or PurePath Patch by Roger Aiudi bpo 34749 binascii a2b_base64 is now up to 2 times faster Patch by Sergey Fedoseev bpo 34519 Add additional aliases for HP Roman 8 Patch by Michael Osipov bpo 28009 Fix uuid getnode on platforms with as MAC Addr delimiter as well fix for MAC Addr format that omits a leading 0 in MAC Addr values Currently AIX is the only know ,en
1669,platform with these settings Patch by Michael Felt bpo 30618 Add readlink Patch by Girts Folkmanis bpo 32498 Made urllib parse unquote accept bytes in addition to strings Patch by Stein Karlsen bpo 33348 lib2to3 now recognizes expressions after and like in f or bpo 32689 Update shutil move function to allow for Path objects to be used as source argument Patch by Emily Morehouse and Maxwell 5 13b McKinnon bpo 32820 Added __format__ to IPv4 and IPv6 classes Always outputs a fully zero padded string Supports b x n modifiers bin hex native format Native format for IPv4 is bin native format for IPv6 is hex Also supports and _ modifiers bpo 27657 Fix urllib parse urlparse with numeric paths A string like path 80 is no longer parsed as a path but as a scheme path and a path 80 bpo 4963 Fixed non deterministic behavior related to mimetypes extension mapping and module reinitialization Documentation bpo 21767 Explicitly mention abc support in functools singledispatch bpo 38816 Provides more details about the interaction between fork and CPython s runtime focusing just on the C API This includes cautions about where fork should and shouldn t be called bpo 38351 Modernize email examples from formatting to f strings bpo 38778 Document the fact that RuntimeError is raised if os fork is called in a subinterpreter bpo 38592 Add Brazilian Portuguese to the language switcher at Python Documentation website bpo 38294 Add list of no longer escaped chars to re escape documentation bpo 38053 Modernized the plistlib documentation bpo 26868 Fix example usage of PyModule_AddObject to properly handle errors bpo 36797 Fix a dead link in the distutils API Reference bpo 37977 Warn more strongly and clearly about pickle insecurity bpo 37979 Added a link to dateutil parser isoparse in the datetime fromisoformat documentation Patch by Paul Ganssle bpo 12707 Deprecate info geturl getcode methods in favor of the headers url and status properties respectively for HTTPResponse and addinfourl Also deprecate the code attribute of addinfourl in favor of the status attribute Patch by Ashwin Ramaswami bpo 37937 Mention frame f_trace in sys settrace docs bpo 37878 Make PyThreadState_DeleteCurrent Internal bpo 37759 Beginning edits to Whatsnew 3 8 bpo 37726 Stop recommending getopt in the tutorial for command line argument parsing and promote argparse bpo 32910 Remove implementation specific behaviour of how venv s Deactivate works bpo 37256 Fix wording of arguments for Request in urllib request bpo 37284 Add a brief note to indicate that any new sys implementation required attributes must go through the PEP process bpo 30088 Documented that mailbox Maildir constructor doesn t attempt to verify the maildir folder layout correctness Patch by Sviatoslav Sydorenko bpo 37521 Fix importlib examples to insert any newly created modules via importlib util module_from_spec immediately into sys modules instead of after calling loader exec_module Thanks to Benjamin Mintz for finding the bug bpo 37456 Slash is now part of syntax bpo 37487 Fix PyList_GetItem index description to include 0 bpo 37149 Replace the dead link to the Tkinter 8 5 reference by John Shipman New Mexico Tech with a link to the archive org copy bpo 37478 Added possible exceptions to the description of os chdir bpo 34903 Documented that in datetime datetime strptime the leading zero in some two digit formats is optional Patch by Mike Gleen bpo 36260 Add decompression pitfalls to zipfile module documentation bpo 37004 In the documentation for difflib a note was added explicitly warning that the results of SequenceMatcher s ratio method may depend on the order of the input strings bpo 36960 Restructured the datetime docs in the interest of making them more user friendly and improving readability Patch by Brad Solomon bpo 36487 Make C API docs clear about what the main interpreter is bpo 23460 The documentation for decimal string formatting using the g specifier has been updated to reflect the correct exponential notation cutoff point Original patch contributed by Tuomas Suutari bpo 35803 Document and test t,en
1670,hat tempfile functions may accept a path like object for the dir argument Patch by Anthony Sottile bpo 33944 Added a note about the intended use of code in pth files bpo 34293 Fix the Doc Makefile regarding PAPER environment variable and PDF builds bpo 25237 Add documentation for tkinter modules Tests bpo 38614 Fix test_communicate of test_asyncio test_subprocess use support LONG_TIMEOUT 5 minutes instead of just 1 minute bpo 38614 Add timeout constants to test support LOOPBACK_TIMEOUT INTERNET_TIMEOUT SHORT_TIMEOUT and LONG_TIMEOUT bpo 38502 test regrtest now uses process groups in the multiprocessing mode jN command line option if process groups are available if os setsid and os killpg functions are available bpo 35998 Fix a race condition in test_asyncio test_start_tls_server_1 Previously there was a race condition between the test main function which replaces the protocol and the test ServerProto protocol which sends ANSWER once it gets HELLO Now only the test main function is responsible to send data ServerProto no longer sends data bpo 38470 Fix test_compileall test_compile_dir_maxlevels on Windows without long path support only create 3 subdirectories instead of between 20 and 100 subdirectories bpo 37531 On timeout regrtest no longer attempts to call popen communicate again it can hang until all child processes using stdout and stderr pipes completes Kill the worker process and ignores its output Change also the faulthandler timeout of the main process from 1 minute to 5 minutes for Python slowest buildbots bpo 38239 Fix test_gdb for Link Time Optimization LTO builds bpo 38275 test_ssl now handles disabled TLS SSL versions better OpenSSL s crypto policy and run time settings are recognized and tests for disabled versions are skipped Tests also accept more TLS minimum_versions for platforms that override OpenSSL s default with strict settings bpo 38271 The private keys for test_ssl were encrypted with 3DES in traditional PKCS 5 format 3DES and the digest algorithm of PKCS 5 are blocked by some strict crypto policies Use PKCS 8 format with AES256 encryption instead bpo 38270 test support now has a helper function to check for availability of a hash digest function Several tests are refactored avoid MD5 and use SHA256 instead Other tests are marked to use MD5 and skipped when MD5 is disabled bpo 37123 Multiprocessing test test_mymanager now also expects SIGTERM not only exitcode 0 BaseManager _finalize_manager sends SIGTERM to the manager process if it takes longer than 1 second to stop which happens on slow buildbots bpo 38212 Multiprocessing tests increase test_queue_feeder_donot_stop_onexc timeout from 1 to 60 seconds bpo 38117 Test with OpenSSL 1 1 1d bpo 38018 Increase code coverage for multiprocessing shared_memory bpo 37805 Add tests for json dump skipkeys True Patch by Donghee Na bpo 37531 Enhance regrtest multiprocess timeout write a message when killing a worker process catch popen kill and popen wait exceptions put a timeout on the second call to popen communicate bpo 37876 Add tests for ROT 13 codec bpo 36833 Added tests for PyDateTime_ xxx _GET_ xxx macros of the C API of the datetime module Patch by Joannah Nanjekye bpo 37558 Fix test_shared_memory_cleaned_after_process_termination name handling bpo 37526 Add test support catch_threading_exception context manager catching threading Thread exception using threading excepthook bpo 37421 test_concurrent_futures now explicitly stops the ForkServer instance if it s running bpo 37421 multiprocessing tests now stop the ForkServer instance if it s running close the alive file descriptor to ask the server to stop and then remove its UNIX address bpo 37421 test_distutils test_build_ext is now able to remove the temporary directory on Windows don t import the newly built C extension xx in the current process but test it in a separated process bpo 37421 test_concurrent_futures now cleans up multiprocessing to remove immediately temporary directories created by multiprocessing util get_temp_dir bpo 37421 test_winconsoleio doesn t leak a temporary file anymore use t,en
1671,empfile TemporaryFile to remove it when the test completes bpo 37421 multiprocessing tests now explicitly call _run_finalizers to immediately remove temporary directories created by tests bpo 37421 urllib request tests now call urlcleanup to remove temporary files created by urlretrieve tests and to clear the _opener global variable set by urlopen and functions calling indirectly urlopen bpo 37472 Remove Lib test outstanding_bugs py bpo 37199 Fix test failures when IPv6 is unavailable or disabled bpo 19696 Replace deprecated method random choose with random choice in test_pkg_import py bpo 37335 Remove no longer necessary code from c locale coercion tests bpo 37421 Fix test_shutil to no longer leak temporary files bpo 37411 Fix test_wsgiref testEnviron to no longer depend on the environment variables don t fail if X variable is set bpo 37400 Fix test_os test_chown use os getgroups rather than grp getgrall to get groups Rename also the test to test_chown_gid bpo 37359 Add cleanup option to python3 m test to remove test_python_ directories of previous failed jobs Add make cleantest to run python3 m test cleanup bpo 37362 test_gdb no longer fails if it gets an unexpected message on stderr it now ignores stderr The purpose of test_gdb is to test that python gdb py commands work as expected not to test gdb bpo 35998 Avoid TimeoutError in test_asyncio test_start_tls_server_1 bpo 37278 Fix test_asyncio ProactorLoopCtrlC join the thread to prevent leaking a running thread and leaking a reference bpo 37261 Fix test support catch_unraisable_exception its __exit__ method now ignores unraisable exception raised when clearing its unraisable attribute bpo 37069 regrtest now uses sys unraisablehook to mark a test as environment altered ENV_CHANGED if it emits an unraisable exception Moreover regrtest logs a warning in this case Use python3 m test fail env changed to catch unraisable exceptions in tests bpo 37252 Fix assertions in test_close and test_events_mask_overflow devpoll tests bpo 37169 Rewrite _PyObject_IsFreed unit tests bpo 37153 test_venv test_multiprocessing now explicitly calls pool terminate to wait until the pool completes bpo 34001 Make test_ssl pass with LibreSSL LibreSSL handles minimum and maximum TLS version differently than OpenSSL bpo 36919 Make test_source_encoding test_issue2301 implementation independent The test will work now for both CPython and IronPython bpo 30202 Update test test_importlib test_abc to test find_spec bpo 28009 Modify the test_uuid logic to test when a program is available AND can be used to obtain a MACADDR as basis for an UUID Patch by M Felt bpo 34596 Fallback to a default reason when unittest skip is uncalled Patch by Naitree Zhu Build bpo 38809 On Windows build scripts will now recognize and use python exe from an active virtual env bpo 38684 Fix _hashlib build when Blake2 is disabled but OpenSSL supports it bpo 38468 Misc python config in now uses getvar for all still existing sysconfig get_config_var calls Patch by Joannah Nanjekye bpo 37415 Fix stdatomic h header check for ICC compiler the ICC implementation lacks atomic_uintptr_t type which is needed by Python bpo 38301 In Solaris family we must be sure to use D_REENTRANT Patch by Jesús Cea Avión bpo 36002 Locate llvm profdata and llvm ar binaries using AC_PATH_TOOL rather than AC_PATH_TARGET_TOOL bpo 37936 The gitignore file systematically keeps rooted with a non trailing slash all the rules that are meant to apply to files in a specific place in the repo Previously when the intended file to ignore happened to be at the root of the repo we d most often accidentally also ignore files and directories with the same name anywhere in the tree bpo 37760 The Tools unicode makeunicodedata py script which is used for converting information from the Unicode Character Database into generated code and data used by the methods of str and by the unicodedata module now handles each character s data as a dataclass with named attributes rather than a length 18 list of different fields bpo 37936 The gitignore file no longer applies to any files that,en
1672, are in fact tracked in the Git repository Patch by Greg Price bpo 37725 Change clean makefile target to also clean the program guided optimization PGO data Previously you would have to use make clean and make profile removal or make clobber bpo 37707 Mark some individual tests to skip when pgo is used The tests marked increase the PGO task time significantly and likely don t help improve optimization of the final executable bpo 36044 Reduce the number of unit tests run for the PGO generation task This speeds up the task by a factor of about 15x Running the full unit test suite is slow This change may result in a slightly less optimized build since not as many code branches will be executed If you are willing to wait for the much slower build the old behavior can be restored using configure PROFILE_TASK m test pgo extended We make no guarantees as to which PGO task set produces a faster build Users who care should run their own relevant benchmarks as results can depend on the environment workload and compiler tool chain bpo 37468 make install no longer installs wininst exe files used by distutils bdist_wininst bdist_wininst only works on Windows bpo 37189 Many PyRun_ XXX functions like PyRun_String were no longer exported in libpython38 dll by mistake Export them again to fix the ABI compatibility bpo 25361 Enables use of SSE2 instructions in Windows 32 bit build bpo 36210 Update optional extension module detection for AIX ossaudiodev and spwd are not applicable for AIX and are no longer reported as missing 3rd party packaging of ncurses with ASIS support conflicts with officially supported AIX curses library so configure AIX to use libcurses a However skip trying to build _curses_panel patch by M Felt Windows bpo 38589 Fixes HTML Help shortcut when Windows is not installed to C drive bpo 38453 Ensure ntpath realpath correctly resolves relative paths bpo 38519 Restores the internal C headers that were missing from the nuget org and Microsoft Store packages bpo 38492 Remove pythonw exe dependency on the Microsoft C runtime bpo 38344 Fix error message in activate bat bpo 38359 Ensures pyw exe launcher reads correct registry key bpo 38355 Fixes ntpath realpath failing on sys executable bpo 38117 Update bundled OpenSSL to 1 1 1d bpo 38092 Reduce overhead when using multiprocessing in a Windows virtual environment bpo 38133 Allow py exe launcher to locate installations from the Microsoft Store and improve display of active virtual environments bpo 38114 The pip ini is no longer included in the Nuget package bpo 32592 Set Windows 8 as the minimum required version for API support bpo 36634 os cpu_count now returns active processors rather than maximum processors bpo 36634 venv activate bat now works when the existing variables contain double quote characters bpo 38081 Prevent error calling os path realpath on NUL bpo 38087 Fix case sensitivity in test_pathlib and test_ntpath bpo 38088 Fixes distutils not finding vcruntime140 dll with only the v142 toolset installed bpo 37283 Ensure command line and unattend xml setting override previously detected states in Windows installer bpo 38030 Fixes os stat failing for block devices on Windows bpo 38020 Fixes potential crash when calling os readlink or indirectly through realpath on a file that is not a supported link bpo 37705 Improve the implementation of winerror_to_errno bpo 37549 os dup no longer fails for standard streams on Windows 7 bpo 1311 The nul file on Windows now returns True from exists and a valid result from os stat with S_IFCHR set bpo 9949 Enable support for following symlinks in os realpath bpo 37834 Treat all name surrogate reparse points on Windows in os lstat and other reparse points as regular files in os stat bpo 36266 Add the module name in the formatted error message when DLL load fail happens during module import in _PyImport_FindSharedFuncptrWindows Patch by Srinivas Nyayapati bpo 25172 Trying to import the crypt module on Windows will result in an ImportError with a message explaining that the module isn t supported on Windows On other platforms if the unde,en
1673,rlying _crypt module is not available the ImportError will include a message explaining the problem bpo 37778 Fixes the icons used for file associations to the Microsoft Store package bpo 37734 Fix use of registry values to launch Python from Microsoft Store app bpo 37702 Fix memory leak on Windows in creating an SSLContext object or running urllib request urlopen https bpo 37672 Switch Windows Store package s pip to use bundled pip ini instead of PIP_USER variable bpo 10945 Officially drop support for creating bdist_wininst installers on non Windows systems bpo 37445 Include the FORMAT_MESSAGE_IGNORE_INSERTS flag in FormatMessageW calls bpo 37369 Fixes path for sys executable when running from the Microsoft Store bpo 37380 Don t collect unfinished processes with subprocess _active on Windows to cleanup later Patch by Ruslan Kuprieiev bpo 37351 Removes libpython38 a from standard Windows distribution bpo 35360 Update Windows builds to use SQLite 3 28 0 bpo 37267 On Windows os dup no longer creates an inheritable fd when handling a character file bpo 36779 Ensure time tzname is correct on Windows when the active code page is set to CP_UTF7 or CP_UTF8 bpo 32587 Make winreg REG_MULTI_SZ support zero length strings bpo 28269 Replace use of strcasecmp for the system function _stricmp Patch by Minmin Gong bpo 36590 Add native Bluetooth RFCOMM support to socket module macOS bpo 38117 Updated OpenSSL to 1 1 1d in macOS installer bpo 38089 Move Azure Pipelines to latest VM versions and make macOS tests optional bpo 18049 Increase the default stack size of threads from 5MB to 16MB on macOS to match the stack size of the main thread This avoids crashes on deep recursion in threads bpo 34602 Avoid test suite failures on macOS by no longer calling resource setrlimit to increase the process stack size limit at runtime The runtime change is no longer needed since the interpreter is being built with a larger default stack size bpo 35360 Update macOS installer to use SQLite 3 28 0 bpo 34631 Updated OpenSSL to 1 1 1c in macOS installer IDLE bpo 26353 Stop adding newline when saving an IDLE shell window bpo 4630 Add an option to toggle IDLE s cursor blink for shell editor and output windows See Settings General Window Preferences Cursor Blink Patch by Zackery Spytz bpo 38598 Do not try to compile IDLE shell or output windows bpo 36698 IDLE no longer fails when write non encodable characters to stderr It now escapes them with a backslash as the regular Python interpreter Added the errors field to the standard streams bpo 35379 When exiting IDLE catch any AttributeError One happens when EditorWindow close is called twice Printing a traceback when IDLE is run from a terminal is useless and annoying bpo 38183 To avoid problems test_idle ignores the user config directory It no longer tries to create or access idlerc or any files within Users must run IDLE to discover problems with saving settings bpo 38077 IDLE no longer adds argv to the user namespace when initializing it This bug only affected 3 7 4 and 3 8 0b2 to 3 8 0b4 bpo 38041 Shell restart lines now fill the window width always start with and avoid wrapping unnecessarily The line will still wrap if the included file name is long relative to the width bpo 35771 To avoid occasional spurious test_idle failures on slower machines increase the hover_delay in test_tooltip bpo 37824 Properly handle user input warnings in IDLE shell Cease turning SyntaxWarnings into SyntaxErrors bpo 37929 IDLE Settings dialog now closes properly when there is no shell window bpo 37902 Add mousewheel scrolling for IDLE module path and stack browsers Patch by George Zhang bpo 37849 Fixed completions list appearing too high or low when shown above the current line bpo 36419 Refactor IDLE autocomplete and improve testing bpo 37748 Reorder the Run menu Put the most common choice Run Module at the top bpo 37692 Improve highlight config sample with example shell interaction and better labels for shell elements bpo 37628 Settings dialog no longer expands with font size bpo 37627 Initialize the Customize Run dialog with,en
1674, the command line arguments most recently entered before The user can optionally edit before submitting them bpo 33610 Fix code context not showing the correct context when first toggled on bpo 37530 Optimize code context to reduce unneeded background activity Font and highlight changes now occur along with text changes instead of after a random delay bpo 27452 Cleanup config py by inlining RemoveFile and simplifying the handling of file in CreateConfigHandlers bpo 37325 Fix tab focus traversal order for help source and custom run dialogs bpo 37321 Both subprocess connection error messages now refer to the Startup failure section of the IDLE doc bpo 17535 Add optional line numbers for IDLE editor windows Windows open without line numbers unless set otherwise in the General tab of the configuration dialog bpo 26806 To compensate for stack frames added by IDLE and avoid possible problems with low recursion limits add 30 to limits in the user code execution process Subtract 30 when reporting recursion limits to make this addition mostly transparent bpo 37177 Properly attach search dialogs to their main window so that they behave like other dialogs and do not get hidden behind their main window bpo 37039 Adjust Zoom Height to individual screens by momentarily maximizing the window on first use with a particular screen Changing screen settings may invalidate the saved height While a window is maximized Zoom Height has no effect bpo 35763 Make calltip reminder about meaning positional only less obtrusive by only adding it when there is room on the first line bpo 5680 Add Run Customized to the Run menu to run a module with customized settings Any command line arguments entered are added to sys argv One can suppress the normal Shell main module restart bpo 36390 Gather Format menu functions into format py Combine paragraph py rstrip py and format methods from editor py Tools Demos bpo 38118 Update Valgrind suppression file to ignore a false alarm in PyUnicode_Decode when using GCC builtin strcmp bpo 38347 pathfix py Assume all files that end on py are Python scripts when working recursively bpo 37803 pdb s help and version long options now work bpo 37942 Improve ArgumentClinic converter for floats bpo 37704 Remove Tools scripts h2py py use cffi to access a C API in Python bpo 37675 2to3 now works when run from a zipped standard library bpo 37034 Argument Clinic now uses the argument name on errors with keyword only argument instead of their position Patch contributed by Rémi Lapeyre bpo 37064 Add option k to pathscript py script preserve shebang flags Add option a to pathscript py script add flags C API bpo 37633 Re export some function compatibility wrappers for macros in pythonrun h bpo 38644 Provide Py_EnterRecursiveCall and Py_LeaveRecursiveCall as regular functions for the limited API Previously there were defined as macros but these macros didn t work with the limited API which cannot access PyThreadState recursion_depth field Remove _Py_CheckRecursionLimit from the stable ABI bpo 38650 The global variable PyStructSequence_UnnamedField is now a constant and refers to a constant string bpo 38540 Fixed possible leak in PyArg_Parse and similar functions for format units es and et when the macro PY_SSIZE_T_CLEAN is not defined bpo 38395 Fix a crash in weakref proxy objects due to incorrect lifetime management when calling some associated methods that may delete the last reference to object being referenced by the proxy Patch by Pablo Galindo bpo 36389 The _PyObject_CheckConsistency function is now also available in release mode For example it can be used to debug a crash in the visit_decref function of the GC bpo 38266 Revert the removal of PyThreadState_DeleteCurrent with documentation bpo 38303 Update audioop extension module to use the stable ABI PEP 384 Patch by Tyler Kieft bpo 38234 Py_SetPath now sets sys executable to the program full path Py_GetProgramFullPath rather than to the program name Py_GetProgramName bpo 38234 Python ignored arguments passed to Py_SetPath Py_SetPythonHome and Py_SetProgramName fix Python initi,en
1675,alization to use specified arguments bpo 38205 The Py_UNREACHABLE macro now calls Py_FatalError bpo 38140 Make dict and weakref offsets opaque for C heap types by passing the offsets through PyMemberDef bpo 15088 The C function PyGen_NeedsFinalizing has been removed It was not documented tested or used anywhere within CPython after the implementation of PEP 442 Patch by Joannah Nanjekye Patch by Joannah Nanjekye bpo 36763 Options added by PySys_AddXOption are now handled the same way than PyConfig xoptions and command line X options bpo 37926 Fix a crash in PySys_SetArgvEx 0 NULL 0 bpo 37879 Fix subtype_dealloc to suppress the type decref when the base type is a C heap type bpo 37645 Add _PyObject_FunctionStr to get a user friendly string representation of a function like object Patch by Jeroen Demeyer bpo 29548 The functions PyEval_CallObject PyEval_CallFunction PyEval_CallMethod and PyEval_CallObjectWithKeywords are deprecated Use PyObject_Call and its variants instead bpo 37151 PyCFunction_Call is now a deprecated alias of PyObject_Call bpo 37540 The vectorcall protocol now requires that the caller passes only strings as keyword names bpo 37207 The vectorcall protocol is now enabled for type objects set tp_vectorcall to a vectorcall function to be used instead of tp_new and tp_init when calling the class itself bpo 21120 Exclude Python ast h ast h and asdl h from the limited API bpo 37483 Add new function _PyObject_CallOneArg for calling an object with one positional argument bpo 36763 Add PyConfig_SetWideStringList function bpo 37337 Add fast functions for calling methods _PyObject_VectorcallMethod _PyObject_CallMethodNoArgs and _PyObject_CallMethodOneArg bpo 28805 The METH_FASTCALL calling convention has been documented bpo 37221 The new function PyCode_NewWithPosOnlyArgs allows to create code objects like PyCode_New but with an extra posonlyargcount parameter for indicating the number of positonal only arguments bpo 37215 Fix dtrace issue introduce by bpo 36842 bpo 37194 Add a new public PyObject_CallNoArgs function to the C API call a callable Python object without any arguments It is the most efficient way to call a callback without any argument On x86 64 for example PyObject_CallFunctionObjArgs func NULL allocates 960 bytes on the stack per call whereas PyObject_CallNoArgs func only allocates 624 bytes per call bpo 37170 Fix the cast on error in PyLong_AsUnsignedLongLongMask bpo 35381 Convert posixmodule c statically allocated types DirEntryType and ScandirIteratorType to heap allocated types bpo 34331 Use singular plural noun in error message when instantiating an abstract class with non overridden abstract method s Python 3 8 0 beta 1 Release date 2019 06 04 Security bpo 35907 CVE 2019 9948 Avoid file reading by disallowing local file and local_file URL schemes in URLopener open and URLopener retrieve of urllib request bpo 33529 Prevent fold function used in email header encoding from entering infinite loop when there are too many non ASCII characters in a header bpo 33164 Updated blake2 implementation which uses secure memset implementation provided by platform Core and Builtins bpo 35814 Allow unpacking in the right hand side of annotated assignments In particular t Tuple int x y z is now allowed bpo 37126 All structseq objects are now tracked by the garbage collector Patch by Pablo Galindo bpo 37122 Make the co_argcount attribute of code objects represent the total number of positional arguments including positional only arguments The value of co_posonlyargcount can be used to distinguish which arguments are positional only and the difference co_argcount co_posonlyargcount is the number of positional or keyword arguments Patch by Pablo Galindo bpo 20092 Constructors of int float and complex will now use the __index__ special method if available and the corresponding method __int__ __float__ or __complex__ is not available bpo 37087 Add native thread ID TID support to OpenBSD bpo 26219 Implemented per opcode cache mechanism and LOAD_GLOBAL instruction use it LOAD_GLOBAL is now about 40 faster Contributed by ,en
1676,Yury Selivanov and Inada Naoki bpo 37072 Fix crash in PyAST_FromNodeObject when flags is NULL bpo 37029 Freeing a great many small objects could take time quadratic in the number of arenas due to using linear search to keep obmalloc c s list of usable arenas sorted by order of number of free memory pools This is accomplished without search now leaving the worst case time linear in the number of arenas For programs where this quite visibly matters typically with more than 100 thousand small objects alive simultaneously this can greatly reduce the time needed to release their memory bpo 26423 Fix possible overflow in wrap_lenfunc when sizeof long sizeof Py_ssize_t e g 64 bit Windows bpo 37050 Improve the AST for debug f strings which use to print out the source of the expression being evaluated Delete expr_text from the FormattedValue node and instead use a Constant string node possibly merged with adjacent constant expressions inside the f string bpo 22385 The bytes hex bytearray hex and memoryview hex methods as well as the binascii hexlify and b2a_hex functions now have the ability to include an optional separator between hex bytes This functionality was inspired by MicroPython s hexlify implementation bpo 26836 Add os memfd_create bpo 37032 Added new replace method to the code type types CodeType bpo 37007 Implement socket if_nameindex socket if_nametoindex and socket if_indextoname on Windows bpo 36829 PyErr_WriteUnraisable now creates a traceback object if there is no current traceback Moreover call PyErr_NormalizeException and PyException_SetTraceback to normalize the exception value Ignore any error bpo 36878 Only accept text after type ignore if the first character is ASCII This is to disallow things like type ignoreé bpo 36878 Store text appearing after a type ignore comment in the AST For example a type ignore like type ignore E1000 will have the string E1000 stored in its AST node bpo 2180 Treat line continuation at EOF as a SyntaxError by Anthony Sottile bpo 36907 Fix a crash when calling a C function with a keyword dict f kwargs and changing the dict kwargs while that function is running bpo 36946 Fix possible signed integer overflow when handling slices bpo 36826 Add NamedExpression kind support to ast_unparse c bpo 1875 A SyntaxError is now raised if a code blocks that will be optimized away e g if conditions that are always false contains syntax errors Patch by Pablo Galindo bpo 36027 Allow computation of modular inverses via three argument pow the second argument is now permitted to be negative in the case where the first and third arguments are relatively prime bpo 36861 Update the Unicode database to version 12 1 0 bpo 28866 Avoid caching attributes of classes which type defines mro to avoid a hard cache invalidation problem bpo 36851 The FrameType stack is now correctly cleaned up if the execution ends with a return and the stack is not empty bpo 34616 The compile builtin functions now support the ast PyCF_ALLOW_TOP_LEVEL_AWAIT flag which allow to compile sources that contains top level await async with or async for This is useful to evaluate async code from with an already async functions for example in a custom REPL bpo 36842 Implement PEP 578 adding sys audit io open_code and related APIs bpo 27639 Correct return type for UserList slicing operations Patch by Michael Blahay Erick Cervantes and vaultah bpo 36737 Move PyRuntimeState warnings into per interpreter state via module state bpo 36793 Removed __str__ implementations from builtin types bool int float complex and few classes from the standard library They now inherit __str__ from object bpo 36817 Add a feature f strings for debugging This can precede s r or a It produces the text of the expression followed by an equal sign followed by the repr of the value of the expression So f 3 9 15 would be equal to the string 3 9 15 42 If is specified the default conversion is set to r unless a format spec is given in which case the formatting behavior is unchanged and __format__ will be used bpo 24048 Save the live exception during import c s remove_modul,en
1677,e bpo 27987 pymalloc returns memory blocks aligned by 16 bytes instead of 8 bytes on 64 bit platforms to conform x86 64 ABI Recent compilers assume this alignment more often Patch by Inada Naoki bpo 36601 A long since meaningless check for getpid main_pid was removed from Python s internal C signal handler bpo 36594 Fix incorrect use of p in format strings Patch by Zackery Spytz bpo 36045 builtins help now prefixes async for async functions bpo 36084 Add native thread ID TID to threading Thread objects supported platforms Windows FreeBSD Linux macOS bpo 36035 Added fix for broken symlinks in combination with pathlib bpo 35983 Added new trashcan macros to deal with a double deallocation that could occur when the tp_dealloc of a subclass calls the tp_dealloc of a base class and that base class uses the trashcan mechanism Patch by Jeroen Demeyer bpo 20602 Do not clear sys flags and sys float_info during shutdown Patch by Zackery Spytz bpo 26826 Expose copy_file_range as a low level API in the os module bpo 32388 Remove cross version binary compatibility requirement in tp_flags bpo 31862 Port binascii to PEP 489 multiphase initialization Patch by Marcel Plch Library bpo 37128 Added math perm bpo 37120 Add SSLContext num_tickets to control the number of TLSv1 3 session tickets bpo 12202 Fix the error handling in msilib SummaryInformation GetProperty Patch by Zackery Spytz bpo 26835 The fcntl module now contains file sealing constants for sealing of memfds bpo 29262 Add get_origin and get_args introspection helpers to typing module bpo 12639 msilib Directory start_component no longer fails if keyfile is not None bpo 36999 Add the asyncio Task get_coro method to publicly expose the tasks s coroutine object bpo 35246 Make asyncio create_subprocess_exec accept path like arguments bpo 35279 Change default max_workers of ThreadPoolExecutor from cpu_count 5 to min 32 cpu_count 4 Previous value was unreasonably large on many cores machines bpo 37076 _thread start_new_thread now logs uncaught exception raised by the function using sys unraisablehook rather than sys excepthook so the hook gets access to the function which raised the exception bpo 33725 On macOS the multiprocessing module now uses spawn start method by default bpo 37054 Fix destructor _pyio BytesIO and _pyio TextIOWrapper initialize their _buffer attribute as soon as possible in the class body because it s used by __del__ which calls close bpo 37058 PEP 544 Add Protocol and runtime_checkable to the typing module bpo 36933 The functions sys set_coroutine_wrapper and sys get_coroutine_wrapper that were deprecated and marked for removal in 3 8 have been removed bpo 37047 Handle late binding and attribute access in unittest mock AsyncMock setup for autospeccing Document newly implemented async methods in unittest mock MagicMock bpo 37049 PEP 589 Add TypedDict to the typing module bpo 37046 PEP 586 Add Literal to the typing module bpo 37045 PEP 591 Add Final qualifier and final decorator to the typing module bpo 37035 Don t log OSError based exceptions if a fatal error has occurred in asyncio transport Peer can generate almost any OSError user cannot avoid these exceptions by fixing own code Errors are still propagated to user code it s just logging them is pointless and pollute asyncio logs bpo 37001 symtable symtable now accepts the same input types for source code as the built in compile function Patch by Dino Viehland bpo 37028 Implement asyncio REPL bpo 37027 Return safe to use proxy socket object from transport get_extra_info socket bpo 32528 Make asyncio CancelledError a BaseException This will address the common mistake many asyncio users make an except Exception clause breaking Tasks cancellation In addition to this change we stop inheriting asyncio TimeoutError and asyncio InvalidStateError from their concurrent futures counterparts There s no point for these exceptions to share the inheritance chain bpo 1230540 Add a new threading excepthook function which handles uncaught threading Thread run exception It can be overridden to control how uncaught threading Thread,en
1678, run exceptions are handled bpo 36996 Handle unittest mock patch used as a decorator on async functions bpo 37008 Add support for calling next with the mock resulting from unittest mock mock_open bpo 27737 Allow whitespace only header encoding in email header by Batuhan Taskaya bpo 36969 PDB command args now display positional only arguments Patch contributed by Rémi Lapeyre bpo 36969 PDB command args now display keyword only arguments Patch contributed by Rémi Lapeyre bpo 36983 Add missing names to typing __all__ ChainMap ForwardRef OrderedDict by Anthony Sottile bpo 36972 Add SupportsIndex protocol to the typing module to allow type checking to detect classes that can be passed to hex oct and bin bpo 32972 Implement unittest IsolatedAsyncioTestCase to help testing asyncio based code bpo 36952 fileinput input and fileinput FileInput bufsize argument has been removed was deprecated and ignored since Python 3 6 and as a result the mode and openhook arguments have been made keyword only bpo 36952 Starting with Python 3 3 importing ABCs from collections is deprecated and import should be done from collections abc Still being able to import from collections was marked for removal in 3 8 but has been delayed to 3 9 documentation and DeprecationWarning clarified bpo 36949 Implement __repr__ for WeakSet objects bpo 36948 Fix NameError in urllib request URLopener retrieve Patch by Karthikeyan Singaravelan bpo 33524 Fix the folding of email header when the max_line_length is 0 or None and the header contains non ascii characters Contributed by Licht Takeuchi Licht T bpo 24564 shutil copystat now ignores errno EINVAL on os setxattr which may occur when copying files on filesystems without extended attributes support Original patch by Giampaolo Rodola updated by Ying Wang bpo 36888 Python child processes can now access the status of their parent process using multiprocessing process parent_process bpo 36921 Deprecate coroutine for sake of async def bpo 25652 Fix bug in __rmod__ of UserString by Batuhan Taskaya bpo 36916 Remove a message about an unhandled exception in a task when writer write is used without await and writer drain fails with an exception bpo 36889 Introduce asyncio Stream class that merges asyncio StreamReader and asyncio StreamWriter functionality asyncio Stream can work in readonly writeonly and readwrite modes Provide asyncio connect asyncio connect_unix asyncio connect_read_pipe and asyncio connect_write_pipe factories to open asyncio Stream connections Provide asyncio StreamServer and UnixStreamServer to serve servers with asyncio Stream API Modify asyncio create_subprocess_shell and asyncio create_subprocess_exec to use asyncio Stream instead of deprecated StreamReader and StreamWriter Deprecate asyncio StreamReader and asyncio StreamWriter Deprecate usage of private classes e g asyncio FlowControlMixing and asyncio StreamReaderProtocol outside of asyncio package bpo 36845 Added validation of integer prefixes to the construction of IP networks and interfaces in the ipaddress module bpo 23378 Add an extend action to argparser bpo 36867 Fix a bug making a SharedMemoryManager instance and its parent process use two separate resource_tracker processes bpo 23896 Adds a grammar to lib2to3 pygram that contains exec as a function not as statement bpo 36895 The function time clock was deprecated in 3 3 in favor of time perf_counter and marked for removal in 3 8 it has removed bpo 35545 Fix asyncio discarding IPv6 scopes when ensuring hostname resolutions internally bpo 36887 Add new function math isqrt to compute integer square roots bpo 34632 Introduce the importlib metadata module with provisional support for reading metadata from third party packages bpo 36878 When using type_comments True in ast parse treat type ignore followed by a non alphanumeric character and then arbitrary text as a type ignore instead of requiring nothing but whitespace or another comment This is to permit formations such as type ignore E1000 bpo 36778 cp65001 encoding Windows code page 65001 becomes an alias to utf_8 encoding bpo 36867 The ,en
1679,multiprocessing resource_tracker replaces the multiprocessing semaphore_tracker module Other than semaphores resource_tracker also tracks shared_memory segments bpo 30262 The Cache and Statement objects of the sqlite3 module are not exposed to the user Patch by Aviv Palivoda bpo 24538 In shutil copystat first copy extended file attributes and then file permissions since extended attributes can only be set on the destination while it is still writeable bpo 36829 Add new sys unraisablehook function which can be overridden to control how unraisable exceptions are handled It is called when an exception has occurred but there is no way for Python to handle it For example when a destructor raises an exception or during garbage collection gc collect bpo 36832 Introducing zipfile Path a pathlib compatible wrapper for traversing zip files bpo 36814 Fix an issue where os posix_spawnp would incorrectly raise a TypeError when file_actions is None bpo 33110 Handle exceptions raised by functions added by concurrent futures add_done_callback correctly when the Future has already completed bpo 26903 Limit max_workers in ProcessPoolExecutor to 61 to work around a WaitForMultipleObjects limitation bpo 36813 Fix QueueListener to call queue task_done upon stopping Patch by Bar Harel bpo 36806 Forbid creation of asyncio stream objects like StreamReader StreamWriter Process and their protocols outside of asyncio package bpo 36802 Provide both sync and async calls for StreamWriter write and StreamWriter close bpo 36801 Properly handle SSL connection closing in asyncio StreamWriter drain call bpo 36785 Implement PEP 574 pickle protocol 5 with out of band buffers bpo 36772 functools lru_cache can now be used as a straight decorator in addition to its existing usage as a function that returns a decorator bpo 6584 Add a BadGzipFile exception to the gzip module bpo 36748 Optimized write buffering in C implementation of TextIOWrapper Writing ASCII string to TextIOWrapper with ascii latin1 or utf 8 encoding is about 20 faster Patch by Inada Naoki bpo 8138 Don t mark wsgiref simple_server SimpleServer as multi threaded since wsgiref simple_server WSGIServer is single threaded bpo 22640 py_compile compile now supports silent mode Patch by Joannah Nanjekye bpo 29183 Fix double exceptions in wsgiref handlers BaseHandler by calling its close method only when no exception is raised bpo 36548 Improved the repr of regular expression flags bpo 36542 The signature of Python functions can now be overridden by specifying the __text_signature__ attribute bpo 36533 Reinitialize logging Handler locks in forked child processes instead of attempting to acquire them all in the parent before forking only to be released in the child process The acquire release pattern was leading to deadlocks in code that has implemented any form of chained logging handlers that depend upon one another as the lock acquisition order cannot be guaranteed bpo 35252 Throw a TypeError instead of an AssertionError when using an invalid type annotation with singledispatch bpo 35900 Allow reduction methods to return a 6 item tuple where the 6th item specifies a custom state setting method that s called instead of the regular __setstate__ method bpo 35900 enable custom reduction callback registration for functions and classes in _pickle c using the new Pickler s attribute reducer_override bpo 36368 Fix a bug crashing SharedMemoryManager instances in interactive sessions after a ctrl c KeyboardInterrupt was sent bpo 31904 Fix mmap fail for VxWorks bpo 27497 csv DictWriter writeheader now returns the return value of the underlying csv Writer writerow method Patch contributed by Ashish Nitin Patil bpo 36239 Parsing mo files now ignores comments starting and ending with bpo 26707 Enable plistlib to read and write binary plist files that were created as a KeyedArchive file Specifically this allows the plistlib to process 0x80 tokens as UID objects bpo 31904 Add posix module support for VxWorks bpo 35125 Asyncio Remove inner callback on outer cancellation in shield bpo 35721 Fix asyncio SelectorEventL,en
1680,oop subprocess_exec leaks file descriptors if Popen fails and called with stdin subprocess PIPE Patch by Niklas Fiekas bpo 31855 unittest mock mock_open results now respects the argument of read size Patch contributed by Rémi Lapeyre bpo 35431 Implement math comb that returns binomial coefficient that computes the number of ways to choose k items from n items without repetition and without order Patch by Yash Aggarwal and Keller Fuchs bpo 26660 Fixed permission errors in TemporaryDirectory clean up Previously TemporaryDirectory cleanup failed when non writeable or non searchable files or directories were created inside a temporary directory bpo 34271 Add debugging helpers to ssl module It s now possible to dump key material and to trace TLS protocol The default and stdlib contexts also support SSLKEYLOGFILE env var bpo 26467 Added AsyncMock to support using unittest to mock asyncio coroutines Patch by Lisa Roach bpo 33569 dataclasses InitVar Exposes the type used to create the init var bpo 34424 Fix serialization of messages containing encoded strings when the policy linesep is set to a multi character string Patch by Jens Troeger bpo 34303 Performance of functools reduce is slightly improved Patch by Sergey Fedoseev bpo 33361 Fix a bug in codecs StreamRecoder where seeking might leave old data in a buffer and break subsequent read calls Patch by Ammar Askar bpo 22454 The shlex module now exposes shlex join the inverse of shlex split Patch by Bo Bayles bpo 31922 asyncio AbstractEventLoop create_datagram_endpoint Do not connect UDP socket when broadcast is allowed This allows to receive replies after a UDP broadcast bpo 24882 Change ThreadPoolExecutor to use existing idle threads before spinning up new ones bpo 31961 Added support for bytes and path like objects in subprocess Popen on Windows The args parameter now accepts a path like object if shell is False and a sequence containing bytes and path like objects The executable parameter now accepts a bytes and path like object The cwd parameter now accepts a bytes object Based on patch by Anders Lorentsen bpo 33123 pathlib Path unlink now accepts a missing_ok parameter to avoid a FileNotFoundError from being raised Patch by Robert Buchholz bpo 32941 Allow mmap mmap objects to access the madvise system call through mmap mmap madvise bpo 22102 Added support for ZIP files with disks set to 0 Such files are commonly created by builtin tools on Windows when use ZIP64 extension Patch by Francisco Facioni bpo 32515 trace py can now run modules via python3 m trace t module module_name bpo 32299 Changed unittest mock patch dict to return the patched dictionary when used as context manager Patch by Vadim Tsander bpo 27141 Added a __copy__ to collections UserList and collections UserDict in order to correctly implement shallow copying of the objects Patch by Bar Harel bpo 31829 r 0 and x1a end of file on Windows are now escaped in protocol 0 pickles of Unicode strings This allows to load them without loss from files open in text mode in Python 2 bpo 23395 _thread interrupt_main now avoids setting the Python error status if the SIGINT signal is ignored or not handled by Python Documentation bpo 36896 Clarify that some types have unstable constructor signature between Python versions bpo 36686 Improve documentation of the stdin stdout and stderr arguments of the asyncio subprocess_exec function to specify which values are supported Also mention that decoding as text is not supported Add a few tests to verify that the various values passed to the std arguments actually work bpo 36984 Improve version added references in typing module by Anthony Sottile bpo 36868 What s new now mentions SSLContext hostname_checks_common_name instead of SSLContext host_flags bpo 35924 Add a note to the curses addstr documentation to warn that multiline strings can cause segfaults because of an ncurses bug bpo 36783 Added C API Documentation for Time_FromTimeAndFold and PyDateTime_FromDateAndTimeAndFold as per PEP 495 Patch by Edison Abahurire bpo 36797 More of the legacy distutils documentation has been e,en
1681,ither pruned or else more clearly marked as being retained solely until the setuptools documentation covers it independently bpo 22865 Add detail to the documentation on the pty spawn function bpo 35397 Remove deprecation and document urllib parse unwrap Patch contributed by Rémi Lapeyre bpo 32995 Added the context variable in glossary bpo 33519 Clarify that copy is not part of the MutableSequence ABC bpo 33482 Make codecs StreamRecoder writelines take a list of bytes bpo 25735 Added documentation for func factorial to indicate that returns integer values bpo 20285 Expand object __doc__ docstring to make it clearer Modify pydoc py so that help object lists object methods for other classes help omits methods of the object base class Tests bpo 37069 Modify test_coroutines test_cprofile test_generators test_raise test_ssl and test_yield_from to use test support catch_unraisable_exception rather than test support captured_stderr bpo 37098 Fix test_memfd_create on older Linux Kernels bpo 37081 Test with OpenSSL 1 1 1c bpo 36829 Add test support catch_unraisable_exception context manager catching unraisable exception using sys unraisablehook bpo 36915 The main regrtest process now always removes all temporary directories of worker processes even if they crash or if they are killed on KeyboardInterrupt CTRL c bpo 36719 python3 m test jN now continues the execution of next tests when a worker process crash CHILD_ERROR state Previously the test suite stopped immediately Use failfast to stop at the first error bpo 36816 Update Lib test selfsigned_pythontestdotnet pem to match self signed pythontest net s new TLS certificate bpo 35925 Skip httplib and nntplib networking tests when they would otherwise fail due to a modern OS or distro with a default OpenSSL policy of rejecting connections to servers with weak certificates bpo 36782 Add tests for several C API functions in the datetime module Patch by Edison Abahurire bpo 36342 Fix test_multiprocessing in test_venv if platform lacks functioning sem_open Build bpo 36721 To embed Python into an application a new embed option must be passed to python3 config libs embed to get lpython3 8 link the application to libpython To support both 3 8 and older try python3 config libs embed first and fallback to python3 config libs without embed if the previous command fails Add a pkg config python 3 8 embed module to embed Python into an application pkg config python 3 8 embed libs includes lpython3 8 To support both 3 8 and older try pkg config python X Y embed libs first and fallback to pkg config python X Y libs without embed if the previous command fails replace X Y with the Python version On the other hand pkg config python3 8 libs no longer contains lpython3 8 C extensions must not be linked to libpython except on Android case handled by the script this change is backward incompatible on purpose bpo 36786 make install now runs compileall in parallel Windows bpo 36965 include of STATUS_CONTROL_C_EXIT without depending on MSC compiler bpo 35926 Update to OpenSSL 1 1 1b for Windows bpo 29883 Add Windows support for UDP transports for the Proactor Event Loop Patch by Adam Meily bpo 33407 The Py_DEPRECATED macro has been implemented for MSVC macOS bpo 36231 Support building Python on macOS without usr include installed As of macOS 10 14 system header files are only available within an SDK provided by either the Command Line Tools or the Xcode app IDLE bpo 35610 Replace now redundant context_use_ps1 with prompt_last_line This finishes change started in bpo 31858 bpo 37038 Make idlelib run runnable add test clause bpo 36958 Print any argument other than None or int passed to SystemExit or sys exit bpo 36807 When saving a file call os fsync so bits are flushed to e g USB drive bpo 32411 In browser py remove extraneous sorting by line number since dictionary was created in line number order Tools Demos bpo 37053 Handle strings like u bar correctly in Tools parser unparse py Patch by Chih Hsuan Yen C API bpo 36763 Implement the PEP 587 Python Initialization Configuration bpo 36379 Fix crashes when at,en
1682,tempting to use the modulo parameter when __ipow__ is implemented in C bpo 37107 Update PyObject_CallMethodObjArgs and _PyObject_CallMethodIdObjArgs to use _PyObject_GetMethod to avoid creating a bound method object in many cases Patch by Michael J Sullivan bpo 36974 Implement PEP 590 Vectorcall a fast calling protocol for CPython This is a new protocol to optimize calls of custom callable objects bpo 36763 Py_Main now returns the exitcode rather than calling Py_Exit exitcode when calling PyErr_Print if the current exception type is SystemExit bpo 36922 Add new type flag Py_TPFLAGS_METHOD_DESCRIPTOR for objects behaving like unbound methods These are objects supporting the optimization given by the LOAD_METHOD CALL_METHOD opcodes See PEP 590 bpo 36728 The PyEval_ReInitThreads function has been removed from the C API It should not be called explicitly use PyOS_AfterFork_Child instead Python 3 8 0 alpha 4 Release date 2019 05 06 Security bpo 36742 Fixes mishandling of pre normalization characters in urlsplit bpo 30458 Address CVE 2019 9740 by disallowing URL paths with embedded whitespace or control characters through into the underlying http client request Such potentially malicious header injection URLs now cause an http client InvalidURL exception to be raised bpo 35755 shutil which now uses os confstr CS_PATH if available and if the PATH environment variable is not set Remove also the current directory from posixpath defpath On Unix shutil which and the subprocess module no longer search the executable in the current directory if the PATH environment variable is not set Core and Builtins bpo 36722 In debug build import now also looks for C extensions compiled in release mode and for C extensions compiled in the stable ABI bpo 32849 Fix Python Initialization code on FreeBSD to detect properly when stdin file descriptor fd 0 is invalid bpo 36623 Remove parser headers and related function declarations that lack implementations after the removal of pgen bpo 20180 dict pop is now up to 33 faster thanks to Argument Clinic Patch by Inada Naoki bpo 36611 Debug memory allocators disable serialno field by default from debug hooks on Python memory allocators to reduce the memory footprint by 5 Enable tracemalloc to get the traceback where a memory block has been allocated when a fatal memory error is logged to decide where to put a breakpoint Compile Python with PYMEM_DEBUG_SERIALNO defined to get back the field bpo 36588 On AIX sys platform doesn t contain the major version anymore Always return aix instead of aix3 aix7 Since older Python versions include the version number it is recommended to always use sys platform startswith aix Contributed by M Felt bpo 36549 Change str capitalize to use titlecase for the first character instead of uppercase bpo 36540 Implement PEP 570 Python positional only parameters Patch by Pablo Galindo bpo 36475 PyEval_AcquireLock and PyEval_AcquireThread now terminate the current thread if called while the interpreter is finalizing making them consistent with PyEval_RestoreThread Py_END_ALLOW_THREADS and PyGILState_Ensure bpo 36504 Fix signed integer overflow in _ctypes c s PyCArrayType_new bpo 20844 Fix running script with encoding cookie and LF line ending may fail on Windows bpo 24214 Fixed support of the surrogatepass error handler in the UTF 8 incremental decoder bpo 36452 Changing dict keys during iteration of the dict itself keys values or items will now be detected in certain corner cases where keys are deleted added so that the number of keys isn t changed A RuntimeError will be raised after len dict iterations Contributed by Thomas Perl bpo 36459 Fix a possible double PyMem_FREE due to tokenizer c s tok_nextc bpo 36433 Fixed TypeError message in classmethoddescr_call bpo 36430 Fix a possible reference leak in itertools count bpo 36440 Include node names in ParserError messages instead of numeric IDs Patch by A Skrobov bpo 36143 Regenerate keyword from the Grammar and Tokens file using pgen Patch by Pablo Galindo bpo 18372 Add missing PyObject_GC_Track calls in the pickle module Patch by Zac,en
1683,kery Spytz Library bpo 35952 Fix pythoninfo when the compiler is missing bpo 28238 The find methods of xml etree ElementTree can now search for wildcards like tag and ns that match a tag in any namespace or all tags in a namespace Patch by Stefan Behnel bpo 26978 pathlib path link_to is now implemented It creates a hard link pointing to a path bpo 1613500 fileinput FileInput now uses the input file mode to correctly set the output file mode previously it was hardcoded to w when inplace True is passed to its constructor bpo 36734 Fix compilation of faulthandler c on HP UX Initialize stack_t current_stack to zero using memset bpo 13611 The xml etree ElementTree packages gained support for C14N 2 0 serialisation Patch by Stefan Behnel bpo 36669 Add missing matrix multiplication operator support to weakref proxy bpo 36676 The XMLParser in xml etree ElementTree provides namespace prefix context to the parser target if it defines the callback methods start_ns and or end_ns Patch by Stefan Behnel bpo 36673 The TreeBuilder and XMLPullParser in xml etree ElementTree gained support for parsing comments and processing instructions Patch by Stefan Behnel bpo 36650 The C version of functools lru_cache was treating calls with an empty kwargs dictionary as being distinct from calls with no keywords at all This did not result in an incorrect answer but it did trigger an unexpected cache miss bpo 28552 Fix distutils sysconfig if sys executable is None or an empty string use os getcwd to initialize project_base Fix also the distutils build command don t use sys executable if it is None or an empty string bpo 35755 shutil which and distutils spawn find_executable now use os confstr CS_PATH if available instead of os defpath if the PATH environment variable is not set Moreover don t use os confstr CS_PATH nor os defpath if the PATH environment variable is set to an empty string bpo 25430 improve performance of IPNetwork __contains__ bpo 30485 Path expressions in xml etree ElementTree can now avoid explicit namespace prefixes for tags or the namespace tag notation by passing a default namespace with an empty string prefix bpo 36613 Fix asyncio wait not removing callback if exception bpo 36598 Fix isinstance check for Mock objects with spec when the code is executed under tracing Patch by Karthikeyan Singaravelan bpo 18748 In development mode X dev and in debug build the io IOBase destructor now logs close exceptions These exceptions are silent by default in release mode bpo 36575 The _lsprof module now uses internal timer same to time perf_counter by default gettimeofday 2 was used on Unix New timer has better resolution on most Unix platforms and timings are no longer impacted by system clock updates since perf_counter is monotonic Patch by Inada Naoki bpo 33461 json loads now emits DeprecationWarning when encoding option is specified Patch by Matthias Bussonnier bpo 36559 The random module now prefers the lean internal _sha512 module over hashlib for seed version 2 to optimize import time bpo 17561 Set backlog None as the default for socket create_server bpo 34373 Fix time mktime error handling on AIX for year before 1970 bpo 36232 Improve error message when trying to open existing DBM database that actually doesn t exist Patch by Marco Rougeth bpo 36546 Add statistics quantiles bpo 36050 Optimized http client HTTPResponse read for large response Patch by Inada Naoki bpo 36522 If debuglevel is set to 0 in http client print all values for headers with multiple values for the same header name Patch by Matt Houglum bpo 36492 Deprecated passing required arguments like func as keyword arguments in functions which should accept arbitrary keyword arguments and pass them to other function Arbitrary keyword arguments even with names self and func can now be passed to these functions if the required arguments are passed as positional arguments bpo 27181 Add statistics geometric_mean bpo 30427 os path normcase relies on os fspath to check the type of its argument Redundant checks have been removed from its posixpath normcase and ntpath normcase imple,en
1684,mentations Patch by Wolfgang Maier bpo 36385 Stop rejecting IPv4 octets for being ambiguously octal Leading zeros are ignored and no longer are assumed to specify octal octets Octets are always decimal numbers Octets must still be no more than three digits including leading zeroes bpo 36434 Errors during writing to a ZIP file no longer prevent to properly close it bpo 36407 Fixed wrong indentation writing for CDATA section in xml dom minidom Patch by Vladimir Surjaninov bpo 36326 inspect getdoc can now find docstrings for member objects when __slots__ is a dictionary bpo 36366 Calling stop on an unstarted or stopped unittest mock patch object will now return None instead of raising RuntimeError making the method idempotent Patch by Karthikeyan Singaravelan bpo 36348 The imap IMAP4 logout method no longer ignores silently arbitrary exceptions bpo 31904 Add time module support and fix test_time faiures for VxWorks bpo 36227 Added support for keyword arguments default_namespace and xml_declaration in functions ElementTree tostring and ElementTree tostringlist bpo 36004 Added new alternate constructors datetime date fromisocalendar and datetime datetime fromisocalendar which construct date objects from ISO year week number and weekday these are the inverse of each class s isocalendar method Patch by Paul Ganssle bpo 35936 modulefinder no longer depends on the deprecated imp module and the initializer for modulefinder ModuleFinder now has immutable default arguments Patch by Brandt Bucher bpo 35376 modulefinder correctly handles modules that have the same name as a bad package Patch by Brandt Bucher bpo 17396 modulefinder no longer crashes when encountering syntax errors in followed imports Patch by Brandt Bucher bpo 35934 Added create_server and has_dualstack_ipv6 convenience functions to automate the necessary tasks usually involved when creating a server socket including accepting both IPv4 and IPv6 connections on the same socket Contributed by Giampaolo Rodola in bpo 17561 bpo 23078 Add support for classmethod and staticmethod to unittest mock create_autospec Initial patch by Felipe Ochoa bpo 35416 Fix potential resource warnings in distutils Patch by Mickaël Schoentgen bpo 25451 Add transparency methods to tkinter PhotoImage Patch by Zackery Spytz bpo 35082 Don t return deleted attributes when calling dir on a unittest mock Mock bpo 34547 wsgiref handlers BaseHandler now handles abrupt client connection terminations gracefully Patch by Petter Strandmark bpo 31658 xml sax parse now supports path like Patch by Mickaël Schoentgen bpo 34139 Remove stale unix datagram socket before binding bpo 33530 Implemented Happy Eyeballs in asyncio create_connection Added two new arguments happy_eyeballs_delay and interleave to specify Happy Eyeballs behavior bpo 33291 Do not raise AttributeError when calling the inspect functions isgeneratorfunction iscoroutinefunction isasyncgenfunction on a method created from an arbitrary callable Instead return False bpo 31310 Fix the multiprocessing semaphore_tracker so it is reused by child processes bpo 31292 Fix setup py check restructuredtext for files containing include directives Documentation bpo 36625 Remove obsolete comments from docstrings in fractions Fraction bpo 30840 Document relative imports bpo 36523 Add docstring for io IOBase writelines bpo 36425 New documentation translation Simplified Chinese bpo 36345 Avoid the duplication of code from Tools scripts serve py in using the literalinclude directive for the basic wsgiref based web server in the documentation of wsgiref Contributed by Stéphane Wirtel bpo 36345 Using the code of the Tools scripts serve py script as an example in the wsgiref documentation Contributed by Stéphane Wirtel bpo 36157 Added Documention for PyInterpreterState_Main bpo 33043 Updates the docs python org page with the addition of a Contributing to Docs link at the end of the page between Reporting Bugs and About Documentation Updates the Found a Bug page with additional links and information in the Documentation Bugs section bpo 35581 typing type_check_only now,en
1685, allows type stubs to mark functions and classes not available during runtime bpo 33832 Add glossary entry for magic method bpo 32913 Added re Match groupdict example to regex HOWTO Tests bpo 36719 regrtest now always detects uncollectable objects Previously the check was only enabled by findleaks The check now also works with jN multiprocess N findleaks becomes a deprecated alias to fail env changed bpo 36725 When using multiprocessing mode jN regrtest now better reports errors if a worker process fails and it exits immediately on a worker thread failure or when interrupted bpo 36454 Change test_time test_monotonic to test only the lower bound of elapsed time after a sleep command rather than the upper bound This prevents unnecessary test failures on slow buildbots Patch by Victor Stinner bpo 32424 Improve test coverage for xml etree ElementTree Patch by Gordon P Hemsley bpo 32424 Fix typo in test_cyclic_gc test for xml etree ElementTree Patch by Gordon P Hemsley bpo 36635 Add a new _testinternalcapi module to test the internal C API bpo 36629 Fix test_imap4_host_default_value of test_imaplib catch also errno ENETUNREACH error bpo 36611 Fix test_sys test_getallocatedblocks when tracemalloc is enabled bpo 36560 Fix reference leak hunting in regrtest compute also deltas of reference count allocated memory blocks file descriptor count during warmup to ensure that everything is initialized before starting to hunt reference leaks bpo 36565 Fix reference hunting python3 m test R 3 3 when Python has no built in abc module bpo 31904 Port test_resource to VxWorks skip tests cases setting RLIMIT_FSIZE and RLIMIT_CPU bpo 31904 Fix test_tabnanny on VxWorks adjust ENOENT error message bpo 36436 Fix _testcapi pymem_buffer_overflow handle memory allocation failure bpo 31904 Fix test_utf8_mode on VxWorks Python always use UTF 8 on VxWorks bpo 36341 Fix tests that may fail with PermissionError upon calling bind on AF_UNIX sockets Build bpo 36747 Remove the stale scriptsinstall Makefile target bpo 21536 On Unix C extensions are no longer linked to libpython except on Android and Cygwin It is now possible for a statically linked Python to load a C extension built using a shared library Python When Python is embedded libpython must not be loaded with RTLD_LOCAL but RTLD_GLOBAL instead Previously using RTLD_LOCAL it was already not possible to load C extensions which were not linked to libpython such as C extensions of the standard library built by the shared section of Modules Setup distutils python config and python config py have been modified bpo 36707 configure with pymalloc no longer adds the m flag to SOABI sys implementation cache_tag Enabling or disabling pymalloc has no impact on the ABI bpo 36635 Change PyAPI_FUNC type PyAPI_DATA type and PyMODINIT_FUNC macros of pyport h when Py_BUILD_CORE_MODULE is defined The Py_BUILD_CORE_MODULE define must be now be used to build a C extension as a dynamic library accessing Python internals export the PyInit_ xxx function in DLL exports on Windows bpo 31904 Don t build the _crypt extension on VxWorks bpo 36618 Add fmax type align 8 to CFLAGS when clang compiler is detected The pymalloc memory allocator aligns memory on 8 bytes On x86 64 clang expects alignment on 16 bytes by default and so uses MOVAPS instruction which can lead to segmentation fault Instruct clang that Python is limited to alignment on 8 bytes to use MOVUPS instruction instead slower but don t trigger a SIGSEGV if the memory is not aligned on 16 bytes Sadly the flag must be added to CFLAGS and not just CFLAGS_NODIST since third party C extensions can have the same issue bpo 36605 make tags and make TAGS now also parse Modules _io c and Modules _io h bpo 36465 Release builds and debug builds are now ABI compatible defining the Py_DEBUG macro no longer implies the Py_TRACE_REFS macro which introduces the only ABI incompatibility The Py_TRACE_REFS macro which adds the sys getobjects function and the PYTHONDUMPREFS environment variable can be set using the new configure with trace refs build option bpo 36577 setup py now correct,en
1686,ly reports missing OpenSSL headers and libraries again bpo 36544 Fix regression introduced in bpo 36146 refactoring setup py bpo 36508 python config ldflags no longer includes flags of the LINKFORSHARED variable The LINKFORSHARED variable must only be used to build executables bpo 36503 Remove references to aix3 and aix4 Patch by M Felt Windows bpo 35920 Added platform win32_edition and platform win32_is_iot Added support for cross compiling packages for Windows ARM32 Skip tests that are not expected to work on Windows IoT Core ARM32 bpo 36649 Remove trailing spaces for registry keys when installed via the Store bpo 34144 Fixed activate bat to correctly update codepage when chcp com returns dots in output Patch by Lorenz Mende bpo 36509 Added preset iot layout for Windows IoT ARM containers This layout doesn t contain UI components like tkinter or IDLE It also doesn t contain files to support on target builds since Windows ARM32 builds must be cross compiled when using MSVC bpo 35941 enum_certificates function of the ssl module now returns certificates from all available certificate stores inside windows in a query instead of returning only certificates from the system wide certificate store This includes certificates from these certificate stores local machine local machine enterprise local machine group policy current user current user group policy services users ssl enum_crls function is changed in the same way to return all certificate revocation lists inside the windows certificate revocation list stores bpo 36441 Fixes creating a venv when debug binaries are installed bpo 36085 Enable better DLL resolution on Windows by using safe DLL search paths and adding os add_dll_directory bpo 36010 Add the venv standard library module to the nuget distribution for Windows bpo 29515 Add the following socket module constants on Windows IPPROTO_AH IPPROTO_CBT IPPROTO_DSTOPTS IPPROTO_EGP IPPROTO_ESP IPPROTO_FRAGMENT IPPROTO_GGP IPPROTO_HOPOPTS IPPROTO_ICLFXBM IPPROTO_ICMPV6 IPPROTO_IDP IPPROTO_IGMP IPPROTO_IGP IPPROTO_IPV4 IPPROTO_IPV6 IPPROTO_L2TP IPPROTO_MAX IPPROTO_ND IPPROTO_NONE IPPROTO_PGM IPPROTO_PIM IPPROTO_PUP IPPROTO_RDP IPPROTO_ROUTING IPPROTO_SCTP IPPROTO_ST bpo 35947 Added current version of libffi to cpython source deps Change _ctypes to use current version of libffi on Windows bpo 34060 Report system load when running test suite on Windows Patch by Ammar Askar Based on prior work by Jeremy Kloth bpo 31512 With the Windows 10 Creators Update non elevated users can now create symlinks as long as the computer has Developer Mode enabled macOS bpo 34602 Avoid failures setting macOS stack resource limit with resource setrlimit This reverts an earlier fix for bpo 18075 which forced a non default stack size when building the interpreter executable on macOS IDLE bpo 36429 Fix starting IDLE with pyshell Add idlelib pyshell alias at top remove pyshell alias at bottom Remove obsolete __name__ __main__ command Tools Demos bpo 14546 Fix the argument handling in Tools scripts lll py C API bpo 36763 Fix memory leak in Py_SetStandardStreamEncoding release memory if the function is called twice bpo 36641 PyDoc_VAR name and PyDoc_STRVAR name str now create static const char name instead of static char name Patch by Inada Naoki bpo 36389 Change the value of CLEANBYTE DEADDYTE and FORBIDDENBYTE internal constants used by debug hooks on Python memory allocators PyMem_SetupDebugHooks function Byte patterns 0xCB 0xDB and 0xFB have been replaced with 0xCD 0xDD and 0xFD to use the same values than Windows CRT debug malloc and free bpo 36443 Since Python 3 7 0 calling Py_DecodeLocale before Py_Initialize produces mojibake if the LC_CTYPE locale is coerced and or if the UTF 8 Mode is enabled by the user configuration The LC_CTYPE coercion and UTF 8 Mode are now disabled by default to fix the mojibake issue They must now be enabled explicitly opt in using the new _Py_PreInitialize API with _PyPreConfig bpo 36025 Fixed an accidental change to the datetime C API where the arguments to the PyDate_FromTimestamp function were incorrectly interpret,en
1687,ed as a single timestamp rather than an arguments tuple which causes existing code to start raising TypeError The backwards incompatible change was only present in alpha releases of Python 3 8 Patch by Paul Ganssle bpo 35810 Modify PyObject_Init to correctly increase the refcount of heap allocated Type objects Also fix the refcounts of the heap allocated types that were either doing this manually or not decreasing the type s refcount in tp_dealloc Python 3 8 0 alpha 3 Release date 2019 03 25 Security bpo 36216 Changes urlsplit to raise ValueError when the URL contains characters that decompose under IDNA encoding NFKC normalization into characters that affect how the URL is parsed bpo 35121 Don t send cookies of domain A without Domain attribute to domain B when domain A is a suffix match of domain B while using a cookiejar with http cookiejar DefaultCookiePolicy policy Patch by Karthikeyan Singaravelan Core and Builtins bpo 36421 Fix a possible double decref in _ctypes c s PyCArrayType_new bpo 36412 Fix a possible crash when creating a new dictionary bpo 36398 Fix a possible crash in structseq_repr bpo 36256 Fix bug in parsermodule when parsing a state in a DFA that has two or more arcs with labels of the same type Patch by Pablo Galindo bpo 36365 repr structseq is no longer limited to 512 bytes bpo 36374 Fix a possible null pointer dereference in merge_consts_recursive Patch by Zackery Spytz bpo 36236 At Python initialization the current directory is no longer prepended to sys path if it has been removed bpo 36352 Python initialization now fails with an error rather than silently truncating paths if a path is too long bpo 36301 Python initialization now fails if decoding pybuilddir txt configuration file fails at startup bpo 36333 Fix leak in _PyRuntimeState_Fini Contributed by Stéphane Wirtel bpo 36332 The builtin compile can now handle AST objects that contain assignment expressions Patch by Pablo Galindo bpo 36282 Improved error message for too much positional arguments in some builtin functions bpo 30040 New empty dict uses fewer memory for now It used more memory than empty dict created by dict clear And empty dict creation and deletion is about 2x faster Patch by Inada Naoki bpo 36262 Fix an unlikely memory leak on conversion from string to float in the function _Py_dg_strtod used by float str complex str pickle load marshal load etc bpo 36252 Update Unicode databases to version 12 0 0 bpo 36218 Fix a segfault occurring when sorting a list of heterogeneous values Patch contributed by Rémi Lapeyre and Elliot Gorokhovsky bpo 36188 Cleaned up left over vestiges of Python 2 unbound method handling in method objects and documentation Patch by Martijn Pieters bpo 36124 Add a new interpreter specific dict and expose it in the C API via PyInterpreterState_GetDict This parallels PyThreadState_GetDict However extension modules should continue using PyModule_GetState for their own internal per interpreter state bpo 35975 Add a feature_version flag to ast parse documented and compile hidden that allows tweaking the parser to support older versions of the grammar In particular if feature_version is 5 or 6 the hacks for the async and await keyword from PEP 492 are reinstated For 7 or higher these are unconditionally treated as keywords but they are still special tokens rather than NAME tokens that the parser driver recognizes bpo 31904 Use UTF 8 as the system encoding on VxWorks bpo 36048 The __index__ special method will be used instead of __int__ for implicit conversion of Python numbers to C integers Using the __int__ method in implicit conversions has been deprecated bpo 35808 Retire pgen and use a modified version of pgen2 to generate the parser Patch by Pablo Galindo Library bpo 36401 The class documentation created by pydoc now has a separate section for readonly properties bpo 36320 The typing NamedTuple class has deprecated the _field_types attribute in favor of the __annotations__ attribute which carried the same information Also both attributes were converted from OrderedDict to a regular dict bpo 34745 Fix asyncio ,en
1688,ssl memory issues caused by circular references bpo 36324 Add method to statistics NormalDist for computing the inverse cumulative normal distribution bpo 36321 collections namedtuple misspelled the name of an attribute To be consistent with typing NamedTuple the attribute name should have been _field_defaults instead of _fields_defaults For backwards compatibility both spellings are now created The misspelled version may be removed in the future bpo 36297 unicode_internal codec is removed It was deprecated since Python 3 3 Patch by Inada Naoki bpo 36298 Raise ModuleNotFoundError in pyclbr when a module can t be found Thanks to mental for the bug report bpo 36268 Switch the default format used for writing tars with tarfile to the modern POSIX 1 2001 pax standard from the vendor specific GNU Contributed by C A M Gerlach bpo 36285 Fix integer overflows in the array module Patch by Stephan Hohe bpo 31904 Add _signal module support for VxWorks bpo 36272 logging does not silently ignore RecursionError anymore Patch contributed by Rémi Lapeyre bpo 36280 Add a kind field to ast Constant It is u if the literal has a u prefix i e a Python 2 style unicode literal else None bpo 35931 The pdb debug command now gracefully handles all exceptions bpo 36251 Fix format strings used for stderrprinter and re Match reprs Patch by Stephan Hohe bpo 36235 Fix CFLAGS in customize_compiler of distutils sysconfig when the CFLAGS environment variable is defined don t override CFLAGS variable with the OPT variable anymore Initial patch written by David Malcolm bpo 35807 Update ensurepip to install pip 19 0 3 and setuptools 40 8 0 bpo 36139 Release GIL when closing mmap objects bpo 36179 Fix two unlikely reference leaks in _hashopenssl The leaks only occur in out of memory cases bpo 36169 Add overlap method to statistics NormalDist Computes the overlapping coefficient for two normal distributions bpo 36103 Default buffer size used by shutil copyfileobj is changed from 16 KiB to 64 KiB on non Windows platform to reduce system call overhead Contributed by Inada Naoki bpo 36130 Fix pdb with skip when stepping into a frame without a __name__ global Patch by Anthony Sottile bpo 35652 shutil copytree copy_function erroneously pass DirEntry instead of a path string bpo 35178 Ensure custom warnings formatwarning function can receive line as positional argument Based on patch by Tashrif Billah bpo 36106 Resolve potential name clash with libm s sinpi Patch by Dmitrii Pasechnik bpo 36091 Clean up reference to async generator in Lib types Patch by Henry Chen bpo 36043 FileCookieJar supports path like object Contributed by Stéphane Wirtel bpo 35899 Enum has been fixed to correctly handle empty strings and strings with non Latin characters ie α א without crashing Original patch contributed by Maxwell Assisted by Stéphane Wirtel bpo 21269 Add args and kwargs properties to mock call objects Contributed by Kumar Akshay bpo 30670 pprint pp has been added to pretty print objects with dictionary keys being sorted with their insertion order by default Parameter sort_dicts has been added to pprint pprint pprint pformat and pprint PrettyPrinter Contributed by Rémi Lapeyre bpo 35843 Implement __getitem__ for _NamespacePath Patch by Anthony Sottile bpo 35802 Clean up code which checked presence of os stat os lstat os chmod which are always present Patch by Anthony Sottile bpo 35715 Librates the return value of a ProcessPoolExecutor _process_worker after it s no longer needed to free memory bpo 35493 Use multiprocessing connection wait instead of polling each 0 2 seconds for worker updates in multiprocessing Pool Patch by Pablo Galindo bpo 35661 Store the venv prompt in pyvenv cfg bpo 35121 Don t set cookie for a request when the request path is a prefix match of the cookie s path attribute but doesn t end with Patch by Karthikeyan Singaravelan bpo 21478 Calls to a child function created with unittest mock create_autospec should propagate to the parent Patch by Karthikeyan Singaravelan bpo 35198 Fix C extension compilation on AIX Documentation bpo 36329 Declare the path of t,en
1689,he Python binary for the usage of Tools scripts serve py when executing make C Doc serve Contributed by Stéphane Wirtel bpo 36138 Improve documentation about converting datetime timedelta to scalars bpo 21314 A new entry was added to the Core Language Section of the Programming FAQ which explaines the usage of slash in the signature of a function Patch by Lysandros Nikolaou Tests bpo 36234 test_posix PosixUidGidTests add tests for invalid uid gid type str Initial patch written by David Malcolm bpo 29571 Fix test_re test_locale_flag use locale getpreferredencoding rather than locale getlocale to get the locale encoding With some locales locale getlocale returns the wrong encoding bpo 36123 Fix race condition in test_socket Build bpo 36356 Fix leaks that led to build failure when configured with address sanitizer bpo 36146 Add TEST_EXTENSIONS constant to setup py to allow to not build test extensions like _testcapi bpo 36146 Fix setup py on macOS only add usr include ffi to include directories of _ctypes not for all extensions bpo 31904 Enable build system to cross build for VxWorks RTOS Windows bpo 36312 Fixed decoders for the following code pages 50220 50221 50222 50225 50227 50229 57002 through 57011 65000 and 42 bpo 36264 Don t honor POSIX HOME in os path expanduser on windows Patch by Anthony Sottile bpo 24643 Fix name collisions due to define timezone _timezone in PC pyconfig h IDLE bpo 36405 Use dict unpacking in idlelib bpo 36396 Remove fgBg param of idlelib config GetHighlight This param was only used twice and changed the return type bpo 36176 Fix IDLE autocomplete calltip popup colors Prevent conflicts with Linux dark themes and slightly darken calltip background bpo 23205 For the grep module add tests for findfiles refactor findfiles to be a module level function and refactor findfiles to use os walk bpo 23216 Add docstrings to IDLE search modules bpo 36152 Remove colorizer ColorDelegator close_when_done and the corresponding argument of close In IDLE both have always been None or False since 2007 bpo 32129 Avoid blurry IDLE application icon on macOS with Tk 8 6 Patch by Kevin Walzer bpo 36096 Refactor class variables to instance variables in colorizer bpo 30348 Increase test coverage of idlelib autocomplete by 30 Patch by Louie Lu Tools Demos bpo 35132 Fix py list and py bt commands of python gdb py on gdb7 bpo 32217 Fix freeze script on Windows C API bpo 36381 Raise DeprecationWarning when formats are used for building or parsing values without PY_SSIZE_T_CLEAN bpo 36142 The whole coreconfig h header is now excluded from Py_LIMITED_API Move functions definitions into a new internal pycore_coreconfig h header Python 3 8 0 alpha 2 Release date 2019 02 25 Core and Builtins bpo 36052 Raise a SyntaxError when assigning a value to __debug__ with the Assignment Operator Contributed by Stéphane Wirtel and Pablo Galindo bpo 36012 Doubled the speed of class variable writes When a non dunder attribute was updated there was an unnecessary call to update slots bpo 35942 The error message emitted when returning invalid types from __fspath__ in interfaces that allow passing PathLike objects has been improved and now it does explain the origin of the error bpo 36016 gc get_objects can now receive an optional parameter indicating a generation to get objects from Patch by Pablo Galindo bpo 1054041 When the main interpreter exits due to an uncaught KeyboardInterrupt the process now exits in the appropriate manner for its parent process to detect that a SIGINT or C terminated the process This allows shells and batch scripts to understand that the user has asked them to stop bpo 35992 Fix __class_getitem__ not being called on a class with a custom non subscriptable metaclass bpo 35993 Fix a crash on fork when using subinterpreters Contributed by Stéphane Wirtel bpo 35991 Fix a potential double free in Modules _randommodule c bpo 35961 Fix a crash in slice_richcompare use strong references rather than stolen references for the two temporary internal tuples bpo 35911 Enable the creation of cell objects by adding a cell __new__ meth,en
1690,od and expose the type cell in Lib types py under the name CellType Patch by Pierre Glaser bpo 12822 Use monotonic clock for pthread_cond_timedwait when pthread_condattr_setclock and CLOCK_MONOTONIC are available bpo 15248 The compiler emits now syntax warnings in the case when a comma is likely missed before tuple or list bpo 35886 The implementation of PyInterpreterState has been moved into the internal header files guarded by Py_BUILD_CORE bpo 31506 Clarify the errors reported when object __new__ and object __init__ receive more than one argument Contributed by Sanyam Khurana bpo 35724 Signal handling is now guaranteed to happen relative to the main interpreter bpo 33608 We added a new internal _Py_AddPendingCall that operates relative to the provided interpreter This allows us to use the existing implementation to ask another interpreter to do work that cannot be done in the current interpreter like decref an object the other interpreter owns The existing Py_AddPendingCall only operates relative to the main interpreter bpo 33989 Fix a possible crash in list sort when sorting objects with ob_type tp_richcompare NULL Patch by Zackery Spytz Library bpo 35512 unittest mock patch dict used as a decorator with string target resolves the target during function call instead of during decorator construction Patch by Karthikeyan Singaravelan bpo 36018 Add statistics NormalDist a tool for creating and manipulating normal distributions of random variable Features a composite class that treats the mean and standard deviation of measurement data as single entity bpo 35904 Added statistics fmean as a faster floating point variant of the existing mean function bpo 35918 Removed broken has_key method from multiprocessing managers SyncManager dict Contributed by Rémi Lapeyre bpo 18283 Add support for bytes to shutil which bpo 35960 Fix dataclasses field throwing away empty mapping objects passed as metadata bpo 35500 Write expected and actual call parameters on separate lines in unittest mock Mock assert_called_with assertion errors Contributed by Susan Su bpo 35931 The pdb debug command now gracefully handles syntax errors bpo 24209 In http server script rely on getaddrinfo to bind to preferred address based on the bind parameter Now default bind or binding to a name may bind to IPv6 or dual stack depending on the environment bpo 35321 Set __spec__ origin of _frozen_importlib to frozen so that it matches the behavior of _frozen_importlib_external Patch by Nina Zakharenko bpo 35378 Fix a reference issue inside multiprocessing Pool that caused the pool to remain alive if it was deleted without being closed or terminated explicitly A new strong reference is added to the pool iterators to link the lifetime of the pool to the lifetime of its iterators so the pool does not get destroyed if a pool iterator is still alive bpo 34294 re module fix wrong capturing groups in rare cases re search re findall re sub and other functions that scan through string looking for a match should reset capturing groups between two match attempts Patch by Ma Lin bpo 35615 weakref Fix a RuntimeError when copying a WeakKeyDictionary or a WeakValueDictionary due to some keys or values disappearing while iterating bpo 35606 Implement math prod as analogous function to sum that returns the product of a start value default 1 times an iterable of numbers Patch by Pablo Galindo bpo 32417 Performing arithmetic between datetime datetime subclasses and datetime timedelta now returns an object of the same type as the datetime datetime subclass As a result datetime datetime astimezone and alternate constructors like datetime datetime now and datetime fromtimestamp called with a tz argument now also retain their subclass bpo 35153 Add headers optional keyword only parameter to xmlrpc client ServerProxy xmlrpc client Transport and xmlrpc client SafeTransport Patch by Cédric Krier bpo 34572 Fix C implementation of pickle loads to use importlib s locking mechanisms and thereby avoid using partially loaded modules Patch by Tim Burgess Documentation bpo 36083 Fix formatting of ,en
1691,check hash based pycs options in the manpage Synopsis bpo 36007 Bump minimum sphinx version to 1 8 Patch by Anthony Sottile bpo 22062 Update documentation and docstrings for pathlib Original patch by Mike Short Tests bpo 27313 Avoid test_ttk_guionly ComboboxTest failure with macOS Cocoa Tk bpo 36019 Add test support TEST_HTTP_URL and replace references of http www example com by this new constant Contributed by Stéphane Wirtel bpo 36037 Fix test_ssl for strict OpenSSL configuration like RHEL8 strict crypto policy Use older TLS version for minimum TLS version of the server SSL context if needed to test TLS version older than default minimum TLS version bpo 35798 Added test support check_syntax_warning bpo 35505 Make test_imap4_host_default_value independent on whether the local IMAP server is running bpo 35917 multiprocessing provide unit tests for SyncManager and SharedMemoryManager classes all the shareable types which are supposed to be supported by them patch by Giampaolo Rodola bpo 35704 Skip test_shutil test_unpack_archive_xztar to prevent a MemoryError on 32 bit AIX when MAXDATA setting is less than 0x20000000 Patch by Michael Felt aixtools bpo 34720 Assert m_state NULL to mimic GC traversal functions that do not correctly handle module creation when the module state has not been created Windows bpo 35976 Added ARM build support to Windows build files in PCBuild bpo 35692 pathlib no longer raises when checking file and directory existence on drives that are not ready bpo 35872 Uses the base Python executable when invoking venv in a virtual environment bpo 35873 Prevents venv paths being inherited by child processes bpo 35299 Fix sysconfig detection of the source directory and distutils handling of pyconfig h during PGO profiling IDLE bpo 24310 IDLE Document settings dialog font tab sample bpo 35833 Revise IDLE doc for control codes sent to Shell Add a code example block bpo 35689 Add docstrings and unittests for colorizer py Python 3 8 0 alpha 1 Release date 2019 02 03 Security bpo 35746 CVE 2019 5010 Fix a NULL pointer deref in ssl module The cert parser did not handle CRL distribution points with empty DP or URI correctly A malicious or buggy certificate can result into segfault Vulnerability TALOS 2018 0758 reported by Colin Read and Nicolas Edet of Cisco bpo 34812 The I command line option run Python in isolated mode is now also copied by the multiprocessing and distutils modules when spawning child processes Previously only E and s options enabled by I were copied bpo 34791 The xml sax and xml dom domreg no longer use environment variables to override parser implementations when sys flags ignore_environment is set by E or I arguments bpo 17239 The xml sax and xml dom minidom parsers no longer processes external entities by default External DTD and ENTITY declarations no longer load files or create network connections bpo 34623 CVE 2018 14647 The C accelerated _elementtree module now initializes hash randomization salt from _Py_HashSecret instead of libexpat s default CSPRNG bpo 34405 Updated to OpenSSL 1 1 0i for Windows builds bpo 33871 Fixed sending the part of the file in os sendfile on macOS Using the trailers argument could cause sending more bytes from the input file than was specified bpo 32533 Fixed thread safety of error handling in _ssl bpo 33136 Harden ssl module against LibreSSL CVE 2018 8970 X509_VERIFY_PARAM_set1_host is called with an explicit namelen A new test ensures that NULL bytes are not allowed bpo 33001 Minimal fix to prevent buffer overrun in os symlink on Windows bpo 32981 Regexes in difflib and poplib were vulnerable to catastrophic backtracking These regexes formed potential DOS vectors REDOS They have been refactored This resolves CVE 2018 1060 and CVE 2018 1061 Patch by Jamie Davis bpo 28414 The ssl module now allows users to perform their own IDN en decoding when using SNI Core and Builtins bpo 35877 Make parenthesis optional for named expressions in while statement Patch by Karthikeyan Singaravelan bpo 35814 Allow same right hand side expressions in annotated assignments as in no,en
1692,rmal ones In particular x Tuple int int 1 2 without parentheses on the right is now allowed bpo 35766 Add the option to parse PEP 484 type comments in the ast module Off by default This is merging the key functionality of the third party fork thereof typed_ast https github com python typed_ast bpo 35713 Reorganize Python initialization to get working exceptions and sys stderr earlier bpo 33416 Add end line and end column position information to the Python AST nodes This is a C level backwards incompatible change bpo 35720 Fixed a minor memory leak in pymain_parse_cmdline_impl function in Modules main c bpo 35634 func kwargs will now raise an error when kwargs is a mapping containing multiple entries with the same key An error was already raised when other keyword arguments are passed before kwargs since Python 3 6 bpo 35623 Fix a crash when sorting very long lists Patch by Stephan Hohe bpo 35214 clang Memory Sanitizer build instrumentation was added to work around false positives from posix socket time test_io and test_faulthandler bpo 35560 Fix an assertion error in format in debug build for floating point formatting with n format zero padding and small width Release build is not impacted Patch by Karthikeyan Singaravelan bpo 35552 Format characters s and V in PyUnicode_FromFormat and s in PyBytes_FromFormat no longer read memory past the limit if precision is specified bpo 35504 Fix segfaults and SystemError s when deleting certain attributes Patch by Zackery Spytz bpo 35504 Fixed a SystemError when delete the characters_written attribute of an OSError bpo 35494 Improved syntax error messages for unbalanced parentheses in f string bpo 35444 Fixed error handling in pickling methods when fail to look up builtin getattr Sped up pickling iterators bpo 35436 Fix various issues with memory allocation error handling Patch by Zackery Spytz bpo 35423 Separate the signal handling trigger in the eval loop from the pending calls machinery There is no semantic change and the difference in performance is insignificant bpo 35357 Internal attributes names of unittest mock _Call and unittest mock MagicProxy name parent from_kall are now prefixed with _mock_ in order to prevent clashes with widely used object attributes Fixed minor typo in test function name bpo 35372 Fixed the code page decoder for input longer than 2 GiB containing undecodable bytes bpo 35336 Fix PYTHONCOERCECLOCALE 1 environment variable only coerce the C locale if the LC_CTYPE locale is C bpo 31241 The lineno and col_offset attributes of AST nodes for list comprehensions generator expressions and tuples are now point to the opening parenthesis or square brace For tuples without parenthesis they point to the position of the first item bpo 33954 For str format float __format__ and complex __format__ methods for non ASCII decimal point when using the n formatter bpo 35269 Fix a possible segfault involving a newly created coroutine Patch by Zackery Spytz bpo 35224 Implement PEP 572 assignment expressions Patch by Emily Morehouse bpo 32492 Speed up namedtuple attribute access by 1 6x using a C fast path for the name descriptors Patch by Pablo Galindo bpo 35214 Fixed an out of bounds memory access when parsing a truncated unicode escape sequence at the end of a string such as N It would read one byte beyond the end of the memory allocation bpo 35214 The interpreter and extension modules have had annotations added so that they work properly under clang s Memory Sanitizer A new configure flag with memory sanitizer has been added to make test builds of this nature easier to perform bpo 35193 Fix an off by one error in the bytecode peephole optimizer where it could read bytes beyond the end of bounds of an array when removing unreachable code This bug was present in every release of Python 3 6 and 3 7 until now bpo 35169 Improved error messages for forbidden assignments bpo 34022 Fix handling of hash based bytecode files in zipimport Patch by Elvis Pranskevichus bpo 28401 Debug builds will no longer to attempt to import extension modules built for the ABI as they were never c,en
1693,ompatible to begin with Patch by Stefano Rivera bpo 29341 Clarify in the docstrings of os methods that path like objects are also accepted as input parameters bpo 35050 socket Fix off by one bug in length check for AF_ALG name and type bpo 29743 Raise ValueError instead of OverflowError in case of a negative _length_ in a ctypes Array subclass Also raise TypeError instead of AttributeError for non integer _length_ Original patch by Oren Milman bpo 16806 Fix lineno and col_offset for multi line string tokens bpo 35029 SyntaxWarning raised as an exception at code generation time will be now replaced with a SyntaxError for better error reporting bpo 34983 Expose symtable Symbol is_nonlocal in the symtable module Patch by Pablo Galindo bpo 34974 bytes and bytearray constructors no longer convert unexpected exceptions e g MemoryError and KeyboardInterrupt to TypeError bpo 34939 Allow annotated names in module namespace that are declared global before the annotation happens Patch by Pablo Galindo bpo 34973 Fixed crash in bytes when the list argument is mutated while it is iterated bpo 34876 The lineno and col_offset attributes of the AST for decorated function and class refer now to the position of the corresponding def async def and class instead of the position of the first decorator This leads to more correct line reporting in tracing This is the only case when the position of child AST nodes can precede the position of the parent AST node bpo 34879 Fix a possible null pointer dereference in bytesobject c Patch by Zackery Spytz bpo 34784 Fix the implementation of PyStructSequence_NewType in order to create heap allocated StructSequences bpo 32912 A SyntaxWarning is now emitted instead of a DeprecationWarning for invalid escape sequences in string and bytes literals bpo 34854 Fixed a crash in compiling string annotations containing a lambda with a keyword only argument that doesn t have a default value bpo 34850 The compiler now produces a SyntaxWarning when identity checks is and is not are used with certain types of literals e g strings ints These can often work by accident in CPython but are not guaranteed by the language spec The warning advises users to use equality tests and instead bpo 34824 Fix a possible null pointer dereference in Modules _ssl c Patch by Zackery Spytz bpo 30156 The C function property_descr_get uses a cached tuple to optimize function calls But this tuple can be discovered in debug mode with sys getobjects Remove the optimization it s not really worth it and it causes 3 different crashes last years bpo 34762 Fix contextvars C API to use PyObject pointer types bpo 34751 The hash function for tuples is now based on xxHash which gives better collision results on formerly pathological cases Additionally on 64 bit systems it improves tuple hashes in general Patch by Jeroen Demeyer with substantial contributions by Tim Peters bpo 34735 Fix a memory leak in Modules timemodule c Patch by Zackery Spytz bpo 34683 Fixed a bug where some SyntaxError error pointed to locations that were off by one bpo 34651 Only allow the main interpreter to fork The avoids the possibility of affecting the main interpreter which is critical to operation of the runtime bpo 34653 Remove unused function PyParser_SimpleParseStringFilename bpo 32236 Warn that line buffering is not supported if open is called with binary mode and buffering 1 bpo 34641 Further restrict the syntax of the left hand side of keyword arguments in function calls In particular f keyword arg is now disallowed bpo 34637 Make the start argument to sum visible as a keyword argument bpo 1621 Do not assume signed integer overflow behavior C undefined behavior when performing set hash table resizing bpo 34588 Fix an off by one in the recursive call pruning feature of traceback formatting bpo 34485 On Windows the LC_CTYPE is now set to the user preferred locale at startup Previously the LC_CTYPE locale was C at startup but changed when calling setlocale LC_CTYPE or setlocale LC_ALL bpo 34485 Standard streams like sys stdout now use the surrogateescape error handler ,en
1694,instead of strict on the POSIX locale when the C locale is not coerced and the UTF 8 Mode is disabled bpo 34485 Fix the error handler of standard streams like sys stdout PYTHONIOENCODING is now ignored instead of setting the error handler to strict bpo 34485 Python now gets the locale encoding with C code to initialize the encoding of standard streams like sys stdout Moreover the encoding is now initialized to the Python codec name to get a normalized encoding name and to ensure that the codec is loaded The change avoids importing _bootlocale and _locale modules at startup by default bpo 34527 On FreeBSD Py_DecodeLocale and Py_EncodeLocale now also forces the ASCII encoding if the LC_CTYPE locale is POSIX not only if the LC_CTYPE locale is C bpo 34527 The UTF 8 Mode is now also enabled by the POSIX locale not only by the C locale bpo 34403 On HP UX with C or POSIX locale sys getfilesystemencoding now returns ascii instead of roman8 when the UTF 8 Mode is disabled and the C locale is not coerced bpo 34523 The Python filesystem encoding is now read earlier during the Python initialization bpo 12458 Tracebacks show now correct line number for subexpressions in multiline expressions Tracebacks show now the line number of the first line for multiline expressions instead of the line number of the last subexpression bpo 34408 Prevent a null pointer dereference and resource leakage in PyInterpreterState_New bpo 34400 Fix undefined behavior in parsetok c Patch by Zackery Spytz bpo 33073 Added as_integer_ratio to ints to make them more interoperable with floats bpo 34377 Update valgrind suppression list to use _PyObject_Free _PyObject_Realloc instead of PyObject_Free PyObject_Realloc bpo 34353 Added the socket option in the stat filemode Python implementation to match the C implementation bpo 34320 Fix dict od didn t copy iteration order of OrderedDict bpo 34113 Fixed crash on debug builds when opcode stack was adjusted with negative numbers Patch by Constantin Petrisor bpo 34100 Compiler now merges constants in tuples and frozensets recursively Code attributes like co_names are merged too bpo 34151 Performance of list concatenation repetition and slicing operations is slightly improved Patch by Sergey Fedoseev bpo 34170 X dev it is now possible to override the memory allocator using PYTHONMALLOC even if the developer mode is enabled bpo 33237 Improved AttributeError message for partially initialized module bpo 34149 Fix min and max functions to get default behavior when key is None bpo 34125 Profiling of unbound built in methods now works when kwargs is given bpo 34141 Optimized pickling atomic types None bool int float bytes str bpo 34126 Fix crashes when profiling certain invalid calls of unbound methods Patch by Jeroen Demeyer bpo 24618 Fixed reading invalid memory when create the code object with too small varnames tuple or too large argument counts bpo 34068 In io IOBase close ensure that the closed attribute is not set with a live exception Patch by Zackery Spytz and Serhiy Storchaka bpo 34087 Fix buffer overflow while converting unicode to numeric values bpo 34080 Fixed a memory leak in the compiler when it raised some uncommon errors during tokenizing bpo 34066 Disabled interruption by Ctrl C between calling open and entering a with block in with open bpo 34042 Fix dict copy to maintain correct total refcount as reported by sys gettotalrefcount bpo 33418 Fix potential memory leak in function object when it creates reference cycle bpo 33985 Implement contextvars ContextVar name attribute bpo 33956 Update vendored Expat library copy to version 2 2 5 bpo 24596 Decref the module object in PyRun_SimpleFileExFlags before calling PyErr_Print Patch by Zackery Spytz bpo 33451 Close directly executed pyc files before calling PyEval_EvalCode bpo 1617161 The hash of BuiltinMethodType instances methods of built in classes now depends on the hash of the identity of __self__ instead of its value The hash and equality of ModuleType and MethodWrapperType instances methods of user defined classes and some methods of built in classes like s,en
1695,tr __add__ now depend on the hash and equality of the identity of __self__ instead of its value MethodWrapperType instances no longer support ordering bpo 33824 Fix LC_ALL C python3 7 V reset properly the command line parser when the encoding changes after reading the Python configuration bpo 33803 Fix a crash in hamt c caused by enabling GC tracking for an object that hadn t all of its fields set to NULL bpo 33738 Seven macro incompatibilities with the Limited API were fixed and the macros PyIter_Check PyIndex_Check and PyExceptionClass_Name were added as functions A script for automatic macro checks was added bpo 33786 Fix asynchronous generators to handle GeneratorExit in athrow correctly bpo 30167 PyRun_SimpleFileExFlags removes __cached__ from module in addition to __file__ bpo 33706 Fix a crash in Python initialization when parsing the command line options Thanks Christoph Gohlke for the bug report and the fix bpo 33597 Reduce PyGC_Head size from 3 words to 2 words bpo 30654 Fixed reset of the SIGINT handler to SIG_DFL on interpreter shutdown even when there was a custom handler set previously Patch by Philipp Kerling bpo 33622 Fixed a leak when the garbage collector fails to add an object with the __del__ method or referenced by it into the gc garbage list PyGC_Collect can now be called when an exception is set and preserves it bpo 33462 Make dict and dict views reversible Patch by Rémi Lapeyre bpo 23722 A RuntimeError is now raised when the custom metaclass doesn t provide the __classcell__ entry in the namespace passed to type __new__ A DeprecationWarning was emitted in Python 3 6 3 7 bpo 33499 Add PYTHONPYCACHEPREFIX environment variable and X pycache_prefix command line option to set an alternate root directory for writing module bytecode cache files bpo 25711 The zipimport module has been rewritten in pure Python bpo 33509 Fix module_globals parameter of warnings warn_explicit don t crash if module_globals is not a dict bpo 31849 Fix signed unsigned comparison warning in pyhash c bpo 33475 Fixed miscellaneous bugs in converting annotations to strings and optimized parentheses in the string representation bpo 20104 Added support for the setpgroup resetids setsigmask setsigdef and scheduler parameters of posix_spawn Patch by Pablo Galindo bpo 33391 Fix a leak in set_symmetric_difference bpo 33363 Raise a SyntaxError for async with and async for statements outside of async functions bpo 28055 Fix unaligned accesses in siphash24 Patch by Rolf Eike Beer bpo 33128 Fix a bug that causes PathFinder to appear twice on sys meta_path Patch by Pablo Galindo Salgado bpo 33331 Modules imported last are now cleared first at interpreter shutdown bpo 33312 Fixed clang ubsan undefined behavior sanitizer warnings in dictobject c by adjusting how the internal struct _dictkeysobject shared keys structure is declared bpo 33305 Improved syntax error messages for invalid numerical literals bpo 33306 Improved syntax error messages for unbalanced parentheses bpo 33234 The list constructor will pre size and not over allocate when the input length is known bpo 33270 Intern the names for all anonymous code objects Patch by Zackery Spytz bpo 30455 The C and Python code and the documentation related to tokens are now generated from a single source file Grammar Tokens bpo 33176 Add a toreadonly method to memoryviews bpo 33231 Fix potential memory leak in normalizestring bpo 33205 Change dict growth function from round_up_to_power_2 used 2 hashtable_size 2 to round_up_to_power_2 used 3 Previously dict is shrinked only when used 0 Now dict has more chance to be shrinked bpo 29922 Improved error messages in async with when __aenter__ or __aexit__ return non awaitable object bpo 33199 Fix ma_version_tag in dict implementation is uninitialized when copying from key sharing dict bpo 33053 When using the m switch sys path 0 is now explicitly expanded as the starting working directory rather than being left as the empty path which allows imports from the current working directory at the time of the import bpo 33138 Changed standard error message fo,en
1696,r non pickleable and non copyable types It now says cannot pickle instead of can t pickle or cannot serialize bpo 33018 Improve consistency of errors raised by issubclass when called with a non class and an abstract base class as the first and second arguments respectively Patch by Josh Bronson bpo 33083 math factorial no longer accepts arguments that are not int like Patch by Pablo Galindo bpo 33041 Added new opcode END_ASYNC_FOR and fixes the following issues Setting global StopAsyncIteration no longer breaks async for loops Jumping into an async for loop is now disabled Jumping out of an async for loop no longer corrupts the stack bpo 25750 Fix rare Python crash due to bad refcounting in type_getattro if a descriptor deletes itself from the class Patch by Jeroen Demeyer bpo 33041 Fixed bytecode generation for async for with a complex target A StopAsyncIteration raised on assigning or unpacking will be now propagated instead of stopping the iteration bpo 33026 Fixed jumping out of with block by setting f_lineno bpo 33005 Fix a crash on fork when using a custom memory allocator ex using PYTHONMALLOC env var _PyGILState_Reinit and _PyInterpreterState_Enable now use the default RAW memory allocator to allocate a new interpreters mutex on fork bpo 32911 Due to unexpected compatibility issues discovered during downstream beta testing reverted bpo 29463 docstring field is removed from Module ClassDef FunctionDef and AsyncFunctionDef ast nodes which was added in 3 7a1 Docstring expression is restored as a first statement in their body Based on patch by Inada Naoki bpo 17288 Prevent jumps from return and exception trace events bpo 32946 Importing names from already imported module with from import is now 30 faster if the module is not a package bpo 32932 Make error message more revealing when there are non str objects in __all__ bpo 32925 Optimized iterating and containing test for literal lists consisting of non constants x in a b and for x in a b The case of all constant elements already was optimized bpo 32889 Update Valgrind suppression list to account for the rename of Py_ADDRESS_IN_RANG to address_in_range bpo 32836 Don t use temporary variables in cases of list dict set comprehensions bpo 31356 Remove the new API added in bpo 31356 gc ensure_disabled context manager bpo 32305 For namespace packages ensure that both __file__ and __spec__ origin are set to None bpo 32303 Make sure __spec__ loader matches __loader__ for namespace packages bpo 32711 Fix the warning messages for Python ast_unparse c Patch by Stéphane Wirtel bpo 32583 Fix possible crashing in builtin Unicode decoders caused by write out of bound errors when using customized decode error handlers bpo 32489 A continue statement is now allowed in the finally clause bpo 17611 Simplified the interpreter loop by moving the logic of unrolling the stack of blocks into the compiler The compiler emits now explicit instructions for adjusting the stack of values and calling the cleaning up code for break continue and return Removed opcodes BREAK_LOOP CONTINUE_LOOP SETUP_LOOP and SETUP_EXCEPT Added new opcodes ROT_FOUR BEGIN_FINALLY and CALL_FINALLY and POP_FINALLY Changed the behavior of END_FINALLY and WITH_CLEANUP_START bpo 32285 New function unicodedata is_normalized which can check whether a string is in a specific normal form bpo 10544 Yield expressions are now disallowed in comprehensions and generator expressions except the expression for the outermost iterable bpo 32117 Iterable unpacking is now allowed without parentheses in yield and return statements e g yield 1 2 3 rest Thanks to David Cuthbert for the change and Jordan Chapman for added tests bpo 31902 Fix the col_offset attribute for ast nodes ast AsyncFor ast AsyncFunctionDef and ast AsyncWith Previously col_offset pointed to the keyword after async bpo 25862 Fix assertion failures in the tell method of io TextIOWrapper Patch by Zackery Spytz bpo 21983 Fix a crash in ctypes cast in case the type argument is a ctypes structured data type Patch by Eryk Sun and Oren Milman bpo 31577 Fix a crash in os utime in,en
1697, case of a bad ns argument Patch by Oren Milman bpo 29832 Remove references to getsockaddrarg from various socket error messages Patch by Oren Milman Library bpo 35845 Add order parameter to memoryview tobytes bpo 35864 The _asdict method for collections namedtuple now returns a regular dict instead of an OrderedDict bpo 35537 An ExitStack is now used internally within subprocess Popen to clean up pipe file handles No behavior change in normal operation But if closing one handle were ever to cause an exception the others will now be closed instead of leaked patch by Giampaolo Rodola bpo 35847 RISC V needed the CTYPES_PASS_BY_REF_HACK Fixes ctypes Structure test_pass_by_value bpo 35813 Shared memory submodule added to multiprocessing to avoid need for serialization between processes bpo 35780 Fix lru_cache errors arising in recursive reentrant or multi threaded code These errors could result in orphan links and in the cache being trapped in a state with fewer than the specified maximum number of links Fix handling of negative maxsize which should have been treated as zero Fix errors in toggling the full status flag Fix misordering of links when errors are encountered Sync up the C code and pure Python code for the space saving path in functions with a single positional argument In this common case the space overhead of an lru cache entry is reduced by almost half Fix counting of cache misses In error cases the miss count was out of sync with the actual number of times the underlying user function was called bpo 35537 os posix_spawn and os posix_spawnp now have a setsid parameter bpo 23846 asyncio ProactorEventLoop now catches and logs send errors when the self pipe is full bpo 34323 asyncio Enhance IocpProactor close log wait 1 second before the first log then log every second Log also the number of seconds since close was called bpo 35674 Add a new os posix_spawnp function Patch by Joannah Nanjekye bpo 35733 ast Constant boolean no longer an instance of ast Num Patch by Anthony Sottile bpo 35726 QueueHandler prepare now makes a copy of the record before modifying and enqueueing it to avoid affecting other handlers in the chain bpo 35719 Sped up multi argument math functions atan2 copysign remainder and hypot by 1 3 2 5 times bpo 35717 Fix KeyError exception raised when using enums and compile Patch contributed by Rémi Lapeyre bpo 35699 Fixed detection of Visual Studio Build Tools 2017 in distutils bpo 32710 Fix memory leaks in asyncio ProactorEventLoop on overlapped operation failure bpo 35702 The time CLOCK_UPTIME_RAW constant is now available for macOS 10 12 bpo 32710 Fix a memory leak in asyncio in the ProactorEventLoop when ReadFile or WSASend overlapped operation fail immediately release the internal buffer bpo 35682 Fix asyncio ProactorEventLoop sendfile don t attempt to set the result of an internal future if it s already done bpo 35283 Add a deprecated warning for the threading Thread isAlive method Patch by Donghee Na bpo 35664 Improve operator itemgetter performance by 33 with optimized argument handling and with adding a fast path for the common case of a single non negative integer index into a tuple which is the typical use case in the standard library bpo 35643 Fixed a SyntaxWarning invalid escape sequence in Modules _sha3 cleanup py Patch by Mickaël Schoentgen bpo 35619 Improved support of custom data descriptors in help and pydoc bpo 28503 The crypt module now internally uses the crypt_r library function instead of crypt when available bpo 35614 Fixed help on metaclasses Patch by Sanyam Khurana bpo 35568 Expose raise signum as raise_signal bpo 35588 The floor division and modulo operations and the divmod function on fractions Fraction types are 2 4x faster Patch by Stefan Behnel bpo 35585 Speed up building enums by value e g http HTTPStatus 200 bpo 30561 random gammavariate 1 0 beta now computes the same result as random expovariate 1 0 beta This synchronizes the two algorithms and eliminates some idiosyncrasies in the old implementation It does however produce a difference stream of random variables than,en
1698, it used to bpo 35537 The subprocess module can now use the os posix_spawn function in some cases for better performance bpo 35526 Delaying the joke of barry_as_FLUFL mandatory to Python version 4 0 bpo 35523 Remove ctypes callback workaround no longer create a callback at startup Avoid SELinux alert on import ctypes and import uuid bpo 31784 uuid uuid1 now calls time time_ns rather than int time time 1e9 bpo 35513 TextTestRunner of unittest runner now uses time perf_counter rather than time time to measure the execution time of a test time time can go backwards whereas time perf_counter is monotonic bpo 35502 Fixed reference leaks in xml etree ElementTree TreeBuilder in case of unfinished building of the tree in particular when an error was raised during parsing XML bpo 35348 Make platform architecture parsing of file command output more reliable add the b option to the file command to omit the filename force the usage of the C locale and search also the shared object pattern bpo 35491 multiprocessing Add Pool __repr__ and enhance BaseProcess __repr__ add pid and parent pid to ease debugging Pool state constant values are now strings instead of integers for example RUN value becomes RUN instead of 0 bpo 35477 multiprocessing Pool __enter__ now fails if the pool is not running with pool fails if used more than once bpo 31446 Copy command line that was passed to CreateProcessW since this function can change the content of the input buffer bpo 35471 Python 2 4 dropped MacOS 9 support The macpath module was deprecated in Python 3 7 The module is now removed bpo 23057 Unblock Proactor event loop when keyboard interrupt is received on Windows bpo 35052 Fix xml dom minidom cloneNode on a document with an entity pass the correct arguments to the user data handler of an entity bpo 20239 Allow repeated assignment deletion of unittest mock Mock attributes Patch by Pablo Galindo bpo 17185 Set __signature__ on mock for inspect to get signature Patch by Karthikeyan Singaravelan bpo 35445 Memory errors during creating posix environ no longer ignored bpo 35415 Validate fileno argument to socket socket bpo 35424 multiprocessing Pool destructor now emits ResourceWarning if the pool is still running bpo 35330 When a Mock instance was used to wrap an object if side_effect is used in one of the mocks of it methods don t call the original implementation and return the result of using the side effect the same way that it is done with return_value bpo 35346 Drop Mac OS 9 and Rhapsody support from the platform module Rhapsody last release was in 2000 Mac OS 9 last release was in 2001 bpo 10496 check_environ of distutils utils now catches KeyError on calling pwd getpwuid don t create the HOME environment variable in this case bpo 10496 posixpath expanduser now returns the input path unchanged if the HOME environment variable is not set and the current user has no home directory if the current user identifier doesn t exist in the password database This change fix the site module if the current user doesn t exist in the password database if the user has no home directory bpo 35389 platform libc_ver now uses os confstr CS_GNU_LIBC_VERSION if available and the executable parameter is not set bpo 35394 Add empty slots to asyncio abstract protocols bpo 35310 Fix a bug in select select where in some cases the file descriptor sequences were returned unmodified after a signal interruption even though the file descriptors might not be ready yet select select will now always return empty lists if a timeout has occurred Patch by Oran Avraham bpo 35380 Enable TCP_NODELAY on Windows for proactor asyncio event loop bpo 35341 Add generic version of collections OrderedDict to the typing module Patch by Ismo Toijala bpo 35371 Fixed possible crash in os utime on Windows when pass incorrect arguments bpo 35346 platform uname now redirects stderr to os devnull when running external programs like cmd c ver bpo 35066 Previously calling the strftime method on a datetime object with a trailing in the format string would result in an exception However this only occurred ,en
1699,when the datetime C module was being used the python implementation did not match this behavior Datetime is now PEP 399 compliant and will not throw an exception on a trailing bpo 35345 The function platform popen has been removed it was deprecated since Python 3 3 use os popen instead bpo 35344 On macOS platform platform now uses platform mac_ver if it returns a non empty release string to get the macOS version rather than the darwin version bpo 35312 Make lib2to3 pgen2 parse ParseError round trip pickle able Patch by Anthony Sottile bpo 35308 Fix regression in webbrowser where default browsers may be preferred over browsers in the BROWSER environment variable bpo 24746 Avoid stripping trailing whitespace in doctest fancy diff Original patch by R David Murray Jairo Trad Enhanced by Sanyam Khurana bpo 28604 locale localeconv now sets temporarily the LC_CTYPE locale to the LC_MONETARY locale if the two locales are different and monetary strings are non ASCII This temporary change affects other threads bpo 35277 Update ensurepip to install pip 18 1 and setuptools 40 6 2 bpo 24209 Adds IPv6 support when invoking http server directly bpo 35226 Recursively check arguments when testing for equality of unittest mock call objects and add note that tracking of parameters used to create ancestors of mocks in mock_calls is not possible bpo 29564 The warnings module now suggests to enable tracemalloc if the source is specified the tracemalloc module is available but tracemalloc is not tracing memory allocations bpo 35189 Modify the following fnctl function to retry if interrupted by a signal EINTR flock lockf fnctl bpo 30064 Use add_done_callback in sock_ asyncio API to unsubscribe reader writer early on calcellation bpo 35186 Removed the built with comment added when setup py upload is used with either bdist_rpm or bdist_dumb bpo 35152 Allow sending more than 2 GB at once on a multiprocessing connection on non Windows systems bpo 35062 Fix incorrect parsing of _io IncrementalNewlineDecoder s translate argument bpo 35065 Remove StreamReaderProtocol _untrack_reader The call to _untrack_reader is currently performed too soon causing the protocol to forget about the reader before connection_lost can run and feed the EOF to the reader bpo 34160 ElementTree and minidom now preserve the attribute order specified by the user bpo 35079 Improve difflib SequenceManager get_matching_blocks doc by adding non overlapping and changing to bpo 33710 Deprecated l gettext functions and methods in the gettext module They return encoded bytes instead of Unicode strings and are artifacts from Python 2 times Also deprecated functions and methods related to setting the charset for l gettext functions and methods bpo 35017 socketserver BaseServer serve_forever now exits immediately if it s shutdown method is called while it is polling for new events bpo 35024 importlib no longer logs wrote bytecode path redundantly after created could not create bytecode path is already logged Patch by Quentin Agren bpo 35047 unittest mock now includes mock calls in exception messages if assert_not_called assert_called_once or assert_called_once_with fails Patch by Petter Strandmark bpo 31047 Fix ntpath abspath regression where it didn t remove a trailing separator on Windows Patch by Tim Graham bpo 35053 tracemalloc now tries to update the traceback when an object is reused from a free list optimization for faster object creation used by the builtin list type for example bpo 31553 Add the json lines option to json tool Patch by hongweipeng bpo 34794 Fixed a leak in Tkinter when pass the Python wrapper around Tcl_Obj back to Tcl Tk bpo 34909 Enum fix grandchildren subclassing when parent mixed with concrete data types bpo 35022 unittest mock MagicMock now supports the __fspath__ method from os PathLike bpo 35008 Fixed references leaks when call the __setstate__ method of xml etree ElementTree Element in the C implementation for already initialized element bpo 23420 Verify the value for the parameter s of the cProfile CLI Patch by Robert Kuska bpo 33947 dataclasses now hand,en
1700,le recursive reprs without raising RecursionError bpo 34890 Make inspect iscoroutinefunction inspect isgeneratorfunction and inspect isasyncgenfunction work with functools partial Patch by Pablo Galindo bpo 34521 Use socket CMSG_SPACE to calculate ancillary data size instead of socket CMSG_LEN in multiprocessing reduction recvfds as RFC 3542 requires the use of the former for portable applications bpo 31522 The mailbox mbox get_string function from_ parameter can now successfully be set to a non default value bpo 34970 Protect tasks weak set manipulation in asyncio all_tasks bpo 34969 gzip Add fast best on the gzip CLI these parameters will be used for the fast compression method quick or the best method compress slower but smaller file Also change the default compression level to 6 tradeoff bpo 16965 The 2to3 execfile fixer now opens the file with mode rb Patch by Zackery Spytz bpo 34966 pydoc now supports aliases not only to methods defined in the end class but also to inherited methods The docstring is not duplicated for aliases bpo 34926 mimetypes MimeTypes guess_type now accepts path like object in addition to url strings Patch by Mayank Asthana bpo 23831 Add moveto method to the tkinter Canvas widget Patch by Juliette Monsel bpo 34941 Methods find findtext and findall of the Element class in the xml etree ElementTree module are now able to find children which are instances of Element subclasses bpo 32680 smtplib SMTP objects now always have a sock attribute present bpo 34769 Fix for async generators not finalizing when event loop is in debug mode and garbage collector runs in another thread bpo 34936 Fix TclError in tkinter Spinbox selection_element Patch by Juliette Monsel bpo 34829 Add methods selection_from selection_range selection_present and selection_to to the tkinter Spinbox for consistency with the tkinter Entry widget Patch by Juliette Monsel bpo 34911 Added secure_protocols argument to http cookiejar DefaultCookiePolicy to allow for tweaking of protocols and also to add support by default for wss the secure websocket protocol bpo 34922 Fixed integer overflow in the digest and hexdigest methods for the SHAKE algorithm in the hashlib module bpo 34925 25 speedup in argument parsing for the functions in the bisect module bpo 34900 Fixed unittest TestCase debug when used to call test methods with subtests Patch by Bruno Oliveira bpo 34844 logging Formatter enhancement Ensure styles and fmt matches in logging Formatter Added validate method in each format style class StrFormatStyle PercentStyle StringTemplateStyle This method is called in the constructor of logging Formatter class Also re raise the KeyError in the format method of each style class so it would a bit clear that it s an error with the invalid format fields bpo 34897 Adjust test support missing_compiler_executable check so that a nominal command name of is ignored Patch by Michael Felt bpo 34871 Fix inspect module polluted sys modules when parsing __text_signature__ of callable bpo 34898 Add mtime argument to gzip compress for reproducible output Patch by Guo Ci Teo bpo 28441 On Cygwin and MinGW ensure that sys executable always includes the full filename in the path including the exe suffix unless it is a symbolic link bpo 34866 Adding max_num_fields to cgi FieldStorage to make DOS attacks harder by limiting the number of MiniFieldStorage objects created by FieldStorage bpo 34711 http server ensures it reports HTTPStatus NOT_FOUND when the local path ends with and is not a directory even if the underlying OS e g AIX accepts such paths as a valid file reference Patch by Michael Felt bpo 34872 Fix self cancellation in C implementation of asyncio Task bpo 34849 Don t log waiting for selector select in asyncio loop iteration The waiting is pretty normal for any asyncio program logging its time just adds a noise to logs without any useful information provided bpo 34022 The SOURCE_DATE_EPOCH environment variable no longer overrides the value of the invalidation_mode argument to py_compile compile and determines its default value instead bpo 34819 Use a,en
1701, monotonic clock to compute timeouts in Executor map and as_completed in order to prevent timeouts from deviating when the system clock is adjusted bpo 34758 Add wasm application wasm to list of recognized file types and content type headers bpo 34789 xml sax make_parser now accepts any iterable as its parser_list argument Patch by Andrés Delfino bpo 34334 In QueueHandler clear exc_text from LogRecord to prevent traceback from being written twice bpo 34687 On Windows asyncio now uses ProactorEventLoop instead of SelectorEventLoop by default bpo 5950 Support reading zip files with archive comments in zipimport bpo 32892 The parser now represents all constants as ast Constant instead of using specific constant AST types Num Str Bytes NameConstant and Ellipsis These classes are considered deprecated and will be removed in future Python versions bpo 34728 Add deprecation warning when loop is used in methods asyncio sleep asyncio wait and asyncio wait_for bpo 34738 ZIP files created by distutils will now include entries for directories bpo 34659 Add an optional initial argument to itertools accumulate bpo 29577 Support multiple mixin classes when creating Enums bpo 34670 Add SSLContext post_handshake_auth and SSLSocket verify_client_post_handshake for TLS 1 3 s post handshake authentication feature bpo 32718 The Activate ps1 script from venv works with PowerShell Core 6 1 and is now available under all operating systems bpo 31177 Fix bug that prevented using reset_mock on mock instances with deleted attributes bpo 34672 Add a workaround so the Z time strftime specifier on the musl C library can work in some cases bpo 34666 Implement asyncio StreamWriter awrite and asyncio StreamWriter aclose coroutines Methods are needed for providing a consistent stream API with control flow switched on by default bpo 6721 Acquire the logging module s commonly used internal locks while fork ing to avoid deadlocks in the child process bpo 34658 Fix a rare interpreter unhandled exception state SystemError only seen when using subprocess with a preexec_fn while an after_parent handler has been registered with os register_at_fork and the fork system call fails bpo 34652 Ensure os lchmod is never defined on Linux bpo 34638 Store a weak reference to stream reader to break strong references loop between reader and protocol It allows to detect and close the socket if the stream is deleted garbage collected without close call bpo 34536 Enum _missing_ raise ValueError if None returned and TypeError if non member is returned bpo 34636 Speed up re scanning of many non matching characters for s w and d within bytes objects microoptimization bpo 24412 Add addModuleCleanup and addClassCleanup to unittest to support cleanups for setUpModule and setUpClass Patch by Lisa Roach bpo 34630 Don t log SSL certificate errors in asyncio code connection error logging is skipped already bpo 32490 Prevent filename duplication in subprocess exception messages Patch by Zackery Spytz bpo 34363 dataclasses asdict and astuple now handle namedtuples correctly bpo 34625 Update vendorized expat library version to 2 2 6 bpo 32270 The subprocess module no longer mistakenly closes redirected fds even when they were in pass_fds when outside of the default 0 1 2 set bpo 34622 Create a dedicated asyncio CancelledError asyncio InvalidStateError and asyncio TimeoutError exception classes Inherit them from corresponding exceptions from concurrent futures package Extract asyncio exceptions into a separate file bpo 34610 Fixed iterator of multiprocessing managers DictProxy bpo 34421 Fix distutils logging for non ASCII strings This caused installation issues on Windows bpo 34604 Fix possible mojibake in the error message of pwd getpwnam and grp getgrnam using string representation because of invisible characters or trailing whitespaces Patch by William Grzybowski bpo 30977 Make uuid UUID use __slots__ to reduce its memory footprint Based on original patch by Wouter Bolsterlee bpo 34574 OrderedDict iterators are not exhausted during pickling anymore Patch by Sergey Fedoseev bpo 8110 Refact,en
1702,ored subprocess to check for Windows specific modules rather than sys platform win32 bpo 34530 distutils spawn find_executable now falls back on os defpath if the PATH environment variable is not set bpo 34563 On Windows fix multiprocessing Connection for very large read fix _winapi PeekNamedPipe and _winapi ReadFile for read larger than INT_MAX usually 2 31 1 bpo 34558 Correct typo in Lib ctypes _aix py bpo 34282 Move Enum _convert to EnumMeta _convert_ and fix enum members getting shadowed by parent attributes bpo 22872 When the queue is closed ValueError is now raised by multiprocessing Queue put and multiprocessing Queue get instead of AssertionError and OSError respectively Patch by Zackery Spytz bpo 34515 Fix parsing non ASCII identifiers in lib2to3 pgen2 tokenize PEP 3131 bpo 13312 Avoids a possible integer underflow undefined behavior in the time module s year handling code when passed a very low negative year value bpo 34472 Improved compatibility for streamed files in zipfile Previously an optional signature was not being written and certain ZIP applications were not supported Patch by Silas Sewell bpo 34454 Fix the fromisoformat methods of datetime types crashing when given unicode with non UTF 8 encodable code points Specifically datetime fromisoformat now accepts surrogate unicode code points used as the separator Report and tests by Alexey Izbyshev patch by Paul Ganssle bpo 6700 Fix inspect getsourcelines for module level frames tracebacks Patch by Vladimir Matveev bpo 34171 Running the trace module no longer creates the trace cover file bpo 34441 Fix crash when an ABC derived class with invalid __subclasses__ is passed as the second argument to issubclass Patch by Alexey Izbyshev bpo 34427 Fix infinite loop in a extend a for MutableSequence subclasses bpo 34412 Make signal strsignal work on HP UX Patch by Michael Osipov bpo 20849 shutil copytree now accepts a new dirs_exist_ok keyword argument Patch by Josh Bronson bpo 31715 Associate mjs file extension with application javascript MIME Type bpo 34384 os readlink now accepts path like and bytes objects on Windows bpo 22602 The UTF 7 decoder now raises UnicodeDecodeError for ill formed sequences starting with as specified in RFC 2152 Patch by Zackery Spytz bpo 2122 The mmap flush method now returns None on success raises an exception on error under all platforms bpo 34341 Appending to the ZIP archive with the ZIP64 extension no longer grows the size of extra fields of existing entries bpo 34333 Fix formatting in pathlib PurePath with_suffix when formatting an error message bpo 18540 The imaplib IMAP4 and imaplib IMAP4_SSL classes now resolve to the local host IP correctly when the default value of host parameter is used bpo 26502 Implement traceback FrameSummary __len__ method to preserve compatibility with the old tuple API bpo 34318 assertRaises assertRaisesRegex assertWarns and assertWarnsRegex no longer success if the passed callable is None They no longer ignore unknown keyword arguments in the context manager mode A DeprecationWarning was raised in these cases since Python 3 5 bpo 9372 Deprecate __getitem__ methods of xml dom pulldom DOMEventStream wsgiref util FileWrapper and fileinput FileInput bpo 33613 Fix a race condition in multiprocessing semaphore_tracker when the tracker receives SIGINT before it can register signal handlers for ignoring it bpo 34248 Report filename in the exception raised when the database file cannot be opened by dbm gnu open and dbm ndbm open due to OS related error Patch by Zsolt Cserna bpo 33089 Add math dist to compute the Euclidean distance between two points bpo 34246 smtplib SMTP send_message no longer modifies the content of the mail_options argument Patch by Pablo S Blum de Aguiar bpo 31047 Fix ntpath abspath for invalid paths on windows Patch by Franz Woellert bpo 32321 Add pure Python fallback for functools reduce Patch by Robert Wright bpo 34270 The default asyncio task class now always has a name which can be get or set using two new methods get_name and set_name and is visible in the repr output An initial name,en
1703, can also be set using the new name keyword argument to asyncio create_task or the create_task method of the event loop If no initial name is set the default Task implementation generates a name like Task 1 using a monotonic counter bpo 34263 asyncio s event loop will not pass timeouts longer than one day to epoll select etc bpo 34035 Fix several AttributeError in zipfile seek methods Patch by Mickaël Schoentgen bpo 32215 Fix performance regression in sqlite3 when a DML statement appeared in a different line than the rest of the SQL query bpo 34075 Deprecate passing non ThreadPoolExecutor instances to AbstractEventLoop set_default_executor bpo 34251 Restore msilib Win64 to preserve backwards compatibility since it s already used by distutils bdist_msi command bpo 19891 Ignore errors caused by missing non writable homedir while writing history during exit of an interactive session Patch by Anthony Sottile bpo 33089 Enhanced math hypot to support more than two dimensions bpo 34228 tracemalloc PYTHONTRACEMALLOC 0 environment variable and X tracemalloc 0 command line option are now allowed to disable explicitly tracemalloc at startup bpo 13041 Use shutil get_terminal_size to calculate the terminal width correctly in the argparse HelpFormatter class Initial patch by Zbyszek Jędrzejewski Szmek bpo 34213 Allow frozen dataclasses to have a field named object Previously this conflicted with an internal use of object bpo 34052 sqlite3 Connection create_aggregate sqlite3 Connection create_function sqlite3 Connection set_authorizer sqlite3 Connection set_progress_handler methods raises TypeError when unhashable objects are passed as callable These methods now don t pass such objects to SQLite API Previous behavior could lead to segfaults Patch by Sergey Fedoseev bpo 34197 Attributes skipinitialspace doublequote and strict of the dialect attribute of the csv reader are now bool instances instead of integers 0 or 1 bpo 32788 Errors other than TypeError raised in methods __adapt__ and __conform__ in the sqlite3 module are now propagated to the user bpo 21446 The reload fixer now uses importlib reload instead of deprecated imp reload bpo 940286 pydoc s Helper showtopic method now prints the cross references of a topic correctly bpo 34164 base64 b32decode could raise UnboundLocalError or OverflowError for incorrect padding Now it always raises base64 Error in these cases bpo 33729 Fixed issues with arguments parsing in hashlib bpo 34097 ZipFile can zip files older than 1980 01 01 and newer than 2107 12 31 using a new strict_timestamps parameter at the cost of setting the timestamp to the limit bpo 34108 Remove extraneous CR in 2to3 refactor bpo 34070 Make sure to only check if the handle is a tty when opening a file with buffering 1 bpo 27494 Reverted bpo 27494 2to3 rejects now a trailing comma in generator expressions bpo 33967 functools singledispatch now raises TypeError instead of IndexError when no positional arguments are passed bpo 34041 Add the parameter deterministic to the sqlite3 Connection create_function method Patch by Sergey Fedoseev bpo 34056 Ensure the loader shim created by imp load_module always returns bytes from its get_data function This fixes using imp load_module with PEP 552 hash based pycs bpo 34054 The multiprocessing module now uses the monotonic clock time monotonic instead of the system clock time time to implement timeout bpo 34043 Optimize tarfile uncompress performance about 15 when gzip is used bpo 34044 subprocess Popen now copies the startupinfo argument to leave it unchanged it will modify the copy so that the same STARTUPINFO object can be used multiple times bpo 34010 Fixed a performance regression for reading streams with tarfile The buffered read should use a list instead of appending to a bytes object bpo 34019 webbrowser Correct the arguments passed to Opera Browser when opening a new URL using the webbrowser module Patch by Bumsik Kim bpo 34003 csv DictReader now creates dicts instead of OrderedDicts Patch by Michael Selik bpo 33978 Closed existing logging handlers before reconfiguration via fi,en
1704,leConfig and dictConfig Patch by Karthikeyan Singaravelan bpo 14117 Make minor tweaks to turtledemo The wikipedia example is now rosette describing what it draws The penrose print output is reduced The 1024 output of tree is eliminated bpo 33974 Fixed passing lists and tuples of strings containing special characters and n as options to ttk widgets bpo 27500 Fix getaddrinfo to resolve IPv6 addresses correctly bpo 24567 Improve random choices to handle subnormal input weights that could occasionally trigger an IndexError bpo 33871 Fixed integer overflow in os readv os writev os preadv and os pwritev and in os sendfile with headers or trailers arguments on BSD based OSes and macOS bpo 25007 Add copy copy and copy deepcopy support to zlib compressors and decompressors Patch by Zackery Spytz bpo 33929 multiprocessing Fix a race condition in Popen of multiprocessing popen_spawn_win32 The child process now duplicates the read end of pipe instead of stealing it Previously the read end of pipe was stolen by the child process but it leaked a handle if the child process had been terminated before it could steal the handle from the parent process bpo 33899 Tokenize module now implicitly emits a NEWLINE when provided with input that does not have a trailing new line This behavior now matches what the C tokenizer does internally Contributed by Ammar Askar bpo 33897 Added a force keyword argument to logging basicConfig bpo 33695 shutil copytree uses os scandir function and all copy functions depending from it use cached os stat values The speedup for copying a directory with 8000 files is around 9 on Linux 20 on Windows and 30 on a Windows SMB share Also the number of os stat syscalls is reduced by 38 making shutil copytree especially faster on network filesystems Contributed by Giampaolo Rodola in bpo 33695 bpo 33916 bz2 and lzma When Decompressor __init__ is called twice free the old lock to not leak memory bpo 32568 Make select epoll and its documentation consistent regarding sizehint and flags bpo 33833 Fixed bug in asyncio where ProactorSocketTransport logs AssertionError if force closed during write bpo 33663 Convert content length to string before putting to header bpo 33721 os path functions that return a boolean result like exists lexists isdir isfile islink and ismount and pathlib Path methods that return a boolean result like exists is_dir is_file is_mount is_symlink is_block_device is_char_device is_fifo is_socket now return False instead of raising ValueError or its subclasses UnicodeEncodeError and UnicodeDecodeError for paths that contain characters or bytes unrepresentable at the OS level bpo 26544 Fixed implementation of platform libc_ver It almost always returned version 2 9 for glibc bpo 33843 Remove deprecated cgi escape cgi parse_qs and cgi parse_qsl bpo 33842 Remove tarfile filemode which is deprecated since Python 3 3 bpo 30167 Prevent site main exception if PYTHONSTARTUP is set Patch by Steve Weber bpo 33805 Improve error message of dataclasses replace when an InitVar is not specified bpo 33687 Fix the call to os chmod for uu decode if a mode is given or decoded Patch by Timo Furrer bpo 33812 Datetime instance d with non None tzinfo but with d tzinfo utcoffset d returning None is now treated as naive by the astimezone method bpo 32108 In configparser don t clear section when it is assigned to itself bpo 27397 Make email module properly handle invalid length base64 strings bpo 33578 Implement multibyte encoder decoder state methods bpo 30805 Avoid race condition with debug logging bpo 33476 Fix _header_value_parser py when address group is missing final Contributed by Enrique Perez Terron bpo 33694 asyncio Fix a race condition causing data loss on pause_reading resume_reading when using the ProactorEventLoop bpo 32493 Correct test for uuid_enc_be availability in configure ac Patch by Michael Felt bpo 33792 Add asyncio WindowsSelectorEventLoopPolicy and asyncio WindowsProactorEventLoopPolicy bpo 33274 W3C DOM Level 1 specifies return value of Element removeAttributeNode as The Attr node that was removed xml dom mi,en
1705,nidom now complies with this requirement bpo 33778 Update unicodedata s database to Unicode version 11 0 0 bpo 33165 Added a stacklevel parameter to logging calls to allow use of wrapper helper functions for logging APIs bpo 33770 improve base64 exception message for encoded inputs of invalid length bpo 33769 asyncio start_tls Fix error message cancel callbacks in case of an unhandled error mark SSLTransport as closed if it is aborted bpo 33767 The concatenation and repetition sequence operations now raise TypeError instead of SystemError when performed on mmap mmap objects Patch by Zackery Spytz bpo 33734 asyncio ssl Fix AttributeError increase default handshake timeout bpo 31014 Fixed creating a controller for webbrowser when a user specifies a path to an entry in the BROWSER environment variable Based on patch by John Still bpo 2504 Add gettext pgettext and variants bpo 33197 Add description property for _ParameterKind bpo 32751 When cancelling the task due to a timeout asyncio wait_for will now wait until the cancellation is complete bpo 32684 Fix gather to propagate cancellation of itself even with return_exceptions bpo 33654 Support protocol type switching in SSLTransport set_protocol bpo 33674 Pause the transport as early as possible to further reduce the risk of data_received being called before connection_made bpo 33671 shutil copyfile shutil copy shutil copy2 shutil copytree and shutil move use platform specific fast copy syscalls on Linux and macOS in order to copy the file more efficiently On Windows shutil copyfile uses a bigger default buffer size 1 MiB instead of 16 KiB and a memoryview based variant of shutil copyfileobj is used The speedup for copying a 512MiB file is about 26 on Linux 50 on macOS and 40 on Windows Also much less CPU cycles are consumed Contributed by Giampaolo Rodola in bpo 25427 bpo 33674 Fix a race condition in SSLProtocol connection_made of asyncio sslproto start immediately the handshake instead of using call_soon Previously data_received could be called before the handshake started causing the handshake to hang or fail bpo 31647 Fixed bug where calling write_eof on a _SelectorSocketTransport after it s already closed raises AttributeError bpo 32610 Make asyncio all_tasks return only pending tasks bpo 32410 Avoid blocking on file IO in sendfile fallback code bpo 33469 Fix RuntimeError after closing loop that used run_in_executor bpo 33672 Fix Task __repr__ crash with Cython s bogus coroutines bpo 33654 Fix transport set_protocol to support switching between asyncio Protocol and asyncio BufferedProtocol Fix loop start_tls to work with asyncio BufferedProtocols bpo 33652 Pickles of type variables and subscripted generics are now future proof and compatible with older Python versions bpo 32493 Fixed uuid uuid1 on FreeBSD bpo 33238 Add InvalidStateError to concurrent futures Future set_result and Future set_exception now raise InvalidStateError if the futures are not pending or running Patch by Jason Haydaman bpo 33618 Finalize and document preliminary and experimental TLS 1 3 support with OpenSSL 1 1 1 bpo 33625 Release GIL on grp getgrnam grp getgrgid pwd getpwnam and pwd getpwuid if reentrant variants of these functions are available Patch by William Grzybowski bpo 33623 Fix possible SIGSGV when asyncio Future is created in __del__ bpo 11874 Use a better regex when breaking usage into wrappable parts Avoids bogus assertion errors from custom metavar strings bpo 30877 Fixed a bug in the Python implementation of the JSON decoder that prevented the cache of parsed strings from clearing after finishing the decoding Based on patch by c fos bpo 33604 Remove HMAC default to md5 marked for removal in 3 8 removal originally planned in 3 6 bump to 3 8 in PR 7062 bpo 33582 Emit a deprecation warning for inspect formatargspec bpo 21145 Add functools cached_property decorator for computed properties cached for the life of the instance bpo 33570 Change TLS 1 3 cipher suite settings for compatibility with OpenSSL 1 1 1 pre6 and newer OpenSSL 1 1 1 will have TLS 1 3 ciphers enabled by default bpo 28,en
1706,556 Do not simplify arguments to typing Union Now Union Manager Employee is not simplified to Employee at runtime Such simplification previously caused several bugs and limited possibilities for introspection bpo 12486 tokenize generate_tokens is now documented as a public API to tokenize unicode strings It was previously present but undocumented bpo 33540 Add a new block_on_close class attribute to ForkingMixIn and ThreadingMixIn classes of socketserver bpo 33548 tempfile _candidate_tempdir_list should consider common TEMP locations bpo 33109 argparse subparsers are once again not required by default reverting the change in behavior introduced by bpo 26510 in 3 7 0a2 bpo 33541 Remove unused private method _strptime LocaleTime __pad a k a _LocaleTime__pad bpo 33536 dataclasses make_dataclass now checks for invalid field names and duplicate fields Also added a check for invalid field specifications bpo 33542 Prevent uuid get_node from using a DUID instead of a MAC on Windows Patch by Zvi Effron bpo 26819 Fix race condition with ReadTransport resume_reading in Windows proactor event loop Fix failure in typing get_type_hints when ClassVar was provided as a string forward reference bpo 33516 unittest mock MagicMock now supports the __round__ magic method bpo 28612 Added support for Site Maps to urllib s RobotFileParser as RobotFileParser site_maps Patch by Lady Red based on patch by Peter Wirtz bpo 28167 Remove platform linux_distribution which was deprecated since 3 5 bpo 33504 Switch the default dictionary implementation for configparser from collections OrderedDict to the standard dict type bpo 33505 Optimize asyncio ensure_future by reordering if checks 1 17x faster bpo 33497 Add errors param to cgi parse_multipart and make an encoding in FieldStorage use the given errors needed for Twisted Patch by Amber Brown bpo 29235 The cProfile Profile class can now be used as a context manager Patch by Scott Sanderson bpo 33495 Change dataclasses Fields repr to use the repr of each of its members instead of str This makes it more clear what each field actually represents This is especially true for the type member bpo 26103 Correct inspect isdatadescriptor to look for __set__ or __delete__ Patch by Aaron Hall bpo 29209 Removed the doctype method and the html parameter of the constructor of XMLParser The doctype method defined in a subclass will no longer be called Deprecated methods getchildren and getiterator in the ElementTree module emit now a DeprecationWarning instead of PendingDeprecationWarning bpo 33453 Fix dataclasses to work if using literal string type annotations or if using PEP 563 Postponed Evaluation of Annotations Only specific string prefixes are detected for both ClassVar ClassVar and typing ClassVar and InitVar InitVar and dataclasses InitVar bpo 28556 Minor fixes in typing module add annotations to NamedTuple __new__ pass args and kwds in Generic __new__ Original PRs by Paulius Šarka and Chad Dombrova bpo 33365 Print the header values besides the header keys instead just the header keys if debuglevel is set to 0 in http client Patch by Marco Strigl bpo 20087 Updated alias mapping with glibc 2 27 supported locales bpo 33422 Fix trailing quotation marks getting deleted when looking up byte string literals on pydoc Patch by Andrés Delfino bpo 28167 The function platform linux_distribution and platform dist now trigger a DeprecationWarning and have been marked for removal in Python 3 8 bpo 33281 Fix ctypes util find_library regression on macOS bpo 33311 Text and html output generated by cgitb does not display parentheses if the current call is done directly in the module Patch by Stéphane Blondon bpo 27300 The file classes in tempfile now accept an errors parameter that complements the already existing encoding Patch by Stephan Hohe bpo 32933 unittest mock mock_open now supports iteration over the file contents Patch by Tony Flury bpo 33217 Raise TypeError when looking up non Enum objects in Enum classes and Enum members bpo 33197 Update error message when constructing invalid inspect Parameters Patch by Donghee Na,en
1707, bpo 33383 Fixed crash in the get method of the dbm ndbm database object when it is called with a single argument bpo 33375 The warnings module now finds the Python file associated with a warning from the code object rather than the frame s global namespace This is consistent with how tracebacks and pdb find filenames and should work better for dynamically executed code bpo 33336 imaplib now allows MOVE command in IMAP4 uid RFC 6851 IMAP MOVE Extension and potentially as a name of supported method of IMAP4 object bpo 32455 Added jump parameter to dis stack_effect bpo 27485 Rename and deprecate undocumented functions in urllib parse bpo 33332 Add signal valid_signals to expose the POSIX sigfillset functionality bpo 33251 ConfigParser items was fixed so that key value pairs passed in via vars are not included in the resulting output bpo 33329 Fix multiprocessing regression on newer glibcs bpo 33334 dis stack_effect now supports all defined opcodes including NOP and EXTENDED_ARG bpo 991266 Fix quoting of the Comment attribute of http cookies SimpleCookie bpo 33131 Upgrade bundled version of pip to 10 0 1 bpo 33308 Fixed a crash in the parser module when converting an ST object to a tree of tuples or lists with line_info False and col_info True bpo 23403 lib2to3 now uses pickle protocol 4 for pre computed grammars bpo 33266 lib2to3 now recognizes rf strings bpo 11594 Ensure line endings are respected when using lib2to3 bpo 33254 Have importlib resources contents and importlib abc ResourceReader contents return an iterable instead of an iterator bpo 33265 contextlib ExitStack and contextlib AsyncExitStack now use a method instead of a wrapper function for exit callbacks bpo 33263 Fix FD leak in _SelectorSocketTransport Patch by Vlad Starostin bpo 33256 Fix display of module call in the html produced by cgitb html Patch by Stéphane Blondon bpo 33144 random Random and its subclassing mechanism got optimized to check only once at class subclass instantiation time whether its getrandbits method can be relied on by other methods including randrange for the generation of arbitrarily large random integers Patch by Wolfgang Maier bpo 33185 Fixed regression when running pydoc with the m switch The regression was introduced in 3 7 0b3 by the resolution of bpo 33053 This fix also changed pydoc to add os getcwd to sys path when necessary rather than adding bpo 29613 Added support for the SameSite cookie flag to the http cookies module bpo 33169 Delete entries of None in sys path_importer_cache when importlib machinery invalidate_caches is called bpo 33203 random Random choice now raises IndexError for empty sequences consistently even when called from subclasses without a getrandbits implementation bpo 33224 Update difflib mdiff for PEP 479 Convert an uncaught StopIteration in a generator into a return statement bpo 33209 End framing at the end of C implementation of pickle Pickler dump bpo 32861 The urllib robotparser s __str__ representation now includes wildcard entries and the Crawl delay and Request rate fields Also removes extra newlines that were being appended to the end of the string Patch by Michael Lazar bpo 23403 DEFAULT_PROTOCOL in pickle was bumped to 4 Protocol 4 is described in PEP 3154 and available since Python 3 4 It offers better performance and smaller size compared to protocol 3 introduced in Python 3 0 bpo 20104 Improved error handling and fixed a reference leak in os posix_spawn bpo 33106 Deleting a key from a read only dbm database raises module specific error instead of KeyError bpo 33175 In dataclasses Field __set_name__ now looks up the __set_name__ special method on the class not the instance of the default value bpo 32380 Create functools singledispatchmethod to support generic single dispatch on descriptors and methods bpo 33141 Have Field objects pass through __set_name__ to their default values if they have their own __set_name__ bpo 33096 Allow ttk Treeview insert to insert iid that has a false boolean value Note iid 0 and iid False would be same Patch by Garvit Khatri bpo 32873 Treat type variables and ,en
1708,special typing forms as immutable by copy and pickle This fixes several minor issues and inconsistencies and improves backwards compatibility with Python 3 6 bpo 33134 When computing dataclass s __hash__ use the lookup table to contain the function which returns the __hash__ value This is an improvement over looking up a string and then testing that string to see what to do bpo 33127 The ssl module now compiles with LibreSSL 2 7 1 bpo 32505 Raise TypeError if a member variable of a dataclass is of type Field but doesn t have a type annotation bpo 33078 Fix the failure on OSX caused by the tests relying on sem_getvalue bpo 33116 Add Field to dataclasses __all__ bpo 32896 Fix an error where subclassing a dataclass with a field that uses a default_factory would generate an incorrect class bpo 33100 Dataclasses If a field has a default value that s a MemberDescriptorType then it s from that field being in __slots__ not an actual default value bpo 32953 If a non dataclass inherits from a frozen dataclass allow attributes to be added to the derived class Only attributes from the frozen dataclass cannot be assigned to Require all dataclasses in a hierarchy to be either all frozen or all non frozen bpo 33097 Raise RuntimeError when executor submit is called during interpreter shutdown bpo 32968 Modulo and floor division involving Fraction and float should return float bpo 33061 Add missing NoReturn to __all__ in typing py bpo 33078 Fix the size handling in multiprocessing Queue when a pickling error occurs bpo 33064 lib2to3 now properly supports trailing commas after args and kwargs in function signatures bpo 33056 FIX properly close leaking fds in concurrent futures ProcessPoolExecutor bpo 33021 Release the GIL during fstat calls avoiding hang of all threads when calling mmap mmap os urandom and random seed Patch by Nir Soffer bpo 31804 Avoid failing in multiprocessing Process if the standard streams are closed or None at exit bpo 33034 Providing an explicit error message when casting the port property to anything that is not an integer value using urlparse and urlsplit Patch by Matt Eaton bpo 30249 Improve struct unpack_from exception messages for problems with the buffer size and offset bpo 33037 Skip sending receiving data after SSL transport closing bpo 27683 Fix a regression in ipaddress that result of hosts is empty when the network is constructed by a tuple containing an integer mask and only 1 bit left for addresses bpo 22674 Add the strsignal function in the signal module that returns the system description of the given signal as returned by strsignal 3 bpo 32999 Fix C implementation of ABC __subclasscheck__ cls subclass crashed when subclass is not a type object bpo 33009 Fix inspect signature for single parameter partialmethods bpo 32969 Expose several missing constants in zlib and fix corresponding documentation bpo 32056 Improved exceptions raised for invalid number of channels and sample width when read an audio file in modules aifc wave and sunau bpo 32970 Improved disassembly of the MAKE_FUNCTION instruction bpo 32844 Fix wrong redirection of a low descriptor 0 or 1 to stderr in subprocess if another low descriptor is closed bpo 32960 For dataclasses disallow inheriting frozen from non frozen classes and also disallow inheriting non frozen from frozen classes This restriction will be relaxed at a future date bpo 32713 Fixed tarfile itn handling of out of bounds float values Patch by Joffrey Fuhrer bpo 32257 The ssl module now contains OP_NO_RENEGOTIATION constant available with OpenSSL 1 1 0h or 1 1 1 bpo 32951 Direct instantiation of SSLSocket and SSLObject objects is now prohibited The constructors were never documented tested or designed as public constructors Users were suppose to use ssl wrap_socket or SSLContext bpo 32929 Remove the tri state parameter hash and add the boolean unsafe_hash If unsafe_hash is True add a __hash__ function but if a __hash__ exists raise TypeError If unsafe_hash is False add a __hash__ based on the values of eq and frozen The unsafe_hash False behavior is the same as the old has,en
1709,h None behavior unsafe_hash False is the default just as hash None used to be bpo 32947 Add OP_ENABLE_MIDDLEBOX_COMPAT and test workaround for TLSv1 3 for future compatibility with OpenSSL 1 1 1 bpo 32146 Document the interaction between frozen executables and the spawn and forkserver start methods in multiprocessing bpo 30622 The ssl module now detects missing NPN support in LibreSSL bpo 32922 dbm open now encodes filename with the filesystem encoding rather than default encoding bpo 32759 Free unused arenas in multiprocessing heap bpo 32859 In os dup2 don t check every call whether the dup3 syscall exists or not bpo 32556 nt _getfinalpathname nt _getvolumepathname and nt _getdiskusage now correctly convert from bytes bpo 21060 Rewrite confusing message from setup py upload from No dist file created in earlier command to the more helpful Must create and upload files in one command bpo 32857 In tkinter after_cancel None now raises a ValueError instead of canceling the first scheduled function Patch by Cheryl Sabella bpo 32852 Make sure sys argv remains as a list when running trace bpo 31333 _abc module is added It is a speedup module with C implementations for various functions and methods in abc Creating an ABC subclass and calling isinstance or issubclass with an ABC subclass are up to 1 5x faster In addition this makes Python start up up to 10 faster Note that the new implementation hides internal registry and caches previously accessible via private attributes _abc_registry _abc_cache and _abc_negative_cache There are three debugging helper methods that can be used instead _dump_registry _abc_registry_clear and _abc_caches_clear bpo 32841 Fixed asyncio Condition issue which silently ignored cancellation after notifying and cancelling a conditional lock Patch by Bar Harel bpo 32819 ssl match_hostname has been simplified and no longer depends on re and ipaddress module for wildcard and IP addresses Error reporting for invalid wildcards has been improved bpo 19675 multiprocessing Pool no longer leaks processes if its initialization fails bpo 32394 socket Remove TCP_FASTOPEN TCP_KEEPCNT TCP_KEEPIDLE TCP_KEEPINTVL flags on older version Windows during run time bpo 31787 Fixed refleaks of __init__ methods in various modules Contributed by Oren Milman bpo 30157 Fixed guessing quote and delimiter in csv Sniffer sniff when only the last field is quoted Patch by Jake Davis bpo 30688 Added support of N name escapes in regular expressions Based on patch by Jonathan Eunice bpo 32792 collections ChainMap preserves the order of the underlying mappings bpo 32775 fnmatch translate no longer produces patterns which contain set operations Sets starting with or containing or will be interpreted differently in regular expressions in future versions Currently they emit warnings fnmatch translate now avoids producing patterns containing such sets by accident bpo 32622 Implement native fast sendfile for Windows proactor event loop bpo 32777 Fix a rare but potential pre exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process This bug appears to have been introduced in 3 4 bpo 32647 The ctypes module used to depend on indirect linking for dlopen The shared extension is now explicitly linked against libdl on platforms with dl bpo 32749 A dbm dumb database opened with flags r is now read only dbm dumb open with flags r and w no longer creates a database if it does not exist bpo 32741 Implement asyncio TimerHandle when method bpo 32691 Use mod_spec parent when running modules with pdb bpo 32734 Fixed asyncio Lock safety issue which allowed acquiring and locking the same lock multiple times without it being free Patch by Bar Harel bpo 32727 Do not include name field in SMTP envelope from address Patch by Stéphane Wirtel bpo 31453 Add TLSVersion constants and SSLContext maximum_version minimum_version attributes The new API wraps OpenSSL 1 1 https w eb archive org web 20180309043602 https www openssl org docs man1 1 0 ssl SSL_CTX_set_min_proto_version html feature bpo 24334 ,en
1710,Internal implementation details of ssl module were cleaned up The SSLSocket has one less layer of indirection Owner and session information are now handled by the SSLSocket and SSLObject constructor Channel binding implementation has been simplified bpo 31848 Fix the error handling in Aifc_read initfp when the SSND chunk is not found Patch by Zackery Spytz bpo 32585 Add Ttk spinbox widget to tkinter ttk Patch by Alan D Moore bpo 32512 profile CLI accepts m module_name as an alternative to script path bpo 8525 help on a type now displays builtin subclasses This is intended primarily to help with notification of more specific exception subclasses Patch by Sanyam Khurana bpo 31639 http server now exposes a ThreadingHTTPServer class and uses it when the module is run with m to cope with web browsers pre opening sockets bpo 29877 compileall import ProcessPoolExecutor only when needed preventing hangs on low resource platforms bpo 32221 Various functions returning tuple containing IPv6 addresses now omit scope part since the same information is already encoded in scopeid tuple item Especially this speeds up socket recvfrom when it receives multicast packet since useless resolving of network interface name is omitted bpo 32147 binascii unhexlify is now up to 2 times faster Patch by Sergey Fedoseev bpo 30693 The TarFile class now recurses directories in a reproducible way bpo 30693 The ZipFile class now recurses directories in a reproducible way bpo 31680 Added curses ncurses_version bpo 31908 Fix output of cover files for trace module command line tool Previously emitted cover files only when missing option was used Patch by Michael Selik bpo 31608 Raise a TypeError instead of crashing if a collections deque subclass returns a non deque from __new__ Patch by Oren Milman bpo 31425 Add support for sockets of the AF_QIPCRTR address family supported by the Linux kernel This is used to communicate with services such as GPS or radio running on Qualcomm devices Patch by Bjorn Andersson bpo 22005 Implemented unpickling instances of datetime date and time pickled by Python 2 encoding latin1 should be used for successful decoding bpo 27645 sqlite3 Connection now exposes a backup method if the underlying SQLite library is at version 3 6 11 or higher Patch by Lele Gaifax bpo 16865 Support arrays 2GiB in ctypes Patch by Segev Finer bpo 31508 Removed support of arguments in tkinter ttk Treeview selection It was deprecated in 3 6 Use specialized methods like selection_set for changing the selection bpo 29456 Fix bugs in hangul normalization u1176 u11a7 and u11c3 Documentation bpo 21257 Document http client parse_headers bpo 34764 Improve example of iter with 2nd sentinel argument bpo 35564 Explicitly set master_doc variable in conf py for compliance with Sphinx 2 0 bpo 35511 Specified that profile Profile class doesn t not support enable or disable methods Also elaborated that Profile object as a context manager is only supported in cProfile module bpo 10536 Enhance the gettext docs Patch by Éric Araujo bpo 35089 Remove mention of typing io and typing re Their types should be imported from typing directly bpo 35038 Fix the documentation about an unexisting f_restricted attribute in the frame object Patch by Stéphane Wirtel bpo 35042 Replace PEP XYZ by the pep role and allow to use the direct links to the PEPs bpo 35044 Fix the documentation with the role exc for the appropriated exception Patch by Stéphane Wirtel bpo 35035 Rename documentation for email utils to email utils rst bpo 34967 Use app add_object_type instead of the deprecated Sphinx function app description_unit bpo 34913 Add documentation about the new command line interface of the gzip module bpo 32174 chm document displays non ASCII charaters properly on some MBCS Windows systems bpo 11233 Create availability directive for documentation Original patch by Georg Brandl bpo 34790 Document how passing coroutines to asyncio wait can be confusing bpo 34552 Make clear that operator sometimes is equivalent to is The and operators are only defined where they make sense bpo 28617 Fixed in,en
1711,fo in the stdtypes docs concerning the types that support membership tests bpo 20177 Migrate datetime date fromtimestamp to Argument Clinic Patch by Tim Hoffmann bpo 34065 Fix wrongly written basicConfig documentation markup syntax bpo 33460 replaced ellipsis with correct error codes in tutorial chapter 3 bpo 33847 Add operator entry to index bpo 33409 Clarified the relationship between PEP 538 s PYTHONCOERCECLOCALE and PEP 540 s PYTHONUTF8 mode bpo 33197 Add versionadded tag to the documentation of ParameterKind description bpo 17045 Improve the C API doc for PyTypeObject This includes adding several quick reference tables and a lot of missing slot typedef entries The existing entries were also cleaned up with a slightly more consistent format bpo 33736 Improve the documentation of asyncio open_connection asyncio start_server and their UNIX socket counterparts bpo 23859 Document that asyncio wait does not cancel its futures on timeout bpo 32436 Document PEP 567 changes to asyncio bpo 33604 Update HMAC md5 default to a DeprecationWarning bump removal to 3 8 bpo 33594 Document getargspec from_function and from_builtin as deprecated in their respective docstring and include version since deprecation in DeprecationWarning message bpo 33503 Fix broken pypi link bpo 33421 Add missing documentation for typing AsyncContextManager bpo 33487 BZ2file now emit a DeprecationWarning when buffering None is passed the deprecation message and documentation also now explicitly state it is deprecated since 3 0 bpo 33378 Add Korean language switcher for https docs python org 3 bpo 33276 Clarify that the __path__ attribute on modules cannot be just any value bpo 33201 Modernize documentation for writing C extension types bpo 33195 Deprecate Py_UNICODE usage in c api arg document Py_UNICODE related APIs are deprecated since Python 3 3 but it is missed in the document bpo 33126 Document PyBuffer_ToContiguous bpo 27212 Modify documentation for the islice recipe to consume initial values up to the start index bpo 28247 Update zipapp documentation to describe how to make standalone applications bpo 18802 Documentation changes for ipaddress Patch by Jon Foster and Berker Peksag bpo 27428 Update documentation to clarify that WindowsRegistryFinder implements MetaPathFinder Patch by Himanshu Lakhara bpo 28124 The ssl module function ssl wrap_socket has been de emphasized and deprecated in favor of the more secure and efficient SSLContext wrap_socket method bpo 17232 Clarify docs for O and OO Patch by Terry Reedy bpo 32436 Add documentation for the contextvars module PEP 567 bpo 32800 Update link to w3c doc for xml default namespaces bpo 11015 Update test support documentation bpo 32613 Update the faq windows html to use the py command from PEP 397 instead of python bpo 8722 Document __getattr__ behavior when property get method raises AttributeError bpo 32614 Modify RE examples in documentation to use raw strings to prevent DeprecationWarning and add text to REGEX HOWTO to highlight the deprecation bpo 20709 Remove the paragraph where we explain that os utime does not support a directory as path under Windows Patch by Jan Philip Gehrcke bpo 32722 Remove the bad example in the tutorial of the Generator Expression Patch by Stéphane Wirtel bpo 31972 Improve docstrings for pathlib PurePath subclasses bpo 30607 Use the externalized python docs theme package when building the documentation bpo 8243 Add a note about curses addch and curses addstr exception behavior when writing outside a window or pad bpo 32337 Update documentation related with dict order bpo 25041 Document AF_PACKET in the socket module bpo 31432 Clarify meaning of CERT_NONE CERT_OPTIONAL and CERT_REQUIRED flags for ssl SSLContext verify_mode Tests bpo 35772 Fix sparse file tests of test_tarfile on ppc64 with the tmpfs filesystem Fix the function testing if the filesystem supports sparse files create a file which contains data and holes instead of creating a file which contains no data tmpfs effective block size is a page size tmpfs lives in the page cache RHEL uses 64 KiB pages on aarch6,en
1712,4 ppc64 ppc64le only s390x and x86_64 use 4 KiB pages whereas the test punch holes of 4 KiB bpo 35045 Make ssl tests less strict and also accept TLSv1 as system default The changes unbreaks test_min_max_version on Fedora 29 bpo 32710 test_asyncio test_sendfile py now resets the event loop policy using tearDownModule as done in other tests to prevent a warning when running tests on Windows bpo 33717 test pythoninfo now logs information of all clocks not only time time and time perf_counter bpo 35488 Add a test to pathlib s Path match to verify it does not support glob style recursive pattern matching bpo 31731 Fix a race condition in check_interrupted_write of test_io create directly the thread with SIGALRM signal blocked rather than blocking the signal later from the thread Previously it was possible that the thread gets the signal before the signal is blocked bpo 35424 Fix test_multiprocessing_main_handling use multiprocessing Pool with a context manager and then explicitly join the pool bpo 35519 Rename test bisect module to test bisect_cmd to avoid conflict with bisect module when running directly a test like python Lib test test_xmlrpc py bpo 35513 Replace time time with time monotonic in tests to measure time delta bpo 34279 test support run_unittest no longer raise TestDidNotRun if the test result contains skipped tests The exception is now only raised if no test have been run and no test have been skipped bpo 35412 Add testcase to test_future4 check unicode literal bpo 26704 Added test demonstrating double patching of an instance method Patch by Anthony Sottile bpo 33725 test_multiprocessing_fork may crash on recent versions of macOS Until the issue is resolved skip the test on macOS bpo 35352 Modify test_asyncio to use the certificate set from the test directory bpo 35317 Fix mktime overflow error in test_email run test_localtime_daylight_true_dst_true and test_localtime_daylight_false_dst_true with a specific timezone bpo 21263 After several reports that test_gdb does not work properly on macOS and since gdb is not shipped by default anymore test_gdb is now skipped on macOS when LLVM Clang has been used to compile Python Patch by Lysandros Nikolaou bpo 34279 regrtest issue a warning when no tests have been executed in a particular test file Also a new final result state is issued if no test have been executed across all test files Patch by Pablo Galindo bpo 34962 make docstest in Doc now passes and is enforced in CI bpo 23596 Use argparse for the command line of the gzip module Patch by Antony Lee bpo 34537 Fix test_gdb test_strings when LC_ALL C and GDB was compiled with Python 3 6 or earlier bpo 34587 test_socket Remove RDSTest testCongestion The test tries to fill the receiver s socket buffer and expects an error But the RDS protocol doesn t require that Moreover the Linux implementation of RDS expects that the producer of the messages reduces its rate it s not the role of the receiver to trigger an error The test fails on Fedora 28 by design so just remove it bpo 34661 Fix test_shutil if unzip doesn t support t bpo 34200 Fixed non deterministic flakiness of test_pkg by not using the scary test support module_cleanup logic to save and restore sys modules contents between test cases bpo 34569 The experimental PEP 554 data channels now correctly pass negative PyLong objects between subinterpreters on 32 bit systems Patch by Michael Felt bpo 34594 Fix usage of hardcoded errno values in the tests bpo 34579 Fix test_embed for AIX Patch by Michael Felt bpo 34542 Use 3072 RSA keys and SHA 256 signature for test certs and keys bpo 11193 Remove special condition for AIX in test_subprocess test_undecodable_env bpo 34347 Fix test_utf8_mode test_cmd_line for AIX bpo 34490 On AIX with AF_UNIX family sockets getsockname does not provide sockname so skip calls to transport get_extra_info sockname bpo 34391 Fix ftplib test for TLS 1 3 by reading from data socket bpo 11192 Fix test_socket on AIX 6 1 and later IPv6 zone id supports only supported by inet_pton6_zone Switch to runtime based platform system to establish current p,en
1713,latform rather than build time based sys platform bpo 34399 Update all RSA keys and DH params to use at least 2048 bits bpo 34373 Fix test_mktime and test_pthread_getcpuclickid tests for AIX Add range checking for _PyTime_localtime for AIX Patch by Michael Felt bpo 11191 Skip the distutils test test_search_cpp when using XLC as compiler patch by aixtools Michael Felt Improved an error message when mock assert_has_calls fails bpo 33746 Fix test_unittest when run in verbose mode bpo 33901 Fix test_dbm_gnu on macOS with gdbm 1 15 add a larger value to make sure that the file size changes bpo 33873 Fix a bug in regrtest that caused an extra test to run if huntrleaks R was used Exit with error in case that invalid parameters are specified to huntrleaks R at least one warmup run and one repetition must be used bpo 33562 Check that a global asyncio event loop policy is not left behind by any tests bpo 33655 Ignore test_posix_fallocate failures on BSD platforms that might be due to running on ZFS bpo 32962 Fixed test_gdb when Python is compiled with flags mcet fcf protection O0 bpo 33358 Fix test_embed test_pre_initialization_sys_options when the interpreter is built with enable shared bpo 32872 Avoid regrtest compatibility issue with namespace packages bpo 32517 Fix failing test_asyncio on macOS 10 12 2 due to transport of KqueueSelector loop was not being closed bpo 32663 Making sure the SMTPUTF8SimTests class of tests gets run in test_smtplib py bpo 27643 Test_C test case needs signed short bitfields but the IBM XLC compiler on AIX does not support this Skip the code and test when AIX and XLC are used Applicable to Python2 2 7 and later bpo 19417 Add test_bdb py bpo 31809 Add tests to verify connection with secp ECDH curves Build bpo 34691 The _contextvars module is now built into the core Python library on Windows bpo 35683 Improved Azure Pipelines build steps and now verifying layouts correctly bpo 35642 Remove asynciomodule c from pythoncore vcxproj bpo 35550 Fix incorrect Solaris ifdef checks to look for __sun __SVR4 instead of sun when compiling bpo 35499 make profile opt no longer replaces CFLAGS_NODIST with CFLAGS It now adds profile guided optimization PGO flags to CFLAGS_NODIST existing CFLAGS_NODIST flags are kept bpo 35257 Avoid leaking the linker flags from Link Time Optimizations LTO into distutils when compiling C extensions bpo 35351 When building Python with clang and LTO LTO flags are no longer passed into CFLAGS to build third party C extensions through distutils bpo 35139 Fix a compiler error when statically linking pyexpat in Modules Setup bpo 35059 PCbuild Set InlineFunctionExpansion to OnlyExplicitInline Ob1 option in pyproject props in Debug mode to expand functions marked as inline This change should make Python compiled in Debug mode a little bit faster on Windows bpo 35011 Restores the use of pyexpatns h to isolate our embedded copy of the expat C library so that its symbols do not conflict at link or dynamic loading time with an embedding application or other extension modules with their own version of libexpat bpo 28015 Have with lto works correctly with clang bpo 34765 Update the outdated install sh file to the latest revision from automake v1 16 1 bpo 34585 Check for floating point byte order in configure ac using compilation tests instead of executing code so that these checks work in cross compiled builds bpo 34710 Fixed SSL module build with OpenSSL pedantic CFLAGS bpo 34582 Add JUnit XML output for regression tests and update Azure DevOps builds bpo 34081 Make Sphinx warnings as errors in the Docs Makefile bpo 34555 Fix for case where it was not possible to have both HAVE_LINUX_VM_SOCKETS_H and HAVE_SOCKADDR_ALG be undefined bpo 33015 Fix an undefined behaviour in the pthread implementation of PyThread_start_new_thread add a function wrapper to always return NULL bpo 34245 The Python shared library is now installed with write permission mode 0755 which is the standard way of installing such libraries bpo 34121 Fix detection of C11 atomic support on clang bpo 32430 Rename Modules Setup dist to,en
1714, Modules Setup and remove the necessity to copy the former manually to the latter when updating the local source tree bpo 30345 Add g to LDFLAGS when compiling with LTO to get debug symbols bpo 5755 Move Wstrict prototypes option to CFLAGS_NODIST from OPT This option emitted annoying warnings when building extension modules written in C bpo 33614 Ensures module definition files for the stable ABI on Windows are correctly regenerated bpo 33648 The with c locale warning configuration flag has been removed It has had no effect for about a year bpo 33522 Enable CI builds on Visual Studio Team Services at https python visualstudio com cpython bpo 33512 configure s check for long double has been simplified bpo 33483 C compiler is now correctly detected from the standard environment variables without gcc and with icc options have been removed bpo 33394 Enable the verbose build for extension modules when GNU make is passed macros on the command line bpo 33393 Update config guess and config sub files bpo 33377 Add new triplets for mips r6 and riscv variants used in extension suffixes bpo 32232 By default modules configured in Modules Setup are no longer built with DPy_BUILD_CORE Instead modules that specifically need that preprocessor definition include it in their individual entries bpo 33182 The embedding tests can once again be built with clang 6 0 bpo 33163 Upgrade pip to 9 0 3 and setuptools to v39 0 1 bpo 33012 gcc 8 has added a new warning heuristic to detect invalid function casts and a stock python build seems to hit that warning quite often The most common is the cast of a METH_NOARGS function that uses just one argument to a PyCFunction Fix this by adding a dummy argument to all functions that implement METH_NOARGS bpo 32898 Fix the python debug build when using COUNT_ALLOCS bpo 29442 Replace optparse with argparse in setup py Windows bpo 35890 Fix API calling consistency of GetVersionEx and wcstok bpo 32560 The py launcher now forwards its STARTUPINFO structure to child processes bpo 35854 Fix EnvBuilder and symlinks in venv on Windows bpo 35811 Avoid propagating venv settings when launching via py exe bpo 35797 Fix default executable used by the multiprocessing module bpo 35758 Allow building on ARM with MSVC bpo 29734 Fix handle leaks in os stat on Windows bpo 35596 Use unchecked PYCs for the embeddable distro to avoid zipimport restrictions bpo 35596 Fix vcruntime140 dll being added to embeddable distro multiple times bpo 35402 Update Windows build to use Tcl and Tk 8 6 9 bpo 35401 Updates Windows build to OpenSSL 1 1 0j bpo 34977 venv on Windows will now use a python exe redirector rather than copying the actual binaries from the base environment bpo 34977 Adds support for building a Windows App Store package bpo 35067 Remove _distutils_findvs module and use vswhere exe instead bpo 32557 Allow shutil disk_usage to take a file path on Windows bpo 34770 Fix a possible null pointer dereference in pyshellext cpp bpo 34603 Fix returning structs from functions produced by MSVC bpo 34581 Guard MSVC specific code in socketmodule c with ifdef _MSC_VER bpo 34532 Fixes exit code of list version arguments for py exe bpo 34062 Fixed the list and list paths arguments for the py exe launcher bpo 34225 Ensure INCLUDE and LIB directories do not end with a backslash bpo 34011 A suite of code has been changed which copied across DLLs and init tcl from the running Python location into a venv being created These copies are needed only when running from a Python source build and the copying code is now only run when that is the case rather than whenever a venv is created bpo 34006 Revert line length limit for Windows help docs The line length limit is not needed because the pages appear in a separate app rather than on a browser tab It can also interact badly with the DPI setting bpo 31546 Restore running PyOS_InputHook while waiting for user input at the prompt The restores integration of interactive GUI windows such as Matplotlib figures with the prompt on Windows bpo 30237 Output error when ReadConsole is canceled by CancelSynchrono,en
1715,usIo instead of crashing bpo 33895 GIL is released while calling functions that acquire Windows loader lock bpo 33720 Reduces maximum marshal recursion depth on release builds bpo 29097 Fix bug where datetime fromtimestamp erroneously throws an OSError on Windows for values between 0 and 86400 Patch by Ammar Askar bpo 33316 PyThread_release_lock always fails bpo 33184 Update Windows installer to use OpenSSL 1 1 0h bpo 32890 Fix usage of GetLastError instead of errno in os execve and os truncate bpo 33016 Fix potential use of uninitialized memory in nt _getfinalpathname bpo 32903 Fix a memory leak in os chdir on Windows if the current directory is set to a UNC path bpo 32901 Update Tcl and Tk versions to 8 6 8 bpo 31966 Fixed WindowsConsoleIO write for writing empty data bpo 32409 Ensures activate bat can handle Unicode contents bpo 32457 Improves handling of denormalized executable path when launching Python bpo 32370 Use the correct encoding for ipconfig output in the uuid module Patch by Segev Finer bpo 29248 Fix os readlink on Windows which was mistakenly treating the PrintNameOffset field of the reparse data buffer as a number of characters instead of bytes Patch by Craig Holmquist and SSE4 bpo 1104 Correctly handle string length in msilib SummaryInfo GetProperty to prevent it from truncating the last character macOS bpo 35401 Update macOS installer to use OpenSSL 1 1 0j bpo 35025 Properly guard the use of the CLOCK_GETTIME et al macros in timemodule on macOS bpo 24658 On macOS fix reading from and writing into a file with a size larger than 2 GiB bpo 34405 Update to OpenSSL 1 1 0i for macOS installer builds bpo 33635 In macOS stat on some file descriptors dev fd 3 f e will result in bad file descriptor OSError Guard against this exception was added in is_dir is_file and similar methods DirEntry is_dir can also throw this exception so _RecursiveWildcardSelector _iterate_directories was also extended with the same error ignoring pattern bpo 13631 The editrc file in user s home directory is now processed correctly during the readline initialization through editline emulation on macOS bpo 33184 Update macOS installer build to use OpenSSL 1 1 0h bpo 32726 Build and link with private copy of Tcl Tk 8 6 for the macOS 10 6 installer The 10 9 installer variant already does this This means that the Python 3 7 provided by the python org macOS installers no longer need or use any external versions of Tcl Tk either system provided or user installed such as ActiveTcl bpo 32901 Update macOS 10 9 installer to Tcl Tk 8 6 8 bpo 31903 In _scproxy drop the GIL when calling into SystemConfiguration to avoid deadlocks IDLE bpo 35770 IDLE macosx deletes Options Configure IDLE It previously deleted Window Zoom Height by mistake Zoom Height is now on the Options menu On Mac the settings dialog is accessed via Preferences on the IDLE menu bpo 35769 Change IDLE s new file name from Untitled to untitled bpo 35660 Fix imports in idlelib window bpo 35641 Proper format calltip when the function has no docstring bpo 33987 Use ttk Frame for ttk widgets bpo 34055 Fix erroneous smart indents and newlines in IDLE Shell bpo 35591 Find Selection now works when selection not found bpo 35196 Speed up squeezer line counting bpo 35598 Update config_key use PEP 8 names and ttk widgets make some objects global and add tests bpo 28097 Add Previous Next History entries to Shell menu bpo 35208 Squeezer now properly counts wrapped lines before newlines bpo 35555 Gray out Code Context menu entry when it s not applicable bpo 35521 Document the IDLE editor code context feature Add some internal references within the IDLE doc bpo 22703 The Code Context menu label now toggles between Show Hide Code Context The Zoom Height menu now toggles between Zoom Restore Height Zoom Height has moved from the Window menu to the Options menu bpo 35213 Where appropriate use macOS in idlelib bpo 34864 On macOS warn if the system preference Prefer tabs when opening documents is set to Always bpo 34864 Document two IDLE on MacOS issues The System Preferences Dock prefer tabs always set,en
1716,ting disables some IDLE features Menus are a bit different than as described for Windows and Linux bpo 35202 Remove unused imports from lib idlelib bpo 33000 Document that IDLE s shell has no line limit A program that runs indefinitely can overfill memory bpo 23220 Explain how IDLE s Shell displays output bpo 35099 Improve the doc about IDLE running user code The section is renamed from IDLE console differences is renamed Running user code It mostly covers the implications of using custom sys std xxx objects bpo 35097 Add IDLE doc subsection explaining editor windows Topics include opening title and status bar py extension and running bpo 35093 Document the IDLE document viewer in the IDLE doc Add a paragraph in Help and preferences Help sources subsection bpo 35088 Update idlelib help copy_string docstring We now use git and backporting instead of hg and forward merging bpo 35087 Update idlelib help files for the current doc build The main change is the elimination of chapter section numbers bpo 34548 Use configured color theme for read only text views bpo 1529353 Enable squeezing of long outputs in the shell to avoid performance degradation and to clean up the history without losing it Squeezed outputs may be copied viewed in a separate window and unsqueezed bpo 34047 Fixed mousewheel scrolling direction on macOS bpo 34275 Make IDLE calltips always visible on Mac Some MacOS tk combinations need update_idletasks Patch by Kevin Walzer bpo 34120 Fix unresponsiveness after closing certain windows and dialogs bpo 33975 Avoid small type when running htests Since part of the purpose of human viewed tests is to determine that widgets look right it is important that they look the same for testing as when running IDLE bpo 33905 Add test for idlelib stackview StackBrowser bpo 33924 Change mainmenu menudefs key windows to window Every other menudef key is lowercase version of main menu entry bpo 33906 Rename idlelib windows as window Match Window on the main menu and remove last plural module name bpo 33917 Fix and document idlelib idle_test template py The revised file compiles runs and tests OK idle_test README txt explains how to use it to create new IDLE test files bpo 33904 IDLE In rstrip rename class RstripExtension as Rstrip bpo 33907 For consistency and clarity rename an IDLE module and classes Module calltips and its class CallTips are now calltip and Calltip In module calltip_w class CallTip is now CalltipWindow bpo 33856 Add help in the welcome message of IDLE bpo 33839 IDLE refactor ToolTip and CallTip and add documentation and tests bpo 33855 Minimally test all IDLE modules Add missing files import module instantiate classes and check coverage Check existing files bpo 33656 On Windows add API call saying that tk scales for DPI On Windows 8 1 or 10 with DPI compatibility properties of the Python binary unchanged and a monitor resolution greater than 96 DPI this should make text and lines sharper It should otherwise have no effect bpo 33768 Clicking on a context line moves that line to the top of the editor window bpo 33763 IDLE Use read only text widget for code context instead of label widget bpo 33664 Scroll IDLE editor text by lines Previously the mouse wheel and scrollbar slider moved text by a fixed number of pixels resulting in partial lines at the top of the editor box The change also applies to the shell and grep output windows but not to read only text views bpo 33679 Enable theme specific color configuration for Code Context Use the Highlights tab to see the setting for built in themes or add settings to custom themes bpo 33642 Display up to maxlines non blank lines for Code Context If there is no current context show a single blank line bpo 33628 IDLE Cleanup codecontext py and its test bpo 33564 IDLE s code context now recognizes async as a block opener bpo 21474 Update word identifier definition from ascii to unicode In text and entry boxes this affects selection by double click movement left right by control left right and deletion left right by control BACKSPACE DEL bpo 33204 IDLE consistently color inva,en
1717,lid string prefixes A u string prefix cannot be paired with either r or f Consistently color as much of the prefix starting at the right as is valid Revise and extend colorizer test bpo 32984 Set __file__ while running a startup file Like Python IDLE optionally runs one startup file in the Shell window before presenting the first interactive input prompt For IDLE s runs a file named in environmental variable IDLESTARTUP or PYTHONSTARTUP r file runs file Python sets __file__ to the startup file name before running the file and unsets it before the first prompt IDLE now does the same when run normally without the n option bpo 32940 Simplify and rename StringTranslatePseudoMapping in pyparse bpo 32916 Change str to code in pyparse bpo 32905 Remove unused code in pyparse module bpo 32874 Add tests for pyparse bpo 32837 Using the system and place dependent default encoding for open is a bad idea for IDLE s system and location independent files bpo 32826 Add encoding utf 8 to open in IDLE s test_help_about GUI test test_file_buttons only looks at initial ascii only lines but failed on systems where open defaults to ascii because readline internally reads and decodes far enough ahead to encounter a non ascii character in CREDITS txt bpo 32831 Add docstrings and tests for codecontext bpo 32765 Update configdialog General tab docstring to add new widgets to the widget list Tools Demos bpo 35884 Add a benchmark script for timing various ways to access variables Tools scripts var_access_benchmark py bpo 34989 python gdb py now handles errors on computing the line number of a Python frame bpo 20260 Argument Clinic now has non bitwise unsigned int converters bpo 32962 python gdb now catches UnicodeDecodeError exceptions when calling string bpo 32962 python gdb now catches ValueError on read_var when Python has no debug symbols for example bpo 33189 pygettext py now recognizes only literal strings as docstrings and translatable strings and rejects bytes literals and f string expressions bpo 31920 Fixed handling directories as arguments in the pygettext script Based on patch by Oleg Krasnikov bpo 29673 Fix pystackv and pystack gdbinit macros bpo 25427 Remove the pyvenv script in favor of python3 m venv in order to lower confusion as to what Python interpreter a virtual environment will be created for bpo 32885 Add an n flag for Tools scripts pathfix py to disable automatic backup creation files with suffix bpo 32222 Fix pygettext not extracting docstrings for functions with type annotated arguments Patch by Toby Harradine bpo 31583 Fix 2to3 for using with add suffix option but without output dir option for relative path to files in current directory C API bpo 35713 The PyByteArray_Init and PyByteArray_Fini functions have been removed They did nothing since Python 2 7 4 and Python 3 2 0 were excluded from the limited API stable ABI and were not documented bpo 33817 Fixed _PyBytes_Resize for empty bytes objects bpo 35322 Fix memory leak in PyUnicode_EncodeLocale and PyUnicode_EncodeFSDefault on error handling bpo 35059 The following C macros have been converted to static inline functions Py_INCREF Py_DECREF Py_XINCREF Py_XDECREF PyObject_INIT PyObject_INIT_VAR bpo 35296 make install now also installs the internal API Include internal h header files bpo 35081 Internal APIs surrounded by ifdef Py_BUILD_CORE have been moved from Include h headers to new header files Include internal pycore_ h bpo 35259 Conditionally declare Py_FinalizeEx new in 3 6 based on Py_LIMITED_API Patch by Arthur Neufeld bpo 35081 The _PyObject_GC_TRACK and _PyObject_GC_UNTRACK macros have been removed from the public C API bpo 35134 Creation of a new Include cpython subdirectory bpo 34725 Adds _Py_SetProgramFullPath so embedders may override sys executable bpo 34910 Ensure that PyObject_Print always returns 1 on error Patch by Zackery Spytz bpo 34523 Py_DecodeLocale and Py_EncodeLocale now use the UTF 8 encoding on Windows if Py_LegacyWindowsFSEncodingFlag is zero bpo 34193 Fix pluralization in TypeError messages in getargs c and typeobject c 1 argument instead of ,en
1718,1 arguments and 1 element instead of 1 elements bpo 34127 Return grammatically correct error message based on argument count Patch by Karthikeyan Singaravelan bpo 23927 Fixed SystemError in PyArg_ParseTupleAndKeywords when the w format unit is used for optional parameter bpo 32455 Added PyCompile_OpcodeStackEffectWithJump bpo 34008 Py_Main can again be called after Py_Initialize as in Python 3 6 bpo 32500 Fixed error messages for PySequence_Size PySequence_GetItem PySequence_SetItem and PySequence_DelItem called with a mapping and PyMapping_Size called with a sequence bpo 33818 PyExceptionClass_Name will now return const char instead of char bpo 33042 Embedding applications may once again call PySys_ResetWarnOptions PySys_AddWarnOption and PySys_AddXOption prior to calling Py_Initialize bpo 32374 Document that m_traverse for multi phase initialized modules can be called with m_state NULL and add a sanity check bpo 30863 PyUnicode_AsWideChar and PyUnicode_AsWideCharString no longer cache the wchar_t representation of string objects Python 3 7 0 final Release date 2018 06 27 Library bpo 33851 Fix ast get_docstring for a node that lacks a docstring C API bpo 33932 Calling Py_Initialize twice does nothing instead of failing with a fatal error restore the Python 3 6 behaviour Python 3 7 0 release candidate 1 Release date 2018 06 12 Core and Builtins bpo 33803 Fix a crash in hamt c caused by enabling GC tracking for an object that hadn t all of its fields set to NULL bpo 33706 Fix a crash in Python initialization when parsing the command line options Thanks Christoph Gohlke for the bug report and the fix bpo 30654 Fixed reset of the SIGINT handler to SIG_DFL on interpreter shutdown even when there was a custom handler set previously Patch by Philipp Kerling bpo 31849 Fix signed unsigned comparison warning in pyhash c Library bpo 30167 Prevent site main exception if PYTHONSTARTUP is set Patch by Steve Weber bpo 33812 Datetime instance d with non None tzinfo but with d tzinfo utcoffset d returning None is now treated as naive by the astimezone method bpo 30805 Avoid race condition with debug logging bpo 33694 asyncio Fix a race condition causing data loss on pause_reading resume_reading when using the ProactorEventLoop bpo 32493 Correct test for uuid_enc_be availability in configure ac Patch by Michael Felt bpo 33792 Add asyncio WindowsSelectorEventLoopPolicy and asyncio WindowsProactorEventLoopPolicy bpo 33778 Update unicodedata s database to Unicode version 11 0 0 bpo 33770 improve base64 exception message for encoded inputs of invalid length bpo 33769 asyncio start_tls Fix error message cancel callbacks in case of an unhandled error mark SSLTransport as closed if it is aborted bpo 33767 The concatenation and repetition sequence operations now raise TypeError instead of SystemError when performed on mmap mmap objects Patch by Zackery Spytz bpo 33734 asyncio ssl Fix AttributeError increase default handshake timeout bpo 11874 Use a better regex when breaking usage into wrappable parts Avoids bogus assertion errors from custom metavar strings bpo 33582 Emit a deprecation warning for inspect formatargspec Documentation bpo 33409 Clarified the relationship between PEP 538 s PYTHONCOERCECLOCALE and PEP 540 s PYTHONUTF8 mode bpo 33736 Improve the documentation of asyncio open_connection asyncio start_server and their UNIX socket counterparts bpo 31432 Clarify meaning of CERT_NONE CERT_OPTIONAL and CERT_REQUIRED flags for ssl SSLContext verify_mode Build bpo 5755 Move Wstrict prototypes option to CFLAGS_NODIST from OPT This option emitted annoying warnings when building extension modules written in C Windows bpo 33720 Reduces maximum marshal recursion depth on release builds IDLE bpo 33656 On Windows add API call saying that tk scales for DPI On Windows 8 1 or 10 with DPI compatibility properties of the Python binary unchanged and a monitor resolution greater than 96 DPI this should make text and lines sharper It should otherwise have no effect bpo 33768 Clicking on a context line moves that line to the top of the editor window bpo 33,en
1719,763 IDLE Use read only text widget for code context instead of label widget bpo 33664 Scroll IDLE editor text by lines Previously the mouse wheel and scrollbar slider moved text by a fixed number of pixels resulting in partial lines at the top of the editor box The change also applies to the shell and grep output windows but not to read only text views bpo 33679 Enable theme specific color configuration for Code Context Use the Highlights tab to see the setting for built in themes or add settings to custom themes bpo 33642 Display up to maxlines non blank lines for Code Context If there is no current context show a single blank line Python 3 7 0 beta 5 Release date 2018 05 30 Core and Builtins bpo 33622 Fixed a leak when the garbage collector fails to add an object with the __del__ method or referenced by it into the gc garbage list PyGC_Collect can now be called when an exception is set and preserves it bpo 33509 Fix module_globals parameter of warnings warn_explicit don t crash if module_globals is not a dict bpo 20104 The new os posix_spawn added in 3 7 0b1 was removed as we are still working on what the API should look like Expect this in 3 8 instead bpo 33475 Fixed miscellaneous bugs in converting annotations to strings and optimized parentheses in the string representation bpo 33391 Fix a leak in set_symmetric_difference bpo 28055 Fix unaligned accesses in siphash24 Patch by Rolf Eike Beer bpo 32911 Due to unexpected compatibility issues discovered during downstream beta testing reverted bpo 29463 docstring field is removed from Module ClassDef FunctionDef and AsyncFunctionDef ast nodes which was added in 3 7a1 Docstring expression is restored as a first statement in their body Based on patch by Inada Naoki bpo 21983 Fix a crash in ctypes cast in case the type argument is a ctypes structured data type Patch by Eryk Sun and Oren Milman Library bpo 32751 When cancelling the task due to a timeout asyncio wait_for will now wait until the cancellation is complete bpo 32684 Fix gather to propagate cancellation of itself even with return_exceptions bpo 33654 Support protocol type switching in SSLTransport set_protocol bpo 33674 Pause the transport as early as possible to further reduce the risk of data_received being called before connection_made bpo 33674 Fix a race condition in SSLProtocol connection_made of asyncio sslproto start immediately the handshake instead of using call_soon Previously data_received could be called before the handshake started causing the handshake to hang or fail bpo 31647 Fixed bug where calling write_eof on a _SelectorSocketTransport after it s already closed raises AttributeError bpo 32610 Make asyncio all_tasks return only pending tasks bpo 32410 Avoid blocking on file IO in sendfile fallback code bpo 33469 Fix RuntimeError after closing loop that used run_in_executor bpo 33672 Fix Task __repr__ crash with Cython s bogus coroutines bpo 33654 Fix transport set_protocol to support switching between asyncio Protocol and asyncio BufferedProtocol Fix loop start_tls to work with asyncio BufferedProtocols bpo 33652 Pickles of type variables and subscripted generics are now future proof and compatible with older Python versions bpo 32493 Fixed uuid uuid1 on FreeBSD bpo 33618 Finalize and document preliminary and experimental TLS 1 3 support with OpenSSL 1 1 1 bpo 33623 Fix possible SIGSGV when asyncio Future is created in __del__ bpo 30877 Fixed a bug in the Python implementation of the JSON decoder that prevented the cache of parsed strings from clearing after finishing the decoding Based on patch by c fos bpo 33570 Change TLS 1 3 cipher suite settings for compatibility with OpenSSL 1 1 1 pre6 and newer OpenSSL 1 1 1 will have TLS 1 3 ciphers enabled by default bpo 28556 Do not simplify arguments to typing Union Now Union Manager Employee is not simplified to Employee at runtime Such simplification previously caused several bugs and limited possibilities for introspection bpo 33540 Add a new block_on_close class attribute to ForkingMixIn and ThreadingMixIn classes of socketserver bpo 33548 tempfil,en
1720,e _candidate_tempdir_list should consider common TEMP locations bpo 33109 argparse subparsers are once again not required by default reverting the change in behavior introduced by bpo 26510 in 3 7 0a2 bpo 33536 dataclasses make_dataclass now checks for invalid field names and duplicate fields Also added a check for invalid field specifications bpo 33542 Prevent uuid get_node from using a DUID instead of a MAC on Windows Patch by Zvi Effron bpo 26819 Fix race condition with ReadTransport resume_reading in Windows proactor event loop Fix failure in typing get_type_hints when ClassVar was provided as a string forward reference bpo 33505 Optimize asyncio ensure_future by reordering if checks 1 17x faster bpo 33497 Add errors param to cgi parse_multipart and make an encoding in FieldStorage use the given errors needed for Twisted Patch by Amber Brown bpo 33495 Change dataclasses Fields repr to use the repr of each of its members instead of str This makes it more clear what each field actually represents This is especially true for the type member bpo 33453 Fix dataclasses to work if using literal string type annotations or if using PEP 563 Postponed Evaluation of Annotations Only specific string prefixes are detected for both ClassVar ClassVar and typing ClassVar and InitVar InitVar and dataclasses InitVar bpo 28556 Minor fixes in typing module add annotations to NamedTuple __new__ pass args and kwds in Generic __new__ Original PRs by Paulius Šarka and Chad Dombrova bpo 20087 Updated alias mapping with glibc 2 27 supported locales bpo 33422 Fix trailing quotation marks getting deleted when looking up byte string literals on pydoc Patch by Andrés Delfino bpo 28167 The function platform linux_distribution and platform dist now trigger a DeprecationWarning and have been marked for removal in Python 3 8 bpo 33197 Update error message when constructing invalid inspect Parameters Patch by Donghee Na bpo 33263 Fix FD leak in _SelectorSocketTransport Patch by Vlad Starostin bpo 32861 The urllib robotparser s __str__ representation now includes wildcard entries and the Crawl delay and Request rate fields Patch by Michael Lazar bpo 32257 The ssl module now contains OP_NO_RENEGOTIATION constant available with OpenSSL 1 1 0h or 1 1 1 bpo 16865 Support arrays 2GiB in ctypes Patch by Segev Finer Documentation bpo 23859 Document that asyncio wait does not cancel its futures on timeout bpo 32436 Document PEP 567 changes to asyncio bpo 33604 Update HMAC md5 default to a DeprecationWarning bump removal to 3 8 bpo 33503 Fix broken pypi link bpo 33421 Add missing documentation for typing AsyncContextManager Tests bpo 33655 Ignore test_posix_fallocate failures on BSD platforms that might be due to running on ZFS bpo 32604 Remove the _xxsubinterpreters module meant for testing and associated helpers This module was originally added recently in 3 7b1 Build bpo 33614 Ensures module definition files for the stable ABI on Windows are correctly regenerated bpo 33522 Enable CI builds on Visual Studio Team Services at https python visualstudio com cpython bpo 33012 Add Wno cast function type for gcc 8 for silencing warnings about function casts like casting to PyCFunction in method definition lists macOS bpo 13631 The editrc file in user s home directory is now processed correctly during the readline initialization through editline emulation on macOS IDLE bpo 33628 IDLE Cleanup codecontext py and its test bpo 33564 IDLE s code context now recognizes async as a block opener bpo 32831 Add docstrings and tests for codecontext Python 3 7 0 beta 4 Release date 2018 05 02 Core and Builtins bpo 33363 Raise a SyntaxError for async with and async for statements outside of async functions bpo 33128 Fix a bug that causes PathFinder to appear twice on sys meta_path Patch by Pablo Galindo Salgado bpo 33312 Fixed clang ubsan undefined behavior sanitizer warnings in dictobject c by adjusting how the internal struct _dictkeysobject shared keys structure is declared bpo 33231 Fix potential memory leak in normalizestring bpo 33205 Change dict growth function from round_up,en
1721,_to_power_2 used 2 hashtable_size 2 to round_up_to_power_2 used 3 Previously dict is shrinked only when used 0 Now dict has more chance to be shrinked bpo 29922 Improved error messages in async with when __aenter__ or __aexit__ return non awaitable object bpo 33199 Fix ma_version_tag in dict implementation is uninitialized when copying from key sharing dict Library bpo 33281 Fix ctypes util find_library regression on macOS bpo 33383 Fixed crash in the get method of the dbm ndbm database object when it is called with a single argument bpo 33329 Fix multiprocessing regression on newer glibcs bpo 991266 Fix quoting of the Comment attribute of http cookies SimpleCookie bpo 33131 Upgrade bundled version of pip to 10 0 1 bpo 33308 Fixed a crash in the parser module when converting an ST object to a tree of tuples or lists with line_info False and col_info True bpo 33266 lib2to3 now recognizes rf strings bpo 11594 Ensure line endings are respected when using lib2to3 bpo 33254 Have importlib resources contents and importlib abc ResourceReader contents return an iterable instead of an iterator bpo 33256 Fix display of module call in the html produced by cgitb html Patch by Stéphane Blondon bpo 33185 Fixed regression when running pydoc with the m switch The regression was introduced in 3 7 0b3 by the resolution of bpo 33053 This fix also changed pydoc to add os getcwd to sys path when necessary rather than adding bpo 33169 Delete entries of None in sys path_importer_cache when importlib machinery invalidate_caches is called bpo 33217 Deprecate looking up non Enum objects in Enum classes and Enum members will raise TypeError in 3 8 bpo 33203 random Random choice now raises IndexError for empty sequences consistently even when called from subclasses without a getrandbits implementation bpo 33224 Update difflib mdiff for PEP 479 Convert an uncaught StopIteration in a generator into a return statement bpo 33209 End framing at the end of C implementation of pickle Pickler dump bpo 20104 Improved error handling and fixed a reference leak in os posix_spawn bpo 33175 In dataclasses Field __set_name__ now looks up the __set_name__ special method on the class not the instance of the default value bpo 33097 Raise RuntimeError when executor submit is called during interpreter shutdown bpo 31908 Fix output of cover files for trace module command line tool Previously emitted cover files only when missing option was used Patch by Michael Selik Documentation bpo 33378 Add Korean language switcher for https docs python org 3 bpo 33276 Clarify that the __path__ attribute on modules cannot be just any value bpo 33201 Modernize documentation for writing C extension types bpo 33195 Deprecate Py_UNICODE usage in c api arg document Py_UNICODE related APIs are deprecated since Python 3 3 but it is missed in the document bpo 8243 Add a note about curses addch and curses addstr exception behavior when writing outside a window or pad bpo 32337 Update documentation related with dict order Tests bpo 33358 Fix test_embed test_pre_initialization_sys_options when the interpreter is built with enable shared Build bpo 33394 Enable the verbose build for extension modules when GNU make is passed macros on the command line bpo 33393 Update config guess and config sub files bpo 33377 Add new triplets for mips r6 and riscv variants used in extension suffixes bpo 32232 By default modules configured in Modules Setup are no longer built with DPy_BUILD_CORE Instead modules that specifically need that preprocessor definition include it in their individual entries bpo 33182 The embedding tests can once again be built with clang 6 0 Windows bpo 33184 Update Windows installer to use OpenSSL 1 1 0h macOS bpo 33184 Update macOS installer build to use OpenSSL 1 1 0h IDLE bpo 21474 Update word identifier definition from ascii to unicode In text and entry boxes this affects selection by double click movement left right by control left right and deletion left right by control BACKSPACE DEL bpo 33204 IDLE consistently color invalid string prefixes A u string prefix cannot be paired w,en
1722,ith either r or f Consistently color as much of the prefix starting at the right as is valid Revise and extend colorizer test Tools Demos bpo 33189 pygettext py now recognizes only literal strings as docstrings and translatable strings and rejects bytes literals and f string expressions bpo 31920 Fixed handling directories as arguments in the pygettext script Based on patch by Oleg Krasnikov bpo 29673 Fix pystackv and pystack gdbinit macros bpo 31583 Fix 2to3 for using with add suffix option but without output dir option for relative path to files in current directory Python 3 7 0 beta 3 Release date 2018 03 29 Security bpo 33136 Harden ssl module against LibreSSL CVE 2018 8970 X509_VERIFY_PARAM_set1_host is called with an explicit namelen A new test ensures that NULL bytes are not allowed bpo 33001 Minimal fix to prevent buffer overrun in os symlink on Windows bpo 32981 Regexes in difflib and poplib were vulnerable to catastrophic backtracking These regexes formed potential DOS vectors REDOS They have been refactored This resolves CVE 2018 1060 and CVE 2018 1061 Patch by Jamie Davis Core and Builtins bpo 33053 When using the m switch sys path 0 is now explicitly expanded as the starting working directory rather than being left as the empty path which allows imports from the current working directory at the time of the import bpo 33018 Improve consistency of errors raised by issubclass when called with a non class and an abstract base class as the first and second arguments respectively Patch by Josh Bronson bpo 33041 Fixed jumping when the function contains an async for loop bpo 33026 Fixed jumping out of with block by setting f_lineno bpo 33005 Fix a crash on fork when using a custom memory allocator ex using PYTHONMALLOC env var _PyGILState_Reinit and _PyInterpreterState_Enable now use the default RAW memory allocator to allocate a new interpreters mutex on fork bpo 17288 Prevent jumps from return and exception trace events bpo 32836 Don t use temporary variables in cases of list dict set comprehensions Library bpo 33141 Have Field objects pass through __set_name__ to their default values if they have their own __set_name__ bpo 33096 Allow ttk Treeview insert to insert iid that has a false boolean value Note iid 0 and iid False would be same Patch by Garvit Khatri bpo 32873 Treat type variables and special typing forms as immutable by copy and pickle This fixes several minor issues and inconsistencies and improves backwards compatibility with Python 3 6 bpo 33134 When computing dataclass s __hash__ use the lookup table to contain the function which returns the __hash__ value This is an improvement over looking up a string and then testing that string to see what to do bpo 33127 The ssl module now compiles with LibreSSL 2 7 1 bpo 32505 Raise TypeError if a member variable of a dataclass is of type Field but doesn t have a type annotation bpo 33078 Fix the failure on OSX caused by the tests relying on sem_getvalue bpo 33116 Add Field to dataclasses __all__ bpo 32896 Fix an error where subclassing a dataclass with a field that uses a default_factory would generate an incorrect class bpo 33100 Dataclasses If a field has a default value that s a MemberDescriptorType then it s from that field being in __slots__ not an actual default value bpo 32953 If a non dataclass inherits from a frozen dataclass allow attributes to be added to the derived class Only attributes from the frozen dataclass cannot be assigned to Require all dataclasses in a hierarchy to be either all frozen or all non frozen bpo 33061 Add missing NoReturn to __all__ in typing py bpo 33078 Fix the size handling in multiprocessing Queue when a pickling error occurs bpo 33064 lib2to3 now properly supports trailing commas after args and kwargs in function signatures bpo 33056 FIX properly close leaking fds in concurrent futures ProcessPoolExecutor bpo 33021 Release the GIL during fstat calls avoiding hang of all threads when calling mmap mmap os urandom and random seed Patch by Nir Soffer bpo 31804 Avoid failing in multiprocessing Process if the standard streams,en
1723, are closed or None at exit bpo 33037 Skip sending receiving data after SSL transport closing bpo 27683 Fix a regression in ipaddress that result of hosts is empty when the network is constructed by a tuple containing an integer mask and only 1 bit left for addresses bpo 32999 Fix C implementation of ABC __subclasscheck__ cls subclass crashed when subclass is not a type object bpo 33009 Fix inspect signature for single parameter partialmethods bpo 32969 Expose several missing constants in zlib and fix corresponding documentation bpo 32056 Improved exceptions raised for invalid number of channels and sample width when read an audio file in modules aifc wave and sunau bpo 32844 Fix wrong redirection of a low descriptor 0 or 1 to stderr in subprocess if another low descriptor is closed bpo 32857 In tkinter after_cancel None now raises a ValueError instead of canceling the first scheduled function Patch by Cheryl Sabella bpo 31639 http server now exposes a ThreadedHTTPServer class and uses it when the module is run with m to cope with web browsers pre opening sockets bpo 27645 sqlite3 Connection now exposes a backup method if the underlying SQLite library is at version 3 6 11 or higher Patch by Lele Gaifax Documentation bpo 33126 Document PyBuffer_ToContiguous bpo 27212 Modify documentation for the islice recipe to consume initial values up to the start index bpo 28247 Update zipapp documentation to describe how to make standalone applications bpo 18802 Documentation changes for ipaddress Patch by Jon Foster and Berker Peksag bpo 27428 Update documentation to clarify that WindowsRegistryFinder implements MetaPathFinder Patch by Himanshu Lakhara Tests bpo 32872 Avoid regrtest compatibility issue with namespace packages bpo 32517 Fix failing test_asyncio on macOS 10 12 2 due to transport of KqueueSelector loop was not being closed bpo 19417 Add test_bdb py Build bpo 33163 Upgrade pip to 9 0 3 and setuptools to v39 0 1 Windows bpo 33016 Fix potential use of uninitialized memory in nt _getfinalpathname bpo 32903 Fix a memory leak in os chdir on Windows if the current directory is set to a UNC path macOS bpo 32726 Build and link with private copy of Tcl Tk 8 6 for the macOS 10 6 installer The 10 9 installer variant already does this This means that the Python 3 7 provided by the python org macOS installers no longer need or use any external versions of Tcl Tk either system provided or user installed such as ActiveTcl IDLE bpo 32984 Set __file__ while running a startup file Like Python IDLE optionally runs one startup file in the Shell window before presenting the first interactive input prompt For IDLE s runs a file named in environmental variable IDLESTARTUP or PYTHONSTARTUP r file runs file Python sets __file__ to the startup file name before running the file and unsets it before the first prompt IDLE now does the same when run normally without the n option bpo 32940 Simplify and rename StringTranslatePseudoMapping in pyparse Tools Demos bpo 32885 Add an n flag for Tools scripts pathfix py to disable automatic backup creation files with suffix C API bpo 33042 Embedding applications may once again call PySys_ResetWarnOptions PySys_AddWarnOption and PySys_AddXOption prior to calling Py_Initialize bpo 32374 Document that m_traverse for multi phase initialized modules can be called with m_state NULL and add a sanity check Python 3 7 0 beta 2 Release date 2018 02 27 Security bpo 28414 The ssl module now allows users to perform their own IDN en decoding when using SNI Core and Builtins bpo 32889 Update Valgrind suppression list to account for the rename of Py_ADDRESS_IN_RANG to address_in_range bpo 31356 Remove the new API added in bpo 31356 gc ensure_disabled context manager bpo 32305 For namespace packages ensure that both __file__ and __spec__ origin are set to None bpo 32303 Make sure __spec__ loader matches __loader__ for namespace packages bpo 32711 Fix the warning messages for Python ast_unparse c Patch by Stéphane Wirtel bpo 32583 Fix possible crashing in builtin Unicode decoders caused by write out of bound errors when using,en
1724, customized decode error handlers Library bpo 32960 For dataclasses disallow inheriting frozen from non frozen classes and also disallow inheriting non frozen from frozen classes This restriction will be relaxed at a future date bpo 32713 Fixed tarfile itn handling of out of bounds float values Patch by Joffrey Fuhrer bpo 32951 Direct instantiation of SSLSocket and SSLObject objects is now prohibited The constructors were never documented tested or designed as public constructors Users were suppose to use ssl wrap_socket or SSLContext bpo 32929 Remove the tri state parameter hash and add the boolean unsafe_hash If unsafe_hash is True add a __hash__ function but if a __hash__ exists raise TypeError If unsafe_hash is False add a __hash__ based on the values of eq and frozen The unsafe_hash False behavior is the same as the old hash None behavior unsafe_hash False is the default just as hash None used to be bpo 32947 Add OP_ENABLE_MIDDLEBOX_COMPAT and test workaround for TLSv1 3 for future compatibility with OpenSSL 1 1 1 bpo 30622 The ssl module now detects missing NPN support in LibreSSL bpo 32922 dbm open now encodes filename with the filesystem encoding rather than default encoding bpo 32859 In os dup2 don t check every call whether the dup3 syscall exists or not bpo 32556 nt _getfinalpathname nt _getvolumepathname and nt _getdiskusage now correctly convert from bytes bpo 25988 Emit a DeprecationWarning when using or importing an ABC directly from collections rather than from collections abc bpo 21060 Rewrite confusing message from setup py upload from No dist file created in earlier command to the more helpful Must create and upload files in one command bpo 32852 Make sure sys argv remains as a list when running trace bpo 31333 _abc module is added It is a speedup module with C implementations for various functions and methods in abc Creating an ABC subclass and calling isinstance or issubclass with an ABC subclass are up to 1 5x faster In addition this makes Python start up up to 10 faster Note that the new implementation hides internal registry and caches previously accessible via private attributes _abc_registry _abc_cache and _abc_negative_cache There are three debugging helper methods that can be used instead _dump_registry _abc_registry_clear and _abc_caches_clear bpo 32841 Fixed asyncio Condition issue which silently ignored cancellation after notifying and cancelling a conditional lock Patch by Bar Harel bpo 32819 ssl match_hostname has been simplified and no longer depends on re and ipaddress module for wildcard and IP addresses Error reporting for invalid wildcards has been improved bpo 32394 socket Remove TCP_FASTOPEN TCP_KEEPCNT TCP_KEEPIDLE TCP_KEEPINTVL flags on older version Windows during run time bpo 31787 Fixed refleaks of __init__ methods in various modules Contributed by Oren Milman bpo 30157 Fixed guessing quote and delimiter in csv Sniffer sniff when only the last field is quoted Patch by Jake Davis bpo 32792 collections ChainMap preserves the order of the underlying mappings bpo 32775 fnmatch translate no longer produces patterns which contain set operations Sets starting with or containing or will be interpreted differently in regular expressions in future versions Currently they emit warnings fnmatch translate now avoids producing patterns containing such sets by accident bpo 32622 Implement native fast sendfile for Windows proactor event loop bpo 32777 Fix a rare but potential pre exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process This bug appears to have been introduced in 3 4 bpo 32647 The ctypes module used to depend on indirect linking for dlopen The shared extension is now explicitly linked against libdl on platforms with dl bpo 32741 Implement asyncio TimerHandle when method bpo 32691 Use mod_spec parent when running modules with pdb bpo 32734 Fixed asyncio Lock safety issue which allowed acquiring and locking the same lock multiple times without it being free Patch by Bar Harel bpo 32727 Do not include name f,en
1725,ield in SMTP envelope from address Patch by Stéphane Wirtel bpo 31453 Add TLSVersion constants and SSLContext maximum_version minimum_version attributes The new API wraps OpenSSL 1 1 https w eb archive org web 20180309043602 https www openssl org docs man1 1 0 ssl SSL_CTX_set_min_proto_version html feature bpo 24334 Internal implementation details of ssl module were cleaned up The SSLSocket has one less layer of indirection Owner and session information are now handled by the SSLSocket and SSLObject constructor Channel binding implementation has been simplified bpo 31848 Fix the error handling in Aifc_read initfp when the SSND chunk is not found Patch by Zackery Spytz bpo 32585 Add Ttk spinbox widget to tkinter ttk Patch by Alan D Moore bpo 32221 Various functions returning tuple containing IPv6 addresses now omit scope part since the same information is already encoded in scopeid tuple item Especially this speeds up socket recvfrom when it receives multicast packet since useless resolving of network interface name is omitted bpo 30693 The TarFile class now recurses directories in a reproducible way bpo 30693 The ZipFile class now recurses directories in a reproducible way Documentation bpo 28124 The ssl module function ssl wrap_socket has been de emphasized and deprecated in favor of the more secure and efficient SSLContext wrap_socket method bpo 17232 Clarify docs for O and OO Patch by Terry Reedy bpo 32436 Add documentation for the contextvars module PEP 567 bpo 32800 Update link to w3c doc for xml default namespaces bpo 11015 Update test support documentation bpo 8722 Document __getattr__ behavior when property get method raises AttributeError bpo 32614 Modify RE examples in documentation to use raw strings to prevent DeprecationWarning and add text to REGEX HOWTO to highlight the deprecation bpo 31972 Improve docstrings for pathlib PurePath subclasses Tests bpo 31809 Add tests to verify connection with secp ECDH curves Build bpo 32898 Fix the python debug build when using COUNT_ALLOCS Windows bpo 32901 Update Tcl and Tk versions to 8 6 8 bpo 31966 Fixed WindowsConsoleIO write for writing empty data bpo 32409 Ensures activate bat can handle Unicode contents bpo 32457 Improves handling of denormalized executable path when launching Python bpo 32370 Use the correct encoding for ipconfig output in the uuid module Patch by Segev Finer bpo 29248 Fix os readlink on Windows which was mistakenly treating the PrintNameOffset field of the reparse data buffer as a number of characters instead of bytes Patch by Craig Holmquist and SSE4 macOS bpo 32901 Update macOS 10 9 installer to Tcl Tk 8 6 8 IDLE bpo 32916 Change str to code in pyparse bpo 32905 Remove unused code in pyparse module bpo 32874 Add tests for pyparse bpo 32837 Using the system and place dependent default encoding for open is a bad idea for IDLE s system and location independent files bpo 32826 Add encoding utf 8 to open in IDLE s test_help_about GUI test test_file_buttons only looks at initial ascii only lines but failed on systems where open defaults to ascii because readline internally reads and decodes far enough ahead to encounter a non ascii character in CREDITS txt bpo 32765 Update configdialog General tab docstring to add new widgets to the widget list Tools Demos bpo 32222 Fix pygettext not extracting docstrings for functions with type annotated arguments Patch by Toby Harradine Python 3 7 0 beta 1 Release date 2018 01 30 Core and Builtins bpo 32703 Fix coroutine s ResourceWarning when there s an active error set when it s being finalized bpo 32650 Pdb and other debuggers dependent on bdb py will correctly step over next command native coroutines Patch by Pablo Galindo bpo 28685 Optimize list sort and sorted by using type specialized comparisons when possible bpo 32685 Improve suggestion when the Python 2 form of print statement is either present on the same line as the header of a compound statement or else terminated by a semi colon instead of a newline Patch by Nitish Chandra bpo 32697 Python now explicitly preserves the definition order of keyword onl,en
1726,y parameters It s always preserved their order but this behavior was never guaranteed before this behavior is now guaranteed and tested bpo 32690 The locals dictionary now displays in the lexical order that variables were defined Previously the order was reversed bpo 32677 Add isascii method to str bytes and bytearray It can be used to test that string contains only ASCII characters bpo 32670 Enforce PEP 479 for all code This means that manually raising a StopIteration exception from a generator is prohibited for all code regardless of whether from __future__ import generator_stop was used or not bpo 32591 Added built in support for tracking the origin of coroutine objects see sys set_coroutine_origin_tracking_depth and CoroutineType cr_origin This replaces the asyncio debug mode s use of coroutine wrapping for native coroutine objects bpo 31368 Expose preadv and pwritev system calls in the os module Patch by Pablo Galindo bpo 32544 hasattr obj name and getattr obj name default are about 4 times faster than before when name is not found and obj doesn t override __getattr__ or __getattribute__ bpo 26163 Improved frozenset hash to create more distinct hash values when faced with datasets containing many similar values bpo 32550 Remove the STORE_ANNOTATION bytecode bpo 20104 Expose posix_spawn as a low level API in the os module removed before 3 7 0rc1 bpo 24340 Fixed estimation of the code stack size bpo 32436 Implement PEP 567 Context Variables bpo 18533 repr on a dict containing its own values or items no longer raises RecursionError OrderedDict similarly Instead use as for other recursive structures Patch by Ben North bpo 20891 Py_Initialize now creates the GIL The GIL is no longer created on demand to fix a race condition when PyGILState_Ensure is called in a non Python thread bpo 32028 Leading whitespace is now correctly ignored when generating suggestions for converting Py2 print statements to Py3 builtin print function calls Patch by Sanyam Khurana bpo 31179 Make dict copy up to 5 5 times faster bpo 31113 Get rid of recursion in the compiler for normal control flow Library bpo 25988 Deprecate exposing the contents of collections abc in the regular collections module bpo 31429 The default cipher suite selection of the ssl module now uses a blacklist approach rather than a hard coded whitelist Python no longer re enables ciphers that have been blocked by OpenSSL security update Default cipher suite selection can be configured on compile time bpo 30306 contextlib contextmanager now releases the arguments passed to the underlying generator as soon as the context manager is entered Previously it would keep them alive for as long as the context manager was alive even when not being used as a function decorator Patch by Martin Teichmann bpo 21417 Added support for setting the compression level for zipfile ZipFile bpo 32251 Implement asyncio BufferedProtocol provisional API bpo 32513 In dataclasses allow easier overriding of dunder methods without specifying decorator parameters bpo 32660 termios makes available FIONREAD FIONCLEX FIOCLEX FIOASYNC and FIONBIO also under Solaris derivatives bpo 27931 Fix email address header parsing error when the username is an empty quoted string Patch by Xiang Zhang bpo 32659 Under Solaris and derivatives os stat_result provides a st_fstype attribute bpo 32662 Implement Server start_serving Server serve_forever and Server is_serving methods Add start_serving keyword parameter to loop create_server and loop create_unix_server bpo 32391 Implement asyncio StreamWriter wait_closed and asyncio StreamWriter is_closing methods bpo 32643 Make Task _step Task _wakeup and Future _schedule_callbacks methods private bpo 32630 Refactor decimal module to use contextvars to store decimal context bpo 32622 Add asyncio AbstractEventLoop sendfile method bpo 32304 distutils upload command no longer corrupts tar files ending with a CR byte and no longer tries to convert CR to CRLF in any of the upload text fields bpo 32502 uuid uuid1 no longer raises an exception if a 64 bit hardware address is encountered bp,en
1727,o 32596 concurrent futures imports ThreadPoolExecutor and ProcessPoolExecutor lazily using PEP 562 It makes import asyncio about 15 faster because asyncio uses only ThreadPoolExecutor by default bpo 31801 Add _ignore_ to Enum so temporary variables can be used during class construction without being turned into members bpo 32576 Use queue SimpleQueue in places where it can be invoked from a weakref callback bpo 32574 Fix memory leak in asyncio Queue when the queue has limited size and it is full the cancelation of queue put can cause a memory leak Patch by José Melero bpo 32521 The nis module is now compatible with new libnsl and headers location bpo 32467 collections abc ValuesView now inherits from collections abc Collection bpo 32473 Improve ABCMeta _dump_registry output readability bpo 32102 New argument capture_output for subprocess run bpo 32521 glibc has removed Sun RPC Use replacement libtirpc headers and library in nis module bpo 32493 UUID module fixes build for FreeBSD OpenBSD bpo 32503 Pickling with protocol 4 no longer creates too small frames bpo 29237 Create enum for pstats sorting options bpo 32454 Add close fd function to the socket module bpo 25942 The subprocess module is now more graceful when handling a Ctrl C KeyboardInterrupt during subprocess call subprocess run or a Popen context manager It now waits a short amount of time for the child presumed to have also gotten the SIGINT to exit before continuing the KeyboardInterrupt exception handling This still includes a SIGKILL in the call and run APIs but at least the child had a chance first bpo 32433 The hmac module now has hmac digest which provides an optimized HMAC digest bpo 28134 Sockets now auto detect family type and protocol from file descriptor by default bpo 32404 Fix bug where datetime datetime fromtimestamp did not call __new__ in datetime datetime subclasses bpo 32403 Improved speed of datetime date and datetime datetime alternate constructors bpo 32228 Ensure that truncate preserves the file position as reported by tell after writes longer than the buffer size bpo 32410 Implement loop sock_sendfile for asyncio event loop bpo 22908 Added seek and tell to the ZipExtFile class This only works if the file object used to open the zipfile is seekable bpo 32373 Add socket getblocking method bpo 32248 Add importlib resources and importlib abc ResourceReader as the unified API for reading resources contained within packages Loaders wishing to support resource reading must implement the get_resource_reader method File based and zipimport based loaders both implement these APIs importlib abc ResourceLoader is deprecated in favor of these new APIs bpo 32320 collections namedtuple now supports default values bpo 29302 Add contextlib AsyncExitStack Patch by Alexander Mohr and Ilya Kulakov bpo 31961 Removed in Python 3 7 0b2 The args argument of subprocess Popen can now be a path like object If args is given as a sequence it s first element can now be a path like object as well bpo 31900 The locale localeconv function now sets temporarily the LC_CTYPE locale to the LC_NUMERIC locale to decode decimal_point and thousands_sep byte strings if they are non ASCII or longer than 1 byte and the LC_NUMERIC locale is different than the LC_CTYPE locale This temporary change affects other threads Same change for the str format method when formatting a number int float float and subclasses with the n type ex n format 1234 bpo 31853 Use super method instead of socket method in SSLSocket They were there most likely for legacy reasons bpo 31399 The ssl module now uses OpenSSL s X509_VERIFY_PARAM_set1_host and X509_VERIFY_PARAM_set1_ip API to verify hostname and IP addresses Subject common name fallback can be disabled with SSLContext hostname_checks_common_name bpo 14976 Add a queue SimpleQueue class an unbounded FIFO queue with a reentrant C implementation of put Documentation bpo 32724 Add references to some commands in the documentation of Pdb Patch by Stéphane Wirtel bpo 32649 Complete the C API documentation profiling and tracing part with the newly added per o,en
1728,pcode events bpo 17799 Explain real behaviour of sys settrace and sys setprofile and their C API counterparts regarding which type of events are received in each function Patch by Pablo Galindo Salgado Tests bpo 32721 Fix test_hashlib to not fail if the _md5 module is not built bpo 28414 Add test cases for IDNA 2003 and 2008 host names IDNA 2003 internationalized host names are working since bpo 31399 has landed IDNA 2008 are still broken bpo 32604 Add a new _xxsubinterpreters extension module that exposes the existing subinterpreter C API and a new cross interpreter data sharing mechanism The module is primarily intended for more thorough testing of the existing subinterpreter support Note that the _xxsubinterpreters module has been removed in 3 7 0rc1 bpo 32602 Add test certs and test for ECDSA cert and EC RSA dual mode bpo 32549 On Travis CI Python now Compiles and uses a local copy of OpenSSL 1 1 0g for testing Build bpo 32635 Fix segfault of the crypt module when libxcrypt is provided instead of libcrypt at the system bpo 32598 Use autoconf to detect OpenSSL libs headers and supported features The ax_check_openssl M4 macro uses pkg config to locate OpenSSL and falls back to manual search bpo 32593 Drop support of FreeBSD 9 and older bpo 29708 If the SOURCE_DATE_EPOCH environment variable is set py_compile will always create hash based pyc files Windows bpo 32588 Create standalone _distutils_findvs module and add missing _queue module to installer bpo 29911 Ensure separate Modify and Uninstall buttons are displayed bpo 32507 Use app local UCRT install rather than the proper update for old versions of Windows macOS bpo 32726 Provide an additional more modern macOS installer variant that supports macOS 10 9 systems in 64 bit mode only Upgrade the supplied third party libraries to OpenSSL 1 1 0g and to SQLite 3 22 0 The 10 9 installer now links with and supplies its own copy of Tcl Tk 8 6 bpo 28440 No longer add Library Python 3 x site packages to sys path for macOS framework builds to avoid future conflicts C API bpo 32681 Fix uninitialized variable res in the C implementation of os dup2 Patch by Stéphane Wirtel bpo 10381 Add C API access to the datetime timezone constructor and datetime timzone UTC singleton Python 3 7 0 alpha 4 Release date 2018 01 08 Core and Builtins bpo 31975 The default warning filter list now starts with a default DeprecationWarning __main__ entry so deprecation warnings are once again shown by default in single file scripts and at the interactive prompt bpo 32226 __class_getitem__ is now an automatic class method bpo 32399 Add AIX uuid library support for RFC4122 using uuid_create in libc a bpo 32390 Fix the compilation failure on AIX after the f_fsid field has been added to the object returned by os statvfs bpo 32143 Original patch by Michael Felt bpo 32379 Make MRO computation faster when a class inherits from a single base bpo 32259 The error message of a TypeError raised when unpack non iterable is now more specific bpo 27169 The __debug__ constant is now optimized out at compile time This fixes also bpo 22091 bpo 32329 The R option now turns on hash randomization when the PYTHONHASHSEED environment variable is set to 0 Previously the option was ignored Moreover sys flags hash_randomization is now properly set to 0 when hash randomization is turned off by PYTHONHASHSEED 0 bpo 30416 The optimizer is now protected from spending much time doing complex calculations and consuming much memory for creating large constants in constant folding Increased limits for constants that can be produced in constant folding bpo 32282 Fix an unnecessary ifdef in the include of VersionHelpers h in socketmodule on Windows bpo 30579 Implement TracebackType __new__ to allow Python level creation of traceback objects and make TracebackType tb_next mutable bpo 32260 Don t byte swap the input keys to the SipHash algorithm on big endian platforms This should ensure siphash gives consistent results across platforms bpo 31506 Improve the error message logic for object __new__ and object __init__ Patch by Sanyam Khurana,en
1729, bpo 20361 b and bb now inject default BytesWarning and error BytesWarning entries into sys warnoptions ensuring that they take precedence over any other warning filters configured via the W option or the PYTHONWARNINGS environment variable bpo 32230 X dev now injects a default entry into sys warnoptions ensuring that it behaves identically to actually passing Wdefault at the command line bpo 29240 Add a new UTF 8 mode implementation of the PEP 540 bpo 32226 PEP 560 Add support for __mro_entries__ and __class_getitem__ Implemented by Ivan Levkivskyi bpo 32225 PEP 562 Add support for module __getattr__ and __dir__ Implemented by Ivan Levkivskyi bpo 31901 The atexit module now has its callback stored per interpreter bpo 31650 Implement PEP 552 Deterministic pycs Python now supports invalidating bytecode cache files bashed on a source content hash rather than source last modified time bpo 29469 Move constant folding from bytecode layer to AST layer Original patch by Eugene Toder Library bpo 32506 Now that dict is defined as keeping insertion order drop OrderedDict and just use plain dict bpo 32279 Add params to dataclasses make_dataclasses init repr eq order hash and frozen Pass them through to dataclass bpo 32278 Make type information optional on dataclasses make_dataclass If omitted the string typing Any is used bpo 32499 Add dataclasses is_dataclass obj which returns True if obj is a dataclass or an instance of one bpo 32468 Improve frame repr to mention filename code name and current line number bpo 23749 asyncio Implement loop start_tls bpo 32441 Return the new file descriptor i e the second argument from os dup2 Previously None was always returned bpo 32422 functools lru_cache uses less memory 3 words for each cached key and takes about 1 3 time for cyclic GC bpo 31721 Prevent Python crash from happening when Future _log_traceback is set to True manually Now it can only be set to False or a ValueError is raised bpo 32415 asyncio Add Task get_loop and Future get_loop bpo 26133 Don t unsubscribe signals in asyncio UNIX event loop on interpreter shutdown bpo 32363 Make asyncio Task set_exception and set_result raise NotImplementedError Task _step and Future __await__ raise proper exceptions when they are in an invalid state instead of raising an AssertionError bpo 32357 Optimize asyncio iscoroutine and loop create_task for non native coroutines e g async await compiled with Cython loop create_task python_coroutine used to be 20 faster than loop create_task cython_coroutine Now the latter is as fast bpo 32356 asyncio transport resume_reading and pause_reading are now idempotent New transport is_reading method is added bpo 32355 Optimize asyncio gather now up to 15 faster bpo 32351 Use fastpath in asyncio sleep if delay 0 2x boost bpo 32348 Optimize asyncio Future schedule add remove callback The optimization shows 3 6 performance improvements of async await code bpo 32331 Fix socket settimeout and socket setblocking to keep socket type as is Fix socket socket constructor to reset any bit flags applied to socket s type This change only affects OSes that have SOCK_NONBLOCK and or SOCK_CLOEXEC bpo 32248 Add importlib abc ResourceReader as an ABC for loaders to provide a unified API for reading resources contained within packages Also add importlib resources as the port of importlib_resources bpo 32311 Implement asyncio create_task coro shortcut bpo 32327 Convert asyncio functions that were documented as coroutines to coroutines Affected functions loop sock_sendall loop sock_recv loop sock_accept loop getaddrinfo loop getnameinfo bpo 32323 urllib parse urlsplit does not convert zone id scope to lower case for scoped IPv6 addresses in hostnames now bpo 32302 Fix bdist_wininst of distutils for CRT v142 it binary compatible with CRT v140 bpo 29711 Fix stop_serving in asyncio proactor loop kill all listening servers bpo 32308 re sub now replaces empty matches adjacent to a previous non empty match bpo 29970 Abort asyncio SSLProtocol connection if handshake not complete within 10 seconds bpo 32314 Implement asyncio run bpo 17852 R,en
1730,evert incorrect fix based on misunderstanding of _Py_PyAtExit semantics bpo 32296 Implement asyncio _get_running_loop and get_event_loop in C This makes them 4x faster bpo 32250 Implement asyncio current_task and asyncio all_tasks Add helpers intended to be used by alternative task implementations asyncio _register_task asyncio _enter_task asyncio _leave_task and asyncio _unregister_task Deprecate asyncio Task current_task and asyncio Task all_tasks bpo 32255 A single empty field is now always quoted when written into a CSV file This allows to distinguish an empty row from a row consisting of a single empty field Patch by Licht Takeuchi bpo 32277 Raise NotImplementedError instead of SystemError on platforms where chmod follow_symlinks False is not supported Patch by Anthony Sottile bpo 30050 New argument warn_on_full_buffer to signal set_wakeup_fd lets you control whether Python prints a warning on stderr when the wakeup fd buffer overflows bpo 29137 The fpectl library has been removed It was never enabled by default never worked correctly on x86 64 and it changed the Python ABI in ways that caused unexpected breakage of C extensions bpo 32273 Move asyncio test_utils to test test_asyncio bpo 32272 Remove asyncio async function bpo 32269 Add asyncio get_running_loop function bpo 32265 All class and static methods of builtin types now are correctly classified by inspect classify_class_attrs and grouped in pydoc ouput Added types ClassMethodDescriptorType for unbound class methods of builtin types bpo 32253 Deprecate yield from lock await lock with yield from lock and with await lock for asyncio synchronization primitives bpo 22589 Changed MIME type of bmp from image x ms bmp to image bmp bpo 32193 Convert asyncio to use async await syntax Old styled yield from is still supported too bpo 32206 Add support to run modules with pdb bpo 32227 functools singledispatch now supports registering implementations using type annotations bpo 15873 Added new alternate constructors datetime datetime fromisoformat datetime time fromisoformat and datetime date fromisoformat as the inverse operation of each classes s respective isoformat methods bpo 32199 The getnode ip getter now uses ip link instead of ip link list bpo 32143 os statvfs includes the f_fsid field from statvfs 2 bpo 26439 Fix ctypes util find_library for AIX by implementing ctypes _aix find_library Patch by Michael Felt bpo 31993 The pickler now uses less memory when serializing large bytes and str objects into a file Pickles created with protocol 4 will require less memory for unpickling large bytes and str objects bpo 27456 Ensure TCP_NODELAY is set on Linux Tests by Victor Stinner bpo 31778 ast literal_eval is now more strict Addition and subtraction of arbitrary numbers no longer allowed bpo 31802 Importing native path module posixpath ntpath now works even if the os module still is not imported bpo 30241 Add contextlib AbstractAsyncContextManager Patch by Jelle Zijlstra bpo 31699 Fix deadlocks in concurrent futures ProcessPoolExecutor when task arguments or results cause pickling or unpickling errors This should make sure that calls to the ProcessPoolExecutor API always eventually return bpo 15216 TextIOWrapper reconfigure supports changing encoding errors and newline Documentation bpo 32418 Add get_loop method to Server and AbstractServer classes Tests bpo 32252 Fix faulthandler_suppress_crash_report used to prevent core dump files when testing crashes getrlimit returns zero on success bpo 32002 Adjust C locale coercion testing for the empty locale and POSIX locale cases to more readily adjust to platform dependent behaviour Windows bpo 19764 Implement support for subprocess Popen close_fds True on Windows Patch by Segev Finer Tools Demos bpo 24960 2to3 and lib2to3 can now read pickled grammar files using pkgutil get_data rather than probing the filesystem This lets 2to3 and lib2to3 work when run from a zipfile C API bpo 32030 Py_Initialize doesn t reset the memory allocators to default if the PYTHONMALLOC environment variable is not set bpo 29084 Undocumented C API fo,en
1731,r OrderedDict has been excluded from the limited C API It was added by mistake and actually never worked in the limited C API bpo 32264 Moved the pygetopt h header into internal since it has no public APIs bpo 32241 Py_SetProgramName and Py_SetPythonHome now take the const wchar arguments instead of wchar Python 3 7 0 alpha 3 Release date 2017 12 05 Core and Builtins bpo 32176 co_flags CO_NOFREE is now always set correctly by the code object constructor based on freevars and cellvars rather than needing to be set correctly by the caller This ensures it will be cleared automatically when additional cell references are injected into a modified code object and function bpo 10544 Yield expressions are now deprecated in comprehensions and generator expressions They are still permitted in the definition of the outermost iterable as that is evaluated directly in the enclosing scope bpo 32137 The repr of deeply nested dict now raises a RecursionError instead of crashing due to a stack overflow bpo 32096 Revert memory allocator changes in the C API move structures back from _PyRuntime to Objects obmalloc c The memory allocators are once again initialized statically and so PyMem_RawMalloc and Py_DecodeLocale can be called before _PyRuntime_Initialize bpo 32043 Add a new developer mode new X dev command line option to enable debug checks at runtime bpo 32023 SyntaxError is now correctly raised when a generator expression without parenthesis is used instead of an inheritance list in a class definition The duplication of the parentheses can be omitted only on calls bpo 32012 SyntaxError is now correctly raised when a generator expression without parenthesis is passed as an argument but followed by a trailing comma A generator expression always needs to be directly inside a set of parentheses and cannot have a comma on either side bpo 28180 A new internal _Py_SetLocaleFromEnv category helper function has been added in order to improve the consistency of behaviour across different libc implementations e g Android doesn t support setting the locale from the environment by default bpo 31949 Fixed several issues in printing tracebacks PyTraceBack_Print Setting sys tracebacklimit to 0 or less now suppresses printing tracebacks Setting sys tracebacklimit to None now causes using the default limit Setting sys tracebacklimit to an integer larger than LONG_MAX now means using the limit LONG_MAX rather than the default limit Fixed integer overflows in the case of more than 2 31 traceback items on Windows Fixed output errors handling bpo 30696 Fix the interactive interpreter looping endlessly when no memory bpo 20047 Bytearray methods partition and rpartition now accept only bytes like objects as separator as documented In particular they now raise TypeError rather of returning a bogus result when an integer is passed as a separator bpo 21720 BytesWarning no longer emitted when the fromlist argument of __import__ or the __all__ attribute of the module contain bytes instances bpo 31845 Environment variables are once more read correctly at interpreter startup bpo 28936 Ensure that lexically first syntax error involving a parameter and global or nonlocal is detected first at a given scope Patch by Ivan Levkivskyi bpo 31825 Fixed OverflowError in the unicode escape codec and in codecs escape_decode when decode an escaped non ascii byte bpo 31618 The per frame tracing logic added in 3 7a1 has been altered so that frame f_lineno is updated before either line or opcode events are emitted Previously opcode events were emitted first and therefore would occasionally see stale line numbers on the frame The behavior of this feature has changed slightly as a result when both f_trace_lines and f_trace_opcodes are enabled line events now occur first bpo 28603 Print the full context cause chain of exceptions on interpreter exit even if an exception in the chain is unhashable or compares equal to later ones Patch by Zane Bitter bpo 31786 Fix timeout rounding in the select module to round correctly negative timeouts between 1 0 and 0 0 The functions now block wai,en
1732,ting for events as expected Previously the call was incorrectly non blocking Patch by Pablo Galindo bpo 31781 Prevent crashes when calling methods of an uninitialized zipimport zipimporter object Patch by Oren Milman bpo 30399 Standard repr of BaseException with a single argument no longer contains redundant trailing comma bpo 31626 Fixed a bug in debug memory allocator There was a write to freed memory after shrinking a memory block bpo 30817 PyErr_PrintEx clears now the ignored exception that may be raised by _PySys_SetObjectId for example when no memory Library bpo 28556 Two minor fixes for typing module allow shallow copying instances of generic classes improve interaction of __init_subclass__ with generics Original PRs by Ivan Levkivskyi bpo 32214 PEP 557 Data Classes Provides a decorator which adds boilerplate methods to classes which use type annotations so specify fields bpo 27240 The header folding algorithm for the new email policies has been rewritten which also fixes bpo 30788 bpo 31831 and bpo 32182 In particular RFC2231 folding is now done correctly bpo 32186 io FileIO readall and io FileIO read now release the GIL when getting the file size Fixed hang of all threads with inaccessible NFS server Patch by Nir Soffer bpo 32101 Add sys flags dev_mode flag bpo 32154 The asyncio windows_utils socketpair function has been removed use directly socket socketpair which is available on all platforms since Python 3 5 before it wasn t available on Windows asyncio windows_utils socketpair was just an alias to socket socketpair on Python 3 5 and newer bpo 32089 warnings In development X dev and debug mode pydebug build use the default action for ResourceWarning rather than the always action in the default warnings filters bpo 32107 uuid getnode now preferentially returns universally administered MAC addresses if available over locally administered MAC addresses This makes a better guarantee for global uniqueness of UUIDs returned from uuid uuid1 If only locally administered MAC addresses are available the first such one found is returned bpo 23033 Wildcard is now supported in hostname when it is one and only character in the left most segment of hostname in second argument of ssl match_hostname Patch by Mandeep Singh bpo 12239 Make msilib SummaryInformation GetProperty return None when the value of property is VT_EMPTY Initial patch by Mark Mc Mahon bpo 28334 Use os path expanduser to find the netrc file in netrc netrc If it does not exist FileNotFoundError is raised Patch by Dimitri Merejkowsky bpo 32121 Made tracemalloc Traceback behave more like the traceback module sorting the frames from oldest to most recent Traceback format now accepts negative limit truncating the result to the abs limit oldest frames To get the old behaviour one can use the new most_recent_first argument to Traceback format Patch by Jesse Bakker bpo 31325 Fix wrong usage of collections namedtuple in the RobotFileParser parse method Initial patch by Robin Wellner bpo 12382 msilib OpenDatabase now raises a better exception message when it couldn t open or create an MSI file Initial patch by William Tisäter bpo 19610 setup now warns about invalid types for some fields The distutils dist Distribution class now warns when classifiers keywords and platforms fields are not specified as a list or a string bpo 32071 Added the k command line option to python m unittest to run only tests that match the given pattern s bpo 10049 Added nullcontext no op context manager to contextlib This provides a simpler and faster alternative to ExitStack when handling optional context managers bpo 28684 The new test support skip_unless_bind_unix_socket decorator is used here to skip asyncio tests that fail because the platform lacks a functional bind function for unix domain sockets as it is the case for non root users on the recent Android versions that run now SELinux in enforcing mode bpo 32110 codecs StreamReader read n now returns not more than n characters bytes for non negative n This makes it compatible with read methods of other file like objects bpo 27535 The w,en
1733,arnings module doesn t leak memory anymore in the hidden warnings registry for the ignore action of warnings filters warn_explicit function doesn t add the warning key to the registry anymore for the ignore action bpo 32088 warnings When Python is build is debug mode Py_DEBUG DeprecationWarning PendingDeprecationWarning and ImportWarning warnings are now displayed by default bpo 1647489 Fixed searching regular expression patterns that could match an empty string Non empty string can now be correctly found after matching an empty string bpo 25054 Added support of splitting on a pattern that could match an empty string bpo 32072 Fixed issues with binary plists Fixed saving bytearrays Identical objects will be saved only once Equal references will be load as identical objects Added support for saving and loading recursive data structures bpo 32069 Drop legacy SSL transport from asyncio ssl MemoryBIO is always used anyway bpo 32066 asyncio Support pathlib Path in create_unix_connection sock arg should be optional bpo 32046 Updates 2to3 to convert from operator isCallable obj to callable obj Patch by Donghee Na bpo 32018 inspect signature should follow PEP 8 if the parameter has an annotation and a default value Patch by Donghee Na bpo 32025 Add time thread_time and time thread_time_ns bpo 32037 Integers that fit in a signed 32 bit integer will be now pickled with protocol 0 using the INT opcode This will decrease the size of a pickle speed up pickling and unpickling and make these integers be unpickled as int instances in Python 2 bpo 32034 Make asyncio IncompleteReadError and LimitOverrunError pickleable bpo 32015 Fixed the looping of asyncio in the case of reconnection the socket during waiting async read write from to the socket bpo 32011 Restored support of loading marshal files with the TYPE_INT64 code These files can be produced in Python 2 7 bpo 28369 Enhance add_reader writer check that socket is not used by some transport Before only cases when add_reader writer were called with an int FD were supported Now the check is implemented correctly for all file like objects bpo 31976 Fix race condition when flushing a file is slow which can cause a segfault if closing the file from another thread bpo 31985 Formally deprecated aifc openfp sunau openfp and wave openfp Since change 7bc817d5ba917528e8bd07ec461c635291e7b06a in 1993 openfp in each of the three modules had been pointing to that module s open function as a matter of backwards compatibility though it had been both untested and undocumented bpo 21862 cProfile command line now accepts m module_name as an alternative to script path Patch by Sanyam Khurana bpo 31970 Reduce performance overhead of asyncio debug mode bpo 31843 database argument of sqlite3 connect now accepts a path like object instead of just a string bpo 31945 Add Configurable blocksize to HTTPConnection and HTTPSConnection for improved upload throughput Patch by Nir Soffer bpo 31943 Add a cancelled method to asyncio Handle Patch by Marat Sharafutdinov bpo 9678 Fixed determining the MAC address in the uuid module Using ifconfig on NetBSD and OpenBSD Using arp on Linux FreeBSD NetBSD and OpenBSD Based on patch by Takayuki Shimizukawa bpo 30057 Fix potential missed signal in signal signal bpo 31933 Fix Blake2 params leaf_size and node_offset on big endian platforms Patch by Jack O Connor bpo 21423 Add an initializer argument to Process Thread PoolExecutor bpo 31927 Fixed compilation of the socket module on NetBSD 8 Fixed assertion failure or reading arbitrary data when parse a AF_BLUETOOTH address on NetBSD and DragonFly BSD bpo 27666 Fixed stack corruption in curses box and curses ungetmouse when the size of types chtype or mmask_t is less than the size of C long curses box now accepts characters as arguments Based on patch by Steve Fink bpo 31917 Add 3 new clock identifiers time CLOCK_BOOTTIME time CLOCK_PROF and time CLOCK_UPTIME bpo 31897 plistlib now catches more errors when read binary plists and raises InvalidFileException instead of unexpected exceptions bpo 25720 Fix the method for checking pad s,en
1734,tate of curses WINDOW Patch by Masayuki Yamamoto bpo 31893 Fixed the layout of the kqueue_event structure on OpenBSD and NetBSD Fixed the comparison of the kqueue_event objects bpo 31891 Fixed building the curses module on NetBSD bpo 31884 added required constants to subprocess module for setting priority on windows bpo 28281 Remove year 1 9999 limits on the Calendar weekday function Patch by Mark Gollahon bpo 31702 crypt mksalt now allows to specify the number of rounds for SHA 256 and SHA 512 hashing bpo 30639 inspect getfile no longer computes the repr of unknown objects to display in an error message to protect against badly behaved custom reprs bpo 30768 Fix the pthread semaphore implementation of PyThread_acquire_lock_timed when called with timeout 0 and intr_flag 0 recompute the timeout if sem_timedwait is interrupted by a signal EINTR See also the PEP 475 bpo 31854 Add mmap ACCESS_DEFAULT constant bpo 31834 Use optimized code for BLAKE2 only with SSSE3 The pure SSE2 implementation is slower than the pure C reference implementation bpo 28292 Calendar itermonthdates will now consistently raise an exception when a date falls outside of the 0001 01 01 through 9999 12 31 range To support applications that cannot tolerate such exceptions the new methods itermonthdays3 and itermonthdays4 are added The new methods return tuples and are not restricted by the range supported by datetime date bpo 28564 The shutil rmtree function has been sped up to 20 40 This was done using the os scandir function bpo 28416 Instances of pickle Pickler subclass with the persistent_id method and pickle Unpickler subclass with the persistent_load method no longer create reference cycles bpo 31653 Don t release the GIL if we can acquire a multiprocessing semaphore immediately bpo 28326 Fix multiprocessing Process when stdout and or stderr is closed or None bpo 20825 Add subnet_of and superset_of containment tests to ipaddress IPv6Network and ipaddress IPv4Network Patch by Michel Albert and Cheryl Sabella bpo 31827 Remove the os stat_float_times function It was introduced in Python 2 3 for backward compatibility with Python 2 2 and was deprecated since Python 3 1 bpo 31756 Add a subprocess Popen text False keyword argument to subprocess functions to be more explicit about when the library should attempt to decode outputs into text Patch by Andrew Clegg bpo 31819 Add AbstractEventLoop sock_recv_into bpo 31457 If nested log adapters are used the inner process methods are no longer omitted bpo 31457 The manager property on LoggerAdapter objects is now properly settable bpo 31806 Fix timeout rounding in time sleep threading Lock acquire and socket socket settimeout to round correctly negative timeouts between 1 0 and 0 0 The functions now block waiting for events as expected Previously the call was incorrectly non blocking Patch by Pablo Galindo bpo 31803 time clock and time get_clock_info clock now emit a DeprecationWarning warning bpo 31800 Extended support for parsing UTC offsets strptime z can now parse the output generated by datetime isoformat including seconds and microseconds bpo 28603 traceback Fix a TypeError that occurred during printing of exception tracebacks when either the current exception or an exception in its context cause chain is unhashable Patch by Zane Bitter bpo 30541 Add new function to seal a mock and prevent the automatically creation of child mocks Patch by Mario Corchero bpo 31784 Implement the PEP 564 add new 6 new functions with nanosecond resolution to the time module clock_gettime_ns clock_settime_ns monotonic_ns perf_counter_ns process_time_ns time_ns bpo 30143 2to3 now generates a code that uses abstract collection classes from collections abc rather than collections bpo 31770 Prevent a crash when calling the __init__ method of a sqlite3 Cursor object more than once Patch by Oren Milman bpo 31764 Prevent a crash in sqlite3 Cursor close in case the Cursor object is uninitialized Patch by Oren Milman bpo 31752 Fix possible crash in timedelta constructor called with custom integers bpo 31620 an empty asyncio Queue now,en
1735, doesn t leak memory when queue get pollers timeout bpo 31690 Allow the flags re ASCII re LOCALE and re UNICODE to be used as group flags for regular expressions bpo 30349 FutureWarning is now emitted if a regular expression contains character set constructs that will change semantically in the future nested sets and set operations bpo 31664 Added support for the Blowfish hashing in the crypt module bpo 31632 Fix method set_protocol of class _SSLProtocolTransport in asyncio module This method was previously modifying a wrong reference to the protocol bpo 15037 Added a workaround for getkey in curses for ncurses 5 7 and earlier bpo 31307 Allow use of bytes objects for arguments to configparser ConfigParser read Patch by Vincent Michel bpo 31334 Fix poll poll timeout in the select module for arbitrary negative timeouts on all OSes where it can only be a non negative integer or 1 Patch by Riccardo Coccioli bpo 31310 multiprocessing s semaphore tracker should be launched again if crashed bpo 31308 Make multiprocessing s forkserver process immune to Ctrl C and other user interruptions If it crashes restart it when necessary bpo 31245 Added support for AF_UNIX socket in asyncio create_datagram_endpoint bpo 30553 Add HTTP 2 status code 421 Misdirected Request to http HTTPStatus Patch by Vitor Pereira Documentation bpo 32105 Added asyncio BaseEventLoop connect_accepted_socket versionadded marker Tests bpo 31380 Skip test_httpservers test_undecodable_file on macOS fails on APFS bpo 31705 Skip test_socket test_sha256 on Linux kernel older than 4 5 The test fails with ENOKEY on kernel 3 10 on ppc64le A fix was merged into the kernel 4 5 bpo 32138 Skip on Android test_faulthandler tests that raise SIGSEGV and remove the test support requires_android_level decorator bpo 32136 The runtime embedding tests have been split out from Lib test test_capi py into a new Lib test test_embed py file bpo 28668 test support requires_multiprocessing_queue is removed Skip tests with test support import_module multiprocessing synchronize instead when the semaphore implementation is broken or missing bpo 32126 Skip test_get_event_loop_new_process in test test_asyncio test_events when sem_open is not functional bpo 31174 Fix test_tools test_unparse DirectoryTestCase now stores the names sample to always test the same files It prevents false alarms when hunting reference leaks Build bpo 28538 Revert the previous changes the if_nameindex structure is defined by Unified Headers bpo 28762 Revert the last commit the F_LOCK macro is defined by Android Unified Headers bpo 29040 Support building Android with Unified Headers The first NDK release to support Unified Headers is android ndk r14 bpo 32059 detect_modules in setup py now also searches the sysroot paths when cross compiling bpo 31957 Fixes Windows SDK version detection when building for Windows bpo 31609 Fixes quotes in PCbuild clean bat bpo 31934 Abort the build when building out of a not clean source tree bpo 31926 Fixed Argument Clinic sometimes causing compilation errors when there was more than one function and or method in a c file with the same name bpo 28791 Update Windows builds to use SQLite 3 21 0 bpo 28791 Update OS X installer to use SQLite 3 21 0 bpo 28643 Record profile opt build progress with stamp files bpo 31866 Finish removing support for AtheOS Windows bpo 1102 Return None when View Fetch returns ERROR_NO_MORE_ITEMS instead of raising MSIError Initial patch by Anthony Tuininga bpo 31944 Fixes Modify button in Apps and Features dialog bpo 20486 Implement the Database Close method to help closing MSI database objects bpo 31857 Make the behavior of USE_STACKCHECK deterministic in a multi threaded environment macOS bpo 31392 Update macOS installer to use OpenSSL 1 0 2m IDLE bpo 32207 Improve tk event exception tracebacks in IDLE When tk event handling is driven by IDLE s run loop a confusing and distracting queue EMPTY traceback context is no longer added to tk event exception tracebacks The traceback is now the same as when event handling is driven by user code Patch based on a sugges,en
1736,tion by Serhiy Storchaka bpo 32164 Delete unused file idlelib tabbedpages py Use of TabbedPageSet in configdialog was replaced by ttk Notebook bpo 32100 IDLE Fix old and new bugs in pathbrowser improve tests Patch mostly by Cheryl Sabella bpo 31858 IDLE Restrict shell prompt manipulation to the shell Editor and output windows only see an empty last prompt line This simplifies the code and fixes a minor bug when newline is inserted Sys ps1 if present is read on Shell start up but is not set or changed bpo 31860 The font sample in the IDLE configuration dialog is now editable Changes persist while IDLE remains open bpo 31836 Test_code_module now passes if run after test_idle which sets ps1 The code module uses sys ps1 if present or sets it to if not Test_code_module now properly tests both behaviors Ditto for ps2 bpo 28603 Fix a TypeError that caused a shell restart when printing a traceback that includes an exception that is unhashable Patch by Zane Bitter bpo 13802 Use non Latin characters in the IDLE s Font settings sample Even if one selects a font that defines a limited subset of the unicode Basic Multilingual Plane tcl tk will use other fonts that define a character The expanded example give users of non Latin characters a better idea of what they might see in IDLE s shell and editors To make room for the expanded sample frames on the Font tab are re arranged The Font Tabs help explains a bit about the additions Tools Demos bpo 32159 Remove CVS and Subversion tools remove svneol py and treesync py scripts CPython migrated from CVS to Subversion to Mercurial and then to Git CVS and Subversion are no longer used to develop CPython bpo 30722 Make redemo work with Python 3 6 and newer versions Also remove the LOCALE option since it doesn t work with string patterns in Python 3 Patch by Christoph Sarnowski C API bpo 20891 Fix PyGILState_Ensure When PyGILState_Ensure is called in a non Python thread before PyEval_InitThreads only call PyEval_InitThreads after calling PyThreadState_New to fix a crash bpo 32125 The Py_UseClassExceptionsFlag flag has been removed It was deprecated and wasn t used anymore since Python 2 0 bpo 25612 Move the current exception state from the frame object to the co routine This simplifies the interpreter and fixes a couple of obscure bugs caused by having swap exception state when entering or exiting a generator bpo 23699 Add Py_RETURN_RICHCOMPARE macro to reduce boilerplate code in rich comparison functions bpo 30697 The PyExc_RecursionErrorInst singleton is removed and PyErr_NormalizeException does not use it anymore This singleton is persistent and its members being never cleared may cause a segfault during finalization of the interpreter See also bpo 22898 Python 3 7 0 alpha 2 Release date 2017 10 16 Core and Builtins bpo 31558 gc freeze is a new API that allows for moving all objects currently tracked by the garbage collector to a permanent generation effectively removing them from future collection events This can be used to protect those objects from having their PyGC_Head mutated In effect this enables great copy on write stability at fork bpo 31642 Restored blocking from package import module by setting sys modules package module to None bpo 31708 Allow use of asynchronous generator expressions in synchronous functions bpo 31709 Drop support of asynchronous __aiter__ bpo 30404 The u option now makes the stdout and stderr streams unbuffered rather than line buffered bpo 31619 Fixed a ValueError when convert a string with large number of underscores to integer with binary base bpo 31602 Fix an assertion failure in zipimporter get_source in case of a bad zlib decompress Patch by Oren Milman bpo 31592 Fixed an assertion failure in Python parser in case of a bad unicodedata normalize Patch by Oren Milman bpo 31588 Raise a TypeError with a helpful error message when class creation fails due to a metaclass with a bad __prepare__ method Patch by Oren Milman bpo 31574 Importlib was instrumented with two dtrace probes to profile import timing bpo 31566 Fix an assertion failure in _warnings warn in,en
1737, case of a bad __name__ global Patch by Oren Milman bpo 31506 Improved the error message logic for object __new__ and object __init__ bpo 31505 Fix an assertion failure in json in case _json make_encoder received a bad encoder argument Patch by Oren Milman bpo 31492 Fix assertion failures in case of failing to import from a module with a bad __name__ attribute and in case of failing to access an attribute of such a module Patch by Oren Milman bpo 31478 Fix an assertion failure in _random Random seed in case the argument has a bad __abs__ method Patch by Oren Milman bpo 31336 Speed up class creation by 10 20 by reducing the overhead in the necessary special method lookups Patch by Stefan Behnel bpo 31415 Add X importtime option to show how long each import takes It can be used to optimize application s startup time Support the PYTHONPROFILEIMPORTTIME as an equivalent way to enable this bpo 31410 Optimized calling wrapper and classmethod descriptors bpo 31353 PEP 553 Add a new built in called breakpoint which calls sys breakpointhook By default this imports pdb and calls pdb set_trace but users may override sys breakpointhook to call whatever debugger they want The original value of the hook is saved in sys __breakpointhook__ bpo 17852 Maintain a list of open buffered files flush them before exiting the interpreter Based on a patch from Armin Rigo bpo 31315 Fix an assertion failure in imp create_dynamic when spec name is not a string Patch by Oren Milman bpo 31311 Fix a crash in the __setstate__ method of ctypes _CData in case of a bad __dict__ Patch by Oren Milman bpo 31293 Fix crashes in true division and multiplication of a timedelta object by a float with a bad as_integer_ratio method Patch by Oren Milman bpo 31285 Fix an assertion failure in warnings warn_explicit when the return value of the received loader s get_source has a bad splitlines method Patch by Oren Milman bpo 30406 Make async and await proper keywords as specified in PEP 492 Library bpo 30058 Fixed buffer overflow in select kqueue control bpo 31672 idpattern in string Template matched some non ASCII characters Now it uses i regular expression local flag to avoid non ASCII characters bpo 31701 On Windows faulthandler enable now ignores MSC and COM exceptions bpo 31728 Prevent crashes in _elementtree due to unsafe cleanup of Element text and Element tail Patch by Oren Milman bpo 31671 Now re compile converts passed RegexFlag to normal int object before compiling bm_regex_compile benchmark shows 14 performance improvements bpo 30397 The types of compiled regular objects and match objects are now exposed as re Pattern and re Match This adds information in pydoc output for the re module bpo 31675 Fixed memory leaks in Tkinter s methods splitlist and split when pass a string larger than 2 GiB bpo 31673 Fixed typo in the name of Tkinter s method adderrorinfo bpo 31648 Improvements to path predicates in ElementTree Allow whitespace around predicate parts i e a text instead of requiring the less readable a text Add support for text comparison of the current node like text Patch by Stefan Behnel bpo 30806 Fix the string representation of a netrc object bpo 31638 Add optional argument compressed to zipapp create_archive and add option compress to the command line interface of zipapp bpo 25351 Avoid venv activate failures with undefined variables bpo 20519 Avoid ctypes use if possible and improve import time for uuid bpo 28293 The regular expression cache is no longer completely dumped when it is full bpo 31596 Added pthread_getcpuclockid to the time module bpo 27494 Make 2to3 accept a trailing comma in generator expressions For example set x for x in is now allowed bpo 30347 Stop crashes when concurrently iterate over itertools groupby iterators bpo 30346 An iterator produced by itertools groupby iterator now becomes exhausted after advancing the groupby iterator bpo 31556 Cancel asyncio wait_for future faster if timeout 0 bpo 31540 Allow passing a context object in concurrent futures ProcessPoolExecutor constructor Also free job resources in concurrent futures Pro,en
1738,cessPoolExecutor earlier to improve memory usage when a worker waits for new jobs bpo 31516 threading current_thread should not return a dummy thread at shutdown bpo 31525 In the sqlite module require the sqlite3_prepare_v2 API Thus the sqlite module now requires sqlite version at least 3 3 9 bpo 26510 argparse subparsers are now required by default This matches behaviour in Python 2 For optional subparsers use the new parameter add_subparsers required False Patch by Anthony Sottile As of 3 7 0rc1 the default was changed to not required as had been the case since Python 3 3 bpo 27541 Reprs of subclasses of some collection and iterator classes bytearray array array collections deque collections defaultdict itertools count itertools repeat now contain actual type name instead of hardcoded names of the base class bpo 31351 python m ensurepip now exits with non zero exit code if pip bootstrapping has failed bpo 31389 pdb set_trace now takes an optional keyword only argument header If given this is printed to the console just before debugging begins Documentation bpo 31537 Fix incorrect usage of get_history_length in readline documentation example code Patch by Brad Smith bpo 30085 The operator functions without double underscores are preferred for clarity The one with underscores are only kept for back compatibility Build bpo 31696 Improve compiler version information in sys version when Python is built with Clang bpo 31625 Stop using ranlib on static libraries Instead we assume ar supports the s flag bpo 31624 Remove support for BSD OS bpo 22140 Prevent double substitution of prefix in python config sh bpo 31569 Correct PCBuild case to PCbuild in build scripts and documentation bpo 31536 Avoid wholesale rebuild after make regen all if nothing changed IDLE bpo 31460 Simplify the API of IDLE s Module Browser Passing a widget instead of an flist with a root widget opens the option of creating a browser frame that is only part of a window Passing a full file name instead of pieces assumed to come from a py file opens the possibility of browsing python files that do not end in py bpo 31649 IDLE Make _htest _utest parameters keyword only bpo 31559 Remove test order dependence in idle_test test_browser bpo 31459 Rename IDLE s module browser from Class Browser to Module Browser The original module level class and method browser became a module browser with the addition of module level functions years ago Nested classes and functions were added yesterday For back compatibility the virtual event open class browser which appears on the Keys tab of the Settings dialog is not changed Patch by Cheryl Sabella bpo 31500 Default fonts now are scaled on HiDPI displays bpo 1612262 IDLE module browser now shows nested classes and functions Original patches for code and tests by Guilherme Polo and Cheryl Sabella respectively C API bpo 28280 Make PyMapping_Keys PyMapping_Values and PyMapping_Items always return a list rather than a list or a tuple Patch by Oren Milman bpo 31532 Fix memory corruption due to allocator mix in getpath c between Py_GetPath and Py_SetPath bpo 25658 Implement PEP 539 for Thread Specific Storage TSS API it is a new Thread Local Storage TLS API to CPython which would supersede use of the existing TLS API within the CPython interpreter while deprecating the existing API PEP written by Erik M Bray patch by Masayuki Yamamoto Python 3 7 0 alpha 1 Release date 2017 09 19 Security bpo 29781 SSLObject version now correctly returns None when handshake over BIO has not been performed yet bpo 29505 Add fuzz tests for float str int str unicode str for oss fuzz bpo 30947 Upgrade libexpat embedded copy from version 2 2 1 to 2 2 3 to get security fixes bpo 30730 Prevent environment variables injection in subprocess on Windows Prevent passing other environment variables and command arguments bpo 30694 Upgrade expat copy from 2 2 0 to 2 2 1 to get fixes of multiple security vulnerabilities including CVE 2017 9233 External entity infinite loop DoS CVE 2016 9063 Integer overflow re fix CVE 2016 0718 Fix regression bugs from 2 2 0 s fix to,en
1739, CVE 2016 0718 and CVE 2012 0876 Counter hash flooding with SipHash Note the CVE 2016 5300 Use os specific entropy sources like getrandom doesn t impact Python since Python already gets entropy from the OS to set the expat secret using XML_SetHashSalt bpo 30500 Fix urllib parse splithost to correctly parse fragments For example splithost 127 0 0 1 evil com now correctly returns the 127 0 0 1 host instead of treating evil com as the host in an authentication login host bpo 29591 Update expat copy from 2 1 1 to 2 2 0 to get fixes of CVE 2016 0718 and CVE 2016 4472 See https sourceforge net p expat bugs 537 for more information Core and Builtins bpo 31490 Fix an assertion failure in ctypes class definition in case the class has an attribute whose name is specified in _anonymous_ but not in _fields_ Patch by Oren Milman bpo 31471 Fix an assertion failure in subprocess Popen on Windows in case the env argument has a bad keys method Patch by Oren Milman bpo 31418 Fix an assertion failure in PyErr_WriteUnraisable in case of an exception with a bad __module__ attribute Patch by Oren Milman bpo 31416 Fix assertion failures in case of a bad warnings filters or warnings defaultaction Patch by Oren Milman bpo 28411 Change direct usage of PyInterpreterState modules to PyImport_GetModuleDict Also introduce more uniformity in other code that deals with sys modules This helps reduce complications when working on sys modules bpo 28411 Switch to the abstract API when dealing with PyInterpreterState modules This allows later support for all dict subclasses and other Mapping implementations Also add a PyImport_GetModule function to reduce a bunch of duplicated code bpo 31411 Raise a TypeError instead of SystemError in case warnings onceregistry is not a dictionary Patch by Oren Milman bpo 31344 For finer control of tracing behaviour when testing the interpreter two new frame attributes have been added to control the emission of particular trace events f_trace_lines True by default to turn off per line trace events and f_trace_opcodes False by default to turn on per opcode trace events bpo 31373 Fix several possible instances of undefined behavior due to floating point demotions bpo 30465 Location information lineno and col_offset in f strings is now mostly correct This fixes tools like flake8 from showing warnings on the wrong line typically the first line of the file bpo 30860 Consolidate CPython s global runtime state under a single struct This improves discoverability of the runtime state bpo 31347 Fix possible undefined behavior in _PyObject_FastCall_Prepend bpo 31343 Include sys sysmacros h for major minor and makedev GNU C libray plans to remove the functions from sys types h bpo 31291 Fix an assertion failure in zipimport zipimporter get_data on Windows when the return value of pathname replace isn t a string Patch by Oren Milman bpo 31271 Fix an assertion failure in the write method of io TextIOWrapper when the encoder doesn t return a bytes object Patch by Oren Milman bpo 31243 Fix a crash in some methods of io TextIOWrapper when the decoder s state is invalid Patch by Oren Milman bpo 30721 print now shows correct usage hint for using Python 2 redirection syntax Patch by Sanyam Khurana bpo 31070 Fix a race condition in importlib _get_module_lock bpo 30747 Add a non dummy implementation of _Py_atomic_store and _Py_atomic_load on MSVC bpo 31095 Fix potential crash during GC caused by tp_dealloc which doesn t call PyObject_GC_UnTrack bpo 31071 Avoid masking original TypeError in call with unpacking when other arguments are passed bpo 30978 str format_map now passes key lookup exceptions through Previously any exception was replaced with a KeyError exception bpo 30808 Use _Py_atomic API for concurrency sensitive signal state bpo 30876 Relative import from unloaded package now reimports the package instead of failing with SystemError Relative import from non package now fails with ImportError rather than SystemError bpo 30703 Improve signal delivery Avoid using Py_AddPendingCall from signal handler to avoid calling signal unsafe functio,en
1740,ns The tests I m adding here fail without the rest of the patch on Linux and OS X This means our signal delivery logic had defects some signals could be lost bpo 30765 Avoid blocking in pthread_mutex_lock when PyThread_acquire_lock is asked not to block bpo 31161 Make sure the Missing parentheses syntax error message is only applied to SyntaxError not to subclasses Patch by Martijn Pieters bpo 30814 Fixed a race condition when import a submodule from a package bpo 30736 The internal unicodedata database has been upgraded to Unicode 10 0 bpo 30604 Move co_extra_freefuncs from per thread to per interpreter to avoid crashes bpo 30597 print now shows expected input in custom error message when used as a Python 2 statement Patch by Sanyam Khurana bpo 30682 Removed a too strict assertion that failed for certain f strings such as eval f n and eval f r bpo 30501 The compiler now produces more optimal code for complex condition expressions in the if while and assert statement the if expression and generator expressions and comprehensions bpo 28180 Implement PEP 538 legacy C locale coercion This means that when a suitable coercion target locale is available both the core interpreter and locale aware C extensions will assume the use of UTF 8 as the default text encoding rather than ASCII bpo 30486 Allows setting cell values for __closure__ Patch by Lisa Roach bpo 30537 itertools islice now accepts integer like objects having an __index__ method as start stop and slice arguments bpo 25324 Tokens needed for parsing in Python moved to C COMMENT NL and ENCODING This way the tokens and tok_names in the token module don t get changed when you import the tokenize module bpo 29104 Fixed parsing backslashes in f strings bpo 27945 Fixed various segfaults with dict when input collections are mutated during searching inserting or comparing Based on patches by Duane Griffin and Tim Mitchell bpo 25794 Fixed type __setattr__ and type __delattr__ for non interned attribute names Based on patch by Eryk Sun bpo 30039 If a KeyboardInterrupt happens when the interpreter is in the middle of resuming a chain of nested yield from or await calls it s now correctly delivered to the innermost frame bpo 28974 object __format__ x is now equivalent to str x rather than format str self bpo 30024 Circular imports involving absolute imports with binding a submodule to a name are now supported bpo 12414 sys getsizeof on a code object now returns the sizes which includes the code struct and sizes of objects which it references Patch by Donghee Na bpo 29839 len now raises ValueError rather than OverflowError if __len__ returned a large negative integer bpo 11913 README rst is now included in the list of distutils standard READMEs and therefore included in source distributions bpo 29914 Fixed default implementations of __reduce__ and __reduce_ex__ object __reduce__ no longer takes arguments object __reduce_ex__ now requires one argument bpo 29949 Fix memory usage regression of set and frozenset object bpo 29935 Fixed error messages in the index method of tuple list and deque when pass indices of wrong type bpo 29816 Shift operation now has less opportunity to raise OverflowError ValueError always is raised rather than OverflowError for negative counts Shifting zero with non negative count always returns zero bpo 24821 Fixed the slowing down to 25 times in the searching of some unlucky Unicode characters bpo 29102 Add a unique ID to PyInterpreterState This makes it easier to identify each subinterpreter bpo 29894 The deprecation warning is emitted if __complex__ returns an instance of a strict subclass of complex In a future versions of Python this can be an error bpo 29859 Show correct error messages when any of the pthread_ calls in thread_pthread h fails bpo 29849 Fix a memory leak when an ImportError is raised during from import bpo 28856 Fix an oversight that b format for bytes should support objects follow the buffer protocol bpo 29723 The sys path 0 initialization change for bpo 29139 caused a regression by revealing an inconsistency in how sys path is initiali,en
1741,zed when executing __main__ from a zipfile directory or other import location The interpreter now consistently avoids ever adding the import location s parent directory to sys path and ensures no other sys path entries are inadvertently modified when inserting the import location named on the command line bpo 29568 Escaped percent in the format string for classic string formatting no longer allows any characters between two percents bpo 29714 Fix a regression that bytes format may fail when containing zero bytes inside bpo 29695 bool float list and tuple no longer take keyword arguments The first argument of int can now be passes only as positional argument bpo 28893 Set correct __cause__ for errors about invalid awaitables returned from __aiter__ and __anext__ bpo 28876 bool range works even if len range raises OverflowError bpo 29683 Fixes to memory allocation in _PyCode_SetExtra Patch by Brian Coleman bpo 29684 Fix minor regression of PyEval_CallObjectWithKeywords It should raise TypeError when kwargs is not a dict But it might cause segv when args NULL and kwargs is not a dict bpo 28598 Support __rmod__ for subclasses of str being called before str __mod__ Patch by Martijn Pieters bpo 29607 Fix stack_effect computation for CALL_FUNCTION_EX Patch by Matthieu Dartiailh bpo 29602 Fix incorrect handling of signed zeros in complex constructor for complex subclasses and for inputs having a __complex__ method Patch by Serhiy Storchaka bpo 29347 Fixed possibly dereferencing undefined pointers when creating weakref objects bpo 29463 Add docstring field to Module ClassDef FunctionDef and AsyncFunctionDef ast nodes docstring is not first stmt in their body anymore It affects co_firstlineno and co_lnotab of code object for module and class Reverted in bpo 32911 bpo 29438 Fixed use after free problem in key sharing dict bpo 29546 Set the path and name attribute on ImportError for from import bpo 29546 Improve from import error message with location bpo 29478 If max_line_length None is specified while using the Compat32 policy it is no longer ignored Patch by Mircea Cosbuc bpo 29319 Prevent RunMainFromImporter overwriting sys path 0 bpo 29337 Fixed possible BytesWarning when compare the code objects Warnings could be emitted at compile time bpo 29327 Fixed a crash when pass the iterable keyword argument to sorted bpo 29034 Fix memory leak and use after free in os module path_converter bpo 29159 Fix regression in bytes x when x __index__ raises Exception bpo 29049 Call _PyObject_GC_TRACK lazily when calling Python function Calling function is up to 5 faster bpo 28927 bytes fromhex and bytearray fromhex now ignore all ASCII whitespace not only spaces Patch by Robert Xiao bpo 28932 Do not include sys random h if it does not exist bpo 25677 Correct the positioning of the syntax error caret for indented blocks Based on patch by Michael Layzell bpo 29000 Fixed bytes formatting of octals with zero padding in alternate form bpo 18896 Python function can now have more than 255 parameters collections namedtuple now supports tuples with more than 255 elements bpo 28596 The preferred encoding is UTF 8 on Android Patch written by Chi Hsuan Yen bpo 22257 Clean up interpreter startup see PEP 432 bpo 26919 On Android operating system data is now always encoded decoded to from UTF 8 instead of the locale encoding to avoid inconsistencies with os fsencode and os fsdecode which are already using UTF 8 bpo 28991 functools lru_cache was susceptible to an obscure reentrancy bug triggerable by a monkey patched len function bpo 28147 Fix a memory leak in split table dictionaries setattr must not convert combined table into split table Patch written by INADA Naoki bpo 28739 f string expressions are no longer accepted as docstrings and by ast literal_eval even if they do not include expressions bpo 28512 Fixed setting the offset attribute of SyntaxError by PyErr_SyntaxLocationEx and PyErr_SyntaxLocationObject bpo 28918 Fix the cross compilation of xxlimited when Python has been built with Py_DEBUG defined bpo 23722 Rather than silently producing a class th,en
1742,at doesn t support zero argument super in methods failing to pass the new __classcell__ namespace entry up to type __new__ now results in a DeprecationWarning and a class that supports zero argument super bpo 28797 Modifying the class __dict__ inside the __set_name__ method of a descriptor that is used inside that class no longer prevents calling the __set_name__ method of other descriptors bpo 28799 Remove the PyEval_GetCallStats function and deprecate the untested and undocumented sys callstats function Remove the CALL_PROFILE special build use the sys setprofile function cProfile or profile to profile function calls bpo 12844 More than 255 arguments can now be passed to a function bpo 28782 Fix a bug in the implementation yield from when checking if the next instruction is YIELD_FROM Regression introduced by WORDCODE bpo 26647 bpo 28774 Fix error position of the unicode error in ASCII and Latin1 encoders when a string returned by the error handler contains multiple non encodable characters non ASCII for the ASCII codec characters out of the U 0000 U 00FF range for Latin1 bpo 28731 Optimize _PyDict_NewPresized to create correct size dict Improve speed of dict literal with constant keys up to 30 bpo 28532 Show sys version when V option is supplied twice bpo 27100 The with statement now checks for __enter__ before it checks for __exit__ This gives less confusing error messages when both methods are missing Patch by Jonathan Ellington bpo 28746 Fix the set_inheritable file descriptor method on platforms that do not have the ioctl FIOCLEX and FIONCLEX commands bpo 26920 Fix not getting the locale s charset upon initializing the interpreter on platforms that do not have langinfo bpo 28648 Fixed crash in Py_DecodeLocale in debug build on Mac OS X when decode astral characters Patch by Xiang Zhang bpo 28665 Improve speed of the STORE_DEREF opcode by 40 bpo 19398 Extra slash no longer added to sys path components in case of empty compile time PYTHONPATH components bpo 28621 Sped up converting int to float by reusing faster bits counting implementation Patch by Adrian Wielgosik bpo 28580 Optimize iterating split table values Patch by Xiang Zhang bpo 28583 PyDict_SetDefault didn t combine split table when needed Patch by Xiang Zhang bpo 28128 Deprecation warning for invalid str and byte escape sequences now prints better information about where the error occurs Patch by Serhiy Storchaka and Eric Smith bpo 28509 dict update no longer allocate unnecessary large memory bpo 28426 Fixed potential crash in PyUnicode_AsDecodedObject in debug build bpo 28517 Fixed of by one error in the peephole optimizer that caused keeping unreachable code bpo 28214 Improved exception reporting for problematic __set_name__ attributes bpo 23782 Fixed possible memory leak in _PyTraceback_Add and exception loss in PyTraceBack_Here bpo 28183 Optimize and cleanup dict iteration bpo 26081 Added C implementation of asyncio Future Original patch by Yury Selivanov bpo 28379 Added sanity checks and tests for PyUnicode_CopyCharacters Patch by Xiang Zhang bpo 28376 The type of long range iterator is now registered as Iterator Patch by Oren Milman bpo 28376 Creating instances of range_iterator by calling range_iterator type now is disallowed Calling iter on range instance is the only way Patch by Oren Milman bpo 26906 Resolving special methods of uninitialized type now causes implicit initialization of the type instead of a fail bpo 18287 PyType_Ready now checks that tp_name is not NULL Original patch by Niklas Koep bpo 24098 Fixed possible crash when AST is changed in process of compiling it bpo 28201 Dict reduces possibility of 2nd conflict in hash table when hashes have same lower bits bpo 28350 String constants with null character no longer interned bpo 26617 Fix crash when GC runs during weakref callbacks bpo 27942 String constants now interned recursively in tuples and frozensets bpo 28289 ImportError __init__ now resets not specified attributes bpo 21578 Fixed misleading error message when ImportError called with invalid keyword args bpo 28203 Fix incorrect,en
1743, type in complex 1 0 2 3 error message Patch by Soumya Sharma bpo 28086 Single var positional argument of tuple subtype was passed unscathed to the C defined function Now it is converted to exact tuple bpo 28214 Now __set_name__ is looked up on the class instead of the instance bpo 27955 Fallback on reading dev urandom device when the getrandom syscall fails with EPERM for example when blocked by SECCOMP bpo 28192 Don t import readline in isolated mode bpo 27441 Remove some redundant assignments to ob_size in longobject c Thanks Oren Milman bpo 27222 Clean up redundant code in long_rshift function Thanks Oren Milman Upgrade internal unicode databases to Unicode version 9 0 0 bpo 28131 Fix a regression in zipimport s compile_source zipimport should use the same optimization level as the interpreter bpo 28126 Replace Py_MEMCPY with memcpy Visual Studio can properly optimize memcpy bpo 28120 Fix dict pop for splitted dictionary when trying to remove a pending key Not yet inserted in split table Patch by Xiang Zhang bpo 26182 Raise DeprecationWarning when async and await keywords are used as variable attribute class function name bpo 26182 Fix a refleak in code that raises DeprecationWarning bpo 28721 Fix asynchronous generators aclose and athrow to handle StopAsyncIteration propagation properly bpo 26110 Speed up method calls add LOAD_METHOD and CALL_METHOD opcodes Library bpo 31499 xml etree Fix a crash when a parser is part of a reference cycle bpo 31482 random seed now works with bytes in version 1 bpo 28556 typing get_type_hints now finds the right globalns for classes and modules by default when no globalns was specified by the caller bpo 28556 Speed improvements to the typing module Original PRs by Ivan Levkivskyi and Mitar bpo 31544 The C accelerator module of ElementTree ignored exceptions raised when looking up TreeBuilder target methods in XMLParser bpo 31234 socket create_connection now fixes manually a reference cycle clear the variable storing the last exception on success bpo 31457 LoggerAdapter objects can now be nested bpo 31431 SSLContext check_hostname now automatically sets SSLContext verify_mode to ssl CERT_REQUIRED instead of failing with a ValueError bpo 31233 socketserver ThreadingMixIn now keeps a list of non daemonic threads to wait until all these threads complete in server_close bpo 28638 Changed the implementation strategy for collections namedtuple to substantially reduce the use of exec in favor of precomputed methods As a result the verbose parameter and _source attribute are no longer supported The benefits include 1 having a smaller memory footprint for applications using multiple named tuples 2 faster creation of the named tuple class approx 4x to 6x depending on how it is measured and 3 minor speed ups for instance creation using __new__ _make and _replace The primary patch contributor is Jelle Zijlstra with further improvements by INADA Naoki Serhiy Storchaka and Raymond Hettinger bpo 31400 Improves SSL error handling to avoid losing error numbers bpo 27629 Make return types of SSLContext wrap_bio and SSLContext wrap_socket customizable bpo 28958 ssl SSLContext now uses OpenSSL error information when a context cannot be instantiated bpo 28182 The SSL module now raises SSLCertVerificationError when OpenSSL fails to verify the peer s certificate The exception contains more information about the error bpo 27340 SSLSocket sendall now uses memoryview to create slices of data This fixes support for all bytes like object It is also more efficient and avoids costly copies bpo 14191 A new function argparse ArgumentParser parse_intermixed_args provides the ability to parse command lines where there user intermixes options and positional arguments bpo 31178 Fix string concatenation bug in rare error path in the subprocess module bpo 31350 Micro optimize asyncio _get_running_loop to become up to 10 faster bpo 31170 expat Update libexpat from 2 2 3 to 2 2 4 Fix copying of partial characters for UTF 8 input libexpat bug 115 https github com libexpat libexpat issues 115 bpo 29136 Add TLS 1 3 cipher suit,en
1744,es and OP_NO_TLSv1_3 bpo 1198569 string Template subclasses can optionally define braceidpattern if they want to specify different placeholder patterns inside and outside the braces If None the default it falls back to idpattern bpo 31326 concurrent futures ProcessPoolExecutor shutdown now explicitly closes the call queue Moreover shutdown wait True now also join the call queue thread to prevent leaking a dangling thread bpo 27144 The map and as_completed iterators in concurrent futures now avoid keeping a reference to yielded objects bpo 31281 Fix fileinput FileInput files inplace True when files contain pathlib Path objects bpo 10746 Fix ctypes producing wrong PEP 3118 type codes for integer types bpo 27584 AF_VSOCK has been added to the socket interface which allows communication between virtual machines and their host bpo 22536 The subprocess module now sets the filename when FileNotFoundError is raised on POSIX systems due to the executable or cwd not being found bpo 29741 Update some methods in the _pyio module to also accept integer types Patch by Oren Milman bpo 31249 concurrent futures WorkItem run used by ThreadPoolExecutor now breaks a reference cycle between an exception object and the WorkItem object bpo 31247 xmlrpc server now explicitly breaks reference cycles when using sys exc_info in code handling exceptions bpo 23835 configparser reading defaults in the ConfigParser constructor is now using read_dict making its behavior consistent with the rest of the parser Non string keys and values in the defaults dictionary are now being implicitly converted to strings Patch by James Tocknell bpo 31238 pydoc the stop method of the private ServerThread class now waits until DocServer serve_until_quit completes and then explicitly sets its docserver attribute to None to break a reference cycle bpo 5001 Many asserts in multiprocessing are now more informative and some error types have been changed to more specific ones bpo 31109 Convert zipimport to use Argument Clinic bpo 30102 The ssl and hashlib modules now call OPENSSL_add_all_algorithms_noconf on OpenSSL 1 1 0 The function detects CPU features and enables optimizations on some CPU architectures such as POWER8 Patch is based on research from Gustavo Serra Scalet bpo 18966 Non daemonic threads created by a multiprocessing Process are now joined on child exit bpo 31183 dis now works with asynchronous generator and coroutine objects Patch by George Collins based on diagnosis by Luciano Ramalho bpo 5001 There are a number of uninformative asserts in the multiprocessing module as noted in issue 5001 This change fixes two of the most potentially problematic ones since they are in error reporting code in the multiprocessing managers convert_to_error function It also makes more informative a ValueError message The only potentially problematic change is that the AssertionError is now a TypeError however this should also help distinguish it from an AssertionError being reported by the function its caller such as in issue 31169 Patch by Allen W Smith drallensmith on github bpo 31185 Fixed miscellaneous errors in asyncio speedup module bpo 31151 socketserver ForkingMixIn server_close now waits until all child processes completed to prevent leaking zombie processes bpo 31072 Add an include_file parameter to zipapp create_archive bpo 24700 Optimize array array comparison It is now from 10x up to 70x faster when comparing arrays holding values of the same integer type bpo 31135 ttk fix the destroy method of LabeledScale and OptionMenu classes Call the parent destroy method even if the used attribute doesn t exist The LabeledScale destroy method now also explicitly clears label and scale attributes to help the garbage collector to destroy all widgets bpo 31107 Fix copyreg _slotnames mangled attribute calculation for classes whose name begins with an underscore Patch by Shane Harvey bpo 31080 Allow logging config fileConfig to accept kwargs and or args bpo 30897 pathlib Path objects now include an is_mount method only implemented on POSIX This is similar to os path ismount p Patch,en
1745, by Cooper Ry Lees bpo 31061 Fixed a crash when using asyncio and threads bpo 30987 Added support for CAN ISO TP protocol in the socket module bpo 30522 Added a setStream method to logging StreamHandler to allow the stream to be set after creation bpo 30502 Fix handling of long oids in ssl Based on patch by Christian Heimes bpo 5288 Support tzinfo objects with sub minute offsets bpo 30919 Fix shared memory performance regression in multiprocessing in 3 x Shared memory used anonymous memory mappings in 2 x while 3 x mmaps actual files Try to be careful to do as little disk I O as possible bpo 26732 Fix too many fds in processes started with the forkserver method A child process would inherit as many fds as the number of still running children bpo 29403 Fix unittest mock s autospec to not fail on method bound builtin functions Patch by Aaron Gallagher bpo 30961 Fix decrementing a borrowed reference in tracemalloc bpo 19896 Fix multiprocessing sharedctypes to recognize typecodes q and Q bpo 30946 Remove obsolete code in readline module for platforms where GNU readline is older than 2 1 or where select is not available bpo 25684 Change ttk OptionMenu radiobuttons to be unique across instances of OptionMenu bpo 30886 Fix multiprocessing Queue join_thread it now waits until the thread completes even if the thread was started by the same process which created the queue bpo 29854 Fix segfault in readline when using readline s history size option Patch by Nir Soffer bpo 30794 Added multiprocessing Process kill method to terminate using the SIGKILL signal on Unix bpo 30319 socket close now ignores ECONNRESET error bpo 30828 Fix out of bounds write in asyncio CFuture remove_done_callback bpo 30302 Use keywords in the repr of datetime timedelta bpo 30807 signal setitimer may disable the timer when passed a tiny value Tiny values such as 1e 6 are valid non zero values for setitimer which is specified as taking microsecond resolution intervals However on some platform our conversion routine could convert 1e 6 into a zero interval therefore disabling the timer instead of re scheduling it bpo 30441 Fix bug when modifying os environ while iterating over it bpo 29585 Avoid importing sysconfig from site to improve startup speed Python startup is about 5 faster on Linux and 30 faster on macOS bpo 29293 Add missing parameter n on multiprocessing Condition notify The doc claims multiprocessing Condition behaves like threading Condition but its notify method lacked the optional n argument to specify the number of sleepers to wake up that threading Condition notify accepts bpo 30532 Fix email header value parser dropping folding white space in certain cases bpo 30596 Add a close method to multiprocessing Process bpo 9146 Fix a segmentation fault in _hashopenssl when standard hash functions such as md5 are not available in the linked OpenSSL library As in some special FIPS 140 build environments bpo 29169 Update zlib to 1 2 11 bpo 30119 ftplib FTP putline now throws ValueError on commands that contains CR or LF Patch by Donghee Na bpo 30879 os listdir and os scandir now emit bytes names when called with bytes like argument bpo 30746 Prohibited the character in environment variable names in os putenv and os spawn bpo 30664 The description of a unittest subtest now preserves the order of keyword arguments of TestCase subTest bpo 21071 struct Struct format type is now str instead of bytes bpo 29212 Fix concurrent futures thread ThreadPoolExecutor threads to have a non repr based thread name by default when no thread_name_prefix is supplied They will now identify themselves as ThreadPoolExecutor y_n bpo 29755 Fixed the lgettext family of functions in the gettext module They now always return bytes bpo 30616 Functional API of enum allows to create empty enums Patched by Donghee Na bpo 30038 Fix race condition between signal delivery and wakeup file descriptor Patch by Nathaniel Smith bpo 23894 lib2to3 now recognizes rb and f strings bpo 24744 pkgutil walk_packages function now raises ValueError if path is a string Patch by Sanyam Khurana bpo 24484 Av,en
1746,oid race condition in multiprocessing cleanup bpo 30589 Fix multiprocessing Process exitcode to return the opposite of the signal number when the process is killed by a signal instead of 255 when using the forkserver method bpo 28994 The traceback no longer displayed for SystemExit raised in a callback registered by atexit bpo 30508 Don t log exceptions if Task Future cancel method was called bpo 30645 Fix path calculation in imp load_package fixing it for cases when a package is only shipped with bytecodes Patch by Alexandru Ardelean bpo 11822 The dis dis function now is able to disassemble nested code objects bpo 30624 selectors does not take KeyboardInterrupt and SystemExit into account leaving a fd in a bad state in case of error Patch by Giampaolo Rodola bpo 30595 multiprocessing Queue get with a timeout now polls its reader in non blocking mode if it succeeded to acquire the lock but the acquire took longer than the timeout bpo 28556 Updates to typing module Add generic AsyncContextManager add support for ContextManager on all versions Original PRs by Jelle Zijlstra and Ivan Levkivskyi bpo 30605 re compile no longer raises a BytesWarning when compiling a bytes instance with misplaced inline modifier Patch by Roy Williams bpo 29870 Fix ssl sockets leaks when connection is aborted in asyncio ssl implementation Patch by Michaël Sghaïer bpo 29743 Closing transport during handshake process leaks open socket Patch by Nikolay Kim bpo 27585 Fix waiter cancellation in asyncio Lock Patch by Mathieu Sornay bpo 30014 modify method of poll epoll and devpoll based classes of selectors module is around 10 faster Patch by Giampaolo Rodola bpo 30418 On Windows subprocess Popen communicate now also ignore EINVAL on stdin write if the child process is still running but closed the pipe bpo 30463 Addded empty __slots__ to abc ABC This allows subclassers to deny __dict__ and __weakref__ creation Patch by Aaron Hall bpo 30520 Loggers are now pickleable bpo 30557 faulthandler now correctly filters and displays exception codes on Windows bpo 30526 Add TextIOWrapper reconfigure and a TextIOWrapper write_through attribute bpo 30245 Fix possible overflow when organize struct pack_into error message Patch by Yuan Liu bpo 30378 Fix the problem that logging handlers SysLogHandler cannot handle IPv6 addresses bpo 16500 Allow registering at fork handlers bpo 30470 Deprecate invalid ctypes call protection on Windows Patch by Mariatta Wijaya bpo 30414 multiprocessing Queue _feed background running thread do not break from main loop on exception bpo 30003 Fix handling escape characters in HZ codec Based on patch by Ma Lin bpo 30149 inspect signature now supports callables with variable argument parameters wrapped with partialmethod Patch by Donghee Na bpo 30436 importlib find_spec raises ModuleNotFoundError instead of AttributeError if the specified parent module is not a package i e lacks a __path__ attribute bpo 30301 Fix AttributeError when using SimpleQueue empty under spawn and forkserver start methods bpo 30375 Warnings emitted when compile a regular expression now always point to the line in the user code Previously they could point into inners of the re module if emitted from inside of groups or conditionals bpo 30329 imaplib and poplib now catch the Windows socket WSAEINVAL error code 10022 on shutdown SHUT_RDWR An invalid operation was attempted This error occurs sometimes on SSL connections bpo 29196 Removed previously deprecated in Python 2 4 classes Plist Dict and _InternalDict in the plistlib module Dict values in the result of functions readPlist and readPlistFromBytes are now normal dicts You no longer can use attribute access to access items of these dictionaries bpo 9850 The macpath is now deprecated and will be removed in Python 3 8 bpo 30299 Compiling regular expression in debug mode on CPython now displays the compiled bytecode in human readable form bpo 30048 Fixed Task cancel can be ignored when the task is running coroutine and the coroutine returned without any more await bpo 30266 contextlib AbstractContextManager now suppor,en
1747,ts anti registration by setting __enter__ None or __exit__ None following the pattern introduced in bpo 25958 Patch by Jelle Zijlstra bpo 30340 Enhanced regular expressions optimization This increased the performance of matching some patterns up to 25 times bpo 30298 Weaken the condition of deprecation warnings for inline modifiers Now allowed several subsequential inline modifiers at the start of the pattern e g i s In verbose mode whitespaces and comments now are allowed before and between inline modifiers e g x i s bpo 30285 Optimized case insensitive matching and searching of regular expressions bpo 29990 Fix range checking in GB18030 decoder Original patch by Ma Lin bpo 29979 rewrite cgi parse_multipart reusing the FieldStorage class and making its results consistent with those of FieldStorage for multipart form data requests Patch by Pierre Quentel bpo 30243 Removed the __init__ methods of _json s scanner and encoder Misusing them could cause memory leaks or crashes Now scanner and encoder objects are completely initialized in the __new__ methods bpo 30215 Compiled regular expression objects with the re LOCALE flag no longer depend on the locale at compile time Only the locale at matching time affects the result of matching bpo 30185 Avoid KeyboardInterrupt tracebacks in forkserver helper process when Ctrl C is received bpo 30103 binascii b2a_uu and uu encode now support using as zero instead of space bpo 28556 Various updates to typing module add typing NoReturn type use WrapperDescriptorType minor bug fixes Original PRs by Jim Fasarakis Hilliard and Ivan Levkivskyi bpo 30205 Fix getsockname for unbound AF_UNIX sockets on Linux bpo 30228 The seek and tell methods of io FileIO now set the internal seekable attribute to avoid one syscall on open in buffered or text mode bpo 30190 unittest s assertAlmostEqual and assertNotAlmostEqual provide a better message in case of failure which includes the difference between left and right arguments patch by Giampaolo Rodola bpo 30101 Add support for curses A_ITALIC bpo 29822 inspect isabstract now works during __init_subclass__ Patch by Nate Soares bpo 29960 Preserve generator state when _random Random setstate raises an exception Patch by Bryan Olson bpo 30070 Fixed leaks and crashes in errors handling in the parser module bpo 22352 Column widths in the output of dis dis are now adjusted for large line numbers and instruction offsets bpo 30061 Fixed crashes in IOBase methods __next__ and readlines when readline or __next__ respectively return non sizeable object Fixed possible other errors caused by not checking results of PyObject_Size PySequence_Size or PyMapping_Size bpo 30218 Fix PathLike support for shutil unpack_archive Patch by Jelle Zijlstra bpo 10076 Compiled regular expression and match objects in the re module now support copy copy and copy deepcopy they are considered atomic bpo 30068 _io _IOBase readlines will check if it s closed first when hint is present bpo 29694 Fixed race condition in pathlib mkdir with flags parents True Patch by Armin Rigo bpo 29692 Fixed arbitrary unchaining of RuntimeError exceptions in contextlib contextmanager Patch by Siddharth Velankar bpo 26187 Test that sqlite3 trace callback is not called multiple times when schema is changing Indirectly fixed by switching to use sqlite3_prepare_v2 in bpo 9303 Patch by Aviv Palivoda bpo 30017 Allowed calling the close method of the zip entry writer object multiple times Writing to a closed writer now always produces a ValueError bpo 29998 Pickling and copying ImportError now preserves name and path attributes bpo 29995 re escape now escapes only regex special characters bpo 29962 Add math remainder operation implementing remainder as specified in IEEE 754 bpo 29649 Improve struct pack_into exception messages for problems with the buffer size and offset Patch by Andrew Nester bpo 29654 Support If Modified Since HTTP header browser cache Patch by Pierre Quentel bpo 29931 Fixed comparison check for ipaddress ip_interface objects Patch by Sanjay Sundaresan bpo 29953 Fixed memory leaks in the replace ,en
1748,method of datetime and time objects when pass out of bound fold argument bpo 29942 Fix a crash in itertools chain from_iterable when encountering long runs of empty iterables bpo 10030 Sped up reading encrypted ZIP files by 2 times bpo 29204 Element getiterator and the html parameter of XMLParser were deprecated only in the documentation since Python 3 2 and 3 4 correspondingly Now using them emits a deprecation warning bpo 27863 Fixed multiple crashes in ElementTree caused by race conditions and wrong types bpo 25996 Added support of file descriptors in os scandir on Unix os fwalk is sped up by 2 times by using os scandir bpo 28699 Fixed a bug in pools in multiprocessing pool that raising an exception at the very first of an iterable may swallow the exception or make the program hang Patch by Davin Potts and Xiang Zhang bpo 23890 unittest TestCase assertRaises now manually breaks a reference cycle to not keep objects alive longer than expected bpo 29901 The zipapp module now supports general path like objects not just pathlib Path bpo 25803 Avoid incorrect errors raised by Path mkdir exist_ok True when the OS gives priority to errors such as EACCES over EEXIST bpo 29861 Release references to tasks their arguments and their results as soon as they are finished in multiprocessing Pool bpo 19930 The mode argument of os makedirs no longer affects the file permission bits of newly created intermediate level directories bpo 29884 faulthandler Restore the old sigaltstack during teardown Patch by Christophe Zeitouny bpo 25455 Fixed crashes in repr of recursive buffered file like objects bpo 29800 Fix crashes in partial __repr__ if the keys of partial keywords are not strings Patch by Michael Seifert bpo 8256 Fixed possible failing or crashing input if attributes encoding or errors of sys stdin or sys stdout are not set or are not strings bpo 28692 Using non integer value for selecting a plural form in gettext is now deprecated bpo 26121 Use C library implementation for math functions erf and erfc bpo 29619 os stat and os DirEntry inode now convert inode st_ino using unsigned integers bpo 28298 Fix a bug that prevented array Q L and I from accepting big intables objects that have __int__ as elements bpo 29645 Speed up importing the webbrowser module webbrowser register is now thread safe bpo 28231 The zipfile module now accepts path like objects for external paths bpo 26915 index and count methods of collections abc Sequence now check identity before checking equality when do comparisons bpo 28682 Added support for bytes paths in os fwalk bpo 29728 Add new socket TCP_NOTSENT_LOWAT Linux 3 12 constant Patch by Nathaniel J Smith bpo 29623 Allow use of path like object as a single argument in ConfigParser read Patch by David Ellis bpo 9303 Migrate sqlite3 module to _v2 API Patch by Aviv Palivoda bpo 28963 Fix out of bound iteration in asyncio Future remove_done_callback implemented in C bpo 29704 asyncio subprocess SubprocessStreamProtocol no longer closes before all pipes are closed bpo 29271 Fix Task current_task and Task all_tasks implemented in C to accept None argument as their pure Python implementation bpo 29703 Fix asyncio to support instantiation of new event loops in child processes bpo 29615 SimpleXMLRPCDispatcher no longer chains KeyError or any other exception to exception s raised in the dispatched methods Patch by Petr Motejlek bpo 7769 Method register_function of xmlrpc server SimpleXMLRPCDispatcher and its subclasses can now be used as a decorator bpo 29376 Fix assertion error in threading _DummyThread is_alive bpo 28624 Add a test that checks that cwd parameter of Popen accepts PathLike objects Patch by Sayan Chowdhury bpo 28518 Start a transaction implicitly before a DML statement Patch by Aviv Palivoda bpo 29742 get_extra_info raises exception if get called on closed ssl transport Patch by Nikolay Kim bpo 16285 urllib parse quote is now based on RFC 3986 and hence includes in the set of characters that is not quoted by default Patch by Christian Theune and Ratnadeep Debnath bpo 29532 Altering a kwarg dictionary ,en
1749,passed to functools partial no longer affects a partial object after creation bpo 29110 Fix file object leak in aifc open when file is given as a filesystem path and is not in valid AIFF format Patch by Anthony Zhang bpo 22807 Add uuid SafeUUID and uuid UUID is_safe to relay information from the platform about whether generated UUIDs are generated with a multiprocessing safe method bpo 29576 Improve some deprecations in importlib Some deprecated methods now emit DeprecationWarnings and have better descriptive messages bpo 29534 Fixed different behaviour of Decimal from_float for _decimal and _pydecimal Thanks Andrew Nester bpo 10379 locale format_string now supports the monetary keyword argument and locale format is deprecated bpo 29851 importlib reload now raises ModuleNotFoundError if the module lacks a spec bpo 28556 Various updates to typing module typing Counter typing ChainMap improved ABC caching etc Original PRs by Jelle Zijlstra Ivan Levkivskyi Manuel Krebber and Łukasz Langa bpo 29100 Fix datetime fromtimestamp regression introduced in Python 3 6 0 check minimum and maximum years bpo 29416 Prevent infinite loop in pathlib Path mkdir bpo 29444 Fixed out of bounds buffer access in the group method of the match object Based on patch by WGH bpo 29377 Add WrapperDescriptorType MethodWrapperType and MethodDescriptorType built in types to types module Original patch by Manuel Krebber bpo 29218 Unused install_misc command is now removed It has been documented as unused since 2000 Patch by Eric N Vander Weele bpo 29368 The extend method is now called instead of the append method when unpickle collections deque and other list like objects This can speed up unpickling to 2 times bpo 29338 The help of a builtin or extension class now includes the constructor signature if __text_signature__ is provided for the class bpo 29335 Fix subprocess Popen wait when the child process has exited to a stopped instead of terminated state ex when under ptrace bpo 29290 Fix a regression in argparse that help messages would wrap at non breaking spaces bpo 28735 Fixed the comparison of mock MagickMock with mock ANY bpo 29197 Removed deprecated function ntpath splitunc bpo 29210 Removed support of deprecated argument exclude in tarfile TarFile add bpo 29219 Fixed infinite recursion in the repr of uninitialized ctypes CDLL instances bpo 29192 Removed deprecated features in the http cookies module bpo 29193 A format string argument for string Formatter format is now positional only bpo 29195 Removed support of deprecated undocumented keyword arguments in methods of regular expression objects bpo 28969 Fixed race condition in C implementation of functools lru_cache KeyError could be raised when cached function with full cache was simultaneously called from different threads with the same uncached arguments bpo 20804 The unittest mock sentinel attributes now preserve their identity when they are copied or pickled bpo 29142 In urllib request suffixes in no_proxy environment variable with leading dots could match related hostnames again e g b c matches a b c Patch by Milan Oberkirch bpo 28961 Fix unittest mock _Call helper don t ignore the name parameter anymore Patch written by Jiajun Huang bpo 15812 inspect getframeinfo now correctly shows the first line of a context Patch by Sam Breese bpo 28985 Update authorizer constants in sqlite3 module Patch by Dingyuan Wang bpo 29079 Prevent infinite loop in pathlib resolve on Windows bpo 13051 Fixed recursion errors in large or resized curses textpad Textbox Based on patch by Tycho Andersen bpo 9770 curses ascii predicates now work correctly with negative integers bpo 28427 old keys should not remove new values from WeakValueDictionary when collecting from another thread bpo 28923 Remove editor artifacts from Tix py bpo 28871 Fixed a crash when deallocate deep ElementTree bpo 19542 Fix bugs in WeakValueDictionary setdefault and WeakValueDictionary pop when a GC collection happens in another thread bpo 20191 Fixed a crash in resource prlimit when passing a sequence that doesn t own its elements as limits ,en
1750,bpo 16255 subprocess Popen uses system bin sh on Android as the shell instead of bin sh bpo 28779 multiprocessing set_forkserver_preload would crash the forkserver process if a preloaded module instantiated some multiprocessing objects such as locks bpo 26937 The chown method of the tarfile TarFile class does not fail now when the grp module cannot be imported as for example on Android platforms bpo 28847 dbm dumb now supports reading read only files and no longer writes the index file when it is not changed A deprecation warning is now emitted if the index file is missed and recreated in the r and w modes will be an error in future Python releases bpo 27030 Unknown escapes consisting of and an ASCII letter in re sub replacement templates regular expressions now are errors bpo 28835 Fix a regression introduced in warnings catch_warnings call warnings showwarning if it was overridden inside the context manager bpo 27172 To assist with upgrades from 2 7 the previously documented deprecation of inspect getfullargspec has been reversed This decision may be revisited again after the Python 2 7 branch is no longer officially supported bpo 28740 Add sys getandroidapilevel return the build time API version of Android as an integer Function only available on Android bpo 26273 Add new socket TCP_CONGESTION Linux 2 6 13 and socket TCP_USER_TIMEOUT Linux 2 6 37 constants Patch written by Omar Sandoval bpo 28752 Restored the __reduce__ methods of datetime objects bpo 28727 Regular expression patterns _sre SRE_Pattern objects created by re compile become comparable only x y and x y operators This change should fix the bpo 18383 don t duplicate warning filters when the warnings module is reloaded thing usually only done in unit tests bpo 20572 Remove the subprocess Popen wait endtime parameter It was deprecated in 3 4 and undocumented prior to that bpo 25659 In ctypes prevent a crash calling the from_buffer and from_buffer_copy methods on abstract classes like Array bpo 28548 In the http server module parse the protocol version if possible to avoid using HTTP 0 9 in some error responses bpo 19717 Makes Path resolve succeed on paths that do not exist Patch by Vajrasky Kok bpo 28563 Fixed possible DoS and arbitrary code execution when handle plural form selections in the gettext module The expression parser now supports exact syntax supported by GNU gettext bpo 28387 Fixed possible crash in _io TextIOWrapper deallocator when the garbage collector is invoked in other thread Based on patch by Sebastian Cufre bpo 27517 LZMA compressor and decompressor no longer raise exceptions if given empty data twice Patch by Benjamin Fogle bpo 28549 Fixed segfault in curses s addch with ncurses6 bpo 28449 tarfile open with mode r or r now tries to open a tar file with compression before trying to open it without compression Otherwise it had 50 chance failed with ignore_zeros True bpo 23262 The webbrowser module now supports Firefox 36 and derived browsers Based on patch by Oleg Broytman bpo 24241 The webbrowser in an X environment now prefers using the default browser directly Also the webbrowser register function now has a documented preferred argument to specify browsers to be returned by get with no arguments Patch by David Steele bpo 27939 Fixed bugs in tkinter ttk LabeledScale and tkinter Scale caused by representing the scale as float value internally in Tk tkinter IntVar now works if float value is set to underlying Tk variable bpo 28255 calendar TextCalendar prweek no longer prints a space after a weeks s calendar calendar TextCalendar pryear no longer prints redundant newline after a year s calendar Based on patch by Xiang Zhang bpo 28255 calendar TextCalendar prmonth no longer prints a space at the start of new line after printing a month s calendar Patch by Xiang Zhang bpo 20491 The textwrap TextWrapper class now honors non breaking spaces Based on patch by Kaarle Ritvanen bpo 28353 os fwalk no longer fails on broken links bpo 28430 Fix iterator of C implemented asyncio Future doesn t accept non None value is passed to it send val bpo 27025 G,en
1751,enerated names for Tkinter widgets now start by the prefix for readability bpo 25464 Fixed HList header_exists in tkinter tix module by addin a workaround to Tix library bug bpo 28488 shutil make_archive no longer adds entry to ZIP archive bpo 25953 re sub now raises an error for invalid numerical group reference in replacement template even if the pattern is not found in the string Error message for invalid group reference now includes the group index and the position of the reference Based on patch by SilentGhost bpo 28469 timeit now uses the sequence 1 2 5 10 20 50 instead of 1 10 100 for autoranging bpo 28115 Command line interface of the zipfile module now uses argparse Added support of long options bpo 18219 Optimize csv DictWriter for large number of columns Patch by Mariatta Wijaya bpo 28448 Fix C implemented asyncio Future didn t work on Windows bpo 23214 In the io module the argument to BufferedReader and BytesIO s read1 methods is now optional and can be 1 matching the BufferedIOBase specification bpo 28480 Fix error building socket module when multithreading is disabled bpo 28240 timeit remove c clock and t time command line options which were deprecated since Python 3 3 bpo 28240 timeit now repeats the benchmarks 5 times instead of only 3 to make benchmarks more reliable bpo 28240 timeit autorange now uses a single loop iteration if the benchmark takes less than 10 seconds instead of 10 iterations python3 m timeit s import time time sleep 1 now takes 4 seconds instead of 40 seconds Distutils sdist now looks for README and setup py files with case sensitivity This behavior matches that found in Setuptools 6 0 and later See setuptools 100 for rationale bpo 24452 Make webbrowser support Chrome on Mac OS X Patch by Ned Batchelder bpo 20766 Fix references leaked by pdb in the handling of SIGINT handlers bpo 27998 Fixed bytes path support in os scandir on Windows Patch by Eryk Sun bpo 28317 The disassembler now decodes FORMAT_VALUE argument bpo 28380 unittest mock Mock autospec functions now properly support assert_called assert_not_called and assert_called_once bpo 28229 lzma module now supports pathlib bpo 28321 Fixed writing non BMP characters with binary format in plistlib bpo 28225 bz2 module now supports pathlib Initial patch by Ethan Furman bpo 28227 gzip now supports pathlib Patch by Ethan Furman bpo 28332 Deprecated silent truncations in socket htons and socket ntohs Original patch by Oren Milman bpo 27358 Optimized merging var keyword arguments and improved error message when passing a non mapping as a var keyword argument bpo 28257 Improved error message when passing a non iterable as a var positional argument Added opcode BUILD_TUPLE_UNPACK_WITH_CALL bpo 28322 Fixed possible crashes when unpickle itertools objects from incorrect pickle data Based on patch by John Leitch bpo 28228 imghdr now supports pathlib bpo 28226 compileall now supports pathlib bpo 28314 Fix function declaration C flags for the getiterator method of xml etree ElementTree Element bpo 28148 Stop using localtime and gmtime in the time module Introduced platform independent _PyTime_localtime API that is similar to POSIX localtime_r but available on all platforms Patch by Ed Schouten bpo 28253 Fixed calendar functions for extreme months 0001 01 and 9999 12 Methods itermonthdays and itermonthdays2 are reimplemented so that they don t call itermonthdates which can cause datetime date under overflow bpo 28275 Fixed possible use after free in the decompress methods of the LZMADecompressor and BZ2Decompressor classes Original patch by John Leitch bpo 27897 Fixed possible crash in sqlite3 Connection create_collation if pass invalid string like object as a name Patch by Xiang Zhang bpo 18844 random choices now has k as a keyword only argument to improve the readability of common cases and come into line with the signature used in other languages bpo 18893 Fix invalid exception handling in Lib ctypes macholib dyld py Patch by Madison May bpo 27611 Fixed support of default root window in the tkinter tix module Added the master parameter in the D,en
1752,isplayStyle constructor bpo 27348 In the traceback module restore the formatting of exception messages like Exception None This fixes a regression introduced in 3 5a2 bpo 25651 Allow false values to be used for msg parameter of subTest bpo 27778 Fix a memory leak in os getrandom when the getrandom is interrupted by a signal and a signal handler raises a Python exception bpo 28200 Fix memory leak on Windows in the os module fix path_converter function bpo 25400 RobotFileParser now correctly returns default values for crawl_delay and request_rate Initial patch by Peter Wirtz bpo 27932 Prevent memory leak in win32_ver Fix UnboundLocalError in socket _sendfile_use_sendfile bpo 28075 Check for ERROR_ACCESS_DENIED in Windows implementation of os stat Patch by Eryk Sun bpo 22493 Warning message emitted by using inline flags in the middle of regular expression now contains a truncated regex pattern Patch by Tim Graham bpo 25270 Prevent codecs escape_encode from raising SystemError when an empty bytestring is passed bpo 28181 Get antigravity over HTTPS Patch by Kaartic Sivaraam bpo 25895 Enable WebSocket URL schemes in urllib parse urljoin Patch by Gergely Imreh and Markus Holtermann bpo 28114 Fix a crash in parse_envlist when env contains byte strings Patch by Eryk Sun bpo 27599 Fixed buffer overrun in binascii b2a_qp and binascii a2b_qp bpo 27906 Fix socket accept exhaustion during high TCP traffic Patch by Kevin Conway bpo 28174 Handle when SO_REUSEPORT isn t properly supported Patch by Seth Michael Larson bpo 26654 Inspect functools partial in asyncio Handle __repr__ Patch by iceboy bpo 26909 Fix slow pipes IO in asyncio Patch by INADA Naoki bpo 28176 Fix callbacks race in asyncio SelectorLoop sock_connect bpo 27759 Fix selectors incorrectly retain invalid file descriptors Patch by Mark Williams bpo 28325 Remove vestigial MacOS 9 macurl2path module and its tests bpo 28368 Refuse monitoring processes if the child watcher has no loop attached Patch by Vincent Michel bpo 28369 Raise RuntimeError when transport s FD is used with add_reader add_writer etc bpo 28370 Speedup asyncio StreamReader readexactly Patch by Коренберг Марк bpo 28371 Deprecate passing asyncio Handles to run_in_executor bpo 28372 Fix asyncio to support formatting of non python coroutines bpo 28399 Remove UNIX socket from FS before binding Patch by Коренберг Марк bpo 27972 Prohibit Tasks to await on themselves bpo 24142 Reading a corrupt config file left configparser in an invalid state Original patch by Florian Höch bpo 29581 ABCMeta __new__ now accepts kwargs allowing abstract base classes to use keyword parameters in __init_subclass__ Patch by Nate Soares bpo 25532 inspect unwrap will now only try to unwrap an object sys getrecursionlimit times to protect against objects which create a new object on every attribute access bpo 30177 path resolve strict False no longer cuts the path after the first element not present in the filesystem Patch by Antoine Pietri Documentation bpo 31294 Fix incomplete code snippet in the ZeroMQSocketListener and ZeroMQSocketHandler examples and adapt them to Python 3 bpo 21649 Add RFC 7525 and Mozilla server side TLS links to SSL documentation bpo 31128 Allow the pydoc server to bind to arbitrary hostnames bpo 30803 Clarify doc on truth value testing Original patch by Peter Thomassen bpo 30176 Add missing attribute related constants in curses documentation bpo 30052 the link targets for bytes and bytearray are now their respective type definitions rather than the corresponding builtin function entries Use bytes and bytearray to reference the latter In order to ensure this and future cross reference updates are applied automatically the daily documentation builds now disable the default output caching features in Sphinx bpo 26985 Add missing info of code object in inspect documentation bpo 19824 Improve the documentation for and links to template strings by emphasizing their utility for internationalization and by clarifying some usage constraints See also bpo 20314 bpo 12518 bpo 28929 Link the documentation to its source file on G,en
1753,itHub bpo 25008 Document smtpd py as effectively deprecated and add a pointer to aiosmtpd a third party asyncio based replacement bpo 26355 Add canonical header link on each page to corresponding major version of the documentation Patch by Matthias Bussonnier bpo 29349 Fix Python 2 syntax in code for building the documentation bpo 23722 The data model reference and the porting section in the 3 6 What s New guide now cover the additional __classcell__ handling needed for custom metaclasses to fully support PEP 487 and zero argument super bpo 28513 Documented command line interface of zipfile Tests bpo 29639 test support HOST is now localhost a new HOSTv4 constant has been added for your 127 0 0 1 needs similar to the existing HOSTv6 constant bpo 31320 Silence traceback in test_ssl bpo 31346 Prefer PROTOCOL_TLS_CLIENT and PROTOCOL_TLS_SERVER protocols for SSLContext bpo 25674 Remove sha256 tbs internet com ssl test bpo 30715 Address ALPN callback changes for OpenSSL 1 1 0f The latest version behaves like OpenSSL 1 0 2 and no longer aborts handshake bpo 30822 regrtest Exclude tzdata from regrtest all When running the test suite using use all u all exclude tzdata since it makes test_datetime too slow 15 20 min on some buildbots which then times out on some buildbots Fix also regrtest command line parser to allow passing u extralargefile to run test_zipfile64 bpo 30695 Add the set_nomemory start stop and remove_mem_hooks functions to the _testcapi module bpo 30357 test_thread setUp now uses support threading_setup and support threading_cleanup to wait until threads complete to avoid random side effects on following tests Initial patch written by Grzegorz Grzywacz bpo 30197 Enhanced functions swap_attr and swap_item in the test support module They now work when delete replaced attribute or item inside the with statement The old value of the attribute or item or None if it doesn t exist now will be assigned to the target of the as clause if there is one bpo 24932 Use proper command line parsing in _testembed bpo 28950 Disallow j0 to be combined with T l in regrtest command line arguments bpo 28683 Fix the tests that bind a unix socket and raise PermissionError on Android for a non root user bpo 26936 Fix the test_socket failures on Android getservbyname getservbyport and getaddrinfo are broken on some Android API levels bpo 28666 Now test support rmtree is able to remove unwritable or unreadable directories bpo 23839 Various caches now are cleared before running every test file bpo 26944 Fix test_posix for Android where id G is entirely wrong or missing the effective gid bpo 28409 regrtest fix the parser of command line arguments bpo 28217 Adds _testconsole module to test console input bpo 26939 Add the support setswitchinterval function to fix test_functools hanging on the Android armv7 qemu emulator Build bpo 31354 Allow with lto to be used on all builds not just make profile opt bpo 31370 Remove support for building without threads This option is not really useful anymore in the 21st century Removing lots of conditional paths allows us to simplify the code base including in difficult to maintain low level internal code bpo 31341 Per PEP 11 support for the IRIX operating system was removed bpo 30854 Fix compile error when compiling without threads Patch by Masayuki Yamamoto bpo 30687 Locate msbuild exe on Windows when building rather than vcvarsall bat bpo 20210 Support the disabled marker in Setup files Extension modules listed after this marker are not built at all neither by the Makefile nor by setup py bpo 29941 Add with assertions configure flag to explicitly enable C assert checks Defaults to off with pydebug implies with assertions bpo 28787 Fix out of tree builds of Python when configured with with dtrace bpo 29243 Prevent unnecessary rebuilding of Python during make test make install and some other make targets when configured with enable optimizations bpo 23404 Don t regenerate generated files based on file modification time anymore the action is now explicit Replace make touch with make regen all bpo 29643 Fix enab,en
1754,le optimization didn t work bpo 27593 sys version and the platform module python_build python_branch and python_revision functions now use git information rather than hg when building from a repo bpo 29572 Update Windows build and OS X installers to use OpenSSL 1 0 2k bpo 27659 Prohibit implicit C function declarations use Werror implicit function declaration when possible GCC and Clang but it depends on the compiler version Patch written by Chi Hsuan Yen bpo 29384 Remove old Be OS helper scripts bpo 26851 Set Android compilation and link flags bpo 28768 Fix implicit declaration of function _setmode Patch by Masayuki Yamamoto bpo 29080 Removes hard dependency on hg exe from PCBuild build bat bpo 23903 Added missed names to PC python3 def bpo 28762 lockf is available on Android API level 24 but the F_LOCK macro is not defined in android ndk r13 bpo 28538 Fix the compilation error that occurs because if_nameindex is available on Android API level 24 but the if_nameindex structure is not defined bpo 20211 Do not add the directory for installing C header files and the directory for installing object code libraries to the cross compilation search paths Original patch by Thomas Petazzoni bpo 28849 Do not define sys implementation _multiarch on Android bpo 10656 Fix out of tree building on AIX Patch by Tristan Carel and Michael Haubenwallner bpo 26359 Rename with optimiations to enable optimizations bpo 28444 Fix missing extensions modules when cross compiling bpo 28208 Update Windows build and OS X installers to use SQLite 3 14 2 bpo 28248 Update Windows build and OS X installers to use OpenSSL 1 0 2j bpo 21124 Fix building the _struct module on Cygwin by passing NULL instead of PyType_Type to PyVarObject_HEAD_INIT Patch by Masayuki Yamamoto bpo 13756 Fix building extensions modules on Cygwin Patch by Roumen Petrov based on original patch by Jason Tishler bpo 21085 Add configure check for siginfo_t si_band which Cygwin does not provide Patch by Masayuki Yamamoto with review and rebase by Erik Bray bpo 28258 Fixed build with Estonian locale python config and distclean targets in Makefile Patch by Arfrever Frehtes Taifersar Arahesis bpo 26661 setup py now detects system libffi with multiarch wrapper bpo 27979 A full copy of libffi is no longer bundled for use when building _ctypes on non OSX UNIX platforms An installed copy of libffi is now required when building _ctypes on such platforms bpo 15819 Remove redundant include search directory option for building outside the source tree bpo 28676 Prevent missing getentropy declaration warning on macOS Patch by Gareth Rees Windows bpo 31392 Update Windows build to use OpenSSL 1 1 0f bpo 30389 Adds detection of Visual Studio 2017 to distutils on Windows bpo 31358 zlib is no longer bundled in the CPython source instead it is downloaded on demand just like bz2 lzma OpenSSL Tcl Tk and SQLite bpo 31340 Change to building with MSVC v141 included with Visual Studio 2017 bpo 30581 os cpu_count now returns the correct number of processors on Windows when the number of logical processors is greater than 64 bpo 30916 Pre build OpenSSL Tcl and Tk and include the binaries in the build bpo 30731 Add a missing xmlns to python manifest so that it matches the schema bpo 30291 Allow requiring 64 bit interpreters from py exe using 64 suffix Contributed by Steve Gadget Barnes bpo 30362 Adds list options 0 0p to py exe launcher Contributed by Steve Barnes bpo 23451 Fix socket deprecation warnings in socketmodule c Patch by Segev Finer bpo 30450 The build process on Windows no longer depends on Subversion instead pulling external code from GitHub via a Python script If Python 3 6 is not found on the system via py 3 6 NuGet is used to download a copy of 32 bit Python bpo 29579 Removes readme txt from the installer bpo 25778 winreg does not truncate string correctly Patch by Eryk Sun bpo 28896 Deprecate WindowsRegistryFinder and disable it by default bpo 28522 Fixes mishandled buffer reallocation in getpathp c bpo 28402 Adds signed catalog files for stdlib on Windows bpo 28333 Enables Unicode for ps1 ps2 an,en
1755,d input prompts Patch by Eryk Sun bpo 28251 Improvements to help manuals on Windows bpo 28110 launcher msi has different product codes between 32 bit and 64 bit bpo 28161 Opening CON for write access fails bpo 28162 WindowsConsoleIO readall fails if first line starts with Ctrl Z bpo 28163 WindowsConsoleIO fileno passes wrong flags to _open_osfhandle bpo 28164 _PyIO_get_console_type fails for various paths bpo 28137 Renames Windows path file to _pth bpo 28138 Windows _pth file should allow import site IDLE bpo 31493 IDLE code context fix code update and font update timers Canceling timers prevents a warning message when test_idle completes bpo 31488 IDLE Update non key options in former extension classes When applying configdialog changes call reload for each feature class Change ParenMatch so updated options affect existing instances attached to existing editor windows bpo 31477 IDLE Improve rstrip entry in doc Strip trailing whitespace strips more than blank spaces Multiline string literals are not skipped bpo 31480 IDLE make tests pass with zzdummy extension disabled by default bpo 31421 Document how IDLE runs tkinter programs IDLE calls tcl tk update in the background in order to make live interaction and experimentation with tkinter applications much easier bpo 31414 IDLE fix tk entry box tests by deleting first Adding to an int entry is not the same as deleting and inserting because int will fail bpo 31051 Rearrange IDLE configdialog GenPage into Window Editor and Help sections bpo 30617 IDLE Add docstrings and tests for outwin subclass of editor Move some data and functions from the class to module level Patch by Cheryl Sabella bpo 31287 IDLE Do not modify tkinter message in test_configdialog bpo 27099 Convert IDLE s built in extensions to regular features About 10 IDLE features were implemented as supposedly optional extensions Their different behavior could be confusing or worse for users and not good for maintenance Hence the conversion The main difference for users is that user configurable key bindings for builtin features are now handled uniformly Now editing a binding in a keyset only affects its value in the keyset All bindings are defined together in the system specific default keysets in config extensions def All custom keysets are saved as a whole in config extension cfg All take effect as soon as one clicks Apply or Ok The affected events are force open completions expand word force open calltip flash paren format paragraph run module check module and zoom height Any global customizations made before 3 6 3 will not affect their keyset specific customization after 3 6 3 and vice versa Initial patch by Charles Wohlganger bpo 31206 IDLE Factor HighPage Frame class from ConfigDialog Patch by Cheryl Sabella bpo 31001 Add tests for configdialog highlight tab Patch by Cheryl Sabella bpo 31205 IDLE Factor KeysPage Frame class from ConfigDialog The slightly modified tests continue to pass Patch by Cheryl Sabella bpo 31130 IDLE stop leaks in test_configdialog Initial patch by Victor Stinner bpo 31002 Add tests for configdialog keys tab Patch by Cheryl Sabella bpo 19903 IDLE Calltips use inspect signature instead of inspect getfullargspec This improves calltips for builtins converted to use Argument Clinic Patch by Louie Lu bpo 31083 IDLE Add an outline of a TabPage class in configdialog Update existing classes to match outline Initial patch by Cheryl Sabella bpo 31050 Factor GenPage Frame class from ConfigDialog The slightly modified tests continue to pass Patch by Cheryl Sabella bpo 31004 IDLE Factor FontPage Frame class from ConfigDialog Slightly modified tests continue to pass Fix General tests Patch mostly by Cheryl Sabella bpo 30781 IDLE Use ttk widgets in ConfigDialog Patches by Terry Jan Reedy and Cheryl Sabella bpo 31060 IDLE Finish rearranging methods of ConfigDialog Grouping methods pertaining to each tab and the buttons will aid writing tests and improving the tabs and will enable splitting the groups into classes bpo 30853 IDLE Factor a VarTrace class out of ConfigDialog Instance tracers manages pairs,en
1756, consisting of a tk variable and a callback function When tracing is turned on setting the variable calls the function Test coverage for the new class is 100 bpo 31003 IDLE Add more tests for General tab bpo 30993 IDLE Improve configdialog font page and tests In configdialog Document causal pathways in create_font_tab docstring Simplify some attribute names Move set_samples calls to var_changed_font idea from Cheryl Sabella Move related functions to positions after the create widgets function In test_configdialog Fix test_font_set so not order dependent Fix renamed test_indent_scale so it tests the widget Adjust tests for movement of set_samples call Add tests for load functions Put all font tests in one class and tab indent tests in another Except for two lines these tests completely cover the related functions bpo 30981 IDLE Add more configdialog font page tests bpo 28523 IDLE replace colour with color in configdialog bpo 30917 Add tests for idlelib config IdleConf Increase coverage from 46 to 96 Patch by Louie Lu bpo 30934 Document coverage details for idlelib tests Add section to idlelib idle test README txt Include check that branches are taken both ways Exclude IDLE specific code that does not run during unit tests bpo 30913 IDLE Document ConfigDialog tk Vars methods and widgets in docstrings This will facilitate improving the dialog and splitting up the class Original patch by Cheryl Sabella bpo 30899 IDLE Add tests for ConfigParser subclasses in config Patch by Louie Lu bpo 30881 IDLE Add docstrings to browser py Patch by Cheryl Sabella bpo 30851 IDLE Remove unused variables in configdialog One is a duplicate one is set but cannot be altered by users Patch by Cheryl Sabella bpo 30870 IDLE In Settings dialog select font with Up Down keys as well as mouse Initial patch by Louie Lu bpo 8231 IDLE call config IdleConf GetUserCfgDir only once bpo 30779 IDLE Factor ConfigChanges class from configdialog put in config test In config put dump test code in a function run it and unittest in if __name__ __main__ Add class config ConfigChanges based on changes_class_v4 py on bpo issue Add class test_config ChangesTest partly using configdialog_tests_v1 py Revise configdialog to use ConfigChanges see tracker msg297804 Revise test_configdialog to match configdialog changes Remove configdialog functions unused or moved to ConfigChanges Cheryl Sabella contributed parts of the patch bpo 30777 IDLE configdialog Add docstrings and fix comments Patch by Cheryl Sabella bpo 30495 IDLE Improve textview with docstrings PEP8 names and more tests Patch by Cheryl Sabella bpo 30723 IDLE Make several improvements to parenmatch Add parens style to highlight both opener and closer Make default style which is not default a synonym for opener Make time delay work the same with all styles Add help for config dialog extensions tab including help for parenmatch Add new tests Original patch by Charles Wohlganger bpo 30674 IDLE add docstrings to grep module Patch by Cheryl Sabella bpo 21519 IDLE s basic custom key entry dialog now detects duplicates properly Original patch by Saimadhav Heblikar bpo 29910 IDLE no longer deletes a character after commenting out a region by a key shortcut Add return break for this and other potential conflicts between IDLE and default key bindings bpo 30728 Review and change idlelib configdialog names Lowercase method and attribute names Replace colour with color expand overly cryptic names delete unneeded underscores Replace import with specific imports Patches by Cheryl Sabella bpo 6739 IDLE Verify user entered key sequences by trying to bind them with tk Add tests for all 3 validation functions Original patch by G Polo Tests added by Cheryl Sabella bpo 15786 Fix several problems with IDLE s autocompletion box The following should now work clicking on selection box items using the scrollbar selecting an item by hitting Return Hangs on MacOSX should no longer happen Patch by Louie Lu bpo 25514 Add doc subsubsection about IDLE failure to start Popup no connection message directs users to this section bpo 30642 Fix referen,en
1757,ce leaks in IDLE tests Patches by Louie Lu and Terry Jan Reedy bpo 30495 Add docstrings for textview py and use PEP8 names Patches by Cheryl Sabella and Terry Jan Reedy bpo 30290 Help about use pep8 names and add tests Increase coverage to 100 Patches by Louie Lu Cheryl Sabella and Terry Jan Reedy bpo 30303 Add _utest option to textview add new tests Increase coverage to 100 Patches by Louie Lu and Terry Jan Reedy bpo 29071 IDLE colors f string prefixes but not invalid ur prefixes bpo 28572 Add 10 to coverage of IDLE s test_configdialog Update and augment description of the configuration system Tools Demos bpo 30983 gdb integration commands py bt etc work on optimized shared builds now too PEP 523 introduced _PyEval_EvalFrameDefault which inlines PyEval_EvalFrameEx on non debug shared builds This broke the ability to use py bt py up and a few other Python specific gdb integrations The problem is fixed by only looking for _PyEval_EvalFrameDefault frames in python gdb py Original patch by Bruno Polaco Penteado bpo 29748 Added the slice index converter in Argument Clinic bpo 24037 Argument Clinic now uses the converter bool accept int rather than int for semantical booleans This avoids repeating the default value for Python and C and will help in converting to bool in future bpo 29367 python gdb py now supports also method wrapper wrapperobject objects bpo 28023 Fix python gdb py didn t support new dict implementation bpo 15369 The pybench and pystone microbenchmark have been removed from Tools Please use the new Python benchmark suite https github com python pyperformance which is more reliable and includes a portable version of pybench working on Python 2 and Python 3 bpo 28102 The zipfile module CLI now prints usage to stderr Patch by Stephen J Turnbull C API bpo 31338 Added the Py_UNREACHABLE macro for code paths which are never expected to be reached This and a few other useful macros are now documented in the C API manual bpo 30832 Remove own implementation for thread local storage CPython has provided the own implementation for thread local storage TLS on Python thread c it s used in the case which a platform has not supplied native TLS However currently all supported platforms Windows and pthreads have provided native TLS and defined the Py_HAVE_NATIVE_TLS macro with unconditional in any case bpo 30708 PyUnicode_AsWideCharString now raises a ValueError if the second argument is NULL and the wchar_t string contains null characters bpo 16500 Deprecate PyOS_AfterFork and add PyOS_BeforeFork PyOS_AfterFork_Parent and PyOS_AfterFork_Child bpo 6532 The type of results of PyThread_start_new_thread and PyThread_get_thread_ident and the id parameter of PyThreadState_SetAsyncExc changed from long to unsigned long bpo 27867 Function PySlice_GetIndicesEx is deprecated and replaced with a macro if Py_LIMITED_API is not set or set to the value between 0x03050400 and 0x03060000 not including or 0x03060100 or higher Added functions PySlice_Unpack and PySlice_AdjustIndices bpo 29083 Fixed the declaration of some public API functions PyArg_VaParse and PyArg_VaParseTupleAndKeywords were not available in limited API PyArg_ValidateKeywordArguments PyArg_UnpackTuple and Py_BuildValue were not available in limited API of version 3 3 when PY_SSIZE_T_CLEAN is defined bpo 28769 The result of PyUnicode_AsUTF8AndSize and PyUnicode_AsUTF8 is now of type const char rather of char bpo 29058 All stable API extensions added after Python 3 2 are now available only when Py_LIMITED_API is set to the PY_VERSION_HEX value of the minimum Python version supporting this API bpo 28822 The index parameters start and end of PyUnicode_FindChar are now adjusted to behave like str start end bpo 28808 PyUnicode_CompareWithASCIIString now never raises exceptions bpo 28761 The fields name and doc of structures PyMemberDef PyGetSetDef PyStructSequence_Field PyStructSequence_Desc and wrapperbase are now of type const char rather of char bpo 28748 Private variable _Py_PackageContext is now of type const char rather of char bpo 19569 Compiler warnings are now emitted i,en
1758,f use most of deprecated functions bpo 28426 Deprecated undocumented functions PyUnicode_AsEncodedObject PyUnicode_AsDecodedObject PyUnicode_AsDecodedUnicode and PyUnicode_AsEncodedUnicode Python 3 6 6 final Release date 2018 06 27 There were no new changes in version 3 6 6 Python 3 6 6 release candidate 1 Release date 2018 06 11 Core and Builtins bpo 33786 Fix asynchronous generators to handle GeneratorExit in athrow correctly bpo 30654 Fixed reset of the SIGINT handler to SIG_DFL on interpreter shutdown even when there was a custom handler set previously Patch by Philipp Kerling bpo 33622 Fixed a leak when the garbage collector fails to add an object with the __del__ method or referenced by it into the gc garbage list PyGC_Collect can now be called when an exception is set and preserves it bpo 31849 Fix signed unsigned comparison warning in pyhash c bpo 33391 Fix a leak in set_symmetric_difference bpo 28055 Fix unaligned accesses in siphash24 Patch by Rolf Eike Beer bpo 33231 Fix potential memory leak in normalizestring bpo 29922 Improved error messages in async with when __aenter__ or __aexit__ return non awaitable object bpo 33199 Fix ma_version_tag in dict implementation is uninitialized when copying from key sharing dict bpo 33041 Fixed jumping when the function contains an async for loop bpo 32282 Fix an unnecessary ifdef in the include of VersionHelpers h in socketmodule on Windows bpo 21983 Fix a crash in ctypes cast in case the type argument is a ctypes structured data type Patch by Eryk Sun and Oren Milman Library bpo 30167 Prevent site main exception if PYTHONSTARTUP is set Patch by Steve Weber bpo 33812 Datetime instance d with non None tzinfo but with d tzinfo utcoffset d returning None is now treated as naive by the astimezone method bpo 30805 Avoid race condition with debug logging bpo 33767 The concatenation and repetition sequence operations now raise TypeError instead of SystemError when performed on mmap mmap objects Patch by Zackery Spytz bpo 32684 Fix gather to propagate cancellation of itself even with return_exceptions bpo 33674 Fix a race condition in SSLProtocol connection_made of asyncio sslproto start immediately the handshake instead of using call_soon Previously data_received could be called before the handshake started causing the handshake to hang or fail bpo 31647 Fixed bug where calling write_eof on a _SelectorSocketTransport after it s already closed raises AttributeError bpo 33672 Fix Task __repr__ crash with Cython s bogus coroutines bpo 33469 Fix RuntimeError after closing loop that used run_in_executor bpo 11874 Use a better regex when breaking usage into wrappable parts Avoids bogus assertion errors from custom metavar strings bpo 30877 Fixed a bug in the Python implementation of the JSON decoder that prevented the cache of parsed strings from clearing after finishing the decoding Based on patch by c fos bpo 33548 tempfile _candidate_tempdir_list should consider common TEMP locations bpo 33542 Prevent uuid get_node from using a DUID instead of a MAC on Windows Patch by Zvi Effron bpo 26819 Fix race condition with ReadTransport resume_reading in Windows proactor event loop bpo 28556 Minor fixes in typing module add annotations to NamedTuple __new__ pass args and kwds in Generic __new__ Original PRs by Paulius Šarka and Chad Dombrova bpo 20087 Updated alias mapping with glibc 2 27 supported locales bpo 33422 Fix trailing quotation marks getting deleted when looking up byte string literals on pydoc Patch by Andrés Delfino bpo 33197 Update error message when constructing invalid inspect Parameters Patch by Donghee Na bpo 33383 Fixed crash in the get method of the dbm ndbm database object when it is called with a single argument bpo 33329 Fix multiprocessing regression on newer glibcs bpo 991266 Fix quoting of the Comment attribute of http cookies SimpleCookie bpo 33131 Upgrade bundled version of pip to 10 0 1 bpo 33308 Fixed a crash in the parser module when converting an ST object to a tree of tuples or lists with line_info False and col_info True bpo 33263 Fix FD leak in _SelectorSoc,en
1759,ketTransport Patch by Vlad Starostin bpo 33256 Fix display of module call in the html produced by cgitb html Patch by Stéphane Blondon bpo 33203 random Random choice now raises IndexError for empty sequences consistently even when called from subclasses without a getrandbits implementation bpo 33224 Update difflib mdiff for PEP 479 Convert an uncaught StopIteration in a generator into a return statement bpo 33209 End framing at the end of C implementation of pickle Pickler dump bpo 32861 The urllib robotparser s __str__ representation now includes wildcard entries and the Crawl delay and Request rate fields Patch by Michael Lazar bpo 33096 Allow ttk Treeview insert to insert iid that has a false boolean value Note iid 0 and iid False would be same Patch by Garvit Khatri bpo 33127 The ssl module now compiles with LibreSSL 2 7 1 bpo 33021 Release the GIL during fstat calls avoiding hang of all threads when calling mmap mmap os urandom and random seed Patch by Nir Soffer bpo 27683 Fix a regression in ipaddress that result of hosts is empty when the network is constructed by a tuple containing an integer mask and only 1 bit left for addresses bpo 32844 Fix wrong redirection of a low descriptor 0 or 1 to stderr in subprocess if another low descriptor is closed bpo 31908 Fix output of cover files for trace module command line tool Previously emitted cover files only when missing option was used Patch by Michael Selik bpo 31457 If nested log adapters are used the inner process methods are no longer omitted bpo 16865 Support arrays 2GiB in ctypes Patch by Segev Finer bpo 31238 pydoc the stop method of the private ServerThread class now waits until DocServer serve_until_quit completes and then explicitly sets its docserver attribute to None to break a reference cycle Documentation bpo 33503 Fix broken pypi link bpo 33421 Add missing documentation for typing AsyncContextManager bpo 33378 Add Korean language switcher for https docs python org 3 bpo 33276 Clarify that the __path__ attribute on modules cannot be just any value bpo 33201 Modernize documentation for writing C extension types bpo 33195 Deprecate Py_UNICODE usage in c api arg document Py_UNICODE related APIs are deprecated since Python 3 3 but it is missed in the document bpo 33126 Document PyBuffer_ToContiguous bpo 27212 Modify documentation for the islice recipe to consume initial values up to the start index bpo 28247 Update zipapp documentation to describe how to make standalone applications bpo 18802 Documentation changes for ipaddress Patch by Jon Foster and Berker Peksag bpo 27428 Update documentation to clarify that WindowsRegistryFinder implements MetaPathFinder Patch by Himanshu Lakhara bpo 8243 Add a note about curses addch and curses addstr exception behavior when writing outside a window or pad bpo 31432 Clarify meaning of CERT_NONE CERT_OPTIONAL and CERT_REQUIRED flags for ssl SSLContext verify_mode Tests bpo 33655 Ignore test_posix_fallocate failures on BSD platforms that might be due to running on ZFS bpo 19417 Add test_bdb py Build bpo 5755 Move Wstrict prototypes option to CFLAGS_NODIST from OPT This option emitted annoying warnings when building extension modules written in C bpo 33614 Ensures module definition files for the stable ABI on Windows are correctly regenerated bpo 33522 Enable CI builds on Visual Studio Team Services at https python visualstudio com cpython bpo 33012 Add Wno cast function type for gcc 8 for silencing warnings about function casts like casting to PyCFunction in method definition lists bpo 33394 Enable the verbose build for extension modules when GNU make is passed macros on the command line Windows bpo 33184 Update Windows installer to OpenSSL 1 0 2o macOS bpo 33184 Update macOS installer build to use OpenSSL 1 0 2o IDLE bpo 33656 On Windows add API call saying that tk scales for DPI On Windows 8 1 or 10 with DPI compatibility properties of the Python binary unchanged and a monitor resolution greater than 96 DPI this should make text and lines sharper It should otherwise have no effect bpo 33768 Clicking on a context line mo,en
1760,ves that line to the top of the editor window bpo 33763 IDLE Use read only text widget for code context instead of label widget bpo 33664 Scroll IDLE editor text by lines Previously the mouse wheel and scrollbar slider moved text by a fixed number of pixels resulting in partial lines at the top of the editor box The change also applies to the shell and grep output windows but not to read only text views bpo 33679 Enable theme specific color configuration for Code Context Use the Highlights tab to see the setting for built in themes or add settings to custom themes bpo 33642 Display up to maxlines non blank lines for Code Context If there is no current context show a single blank line bpo 33628 IDLE Cleanup codecontext py and its test bpo 33564 IDLE s code context now recognizes async as a block opener bpo 29706 IDLE now colors async and await as keywords in 3 6 They become full keywords in 3 7 bpo 21474 Update word identifier definition from ascii to unicode In text and entry boxes this affects selection by double click movement left right by control left right and deletion left right by control BACKSPACE DEL bpo 33204 IDLE consistently color invalid string prefixes A u string prefix cannot be paired with either r or f Consistently color as much of the prefix starting at the right as is valid Revise and extend colorizer test bpo 32831 Add docstrings and tests for codecontext Tools Demos bpo 33189 pygettext py now recognizes only literal strings as docstrings and translatable strings and rejects bytes literals and f string expressions bpo 31920 Fixed handling directories as arguments in the pygettext script Based on patch by Oleg Krasnikov bpo 29673 Fix pystackv and pystack gdbinit macros bpo 32885 Add an n flag for Tools scripts pathfix py to disable automatic backup creation files with suffix bpo 31583 Fix 2to3 for using with add suffix option but without output dir option for relative path to files in current directory C API bpo 32374 Document that m_traverse for multi phase initialized modules can be called with m_state NULL and add a sanity check Python 3 6 5 final Release date 2018 03 28 Tests bpo 32872 Avoid regrtest compatibility issue with namespace packages Build bpo 33163 Upgrade pip to 9 0 3 and setuptools to v39 0 1 Python 3 6 5 release candidate 1 Release date 2018 03 13 Security bpo 33001 Minimal fix to prevent buffer overrun in os symlink on Windows bpo 32981 Regexes in difflib and poplib were vulnerable to catastrophic backtracking These regexes formed potential DOS vectors REDOS They have been refactored This resolves CVE 2018 1060 and CVE 2018 1061 Patch by Jamie Davis Core and Builtins bpo 33026 Fixed jumping out of with block by setting f_lineno bpo 17288 Prevent jumps from return and exception trace events bpo 32889 Update Valgrind suppression list to account for the rename of Py_ADDRESS_IN_RANG to address_in_range bpo 32650 Pdb and other debuggers dependent on bdb py will correctly step over next command native coroutines Patch by Pablo Galindo bpo 32685 Improve suggestion when the Python 2 form of print statement is either present on the same line as the header of a compound statement or else terminated by a semi colon instead of a newline Patch by Nitish Chandra bpo 32583 Fix possible crashing in builtin Unicode decoders caused by write out of bound errors when using customized decode error handlers bpo 26163 Improved frozenset hash to create more distinct hash values when faced with datasets containing many similar values bpo 27169 The __debug__ constant is now optimized out at compile time This fixes also bpo 22091 bpo 32329 sys flags hash_randomization is now properly set to 0 when hash randomization is turned off by PYTHONHASHSEED 0 bpo 30416 The optimizer is now protected from spending much time doing complex calculations and consuming much memory for creating large constants in constant folding bpo 18533 repr on a dict containing its own values or items no longer raises RecursionError OrderedDict similarly Instead use as for other recursive structures Patch by Ben North bpo 32028 Leading whi,en
1761,tespace is now correctly ignored when generating suggestions for converting Py2 print statements to Py3 builtin print function calls Patch by Sanyam Khurana bpo 32137 The repr of deeply nested dict now raises a RecursionError instead of crashing due to a stack overflow Library bpo 33064 lib2to3 now properly supports trailing commas after args and kwargs in function signatures bpo 31804 Avoid failing in multiprocessing Process if the standard streams are closed or None at exit bpo 33037 Skip sending receiving data after SSL transport closing bpo 30353 Fix ctypes pass by value for structs on 64 bit Cygwin MinGW bpo 33009 Fix inspect signature for single parameter partialmethods bpo 32969 Expose several missing constants in zlib and fix corresponding documentation bpo 32713 Fixed tarfile itn handling of out of bounds float values Patch by Joffrey Fuhrer bpo 30622 The ssl module now detects missing NPN support in LibreSSL bpo 32922 dbm open now encodes filename with the filesystem encoding rather than default encoding bpo 32859 In os dup2 don t check every call whether the dup3 syscall exists or not bpo 21060 Rewrite confusing message from setup py upload from No dist file created in earlier command to the more helpful Must create and upload files in one command bpo 32857 In tkinter after_cancel None now raises a ValueError instead of canceling the first scheduled function Patch by Cheryl Sabella bpo 32852 Make sure sys argv remains as a list when running trace bpo 32841 Fixed asyncio Condition issue which silently ignored cancellation after notifying and cancelling a conditional lock Patch by Bar Harel bpo 31787 Fixed refleaks of __init__ methods in various modules Contributed by Oren Milman bpo 30157 Fixed guessing quote and delimiter in csv Sniffer sniff when only the last field is quoted Patch by Jake Davis bpo 32394 socket Remove TCP_FASTOPEN TCP_KEEPCNT flags on older version Windows during run time bpo 32777 Fix a rare but potential pre exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process This bug appears to have been introduced in 3 4 bpo 32647 The ctypes module used to depend on indirect linking for dlopen The shared extension is now explicitly linked against libdl on platforms with dl bpo 32734 Fixed asyncio Lock safety issue which allowed acquiring and locking the same lock multiple times without it being free Patch by Bar Harel bpo 32727 Do not include name field in SMTP envelope from address Patch by Stéphane Wirtel bpo 27931 Fix email address header parsing error when the username is an empty quoted string Patch by Xiang Zhang bpo 32304 distutils upload command no longer corrupts tar files ending with a CR byte and no longer tries to convert CR to CRLF in any of the upload text fields bpo 32502 uuid uuid1 no longer raises an exception if a 64 bit hardware address is encountered bpo 31848 Fix the error handling in Aifc_read initfp when the SSND chunk is not found Patch by Zackery Spytz bpo 32555 On FreeBSD and Solaris os strerror now always decode the byte string from the current locale encoding rather than using ASCII surrogateescape in some cases bpo 32521 The nis module is now compatible with new libnsl and headers location bpo 32473 Improve ABCMeta _dump_registry output readability bpo 32521 glibc has removed Sun RPC Use replacement libtirpc headers and library in nis module bpo 32228 Ensure that truncate preserves the file position as reported by tell after writes longer than the buffer size bpo 26133 Don t unsubscribe signals in asyncio UNIX event loop on interpreter shutdown bpo 32185 The SSL module no longer sends IP addresses in SNI TLS extension on platforms with OpenSSL 1 0 2 or inet_pton bpo 32323 urllib parse urlsplit does not convert zone id scope to lower case for scoped IPv6 addresses in hostnames now bpo 32302 Fix bdist_wininst of distutils for CRT v142 it binary compatible with CRT v140 bpo 32255 A single empty field is now always quoted when written into a CSV file This allows to distinguish an empty row from a row co,en
1762,nsisting of a single empty field Patch by Licht Takeuchi bpo 32277 Raise NotImplementedError instead of SystemError on platforms where chmod follow_symlinks False is not supported Patch by Anthony Sottile bpo 32199 The getnode ip getter now uses ip link instead of ip link list bpo 27456 Ensure TCP_NODELAY is set on Linux Tests by Victor Stinner bpo 31900 The locale localeconv function now sets temporarily the LC_CTYPE locale to the LC_NUMERIC locale to decode decimal_point and thousands_sep byte strings if they are non ASCII or longer than 1 byte and the LC_NUMERIC locale is different than the LC_CTYPE locale This temporary change affects other threads Same change for the str format method when formatting a number int float float and subclasses with the n type ex n format 1234 bpo 31802 Importing native path module posixpath ntpath now works even if the os module still is not imported Documentation bpo 17232 Clarify docs for O and OO Patch by Terry Reedy bpo 32800 Update link to w3c doc for xml default namespaces bpo 8722 Document __getattr__ behavior when property get method raises AttributeError bpo 32614 Modify RE examples in documentation to use raw strings to prevent DeprecationWarning and add text to REGEX HOWTO to highlight the deprecation bpo 31972 Improve docstrings for pathlib PurePath subclasses bpo 17799 Explain real behaviour of sys settrace and sys setprofile and their C API counterparts regarding which type of events are received in each function Patch by Pablo Galindo Salgado Tests bpo 32517 Fix failing test_asyncio on macOS 10 12 2 due to transport of KqueueSelector loop was not being closed bpo 32721 Fix test_hashlib to not fail if the _md5 module is not built bpo 32252 Fix faulthandler_suppress_crash_report used to prevent core dump files when testing crashes getrlimit returns zero on success bpo 31518 Debian Unstable has disabled TLS 1 0 and 1 1 for SSLv23_METHOD Change TLS SSL protocol of some tests to PROTOCOL_TLS or PROTOCOL_TLSv1_2 to make them pass on Debian Build bpo 32635 Fix segfault of the crypt module when libxcrypt is provided instead of libcrypt at the system Windows bpo 33016 Fix potential use of uninitialized memory in nt _getfinalpathname bpo 32903 Fix a memory leak in os chdir on Windows if the current directory is set to a UNC path bpo 31966 Fixed WindowsConsoleIO write for writing empty data bpo 32409 Ensures activate bat can handle Unicode contents bpo 32457 Improves handling of denormalized executable path when launching Python bpo 32370 Use the correct encoding for ipconfig output in the uuid module Patch by Segev Finer bpo 29248 Fix os readlink on Windows which was mistakenly treating the PrintNameOffset field of the reparse data buffer as a number of characters instead of bytes Patch by Craig Holmquist and SSE4 bpo 32588 Create standalone _distutils_findvs module macOS bpo 32726 Provide an additional more modern macOS installer variant that supports macOS 10 9 systems in 64 bit mode only Upgrade the supplied third party libraries to OpenSSL 1 0 2n XZ 5 2 3 and SQLite 3 22 0 The 10 9 installer now links with and supplies its own copy of Tcl Tk 8 6 8 IDLE bpo 32984 Set __file__ while running a startup file Like Python IDLE optionally runs one startup file in the Shell window before presenting the first interactive input prompt For IDLE s runs a file named in environmental variable IDLESTARTUP or PYTHONSTARTUP r file runs file Python sets __file__ to the startup file name before running the file and unsets it before the first prompt IDLE now does the same when run normally without the n option bpo 32940 Simplify and rename StringTranslatePseudoMapping in pyparse bpo 32916 Change str to code in pyparse bpo 32905 Remove unused code in pyparse module bpo 32874 Add tests for pyparse bpo 32837 Using the system and place dependent default encoding for open is a bad idea for IDLE s system and location independent files bpo 32826 Add encoding utf 8 to open in IDLE s test_help_about GUI test test_file_buttons only looks at initial ascii only lines but failed on systems where open defaults t,en
1763,o ascii because readline internally reads and decodes far enough ahead to encounter a non ascii character in CREDITS txt bpo 32765 Update configdialog General tab docstring to add new widgets to the widget list Tools Demos bpo 24960 2to3 and lib2to3 can now read pickled grammar files using pkgutil get_data rather than probing the filesystem This lets 2to3 and lib2to3 work when run from a zipfile bpo 32222 Fix pygettext not extracting docstrings for functions with type annotated arguments Patch by Toby Harradine C API bpo 29084 Undocumented C API for OrderedDict has been excluded from the limited C API It was added by mistake and actually never worked in the limited C API Python 3 6 4 final Release date 2017 12 18 There were no new code changes in version 3 6 4 since v3 6 4rc1 Python 3 6 4 release candidate 1 Release date 2017 12 05 Core and Builtins bpo 32176 co_flags CO_NOFREE is now always set correctly by the code object constructor based on freevars and cellvars rather than needing to be set correctly by the caller This ensures it will be cleared automatically when additional cell references are injected into a modified code object and function bpo 31949 Fixed several issues in printing tracebacks PyTraceBack_Print Setting sys tracebacklimit to 0 or less now suppresses printing tracebacks Setting sys tracebacklimit to None now causes using the default limit Setting sys tracebacklimit to an integer larger than LONG_MAX now means using the limit LONG_MAX rather than the default limit Fixed integer overflows in the case of more than 2 31 traceback items on Windows Fixed output errors handling bpo 30696 Fix the interactive interpreter looping endlessly when no memory bpo 20047 Bytearray methods partition and rpartition now accept only bytes like objects as separator as documented In particular they now raise TypeError rather of returning a bogus result when an integer is passed as a separator bpo 31852 Fix a segmentation fault caused by a combination of the async soft keyword and continuation lines bpo 21720 BytesWarning no longer emitted when the fromlist argument of __import__ or the __all__ attribute of the module contain bytes instances bpo 31825 Fixed OverflowError in the unicode escape codec and in codecs escape_decode when decode an escaped non ascii byte bpo 28603 Print the full context cause chain of exceptions on interpreter exit even if an exception in the chain is unhashable or compares equal to later ones Patch by Zane Bitter bpo 31786 Fix timeout rounding in the select module to round correctly negative timeouts between 1 0 and 0 0 The functions now block waiting for events as expected Previously the call was incorrectly non blocking Patch by Pablo Galindo bpo 31642 Restored blocking from package import module by setting sys modules package module to None bpo 31626 Fixed a bug in debug memory allocator There was a write to freed memory after shrinking a memory block bpo 31619 Fixed a ValueError when convert a string with large number of underscores to integer with binary base bpo 31592 Fixed an assertion failure in Python parser in case of a bad unicodedata normalize Patch by Oren Milman bpo 31588 Raise a TypeError with a helpful error message when class creation fails due to a metaclass with a bad __prepare__ method Patch by Oren Milman bpo 31566 Fix an assertion failure in _warnings warn in case of a bad __name__ global Patch by Oren Milman bpo 31505 Fix an assertion failure in json in case _json make_encoder received a bad encoder argument Patch by Oren Milman bpo 31492 Fix assertion failures in case of failing to import from a module with a bad __name__ attribute and in case of failing to access an attribute of such a module Patch by Oren Milman bpo 31490 Fix an assertion failure in ctypes class definition in case the class has an attribute whose name is specified in _anonymous_ but not in _fields_ Patch by Oren Milman bpo 31478 Fix an assertion failure in _random Random seed in case the argument has a bad __abs__ method Patch by Oren Milman bpo 31315 Fix an assertion failure in imp create_dynamic when ,en
1764,spec name is not a string Patch by Oren Milman bpo 31311 Fix a crash in the __setstate__ method of ctypes _CData in case of a bad __dict__ Patch by Oren Milman bpo 31293 Fix crashes in true division and multiplication of a timedelta object by a float with a bad as_integer_ratio method Patch by Oren Milman bpo 31285 Fix an assertion failure in warnings warn_explicit when the return value of the received loader s get_source has a bad splitlines method Patch by Oren Milman bpo 30817 PyErr_PrintEx clears now the ignored exception that may be raised by _PySys_SetObjectId for example when no memory Library bpo 28556 Two minor fixes for typing module allow shallow copying instances of generic classes improve interaction of __init_subclass__ with generics Original PRs by Ivan Levkivskyi bpo 27240 The header folding algorithm for the new email policies has been rewritten which also fixes bpo 30788 bpo 31831 and bpo 32182 In particular RFC2231 folding is now done correctly bpo 32186 io FileIO readall and io FileIO read now release the GIL when getting the file size Fixed hang of all threads with inaccessible NFS server Patch by Nir Soffer bpo 12239 Make msilib SummaryInformation GetProperty return None when the value of property is VT_EMPTY Initial patch by Mark Mc Mahon bpo 31325 Fix wrong usage of collections namedtuple in the RobotFileParser parse method Initial patch by Robin Wellner bpo 12382 msilib OpenDatabase now raises a better exception message when it couldn t open or create an MSI file Initial patch by William Tisäter bpo 32110 codecs StreamReader read n now returns not more than n characters bytes for non negative n This makes it compatible with read methods of other file like objects bpo 32072 Fixed issues with binary plists Fixed saving bytearrays Identical objects will be saved only once Equal references will be load as identical objects Added support for saving and loading recursive data structures bpo 32034 Make asyncio IncompleteReadError and LimitOverrunError pickleable bpo 32015 Fixed the looping of asyncio in the case of reconnection the socket during waiting async read write from to the socket bpo 32011 Restored support of loading marshal files with the TYPE_INT64 code These files can be produced in Python 2 7 bpo 31970 Reduce performance overhead of asyncio debug mode bpo 9678 Fixed determining the MAC address in the uuid module Using ifconfig on NetBSD and OpenBSD Using arp on Linux FreeBSD NetBSD and OpenBSD Based on patch by Takayuki Shimizukawa bpo 30057 Fix potential missed signal in signal signal bpo 31933 Fix Blake2 params leaf_size and node_offset on big endian platforms Patch by Jack O Connor bpo 31927 Fixed compilation of the socket module on NetBSD 8 Fixed assertion failure or reading arbitrary data when parse a AF_BLUETOOTH address on NetBSD and DragonFly BSD bpo 27666 Fixed stack corruption in curses box and curses ungetmouse when the size of types chtype or mmask_t is less than the size of C long curses box now accepts characters as arguments Based on patch by Steve Fink bpo 31897 plistlib now catches more errors when read binary plists and raises InvalidFileException instead of unexpected exceptions bpo 25720 Fix the method for checking pad state of curses WINDOW Patch by Masayuki Yamamoto bpo 31893 Fixed the layout of the kqueue_event structure on OpenBSD and NetBSD Fixed the comparison of the kqueue_event objects bpo 31891 Fixed building the curses module on NetBSD bpo 28416 Instances of pickle Pickler subclass with the persistent_id method and pickle Unpickler subclass with the persistent_load method no longer create reference cycles bpo 28326 Fix multiprocessing Process when stdout and or stderr is closed or None bpo 31457 If nested log adapters are used the inner process methods are no longer omitted bpo 31457 The manager property on LoggerAdapter objects is now properly settable bpo 31806 Fix timeout rounding in time sleep threading Lock acquire and socket socket settimeout to round correctly negative timeouts between 1 0 and 0 0 The functions now block waiting for events as expected Pr,en
1765,eviously the call was incorrectly non blocking Patch by Pablo Galindo bpo 28603 traceback Fix a TypeError that occurred during printing of exception tracebacks when either the current exception or an exception in its context cause chain is unhashable Patch by Zane Bitter bpo 30058 Fixed buffer overflow in select kqueue control bpo 31770 Prevent a crash when calling the __init__ method of a sqlite3 Cursor object more than once Patch by Oren Milman bpo 31672 idpattern in string Template matched some non ASCII characters Now it uses i regular expression local flag to avoid non ASCII characters bpo 31764 Prevent a crash in sqlite3 Cursor close in case the Cursor object is uninitialized Patch by Oren Milman bpo 31752 Fix possible crash in timedelta constructor called with custom integers bpo 31701 On Windows faulthandler enable now ignores MSC and COM exceptions bpo 31728 Prevent crashes in _elementtree due to unsafe cleanup of Element text and Element tail Patch by Oren Milman bpo 31620 an empty asyncio Queue now doesn t leak memory when queue get pollers timeout bpo 31632 Fix method set_protocol of class _SSLProtocolTransport in asyncio module This method was previously modifying a wrong reference to the protocol bpo 31675 Fixed memory leaks in Tkinter s methods splitlist and split when pass a string larger than 2 GiB bpo 31673 Fixed typo in the name of Tkinter s method adderrorinfo bpo 30806 Fix the string representation of a netrc object bpo 15037 Added a workaround for getkey in curses for ncurses 5 7 and earlier bpo 25351 Avoid venv activate failures with undefined variables bpo 25532 inspect unwrap will now only try to unwrap an object sys getrecursionlimit times to protect against objects which create a new object on every attribute access bpo 30347 Stop crashes when concurrently iterate over itertools groupby iterators bpo 31516 threading current_thread should not return a dummy thread at shutdown bpo 31351 python m ensurepip now exits with non zero exit code if pip bootstrapping has failed bpo 31482 random seed now works with bytes in version 1 bpo 31334 Fix poll poll timeout in the select module for arbitrary negative timeouts on all OSes where it can only be a non negative integer or 1 Patch by Riccardo Coccioli bpo 31310 multiprocessing s semaphore tracker should be launched again if crashed bpo 31308 Make multiprocessing s forkserver process immune to Ctrl C and other user interruptions If it crashes restart it when necessary Documentation bpo 32105 Added asyncio BaseEventLoop connect_accepted_socket versionadded marker bpo 31537 Fix incorrect usage of get_history_length in readline documentation example code Patch by Brad Smith bpo 30085 The operator functions without double underscores are preferred for clarity The one with underscores are only kept for back compatibility Tests bpo 31380 Skip test_httpservers test_undecodable_file on macOS fails on APFS bpo 31705 Skip test_socket test_sha256 on Linux kernel older than 4 5 The test fails with ENOKEY on kernel 3 10 on ppc64le A fix was merged into the kernel 4 5 bpo 31174 Fix test_tools test_unparse DirectoryTestCase now stores the names sample to always test the same files It prevents false alarms when hunting reference leaks bpo 30695 Add the set_nomemory start stop and remove_mem_hooks functions to the _testcapi module Build bpo 32059 detect_modules in setup py now also searches the sysroot paths when cross compiling bpo 31957 Fixes Windows SDK version detection when building for Windows bpo 31609 Fixes quotes in PCbuild clean bat bpo 31934 Abort the build when building out of a not clean source tree bpo 31926 Fixed Argument Clinic sometimes causing compilation errors when there was more than one function and or method in a c file with the same name bpo 28791 Update Windows builds to use SQLite 3 21 0 bpo 28791 Update OS X installer to use SQLite 3 21 0 bpo 22140 Prevent double substitution of prefix in python config sh bpo 31536 Avoid wholesale rebuild after make regen all if nothing changed Windows bpo 1102 Return None when View Fetch returns ERROR_NO_MORE_,en
1766,ITEMS instead of raising MSIError Initial patch by Anthony Tuininga bpo 31944 Fixes Modify button in Apps and Features dialog macOS bpo 31392 Update macOS installer to use OpenSSL 1 0 2m IDLE bpo 32207 Improve tk event exception tracebacks in IDLE When tk event handling is driven by IDLE s run loop a confusing and distracting queue EMPTY traceback context is no longer added to tk event exception tracebacks The traceback is now the same as when event handling is driven by user code Patch based on a suggestion by Serhiy Storchaka bpo 32164 Delete unused file idlelib tabbedpages py Use of TabbedPageSet in configdialog was replaced by ttk Notebook bpo 32100 IDLE Fix old and new bugs in pathbrowser improve tests Patch mostly by Cheryl Sabella bpo 31858 IDLE Restrict shell prompt manipulation to the shell Editor and output windows only see an empty last prompt line This simplifies the code and fixes a minor bug when newline is inserted Sys ps1 if present is read on Shell start up but is not set or changed bpo 31860 The font sample in the IDLE configuration dialog is now editable Changes persist while IDLE remains open bpo 31836 Test_code_module now passes if run after test_idle which sets ps1 The code module uses sys ps1 if present or sets it to if not Test_code_module now properly tests both behaviors Ditto for ps2 bpo 28603 Fix a TypeError that caused a shell restart when printing a traceback that includes an exception that is unhashable Patch by Zane Bitter bpo 13802 Use non Latin characters in the IDLE s Font settings sample Even if one selects a font that defines a limited subset of the unicode Basic Multilingual Plane tcl tk will use other fonts that define a character The expanded example give users of non Latin characters a better idea of what they might see in IDLE s shell and editors To make room for the expanded sample frames on the Font tab are re arranged The Font Tabs help explains a bit about the additions bpo 31460 Simplify the API of IDLE s Module Browser Passing a widget instead of an flist with a root widget opens the option of creating a browser frame that is only part of a window Passing a full file name instead of pieces assumed to come from a py file opens the possibility of browsing python files that do not end in py bpo 31649 IDLE Make _htest _utest parameters keyword only bpo 31559 Remove test order dependence in idle_test test_browser bpo 31459 Rename IDLE s module browser from Class Browser to Module Browser The original module level class and method browser became a module browser with the addition of module level functions years ago Nested classes and functions were added yesterday For back compatibility the virtual event open class browser which appears on the Keys tab of the Settings dialog is not changed Patch by Cheryl Sabella bpo 31500 Default fonts now are scaled on HiDPI displays bpo 1612262 IDLE module browser now shows nested classes and functions Original patches for code and tests by Guilherme Polo and Cheryl Sabella respectively Tools Demos bpo 30722 Make redemo work with Python 3 6 and newer versions Also remove the LOCALE option since it doesn t work with string patterns in Python 3 Patch by Christoph Sarnowski C API bpo 20891 Fix PyGILState_Ensure When PyGILState_Ensure is called in a non Python thread before PyEval_InitThreads only call PyEval_InitThreads after calling PyThreadState_New to fix a crash bpo 31532 Fix memory corruption due to allocator mix in getpath c between Py_GetPath and Py_SetPath bpo 30697 The PyExc_RecursionErrorInst singleton is removed and PyErr_NormalizeException does not use it anymore This singleton is persistent and its members being never cleared may cause a segfault during finalization of the interpreter See also bpo 22898 Python 3 6 3 final Release date 2017 10 03 Library bpo 31641 Re allow arbitrary iterables in concurrent futures as_completed Fixes regression in 3 6 3rc1 Build bpo 31662 Fix typos in Windows uploadrelease bat script Fix Windows Doc build issues in Doc make bat bpo 31423 Fix building the PDF documentation with newer versions of Sphinx ,en
1767,Python 3 6 3 release candidate 1 Release date 2017 09 18 Security bpo 29781 SSLObject version now correctly returns None when handshake over BIO has not been performed yet bpo 30947 Upgrade libexpat embedded copy from version 2 2 1 to 2 2 3 to get security fixes Core and Builtins bpo 31471 Fix an assertion failure in subprocess Popen on Windows in case the env argument has a bad keys method Patch by Oren Milman bpo 31418 Fix an assertion failure in PyErr_WriteUnraisable in case of an exception with a bad __module__ attribute Patch by Oren Milman bpo 31416 Fix assertion failures in case of a bad warnings filters or warnings defaultaction Patch by Oren Milman bpo 31411 Raise a TypeError instead of SystemError in case warnings onceregistry is not a dictionary Patch by Oren Milman bpo 31373 Fix several possible instances of undefined behavior due to floating point demotions bpo 30465 Location information lineno and col_offset in f strings is now mostly correct This fixes tools like flake8 from showing warnings on the wrong line typically the first line of the file bpo 31343 Include sys sysmacros h for major minor and makedev GNU C libray plans to remove the functions from sys types h bpo 31291 Fix an assertion failure in zipimport zipimporter get_data on Windows when the return value of pathname replace isn t a string Patch by Oren Milman bpo 31271 Fix an assertion failure in the write method of io TextIOWrapper when the encoder doesn t return a bytes object Patch by Oren Milman bpo 31243 Fix a crash in some methods of io TextIOWrapper when the decoder s state is invalid Patch by Oren Milman bpo 30721 print now shows correct usage hint for using Python 2 redirection syntax Patch by Sanyam Khurana bpo 31070 Fix a race condition in importlib _get_module_lock bpo 31095 Fix potential crash during GC caused by tp_dealloc which doesn t call PyObject_GC_UnTrack bpo 31071 Avoid masking original TypeError in call with unpacking when other arguments are passed bpo 30978 str format_map now passes key lookup exceptions through Previously any exception was replaced with a KeyError exception bpo 30808 Use _Py_atomic API for concurrency sensitive signal state bpo 30876 Relative import from unloaded package now reimports the package instead of failing with SystemError Relative import from non package now fails with ImportError rather than SystemError bpo 30703 Improve signal delivery Avoid using Py_AddPendingCall from signal handler to avoid calling signal unsafe functions The tests I m adding here fail without the rest of the patch on Linux and OS X This means our signal delivery logic had defects some signals could be lost bpo 30765 Avoid blocking in pthread_mutex_lock when PyThread_acquire_lock is asked not to block bpo 31161 Make sure the Missing parentheses syntax error message is only applied to SyntaxError not to subclasses Patch by Martijn Pieters bpo 30814 Fixed a race condition when import a submodule from a package bpo 30597 print now shows expected input in custom error message when used as a Python 2 statement Patch by Sanyam Khurana Library bpo 31499 xml etree Fix a crash when a parser is part of a reference cycle bpo 28556 typing get_type_hints now finds the right globalns for classes and modules by default when no globalns was specified by the caller bpo 28556 Speed improvements to the typing module Original PRs by Ivan Levkivskyi and Mitar bpo 31544 The C accelerator module of ElementTree ignored exceptions raised when looking up TreeBuilder target methods in XMLParser bpo 31234 socket create_connection now fixes manually a reference cycle clear the variable storing the last exception on success bpo 31457 LoggerAdapter objects can now be nested bpo 31400 Improves SSL error handling to avoid losing error numbers bpo 28958 ssl SSLContext now uses OpenSSL error information when a context cannot be instantiated bpo 27340 SSLSocket sendall now uses memoryview to create slices of data This fixes support for all bytes like object It is also more efficient and avoids costly copies bpo 31178 Fix string concatenation bug in rare erro,en
1768,r path in the subprocess module bpo 31350 Micro optimize asyncio _get_running_loop to become up to 10 faster bpo 31170 expat Update libexpat from 2 2 3 to 2 2 4 Fix copying of partial characters for UTF 8 input libexpat bug 115 https github com libexpat libexpat issues 115 bpo 29136 Add TLS 1 3 cipher suites and OP_NO_TLSv1_3 bpo 29212 Fix concurrent futures thread ThreadPoolExecutor threads to have a non repr based thread name by default when no thread_name_prefix is supplied They will now identify themselves as ThreadPoolExecutor y_n bpo 9146 Fix a segmentation fault in _hashopenssl when standard hash functions such as md5 are not available in the linked OpenSSL library As in some special FIPS 140 build environments bpo 27144 The map and as_completed iterators in concurrent futures now avoid keeping a reference to yielded objects bpo 10746 Fix ctypes producing wrong PEP 3118 type codes for integer types bpo 22536 The subprocess module now sets the filename when FileNotFoundError is raised on POSIX systems due to the executable or cwd not being found bpo 31249 concurrent futures WorkItem run used by ThreadPoolExecutor now breaks a reference cycle between an exception object and the WorkItem object bpo 31247 xmlrpc server now explicitly breaks reference cycles when using sys exc_info in code handling exceptions bpo 30102 The ssl and hashlib modules now call OPENSSL_add_all_algorithms_noconf on OpenSSL 1 1 0 The function detects CPU features and enables optimizations on some CPU architectures such as POWER8 Patch is based on research from Gustavo Serra Scalet bpo 31185 Fixed miscellaneous errors in asyncio speedup module bpo 31135 ttk fix the destroy method of LabeledScale and OptionMenu classes Call the parent destroy method even if the used attribute doesn t exist The LabeledScale destroy method now also explicitly clears label and scale attributes to help the garbage collector to destroy all widgets bpo 31107 Fix copyreg _slotnames mangled attribute calculation for classes whose name begins with an underscore Patch by Shane Harvey bpo 31061 Fixed a crash when using asyncio and threads bpo 30502 Fix handling of long oids in ssl Based on patch by Christian Heimes bpo 30119 ftplib FTP putline now throws ValueError on commands that contains CR or LF Patch by Donghee Na bpo 30595 multiprocessing Queue get with a timeout now polls its reader in non blocking mode if it succeeded to acquire the lock but the acquire took longer than the timeout bpo 29403 Fix unittest mock s autospec to not fail on method bound builtin functions Patch by Aaron Gallagher bpo 30961 Fix decrementing a borrowed reference in tracemalloc bpo 25684 Change ttk OptionMenu radiobuttons to be unique across instances of OptionMenu bpo 30886 Fix multiprocessing Queue join_thread it now waits until the thread completes even if the thread was started by the same process which created the queue bpo 29854 Fix segfault in readline when using readline s history size option Patch by Nir Soffer bpo 30319 socket close now ignores ECONNRESET error bpo 30828 Fix out of bounds write in asyncio CFuture remove_done_callback bpo 30807 signal setitimer may disable the timer when passed a tiny value Tiny values such as 1e 6 are valid non zero values for setitimer which is specified as taking microsecond resolution intervals However on some platform our conversion routine could convert 1e 6 into a zero interval therefore disabling the timer instead of re scheduling it bpo 30441 Fix bug when modifying os environ while iterating over it bpo 30532 Fix email header value parser dropping folding white space in certain cases bpo 30879 os listdir and os scandir now emit bytes names when called with bytes like argument bpo 30746 Prohibited the character in environment variable names in os putenv and os spawn bpo 29755 Fixed the lgettext family of functions in the gettext module They now always return bytes Documentation bpo 31294 Fix incomplete code snippet in the ZeroMQSocketListener and ZeroMQSocketHandler examples and adapt them to Python 3 bpo 21649 Add RFC 7525 and Mozilla serve,en
1769,r side TLS links to SSL documentation bpo 30803 Clarify doc on truth value testing Original patch by Peter Thomassen Tests bpo 31320 Silence traceback in test_ssl bpo 25674 Remove sha256 tbs internet com ssl test bpo 30715 Address ALPN callback changes for OpenSSL 1 1 0f The latest version behaves like OpenSSL 1 0 2 and no longer aborts handshake bpo 30822 regrtest Exclude tzdata from regrtest all When running the test suite using use all u all exclude tzdata since it makes test_datetime too slow 15 20 min on some buildbots which then times out on some buildbots Fix also regrtest command line parser to allow passing u extralargefile to run test_zipfile64 Build bpo 30854 Fix compile error when compiling without threads Patch by Masayuki Yamamoto Windows bpo 30389 Adds detection of Visual Studio 2017 to distutils on Windows bpo 31340 Change to building with MSVC v141 included with Visual Studio 2017 bpo 30581 os cpu_count now returns the correct number of processors on Windows when the number of logical processors is greater than 64 bpo 30731 Add a missing xmlns to python manifest so that it matches the schema IDLE bpo 31493 IDLE code context fix code update and font update timers Canceling timers prevents a warning message when test_idle completes bpo 31488 IDLE Update non key options in former extension classes When applying configdialog changes call reload for each feature class Change ParenMatch so updated options affect existing instances attached to existing editor windows bpo 31477 IDLE Improve rstrip entry in doc Strip trailing whitespace strips more than blank spaces Multiline string literals are not skipped bpo 31480 IDLE make tests pass with zzdummy extension disabled by default bpo 31421 Document how IDLE runs tkinter programs IDLE calls tcl tk update in the background in order to make live interaction and experimentation with tkinter applications much easier bpo 31414 IDLE fix tk entry box tests by deleting first Adding to an int entry is not the same as deleting and inserting because int will fail bpo 31051 Rearrange IDLE configdialog GenPage into Window Editor and Help sections bpo 30617 IDLE Add docstrings and tests for outwin subclass of editor Move some data and functions from the class to module level Patch by Cheryl Sabella bpo 31287 IDLE Do not modify tkinter message in test_configdialog bpo 27099 Convert IDLE s built in extensions to regular features About 10 IDLE features were implemented as supposedly optional extensions Their different behavior could be confusing or worse for users and not good for maintenance Hence the conversion The main difference for users is that user configurable key bindings for builtin features are now handled uniformly Now editing a binding in a keyset only affects its value in the keyset All bindings are defined together in the system specific default keysets in config extensions def All custom keysets are saved as a whole in config extension cfg All take effect as soon as one clicks Apply or Ok The affected events are force open completions expand word force open calltip flash paren format paragraph run module check module and zoom height Any global customizations made before 3 6 3 will not affect their keyset specific customization after 3 6 3 and vice versa Initial patch by Charles Wohlganger bpo 31206 IDLE Factor HighPage Frame class from ConfigDialog Patch by Cheryl Sabella bpo 31001 Add tests for configdialog highlight tab Patch by Cheryl Sabella bpo 31205 IDLE Factor KeysPage Frame class from ConfigDialog The slightly modified tests continue to pass Patch by Cheryl Sabella bpo 31130 IDLE stop leaks in test_configdialog Initial patch by Victor Stinner bpo 31002 Add tests for configdialog keys tab Patch by Cheryl Sabella bpo 19903 IDLE Calltips use inspect signature instead of inspect getfullargspec This improves calltips for builtins converted to use Argument Clinic Patch by Louie Lu bpo 31083 IDLE Add an outline of a TabPage class in configdialog Update existing classes to match outline Initial patch by Cheryl Sabella bpo 31050 Factor GenPage Frame class from Confi,en
1770,gDialog The slightly modified tests continue to pass Patch by Cheryl Sabella bpo 31004 IDLE Factor FontPage Frame class from ConfigDialog Slightly modified tests continue to pass Fix General tests Patch mostly by Cheryl Sabella bpo 30781 IDLE Use ttk widgets in ConfigDialog Patches by Terry Jan Reedy and Cheryl Sabella bpo 31060 IDLE Finish rearranging methods of ConfigDialog Grouping methods pertaining to each tab and the buttons will aid writing tests and improving the tabs and will enable splitting the groups into classes bpo 30853 IDLE Factor a VarTrace class out of ConfigDialog Instance tracers manages pairs consisting of a tk variable and a callback function When tracing is turned on setting the variable calls the function Test coverage for the new class is 100 bpo 31003 IDLE Add more tests for General tab bpo 30993 IDLE Improve configdialog font page and tests In configdialog Document causal pathways in create_font_tab docstring Simplify some attribute names Move set_samples calls to var_changed_font idea from Cheryl Sabella Move related functions to positions after the create widgets function In test_configdialog Fix test_font_set so not order dependent Fix renamed test_indent_scale so it tests the widget Adjust tests for movement of set_samples call Add tests for load functions Put all font tests in one class and tab indent tests in another Except for two lines these tests completely cover the related functions bpo 30981 IDLE Add more configdialog font page tests bpo 28523 IDLE replace colour with color in configdialog bpo 30917 Add tests for idlelib config IdleConf Increase coverage from 46 to 96 Patch by Louie Lu bpo 30934 Document coverage details for idlelib tests Add section to idlelib idle test README txt Include check that branches are taken both ways Exclude IDLE specific code that does not run during unit tests bpo 30913 IDLE Document ConfigDialog tk Vars methods and widgets in docstrings This will facilitate improving the dialog and splitting up the class Original patch by Cheryl Sabella bpo 30899 IDLE Add tests for ConfigParser subclasses in config Patch by Louie Lu bpo 30881 IDLE Add docstrings to browser py Patch by Cheryl Sabella bpo 30851 IDLE Remove unused variables in configdialog One is a duplicate one is set but cannot be altered by users Patch by Cheryl Sabella bpo 30870 IDLE In Settings dialog select font with Up Down keys as well as mouse Initial patch by Louie Lu bpo 8231 IDLE call config IdleConf GetUserCfgDir only once bpo 30779 IDLE Factor ConfigChanges class from configdialog put in config test In config put dump test code in a function run it and unittest in if __name__ __main__ Add class config ConfigChanges based on changes_class_v4 py on bpo issue Add class test_config ChangesTest partly using configdialog_tests_v1 py Revise configdialog to use ConfigChanges see tracker msg297804 Revise test_configdialog to match configdialog changes Remove configdialog functions unused or moved to ConfigChanges Cheryl Sabella contributed parts of the patch bpo 30777 IDLE configdialog Add docstrings and fix comments Patch by Cheryl Sabella bpo 30495 IDLE Improve textview with docstrings PEP8 names and more tests Patch by Cheryl Sabella bpo 30723 IDLE Make several improvements to parenmatch Add parens style to highlight both opener and closer Make default style which is not default a synonym for opener Make time delay work the same with all styles Add help for config dialog extensions tab including help for parenmatch Add new tests Original patch by Charles Wohlganger bpo 30674 IDLE add docstrings to grep module Patch by Cheryl Sabella bpo 21519 IDLE s basic custom key entry dialog now detects duplicates properly Original patch by Saimadhav Heblikar bpo 29910 IDLE no longer deletes a character after commenting out a region by a key shortcut Add return break for this and other potential conflicts between IDLE and default key bindings bpo 30728 Review and change idlelib configdialog names Lowercase method and attribute names Replace colour with color expand overly cryptic names delete unneeded undersc,en
1771,ores Replace import with specific imports Patches by Cheryl Sabella bpo 6739 IDLE Verify user entered key sequences by trying to bind them with tk Add tests for all 3 validation functions Original patch by G Polo Tests added by Cheryl Sabella Tools Demos bpo 30983 gdb integration commands py bt etc work on optimized shared builds now too PEP 523 introduced _PyEval_EvalFrameDefault which inlines PyEval_EvalFrameEx on non debug shared builds This broke the ability to use py bt py up and a few other Python specific gdb integrations The problem is fixed by only looking for _PyEval_EvalFrameDefault frames in python gdb py Original patch by Bruno Polaco Penteado Python 3 6 2 final Release date 2017 07 17 No changes since release candidate 2 Python 3 6 2 release candidate 2 Release date 2017 07 07 Security bpo 30730 Prevent environment variables injection in subprocess on Windows Prevent passing other environment variables and command arguments bpo 30694 Upgrade expat copy from 2 2 0 to 2 2 1 to get fixes of multiple security vulnerabilities including CVE 2017 9233 External entity infinite loop DoS CVE 2016 9063 Integer overflow re fix CVE 2016 0718 Fix regression bugs from 2 2 0 s fix to CVE 2016 0718 and CVE 2012 0876 Counter hash flooding with SipHash Note the CVE 2016 5300 Use os specific entropy sources like getrandom doesn t impact Python since Python already gets entropy from the OS to set the expat secret using XML_SetHashSalt bpo 30500 Fix urllib parse splithost to correctly parse fragments For example splithost 127 0 0 1 evil com now correctly returns the 127 0 0 1 host instead of treating evil com as the host in an authentication login host Python 3 6 2 release candidate 1 Release date 2017 06 17 Security bpo 29591 Update expat copy from 2 1 1 to 2 2 0 to get fixes of CVE 2016 0718 and CVE 2016 4472 See https sourceforge net p expat bugs 537 for more information Core and Builtins bpo 30682 Removed a too strict assertion that failed for certain f strings such as eval f n and eval f r bpo 30604 Move co_extra_freefuncs to not be per thread to avoid crashes bpo 29104 Fixed parsing backslashes in f strings bpo 27945 Fixed various segfaults with dict when input collections are mutated during searching inserting or comparing Based on patches by Duane Griffin and Tim Mitchell bpo 25794 Fixed type __setattr__ and type __delattr__ for non interned attribute names Based on patch by Eryk Sun bpo 30039 If a KeyboardInterrupt happens when the interpreter is in the middle of resuming a chain of nested yield from or await calls it s now correctly delivered to the innermost frame bpo 12414 sys getsizeof on a code object now returns the sizes which includes the code struct and sizes of objects which it references Patch by Donghee Na bpo 29949 Fix memory usage regression of set and frozenset object bpo 29935 Fixed error messages in the index method of tuple list and deque when pass indices of wrong type bpo 29859 Show correct error messages when any of the pthread_ calls in thread_pthread h fails bpo 28876 bool range works even if len range raises OverflowError bpo 29600 Fix wrapping coroutine return values in StopIteration bpo 28856 Fix an oversight that b format for bytes should support objects follow the buffer protocol bpo 29714 Fix a regression that bytes format may fail when containing zero bytes inside bpo 29478 If max_line_length None is specified while using the Compat32 policy it is no longer ignored Patch by Mircea Cosbuc Library bpo 30616 Functional API of enum allows to create empty enums Patched by Donghee Na bpo 30038 Fix race condition between signal delivery and wakeup file descriptor Patch by Nathaniel Smith bpo 23894 lib2to3 now recognizes rb and f strings bpo 23890 unittest TestCase assertRaises now manually breaks a reference cycle to not keep objects alive longer than expected bpo 30149 inspect signature now supports callables with variable argument parameters wrapped with partialmethod Patch by Donghee Na bpo 30645 Fix path calculation in imp load_package fixing it for cases when a package is only shipped with by,en
1772,tecodes Patch by Alexandru Ardelean bpo 29931 Fixed comparison check for ipaddress ip_interface objects Patch by Sanjay Sundaresan bpo 30605 re compile no longer raises a BytesWarning when compiling a bytes instance with misplaced inline modifier Patch by Roy Williams bpo 24484 Avoid race condition in multiprocessing cleanup 2159 bpo 28994 The traceback no longer displayed for SystemExit raised in a callback registered by atexit bpo 30508 Don t log exceptions if Task Future cancel method was called bpo 28556 Updates to typing module Add generic AsyncContextManager add support for ContextManager on all versions Original PRs by Jelle Zijlstra and Ivan Levkivskyi bpo 29870 Fix ssl sockets leaks when connection is aborted in asyncio ssl implementation Patch by Michaël Sghaïer bpo 29743 Closing transport during handshake process leaks open socket Patch by Nikolay Kim bpo 27585 Fix waiter cancellation in asyncio Lock Patch by Mathieu Sornay bpo 30418 On Windows subprocess Popen communicate now also ignore EINVAL on stdin write if the child process is still running but closed the pipe bpo 29822 inspect isabstract now works during __init_subclass__ Patch by Nate Soares bpo 29581 ABCMeta __new__ now accepts kwargs allowing abstract base classes to use keyword parameters in __init_subclass__ Patch by Nate Soares bpo 30557 faulthandler now correctly filters and displays exception codes on Windows bpo 30378 Fix the problem that logging handlers SysLogHandler cannot handle IPv6 addresses bpo 29960 Preserve generator state when _random Random setstate raises an exception Patch by Bryan Olson bpo 30414 multiprocessing Queue _feed background running thread do not break from main loop on exception bpo 30003 Fix handling escape characters in HZ codec Based on patch by Ma Lin bpo 30301 Fix AttributeError when using SimpleQueue empty under spawn and forkserver start methods bpo 30329 imaplib and poplib now catch the Windows socket WSAEINVAL error code 10022 on shutdown SHUT_RDWR An invalid operation was attempted This error occurs sometimes on SSL connections bpo 30375 Warnings emitted when compile a regular expression now always point to the line in the user code Previously they could point into inners of the re module if emitted from inside of groups or conditionals bpo 30048 Fixed Task cancel can be ignored when the task is running coroutine and the coroutine returned without any more await bpo 30266 contextlib AbstractContextManager now supports anti registration by setting __enter__ None or __exit__ None following the pattern introduced in bpo 25958 Patch by Jelle Zijlstra bpo 30298 Weaken the condition of deprecation warnings for inline modifiers Now allowed several subsequential inline modifiers at the start of the pattern e g i s In verbose mode whitespaces and comments now are allowed before and between inline modifiers e g x i s bpo 29990 Fix range checking in GB18030 decoder Original patch by Ma Lin bpo 26293 Change resulted because of zipfile breakage See also bpo 29094 bpo 30243 Removed the __init__ methods of _json s scanner and encoder Misusing them could cause memory leaks or crashes Now scanner and encoder objects are completely initialized in the __new__ methods bpo 30185 Avoid KeyboardInterrupt tracebacks in forkserver helper process when Ctrl C is received bpo 28556 Various updates to typing module add typing NoReturn type use WrapperDescriptorType minor bug fixes Original PRs by Jim Fasarakis Hilliard and Ivan Levkivskyi bpo 30205 Fix getsockname for unbound AF_UNIX sockets on Linux bpo 30070 Fixed leaks and crashes in errors handling in the parser module bpo 30061 Fixed crashes in IOBase methods __next__ and readlines when readline or __next__ respectively return non sizeable object Fixed possible other errors caused by not checking results of PyObject_Size PySequence_Size or PyMapping_Size bpo 30017 Allowed calling the close method of the zip entry writer object multiple times Writing to a closed writer now always produces a ValueError bpo 30068 _io _IOBase readlines will check if it s closed first when hint is presen,en
1773,t bpo 29694 Fixed race condition in pathlib mkdir with flags parents True Patch by Armin Rigo bpo 29692 Fixed arbitrary unchaining of RuntimeError exceptions in contextlib contextmanager Patch by Siddharth Velankar bpo 29998 Pickling and copying ImportError now preserves name and path attributes bpo 29953 Fixed memory leaks in the replace method of datetime and time objects when pass out of bound fold argument bpo 29942 Fix a crash in itertools chain from_iterable when encountering long runs of empty iterables bpo 27863 Fixed multiple crashes in ElementTree caused by race conditions and wrong types bpo 28699 Fixed a bug in pools in multiprocessing pool that raising an exception at the very first of an iterable may swallow the exception or make the program hang Patch by Davin Potts and Xiang Zhang bpo 25803 Avoid incorrect errors raised by Path mkdir exist_ok True when the OS gives priority to errors such as EACCES over EEXIST bpo 29861 Release references to tasks their arguments and their results as soon as they are finished in multiprocessing Pool bpo 29884 faulthandler Restore the old sigaltstack during teardown Patch by Christophe Zeitouny bpo 25455 Fixed crashes in repr of recursive buffered file like objects bpo 29800 Fix crashes in partial __repr__ if the keys of partial keywords are not strings Patch by Michael Seifert bpo 29742 get_extra_info raises exception if get called on closed ssl transport Patch by Nikolay Kim bpo 8256 Fixed possible failing or crashing input if attributes encoding or errors of sys stdin or sys stdout are not set or are not strings bpo 28298 Fix a bug that prevented array Q L and I from accepting big intables objects that have __int__ as elements Patch by Oren Milman bpo 28231 The zipfile module now accepts path like objects for external paths bpo 26915 index and count methods of collections abc Sequence now check identity before checking equality when do comparisons bpo 29615 SimpleXMLRPCDispatcher no longer chains KeyError or any other exception to exception s raised in the dispatched methods Patch by Petr Motejlek bpo 30177 path resolve strict False no longer cuts the path after the first element not present in the filesystem Patch by Antoine Pietri IDLE bpo 15786 Fix several problems with IDLE s autocompletion box The following should now work clicking on selection box items using the scrollbar selecting an item by hitting Return Hangs on MacOSX should no longer happen Patch by Louie Lu bpo 25514 Add doc subsubsection about IDLE failure to start Popup no connection message directs users to this section bpo 30642 Fix reference leaks in IDLE tests Patches by Louie Lu and Terry Jan Reedy bpo 30495 Add docstrings for textview py and use PEP8 names Patches by Cheryl Sabella and Terry Jan Reedy bpo 30290 Help about use pep8 names and add tests Increase coverage to 100 Patches by Louie Lu Cheryl Sabella and Terry Jan Reedy bpo 30303 Add _utest option to textview add new tests Increase coverage to 100 Patches by Louie Lu and Terry Jan Reedy C API bpo 27867 Function PySlice_GetIndicesEx no longer replaced with a macro if Py_LIMITED_API is not set Build bpo 29941 Add with assertions configure flag to explicitly enable C assert checks Defaults to off with pydebug implies with assertions bpo 28787 Fix out of tree builds of Python when configured with with dtrace bpo 29243 Prevent unnecessary rebuilding of Python during make test make install and some other make targets when configured with enable optimizations bpo 23404 Don t regenerate generated files based on file modification time anymore the action is now explicit Replace make touch with make regen all bpo 29643 Fix enable optimization didn t work Documentation bpo 30176 Add missing attribute related constants in curses documentation bpo 30052 the link targets for bytes and bytearray are now their respective type definitions rather than the corresponding builtin function entries Use bytes and bytearray to reference the latter In order to ensure this and future cross reference updates are applied automatically the daily documentation builds now,en
1774, disable the default output caching features in Sphinx bpo 26985 Add missing info of code object in inspect documentation Tools Demos bpo 29367 python gdb py now supports also method wrapper wrapperobject objects Tests bpo 30357 test_thread setUp now uses support threading_setup and support threading_cleanup to wait until threads complete to avoid random side effects on following tests Initial patch written by Grzegorz Grzywacz bpo 30197 Enhanced functions swap_attr and swap_item in the test support module They now work when delete replaced attribute or item inside the with statement The old value of the attribute or item or None if it doesn t exist now will be assigned to the target of the as clause if there is one Windows bpo 30687 Locate msbuild exe on Windows when building rather than vcvarsall bat bpo 30450 The build process on Windows no longer depends on Subversion instead pulling external code from GitHub via a Python script If Python 3 6 is not found on the system via py 3 6 NuGet is used to download a copy of 32 bit Python Python 3 6 1 final Release date 2017 03 21 Core and Builtins bpo 29723 The sys path 0 initialization change for bpo 29139 caused a regression by revealing an inconsistency in how sys path is initialized when executing __main__ from a zipfile directory or other import location The interpreter now consistently avoids ever adding the import location s parent directory to sys path and ensures no other sys path entries are inadvertently modified when inserting the import location named on the command line Build bpo 27593 fix format of git information used in sys version Fix incompatible comment in python h Python 3 6 1 release candidate 1 Release date 2017 03 04 Core and Builtins bpo 28893 Set correct __cause__ for errors about invalid awaitables returned from __aiter__ and __anext__ bpo 29683 Fixes to memory allocation in _PyCode_SetExtra Patch by Brian Coleman bpo 29684 Fix minor regression of PyEval_CallObjectWithKeywords It should raise TypeError when kwargs is not a dict But it might cause segv when args NULL and kwargs is not a dict bpo 28598 Support __rmod__ for subclasses of str being called before str __mod__ Patch by Martijn Pieters bpo 29607 Fix stack_effect computation for CALL_FUNCTION_EX Patch by Matthieu Dartiailh bpo 29602 Fix incorrect handling of signed zeros in complex constructor for complex subclasses and for inputs having a __complex__ method Patch by Serhiy Storchaka bpo 29347 Fixed possibly dereferencing undefined pointers when creating weakref objects bpo 29438 Fixed use after free problem in key sharing dict bpo 29319 Prevent RunMainFromImporter overwriting sys path 0 bpo 29337 Fixed possible BytesWarning when compare the code objects Warnings could be emitted at compile time bpo 29327 Fixed a crash when pass the iterable keyword argument to sorted bpo 29034 Fix memory leak and use after free in os module path_converter bpo 29159 Fix regression in bytes x when x __index__ raises Exception bpo 28932 Do not include sys random h if it does not exist bpo 25677 Correct the positioning of the syntax error caret for indented blocks Based on patch by Michael Layzell bpo 29000 Fixed bytes formatting of octals with zero padding in alternate form bpo 26919 On Android operating system data is now always encoded decoded to from UTF 8 instead of the locale encoding to avoid inconsistencies with os fsencode and os fsdecode which are already using UTF 8 bpo 28991 functools lru_cache was susceptible to an obscure reentrancy bug triggerable by a monkey patched len function bpo 28739 f string expressions are no longer accepted as docstrings and by ast literal_eval even if they do not include expressions bpo 28512 Fixed setting the offset attribute of SyntaxError by PyErr_SyntaxLocationEx and PyErr_SyntaxLocationObject bpo 28918 Fix the cross compilation of xxlimited when Python has been built with Py_DEBUG defined bpo 28731 Optimize _PyDict_NewPresized to create correct size dict Improve speed of dict literal with constant keys up to 30 Library bpo 29169 Update zlib to 1 2 11 bpo 29623 Allo,en
1775,w use of path like object as a single argument in ConfigParser read Patch by David Ellis bpo 28963 Fix out of bound iteration in asyncio Future remove_done_callback implemented in C bpo 29704 asyncio subprocess SubprocessStreamProtocol no longer closes before all pipes are closed bpo 29271 Fix Task current_task and Task all_tasks implemented in C to accept None argument as their pure Python implementation bpo 29703 Fix asyncio to support instantiation of new event loops in child processes bpo 29376 Fix assertion error in threading _DummyThread is_alive bpo 28624 Add a test that checks that cwd parameter of Popen accepts PathLike objects Patch by Sayan Chowdhury bpo 28518 Start a transaction implicitly before a DML statement Patch by Aviv Palivoda bpo 29532 Altering a kwarg dictionary passed to functools partial no longer affects a partial object after creation bpo 29110 Fix file object leak in aifc open when file is given as a filesystem path and is not in valid AIFF format Patch by Anthony Zhang bpo 28556 Various updates to typing module typing Counter typing ChainMap improved ABC caching etc Original PRs by Jelle Zijlstra Ivan Levkivskyi Manuel Krebber and Łukasz Langa bpo 29100 Fix datetime fromtimestamp regression introduced in Python 3 6 0 check minimum and maximum years bpo 29519 Fix weakref spewing exceptions during interpreter shutdown when used with a rare combination of multiprocessing and custom codecs bpo 29416 Prevent infinite loop in pathlib Path mkdir bpo 29444 Fixed out of bounds buffer access in the group method of the match object Based on patch by WGH bpo 29335 Fix subprocess Popen wait when the child process has exited to a stopped instead of terminated state ex when under ptrace bpo 29290 Fix a regression in argparse that help messages would wrap at non breaking spaces bpo 28735 Fixed the comparison of mock MagickMock with mock ANY bpo 29316 Restore the provisional status of typing module add corresponding note to documentation Patch by Ivan L bpo 29219 Fixed infinite recursion in the repr of uninitialized ctypes CDLL instances bpo 29011 Fix an important omission by adding Deque to the typing module bpo 28969 Fixed race condition in C implementation of functools lru_cache KeyError could be raised when cached function with full cache was simultaneously called from different threads with the same uncached arguments bpo 29142 In urllib request suffixes in no_proxy environment variable with leading dots could match related hostnames again e g b c matches a b c Patch by Milan Oberkirch bpo 28961 Fix unittest mock _Call helper don t ignore the name parameter anymore Patch written by Jiajun Huang bpo 29203 functools lru_cache now respects PEP 468 and preserves the order of keyword arguments f a 1 b 2 is now cached separately from f b 2 a 1 since both calls could potentially give different results bpo 15812 inspect getframeinfo now correctly shows the first line of a context Patch by Sam Breese bpo 29094 Offsets in a ZIP file created with extern file object and modes w and x now are relative to the start of the file bpo 29085 Allow random Random seed to use high quality OS randomness rather than the pid and time bpo 29061 Fixed bug in secrets randbelow which would hang when given a negative input Patch by Brendan Donegan bpo 29079 Prevent infinite loop in pathlib resolve on Windows bpo 13051 Fixed recursion errors in large or resized curses textpad Textbox Based on patch by Tycho Andersen bpo 29119 Fix weakrefs in the pure python version of collections OrderedDict move_to_end method Contributed by Andra Bogildea bpo 9770 curses ascii predicates now work correctly with negative integers bpo 28427 old keys should not remove new values from WeakValueDictionary when collecting from another thread bpo 28923 Remove editor artifacts from Tix py bpo 29055 Neaten up empty population error on random choice by suppressing the upstream exception bpo 28871 Fixed a crash when deallocate deep ElementTree bpo 19542 Fix bugs in WeakValueDictionary setdefault and WeakValueDictionary pop when a GC collection happens in another,en
1776, thread bpo 20191 Fixed a crash in resource prlimit when passing a sequence that doesn t own its elements as limits bpo 28779 multiprocessing set_forkserver_preload would crash the forkserver process if a preloaded module instantiated some multiprocessing objects such as locks bpo 28847 dbm dumb now supports reading read only files and no longer writes the index file when it is not changed bpo 26937 The chown method of the tarfile TarFile class does not fail now when the grp module cannot be imported as for example on Android platforms IDLE bpo 29071 IDLE colors f string prefixes but not invalid ur prefixes bpo 28572 Add 10 to coverage of IDLE s test_configdialog Update and augment description of the configuration system Windows bpo 29579 Removes readme txt from the installer bpo 29326 Ignores blank lines in _pth files Patch by Alexey Izbyshev bpo 28164 Correctly handle special console filenames patch by Eryk Sun bpo 29409 Implement PEP 529 for io FileIO Patch by Eryk Sun bpo 29392 Prevent crash when passing invalid arguments into msvcrt module bpo 25778 winreg does not truncate string correctly Patch by Eryk Sun bpo 28896 Deprecate WindowsRegistryFinder and disable it by default C API bpo 27867 Function PySlice_GetIndicesEx is replaced with a macro if Py_LIMITED_API is not set or set to the value between 0x03050400 and 0x03060000 not including or 0x03060100 or higher bpo 29083 Fixed the declaration of some public API functions PyArg_VaParse and PyArg_VaParseTupleAndKeywords were not available in limited API PyArg_ValidateKeywordArguments PyArg_UnpackTuple and Py_BuildValue were not available in limited API of version 3 3 when PY_SSIZE_T_CLEAN is defined bpo 29058 All stable API extensions added after Python 3 2 are now available only when Py_LIMITED_API is set to the PY_VERSION_HEX value of the minimum Python version supporting this API Documentation bpo 28929 Link the documentation to its source file on GitHub bpo 25008 Document smtpd py as effectively deprecated and add a pointer to aiosmtpd a third party asyncio based replacement bpo 26355 Add canonical header link on each page to corresponding major version of the documentation Patch by Matthias Bussonnier bpo 29349 Fix Python 2 syntax in code for building the documentation Tests bpo 28087 Skip test_asyncore and test_eintr poll failures on macOS Skip some tests of select poll when running on macOS due to unresolved issues with the underlying system poll function on some macOS versions bpo 29571 to match the behaviour of the re LOCALE flag test_re test_locale_flag now uses locale getpreferredencoding False to determine the candidate encoding for the test regex allowing it to correctly skip the test when the default locale encoding is a multi byte encoding bpo 28950 Disallow j0 to be combined with T l in regrtest command line arguments bpo 28683 Fix the tests that bind a unix socket and raise PermissionError on Android for a non root user bpo 26939 Add the support setswitchinterval function to fix test_functools hanging on the Android armv7 qemu emulator Build bpo 27593 sys version and the platform module python_build python_branch and python_revision functions now use git information rather than hg when building from a repo bpo 29572 Update Windows build and OS X installers to use OpenSSL 1 0 2k bpo 26851 Set Android compilation and link flags bpo 28768 Fix implicit declaration of function _setmode Patch by Masayuki Yamamoto bpo 29080 Removes hard dependency on hg exe from PCBuild build bat bpo 23903 Added missed names to PC python3 def bpo 28762 lockf is available on Android API level 24 but the F_LOCK macro is not defined in android ndk r13 bpo 28538 Fix the compilation error that occurs because if_nameindex is available on Android API level 24 but the if_nameindex structure is not defined bpo 20211 Do not add the directory for installing C header files and the directory for installing object code libraries to the cross compilation search paths Original patch by Thomas Petazzoni bpo 28849 Do not define sys implementation _multiarch on Android Python 3 6 0 final Rel,en
1777,ease date 2016 12 23 No changes since release candidate 2 Python 3 6 0 release candidate 2 Release date 2016 12 16 Core and Builtins bpo 28147 Fix a memory leak in split table dictionaries setattr must not convert combined table into split table Patch written by INADA Naoki bpo 28990 Fix asyncio SSL hanging if connection is closed before handshake is completed Patch by HoHo Ho Tools Demos bpo 28770 Fix python gdb py for fastcalls Windows bpo 28896 Deprecate WindowsRegistryFinder Build bpo 28898 Prevent gdb build errors due to HAVE_LONG_LONG redefinition Python 3 6 0 release candidate 1 Release date 2016 12 06 Core and Builtins bpo 23722 Rather than silently producing a class that doesn t support zero argument super in methods failing to pass the new __classcell__ namespace entry up to type __new__ now results in a DeprecationWarning and a class that supports zero argument super bpo 28797 Modifying the class __dict__ inside the __set_name__ method of a descriptor that is used inside that class no longer prevents calling the __set_name__ method of other descriptors bpo 28782 Fix a bug in the implementation yield from when checking if the next instruction is YIELD_FROM Regression introduced by WORDCODE bpo 26647 Library bpo 27030 Unknown escapes in re sub replacement template are allowed again But they still are deprecated and will be disabled in 3 7 bpo 28835 Fix a regression introduced in warnings catch_warnings call warnings showwarning if it was overridden inside the context manager bpo 27172 To assist with upgrades from 2 7 the previously documented deprecation of inspect getfullargspec has been reversed This decision may be revisited again after the Python 2 7 branch is no longer officially supported bpo 26273 Add new socket TCP_CONGESTION Linux 2 6 13 and socket TCP_USER_TIMEOUT Linux 2 6 37 constants Patch written by Omar Sandoval bpo 24142 Reading a corrupt config file left configparser in an invalid state Original patch by Florian Höch bpo 28843 Fix asyncio C Task to handle exceptions __traceback__ C API bpo 28808 PyUnicode_CompareWithASCIIString now never raises exceptions Documentation bpo 23722 The data model reference and the porting section in the What s New guide now cover the additional __classcell__ handling needed for custom metaclasses to fully support PEP 487 and zero argument super Tools Demos bpo 28023 Fix python gdb py didn t support new dict implementation Python 3 6 0 beta 4 Release date 2016 11 21 Core and Builtins bpo 28532 Show sys version when V option is supplied twice bpo 27100 The with statement now checks for __enter__ before it checks for __exit__ This gives less confusing error messages when both methods are missing Patch by Jonathan Ellington bpo 28746 Fix the set_inheritable file descriptor method on platforms that do not have the ioctl FIOCLEX and FIONCLEX commands bpo 26920 Fix not getting the locale s charset upon initializing the interpreter on platforms that do not have langinfo bpo 28648 Fixed crash in Py_DecodeLocale in debug build on Mac OS X when decode astral characters Patch by Xiang Zhang bpo 19398 Extra slash no longer added to sys path components in case of empty compile time PYTHONPATH components bpo 28665 Improve speed of the STORE_DEREF opcode by 40 bpo 28583 PyDict_SetDefault didn t combine split table when needed Patch by Xiang Zhang bpo 27243 Change PendingDeprecationWarning DeprecationWarning As it was agreed in the issue __aiter__ returning an awaitable should result in PendingDeprecationWarning in 3 5 and in DeprecationWarning in 3 6 bpo 26182 Fix a refleak in code that raises DeprecationWarning bpo 28721 Fix asynchronous generators aclose and athrow to handle StopAsyncIteration propagation properly Library bpo 28752 Restored the __reduce__ methods of datetime objects bpo 28727 Regular expression patterns _sre SRE_Pattern objects created by re compile become comparable only x y and x y operators This change should fix the bpo 18383 don t duplicate warning filters when the warnings module is reloaded thing usually only done in unit tests bpo 20572 The subprocess Po,en
1778,pen wait method s undocumented endtime parameter now raises a DeprecationWarning bpo 25659 In ctypes prevent a crash calling the from_buffer and from_buffer_copy methods on abstract classes like Array bpo 19717 Makes Path resolve succeed on paths that do not exist Patch by Vajrasky Kok bpo 28563 Fixed possible DoS and arbitrary code execution when handle plural form selections in the gettext module The expression parser now supports exact syntax supported by GNU gettext bpo 28387 Fixed possible crash in _io TextIOWrapper deallocator when the garbage collector is invoked in other thread Based on patch by Sebastian Cufre bpo 28600 Optimize loop call_soon bpo 28613 Fix get_event_loop return the current loop if called from coroutines callbacks bpo 28634 Fix asyncio isfuture to support unittest Mock bpo 26081 Fix refleak in _asyncio Future __iter__ throw bpo 28639 Fix inspect isawaitable to always return bool Patch by Justin Mayfield bpo 28652 Make loop methods reject socket kinds they do not support bpo 28653 Fix a refleak in functools lru_cache bpo 28703 Fix asyncio iscoroutinefunction to handle Mock objects bpo 28704 Fix create_unix_server to support Path like objects PEP 519 bpo 28720 Add collections abc AsyncGenerator Documentation bpo 28513 Documented command line interface of zipfile Tests bpo 28666 Now test support rmtree is able to remove unwritable or unreadable directories bpo 23839 Various caches now are cleared before running every test file Build bpo 10656 Fix out of tree building on AIX Patch by Tristan Carel and Michael Haubenwallner bpo 26359 Rename with optimiations to enable optimizations bpo 28676 Prevent missing getentropy declaration warning on macOS Patch by Gareth Rees Python 3 6 0 beta 3 Release date 2016 10 31 Core and Builtins bpo 28128 Deprecation warning for invalid str and byte escape sequences now prints better information about where the error occurs Patch by Serhiy Storchaka and Eric Smith bpo 28509 dict update no longer allocate unnecessary large memory bpo 28426 Fixed potential crash in PyUnicode_AsDecodedObject in debug build bpo 28517 Fixed of by one error in the peephole optimizer that caused keeping unreachable code bpo 28214 Improved exception reporting for problematic __set_name__ attributes bpo 23782 Fixed possible memory leak in _PyTraceback_Add and exception loss in PyTraceBack_Here bpo 28471 Fix Python memory allocator called without holding the GIL crash in socket setblocking Library bpo 27517 LZMA compressor and decompressor no longer raise exceptions if given empty data twice Patch by Benjamin Fogle bpo 28549 Fixed segfault in curses s addch with ncurses6 bpo 28449 tarfile open with mode r or r now tries to open a tar file with compression before trying to open it without compression Otherwise it had 50 chance failed with ignore_zeros True bpo 23262 The webbrowser module now supports Firefox 36 and derived browsers Based on patch by Oleg Broytman bpo 27939 Fixed bugs in tkinter ttk LabeledScale and tkinter Scale caused by representing the scale as float value internally in Tk tkinter IntVar now works if float value is set to underlying Tk variable bpo 18844 The various ways of specifying weights for random choices now produce the same result sequences bpo 28255 calendar TextCalendar prmonth no longer prints a space at the start of new line after printing a month s calendar Patch by Xiang Zhang bpo 20491 The textwrap TextWrapper class now honors non breaking spaces Based on patch by Kaarle Ritvanen bpo 28353 os fwalk no longer fails on broken links bpo 28430 Fix iterator of C implemented asyncio Future doesn t accept non None value is passed to it send val bpo 27025 Generated names for Tkinter widgets now start by the prefix for readability bpo 25464 Fixed HList header_exists in tkinter tix module by addin a workaround to Tix library bug bpo 28488 shutil make_archive no longer adds entry to ZIP archive bpo 25953 re sub now raises an error for invalid numerical group reference in replacement template even if the pattern is not found in the string Error message for invalid group re,en
1779,ference now includes the group index and the position of the reference Based on patch by SilentGhost bpo 18219 Optimize csv DictWriter for large number of columns Patch by Mariatta Wijaya bpo 28448 Fix C implemented asyncio Future didn t work on Windows bpo 28480 Fix error building socket module when multithreading is disabled bpo 24452 Make webbrowser support Chrome on Mac OS X bpo 20766 Fix references leaked by pdb in the handling of SIGINT handlers bpo 28492 Fix how StopIteration exception is raised in _asyncio Future bpo 28500 Fix asyncio to handle async gens GC from another thread bpo 26923 Fix asyncio Gather to refuse being cancelled once all children are done Patch by Johannes Ebke bpo 26796 Don t configure the number of workers for default threadpool executor Initial patch by Hans Lawrenz bpo 28544 Implement asyncio Task in C Windows bpo 28522 Fixes mishandled buffer reallocation in getpathp c Build bpo 28444 Fix missing extensions modules when cross compiling bpo 28208 Update Windows build and OS X installers to use SQLite 3 14 2 bpo 28248 Update Windows build and OS X installers to use OpenSSL 1 0 2j Tests bpo 26944 Fix test_posix for Android where id G is entirely wrong or missing the effective gid bpo 28409 regrtest fix the parser of command line arguments Python 3 6 0 beta 2 Release date 2016 10 10 Core and Builtins bpo 28183 Optimize and cleanup dict iteration bpo 26081 Added C implementation of asyncio Future Original patch by Yury Selivanov bpo 28379 Added sanity checks and tests for PyUnicode_CopyCharacters Patch by Xiang Zhang bpo 28376 The type of long range iterator is now registered as Iterator Patch by Oren Milman bpo 28376 Creating instances of range_iterator by calling range_iterator type now is deprecated Patch by Oren Milman bpo 28376 The constructor of range_iterator now checks that step is not 0 Patch by Oren Milman bpo 26906 Resolving special methods of uninitialized type now causes implicit initialization of the type instead of a fail bpo 18287 PyType_Ready now checks that tp_name is not NULL Original patch by Niklas Koep bpo 24098 Fixed possible crash when AST is changed in process of compiling it bpo 28201 Dict reduces possibility of 2nd conflict in hash table when hashes have same lower bits bpo 28350 String constants with null character no longer interned bpo 26617 Fix crash when GC runs during weakref callbacks bpo 27942 String constants now interned recursively in tuples and frozensets bpo 21578 Fixed misleading error message when ImportError called with invalid keyword args bpo 28203 Fix incorrect type in complex 1 0 2 3 error message Patch by Soumya Sharma bpo 28086 Single var positional argument of tuple subtype was passed unscathed to the C defined function Now it is converted to exact tuple bpo 28214 Now __set_name__ is looked up on the class instead of the instance bpo 27955 Fallback on reading dev urandom device when the getrandom syscall fails with EPERM for example when blocked by SECCOMP bpo 28192 Don t import readline in isolated mode Upgrade internal unicode databases to Unicode version 9 0 0 bpo 28131 Fix a regression in zipimport s compile_source zipimport should use the same optimization level as the interpreter bpo 28126 Replace Py_MEMCPY with memcpy Visual Studio can properly optimize memcpy bpo 28120 Fix dict pop for splitted dictionary when trying to remove a pending key Not yet inserted in split table Patch by Xiang Zhang bpo 26182 Raise DeprecationWarning when async and await keywords are used as variable attribute class function name Library bpo 27998 Fixed bytes path support in os scandir on Windows Patch by Eryk Sun bpo 28317 The disassembler now decodes FORMAT_VALUE argument bpo 26293 Fixed writing ZIP files that starts not from the start of the file Offsets in ZIP file now are relative to the start of the archive in conforming to the specification bpo 28380 unittest mock Mock autospec functions now properly support assert_called assert_not_called and assert_called_once bpo 27181 remove statistics geometric_mean and defer until 3 7 bpo 28229 lzma module now sup,en
1780,ports pathlib bpo 28321 Fixed writing non BMP characters with binary format in plistlib bpo 28225 bz2 module now supports pathlib Initial patch by Ethan Furman bpo 28227 gzip now supports pathlib Patch by Ethan Furman bpo 27358 Optimized merging var keyword arguments and improved error message when passing a non mapping as a var keyword argument bpo 28257 Improved error message when passing a non iterable as a var positional argument Added opcode BUILD_TUPLE_UNPACK_WITH_CALL bpo 28322 Fixed possible crashes when unpickle itertools objects from incorrect pickle data Based on patch by John Leitch bpo 28228 imghdr now supports pathlib bpo 28226 compileall now supports pathlib bpo 28314 Fix function declaration C flags for the getiterator method of xml etree ElementTree Element bpo 28148 Stop using localtime and gmtime in the time module Introduced platform independent _PyTime_localtime API that is similar to POSIX localtime_r but available on all platforms Patch by Ed Schouten bpo 28253 Fixed calendar functions for extreme months 0001 01 and 9999 12 Methods itermonthdays and itermonthdays2 are reimplemented so that they don t call itermonthdates which can cause datetime date under overflow bpo 28275 Fixed possible use after free in the decompress methods of the LZMADecompressor and BZ2Decompressor classes Original patch by John Leitch bpo 27897 Fixed possible crash in sqlite3 Connection create_collation if pass invalid string like object as a name Patch by Xiang Zhang bpo 18844 random choices now has k as a keyword only argument to improve the readability of common cases and come into line with the signature used in other languages bpo 18893 Fix invalid exception handling in Lib ctypes macholib dyld py Patch by Madison May bpo 27611 Fixed support of default root window in the tkinter tix module Added the master parameter in the DisplayStyle constructor bpo 27348 In the traceback module restore the formatting of exception messages like Exception None This fixes a regression introduced in 3 5a2 bpo 25651 Allow false values to be used for msg parameter of subTest bpo 27778 Fix a memory leak in os getrandom when the getrandom is interrupted by a signal and a signal handler raises a Python exception bpo 28200 Fix memory leak on Windows in the os module fix path_converter function bpo 25400 RobotFileParser now correctly returns default values for crawl_delay and request_rate Initial patch by Peter Wirtz bpo 27932 Prevent memory leak in win32_ver Fix UnboundLocalError in socket _sendfile_use_sendfile bpo 28075 Check for ERROR_ACCESS_DENIED in Windows implementation of os stat Patch by Eryk Sun bpo 22493 Warning message emitted by using inline flags in the middle of regular expression now contains a truncated regex pattern Patch by Tim Graham bpo 25270 Prevent codecs escape_encode from raising SystemError when an empty bytestring is passed bpo 28181 Get antigravity over HTTPS Patch by Kaartic Sivaraam bpo 25895 Enable WebSocket URL schemes in urllib parse urljoin Patch by Gergely Imreh and Markus Holtermann bpo 28114 Fix a crash in parse_envlist when env contains byte strings Patch by Eryk Sun bpo 27599 Fixed buffer overrun in binascii b2a_qp and binascii a2b_qp bpo 27906 Fix socket accept exhaustion during high TCP traffic Patch by Kevin Conway bpo 28174 Handle when SO_REUSEPORT isn t properly supported Patch by Seth Michael Larson bpo 26654 Inspect functools partial in asyncio Handle __repr__ Patch by iceboy bpo 26909 Fix slow pipes IO in asyncio Patch by INADA Naoki bpo 28176 Fix callbacks race in asyncio SelectorLoop sock_connect bpo 27759 Fix selectors incorrectly retain invalid file descriptors Patch by Mark Williams bpo 28368 Refuse monitoring processes if the child watcher has no loop attached Patch by Vincent Michel bpo 28369 Raise RuntimeError when transport s FD is used with add_reader add_writer etc bpo 28370 Speedup asyncio StreamReader readexactly Patch by Коренберг Марк bpo 28371 Deprecate passing asyncio Handles to run_in_executor bpo 28372 Fix asyncio to support formatting of non python coroutines bpo 28399 Remove ,en
1781,UNIX socket from FS before binding Patch by Коренберг Марк bpo 27972 Prohibit Tasks to await on themselves Windows bpo 28402 Adds signed catalog files for stdlib on Windows bpo 28333 Enables Unicode for ps1 ps2 and input prompts Patch by Eryk Sun bpo 28251 Improvements to help manuals on Windows bpo 28110 launcher msi has different product codes between 32 bit and 64 bit bpo 28161 Opening CON for write access fails bpo 28162 WindowsConsoleIO readall fails if first line starts with Ctrl Z bpo 28163 WindowsConsoleIO fileno passes wrong flags to _open_osfhandle bpo 28164 _PyIO_get_console_type fails for various paths bpo 28137 Renames Windows path file to _pth bpo 28138 Windows _pth file should allow import site C API bpo 28426 Deprecated undocumented functions PyUnicode_AsEncodedObject PyUnicode_AsDecodedObject PyUnicode_AsDecodedUnicode and PyUnicode_AsEncodedUnicode Build bpo 28258 Fixed build with Estonian locale python config and distclean targets in Makefile Patch by Arfrever Frehtes Taifersar Arahesis bpo 26661 setup py now detects system libffi with multiarch wrapper bpo 15819 Remove redundant include search directory option for building outside the source tree Tests bpo 28217 Adds _testconsole module to test console input Python 3 6 0 beta 1 Release date 2016 09 12 Core and Builtins bpo 23722 The __class__ cell used by zero argument super is now initialized from type __new__ rather than __build_class__ so class methods relying on that will now work correctly when called from metaclass methods during class creation Patch by Martin Teichmann bpo 25221 Fix corrupted result from PyLong_FromLong 0 when Python is compiled with NSMALLPOSINTS 0 bpo 27080 Implement formatting support for PEP 515 Initial patch by Chris Angelico bpo 27199 In tarfile expose copyfileobj bufsize to improve throughput Patch by Jason Fried bpo 27948 In f strings only allow backslashes inside the braces where the expressions are This is a breaking change from the 3 6 alpha releases where backslashes are allowed anywhere in an f string Also require that expressions inside f strings be enclosed within literal braces and not escapes like f x7b hi x7d bpo 28046 Remove platform specific directories from sys path bpo 28071 Add early out for differencing from an empty set bpo 25758 Prevents zipimport from unnecessarily encoding a filename patch by Eryk Sun bpo 25856 The __module__ attribute of extension classes and functions now is interned This leads to more compact pickle data with protocol 4 bpo 27213 Rework CALL_FUNCTION opcodes to produce shorter and more efficient bytecode Patch by Demur Rumed design by Serhiy Storchaka reviewed by Serhiy Storchaka and Victor Stinner bpo 26331 Implement tokenizing support for PEP 515 Patch by Georg Brandl bpo 27999 Make global after use a SyntaxError and ditto for nonlocal Patch by Ivan Levkivskyi bpo 28003 Implement PEP 525 Asynchronous Generators bpo 27985 Implement PEP 526 Syntax for Variable Annotations Patch by Ivan Levkivskyi bpo 26058 Add a new private version to the builtin dict type incremented at each dictionary creation and at each dictionary change Implementation of the PEP 509 bpo 27364 A backslash character pair that is not a valid escape sequence now generates a DeprecationWarning Patch by Emanuel Barry bpo 27350 dict implementation is changed like PyPy It is more compact and preserves insertion order Concept developed by Raymond Hettinger and patch by Inada Naoki bpo 27911 Remove unnecessary error checks in exec_builtin_or_dynamic bpo 27078 Added BUILD_STRING opcode Optimized f strings evaluation bpo 17884 Python now requires systems with inttypes h and stdint h bpo 27961 Require platforms to support long long Python hasn t compiled without long long for years so this is basically a formality bpo 27355 Removed support for Windows CE It was never finished and Windows CE is no longer a relevant platform for Python Implement PEP 523 bpo 27870 A left shift of zero by a large integer no longer attempts to allocate large amounts of memory bpo 25402 In int to decimal string conversion improve the estimate o,en
1782,f the intermediate memory required and remove an unnecessarily strict overflow check Patch by Serhiy Storchaka bpo 27214 In long_invert be more careful about modifying object returned by long_add and remove an unnecessary check for small longs Thanks Oren Milman for analysis and patch bpo 27506 Support passing the bytes bytearray translate delete argument by keyword bpo 27812 Properly clear out a generator s frame s backreference to the generator to prevent crashes in frame clear bpo 27811 Fix a crash when a coroutine that has not been awaited is finalized with warnings as errors enabled bpo 27587 Fix another issue found by PVS Studio Null pointer check after use of def in _PyState_AddModule Initial patch by Christian Heimes bpo 27792 The modulo operation applied to bool and other int subclasses now always returns an int Previously the return type depended on the input values Patch by Xiang Zhang bpo 26984 int now always returns an instance of exact int bpo 25604 Fix a minor bug in integer true division this bug could potentially have caused off by one ulp results on platforms with unreliable ldexp implementations bpo 24254 Make class definition namespace ordered by default bpo 27662 Fix an overflow check in List_New the original code was checking against Py_SIZE_MAX instead of the correct upper bound of Py_SSIZE_T_MAX Patch by Xiang Zhang bpo 27782 Multi phase extension module import now correctly allows the m_methods field to be used to add module level functions to instances of non module types returned from Py_create_mod Patch by Xiang Zhang bpo 27936 The round function accepted a second None argument for some types but not for others Fixed the inconsistency by accepting None for all numeric types bpo 27487 Warn if a submodule argument to python m or runpy run_module is found in sys modules after parent packages are imported but before the submodule is executed bpo 27157 Make only type itself accept the one argument form Patch by Eryk Sun and Emanuel Barry bpo 27558 Fix a SystemError in the implementation of raise statement In a brand new thread raise a RuntimeError since there is no active exception to reraise Patch written by Xiang Zhang bpo 28008 Implement PEP 530 asynchronous comprehensions bpo 27942 Fix memory leak in codeobject c Library bpo 28732 Fix crash in os spawnv with no elements in args bpo 28485 Always raise ValueError for negative compileall compile_dir workers parameter even when multithreading is unavailable bpo 28037 Use sqlite3_get_autocommit instead of setting Connection inTransaction manually bpo 25283 Attributes tm_gmtoff and tm_zone are now available on all platforms in the return values of time localtime and time gmtime bpo 24454 Regular expression match object groups are now accessible using __getitem__ mo x is equivalent to mo group x bpo 10740 sqlite3 no longer implicitly commit an open transaction before DDL statements bpo 17941 Add a module parameter to collections namedtuple bpo 22493 Inline flags now should be used only at the start of the regular expression Deprecation warning is emitted if uses them in the middle of the regular expression bpo 26885 xmlrpc now supports unmarshalling additional data types used by Apache XML RPC implementation for numerics and None bpo 28070 Fixed parsing inline verbose flag in regular expressions bpo 19500 Add client side SSL session resumption to the ssl module bpo 28022 Deprecate ssl related arguments in favor of SSLContext The deprecation include manual creation of SSLSocket and certfile keyfile or similar in ftplib httplib imaplib smtplib poplib and urllib bpo 28043 SSLContext has improved default settings OP_NO_SSLv2 OP_NO_SSLv3 OP_NO_COMPRESSION OP_CIPHER_SERVER_PREFERENCE OP_SINGLE_DH_USE OP_SINGLE_ECDH_USE and HIGH ciphers without MD5 bpo 24693 Changed some RuntimeError s in the zipfile module to more appropriate types Improved some error messages and debugging output bpo 17909 json load and json loads now support binary input encoded as UTF 8 UTF 16 or UTF 32 Patch by Serhiy Storchaka bpo 27137 the pure Python fallback implementation of functo,en
1783,ols partial now matches the behaviour of its accelerated C counterpart for subclassing pickling and text representation purposes Patch by Emanuel Barry and Serhiy Storchaka Fix possible integer overflows and crashes in the mmap module with unusual usage patterns bpo 1703178 Fix the ability to pass the link objects option to the distutils build_ext command bpo 28019 itertools count no longer rounds non integer step in range between 1 0 and 2 0 to 1 bpo 18401 Pdb now supports the readrc keyword argument to control whether pdbrc files should be read Patch by Martin Matusiak and Sam Kimbrel bpo 25969 Update the lib2to3 grammar to handle the unpacking generalizations added in 3 5 bpo 14977 mailcap now respects the order of the lines in the mailcap files first match as required by RFC 1542 Patch by Michael Lazar bpo 28082 Convert re flag constants to IntFlag bpo 28025 Convert all ssl module constants to IntEnum and IntFlags SSLContext properties now return flags and enums bpo 23591 Add Flag IntFlag and auto to enum module bpo 433028 Added support of modifier spans in regular expressions bpo 24594 Validates persist parameter when opening MSI database bpo 17582 xml etree ElementTree nows preserves whitespaces in attributes Patch by Duane Griffin Reviewed and approved by Stefan Behnel bpo 28047 Fixed calculation of line length used for the base64 CTE in the new email policies bpo 27576 Fix call order in OrderedDict __init__ email generator DecodedGenerator now supports the policy keyword bpo 28027 Remove undocumented modules from Lib plat IN CDROM DLFCN TYPES CDIO and STROPTS bpo 27445 Don t pass str _charset to MIMEText set_payload Patch by Claude Paroz bpo 24277 The new email API is no longer provisional and the docs have been reorganized and rewritten to emphasize the new API bpo 22450 urllib now includes an Accept header among the default headers This makes the results of REST API requests more consistent and predictable especially when proxy servers are involved lib2to3 pgen3 driver load_grammar now creates a stable cache file between runs given the same Grammar txt input regardless of the hash randomization setting bpo 28005 Allow ImportErrors in encoding implementation to propagate bpo 26667 Support path like objects in importlib util bpo 27570 Avoid zero length memcpy etc calls with null source pointers in the ctypes and array modules bpo 22233 Break email header lines only on the RFC specified CR and LF characters not on arbitrary unicode line breaks This also fixes a bug in HTTP header parsing bpo 27331 The email mime classes now all accept an optional policy keyword bpo 27988 Fix email iter_attachments incorrect mutation of payload list bpo 16113 Add SHA 3 and SHAKE support to hashlib module Eliminate a tautological pointer compare warning in _scproxy c bpo 27776 The os urandom function does now block on Linux 3 17 and newer until the system urandom entropy pool is initialized to increase the security This change is part of the PEP 524 bpo 27778 Expose the Linux getrandom syscall as a new os getrandom function This change is part of the PEP 524 bpo 27691 Fix ssl module s parsing of GEN_RID subject alternative name fields in X 509 certs bpo 18844 Add random choices bpo 25761 Improved error reporting about truncated pickle data in C implementation of unpickler UnpicklingError is now raised instead of AttributeError and ValueError in some cases bpo 26798 Add BLAKE2 blake2b and blake2s to hashlib bpo 26032 Optimized globbing in pathlib by using os scandir it is now about 1 5 4 times faster bpo 25596 Optimized glob and iglob functions in the glob module they are now about 3 6 times faster bpo 27928 Add scrypt password based key derivation function to hashlib module requires OpenSSL 1 1 0 bpo 27850 Remove 3DES from ssl module s default cipher list to counter measure sweet32 attack CVE 2016 2183 bpo 27766 Add ChaCha20 Poly1305 to ssl module s default cipher list Required OpenSSL 1 1 0 or LibreSSL bpo 25387 Check return value of winsound MessageBeep bpo 27866 Add SSLContext get_ciphers method to get a list of all enabled ciphe,en
1784,rs bpo 27744 Add AF_ALG Linux Kernel crypto to socket module bpo 26470 Port ssl and hashlib module to OpenSSL 1 1 0 bpo 11620 Fix support for SND_MEMORY in winsound PlaySound Based on a patch by Tim Lesher bpo 11734 Add support for IEEE 754 half precision floats to the struct module Based on a patch by Eli Stevens bpo 27919 Deprecated extra_path distribution option in distutils packaging bpo 23229 Add new cmath constants cmath inf and cmath nan to match math inf and math nan and also cmath infj and cmath nanj to match the format used by complex repr bpo 27842 The csv DictReader now returns rows of type OrderedDict Contributed by Steve Holden Remove support for passing a file descriptor to os access It never worked but previously didn t raise bpo 12885 Fix error when distutils encounters symlink bpo 27881 Fixed possible bugs when setting sqlite3 Connection isolation_level Based on patch by Xiang Zhang bpo 27861 Fixed a crash in sqlite3 Connection cursor when a factory creates not a cursor Patch by Xiang Zhang bpo 19884 Avoid spurious output on OS X with Gnu Readline bpo 27706 Restore deterministic behavior of random Random seed for string seeds using seeding version 1 Allows sequences of calls to random to exactly match those obtained in Python 2 Patch by Nofar Schnider bpo 10513 Fix a regression in Connection commit Statements should not be reset after a commit bpo 12319 Chunked transfer encoding support added to http client HTTPConnection requests The urllib request AbstractHTTPHandler class does not enforce a Content Length header any more If a HTTP request has a file or iterable body but no Content Length header the library now falls back to use chunked transfer encoding A new version of typing py from https github com python typing Collection only for 3 6 bpo 27598 Add FrozenSet to __all__ upstream 261 fix crash in _get_type_vars upstream 259 Remove the dict constraint in ForwardRef _eval_type upstream 252 bpo 27832 Make _normalize parameter to Fraction constructor keyword only so that Fraction 2 3 4 now raises TypeError bpo 27539 Fix unnormalised Fraction __pow__ result in the case of negative exponent and negative base bpo 21718 cursor description is now available for queries using CTEs bpo 27819 In distutils sdists simply produce the gztar gzipped tar format distributions on all platforms unless formats is supplied bpo 2466 posixpath ismount now correctly recognizes mount points which the user does not have permission to access bpo 9998 On Linux ctypes util find_library now looks in LD_LIBRARY_PATH for shared libraries bpo 27573 exit message for code interact is now configurable bpo 27930 Improved behaviour of logging handlers QueueListener Thanks to Paulo Andrade and Petr Viktorin for the analysis and patch bpo 6766 Distributed reference counting added to multiprocessing to support nesting of shared values proxy objects bpo 21201 Improves readability of multiprocessing error message Thanks to Wojciech Walczak for patch asyncio Add set_protocol get_protocol to Transports bpo 27456 asyncio Set TCP_NODELAY by default IDLE bpo 15308 Add interrupt execution C to Shell menu Patch by Roger Serwy updated by Bayard Randel bpo 27922 Stop IDLE tests from flashing gui widgets on the screen bpo 27891 Consistently group and sort imports within idlelib modules bpo 17642 add larger font sizes for classroom projection Add version to title of IDLE help window bpo 25564 In section on IDLE console differences mention that using exec means that __builtins__ is defined for each statement bpo 27821 Fix 3 6 0a3 regression that prevented custom key sets from being selected when no custom theme was defined C API bpo 26900 Excluded underscored names and other private API from limited API bpo 26027 Add support for path like objects in PyUnicode_FSConverter PyUnicode_FSDecoder Tests bpo 27427 Additional tests for the math module Patch by Francisco Couzo bpo 27953 Skip math and cmath tests that fail on OS X 10 4 due to a poor libm implementation of tan bpo 26040 Improve test_math and test_cmath coverage and rigour Patch by Jeff Allen bpo 2778,en
1785,7 Call gc collect before checking each test for dangling threads since the dangling threads are weak references Build bpo 27566 Fix clean target in freeze makefile patch by Lisa Roach bpo 27705 Update message in validate_ucrtbase py bpo 27976 Deprecate building _ctypes with the bundled copy of libffi on non OSX UNIX platforms bpo 27983 Cause lack of llvm profdata tool when using clang as required for PGO linking to be a configure time error rather than make time when with optimizations is enabled Also improve our ability to find the llvm profdata tool on MacOS and some Linuxes bpo 21590 Support for DTrace and SystemTap probes bpo 26307 The profile opt build now applies PGO to the built in modules bpo 26359 Add the with optimizations flag to turn on LTO and PGO build support when available bpo 27917 Set platform triplets for Android builds bpo 25825 Update references to the LIBPL installation path on AIX This path was changed in 3 2a4 Update OS X installer to use SQLite 3 14 1 and XZ 5 2 2 bpo 21122 Fix LTO builds on OS X bpo 17128 Build OS X installer with a private copy of OpenSSL Also provide a sample Install Certificates command script to install a set of root certificates from the third party certifi module Tools Demos bpo 27952 Get Tools scripts fixcid py working with Python 3 and the current re module avoid invalid Python backslash escapes and fix a bug parsing escaped C quote signs Windows bpo 28065 Update xz dependency to 5 2 2 and build it from source bpo 25144 Ensures TargetDir is set before continuing with custom install bpo 1602 Windows console doesn t input or print Unicode PEP 528 bpo 27781 Change file system encoding on Windows to UTF 8 PEP 529 bpo 27731 Opt out of MAX_PATH on Windows 10 bpo 6135 Adds encoding and errors parameters to subprocess bpo 27959 Adds oem encoding alias ansi to mbcs move aliasmbcs to codec lookup bpo 27982 The functions of the winsound module now accept keyword arguments bpo 20366 Build full text search support into SQLite on Windows bpo 27756 Adds new icons for Python files and processes on Windows Designs by Cherry Wang bpo 27883 Update sqlite to 3 14 1 0 on Windows Python 3 6 0 alpha 4 Release date 2016 08 15 Core and Builtins bpo 27704 Optimized creating bytes and bytearray from byte like objects and iterables Speed up to 3 times for short objects Original patch by Naoki Inada bpo 26823 Large sections of repeated lines in tracebacks are now abbreviated as Previous line repeated count more times by the builtin traceback rendering Patch by Emanuel Barry bpo 27574 Decreased an overhead of parsing keyword arguments in functions implemented with using Argument Clinic bpo 22557 Now importing already imported modules is up to 2 5 times faster bpo 17596 Include wincrypt h to help with Min GW building bpo 17599 On Windows rename the privately defined REPARSE_DATA_BUFFER structure to avoid conflicting with the definition from Min GW bpo 27507 Add integer overflow check in bytearray extend Patch by Xiang Zhang bpo 27581 Don t rely on wrapping for overflow check in PySequence_Tuple Patch by Xiang Zhang bpo 1621 Avoid signed integer overflow in list and tuple operations Patch by Xiang Zhang bpo 27419 Standard __import__ no longer look up __import__ in globals or builtins for importing submodules or from import Fixed a crash if raise a warning about unabling to resolve package from __spec__ or __package__ bpo 27083 Respect the PYTHONCASEOK environment variable under Windows bpo 27514 Make having too many statically nested blocks a SyntaxError instead of SystemError bpo 27366 Implemented PEP 487 Simpler customization of class creation Upon subclassing the __init_subclass__ classmethod is called on the base class Descriptors are initialized with __set_name__ after class creation Library bpo 26027 Add PEP 519 __fspath__ support to the os and os path modules Includes code from Jelle Zijlstra See also bpo 27524 bpo 27598 Add Collections to collections abc Patch by Ivan Levkivskyi docs by Neil Girdhar bpo 25958 Support anti registration of special methods from various ABCs like __hash__ __iter__ ,en
1786,or __len__ All these and several more can be set to None in an implementation class and the behavior will be as if the method is not defined at all Previously this mechanism existed only for __hash__ to make mutable classes unhashable Code contributed by Andrew Barnert and Ivan Levkivskyi bpo 16764 Support keyword arguments to zlib decompress Patch by Xiang Zhang bpo 27736 Prevent segfault after interpreter re initialization due to ref count problem introduced in code for bpo 27038 in 3 6 0a3 Patch by Xiang Zhang bpo 25628 The verbose and rename parameters for collections namedtuple are now keyword only bpo 12345 Add mathematical constant tau to math and cmath See also PEP 628 bpo 26823 traceback StackSummary format now abbreviates large sections of repeated lines as Previous line repeated count more times this change then further affects other traceback display operations in the module Patch by Emanuel Barry bpo 27664 Add to concurrent futures thread ThreadPoolExecutor the ability to specify a thread name prefix bpo 27181 Add geometric_mean and harmonic_mean to statistics module bpo 27573 code interact now prints an message when exiting bpo 6422 Add autorange method to timeit Timer objects bpo 27773 Correct some memory management errors server_hostname in _ssl wrap_socket bpo 26750 unittest mock create_autospec now works properly for subclasses of property and other data descriptors Removes the never publicly used never documented unittest mock DescriptorTypes tuple bpo 26754 Undocumented support of general bytes like objects as path in compile and similar functions is now deprecated bpo 26800 Undocumented support of general bytes like objects as paths in os functions is now deprecated bpo 26981 Add _order_ compatibility shim to enum Enum for Python 2 3 code bases bpo 27661 Added tzinfo keyword argument to datetime combine In the curses module raise an error if window getstr or window instr is passed a negative value bpo 27783 Fix possible usage of uninitialized memory in operator methodcaller bpo 27774 Fix possible Py_DECREF on unowned object in _sre bpo 27760 Fix possible integer overflow in binascii b2a_qp bpo 27758 Fix possible integer overflow in the _csv module for large record lengths bpo 27568 Prevent HTTPoxy attack CVE 2016 1000110 Ignore the HTTP_PROXY variable when REQUEST_METHOD environment is set which indicates that the script is in CGI mode bpo 7063 Remove dead code from the array module s slice handling Patch by Chuck bpo 27656 Do not assume sched h defines any SCHED_ constants bpo 27130 In the zlib module fix handling of large buffers typically 4 GiB when compressing and decompressing Previously inputs were limited to 4 GiB and compression and decompression operations did not properly handle results of 4 GiB bpo 24773 Implemented PEP 495 Local Time Disambiguation Expose the EPOLLEXCLUSIVE constant when it is defined in the select module bpo 27567 Expose the EPOLLRDHUP and POLLRDHUP constants in the select module bpo 1621 Avoid signed int negation overflow in the audioop module bpo 27533 Release GIL in nt _isdir bpo 17711 Fixed unpickling by the persistent ID with protocol 0 Original patch by Alexandre Vassalotti bpo 27522 Avoid an unintentional reference cycle in email feedparser bpo 27512 Fix a segfault when os fspath called an __fspath__ method that raised an exception Patch by Xiang Zhang IDLE bpo 27714 text_textview and test_autocomplete now pass when re run in the same process This occurs when test_idle fails when run with the w option but without jn Fix warning from test_config bpo 27621 Put query response validation error messages in the query box itself instead of in a separate messagebox Redo tests to match Add Mac OSX refinements Original patch by Mark Roseman bpo 27620 Escape key now closes Query box as cancelled bpo 27609 IDLE tab after initial whitespace should tab not autocomplete This fixes problem with writing docstrings at least twice indented bpo 27609 Explicitly return None when there are also non None returns In a few cases reverse a condition and eliminate a return bpo 25507 IDLE no,en
1787, longer runs buggy code because of its tkinter imports Users must include the same imports required to run directly in Python bpo 27173 Add IDLE Modern Unix to the built in key sets Make the default key set depend on the platform Add tests for the changes to the config module bpo 27452 add line counter and crc to IDLE configHandler test dump Tests bpo 25805 Skip a test in test_pkgutil as needed that doesn t work when __name__ __main__ Patch by SilentGhost bpo 27472 Add test support unix_shell as the path to the default shell bpo 27369 In test_pyexpat avoid testing an error message detail that changed in Expat 2 2 0 bpo 27594 Prevent assertion error when running test_ast with coverage enabled ensure code object has a valid first line number Patch suggested by Ivan Levkivskyi Windows bpo 27647 Update bundled Tcl Tk to 8 6 6 bpo 27610 Adds PEP 514 metadata to Windows installer bpo 27469 Adds a shell extension to the launcher so that drag and drop works correctly bpo 27309 Enables proper Windows styles in python w exe manifest Build bpo 27713 Suppress spurious build warnings when updating importlib s bootstrap files Patch by Xiang Zhang bpo 25825 Correct the references to Modules python exp which is required on AIX The references were accidentally changed in 3 5 0a1 bpo 27453 CPP invocation in configure must use CPPFLAGS Patch by Chi Hsuan Yen bpo 27641 The configure script now inserts comments into the makefile to prevent the pgen and _freeze_importlib executables from being cross compiled bpo 26662 Set PYTHON_FOR_GEN in configure as the Python program to be used for file generation during the build bpo 10910 Avoid C compilation errors on FreeBSD and OS X Also update FreedBSD version checks for the original ctype UTF 8 workaround Python 3 6 0 alpha 3 Release date 2016 07 11 Security bpo 27278 Fix os urandom implementation using getrandom on Linux Truncate size to INT_MAX and loop until we collected enough random bytes instead of casting a directly Py_ssize_t to int bpo 22636 Avoid shell injection problems with ctypes util find_library Core and Builtins bpo 27473 Fixed possible integer overflow in bytes and bytearray concatenations Patch by Xiang Zhang bpo 23034 The output of a special Python build with defined COUNT_ALLOCS SHOW_ALLOC_COUNT or SHOW_TRACK_COUNT macros is now off by default It can be re enabled using the X showalloccount option It now outputs to stderr instead of stdout bpo 27443 __length_hint__ of bytearray iterators no longer return a negative integer for a resized bytearray bpo 27007 The fromhex class methods of bytes and bytearray subclasses now return an instance of corresponding subclass Library bpo 26844 Fix error message for imp find_module to refer to path instead of name Patch by Lev Maximov bpo 23804 Fix SSL zero length recv calls to not block and not raise an error about unclean EOF bpo 27466 Change time format returned by http cookie time2netscape confirming the netscape cookie format and making it consistent with documentation bpo 21708 Deprecated dbm dumb behavior that differs from common dbm behavior creating a database in r and w modes and modifying a database in r mode bpo 26721 Change the socketserver StreamRequestHandler wfile attribute to implement BufferedIOBase In particular the write method no longer does partial writes bpo 22115 Added methods trace_add trace_remove and trace_info in the tkinter Variable class They replace old methods trace_variable trace trace_vdelete and trace_vinfo that use obsolete Tcl commands and might not work in future versions of Tcl Fixed old tracing methods trace_vdelete with wrong mode no longer break tracing trace_vinfo now always returns a list of pairs of strings tracing in the u mode now works bpo 26243 Only the level argument to zlib compress is keyword argument now The first argument is positional only bpo 27038 Expose the DirEntry type as os DirEntry Code patch by Jelle Zijlstra bpo 27186 Update os fspath PyOS_FSPath to check the return value of __fspath__ to be either str or bytes bpo 18726 All optional parameters of the dump dumps load and loads fun,en
1788,ctions and JSONEncoder and JSONDecoder class constructors in the json module are now keyword only bpo 27319 Methods selection_set selection_add selection_remove and selection_toggle of ttk TreeView now allow passing multiple items as multiple arguments instead of passing them as a tuple Deprecated undocumented ability of calling the selection method with arguments bpo 27079 Fixed curses ascii functions isblank iscntrl and ispunct bpo 27294 Numerical state in the repr for Tkinter event objects is now represented as a combination of known flags bpo 27177 Match objects in the re module now support index like objects as group indices Based on patches by Jeroen Demeyer and Xiang Zhang bpo 26754 Some functions compile etc accepted a filename argument encoded as an iterable of integers Now only strings and byte like objects are accepted bpo 26536 socket ioctl now supports SIO_LOOPBACK_FAST_PATH Patch by Daniel Stokes bpo 27048 Prevents distutils failing on Windows when environment variables contain non ASCII characters bpo 27330 Fixed possible leaks in the ctypes module bpo 27238 Got rid of bare excepts in the turtle module Original patch by Jelle Zijlstra bpo 27122 When an exception is raised within the context being managed by a contextlib ExitStack and one of the exit stack generators catches and raises it in a chain do not re raise the original exception when exiting let the new chained one through This avoids the PEP 479 bug described in issue25782 bpo 16864 sqlite3 Cursor lastrowid now supports REPLACE statement Initial patch by Alex LordThorsen bpo 26386 Fixed ttk TreeView selection operations with item id s containing spaces bpo 8637 Honor a pager set by the env var MANPAGER in preference to one set by the env var PAGER bpo 16182 Fix various functions in the readline module to use the locale encoding and fix get_begidx and get_endidx to return code point indexes bpo 27392 Add loop connect_accepted_socket Patch by Jim Fulton IDLE bpo 27477 IDLE search dialogs now use ttk widgets bpo 27173 Add IDLE Modern Unix to the built in key sets Make the default key set depend on the platform Add tests for the changes to the config module bpo 27452 make command line idle test python test_help py work __file__ is relative when python is started in the file s directory bpo 27452 add line counter and crc to IDLE configHandler test dump bpo 27380 IDLE add query py with base Query dialog and ttk widgets Module had subclasses SectionName ModuleName and HelpSource which are used to get information from users by configdialog and file Load Module Each subclass has itw own validity checks Using ModuleName allows users to edit bad module names instead of starting over Add tests and delete the two files combined into the new one bpo 27372 Test_idle no longer changes the locale bpo 27365 Allow non ascii chars in IDLE NEWS txt for contributor names bpo 27245 IDLE Cleanly delete custom themes and key bindings Previously when IDLE was started from a console or by import a cascade of warnings was emitted Patch by Serhiy Storchaka bpo 24137 Run IDLE test_idle and htest with tkinter default root disabled Fix code and tests that fail with this restriction Fix htests to not create a second and redundant root and mainloop bpo 27310 Fix IDLE app failure to launch on OS X due to vestigial import C API bpo 26754 PyUnicode_FSDecoder accepted a filename argument encoded as an iterable of integers Now only strings and byte like objects are accepted Build bpo 28066 Fix the logic that searches build directories for generated include files when building outside the source tree bpo 27442 Expose the Android API level that python was built against in sysconfig get_config_vars as ANDROID_API_LEVEL bpo 27434 The interpreter that runs the cross build found in PATH must now be of the same feature version e g 3 6 as the source being built bpo 26930 Update Windows builds to use OpenSSL 1 0 2h bpo 23968 Rename the platform directory from plat MACHDEP to plat PLATFORM_TRIPLET Rename the config directory LIBPL from config LDVERSION to config LDVERSION PLATFORM_TRIPLET Instal,en
1789,l the platform specific _sysconfigdata module into the platform directory and rename it to include the ABIFLAGS Don t use largefile support for GNU Hurd Tools Demos bpo 27332 Fixed the type of the first argument of module level functions generated by Argument Clinic Patch by Petr Viktorin bpo 27418 Fixed Tools importbench importbench py Documentation bpo 19489 Moved the search box from the sidebar to the header and footer of each page Patch by Ammar Askar bpo 27285 Update documentation to reflect the deprecation of pyvenv and normalize on the term virtual environment Patch by Steve Piercy Tests bpo 27027 Added test support is_android that is True when this is an Android build Python 3 6 0 alpha 2 Release date 2016 06 13 Security bpo 26556 Update expat to 2 1 1 fixes CVE 2015 1283 Fix TLS stripping vulnerability in smtplib CVE 2016 0772 Reported by Team Oststrom bpo 26839 On Linux os urandom now calls getrandom with GRND_NONBLOCK to fall back on reading dev urandom if the urandom entropy pool is not initialized yet Patch written by Colm Buckley Core and Builtins bpo 27095 Simplified MAKE_FUNCTION and removed MAKE_CLOSURE opcodes Patch by Demur Rumed bpo 27190 Raise NotSupportedError if sqlite3 is older than 3 3 1 Patch by Dave Sawyer bpo 27286 Fixed compiling BUILD_MAP_UNPACK_WITH_CALL opcode Calling function with generalized unpacking PEP 448 and conflicting keyword names could cause undefined behavior bpo 27140 Added BUILD_CONST_KEY_MAP opcode bpo 27186 Add support for os PathLike objects to open part of PEP 519 bpo 27066 Fixed SystemError if a custom opener for open returns a negative number without setting an exception bpo 26983 float now always return an instance of exact float The deprecation warning is emitted if __float__ returns an instance of a strict subclass of float In a future versions of Python this can be an error bpo 27097 Python interpreter is now about 7 faster due to optimized instruction decoding Based on patch by Demur Rumed bpo 26647 Python interpreter now uses 16 bit wordcode instead of bytecode Patch by Demur Rumed bpo 23275 Allow assigning to an empty target list in round brackets iterable bpo 27243 Update the __aiter__ protocol instead of returning an awaitable that resolves to an asynchronous iterator the asynchronous iterator should be returned directly Doing the former will trigger a PendingDeprecationWarning Library Comment out socket SO_REUSEPORT and posix O_SHLOCK O_EXLOCK constants exposed on the API which are not implemented on GNU Hurd They would not work at runtime anyway bpo 27025 Generated names for Tkinter widgets are now more meaningful and recognizable bpo 25455 Fixed crashes in repr of recursive ElementTree Element and functools partial objects bpo 27294 Improved repr for Tkinter event objects bpo 20508 Improve exception message of IPv 4 6 Network __getitem__ Patch by Gareth Rees bpo 21386 Implement missing IPv4Address is_global property It was documented since 07a5610bae9d Initial patch by Roger Luethi bpo 27029 Removed deprecated support of universal newlines mode from ZipFile open bpo 27030 Unknown escapes consisting of and an ASCII letter in regular expressions now are errors The re LOCALE flag now can be used only with bytes patterns bpo 27186 Add os PathLike support to DirEntry part of PEP 519 Initial patch by Jelle Zijlstra bpo 20900 distutils register command now decodes HTTP responses correctly Initial patch by ingrid bpo 27186 Add os PathLike support to pathlib removing its provisional status part of PEP 519 Initial patch by Dusty Phillips bpo 27186 Add support for os PathLike objects to os fsencode and os fsdecode part of PEP 519 bpo 27186 Introduce os PathLike and os fspath part of PEP 519 A new version of typing py provides several new classes and features overload outside stubs Reversible DefaultDict Text ContextManager Type NewType TYPE_CHECKING and numerous bug fixes note that some of the new features are not yet implemented in mypy or other static analyzers Also classes for PEP 492 Awaitable AsyncIterable AsyncIterator have been added in fact they made it into 3 ,en
1790,5 1 but were never mentioned bpo 25738 Stop http server BaseHTTPRequestHandler send_error from sending a message body for 205 Reset Content Also don t send Content header fields in responses that don t have a body Patch by Susumu Koshiba bpo 21313 Fix the platform module to tolerate when sys version contains truncated build information bpo 23883 Added missing APIs to __all__ to match the documented APIs for the following modules cgi mailbox mimetypes plistlib and smtpd Patches by Jacek Kołodziej bpo 27164 In the zlib module allow decompressing raw Deflate streams with a predefined zdict Based on patch by Xiang Zhang bpo 24291 Fix wsgiref simple_server WSGIRequestHandler to completely write data to the client Previously it could do partial writes and truncate data Also wsgiref handler ServerHandler can now handle stdout doing partial writes but this is deprecated bpo 21272 Use _sysconfigdata py to initialize distutils sysconfig bpo 19611 inspect now reports the implicit 0 parameters generated by the compiler for comprehension and generator expression scopes as if they were positional only parameters called implicit0 Patch by Jelle Zijlstra bpo 26809 Add __all__ to string Patch by Emanuel Barry bpo 26373 subprocess Popen communicate now correctly ignores BrokenPipeError when the child process dies before communicate is called in more all circumstances signal socket and ssl module IntEnum constant name lookups now return a consistent name for values having multiple names Ex signal Signals 6 now refers to itself as signal SIGALRM rather than flipping between that and signal SIGIOT based on the interpreter s hash randomization seed bpo 27167 Clarify the subprocess CalledProcessError error message text when the child process died due to a signal bpo 25931 Don t define socketserver Forking names on platforms such as Windows that do not support os fork bpo 21776 distutils upload now correctly handles HTTPError Initial patch by Claudiu Popa bpo 26526 Replace custom parse tree validation in the parser module with a simple DFA validator bpo 27114 Fix SSLContext _load_windows_store_certs fails with PermissionError bpo 18383 Avoid creating duplicate filters when using filterwarnings and simplefilter Based on patch by Alex Shkop bpo 23026 winreg QueryValueEx now return an integer for REG_QWORD type bpo 26741 subprocess Popen destructor now emits a ResourceWarning warning if the child process is still running bpo 27056 Optimize pickle load and pickle loads up to 10 faster to deserialize a lot of small objects bpo 21271 New keyword only parameters in reset_mock call IDLE bpo 5124 Paste with text selected now replaces the selection on X11 This matches how paste works on Windows Mac most modern Linux apps and ttk widgets Original patch by Serhiy Storchaka bpo 24750 Switch all scrollbars in IDLE to ttk versions Where needed minimal tests are added to cover changes bpo 24759 IDLE requires tk 8 5 and availability ttk widgets Delete now unneeded tk version tests and code for older versions Add test for IDLE syntax colorizer bpo 27239 idlelib macosx isXyzTk functions initialize as needed bpo 27262 move Aqua unbinding code which enable context menus to macosx bpo 24759 Make clear in idlelib idle_test __init__ that the directory is a private implementation of test test_idle and tool for maintainers bpo 27196 Stop ThemeChanged warnings when running IDLE tests These persisted after other warnings were suppressed in 20567 Apply Serhiy Storchaka s update_idletasks solution to four test files Record this additional advice in idle_test README txt bpo 20567 Revise idle_test README txt with advice about avoiding tk warning messages from tests Apply advice to several IDLE tests bpo 24225 Update idlelib README txt with new file names and event handlers bpo 27156 Remove obsolete code not used by IDLE bpo 27117 Make colorizer htest and turtledemo work with dark themes Move code for configuring text widget colors to a new function bpo 24225 Rename many idlelib py and idle_test test_ py files Edit files to replace old names with new names when the old name re,en
1791,ferred to the module rather than the class it contained See the issue and IDLE section in What s New in 3 6 for more bpo 26673 When tk reports font size as 0 change to size 10 Such fonts on Linux prevented the configuration dialog from opening bpo 21939 Add test for IDLE s percolator Original patch by Saimadhav Heblikar bpo 21676 Add test for IDLE s replace dialog Original patch by Saimadhav Heblikar bpo 18410 Add test for IDLE s search dialog Original patch by Westley Martínez bpo 21703 Add test for undo delegator Patch mostly by Saimadhav Heblikar bpo 27044 Add ConfigDialog remove_var_callbacks to stop memory leaks bpo 23977 Add more asserts to test_delegator Documentation bpo 16484 Change the default PYTHONDOCS URL to https and fix the resulting links to use lowercase Patch by Sean Rodman test by Kaushik Nadikuditi bpo 24136 Document the new PEP 448 unpacking syntax of 3 5 bpo 22558 Add remaining doc links to source code for Python coded modules Patch by Yoni Lavi Tests bpo 25285 regrtest now uses subprocesses when the j1 command line option is used each test file runs in a fresh child process Before the j1 option was ignored bpo 25285 Tools buildbot test bat script now uses j1 by default to run each test file in fresh child process Windows bpo 27064 The py exe launcher now defaults to Python 3 The Windows launcher py exe no longer prefers an installed Python 2 version over Python 3 by default when used interactively bpo 17500 Remove unused and outdated icons See also https github com python pythondotorg issues 945 Build bpo 27229 Fix the cross compiling pgen rule for in tree builds Patch by Xavier de Gaye bpo 26930 Update OS X 10 5 32 bit only installer to build and link with OpenSSL 1 0 2h C API bpo 27186 Add the PyOS_FSPath function part of PEP 519 bpo 26282 PyArg_ParseTupleAndKeywords now supports positional only parameters Tools Demos bpo 26282 Argument Clinic now supports positional only and keyword parameters in the same function Python 3 6 0 alpha 1 Release date 2016 05 16 Security bpo 26657 Fix directory traversal vulnerability with http server on Windows This fixes a regression that was introduced in 3 3 4rc1 and 3 4 0rc1 Based on patch by Philipp Hagemeister bpo 26313 ssl py _load_windows_store_certs fails if windows cert store is empty Patch by Baji bpo 25939 On Windows open the cert store readonly in ssl enum_certificates Core and Builtins bpo 20041 Fixed TypeError when frame f_trace is set to None Patch by Xavier de Gaye bpo 26168 Fixed possible refleaks in failing Py_BuildValue with the N format unit bpo 26991 Fix possible refleak when creating a function with annotations bpo 27039 Fixed bytearray remove for values greater than 127 Based on patch by Joe Jevnik bpo 23640 int from_bytes no longer bypasses constructors for subclasses bpo 27005 Optimized the float fromhex class method for exact float It is now 2 times faster bpo 18531 Single var keyword argument of dict subtype was passed unscathed to the C defined function Now it is converted to exact dict bpo 26811 gc get_objects no longer contains a broken tuple with NULL pointer bpo 20120 Use RawConfigParser for pypirc parsing removing support for interpolation unintentionally added with move to Python 3 Behavior no longer does any interpolation in pypirc files matching behavior in Python 2 7 and Setuptools 19 0 bpo 26249 Memory functions of the PyMem_Malloc domain PYMEM_DOMAIN_MEM now use the pymalloc allocator rather than system malloc Applications calling PyMem_Malloc without holding the GIL can now crash use PYTHONMALLOC debug environment variable to validate the usage of memory allocators in your application bpo 26802 Optimize function calls only using unpacking like func tuple no other positional argument no keyword avoid copying the tuple Patch written by Joe Jevnik bpo 26659 Make the builtin slice type support cycle collection bpo 26718 super __init__ no longer leaks memory if called multiple times NOTE A direct call of super __init__ is not endorsed bpo 27138 Fix the doc comment for FileFinder find_spec bpo 27147 Mention PEP 420 in the importli,en
1792,b docs bpo 25339 PYTHONIOENCODING now has priority over locale in setting the error handler for stdin and stdout bpo 26494 Fixed crash on iterating exhausting iterators Affected classes are generic sequence iterators iterators of str bytes bytearray list tuple set frozenset dict OrderedDict corresponding views and os scandir iterator bpo 26574 Optimize bytes replace b b and bytearray replace b b Patch written by Josh Snider bpo 26581 If coding cookie is specified multiple times on a line in Python source code file only the first one is taken to account bpo 19711 Add tests for reloading namespace packages bpo 21099 Switch applicable importlib tests to use PEP 451 API bpo 26563 Debug hooks on Python memory allocators now raise a fatal error if functions of the PyMem_Malloc family are called without holding the GIL bpo 26564 On error the debug hooks on Python memory allocators now use the tracemalloc module to get the traceback where a memory block was allocated bpo 26558 The debug hooks on Python memory allocator PyObject_Malloc now detect when functions are called without holding the GIL bpo 26516 Add PYTHONMALLOC environment variable to set the Python memory allocators and or install debug hooks bpo 26516 The PyMem_SetupDebugHooks function can now also be used on Python compiled in release mode bpo 26516 The PYTHONMALLOCSTATS environment variable can now also be used on Python compiled in release mode It now has no effect if set to an empty string bpo 26516 In debug mode debug hooks are now also installed on Python memory allocators when Python is configured without pymalloc bpo 26464 Fix str translate when string is ASCII and first replacements removes character but next replacement uses a non ASCII character or a string longer than 1 character Regression introduced in Python 3 5 0 bpo 22836 Ensure exception reports from PyErr_Display and PyErr_WriteUnraisable are sensible even when formatting them produces secondary errors This affects the reports produced by sys __excepthook__ and when __del__ raises an exception bpo 26302 Correct behavior to reject comma as a legal character for cookie names bpo 26136 Upgrade the warning when a generator raises StopIteration from PendingDeprecationWarning to DeprecationWarning Patch by Anish Shah bpo 26204 The compiler now ignores all constant statements bytes str int float complex name constants None False True Ellipsis and ast Constant not only str and int For example 1 0 is now ignored in def f 1 0 bpo 4806 Avoid masking the original TypeError exception when using star unpacking in function calls Based on patch by Hagen Fürstenau and Daniel Urban bpo 26146 Add a new kind of AST node ast Constant It can be used by external AST optimizers but the compiler does not emit directly such node bpo 23601 Sped up allocation of dict key objects by using Python s small object allocator Contributed by Julian Taylor bpo 18018 Import raises ImportError instead of SystemError if a relative import is attempted without a known parent package bpo 25843 When compiling code don t merge constants if they are equal but have a different types For example f1 f2 lambda 1 lambda 1 0 is now correctly compiled to two different functions f1 returns 1 int and f2 returns 1 0 float even if 1 and 1 0 are equal bpo 26107 The format of the co_lnotab attribute of code objects changes to support negative line number delta bpo 26154 Add a new private _PyThreadState_UncheckedGet function to get the current Python thread state but don t issue a fatal error if it is NULL This new function must be used instead of accessing directly the _PyThreadState_Current variable The variable is no more exposed since Python 3 5 1 to hide the exact implementation of atomic C types to avoid compiler issues bpo 25791 If __package__ __spec__ parent or if neither __package__ or __spec__ are defined then ImportWarning is raised bpo 22995 UPDATE Comment out the one of the pickleability tests in _PyObject_GetState due to regressions observed in Cython based projects bpo 25961 Disallowed null characters in the type name bpo 25973 Fix segfault w,en
1793,hen an invalid nonlocal statement binds a name starting with two underscores bpo 22995 Instances of extension types with a state that aren t subclasses of list or dict and haven t implemented any pickle related methods __reduce__ __reduce_ex__ __getnewargs__ __getnewargs_ex__ or __getstate__ can no longer be pickled Including memoryview bpo 20440 Massive replacing unsafe attribute setting code with special macro Py_SETREF bpo 25766 Special method __bytes__ now works in str subclasses bpo 25421 __sizeof__ methods of builtin types now use dynamic basic size This allows sys getsize to work correctly with their subclasses with __slots__ defined bpo 25709 Fixed problem with in place string concatenation and utf 8 cache bpo 5319 New Py_FinalizeEx API allowing Python to set an exit status of 120 on failure to flush buffered streams bpo 25485 telnetlib Telnet is now a context manager bpo 24097 Fixed crash in object __reduce__ if slot name is freed inside __getattr__ bpo 24731 Fixed crash on converting objects with special methods __bytes__ __trunc__ and __float__ returning instances of subclasses of bytes int and float to subclasses of bytes int and float correspondingly bpo 25630 Fix a possible segfault during argument parsing in functions that accept filesystem paths bpo 23564 Fixed a partially broken sanity check in the _posixsubprocess internals regarding how fds_to_pass were passed to the child The bug had no actual impact as subprocess py already avoided it bpo 25388 Fixed tokenizer crash when processing undecodable source code with a null byte bpo 25462 The hash of the key now is calculated only once in most operations in C implementation of OrderedDict bpo 22995 Default implementation of __reduce__ and __reduce_ex__ now rejects builtin types with not defined __new__ bpo 24802 Avoid buffer overreads when int float compile exec and eval are passed bytes like objects These objects are not necessarily terminated by a null byte but the functions assumed they were bpo 25555 Fix parser and AST fill lineno and col_offset of arg node when compiling AST from Python objects bpo 24726 Fixed a crash and leaking NULL in repr of OrderedDict that was mutated by direct calls of dict methods bpo 25449 Iterating OrderedDict with keys with unstable hash now raises KeyError in C implementations as well as in Python implementation bpo 25395 Fixed crash when highly nested OrderedDict structures were garbage collected bpo 25401 Optimize bytes fromhex and bytearray fromhex they are now between 2x and 3 5x faster bpo 25399 Optimize bytearray args using the new private _PyBytesWriter API Formatting is now between 2 5 and 5 times faster bpo 25274 sys setrecursionlimit now raises a RecursionError if the new recursion limit is too low depending at the current recursion depth Modify also the lower water mark formula to make it monotonic This mark is used to decide when the overflowed flag of the thread state is reset bpo 24402 Fix input to prompt to the redirected stdout when sys stdout fileno fails bpo 25349 Optimize bytes args using the new private _PyBytesWriter API Formatting is now up to 2 times faster bpo 24806 Prevent builtin types that are not allowed to be subclassed from being subclassed through multiple inheritance bpo 25301 The UTF 8 decoder is now up to 15 times as fast for error handlers ignore replace and surrogateescape bpo 24848 Fixed a number of bugs in UTF 7 decoding of misformed data bpo 25267 The UTF 8 encoder is now up to 75 times as fast for error handlers ignore replace surrogateescape surrogatepass Patch co written with Serhiy Storchaka bpo 25280 Import trace messages emitted in verbose v mode are no longer formatted twice bpo 25227 Optimize ASCII and latin1 encoders with the surrogateescape error handler the encoders are now up to 3 times as fast Initial patch written by Serhiy Storchaka bpo 25003 On Solaris 11 3 or newer os urandom now uses the getrandom function instead of the getentropy function The getentropy function is blocking to generate very good quality entropy os urandom doesn t need such high quality entropy bpo 9,en
1794,232 Modify Python s grammar to allow trailing commas in the argument list of a function declaration For example def f a 3 pass is now legal Patch from Mark Dickinson bpo 24965 Implement PEP 498 Literal String Interpolation This allows you to embed expressions inside f strings which are converted to normal strings at run time Given x 3 then f value x value 3 Patch by Eric V Smith bpo 26478 Fix semantic bugs when using binary operators with dictionary views and tuples bpo 26171 Fix possible integer overflow and heap corruption in zipimporter get_data bpo 25660 Fix TAB key behaviour in REPL with readline bpo 26288 Optimize PyLong_AsDouble bpo 26289 Optimize floor and modulo division for single digit longs Microbenchmarks show 2 2 5x improvement Built in divmod function is now also 10 faster See also bpo 26315 bpo 25887 Raise a RuntimeError when a coroutine object is awaited more than once Library bpo 27057 Fix os set_inheritable on Android ioctl is blocked by SELinux and fails with EACCESS The function now falls back to fcntl Patch written by Michał Bednarski bpo 27014 Fix infinite recursion using typing py Thanks to Kalle Tuure bpo 27031 Removed dummy methods in Tkinter widget classes tk_menuBar and tk_bindForTraversal bpo 14132 Fix urllib request redirect handling when the target only has a query string Original fix by Ján Janech bpo 17214 The urllib request module now percent encodes non ASCII bytes found in redirect target URLs Some servers send Location header fields with non ASCII bytes but http client requires the request target to be ASCII encodable otherwise a UnicodeEncodeError is raised Based on patch by Christian Heimes bpo 27033 The default value of the decode_data parameter for smtpd SMTPChannel and smtpd SMTPServer constructors is changed to False bpo 27034 Removed deprecated class asynchat fifo bpo 26870 Added readline set_auto_history which can stop entries being automatically added to the history list Based on patch by Tyler Crompton bpo 26039 zipfile ZipFile open can now be used to write data into a ZIP file as well as for extracting data Patch by Thomas Kluyver bpo 26892 Honor debuglevel flag in urllib request HTTPHandler Patch contributed by Chi Hsuan Yen bpo 22274 In the subprocess module allow stderr to be redirected to stdout even when stdout is not redirected Patch by Akira Li bpo 26807 mock_open files no longer error on readline at end of file Patch from Yolanda Robla bpo 25745 Fixed leaking a userptr in curses panel destructor bpo 26977 Removed unnecessary and ignored call to sum of squares helper in statistics pvariance bpo 26002 Use bisect in statistics median instead of a linear search Patch by Upendra Kuma bpo 25974 Make use of new Decimal as_integer_ratio method in statistics module Patch by Stefan Krah bpo 26996 Add secrets module as described in PEP 506 bpo 26881 The modulefinder module now supports extended opcode arguments bpo 23815 Fixed crashes related to directly created instances of types in _tkinter and curses panel modules bpo 17765 weakref ref no longer silently ignores keyword arguments Patch by Georg Brandl bpo 26873 xmlrpc now raises ResponseError on unsupported type tags instead of silently return incorrect result bpo 26915 The __contains__ methods in the collections ABCs now check for identity before checking equality This better matches the behavior of the concrete classes allows sensible handling of NaNs and makes it easier to reason about container invariants bpo 26711 Fixed the comparison of plistlib Data with other types bpo 24114 Fix an uninitialized variable in ctypes util The bug only occurs on SunOS when the ctypes implementation searches for the crle program Patch by Xiang Zhang Tested on SunOS by Kees Bos bpo 26864 In urllib request change the proxy bypass host checking against no_proxy to be case insensitive and to not match unrelated host names that happen to have a bypassed hostname as a suffix Patch by Xiang Zhang bpo 24902 Print server URL on http server startup Initial patch by Felix Kaiser bpo 25788 fileinput hook_encoded now supports an errors argument for p,en
1795,assing to open Original patch by Joseph Hackman bpo 26634 recursive_repr now sets __qualname__ of wrapper Patch by Xiang Zhang bpo 26804 urllib request will prefer lower_case proxy environment variables over UPPER_CASE or Mixed_Case ones Patch contributed by Hans Peter Jansen bpo 26837 assertSequenceEqual now correctly outputs non stringified differing items like bytes in the b mode This affects assertListEqual and assertTupleEqual bpo 26041 Remove will be removed in Python 3 7 from deprecation messages of platform dist and platform linux_distribution Patch by Kumaripaba Miyurusara Athukorala bpo 26822 itemgetter attrgetter and methodcaller objects no longer silently ignore keyword arguments bpo 26733 Disassembling a class now disassembles class and static methods Patch by Xiang Zhang bpo 26801 Fix error handling in shutil get_terminal_size catch AttributeError instead of NameError Patch written by Emanuel Barry bpo 24838 tarfile s ustar and gnu formats now correctly calculate name and link field limits for multibyte character encodings like utf 8 bpo 26717 Stop encoding Latin 1 ized WSGI paths with UTF 8 Patch by Anthony Sottile bpo 26782 Add STARTUPINFO to subprocess __all__ on Windows bpo 26404 Add context manager to socketserver Patch by Aviv Palivoda bpo 26735 Fix os urandom on Solaris 11 3 and newer when reading more than 1 024 bytes call getrandom multiple times with a limit of 1024 bytes per call bpo 26585 Eliminate http server _quote_html and use html escape quote False Patch by Xiang Zhang bpo 26685 Raise OSError if closing a socket fails bpo 16329 Add webm to mimetypes types_map Patch by Giampaolo Rodola bpo 13952 Add csv to mimetypes types_map Patch by Geoff Wilson bpo 26587 the site module now allows pth files to specify files to be added to sys path e g zip files bpo 25609 Introduce contextlib AbstractContextManager and typing ContextManager bpo 26709 Fixed Y2038 problem in loading binary PLists bpo 23735 Handle terminal resizing with Readline 6 3 by installing our own SIGWINCH handler Patch by Eric Price bpo 25951 Change SSLSocket sendall to return None as explicitly documented for plain socket objects Patch by Aviv Palivoda bpo 26586 In http server respond with 413 Request header fields too large if there are too many header fields to parse rather than killing the connection and raising an unhandled exception Patch by Xiang Zhang bpo 26676 Added missing XMLPullParser to ElementTree __all__ bpo 22854 Change BufferedReader writable and BufferedWriter readable to always return False bpo 26492 Exhausted iterator of array array now conforms with the behavior of iterators of other mutable sequences it lefts exhausted even if iterated array is extended bpo 26641 doctest DocFileTest and doctest testfile now support packages module splitted into multiple directories for the package parameter bpo 25195 Fix a regression in mock MagicMock _Call is a subclass of tuple changeset 3603bae63c13 only works for classes so we need to implement __ne__ ourselves Patch by Andrew Plummer bpo 26644 Raise ValueError rather than SystemError when a negative length is passed to SSLSocket recv or read bpo 23804 Fix SSL recv 0 and read 0 methods to return zero bytes instead of up to 1024 bpo 26616 Fixed a bug in datetime astimezone method bpo 26637 The importlib module now emits an ImportError rather than a TypeError if __import__ is tried during the Python shutdown process but sys path is already cleared set to None bpo 21925 warnings formatwarning now catches exceptions when calling linecache getline and tracemalloc get_object_traceback to be able to log ResourceWarning emitted late during the Python shutdown process bpo 23848 On Windows faulthandler enable now also installs an exception handler to dump the traceback of all Python threads on any Windows exception not only on UNIX signals SIGSEGV SIGFPE SIGABRT bpo 26530 Add C functions _PyTraceMalloc_Track and _PyTraceMalloc_Untrack to track memory blocks using the tracemalloc module Add _PyTraceMalloc_GetTraceback to get the traceback of an object bpo 26588 The _tracemalloc now supp,en
1796,orts tracing memory allocations of multiple address spaces domains bpo 24266 Ctrl C during Readline history search now cancels the search mode when compiled with Readline 7 bpo 26590 Implement a safe finalizer for the _socket socket type It now releases the GIL to close the socket bpo 18787 spwd getspnam now raises a PermissionError if the user doesn t have privileges bpo 26560 Avoid potential ValueError in BaseHandler start_response Initial patch by Peter Inglesby bpo 26567 Add a new function PyErr_ResourceWarning function to pass the destroyed object Add a source attribute to warnings WarningMessage Add warnings _showwarnmsg which uses tracemalloc to get the traceback where source object was allocated bpo 26569 Fix pyclbr readmodule and pyclbr readmodule_ex to support importing packages bpo 26499 Account for remaining Content Length in HTTPResponse readline and read1 Based on patch by Silent Ghost Also document that HTTPResponse now supports these methods bpo 25320 Handle sockets in directories unittest discovery is scanning Patch from Victor van den Elzen bpo 16181 cookiejar http2time now returns None if year is higher than datetime MAXYEAR bpo 26513 Fixes platform module detection of Windows Server bpo 23718 Fixed parsing time in week 0 before Jan 1 Original patch by Tamás Bence Gedai bpo 26323 Add Mock assert_called and Mock assert_called_once methods to unittest mock Patch written by Amit Saha bpo 20589 Invoking Path owner and Path group on Windows now raise NotImplementedError instead of ImportError bpo 26177 Fixed the keys method for Canvas and Scrollbar widgets bpo 15068 Got rid of excessive buffering in fileinput The bufsize parameter is now deprecated and ignored bpo 19475 Added an optional argument timespec to the datetime isoformat method to choose the precision of the time component bpo 2202 Fix UnboundLocalError in AbstractDigestAuthHandler get_algorithm_impls Initial patch by Mathieu Dupuy bpo 26167 Minimized overhead in copy copy and copy deepcopy Optimized copying and deepcopying bytearrays NotImplemented slices short lists tuples dicts sets bpo 25718 Fixed pickling and copying the accumulate iterator with total is None bpo 26475 Fixed debugging output for regular expressions with the x flag bpo 26482 Allowed pickling recursive dequeues bpo 26335 Make mmap write return the number of bytes written like other write methods Patch by Jakub Stasiak bpo 26457 Fixed the subnets methods in IP network classes for the case when resulting prefix length is equal to maximal prefix length Based on patch by Xiang Zhang bpo 26385 Remove the file if the internal open call in NamedTemporaryFile fails Patch by Silent Ghost bpo 26402 Fix XML RPC client to retry when the server shuts down a persistent connection This was a regression related to the new http client RemoteDisconnected exception in 3 5 0a4 bpo 25913 Leading is optional now in base64 a85decode with adobe True Patch by Swati Jaiswal bpo 26186 Remove an invalid type check in importlib util LazyLoader bpo 26367 importlib __import__ raises ImportError like builtins __import__ when level is specified but without an accompanying package specified bpo 26309 In the socketserver module shut down the request closing the connected socket when verify_request returns false Patch by Aviv Palivoda bpo 23430 Change the socketserver module to only catch exceptions raised from a request handler that are derived from Exception instead of BaseException Therefore SystemExit and KeyboardInterrupt no longer trigger the handle_error method and will now to stop a single threaded server bpo 25995 os walk no longer uses FDs proportional to the tree depth bpo 25994 Added the close method and the support of the context manager protocol for the os scandir iterator bpo 23992 multiprocessing make MapResult not fail fast upon exception bpo 26243 Support keyword arguments to zlib compress Patch by Aviv Palivoda bpo 26117 The os scandir iterator now closes file descriptor not only when the iteration is finished but when it was failed with error bpo 25949 __dict__ for an OrderedDict instance is n,en
1797,ow created only when needed bpo 25911 Restored support of bytes paths in os walk on Windows bpo 26045 Add UTF 8 suggestion to error message when posting a non Latin 1 string with http client bpo 26039 Added zipfile ZipInfo from_file and zipinfo ZipInfo is_dir Patch by Thomas Kluyver bpo 12923 Reset FancyURLopener s redirect counter even if there is an exception Based on patches by Brian Brazil and Daniel Rocco bpo 25945 Fixed a crash when unpickle the functools partial object with wrong state Fixed a leak in failed functools partial constructor args and keywords attributes of functools partial have now always types tuple and dict correspondingly bpo 26202 copy deepcopy now correctly copies range objects with non atomic attributes bpo 23076 Path glob now raises a ValueError if it s called with an invalid pattern Patch by Thomas Nyberg bpo 19883 Fixed possible integer overflows in zipimport bpo 26227 On Windows getnameinfo gethostbyaddr and gethostbyname_ex functions of the socket module now decode the hostname from the ANSI code page rather than UTF 8 bpo 26099 The site module now writes an error into stderr if sitecustomize module can be imported but executing the module raise an ImportError Same change for usercustomize bpo 26147 xmlrpc now works with strings not encodable with used non UTF 8 encoding bpo 25935 Garbage collector now breaks reference loops with OrderedDict bpo 16620 Fixed AttributeError in msilib Directory glob bpo 26013 Added compatibility with broken protocol 2 pickles created in old Python 3 versions 3 4 3 and lower bpo 26129 Deprecated accepting non integers in grp getgrgid bpo 25850 Use cross compilation by default for 64 bit Windows bpo 25822 Add docstrings to the fields of urllib parse results Patch contributed by Swati Jaiswal bpo 22642 Convert trace module option parsing mechanism to argparse Patch contributed by SilentGhost bpo 24705 Fix sysconfig _parse_makefile not expanding vars appearing before vars bpo 26069 Remove the deprecated apis in the trace module bpo 22138 Fix mock patch behavior when patching descriptors Restore original values after patching Patch contributed by Sean McCully bpo 25672 In the ssl module enable the SSL_MODE_RELEASE_BUFFERS mode option if it is safe to do so bpo 26012 Don t traverse into symlinks for pattern in pathlib Path r glob bpo 24120 Ignore PermissionError when traversing a tree with pathlib Path r glob Patch by Ulrich Petri bpo 21815 Accept characters in the data portion of imap responses in order to handle the flags with square brackets accepted and produced by servers such as gmail bpo 25447 fileinput now uses sys stdin as is if it does not have a buffer attribute restores backward compatibility bpo 25971 Optimized creating Fractions from floats by 2 times and from Decimals by 3 times bpo 25802 Document as deprecated the remaining implementations of importlib abc Loader load_module bpo 25928 Add Decimal as_integer_ratio bpo 25447 Copying the lru_cache wrapper object now always works independently from the type of the wrapped object by returning the original object unchanged bpo 25768 Have the functions in compileall return booleans instead of ints and add proper documentation and tests for the return values bpo 24103 Fixed possible use after free in ElementTree XMLPullParser bpo 25860 os fwalk no longer skips remaining directories when error occurs Original patch by Samson Lee bpo 25914 Fixed and simplified OrderedDict __sizeof__ bpo 25869 Optimized deepcopying ElementTree it is now 20 times faster bpo 25873 Optimized iterating ElementTree Iterating elements Element iter is now 40 faster iterating text Element itertext is now up to 2 5 times faster bpo 25902 Fixed various refcount issues in ElementTree iteration bpo 22227 The TarFile iterator is reimplemented using generator This implementation is simpler that using class bpo 25638 Optimized ElementTree iterparse it is now 2x faster Optimized ElementTree parsing it is now 10 faster bpo 25761 Improved detecting errors in broken pickle data bpo 25717 Restore the previous behaviour of tolerating most fstat er,en
1798,rors when opening files This was a regression in 3 5a1 and stopped anonymous temporary files from working in special cases bpo 24903 Fix regression in number of arguments compileall accepts when d is specified The check on the number of arguments has been dropped completely as it never worked correctly anyway bpo 25764 In the subprocess module preserve any exception caused by fork failure when preexec_fn is used bpo 25771 Tweak the exception message for importlib util resolve_name when package isn t specified but necessary bpo 6478 _strptime s regexp cache now is reset after changing timezone with time tzset bpo 14285 When executing a package with the python m package option and package initialization fails a proper traceback is now reported The runpy module now lets exceptions from package initialization pass back to the caller rather than raising ImportError bpo 19771 Also in runpy and the m option omit the irrelevant message is a package and cannot be directly executed if the package could not even be initialized e g due to a bad pyc file bpo 25177 Fixed problem with the mean of very small and very large numbers As a side effect statistics mean and statistics variance should be significantly faster bpo 25718 Fixed copying object with state with boolean value is false bpo 10131 Fixed deep copying of minidom documents Based on patch by Marian Ganisin bpo 7990 dir on ElementTree Element now lists properties tag text tail and attrib Original patch by Santoso Wijaya bpo 25725 Fixed a reference leak in pickle loads when unpickling invalid data including tuple instructions bpo 25663 In the Readline completer avoid listing duplicate global names and search the global namespace before searching builtins bpo 25688 Fixed file leak in ElementTree iterparse raising an error bpo 23914 Fixed SystemError raised by unpickler on broken pickle data bpo 25691 Fixed crash on deleting ElementTree Element attributes bpo 25624 ZipFile now always writes a ZIP_STORED header for directory entries Patch by Dingyuan Wang bpo 25626 Change three zlib functions to accept sizes that fit in Py_ssize_t but internally cap those sizes to UINT_MAX This resolves a regression in 3 5 where GzipFile read failed to read chunks larger than 2 or 4 GiB The change affects the zlib Decompress decompress max_length parameter the zlib decompress bufsize parameter and the zlib Decompress flush length parameter bpo 25583 Avoid incorrect errors raised by os makedirs exist_ok True when the OS gives priority to errors such as EACCES over EEXIST bpo 25593 Change semantics of EventLoop stop in asyncio bpo 6973 When we know a subprocess Popen process has died do not allow the send_signal terminate or kill methods to do anything as they could potentially signal a different process bpo 23883 Added missing APIs to __all__ to match the documented APIs for the following modules calendar csv enum fileinput ftplib logging optparse tarfile threading and wave Also added a test support check__all__ helper Patches by Jacek Kołodziej Mauro S M Rodrigues and Joel Taddei bpo 25590 In the Readline completer only call getattr once per attribute Also complete names of attributes such as properties and slots which are listed by dir but not yet created on an instance bpo 25498 Fix a crash when garbage collecting ctypes objects created by wrapping a memoryview This was a regression made in 3 5a1 Based on patch by Eryksun bpo 25584 Added escape to the __all__ list in the glob module bpo 25584 Fixed recursive glob with patterns starting with bpo 25446 Fix regression in smtplib s AUTH LOGIN support bpo 18010 Fix the pydoc web server s module search function to handle exceptions from importing packages bpo 25554 Got rid of circular references in regular expression parsing bpo 18973 Command line interface of the calendar module now uses argparse instead of optparse bpo 25510 fileinput FileInput readline now returns b instead of at the end if the FileInput was opened with binary mode Patch by Ryosuke Ito bpo 25503 Fixed inspect getdoc for inherited docstrings of properties Original patch by John Mark,en
1799, Vandenberg bpo 25515 Always use os urandom as a source of randomness in uuid uuid4 bpo 21827 Fixed textwrap dedent for the case when largest common whitespace is a substring of smallest leading whitespace Based on patch by Robert Li bpo 25447 The lru_cache wrapper objects now can be copied and pickled by returning the original object unchanged bpo 25390 typing Don t crash on Union str Pattern bpo 25441 asyncio Raise error from drain when socket is closed bpo 25410 Cleaned up and fixed minor bugs in C implementation of OrderedDict bpo 25411 Improved Unicode support in SMTPHandler through better use of the email package Thanks to user simon04 for the patch Move the imp module from a PendingDeprecationWarning to DeprecationWarning bpo 25407 Remove mentions of the formatter module being removed in Python 3 6 bpo 25406 Fixed a bug in C implementation of OrderedDict move_to_end that caused segmentation fault or hang in iterating after moving several items to the start of ordered dict bpo 25382 pickletools dis now outputs implicit memo index for the MEMOIZE opcode bpo 25357 Add an optional newline parameter to binascii b2a_base64 base64 b64encode uses it to avoid a memory copy bpo 24164 Objects that need calling __new__ with keyword arguments can now be pickled using pickle protocols older than protocol version 4 bpo 25364 zipfile now works in threads disabled builds bpo 25328 smtpd s SMTPChannel now correctly raises a ValueError if both decode_data and enable_SMTPUTF8 are set to true bpo 16099 RobotFileParser now supports Crawl delay and Request rate extensions Patch by Nikolay Bogoychev bpo 25316 distutils raises OSError instead of DistutilsPlatformError when MSVC is not installed bpo 25380 Fixed protocol for the STACK_GLOBAL opcode in pickletools opcodes bpo 23972 Updates asyncio datagram create method allowing reuseport and reuseaddr socket options to be set prior to binding the socket Mirroring the existing asyncio create_server method the reuseaddr option for datagram sockets defaults to True if the O S is posix except if the platform is Cygwin Patch by Chris Laws bpo 25304 Add asyncio run_coroutine_threadsafe This lets you submit a coroutine to a loop from another thread returning a concurrent futures Future By Vincent Michel bpo 25232 Fix CGIRequestHandler to split the query from the URL at the first question mark rather than the last Patch from Xiang Zhang bpo 24657 Prevent CGIRequestHandler from collapsing slashes in the query part of the URL as if it were a path Patch from Xiang Zhang bpo 25287 Don t add crypt METHOD_CRYPT to crypt methods if it s not supported Check if it is supported it may not be supported on OpenBSD for example bpo 23600 Default implementation of tzinfo fromutc was returning wrong results in some cases bpo 25203 Failed readline set_completer_delims no longer left the module in inconsistent state bpo 25011 rlcompleter now omits private and special attribute names unless the prefix starts with underscores bpo 25209 rlcompleter now can add a space or a colon after completed keyword bpo 22241 timezone utc name is now plain UTC not UTC 00 00 bpo 23517 fromtimestamp and utcfromtimestamp methods of datetime datetime now round microseconds to nearest with ties going to nearest even integer ROUND_HALF_EVEN as round float instead of rounding towards Infinity ROUND_FLOOR bpo 23552 Timeit now warns when there is substantial 4x variance between best and worst times Patch from Serhiy Storchaka bpo 24633 site packages README README txt bpo 24879 help and pydoc can now list named tuple fields in the order they were defined rather than alphabetically The ordering is determined by the _fields attribute if present bpo 24874 Improve speed of itertools cycle and make its pickle more compact Fix crash in itertools cycle __setstate__ when the first argument wasn t a list bpo 20059 urllib parse raises ValueError on all invalid ports Patch by Martin Panter bpo 24360 Improve __repr__ of argparse Namespace for invalid identifiers Patch by Matthias Bussonnier bpo 23426 run_setup was broken in distutils Patch from Alexander,en
1800, Belopolsky bpo 13938 2to3 converts StringTypes to a tuple Patch from Mark Hammond bpo 2091 open accepted a U mode string containing but U can only be used with r Patch from Jeff Balogh and John O Connor bpo 8585 improved tests for zipimporter2 Patch from Mark Lawrence bpo 18622 unittest mock mock_open reset_mock would recurse infinitely Patch from Nicola Palumbo and Laurent De Buyst bpo 24426 Fast searching optimization in regular expressions now works for patterns that starts with capturing groups Fast searching optimization now can t be disabled at compile time bpo 23661 unittest mock side_effects can now be exceptions again This was a regression vs Python 3 4 Patch from Ignacio Rossi bpo 13248 Remove deprecated inspect getmoduleinfo function bpo 25578 Fix another memory leak in SSLSocket getpeercer bpo 25530 Disable the vulnerable SSLv3 protocol by default when creating ssl SSLContext bpo 25569 Fix memory leak in SSLSocket getpeercert bpo 25471 Sockets returned from accept shouldn t appear to be nonblocking bpo 25319 When threading Event is reinitialized the underlying condition should use a regular lock rather than a recursive lock Skip getaddrinfo if host is already resolved Patch by A Jesse Jiryu Davis bpo 26050 Add asyncio StreamReader readuntil method Patch by Марк Коренберг bpo 25924 Avoid unnecessary serialization of getaddrinfo 3 calls on OS X versions 10 5 or higher Original patch by A Jesse Jiryu Davis bpo 26406 Avoid unnecessary serialization of getaddrinfo 3 calls on current versions of OpenBSD and NetBSD Patch by A Jesse Jiryu Davis bpo 26848 Fix asyncio subprocess communicate to handle empty input Patch by Jack O Connor bpo 27040 Add loop get_exception_handler method bpo 27041 asyncio Add loop create_future method IDLE bpo 20640 Add tests for idlelib configHelpSourceEdit Patch by Saimadhav Heblikar In the IDLE console differences section of the IDLE doc clarify how running with IDLE affects sys modules and the standard streams bpo 25507 fix incorrect change in IOBinding that prevented printing Augment IOBinding htest to include all major IOBinding functions bpo 25905 Revert unwanted conversion of to RIGHT SINGLE QUOTATION MARK in README txt and open this and NEWS txt with ascii Re encode CREDITS txt to utf 8 and open it with utf 8 bpo 15348 Stop the debugger engine normally in a user process before closing the debugger window running in the IDLE process This prevents the RuntimeErrors that were being caught and ignored bpo 24455 Prevent IDLE from hanging when a closing the shell while the debugger is active 15347 b closing the debugger with the X button 15348 and c activating the debugger when already active 24455 The patch by Mark Roseman does this by making two changes 1 Suspend and resume the gui interaction method with the tcl vwait mechanism intended for this purpose instead of root mainloop quit 2 In gui run allow any existing interaction to terminate first Change The program to Your program in an IDLE kill program message to make it clearer that the program referred to is the currently running user program not IDLE itself bpo 24750 Improve the appearance of the IDLE editor window status bar Patch by Mark Roseman bpo 25313 Change the handling of new built in text color themes to better address the compatibility problem introduced by the addition of IDLE Dark Consistently use the revised idleConf CurrentTheme everywhere in idlelib bpo 24782 Extension configuration is now a tab in the IDLE Preferences dialog rather than a separate dialog The former tabs are now a sorted list Patch by Mark Roseman bpo 22726 Re activate the config dialog help button with some content about the other buttons and the new IDLE Dark theme bpo 24820 IDLE now has an IDLE Dark built in text color theme It is more or less IDLE Classic inverted with a cobalt blue background Strings comments keywords are still green red orange To use it with IDLEs released before November 2015 hit the Save as New Custom Theme button and enter a new name such as Custom Dark The custom theme will work with any IDLE release and can be modified bpo,en
1801, 25224 README txt is now an idlelib index for IDLE developers and curious users The previous user content is now in the IDLE doc chapter IDLE now means Integrated Development and Learning Environment bpo 24820 Users can now set breakpoint colors in Settings Custom Highlighting Original patch by Mark Roseman bpo 24972 Inactive selection background now matches active selection background as configured by users on all systems Found items are now always highlighted on Windows Initial patch by Mark Roseman bpo 24570 Idle make calltip and completion boxes appear on Macs affected by a tk regression Initial patch by Mark Roseman bpo 24988 Idle ScrolledList context menus used in debugger now work on Mac Aqua Patch by Mark Roseman bpo 24801 Make right click for context menu work on Mac Aqua Patch by Mark Roseman bpo 25173 Associate tkinter messageboxes with a specific widget For Mac OSX make them a sheet Patch by Mark Roseman bpo 25198 Enhance the initial html viewer now used for Idle Help Properly indent fixed pitch text patch by Mark Roseman Give code snippet a very Sphinx like light blueish gray background Re use initial width and height set by users for shell and editor When the Table of Contents TOC menu is used put the section header at the top of the screen bpo 25225 Condense and rewrite Idle doc section on text colors bpo 21995 Explain some differences between IDLE and console Python bpo 22820 Explain need for print when running file from Idle editor bpo 25224 Doc augment Idle feature list and no subprocess section bpo 25219 Update doc for Idle command line options Some were missing and notes were not correct bpo 24861 Most of idlelib is private and subject to change Use idleib idle to start Idle See idlelib __init__ __doc__ bpo 25199 Idle add synchronization comments for future maintainers bpo 16893 Replace help txt with help html for Idle doc display The new idlelib help html is rstripped Doc build html library idle html It looks better than help txt and will better document Idle as released The tkinter html viewer that works for this file was written by Rose Roseman The now unused EditorWindow HelpDialog class and helt txt file are deprecated bpo 24199 Deprecate unused idlelib idlever with possible removal in 3 6 bpo 24790 Remove extraneous code which also create 2 3 conflicts Documentation bpo 26736 Used HTTPS for external links in the documentation if possible bpo 6953 Rework the Readline module documentation to group related functions together and add more details such as what underlying Readline functions and variables are accessed bpo 23606 Adds note to ctypes documentation regarding cdll msvcrt bpo 24952 Clarify the default size argument of stack_size in the threading and _thread modules Patch from Mattip bpo 26014 Update 3 x packaging documentation See also links to the new docs are now provided in the legacy pages links to setuptools documentation have been updated Tests bpo 21916 Added tests for the turtle module Patch by ingrid Gregory Loyse and Jelle Zijlstra bpo 26295 When using python3 m test testdir TESTDIR regrtest doesn t add test prefix to test module names bpo 26523 The multiprocessing thread pool multiprocessing dummy Pool was untested bpo 26015 Added new tests for pickling iterators of mutable sequences bpo 26325 Added test support check_no_resource_warning to check that no ResourceWarning is emitted bpo 25940 Changed test_ssl to use its internal local server more This avoids relying on svn python org which recently changed root certificate bpo 25616 Tests for OrderedDict are extracted from test_collections into separate file test_ordered_dict bpo 25449 Added tests for OrderedDict subclasses bpo 25188 Add P pgo to test regrtest to suppress error output when running the test suite for the purposes of a PGO build Initial patch by Alecsandru Patrascu bpo 22806 Add python m test list tests command to list tests bpo 18174 python m test huntrleaks now also checks for leak of file descriptors Patch written by Richard Oudkerk bpo 25260 Fix python m test coverage on Windows Remove the list of ignored director,en
1802,ies PCbuild rt bat now accepts an unlimited number of arguments to pass along to regrtest py Previously there was a limit of 9 bpo 26583 Skip test_timestamp_overflow in test_import if bytecode files cannot be written Build bpo 21277 Don t try to link _ctypes with a ffi_convenience library bpo 26884 Fix linking extension modules for cross builds Patch by Xavier de Gaye bpo 26932 Fixed support of RTLD_ constants defined as enum values not via macros in particular on Android Patch by Chi Hsuan Yen bpo 22359 Disable the rules for running _freeze_importlib and pgen when cross compiling The output of these programs is normally saved with the source code anyway and is still regenerated when doing a native build Patch by Xavier de Gaye bpo 21668 Link audioop _datetime _ctypes_test modules to libm except on Mac OS X Patch written by Chi Hsuan Yen bpo 25702 A with lto configure option has been added that will enable link time optimizations at build time during a make profile opt Some compilers and toolchains are known to not produce stable code when using LTO be sure to test things thoroughly before relying on it It can provide a few speed up over profile opt alone bpo 26624 Adds validation of ucrtbase d dll version with warning for old versions bpo 17603 Avoid error about nonexistent fileblocks o file by using a lower level check for st_blocks in struct stat bpo 26079 Fixing the build output folder for tix 8 4 3 6 Patch by Bjoern Thiel bpo 26465 Update Windows builds to use OpenSSL 1 0 2g bpo 25348 Added pgo and pgo job arguments to PCbuild build bat for building with Profile Guided Optimization The old PCbuild build_pgo bat script is removed bpo 25827 Add support for building with ICC to configure including a new with icc flag bpo 25696 Fix installation of Python on UNIX with make j9 bpo 24986 It is now possible to build Python on Windows without errors when external libraries are not available bpo 24421 Compile Modules _math c once before building extensions Previously it could fail to compile properly if the math and cmath builds were concurrent bpo 26465 Update OS X 10 5 32 bit only installer to build and link with OpenSSL 1 0 2g bpo 26268 Update Windows builds to use OpenSSL 1 0 2f bpo 25136 Support Apple Xcode 7 s new textual SDK stub libraries bpo 24324 Do not enable unreachable code warnings when using gcc as the option does not work correctly in older versions of gcc and has been silently removed as of gcc 4 5 Windows bpo 27053 Updates make_zip py to correctly generate library ZIP file bpo 26268 Update the prepare_ssl py script to handle OpenSSL releases that don t include the contents of the include directory that is 1 0 2e and later bpo 26071 bdist_wininst created binaries fail to start and find 32bit Python bpo 26073 Update the list of magic numbers in launcher bpo 26065 Excludes venv from library when generating embeddable distro bpo 25022 Removed very outdated PC example_nt directory Tools Demos bpo 26799 Fix python gdb py don t get C types once when the Python code is loaded but get C types on demand The C types can change if python gdb py is loaded before the Python executable Patch written by Thomas Ilsche bpo 26271 Fix the Freeze tool to properly use flags passed through configure Patch by Daniel Shaulov bpo 26489 Add dictionary unpacking support to Tools parser unparse py Patch by Guo Ci Teo bpo 26316 Fix variable name typo in Argument Clinic bpo 25440 Fix output of python config extension suffix bpo 25154 The pyvenv script has been deprecated in favour of python3 m venv C API bpo 26312 SystemError is now raised in all programming bugs with using PyArg_ParseTupleAndKeywords RuntimeError did raised before in some programming bugs bpo 26198 ValueError is now raised instead of TypeError on buffer overflow in parsing es and et format units SystemError is now raised instead of TypeError on programmatical error in parsing format string Python 3 5 5 final Release date 2018 02 04 There were no new changes in version 3 5 5 Python 3 5 5 release candidate 1 Release date 2018 01 23 Security bpo 32551 The sys path 0 initial,en
1803,ization change for bpo 29139 caused a regression by revealing an inconsistency in how sys path is initialized when executing __main__ from a zipfile directory or other import location This is considered a potential security issue as it may lead to privileged processes unexpectedly loading code from user controlled directories in situations where that was not previously the case The interpreter now consistently avoids ever adding the import location s parent directory to sys path and ensures no other sys path entries are inadvertently modified when inserting the import location named on the command line Originally reported as bpo 29723 against Python 3 6rc1 but it was missed at the time that the then upcoming Python 3 5 4 release would also be affected bpo 30657 Fixed possible integer overflow in PyBytes_DecodeEscape CVE 2017 1000158 Original patch by Jay Bosamiya rebased to Python 3 by Miro Hrončok bpo 30947 Upgrade libexpat embedded copy from version 2 2 1 to 2 2 3 to get security fixes Core and Builtins bpo 31095 Fix potential crash during GC caused by tp_dealloc which doesn t call PyObject_GC_UnTrack Library bpo 32072 Fixed issues with binary plists Fixed saving bytearrays Identical objects will be saved only once Equal references will be load as identical objects Added support for saving and loading recursive data structures bpo 31170 expat Update libexpat from 2 2 3 to 2 2 4 Fix copying of partial characters for UTF 8 input libexpat bug 115 https github com libexpat libexpat issues 115 Python 3 5 4 final Release date 2017 08 07 Library bpo 30119 ftplib FTP putline now throws ValueError on commands that contains CR or LF Patch by Donghee Na Python 3 5 4 release candidate 1 Release date 2017 07 23 Security bpo 30730 Prevent environment variables injection in subprocess on Windows Prevent passing other environment variables and command arguments bpo 30694 Upgrade expat copy from 2 2 0 to 2 2 1 to get fixes of multiple security vulnerabilities including CVE 2017 9233 External entity infinite loop DoS CVE 2016 9063 Integer overflow re fix CVE 2016 0718 Fix regression bugs from 2 2 0 s fix to CVE 2016 0718 and CVE 2012 0876 Counter hash flooding with SipHash Note the CVE 2016 5300 Use os specific entropy sources like getrandom doesn t impact Python since Python already gets entropy from the OS to set the expat secret using XML_SetHashSalt bpo 30500 Fix urllib parse splithost to correctly parse fragments For example splithost 127 0 0 1 evil com now correctly returns the 127 0 0 1 host instead of treating evil com as the host in an authentication login host bpo 29591 Update expat copy from 2 1 1 to 2 2 0 to get fixes of CVE 2016 0718 and CVE 2016 4472 See https sourceforge net p expat bugs 537 for more information Core and Builtins bpo 30876 Relative import from unloaded package now reimports the package instead of failing with SystemError Relative import from non package now fails with ImportError rather than SystemError bpo 30765 Avoid blocking in pthread_mutex_lock when PyThread_acquire_lock is asked not to block bpo 27945 Fixed various segfaults with dict when input collections are mutated during searching inserting or comparing Based on patches by Duane Griffin and Tim Mitchell bpo 25794 Fixed type __setattr__ and type __delattr__ for non interned attribute names Based on patch by Eryk Sun bpo 29935 Fixed error messages in the index method of tuple list and deque when pass indices of wrong type bpo 28876 bool range works even if len range raises OverflowError bpo 29600 Fix wrapping coroutine return values in StopIteration bpo 29537 Restore runtime compatibility with bytecode files generated by CPython 3 5 0 to 3 5 2 and adjust the eval loop to avoid the problems that could be caused by the malformed variant of the BUILD_MAP_UNPACK_WITH_CALL opcode that they may contain Patch by Petr Viktorin Serhiy Storchaka and Nick Coghlan bpo 28598 Support __rmod__ for subclasses of str being called before str __mod__ Patch by Martijn Pieters bpo 29602 Fix incorrect handling of signed zeros in complex constructor for complex subclas,en
1804,ses and for inputs having a __complex__ method Patch by Serhiy Storchaka bpo 29347 Fixed possibly dereferencing undefined pointers when creating weakref objects bpo 29438 Fixed use after free problem in key sharing dict bpo 29319 Prevent RunMainFromImporter overwriting sys path 0 bpo 29337 Fixed possible BytesWarning when compare the code objects Warnings could be emitted at compile time bpo 29478 If max_line_length None is specified while using the Compat32 policy it is no longer ignored Patch by Mircea Cosbuc Library bpo 29403 Fix unittest mock s autospec to not fail on method bound builtin functions Patch by Aaron Gallagher bpo 30961 Fix decrementing a borrowed reference in tracemalloc bpo 30886 Fix multiprocessing Queue join_thread it now waits until the thread completes even if the thread was started by the same process which created the queue bpo 29854 Fix segfault in readline when using readline s history size option Patch by Nir Soffer bpo 30807 signal setitimer may disable the timer when passed a tiny value Tiny values such as 1e 6 are valid non zero values for setitimer which is specified as taking microsecond resolution intervals However on some platform our conversion routine could convert 1e 6 into a zero interval therefore disabling the timer instead of re scheduling it bpo 30441 Fix bug when modifying os environ while iterating over it bpo 30532 Fix email header value parser dropping folding white space in certain cases bpo 29169 Update zlib to 1 2 11 bpo 30879 os listdir and os scandir now emit bytes names when called with bytes like argument bpo 30746 Prohibited the character in environment variable names in os putenv and os spawn bpo 29755 Fixed the lgettext family of functions in the gettext module They now always return bytes bpo 30645 Fix path calculation in imp load_package fixing it for cases when a package is only shipped with bytecodes Patch by Alexandru Ardelean bpo 23890 unittest TestCase assertRaises now manually breaks a reference cycle to not keep objects alive longer than expected bpo 30149 inspect signature now supports callables with variable argument parameters wrapped with partialmethod Patch by Donghee Na bpo 29931 Fixed comparison check for ipaddress ip_interface objects Patch by Sanjay Sundaresan bpo 24484 Avoid race condition in multiprocessing cleanup bpo 28994 The traceback no longer displayed for SystemExit raised in a callback registered by atexit bpo 30508 Don t log exceptions if Task Future cancel method was called bpo 28556 Updates to typing module Add generic AsyncContextManager add support for ContextManager on all versions Original PRs by Jelle Zijlstra and Ivan Levkivskyi bpo 29870 Fix ssl sockets leaks when connection is aborted in asyncio ssl implementation Patch by Michaël Sghaïer bpo 29743 Closing transport during handshake process leaks open socket Patch by Nikolay Kim bpo 27585 Fix waiter cancellation in asyncio Lock Patch by Mathieu Sornay bpo 30418 On Windows subprocess Popen communicate now also ignore EINVAL on stdin write if the child process is still running but closed the pipe bpo 30378 Fix the problem that logging handlers SysLogHandler cannot handle IPv6 addresses bpo 29960 Preserve generator state when _random Random setstate raises an exception Patch by Bryan Olson bpo 30414 multiprocessing Queue _feed background running thread do not break from main loop on exception bpo 30003 Fix handling escape characters in HZ codec Based on patch by Ma Lin bpo 30301 Fix AttributeError when using SimpleQueue empty under spawn and forkserver start methods bpo 30329 imaplib and poplib now catch the Windows socket WSAEINVAL error code 10022 on shutdown SHUT_RDWR An invalid operation was attempted This error occurs sometimes on SSL connections bpo 30375 Warnings emitted when compile a regular expression now always point to the line in the user code Previously they could point into inners of the re module if emitted from inside of groups or conditionals bpo 30048 Fixed Task cancel can be ignored when the task is running coroutine and the coroutine returned without any more,en
1805, await bpo 29990 Fix range checking in GB18030 decoder Original patch by Ma Lin bpo 26293 Change resulted because of zipfile breakage See also bpo 29094 bpo 30243 Removed the __init__ methods of _json s scanner and encoder Misusing them could cause memory leaks or crashes Now scanner and encoder objects are completely initialized in the __new__ methods bpo 30185 Avoid KeyboardInterrupt tracebacks in forkserver helper process when Ctrl C is received bpo 28556 Various updates to typing module add typing NoReturn type use WrapperDescriptorType minor bug fixes Original PRs by Jim Fasarakis Hilliard and Ivan Levkivskyi bpo 30205 Fix getsockname for unbound AF_UNIX sockets on Linux bpo 30070 Fixed leaks and crashes in errors handling in the parser module bpo 30061 Fixed crashes in IOBase methods __next__ and readlines when readline or __next__ respectively return non sizeable object Fixed possible other errors caused by not checking results of PyObject_Size PySequence_Size or PyMapping_Size bpo 30068 _io _IOBase readlines will check if it s closed first when hint is present bpo 29694 Fixed race condition in pathlib mkdir with flags parents True Patch by Armin Rigo bpo 29692 Fixed arbitrary unchaining of RuntimeError exceptions in contextlib contextmanager Patch by Siddharth Velankar bpo 29998 Pickling and copying ImportError now preserves name and path attributes bpo 29942 Fix a crash in itertools chain from_iterable when encountering long runs of empty iterables bpo 27863 Fixed multiple crashes in ElementTree caused by race conditions and wrong types bpo 28699 Fixed a bug in pools in multiprocessing pool that raising an exception at the very first of an iterable may swallow the exception or make the program hang Patch by Davin Potts and Xiang Zhang bpo 25803 Avoid incorrect errors raised by Path mkdir exist_ok True when the OS gives priority to errors such as EACCES over EEXIST bpo 29861 Release references to tasks their arguments and their results as soon as they are finished in multiprocessing Pool bpo 29884 faulthandler Restore the old sigaltstack during teardown Patch by Christophe Zeitouny bpo 25455 Fixed crashes in repr of recursive buffered file like objects bpo 29800 Fix crashes in partial __repr__ if the keys of partial keywords are not strings Patch by Michael Seifert bpo 29742 get_extra_info raises exception if get called on closed ssl transport Patch by Nikolay Kim bpo 8256 Fixed possible failing or crashing input if attributes encoding or errors of sys stdin or sys stdout are not set or are not strings bpo 28298 Fix a bug that prevented array Q L and I from accepting big intables objects that have __int__ as elements Patch by Oren Milman bpo 29615 SimpleXMLRPCDispatcher no longer chains KeyError or any other exception to exception s raised in the dispatched methods Patch by Petr Motejlek bpo 29704 asyncio subprocess SubprocessStreamProtocol no longer closes before all pipes are closed bpo 29703 Fix asyncio to support instantiation of new event loops in child processes bpo 29376 Fix assertion error in threading _DummyThread is_alive bpo 29110 Fix file object leak in aifc open when file is given as a filesystem path and is not in valid AIFF format Patch by Anthony Zhang bpo 28961 Fix unittest mock _Call helper don t ignore the name parameter anymore Patch written by Jiajun Huang bpo 29532 Altering a kwarg dictionary passed to functools partial no longer affects a partial object after creation bpo 28556 Various updates to typing module typing Counter typing ChainMap improved ABC caching etc Original PRs by Jelle Zijlstra Ivan Levkivskyi Manuel Krebber and Łukasz Langa bpo 29100 Fix datetime fromtimestamp regression introduced in Python 3 6 0 check minimum and maximum years bpo 29519 Fix weakref spewing exceptions during interpreter shutdown when used with a rare combination of multiprocessing and custom codecs bpo 29416 Prevent infinite loop in pathlib Path mkdir bpo 29444 Fixed out of bounds buffer access in the group method of the match object Based on patch by WGH bpo 29335 Fix subprocess Popen wait when the chil,en
1806,d process has exited to a stopped instead of terminated state ex when under ptrace bpo 29290 Fix a regression in argparse that help messages would wrap at non breaking spaces bpo 28735 Fixed the comparison of mock MagickMock with mock ANY bpo 29011 Fix an important omission by adding Deque to the typing module bpo 29219 Fixed infinite recursion in the repr of uninitialized ctypes CDLL instances bpo 28969 Fixed race condition in C implementation of functools lru_cache KeyError could be raised when cached function with full cache was simultaneously called from different threads with the same uncached arguments bpo 29142 In urllib request suffixes in no_proxy environment variable with leading dots could match related hostnames again e g b c matches a b c Patch by Milan Oberkirch Documentation bpo 30176 Add missing attribute related constants in curses documentation bpo 26985 Add missing info of code object in inspect documentation bpo 28929 Link the documentation to its source file on GitHub bpo 25008 Document smtpd py as effectively deprecated and add a pointer to aiosmtpd a third party asyncio based replacement bpo 26355 Add canonical header link on each page to corresponding major version of the documentation Patch by Matthias Bussonnier bpo 29349 Fix Python 2 syntax in code for building the documentation Tests bpo 30822 Fix regrtest command line parser to allow passing u extralargefile to run test_zipfile64 bpo 30383 regrtest Enhance regrtest and backport features from the master branch Add options coverage testdir list tests list test files don t run them list cases list test identifiers don t run them bpo 30523 matchfile load a list of test filters from a text file bpo 30540 slowest alias to slow Enhance output add timestamp test result currently running tests Tests result xxx summary with total duration etc Fix reference leak hunting in regrtest huntrleaks regrtest now warms up caches create explicitly all internal singletons which are created on demand to prevent false positives when checking for reference leaks bpo 30675 bpo 30357 test_thread setUp now uses support threading_setup and support threading_cleanup to wait until threads complete to avoid random side effects on following tests Initial patch written by Grzegorz Grzywacz bpo 28087 Skip test_asyncore and test_eintr poll failures on macOS Skip some tests of select poll when running on macOS due to unresolved issues with the underlying system poll function on some macOS versions bpo 30197 Enhanced functions swap_attr and swap_item in the test support module They now work when delete replaced attribute or item inside the with statement The old value of the attribute or item or None if it doesn t exist now will be assigned to the target of the as clause if there is one bpo 29571 to match the behaviour of the re LOCALE flag test_re test_locale_flag now uses locale getpreferredencoding False to determine the candidate encoding for the test regex allowing it to correctly skip the test when the default locale encoding is a multi byte encoding Build bpo 29243 Prevent unnecessary rebuilding of Python during make test make install and some other make targets when configured with enable optimizations bpo 23404 Don t regenerate generated files based on file modification time anymore the action is now explicit Replace make touch with make regen all bpo 29643 Fix enable optimization didn t work Windows bpo 30687 Locate msbuild exe on Windows when building rather than vcvarsall bat bpo 29392 Prevent crash when passing invalid arguments into msvcrt module C API bpo 27867 Function PySlice_GetIndicesEx is replaced with a macro if Py_LIMITED_API is set to the value between 0x03050400 and 0x03060000 not including or 0x03060100 or higher bpo 29083 Fixed the declaration of some public API functions PyArg_VaParse and PyArg_VaParseTupleAndKeywords were not available in limited API PyArg_ValidateKeywordArguments PyArg_UnpackTuple and Py_BuildValue were not available in limited API of version 3 3 when PY_SSIZE_T_CLEAN is defined Python 3 5 3 final Release date 2017 01 17 There were n,en
1807,o code changes between 3 5 3rc1 and 3 5 3 final Python 3 5 3 release candidate 1 Release date 2017 01 02 Security bpo 27278 Fix os urandom implementation using getrandom on Linux Truncate size to INT_MAX and loop until we collected enough random bytes instead of casting a directly Py_ssize_t to int bpo 22636 Avoid shell injection problems with ctypes util find_library Core and Builtins bpo 29073 bytearray formatting no longer truncates on first null byte bpo 28932 Do not include sys random h if it does not exist bpo 28147 Fix a memory leak in split table dictionaries setattr must not convert combined table into split table bpo 25677 Correct the positioning of the syntax error caret for indented blocks Based on patch by Michael Layzell bpo 29000 Fixed bytes formatting of octals with zero padding in alternate form bpo 28512 Fixed setting the offset attribute of SyntaxError by PyErr_SyntaxLocationEx and PyErr_SyntaxLocationObject bpo 28991 functools lru_cache was susceptible to an obscure reentrancy bug caused by a monkey patched len function bpo 28648 Fixed crash in Py_DecodeLocale in debug build on Mac OS X when decode astral characters Patch by Xiang Zhang bpo 19398 Extra slash no longer added to sys path components in case of empty compile time PYTHONPATH components bpo 28426 Fixed potential crash in PyUnicode_AsDecodedObject in debug build bpo 23782 Fixed possible memory leak in _PyTraceback_Add and exception loss in PyTraceBack_Here bpo 28379 Added sanity checks and tests for PyUnicode_CopyCharacters Patch by Xiang Zhang bpo 28376 The type of long range iterator is now registered as Iterator Patch by Oren Milman bpo 28376 The constructor of range_iterator now checks that step is not 0 Patch by Oren Milman bpo 26906 Resolving special methods of uninitialized type now causes implicit initialization of the type instead of a fail bpo 18287 PyType_Ready now checks that tp_name is not NULL Original patch by Niklas Koep bpo 24098 Fixed possible crash when AST is changed in process of compiling it bpo 28350 String constants with null character no longer interned bpo 26617 Fix crash when GC runs during weakref callbacks bpo 27942 String constants now interned recursively in tuples and frozensets bpo 21578 Fixed misleading error message when ImportError called with invalid keyword args bpo 28203 Fix incorrect type in error message from complex 1 0 2 3 Patch by Soumya Sharma bpo 27955 Fallback on reading dev urandom device when the getrandom syscall fails with EPERM for example when blocked by SECCOMP bpo 28131 Fix a regression in zipimport s compile_source zipimport should use the same optimization level as the interpreter bpo 25221 Fix corrupted result from PyLong_FromLong 0 when Python is compiled with NSMALLPOSINTS 0 bpo 25758 Prevents zipimport from unnecessarily encoding a filename patch by Eryk Sun bpo 28189 dictitems_contains no longer swallows compare errors Patch by Xiang Zhang bpo 27812 Properly clear out a generator s frame s backreference to the generator to prevent crashes in frame clear bpo 27811 Fix a crash when a coroutine that has not been awaited is finalized with warnings as errors enabled bpo 27587 Fix another issue found by PVS Studio Null pointer check after use of def in _PyState_AddModule Initial patch by Christian Heimes bpo 26020 set literal evaluation order did not match documented behaviour bpo 27782 Multi phase extension module import now correctly allows the m_methods field to be used to add module level functions to instances of non module types returned from Py_create_mod Patch by Xiang Zhang bpo 27936 The round function accepted a second None argument for some types but not for others Fixed the inconsistency by accepting None for all numeric types bpo 27487 Warn if a submodule argument to python m or runpy run_module is found in sys modules after parent packages are imported but before the submodule is executed bpo 27558 Fix a SystemError in the implementation of raise statement In a brand new thread raise a RuntimeError since there is no active exception to reraise Patch written by Xiang Zhang ,en
1808,bpo 27419 Standard __import__ no longer look up __import__ in globals or builtins for importing submodules or from import Fixed handling an error of non string package name bpo 27083 Respect the PYTHONCASEOK environment variable under Windows bpo 27514 Make having too many statically nested blocks a SyntaxError instead of SystemError bpo 27473 Fixed possible integer overflow in bytes and bytearray concatenations Patch by Xiang Zhang bpo 27507 Add integer overflow check in bytearray extend Patch by Xiang Zhang bpo 27581 Don t rely on wrapping for overflow check in PySequence_Tuple Patch by Xiang Zhang bpo 27443 __length_hint__ of bytearray iterators no longer return a negative integer for a resized bytearray bpo 27942 Fix memory leak in codeobject c Library bpo 15812 inspect getframeinfo now correctly shows the first line of a context Patch by Sam Breese bpo 29094 Offsets in a ZIP file created with extern file object and modes w and x now are relative to the start of the file bpo 13051 Fixed recursion errors in large or resized curses textpad Textbox Based on patch by Tycho Andersen bpo 29119 Fix weakrefs in the pure python version of collections OrderedDict move_to_end method Contributed by Andra Bogildea bpo 9770 curses ascii predicates now work correctly with negative integers bpo 28427 old keys should not remove new values from WeakValueDictionary when collecting from another thread bpo 28923 Remove editor artifacts from Tix py bpo 28871 Fixed a crash when deallocate deep ElementTree bpo 19542 Fix bugs in WeakValueDictionary setdefault and WeakValueDictionary pop when a GC collection happens in another thread bpo 20191 Fixed a crash in resource prlimit when pass a sequence that doesn t own its elements as limits bpo 28779 multiprocessing set_forkserver_preload would crash the forkserver process if a preloaded module instantiated some multiprocessing objects such as locks bpo 28847 dbm dumb now supports reading read only files and no longer writes the index file when it is not changed bpo 25659 In ctypes prevent a crash calling the from_buffer and from_buffer_copy methods on abstract classes like Array bpo 28732 Fix crash in os spawnv with no elements in args bpo 28485 Always raise ValueError for negative compileall compile_dir workers parameter even when multithreading is unavailable bpo 28387 Fixed possible crash in _io TextIOWrapper deallocator when the garbage collector is invoked in other thread Based on patch by Sebastian Cufre bpo 27517 LZMA compressor and decompressor no longer raise exceptions if given empty data twice Patch by Benjamin Fogle bpo 28549 Fixed segfault in curses s addch with ncurses6 bpo 28449 tarfile open with mode r or r now tries to open a tar file with compression before trying to open it without compression Otherwise it had 50 chance failed with ignore_zeros True bpo 23262 The webbrowser module now supports Firefox 36 and derived browsers Based on patch by Oleg Broytman bpo 27939 Fixed bugs in tkinter ttk LabeledScale and tkinter Scale caused by representing the scale as float value internally in Tk tkinter IntVar now works if float value is set to underlying Tk variable bpo 28255 calendar TextCalendar prmonth no longer prints a space at the start of new line after printing a month s calendar Patch by Xiang Zhang bpo 20491 The textwrap TextWrapper class now honors non breaking spaces Based on patch by Kaarle Ritvanen bpo 28353 os fwalk no longer fails on broken links bpo 25464 Fixed HList header_exists in tkinter tix module by addin a workaround to Tix library bug bpo 28488 shutil make_archive no longer add entry to ZIP archive bpo 24452 Make webbrowser support Chrome on Mac OS X bpo 20766 Fix references leaked by pdb in the handling of SIGINT handlers bpo 26293 Fixed writing ZIP files that starts not from the start of the file Offsets in ZIP file now are relative to the start of the archive in conforming to the specification bpo 28321 Fixed writing non BMP characters with binary format in plistlib bpo 28322 Fixed possible crashes when unpickle itertools objects from incorrect pickle data B,en
1809,ased on patch by John Leitch Fix possible integer overflows and crashes in the mmap module with unusual usage patterns bpo 1703178 Fix the ability to pass the link objects option to the distutils build_ext command bpo 28253 Fixed calendar functions for extreme months 0001 01 and 9999 12 Methods itermonthdays and itermonthdays2 are reimplemented so that they don t call itermonthdates which can cause datetime date under overflow bpo 28275 Fixed possible use after free in the decompress methods of the LZMADecompressor and BZ2Decompressor classes Original patch by John Leitch bpo 27897 Fixed possible crash in sqlite3 Connection create_collation if pass invalid string like object as a name Patch by Xiang Zhang bpo 18893 Fix invalid exception handling in Lib ctypes macholib dyld py Patch by Madison May bpo 27611 Fixed support of default root window in the tkinter tix module bpo 27348 In the traceback module restore the formatting of exception messages like Exception None This fixes a regression introduced in 3 5a2 bpo 25651 Allow false values to be used for msg parameter of subTest bpo 27932 Prevent memory leak in win32_ver Fix UnboundLocalError in socket _sendfile_use_sendfile bpo 28075 Check for ERROR_ACCESS_DENIED in Windows implementation of os stat Patch by Eryk Sun bpo 25270 Prevent codecs escape_encode from raising SystemError when an empty bytestring is passed bpo 28181 Get antigravity over HTTPS Patch by Kaartic Sivaraam bpo 25895 Enable WebSocket URL schemes in urllib parse urljoin Patch by Gergely Imreh and Markus Holtermann bpo 27599 Fixed buffer overrun in binascii b2a_qp and binascii a2b_qp bpo 19003 m email generator now replaces only r and or n line endings per the RFC instead of all unicode line endings bpo 28019 itertools count no longer rounds non integer step in range between 1 0 and 2 0 to 1 bpo 25969 Update the lib2to3 grammar to handle the unpacking generalizations added in 3 5 bpo 14977 mailcap now respects the order of the lines in the mailcap files first match as required by RFC 1542 Patch by Michael Lazar bpo 24594 Validates persist parameter when opening MSI database bpo 17582 xml etree ElementTree nows preserves whitespaces in attributes Patch by Duane Griffin Reviewed and approved by Stefan Behnel bpo 28047 Fixed calculation of line length used for the base64 CTE in the new email policies bpo 27445 Don t pass str _charset to MIMEText set_payload Patch by Claude Paroz bpo 22450 urllib now includes an Accept header among the default headers This makes the results of REST API requests more consistent and predictable especially when proxy servers are involved lib2to3 pgen3 driver load_grammar now creates a stable cache file between runs given the same Grammar txt input regardless of the hash randomization setting bpo 27570 Avoid zero length memcpy etc calls with null source pointers in the ctypes and array modules bpo 22233 Break email header lines only on the RFC specified CR and LF characters not on arbitrary unicode line breaks This also fixes a bug in HTTP header parsing bpo 27988 Fix email iter_attachments incorrect mutation of payload list bpo 27691 Fix ssl module s parsing of GEN_RID subject alternative name fields in X 509 certs bpo 27850 Remove 3DES from ssl module s default cipher list to counter measure sweet32 attack CVE 2016 2183 bpo 27766 Add ChaCha20 Poly1305 to ssl module s default cipher list Required OpenSSL 1 1 0 or LibreSSL bpo 26470 Port ssl and hashlib module to OpenSSL 1 1 0 Remove support for passing a file descriptor to os access It never worked but previously didn t raise bpo 12885 Fix error when distutils encounters symlink bpo 27881 Fixed possible bugs when setting sqlite3 Connection isolation_level Based on patch by Xiang Zhang bpo 27861 Fixed a crash in sqlite3 Connection cursor when a factory creates not a cursor Patch by Xiang Zhang bpo 19884 Avoid spurious output on OS X with Gnu Readline bpo 27706 Restore deterministic behavior of random Random seed for string seeds using seeding version 1 Allows sequences of calls to random to exactly match those obtained in Python 2,en
1810, Patch by Nofar Schnider bpo 10513 Fix a regression in Connection commit Statements should not be reset after a commit A new version of typing py from https github com python typing Collection only for 3 6 bpo 27598 Add FrozenSet to __all__ upstream 261 Fix crash in _get_type_vars upstream 259 Remove the dict constraint in ForwardRef _eval_type upstream 252 bpo 27539 Fix unnormalised Fraction __pow__ result in the case of negative exponent and negative base bpo 21718 cursor description is now available for queries using CTEs bpo 2466 posixpath ismount now correctly recognizes mount points which the user does not have permission to access bpo 27773 Correct some memory management errors server_hostname in _ssl wrap_socket bpo 26750 unittest mock create_autospec now works properly for subclasses of property and other data descriptors In the curses module raise an error if window getstr or window instr is passed a negative value bpo 27783 Fix possible usage of uninitialized memory in operator methodcaller bpo 27774 Fix possible Py_DECREF on unowned object in _sre bpo 27760 Fix possible integer overflow in binascii b2a_qp bpo 27758 Fix possible integer overflow in the _csv module for large record lengths bpo 27568 Prevent HTTPoxy attack CVE 2016 1000110 Ignore the HTTP_PROXY variable when REQUEST_METHOD environment is set which indicates that the script is in CGI mode bpo 27656 Do not assume sched h defines any SCHED_ constants bpo 27130 In the zlib module fix handling of large buffers typically 4 GiB when compressing and decompressing Previously inputs were limited to 4 GiB and compression and decompression operations did not properly handle results of 4 GiB bpo 27533 Release GIL in nt _isdir bpo 17711 Fixed unpickling by the persistent ID with protocol 0 Original patch by Alexandre Vassalotti bpo 27522 Avoid an unintentional reference cycle in email feedparser bpo 26844 Fix error message for imp find_module to refer to path instead of name Patch by Lev Maximov bpo 23804 Fix SSL zero length recv calls to not block and not raise an error about unclean EOF bpo 27466 Change time format returned by http cookie time2netscape confirming the netscape cookie format and making it consistent with documentation bpo 26664 Fix activate fish by removing mis use of bpo 22115 Fixed tracing Tkinter variables trace_vdelete with wrong mode no longer break tracing trace_vinfo now always returns a list of pairs of strings tracing in the u mode now works Fix a scoping issue in importlib util LazyLoader which triggered an UnboundLocalError when lazy loading a module that was already put into sys modules bpo 27079 Fixed curses ascii functions isblank iscntrl and ispunct bpo 26754 Some functions compile etc accepted a filename argument encoded as an iterable of integers Now only strings and byte like objects are accepted bpo 27048 Prevents distutils failing on Windows when environment variables contain non ASCII characters bpo 27330 Fixed possible leaks in the ctypes module bpo 27238 Got rid of bare excepts in the turtle module Original patch by Jelle Zijlstra bpo 27122 When an exception is raised within the context being managed by a contextlib ExitStack and one of the exit stack generators catches and raises it in a chain do not re raise the original exception when exiting let the new chained one through This avoids the PEP 479 bug described in issue25782 bpo 26386 Fixed ttk TreeView selection operations with item id s containing spaces bpo 16182 Fix various functions in the readline module to use the locale encoding and fix get_begidx and get_endidx to return code point indexes bpo 27392 Add loop connect_accepted_socket Patch by Jim Fulton bpo 27930 Improved behaviour of logging handlers QueueListener Thanks to Paulo Andrade and Petr Viktorin for the analysis and patch bpo 21201 Improves readability of multiprocessing error message Thanks to Wojciech Walczak for patch bpo 27456 asyncio Set TCP_NODELAY by default bpo 27906 Fix socket accept exhaustion during high TCP traffic Patch by Kevin Conway bpo 28174 Handle when SO_REUSEPORT isn t properly s,en
1811,upported Patch by Seth Michael Larson bpo 26654 Inspect functools partial in asyncio Handle __repr__ Patch by iceboy bpo 26909 Fix slow pipes IO in asyncio Patch by INADA Naoki bpo 28176 Fix callbacks race in asyncio SelectorLoop sock_connect bpo 27759 Fix selectors incorrectly retain invalid file descriptors Patch by Mark Williams bpo 28368 Refuse monitoring processes if the child watcher has no loop attached Patch by Vincent Michel bpo 28369 Raise RuntimeError when transport s FD is used with add_reader add_writer etc bpo 28370 Speedup asyncio StreamReader readexactly Patch by Коренберг Марк bpo 28371 Deprecate passing asyncio Handles to run_in_executor bpo 28372 Fix asyncio to support formatting of non python coroutines bpo 28399 Remove UNIX socket from FS before binding Patch by Коренберг Марк bpo 27972 Prohibit Tasks to await on themselves bpo 26923 Fix asyncio Gather to refuse being cancelled once all children are done Patch by Johannes Ebke bpo 26796 Don t configure the number of workers for default threadpool executor Initial patch by Hans Lawrenz bpo 28600 Optimize loop call_soon bpo 28613 Fix get_event_loop return the current loop if called from coroutines callbacks bpo 28639 Fix inspect isawaitable to always return bool Patch by Justin Mayfield bpo 28652 Make loop methods reject socket kinds they do not support bpo 28653 Fix a refleak in functools lru_cache bpo 28703 Fix asyncio iscoroutinefunction to handle Mock objects bpo 24142 Reading a corrupt config file left the parser in an invalid state Original patch by Florian Höch bpo 28990 Fix SSL hanging if connection is closed before handshake completed Patch by HoHo Ho IDLE bpo 15308 Add interrupt execution C to Shell menu Patch by Roger Serwy updated by Bayard Randel bpo 27922 Stop IDLE tests from flashing gui widgets on the screen Add version to title of IDLE help window bpo 25564 In section on IDLE console differences mention that using exec means that __builtins__ is defined for each statement bpo 27714 text_textview and test_autocomplete now pass when re run in the same process This occurs when test_idle fails when run with the w option but without jn Fix warning from test_config bpo 25507 IDLE no longer runs buggy code because of its tkinter imports Users must include the same imports required to run directly in Python bpo 27452 add line counter and crc to IDLE configHandler test dump bpo 27365 Allow non ascii chars in IDLE NEWS txt for contributor names bpo 27245 IDLE Cleanly delete custom themes and key bindings Previously when IDLE was started from a console or by import a cascade of warnings was emitted Patch by Serhiy Storchaka C API bpo 28808 PyUnicode_CompareWithASCIIString now never raises exceptions bpo 26754 PyUnicode_FSDecoder accepted a filename argument encoded as an iterable of integers Now only strings and bytes like objects are accepted Documentation bpo 28513 Documented command line interface of zipfile Tests bpo 28950 Disallow j0 to be combined with T l M in regrtest command line arguments bpo 28666 Now test support rmtree is able to remove unwritable or unreadable directories bpo 23839 Various caches now are cleared before running every test file bpo 28409 regrtest fix the parser of command line arguments bpo 27787 Call gc collect before checking each test for dangling threads since the dangling threads are weak references bpo 27369 In test_pyexpat avoid testing an error message detail that changed in Expat 2 2 0 Tools Demos bpo 27952 Get Tools scripts fixcid py working with Python 3 and the current re module avoid invalid Python backslash escapes and fix a bug parsing escaped C quote signs bpo 27332 Fixed the type of the first argument of module level functions generated by Argument Clinic Patch by Petr Viktorin bpo 27418 Fixed Tools importbench importbench py Windows bpo 28251 Improvements to help manuals on Windows bpo 28110 launcher msi has different product codes between 32 bit and 64 bit bpo 25144 Ensures TargetDir is set before continuing with custom install bpo 27469 Adds a shell extension to the launcher so that drag and drop w,en
1812,orks correctly bpo 27309 Enabled proper Windows styles in python w exe manifest Build bpo 29080 Removes hard dependency on hg exe from PCBuild build bat bpo 23903 Added missed names to PC python3 def bpo 10656 Fix out of tree building on AIX Patch by Tristan Carel and Michael Haubenwallner bpo 26359 Rename with optimiations to enable optimizations bpo 28444 Fix missing extensions modules when cross compiling bpo 28248 Update Windows build and OS X installers to use OpenSSL 1 0 2j bpo 28258 Fixed build with Estonian locale python config and distclean targets in Makefile Patch by Arfrever Frehtes Taifersar Arahesis bpo 26661 setup py now detects system libffi with multiarch wrapper bpo 28066 Fix the logic that searches build directories for generated include files when building outside the source tree bpo 15819 Remove redundant include search directory option for building outside the source tree bpo 27566 Fix clean target in freeze makefile patch by Lisa Roach bpo 27705 Update message in validate_ucrtbase py bpo 27983 Cause lack of llvm profdata tool when using clang as required for PGO linking to be a configure time error rather than make time when with optimizations is enabled Also improve our ability to find the llvm profdata tool on MacOS and some Linuxes bpo 26307 The profile opt build now applies PGO to the built in modules bpo 26359 Add the with optimizations configure flag bpo 27713 Suppress spurious build warnings when updating importlib s bootstrap files Patch by Xiang Zhang bpo 25825 Correct the references to Modules python exp and ld_so_aix which are required on AIX This updates references to an installation path that was changed in 3 2a4 and undoes changed references to the build tree that were made in 3 5 0a1 bpo 27453 CPP invocation in configure must use CPPFLAGS Patch by Chi Hsuan Yen bpo 27641 The configure script now inserts comments into the makefile to prevent the pgen and _freeze_importlib executables from being cross compiled bpo 26662 Set PYTHON_FOR_GEN in configure as the Python program to be used for file generation during the build bpo 10910 Avoid C compilation errors on FreeBSD and OS X Also update FreedBSD version checks for the original ctype UTF 8 workaround bpo 28676 Prevent missing getentropy declaration warning on macOS Patch by Gareth Rees Python 3 5 2 final Release date 2016 06 26 Core and Builtins bpo 26930 Update Windows builds to use OpenSSL 1 0 2h Tests bpo 26867 Ubuntu s openssl OP_NO_SSLv3 is forced on by default fix test IDLE bpo 27365 Allow non ascii in idlelib NEWS txt minimal part for 3 5 2 Python 3 5 2 release candidate 1 Release date 2016 06 12 Security bpo 26556 Update expat to 2 1 1 fixes CVE 2015 1283 Fix TLS stripping vulnerability in smtplib CVE 2016 0772 Reported by Team Oststrom bpo 26839 On Linux os urandom now calls getrandom with GRND_NONBLOCK to fall back on reading dev urandom if the urandom entropy pool is not initialized yet Patch written by Colm Buckley bpo 26657 Fix directory traversal vulnerability with http server on Windows This fixes a regression that was introduced in 3 3 4rc1 and 3 4 0rc1 Based on patch by Philipp Hagemeister bpo 26313 ssl py _load_windows_store_certs fails if windows cert store is empty Patch by Baji bpo 25939 On Windows open the cert store readonly in ssl enum_certificates Core and Builtins bpo 27066 Fixed SystemError if a custom opener for open returns a negative number without setting an exception bpo 20041 Fixed TypeError when frame f_trace is set to None Patch by Xavier de Gaye bpo 26168 Fixed possible refleaks in failing Py_BuildValue with the N format unit bpo 26991 Fix possible refleak when creating a function with annotations bpo 27039 Fixed bytearray remove for values greater than 127 Patch by Joe Jevnik bpo 23640 int from_bytes no longer bypasses constructors for subclasses bpo 26811 gc get_objects no longer contains a broken tuple with NULL pointer bpo 20120 Use RawConfigParser for pypirc parsing removing support for interpolation unintentionally added with move to Python 3 Behavior no longer does any interpolation in pypirc ,en
1813,files matching behavior in Python 2 7 and Setuptools 19 0 bpo 26659 Make the builtin slice type support cycle collection bpo 26718 super __init__ no longer leaks memory if called multiple times NOTE A direct call of super __init__ is not endorsed bpo 25339 PYTHONIOENCODING now has priority over locale in setting the error handler for stdin and stdout bpo 26494 Fixed crash on iterating exhausting iterators Affected classes are generic sequence iterators iterators of str bytes bytearray list tuple set frozenset dict OrderedDict corresponding views and os scandir iterator bpo 26581 If coding cookie is specified multiple times on a line in Python source code file only the first one is taken to account bpo 26464 Fix str translate when string is ASCII and first replacements removes character but next replacement uses a non ASCII character or a string longer than 1 character Regression introduced in Python 3 5 0 bpo 22836 Ensure exception reports from PyErr_Display and PyErr_WriteUnraisable are sensible even when formatting them produces secondary errors This affects the reports produced by sys __excepthook__ and when __del__ raises an exception bpo 26302 Correct behavior to reject comma as a legal character for cookie names bpo 4806 Avoid masking the original TypeError exception when using star unpacking in function calls Based on patch by Hagen Fürstenau and Daniel Urban bpo 27138 Fix the doc comment for FileFinder find_spec bpo 26154 Add a new private _PyThreadState_UncheckedGet function to get the current Python thread state but don t issue a fatal error if it is NULL This new function must be used instead of accessing directly the _PyThreadState_Current variable The variable is no more exposed since Python 3 5 1 to hide the exact implementation of atomic C types to avoid compiler issues bpo 26194 Deque insert gave odd results for bounded deques that had reached their maximum size Now an IndexError will be raised when attempting to insert into a full deque bpo 25843 When compiling code don t merge constants if they are equal but have a different types For example f1 f2 lambda 1 lambda 1 0 is now correctly compiled to two different functions f1 returns 1 int and f2 returns 1 0 int even if 1 and 1 0 are equal bpo 22995 UPDATE Comment out the one of the pickleability tests in _PyObject_GetState due to regressions observed in Cython based projects bpo 25961 Disallowed null characters in the type name bpo 25973 Fix segfault when an invalid nonlocal statement binds a name starting with two underscores bpo 22995 Instances of extension types with a state that aren t subclasses of list or dict and haven t implemented any pickle related methods __reduce__ __reduce_ex__ __getnewargs__ __getnewargs_ex__ or __getstate__ can no longer be pickled Including memoryview bpo 20440 Massive replacing unsafe attribute setting code with special macro Py_SETREF bpo 25766 Special method __bytes__ now works in str subclasses bpo 25421 __sizeof__ methods of builtin types now use dynamic basic size This allows sys getsize to work correctly with their subclasses with __slots__ defined bpo 25709 Fixed problem with in place string concatenation and utf 8 cache bpo 27147 Mention PEP 420 in the importlib docs bpo 24097 Fixed crash in object __reduce__ if slot name is freed inside __getattr__ bpo 24731 Fixed crash on converting objects with special methods __bytes__ __trunc__ and __float__ returning instances of subclasses of bytes int and float to subclasses of bytes int and float correspondingly bpo 26478 Fix semantic bugs when using binary operators with dictionary views and tuples bpo 26171 Fix possible integer overflow and heap corruption in zipimporter get_data bpo 25660 Fix TAB key behaviour in REPL with readline bpo 25887 Raise a RuntimeError when a coroutine object is awaited more than once bpo 27243 Update the __aiter__ protocol instead of returning an awaitable that resolves to an asynchronous iterator the asynchronous iterator should be returned directly Doing the former will trigger a PendingDeprecationWarning Library bpo 21386 Implement missin,en
1814,g IPv4Address is_global property It was documented since 07a5610bae9d Initial patch by Roger Luethi bpo 20900 distutils register command now decodes HTTP responses correctly Initial patch by ingrid A new version of typing py provides several new classes and features overload outside stubs Reversible DefaultDict Text ContextManager Type NewType TYPE_CHECKING and numerous bug fixes note that some of the new features are not yet implemented in mypy or other static analyzers Also classes for PEP 492 Awaitable AsyncIterable AsyncIterator have been added in fact they made it into 3 5 1 but were never mentioned bpo 25738 Stop http server BaseHTTPRequestHandler send_error from sending a message body for 205 Reset Content Also don t send Content header fields in responses that don t have a body Patch by Susumu Koshiba bpo 21313 Fix the platform module to tolerate when sys version contains truncated build information bpo 27164 In the zlib module allow decompressing raw Deflate streams with a predefined zdict Based on patch by Xiang Zhang bpo 24291 Fix wsgiref simple_server WSGIRequestHandler to completely write data to the client Previously it could do partial writes and truncate data Also wsgiref handler ServerHandler can now handle stdout doing partial writes but this is deprecated bpo 26809 Add __all__ to string Patch by Emanuel Barry bpo 26373 subprocess Popen communicate now correctly ignores BrokenPipeError when the child process dies before communicate is called in more all circumstances bpo 21776 distutils upload now correctly handles HTTPError Initial patch by Claudiu Popa bpo 27114 Fix SSLContext _load_windows_store_certs fails with PermissionError bpo 18383 Avoid creating duplicate filters when using filterwarnings and simplefilter Based on patch by Alex Shkop bpo 27057 Fix os set_inheritable on Android ioctl is blocked by SELinux and fails with EACCESS The function now falls back to fcntl Patch written by Michał Bednarski bpo 27014 Fix infinite recursion using typing py Thanks to Kalle Tuure bpo 14132 Fix urllib request redirect handling when the target only has a query string Original fix by Ján Janech bpo 17214 The urllib request module now percent encodes non ASCII bytes found in redirect target URLs Some servers send Location header fields with non ASCII bytes but http client requires the request target to be ASCII encodable otherwise a UnicodeEncodeError is raised Based on patch by Christian Heimes bpo 26892 Honor debuglevel flag in urllib request HTTPHandler Patch contributed by Chi Hsuan Yen bpo 22274 In the subprocess module allow stderr to be redirected to stdout even when stdout is not redirected Patch by Akira Li bpo 26807 mock_open files no longer error on readline at end of file Patch from Yolanda Robla bpo 25745 Fixed leaking a userptr in curses panel destructor bpo 26977 Removed unnecessary and ignored call to sum of squares helper in statistics pvariance bpo 26881 The modulefinder module now supports extended opcode arguments bpo 23815 Fixed crashes related to directly created instances of types in _tkinter and curses panel modules bpo 17765 weakref ref no longer silently ignores keyword arguments Patch by Georg Brandl bpo 26873 xmlrpc now raises ResponseError on unsupported type tags instead of silently return incorrect result bpo 26711 Fixed the comparison of plistlib Data with other types bpo 24114 Fix an uninitialized variable in ctypes util The bug only occurs on SunOS when the ctypes implementation searches for the crle program Patch by Xiang Zhang Tested on SunOS by Kees Bos bpo 26864 In urllib request change the proxy bypass host checking against no_proxy to be case insensitive and to not match unrelated host names that happen to have a bypassed hostname as a suffix Patch by Xiang Zhang bpo 26634 recursive_repr now sets __qualname__ of wrapper Patch by Xiang Zhang bpo 26804 urllib request will prefer lower_case proxy environment variables over UPPER_CASE or Mixed_Case ones Patch contributed by Hans Peter Jansen bpo 26837 assertSequenceEqual now correctly outputs non stringified differing items l,en
1815,ike bytes in the b mode This affects assertListEqual and assertTupleEqual bpo 26041 Remove will be removed in Python 3 7 from deprecation messages of platform dist and platform linux_distribution Patch by Kumaripaba Miyurusara Athukorala bpo 26822 itemgetter attrgetter and methodcaller objects no longer silently ignore keyword arguments bpo 26733 Disassembling a class now disassembles class and static methods Patch by Xiang Zhang bpo 26801 Fix error handling in shutil get_terminal_size catch AttributeError instead of NameError Patch written by Emanuel Barry bpo 24838 tarfile s ustar and gnu formats now correctly calculate name and link field limits for multibyte character encodings like utf 8 bpo 26717 Stop encoding Latin 1 ized WSGI paths with UTF 8 Patch by Anthony Sottile bpo 26735 Fix os urandom on Solaris 11 3 and newer when reading more than 1 024 bytes call getrandom multiple times with a limit of 1024 bytes per call bpo 16329 Add webm to mimetypes types_map Patch by Giampaolo Rodola bpo 13952 Add csv to mimetypes types_map Patch by Geoff Wilson bpo 26709 Fixed Y2038 problem in loading binary PLists bpo 23735 Handle terminal resizing with Readline 6 3 by installing our own SIGWINCH handler Patch by Eric Price bpo 26586 In http server respond with 413 Request header fields too large if there are too many header fields to parse rather than killing the connection and raising an unhandled exception Patch by Xiang Zhang bpo 22854 Change BufferedReader writable and BufferedWriter readable to always return False bpo 25195 Fix a regression in mock MagicMock _Call is a subclass of tuple changeset 3603bae63c13 only works for classes so we need to implement __ne__ ourselves Patch by Andrew Plummer bpo 26644 Raise ValueError rather than SystemError when a negative length is passed to SSLSocket recv or read bpo 23804 Fix SSL recv 0 and read 0 methods to return zero bytes instead of up to 1024 bpo 26616 Fixed a bug in datetime astimezone method bpo 21925 warnings formatwarning now catches exceptions on linecache getline to be able to log ResourceWarning emitted late during the Python shutdown process bpo 24266 Ctrl C during Readline history search now cancels the search mode when compiled with Readline 7 bpo 26560 Avoid potential ValueError in BaseHandler start_response Initial patch by Peter Inglesby bpo 26569 Fix pyclbr readmodule and pyclbr readmodule_ex to support importing packages bpo 26499 Account for remaining Content Length in HTTPResponse readline and read1 Based on patch by Silent Ghost Also document that HTTPResponse now supports these methods bpo 25320 Handle sockets in directories unittest discovery is scanning Patch from Victor van den Elzen bpo 16181 cookiejar http2time now returns None if year is higher than datetime MAXYEAR bpo 26513 Fixes platform module detection of Windows Server bpo 23718 Fixed parsing time in week 0 before Jan 1 Original patch by Tamás Bence Gedai bpo 20589 Invoking Path owner and Path group on Windows now raise NotImplementedError instead of ImportError bpo 26177 Fixed the keys method for Canvas and Scrollbar widgets bpo 15068 Got rid of excessive buffering in the fileinput module The bufsize parameter is no longer used bpo 2202 Fix UnboundLocalError in AbstractDigestAuthHandler get_algorithm_impls Initial patch by Mathieu Dupuy bpo 25718 Fixed pickling and copying the accumulate iterator with total is None bpo 26475 Fixed debugging output for regular expressions with the x flag bpo 26457 Fixed the subnets methods in IP network classes for the case when resulting prefix length is equal to maximal prefix length Based on patch by Xiang Zhang bpo 26385 Remove the file if the internal open call in NamedTemporaryFile fails Patch by Silent Ghost bpo 26402 Fix XML RPC client to retry when the server shuts down a persistent connection This was a regression related to the new http client RemoteDisconnected exception in 3 5 0a4 bpo 25913 Leading is optional now in base64 a85decode with adobe True Patch by Swati Jaiswal bpo 26186 Remove an invalid type check in importlib util LazyLoader bpo 26367 i,en
1816,mportlib __import__ raises SystemError like builtins __import__ when level is specified but without an accompanying package specified bpo 26309 In the socketserver module shut down the request closing the connected socket when verify_request returns false Patch by Aviv Palivoda bpo 25995 os walk no longer uses FDs proportional to the tree depth bpo 26117 The os scandir iterator now closes file descriptor not only when the iteration is finished but when it was failed with error bpo 25911 Restored support of bytes paths in os walk on Windows bpo 26045 Add UTF 8 suggestion to error message when posting a non Latin 1 string with http client bpo 12923 Reset FancyURLopener s redirect counter even if there is an exception Based on patches by Brian Brazil and Daniel Rocco bpo 25945 Fixed a crash when unpickle the functools partial object with wrong state Fixed a leak in failed functools partial constructor args and keywords attributes of functools partial have now always types tuple and dict correspondingly bpo 26202 copy deepcopy now correctly copies range objects with non atomic attributes bpo 23076 Path glob now raises a ValueError if it s called with an invalid pattern Patch by Thomas Nyberg bpo 19883 Fixed possible integer overflows in zipimport bpo 26227 On Windows getnameinfo gethostbyaddr and gethostbyname_ex functions of the socket module now decode the hostname from the ANSI code page rather than UTF 8 bpo 26147 xmlrpc now works with strings not encodable with used non UTF 8 encoding bpo 25935 Garbage collector now breaks reference loops with OrderedDict bpo 16620 Fixed AttributeError in msilib Directory glob bpo 26013 Added compatibility with broken protocol 2 pickles created in old Python 3 versions 3 4 3 and lower bpo 25850 Use cross compilation by default for 64 bit Windows bpo 17633 Improve zipimport s support for namespace packages bpo 24705 Fix sysconfig _parse_makefile not expanding vars appearing before vars bpo 22138 Fix mock patch behavior when patching descriptors Restore original values after patching Patch contributed by Sean McCully bpo 25672 In the ssl module enable the SSL_MODE_RELEASE_BUFFERS mode option if it is safe to do so bpo 26012 Don t traverse into symlinks for pattern in pathlib Path r glob bpo 24120 Ignore PermissionError when traversing a tree with pathlib Path r glob Patch by Ulrich Petri bpo 25447 fileinput now uses sys stdin as is if it does not have a buffer attribute restores backward compatibility bpo 25447 Copying the lru_cache wrapper object now always works independently from the type of the wrapped object by returning the original object unchanged bpo 24103 Fixed possible use after free in ElementTree XMLPullParser bpo 25860 os fwalk no longer skips remaining directories when error occurs Original patch by Samson Lee bpo 25914 Fixed and simplified OrderedDict __sizeof__ bpo 25902 Fixed various refcount issues in ElementTree iteration bpo 25717 Restore the previous behaviour of tolerating most fstat errors when opening files This was a regression in 3 5a1 and stopped anonymous temporary files from working in special cases bpo 24903 Fix regression in number of arguments compileall accepts when d is specified The check on the number of arguments has been dropped completely as it never worked correctly anyway bpo 25764 In the subprocess module preserve any exception caused by fork failure when preexec_fn is used bpo 6478 _strptime s regexp cache now is reset after changing timezone with time tzset bpo 14285 When executing a package with the python m package option and package initialization fails a proper traceback is now reported The runpy module now lets exceptions from package initialization pass back to the caller rather than raising ImportError bpo 19771 Also in runpy and the m option omit the irrelevant message is a package and cannot be directly executed if the package could not even be initialized e g due to a bad pyc file bpo 25177 Fixed problem with the mean of very small and very large numbers As a side effect statistics mean and statistics variance should be significantly ,en
1817,faster bpo 25718 Fixed copying object with state with boolean value is false bpo 10131 Fixed deep copying of minidom documents Based on patch by Marian Ganisin bpo 25725 Fixed a reference leak in pickle loads when unpickling invalid data including tuple instructions bpo 25663 In the Readline completer avoid listing duplicate global names and search the global namespace before searching builtins bpo 25688 Fixed file leak in ElementTree iterparse raising an error bpo 23914 Fixed SystemError raised by unpickler on broken pickle data bpo 25691 Fixed crash on deleting ElementTree Element attributes bpo 25624 ZipFile now always writes a ZIP_STORED header for directory entries Patch by Dingyuan Wang Skip getaddrinfo if host is already resolved Patch by A Jesse Jiryu Davis bpo 26050 Add asyncio StreamReader readuntil method Patch by Марк Коренберг bpo 25924 Avoid unnecessary serialization of getaddrinfo 3 calls on OS X versions 10 5 or higher Original patch by A Jesse Jiryu Davis bpo 26406 Avoid unnecessary serialization of getaddrinfo 3 calls on current versions of OpenBSD and NetBSD Patch by A Jesse Jiryu Davis bpo 26848 Fix asyncio subprocess communicate to handle empty input Patch by Jack O Connor bpo 27040 Add loop get_exception_handler method bpo 27041 asyncio Add loop create_future method bpo 27223 asyncio Fix _read_ready and _write_ready to respect _conn_lost Patch by Łukasz Langa bpo 22970 asyncio Fix inconsistency cancelling Condition wait Patch by David Coles IDLE bpo 5124 Paste with text selected now replaces the selection on X11 This matches how paste works on Windows Mac most modern Linux apps and ttk widgets Original patch by Serhiy Storchaka bpo 24759 Make clear in idlelib idle_test __init__ that the directory is a private implementation of test test_idle and tool for maintainers bpo 27196 Stop ThemeChanged warnings when running IDLE tests These persisted after other warnings were suppressed in 20567 Apply Serhiy Storchaka s update_idletasks solution to four test files Record this additional advice in idle_test README txt bpo 20567 Revise idle_test README txt with advice about avoiding tk warning messages from tests Apply advice to several IDLE tests bpo 27117 Make colorizer htest and turtledemo work with dark themes Move code for configuring text widget colors to a new function bpo 26673 When tk reports font size as 0 change to size 10 Such fonts on Linux prevented the configuration dialog from opening bpo 21939 Add test for IDLE s percolator Original patch by Saimadhav Heblikar bpo 21676 Add test for IDLE s replace dialog Original patch by Saimadhav Heblikar bpo 18410 Add test for IDLE s search dialog Original patch by Westley Martínez bpo 21703 Add test for IDLE s undo delegator Original patch by Saimadhav Heblikar bpo 27044 Add ConfigDialog remove_var_callbacks to stop memory leaks bpo 23977 Add more asserts to test_delegator bpo 20640 Add tests for idlelib configHelpSourceEdit Patch by Saimadhav Heblikar In the IDLE console differences section of the IDLE doc clarify how running with IDLE affects sys modules and the standard streams bpo 25507 fix incorrect change in IOBinding that prevented printing Augment IOBinding htest to include all major IOBinding functions bpo 25905 Revert unwanted conversion of to RIGHT SINGLE QUOTATION MARK in README txt and open this and NEWS txt with ascii Re encode CREDITS txt to utf 8 and open it with utf 8 Documentation bpo 19489 Moved the search box from the sidebar to the header and footer of each page Patch by Ammar Askar bpo 24136 Document the new PEP 448 unpacking syntax of 3 5 bpo 26736 Used HTTPS for external links in the documentation if possible bpo 6953 Rework the Readline module documentation to group related functions together and add more details such as what underlying Readline functions and variables are accessed bpo 23606 Adds note to ctypes documentation regarding cdll msvcrt bpo 25500 Fix documentation to not claim that __import__ is searched for in the global scope bpo 26014 Update 3 x packaging documentation See also links to the new docs are now provided in,en
1818, the legacy pages links to setuptools documentation have been updated Tests bpo 21916 Added tests for the turtle module Patch by ingrid Gregory Loyse and Jelle Zijlstra bpo 26523 The multiprocessing thread pool multiprocessing dummy Pool was untested bpo 26015 Added new tests for pickling iterators of mutable sequences bpo 26325 Added test support check_no_resource_warning to check that no ResourceWarning is emitted bpo 25940 Changed test_ssl to use self signed pythontest net This avoids relying on svn python org which recently changed root certificate bpo 25616 Tests for OrderedDict are extracted from test_collections into separate file test_ordered_dict bpo 26583 Skip test_timestamp_overflow in test_import if bytecode files cannot be written Build bpo 26884 Fix linking extension modules for cross builds Patch by Xavier de Gaye bpo 22359 Disable the rules for running _freeze_importlib and pgen when cross compiling The output of these programs is normally saved with the source code anyway and is still regenerated when doing a native build Patch by Xavier de Gaye bpo 27229 Fix the cross compiling pgen rule for in tree builds Patch by Xavier de Gaye bpo 21668 Link audioop _datetime _ctypes_test modules to libm except on Mac OS X Patch written by Xavier de Gaye bpo 25702 A with lto configure option has been added that will enable link time optimizations at build time during a make profile opt Some compilers and toolchains are known to not produce stable code when using LTO be sure to test things thoroughly before relying on it It can provide a few speed up over profile opt alone bpo 26624 Adds validation of ucrtbase d dll version with warning for old versions bpo 17603 Avoid error about nonexistent fileblocks o file by using a lower level check for st_blocks in struct stat bpo 26079 Fixing the build output folder for tix 8 4 3 6 Patch by Bjoern Thiel bpo 26465 Update Windows builds to use OpenSSL 1 0 2g bpo 24421 Compile Modules _math c once before building extensions Previously it could fail to compile properly if the math and cmath builds were concurrent bpo 25348 Added pgo and pgo job arguments to PCbuild build bat for building with Profile Guided Optimization The old PCbuild build_pgo bat script is now deprecated and simply calls PCbuild build bat pgo bpo 25827 Add support for building with ICC to configure including a new with icc flag bpo 25696 Fix installation of Python on UNIX with make j9 bpo 26930 Update OS X 10 5 32 bit only installer to build and link with OpenSSL 1 0 2h bpo 26268 Update Windows builds to use OpenSSL 1 0 2f bpo 25136 Support Apple Xcode 7 s new textual SDK stub libraries bpo 24324 Do not enable unreachable code warnings when using gcc as the option does not work correctly in older versions of gcc and has been silently removed as of gcc 4 5 Windows bpo 27053 Updates make_zip py to correctly generate library ZIP file bpo 26268 Update the prepare_ssl py script to handle OpenSSL releases that don t include the contents of the include directory that is 1 0 2e and later bpo 26071 bdist_wininst created binaries fail to start and find 32bit Python bpo 26073 Update the list of magic numbers in launcher bpo 26065 Excludes venv from library when generating embeddable distro bpo 17500 Remove unused and outdated icons See also https github com python pythondotorg issues 945 Tools Demos bpo 26799 Fix python gdb py don t get C types once when the Python code is loaded but get C types on demand The C types can change if python gdb py is loaded before the Python executable Patch written by Thomas Ilsche bpo 26271 Fix the Freeze tool to properly use flags passed through configure Patch by Daniel Shaulov bpo 26489 Add dictionary unpacking support to Tools parser unparse py Patch by Guo Ci Teo bpo 26316 Fix variable name typo in Argument Clinic Python 3 5 1 final Release date 2015 12 06 Core and Builtins bpo 25709 Fixed problem with in place string concatenation and utf 8 cache Windows bpo 25715 Python 3 5 1 installer shows wrong upgrade path and incorrect logic for launcher detection Python 3 5 1 release candidate,en
1819, 1 Release date 2015 11 22 Core and Builtins bpo 25630 Fix a possible segfault during argument parsing in functions that accept filesystem paths bpo 23564 Fixed a partially broken sanity check in the _posixsubprocess internals regarding how fds_to_pass were passed to the child The bug had no actual impact as subprocess py already avoided it bpo 25388 Fixed tokenizer crash when processing undecodable source code with a null byte bpo 25462 The hash of the key now is calculated only once in most operations in C implementation of OrderedDict bpo 22995 Default implementation of __reduce__ and __reduce_ex__ now rejects builtin types with not defined __new__ bpo 25555 Fix parser and AST fill lineno and col_offset of arg node when compiling AST from Python objects bpo 24802 Avoid buffer overreads when int float compile exec and eval are passed bytes like objects These objects are not necessarily terminated by a null byte but the functions assumed they were bpo 24726 Fixed a crash and leaking NULL in repr of OrderedDict that was mutated by direct calls of dict methods bpo 25449 Iterating OrderedDict with keys with unstable hash now raises KeyError in C implementations as well as in Python implementation bpo 25395 Fixed crash when highly nested OrderedDict structures were garbage collected bpo 25274 sys setrecursionlimit now raises a RecursionError if the new recursion limit is too low depending at the current recursion depth Modify also the lower water mark formula to make it monotonic This mark is used to decide when the overflowed flag of the thread state is reset bpo 24402 Fix input to prompt to the redirected stdout when sys stdout fileno fails bpo 24806 Prevent builtin types that are not allowed to be subclassed from being subclassed through multiple inheritance bpo 24848 Fixed a number of bugs in UTF 7 decoding of misformed data bpo 25280 Import trace messages emitted in verbose v mode are no longer formatted twice bpo 25003 On Solaris 11 3 or newer os urandom now uses the getrandom function instead of the getentropy function The getentropy function is blocking to generate very good quality entropy os urandom doesn t need such high quality entropy bpo 25182 The stdprinter used as sys stderr before the io module is imported at startup now uses the backslashreplace error handler bpo 25131 Make the line number and column offset of set dict literals and comprehensions correspond to the opening brace bpo 25150 Hide the private _Py_atomic_ xxx symbols from the public Python h header to fix a compilation error with OpenMP PyThreadState_GET becomes an alias to PyThreadState_Get to avoid ABI incompatibilities Library bpo 25626 Change three zlib functions to accept sizes that fit in Py_ssize_t but internally cap those sizes to UINT_MAX This resolves a regression in 3 5 where GzipFile read failed to read chunks larger than 2 or 4 GiB The change affects the zlib Decompress decompress max_length parameter the zlib decompress bufsize parameter and the zlib Decompress flush length parameter bpo 25583 Avoid incorrect errors raised by os makedirs exist_ok True when the OS gives priority to errors such as EACCES over EEXIST bpo 25593 Change semantics of EventLoop stop in asyncio bpo 6973 When we know a subprocess Popen process has died do not allow the send_signal terminate or kill methods to do anything as they could potentially signal a different process bpo 25590 In the Readline completer only call getattr once per attribute bpo 25498 Fix a crash when garbage collecting ctypes objects created by wrapping a memoryview This was a regression made in 3 5a1 Based on patch by Eryksun bpo 25584 Added escape to the __all__ list in the glob module bpo 25584 Fixed recursive glob with patterns starting with bpo 25446 Fix regression in smtplib s AUTH LOGIN support bpo 18010 Fix the pydoc web server s module search function to handle exceptions from importing packages bpo 25554 Got rid of circular references in regular expression parsing bpo 25510 fileinput FileInput readline now returns b instead of at the end if the FileInput was opened with binary ,en
1820,mode Patch by Ryosuke Ito bpo 25503 Fixed inspect getdoc for inherited docstrings of properties Original patch by John Mark Vandenberg bpo 25515 Always use os urandom as a source of randomness in uuid uuid4 bpo 21827 Fixed textwrap dedent for the case when largest common whitespace is a substring of smallest leading whitespace Based on patch by Robert Li bpo 25447 The lru_cache wrapper objects now can be copied and pickled by returning the original object unchanged bpo 25390 typing Don t crash on Union str Pattern bpo 25441 asyncio Raise error from drain when socket is closed bpo 25410 Cleaned up and fixed minor bugs in C implementation of OrderedDict bpo 25411 Improved Unicode support in SMTPHandler through better use of the email package Thanks to user simon04 for the patch bpo 25407 Remove mentions of the formatter module being removed in Python 3 6 bpo 25406 Fixed a bug in C implementation of OrderedDict move_to_end that caused segmentation fault or hang in iterating after moving several items to the start of ordered dict bpo 25364 zipfile now works in threads disabled builds bpo 25328 smtpd s SMTPChannel now correctly raises a ValueError if both decode_data and enable_SMTPUTF8 are set to true bpo 25316 distutils raises OSError instead of DistutilsPlatformError when MSVC is not installed bpo 25380 Fixed protocol for the STACK_GLOBAL opcode in pickletools opcodes bpo 23972 Updates asyncio datagram create method allowing reuseport and reuseaddr socket options to be set prior to binding the socket Mirroring the existing asyncio create_server method the reuseaddr option for datagram sockets defaults to True if the O S is posix except if the platform is Cygwin Patch by Chris Laws bpo 25304 Add asyncio run_coroutine_threadsafe This lets you submit a coroutine to a loop from another thread returning a concurrent futures Future By Vincent Michel bpo 25232 Fix CGIRequestHandler to split the query from the URL at the first question mark rather than the last Patch from Xiang Zhang bpo 24657 Prevent CGIRequestHandler from collapsing slashes in the query part of the URL as if it were a path Patch from Xiang Zhang bpo 24483 C implementation of functools lru_cache now calculates key s hash only once bpo 22958 Constructor and update method of weakref WeakValueDictionary now accept the self and the dict keyword arguments bpo 22609 Constructor of collections UserDict now accepts the self keyword argument bpo 25111 Fixed comparison of traceback FrameSummary bpo 25262 Added support for BINBYTES8 opcode in Python implementation of unpickler Highest 32 bits of 64 bit size for BINUNICODE8 and BINBYTES8 opcodes no longer silently ignored on 32 bit platforms in C implementation bpo 25034 Fix string Formatter problem with auto numbering and nested format_specs Patch by Anthon van der Neut bpo 25233 Rewrite the guts of asyncio Queue and asyncio Semaphore to be more understandable and correct bpo 25203 Failed readline set_completer_delims no longer left the module in inconsistent state bpo 23600 Default implementation of tzinfo fromutc was returning wrong results in some cases bpo 23329 Allow the ssl module to be built with older versions of LibreSSL Prevent overflow in _Unpickler_Read bpo 25047 The XML encoding declaration written by Element Tree now respects the letter case given by the user This restores the ability to write encoding names in uppercase like UTF 8 which worked in Python 2 bpo 25135 Make deque_clear safer by emptying the deque before clearing This helps avoid possible reentrancy issues bpo 19143 platform module now reads Windows version from kernel32 dll to avoid compatibility shims bpo 25092 Fix datetime strftime failure when errno was already set to EINVAL bpo 23517 Fix rounding in fromtimestamp and utcfromtimestamp methods of datetime datetime microseconds are now rounded to nearest with ties going to nearest even integer ROUND_HALF_EVEN instead of being rounding towards minus infinity ROUND_FLOOR It s important that these methods use the same rounding mode than datetime timedelta to keep the property datetime 1970 1 1 time,en
1821,delta seconds t datetime utcfromtimestamp t It also the rounding mode used by round float for example bpo 25155 Fix datetime datetime now and datetime datetime utcnow on Windows to support date after year 2038 It was a regression introduced in Python 3 5 0 bpo 25108 Omitted internal frames in traceback functions print_stack format_stack and extract_stack called without arguments bpo 25118 Fix a regression of Python 3 5 0 in os waitpid on Windows bpo 24684 socket socket getaddrinfo now calls PyUnicode_AsEncodedString instead of calling the encode method of the host to handle correctly custom string with an encode method which doesn t return a byte string The encoder of the IDNA codec is now called directly instead of calling the encode method of the string bpo 25060 Correctly compute stack usage of the BUILD_MAP opcode bpo 24857 Comparing call_args to a long sequence now correctly returns a boolean result instead of raising an exception Patch by A Kaptur bpo 23144 Make sure that HTMLParser feed returns all the data even when convert_charrefs is True bpo 24982 shutil make_archive with the zip format now adds entries for directories including empty directories in ZIP file bpo 25019 Fixed a crash caused by setting non string key of expat parser Based on patch by John Leitch bpo 16180 Exit pdb if file has syntax error instead of trapping user in an infinite loop Patch by Xavier de Gaye bpo 24891 Fix a race condition at Python startup if the file descriptor of stdin 0 stdout 1 or stderr 2 is closed while Python is creating sys stdin sys stdout and sys stderr objects These attributes are now set to None if the creation of the object failed instead of raising an OSError exception Initial patch written by Marco Paolini bpo 24992 Fix error handling and a race condition related to garbage collection in collections OrderedDict constructor bpo 24881 Fixed setting binary mode in Python implementation of FileIO on Windows and Cygwin Patch from Akira Li bpo 25578 Fix another memory leak in SSLSocket getpeercer bpo 25530 Disable the vulnerable SSLv3 protocol by default when creating ssl SSLContext bpo 25569 Fix memory leak in SSLSocket getpeercert bpo 25471 Sockets returned from accept shouldn t appear to be nonblocking bpo 25319 When threading Event is reinitialized the underlying condition should use a regular lock rather than a recursive lock bpo 21112 Fix regression in unittest expectedFailure on subclasses Patch from Berker Peksag bpo 24764 cgi FieldStorage read_multi now ignores the Content Length header in part headers Patch written by Peter Landry and reviewed by Pierre Quentel bpo 24913 Fix overrun error in deque index Found by John Leitch and Bryce Darling bpo 24774 Fix docstring in http server test Patch from Chiu Hsiang Hsu bpo 21159 Improve message in configparser InterpolationMissingOptionError Patch from Łukasz Langa bpo 20362 Honour TestCase longMessage correctly in assertRegex Patch from Ilia Kurenkov bpo 23572 Fixed functools singledispatch on classes with false metaclasses Patch by Ethan Furman asyncio ensure_future now accepts awaitable objects IDLE bpo 15348 Stop the debugger engine normally in a user process before closing the debugger window running in the IDLE process This prevents the RuntimeErrors that were being caught and ignored bpo 24455 Prevent IDLE from hanging when a closing the shell while the debugger is active 15347 b closing the debugger with the X button 15348 and c activating the debugger when already active 24455 The patch by Mark Roseman does this by making two changes 1 Suspend and resume the gui interaction method with the tcl vwait mechanism intended for this purpose instead of root mainloop quit 2 In gui run allow any existing interaction to terminate first Change The program to Your program in an IDLE kill program message to make it clearer that the program referred to is the currently running user program not IDLE itself bpo 24750 Improve the appearance of the IDLE editor window status bar Patch by Mark Roseman bpo 25313 Change the handling of new built in text color themes to better address,en
1822, the compatibility problem introduced by the addition of IDLE Dark Consistently use the revised idleConf CurrentTheme everywhere in idlelib bpo 24782 Extension configuration is now a tab in the IDLE Preferences dialog rather than a separate dialog The former tabs are now a sorted list Patch by Mark Roseman bpo 22726 Re activate the config dialog help button with some content about the other buttons and the new IDLE Dark theme bpo 24820 IDLE now has an IDLE Dark built in text color theme It is more or less IDLE Classic inverted with a cobalt blue background Strings comments keywords are still green red orange To use it with IDLEs released before November 2015 hit the Save as New Custom Theme button and enter a new name such as Custom Dark The custom theme will work with any IDLE release and can be modified bpo 25224 README txt is now an idlelib index for IDLE developers and curious users The previous user content is now in the IDLE doc chapter IDLE now means Integrated Development and Learning Environment bpo 24820 Users can now set breakpoint colors in Settings Custom Highlighting Original patch by Mark Roseman bpo 24972 Inactive selection background now matches active selection background as configured by users on all systems Found items are now always highlighted on Windows Initial patch by Mark Roseman bpo 24570 Idle make calltip and completion boxes appear on Macs affected by a tk regression Initial patch by Mark Roseman bpo 24988 Idle ScrolledList context menus used in debugger now work on Mac Aqua Patch by Mark Roseman bpo 24801 Make right click for context menu work on Mac Aqua Patch by Mark Roseman bpo 25173 Associate tkinter messageboxes with a specific widget For Mac OSX make them a sheet Patch by Mark Roseman bpo 25198 Enhance the initial html viewer now used for Idle Help Properly indent fixed pitch text patch by Mark Roseman Give code snippet a very Sphinx like light blueish gray background Re use initial width and height set by users for shell and editor When the Table of Contents TOC menu is used put the section header at the top of the screen bpo 25225 Condense and rewrite Idle doc section on text colors bpo 21995 Explain some differences between IDLE and console Python bpo 22820 Explain need for print when running file from Idle editor bpo 25224 Doc augment Idle feature list and no subprocess section bpo 25219 Update doc for Idle command line options Some were missing and notes were not correct bpo 24861 Most of idlelib is private and subject to change Use idleib idle to start Idle See idlelib __init__ __doc__ bpo 25199 Idle add synchronization comments for future maintainers bpo 16893 Replace help txt with help html for Idle doc display The new idlelib help html is rstripped Doc build html library idle html It looks better than help txt and will better document Idle as released The tkinter html viewer that works for this file was written by Mark Roseman The now unused EditorWindow HelpDialog class and helt txt file are deprecated bpo 24199 Deprecate unused idlelib idlever with possible removal in 3 6 bpo 24790 Remove extraneous code which also create 2 3 conflicts Documentation bpo 22558 Add remaining doc links to source code for Python coded modules Patch by Yoni Lavi bpo 12067 Rewrite Comparisons section in the Expressions chapter of the language reference Some of the details of comparing mixed types were incorrect or ambiguous NotImplemented is only relevant at a lower level than the Expressions chapter Added details of comparing range objects and default behaviour and consistency suggestions for user defined classes Patch from Andy Maier bpo 24952 Clarify the default size argument of stack_size in the threading and _thread modules Patch from Mattip bpo 23725 Overhaul tempfile docs Note deprecated status of mktemp Patch from Zbigniew Jędrzejewski Szmek bpo 24808 Update the types of some PyTypeObject fields Patch by Joseph Weston bpo 22812 Fix unittest discovery examples Patch from Pam McA Nulty Tests bpo 25449 Added tests for OrderedDict subclasses bpo 25099 Make test_compileall not fail when an entr,en
1823,y on sys path cannot be written to commonly seen in administrative installs on Windows bpo 23919 Prevents assert dialogs appearing in the test suite PCbuild rt bat now accepts an unlimited number of arguments to pass along to regrtest py Previously there was a limit of 9 Build bpo 24915 Add LLVM support for PGO builds and use the test suite to generate the profile data Initial patch by Alecsandru Patrascu of Intel bpo 24910 Windows MSIs now have unique display names bpo 24986 It is now possible to build Python on Windows without errors when external libraries are not available Windows bpo 25450 Updates shortcuts to start Python in installation directory bpo 25164 Changes default all users install directory to match per user directory bpo 25143 Improves installer error messages for unsupported platforms bpo 25163 Display correct directory in installer when using non default settings bpo 25361 Disables use of SSE2 instructions in Windows 32 bit build bpo 25089 Adds logging to installer for case where launcher is not selected on upgrade bpo 25165 Windows uninstallation should not remove launcher if other versions remain bpo 25112 py exe launcher is missing icons bpo 25102 Windows installer does not precompile for O or OO bpo 25081 Makes Back button in installer go back to upgrade page when upgrading bpo 25091 Increases font size of the installer bpo 25126 Clarifies that the non web installer will download some components bpo 25213 Restores requestedExecutionLevel to manifest to disable UAC virtualization bpo 25022 Removed very outdated PC example_nt directory Tools Demos bpo 25440 Fix output of python config extension suffix Python 3 5 0 final Release date 2015 09 13 Build bpo 25071 Windows installer should not require TargetDir parameter when installing quietly Python 3 5 0 release candidate 4 Release date 2015 09 09 Library bpo 25029 Fixes MemoryError in test_strptime Build bpo 25027 Reverts partial static build options and adds vcruntime140 dll to Windows installation Python 3 5 0 release candidate 3 Release date 2015 09 07 Core and Builtins bpo 24305 Prevent import subsystem stack frames from being counted by the warnings warn stacklevel parameter bpo 24912 Prevent __class__ assignment to immutable built in objects bpo 24975 Fix AST compilation for PEP 448 syntax Library bpo 24917 time_strftime buffer over read bpo 24748 To resolve a compatibility problem found with py2exe and pywin32 imp load_dynamic once again ignores previously loaded modules to support Python modules replacing themselves with extension modules Patch by Petr Viktorin bpo 24635 Fixed a bug in typing py where isinstance typing Iterable would return True once then False on subsequent calls bpo 24989 Fixed buffer overread in BytesIO readline if a position is set beyond size Based on patch by John Leitch bpo 24913 Fix overrun error in deque index Found by John Leitch and Bryce Darling Python 3 5 0 release candidate 2 Release date 2015 08 25 Core and Builtins bpo 24769 Interpreter now starts properly when dynamic loading is disabled Patch by Petr Viktorin bpo 21167 NAN operations are now handled correctly when python is compiled with ICC even if fp model strict is not specified bpo 24492 A package lacking a __name__ attribute when trying to perform a from import statement will trigger an ImportError instead of an AttributeError Library bpo 24847 Removes vcruntime140 dll dependency from Tcl Tk bpo 24839 platform _syscmd_ver raises DeprecationWarning bpo 24867 Fix Task get_stack for async def coroutines Python 3 5 0 release candidate 1 Release date 2015 08 09 Core and Builtins bpo 24667 Resize odict in all cases that the underlying dict resizes Library bpo 24824 Signatures of codecs encode and codecs decode now are compatible with pydoc bpo 24634 Importing uuid should not try to load libc on Windows bpo 24798 _msvccompiler py doesn t properly support manifests bpo 4395 Better testing and documentation of binary operators Patch by Martin Panter bpo 23973 Update typing py from GitHub repo bpo 23004 mock_open now reads binary data correctly when the type of rea,en
1824,d_data is bytes Initial patch by Aaron Hill bpo 23888 Handle fractional time in cookie expiry Patch by ssh bpo 23652 Make it possible to compile the select module against the libc headers from the Linux Standard Base which do not include some EPOLL macros Patch by Matt Frank bpo 22932 Fix timezones in email utils formatdate Patch from Dmitry Shachnev bpo 23779 imaplib raises TypeError if authenticator tries to abort Patch from Craig Holmquist bpo 23319 Fix ctypes BigEndianStructure swap correctly bytes Patch written by Matthieu Gautier bpo 23254 Document how to close the TCPServer listening socket Patch from Martin Panter bpo 19450 Update Windows and OS X installer builds to use SQLite 3 8 11 bpo 17527 Add PATCH to wsgiref validator Patch from Luca Sbardella bpo 24791 Fix grammar regression for call syntax g a or b IDLE bpo 23672 Allow Idle to edit and run files with astral chars in name Patch by Mohd Sanad Zaki Rizvi bpo 24745 Idle editor default font Switch from Courier to platform sensitive TkFixedFont This should not affect current customized font selections If there is a problem edit HOME idlerc config main cfg and remove font xxx entries from Editor Window Patch by Mark Roseman bpo 21192 Idle editor When a file is run put its name in the restart bar Do not print false prompts Original patch by Adnan Umer bpo 13884 Idle menus Remove tearoff lines Patch by Roger Serwy Documentation bpo 24129 Clarify the reference documentation for name resolution This includes removing the assumption that readers will be familiar with the name resolution scheme Python used prior to the introduction of lexical scoping for function namespaces Patch by Ivan Levkivskyi bpo 20769 Improve reload docs Patch by Dorian Pula bpo 23589 Remove duplicate sentence from the FAQ Patch by Yongzhi Pan bpo 24729 Correct IO tutorial to match implementation regarding encoding parameter to open function Tests bpo 24751 When running regrtest with the w command line option a test run is no longer marked as a failure if all tests succeed when re run Python 3 5 0 beta 4 Release date 2015 07 26 Core and Builtins bpo 23573 Restored optimization of bytes rfind and bytearray rfind for single byte argument on Linux bpo 24569 Make PEP 448 dictionary evaluation more consistent bpo 24583 Fix crash when set is mutated while being updated bpo 24407 Fix crash when dict is mutated while being updated bpo 24619 New approach for tokenizing async await As a consequence it is now possible to have one line async def foo await functions bpo 24687 Plug refleak on SyntaxError in function parameters annotations bpo 15944 memoryview Allow arbitrary formats when casting to bytes Patch by Martin Panter Library bpo 23441 rcompleter now prints a tab character instead of displaying possible completions for an empty word Initial patch by Martin Sekera bpo 24683 Fixed crashes in _json functions called with arguments of inappropriate type bpo 21697 shutil copytree now correctly handles symbolic links that point to directories Patch by Eduardo Seabra and Thomas Kluyver bpo 14373 Fixed segmentation fault when gc collect is called during constructing lru_cache C implementation bpo 24695 Fix a regression in traceback print_exception If exc_traceback is None we shouldn t print a traceback header like described in the documentation bpo 24620 Random setstate now validates the value of state last element bpo 22485 Fixed an issue that caused inspect getsource to return incorrect results on nested functions bpo 22153 Improve unittest docs Patch from Martin Panter and evilzero bpo 24580 Symbolic group references to open group in re patterns now are explicitly forbidden as well as numeric group references bpo 24206 Fixed __eq__ and __ne__ methods of inspect classes bpo 24631 Fixed regression in the timeit module with multiline setup bpo 18622 unittest mock mock_open reset_mock would recurse infinitely Patch from Nicola Palumbo and Laurent De Buyst bpo 23661 unittest mock side_effects can now be exceptions again This was a regression vs Python 3 4 Patch from Ignacio Rossi bpo 24608 chunk Chunk read no,en
1825,w always returns bytes not str bpo 18684 Fixed reading out of the buffer in the re module bpo 24259 tarfile now raises a ReadError if an archive is truncated inside a data segment bpo 15014 SMTP auth and SMTP login now support RFC 4954 s optional initial response argument to the SMTP AUTH command bpo 24669 Fix inspect getsource for async def functions Patch by Kai Groner bpo 24688 ast get_docstring for async def functions Build bpo 24603 Update Windows builds and OS X 10 5 installer to use OpenSSL 1 0 2d Python 3 5 0 beta 3 Release date 2015 07 05 Core and Builtins bpo 24467 Fixed possible buffer over read in bytearray The bytearray object now always allocates place for trailing null byte and it s buffer now is always null terminated Upgrade to Unicode 8 0 0 bpo 24345 Add Py_tp_finalize slot for the stable ABI bpo 24400 Introduce a distinct type for PEP 492 coroutines add types CoroutineType inspect getcoroutinestate inspect getcoroutinelocals coroutines no longer use CO_GENERATOR flag sys set_coroutine_wrapper works only for async def coroutines inspect iscoroutine no longer uses collections abc Coroutine it s intended to test for pure async def coroutines only add new opcode GET_YIELD_FROM_ITER fix generators wrapper used in types coroutine to be instance of collections abc Generator collections abc Awaitable and collections abc Coroutine can no longer be used to detect generator based coroutines use inspect isawaitable instead bpo 24450 Add gi_yieldfrom to generators and cr_await to coroutines Contributed by Benno Leslie and Yury Selivanov bpo 19235 Add new RecursionError exception Patch by Georg Brandl Library bpo 21750 mock_open read_data can now be read from each instance as it could in Python 3 3 bpo 24552 Fix use after free in an error case of the _pickle module bpo 24514 tarfile now tolerates number fields consisting of only whitespace bpo 19176 Fixed doctype related bugs in C implementation of ElementTree A deprecation warning no longer issued by XMLParser subclass with default doctype method Direct call of doctype now issues a warning Parser s doctype now is not called if target s doctype is called Based on patch by Martin Panter bpo 20387 Restore semantic round trip correctness in tokenize untokenize for tab indented blocks bpo 24456 Fixed possible buffer over read in adpcm2lin and lin2adpcm functions of the audioop module bpo 24336 The contextmanager decorator now works with functions with keyword arguments called func and self Patch by Martin Panter bpo 24522 Fix possible integer overflow in json accelerator module bpo 24489 ensure a previously set C errno doesn t disturb cmath polar bpo 24408 Fixed AttributeError in measure and metrics methods of tkinter Font bpo 14373 C implementation of functools lru_cache now can be used with methods bpo 24347 Set KeyError if PyDict_GetItemWithError returns NULL bpo 24348 Drop superfluous incref decref bpo 24359 Check for changed OrderedDict size during iteration bpo 24368 Support keyword arguments in OrderedDict methods bpo 24362 Simplify the C OrderedDict fast nodes resize logic bpo 24377 Fix a ref leak in OrderedDict __repr__ bpo 24369 Defend against key changes during iteration Tests bpo 24373 _testmultiphase and xxlimited now use tp_traverse and tp_finalize to avoid reference leaks encountered when combining tp_dealloc with PyType_FromSpec see bpo 16690 for details Documentation bpo 24458 Update documentation to cover multi phase initialization for extension modules PEP 489 Patch by Petr Viktorin bpo 24351 Clarify what is meant by identifier in the context of string Template instances Build bpo 24432 Update Windows builds and OS X 10 5 installer to use OpenSSL 1 0 2c Python 3 5 0 beta 2 Release date 2015 05 31 Core and Builtins bpo 24284 The startswith and endswith methods of the str class no longer return True when finding the empty string and the indexes are completely out of range bpo 24115 Update uses of PyObject_IsTrue PyObject_Not PyObject_IsInstance PyObject_RichCompareBool and _PyDict_Contains to check for and handle errors correctly bpo 24328 Fix importing,en
1826, one character extension modules bpo 11205 In dictionary displays evaluate the key before the value bpo 24285 Fixed regression that prevented importing extension modules from inside packages Patch by Petr Viktorin Library bpo 23247 Fix a crash in the StreamWriter reset of CJK codecs bpo 24270 Add math isclose and cmath isclose functions as per PEP 485 Contributed by Chris Barker and Tal Einat bpo 5633 Fixed timeit when the statement is a string and the setup is not bpo 24326 Fixed audioop ratecv with non default weightB argument Original patch by David Moore bpo 16991 Add a C implementation of OrderedDict bpo 23934 Fix inspect signature to fail correctly for builtin types lacking signature information Initial patch by James Powell Python 3 5 0 beta 1 Release date 2015 05 24 Core and Builtins bpo 24276 Fixed optimization of property descriptor getter bpo 24268 PEP 489 Multi phase extension module initialization Patch by Petr Viktorin bpo 23955 Add pyvenv cfg option to suppress registry environment lookup for generating sys path on Windows bpo 24257 Fixed system error in the comparison of faked types SimpleNamespace bpo 22939 Fixed integer overflow in iterator object Patch by Clement Rouault bpo 23985 Fix a possible buffer overrun when deleting a slice from the front of a bytearray and then appending some other bytes data bpo 24102 Fixed exception type checking in standard error handlers bpo 15027 The UTF 32 encoder is now 3x to 7x faster bpo 23290 Optimize set_merge for cases where the target is empty Contributed by Serhiy Storchaka bpo 2292 PEP 448 Additional Unpacking Generalizations bpo 24096 Make warnings warn_explicit more robust against mutation of the warnings filters list bpo 23996 Avoid a crash when a delegated generator raises an unnormalized StopIteration exception Patch by Stefan Behnel bpo 23910 Optimize property getter calls Patch by Joe Jevnik bpo 23911 Move path based importlib bootstrap code to a separate frozen module bpo 24192 Fix namespace package imports bpo 24022 Fix tokenizer crash when processing undecodable source code bpo 9951 Added a hex method to bytes bytearray and memoryview bpo 22906 PEP 479 Change StopIteration handling inside generators bpo 24017 PEP 492 Coroutines with async and await syntax Library bpo 14373 Added C implementation of functools lru_cache Based on patches by Matt Joiner and Alexey Kachayev bpo 24230 The tempfile module now accepts bytes for prefix suffix and dir parameters and returns bytes in such situations matching the os module APIs bpo 22189 collections UserString now supports __getnewargs__ __rmod__ casefold format_map isprintable and maketrans Patch by Joe Jevnik bpo 24244 Prevents termination when an invalid format string is encountered on Windows in strftime bpo 23973 PEP 484 Add the typing module bpo 23086 The collections abc Sequence abstract base class added start and stop parameters to the index mixin Patch by Devin Jeanpierre bpo 20035 Replaced the tkinter _fix module used for setting up the Tcl Tk environment on Windows with a private function in the _tkinter module that makes no permanent changes to the environment bpo 24257 Fixed segmentation fault in sqlite3 Row constructor with faked cursor type bpo 15836 assertRaises assertRaisesRegex assertWarns and assertWarnsRegex assertments now check the type of the first argument to prevent possible user error Based on patch by Daniel Wagner Hall bpo 9858 Add missing method stubs to _io RawIOBase Patch by Laura Rupprecht bpo 22955 attrgetter itemgetter and methodcaller objects in the operator module now support pickling Added readable and evaluable repr for these objects Based on patch by Josh Rosenberg bpo 22107 tempfile gettempdir and tempfile mkdtemp now try again when a directory with the chosen name already exists on Windows as well as on Unix tempfile mkstemp now fails early if parent directory is not valid not exists or is a file on Windows bpo 23780 Improved error message in os path join with single argument bpo 6598 Increased time precision and random number range in email utils make_msgid to strengthen t,en
1827,he uniqueness of the message ID bpo 24091 Fixed various crashes in corner cases in C implementation of ElementTree bpo 21931 msilib FCICreate now raises TypeError in the case of a bad argument instead of a ValueError with a bogus FCI error number Patch by Jeffrey Armstrong bpo 13866 quote_via argument added to urllib parse urlencode bpo 20098 New mangle_from policy option for email default True for compat32 but False for all other policies bpo 24211 The email library now supports RFC 6532 it can generate headers using utf 8 instead of encoded words bpo 16314 Added support for the LZMA compression in distutils bpo 21804 poplib now supports RFC 6856 UTF8 bpo 18682 Optimized pprint functions for builtin scalar types bpo 22027 smtplib now supports RFC 6531 SMTPUTF8 bpo 23488 Random generator objects now consume 2x less memory on 64 bit bpo 1322 platform dist and platform linux_distribution functions are now deprecated Initial patch by Vajrasky Kok bpo 22486 Added the math gcd function The fractions gcd function now is deprecated Based on patch by Mark Dickinson bpo 24064 Property docstrings are now writeable Patch by Berker Peksag bpo 22681 Added support for the koi8_t encoding bpo 22682 Added support for the kz1048 encoding bpo 23796 peek and read1 methods of BufferedReader now raise ValueError if they called on a closed object Patch by John Hergenroeder bpo 21795 smtpd now supports the 8BITMIME extension whenever the new decode_data constructor argument is set to False bpo 24155 optimize heapq heapify for better cache performance when heapifying large lists bpo 21800 imaplib now supports RFC 5161 enable RFC 6855 utf8 internationalized email and automatically encodes non ASCII usernames and passwords to UTF8 bpo 20274 When calling a _sqlite Connection it now complains if passed any keyword arguments Previously it silently ignored them bpo 20274 Remove ignored and erroneous kwargs parameters from three METH_VARARGS methods on _sqlite Connection bpo 24134 assertRaises assertRaisesRegex assertWarns and assertWarnsRegex checks now emits a deprecation warning when callable is None or keyword arguments except msg is passed in the context manager mode bpo 24018 Add a collections abc Generator abstract base class Contributed by Stefan Behnel bpo 23880 Tkinter s getint and getdouble now support Tcl_Obj Tkinter s getdouble now supports any numbers in particular int bpo 22619 Added negative limit support in the traceback module Based on patch by Dmitry Kazakov bpo 24094 Fix possible crash in json encode with poorly behaved dict subclasses bpo 9246 On POSIX os getcwd now supports paths longer than 1025 bytes Patch written by William Orr bpo 17445 add difflib diff_bytes to support comparison of byte strings fixes a regression from Python 2 bpo 23917 Fall back to sequential compilation when ProcessPoolExecutor doesn t exist Patch by Claudiu Popa bpo 23008 Fixed resolving attributes with boolean value is False in pydoc Fix asyncio issue 235 LifoQueue and PriorityQueue s put didn t increment unfinished tasks this bug was introduced when JoinableQueue was merged with Queue bpo 23908 os functions now reject paths with embedded null character on Windows instead of silently truncating them bpo 23728 binascii crc_hqx could return an integer outside of the range 0 0xffff for empty data bpo 23887 urllib error HTTPError now has a proper repr representation Patch by Berker Peksag asyncio New event loop APIs set_task_factory and get_task_factory asyncio async function is deprecated in favour of ensure_future bpo 24178 asyncio Lock Condition Semaphore and BoundedSemaphore support new async with syntax Contributed by Yury Selivanov bpo 24179 Support async for for asyncio StreamReader Contributed by Yury Selivanov bpo 24184 Add AsyncIterator and AsyncIterable ABCs to collections abc Contributed by Yury Selivanov bpo 22547 Implement informative __repr__ for inspect BoundArguments Contributed by Yury Selivanov bpo 24190 Implement inspect BoundArgument apply_defaults method Contributed by Yury Selivanov bpo 20691 Add follow_wrapped argument to inspect Sig,en
1828,nature from_callable and inspect signature Contributed by Yury Selivanov bpo 24248 Deprecate inspect Signature from_function and inspect Signature from_builtin bpo 23898 Fix inspect classify_class_attrs to support attributes with overloaded __eq__ and __bool__ Patch by Mike Bayer bpo 24298 Fix inspect signature to correctly unwrap wrappers around bound methods IDLE bpo 23184 remove unused names and imports in idlelib Initial patch by Al Sweigart Tests bpo 21520 test_zipfile no longer fails if the word bad appears anywhere in the name of the current directory bpo 9517 Move script_helper into the support package Patch by Christie Wilson Documentation bpo 22155 Add File Handlers subsection with createfilehandler to tkinter doc Remove obsolete example from FAQ Patch by Martin Panter bpo 24029 Document the name binding behavior for submodule imports bpo 24077 Fix typo in man page for I command option s not S Tools Demos bpo 24000 Improved Argument Clinic s mapping of converters to legacy format units Updated the documentation to match bpo 24001 Argument Clinic converters now use accept type instead of types type to specify the types the converter accepts bpo 23330 h2py now supports arbitrary filenames in include bpo 24031 make patchcheck now supports git checkouts too Python 3 5 0 alpha 4 Release date 2015 04 19 Core and Builtins bpo 22980 Under Linux GNU KFreeBSD and the Hurd C extensions now include the architecture triplet in the extension name to make it easy to test builds for different ABIs in the same working tree Under OS X the extension name now includes PEP 3149 style information bpo 22631 Added Linux specific socket constant CAN_RAW_FD_FRAMES Patch courtesy of Joe Jevnik bpo 23731 Implement PEP 488 removal of pyo files bpo 23726 Don t enable GC for user subclasses of non GC types that don t add any new fields Patch by Eugene Toder bpo 23309 Avoid a deadlock at shutdown if a daemon thread is aborted while it is holding a lock to a buffered I O object and the main thread tries to use the same I O object typically stdout or stderr A fatal error is emitted instead bpo 22977 Fixed formatting Windows error messages on Wine Patch by Martin Panter bpo 23466 c o x and X in bytes formatting now raise TypeError on non integer input bpo 24044 Fix possible null pointer dereference in list sort in out of memory conditions bpo 21354 PyCFunction_New function is exposed by python DLL again Library bpo 23840 tokenize open now closes the temporary binary file on error to fix a resource warning bpo 16914 new debuglevel 2 in smtplib adds timestamps to debug output bpo 7159 urllib request now supports sending auth credentials automatically after the first 401 This enhancement is a superset of the enhancement from bpo 19494 and supersedes that change bpo 23703 Fix a regression in urljoin introduced in 901e4e52b20a Patch by Demian Brecht bpo 4254 Adds _curses update_lines_cols Patch by Arnon Yaari bpo 19933 Provide default argument for ndigits in round Patch by Vajrasky Kok bpo 23193 Add a numeric_owner parameter to tarfile TarFile extract and tarfile TarFile extractall Patch by Michael Vogt and Eric Smith bpo 23342 Add a subprocess run function than returns a CalledProcess instance for a more consistent API than the existing call functions bpo 21217 inspect getsourcelines now tries to compute the start and end lines from the code object fixing an issue when a lambda function is used as decorator argument Patch by Thomas Ballinger and Allison Kaptur bpo 24521 Fix possible integer overflows in the pickle module bpo 22931 Allow and in cookie values The keywords attribute of functools partial is now always a dictionary bpo 23811 Add missing newline to the PyCompileError error message Patch by Alex Shkop bpo 21116 Avoid blowing memory when allocating a multiprocessing shared array that s larger than 50 of the available RAM Patch by Médéric Boquien bpo 22982 Improve BOM handling when seeking to multiple positions of a writable text file bpo 23464 Removed deprecated asyncio JoinableQueue bpo 23529 Limit the size of decompressed data when readin,en
1829,g from GzipFile BZ2File or LZMAFile This defeats denial of service attacks using compressed bombs i e compressed payloads which decompress to a huge size Patch by Martin Panter and Nikolaus Rath bpo 21859 Added Python implementation of io FileIO bpo 23865 close methods in multiple modules now are idempotent and more robust at shutdown If they need to release multiple resources all are released even if errors occur bpo 23400 Raise same exception on both Python 2 and 3 if sem_open is not available Patch by Davin Potts bpo 10838 The subprocess now module includes SubprocessError and TimeoutError in its list of exported names for the users wild enough to use from subprocess import bpo 23411 Added DefragResult ParseResult SplitResult DefragResultBytes ParseResultBytes and SplitResultBytes to urllib parse __all__ Patch by Martin Panter bpo 23881 urllib request ftpwrapper constructor now closes the socket if the FTP connection failed to fix a ResourceWarning bpo 23853 socket socket sendall does no more reset the socket timeout each time data is sent successfully The socket timeout is now the maximum total duration to send all data bpo 22721 An order of multiline pprint output of set or dict containing orderable and non orderable elements no longer depends on iteration order of set or dict bpo 15133 _tkinter tkapp getboolean now supports Tcl_Obj and always returns bool tkinter BooleanVar now validates input values accepted bool int str and Tcl_Obj tkinter BooleanVar get now always returns bool bpo 10590 xml sax parseString now supports string argument bpo 23338 Fixed formatting ctypes error messages on Cygwin Patch by Makoto Kato bpo 15582 inspect getdoc now follows inheritance chains bpo 2175 SAX parsers now support a character stream of InputSource object bpo 16840 Tkinter now supports 64 bit integers added in Tcl 8 4 and arbitrary precision integers added in Tcl 8 5 bpo 23834 Fix socket sendto use the C Py_ssize_t type to store the result of sendto instead of the C int type bpo 23618 socket socket connect now waits until the connection completes instead of raising InterruptedError if the connection is interrupted by signals signal handlers don t raise an exception and the socket is blocking or has a timeout socket socket connect still raise InterruptedError for non blocking sockets bpo 21526 Tkinter now supports new boolean type in Tcl 8 5 bpo 23836 Fix the faulthandler module to handle reentrant calls to its signal handlers bpo 23838 linecache now clears the cache and returns an empty result on MemoryError bpo 10395 Added os path commonpath Implemented in posixpath and ntpath Based on patch by Rafik Draoui bpo 23611 Serializing more lookupable objects such as unbound methods or nested classes now are supported with pickle protocols 4 bpo 13583 sqlite3 Row now supports slice indexing bpo 18473 Fixed 2to3 and 3to2 compatible pickle mappings Fixed ambiguous reverse mappings Added many new mappings Import mapping is no longer applied to modules already mapped with full name mapping bpo 23485 select select is now retried automatically with the recomputed timeout when interrupted by a signal except if the signal handler raises an exception This change is part of the PEP 475 bpo 23752 When built from an existing file descriptor io FileIO now only calls fstat once Before fstat was called twice which was not necessary bpo 23704 collections deque objects now support __add__ __mul__ and __imul__ bpo 23171 csv Writer writerow now supports arbitrary iterables bpo 23745 The new email header parser now handles duplicate MIME parameter names without error similar to how get_param behaves bpo 22117 Fix os utime it now rounds the timestamp towards minus infinity inf instead of rounding towards zero bpo 23310 Fix MagicMock s initializer to work with __methods__ just like configure_mock Patch by Kasia Jachim Build bpo 23817 FreeBSD now uses 1 0 in the SOVERSION as other operating systems instead of just 1 bpo 23501 Argument Clinic now generates code into separate files by default Tests bpo 23799 Added test support start_threads for running and ,en
1830,cleaning up multiple threads bpo 22390 test regrtest now emits a warning if temporary files or directories are left after running a test Tools Demos bpo 18128 pygettext now uses standard NNNN format in the POT Creation Date header bpo 23935 Argument Clinic s understanding of format units accepting bytes bytearrays and buffers is now consistent with both the documentation and the implementation bpo 23944 Argument Clinic now wraps long impl prototypes at column 78 bpo 20586 Argument Clinic now ensures that functions without docstrings have signatures bpo 23492 Argument Clinic now generates argument parsing code with PyArg_Parse instead of PyArg_ParseTuple if possible bpo 23500 Argument Clinic is now smarter about generating the ifndef empty definition of the methoddef macro it s only generated once even if Argument Clinic processes the same symbol multiple times and it s emitted at the end of all processing rather than immediately after the first use C API bpo 23998 PyImport_ReInitLock now checks for lock allocation error Python 3 5 0 alpha 3 Release date 2015 03 28 Core and Builtins bpo 23573 Increased performance of string search operations str find str index str count the in operator str split str partition with arguments of different kinds UCS1 UCS2 UCS4 bpo 23753 Python doesn t support anymore platforms without stat or fstat these functions are always required bpo 23681 The b option now affects comparisons of bytes with int bpo 23632 Memoryviews now allow tuple indexing including for multi dimensional memoryviews bpo 23192 Fixed generator lambdas Patch by Bruno Cauet bpo 23629 Fix the default __sizeof__ implementation for variable sized objects Library bpo 14260 The groupindex attribute of regular expression pattern object now is non modifiable mapping bpo 23792 Ignore KeyboardInterrupt when the pydoc pager is active This mimics the behavior of the standard unix pagers and prevents pipepager from shutting down while the pager itself is still running bpo 23775 pprint of OrderedDict now outputs the same representation as repr bpo 23765 Removed IsBadStringPtr calls in ctypes bpo 22364 Improved some re error messages using regex for hints bpo 23742 ntpath expandvars no longer loses unbalanced single quotes bpo 21717 The zipfile ZipFile open function now supports x exclusive creation mode bpo 21802 The reader in BufferedRWPair now is closed even when closing writer failed in BufferedRWPair close bpo 23622 Unknown escapes in regular expressions that consist of and ASCII letter now raise a deprecation warning and will be forbidden in Python 3 6 bpo 23671 string Template now allows specifying the self parameter as a keyword argument string Formatter now allows specifying the self and the format_string parameters as keyword arguments bpo 23502 The pprint module now supports mapping proxies bpo 17530 pprint now wraps long bytes objects and bytearrays bpo 22687 Fixed some corner cases in breaking words in tetxtwrap Got rid of quadratic complexity in breaking long words bpo 4727 The copy module now uses pickle protocol 4 PEP 3154 and supports copying of instances of classes whose __new__ method takes keyword only arguments bpo 23491 Added a zipapp module to support creating executable zip file archives of Python code Registered pyz and pyzw extensions on Windows for these archives PEP 441 bpo 23657 Avoid explicit checks for str in zipapp adding support for pathlib Path objects as arguments bpo 23688 Added support of arbitrary bytes like objects and avoided unnecessary copying of memoryview in gzip GzipFile write Original patch by Wolfgang Maier bpo 23252 Added support for writing ZIP files to unseekable streams bpo 23647 Increase imaplib s MAXLINE to accommodate modern mailbox sizes bpo 23539 If body is None http client HTTPConnection request now sets Content Length to 0 for PUT POST and PATCH headers to avoid 411 errors from some web servers bpo 22351 The nntplib NNTP constructor no longer leaves the connection and socket open until the garbage collector cleans them up Patch by Martin Panter bpo 23704 collections deque objects n,en
1831,ow support methods for index insert and copy This allows deques to be registered as a MutableSequence and it improves their substitutability for lists bpo 23715 signal sigwaitinfo and signal sigtimedwait are now retried when interrupted by a signal not in the sigset parameter if the signal handler does not raise an exception signal sigtimedwait recomputes the timeout with a monotonic clock when it is retried bpo 23001 Few functions in modules mmap ossaudiodev socket ssl and codecs that accepted only read only bytes like object now accept writable bytes like object too bpo 23646 If time sleep is interrupted by a signal the sleep is now retried with the recomputed delay except if the signal handler raises an exception PEP 475 bpo 23136 _strptime now uniformly handles all days in week 0 including Dec 30 of previous year Based on patch by Jim Carroll bpo 23700 Iterator of NamedTemporaryFile now keeps a reference to NamedTemporaryFile instance Patch by Bohuslav Kabrda bpo 22903 The fake test case created by unittest loader when it fails importing a test module is now picklable bpo 22181 On Linux os urandom now uses the new getrandom syscall if available syscall introduced in the Linux kernel 3 17 It is more reliable and more secure because it avoids the need of a file descriptor and waits until the kernel has enough entropy bpo 2211 Updated the implementation of the http cookies Morsel class Setting attributes key value and coded_value directly now is deprecated update and setdefault now transform and check keys Comparing for equality now takes into account attributes key value and coded_value copy now returns a Morsel not a dict repr now contains all attributes Optimized checking keys and quoting values Added new tests Original patch by Demian Brecht bpo 18983 Allow selection of output units in timeit Patch by Julian Gindi bpo 23631 Fix traceback format_list when a traceback has been mutated bpo 23568 Add rdivmod support to MagicMock objects Patch by Håkan Lövdahl bpo 2052 Add charset parameter to HtmlDiff make_file bpo 23668 Support os truncate and os ftruncate on Windows bpo 23138 Fixed parsing cookies with absent keys or values in cookiejar Patch by Demian Brecht bpo 23051 multiprocessing Pool methods imap and imap_unordered now handle exceptions raised by an iterator Patch by Alon Diamant and Davin Potts bpo 23581 Add matmul support to MagicMock Patch by Håkan Lövdahl bpo 23566 enable register dump_traceback and dump_traceback_later functions of faulthandler now accept file descriptors Patch by Wei Wu bpo 22928 Disabled HTTP header injections in http client Original patch by Demian Brecht bpo 23615 Modules bz2 tarfile and tokenize now can be reloaded with imp reload Patch by Thomas Kluyver bpo 23605 os walk now calls os scandir instead of os listdir The usage of os scandir reduces the number of calls to os stat Initial patch written by Ben Hoyt Build bpo 23585 make patchcheck will ensure the interpreter is built Tests bpo 23583 Added tests for standard IO streams in IDLE bpo 22289 Prevent test_urllib2net failures due to ftp connection timeout Tools Demos bpo 22826 The result of open in Tools freeze bkfile py is now better compatible with regular files in particular it now supports the context management protocol Python 3 5 0 alpha 2 Release date 2015 03 09 Core and Builtins bpo 23571 PyObject_Call and PyCFunction_Call now raise a SystemError if a function returns a result and raises an exception The SystemError is chained to the previous exception Library bpo 22524 New os scandir function part of the PEP 471 os scandir function a better and faster directory iterator Patch written by Ben Hoyt bpo 23103 Reduced the memory consumption of IPv4Address and IPv6Address bpo 21793 BaseHTTPRequestHandler again logs response code as numeric not as stringified enum Patch by Demian Brecht bpo 23476 In the ssl module enable OpenSSL s X509_V_FLAG_TRUSTED_FIRST flag on certificate stores when it is available bpo 23576 Avoid stalling in SSL reads when EOF has been reached in the SSL layer but the underlying connection hasn t been closed ,en
1832,bpo 23504 Added an __all__ to the types module bpo 23563 Optimized utility functions in urllib parse bpo 7830 Flatten nested functools partial bpo 20204 Added the __module__ attribute to _tkinter classes bpo 19980 Improved help for non recognized strings help now shows the help on str help help now shows the help on help Original patch by Mark Lawrence bpo 23521 Corrected pure python implementation of timedelta division Eliminated OverflowError from timedelta float for some floats Corrected rounding in timedelta true division bpo 21619 Popen objects no longer leave a zombie after exit in the with statement if the pipe was broken Patch by Martin Panter bpo 22936 Make it possible to show local variables in tracebacks for both the traceback module and unittest bpo 15955 Add an option to limit the output size in bz2 decompress Patch by Nikolaus Rath bpo 6639 Module level turtle functions no longer raise TclError after closing the window bpo 814253 Group references and conditional group references now work in lookbehind assertions in regular expressions See also bpo 9179 bpo 23215 Multibyte codecs with custom error handlers that ignores errors consumed too much memory and raised SystemError or MemoryError Original patch by Aleksi Torhamo bpo 5700 io FileIO called flush after closing the file flush was not called in close if closefd False bpo 23374 Fixed pydoc failure with non ASCII files when stdout encoding differs from file system encoding e g on Mac OS bpo 23481 Remove RC4 from the SSL module s default cipher list bpo 21548 Fix pydoc synopsis and pydoc apropos on modules with empty docstrings bpo 22885 Fixed arbitrary code execution vulnerability in the dbm dumb module Original patch by Claudiu Popa bpo 23239 ssl match_hostname now supports matching of IP addresses bpo 23146 Fix mishandling of absolute Windows paths with forward slashes in pathlib bpo 23096 Pickle representation of floats with protocol 0 now is the same for both Python and C implementations bpo 19105 pprint now more efficiently uses free space at the right bpo 14910 Add allow_abbrev parameter to argparse ArgumentParser Patch by Jonathan Paugh Steven Bethard paul j3 and Daniel Eriksson bpo 21717 tarfile open now supports x exclusive creation mode bpo 23344 marshal dumps is now 20 25 faster on average bpo 20416 marshal dumps with protocols 3 and 4 is now 40 50 faster on average bpo 23421 Fixed compression in tarfile CLI Patch by wdv4758h bpo 23367 Fix possible overflows in the unicodedata module bpo 23361 Fix possible overflow in Windows subprocess creation code logging handlers QueueListener now takes a respect_handler_level keyword argument which if set to True will pass messages to handlers taking handler levels into account bpo 19705 turtledemo now has a visual sorting algorithm demo Original patch from Jason Yeo bpo 23801 Fix issue where cgi FieldStorage did not always ignore the entire preamble to a multipart body Build bpo 23445 pydebug builds now use gcc Og where possible to make the resulting executable faster bpo 23686 Update OS X 10 5 installer build to use OpenSSL 1 0 2a C API bpo 20204 Deprecation warning is now raised for builtin types without the __module__ attribute Windows bpo 23465 Implement PEP 486 Make the Python Launcher aware of virtual environments Patch by Paul Moore bpo 23437 Make user scripts directory versioned on Windows Patch by Paul Moore Python 3 5 0 alpha 1 Release date 2015 02 08 Core and Builtins bpo 23285 PEP 475 EINTR handling bpo 22735 Fix many edge cases including crashes involving custom mro implementations bpo 22896 Avoid using PyObject_AsCharBuffer PyObject_AsReadBuffer and PyObject_AsWriteBuffer bpo 21295 Revert some changes bpo 16795 to AST line numbers and column offsets that constituted a regression bpo 22986 Allow changing an object s __class__ between a dynamic type and static type in some cases bpo 15859 PyUnicode_EncodeFSDefault PyUnicode_EncodeMBCS and PyUnicode_EncodeCodePage now raise an exception if the object is not a Unicode object For PyUnicode_EncodeFSDefault it was already the case on platforms other ,en
1833,than Windows Patch written by Campbell Barton bpo 21408 The default __ne__ now returns NotImplemented if __eq__ returned NotImplemented Original patch by Martin Panter bpo 23321 Fixed a crash in str decode when error handler returned replacement string longer than malformed input data bpo 22286 The backslashreplace error handlers now works with decoding and translating bpo 23253 Delay load ShellExecute AW in os startfile for reduced startup overhead on Windows bpo 22038 pyatomic h now uses stdatomic h or GCC built in functions for atomic memory access if available Patch written by Vitor de Lima and Gustavo Temple bpo 20284 interpolation aka printf formatting added for bytes and bytearray bpo 23048 Fix jumping out of an infinite while loop in the pdb bpo 20335 bytes constructor now raises TypeError when encoding or errors is specified with non string argument Based on patch by Renaud Blanch bpo 22834 If the current working directory ends up being set to a non existent directory then import will no longer raise FileNotFoundError bpo 22869 Move the interpreter startup shutdown code to a new dedicated pylifecycle c module bpo 22847 Improve method cache efficiency bpo 22335 Fix crash when trying to enlarge a bytearray to 0x7fffffff bytes on a 32 bit platform bpo 22653 Fix an assertion failure in debug mode when doing a reentrant dict insertion in debug mode bpo 22643 Fix integer overflow in Unicode case operations upper lower title swapcase casefold bpo 17636 Circular imports involving relative imports are now supported bpo 22604 Fix assertion error in debug mode when dividing a complex number by nan 0j bpo 21052 Do not raise ImportWarning when sys path_hooks or sys meta_path are set to None bpo 16518 Use bytes like object required in error messages that previously used the far more cryptic x does not support the buffer protocol bpo 22470 Fixed integer overflow issues in backslashreplace xmlcharrefreplace and surrogatepass error handlers bpo 22540 speed up PyObject_IsInstance and PyObject_IsSubclass in the common case that the second argument has metaclass type bpo 18711 Add a new PyErr_FormatV function similar to PyErr_Format but accepting a va_list argument bpo 22520 Fix overflow checking when generating the repr of a unicode object bpo 22519 Fix overflow checking in PyBytes_Repr bpo 22518 Fix integer overflow issues in latin 1 encoding bpo 16324 _charset parameter of MIMEText now also accepts email charset Charset instances Initial patch by Claude Paroz bpo 1764286 Fix inspect getsource to support decorated functions Patch by Claudiu Popa bpo 18554 os __all__ includes posix functions bpo 21391 Use os path abspath in the shutil module bpo 11471 avoid generating a JUMP_FORWARD instruction at the end of an if block if there is no else clause Original patch by Eugene Toder bpo 22215 Now ValueError is raised instead of TypeError when str or bytes argument contains not permitted null character or byte bpo 22258 Fix the internal function set_inheritable on Illumos This platform exposes the function ioctl FIOCLEX but calling it fails with errno is ENOTTY Inappropriate ioctl for device set_inheritable now falls back to the slower fcntl F_GETFD and then F_SETFD bpo 21389 Displaying the __qualname__ of the underlying function in the repr of a bound method bpo 22206 Using pthread PyThread_create_key now sets errno to ENOMEM and returns 1 error on integer overflow bpo 20184 Argument Clinic based signature introspection added for 30 of the builtin functions bpo 22116 C functions and methods of the builtin_function_or_method type can now be weakref ed Patch by Wei Wu bpo 22077 Improve index error messages for bytearrays bytes lists and tuples by adding or slices Added not typename for bytearrays Original patch by Claudiu Popa bpo 20179 Apply Argument Clinic to bytes and bytearray Patch by Tal Einat bpo 22082 Clear interned strings in slotdefs Upgrade Unicode database to Unicode 7 0 0 bpo 21897 Fix a crash with the f_locals attribute with closure variables when frame clear has been called bpo 21205 Add a new __qualname__ attribute to gene,en
1834,rator the qualified name and use it in the representation of a generator repr gen The default name of the generator __name__ attribute is now get from the function instead of the code Use gen gi_code co_name to get the name of the code bpo 21669 With the aid of heuristics in SyntaxError __init__ the parser now attempts to generate more meaningful or at least more search engine friendly error messages when exec and print are used as statements bpo 21642 In the conditional if else expression allow an integer written with no space between itself and the else keyword e g True if 42else False to be valid syntax bpo 21523 Fix over pessimistic computation of the stack effect of some opcodes in the compiler This also fixes a quadratic compilation time issue noticeable when compiling code with a large number of and and or operators bpo 21418 Fix a crash in the builtin function super when called without argument and without current frame ex embedded Python bpo 21425 Fix flushing of standard streams in the interactive interpreter bpo 21435 In rare cases when running finalizers on objects in cyclic trash a bad pointer dereference could occur due to a subtle flaw in internal iteration logic bpo 21377 PyBytes_Concat now tries to concatenate in place when the first argument has a reference count of 1 Patch by Nikolaus Rath bpo 20355 W command line options now have higher priority than the PYTHONWARNINGS environment variable Patch by Arfrever bpo 21274 Define PATH_MAX for GNU Hurd in Python pythonrun c bpo 20904 Support setting FPU precision on m68k bpo 21209 Fix sending tuples to custom generator objects with the yield from syntax bpo 21193 pow a b c now raises ValueError rather than TypeError when b is negative Patch by Josh Rosenberg bpo 21176 PEP 465 Add the operator for matrix multiplication bpo 21134 Fix segfault when str is called on an uninitialized UnicodeEncodeError UnicodeDecodeError or UnicodeTranslateError object bpo 19537 Fix PyUnicode_DATA alignment under m68k Patch by Andreas Schwab bpo 20929 Add a type cast to avoid shifting a negative number bpo 20731 Properly position in source code files even if they are opened in text mode Patch by Serhiy Storchaka bpo 20637 Key sharing now also works for instance dictionaries of subclasses Patch by Peter Ingebretson bpo 8297 Attributes missing from modules now include the module name in the error text Original patch by ysj ray bpo 19995 c o x and X now raise TypeError on non integer input bpo 19655 The ASDL parser used by the build process to generate code for managing the Python AST in C was rewritten The new parser is self contained and does not require to carry long the spark py parser generator library spark py was removed from the source base bpo 12546 Allow x00 to be used as a fill character when using str int float and complex __format__ methods bpo 20480 Add ipaddress reverse_pointer Patch by Leon Weber bpo 13598 Modify string Formatter to support auto numbering of replacement fields It now matches the behavior of str format in this regard Patches by Phil Elson and Ramchandra Apte bpo 8931 Make alternate formatting for type c raise an exception In versions prior to 3 5 with c had no effect Now specifying it is an error Patch by Torsten Landschoff bpo 23165 Perform overflow checks before allocating memory in the _Py_char2wchar function Library bpo 23399 pyvenv creates relative symlinks where possible bpo 20289 cgi FieldStorage now supports the context management protocol bpo 13128 Print response headers for CONNECT requests when debuglevel 0 Patch by Demian Brecht bpo 15381 Optimized io BytesIO to make less allocations and copyings bpo 22818 Splitting on a pattern that could match an empty string now raises a warning Patterns that can only match empty strings are now rejected bpo 23099 Closing io BytesIO with exported buffer is rejected now to prevent corrupting exported buffer bpo 23326 Removed __ne__ implementations Since fixing default __ne__ implementation in bpo 21408 they are redundant bpo 23363 Fix possible overflow in itertools permutations bpo 23364 Fix possible ove,en
1835,rflow in itertools product bpo 23366 Fixed possible integer overflow in itertools combinations bpo 23369 Fixed possible integer overflow in _json encode_basestring_ascii bpo 23353 Fix the exception handling of generators in PyEval_EvalFrameEx At entry save or swap the exception state even if PyEval_EvalFrameEx is called with throwflag 0 At exit the exception state is now always restored or swapped not only if why is WHY_YIELD or WHY_RETURN Patch co written with Antoine Pitrou bpo 14099 Restored support of writing ZIP files to tellable but non seekable streams bpo 14099 Writing to ZipFile and reading multiple ZipExtFiles is threadsafe now bpo 19361 JSON decoder now raises JSONDecodeError instead of ValueError bpo 18518 timeit now rejects statements which can t be compiled outside a function or a loop e g return or break bpo 23094 Fixed readline with frames in Python implementation of pickle bpo 23268 Fixed bugs in the comparison of ipaddress classes bpo 21408 Removed incorrect implementations of __ne__ which didn t returned NotImplemented if __eq__ returned NotImplemented The default __ne__ now works correctly bpo 19996 email feedparser FeedParser now handles malformed headers with no key rather than assuming the body has started bpo 20188 Support Application Layer Protocol Negotiation ALPN in the ssl module bpo 23133 Pickling of ipaddress objects now produces more compact and portable representation bpo 23248 Update ssl error codes from latest OpenSSL git master bpo 23266 Much faster implementation of ipaddress collapse_addresses when there are many non consecutive addresses bpo 23098 64 bit dev_t is now supported in the os module bpo 21817 When an exception is raised in a task submitted to a ProcessPoolExecutor the remote traceback is now displayed in the parent process Patch by Claudiu Popa bpo 15955 Add an option to limit output size when decompressing LZMA data Patch by Nikolaus Rath and Martin Panter bpo 23250 In the http cookies module capitalize HttpOnly and Secure as they are written in the standard bpo 23063 In the distutils check command fix parsing of reST with code or code block directives bpo 23209 selectors BaseSelector get_key now raises a RuntimeError if the selector is closed And selectors BaseSelector close now clears its internal reference to the selector mapping to break a reference cycle Initial patch written by Martin Richard See also bpo 23225 bpo 17911 Provide a way to seed the linecache for a PEP 302 module without actually loading the code bpo 17911 Provide a new object API for traceback including the ability to not lookup lines at all until the traceback is actually rendered without any trace of the original objects being kept alive bpo 19777 Provide a home classmethod on Path objects Contributed by Victor Salgado and Mayank Tripathi bpo 23206 Make json dumps ensure_ascii False as fast as the default case of ensure_ascii True Patch by Naoki Inada bpo 23185 Add math inf and math nan constants bpo 23186 Add ssl SSLObject shared_ciphers and ssl SSLSocket shared_ciphers to fetch the client s list ciphers sent at handshake bpo 23143 Remove compatibility with OpenSSLs older than 0 9 8 bpo 23132 Improve performance and introspection support of comparison methods created by functool total_ordering bpo 19776 Add an expanduser method on Path objects bpo 23112 Fix SimpleHTTPServer to correctly carry the query string and fragment when it redirects to add a trailing slash bpo 21793 Added http HTTPStatus enums i e HTTPStatus OK HTTPStatus NOT_FOUND Patch by Demian Brecht bpo 23093 In the io module allow more operations to work on detached streams bpo 23111 In the ftplib make ssl PROTOCOL_SSLv23 the default protocol version bpo 22585 On OpenBSD 5 6 and newer os urandom now calls getentropy instead of reading dev urandom to get pseudo random bytes bpo 19104 pprint now produces evaluable output for wrapped strings bpo 23071 Added missing names to codecs __all__ Patch by Martin Panter bpo 22783 Pickling now uses the NEWOBJ opcode instead of the NEWOBJ_EX opcode if possible bpo 15513 Added a __sizeof__ implementa,en
1836,tion for pickle classes bpo 19858 pickletools optimize now aware of the MEMOIZE opcode can produce more compact result and no longer produces invalid output if input data contains MEMOIZE opcodes together with PUT or BINPUT opcodes bpo 22095 Fixed HTTPConnection set_tunnel with default port The port value in the host header was set to None Patch by Demian Brecht bpo 23016 A warning no longer produces an AttributeError when the program is run with pythonw exe bpo 21775 shutil copytree fix crash when copying to VFAT An exception handler assumed that OSError objects always have a winerror attribute That is not the case so the exception handler itself raised AttributeError when run on Linux and presumably any other non Windows OS Patch by Greg Ward bpo 1218234 Fix inspect getsource to load updated source of reloaded module Initial patch by Berker Peksag bpo 21740 Support wrapped callables in doctest Patch by Claudiu Popa bpo 23009 Make sure selectors EpollSelector select works when no FD is registered bpo 22959 In the constructor of http client HTTPSConnection prefer the context s check_hostname attribute over the check_hostname parameter bpo 22696 Add function sys is_finalizing to know about interpreter shutdown bpo 16043 Add a default limit for the amount of data xmlrpclib gzip_decode will return This resolves CVE 2013 1753 bpo 14099 ZipFile open no longer reopen the underlying file Objects returned by ZipFile open can now operate independently of the ZipFile even if the ZipFile was created by passing in a file like object as the first argument to the constructor bpo 22966 Fix __pycache__ pyc file name clobber when pyc_compile is asked to compile a source file containing multiple dots in the source file name bpo 21971 Update turtledemo doc and add module to the index bpo 21032 Fixed socket leak if HTTPConnection getresponse fails Original patch by Martin Panter bpo 22407 Deprecated the use of re LOCALE flag with str patterns or re ASCII It was newer worked bpo 22902 The ip command is now used on Linux to determine MAC address in uuid getnode Pach by Bruno Cauet bpo 22960 Add a context argument to xmlrpclib ServerProxy constructor bpo 22389 Add contextlib redirect_stderr bpo 21356 Make ssl RAND_egd optional to support LibreSSL The availability of the function is checked during the compilation Patch written by Bernard Spil bpo 22915 SAX parser now supports files opened with file descriptor or bytes path bpo 22609 Constructors and update methods of mapping classes in the collections module now accept the self keyword argument bpo 22940 Add readline append_history_file bpo 19676 Added the namereplace error handler bpo 22788 Add context parameter to logging handlers HTTPHandler bpo 22921 Allow SSLContext to take the hostname parameter even if OpenSSL doesn t support SNI bpo 22894 TestCase subTest would cause the test suite to be stopped when in failfast mode even in the absence of failures bpo 22796 HTTP cookie parsing is now stricter in order to protect against potential injection attacks bpo 22370 Windows detection in pathlib is now more robust bpo 22841 Reject coroutines in asyncio add_signal_handler Patch by Ludovic Gasc bpo 19494 Added urllib request HTTPBasicPriorAuthHandler Patch by Matej Cepl bpo 22578 Added attributes to the re error class bpo 22849 Fix possible double free in the io TextIOWrapper constructor bpo 12728 Different Unicode characters having the same uppercase but different lowercase are now matched in case insensitive regular expressions bpo 22821 Fixed fcntl with integer argument on 64 bit big endian platforms bpo 21650 Add an sort keys option to json tool CLI bpo 22824 Updated reprlib output format for sets to use set literals Patch contributed by Berker Peksag bpo 22824 Updated reprlib output format for arrays to display empty arrays without an unnecessary empty list Suggested by Serhiy Storchaka bpo 22406 Fixed the uu_codec codec incorrectly ported to 3 x Based on patch by Martin Panter bpo 17293 uuid getnode now determines MAC address on AIX using netstat Based on patch by Aivars Kalvāns bpo 22769 Fi,en
1837,xed ttk Treeview tag_has when called without arguments bpo 22417 Verify certificates by default in httplib PEP 476 bpo 22775 Fixed unpickling of http cookies SimpleCookie with protocol 2 and above Patch by Tim Graham bpo 22776 Brought excluded code into the scope of a try block in SysLogHandler emit bpo 22665 Add missing get_terminal_size and SameFileError to shutil __all__ bpo 6623 Remove deprecated Netrc class in the ftplib module Patch by Matt Chaput bpo 17381 Fixed handling of case insensitive ranges in regular expressions bpo 22410 Module level functions in the re module now cache compiled locale dependent regular expressions taking into account the locale bpo 22759 Query methods on pathlib Path exists is_dir etc now return False when the underlying stat call raises NotADirectoryError bpo 8876 distutils now falls back to copying files when hard linking doesn t work This allows use with special filesystems such as VirtualBox shared folders bpo 22217 Implemented reprs of classes in the zipfile module bpo 22457 Honour load_tests in the start_dir of discovery bpo 18216 gettext now raises an error when a mo file has an unsupported major version number Patch by Aaron Hill bpo 13918 Provide a locale delocalize function which can remove locale specific number formatting from a string representing a number without then converting it to a specific type Patch by Cédric Krier bpo 22676 Make the pickling of global objects which don t have a __module__ attribute less slow bpo 18853 Fixed ResourceWarning in shlex __nain__ bpo 9351 Defaults set with set_defaults on an argparse subparser are no longer ignored when also set on the parent parser bpo 7559 unittest test loading ImportErrors are reported as import errors with their import exception rather than as attribute errors after the import has already failed bpo 19746 Make it possible to examine the errors from unittest discovery without executing the test suite The new errors attribute on TestLoader exposes these non fatal errors encountered during discovery bpo 21991 Make email headerregistry s header params attributes be read only MappingProxyType Previously the dictionary was modifiable but a new one was created on each access of the attribute bpo 22638 SSLv3 is now disabled throughout the standard library It can still be enabled by instantiating a SSLContext manually bpo 22641 In asyncio the default SSL context for client connections is now created using ssl create_default_context for stronger security bpo 17401 Include closefd in io FileIO repr bpo 21338 Add silent mode for compileall quiet parameters of compile_ dir file path functions now have a multilevel value Also q option of the CLI now have a multilevel value Patch by Thomas Kluyver bpo 20152 Convert the array and cmath modules to Argument Clinic bpo 18643 Add socket socketpair on Windows bpo 22435 Fix a file descriptor leak when socketserver bind fails bpo 13096 Fixed segfault in CTypes POINTER handling of large values bpo 11694 Raise ConversionError in xdrlib as documented Patch by Filip Gruszczyński and Claudiu Popa bpo 19380 Optimized parsing of regular expressions bpo 1519638 Now unmatched groups are replaced with empty strings in re sub and re subn bpo 18615 sndhdr what whathdr now return a namedtuple bpo 22462 Fix pyexpat s creation of a dummy frame to make it appear in exception tracebacks bpo 21965 Add support for in memory SSL to the ssl module Patch by Geert Jansen bpo 21173 Fix len on a WeakKeyDictionary when clear was called with an iterator alive bpo 11866 Eliminated race condition in the computation of names for new threads bpo 21905 Avoid RuntimeError in pickle whichmodule when sys modules is mutated while iterating Patch by Olivier Grisel bpo 11271 concurrent futures Executor map now takes a chunksize argument to allow batching of tasks in child processes and improve performance of ProcessPoolExecutor Patch by Dan O Reilly bpo 21883 os path join and os path relpath now raise a TypeError with more helpful error message for unsupported or mismatched types of arguments bpo 22219 The zipfile module CLI no,en
1838,w adds entries for directories including empty directories in ZIP file bpo 22449 In the ssl SSLContext load_default_certs consult the environmental variables SSL_CERT_DIR and SSL_CERT_FILE on Windows bpo 22508 The email __version__ variable has been removed the email code is no longer shipped separately from the stdlib and __version__ hasn t been updated in several releases bpo 20076 Added non derived UTF 8 aliases to locale aliases table bpo 20079 Added locales supported in glibc 2 18 to locale alias table bpo 20218 Added convenience methods read_text write_text and read_bytes write_bytes to pathlib Path objects bpo 22396 On 32 bit AIX platform don t expose os posix_fadvise nor os posix_fallocate because their prototypes in system headers are wrong bpo 22517 When an io BufferedRWPair object is deallocated clear its weakrefs bpo 22437 Number of capturing groups in regular expression is no longer limited by 100 bpo 17442 InteractiveInterpreter now displays the full chained traceback in its showtraceback method to match the built in interactive interpreter bpo 23392 Added tests for marshal C API that works with FILE bpo 10510 distutils register and upload methods now use HTML standards compliant CRLF line endings bpo 9850 Fixed macpath join for empty first component Patch by Oleg Oshmyan bpo 5309 distutils build and build_ext commands now accept a j option to enable parallel building of extension modules bpo 22448 Improve canceled timer handles cleanup to prevent unbound memory usage Patch by Joshua Moore Oliva bpo 22427 TemporaryDirectory no longer attempts to clean up twice when used in the with statement in generator bpo 22362 Forbidden ambiguous octal escapes out of range 0 0o377 in regular expressions bpo 20912 Now directories added to ZIP file have correct Unix and MS DOS directory attributes bpo 21866 ZipFile close no longer writes ZIP64 central directory records if allowZip64 is false bpo 22278 Fix urljoin problem with relative urls a regression observed after changes to issue22118 were submitted bpo 22415 Fixed debugging output of the GROUPREF_EXISTS opcode in the re module Removed trailing spaces in debugging output bpo 22423 Unhandled exception in thread no longer causes unhandled AttributeError when sys stderr is None bpo 21332 Ensure that bufsize 1 in subprocess Popen selects line buffering rather than block buffering Patch by Akira Li bpo 21091 Fix API bug email message EmailMessage is_attachment is now a method bpo 21079 Fix email message EmailMessage is_attachment to return the correct result when the header has parameters as well as a value bpo 22247 Add NNTPError to nntplib __all__ bpo 22366 urllib request urlopen will accept a context object SSLContext as an argument which will then be used for HTTPS connection Patch by Alex Gaynor bpo 4180 The warnings registries are now reset when the filters are modified bpo 22419 Limit the length of incoming HTTP request in wsgiref server to 65536 bytes and send a 414 error code for higher lengths Patch contributed by Devin Cook Lax cookie parsing in http cookies could be a security issue when combined with non standard cookie handling in some web browsers Reported by Sergey Bobrov bpo 20537 logging methods now accept an exception instance as well as a Boolean value or exception tuple Thanks to Yury Selivanov for the patch bpo 22384 An exception in Tkinter callback no longer crashes the program when it is run with pythonw exe bpo 22168 Prevent turtle AttributeError with non default Canvas on OS X bpo 21147 sqlite3 now raises an exception if the request contains a null character instead of truncating it Based on patch by Victor Stinner bpo 13968 The glob module now supports recursive search in subdirectories using the pattern bpo 21951 Fixed a crash in Tkinter on AIX when called Tcl command with empty string or tuple argument bpo 21951 Tkinter now most likely raises MemoryError instead of crash if the memory allocation fails bpo 22338 Fix a crash in the json module on memory allocation failure bpo 12410 imaplib IMAP4 now supports the context management protocol Origin,en
1839,al patch by Tarek Ziadé bpo 21270 We now override tuple methods in mock call objects so that they can be used as normal call attributes bpo 16662 load_tests is now unconditionally run when it is present in a package s __init__ py TestLoader loadTestsFromModule still accepts use_load_tests but it is deprecated and ignored A new keyword only attribute pattern is added and documented Patch given by Robert Collins tweaked by Barry Warsaw bpo 22226 First letter no longer is stripped from the status key in the result of Treeview heading bpo 19524 Fixed resource leak in the HTTP connection when an invalid response is received Patch by Martin Panter bpo 20421 Add a version method to SSL sockets exposing the actual protocol version in use bpo 19546 configparser exceptions no longer expose implementation details Chained KeyErrors are removed which leads to cleaner tracebacks Patch by Claudiu Popa bpo 22051 turtledemo no longer reloads examples to re run them Initialization of variables and gui setup should be done in main which is called each time a demo is run but not on import bpo 21933 Turtledemo users can change the code font size with a menu selection or control command or or control mousewheel Original patch by Lita Cho bpo 21597 The separator between the turtledemo text pane and the drawing canvas can now be grabbed and dragged with a mouse The code text pane can be widened to easily view or copy the full width of the text The canvas can be widened on small screens Original patches by Jan Kanis and Lita Cho bpo 18132 Turtledemo buttons no longer disappear when the window is shrunk Original patches by Jan Kanis and Lita Cho bpo 22043 time monotonic is now always available threading Lock acquire threading RLock acquire and socket operations now use a monotonic clock instead of the system clock when a timeout is used bpo 21527 Add a default number of workers to ThreadPoolExecutor equal to 5 times the number of CPUs Patch by Claudiu Popa bpo 22216 smtplib now resets its state more completely after a quit The most obvious consequence of the previous behavior was a STARTTLS failure during a connect starttls quit connect starttls sequence bpo 22098 ctypes BigEndianStructure and LittleEndianStructure now define an empty __slots__ so that subclasses don t always get an instance dict Patch by Claudiu Popa bpo 22185 Fix an occasional RuntimeError in threading Condition wait caused by mutation of the waiters queue without holding the lock Patch by Doug Zongker bpo 22287 On UNIX _PyTime_gettimeofday now uses clock_gettime CLOCK_REALTIME if available As a side effect Python now depends on the librt library on Solaris and on Linux only with glibc older than 2 17 bpo 22182 Use e args to unpack exceptions correctly in distutils file_util move_file Patch by Claudiu Popa The webbrowser module now uses subprocess s start_new_session True rather than a potentially risky preexec_fn os setsid call bpo 22042 signal set_wakeup_fd fd now raises an exception if the file descriptor is in blocking mode bpo 16808 inspect stack now returns a named tuple instead of a tuple Patch by Daniel Shahaf bpo 22236 Fixed Tkinter images copying operations in NoDefaultRoot mode bpo 2527 Add a globals argument to timeit functions in order to override the globals namespace in which the timed code is executed Patch by Ben Roberts bpo 22118 Switch urllib parse to use RFC 3986 semantics for the resolution of relative URLs rather than RFCs 1808 and 2396 Patch by Demian Brecht bpo 21549 Added the members parameter to TarFile list bpo 19628 Allow compileall recursion depth to be specified with a r option bpo 15696 Add a __sizeof__ implementation for mmap objects on Windows bpo 22068 Avoided reference loops with Variables and Fonts in Tkinter bpo 22165 SimpleHTTPRequestHandler now supports undecodable file names bpo 15381 Optimized line reading in io BytesIO bpo 8797 Raise HTTPError on failed Basic Authentication immediately Initial patch by Sam Bull bpo 20729 Restored the use of lazy iterkeys itervalues iteritems in the mailbox module bpo 21448 Changed FeedParser feed to avo,en
1840,id O n 2 behavior when parsing long line Original patch by Raymond Hettinger bpo 22184 The functools LRU Cache decorator factory now gives an earlier and clearer error message when the user forgets the required parameters bpo 17923 glob patterns ending with a slash no longer match non dirs on AIX Based on patch by Delhallt bpo 21725 Added support for RFC 6531 SMTPUTF8 in smtpd bpo 22176 Update the ctypes module s libffi to v3 1 This release adds support for the Linux AArch64 and POWERPC ELF ABIv2 little endian architectures bpo 5411 Added support for the xztar format in the shutil module bpo 21121 Don t force 3rd party C extensions to be built with Werror declaration after statement bpo 21975 Fixed crash when using uninitialized sqlite3 Row in particular when unpickling pickled sqlite3 Row sqlite3 Row is now initialized in the __new__ method bpo 20170 Convert posixmodule to use Argument Clinic bpo 21539 Add an exists_ok argument to Pathlib mkdir to mimic mkdir p and os makedirs functionality When true ignore FileExistsErrors Patch by Berker Peksag bpo 22127 Bypass IDNA for pure ASCII host names in the socket module in particular for numeric IPs bpo 21047 set the default value for the convert_charrefs argument of HTMLParser to True Patch by Berker Peksag Add an __all__ to html entities bpo 15114 the strict mode and argument of HTMLParser HTMLParser error and the HTMLParserError exception have been removed bpo 22085 Dropped support of Tk 8 3 in Tkinter bpo 21580 Now Tkinter correctly handles bytes arguments passed to Tk In particular this allows initializing images from binary data bpo 22003 When initialized from a bytes object io BytesIO now defers making a copy until it is mutated improving performance and memory use on some use cases Patch by David Wilson bpo 22018 On Windows signal set_wakeup_fd now also supports sockets A side effect is that Python depends to the WinSock library bpo 22054 Add os get_blocking and os set_blocking functions to get and set the blocking mode of a file descriptor False if the O_NONBLOCK flag is set True otherwise These functions are not available on Windows bpo 17172 Make turtledemo start as active on OS X even when run with subprocess Patch by Lita Cho bpo 21704 Fix build error for _multiprocessing when semaphores are not available Patch by Arfrever Frehtes Taifersar Arahesis bpo 20173 Convert sha1 sha256 sha512 and md5 to ArgumentClinic Patch by Vajrasky Kok Fix repr _socket socket on Windows 64 bit don t fail with OverflowError on closed socket repr socket socket already works fine bpo 22033 Reprs of most Python implemented classes now contain actual class name instead of hardcoded one bpo 21947 The dis module can now disassemble generator iterator objects based on their gi_code attribute Patch by Clement Rouault bpo 16133 The asynchat async_chat handle_read method now ignores BlockingIOError exceptions bpo 22044 Fixed premature DECREF in call_tzinfo_method Patch by Tom Flanagan bpo 19884 readline Disable the meta modifier key if stdout is not a terminal to not write the ANSI sequence 033 1034h into stdout This sequence is used on some terminal ex TERM xterm 256color to enable support of 8 bit characters bpo 4350 Removed a number of out of dated and non working for a long time Tkinter methods bpo 6167 Scrollbar activate now returns the name of active element if the argument is not specified Scrollbar set now always accepts only 2 arguments bpo 15275 Clean up and speed up the ntpath module bpo 21888 plistlib s load and loads now work if the fmt parameter is specified bpo 22032 __qualname__ instead of __name__ is now always used to format fully qualified class names of Python implemented classes bpo 22031 Reprs now always use hexadecimal format with the 0x prefix when contain an id in form at 0x bpo 22018 signal set_wakeup_fd now raises an OSError instead of a ValueError on fstat failure bpo 21044 tarfile open now handles fileobj with an integer name attribute Based on patch by Antoine Pietri bpo 21966 Respect q command line option when code module is ran bpo 19076 Don t pass the redundant,en
1841, file argument to self error bpo 16382 Improve exception message of warnings warn for bad category Initial patch by Phil Elson bpo 21932 os read now uses a Py_ssize_t type instead of int for the size to support reading more than 2 GB at once On Windows the size is truncated to INT_MAX As any call to os read the OS may read less bytes than the number of requested bytes bpo 21942 Fixed source file viewing in pydoc s server mode on Windows bpo 11259 asynchat async_chat set_terminator now raises a ValueError if the number of received bytes is negative bpo 12523 asynchat async_chat push now raises a TypeError if it doesn t get a bytes string bpo 21707 Add missing kwonlyargcount argument to ModuleFinder replace_paths_in_code bpo 20639 calling Path with_suffix allows removing the suffix again Patch by July Tikhonov bpo 21714 Disallow the construction of invalid paths using Path with_name Original patch by Antony Lee bpo 15014 Added auth method to smtplib to make implementing auth mechanisms simpler and used it internally in the login method bpo 21151 Fixed a segfault in the winreg module when None is passed as a REG_BINARY value to SetValueEx Patch by John Ehresman bpo 21090 io FileIO readall does not ignore I O errors anymore Before it ignored I O errors if at least the first C call read succeed bpo 5800 headers parameter of wsgiref headers Headers is now optional Initial patch by Pablo Torres Navarrete and SilentGhost bpo 21781 ssl RAND_add now supports strings longer than 2 GB bpo 21679 Prevent extraneous fstat calls during open Patch by Bohuslav Kabrda bpo 21863 cProfile now displays the module name of C extension functions in addition to their own name bpo 11453 asyncore emit a ResourceWarning when an unclosed file_wrapper object is destroyed The destructor now closes the file if needed The close method can now be called twice the second call does nothing bpo 21858 Better handling of Python exceptions in the sqlite3 module bpo 21476 Make sure the email parser BytesParser TextIOWrapper is discarded after parsing so the input file isn t unexpectedly closed bpo 20295 imghdr now recognizes OpenEXR format images bpo 21729 Used the with statement in the dbm dumb module to ensure files closing Patch by Claudiu Popa bpo 21491 socketserver Fix a race condition in child processes reaping bpo 21719 Added the st_file_attributes field to os stat_result on Windows bpo 21832 Require named tuple inputs to be exact strings bpo 21722 The distutils upload command now exits with a non zero return code when uploading fails Patch by Martin Dengler bpo 21723 asyncio Queue support any type of number ex float for the maximum size Patch written by Vajrasky Kok bpo 21711 support for site python directories has now been removed from the site module it was deprecated in 3 4 bpo 17552 new socket sendfile method allowing a file to be sent over a socket by using high performance os sendfile on UNIX Patch by Giampaolo Rodola bpo 18039 dbm dump open now always creates a new database when the flag has the value n Patch by Claudiu Popa bpo 21326 Add a new is_closed method to asyncio BaseEventLoop run_forever and run_until_complete methods of asyncio BaseEventLoop now raise an exception if the event loop was closed bpo 21766 Prevent a security hole in CGIHTTPServer by URL unquoting paths before checking for a CGI script at that path bpo 21310 Fixed possible resource leak in failed open bpo 21256 Printout of keyword args should be in deterministic order in a mock function call This will help to write better doctests bpo 21677 Fixed chaining nonnormalized exceptions in io close methods bpo 11709 Fix the pydoc help function to not fail when sys stdin is not a valid file bpo 21515 tempfile TemporaryFile now uses os O_TMPFILE flag is available bpo 13223 Fix pydoc writedoc so that the HTML documentation for methods that use self in the example code is generated correctly bpo 21463 In urllib request fix pruning of the FTP cache bpo 21618 The subprocess module could fail to close open fds that were inherited by the calling process and already higher than POSIX resour,en
1842,ce limits would otherwise allow On systems with a functioning proc self fd or dev fd interface the max is now ignored and all fds are closed bpo 20383 Introduce importlib util module_from_spec as the preferred way to create a new module bpo 21552 Fixed possible integer overflow of too long string lengths in the tkinter module on 64 bit platforms bpo 14315 The zipfile module now ignores extra fields in the central directory that are too short to be parsed instead of letting a struct unpack error bubble up as this bad data appears in many real world zip files in the wild and is ignored by other zip tools bpo 13742 Added key and reverse parameters to heapq merge First draft of patch contributed by Simon Sapin bpo 21402 tkinter ttk now works when default root window is not set bpo 3015 _tkinter create now creates tkapp object with wantobject 1 by default bpo 10203 sqlite3 Row now truly supports sequence protocol In particular it supports reverse and negative indices Original patch by Claudiu Popa bpo 18807 If copying no symlinks specified for a venv then the python interpreter aliases python python3 are now created by copying rather than symlinking bpo 20197 Added support for the WebP image type in the imghdr module Patch by Fabrice Aneche and Claudiu Popa bpo 21513 Speedup some properties of IP addresses IPv4Address IPv6Address such as is_private or is_multicast bpo 21137 Improve the repr for threading Lock and its variants by showing the locked or unlocked status Patch by Berker Peksag bpo 21538 The plistlib module now supports loading of binary plist files when reference or offset size is not a power of two bpo 21455 Add a default backlog to socket listen bpo 21525 Most Tkinter methods which accepted tuples now accept lists too bpo 22166 With the assistance of a new internal _codecs _forget_codec helping function test_codecs now clears the encoding caches to avoid the appearance of a reference leak bpo 22236 Tkinter tests now don t reuse default root window New root window is created for every test class bpo 10744 Fix PEP 3118 format strings on ctypes objects with a nontrivial shape bpo 20826 Optimize ipaddress collapse_addresses bpo 21487 Optimize ipaddress summarize_address_range and ipaddress IPv4Network IPv6Network subnets bpo 21486 Optimize parsing of netmasks in ipaddress IPv4Network and ipaddress IPv6Network bpo 13916 Disallowed the surrogatepass error handler for non UTF encodings bpo 20998 Fixed re fullmatch of repeated single character pattern with ignore case Original patch by Matthew Barnett bpo 21075 fileinput FileInput now reads bytes from standard stream if binary mode is specified Patch by Sam Kimbrel bpo 19775 Add a samefile method to pathlib Path objects Initial patch by Vajrasky Kok bpo 21226 Set up modules properly in PyImport_ExecCodeModuleObject and friends bpo 21398 Fix a unicode error in the pydoc pager when the documentation contains characters not encodable to the stdout encoding bpo 16531 ipaddress IPv4Network and ipaddress IPv6Network now accept an address netmask tuple argument so as to easily construct network objects from existing addresses bpo 21156 importlib abc InspectLoader source_to_code is now a staticmethod bpo 21424 Simplified and optimized heaqp nlargest and nmsmallest to make fewer tuple comparisons bpo 21396 Fix TextIOWrapper write_through True to not force a flush on the underlying binary stream Patch by akira bpo 18314 Unlink now removes junctions on Windows Patch by Kim Gräsman bpo 21088 Bugfix for curses window addch regression in 3 4 0 In porting to Argument Clinic the first two arguments were reversed bpo 21407 _decimal The module now supports function signatures bpo 10650 Remove the non standard watchexp parameter from the Decimal quantize method in the Python version It had never been present in the C version bpo 21469 Reduced the risk of false positives in robotparser by checking to make sure that robots txt has been read or does not exist prior to returning True in can_fetch bpo 19414 Have the OrderedDict mark deleted links as unusable This gives an early failure if the ,en
1843,link is deleted during iteration bpo 21421 Add __slots__ to the MappingViews ABC Patch by Josh Rosenberg bpo 21101 Eliminate double hashing in the C speed up code for collections Counter bpo 21321 itertools islice now releases the reference to the source iterator when the slice is exhausted Patch by Anton Afanasyev bpo 21057 TextIOWrapper now allows the underlying binary stream s read or read1 method to return an arbitrary bytes like object such as a memoryview Patch by Nikolaus Rath bpo 20951 SSLSocket send now raises either SSLWantReadError or SSLWantWriteError on a non blocking socket if the operation would block Previously it would return 0 Patch by Nikolaus Rath bpo 13248 removed previously deprecated asyncore dispatcher __getattr__ cheap inheritance hack bpo 9815 assertRaises now tries to clear references to local variables in the exception s traceback bpo 19940 ssl cert_time_to_seconds now interprets the given time string in the UTC timezone as specified in RFC 5280 not the local timezone bpo 13204 Calling sys flags __new__ would crash the interpreter now it raises a TypeError bpo 19385 Make operations on a closed dbm dumb database always raise the same exception bpo 21207 Detect when the os urandom cached fd has been closed or replaced and open it anew bpo 21291 subprocess s Popen wait is now thread safe so that multiple threads may be calling wait or poll on a Popen instance at the same time without losing the Popen returncode value bpo 21127 Path objects can now be instantiated from str subclass instances such as numpy str_ bpo 15002 urllib response object to use _TemporaryFileWrapper and _TemporaryFileCloser facility Provides a better way to handle file descriptor close Patch contributed by Christian Theune bpo 12220 mindom now raises a custom ValueError indicating it doesn t support spaces in URIs instead of letting a split ValueError bubble up bpo 21068 The ssl PROTOCOL constants are now enum members bpo 21276 posixmodule Don t define USE_XATTRS on KFreeBSD and the Hurd bpo 21262 New method assert_not_called for Mock It raises AssertionError if the mock has been called bpo 21238 New keyword argument unsafe to Mock It raises AttributeError incase of an attribute startswith assert or assret bpo 20896 ssl get_server_certificate now uses PROTOCOL_SSLv23 not PROTOCOL_SSLv3 for maximum compatibility bpo 21239 patch stopall didn t work deterministically when the same name was patched more than once bpo 21203 Updated fileConfig and dictConfig to remove inconsistencies Thanks to Jure Koren for the patch bpo 21222 Passing name keyword argument to mock create_autospec now works bpo 21197 Add lib64 lib symlink in venvs on 64 bit non OS X POSIX bpo 17498 Some SMTP servers disconnect after certain errors violating strict RFC conformance Instead of losing the error code when we issue the subsequent RSET smtplib now returns the error code and defers raising the SMTPServerDisconnected error until the next command is issued bpo 17826 setting an iterable side_effect on a mock function created by create_autospec now works Patch by Kushal Das bpo 7776 Fix Host header and reconnection when using http client HTTPConnection set_tunnel Patch by Nikolaus Rath bpo 20968 unittest mock MagicMock now supports division Patch by Johannes Baiter bpo 21529 Fix arbitrary memory access in JSONDecoder raw_decode with a negative second parameter Bug reported by Guido Vranken See also CVE 2014 4616 bpo 21169 getpass now handles non ascii characters that the input stream encoding cannot encode by re encoding using the replace error handler bpo 21171 Fixed undocumented filter API of the rot13 codec Patch by Berker Peksag bpo 20539 Improved math factorial error message for large positive inputs and changed exception type OverflowError ValueError for large negative inputs bpo 21172 isinstance check relaxed from dict to collections Mapping bpo 21155 asyncio EventLoop create_unix_server now raises a ValueError if path and sock are specified at the same time bpo 21136 Avoid unnecessary normalization of Fractions resulting from power and other operations,en
1844, Patch by Raymond Hettinger bpo 17621 Introduce importlib util LazyLoader bpo 21076 signal module constants were turned into enums Patch by Giampaolo Rodola bpo 20636 Improved the repr of Tkinter widgets bpo 19505 The items keys and values views of OrderedDict now support reverse iteration using reversed bpo 21149 Improved thread safety in logging cleanup during interpreter shutdown Thanks to Devin Jeanpierre for the patch bpo 21058 Fix a leak of file descriptor in tempfile NamedTemporaryFile close the file descriptor if io open fails bpo 21200 Return None from pkgutil get_loader when __spec__ is missing bpo 21013 Enhance ssl create_default_context when used for server side sockets to provide better security by default bpo 20145 assertRaisesRegex and assertWarnsRegex now raise a TypeError if the second argument is not a string or compiled regex bpo 20633 Replace relative import by absolute import bpo 20980 Stop wrapping exception when using ThreadPool bpo 21082 In os makedirs do not set the process wide umask Note this changes behavior of makedirs when exist_ok True bpo 20990 Fix issues found by pyflakes for multiprocessing bpo 21015 SSL contexts will now automatically select an elliptic curve for ECDH key exchange on OpenSSL 1 0 2 and later and otherwise default to prime256v1 bpo 21000 Improve the command line interface of json tool bpo 20995 Enhance default ciphers used by the ssl module to enable better security and prioritize perfect forward secrecy bpo 20884 Don t assume that __file__ is defined on importlib __init__ bpo 21499 Ignore __builtins__ in several test_importlib test_api tests bpo 20627 xmlrpc client ServerProxy is now a context manager bpo 19165 The formatter module now raises DeprecationWarning instead of PendingDeprecationWarning bpo 13936 Remove the ability of datetime time instances to be considered false in boolean contexts bpo 18931 selectors module now supports dev poll on Solaris Patch by Giampaolo Rodola bpo 19977 When the LC_TYPE locale is the POSIX locale C locale sys stdin and sys stdout are now using the surrogateescape error handler instead of the strict error handler bpo 20574 Implement incremental decoder for cp65001 code Windows code page 65001 Microsoft UTF 8 bpo 20879 Delay the initialization of encoding and decoding tables for base32 ascii85 and base85 codecs in the base64 module and delay the initialization of the unquote_to_bytes table of the urllib parse module to not waste memory if these modules are not used bpo 19157 Include the broadcast address in the usuable hosts for IPv6 in ipaddress bpo 11599 When an external command e g compiler fails distutils now prints out the whole command line instead of just the command name if the environment variable DISTUTILS_DEBUG is set bpo 4931 distutils should not produce unhelpful error None messages anymore distutils util grok_environment_error is kept but doc deprecated bpo 20875 Prevent possible gzip read is not defined NameError Patch by Claudiu Popa bpo 11558 email message Message attach now returns a more useful error message if attach is called on a message for which is_multipart is False bpo 20283 RE pattern methods now accept the string keyword parameters as documented The pattern and source keyword parameters are left as deprecated aliases bpo 20778 Fix modulefinder to work with bytecode only modules bpo 20791 copy copy now doesn t make a copy when the input is a bytes object Initial patch by Peter Otten bpo 19748 On AIX time mktime now raises an OverflowError for year outsize range 1902 2037 bpo 19573 inspect signature Use enum for parameter kind constants bpo 20726 inspect signature Make Signature and Parameter picklable bpo 17373 Add inspect Signature from_callable method bpo 20378 Improve repr of inspect Signature and inspect Parameter bpo 20816 Fix inspect getcallargs to raise correct TypeError for missing keyword only arguments Patch by Jeremiah Lowin bpo 20817 Fix inspect getcallargs to fail correctly if more than 3 arguments are missing Patch by Jeremiah Lowin bpo 6676 Ensure a meaningful exception is raised when attempting ,en
1845,to parse more than one XML document per pyexpat xmlparser instance Original patches by Hirokazu Yamamoto and Amaury Forgeot d Arc with suggested wording by David Gutteridge bpo 21117 Fix inspect signature to better support functools partial Due to the specifics of functools partial implementation positional or keyword arguments passed as keyword arguments become keyword only bpo 20334 inspect Signature and inspect Parameter are now hashable Thanks to Antony Lee for bug reports and suggestions bpo 15916 doctest DocTestSuite returns an empty unittest TestSuite instead of raising ValueError if it finds no tests bpo 21209 Fix asyncio tasks CoroWrapper to workaround a bug in yield from implementation in CPythons prior to 3 4 1 asyncio Add gi_ frame running code properties to CoroWrapper upstream bpo 163 bpo 21311 Avoid exception in _osx_support with non standard compiler configurations Patch by John Szakmeister bpo 11571 Ensure that the turtle window becomes the topmost window when launched on OS X bpo 21801 Validate that __signature__ is None or an instance of Signature bpo 21923 Prevent AttributeError in distutils sysconfig customize_compiler due to possible uninitialized _config_vars bpo 21323 Fix http server to again handle scripts in CGI subdirectories broken by the fix for security bpo 19435 Patch by Zach Byrne bpo 22733 Fix ffi_prep_args not zero extending argument values correctly on 64 bit Windows bpo 23302 Default to TCP_NODELAY 1 upon establishing an HTTPConnection Removed use of hard coded MSS as it s an optimization that s no longer needed with Nagle disabled IDLE bpo 20577 Configuration of the max line length for the FormatParagraph extension has been moved from the General tab of the Idle preferences dialog to the FormatParagraph tab of the Config Extensions dialog Patch by Tal Einat bpo 16893 Update Idle doc chapter to match current Idle and add new information bpo 3068 Add Idle extension configuration dialog to Options menu Changes are written to HOME idlerc config extensions cfg Original patch by Tal Einat bpo 16233 A module browser File Class Browser Alt C requires an editor window with a filename When Class Browser is requested otherwise from a shell output window or Untitled editor Idle no longer displays an error box It now pops up an Open Module box Alt M If a valid name is entered and a module is opened a corresponding browser is also opened bpo 4832 Save As to type Python files automatically adds py to the name you enter even if your system does not display it Some systems automatically add txt when type is Text files bpo 21986 Code objects are not normally pickled by the pickle module To match this they are no longer pickled when running under Idle bpo 17390 Adjust Editor window title remove Python move version to end bpo 14105 Idle debugger breakpoints no longer disappear when inserting or deleting lines bpo 17172 Turtledemo can now be run from Idle Currently the entry is on the Help menu but it may move to Run Patch by Ramchandra Apt and Lita Cho bpo 21765 Add support for non ascii identifiers to HyperParser bpo 21940 Add unittest for WidgetRedirector Initial patch by Saimadhav Heblikar bpo 18592 Add unittest for SearchDialogBase Patch by Phil Webster bpo 21694 Add unittest for ParenMatch Patch by Saimadhav Heblikar bpo 21686 add unittest for HyperParser Original patch by Saimadhav Heblikar bpo 12387 Add missing upper lower case versions of default Windows key bindings for Idle so Caps Lock does not disable them Patch by Roger Serwy bpo 21695 Closing a Find in files output window while the search is still in progress no longer closes Idle bpo 18910 Add unittest for textView Patch by Phil Webster bpo 18292 Add unittest for AutoExpand Patch by Saihadhav Heblikar bpo 18409 Add unittest for AutoComplete Patch by Phil Webster bpo 21477 htest py Improve framework complete set of tests Patches by Saimadhav Heblikar bpo 18104 Add idlelib idle_test htest py with a few sample tests to begin consolidating and improving human validated tests of Idle Change other files as needed to work with htest Running the m,en
1846,odule as __main__ runs all tests bpo 21139 Change default paragraph width to 72 the PEP 8 recommendation bpo 21284 Paragraph reformat test passes after user changes reformat width bpo 17654 Ensure IDLE menus are customized properly on OS X for non framework builds and for all variants of Tk bpo 23180 Rename IDLE Windows menu item to Window Patch by Al Sweigart Build bpo 15506 Use standard PKG_PROG_PKG_CONFIG autoconf macro in the configure script bpo 22935 Allow the ssl module to be compiled if openssl doesn t support SSL 3 bpo 22592 Drop support of the Borland C compiler to build Python The distutils module still supports it to build extensions bpo 22591 Drop support of MS DOS especially of the DJGPP compiler MS DOS port of GCC bpo 16537 Check whether self extensions is empty in setup py Patch by Jonathan Hosmer bpo 22359 Remove incorrect uses of recursive make Patch by Jonas Wagner bpo 21958 Define HAVE_ROUND when building with Visual Studio 2013 and above Patch by Zachary Turner bpo 18093 the programs that embed the CPython runtime are now in a separate Programs directory rather than being kept in the Modules directory bpo 15759 make suspicious make linkcheck and make doctest in Doc now display special message when and only when there are failures bpo 21141 The Windows build process no longer attempts to find Perl instead relying on OpenSSL source being configured and ready to build The PCbuild build_ssl py script has been re written and re named to PCbuild prepare_ssl py and takes care of configuring OpenSSL source for both 32 and 64 bit platforms OpenSSL sources obtained from svn python org will always be pre configured and ready to build bpo 21037 Add a build option to enable AddressSanitizer support bpo 19962 The Windows build process now creates python bat in the root of the source tree which passes all arguments through to the most recently built interpreter bpo 21285 Refactor and fix curses configure check to always search in a ncursesw directory bpo 15234 For BerkeleyDB and Sqlite only add the found library and include directories if they aren t already being searched This avoids an explicit runtime library dependency bpo 17861 Tools scripts generate_opcode_h py automatically regenerates Include opcode h from Lib opcode py if the latter gets any change bpo 20644 OS X installer build support for documentation build changes in 3 4 1 assume externally supplied sphinx build is available in usr bin bpo 20022 Eliminate use of deprecated bundlebuilder in OS X builds bpo 15968 Incorporated Tcl Tk and Tix builds into the Windows build solution bpo 17095 Fix Modules Setup shared support bpo 21811 Anticipated fixes to support OS X versions 10 9 bpo 21166 Prevent possible segfaults and other random failures of python generate posix vars in pybuilddir txt build target bpo 18096 Fix library order returned by python config bpo 17219 Add library build dir for Python extension cross builds bpo 22919 Windows build updated to support VC 14 0 Visual Studio 2015 which will be used for the official release bpo 21236 Build _msi pyd with cabinet lib instead of fci lib bpo 17128 Use private version of OpenSSL for OS X 10 5 installer C API bpo 14203 Remove obsolete support for view NULL in PyBuffer_FillInfo bytearray_getbuffer bytesiobuf_getbuffer and array_buffer_getbuf All functions now raise BufferError in that case bpo 22445 PyBuffer_IsContiguous now implements precise contiguity tests compatible with NumPy s NPY_RELAXED_STRIDES_CHECKING compilation flag Previously the function reported false negatives for corner cases bpo 22079 PyType_Ready now checks that statically allocated type has no dynamically allocated bases bpo 22453 Removed non documented macro PyObject_REPR bpo 18395 Rename _Py_char2wchar to Py_DecodeLocale rename _Py_wchar2char to Py_EncodeLocale and document these functions bpo 21233 Add new C functions PyMem_RawCalloc PyMem_Calloc PyObject_Calloc _PyObject_GC_Calloc bytes int is now using calloc instead of malloc for large objects which is faster and use less memory bpo 20942 PyImport_ImportFrozenModuleObject no long,en
1847,er sets __file__ to match what importlib does this affects _frozen_importlib as well as any module loaded using imp init_frozen Documentation bpo 19548 Update the codecs module documentation to better cover the distinction between text encodings and other codecs together with other clarifications Patch by Martin Panter bpo 22394 Doc Makefile now supports make venv PYTHON python to create a venv for generating the documentation e g make html PYTHON venv bin python3 bpo 21514 The documentation of the json module now refers to new JSON RFC 7159 instead of obsoleted RFC 4627 bpo 21777 The binary sequence methods on bytes and bytearray are now documented explicitly rather than assuming users will be able to derive the expected behaviour from the behaviour of the corresponding str methods bpo 6916 undocument deprecated asynchat fifo class bpo 17386 Expanded functionality of the Doc make bat script to make it much more comparable to Doc Makefile bpo 21312 Update the thread_foobar h template file to include newer threading APIs Patch by Jack McCracken bpo 21043 Remove the recommendation for specific CA organizations and to mention the ability to load the OS certificates bpo 20765 Add missing documentation for PurePath with_name and PurePath with_suffix bpo 19407 New package installation and distribution guides based on the Python Packaging Authority tools Existing guides have been retained as legacy links from the distutils docs as they still contain some required reference material for tool developers that isn t recorded anywhere else bpo 19697 Document cases where __main__ __spec__ is None Tests bpo 18982 Add tests for CLI of the calendar module bpo 19548 Added some additional checks to test_codecs to ensure that statements in the updated documentation remain accurate Patch by Martin Panter bpo 22838 All test_re tests now work with unittest test discovery bpo 22173 Update lib2to3 tests to use unittest test discovery bpo 16000 Convert test_curses to use unittest bpo 21456 Skip two tests in test_urllib2net py if _ssl module not present Patch by Remi Pointel bpo 20746 Fix test_pdb to run in refleak mode R Patch by Xavier de Gaye bpo 22060 test_ctypes has been somewhat cleaned up and simplified it now uses unittest test discovery to find its tests bpo 22104 regrtest py no longer holds a reference to the suite of tests loaded from test modules that don t define test_main bpo 22111 Assorted cleanups in test_imaplib Patch by Milan Oberkirch bpo 22002 Added load_package_tests function to test support and used it to implement augment test discovery in test_asyncio test_email test_importlib test_json and test_tools bpo 21976 Fix test_ssl to accept LibreSSL version strings Thanks to William Orr bpo 21918 Converted test_tools from a module to a package containing separate test files for each tested script bpo 9554 Use modern unittest features in test_argparse Initial patch by Denver Coneybeare and Radu Voicilas bpo 20155 Changed HTTP method names in failing tests in test_httpservers so that packet filtering software specifically Windows Base Filtering Engine does not interfere with the transaction semantics expected by the tests bpo 19493 Refactored the ctypes test package to skip tests explicitly rather than silently bpo 18492 All resources are now allowed when tests are not run by regrtest py bpo 21634 Fix pystone micro benchmark use floor division instead of true division to benchmark integers instead of floating point numbers Set pystone version to 1 2 Patch written by Lennart Regebro bpo 21605 Added tests for Tkinter images bpo 21493 Added test for ntpath expanduser Original patch by Claudiu Popa bpo 19925 Added tests for the spwd module Original patch by Vajrasky Kok bpo 21522 Added Tkinter tests for Listbox itemconfigure PanedWindow paneconfigure and Menu entryconfigure bpo 17756 Fix test_code test when run from the installed location bpo 17752 Fix distutils tests when run from the installed location bpo 18604 Consolidated checks for GUI availability All platforms now at least check whether Tk can be instantiated when the GUI resou,en
1848,rce is requested bpo 21275 Fix a socket test on KFreeBSD bpo 21223 Pass test_site test_startup_imports when some of the extensions are built as builtins bpo 20635 Added tests for Tk geometry managers Add test case for freeze bpo 20743 Fix a reference leak in test_tcl bpo 21097 Move test_namespace_pkgs into test_importlib bpo 21503 Use test_both consistently in test_importlib bpo 20939 Avoid various network test failures due to new redirect of http www python org to https www python org use http www example com instead bpo 20668 asyncio tests no longer rely on tests txt file Patch by Vajrasky Kok bpo 21093 Prevent failures of ctypes test_macholib on OS X if a copy of libz exists in HOME lib or usr local lib bpo 22770 Prevent some Tk segfaults on OS X when running gui tests bpo 23211 Workaround test_logging failure on some OS X 10 6 systems bpo 23345 Prevent test_ssl failures with large OpenSSL patch level values like 0 9 8zc Tools Demos bpo 22314 pydoc now works when the LINES environment variable is set bpo 22615 Argument Clinic now supports the type argument for the int converter This permits using the int converter with enums and typedefs bpo 20076 The makelocalealias py script no longer ignores UTF 8 mapping bpo 20079 The makelocalealias py script now can parse the SUPPORTED file from glibc sources and supports command line options for source paths bpo 22201 Command line interface of the zipfile module now correctly extracts ZIP files with directory entries Patch by Ryan Wilson bpo 22120 For functions using an unsigned integer return converter Argument Clinic now generates a cast to that type for the comparison to 1 in the generated code This suppresses a compilation warning bpo 18974 Tools scripts diff py now uses argparse instead of optparse bpo 21906 Make Tools scripts md5sum py work in Python 3 Patch by Zachary Ware bpo 21629 Fix Argument Clinic s converters feature Add support for yield from to 2to3 Add support for the PEP 465 matrix multiplication operator to 2to3 bpo 16047 Fix module exception list and __file__ handling in freeze Patch by Meador Inge bpo 11824 Consider ABI tags in freeze Patch by Meador Inge bpo 20535 PYTHONWARNING no longer affects the run_tests py script Patch by Arfrever Frehtes Taifersar Arahesis Windows bpo 23260 Update Windows installer The bundled version of Tcl Tk has been updated to 8 6 3 The most visible result of this change is the addition of new native file dialogs when running on Windows Vista or newer See Tcl Tk s TIP 432 for more information Also this version of Tcl Tk includes support for Windows 10 bpo 17896 The Windows build scripts now expect external library sources to be in PCbuild externals rather than PCbuild bpo 17717 The Windows build scripts now use a copy of NASM pulled from svn python org to build OpenSSL bpo 21907 Improved the batch scripts provided for building Python bpo 22644 The bundled version of OpenSSL has been updated to 1 0 1j bpo 10747 Use versioned labels in the Windows start menu Patch by Olive Kilburn bpo 22980 pyd files with a version and platform tag for example cp35 win32 pyd will now be loaded in preference to those without tags For information about older versions consult the HISTORY file,en
1849,xmlrpc client XML RPC client access Source code Lib xmlrpc client py XML RPC is a Remote Procedure Call method that uses XML passed via HTTP S as a transport With it a client can call methods with parameters on a remote server the server is named by a URI and get back structured data This module supports writing XML RPC client code it handles all the details of translating between conformable Python objects and XML on the wire Warning The xmlrpc client module is not secure against maliciously constructed data If you need to parse untrusted or unauthenticated data see XML vulnerabilities Changed in version 3 5 For HTTPS URIs xmlrpc client now performs all the necessary certificate and hostname checks by default Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information class xmlrpc client ServerProxy uri transport None encoding None verbose False allow_none False use_datetime False use_builtin_types False headers context None A ServerProxy instance is an object that manages communication with a remote XML RPC server The required first argument is a URI Uniform Resource Indicator and will normally be the URL of the server The optional second argument is a transport factory instance by default it is an internal SafeTransport instance for https URLs and an internal HTTP Transport instance otherwise The optional third argument is an encoding by default UTF 8 The optional fourth argument is a debugging flag The following parameters govern the use of the returned proxy instance If allow_none is true the Python constant None will be translated into XML the default behaviour is for None to raise a TypeError This is a commonly used extension to the XML RPC specification but isn t supported by all clients and servers see http ontosys com xml rpc extensions php for a description The use_builtin_types flag can be used to cause date time values to be presented as datetime datetime objects and binary data to be presented as bytes objects this flag is false by default datetime datetime bytes and bytearray objects may be passed to calls The headers parameter is an optional sequence of HTTP headers to send with each request expressed as a sequence of 2 tuples representing the header name and value e g Header Name value The obsolete use_datetime flag is similar to use_builtin_types but it applies only to date time values Changed in version 3 3 The use_builtin_types flag was added Changed in version 3 8 The headers parameter was added Both the HTTP and HTTPS transports support the URL syntax extension for HTTP Basic Authentication http user pass host port path The user pass portion will be base64 encoded as an HTTP Authorization header and sent to the remote server as part of the connection process when invoking an XML RPC method You only need to use this if the remote server requires a Basic Authentication user and password If an HTTPS URL is provided context may be ssl SSLContext and configures the SSL settings of the underlying HTTPS connection The returned instance is a proxy object with methods that can be used to invoke corresponding RPC calls on the remote server If the remote server supports the introspection API the proxy can also be used to query the remote server for the methods it supports service discovery and fetch other server associated metadata Types that are conformable e g that can be marshalled through XML include the following and except where noted they are unmarshalled as the same Python type XML RPC type Python type boolean bool int i1 i2 int in range from 2147483648 to 2147483647 Values i4 i8 or get the int tag biginteger double or float float Values get the double tag string str array list or tuple containing conformable elements Arrays are returned as lists struct dict Keys must be strings values may be any conformable type Objects of user defined classes can be passed in only their __dict__ attribute is transmitted dateTime iso8601 DateTime or datetime datetime Returned type depends on,en
1850, values of use_builtin_types and use_datetime flags base64 Binary bytes or bytearray Returned type depends on the value of the use_builtin_types flag nil The None constant Passing is allowed only if allow_none is true bigdecimal decimal Decimal Returned type only This is the full set of data types supported by XML RPC Method calls may also raise a special Fault instance used to signal XML RPC server errors or ProtocolError used to signal an error in the HTTP HTTPS transport layer Both Fault and ProtocolError derive from a base class called Error Note that the xmlrpc client module currently does not marshal instances of subclasses of built in types When passing strings characters special to XML such as and will be automatically escaped However it s the caller s responsibility to ensure that the string is free of characters that aren t allowed in XML such as the control characters with ASCII values between 0 and 31 except of course tab newline and carriage return failing to do this will result in an XML RPC request that isn t well formed XML If you have to pass arbitrary bytes via XML RPC use bytes or bytearray classes or the Binary wrapper class described below Server is retained as an alias for ServerProxy for backwards compatibility New code should use ServerProxy Changed in version 3 5 Added the context argument Changed in version 3 6 Added support of type tags with prefixes e g ex nil Added support of unmarshalling additional types used by Apache XML RPC implementation for numerics i1 i2 i8 biginteger float and bigdecimal See https ws apache org xmlrpc types html for a description See also XML RPC HOWTO A good description of XML RPC operation and client software in several languages Contains pretty much everything an XML RPC client developer needs to know XML RPC Introspection Describes the XML RPC protocol extension for introspection XML RPC Specification The official specification ServerProxy Objects A ServerProxy instance has a method corresponding to each remote procedure call accepted by the XML RPC server Calling the method performs an RPC dispatched by both name and argument signature e g the same method name can be overloaded with multiple argument signatures The RPC finishes by returning a value which may be either returned data in a conformant type or a Fault or ProtocolError object indicating an error Servers that support the XML introspection API support some common methods grouped under the reserved system attribute ServerProxy system listMethods This method returns a list of strings one for each non system method supported by the XML RPC server ServerProxy system methodSignature name This method takes one parameter the name of a method implemented by the XML RPC server It returns an array of possible signatures for this method A signature is an array of types The first of these types is the return type of the method the rest are parameters Because multiple signatures ie overloading is permitted this method returns a list of signatures rather than a singleton Signatures themselves are restricted to the top level parameters expected by a method For instance if a method expects one array of structs as a parameter and it returns a string its signature is simply string array If it expects three integers and returns a string its signature is string int int int If no signature is defined for the method a non array value is returned In Python this means that the type of the returned value will be something other than list ServerProxy system methodHelp name This method takes one parameter the name of a method implemented by the XML RPC server It returns a documentation string describing the use of that method If no such string is available an empty string is returned The documentation string may contain HTML markup Changed in version 3 5 Instances of ServerProxy support the context manager protocol for closing the underlying transport A working example follows The server code from xmlrpc server import SimpleXMLRPCServer def is_even n return n 2 0 server SimpleXMLRPCServer localhost 8000 print Listening on port 80,en
1851,00 server register_function is_even is_even server serve_forever The client code for the preceding server import xmlrpc client with xmlrpc client ServerProxy http localhost 8000 as proxy print 3 is even s str proxy is_even 3 print 100 is even s str proxy is_even 100 DateTime Objects class xmlrpc client DateTime This class may be initialized with seconds since the epoch a time tuple an ISO 8601 time date string or a datetime datetime instance It has the following methods supported mainly for internal use by the marshalling unmarshalling code decode string Accept a string as the instance s new time value encode out Write the XML RPC encoding of this DateTime item to the out stream object It also supports certain of Python s built in operators through rich comparison and __repr__ methods A working example follows The server code import datetime from xmlrpc server import SimpleXMLRPCServer import xmlrpc client def today today datetime datetime today return xmlrpc client DateTime today server SimpleXMLRPCServer localhost 8000 print Listening on port 8000 server register_function today today server serve_forever The client code for the preceding server import xmlrpc client import datetime proxy xmlrpc client ServerProxy http localhost 8000 today proxy today convert the ISO8601 string to a datetime object converted datetime datetime strptime today value Y m dT H M S print Today s converted strftime d m Y H M Binary Objects class xmlrpc client Binary This class may be initialized from bytes data which may include NULs The primary access to the content of a Binary object is provided by an attribute data The binary data encapsulated by the Binary instance The data is provided as a bytes object Binary objects have the following methods supported mainly for internal use by the marshalling unmarshalling code decode bytes Accept a base64 bytes object and decode it as the instance s new data encode out Write the XML RPC base 64 encoding of this binary item to the out stream object The encoded data will have newlines every 76 characters as per RFC 2045 section 6 8 which was the de facto standard base64 specification when the XML RPC spec was written It also supports certain of Python s built in operators through __eq__ and __ne__ methods Example usage of the binary objects We re going to transfer an image over XMLRPC from xmlrpc server import SimpleXMLRPCServer import xmlrpc client def python_logo with open python_logo jpg rb as handle return xmlrpc client Binary handle read server SimpleXMLRPCServer localhost 8000 print Listening on port 8000 server register_function python_logo python_logo server serve_forever The client gets the image and saves it to a file import xmlrpc client proxy xmlrpc client ServerProxy http localhost 8000 with open fetched_python_logo jpg wb as handle handle write proxy python_logo data Fault Objects class xmlrpc client Fault A Fault object encapsulates the content of an XML RPC fault tag Fault objects have the following attributes faultCode An int indicating the fault type faultString A string containing a diagnostic message associated with the fault In the following example we re going to intentionally cause a Fault by returning a complex type object The server code from xmlrpc server import SimpleXMLRPCServer A marshalling error is going to occur because we re returning a complex number def add x y return x y 0j server SimpleXMLRPCServer localhost 8000 print Listening on port 8000 server register_function add add server serve_forever The client code for the preceding server import xmlrpc client proxy xmlrpc client ServerProxy http localhost 8000 try proxy add 2 5 except xmlrpc client Fault as err print A fault occurred print Fault code d err faultCode print Fault string s err faultString ProtocolError Objects class xmlrpc client ProtocolError A ProtocolError object describes a protocol error in the underlying transport layer such as a 404 not found error if the server named by the URI does not exist It has the following attributes url The URI or URL that triggered the error errcode The error code errmsg The,en
1852, error message or diagnostic string headers A dict containing the headers of the HTTP HTTPS request that triggered the error In the following example we re going to intentionally cause a ProtocolError by providing an invalid URI import xmlrpc client create a ServerProxy with a URI that doesn t respond to XMLRPC requests proxy xmlrpc client ServerProxy http google com try proxy some_method except xmlrpc client ProtocolError as err print A protocol error occurred print URL s err url print HTTP HTTPS headers s err headers print Error code d err errcode print Error message s err errmsg MultiCall Objects The MultiCall object provides a way to encapsulate multiple calls to a remote server into a single request 1 class xmlrpc client MultiCall server Create an object used to boxcar method calls server is the eventual target of the call Calls can be made to the result object but they will immediately return None and only store the call name and parameters in the MultiCall object Calling the object itself causes all stored calls to be transmitted as a single system multicall request The result of this call is a generator iterating over this generator yields the individual results A usage example of this class follows The server code from xmlrpc server import SimpleXMLRPCServer def add x y return x y def subtract x y return x y def multiply x y return x y def divide x y return x y A simple server with simple arithmetic functions server SimpleXMLRPCServer localhost 8000 print Listening on port 8000 server register_multicall_functions server register_function add add server register_function subtract subtract server register_function multiply multiply server register_function divide divide server serve_forever The client code for the preceding server import xmlrpc client proxy xmlrpc client ServerProxy http localhost 8000 multicall xmlrpc client MultiCall proxy multicall add 7 3 multicall subtract 7 3 multicall multiply 7 3 multicall divide 7 3 result multicall print 7 3 d 7 3 d 7 3 d 7 3 d tuple result Convenience Functions xmlrpc client dumps params methodname None methodresponse None encoding None allow_none False Convert params into an XML RPC request or into a response if methodresponse is true params can be either a tuple of arguments or an instance of the Fault exception class If methodresponse is true only a single value can be returned meaning that params must be of length 1 encoding if supplied is the encoding to use in the generated XML the default is UTF 8 Python s None value cannot be used in standard XML RPC to allow using it via an extension provide a true value for allow_none xmlrpc client loads data use_datetime False use_builtin_types False Convert an XML RPC request or response into Python objects a params methodname params is a tuple of argument methodname is a string or None if no method name is present in the packet If the XML RPC packet represents a fault condition this function will raise a Fault exception The use_builtin_types flag can be used to cause date time values to be presented as datetime datetime objects and binary data to be presented as bytes objects this flag is false by default The obsolete use_datetime flag is similar to use_builtin_types but it applies only to date time values Changed in version 3 3 The use_builtin_types flag was added Example of Client Usage simple test program from the XML RPC specification from xmlrpc client import ServerProxy Error server ServerProxy http localhost 8000 local server with ServerProxy http betty userland com as proxy print proxy try print proxy examples getStateName 41 except Error as v print ERROR v To access an XML RPC server through a HTTP proxy you need to define a custom transport The following example shows how import http client import xmlrpc client class ProxiedTransport xmlrpc client Transport def set_proxy self host port None headers None self proxy host port self proxy_headers headers def make_connection self host connection http client HTTPConnection self proxy connection set_tunnel host headers self proxy_headers self _connection host connection ,en
1853,return connection transport ProxiedTransport transport set_proxy proxy server 8080 server xmlrpc client ServerProxy http betty userland com transport transport print server examples getStateName 41 Example of Client and Server Usage See SimpleXMLRPCServer Example Footnotes 1 This approach has been first presented in a discussion on xmlrpc com,en
1854,shlex Simple lexical analysis Source code Lib shlex py The shlex class makes it easy to write lexical analyzers for simple syntaxes resembling that of the Unix shell This will often be useful for writing minilanguages for example in run control files for Python applications or for parsing quoted strings The shlex module defines the following functions shlex split s comments False posix True Split the string s using shell like syntax If comments is False the default the parsing of comments in the given string will be disabled setting the commenters attribute of the shlex instance to the empty string This function operates in POSIX mode by default but uses non POSIX mode if the posix argument is false Changed in version 3 12 Passing None for s argument now raises an exception rather than reading sys stdin shlex join split_command Concatenate the tokens of the list split_command and return a string This function is the inverse of split from shlex import join print join echo n Multiple words echo n Multiple words The returned value is shell escaped to protect against injection vulnerabilities see quote New in version 3 8 shlex quote s Return a shell escaped version of the string s The returned value is a string that can safely be used as one token in a shell command line for cases where you cannot use a list Warning The shlex module is only designed for Unix shells The quote function is not guaranteed to be correct on non POSIX compliant shells or shells from other operating systems such as Windows Executing commands quoted by this module on such shells can open up the possibility of a command injection vulnerability Consider using functions that pass command arguments with lists such as subprocess run with shell False This idiom would be unsafe filename somefile rm rf command ls l format filename print command executed by a shell boom ls l somefile rm rf quote lets you plug the security hole from shlex import quote command ls l format quote filename print command ls l somefile rm rf remote_command ssh home format quote command print remote_command ssh home ls l somefile rm rf The quoting is compatible with UNIX shells and with split from shlex import split remote_command split remote_command remote_command ssh home ls l somefile rm rf command split remote_command 1 command ls l somefile rm rf New in version 3 3 The shlex module defines the following class class shlex shlex instream None infile None posix False punctuation_chars False A shlex instance or subclass instance is a lexical analyzer object The initialization argument if present specifies where to read characters from It must be a file stream like object with read and readline methods or a string If no argument is given input will be taken from sys stdin The second optional argument is a filename string which sets the initial value of the infile attribute If the instream argument is omitted or equal to sys stdin this second argument defaults to stdin The posix argument defines the operational mode when posix is not true default the shlex instance will operate in compatibility mode When operating in POSIX mode shlex will try to be as close as possible to the POSIX shell parsing rules The punctuation_chars argument provides a way to make the behaviour even closer to how real shells parse This can take a number of values the default value False preserves the behaviour seen under Python 3 5 and earlier If set to True then parsing of the characters is changed any run of these characters considered punctuation characters is returned as a single token If set to a non empty string of characters those characters will be used as the punctuation characters Any characters in the wordchars attribute that appear in punctuation_chars will be removed from wordchars See Improved Compatibility with Shells for more information punctuation_chars can be set only upon shlex instance creation and can t be modified later Changed in version 3 6 The punctuation_chars parameter was added See also Module configparser Parser for configuration files similar to the Windows ini files shlex Object,en
1855,s A shlex instance has the following methods shlex get_token Return a token If tokens have been stacked using push_token pop a token off the stack Otherwise read one from the input stream If reading encounters an immediate end of file eof is returned the empty string in non POSIX mode and None in POSIX mode shlex push_token str Push the argument onto the token stack shlex read_token Read a raw token Ignore the pushback stack and do not interpret source requests This is not ordinarily a useful entry point and is documented here only for the sake of completeness shlex sourcehook filename When shlex detects a source request see source below this method is given the following token as argument and expected to return a tuple consisting of a filename and an open file like object Normally this method first strips any quotes off the argument If the result is an absolute pathname or there was no previous source request in effect or the previous source was a stream such as sys stdin the result is left alone Otherwise if the result is a relative pathname the directory part of the name of the file immediately before it on the source inclusion stack is prepended this behavior is like the way the C preprocessor handles include file h The result of the manipulations is treated as a filename and returned as the first component of the tuple with open called on it to yield the second component Note this is the reverse of the order of arguments in instance initialization This hook is exposed so that you can use it to implement directory search paths addition of file extensions and other namespace hacks There is no corresponding close hook but a shlex instance will call the close method of the sourced input stream when it returns EOF For more explicit control of source stacking use the push_source and pop_source methods shlex push_source newstream newfile None Push an input source stream onto the input stack If the filename argument is specified it will later be available for use in error messages This is the same method used internally by the sourcehook method shlex pop_source Pop the last pushed input source from the input stack This is the same method used internally when the lexer reaches EOF on a stacked input stream shlex error_leader infile None lineno None This method generates an error message leader in the format of a Unix C compiler error label the format is s line d where the s is replaced with the name of the current source file and the d with the current input line number the optional arguments can be used to override these This convenience is provided to encourage shlex users to generate error messages in the standard parseable format understood by Emacs and other Unix tools Instances of shlex subclasses have some public instance variables which either control lexical analysis or can be used for debugging shlex commenters The string of characters that are recognized as comment beginners All characters from the comment beginner to end of line are ignored Includes just by default shlex wordchars The string of characters that will accumulate into multi character tokens By default includes all ASCII alphanumerics and underscore In POSIX mode the accented characters in the Latin 1 set are also included If punctuation_chars is not empty the characters which can appear in filename specifications and command line parameters will also be included in this attribute and any characters which appear in punctuation_chars will be removed from wordchars if they are present there If whitespace_split is set to True this will have no effect shlex whitespace Characters that will be considered whitespace and skipped Whitespace bounds tokens By default includes space tab linefeed and carriage return shlex escape Characters that will be considered as escape This will be only used in POSIX mode and includes just by default shlex quotes Characters that will be considered string quotes The token accumulates until the same quote is encountered again thus different quote types protect each other as in the shell By default includes ASCII single and doubl,en
1856,e quotes shlex escapedquotes Characters in quotes that will interpret escape characters defined in escape This is only used in POSIX mode and includes just by default shlex whitespace_split If True tokens will only be split in whitespaces This is useful for example for parsing command lines with shlex getting tokens in a similar way to shell arguments When used in combination with punctuation_chars tokens will be split on whitespace in addition to those characters Changed in version 3 8 The punctuation_chars attribute was made compatible with the whitespace_split attribute shlex infile The name of the current input file as initially set at class instantiation time or stacked by later source requests It may be useful to examine this when constructing error messages shlex instream The input stream from which this shlex instance is reading characters shlex source This attribute is None by default If you assign a string to it that string will be recognized as a lexical level inclusion request similar to the source keyword in various shells That is the immediately following token will be opened as a filename and input will be taken from that stream until EOF at which point the close method of that stream will be called and the input source will again become the original input stream Source requests may be stacked any number of levels deep shlex debug If this attribute is numeric and 1 or more a shlex instance will print verbose progress output on its behavior If you need to use this you can read the module source code to learn the details shlex lineno Source line number count of newlines seen so far plus one shlex token The token buffer It may be useful to examine this when catching exceptions shlex eof Token used to determine end of file This will be set to the empty string in non POSIX mode and to None in POSIX mode shlex punctuation_chars A read only property Characters that will be considered punctuation Runs of punctuation characters will be returned as a single token However note that no semantic validity checking will be performed for example could be returned as a token even though it may not be recognised as such by shells New in version 3 6 Parsing Rules When operating in non POSIX mode shlex will try to obey to the following rules Quote characters are not recognized within words Do Not Separate is parsed as the single word Do Not Separate Escape characters are not recognized Enclosing characters in quotes preserve the literal value of all characters within the quotes Closing quotes separate words Do Separate is parsed as Do and Separate If whitespace_split is False any character not declared to be a word character whitespace or a quote will be returned as a single character token If it is True shlex will only split words in whitespaces EOF is signaled with an empty string It s not possible to parse empty strings even if quoted When operating in POSIX mode shlex will try to obey to the following parsing rules Quotes are stripped out and do not separate words Do Not Separate is parsed as the single word DoNotSeparate Non quoted escape characters e g preserve the literal value of the next character that follows Enclosing characters in quotes which are not part of escapedquotes e g preserve the literal value of all characters within the quotes Enclosing characters in quotes which are part of escapedquotes e g preserves the literal value of all characters within the quotes with the exception of the characters mentioned in escape The escape characters retain its special meaning only when followed by the quote in use or the escape character itself Otherwise the escape character will be considered a normal character EOF is signaled with a None value Quoted empty strings are allowed Improved Compatibility with Shells New in version 3 6 The shlex class provides compatibility with the parsing performed by common Unix shells like bash dash and sh To take advantage of this compatibility specify the punctuation_chars argument in the constructor This defaults to False which preserves pre 3 6 behaviour However if it is set to True,en
1857, then parsing of the characters is changed any run of these characters is returned as a single token While this is short of a full parser for shells which would be out of scope for the standard library given the multiplicity of shells out there it does allow you to perform processing of command lines more easily than you could otherwise To illustrate you can see the difference in the following snippet import shlex text a b c d e f abc def ghi s shlex shlex text posix True s whitespace_split True list s a b c d e f abc def ghi s shlex shlex text posix True punctuation_chars True s whitespace_split True list s a b c d e f abc def ghi Of course tokens will be returned which are not valid for shells and you ll need to implement your own error checks on the returned tokens Instead of passing True as the value for the punctuation_chars parameter you can pass a string with specific characters which will be used to determine which characters constitute punctuation For example import shlex s shlex shlex a b c punctuation_chars list s a b c Note When punctuation_chars is specified the wordchars attribute is augmented with the characters That is because these characters can appear in file names including wildcards and command line arguments e g color auto Hence import shlex s shlex shlex a b c color auto d py punctuation_chars True list s a b c color auto d py However to match the shell as closely as possible it is recommended to always use posix and whitespace_split when using punctuation_chars which will negate wordchars entirely For best effect punctuation_chars should be set in conjunction with posix True Note that posix False is the default for shlex,en
1858,Copyright Python and this documentation is Copyright 2001 2023 Python Software Foundation All rights reserved Copyright 2000 BeOpen com All rights reserved Copyright 1995 2000 Corporation for National Research Initiatives All rights reserved Copyright 1991 1995 Stichting Mathematisch Centrum All rights reserved See History and License for complete license and permissions information,en
1859,1 Embedding Python in Another Application The previous chapters discussed how to extend Python that is how to extend the functionality of Python by attaching a library of C functions to it It is also possible to do it the other way around enrich your C C application by embedding Python in it Embedding provides your application with the ability to implement some of the functionality of your application in Python rather than C or C This can be used for many purposes one example would be to allow users to tailor the application to their needs by writing some scripts in Python You can also use it yourself if some of the functionality can be written in Python more easily Embedding Python is similar to extending it but not quite The difference is that when you extend Python the main program of the application is still the Python interpreter while if you embed Python the main program may have nothing to do with Python instead some parts of the application occasionally call the Python interpreter to run some Python code So if you are embedding Python you are providing your own main program One of the things this main program has to do is initialize the Python interpreter At the very least you have to call the function Py_Initialize There are optional calls to pass command line arguments to Python Then later you can call the interpreter from any part of the application There are several different ways to call the interpreter you can pass a string containing Python statements to PyRun_SimpleString or you can pass a stdio file pointer and a file name for identification in error messages only to PyRun_SimpleFile You can also call the lower level operations described in the previous chapters to construct and use Python objects See also Python C API Reference Manual The details of Python s C interface are given in this manual A great deal of necessary information can be found here 1 1 Very High Level Embedding The simplest form of embedding Python is the use of the very high level interface This interface is intended to execute a Python script without needing to interact with the application directly This can for example be used to perform some operation on a file define PY_SSIZE_T_CLEAN include Python h int main int argc char argv wchar_t program Py_DecodeLocale argv 0 NULL if program NULL fprintf stderr Fatal error cannot decode argv 0 n exit 1 Py_SetProgramName program optional but recommended Py_Initialize PyRun_SimpleString from time import time ctime n print Today is ctime time n if Py_FinalizeEx 0 exit 120 PyMem_RawFree program return 0 The Py_SetProgramName function should be called before Py_Initialize to inform the interpreter about paths to Python run time libraries Next the Python interpreter is initialized with Py_Initialize followed by the execution of a hard coded Python script that prints the date and time Afterwards the Py_FinalizeEx call shuts the interpreter down followed by the end of the program In a real program you may want to get the Python script from another source perhaps a text editor routine a file or a database Getting the Python code from a file can better be done by using the PyRun_SimpleFile function which saves you the trouble of allocating memory space and loading the file contents 1 2 Beyond Very High Level Embedding An overview The high level interface gives you the ability to execute arbitrary pieces of Python code from your application but exchanging data values is quite cumbersome to say the least If you want that you should use lower level calls At the cost of having to write more C code you can achieve almost anything It should be noted that extending Python and embedding Python is quite the same activity despite the different intent Most topics discussed in the previous chapters are still valid To show this consider what the extension code from Python to C really does 1 Convert data values from Python to C 2 Perform a function call to a C routine using the converted values and 3 Convert the data values from the call from C to Python When embedding Python the interface code does 1 Convert data,en
1860, values from C to Python 2 Perform a function call to a Python interface routine using the converted values and 3 Convert the data values from the call from Python to C As you can see the data conversion steps are simply swapped to accommodate the different direction of the cross language transfer The only difference is the routine that you call between both data conversions When extending you call a C routine when embedding you call a Python routine This chapter will not discuss how to convert data from Python to C and vice versa Also proper use of references and dealing with errors is assumed to be understood Since these aspects do not differ from extending the interpreter you can refer to earlier chapters for the required information 1 3 Pure Embedding The first program aims to execute a function in a Python script Like in the section about the very high level interface the Python interpreter does not directly interact with the application but that will change in the next section The code to run a function defined in a Python script is define PY_SSIZE_T_CLEAN include Python h int main int argc char argv PyObject pName pModule pFunc PyObject pArgs pValue int i if argc 3 fprintf stderr Usage call pythonfile funcname args n return 1 Py_Initialize pName PyUnicode_DecodeFSDefault argv 1 Error checking of pName left out pModule PyImport_Import pName Py_DECREF pName if pModule NULL pFunc PyObject_GetAttrString pModule argv 2 pFunc is a new reference if pFunc PyCallable_Check pFunc pArgs PyTuple_New argc 3 for i 0 i argc 3 i pValue PyLong_FromLong atoi argv i 3 if pValue Py_DECREF pArgs Py_DECREF pModule fprintf stderr Cannot convert argument n return 1 pValue reference stolen here PyTuple_SetItem pArgs i pValue pValue PyObject_CallObject pFunc pArgs Py_DECREF pArgs if pValue NULL printf Result of call ld n PyLong_AsLong pValue Py_DECREF pValue else Py_DECREF pFunc Py_DECREF pModule PyErr_Print fprintf stderr Call failed n return 1 else if PyErr_Occurred PyErr_Print fprintf stderr Cannot find function s n argv 2 Py_XDECREF pFunc Py_DECREF pModule else PyErr_Print fprintf stderr Failed to load s n argv 1 return 1 if Py_FinalizeEx 0 return 120 return 0 This code loads a Python script using argv 1 and calls the function named in argv 2 Its integer arguments are the other values of the argv array If you compile and link this program let s call the finished executable call and use it to execute a Python script such as def multiply a b print Will compute a times b c 0 for i in range 0 a c c b return c then the result should be call multiply multiply 3 2 Will compute 3 times 2 Result of call 6 Although the program is quite large for its functionality most of the code is for data conversion between Python and C and for error reporting The interesting part with respect to embedding Python starts with Py_Initialize pName PyUnicode_DecodeFSDefault argv 1 Error checking of pName left out pModule PyImport_Import pName After initializing the interpreter the script is loaded using PyImport_Import This routine needs a Python string as its argument which is constructed using the PyUnicode_FromString data conversion routine pFunc PyObject_GetAttrString pModule argv 2 pFunc is a new reference if pFunc PyCallable_Check pFunc Py_XDECREF pFunc Once the script is loaded the name we re looking for is retrieved using PyObject_GetAttrString If the name exists and the object returned is callable you can safely assume that it is a function The program then proceeds by constructing a tuple of arguments as normal The call to the Python function is then made with pValue PyObject_CallObject pFunc pArgs Upon return of the function pValue is either NULL or it contains a reference to the return value of the function Be sure to release the reference after examining the value 1 4 Extending Embedded Python Until now the embedded Python interpreter had no access to functionality from the application itself The Python API allows this by extending the embedded interpreter That is the embedded interpreter gets extended with routines provided by the application While ,en
1861,it sounds complex it is not so bad Simply forget for a while that the application starts the Python interpreter Instead consider the application to be a set of subroutines and write some glue code that gives Python access to those routines just like you would write a normal Python extension For example static int numargs 0 Return the number of arguments of the application command line static PyObject emb_numargs PyObject self PyObject args if PyArg_ParseTuple args numargs return NULL return PyLong_FromLong numargs static PyMethodDef EmbMethods numargs emb_numargs METH_VARARGS Return the number of arguments received by the process NULL NULL 0 NULL static PyModuleDef EmbModule PyModuleDef_HEAD_INIT emb NULL 1 EmbMethods NULL NULL NULL NULL static PyObject PyInit_emb void return PyModule_Create EmbModule Insert the above code just above the main function Also insert the following two statements before the call to Py_Initialize numargs argc PyImport_AppendInittab emb PyInit_emb These two lines initialize the numargs variable and make the emb numargs function accessible to the embedded Python interpreter With these extensions the Python script can do things like import emb print Number of arguments emb numargs In a real application the methods will expose an API of the application to Python 1 5 Embedding Python in C It is also possible to embed Python in a C program precisely how this is done will depend on the details of the C system used in general you will need to write the main program in C and use the C compiler to compile and link your program There is no need to recompile Python itself using C 1 6 Compiling and Linking under Unix like systems It is not necessarily trivial to find the right flags to pass to your compiler and linker in order to embed the Python interpreter into your application particularly because Python needs to load library modules implemented as C dynamic extensions so files linked against it To find out the required compiler and linker flags you can execute the python X Y config script which is generated as part of the installation process a python3 config script may also be available This script has several options of which the following will be directly useful to you pythonX Y config cflags will give you the recommended flags when compiling opt bin python3 11 config cflags I opt include python3 11 I opt include python3 11 Wsign compare DNDEBUG g fwrapv O3 Wall pythonX Y config ldflags embed will give you the recommended flags when linking opt bin python3 11 config ldflags embed L opt lib python3 11 config 3 11 x86_64 linux gnu L opt lib lpython3 11 lpthread ldl lutil lm Note To avoid confusion between several Python installations and especially between the system Python and your own compiled Python it is recommended that you use the absolute path to python X Y config as in the above example If this procedure doesn t work for you it is not guaranteed to work for all Unix like platforms however we welcome bug reports you will have to read your system s documentation about dynamic linking and or examine Python s Makefile use sysconfig get_makefile_filename to find its location and compilation options In this case the sysconfig module is a useful tool to programmatically extract the configuration values that you will want to combine together For example import sysconfig sysconfig get_config_var LIBS lpthread ldl lutil sysconfig get_config_var LINKFORSHARED Xlinker export dynamic,en
1862,resource Resource usage information This module provides basic mechanisms for measuring and controlling system resources utilized by a program Availability Unix not Emscripten not WASI Symbolic constants are used to specify particular system resources and to request usage information about either the current process or its children An OSError is raised on syscall failure exception resource error A deprecated alias of OSError Changed in version 3 3 Following PEP 3151 this class was made an alias of OSError Resource Limits Resources usage can be limited using the setrlimit function described below Each resource is controlled by a pair of limits a soft limit and a hard limit The soft limit is the current limit and may be lowered or raised by a process over time The soft limit can never exceed the hard limit The hard limit can be lowered to any value greater than the soft limit but not raised Only processes with the effective UID of the super user can raise a hard limit The specific resources that can be limited are system dependent They are described in the getrlimit 2 man page The resources listed below are supported when the underlying operating system supports them resources which cannot be checked or controlled by the operating system are not defined in this module for those platforms resource RLIM_INFINITY Constant used to represent the limit for an unlimited resource resource getrlimit resource Returns a tuple soft hard with the current soft and hard limits of resource Raises ValueError if an invalid resource is specified or error if the underlying system call fails unexpectedly resource setrlimit resource limits Sets new limits of consumption of resource The limits argument must be a tuple soft hard of two integers describing the new limits A value of RLIM_INFINITY can be used to request a limit that is unlimited Raises ValueError if an invalid resource is specified if the new soft limit exceeds the hard limit or if a process tries to raise its hard limit Specifying a limit of RLIM_INFINITY when the hard or system limit for that resource is not unlimited will result in a ValueError A process with the effective UID of super user can request any valid limit value including unlimited but ValueError will still be raised if the requested limit exceeds the system imposed limit setrlimit may also raise error if the underlying system call fails VxWorks only supports setting RLIMIT_NOFILE Raises an auditing event resource setrlimit with arguments resource limits resource prlimit pid resource limits Combines setrlimit and getrlimit in one function and supports to get and set the resources limits of an arbitrary process If pid is 0 then the call applies to the current process resource and limits have the same meaning as in setrlimit except that limits is optional When limits is not given the function returns the resource limit of the process pid When limits is given the resource limit of the process is set and the former resource limit is returned Raises ProcessLookupError when pid can t be found and PermissionError when the user doesn t have CAP_SYS_RESOURCE for the process Raises an auditing event resource prlimit with arguments pid resource limits Availability Linux 2 6 36 with glibc 2 13 New in version 3 4 These symbols define resources whose consumption can be controlled using the setrlimit and getrlimit functions described below The values of these symbols are exactly the constants used by C programs The Unix man page for getrlimit 2 lists the available resources Note that not all systems use the same symbol or same value to denote the same resource This module does not attempt to mask platform differences symbols not defined for a platform will not be available from this module on that platform resource RLIMIT_CORE The maximum size in bytes of a core file that the current process can create This may result in the creation of a partial core file if a larger core would be required to contain the entire process image resource RLIMIT_CPU The maximum amount of processor time in seconds that a process can use If this limit is ,en
1863,exceeded a SIGXCPU signal is sent to the process See the signal module documentation for information about how to catch this signal and do something useful e g flush open files to disk resource RLIMIT_FSIZE The maximum size of a file which the process may create resource RLIMIT_DATA The maximum size in bytes of the process s heap resource RLIMIT_STACK The maximum size in bytes of the call stack for the current process This only affects the stack of the main thread in a multi threaded process resource RLIMIT_RSS The maximum resident set size that should be made available to the process resource RLIMIT_NPROC The maximum number of processes the current process may create resource RLIMIT_NOFILE The maximum number of open file descriptors for the current process resource RLIMIT_OFILE The BSD name for RLIMIT_NOFILE resource RLIMIT_MEMLOCK The maximum address space which may be locked in memory resource RLIMIT_VMEM The largest area of mapped memory which the process may occupy Availability FreeBSD 11 resource RLIMIT_AS The maximum area in bytes of address space which may be taken by the process resource RLIMIT_MSGQUEUE The number of bytes that can be allocated for POSIX message queues Availability Linux 2 6 8 New in version 3 4 resource RLIMIT_NICE The ceiling for the process s nice level calculated as 20 rlim_cur Availability Linux 2 6 12 New in version 3 4 resource RLIMIT_RTPRIO The ceiling of the real time priority Availability Linux 2 6 12 New in version 3 4 resource RLIMIT_RTTIME The time limit in microseconds on CPU time that a process can spend under real time scheduling without making a blocking syscall Availability Linux 2 6 25 New in version 3 4 resource RLIMIT_SIGPENDING The number of signals which the process may queue Availability Linux 2 6 8 New in version 3 4 resource RLIMIT_SBSIZE The maximum size in bytes of socket buffer usage for this user This limits the amount of network memory and hence the amount of mbufs that this user may hold at any time Availability FreeBSD New in version 3 4 resource RLIMIT_SWAP The maximum size in bytes of the swap space that may be reserved or used by all of this user id s processes This limit is enforced only if bit 1 of the vm overcommit sysctl is set Please see tuning 7 for a complete description of this sysctl Availability FreeBSD New in version 3 4 resource RLIMIT_NPTS The maximum number of pseudo terminals created by this user id Availability FreeBSD New in version 3 4 resource RLIMIT_KQUEUES The maximum number of kqueues this user id is allowed to create Availability FreeBSD 11 New in version 3 10 Resource Usage These functions are used to retrieve resource usage information resource getrusage who This function returns an object that describes the resources consumed by either the current process or its children as specified by the who parameter The who parameter should be specified using one of the RUSAGE_ constants described below A simple example from resource import import time a non CPU bound task time sleep 3 print getrusage RUSAGE_SELF a CPU bound task for i in range 10 8 _ 1 1 print getrusage RUSAGE_SELF The fields of the return value each describe how a particular system resource has been used e g amount of time spent running is user mode or number of times the process was swapped out of main memory Some values are dependent on the clock tick internal e g the amount of memory the process is using For backward compatibility the return value is also accessible as a tuple of 16 elements The fields ru_utime and ru_stime of the return value are floating point values representing the amount of time spent executing in user mode and the amount of time spent executing in system mode respectively The remaining values are integers Consult the getrusage 2 man page for detailed information about these values A brief summary is presented here Index Field Resource 0 ru_utime time in user mode float seconds 1 ru_stime time in system mode float seconds 2 ru_maxrss maximum resident set size 3 ru_ixrss shared memory size 4 ru_idrss unshared memory size 5 ru_isrss unshared stack size 6 ,en
1864,ru_minflt page faults not requiring I O 7 ru_majflt page faults requiring I O 8 ru_nswap number of swap outs 9 ru_inblock block input operations 10 ru_oublock block output operations 11 ru_msgsnd messages sent 12 ru_msgrcv messages received 13 ru_nsignals signals received 14 ru_nvcsw voluntary context switches 15 ru_nivcsw involuntary context switches This function will raise a ValueError if an invalid who parameter is specified It may also raise error exception in unusual circumstances resource getpagesize Returns the number of bytes in a system page This need not be the same as the hardware page size The following RUSAGE_ symbols are passed to the getrusage function to specify which processes information should be provided for resource RUSAGE_SELF Pass to getrusage to request resources consumed by the calling process which is the sum of resources used by all threads in the process resource RUSAGE_CHILDREN Pass to getrusage to request resources consumed by child processes of the calling process which have been terminated and waited for resource RUSAGE_BOTH Pass to getrusage to request resources consumed by both the current process and child processes May not be available on all systems resource RUSAGE_THREAD Pass to getrusage to request resources consumed by the current thread May not be available on all systems New in version 3 2,en
1865,html parser Simple HTML and XHTML parser Source code Lib html parser py This module defines a class HTMLParser which serves as the basis for parsing text files formatted in HTML HyperText Mark up Language and XHTML class html parser HTMLParser convert_charrefs True Create a parser instance able to parse invalid markup If convert_charrefs is True the default all character references except the ones in script style elements are automatically converted to the corresponding Unicode characters An HTMLParser instance is fed HTML data and calls handler methods when start tags end tags text comments and other markup elements are encountered The user should subclass HTMLParser and override its methods to implement the desired behavior This parser does not check that end tags match start tags or call the end tag handler for elements which are closed implicitly by closing an outer element Changed in version 3 4 convert_charrefs keyword argument added Changed in version 3 5 The default value for argument convert_charrefs is now True Example HTML Parser Application As a basic example below is a simple HTML parser that uses the HTMLParser class to print out start tags end tags and data as they are encountered from html parser import HTMLParser class MyHTMLParser HTMLParser def handle_starttag self tag attrs print Encountered a start tag tag def handle_endtag self tag print Encountered an end tag tag def handle_data self data print Encountered some data data parser MyHTMLParser parser feed html head title Test title head body h1 Parse me h1 body html The output will then be Encountered a start tag html Encountered a start tag head Encountered a start tag title Encountered some data Test Encountered an end tag title Encountered an end tag head Encountered a start tag body Encountered a start tag h1 Encountered some data Parse me Encountered an end tag h1 Encountered an end tag body Encountered an end tag html HTMLParser Methods HTMLParser instances have the following methods HTMLParser feed data Feed some text to the parser It is processed insofar as it consists of complete elements incomplete data is buffered until more data is fed or close is called data must be str HTMLParser close Force processing of all buffered data as if it were followed by an end of file mark This method may be redefined by a derived class to define additional processing at the end of the input but the redefined version should always call the HTMLParser base class method close HTMLParser reset Reset the instance Loses all unprocessed data This is called implicitly at instantiation time HTMLParser getpos Return current line number and offset HTMLParser get_starttag_text Return the text of the most recently opened start tag This should not normally be needed for structured processing but may be useful in dealing with HTML as deployed or for re generating input with minimal changes whitespace between attributes can be preserved etc The following methods are called when data or markup elements are encountered and they are meant to be overridden in a subclass The base class implementations do nothing except for handle_startendtag HTMLParser handle_starttag tag attrs This method is called to handle the start tag of an element e g div id main The tag argument is the name of the tag converted to lower case The attrs argument is a list of name value pairs containing the attributes found inside the tag s brackets The name will be translated to lower case and quotes in the value have been removed and character and entity references have been replaced For instance for the tag A HREF https www cwi nl this method would be called as handle_starttag a href https www cwi nl All entity references from html entities are replaced in the attribute values HTMLParser handle_endtag tag This method is called to handle the end tag of an element e g div The tag argument is the name of the tag converted to lower case HTMLParser handle_startendtag tag attrs Similar to handle_starttag but called when the parser encounters an XHTML style empty tag img This method may be overridden by subclass,en
1866,es which require this particular lexical information the default implementation simply calls handle_starttag and handle_endtag HTMLParser handle_data data This method is called to process arbitrary data e g text nodes and the content of script script and style style HTMLParser handle_entityref name This method is called to process a named character reference of the form name e g gt where name is a general entity reference e g gt This method is never called if convert_charrefs is True HTMLParser handle_charref name This method is called to process decimal and hexadecimal numeric character references of the form NNN and x NNN For example the decimal equivalent for gt is 62 whereas the hexadecimal is x3E in this case the method will receive 62 or x3E This method is never called if convert_charrefs is True HTMLParser handle_comment data This method is called when a comment is encountered e g comment For example the comment comment will cause this method to be called with the argument comment The content of Internet Explorer conditional comments condcoms will also be sent to this method so for if IE 9 IE9 specific content endif this method will receive if IE 9 IE9 specific content endif HTMLParser handle_decl decl This method is called to handle an HTML doctype declaration e g DOCTYPE html The decl parameter will be the entire contents of the declaration inside the markup e g DOCTYPE html HTMLParser handle_pi data Method called when a processing instruction is encountered The data parameter will contain the entire processing instruction For example for the processing instruction proc color red this method would be called as handle_pi proc color red It is intended to be overridden by a derived class the base class implementation does nothing Note The HTMLParser class uses the SGML syntactic rules for processing instructions An XHTML processing instruction using the trailing will cause the to be included in data HTMLParser unknown_decl data This method is called when an unrecognized declaration is read by the parser The data parameter will be the entire contents of the declaration inside the markup It is sometimes useful to be overridden by a derived class The base class implementation does nothing Examples The following class implements a parser that will be used to illustrate more examples from html parser import HTMLParser from html entities import name2codepoint class MyHTMLParser HTMLParser def handle_starttag self tag attrs print Start tag tag for attr in attrs print attr attr def handle_endtag self tag print End tag tag def handle_data self data print Data data def handle_comment self data print Comment data def handle_entityref self name c chr name2codepoint name print Named ent c def handle_charref self name if name startswith x c chr int name 1 16 else c chr int name print Num ent c def handle_decl self data print Decl data parser MyHTMLParser Parsing a doctype parser feed DOCTYPE HTML PUBLIC W3C DTD HTML 4 01 EN http www w3 org TR html4 strict dtd Decl DOCTYPE HTML PUBLIC W3C DTD HTML 4 01 EN http www w3 org TR html4 strict dtd Parsing an element with a few attributes and a title parser feed img src python logo png alt The Python logo Start tag img attr src python logo png attr alt The Python logo parser feed h1 Python h1 Start tag h1 Data Python End tag h1 The content of script and style elements is returned as is without further parsing parser feed style type text css python color green style Start tag style attr type text css Data python color green End tag style parser feed script type text javascript alert strong hello strong script Start tag script attr type text javascript Data alert strong hello strong End tag script Parsing comments parser feed a comment if IE 9 IE specific content endif Comment a comment Comment if IE 9 IE specific content endif Parsing named and numeric character references and converting them to the correct char note these 3 references are all equivalent to parser feed gt 62 x3E Named ent Num ent Num ent Feeding incomplete chunks to feed works but handle_data might be called more than onc,en
1867,e unless convert_charrefs is set to True for chunk in sp an buff ered text s pan parser feed chunk Start tag span Data buff Data ered Data text End tag span Parsing invalid HTML e g unquoted attributes also works parser feed p a class link href main tag soup p a Start tag p Start tag a attr class link attr href main Data tag soup End tag p End tag a,en
1868,xml sax saxutils SAX Utilities Source code Lib xml sax saxutils py The module xml sax saxutils contains a number of classes and functions that are commonly useful when creating SAX applications either in direct use or as base classes xml sax saxutils escape data entities Escape and in a string of data You can escape other strings of data by passing a dictionary as the optional entities parameter The keys and values must all be strings each key will be replaced with its corresponding value The characters and are always escaped even if entities is provided Note This function should only be used to escape characters that can t be used directly in XML Do not use this function as a general string translation function xml sax saxutils unescape data entities Unescape amp lt and gt in a string of data You can unescape other strings of data by passing a dictionary as the optional entities parameter The keys and values must all be strings each key will be replaced with its corresponding value amp lt and gt are always unescaped even if entities is provided xml sax saxutils quoteattr data entities Similar to escape but also prepares data to be used as an attribute value The return value is a quoted version of data with any additional required replacements quoteattr will select a quote character based on the content of data attempting to avoid encoding any quote characters in the string If both single and double quote characters are already in data the double quote characters will be encoded and data will be wrapped in double quotes The resulting string can be used directly as an attribute value print element attr s quoteattr ab cd ef element attr ab cd quot ef This function is useful when generating attribute values for HTML or any SGML using the reference concrete syntax class xml sax saxutils XMLGenerator out None encoding iso 8859 1 short_empty_elements False This class implements the ContentHandler interface by writing SAX events back into an XML document In other words using an XMLGenerator as the content handler will reproduce the original document being parsed out should be a file like object which will default to sys stdout encoding is the encoding of the output stream which defaults to iso 8859 1 short_empty_elements controls the formatting of elements that contain no content if False the default they are emitted as a pair of start end tags if set to True they are emitted as a single self closed tag Changed in version 3 2 Added the short_empty_elements parameter class xml sax saxutils XMLFilterBase base This class is designed to sit between an XMLReader and the client application s event handlers By default it does nothing but pass requests up to the reader and events on to the handlers unmodified but subclasses can override specific methods to modify the event stream or the configuration requests as they pass through xml sax saxutils prepare_input_source source base This function takes an input source and an optional base URL and returns a fully resolved InputSource object ready for reading The input source can be given as a string a file like object or an InputSource object parsers will use this function to implement the polymorphic source argument to their parse method,en
1869,XML Processing Modules Source code Lib xml Python s interfaces for processing XML are grouped in the xml package Warning The XML modules are not secure against erroneous or maliciously constructed data If you need to parse untrusted or unauthenticated data see the XML vulnerabilities and The defusedxml Package sections It is important to note that modules in the xml package require that there be at least one SAX compliant XML parser available The Expat parser is included with Python so the xml parsers expat module will always be available The documentation for the xml dom and xml sax packages are the definition of the Python bindings for the DOM and SAX interfaces The XML handling submodules are xml etree ElementTree the ElementTree API a simple and lightweight XML processor xml dom the DOM API definition xml dom minidom a minimal DOM implementation xml dom pulldom support for building partial DOM trees xml sax SAX2 base classes and convenience functions xml parsers expat the Expat parser binding XML vulnerabilities The XML processing modules are not secure against maliciously constructed data An attacker can abuse XML features to carry out denial of service attacks access local files generate network connections to other machines or circumvent firewalls The following table gives an overview of the known attacks and whether the various modules are vulnerable to them kind sax etree minidom pulldom xmlrpc billion laughs Vulnerable 1 Vulnerable 1 Vulnerable 1 Vulnerable 1 Vulnerable 1 quadratic blowup Vulnerable 1 Vulnerable 1 Vulnerable 1 Vulnerable 1 Vulnerable 1 external entity expansion Safe 5 Safe 2 Safe 3 Safe 5 Safe 4 DTD retrieval Safe 5 Safe Safe Safe 5 Safe decompression bomb Safe Safe Safe Safe Vulnerable large tokens Vulnerable 6 Vulnerable 6 Vulnerable 6 Vulnerable 6 Vulnerable 6 1 Expat 2 4 1 and newer is not vulnerable to the billion laughs and quadratic blowup vulnerabilities Items still listed as vulnerable due to potential reliance on system provided libraries Check pyexpat EXPAT_VERSION 2 xml etree ElementTree doesn t expand external entities and raises a ParseError when an entity occurs 3 xml dom minidom doesn t expand external entities and simply returns the unexpanded entity verbatim 4 xmlrpc client doesn t expand external entities and omits them 5 Since Python 3 7 1 external general entities are no longer processed by default 6 Expat 2 6 0 and newer is not vulnerable to denial of service through quadratic runtime caused by parsing large tokens Items still listed as vulnerable due to potential reliance on system provided libraries Check pyexpat EXPAT_VERSION billion laughs exponential entity expansion The Billion Laughs attack also known as exponential entity expansion uses multiple levels of nested entities Each entity refers to another entity several times and the final entity definition contains a small string The exponential expansion results in several gigabytes of text and consumes lots of memory and CPU time quadratic blowup entity expansion A quadratic blowup attack is similar to a Billion Laughs attack it abuses entity expansion too Instead of nested entities it repeats one large entity with a couple of thousand chars over and over again The attack isn t as efficient as the exponential case but it avoids triggering parser countermeasures that forbid deeply nested entities external entity expansion Entity declarations can contain more than just text for replacement They can also point to external resources or local files The XML parser accesses the resource and embeds the content into the XML document DTD retrieval Some XML libraries like Python s xml dom pulldom retrieve document type definitions from remote or local locations The feature has similar implications as the external entity expansion issue decompression bomb Decompression bombs aka ZIP bomb apply to all XML libraries that can parse compressed XML streams such as gzipped HTTP streams or LZMA compressed files For an attacker it can reduce the amount of transmitted data by three magnitudes or more large tokens Expat needs to re parse ,en
1870,unfinished tokens without the protection introduced in Expat 2 6 0 this can lead to quadratic runtime that can be used to cause denial of service in the application parsing XML The issue is known as CVE 2023 52425 The documentation for defusedxml on PyPI has further information about all known attack vectors with examples and references The defusedxml Package defusedxml is a pure Python package with modified subclasses of all stdlib XML parsers that prevent any potentially malicious operation Use of this package is recommended for any server code that parses untrusted XML data The package also ships with example exploits and extended documentation on more XML exploits such as XPath injection,en
1871,sys System specific parameters and functions This module provides access to some variables used or maintained by the interpreter and to functions that interact strongly with the interpreter It is always available sys abiflags On POSIX systems where Python was built with the standard configure script this contains the ABI flags as specified by PEP 3149 New in version 3 2 Changed in version 3 8 Default flags became an empty string m flag for pymalloc has been removed Availability Unix sys addaudithook hook Append the callable hook to the list of active auditing hooks for the current sub interpreter When an auditing event is raised through the sys audit function each hook will be called in the order it was added with the event name and the tuple of arguments Native hooks added by PySys_AddAuditHook are called first followed by hooks added in the current sub interpreter Hooks can then log the event raise an exception to abort the operation or terminate the process entirely Note that audit hooks are primarily for collecting information about internal or otherwise unobservable actions whether by Python or libraries written in Python They are not suitable for implementing a sandbox In particular malicious code can trivially disable or bypass hooks added using this function At a minimum any security sensitive hooks must be added using the C API PySys_AddAuditHook before initialising the runtime and any modules allowing arbitrary memory modification such as ctypes should be completely removed or closely monitored Calling sys addaudithook will itself raise an auditing event named sys addaudithook with no arguments If any existing hooks raise an exception derived from RuntimeError the new hook will not be added and the exception suppressed As a result callers cannot assume that their hook has been added unless they control all existing hooks See the audit events table for all events raised by CPython and PEP 578 for the original design discussion New in version 3 8 Changed in version 3 8 1 Exceptions derived from Exception but not RuntimeError are no longer suppressed CPython implementation detail When tracing is enabled see settrace Python hooks are only traced if the callable has a __cantrace__ member that is set to a true value Otherwise trace functions will skip the hook sys argv The list of command line arguments passed to a Python script argv 0 is the script name it is operating system dependent whether this is a full pathname or not If the command was executed using the c command line option to the interpreter argv 0 is set to the string c If no script name was passed to the Python interpreter argv 0 is the empty string To loop over the standard input or the list of files given on the command line see the fileinput module See also sys orig_argv Note On Unix command line arguments are passed by bytes from OS Python decodes them with filesystem encoding and surrogateescape error handler When you need original bytes you can get it by os fsencode arg for arg in sys argv sys audit event args Raise an auditing event and trigger any active auditing hooks event is a string identifying the event and args may contain optional arguments with more information about the event The number and types of arguments for a given event are considered a public and stable API and should not be modified between releases For example one auditing event is named os chdir This event has one argument called path that will contain the requested new working directory sys audit will call the existing auditing hooks passing the event name and arguments and will re raise the first exception from any hook In general if an exception is raised it should not be handled and the process should be terminated as quickly as possible This allows hook implementations to decide how to respond to particular events they can merely log the event or abort the operation by raising an exception Hooks are added using the sys addaudithook or PySys_AddAuditHook functions The native equivalent of this function is PySys_Audit Using the native function is preferred when possible See,en
1872, the audit events table for all events raised by CPython New in version 3 8 sys base_exec_prefix Set during Python startup before site py is run to the same value as exec_prefix If not running in a virtual environment the values will stay the same if site py finds that a virtual environment is in use the values of prefix and exec_prefix will be changed to point to the virtual environment whereas base_prefix and base_exec_prefix will remain pointing to the base Python installation the one which the virtual environment was created from New in version 3 3 sys base_prefix Set during Python startup before site py is run to the same value as prefix If not running in a virtual environment the values will stay the same if site py finds that a virtual environment is in use the values of prefix and exec_prefix will be changed to point to the virtual environment whereas base_prefix and base_exec_prefix will remain pointing to the base Python installation the one which the virtual environment was created from New in version 3 3 sys byteorder An indicator of the native byte order This will have the value big on big endian most significant byte first platforms and little on little endian least significant byte first platforms sys builtin_module_names A tuple of strings containing the names of all modules that are compiled into this Python interpreter This information is not available in any other way modules keys only lists the imported modules See also the sys stdlib_module_names list sys call_tracing func args Call func args while tracing is enabled The tracing state is saved and restored afterwards This is intended to be called from a debugger from a checkpoint to recursively debug or profile some other code Tracing is suspended while calling a tracing function set by settrace or setprofile to avoid infinite recursion call_tracing enables explicit recursion of the tracing function sys copyright A string containing the copyright pertaining to the Python interpreter sys _clear_type_cache Clear the internal type cache The type cache is used to speed up attribute and method lookups Use the function only to drop unnecessary references during reference leak debugging This function should be used for internal and specialized purposes only sys _current_frames Return a dictionary mapping each thread s identifier to the topmost stack frame currently active in that thread at the time the function is called Note that functions in the traceback module can build the call stack given such a frame This is most useful for debugging deadlock this function does not require the deadlocked threads cooperation and such threads call stacks are frozen for as long as they remain deadlocked The frame returned for a non deadlocked thread may bear no relationship to that thread s current activity by the time calling code examines the frame This function should be used for internal and specialized purposes only Raises an auditing event sys _current_frames with no arguments sys _current_exceptions Return a dictionary mapping each thread s identifier to the topmost exception currently active in that thread at the time the function is called If a thread is not currently handling an exception it is not included in the result dictionary This is most useful for statistical profiling This function should be used for internal and specialized purposes only Raises an auditing event sys _current_exceptions with no arguments Changed in version 3 12 Each value in the dictionary is now a single exception instance rather than a 3 tuple as returned from sys exc_info sys breakpointhook This hook function is called by built in breakpoint By default it drops you into the pdb debugger but it can be set to any other function so that you can choose which debugger gets used The signature of this function is dependent on what it calls For example the default binding e g pdb set_trace expects no arguments but you might bind it to a function that expects additional arguments positional and or keyword The built in breakpoint function passes its args and kws straight through Whatever bre,en
1873,akpointhooks returns is returned from breakpoint The default implementation first consults the environment variable PYTHONBREAKPOINT If that is set to 0 then this function returns immediately i e it is a no op If the environment variable is not set or is set to the empty string pdb set_trace is called Otherwise this variable should name a function to run using Python s dotted import nomenclature e g package subpackage module function In this case package subpackage module would be imported and the resulting module must have a callable named function This is run passing in args and kws and whatever function returns sys breakpointhook returns to the built in breakpoint function Note that if anything goes wrong while importing the callable named by PYTHONBREAKPOINT a RuntimeWarning is reported and the breakpoint is ignored Also note that if sys breakpointhook is overridden programmatically PYTHONBREAKPOINT is not consulted New in version 3 7 sys _debugmallocstats Print low level information to stderr about the state of CPython s memory allocator If Python is built in debug mode configure with pydebug option it also performs some expensive internal consistency checks New in version 3 3 CPython implementation detail This function is specific to CPython The exact output format is not defined here and may change sys dllhandle Integer specifying the handle of the Python DLL Availability Windows sys displayhook value If value is not None this function prints repr value to sys stdout and saves value in builtins _ If repr value is not encodable to sys stdout encoding with sys stdout errors error handler which is probably strict encode it to sys stdout encoding with backslashreplace error handler sys displayhook is called on the result of evaluating an expression entered in an interactive Python session The display of these values can be customized by assigning another one argument function to sys displayhook Pseudo code def displayhook value if value is None return Set _ to None to avoid recursion builtins _ None text repr value try sys stdout write text except UnicodeEncodeError bytes text encode sys stdout encoding backslashreplace if hasattr sys stdout buffer sys stdout buffer write bytes else text bytes decode sys stdout encoding strict sys stdout write text sys stdout write n builtins _ value Changed in version 3 2 Use backslashreplace error handler on UnicodeEncodeError sys dont_write_bytecode If this is true Python won t try to write pyc files on the import of source modules This value is initially set to True or False depending on the B command line option and the PYTHONDONTWRITEBYTECODE environment variable but you can set it yourself to control bytecode file generation sys _emscripten_info A named tuple holding information about the environment on the wasm32 emscripten platform The named tuple is provisional and may change in the future _emscripten_info emscripten_version Emscripten version as tuple of ints major minor micro e g 3 1 8 _emscripten_info runtime Runtime string e g browser user agent Node js v14 18 2 or UNKNOWN _emscripten_info pthreads True if Python is compiled with Emscripten pthreads support _emscripten_info shared_memory True if Python is compiled with shared memory support Availability Emscripten New in version 3 11 sys pycache_prefix If this is set not None Python will write bytecode cache pyc files to and read them from a parallel directory tree rooted at this directory rather than from __pycache__ directories in the source code tree Any __pycache__ directories in the source code tree will be ignored and new pyc files written within the pycache prefix Thus if you use compileall as a pre build step you must ensure you run it with the same pycache prefix if any that you will use at runtime A relative path is interpreted relative to the current working directory This value is initially set based on the value of the X pycache_prefix PATH command line option or the PYTHONPYCACHEPREFIX environment variable command line takes precedence If neither are set it is None New in version 3 8 sys excepthook type val,en
1874,ue traceback This function prints out a given traceback and exception to sys stderr When an exception other than SystemExit is raised and uncaught the interpreter calls sys excepthook with three arguments the exception class exception instance and a traceback object In an interactive session this happens just before control is returned to the prompt in a Python program this happens just before the program exits The handling of such top level exceptions can be customized by assigning another three argument function to sys excepthook Raise an auditing event sys excepthook with arguments hook type value traceback when an uncaught exception occurs If no hook has been set hook may be None If any hook raises an exception derived from RuntimeError the call to the hook will be suppressed Otherwise the audit hook exception will be reported as unraisable and sys excepthook will be called See also The sys unraisablehook function handles unraisable exceptions and the threading excepthook function handles exception raised by threading Thread run sys __breakpointhook__ sys __displayhook__ sys __excepthook__ sys __unraisablehook__ These objects contain the original values of breakpointhook displayhook excepthook and unraisablehook at the start of the program They are saved so that breakpointhook displayhook and excepthook unraisablehook can be restored in case they happen to get replaced with broken or alternative objects New in version 3 7 __breakpointhook__ New in version 3 8 __unraisablehook__ sys exception This function when called while an exception handler is executing such as an except or except clause returns the exception instance that was caught by this handler When exception handlers are nested within one another only the exception handled by the innermost handler is accessible If no exception handler is executing this function returns None New in version 3 11 sys exc_info This function returns the old style representation of the handled exception If an exception e is currently handled so exception would return e exc_info returns the tuple type e e e __traceback__ That is a tuple containing the type of the exception a subclass of BaseException the exception itself and a traceback object which typically encapsulates the call stack at the point where the exception last occurred If no exception is being handled anywhere on the stack this function return a tuple containing three None values Changed in version 3 11 The type and traceback fields are now derived from the value the exception instance so when an exception is modified while it is being handled the changes are reflected in the results of subsequent calls to exc_info sys exec_prefix A string giving the site specific directory prefix where the platform dependent Python files are installed by default this is also usr local This can be set at build time with the exec prefix argument to the configure script Specifically all configuration files e g the pyconfig h header file are installed in the directory exec_prefix lib python X Y config and shared library modules are installed in exec_prefix lib python X Y lib dynload where X Y is the version number of Python for example 3 2 Note If a virtual environment is in effect this value will be changed in site py to point to the virtual environment The value for the Python installation will still be available via base_exec_prefix sys executable A string giving the absolute path of the executable binary for the Python interpreter on systems where this makes sense If Python is unable to retrieve the real path to its executable sys executable will be an empty string or None sys exit arg Raise a SystemExit exception signaling an intention to exit the interpreter The optional argument arg can be an integer giving the exit status defaulting to zero or another type of object If it is an integer zero is considered successful termination and any nonzero value is considered abnormal termination by shells and the like Most systems require it to be in the range 0 127 and produce undefined results otherwise Some systems have a convention for as,en
1875,signing specific meanings to specific exit codes but these are generally underdeveloped Unix programs generally use 2 for command line syntax errors and 1 for all other kind of errors If another type of object is passed None is equivalent to passing zero and any other object is printed to stderr and results in an exit code of 1 In particular sys exit some error message is a quick way to exit a program when an error occurs Since exit ultimately only raises an exception it will only exit the process when called from the main thread and the exception is not intercepted Cleanup actions specified by finally clauses of try statements are honored and it is possible to intercept the exit attempt at an outer level Changed in version 3 6 If an error occurs in the cleanup after the Python interpreter has caught SystemExit such as an error flushing buffered data in the standard streams the exit status is changed to 120 sys flags The named tuple flags exposes the status of command line flags The attributes are read only flags debug d flags inspect i flags interactive i flags isolated I flags optimize O or OO flags dont_write_bytecode B flags no_user_site s flags no_site S flags ignore_environment E flags verbose v flags bytes_warning b flags quiet q flags hash_randomization R flags dev_mode X dev Python Development Mode flags utf8_mode X utf8 flags safe_path P flags int_max_str_digits X int_max_str_digits integer string conversion length limitation flags warn_default_encoding X warn_default_encoding Changed in version 3 2 Added quiet attribute for the new q flag New in version 3 2 3 The hash_randomization attribute Changed in version 3 3 Removed obsolete division_warning attribute Changed in version 3 4 Added isolated attribute for I isolated flag Changed in version 3 7 Added the dev_mode attribute for the new Python Development Mode and the utf8_mode attribute for the new X utf8 flag Changed in version 3 10 Added warn_default_encoding attribute for X warn_default_encoding flag Changed in version 3 11 Added the safe_path attribute for P option Changed in version 3 11 Added the int_max_str_digits attribute sys float_info A named tuple holding information about the float type It contains low level information about the precision and internal representation The values correspond to the various floating point constants defined in the standard header file float h for the C programming language see section 5 2 4 2 2 of the 1999 ISO IEC C standard C99 Characteristics of floating types for details Attributes of the float_info named tuple attribute float h macro explanation float_info epsilon DBL_EPSILON difference between 1 0 and the least value greater than 1 0 that is representable as a float See also math ulp float_info dig DBL_DIG The maximum number of decimal digits that can be faithfully represented in a float see below float_info mant_dig DBL_MANT_DIG Float precision the number of base radix digits in the significand of a float float_info max DBL_MAX The maximum representable positive finite float float_info max_exp DBL_MAX_EXP The maximum integer e such that radix e 1 is a representable finite float float_info max_10_exp DBL_MAX_10_EXP The maximum integer e such that 10 e is in the range of representable finite floats float_info min DBL_MIN The minimum representable positive normalized float Use math ulp 0 0 to get the smallest positive denormalized representable float float_info min_exp DBL_MIN_EXP The minimum integer e such that radix e 1 is a normalized float float_info min_10_exp DBL_MIN_10_EXP The minimum integer e such that 10 e is a normalized float float_info radix FLT_RADIX The radix of exponent representation float_info rounds FLT_ROUNDS An integer representing the rounding mode for floating point arithmetic This reflects the value of the system FLT_ROUNDS macro at interpreter startup time 1 indeterminable 0 toward zero 1 to nearest 2 toward positive infinity 3 toward negative infinity All other values for FLT_ROUNDS characterize implementation defined rounding behavior The attribute sys float_info dig needs further explana,en
1876,tion If s is any string representing a decimal number with at most sys float_info dig significant digits then converting s to a float and back again will recover a string representing the same decimal value import sys sys float_info dig 15 s 3 14159265358979 decimal string with 15 significant digits format float s 15g convert to float and back same value 3 14159265358979 But for strings with more than sys float_info dig significant digits this isn t always true s 9876543211234567 16 significant digits is too many format float s 16g conversion changes value 9876543211234568 sys float_repr_style A string indicating how the repr function behaves for floats If the string has value short then for a finite float x repr x aims to produce a short string with the property that float repr x x This is the usual behaviour in Python 3 1 and later Otherwise float_repr_style has value legacy and repr x behaves in the same way as it did in versions of Python prior to 3 1 New in version 3 1 sys getallocatedblocks Return the number of memory blocks currently allocated by the interpreter regardless of their size This function is mainly useful for tracking and debugging memory leaks Because of the interpreter s internal caches the result can vary from call to call you may have to call _clear_type_cache and gc collect to get more predictable results If a Python build or implementation cannot reasonably compute this information getallocatedblocks is allowed to return 0 instead New in version 3 4 sys getunicodeinternedsize Return the number of unicode objects that have been interned New in version 3 12 sys getandroidapilevel Return the build time API version of Android as an integer Availability Android New in version 3 7 sys getdefaultencoding Return the name of the current default string encoding used by the Unicode implementation sys getdlopenflags Return the current value of the flags that are used for dlopen calls Symbolic names for the flag values can be found in the os module RTLD_ xxx constants e g os RTLD_LAZY Availability Unix sys getfilesystemencoding Get the filesystem encoding the encoding used with the filesystem error handler to convert between Unicode filenames and bytes filenames The filesystem error handler is returned from getfilesystemencodeerrors For best compatibility str should be used for filenames in all cases although representing filenames as bytes is also supported Functions accepting or returning filenames should support either str or bytes and internally convert to the system s preferred representation os fsencode and os fsdecode should be used to ensure that the correct encoding and errors mode are used The filesystem encoding and error handler are configured at Python startup by the PyConfig_Read function see filesystem_encoding and filesystem_errors members of PyConfig Changed in version 3 2 getfilesystemencoding result cannot be None anymore Changed in version 3 6 Windows is no longer guaranteed to return mbcs See PEP 529 and _enablelegacywindowsfsencoding for more information Changed in version 3 7 Return utf 8 if the Python UTF 8 Mode is enabled sys getfilesystemencodeerrors Get the filesystem error handler the error handler used with the filesystem encoding to convert between Unicode filenames and bytes filenames The filesystem encoding is returned from getfilesystemencoding os fsencode and os fsdecode should be used to ensure that the correct encoding and errors mode are used The filesystem encoding and error handler are configured at Python startup by the PyConfig_Read function see filesystem_encoding and filesystem_errors members of PyConfig New in version 3 6 sys get_int_max_str_digits Returns the current value for the integer string conversion length limitation See also set_int_max_str_digits New in version 3 11 sys getrefcount object Return the reference count of the object The count returned is generally one higher than you might expect because it includes the temporary reference as an argument to getrefcount Note that the returned value may not actually reflect how many references to the object are ,en
1877,actually held For example some objects are immortal and have a very high refcount that does not reflect the actual number of references Consequently do not rely on the returned value to be accurate other than a value of 0 or 1 Changed in version 3 12 Immortal objects have very large refcounts that do not match the actual number of references to the object sys getrecursionlimit Return the current value of the recursion limit the maximum depth of the Python interpreter stack This limit prevents infinite recursion from causing an overflow of the C stack and crashing Python It can be set by setrecursionlimit sys getsizeof object default Return the size of an object in bytes The object can be any type of object All built in objects will return correct results but this does not have to hold true for third party extensions as it is implementation specific Only the memory consumption directly attributed to the object is accounted for not the memory consumption of objects it refers to If given default will be returned if the object does not provide means to retrieve the size Otherwise a TypeError will be raised getsizeof calls the object s __sizeof__ method and adds an additional garbage collector overhead if the object is managed by the garbage collector See recursive sizeof recipe for an example of using getsizeof recursively to find the size of containers and all their contents sys getswitchinterval Return the interpreter s thread switch interval see setswitchinterval New in version 3 2 sys _getframe depth Return a frame object from the call stack If optional integer depth is given return the frame object that many calls below the top of the stack If that is deeper than the call stack ValueError is raised The default for depth is zero returning the frame at the top of the call stack Raises an auditing event sys _getframe with argument frame CPython implementation detail This function should be used for internal and specialized purposes only It is not guaranteed to exist in all implementations of Python sys _getframemodulename depth Return the name of a module from the call stack If optional integer depth is given return the module that many calls below the top of the stack If that is deeper than the call stack or if the module is unidentifiable None is returned The default for depth is zero returning the module at the top of the call stack Raises an auditing event sys _getframemodulename with argument depth CPython implementation detail This function should be used for internal and specialized purposes only It is not guaranteed to exist in all implementations of Python sys getprofile Get the profiler function as set by setprofile sys gettrace Get the trace function as set by settrace CPython implementation detail The gettrace function is intended only for implementing debuggers profilers coverage tools and the like Its behavior is part of the implementation platform rather than part of the language definition and thus may not be available in all Python implementations sys getwindowsversion Return a named tuple describing the Windows version currently running The named elements are major minor build platform service_pack service_pack_minor service_pack_major suite_mask product_type and platform_version service_pack contains a string platform_version a 3 tuple and all other values are integers The components can also be accessed by name so sys getwindowsversion 0 is equivalent to sys getwindowsversion major For compatibility with prior versions only the first 5 elements are retrievable by indexing platform will be 2 VER_PLATFORM_WIN32_NT product_type may be one of the following values Constant Meaning 1 VER_NT_WORKSTATION The system is a workstation 2 VER_NT_DOMAIN_CONTROLLER The system is a domain controller 3 VER_NT_SERVER The system is a server but not a domain controller This function wraps the Win32 GetVersionEx function see the Microsoft documentation on OSVERSIONINFOEX for more information about these fields platform_version returns the major version minor version and build number of the current operating system rather th,en
1878,an the version that is being emulated for the process It is intended for use in logging rather than for feature detection Note platform_version derives the version from kernel32 dll which can be of a different version than the OS version Please use platform module for achieving accurate OS version Availability Windows Changed in version 3 2 Changed to a named tuple and added service_pack_minor service_pack_major suite_mask and product_type Changed in version 3 6 Added platform_version sys get_asyncgen_hooks Returns an asyncgen_hooks object which is similar to a namedtuple of the form firstiter finalizer where firstiter and finalizer are expected to be either None or functions which take an asynchronous generator iterator as an argument and are used to schedule finalization of an asynchronous generator by an event loop New in version 3 6 See PEP 525 for more details Note This function has been added on a provisional basis see PEP 411 for details sys get_coroutine_origin_tracking_depth Get the current coroutine origin tracking depth as set by set_coroutine_origin_tracking_depth New in version 3 7 Note This function has been added on a provisional basis see PEP 411 for details Use it only for debugging purposes sys hash_info A named tuple giving parameters of the numeric hash implementation For more details about hashing of numeric types see Hashing of numeric types hash_info width The width in bits used for hash values hash_info modulus The prime modulus P used for numeric hash scheme hash_info inf The hash value returned for a positive infinity hash_info nan This attribute is no longer used hash_info imag The multiplier used for the imaginary part of a complex number hash_info algorithm The name of the algorithm for hashing of str bytes and memoryview hash_info hash_bits The internal output size of the hash algorithm hash_info seed_bits The size of the seed key of the hash algorithm New in version 3 2 Changed in version 3 4 Added algorithm hash_bits and seed_bits sys hexversion The version number encoded as a single integer This is guaranteed to increase with each version including proper support for non production releases For example to test that the Python interpreter is at least version 1 5 2 use if sys hexversion 0x010502F0 use some advanced feature else use an alternative implementation or warn the user This is called hexversion since it only really looks meaningful when viewed as the result of passing it to the built in hex function The named tuple sys version_info may be used for a more human friendly encoding of the same information More details of hexversion can be found at API and ABI Versioning sys implementation An object containing information about the implementation of the currently running Python interpreter The following attributes are required to exist in all Python implementations name is the implementation s identifier e g cpython The actual string is defined by the Python implementation but it is guaranteed to be lower case version is a named tuple in the same format as sys version_info It represents the version of the Python implementation This has a distinct meaning from the specific version of the Python language to which the currently running interpreter conforms which sys version_info represents For example for PyPy 1 8 sys implementation version might be sys version_info 1 8 0 final 0 whereas sys version_info would be sys version_info 2 7 2 final 0 For CPython they are the same value since it is the reference implementation hexversion is the implementation version in hexadecimal format like sys hexversion cache_tag is the tag used by the import machinery in the filenames of cached modules By convention it would be a composite of the implementation s name and version like cpython 33 However a Python implementation may use some other value if appropriate If cache_tag is set to None it indicates that module caching should be disabled sys implementation may contain additional attributes specific to the Python implementation These non standard attributes must start with an underscore and are not des,en
1879,cribed here Regardless of its contents sys implementation will not change during a run of the interpreter nor between implementation versions It may change between Python language versions however See PEP 421 for more information New in version 3 3 Note The addition of new required attributes must go through the normal PEP process See PEP 421 for more information sys int_info A named tuple that holds information about Python s internal representation of integers The attributes are read only int_info bits_per_digit The number of bits held in each digit Python integers are stored internally in base 2 int_info bits_per_digit int_info sizeof_digit The size in bytes of the C type used to represent a digit int_info default_max_str_digits The default value for sys get_int_max_str_digits when it is not otherwise explicitly configured int_info str_digits_check_threshold The minimum non zero value for sys set_int_max_str_digits PYTHONINTMAXSTRDIGITS or X int_max_str_digits New in version 3 1 Changed in version 3 11 Added default_max_str_digits and str_digits_check_threshold sys __interactivehook__ When this attribute exists its value is automatically called with no arguments when the interpreter is launched in interactive mode This is done after the PYTHONSTARTUP file is read so that you can set this hook there The site module sets this Raises an auditing event cpython run_interactivehook with the hook object as the argument when the hook is called on startup New in version 3 4 sys intern string Enter string in the table of interned strings and return the interned string which is string itself or a copy Interning strings is useful to gain a little performance on dictionary lookup if the keys in a dictionary are interned and the lookup key is interned the key comparisons after hashing can be done by a pointer compare instead of a string compare Normally the names used in Python programs are automatically interned and the dictionaries used to hold module class or instance attributes have interned keys Interned strings are not immortal you must keep a reference to the return value of intern around to benefit from it sys is_finalizing Return True if the Python interpreter is shutting down False otherwise New in version 3 5 sys last_exc This variable is not always defined it is set to the exception instance when an exception is not handled and the interpreter prints an error message and a stack traceback Its intended use is to allow an interactive user to import a debugger module and engage in post mortem debugging without having to re execute the command that caused the error Typical use is import pdb pdb pm to enter the post mortem debugger see pdb module for more information New in version 3 12 sys last_type sys last_value sys last_traceback These three variables are deprecated use sys last_exc instead They hold the legacy representation of sys last_exc as returned from exc_info above sys maxsize An integer giving the maximum value a variable of type Py_ssize_t can take It s usually 2 31 1 on a 32 bit platform and 2 63 1 on a 64 bit platform sys maxunicode An integer giving the value of the largest Unicode code point i e 1114111 0x10FFFF in hexadecimal Changed in version 3 3 Before PEP 393 sys maxunicode used to be either 0xFFFF or 0x10FFFF depending on the configuration option that specified whether Unicode characters were stored as UCS 2 or UCS 4 sys meta_path A list of meta path finder objects that have their find_spec methods called to see if one of the objects can find the module to be imported By default it holds entries that implement Python s default import semantics The find_spec method is called with at least the absolute name of the module being imported If the module to be imported is contained in a package then the parent package s __path__ attribute is passed in as a second argument The method returns a module spec or None if the module cannot be found See also importlib abc MetaPathFinder The abstract base class defining the interface of finder objects on meta_path importlib machinery ModuleSpec The concrete class whi,en
1880,ch find_spec should return instances of Changed in version 3 4 Module specs were introduced in Python 3 4 by PEP 451 Changed in version 3 12 Removed the fallback that looked for a find_module method if a meta_path entry didn t have a find_spec method sys modules This is a dictionary that maps module names to modules which have already been loaded This can be manipulated to force reloading of modules and other tricks However replacing the dictionary will not necessarily work as expected and deleting essential items from the dictionary may cause Python to fail If you want to iterate over this global dictionary always use sys modules copy or tuple sys modules to avoid exceptions as its size may change during iteration as a side effect of code or activity in other threads sys orig_argv The list of the original command line arguments passed to the Python executable The elements of sys orig_argv are the arguments to the Python interpreter while the elements of sys argv are the arguments to the user s program Arguments consumed by the interpreter itself will be present in sys orig_argv and missing from sys argv New in version 3 10 sys path A list of strings that specifies the search path for modules Initialized from the environment variable PYTHONPATH plus an installation dependent default By default as initialized upon program startup a potentially unsafe path is prepended to sys path before the entries inserted as a result of PYTHONPATH python m module command line prepend the current working directory python script py command line prepend the script s directory If it s a symbolic link resolve symbolic links python c code and python REPL command lines prepend an empty string which means the current working directory To not prepend this potentially unsafe path use the P command line option or the PYTHONSAFEPATH environment variable A program is free to modify this list for its own purposes Only strings should be added to sys path all other data types are ignored during import See also Module site This describes how to use pth files to extend sys path sys path_hooks A list of callables that take a path argument to try to create a finder for the path If a finder can be created it is to be returned by the callable else raise ImportError Originally specified in PEP 302 sys path_importer_cache A dictionary acting as a cache for finder objects The keys are paths that have been passed to sys path_hooks and the values are the finders that are found If a path is a valid file system path but no finder is found on sys path_hooks then None is stored Originally specified in PEP 302 sys platform This string contains a platform identifier that can be used to append platform specific components to sys path for instance For Unix systems except on Linux and AIX this is the lowercased OS name as returned by uname s with the first part of the version as returned by uname r appended e g sunos5 or freebsd8 at the time when Python was built Unless you want to test for a specific system version it is therefore recommended to use the following idiom if sys platform startswith freebsd FreeBSD specific code here elif sys platform startswith linux Linux specific code here elif sys platform startswith aix AIX specific code here For other systems the values are System platform value AIX aix Emscripten emscripten Linux linux WASI wasi Windows win32 Windows Cygwin cygwin macOS darwin Changed in version 3 3 On Linux sys platform doesn t contain the major version anymore It is always linux instead of linux2 or linux3 Since older Python versions include the version number it is recommended to always use the startswith idiom presented above Changed in version 3 8 On AIX sys platform doesn t contain the major version anymore It is always aix instead of aix5 or aix7 Since older Python versions include the version number it is recommended to always use the startswith idiom presented above See also os name has a coarser granularity os uname gives system dependent version information The platform module provides detailed checks for the system s identity sys platlibdi,en
1881,r Name of the platform specific library directory It is used to build the path of standard library and the paths of installed extension modules It is equal to lib on most platforms On Fedora and SuSE it is equal to lib64 on 64 bit platforms which gives the following sys path paths where X Y is the Python major minor version usr lib64 pythonX Y Standard library like os py of the os module usr lib64 pythonX Y lib dynload C extension modules of the standard library like the errno module the exact filename is platform specific usr lib pythonX Y site packages always use lib not sys platlibdir Third party modules usr lib64 pythonX Y site packages C extension modules of third party packages New in version 3 9 sys prefix A string giving the site specific directory prefix where the platform independent Python files are installed on Unix the default is usr local This can be set at build time with the prefix argument to the configure script See Installation paths for derived paths Note If a virtual environment is in effect this value will be changed in site py to point to the virtual environment The value for the Python installation will still be available via base_prefix sys ps1 sys ps2 Strings specifying the primary and secondary prompt of the interpreter These are only defined if the interpreter is in interactive mode Their initial values in this case are and If a non string object is assigned to either variable its str is re evaluated each time the interpreter prepares to read a new interactive command this can be used to implement a dynamic prompt sys setdlopenflags n Set the flags used by the interpreter for dlopen calls such as when the interpreter loads extension modules Among other things this will enable a lazy resolving of symbols when importing a module if called as sys setdlopenflags 0 To share symbols across extension modules call as sys setdlopenflags os RTLD_GLOBAL Symbolic names for the flag values can be found in the os module RTLD_ xxx constants e g os RTLD_LAZY Availability Unix sys set_int_max_str_digits maxdigits Set the integer string conversion length limitation used by this interpreter See also get_int_max_str_digits New in version 3 11 sys setprofile profilefunc Set the system s profile function which allows you to implement a Python source code profiler in Python See chapter The Python Profilers for more information on the Python profiler The system s profile function is called similarly to the system s trace function see settrace but it is called with different events for example it isn t called for each executed line of code only on call and return but the return event is reported even when an exception has been set The function is thread specific but there is no way for the profiler to know about context switches between threads so it does not make sense to use this in the presence of multiple threads Also its return value is not used so it can simply return None Error in the profile function will cause itself unset Note The same tracing mechanism is used for setprofile as settrace To trace calls with setprofile inside a tracing function e g in a debugger breakpoint see call_tracing Profile functions should have three arguments frame event and arg frame is the current stack frame event is a string call return c_call c_return or c_exception arg depends on the event type The events have the following meaning call A function is called or some other code block entered The profile function is called arg is None return A function or other code block is about to return The profile function is called arg is the value that will be returned or None if the event is caused by an exception being raised c_call A C function is about to be called This may be an extension function or a built in arg is the C function object c_return A C function has returned arg is the C function object c_exception A C function has raised an exception arg is the C function object Raises an auditing event sys setprofile with no arguments sys setrecursionlimit limit Set the maximum depth of the Python interpreter stack to limit This limit,en
1882, prevents infinite recursion from causing an overflow of the C stack and crashing Python The highest possible limit is platform dependent A user may need to set the limit higher when they have a program that requires deep recursion and a platform that supports a higher limit This should be done with care because a too high limit can lead to a crash If the new limit is too low at the current recursion depth a RecursionError exception is raised Changed in version 3 5 1 A RecursionError exception is now raised if the new limit is too low at the current recursion depth sys setswitchinterval interval Set the interpreter s thread switch interval in seconds This floating point value determines the ideal duration of the timeslices allocated to concurrently running Python threads Please note that the actual value can be higher especially if long running internal functions or methods are used Also which thread becomes scheduled at the end of the interval is the operating system s decision The interpreter doesn t have its own scheduler New in version 3 2 sys settrace tracefunc Set the system s trace function which allows you to implement a Python source code debugger in Python The function is thread specific for a debugger to support multiple threads it must register a trace function using settrace for each thread being debugged or use threading settrace Trace functions should have three arguments frame event and arg frame is the current stack frame event is a string call line return exception or opcode arg depends on the event type The trace function is invoked with event set to call whenever a new local scope is entered it should return a reference to a local trace function to be used for the new scope or None if the scope shouldn t be traced The local trace function should return a reference to itself or to another function which would then be used as the local trace function for the scope If there is any error occurred in the trace function it will be unset just like settrace None is called Note Tracing is disabled while calling the trace function e g a function set by settrace For recursive tracing see call_tracing The events have the following meaning call A function is called or some other code block entered The global trace function is called arg is None the return value specifies the local trace function line The interpreter is about to execute a new line of code or re execute the condition of a loop The local trace function is called arg is None the return value specifies the new local trace function See Objects lnotab_notes txt for a detailed explanation of how this works Per line events may be disabled for a frame by setting f_trace_lines to False on that frame return A function or other code block is about to return The local trace function is called arg is the value that will be returned or None if the event is caused by an exception being raised The trace function s return value is ignored exception An exception has occurred The local trace function is called arg is a tuple exception value traceback the return value specifies the new local trace function opcode The interpreter is about to execute a new opcode see dis for opcode details The local trace function is called arg is None the return value specifies the new local trace function Per opcode events are not emitted by default they must be explicitly requested by setting f_trace_opcodes to True on the frame Note that as an exception is propagated down the chain of callers an exception event is generated at each level For more fine grained usage it s possible to set a trace function by assigning frame f_trace tracefunc explicitly rather than relying on it being set indirectly via the return value from an already installed trace function This is also required for activating the trace function on the current frame which settrace doesn t do Note that in order for this to work a global tracing function must have been installed with settrace in order to enable the runtime tracing machinery but it doesn t need to be the same tracing function e g it could be a low overhe,en
1883,ad tracing function that simply returns None to disable itself immediately on each frame For more information on code and frame objects refer to The standard type hierarchy Raises an auditing event sys settrace with no arguments CPython implementation detail The settrace function is intended only for implementing debuggers profilers coverage tools and the like Its behavior is part of the implementation platform rather than part of the language definition and thus may not be available in all Python implementations Changed in version 3 7 opcode event type added f_trace_lines and f_trace_opcodes attributes added to frames Changed in version 3 12 opcode event will only be emitted if f_trace_opcodes of at least one frame has been set to True before settrace is called This behavior will be changed back in 3 13 to be consistent with previous versions sys set_asyncgen_hooks firstiter finalizer Accepts two optional keyword arguments which are callables that accept an asynchronous generator iterator as an argument The firstiter callable will be called when an asynchronous generator is iterated for the first time The finalizer will be called when an asynchronous generator is about to be garbage collected Raises an auditing event sys set_asyncgen_hooks_firstiter with no arguments Raises an auditing event sys set_asyncgen_hooks_finalizer with no arguments Two auditing events are raised because the underlying API consists of two calls each of which must raise its own event New in version 3 6 See PEP 525 for more details and for a reference example of a finalizer method see the implementation of asyncio Loop shutdown_asyncgens in Lib asyncio base_events py Note This function has been added on a provisional basis see PEP 411 for details sys set_coroutine_origin_tracking_depth depth Allows enabling or disabling coroutine origin tracking When enabled the cr_origin attribute on coroutine objects will contain a tuple of filename line number function name tuples describing the traceback where the coroutine object was created with the most recent call first When disabled cr_origin will be None To enable pass a depth value greater than zero this sets the number of frames whose information will be captured To disable pass set depth to zero This setting is thread specific New in version 3 7 Note This function has been added on a provisional basis see PEP 411 for details Use it only for debugging purposes sys activate_stack_trampoline backend Activate the stack profiler trampoline backend The only supported backend is perf Availability Linux New in version 3 12 See also Python support for the Linux perf profiler https perf wiki kernel org sys deactivate_stack_trampoline Deactivate the current stack profiler trampoline backend If no stack profiler is activated this function has no effect Availability Linux New in version 3 12 sys is_stack_trampoline_active Return True if a stack profiler trampoline is active Availability Linux New in version 3 12 sys _enablelegacywindowsfsencoding Changes the filesystem encoding and error handler to mbcs and replace respectively for consistency with versions of Python prior to 3 6 This is equivalent to defining the PYTHONLEGACYWINDOWSFSENCODING environment variable before launching Python See also sys getfilesystemencoding and sys getfilesystemencodeerrors Availability Windows New in version 3 6 See PEP 529 for more details sys stdin sys stdout sys stderr File objects used by the interpreter for standard input output and errors stdin is used for all interactive input including calls to input stdout is used for the output of print and expression statements and for the prompts of input The interpreter s own prompts and its error messages go to stderr These streams are regular text files like those returned by the open function Their parameters are chosen as follows The encoding and error handling are is initialized from PyConfig stdio_encoding and PyConfig stdio_errors On Windows UTF 8 is used for the console device Non character devices such as disk files and pipes use the system locale encoding i e the ANSI codepa,en
1884,ge Non console character devices such as NUL i e where isatty returns True use the value of the console input and output codepages at startup respectively for stdin and stdout stderr This defaults to the system locale encoding if the process is not initially attached to a console The special behaviour of the console can be overridden by setting the environment variable PYTHONLEGACYWINDOWSSTDIO before starting Python In that case the console codepages are used as for any other character device Under all platforms you can override the character encoding by setting the PYTHONIOENCODING environment variable before starting Python or by using the new X utf8 command line option and PYTHONUTF8 environment variable However for the Windows console this only applies when PYTHONLEGACYWINDOWSSTDIO is also set When interactive the stdout stream is line buffered Otherwise it is block buffered like regular text files The stderr stream is line buffered in both cases You can make both streams unbuffered by passing the u command line option or setting the PYTHONUNBUFFERED environment variable Changed in version 3 9 Non interactive stderr is now line buffered instead of fully buffered Note To write or read binary data from to the standard streams use the underlying binary buffer object For example to write bytes to stdout use sys stdout buffer write b abc However if you are writing a library and do not control in which context its code will be executed be aware that the standard streams may be replaced with file like objects like io StringIO which do not support the buffer attribute sys __stdin__ sys __stdout__ sys __stderr__ These objects contain the original values of stdin stderr and stdout at the start of the program They are used during finalization and could be useful to print to the actual standard stream no matter if the sys std object has been redirected It can also be used to restore the actual files to known working file objects in case they have been overwritten with a broken object However the preferred way to do this is to explicitly save the previous stream before replacing it and restore the saved object Note Under some conditions stdin stdout and stderr as well as the original values __stdin__ __stdout__ and __stderr__ can be None It is usually the case for Windows GUI apps that aren t connected to a console and Python apps started with pythonw sys stdlib_module_names A frozenset of strings containing the names of standard library modules It is the same on all platforms Modules which are not available on some platforms and modules disabled at Python build are also listed All module kinds are listed pure Python built in frozen and extension modules Test modules are excluded For packages only the main package is listed sub packages and sub modules are not listed For example the email package is listed but the email mime sub package and the email message sub module are not listed See also the sys builtin_module_names list New in version 3 10 sys thread_info A named tuple holding information about the thread implementation thread_info name The name of the thread implementation nt Windows threads pthread POSIX threads pthread stubs stub POSIX threads on WebAssembly platforms without threading support solaris Solaris threads thread_info lock The name of the lock implementation semaphore a lock uses a semaphore mutex cond a lock uses a mutex and a condition variable None if this information is unknown thread_info version The name and version of the thread library It is a string or None if this information is unknown New in version 3 3 sys tracebacklimit When this variable is set to an integer value it determines the maximum number of levels of traceback information printed when an unhandled exception occurs The default is 1000 When set to 0 or less all traceback information is suppressed and only the exception type and value are printed sys unraisablehook unraisable Handle an unraisable exception Called when an exception has occurred but there is no way for Python to handle it For example when a destructor raises an exception or ,en
1885,during garbage collection gc collect The unraisable argument has the following attributes exc_type Exception type exc_value Exception value can be None exc_traceback Exception traceback can be None err_msg Error message can be None object Object causing the exception can be None The default hook formats err_msg and object as f err_msg object r use Exception ignored in error message if err_msg is None sys unraisablehook can be overridden to control how unraisable exceptions are handled See also excepthook which handles uncaught exceptions Warning Storing exc_value using a custom hook can create a reference cycle It should be cleared explicitly to break the reference cycle when the exception is no longer needed Storing object using a custom hook can resurrect it if it is set to an object which is being finalized Avoid storing object after the custom hook completes to avoid resurrecting objects Raise an auditing event sys unraisablehook with arguments hook unraisable when an exception that cannot be handled occurs The unraisable object is the same as what will be passed to the hook If no hook has been set hook may be None New in version 3 8 sys version A string containing the version number of the Python interpreter plus additional information on the build number and compiler used This string is displayed when the interactive interpreter is started Do not extract version information out of it rather use version_info and the functions provided by the platform module sys api_version The C API version for this interpreter Programmers may find this useful when debugging version conflicts between Python and extension modules sys version_info A tuple containing the five components of the version number major minor micro releaselevel and serial All values except releaselevel are integers the release level is alpha beta candidate or final The version_info value corresponding to the Python version 2 0 is 2 0 0 final 0 The components can also be accessed by name so sys version_info 0 is equivalent to sys version_info major and so on Changed in version 3 1 Added named component attributes sys warnoptions This is an implementation detail of the warnings framework do not modify this value Refer to the warnings module for more information on the warnings framework sys winver The version number used to form registry keys on Windows platforms This is stored as string resource 1000 in the Python DLL The value is normally the major and minor versions of the running Python interpreter It is provided in the sys module for informational purposes modifying this value has no effect on the registry keys used by Python Availability Windows sys monitoring Namespace containing functions and constants for register callbacks and controlling monitoring events See sys monitoring for details sys _xoptions A dictionary of the various implementation specific flags passed through the X command line option Option names are either mapped to their values if given explicitly or to True Example python Xa b Xc Python 3 2a3 py3k Oct 16 2010 20 14 50 GCC 4 4 3 on linux2 Type help copyright credits or license for more information import sys sys _xoptions a b c True CPython implementation detail This is a CPython specific way of accessing options passed through X Other implementations may export them through other means or not at all New in version 3 2 Citations C99 ISO IEC 9899 1999 Programming languages C A public draft of this standard is available at https www open std org jtc1 sc22 wg14 www docs n1256 pdf,en
1886,What s New In Python 3 8 Editor Raymond Hettinger This article explains the new features in Python 3 8 compared to 3 7 Python 3 8 was released on October 14 2019 For full details see the changelog Summary Release highlights New Features Assignment expressions There is new syntax that assigns values to variables as part of a larger expression It is affectionately known as the walrus operator due to its resemblance to the eyes and tusks of a walrus In this example the assignment expression helps avoid calling len twice if n len a 10 print f List is too long n elements expected 10 A similar benefit arises during regular expression matching where match objects are needed twice once to test whether a match occurred and another to extract a subgroup discount 0 0 if mo re search r d discount advertisement discount float mo group 1 100 0 The operator is also useful with while loops that compute a value to test loop termination and then need that same value again in the body of the loop Loop over fixed length blocks while block f read 256 process block Another motivating use case arises in list comprehensions where a value computed in a filtering condition is also needed in the expression body clean_name title for name in names if clean_name normalize NFC name in allowed_names Try to limit use of the walrus operator to clean cases that reduce complexity and improve readability See PEP 572 for a full description Contributed by Emily Morehouse in bpo 35224 Positional only parameters There is a new function parameter syntax to indicate that some function parameters must be specified positionally and cannot be used as keyword arguments This is the same notation shown by help for C functions annotated with Larry Hastings Argument Clinic tool In the following example parameters a and b are positional only while c or d can be positional or keyword and e or f are required to be keywords def f a b c d e f print a b c d e f The following is a valid call f 10 20 30 d 40 e 50 f 60 However these are invalid calls f 10 b 20 c 30 d 40 e 50 f 60 b cannot be a keyword argument f 10 20 30 40 50 f 60 e must be a keyword argument One use case for this notation is that it allows pure Python functions to fully emulate behaviors of existing C coded functions For example the built in divmod function does not accept keyword arguments def divmod a b Emulate the built in divmod function return a b a b Another use case is to preclude keyword arguments when the parameter name is not helpful For example the builtin len function has the signature len obj This precludes awkward calls such as len obj hello The obj keyword argument impairs readability A further benefit of marking a parameter as positional only is that it allows the parameter name to be changed in the future without risk of breaking client code For example in the statistics module the parameter name dist may be changed in the future This was made possible with the following function specification def quantiles dist n 4 method exclusive Since the parameters to the left of are not exposed as possible keywords the parameters names remain available for use in kwargs def f a b kwargs print a b kwargs f 10 20 a 1 b 2 c 3 a and b are used in two ways 10 20 a 1 b 2 c 3 This greatly simplifies the implementation of functions and methods that need to accept arbitrary keyword arguments For example here is an excerpt from code in the collections module class Counter dict def __init__ self iterable None kwds Note iterable is a possible keyword argument See PEP 570 for a full description Contributed by Pablo Galindo in bpo 36540 Parallel filesystem cache for compiled bytecode files The new PYTHONPYCACHEPREFIX setting also available as X pycache_prefix configures the implicit bytecode cache to use a separate parallel filesystem tree rather than the default __pycache__ subdirectories within each source directory The location of the cache is reported in sys pycache_prefix None indicates the default location in __pycache__ subdirectories Contributed by Carl Meyer in bpo 33499 Debug build uses the same ABI as releas,en
1887,e build Python now uses the same ABI whether it s built in release or debug mode On Unix when Python is built in debug mode it is now possible to load C extensions built in release mode and C extensions built using the stable ABI Release builds and debug builds are now ABI compatible defining the Py_DEBUG macro no longer implies the Py_TRACE_REFS macro which introduces the only ABI incompatibility The Py_TRACE_REFS macro which adds the sys getobjects function and the PYTHONDUMPREFS environment variable can be set using the new configure with trace refs build option Contributed by Victor Stinner in bpo 36465 On Unix C extensions are no longer linked to libpython except on Android and Cygwin It is now possible for a statically linked Python to load a C extension built using a shared library Python Contributed by Victor Stinner in bpo 21536 On Unix when Python is built in debug mode import now also looks for C extensions compiled in release mode and for C extensions compiled with the stable ABI Contributed by Victor Stinner in bpo 36722 To embed Python into an application a new embed option must be passed to python3 config libs embed to get lpython3 8 link the application to libpython To support both 3 8 and older try python3 config libs embed first and fallback to python3 config libs without embed if the previous command fails Add a pkg config python 3 8 embed module to embed Python into an application pkg config python 3 8 embed libs includes lpython3 8 To support both 3 8 and older try pkg config python X Y embed libs first and fallback to pkg config python X Y libs without embed if the previous command fails replace X Y with the Python version On the other hand pkg config python3 8 libs no longer contains lpython3 8 C extensions must not be linked to libpython except on Android and Cygwin whose cases are handled by the script this change is backward incompatible on purpose Contributed by Victor Stinner in bpo 36721 f strings support for self documenting expressions and debugging Added an specifier to f string s An f string such as f expr will expand to the text of the expression an equal sign then the representation of the evaluated expression For example user eric_idle member_since date 1975 7 31 f user member_since user eric_idle member_since datetime date 1975 7 31 The usual f string format specifiers allow more control over how the result of the expression is displayed delta date today member_since f user s delta days d user eric_idle delta days 16 075 The specifier will display the whole expression so that calculations can be shown print f theta cos radians theta 3f theta 30 cos radians theta 0 866 Contributed by Eric V Smith and Larry Hastings in bpo 36817 PEP 578 Python Runtime Audit Hooks The PEP adds an Audit Hook and Verified Open Hook Both are available from Python and native code allowing applications and frameworks written in pure Python code to take advantage of extra notifications while also allowing embedders or system administrators to deploy builds of Python where auditing is always enabled See PEP 578 for full details PEP 587 Python Initialization Configuration The PEP 587 adds a new C API to configure the Python Initialization providing finer control on the whole configuration and better error reporting New structures PyConfig PyPreConfig PyStatus PyWideStringList New functions PyConfig_Clear PyConfig_InitIsolatedConfig PyConfig_InitPythonConfig PyConfig_Read PyConfig_SetArgv PyConfig_SetBytesArgv PyConfig_SetBytesString PyConfig_SetString PyPreConfig_InitIsolatedConfig PyPreConfig_InitPythonConfig PyStatus_Error PyStatus_Exception PyStatus_Exit PyStatus_IsError PyStatus_IsExit PyStatus_NoMemory PyStatus_Ok PyWideStringList_Append PyWideStringList_Insert Py_BytesMain Py_ExitStatusException Py_InitializeFromConfig Py_PreInitialize Py_PreInitializeFromArgs Py_PreInitializeFromBytesArgs Py_RunMain This PEP also adds _PyRuntimeState preconfig PyPreConfig type and PyInterpreterState config PyConfig type fields to these internal structures PyInterpreterState config becomes the new reference configuration r,en
1888,eplacing global configuration variables and other private variables See Python Initialization Configuration for the documentation See PEP 587 for a full description Contributed by Victor Stinner in bpo 36763 PEP 590 Vectorcall a fast calling protocol for CPython The Vectorcall Protocol is added to the Python C API It is meant to formalize existing optimizations which were already done for various classes Any static type implementing a callable can use this protocol This is currently provisional The aim is to make it fully public in Python 3 9 See PEP 590 for a full description Contributed by Jeroen Demeyer Mark Shannon and Petr Viktorin in bpo 36974 Pickle protocol 5 with out of band data buffers When pickle is used to transfer large data between Python processes in order to take advantage of multi core or multi machine processing it is important to optimize the transfer by reducing memory copies and possibly by applying custom techniques such as data dependent compression The pickle protocol 5 introduces support for out of band buffers where PEP 3118 compatible data can be transmitted separately from the main pickle stream at the discretion of the communication layer See PEP 574 for a full description Contributed by Antoine Pitrou in bpo 36785 Other Language Changes A continue statement was illegal in the finally clause due to a problem with the implementation In Python 3 8 this restriction was lifted Contributed by Serhiy Storchaka in bpo 32489 The bool int and fractions Fraction types now have an as_integer_ratio method like that found in float and decimal Decimal This minor API extension makes it possible to write numerator denominator x as_integer_ratio and have it work across multiple numeric types Contributed by Lisa Roach in bpo 33073 and Raymond Hettinger in bpo 37819 Constructors of int float and complex will now use the __index__ special method if available and the corresponding method __int__ __float__ or __complex__ is not available Contributed by Serhiy Storchaka in bpo 20092 Added support of N name escapes in regular expressions notice Copyright 2019 copyright_year_pattern re compile r N copyright sign s d 4 int copyright_year_pattern search notice group 1 2019 Contributed by Jonathan Eunice and Serhiy Storchaka in bpo 30688 Dict and dictviews are now iterable in reversed insertion order using reversed Contributed by Rémi Lapeyre in bpo 33462 The syntax allowed for keyword names in function calls was further restricted In particular f keyword arg is no longer allowed It was never intended to permit more than a bare name on the left hand side of a keyword argument assignment term Contributed by Benjamin Peterson in bpo 34641 Generalized iterable unpacking in yield and return statements no longer requires enclosing parentheses This brings the yield and return syntax into better agreement with normal assignment syntax def parse family lastname members family split return lastname upper members parse simpsons homer marge bart lisa maggie SIMPSONS homer marge bart lisa maggie Contributed by David Cuthbert and Jordan Chapman in bpo 32117 When a comma is missed in code such as 10 20 30 40 the compiler displays a SyntaxWarning with a helpful suggestion This improves on just having a TypeError indicating that the first tuple was not callable Contributed by Serhiy Storchaka in bpo 15248 Arithmetic operations between subclasses of datetime date or datetime datetime and datetime timedelta objects now return an instance of the subclass rather than the base class This also affects the return type of operations whose implementation directly or indirectly uses datetime timedelta arithmetic such as astimezone Contributed by Paul Ganssle in bpo 32417 When the Python interpreter is interrupted by Ctrl C SIGINT and the resulting KeyboardInterrupt exception is not caught the Python process now exits via a SIGINT signal or with the correct exit code such that the calling process can detect that it died due to a Ctrl C Shells on POSIX and Windows use this to properly terminate scripts in interactive sessions Contributed by Googl,en
1889,e via Gregory P Smith in bpo 1054041 Some advanced styles of programming require updating the types CodeType object for an existing function Since code objects are immutable a new code object needs to be created one that is modeled on the existing code object With 19 parameters this was somewhat tedious Now the new replace method makes it possible to create a clone with a few altered parameters Here s an example that alters the statistics mean function to prevent the data parameter from being used as a keyword argument from statistics import mean mean data 10 20 90 40 mean __code__ mean __code__ replace co_posonlyargcount 1 mean data 10 20 90 Traceback most recent call last TypeError mean got some positional only arguments passed as keyword arguments data Contributed by Victor Stinner in bpo 37032 For integers the three argument form of the pow function now permits the exponent to be negative in the case where the base is relatively prime to the modulus It then computes a modular inverse to the base when the exponent is 1 and a suitable power of that inverse for other negative exponents For example to compute the modular multiplicative inverse of 38 modulo 137 write pow 38 1 137 119 119 38 137 1 Modular inverses arise in the solution of linear Diophantine equations For example to find integer solutions for 4258𝑥 147𝑦 369 first rewrite as 4258𝑥 369 mod 147 then solve x 369 pow 4258 1 147 147 y 4258 x 369 147 4258 x 147 y 369 Contributed by Mark Dickinson in bpo 36027 Dict comprehensions have been synced up with dict literals so that the key is computed first and the value second Dict comprehension cast input role input actor for i in range 2 role King Arthur actor Chapman role Black Knight actor Cleese Dict literal cast input role input actor role Sir Robin actor Eric Idle The guaranteed execution order is helpful with assignment expressions because variables assigned in the key expression will be available in the value expression names Martin von Löwis Łukasz Langa Walter Dörwald n normalize NFC name casefold n for name in names martin von löwis Martin von Löwis łukasz langa Łukasz Langa walter dörwald Walter Dörwald Contributed by Jörn Heissler in bpo 35224 The object __reduce__ method can now return a tuple from two to six elements long Formerly five was the limit The new optional sixth element is a callable with a obj state signature This allows the direct control over the state updating behavior of a specific object If not None this callable will have priority over the object s __setstate__ method Contributed by Pierre Glaser and Olivier Grisel in bpo 35900 New Modules The new importlib metadata module provides provisional support for reading metadata from third party packages For example it can extract an installed package s version number list of entry points and more Note following example requires that the popular requests package has been installed from importlib metadata import version requires files version requests 2 22 0 list requires requests chardet 3 1 0 3 0 2 list files requests 5 PackagePath requests 2 22 0 dist info INSTALLER PackagePath requests 2 22 0 dist info LICENSE PackagePath requests 2 22 0 dist info METADATA PackagePath requests 2 22 0 dist info RECORD PackagePath requests 2 22 0 dist info WHEEL Contributed by Barry Warsaw and Jason R Coombs in bpo 34632 Improved Modules ast AST nodes now have end_lineno and end_col_offset attributes which give the precise location of the end of the node This only applies to nodes that have lineno and col_offset attributes New function ast get_source_segment returns the source code for a specific AST node Contributed by Ivan Levkivskyi in bpo 33416 The ast parse function has some new flags type_comments True causes it to return the text of PEP 484 and PEP 526 type comments associated with certain AST nodes mode func_type can be used to parse PEP 484 signature type comments returned for function definition AST nodes feature_version 3 N allows specifying an earlier Python 3 version For example feature_version 3 4 will treat async and await as non reserved words ,en
1890,Contributed by Guido van Rossum in bpo 35766 asyncio asyncio run has graduated from the provisional to stable API This function can be used to execute a coroutine and return the result while automatically managing the event loop For example import asyncio async def main await asyncio sleep 0 return 42 asyncio run main This is roughly equivalent to import asyncio async def main await asyncio sleep 0 return 42 loop asyncio new_event_loop asyncio set_event_loop loop try loop run_until_complete main finally asyncio set_event_loop None loop close The actual implementation is significantly more complex Thus asyncio run should be the preferred way of running asyncio programs Contributed by Yury Selivanov in bpo 32314 Running python m asyncio launches a natively async REPL This allows rapid experimentation with code that has a top level await There is no longer a need to directly call asyncio run which would spawn a new event loop on every invocation python m asyncio asyncio REPL 3 8 0 Use await directly instead of asyncio run Type help copyright credits or license for more information import asyncio await asyncio sleep 10 result hello hello Contributed by Yury Selivanov in bpo 37028 The exception asyncio CancelledError now inherits from BaseException rather than Exception and no longer inherits from concurrent futures CancelledError Contributed by Yury Selivanov in bpo 32528 On Windows the default event loop is now ProactorEventLoop Contributed by Victor Stinner in bpo 34687 ProactorEventLoop now also supports UDP Contributed by Adam Meily and Andrew Svetlov in bpo 29883 ProactorEventLoop can now be interrupted by KeyboardInterrupt CTRL C Contributed by Vladimir Matveev in bpo 23057 Added asyncio Task get_coro for getting the wrapped coroutine within an asyncio Task Contributed by Alex Grönholm in bpo 36999 Asyncio tasks can now be named either by passing the name keyword argument to asyncio create_task or the create_task event loop method or by calling the set_name method on the task object The task name is visible in the repr output of asyncio Task and can also be retrieved using the get_name method Contributed by Alex Grönholm in bpo 34270 Added support for Happy Eyeballs to asyncio loop create_connection To specify the behavior two new parameters have been added happy_eyeballs_delay and interleave The Happy Eyeballs algorithm improves responsiveness in applications that support IPv4 and IPv6 by attempting to simultaneously connect using both Contributed by twisteroid ambassador in bpo 33530 builtins The compile built in has been improved to accept the ast PyCF_ALLOW_TOP_LEVEL_AWAIT flag With this new flag passed compile will allow top level await async for and async with constructs that are usually considered invalid syntax Asynchronous code object marked with the CO_COROUTINE flag may then be returned Contributed by Matthias Bussonnier in bpo 34616 collections The _asdict method for collections namedtuple now returns a dict instead of a collections OrderedDict This works because regular dicts have guaranteed ordering since Python 3 7 If the extra features of OrderedDict are required the suggested remediation is to cast the result to the desired type OrderedDict nt _asdict Contributed by Raymond Hettinger in bpo 35864 cProfile The cProfile Profile class can now be used as a context manager Profile a block of code by running import cProfile with cProfile Profile as profiler code to be profiled Contributed by Scott Sanderson in bpo 29235 csv The csv DictReader now returns instances of dict instead of a collections OrderedDict The tool is now faster and uses less memory while still preserving the field order Contributed by Michael Selik in bpo 34003 curses Added a new variable holding structured version information for the underlying ncurses library ncurses_version Contributed by Serhiy Storchaka in bpo 31680 ctypes On Windows CDLL and subclasses now accept a winmode parameter to specify flags for the underlying LoadLibraryEx call The default flags are set to only load DLL dependencies from trusted locations including the path,en
1891, where the DLL is stored if a full or partial path is used to load the initial DLL and paths added by add_dll_directory Contributed by Steve Dower in bpo 36085 datetime Added new alternate constructors datetime date fromisocalendar and datetime datetime fromisocalendar which construct date and datetime objects respectively from ISO year week number and weekday these are the inverse of each class s isocalendar method Contributed by Paul Ganssle in bpo 36004 functools functools lru_cache can now be used as a straight decorator rather than as a function returning a decorator So both of these are now supported lru_cache def f x lru_cache maxsize 256 def f x Contributed by Raymond Hettinger in bpo 36772 Added a new functools cached_property decorator for computed properties cached for the life of the instance import functools import statistics class Dataset def __init__ self sequence_of_numbers self data sequence_of_numbers functools cached_property def variance self return statistics variance self data Contributed by Carl Meyer in bpo 21145 Added a new functools singledispatchmethod decorator that converts methods into generic functions using single dispatch from functools import singledispatchmethod from contextlib import suppress class TaskManager def __init__ self tasks self tasks list tasks singledispatchmethod def discard self value with suppress ValueError self tasks remove value discard register list def _ self tasks targets set tasks self tasks x for x in self tasks if x not in targets Contributed by Ethan Smith in bpo 32380 gc get_objects can now receive an optional generation parameter indicating a generation to get objects from Contributed by Pablo Galindo in bpo 36016 gettext Added pgettext and its variants Contributed by Franz Glasner Éric Araujo and Cheryl Sabella in bpo 2504 gzip Added the mtime parameter to gzip compress for reproducible output Contributed by Guo Ci Teo in bpo 34898 A BadGzipFile exception is now raised instead of OSError for certain types of invalid or corrupt gzip files Contributed by Filip Gruszczyński Michele Orrù and Zackery Spytz in bpo 6584 IDLE and idlelib Output over N lines 50 by default is squeezed down to a button N can be changed in the PyShell section of the General page of the Settings dialog Fewer but possibly extra long lines can be squeezed by right clicking on the output Squeezed output can be expanded in place by double clicking the button or into the clipboard or a separate window by right clicking the button Contributed by Tal Einat in bpo 1529353 Add Run Customized to the Run menu to run a module with customized settings Any command line arguments entered are added to sys argv They also re appear in the box for the next customized run One can also suppress the normal Shell main module restart Contributed by Cheryl Sabella Terry Jan Reedy and others in bpo 5680 and bpo 37627 Added optional line numbers for IDLE editor windows Windows open without line numbers unless set otherwise in the General tab of the configuration dialog Line numbers for an existing window are shown and hidden in the Options menu Contributed by Tal Einat and Saimadhav Heblikar in bpo 17535 OS native encoding is now used for converting between Python strings and Tcl objects This allows IDLE to work with emoji and other non BMP characters These characters can be displayed or copied and pasted to or from the clipboard Converting strings from Tcl to Python and back now never fails Many people worked on this for eight years but the problem was finally solved by Serhiy Storchaka in bpo 13153 New in 3 8 1 Add option to toggle cursor blink off Contributed by Zackery Spytz in bpo 4603 Escape key now closes IDLE completion windows Contributed by Johnny Najera in bpo 38944 The changes above have been backported to 3 7 maintenance releases Add keywords to module name completion list Contributed by Terry J Reedy in bpo 37765 inspect The inspect getdoc function can now find docstrings for __slots__ if that attribute is a dict where the values are docstrings This provides documentation options similar to what we a,en
1892,lready have for property classmethod and staticmethod class AudioClip __slots__ bit_rate expressed in kilohertz to one decimal place duration in seconds rounded up to an integer def __init__ self bit_rate duration self bit_rate round bit_rate 1000 0 1 self duration ceil duration Contributed by Raymond Hettinger in bpo 36326 io In development mode X env and in debug build the io IOBase finalizer now logs the exception if the close method fails The exception is ignored silently by default in release build Contributed by Victor Stinner in bpo 18748 itertools The itertools accumulate function added an option initial keyword argument to specify an initial value from itertools import accumulate list accumulate 10 5 30 15 initial 1000 1000 1010 1015 1045 1060 Contributed by Lisa Roach in bpo 34659 json tool Add option json lines to parse every input line as a separate JSON object Contributed by Weipeng Hong in bpo 31553 logging Added a force keyword argument to logging basicConfig When set to true any existing handlers attached to the root logger are removed and closed before carrying out the configuration specified by the other arguments This solves a long standing problem Once a logger or basicConfig had been called subsequent calls to basicConfig were silently ignored This made it difficult to update experiment with or teach the various logging configuration options using the interactive prompt or a Jupyter notebook Suggested by Raymond Hettinger implemented by Donghee Na and reviewed by Vinay Sajip in bpo 33897 math Added new function math dist for computing Euclidean distance between two points Contributed by Raymond Hettinger in bpo 33089 Expanded the math hypot function to handle multiple dimensions Formerly it only supported the 2 D case Contributed by Raymond Hettinger in bpo 33089 Added new function math prod as analogous function to sum that returns the product of a start value default 1 times an iterable of numbers prior 0 8 likelihoods 0 625 0 84 0 30 math prod likelihoods start prior 0 126 Contributed by Pablo Galindo in bpo 35606 Added two new combinatoric functions math perm and math comb math perm 10 3 Permutations of 10 things taken 3 at a time 720 math comb 10 3 Combinations of 10 things taken 3 at a time 120 Contributed by Yash Aggarwal Keller Fuchs Serhiy Storchaka and Raymond Hettinger in bpo 37128 bpo 37178 and bpo 35431 Added a new function math isqrt for computing accurate integer square roots without conversion to floating point The new function supports arbitrarily large integers It is faster than floor sqrt n but slower than math sqrt r 650320427 s r 2 isqrt s 1 correct 650320426 floor sqrt s 1 incorrect 650320427 Contributed by Mark Dickinson in bpo 36887 The function math factorial no longer accepts arguments that are not int like Contributed by Pablo Galindo in bpo 33083 mmap The mmap mmap class now has an madvise method to access the madvise system call Contributed by Zackery Spytz in bpo 32941 multiprocessing Added new multiprocessing shared_memory module Contributed by Davin Potts in bpo 35813 On macOS the spawn start method is now used by default Contributed by Victor Stinner in bpo 33725 os Added new function add_dll_directory on Windows for providing additional search paths for native dependencies when importing extension modules or loading DLLs using ctypes Contributed by Steve Dower in bpo 36085 A new os memfd_create function was added to wrap the memfd_create syscall Contributed by Zackery Spytz and Christian Heimes in bpo 26836 On Windows much of the manual logic for handling reparse points including symlinks and directory junctions has been delegated to the operating system Specifically os stat will now traverse anything supported by the operating system while os lstat will only open reparse points that identify as name surrogates while others are opened as for os stat In all cases stat_result st_mode will only have S_IFLNK set for symbolic links and not other kinds of reparse points To identify other kinds of reparse point check the new stat_result st_reparse_tag attribute On Windows o,en
1893,s readlink is now able to read directory junctions Note that islink will return False for directory junctions and so code that checks islink first will continue to treat junctions as directories while code that handles errors from os readlink may now treat junctions as links Contributed by Steve Dower in bpo 37834 os path os path functions that return a boolean result like exists lexists isdir isfile islink and ismount now return False instead of raising ValueError or its subclasses UnicodeEncodeError and UnicodeDecodeError for paths that contain characters or bytes unrepresentable at the OS level Contributed by Serhiy Storchaka in bpo 33721 expanduser on Windows now prefers the USERPROFILE environment variable and does not use HOME which is not normally set for regular user accounts Contributed by Anthony Sottile in bpo 36264 isdir on Windows no longer returns True for a link to a non existent directory realpath on Windows now resolves reparse points including symlinks and directory junctions Contributed by Steve Dower in bpo 37834 pathlib pathlib Path methods that return a boolean result like exists is_dir is_file is_mount is_symlink is_block_device is_char_device is_fifo is_socket now return False instead of raising ValueError or its subclass UnicodeEncodeError for paths that contain characters unrepresentable at the OS level Contributed by Serhiy Storchaka in bpo 33721 Added pathlib Path link_to which creates a hard link pointing to a path Contributed by Joannah Nanjekye in bpo 26978 Note that link_to was deprecated in 3 10 and removed in 3 12 in favor of a hardlink_to method added in 3 10 which matches the semantics of the existing symlink_to method pickle pickle extensions subclassing the C optimized Pickler can now override the pickling logic of functions and classes by defining the special reducer_override method Contributed by Pierre Glaser and Olivier Grisel in bpo 35900 plistlib Added new plistlib UID and enabled support for reading and writing NSKeyedArchiver encoded binary plists Contributed by Jon Janzen in bpo 26707 pprint The pprint module added a sort_dicts parameter to several functions By default those functions continue to sort dictionaries before rendering or printing However if sort_dicts is set to false the dictionaries retain the order that keys were inserted This can be useful for comparison to JSON inputs during debugging In addition there is a convenience new function pprint pp that is like pprint pprint but with sort_dicts defaulting to False from pprint import pprint pp d dict source input txt operation filter destination output txt pp d width 40 Original order source input txt operation filter destination output txt pprint d width 40 Keys sorted alphabetically destination output txt operation filter source input txt Contributed by Rémi Lapeyre in bpo 30670 py_compile py_compile compile now supports silent mode Contributed by Joannah Nanjekye in bpo 22640 shlex The new shlex join function acts as the inverse of shlex split Contributed by Bo Bayles in bpo 32102 shutil shutil copytree now accepts a new dirs_exist_ok keyword argument Contributed by Josh Bronson in bpo 20849 shutil make_archive now defaults to the modern pax POSIX 1 2001 format for new archives to improve portability and standards conformance inherited from the corresponding change to the tarfile module Contributed by C A M Gerlach in bpo 30661 shutil rmtree on Windows now removes directory junctions without recursively removing their contents first Contributed by Steve Dower in bpo 37834 socket Added create_server and has_dualstack_ipv6 convenience functions to automate the necessary tasks usually involved when creating a server socket including accepting both IPv4 and IPv6 connections on the same socket Contributed by Giampaolo Rodolà in bpo 17561 The socket if_nameindex socket if_nametoindex and socket if_indextoname functions have been implemented on Windows Contributed by Zackery Spytz in bpo 37007 ssl Added post_handshake_auth to enable and verify_client_post_handshake to initiate TLS 1 3 post handshake authentication Contr,en
1894,ibuted by Christian Heimes in bpo 34670 statistics Added statistics fmean as a faster floating point variant of statistics mean Contributed by Raymond Hettinger and Steven D Aprano in bpo 35904 Added statistics geometric_mean Contributed by Raymond Hettinger in bpo 27181 Added statistics multimode that returns a list of the most common values Contributed by Raymond Hettinger in bpo 35892 Added statistics quantiles that divides data or a distribution in to equiprobable intervals e g quartiles deciles or percentiles Contributed by Raymond Hettinger in bpo 36546 Added statistics NormalDist a tool for creating and manipulating normal distributions of a random variable Contributed by Raymond Hettinger in bpo 36018 temperature_feb NormalDist from_samples 4 12 3 2 7 14 temperature_feb mean 6 0 temperature_feb stdev 6 356099432828281 temperature_feb cdf 3 Chance of being under 3 degrees 0 3184678262814532 Relative chance of being 7 degrees versus 10 degrees temperature_feb pdf 7 temperature_feb pdf 10 1 2039930378537762 el_niño NormalDist 4 2 5 temperature_feb el_niño Add in a climate effect temperature_feb NormalDist mu 10 0 sigma 6 830080526611674 temperature_feb 9 5 32 Convert to Fahrenheit NormalDist mu 50 0 sigma 12 294144947901014 temperature_feb samples 3 Generate random samples 7 672102882379219 12 000027119750287 4 647488369766392 sys Add new sys unraisablehook function which can be overridden to control how unraisable exceptions are handled It is called when an exception has occurred but there is no way for Python to handle it For example when a destructor raises an exception or during garbage collection gc collect Contributed by Victor Stinner in bpo 36829 tarfile The tarfile module now defaults to the modern pax POSIX 1 2001 format for new archives instead of the previous GNU specific one This improves cross platform portability with a consistent encoding UTF 8 in a standardized and extensible format and offers several other benefits Contributed by C A M Gerlach in bpo 36268 threading Add a new threading excepthook function which handles uncaught threading Thread run exception It can be overridden to control how uncaught threading Thread run exceptions are handled Contributed by Victor Stinner in bpo 1230540 Add a new threading get_native_id function and a native_id attribute to the threading Thread class These return the native integral Thread ID of the current thread assigned by the kernel This feature is only available on certain platforms see get_native_id for more information Contributed by Jake Tesler in bpo 36084 tokenize The tokenize module now implicitly emits a NEWLINE token when provided with input that does not have a trailing new line This behavior now matches what the C tokenizer does internally Contributed by Ammar Askar in bpo 33899 tkinter Added methods selection_from selection_present selection_range and selection_to in the tkinter Spinbox class Contributed by Juliette Monsel in bpo 34829 Added method moveto in the tkinter Canvas class Contributed by Juliette Monsel in bpo 23831 The tkinter PhotoImage class now has transparency_get and transparency_set methods Contributed by Zackery Spytz in bpo 25451 time Added new clock CLOCK_UPTIME_RAW for macOS 10 12 Contributed by Joannah Nanjekye in bpo 35702 typing The typing module incorporates several new features A dictionary type with per key types See PEP 589 and typing TypedDict TypedDict uses only string keys By default every key is required to be present Specify total False to allow keys to be optional class Location TypedDict total False lat_long tuple grid_square str xy_coordinate tuple Literal types See PEP 586 and typing Literal Literal types indicate that a parameter or return value is constrained to one or more specific literal values def get_status port int Literal connected disconnected Final variables functions methods and classes See PEP 591 typing Final and typing final The final qualifier instructs a static type checker to restrict subclassing overriding or reassignment pi Final float 3 1415926536 Protocol definitions See PEP 544 typing Pr,en
1895,otocol and typing runtime_checkable Simple ABCs like typing SupportsInt are now Protocol subclasses New protocol class typing SupportsIndex New functions typing get_origin and typing get_args unicodedata The unicodedata module has been upgraded to use the Unicode 12 1 0 release New function is_normalized can be used to verify a string is in a specific normal form often much faster than by actually normalizing the string Contributed by Max Belanger David Euresti and Greg Price in bpo 32285 and bpo 37966 unittest Added AsyncMock to support an asynchronous version of Mock Appropriate new assert functions for testing have been added as well Contributed by Lisa Roach in bpo 26467 Added addModuleCleanup and addClassCleanup to unittest to support cleanups for setUpModule and setUpClass Contributed by Lisa Roach in bpo 24412 Several mock assert functions now also print a list of actual calls upon failure Contributed by Petter Strandmark in bpo 35047 unittest module gained support for coroutines to be used as test cases with unittest IsolatedAsyncioTestCase Contributed by Andrew Svetlov in bpo 32972 Example import unittest class TestRequest unittest IsolatedAsyncioTestCase async def asyncSetUp self self connection await AsyncConnection async def test_get self response await self connection get https example com self assertEqual response status_code 200 async def asyncTearDown self await self connection close if __name__ __main__ unittest main venv venv now includes an Activate ps1 script on all platforms for activating virtual environments under PowerShell Core 6 1 Contributed by Brett Cannon in bpo 32718 weakref The proxy objects returned by weakref proxy now support the matrix multiplication operators and in addition to the other numeric operators Contributed by Mark Dickinson in bpo 36669 xml As mitigation against DTD and external entity retrieval the xml dom minidom and xml sax modules no longer process external entities by default Contributed by Christian Heimes in bpo 17239 The find methods in the xml etree ElementTree module support wildcard searches like tag which ignores the namespace and namespace which returns all tags in the given namespace Contributed by Stefan Behnel in bpo 28238 The xml etree ElementTree module provides a new function xml etree ElementTree canonicalize that implements C14N 2 0 Contributed by Stefan Behnel in bpo 13611 The target object of xml etree ElementTree XMLParser can receive namespace declaration events through the new callback methods start_ns and end_ns Additionally the xml etree ElementTree TreeBuilder target can be configured to process events about comments and processing instructions to include them in the generated tree Contributed by Stefan Behnel in bpo 36676 and bpo 36673 xmlrpc xmlrpc client ServerProxy now supports an optional headers keyword argument for a sequence of HTTP headers to be sent with each request Among other things this makes it possible to upgrade from default basic authentication to faster session authentication Contributed by Cédric Krier in bpo 35153 Optimizations The subprocess module can now use the os posix_spawn function in some cases for better performance Currently it is only used on macOS and Linux using glibc 2 24 or newer if all these conditions are met close_fds is false preexec_fn pass_fds cwd and start_new_session parameters are not set the executable path contains a directory Contributed by Joannah Nanjekye and Victor Stinner in bpo 35537 shutil copyfile shutil copy shutil copy2 shutil copytree and shutil move use platform specific fast copy syscalls on Linux and macOS in order to copy the file more efficiently fast copy means that the copying operation occurs within the kernel avoiding the use of userspace buffers in Python as in outfd write infd read On Windows shutil copyfile uses a bigger default buffer size 1 MiB instead of 16 KiB and a memoryview based variant of shutil copyfileobj is used The speedup for copying a 512 MiB file within the same partition is about 26 on Linux 50 on macOS and 40 on Windows Also much less CPU cycles are consumed S,en
1896,ee Platform dependent efficient copy operations section Contributed by Giampaolo Rodolà in bpo 33671 shutil copytree uses os scandir function and all copy functions depending from it use cached os stat values The speedup for copying a directory with 8000 files is around 9 on Linux 20 on Windows and 30 on a Windows SMB share Also the number of os stat syscalls is reduced by 38 making shutil copytree especially faster on network filesystems Contributed by Giampaolo Rodolà in bpo 33695 The default protocol in the pickle module is now Protocol 4 first introduced in Python 3 4 It offers better performance and smaller size compared to Protocol 3 available since Python 3 0 Removed one Py_ssize_t member from PyGC_Head All GC tracked objects e g tuple list dict size is reduced 4 or 8 bytes Contributed by Inada Naoki in bpo 33597 uuid UUID now uses __slots__ to reduce its memory footprint Contributed by Wouter Bolsterlee and Tal Einat in bpo 30977 Improved performance of operator itemgetter by 33 Optimized argument handling and added a fast path for the common case of a single non negative integer index into a tuple which is the typical use case in the standard library Contributed by Raymond Hettinger in bpo 35664 Sped up field lookups in collections namedtuple They are now more than two times faster making them the fastest form of instance variable lookup in Python Contributed by Raymond Hettinger Pablo Galindo and Joe Jevnik Serhiy Storchaka in bpo 32492 The list constructor does not overallocate the internal item buffer if the input iterable has a known length the input implements __len__ This makes the created list 12 smaller on average Contributed by Raymond Hettinger and Pablo Galindo in bpo 33234 Doubled the speed of class variable writes When a non dunder attribute was updated there was an unnecessary call to update slots Contributed by Stefan Behnel Pablo Galindo Salgado Raymond Hettinger Neil Schemenauer and Serhiy Storchaka in bpo 36012 Reduced an overhead of converting arguments passed to many builtin functions and methods This sped up calling some simple builtin functions and methods up to 20 50 Contributed by Serhiy Storchaka in bpo 23867 bpo 35582 and bpo 36127 LOAD_GLOBAL instruction now uses new per opcode cache mechanism It is about 40 faster now Contributed by Yury Selivanov and Inada Naoki in bpo 26219 Build and C API Changes Default sys abiflags became an empty string the m flag for pymalloc became useless builds with and without pymalloc are ABI compatible and so has been removed Contributed by Victor Stinner in bpo 36707 Example of changes Only python3 8 program is installed python3 8m program is gone Only python3 8 config script is installed python3 8m config script is gone The m flag has been removed from the suffix of dynamic library filenames extension modules in the standard library as well as those produced and installed by third party packages like those downloaded from PyPI On Linux for example the Python 3 7 suffix cpython 37m x86_64 linux gnu so became cpython 38 x86_64 linux gnu so in Python 3 8 The header files have been reorganized to better separate the different kinds of APIs Include h should be the portable public stable C API Include cpython h should be the unstable C API specific to CPython public API with some private API prefixed by _Py or _PY Include internal h is the private internal C API very specific to CPython This API comes with no backward compatibility warranty and should not be used outside CPython It is only exposed for very specific needs like debuggers and profiles which has to access to CPython internals without calling functions This API is now installed by make install Contributed by Victor Stinner in bpo 35134 and bpo 35081 work initiated by Eric Snow in Python 3 7 Some macros have been converted to static inline functions parameter types and return type are well defined they don t have issues specific to macros variables have a local scopes Examples Py_INCREF Py_DECREF Py_XINCREF Py_XDECREF PyObject_INIT PyObject_INIT_VAR Private functions _PyObject_GC_TRACK _PyObject_GC,en
1897,_UNTRACK _Py_Dealloc Contributed by Victor Stinner in bpo 35059 The PyByteArray_Init and PyByteArray_Fini functions have been removed They did nothing since Python 2 7 4 and Python 3 2 0 were excluded from the limited API stable ABI and were not documented Contributed by Victor Stinner in bpo 35713 The result of PyExceptionClass_Name is now of type const char rather of char Contributed by Serhiy Storchaka in bpo 33818 The duality of Modules Setup dist and Modules Setup has been removed Previously when updating the CPython source tree one had to manually copy Modules Setup dist inside the source tree to Modules Setup inside the build tree in order to reflect any changes upstream This was of a small benefit to packagers at the expense of a frequent annoyance to developers following CPython development as forgetting to copy the file could produce build failures Now the build system always reads from Modules Setup inside the source tree People who want to customize that file are encouraged to maintain their changes in a git fork of CPython or as patch files as they would do for any other change to the source tree Contributed by Antoine Pitrou in bpo 32430 Functions that convert Python number to C integer like PyLong_AsLong and argument parsing functions like PyArg_ParseTuple with integer converting format units like i will now use the __index__ special method instead of __int__ if available The deprecation warning will be emitted for objects with the __int__ method but without the __index__ method like Decimal and Fraction PyNumber_Check will now return 1 for objects implementing __index__ PyNumber_Long PyNumber_Float and PyFloat_AsDouble also now use the __index__ method if available Contributed by Serhiy Storchaka in bpo 36048 and bpo 20092 Heap allocated type objects will now increase their reference count in PyObject_Init and its parallel macro PyObject_INIT instead of in PyType_GenericAlloc Types that modify instance allocation or deallocation may need to be adjusted Contributed by Eddie Elizondo in bpo 35810 The new function PyCode_NewWithPosOnlyArgs allows to create code objects like PyCode_New but with an extra posonlyargcount parameter for indicating the number of positional only arguments Contributed by Pablo Galindo in bpo 37221 Py_SetPath now sets sys executable to the program full path Py_GetProgramFullPath rather than to the program name Py_GetProgramName Contributed by Victor Stinner in bpo 38234 Deprecated The distutils bdist_wininst command is now deprecated use bdist_wheel wheel packages instead Contributed by Victor Stinner in bpo 37481 Deprecated methods getchildren and getiterator in the ElementTree module now emit a DeprecationWarning instead of PendingDeprecationWarning They will be removed in Python 3 9 Contributed by Serhiy Storchaka in bpo 29209 Passing an object that is not an instance of concurrent futures ThreadPoolExecutor to loop set_default_executor is deprecated and will be prohibited in Python 3 9 Contributed by Elvis Pranskevichus in bpo 34075 The __getitem__ methods of xml dom pulldom DOMEventStream wsgiref util FileWrapper and fileinput FileInput have been deprecated Implementations of these methods have been ignoring their index parameter and returning the next item instead Contributed by Berker Peksag in bpo 9372 The typing NamedTuple class has deprecated the _field_types attribute in favor of the __annotations__ attribute which has the same information Contributed by Raymond Hettinger in bpo 36320 ast classes Num Str Bytes NameConstant and Ellipsis are considered deprecated and will be removed in future Python versions Constant should be used instead Contributed by Serhiy Storchaka in bpo 32892 ast NodeVisitor methods visit_Num visit_Str visit_Bytes visit_NameConstant and visit_Ellipsis are deprecated now and will not be called in future Python versions Add the visit_Constant method to handle all constant nodes Contributed by Serhiy Storchaka in bpo 36917 The asyncio coroutine decorator is deprecated and will be removed in version 3 10 Instead of asyncio coroutine use async def instead,en
1898, Contributed by Andrew Svetlov in bpo 36921 In asyncio the explicit passing of a loop argument has been deprecated and will be removed in version 3 10 for the following asyncio sleep asyncio gather asyncio shield asyncio wait_for asyncio wait asyncio as_completed asyncio Task asyncio Lock asyncio Event asyncio Condition asyncio Semaphore asyncio BoundedSemaphore asyncio Queue asyncio create_subprocess_exec and asyncio create_subprocess_shell The explicit passing of coroutine objects to asyncio wait has been deprecated and will be removed in version 3 11 Contributed by Yury Selivanov in bpo 34790 The following functions and methods are deprecated in the gettext module lgettext ldgettext lngettext and ldngettext They return encoded bytes and it s possible that you will get unexpected Unicode related exceptions if there are encoding problems with the translated strings It s much better to use alternatives which return Unicode strings in Python 3 These functions have been broken for a long time Function bind_textdomain_codeset methods output_charset and set_output_charset and the codeset parameter of functions translation and install are also deprecated since they are only used for the l gettext functions Contributed by Serhiy Storchaka in bpo 33710 The isAlive method of threading Thread has been deprecated Contributed by Donghee Na in bpo 35283 Many builtin and extension functions that take integer arguments will now emit a deprecation warning for Decimal s Fraction s and any other objects that can be converted to integers only with a loss e g that have the __int__ method but do not have the __index__ method In future version they will be errors Contributed by Serhiy Storchaka in bpo 36048 Deprecated passing the following arguments as keyword arguments func in functools partialmethod weakref finalize profile Profile runcall cProfile Profile runcall bdb Bdb runcall trace Trace runfunc and curses wrapper function in unittest TestCase addCleanup fn in the submit method of concurrent futures ThreadPoolExecutor and concurrent futures ProcessPoolExecutor callback in contextlib ExitStack callback contextlib AsyncExitStack callback and contextlib AsyncExitStack push_async_callback c and typeid in the create method of multiprocessing managers Server and multiprocessing managers SharedMemoryServer obj in weakref finalize In future releases of Python they will be positional only Contributed by Serhiy Storchaka in bpo 36492 API and Feature Removals The following features and APIs have been removed from Python 3 8 Starting with Python 3 3 importing ABCs from collections was deprecated and importing should be done from collections abc Being able to import from collections was marked for removal in 3 8 but has been delayed to 3 9 See bpo 36952 The macpath module deprecated in Python 3 7 has been removed Contributed by Victor Stinner in bpo 35471 The function platform popen has been removed after having been deprecated since Python 3 3 use os popen instead Contributed by Victor Stinner in bpo 35345 The function time clock has been removed after having been deprecated since Python 3 3 use time perf_counter or time process_time instead depending on your requirements to have well defined behavior Contributed by Matthias Bussonnier in bpo 36895 The pyvenv script has been removed in favor of python3 8 m venv to help eliminate confusion as to what Python interpreter the pyvenv script is tied to Contributed by Brett Cannon in bpo 25427 parse_qs parse_qsl and escape are removed from the cgi module They are deprecated in Python 3 2 or older They should be imported from the urllib parse and html modules instead filemode function is removed from the tarfile module It is not documented and deprecated since Python 3 3 The XMLParser constructor no longer accepts the html argument It never had an effect and was deprecated in Python 3 4 All other parameters are now keyword only Contributed by Serhiy Storchaka in bpo 29209 Removed the doctype method of XMLParser Contributed by Serhiy Storchaka in bpo 29209 unicode_internal codec is removed Contributed by I,en
1899,nada Naoki in bpo 36297 The Cache and Statement objects of the sqlite3 module are not exposed to the user Contributed by Aviv Palivoda in bpo 30262 The bufsize keyword argument of fileinput input and fileinput FileInput which was ignored and deprecated since Python 3 6 has been removed bpo 36952 Contributed by Matthias Bussonnier The functions sys set_coroutine_wrapper and sys get_coroutine_wrapper deprecated in Python 3 7 have been removed bpo 36933 Contributed by Matthias Bussonnier Porting to Python 3 8 This section lists previously described changes and other bugfixes that may require changes to your code Changes in Python behavior Yield expressions both yield and yield from clauses are now disallowed in comprehensions and generator expressions aside from the iterable expression in the leftmost for clause Contributed by Serhiy Storchaka in bpo 10544 The compiler now produces a SyntaxWarning when identity checks is and is not are used with certain types of literals e g strings numbers These can often work by accident in CPython but are not guaranteed by the language spec The warning advises users to use equality tests and instead Contributed by Serhiy Storchaka in bpo 34850 The CPython interpreter can swallow exceptions in some circumstances In Python 3 8 this happens in fewer cases In particular exceptions raised when getting the attribute from the type dictionary are no longer ignored Contributed by Serhiy Storchaka in bpo 35459 Removed __str__ implementations from builtin types bool int float complex and few classes from the standard library They now inherit __str__ from object As result defining the __repr__ method in the subclass of these classes will affect their string representation Contributed by Serhiy Storchaka in bpo 36793 On AIX sys platform doesn t contain the major version anymore It is always aix instead of aix3 aix7 Since older Python versions include the version number so it is recommended to always use sys platform startswith aix Contributed by M Felt in bpo 36588 PyEval_AcquireLock and PyEval_AcquireThread now terminate the current thread if called while the interpreter is finalizing making them consistent with PyEval_RestoreThread Py_END_ALLOW_THREADS and PyGILState_Ensure If this behavior is not desired guard the call by checking _Py_IsFinalizing or sys is_finalizing Contributed by Joannah Nanjekye in bpo 36475 Changes in the Python API The os getcwdb function now uses the UTF 8 encoding on Windows rather than the ANSI code page see PEP 529 for the rationale The function is no longer deprecated on Windows Contributed by Victor Stinner in bpo 37412 subprocess Popen can now use os posix_spawn in some cases for better performance On Windows Subsystem for Linux and QEMU User Emulation the Popen constructor using os posix_spawn no longer raises an exception on errors like missing program Instead the child process fails with a non zero returncode Contributed by Joannah Nanjekye and Victor Stinner in bpo 35537 The preexec_fn argument of subprocess Popen is no longer compatible with subinterpreters The use of the parameter in a subinterpreter now raises RuntimeError Contributed by Eric Snow in bpo 34651 modified by Christian Heimes in bpo 37951 The imap IMAP4 logout method no longer silently ignores arbitrary exceptions Contributed by Victor Stinner in bpo 36348 The function platform popen has been removed after having been deprecated since Python 3 3 use os popen instead Contributed by Victor Stinner in bpo 35345 The statistics mode function no longer raises an exception when given multimodal data Instead it returns the first mode encountered in the input data Contributed by Raymond Hettinger in bpo 35892 The selection method of the tkinter ttk Treeview class no longer takes arguments Using it with arguments for changing the selection was deprecated in Python 3 6 Use specialized methods like selection_set for changing the selection Contributed by Serhiy Storchaka in bpo 31508 The writexml toxml and toprettyxml methods of xml dom minidom and the write method of xml etree now preserve the attribute order ,en
1900,specified by the user Contributed by Diego Rojas and Raymond Hettinger in bpo 34160 A dbm dumb database opened with flags r is now read only dbm dumb open with flags r and w no longer creates a database if it does not exist Contributed by Serhiy Storchaka in bpo 32749 The doctype method defined in a subclass of XMLParser will no longer be called and will emit a RuntimeWarning instead of a DeprecationWarning Define the doctype method on a target for handling an XML doctype declaration Contributed by Serhiy Storchaka in bpo 29209 A RuntimeError is now raised when the custom metaclass doesn t provide the __classcell__ entry in the namespace passed to type __new__ A DeprecationWarning was emitted in Python 3 6 3 7 Contributed by Serhiy Storchaka in bpo 23722 The cProfile Profile class can now be used as a context manager Contributed by Scott Sanderson in bpo 29235 shutil copyfile shutil copy shutil copy2 shutil copytree and shutil move use platform specific fast copy syscalls see Platform dependent efficient copy operations section shutil copyfile default buffer size on Windows was changed from 16 KiB to 1 MiB The PyGC_Head struct has changed completely All code that touched the struct member should be rewritten See bpo 33597 The PyInterpreterState struct has been moved into the internal header files specifically Include internal pycore_pystate h An opaque PyInterpreterState is still available as part of the public API and stable ABI The docs indicate that none of the struct s fields are public so we hope no one has been using them However if you do rely on one or more of those private fields and have no alternative then please open a BPO issue We ll work on helping you adjust possibly including adding accessor functions to the public API See bpo 35886 The mmap flush method now returns None on success and raises an exception on error under all platforms Previously its behavior was platform dependent a nonzero value was returned on success zero was returned on error under Windows A zero value was returned on success an exception was raised on error under Unix Contributed by Berker Peksag in bpo 2122 xml dom minidom and xml sax modules no longer process external entities by default Contributed by Christian Heimes in bpo 17239 Deleting a key from a read only dbm database dbm dumb dbm gnu or dbm ndbm raises error dbm dumb error dbm gnu error or dbm ndbm error instead of KeyError Contributed by Xiang Zhang in bpo 33106 Simplified AST for literals All constants will be represented as ast Constant instances Instantiating old classes Num Str Bytes NameConstant and Ellipsis will return an instance of Constant Contributed by Serhiy Storchaka in bpo 32892 expanduser on Windows now prefers the USERPROFILE environment variable and does not use HOME which is not normally set for regular user accounts Contributed by Anthony Sottile in bpo 36264 The exception asyncio CancelledError now inherits from BaseException rather than Exception and no longer inherits from concurrent futures CancelledError Contributed by Yury Selivanov in bpo 32528 The function asyncio wait_for now correctly waits for cancellation when using an instance of asyncio Task Previously upon reaching timeout it was cancelled and immediately returned Contributed by Elvis Pranskevichus in bpo 32751 The function asyncio BaseTransport get_extra_info now returns a safe to use socket object when socket is passed to the name parameter Contributed by Yury Selivanov in bpo 37027 asyncio BufferedProtocol has graduated to the stable API DLL dependencies for extension modules and DLLs loaded with ctypes on Windows are now resolved more securely Only the system paths the directory containing the DLL or PYD file and directories added with add_dll_directory are searched for load time dependencies Specifically PATH and the current working directory are no longer used and modifications to these will no longer have any effect on normal DLL resolution If your application relies on these mechanisms you should check for add_dll_directory and if it exists use it to add your DLLs directory while l,en
1901,oading your library Note that Windows 7 users will need to ensure that Windows Update KB2533623 has been installed this is also verified by the installer Contributed by Steve Dower in bpo 36085 The header files and functions related to pgen have been removed after its replacement by a pure Python implementation Contributed by Pablo Galindo in bpo 36623 types CodeType has a new parameter in the second position of the constructor posonlyargcount to support positional only arguments defined in PEP 570 The first argument argcount now represents the total number of positional arguments including positional only arguments The new replace method of types CodeType can be used to make the code future proof The parameter digestmod for hmac new no longer uses the MD5 digest by default Changes in the C API The PyCompilerFlags structure got a new cf_feature_version field It should be initialized to PY_MINOR_VERSION The field is ignored by default and is used if and only if PyCF_ONLY_AST flag is set in cf_flags Contributed by Guido van Rossum in bpo 35766 The PyEval_ReInitThreads function has been removed from the C API It should not be called explicitly use PyOS_AfterFork_Child instead Contributed by Victor Stinner in bpo 36728 On Unix C extensions are no longer linked to libpython except on Android and Cygwin When Python is embedded libpython must not be loaded with RTLD_LOCAL but RTLD_GLOBAL instead Previously using RTLD_LOCAL it was already not possible to load C extensions which were not linked to libpython like C extensions of the standard library built by the shared section of Modules Setup Contributed by Victor Stinner in bpo 21536 Use of variants of formats in parsing or building value e g PyArg_ParseTuple Py_BuildValue PyObject_CallFunction etc without PY_SSIZE_T_CLEAN defined raises DeprecationWarning now It will be removed in 3 10 or 4 0 Read Parsing arguments and building values for detail Contributed by Inada Naoki in bpo 36381 Instances of heap allocated types such as those created with PyType_FromSpec hold a reference to their type object Increasing the reference count of these type objects has been moved from PyType_GenericAlloc to the more low level functions PyObject_Init and PyObject_INIT This makes types created through PyType_FromSpec behave like other classes in managed code Statically allocated types are not affected For the vast majority of cases there should be no side effect However types that manually increase the reference count after allocating an instance perhaps to work around the bug may now become immortal To avoid this these classes need to call Py_DECREF on the type object during instance deallocation To correctly port these types into 3 8 please apply the following changes Remove Py_INCREF on the type object after allocating an instance if any This may happen after calling PyObject_New PyObject_NewVar PyObject_GC_New PyObject_GC_NewVar or any other custom allocator that uses PyObject_Init or PyObject_INIT Example static foo_struct foo_new PyObject type foo_struct foo PyObject_GC_New foo_struct PyTypeObject type if foo NULL return NULL if PY_VERSION_HEX 0x03080000 Workaround for Python issue 35810 no longer necessary in Python 3 8 PY_INCREF type endif return foo Ensure that all custom tp_dealloc functions of heap allocated types decrease the type s reference count Example static void foo_dealloc foo_struct instance PyObject type Py_TYPE instance PyObject_GC_Del instance if PY_VERSION_HEX 0x03080000 This was not needed before Python 3 8 Python issue 35810 Py_DECREF type endif Contributed by Eddie Elizondo in bpo 35810 The Py_DEPRECATED macro has been implemented for MSVC The macro now must be placed before the symbol name Example Py_DEPRECATED 3 8 PyAPI_FUNC int Py_OldFunction void Contributed by Zackery Spytz in bpo 33407 The interpreter does not pretend to support binary compatibility of extension types across feature releases anymore A PyTypeObject exported by a third party extension module is supposed to have all the slots expected in the current Python version including tp_finalize Py_TPFLAGS_HA,en
1902,VE_FINALIZE is not checked anymore before reading tp_finalize Contributed by Antoine Pitrou in bpo 32388 The functions PyNode_AddChild and PyParser_AddToken now accept two additional int arguments end_lineno and end_col_offset The libpython38 a file to allow MinGW tools to link directly against python38 dll is no longer included in the regular Windows distribution If you require this file it may be generated with the gendef and dlltool tools which are part of the MinGW binutils package gendef python38 dll tmp def dlltool dllname python38 dll def tmp def output lib libpython38 a The location of an installed pythonXY dll will depend on the installation options and the version and language of Windows See Using Python on Windows for more information The resulting library should be placed in the same directory as pythonXY lib which is generally the libs directory under your Python installation Contributed by Steve Dower in bpo 37351 CPython bytecode changes The interpreter loop has been simplified by moving the logic of unrolling the stack of blocks into the compiler The compiler emits now explicit instructions for adjusting the stack of values and calling the cleaning up code for break continue and return Removed opcodes BREAK_LOOP CONTINUE_LOOP SETUP_LOOP and SETUP_EXCEPT Added new opcodes ROT_FOUR BEGIN_FINALLY CALL_FINALLY and POP_FINALLY Changed the behavior of END_FINALLY and WITH_CLEANUP_START Contributed by Mark Shannon Antoine Pitrou and Serhiy Storchaka in bpo 17611 Added new opcode END_ASYNC_FOR for handling exceptions raised when awaiting a next item in an async for loop Contributed by Serhiy Storchaka in bpo 33041 The MAP_ADD now expects the value as the first element in the stack and the key as the second element This change was made so the key is always evaluated before the value in dictionary comprehensions as proposed by PEP 572 Contributed by Jörn Heissler in bpo 35224 Demos and Tools Added a benchmark script for timing various ways to access variables Tools scripts var_access_benchmark py Contributed by Raymond Hettinger in bpo 35884 Here s a summary of performance improvements since Python 3 3 Python version 3 3 3 4 3 5 3 6 3 7 3 8 Variable and attribute read access read_local 4 0 7 1 7 1 5 4 5 1 3 9 read_nonlocal 5 3 7 1 8 1 5 8 5 4 4 4 read_global 13 3 15 5 19 0 14 3 13 6 7 6 read_builtin 20 0 21 1 21 6 18 5 19 0 7 5 read_classvar_from_class 20 5 25 6 26 5 20 7 19 5 18 4 read_classvar_from_instance 18 5 22 8 23 5 18 8 17 1 16 4 read_instancevar 26 8 32 4 33 1 28 0 26 3 25 4 read_instancevar_slots 23 7 27 8 31 3 20 8 20 8 20 2 read_namedtuple 68 5 73 8 57 5 45 0 46 8 18 4 read_boundmethod 29 8 37 6 37 9 29 6 26 9 27 7 Variable and attribute write access write_local 4 6 8 7 9 3 5 5 5 3 4 3 write_nonlocal 7 3 10 5 11 1 5 6 5 5 4 7 write_global 15 9 19 7 21 2 18 0 18 0 15 8 write_classvar 81 9 92 9 96 0 104 6 102 1 39 2 write_instancevar 36 4 44 6 45 8 40 0 38 9 35 5 write_instancevar_slots 28 7 35 6 36 1 27 3 26 6 25 7 Data structure read access read_list 19 2 24 2 24 5 20 8 20 8 19 0 read_deque 19 9 24 7 25 5 20 2 20 6 19 8 read_dict 19 7 24 3 25 7 22 3 23 0 21 0 read_strdict 17 9 22 6 24 3 19 5 21 2 18 9 Data structure write access write_list 21 2 27 1 28 5 22 5 21 6 20 0 write_deque 23 8 28 7 30 1 22 7 21 8 23 5 write_dict 25 9 31 4 33 3 29 3 29 2 24 7 write_strdict 22 9 28 4 29 9 27 5 25 2 23 1 Stack or queue operations list_append_pop 144 2 93 4 112 7 75 4 74 2 50 8 deque_append_pop 30 4 43 5 57 0 49 4 49 2 42 5 deque_append_popleft 30 8 43 7 57 3 49 7 49 7 42 8 Timing loop loop_overhead 0 3 0 5 0 6 0 4 0 3 0 3 The benchmarks were measured on an Intel Core i7 4960HQ processor running the macOS 64 bit builds found at python org The benchmark script displays timings in nanoseconds Notable changes in Python 3 8 1 Due to significant security concerns the reuse_address parameter of asyncio loop create_datagram_endpoint is no longer supported This is because of the behavior of the socket option SO_REUSEADDR in UDP For more details see the documentation for loop create_datagram_endpoint Contributed by Kyle St,en
1903,anley Antoine Pitrou and Yury Selivanov in bpo 37228 Notable changes in Python 3 8 2 Fixed a regression with the ignore callback of shutil copytree The argument types are now str and List str again Contributed by Manuel Barkhau and Giampaolo Rodola in gh 83571 Notable changes in Python 3 8 3 The constant values of future flags in the __future__ module are updated in order to prevent collision with compiler flags Previously PyCF_ALLOW_TOP_LEVEL_AWAIT was clashing with CO_FUTURE_DIVISION Contributed by Batuhan Taskaya in gh 83743 Notable changes in Python 3 8 8 Earlier Python versions allowed using both and as query parameter separators in urllib parse parse_qs and urllib parse parse_qsl Due to security concerns and to conform with newer W3C recommendations this has been changed to allow only a single separator key with as the default This change also affects cgi parse and cgi parse_multipart as they use the affected functions internally For more details please see their respective documentation Contributed by Adam Goldschmidt Senthil Kumaran and Ken Jin in bpo 42967 Notable changes in Python 3 8 9 A security fix alters the ftplib FTP behavior to not trust the IPv4 address sent from the remote server when setting up a passive data channel We reuse the ftp server IP address instead For unusual code requiring the old behavior set a trust_server_pasv_ipv4_address attribute on your FTP instance to True See gh 87451 Notable changes in Python 3 8 10 macOS 11 0 Big Sur and Apple Silicon Mac support As of 3 8 10 Python now supports building and running on macOS 11 Big Sur and on Apple Silicon Macs based on the ARM64 architecture A new universal build variant universal2 is now available to natively support both ARM64 and Intel 64 in one set of executables Note that support for weaklinking building binaries targeted for newer versions of macOS that will also run correctly on older versions by testing at runtime for missing features is not included in this backport from Python 3 9 to support a range of macOS versions continue to target for and build on the oldest version in the range Originally contributed by Ronald Oussoren and Lawrence D Anna in gh 85272 with fixes by FX Coudert and Eli Rykoff and backported to 3 8 by Maxime Bélanger and Ned Deily Notable changes in Python 3 8 10 urllib parse The presence of newline or tab characters in parts of a URL allows for some forms of attacks Following the WHATWG specification that updates RFC 3986 ASCII newline n r and tab t characters are stripped from the URL by the parser in urllib parse preventing such attacks The removal characters are controlled by a new module level variable urllib parse _UNSAFE_URL_BYTES_TO_REMOVE See bpo 43882 Notable changes in Python 3 8 12 Changes in the Python API Starting with Python 3 8 12 the ipaddress module no longer accepts any leading zeros in IPv4 address strings Leading zeros are ambiguous and interpreted as octal notation by some libraries For example the legacy function socket inet_aton treats leading zeros as octal notation glibc implementation of modern inet_pton does not accept any leading zeros Originally contributed by Christian Heimes in bpo 36384 and backported to 3 8 by Achraf Merzouki Notable security feature in 3 8 14 Converting between int and str in bases other than 2 binary 4 8 octal 16 hexadecimal or 32 such as base 10 decimal now raises a ValueError if the number of digits in string form is above a limit to avoid potential denial of service attacks due to the algorithmic complexity This is a mitigation for CVE 2020 10735 This limit can be configured or disabled by environment variable command line flag or sys APIs See the integer string conversion length limitation documentation The default limit is 4300 digits in string form Notable changes in 3 8 17 tarfile The extraction methods in tarfile and shutil unpack_archive have a new a filter argument that allows limiting tar features than may be surprising or dangerous such as creating files outside the destination directory See Extraction filters for details In Python 3 12 use without th,en
1904,e filter argument will show a DeprecationWarning In Python 3 14 the default will switch to data Contributed by Petr Viktorin in PEP 706,en
1905,codeop Compile Python code Source code Lib codeop py The codeop module provides utilities upon which the Python read eval print loop can be emulated as is done in the code module As a result you probably don t want to use the module directly if you want to include such a loop in your program you probably want to use the code module instead There are two parts to this job 1 Being able to tell if a line of input completes a Python statement in short telling whether to print or next 2 Remembering which future statements the user has entered so subsequent input can be compiled with these in effect The codeop module provides a way of doing each of these things and a way of doing them both To do just the former codeop compile_command source filename input symbol single Tries to compile source which should be a string of Python code and return a code object if source is valid Python code In that case the filename attribute of the code object will be filename which defaults to input Returns None if source is not valid Python code but is a prefix of valid Python code If there is a problem with source an exception will be raised SyntaxError is raised if there is invalid Python syntax and OverflowError or ValueError if there is an invalid literal The symbol argument determines whether source is compiled as a statement single the default as a sequence of statement exec or as an expression eval Any other value will cause ValueError to be raised Note It is possible but not likely that the parser stops parsing with a successful outcome before reaching the end of the source in this case trailing symbols may be ignored instead of causing an error For example a backslash followed by two newlines may be followed by arbitrary garbage This will be fixed once the API for the parser is better class codeop Compile Instances of this class have __call__ methods identical in signature to the built in function compile but with the difference that if the instance compiles program text containing a __future__ statement the instance remembers and compiles all subsequent program texts with the statement in force class codeop CommandCompiler Instances of this class have __call__ methods identical in signature to compile_command the difference is that if the instance compiles program text containing a __future__ statement the instance remembers and compiles all subsequent program texts with the statement in force,en
1906,Graphical User Interfaces with Tk Tk Tcl has long been an integral part of Python It provides a robust and platform independent windowing toolkit that is available to Python programmers using the tkinter package and its extension the tkinter tix and the tkinter ttk modules The tkinter package is a thin object oriented layer on top of Tcl Tk To use tkinter you don t need to write Tcl code but you will need to consult the Tk documentation and occasionally the Tcl documentation tkinter is a set of wrappers that implement the Tk widgets as Python classes tkinter s chief virtues are that it is fast and that it usually comes bundled with Python Although its standard documentation is weak good material is available which includes references tutorials a book and others tkinter is also famous for having an outdated look and feel which has been vastly improved in Tk 8 5 Nevertheless there are many other GUI libraries that you could be interested in The Python wiki lists several alternative GUI frameworks and tools tkinter Python interface to Tcl Tk Architecture Tkinter Modules Tkinter Life Preserver A Hello World Program Important Tk Concepts Understanding How Tkinter Wraps Tcl Tk How do I What option does Navigating the Tcl Tk Reference Manual Threading model Handy Reference Setting Options The Packer Packer Options Coupling Widget Variables The Window Manager Tk Option Data Types Bindings and Events The index Parameter Images File Handlers tkinter colorchooser Color choosing dialog tkinter font Tkinter font wrapper Tkinter Dialogs tkinter simpledialog Standard Tkinter input dialogs tkinter filedialog File selection dialogs Native Load Save Dialogs tkinter commondialog Dialog window templates tkinter messagebox Tkinter message prompts tkinter scrolledtext Scrolled Text Widget tkinter dnd Drag and drop support tkinter ttk Tk themed widgets Using Ttk Ttk Widgets Widget Standard Options Scrollable Widget Options Label Options Compatibility Options Widget States ttk Widget Combobox Options Virtual events ttk Combobox Spinbox Options Virtual events ttk Spinbox Notebook Options Tab Options Tab Identifiers Virtual Events ttk Notebook Progressbar Options ttk Progressbar Separator Options Sizegrip Platform specific notes Bugs Treeview Options Item Options Tag Options Column Identifiers Virtual Events ttk Treeview Ttk Styling Layouts tkinter tix Extension widgets for Tk Using Tix Tix Widgets Basic Widgets File Selectors Hierarchical ListBox Tabular ListBox Manager Widgets Image Types Miscellaneous Widgets Form Geometry Manager Tix Commands IDLE Menus File menu Shell and Editor Edit menu Shell and Editor Format menu Editor window only Run menu Editor window only Shell menu Shell window only Debug menu Shell window only Options menu Shell and Editor Window menu Shell and Editor Help menu Shell and Editor Context menus Editing and Navigation Editor windows Key bindings Automatic indentation Search and Replace Completions Calltips Code Context Shell window Text colors Startup and Code Execution Command line usage Startup failure Running user code User output in Shell Developing tkinter applications Running without a subprocess Help and Preferences Help sources Setting preferences IDLE on macOS Extensions idlelib,en
1907,reprlib Alternate repr implementation Source code Lib reprlib py The reprlib module provides a means for producing object representations with limits on the size of the resulting strings This is used in the Python debugger and may be useful in other contexts as well This module provides a class an instance and a function class reprlib Repr maxlevel 6 maxtuple 6 maxlist 6 maxarray 5 maxdict 4 maxset 6 maxfrozenset 6 maxdeque 6 maxstring 30 maxlong 40 maxother 30 fillvalue indent None Class which provides formatting services useful in implementing functions similar to the built in repr size limits for different object types are added to avoid the generation of representations which are excessively long The keyword arguments of the constructor can be used as a shortcut to set the attributes of the Repr instance Which means that the following initialization aRepr reprlib Repr maxlevel 3 Is equivalent to aRepr reprlib Repr aRepr maxlevel 3 See section Repr Objects for more information about Repr attributes Changed in version 3 12 Allow attributes to be set via keyword arguments reprlib aRepr This is an instance of Repr which is used to provide the repr function described below Changing the attributes of this object will affect the size limits used by repr and the Python debugger reprlib repr obj This is the repr method of aRepr It returns a string similar to that returned by the built in function of the same name but with limits on most sizes In addition to size limiting tools the module also provides a decorator for detecting recursive calls to __repr__ and substituting a placeholder string instead reprlib recursive_repr fillvalue Decorator for __repr__ methods to detect recursive calls within the same thread If a recursive call is made the fillvalue is returned otherwise the usual __repr__ call is made For example from reprlib import recursive_repr class MyList list recursive_repr def __repr__ self return join map repr self m MyList abc m append m m append x print m a b c x New in version 3 2 Repr Objects Repr instances provide several attributes which can be used to provide size limits for the representations of different object types and methods which format specific object types Repr fillvalue This string is displayed for recursive references It defaults to New in version 3 11 Repr maxlevel Depth limit on the creation of recursive representations The default is 6 Repr maxdict Repr maxlist Repr maxtuple Repr maxset Repr maxfrozenset Repr maxdeque Repr maxarray Limits on the number of entries represented for the named object type The default is 4 for maxdict 5 for maxarray and 6 for the others Repr maxlong Maximum number of characters in the representation for an integer Digits are dropped from the middle The default is 40 Repr maxstring Limit on the number of characters in the representation of the string Note that the normal representation of the string is used as the character source if escape sequences are needed in the representation these may be mangled when the representation is shortened The default is 30 Repr maxother This limit is used to control the size of object types for which no specific formatting method is available on the Repr object It is applied in a similar manner as maxstring The default is 20 Repr indent If this attribute is set to None the default the output is formatted with no line breaks or indentation like the standard repr For example example 1 spam a 2 b spam eggs c 3 4 5 6 ham import reprlib aRepr reprlib Repr print aRepr repr example 1 spam a 2 b spam eggs c 3 4 5 6 ham If indent is set to a string each recursion level is placed on its own line indented by that string aRepr indent print aRepr repr example 1 spam a 2 b spam eggs c 3 4 5 6 ham Setting indent to a positive integer value behaves as if it was set to a string with that number of spaces aRepr indent 4 print aRepr repr example 1 spam a 2 b spam eggs c 3 4 5 6 ham New in version 3 12 Repr repr obj The equivalent to the built in repr that uses the formatting imposed by the instance Repr repr1 obj level Recursive implementation used by,en
1908, repr This uses the type of obj to determine which formatting method to call passing it obj and level The type specific methods should call repr1 to perform recursive formatting with level 1 for the value of level in the recursive call Repr repr_TYPE obj level Formatting methods for specific types are implemented as methods with a name based on the type name In the method name TYPE is replaced by _ join type obj __name__ split Dispatch to these methods is handled by repr1 Type specific methods which need to recursively format a value should call self repr1 subobj level 1 Subclassing Repr Objects The use of dynamic dispatching by Repr repr1 allows subclasses of Repr to add support for additional built in object types or to modify the handling of types already supported This example shows how special support for file objects could be added import reprlib import sys class MyRepr reprlib Repr def repr_TextIOWrapper self obj level if obj name in stdin stdout stderr return obj name return repr obj aRepr MyRepr print aRepr repr sys stdin prints stdin stdin,en
1909,email An email and MIME handling package Source code Lib email __init__ py The email package is a library for managing email messages It is specifically not designed to do any sending of email messages to SMTP RFC 2821 NNTP or other servers those are functions of modules such as smtplib and nntplib The email package attempts to be as RFC compliant as possible supporting RFC 5322 and RFC 6532 as well as such MIME related RFCs as RFC 2045 RFC 2046 RFC 2047 RFC 2183 and RFC 2231 The overall structure of the email package can be divided into three major components plus a fourth component that controls the behavior of the other components The central component of the package is an object model that represents email messages An application interacts with the package primarily through the object model interface defined in the message sub module The application can use this API to ask questions about an existing email to construct a new email or to add or remove email subcomponents that themselves use the same object model interface That is following the nature of email messages and their MIME subcomponents the email object model is a tree structure of objects that all provide the EmailMessage API The other two major components of the package are the parser and the generator The parser takes the serialized version of an email message a stream of bytes and converts it into a tree of EmailMessage objects The generator takes an EmailMessage and turns it back into a serialized byte stream The parser and generator also handle streams of text characters but this usage is discouraged as it is too easy to end up with messages that are not valid in one way or another The control component is the policy module Every EmailMessage every generator and every parser has an associated policy object that controls its behavior Usually an application only needs to specify the policy when an EmailMessage is created either by directly instantiating an EmailMessage to create a new email or by parsing an input stream using a parser But the policy can be changed when the message is serialized using a generator This allows for example a generic email message to be parsed from disk but to serialize it using standard SMTP settings when sending it to an email server The email package does its best to hide the details of the various governing RFCs from the application Conceptually the application should be able to treat the email message as a structured tree of unicode text and binary attachments without having to worry about how these are represented when serialized In practice however it is often necessary to be aware of at least some of the rules governing MIME messages and their structure specifically the names and nature of the MIME content types and how they identify multipart documents For the most part this knowledge should only be required for more complex applications and even then it should only be the high level structure in question and not the details of how those structures are represented Since MIME content types are used widely in modern internet software not just email this will be a familiar concept to many programmers The following sections describe the functionality of the email package We start with the message object model which is the primary interface an application will use and follow that with the parser and generator components Then we cover the policy controls which completes the treatment of the main components of the library The next three sections cover the exceptions the package may raise and the defects non compliance with the RFCs that the parser may detect Then we cover the headerregistry and the contentmanager sub components which provide tools for doing more detailed manipulation of headers and payloads respectively Both of these components contain features relevant to consuming and producing non trivial messages but also document their extensibility APIs which will be of interest to advanced applications Following those is a set of examples of using the fundamental parts of the APIs covered in the preceding sections Th,en
1910,e foregoing represent the modern unicode friendly API of the email package The remaining sections starting with the Message class cover the legacy compat32 API that deals much more directly with the details of how email messages are represented The compat32 API does not hide the details of the RFCs from the application but for applications that need to operate at that level they can be useful tools This documentation is also relevant for applications that are still using the compat32 API for backward compatibility reasons Changed in version 3 6 Docs reorganized and rewritten to promote the new EmailMessage EmailPolicy API Contents of the email package documentation email message Representing an email message email parser Parsing email messages FeedParser API Parser API Additional notes email generator Generating MIME documents email policy Policy Objects email errors Exception and Defect classes email headerregistry Custom Header Objects email contentmanager Managing MIME Content Content Manager Instances email Examples Legacy API email message Message Representing an email message using the compat32 API email mime Creating email and MIME objects from scratch email header Internationalized headers email charset Representing character sets email encoders Encoders email utils Miscellaneous utilities email iterators Iterators See also Module smtplib SMTP Simple Mail Transport Protocol client Module poplib POP Post Office Protocol client Module imaplib IMAP Internet Message Access Protocol client Module nntplib NNTP Net News Transport Protocol client Module mailbox Tools for creating reading and managing collections of messages on disk using a variety standard formats,en
1911,unittest mock getting started New in version 3 3 Using Mock Mock Patching Methods Common uses for Mock objects include Patching methods Recording method calls on objects You might want to replace a method on an object to check that it is called with the correct arguments by another part of the system real SomeClass real method MagicMock name method real method 3 4 5 key value MagicMock name method id Once our mock has been used real method in this example it has methods and attributes that allow you to make assertions about how it has been used Note In most of these examples the Mock and MagicMock classes are interchangeable As the MagicMock is the more capable class it makes a sensible one to use by default Once the mock has been called its called attribute is set to True More importantly we can use the assert_called_with or assert_called_once_with method to check that it was called with the correct arguments This example tests that calling ProductionClass method results in a call to the something method class ProductionClass def method self self something 1 2 3 def something self a b c pass real ProductionClass real something MagicMock real method real something assert_called_once_with 1 2 3 Mock for Method Calls on an Object In the last example we patched a method directly on an object to check that it was called correctly Another common use case is to pass an object into a method or some part of the system under test and then check that it is used in the correct way The simple ProductionClass below has a closer method If it is called with an object then it calls close on it class ProductionClass def closer self something something close So to test it we need to pass in an object with a close method and check that it was called correctly real ProductionClass mock Mock real closer mock mock close assert_called_with We don t have to do any work to provide the close method on our mock Accessing close creates it So if close hasn t already been called then accessing it in the test will create it but assert_called_with will raise a failure exception Mocking Classes A common use case is to mock out classes instantiated by your code under test When you patch a class then that class is replaced with a mock Instances are created by calling the class This means you access the mock instance by looking at the return value of the mocked class In the example below we have a function some_function that instantiates Foo and calls a method on it The call to patch replaces the class Foo with a mock The Foo instance is the result of calling the mock so it is configured by modifying the mock return_value def some_function instance module Foo return instance method with patch module Foo as mock instance mock return_value instance method return_value the result result some_function assert result the result Naming your mocks It can be useful to give your mocks a name The name is shown in the repr of the mock and can be helpful when the mock appears in test failure messages The name is also propagated to attributes or methods of the mock mock MagicMock name foo mock MagicMock name foo id mock method MagicMock name foo method id Tracking all Calls Often you want to track more than a single call to a method The mock_calls attribute records all calls to child attributes of the mock and also to their children mock MagicMock mock method MagicMock name mock method id mock attribute method 10 x 53 MagicMock name mock attribute method id mock mock_calls call method call attribute method 10 x 53 If you make an assertion about mock_calls and any unexpected methods have been called then the assertion will fail This is useful because as well as asserting that the calls you expected have been made you are also checking that they were made in the right order and with no additional calls You use the call object to construct lists for comparing with mock_calls expected call method call attribute method 10 x 53 mock mock_calls expected True However parameters to calls that return mocks are not recorded which means it is not possible to track nested calls wher,en
1912,e the parameters used to create ancestors are important m Mock m factory important True deliver Mock name mock factory deliver id m mock_calls 1 call factory important False deliver True Setting Return Values and Attributes Setting the return values on a mock object is trivially easy mock Mock mock return_value 3 mock 3 Of course you can do the same for methods on the mock mock Mock mock method return_value 3 mock method 3 The return value can also be set in the constructor mock Mock return_value 3 mock 3 If you need an attribute setting on your mock just do it mock Mock mock x 3 mock x 3 Sometimes you want to mock up a more complex situation like for example mock connection cursor execute SELECT 1 If we wanted this call to return a list then we have to configure the result of the nested call We can use call to construct the set of calls in a chained call like this for easy assertion afterwards mock Mock cursor mock connection cursor return_value cursor execute return_value foo mock connection cursor execute SELECT 1 foo expected call connection cursor execute SELECT 1 call_list mock mock_calls call connection cursor call connection cursor execute SELECT 1 mock mock_calls expected True It is the call to call_list that turns our call object into a list of calls representing the chained calls Raising exceptions with mocks A useful attribute is side_effect If you set this to an exception class or instance then the exception will be raised when the mock is called mock Mock side_effect Exception Boom mock Traceback most recent call last Exception Boom Side effect functions and iterables side_effect can also be set to a function or an iterable The use case for side_effect as an iterable is where your mock is going to be called several times and you want each call to return a different value When you set side_effect to an iterable every call to the mock returns the next value from the iterable mock MagicMock side_effect 4 5 6 mock 4 mock 5 mock 6 For more advanced use cases like dynamically varying the return values depending on what the mock is called with side_effect can be a function The function will be called with the same arguments as the mock Whatever the function returns is what the call returns vals 1 2 1 2 3 2 def side_effect args return vals args mock MagicMock side_effect side_effect mock 1 2 1 mock 2 3 2 Mocking asynchronous iterators Since Python 3 8 AsyncMock and MagicMock have support to mock Asynchronous Iterators through __aiter__ The return_value attribute of __aiter__ can be used to set the return values to be used for iteration mock MagicMock AsyncMock also works here mock __aiter__ return_value 1 2 3 async def main return i async for i in mock asyncio run main 1 2 3 Mocking asynchronous context manager Since Python 3 8 AsyncMock and MagicMock have support to mock Asynchronous Context Managers through __aenter__ and __aexit__ By default __aenter__ and __aexit__ are AsyncMock instances that return an async function class AsyncContextManager async def __aenter__ self return self async def __aexit__ self exc_type exc tb pass mock_instance MagicMock AsyncContextManager AsyncMock also works here async def main async with mock_instance as result pass asyncio run main mock_instance __aenter__ assert_awaited_once mock_instance __aexit__ assert_awaited_once Creating a Mock from an Existing Object One problem with over use of mocking is that it couples your tests to the implementation of your mocks rather than your real code Suppose you have a class that implements some_method In a test for another class you provide a mock of this object that also provides some_method If later you refactor the first class so that it no longer has some_method then your tests will continue to pass even though your code is now broken Mock allows you to provide an object as a specification for the mock using the spec keyword argument Accessing methods attributes on the mock that don t exist on your specification object will immediately raise an attribute error If you change the implementation of your specification then tests that use tha,en
1913,t class will start failing immediately without you having to instantiate the class in those tests mock Mock spec SomeClass mock old_method Traceback most recent call last AttributeError object has no attribute old_method Using a specification also enables a smarter matching of calls made to the mock regardless of whether some parameters were passed as positional or named arguments def f a b c pass mock Mock spec f mock 1 2 3 Mock name mock id 140161580456576 mock assert_called_with a 1 b 2 c 3 If you want this smarter matching to also work with method calls on the mock you can use auto speccing If you want a stronger form of specification that prevents the setting of arbitrary attributes as well as the getting of them then you can use spec_set instead of spec Using side_effect to return per file content mock_open is used to patch open method side_effect can be used to return a new Mock object per call This can be used to return different contents per file stored in a dictionary DEFAULT default data_dict file1 data1 file2 data2 def open_side_effect name return mock_open read_data data_dict get name DEFAULT with patch builtins open side_effect open_side_effect with open file1 as file1 assert file1 read data1 with open file2 as file2 assert file2 read data2 with open file3 as file2 assert file2 read default Patch Decorators Note With patch it matters that you patch objects in the namespace where they are looked up This is normally straightforward but for a quick guide read where to patch A common need in tests is to patch a class attribute or a module attribute for example patching a builtin or patching a class in a module to test that it is instantiated Modules and classes are effectively global so patching on them has to be undone after the test or the patch will persist into other tests and cause hard to diagnose problems mock provides three convenient decorators for this patch patch object and patch dict patch takes a single string of the form package module Class attribute to specify the attribute you are patching It also optionally takes a value that you want the attribute or class or whatever to be replaced with patch object takes an object and the name of the attribute you would like patched plus optionally the value to patch it with patch object original SomeClass attribute patch object SomeClass attribute sentinel attribute def test assert SomeClass attribute sentinel attribute test assert SomeClass attribute original patch package module attribute sentinel attribute def test from package module import attribute assert attribute is sentinel attribute test If you are patching a module including builtins then use patch instead of patch object mock MagicMock return_value sentinel file_handle with patch builtins open mock handle open filename r mock assert_called_with filename r assert handle sentinel file_handle incorrect file handle returned The module name can be dotted in the form package module if needed patch package module ClassName attribute sentinel attribute def test from package module import ClassName assert ClassName attribute sentinel attribute test A nice pattern is to actually decorate test methods themselves class MyTest unittest TestCase patch object SomeClass attribute sentinel attribute def test_something self self assertEqual SomeClass attribute sentinel attribute original SomeClass attribute MyTest test_something test_something assert SomeClass attribute original If you want to patch with a Mock you can use patch with only one argument or patch object with two arguments The mock will be created for you and passed into the test function method class MyTest unittest TestCase patch object SomeClass static_method def test_something self mock_method SomeClass static_method mock_method assert_called_with MyTest test_something test_something You can stack up multiple patch decorators using this pattern class MyTest unittest TestCase patch package module ClassName1 patch package module ClassName2 def test_something self MockClass2 MockClass1 self assertIs package module ClassName1 MockClass1 self assertI,en
1914,s package module ClassName2 MockClass2 MyTest test_something test_something When you nest patch decorators the mocks are passed in to the decorated function in the same order they applied the normal Python order that decorators are applied This means from the bottom up so in the example above the mock for test_module ClassName2 is passed in first There is also patch dict for setting values in a dictionary just during a scope and restoring the dictionary to its original state when the test ends foo key value original foo copy with patch dict foo newkey newvalue clear True assert foo newkey newvalue assert foo original patch patch object and patch dict can all be used as context managers Where you use patch to create a mock for you you can get a reference to the mock using the as form of the with statement class ProductionClass def method self pass with patch object ProductionClass method as mock_method mock_method return_value None real ProductionClass real method 1 2 3 mock_method assert_called_with 1 2 3 As an alternative patch patch object and patch dict can be used as class decorators When used in this way it is the same as applying the decorator individually to every method whose name starts with test Further Examples Here are some more examples for some slightly more advanced scenarios Mocking chained calls Mocking chained calls is actually straightforward with mock once you understand the return_value attribute When a mock is called for the first time or you fetch its return_value before it has been called a new Mock is created This means that you can see how the object returned from a call to a mocked object has been used by interrogating the return_value mock mock Mock mock foo a 2 b 3 Mock name mock foo id mock return_value foo assert_called_with a 2 b 3 From here it is a simple step to configure and then make assertions about chained calls Of course another alternative is writing your code in a more testable way in the first place So suppose we have some code that looks a little bit like this class Something def __init__ self self backend BackendProvider def method self response self backend get_endpoint foobar create_call spam eggs start_call more code Assuming that BackendProvider is already well tested how do we test method Specifically we want to test that the code section more code uses the response object in the correct way As this chain of calls is made from an instance attribute we can monkey patch the backend attribute on a Something instance In this particular case we are only interested in the return value from the final call to start_call so we don t have much configuration to do Let s assume the object it returns is file like so we ll ensure that our response object uses the builtin open as its spec To do this we create a mock instance as our mock backend and create a mock response object for it To set the response as the return value for that final start_call we could do this mock_backend get_endpoint return_value create_call return_value start_call return_value mock_response We can do that in a slightly nicer way using the configure_mock method to directly set the return value for us something Something mock_response Mock spec open mock_backend Mock config get_endpoint return_value create_call return_value start_call return_value mock_response mock_backend configure_mock config With these we monkey patch the mock backend in place and can make the real call something backend mock_backend something method Using mock_calls we can check the chained call with a single assert A chained call is several calls in one line of code so there will be several entries in mock_calls We can use call call_list to create this list of calls for us chained call get_endpoint foobar create_call spam eggs start_call call_list chained call_list assert mock_backend mock_calls call_list Partial mocking In some tests I wanted to mock out a call to datetime date today to return a known date but I didn t want to prevent the code under test from creating new date objects Unfortunately datetime date is written in C and so I cou,en
1915,ldn t just monkey patch out the static datetime date today method I found a simple way of doing this that involved effectively wrapping the date class with a mock but passing through calls to the constructor to the real class and returning real instances The patch decorator is used here to mock out the date class in the module under test The side_effect attribute on the mock date class is then set to a lambda function that returns a real date When the mock date class is called a real date will be constructed and returned by side_effect from datetime import date with patch mymodule date as mock_date mock_date today return_value date 2010 10 8 mock_date side_effect lambda args kw date args kw assert mymodule date today date 2010 10 8 assert mymodule date 2009 6 8 date 2009 6 8 Note that we don t patch datetime date globally we patch date in the module that uses it See where to patch When date today is called a known date is returned but calls to the date constructor still return normal dates Without this you can find yourself having to calculate an expected result using exactly the same algorithm as the code under test which is a classic testing anti pattern Calls to the date constructor are recorded in the mock_date attributes call_count and friends which may also be useful for your tests An alternative way of dealing with mocking dates or other builtin classes is discussed in this blog entry Mocking a Generator Method A Python generator is a function or method that uses the yield statement to return a series of values when iterated over 1 A generator method function is called to return the generator object It is the generator object that is then iterated over The protocol method for iteration is __iter__ so we can mock this using a MagicMock Here s an example class with an iter method implemented as a generator class Foo def iter self for i in 1 2 3 yield i foo Foo list foo iter 1 2 3 How would we mock this class and in particular its iter method To configure the values returned from the iteration implicit in the call to list we need to configure the object returned by the call to foo iter mock_foo MagicMock mock_foo iter return_value iter 1 2 3 list mock_foo iter 1 2 3 1 There are also generator expressions and more advanced uses of generators but we aren t concerned about them here A very good introduction to generators and how powerful they are is Generator Tricks for Systems Programmers Applying the same patch to every test method If you want several patches in place for multiple test methods the obvious way is to apply the patch decorators to every method This can feel like unnecessary repetition Instead you can use patch in all its various forms as a class decorator This applies the patches to all test methods on the class A test method is identified by methods whose names start with test patch mymodule SomeClass class MyTest unittest TestCase def test_one self MockSomeClass self assertIs mymodule SomeClass MockSomeClass def test_two self MockSomeClass self assertIs mymodule SomeClass MockSomeClass def not_a_test self return something MyTest test_one test_one MyTest test_two test_two MyTest test_two not_a_test something An alternative way of managing patches is to use the patch methods start and stop These allow you to move the patching into your setUp and tearDown methods class MyTest unittest TestCase def setUp self self patcher patch mymodule foo self mock_foo self patcher start def test_foo self self assertIs mymodule foo self mock_foo def tearDown self self patcher stop MyTest test_foo run If you use this technique you must ensure that the patching is undone by calling stop This can be fiddlier than you might think because if an exception is raised in the setUp then tearDown is not called unittest TestCase addCleanup makes this easier class MyTest unittest TestCase def setUp self patcher patch mymodule foo self addCleanup patcher stop self mock_foo patcher start def test_foo self self assertIs mymodule foo self mock_foo MyTest test_foo run Mocking Unbound Methods Whilst writing tests today I needed to patch an,en
1916, unbound method patching the method on the class rather than on the instance I needed self to be passed in as the first argument because I want to make asserts about which objects were calling this particular method The issue is that you can t patch with a mock for this because if you replace an unbound method with a mock it doesn t become a bound method when fetched from the instance and so it doesn t get self passed in The workaround is to patch the unbound method with a real function instead The patch decorator makes it so simple to patch out methods with a mock that having to create a real function becomes a nuisance If you pass autospec True to patch then it does the patching with a real function object This function object has the same signature as the one it is replacing but delegates to a mock under the hood You still get your mock auto created in exactly the same way as before What it means though is that if you use it to patch out an unbound method on a class the mocked function will be turned into a bound method if it is fetched from an instance It will have self passed in as the first argument which is exactly what I wanted class Foo def foo self pass with patch object Foo foo autospec True as mock_foo mock_foo return_value foo foo Foo foo foo foo mock_foo assert_called_once_with foo If we don t use autospec True then the unbound method is patched out with a Mock instance instead and isn t called with self Checking multiple calls with mock mock has a nice API for making assertions about how your mock objects are used mock Mock mock foo_bar return_value None mock foo_bar baz spam eggs mock foo_bar assert_called_with baz spam eggs If your mock is only being called once you can use the assert_called_once_with method that also asserts that the call_count is one mock foo_bar assert_called_once_with baz spam eggs mock foo_bar mock foo_bar assert_called_once_with baz spam eggs Traceback most recent call last AssertionError Expected to be called once Called 2 times Both assert_called_with and assert_called_once_with make assertions about the most recent call If your mock is going to be called several times and you want to make assertions about all those calls you can use call_args_list mock Mock return_value None mock 1 2 3 mock 4 5 6 mock mock call_args_list call 1 2 3 call 4 5 6 call The call helper makes it easy to make assertions about these calls You can build up a list of expected calls and compare it to call_args_list This looks remarkably similar to the repr of the call_args_list expected call 1 2 3 call 4 5 6 call mock call_args_list expected True Coping with mutable arguments Another situation is rare but can bite you is when your mock is called with mutable arguments call_args and call_args_list store references to the arguments If the arguments are mutated by the code under test then you can no longer make assertions about what the values were when the mock was called Here s some example code that shows the problem Imagine the following functions defined in mymodule def frob val pass def grob val First frob and then clear val frob val val clear When we try to test that grob calls frob with the correct argument look what happens with patch mymodule frob as mock_frob val 6 mymodule grob val val set mock_frob assert_called_with 6 Traceback most recent call last AssertionError Expected 6 Called with set One possibility would be for mock to copy the arguments you pass in This could then cause problems if you do assertions that rely on object identity for equality Here s one solution that uses the side_effect functionality If you provide a side_effect function for a mock then side_effect will be called with the same args as the mock This gives us an opportunity to copy the arguments and store them for later assertions In this example I m using another mock to store the arguments so that I can use the mock methods for doing the assertion Again a helper function sets this up for me from copy import deepcopy from unittest mock import Mock patch DEFAULT def copy_call_args mock new_mock Mock def side_effect args kwa,en
1917,rgs args deepcopy args kwargs deepcopy kwargs new_mock args kwargs return DEFAULT mock side_effect side_effect return new_mock with patch mymodule frob as mock_frob new_mock copy_call_args mock_frob val 6 mymodule grob val new_mock assert_called_with 6 new_mock call_args call 6 copy_call_args is called with the mock that will be called It returns a new mock that we do the assertion on The side_effect function makes a copy of the args and calls our new_mock with the copy Note If your mock is only going to be used once there is an easier way of checking arguments at the point they are called You can simply do the checking inside a side_effect function def side_effect arg assert arg 6 mock Mock side_effect side_effect mock 6 mock set Traceback most recent call last AssertionError An alternative approach is to create a subclass of Mock or MagicMock that copies using copy deepcopy the arguments Here s an example implementation from copy import deepcopy class CopyingMock MagicMock def __call__ self args kwargs args deepcopy args kwargs deepcopy kwargs return super __call__ args kwargs c CopyingMock return_value None arg set c arg arg add 1 c assert_called_with set c assert_called_with arg Traceback most recent call last AssertionError Expected call mock 1 Actual call mock set c foo CopyingMock name mock foo id When you subclass Mock or MagicMock all dynamically created attributes and the return_value will use your subclass automatically That means all children of a CopyingMock will also have the type CopyingMock Nesting Patches Using patch as a context manager is nice but if you do multiple patches you can end up with nested with statements indenting further and further to the right class MyTest unittest TestCase def test_foo self with patch mymodule Foo as mock_foo with patch mymodule Bar as mock_bar with patch mymodule Spam as mock_spam assert mymodule Foo is mock_foo assert mymodule Bar is mock_bar assert mymodule Spam is mock_spam original mymodule Foo MyTest test_foo test_foo assert mymodule Foo is original With unittest cleanup functions and the patch methods start and stop we can achieve the same effect without the nested indentation A simple helper method create_patch puts the patch in place and returns the created mock for us class MyTest unittest TestCase def create_patch self name patcher patch name thing patcher start self addCleanup patcher stop return thing def test_foo self mock_foo self create_patch mymodule Foo mock_bar self create_patch mymodule Bar mock_spam self create_patch mymodule Spam assert mymodule Foo is mock_foo assert mymodule Bar is mock_bar assert mymodule Spam is mock_spam original mymodule Foo MyTest test_foo run assert mymodule Foo is original Mocking a dictionary with MagicMock You may want to mock a dictionary or other container object recording all access to it whilst having it still behave like a dictionary We can do this with MagicMock which will behave like a dictionary and using side_effect to delegate dictionary access to a real underlying dictionary that is under our control When the __getitem__ and __setitem__ methods of our MagicMock are called normal dictionary access then side_effect is called with the key and in the case of __setitem__ the value too We can also control what is returned After the MagicMock has been used we can use attributes like call_args_list to assert about how the dictionary was used my_dict a 1 b 2 c 3 def getitem name return my_dict name def setitem name val my_dict name val mock MagicMock mock __getitem__ side_effect getitem mock __setitem__ side_effect setitem Note An alternative to using MagicMock is to use Mock and only provide the magic methods you specifically want mock Mock mock __getitem__ Mock side_effect getitem mock __setitem__ Mock side_effect setitem A third option is to use MagicMock but passing in dict as the spec or spec_set argument so that the MagicMock created only has dictionary magic methods available mock MagicMock spec_set dict mock __getitem__ side_effect getitem mock __setitem__ side_effect setitem With these side effect functions in,en
1918, place the mock will behave like a normal dictionary but recording the access It even raises a KeyError if you try to access a key that doesn t exist mock a 1 mock c 3 mock d Traceback most recent call last KeyError d mock b fish mock d eggs mock b fish mock d eggs After it has been used you can make assertions about the access using the normal mock methods and attributes mock __getitem__ call_args_list call a call c call d call b call d mock __setitem__ call_args_list call b fish call d eggs my_dict a 1 b fish c 3 d eggs Mock subclasses and their attributes There are various reasons why you might want to subclass Mock One reason might be to add helper methods Here s a silly example class MyMock MagicMock def has_been_called self return self called mymock MyMock return_value None mymock MyMock id mymock has_been_called False mymock mymock has_been_called True The standard behaviour for Mock instances is that attributes and the return value mocks are of the same type as the mock they are accessed on This ensures that Mock attributes are Mocks and MagicMock attributes are MagicMocks 2 So if you re subclassing to add helper methods then they ll also be available on the attributes and return value mock of instances of your subclass mymock foo MyMock name mock foo id mymock foo has_been_called False mymock foo MyMock name mock foo id mymock foo has_been_called True Sometimes this is inconvenient For example one user is subclassing mock to created a Twisted adaptor Having this applied to attributes too actually causes errors Mock in all its flavours uses a method called _get_child_mock to create these sub mocks for attributes and return values You can prevent your subclass being used for attributes by overriding this method The signature is that it takes arbitrary keyword arguments kwargs which are then passed onto the mock constructor class Subclass MagicMock def _get_child_mock self kwargs return MagicMock kwargs mymock Subclass mymock foo MagicMock name mock foo id assert isinstance mymock Subclass assert not isinstance mymock foo Subclass assert not isinstance mymock Subclass 2 An exception to this rule are the non callable mocks Attributes use the callable variant because otherwise non callable mocks couldn t have callable methods Mocking imports with patch dict One situation where mocking can be hard is where you have a local import inside a function These are harder to mock because they aren t using an object from the module namespace that we can patch out Generally local imports are to be avoided They are sometimes done to prevent circular dependencies for which there is usually a much better way to solve the problem refactor the code or to prevent up front costs by delaying the import This can also be solved in better ways than an unconditional local import store the module as a class or module attribute and only do the import on first use That aside there is a way to use mock to affect the results of an import Importing fetches an object from the sys modules dictionary Note that it fetches an object which need not be a module Importing a module for the first time results in a module object being put in sys modules so usually when you import something you get a module back This need not be the case however This means you can use patch dict to temporarily put a mock in place in sys modules Any imports whilst this patch is active will fetch the mock When the patch is complete the decorated function exits the with statement body is complete or patcher stop is called then whatever was there previously will be restored safely Here s an example that mocks out the fooble module import sys mock Mock with patch dict sys modules fooble mock import fooble fooble blob Mock name mock blob id assert fooble not in sys modules mock blob assert_called_once_with As you can see the import fooble succeeds but on exit there is no fooble left in sys modules This also works for the from module import name form mock Mock with patch dict sys modules fooble mock from fooble import blob blob blip Mock name mock blob blip id mock blob blip asser,en
1919,t_called_once_with With slightly more work you can also mock package imports mock Mock modules package mock package module mock module with patch dict sys modules modules from package module import fooble fooble Mock name mock module fooble id mock module fooble assert_called_once_with Tracking order of calls and less verbose call assertions The Mock class allows you to track the order of method calls on your mock objects through the method_calls attribute This doesn t allow you to track the order of calls between separate mock objects however we can use mock_calls to achieve the same effect Because mocks track calls to child mocks in mock_calls and accessing an arbitrary attribute of a mock creates a child mock we can create our separate mocks from a parent one Calls to those child mock will then all be recorded in order in the mock_calls of the parent manager Mock mock_foo manager foo mock_bar manager bar mock_foo something Mock name mock foo something id mock_bar other thing Mock name mock bar other thing id manager mock_calls call foo something call bar other thing We can then assert about the calls including the order by comparing with the mock_calls attribute on the manager mock expected_calls call foo something call bar other thing manager mock_calls expected_calls True If patch is creating and putting in place your mocks then you can attach them to a manager mock using the attach_mock method After attaching calls will be recorded in mock_calls of the manager manager MagicMock with patch mymodule Class1 as MockClass1 with patch mymodule Class2 as MockClass2 manager attach_mock MockClass1 MockClass1 manager attach_mock MockClass2 MockClass2 MockClass1 foo MockClass2 bar MagicMock name mock MockClass1 foo id MagicMock name mock MockClass2 bar id manager mock_calls call MockClass1 call MockClass1 foo call MockClass2 call MockClass2 bar If many calls have been made but you re only interested in a particular sequence of them then an alternative is to use the assert_has_calls method This takes a list of calls constructed with the call object If that sequence of calls are in mock_calls then the assert succeeds m MagicMock m foo bar baz MagicMock name mock foo bar baz id m one two three MagicMock name mock one two three id calls call one two three call_list m assert_has_calls calls Even though the chained call m one two three aren t the only calls that have been made to the mock the assert still succeeds Sometimes a mock may have several calls made to it and you are only interested in asserting about some of those calls You may not even care about the order In this case you can pass any_order True to assert_has_calls m MagicMock m 1 m two 2 3 m seven 7 m fifty 50 calls call fifty 50 call 1 call seven 7 m assert_has_calls calls any_order True More complex argument matching Using the same basic concept as ANY we can implement matchers to do more complex assertions on objects used as arguments to mocks Suppose we expect some object to be passed to a mock that by default compares equal based on object identity which is the Python default for user defined classes To use assert_called_with we would need to pass in the exact same object If we are only interested in some of the attributes of this object then we can create a matcher that will check these attributes for us You can see in this example how a standard call to assert_called_with isn t sufficient class Foo def __init__ self a b self a self b a b mock Mock return_value None mock Foo 1 2 mock assert_called_with Foo 1 2 Traceback most recent call last AssertionError Expected call __main__ Foo object at 0x Actual call call __main__ Foo object at 0x A comparison function for our Foo class might look something like this def compare self other if not type self type other return False if self a other a return False if self b other b return False return True And a matcher object that can use comparison functions like this for its equality operation would look something like this class Matcher def __init__ self compare some_obj self compare compare self some_obj some_obj def __eq,en
1920,__ self other return self compare self some_obj other Putting all this together match_foo Matcher compare Foo 1 2 mock assert_called_with match_foo The Matcher is instantiated with our compare function and the Foo object we want to compare against In assert_called_with the Matcher equality method will be called which compares the object the mock was called with against the one we created our matcher with If they match then assert_called_with passes and if they don t an AssertionError is raised match_wrong Matcher compare Foo 3 4 mock assert_called_with match_wrong Traceback most recent call last AssertionError Expected Matcher object at 0x Called with Foo object at 0x With a bit of tweaking you could have the comparison function raise the AssertionError directly and provide a more useful failure message As of version 1 5 the Python testing library PyHamcrest provides similar functionality that may be useful here in the form of its equality matcher hamcrest library integration match_equality,en
1921,Graphic User Interface FAQ General GUI Questions What GUI toolkits exist for Python Standard builds of Python include an object oriented interface to the Tcl Tk widget set called tkinter This is probably the easiest to install since it comes included with most binary distributions of Python and use For more info about Tk including pointers to the source see the Tcl Tk home page Tcl Tk is fully portable to the macOS Windows and Unix platforms Depending on what platform s you are aiming at there are also several alternatives A list of cross platform and platform specific GUI frameworks can be found on the python wiki Tkinter questions How do I freeze Tkinter applications Freeze is a tool to create stand alone applications When freezing Tkinter applications the applications will not be truly stand alone as the application will still need the Tcl and Tk libraries One solution is to ship the application with the Tcl and Tk libraries and point to them at run time using the TCL_LIBRARY and TK_LIBRARY environment variables To get truly stand alone applications the Tcl scripts that form the library have to be integrated into the application as well One tool supporting that is SAM stand alone modules which is part of the Tix distribution https tix sourceforge net Build Tix with SAM enabled perform the appropriate call to Tclsam_init etc inside Python s Modules tkappinit c and link with libtclsam and libtksam you might include the Tix libraries as well Can I have Tk events handled while waiting for I O On platforms other than Windows yes and you don t even need threads But you ll have to restructure your I O code a bit Tk has the equivalent of Xt s XtAddInput call which allows you to register a callback function which will be called from the Tk mainloop when I O is possible on a file descriptor See File Handlers I can t get key bindings to work in Tkinter why An often heard complaint is that event handlers bound to events with the bind method don t get handled even when the appropriate key is pressed The most common cause is that the widget to which the binding applies doesn t have keyboard focus Check out the Tk documentation for the focus command Usually a widget is given the keyboard focus by clicking in it but not for labels see the takefocus option,en
1922,bdb Debugger framework Source code Lib bdb py The bdb module handles basic debugger functions like setting breakpoints or managing execution via the debugger The following exception is defined exception bdb BdbQuit Exception raised by the Bdb class for quitting the debugger The bdb module also defines two classes class bdb Breakpoint self file line temporary False cond None funcname None This class implements temporary breakpoints ignore counts disabling and re enabling and conditionals Breakpoints are indexed by number through a list called bpbynumber and by file line pairs through bplist The former points to a single instance of class Breakpoint The latter points to a list of such instances since there may be more than one breakpoint per line When creating a breakpoint its associated file name should be in canonical form If a funcname is defined a breakpoint hit will be counted when the first line of that function is executed A conditional breakpoint always counts a hit Breakpoint instances have the following methods deleteMe Delete the breakpoint from the list associated to a file line If it is the last breakpoint in that position it also deletes the entry for the file line enable Mark the breakpoint as enabled disable Mark the breakpoint as disabled bpformat Return a string with all the information about the breakpoint nicely formatted Breakpoint number Temporary status del or keep File line position Break condition Number of times to ignore Number of times hit New in version 3 2 bpprint out None Print the output of bpformat to the file out or if it is None to standard output Breakpoint instances have the following attributes file File name of the Breakpoint line Line number of the Breakpoint within file temporary True if a Breakpoint at file line is temporary cond Condition for evaluating a Breakpoint at file line funcname Function name that defines whether a Breakpoint is hit upon entering the function enabled True if Breakpoint is enabled bpbynumber Numeric index for a single instance of a Breakpoint bplist Dictionary of Breakpoint instances indexed by file line tuples ignore Number of times to ignore a Breakpoint hits Count of the number of times a Breakpoint has been hit class bdb Bdb skip None The Bdb class acts as a generic Python debugger base class This class takes care of the details of the trace facility a derived class should implement user interaction The standard debugger class pdb Pdb is an example The skip argument if given must be an iterable of glob style module name patterns The debugger will not step into frames that originate in a module that matches one of these patterns Whether a frame is considered to originate in a certain module is determined by the __name__ in the frame globals Changed in version 3 1 Added the skip parameter The following methods of Bdb normally don t need to be overridden canonic filename Return canonical form of filename For real file names the canonical form is an operating system dependent case normalized absolute path A filename with angle brackets such as stdin generated in interactive mode is returned unchanged reset Set the botframe stopframe returnframe and quitting attributes with values ready to start debugging trace_dispatch frame event arg This function is installed as the trace function of debugged frames Its return value is the new trace function in most cases that is itself The default implementation decides how to dispatch a frame depending on the type of event passed as a string that is about to be executed event can be one of the following line A new line of code is going to be executed call A function is about to be called or another code block entered return A function or other code block is about to return exception An exception has occurred c_call A C function is about to be called c_return A C function has returned c_exception A C function has raised an exception For the Python events specialized functions see below are called For the C events no action is taken The arg parameter depends on the previous event See the documentation for sys settrace fo,en
1923,r more information on the trace function For more information on code and frame objects refer to The standard type hierarchy dispatch_line frame If the debugger should stop on the current line invoke the user_line method which should be overridden in subclasses Raise a BdbQuit exception if the quitting flag is set which can be set from user_line Return a reference to the trace_dispatch method for further tracing in that scope dispatch_call frame arg If the debugger should stop on this function call invoke the user_call method which should be overridden in subclasses Raise a BdbQuit exception if the quitting flag is set which can be set from user_call Return a reference to the trace_dispatch method for further tracing in that scope dispatch_return frame arg If the debugger should stop on this function return invoke the user_return method which should be overridden in subclasses Raise a BdbQuit exception if the quitting flag is set which can be set from user_return Return a reference to the trace_dispatch method for further tracing in that scope dispatch_exception frame arg If the debugger should stop at this exception invokes the user_exception method which should be overridden in subclasses Raise a BdbQuit exception if the quitting flag is set which can be set from user_exception Return a reference to the trace_dispatch method for further tracing in that scope Normally derived classes don t override the following methods but they may if they want to redefine the definition of stopping and breakpoints is_skipped_line module_name Return True if module_name matches any skip pattern stop_here frame Return True if frame is below the starting frame in the stack break_here frame Return True if there is an effective breakpoint for this line Check whether a line or function breakpoint exists and is in effect Delete temporary breakpoints based on information from effective break_anywhere frame Return True if any breakpoint exists for frame s filename Derived classes should override these methods to gain control over debugger operation user_call frame argument_list Called from dispatch_call if a break might stop inside the called function user_line frame Called from dispatch_line when either stop_here or break_here returns True user_return frame return_value Called from dispatch_return when stop_here returns True user_exception frame exc_info Called from dispatch_exception when stop_here returns True do_clear arg Handle how a breakpoint must be removed when it is a temporary one This method must be implemented by derived classes Derived classes and clients can call the following methods to affect the stepping state set_step Stop after one line of code set_next frame Stop on the next line in or below the given frame set_return frame Stop when returning from the given frame set_until frame lineno None Stop when the line with the lineno greater than the current one is reached or when returning from current frame set_trace frame Start debugging from frame If frame is not specified debugging starts from caller s frame set_continue Stop only at breakpoints or when finished If there are no breakpoints set the system trace function to None set_quit Set the quitting attribute to True This raises BdbQuit in the next call to one of the dispatch_ methods Derived classes and clients can call the following methods to manipulate breakpoints These methods return a string containing an error message if something went wrong or None if all is well set_break filename lineno temporary False cond None funcname None Set a new breakpoint If the lineno line doesn t exist for the filename passed as argument return an error message The filename should be in canonical form as described in the canonic method clear_break filename lineno Delete the breakpoints in filename and lineno If none were set return an error message clear_bpbynumber arg Delete the breakpoint which has the index arg in the Breakpoint bpbynumber If arg is not numeric or out of range return an error message clear_all_file_breaks filename Delete all breakpoints in filename If none were set re,en
1924,turn an error message clear_all_breaks Delete all existing breakpoints If none were set return an error message get_bpbynumber arg Return a breakpoint specified by the given number If arg is a string it will be converted to a number If arg is a non numeric string if the given breakpoint never existed or has been deleted a ValueError is raised New in version 3 2 get_break filename lineno Return True if there is a breakpoint for lineno in filename get_breaks filename lineno Return all breakpoints for lineno in filename or an empty list if none are set get_file_breaks filename Return all breakpoints in filename or an empty list if none are set get_all_breaks Return all breakpoints that are set Derived classes and clients can call the following methods to get a data structure representing a stack trace get_stack f t Return a list of frame lineno tuples in a stack trace and a size The most recently called frame is last in the list The size is the number of frames below the frame where the debugger was invoked format_stack_entry frame_lineno lprefix Return a string with information about a stack entry which is a frame lineno tuple The return string contains The canonical filename which contains the frame The function name or lambda The input arguments The return value The line of code if it exists The following two methods can be called by clients to use a debugger to debug a statement given as a string run cmd globals None locals None Debug a statement executed via the exec function globals defaults to __main__ __dict__ locals defaults to globals runeval expr globals None locals None Debug an expression executed via the eval function globals and locals have the same meaning as in run runctx cmd globals locals For backwards compatibility Calls the run method runcall func args kwds Debug a single function call and return its result Finally the module defines the following functions bdb checkfuncname b frame Return True if we should break here depending on the way the Breakpoint b was set If it was set via line number it checks if b line is the same as the one in frame If the breakpoint was set via function name we have to check we are in the right frame the right function and if we are on its first executable line bdb effective file line frame Return active breakpoint delete temporary flag or None None as the breakpoint to act upon The active breakpoint is the first entry in bplist for the file line which must exist that is enabled for which checkfuncname is True and that has neither a False condition nor positive ignore count The flag meaning that a temporary breakpoint should be deleted is False only when the cond cannot be evaluated in which case ignore count is ignored If no such entry exists then None None is returned bdb set_trace Start debugging with a Bdb instance from caller s frame,en
1925,heapq Heap queue algorithm Source code Lib heapq py This module provides an implementation of the heap queue algorithm also known as the priority queue algorithm Heaps are binary trees for which every parent node has a value less than or equal to any of its children This implementation uses arrays for which heap k heap 2 k 1 and heap k heap 2 k 2 for all k counting elements from zero For the sake of comparison non existing elements are considered to be infinite The interesting property of a heap is that its smallest element is always the root heap 0 The API below differs from textbook heap algorithms in two aspects a We use zero based indexing This makes the relationship between the index for a node and the indexes for its children slightly less obvious but is more suitable since Python uses zero based indexing b Our pop method returns the smallest item not the largest called a min heap in textbooks a max heap is more common in texts because of its suitability for in place sorting These two make it possible to view the heap as a regular Python list without surprises heap 0 is the smallest item and heap sort maintains the heap invariant To create a heap use a list initialized to or you can transform a populated list into a heap via function heapify The following functions are provided heapq heappush heap item Push the value item onto the heap maintaining the heap invariant heapq heappop heap Pop and return the smallest item from the heap maintaining the heap invariant If the heap is empty IndexError is raised To access the smallest item without popping it use heap 0 heapq heappushpop heap item Push item on the heap then pop and return the smallest item from the heap The combined action runs more efficiently than heappush followed by a separate call to heappop heapq heapify x Transform list x into a heap in place in linear time heapq heapreplace heap item Pop and return the smallest item from the heap and also push the new item The heap size doesn t change If the heap is empty IndexError is raised This one step operation is more efficient than a heappop followed by heappush and can be more appropriate when using a fixed size heap The pop push combination always returns an element from the heap and replaces it with item The value returned may be larger than the item added If that isn t desired consider using heappushpop instead Its push pop combination returns the smaller of the two values leaving the larger value on the heap The module also offers three general purpose functions based on heaps heapq merge iterables key None reverse False Merge multiple sorted inputs into a single sorted output for example merge timestamped entries from multiple log files Returns an iterator over the sorted values Similar to sorted itertools chain iterables but returns an iterable does not pull the data into memory all at once and assumes that each of the input streams is already sorted smallest to largest Has two optional arguments which must be specified as keyword arguments key specifies a key function of one argument that is used to extract a comparison key from each input element The default value is None compare the elements directly reverse is a boolean value If set to True then the input elements are merged as if each comparison were reversed To achieve behavior similar to sorted itertools chain iterables reverse True all iterables must be sorted from largest to smallest Changed in version 3 5 Added the optional key and reverse parameters heapq nlargest n iterable key None Return a list with the n largest elements from the dataset defined by iterable key if provided specifies a function of one argument that is used to extract a comparison key from each element in iterable for example key str lower Equivalent to sorted iterable key key reverse True n heapq nsmallest n iterable key None Return a list with the n smallest elements from the dataset defined by iterable key if provided specifies a function of one argument that is used to extract a comparison key from each element in iterable for example key str lower Equivalent to sorted i,en
1926,terable key key n The latter two functions perform best for smaller values of n For larger values it is more efficient to use the sorted function Also when n 1 it is more efficient to use the built in min and max functions If repeated usage of these functions is required consider turning the iterable into an actual heap Basic Examples A heapsort can be implemented by pushing all values onto a heap and then popping off the smallest values one at a time def heapsort iterable h for value in iterable heappush h value return heappop h for i in range len h heapsort 1 3 5 7 9 2 4 6 8 0 0 1 2 3 4 5 6 7 8 9 This is similar to sorted iterable but unlike sorted this implementation is not stable Heap elements can be tuples This is useful for assigning comparison values such as task priorities alongside the main record being tracked h heappush h 5 write code heappush h 7 release product heappush h 1 write spec heappush h 3 create tests heappop h 1 write spec Priority Queue Implementation Notes A priority queue is common use for a heap and it presents several implementation challenges Sort stability how do you get two tasks with equal priorities to be returned in the order they were originally added Tuple comparison breaks for priority task pairs if the priorities are equal and the tasks do not have a default comparison order If the priority of a task changes how do you move it to a new position in the heap Or if a pending task needs to be deleted how do you find it and remove it from the queue A solution to the first two challenges is to store entries as 3 element list including the priority an entry count and the task The entry count serves as a tie breaker so that two tasks with the same priority are returned in the order they were added And since no two entry counts are the same the tuple comparison will never attempt to directly compare two tasks Another solution to the problem of non comparable tasks is to create a wrapper class that ignores the task item and only compares the priority field from dataclasses import dataclass field from typing import Any dataclass order True class PrioritizedItem priority int item Any field compare False The remaining challenges revolve around finding a pending task and making changes to its priority or removing it entirely Finding a task can be done with a dictionary pointing to an entry in the queue Removing the entry or changing its priority is more difficult because it would break the heap structure invariants So a possible solution is to mark the entry as removed and add a new entry with the revised priority pq list of entries arranged in a heap entry_finder mapping of tasks to entries REMOVED removed task placeholder for a removed task counter itertools count unique sequence count def add_task task priority 0 Add a new task or update the priority of an existing task if task in entry_finder remove_task task count next counter entry priority count task entry_finder task entry heappush pq entry def remove_task task Mark an existing task as REMOVED Raise KeyError if not found entry entry_finder pop task entry 1 REMOVED def pop_task Remove and return the lowest priority task Raise KeyError if empty while pq priority count task heappop pq if task is not REMOVED del entry_finder task return task raise KeyError pop from an empty priority queue Theory Heaps are arrays for which a k a 2 k 1 and a k a 2 k 2 for all k counting elements from 0 For the sake of comparison non existing elements are considered to be infinite The interesting property of a heap is that a 0 is always its smallest element The strange invariant above is meant to be an efficient memory representation for a tournament The numbers below are k not a k 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 In the tree above each cell k is topping 2 k 1 and 2 k 2 In a usual binary tournament we see in sports each cell is the winner over the two cells it tops and we can trace the winner down the tree to see all opponents s he had However in many computer applications of such tournaments we do not need to tra,en
1927,ce the history of a winner To be more memory efficient when a winner is promoted we try to replace it by something else at a lower level and the rule becomes that a cell and the two cells it tops contain three different items but the top cell wins over the two topped cells If this heap invariant is protected at all time index 0 is clearly the overall winner The simplest algorithmic way to remove it and find the next winner is to move some loser let s say cell 30 in the diagram above into the 0 position and then percolate this new 0 down the tree exchanging values until the invariant is re established This is clearly logarithmic on the total number of items in the tree By iterating over all items you get an O n log n sort A nice feature of this sort is that you can efficiently insert new items while the sort is going on provided that the inserted items are not better than the last 0 th element you extracted This is especially useful in simulation contexts where the tree holds all incoming events and the win condition means the smallest scheduled time When an event schedules other events for execution they are scheduled into the future so they can easily go into the heap So a heap is a good structure for implementing schedulers this is what I used for my MIDI sequencer Various structures for implementing schedulers have been extensively studied and heaps are good for this as they are reasonably speedy the speed is almost constant and the worst case is not much different than the average case However there are other representations which are more efficient overall yet the worst cases might be terrible Heaps are also very useful in big disk sorts You most probably all know that a big sort implies producing runs which are pre sorted sequences whose size is usually related to the amount of CPU memory followed by a merging passes for these runs which merging is often very cleverly organised 1 It is very important that the initial sort produces the longest runs possible Tournaments are a good way to achieve that If using all the memory available to hold a tournament you replace and percolate items that happen to fit the current run you ll produce runs which are twice the size of the memory for random input and much better for input fuzzily ordered Moreover if you output the 0 th item on disk and get an input which may not fit in the current tournament because the value wins over the last output value it cannot fit in the heap so the size of the heap decreases The freed memory could be cleverly reused immediately for progressively building a second heap which grows at exactly the same rate the first heap is melting When the first heap completely vanishes you switch heaps and start a new run Clever and quite effective In a word heaps are useful memory structures to know I use them in a few applications and I think it is good to keep a heap module around Footnotes 1 The disk balancing algorithms which are current nowadays are more annoying than clever and this is a consequence of the seeking capabilities of the disks On devices which cannot seek like big tape drives the story was quite different and one had to be very clever to ensure far in advance that each tape movement will be the most effective possible that is will best participate at progressing the merge Some tapes were even able to read backwards and this was also used to avoid the rewinding time Believe me real good tape sorts were quite spectacular to watch From all times sorting has always been a Great Art,en
1928,Instrumenting CPython with DTrace and SystemTap author David Malcolm author Łukasz Langa DTrace and SystemTap are monitoring tools each providing a way to inspect what the processes on a computer system are doing They both use domain specific languages allowing a user to write scripts which filter which processes are to be observed gather data from the processes of interest generate reports on the data As of Python 3 6 CPython can be built with embedded markers also known as probes that can be observed by a DTrace or SystemTap script making it easier to monitor what the CPython processes on a system are doing CPython implementation detail DTrace markers are implementation details of the CPython interpreter No guarantees are made about probe compatibility between versions of CPython DTrace scripts can stop working or work incorrectly without warning when changing CPython versions Enabling the static markers macOS comes with built in support for DTrace On Linux in order to build CPython with the embedded markers for SystemTap the SystemTap development tools must be installed On a Linux machine this can be done via yum install systemtap sdt devel or sudo apt get install systemtap sdt dev CPython must then be configured with the with dtrace option checking for with dtrace yes On macOS you can list available DTrace probes by running a Python process in the background and listing all probes made available by the Python provider python3 6 q sudo dtrace l P python or dtrace l m python3 6 ID PROVIDER MODULE FUNCTION NAME 29564 python18035 python3 6 _PyEval_EvalFrameDefault function entry 29565 python18035 python3 6 dtrace_function_entry function entry 29566 python18035 python3 6 _PyEval_EvalFrameDefault function return 29567 python18035 python3 6 dtrace_function_return function return 29568 python18035 python3 6 collect gc done 29569 python18035 python3 6 collect gc start 29570 python18035 python3 6 _PyEval_EvalFrameDefault line 29571 python18035 python3 6 maybe_dtrace_line line On Linux you can verify if the SystemTap static markers are present in the built binary by seeing if it contains a note stapsdt section readelf S python grep note stapsdt 30 note stapsdt NOTE 0000000000000000 00308d78 If you ve built Python as a shared library with the enable shared configure option you need to look instead within the shared library For example readelf S libpython3 3dm so 1 0 grep note stapsdt 29 note stapsdt NOTE 0000000000000000 00365b68 Sufficiently modern readelf can print the metadata readelf n python Displaying notes found at file offset 0x00000254 with length 0x00000020 Owner Data size Description GNU 0x00000010 NT_GNU_ABI_TAG ABI version tag OS Linux ABI 2 6 32 Displaying notes found at file offset 0x00000274 with length 0x00000024 Owner Data size Description GNU 0x00000014 NT_GNU_BUILD_ID unique build ID bitstring Build ID df924a2b08a7e89f6e11251d4602022977af2670 Displaying notes found at file offset 0x002d6c30 with length 0x00000144 Owner Data size Description stapsdt 0x00000031 NT_STAPSDT SystemTap probe descriptors Provider python Name gc__start Location 0x00000000004371c3 Base 0x0000000000630ce2 Semaphore 0x00000000008d6bf6 Arguments 4 ebx stapsdt 0x00000030 NT_STAPSDT SystemTap probe descriptors Provider python Name gc__done Location 0x00000000004374e1 Base 0x0000000000630ce2 Semaphore 0x00000000008d6bf8 Arguments 8 rax stapsdt 0x00000045 NT_STAPSDT SystemTap probe descriptors Provider python Name function__entry Location 0x000000000053db6c Base 0x0000000000630ce2 Semaphore 0x00000000008d6be8 Arguments 8 rbp 8 r12 4 eax stapsdt 0x00000046 NT_STAPSDT SystemTap probe descriptors Provider python Name function__return Location 0x000000000053dba8 Base 0x0000000000630ce2 Semaphore 0x00000000008d6bea Arguments 8 rbp 8 r12 4 eax The above metadata contains information for SystemTap describing how it can patch strategically placed machine code instructions to enable the tracing hooks used by a SystemTap script Static DTrace probes The following example DTrace script can be used to show the call return hierarchy of a Python script onl,en
1929,y tracing within the invocation of a function called start In other words import time function invocations are not going to be listed self int indent python target function entry copyinstr arg1 start self trace 1 python target function entry self trace printf d t s timestamp 15 probename printf s self indent printf s s d n basename copyinstr arg0 copyinstr arg1 arg2 self indent python target function return self trace self indent printf d t s timestamp 15 probename printf s self indent printf s s d n basename copyinstr arg0 copyinstr arg1 arg2 python target function return copyinstr arg1 start self trace 0 It can be invoked like this sudo dtrace q s call_stack d c python3 6 script py The output looks like this 156641360502280 function entry call_stack py start 23 156641360518804 function entry call_stack py function_1 1 156641360532797 function entry call_stack py function_3 9 156641360546807 function return call_stack py function_3 10 156641360563367 function return call_stack py function_1 2 156641360578365 function entry call_stack py function_2 5 156641360591757 function entry call_stack py function_1 1 156641360605556 function entry call_stack py function_3 9 156641360617482 function return call_stack py function_3 10 156641360629814 function return call_stack py function_1 2 156641360642285 function return call_stack py function_2 6 156641360656770 function entry call_stack py function_3 9 156641360669707 function return call_stack py function_3 10 156641360687853 function entry call_stack py function_4 13 156641360700719 function return call_stack py function_4 14 156641360719640 function entry call_stack py function_5 18 156641360732567 function return call_stack py function_5 21 156641360747370 function return call_stack py start 28 Static SystemTap markers The low level way to use the SystemTap integration is to use the static markers directly This requires you to explicitly state the binary file containing them For example this SystemTap script can be used to show the call return hierarchy of a Python script probe process python mark function__entry filename user_string arg1 funcname user_string arg2 lineno arg3 printf s s in s d n thread_indent 1 funcname filename lineno probe process python mark function__return filename user_string arg1 funcname user_string arg2 lineno arg3 printf s s in s d n thread_indent 1 funcname filename lineno It can be invoked like this stap show call hierarchy stp c python test py The output looks like this 11408 python 8274 __contains__ in Lib _abcoll py 362 11414 python 8274 __getitem__ in Lib os py 425 11418 python 8274 encode in Lib os py 490 11424 python 8274 encode in Lib os py 493 11428 python 8274 __getitem__ in Lib os py 426 11433 python 8274 __contains__ in Lib _abcoll py 366 where the columns are time in microseconds since start of script name of executable PID of process and the remainder indicates the call return hierarchy as the script executes For a enable shared build of CPython the markers are contained within the libpython shared library and the probe s dotted path needs to reflect this For example this line from the above example probe process python mark function__entry should instead read probe process python library libpython3 6dm so 1 0 mark function__entry assuming a debug build of CPython 3 6 Available static markers function__entry str filename str funcname int lineno This marker indicates that execution of a Python function has begun It is only triggered for pure Python bytecode functions The filename function name and line number are provided back to the tracing script as positional arguments which must be accessed using arg1 arg2 arg3 arg1 const char filename accessible using user_string arg1 arg2 const char function name accessible using user_string arg2 arg3 int line number function__return str filename str funcname int lineno This marker is the converse of function__entry and indicates that execution of a Python function has ended either via return or via an exception It is only triggered for pure Python bytecode functions The arguments are the same ,en
1930,as for function__entry line str filename str funcname int lineno This marker indicates a Python line is about to be executed It is the equivalent of line by line tracing with a Python profiler It is not triggered within C functions The arguments are the same as for function__entry gc__start int generation Fires when the Python interpreter starts a garbage collection cycle arg0 is the generation to scan like gc collect gc__done long collected Fires when the Python interpreter finishes a garbage collection cycle arg0 is the number of collected objects import__find__load__start str modulename Fires before importlib attempts to find and load the module arg0 is the module name New in version 3 7 import__find__load__done str modulename int found Fires after importlib s find_and_load function is called arg0 is the module name arg1 indicates if module was successfully loaded New in version 3 7 audit str event void tuple Fires when sys audit or PySys_Audit is called arg0 is the event name as C string arg1 is a PyObject pointer to a tuple object New in version 3 8 SystemTap Tapsets The higher level way to use the SystemTap integration is to use a tapset SystemTap s equivalent of a library which hides some of the lower level details of the static markers Here is a tapset file based on a non shared build of CPython Provide a higher level wrapping around the function__entry and function__return markers probe python function entry process python mark function__entry filename user_string arg1 funcname user_string arg2 lineno arg3 frameptr arg4 probe python function return process python mark function__return filename user_string arg1 funcname user_string arg2 lineno arg3 frameptr arg4 If this file is installed in SystemTap s tapset directory e g usr share systemtap tapset then these additional probepoints become available python function entry str filename str funcname int lineno frameptr This probe point indicates that execution of a Python function has begun It is only triggered for pure Python bytecode functions python function return str filename str funcname int lineno frameptr This probe point is the converse of python function return and indicates that execution of a Python function has ended either via return or via an exception It is only triggered for pure Python bytecode functions Examples This SystemTap script uses the tapset above to more cleanly implement the example given above of tracing the Python function call hierarchy without needing to directly name the static markers probe python function entry printf s s in s d n thread_indent 1 funcname filename lineno probe python function return printf s s in s d n thread_indent 1 funcname filename lineno The following script uses the tapset above to provide a top like view of all running CPython code showing the top 20 most frequently entered bytecode frames each second across the whole system global fn_calls probe python function entry fn_calls pid filename funcname lineno 1 probe timer ms 1000 printf 033 2J 033 1 1H clear screen printf 6s 80s 6s 30s 6s n PID FILENAME LINE FUNCTION CALLS foreach pid filename funcname lineno in fn_calls limit 20 printf 6d 80s 6d 30s 6d n pid filename lineno funcname fn_calls pid filename funcname lineno delete fn_calls,en
1931,Extending and Embedding the Python Interpreter This document describes how to write modules in C or C to extend the Python interpreter with new modules Those modules can not only define new functions but also new object types and their methods The document also describes how to embed the Python interpreter in another application for use as an extension language Finally it shows how to compile and link extension modules so that they can be loaded dynamically at run time into the interpreter if the underlying operating system supports this feature This document assumes basic knowledge about Python For an informal introduction to the language see The Python Tutorial The Python Language Reference gives a more formal definition of the language The Python Standard Library documents the existing object types functions and modules both built in and written in Python that give the language its wide application range For a detailed description of the whole Python C API see the separate Python C API Reference Manual Recommended third party tools This guide only covers the basic tools for creating extensions provided as part of this version of CPython Third party tools like Cython cffi SWIG and Numba offer both simpler and more sophisticated approaches to creating C and C extensions for Python See also Python Packaging User Guide Binary Extensions The Python Packaging User Guide not only covers several available tools that simplify the creation of binary extensions but also discusses the various reasons why creating an extension module may be desirable in the first place Creating extensions without third party tools This section of the guide covers creating C and C extensions without assistance from third party tools It is intended primarily for creators of those tools rather than being a recommended way to create your own C extensions 1 Extending Python with C or C 1 1 A Simple Example 1 2 Intermezzo Errors and Exceptions 1 3 Back to the Example 1 4 The Module s Method Table and Initialization Function 1 5 Compilation and Linkage 1 6 Calling Python Functions from C 1 7 Extracting Parameters in Extension Functions 1 8 Keyword Parameters for Extension Functions 1 9 Building Arbitrary Values 1 10 Reference Counts 1 11 Writing Extensions in C 1 12 Providing a C API for an Extension Module 2 Defining Extension Types Tutorial 2 1 The Basics 2 2 Adding data and methods to the Basic example 2 3 Providing finer control over data attributes 2 4 Supporting cyclic garbage collection 2 5 Subclassing other types 3 Defining Extension Types Assorted Topics 3 1 Finalization and De allocation 3 2 Object Presentation 3 3 Attribute Management 3 4 Object Comparison 3 5 Abstract Protocol Support 3 6 Weak Reference Support 3 7 More Suggestions 4 Building C and C Extensions 4 1 Building C and C Extensions with setuptools 5 Building C and C Extensions on Windows 5 1 A Cookbook Approach 5 2 Differences Between Unix and Windows 5 3 Using DLLs in Practice Embedding the CPython runtime in a larger application Sometimes rather than creating an extension that runs inside the Python interpreter as the main application it is desirable to instead embed the CPython runtime inside a larger application This section covers some of the details involved in doing that successfully 1 Embedding Python in Another Application 1 1 Very High Level Embedding 1 2 Beyond Very High Level Embedding An overview 1 3 Pure Embedding 1 4 Extending Embedded Python 1 5 Embedding Python in C 1 6 Compiling and Linking under Unix like systems,en
1932,6 Editors and IDEs There are a number of IDEs that support Python programming language Many editors and IDEs provide syntax highlighting debugging tools and PEP 8 checks Please go to Python Editors and Integrated Development Environments for a comprehensive list,en
1933,Data Types The modules described in this chapter provide a variety of specialized data types such as dates and times fixed type arrays heap queues double ended queues and enumerations Python also provides some built in data types in particular dict list set and frozenset and tuple The str class is used to hold Unicode strings and the bytes and bytearray classes are used to hold binary data The following modules are documented in this chapter datetime Basic date and time types Aware and Naive Objects Constants Available Types Common Properties Determining if an Object is Aware or Naive timedelta Objects Examples of usage timedelta date Objects Examples of Usage date datetime Objects Examples of Usage datetime time Objects Examples of Usage time tzinfo Objects timezone Objects strftime and strptime Behavior strftime and strptime Format Codes Technical Detail zoneinfo IANA time zone support Using ZoneInfo Data sources Configuring the data sources Compile time configuration Environment configuration Runtime configuration The ZoneInfo class String representations Pickle serialization Functions Globals Exceptions and warnings calendar General calendar related functions Command Line Usage collections Container datatypes ChainMap objects ChainMap Examples and Recipes Counter objects deque objects deque Recipes defaultdict objects defaultdict Examples namedtuple Factory Function for Tuples with Named Fields OrderedDict objects OrderedDict Examples and Recipes UserDict objects UserList objects UserString objects collections abc Abstract Base Classes for Containers Collections Abstract Base Classes Collections Abstract Base Classes Detailed Descriptions Examples and Recipes heapq Heap queue algorithm Basic Examples Priority Queue Implementation Notes Theory bisect Array bisection algorithm Performance Notes Searching Sorted Lists Examples array Efficient arrays of numeric values weakref Weak references Weak Reference Objects Example Finalizer Objects Comparing finalizers with __del__ methods types Dynamic type creation and names for built in types Dynamic Type Creation Standard Interpreter Types Additional Utility Classes and Functions Coroutine Utility Functions copy Shallow and deep copy operations pprint Data pretty printer Functions PrettyPrinter Objects Example reprlib Alternate repr implementation Repr Objects Subclassing Repr Objects enum Support for enumerations Module Contents Data Types Supported __dunder__ names Supported _sunder_ names Utilities and Decorators Notes graphlib Functionality to operate with graph like structures Exceptions,en
1934,turtle Turtle graphics Source code Lib turtle py Introduction Turtle graphics is an implementation of the popular geometric drawing tools introduced in Logo developed by Wally Feurzeig Seymour Papert and Cynthia Solomon in 1967 Turtle star Turtle can draw intricate shapes using programs that repeat simple moves image In Python turtle graphics provides a representation of a physical turtle a little robot with a pen that draws on a sheet of paper on the floor It s an effective and well proven way for learners to encounter programming concepts and interaction with software as it provides instant visible feedback It also provides convenient access to graphical output in general Turtle drawing was originally created as an educational tool to be used by teachers in the classroom For the programmer who needs to produce some graphical output it can be a way to do that without the overhead of introducing more complex or external libraries into their work Tutorial New users should start here In this tutorial we ll explore some of the basics of turtle drawing Starting a turtle environment In a Python shell import all the objects of the turtle module from turtle import If you run into a No module named _tkinter error you ll have to install the Tk interface package on your system Basic drawing Send the turtle forward 100 steps forward 100 You should see most likely in a new window on your display a line drawn by the turtle heading East Change the direction of the turtle so that it turns 120 degrees left anti clockwise left 120 Let s continue by drawing a triangle forward 100 left 120 forward 100 Notice how the turtle represented by an arrow points in different directions as you steer it Experiment with those commands and also with backward and right Pen control Try changing the color for example color blue and width of the line for example width 3 and then drawing again You can also move the turtle around without drawing by lifting up the pen up before moving To start drawing again use down The turtle s position Send your turtle back to its starting point useful if it has disappeared off screen home The home position is at the center of the turtle s screen If you ever need to know them get the turtle s x y co ordinates with pos Home is at 0 0 And after a while it will probably help to clear the window so we can start anew clearscreen Making algorithmic patterns Using loops it s possible to build up geometric patterns for steps in range 100 for c in blue red green color c forward steps right 30 which of course are limited only by the imagination Let s draw the star shape at the top of this page We want red lines filled in with yellow color red fillcolor yellow Just as up and down determine whether lines will be drawn filling can be turned on and off begin_fill Next we ll create a loop while True forward 200 left 170 if abs pos 1 break abs pos 1 is a good way to know when the turtle is back at its home position Finally complete the filling end_fill Note that filling only actually takes place when you give the end_fill command How to This section covers some typical turtle use cases and approaches Get started as quickly as possible One of the joys of turtle graphics is the immediate visual feedback that s available from simple commands it s an excellent way to introduce children to programming ideas with a minimum of overhead not just children of course The turtle module makes this possible by exposing all its basic functionality as functions available with from turtle import The turtle graphics tutorial covers this approach It s worth noting that many of the turtle commands also have even more terse equivalents such as fd for forward These are especially useful when working with learners for whom typing is not a skill You ll need to have the Tk interface package installed on your system for turtle graphics to work Be warned that this is not always straightforward so check this in advance if you re planning to use turtle graphics with a learner Use the turtle module namespace Using from turtle import is convenient but be warned that it ,en
1935,imports a rather large collection of objects and if you re doing anything but turtle graphics you run the risk of a name conflict this becomes even more an issue if you re using turtle graphics in a script where other modules might be imported The solution is to use import turtle fd becomes turtle fd width becomes turtle width and so on If typing turtle over and over again becomes tedious use for example import turtle as t instead Use turtle graphics in a script It s recommended to use the turtle module namespace as described immediately above for example import turtle as t from random import random for i in range 100 steps int random 100 angle int random 360 t right angle t fd steps Another step is also required though as soon as the script ends Python will also close the turtle s window Add t mainloop to the end of the script The script will now wait to be dismissed and will not exit until it is terminated for example by closing the turtle graphics window Use object oriented turtle graphics See also Explanation of the object oriented interface Other than for very basic introductory purposes or for trying things out as quickly as possible it s more usual and much more powerful to use the object oriented approach to turtle graphics For example this allows multiple turtles on screen at once In this approach the various turtle commands are methods of objects mostly of Turtle objects You can use the object oriented approach in the shell but it would be more typical in a Python script The example above then becomes from turtle import Turtle from random import random t Turtle for i in range 100 steps int random 100 angle int random 360 t right angle t fd steps t screen mainloop Note the last line t screen is an instance of the Screen that a Turtle instance exists on it s created automatically along with the turtle The turtle s screen can be customised for example t screen title Object oriented turtle demo t screen bgcolor orange Turtle graphics reference Note In the following documentation the argument list for functions is given Methods of course have the additional first argument self which is omitted here Turtle methods Turtle motion Move and draw forward fd backward bk back right rt left lt goto setpos setposition teleport setx sety setheading seth home circle dot stamp clearstamp clearstamps undo speed Tell Turtle s state position pos towards xcor ycor heading distance Setting and measurement degrees radians Pen control Drawing state pendown pd down penup pu up pensize width pen isdown Color control color pencolor fillcolor Filling filling begin_fill end_fill More drawing control reset clear write Turtle state Visibility showturtle st hideturtle ht isvisible Appearance shape resizemode shapesize turtlesize shearfactor settiltangle tiltangle tilt shapetransform get_shapepoly Using events onclick onrelease ondrag Special Turtle methods begin_poly end_poly get_poly clone getturtle getpen getscreen setundobuffer undobufferentries Methods of TurtleScreen Screen Window control bgcolor bgpic clearscreen resetscreen screensize setworldcoordinates Animation control delay tracer update Using screen events listen onkey onkeyrelease onkeypress onclick onscreenclick ontimer mainloop done Settings and special methods mode colormode getcanvas getshapes register_shape addshape turtles window_height window_width Input methods textinput numinput Methods specific to Screen bye exitonclick setup title Methods of RawTurtle Turtle and corresponding functions Most of the examples in this section refer to a Turtle instance called turtle Turtle motion turtle forward distance turtle fd distance Parameters distance a number integer or float Move the turtle forward by the specified distance in the direction the turtle is headed turtle position 0 00 0 00 turtle forward 25 turtle position 25 00 0 00 turtle forward 75 turtle position 50 00 0 00 turtle back distance turtle bk distance turtle backward distance Parameters distance a number Move the turtle backward by distance opposite to the direction the turtle is headed Do not change the turtle s headi,en
1936,ng turtle position 0 00 0 00 turtle backward 30 turtle position 30 00 0 00 turtle right angle turtle rt angle Parameters angle a number integer or float Turn turtle right by angle units Units are by default degrees but can be set via the degrees and radians functions Angle orientation depends on the turtle mode see mode turtle heading 22 0 turtle right 45 turtle heading 337 0 turtle left angle turtle lt angle Parameters angle a number integer or float Turn turtle left by angle units Units are by default degrees but can be set via the degrees and radians functions Angle orientation depends on the turtle mode see mode turtle heading 22 0 turtle left 45 turtle heading 67 0 turtle goto x y None turtle setpos x y None turtle setposition x y None Parameters x a number or a pair vector of numbers y a number or None If y is None x must be a pair of coordinates or a Vec2D e g as returned by pos Move turtle to an absolute position If the pen is down draw line Do not change the turtle s orientation tp turtle pos tp 0 00 0 00 turtle setpos 60 30 turtle pos 60 00 30 00 turtle setpos 20 80 turtle pos 20 00 80 00 turtle setpos tp turtle pos 0 00 0 00 turtle teleport x y None fill_gap False Parameters x a number or None y a number or None fill_gap a boolean Move turtle to an absolute position Unlike goto x y a line will not be drawn The turtle s orientation does not change If currently filling the polygon s teleported from will be filled after leaving and filling will begin again after teleporting This can be disabled with fill_gap True which makes the imaginary line traveled during teleporting act as a fill barrier like in goto x y tp turtle pos tp 0 00 0 00 turtle teleport 60 turtle pos 60 00 0 00 turtle teleport y 10 turtle pos 60 00 10 00 turtle teleport 20 30 turtle pos 20 00 30 00 New in version 3 12 turtle setx x Parameters x a number integer or float Set the turtle s first coordinate to x leave second coordinate unchanged turtle position 0 00 240 00 turtle setx 10 turtle position 10 00 240 00 turtle sety y Parameters y a number integer or float Set the turtle s second coordinate to y leave first coordinate unchanged turtle position 0 00 40 00 turtle sety 10 turtle position 0 00 10 00 turtle setheading to_angle turtle seth to_angle Parameters to_angle a number integer or float Set the orientation of the turtle to to_angle Here are some common directions in degrees standard mode logo mode 0 east 0 north 90 north 90 east 180 west 180 south 270 south 270 west turtle setheading 90 turtle heading 90 0 turtle home Move turtle to the origin coordinates 0 0 and set its heading to its start orientation which depends on the mode see mode turtle heading 90 0 turtle position 0 00 10 00 turtle home turtle position 0 00 0 00 turtle heading 0 0 turtle circle radius extent None steps None Parameters radius a number extent a number or None steps an integer or None Draw a circle with given radius The center is radius units left of the turtle extent an angle determines which part of the circle is drawn If extent is not given draw the entire circle If extent is not a full circle one endpoint of the arc is the current pen position Draw the arc in counterclockwise direction if radius is positive otherwise in clockwise direction Finally the direction of the turtle is changed by the amount of extent As the circle is approximated by an inscribed regular polygon steps determines the number of steps to use If not given it will be calculated automatically May be used to draw regular polygons turtle home turtle position 0 00 0 00 turtle heading 0 0 turtle circle 50 turtle position 0 00 0 00 turtle heading 0 0 turtle circle 120 180 draw a semicircle turtle position 0 00 240 00 turtle heading 180 0 turtle dot size None color Parameters size an integer 1 if given color a colorstring or a numeric color tuple Draw a circular dot with diameter size using color If size is not given the maximum of pensize 4 and 2 pensize is used turtle home turtle dot turtle fd 50 turtle dot 20 blue turtle fd 50 turtle position 100 00 0 00 turtle heading 0 0 turtle stamp Stamp a cop,en
1937,y of the turtle shape onto the canvas at the current turtle position Return a stamp_id for that stamp which can be used to delete it by calling clearstamp stamp_id turtle color blue stamp_id turtle stamp turtle fd 50 turtle clearstamp stampid Parameters stampid an integer must be return value of previous stamp call Delete stamp with given stampid turtle position 150 00 0 00 turtle color blue astamp turtle stamp turtle fd 50 turtle position 200 00 0 00 turtle clearstamp astamp turtle position 200 00 0 00 turtle clearstamps n None Parameters n an integer or None Delete all or first last n of turtle s stamps If n is None delete all stamps if n 0 delete first n stamps else if n 0 delete last n stamps for i in range 8 unused_stamp_id turtle stamp turtle fd 30 turtle clearstamps 2 turtle clearstamps 2 turtle clearstamps turtle undo Undo repeatedly the last turtle action s Number of available undo actions is determined by the size of the undobuffer for i in range 4 turtle fd 50 turtle lt 80 for i in range 8 turtle undo turtle speed speed None Parameters speed an integer in the range 0 10 or a speedstring see below Set the turtle s speed to an integer value in the range 0 10 If no argument is given return current speed If input is a number greater than 10 or smaller than 0 5 speed is set to 0 Speedstrings are mapped to speedvalues as follows fastest 0 fast 10 normal 6 slow 3 slowest 1 Speeds from 1 to 10 enforce increasingly faster animation of line drawing and turtle turning Attention speed 0 means that no animation takes place forward back makes turtle jump and likewise left right make the turtle turn instantly turtle speed 3 turtle speed normal turtle speed 6 turtle speed 9 turtle speed 9 Tell Turtle s state turtle position turtle pos Return the turtle s current location x y as a Vec2D vector turtle pos 440 00 0 00 turtle towards x y None Parameters x a number or a pair vector of numbers or a turtle instance y a number if x is a number else None Return the angle between the line from turtle position to position specified by x y the vector or the other turtle This depends on the turtle s start orientation which depends on the mode standard world or logo turtle goto 10 10 turtle towards 0 0 225 0 turtle xcor Return the turtle s x coordinate turtle home turtle left 50 turtle forward 100 turtle pos 64 28 76 60 print round turtle xcor 5 64 27876 turtle ycor Return the turtle s y coordinate turtle home turtle left 60 turtle forward 100 print turtle pos 50 00 86 60 print round turtle ycor 5 86 60254 turtle heading Return the turtle s current heading value depends on the turtle mode see mode turtle home turtle left 67 turtle heading 67 0 turtle distance x y None Parameters x a number or a pair vector of numbers or a turtle instance y a number if x is a number else None Return the distance from the turtle to x y the given vector or the given other turtle in turtle step units turtle home turtle distance 30 40 50 0 turtle distance 30 40 50 0 joe Turtle joe forward 77 turtle distance joe 77 0 Settings for measurement turtle degrees fullcircle 360 0 Parameters fullcircle a number Set angle measurement units i e set number of degrees for a full circle Default value is 360 degrees turtle home turtle left 90 turtle heading 90 0 Change angle measurement unit to grad also known as gon grade or gradian and equals 1 100 th of the right angle turtle degrees 400 0 turtle heading 100 0 turtle degrees 360 turtle heading 90 0 turtle radians Set the angle measurement units to radians Equivalent to degrees 2 math pi turtle home turtle left 90 turtle heading 90 0 turtle radians turtle heading 1 5707963267948966 Pen control Drawing state turtle pendown turtle pd turtle down Pull the pen down drawing when moving turtle penup turtle pu turtle up Pull the pen up no drawing when moving turtle pensize width None turtle width width None Parameters width a positive number Set the line thickness to width or return it If resizemode is set to auto and turtleshape is a polygon that polygon is drawn with the same line thickness If no argument is given the current pe,en
1938,nsize is returned turtle pensize 1 turtle pensize 10 from here on lines of width 10 are drawn turtle pen pen None pendict Parameters pen a dictionary with some or all of the below listed keys pendict one or more keyword arguments with the below listed keys as keywords Return or set the pen s attributes in a pen dictionary with the following key value pairs shown True False pendown True False pencolor color string or color tuple fillcolor color string or color tuple pensize positive number speed number in range 0 10 resizemode auto or user or noresize stretchfactor positive number positive number outline positive number tilt number This dictionary can be used as argument for a subsequent call to pen to restore the former pen state Moreover one or more of these attributes can be provided as keyword arguments This can be used to set several pen attributes in one statement turtle pen fillcolor black pencolor red pensize 10 sorted turtle pen items fillcolor black outline 1 pencolor red pendown True pensize 10 resizemode noresize shearfactor 0 0 shown True speed 9 stretchfactor 1 0 1 0 tilt 0 0 penstate turtle pen turtle color yellow turtle penup sorted turtle pen items 3 fillcolor outline 1 pencolor yellow turtle pen penstate fillcolor green sorted turtle pen items 3 fillcolor green outline 1 pencolor red turtle isdown Return True if pen is down False if it s up turtle penup turtle isdown False turtle pendown turtle isdown True Color control turtle pencolor args Return or set the pencolor Four input formats are allowed pencolor Return the current pencolor as color specification string or as a tuple see example May be used as input to another color pencolor fillcolor call pencolor colorstring Set pencolor to colorstring which is a Tk color specification string such as red yellow or 33cc8c pencolor r g b Set pencolor to the RGB color represented by the tuple of r g and b Each of r g and b must be in the range 0 colormode where colormode is either 1 0 or 255 see colormode pencolor r g b Set pencolor to the RGB color represented by r g and b Each of r g and b must be in the range 0 colormode If turtleshape is a polygon the outline of that polygon is drawn with the newly set pencolor colormode 1 0 turtle pencolor red turtle pencolor brown turtle pencolor brown tup 0 2 0 8 0 55 turtle pencolor tup turtle pencolor 0 2 0 8 0 5490196078431373 colormode 255 turtle pencolor 51 0 204 0 140 0 turtle pencolor 32c18f turtle pencolor 50 0 193 0 143 0 turtle fillcolor args Return or set the fillcolor Four input formats are allowed fillcolor Return the current fillcolor as color specification string possibly in tuple format see example May be used as input to another color pencolor fillcolor call fillcolor colorstring Set fillcolor to colorstring which is a Tk color specification string such as red yellow or 33cc8c fillcolor r g b Set fillcolor to the RGB color represented by the tuple of r g and b Each of r g and b must be in the range 0 colormode where colormode is either 1 0 or 255 see colormode fillcolor r g b Set fillcolor to the RGB color represented by r g and b Each of r g and b must be in the range 0 colormode If turtleshape is a polygon the interior of that polygon is drawn with the newly set fillcolor turtle fillcolor violet turtle fillcolor violet turtle pencolor 50 0 193 0 143 0 turtle fillcolor 50 193 143 Integers not floats turtle fillcolor 50 0 193 0 143 0 turtle fillcolor ffffff turtle fillcolor 255 0 255 0 255 0 turtle color args Return or set pencolor and fillcolor Several input formats are allowed They use 0 to 3 arguments as follows color Return the current pencolor and the current fillcolor as a pair of color specification strings or tuples as returned by pencolor and fillcolor color colorstring color r g b color r g b Inputs as in pencolor set both fillcolor and pencolor to the given value color colorstring1 colorstring2 color r1 g1 b1 r2 g2 b2 Equivalent to pencolor colorstring1 and fillcolor colorstring2 and analogously if the other input format is used If turtleshape is a polygon outline and interior of that polygon i,en
1939,s drawn with the newly set colors turtle color red green turtle color red green color 285078 a0c8f0 color 40 0 80 0 120 0 160 0 200 0 240 0 See also Screen method colormode Filling turtle filling Return fillstate True if filling False else turtle begin_fill if turtle filling turtle pensize 5 else turtle pensize 3 turtle begin_fill To be called just before drawing a shape to be filled turtle end_fill Fill the shape drawn after the last call to begin_fill Whether or not overlap regions for self intersecting polygons or multiple shapes are filled depends on the operating system graphics type of overlap and number of overlaps For example the Turtle star above may be either all yellow or have some white regions turtle color black red turtle begin_fill turtle circle 80 turtle end_fill More drawing control turtle reset Delete the turtle s drawings from the screen re center the turtle and set variables to the default values turtle goto 0 22 turtle left 100 turtle position 0 00 22 00 turtle heading 100 0 turtle reset turtle position 0 00 0 00 turtle heading 0 0 turtle clear Delete the turtle s drawings from the screen Do not move turtle State and position of the turtle as well as drawings of other turtles are not affected turtle write arg move False align left font Arial 8 normal Parameters arg object to be written to the TurtleScreen move True False align one of the strings left center or right font a triple fontname fontsize fonttype Write text the string representation of arg at the current turtle position according to align left center or right and with the given font If move is true the pen is moved to the bottom right corner of the text By default move is False turtle write Home True align center turtle write 0 0 True Turtle state Visibility turtle hideturtle turtle ht Make the turtle invisible It s a good idea to do this while you re in the middle of doing some complex drawing because hiding the turtle speeds up the drawing observably turtle hideturtle turtle showturtle turtle st Make the turtle visible turtle showturtle turtle isvisible Return True if the Turtle is shown False if it s hidden turtle hideturtle turtle isvisible False turtle showturtle turtle isvisible True Appearance turtle shape name None Parameters name a string which is a valid shapename Set turtle shape to shape with given name or if name is not given return name of current shape Shape with name must exist in the TurtleScreen s shape dictionary Initially there are the following polygon shapes arrow turtle circle square triangle classic To learn about how to deal with shapes see Screen method register_shape turtle shape classic turtle shape turtle turtle shape turtle turtle resizemode rmode None Parameters rmode one of the strings auto user noresize Set resizemode to one of the values auto user noresize If rmode is not given return current resizemode Different resizemodes have the following effects auto adapts the appearance of the turtle corresponding to the value of pensize user adapts the appearance of the turtle according to the values of stretchfactor and outlinewidth outline which are set by shapesize noresize no adaption of the turtle s appearance takes place resizemode user is called by shapesize when used with arguments turtle resizemode noresize turtle resizemode auto turtle resizemode auto turtle shapesize stretch_wid None stretch_len None outline None turtle turtlesize stretch_wid None stretch_len None outline None Parameters stretch_wid positive number stretch_len positive number outline positive number Return or set the pen s attributes x y stretchfactors and or outline Set resizemode to user If and only if resizemode is set to user the turtle will be displayed stretched according to its stretchfactors stretch_wid is stretchfactor perpendicular to its orientation stretch_len is stretchfactor in direction of its orientation outline determines the width of the shape s outline turtle shapesize 1 0 1 0 1 turtle resizemode user turtle shapesize 5 5 12 turtle shapesize 5 5 12 turtle shapesize outline 8 turtle shapesize 5 5 8 turtle shearfactor sh,en
1940,ear None Parameters shear number optional Set or return the current shearfactor Shear the turtleshape according to the given shearfactor shear which is the tangent of the shear angle Do not change the turtle s heading direction of movement If shear is not given return the current shearfactor i e the tangent of the shear angle by which lines parallel to the heading of the turtle are sheared turtle shape circle turtle shapesize 5 2 turtle shearfactor 0 5 turtle shearfactor 0 5 turtle tilt angle Parameters angle a number Rotate the turtleshape by angle from its current tilt angle but do not change the turtle s heading direction of movement turtle reset turtle shape circle turtle shapesize 5 2 turtle tilt 30 turtle fd 50 turtle tilt 30 turtle fd 50 turtle settiltangle angle Parameters angle a number Rotate the turtleshape to point in the direction specified by angle regardless of its current tilt angle Do not change the turtle s heading direction of movement turtle reset turtle shape circle turtle shapesize 5 2 turtle settiltangle 45 turtle fd 50 turtle settiltangle 45 turtle fd 50 Deprecated since version 3 1 turtle tiltangle angle None Parameters angle a number optional Set or return the current tilt angle If angle is given rotate the turtleshape to point in the direction specified by angle regardless of its current tilt angle Do not change the turtle s heading direction of movement If angle is not given return the current tilt angle i e the angle between the orientation of the turtleshape and the heading of the turtle its direction of movement turtle reset turtle shape circle turtle shapesize 5 2 turtle tilt 45 turtle tiltangle 45 0 turtle shapetransform t11 None t12 None t21 None t22 None Parameters t11 a number optional t12 a number optional t21 a number optional t12 a number optional Set or return the current transformation matrix of the turtle shape If none of the matrix elements are given return the transformation matrix as a tuple of 4 elements Otherwise set the given elements and transform the turtleshape according to the matrix consisting of first row t11 t12 and second row t21 t22 The determinant t11 t22 t12 t21 must not be zero otherwise an error is raised Modify stretchfactor shearfactor and tiltangle according to the given matrix turtle Turtle turtle shape square turtle shapesize 4 2 turtle shearfactor 0 5 turtle shapetransform 4 0 1 0 0 0 2 0 turtle get_shapepoly Return the current shape polygon as tuple of coordinate pairs This can be used to define a new shape or components of a compound shape turtle shape square turtle shapetransform 4 1 0 2 turtle get_shapepoly 50 20 30 20 50 20 30 20 Using events turtle onclick fun btn 1 add None Parameters fun a function with two arguments which will be called with the coordinates of the clicked point on the canvas btn number of the mouse button defaults to 1 left mouse button add True or False if True a new binding will be added otherwise it will replace a former binding Bind fun to mouse click events on this turtle If fun is None existing bindings are removed Example for the anonymous turtle i e the procedural way def turn x y left 180 onclick turn Now clicking into the turtle will turn it onclick None event binding will be removed turtle onrelease fun btn 1 add None Parameters fun a function with two arguments which will be called with the coordinates of the clicked point on the canvas btn number of the mouse button defaults to 1 left mouse button add True or False if True a new binding will be added otherwise it will replace a former binding Bind fun to mouse button release events on this turtle If fun is None existing bindings are removed class MyTurtle Turtle def glow self x y self fillcolor red def unglow self x y self fillcolor turtle MyTurtle turtle onclick turtle glow clicking on turtle turns fillcolor red turtle onrelease turtle unglow releasing turns it to transparent turtle ondrag fun btn 1 add None Parameters fun a function with two arguments which will be called with the coordinates of the clicked point on the canvas btn number of the mouse button default,en
1941,s to 1 left mouse button add True or False if True a new binding will be added otherwise it will replace a former binding Bind fun to mouse move events on this turtle If fun is None existing bindings are removed Remark Every sequence of mouse move events on a turtle is preceded by a mouse click event on that turtle turtle ondrag turtle goto Subsequently clicking and dragging the Turtle will move it across the screen thereby producing handdrawings if pen is down Special Turtle methods turtle begin_poly Start recording the vertices of a polygon Current turtle position is first vertex of polygon turtle end_poly Stop recording the vertices of a polygon Current turtle position is last vertex of polygon This will be connected with the first vertex turtle get_poly Return the last recorded polygon turtle home turtle begin_poly turtle fd 100 turtle left 20 turtle fd 30 turtle left 60 turtle fd 50 turtle end_poly p turtle get_poly register_shape myFavouriteShape p turtle clone Create and return a clone of the turtle with same position heading and turtle properties mick Turtle joe mick clone turtle getturtle turtle getpen Return the Turtle object itself Only reasonable use as a function to return the anonymous turtle pet getturtle pet fd 50 pet turtle Turtle object at 0x turtle getscreen Return the TurtleScreen object the turtle is drawing on TurtleScreen methods can then be called for that object ts turtle getscreen ts turtle _Screen object at 0x ts bgcolor pink turtle setundobuffer size Parameters size an integer or None Set or disable undobuffer If size is an integer an empty undobuffer of given size is installed size gives the maximum number of turtle actions that can be undone by the undo method function If size is None the undobuffer is disabled turtle setundobuffer 42 turtle undobufferentries Return number of entries in the undobuffer while undobufferentries undo Compound shapes To use compound turtle shapes which consist of several polygons of different color you must use the helper class Shape explicitly as described below 1 Create an empty Shape object of type compound 2 Add as many components to this object as desired using the addcomponent method For example s Shape compound poly1 0 0 10 5 0 10 10 5 s addcomponent poly1 red blue poly2 0 0 10 5 10 5 s addcomponent poly2 blue red 3 Now add the Shape to the Screen s shapelist and use it register_shape myshape s shape myshape Note The Shape class is used internally by the register_shape method in different ways The application programmer has to deal with the Shape class only when using compound shapes like shown above Methods of TurtleScreen Screen and corresponding functions Most of the examples in this section refer to a TurtleScreen instance called screen Window control turtle bgcolor args Parameters args a color string or three numbers in the range 0 colormode or a 3 tuple of such numbers Set or return background color of the TurtleScreen screen bgcolor orange screen bgcolor orange screen bgcolor 800080 screen bgcolor 128 0 0 0 128 0 turtle bgpic picname None Parameters picname a string name of a gif file or nopic or None Set background image or return name of current backgroundimage If picname is a filename set the corresponding image as background If picname is nopic delete background image if present If picname is None return the filename of the current backgroundimage screen bgpic nopic screen bgpic landscape gif screen bgpic landscape gif turtle clear Note This TurtleScreen method is available as a global function only under the name clearscreen The global function clear is a different one derived from the Turtle method clear turtle clearscreen Delete all drawings and all turtles from the TurtleScreen Reset the now empty TurtleScreen to its initial state white background no background image no event bindings and tracing on turtle reset Note This TurtleScreen method is available as a global function only under the name resetscreen The global function reset is another one derived from the Turtle method reset turtle resetscreen Reset all Turtles on the Screen to their,en
1942, initial state turtle screensize canvwidth None canvheight None bg None Parameters canvwidth positive integer new width of canvas in pixels canvheight positive integer new height of canvas in pixels bg colorstring or color tuple new background color If no arguments are given return current canvaswidth canvasheight Else resize the canvas the turtles are drawing on Do not alter the drawing window To observe hidden parts of the canvas use the scrollbars With this method one can make visible those parts of a drawing which were outside the canvas before screen screensize 400 300 screen screensize 2000 1500 screen screensize 2000 1500 e g to search for an erroneously escaped turtle turtle setworldcoordinates llx lly urx ury Parameters llx a number x coordinate of lower left corner of canvas lly a number y coordinate of lower left corner of canvas urx a number x coordinate of upper right corner of canvas ury a number y coordinate of upper right corner of canvas Set up user defined coordinate system and switch to mode world if necessary This performs a screen reset If mode world is already active all drawings are redrawn according to the new coordinates ATTENTION in user defined coordinate systems angles may appear distorted screen reset screen setworldcoordinates 50 7 5 50 7 5 for _ in range 72 left 10 for _ in range 8 left 45 fd 2 a regular octagon Animation control turtle delay delay None Parameters delay positive integer Set or return the drawing delay in milliseconds This is approximately the time interval between two consecutive canvas updates The longer the drawing delay the slower the animation Optional argument screen delay 10 screen delay 5 screen delay 5 turtle tracer n None delay None Parameters n nonnegative integer delay nonnegative integer Turn turtle animation on off and set delay for update drawings If n is given only each n th regular screen update is really performed Can be used to accelerate the drawing of complex graphics When called without arguments returns the currently stored value of n Second argument sets delay value see delay screen tracer 8 25 dist 2 for i in range 200 fd dist rt 90 dist 2 turtle update Perform a TurtleScreen update To be used when tracer is turned off See also the RawTurtle Turtle method speed Using screen events turtle listen xdummy None ydummy None Set focus on TurtleScreen in order to collect key events Dummy arguments are provided in order to be able to pass listen to the onclick method turtle onkey fun key turtle onkeyrelease fun key Parameters fun a function with no arguments or None key a string key e g a or key symbol e g space Bind fun to key release event of key If fun is None event bindings are removed Remark in order to be able to register key events TurtleScreen must have the focus See method listen def f fd 50 lt 60 screen onkey f Up screen listen turtle onkeypress fun key None Parameters fun a function with no arguments or None key a string key e g a or key symbol e g space Bind fun to key press event of key if key is given or to any key press event if no key is given Remark in order to be able to register key events TurtleScreen must have focus See method listen def f fd 50 screen onkey f Up screen listen turtle onclick fun btn 1 add None turtle onscreenclick fun btn 1 add None Parameters fun a function with two arguments which will be called with the coordinates of the clicked point on the canvas btn number of the mouse button defaults to 1 left mouse button add True or False if True a new binding will be added otherwise it will replace a former binding Bind fun to mouse click events on this screen If fun is None existing bindings are removed Example for a TurtleScreen instance named screen and a Turtle instance named turtle screen onclick turtle goto Subsequently clicking into the TurtleScreen will make the turtle move to the clicked point screen onclick None remove event binding again Note This TurtleScreen method is available as a global function only under the name onscreenclick The global function onclick is another one derived from the Turtle method onclick tu,en
1943,rtle ontimer fun t 0 Parameters fun a function with no arguments t a number 0 Install a timer that calls fun after t milliseconds running True def f if running fd 50 lt 60 screen ontimer f 250 f makes the turtle march around running False turtle mainloop turtle done Starts event loop calling Tkinter s mainloop function Must be the last statement in a turtle graphics program Must not be used if a script is run from within IDLE in n mode No subprocess for interactive use of turtle graphics screen mainloop Input methods turtle textinput title prompt Parameters title string prompt string Pop up a dialog window for input of a string Parameter title is the title of the dialog window prompt is a text mostly describing what information to input Return the string input If the dialog is canceled return None screen textinput NIM Name of first player turtle numinput title prompt default None minval None maxval None Parameters title string prompt string default number optional minval number optional maxval number optional Pop up a dialog window for input of a number title is the title of the dialog window prompt is a text mostly describing what numerical information to input default default value minval minimum value for input maxval maximum value for input The number input must be in the range minval maxval if these are given If not a hint is issued and the dialog remains open for correction Return the number input If the dialog is canceled return None screen numinput Poker Your stakes 1000 minval 10 maxval 10000 Settings and special methods turtle mode mode None Parameters mode one of the strings standard logo or world Set turtle mode standard logo or world and perform reset If mode is not given current mode is returned Mode standard is compatible with old turtle Mode logo is compatible with most Logo turtle graphics Mode world uses user defined world coordinates Attention in this mode angles appear distorted if x y unit ratio doesn t equal 1 Mode Initial turtle heading positive angles standard to the right east counterclockwise logo upward north clockwise mode logo resets turtle heading to north mode logo turtle colormode cmode None Parameters cmode one of the values 1 0 or 255 Return the colormode or set it to 1 0 or 255 Subsequently r g b values of color triples have to be in the range 0 cmode screen colormode 1 turtle pencolor 240 160 80 Traceback most recent call last TurtleGraphicsError bad color sequence 240 160 80 screen colormode 1 0 screen colormode 255 screen colormode 255 turtle pencolor 240 160 80 turtle getcanvas Return the Canvas of this TurtleScreen Useful for insiders who know what to do with a Tkinter Canvas cv screen getcanvas cv turtle ScrolledCanvas object turtle getshapes Return a list of names of all currently available turtle shapes screen getshapes arrow blank circle turtle turtle register_shape name shape None turtle addshape name shape None There are three different ways to call this function 1 name is the name of a gif file and shape is None Install the corresponding image shape screen register_shape turtle gif Note Image shapes do not rotate when turning the turtle so they do not display the heading of the turtle 2 name is an arbitrary string and shape is a tuple of pairs of coordinates Install the corresponding polygon shape screen register_shape triangle 5 3 0 5 5 3 3 name is an arbitrary string and shape is a compound Shape object Install the corresponding compound shape Add a turtle shape to TurtleScreen s shapelist Only thusly registered shapes can be used by issuing the command shape shapename turtle turtles Return the list of turtles on the screen for turtle in screen turtles turtle color red turtle window_height Return the height of the turtle window screen window_height 480 turtle window_width Return the width of the turtle window screen window_width 640 Methods specific to Screen not inherited from TurtleScreen turtle bye Shut the turtlegraphics window turtle exitonclick Bind bye method to mouse clicks on the Screen If the value using_IDLE in the configuration dictionary is False default value,en
1944, also enter mainloop Remark If IDLE with the n switch no subprocess is used this value should be set to True in turtle cfg In this case IDLE s own mainloop is active also for the client script turtle setup width _CFG width height _CFG height startx _CFG leftright starty _CFG topbottom Set the size and position of the main window Default values of arguments are stored in the configuration dictionary and can be changed via a turtle cfg file Parameters width if an integer a size in pixels if a float a fraction of the screen default is 50 of screen height if an integer the height in pixels if a float a fraction of the screen default is 75 of screen startx if positive starting position in pixels from the left edge of the screen if negative from the right edge if None center window horizontally starty if positive starting position in pixels from the top edge of the screen if negative from the bottom edge if None center window vertically screen setup width 200 height 200 startx 0 starty 0 sets window to 200x200 pixels in upper left of screen screen setup width 75 height 0 5 startx None starty None sets window to 75 of screen by 50 of screen and centers turtle title titlestring Parameters titlestring a string that is shown in the titlebar of the turtle graphics window Set title of turtle window to titlestring screen title Welcome to the turtle zoo Public classes class turtle RawTurtle canvas class turtle RawPen canvas Parameters canvas a tkinter Canvas a ScrolledCanvas or a TurtleScreen Create a turtle The turtle has all methods described above as methods of Turtle RawTurtle class turtle Turtle Subclass of RawTurtle has the same interface but draws on a default Screen object created automatically when needed for the first time class turtle TurtleScreen cv Parameters cv a tkinter Canvas Provides screen oriented methods like bgcolor etc that are described above class turtle Screen Subclass of TurtleScreen with four methods added class turtle ScrolledCanvas master Parameters master some Tkinter widget to contain the ScrolledCanvas i e a Tkinter canvas with scrollbars added Used by class Screen which thus automatically provides a ScrolledCanvas as playground for the turtles class turtle Shape type_ data Parameters type_ one of the strings polygon image compound Data structure modeling shapes The pair type_ data must follow this specification type_ data polygon a polygon tuple i e a tuple of pairs of coordinates image an image in this form only used internally compound None a compound shape has to be constructed using the addcomponent method addcomponent poly fill outline None Parameters poly a polygon i e a tuple of pairs of numbers fill a color the poly will be filled with outline a color for the poly s outline if given Example poly 0 0 10 5 0 10 10 5 s Shape compound s addcomponent poly red blue add more components and then use register_shape See Compound shapes class turtle Vec2D x y A two dimensional vector class used as a helper class for implementing turtle graphics May be useful for turtle graphics programs too Derived from tuple so a vector is a tuple Provides for a b vectors k number a b vector addition a b vector subtraction a b inner product k a and a k multiplication with scalar abs a absolute value of a a rotate angle rotation Explanation A turtle object draws on a screen object and there a number of key classes in the turtle object oriented interface that can be used to create them and relate them to each other A Turtle instance will automatically create a Screen instance if one is not already present Turtle is a subclass of RawTurtle which doesn t automatically create a drawing surface a canvas will need to be provided or created for it The canvas can be a tkinter Canvas ScrolledCanvas or TurtleScreen TurtleScreen is the basic drawing surface for a turtle Screen is a subclass of TurtleScreen and includes some additional methods for managing its appearance including size and title and behaviour TurtleScreen s constructor needs a tkinter Canvas or a ScrolledCanvas as an argument The functional interface for turtle graph,en
1945,ics uses the various methods of Turtle and TurtleScreen Screen Behind the scenes a screen object is automatically created whenever a function derived from a Screen method is called Similarly a turtle object is automatically created whenever any of the functions derived from a Turtle method is called To use multiple turtles on a screen the object oriented interface must be used Help and configuration How to use help The public methods of the Screen and Turtle classes are documented extensively via docstrings So these can be used as online help via the Python help facilities When using IDLE tooltips show the signatures and first lines of the docstrings of typed in function method calls Calling help on methods or functions displays the docstrings help Screen bgcolor Help on method bgcolor in module turtle bgcolor self args unbound turtle Screen method Set or return backgroundcolor of the TurtleScreen Arguments if given a color string or three numbers in the range 0 colormode or a 3 tuple of such numbers screen bgcolor orange screen bgcolor orange screen bgcolor 0 5 0 0 5 screen bgcolor 800080 help Turtle penup Help on method penup in module turtle penup self unbound turtle Turtle method Pull the pen up no drawing when moving Aliases penup pu up No argument turtle penup The docstrings of the functions which are derived from methods have a modified form help bgcolor Help on function bgcolor in module turtle bgcolor args Set or return backgroundcolor of the TurtleScreen Arguments if given a color string or three numbers in the range 0 colormode or a 3 tuple of such numbers Example bgcolor orange bgcolor orange bgcolor 0 5 0 0 5 bgcolor 800080 help penup Help on function penup in module turtle penup Pull the pen up no drawing when moving Aliases penup pu up No argument Example penup These modified docstrings are created automatically together with the function definitions that are derived from the methods at import time Translation of docstrings into different languages There is a utility to create a dictionary the keys of which are the method names and the values of which are the docstrings of the public methods of the classes Screen and Turtle turtle write_docstringdict filename turtle_docstringdict Parameters filename a string used as filename Create and write docstring dictionary to a Python script with the given filename This function has to be called explicitly it is not used by the turtle graphics classes The docstring dictionary will be written to the Python script filename py It is intended to serve as a template for translation of the docstrings into different languages If you or your students want to use turtle with online help in your native language you have to translate the docstrings and save the resulting file as e g turtle_docstringdict_german py If you have an appropriate entry in your turtle cfg file this dictionary will be read in at import time and will replace the original English docstrings At the time of this writing there are docstring dictionaries in German and in Italian Requests please to glingl aon at How to configure Screen and Turtles The built in default configuration mimics the appearance and behaviour of the old turtle module in order to retain best possible compatibility with it If you want to use a different configuration which better reflects the features of this module or which better fits to your needs e g for use in a classroom you can prepare a configuration file turtle cfg which will be read at import time and modify the configuration according to its settings The built in configuration would correspond to the following turtle cfg width 0 5 height 0 75 leftright None topbottom None canvwidth 400 canvheight 300 mode standard colormode 1 0 delay 10 undobuffersize 1000 shape classic pencolor black fillcolor black resizemode noresize visible True language english exampleturtle turtle examplescreen screen title Python Turtle Graphics using_IDLE False Short explanation of selected entries The first four lines correspond to the arguments of the Screen setup method Line 5 and 6 correspond to th,en
1946,e arguments of the method Screen screensize shape can be any of the built in shapes e g arrow turtle etc For more info try help shape If you want to use no fill color i e make the turtle transparent you have to write fillcolor but all nonempty strings must not have quotes in the cfg file If you want to reflect the turtle its state you have to use resizemode auto If you set e g language italian the docstringdict turtle_docstringdict_italian py will be loaded at import time if present on the import path e g in the same directory as turtle The entries exampleturtle and examplescreen define the names of these objects as they occur in the docstrings The transformation of method docstrings to function docstrings will delete these names from the docstrings using_IDLE Set this to True if you regularly work with IDLE and its n switch no subprocess This will prevent exitonclick to enter the mainloop There can be a turtle cfg file in the directory where turtle is stored and an additional one in the current working directory The latter will override the settings of the first one The Lib turtledemo directory contains a turtle cfg file You can study it as an example and see its effects when running the demos preferably not from within the demo viewer turtledemo Demo scripts The turtledemo package includes a set of demo scripts These scripts can be run and viewed using the supplied demo viewer as follows python m turtledemo Alternatively you can run the demo scripts individually For example python m turtledemo bytedesign The turtledemo package directory contains A demo viewer __main__ py which can be used to view the sourcecode of the scripts and run them at the same time Multiple scripts demonstrating different features of the turtle module Examples can be accessed via the Examples menu They can also be run standalone A turtle cfg file which serves as an example of how to write and use such files The demo scripts are Name Description Features bytedesign complex classical turtle tracer delay graphics pattern update chaos graphs Verhulst dynamics world coordinates shows that computer s computations can generate results sometimes against the common sense expectations clock analog clock showing time of turtles as clock s your computer hands ontimer colormixer experiment with r g b ondrag forest 3 breadth first trees randomization fractalcurves Hilbert Koch curves recursion lindenmayer ethnomathematics indian L System kolams minimal_hanoi Towers of Hanoi Rectangular Turtles as Hanoi discs shape shapesize nim play the classical nim game turtles as nimsticks with three heaps of sticks event driven mouse against the computer keyboard paint super minimalistic drawing onclick program peace elementary turtle appearance and animation penrose aperiodic tiling with kites stamp and darts planet_and_moon simulation of gravitational compound shapes system Vec2D rosette a pattern from the wikipedia clone undo article on turtle graphics round_dance dancing turtles rotating compound shapes clone pairwise in opposite direction shapesize tilt get_shapepoly update sorting_animate visual demonstration of simple alignment different sorting methods randomization tree a graphical breadth first clone tree using generators two_canvases simple design turtles on two canvases yinyang another elementary example circle Have fun Changes since Python 2 6 The methods Turtle tracer Turtle window_width and Turtle window_height have been eliminated Methods with these names and functionality are now available only as methods of Screen The functions derived from these remain available In fact already in Python 2 6 these methods were merely duplications of the corresponding TurtleScreen Screen methods The method Turtle fill has been eliminated The behaviour of begin_fill and end_fill have changed slightly now every filling process must be completed with an end_fill call A method Turtle filling has been added It returns a boolean value True if a filling process is under way False otherwise This behaviour corresponds to a fill call without arguments in Python 2 6 Changes since P,en
1947,ython 3 0 The Turtle methods shearfactor shapetransform and get_shapepoly have been added Thus the full range of regular linear transforms is now available for transforming turtle shapes tiltangle has been enhanced in functionality it now can be used to get or set the tilt angle settiltangle has been deprecated The Screen method onkeypress has been added as a complement to onkey As the latter binds actions to the key release event an alias onkeyrelease was also added for it The method Screen mainloop has been added so there is no longer a need to use the standalone mainloop function when working with Screen and Turtle objects Two input methods have been added Screen textinput and Screen numinput These pop up input dialogs and return strings and numbers respectively Two example scripts tdemo_nim py and tdemo_round_dance py have been added to the Lib turtledemo directory,en
1948,wave Read and write WAV files Source code Lib wave py The wave module provides a convenient interface to the Waveform Audio WAVE or WAV file format Only uncompressed PCM encoded wave files are supported Changed in version 3 12 Support for WAVE_FORMAT_EXTENSIBLE headers was added provided that the extended format is KSDATAFORMAT_SUBTYPE_PCM The wave module defines the following function and exception wave open file mode None If file is a string open the file by that name otherwise treat it as a file like object mode can be rb Read only mode wb Write only mode Note that it does not allow read write WAV files A mode of rb returns a Wave_read object while a mode of wb returns a Wave_write object If mode is omitted and a file like object is passed as file file mode is used as the default value for mode If you pass in a file like object the wave object will not close it when its close method is called it is the caller s responsibility to close the file object The open function may be used in a with statement When the with block completes the Wave_read close or Wave_write close method is called Changed in version 3 4 Added support for unseekable files exception wave Error An error raised when something is impossible because it violates the WAV specification or hits an implementation deficiency Wave_read Objects class wave Wave_read Read a WAV file Wave_read objects as returned by open have the following methods close Close the stream if it was opened by wave and make the instance unusable This is called automatically on object collection getnchannels Returns number of audio channels 1 for mono 2 for stereo getsampwidth Returns sample width in bytes getframerate Returns sampling frequency getnframes Returns number of audio frames getcomptype Returns compression type NONE is the only supported type getcompname Human readable version of getcomptype Usually not compressed parallels NONE getparams Returns a namedtuple nchannels sampwidth framerate nframes comptype compname equivalent to output of the get methods readframes n Reads and returns at most n frames of audio as a bytes object rewind Rewind the file pointer to the beginning of the audio stream The following two methods are defined for compatibility with the aifc module and don t do anything interesting getmarkers Returns None getmark id Raise an error The following two methods define a term position which is compatible between them and is otherwise implementation dependent setpos pos Set the file pointer to the specified position tell Return current file pointer position Wave_write Objects class wave Wave_write Write a WAV file Wave_write objects as returned by open For seekable output streams the wave header will automatically be updated to reflect the number of frames actually written For unseekable streams the nframes value must be accurate when the first frame data is written An accurate nframes value can be achieved either by calling setnframes or setparams with the number of frames that will be written before close is called and then using writeframesraw to write the frame data or by calling writeframes with all of the frame data to be written In the latter case writeframes will calculate the number of frames in the data and set nframes accordingly before writing the frame data Changed in version 3 4 Added support for unseekable files Wave_write objects have the following methods close Make sure nframes is correct and close the file if it was opened by wave This method is called upon object collection It will raise an exception if the output stream is not seekable and nframes does not match the number of frames actually written setnchannels n Set the number of channels setsampwidth n Set the sample width to n bytes setframerate n Set the frame rate to n Changed in version 3 2 A non integral input to this method is rounded to the nearest integer setnframes n Set the number of frames to n This will be changed later if the number of frames actually written is different this update attempt will raise an error if the output stream is not seekable setcomptype type name Set ,en
1949,the compression type and description At the moment only compression type NONE is supported meaning no compression setparams tuple The tuple should be nchannels sampwidth framerate nframes comptype compname with values valid for the set methods Sets all parameters tell Return current position in the file with the same disclaimer for the Wave_read tell and Wave_read setpos methods writeframesraw data Write audio frames without correcting nframes Changed in version 3 4 Any bytes like object is now accepted writeframes data Write audio frames and make sure nframes is correct It will raise an error if the output stream is not seekable and the total number of frames that have been written after data has been written does not match the previously set value for nframes Changed in version 3 4 Any bytes like object is now accepted Note that it is invalid to set any parameters after calling writeframes or writeframesraw and any attempt to do so will raise wave Error,en
1950,Operating System Utilities PyObject PyOS_FSPath PyObject path Return value New reference Part of the Stable ABI since version 3 6 Return the file system representation for path If the object is a str or bytes object then a new strong reference is returned If the object implements the os PathLike interface then __fspath__ is returned as long as it is a str or bytes object Otherwise TypeError is raised and NULL is returned New in version 3 6 int Py_FdIsInteractive FILE fp const char filename Return true nonzero if the standard I O file fp with name filename is deemed interactive This is the case for files for which isatty fileno fp is true If the PyConfig interactive is non zero this function also returns true if the filename pointer is NULL or if the name is equal to one of the strings stdin or This function must not be called before Python is initialized void PyOS_BeforeFork Part of the Stable ABI on platforms with fork since version 3 7 Function to prepare some internal state before a process fork This should be called before calling fork or any similar function that clones the current process Only available on systems where fork is defined Warning The C fork call should only be made from the main thread of the main interpreter The same is true for PyOS_BeforeFork New in version 3 7 void PyOS_AfterFork_Parent Part of the Stable ABI on platforms with fork since version 3 7 Function to update some internal state after a process fork This should be called from the parent process after calling fork or any similar function that clones the current process regardless of whether process cloning was successful Only available on systems where fork is defined Warning The C fork call should only be made from the main thread of the main interpreter The same is true for PyOS_AfterFork_Parent New in version 3 7 void PyOS_AfterFork_Child Part of the Stable ABI on platforms with fork since version 3 7 Function to update internal interpreter state after a process fork This must be called from the child process after calling fork or any similar function that clones the current process if there is any chance the process will call back into the Python interpreter Only available on systems where fork is defined Warning The C fork call should only be made from the main thread of the main interpreter The same is true for PyOS_AfterFork_Child New in version 3 7 See also os register_at_fork allows registering custom Python functions to be called by PyOS_BeforeFork PyOS_AfterFork_Parent and PyOS_AfterFork_Child void PyOS_AfterFork Part of the Stable ABI on platforms with fork Function to update some internal state after a process fork this should be called in the new process if the Python interpreter will continue to be used If a new executable is loaded into the new process this function does not need to be called Deprecated since version 3 7 This function is superseded by PyOS_AfterFork_Child int PyOS_CheckStack Part of the Stable ABI on platforms with USE_STACKCHECK since version 3 7 Return true when the interpreter runs out of stack space This is a reliable check but is only available when USE_STACKCHECK is defined currently on certain versions of Windows using the Microsoft Visual C compiler USE_STACKCHECK will be defined automatically you should never change the definition in your own code typedef void PyOS_sighandler_t int Part of the Stable ABI PyOS_sighandler_t PyOS_getsig int i Part of the Stable ABI Return the current signal handler for signal i This is a thin wrapper around either sigaction or signal Do not call those functions directly PyOS_sighandler_t PyOS_setsig int i PyOS_sighandler_t h Part of the Stable ABI Set the signal handler for signal i to be h return the old signal handler This is a thin wrapper around either sigaction or signal Do not call those functions directly wchar_t Py_DecodeLocale const char arg size_t size Part of the Stable ABI since version 3 7 Warning This function should not be called directly use the PyConfig API with the PyConfig_SetBytesString function which ensures that Python is preinitialized This func,en
1951,tion must not be called before Python is preinitialized and so that the LC_CTYPE locale is properly configured see the Py_PreInitialize function Decode a byte string from the filesystem encoding and error handler If the error handler is surrogateescape error handler undecodable bytes are decoded as characters in range U DC80 U DCFF and if a byte sequence can be decoded as a surrogate character the bytes are escaped using the surrogateescape error handler instead of decoding them Return a pointer to a newly allocated wide character string use PyMem_RawFree to free the memory If size is not NULL write the number of wide characters excluding the null character into size Return NULL on decoding error or memory allocation error If size is not NULL size is set to size_t 1 on memory error or set to size_t 2 on decoding error The filesystem encoding and error handler are selected by PyConfig_Read see filesystem_encoding and filesystem_errors members of PyConfig Decoding errors should never happen unless there is a bug in the C library Use the Py_EncodeLocale function to encode the character string back to a byte string See also The PyUnicode_DecodeFSDefaultAndSize and PyUnicode_DecodeLocaleAndSize functions New in version 3 5 Changed in version 3 7 The function now uses the UTF 8 encoding in the Python UTF 8 Mode Changed in version 3 8 The function now uses the UTF 8 encoding on Windows if PyPreConfig legacy_windows_fs_encoding is zero char Py_EncodeLocale const wchar_t text size_t error_pos Part of the Stable ABI since version 3 7 Encode a wide character string to the filesystem encoding and error handler If the error handler is surrogateescape error handler surrogate characters in the range U DC80 U DCFF are converted to bytes 0x80 0xFF Return a pointer to a newly allocated byte string use PyMem_Free to free the memory Return NULL on encoding error or memory allocation error If error_pos is not NULL error_pos is set to size_t 1 on success or set to the index of the invalid character on encoding error The filesystem encoding and error handler are selected by PyConfig_Read see filesystem_encoding and filesystem_errors members of PyConfig Use the Py_DecodeLocale function to decode the bytes string back to a wide character string Warning This function must not be called before Python is preinitialized and so that the LC_CTYPE locale is properly configured see the Py_PreInitialize function See also The PyUnicode_EncodeFSDefault and PyUnicode_EncodeLocale functions New in version 3 5 Changed in version 3 7 The function now uses the UTF 8 encoding in the Python UTF 8 Mode Changed in version 3 8 The function now uses the UTF 8 encoding on Windows if PyPreConfig legacy_windows_fs_encoding is zero System Functions These are utility functions that make functionality from the sys module accessible to C code They all work with the current interpreter thread s sys module s dict which is contained in the internal thread state structure PyObject PySys_GetObject const char name Return value Borrowed reference Part of the Stable ABI Return the object name from the sys module or NULL if it does not exist without setting an exception int PySys_SetObject const char name PyObject v Part of the Stable ABI Set name in the sys module to v unless v is NULL in which case name is deleted from the sys module Returns 0 on success 1 on error void PySys_ResetWarnOptions Part of the Stable ABI Reset sys warnoptions to an empty list This function may be called prior to Py_Initialize void PySys_AddWarnOption const wchar_t s Part of the Stable ABI This API is kept for backward compatibility setting PyConfig warnoptions should be used instead see Python Initialization Configuration Append s to sys warnoptions This function must be called prior to Py_Initialize in order to affect the warnings filter list Deprecated since version 3 11 void PySys_AddWarnOptionUnicode PyObject unicode Part of the Stable ABI This API is kept for backward compatibility setting PyConfig warnoptions should be used instead see Python Initialization Configuration Append unicode to sys warn,en
1952,options Note this function is not currently usable from outside the CPython implementation as it must be called prior to the implicit import of warnings in Py_Initialize to be effective but can t be called until enough of the runtime has been initialized to permit the creation of Unicode objects Deprecated since version 3 11 void PySys_SetPath const wchar_t path Part of the Stable ABI This API is kept for backward compatibility setting PyConfig module_search_paths and PyConfig module_search_paths_set should be used instead see Python Initialization Configuration Set sys path to a list object of paths found in path which should be a list of paths separated with the platform s search path delimiter on Unix on Windows Deprecated since version 3 11 void PySys_WriteStdout const char format Part of the Stable ABI Write the output string described by format to sys stdout No exceptions are raised even if truncation occurs see below format should limit the total size of the formatted output string to 1000 bytes or less after 1000 bytes the output string is truncated In particular this means that no unrestricted s formats should occur these should be limited using N s where N is a decimal number calculated so that N plus the maximum size of other formatted text does not exceed 1000 bytes Also watch out for f which can print hundreds of digits for very large numbers If a problem occurs or sys stdout is unset the formatted message is written to the real C level stdout void PySys_WriteStderr const char format Part of the Stable ABI As PySys_WriteStdout but write to sys stderr or stderr instead void PySys_FormatStdout const char format Part of the Stable ABI Function similar to PySys_WriteStdout but format the message using PyUnicode_FromFormatV and don t truncate the message to an arbitrary length New in version 3 2 void PySys_FormatStderr const char format Part of the Stable ABI As PySys_FormatStdout but write to sys stderr or stderr instead New in version 3 2 void PySys_AddXOption const wchar_t s Part of the Stable ABI since version 3 7 This API is kept for backward compatibility setting PyConfig xoptions should be used instead see Python Initialization Configuration Parse s as a set of X options and add them to the current options mapping as returned by PySys_GetXOptions This function may be called prior to Py_Initialize New in version 3 2 Deprecated since version 3 11 PyObject PySys_GetXOptions Return value Borrowed reference Part of the Stable ABI since version 3 7 Return the current dictionary of X options similarly to sys _xoptions On error NULL is returned and an exception is set New in version 3 2 int PySys_Audit const char event const char format Raise an auditing event with any active hooks Return zero for success and non zero with an exception set on failure If any hooks have been added format and other arguments will be used to construct a tuple to pass Apart from N the same format characters as used in Py_BuildValue are available If the built value is not a tuple it will be added into a single element tuple The N format option consumes a reference but since there is no way to know whether arguments to this function will be consumed using it may cause reference leaks Note that format characters should always be treated as Py_ssize_t regardless of whether PY_SSIZE_T_CLEAN was defined sys audit performs the same function from Python code New in version 3 8 Changed in version 3 8 2 Require Py_ssize_t for format characters Previously an unavoidable deprecation warning was raised int PySys_AddAuditHook Py_AuditHookFunction hook void userData Append the callable hook to the list of active auditing hooks Return zero on success and non zero on failure If the runtime has been initialized also set an error on failure Hooks added through this API are called for all interpreters created by the runtime The userData pointer is passed into the hook function Since hook functions may be called from different runtimes this pointer should not refer directly to Python state This function is safe to call before Py_Initialize When called afte,en
1953,r runtime initialization existing audit hooks are notified and may silently abort the operation by raising an error subclassed from Exception other errors will not be silenced The hook function is always called with the GIL held by the Python interpreter that raised the event See PEP 578 for a detailed description of auditing Functions in the runtime and standard library that raise events are listed in the audit events table Details are in each function s documentation If the interpreter is initialized this function raises an auditing event sys addaudithook with no arguments If any existing hooks raise an exception derived from Exception the new hook will not be added and the exception is cleared As a result callers cannot assume that their hook has been added unless they control all existing hooks typedef int Py_AuditHookFunction const char event PyObject args void userData The type of the hook function event is the C string event argument passed to PySys_Audit args is guaranteed to be a PyTupleObject userData is the argument passed to PySys_AddAuditHook New in version 3 8 Process Control void Py_FatalError const char message Part of the Stable ABI Print a fatal error message and kill the process No cleanup is performed This function should only be invoked when a condition is detected that would make it dangerous to continue using the Python interpreter e g when the object administration appears to be corrupted On Unix the standard C library function abort is called which will attempt to produce a core file The Py_FatalError function is replaced with a macro which logs automatically the name of the current function unless the Py_LIMITED_API macro is defined Changed in version 3 9 Log the function name automatically void Py_Exit int status Part of the Stable ABI Exit the current process This calls Py_FinalizeEx and then calls the standard C library function exit status If Py_FinalizeEx indicates an error the exit status is set to 120 Changed in version 3 6 Errors from finalization no longer ignored int Py_AtExit void func Part of the Stable ABI Register a cleanup function to be called by Py_FinalizeEx The cleanup function will be called with no arguments and should return no value At most 32 cleanup functions can be registered When the registration is successful Py_AtExit returns 0 on failure it returns 1 The cleanup function registered last is called first Each cleanup function will be called at most once Since Python s internal finalization will have completed before the cleanup function no Python APIs should be called by func,en
1954,Audit events table This table contains all events raised by sys audit or PySys_Audit calls throughout the CPython runtime and the standard library These calls were added in 3 8 or later see PEP 578 See sys addaudithook and PySys_AddAuditHook for information on handling these events CPython implementation detail This table is generated from the CPython documentation and may not represent events raised by other implementations See your runtime specific documentation for actual events raised Audit event Arguments References _thread start_new_thread function args kwargs 1 array __new__ typecode initializer 1 builtins breakpoint breakpointhook 1 builtins id id 1 builtins input prompt 1 builtins input result result 1 code __new__ code filename name argcount 1 posonlyargcount kwonlyargcount nlocals stacksize flags compile source filename 1 cpython PyInterpreterState_Cl 1 ear cpython PyInterpreterState_New 1 cpython _PySys_ClearAuditHooks 1 cpython run_command command 1 cpython run_file filename 1 cpython run_interactivehook hook 1 cpython run_module module name 1 cpython run_startup filename 1 cpython run_stdin 1 ctypes addressof obj 1 ctypes call_function func_pointer arguments 1 ctypes cdata address 1 ctypes cdata buffer pointer size offset 1 2 ctypes create_string_buffer init size 1 ctypes create_unicode_buffer init size 1 ctypes dlopen name 1 ctypes dlsym library name 1 ctypes dlsym handle handle name 1 ctypes get_errno 1 ctypes get_last_error 1 ctypes set_errno errno 1 ctypes set_exception code 1 ctypes set_last_error error 1 ctypes string_at address size 1 ctypes wstring_at address size 1 ensurepip bootstrap root 1 exec code_object 1 2 fcntl fcntl fd cmd arg 1 fcntl flock fd operation 1 fcntl ioctl fd request arg 1 fcntl lockf fd cmd len start whence 1 ftplib connect self host port 1 ftplib sendcmd self cmd 1 2 function __new__ code 1 gc get_objects generation 1 gc get_referents objs 1 gc get_referrers objs 1 glob glob pathname recursive 1 2 glob glob 2 pathname recursive root_dir dir_fd 1 2 http client connect self host port 1 http client send self data 1 imaplib open self host port 1 imaplib send self data 1 import module filename sys path sys meta_path 1 sys path_hooks marshal dumps value version 1 marshal load 1 marshal loads bytes 1 mmap __new__ fileno length access offset 1 msvcrt get_osfhandle fd 1 msvcrt locking fd mode nbytes 1 msvcrt open_osfhandle handle flags 1 nntplib connect self host port 1 2 nntplib putline self line 1 2 object __delattr__ obj name 1 object __getattr__ obj name 1 object __setattr__ obj name value 1 open path mode flags 1 2 3 os add_dll_directory path 1 os chdir path 1 2 os chflags path flags 1 2 os chmod path mode dir_fd 1 2 3 os chown path uid gid dir_fd 1 2 3 os exec path args env 1 os fork 1 os forkpty 1 os fwalk top topdown onerror follow_symlinks 1 dir_fd os getxattr path attribute 1 os kill pid sig 1 os killpg pgid sig 1 os link src dst src_dir_fd dst_dir_fd 1 os listdir path 1 os listdrives 1 os listmounts volume 1 os listvolumes 1 os listxattr path 1 os lockf fd cmd len 1 os mkdir path mode dir_fd 1 2 os posix_spawn path argv env 1 2 os putenv key value 1 os remove path dir_fd 1 2 3 os removexattr path attribute 1 os rename src dst src_dir_fd dst_dir_fd 1 2 3 os rmdir path dir_fd 1 os scandir path 1 os setxattr path attribute value flags 1 os spawn mode path args env 1 os startfile path operation 1 os startfile 2 path operation arguments cwd show_cmd 1 os symlink src dst dir_fd 1 os system command 1 os truncate fd length 1 2 os unsetenv key 1 os utime path times ns dir_fd 1 os walk top topdown onerror followlinks 1 pathlib Path glob self pattern 1 pathlib Path rglob self pattern 1 pdb Pdb 1 pickle find_class module name 1 poplib connect self host port 1 2 poplib putline self line 1 2 pty spawn argv 1 resource prlimit pid resource limits 1 resource setrlimit resource limits 1 setopencodehook 1 shutil chown path user group 1 shutil copyfile src dst 1 2 3 shutil copymode src dst 1 2 shutil copystat src dst 1 2 shutil copytree src dst 1 shutil make_archive base_name format root_dir bas,en
1955,e_dir 1 shutil move src dst 1 shutil rmtree path dir_fd 1 shutil unpack_archive filename extract_dir format 1 signal pthread_kill thread_id signalnum 1 smtplib connect self host port 1 smtplib send self data 1 socket __new__ self family type protocol 1 socket bind self address 1 socket connect self address 1 2 socket getaddrinfo host port family type protocol 1 socket gethostbyaddr ip_address 1 socket gethostbyname hostname 1 2 socket gethostname 1 socket getnameinfo sockaddr 1 socket getservbyname servicename protocolname 1 socket getservbyport port protocolname 1 socket sendmsg self address 1 socket sendto self address 1 socket sethostname name 1 sqlite3 connect database 1 sqlite3 connect handle connection_handle 1 sqlite3 enable_load_extension connection enabled 1 sqlite3 load_extension connection path 1 subprocess Popen executable args cwd env 1 sys _current_exceptions 1 sys _current_frames 1 sys _getframe frame 1 sys _getframemodulename depth 1 sys addaudithook 1 2 sys excepthook hook type value traceback 1 sys set_asyncgen_hooks_finali 1 zer sys set_asyncgen_hooks_firsti 1 ter sys setprofile 1 sys settrace 1 sys unraisablehook hook unraisable 1 syslog closelog 1 syslog openlog ident logoption facility 1 syslog setlogmask maskpri 1 syslog syslog priority message 1 telnetlib Telnet open self host port 1 telnetlib Telnet write self buffer 1 tempfile mkdtemp fullpath 1 2 tempfile mkstemp fullpath 1 2 3 urllib Request fullurl data headers method 1 webbrowser open url 1 winreg ConnectRegistry computer_name key 1 winreg CreateKey key sub_key access 1 2 winreg DeleteKey key sub_key access 1 2 winreg DeleteValue key value 1 winreg DisableReflectionKey key 1 winreg EnableReflectionKey key 1 winreg EnumKey key index 1 winreg EnumValue key index 1 winreg ExpandEnvironmentStrin str 1 gs winreg LoadKey key sub_key file_name 1 winreg OpenKey key sub_key access 1 winreg OpenKey result key 1 2 3 winreg PyHKEY Detach key 1 winreg QueryInfoKey key 1 winreg QueryReflectionKey key 1 winreg QueryValue key sub_key value_name 1 2 winreg SaveKey key file_name 1 winreg SetValue key sub_key type value 1 2 The following events are raised internally and do not correspond to any public API of CPython Audit event Arguments _winapi CreateFile file_name desired_access share_mode creation_disposition flags_and_attributes _winapi CreateJunction src_path dst_path _winapi CreateNamedPipe name open_mode pipe_mode _winapi CreatePipe _winapi CreateProcess application_name command_line current_directory _winapi OpenProcess process_id desired_access _winapi TerminateProcess handle exit_code ctypes PyObj_FromPtr obj,en
1956,numbers Numeric abstract base classes Source code Lib numbers py The numbers module PEP 3141 defines a hierarchy of numeric abstract base classes which progressively define more operations None of the types defined in this module are intended to be instantiated class numbers Number The root of the numeric hierarchy If you just want to check if an argument x is a number without caring what kind use isinstance x Number The numeric tower class numbers Complex Subclasses of this type describe complex numbers and include the operations that work on the built in complex type These are conversions to complex and bool real imag abs conjugate and All except and are abstract real Abstract Retrieves the real component of this number imag Abstract Retrieves the imaginary component of this number abstractmethod conjugate Abstract Returns the complex conjugate For example 1 3j conjugate 1 3j class numbers Real To Complex Real adds the operations that work on real numbers In short those are a conversion to float math trunc round math floor math ceil divmod and Real also provides defaults for complex real imag and conjugate class numbers Rational Subtypes Real and adds numerator and denominator properties It also provides a default for float The numerator and denominator values should be instances of Integral and should be in lowest terms with denominator positive numerator Abstract denominator Abstract class numbers Integral Subtypes Rational and adds a conversion to int Provides defaults for float numerator and denominator Adds abstract methods for pow with modulus and bit string operations Notes for type implementors Implementors should be careful to make equal numbers equal and hash them to the same values This may be subtle if there are two different extensions of the real numbers For example fractions Fraction implements hash as follows def __hash__ self if self denominator 1 Get integers right return hash self numerator Expensive check but definitely correct if self float self return hash float self else Use tuple s hash to avoid a high collision rate on simple fractions return hash self numerator self denominator Adding More Numeric ABCs There are of course more possible ABCs for numbers and this would be a poor hierarchy if it precluded the possibility of adding those You can add MyFoo between Complex and Real with class MyFoo Complex MyFoo register Real Implementing the arithmetic operations We want to implement the arithmetic operations so that mixed mode operations either call an implementation whose author knew about the types of both arguments or convert both to the nearest built in type and do the operation there For subtypes of Integral this means that __add__ and __radd__ should be defined as class MyIntegral Integral def __add__ self other if isinstance other MyIntegral return do_my_adding_stuff self other elif isinstance other OtherTypeIKnowAbout return do_my_other_adding_stuff self other else return NotImplemented def __radd__ self other if isinstance other MyIntegral return do_my_adding_stuff other self elif isinstance other OtherTypeIKnowAbout return do_my_other_adding_stuff other self elif isinstance other Integral return int other int self elif isinstance other Real return float other float self elif isinstance other Complex return complex other complex self else return NotImplemented There are 5 different cases for a mixed type operation on subclasses of Complex I ll refer to all of the above code that doesn t refer to MyIntegral and OtherTypeIKnowAbout as boilerplate a will be an instance of A which is a subtype of Complex a A Complex and b B Complex I ll consider a b 1 If A defines an __add__ which accepts b all is well 2 If A falls back to the boilerplate code and it were to return a value from __add__ we d miss the possibility that B defines a more intelligent __radd__ so the boilerplate should return NotImplemented from __add__ Or A may not implement __add__ at all 3 Then B s __radd__ gets a chance If it accepts a all is well 4 If it falls back to the boilerplate there are no more possible methods to try so,en
1957, this is where the default implementation should live 5 If B A Python tries B __radd__ before A __add__ This is ok because it was implemented with knowledge of A so it can handle those instances before delegating to Complex If A Complex and B Real without sharing any other knowledge then the appropriate shared operation is the one involving the built in complex and both __radd__ s land there so a b b a Because most of the operations on any given type will be very similar it can be useful to define a helper function which generates the forward and reverse instances of any given operator For example fractions Fraction uses def _operator_fallbacks monomorphic_operator fallback_operator def forward a b if isinstance b int Fraction return monomorphic_operator a b elif isinstance b float return fallback_operator float a b elif isinstance b complex return fallback_operator complex a b else return NotImplemented forward __name__ __ fallback_operator __name__ __ forward __doc__ monomorphic_operator __doc__ def reverse b a if isinstance a Rational Includes ints return monomorphic_operator a b elif isinstance a Real return fallback_operator float a float b elif isinstance a Complex return fallback_operator complex a complex b else return NotImplemented reverse __name__ __r fallback_operator __name__ __ reverse __doc__ monomorphic_operator __doc__ return forward reverse def _add a b a b return Fraction a numerator b denominator b numerator a denominator a denominator b denominator __add__ __radd__ _operator_fallbacks _add operator add,en
1958,token Constants used with Python parse trees Source code Lib token py This module provides constants which represent the numeric values of leaf nodes of the parse tree terminal tokens Refer to the file Grammar Tokens in the Python distribution for the definitions of the names in the context of the language grammar The specific numeric values which the names map to may change between Python versions The module also provides a mapping from numeric codes to names and some functions The functions mirror definitions in the Python C header files token tok_name Dictionary mapping the numeric values of the constants defined in this module back to name strings allowing more human readable representation of parse trees to be generated token ISTERMINAL x Return True for terminal token values token ISNONTERMINAL x Return True for non terminal token values token ISEOF x Return True if x is the marker indicating the end of input The token constants are token ENDMARKER token NAME token NUMBER token STRING token NEWLINE token INDENT token DEDENT token LPAR Token value for token RPAR Token value for token LSQB Token value for token RSQB Token value for token COLON Token value for token COMMA Token value for token SEMI Token value for token PLUS Token value for token MINUS Token value for token STAR Token value for token SLASH Token value for token VBAR Token value for token AMPER Token value for token LESS Token value for token GREATER Token value for token EQUAL Token value for token DOT Token value for token PERCENT Token value for token LBRACE Token value for token RBRACE Token value for token EQEQUAL Token value for token NOTEQUAL Token value for token LESSEQUAL Token value for token GREATEREQUAL Token value for token TILDE Token value for token CIRCUMFLEX Token value for token LEFTSHIFT Token value for token RIGHTSHIFT Token value for token DOUBLESTAR Token value for token PLUSEQUAL Token value for token MINEQUAL Token value for token STAREQUAL Token value for token SLASHEQUAL Token value for token PERCENTEQUAL Token value for token AMPEREQUAL Token value for token VBAREQUAL Token value for token CIRCUMFLEXEQUAL Token value for token LEFTSHIFTEQUAL Token value for token RIGHTSHIFTEQUAL Token value for token DOUBLESTAREQUAL Token value for token DOUBLESLASH Token value for token DOUBLESLASHEQUAL Token value for token AT Token value for token ATEQUAL Token value for token RARROW Token value for token ELLIPSIS Token value for token COLONEQUAL Token value for token EXCLAMATION Token value for token OP token AWAIT token ASYNC token TYPE_IGNORE token TYPE_COMMENT token SOFT_KEYWORD token FSTRING_START token FSTRING_MIDDLE token FSTRING_END token COMMENT token NL token ERRORTOKEN token N_TOKENS token NT_OFFSET The following token type values aren t used by the C tokenizer but are needed for the tokenize module token COMMENT Token value used to indicate a comment token NL Token value used to indicate a non terminating newline The NEWLINE token indicates the end of a logical line of Python code NL tokens are generated when a logical line of code is continued over multiple physical lines token ENCODING Token value that indicates the encoding used to decode the source bytes into text The first token returned by tokenize tokenize will always be an ENCODING token token TYPE_COMMENT Token value indicating that a type comment was recognized Such tokens are only produced when ast parse is invoked with type_comments True Changed in version 3 5 Added AWAIT and ASYNC tokens Changed in version 3 7 Added COMMENT NL and ENCODING tokens Changed in version 3 7 Removed AWAIT and ASYNC tokens async and await are now tokenized as NAME tokens Changed in version 3 8 Added TYPE_COMMENT TYPE_IGNORE COLONEQUAL Added AWAIT and ASYNC tokens back they re needed to support parsing older Python versions for ast parse with feature_version set to 6 or lower,en
1959,mimetypes Map filenames to MIME types Source code Lib mimetypes py The mimetypes module converts between a filename or URL and the MIME type associated with the filename extension Conversions are provided from filename to MIME type and from MIME type to filename extension encodings are not supported for the latter conversion The module provides one class and a number of convenience functions The functions are the normal interface to this module but some applications may be interested in the class as well The functions described below provide the primary interface for this module If the module has not been initialized they will call init if they rely on the information init sets up mimetypes guess_type url strict True Guess the type of a file based on its filename path or URL given by url URL can be a string or a path like object The return value is a tuple type encoding where type is None if the type can t be guessed missing or unknown suffix or a string of the form type subtype usable for a MIME content type header encoding is None for no encoding or the name of the program used to encode e g compress or gzip The encoding is suitable for use as a Content Encoding header not as a Content Transfer Encoding header The mappings are table driven Encoding suffixes are case sensitive type suffixes are first tried case sensitively then case insensitively The optional strict argument is a flag specifying whether the list of known MIME types is limited to only the official types registered with IANA When strict is True the default only the IANA types are supported when strict is False some additional non standard but commonly used MIME types are also recognized Changed in version 3 8 Added support for url being a path like object mimetypes guess_all_extensions type strict True Guess the extensions for a file based on its MIME type given by type The return value is a list of strings giving all possible filename extensions including the leading dot The extensions are not guaranteed to have been associated with any particular data stream but would be mapped to the MIME type type by guess_type The optional strict argument has the same meaning as with the guess_type function mimetypes guess_extension type strict True Guess the extension for a file based on its MIME type given by type The return value is a string giving a filename extension including the leading dot The extension is not guaranteed to have been associated with any particular data stream but would be mapped to the MIME type type by guess_type If no extension can be guessed for type None is returned The optional strict argument has the same meaning as with the guess_type function Some additional functions and data items are available for controlling the behavior of the module mimetypes init files None Initialize the internal data structures If given files must be a sequence of file names which should be used to augment the default type map If omitted the file names to use are taken from knownfiles on Windows the current registry settings are loaded Each file named in files or knownfiles takes precedence over those named before it Calling init repeatedly is allowed Specifying an empty list for files will prevent the system defaults from being applied only the well known values will be present from a built in list If files is None the internal data structure is completely rebuilt to its initial default value This is a stable operation and will produce the same results when called multiple times Changed in version 3 2 Previously Windows registry settings were ignored mimetypes read_mime_types filename Load the type map given in the file filename if it exists The type map is returned as a dictionary mapping filename extensions including the leading dot to strings of the form type subtype If the file filename does not exist or cannot be read None is returned mimetypes add_type type ext strict True Add a mapping from the MIME type type to the extension ext When the extension is already known the new type will replace the old one When the type is already known the extension will,en
1960, be added to the list of known extensions When strict is True the default the mapping will be added to the official MIME types otherwise to the non standard ones mimetypes inited Flag indicating whether or not the global data structures have been initialized This is set to True by init mimetypes knownfiles List of type map file names commonly installed These files are typically named mime types and are installed in different locations by different packages mimetypes suffix_map Dictionary mapping suffixes to suffixes This is used to allow recognition of encoded files for which the encoding and the type are indicated by the same extension For example the tgz extension is mapped to tar gz to allow the encoding and type to be recognized separately mimetypes encodings_map Dictionary mapping filename extensions to encoding types mimetypes types_map Dictionary mapping filename extensions to MIME types mimetypes common_types Dictionary mapping filename extensions to non standard but commonly found MIME types An example usage of the module import mimetypes mimetypes init mimetypes knownfiles etc mime types etc httpd mime types mimetypes suffix_map tgz tar gz mimetypes encodings_map gz gzip mimetypes types_map tgz application x tar gz MimeTypes Objects The MimeTypes class may be useful for applications which may want more than one MIME type database it provides an interface similar to the one of the mimetypes module class mimetypes MimeTypes filenames strict True This class represents a MIME types database By default it provides access to the same database as the rest of this module The initial database is a copy of that provided by the module and may be extended by loading additional mime types style files into the database using the read or readfp methods The mapping dictionaries may also be cleared before loading additional data if the default data is not desired The optional filenames parameter can be used to cause additional files to be loaded on top of the default database suffix_map Dictionary mapping suffixes to suffixes This is used to allow recognition of encoded files for which the encoding and the type are indicated by the same extension For example the tgz extension is mapped to tar gz to allow the encoding and type to be recognized separately This is initially a copy of the global suffix_map defined in the module encodings_map Dictionary mapping filename extensions to encoding types This is initially a copy of the global encodings_map defined in the module types_map Tuple containing two dictionaries mapping filename extensions to MIME types the first dictionary is for the non standards types and the second one is for the standard types They are initialized by common_types and types_map types_map_inv Tuple containing two dictionaries mapping MIME types to a list of filename extensions the first dictionary is for the non standards types and the second one is for the standard types They are initialized by common_types and types_map guess_extension type strict True Similar to the guess_extension function using the tables stored as part of the object guess_type url strict True Similar to the guess_type function using the tables stored as part of the object guess_all_extensions type strict True Similar to the guess_all_extensions function using the tables stored as part of the object read filename strict True Load MIME information from a file named filename This uses readfp to parse the file If strict is True information will be added to list of standard types else to the list of non standard types readfp fp strict True Load MIME type information from an open file fp The file must have the format of the standard mime types files If strict is True information will be added to the list of standard types else to the list of non standard types read_windows_registry strict True Load MIME type information from the Windows registry Availability Windows If strict is True information will be added to the list of standard types else to the list of non standard types New in version 3 2,en
1961,tkinter dnd Drag and drop support Source code Lib tkinter dnd py Note This is experimental and due to be deprecated when it is replaced with the Tk DND The tkinter dnd module provides drag and drop support for objects within a single application within the same window or between windows To enable an object to be dragged you must create an event binding for it that starts the drag and drop process Typically you bind a ButtonPress event to a callback function that you write see Bindings and Events The function should call dnd_start where source is the object to be dragged and event is the event that invoked the call the argument to your callback function Selection of a target object occurs as follows 1 Top down search of area under mouse for target widget Target widget should have a callable dnd_accept attribute If dnd_accept is not present or returns None search moves to parent widget If no target widget is found then the target object is None 2 Call to old_target dnd_leave source event 3 Call to new_target dnd_enter source event 4 Call to target dnd_commit source event to notify of drop 5 Call to source dnd_end target event to signal end of drag and drop class tkinter dnd DndHandler source event The DndHandler class handles drag and drop events tracking Motion and ButtonRelease events on the root of the event widget cancel event None Cancel the drag and drop process finish event commit 0 Execute end of drag and drop functions on_motion event Inspect area below mouse for target objects while drag is performed on_release event Signal end of drag when the release pattern is triggered tkinter dnd dnd_start source event Factory function for drag and drop process See also Bindings and Events,en
1962,pathlib Object oriented filesystem paths New in version 3 4 Source code Lib pathlib py This module offers classes representing filesystem paths with semantics appropriate for different operating systems Path classes are divided between pure paths which provide purely computational operations without I O and concrete paths which inherit from pure paths but also provide I O operations image If you ve never used this module before or just aren t sure which class is right for your task Path is most likely what you need It instantiates a concrete path for the platform the code is running on Pure paths are useful in some special cases for example 1 If you want to manipulate Windows paths on a Unix machine or vice versa You cannot instantiate a WindowsPath when running on Unix but you can instantiate PureWindowsPath 2 You want to make sure that your code only manipulates paths without actually accessing the OS In this case instantiating one of the pure classes may be useful since those simply don t have any OS accessing operations See also PEP 428 The pathlib module object oriented filesystem paths See also For low level path manipulation on strings you can also use the os path module Basic use Importing the main class from pathlib import Path Listing subdirectories p Path x for x in p iterdir if x is_dir PosixPath hg PosixPath docs PosixPath dist PosixPath __pycache__ PosixPath build Listing Python source files in this directory tree list p glob py PosixPath test_pathlib py PosixPath setup py PosixPath pathlib py PosixPath docs conf py PosixPath build lib pathlib py Navigating inside a directory tree p Path etc q p init d reboot q PosixPath etc init d reboot q resolve PosixPath etc rc d init d halt Querying path properties q exists True q is_dir False Opening a file with q open as f f readline bin bash n Pure paths Pure path objects provide path handling operations which don t actually access a filesystem There are three ways to access these classes which we also call flavours class pathlib PurePath pathsegments A generic class that represents the system s path flavour instantiating it creates either a PurePosixPath or a PureWindowsPath PurePath setup py Running on a Unix machine PurePosixPath setup py Each element of pathsegments can be either a string representing a path segment or an object implementing the os PathLike interface where the __fspath__ method returns a string such as another path object PurePath foo some path bar PurePosixPath foo some path bar PurePath Path foo Path bar PurePosixPath foo bar When pathsegments is empty the current directory is assumed PurePath PurePosixPath If a segment is an absolute path all previous segments are ignored like os path join PurePath etc usr lib64 PurePosixPath usr lib64 PureWindowsPath c Windows d bar PureWindowsPath d bar On Windows the drive is not reset when a rooted relative path segment e g r foo is encountered PureWindowsPath c Windows Program Files PureWindowsPath c Program Files Spurious slashes and single dots are collapsed but double dots and leading double slashes are not since this would change the meaning of a path for various reasons e g symbolic links UNC paths PurePath foo bar PurePosixPath foo bar PurePath foo bar PurePosixPath foo bar PurePath foo bar PurePosixPath foo bar PurePath foo bar PurePosixPath foo bar a naïve approach would make PurePosixPath foo bar equivalent to PurePosixPath bar which is wrong if foo is a symbolic link to another directory Pure path objects implement the os PathLike interface allowing them to be used anywhere the interface is accepted Changed in version 3 6 Added support for the os PathLike interface class pathlib PurePosixPath pathsegments A subclass of PurePath this path flavour represents non Windows filesystem paths PurePosixPath etc PurePosixPath etc pathsegments is specified similarly to PurePath class pathlib PureWindowsPath pathsegments A subclass of PurePath this path flavour represents Windows filesystem paths including UNC paths PureWindowsPath c Program Files PureWindowsPath c Program Files PureWindowsPath server shar,en
1963,e file PureWindowsPath server share file pathsegments is specified similarly to PurePath Regardless of the system you re running on you can instantiate all of these classes since they don t provide any operation that does system calls General properties Paths are immutable and hashable Paths of a same flavour are comparable and orderable These properties respect the flavour s case folding semantics PurePosixPath foo PurePosixPath FOO False PureWindowsPath foo PureWindowsPath FOO True PureWindowsPath FOO in PureWindowsPath foo True PureWindowsPath C PureWindowsPath d True Paths of a different flavour compare unequal and cannot be ordered PureWindowsPath foo PurePosixPath foo False PureWindowsPath foo PurePosixPath foo Traceback most recent call last File stdin line 1 in module TypeError not supported between instances of PureWindowsPath and PurePosixPath Operators The slash operator helps create child paths like os path join If the argument is an absolute path the previous path is ignored On Windows the drive is not reset when the argument is a rooted relative path e g r foo p PurePath etc p PurePosixPath etc p init d apache2 PurePosixPath etc init d apache2 q PurePath bin usr q PurePosixPath usr bin p an_absolute_path PurePosixPath an_absolute_path PureWindowsPath c Windows Program Files PureWindowsPath c Program Files A path object can be used anywhere an object implementing os PathLike is accepted import os p PurePath etc os fspath p etc The string representation of a path is the raw filesystem path itself in native form e g with backslashes under Windows which you can pass to any function taking a file path as a string p PurePath etc str p etc p PureWindowsPath c Program Files str p c Program Files Similarly calling bytes on a path gives the raw filesystem path as a bytes object as encoded by os fsencode bytes p b etc Note Calling bytes is only recommended under Unix Under Windows the unicode form is the canonical representation of filesystem paths Accessing individual parts To access the individual parts components of a path use the following property PurePath parts A tuple giving access to the path s various components p PurePath usr bin python3 p parts usr bin python3 p PureWindowsPath c Program Files PSF p parts c Program Files PSF note how the drive and local root are regrouped in a single part Methods and properties Pure paths provide the following methods and properties PurePath drive A string representing the drive letter or name if any PureWindowsPath c Program Files drive c PureWindowsPath Program Files drive PurePosixPath etc drive UNC shares are also considered drives PureWindowsPath host share foo txt drive host share PurePath root A string representing the local or global root if any PureWindowsPath c Program Files root PureWindowsPath c Program Files root PurePosixPath etc root UNC shares always have a root PureWindowsPath host share root If the path starts with more than two successive slashes PurePosixPath collapses them PurePosixPath etc root PurePosixPath etc root PurePosixPath etc root Note This behavior conforms to The Open Group Base Specifications Issue 6 paragraph 4 11 Pathname Resolution A pathname that begins with two successive slashes may be interpreted in an implementation defined manner although more than two leading slashes shall be treated as a single slash PurePath anchor The concatenation of the drive and root PureWindowsPath c Program Files anchor c PureWindowsPath c Program Files anchor c PurePosixPath etc anchor PureWindowsPath host share anchor host share PurePath parents An immutable sequence providing access to the logical ancestors of the path p PureWindowsPath c foo bar setup py p parents 0 PureWindowsPath c foo bar p parents 1 PureWindowsPath c foo p parents 2 PureWindowsPath c Changed in version 3 10 The parents sequence now supports slices and negative index values PurePath parent The logical parent of the path p PurePosixPath a b c d p parent PurePosixPath a b c You cannot go past an anchor or empty path p PurePosixPath p parent PurePosixPath p PurePosixPath p parent PureP,en
1964,osixPath Note This is a purely lexical operation hence the following behaviour p PurePosixPath foo p parent PurePosixPath foo If you want to walk an arbitrary filesystem path upwards it is recommended to first call Path resolve so as to resolve symlinks and eliminate components PurePath name A string representing the final path component excluding the drive and root if any PurePosixPath my library setup py name setup py UNC drive names are not considered PureWindowsPath some share setup py name setup py PureWindowsPath some share name PurePath suffix The file extension of the final component if any PurePosixPath my library setup py suffix py PurePosixPath my library tar gz suffix gz PurePosixPath my library suffix PurePath suffixes A list of the path s file extensions PurePosixPath my library tar gar suffixes tar gar PurePosixPath my library tar gz suffixes tar gz PurePosixPath my library suffixes PurePath stem The final path component without its suffix PurePosixPath my library tar gz stem library tar PurePosixPath my library tar stem library PurePosixPath my library stem library PurePath as_posix Return a string representation of the path with forward slashes p PureWindowsPath c windows str p c windows p as_posix c windows PurePath as_uri Represent the path as a file URI ValueError is raised if the path isn t absolute p PurePosixPath etc passwd p as_uri file etc passwd p PureWindowsPath c Windows p as_uri file c Windows PurePath is_absolute Return whether the path is absolute or not A path is considered absolute if it has both a root and if the flavour allows a drive PurePosixPath a b is_absolute True PurePosixPath a b is_absolute False PureWindowsPath c a b is_absolute True PureWindowsPath a b is_absolute False PureWindowsPath c is_absolute False PureWindowsPath some share is_absolute True PurePath is_relative_to other Return whether or not this path is relative to the other path p PurePath etc passwd p is_relative_to etc True p is_relative_to usr False This method is string based it neither accesses the filesystem nor treats segments specially The following code is equivalent u PurePath usr u p or u in p parents False New in version 3 9 Deprecated since version 3 12 will be removed in version 3 14 Passing additional arguments is deprecated if supplied they are joined with other PurePath is_reserved With PureWindowsPath return True if the path is considered reserved under Windows False otherwise With PurePosixPath False is always returned PureWindowsPath nul is_reserved True PurePosixPath nul is_reserved False File system calls on reserved paths can fail mysteriously or have unintended effects PurePath joinpath pathsegments Calling this method is equivalent to combining the path with each of the given pathsegments in turn PurePosixPath etc joinpath passwd PurePosixPath etc passwd PurePosixPath etc joinpath PurePosixPath passwd PurePosixPath etc passwd PurePosixPath etc joinpath init d apache2 PurePosixPath etc init d apache2 PureWindowsPath c joinpath Program Files PureWindowsPath c Program Files PurePath match pattern case_sensitive None Match this path against the provided glob style pattern Return True if matching is successful False otherwise If pattern is relative the path can be either relative or absolute and matching is done from the right PurePath a b py match py True PurePath a b c py match b py True PurePath a b c py match a py False If pattern is absolute the path must be absolute and the whole path must match PurePath a py match py True PurePath a b py match py False The pattern may be another path object this speeds up matching the same pattern against multiple files pattern PurePath py PurePath a b py match pattern True Changed in version 3 12 Accepts an object implementing the os PathLike interface As with other methods case sensitivity follows platform defaults PurePosixPath b py match PY False PureWindowsPath b py match PY True Set case_sensitive to True or False to override this behaviour Changed in version 3 12 The case_sensitive parameter was added PurePath relative_to other walk_up False Compute ,en
1965,a version of this path relative to the path represented by other If it s impossible ValueError is raised p PurePosixPath etc passwd p relative_to PurePosixPath etc passwd p relative_to etc PurePosixPath passwd p relative_to usr Traceback most recent call last File stdin line 1 in module File pathlib py line 941 in relative_to raise ValueError error_message format str self str formatted ValueError etc passwd is not in the subpath of usr OR one path is relative and the other is absolute When walk_up is False the default the path must start with other When the argument is True entries may be added to form the relative path In all other cases such as the paths referencing different drives ValueError is raised p relative_to usr walk_up True PurePosixPath etc passwd p relative_to foo walk_up True Traceback most recent call last File stdin line 1 in module File pathlib py line 941 in relative_to raise ValueError error_message format str self str formatted ValueError etc passwd is not on the same drive as foo OR one path is relative and the other is absolute Warning This function is part of PurePath and works with strings It does not check or access the underlying file structure This can impact the walk_up option as it assumes that no symlinks are present in the path call resolve first if necessary to resolve symlinks Changed in version 3 12 The walk_up parameter was added old behavior is the same as walk_up False Deprecated since version 3 12 will be removed in version 3 14 Passing additional positional arguments is deprecated if supplied they are joined with other PurePath with_name name Return a new path with the name changed If the original path doesn t have a name ValueError is raised p PureWindowsPath c Downloads pathlib tar gz p with_name setup py PureWindowsPath c Downloads setup py p PureWindowsPath c p with_name setup py Traceback most recent call last File stdin line 1 in module File home antoine cpython default Lib pathlib py line 751 in with_name raise ValueError r has an empty name self ValueError PureWindowsPath c has an empty name PurePath with_stem stem Return a new path with the stem changed If the original path doesn t have a name ValueError is raised p PureWindowsPath c Downloads draft txt p with_stem final PureWindowsPath c Downloads final txt p PureWindowsPath c Downloads pathlib tar gz p with_stem lib PureWindowsPath c Downloads lib gz p PureWindowsPath c p with_stem Traceback most recent call last File stdin line 1 in module File home antoine cpython default Lib pathlib py line 861 in with_stem return self with_name stem self suffix File home antoine cpython default Lib pathlib py line 851 in with_name raise ValueError r has an empty name self ValueError PureWindowsPath c has an empty name New in version 3 9 PurePath with_suffix suffix Return a new path with the suffix changed If the original path doesn t have a suffix the new suffix is appended instead If the suffix is an empty string the original suffix is removed p PureWindowsPath c Downloads pathlib tar gz p with_suffix bz2 PureWindowsPath c Downloads pathlib tar bz2 p PureWindowsPath README p with_suffix txt PureWindowsPath README txt p PureWindowsPath README txt p with_suffix PureWindowsPath README PurePath with_segments pathsegments Create a new path object of the same type by combining the given pathsegments This method is called whenever a derivative path is created such as from parent and relative_to Subclasses may override this method to pass information to derivative paths for example from pathlib import PurePosixPath class MyPath PurePosixPath def __init__ self pathsegments session_id super __init__ pathsegments self session_id session_id def with_segments self pathsegments return type self pathsegments session_id self session_id etc MyPath etc session_id 42 hosts etc hosts print hosts session_id 42 New in version 3 12 Concrete paths Concrete paths are subclasses of the pure path classes In addition to operations provided by the latter they also provide methods to do system calls on path objects There are three ways to instantiate concrete pa,en
1966,ths class pathlib Path pathsegments A subclass of PurePath this class represents concrete paths of the system s path flavour instantiating it creates either a PosixPath or a WindowsPath Path setup py PosixPath setup py pathsegments is specified similarly to PurePath class pathlib PosixPath pathsegments A subclass of Path and PurePosixPath this class represents concrete non Windows filesystem paths PosixPath etc PosixPath etc pathsegments is specified similarly to PurePath class pathlib WindowsPath pathsegments A subclass of Path and PureWindowsPath this class represents concrete Windows filesystem paths WindowsPath c Program Files WindowsPath c Program Files pathsegments is specified similarly to PurePath You can only instantiate the class flavour that corresponds to your system allowing system calls on non compatible path flavours could lead to bugs or failures in your application import os os name posix Path setup py PosixPath setup py PosixPath setup py PosixPath setup py WindowsPath setup py Traceback most recent call last File stdin line 1 in module File pathlib py line 798 in __new__ cls __name__ NotImplementedError cannot instantiate WindowsPath on your system Methods Concrete paths provide the following methods in addition to pure paths methods Many of these methods can raise an OSError if a system call fails for example because the path doesn t exist Changed in version 3 8 exists is_dir is_file is_mount is_symlink is_block_device is_char_device is_fifo is_socket now return False instead of raising an exception for paths that contain characters unrepresentable at the OS level classmethod Path cwd Return a new path object representing the current directory as returned by os getcwd Path cwd PosixPath home antoine pathlib classmethod Path home Return a new path object representing the user s home directory as returned by os path expanduser with construct If the home directory can t be resolved RuntimeError is raised Path home PosixPath home antoine New in version 3 5 Path stat follow_symlinks True Return a os stat_result object containing information about this path like os stat The result is looked up at each call to this method This method normally follows symlinks to stat a symlink add the argument follow_symlinks False or use lstat p Path setup py p stat st_size 956 p stat st_mtime 1327883547 852554 Changed in version 3 10 The follow_symlinks parameter was added Path chmod mode follow_symlinks True Change the file mode and permissions like os chmod This method normally follows symlinks Some Unix flavours support changing permissions on the symlink itself on these platforms you may add the argument follow_symlinks False or use lchmod p Path setup py p stat st_mode 33277 p chmod 0o444 p stat st_mode 33060 Changed in version 3 10 The follow_symlinks parameter was added Path exists follow_symlinks True Return True if the path points to an existing file or directory This method normally follows symlinks to check if a symlink exists add the argument follow_symlinks False Path exists True Path setup py exists True Path etc exists True Path nonexistentfile exists False Changed in version 3 12 The follow_symlinks parameter was added Path expanduser Return a new path with expanded and user constructs as returned by os path expanduser If a home directory can t be resolved RuntimeError is raised p PosixPath films Monty Python p expanduser PosixPath home eric films Monty Python New in version 3 5 Path glob pattern case_sensitive None Glob the given relative pattern in the directory represented by this path yielding all matching files of any kind sorted Path glob py PosixPath pathlib py PosixPath setup py PosixPath test_pathlib py sorted Path glob py PosixPath docs conf py Patterns are the same as for fnmatch with the addition of which means this directory and all subdirectories recursively In other words it enables recursive globbing sorted Path glob py PosixPath build lib pathlib py PosixPath docs conf py PosixPath pathlib py PosixPath setup py PosixPath test_pathlib py This method calls Path is_dir on the top level directo,en
1967,ry and propagates any OSError exception that is raised Subsequent OSError exceptions from scanning directories are suppressed By default or when the case_sensitive keyword only argument is set to None this method matches paths using platform specific casing rules typically case sensitive on POSIX and case insensitive on Windows Set case_sensitive to True or False to override this behaviour Note Using the pattern in large directory trees may consume an inordinate amount of time Raises an auditing event pathlib Path glob with arguments self pattern Changed in version 3 11 Return only directories if pattern ends with a pathname components separator sep or altsep Changed in version 3 12 The case_sensitive parameter was added Path group Return the name of the group owning the file KeyError is raised if the file s gid isn t found in the system database Path is_dir Return True if the path points to a directory or a symbolic link pointing to a directory False if it points to another kind of file False is also returned if the path doesn t exist or is a broken symlink other errors such as permission errors are propagated Path is_file Return True if the path points to a regular file or a symbolic link pointing to a regular file False if it points to another kind of file False is also returned if the path doesn t exist or is a broken symlink other errors such as permission errors are propagated Path is_junction Return True if the path points to a junction and False for any other type of file Currently only Windows supports junctions New in version 3 12 Path is_mount Return True if the path is a mount point a point in a file system where a different file system has been mounted On POSIX the function checks whether path s parent path is on a different device than path or whether path and path point to the same i node on the same device this should detect mount points for all Unix and POSIX variants On Windows a mount point is considered to be a drive letter root e g c a UNC share e g server share or a mounted filesystem directory New in version 3 7 Changed in version 3 12 Windows support was added Path is_symlink Return True if the path points to a symbolic link False otherwise False is also returned if the path doesn t exist other errors such as permission errors are propagated Path is_socket Return True if the path points to a Unix socket or a symbolic link pointing to a Unix socket False if it points to another kind of file False is also returned if the path doesn t exist or is a broken symlink other errors such as permission errors are propagated Path is_fifo Return True if the path points to a FIFO or a symbolic link pointing to a FIFO False if it points to another kind of file False is also returned if the path doesn t exist or is a broken symlink other errors such as permission errors are propagated Path is_block_device Return True if the path points to a block device or a symbolic link pointing to a block device False if it points to another kind of file False is also returned if the path doesn t exist or is a broken symlink other errors such as permission errors are propagated Path is_char_device Return True if the path points to a character device or a symbolic link pointing to a character device False if it points to another kind of file False is also returned if the path doesn t exist or is a broken symlink other errors such as permission errors are propagated Path iterdir When the path points to a directory yield path objects of the directory contents p Path docs for child in p iterdir child PosixPath docs conf py PosixPath docs _templates PosixPath docs make bat PosixPath docs index rst PosixPath docs _build PosixPath docs _static PosixPath docs Makefile The children are yielded in arbitrary order and the special entries and are not included If a file is removed from or added to the directory after creating the iterator whether a path object for that file be included is unspecified Path walk top_down True on_error None follow_symlinks False Generate the file names in a directory tree by walking the tree either top down o,en
1968,r bottom up For each directory in the directory tree rooted at self including self but excluding and the method yields a 3 tuple of dirpath dirnames filenames dirpath is a Path to the directory currently being walked dirnames is a list of strings for the names of subdirectories in dirpath excluding and and filenames is a list of strings for the names of the non directory files in dirpath To get a full path which begins with self to a file or directory in dirpath do dirpath name Whether or not the lists are sorted is file system dependent If the optional argument top_down is true which is the default the triple for a directory is generated before the triples for any of its subdirectories directories are walked top down If top_down is false the triple for a directory is generated after the triples for all of its subdirectories directories are walked bottom up No matter the value of top_down the list of subdirectories is retrieved before the triples for the directory and its subdirectories are walked When top_down is true the caller can modify the dirnames list in place for example using del or slice assignment and Path walk will only recurse into the subdirectories whose names remain in dirnames This can be used to prune the search or to impose a specific order of visiting or even to inform Path walk about directories the caller creates or renames before it resumes Path walk again Modifying dirnames when top_down is false has no effect on the behavior of Path walk since the directories in dirnames have already been generated by the time dirnames is yielded to the caller By default errors from os scandir are ignored If the optional argument on_error is specified it should be a callable it will be called with one argument an OSError instance The callable can handle the error to continue the walk or re raise it to stop the walk Note that the filename is available as the filename attribute of the exception object By default Path walk does not follow symbolic links and instead adds them to the filenames list Set follow_symlinks to true to resolve symlinks and place them in dirnames and filenames as appropriate for their targets and consequently visit directories pointed to by symlinks where supported Note Be aware that setting follow_symlinks to true can lead to infinite recursion if a link points to a parent directory of itself Path walk does not keep track of the directories it has already visited Note Path walk assumes the directories it walks are not modified during execution For example if a directory from dirnames has been replaced with a symlink and follow_symlinks is false Path walk will still try to descend into it To prevent such behavior remove directories from dirnames as appropriate Note Unlike os walk Path walk lists symlinks to directories in filenames if follow_symlinks is false This example displays the number of bytes used by all files in each directory while ignoring __pycache__ directories from pathlib import Path for root dirs files in Path cpython Lib concurrent walk on_error print print root consumes sum root file stat st_size for file in files bytes in len files non directory files if __pycache__ in dirs dirs remove __pycache__ This next example is a simple implementation of shutil rmtree Walking the tree bottom up is essential as rmdir doesn t allow deleting a directory before it is empty Delete everything reachable from the directory top CAUTION This is dangerous For example if top Path it could delete all of your files for root dirs files in top walk top_down False for name in files root name unlink for name in dirs root name rmdir New in version 3 12 Path lchmod mode Like Path chmod but if the path points to a symbolic link the symbolic link s mode is changed rather than its target s Path lstat Like Path stat but if the path points to a symbolic link return the symbolic link s information rather than its target s Path mkdir mode 0o777 parents False exist_ok False Create a new directory at this given path If mode is given it is combined with the process umask value to determine the file mode and acces,en
1969,s flags If the path already exists FileExistsError is raised If parents is true any missing parents of this path are created as needed they are created with the default permissions without taking mode into account mimicking the POSIX mkdir p command If parents is false the default a missing parent raises FileNotFoundError If exist_ok is false the default FileExistsError is raised if the target directory already exists If exist_ok is true FileExistsError will not be raised unless the given path already exists in the file system and is not a directory same behavior as the POSIX mkdir p command Changed in version 3 5 The exist_ok parameter was added Path open mode r buffering 1 encoding None errors None newline None Open the file pointed to by the path like the built in open function does p Path setup py with p open as f f readline usr bin env python3 n Path owner Return the name of the user owning the file KeyError is raised if the file s uid isn t found in the system database Path read_bytes Return the binary contents of the pointed to file as a bytes object p Path my_binary_file p write_bytes b Binary file contents 20 p read_bytes b Binary file contents New in version 3 5 Path read_text encoding None errors None Return the decoded contents of the pointed to file as a string p Path my_text_file p write_text Text file contents 18 p read_text Text file contents The file is opened and then closed The optional parameters have the same meaning as in open New in version 3 5 Path readlink Return the path to which the symbolic link points as returned by os readlink p Path mylink p symlink_to setup py p readlink PosixPath setup py New in version 3 9 Path rename target Rename this file or directory to the given target and return a new Path instance pointing to target On Unix if target exists and is a file it will be replaced silently if the user has permission On Windows if target exists FileExistsError will be raised target can be either a string or another path object p Path foo p open w write some text 9 target Path bar p rename target PosixPath bar target open read some text The target path may be absolute or relative Relative paths are interpreted relative to the current working directory not the directory of the Path object It is implemented in terms of os rename and gives the same guarantees Changed in version 3 8 Added return value return the new Path instance Path replace target Rename this file or directory to the given target and return a new Path instance pointing to target If target points to an existing file or empty directory it will be unconditionally replaced The target path may be absolute or relative Relative paths are interpreted relative to the current working directory not the directory of the Path object Changed in version 3 8 Added return value return the new Path instance Path absolute Make the path absolute without normalization or resolving symlinks Returns a new path object p Path tests p PosixPath tests p absolute PosixPath home antoine pathlib tests Path resolve strict False Make the path absolute resolving any symlinks A new path object is returned p Path p PosixPath p resolve PosixPath home antoine pathlib components are also eliminated this is the only method to do so p Path docs setup py p resolve PosixPath home antoine pathlib setup py If the path doesn t exist and strict is True FileNotFoundError is raised If strict is False the path is resolved as far as possible and any remainder is appended without checking whether it exists If an infinite loop is encountered along the resolution path RuntimeError is raised Changed in version 3 6 The strict parameter was added pre 3 6 behavior is strict Path rglob pattern case_sensitive None Glob the given relative pattern recursively This is like calling Path glob with added in front of the pattern where patterns are the same as for fnmatch sorted Path rglob py PosixPath build lib pathlib py PosixPath docs conf py PosixPath pathlib py PosixPath setup py PosixPath test_pathlib py By default or when the case_sensitive keyword only argument is set to None this m,en
1970,ethod matches paths using platform specific casing rules typically case sensitive on POSIX and case insensitive on Windows Set case_sensitive to True or False to override this behaviour Raises an auditing event pathlib Path rglob with arguments self pattern Changed in version 3 11 Return only directories if pattern ends with a pathname components separator sep or altsep Changed in version 3 12 The case_sensitive parameter was added Path rmdir Remove this directory The directory must be empty Path samefile other_path Return whether this path points to the same file as other_path which can be either a Path object or a string The semantics are similar to os path samefile and os path samestat An OSError can be raised if either file cannot be accessed for some reason p Path spam q Path eggs p samefile q False p samefile spam True New in version 3 5 Path symlink_to target target_is_directory False Make this path a symbolic link pointing to target On Windows a symlink represents either a file or a directory and does not morph to the target dynamically If the target is present the type of the symlink will be created to match Otherwise the symlink will be created as a directory if target_is_directory is True or a file symlink the default otherwise On non Windows platforms target_is_directory is ignored p Path mylink p symlink_to setup py p resolve PosixPath home antoine pathlib setup py p stat st_size 956 p lstat st_size 8 Note The order of arguments link target is the reverse of os symlink s Path hardlink_to target Make this path a hard link to the same file as target Note The order of arguments link target is the reverse of os link s New in version 3 10 Path touch mode 0o666 exist_ok True Create a file at this given path If mode is given it is combined with the process umask value to determine the file mode and access flags If the file already exists the function succeeds if exist_ok is true and its modification time is updated to the current time otherwise FileExistsError is raised Path unlink missing_ok False Remove this file or symbolic link If the path points to a directory use Path rmdir instead If missing_ok is false the default FileNotFoundError is raised if the path does not exist If missing_ok is true FileNotFoundError exceptions will be ignored same behavior as the POSIX rm f command Changed in version 3 8 The missing_ok parameter was added Path write_bytes data Open the file pointed to in bytes mode write data to it and close the file p Path my_binary_file p write_bytes b Binary file contents 20 p read_bytes b Binary file contents An existing file of the same name is overwritten New in version 3 5 Path write_text data encoding None errors None newline None Open the file pointed to in text mode write data to it and close the file p Path my_text_file p write_text Text file contents 18 p read_text Text file contents An existing file of the same name is overwritten The optional parameters have the same meaning as in open New in version 3 5 Changed in version 3 10 The newline parameter was added Correspondence to tools in the os module Below is a table mapping various os functions to their corresponding PurePath Path equivalent Note Not all pairs of functions methods below are equivalent Some of them despite having some overlapping use cases have different semantics They include os path abspath and Path absolute os path relpath and PurePath relative_to os and os path pathlib os path abspath Path absolute 1 os path realpath Path resolve os chmod Path chmod os mkdir Path mkdir os makedirs Path mkdir os rename Path rename os replace Path replace os rmdir Path rmdir os remove os unlink Path unlink os getcwd Path cwd os path exists Path exists os path expanduser Path expanduser and Path home os listdir Path iterdir os walk Path walk os path isdir Path is_dir os path isfile Path is_file os path islink Path is_symlink os link Path hardlink_to os symlink Path symlink_to os readlink Path readlink os path relpath PurePath relative_to 2 os stat Path stat Path owner Path group os path isabs PurePath is_absolute os path join PurePath ,en
1971,joinpath os path basename PurePath name os path dirname PurePath parent os path samefile Path samefile os path splitext PurePath stem and PurePath suffix Footnotes 1 os path abspath normalizes the resulting path which may change its meaning in the presence of symlinks while Path absolute does not 2 PurePath relative_to requires self to be the subpath of the argument but os path relpath does not,en
1972,__future__ Future statement definitions Source code Lib __future__ py Imports of the form from __future__ import feature are called future statements These are special cased by the Python compiler to allow the use of new Python features in modules containing the future statement before the release in which the feature becomes standard While these future statements are given additional special meaning by the Python compiler they are still executed like any other import statement and the __future__ exists and is handled by the import system the same way any other Python module would be This design serves three purposes To avoid confusing existing tools that analyze import statements and expect to find the modules they re importing To document when incompatible changes were introduced and when they will be or were made mandatory This is a form of executable documentation and can be inspected programmatically via importing __future__ and examining its contents To ensure that future statements run under releases prior to Python 2 1 at least yield runtime exceptions the import of __future__ will fail because there was no module of that name prior to 2 1 Module Contents No feature description will ever be deleted from __future__ Since its introduction in Python 2 1 the following features have found their way into the language using this mechanism feature optional in mandatory in effect nested_scopes 2 1 0b1 2 2 PEP 227 Statically Nested Scopes generators 2 2 0a1 2 3 PEP 255 Simple Generators division 2 2 0a2 3 0 PEP 238 Changing the Division Operator absolute_import 2 5 0a1 3 0 PEP 328 Imports Multi Line and Absolute Relative with_statement 2 5 0a1 2 6 PEP 343 The with Statement print_function 2 6 0a2 3 0 PEP 3105 Make print a function unicode_literals 2 6 0a2 3 0 PEP 3112 Bytes literals in Python 3000 generator_stop 3 5 0b1 3 7 PEP 479 StopIteration handling inside generators annotations 3 7 0b1 TBD 1 PEP 563 Postponed evaluation of annotations class __future__ _Feature Each statement in __future__ py is of the form FeatureName _Feature OptionalRelease MandatoryRelease CompilerFlag where normally OptionalRelease is less than MandatoryRelease and both are 5 tuples of the same form as sys version_info PY_MAJOR_VERSION the 2 in 2 1 0a3 an int PY_MINOR_VERSION the 1 an int PY_MICRO_VERSION the 0 an int PY_RELEASE_LEVEL alpha beta candidate or final string PY_RELEASE_SERIAL the 3 an int _Feature getOptionalRelease OptionalRelease records the first release in which the feature was accepted _Feature getMandatoryRelease In the case of a MandatoryRelease that has not yet occurred MandatoryRelease predicts the release in which the feature will become part of the language Else MandatoryRelease records when the feature became part of the language in releases at or after that modules no longer need a future statement to use the feature in question but may continue to use such imports MandatoryRelease may also be None meaning that a planned feature got dropped or that it is not yet decided _Feature compiler_flag CompilerFlag is the bitfield flag that should be passed in the fourth argument to the built in function compile to enable the feature in dynamically compiled code This flag is stored in the _Feature compiler_flag attribute on _Feature instances 1 from __future__ import annotations was previously scheduled to become mandatory in Python 3 10 but the Python Steering Council twice decided to delay the change announcement for Python 3 10 announcement for Python 3 11 No final decision has been made yet See also PEP 563 and PEP 649 See also Future statements How the compiler treats future imports PEP 236 Back to the __future__ The original proposal for the __future__ mechanism,en
1973,Weak Reference Objects Python supports weak references as first class objects There are two specific object types which directly implement weak references The first is a simple reference object and the second acts as a proxy for the original object as much as it can int PyWeakref_Check PyObject ob Return true if ob is either a reference or proxy object This function always succeeds int PyWeakref_CheckRef PyObject ob Return true if ob is a reference object This function always succeeds int PyWeakref_CheckProxy PyObject ob Return true if ob is a proxy object This function always succeeds PyObject PyWeakref_NewRef PyObject ob PyObject callback Return value New reference Part of the Stable ABI Return a weak reference object for the object ob This will always return a new reference but is not guaranteed to create a new object an existing reference object may be returned The second parameter callback can be a callable object that receives notification when ob is garbage collected it should accept a single parameter which will be the weak reference object itself callback may also be None or NULL If ob is not a weakly referencable object or if callback is not callable None or NULL this will return NULL and raise TypeError PyObject PyWeakref_NewProxy PyObject ob PyObject callback Return value New reference Part of the Stable ABI Return a weak reference proxy object for the object ob This will always return a new reference but is not guaranteed to create a new object an existing proxy object may be returned The second parameter callback can be a callable object that receives notification when ob is garbage collected it should accept a single parameter which will be the weak reference object itself callback may also be None or NULL If ob is not a weakly referencable object or if callback is not callable None or NULL this will return NULL and raise TypeError PyObject PyWeakref_GetObject PyObject ref Return value Borrowed reference Part of the Stable ABI Return the referenced object from a weak reference ref If the referent is no longer live returns Py_None Note This function returns a borrowed reference to the referenced object This means that you should always call Py_INCREF on the object except when it cannot be destroyed before the last usage of the borrowed reference PyObject PyWeakref_GET_OBJECT PyObject ref Return value Borrowed reference Similar to PyWeakref_GetObject but does no error checking void PyObject_ClearWeakRefs PyObject object Part of the Stable ABI This function is called by the tp_dealloc handler to clear weak references This iterates through the weak references for object and calls callbacks for those references which have one It returns when all callbacks have been attempted,en
1974,Isolating Extension Modules Abstract Traditionally state belonging to Python extension modules was kept in C static variables which have process wide scope This document describes problems of such per process state and shows a safer way per module state The document also describes how to switch to per module state where possible This transition involves allocating space for that state potentially switching from static types to heap types and perhaps most importantly accessing per module state from code Who should read this This guide is written for maintainers of C API extensions who would like to make that extension safer to use in applications where Python itself is used as a library Background An interpreter is the context in which Python code runs It contains configuration e g the import path and runtime state e g the set of imported modules Python supports running multiple interpreters in one process There are two cases to think about users may run interpreters in sequence with several Py_InitializeEx Py_FinalizeEx cycles and in parallel managing sub interpreters using Py_NewInterpreter Py_EndInterpreter Both cases and combinations of them would be most useful when embedding Python within a library Libraries generally shouldn t make assumptions about the application that uses them which include assuming a process wide main Python interpreter Historically Python extension modules don t handle this use case well Many extension modules and even some stdlib modules use per process global state because C static variables are extremely easy to use Thus data that should be specific to an interpreter ends up being shared between interpreters Unless the extension developer is careful it is very easy to introduce edge cases that lead to crashes when a module is loaded in more than one interpreter in the same process Unfortunately per interpreter state is not easy to achieve Extension authors tend to not keep multiple interpreters in mind when developing and it is currently cumbersome to test the behavior Enter Per Module State Instead of focusing on per interpreter state Python s C API is evolving to better support the more granular per module state This means that C level data should be attached to a module object Each interpreter creates its own module object keeping the data separate For testing the isolation multiple module objects corresponding to a single extension can even be loaded in a single interpreter Per module state provides an easy way to think about lifetime and resource ownership the extension module will initialize when a module object is created and clean up when it s freed In this regard a module is just like any other PyObject there are no on interpreter shutdown hooks to think or forget about Note that there are use cases for different kinds of globals per process per interpreter per thread or per task state With per module state as the default these are still possible but you should treat them as exceptional cases if you need them you should give them additional care and testing Note that this guide does not cover them Isolated Module Objects The key point to keep in mind when developing an extension module is that several module objects can be created from a single shared library For example import sys import binascii old_binascii binascii del sys modules binascii import binascii create a new module object old_binascii binascii False As a rule of thumb the two modules should be completely independent All objects and state specific to the module should be encapsulated within the module object not shared with other module objects and cleaned up when the module object is deallocated Since this just is a rule of thumb exceptions are possible see Managing Global State but they will need more thought and attention to edge cases While some modules could do with less stringent restrictions isolated modules make it easier to set clear expectations and guidelines that work across a variety of use cases Surprising Edge Cases Note that isolated modules do create some surprising edge cases Most notably each module ,en
1975,object will typically not share its classes and exceptions with other similar modules Continuing from the example above note that old_binascii Error and binascii Error are separate objects In the following code the exception is not caught old_binascii Error binascii Error False try old_binascii unhexlify b qwertyuiop except binascii Error print boo Traceback most recent call last File stdin line 2 in module binascii Error Non hexadecimal digit found This is expected Notice that pure Python modules behave the same way it is a part of how Python works The goal is to make extension modules safe at the C level not to make hacks behave intuitively Mutating sys modules manually counts as a hack Making Modules Safe with Multiple Interpreters Managing Global State Sometimes the state associated with a Python module is not specific to that module but to the entire process or something else more global than a module For example The readline module manages the terminal A module running on a circuit board wants to control the on board LED In these cases the Python module should provide access to the global state rather than own it If possible write the module so that multiple copies of it can access the state independently along with other libraries whether for Python or other languages If that is not possible consider explicit locking If it is necessary to use process global state the simplest way to avoid issues with multiple interpreters is to explicitly prevent a module from being loaded more than once per process see Opt Out Limiting to One Module Object per Process Managing Per Module State To use per module state use multi phase extension module initialization This signals that your module supports multiple interpreters correctly Set PyModuleDef m_size to a positive number to request that many bytes of storage local to the module Usually this will be set to the size of some module specific struct which can store all of the module s C level state In particular it is where you should put pointers to classes including exceptions but excluding static types and settings e g csv s field_size_limit which the C code needs to function Note Another option is to store state in the module s __dict__ but you must avoid crashing when users modify __dict__ from Python code This usually means error and type checking at the C level which is easy to get wrong and hard to test sufficiently However if module state is not needed in C code storing it in __dict__ only is a good idea If the module state includes PyObject pointers the module object must hold references to those objects and implement the module level hooks m_traverse m_clear and m_free These work like tp_traverse tp_clear and tp_free of a class Adding them will require some work and make the code longer this is the price for modules which can be unloaded cleanly An example of a module with per module state is currently available as xxlimited example module initialization shown at the bottom of the file Opt Out Limiting to One Module Object per Process A non negative PyModuleDef m_size signals that a module supports multiple interpreters correctly If this is not yet the case for your module you can explicitly make your module loadable only once per process For example static int loaded 0 static int exec_module PyObject module if loaded PyErr_SetString PyExc_ImportError cannot load module more than once per process return 1 loaded 1 rest of initialization Module State Access from Functions Accessing the state from module level functions is straightforward Functions get the module object as their first argument for extracting the state you can use PyModule_GetState static PyObject func PyObject module PyObject args my_struct state my_struct PyModule_GetState module if state NULL return NULL rest of logic Note PyModule_GetState may return NULL without setting an exception if there is no module state i e PyModuleDef m_size was zero In your own module you re in control of m_size so this is easy to prevent Heap Types Traditionally types defined in C code are static that is static PyTypeObjec,en
1976,t structures defined directly in code and initialized using PyType_Ready Such types are necessarily shared across the process Sharing them between module objects requires paying attention to any state they own or access To limit the possible issues static types are immutable at the Python level for example you can t set str myattribute 123 CPython implementation detail Sharing truly immutable objects between interpreters is fine as long as they don t provide access to mutable objects However in CPython every Python object has a mutable implementation detail the reference count Changes to the refcount are guarded by the GIL Thus code that shares any Python objects across interpreters implicitly depends on CPython s current process wide GIL Because they are immutable and process global static types cannot access their module state If any method of such a type requires access to module state the type must be converted to a heap allocated type or heap type for short These correspond more closely to classes created by Python s class statement For new modules using heap types by default is a good rule of thumb Changing Static Types to Heap Types Static types can be converted to heap types but note that the heap type API was not designed for lossless conversion from static types that is creating a type that works exactly like a given static type So when rewriting the class definition in a new API you are likely to unintentionally change a few details e g pickleability or inherited slots Always test the details that are important to you Watch out for the following two points in particular but note that this is not a comprehensive list Unlike static types heap type objects are mutable by default Use the Py_TPFLAGS_IMMUTABLETYPE flag to prevent mutability Heap types inherit tp_new by default so it may become possible to instantiate them from Python code You can prevent this with the Py_TPFLAGS_DISALLOW_INSTANTIATION flag Defining Heap Types Heap types can be created by filling a PyType_Spec structure a description or blueprint of a class and calling PyType_FromModuleAndSpec to construct a new class object Note Other functions like PyType_FromSpec can also create heap types but PyType_FromModuleAndSpec associates the module with the class allowing access to the module state from methods The class should generally be stored in both the module state for safe access from C and the module s __dict__ for access from Python code Garbage Collection Protocol Instances of heap types hold a reference to their type This ensures that the type isn t destroyed before all its instances are but may result in reference cycles that need to be broken by the garbage collector To avoid memory leaks instances of heap types must implement the garbage collection protocol That is heap types should Have the Py_TPFLAGS_HAVE_GC flag Define a traverse function using Py_tp_traverse which visits the type e g using Py_VISIT Py_TYPE self Please refer to the the documentation of Py_TPFLAGS_HAVE_GC and tp_traverse for additional considerations The API for defining heap types grew organically leaving it somewhat awkward to use in its current state The following sections will guide you through common issues tp_traverse in Python 3 8 and lower The requirement to visit the type from tp_traverse was added in Python 3 9 If you support Python 3 8 and lower the traverse function must not visit the type so it must be more complicated static int my_traverse PyObject self visitproc visit void arg if Py_Version 0x03090000 Py_VISIT Py_TYPE self return 0 Unfortunately Py_Version was only added in Python 3 11 As a replacement use PY_VERSION_HEX if not using the stable ABI or sys version_info via PySys_GetObject and PyArg_ParseTuple Delegating tp_traverse If your traverse function delegates to the tp_traverse of its base class or another type ensure that Py_TYPE self is visited only once Note that only heap type are expected to visit the type in tp_traverse For example if your traverse function includes base tp_traverse self visit arg and base may be a static type then it should al,en
1977,so include if base tp_flags Py_TPFLAGS_HEAPTYPE a heap type s tp_traverse already visited Py_TYPE self else if Py_Version 0x03090000 Py_VISIT Py_TYPE self It is not necessary to handle the type s reference count in tp_new and tp_clear Defining tp_dealloc If your type has a custom tp_dealloc function it needs to call PyObject_GC_UnTrack before any fields are invalidated and decrement the reference count of the type To keep the type valid while tp_free is called the type s refcount needs to be decremented after the instance is deallocated For example static void my_dealloc PyObject self PyObject_GC_UnTrack self PyTypeObject type Py_TYPE self type tp_free self Py_DECREF type The default tp_dealloc function does this so if your type does not override tp_dealloc you don t need to add it Not overriding tp_free The tp_free slot of a heap type must be set to PyObject_GC_Del This is the default do not override it Avoiding PyObject_New GC tracked objects need to be allocated using GC aware functions If you use use PyObject_New or PyObject_NewVar Get and call type s tp_alloc slot if possible That is replace TYPE o PyObject_New TYPE typeobj with TYPE o typeobj tp_alloc typeobj 0 Replace o PyObject_NewVar TYPE typeobj size with the same but use size instead of the 0 If the above is not possible e g inside a custom tp_alloc call PyObject_GC_New or PyObject_GC_NewVar TYPE o PyObject_GC_New TYPE typeobj TYPE o PyObject_GC_NewVar TYPE typeobj size Module State Access from Classes If you have a type object defined with PyType_FromModuleAndSpec you can call PyType_GetModule to get the associated module and then PyModule_GetState to get the module s state To save a some tedious error handling boilerplate code you can combine these two steps with PyType_GetModuleState resulting in my_struct state my_struct PyType_GetModuleState type if state NULL return NULL Module State Access from Regular Methods Accessing the module level state from methods of a class is somewhat more complicated but is possible thanks to API introduced in Python 3 9 To get the state you need to first get the defining class and then get the module state from it The largest roadblock is getting the class a method was defined in or that method s defining class for short The defining class can have a reference to the module it is part of Do not confuse the defining class with Py_TYPE self If the method is called on a subclass of your type Py_TYPE self will refer to that subclass which may be defined in different module than yours Note The following Python code can illustrate the concept Base get_defining_class returns Base even if type self Sub class Base def get_type_of_self self return type self def get_defining_class self return __class__ class Sub Base pass For a method to get its defining class it must use the METH_METHOD METH_FASTCALL METH_KEYWORDS calling convention and the corresponding PyCMethod signature PyObject PyCMethod PyObject self object the method was called on PyTypeObject defining_class defining class PyObject const args C array of arguments Py_ssize_t nargs length of args PyObject kwnames NULL or dict of keyword arguments Once you have the defining class call PyType_GetModuleState to get the state of its associated module For example static PyObject example_method PyObject self PyTypeObject defining_class PyObject const args Py_ssize_t nargs PyObject kwnames my_struct state my_struct PyType_GetModuleState defining_class if state NULL return NULL rest of logic PyDoc_STRVAR example_method_doc static PyMethodDef my_methods example_method PyCFunction void void example_method METH_METHOD METH_FASTCALL METH_KEYWORDS example_method_doc NULL Module State Access from Slot Methods Getters and Setters Note This is new in Python 3 11 Slot methods the fast C equivalents for special methods such as nb_add for __add__ or tp_new for initialization have a very simple API that doesn t allow passing in the defining class unlike with PyCMethod The same goes for getters and setters defined with PyGetSetDef To access the module state in these cases use the PyType_GetModuleByDe,en
1978,f function and pass in the module definition Once you have the module call PyModule_GetState to get the state PyObject module PyType_GetModuleByDef Py_TYPE self module_def my_struct state my_struct PyModule_GetState module if state NULL return NULL PyType_GetModuleByDef works by searching the method resolution order i e all superclasses for the first superclass that has a corresponding module Note In very exotic cases inheritance chains spanning multiple modules created from the same definition PyType_GetModuleByDef might not return the module of the true defining class However it will always return a module with the same definition ensuring a compatible C memory layout Lifetime of the Module State When a module object is garbage collected its module state is freed For each pointer to a part of the module state you must hold a reference to the module object Usually this is not an issue because types created with PyType_FromModuleAndSpec and their instances hold a reference to the module However you must be careful in reference counting when you reference module state from other places such as callbacks for external libraries Open Issues Several issues around per module state and heap types are still open Discussions about improving the situation are best held on the capi sig mailing list Per Class Scope It is currently as of Python 3 11 not possible to attach state to individual types without relying on CPython implementation details which may change in the future perhaps ironically to allow a proper solution for per class scope Lossless Conversion to Heap Types The heap type API was not designed for lossless conversion from static types that is creating a type that works exactly like a given static type,en
1979,4 Building C and C Extensions A C extension for CPython is a shared library e g a so file on Linux pyd on Windows which exports an initialization function To be importable the shared library must be available on PYTHONPATH and must be named after the module name with an appropriate extension When using setuptools the correct filename is generated automatically The initialization function has the signature PyObject PyInit_modulename void It returns either a fully initialized module or a PyModuleDef instance See Initializing C modules for details For modules with ASCII only names the function must be named PyInit_ modulename with modulename replaced by the name of the module When using Multi phase initialization non ASCII module names are allowed In this case the initialization function name is PyInitU_ modulename with modulename encoded using Python s punycode encoding with hyphens replaced by underscores In Python def initfunc_name name try suffix b _ name encode ascii except UnicodeEncodeError suffix b U_ name encode punycode replace b b _ return b PyInit suffix It is possible to export multiple modules from a single shared library by defining multiple initialization functions However importing them requires using symbolic links or a custom importer because by default only the function corresponding to the filename is found See the Multiple modules in one library section in PEP 489 for details 4 1 Building C and C Extensions with setuptools Python 3 12 and newer no longer come with distutils Please refer to the setuptools documentation at https setuptools readthedocs io en latest setuptools html to learn more about how build and distribute C C extensions with setuptools,en
1980,Complex Number Objects Python s complex number objects are implemented as two distinct types when viewed from the C API one is the Python object exposed to Python programs and the other is a C structure which represents the actual complex number value The API provides functions for working with both Complex Numbers as C Structures Note that the functions which accept these structures as parameters and return them as results do so by value rather than dereferencing them through pointers This is consistent throughout the API type Py_complex The C structure which corresponds to the value portion of a Python complex number object Most of the functions for dealing with complex number objects use structures of this type as input or output values as appropriate It is defined as typedef struct double real double imag Py_complex Py_complex _Py_c_sum Py_complex left Py_complex right Return the sum of two complex numbers using the C Py_complex representation Py_complex _Py_c_diff Py_complex left Py_complex right Return the difference between two complex numbers using the C Py_complex representation Py_complex _Py_c_neg Py_complex num Return the negation of the complex number num using the C Py_complex representation Py_complex _Py_c_prod Py_complex left Py_complex right Return the product of two complex numbers using the C Py_complex representation Py_complex _Py_c_quot Py_complex dividend Py_complex divisor Return the quotient of two complex numbers using the C Py_complex representation If divisor is null this method returns zero and sets errno to EDOM Py_complex _Py_c_pow Py_complex num Py_complex exp Return the exponentiation of num by exp using the C Py_complex representation If num is null and exp is not a positive real number this method returns zero and sets errno to EDOM Complex Numbers as Python Objects type PyComplexObject This subtype of PyObject represents a Python complex number object PyTypeObject PyComplex_Type Part of the Stable ABI This instance of PyTypeObject represents the Python complex number type It is the same object as complex in the Python layer int PyComplex_Check PyObject p Return true if its argument is a PyComplexObject or a subtype of PyComplexObject This function always succeeds int PyComplex_CheckExact PyObject p Return true if its argument is a PyComplexObject but not a subtype of PyComplexObject This function always succeeds PyObject PyComplex_FromCComplex Py_complex v Return value New reference Create a new Python complex number object from a C Py_complex value PyObject PyComplex_FromDoubles double real double imag Return value New reference Part of the Stable ABI Return a new PyComplexObject object from real and imag double PyComplex_RealAsDouble PyObject op Part of the Stable ABI Return the real part of op as a C double double PyComplex_ImagAsDouble PyObject op Part of the Stable ABI Return the imaginary part of op as a C double Py_complex PyComplex_AsCComplex PyObject op Return the Py_complex value of the complex number op If op is not a Python complex number object but has a __complex__ method this method will first be called to convert op to a Python complex number object If __complex__ is not defined then it falls back to __float__ If __float__ is not defined then it falls back to __index__ Upon failure this method returns 1 0 as a real value Changed in version 3 8 Use __index__ if available,en
1981,importlib metadata Accessing package metadata New in version 3 8 Changed in version 3 10 importlib metadata is no longer provisional Source code Lib importlib metadata __init__ py importlib metadata is a library that provides access to the metadata of an installed Distribution Package such as its entry points or its top level names Import Packages modules if any Built in part on Python s import system this library intends to replace similar functionality in the entry point API and metadata API of pkg_resources Along with importlib resources this package can eliminate the need to use the older and less efficient pkg_resources package importlib metadata operates on third party distribution packages installed into Python s site packages directory via tools such as pip Specifically it works with distributions with discoverable dist info or egg info directories and metadata defined by the Core metadata specifications Important These are not necessarily equivalent to or correspond 1 1 with the top level import package names that can be imported inside Python code One distribution package can contain multiple import packages and single modules and one top level import package may map to multiple distribution packages if it is a namespace package You can use package_distributions to get a mapping between them By default distribution metadata can live on the file system or in zip archives on sys path Through an extension mechanism the metadata can live almost anywhere See also https importlib metadata readthedocs io The documentation for importlib_metadata which supplies a backport of importlib metadata This includes an API reference for this module s classes and functions as well as a migration guide for existing users of pkg_resources Overview Let s say you wanted to get the version string for a Distribution Package you ve installed using pip We start by creating a virtual environment and installing something into it python m venv example source example bin activate example python m pip install wheel You can get the version string for wheel by running the following example python from importlib metadata import version version wheel 0 32 3 You can also get a collection of entry points selectable by properties of the EntryPoint typically group or name such as console_scripts distutils commands and others Each group contains a collection of EntryPoint objects You can get the metadata for a distribution list metadata wheel Metadata Version Name Version Summary Home page Author Author email Maintainer Maintainer email License Project URL Project URL Project URL Keywords Platform Classifier Classifier Classifier Classifier Classifier Classifier Classifier Classifier Classifier Classifier Classifier Classifier Requires Python Provides Extra Requires Dist Requires Dist You can also get a distribution s version number list its constituent files and get a list of the distribution s Distribution requirements Functional API This package provides the following functionality via its public API Entry points The entry_points function returns a collection of entry points Entry points are represented by EntryPoint instances each EntryPoint has a name group and value attributes and a load method to resolve the value There are also module attr and extras attributes for getting the components of the value attribute Query all entry points eps entry_points The entry_points function returns an EntryPoints object a collection of all EntryPoint objects with names and groups attributes for convenience sorted eps groups console_scripts distutils commands distutils setup_keywords egg_info writers setuptools installation EntryPoints has a select method to select entry points matching specific properties Select entry points in the console_scripts group scripts eps select group console_scripts Equivalently since entry_points passes keyword arguments through to select scripts entry_points group console_scripts Pick out a specific script named wheel found in the wheel project wheel in scripts names True wheel scripts wheel Equivalently query for that entry poin,en
1982,t during selection wheel entry_points group console_scripts name wheel wheel entry_points select group console_scripts name wheel Inspect the resolved entry point wheel EntryPoint name wheel value wheel cli main group console_scripts wheel module wheel cli wheel attr main wheel extras main wheel load main function main at 0x103528488 The group and name are arbitrary values defined by the package author and usually a client will wish to resolve all entry points for a particular group Read the setuptools docs for more information on entry points their definition and usage Compatibility Note The selectable entry points were introduced in importlib_metadata 3 6 and Python 3 10 Prior to those changes entry_points accepted no parameters and always returned a dictionary of entry points keyed by group With importlib_metadata 5 0 and Python 3 12 entry_points always returns an EntryPoints object See backports entry_points_selectable for compatibility options Distribution metadata Every Distribution Package includes some metadata which you can extract using the metadata function wheel_metadata metadata wheel The keys of the returned data structure a PackageMetadata name the metadata keywords and the values are returned unparsed from the distribution metadata wheel_metadata Requires Python 2 7 3 0 3 1 3 2 3 3 PackageMetadata also presents a json attribute that returns all the metadata in a JSON compatible form per PEP 566 wheel_metadata json requires_python 2 7 3 0 3 1 3 2 3 3 Note The actual type of the object returned by metadata is an implementation detail and should be accessed only through the interface described by the PackageMetadata protocol Changed in version 3 10 The Description is now included in the metadata when presented through the payload Line continuation characters have been removed The json attribute was added Distribution versions The version function is the quickest way to get a Distribution Package s version number as a string version wheel 0 32 3 Distribution files You can also get the full set of files contained within a distribution The files function takes a Distribution Package name and returns all of the files installed by this distribution Each file object returned is a PackagePath a pathlib PurePath derived object with additional dist size and hash properties as indicated by the metadata For example util p for p in files wheel if util py in str p 0 util PackagePath wheel util py util size 859 util dist importlib metadata _hooks PathDistribution object at 0x101e0cef0 util hash FileHash mode sha256 value bYkw5oMccfazVCoYQwKkkemoVyMAFoR34mmKBx8R1NI Once you have the file you can also read its contents print util read_text import base64 import sys def as_bytes s if isinstance s text_type return s encode utf 8 return s You can also use the locate method to get a the absolute path to the file util locate PosixPath home gustav example lib site packages wheel util py In the case where the metadata file listing files RECORD or SOURCES txt is missing files will return None The caller may wish to wrap calls to files in always_iterable or otherwise guard against this condition if the target distribution is not known to have the metadata present Distribution requirements To get the full set of requirements for a Distribution Package use the requires function requires wheel pytest 3 0 0 extra test pytest cov extra test Mapping import to distribution packages A convenience method to resolve the Distribution Package name or names in the case of a namespace package that provide each importable top level Python module or Import Package packages_distributions importlib_metadata importlib metadata yaml PyYAML jaraco jaraco classes jaraco functools Some editable installs do not supply top level names and thus this function is not reliable with such installs New in version 3 10 Distributions While the above API is the most common and convenient usage you can get all of that information from the Distribution class A Distribution is an abstract object that represents the metadata for a Python Distribution Package You can get t,en
1983,he Distribution instance from importlib metadata import distribution dist distribution wheel Thus an alternative way to get the version number is through the Distribution instance dist version 0 32 3 There are all kinds of additional metadata available on the Distribution instance dist metadata Requires Python 2 7 3 0 3 1 3 2 3 3 dist metadata License MIT The full set of available metadata is not described here See the Core metadata specifications for additional details Distribution Discovery By default this package provides built in support for discovery of metadata for file system and zip file Distribution Packages This metadata finder search defaults to sys path but varies slightly in how it interprets those values from how other import machinery does In particular importlib metadata does not honor bytes objects on sys path importlib metadata will incidentally honor pathlib Path objects on sys path even though such values will be ignored for imports Extending the search algorithm Because Distribution Package metadata is not available through sys path searches or package loaders directly the metadata for a distribution is found through import system finders To find a distribution package s metadata importlib metadata queries the list of meta path finders on sys meta_path By default importlib metadata installs a finder for distribution packages found on the file system This finder doesn t actually find any distributions but it can find their metadata The abstract class importlib abc MetaPathFinder defines the interface expected of finders by Python s import system importlib metadata extends this protocol by looking for an optional find_distributions callable on the finders from sys meta_path and presents this extended interface as the DistributionFinder abstract base class which defines this abstract method abc abstractmethod def find_distributions context DistributionFinder Context Return an iterable of all Distribution instances capable of loading the metadata for packages for the indicated context The DistributionFinder Context object provides path and name properties indicating the path to search and name to match and may supply other relevant context What this means in practice is that to support finding distribution package metadata in locations other than the file system subclass Distribution and implement the abstract methods Then from a custom finder return instances of this derived Distribution in the find_distributions method,en
1984,tkinter Python interface to Tcl Tk Source code Lib tkinter __init__ py The tkinter package Tk interface is the standard Python interface to the Tcl Tk GUI toolkit Both Tk and tkinter are available on most Unix platforms including macOS as well as on Windows systems Running python m tkinter from the command line should open a window demonstrating a simple Tk interface letting you know that tkinter is properly installed on your system and also showing what version of Tcl Tk is installed so you can read the Tcl Tk documentation specific to that version Tkinter supports a range of Tcl Tk versions built either with or without thread support The official Python binary release bundles Tcl Tk 8 6 threaded See the source code for the _tkinter module for more information about supported versions Tkinter is not a thin wrapper but adds a fair amount of its own logic to make the experience more pythonic This documentation will concentrate on these additions and changes and refer to the official Tcl Tk documentation for details that are unchanged Note Tcl Tk 8 5 2007 introduced a modern set of themed user interface components along with a new API to use them Both old and new APIs are still available Most documentation you will find online still uses the old API and can be woefully outdated See also TkDocs Extensive tutorial on creating user interfaces with Tkinter Explains key concepts and illustrates recommended approaches using the modern API Tkinter 8 5 reference a GUI for Python Reference documentation for Tkinter 8 5 detailing available classes methods and options Tcl Tk Resources Tk commands Comprehensive reference to each of the underlying Tcl Tk commands used by Tkinter Tcl Tk Home Page Additional documentation and links to Tcl Tk core development Books Modern Tkinter for Busy Python Developers By Mark Roseman ISBN 978 1999149567 Python GUI programming with Tkinter By Alan D Moore ISBN 978 1788835886 Programming Python By Mark Lutz has excellent coverage of Tkinter ISBN 978 0596158101 Tcl and the Tk Toolkit 2nd edition By John Ousterhout inventor of Tcl Tk and Ken Jones does not cover Tkinter ISBN 978 0321336330 Architecture Tcl Tk is not a single library but rather consists of a few distinct modules each with separate functionality and its own official documentation Python s binary releases also ship an add on module together with it Tcl Tcl is a dynamic interpreted programming language just like Python Though it can be used on its own as a general purpose programming language it is most commonly embedded into C applications as a scripting engine or an interface to the Tk toolkit The Tcl library has a C interface to create and manage one or more instances of a Tcl interpreter run Tcl commands and scripts in those instances and add custom commands implemented in either Tcl or C Each interpreter has an event queue and there are facilities to send events to it and process them Unlike Python Tcl s execution model is designed around cooperative multitasking and Tkinter bridges this difference see Threading model for details Tk Tk is a Tcl package implemented in C that adds custom commands to create and manipulate GUI widgets Each Tk object embeds its own Tcl interpreter instance with Tk loaded into it Tk s widgets are very customizable though at the cost of a dated appearance Tk uses Tcl s event queue to generate and process GUI events Ttk Themed Tk Ttk is a newer family of Tk widgets that provide a much better appearance on different platforms than many of the classic Tk widgets Ttk is distributed as part of Tk starting with Tk version 8 5 Python bindings are provided in a separate module tkinter ttk Internally Tk and Ttk use facilities of the underlying operating system i e Xlib on Unix X11 Cocoa on macOS GDI on Windows When your Python application uses a class in Tkinter e g to create a widget the tkinter module first assembles a Tcl Tk command string It passes that Tcl command string to an internal _tkinter binary module which then calls the Tcl interpreter to evaluate it The Tcl interpreter will then call into the Tk and or T,en
1985,tk packages which will in turn make calls to Xlib Cocoa or GDI Tkinter Modules Support for Tkinter is spread across several modules Most applications will need the main tkinter module as well as the tkinter ttk module which provides the modern themed widget set and API from tkinter import from tkinter import ttk class tkinter Tk screenName None baseName None className Tk useTk True sync False use None Construct a toplevel Tk widget which is usually the main window of an application and initialize a Tcl interpreter for this widget Each instance has its own associated Tcl interpreter The Tk class is typically instantiated using all default values However the following keyword arguments are currently recognized screenName When given as a string sets the DISPLAY environment variable X11 only baseName Name of the profile file By default baseName is derived from the program name sys argv 0 className Name of the widget class Used as a profile file and also as the name with which Tcl is invoked argv0 in interp useTk If True initialize the Tk subsystem The tkinter Tcl function sets this to False sync If True execute all X server commands synchronously so that errors are reported immediately Can be used for debugging X11 only use Specifies the id of the window in which to embed the application instead of it being created as an independent toplevel window id must be specified in the same way as the value for the use option for toplevel widgets that is it has a form like that returned by winfo_id Note that on some platforms this will only work correctly if id refers to a Tk frame or toplevel that has its container option enabled Tk reads and interprets profile files named className tcl and baseName tcl into the Tcl interpreter and calls exec on the contents of className py and baseName py The path for the profile files is the HOME environment variable or if that isn t defined then os curdir tk The Tk application object created by instantiating Tk This provides access to the Tcl interpreter Each widget that is attached the same instance of Tk has the same value for its tk attribute master The widget object that contains this widget For Tk the master is None because it is the main window The terms master and parent are similar and sometimes used interchangeably as argument names however calling winfo_parent returns a string of the widget name whereas master returns the object parent child reflects the tree like relationship while master slave reflects the container structure children The immediate descendants of this widget as a dict with the child widget names as the keys and the child instance objects as the values tkinter Tcl screenName None baseName None className Tk useTk False The Tcl function is a factory function which creates an object much like that created by the Tk class except that it does not initialize the Tk subsystem This is most often useful when driving the Tcl interpreter in an environment where one doesn t want to create extraneous toplevel windows or where one cannot such as Unix Linux systems without an X server An object created by the Tcl object can have a Toplevel window created and the Tk subsystem initialized by calling its loadtk method The modules that provide Tk support include tkinter Main Tkinter module tkinter colorchooser Dialog to let the user choose a color tkinter commondialog Base class for the dialogs defined in the other modules listed here tkinter filedialog Common dialogs to allow the user to specify a file to open or save tkinter font Utilities to help work with fonts tkinter messagebox Access to standard Tk dialog boxes tkinter scrolledtext Text widget with a vertical scroll bar built in tkinter simpledialog Basic dialogs and convenience functions tkinter ttk Themed widget set introduced in Tk 8 5 providing modern alternatives for many of the classic widgets in the main tkinter module Additional modules _tkinter A binary module that contains the low level interface to Tcl Tk It is automatically imported by the main tkinter module and should never be used directly by application programmers ,en
1986,It is usually a shared library or DLL but might in some cases be statically linked with the Python interpreter idlelib Python s Integrated Development and Learning Environment IDLE Based on tkinter tkinter constants Symbolic constants that can be used in place of strings when passing various parameters to Tkinter calls Automatically imported by the main tkinter module tkinter dnd experimental Drag and drop support for tkinter This will become deprecated when it is replaced with the Tk DND tkinter tix deprecated An older third party Tcl Tk package that adds several new widgets Better alternatives for most can be found in tkinter ttk turtle Turtle graphics in a Tk window Tkinter Life Preserver This section is not designed to be an exhaustive tutorial on either Tk or Tkinter For that refer to one of the external resources noted earlier Instead this section provides a very quick orientation to what a Tkinter application looks like identifies foundational Tk concepts and explains how the Tkinter wrapper is structured The remainder of this section will help you to identify the classes methods and options you ll need in your Tkinter application and where to find more detailed documentation on them including in the official Tcl Tk reference manual A Hello World Program We ll start by walking through a Hello World application in Tkinter This isn t the smallest one we could write but has enough to illustrate some key concepts you ll need to know from tkinter import from tkinter import ttk root Tk frm ttk Frame root padding 10 frm grid ttk Label frm text Hello World grid column 0 row 0 ttk Button frm text Quit command root destroy grid column 1 row 0 root mainloop After the imports the next line creates an instance of the Tk class which initializes Tk and creates its associated Tcl interpreter It also creates a toplevel window known as the root window which serves as the main window of the application The following line creates a frame widget which in this case will contain a label and a button we ll create next The frame is fit inside the root window The next line creates a label widget holding a static text string The grid method is used to specify the relative layout position of the label within its containing frame widget similar to how tables in HTML work A button widget is then created and placed to the right of the label When pressed it will call the destroy method of the root window Finally the mainloop method puts everything on the display and responds to user input until the program terminates Important Tk Concepts Even this simple program illustrates the following key Tk concepts widgets A Tkinter user interface is made up of individual widgets Each widget is represented as a Python object instantiated from classes like ttk Frame ttk Label and ttk Button widget hierarchy Widgets are arranged in a hierarchy The label and button were contained within a frame which in turn was contained within the root window When creating each child widget its parent widget is passed as the first argument to the widget constructor configuration options Widgets have configuration options which modify their appearance and behavior such as the text to display in a label or button Different classes of widgets will have different sets of options geometry management Widgets aren t automatically added to the user interface when they are created A geometry manager like grid controls where in the user interface they are placed event loop Tkinter reacts to user input changes from your program and even refreshes the display only when actively running an event loop If your program isn t running the event loop your user interface won t update Understanding How Tkinter Wraps Tcl Tk When your application uses Tkinter s classes and methods internally Tkinter is assembling strings representing Tcl Tk commands and executing those commands in the Tcl interpreter attached to your application s Tk instance Whether it s trying to navigate reference documentation trying to find the right method or option adapting some existing code or debugging your Tkinter appl,en
1987,ication there are times that it will be useful to understand what those underlying Tcl Tk commands look like To illustrate here is the Tcl Tk equivalent of the main part of the Tkinter script above ttk frame frm padding 10 grid frm grid ttk label frm lbl text Hello World column 0 row 0 grid ttk button frm btn text Quit command destroy column 1 row 0 Tcl s syntax is similar to many shell languages where the first word is the command to be executed with arguments to that command following it separated by spaces Without getting into too many details notice the following The commands used to create widgets like ttk frame correspond to widget classes in Tkinter Tcl widget options like text correspond to keyword arguments in Tkinter Widgets are referred to by a pathname in Tcl like frm btn whereas Tkinter doesn t use names but object references A widget s place in the widget hierarchy is encoded in its hierarchical pathname which uses a dot as a path separator The pathname for the root window is just dot In Tkinter the hierarchy is defined not by pathname but by specifying the parent widget when creating each child widget Operations which are implemented as separate commands in Tcl like grid or destroy are represented as methods on Tkinter widget objects As you ll see shortly at other times Tcl uses what appear to be method calls on widget objects which more closely mirror what would is used in Tkinter How do I What option does If you re not sure how to do something in Tkinter and you can t immediately find it in the tutorial or reference documentation you re using there are a few strategies that can be helpful First remember that the details of how individual widgets work may vary across different versions of both Tkinter and Tcl Tk If you re searching documentation make sure it corresponds to the Python and Tcl Tk versions installed on your system When searching for how to use an API it helps to know the exact name of the class option or method that you re using Introspection either in an interactive Python shell or with print can help you identify what you need To find out what configuration options are available on any widget call its configure method which returns a dictionary containing a variety of information about each object including its default and current values Use keys to get just the names of each option btn ttk Button frm print btn configure keys As most widgets have many configuration options in common it can be useful to find out which are specific to a particular widget class Comparing the list of options to that of a simpler widget like a frame is one way to do that print set btn configure keys set frm configure keys Similarly you can find the available methods for a widget object using the standard dir function If you try it you ll see there are over 200 common widget methods so again identifying those specific to a widget class is helpful print dir btn print set dir btn set dir frm Navigating the Tcl Tk Reference Manual As noted the official Tk commands reference manual man pages is often the most accurate description of what specific operations on widgets do Even when you know the name of the option or method that you need you may still have a few places to look While all operations in Tkinter are implemented as method calls on widget objects you ve seen that many Tcl Tk operations appear as commands that take a widget pathname as its first parameter followed by optional parameters e g destroy grid frm btn column 0 row 0 Others however look more like methods called on a widget object in fact when you create a widget in Tcl Tk it creates a Tcl command with the name of the widget pathname with the first parameter to that command being the name of a method to call frm btn invoke frm lbl configure text Goodbye In the official Tcl Tk reference documentation you ll find most operations that look like method calls on the man page for a specific widget e g you ll find the invoke method on the ttk button man page while functions that take a widget as a parameter often have their own man page e g grid You ll find,en
1988, many common options and methods in the options or ttk widget man pages while others are found in the man page for a specific widget class You ll also find that many Tkinter methods have compound names e g winfo_x winfo_height winfo_viewable You d find documentation for all of these in the winfo man page Note Somewhat confusingly there are also methods on all Tkinter widgets that don t actually operate on the widget but operate at a global scope independent of any widget Examples are methods for accessing the clipboard or the system bell They happen to be implemented as methods in the base Widget class that all Tkinter widgets inherit from Threading model Python and Tcl Tk have very different threading models which tkinter tries to bridge If you use threads you may need to be aware of this A Python interpreter may have many threads associated with it In Tcl multiple threads can be created but each thread has a separate Tcl interpreter instance associated with it Threads can also create more than one interpreter instance though each interpreter instance can be used only by the one thread that created it Each Tk object created by tkinter contains a Tcl interpreter It also keeps track of which thread created that interpreter Calls to tkinter can be made from any Python thread Internally if a call comes from a thread other than the one that created the Tk object an event is posted to the interpreter s event queue and when executed the result is returned to the calling Python thread Tcl Tk applications are normally event driven meaning that after initialization the interpreter runs an event loop i e Tk mainloop and responds to events Because it is single threaded event handlers must respond quickly otherwise they will block other events from being processed To avoid this any long running computations should not run in an event handler but are either broken into smaller pieces using timers or run in another thread This is different from many GUI toolkits where the GUI runs in a completely separate thread from all application code including event handlers If the Tcl interpreter is not running the event loop and processing events any tkinter calls made from threads other than the one running the Tcl interpreter will fail A number of special cases exist Tcl Tk libraries can be built so they are not thread aware In this case tkinter calls the library from the originating Python thread even if this is different than the thread that created the Tcl interpreter A global lock ensures only one call occurs at a time While tkinter allows you to create more than one instance of a Tk object with its own interpreter all interpreters that are part of the same thread share a common event queue which gets ugly fast In practice don t create more than one instance of Tk at a time Otherwise it s best to create them in separate threads and ensure you re running a thread aware Tcl Tk build Blocking event handlers are not the only way to prevent the Tcl interpreter from reentering the event loop It is even possible to run multiple nested event loops or abandon the event loop entirely If you re doing anything tricky when it comes to events or threads be aware of these possibilities There are a few select tkinter functions that presently work only when called from the thread that created the Tcl interpreter Handy Reference Setting Options Options control things like the color and border width of a widget Options can be set in three ways At object creation time using keyword arguments fred Button self fg red bg blue After object creation treating the option name like a dictionary index fred fg red fred bg blue Use the config method to update multiple attrs subsequent to object creation fred config fg red bg blue For a complete explanation of a given option and its behavior see the Tk man pages for the widget in question Note that the man pages list STANDARD OPTIONS and WIDGET SPECIFIC OPTIONS for each widget The former is a list of options that are common to many widgets the latter are the options that are idiosyncratic to that particular widget The St,en
1989,andard Options are documented on the options 3 man page No distinction between standard and widget specific options is made in this document Some options don t apply to some kinds of widgets Whether a given widget responds to a particular option depends on the class of the widget buttons have a command option labels do not The options supported by a given widget are listed in that widget s man page or can be queried at runtime by calling the config method without arguments or by calling the keys method on that widget The return value of these calls is a dictionary whose key is the name of the option as a string for example relief and whose values are 5 tuples Some options like bg are synonyms for common options with long names bg is shorthand for background Passing the config method the name of a shorthand option will return a 2 tuple not 5 tuple The 2 tuple passed back will contain the name of the synonym and the real option such as bg background Index Meaning Example 0 option name relief 1 option name for database lookup relief 2 option class for database lookup Relief 3 default value raised 4 current value groove Example print fred config relief relief relief Relief raised groove Of course the dictionary printed will include all the options available and their values This is meant only as an example The Packer The packer is one of Tk s geometry management mechanisms Geometry managers are used to specify the relative positioning of widgets within their container their mutual master In contrast to the more cumbersome placer which is used less commonly and we do not cover here the packer takes qualitative relationship specification above to the left of filling etc and works everything out to determine the exact placement coordinates for you The size of any master widget is determined by the size of the slave widgets inside The packer is used to control where slave widgets appear inside the master into which they are packed You can pack widgets into frames and frames into other frames in order to achieve the kind of layout you desire Additionally the arrangement is dynamically adjusted to accommodate incremental changes to the configuration once it is packed Note that widgets do not appear until they have had their geometry specified with a geometry manager It s a common early mistake to leave out the geometry specification and then be surprised when the widget is created but nothing appears A widget will appear only after it has had for example the packer s pack method applied to it The pack method can be called with keyword option value pairs that control where the widget is to appear within its container and how it is to behave when the main application window is resized Here are some examples fred pack defaults to side top fred pack side left fred pack expand 1 Packer Options For more extensive information on the packer and the options that it can take see the man pages and page 183 of John Ousterhout s book anchor Anchor type Denotes where the packer is to place each slave in its parcel expand Boolean 0 or 1 fill Legal values x y both none ipadx and ipady A distance designating internal padding on each side of the slave widget padx and pady A distance designating external padding on each side of the slave widget side Legal values are left right top bottom Coupling Widget Variables The current value setting of some widgets like text entry widgets can be connected directly to application variables by using special options These options are variable textvariable onvalue offvalue and value This connection works both ways if the variable changes for any reason the widget it s connected to will be updated to reflect the new value Unfortunately in the current implementation of tkinter it is not possible to hand over an arbitrary Python variable to a widget through a variable or textvariable option The only kinds of variables for which this works are variables that are subclassed from a class called Variable defined in tkinter There are many useful subclasses of Variable already defined StringVar IntVar DoubleVar and Boolean,en
1990,Var To read the current value of such a variable call the get method on it and to change its value you call the set method If you follow this protocol the widget will always track the value of the variable with no further intervention on your part For example import tkinter as tk class App tk Frame def __init__ self master super __init__ master self pack self entrythingy tk Entry self entrythingy pack Create the application variable self contents tk StringVar Set it to some value self contents set this is a variable Tell the entry widget to watch this variable self entrythingy textvariable self contents Define a callback for when the user hits return It prints the current value of the variable self entrythingy bind Key Return self print_contents def print_contents self event print Hi The current entry content is self contents get root tk Tk myapp App root myapp mainloop The Window Manager In Tk there is a utility command wm for interacting with the window manager Options to the wm command allow you to control things like titles placement icon bitmaps and the like In tkinter these commands have been implemented as methods on the Wm class Toplevel widgets are subclassed from the Wm class and so can call the Wm methods directly To get at the toplevel window that contains a given widget you can often just refer to the widget s master Of course if the widget has been packed inside of a frame the master won t represent a toplevel window To get at the toplevel window that contains an arbitrary widget you can call the _root method This method begins with an underscore to denote the fact that this function is part of the implementation and not an interface to Tk functionality Here are some examples of typical usage import tkinter as tk class App tk Frame def __init__ self master None super __init__ master self pack create the application myapp App here are method calls to the window manager class myapp master title My Do Nothing Application myapp master maxsize 1000 400 start the program myapp mainloop Tk Option Data Types anchor Legal values are points of the compass n ne e se s sw w nw and also center bitmap There are eight built in named bitmaps error gray25 gray50 hourglass info questhead question warning To specify an X bitmap filename give the full path to the file preceded with an as in usr contrib bitmap gumby bit boolean You can pass integers 0 or 1 or the strings yes or no callback This is any Python function that takes no arguments For example def print_it print hi there fred command print_it color Colors can be given as the names of X colors in the rgb txt file or as strings representing RGB values in 4 bit RGB 8 bit RRGGBB 12 bit RRRGGGBBB or 16 bit RRRRGGGGBBBB ranges where R G B here represent any legal hex digit See page 160 of Ousterhout s book for details cursor The standard X cursor names from cursorfont h can be used without the XC_ prefix For example to get a hand cursor XC_hand2 use the string hand2 You can also specify a bitmap and mask file of your own See page 179 of Ousterhout s book distance Screen distances can be specified in either pixels or absolute distances Pixels are given as numbers and absolute distances as strings with the trailing character denoting units c for centimetres i for inches m for millimetres p for printer s points For example 3 5 inches is expressed as 3 5i font Tk uses a list font name format such as courier 10 bold Font sizes with positive numbers are measured in points sizes with negative numbers are measured in pixels geometry This is a string of the form widthxheight where width and height are measured in pixels for most widgets in characters for widgets displaying text For example fred geometry 200x100 justify Legal values are the strings left center right and fill region This is a string with four space delimited elements each of which is a legal distance see above For example 2 3 4 5 and 3i 2i 4 5i 2i and 3c 2c 4c 10 43c are all legal regions relief Determines what the border style of a widget will be Legal values are raised sunken flat groove and ridge scrollcommand This ,en
1991,is almost always the set method of some scrollbar widget but can be any widget method that takes a single argument wrap Must be one of none char or word Bindings and Events The bind method from the widget command allows you to watch for certain events and to have a callback function trigger when that event type occurs The form of the bind method is def bind self sequence func add where sequence is a string that denotes the target kind of event See the bind 3tk man page and page 201 of John Ousterhout s book Tcl and the Tk Toolkit 2nd edition for details func is a Python function taking one argument to be invoked when the event occurs An Event instance will be passed as the argument Functions deployed this way are commonly known as callbacks add is optional either or Passing an empty string denotes that this binding is to replace any other bindings that this event is associated with Passing a means that this function is to be added to the list of functions bound to this event type For example def turn_red self event event widget activeforeground red self button bind Enter self turn_red Notice how the widget field of the event is being accessed in the turn_red callback This field contains the widget that caught the X event The following table lists the other event fields you can access and how they are denoted in Tk which can be useful when referring to the Tk man pages Tk Tkinter Event Field Tk Tkinter Event Field f focus A char h height E send_event k keycode K keysym s state N keysym_num t time T type w width W widget x x X x_root y y Y y_root The index Parameter A number of widgets require index parameters to be passed These are used to point at a specific place in a Text widget or to particular characters in an Entry widget or to particular menu items in a Menu widget Entry widget indexes index view index etc Entry widgets have options that refer to character positions in the text being displayed You can use these tkinter functions to access these special points in text widgets Text widget indexes The index notation for Text widgets is very rich and is best described in the Tk man pages Menu indexes menu invoke menu entryconfig etc Some options and methods for menus manipulate specific menu entries Anytime a menu index is needed for an option or a parameter you may pass in an integer which refers to the numeric position of the entry in the widget counted from the top starting with 0 the string active which refers to the menu position that is currently under the cursor the string last which refers to the last menu item An integer preceded by as in 6 where the integer is interpreted as a y pixel coordinate in the menu s coordinate system the string none which indicates no menu entry at all most often used with menu activate to deactivate all entries and finally a text string that is pattern matched against the label of the menu entry as scanned from the top of the menu to the bottom Note that this index type is considered after all the others which means that matches for menu items labelled last active or none may be interpreted as the above literals instead Images Images of different formats can be created through the corresponding subclass of tkinter Image BitmapImage for images in XBM format PhotoImage for images in PGM PPM GIF and PNG formats The latter is supported starting with Tk 8 6 Either type of image is created through either the file or the data option other options are available as well The image object can then be used wherever an image option is supported by some widget e g labels buttons menus In these cases Tk will not keep a reference to the image When the last Python reference to the image object is deleted the image data is deleted as well and Tk will display an empty box wherever the image was used See also The Pillow package adds support for formats such as BMP JPEG TIFF and WebP among others File Handlers Tk allows you to register and unregister a callback function which will be called from the Tk mainloop when I O is possible on a file descriptor Only one handler may be registered per file descri,en
1992,ptor Example code import tkinter widget tkinter Tk mask tkinter READABLE tkinter WRITABLE widget tk createfilehandler file mask callback widget tk deletefilehandler file This feature is not available on Windows Since you don t know how many bytes are available for reading you may not want to use the BufferedIOBase or TextIOBase read or readline methods since these will insist on reading a predefined number of bytes For sockets the recv or recvfrom methods will work fine for other files use raw reads or os read file fileno maxbytecount Widget tk createfilehandler file mask func Registers the file handler callback function func The file argument may either be an object with a fileno method such as a file or socket object or an integer file descriptor The mask argument is an ORed combination of any of the three constants below The callback is called as follows callback file mask Widget tk deletefilehandler file Unregisters a file handler _tkinter READABLE _tkinter WRITABLE _tkinter EXCEPTION Constants used in the mask arguments,en
1993,Low level API Index This page lists all low level asyncio APIs Obtaining the Event Loop asyncio get_running_loop The preferred function to get the running event loop asyncio get_event_loop Get an event loop instance running or current via the current policy asyncio set_event_loop Set the event loop as current via the current policy asyncio new_event_loop Create a new event loop Examples Using asyncio get_running_loop Event Loop Methods See also the main documentation section about the Event Loop Methods Lifecycle loop run_until_complete Run a Future Task awaitable until complete loop run_forever Run the event loop forever loop stop Stop the event loop loop close Close the event loop loop is_running Return True if the event loop is running loop is_closed Return True if the event loop is closed await loop shutdown_asyncgens Close asynchronous generators Debugging loop set_debug Enable or disable the debug mode loop get_debug Get the current debug mode Scheduling Callbacks loop call_soon Invoke a callback soon loop call_soon_threadsafe A thread safe variant of loop call_soon loop call_later Invoke a callback after the given time loop call_at Invoke a callback at the given time Thread Process Pool await loop run_in_executor Run a CPU bound or other blocking function in a concurrent futures executor loop set_default_executor Set the default executor for loop run_in_executor Tasks and Futures loop create_future Create a Future object loop create_task Schedule coroutine as a Task loop set_task_factory Set a factory used by loop create_task to create Tasks loop get_task_factory Get the factory loop create_task uses to create Tasks DNS await loop getaddrinfo Asynchronous version of socket getaddrinfo await loop getnameinfo Asynchronous version of socket getnameinfo Networking and IPC await loop create_connection Open a TCP connection await loop create_server Create a TCP server await loop create_unix_connection Open a Unix socket connection await loop create_unix_server Create a Unix socket server await loop connect_accepted_socket Wrap a socket into a transport protocol pair await loop create_datagram_endpoint Open a datagram UDP connection await loop sendfile Send a file over a transport await loop start_tls Upgrade an existing connection to TLS await loop connect_read_pipe Wrap a read end of a pipe into a transport protocol pair await loop connect_write_pipe Wrap a write end of a pipe into a transport protocol pair Sockets await loop sock_recv Receive data from the socket await loop sock_recv_into Receive data from the socket into a buffer await loop sock_recvfrom Receive a datagram from the socket await loop sock_recvfrom_into Receive a datagram from the socket into a buffer await loop sock_sendall Send data to the socket await loop sock_sendto Send a datagram via the socket to the given address await loop sock_connect Connect the socket await loop sock_accept Accept a socket connection await loop sock_sendfile Send a file over the socket loop add_reader Start watching a file descriptor for read availability loop remove_reader Stop watching a file descriptor for read availability loop add_writer Start watching a file descriptor for write availability loop remove_writer Stop watching a file descriptor for write availability Unix Signals loop add_signal_handler Add a handler for a signal loop remove_signal_handler Remove a handler for a signal Subprocesses loop subprocess_exec Spawn a subprocess loop subprocess_shell Spawn a subprocess from a shell command Error Handling loop call_exception_handler Call the exception handler loop set_exception_handler Set a new exception handler loop get_exception_handler Get the current exception handler loop default_exception_handler The default exception handler implementation Examples Using asyncio new_event_loop and loop run_forever Using loop call_later Using loop create_connection to implement an echo client Using loop create_connection to connect a socket Using add_reader to watch an FD for read events Using loop add_signal_handler Using loop subprocess_exec Transports All transports im,en
1994,plement the following methods transport close Close the transport transport is_closing Return True if the transport is closing or is closed transport get_extra_info Request for information about the transport transport set_protocol Set a new protocol transport get_protocol Return the current protocol Transports that can receive data TCP and Unix connections pipes etc Returned from methods like loop create_connection loop create_unix_connection loop connect_read_pipe etc Read Transports transport is_reading Return True if the transport is receiving transport pause_reading Pause receiving transport resume_reading Resume receiving Transports that can Send data TCP and Unix connections pipes etc Returned from methods like loop create_connection loop create_unix_connection loop connect_write_pipe etc Write Transports transport write Write data to the transport transport writelines Write buffers to the transport transport can_write_eof Return True if the transport supports sending EOF transport write_eof Close and send EOF after flushing buffered data transport abort Close the transport immediately transport get_write_buffer_size Return the current size of the output buffer transport get_write_buffer_limits Return high and low water marks for write flow control transport set_write_buffer_limits Set new high and low water marks for write flow control Transports returned by loop create_datagram_endpoint Datagram Transports transport sendto Send data to the remote peer transport abort Close the transport immediately Low level transport abstraction over subprocesses Returned by loop subprocess_exec and loop subprocess_shell Subprocess Transports transport get_pid Return the subprocess process id transport get_pipe_transport Return the transport for the requested communication pipe stdin stdout or stderr transport get_returncode Return the subprocess return code transport kill Kill the subprocess transport send_signal Send a signal to the subprocess transport terminate Stop the subprocess transport close Kill the subprocess and close all pipes Protocols Protocol classes can implement the following callback methods callback connection_made Called when a connection is made callback connection_lost Called when the connection is lost or closed callback pause_writing Called when the transport s buffer goes over the high water mark callback resume_writing Called when the transport s buffer drains below the low water mark Streaming Protocols TCP Unix Sockets Pipes callback data_received Called when some data is received callback eof_received Called when an EOF is received Buffered Streaming Protocols callback get_buffer Called to allocate a new receive buffer callback buffer_updated Called when the buffer was updated with the received data callback eof_received Called when an EOF is received Datagram Protocols callback datagram_received Called when a datagram is received callback error_received Called when a previous send or receive operation raises an OSError Subprocess Protocols callback pipe_data_received Called when the child process writes data into its stdout or stderr pipe callback pipe_connection_lost Called when one of the pipes communicating with the child process is closed callback process_exited Called when the child process has exited It can be called before pipe_data_received and pipe_connection_lost methods Event Loop Policies Policies is a low level mechanism to alter the behavior of functions like asyncio get_event_loop See also the main policies section for more details Accessing Policies asyncio get_event_loop_policy Return the current process wide policy asyncio set_event_loop_policy Set a new process wide policy AbstractEventLoopPolicy Base class for policy objects,en
1995,syslog Unix syslog library routines This module provides an interface to the Unix syslog library routines Refer to the Unix manual pages for a detailed description of the syslog facility Availability Unix not Emscripten not WASI This module wraps the system syslog family of routines A pure Python library that can speak to a syslog server is available in the logging handlers module as SysLogHandler The module defines the following functions syslog syslog message syslog syslog priority message Send the string message to the system logger A trailing newline is added if necessary Each message is tagged with a priority composed of a facility and a level The optional priority argument which defaults to LOG_INFO determines the message priority If the facility is not encoded in priority using logical or LOG_INFO LOG_USER the value given in the openlog call is used If openlog has not been called prior to the call to syslog openlog will be called with no arguments Raises an auditing event syslog syslog with arguments priority message Changed in version 3 2 In previous versions openlog would not be called automatically if it wasn t called prior to the call to syslog deferring to the syslog implementation to call openlog Changed in version 3 12 This function is restricted in subinterpreters Only code that runs in multiple interpreters is affected and the restriction is not relevant for most users openlog must be called in the main interpreter before syslog may be used in a subinterpreter Otherwise it will raise RuntimeError syslog openlog ident logoption facility Logging options of subsequent syslog calls can be set by calling openlog syslog will call openlog with no arguments if the log is not currently open The optional ident keyword argument is a string which is prepended to every message and defaults to sys argv 0 with leading path components stripped The optional logoption keyword argument default is 0 is a bit field see below for possible values to combine The optional facility keyword argument default is LOG_USER sets the default facility for messages which do not have a facility explicitly encoded Raises an auditing event syslog openlog with arguments ident logoption facility Changed in version 3 2 In previous versions keyword arguments were not allowed and ident was required Changed in version 3 12 This function is restricted in subinterpreters Only code that runs in multiple interpreters is affected and the restriction is not relevant for most users This may only be called in the main interpreter It will raise RuntimeError if called in a subinterpreter syslog closelog Reset the syslog module values and call the system library closelog This causes the module to behave as it does when initially imported For example openlog will be called on the first syslog call if openlog hasn t already been called and ident and other openlog parameters are reset to defaults Raises an auditing event syslog closelog with no arguments Changed in version 3 12 This function is restricted in subinterpreters Only code that runs in multiple interpreters is affected and the restriction is not relevant for most users This may only be called in the main interpreter It will raise RuntimeError if called in a subinterpreter syslog setlogmask maskpri Set the priority mask to maskpri and return the previous mask value Calls to syslog with a priority level not set in maskpri are ignored The default is to log all priorities The function LOG_MASK pri calculates the mask for the individual priority pri The function LOG_UPTO pri calculates the mask for all priorities up to and including pri Raises an auditing event syslog setlogmask with argument maskpri The module defines the following constants Priority levels high to low LOG_EMERG LOG_ALERT LOG_CRIT LOG_ERR LOG_WARNING LOG_NOTICE LOG_INFO LOG_DEBUG Facilities LOG_KERN LOG_USER LOG_MAIL LOG_DAEMON LOG_AUTH LOG_LPR LOG_NEWS LOG_UUCP LOG_CRON LOG_SYSLOG LOG_LOCAL0 to LOG_LOCAL7 and if defined in syslog h LOG_AUTHPRIV Log options LOG_PID LOG_CONS LOG_NDELAY and if defined in syslog h LOG_ODELAY LOG_NOWAIT and L,en
1996,OG_PERROR Examples Simple example A simple set of examples import syslog syslog syslog Processing started if error syslog syslog syslog LOG_ERR Processing started An example of setting some log options these would include the process ID in logged messages and write the messages to the destination facility used for mail logging syslog openlog logoption syslog LOG_PID facility syslog LOG_MAIL syslog syslog E mail processing initiated,en
1997,Reflection PyObject PyEval_GetBuiltins void Return value Borrowed reference Part of the Stable ABI Return a dictionary of the builtins in the current execution frame or the interpreter of the thread state if no frame is currently executing PyObject PyEval_GetLocals void Return value Borrowed reference Part of the Stable ABI Return a dictionary of the local variables in the current execution frame or NULL if no frame is currently executing PyObject PyEval_GetGlobals void Return value Borrowed reference Part of the Stable ABI Return a dictionary of the global variables in the current execution frame or NULL if no frame is currently executing PyFrameObject PyEval_GetFrame void Return value Borrowed reference Part of the Stable ABI Return the current thread state s frame which is NULL if no frame is currently executing See also PyThreadState_GetFrame const char PyEval_GetFuncName PyObject func Part of the Stable ABI Return the name of func if it is a function class or instance object else the name of func s type const char PyEval_GetFuncDesc PyObject func Part of the Stable ABI Return a description string depending on the type of func Return values include for functions and methods constructor instance and object Concatenated with the result of PyEval_GetFuncName the result will be a description of func,en
1998,faulthandler Dump the Python traceback New in version 3 3 This module contains functions to dump Python tracebacks explicitly on a fault after a timeout or on a user signal Call faulthandler enable to install fault handlers for the SIGSEGV SIGFPE SIGABRT SIGBUS and SIGILL signals You can also enable them at startup by setting the PYTHONFAULTHANDLER environment variable or by using the X faulthandler command line option The fault handler is compatible with system fault handlers like Apport or the Windows fault handler The module uses an alternative stack for signal handlers if the sigaltstack function is available This allows it to dump the traceback even on a stack overflow The fault handler is called on catastrophic cases and therefore can only use signal safe functions e g it cannot allocate memory on the heap Because of this limitation traceback dumping is minimal compared to normal Python tracebacks Only ASCII is supported The backslashreplace error handler is used on encoding Each string is limited to 500 characters Only the filename the function name and the line number are displayed no source code It is limited to 100 frames and 100 threads The order is reversed the most recent call is shown first By default the Python traceback is written to sys stderr To see tracebacks applications must be run in the terminal A log file can alternatively be passed to faulthandler enable The module is implemented in C so tracebacks can be dumped on a crash or when Python is deadlocked The Python Development Mode calls faulthandler enable at Python startup See also Module pdb Interactive source code debugger for Python programs Module traceback Standard interface to extract format and print stack traces of Python programs Dumping the traceback faulthandler dump_traceback file sys stderr all_threads True Dump the tracebacks of all threads into file If all_threads is False dump only the current thread See also traceback print_tb which can be used to print a traceback object Changed in version 3 5 Added support for passing file descriptor to this function Fault handler state faulthandler enable file sys stderr all_threads True Enable the fault handler install handlers for the SIGSEGV SIGFPE SIGABRT SIGBUS and SIGILL signals to dump the Python traceback If all_threads is True produce tracebacks for every running thread Otherwise dump only the current thread The file must be kept open until the fault handler is disabled see issue with file descriptors Changed in version 3 5 Added support for passing file descriptor to this function Changed in version 3 6 On Windows a handler for Windows exception is also installed Changed in version 3 10 The dump now mentions if a garbage collector collection is running if all_threads is true faulthandler disable Disable the fault handler uninstall the signal handlers installed by enable faulthandler is_enabled Check if the fault handler is enabled Dumping the tracebacks after a timeout faulthandler dump_traceback_later timeout repeat False file sys stderr exit False Dump the tracebacks of all threads after a timeout of timeout seconds or every timeout seconds if repeat is True If exit is True call _exit with status 1 after dumping the tracebacks Note _exit exits the process immediately which means it doesn t do any cleanup like flushing file buffers If the function is called twice the new call replaces previous parameters and resets the timeout The timer has a sub second resolution The file must be kept open until the traceback is dumped or cancel_dump_traceback_later is called see issue with file descriptors This function is implemented using a watchdog thread Changed in version 3 5 Added support for passing file descriptor to this function Changed in version 3 7 This function is now always available faulthandler cancel_dump_traceback_later Cancel the last call to dump_traceback_later Dumping the traceback on a user signal faulthandler register signum file sys stderr all_threads True chain False Register a user signal install a handler for the signum signal to dump the traceback of all threads or of ,en
1999,the current thread if all_threads is False into file Call the previous handler if chain is True The file must be kept open until the signal is unregistered by unregister see issue with file descriptors Not available on Windows Changed in version 3 5 Added support for passing file descriptor to this function faulthandler unregister signum Unregister a user signal uninstall the handler of the signum signal installed by register Return True if the signal was registered False otherwise Not available on Windows Issue with file descriptors enable dump_traceback_later and register keep the file descriptor of their file argument If the file is closed and its file descriptor is reused by a new file or if os dup2 is used to replace the file descriptor the traceback will be written into a different file Call these functions again each time that the file is replaced Example Example of a segmentation fault on Linux with and without enabling the fault handler python c import ctypes ctypes string_at 0 Segmentation fault python q X faulthandler import ctypes ctypes string_at 0 Fatal Python error Segmentation fault Current thread 0x00007fb899f39700 most recent call first File home python cpython Lib ctypes __init__ py line 486 in string_at File stdin line 1 in module Segmentation fault,en
2000,dataclasses Data Classes Source code Lib dataclasses py This module provides a decorator and functions for automatically adding generated special method s such as __init__ and __repr__ to user defined classes It was originally described in PEP 557 The member variables to use in these generated methods are defined using PEP 526 type annotations For example this code from dataclasses import dataclass dataclass class InventoryItem Class for keeping track of an item in inventory name str unit_price float quantity_on_hand int 0 def total_cost self float return self unit_price self quantity_on_hand will add among other things a __init__ that looks like def __init__ self name str unit_price float quantity_on_hand int 0 self name name self unit_price unit_price self quantity_on_hand quantity_on_hand Note that this method is automatically added to the class it is not directly specified in the InventoryItem definition shown above New in version 3 7 Module contents dataclasses dataclass init True repr True eq True order False unsafe_hash False frozen False match_args True kw_only False slots False weakref_slot False This function is a decorator that is used to add generated special method s to classes as described below The dataclass decorator examines the class to find field s A field is defined as a class variable that has a type annotation With two exceptions described below nothing in dataclass examines the type specified in the variable annotation The order of the fields in all of the generated methods is the order in which they appear in the class definition The dataclass decorator will add various dunder methods to the class described below If any of the added methods already exist in the class the behavior depends on the parameter as documented below The decorator returns the same class that it is called on no new class is created If dataclass is used just as a simple decorator with no parameters it acts as if it has the default values documented in this signature That is these three uses of dataclass are equivalent dataclass class C dataclass class C dataclass init True repr True eq True order False unsafe_hash False frozen False match_args True kw_only False slots False weakref_slot False class C The parameters to dataclass are init If true the default a __init__ method will be generated If the class already defines __init__ this parameter is ignored repr If true the default a __repr__ method will be generated The generated repr string will have the class name and the name and repr of each field in the order they are defined in the class Fields that are marked as being excluded from the repr are not included For example InventoryItem name widget unit_price 3 0 quantity_on_hand 10 If the class already defines __repr__ this parameter is ignored eq If true the default an __eq__ method will be generated This method compares the class as if it were a tuple of its fields in order Both instances in the comparison must be of the identical type If the class already defines __eq__ this parameter is ignored order If true the default is False __lt__ __le__ __gt__ and __ge__ methods will be generated These compare the class as if it were a tuple of its fields in order Both instances in the comparison must be of the identical type If order is true and eq is false a ValueError is raised If the class already defines any of __lt__ __le__ __gt__ or __ge__ then TypeError is raised unsafe_hash If False the default a __hash__ method is generated according to how eq and frozen are set __hash__ is used by built in hash and when objects are added to hashed collections such as dictionaries and sets Having a __hash__ implies that instances of the class are immutable Mutability is a complicated property that depends on the programmer s intent the existence and behavior of __eq__ and the values of the eq and frozen flags in the dataclass decorator By default dataclass will not implicitly add a __hash__ method unless it is safe to do so Neither will it add or change an existing explicitly defined __hash__ method Setting the class attribute __hash__ N,en
2001,one has a specific meaning to Python as described in the __hash__ documentation If __hash__ is not explicitly defined or if it is set to None then dataclass may add an implicit __hash__ method Although not recommended you can force dataclass to create a __hash__ method with unsafe_hash True This might be the case if your class is logically immutable but can nonetheless be mutated This is a specialized use case and should be considered carefully Here are the rules governing implicit creation of a __hash__ method Note that you cannot both have an explicit __hash__ method in your dataclass and set unsafe_hash True this will result in a TypeError If eq and frozen are both true by default dataclass will generate a __hash__ method for you If eq is true and frozen is false __hash__ will be set to None marking it unhashable which it is since it is mutable If eq is false __hash__ will be left untouched meaning the __hash__ method of the superclass will be used if the superclass is object this means it will fall back to id based hashing frozen If true the default is False assigning to fields will generate an exception This emulates read only frozen instances If __setattr__ or __delattr__ is defined in the class then TypeError is raised See the discussion below match_args If true the default is True the __match_args__ tuple will be created from the list of parameters to the generated __init__ method even if __init__ is not generated see above If false or if __match_args__ is already defined in the class then __match_args__ will not be generated New in version 3 10 kw_only If true the default value is False then all fields will be marked as keyword only If a field is marked as keyword only then the only effect is that the __init__ parameter generated from a keyword only field must be specified with a keyword when __init__ is called There is no effect on any other aspect of dataclasses See the parameter glossary entry for details Also see the KW_ONLY section New in version 3 10 slots If true the default is False __slots__ attribute will be generated and new class will be returned instead of the original one If __slots__ is already defined in the class then TypeError is raised New in version 3 10 Changed in version 3 11 If a field name is already included in the __slots__ of a base class it will not be included in the generated __slots__ to prevent overriding them Therefore do not use __slots__ to retrieve the field names of a dataclass Use fields instead To be able to determine inherited slots base class __slots__ may be any iterable but not an iterator weakref_slot If true the default is False add a slot named __weakref__ which is required to make an instance weakref able It is an error to specify weakref_slot True without also specifying slots True New in version 3 11 field s may optionally specify a default value using normal Python syntax dataclass class C a int a has no default value b int 0 assign a default value for b In this example both a and b will be included in the added __init__ method which will be defined as def __init__ self a int b int 0 TypeError will be raised if a field without a default value follows a field with a default value This is true whether this occurs in a single class or as a result of class inheritance dataclasses field default MISSING default_factory MISSING init True repr True hash None compare True metadata None kw_only MISSING For common and simple use cases no other functionality is required There are however some dataclass features that require additional per field information To satisfy this need for additional information you can replace the default field value with a call to the provided field function For example dataclass class C mylist list int field default_factory list c C c mylist 1 2 3 As shown above the MISSING value is a sentinel object used to detect if some parameters are provided by the user This sentinel is used because None is a valid value for some parameters with a distinct meaning No code should directly use the MISSING value The parameters to field are default If provided th,en
2002,is will be the default value for this field This is needed because the field call itself replaces the normal position of the default value default_factory If provided it must be a zero argument callable that will be called when a default value is needed for this field Among other purposes this can be used to specify fields with mutable default values as discussed below It is an error to specify both default and default_factory init If true the default this field is included as a parameter to the generated __init__ method repr If true the default this field is included in the string returned by the generated __repr__ method hash This can be a bool or None If true this field is included in the generated __hash__ method If None the default use the value of compare this would normally be the expected behavior A field should be considered in the hash if it s used for comparisons Setting this value to anything other than None is discouraged One possible reason to set hash False but compare True would be if a field is expensive to compute a hash value for that field is needed for equality testing and there are other fields that contribute to the type s hash value Even if a field is excluded from the hash it will still be used for comparisons compare If true the default this field is included in the generated equality and comparison methods __eq__ __gt__ et al metadata This can be a mapping or None None is treated as an empty dict This value is wrapped in MappingProxyType to make it read only and exposed on the Field object It is not used at all by Data Classes and is provided as a third party extension mechanism Multiple third parties can each have their own key to use as a namespace in the metadata kw_only If true this field will be marked as keyword only This is used when the generated __init__ method s parameters are computed New in version 3 10 If the default value of a field is specified by a call to field then the class attribute for this field will be replaced by the specified default value If no default is provided then the class attribute will be deleted The intent is that after the dataclass decorator runs the class attributes will all contain the default values for the fields just as if the default value itself were specified For example after dataclass class C x int y int field repr False z int field repr False default 10 t int 20 The class attribute C z will be 10 the class attribute C t will be 20 and the class attributes C x and C y will not be set class dataclasses Field Field objects describe each defined field These objects are created internally and are returned by the fields module level method see below Users should never instantiate a Field object directly Its documented attributes are name The name of the field type The type of the field default default_factory init repr hash compare metadata and kw_only have the identical meaning and values as they do in the field function Other attributes may exist but they are private and must not be inspected or relied on dataclasses fields class_or_instance Returns a tuple of Field objects that define the fields for this dataclass Accepts either a dataclass or an instance of a dataclass Raises TypeError if not passed a dataclass or instance of one Does not return pseudo fields which are ClassVar or InitVar dataclasses asdict obj dict_factory dict Converts the dataclass obj to a dict by using the factory function dict_factory Each dataclass is converted to a dict of its fields as name value pairs dataclasses dicts lists and tuples are recursed into Other objects are copied with copy deepcopy Example of using asdict on nested dataclasses dataclass class Point x int y int dataclass class C mylist list Point p Point 10 20 assert asdict p x 10 y 20 c C Point 0 0 Point 10 4 assert asdict c mylist x 0 y 0 x 10 y 4 To create a shallow copy the following workaround may be used dict field name getattr obj field name for field in fields obj asdict raises TypeError if obj is not a dataclass instance dataclasses astuple obj tuple_factory tuple Converts the dataclass obj to a tupl,en
2003,e by using the factory function tuple_factory Each dataclass is converted to a tuple of its field values dataclasses dicts lists and tuples are recursed into Other objects are copied with copy deepcopy Continuing from the previous example assert astuple p 10 20 assert astuple c 0 0 10 4 To create a shallow copy the following workaround may be used tuple getattr obj field name for field in dataclasses fields obj astuple raises TypeError if obj is not a dataclass instance dataclasses make_dataclass cls_name fields bases namespace None init True repr True eq True order False unsafe_hash False frozen False match_args True kw_only False slots False weakref_slot False module None Creates a new dataclass with name cls_name fields as defined in fields base classes as given in bases and initialized with a namespace as given in namespace fields is an iterable whose elements are each either name name type or name type Field If just name is supplied typing Any is used for type The values of init repr eq order unsafe_hash frozen match_args kw_only slots and weakref_slot have the same meaning as they do in dataclass If module is defined the __module__ attribute of the dataclass is set to that value By default it is set to the module name of the caller This function is not strictly required because any Python mechanism for creating a new class with __annotations__ can then apply the dataclass function to convert that class to a dataclass This function is provided as a convenience For example C make_dataclass C x int y z int field default 5 namespace add_one lambda self self x 1 Is equivalent to dataclass class C x int y typing Any z int 5 def add_one self return self x 1 dataclasses replace obj changes Creates a new object of the same type as obj replacing fields with values from changes If obj is not a Data Class raises TypeError If values in changes do not specify fields raises TypeError The newly returned object is created by calling the __init__ method of the dataclass This ensures that __post_init__ if present is also called Init only variables without default values if any exist must be specified on the call to replace so that they can be passed to __init__ and __post_init__ It is an error for changes to contain any fields that are defined as having init False A ValueError will be raised in this case Be forewarned about how init False fields work during a call to replace They are not copied from the source object but rather are initialized in __post_init__ if they re initialized at all It is expected that init False fields will be rarely and judiciously used If they are used it might be wise to have alternate class constructors or perhaps a custom replace or similarly named method which handles instance copying dataclasses is_dataclass obj Return True if its parameter is a dataclass or an instance of one otherwise return False If you need to know if a class is an instance of a dataclass and not a dataclass itself then add a further check for not isinstance obj type def is_dataclass_instance obj return is_dataclass obj and not isinstance obj type dataclasses MISSING A sentinel value signifying a missing default or default_factory dataclasses KW_ONLY A sentinel value used as a type annotation Any fields after a pseudo field with the type of KW_ONLY are marked as keyword only fields Note that a pseudo field of type KW_ONLY is otherwise completely ignored This includes the name of such a field By convention a name of _ is used for a KW_ONLY field Keyword only fields signify __init__ parameters that must be specified as keywords when the class is instantiated In this example the fields y and z will be marked as keyword only fields dataclass class Point x float _ KW_ONLY y float z float p Point 0 y 1 5 z 2 0 In a single dataclass it is an error to specify more than one field whose type is KW_ONLY New in version 3 10 exception dataclasses FrozenInstanceError Raised when an implicitly defined __setattr__ or __delattr__ is called on a dataclass which was defined with frozen True It is a subclass of AttributeError Post init processing data,en
2004,classes __post_init__ When defined on the class it will be called by the generated __init__ normally as self __post_init__ However if any InitVar fields are defined they will also be passed to __post_init__ in the order they were defined in the class If no __init__ method is generated then __post_init__ will not automatically be called Among other uses this allows for initializing field values that depend on one or more other fields For example dataclass class C a float b float c float field init False def __post_init__ self self c self a self b The __init__ method generated by dataclass does not call base class __init__ methods If the base class has an __init__ method that has to be called it is common to call this method in a __post_init__ method class Rectangle def __init__ self height width self height height self width width dataclass class Square Rectangle side float def __post_init__ self super __init__ self side self side Note however that in general the dataclass generated __init__ methods don t need to be called since the derived dataclass will take care of initializing all fields of any base class that is a dataclass itself See the section below on init only variables for ways to pass parameters to __post_init__ Also see the warning about how replace handles init False fields Class variables One of the few places where dataclass actually inspects the type of a field is to determine if a field is a class variable as defined in PEP 526 It does this by checking if the type of the field is typing ClassVar If a field is a ClassVar it is excluded from consideration as a field and is ignored by the dataclass mechanisms Such ClassVar pseudo fields are not returned by the module level fields function Init only variables Another place where dataclass inspects a type annotation is to determine if a field is an init only variable It does this by seeing if the type of a field is of type dataclasses InitVar If a field is an InitVar it is considered a pseudo field called an init only field As it is not a true field it is not returned by the module level fields function Init only fields are added as parameters to the generated __init__ method and are passed to the optional __post_init__ method They are not otherwise used by dataclasses For example suppose a field will be initialized from a database if a value is not provided when creating the class dataclass class C i int j int None None database InitVar DatabaseType None None def __post_init__ self database if self j is None and database is not None self j database lookup j c C 10 database my_database In this case fields will return Field objects for i and j but not for database Frozen instances It is not possible to create truly immutable Python objects However by passing frozen True to the dataclass decorator you can emulate immutability In that case dataclasses will add __setattr__ and __delattr__ methods to the class These methods will raise a FrozenInstanceError when invoked There is a tiny performance penalty when using frozen True __init__ cannot use simple assignment to initialize fields and must use object __setattr__ Inheritance When the dataclass is being created by the dataclass decorator it looks through all of the class s base classes in reverse MRO that is starting at object and for each dataclass that it finds adds the fields from that base class to an ordered mapping of fields After all of the base class fields are added it adds its own fields to the ordered mapping All of the generated methods will use this combined calculated ordered mapping of fields Because the fields are in insertion order derived classes override base classes An example dataclass class Base x Any 15 0 y int 0 dataclass class C Base z int 10 x int 15 The final list of fields is in order x y z The final type of x is int as specified in class C The generated __init__ method for C will look like def __init__ self x int 15 y int 0 z int 10 Re ordering of keyword only parameters in __init__ After the parameters needed for __init__ are computed any keyword only parameters are moved to come af,en
2005,ter all regular non keyword only parameters This is a requirement of how keyword only parameters are implemented in Python they must come after non keyword only parameters In this example Base y Base w and D t are keyword only fields and Base x and D z are regular fields dataclass class Base x Any 15 0 _ KW_ONLY y int 0 w int 1 dataclass class D Base z int 10 t int field kw_only True default 0 The generated __init__ method for D will look like def __init__ self x Any 15 0 z int 10 y int 0 w int 1 t int 0 Note that the parameters have been re ordered from how they appear in the list of fields parameters derived from regular fields are followed by parameters derived from keyword only fields The relative ordering of keyword only parameters is maintained in the re ordered __init__ parameter list Default factory functions If a field specifies a default_factory it is called with zero arguments when a default value for the field is needed For example to create a new instance of a list use mylist list field default_factory list If a field is excluded from __init__ using init False and the field also specifies default_factory then the default factory function will always be called from the generated __init__ function This happens because there is no other way to give the field an initial value Mutable default values Python stores default member variable values in class attributes Consider this example not using dataclasses class C x def add self element self x append element o1 C o2 C o1 add 1 o2 add 2 assert o1 x 1 2 assert o1 x is o2 x Note that the two instances of class C share the same class variable x as expected Using dataclasses if this code was valid dataclass class D x list This code raises ValueError def add self element self x append element it would generate code similar to class D x def __init__ self x x self x x def add self element self x append element assert D x is D x This has the same issue as the original example using class C That is two instances of class D that do not specify a value for x when creating a class instance will share the same copy of x Because dataclasses just use normal Python class creation they also share this behavior There is no general way for Data Classes to detect this condition Instead the dataclass decorator will raise a ValueError if it detects an unhashable default parameter The assumption is that if a value is unhashable it is mutable This is a partial solution but it does protect against many common errors Using default factory functions is a way to create new instances of mutable types as default values for fields dataclass class D x list field default_factory list assert D x is not D x Changed in version 3 11 Instead of looking for and disallowing objects of type list dict or set unhashable objects are now not allowed as default values Unhashability is used to approximate mutability Descriptor typed fields Fields that are assigned descriptor objects as their default value have the following special behaviors The value for the field passed to the dataclass s __init__ method is passed to the descriptor s __set__ method rather than overwriting the descriptor object Similarly when getting or setting the field the descriptor s __get__ or __set__ method is called rather than returning or overwriting the descriptor object To determine whether a field contains a default value dataclasses will call the descriptor s __get__ method using its class access form i e descriptor __get__ obj None type cls If the descriptor returns a value in this case it will be used as the field s default On the other hand if the descriptor raises AttributeError in this situation no default value will be provided for the field class IntConversionDescriptor def __init__ self default self _default default def __set_name__ self owner name self _name _ name def __get__ self obj type if obj is None return self _default return getattr obj self _name self _default def __set__ self obj value setattr obj self _name int value dataclass class InventoryItem quantity_on_hand IntConversionDescriptor IntConversionDescriptor,en
2006, default 100 i InventoryItem print i quantity_on_hand 100 i quantity_on_hand 2 5 calls __set__ with 2 5 print i quantity_on_hand 2 Note that if a field is annotated with a descriptor type but is not assigned a descriptor object as its default value the field will act like a normal field,en
2007,site Site specific configuration hook Source code Lib site py This module is automatically imported during initialization The automatic import can be suppressed using the interpreter s S option Importing this module will append site specific paths to the module search path and add a few builtins unless S was used In that case this module can be safely imported with no automatic modifications to the module search path or additions to the builtins To explicitly trigger the usual site specific additions call the main function Changed in version 3 3 Importing the module used to trigger paths manipulation even when using S It starts by constructing up to four directories from a head and a tail part For the head part it uses sys prefix and sys exec_prefix empty heads are skipped For the tail part it uses the empty string and then lib site packages on Windows or lib python X Y site packages on Unix and macOS For each of the distinct head tail combinations it sees if it refers to an existing directory and if so adds it to sys path and also inspects the newly added path for configuration files Changed in version 3 5 Support for the site python directory has been removed If a file named pyvenv cfg exists one directory above sys executable sys prefix and sys exec_prefix are set to that directory and it is also checked for site packages sys base_prefix and sys base_exec_prefix will always be the real prefixes of the Python installation If pyvenv cfg a bootstrap configuration file contains the key include system site packages set to anything other than true case insensitive the system level prefixes will not be searched for site packages otherwise they will A path configuration file is a file whose name has the form name pth and exists in one of the four directories mentioned above its contents are additional items one per line to be added to sys path Non existing items are never added to sys path and no check is made that the item refers to a directory rather than a file No item is added to sys path more than once Blank lines and lines beginning with are skipped Lines starting with import followed by space or tab are executed Note An executable line in a pth file is run at every Python startup regardless of whether a particular module is actually going to be used Its impact should thus be kept to a minimum The primary intended purpose of executable lines is to make the corresponding module s importable load 3rd party import hooks adjust PATH etc Any other initialization is supposed to be done upon a module s actual import if and when it happens Limiting a code chunk to a single line is a deliberate measure to discourage putting anything more complex here For example suppose sys prefix and sys exec_prefix are set to usr local The Python X Y library is then installed in usr local lib python X Y Suppose this has a subdirectory usr local lib python X Y site packages with three subsubdirectories foo bar and spam and two path configuration files foo pth and bar pth Assume foo pth contains the following foo package configuration foo bar bletch and bar pth contains bar package configuration bar Then the following version specific directories are added to sys path in this order usr local lib pythonX Y site packages bar usr local lib pythonX Y site packages foo Note that bletch is omitted because it doesn t exist the bar directory precedes the foo directory because bar pth comes alphabetically before foo pth and spam is omitted because it is not mentioned in either path configuration file sitecustomize After these path manipulations an attempt is made to import a module named sitecustomize which can perform arbitrary site specific customizations It is typically created by a system administrator in the site packages directory If this import fails with an ImportError or its subclass exception and the exception s name attribute equals to sitecustomize it is silently ignored If Python is started without output streams available as with pythonw exe on Windows which is used by default to start IDLE attempted output from sitecustomize is ignored Any,en
2008, other exception causes a silent and perhaps mysterious failure of the process usercustomize After this an attempt is made to import a module named usercustomize which can perform arbitrary user specific customizations if ENABLE_USER_SITE is true This file is intended to be created in the user site packages directory see below which is part of sys path unless disabled by s If this import fails with an ImportError or its subclass exception and the exception s name attribute equals to usercustomize it is silently ignored Note that for some non Unix systems sys prefix and sys exec_prefix are empty and the path manipulations are skipped however the import of sitecustomize and usercustomize is still attempted Readline configuration On systems that support readline this module will also import and configure the rlcompleter module if Python is started in interactive mode and without the S option The default behavior is enable tab completion and to use python_history as the history save file To disable it delete or override the sys __interactivehook__ attribute in your sitecustomize or usercustomize module or your PYTHONSTARTUP file Changed in version 3 4 Activation of rlcompleter and history was made automatic Module contents site PREFIXES A list of prefixes for site packages directories site ENABLE_USER_SITE Flag showing the status of the user site packages directory True means that it is enabled and was added to sys path False means that it was disabled by user request with s or PYTHONNOUSERSITE None means it was disabled for security reasons mismatch between user or group id and effective id or by an administrator site USER_SITE Path to the user site packages for the running Python Can be None if getusersitepackages hasn t been called yet Default value is local lib python X Y site packages for UNIX and non framework macOS builds Library Python X Y lib python site packages for macOS framework builds and APPDATA Python Python XY site packages on Windows This directory is a site directory which means that pth files in it will be processed site USER_BASE Path to the base directory for the user site packages Can be None if getuserbase hasn t been called yet Default value is local for UNIX and macOS non framework builds Library Python X Y for macOS framework builds and APPDATA Python for Windows This value is used to compute the installation directories for scripts data files Python modules etc for the user installation scheme See also PYTHONUSERBASE site main Adds all the standard site specific directories to the module search path This function is called automatically when this module is imported unless the Python interpreter was started with the S flag Changed in version 3 3 This function used to be called unconditionally site addsitedir sitedir known_paths None Add a directory to sys path and process its pth files Typically used in sitecustomize or usercustomize see above site getsitepackages Return a list containing all global site packages directories New in version 3 2 site getuserbase Return the path of the user base directory USER_BASE If it is not initialized yet this function will also set it respecting PYTHONUSERBASE New in version 3 2 site getusersitepackages Return the path of the user specific site packages directory USER_SITE If it is not initialized yet this function will also set it respecting USER_BASE To determine if the user specific site packages was added to sys path ENABLE_USER_SITE should be used New in version 3 2 Command Line Interface The site module also provides a way to get the user directories from the command line python m site user site home user local lib python3 11 site packages If it is called without arguments it will print the contents of sys path on the standard output followed by the value of USER_BASE and whether the directory exists then the same thing for USER_SITE and finally the value of ENABLE_USER_SITE user base Print the path to the user base directory user site Print the path to the user site packages directory If both options are given user base and user site will be printed alway,en
2009,s in this order separated by os pathsep If any option is given the script will exit with one of these values 0 if the user site packages directory is enabled 1 if it was disabled by the user 2 if it is disabled for security reasons or by an administrator and a value greater than 2 if there is an error See also PEP 370 Per user site packages directory The initialization of the sys path module search path The initialization of sys path,en
2010,http HTTP modules Source code Lib http __init__ py http is a package that collects several modules for working with the HyperText Transfer Protocol http client is a low level HTTP protocol client for high level URL opening use urllib request http server contains basic HTTP server classes based on socketserver http cookies has utilities for implementing state management with cookies http cookiejar provides persistence of cookies The http module also defines the following enums that help you work with http related code class http HTTPStatus New in version 3 5 A subclass of enum IntEnum that defines a set of HTTP status codes reason phrases and long descriptions written in English Usage from http import HTTPStatus HTTPStatus OK HTTPStatus OK HTTPStatus OK 200 True HTTPStatus OK value 200 HTTPStatus OK phrase OK HTTPStatus OK description Request fulfilled document follows list HTTPStatus HTTPStatus CONTINUE HTTPStatus SWITCHING_PROTOCOLS HTTP status codes Supported IANA registered status codes available in http HTTPStatus are Code Enum Name Details 100 CONTINUE HTTP 1 1 RFC 7231 Section 6 2 1 101 SWITCHING_PROTOCOLS HTTP 1 1 RFC 7231 Section 6 2 2 102 PROCESSING WebDAV RFC 2518 Section 10 1 103 EARLY_HINTS An HTTP Status Code for Indicating Hints RFC 8297 200 OK HTTP 1 1 RFC 7231 Section 6 3 1 201 CREATED HTTP 1 1 RFC 7231 Section 6 3 2 202 ACCEPTED HTTP 1 1 RFC 7231 Section 6 3 3 203 NON_AUTHORITATIVE_INFORMATION HTTP 1 1 RFC 7231 Section 6 3 4 204 NO_CONTENT HTTP 1 1 RFC 7231 Section 6 3 5 205 RESET_CONTENT HTTP 1 1 RFC 7231 Section 6 3 6 206 PARTIAL_CONTENT HTTP 1 1 RFC 7233 Section 4 1 207 MULTI_STATUS WebDAV RFC 4918 Section 11 1 208 ALREADY_REPORTED WebDAV Binding Extensions RFC 5842 Section 7 1 Experimental 226 IM_USED Delta Encoding in HTTP RFC 3229 Section 10 4 1 300 MULTIPLE_CHOICES HTTP 1 1 RFC 7231 Section 6 4 1 301 MOVED_PERMANENTLY HTTP 1 1 RFC 7231 Section 6 4 2 302 FOUND HTTP 1 1 RFC 7231 Section 6 4 3 303 SEE_OTHER HTTP 1 1 RFC 7231 Section 6 4 4 304 NOT_MODIFIED HTTP 1 1 RFC 7232 Section 4 1 305 USE_PROXY HTTP 1 1 RFC 7231 Section 6 4 5 307 TEMPORARY_REDIRECT HTTP 1 1 RFC 7231 Section 6 4 7 308 PERMANENT_REDIRECT Permanent Redirect RFC 7238 Section 3 Experimental 400 BAD_REQUEST HTTP 1 1 RFC 7231 Section 6 5 1 401 UNAUTHORIZED HTTP 1 1 Authentication RFC 7235 Section 3 1 402 PAYMENT_REQUIRED HTTP 1 1 RFC 7231 Section 6 5 2 403 FORBIDDEN HTTP 1 1 RFC 7231 Section 6 5 3 404 NOT_FOUND HTTP 1 1 RFC 7231 Section 6 5 4 405 METHOD_NOT_ALLOWED HTTP 1 1 RFC 7231 Section 6 5 5 406 NOT_ACCEPTABLE HTTP 1 1 RFC 7231 Section 6 5 6 407 PROXY_AUTHENTICATION_REQUIRED HTTP 1 1 Authentication RFC 7235 Section 3 2 408 REQUEST_TIMEOUT HTTP 1 1 RFC 7231 Section 6 5 7 409 CONFLICT HTTP 1 1 RFC 7231 Section 6 5 8 410 GONE HTTP 1 1 RFC 7231 Section 6 5 9 411 LENGTH_REQUIRED HTTP 1 1 RFC 7231 Section 6 5 10 412 PRECONDITION_FAILED HTTP 1 1 RFC 7232 Section 4 2 413 REQUEST_ENTITY_TOO_LARGE HTTP 1 1 RFC 7231 Section 6 5 11 414 REQUEST_URI_TOO_LONG HTTP 1 1 RFC 7231 Section 6 5 12 415 UNSUPPORTED_MEDIA_TYPE HTTP 1 1 RFC 7231 Section 6 5 13 416 REQUESTED_RANGE_NOT_SATISFIABLE HTTP 1 1 Range Requests RFC 7233 Section 4 4 417 EXPECTATION_FAILED HTTP 1 1 RFC 7231 Section 6 5 14 418 IM_A_TEAPOT HTCPCP 1 0 RFC 2324 Section 2 3 2 421 MISDIRECTED_REQUEST HTTP 2 RFC 7540 Section 9 1 2 422 UNPROCESSABLE_ENTITY WebDAV RFC 4918 Section 11 2 423 LOCKED WebDAV RFC 4918 Section 11 3 424 FAILED_DEPENDENCY WebDAV RFC 4918 Section 11 4 425 TOO_EARLY Using Early Data in HTTP RFC 8470 426 UPGRADE_REQUIRED HTTP 1 1 RFC 7231 Section 6 5 15 428 PRECONDITION_REQUIRED Additional HTTP Status Codes RFC 6585 429 TOO_MANY_REQUESTS Additional HTTP Status Codes RFC 6585 431 REQUEST_HEADER_FIELDS_TOO_LARGE Additional HTTP Status Codes RFC 6585 451 UNAVAILABLE_FOR_LEGAL_REASONS An HTTP Status Code to Report Legal Obstacles RFC 7725 500 INTERNAL_SERVER_ERROR HTTP 1 1 RFC 7231 Section 6 6 1 501 NOT_IMPLEMENTED HTTP 1 1 RFC 7231 Section 6 6 2 502 BAD_GATEWAY HTTP 1 1 RFC 7231 Section 6 6 3 503 SERVICE_UNAVAILABLE HTTP 1 1 RFC 7231 Section 6 6 4 504 GATEWAY_TIMEOUT HTTP 1,en
2011, 1 RFC 7231 Section 6 6 5 505 HTTP_VERSION_NOT_SUPPORTED HTTP 1 1 RFC 7231 Section 6 6 6 506 VARIANT_ALSO_NEGOTIATES Transparent Content Negotiation in HTTP RFC 2295 Section 8 1 Experimental 507 INSUFFICIENT_STORAGE WebDAV RFC 4918 Section 11 5 508 LOOP_DETECTED WebDAV Binding Extensions RFC 5842 Section 7 2 Experimental 510 NOT_EXTENDED An HTTP Extension Framework RFC 2774 Section 7 Experimental 511 NETWORK_AUTHENTICATION_REQUIRED Additional HTTP Status Codes RFC 6585 Section 6 In order to preserve backwards compatibility enum values are also present in the http client module in the form of constants The enum name is equal to the constant name i e http HTTPStatus OK is also available as http client OK Changed in version 3 7 Added 421 MISDIRECTED_REQUEST status code New in version 3 8 Added 451 UNAVAILABLE_FOR_LEGAL_REASONS status code New in version 3 9 Added 103 EARLY_HINTS 418 IM_A_TEAPOT and 425 TOO_EARLY status codes HTTP status category New in version 3 12 The enum values have several properties to indicate the HTTP status category Property Indicates that Details is_informational 100 status 199 HTTP 1 1 RFC 7231 Section 6 is_success 200 status 299 HTTP 1 1 RFC 7231 Section 6 is_redirection 300 status 399 HTTP 1 1 RFC 7231 Section 6 is_client_error 400 status 499 HTTP 1 1 RFC 7231 Section 6 is_server_error 500 status 599 HTTP 1 1 RFC 7231 Section 6 Usage from http import HTTPStatus HTTPStatus OK is_success True HTTPStatus OK is_client_error False class http HTTPMethod New in version 3 11 A subclass of enum StrEnum that defines a set of HTTP methods and descriptions written in English Usage from http import HTTPMethod HTTPMethod GET HTTPMethod GET HTTPMethod GET GET True HTTPMethod GET value GET HTTPMethod GET description Retrieve the target list HTTPMethod HTTPMethod CONNECT HTTPMethod DELETE HTTPMethod GET HTTPMethod HEAD HTTPMethod OPTIONS HTTPMethod PATCH HTTPMethod POST HTTPMethod PUT HTTPMethod TRACE HTTP methods Supported IANA registered methods available in http HTTPMethod are Method Enum Name Details GET GET HTTP 1 1 RFC 7231 Section 4 3 1 HEAD HEAD HTTP 1 1 RFC 7231 Section 4 3 2 POST POST HTTP 1 1 RFC 7231 Section 4 3 3 PUT PUT HTTP 1 1 RFC 7231 Section 4 3 4 DELETE DELETE HTTP 1 1 RFC 7231 Section 4 3 5 CONNECT CONNECT HTTP 1 1 RFC 7231 Section 4 3 6 OPTIONS OPTIONS HTTP 1 1 RFC 7231 Section 4 3 7 TRACE TRACE HTTP 1 1 RFC 7231 Section 4 3 8 PATCH PATCH HTTP 1 1 RFC 5789,en
2012,Program Frameworks The modules described in this chapter are frameworks that will largely dictate the structure of your program Currently the modules described here are all oriented toward writing command line interfaces The full list of modules described in this chapter is turtle Turtle graphics Introduction Tutorial Starting a turtle environment Basic drawing Pen control The turtle s position Making algorithmic patterns How to Get started as quickly as possible Use the turtle module namespace Use turtle graphics in a script Use object oriented turtle graphics Turtle graphics reference Turtle methods Methods of TurtleScreen Screen Methods of RawTurtle Turtle and corresponding functions Turtle motion Tell Turtle s state Settings for measurement Pen control Drawing state Color control Filling More drawing control Turtle state Visibility Appearance Using events Special Turtle methods Compound shapes Methods of TurtleScreen Screen and corresponding functions Window control Animation control Using screen events Input methods Settings and special methods Methods specific to Screen not inherited from TurtleScreen Public classes Explanation Help and configuration How to use help Translation of docstrings into different languages How to configure Screen and Turtles turtledemo Demo scripts Changes since Python 2 6 Changes since Python 3 0 cmd Support for line oriented command interpreters Cmd Objects Cmd Example shlex Simple lexical analysis shlex Objects Parsing Rules Improved Compatibility with Shells,en
2013,Sorting Techniques Author Andrew Dalke and Raymond Hettinger Python lists have a built in list sort method that modifies the list in place There is also a sorted built in function that builds a new sorted list from an iterable In this document we explore the various techniques for sorting data using Python Sorting Basics A simple ascending sort is very easy just call the sorted function It returns a new sorted list sorted 5 2 3 1 4 1 2 3 4 5 You can also use the list sort method It modifies the list in place and returns None to avoid confusion Usually it s less convenient than sorted but if you don t need the original list it s slightly more efficient a 5 2 3 1 4 a sort a 1 2 3 4 5 Another difference is that the list sort method is only defined for lists In contrast the sorted function accepts any iterable sorted 1 D 2 B 3 B 4 E 5 A 1 2 3 4 5 Key Functions Both list sort and sorted have a key parameter to specify a function or other callable to be called on each list element prior to making comparisons For example here s a case insensitive string comparison sorted This is a test string from Andrew split key str casefold a Andrew from is string test This The value of the key parameter should be a function or other callable that takes a single argument and returns a key to use for sorting purposes This technique is fast because the key function is called exactly once for each input record A common pattern is to sort complex objects using some of the object s indices as keys For example student_tuples john A 15 jane B 12 dave B 10 sorted student_tuples key lambda student student 2 sort by age dave B 10 jane B 12 john A 15 The same technique works for objects with named attributes For example class Student def __init__ self name grade age self name name self grade grade self age age def __repr__ self return repr self name self grade self age student_objects Student john A 15 Student jane B 12 Student dave B 10 sorted student_objects key lambda student student age sort by age dave B 10 jane B 12 john A 15 Objects with named attributes can be made by a regular class as shown above or they can be instances of dataclass or a named tuple Operator Module Functions and Partial Function Evaluation The key function patterns shown above are very common so Python provides convenience functions to make accessor functions easier and faster The operator module has itemgetter attrgetter and a methodcaller function Using those functions the above examples become simpler and faster from operator import itemgetter attrgetter sorted student_tuples key itemgetter 2 dave B 10 jane B 12 john A 15 sorted student_objects key attrgetter age dave B 10 jane B 12 john A 15 The operator module functions allow multiple levels of sorting For example to sort by grade then by age sorted student_tuples key itemgetter 1 2 john A 15 dave B 10 jane B 12 sorted student_objects key attrgetter grade age john A 15 dave B 10 jane B 12 The functools module provides another helpful tool for making key functions The partial function can reduce the arity of a multi argument function making it suitable for use as a key function from functools import partial from unicodedata import normalize names Zoë Åbjørn Núñez Élana Zeke Abe Nubia Eloise split sorted names key partial normalize NFD Abe Åbjørn Eloise Élana Nubia Núñez Zeke Zoë sorted names key partial normalize NFC Abe Eloise Nubia Núñez Zeke Zoë Åbjørn Élana Ascending and Descending Both list sort and sorted accept a reverse parameter with a boolean value This is used to flag descending sorts For example to get the student data in reverse age order sorted student_tuples key itemgetter 2 reverse True john A 15 jane B 12 dave B 10 sorted student_objects key attrgetter age reverse True john A 15 jane B 12 dave B 10 Sort Stability and Complex Sorts Sorts are guaranteed to be stable That means that when multiple records have the same key their original order is preserved data red 1 blue 1 red 2 blue 2 sorted data key itemgetter 0 blue 1 blue 2 red 1 red 2 Notice how the two records for blue retain their original order so t,en
2014,hat blue 1 is guaranteed to precede blue 2 This wonderful property lets you build complex sorts in a series of sorting steps For example to sort the student data by descending grade and then ascending age do the age sort first and then sort again using grade s sorted student_objects key attrgetter age sort on secondary key sorted s key attrgetter grade reverse True now sort on primary key descending dave B 10 jane B 12 john A 15 This can be abstracted out into a wrapper function that can take a list and tuples of field and order to sort them on multiple passes def multisort xs specs for key reverse in reversed specs xs sort key attrgetter key reverse reverse return xs multisort list student_objects grade True age False dave B 10 jane B 12 john A 15 The Timsort algorithm used in Python does multiple sorts efficiently because it can take advantage of any ordering already present in a dataset Decorate Sort Undecorate This idiom is called Decorate Sort Undecorate after its three steps First the initial list is decorated with new values that control the sort order Second the decorated list is sorted Finally the decorations are removed creating a list that contains only the initial values in the new order For example to sort the student data by grade using the DSU approach decorated student grade i student for i student in enumerate student_objects decorated sort student for grade i student in decorated undecorate john A 15 jane B 12 dave B 10 This idiom works because tuples are compared lexicographically the first items are compared if they are the same then the second items are compared and so on It is not strictly necessary in all cases to include the index i in the decorated list but including it gives two benefits The sort is stable if two items have the same key their order will be preserved in the sorted list The original items do not have to be comparable because the ordering of the decorated tuples will be determined by at most the first two items So for example the original list could contain complex numbers which cannot be sorted directly Another name for this idiom is Schwartzian transform after Randal L Schwartz who popularized it among Perl programmers Now that Python sorting provides key functions this technique is not often needed Comparison Functions Unlike key functions that return an absolute value for sorting a comparison function computes the relative ordering for two inputs For example a balance scale compares two samples giving a relative ordering lighter equal or heavier Likewise a comparison function such as cmp a b will return a negative value for less than zero if the inputs are equal or a positive value for greater than It is common to encounter comparison functions when translating algorithms from other languages Also some libraries provide comparison functions as part of their API For example locale strcoll is a comparison function To accommodate those situations Python provides functools cmp_to_key to wrap the comparison function to make it usable as a key function sorted words key cmp_to_key strcoll locale aware sort order Odds and Ends For locale aware sorting use locale strxfrm for a key function or locale strcoll for a comparison function This is necessary because alphabetical sort orderings can vary across cultures even if the underlying alphabet is the same The reverse parameter still maintains sort stability so that records with equal keys retain the original order Interestingly that effect can be simulated without the parameter by using the builtin reversed function twice data red 1 blue 1 red 2 blue 2 standard_way sorted data key itemgetter 0 reverse True double_reversed list reversed sorted reversed data key itemgetter 0 assert standard_way double_reversed standard_way red 1 red 2 blue 1 blue 2 The sort routines use when making comparisons between two objects So it is easy to add a standard sort order to a class by defining an __lt__ method Student __lt__ lambda self other self age other age sorted student_objects dave B 10 jane B 12 john A 15 However note that can fall back to using __,en
2015,gt__ if __lt__ is not implemented see object __lt__ for details on the mechanics To avoid surprises PEP 8 recommends that all six comparison methods be implemented The total_ordering decorator is provided to make that task easier Key functions need not depend directly on the objects being sorted A key function can also access external resources For instance if the student grades are stored in a dictionary they can be used to sort a separate list of student names students dave john jane newgrades john F jane A dave C sorted students key newgrades __getitem__ jane dave john Partial Sorts Some applications require only some of the data to be ordered The standard library provides several tools that do less work than a full sort min and max return the smallest and largest values respectively These functions make a single pass over the input data and require almost no auxiliary memory heapq nsmallest and heapq nlargest return the n smallest and largest values respectively These functions make a single pass over the data keeping only n elements in memory at a time For values of n that are small relative to the number of inputs these functions make far fewer comparisons than a full sort heapq heappush and heapq heappop create and maintain a partially sorted arrangement of data that keeps the smallest element at position 0 These functions are suitable for implementing priority queues which are commonly used for task scheduling,en
2016,bz2 Support for bzip2 compression Source code Lib bz2 py This module provides a comprehensive interface for compressing and decompressing data using the bzip2 compression algorithm The bz2 module contains The open function and BZ2File class for reading and writing compressed files The BZ2Compressor and BZ2Decompressor classes for incremental de compression The compress and decompress functions for one shot de compression De compression of files bz2 open filename mode rb compresslevel 9 encoding None errors None newline None Open a bzip2 compressed file in binary or text mode returning a file object As with the constructor for BZ2File the filename argument can be an actual filename a str or bytes object or an existing file object to read from or write to The mode argument can be any of r rb w wb x xb a or ab for binary mode or rt wt xt or at for text mode The default is rb The compresslevel argument is an integer from 1 to 9 as for the BZ2File constructor For binary mode this function is equivalent to the BZ2File constructor BZ2File filename mode compresslevel compresslevel In this case the encoding errors and newline arguments must not be provided For text mode a BZ2File object is created and wrapped in an io TextIOWrapper instance with the specified encoding error handling behavior and line ending s New in version 3 3 Changed in version 3 4 The x exclusive creation mode was added Changed in version 3 6 Accepts a path like object class bz2 BZ2File filename mode r compresslevel 9 Open a bzip2 compressed file in binary mode If filename is a str or bytes object open the named file directly Otherwise filename should be a file object which will be used to read or write the compressed data The mode argument can be either r for reading default w for overwriting x for exclusive creation or a for appending These can equivalently be given as rb wb xb and ab respectively If filename is a file object rather than an actual file name a mode of w does not truncate the file and is instead equivalent to a If mode is w or a compresslevel can be an integer between 1 and 9 specifying the level of compression 1 produces the least compression and 9 default produces the most compression If mode is r the input file may be the concatenation of multiple compressed streams BZ2File provides all of the members specified by the io BufferedIOBase except for detach and truncate Iteration and the with statement are supported BZ2File also provides the following methods peek n Return buffered data without advancing the file position At least one byte of data will be returned unless at EOF The exact number of bytes returned is unspecified Note While calling peek does not change the file position of the BZ2File it may change the position of the underlying file object e g if the BZ2File was constructed by passing a file object for filename New in version 3 3 fileno Return the file descriptor for the underlying file New in version 3 3 readable Return whether the file was opened for reading New in version 3 3 seekable Return whether the file supports seeking New in version 3 3 writable Return whether the file was opened for writing New in version 3 3 read1 size 1 Read up to size uncompressed bytes while trying to avoid making multiple reads from the underlying stream Reads up to a buffer s worth of data if size is negative Returns b if the file is at EOF New in version 3 3 readinto b Read bytes into b Returns the number of bytes read 0 for EOF New in version 3 3 Changed in version 3 1 Support for the with statement was added Changed in version 3 3 Support was added for filename being a file object instead of an actual filename The a append mode was added along with support for reading multi stream files Changed in version 3 4 The x exclusive creation mode was added Changed in version 3 5 The read method now accepts an argument of None Changed in version 3 6 Accepts a path like object Changed in version 3 9 The buffering parameter has been removed It was ignored and deprecated since Python 3 0 Pass an open file object to control how the file is opened The compr,en
2017,esslevel parameter became keyword only Changed in version 3 10 This class is thread unsafe in the face of multiple simultaneous readers or writers just like its equivalent classes in gzip and lzma have always been Incremental de compression class bz2 BZ2Compressor compresslevel 9 Create a new compressor object This object may be used to compress data incrementally For one shot compression use the compress function instead compresslevel if given must be an integer between 1 and 9 The default is 9 compress data Provide data to the compressor object Returns a chunk of compressed data if possible or an empty byte string otherwise When you have finished providing data to the compressor call the flush method to finish the compression process flush Finish the compression process Returns the compressed data left in internal buffers The compressor object may not be used after this method has been called class bz2 BZ2Decompressor Create a new decompressor object This object may be used to decompress data incrementally For one shot compression use the decompress function instead Note This class does not transparently handle inputs containing multiple compressed streams unlike decompress and BZ2File If you need to decompress a multi stream input with BZ2Decompressor you must use a new decompressor for each stream decompress data max_length 1 Decompress data a bytes like object returning uncompressed data as bytes Some of data may be buffered internally for use in later calls to decompress The returned data should be concatenated with the output of any previous calls to decompress If max_length is nonnegative returns at most max_length bytes of decompressed data If this limit is reached and further output can be produced the needs_input attribute will be set to False In this case the next call to decompress may provide data as b to obtain more of the output If all of the input data was decompressed and returned either because this was less than max_length bytes or because max_length was negative the needs_input attribute will be set to True Attempting to decompress data after the end of stream is reached raises an EOFError Any data found after the end of the stream is ignored and saved in the unused_data attribute Changed in version 3 5 Added the max_length parameter eof True if the end of stream marker has been reached New in version 3 3 unused_data Data found after the end of the compressed stream If this attribute is accessed before the end of the stream has been reached its value will be b needs_input False if the decompress method can provide more decompressed data before requiring new uncompressed input New in version 3 5 One shot de compression bz2 compress data compresslevel 9 Compress data a bytes like object compresslevel if given must be an integer between 1 and 9 The default is 9 For incremental compression use a BZ2Compressor instead bz2 decompress data Decompress data a bytes like object If data is the concatenation of multiple compressed streams decompress all of the streams For incremental decompression use a BZ2Decompressor instead Changed in version 3 3 Support for multi stream inputs was added Examples of usage Below are some examples of typical usage of the bz2 module Using compress and decompress to demonstrate round trip compression import bz2 data b Donec rhoncus quis sapien sit amet molestie Fusce scelerisque vel augue nec ullamcorper Nam rutrum pretium placerat Aliquam vel tristique lorem sit amet cursus ante In interdum laoreet mi sit amet ultrices purus pulvinar a Nam gravida euismod magna non varius justo tincidunt feugiat Aliquam pharetra lacus non risus vehicula rutrum Maecenas aliquam leo felis Pellentesque semper nunc sit amet nibh ullamcorper ac elementum dolor luctus Curabitur lacinia mi ornare consectetur vestibulum c bz2 compress data len data len c Data compression ratio 1 513595166163142 d bz2 decompress c data d Check equality to original object after round trip True Using BZ2Compressor for incremental compression import bz2 def gen_data chunks 10 chunksize 1000 Yield incremental blocks of chunk,en
2018,size bytes for _ in range chunks yield b z chunksize comp bz2 BZ2Compressor out b for chunk in gen_data Provide data to the compressor object out out comp compress chunk Finish the compression process Call this once you have finished providing data to the compressor out out comp flush The example above uses a very nonrandom stream of data a stream of b z chunks Random data tends to compress poorly while ordered repetitive data usually yields a high compression ratio Writing and reading a bzip2 compressed file in binary mode import bz2 data b Donec rhoncus quis sapien sit amet molestie Fusce scelerisque vel augue nec ullamcorper Nam rutrum pretium placerat Aliquam vel tristique lorem sit amet cursus ante In interdum laoreet mi sit amet ultrices purus pulvinar a Nam gravida euismod magna non varius justo tincidunt feugiat Aliquam pharetra lacus non risus vehicula rutrum Maecenas aliquam leo felis Pellentesque semper nunc sit amet nibh ullamcorper ac elementum dolor luctus Curabitur lacinia mi ornare consectetur vestibulum with bz2 open myfile bz2 wb as f Write compressed data to file unused f write data with bz2 open myfile bz2 rb as f Decompress data from file content f read content data Check equality to original object after round trip True,en
2019,Structured Markup Processing Tools Python supports a variety of modules to work with various forms of structured data markup This includes modules to work with the Standard Generalized Markup Language SGML and the Hypertext Markup Language HTML and several interfaces for working with the Extensible Markup Language XML html HyperText Markup Language support html parser Simple HTML and XHTML parser Example HTML Parser Application HTMLParser Methods Examples html entities Definitions of HTML general entities XML Processing Modules XML vulnerabilities The defusedxml Package xml etree ElementTree The ElementTree XML API Tutorial XML tree and elements Parsing XML Pull API for non blocking parsing Finding interesting elements Modifying an XML File Building XML documents Parsing XML with Namespaces XPath support Example Supported XPath syntax Reference Functions XInclude support Example Reference Functions Element Objects ElementTree Objects QName Objects TreeBuilder Objects XMLParser Objects XMLPullParser Objects Exceptions xml dom The Document Object Model API Module Contents Objects in the DOM DOMImplementation Objects Node Objects NodeList Objects DocumentType Objects Document Objects Element Objects Attr Objects NamedNodeMap Objects Comment Objects Text and CDATASection Objects ProcessingInstruction Objects Exceptions Conformance Type Mapping Accessor Methods xml dom minidom Minimal DOM implementation DOM Objects DOM Example minidom and the DOM standard xml dom pulldom Support for building partial DOM trees DOMEventStream Objects xml sax Support for SAX2 parsers SAXException Objects xml sax handler Base classes for SAX handlers ContentHandler Objects DTDHandler Objects EntityResolver Objects ErrorHandler Objects LexicalHandler Objects xml sax saxutils SAX Utilities xml sax xmlreader Interface for XML parsers XMLReader Objects IncrementalParser Objects Locator Objects InputSource Objects The Attributes Interface The AttributesNS Interface xml parsers expat Fast XML parsing using Expat XMLParser Objects ExpatError Exceptions Example Content Model Descriptions Expat error constants,en
2020,10 Brief Tour of the Standard Library 10 1 Operating System Interface The os module provides dozens of functions for interacting with the operating system import os os getcwd Return the current working directory C Python312 os chdir server accesslogs Change current working directory os system mkdir today Run the command mkdir in the system shell 0 Be sure to use the import os style instead of from os import This will keep os open from shadowing the built in open function which operates much differently The built in dir and help functions are useful as interactive aids for working with large modules like os import os dir os returns a list of all module functions help os returns an extensive manual page created from the module s docstrings For daily file and directory management tasks the shutil module provides a higher level interface that is easier to use import shutil shutil copyfile data db archive db archive db shutil move build executables installdir installdir 10 2 File Wildcards The glob module provides a function for making file lists from directory wildcard searches import glob glob glob py primes py random py quote py 10 3 Command Line Arguments Common utility scripts often need to process command line arguments These arguments are stored in the sys module s argv attribute as a list For instance let s take the following demo py file File demo py import sys print sys argv Here is the output from running python demo py one two three at the command line demo py one two three The argparse module provides a more sophisticated mechanism to process command line arguments The following script extracts one or more filenames and an optional number of lines to be displayed import argparse parser argparse ArgumentParser prog top description Show top lines from each file parser add_argument filenames nargs parser add_argument l lines type int default 10 args parser parse_args print args When run at the command line with python top py lines 5 alpha txt beta txt the script sets args lines to 5 and args filenames to alpha txt beta txt 10 4 Error Output Redirection and Program Termination The sys module also has attributes for stdin stdout and stderr The latter is useful for emitting warnings and error messages to make them visible even when stdout has been redirected sys stderr write Warning log file not found starting a new one n Warning log file not found starting a new one The most direct way to terminate a script is to use sys exit 10 5 String Pattern Matching The re module provides regular expression tools for advanced string processing For complex matching and manipulation regular expressions offer succinct optimized solutions import re re findall r bf a z which foot or hand fell fastest foot fell fastest re sub r b a z 1 r 1 cat in the the hat cat in the hat When only simple capabilities are needed string methods are preferred because they are easier to read and debug tea for too replace too two tea for two 10 6 Mathematics The math module gives access to the underlying C library functions for floating point math import math math cos math pi 4 0 70710678118654757 math log 1024 2 10 0 The random module provides tools for making random selections import random random choice apple pear banana apple random sample range 100 10 sampling without replacement 30 83 16 4 8 81 41 50 18 33 random random random float 0 17970987693706186 random randrange 6 random integer chosen from range 6 4 The statistics module calculates basic statistical properties the mean median variance etc of numeric data import statistics data 2 75 1 75 1 25 0 25 0 5 1 25 3 5 statistics mean data 1 6071428571428572 statistics median data 1 25 statistics variance data 1 3720238095238095 The SciPy project https scipy org has many other modules for numerical computations 10 7 Internet Access There are a number of modules for accessing the internet and processing internet protocols Two of the simplest are urllib request for retrieving data from URLs and smtplib for sending mail from urllib request import urlopen with urlopen http worldtimeapi org api timezone et,en
2021,c UTC txt as response for line in response line line decode Convert bytes to a str if line startswith datetime print line rstrip Remove trailing newline datetime 2022 01 01T01 36 47 689215 00 00 import smtplib server smtplib SMTP localhost server sendmail soothsayer example org jcaesar example org To jcaesar example org From soothsayer example org Beware the Ides of March server quit Note that the second example needs a mailserver running on localhost 10 8 Dates and Times The datetime module supplies classes for manipulating dates and times in both simple and complex ways While date and time arithmetic is supported the focus of the implementation is on efficient member extraction for output formatting and manipulation The module also supports objects that are timezone aware dates are easily constructed and formatted from datetime import date now date today now datetime date 2003 12 2 now strftime m d y d b Y is a A on the d day of B 12 02 03 02 Dec 2003 is a Tuesday on the 02 day of December dates support calendar arithmetic birthday date 1964 7 31 age now birthday age days 14368 10 9 Data Compression Common data archiving and compression formats are directly supported by modules including zlib gzip bz2 lzma zipfile and tarfile import zlib s b witch which has which witches wrist watch len s 41 t zlib compress s len t 37 zlib decompress t b witch which has which witches wrist watch zlib crc32 s 226805979 10 10 Performance Measurement Some Python users develop a deep interest in knowing the relative performance of different approaches to the same problem Python provides a measurement tool that answers those questions immediately For example it may be tempting to use the tuple packing and unpacking feature instead of the traditional approach to swapping arguments The timeit module quickly demonstrates a modest performance advantage from timeit import Timer Timer t a a b b t a 1 b 2 timeit 0 57535828626024577 Timer a b b a a 1 b 2 timeit 0 54962537085770791 In contrast to timeit s fine level of granularity the profile and pstats modules provide tools for identifying time critical sections in larger blocks of code 10 11 Quality Control One approach for developing high quality software is to write tests for each function as it is developed and to run those tests frequently during the development process The doctest module provides a tool for scanning a module and validating tests embedded in a program s docstrings Test construction is as simple as cutting and pasting a typical call along with its results into the docstring This improves the documentation by providing the user with an example and it allows the doctest module to make sure the code remains true to the documentation def average values Computes the arithmetic mean of a list of numbers print average 20 30 70 40 0 return sum values len values import doctest doctest testmod automatically validate the embedded tests The unittest module is not as effortless as the doctest module but it allows a more comprehensive set of tests to be maintained in a separate file import unittest class TestStatisticalFunctions unittest TestCase def test_average self self assertEqual average 20 30 70 40 0 self assertEqual round average 1 5 7 1 4 3 with self assertRaises ZeroDivisionError average with self assertRaises TypeError average 20 30 70 unittest main Calling from the command line invokes all tests 10 12 Batteries Included Python has a batteries included philosophy This is best seen through the sophisticated and robust capabilities of its larger packages For example The xmlrpc client and xmlrpc server modules make implementing remote procedure calls into an almost trivial task Despite the modules names no direct knowledge or handling of XML is needed The email package is a library for managing email messages including MIME and other RFC 2822 based message documents Unlike smtplib and poplib which actually send and receive messages the email package has a complete toolset for building or decoding complex message structures including attachments and for implementing internet encoding a,en
2022,nd header protocols The json package provides robust support for parsing this popular data interchange format The csv module supports direct reading and writing of files in Comma Separated Value format commonly supported by databases and spreadsheets XML processing is supported by the xml etree ElementTree xml dom and xml sax packages Together these modules and packages greatly simplify data interchange between Python applications and other tools The sqlite3 module is a wrapper for the SQLite database library providing a persistent database that can be updated and accessed using slightly nonstandard SQL syntax Internationalization is supported by a number of modules including gettext locale and the codecs package,en
2023,mailcap Mailcap file handling Source code Lib mailcap py Deprecated since version 3 11 will be removed in version 3 13 The mailcap module is deprecated see PEP 594 for details The mimetypes module provides an alternative Mailcap files are used to configure how MIME aware applications such as mail readers and web browsers react to files with different MIME types The name mailcap is derived from the phrase mail capability For example a mailcap file might contain a line like video mpeg xmpeg s Then if the user encounters an email message or web document with the MIME type video mpeg s will be replaced by a filename usually one belonging to a temporary file and the xmpeg program can be automatically started to view the file The mailcap format is documented in RFC 1524 A User Agent Configuration Mechanism For Multimedia Mail Format Information but is not an internet standard However mailcap files are supported on most Unix systems mailcap findmatch caps MIMEtype key view filename dev null plist Return a 2 tuple the first element is a string containing the command line to be executed which can be passed to os system and the second element is the mailcap entry for a given MIME type If no matching MIME type can be found None None is returned key is the name of the field desired which represents the type of activity to be performed the default value is view since in the most common case you simply want to view the body of the MIME typed data Other possible values might be compose and edit if you wanted to create a new body of the given MIME type or alter the existing body data See RFC 1524 for a complete list of these fields filename is the filename to be substituted for s in the command line the default value is dev null which is almost certainly not what you want so usually you ll override it by specifying a filename plist can be a list containing named parameters the default value is simply an empty list Each entry in the list must be a string containing the parameter name an equals sign and the parameter s value Mailcap entries can contain named parameters like foo which will be replaced by the value of the parameter named foo For example if the command line showpartial id number total was in a mailcap file and plist was set to id 1 number 2 total 3 the resulting command line would be showpartial 1 2 3 In a mailcap file the test field can optionally be specified to test some external condition such as the machine architecture or the window system in use to determine whether or not the mailcap line applies findmatch will automatically check such conditions and skip the entry if the check fails Changed in version 3 11 To prevent security issues with shell metacharacters symbols that have special effects in a shell command line findmatch will refuse to inject ASCII characters other than alphanumerics and _ into the returned command line If a disallowed character appears in filename findmatch will always return None None as if no entry was found If such a character appears elsewhere a value in plist or in MIMEtype findmatch will ignore all mailcap entries which use that value A warning will be raised in either case mailcap getcaps Returns a dictionary mapping MIME types to a list of mailcap file entries This dictionary must be passed to the findmatch function An entry is stored as a list of dictionaries but it shouldn t be necessary to know the details of this representation The information is derived from all of the mailcap files found on the system Settings in the user s mailcap file HOME mailcap will override settings in the system mailcap files etc mailcap usr etc mailcap and usr local etc mailcap An example usage import mailcap d mailcap getcaps mailcap findmatch d video mpeg filename tmp1223 xmpeg tmp1223 view xmpeg s,en
2024,Initialization Finalization and Threads See also Python Initialization Configuration Before Python Initialization In an application embedding Python the Py_Initialize function must be called before using any other Python C API functions with the exception of a few functions and the global configuration variables The following functions can be safely called before Python is initialized Configuration functions PyImport_AppendInittab PyImport_ExtendInittab PyInitFrozenExtensions PyMem_SetAllocator PyMem_SetupDebugHooks PyObject_SetArenaAllocator Py_SetPath Py_SetProgramName Py_SetPythonHome Py_SetStandardStreamEncoding PySys_AddWarnOption PySys_AddXOption PySys_ResetWarnOptions Informative functions Py_IsInitialized PyMem_GetAllocator PyObject_GetArenaAllocator Py_GetBuildInfo Py_GetCompiler Py_GetCopyright Py_GetPlatform Py_GetVersion Utilities Py_DecodeLocale Memory allocators PyMem_RawMalloc PyMem_RawRealloc PyMem_RawCalloc PyMem_RawFree Note The following functions should not be called before Py_Initialize Py_EncodeLocale Py_GetPath Py_GetPrefix Py_GetExecPrefix Py_GetProgramFullPath Py_GetPythonHome Py_GetProgramName and PyEval_InitThreads Global configuration variables Python has variables for the global configuration to control different features and options By default these flags are controlled by command line options When a flag is set by an option the value of the flag is the number of times that the option was set For example b sets Py_BytesWarningFlag to 1 and bb sets Py_BytesWarningFlag to 2 int Py_BytesWarningFlag This API is kept for backward compatibility setting PyConfig bytes_warning should be used instead see Python Initialization Configuration Issue a warning when comparing bytes or bytearray with str or bytes with int Issue an error if greater or equal to 2 Set by the b option Deprecated since version 3 12 int Py_DebugFlag This API is kept for backward compatibility setting PyConfig parser_debug should be used instead see Python Initialization Configuration Turn on parser debugging output for expert only depending on compilation options Set by the d option and the PYTHONDEBUG environment variable Deprecated since version 3 12 int Py_DontWriteBytecodeFlag This API is kept for backward compatibility setting PyConfig write_bytecode should be used instead see Python Initialization Configuration If set to non zero Python won t try to write pyc files on the import of source modules Set by the B option and the PYTHONDONTWRITEBYTECODE environment variable Deprecated since version 3 12 int Py_FrozenFlag This API is kept for backward compatibility setting PyConfig pathconfig_warnings should be used instead see Python Initialization Configuration Suppress error messages when calculating the module search path in Py_GetPath Private flag used by _freeze_module and frozenmain programs Deprecated since version 3 12 int Py_HashRandomizationFlag This API is kept for backward compatibility setting PyConfig hash_seed and PyConfig use_hash_seed should be used instead see Python Initialization Configuration Set to 1 if the PYTHONHASHSEED environment variable is set to a non empty string If the flag is non zero read the PYTHONHASHSEED environment variable to initialize the secret hash seed Deprecated since version 3 12 int Py_IgnoreEnvironmentFlag This API is kept for backward compatibility setting PyConfig use_environment should be used instead see Python Initialization Configuration Ignore all PYTHON environment variables e g PYTHONPATH and PYTHONHOME that might be set Set by the E and I options Deprecated since version 3 12 int Py_InspectFlag This API is kept for backward compatibility setting PyConfig inspect should be used instead see Python Initialization Configuration When a script is passed as first argument or the c option is used enter interactive mode after executing the script or the command even when sys stdin does not appear to be a terminal Set by the i option and the PYTHONINSPECT environment variable Deprecated since version 3 12 int Py_InteractiveFlag This API is kept for backward compatibility setting PyCo,en
2025,nfig interactive should be used instead see Python Initialization Configuration Set by the i option Deprecated since version 3 12 int Py_IsolatedFlag This API is kept for backward compatibility setting PyConfig isolated should be used instead see Python Initialization Configuration Run Python in isolated mode In isolated mode sys path contains neither the script s directory nor the user s site packages directory Set by the I option New in version 3 4 Deprecated since version 3 12 int Py_LegacyWindowsFSEncodingFlag This API is kept for backward compatibility setting PyPreConfig legacy_windows_fs_encoding should be used instead see Python Initialization Configuration If the flag is non zero use the mbcs encoding with replace error handler instead of the UTF 8 encoding with surrogatepass error handler for the filesystem encoding and error handler Set to 1 if the PYTHONLEGACYWINDOWSFSENCODING environment variable is set to a non empty string See PEP 529 for more details Availability Windows Deprecated since version 3 12 int Py_LegacyWindowsStdioFlag This API is kept for backward compatibility setting PyConfig legacy_windows_stdio should be used instead see Python Initialization Configuration If the flag is non zero use io FileIO instead of io _WindowsConsoleIO for sys standard streams Set to 1 if the PYTHONLEGACYWINDOWSSTDIO environment variable is set to a non empty string See PEP 528 for more details Availability Windows Deprecated since version 3 12 int Py_NoSiteFlag This API is kept for backward compatibility setting PyConfig site_import should be used instead see Python Initialization Configuration Disable the import of the module site and the site dependent manipulations of sys path that it entails Also disable these manipulations if site is explicitly imported later call site main if you want them to be triggered Set by the S option Deprecated since version 3 12 int Py_NoUserSiteDirectory This API is kept for backward compatibility setting PyConfig user_site_directory should be used instead see Python Initialization Configuration Don t add the user site packages directory to sys path Set by the s and I options and the PYTHONNOUSERSITE environment variable Deprecated since version 3 12 int Py_OptimizeFlag This API is kept for backward compatibility setting PyConfig optimization_level should be used instead see Python Initialization Configuration Set by the O option and the PYTHONOPTIMIZE environment variable Deprecated since version 3 12 int Py_QuietFlag This API is kept for backward compatibility setting PyConfig quiet should be used instead see Python Initialization Configuration Don t display the copyright and version messages even in interactive mode Set by the q option New in version 3 2 Deprecated since version 3 12 int Py_UnbufferedStdioFlag This API is kept for backward compatibility setting PyConfig buffered_stdio should be used instead see Python Initialization Configuration Force the stdout and stderr streams to be unbuffered Set by the u option and the PYTHONUNBUFFERED environment variable Deprecated since version 3 12 int Py_VerboseFlag This API is kept for backward compatibility setting PyConfig verbose should be used instead see Python Initialization Configuration Print a message each time a module is initialized showing the place filename or built in module from which it is loaded If greater or equal to 2 print a message for each file that is checked for when searching for a module Also provides information on module cleanup at exit Set by the v option and the PYTHONVERBOSE environment variable Deprecated since version 3 12 Initializing and finalizing the interpreter void Py_Initialize Part of the Stable ABI Initialize the Python interpreter In an application embedding Python this should be called before using any other Python C API functions see Before Python Initialization for the few exceptions This initializes the table of loaded modules sys modules and creates the fundamental modules builtins __main__ and sys It also initializes the module search path sys path It does not set sys argv use PySys_Set,en
2026,ArgvEx for that This is a no op when called for a second time without calling Py_FinalizeEx first There is no return value it is a fatal error if the initialization fails Use the Py_InitializeFromConfig function to customize the Python Initialization Configuration Note On Windows changes the console mode from O_TEXT to O_BINARY which will also affect non Python uses of the console using the C Runtime void Py_InitializeEx int initsigs Part of the Stable ABI This function works like Py_Initialize if initsigs is 1 If initsigs is 0 it skips initialization registration of signal handlers which might be useful when Python is embedded Use the Py_InitializeFromConfig function to customize the Python Initialization Configuration int Py_IsInitialized Part of the Stable ABI Return true nonzero when the Python interpreter has been initialized false zero if not After Py_FinalizeEx is called this returns false until Py_Initialize is called again int Py_FinalizeEx Part of the Stable ABI since version 3 6 Undo all initializations made by Py_Initialize and subsequent use of Python C API functions and destroy all sub interpreters see Py_NewInterpreter below that were created and not yet destroyed since the last call to Py_Initialize Ideally this frees all memory allocated by the Python interpreter This is a no op when called for a second time without calling Py_Initialize again first Normally the return value is 0 If there were errors during finalization flushing buffered data 1 is returned This function is provided for a number of reasons An embedding application might want to restart Python without having to restart the application itself An application that has loaded the Python interpreter from a dynamically loadable library or DLL might want to free all memory allocated by Python before unloading the DLL During a hunt for memory leaks in an application a developer might want to free all memory allocated by Python before exiting from the application Bugs and caveats The destruction of modules and objects in modules is done in random order this may cause destructors __del__ methods to fail when they depend on other objects even functions or modules Dynamically loaded extension modules loaded by Python are not unloaded Small amounts of memory allocated by the Python interpreter may not be freed if you find a leak please report it Memory tied up in circular references between objects is not freed Some memory allocated by extension modules may not be freed Some extensions may not work properly if their initialization routine is called more than once this can happen if an application calls Py_Initialize and Py_FinalizeEx more than once Raises an auditing event cpython _PySys_ClearAuditHooks with no arguments New in version 3 6 void Py_Finalize Part of the Stable ABI This is a backwards compatible version of Py_FinalizeEx that disregards the return value Process wide parameters int Py_SetStandardStreamEncoding const char encoding const char errors This API is kept for backward compatibility setting PyConfig stdio_encoding and PyConfig stdio_errors should be used instead see Python Initialization Configuration This function should be called before Py_Initialize if it is called at all It specifies which encoding and error handling to use with standard IO with the same meanings as in str encode It overrides PYTHONIOENCODING values and allows embedding code to control IO encoding when the environment variable does not work encoding and or errors may be NULL to use PYTHONIOENCODING and or default values depending on other settings Note that sys stderr always uses the backslashreplace error handler regardless of this or any other setting If Py_FinalizeEx is called this function will need to be called again in order to affect subsequent calls to Py_Initialize Returns 0 if successful a nonzero value on error e g calling after the interpreter has already been initialized New in version 3 4 Deprecated since version 3 11 void Py_SetProgramName const wchar_t name Part of the Stable ABI This API is kept for backward compatibility setting PyConfig progra,en
2027,m_name should be used instead see Python Initialization Configuration This function should be called before Py_Initialize is called for the first time if it is called at all It tells the interpreter the value of the argv 0 argument to the main function of the program converted to wide characters This is used by Py_GetPath and some other functions below to find the Python run time libraries relative to the interpreter executable The default value is python The argument should point to a zero terminated wide character string in static storage whose contents will not change for the duration of the program s execution No code in the Python interpreter will change the contents of this storage Use Py_DecodeLocale to decode a bytes string to get a wchar_t string Deprecated since version 3 11 wchar_t Py_GetProgramName Part of the Stable ABI Return the program name set with Py_SetProgramName or the default The returned string points into static storage the caller should not modify its value This function should not be called before Py_Initialize otherwise it returns NULL Changed in version 3 10 It now returns NULL if called before Py_Initialize wchar_t Py_GetPrefix Part of the Stable ABI Return the prefix for installed platform independent files This is derived through a number of complicated rules from the program name set with Py_SetProgramName and some environment variables for example if the program name is usr local bin python the prefix is usr local The returned string points into static storage the caller should not modify its value This corresponds to the prefix variable in the top level Makefile and the prefix argument to the configure script at build time The value is available to Python code as sys prefix It is only useful on Unix See also the next function This function should not be called before Py_Initialize otherwise it returns NULL Changed in version 3 10 It now returns NULL if called before Py_Initialize wchar_t Py_GetExecPrefix Part of the Stable ABI Return the exec prefix for installed platform dependent files This is derived through a number of complicated rules from the program name set with Py_SetProgramName and some environment variables for example if the program name is usr local bin python the exec prefix is usr local The returned string points into static storage the caller should not modify its value This corresponds to the exec_prefix variable in the top level Makefile and the exec prefix argument to the configure script at build time The value is available to Python code as sys exec_prefix It is only useful on Unix Background The exec prefix differs from the prefix when platform dependent files such as executables and shared libraries are installed in a different directory tree In a typical installation platform dependent files may be installed in the usr local plat subtree while platform independent may be installed in usr local Generally speaking a platform is a combination of hardware and software families e g Sparc machines running the Solaris 2 x operating system are considered the same platform but Intel machines running Solaris 2 x are another platform and Intel machines running Linux are yet another platform Different major revisions of the same operating system generally also form different platforms Non Unix operating systems are a different story the installation strategies on those systems are so different that the prefix and exec prefix are meaningless and set to the empty string Note that compiled Python bytecode files are platform independent but not independent from the Python version by which they were compiled System administrators will know how to configure the mount or automount programs to share usr local between platforms while having usr local plat be a different filesystem for each platform This function should not be called before Py_Initialize otherwise it returns NULL Changed in version 3 10 It now returns NULL if called before Py_Initialize wchar_t Py_GetProgramFullPath Part of the Stable ABI Return the full program name of the Python executable this is computed as a side,en
2028, effect of deriving the default module search path from the program name set by Py_SetProgramName above The returned string points into static storage the caller should not modify its value The value is available to Python code as sys executable This function should not be called before Py_Initialize otherwise it returns NULL Changed in version 3 10 It now returns NULL if called before Py_Initialize wchar_t Py_GetPath Part of the Stable ABI Return the default module search path this is computed from the program name set by Py_SetProgramName above and some environment variables The returned string consists of a series of directory names separated by a platform dependent delimiter character The delimiter character is on Unix and macOS on Windows The returned string points into static storage the caller should not modify its value The list sys path is initialized with this value on interpreter startup it can be and usually is modified later to change the search path for loading modules This function should not be called before Py_Initialize otherwise it returns NULL Changed in version 3 10 It now returns NULL if called before Py_Initialize void Py_SetPath const wchar_t Part of the Stable ABI since version 3 7 This API is kept for backward compatibility setting PyConfig module_search_paths and PyConfig module_search_paths_set should be used instead see Python Initialization Configuration Set the default module search path If this function is called before Py_Initialize then Py_GetPath won t attempt to compute a default search path but uses the one provided instead This is useful if Python is embedded by an application that has full knowledge of the location of all modules The path components should be separated by the platform dependent delimiter character which is on Unix and macOS on Windows This also causes sys executable to be set to the program full path see Py_GetProgramFullPath and for sys prefix and sys exec_prefix to be empty It is up to the caller to modify these if required after calling Py_Initialize Use Py_DecodeLocale to decode a bytes string to get a wchar_ string The path argument is copied internally so the caller may free it after the call completes Changed in version 3 8 The program full path is now used for sys executable instead of the program name Deprecated since version 3 11 const char Py_GetVersion Part of the Stable ABI Return the version of this Python interpreter This is a string that looks something like 3 0a5 py3k 63103M May 12 2008 00 53 55 n GCC 4 2 3 The first word up to the first space character is the current Python version the first characters are the major and minor version separated by a period The returned string points into static storage the caller should not modify its value The value is available to Python code as sys version See also the Py_Version constant const char Py_GetPlatform Part of the Stable ABI Return the platform identifier for the current platform On Unix this is formed from the official name of the operating system converted to lower case followed by the major revision number e g for Solaris 2 x which is also known as SunOS 5 x the value is sunos5 On macOS it is darwin On Windows it is win The returned string points into static storage the caller should not modify its value The value is available to Python code as sys platform const char Py_GetCopyright Part of the Stable ABI Return the official copyright string for the current Python version for example Copyright 1991 1995 Stichting Mathematisch Centrum Amsterdam The returned string points into static storage the caller should not modify its value The value is available to Python code as sys copyright const char Py_GetCompiler Part of the Stable ABI Return an indication of the compiler used to build the current Python version in square brackets for example GCC 2 7 2 2 The returned string points into static storage the caller should not modify its value The value is available to Python code as part of the variable sys version const char Py_GetBuildInfo Part of the Stable ABI Return information about the sequence numbe,en
2029,r and build date and time of the current Python interpreter instance for example 67 Aug 1 1997 22 34 28 The returned string points into static storage the caller should not modify its value The value is available to Python code as part of the variable sys version void PySys_SetArgvEx int argc wchar_t argv int updatepath Part of the Stable ABI This API is kept for backward compatibility setting PyConfig argv PyConfig parse_argv and PyConfig safe_path should be used instead see Python Initialization Configuration Set sys argv based on argc and argv These parameters are similar to those passed to the program s main function with the difference that the first entry should refer to the script file to be executed rather than the executable hosting the Python interpreter If there isn t a script that will be run the first entry in argv can be an empty string If this function fails to initialize sys argv a fatal condition is signalled using Py_FatalError If updatepath is zero this is all the function does If updatepath is non zero the function also modifies sys path according to the following algorithm If the name of an existing script is passed in argv 0 the absolute path of the directory where the script is located is prepended to sys path Otherwise that is if argc is 0 or argv 0 doesn t point to an existing file name an empty string is prepended to sys path which is the same as prepending the current working directory Use Py_DecodeLocale to decode a bytes string to get a wchar_ string See also PyConfig orig_argv and PyConfig argv members of the Python Initialization Configuration Note It is recommended that applications embedding the Python interpreter for purposes other than executing a single script pass 0 as updatepath and update sys path themselves if desired See CVE 2008 5983 On versions before 3 1 3 you can achieve the same effect by manually popping the first sys path element after having called PySys_SetArgv for example using PyRun_SimpleString import sys sys path pop 0 n New in version 3 1 3 Deprecated since version 3 11 void PySys_SetArgv int argc wchar_t argv Part of the Stable ABI This API is kept for backward compatibility setting PyConfig argv and PyConfig parse_argv should be used instead see Python Initialization Configuration This function works like PySys_SetArgvEx with updatepath set to 1 unless the python interpreter was started with the I Use Py_DecodeLocale to decode a bytes string to get a wchar_ string See also PyConfig orig_argv and PyConfig argv members of the Python Initialization Configuration Changed in version 3 4 The updatepath value depends on I Deprecated since version 3 11 void Py_SetPythonHome const wchar_t home Part of the Stable ABI This API is kept for backward compatibility setting PyConfig home should be used instead see Python Initialization Configuration Set the default home directory that is the location of the standard Python libraries See PYTHONHOME for the meaning of the argument string The argument should point to a zero terminated character string in static storage whose contents will not change for the duration of the program s execution No code in the Python interpreter will change the contents of this storage Use Py_DecodeLocale to decode a bytes string to get a wchar_ string Deprecated since version 3 11 wchar_t Py_GetPythonHome Part of the Stable ABI Return the default home that is the value set by a previous call to Py_SetPythonHome or the value of the PYTHONHOME environment variable if it is set This function should not be called before Py_Initialize otherwise it returns NULL Changed in version 3 10 It now returns NULL if called before Py_Initialize Thread State and the Global Interpreter Lock The Python interpreter is not fully thread safe In order to support multi threaded Python programs there s a global lock called the global interpreter lock or GIL that must be held by the current thread before it can safely access Python objects Without the lock even the simplest operations could cause problems in a multi threaded program for example when two threads simultaneously i,en
2030,ncrement the reference count of the same object the reference count could end up being incremented only once instead of twice Therefore the rule exists that only the thread that has acquired the GIL may operate on Python objects or call Python C API functions In order to emulate concurrency of execution the interpreter regularly tries to switch threads see sys setswitchinterval The lock is also released around potentially blocking I O operations like reading or writing a file so that other Python threads can run in the meantime The Python interpreter keeps some thread specific bookkeeping information inside a data structure called PyThreadState There s also one global variable pointing to the current PyThreadState it can be retrieved using PyThreadState_Get Releasing the GIL from extension code Most extension code manipulating the GIL has the following simple structure Save the thread state in a local variable Release the global interpreter lock Do some blocking I O operation Reacquire the global interpreter lock Restore the thread state from the local variable This is so common that a pair of macros exists to simplify it Py_BEGIN_ALLOW_THREADS Do some blocking I O operation Py_END_ALLOW_THREADS The Py_BEGIN_ALLOW_THREADS macro opens a new block and declares a hidden local variable the Py_END_ALLOW_THREADS macro closes the block The block above expands to the following code PyThreadState _save _save PyEval_SaveThread Do some blocking I O operation PyEval_RestoreThread _save Here is how these functions work the global interpreter lock is used to protect the pointer to the current thread state When releasing the lock and saving the thread state the current thread state pointer must be retrieved before the lock is released since another thread could immediately acquire the lock and store its own thread state in the global variable Conversely when acquiring the lock and restoring the thread state the lock must be acquired before storing the thread state pointer Note Calling system I O functions is the most common use case for releasing the GIL but it can also be useful before calling long running computations which don t need access to Python objects such as compression or cryptographic functions operating over memory buffers For example the standard zlib and hashlib modules release the GIL when compressing or hashing data Non Python created threads When threads are created using the dedicated Python APIs such as the threading module a thread state is automatically associated to them and the code showed above is therefore correct However when threads are created from C for example by a third party library with its own thread management they don t hold the GIL nor is there a thread state structure for them If you need to call Python code from these threads often this will be part of a callback API provided by the aforementioned third party library you must first register these threads with the interpreter by creating a thread state data structure then acquiring the GIL and finally storing their thread state pointer before you can start using the Python C API When you are done you should reset the thread state pointer release the GIL and finally free the thread state data structure The PyGILState_Ensure and PyGILState_Release functions do all of the above automatically The typical idiom for calling into Python from a C thread is PyGILState_STATE gstate gstate PyGILState_Ensure Perform Python actions here result CallSomeFunction evaluate result or handle exception Release the thread No Python API allowed beyond this point PyGILState_Release gstate Note that the PyGILState_ functions assume there is only one global interpreter created automatically by Py_Initialize Python supports the creation of additional interpreters using Py_NewInterpreter but mixing multiple interpreters and the PyGILState_ API is unsupported Cautions about fork Another important thing to note about threads is their behaviour in the face of the C fork call On most systems with fork after a process forks only the thread that issued the fork will exist This h,en
2031,as a concrete impact both on how locks must be handled and on all stored state in CPython s runtime The fact that only the current thread remains means any locks held by other threads will never be released Python solves this for os fork by acquiring the locks it uses internally before the fork and releasing them afterwards In addition it resets any Lock Objects in the child When extending or embedding Python there is no way to inform Python of additional non Python locks that need to be acquired before or reset after a fork OS facilities such as pthread_atfork would need to be used to accomplish the same thing Additionally when extending or embedding Python calling fork directly rather than through os fork and returning to or calling into Python may result in a deadlock by one of Python s internal locks being held by a thread that is defunct after the fork PyOS_AfterFork_Child tries to reset the necessary locks but is not always able to The fact that all other threads go away also means that CPython s runtime state there must be cleaned up properly which os fork does This means finalizing all other PyThreadState objects belonging to the current interpreter and all other PyInterpreterState objects Due to this and the special nature of the main interpreter fork should only be called in that interpreter s main thread where the CPython global runtime was originally initialized The only exception is if exec will be called immediately after High level API These are the most commonly used types and functions when writing C extension code or when embedding the Python interpreter type PyInterpreterState Part of the Limited API as an opaque struct This data structure represents the state shared by a number of cooperating threads Threads belonging to the same interpreter share their module administration and a few other internal items There are no public members in this structure Threads belonging to different interpreters initially share nothing except process state like available memory open file descriptors and such The global interpreter lock is also shared by all threads regardless of to which interpreter they belong type PyThreadState Part of the Limited API as an opaque struct This data structure represents the state of a single thread The only public data member is PyInterpreterState interp This thread s interpreter state void PyEval_InitThreads Part of the Stable ABI Deprecated function which does nothing In Python 3 6 and older this function created the GIL if it didn t exist Changed in version 3 9 The function now does nothing Changed in version 3 7 This function is now called by Py_Initialize so you don t have to call it yourself anymore Changed in version 3 2 This function cannot be called before Py_Initialize anymore Deprecated since version 3 9 int PyEval_ThreadsInitialized Part of the Stable ABI Returns a non zero value if PyEval_InitThreads has been called This function can be called without holding the GIL and therefore can be used to avoid calls to the locking API when running single threaded Changed in version 3 7 The GIL is now initialized by Py_Initialize Deprecated since version 3 9 PyThreadState PyEval_SaveThread Part of the Stable ABI Release the global interpreter lock if it has been created and reset the thread state to NULL returning the previous thread state which is not NULL If the lock has been created the current thread must have acquired it void PyEval_RestoreThread PyThreadState tstate Part of the Stable ABI Acquire the global interpreter lock if it has been created and set the thread state to tstate which must not be NULL If the lock has been created the current thread must not have acquired it otherwise deadlock ensues Note Calling this function from a thread when the runtime is finalizing will terminate the thread even if the thread was not created by Python You can use _Py_IsFinalizing or sys is_finalizing to check if the interpreter is in process of being finalized before calling this function to avoid unwanted termination PyThreadState PyThreadState_Get Part of the Stable ABI Return the curr,en
2032,ent thread state The global interpreter lock must be held When the current thread state is NULL this issues a fatal error so that the caller needn t check for NULL PyThreadState PyThreadState_Swap PyThreadState tstate Part of the Stable ABI Swap the current thread state with the thread state given by the argument tstate which may be NULL The global interpreter lock must be held and is not released The following functions use thread local storage and are not compatible with sub interpreters PyGILState_STATE PyGILState_Ensure Part of the Stable ABI Ensure that the current thread is ready to call the Python C API regardless of the current state of Python or of the global interpreter lock This may be called as many times as desired by a thread as long as each call is matched with a call to PyGILState_Release In general other thread related APIs may be used between PyGILState_Ensure and PyGILState_Release calls as long as the thread state is restored to its previous state before the Release For example normal usage of the Py_BEGIN_ALLOW_THREADS and Py_END_ALLOW_THREADS macros is acceptable The return value is an opaque handle to the thread state when PyGILState_Ensure was called and must be passed to PyGILState_Release to ensure Python is left in the same state Even though recursive calls are allowed these handles cannot be shared each unique call to PyGILState_Ensure must save the handle for its call to PyGILState_Release When the function returns the current thread will hold the GIL and be able to call arbitrary Python code Failure is a fatal error Note Calling this function from a thread when the runtime is finalizing will terminate the thread even if the thread was not created by Python You can use _Py_IsFinalizing or sys is_finalizing to check if the interpreter is in process of being finalized before calling this function to avoid unwanted termination void PyGILState_Release PyGILState_STATE Part of the Stable ABI Release any resources previously acquired After this call Python s state will be the same as it was prior to the corresponding PyGILState_Ensure call but generally this state will be unknown to the caller hence the use of the GILState API Every call to PyGILState_Ensure must be matched by a call to PyGILState_Release on the same thread PyThreadState PyGILState_GetThisThreadState Part of the Stable ABI Get the current thread state for this thread May return NULL if no GILState API has been used on the current thread Note that the main thread always has such a thread state even if no auto thread state call has been made on the main thread This is mainly a helper diagnostic function int PyGILState_Check Return 1 if the current thread is holding the GIL and 0 otherwise This function can be called from any thread at any time Only if it has had its Python thread state initialized and currently is holding the GIL will it return 1 This is mainly a helper diagnostic function It can be useful for example in callback contexts or memory allocation functions when knowing that the GIL is locked can allow the caller to perform sensitive actions or otherwise behave differently New in version 3 4 The following macros are normally used without a trailing semicolon look for example usage in the Python source distribution Py_BEGIN_ALLOW_THREADS Part of the Stable ABI This macro expands to PyThreadState _save _save PyEval_SaveThread Note that it contains an opening brace it must be matched with a following Py_END_ALLOW_THREADS macro See above for further discussion of this macro Py_END_ALLOW_THREADS Part of the Stable ABI This macro expands to PyEval_RestoreThread _save Note that it contains a closing brace it must be matched with an earlier Py_BEGIN_ALLOW_THREADS macro See above for further discussion of this macro Py_BLOCK_THREADS Part of the Stable ABI This macro expands to PyEval_RestoreThread _save it is equivalent to Py_END_ALLOW_THREADS without the closing brace Py_UNBLOCK_THREADS Part of the Stable ABI This macro expands to _save PyEval_SaveThread it is equivalent to Py_BEGIN_ALLOW_THREADS without the opening brace and var,en
2033,iable declaration Low level API All of the following functions must be called after Py_Initialize Changed in version 3 7 Py_Initialize now initializes the GIL PyInterpreterState PyInterpreterState_New Part of the Stable ABI Create a new interpreter state object The global interpreter lock need not be held but may be held if it is necessary to serialize calls to this function Raises an auditing event cpython PyInterpreterState_New with no arguments void PyInterpreterState_Clear PyInterpreterState interp Part of the Stable ABI Reset all information in an interpreter state object The global interpreter lock must be held Raises an auditing event cpython PyInterpreterState_Clear with no arguments void PyInterpreterState_Delete PyInterpreterState interp Part of the Stable ABI Destroy an interpreter state object The global interpreter lock need not be held The interpreter state must have been reset with a previous call to PyInterpreterState_Clear PyThreadState PyThreadState_New PyInterpreterState interp Part of the Stable ABI Create a new thread state object belonging to the given interpreter object The global interpreter lock need not be held but may be held if it is necessary to serialize calls to this function void PyThreadState_Clear PyThreadState tstate Part of the Stable ABI Reset all information in a thread state object The global interpreter lock must be held Changed in version 3 9 This function now calls the PyThreadState on_delete callback Previously that happened in PyThreadState_Delete void PyThreadState_Delete PyThreadState tstate Part of the Stable ABI Destroy a thread state object The global interpreter lock need not be held The thread state must have been reset with a previous call to PyThreadState_Clear void PyThreadState_DeleteCurrent void Destroy the current thread state and release the global interpreter lock Like PyThreadState_Delete the global interpreter lock need not be held The thread state must have been reset with a previous call to PyThreadState_Clear PyFrameObject PyThreadState_GetFrame PyThreadState tstate Part of the Stable ABI since version 3 10 Get the current frame of the Python thread state tstate Return a strong reference Return NULL if no frame is currently executing See also PyEval_GetFrame tstate must not be NULL New in version 3 9 uint64_t PyThreadState_GetID PyThreadState tstate Part of the Stable ABI since version 3 10 Get the unique thread state identifier of the Python thread state tstate tstate must not be NULL New in version 3 9 PyInterpreterState PyThreadState_GetInterpreter PyThreadState tstate Part of the Stable ABI since version 3 10 Get the interpreter of the Python thread state tstate tstate must not be NULL New in version 3 9 void PyThreadState_EnterTracing PyThreadState tstate Suspend tracing and profiling in the Python thread state tstate Resume them using the PyThreadState_LeaveTracing function New in version 3 11 void PyThreadState_LeaveTracing PyThreadState tstate Resume tracing and profiling in the Python thread state tstate suspended by the PyThreadState_EnterTracing function See also PyEval_SetTrace and PyEval_SetProfile functions New in version 3 11 PyInterpreterState PyInterpreterState_Get void Part of the Stable ABI since version 3 9 Get the current interpreter Issue a fatal error if there no current Python thread state or no current interpreter It cannot return NULL The caller must hold the GIL New in version 3 9 int64_t PyInterpreterState_GetID PyInterpreterState interp Part of the Stable ABI since version 3 7 Return the interpreter s unique ID If there was any error in doing so then 1 is returned and an error is set The caller must hold the GIL New in version 3 7 PyObject PyInterpreterState_GetDict PyInterpreterState interp Part of the Stable ABI since version 3 8 Return a dictionary in which interpreter specific data may be stored If this function returns NULL then no exception has been raised and the caller should assume no interpreter specific dict is available This is not a replacement for PyModule_GetState which extensions should use to store interpreter sp,en
2034,ecific state information New in version 3 8 typedef PyObject _PyFrameEvalFunction PyThreadState tstate _PyInterpreterFrame frame int throwflag Type of a frame evaluation function The throwflag parameter is used by the throw method of generators if non zero handle the current exception Changed in version 3 9 The function now takes a tstate parameter Changed in version 3 11 The frame parameter changed from PyFrameObject to _PyInterpreterFrame _PyFrameEvalFunction _PyInterpreterState_GetEvalFrameFunc PyInterpreterState interp Get the frame evaluation function See the PEP 523 Adding a frame evaluation API to CPython New in version 3 9 void _PyInterpreterState_SetEvalFrameFunc PyInterpreterState interp _PyFrameEvalFunction eval_frame Set the frame evaluation function See the PEP 523 Adding a frame evaluation API to CPython New in version 3 9 PyObject PyThreadState_GetDict Return value Borrowed reference Part of the Stable ABI Return a dictionary in which extensions can store thread specific state information Each extension should use a unique key to use to store state in the dictionary It is okay to call this function when no current thread state is available If this function returns NULL no exception has been raised and the caller should assume no current thread state is available int PyThreadState_SetAsyncExc unsigned long id PyObject exc Part of the Stable ABI Asynchronously raise an exception in a thread The id argument is the thread id of the target thread exc is the exception object to be raised This function does not steal any references to exc To prevent naive misuse you must write your own C extension to call this Must be called with the GIL held Returns the number of thread states modified this is normally one but will be zero if the thread id isn t found If exc is NULL the pending exception if any for the thread is cleared This raises no exceptions Changed in version 3 7 The type of the id parameter changed from long to unsigned long void PyEval_AcquireThread PyThreadState tstate Part of the Stable ABI Acquire the global interpreter lock and set the current thread state to tstate which must not be NULL The lock must have been created earlier If this thread already has the lock deadlock ensues Note Calling this function from a thread when the runtime is finalizing will terminate the thread even if the thread was not created by Python You can use _Py_IsFinalizing or sys is_finalizing to check if the interpreter is in process of being finalized before calling this function to avoid unwanted termination Changed in version 3 8 Updated to be consistent with PyEval_RestoreThread Py_END_ALLOW_THREADS and PyGILState_Ensure and terminate the current thread if called while the interpreter is finalizing PyEval_RestoreThread is a higher level function which is always available even when threads have not been initialized void PyEval_ReleaseThread PyThreadState tstate Part of the Stable ABI Reset the current thread state to NULL and release the global interpreter lock The lock must have been created earlier and must be held by the current thread The tstate argument which must not be NULL is only used to check that it represents the current thread state if it isn t a fatal error is reported PyEval_SaveThread is a higher level function which is always available even when threads have not been initialized void PyEval_AcquireLock Part of the Stable ABI Acquire the global interpreter lock The lock must have been created earlier If this thread already has the lock a deadlock ensues Deprecated since version 3 2 This function does not update the current thread state Please use PyEval_RestoreThread or PyEval_AcquireThread instead Note Calling this function from a thread when the runtime is finalizing will terminate the thread even if the thread was not created by Python You can use _Py_IsFinalizing or sys is_finalizing to check if the interpreter is in process of being finalized before calling this function to avoid unwanted termination Changed in version 3 8 Updated to be consistent with PyEval_RestoreThread Py_END_ALLOW_THREADS and PyGI,en
2035,LState_Ensure and terminate the current thread if called while the interpreter is finalizing void PyEval_ReleaseLock Part of the Stable ABI Release the global interpreter lock The lock must have been created earlier Deprecated since version 3 2 This function does not update the current thread state Please use PyEval_SaveThread or PyEval_ReleaseThread instead Sub interpreter support While in most uses you will only embed a single Python interpreter there are cases where you need to create several independent interpreters in the same process and perhaps even in the same thread Sub interpreters allow you to do that The main interpreter is the first one created when the runtime initializes It is usually the only Python interpreter in a process Unlike sub interpreters the main interpreter has unique process global responsibilities like signal handling It is also responsible for execution during runtime initialization and is usually the active interpreter during runtime finalization The PyInterpreterState_Main function returns a pointer to its state You can switch between sub interpreters using the PyThreadState_Swap function You can create and destroy them using the following functions type PyInterpreterConfig Structure containing most parameters to configure a sub interpreter Its values are used only in Py_NewInterpreterFromConfig and never modified by the runtime New in version 3 12 Structure fields int use_main_obmalloc If this is 0 then the sub interpreter will use its own object allocator state Otherwise it will use share the main interpreter s If this is 0 then check_multi_interp_extensions must be 1 non zero If this is 1 then gil must not be PyInterpreterConfig_OWN_GIL int allow_fork If this is 0 then the runtime will not support forking the process in any thread where the sub interpreter is currently active Otherwise fork is unrestricted Note that the subprocess module still works when fork is disallowed int allow_exec If this is 0 then the runtime will not support replacing the current process via exec e g os execv in any thread where the sub interpreter is currently active Otherwise exec is unrestricted Note that the subprocess module still works when exec is disallowed int allow_threads If this is 0 then the sub interpreter s threading module won t create threads Otherwise threads are allowed int allow_daemon_threads If this is 0 then the sub interpreter s threading module won t create daemon threads Otherwise daemon threads are allowed as long as allow_threads is non zero int check_multi_interp_extensions If this is 0 then all extension modules may be imported including legacy single phase init modules in any thread where the sub interpreter is currently active Otherwise only multi phase init extension modules see PEP 489 may be imported Also see Py_mod_multiple_interpreters This must be 1 non zero if use_main_obmalloc is 0 int gil This determines the operation of the GIL for the sub interpreter It may be one of the following PyInterpreterConfig_DEFAULT_GIL Use the default selection PyInterpreterConfig_SHARED_GIL PyInterpreterConfig_SHARED_GIL Use share the main interpreter s GIL PyInterpreterConfig_OWN_GIL Use the sub interpreter s own GIL If this is PyInterpreterConfig_OWN_GIL then PyInterpreterConfig use_main_obmalloc must be 0 PyStatus Py_NewInterpreterFromConfig PyThreadState tstate_p const PyInterpreterConfig config Create a new sub interpreter This is an almost totally separate environment for the execution of Python code In particular the new interpreter has separate independent versions of all imported modules including the fundamental modules builtins __main__ and sys The table of loaded modules sys modules and the module search path sys path are also separate The new environment has no sys argv variable It has new standard I O stream file objects sys stdin sys stdout and sys stderr however these refer to the same underlying file descriptors The given config controls the options with which the interpreter is initialized Upon success tstate_p will be set to the first thread state created in the new sub in,en
2036,terpreter This thread state is made in the current thread state Note that no actual thread is created see the discussion of thread states below If creation of the new interpreter is unsuccessful tstate_p is set to NULL no exception is set since the exception state is stored in the current thread state and there may not be a current thread state Like all other Python C API functions the global interpreter lock must be held before calling this function and is still held when it returns Likewise a current thread state must be set on entry On success the returned thread state will be set as current If the sub interpreter is created with its own GIL then the GIL of the calling interpreter will be released When the function returns the new interpreter s GIL will be held by the current thread and the previously interpreter s GIL will remain released here New in version 3 12 Sub interpreters are most effective when isolated from each other with certain functionality restricted PyInterpreterConfig config use_main_obmalloc 0 allow_fork 0 allow_exec 0 allow_threads 1 allow_daemon_threads 0 check_multi_interp_extensions 1 gil PyInterpreterConfig_OWN_GIL PyThreadState tstate Py_NewInterpreterFromConfig config Note that the config is used only briefly and does not get modified During initialization the config s values are converted into various PyInterpreterState values A read only copy of the config may be stored internally on the PyInterpreterState Extension modules are shared between sub interpreters as follows For modules using multi phase initialization e g PyModule_FromDefAndSpec a separate module object is created and initialized for each interpreter Only C level static and global variables are shared between these module objects For modules using single phase initialization e g PyModule_Create the first time a particular extension is imported it is initialized normally and a shallow copy of its module s dictionary is squirreled away When the same extension is imported by another sub interpreter a new module is initialized and filled with the contents of this copy the extension s init function is not called Objects in the module s dictionary thus end up shared across sub interpreters which might cause unwanted behavior see Bugs and caveats below Note that this is different from what happens when an extension is imported after the interpreter has been completely re initialized by calling Py_FinalizeEx and Py_Initialize in that case the extension s initmodule function is called again As with multi phase initialization this means that only C level static and global variables are shared between these modules PyThreadState Py_NewInterpreter void Part of the Stable ABI Create a new sub interpreter This is essentially just a wrapper around Py_NewInterpreterFromConfig with a config that preserves the existing behavior The result is an unisolated sub interpreter that shares the main interpreter s GIL allows fork exec allows daemon threads and allows single phase init modules void Py_EndInterpreter PyThreadState tstate Part of the Stable ABI Destroy the sub interpreter represented by the given thread state The given thread state must be the current thread state See the discussion of thread states below When the call returns the current thread state is NULL All thread states associated with this interpreter are destroyed The global interpreter lock used by the target interpreter must be held before calling this function No GIL is held when it returns Py_FinalizeEx will destroy all sub interpreters that haven t been explicitly destroyed at that point A Per Interpreter GIL Using Py_NewInterpreterFromConfig you can create a sub interpreter that is completely isolated from other interpreters including having its own GIL The most important benefit of this isolation is that such an interpreter can execute Python code without being blocked by other interpreters or blocking any others Thus a single Python process can truly take advantage of multiple CPU cores when running Python code The isolation also encourages a different approach to concurren,en
2037,cy than that of just using threads See PEP 554 Using an isolated interpreter requires vigilance in preserving that isolation That especially means not sharing any objects or mutable state without guarantees about thread safety Even objects that are otherwise immutable e g None 1 5 can t normally be shared because of the refcount One simple but less efficient approach around this is to use a global lock around all use of some state or object Alternately effectively immutable objects like integers or strings can be made safe in spite of their refcounts by making them immortal In fact this has been done for the builtin singletons small integers and a number of other builtin objects If you preserve isolation then you will have access to proper multi core computing without the complications that come with free threading Failure to preserve isolation will expose you to the full consequences of free threading including races and hard to debug crashes Aside from that one of the main challenges of using multiple isolated interpreters is how to communicate between them safely not break isolation and efficiently The runtime and stdlib do not provide any standard approach to this yet A future stdlib module would help mitigate the effort of preserving isolation and expose effective tools for communicating and sharing data between interpreters New in version 3 12 Bugs and caveats Because sub interpreters and the main interpreter are part of the same process the insulation between them isn t perfect for example using low level file operations like os close they can accidentally or maliciously affect each other s open files Because of the way extensions are shared between sub interpreters some extensions may not work properly this is especially likely when using single phase initialization or static global variables It is possible to insert objects created in one sub interpreter into a namespace of another sub interpreter this should be avoided if possible Special care should be taken to avoid sharing user defined functions methods instances or classes between sub interpreters since import operations executed by such objects may affect the wrong sub interpreter s dictionary of loaded modules It is equally important to avoid sharing objects from which the above are reachable Also note that combining this functionality with PyGILState_ APIs is delicate because these APIs assume a bijection between Python thread states and OS level threads an assumption broken by the presence of sub interpreters It is highly recommended that you don t switch sub interpreters between a pair of matching PyGILState_Ensure and PyGILState_Release calls Furthermore extensions such as ctypes using these APIs to allow calling of Python code from non Python created threads will probably be broken when using sub interpreters Asynchronous Notifications A mechanism is provided to make asynchronous notifications to the main interpreter thread These notifications take the form of a function pointer and a void pointer argument int Py_AddPendingCall int func void void arg Part of the Stable ABI Schedule a function to be called from the main interpreter thread On success 0 is returned and func is queued for being called in the main thread On failure 1 is returned without setting any exception When successfully queued func will be eventually called from the main interpreter thread with the argument arg It will be called asynchronously with respect to normally running Python code but with both these conditions met on a bytecode boundary with the main thread holding the global interpreter lock func can therefore use the full C API func must return 0 on success or 1 on failure with an exception set func won t be interrupted to perform another asynchronous notification recursively but it can still be interrupted to switch threads if the global interpreter lock is released This function doesn t need a current thread state to run and it doesn t need the global interpreter lock To call this function in a subinterpreter the caller must hold the GIL Otherwise the function func can b,en
2038,e scheduled to be called from the wrong interpreter Warning This is a low level function only useful for very special cases There is no guarantee that func will be called as quick as possible If the main thread is busy executing a system call func won t be called before the system call returns This function is generally not suitable for calling Python code from arbitrary C threads Instead use the PyGILState API New in version 3 1 Changed in version 3 9 If this function is called in a subinterpreter the function func is now scheduled to be called from the subinterpreter rather than being called from the main interpreter Each subinterpreter now has its own list of scheduled calls Profiling and Tracing The Python interpreter provides some low level support for attaching profiling and execution tracing facilities These are used for profiling debugging and coverage analysis tools This C interface allows the profiling or tracing code to avoid the overhead of calling through Python level callable objects making a direct C function call instead The essential attributes of the facility have not changed the interface allows trace functions to be installed per thread and the basic events reported to the trace function are the same as had been reported to the Python level trace functions in previous versions typedef int Py_tracefunc PyObject obj PyFrameObject frame int what PyObject arg The type of the trace function registered using PyEval_SetProfile and PyEval_SetTrace The first parameter is the object passed to the registration function as obj frame is the frame object to which the event pertains what is one of the constants PyTrace_CALL PyTrace_EXCEPTION PyTrace_LINE PyTrace_RETURN PyTrace_C_CALL PyTrace_C_EXCEPTION PyTrace_C_RETURN or PyTrace_OPCODE and arg depends on the value of what Value of what Meaning of arg PyTrace_CALL Always Py_None PyTrace_EXCEPTION Exception information as returned by sys exc_info PyTrace_LINE Always Py_None PyTrace_RETURN Value being returned to the caller or NULL if caused by an exception PyTrace_C_CALL Function object being called PyTrace_C_EXCEPTION Function object being called PyTrace_C_RETURN Function object being called PyTrace_OPCODE Always Py_None int PyTrace_CALL The value of the what parameter to a Py_tracefunc function when a new call to a function or method is being reported or a new entry into a generator Note that the creation of the iterator for a generator function is not reported as there is no control transfer to the Python bytecode in the corresponding frame int PyTrace_EXCEPTION The value of the what parameter to a Py_tracefunc function when an exception has been raised The callback function is called with this value for what when after any bytecode is processed after which the exception becomes set within the frame being executed The effect of this is that as exception propagation causes the Python stack to unwind the callback is called upon return to each frame as the exception propagates Only trace functions receives these events they are not needed by the profiler int PyTrace_LINE The value passed as the what parameter to a Py_tracefunc function but not a profiling function when a line number event is being reported It may be disabled for a frame by setting f_trace_lines to 0 on that frame int PyTrace_RETURN The value for the what parameter to Py_tracefunc functions when a call is about to return int PyTrace_C_CALL The value for the what parameter to Py_tracefunc functions when a C function is about to be called int PyTrace_C_EXCEPTION The value for the what parameter to Py_tracefunc functions when a C function has raised an exception int PyTrace_C_RETURN The value for the what parameter to Py_tracefunc functions when a C function has returned int PyTrace_OPCODE The value for the what parameter to Py_tracefunc functions but not profiling functions when a new opcode is about to be executed This event is not emitted by default it must be explicitly requested by setting f_trace_opcodes to 1 on the frame void PyEval_SetProfile Py_tracefunc func PyObject obj Set the profiler funct,en
2039,ion to func The obj parameter is passed to the function as its first parameter and may be any Python object or NULL If the profile function needs to maintain state using a different value for obj for each thread provides a convenient and thread safe place to store it The profile function is called for all monitored events except PyTrace_LINE PyTrace_OPCODE and PyTrace_EXCEPTION See also the sys setprofile function The caller must hold the GIL void PyEval_SetProfileAllThreads Py_tracefunc func PyObject obj Like PyEval_SetProfile but sets the profile function in all running threads belonging to the current interpreter instead of the setting it only on the current thread The caller must hold the GIL As PyEval_SetProfile this function ignores any exceptions raised while setting the profile functions in all threads New in version 3 12 void PyEval_SetTrace Py_tracefunc func PyObject obj Set the tracing function to func This is similar to PyEval_SetProfile except the tracing function does receive line number events and per opcode events but does not receive any event related to C function objects being called Any trace function registered using PyEval_SetTrace will not receive PyTrace_C_CALL PyTrace_C_EXCEPTION or PyTrace_C_RETURN as a value for the what parameter See also the sys settrace function The caller must hold the GIL void PyEval_SetTraceAllThreads Py_tracefunc func PyObject obj Like PyEval_SetTrace but sets the tracing function in all running threads belonging to the current interpreter instead of the setting it only on the current thread The caller must hold the GIL As PyEval_SetTrace this function ignores any exceptions raised while setting the trace functions in all threads New in version 3 12 Advanced Debugger Support These functions are only intended to be used by advanced debugging tools PyInterpreterState PyInterpreterState_Head Return the interpreter state object at the head of the list of all such objects PyInterpreterState PyInterpreterState_Main Return the main interpreter state object PyInterpreterState PyInterpreterState_Next PyInterpreterState interp Return the next interpreter state object after interp from the list of all such objects PyThreadState PyInterpreterState_ThreadHead PyInterpreterState interp Return the pointer to the first PyThreadState object in the list of threads associated with the interpreter interp PyThreadState PyThreadState_Next PyThreadState tstate Return the next thread state object after tstate from the list of all such objects belonging to the same PyInterpreterState object Thread Local Storage Support The Python interpreter provides low level support for thread local storage TLS which wraps the underlying native TLS implementation to support the Python level thread local storage API threading local The CPython C level APIs are similar to those offered by pthreads and Windows use a thread key and functions to associate a void value per thread The GIL does not need to be held when calling these functions they supply their own locking Note that Python h does not include the declaration of the TLS APIs you need to include pythread h to use thread local storage Note None of these API functions handle memory management on behalf of the void values You need to allocate and deallocate them yourself If the void values happen to be PyObject these functions don t do refcount operations on them either Thread Specific Storage TSS API TSS API is introduced to supersede the use of the existing TLS API within the CPython interpreter This API uses a new type Py_tss_t instead of int to represent thread keys New in version 3 7 See also A New C API for Thread Local Storage in CPython PEP 539 type Py_tss_t This data structure represents the state of a thread key the definition of which may depend on the underlying TLS implementation and it has an internal field representing the key s initialization state There are no public members in this structure When Py_LIMITED_API is not defined static allocation of this type by Py_tss_NEEDS_INIT is allowed Py_tss_NEEDS_INIT This macro expands to the initializ,en
2040,er for Py_tss_t variables Note that this macro won t be defined with Py_LIMITED_API Dynamic Allocation Dynamic allocation of the Py_tss_t required in extension modules built with Py_LIMITED_API where static allocation of this type is not possible due to its implementation being opaque at build time Py_tss_t PyThread_tss_alloc Part of the Stable ABI since version 3 7 Return a value which is the same state as a value initialized with Py_tss_NEEDS_INIT or NULL in the case of dynamic allocation failure void PyThread_tss_free Py_tss_t key Part of the Stable ABI since version 3 7 Free the given key allocated by PyThread_tss_alloc after first calling PyThread_tss_delete to ensure any associated thread locals have been unassigned This is a no op if the key argument is NULL Note A freed key becomes a dangling pointer You should reset the key to NULL Methods The parameter key of these functions must not be NULL Moreover the behaviors of PyThread_tss_set and PyThread_tss_get are undefined if the given Py_tss_t has not been initialized by PyThread_tss_create int PyThread_tss_is_created Py_tss_t key Part of the Stable ABI since version 3 7 Return a non zero value if the given Py_tss_t has been initialized by PyThread_tss_create int PyThread_tss_create Py_tss_t key Part of the Stable ABI since version 3 7 Return a zero value on successful initialization of a TSS key The behavior is undefined if the value pointed to by the key argument is not initialized by Py_tss_NEEDS_INIT This function can be called repeatedly on the same key calling it on an already initialized key is a no op and immediately returns success void PyThread_tss_delete Py_tss_t key Part of the Stable ABI since version 3 7 Destroy a TSS key to forget the values associated with the key across all threads and change the key s initialization state to uninitialized A destroyed key is able to be initialized again by PyThread_tss_create This function can be called repeatedly on the same key calling it on an already destroyed key is a no op int PyThread_tss_set Py_tss_t key void value Part of the Stable ABI since version 3 7 Return a zero value to indicate successfully associating a void value with a TSS key in the current thread Each thread has a distinct mapping of the key to a void value void PyThread_tss_get Py_tss_t key Part of the Stable ABI since version 3 7 Return the void value associated with a TSS key in the current thread This returns NULL if no value is associated with the key in the current thread Thread Local Storage TLS API Deprecated since version 3 7 This API is superseded by Thread Specific Storage TSS API Note This version of the API does not support platforms where the native TLS key is defined in a way that cannot be safely cast to int On such platforms PyThread_create_key will return immediately with a failure status and the other TLS functions will all be no ops on such platforms Due to the compatibility problem noted above this version of the API should not be used in new code int PyThread_create_key Part of the Stable ABI void PyThread_delete_key int key Part of the Stable ABI int PyThread_set_key_value int key void value Part of the Stable ABI void PyThread_get_key_value int key Part of the Stable ABI void PyThread_delete_key_value int key Part of the Stable ABI void PyThread_ReInitTLS Part of the Stable ABI,en
2041,13 What Now Reading this tutorial has probably reinforced your interest in using Python you should be eager to apply Python to solving your real world problems Where should you go to learn more This tutorial is part of Python s documentation set Some other documents in the set are The Python Standard Library You should browse through this manual which gives complete though terse reference material about types functions and the modules in the standard library The standard Python distribution includes a lot of additional code There are modules to read Unix mailboxes retrieve documents via HTTP generate random numbers parse command line options compress data and many other tasks Skimming through the Library Reference will give you an idea of what s available Installing Python Modules explains how to install additional modules written by other Python users The Python Language Reference A detailed explanation of Python s syntax and semantics It s heavy reading but is useful as a complete guide to the language itself More Python resources https www python org The major Python web site It contains code documentation and pointers to Python related pages around the web https docs python org Fast access to Python s documentation https pypi org The Python Package Index previously also nicknamed the Cheese Shop 1 is an index of user created Python modules that are available for download Once you begin releasing code you can register it here so that others can find it https code activestate com recipes langs python The Python Cookbook is a sizable collection of code examples larger modules and useful scripts Particularly notable contributions are collected in a book also titled Python Cookbook O Reilly Associates ISBN 0 596 00797 3 https pyvideo org collects links to Python related videos from conferences and user group meetings https scipy org The Scientific Python project includes modules for fast array computations and manipulations plus a host of packages for such things as linear algebra Fourier transforms non linear solvers random number distributions statistical analysis and the like For Python related questions and problem reports you can post to the newsgroup comp lang python or send them to the mailing list at python list python org The newsgroup and mailing list are gatewayed so messages posted to one will automatically be forwarded to the other There are hundreds of postings a day asking and answering questions suggesting new features and announcing new modules Mailing list archives are available at https mail python org pipermail Before posting be sure to check the list of Frequently Asked Questions also called the FAQ The FAQ answers many of the questions that come up again and again and may already contain the solution for your problem Footnotes 1 Cheese Shop is a Monty Python s sketch a customer enters a cheese shop but whatever cheese he asks for the clerk says it s missing,en
2042,Queues Source code Lib asyncio queues py asyncio queues are designed to be similar to classes of the queue module Although asyncio queues are not thread safe they are designed to be used specifically in async await code Note that methods of asyncio queues don t have a timeout parameter use asyncio wait_for function to do queue operations with a timeout See also the Examples section below Queue class asyncio Queue maxsize 0 A first in first out FIFO queue If maxsize is less than or equal to zero the queue size is infinite If it is an integer greater than 0 then await put blocks when the queue reaches maxsize until an item is removed by get Unlike the standard library threading queue the size of the queue is always known and can be returned by calling the qsize method Changed in version 3 10 Removed the loop parameter This class is not thread safe maxsize Number of items allowed in the queue empty Return True if the queue is empty False otherwise full Return True if there are maxsize items in the queue If the queue was initialized with maxsize 0 the default then full never returns True coroutine get Remove and return an item from the queue If queue is empty wait until an item is available get_nowait Return an item if one is immediately available else raise QueueEmpty coroutine join Block until all items in the queue have been received and processed The count of unfinished tasks goes up whenever an item is added to the queue The count goes down whenever a consumer coroutine calls task_done to indicate that the item was retrieved and all work on it is complete When the count of unfinished tasks drops to zero join unblocks coroutine put item Put an item into the queue If the queue is full wait until a free slot is available before adding the item put_nowait item Put an item into the queue without blocking If no free slot is immediately available raise QueueFull qsize Return the number of items in the queue task_done Indicate that a formerly enqueued task is complete Used by queue consumers For each get used to fetch a task a subsequent call to task_done tells the queue that the processing on the task is complete If a join is currently blocking it will resume when all items have been processed meaning that a task_done call was received for every item that had been put into the queue Raises ValueError if called more times than there were items placed in the queue Priority Queue class asyncio PriorityQueue A variant of Queue retrieves entries in priority order lowest first Entries are typically tuples of the form priority_number data LIFO Queue class asyncio LifoQueue A variant of Queue that retrieves most recently added entries first last in first out Exceptions exception asyncio QueueEmpty This exception is raised when the get_nowait method is called on an empty queue exception asyncio QueueFull Exception raised when the put_nowait method is called on a queue that has reached its maxsize Examples Queues can be used to distribute workload between several concurrent tasks import asyncio import random import time async def worker name queue while True Get a work item out of the queue sleep_for await queue get Sleep for the sleep_for seconds await asyncio sleep sleep_for Notify the queue that the work item has been processed queue task_done print f name has slept for sleep_for 2f seconds async def main Create a queue that we will use to store our workload queue asyncio Queue Generate random timings and put them into the queue total_sleep_time 0 for _ in range 20 sleep_for random uniform 0 05 1 0 total_sleep_time sleep_for queue put_nowait sleep_for Create three worker tasks to process the queue concurrently tasks for i in range 3 task asyncio create_task worker f worker i queue tasks append task Wait until the queue is fully processed started_at time monotonic await queue join total_slept_for time monotonic started_at Cancel our worker tasks for task in tasks task cancel Wait until all worker tasks are cancelled await asyncio gather tasks return_exceptions True print print f 3 workers slept in parallel for total_slept_for 2f secon,en
2043,ds print f total expected sleep time total_sleep_time 2f seconds asyncio run main,en
2044,Boolean Objects Booleans in Python are implemented as a subclass of integers There are only two booleans Py_False and Py_True As such the normal creation and deletion functions don t apply to booleans The following macros are available however PyTypeObject PyBool_Type Part of the Stable ABI This instance of PyTypeObject represents the Python boolean type it is the same object as bool in the Python layer int PyBool_Check PyObject o Return true if o is of type PyBool_Type This function always succeeds PyObject Py_False The Python False object This object has no methods and is immortal Changed in version 3 12 Py_False is immortal PyObject Py_True The Python True object This object has no methods and is immortal Changed in version 3 12 Py_True is immortal Py_RETURN_FALSE Return Py_False from a function Py_RETURN_TRUE Return Py_True from a function PyObject PyBool_FromLong long v Return value New reference Part of the Stable ABI Return Py_True or Py_False depending on the truth value of v,en
2045,Python Runtime Services The modules described in this chapter provide a wide range of services related to the Python interpreter and its interaction with its environment Here s an overview sys System specific parameters and functions sys monitoring Execution event monitoring Tool identifiers Registering and using tools Events Local events Ancillary events Other events The STOP_ITERATION event Turning events on and off Setting events globally Per code object events Disabling events Registering callback functions Callback function arguments sysconfig Provide access to Python s configuration information Configuration variables Installation paths User scheme posix_user nt_user osx_framework_user Home scheme posix_home Prefix scheme posix_prefix nt Installation path functions Other functions Using sysconfig as a script builtins Built in objects __main__ Top level code environment __name__ __main__ What is the top level code environment Idiomatic Usage Packaging Considerations __main__ py in Python Packages Idiomatic Usage import __main__ warnings Warning control Warning Categories The Warnings Filter Describing Warning Filters Default Warning Filter Overriding the default filter Temporarily Suppressing Warnings Testing Warnings Updating Code For New Versions of Dependencies Available Functions Available Context Managers dataclasses Data Classes Module contents Post init processing Class variables Init only variables Frozen instances Inheritance Re ordering of keyword only parameters in __init__ Default factory functions Mutable default values Descriptor typed fields contextlib Utilities for with statement contexts Utilities Examples and Recipes Supporting a variable number of context managers Catching exceptions from __enter__ methods Cleaning up in an __enter__ implementation Replacing any use of try finally and flag variables Using a context manager as a function decorator Single use reusable and reentrant context managers Reentrant context managers Reusable context managers abc Abstract Base Classes atexit Exit handlers atexit Example traceback Print or retrieve a stack traceback TracebackException Objects StackSummary Objects FrameSummary Objects Traceback Examples __future__ Future statement definitions Module Contents gc Garbage Collector interface inspect Inspect live objects Types and members Retrieving source code Introspecting callables with the Signature object Classes and functions The interpreter stack Fetching attributes statically Current State of Generators Coroutines and Asynchronous Generators Code Objects Bit Flags Buffer flags Command Line Interface site Site specific configuration hook sitecustomize usercustomize Readline configuration Module contents Command Line Interface,en
2046,telnetlib Telnet client Source code Lib telnetlib py Deprecated since version 3 11 will be removed in version 3 13 The telnetlib module is deprecated see PEP 594 for details and alternatives The telnetlib module provides a Telnet class that implements the Telnet protocol See RFC 854 for details about the protocol In addition it provides symbolic constants for the protocol characters see below and for the telnet options The symbolic names of the telnet options follow the definitions in arpa telnet h with the leading TELOPT_ removed For symbolic names of options which are traditionally not included in arpa telnet h see the module source itself The symbolic constants for the telnet commands are IAC DONT DO WONT WILL SE Subnegotiation End NOP No Operation DM Data Mark BRK Break IP Interrupt process AO Abort output AYT Are You There EC Erase Character EL Erase Line GA Go Ahead SB Subnegotiation Begin Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information class telnetlib Telnet host None port 0 timeout Telnet represents a connection to a Telnet server The instance is initially not connected by default the open method must be used to establish a connection Alternatively the host name and optional port number can be passed to the constructor too in which case the connection to the server will be established before the constructor returns The optional timeout parameter specifies a timeout in seconds for blocking operations like the connection attempt if not specified the global default timeout setting will be used Do not reopen an already connected instance This class has many read_ methods Note that some of them raise EOFError when the end of the connection is read because they can return an empty string for other reasons See the individual descriptions below A Telnet object is a context manager and can be used in a with statement When the with block ends the close method is called from telnetlib import Telnet with Telnet localhost 23 as tn tn interact Changed in version 3 6 Context manager support added See also RFC 854 Telnet Protocol Specification Definition of the Telnet protocol Telnet Objects Telnet instances have the following methods Telnet read_until expected timeout None Read until a given byte string expected is encountered or until timeout seconds have passed When no match is found return whatever is available instead possibly empty bytes Raise EOFError if the connection is closed and no cooked data is available Telnet read_all Read all data until EOF as bytes block until connection closed Telnet read_some Read at least one byte of cooked data unless EOF is hit Return b if EOF is hit Block if no data is immediately available Telnet read_very_eager Read everything that can be without blocking in I O eager Raise EOFError if connection closed and no cooked data available Return b if no cooked data available otherwise Do not block unless in the midst of an IAC sequence Telnet read_eager Read readily available data Raise EOFError if connection closed and no cooked data available Return b if no cooked data available otherwise Do not block unless in the midst of an IAC sequence Telnet read_lazy Process and return data already in the queues lazy Raise EOFError if connection closed and no data available Return b if no cooked data available otherwise Do not block unless in the midst of an IAC sequence Telnet read_very_lazy Return any data available in the cooked queue very lazy Raise EOFError if connection closed and no data available Return b if no cooked data available otherwise This method never blocks Telnet read_sb_data Return the data collected between a SB SE pair suboption begin end The callback should access these data when it was invoked with a SE command This method never blocks Telnet open host port 0 timeout Connect to a host The optional second argument is the port number which defaults to the standard Telnet port 23 The optional timeout parameter specifies a timeout in seconds for,en
2047, blocking operations like the connection attempt if not specified the global default timeout setting will be used Do not try to reopen an already connected instance Raises an auditing event telnetlib Telnet open with arguments self host port Telnet msg msg args Print a debug message when the debug level is 0 If extra arguments are present they are substituted in the message using the standard string formatting operator Telnet set_debuglevel debuglevel Set the debug level The higher the value of debuglevel the more debug output you get on sys stdout Telnet close Close the connection Telnet get_socket Return the socket object used internally Telnet fileno Return the file descriptor of the socket object used internally Telnet write buffer Write a byte string to the socket doubling any IAC characters This can block if the connection is blocked May raise OSError if the connection is closed Raises an auditing event telnetlib Telnet write with arguments self buffer Changed in version 3 3 This method used to raise socket error which is now an alias of OSError Telnet interact Interaction function emulates a very dumb Telnet client Telnet mt_interact Multithreaded version of interact Telnet expect list timeout None Read until one from a list of a regular expressions matches The first argument is a list of regular expressions either compiled regex objects or uncompiled byte strings The optional second argument is a timeout in seconds the default is to block indefinitely Return a tuple of three items the index in the list of the first regular expression that matches the match object returned and the bytes read up till and including the match If end of file is found and no bytes were read raise EOFError Otherwise when nothing matches return 1 None data where data is the bytes received so far may be empty bytes if a timeout happened If a regular expression ends with a greedy match such as or if more than one expression can match the same input the results are non deterministic and may depend on the I O timing Telnet set_option_negotiation_callback callback Each time a telnet option is read on the input flow this callback if set is called with the following parameters callback telnet socket command DO DONT WILL WONT option No other action is done afterwards by telnetlib Telnet Example A simple example illustrating typical use import getpass import telnetlib HOST localhost user input Enter your remote account password getpass getpass tn telnetlib Telnet HOST tn read_until b login tn write user encode ascii b n if password tn read_until b Password tn write password encode ascii b n tn write b ls n tn write b exit n print tn read_all decode ascii,en
2048,cmath Mathematical functions for complex numbers This module provides access to mathematical functions for complex numbers The functions in this module accept integers floating point numbers or complex numbers as arguments They will also accept any Python object that has either a __complex__ or a __float__ method these methods are used to convert the object to a complex or floating point number respectively and the function is then applied to the result of the conversion Note For functions involving branch cuts we have the problem of deciding how to define those functions on the cut itself Following Kahan s Branch cuts for complex elementary functions paper as well as Annex G of C99 and later C standards we use the sign of zero to distinguish one side of the branch cut from the other for a branch cut along a portion of the real axis we look at the sign of the imaginary part while for a branch cut along the imaginary axis we look at the sign of the real part For example the cmath sqrt function has a branch cut along the negative real axis An argument of complex 2 0 0 0 is treated as though it lies below the branch cut and so gives a result on the negative imaginary axis cmath sqrt complex 2 0 0 0 1 4142135623730951j But an argument of complex 2 0 0 0 is treated as though it lies above the branch cut cmath sqrt complex 2 0 0 0 1 4142135623730951j Conversions to and from polar coordinates A Python complex number z is stored internally using rectangular or Cartesian coordinates It is completely determined by its real part z real and its imaginary part z imag In other words z z real z imag 1j Polar coordinates give an alternative way to represent a complex number In polar coordinates a complex number z is defined by the modulus r and the phase angle phi The modulus r is the distance from z to the origin while the phase phi is the counterclockwise angle measured in radians from the positive x axis to the line segment that joins the origin to z The following functions can be used to convert from the native rectangular coordinates to polar coordinates and back cmath phase x Return the phase of x also known as the argument of x as a float phase x is equivalent to math atan2 x imag x real The result lies in the range π π and the branch cut for this operation lies along the negative real axis The sign of the result is the same as the sign of x imag even when x imag is zero phase complex 1 0 0 0 3 141592653589793 phase complex 1 0 0 0 3 141592653589793 Note The modulus absolute value of a complex number x can be computed using the built in abs function There is no separate cmath module function for this operation cmath polar x Return the representation of x in polar coordinates Returns a pair r phi where r is the modulus of x and phi is the phase of x polar x is equivalent to abs x phase x cmath rect r phi Return the complex number x with polar coordinates r and phi Equivalent to r math cos phi math sin phi 1j Power and logarithmic functions cmath exp x Return e raised to the power x where e is the base of natural logarithms cmath log x base Returns the logarithm of x to the given base If the base is not specified returns the natural logarithm of x There is one branch cut from 0 along the negative real axis to cmath log10 x Return the base 10 logarithm of x This has the same branch cut as log cmath sqrt x Return the square root of x This has the same branch cut as log Trigonometric functions cmath acos x Return the arc cosine of x There are two branch cuts One extends right from 1 along the real axis to The other extends left from 1 along the real axis to cmath asin x Return the arc sine of x This has the same branch cuts as acos cmath atan x Return the arc tangent of x There are two branch cuts One extends from 1j along the imaginary axis to j The other extends from 1j along the imaginary axis to j cmath cos x Return the cosine of x cmath sin x Return the sine of x cmath tan x Return the tangent of x Hyperbolic functions cmath acosh x Return the inverse hyperbolic cosine of x There is one branch cut extending left from 1 along the ,en
2049,real axis to cmath asinh x Return the inverse hyperbolic sine of x There are two branch cuts One extends from 1j along the imaginary axis to j The other extends from 1j along the imaginary axis to j cmath atanh x Return the inverse hyperbolic tangent of x There are two branch cuts One extends from 1 along the real axis to The other extends from 1 along the real axis to cmath cosh x Return the hyperbolic cosine of x cmath sinh x Return the hyperbolic sine of x cmath tanh x Return the hyperbolic tangent of x Classification functions cmath isfinite x Return True if both the real and imaginary parts of x are finite and False otherwise New in version 3 2 cmath isinf x Return True if either the real or the imaginary part of x is an infinity and False otherwise cmath isnan x Return True if either the real or the imaginary part of x is a NaN and False otherwise cmath isclose a b rel_tol 1e 09 abs_tol 0 0 Return True if the values a and b are close to each other and False otherwise Whether or not two values are considered close is determined according to given absolute and relative tolerances rel_tol is the relative tolerance it is the maximum allowed difference between a and b relative to the larger absolute value of a or b For example to set a tolerance of 5 pass rel_tol 0 05 The default tolerance is 1e 09 which assures that the two values are the same within about 9 decimal digits rel_tol must be greater than zero abs_tol is the minimum absolute tolerance useful for comparisons near zero abs_tol must be at least zero If no errors occur the result will be abs a b max rel_tol max abs a abs b abs_tol The IEEE 754 special values of NaN inf and inf will be handled according to IEEE rules Specifically NaN is not considered close to any other value including NaN inf and inf are only considered close to themselves New in version 3 5 See also PEP 485 A function for testing approximate equality Constants cmath pi The mathematical constant π as a float cmath e The mathematical constant e as a float cmath tau The mathematical constant τ as a float New in version 3 6 cmath inf Floating point positive infinity Equivalent to float inf New in version 3 6 cmath infj Complex number with zero real part and positive infinity imaginary part Equivalent to complex 0 0 float inf New in version 3 6 cmath nan A floating point not a number NaN value Equivalent to float nan New in version 3 6 cmath nanj Complex number with zero real part and NaN imaginary part Equivalent to complex 0 0 float nan New in version 3 6 Note that the selection of functions is similar but not identical to that in module math The reason for having two modules is that some users aren t interested in complex numbers and perhaps don t even know what they are They would rather have math sqrt 1 raise an exception than return a complex number Also note that the functions defined in cmath always return a complex number even if the answer can be expressed as a real number in which case the complex number has an imaginary part of zero A note on branch cuts They are curves along which the given function fails to be continuous They are a necessary feature of many complex functions It is assumed that if you need to compute with complex functions you will understand about branch cuts Consult almost any not too elementary book on complex variables for enlightenment For information of the proper choice of branch cuts for numerical purposes a good reference should be the following See also Kahan W Branch cuts for complex elementary functions or Much ado about nothing s sign bit In Iserles A and Powell M eds The state of the art in numerical analysis Clarendon Press 1987 pp165 211,en
2050,7 Simple statements A simple statement is comprised within a single logical line Several simple statements may occur on a single line separated by semicolons The syntax for simple statements is simple_stmt expression_stmt assert_stmt assignment_stmt augmented_assignment_stmt annotated_assignment_stmt pass_stmt del_stmt return_stmt yield_stmt raise_stmt break_stmt continue_stmt import_stmt future_stmt global_stmt nonlocal_stmt type_stmt 7 1 Expression statements Expression statements are used mostly interactively to compute and write a value or usually to call a procedure a function that returns no meaningful result in Python procedures return the value None Other uses of expression statements are allowed and occasionally useful The syntax for an expression statement is expression_stmt starred_expression An expression statement evaluates the expression list which may be a single expression In interactive mode if the value is not None it is converted to a string using the built in repr function and the resulting string is written to standard output on a line by itself except if the result is None so that procedure calls do not cause any output 7 2 Assignment statements Assignment statements are used to re bind names to values and to modify attributes or items of mutable objects assignment_stmt target_list starred_expression yield_expression target_list target target target identifier target_list target_list attributeref subscription slicing target See section Primaries for the syntax definitions for attributeref subscription and slicing An assignment statement evaluates the expression list remember that this can be a single expression or a comma separated list the latter yielding a tuple and assigns the single resulting object to each of the target lists from left to right Assignment is defined recursively depending on the form of the target list When a target is part of a mutable object an attribute reference subscription or slicing the mutable object must ultimately perform the assignment and decide about its validity and may raise an exception if the assignment is unacceptable The rules observed by various types and the exceptions raised are given with the definition of the object types see section The standard type hierarchy Assignment of an object to a target list optionally enclosed in parentheses or square brackets is recursively defined as follows If the target list is a single target with no trailing comma optionally in parentheses the object is assigned to that target Else If the target list contains one target prefixed with an asterisk called a starred target The object must be an iterable with at least as many items as there are targets in the target list minus one The first items of the iterable are assigned from left to right to the targets before the starred target The final items of the iterable are assigned to the targets after the starred target A list of the remaining items in the iterable is then assigned to the starred target the list can be empty Else The object must be an iterable with the same number of items as there are targets in the target list and the items are assigned from left to right to the corresponding targets Assignment of an object to a single target is recursively defined as follows If the target is an identifier name If the name does not occur in a global or nonlocal statement in the current code block the name is bound to the object in the current local namespace Otherwise the name is bound to the object in the global namespace or the outer namespace determined by nonlocal respectively The name is rebound if it was already bound This may cause the reference count for the object previously bound to the name to reach zero causing the object to be deallocated and its destructor if it has one to be called If the target is an attribute reference The primary expression in the reference is evaluated It should yield an object with assignable attributes if this is not the case TypeError is raised That object is then asked to assign the assigned object to the given attribute if it cannot perf,en
2051,orm the assignment it raises an exception usually but not necessarily AttributeError Note If the object is a class instance and the attribute reference occurs on both sides of the assignment operator the right hand side expression a x can access either an instance attribute or if no instance attribute exists a class attribute The left hand side target a x is always set as an instance attribute creating it if necessary Thus the two occurrences of a x do not necessarily refer to the same attribute if the right hand side expression refers to a class attribute the left hand side creates a new instance attribute as the target of the assignment class Cls x 3 class variable inst Cls inst x inst x 1 writes inst x as 4 leaving Cls x as 3 This description does not necessarily apply to descriptor attributes such as properties created with property If the target is a subscription The primary expression in the reference is evaluated It should yield either a mutable sequence object such as a list or a mapping object such as a dictionary Next the subscript expression is evaluated If the primary is a mutable sequence object such as a list the subscript must yield an integer If it is negative the sequence s length is added to it The resulting value must be a nonnegative integer less than the sequence s length and the sequence is asked to assign the assigned object to its item with that index If the index is out of range IndexError is raised assignment to a subscripted sequence cannot add new items to a list If the primary is a mapping object such as a dictionary the subscript must have a type compatible with the mapping s key type and the mapping is then asked to create a key value pair which maps the subscript to the assigned object This can either replace an existing key value pair with the same key value or insert a new key value pair if no key with the same value existed For user defined objects the __setitem__ method is called with appropriate arguments If the target is a slicing The primary expression in the reference is evaluated It should yield a mutable sequence object such as a list The assigned object should be a sequence object of the same type Next the lower and upper bound expressions are evaluated insofar they are present defaults are zero and the sequence s length The bounds should evaluate to integers If either bound is negative the sequence s length is added to it The resulting bounds are clipped to lie between zero and the sequence s length inclusive Finally the sequence object is asked to replace the slice with the items of the assigned sequence The length of the slice may be different from the length of the assigned sequence thus changing the length of the target sequence if the target sequence allows it CPython implementation detail In the current implementation the syntax for targets is taken to be the same as for expressions and invalid syntax is rejected during the code generation phase causing less detailed error messages Although the definition of assignment implies that overlaps between the left hand side and the right hand side are simultaneous for example a b b a swaps two variables overlaps within the collection of assigned to variables occur left to right sometimes resulting in confusion For instance the following program prints 0 2 x 0 1 i 0 i x i 1 2 i is updated then x i is updated print x See also PEP 3132 Extended Iterable Unpacking The specification for the target feature 7 2 1 Augmented assignment statements Augmented assignment is the combination in a single statement of a binary operation and an assignment statement augmented_assignment_stmt augtarget augop expression_list yield_expression augtarget identifier attributeref subscription slicing augop See section Primaries for the syntax definitions of the last three symbols An augmented assignment evaluates the target which unlike normal assignment statements cannot be an unpacking and the expression list performs the binary operation specific to the type of assignment on the two operands and assigns the result to the original target The target is ,en
2052,only evaluated once An augmented assignment expression like x 1 can be rewritten as x x 1 to achieve a similar but not exactly equal effect In the augmented version x is only evaluated once Also when possible the actual operation is performed in place meaning that rather than creating a new object and assigning that to the target the old object is modified instead Unlike normal assignments augmented assignments evaluate the left hand side before evaluating the right hand side For example a i f x first looks up a i then it evaluates f x and performs the addition and lastly it writes the result back to a i With the exception of assigning to tuples and multiple targets in a single statement the assignment done by augmented assignment statements is handled the same way as normal assignments Similarly with the exception of the possible in place behavior the binary operation performed by augmented assignment is the same as the normal binary operations For targets which are attribute references the same caveat about class and instance attributes applies as for regular assignments 7 2 2 Annotated assignment statements Annotation assignment is the combination in a single statement of a variable or attribute annotation and an optional assignment statement annotated_assignment_stmt augtarget expression starred_expression yield_expression The difference from normal Assignment statements is that only a single target is allowed For simple names as assignment targets if in class or module scope the annotations are evaluated and stored in a special class or module attribute __annotations__ that is a dictionary mapping from variable names mangled if private to evaluated annotations This attribute is writable and is automatically created at the start of class or module body execution if annotations are found statically For expressions as assignment targets the annotations are evaluated if in class or module scope but not stored If a name is annotated in a function scope then this name is local for that scope Annotations are never evaluated and stored in function scopes If the right hand side is present an annotated assignment performs the actual assignment before evaluating annotations where applicable If the right hand side is not present for an expression target then the interpreter evaluates the target except for the last __setitem__ or __setattr__ call See also PEP 526 Syntax for Variable Annotations The proposal that added syntax for annotating the types of variables including class variables and instance variables instead of expressing them through comments PEP 484 Type hints The proposal that added the typing module to provide a standard syntax for type annotations that can be used in static analysis tools and IDEs Changed in version 3 8 Now annotated assignments allow the same expressions in the right hand side as regular assignments Previously some expressions like un parenthesized tuple expressions caused a syntax error 7 3 The assert statement Assert statements are a convenient way to insert debugging assertions into a program assert_stmt assert expression expression The simple form assert expression is equivalent to if __debug__ if not expression raise AssertionError The extended form assert expression1 expression2 is equivalent to if __debug__ if not expression1 raise AssertionError expression2 These equivalences assume that __debug__ and AssertionError refer to the built in variables with those names In the current implementation the built in variable __debug__ is True under normal circumstances False when optimization is requested command line option O The current code generator emits no code for an assert statement when optimization is requested at compile time Note that it is unnecessary to include the source code for the expression that failed in the error message it will be displayed as part of the stack trace Assignments to __debug__ are illegal The value for the built in variable is determined when the interpreter starts 7 4 The pass statement pass_stmt pass pass is a null operation when it is executed nothing happens,en
2053, It is useful as a placeholder when a statement is required syntactically but no code needs to be executed for example def f arg pass a function that does nothing yet class C pass a class with no methods yet 7 5 The del statement del_stmt del target_list Deletion is recursively defined very similar to the way assignment is defined Rather than spelling it out in full details here are some hints Deletion of a target list recursively deletes each target from left to right Deletion of a name removes the binding of that name from the local or global namespace depending on whether the name occurs in a global statement in the same code block If the name is unbound a NameError exception will be raised Deletion of attribute references subscriptions and slicings is passed to the primary object involved deletion of a slicing is in general equivalent to assignment of an empty slice of the right type but even this is determined by the sliced object Changed in version 3 2 Previously it was illegal to delete a name from the local namespace if it occurs as a free variable in a nested block 7 6 The return statement return_stmt return expression_list return may only occur syntactically nested in a function definition not within a nested class definition If an expression list is present it is evaluated else None is substituted return leaves the current function call with the expression list or None as return value When return passes control out of a try statement with a finally clause that finally clause is executed before really leaving the function In a generator function the return statement indicates that the generator is done and will cause StopIteration to be raised The returned value if any is used as an argument to construct StopIteration and becomes the StopIteration value attribute In an asynchronous generator function an empty return statement indicates that the asynchronous generator is done and will cause StopAsyncIteration to be raised A non empty return statement is a syntax error in an asynchronous generator function 7 7 The yield statement yield_stmt yield_expression A yield statement is semantically equivalent to a yield expression The yield statement can be used to omit the parentheses that would otherwise be required in the equivalent yield expression statement For example the yield statements yield expr yield from expr are equivalent to the yield expression statements yield expr yield from expr Yield expressions and statements are only used when defining a generator function and are only used in the body of the generator function Using yield in a function definition is sufficient to cause that definition to create a generator function instead of a normal function For full details of yield semantics refer to the Yield expressions section 7 8 The raise statement raise_stmt raise expression from expression If no expressions are present raise re raises the exception that is currently being handled which is also known as the active exception If there isn t currently an active exception a RuntimeError exception is raised indicating that this is an error Otherwise raise evaluates the first expression as the exception object It must be either a subclass or an instance of BaseException If it is a class the exception instance will be obtained when needed by instantiating the class with no arguments The type of the exception is the exception instance s class the value is the instance itself A traceback object is normally created automatically when an exception is raised and attached to it as the __traceback__ attribute You can create an exception and set your own traceback in one step using the with_traceback exception method which returns the same exception instance with its traceback set to its argument like so raise Exception foo occurred with_traceback tracebackobj The from clause is used for exception chaining if given the second expression must be another exception class or instance If the second expression is an exception instance it will be attached to the raised exception as the __cause__ attribute which is writable If t,en
2054,he expression is an exception class the class will be instantiated and the resulting exception instance will be attached to the raised exception as the __cause__ attribute If the raised exception is not handled both exceptions will be printed try print 1 0 except Exception as exc raise RuntimeError Something bad happened from exc Traceback most recent call last File stdin line 2 in module print 1 0 ZeroDivisionError division by zero The above exception was the direct cause of the following exception Traceback most recent call last File stdin line 4 in module raise RuntimeError Something bad happened from exc RuntimeError Something bad happened A similar mechanism works implicitly if a new exception is raised when an exception is already being handled An exception may be handled when an except or finally clause or a with statement is used The previous exception is then attached as the new exception s __context__ attribute try print 1 0 except raise RuntimeError Something bad happened Traceback most recent call last File stdin line 2 in module print 1 0 ZeroDivisionError division by zero During handling of the above exception another exception occurred Traceback most recent call last File stdin line 4 in module raise RuntimeError Something bad happened RuntimeError Something bad happened Exception chaining can be explicitly suppressed by specifying None in the from clause try print 1 0 except raise RuntimeError Something bad happened from None Traceback most recent call last File stdin line 4 in module RuntimeError Something bad happened Additional information on exceptions can be found in section Exceptions and information about handling exceptions is in section The try statement Changed in version 3 3 None is now permitted as Y in raise X from Y Added the __suppress_context__ attribute to suppress automatic display of the exception context Changed in version 3 11 If the traceback of the active exception is modified in an except clause a subsequent raise statement re raises the exception with the modified traceback Previously the exception was re raised with the traceback it had when it was caught 7 9 The break statement break_stmt break break may only occur syntactically nested in a for or while loop but not nested in a function or class definition within that loop It terminates the nearest enclosing loop skipping the optional else clause if the loop has one If a for loop is terminated by break the loop control target keeps its current value When break passes control out of a try statement with a finally clause that finally clause is executed before really leaving the loop 7 10 The continue statement continue_stmt continue continue may only occur syntactically nested in a for or while loop but not nested in a function or class definition within that loop It continues with the next cycle of the nearest enclosing loop When continue passes control out of a try statement with a finally clause that finally clause is executed before really starting the next loop cycle 7 11 The import statement import_stmt import module as identifier module as identifier from relative_module import identifier as identifier identifier as identifier from relative_module import identifier as identifier identifier as identifier from relative_module import module identifier identifier relative_module module The basic import statement no from clause is executed in two steps 1 find a module loading and initializing it if necessary 2 define a name or names in the local namespace for the scope where the import statement occurs When the statement contains multiple clauses separated by commas the two steps are carried out separately for each clause just as though the clauses had been separated out into individual import statements The details of the first step finding and loading modules are described in greater detail in the section on the import system which also describes the various types of packages and modules that can be imported as well as all the hooks that can be used to customize the import system Note that failures in this step may indicate ei,en
2055,ther that the module could not be located or that an error occurred while initializing the module which includes execution of the module s code If the requested module is retrieved successfully it will be made available in the local namespace in one of three ways If the module name is followed by as then the name following as is bound directly to the imported module If no other name is specified and the module being imported is a top level module the module s name is bound in the local namespace as a reference to the imported module If the module being imported is not a top level module then the name of the top level package that contains the module is bound in the local namespace as a reference to the top level package The imported module must be accessed using its full qualified name rather than directly The from form uses a slightly more complex process 1 find the module specified in the from clause loading and initializing it if necessary 2 for each of the identifiers specified in the import clauses 1 check if the imported module has an attribute by that name 2 if not attempt to import a submodule with that name and then check the imported module again for that attribute 3 if the attribute is not found ImportError is raised 4 otherwise a reference to that value is stored in the local namespace using the name in the as clause if it is present otherwise using the attribute name Examples import foo foo imported and bound locally import foo bar baz foo foo bar and foo bar baz imported foo bound locally import foo bar baz as fbb foo foo bar and foo bar baz imported foo bar baz bound as fbb from foo bar import baz foo foo bar and foo bar baz imported foo bar baz bound as baz from foo import attr foo imported and foo attr bound as attr If the list of identifiers is replaced by a star all public names defined in the module are bound in the local namespace for the scope where the import statement occurs The public names defined by a module are determined by checking the module s namespace for a variable named __all__ if defined it must be a sequence of strings which are names defined or imported by that module The names given in __all__ are all considered public and are required to exist If __all__ is not defined the set of public names includes all names found in the module s namespace which do not begin with an underscore character _ __all__ should contain the entire public API It is intended to avoid accidentally exporting items that are not part of the API such as library modules which were imported and used within the module The wild card form of import from module import is only allowed at the module level Attempting to use it in class or function definitions will raise a SyntaxError When specifying what module to import you do not have to specify the absolute name of the module When a module or package is contained within another package it is possible to make a relative import within the same top package without having to mention the package name By using leading dots in the specified module or package after from you can specify how high to traverse up the current package hierarchy without specifying exact names One leading dot means the current package where the module making the import exists Two dots means up one package level Three dots is up two levels etc So if you execute from import mod from a module in the pkg package then you will end up importing pkg mod If you execute from subpkg2 import mod from within pkg subpkg1 you will import pkg subpkg2 mod The specification for relative imports is contained in the Package Relative Imports section importlib import_module is provided to support applications that determine dynamically the modules to be loaded Raises an auditing event import with arguments module filename sys path sys meta_path sys path_hooks 7 11 1 Future statements A future statement is a directive to the compiler that a particular module should be compiled using syntax or semantics that will be available in a specified future release of Python where the feature becomes standard The future statement i,en
2056,s intended to ease migration to future versions of Python that introduce incompatible changes to the language It allows use of the new features on a per module basis before the release in which the feature becomes standard future_stmt from __future__ import feature as identifier feature as identifier from __future__ import feature as identifier feature as identifier feature identifier A future statement must appear near the top of the module The only lines that can appear before a future statement are the module docstring if any comments blank lines and other future statements The only feature that requires using the future statement is annotations see PEP 563 All historical features enabled by the future statement are still recognized by Python 3 The list includes absolute_import division generators generator_stop unicode_literals print_function nested_scopes and with_statement They are all redundant because they are always enabled and only kept for backwards compatibility A future statement is recognized and treated specially at compile time Changes to the semantics of core constructs are often implemented by generating different code It may even be the case that a new feature introduces new incompatible syntax such as a new reserved word in which case the compiler may need to parse the module differently Such decisions cannot be pushed off until runtime For any given release the compiler knows which feature names have been defined and raises a compile time error if a future statement contains a feature not known to it The direct runtime semantics are the same as for any import statement there is a standard module __future__ described later and it will be imported in the usual way at the time the future statement is executed The interesting runtime semantics depend on the specific feature enabled by the future statement Note that there is nothing special about the statement import __future__ as name That is not a future statement it s an ordinary import statement with no special semantics or syntax restrictions Code compiled by calls to the built in functions exec and compile that occur in a module M containing a future statement will by default use the new syntax or semantics associated with the future statement This can be controlled by optional arguments to compile see the documentation of that function for details A future statement typed at an interactive interpreter prompt will take effect for the rest of the interpreter session If an interpreter is started with the i option is passed a script name to execute and the script includes a future statement it will be in effect in the interactive session started after the script is executed See also PEP 236 Back to the __future__ The original proposal for the __future__ mechanism 7 12 The global statement global_stmt global identifier identifier The global statement is a declaration which holds for the entire current code block It means that the listed identifiers are to be interpreted as globals It would be impossible to assign to a global variable without global although free variables may refer to globals without being declared global Names listed in a global statement must not be used in the same code block textually preceding that global statement Names listed in a global statement must not be defined as formal parameters or as targets in with statements or except clauses or in a for target list class definition function definition import statement or variable annotation CPython implementation detail The current implementation does not enforce some of these restrictions but programs should not abuse this freedom as future implementations may enforce them or silently change the meaning of the program Programmer s note global is a directive to the parser It applies only to code parsed at the same time as the global statement In particular a global statement contained in a string or code object supplied to the built in exec function does not affect the code block containing the function call and code contained in such a string is unaffected by global statements in th,en
2057,e code containing the function call The same applies to the eval and compile functions 7 13 The nonlocal statement nonlocal_stmt nonlocal identifier identifier The nonlocal statement causes the listed identifiers to refer to previously bound variables in the nearest enclosing scope excluding globals This is important because the default behavior for binding is to search the local namespace first The statement allows encapsulated code to rebind variables outside of the local scope besides the global module scope Names listed in a nonlocal statement unlike those listed in a global statement must refer to pre existing bindings in an enclosing scope the scope in which a new binding should be created cannot be determined unambiguously Names listed in a nonlocal statement must not collide with pre existing bindings in the local scope See also PEP 3104 Access to Names in Outer Scopes The specification for the nonlocal statement 7 14 The type statement type_stmt type identifier type_params expression The type statement declares a type alias which is an instance of typing TypeAliasType For example the following statement creates a type alias type Point tuple float float This code is roughly equivalent to annotation def VALUE_OF_Point return tuple float float Point typing TypeAliasType Point VALUE_OF_Point annotation def indicates an annotation scope which behaves mostly like a function but with several small differences The value of the type alias is evaluated in the annotation scope It is not evaluated when the type alias is created but only when the value is accessed through the type alias s __value__ attribute see Lazy evaluation This allows the type alias to refer to names that are not yet defined Type aliases may be made generic by adding a type parameter list after the name See Generic type aliases for more type is a soft keyword New in version 3 12 See also PEP 695 Type Parameter Syntax Introduced the type statement and syntax for generic classes and functions,en
2058,API and ABI Versioning CPython exposes its version number in the following macros Note that these correspond to the version code is built with not necessarily the version used at run time See C API Stability for a discussion of API and ABI stability across versions PY_MAJOR_VERSION The 3 in 3 4 1a2 PY_MINOR_VERSION The 4 in 3 4 1a2 PY_MICRO_VERSION The 1 in 3 4 1a2 PY_RELEASE_LEVEL The a in 3 4 1a2 This can be 0xA for alpha 0xB for beta 0xC for release candidate or 0xF for final PY_RELEASE_SERIAL The 2 in 3 4 1a2 Zero for final releases PY_VERSION_HEX The Python version number encoded in a single integer The underlying version information can be found by treating it as a 32 bit number in the following manner Bytes Bits big endian order Meaning Value for 3 4 1a2 1 1 8 PY_MAJOR_VERSION 0x03 2 9 16 PY_MINOR_VERSION 0x04 3 17 24 PY_MICRO_VERSION 0x01 4 25 28 PY_RELEASE_LEVEL 0xA 29 32 PY_RELEASE_SERIAL 0x2 Thus 3 4 1a2 is hexversion 0x030401a2 and 3 10 0 is hexversion 0x030a00f0 Use this for numeric comparisons e g if PY_VERSION_HEX This version is also available via the symbol Py_Version const unsigned long Py_Version Part of the Stable ABI since version 3 11 The Python runtime version number encoded in a single constant integer with the same format as the PY_VERSION_HEX macro This contains the Python version used at run time New in version 3 11 All the given macros are defined in Include patchlevel h,en
2059,Security Considerations The following modules have specific security considerations base64 base64 security considerations in RFC 4648 cgi CGI security considerations hashlib all constructors take a usedforsecurity keyword only argument disabling known insecure and blocked algorithms http server is not suitable for production use only implementing basic security checks See the security considerations logging Logging configuration uses eval multiprocessing Connection recv uses pickle pickle Restricting globals in pickle random shouldn t be used for security purposes use secrets instead shelve shelve is based on pickle and thus unsuitable for dealing with untrusted sources ssl SSL TLS security considerations subprocess Subprocess security considerations tempfile mktemp is deprecated due to vulnerability to race conditions xml XML vulnerabilities zipfile maliciously prepared zip files can cause disk volume exhaustion The I command line option can be used to run Python in isolated mode When it cannot be used the P option or the PYTHONSAFEPATH environment variable can be used to not prepend a potentially unsafe path to sys path such as the current directory the script s directory or an empty string,en
2060,Library and Extension FAQ General Library Questions How do I find a module or application to perform task X Check the Library Reference to see if there s a relevant standard library module Eventually you ll learn what s in the standard library and will be able to skip this step For third party packages search the Python Package Index or try Google or another web search engine Searching for Python plus a keyword or two for your topic of interest will usually find something helpful Where is the math py socket py regex py etc source file If you can t find a source file for a module it may be a built in or dynamically loaded module implemented in C C or other compiled language In this case you may not have the source file or it may be something like mathmodule c somewhere in a C source directory not on the Python Path There are at least three kinds of modules in Python 1 modules written in Python py 2 modules written in C and dynamically loaded dll pyd so sl etc 3 modules written in C and linked with the interpreter to get a list of these type import sys print sys builtin_module_names How do I make a Python script executable on Unix You need to do two things the script file s mode must be executable and the first line must begin with followed by the path of the Python interpreter The first is done by executing chmod x scriptfile or perhaps chmod 755 scriptfile The second can be done in a number of ways The most straightforward way is to write usr local bin python as the very first line of your file using the pathname for where the Python interpreter is installed on your platform If you would like the script to be independent of where the Python interpreter lives you can use the env program Almost all Unix variants support the following assuming the Python interpreter is in a directory on the user s PATH usr bin env python Don t do this for CGI scripts The PATH variable for CGI scripts is often very minimal so you need to use the actual absolute pathname of the interpreter Occasionally a user s environment is so full that the usr bin env program fails or there s no env program at all In that case you can try the following hack due to Alex Rezinsky bin sh exec python 0 1 The minor disadvantage is that this defines the script s __doc__ string However you can fix that by adding __doc__ Whatever Is there a curses termcap package for Python For Unix variants The standard Python source distribution comes with a curses module in the Modules subdirectory though it s not compiled by default Note that this is not available in the Windows distribution there is no curses module for Windows The curses module supports basic curses features as well as many additional functions from ncurses and SYSV curses such as colour alternative character set support pads and mouse support This means the module isn t compatible with operating systems that only have BSD curses but there don t seem to be any currently maintained OSes that fall into this category Is there an equivalent to C s onexit in Python The atexit module provides a register function that is similar to C s onexit Why don t my signal handlers work The most common problem is that the signal handler is declared with the wrong argument list It is called as handler signum frame so it should be declared with two parameters def handler signum frame Common tasks How do I test a Python program or component Python comes with two testing frameworks The doctest module finds examples in the docstrings for a module and runs them comparing the output with the expected output given in the docstring The unittest module is a fancier testing framework modelled on Java and Smalltalk testing frameworks To make testing easier you should use good modular design in your program Your program should have almost all functionality encapsulated in either functions or class methods and this sometimes has the surprising and delightful effect of making the program run faster because local variable accesses are faster than global accesses Furthermore the program should avoid depending on mutating global variables sinc,en
2061,e this makes testing much more difficult to do The global main logic of your program may be as simple as if __name__ __main__ main_logic at the bottom of the main module of your program Once your program is organized as a tractable collection of function and class behaviours you should write test functions that exercise the behaviours A test suite that automates a sequence of tests can be associated with each module This sounds like a lot of work but since Python is so terse and flexible it s surprisingly easy You can make coding much more pleasant and fun by writing your test functions in parallel with the production code since this makes it easy to find bugs and even design flaws earlier Support modules that are not intended to be the main module of a program may include a self test of the module if __name__ __main__ self_test Even programs that interact with complex external interfaces may be tested when the external interfaces are unavailable by using fake interfaces implemented in Python How do I create documentation from doc strings The pydoc module can create HTML from the doc strings in your Python source code An alternative for creating API documentation purely from docstrings is epydoc Sphinx can also include docstring content How do I get a single keypress at a time For Unix variants there are several solutions It s straightforward to do this using curses but curses is a fairly large module to learn Threads How do I program using threads Be sure to use the threading module and not the _thread module The threading module builds convenient abstractions on top of the low level primitives provided by the _thread module None of my threads seem to run why As soon as the main thread exits all threads are killed Your main thread is running too quickly giving the threads no time to do any work A simple fix is to add a sleep to the end of the program that s long enough for all the threads to finish import threading time def thread_task name n for i in range n print name i for i in range 10 T threading Thread target thread_task args str i i T start time sleep 10 But now on many platforms the threads don t run in parallel but appear to run sequentially one at a time The reason is that the OS thread scheduler doesn t start a new thread until the previous thread is blocked A simple fix is to add a tiny sleep to the start of the run function def thread_task name n time sleep 0 001 for i in range n print name i for i in range 10 T threading Thread target thread_task args str i i T start time sleep 10 Instead of trying to guess a good delay value for time sleep it s better to use some kind of semaphore mechanism One idea is to use the queue module to create a queue object let each thread append a token to the queue when it finishes and let the main thread read as many tokens from the queue as there are threads How do I parcel out work among a bunch of worker threads The easiest way is to use the concurrent futures module especially the ThreadPoolExecutor class Or if you want fine control over the dispatching algorithm you can write your own logic manually Use the queue module to create a queue containing a list of jobs The Queue class maintains a list of objects and has a put obj method that adds items to the queue and a get method to return them The class will take care of the locking necessary to ensure that each job is handed out exactly once Here s a trivial example import threading queue time The worker thread gets jobs off the queue When the queue is empty it assumes there will be no more work and exits Realistically workers will run until terminated def worker print Running worker time sleep 0 1 while True try arg q get block False except queue Empty print Worker threading current_thread end print queue empty break else print Worker threading current_thread end print running with argument arg time sleep 0 5 Create queue q queue Queue Start a pool of 5 workers for i in range 5 t threading Thread target worker name worker i i 1 t start Begin adding work to the queue for i in range 50 q put i Give threads time to run print,en
2062, Main thread sleeping time sleep 5 When run this will produce the following output Running worker Running worker Running worker Running worker Running worker Main thread sleeping Worker Thread worker 1 started 130283832797456 running with argument 0 Worker Thread worker 2 started 130283824404752 running with argument 1 Worker Thread worker 3 started 130283816012048 running with argument 2 Worker Thread worker 4 started 130283807619344 running with argument 3 Worker Thread worker 5 started 130283799226640 running with argument 4 Worker Thread worker 1 started 130283832797456 running with argument 5 Consult the module s documentation for more details the Queue class provides a featureful interface What kinds of global value mutation are thread safe A global interpreter lock GIL is used internally to ensure that only one thread runs in the Python VM at a time In general Python offers to switch among threads only between bytecode instructions how frequently it switches can be set via sys setswitchinterval Each bytecode instruction and therefore all the C implementation code reached from each instruction is therefore atomic from the point of view of a Python program In theory this means an exact accounting requires an exact understanding of the PVM bytecode implementation In practice it means that operations on shared variables of built in data types ints lists dicts etc that look atomic really are For example the following operations are all atomic L L1 L2 are lists D D1 D2 are dicts x y are objects i j are ints L append x L1 extend L2 x L i x L pop L1 i j L2 L sort x y x field y D x y D1 update D2 D keys These aren t i i 1 L append L 1 L i L j D x D x 1 Operations that replace other objects may invoke those other objects __del__ method when their reference count reaches zero and that can affect things This is especially true for the mass updates to dictionaries and lists When in doubt use a mutex Can t we get rid of the Global Interpreter Lock The global interpreter lock GIL is often seen as a hindrance to Python s deployment on high end multiprocessor server machines because a multi threaded Python program effectively only uses one CPU due to the insistence that almost all Python code can only run while the GIL is held Back in the days of Python 1 5 Greg Stein actually implemented a comprehensive patch set the free threading patches that removed the GIL and replaced it with fine grained locking Adam Olsen recently did a similar experiment in his python safethread project Unfortunately both experiments exhibited a sharp drop in single thread performance at least 30 slower due to the amount of fine grained locking necessary to compensate for the removal of the GIL This doesn t mean that you can t make good use of Python on multi CPU machines You just have to be creative with dividing the work up between multiple processes rather than multiple threads The ProcessPoolExecutor class in the new concurrent futures module provides an easy way of doing so the multiprocessing module provides a lower level API in case you want more control over dispatching of tasks Judicious use of C extensions will also help if you use a C extension to perform a time consuming task the extension can release the GIL while the thread of execution is in the C code and allow other threads to get some work done Some standard library modules such as zlib and hashlib already do this It has been suggested that the GIL should be a per interpreter state lock rather than truly global interpreters then wouldn t be able to share objects Unfortunately this isn t likely to happen either It would be a tremendous amount of work because many object implementations currently have global state For example small integers and short strings are cached these caches would have to be moved to the interpreter state Other object types have their own free list these free lists would have to be moved to the interpreter state And so on And I doubt that it can even be done in finite time because the same problem exists for 3rd party extensions It is likely that 3rd party extension,en
2063,s are being written at a faster rate than you can convert them to store all their global state in the interpreter state And finally once you have multiple interpreters not sharing any state what have you gained over running each interpreter in a separate process Input and Output How do I delete a file And other file questions Use os remove filename or os unlink filename for documentation see the os module The two functions are identical unlink is simply the name of the Unix system call for this function To remove a directory use os rmdir use os mkdir to create one os makedirs path will create any intermediate directories in path that don t exist os removedirs path will remove intermediate directories as long as they re empty if you want to delete an entire directory tree and its contents use shutil rmtree To rename a file use os rename old_path new_path To truncate a file open it using f open filename rb and use f truncate offset offset defaults to the current seek position There s also os ftruncate fd offset for files opened with os open where fd is the file descriptor a small integer The shutil module also contains a number of functions to work on files including copyfile copytree and rmtree How do I copy a file The shutil module contains a copyfile function Note that on Windows NTFS volumes it does not copy alternate data streams nor resource forks on macOS HFS volumes though both are now rarely used It also doesn t copy file permissions and metadata though using shutil copy2 instead will preserve most though not all of it How do I read or write binary data To read or write complex binary data formats it s best to use the struct module It allows you to take a string containing binary data usually numbers and convert it to Python objects and vice versa For example the following code reads two 2 byte integers and one 4 byte integer in big endian format from a file import struct with open filename rb as f s f read 8 x y z struct unpack hhl s The in the format string forces big endian data the letter h reads one short integer 2 bytes and l reads one long integer 4 bytes from the string For data that is more regular e g a homogeneous list of ints or floats you can also use the array module Note To read and write binary data it is mandatory to open the file in binary mode here passing rb to open If you use r instead the default the file will be open in text mode and f read will return str objects rather than bytes objects I can t seem to use os read on a pipe created with os popen why os read is a low level function which takes a file descriptor a small integer representing the opened file os popen creates a high level file object the same type returned by the built in open function Thus to read n bytes from a pipe p created with os popen you need to use p read n How do I access the serial RS232 port For Win32 OSX Linux BSD Jython IronPython https pypi org project pyserial For Unix see a Usenet post by Mitch Chapman https groups google com groups selm 34A04430 CF9 ohioee com Why doesn t closing sys stdout stdin stderr really close it Python file objects are a high level layer of abstraction on low level C file descriptors For most file objects you create in Python via the built in open function f close marks the Python file object as being closed from Python s point of view and also arranges to close the underlying C file descriptor This also happens automatically in f s destructor when f becomes garbage But stdin stdout and stderr are treated specially by Python because of the special status also given to them by C Running sys stdout close marks the Python level file object as being closed but does not close the associated C file descriptor To close the underlying C file descriptor for one of these three you should first be sure that s what you really want to do e g you may confuse extension modules trying to do I O If it is use os close os close stdin fileno os close stdout fileno os close stderr fileno Or you can use the numeric constants 0 1 and 2 respectively Network Internet Programming What WWW tools are there for Py,en
2064,thon See the chapters titled Internet Protocols and Support and Internet Data Handling in the Library Reference Manual Python has many modules that will help you build server side and client side web systems A summary of available frameworks is maintained by Paul Boddie at https wiki python org moin WebProgramming Cameron Laird maintains a useful set of pages about Python web technologies at https web archive org web 20210224183619 http pha seit net claird comp lang python web_python How can I mimic CGI form submission METHOD POST I would like to retrieve web pages that are the result of POSTing a form Is there existing code that would let me do this easily Yes Here s a simple example that uses urllib request usr local bin python import urllib request build the query string qs First Josephine MI Q Last Public connect and send the server a path req urllib request urlopen http www some server out there cgi bin some cgi script data qs with req msg hdrs req read req info Note that in general for percent encoded POST operations query strings must be quoted using urllib parse urlencode For example to send name Guy Steele Jr import urllib parse urllib parse urlencode name Guy Steele Jr name Guy Steele 2C Jr See also HOWTO Fetch Internet Resources Using The urllib Package for extensive examples What module should I use to help with generating HTML You can find a collection of useful links on the Web Programming wiki page How do I send mail from a Python script Use the standard library module smtplib Here s a very simple interactive mail sender that uses it This method will work on any host that supports an SMTP listener import sys smtplib fromaddr input From toaddrs input To split print Enter message end with D msg while True line sys stdin readline if not line break msg line The actual mail send server smtplib SMTP localhost server sendmail fromaddr toaddrs msg server quit A Unix only alternative uses sendmail The location of the sendmail program varies between systems sometimes it is usr lib sendmail sometimes usr sbin sendmail The sendmail manual page will help you out Here s some sample code import os SENDMAIL usr sbin sendmail sendmail location p os popen s t i SENDMAIL w p write To receiver example com n p write Subject test n p write n blank line separating headers from body p write Some text n p write some more text n sts p close if sts 0 print Sendmail exit status sts How do I avoid blocking in the connect method of a socket The select module is commonly used to help with asynchronous I O on sockets To prevent the TCP connect from blocking you can set the socket to non blocking mode Then when you do the connect you will either connect immediately unlikely or get an exception that contains the error number as errno errno EINPROGRESS indicates that the connection is in progress but hasn t finished yet Different OSes will return different values so you re going to have to check what s returned on your system You can use the connect_ex method to avoid creating an exception It will just return the errno value To poll you can call connect_ex again later 0 or errno EISCONN indicate that you re connected or you can pass this socket to select select to check if it s writable Note The asyncio module provides a general purpose single threaded and concurrent asynchronous library which can be used for writing non blocking network code The third party Twisted library is a popular and feature rich alternative Databases Are there any interfaces to database packages in Python Yes Interfaces to disk based hashes such as DBM and GDBM are also included with standard Python There is also the sqlite3 module which provides a lightweight disk based relational database Support for most relational databases is available See the DatabaseProgramming wiki page for details How do you implement persistent objects in Python The pickle library module solves this in a very general way though you still can t store things like open files sockets or windows and the shelve library module uses pickle and g dbm to create persistent mappings containing arbitra,en
2065,ry Python objects Mathematics and Numerics How do I generate random numbers in Python The standard module random implements a random number generator Usage is simple import random random random This returns a random floating point number in the range 0 1 There are also many other specialized generators in this module such as randrange a b chooses an integer in the range a b uniform a b chooses a floating point number in the range a b normalvariate mean sdev samples the normal Gaussian distribution Some higher level functions operate on sequences directly such as choice S chooses a random element from a given sequence shuffle L shuffles a list in place i e permutes it randomly There s also a Random class you can instantiate to create independent multiple random number generators,en
2066,ctypes A foreign function library for Python Source code Lib ctypes ctypes is a foreign function library for Python It provides C compatible data types and allows calling functions in DLLs or shared libraries It can be used to wrap these libraries in pure Python ctypes tutorial Note The code samples in this tutorial use doctest to make sure that they actually work Since some code samples behave differently under Linux Windows or macOS they contain doctest directives in comments Note Some code samples reference the ctypes c_int type On platforms where sizeof long sizeof int it is an alias to c_long So you should not be confused if c_long is printed if you would expect c_int they are actually the same type Loading dynamic link libraries ctypes exports the cdll and on Windows windll and oledll objects for loading dynamic link libraries You load libraries by accessing them as attributes of these objects cdll loads libraries which export functions using the standard cdecl calling convention while windll libraries call functions using the stdcall calling convention oledll also uses the stdcall calling convention and assumes the functions return a Windows HRESULT error code The error code is used to automatically raise an OSError exception when the function call fails Changed in version 3 3 Windows errors used to raise WindowsError which is now an alias of OSError Here are some examples for Windows Note that msvcrt is the MS standard C library containing most standard C functions and uses the cdecl calling convention from ctypes import print windll kernel32 WinDLL kernel32 handle at print cdll msvcrt CDLL msvcrt handle at libc cdll msvcrt Windows appends the usual dll file suffix automatically Note Accessing the standard C library through cdll msvcrt will use an outdated version of the library that may be incompatible with the one being used by Python Where possible use native Python functionality or else import and use the msvcrt module On Linux it is required to specify the filename including the extension to load a library so attribute access can not be used to load libraries Either the LoadLibrary method of the dll loaders should be used or you should load the library by creating an instance of CDLL by calling the constructor cdll LoadLibrary libc so 6 CDLL libc so 6 handle at libc CDLL libc so 6 libc CDLL libc so 6 handle at Accessing functions from loaded dlls Functions are accessed as attributes of dll objects from ctypes import libc printf _FuncPtr object at 0x print windll kernel32 GetModuleHandleA _FuncPtr object at 0x print windll kernel32 MyOwnFunction Traceback most recent call last File stdin line 1 in module File ctypes py line 239 in __getattr__ func _StdcallFuncPtr name self AttributeError function MyOwnFunction not found Note that win32 system dlls like kernel32 and user32 often export ANSI as well as UNICODE versions of a function The UNICODE version is exported with an W appended to the name while the ANSI version is exported with an A appended to the name The win32 GetModuleHandle function which returns a module handle for a given module name has the following C prototype and a macro is used to expose one of them as GetModuleHandle depending on whether UNICODE is defined or not ANSI version HMODULE GetModuleHandleA LPCSTR lpModuleName UNICODE version HMODULE GetModuleHandleW LPCWSTR lpModuleName windll does not try to select one of them by magic you must access the version you need by specifying GetModuleHandleA or GetModuleHandleW explicitly and then call it with bytes or string objects respectively Sometimes dlls export functions with names which aren t valid Python identifiers like 2 YAPAXI Z In this case you have to use getattr to retrieve the function getattr cdll msvcrt 2 YAPAXI Z _FuncPtr object at 0x On Windows some dlls export functions not by name but by ordinal These functions can be accessed by indexing the dll object with the ordinal number cdll kernel32 1 _FuncPtr object at 0x cdll kernel32 0 Traceback most recent call last File stdin line 1 in module File ctypes py line 310 in __getitem__ fun,en
2067,c _StdcallFuncPtr name self AttributeError function ordinal 0 not found Calling functions You can call these functions like any other Python callable This example uses the rand function which takes no arguments and returns a pseudo random integer print libc rand 1804289383 On Windows you can call the GetModuleHandleA function which returns a win32 module handle passing None as single argument to call it with a NULL pointer print hex windll kernel32 GetModuleHandleA None 0x1d000000 ValueError is raised when you call an stdcall function with the cdecl calling convention or vice versa cdll kernel32 GetModuleHandleA None Traceback most recent call last File stdin line 1 in module ValueError Procedure probably called with not enough arguments 4 bytes missing windll msvcrt printf b spam Traceback most recent call last File stdin line 1 in module ValueError Procedure probably called with too many arguments 4 bytes in excess To find out the correct calling convention you have to look into the C header file or the documentation for the function you want to call On Windows ctypes uses win32 structured exception handling to prevent crashes from general protection faults when functions are called with invalid argument values windll kernel32 GetModuleHandleA 32 Traceback most recent call last File stdin line 1 in module OSError exception access violation reading 0x00000020 There are however enough ways to crash Python with ctypes so you should be careful anyway The faulthandler module can be helpful in debugging crashes e g from segmentation faults produced by erroneous C library calls None integers bytes objects and unicode strings are the only native Python objects that can directly be used as parameters in these function calls None is passed as a C NULL pointer bytes objects and strings are passed as pointer to the memory block that contains their data char or wchar_t Python integers are passed as the platforms default C int type their value is masked to fit into the C type Before we move on calling functions with other parameter types we have to learn more about ctypes data types Fundamental data types ctypes defines a number of primitive C compatible data types ctypes type C type Python type c_bool _Bool bool 1 c_char char 1 character bytes object c_wchar wchar_t 1 character string c_byte char int c_ubyte unsigned char int c_short short int c_ushort unsigned short int c_int int int c_uint unsigned int int c_long long int c_ulong unsigned long int c_longlong __int64 or long long int c_ulonglong unsigned __int64 or unsigned long long int c_size_t size_t int c_ssize_t ssize_t or Py_ssize_t int c_time_t time_t int c_float float float c_double double float c_longdouble long double float c_char_p char NUL terminated bytes object or None c_wchar_p wchar_t NUL terminated string or None c_void_p void int or None 1 The constructor accepts any object with a truth value All these types can be created by calling them with an optional initializer of the correct type and value c_int c_long 0 c_wchar_p Hello World c_wchar_p 140018365411392 c_ushort 3 c_ushort 65533 Since these types are mutable their value can also be changed afterwards i c_int 42 print i c_long 42 print i value 42 i value 99 print i value 99 Assigning a new value to instances of the pointer types c_char_p c_wchar_p and c_void_p changes the memory location they point to not the contents of the memory block of course not because Python bytes objects are immutable s Hello World c_s c_wchar_p s print c_s c_wchar_p 139966785747344 print c_s value Hello World c_s value Hi there print c_s the memory location has changed c_wchar_p 139966783348904 print c_s value Hi there print s first object is unchanged Hello World You should be careful however not to pass them to functions expecting pointers to mutable memory If you need mutable memory blocks ctypes has a create_string_buffer function which creates these in various ways The current memory block contents can be accessed or changed with the raw property if you want to access it as NUL terminated string use the value property from ctyp,en
2068,es import p create_string_buffer 3 create a 3 byte buffer initialized to NUL bytes print sizeof p repr p raw 3 b x00 x00 x00 p create_string_buffer b Hello create a buffer containing a NUL terminated string print sizeof p repr p raw 6 b Hello x00 print repr p value b Hello p create_string_buffer b Hello 10 create a 10 byte buffer print sizeof p repr p raw 10 b Hello x00 x00 x00 x00 x00 p value b Hi print sizeof p repr p raw 10 b Hi x00lo x00 x00 x00 x00 x00 The create_string_buffer function replaces the old c_buffer function which is still available as an alias To create a mutable memory block containing unicode characters of the C type wchar_t use the create_unicode_buffer function Calling functions continued Note that printf prints to the real standard output channel not to sys stdout so these examples will only work at the console prompt not from within IDLE or PythonWin printf libc printf printf b Hello s n b World Hello World 14 printf b Hello S n World Hello World 14 printf b d bottles of beer n 42 42 bottles of beer 19 printf b f bottles of beer n 42 5 Traceback most recent call last File stdin line 1 in module ArgumentError argument 2 TypeError Don t know how to convert parameter 2 As has been mentioned before all Python types except integers strings and bytes objects have to be wrapped in their corresponding ctypes type so that they can be converted to the required C data type printf b An int d a double f n 1234 c_double 3 14 An int 1234 a double 3 140000 31 Calling variadic functions On a lot of platforms calling variadic functions through ctypes is exactly the same as calling functions with a fixed number of parameters On some platforms and in particular ARM64 for Apple Platforms the calling convention for variadic functions is different than that for regular functions On those platforms it is required to specify the argtypes attribute for the regular non variadic function arguments libc printf argtypes ctypes c_char_p Because specifying the attribute does not inhibit portability it is advised to always specify argtypes for all variadic functions Calling functions with your own custom data types You can also customize ctypes argument conversion to allow instances of your own classes be used as function arguments ctypes looks for an _as_parameter_ attribute and uses this as the function argument The attribute must be an integer string bytes a ctypes instance or an object with an _as_parameter_ attribute class Bottles def __init__ self number self _as_parameter_ number bottles Bottles 42 printf b d bottles of beer n bottles 42 bottles of beer 19 If you don t want to store the instance s data in the _as_parameter_ instance variable you could define a property which makes the attribute available on request Specifying the required argument types function prototypes It is possible to specify the required argument types of functions exported from DLLs by setting the argtypes attribute argtypes must be a sequence of C data types the printf function is probably not a good example here because it takes a variable number and different types of parameters depending on the format string on the other hand this is quite handy to experiment with this feature printf argtypes c_char_p c_char_p c_int c_double printf b String s Int d Double f n b Hi 10 2 2 String Hi Int 10 Double 2 200000 37 Specifying a format protects against incompatible argument types just as a prototype for a C function and tries to convert the arguments to valid types printf b d d d 1 2 3 Traceback most recent call last File stdin line 1 in module ArgumentError argument 2 TypeError wrong type printf b s d f n b X 2 3 X 2 3 000000 13 If you have defined your own classes which you pass to function calls you have to implement a from_param class method for them to be able to use them in the argtypes sequence The from_param class method receives the Python object passed to the function call it should do a typecheck or whatever is needed to make sure this object is acceptable and then return the object itself its _as_parameter_ attribute or whatever you want to p,en
2069,ass as the C function argument in this case Again the result should be an integer string bytes a ctypes instance or an object with an _as_parameter_ attribute Return types By default functions are assumed to return the C int type Other return types can be specified by setting the restype attribute of the function object The C prototype of time is time_t time time_t Because time_t might be of a different type than the default return type int you should specify the restype attribute libc time restype c_time_t The argument types can be specified using argtypes libc time argtypes POINTER c_time_t To call the function with a NULL pointer as first argument use None print libc time None 1150640792 Here is a more advanced example it uses the strchr function which expects a string pointer and a char and returns a pointer to a string strchr libc strchr strchr b abcdef ord d 8059983 strchr restype c_char_p c_char_p is a pointer to a string strchr b abcdef ord d b def print strchr b abcdef ord x None If you want to avoid the ord x calls above you can set the argtypes attribute and the second argument will be converted from a single character Python bytes object into a C char strchr restype c_char_p strchr argtypes c_char_p c_char strchr b abcdef b d b def strchr b abcdef b def Traceback most recent call last ctypes ArgumentError argument 2 TypeError one character bytes bytearray or integer expected print strchr b abcdef b x None strchr b abcdef b d b def You can also use a callable Python object a function or a class for example as the restype attribute if the foreign function returns an integer The callable will be called with the integer the C function returns and the result of this call will be used as the result of your function call This is useful to check for error return values and automatically raise an exception GetModuleHandle windll kernel32 GetModuleHandleA def ValidHandle value if value 0 raise WinError return value GetModuleHandle restype ValidHandle GetModuleHandle None 486539264 GetModuleHandle something silly Traceback most recent call last File stdin line 1 in module File stdin line 3 in ValidHandle OSError Errno 126 The specified module could not be found WinError is a function which will call Windows FormatMessage api to get the string representation of an error code and returns an exception WinError takes an optional error code parameter if no one is used it calls GetLastError to retrieve it Please note that a much more powerful error checking mechanism is available through the errcheck attribute see the reference manual for details Passing pointers or passing parameters by reference Sometimes a C api function expects a pointer to a data type as parameter probably to write into the corresponding location or if the data is too large to be passed by value This is also known as passing parameters by reference ctypes exports the byref function which is used to pass parameters by reference The same effect can be achieved with the pointer function although pointer does a lot more work since it constructs a real pointer object so it is faster to use byref if you don t need the pointer object in Python itself i c_int f c_float s create_string_buffer b 000 32 print i value f value repr s value 0 0 0 b libc sscanf b 1 3 14 Hello b d f s byref i byref f s 3 print i value f value repr s value 1 3 1400001049 b Hello Structures and unions Structures and unions must derive from the Structure and Union base classes which are defined in the ctypes module Each subclass must define a _fields_ attribute _fields_ must be a list of 2 tuples containing a field name and a field type The field type must be a ctypes type like c_int or any other derived ctypes type structure union array pointer Here is a simple example of a POINT structure which contains two integers named x and y and also shows how to initialize a structure in the constructor from ctypes import class POINT Structure _fields_ x c_int y c_int point POINT 10 20 print point x point y 10 20 point POINT y 5 print point x point y 0 5 POINT 1 2 3 Traceback most recent call last ,en
2070,File stdin line 1 in module TypeError too many initializers You can however build much more complicated structures A structure can itself contain other structures by using a structure as a field type Here is a RECT structure which contains two POINTs named upperleft and lowerright class RECT Structure _fields_ upperleft POINT lowerright POINT rc RECT point print rc upperleft x rc upperleft y 0 5 print rc lowerright x rc lowerright y 0 0 Nested structures can also be initialized in the constructor in several ways r RECT POINT 1 2 POINT 3 4 r RECT 1 2 3 4 Field descriptor s can be retrieved from the class they are useful for debugging because they can provide useful information print POINT x Field type c_long ofs 0 size 4 print POINT y Field type c_long ofs 4 size 4 Warning ctypes does not support passing unions or structures with bit fields to functions by value While this may work on 32 bit x86 it s not guaranteed by the library to work in the general case Unions and structures with bit fields should always be passed to functions by pointer Structure union alignment and byte order By default Structure and Union fields are aligned in the same way the C compiler does it It is possible to override this behavior by specifying a _pack_ class attribute in the subclass definition This must be set to a positive integer and specifies the maximum alignment for the fields This is what pragma pack n also does in MSVC ctypes uses the native byte order for Structures and Unions To build structures with non native byte order you can use one of the BigEndianStructure LittleEndianStructure BigEndianUnion and LittleEndianUnion base classes These classes cannot contain pointer fields Bit fields in structures and unions It is possible to create structures and unions containing bit fields Bit fields are only possible for integer fields the bit width is specified as the third item in the _fields_ tuples class Int Structure _fields_ first_16 c_int 16 second_16 c_int 16 print Int first_16 Field type c_long ofs 0 0 bits 16 print Int second_16 Field type c_long ofs 0 16 bits 16 Arrays Arrays are sequences containing a fixed number of instances of the same type The recommended way to create array types is by multiplying a data type with a positive integer TenPointsArrayType POINT 10 Here is an example of a somewhat artificial data type a structure containing 4 POINTs among other stuff from ctypes import class POINT Structure _fields_ x c_int y c_int class MyStruct Structure _fields_ a c_int b c_float point_array POINT 4 print len MyStruct point_array 4 Instances are created in the usual way by calling the class arr TenPointsArrayType for pt in arr print pt x pt y The above code print a series of 0 0 lines because the array contents is initialized to zeros Initializers of the correct type can also be specified from ctypes import TenIntegers c_int 10 ii TenIntegers 1 2 3 4 5 6 7 8 9 10 print ii c_long_Array_10 object at 0x for i in ii print i end 1 2 3 4 5 6 7 8 9 10 Pointers Pointer instances are created by calling the pointer function on a ctypes type from ctypes import i c_int 42 pi pointer i Pointer instances have a contents attribute which returns the object to which the pointer points the i object above pi contents c_long 42 Note that ctypes does not have OOR original object return it constructs a new equivalent object each time you retrieve an attribute pi contents is i False pi contents is pi contents False Assigning another c_int instance to the pointer s contents attribute would cause the pointer to point to the memory location where this is stored i c_int 99 pi contents i pi contents c_long 99 Pointer instances can also be indexed with integers pi 0 99 Assigning to an integer index changes the pointed to value print i c_long 99 pi 0 22 print i c_long 22 It is also possible to use indexes different from 0 but you must know what you re doing just as in C You can access or change arbitrary memory locations Generally you only use this feature if you receive a pointer from a C function and you know that the pointer actually points to an array ,en
2071,instead of a single item Behind the scenes the pointer function does more than simply create pointer instances it has to create pointer types first This is done with the POINTER function which accepts any ctypes type and returns a new type PI POINTER c_int PI class ctypes LP_c_long PI 42 Traceback most recent call last File stdin line 1 in module TypeError expected c_long instead of int PI c_int 42 ctypes LP_c_long object at 0x Calling the pointer type without an argument creates a NULL pointer NULL pointers have a False boolean value null_ptr POINTER c_int print bool null_ptr False ctypes checks for NULL when dereferencing pointers but dereferencing invalid non NULL pointers would crash Python null_ptr 0 Traceback most recent call last ValueError NULL pointer access null_ptr 0 1234 Traceback most recent call last ValueError NULL pointer access Type conversions Usually ctypes does strict type checking This means if you have POINTER c_int in the argtypes list of a function or as the type of a member field in a structure definition only instances of exactly the same type are accepted There are some exceptions to this rule where ctypes accepts other objects For example you can pass compatible array instances instead of pointer types So for POINTER c_int ctypes accepts an array of c_int class Bar Structure _fields_ count c_int values POINTER c_int bar Bar bar values c_int 3 1 2 3 bar count 3 for i in range bar count print bar values i 1 2 3 In addition if a function argument is explicitly declared to be a pointer type such as POINTER c_int in argtypes an object of the pointed type c_int in this case can be passed to the function ctypes will apply the required byref conversion in this case automatically To set a POINTER type field to NULL you can assign None bar values None Sometimes you have instances of incompatible types In C you can cast one type into another type ctypes provides a cast function which can be used in the same way The Bar structure defined above accepts POINTER c_int pointers or c_int arrays for its values field but not instances of other types bar values c_byte 4 Traceback most recent call last File stdin line 1 in module TypeError incompatible types c_byte_Array_4 instance instead of LP_c_long instance For these cases the cast function is handy The cast function can be used to cast a ctypes instance into a pointer to a different ctypes data type cast takes two parameters a ctypes object that is or can be converted to a pointer of some kind and a ctypes pointer type It returns an instance of the second argument which references the same memory block as the first argument a c_byte 4 cast a POINTER c_int ctypes LP_c_long object at So cast can be used to assign to the values field of Bar the structure bar Bar bar values cast c_byte 4 POINTER c_int print bar values 0 0 Incomplete Types Incomplete Types are structures unions or arrays whose members are not yet specified In C they are specified by forward declarations which are defined later struct cell forward declaration struct cell char name struct cell next The straightforward translation into ctypes code would be this but it does not work class cell Structure _fields_ name c_char_p next POINTER cell Traceback most recent call last File stdin line 1 in module File stdin line 2 in cell NameError name cell is not defined because the new class cell is not available in the class statement itself In ctypes we can define the cell class and set the _fields_ attribute later after the class statement from ctypes import class cell Structure pass cell _fields_ name c_char_p next POINTER cell Let s try it We create two instances of cell and let them point to each other and finally follow the pointer chain a few times c1 cell c1 name b foo c2 cell c2 name b bar c1 next pointer c2 c2 next pointer c1 p c1 for i in range 8 print p name end p p next 0 foo bar foo bar foo bar foo bar Callback functions ctypes allows creating C callable function pointers from Python callables These are sometimes called callback functions First you must create a class for the callback function ,en
2072,The class knows the calling convention the return type and the number and types of arguments this function will receive The CFUNCTYPE factory function creates types for callback functions using the cdecl calling convention On Windows the WINFUNCTYPE factory function creates types for callback functions using the stdcall calling convention Both of these factory functions are called with the result type as first argument and the callback functions expected argument types as the remaining arguments I will present an example here which uses the standard C library s qsort function that is used to sort items with the help of a callback function qsort will be used to sort an array of integers IntArray5 c_int 5 ia IntArray5 5 1 7 33 99 qsort libc qsort qsort restype None qsort must be called with a pointer to the data to sort the number of items in the data array the size of one item and a pointer to the comparison function the callback The callback will then be called with two pointers to items and it must return a negative integer if the first item is smaller than the second a zero if they are equal and a positive integer otherwise So our callback function receives pointers to integers and must return an integer First we create the type for the callback function CMPFUNC CFUNCTYPE c_int POINTER c_int POINTER c_int To get started here is a simple callback that shows the values it gets passed def py_cmp_func a b print py_cmp_func a 0 b 0 return 0 cmp_func CMPFUNC py_cmp_func The result qsort ia len ia sizeof c_int cmp_func py_cmp_func 5 1 py_cmp_func 33 99 py_cmp_func 7 33 py_cmp_func 5 7 py_cmp_func 1 7 Now we can actually compare the two items and return a useful result def py_cmp_func a b print py_cmp_func a 0 b 0 return a 0 b 0 qsort ia len ia sizeof c_int CMPFUNC py_cmp_func py_cmp_func 5 1 py_cmp_func 33 99 py_cmp_func 7 33 py_cmp_func 1 7 py_cmp_func 5 7 As we can easily check our array is sorted now for i in ia print i end 1 5 7 33 99 The function factories can be used as decorator factories so we may as well write CFUNCTYPE c_int POINTER c_int POINTER c_int def py_cmp_func a b print py_cmp_func a 0 b 0 return a 0 b 0 qsort ia len ia sizeof c_int py_cmp_func py_cmp_func 5 1 py_cmp_func 33 99 py_cmp_func 7 33 py_cmp_func 1 7 py_cmp_func 5 7 Note Make sure you keep references to CFUNCTYPE objects as long as they are used from C code ctypes doesn t and if you don t they may be garbage collected crashing your program when a callback is made Also note that if the callback function is called in a thread created outside of Python s control e g by the foreign code that calls the callback ctypes creates a new dummy Python thread on every invocation This behavior is correct for most purposes but it means that values stored with threading local will not survive across different callbacks even when those calls are made from the same C thread Accessing values exported from dlls Some shared libraries not only export functions they also export variables An example in the Python library itself is the Py_Version Python runtime version number encoded in a single constant integer ctypes can access values like this with the in_dll class methods of the type pythonapi is a predefined symbol giving access to the Python C api version ctypes c_int in_dll ctypes pythonapi Py_Version print hex version value 0x30c00a0 An extended example which also demonstrates the use of pointers accesses the PyImport_FrozenModules pointer exported by Python Quoting the docs for that value This pointer is initialized to point to an array of _frozen records terminated by one whose members are all NULL or zero When a frozen module is imported it is searched in this table Third party code could play tricks with this to provide a dynamically created collection of frozen modules So manipulating this pointer could even prove useful To restrict the example size we show only how this table can be read with ctypes from ctypes import class struct_frozen Structure _fields_ name c_char_p code POINTER c_ubyte size c_int get_code POINTER c_ubyte Function pointer We have defined ,en
2073,the _frozen data type so we can get the pointer to the table FrozenTable POINTER struct_frozen table FrozenTable in_dll pythonapi _PyImport_FrozenBootstrap Since table is a pointer to the array of struct_frozen records we can iterate over it but we just have to make sure that our loop terminates because pointers have no size Sooner or later it would probably crash with an access violation or whatever so it s better to break out of the loop when we hit the NULL entry for item in table if item name is None break print item name decode ascii item size _frozen_importlib 31764 _frozen_importlib_external 41499 zipimport 12345 The fact that standard Python has a frozen module and a frozen package indicated by the negative size member is not well known it is only used for testing Try it out with import __hello__ for example Surprises There are some edges in ctypes where you might expect something other than what actually happens Consider the following example from ctypes import class POINT Structure _fields_ x c_int y c_int class RECT Structure _fields_ a POINT b POINT p1 POINT 1 2 p2 POINT 3 4 rc RECT p1 p2 print rc a x rc a y rc b x rc b y 1 2 3 4 now swap the two points rc a rc b rc b rc a print rc a x rc a y rc b x rc b y 3 4 3 4 Hm We certainly expected the last statement to print 3 4 1 2 What happened Here are the steps of the rc a rc b rc b rc a line above temp0 temp1 rc b rc a rc a temp0 rc b temp1 Note that temp0 and temp1 are objects still using the internal buffer of the rc object above So executing rc a temp0 copies the buffer contents of temp0 into rc s buffer This in turn changes the contents of temp1 So the last assignment rc b temp1 doesn t have the expected effect Keep in mind that retrieving sub objects from Structure Unions and Arrays doesn t copy the sub object instead it retrieves a wrapper object accessing the root object s underlying buffer Another example that may behave differently from what one would expect is this s c_char_p s value b abc def ghi s value b abc def ghi s value is s value False Note Objects instantiated from c_char_p can only have their value set to bytes or integers Why is it printing False ctypes instances are objects containing a memory block plus some descriptor s accessing the contents of the memory Storing a Python object in the memory block does not store the object itself instead the contents of the object is stored Accessing the contents again constructs a new Python object each time Variable sized data types ctypes provides some support for variable sized arrays and structures The resize function can be used to resize the memory buffer of an existing ctypes object The function takes the object as first argument and the requested size in bytes as the second argument The memory block cannot be made smaller than the natural memory block specified by the objects type a ValueError is raised if this is tried short_array c_short 4 print sizeof short_array 8 resize short_array 4 Traceback most recent call last ValueError minimum size is 8 resize short_array 32 sizeof short_array 32 sizeof type short_array 8 This is nice and fine but how would one access the additional elements contained in this array Since the type still only knows about 4 elements we get errors accessing other elements short_array 0 0 0 0 short_array 7 Traceback most recent call last IndexError invalid index Another way to use variable sized data types with ctypes is to use the dynamic nature of Python and re define the data type after the required size is already known on a case by case basis ctypes reference Finding shared libraries When programming in a compiled language shared libraries are accessed when compiling linking a program and when the program is run The purpose of the find_library function is to locate a library in a way similar to what the compiler or runtime loader does on platforms with several versions of a shared library the most recent should be loaded while the ctypes library loaders act like when a program is run and call the runtime loader directly The ctypes util module provides a function whic,en
2074,h can help to determine the library to load ctypes util find_library name Try to find a library and return a pathname name is the library name without any prefix like lib suffix like so dylib or version number this is the form used for the posix linker option l If no library can be found returns None The exact functionality is system dependent On Linux find_library tries to run external programs sbin ldconfig gcc objdump and ld to find the library file It returns the filename of the library file Changed in version 3 6 On Linux the value of the environment variable LD_LIBRARY_PATH is used when searching for libraries if a library cannot be found by any other means Here are some examples from ctypes util import find_library find_library m libm so 6 find_library c libc so 6 find_library bz2 libbz2 so 1 0 On macOS find_library tries several predefined naming schemes and paths to locate the library and returns a full pathname if successful from ctypes util import find_library find_library c usr lib libc dylib find_library m usr lib libm dylib find_library bz2 usr lib libbz2 dylib find_library AGL System Library Frameworks AGL framework AGL On Windows find_library searches along the system search path and returns the full pathname but since there is no predefined naming scheme a call like find_library c will fail and return None If wrapping a shared library with ctypes it may be better to determine the shared library name at development time and hardcode that into the wrapper module instead of using find_library to locate the library at runtime Loading shared libraries There are several ways to load shared libraries into the Python process One way is to instantiate one of the following classes class ctypes CDLL name mode DEFAULT_MODE handle None use_errno False use_last_error False winmode None Instances of this class represent loaded shared libraries Functions in these libraries use the standard C calling convention and are assumed to return int On Windows creating a CDLL instance may fail even if the DLL name exists When a dependent DLL of the loaded DLL is not found a OSError error is raised with the message WinError 126 The specified module could not be found This error message does not contain the name of the missing DLL because the Windows API does not return this information making this error hard to diagnose To resolve this error and determine which DLL is not found you need to find the list of dependent DLLs and determine which one is not found using Windows debugging and tracing tools Changed in version 3 12 The name parameter can now be a path like object See also Microsoft DUMPBIN tool A tool to find DLL dependents class ctypes OleDLL name mode DEFAULT_MODE handle None use_errno False use_last_error False winmode None Windows only Instances of this class represent loaded shared libraries functions in these libraries use the stdcall calling convention and are assumed to return the windows specific HRESULT code HRESULT values contain information specifying whether the function call failed or succeeded together with additional error code If the return value signals a failure an OSError is automatically raised Changed in version 3 3 WindowsError used to be raised which is now an alias of OSError Changed in version 3 12 The name parameter can now be a path like object class ctypes WinDLL name mode DEFAULT_MODE handle None use_errno False use_last_error False winmode None Windows only Instances of this class represent loaded shared libraries functions in these libraries use the stdcall calling convention and are assumed to return int by default Changed in version 3 12 The name parameter can now be a path like object The Python global interpreter lock is released before calling any function exported by these libraries and reacquired afterwards class ctypes PyDLL name mode DEFAULT_MODE handle None Instances of this class behave like CDLL instances except that the Python GIL is not released during the function call and after the function execution the Python error flag is checked If the error flag is set a Python exception ,en
2075,is raised Thus this is only useful to call Python C api functions directly Changed in version 3 12 The name parameter can now be a path like object All these classes can be instantiated by calling them with at least one argument the pathname of the shared library If you have an existing handle to an already loaded shared library it can be passed as the handle named parameter otherwise the underlying platforms dlopen or LoadLibrary function is used to load the library into the process and to get a handle to it The mode parameter can be used to specify how the library is loaded For details consult the dlopen 3 manpage On Windows mode is ignored On posix systems RTLD_NOW is always added and is not configurable The use_errno parameter when set to true enables a ctypes mechanism that allows accessing the system errno error number in a safe way ctypes maintains a thread local copy of the systems errno variable if you call foreign functions created with use_errno True then the errno value before the function call is swapped with the ctypes private copy the same happens immediately after the function call The function ctypes get_errno returns the value of the ctypes private copy and the function ctypes set_errno changes the ctypes private copy to a new value and returns the former value The use_last_error parameter when set to true enables the same mechanism for the Windows error code which is managed by the GetLastError and SetLastError Windows API functions ctypes get_last_error and ctypes set_last_error are used to request and change the ctypes private copy of the windows error code The winmode parameter is used on Windows to specify how the library is loaded since mode is ignored It takes any value that is valid for the Win32 API LoadLibraryEx flags parameter When omitted the default is to use the flags that result in the most secure DLL load which avoids issues such as DLL hijacking Passing the full path to the DLL is the safest way to ensure the correct library and dependencies are loaded Changed in version 3 8 Added winmode parameter ctypes RTLD_GLOBAL Flag to use as mode parameter On platforms where this flag is not available it is defined as the integer zero ctypes RTLD_LOCAL Flag to use as mode parameter On platforms where this is not available it is the same as RTLD_GLOBAL ctypes DEFAULT_MODE The default mode which is used to load shared libraries On OSX 10 3 this is RTLD_GLOBAL otherwise it is the same as RTLD_LOCAL Instances of these classes have no public methods Functions exported by the shared library can be accessed as attributes or by index Please note that accessing the function through an attribute caches the result and therefore accessing it repeatedly returns the same object each time On the other hand accessing it through an index returns a new object each time from ctypes import CDLL libc CDLL libc so 6 On Linux libc time libc time True libc time libc time False The following public attributes are available their name starts with an underscore to not clash with exported function names PyDLL _handle The system handle used to access the library PyDLL _name The name of the library passed in the constructor Shared libraries can also be loaded by using one of the prefabricated objects which are instances of the LibraryLoader class either by calling the LoadLibrary method or by retrieving the library as attribute of the loader instance class ctypes LibraryLoader dlltype Class which loads shared libraries dlltype should be one of the CDLL PyDLL WinDLL or OleDLL types __getattr__ has special behavior It allows loading a shared library by accessing it as attribute of a library loader instance The result is cached so repeated attribute accesses return the same library each time LoadLibrary name Load a shared library into the process and return it This method always returns a new instance of the library These prefabricated library loaders are available ctypes cdll Creates CDLL instances ctypes windll Windows only Creates WinDLL instances ctypes oledll Windows only Creates OleDLL instances ctypes pydll Creates PyDLL ,en
2076,instances For accessing the C Python api directly a ready to use Python shared library object is available ctypes pythonapi An instance of PyDLL that exposes Python C API functions as attributes Note that all these functions are assumed to return C int which is of course not always the truth so you have to assign the correct restype attribute to use these functions Loading a library through any of these objects raises an auditing event ctypes dlopen with string argument name the name used to load the library Accessing a function on a loaded library raises an auditing event ctypes dlsym with arguments library the library object and name the symbol s name as a string or integer In cases when only the library handle is available rather than the object accessing a function raises an auditing event ctypes dlsym handle with arguments handle the raw library handle and name Foreign functions As explained in the previous section foreign functions can be accessed as attributes of loaded shared libraries The function objects created in this way by default accept any number of arguments accept any ctypes data instances as arguments and return the default result type specified by the library loader They are instances of a private class class ctypes _FuncPtr Base class for C callable foreign functions Instances of foreign functions are also C compatible data types they represent C function pointers This behavior can be customized by assigning to special attributes of the foreign function object restype Assign a ctypes type to specify the result type of the foreign function Use None for void a function not returning anything It is possible to assign a callable Python object that is not a ctypes type in this case the function is assumed to return a C int and the callable will be called with this integer allowing further processing or error checking Using this is deprecated for more flexible post processing or error checking use a ctypes data type as restype and assign a callable to the errcheck attribute argtypes Assign a tuple of ctypes types to specify the argument types that the function accepts Functions using the stdcall calling convention can only be called with the same number of arguments as the length of this tuple functions using the C calling convention accept additional unspecified arguments as well When a foreign function is called each actual argument is passed to the from_param class method of the items in the argtypes tuple this method allows adapting the actual argument to an object that the foreign function accepts For example a c_char_p item in the argtypes tuple will convert a string passed as argument into a bytes object using ctypes conversion rules New It is now possible to put items in argtypes which are not ctypes types but each item must have a from_param method which returns a value usable as argument integer string ctypes instance This allows defining adapters that can adapt custom objects as function parameters errcheck Assign a Python function or another callable to this attribute The callable will be called with three or more arguments callable result func arguments result is what the foreign function returns as specified by the restype attribute func is the foreign function object itself this allows reusing the same callable object to check or post process the results of several functions arguments is a tuple containing the parameters originally passed to the function call this allows specializing the behavior on the arguments used The object that this function returns will be returned from the foreign function call but it can also check the result value and raise an exception if the foreign function call failed exception ctypes ArgumentError This exception is raised when a foreign function call cannot convert one of the passed arguments On Windows when a foreign function call raises a system exception for example due to an access violation it will be captured and replaced with a suitable Python exception Further an auditing event ctypes set_exception with argument code will be raised allowing an audit ho,en
2077,ok to replace the exception with its own Some ways to invoke foreign function calls may raise an auditing event ctypes call_function with arguments function pointer and arguments Function prototypes Foreign functions can also be created by instantiating function prototypes Function prototypes are similar to function prototypes in C they describe a function return type argument types calling convention without defining an implementation The factory functions must be called with the desired result type and the argument types of the function and can be used as decorator factories and as such be applied to functions through the wrapper syntax See Callback functions for examples ctypes CFUNCTYPE restype argtypes use_errno False use_last_error False The returned function prototype creates functions that use the standard C calling convention The function will release the GIL during the call If use_errno is set to true the ctypes private copy of the system errno variable is exchanged with the real errno value before and after the call use_last_error does the same for the Windows error code ctypes WINFUNCTYPE restype argtypes use_errno False use_last_error False Windows only The returned function prototype creates functions that use the stdcall calling convention The function will release the GIL during the call use_errno and use_last_error have the same meaning as above ctypes PYFUNCTYPE restype argtypes The returned function prototype creates functions that use the Python calling convention The function will not release the GIL during the call Function prototypes created by these factory functions can be instantiated in different ways depending on the type and number of the parameters in the call prototype address Returns a foreign function at the specified address which must be an integer prototype callable Create a C callable function a callback function from a Python callable prototype func_spec paramflags Returns a foreign function exported by a shared library func_spec must be a 2 tuple name_or_ordinal library The first item is the name of the exported function as string or the ordinal of the exported function as small integer The second item is the shared library instance prototype vtbl_index name paramflags iid Returns a foreign function that will call a COM method vtbl_index is the index into the virtual function table a small non negative integer name is name of the COM method iid is an optional pointer to the interface identifier which is used in extended error reporting COM methods use a special calling convention They require a pointer to the COM interface as first argument in addition to those parameters that are specified in the argtypes tuple The optional paramflags parameter creates foreign function wrappers with much more functionality than the features described above paramflags must be a tuple of the same length as argtypes Each item in this tuple contains further information about a parameter it must be a tuple containing one two or three items The first item is an integer containing a combination of direction flags for the parameter 1 Specifies an input parameter to the function 2 Output parameter The foreign function fills in a value 4 Input parameter which defaults to the integer zero The optional second item is the parameter name as string If this is specified the foreign function can be called with named parameters The optional third item is the default value for this parameter The following example demonstrates how to wrap the Windows MessageBoxW function so that it supports default parameters and named arguments The C declaration from the windows header file is this WINUSERAPI int WINAPI MessageBoxW HWND hWnd LPCWSTR lpText LPCWSTR lpCaption UINT uType Here is the wrapping with ctypes from ctypes import c_int WINFUNCTYPE windll from ctypes wintypes import HWND LPCWSTR UINT prototype WINFUNCTYPE c_int HWND LPCWSTR LPCWSTR UINT paramflags 1 hwnd 0 1 text Hi 1 caption Hello from ctypes 1 flags 0 MessageBox prototype MessageBoxW windll user32 paramflags The MessageBox foreign function can now be called in,en
2078, these ways MessageBox MessageBox text Spam spam spam MessageBox flags 2 text foo bar A second example demonstrates output parameters The win32 GetWindowRect function retrieves the dimensions of a specified window by copying them into RECT structure that the caller has to supply Here is the C declaration WINUSERAPI BOOL WINAPI GetWindowRect HWND hWnd LPRECT lpRect Here is the wrapping with ctypes from ctypes import POINTER WINFUNCTYPE windll WinError from ctypes wintypes import BOOL HWND RECT prototype WINFUNCTYPE BOOL HWND POINTER RECT paramflags 1 hwnd 2 lprect GetWindowRect prototype GetWindowRect windll user32 paramflags Functions with output parameters will automatically return the output parameter value if there is a single one or a tuple containing the output parameter values when there are more than one so the GetWindowRect function now returns a RECT instance when called Output parameters can be combined with the errcheck protocol to do further output processing and error checking The win32 GetWindowRect api function returns a BOOL to signal success or failure so this function could do the error checking and raises an exception when the api call failed def errcheck result func args if not result raise WinError return args GetWindowRect errcheck errcheck If the errcheck function returns the argument tuple it receives unchanged ctypes continues the normal processing it does on the output parameters If you want to return a tuple of window coordinates instead of a RECT instance you can retrieve the fields in the function and return them instead the normal processing will no longer take place def errcheck result func args if not result raise WinError rc args 1 return rc left rc top rc bottom rc right GetWindowRect errcheck errcheck Utility functions ctypes addressof obj Returns the address of the memory buffer as integer obj must be an instance of a ctypes type Raises an auditing event ctypes addressof with argument obj ctypes alignment obj_or_type Returns the alignment requirements of a ctypes type obj_or_type must be a ctypes type or instance ctypes byref obj offset Returns a light weight pointer to obj which must be an instance of a ctypes type offset defaults to zero and must be an integer that will be added to the internal pointer value byref obj offset corresponds to this C code char obj offset The returned object can only be used as a foreign function call parameter It behaves similar to pointer obj but the construction is a lot faster ctypes cast obj type This function is similar to the cast operator in C It returns a new instance of type which points to the same memory block as obj type must be a pointer type and obj must be an object that can be interpreted as a pointer ctypes create_string_buffer init_or_size size None This function creates a mutable character buffer The returned object is a ctypes array of c_char init_or_size must be an integer which specifies the size of the array or a bytes object which will be used to initialize the array items If a bytes object is specified as first argument the buffer is made one item larger than its length so that the last element in the array is a NUL termination character An integer can be passed as second argument which allows specifying the size of the array if the length of the bytes should not be used Raises an auditing event ctypes create_string_buffer with arguments init size ctypes create_unicode_buffer init_or_size size None This function creates a mutable unicode character buffer The returned object is a ctypes array of c_wchar init_or_size must be an integer which specifies the size of the array or a string which will be used to initialize the array items If a string is specified as first argument the buffer is made one item larger than the length of the string so that the last element in the array is a NUL termination character An integer can be passed as second argument which allows specifying the size of the array if the length of the string should not be used Raises an auditing event ctypes create_unicode_buffer with arguments init size ctypes DllCan,en
2079,UnloadNow Windows only This function is a hook which allows implementing in process COM servers with ctypes It is called from the DllCanUnloadNow function that the _ctypes extension dll exports ctypes DllGetClassObject Windows only This function is a hook which allows implementing in process COM servers with ctypes It is called from the DllGetClassObject function that the _ctypes extension dll exports ctypes util find_library name Try to find a library and return a pathname name is the library name without any prefix like lib suffix like so dylib or version number this is the form used for the posix linker option l If no library can be found returns None The exact functionality is system dependent ctypes util find_msvcrt Windows only return the filename of the VC runtime library used by Python and by the extension modules If the name of the library cannot be determined None is returned If you need to free memory for example allocated by an extension module with a call to the free void it is important that you use the function in the same library that allocated the memory ctypes FormatError code Windows only Returns a textual description of the error code code If no error code is specified the last error code is used by calling the Windows api function GetLastError ctypes GetLastError Windows only Returns the last error code set by Windows in the calling thread This function calls the Windows GetLastError function directly it does not return the ctypes private copy of the error code ctypes get_errno Returns the current value of the ctypes private copy of the system errno variable in the calling thread Raises an auditing event ctypes get_errno with no arguments ctypes get_last_error Windows only returns the current value of the ctypes private copy of the system LastError variable in the calling thread Raises an auditing event ctypes get_last_error with no arguments ctypes memmove dst src count Same as the standard C memmove library function copies count bytes from src to dst dst and src must be integers or ctypes instances that can be converted to pointers ctypes memset dst c count Same as the standard C memset library function fills the memory block at address dst with count bytes of value c dst must be an integer specifying an address or a ctypes instance ctypes POINTER type Create and return a new ctypes pointer type Pointer types are cached and reused internally so calling this function repeatedly is cheap type must be a ctypes type ctypes pointer obj Create a new pointer instance pointing to obj The returned object is of the type POINTER type obj Note If you just want to pass a pointer to an object to a foreign function call you should use byref obj which is much faster ctypes resize obj size This function resizes the internal memory buffer of obj which must be an instance of a ctypes type It is not possible to make the buffer smaller than the native size of the objects type as given by sizeof type obj but it is possible to enlarge the buffer ctypes set_errno value Set the current value of the ctypes private copy of the system errno variable in the calling thread to value and return the previous value Raises an auditing event ctypes set_errno with argument errno ctypes set_last_error value Windows only set the current value of the ctypes private copy of the system LastError variable in the calling thread to value and return the previous value Raises an auditing event ctypes set_last_error with argument error ctypes sizeof obj_or_type Returns the size in bytes of a ctypes type or instance memory buffer Does the same as the C sizeof operator ctypes string_at address size 1 This function returns the C string starting at memory address address as a bytes object If size is specified it is used as size otherwise the string is assumed to be zero terminated Raises an auditing event ctypes string_at with arguments address size ctypes WinError code None descr None Windows only this function is probably the worst named thing in ctypes It creates an instance of OSError If code is not specified GetLastError is called to determine ,en
2080,the error code If descr is not specified FormatError is called to get a textual description of the error Changed in version 3 3 An instance of WindowsError used to be created which is now an alias of OSError ctypes wstring_at address size 1 This function returns the wide character string starting at memory address address as a string If size is specified it is used as the number of characters of the string otherwise the string is assumed to be zero terminated Raises an auditing event ctypes wstring_at with arguments address size Data types class ctypes _CData This non public class is the common base class of all ctypes data types Among other things all ctypes type instances contain a memory block that hold C compatible data the address of the memory block is returned by the addressof helper function Another instance variable is exposed as _objects this contains other Python objects that need to be kept alive in case the memory block contains pointers Common methods of ctypes data types these are all class methods to be exact they are methods of the metaclass from_buffer source offset This method returns a ctypes instance that shares the buffer of the source object The source object must support the writeable buffer interface The optional offset parameter specifies an offset into the source buffer in bytes the default is zero If the source buffer is not large enough a ValueError is raised Raises an auditing event ctypes cdata buffer with arguments pointer size offset from_buffer_copy source offset This method creates a ctypes instance copying the buffer from the source object buffer which must be readable The optional offset parameter specifies an offset into the source buffer in bytes the default is zero If the source buffer is not large enough a ValueError is raised Raises an auditing event ctypes cdata buffer with arguments pointer size offset from_address address This method returns a ctypes type instance using the memory specified by address which must be an integer This method and others that indirectly call this method raises an auditing event ctypes cdata with argument address from_param obj This method adapts obj to a ctypes type It is called with the actual object used in a foreign function call when the type is present in the foreign function s argtypes tuple it must return an object that can be used as a function call parameter All ctypes data types have a default implementation of this classmethod that normally returns obj if that is an instance of the type Some types accept other objects as well in_dll library name This method returns a ctypes type instance exported by a shared library name is the name of the symbol that exports the data library is the loaded shared library Common instance variables of ctypes data types _b_base_ Sometimes ctypes data instances do not own the memory block they contain instead they share part of the memory block of a base object The _b_base_ read only member is the root ctypes object that owns the memory block _b_needsfree_ This read only variable is true when the ctypes data instance has allocated the memory block itself false otherwise _objects This member is either None or a dictionary containing Python objects that need to be kept alive so that the memory block contents is kept valid This object is only exposed for debugging never modify the contents of this dictionary Fundamental data types class ctypes _SimpleCData This non public class is the base class of all fundamental ctypes data types It is mentioned here because it contains the common attributes of the fundamental ctypes data types _SimpleCData is a subclass of _CData so it inherits their methods and attributes ctypes data types that are not and do not contain pointers can now be pickled Instances have a single attribute value This attribute contains the actual value of the instance For integer and pointer types it is an integer for character types it is a single character bytes object or string for character pointer types it is a Python bytes object or string When the value attribute is retrieved from a ctypes in,en
2081,stance usually a new object is returned each time ctypes does not implement original object return always a new object is constructed The same is true for all other ctypes object instances Fundamental data types when returned as foreign function call results or for example by retrieving structure field members or array items are transparently converted to native Python types In other words if a foreign function has a restype of c_char_p you will always receive a Python bytes object not a c_char_p instance Subclasses of fundamental data types do not inherit this behavior So if a foreign functions restype is a subclass of c_void_p you will receive an instance of this subclass from the function call Of course you can get the value of the pointer by accessing the value attribute These are the fundamental ctypes data types class ctypes c_byte Represents the C signed char datatype and interprets the value as small integer The constructor accepts an optional integer initializer no overflow checking is done class ctypes c_char Represents the C char datatype and interprets the value as a single character The constructor accepts an optional string initializer the length of the string must be exactly one character class ctypes c_char_p Represents the C char datatype when it points to a zero terminated string For a general character pointer that may also point to binary data POINTER c_char must be used The constructor accepts an integer address or a bytes object class ctypes c_double Represents the C double datatype The constructor accepts an optional float initializer class ctypes c_longdouble Represents the C long double datatype The constructor accepts an optional float initializer On platforms where sizeof long double sizeof double it is an alias to c_double class ctypes c_float Represents the C float datatype The constructor accepts an optional float initializer class ctypes c_int Represents the C signed int datatype The constructor accepts an optional integer initializer no overflow checking is done On platforms where sizeof int sizeof long it is an alias to c_long class ctypes c_int8 Represents the C 8 bit signed int datatype Usually an alias for c_byte class ctypes c_int16 Represents the C 16 bit signed int datatype Usually an alias for c_short class ctypes c_int32 Represents the C 32 bit signed int datatype Usually an alias for c_int class ctypes c_int64 Represents the C 64 bit signed int datatype Usually an alias for c_longlong class ctypes c_long Represents the C signed long datatype The constructor accepts an optional integer initializer no overflow checking is done class ctypes c_longlong Represents the C signed long long datatype The constructor accepts an optional integer initializer no overflow checking is done class ctypes c_short Represents the C signed short datatype The constructor accepts an optional integer initializer no overflow checking is done class ctypes c_size_t Represents the C size_t datatype class ctypes c_ssize_t Represents the C ssize_t datatype New in version 3 2 class ctypes c_time_t Represents the C time_t datatype New in version 3 12 class ctypes c_ubyte Represents the C unsigned char datatype it interprets the value as small integer The constructor accepts an optional integer initializer no overflow checking is done class ctypes c_uint Represents the C unsigned int datatype The constructor accepts an optional integer initializer no overflow checking is done On platforms where sizeof int sizeof long it is an alias for c_ulong class ctypes c_uint8 Represents the C 8 bit unsigned int datatype Usually an alias for c_ubyte class ctypes c_uint16 Represents the C 16 bit unsigned int datatype Usually an alias for c_ushort class ctypes c_uint32 Represents the C 32 bit unsigned int datatype Usually an alias for c_uint class ctypes c_uint64 Represents the C 64 bit unsigned int datatype Usually an alias for c_ulonglong class ctypes c_ulong Represents the C unsigned long datatype The constructor accepts an optional integer initializer no overflow checking is done class ctypes c_ulonglong Represents the C un,en
2082,signed long long datatype The constructor accepts an optional integer initializer no overflow checking is done class ctypes c_ushort Represents the C unsigned short datatype The constructor accepts an optional integer initializer no overflow checking is done class ctypes c_void_p Represents the C void type The value is represented as integer The constructor accepts an optional integer initializer class ctypes c_wchar Represents the C wchar_t datatype and interprets the value as a single character unicode string The constructor accepts an optional string initializer the length of the string must be exactly one character class ctypes c_wchar_p Represents the C wchar_t datatype which must be a pointer to a zero terminated wide character string The constructor accepts an integer address or a string class ctypes c_bool Represent the C bool datatype more accurately _Bool from C99 Its value can be True or False and the constructor accepts any object that has a truth value class ctypes HRESULT Windows only Represents a HRESULT value which contains success or error information for a function or method call class ctypes py_object Represents the C PyObject datatype Calling this without an argument creates a NULL PyObject pointer The ctypes wintypes module provides quite some other Windows specific data types for example HWND WPARAM or DWORD Some useful structures like MSG or RECT are also defined Structured data types class ctypes Union args kw Abstract base class for unions in native byte order class ctypes BigEndianUnion args kw Abstract base class for unions in big endian byte order New in version 3 11 class ctypes LittleEndianUnion args kw Abstract base class for unions in little endian byte order New in version 3 11 class ctypes BigEndianStructure args kw Abstract base class for structures in big endian byte order class ctypes LittleEndianStructure args kw Abstract base class for structures in little endian byte order Structures and unions with non native byte order cannot contain pointer type fields or any other data types containing pointer type fields class ctypes Structure args kw Abstract base class for structures in native byte order Concrete structure and union types must be created by subclassing one of these types and at least define a _fields_ class variable ctypes will create descriptor s which allow reading and writing the fields by direct attribute accesses These are the _fields_ A sequence defining the structure fields The items must be 2 tuples or 3 tuples The first item is the name of the field the second item specifies the type of the field it can be any ctypes data type For integer type fields like c_int a third optional item can be given It must be a small positive integer defining the bit width of the field Field names must be unique within one structure or union This is not checked only one field can be accessed when names are repeated It is possible to define the _fields_ class variable after the class statement that defines the Structure subclass this allows creating data types that directly or indirectly reference themselves class List Structure pass List _fields_ pnext POINTER List The _fields_ class variable must however be defined before the type is first used an instance is created sizeof is called on it and so on Later assignments to the _fields_ class variable will raise an AttributeError It is possible to define sub subclasses of structure types they inherit the fields of the base class plus the _fields_ defined in the sub subclass if any _pack_ An optional small integer that allows overriding the alignment of structure fields in the instance _pack_ must already be defined when _fields_ is assigned otherwise it will have no effect Setting this attribute to 0 is the same as not setting it at all _anonymous_ An optional sequence that lists the names of unnamed anonymous fields _anonymous_ must be already defined when _fields_ is assigned otherwise it will have no effect The fields listed in this variable must be structure or union type fields ctypes will create descriptors in the structure type tha,en
2083,t allows accessing the nested fields directly without the need to create the structure or union field Here is an example type Windows class _U Union _fields_ lptdesc POINTER TYPEDESC lpadesc POINTER ARRAYDESC hreftype HREFTYPE class TYPEDESC Structure _anonymous_ u _fields_ u _U vt VARTYPE The TYPEDESC structure describes a COM data type the vt field specifies which one of the union fields is valid Since the u field is defined as anonymous field it is now possible to access the members directly off the TYPEDESC instance td lptdesc and td u lptdesc are equivalent but the former is faster since it does not need to create a temporary union instance td TYPEDESC td vt VT_PTR td lptdesc POINTER some_type td u lptdesc POINTER some_type It is possible to define sub subclasses of structures they inherit the fields of the base class If the subclass definition has a separate _fields_ variable the fields specified in this are appended to the fields of the base class Structure and union constructors accept both positional and keyword arguments Positional arguments are used to initialize member fields in the same order as they are appear in _fields_ Keyword arguments in the constructor are interpreted as attribute assignments so they will initialize _fields_ with the same name or create new attributes for names not present in _fields_ Arrays and pointers class ctypes Array args Abstract base class for arrays The recommended way to create concrete array types is by multiplying any ctypes data type with a non negative integer Alternatively you can subclass this type and define _length_ and _type_ class variables Array elements can be read and written using standard subscript and slice accesses for slice reads the resulting object is not itself an Array _length_ A positive integer specifying the number of elements in the array Out of range subscripts result in an IndexError Will be returned by len _type_ Specifies the type of each element in the array Array subclass constructors accept positional arguments used to initialize the elements in order class ctypes _Pointer Private abstract base class for pointers Concrete pointer types are created by calling POINTER with the type that will be pointed to this is done automatically by pointer If a pointer points to an array its elements can be read and written using standard subscript and slice accesses Pointer objects have no size so len will raise TypeError Negative subscripts will read from the memory before the pointer as in C and out of range subscripts will probably crash with an access violation if you re lucky _type_ Specifies the type pointed to contents Returns the object to which to pointer points Assigning to this attribute changes the pointer to point to the assigned object,en
2084,Cell Objects Cell objects are used to implement variables referenced by multiple scopes For each such variable a cell object is created to store the value the local variables of each stack frame that references the value contains a reference to the cells from outer scopes which also use that variable When the value is accessed the value contained in the cell is used instead of the cell object itself This de referencing of the cell object requires support from the generated byte code these are not automatically de referenced when accessed Cell objects are not likely to be useful elsewhere type PyCellObject The C structure used for cell objects PyTypeObject PyCell_Type The type object corresponding to cell objects int PyCell_Check PyObject ob Return true if ob is a cell object ob must not be NULL This function always succeeds PyObject PyCell_New PyObject ob Return value New reference Create and return a new cell object containing the value ob The parameter may be NULL PyObject PyCell_Get PyObject cell Return value New reference Return the contents of the cell cell PyObject PyCell_GET PyObject cell Return value Borrowed reference Return the contents of the cell cell but without checking that cell is non NULL and a cell object int PyCell_Set PyObject cell PyObject value Set the contents of the cell object cell to value This releases the reference to any current content of the cell value may be NULL cell must be non NULL if it is not a cell object 1 will be returned On success 0 will be returned void PyCell_SET PyObject cell PyObject value Sets the value of the cell object cell to value No reference counts are adjusted and no checks are made for safety cell must be non NULL and must be a cell object,en
2085,imaplib IMAP4 protocol client Source code Lib imaplib py This module defines three classes IMAP4 IMAP4_SSL and IMAP4_stream which encapsulate a connection to an IMAP4 server and implement a large subset of the IMAP4rev1 client protocol as defined in RFC 2060 It is backward compatible with IMAP4 RFC 1730 servers but note that the STATUS command is not supported in IMAP4 Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information Three classes are provided by the imaplib module IMAP4 is the base class class imaplib IMAP4 host port IMAP4_PORT timeout None This class implements the actual IMAP4 protocol The connection is created and protocol version IMAP4 or IMAP4rev1 is determined when the instance is initialized If host is not specified the local host is used If port is omitted the standard IMAP4 port 143 is used The optional timeout parameter specifies a timeout in seconds for the connection attempt If timeout is not given or is None the global default socket timeout is used The IMAP4 class supports the with statement When used like this the IMAP4 LOGOUT command is issued automatically when the with statement exits E g from imaplib import IMAP4 with IMAP4 domain org as M M noop OK b Nothing Accomplished d25if65hy903weo 87 Changed in version 3 5 Support for the with statement was added Changed in version 3 9 The optional timeout parameter was added Three exceptions are defined as attributes of the IMAP4 class exception IMAP4 error Exception raised on any errors The reason for the exception is passed to the constructor as a string exception IMAP4 abort IMAP4 server errors cause this exception to be raised This is a sub class of IMAP4 error Note that closing the instance and instantiating a new one will usually allow recovery from this exception exception IMAP4 readonly This exception is raised when a writable mailbox has its status changed by the server This is a sub class of IMAP4 error Some other client now has write permission and the mailbox will need to be re opened to re obtain write permission There s also a subclass for secure connections class imaplib IMAP4_SSL host port IMAP4_SSL_PORT ssl_context None timeout None This is a subclass derived from IMAP4 that connects over an SSL encrypted socket to use this class you need a socket module that was compiled with SSL support If host is not specified the local host is used If port is omitted the standard IMAP4 over SSL port 993 is used ssl_context is a ssl SSLContext object which allows bundling SSL configuration options certificates and private keys into a single potentially long lived structure Please read Security considerations for best practices The optional timeout parameter specifies a timeout in seconds for the connection attempt If timeout is not given or is None the global default socket timeout is used Changed in version 3 3 ssl_context parameter was added Changed in version 3 4 The class now supports hostname check with ssl SSLContext check_hostname and Server Name Indication see ssl HAS_SNI Changed in version 3 9 The optional timeout parameter was added Changed in version 3 12 The deprecated keyfile and certfile parameters have been removed The second subclass allows for connections created by a child process class imaplib IMAP4_stream command This is a subclass derived from IMAP4 that connects to the stdin stdout file descriptors created by passing command to subprocess Popen The following utility functions are defined imaplib Internaldate2tuple datestr Parse an IMAP4 INTERNALDATE string and return corresponding local time The return value is a time struct_time tuple or None if the string has wrong format imaplib Int2AP num Converts an integer into a bytes representation using characters from the set A P imaplib ParseFlags flagstr Converts an IMAP4 FLAGS response to a tuple of individual flags imaplib Time2Internaldate date_time Convert date_time to an IMAP4 INTERNALDATE representation The return value is a string in the form DD ,en
2086,Mmm YYYY HH MM SS HHMM including double quotes The date_time argument can be a number int or float representing seconds since epoch as returned by time time a 9 tuple representing local time an instance of time struct_time as returned by time localtime an aware instance of datetime datetime or a double quoted string In the last case it is assumed to already be in the correct format Note that IMAP4 message numbers change as the mailbox changes in particular after an EXPUNGE command performs deletions the remaining messages are renumbered So it is highly advisable to use UIDs instead with the UID command At the end of the module there is a test section that contains a more extensive example of usage See also Documents describing the protocol sources for servers implementing it by the University of Washington s IMAP Information Center can all be found at Source Code https github com uw imap imap Not Maintained IMAP4 Objects All IMAP4rev1 commands are represented by methods of the same name either uppercase or lowercase All arguments to commands are converted to strings except for AUTHENTICATE and the last argument to APPEND which is passed as an IMAP4 literal If necessary the string contains IMAP4 protocol sensitive characters and isn t enclosed with either parentheses or double quotes each string is quoted However the password argument to the LOGIN command is always quoted If you want to avoid having an argument string quoted eg the flags argument to STORE then enclose the string in parentheses eg r Deleted Each command returns a tuple type data where type is usually OK or NO and data is either the text from the command response or mandated results from the command Each data is either a bytes or a tuple If a tuple then the first part is the header of the response and the second part contains the data ie literal value The message_set options to commands below is a string specifying one or more messages to be acted upon It may be a simple message number 1 a range of message numbers 2 4 or a group of non contiguous ranges separated by commas 1 3 6 9 A range can contain an asterisk to indicate an infinite upper bound 3 An IMAP4 instance has the following methods IMAP4 append mailbox flags date_time message Append message to named mailbox IMAP4 authenticate mechanism authobject Authenticate command requires response processing mechanism specifies which authentication mechanism is to be used it should appear in the instance variable capabilities in the form AUTH mechanism authobject must be a callable object data authobject response It will be called to process server continuation responses the response argument it is passed will be bytes It should return bytes data that will be base64 encoded and sent to the server It should return None if the client abort response should be sent instead Changed in version 3 5 string usernames and passwords are now encoded to utf 8 instead of being limited to ASCII IMAP4 check Checkpoint mailbox on server IMAP4 close Close currently selected mailbox Deleted messages are removed from writable mailbox This is the recommended command before LOGOUT IMAP4 copy message_set new_mailbox Copy message_set messages onto end of new_mailbox IMAP4 create mailbox Create new mailbox named mailbox IMAP4 delete mailbox Delete old mailbox named mailbox IMAP4 deleteacl mailbox who Delete the ACLs remove any rights set for who on mailbox IMAP4 enable capability Enable capability see RFC 5161 Most capabilities do not need to be enabled Currently only the UTF8 ACCEPT capability is supported see RFC 6855 New in version 3 5 The enable method itself and RFC 6855 support IMAP4 expunge Permanently remove deleted items from selected mailbox Generates an EXPUNGE response for each deleted message Returned data contains a list of EXPUNGE message numbers in order received IMAP4 fetch message_set message_parts Fetch parts of messages message_parts should be a string of message part names enclosed within parentheses eg UID BODY TEXT Returned data are tuples of message part envelope and data IMAP4 getacl mailbox Get the ACL s for,en
2087, mailbox The method is non standard but is supported by the Cyrus server IMAP4 getannotation mailbox entry attribute Retrieve the specified ANNOTATION s for mailbox The method is non standard but is supported by the Cyrus server IMAP4 getquota root Get the quota root s resource usage and limits This method is part of the IMAP4 QUOTA extension defined in rfc2087 IMAP4 getquotaroot mailbox Get the list of quota roots for the named mailbox This method is part of the IMAP4 QUOTA extension defined in rfc2087 IMAP4 list directory pattern List mailbox names in directory matching pattern directory defaults to the top level mail folder and pattern defaults to match anything Returned data contains a list of LIST responses IMAP4 login user password Identify the client using a plaintext password The password will be quoted IMAP4 login_cram_md5 user password Force use of CRAM MD5 authentication when identifying the client to protect the password Will only work if the server CAPABILITY response includes the phrase AUTH CRAM MD5 IMAP4 logout Shutdown connection to server Returns server BYE response Changed in version 3 8 The method no longer ignores silently arbitrary exceptions IMAP4 lsub directory pattern List subscribed mailbox names in directory matching pattern directory defaults to the top level directory and pattern defaults to match any mailbox Returned data are tuples of message part envelope and data IMAP4 myrights mailbox Show my ACLs for a mailbox i e the rights that I have on mailbox IMAP4 namespace Returns IMAP namespaces as defined in RFC 2342 IMAP4 noop Send NOOP to server IMAP4 open host port timeout None Opens socket to port at host The optional timeout parameter specifies a timeout in seconds for the connection attempt If timeout is not given or is None the global default socket timeout is used Also note that if the timeout parameter is set to be zero it will raise a ValueError to reject creating a non blocking socket This method is implicitly called by the IMAP4 constructor The connection objects established by this method will be used in the IMAP4 read IMAP4 readline IMAP4 send and IMAP4 shutdown methods You may override this method Raises an auditing event imaplib open with arguments self host port Changed in version 3 9 The timeout parameter was added IMAP4 partial message_num message_part start length Fetch truncated part of a message Returned data is a tuple of message part envelope and data IMAP4 proxyauth user Assume authentication as user Allows an authorised administrator to proxy into any user s mailbox IMAP4 read size Reads size bytes from the remote server You may override this method IMAP4 readline Reads one line from the remote server You may override this method IMAP4 recent Prompt server for an update Returned data is None if no new messages else value of RECENT response IMAP4 rename oldmailbox newmailbox Rename mailbox named oldmailbox to newmailbox IMAP4 response code Return data for response code if received or None Returns the given code instead of the usual type IMAP4 search charset criterion Search mailbox for matching messages charset may be None in which case no CHARSET will be specified in the request to the server The IMAP protocol requires that at least one criterion be specified an exception will be raised when the server returns an error charset must be None if the UTF8 ACCEPT capability was enabled using the enable command Example M is a connected IMAP4 instance typ msgnums M search None FROM LDJ or typ msgnums M search None FROM LDJ IMAP4 select mailbox INBOX readonly False Select a mailbox Returned data is the count of messages in mailbox EXISTS response The default mailbox is INBOX If the readonly flag is set modifications to the mailbox are not allowed IMAP4 send data Sends data to the remote server You may override this method Raises an auditing event imaplib send with arguments self data IMAP4 setacl mailbox who what Set an ACL for mailbox The method is non standard but is supported by the Cyrus server IMAP4 setannotation mailbox entry attribute Set ANNOTATION s for mailbox The me,en
2088,thod is non standard but is supported by the Cyrus server IMAP4 setquota root limits Set the quota root s resource limits This method is part of the IMAP4 QUOTA extension defined in rfc2087 IMAP4 shutdown Close connection established in open This method is implicitly called by IMAP4 logout You may override this method IMAP4 socket Returns socket instance used to connect to server IMAP4 sort sort_criteria charset search_criterion The sort command is a variant of search with sorting semantics for the results Returned data contains a space separated list of matching message numbers Sort has two arguments before the search_criterion argument s a parenthesized list of sort_criteria and the searching charset Note that unlike search the searching charset argument is mandatory There is also a uid sort command which corresponds to sort the way that uid search corresponds to search The sort command first searches the mailbox for messages that match the given searching criteria using the charset argument for the interpretation of strings in the searching criteria It then returns the numbers of matching messages This is an IMAP4rev1 extension command IMAP4 starttls ssl_context None Send a STARTTLS command The ssl_context argument is optional and should be a ssl SSLContext object This will enable encryption on the IMAP connection Please read Security considerations for best practices New in version 3 2 Changed in version 3 4 The method now supports hostname check with ssl SSLContext check_hostname and Server Name Indication see ssl HAS_SNI IMAP4 status mailbox names Request named status conditions for mailbox IMAP4 store message_set command flag_list Alters flag dispositions for messages in mailbox command is specified by section 6 4 6 of RFC 2060 as being one of FLAGS FLAGS or FLAGS optionally with a suffix of SILENT For example to set the delete flag on all messages typ data M search None ALL for num in data 0 split M store num FLAGS Deleted M expunge Note Creating flags containing for example test violates RFC 3501 the IMAP protocol However imaplib has historically allowed creation of such tags and popular IMAP servers such as Gmail accept and produce such flags There are non Python programs which also create such tags Although it is an RFC violation and IMAP clients and servers are supposed to be strict imaplib nonetheless continues to allow such tags to be created for backward compatibility reasons and as of Python 3 6 handles them if they are sent from the server since this improves real world compatibility IMAP4 subscribe mailbox Subscribe to new mailbox IMAP4 thread threading_algorithm charset search_criterion The thread command is a variant of search with threading semantics for the results Returned data contains a space separated list of thread members Thread members consist of zero or more messages numbers delimited by spaces indicating successive parent and child Thread has two arguments before the search_criterion argument s a threading_algorithm and the searching charset Note that unlike search the searching charset argument is mandatory There is also a uid thread command which corresponds to thread the way that uid search corresponds to search The thread command first searches the mailbox for messages that match the given searching criteria using the charset argument for the interpretation of strings in the searching criteria It then returns the matching messages threaded according to the specified threading algorithm This is an IMAP4rev1 extension command IMAP4 uid command arg Execute command args with messages identified by UID rather than message number Returns response appropriate to command At least one argument must be supplied if none are provided the server will return an error and an exception will be raised IMAP4 unsubscribe mailbox Unsubscribe from old mailbox IMAP4 unselect imaplib IMAP4 unselect frees server s resources associated with the selected mailbox and returns the server to the authenticated state This command performs the same actions as imaplib IMAP4 close except that no messages are permanently ,en
2089,removed from the currently selected mailbox New in version 3 9 IMAP4 xatom name Allow simple extension commands notified by server in CAPABILITY response The following attributes are defined on instances of IMAP4 IMAP4 PROTOCOL_VERSION The most recent supported protocol in the CAPABILITY response from the server IMAP4 debug Integer value to control debugging output The initialize value is taken from the module variable Debug Values greater than three trace each command IMAP4 utf8_enabled Boolean value that is normally False but is set to True if an enable command is successfully issued for the UTF8 ACCEPT capability New in version 3 5 IMAP4 Example Here is a minimal example without error checking that opens a mailbox and retrieves and prints all messages import getpass imaplib M imaplib IMAP4 M login getpass getuser getpass getpass M select typ data M search None ALL for num in data 0 split typ data M fetch num RFC822 print Message s n s n num data 0 1 M close M logout,en
2090,configparser Configuration file parser Source code Lib configparser py This module provides the ConfigParser class which implements a basic configuration language which provides a structure similar to what s found in Microsoft Windows INI files You can use this to write Python programs which can be customized by end users easily Note This library does not interpret or write the value type prefixes used in the Windows Registry extended version of INI syntax See also Module tomllib TOML is a well specified format for application configuration files It is specifically designed to be an improved version of INI Module shlex Support for creating Unix shell like mini languages which can also be used for application configuration files Module json The json module implements a subset of JavaScript syntax which is sometimes used for configuration but does not support comments Quick Start Let s take a very basic configuration file that looks like this DEFAULT ServerAliveInterval 45 Compression yes CompressionLevel 9 ForwardX11 yes forge example User hg topsecret server example Port 50022 ForwardX11 no The structure of INI files is described in the following section Essentially the file consists of sections each of which contains keys with values configparser classes can read and write such files Let s start by creating the above configuration file programmatically import configparser config configparser ConfigParser config DEFAULT ServerAliveInterval 45 Compression yes CompressionLevel 9 config forge example config forge example User hg config topsecret server example topsecret config topsecret server example topsecret Port 50022 mutates the parser topsecret ForwardX11 no same here config DEFAULT ForwardX11 yes with open example ini w as configfile config write configfile As you can see we can treat a config parser much like a dictionary There are differences outlined later but the behavior is very close to what you would expect from a dictionary Now that we have created and saved a configuration file let s read it back and explore the data it holds config configparser ConfigParser config sections config read example ini example ini config sections forge example topsecret server example forge example in config True python org in config False config forge example User hg config DEFAULT Compression yes topsecret config topsecret server example topsecret ForwardX11 no topsecret Port 50022 for key in config forge example print key user compressionlevel serveraliveinterval compression forwardx11 config forge example ForwardX11 yes As we can see above the API is pretty straightforward The only bit of magic involves the DEFAULT section which provides default values for all other sections 1 Note also that keys in sections are case insensitive and stored in lowercase 1 It is possible to read several configurations into a single ConfigParser where the most recently added configuration has the highest priority Any conflicting keys are taken from the more recent configuration while the previously existing keys are retained another_config configparser ConfigParser another_config read example ini example ini another_config topsecret server example Port 50022 another_config read_string topsecret server example nPort 48484 another_config topsecret server example Port 48484 another_config read_dict topsecret server example Port 21212 another_config topsecret server example Port 21212 another_config topsecret server example ForwardX11 no This behaviour is equivalent to a ConfigParser read call with several files passed to the filenames parameter Supported Datatypes Config parsers do not guess datatypes of values in configuration files always storing them internally as strings This means that if you need other datatypes you should convert on your own int topsecret Port 50022 float topsecret CompressionLevel 9 0 Since this task is so common config parsers provide a range of handy getter methods to handle integers floats and booleans The last one is the most interesting because simply passing the value to bool would do no good since bool False is still,en
2091, True This is why config parsers also provide getboolean This method is case insensitive and recognizes Boolean values from yes no on off true false and 1 0 1 For example topsecret getboolean ForwardX11 False config forge example getboolean ForwardX11 True config getboolean forge example Compression True Apart from getboolean config parsers also provide equivalent getint and getfloat methods You can register your own converters and customize the provided ones 1 Fallback Values As with a dictionary you can use a section s get method to provide fallback values topsecret get Port 50022 topsecret get CompressionLevel 9 topsecret get Cipher topsecret get Cipher 3des cbc 3des cbc Please note that default values have precedence over fallback values For instance in our example the CompressionLevel key was specified only in the DEFAULT section If we try to get it from the section topsecret server example we will always get the default even if we specify a fallback topsecret get CompressionLevel 3 9 One more thing to be aware of is that the parser level get method provides a custom more complex interface maintained for backwards compatibility When using this method a fallback value can be provided via the fallback keyword only argument config get forge example monster fallback No such things as monsters No such things as monsters The same fallback argument can be used with the getint getfloat and getboolean methods for example BatchMode in topsecret False topsecret getboolean BatchMode fallback True True config DEFAULT BatchMode no topsecret getboolean BatchMode fallback True False Supported INI File Structure A configuration file consists of sections each led by a section header followed by key value entries separated by a specific string or by default 1 By default section names are case sensitive but keys are not 1 Leading and trailing whitespace is removed from keys and values Values can be omitted if the parser is configured to allow it 1 in which case the key value delimiter may also be left out Values can also span multiple lines as long as they are indented deeper than the first line of the value Depending on the parser s mode blank lines may be treated as parts of multiline values or ignored By default a valid section name can be any string that does not contain n To change this see ConfigParser SECTCRE Configuration files may include comments prefixed by specific characters and by default 1 Comments may appear on their own on an otherwise empty line possibly indented 1 For example Simple Values key value spaces in keys allowed spaces in values allowed as well spaces around the delimiter obviously you can also use to delimit keys from values All Values Are Strings values like this 1000000 or this 3 14159265359 are they treated as numbers no integers floats and booleans are held as strings can use the API to get converted values directly true Multiline Values chorus I m a lumberjack and I m okay I sleep all night and I work all day No Values key_without_value empty string value here You can use comments like this or this By default only in an empty line Inline comments can be harmful because they prevent users from using the delimiting characters as parts of values That being said this can be customized Sections Can Be Indented can_values_be_as_well True does_that_mean_anything_special False purpose formatting for readability multiline_values are handled just fine as long as they are indented deeper than the first line of a value Did I mention we can indent comments too Interpolation of values On top of the core functionality ConfigParser supports interpolation This means values can be preprocessed before returning them from get calls class configparser BasicInterpolation The default implementation used by ConfigParser It enables values to contain format strings which refer to other values in the same section or values in the special default section 1 Additional default values can be provided on initialization For example Paths home_dir Users my_dir home_dir s lumberjack my_pictures my_dir s Pictures Escape use a to escape ,en
2092,the sign is the only character that needs to be escaped gain 80 In the example above ConfigParser with interpolation set to BasicInterpolation would resolve home_dir s to the value of home_dir Users in this case my_dir s in effect would resolve to Users lumberjack All interpolations are done on demand so keys used in the chain of references do not have to be specified in any specific order in the configuration file With interpolation set to None the parser would simply return my_dir s Pictures as the value of my_pictures and home_dir s lumberjack as the value of my_dir class configparser ExtendedInterpolation An alternative handler for interpolation which implements a more advanced syntax used for instance in zc buildout Extended interpolation is using section option to denote a value from a foreign section Interpolation can span multiple levels For convenience if the section part is omitted interpolation defaults to the current section and possibly the default values from the special section For example the configuration specified above with basic interpolation would look like this with extended interpolation Paths home_dir Users my_dir home_dir lumberjack my_pictures my_dir Pictures Escape use a to escape the sign is the only character that needs to be escaped cost 80 Values from other sections can be fetched as well Common home_dir Users library_dir Library system_dir System macports_dir opt local Frameworks Python 3 2 path Common system_dir Library Frameworks Arthur nickname Two Sheds last_name Jackson my_dir Common home_dir twosheds my_pictures my_dir Pictures python_dir Frameworks path Python Versions Frameworks Python Mapping Protocol Access New in version 3 2 Mapping protocol access is a generic name for functionality that enables using custom objects as if they were dictionaries In case of configparser the mapping interface implementation is using the parser section option notation parser section in particular returns a proxy for the section s data in the parser This means that the values are not copied but they are taken from the original parser on demand What s even more important is that when values are changed on a section proxy they are actually mutated in the original parser configparser objects behave as close to actual dictionaries as possible The mapping interface is complete and adheres to the MutableMapping ABC However there are a few differences that should be taken into account By default all keys in sections are accessible in a case insensitive manner 1 E g for option in parser section yields only optionxform ed option key names This means lowercased keys by default At the same time for a section that holds the key a both expressions return True a in parser section A in parser section All sections include DEFAULTSECT values as well which means that clear on a section may not leave the section visibly empty This is because default values cannot be deleted from the section because technically they are not there If they are overridden in the section deleting causes the default value to be visible again Trying to delete a default value causes a KeyError DEFAULTSECT cannot be removed from the parser trying to delete it raises ValueError parser clear leaves it intact parser popitem never returns it parser get section option kwargs the second argument is not a fallback value Note however that the section level get methods are compatible both with the mapping protocol and the classic configparser API parser items is compatible with the mapping protocol returns a list of section_name section_proxy pairs including the DEFAULTSECT However this method can also be invoked with arguments parser items section raw vars The latter call returns a list of option value pairs for a specified section with all interpolations expanded unless raw True is provided The mapping protocol is implemented on top of the existing legacy API so that subclasses overriding the original interface still should have mappings working as expected Customizing Parser Behaviour There are nearly as many INI format variants as there are applica,en
2093,tions using it configparser goes a long way to provide support for the largest sensible set of INI styles available The default functionality is mainly dictated by historical background and it s very likely that you will want to customize some of the features The most common way to change the way a specific config parser works is to use the __init__ options defaults default value None This option accepts a dictionary of key value pairs which will be initially put in the DEFAULT section This makes for an elegant way to support concise configuration files that don t specify values which are the same as the documented default Hint if you want to specify default values for a specific section use read_dict before you read the actual file dict_type default value dict This option has a major impact on how the mapping protocol will behave and how the written configuration files look With the standard dictionary every section is stored in the order they were added to the parser Same goes for options within sections An alternative dictionary type can be used for example to sort sections and options on write back Please note there are ways to add a set of key value pairs in a single operation When you use a regular dictionary in those operations the order of the keys will be ordered For example parser configparser ConfigParser parser read_dict section1 key1 value1 key2 value2 key3 value3 section2 keyA valueA keyB valueB keyC valueC section3 foo x bar y baz z parser sections section1 section2 section3 option for option in parser section3 foo bar baz allow_no_value default value False Some configuration files are known to include settings without values but which otherwise conform to the syntax supported by configparser The allow_no_value parameter to the constructor can be used to indicate that such values should be accepted import configparser sample_config mysqld user mysql pid file var run mysqld mysqld pid skip external locking old_passwords 1 skip bdb we don t need ACID today skip innodb config configparser ConfigParser allow_no_value True config read_string sample_config Settings with values are treated as before config mysqld user mysql Settings without values provide None config mysqld skip bdb Settings which aren t specified still raise an error config mysqld does not exist Traceback most recent call last KeyError does not exist delimiters default value Delimiters are substrings that delimit keys from values within a section The first occurrence of a delimiting substring on a line is considered a delimiter This means values but not keys can contain the delimiters See also the space_around_delimiters argument to ConfigParser write comment_prefixes default value inline_comment_prefixes default value None Comment prefixes are strings that indicate the start of a valid comment within a config file comment_prefixes are used only on otherwise empty lines optionally indented whereas inline_comment_prefixes can be used after every valid value e g section names options and empty lines as well By default inline comments are disabled and and are used as prefixes for whole line comments Changed in version 3 2 In previous versions of configparser behaviour matched comment_prefixes and inline_comment_prefixes Please note that config parsers don t support escaping of comment prefixes so using inline_comment_prefixes may prevent users from specifying option values with characters used as comment prefixes When in doubt avoid setting inline_comment_prefixes In any circumstances the only way of storing comment prefix characters at the beginning of a line in multiline values is to interpolate the prefix for example from configparser import ConfigParser ExtendedInterpolation parser ConfigParser interpolation ExtendedInterpolation the default BasicInterpolation could be used as well parser read_string DEFAULT hash hashes shebang hash usr bin env python hash coding utf 8 extensions enabled_extension another_extension disabled_by_comment yet_another_extension interpolation not necessary if is not at line start even in multiline values line 1 line ,en
2094,2 line 3 print parser hashes shebang usr bin env python coding utf 8 print parser hashes extensions enabled_extension another_extension yet_another_extension print parser hashes interpolation not necessary if is not at line start print parser hashes even in multiline values line 1 line 2 line 3 strict default value True When set to True the parser will not allow for any section or option duplicates while reading from a single source using read_file read_string or read_dict It is recommended to use strict parsers in new applications Changed in version 3 2 In previous versions of configparser behaviour matched strict False empty_lines_in_values default value True In config parsers values can span multiple lines as long as they are indented more than the key that holds them By default parsers also let empty lines to be parts of values At the same time keys can be arbitrarily indented themselves to improve readability In consequence when configuration files get big and complex it is easy for the user to lose track of the file structure Take for instance Section key multiline value with a gotcha this is still a part of the multiline value of key This can be especially problematic for the user to see if she s using a proportional font to edit the file That is why when your application does not need values with empty lines you should consider disallowing them This will make empty lines split keys every time In the example above it would produce two keys key and this default_section default value configparser DEFAULTSECT that is DEFAULT The convention of allowing a special section of default values for other sections or interpolation purposes is a powerful concept of this library letting users create complex declarative configurations This section is normally called DEFAULT but this can be customized to point to any other valid section name Some typical values include general or common The name provided is used for recognizing default sections when reading from any source and is used when writing configuration back to a file Its current value can be retrieved using the parser_instance default_section attribute and may be modified at runtime i e to convert files from one format to another interpolation default value configparser BasicInterpolation Interpolation behaviour may be customized by providing a custom handler through the interpolation argument None can be used to turn off interpolation completely ExtendedInterpolation provides a more advanced variant inspired by zc buildout More on the subject in the dedicated documentation section RawConfigParser has a default value of None converters default value not set Config parsers provide option value getters that perform type conversion By default getint getfloat and getboolean are implemented Should other getters be desirable users may define them in a subclass or pass a dictionary where each key is a name of the converter and each value is a callable implementing said conversion For instance passing decimal decimal Decimal would add getdecimal on both the parser object and all section proxies In other words it will be possible to write both parser_instance getdecimal section key fallback 0 and parser_instance section getdecimal key 0 If the converter needs to access the state of the parser it can be implemented as a method on a config parser subclass If the name of this method starts with get it will be available on all section proxies in the dict compatible form see the getdecimal example above More advanced customization may be achieved by overriding default values of these parser attributes The defaults are defined on the classes so they may be overridden by subclasses or by attribute assignment ConfigParser BOOLEAN_STATES By default when using getboolean config parsers consider the following values True 1 yes true on and the following values False 0 no false off You can override this by specifying a custom dictionary of strings and their Boolean outcomes For example custom configparser ConfigParser custom section1 funky nope custom section1 getboolean funky Traceback most ,en
2095,recent call last ValueError Not a boolean nope custom BOOLEAN_STATES sure True nope False custom section1 getboolean funky False Other typical Boolean pairs include accept reject or enabled disabled ConfigParser optionxform option This method transforms option names on every read get or set operation The default converts the name to lowercase This also means that when a configuration file gets written all keys will be lowercase Override this method if that s unsuitable For example config Section1 Key Value Section2 AnotherKey Value typical configparser ConfigParser typical read_string config list typical Section1 keys key list typical Section2 keys anotherkey custom configparser RawConfigParser custom optionxform lambda option option custom read_string config list custom Section1 keys Key list custom Section2 keys AnotherKey Note The optionxform function transforms option names to a canonical form This should be an idempotent function if the name is already in canonical form it should be returned unchanged ConfigParser SECTCRE A compiled regular expression used to parse section headers The default matches section to the name section Whitespace is considered part of the section name thus larch will be read as a section of name larch Override this attribute if that s unsuitable For example import re config Section 1 option value Section 2 another val typical configparser ConfigParser typical read_string config typical sections Section 1 Section 2 custom configparser ConfigParser custom SECTCRE re compile r P header custom read_string config custom sections Section 1 Section 2 Note While ConfigParser objects also use an OPTCRE attribute for recognizing option lines it s not recommended to override it because that would interfere with constructor options allow_no_value and delimiters Legacy API Examples Mainly because of backwards compatibility concerns configparser provides also a legacy API with explicit get set methods While there are valid use cases for the methods outlined below mapping protocol access is preferred for new projects The legacy API is at times more advanced low level and downright counterintuitive An example of writing to a configuration file import configparser config configparser RawConfigParser Please note that using RawConfigParser s set functions you can assign non string values to keys internally but will receive an error when attempting to write to a file or when you get it in non raw mode Setting values using the mapping protocol or ConfigParser s set does not allow such assignments to take place config add_section Section1 config set Section1 an_int 15 config set Section1 a_bool true config set Section1 a_float 3 1415 config set Section1 baz fun config set Section1 bar Python config set Section1 foo bar s is baz s Writing our configuration file to example cfg with open example cfg w as configfile config write configfile An example of reading the configuration file again import configparser config configparser RawConfigParser config read example cfg getfloat raises an exception if the value is not a float getint and getboolean also do this for their respective types a_float config getfloat Section1 a_float an_int config getint Section1 an_int print a_float an_int Notice that the next output does not interpolate bar s or baz s This is because we are using a RawConfigParser if config getboolean Section1 a_bool print config get Section1 foo To get interpolation use ConfigParser import configparser cfg configparser ConfigParser cfg read example cfg Set the optional raw argument of get to True if you wish to disable interpolation in a single get operation print cfg get Section1 foo raw False Python is fun print cfg get Section1 foo raw True bar s is baz s The optional vars argument is a dict with members that will take precedence in interpolation print cfg get Section1 foo vars bar Documentation baz evil The optional fallback argument can be used to provide a fallback value print cfg get Section1 foo Python is fun print cfg get Section1 foo fallback Monty is not Python is fun print cfg get Section1 mon,en
2096,ster fallback No such things as monsters No such things as monsters A bare print cfg get Section1 monster would raise NoOptionError but we can also use print cfg get Section1 monster fallback None None Default values are available in both types of ConfigParsers They are used in interpolation if an option used is not defined elsewhere import configparser New instance with bar and baz defaulting to Life and hard each config configparser ConfigParser bar Life baz hard config read example cfg print config get Section1 foo Python is fun config remove_option Section1 bar config remove_option Section1 baz print config get Section1 foo Life is hard ConfigParser Objects class configparser ConfigParser defaults None dict_type dict allow_no_value False delimiters comment_prefixes inline_comment_prefixes None strict True empty_lines_in_values True default_section configparser DEFAULTSECT interpolation BasicInterpolation converters The main configuration parser When defaults is given it is initialized into the dictionary of intrinsic defaults When dict_type is given it will be used to create the dictionary objects for the list of sections for the options within a section and for the default values When delimiters is given it is used as the set of substrings that divide keys from values When comment_prefixes is given it will be used as the set of substrings that prefix comments in otherwise empty lines Comments can be indented When inline_comment_prefixes is given it will be used as the set of substrings that prefix comments in non empty lines When strict is True the default the parser won t allow for any section or option duplicates while reading from a single source file string or dictionary raising DuplicateSectionError or DuplicateOptionError When empty_lines_in_values is False default True each empty line marks the end of an option Otherwise internal empty lines of a multiline option are kept as part of the value When allow_no_value is True default False options without values are accepted the value held for these is None and they are serialized without the trailing delimiter When default_section is given it specifies the name for the special section holding default values for other sections and interpolation purposes normally named DEFAULT This value can be retrieved and changed at runtime using the default_section instance attribute This won t re evaluate an already parsed config file but will be used when writing parsed settings to a new config file Interpolation behaviour may be customized by providing a custom handler through the interpolation argument None can be used to turn off interpolation completely ExtendedInterpolation provides a more advanced variant inspired by zc buildout More on the subject in the dedicated documentation section All option names used in interpolation will be passed through the optionxform method just like any other option name reference For example using the default implementation of optionxform which converts option names to lower case the values foo bar s and foo BAR s are equivalent When converters is given it should be a dictionary where each key represents the name of a type converter and each value is a callable implementing the conversion from string to the desired datatype Every converter gets its own corresponding get method on the parser object and section proxies Changed in version 3 1 The default dict_type is collections OrderedDict Changed in version 3 2 allow_no_value delimiters comment_prefixes strict empty_lines_in_values default_section and interpolation were added Changed in version 3 5 The converters argument was added Changed in version 3 7 The defaults argument is read with read_dict providing consistent behavior across the parser non string keys and values are implicitly converted to strings Changed in version 3 8 The default dict_type is dict since it now preserves insertion order defaults Return a dictionary containing the instance wide defaults sections Return a list of the sections available the default section is not included in the list add_section section Add a sectio,en
2097,n named section to the instance If a section by the given name already exists DuplicateSectionError is raised If the default section name is passed ValueError is raised The name of the section must be a string if not TypeError is raised Changed in version 3 2 Non string section names raise TypeError has_section section Indicates whether the named section is present in the configuration The default section is not acknowledged options section Return a list of options available in the specified section has_option section option If the given section exists and contains the given option return True otherwise return False If the specified section is None or an empty string DEFAULT is assumed read filenames encoding None Attempt to read and parse an iterable of filenames returning a list of filenames which were successfully parsed If filenames is a string a bytes object or a path like object it is treated as a single filename If a file named in filenames cannot be opened that file will be ignored This is designed so that you can specify an iterable of potential configuration file locations for example the current directory the user s home directory and some system wide directory and all existing configuration files in the iterable will be read If none of the named files exist the ConfigParser instance will contain an empty dataset An application which requires initial values to be loaded from a file should load the required file or files using read_file before calling read for any optional files import configparser os config configparser ConfigParser config read_file open defaults cfg config read site cfg os path expanduser myapp cfg encoding cp1250 Changed in version 3 2 Added the encoding parameter Previously all files were read using the default encoding for open Changed in version 3 6 1 The filenames parameter accepts a path like object Changed in version 3 7 The filenames parameter accepts a bytes object read_file f source None Read and parse configuration data from f which must be an iterable yielding Unicode strings for example files opened in text mode Optional argument source specifies the name of the file being read If not given and f has a name attribute that is used for source the default is New in version 3 2 Replaces readfp read_string string source string Parse configuration data from a string Optional argument source specifies a context specific name of the string passed If not given string is used This should commonly be a filesystem path or a URL New in version 3 2 read_dict dictionary source dict Load configuration from any object that provides a dict like items method Keys are section names values are dictionaries with keys and values that should be present in the section If the used dictionary type preserves order sections and their keys will be added in order Values are automatically converted to strings Optional argument source specifies a context specific name of the dictionary passed If not given dict is used This method can be used to copy state between parsers New in version 3 2 get section option raw False vars None fallback Get an option value for the named section If vars is provided it must be a dictionary The option is looked up in vars if provided section and in DEFAULTSECT in that order If the key is not found and fallback is provided it is used as a fallback value None can be provided as a fallback value All the interpolations are expanded in the return values unless the raw argument is true Values for interpolation keys are looked up in the same manner as the option Changed in version 3 2 Arguments raw vars and fallback are keyword only to protect users from trying to use the third argument as the fallback fallback especially when using the mapping protocol getint section option raw False vars None fallback A convenience method which coerces the option in the specified section to an integer See get for explanation of raw vars and fallback getfloat section option raw False vars None fallback A convenience method which coerces the option in the specified section to a floating point number See g,en
2098,et for explanation of raw vars and fallback getboolean section option raw False vars None fallback A convenience method which coerces the option in the specified section to a Boolean value Note that the accepted values for the option are 1 yes true and on which cause this method to return True and 0 no false and off which cause it to return False These string values are checked in a case insensitive manner Any other value will cause it to raise ValueError See get for explanation of raw vars and fallback items raw False vars None items section raw False vars None When section is not given return a list of section_name section_proxy pairs including DEFAULTSECT Otherwise return a list of name value pairs for the options in the given section Optional arguments have the same meaning as for the get method Changed in version 3 8 Items present in vars no longer appear in the result The previous behaviour mixed actual parser options with variables provided for interpolation set section option value If the given section exists set the given option to the specified value otherwise raise NoSectionError option and value must be strings if not TypeError is raised write fileobject space_around_delimiters True Write a representation of the configuration to the specified file object which must be opened in text mode accepting strings This representation can be parsed by a future read call If space_around_delimiters is true delimiters between keys and values are surrounded by spaces Note Comments in the original configuration file are not preserved when writing the configuration back What is considered a comment depends on the given values for comment_prefix and inline_comment_prefix remove_option section option Remove the specified option from the specified section If the section does not exist raise NoSectionError If the option existed to be removed return True otherwise return False remove_section section Remove the specified section from the configuration If the section in fact existed return True Otherwise return False optionxform option Transforms the option name option as found in an input file or as passed in by client code to the form that should be used in the internal structures The default implementation returns a lower case version of option subclasses may override this or client code can set an attribute of this name on instances to affect this behavior You don t need to subclass the parser to use this method you can also set it on an instance to a function that takes a string argument and returns a string Setting it to str for example would make option names case sensitive cfgparser ConfigParser cfgparser optionxform str Note that when reading configuration files whitespace around the option names is stripped before optionxform is called configparser MAX_INTERPOLATION_DEPTH The maximum depth for recursive interpolation for get when the raw parameter is false This is relevant only when the default interpolation is used RawConfigParser Objects class configparser RawConfigParser defaults None dict_type dict allow_no_value False delimiters comment_prefixes inline_comment_prefixes None strict True empty_lines_in_values True default_section configparser DEFAULTSECT interpolation Legacy variant of the ConfigParser It has interpolation disabled by default and allows for non string section names option names and values via its unsafe add_section and set methods as well as the legacy defaults keyword argument handling Changed in version 3 8 The default dict_type is dict since it now preserves insertion order Note Consider using ConfigParser instead which checks types of the values to be stored internally If you don t want interpolation you can use ConfigParser interpolation None add_section section Add a section named section to the instance If a section by the given name already exists DuplicateSectionError is raised If the default section name is passed ValueError is raised Type of section is not checked which lets users create non string named sections This behaviour is unsupported and may cause internal errors set section option ,en
2099,value If the given section exists set the given option to the specified value otherwise raise NoSectionError While it is possible to use RawConfigParser or ConfigParser with raw parameters set to true for internal storage of non string values full functionality including interpolation and output to files can only be achieved using string values This method lets users assign non string values to keys internally This behaviour is unsupported and will cause errors when attempting to write to a file or get it in non raw mode Use the mapping protocol API which does not allow such assignments to take place Exceptions exception configparser Error Base class for all other configparser exceptions exception configparser NoSectionError Exception raised when a specified section is not found exception configparser DuplicateSectionError Exception raised if add_section is called with the name of a section that is already present or in strict parsers when a section if found more than once in a single input file string or dictionary Changed in version 3 2 Added the optional source and lineno attributes and parameters to __init__ exception configparser DuplicateOptionError Exception raised by strict parsers if a single option appears twice during reading from a single file string or dictionary This catches misspellings and case sensitivity related errors e g a dictionary may have two keys representing the same case insensitive configuration key exception configparser NoOptionError Exception raised when a specified option is not found in the specified section exception configparser InterpolationError Base class for exceptions raised when problems occur performing string interpolation exception configparser InterpolationDepthError Exception raised when string interpolation cannot be completed because the number of iterations exceeds MAX_INTERPOLATION_DEPTH Subclass of InterpolationError exception configparser InterpolationMissingOptionError Exception raised when an option referenced from a value does not exist Subclass of InterpolationError exception configparser InterpolationSyntaxError Exception raised when the source text into which substitutions are made does not conform to the required syntax Subclass of InterpolationError exception configparser MissingSectionHeaderError Exception raised when attempting to parse a file which has no section headers exception configparser ParsingError Exception raised when errors occur attempting to parse a file Changed in version 3 12 The filename attribute and __init__ constructor argument were removed They have been available using the name source since 3 2 Footnotes 1 Config parsers allow for heavy customization If you are interested in changing the behaviour outlined by the footnote reference consult the Customizing Parser Behaviour section,en
2100,subprocess Subprocess management Source code Lib subprocess py The subprocess module allows you to spawn new processes connect to their input output error pipes and obtain their return codes This module intends to replace several older modules and functions os system os spawn Information about how the subprocess module can be used to replace these modules and functions can be found in the following sections See also PEP 324 PEP proposing the subprocess module Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information Using the subprocess Module The recommended approach to invoking subprocesses is to use the run function for all use cases it can handle For more advanced use cases the underlying Popen interface can be used directly subprocess run args stdin None input None stdout None stderr None capture_output False shell False cwd None timeout None check False encoding None errors None text None env None universal_newlines None other_popen_kwargs Run the command described by args Wait for command to complete then return a CompletedProcess instance The arguments shown above are merely the most common ones described below in Frequently Used Arguments hence the use of keyword only notation in the abbreviated signature The full function signature is largely the same as that of the Popen constructor most of the arguments to this function are passed through to that interface timeout input check and capture_output are not If capture_output is true stdout and stderr will be captured When used the internal Popen object is automatically created with stdout PIPE and stderr PIPE The stdout and stderr arguments may not be supplied at the same time as capture_output If you wish to capture and combine both streams into one use stdout PIPE and stderr STDOUT instead of capture_output A timeout may be specified in seconds it is internally passed on to Popen communicate If the timeout expires the child process will be killed and waited for The TimeoutExpired exception will be re raised after the child process has terminated The initial process creation itself cannot be interrupted on many platform APIs so you are not guaranteed to see a timeout exception until at least after however long process creation takes The input argument is passed to Popen communicate and thus to the subprocess s stdin If used it must be a byte sequence or a string if encoding or errors is specified or text is true When used the internal Popen object is automatically created with stdin PIPE and the stdin argument may not be used as well If check is true and the process exits with a non zero exit code a CalledProcessError exception will be raised Attributes of that exception hold the arguments the exit code and stdout and stderr if they were captured If encoding or errors are specified or text is true file objects for stdin stdout and stderr are opened in text mode using the specified encoding and errors or the io TextIOWrapper default The universal_newlines argument is equivalent to text and is provided for backwards compatibility By default file objects are opened in binary mode If env is not None it must be a mapping that defines the environment variables for the new process these are used instead of the default behavior of inheriting the current process environment It is passed directly to Popen This mapping can be str to str on any platform or bytes to bytes on POSIX platforms much like os environ or os environb Examples subprocess run ls l doesn t capture output CompletedProcess args ls l returncode 0 subprocess run exit 1 shell True check True Traceback most recent call last subprocess CalledProcessError Command exit 1 returned non zero exit status 1 subprocess run ls l dev null capture_output True CompletedProcess args ls l dev null returncode 0 stdout b crw rw rw 1 root root 1 3 Jan 23 16 23 dev null n stderr b New in version 3 5 Changed in version 3 6 Added encoding and errors parameters Changed in version 3 7 Added the text par,en
2101,ameter as a more understandable alias of universal_newlines Added the capture_output parameter Changed in version 3 12 Changed Windows shell search order for shell True The current directory and PATH are replaced with COMSPEC and SystemRoot System32 cmd exe As a result dropping a malicious program named cmd exe into a current directory no longer works class subprocess CompletedProcess The return value from run representing a process that has finished args The arguments used to launch the process This may be a list or a string returncode Exit status of the child process Typically an exit status of 0 indicates that it ran successfully A negative value N indicates that the child was terminated by signal N POSIX only stdout Captured stdout from the child process A bytes sequence or a string if run was called with an encoding errors or text True None if stdout was not captured If you ran the process with stderr subprocess STDOUT stdout and stderr will be combined in this attribute and stderr will be None stderr Captured stderr from the child process A bytes sequence or a string if run was called with an encoding errors or text True None if stderr was not captured check_returncode If returncode is non zero raise a CalledProcessError New in version 3 5 subprocess DEVNULL Special value that can be used as the stdin stdout or stderr argument to Popen and indicates that the special file os devnull will be used New in version 3 3 subprocess PIPE Special value that can be used as the stdin stdout or stderr argument to Popen and indicates that a pipe to the standard stream should be opened Most useful with Popen communicate subprocess STDOUT Special value that can be used as the stderr argument to Popen and indicates that standard error should go into the same handle as standard output exception subprocess SubprocessError Base class for all other exceptions from this module New in version 3 3 exception subprocess TimeoutExpired Subclass of SubprocessError raised when a timeout expires while waiting for a child process cmd Command that was used to spawn the child process timeout Timeout in seconds output Output of the child process if it was captured by run or check_output Otherwise None This is always bytes when any output was captured regardless of the text True setting It may remain None instead of b when no output was observed stdout Alias for output for symmetry with stderr stderr Stderr output of the child process if it was captured by run Otherwise None This is always bytes when stderr output was captured regardless of the text True setting It may remain None instead of b when no stderr output was observed New in version 3 3 Changed in version 3 5 stdout and stderr attributes added exception subprocess CalledProcessError Subclass of SubprocessError raised when a process run by check_call check_output or run with check True returns a non zero exit status returncode Exit status of the child process If the process exited due to a signal this will be the negative signal number cmd Command that was used to spawn the child process output Output of the child process if it was captured by run or check_output Otherwise None stdout Alias for output for symmetry with stderr stderr Stderr output of the child process if it was captured by run Otherwise None Changed in version 3 5 stdout and stderr attributes added Frequently Used Arguments To support a wide variety of use cases the Popen constructor and the convenience functions accept a large number of optional arguments For most typical use cases many of these arguments can be safely left at their default values The arguments that are most commonly needed are args is required for all calls and should be a string or a sequence of program arguments Providing a sequence of arguments is generally preferred as it allows the module to take care of any required escaping and quoting of arguments e g to permit spaces in file names If passing a single string either shell must be True see below or else the string must simply name the program to be executed without specifying any arguments stdin stdo,en
2102,ut and stderr specify the executed program s standard input standard output and standard error file handles respectively Valid values are None PIPE DEVNULL an existing file descriptor a positive integer and an existing file object with a valid file descriptor With the default settings of None no redirection will occur PIPE indicates that a new pipe to the child should be created DEVNULL indicates that the special file os devnull will be used Additionally stderr can be STDOUT which indicates that the stderr data from the child process should be captured into the same file handle as for stdout If encoding or errors are specified or text also known as universal_newlines is true the file objects stdin stdout and stderr will be opened in text mode using the encoding and errors specified in the call or the defaults for io TextIOWrapper For stdin line ending characters n in the input will be converted to the default line separator os linesep For stdout and stderr all line endings in the output will be converted to n For more information see the documentation of the io TextIOWrapper class when the newline argument to its constructor is None If text mode is not used stdin stdout and stderr will be opened as binary streams No encoding or line ending conversion is performed Changed in version 3 6 Added the encoding and errors parameters Changed in version 3 7 Added the text parameter as an alias for universal_newlines Note The newlines attribute of the file objects Popen stdin Popen stdout and Popen stderr are not updated by the Popen communicate method If shell is True the specified command will be executed through the shell This can be useful if you are using Python primarily for the enhanced control flow it offers over most system shells and still want convenient access to other shell features such as shell pipes filename wildcards environment variable expansion and expansion of to a user s home directory However note that Python itself offers implementations of many shell like features in particular glob fnmatch os walk os path expandvars os path expanduser and shutil Changed in version 3 3 When universal_newlines is True the class uses the encoding locale getpreferredencoding False instead of locale getpreferredencoding See the io TextIOWrapper class for more information on this change Note Read the Security Considerations section before using shell True These options along with all of the other options are described in more detail in the Popen constructor documentation Popen Constructor The underlying process creation and management in this module is handled by the Popen class It offers a lot of flexibility so that developers are able to handle the less common cases not covered by the convenience functions class subprocess Popen args bufsize 1 executable None stdin None stdout None stderr None preexec_fn None close_fds True shell False cwd None env None universal_newlines None startupinfo None creationflags 0 restore_signals True start_new_session False pass_fds group None extra_groups None user None umask 1 encoding None errors None text None pipesize 1 process_group None Execute a child program in a new process On POSIX the class uses os execvpe like behavior to execute the child program On Windows the class uses the Windows CreateProcess function The arguments to Popen are as follows args should be a sequence of program arguments or else a single string or path like object By default the program to execute is the first item in args if args is a sequence If args is a string the interpretation is platform dependent and described below See the shell and executable arguments for additional differences from the default behavior Unless otherwise stated it is recommended to pass args as a sequence Warning For maximum reliability use a fully qualified path for the executable To search for an unqualified name on PATH use shutil which On all platforms passing sys executable is the recommended way to launch the current Python interpreter again and use the m command line format to launch an installed module Resolving the path of execu,en
2103,table or the first item of args is platform dependent For POSIX see os execvpe and note that when resolving or searching for the executable path cwd overrides the current working directory and env can override the PATH environment variable For Windows see the documentation of the lpApplicationName and lpCommandLine parameters of WinAPI CreateProcess and note that when resolving or searching for the executable path with shell False cwd does not override the current working directory and env cannot override the PATH environment variable Using a full path avoids all of these variations An example of passing some arguments to an external program as a sequence is Popen usr bin git commit m Fixes a bug On POSIX if args is a string the string is interpreted as the name or path of the program to execute However this can only be done if not passing arguments to the program Note It may not be obvious how to break a shell command into a sequence of arguments especially in complex cases shlex split can illustrate how to determine the correct tokenization for args import shlex subprocess command_line input bin vikings input eggs txt output spam spam txt cmd echo MONEY args shlex split command_line print args bin vikings input eggs txt output spam spam txt cmd echo MONEY p subprocess Popen args Success Note in particular that options such as input and arguments such as eggs txt that are separated by whitespace in the shell go in separate list elements while arguments that need quoting or backslash escaping when used in the shell such as filenames containing spaces or the echo command shown above are single list elements On Windows if args is a sequence it will be converted to a string in a manner described in Converting an argument sequence to a string on Windows This is because the underlying CreateProcess operates on strings Changed in version 3 6 args parameter accepts a path like object if shell is False and a sequence containing path like objects on POSIX Changed in version 3 8 args parameter accepts a path like object if shell is False and a sequence containing bytes and path like objects on Windows The shell argument which defaults to False specifies whether to use the shell as the program to execute If shell is True it is recommended to pass args as a string rather than as a sequence On POSIX with shell True the shell defaults to bin sh If args is a string the string specifies the command to execute through the shell This means that the string must be formatted exactly as it would be when typed at the shell prompt This includes for example quoting or backslash escaping filenames with spaces in them If args is a sequence the first item specifies the command string and any additional items will be treated as additional arguments to the shell itself That is to say Popen does the equivalent of Popen bin sh c args 0 args 1 On Windows with shell True the COMSPEC environment variable specifies the default shell The only time you need to specify shell True on Windows is when the command you wish to execute is built into the shell e g dir or copy You do not need shell True to run a batch file or console based executable Note Read the Security Considerations section before using shell True bufsize will be supplied as the corresponding argument to the open function when creating the stdin stdout stderr pipe file objects 0 means unbuffered read and write are one system call and can return short 1 means line buffered only usable if text True or universal_newlines True any other positive value means use a buffer of approximately that size negative bufsize the default means the system default of io DEFAULT_BUFFER_SIZE will be used Changed in version 3 3 1 bufsize now defaults to 1 to enable buffering by default to match the behavior that most code expects In versions prior to Python 3 2 4 and 3 3 1 it incorrectly defaulted to 0 which was unbuffered and allowed short reads This was unintentional and did not match the behavior of Python 2 as most code expected The executable argument specifies a replacement program to execute It is very seldom,en
2104, needed When shell False executable replaces the program to execute specified by args However the original args is still passed to the program Most programs treat the program specified by args as the command name which can then be different from the program actually executed On POSIX the args name becomes the display name for the executable in utilities such as ps If shell True on POSIX the executable argument specifies a replacement shell for the default bin sh Changed in version 3 6 executable parameter accepts a path like object on POSIX Changed in version 3 8 executable parameter accepts a bytes and path like object on Windows Changed in version 3 12 Changed Windows shell search order for shell True The current directory and PATH are replaced with COMSPEC and SystemRoot System32 cmd exe As a result dropping a malicious program named cmd exe into a current directory no longer works stdin stdout and stderr specify the executed program s standard input standard output and standard error file handles respectively Valid values are None PIPE DEVNULL an existing file descriptor a positive integer and an existing file object with a valid file descriptor With the default settings of None no redirection will occur PIPE indicates that a new pipe to the child should be created DEVNULL indicates that the special file os devnull will be used Additionally stderr can be STDOUT which indicates that the stderr data from the applications should be captured into the same file handle as for stdout If preexec_fn is set to a callable object this object will be called in the child process just before the child is executed POSIX only Warning The preexec_fn parameter is NOT SAFE to use in the presence of threads in your application The child process could deadlock before exec is called Note If you need to modify the environment for the child use the env parameter rather than doing it in a preexec_fn The start_new_session and process_group parameters should take the place of code using preexec_fn to call os setsid or os setpgid in the child Changed in version 3 8 The preexec_fn parameter is no longer supported in subinterpreters The use of the parameter in a subinterpreter raises RuntimeError The new restriction may affect applications that are deployed in mod_wsgi uWSGI and other embedded environments If close_fds is true all file descriptors except 0 1 and 2 will be closed before the child process is executed Otherwise when close_fds is false file descriptors obey their inheritable flag as described in Inheritance of File Descriptors On Windows if close_fds is true then no handles will be inherited by the child process unless explicitly passed in the handle_list element of STARTUPINFO lpAttributeList or by standard handle redirection Changed in version 3 2 The default for close_fds was changed from False to what is described above Changed in version 3 7 On Windows the default for close_fds was changed from False to True when redirecting the standard handles It s now possible to set close_fds to True when redirecting the standard handles pass_fds is an optional sequence of file descriptors to keep open between the parent and child Providing any pass_fds forces close_fds to be True POSIX only Changed in version 3 2 The pass_fds parameter was added If cwd is not None the function changes the working directory to cwd before executing the child cwd can be a string bytes or path like object On POSIX the function looks for executable or for the first item in args relative to cwd if the executable path is a relative path Changed in version 3 6 cwd parameter accepts a path like object on POSIX Changed in version 3 7 cwd parameter accepts a path like object on Windows Changed in version 3 8 cwd parameter accepts a bytes object on Windows If restore_signals is true the default all signals that Python has set to SIG_IGN are restored to SIG_DFL in the child process before the exec Currently this includes the SIGPIPE SIGXFZ and SIGXFSZ signals POSIX only Changed in version 3 2 restore_signals was added If start_new_session is true the setsid system call w,en
2105,ill be made in the child process prior to the execution of the subprocess Availability POSIX Changed in version 3 2 start_new_session was added If process_group is a non negative integer the setpgid 0 value system call will be made in the child process prior to the execution of the subprocess Availability POSIX Changed in version 3 11 process_group was added If group is not None the setregid system call will be made in the child process prior to the execution of the subprocess If the provided value is a string it will be looked up via grp getgrnam and the value in gr_gid will be used If the value is an integer it will be passed verbatim POSIX only Availability POSIX New in version 3 9 If extra_groups is not None the setgroups system call will be made in the child process prior to the execution of the subprocess Strings provided in extra_groups will be looked up via grp getgrnam and the values in gr_gid will be used Integer values will be passed verbatim POSIX only Availability POSIX New in version 3 9 If user is not None the setreuid system call will be made in the child process prior to the execution of the subprocess If the provided value is a string it will be looked up via pwd getpwnam and the value in pw_uid will be used If the value is an integer it will be passed verbatim POSIX only Availability POSIX New in version 3 9 If umask is not negative the umask system call will be made in the child process prior to the execution of the subprocess Availability POSIX New in version 3 9 If env is not None it must be a mapping that defines the environment variables for the new process these are used instead of the default behavior of inheriting the current process environment This mapping can be str to str on any platform or bytes to bytes on POSIX platforms much like os environ or os environb Note If specified env must provide any variables required for the program to execute On Windows in order to run a side by side assembly the specified env must include a valid SystemRoot If encoding or errors are specified or text is true the file objects stdin stdout and stderr are opened in text mode with the specified encoding and errors as described above in Frequently Used Arguments The universal_newlines argument is equivalent to text and is provided for backwards compatibility By default file objects are opened in binary mode New in version 3 6 encoding and errors were added New in version 3 7 text was added as a more readable alias for universal_newlines If given startupinfo will be a STARTUPINFO object which is passed to the underlying CreateProcess function If given creationflags can be one or more of the following flags CREATE_NEW_CONSOLE CREATE_NEW_PROCESS_GROUP ABOVE_NORMAL_PRIORITY_CLASS BELOW_NORMAL_PRIORITY_CLASS HIGH_PRIORITY_CLASS IDLE_PRIORITY_CLASS NORMAL_PRIORITY_CLASS REALTIME_PRIORITY_CLASS CREATE_NO_WINDOW DETACHED_PROCESS CREATE_DEFAULT_ERROR_MODE CREATE_BREAKAWAY_FROM_JOB pipesize can be used to change the size of the pipe when PIPE is used for stdin stdout or stderr The size of the pipe is only changed on platforms that support this only Linux at this time of writing Other platforms will ignore this parameter Changed in version 3 10 Added the pipesize parameter Popen objects are supported as context managers via the with statement on exit standard file descriptors are closed and the process is waited for with Popen ifconfig stdout PIPE as proc log write proc stdout read Popen and the other functions in this module that use it raise an auditing event subprocess Popen with arguments executable args cwd and env The value for args may be a single string or a list of strings depending on platform Changed in version 3 2 Added context manager support Changed in version 3 6 Popen destructor now emits a ResourceWarning warning if the child process is still running Changed in version 3 8 Popen can use os posix_spawn in some cases for better performance On Windows Subsystem for Linux and QEMU User Emulation Popen constructor using os posix_spawn no longer raise an exception on errors like missing program but the child pr,en
2106,ocess fails with a non zero returncode Exceptions Exceptions raised in the child process before the new program has started to execute will be re raised in the parent The most common exception raised is OSError This occurs for example when trying to execute a non existent file Applications should prepare for OSError exceptions Note that when shell True OSError will be raised by the child only if the selected shell itself was not found To determine if the shell failed to find the requested application it is necessary to check the return code or output from the subprocess A ValueError will be raised if Popen is called with invalid arguments check_call and check_output will raise CalledProcessError if the called process returns a non zero return code All of the functions and methods that accept a timeout parameter such as run and Popen communicate will raise TimeoutExpired if the timeout expires before the process exits Exceptions defined in this module all inherit from SubprocessError New in version 3 3 The SubprocessError base class was added Security Considerations Unlike some other popen functions this implementation will never implicitly call a system shell This means that all characters including shell metacharacters can safely be passed to child processes If the shell is invoked explicitly via shell True it is the application s responsibility to ensure that all whitespace and metacharacters are quoted appropriately to avoid shell injection vulnerabilities On some platforms it is possible to use shlex quote for this escaping Popen Objects Instances of the Popen class have the following methods Popen poll Check if child process has terminated Set and return returncode attribute Otherwise returns None Popen wait timeout None Wait for child process to terminate Set and return returncode attribute If the process does not terminate after timeout seconds raise a TimeoutExpired exception It is safe to catch this exception and retry the wait Note This will deadlock when using stdout PIPE or stderr PIPE and the child process generates enough output to a pipe such that it blocks waiting for the OS pipe buffer to accept more data Use Popen communicate when using pipes to avoid that Note When the timeout parameter is not None then on POSIX the function is implemented using a busy loop non blocking call and short sleeps Use the asyncio module for an asynchronous wait see asyncio create_subprocess_exec Changed in version 3 3 timeout was added Popen communicate input None timeout None Interact with process Send data to stdin Read data from stdout and stderr until end of file is reached Wait for process to terminate and set the returncode attribute The optional input argument should be data to be sent to the child process or None if no data should be sent to the child If streams were opened in text mode input must be a string Otherwise it must be bytes communicate returns a tuple stdout_data stderr_data The data will be strings if streams were opened in text mode otherwise bytes Note that if you want to send data to the process s stdin you need to create the Popen object with stdin PIPE Similarly to get anything other than None in the result tuple you need to give stdout PIPE and or stderr PIPE too If the process does not terminate after timeout seconds a TimeoutExpired exception will be raised Catching this exception and retrying communication will not lose any output The child process is not killed if the timeout expires so in order to cleanup properly a well behaved application should kill the child process and finish communication proc subprocess Popen try outs errs proc communicate timeout 15 except TimeoutExpired proc kill outs errs proc communicate Note The data read is buffered in memory so do not use this method if the data size is large or unlimited Changed in version 3 3 timeout was added Popen send_signal signal Sends the signal signal to the child Do nothing if the process completed Note On Windows SIGTERM is an alias for terminate CTRL_C_EVENT and CTRL_BREAK_EVENT can be sent to processes started with a creationflags pa,en
2107,rameter which includes CREATE_NEW_PROCESS_GROUP Popen terminate Stop the child On POSIX OSs the method sends SIGTERM to the child On Windows the Win32 API function TerminateProcess is called to stop the child Popen kill Kills the child On POSIX OSs the function sends SIGKILL to the child On Windows kill is an alias for terminate The following attributes are also set by the class for you to access Reassigning them to new values is unsupported Popen args The args argument as it was passed to Popen a sequence of program arguments or else a single string New in version 3 3 Popen stdin If the stdin argument was PIPE this attribute is a writeable stream object as returned by open If the encoding or errors arguments were specified or the text or universal_newlines argument was True the stream is a text stream otherwise it is a byte stream If the stdin argument was not PIPE this attribute is None Popen stdout If the stdout argument was PIPE this attribute is a readable stream object as returned by open Reading from the stream provides output from the child process If the encoding or errors arguments were specified or the text or universal_newlines argument was True the stream is a text stream otherwise it is a byte stream If the stdout argument was not PIPE this attribute is None Popen stderr If the stderr argument was PIPE this attribute is a readable stream object as returned by open Reading from the stream provides error output from the child process If the encoding or errors arguments were specified or the text or universal_newlines argument was True the stream is a text stream otherwise it is a byte stream If the stderr argument was not PIPE this attribute is None Warning Use communicate rather than stdin write stdout read or stderr read to avoid deadlocks due to any of the other OS pipe buffers filling up and blocking the child process Popen pid The process ID of the child process Note that if you set the shell argument to True this is the process ID of the spawned shell Popen returncode The child return code Initially None returncode is set by a call to the poll wait or communicate methods if they detect that the process has terminated A None value indicates that the process hadn t yet terminated at the time of the last method call A negative value N indicates that the child was terminated by signal N POSIX only Windows Popen Helpers The STARTUPINFO class and following constants are only available on Windows class subprocess STARTUPINFO dwFlags 0 hStdInput None hStdOutput None hStdError None wShowWindow 0 lpAttributeList None Partial support of the Windows STARTUPINFO structure is used for Popen creation The following attributes can be set by passing them as keyword only arguments Changed in version 3 7 Keyword only argument support was added dwFlags A bit field that determines whether certain STARTUPINFO attributes are used when the process creates a window si subprocess STARTUPINFO si dwFlags subprocess STARTF_USESTDHANDLES subprocess STARTF_USESHOWWINDOW hStdInput If dwFlags specifies STARTF_USESTDHANDLES this attribute is the standard input handle for the process If STARTF_USESTDHANDLES is not specified the default for standard input is the keyboard buffer hStdOutput If dwFlags specifies STARTF_USESTDHANDLES this attribute is the standard output handle for the process Otherwise this attribute is ignored and the default for standard output is the console window s buffer hStdError If dwFlags specifies STARTF_USESTDHANDLES this attribute is the standard error handle for the process Otherwise this attribute is ignored and the default for standard error is the console window s buffer wShowWindow If dwFlags specifies STARTF_USESHOWWINDOW this attribute can be any of the values that can be specified in the nCmdShow parameter for the ShowWindow function except for SW_SHOWDEFAULT Otherwise this attribute is ignored SW_HIDE is provided for this attribute It is used when Popen is called with shell True lpAttributeList A dictionary of additional attributes for process creation as given in STARTUPINFOEX see UpdateProcThreadAttribu,en
2108,te Supported attributes handle_list Sequence of handles that will be inherited close_fds must be true if non empty The handles must be temporarily made inheritable by os set_handle_inheritable when passed to the Popen constructor else OSError will be raised with Windows error ERROR_INVALID_PARAMETER 87 Warning In a multithreaded process use caution to avoid leaking handles that are marked inheritable when combining this feature with concurrent calls to other process creation functions that inherit all handles such as os system This also applies to standard handle redirection which temporarily creates inheritable handles New in version 3 7 Windows Constants The subprocess module exposes the following constants subprocess STD_INPUT_HANDLE The standard input device Initially this is the console input buffer CONIN subprocess STD_OUTPUT_HANDLE The standard output device Initially this is the active console screen buffer CONOUT subprocess STD_ERROR_HANDLE The standard error device Initially this is the active console screen buffer CONOUT subprocess SW_HIDE Hides the window Another window will be activated subprocess STARTF_USESTDHANDLES Specifies that the STARTUPINFO hStdInput STARTUPINFO hStdOutput and STARTUPINFO hStdError attributes contain additional information subprocess STARTF_USESHOWWINDOW Specifies that the STARTUPINFO wShowWindow attribute contains additional information subprocess CREATE_NEW_CONSOLE The new process has a new console instead of inheriting its parent s console the default subprocess CREATE_NEW_PROCESS_GROUP A Popen creationflags parameter to specify that a new process group will be created This flag is necessary for using os kill on the subprocess This flag is ignored if CREATE_NEW_CONSOLE is specified subprocess ABOVE_NORMAL_PRIORITY_CLASS A Popen creationflags parameter to specify that a new process will have an above average priority New in version 3 7 subprocess BELOW_NORMAL_PRIORITY_CLASS A Popen creationflags parameter to specify that a new process will have a below average priority New in version 3 7 subprocess HIGH_PRIORITY_CLASS A Popen creationflags parameter to specify that a new process will have a high priority New in version 3 7 subprocess IDLE_PRIORITY_CLASS A Popen creationflags parameter to specify that a new process will have an idle lowest priority New in version 3 7 subprocess NORMAL_PRIORITY_CLASS A Popen creationflags parameter to specify that a new process will have an normal priority default New in version 3 7 subprocess REALTIME_PRIORITY_CLASS A Popen creationflags parameter to specify that a new process will have realtime priority You should almost never use REALTIME_PRIORITY_CLASS because this interrupts system threads that manage mouse input keyboard input and background disk flushing This class can be appropriate for applications that talk directly to hardware or that perform brief tasks that should have limited interruptions New in version 3 7 subprocess CREATE_NO_WINDOW A Popen creationflags parameter to specify that a new process will not create a window New in version 3 7 subprocess DETACHED_PROCESS A Popen creationflags parameter to specify that a new process will not inherit its parent s console This value cannot be used with CREATE_NEW_CONSOLE New in version 3 7 subprocess CREATE_DEFAULT_ERROR_MODE A Popen creationflags parameter to specify that a new process does not inherit the error mode of the calling process Instead the new process gets the default error mode This feature is particularly useful for multithreaded shell applications that run with hard errors disabled New in version 3 7 subprocess CREATE_BREAKAWAY_FROM_JOB A Popen creationflags parameter to specify that a new process is not associated with the job New in version 3 7 Older high level API Prior to Python 3 5 these three functions comprised the high level API to subprocess You can now use run in many cases but lots of existing code calls these functions subprocess call args stdin None stdout None stderr None shell False cwd None timeout None other_popen_kwargs Run the command described by args Wait f,en
2109,or command to complete then return the returncode attribute Code needing to capture stdout or stderr should use run instead run returncode To suppress stdout or stderr supply a value of DEVNULL The arguments shown above are merely some common ones The full function signature is the same as that of the Popen constructor this function passes all supplied arguments other than timeout directly through to that interface Note Do not use stdout PIPE or stderr PIPE with this function The child process will block if it generates enough output to a pipe to fill up the OS pipe buffer as the pipes are not being read from Changed in version 3 3 timeout was added Changed in version 3 12 Changed Windows shell search order for shell True The current directory and PATH are replaced with COMSPEC and SystemRoot System32 cmd exe As a result dropping a malicious program named cmd exe into a current directory no longer works subprocess check_call args stdin None stdout None stderr None shell False cwd None timeout None other_popen_kwargs Run command with arguments Wait for command to complete If the return code was zero then return otherwise raise CalledProcessError The CalledProcessError object will have the return code in the returncode attribute If check_call was unable to start the process it will propagate the exception that was raised Code needing to capture stdout or stderr should use run instead run check True To suppress stdout or stderr supply a value of DEVNULL The arguments shown above are merely some common ones The full function signature is the same as that of the Popen constructor this function passes all supplied arguments other than timeout directly through to that interface Note Do not use stdout PIPE or stderr PIPE with this function The child process will block if it generates enough output to a pipe to fill up the OS pipe buffer as the pipes are not being read from Changed in version 3 3 timeout was added Changed in version 3 12 Changed Windows shell search order for shell True The current directory and PATH are replaced with COMSPEC and SystemRoot System32 cmd exe As a result dropping a malicious program named cmd exe into a current directory no longer works subprocess check_output args stdin None stderr None shell False cwd None encoding None errors None universal_newlines None timeout None text None other_popen_kwargs Run command with arguments and return its output If the return code was non zero it raises a CalledProcessError The CalledProcessError object will have the return code in the returncode attribute and any output in the output attribute This is equivalent to run check True stdout PIPE stdout The arguments shown above are merely some common ones The full function signature is largely the same as that of run most arguments are passed directly through to that interface One API deviation from run behavior exists passing input None will behave the same as input b or input depending on other arguments rather than using the parent s standard input file handle By default this function will return the data as encoded bytes The actual encoding of the output data may depend on the command being invoked so the decoding to text will often need to be handled at the application level This behaviour may be overridden by setting text encoding errors or universal_newlines to True as described in Frequently Used Arguments and run To also capture standard error in the result use stderr subprocess STDOUT subprocess check_output ls non_existent_file exit 0 stderr subprocess STDOUT shell True ls non_existent_file No such file or directory n New in version 3 1 Changed in version 3 3 timeout was added Changed in version 3 4 Support for the input keyword argument was added Changed in version 3 6 encoding and errors were added See run for details New in version 3 7 text was added as a more readable alias for universal_newlines Changed in version 3 12 Changed Windows shell search order for shell True The current directory and PATH are replaced with COMSPEC and SystemRoot System32 cmd exe As a result dropping a malicious program named,en
2110, cmd exe into a current directory no longer works Replacing Older Functions with the subprocess Module In this section a becomes b means that b can be used as a replacement for a Note All a functions in this section fail more or less silently if the executed program cannot be found the b replacements raise OSError instead In addition the replacements using check_output will fail with a CalledProcessError if the requested operation produces a non zero return code The output is still available as the output attribute of the raised exception In the following examples we assume that the relevant functions have already been imported from the subprocess module Replacing bin sh shell command substitution output mycmd myarg becomes output check_output mycmd myarg Replacing shell pipeline output dmesg grep hda becomes p1 Popen dmesg stdout PIPE p2 Popen grep hda stdin p1 stdout stdout PIPE p1 stdout close Allow p1 to receive a SIGPIPE if p2 exits output p2 communicate 0 The p1 stdout close call after starting the p2 is important in order for p1 to receive a SIGPIPE if p2 exits before p1 Alternatively for trusted input the shell s own pipeline support may still be used directly output dmesg grep hda becomes output check_output dmesg grep hda shell True Replacing os system sts os system mycmd myarg becomes retcode call mycmd myarg shell True Notes Calling the program through the shell is usually not required The call return value is encoded differently to that of os system The os system function ignores SIGINT and SIGQUIT signals while the command is running but the caller must do this separately when using the subprocess module A more realistic example would look like this try retcode call mycmd myarg shell True if retcode 0 print Child was terminated by signal retcode file sys stderr else print Child returned retcode file sys stderr except OSError as e print Execution failed e file sys stderr Replacing the os spawn family P_NOWAIT example pid os spawnlp os P_NOWAIT bin mycmd mycmd myarg pid Popen bin mycmd myarg pid P_WAIT example retcode os spawnlp os P_WAIT bin mycmd mycmd myarg retcode call bin mycmd myarg Vector example os spawnvp os P_NOWAIT path args Popen path args 1 Environment example os spawnlpe os P_NOWAIT bin mycmd mycmd myarg env Popen bin mycmd myarg env PATH usr bin Replacing os popen os popen2 os popen3 child_stdin child_stdout os popen2 cmd mode bufsize p Popen cmd shell True bufsize bufsize stdin PIPE stdout PIPE close_fds True child_stdin child_stdout p stdin p stdout child_stdin child_stdout child_stderr os popen3 cmd mode bufsize p Popen cmd shell True bufsize bufsize stdin PIPE stdout PIPE stderr PIPE close_fds True child_stdin child_stdout child_stderr p stdin p stdout p stderr child_stdin child_stdout_and_stderr os popen4 cmd mode bufsize p Popen cmd shell True bufsize bufsize stdin PIPE stdout PIPE stderr STDOUT close_fds True child_stdin child_stdout_and_stderr p stdin p stdout Return code handling translates as follows pipe os popen cmd w rc pipe close if rc is not None and rc 8 print There were some errors process Popen cmd stdin PIPE process stdin close if process wait 0 print There were some errors Replacing functions from the popen2 module Note If the cmd argument to popen2 functions is a string the command is executed through bin sh If it is a list the command is directly executed child_stdout child_stdin popen2 popen2 somestring bufsize mode p Popen somestring shell True bufsize bufsize stdin PIPE stdout PIPE close_fds True child_stdout child_stdin p stdout p stdin child_stdout child_stdin popen2 popen2 mycmd myarg bufsize mode p Popen mycmd myarg bufsize bufsize stdin PIPE stdout PIPE close_fds True child_stdout child_stdin p stdout p stdin popen2 Popen3 and popen2 Popen4 basically work as subprocess Popen except that Popen raises an exception if the execution fails The capturestderr argument is replaced with the stderr argument stdin PIPE and stdout PIPE must be specified popen2 closes all file descriptors by default but you have to specify close_fds True with Popen to guarantee this behavior on,en
2111, all platforms or past Python versions Legacy Shell Invocation Functions This module also provides the following legacy functions from the 2 x commands module These operations implicitly invoke the system shell and none of the guarantees described above regarding security and exception handling consistency are valid for these functions subprocess getstatusoutput cmd encoding None errors None Return exitcode output of executing cmd in a shell Execute the string cmd in a shell with Popen check_output and return a 2 tuple exitcode output encoding and errors are used to decode output see the notes on Frequently Used Arguments for more details A trailing newline is stripped from the output The exit code for the command can be interpreted as the return code of subprocess Example subprocess getstatusoutput ls bin ls 0 bin ls subprocess getstatusoutput cat bin junk 1 cat bin junk No such file or directory subprocess getstatusoutput bin junk 127 sh bin junk not found subprocess getstatusoutput bin kill 15 Availability Unix Windows Changed in version 3 3 4 Windows support was added The function now returns exitcode output instead of status output as it did in Python 3 3 3 and earlier exitcode has the same value as returncode Changed in version 3 11 Added the encoding and errors parameters subprocess getoutput cmd encoding None errors None Return output stdout and stderr of executing cmd in a shell Like getstatusoutput except the exit code is ignored and the return value is a string containing the command s output Example subprocess getoutput ls bin ls bin ls Availability Unix Windows Changed in version 3 3 4 Windows support added Changed in version 3 11 Added the encoding and errors parameters Notes Converting an argument sequence to a string on Windows On Windows an args sequence is converted to a string that can be parsed using the following rules which correspond to the rules used by the MS C runtime 1 Arguments are delimited by white space which is either a space or a tab 2 A string surrounded by double quotation marks is interpreted as a single argument regardless of white space contained within A quoted string can be embedded in an argument 3 A double quotation mark preceded by a backslash is interpreted as a literal double quotation mark 4 Backslashes are interpreted literally unless they immediately precede a double quotation mark 5 If backslashes immediately precede a double quotation mark every pair of backslashes is interpreted as a literal backslash If the number of backslashes is odd the last backslash escapes the next double quotation mark as described in rule 3 See also shlex Module which provides function to parse and escape command lines Disabling use of vfork or posix_spawn On Linux subprocess defaults to using the vfork system call internally when it is safe to do so rather than fork This greatly improves performance If you ever encounter a presumed highly unusual situation where you need to prevent vfork from being used by Python you can set the subprocess _USE_VFORK attribute to a false value subprocess _USE_VFORK False See CPython issue gh NNNNNN Setting this has no impact on use of posix_spawn which could use vfork internally within its libc implementation There is a similar subprocess _USE_POSIX_SPAWN attribute if you need to prevent use of that subprocess _USE_POSIX_SPAWN False See CPython issue gh NNNNNN It is safe to set these to false on any Python version They will have no effect on older versions when unsupported Do not assume the attributes are available to read Despite their names a true value does not indicate that the corresponding function will be used only that it may be Please file issues any time you have to use these private knobs with a way to reproduce the issue you were seeing Link to that issue from a comment in your code New in version 3 8 _USE_POSIX_SPAWN New in version 3 11 _USE_VFORK,en
2112,Mapping Protocol See also PyObject_GetItem PyObject_SetItem and PyObject_DelItem int PyMapping_Check PyObject o Part of the Stable ABI Return 1 if the object provides the mapping protocol or supports slicing and 0 otherwise Note that it returns 1 for Python classes with a __getitem__ method since in general it is impossible to determine what type of keys the class supports This function always succeeds Py_ssize_t PyMapping_Size PyObject o Py_ssize_t PyMapping_Length PyObject o Part of the Stable ABI Returns the number of keys in object o on success and 1 on failure This is equivalent to the Python expression len o PyObject PyMapping_GetItemString PyObject o const char key Return value New reference Part of the Stable ABI This is the same as PyObject_GetItem but key is specified as a const char UTF 8 encoded bytes string rather than a PyObject int PyMapping_SetItemString PyObject o const char key PyObject v Part of the Stable ABI This is the same as PyObject_SetItem but key is specified as a const char UTF 8 encoded bytes string rather than a PyObject int PyMapping_DelItem PyObject o PyObject key This is an alias of PyObject_DelItem int PyMapping_DelItemString PyObject o const char key This is the same as PyObject_DelItem but key is specified as a const char UTF 8 encoded bytes string rather than a PyObject int PyMapping_HasKey PyObject o PyObject key Part of the Stable ABI Return 1 if the mapping object has the key key and 0 otherwise This is equivalent to the Python expression key in o This function always succeeds Note Exceptions which occur when this calls __getitem__ method are silently ignored For proper error handling use PyObject_GetItem instead int PyMapping_HasKeyString PyObject o const char key Part of the Stable ABI This is the same as PyMapping_HasKey but key is specified as a const char UTF 8 encoded bytes string rather than a PyObject Note Exceptions that occur when this calls __getitem__ method or while creating the temporary str object are silently ignored For proper error handling use PyMapping_GetItemString instead PyObject PyMapping_Keys PyObject o Return value New reference Part of the Stable ABI On success return a list of the keys in object o On failure return NULL Changed in version 3 7 Previously the function returned a list or a tuple PyObject PyMapping_Values PyObject o Return value New reference Part of the Stable ABI On success return a list of the values in object o On failure return NULL Changed in version 3 7 Previously the function returned a list or a tuple PyObject PyMapping_Items PyObject o Return value New reference Part of the Stable ABI On success return a list of the items in object o where each item is a tuple containing a key value pair On failure return NULL Changed in version 3 7 Previously the function returned a list or a tuple,en
2113,Glossary The default Python prompt of the interactive shell Often seen for code examples which can be executed interactively in the interpreter Can refer to The default Python prompt of the interactive shell when entering the code for an indented code block when within a pair of matching left and right delimiters parentheses square brackets curly braces or triple quotes or after specifying a decorator The Ellipsis built in constant 2to3 A tool that tries to convert Python 2 x code to Python 3 x code by handling most of the incompatibilities which can be detected by parsing the source and traversing the parse tree 2to3 is available in the standard library as lib2to3 a standalone entry point is provided as Tools scripts 2to3 See 2to3 Automated Python 2 to 3 code translation abstract base class Abstract base classes complement duck typing by providing a way to define interfaces when other techniques like hasattr would be clumsy or subtly wrong for example with magic methods ABCs introduce virtual subclasses which are classes that don t inherit from a class but are still recognized by isinstance and issubclass see the abc module documentation Python comes with many built in ABCs for data structures in the collections abc module numbers in the numbers module streams in the io module import finders and loaders in the importlib abc module You can create your own ABCs with the abc module annotation A label associated with a variable a class attribute or a function parameter or return value used by convention as a type hint Annotations of local variables cannot be accessed at runtime but annotations of global variables class attributes and functions are stored in the __annotations__ special attribute of modules classes and functions respectively See variable annotation function annotation PEP 484 and PEP 526 which describe this functionality Also see Annotations Best Practices for best practices on working with annotations argument A value passed to a function or method when calling the function There are two kinds of argument keyword argument an argument preceded by an identifier e g name in a function call or passed as a value in a dictionary preceded by For example 3 and 5 are both keyword arguments in the following calls to complex complex real 3 imag 5 complex real 3 imag 5 positional argument an argument that is not a keyword argument Positional arguments can appear at the beginning of an argument list and or be passed as elements of an iterable preceded by For example 3 and 5 are both positional arguments in the following calls complex 3 5 complex 3 5 Arguments are assigned to the named local variables in a function body See the Calls section for the rules governing this assignment Syntactically any expression can be used to represent an argument the evaluated value is assigned to the local variable See also the parameter glossary entry the FAQ question on the difference between arguments and parameters and PEP 362 asynchronous context manager An object which controls the environment seen in an async with statement by defining __aenter__ and __aexit__ methods Introduced by PEP 492 asynchronous generator A function which returns an asynchronous generator iterator It looks like a coroutine function defined with async def except that it contains yield expressions for producing a series of values usable in an async for loop Usually refers to an asynchronous generator function but may refer to an asynchronous generator iterator in some contexts In cases where the intended meaning isn t clear using the full terms avoids ambiguity An asynchronous generator function may contain await expressions as well as async for and async with statements asynchronous generator iterator An object created by a asynchronous generator function This is an asynchronous iterator which when called using the __anext__ method returns an awaitable object which will execute the body of the asynchronous generator function until the next yield expression Each yield temporarily suspends processing remembering the location execution state including local vari,en
2114,ables and pending try statements When the asynchronous generator iterator effectively resumes with another awaitable returned by __anext__ it picks up where it left off See PEP 492 and PEP 525 asynchronous iterable An object that can be used in an async for statement Must return an asynchronous iterator from its __aiter__ method Introduced by PEP 492 asynchronous iterator An object that implements the __aiter__ and __anext__ methods __anext__ must return an awaitable object async for resolves the awaitables returned by an asynchronous iterator s __anext__ method until it raises a StopAsyncIteration exception Introduced by PEP 492 attribute A value associated with an object which is usually referenced by name using dotted expressions For example if an object o has an attribute a it would be referenced as o a It is possible to give an object an attribute whose name is not an identifier as defined by Identifiers and keywords for example using setattr if the object allows it Such an attribute will not be accessible using a dotted expression and would instead need to be retrieved with getattr awaitable An object that can be used in an await expression Can be a coroutine or an object with an __await__ method See also PEP 492 BDFL Benevolent Dictator For Life a k a Guido van Rossum Python s creator binary file A file object able to read and write bytes like objects Examples of binary files are files opened in binary mode rb wb or rb sys stdin buffer sys stdout buffer and instances of io BytesIO and gzip GzipFile See also text file for a file object able to read and write str objects borrowed reference In Python s C API a borrowed reference is a reference to an object where the code using the object does not own the reference It becomes a dangling pointer if the object is destroyed For example a garbage collection can remove the last strong reference to the object and so destroy it Calling Py_INCREF on the borrowed reference is recommended to convert it to a strong reference in place except when the object cannot be destroyed before the last usage of the borrowed reference The Py_NewRef function can be used to create a new strong reference bytes like object An object that supports the Buffer Protocol and can export a C contiguous buffer This includes all bytes bytearray and array array objects as well as many common memoryview objects Bytes like objects can be used for various operations that work with binary data these include compression saving to a binary file and sending over a socket Some operations need the binary data to be mutable The documentation often refers to these as read write bytes like objects Example mutable buffer objects include bytearray and a memoryview of a bytearray Other operations require the binary data to be stored in immutable objects read only bytes like objects examples of these include bytes and a memoryview of a bytes object bytecode Python source code is compiled into bytecode the internal representation of a Python program in the CPython interpreter The bytecode is also cached in pyc files so that executing the same file is faster the second time recompilation from source to bytecode can be avoided This intermediate language is said to run on a virtual machine that executes the machine code corresponding to each bytecode Do note that bytecodes are not expected to work between different Python virtual machines nor to be stable between Python releases A list of bytecode instructions can be found in the documentation for the dis module callable A callable is an object that can be called possibly with a set of arguments see argument with the following syntax callable argument1 argument2 argumentN A function and by extension a method is a callable An instance of a class that implements the __call__ method is also a callable callback A subroutine function which is passed as an argument to be executed at some point in the future class A template for creating user defined objects Class definitions normally contain method definitions which operate on instances of the class class variable A variable defi,en
2115,ned in a class and intended to be modified only at class level i e not in an instance of the class complex number An extension of the familiar real number system in which all numbers are expressed as a sum of a real part and an imaginary part Imaginary numbers are real multiples of the imaginary unit the square root of 1 often written i in mathematics or j in engineering Python has built in support for complex numbers which are written with this latter notation the imaginary part is written with a j suffix e g 3 1j To get access to complex equivalents of the math module use cmath Use of complex numbers is a fairly advanced mathematical feature If you re not aware of a need for them it s almost certain you can safely ignore them context manager An object which controls the environment seen in a with statement by defining __enter__ and __exit__ methods See PEP 343 context variable A variable which can have different values depending on its context This is similar to Thread Local Storage in which each execution thread may have a different value for a variable However with context variables there may be several contexts in one execution thread and the main usage for context variables is to keep track of variables in concurrent asynchronous tasks See contextvars contiguous A buffer is considered contiguous exactly if it is either C contiguous or Fortran contiguous Zero dimensional buffers are C and Fortran contiguous In one dimensional arrays the items must be laid out in memory next to each other in order of increasing indexes starting from zero In multidimensional C contiguous arrays the last index varies the fastest when visiting items in order of memory address However in Fortran contiguous arrays the first index varies the fastest coroutine Coroutines are a more generalized form of subroutines Subroutines are entered at one point and exited at another point Coroutines can be entered exited and resumed at many different points They can be implemented with the async def statement See also PEP 492 coroutine function A function which returns a coroutine object A coroutine function may be defined with the async def statement and may contain await async for and async with keywords These were introduced by PEP 492 CPython The canonical implementation of the Python programming language as distributed on python org The term CPython is used when necessary to distinguish this implementation from others such as Jython or IronPython decorator A function returning another function usually applied as a function transformation using the wrapper syntax Common examples for decorators are classmethod and staticmethod The decorator syntax is merely syntactic sugar the following two function definitions are semantically equivalent def f arg f staticmethod f staticmethod def f arg The same concept exists for classes but is less commonly used there See the documentation for function definitions and class definitions for more about decorators descriptor Any object which defines the methods __get__ __set__ or __delete__ When a class attribute is a descriptor its special binding behavior is triggered upon attribute lookup Normally using a b to get set or delete an attribute looks up the object named b in the class dictionary for a but if b is a descriptor the respective descriptor method gets called Understanding descriptors is a key to a deep understanding of Python because they are the basis for many features including functions methods properties class methods static methods and reference to super classes For more information about descriptors methods see Implementing Descriptors or the Descriptor How To Guide dictionary An associative array where arbitrary keys are mapped to values The keys can be any object with __hash__ and __eq__ methods Called a hash in Perl dictionary comprehension A compact way to process all or part of the elements in an iterable and return a dictionary with the results results n n 2 for n in range 10 generates a dictionary containing key n mapped to value n 2 See Displays for lists sets and dictionaries dictionary vie,en
2116,w The objects returned from dict keys dict values and dict items are called dictionary views They provide a dynamic view on the dictionary s entries which means that when the dictionary changes the view reflects these changes To force the dictionary view to become a full list use list dictview See Dictionary view objects docstring A string literal which appears as the first expression in a class function or module While ignored when the suite is executed it is recognized by the compiler and put into the __doc__ attribute of the enclosing class function or module Since it is available via introspection it is the canonical place for documentation of the object duck typing A programming style which does not look at an object s type to determine if it has the right interface instead the method or attribute is simply called or used If it looks like a duck and quacks like a duck it must be a duck By emphasizing interfaces rather than specific types well designed code improves its flexibility by allowing polymorphic substitution Duck typing avoids tests using type or isinstance Note however that duck typing can be complemented with abstract base classes Instead it typically employs hasattr tests or EAFP programming EAFP Easier to ask for forgiveness than permission This common Python coding style assumes the existence of valid keys or attributes and catches exceptions if the assumption proves false This clean and fast style is characterized by the presence of many try and except statements The technique contrasts with the LBYL style common to many other languages such as C expression A piece of syntax which can be evaluated to some value In other words an expression is an accumulation of expression elements like literals names attribute access operators or function calls which all return a value In contrast to many other languages not all language constructs are expressions There are also statement s which cannot be used as expressions such as while Assignments are also statements not expressions extension module A module written in C or C using Python s C API to interact with the core and with user code f string String literals prefixed with f or F are commonly called f strings which is short for formatted string literals See also PEP 498 file object An object exposing a file oriented API with methods such as read or write to an underlying resource Depending on the way it was created a file object can mediate access to a real on disk file or to another type of storage or communication device for example standard input output in memory buffers sockets pipes etc File objects are also called file like objects or streams There are actually three categories of file objects raw binary files buffered binary files and text files Their interfaces are defined in the io module The canonical way to create a file object is by using the open function file like object A synonym for file object filesystem encoding and error handler Encoding and error handler used by Python to decode bytes from the operating system and encode Unicode to the operating system The filesystem encoding must guarantee to successfully decode all bytes below 128 If the file system encoding fails to provide this guarantee API functions can raise UnicodeError The sys getfilesystemencoding and sys getfilesystemencodeerrors functions can be used to get the filesystem encoding and error handler The filesystem encoding and error handler are configured at Python startup by the PyConfig_Read function see filesystem_encoding and filesystem_errors members of PyConfig See also the locale encoding finder An object that tries to find the loader for a module that is being imported Since Python 3 3 there are two types of finder meta path finders for use with sys meta_path and path entry finders for use with sys path_hooks See PEP 302 PEP 420 and PEP 451 for much more detail floor division Mathematical division that rounds down to nearest integer The floor division operator is For example the expression 11 4 evaluates to 2 in contrast to the 2 75 returned by float true division Note ,en
2117,that 11 4 is 3 because that is 2 75 rounded downward See PEP 238 function A series of statements which returns some value to a caller It can also be passed zero or more arguments which may be used in the execution of the body See also parameter method and the Function definitions section function annotation An annotation of a function parameter or return value Function annotations are usually used for type hints for example this function is expected to take two int arguments and is also expected to have an int return value def sum_two_numbers a int b int int return a b Function annotation syntax is explained in section Function definitions See variable annotation and PEP 484 which describe this functionality Also see Annotations Best Practices for best practices on working with annotations __future__ A future statement from __future__ import feature directs the compiler to compile the current module using syntax or semantics that will become standard in a future release of Python The __future__ module documents the possible values of feature By importing this module and evaluating its variables you can see when a new feature was first added to the language and when it will or did become the default import __future__ __future__ division _Feature 2 2 0 alpha 2 3 0 0 alpha 0 8192 garbage collection The process of freeing memory when it is not used anymore Python performs garbage collection via reference counting and a cyclic garbage collector that is able to detect and break reference cycles The garbage collector can be controlled using the gc module generator A function which returns a generator iterator It looks like a normal function except that it contains yield expressions for producing a series of values usable in a for loop or that can be retrieved one at a time with the next function Usually refers to a generator function but may refer to a generator iterator in some contexts In cases where the intended meaning isn t clear using the full terms avoids ambiguity generator iterator An object created by a generator function Each yield temporarily suspends processing remembering the location execution state including local variables and pending try statements When the generator iterator resumes it picks up where it left off in contrast to functions which start fresh on every invocation generator expression An expression that returns an iterator It looks like a normal expression followed by a for clause defining a loop variable range and an optional if clause The combined expression generates values for an enclosing function sum i i for i in range 10 sum of squares 0 1 4 81 285 generic function A function composed of multiple functions implementing the same operation for different types Which implementation should be used during a call is determined by the dispatch algorithm See also the single dispatch glossary entry the functools singledispatch decorator and PEP 443 generic type A type that can be parameterized typically a container class such as list or dict Used for type hints and annotations For more details see generic alias types PEP 483 PEP 484 PEP 585 and the typing module GIL See global interpreter lock global interpreter lock The mechanism used by the CPython interpreter to assure that only one thread executes Python bytecode at a time This simplifies the CPython implementation by making the object model including critical built in types such as dict implicitly safe against concurrent access Locking the entire interpreter makes it easier for the interpreter to be multi threaded at the expense of much of the parallelism afforded by multi processor machines However some extension modules either standard or third party are designed so as to release the GIL when doing computationally intensive tasks such as compression or hashing Also the GIL is always released when doing I O Past efforts to create a free threaded interpreter one which locks shared data at a much finer granularity have not been successful because performance suffered in the common single processor case It is believed that overcoming this performanc,en
2118,e issue would make the implementation much more complicated and therefore costlier to maintain hash based pyc A bytecode cache file that uses the hash rather than the last modified time of the corresponding source file to determine its validity See Cached bytecode invalidation hashable An object is hashable if it has a hash value which never changes during its lifetime it needs a __hash__ method and can be compared to other objects it needs an __eq__ method Hashable objects which compare equal must have the same hash value Hashability makes an object usable as a dictionary key and a set member because these data structures use the hash value internally Most of Python s immutable built in objects are hashable mutable containers such as lists or dictionaries are not immutable containers such as tuples and frozensets are only hashable if their elements are hashable Objects which are instances of user defined classes are hashable by default They all compare unequal except with themselves and their hash value is derived from their id IDLE An Integrated Development and Learning Environment for Python IDLE is a basic editor and interpreter environment which ships with the standard distribution of Python immutable An object with a fixed value Immutable objects include numbers strings and tuples Such an object cannot be altered A new object has to be created if a different value has to be stored They play an important role in places where a constant hash value is needed for example as a key in a dictionary import path A list of locations or path entries that are searched by the path based finder for modules to import During import this list of locations usually comes from sys path but for subpackages it may also come from the parent package s __path__ attribute importing The process by which Python code in one module is made available to Python code in another module importer An object that both finds and loads a module both a finder and loader object interactive Python has an interactive interpreter which means you can enter statements and expressions at the interpreter prompt immediately execute them and see their results Just launch python with no arguments possibly by selecting it from your computer s main menu It is a very powerful way to test out new ideas or inspect modules and packages remember help x interpreted Python is an interpreted language as opposed to a compiled one though the distinction can be blurry because of the presence of the bytecode compiler This means that source files can be run directly without explicitly creating an executable which is then run Interpreted languages typically have a shorter development debug cycle than compiled ones though their programs generally also run more slowly See also interactive interpreter shutdown When asked to shut down the Python interpreter enters a special phase where it gradually releases all allocated resources such as modules and various critical internal structures It also makes several calls to the garbage collector This can trigger the execution of code in user defined destructors or weakref callbacks Code executed during the shutdown phase can encounter various exceptions as the resources it relies on may not function anymore common examples are library modules or the warnings machinery The main reason for interpreter shutdown is that the __main__ module or the script being run has finished executing iterable An object capable of returning its members one at a time Examples of iterables include all sequence types such as list str and tuple and some non sequence types like dict file objects and objects of any classes you define with an __iter__ method or with a __getitem__ method that implements sequence semantics Iterables can be used in a for loop and in many other places where a sequence is needed zip map When an iterable object is passed as an argument to the built in function iter it returns an iterator for the object This iterator is good for one pass over the set of values When using iterables it is usually not necessary to call iter or deal with iterator,en
2119, objects yourself The for statement does that automatically for you creating a temporary unnamed variable to hold the iterator for the duration of the loop See also iterator sequence and generator iterator An object representing a stream of data Repeated calls to the iterator s __next__ method or passing it to the built in function next return successive items in the stream When no more data are available a StopIteration exception is raised instead At this point the iterator object is exhausted and any further calls to its __next__ method just raise StopIteration again Iterators are required to have an __iter__ method that returns the iterator object itself so every iterator is also iterable and may be used in most places where other iterables are accepted One notable exception is code which attempts multiple iteration passes A container object such as a list produces a fresh new iterator each time you pass it to the iter function or use it in a for loop Attempting this with an iterator will just return the same exhausted iterator object used in the previous iteration pass making it appear like an empty container More information can be found in Iterator Types CPython implementation detail CPython does not consistently apply the requirement that an iterator define __iter__ key function A key function or collation function is a callable that returns a value used for sorting or ordering For example locale strxfrm is used to produce a sort key that is aware of locale specific sort conventions A number of tools in Python accept key functions to control how elements are ordered or grouped They include min max sorted list sort heapq merge heapq nsmallest heapq nlargest and itertools groupby There are several ways to create a key function For example the str lower method can serve as a key function for case insensitive sorts Alternatively a key function can be built from a lambda expression such as lambda r r 0 r 2 Also operator attrgetter operator itemgetter and operator methodcaller are three key function constructors See the Sorting HOW TO for examples of how to create and use key functions keyword argument See argument lambda An anonymous inline function consisting of a single expression which is evaluated when the function is called The syntax to create a lambda function is lambda parameters expression LBYL Look before you leap This coding style explicitly tests for pre conditions before making calls or lookups This style contrasts with the EAFP approach and is characterized by the presence of many if statements In a multi threaded environment the LBYL approach can risk introducing a race condition between the looking and the leaping For example the code if key in mapping return mapping key can fail if another thread removes key from mapping after the test but before the lookup This issue can be solved with locks or by using the EAFP approach locale encoding On Unix it is the encoding of the LC_CTYPE locale It can be set with locale setlocale locale LC_CTYPE new_locale On Windows it is the ANSI code page ex cp1252 On Android and VxWorks Python uses utf 8 as the locale encoding locale getencoding can be used to get the locale encoding See also the filesystem encoding and error handler list A built in Python sequence Despite its name it is more akin to an array in other languages than to a linked list since access to elements is O 1 list comprehension A compact way to process all or part of the elements in a sequence and return a list with the results result 04x format x for x in range 256 if x 2 0 generates a list of strings containing even hex numbers 0x in the range from 0 to 255 The if clause is optional If omitted all elements in range 256 are processed loader An object that loads a module It must define a method named load_module A loader is typically returned by a finder See PEP 302 for details and importlib abc Loader for an abstract base class magic method An informal synonym for special method mapping A container object that supports arbitrary key lookups and implements the methods specified in the collections abc ,en
2120,Mapping or collections abc MutableMapping abstract base classes Examples include dict collections defaultdict collections OrderedDict and collections Counter meta path finder A finder returned by a search of sys meta_path Meta path finders are related to but different from path entry finders See importlib abc MetaPathFinder for the methods that meta path finders implement metaclass The class of a class Class definitions create a class name a class dictionary and a list of base classes The metaclass is responsible for taking those three arguments and creating the class Most object oriented programming languages provide a default implementation What makes Python special is that it is possible to create custom metaclasses Most users never need this tool but when the need arises metaclasses can provide powerful elegant solutions They have been used for logging attribute access adding thread safety tracking object creation implementing singletons and many other tasks More information can be found in Metaclasses method A function which is defined inside a class body If called as an attribute of an instance of that class the method will get the instance object as its first argument which is usually called self See function and nested scope method resolution order Method Resolution Order is the order in which base classes are searched for a member during lookup See The Python 2 3 Method Resolution Order for details of the algorithm used by the Python interpreter since the 2 3 release module An object that serves as an organizational unit of Python code Modules have a namespace containing arbitrary Python objects Modules are loaded into Python by the process of importing See also package module spec A namespace containing the import related information used to load a module An instance of importlib machinery ModuleSpec MRO See method resolution order mutable Mutable objects can change their value but keep their id See also immutable named tuple The term named tuple applies to any type or class that inherits from tuple and whose indexable elements are also accessible using named attributes The type or class may have other features as well Several built in types are named tuples including the values returned by time localtime and os stat Another example is sys float_info sys float_info 1 indexed access 1024 sys float_info max_exp named field access 1024 isinstance sys float_info tuple kind of tuple True Some named tuples are built in types such as the above examples Alternatively a named tuple can be created from a regular class definition that inherits from tuple and that defines named fields Such a class can be written by hand or it can be created by inheriting typing NamedTuple or with the factory function collections namedtuple The latter techniques also add some extra methods that may not be found in hand written or built in named tuples namespace The place where a variable is stored Namespaces are implemented as dictionaries There are the local global and built in namespaces as well as nested namespaces in objects in methods Namespaces support modularity by preventing naming conflicts For instance the functions builtins open and os open are distinguished by their namespaces Namespaces also aid readability and maintainability by making it clear which module implements a function For instance writing random seed or itertools islice makes it clear that those functions are implemented by the random and itertools modules respectively namespace package A PEP 420 package which serves only as a container for subpackages Namespace packages may have no physical representation and specifically are not like a regular package because they have no __init__ py file See also module nested scope The ability to refer to a variable in an enclosing definition For instance a function defined inside another function can refer to variables in the outer function Note that nested scopes by default work only for reference and not for assignment Local variables both read and write in the innermost scope Likewise global variables read and write to the g,en
2121,lobal namespace The nonlocal allows writing to outer scopes new style class Old name for the flavor of classes now used for all class objects In earlier Python versions only new style classes could use Python s newer versatile features like __slots__ descriptors properties __getattribute__ class methods and static methods object Any data with state attributes or value and defined behavior methods Also the ultimate base class of any new style class package A Python module which can contain submodules or recursively subpackages Technically a package is a Python module with a __path__ attribute See also regular package and namespace package parameter A named entity in a function or method definition that specifies an argument or in some cases arguments that the function can accept There are five kinds of parameter positional or keyword specifies an argument that can be passed either positionally or as a keyword argument This is the default kind of parameter for example foo and bar in the following def func foo bar None positional only specifies an argument that can be supplied only by position Positional only parameters can be defined by including a character in the parameter list of the function definition after them for example posonly1 and posonly2 in the following def func posonly1 posonly2 positional_or_keyword keyword only specifies an argument that can be supplied only by keyword Keyword only parameters can be defined by including a single var positional parameter or bare in the parameter list of the function definition before them for example kw_only1 and kw_only2 in the following def func arg kw_only1 kw_only2 var positional specifies that an arbitrary sequence of positional arguments can be provided in addition to any positional arguments already accepted by other parameters Such a parameter can be defined by prepending the parameter name with for example args in the following def func args kwargs var keyword specifies that arbitrarily many keyword arguments can be provided in addition to any keyword arguments already accepted by other parameters Such a parameter can be defined by prepending the parameter name with for example kwargs in the example above Parameters can specify both optional and required arguments as well as default values for some optional arguments See also the argument glossary entry the FAQ question on the difference between arguments and parameters the inspect Parameter class the Function definitions section and PEP 362 path entry A single location on the import path which the path based finder consults to find modules for importing path entry finder A finder returned by a callable on sys path_hooks i e a path entry hook which knows how to locate modules given a path entry See importlib abc PathEntryFinder for the methods that path entry finders implement path entry hook A callable on the sys path_hooks list which returns a path entry finder if it knows how to find modules on a specific path entry path based finder One of the default meta path finders which searches an import path for modules path like object An object representing a file system path A path like object is either a str or bytes object representing a path or an object implementing the os PathLike protocol An object that supports the os PathLike protocol can be converted to a str or bytes file system path by calling the os fspath function os fsdecode and os fsencode can be used to guarantee a str or bytes result instead respectively Introduced by PEP 519 PEP Python Enhancement Proposal A PEP is a design document providing information to the Python community or describing a new feature for Python or its processes or environment PEPs should provide a concise technical specification and a rationale for proposed features PEPs are intended to be the primary mechanisms for proposing major new features for collecting community input on an issue and for documenting the design decisions that have gone into Python The PEP author is responsible for building consensus within the community and documenting dissenting opinions See PEP 1 portion,en
2122, A set of files in a single directory possibly stored in a zip file that contribute to a namespace package as defined in PEP 420 positional argument See argument provisional API A provisional API is one which has been deliberately excluded from the standard library s backwards compatibility guarantees While major changes to such interfaces are not expected as long as they are marked provisional backwards incompatible changes up to and including removal of the interface may occur if deemed necessary by core developers Such changes will not be made gratuitously they will occur only if serious fundamental flaws are uncovered that were missed prior to the inclusion of the API Even for provisional APIs backwards incompatible changes are seen as a solution of last resort every attempt will still be made to find a backwards compatible resolution to any identified problems This process allows the standard library to continue to evolve over time without locking in problematic design errors for extended periods of time See PEP 411 for more details provisional package See provisional API Python 3000 Nickname for the Python 3 x release line coined long ago when the release of version 3 was something in the distant future This is also abbreviated Py3k Pythonic An idea or piece of code which closely follows the most common idioms of the Python language rather than implementing code using concepts common to other languages For example a common idiom in Python is to loop over all elements of an iterable using a for statement Many other languages don t have this type of construct so people unfamiliar with Python sometimes use a numerical counter instead for i in range len food print food i As opposed to the cleaner Pythonic method for piece in food print piece qualified name A dotted name showing the path from a module s global scope to a class function or method defined in that module as defined in PEP 3155 For top level functions and classes the qualified name is the same as the object s name class C class D def meth self pass C __qualname__ C C D __qualname__ C D C D meth __qualname__ C D meth When used to refer to modules the fully qualified name means the entire dotted path to the module including any parent packages e g email mime text import email mime text email mime text __name__ email mime text reference count The number of references to an object When the reference count of an object drops to zero it is deallocated Some objects are immortal and have reference counts that are never modified and therefore the objects are never deallocated Reference counting is generally not visible to Python code but it is a key element of the CPython implementation Programmers can call the sys getrefcount function to return the reference count for a particular object regular package A traditional package such as a directory containing an __init__ py file See also namespace package __slots__ A declaration inside a class that saves memory by pre declaring space for instance attributes and eliminating instance dictionaries Though popular the technique is somewhat tricky to get right and is best reserved for rare cases where there are large numbers of instances in a memory critical application sequence An iterable which supports efficient element access using integer indices via the __getitem__ special method and defines a __len__ method that returns the length of the sequence Some built in sequence types are list str tuple and bytes Note that dict also supports __getitem__ and __len__ but is considered a mapping rather than a sequence because the lookups use arbitrary immutable keys rather than integers The collections abc Sequence abstract base class defines a much richer interface that goes beyond just __getitem__ and __len__ adding count index __contains__ and __reversed__ Types that implement this expanded interface can be registered explicitly using register For more documentation on sequence methods generally see Common Sequence Operations set comprehension A compact way to process all or part of the elements in an iterable and return a set ,en
2123,with the results results c for c in abracadabra if c not in abc generates the set of strings r d See Displays for lists sets and dictionaries single dispatch A form of generic function dispatch where the implementation is chosen based on the type of a single argument slice An object usually containing a portion of a sequence A slice is created using the subscript notation with colons between numbers when several are given such as in variable_name 1 3 5 The bracket subscript notation uses slice objects internally special method A method that is called implicitly by Python to execute a certain operation on a type such as addition Such methods have names starting and ending with double underscores Special methods are documented in Special method names statement A statement is part of a suite a block of code A statement is either an expression or one of several constructs with a keyword such as if while or for static type checker An external tool that reads Python code and analyzes it looking for issues such as incorrect types See also type hints and the typing module strong reference In Python s C API a strong reference is a reference to an object which is owned by the code holding the reference The strong reference is taken by calling Py_INCREF when the reference is created and released with Py_DECREF when the reference is deleted The Py_NewRef function can be used to create a strong reference to an object Usually the Py_DECREF function must be called on the strong reference before exiting the scope of the strong reference to avoid leaking one reference See also borrowed reference text encoding A string in Python is a sequence of Unicode code points in range U 0000 U 10FFFF To store or transfer a string it needs to be serialized as a sequence of bytes Serializing a string into a sequence of bytes is known as encoding and recreating the string from the sequence of bytes is known as decoding There are a variety of different text serialization codecs which are collectively referred to as text encodings text file A file object able to read and write str objects Often a text file actually accesses a byte oriented datastream and handles the text encoding automatically Examples of text files are files opened in text mode r or w sys stdin sys stdout and instances of io StringIO See also binary file for a file object able to read and write bytes like objects triple quoted string A string which is bound by three instances of either a quotation mark or an apostrophe While they don t provide any functionality not available with single quoted strings they are useful for a number of reasons They allow you to include unescaped single and double quotes within a string and they can span multiple lines without the use of the continuation character making them especially useful when writing docstrings type The type of a Python object determines what kind of object it is every object has a type An object s type is accessible as its __class__ attribute or can be retrieved with type obj type alias A synonym for a type created by assigning the type to an identifier Type aliases are useful for simplifying type hints For example def remove_gray_shades colors list tuple int int int list tuple int int int pass could be made more readable like this Color tuple int int int def remove_gray_shades colors list Color list Color pass See typing and PEP 484 which describe this functionality type hint An annotation that specifies the expected type for a variable a class attribute or a function parameter or return value Type hints are optional and are not enforced by Python but they are useful to static type checkers They can also aid IDEs with code completion and refactoring Type hints of global variables class attributes and functions but not local variables can be accessed using typing get_type_hints See typing and PEP 484 which describe this functionality universal newlines A manner of interpreting text streams in which all of the following are recognized as ending a line the Unix end of line convention n the Windows convention r n and the old Macintosh c,en
2124,onvention r See PEP 278 and PEP 3116 as well as bytes splitlines for an additional use variable annotation An annotation of a variable or a class attribute When annotating a variable or a class attribute assignment is optional class C field annotation Variable annotations are usually used for type hints for example this variable is expected to take int values count int 0 Variable annotation syntax is explained in section Annotated assignment statements See function annotation PEP 484 and PEP 526 which describe this functionality Also see Annotations Best Practices for best practices on working with annotations virtual environment A cooperatively isolated runtime environment that allows Python users and applications to install and upgrade Python distribution packages without interfering with the behaviour of other Python applications running on the same system See also venv virtual machine A computer defined entirely in software Python s virtual machine executes the bytecode emitted by the bytecode compiler Zen of Python Listing of Python design principles and philosophies that are helpful in understanding and using the language The listing can be found by typing import this at the interactive prompt,en
2125,binascii Convert between binary and ASCII The binascii module contains a number of methods to convert between binary and various ASCII encoded binary representations Normally you will not use these functions directly but use wrapper modules like uu or base64 instead The binascii module contains low level functions written in C for greater speed that are used by the higher level modules Note a2b_ functions accept Unicode strings containing only ASCII characters Other functions only accept bytes like objects such as bytes bytearray and other objects that support the buffer protocol Changed in version 3 3 ASCII only unicode strings are now accepted by the a2b_ functions The binascii module defines the following functions binascii a2b_uu string Convert a single line of uuencoded data back to binary and return the binary data Lines normally contain 45 binary bytes except for the last line Line data may be followed by whitespace binascii b2a_uu data backtick False Convert binary data to a line of ASCII characters the return value is the converted line including a newline char The length of data should be at most 45 If backtick is true zeros are represented by instead of spaces Changed in version 3 7 Added the backtick parameter binascii a2b_base64 string strict_mode False Convert a block of base64 data back to binary and return the binary data More than one line may be passed at a time If strict_mode is true only valid base64 data will be converted Invalid base64 data will raise binascii Error Valid base64 Conforms to RFC 3548 Contains only characters from the base64 alphabet Contains no excess data after padding including excess padding newlines etc Does not start with a padding Changed in version 3 11 Added the strict_mode parameter binascii b2a_base64 data newline True Convert binary data to a line of ASCII characters in base64 coding The return value is the converted line including a newline char if newline is true The output of this function conforms to RFC 3548 Changed in version 3 6 Added the newline parameter binascii a2b_qp data header False Convert a block of quoted printable data back to binary and return the binary data More than one line may be passed at a time If the optional argument header is present and true underscores will be decoded as spaces binascii b2a_qp data quotetabs False istext True header False Convert binary data to a line s of ASCII characters in quoted printable encoding The return value is the converted line s If the optional argument quotetabs is present and true all tabs and spaces will be encoded If the optional argument istext is present and true newlines are not encoded but trailing whitespace will be encoded If the optional argument header is present and true spaces will be encoded as underscores per RFC 1522 If the optional argument header is present and false newline characters will be encoded as well otherwise linefeed conversion might corrupt the binary data stream binascii crc_hqx data value Compute a 16 bit CRC value of data starting with value as the initial CRC and return the result This uses the CRC CCITT polynomial x 16 x 12 x 5 1 often represented as 0x1021 This CRC is used in the binhex4 format binascii crc32 data value Compute CRC 32 the unsigned 32 bit checksum of data starting with an initial CRC of value The default initial CRC is zero The algorithm is consistent with the ZIP file checksum Since the algorithm is designed for use as a checksum algorithm it is not suitable for use as a general hash algorithm Use as follows print binascii crc32 b hello world Or in two pieces crc binascii crc32 b hello crc binascii crc32 b world crc print crc32 010x format crc Changed in version 3 0 The result is always unsigned binascii b2a_hex data sep bytes_per_sep 1 binascii hexlify data sep bytes_per_sep 1 Return the hexadecimal representation of the binary data Every byte of data is converted into the corresponding 2 digit hex representation The returned bytes object is therefore twice as long as the length of data Similar functionality but returning a text string is also conveniently ac,en
2126,cessible using the bytes hex method If sep is specified it must be a single character str or bytes object It will be inserted in the output after every bytes_per_sep input bytes Separator placement is counted from the right end of the output by default if you wish to count from the left supply a negative bytes_per_sep value import binascii binascii b2a_hex b xb9 x01 xef b b901ef binascii hexlify b xb9 x01 xef b b9 01 ef binascii b2a_hex b xb9 x01 xef b _ 2 b b9_01ef binascii b2a_hex b xb9 x01 xef b 2 b b901 ef Changed in version 3 8 The sep and bytes_per_sep parameters were added binascii a2b_hex hexstr binascii unhexlify hexstr Return the binary data represented by the hexadecimal string hexstr This function is the inverse of b2a_hex hexstr must contain an even number of hexadecimal digits which can be upper or lower case otherwise an Error exception is raised Similar functionality accepting only text string arguments but more liberal towards whitespace is also accessible using the bytes fromhex class method exception binascii Error Exception raised on errors These are usually programming errors exception binascii Incomplete Exception raised on incomplete data These are usually not programming errors but may be handled by reading a little more data and trying again See also Module base64 Support for RFC compliant base64 style encoding in base 16 32 64 and 85 Module uu Support for UU encoding used on Unix Module quopri Support for quoted printable encoding used in MIME email messages,en
2127,xml parsers expat Fast XML parsing using Expat Warning The pyexpat module is not secure against maliciously constructed data If you need to parse untrusted or unauthenticated data see XML vulnerabilities The xml parsers expat module is a Python interface to the Expat non validating XML parser The module provides a single extension type xmlparser that represents the current state of an XML parser After an xmlparser object has been created various attributes of the object can be set to handler functions When an XML document is then fed to the parser the handler functions are called for the character data and markup in the XML document This module uses the pyexpat module to provide access to the Expat parser Direct use of the pyexpat module is deprecated This module provides one exception and one type object exception xml parsers expat ExpatError The exception raised when Expat reports an error See section ExpatError Exceptions for more information on interpreting Expat errors exception xml parsers expat error Alias for ExpatError xml parsers expat XMLParserType The type of the return values from the ParserCreate function The xml parsers expat module contains two functions xml parsers expat ErrorString errno Returns an explanatory string for a given error number errno xml parsers expat ParserCreate encoding None namespace_separator None Creates and returns a new xmlparser object encoding if specified must be a string naming the encoding used by the XML data Expat doesn t support as many encodings as Python does and its repertoire of encodings can t be extended it supports UTF 8 UTF 16 ISO 8859 1 Latin1 and ASCII If encoding 1 is given it will override the implicit or explicit encoding of the document Expat can optionally do XML namespace processing for you enabled by providing a value for namespace_separator The value must be a one character string a ValueError will be raised if the string has an illegal length None is considered the same as omission When namespace processing is enabled element type names and attribute names that belong to a namespace will be expanded The element name passed to the element handlers StartElementHandler and EndElementHandler will be the concatenation of the namespace URI the namespace separator character and the local part of the name If the namespace separator is a zero byte chr 0 then the namespace URI and the local part will be concatenated without any separator For example if namespace_separator is set to a space character and the following document is parsed xml version 1 0 root xmlns http default namespace org xmlns py http www python org ns py elem1 elem2 xmlns root StartElementHandler will receive the following strings for each element http default namespace org root http www python org ns elem1 elem2 Due to limitations in the Expat library used by pyexpat the xmlparser instance returned can only be used to parse a single XML document Call ParserCreate for each document to provide unique parser instances See also The Expat XML Parser Home page of the Expat project XMLParser Objects xmlparser objects have the following methods xmlparser Parse data isfinal Parses the contents of the string data calling the appropriate handler functions to process the parsed data isfinal must be true on the final call to this method it allows the parsing of a single file in fragments not the submission of multiple files data can be the empty string at any time xmlparser ParseFile file Parse XML data reading from the object file file only needs to provide the read nbytes method returning the empty string when there s no more data xmlparser SetBase base Sets the base to be used for resolving relative URIs in system identifiers in declarations Resolving relative identifiers is left to the application this value will be passed through as the base argument to the ExternalEntityRefHandler NotationDeclHandler and UnparsedEntityDeclHandler functions xmlparser GetBase Returns a string containing the base set by a previous call to SetBase or None if SetBase hasn t been called xmlparser GetInputContext Returns the ,en
2128,input data that generated the current event as a string The data is in the encoding of the entity which contains the text When called while an event handler is not active the return value is None xmlparser ExternalEntityParserCreate context encoding Create a child parser which can be used to parse an external parsed entity referred to by content parsed by the parent parser The context parameter should be the string passed to the ExternalEntityRefHandler handler function described below The child parser is created with the ordered_attributes and specified_attributes set to the values of this parser xmlparser SetParamEntityParsing flag Control parsing of parameter entities including the external DTD subset Possible flag values are XML_PARAM_ENTITY_PARSING_NEVER XML_PARAM_ENTITY_PARSING_UNLESS_STANDALONE and XML_PARAM_ENTITY_PARSING_ALWAYS Return true if setting the flag was successful xmlparser UseForeignDTD flag Calling this with a true value for flag the default will cause Expat to call the ExternalEntityRefHandler with None for all arguments to allow an alternate DTD to be loaded If the document does not contain a document type declaration the ExternalEntityRefHandler will still be called but the StartDoctypeDeclHandler and EndDoctypeDeclHandler will not be called Passing a false value for flag will cancel a previous call that passed a true value but otherwise has no effect This method can only be called before the Parse or ParseFile methods are called calling it after either of those have been called causes ExpatError to be raised with the code attribute set to errors codes errors XML_ERROR_CANT_CHANGE_FEATURE_ONCE_PARSING xmlparser SetReparseDeferralEnabled enabled Warning Calling SetReparseDeferralEnabled False has security implications as detailed below please make sure to understand these consequences prior to using the SetReparseDeferralEnabled method Expat 2 6 0 introduced a security mechanism called reparse deferral where instead of causing denial of service through quadratic runtime from reparsing large tokens reparsing of unfinished tokens is now delayed by default until a sufficient amount of input is reached Due to this delay registered handlers may depending of the sizing of input chunks pushed to Expat no longer be called right after pushing new input to the parser Where immediate feedback and taking over responsiblity of protecting against denial of service from large tokens are both wanted calling SetReparseDeferralEnabled False disables reparse deferral for the current Expat parser instance temporarily or altogether Calling SetReparseDeferralEnabled True allows re enabling reparse deferral Note that SetReparseDeferralEnabled has been backported to some prior releases of CPython as a security fix Check for availability of SetReparseDeferralEnabled using hasattr if used in code running across a variety of Python versions New in version 3 12 3 xmlparser GetReparseDeferralEnabled Returns whether reparse deferral is currently enabled for the given Expat parser instance New in version 3 12 3 xmlparser objects have the following attributes xmlparser buffer_size The size of the buffer used when buffer_text is true A new buffer size can be set by assigning a new integer value to this attribute When the size is changed the buffer will be flushed xmlparser buffer_text Setting this to true causes the xmlparser object to buffer textual content returned by Expat to avoid multiple calls to the CharacterDataHandler callback whenever possible This can improve performance substantially since Expat normally breaks character data into chunks at every line ending This attribute is false by default and may be changed at any time Note that when it is false data that does not contain newlines may be chunked too xmlparser buffer_used If buffer_text is enabled the number of bytes stored in the buffer These bytes represent UTF 8 encoded text This attribute has no meaningful interpretation when buffer_text is false xmlparser ordered_attributes Setting this attribute to a non zero integer causes the attributes to be reported as a l,en
2129,ist rather than a dictionary The attributes are presented in the order found in the document text For each attribute two list entries are presented the attribute name and the attribute value Older versions of this module also used this format By default this attribute is false it may be changed at any time xmlparser specified_attributes If set to a non zero integer the parser will report only those attributes which were specified in the document instance and not those which were derived from attribute declarations Applications which set this need to be especially careful to use what additional information is available from the declarations as needed to comply with the standards for the behavior of XML processors By default this attribute is false it may be changed at any time The following attributes contain values relating to the most recent error encountered by an xmlparser object and will only have correct values once a call to Parse or ParseFile has raised an xml parsers expat ExpatError exception xmlparser ErrorByteIndex Byte index at which an error occurred xmlparser ErrorCode Numeric code specifying the problem This value can be passed to the ErrorString function or compared to one of the constants defined in the errors object xmlparser ErrorColumnNumber Column number at which an error occurred xmlparser ErrorLineNumber Line number at which an error occurred The following attributes contain values relating to the current parse location in an xmlparser object During a callback reporting a parse event they indicate the location of the first of the sequence of characters that generated the event When called outside of a callback the position indicated will be just past the last parse event regardless of whether there was an associated callback xmlparser CurrentByteIndex Current byte index in the parser input xmlparser CurrentColumnNumber Current column number in the parser input xmlparser CurrentLineNumber Current line number in the parser input Here is the list of handlers that can be set To set a handler on an xmlparser object o use o handlername func handlername must be taken from the following list and func must be a callable object accepting the correct number of arguments The arguments are all strings unless otherwise stated xmlparser XmlDeclHandler version encoding standalone Called when the XML declaration is parsed The XML declaration is the optional declaration of the applicable version of the XML recommendation the encoding of the document text and an optional standalone declaration version and encoding will be strings and standalone will be 1 if the document is declared standalone 0 if it is declared not to be standalone or 1 if the standalone clause was omitted This is only available with Expat version 1 95 0 or newer xmlparser StartDoctypeDeclHandler doctypeName systemId publicId has_internal_subset Called when Expat begins parsing the document type declaration DOCTYPE The doctypeName is provided exactly as presented The systemId and publicId parameters give the system and public identifiers if specified or None if omitted has_internal_subset will be true if the document contains and internal document declaration subset This requires Expat version 1 2 or newer xmlparser EndDoctypeDeclHandler Called when Expat is done parsing the document type declaration This requires Expat version 1 2 or newer xmlparser ElementDeclHandler name model Called once for each element type declaration name is the name of the element type and model is a representation of the content model xmlparser AttlistDeclHandler elname attname type default required Called for each declared attribute for an element type If an attribute list declaration declares three attributes this handler is called three times once for each attribute elname is the name of the element to which the declaration applies and attname is the name of the attribute declared The attribute type is a string passed as type the possible values are CDATA ID IDREF default gives the default value for the attribute used when the attribute is not specified by the document ,en
2130,instance or None if there is no default value IMPLIED values If the attribute is required to be given in the document instance required will be true This requires Expat version 1 95 0 or newer xmlparser StartElementHandler name attributes Called for the start of every element name is a string containing the element name and attributes is the element attributes If ordered_attributes is true this is a list see ordered_attributes for a full description Otherwise it s a dictionary mapping names to values xmlparser EndElementHandler name Called for the end of every element xmlparser ProcessingInstructionHandler target data Called for every processing instruction xmlparser CharacterDataHandler data Called for character data This will be called for normal character data CDATA marked content and ignorable whitespace Applications which must distinguish these cases can use the StartCdataSectionHandler EndCdataSectionHandler and ElementDeclHandler callbacks to collect the required information Note that the character data may be chunked even if it is short and so you may receive more than one call to CharacterDataHandler Set the buffer_text instance attribute to True to avoid that xmlparser UnparsedEntityDeclHandler entityName base systemId publicId notationName Called for unparsed NDATA entity declarations This is only present for version 1 2 of the Expat library for more recent versions use EntityDeclHandler instead The underlying function in the Expat library has been declared obsolete xmlparser EntityDeclHandler entityName is_parameter_entity value base systemId publicId notationName Called for all entity declarations For parameter and internal entities value will be a string giving the declared contents of the entity this will be None for external entities The notationName parameter will be None for parsed entities and the name of the notation for unparsed entities is_parameter_entity will be true if the entity is a parameter entity or false for general entities most applications only need to be concerned with general entities This is only available starting with version 1 95 0 of the Expat library xmlparser NotationDeclHandler notationName base systemId publicId Called for notation declarations notationName base and systemId and publicId are strings if given If the public identifier is omitted publicId will be None xmlparser StartNamespaceDeclHandler prefix uri Called when an element contains a namespace declaration Namespace declarations are processed before the StartElementHandler is called for the element on which declarations are placed xmlparser EndNamespaceDeclHandler prefix Called when the closing tag is reached for an element that contained a namespace declaration This is called once for each namespace declaration on the element in the reverse of the order for which the StartNamespaceDeclHandler was called to indicate the start of each namespace declaration s scope Calls to this handler are made after the corresponding EndElementHandler for the end of the element xmlparser CommentHandler data Called for comments data is the text of the comment excluding the leading and trailing xmlparser StartCdataSectionHandler Called at the start of a CDATA section This and EndCdataSectionHandler are needed to be able to identify the syntactical start and end for CDATA sections xmlparser EndCdataSectionHandler Called at the end of a CDATA section xmlparser DefaultHandler data Called for any characters in the XML document for which no applicable handler has been specified This means characters that are part of a construct which could be reported but for which no handler has been supplied xmlparser DefaultHandlerExpand data This is the same as the DefaultHandler but doesn t inhibit expansion of internal entities The entity reference will not be passed to the default handler xmlparser NotStandaloneHandler Called if the XML document hasn t been declared as being a standalone document This happens when there is an external subset or a reference to a parameter entity but the XML declaration does not set standalone to yes in an XML declarat,en
2131,ion If this handler returns 0 then the parser will raise an XML_ERROR_NOT_STANDALONE error If this handler is not set no exception is raised by the parser for this condition xmlparser ExternalEntityRefHandler context base systemId publicId Called for references to external entities base is the current base as set by a previous call to SetBase The public and system identifiers systemId and publicId are strings if given if the public identifier is not given publicId will be None The context value is opaque and should only be used as described below For external entities to be parsed this handler must be implemented It is responsible for creating the sub parser using ExternalEntityParserCreate context initializing it with the appropriate callbacks and parsing the entity This handler should return an integer if it returns 0 the parser will raise an XML_ERROR_EXTERNAL_ENTITY_HANDLING error otherwise parsing will continue If this handler is not provided external entities are reported by the DefaultHandler callback if provided ExpatError Exceptions ExpatError exceptions have a number of interesting attributes ExpatError code Expat s internal error number for the specific error The errors messages dictionary maps these error numbers to Expat s error messages For example from xml parsers expat import ParserCreate ExpatError errors p ParserCreate try p Parse some_xml_document except ExpatError as err print Error errors messages err code The errors module also provides error message constants and a dictionary codes mapping these messages back to the error codes see below ExpatError lineno Line number on which the error was detected The first line is numbered 1 ExpatError offset Character offset into the line where the error occurred The first column is numbered 0 Example The following program defines three handlers that just print out their arguments import xml parsers expat 3 handler functions def start_element name attrs print Start element name attrs def end_element name print End element name def char_data data print Character data repr data p xml parsers expat ParserCreate p StartElementHandler start_element p EndElementHandler end_element p CharacterDataHandler char_data p Parse xml version 1 0 parent id top child1 name paul Text goes here child1 child2 name fred More text child2 parent 1 The output from this program is Start element parent id top Start element child1 name paul Character data Text goes here End element child1 Character data n Start element child2 name fred Character data More text End element child2 Character data n End element parent Content Model Descriptions Content models are described using nested tuples Each tuple contains four values the type the quantifier the name and a tuple of children Children are simply additional content model descriptions The values of the first two fields are constants defined in the xml parsers expat model module These constants can be collected in two groups the model type group and the quantifier group The constants in the model type group are xml parsers expat model XML_CTYPE_ANY The element named by the model name was declared to have a content model of ANY xml parsers expat model XML_CTYPE_CHOICE The named element allows a choice from a number of options this is used for content models such as A B C xml parsers expat model XML_CTYPE_EMPTY Elements which are declared to be EMPTY have this model type xml parsers expat model XML_CTYPE_MIXED xml parsers expat model XML_CTYPE_NAME xml parsers expat model XML_CTYPE_SEQ Models which represent a series of models which follow one after the other are indicated with this model type This is used for models such as A B C The constants in the quantifier group are xml parsers expat model XML_CQUANT_NONE No modifier is given so it can appear exactly once as for A xml parsers expat model XML_CQUANT_OPT The model is optional it can appear once or not at all as for A xml parsers expat model XML_CQUANT_PLUS The model must occur one or more times like A xml parsers expat model XML_CQUANT_REP The model must occur zero or more times as for A E,en
2132,xpat error constants The following constants are provided in the xml parsers expat errors module These constants are useful in interpreting some of the attributes of the ExpatError exception objects raised when an error has occurred Since for backwards compatibility reasons the constants value is the error message and not the numeric error code you do this by comparing its code attribute with errors codes errors XML_ERROR_ CONSTANT_NAME The errors module has the following attributes xml parsers expat errors codes A dictionary mapping string descriptions to their error codes New in version 3 2 xml parsers expat errors messages A dictionary mapping numeric error codes to their string descriptions New in version 3 2 xml parsers expat errors XML_ERROR_ASYNC_ENTITY xml parsers expat errors XML_ERROR_ATTRIBUTE_EXTERNAL_ENTITY_REF An entity reference in an attribute value referred to an external entity instead of an internal entity xml parsers expat errors XML_ERROR_BAD_CHAR_REF A character reference referred to a character which is illegal in XML for example character 0 or 0 xml parsers expat errors XML_ERROR_BINARY_ENTITY_REF An entity reference referred to an entity which was declared with a notation so cannot be parsed xml parsers expat errors XML_ERROR_DUPLICATE_ATTRIBUTE An attribute was used more than once in a start tag xml parsers expat errors XML_ERROR_INCORRECT_ENCODING xml parsers expat errors XML_ERROR_INVALID_TOKEN Raised when an input byte could not properly be assigned to a character for example a NUL byte value 0 in a UTF 8 input stream xml parsers expat errors XML_ERROR_JUNK_AFTER_DOC_ELEMENT Something other than whitespace occurred after the document element xml parsers expat errors XML_ERROR_MISPLACED_XML_PI An XML declaration was found somewhere other than the start of the input data xml parsers expat errors XML_ERROR_NO_ELEMENTS The document contains no elements XML requires all documents to contain exactly one top level element xml parsers expat errors XML_ERROR_NO_MEMORY Expat was not able to allocate memory internally xml parsers expat errors XML_ERROR_PARAM_ENTITY_REF A parameter entity reference was found where it was not allowed xml parsers expat errors XML_ERROR_PARTIAL_CHAR An incomplete character was found in the input xml parsers expat errors XML_ERROR_RECURSIVE_ENTITY_REF An entity reference contained another reference to the same entity possibly via a different name and possibly indirectly xml parsers expat errors XML_ERROR_SYNTAX Some unspecified syntax error was encountered xml parsers expat errors XML_ERROR_TAG_MISMATCH An end tag did not match the innermost open start tag xml parsers expat errors XML_ERROR_UNCLOSED_TOKEN Some token such as a start tag was not closed before the end of the stream or the next token was encountered xml parsers expat errors XML_ERROR_UNDEFINED_ENTITY A reference was made to an entity which was not defined xml parsers expat errors XML_ERROR_UNKNOWN_ENCODING The document encoding is not supported by Expat xml parsers expat errors XML_ERROR_UNCLOSED_CDATA_SECTION A CDATA marked section was not closed xml parsers expat errors XML_ERROR_EXTERNAL_ENTITY_HANDLING xml parsers expat errors XML_ERROR_NOT_STANDALONE The parser determined that the document was not standalone though it declared itself to be in the XML declaration and the NotStandaloneHandler was set and returned 0 xml parsers expat errors XML_ERROR_UNEXPECTED_STATE xml parsers expat errors XML_ERROR_ENTITY_DECLARED_IN_PE xml parsers expat errors XML_ERROR_FEATURE_REQUIRES_XML_DTD An operation was requested that requires DTD support to be compiled in but Expat was configured without DTD support This should never be reported by a standard build of the xml parsers expat module xml parsers expat errors XML_ERROR_CANT_CHANGE_FEATURE_ONCE_PARSING A behavioral change was requested after parsing started that can only be changed before parsing has started This is currently only raised by UseForeignDTD xml parsers expat errors XML_ERROR_UNBOUND_PREFIX An undeclared prefix was found when namespace processing was enable,en
2133,d xml parsers expat errors XML_ERROR_UNDECLARING_PREFIX The document attempted to remove the namespace declaration associated with a prefix xml parsers expat errors XML_ERROR_INCOMPLETE_PE A parameter entity contained incomplete markup xml parsers expat errors XML_ERROR_XML_DECL The document contained no document element at all xml parsers expat errors XML_ERROR_TEXT_DECL There was an error parsing a text declaration in an external entity xml parsers expat errors XML_ERROR_PUBLICID Characters were found in the public id that are not allowed xml parsers expat errors XML_ERROR_SUSPENDED The requested operation was made on a suspended parser but isn t allowed This includes attempts to provide additional input or to stop the parser xml parsers expat errors XML_ERROR_NOT_SUSPENDED An attempt to resume the parser was made when the parser had not been suspended xml parsers expat errors XML_ERROR_ABORTED This should not be reported to Python applications xml parsers expat errors XML_ERROR_FINISHED The requested operation was made on a parser which was finished parsing input but isn t allowed This includes attempts to provide additional input or to stop the parser xml parsers expat errors XML_ERROR_SUSPEND_PE xml parsers expat errors XML_ERROR_RESERVED_PREFIX_XML An attempt was made to undeclare reserved namespace prefix xml or to bind it to another namespace URI xml parsers expat errors XML_ERROR_RESERVED_PREFIX_XMLNS An attempt was made to declare or undeclare reserved namespace prefix xmlns xml parsers expat errors XML_ERROR_RESERVED_NAMESPACE_URI An attempt was made to bind the URI of one the reserved namespace prefixes xml and xmlns to another namespace prefix xml parsers expat errors XML_ERROR_INVALID_ARGUMENT This should not be reported to Python applications xml parsers expat errors XML_ERROR_NO_BUFFER This should not be reported to Python applications xml parsers expat errors XML_ERROR_AMPLIFICATION_LIMIT_BREACH The limit on input amplification factor from DTD and entities has been breached Footnotes 1 The encoding string included in XML output should conform to the appropriate standards For example UTF 8 is valid but UTF8 is not See https www w3 org TR 2006 REC xml11 20060816 NT EncodingDecl and https www iana org assignments character sets character sets xhtml,en
2134,9 Top level components The Python interpreter can get its input from a number of sources from a script passed to it as standard input or as program argument typed in interactively from a module source file etc This chapter gives the syntax used in these cases 9 1 Complete Python programs While a language specification need not prescribe how the language interpreter is invoked it is useful to have a notion of a complete Python program A complete Python program is executed in a minimally initialized environment all built in and standard modules are available but none have been initialized except for sys various system services builtins built in functions exceptions and None and __main__ The latter is used to provide the local and global namespace for execution of the complete program The syntax for a complete Python program is that for file input described in the next section The interpreter may also be invoked in interactive mode in this case it does not read and execute a complete program but reads and executes one statement possibly compound at a time The initial environment is identical to that of a complete program each statement is executed in the namespace of __main__ A complete program can be passed to the interpreter in three forms with the c string command line option as a file passed as the first command line argument or as standard input If the file or standard input is a tty device the interpreter enters interactive mode otherwise it executes the file as a complete program 9 2 File input All input read from non interactive files has the same form file_input NEWLINE statement This syntax is used in the following situations when parsing a complete Python program from a file or from a string when parsing a module when parsing a string passed to the exec function 9 3 Interactive input Input in interactive mode is parsed using the following grammar interactive_input stmt_list NEWLINE compound_stmt NEWLINE Note that a top level compound statement must be followed by a blank line in interactive mode this is needed to help the parser detect the end of the input 9 4 Expression input eval is used for expression input It ignores leading whitespace The string argument to eval must have the following form eval_input expression_list NEWLINE,en
2135,fractions Rational numbers Source code Lib fractions py The fractions module provides support for rational number arithmetic A Fraction instance can be constructed from a pair of integers from another rational number or from a string class fractions Fraction numerator 0 denominator 1 class fractions Fraction other_fraction class fractions Fraction float class fractions Fraction decimal class fractions Fraction string The first version requires that numerator and denominator are instances of numbers Rational and returns a new Fraction instance with value numerator denominator If denominator is 0 it raises a ZeroDivisionError The second version requires that other_fraction is an instance of numbers Rational and returns a Fraction instance with the same value The next two versions accept either a float or a decimal Decimal instance and return a Fraction instance with exactly the same value Note that due to the usual issues with binary floating point see Floating Point Arithmetic Issues and Limitations the argument to Fraction 1 1 is not exactly equal to 11 10 and so Fraction 1 1 does not return Fraction 11 10 as one might expect But see the documentation for the limit_denominator method below The last version of the constructor expects a string or unicode instance The usual form for this instance is sign numerator denominator where the optional sign may be either or and numerator and denominator if present are strings of decimal digits underscores may be used to delimit digits as with integral literals in code In addition any string that represents a finite value and is accepted by the float constructor is also accepted by the Fraction constructor In either form the input string may also have leading and or trailing whitespace Here are some examples from fractions import Fraction Fraction 16 10 Fraction 8 5 Fraction 123 Fraction 123 1 Fraction Fraction 0 1 Fraction 3 7 Fraction 3 7 Fraction 3 7 Fraction 3 7 Fraction 1 414213 t n Fraction 1414213 1000000 Fraction 125 Fraction 1 8 Fraction 7e 6 Fraction 7 1000000 Fraction 2 25 Fraction 9 4 Fraction 1 1 Fraction 2476979795053773 2251799813685248 from decimal import Decimal Fraction Decimal 1 1 Fraction 11 10 The Fraction class inherits from the abstract base class numbers Rational and implements all of the methods and operations from that class Fraction instances are hashable and should be treated as immutable In addition Fraction has the following properties and methods Changed in version 3 2 The Fraction constructor now accepts float and decimal Decimal instances Changed in version 3 9 The math gcd function is now used to normalize the numerator and denominator math gcd always return a int type Previously the GCD type depended on numerator and denominator Changed in version 3 11 Underscores are now permitted when creating a Fraction instance from a string following PEP 515 rules Changed in version 3 11 Fraction implements __int__ now to satisfy typing SupportsInt instance checks Changed in version 3 12 Space is allowed around the slash for string inputs Fraction 2 3 Changed in version 3 12 Fraction instances now support float style formatting with presentation types e E f F g G and numerator Numerator of the Fraction in lowest term denominator Denominator of the Fraction in lowest term as_integer_ratio Return a tuple of two integers whose ratio is equal to the original Fraction The ratio is in lowest terms and has a positive denominator New in version 3 8 is_integer Return True if the Fraction is an integer New in version 3 12 classmethod from_float flt Alternative constructor which only accepts instances of float or numbers Integral Beware that Fraction from_float 0 3 is not the same value as Fraction 3 10 Note From Python 3 2 onwards you can also construct a Fraction instance directly from a float classmethod from_decimal dec Alternative constructor which only accepts instances of decimal Decimal or numbers Integral Note From Python 3 2 onwards you can also construct a Fraction instance directly from a decimal Decimal instance limit_denominator max_denominator 1000000 Find,en
2136,s and returns the closest Fraction to self that has denominator at most max_denominator This method is useful for finding rational approximations to a given floating point number from fractions import Fraction Fraction 3 1415926535897932 limit_denominator 1000 Fraction 355 113 or for recovering a rational number that s represented as a float from math import pi cos Fraction cos pi 3 Fraction 4503599627370497 9007199254740992 Fraction cos pi 3 limit_denominator Fraction 1 2 Fraction 1 1 limit_denominator Fraction 11 10 __floor__ Returns the greatest int self This method can also be accessed through the math floor function from math import floor floor Fraction 355 113 3 __ceil__ Returns the least int self This method can also be accessed through the math ceil function __round__ __round__ ndigits The first version returns the nearest int to self rounding half to even The second version rounds self to the nearest multiple of Fraction 1 10 ndigits logically if ndigits is negative again rounding half toward even This method can also be accessed through the round function __format__ format_spec Provides support for float style formatting of Fraction instances via the str format method the format built in function or Formatted string literals The presentation types e E f F g G and are supported For these presentation types formatting for a Fraction object x follows the rules outlined for the float type in the Format Specification Mini Language section Here are some examples from fractions import Fraction format Fraction 1 7 40g 0 1428571428571428571428571428571428571429 format Fraction 1234567 855 _ 2f 1_234_567 86 f Fraction 355 113 20 6e 3 141593e 00 old_price new_price 499 672 2 price increase format Fraction new_price old_price 1 34 67 price increase See also Module numbers The abstract base classes making up the numeric tower,en
2137,graphlib Functionality to operate with graph like structures Source code Lib graphlib py class graphlib TopologicalSorter graph None Provides functionality to topologically sort a graph of hashable nodes A topological order is a linear ordering of the vertices in a graph such that for every directed edge u v from vertex u to vertex v vertex u comes before vertex v in the ordering For instance the vertices of the graph may represent tasks to be performed and the edges may represent constraints that one task must be performed before another in this example a topological ordering is just a valid sequence for the tasks A complete topological ordering is possible if and only if the graph has no directed cycles that is if it is a directed acyclic graph If the optional graph argument is provided it must be a dictionary representing a directed acyclic graph where the keys are nodes and the values are iterables of all predecessors of that node in the graph the nodes that have edges that point to the value in the key Additional nodes can be added to the graph using the add method In the general case the steps required to perform the sorting of a given graph are as follows Create an instance of the TopologicalSorter with an optional initial graph Add additional nodes to the graph Call prepare on the graph While is_active is True iterate over the nodes returned by get_ready and process them Call done on each node as it finishes processing In case just an immediate sorting of the nodes in the graph is required and no parallelism is involved the convenience method TopologicalSorter static_order can be used directly graph D B C C A B A ts TopologicalSorter graph tuple ts static_order A C B D The class is designed to easily support parallel processing of the nodes as they become ready For instance topological_sorter TopologicalSorter Add nodes to topological_sorter topological_sorter prepare while topological_sorter is_active for node in topological_sorter get_ready Worker threads or processes take nodes to work on off the task_queue queue task_queue put node When the work for a node is done workers put the node in finalized_tasks_queue so we can get more nodes to work on The definition of is_active guarantees that at this point at least one node has been placed on task_queue that hasn t yet been passed to done so this blocking get must eventually succeed After calling done we loop back to call get_ready again so put newly freed nodes on task_queue as soon as logically possible node finalized_tasks_queue get topological_sorter done node add node predecessors Add a new node and its predecessors to the graph Both the node and all elements in predecessors must be hashable If called multiple times with the same node argument the set of dependencies will be the union of all dependencies passed in It is possible to add a node with no dependencies predecessors is not provided or to provide a dependency twice If a node that has not been provided before is included among predecessors it will be automatically added to the graph with no predecessors of its own Raises ValueError if called after prepare prepare Mark the graph as finished and check for cycles in the graph If any cycle is detected CycleError will be raised but get_ready can still be used to obtain as many nodes as possible until cycles block more progress After a call to this function the graph cannot be modified and therefore no more nodes can be added using add is_active Returns True if more progress can be made and False otherwise Progress can be made if cycles do not block the resolution and either there are still nodes ready that haven t yet been returned by TopologicalSorter get_ready or the number of nodes marked TopologicalSorter done is less than the number that have been returned by TopologicalSorter get_ready The __bool__ method of this class defers to this function so instead of if ts is_active it is possible to simply do if ts Raises ValueError if called without calling prepare previously done nodes Marks a set of nodes returned by TopologicalSorter get_ready as processed,en
2138, unblocking any successor of each node in nodes for being returned in the future by a call to TopologicalSorter get_ready Raises ValueError if any node in nodes has already been marked as processed by a previous call to this method or if a node was not added to the graph by using TopologicalSorter add if called without calling prepare or if node has not yet been returned by get_ready get_ready Returns a tuple with all the nodes that are ready Initially it returns all nodes with no predecessors and once those are marked as processed by calling TopologicalSorter done further calls will return all new nodes that have all their predecessors already processed Once no more progress can be made empty tuples are returned Raises ValueError if called without calling prepare previously static_order Returns an iterator object which will iterate over nodes in a topological order When using this method prepare and done should not be called This method is equivalent to def static_order self self prepare while self is_active node_group self get_ready yield from node_group self done node_group The particular order that is returned may depend on the specific order in which the items were inserted in the graph For example ts TopologicalSorter ts add 3 2 1 ts add 1 0 print ts static_order 2 0 1 3 ts2 TopologicalSorter ts2 add 1 0 ts2 add 3 2 1 print ts2 static_order 0 2 1 3 This is due to the fact that 0 and 2 are in the same level in the graph they would have been returned in the same call to get_ready and the order between them is determined by the order of insertion If any cycle is detected CycleError will be raised New in version 3 9 Exceptions The graphlib module defines the following exception classes exception graphlib CycleError Subclass of ValueError raised by TopologicalSorter prepare if cycles exist in the working graph If multiple cycles exist only one undefined choice among them will be reported and included in the exception The detected cycle can be accessed via the second element in the args attribute of the exception instance and consists in a list of nodes such that each node is in the graph an immediate predecessor of the next node in the list In the reported list the first and the last node will be the same to make it clear that it is cyclic,en
2139,About these documents These documents are generated from reStructuredText sources by Sphinx a document processor specifically written for the Python documentation Development of the documentation and its toolchain is an entirely volunteer effort just like Python itself If you want to contribute please take a look at the Dealing with Bugs page for information on how to do so New volunteers are always welcome Many thanks go to Fred L Drake Jr the creator of the original Python documentation toolset and writer of much of the content the Docutils project for creating reStructuredText and the Docutils suite Fredrik Lundh for his Alternative Python Reference project from which Sphinx got many good ideas Contributors to the Python Documentation Many people have contributed to the Python language the Python standard library and the Python documentation See Misc ACKS in the Python source distribution for a partial list of contributors It is only with the input and contributions of the Python community that Python has such wonderful documentation Thank You,en
2140,What s New In Python 3 3 This article explains the new features in Python 3 3 compared to 3 2 Python 3 3 was released on September 29 2012 For full details see the changelog See also PEP 398 Python 3 3 Release Schedule Summary Release highlights New syntax features New yield from expression for generator delegation The u unicode syntax is accepted again for str objects New library modules faulthandler helps debugging low level crashes ipaddress high level objects representing IP addresses and masks lzma compress data using the XZ LZMA algorithm unittest mock replace parts of your system under test with mock objects venv Python virtual environments as in the popular virtualenv package New built in features Reworked I O exception hierarchy Implementation improvements Rewritten import machinery based on importlib More compact unicode strings More compact attribute dictionaries Significantly Improved Library Modules C Accelerator for the decimal module Better unicode handling in the email module provisional Security improvements Hash randomization is switched on by default Please read on for a comprehensive list of user facing changes PEP 405 Virtual Environments Virtual environments help create separate Python setups while sharing a system wide base install for ease of maintenance Virtual environments have their own set of private site packages i e locally installed libraries and are optionally segregated from the system wide site packages Their concept and implementation are inspired by the popular virtualenv third party package but benefit from tighter integration with the interpreter core This PEP adds the venv module for programmatic access and the pyvenv script for command line access and administration The Python interpreter checks for a pyvenv cfg file whose existence signals the base of a virtual environment s directory tree See also PEP 405 Python Virtual Environments PEP written by Carl Meyer implementation by Carl Meyer and Vinay Sajip PEP 420 Implicit Namespace Packages Native support for package directories that don t require __init__ py marker files and can automatically span multiple path segments inspired by various third party approaches to namespace packages as described in PEP 420 See also PEP 420 Implicit Namespace Packages PEP written by Eric V Smith implementation by Eric V Smith and Barry Warsaw PEP 3118 New memoryview implementation and buffer protocol documentation The implementation of PEP 3118 has been significantly improved The new memoryview implementation comprehensively fixes all ownership and lifetime issues of dynamically allocated fields in the Py_buffer struct that led to multiple crash reports Additionally several functions that crashed or returned incorrect results for non contiguous or multi dimensional input have been fixed The memoryview object now has a PEP 3118 compliant getbufferproc that checks the consumer s request type Many new features have been added most of them work in full generality for non contiguous arrays and arrays with suboffsets The documentation has been updated clearly spelling out responsibilities for both exporters and consumers Buffer request flags are grouped into basic and compound flags The memory layout of non contiguous and multi dimensional NumPy style arrays is explained Features All native single character format specifiers in struct module syntax optionally prefixed with are now supported With some restrictions the cast method allows changing of format and shape of C contiguous arrays Multi dimensional list representations are supported for any array type Multi dimensional comparisons are supported for any array type One dimensional memoryviews of hashable read only types with formats B b or c are now hashable Contributed by Antoine Pitrou in bpo 13411 Arbitrary slicing of any 1 D arrays type is supported For example it is now possible to reverse a memoryview in O 1 by using a negative step API changes The maximum number of dimensions is officially limited to 64 The representation of empty shape strides and suboffsets is now an empty tuple instead of N,en
2141,one Accessing a memoryview element with format B unsigned bytes now returns an integer in accordance with the struct module syntax For returning a bytes object the view must be cast to c first memoryview comparisons now use the logical structure of the operands and compare all array elements by value All format strings in struct module syntax are supported Views with unrecognised format strings are still permitted but will always compare as unequal regardless of view contents For further changes see Build and C API Changes and Porting C code Contributed by Stefan Krah in bpo 10181 See also PEP 3118 Revising the Buffer Protocol PEP 393 Flexible String Representation The Unicode string type is changed to support multiple internal representations depending on the character with the largest Unicode ordinal 1 2 or 4 bytes in the represented string This allows a space efficient representation in common cases but gives access to full UCS 4 on all systems For compatibility with existing APIs several representations may exist in parallel over time this compatibility should be phased out On the Python side there should be no downside to this change On the C API side PEP 393 is fully backward compatible The legacy API should remain available at least five years Applications using the legacy API will not fully benefit of the memory reduction or worse may use a bit more memory because Python may have to maintain two versions of each string in the legacy format and in the new efficient storage Functionality Changes introduced by PEP 393 are the following Python now always supports the full range of Unicode code points including non BMP ones i e from U 0000 to U 10FFFF The distinction between narrow and wide builds no longer exists and Python now behaves like a wide build even under Windows With the death of narrow builds the problems specific to narrow builds have also been fixed for example len now always returns 1 for non BMP characters so len U0010FFFF 1 surrogate pairs are not recombined in string literals so uDBFF uDFFF U0010FFFF indexing or slicing non BMP characters returns the expected value so U0010FFFF 0 now returns U0010FFFF and not uDBFF all other functions in the standard library now correctly handle non BMP code points The value of sys maxunicode is now always 1114111 0x10FFFF in hexadecimal The PyUnicode_GetMax function still returns either 0xFFFF or 0x10FFFF for backward compatibility and it should not be used with the new Unicode API see bpo 13054 The configure flag with wide unicode has been removed Performance and resource usage The storage of Unicode strings now depends on the highest code point in the string pure ASCII and Latin1 strings U 0000 U 00FF use 1 byte per code point BMP strings U 0000 U FFFF use 2 bytes per code point non BMP strings U 10000 U 10FFFF use 4 bytes per code point The net effect is that for most applications memory usage of string storage should decrease significantly especially compared to former wide unicode builds as in many cases strings will be pure ASCII even in international contexts because many strings store non human language data such as XML fragments HTTP headers JSON encoded data etc We also hope that it will for the same reasons increase CPU cache efficiency on non trivial applications The memory usage of Python 3 3 is two to three times smaller than Python 3 2 and a little bit better than Python 2 7 on a Django benchmark see the PEP for details See also PEP 393 Flexible String Representation PEP written by Martin von Löwis implementation by Torsten Becker and Martin von Löwis PEP 397 Python Launcher for Windows The Python 3 3 Windows installer now includes a py launcher application that can be used to launch Python applications in a version independent fashion This launcher is invoked implicitly when double clicking py files If only a single Python version is installed on the system that version will be used to run the file If multiple versions are installed the most recent version is used by default but this can be overridden by including a Unix style shebang line in the Pyt,en
2142,hon script The launcher can also be used explicitly from the command line as the py application Running py follows the same version selection rules as implicitly launching scripts but a more specific version can be selected by passing appropriate arguments such as 3 to request Python 3 when Python 2 is also installed or 2 6 to specifically request an earlier Python version when a more recent version is installed In addition to the launcher the Windows installer now includes an option to add the newly installed Python to the system PATH Contributed by Brian Curtin in bpo 3561 See also PEP 397 Python Launcher for Windows PEP written by Mark Hammond and Martin v Löwis implementation by Vinay Sajip Launcher documentation Python Launcher for Windows Installer PATH modification Finding the Python executable PEP 3151 Reworking the OS and IO exception hierarchy The hierarchy of exceptions raised by operating system errors is now both simplified and finer grained You don t have to worry anymore about choosing the appropriate exception type between OSError IOError EnvironmentError WindowsError mmap error socket error or select error All these exception types are now only one OSError The other names are kept as aliases for compatibility reasons Also it is now easier to catch a specific error condition Instead of inspecting the errno attribute or args 0 for a particular constant from the errno module you can catch the adequate OSError subclass The available subclasses are the following BlockingIOError ChildProcessError ConnectionError FileExistsError FileNotFoundError InterruptedError IsADirectoryError NotADirectoryError PermissionError ProcessLookupError TimeoutError And the ConnectionError itself has finer grained subclasses BrokenPipeError ConnectionAbortedError ConnectionRefusedError ConnectionResetError Thanks to the new exceptions common usages of the errno can now be avoided For example the following code written for Python 3 2 from errno import ENOENT EACCES EPERM try with open document txt as f content f read except IOError as err if err errno ENOENT print document txt file is missing elif err errno in EACCES EPERM print You are not allowed to read document txt else raise can now be written without the errno import and without manual inspection of exception attributes try with open document txt as f content f read except FileNotFoundError print document txt file is missing except PermissionError print You are not allowed to read document txt See also PEP 3151 Reworking the OS and IO Exception Hierarchy PEP written and implemented by Antoine Pitrou PEP 380 Syntax for Delegating to a Subgenerator PEP 380 adds the yield from expression allowing a generator to delegate part of its operations to another generator This allows a section of code containing yield to be factored out and placed in another generator Additionally the subgenerator is allowed to return with a value and the value is made available to the delegating generator While designed primarily for use in delegating to a subgenerator the yield from expression actually allows delegation to arbitrary subiterators For simple iterators yield from iterable is essentially just a shortened form of for item in iterable yield item def g x yield from range x 0 1 yield from range x list g 5 5 4 3 2 1 0 1 2 3 4 However unlike an ordinary loop yield from allows subgenerators to receive sent and thrown values directly from the calling scope and return a final value to the outer generator def accumulate tally 0 while 1 next yield if next is None return tally tally next def gather_tallies tallies while 1 tally yield from accumulate tallies append tally tallies acc gather_tallies tallies next acc Ensure the accumulator is ready to accept values for i in range 4 acc send i acc send None Finish the first tally for i in range 5 acc send i acc send None Finish the second tally tallies 6 10 The main principle driving this change is to allow even generators that are designed to be used with the send and throw methods to be split into multiple subgenerators as easily as a single large functi,en
2143,on can be split into multiple subfunctions See also PEP 380 Syntax for Delegating to a Subgenerator PEP written by Greg Ewing implementation by Greg Ewing integrated into 3 3 by Renaud Blanch Ryan Kelly and Nick Coghlan documentation by Zbigniew Jędrzejewski Szmek and Nick Coghlan PEP 409 Suppressing exception context PEP 409 introduces new syntax that allows the display of the chained exception context to be disabled This allows cleaner error messages in applications that convert between exception types class D def __init__ self extra self _extra_attributes extra def __getattr__ self attr try return self _extra_attributes attr except KeyError raise AttributeError attr from None D x Traceback most recent call last File stdin line 1 in module File stdin line 8 in __getattr__ AttributeError x Without the from None suffix to suppress the cause the original exception would be displayed by default class C def __init__ self extra self _extra_attributes extra def __getattr__ self attr try return self _extra_attributes attr except KeyError raise AttributeError attr C x Traceback most recent call last File stdin line 6 in __getattr__ KeyError x During handling of the above exception another exception occurred Traceback most recent call last File stdin line 1 in module File stdin line 8 in __getattr__ AttributeError x No debugging capability is lost as the original exception context remains available if needed for example if an intervening library has incorrectly suppressed valuable underlying details try D x except AttributeError as exc print repr exc __context__ KeyError x See also PEP 409 Suppressing exception context PEP written by Ethan Furman implemented by Ethan Furman and Nick Coghlan PEP 414 Explicit Unicode literals To ease the transition from Python 2 for Unicode aware Python applications that make heavy use of Unicode literals Python 3 3 once again supports the u prefix for string literals This prefix has no semantic significance in Python 3 it is provided solely to reduce the number of purely mechanical changes in migrating to Python 3 making it easier for developers to focus on the more significant semantic changes such as the stricter default separation of binary and text data See also PEP 414 Explicit Unicode literals PEP written by Armin Ronacher PEP 3155 Qualified name for classes and functions Functions and class objects have a new __qualname__ attribute representing the path from the module top level to their definition For global functions and classes this is the same as __name__ For other functions and classes it provides better information about where they were actually defined and how they might be accessible from the global scope Example with non bound methods class C def meth self pass C meth __name__ meth C meth __qualname__ C meth Example with nested classes class C class D def meth self pass C D __name__ D C D __qualname__ C D C D meth __name__ meth C D meth __qualname__ C D meth Example with nested functions def outer def inner pass return inner outer __name__ inner outer __qualname__ outer locals inner The string representation of those objects is also changed to include the new more precise information str C D class __main__ C D str C D meth function C D meth at 0x7f46b9fe31e0 See also PEP 3155 Qualified name for classes and functions PEP written and implemented by Antoine Pitrou PEP 412 Key Sharing Dictionary Dictionaries used for the storage of objects attributes are now able to share part of their internal storage between each other namely the part which stores the keys and their respective hashes This reduces the memory consumption of programs creating many instances of non builtin types See also PEP 412 Key Sharing Dictionary PEP written and implemented by Mark Shannon PEP 362 Function Signature Object A new function inspect signature makes introspection of python callables easy and straightforward A broad range of callables is supported python functions decorated or not classes and functools partial objects New classes inspect Signature inspect Parameter and inspect BoundArguments hold informa,en
2144,tion about the call signatures such as annotations default values parameters kinds and bound arguments which considerably simplifies writing decorators and any code that validates or amends calling signatures or arguments See also PEP 362 Function Signature Object PEP written by Brett Cannon Yury Selivanov Larry Hastings Jiwon Seo implemented by Yury Selivanov PEP 421 Adding sys implementation A new attribute on the sys module exposes details specific to the implementation of the currently running interpreter The initial set of attributes on sys implementation are name version hexversion and cache_tag The intention of sys implementation is to consolidate into one namespace the implementation specific data used by the standard library This allows different Python implementations to share a single standard library code base much more easily In its initial state sys implementation holds only a small portion of the implementation specific data Over time that ratio will shift in order to make the standard library more portable One example of improved standard library portability is cache_tag As of Python 3 3 sys implementation cache_tag is used by importlib to support PEP 3147 compliance Any Python implementation that uses importlib for its built in import system may use cache_tag to control the caching behavior for modules SimpleNamespace The implementation of sys implementation also introduces a new type to Python types SimpleNamespace In contrast to a mapping based namespace like dict SimpleNamespace is attribute based like object However unlike object SimpleNamespace instances are writable This means that you can add remove and modify the namespace through normal attribute access See also PEP 421 Adding sys implementation PEP written and implemented by Eric Snow Using importlib as the Implementation of Import bpo 2377 Replace __import__ w importlib __import__ bpo 13959 Re implement parts of imp in pure Python bpo 14605 Make import machinery explicit bpo 14646 Require loaders set __loader__ and __package__ The __import__ function is now powered by importlib __import__ This work leads to the completion of phase 2 of PEP 302 There are multiple benefits to this change First it has allowed for more of the machinery powering import to be exposed instead of being implicit and hidden within the C code It also provides a single implementation for all Python VMs supporting Python 3 3 to use helping to end any VM specific deviations in import semantics And finally it eases the maintenance of import allowing for future growth to occur For the common user there should be no visible change in semantics For those whose code currently manipulates import or calls import programmatically the code changes that might possibly be required are covered in the Porting Python code section of this document New APIs One of the large benefits of this work is the exposure of what goes into making the import statement work That means the various importers that were once implicit are now fully exposed as part of the importlib package The abstract base classes defined in importlib abc have been expanded to properly delineate between meta path finders and path entry finders by introducing importlib abc MetaPathFinder and importlib abc PathEntryFinder respectively The old ABC of importlib abc Finder is now only provided for backwards compatibility and does not enforce any method requirements In terms of finders importlib machinery FileFinder exposes the mechanism used to search for source and bytecode files of a module Previously this class was an implicit member of sys path_hooks For loaders the new abstract base class importlib abc FileLoader helps write a loader that uses the file system as the storage mechanism for a module s code The loader for source files importlib machinery SourceFileLoader sourceless bytecode files importlib machinery SourcelessFileLoader and extension modules importlib machinery ExtensionFileLoader are now available for direct use ImportError now has name and path attributes which are set when there is relevant data to provide T,en
2145,he message for failed imports will also provide the full name of the module now instead of just the tail end of the module s name The importlib invalidate_caches function will now call the method with the same name on all finders cached in sys path_importer_cache to help clean up any stored state as necessary Visible Changes For potential required changes to code see the Porting Python code section Beyond the expanse of what importlib now exposes there are other visible changes to import The biggest is that sys meta_path and sys path_hooks now store all of the meta path finders and path entry hooks used by import Previously the finders were implicit and hidden within the C code of import instead of being directly exposed This means that one can now easily remove or change the order of the various finders to fit one s needs Another change is that all modules have a __loader__ attribute storing the loader used to create the module PEP 302 has been updated to make this attribute mandatory for loaders to implement so in the future once 3rd party loaders have been updated people will be able to rely on the existence of the attribute Until such time though import is setting the module post load Loaders are also now expected to set the __package__ attribute from PEP 366 Once again import itself is already setting this on all loaders from importlib and import itself is setting the attribute post load None is now inserted into sys path_importer_cache when no finder can be found on sys path_hooks Since imp NullImporter is not directly exposed on sys path_hooks it could no longer be relied upon to always be available to use as a value representing no finder found All other changes relate to semantic changes which should be taken into consideration when updating code for Python 3 3 and thus should be read about in the Porting Python code section of this document Implementation by Brett Cannon Other Language Changes Some smaller changes made to the core Python language are Added support for Unicode name aliases and named sequences Both unicodedata lookup and N now resolve name aliases and unicodedata lookup resolves named sequences too Contributed by Ezio Melotti in bpo 12753 Unicode database updated to UCD version 6 1 0 Equality comparisons on range objects now return a result reflecting the equality of the underlying sequences generated by those range objects bpo 13201 The count find rfind index and rindex methods of bytes and bytearray objects now accept an integer between 0 and 255 as their first argument Contributed by Petri Lehtinen in bpo 12170 The rjust ljust and center methods of bytes and bytearray now accept a bytearray for the fill argument Contributed by Petri Lehtinen in bpo 12380 New methods have been added to list and bytearray copy and clear bpo 10516 Consequently MutableSequence now also defines a clear method bpo 11388 Raw bytes literals can now be written rb as well as br Contributed by Antoine Pitrou in bpo 13748 dict setdefault now does only one lookup for the given key making it atomic when used with built in types Contributed by Filip Gruszczyński in bpo 13521 The error messages produced when a function call does not match the function signature have been significantly improved Contributed by Benjamin Peterson A Finer Grained Import Lock Previous versions of CPython have always relied on a global import lock This led to unexpected annoyances such as deadlocks when importing a module would trigger code execution in a different thread as a side effect Clumsy workarounds were sometimes employed such as the PyImport_ImportModuleNoBlock C API function In Python 3 3 importing a module takes a per module lock This correctly serializes importation of a given module from multiple threads preventing the exposure of incompletely initialized modules while eliminating the aforementioned annoyances Contributed by Antoine Pitrou in bpo 9260 Builtin functions and types open gets a new opener parameter the underlying file descriptor for the file object is then obtained by calling opener with file flags It can be used to use cu,en
2146,stom flags like os O_CLOEXEC for example The x mode was added open for exclusive creation failing if the file already exists print added the flush keyword argument If the flush keyword argument is true the stream is forcibly flushed hash hash randomization is enabled by default see object __hash__ and PYTHONHASHSEED The str type gets a new casefold method return a casefolded copy of the string casefolded strings may be used for caseless matching For example ß casefold returns ss The sequence documentation has been substantially rewritten to better explain the binary text sequence distinction and to provide specific documentation sections for the individual builtin sequence types bpo 4966 New Modules faulthandler This new debug module faulthandler contains functions to dump Python tracebacks explicitly on a fault a crash like a segmentation fault after a timeout or on a user signal Call faulthandler enable to install fault handlers for the SIGSEGV SIGFPE SIGABRT SIGBUS and SIGILL signals You can also enable them at startup by setting the PYTHONFAULTHANDLER environment variable or by using X faulthandler command line option Example of a segmentation fault on Linux python q X faulthandler import ctypes ctypes string_at 0 Fatal Python error Segmentation fault Current thread 0x00007fb899f39700 File home python cpython Lib ctypes __init__ py line 486 in string_at File stdin line 1 in module Segmentation fault ipaddress The new ipaddress module provides tools for creating and manipulating objects representing IPv4 and IPv6 addresses networks and interfaces i e an IP address associated with a specific IP subnet Contributed by Google and Peter Moody in PEP 3144 lzma The newly added lzma module provides data compression and decompression using the LZMA algorithm including support for the xz and lzma file formats Contributed by Nadeem Vawda and Per Øyvind Karlsen in bpo 6715 Improved Modules abc Improved support for abstract base classes containing descriptors composed with abstract methods The recommended approach to declaring abstract descriptors is now to provide __isabstractmethod__ as a dynamically updated property The built in descriptors have been updated accordingly abc abstractproperty has been deprecated use property with abc abstractmethod instead abc abstractclassmethod has been deprecated use classmethod with abc abstractmethod instead abc abstractstaticmethod has been deprecated use staticmethod with abc abstractmethod instead Contributed by Darren Dale in bpo 11610 abc ABCMeta register now returns the registered subclass which means it can now be used as a class decorator bpo 10868 array The array module supports the long long type using q and Q type codes Contributed by Oren Tirosh and Hirokazu Yamamoto in bpo 1172711 base64 ASCII only Unicode strings are now accepted by the decoding functions of the base64 modern interface For example base64 b64decode YWJj returns b abc Contributed by Catalin Iacob in bpo 13641 binascii In addition to the binary objects they normally accept the a2b_ functions now all also accept ASCII only strings as input Contributed by Antoine Pitrou in bpo 13637 bz2 The bz2 module has been rewritten from scratch In the process several new features have been added New bz2 open function open a bzip2 compressed file in binary or text mode bz2 BZ2File can now read from and write to arbitrary file like objects by means of its constructor s fileobj argument Contributed by Nadeem Vawda in bpo 5863 bz2 BZ2File and bz2 decompress can now decompress multi stream inputs such as those produced by the pbzip2 tool bz2 BZ2File can now also be used to create this type of file using the a append mode Contributed by Nir Aides in bpo 1625 bz2 BZ2File now implements all of the io BufferedIOBase API except for the detach and truncate methods codecs The mbcs codec has been rewritten to handle correctly replace and ignore error handlers on all Windows versions The mbcs codec now supports all error handlers instead of only replace to encode and ignore to decode A new Windows only codec has been added cp65001 bpo 13216 ,en
2147,It is the Windows code page 65001 Windows UTF 8 CP_UTF8 For example it is used by sys stdout if the console output code page is set to cp65001 e g using chcp 65001 command Multibyte CJK decoders now resynchronize faster They only ignore the first byte of an invalid byte sequence For example b xff n decode gb2312 replace now returns a n after the replacement character bpo 12016 Incremental CJK codec encoders are no longer reset at each call to their encode methods For example import codecs encoder codecs getincrementalencoder hz strict b join encoder encode x for x in u52ff u65bd u65bc u4eba u3002 Bye b NpJ l6HK Bye This example gives b Np J l6 HK Bye with older Python versions bpo 12100 The unicode_internal codec has been deprecated collections Addition of a new ChainMap class to allow treating a number of mappings as a single unit Written by Raymond Hettinger for bpo 11089 made public in bpo 11297 The abstract base classes have been moved in a new collections abc module to better differentiate between the abstract and the concrete collections classes Aliases for ABCs are still present in the collections module to preserve existing imports bpo 11085 The Counter class now supports the unary and operators as well as the in place operators and Contributed by Raymond Hettinger in bpo 13121 contextlib ExitStack now provides a solid foundation for programmatic manipulation of context managers and similar cleanup functionality Unlike the previous contextlib nested API which was deprecated and removed the new API is designed to work correctly regardless of whether context managers acquire their resources in their __init__ method for example file objects or in their __enter__ method for example synchronisation objects from the threading module bpo 13585 crypt Addition of salt and modular crypt format hashing method and the mksalt function to the crypt module bpo 10924 curses If the curses module is linked to the ncursesw library use Unicode functions when Unicode strings or characters are passed e g waddwstr and bytes functions otherwise e g waddstr Use the locale encoding instead of utf 8 to encode Unicode strings curses window has a new curses window encoding attribute The curses window class has a new get_wch method to get a wide character The curses module has a new unget_wch function to push a wide character so the next get_wch will return it Contributed by Iñigo Serna in bpo 6755 datetime Equality comparisons between naive and aware datetime instances now return False instead of raising TypeError bpo 15006 New datetime datetime timestamp method Return POSIX timestamp corresponding to the datetime instance The datetime datetime strftime method supports formatting years older than 1000 The datetime datetime astimezone method can now be called without arguments to convert datetime instance to the system timezone decimal bpo 7652 integrate fast native decimal arithmetic C module and libmpdec written by Stefan Krah The new C version of the decimal module integrates the high speed libmpdec library for arbitrary precision correctly rounded decimal floating point arithmetic libmpdec conforms to IBM s General Decimal Arithmetic Specification Performance gains range from 10x for database applications to 100x for numerically intensive applications These numbers are expected gains for standard precisions used in decimal floating point arithmetic Since the precision is user configurable the exact figures may vary For example in integer bignum arithmetic the differences can be significantly higher The following table is meant as an illustration Benchmarks are available at https www bytereef org mpdecimal quickstart html decimal py _decimal speedup pi 42 02s 0 345s 120x telco 172 19s 5 68s 30x psycopg 3 57s 0 29s 12x Features The FloatOperation signal optionally enables stricter semantics for mixing floats and Decimals If Python is compiled without threads the C version automatically disables the expensive thread local context machinery In this case the variable HAVE_THREADS is set to False API changes The C module has the following conte,en
2148,xt limits depending on the machine architecture 32 bit 64 bit MAX_PREC 425000000 999999999999999999 MAX_EMAX 425000000 999999999999999999 MIN_EMIN 425000000 999999999999999999 In the context templates DefaultContext BasicContext and ExtendedContext the magnitude of Emax and Emin has changed to 999999 The Decimal constructor in decimal py does not observe the context limits and converts values with arbitrary exponents or precision exactly Since the C version has internal limits the following scheme is used If possible values are converted exactly otherwise InvalidOperation is raised and the result is NaN In the latter case it is always possible to use create_decimal in order to obtain a rounded or inexact value The power function in decimal py is always correctly rounded In the C version it is defined in terms of the correctly rounded exp and ln functions but the final result is only almost always correctly rounded In the C version the context dictionary containing the signals is a MutableMapping For speed reasons flags and traps always refer to the same MutableMapping that the context was initialized with If a new signal dictionary is assigned flags and traps are updated with the new values but they do not reference the RHS dictionary Pickling a Context produces a different output in order to have a common interchange format for the Python and C versions The order of arguments in the Context constructor has been changed to match the order displayed by repr The watchexp parameter in the quantize method is deprecated email Policy Framework The email package now has a policy framework A Policy is an object with several methods and properties that control how the email package behaves The primary policy for Python 3 3 is the Compat32 policy which provides backward compatibility with the email package in Python 3 2 A policy can be specified when an email message is parsed by a parser or when a Message object is created or when an email is serialized using a generator Unless overridden a policy passed to a parser is inherited by all the Message object and sub objects created by the parser By default a generator will use the policy of the Message object it is serializing The default policy is compat32 The minimum set of controls implemented by all policy objects are max_line_length The maximum length excluding the linesep character s individual lines may have when a Message is serialized Defaults to 78 linesep The character used to separate individual lines when a Message is serialized Defaults to n cte_type 7bit or 8bit 8bit applies only to a Bytes generator and means that non ASCII may be used where allowed by the protocol or where it exists in the original input raise_on_defect Causes a parser to raise error when defects are encountered instead of adding them to the Message object s defects list A new policy instance with new settings is created using the clone method of policy objects clone takes any of the above controls as keyword arguments Any control not specified in the call retains its default value Thus you can create a policy that uses r n linesep characters like this mypolicy compat32 clone linesep r n Policies can be used to make the generation of messages in the format needed by your application simpler Instead of having to remember to specify linesep r n in all the places you call a generator you can specify it once when you set the policy used by the parser or the Message whichever your program uses to create Message objects On the other hand if you need to generate messages in multiple forms you can still specify the parameters in the appropriate generator call Or you can have custom policy instances for your different cases and pass those in when you create the generator Provisional Policy with New Header API While the policy framework is worthwhile all by itself the main motivation for introducing it is to allow the creation of new policies that implement new features for the email package in a way that maintains backward compatibility for those who do not use the new policies Because the new policies introd,en
2149,uce a new API we are releasing them in Python 3 3 as a provisional policy Backwards incompatible changes up to and including removal of the code may occur if deemed necessary by the core developers The new policies are instances of EmailPolicy and add the following additional controls refold_source Controls whether or not headers parsed by a parser are refolded by the generator It can be none long or all The default is long which means that source headers with a line longer than max_line_length get refolded none means no line get refolded and all means that all lines get refolded header_factory A callable that take a name and value and produces a custom header object The header_factory is the key to the new features provided by the new policies When one of the new policies is used any header retrieved from a Message object is an object produced by the header_factory and any time you set a header on a Message it becomes an object produced by header_factory All such header objects have a name attribute equal to the header name Address and Date headers have additional attributes that give you access to the parsed data of the header This means you can now do things like this m Message policy SMTP m To Éric foo example com m to Éric foo example com m to addresses Address display_name Éric username foo domain example com m to addresses 0 username foo m to addresses 0 display_name Éric m Date email utils localtime m Date datetime datetime datetime 2012 5 25 21 39 24 465484 tzinfo datetime timezone datetime timedelta 1 72000 EDT m Date Fri 25 May 2012 21 44 27 0400 print m To utf 8 q C3 89ric foo example com Date Fri 25 May 2012 21 44 27 0400 You will note that the unicode display name is automatically encoded as utf 8 when the message is serialized but that when the header is accessed directly you get the unicode version This eliminates any need to deal with the email header decode_header or make_header functions You can also create addresses from parts m cc Group pals Address Bob bob example com Address Sally sally example com Address Bonzo addr_spec bonz laugh com print m To utf 8 q C3 89ric foo example com Date Fri 25 May 2012 21 44 27 0400 cc pals Bob bob example com Sally sally example com Bonzo bonz laugh com Decoding to unicode is done automatically m2 message_from_string str m m2 to Éric foo example com When you parse a message you can use the addresses and groups attributes of the header objects to access the groups and individual addresses m2 cc addresses Address display_name Bob username bob domain example com Address display_name Sally username sally domain example com Address display_name Bonzo username bonz domain laugh com m2 cc groups Group display_name pals addresses Address display_name Bob username bob domain example com Address display_name Sally username sally domain example com Group display_name None addresses Address display_name Bonzo username bonz domain laugh com In summary if you use one of the new policies header manipulation works the way it ought to your application works with unicode strings and the email package transparently encodes and decodes the unicode to and from the RFC standard Content Transfer Encodings Other API Changes New BytesHeaderParser added to the parser module to complement HeaderParser and complete the Bytes API New utility functions format_datetime given a datetime produce a string formatted for use in an email header parsedate_to_datetime given a date string from an email header convert it into an aware datetime or a naive datetime if the offset is 0000 localtime With no argument returns the current local time as an aware datetime using the local timezone Given an aware datetime converts it into an aware datetime using the local timezone ftplib ftplib FTP now accepts a source_address keyword argument to specify the host port to use as the source address in the bind call when creating the outgoing socket Contributed by Giampaolo Rodolà in bpo 8594 The FTP_TLS class now provides a new ccc function to revert control channel back to plaintext This can be useful to take advantage,en
2150, of firewalls that know how to handle NAT with non secure FTP without opening fixed ports Contributed by Giampaolo Rodolà in bpo 12139 Added ftplib FTP mlsd method which provides a parsable directory listing format and deprecates ftplib FTP nlst and ftplib FTP dir Contributed by Giampaolo Rodolà in bpo 11072 functools The functools lru_cache decorator now accepts a typed keyword argument that defaults to False to ensure that it caches values of different types that compare equal in separate cache slots Contributed by Raymond Hettinger in bpo 13227 gc It is now possible to register callbacks invoked by the garbage collector before and after collection using the new callbacks list hmac A new compare_digest function has been added to prevent side channel attacks on digests through timing analysis Contributed by Nick Coghlan and Christian Heimes in bpo 15061 http http server BaseHTTPRequestHandler now buffers the headers and writes them all at once when end_headers is called A new method flush_headers can be used to directly manage when the accumulated headers are sent Contributed by Andrew Schaaf in bpo 3709 http server now produces valid HTML 4 01 strict output Contributed by Ezio Melotti in bpo 13295 http client HTTPResponse now has a readinto method which means it can be used as an io RawIOBase class Contributed by John Kuhn in bpo 13464 html html parser HTMLParser is now able to parse broken markup without raising errors therefore the strict argument of the constructor and the HTMLParseError exception are now deprecated The ability to parse broken markup is the result of a number of bug fixes that are also available on the latest bug fix releases of Python 2 7 3 2 Contributed by Ezio Melotti in bpo 15114 and bpo 14538 bpo 13993 bpo 13960 bpo 13358 bpo 1745761 bpo 755670 bpo 13357 bpo 12629 bpo 1200313 bpo 670664 bpo 13273 bpo 12888 bpo 7311 A new html5 dictionary that maps HTML5 named character references to the equivalent Unicode character s e g html5 gt has been added to the html entities module The dictionary is now also used by HTMLParser Contributed by Ezio Melotti in bpo 11113 and bpo 15156 imaplib The IMAP4_SSL constructor now accepts an SSLContext parameter to control parameters of the secure channel Contributed by Sijin Joseph in bpo 8808 inspect A new getclosurevars function has been added This function reports the current binding of all names referenced from the function body and where those names were resolved making it easier to verify correct internal state when testing code that relies on stateful closures Contributed by Meador Inge and Nick Coghlan in bpo 13062 A new getgeneratorlocals function has been added This function reports the current binding of local variables in the generator s stack frame making it easier to verify correct internal state when testing generators Contributed by Meador Inge in bpo 15153 io The open function has a new x mode that can be used to exclusively create a new file and raise a FileExistsError if the file already exists It is based on the C11 x mode to fopen Contributed by David Townshend in bpo 12760 The constructor of the TextIOWrapper class has a new write_through optional argument If write_through is True calls to write are guaranteed not to be buffered any data written on the TextIOWrapper object is immediately handled to its underlying binary buffer itertools accumulate now takes an optional func argument for providing a user supplied binary function logging The basicConfig function now supports an optional handlers argument taking an iterable of handlers to be added to the root logger A class level attribute append_nul has been added to SysLogHandler to allow control of the appending of the NUL 000 byte to syslog records since for some daemons it is required while for others it is passed through to the log math The math module has a new function log2 which returns the base 2 logarithm of x Written by Mark Dickinson in bpo 11888 mmap The read method is now more compatible with other file like objects if the argument is omitted or specified as None it returns the byte,en
2151,s from the current file position to the end of the mapping Contributed by Petri Lehtinen in bpo 12021 multiprocessing The new multiprocessing connection wait function allows polling multiple objects such as connections sockets and pipes with a timeout Contributed by Richard Oudkerk in bpo 12328 multiprocessing Connection objects can now be transferred over multiprocessing connections Contributed by Richard Oudkerk in bpo 4892 multiprocessing Process now accepts a daemon keyword argument to override the default behavior of inheriting the daemon flag from the parent process bpo 6064 New attribute multiprocessing Process sentinel allows a program to wait on multiple Process objects at one time using the appropriate OS primitives for example select on posix systems New methods multiprocessing pool Pool starmap and starmap_async provide itertools starmap equivalents to the existing multiprocessing pool Pool map and map_async functions Contributed by Hynek Schlawack in bpo 12708 nntplib The nntplib NNTP class now supports the context management protocol to unconditionally consume socket error exceptions and to close the NNTP connection when done from nntplib import NNTP with NNTP news gmane org as n n group gmane comp python committers 211 1755 1 1755 gmane comp python committers 1755 1 1755 gmane comp python committers Contributed by Giampaolo Rodolà in bpo 9795 os The os module has a new pipe2 function that makes it possible to create a pipe with O_CLOEXEC or O_NONBLOCK flags set atomically This is especially useful to avoid race conditions in multi threaded programs The os module has a new sendfile function which provides an efficient zero copy way for copying data from one file or socket descriptor to another The phrase zero copy refers to the fact that all of the copying of data between the two descriptors is done entirely by the kernel with no copying of data into userspace buffers sendfile can be used to efficiently copy data from a file on disk to a network socket e g for downloading a file Patch submitted by Ross Lagerwall and Giampaolo Rodolà in bpo 10882 To avoid race conditions like symlink attacks and issues with temporary files and directories it is more reliable and also faster to manipulate file descriptors instead of file names Python 3 3 enhances existing functions and introduces new functions to work on file descriptors bpo 4761 bpo 10755 and bpo 14626 The os module has a new fwalk function similar to walk except that it also yields file descriptors referring to the directories visited This is especially useful to avoid symlink races The following functions get new optional dir_fd paths relative to directory descriptors and or follow_symlinks not following symlinks access chflags chmod chown link lstat mkdir mkfifo mknod open readlink remove rename replace rmdir stat symlink unlink utime Platform support for using these parameters can be checked via the sets os supports_dir_fd and os supports_follows_symlinks The following functions now support a file descriptor for their path argument chdir chmod chown execve listdir pathconf exists stat statvfs utime Platform support for this can be checked via the os supports_fd set access accepts an effective_ids keyword argument to turn on using the effective uid gid rather than the real uid gid in the access check Platform support for this can be checked via the supports_effective_ids set The os module has two new functions getpriority and setpriority They can be used to get or set process niceness priority in a fashion similar to os nice but extended to all processes instead of just the current one Patch submitted by Giampaolo Rodolà in bpo 10784 The new os replace function allows cross platform renaming of a file with overwriting the destination With os rename an existing destination file is overwritten under POSIX but raises an error under Windows Contributed by Antoine Pitrou in bpo 8828 The stat family of functions stat fstat and lstat now support reading a file s timestamps with nanosecond precision Symmetrically utime can now write file timestamps with nanosecon,en
2152,d precision Contributed by Larry Hastings in bpo 14127 The new os get_terminal_size function queries the size of the terminal attached to a file descriptor See also shutil get_terminal_size Contributed by Zbigniew Jędrzejewski Szmek in bpo 13609 New functions to support Linux extended attributes bpo 12720 getxattr listxattr removexattr setxattr New interface to the scheduler These functions control how a process is allocated CPU time by the operating system New functions sched_get_priority_max sched_get_priority_min sched_getaffinity sched_getparam sched_getscheduler sched_rr_get_interval sched_setaffinity sched_setparam sched_setscheduler sched_yield New functions to control the file system posix_fadvise Announces an intention to access data in a specific pattern thus allowing the kernel to make optimizations posix_fallocate Ensures that enough disk space is allocated for a file sync Force write of everything to disk Additional new posix functions lockf Apply test or remove a POSIX lock on an open file descriptor pread Read from a file descriptor at an offset the file offset remains unchanged pwrite Write to a file descriptor from an offset leaving the file offset unchanged readv Read from a file descriptor into a number of writable buffers truncate Truncate the file corresponding to path so that it is at most length bytes in size waitid Wait for the completion of one or more child processes writev Write the contents of buffers to a file descriptor where buffers is an arbitrary sequence of buffers getgrouplist bpo 9344 Return list of group ids that specified user belongs to times and uname Return type changed from a tuple to a tuple like object with named attributes Some platforms now support additional constants for the lseek function such as os SEEK_HOLE and os SEEK_DATA New constants RTLD_LAZY RTLD_NOW RTLD_GLOBAL RTLD_LOCAL RTLD_NODELETE RTLD_NOLOAD and RTLD_DEEPBIND are available on platforms that support them These are for use with the sys setdlopenflags function and supersede the similar constants defined in ctypes and DLFCN Contributed by Victor Stinner in bpo 13226 os symlink now accepts and ignores the target_is_directory keyword argument on non Windows platforms to ease cross platform support pdb Tab completion is now available not only for command names but also their arguments For example for the break command function and file names are completed Contributed by Georg Brandl in bpo 14210 pickle pickle Pickler objects now have an optional dispatch_table attribute allowing per pickler reduction functions to be set Contributed by Richard Oudkerk in bpo 14166 pydoc The Tk GUI and the serve function have been removed from the pydoc module pydoc g and serve have been deprecated in Python 3 2 re str regular expressions now support u and U escapes Contributed by Serhiy Storchaka in bpo 3665 sched run now accepts a blocking parameter which when set to false makes the method execute the scheduled events due to expire soonest if any and then return immediately This is useful in case you want to use the scheduler in non blocking applications Contributed by Giampaolo Rodolà in bpo 13449 scheduler class can now be safely used in multi threaded environments Contributed by Josiah Carlson and Giampaolo Rodolà in bpo 8684 timefunc and delayfunct parameters of scheduler class constructor are now optional and defaults to time time and time sleep respectively Contributed by Chris Clark in bpo 13245 enter and enterabs argument parameter is now optional Contributed by Chris Clark in bpo 13245 enter and enterabs now accept a kwargs parameter Contributed by Chris Clark in bpo 13245 select Solaris and derivative platforms have a new class select devpoll for high performance asynchronous sockets via dev poll Contributed by Jesús Cea Avión in bpo 6397 shlex The previously undocumented helper function quote from the pipes modules has been moved to the shlex module and documented quote properly escapes all characters in a string that might be otherwise given special meaning by the shell shutil New functions disk_usage provides total use,en
2153,d and free disk space statistics Contributed by Giampaolo Rodolà in bpo 12442 chown allows one to change user and or group of the given path also specifying the user group names and not only their numeric ids Contributed by Sandro Tosi in bpo 12191 shutil get_terminal_size returns the size of the terminal window to which the interpreter is attached Contributed by Zbigniew Jędrzejewski Szmek in bpo 13609 copy2 and copystat now preserve file timestamps with nanosecond precision on platforms that support it They also preserve file extended attributes on Linux Contributed by Larry Hastings in bpo 14127 and bpo 15238 Several functions now take an optional symlinks argument when that parameter is true symlinks aren t dereferenced and the operation instead acts on the symlink itself or creates one if relevant Contributed by Hynek Schlawack in bpo 12715 When copying files to a different file system move now handles symlinks the way the posix mv command does recreating the symlink rather than copying the target file contents Contributed by Jonathan Niehof in bpo 9993 move now also returns the dst argument as its result rmtree is now resistant to symlink attacks on platforms which support the new dir_fd parameter in os open and os unlink Contributed by Martin von Löwis and Hynek Schlawack in bpo 4489 signal The signal module has new functions pthread_sigmask fetch and or change the signal mask of the calling thread Contributed by Jean Paul Calderone in bpo 8407 pthread_kill send a signal to a thread sigpending examine pending functions sigwait wait a signal sigwaitinfo wait for a signal returning detailed information about it sigtimedwait like sigwaitinfo but with a timeout The signal handler writes the signal number as a single byte instead of a nul byte into the wakeup file descriptor So it is possible to wait more than one signal and know which signals were raised signal signal and signal siginterrupt raise an OSError instead of a RuntimeError OSError has an errno attribute smtpd The smtpd module now supports RFC 5321 extended SMTP and RFC 1870 size extension Per the standard these extensions are enabled if and only if the client initiates the session with an EHLO command Initial ELHO support by Alberto Trevino Size extension by Juhana Jauhiainen Substantial additional work on the patch contributed by Michele Orrù and Dan Boswell bpo 8739 smtplib The SMTP SMTP_SSL and LMTP classes now accept a source_address keyword argument to specify the host port to use as the source address in the bind call when creating the outgoing socket Contributed by Paulo Scardine in bpo 11281 SMTP now supports the context management protocol allowing an SMTP instance to be used in a with statement Contributed by Giampaolo Rodolà in bpo 11289 The SMTP_SSL constructor and the starttls method now accept an SSLContext parameter to control parameters of the secure channel Contributed by Kasun Herath in bpo 8809 socket The socket class now exposes additional methods to process ancillary data when supported by the underlying platform sendmsg recvmsg recvmsg_into Contributed by David Watson in bpo 6560 based on an earlier patch by Heiko Wundram The socket class now supports the PF_CAN protocol family https en wikipedia org wiki Socketcan on Linux https lwn net Articles 253425 Contributed by Matthias Fuchs updated by Tiago Gonçalves in bpo 10141 The socket class now supports the PF_RDS protocol family https en wikipedia org wiki Reliable_Datagram_Sockets and https oss oracle com projects rds The socket class now supports the PF_SYSTEM protocol family on OS X Contributed by Michael Goderbauer in bpo 13777 New function sethostname allows the hostname to be set on Unix systems if the calling process has sufficient privileges Contributed by Ross Lagerwall in bpo 10866 socketserver BaseServer now has an overridable method service_actions that is called by the serve_forever method in the service loop ForkingMixIn now uses this to clean up zombie child processes Contributed by Justin Warkentin in bpo 11109 sqlite3 New sqlite3 Connection method set_trace_callback can,en
2154, be used to capture a trace of all sql commands processed by sqlite Contributed by Torsten Landschoff in bpo 11688 ssl The ssl module has two new random generation functions RAND_bytes generate cryptographically strong pseudo random bytes RAND_pseudo_bytes generate pseudo random bytes Contributed by Victor Stinner in bpo 12049 The ssl module now exposes a finer grained exception hierarchy in order to make it easier to inspect the various kinds of errors Contributed by Antoine Pitrou in bpo 11183 load_cert_chain now accepts a password argument to be used if the private key is encrypted Contributed by Adam Simpkins in bpo 12803 Diffie Hellman key exchange both regular and Elliptic Curve based is now supported through the load_dh_params and set_ecdh_curve methods Contributed by Antoine Pitrou in bpo 13626 and bpo 13627 SSL sockets have a new get_channel_binding method allowing the implementation of certain authentication mechanisms such as SCRAM SHA 1 PLUS Contributed by Jacek Konieczny in bpo 12551 You can query the SSL compression algorithm used by an SSL socket thanks to its new compression method The new attribute OP_NO_COMPRESSION can be used to disable compression Contributed by Antoine Pitrou in bpo 13634 Support has been added for the Next Protocol Negotiation extension using the ssl SSLContext set_npn_protocols method Contributed by Colin Marc in bpo 14204 SSL errors can now be introspected more easily thanks to library and reason attributes Contributed by Antoine Pitrou in bpo 14837 The get_server_certificate function now supports IPv6 Contributed by Charles François Natali in bpo 11811 New attribute OP_CIPHER_SERVER_PREFERENCE allows setting SSLv3 server sockets to use the server s cipher ordering preference rather than the client s bpo 13635 stat The undocumented tarfile filemode function has been moved to stat filemode It can be used to convert a file s mode to a string of the form rwxrwxrwx Contributed by Giampaolo Rodolà in bpo 14807 struct The struct module now supports ssize_t and size_t via the new codes n and N respectively Contributed by Antoine Pitrou in bpo 3163 subprocess Command strings can now be bytes objects on posix platforms Contributed by Victor Stinner in bpo 8513 A new constant DEVNULL allows suppressing output in a platform independent fashion Contributed by Ross Lagerwall in bpo 5870 sys The sys module has a new thread_info named tuple holding information about the thread implementation bpo 11223 tarfile tarfile now supports lzma encoding via the lzma module Contributed by Lars Gustäbel in bpo 5689 tempfile tempfile SpooledTemporaryFile s truncate method now accepts a size parameter Contributed by Ryan Kelly in bpo 9957 textwrap The textwrap module has a new indent that makes it straightforward to add a common prefix to selected lines in a block of text bpo 13857 threading threading Condition threading Semaphore threading BoundedSemaphore threading Event and threading Timer all of which used to be factory functions returning a class instance are now classes and may be subclassed Contributed by Éric Araujo in bpo 10968 The threading Thread constructor now accepts a daemon keyword argument to override the default behavior of inheriting the daemon flag value from the parent thread bpo 6064 The formerly private function _thread get_ident is now available as the public function threading get_ident This eliminates several cases of direct access to the _thread module in the stdlib Third party code that used _thread get_ident should likewise be changed to use the new public interface time The PEP 418 added new functions to the time module get_clock_info Get information on a clock monotonic Monotonic clock cannot go backward not affected by system clock updates perf_counter Performance counter with the highest available resolution to measure a short duration process_time Sum of the system and user CPU time of the current process Other new functions clock_getres clock_gettime and clock_settime functions with CLOCK_ xxx constants Contributed by Victor Stinner in bpo 10278 To improve cross platform con,en
2155,sistency sleep now raises a ValueError when passed a negative sleep value Previously this was an error on posix but produced an infinite sleep on Windows types Add a new types MappingProxyType class Read only proxy of a mapping bpo 14386 The new functions types new_class and types prepare_class provide support for PEP 3115 compliant dynamic type creation bpo 14588 unittest assertRaises assertRaisesRegex assertWarns and assertWarnsRegex now accept a keyword argument msg when used as context managers Contributed by Ezio Melotti and Winston Ewert in bpo 10775 unittest TestCase run now returns the TestResult object urllib The Request class now accepts a method argument used by get_method to determine what HTTP method should be used For example this will send a HEAD request urlopen Request https www python org method HEAD bpo 1673007 webbrowser The webbrowser module supports more browsers Google Chrome named chrome chromium chrome browser or chromium browser depending on the version and operating system and the generic launchers xdg open from the FreeDesktop org project and gvfs open which is the default URI handler for GNOME 3 The former contributed by Arnaud Calmettes in bpo 13620 the latter by Matthias Klose in bpo 14493 xml etree ElementTree The xml etree ElementTree module now imports its C accelerator by default there is no longer a need to explicitly import xml etree cElementTree this module stays for backwards compatibility but is now deprecated In addition the iter family of methods of Element has been optimized rewritten in C The module s documentation has also been greatly improved with added examples and a more detailed reference zlib New attribute zlib Decompress eof makes it possible to distinguish between a properly formed compressed stream and an incomplete or truncated one Contributed by Nadeem Vawda in bpo 12646 New attribute zlib ZLIB_RUNTIME_VERSION reports the version string of the underlying zlib library that is loaded at runtime Contributed by Torsten Landschoff in bpo 12306 Optimizations Major performance enhancements have been added Thanks to PEP 393 some operations on Unicode strings have been optimized the memory footprint is divided by 2 to 4 depending on the text encode an ASCII string to UTF 8 doesn t need to encode characters anymore the UTF 8 representation is shared with the ASCII representation the UTF 8 encoder has been optimized repeating a single ASCII letter and getting a substring of an ASCII string is 4 times faster UTF 8 is now 2x to 4x faster UTF 16 encoding is now up to 10x faster Contributed by Serhiy Storchaka bpo 14624 bpo 14738 and bpo 15026 Build and C API Changes Changes to Python s build process and to the C API include New PEP 3118 related function PyMemoryView_FromMemory PEP 393 added new Unicode types macros and functions High level API PyUnicode_CopyCharacters PyUnicode_FindChar PyUnicode_GetLength PyUnicode_GET_LENGTH PyUnicode_New PyUnicode_Substring PyUnicode_ReadChar PyUnicode_WriteChar Low level API Py_UCS1 Py_UCS2 Py_UCS4 types PyASCIIObject and PyCompactUnicodeObject structures PyUnicode_READY PyUnicode_FromKindAndData PyUnicode_AsUCS4 PyUnicode_AsUCS4Copy PyUnicode_DATA PyUnicode_1BYTE_DATA PyUnicode_2BYTE_DATA PyUnicode_4BYTE_DATA PyUnicode_KIND with PyUnicode_Kind enum PyUnicode_WCHAR_KIND PyUnicode_1BYTE_KIND PyUnicode_2BYTE_KIND PyUnicode_4BYTE_KIND PyUnicode_READ PyUnicode_READ_CHAR PyUnicode_WRITE PyUnicode_MAX_CHAR_VALUE PyArg_ParseTuple now accepts a bytearray for the c format bpo 12380 Deprecated Unsupported Operating Systems OS 2 and VMS are no longer supported due to the lack of a maintainer Windows 2000 and Windows platforms which set COMSPEC to command com are no longer supported due to maintenance burden OSF support which was deprecated in 3 2 has been completely removed Deprecated Python modules functions and methods Passing a non empty string to object __format__ is deprecated and will produce a TypeError in Python 3 4 bpo 9856 The unicode_internal codec has been deprecated because of the PEP 393 use UTF 8 UTF 16 utf 16 le or utf 16 be or UTF 32 utf,en
2156, 32 le or utf 32 be ftplib FTP nlst and ftplib FTP dir use ftplib FTP mlsd platform popen use the subprocess module Check especially the Replacing Older Functions with the subprocess Module section bpo 11377 bpo 13374 The Windows bytes API has been deprecated in the os module Use Unicode filenames instead of bytes filenames to not depend on the ANSI code page anymore and to support any filename bpo 13988 The xml etree cElementTree module is deprecated The accelerator is used automatically whenever available The behaviour of time clock depends on the platform use the new time perf_counter or time process_time function instead depending on your requirements to have a well defined behaviour The os stat_float_times function is deprecated abc module abc abstractproperty has been deprecated use property with abc abstractmethod instead abc abstractclassmethod has been deprecated use classmethod with abc abstractmethod instead abc abstractstaticmethod has been deprecated use staticmethod with abc abstractmethod instead importlib package importlib abc SourceLoader path_mtime is now deprecated in favour of importlib abc SourceLoader path_stats as bytecode files now store both the modification time and size of the source file the bytecode file was compiled from Deprecated functions and types of the C API The Py_UNICODE has been deprecated by PEP 393 and will be removed in Python 4 All functions using this type are deprecated Unicode functions and methods using Py_UNICODE and Py_UNICODE types PyUnicode_FromUnicode use PyUnicode_FromWideChar or PyUnicode_FromKindAndData PyUnicode_AS_UNICODE PyUnicode_AsUnicode PyUnicode_AsUnicodeAndSize use PyUnicode_AsWideCharString PyUnicode_AS_DATA use PyUnicode_DATA with PyUnicode_READ and PyUnicode_WRITE PyUnicode_GET_SIZE PyUnicode_GetSize use PyUnicode_GET_LENGTH or PyUnicode_GetLength PyUnicode_GET_DATA_SIZE use PyUnicode_GET_LENGTH str PyUnicode_KIND str only work on ready strings PyUnicode_AsUnicodeCopy use PyUnicode_AsUCS4Copy or PyUnicode_AsWideCharString PyUnicode_GetMax Functions and macros manipulating Py_UNICODE strings Py_UNICODE_strlen use PyUnicode_GetLength or PyUnicode_GET_LENGTH Py_UNICODE_strcat use PyUnicode_CopyCharacters or PyUnicode_FromFormat Py_UNICODE_strcpy Py_UNICODE_strncpy Py_UNICODE_COPY use PyUnicode_CopyCharacters or PyUnicode_Substring Py_UNICODE_strcmp use PyUnicode_Compare Py_UNICODE_strncmp use PyUnicode_Tailmatch Py_UNICODE_strchr Py_UNICODE_strrchr use PyUnicode_FindChar Py_UNICODE_FILL use PyUnicode_Fill Py_UNICODE_MATCH Encoders PyUnicode_Encode use PyUnicode_AsEncodedObject PyUnicode_EncodeUTF7 PyUnicode_EncodeUTF8 use PyUnicode_AsUTF8 or PyUnicode_AsUTF8String PyUnicode_EncodeUTF32 PyUnicode_EncodeUTF16 PyUnicode_EncodeUnicodeEscape use PyUnicode_AsUnicodeEscapeString PyUnicode_EncodeRawUnicodeEscape use PyUnicode_AsRawUnicodeEscapeString PyUnicode_EncodeLatin1 use PyUnicode_AsLatin1String PyUnicode_EncodeASCII use PyUnicode_AsASCIIString PyUnicode_EncodeCharmap PyUnicode_TranslateCharmap PyUnicode_EncodeMBCS use PyUnicode_AsMBCSString or PyUnicode_EncodeCodePage with CP_ACP code_page PyUnicode_EncodeDecimal PyUnicode_TransformDecimalToASCII Deprecated features The array module s u format code is now deprecated and will be removed in Python 4 together with the rest of the Py_UNICODE API Porting to Python 3 3 This section lists previously described changes and other bugfixes that may require changes to your code Porting Python code Hash randomization is enabled by default Set the PYTHONHASHSEED environment variable to 0 to disable hash randomization See also the object __hash__ method bpo 12326 On Linux sys platform doesn t contain the major version anymore It is now always linux instead of linux2 or linux3 depending on the Linux version used to build Python Replace sys platform linux2 with sys platform startswith linux or directly sys platform linux if you don t need to support older Python versions bpo 13847 bpo 14180 time and datetime OverflowError is now raised instead of ValueError if a timestamp is out of range OSError is now raised if C functions g,en
2157,mtime or localtime failed The default finders used by import now utilize a cache of what is contained within a specific directory If you create a Python source file or sourceless bytecode file make sure to call importlib invalidate_caches to clear out the cache for the finders to notice the new file ImportError now uses the full name of the module that was attempted to be imported Doctests that check ImportErrors message will need to be updated to use the full name of the module instead of just the tail of the name The index argument to __import__ now defaults to 0 instead of 1 and no longer support negative values It was an oversight when PEP 328 was implemented that the default value remained 1 If you need to continue to perform a relative import followed by an absolute import then perform the relative import using an index of 1 followed by another import using an index of 0 It is preferred though that you use importlib import_module rather than call __import__ directly __import__ no longer allows one to use an index value other than 0 for top level modules E g __import__ sys level 1 is now an error Because sys meta_path and sys path_hooks now have finders on them by default you will most likely want to use list insert instead of list append to add to those lists Because None is now inserted into sys path_importer_cache if you are clearing out entries in the dictionary of paths that do not have a finder you will need to remove keys paired with values of None and imp NullImporter to be backwards compatible This will lead to extra overhead on older versions of Python that re insert None into sys path_importer_cache where it represents the use of implicit finders but semantically it should not change anything importlib abc Finder no longer specifies a find_module abstract method that must be implemented If you were relying on subclasses to implement that method make sure to check for the method s existence first You will probably want to check for find_loader first though in the case of working with path entry finders pkgutil has been converted to use importlib internally This eliminates many edge cases where the old behaviour of the PEP 302 import emulation failed to match the behaviour of the real import system The import emulation itself is still present but is now deprecated The pkgutil iter_importers and pkgutil walk_packages functions special case the standard import hooks so they are still supported even though they do not provide the non standard iter_modules method A longstanding RFC compliance bug bpo 1079 in the parsing done by email header decode_header has been fixed Code that uses the standard idiom to convert encoded headers into unicode str make_header decode_header h will see no change but code that looks at the individual tuples returned by decode_header will see that whitespace that precedes or follows ASCII sections is now included in the ASCII section Code that builds headers using make_header should also continue to work without change since make_header continues to add whitespace between ASCII and non ASCII sections if it is not already present in the input strings email utils formataddr now does the correct content transfer encoding when passed non ASCII display names Any code that depended on the previous buggy behavior that preserved the non ASCII unicode in the formatted output string will need to be changed bpo 1690608 poplib POP3 quit may now raise protocol errors like all other poplib methods Code that assumes quit does not raise poplib error_proto errors may need to be changed if errors on quit are encountered by a particular application bpo 11291 The strict argument to email parser Parser deprecated since Python 2 4 has finally been removed The deprecated method unittest TestCase assertSameElements has been removed The deprecated variable time accept2dyear has been removed The deprecated Context _clamp attribute has been removed from the decimal module It was previously replaced by the public attribute clamp See bpo 8540 The undocumented internal helper class SSLFakeFile has been removed fr,en
2158,om smtplib since its functionality has long been provided directly by socket socket makefile Passing a negative value to time sleep on Windows now raises an error instead of sleeping forever It has always raised an error on posix The ast __version__ constant has been removed If you need to make decisions affected by the AST version use sys version_info to make the decision Code that used to work around the fact that the threading module used factory functions by subclassing the private classes will need to change to subclass the now public classes The undocumented debugging machinery in the threading module has been removed simplifying the code This should have no effect on production code but is mentioned here in case any application debug frameworks were interacting with it bpo 13550 Porting C code In the course of changes to the buffer API the undocumented smalltable member of the Py_buffer structure has been removed and the layout of the PyMemoryViewObject has changed All extensions relying on the relevant parts in memoryobject h or object h must be rebuilt Due to PEP 393 the Py_UNICODE type and all functions using this type are deprecated but will stay available for at least five years If you were using low level Unicode APIs to construct and access unicode objects and you want to benefit of the memory footprint reduction provided by PEP 393 you have to convert your code to the new Unicode API However if you only have been using high level functions such as PyUnicode_Concat PyUnicode_Join or PyUnicode_FromFormat your code will automatically take advantage of the new unicode representations PyImport_GetMagicNumber now returns 1 upon failure As a negative value for the level argument to __import__ is no longer valid the same now holds for PyImport_ImportModuleLevel This also means that the value of level used by PyImport_ImportModuleEx is now 0 instead of 1 Building C extensions The range of possible file names for C extensions has been narrowed Very rarely used spellings have been suppressed under POSIX files named xxxmodule so xxxmodule abi3 so and xxxmodule cpython so are no longer recognized as implementing the xxx module If you had been generating such files you have to switch to the other spellings i e remove the module string from the file names implemented in bpo 14040 Command Line Switch Changes The Q command line flag and related artifacts have been removed Code checking sys flags division_warning will need updating bpo 10998 contributed by Éric Araujo When python is started with S import site will no longer add site specific paths to the module search paths In previous versions it did bpo 11591 contributed by Carl Meyer with editions by Éric Araujo,en
2159,3 Defining Extension Types Assorted Topics This section aims to give a quick fly by on the various type methods you can implement and what they do Here is the definition of PyTypeObject with some fields only used in debug builds omitted typedef struct _typeobject PyObject_VAR_HEAD const char tp_name For printing in format module name Py_ssize_t tp_basicsize tp_itemsize For allocation Methods to implement standard operations destructor tp_dealloc Py_ssize_t tp_vectorcall_offset getattrfunc tp_getattr setattrfunc tp_setattr PyAsyncMethods tp_as_async formerly known as tp_compare Python 2 or tp_reserved Python 3 reprfunc tp_repr Method suites for standard classes PyNumberMethods tp_as_number PySequenceMethods tp_as_sequence PyMappingMethods tp_as_mapping More standard operations here for binary compatibility hashfunc tp_hash ternaryfunc tp_call reprfunc tp_str getattrofunc tp_getattro setattrofunc tp_setattro Functions to access object as input output buffer PyBufferProcs tp_as_buffer Flags to define presence of optional expanded features unsigned long tp_flags const char tp_doc Documentation string Assigned meaning in release 2 0 call function for all accessible objects traverseproc tp_traverse delete references to contained objects inquiry tp_clear Assigned meaning in release 2 1 rich comparisons richcmpfunc tp_richcompare weak reference enabler Py_ssize_t tp_weaklistoffset Iterators getiterfunc tp_iter iternextfunc tp_iternext Attribute descriptor and subclassing stuff struct PyMethodDef tp_methods struct PyMemberDef tp_members struct PyGetSetDef tp_getset Strong reference on a heap type borrowed reference on a static type struct _typeobject tp_base PyObject tp_dict descrgetfunc tp_descr_get descrsetfunc tp_descr_set Py_ssize_t tp_dictoffset initproc tp_init allocfunc tp_alloc newfunc tp_new freefunc tp_free Low level free memory routine inquiry tp_is_gc For PyObject_IS_GC PyObject tp_bases PyObject tp_mro method resolution order PyObject tp_cache PyObject tp_subclasses PyObject tp_weaklist destructor tp_del Type attribute cache version tag Added in version 2 6 unsigned int tp_version_tag destructor tp_finalize vectorcallfunc tp_vectorcall bitset of which type watchers care about this type unsigned char tp_watched PyTypeObject Now that s a lot of methods Don t worry too much though if you have a type you want to define the chances are very good that you will only implement a handful of these As you probably expect by now we re going to go over this and give more information about the various handlers We won t go in the order they are defined in the structure because there is a lot of historical baggage that impacts the ordering of the fields It s often easiest to find an example that includes the fields you need and then change the values to suit your new type const char tp_name For printing The name of the type as mentioned in the previous chapter this will appear in various places almost entirely for diagnostic purposes Try to choose something that will be helpful in such a situation Py_ssize_t tp_basicsize tp_itemsize For allocation These fields tell the runtime how much memory to allocate when new objects of this type are created Python has some built in support for variable length structures think strings tuples which is where the tp_itemsize field comes in This will be dealt with later const char tp_doc Here you can put a string or its address that you want returned when the Python script references obj __doc__ to retrieve the doc string Now we come to the basic type methods the ones most extension types will implement 3 1 Finalization and De allocation destructor tp_dealloc This function is called when the reference count of the instance of your type is reduced to zero and the Python interpreter wants to reclaim it If your type has memory to free or other clean up to perform you can put it here The object itself needs to be freed here as well Here is an example of this function static void newdatatype_dealloc newdatatypeobject obj free obj obj_UnderlyingDatatypePtr Py_TYPE obj tp_free PyObject obj If your type sup,en
2160,ports garbage collection the destructor should call PyObject_GC_UnTrack before clearing any member fields static void newdatatype_dealloc newdatatypeobject obj PyObject_GC_UnTrack obj Py_CLEAR obj other_obj Py_TYPE obj tp_free PyObject obj One important requirement of the deallocator function is that it leaves any pending exceptions alone This is important since deallocators are frequently called as the interpreter unwinds the Python stack when the stack is unwound due to an exception rather than normal returns nothing is done to protect the deallocators from seeing that an exception has already been set Any actions which a deallocator performs which may cause additional Python code to be executed may detect that an exception has been set This can lead to misleading errors from the interpreter The proper way to protect against this is to save a pending exception before performing the unsafe action and restoring it when done This can be done using the PyErr_Fetch and PyErr_Restore functions static void my_dealloc PyObject obj MyObject self MyObject obj PyObject cbresult if self my_callback NULL PyObject err_type err_value err_traceback This saves the current exception state PyErr_Fetch err_type err_value err_traceback cbresult PyObject_CallNoArgs self my_callback if cbresult NULL PyErr_WriteUnraisable self my_callback else Py_DECREF cbresult This restores the saved exception state PyErr_Restore err_type err_value err_traceback Py_DECREF self my_callback Py_TYPE obj tp_free PyObject self Note There are limitations to what you can safely do in a deallocator function First if your type supports garbage collection using tp_traverse and or tp_clear some of the object s members can have been cleared or finalized by the time tp_dealloc is called Second in tp_dealloc your object is in an unstable state its reference count is equal to zero Any call to a non trivial object or API as in the example above might end up calling tp_dealloc again causing a double free and a crash Starting with Python 3 4 it is recommended not to put any complex finalization code in tp_dealloc and instead use the new tp_finalize type method See also PEP 442 explains the new finalization scheme 3 2 Object Presentation In Python there are two ways to generate a textual representation of an object the repr function and the str function The print function just calls str These handlers are both optional reprfunc tp_repr reprfunc tp_str The tp_repr handler should return a string object containing a representation of the instance for which it is called Here is a simple example static PyObject newdatatype_repr newdatatypeobject obj return PyUnicode_FromFormat Repr ified_newdatatype size d obj obj_UnderlyingDatatypePtr size If no tp_repr handler is specified the interpreter will supply a representation that uses the type s tp_name and a uniquely identifying value for the object The tp_str handler is to str what the tp_repr handler described above is to repr that is it is called when Python code calls str on an instance of your object Its implementation is very similar to the tp_repr function but the resulting string is intended for human consumption If tp_str is not specified the tp_repr handler is used instead Here is a simple example static PyObject newdatatype_str newdatatypeobject obj return PyUnicode_FromFormat Stringified_newdatatype size d obj obj_UnderlyingDatatypePtr size 3 3 Attribute Management For every object which can support attributes the corresponding type must provide the functions that control how the attributes are resolved There needs to be a function which can retrieve attributes if any are defined and another to set attributes if setting attributes is allowed Removing an attribute is a special case for which the new value passed to the handler is NULL Python supports two pairs of attribute handlers a type that supports attributes only needs to implement the functions for one pair The difference is that one pair takes the name of the attribute as a char while the other accepts a PyObject Each type can use whichever pair makes more sense for t,en
2161,he implementation s convenience getattrfunc tp_getattr char version setattrfunc tp_setattr getattrofunc tp_getattro PyObject version setattrofunc tp_setattro If accessing attributes of an object is always a simple operation this will be explained shortly there are generic implementations which can be used to provide the PyObject version of the attribute management functions The actual need for type specific attribute handlers almost completely disappeared starting with Python 2 2 though there are many examples which have not been updated to use some of the new generic mechanism that is available 3 3 1 Generic Attribute Management Most extension types only use simple attributes So what makes the attributes simple There are only a couple of conditions that must be met 1 The name of the attributes must be known when PyType_Ready is called 2 No special processing is needed to record that an attribute was looked up or set nor do actions need to be taken based on the value Note that this list does not place any restrictions on the values of the attributes when the values are computed or how relevant data is stored When PyType_Ready is called it uses three tables referenced by the type object to create descriptor s which are placed in the dictionary of the type object Each descriptor controls access to one attribute of the instance object Each of the tables is optional if all three are NULL instances of the type will only have attributes that are inherited from their base type and should leave the tp_getattro and tp_setattro fields NULL as well allowing the base type to handle attributes The tables are declared as three fields of the type object struct PyMethodDef tp_methods struct PyMemberDef tp_members struct PyGetSetDef tp_getset If tp_methods is not NULL it must refer to an array of PyMethodDef structures Each entry in the table is an instance of this structure typedef struct PyMethodDef const char ml_name method name PyCFunction ml_meth implementation function int ml_flags flags const char ml_doc docstring PyMethodDef One entry should be defined for each method provided by the type no entries are needed for methods inherited from a base type One additional entry is needed at the end it is a sentinel that marks the end of the array The ml_name field of the sentinel must be NULL The second table is used to define attributes which map directly to data stored in the instance A variety of primitive C types are supported and access may be read only or read write The structures in the table are defined as typedef struct PyMemberDef const char name int type int offset int flags const char doc PyMemberDef For each entry in the table a descriptor will be constructed and added to the type which will be able to extract a value from the instance structure The type field should contain a type code like Py_T_INT or Py_T_DOUBLE the value will be used to determine how to convert Python values to and from C values The flags field is used to store flags which control how the attribute can be accessed you can set it to Py_READONLY to prevent Python code from setting it An interesting advantage of using the tp_members table to build descriptors that are used at runtime is that any attribute defined this way can have an associated doc string simply by providing the text in the table An application can use the introspection API to retrieve the descriptor from the class object and get the doc string using its __doc__ attribute As with the tp_methods table a sentinel entry with a ml_name value of NULL is required 3 3 2 Type specific Attribute Management For simplicity only the char version will be demonstrated here the type of the name parameter is the only difference between the char and PyObject flavors of the interface This example effectively does the same thing as the generic example above but does not use the generic support added in Python 2 2 It explains how the handler functions are called so that if you do need to extend their functionality you ll understand what needs to be done The tp_getattr handler is called when the object requires ,en
2162,an attribute look up It is called in the same situations where the __getattr__ method of a class would be called Here is an example static PyObject newdatatype_getattr newdatatypeobject obj char name if strcmp name data 0 return PyLong_FromLong obj data PyErr_Format PyExc_AttributeError 100s object has no attribute 400s Py_TYPE obj tp_name name return NULL The tp_setattr handler is called when the __setattr__ or __delattr__ method of a class instance would be called When an attribute should be deleted the third parameter will be NULL Here is an example that simply raises an exception if this were really all you wanted the tp_setattr handler should be set to NULL static int newdatatype_setattr newdatatypeobject obj char name PyObject v PyErr_Format PyExc_RuntimeError Read only attribute s name return 1 3 4 Object Comparison richcmpfunc tp_richcompare The tp_richcompare handler is called when comparisons are needed It is analogous to the rich comparison methods like __lt__ and also called by PyObject_RichCompare and PyObject_RichCompareBool This function is called with two Python objects and the operator as arguments where the operator is one of Py_EQ Py_NE Py_LE Py_GE Py_LT or Py_GT It should compare the two objects with respect to the specified operator and return Py_True or Py_False if the comparison is successful Py_NotImplemented to indicate that comparison is not implemented and the other object s comparison method should be tried or NULL if an exception was set Here is a sample implementation for a datatype that is considered equal if the size of an internal pointer is equal static PyObject newdatatype_richcmp newdatatypeobject obj1 newdatatypeobject obj2 int op PyObject result int c size1 size2 code to make sure that both arguments are of type newdatatype omitted size1 obj1 obj_UnderlyingDatatypePtr size size2 obj2 obj_UnderlyingDatatypePtr size switch op case Py_LT c size1 size2 break case Py_LE c size1 size2 break case Py_EQ c size1 size2 break case Py_NE c size1 size2 break case Py_GT c size1 size2 break case Py_GE c size1 size2 break result c Py_True Py_False Py_INCREF result return result 3 5 Abstract Protocol Support Python supports a variety of abstract protocols the specific interfaces provided to use these interfaces are documented in Abstract Objects Layer A number of these abstract interfaces were defined early in the development of the Python implementation In particular the number mapping and sequence protocols have been part of Python since the beginning Other protocols have been added over time For protocols which depend on several handler routines from the type implementation the older protocols have been defined as optional blocks of handlers referenced by the type object For newer protocols there are additional slots in the main type object with a flag bit being set to indicate that the slots are present and should be checked by the interpreter The flag bit does not indicate that the slot values are non NULL The flag may be set to indicate the presence of a slot but a slot may still be unfilled PyNumberMethods tp_as_number PySequenceMethods tp_as_sequence PyMappingMethods tp_as_mapping If you wish your object to be able to act like a number a sequence or a mapping object then you place the address of a structure that implements the C type PyNumberMethods PySequenceMethods or PyMappingMethods respectively It is up to you to fill in this structure with appropriate values You can find examples of the use of each of these in the Objects directory of the Python source distribution hashfunc tp_hash This function if you choose to provide it should return a hash number for an instance of your data type Here is a simple example static Py_hash_t newdatatype_hash newdatatypeobject obj Py_hash_t result result obj some_size 32767 obj some_number if result 1 result 2 return result Py_hash_t is a signed integer type with a platform varying width Returning 1 from tp_hash indicates an error which is why you should be careful to avoid returning it when hash computation is successful as seen above ternaryfunc tp_cal,en
2163,l This function is called when an instance of your data type is called for example if obj1 is an instance of your data type and the Python script contains obj1 hello the tp_call handler is invoked This function takes three arguments 1 self is the instance of the data type which is the subject of the call If the call is obj1 hello then self is obj1 2 args is a tuple containing the arguments to the call You can use PyArg_ParseTuple to extract the arguments 3 kwds is a dictionary of keyword arguments that were passed If this is non NULL and you support keyword arguments use PyArg_ParseTupleAndKeywords to extract the arguments If you do not want to support keyword arguments and this is non NULL raise a TypeError with a message saying that keyword arguments are not supported Here is a toy tp_call implementation static PyObject newdatatype_call newdatatypeobject obj PyObject args PyObject kwds PyObject result const char arg1 const char arg2 const char arg3 if PyArg_ParseTuple args sss call arg1 arg2 arg3 return NULL result PyUnicode_FromFormat Returning value d arg1 s arg2 s arg3 s n obj obj_UnderlyingDatatypePtr size arg1 arg2 arg3 return result Iterators getiterfunc tp_iter iternextfunc tp_iternext These functions provide support for the iterator protocol Both handlers take exactly one parameter the instance for which they are being called and return a new reference In the case of an error they should set an exception and return NULL tp_iter corresponds to the Python __iter__ method while tp_iternext corresponds to the Python __next__ method Any iterable object must implement the tp_iter handler which must return an iterator object Here the same guidelines apply as for Python classes For collections such as lists and tuples which can support multiple independent iterators a new iterator should be created and returned by each call to tp_iter Objects which can only be iterated over once usually due to side effects of iteration such as file objects can implement tp_iter by returning a new reference to themselves and should also therefore implement the tp_iternext handler Any iterator object should implement both tp_iter and tp_iternext An iterator s tp_iter handler should return a new reference to the iterator Its tp_iternext handler should return a new reference to the next object in the iteration if there is one If the iteration has reached the end tp_iternext may return NULL without setting an exception or it may set StopIteration in addition to returning NULL avoiding the exception can yield slightly better performance If an actual error occurs tp_iternext should always set an exception and return NULL 3 6 Weak Reference Support One of the goals of Python s weak reference implementation is to allow any type to participate in the weak reference mechanism without incurring the overhead on performance critical objects such as numbers See also Documentation for the weakref module For an object to be weakly referencable the extension type must set the Py_TPFLAGS_MANAGED_WEAKREF bit of the tp_flags field The legacy tp_weaklistoffset field should be left as zero Concretely here is how the statically declared type object would look static PyTypeObject TrivialType PyVarObject_HEAD_INIT NULL 0 other members omitted for brevity tp_flags Py_TPFLAGS_MANAGED_WEAKREF The only further addition is that tp_dealloc needs to clear any weak references by calling PyObject_ClearWeakRefs static void Trivial_dealloc TrivialObject self Clear weakrefs first before calling any destructors PyObject_ClearWeakRefs PyObject self remainder of destruction code omitted for brevity Py_TYPE self tp_free PyObject self 3 7 More Suggestions In order to learn how to implement any specific method for your new data type get the CPython source code Go to the Objects directory then search the C source files for tp_ plus the function you want for example tp_richcompare You will find examples of the function you want to implement When you need to verify that an object is a concrete instance of the type you are implementing use the PyObject_TypeCheck function A sample of,en
2164, its use might be something like the following if PyObject_TypeCheck some_object MyType PyErr_SetString PyExc_TypeError arg 1 not a mything return NULL See also Download CPython source releases https www python org downloads source The CPython project on GitHub where the CPython source code is developed https github com python cpython,en
2165,copyreg Register pickle support functions Source code Lib copyreg py The copyreg module offers a way to define functions used while pickling specific objects The pickle and copy modules use those functions when pickling copying those objects The module provides configuration information about object constructors which are not classes Such constructors may be factory functions or class instances copyreg constructor object Declares object to be a valid constructor If object is not callable and hence not valid as a constructor raises TypeError copyreg pickle type function constructor_ob None Declares that function should be used as a reduction function for objects of type type function must return either a string or a tuple containing between two and six elements See the dispatch_table for more details on the interface of function The constructor_ob parameter is a legacy feature and is now ignored but if passed it must be a callable Note that the dispatch_table attribute of a pickler object or subclass of pickle Pickler can also be used for declaring reduction functions Example The example below would like to show how to register a pickle function and how it will be used import copyreg copy pickle class C def __init__ self a self a a def pickle_c c print pickling a C instance return C c a copyreg pickle C pickle_c c C 1 d copy copy c pickling a C instance p pickle dumps c pickling a C instance,en
2166,Transports and Protocols Preface Transports and Protocols are used by the low level event loop APIs such as loop create_connection They use callback based programming style and enable high performance implementations of network or IPC protocols e g HTTP Essentially transports and protocols should only be used in libraries and frameworks and never in high level asyncio applications This documentation page covers both Transports and Protocols Introduction At the highest level the transport is concerned with how bytes are transmitted while the protocol determines which bytes to transmit and to some extent when A different way of saying the same thing a transport is an abstraction for a socket or similar I O endpoint while a protocol is an abstraction for an application from the transport s point of view Yet another view is the transport and protocol interfaces together define an abstract interface for using network I O and interprocess I O There is always a 1 1 relationship between transport and protocol objects the protocol calls transport methods to send data while the transport calls protocol methods to pass it data that has been received Most of connection oriented event loop methods such as loop create_connection usually accept a protocol_factory argument used to create a Protocol object for an accepted connection represented by a Transport object Such methods usually return a tuple of transport protocol Contents This documentation page contains the following sections The Transports section documents asyncio BaseTransport ReadTransport WriteTransport Transport DatagramTransport and SubprocessTransport classes The Protocols section documents asyncio BaseProtocol Protocol BufferedProtocol DatagramProtocol and SubprocessProtocol classes The Examples section showcases how to work with transports protocols and low level event loop APIs Transports Source code Lib asyncio transports py Transports are classes provided by asyncio in order to abstract various kinds of communication channels Transport objects are always instantiated by an asyncio event loop asyncio implements transports for TCP UDP SSL and subprocess pipes The methods available on a transport depend on the transport s kind The transport classes are not thread safe Transports Hierarchy class asyncio BaseTransport Base class for all transports Contains methods that all asyncio transports share class asyncio WriteTransport BaseTransport A base transport for write only connections Instances of the WriteTransport class are returned from the loop connect_write_pipe event loop method and are also used by subprocess related methods like loop subprocess_exec class asyncio ReadTransport BaseTransport A base transport for read only connections Instances of the ReadTransport class are returned from the loop connect_read_pipe event loop method and are also used by subprocess related methods like loop subprocess_exec class asyncio Transport WriteTransport ReadTransport Interface representing a bidirectional transport such as a TCP connection The user does not instantiate a transport directly they call a utility function passing it a protocol factory and other information necessary to create the transport and protocol Instances of the Transport class are returned from or used by event loop methods like loop create_connection loop create_unix_connection loop create_server loop sendfile etc class asyncio DatagramTransport BaseTransport A transport for datagram UDP connections Instances of the DatagramTransport class are returned from the loop create_datagram_endpoint event loop method class asyncio SubprocessTransport BaseTransport An abstraction to represent a connection between a parent and its child OS process Instances of the SubprocessTransport class are returned from event loop methods loop subprocess_shell and loop subprocess_exec Base Transport BaseTransport close Close the transport If the transport has a buffer for outgoing data buffered data will be flushed asynchronously No more data will be received After all buffered data is flushed the protocol s protocol connectio,en
2167,n_lost method will be called with None as its argument The transport should not be used once it is closed BaseTransport is_closing Return True if the transport is closing or is closed BaseTransport get_extra_info name default None Return information about the transport or underlying resources it uses name is a string representing the piece of transport specific information to get default is the value to return if the information is not available or if the transport does not support querying it with the given third party event loop implementation or on the current platform For example the following code attempts to get the underlying socket object of the transport sock transport get_extra_info socket if sock is not None print sock getsockopt Categories of information that can be queried on some transports socket peername the remote address to which the socket is connected result of socket socket getpeername None on error socket socket socket instance sockname the socket s own address result of socket socket getsockname SSL socket compression the compression algorithm being used as a string or None if the connection isn t compressed result of ssl SSLSocket compression cipher a three value tuple containing the name of the cipher being used the version of the SSL protocol that defines its use and the number of secret bits being used result of ssl SSLSocket cipher peercert peer certificate result of ssl SSLSocket getpeercert sslcontext ssl SSLContext instance ssl_object ssl SSLObject or ssl SSLSocket instance pipe pipe pipe object subprocess subprocess subprocess Popen instance BaseTransport set_protocol protocol Set a new protocol Switching protocol should only be done when both protocols are documented to support the switch BaseTransport get_protocol Return the current protocol Read only Transports ReadTransport is_reading Return True if the transport is receiving new data New in version 3 7 ReadTransport pause_reading Pause the receiving end of the transport No data will be passed to the protocol s protocol data_received method until resume_reading is called Changed in version 3 7 The method is idempotent i e it can be called when the transport is already paused or closed ReadTransport resume_reading Resume the receiving end The protocol s protocol data_received method will be called once again if some data is available for reading Changed in version 3 7 The method is idempotent i e it can be called when the transport is already reading Write only Transports WriteTransport abort Close the transport immediately without waiting for pending operations to complete Buffered data will be lost No more data will be received The protocol s protocol connection_lost method will eventually be called with None as its argument WriteTransport can_write_eof Return True if the transport supports write_eof False if not WriteTransport get_write_buffer_size Return the current size of the output buffer used by the transport WriteTransport get_write_buffer_limits Get the high and low watermarks for write flow control Return a tuple low high where low and high are positive number of bytes Use set_write_buffer_limits to set the limits New in version 3 4 2 WriteTransport set_write_buffer_limits high None low None Set the high and low watermarks for write flow control These two values measured in number of bytes control when the protocol s protocol pause_writing and protocol resume_writing methods are called If specified the low watermark must be less than or equal to the high watermark Neither high nor low can be negative pause_writing is called when the buffer size becomes greater than or equal to the high value If writing has been paused resume_writing is called when the buffer size becomes less than or equal to the low value The defaults are implementation specific If only the high watermark is given the low watermark defaults to an implementation specific value less than or equal to the high watermark Setting high to zero forces low to zero as well and causes pause_writing to be called whenever the buffer becomes non empty Setting low to zero ,en
2168,causes resume_writing to be called only once the buffer is empty Use of zero for either limit is generally sub optimal as it reduces opportunities for doing I O and computation concurrently Use get_write_buffer_limits to get the limits WriteTransport write data Write some data bytes to the transport This method does not block it buffers the data and arranges for it to be sent out asynchronously WriteTransport writelines list_of_data Write a list or any iterable of data bytes to the transport This is functionally equivalent to calling write on each element yielded by the iterable but may be implemented more efficiently WriteTransport write_eof Close the write end of the transport after flushing all buffered data Data may still be received This method can raise NotImplementedError if the transport e g SSL doesn t support half closed connections Datagram Transports DatagramTransport sendto data addr None Send the data bytes to the remote peer given by addr a transport dependent target address If addr is None the data is sent to the target address given on transport creation This method does not block it buffers the data and arranges for it to be sent out asynchronously DatagramTransport abort Close the transport immediately without waiting for pending operations to complete Buffered data will be lost No more data will be received The protocol s protocol connection_lost method will eventually be called with None as its argument Subprocess Transports SubprocessTransport get_pid Return the subprocess process id as an integer SubprocessTransport get_pipe_transport fd Return the transport for the communication pipe corresponding to the integer file descriptor fd 0 readable streaming transport of the standard input stdin or None if the subprocess was not created with stdin PIPE 1 writable streaming transport of the standard output stdout or None if the subprocess was not created with stdout PIPE 2 writable streaming transport of the standard error stderr or None if the subprocess was not created with stderr PIPE other fd None SubprocessTransport get_returncode Return the subprocess return code as an integer or None if it hasn t returned which is similar to the subprocess Popen returncode attribute SubprocessTransport kill Kill the subprocess On POSIX systems the function sends SIGKILL to the subprocess On Windows this method is an alias for terminate See also subprocess Popen kill SubprocessTransport send_signal signal Send the signal number to the subprocess as in subprocess Popen send_signal SubprocessTransport terminate Stop the subprocess On POSIX systems this method sends SIGTERM to the subprocess On Windows the Windows API function TerminateProcess is called to stop the subprocess See also subprocess Popen terminate SubprocessTransport close Kill the subprocess by calling the kill method If the subprocess hasn t returned yet and close transports of stdin stdout and stderr pipes Protocols Source code Lib asyncio protocols py asyncio provides a set of abstract base classes that should be used to implement network protocols Those classes are meant to be used together with transports Subclasses of abstract base protocol classes may implement some or all methods All these methods are callbacks they are called by transports on certain events for example when some data is received A base protocol method should be called by the corresponding transport Base Protocols class asyncio BaseProtocol Base protocol with methods that all protocols share class asyncio Protocol BaseProtocol The base class for implementing streaming protocols TCP Unix sockets etc class asyncio BufferedProtocol BaseProtocol A base class for implementing streaming protocols with manual control of the receive buffer class asyncio DatagramProtocol BaseProtocol The base class for implementing datagram UDP protocols class asyncio SubprocessProtocol BaseProtocol The base class for implementing protocols communicating with child processes unidirectional pipes Base Protocol All asyncio protocols can implement Base Protocol callbacks Connection Callbacks Connection callb,en
2169,acks are called on all protocols exactly once per a successful connection All other protocol callbacks can only be called between those two methods BaseProtocol connection_made transport Called when a connection is made The transport argument is the transport representing the connection The protocol is responsible for storing the reference to its transport BaseProtocol connection_lost exc Called when the connection is lost or closed The argument is either an exception object or None The latter means a regular EOF is received or the connection was aborted or closed by this side of the connection Flow Control Callbacks Flow control callbacks can be called by transports to pause or resume writing performed by the protocol See the documentation of the set_write_buffer_limits method for more details BaseProtocol pause_writing Called when the transport s buffer goes over the high watermark BaseProtocol resume_writing Called when the transport s buffer drains below the low watermark If the buffer size equals the high watermark pause_writing is not called the buffer size must go strictly over Conversely resume_writing is called when the buffer size is equal or lower than the low watermark These end conditions are important to ensure that things go as expected when either mark is zero Streaming Protocols Event methods such as loop create_server loop create_unix_server loop create_connection loop create_unix_connection loop connect_accepted_socket loop connect_read_pipe and loop connect_write_pipe accept factories that return streaming protocols Protocol data_received data Called when some data is received data is a non empty bytes object containing the incoming data Whether the data is buffered chunked or reassembled depends on the transport In general you shouldn t rely on specific semantics and instead make your parsing generic and flexible However data is always received in the correct order The method can be called an arbitrary number of times while a connection is open However protocol eof_received is called at most once Once eof_received is called data_received is not called anymore Protocol eof_received Called when the other end signals it won t send any more data for example by calling transport write_eof if the other end also uses asyncio This method may return a false value including None in which case the transport will close itself Conversely if this method returns a true value the protocol used determines whether to close the transport Since the default implementation returns None it implicitly closes the connection Some transports including SSL don t support half closed connections in which case returning true from this method will result in the connection being closed State machine start connection_made data_received eof_received connection_lost end Buffered Streaming Protocols New in version 3 7 Buffered Protocols can be used with any event loop method that supports Streaming Protocols BufferedProtocol implementations allow explicit manual allocation and control of the receive buffer Event loops can then use the buffer provided by the protocol to avoid unnecessary data copies This can result in noticeable performance improvement for protocols that receive big amounts of data Sophisticated protocol implementations can significantly reduce the number of buffer allocations The following callbacks are called on BufferedProtocol instances BufferedProtocol get_buffer sizehint Called to allocate a new receive buffer sizehint is the recommended minimum size for the returned buffer It is acceptable to return smaller or larger buffers than what sizehint suggests When set to 1 the buffer size can be arbitrary It is an error to return a buffer with a zero size get_buffer must return an object implementing the buffer protocol BufferedProtocol buffer_updated nbytes Called when the buffer was updated with the received data nbytes is the total number of bytes that were written to the buffer BufferedProtocol eof_received See the documentation of the protocol eof_received method get_buffer can be called an arbitrary number of times,en
2170, during a connection However protocol eof_received is called at most once and if called get_buffer and buffer_updated won t be called after it State machine start connection_made get_buffer buffer_updated eof_received connection_lost end Datagram Protocols Datagram Protocol instances should be constructed by protocol factories passed to the loop create_datagram_endpoint method DatagramProtocol datagram_received data addr Called when a datagram is received data is a bytes object containing the incoming data addr is the address of the peer sending the data the exact format depends on the transport DatagramProtocol error_received exc Called when a previous send or receive operation raises an OSError exc is the OSError instance This method is called in rare conditions when the transport e g UDP detects that a datagram could not be delivered to its recipient In many conditions though undeliverable datagrams will be silently dropped Note On BSD systems macOS FreeBSD etc flow control is not supported for datagram protocols because there is no reliable way to detect send failures caused by writing too many packets The socket always appears ready and excess packets are dropped An OSError with errno set to errno ENOBUFS may or may not be raised if it is raised it will be reported to DatagramProtocol error_received but otherwise ignored Subprocess Protocols Subprocess Protocol instances should be constructed by protocol factories passed to the loop subprocess_exec and loop subprocess_shell methods SubprocessProtocol pipe_data_received fd data Called when the child process writes data into its stdout or stderr pipe fd is the integer file descriptor of the pipe data is a non empty bytes object containing the received data SubprocessProtocol pipe_connection_lost fd exc Called when one of the pipes communicating with the child process is closed fd is the integer file descriptor that was closed SubprocessProtocol process_exited Called when the child process has exited It can be called before pipe_data_received and pipe_connection_lost methods Examples TCP Echo Server Create a TCP echo server using the loop create_server method send back received data and close the connection import asyncio class EchoServerProtocol asyncio Protocol def connection_made self transport peername transport get_extra_info peername print Connection from format peername self transport transport def data_received self data message data decode print Data received r format message print Send r format message self transport write data print Close the client socket self transport close async def main Get a reference to the event loop as we plan to use low level APIs loop asyncio get_running_loop server await loop create_server lambda EchoServerProtocol 127 0 0 1 8888 async with server await server serve_forever asyncio run main See also The TCP echo server using streams example uses the high level asyncio start_server function TCP Echo Client A TCP echo client using the loop create_connection method sends data and waits until the connection is closed import asyncio class EchoClientProtocol asyncio Protocol def __init__ self message on_con_lost self message message self on_con_lost on_con_lost def connection_made self transport transport write self message encode print Data sent r format self message def data_received self data print Data received r format data decode def connection_lost self exc print The server closed the connection self on_con_lost set_result True async def main Get a reference to the event loop as we plan to use low level APIs loop asyncio get_running_loop on_con_lost loop create_future message Hello World transport protocol await loop create_connection lambda EchoClientProtocol message on_con_lost 127 0 0 1 8888 Wait until the protocol signals that the connection is lost and close the transport try await on_con_lost finally transport close asyncio run main See also The TCP echo client using streams example uses the high level asyncio open_connection function UDP Echo Server A UDP echo server using the loop create_datagram_endpoint method sends ba,en
2171,ck received data import asyncio class EchoServerProtocol def connection_made self transport self transport transport def datagram_received self data addr message data decode print Received r from s message addr print Send r to s message addr self transport sendto data addr async def main print Starting UDP server Get a reference to the event loop as we plan to use low level APIs loop asyncio get_running_loop One protocol instance will be created to serve all client requests transport protocol await loop create_datagram_endpoint lambda EchoServerProtocol local_addr 127 0 0 1 9999 try await asyncio sleep 3600 Serve for 1 hour finally transport close asyncio run main UDP Echo Client A UDP echo client using the loop create_datagram_endpoint method sends data and closes the transport when it receives the answer import asyncio class EchoClientProtocol def __init__ self message on_con_lost self message message self on_con_lost on_con_lost self transport None def connection_made self transport self transport transport print Send self message self transport sendto self message encode def datagram_received self data addr print Received data decode print Close the socket self transport close def error_received self exc print Error received exc def connection_lost self exc print Connection closed self on_con_lost set_result True async def main Get a reference to the event loop as we plan to use low level APIs loop asyncio get_running_loop on_con_lost loop create_future message Hello World transport protocol await loop create_datagram_endpoint lambda EchoClientProtocol message on_con_lost remote_addr 127 0 0 1 9999 try await on_con_lost finally transport close asyncio run main Connecting Existing Sockets Wait until a socket receives data using the loop create_connection method with a protocol import asyncio import socket class MyProtocol asyncio Protocol def __init__ self on_con_lost self transport None self on_con_lost on_con_lost def connection_made self transport self transport transport def data_received self data print Received data decode We are done close the transport connection_lost will be called automatically self transport close def connection_lost self exc The socket has been closed self on_con_lost set_result True async def main Get a reference to the event loop as we plan to use low level APIs loop asyncio get_running_loop on_con_lost loop create_future Create a pair of connected sockets rsock wsock socket socketpair Register the socket to wait for data transport protocol await loop create_connection lambda MyProtocol on_con_lost sock rsock Simulate the reception of data from the network loop call_soon wsock send abc encode try await protocol on_con_lost finally transport close wsock close asyncio run main See also The watch a file descriptor for read events example uses the low level loop add_reader method to register an FD The register an open socket to wait for data using streams example uses high level streams created by the open_connection function in a coroutine loop subprocess_exec and SubprocessProtocol An example of a subprocess protocol used to get the output of a subprocess and to wait for the subprocess exit The subprocess is created by the loop subprocess_exec method import asyncio import sys class DateProtocol asyncio SubprocessProtocol def __init__ self exit_future self exit_future exit_future self output bytearray self pipe_closed False self exited False def pipe_connection_lost self fd exc self pipe_closed True self check_for_exit def pipe_data_received self fd data self output extend data def process_exited self self exited True process_exited method can be called before pipe_connection_lost method wait until both methods are called self check_for_exit def check_for_exit self if self pipe_closed and self exited self exit_future set_result True async def get_date Get a reference to the event loop as we plan to use low level APIs loop asyncio get_running_loop code import datetime print datetime datetime now exit_future asyncio Future loop loop Create the subprocess controlled by DateProtocol redirect th,en
2172,e standard output into a pipe transport protocol await loop subprocess_exec lambda DateProtocol exit_future sys executable c code stdin None stderr None Wait for the subprocess exit using the process_exited method of the protocol await exit_future Close the stdout pipe transport close Read the output which was collected by the pipe_data_received method of the protocol data bytes protocol output return data decode ascii rstrip date asyncio run get_date print f Current date date See also the same example written using high level APIs,en
2173,What s New In Python 3 11 Editor Pablo Galindo Salgado This article explains the new features in Python 3 11 compared to 3 10 Python 3 11 was released on October 24 2022 For full details see the changelog Summary Release highlights Python 3 11 is between 10 60 faster than Python 3 10 On average we measured a 1 25x speedup on the standard benchmark suite See Faster CPython for details New syntax features PEP 654 Exception Groups and except New built in features PEP 678 Exceptions can be enriched with notes New standard library modules PEP 680 tomllib Support for parsing TOML in the Standard Library Interpreter improvements PEP 657 Fine grained error locations in tracebacks New P command line option and PYTHONSAFEPATH environment variable to disable automatically prepending potentially unsafe paths to sys path New typing features PEP 646 Variadic generics PEP 655 Marking individual TypedDict items as required or not required PEP 673 Self type PEP 675 Arbitrary literal string type PEP 681 Data class transforms Important deprecations removals and restrictions PEP 594 Many legacy standard library modules have been deprecated and will be removed in Python 3 13 PEP 624 Py_UNICODE encoder APIs have been removed PEP 670 Macros converted to static inline functions New Features PEP 657 Fine grained error locations in tracebacks When printing tracebacks the interpreter will now point to the exact expression that caused the error instead of just the line For example Traceback most recent call last File distance py line 11 in module print manhattan_distance p1 p2 File distance py line 6 in manhattan_distance return abs point_1 x point_2 x abs point_1 y point_2 y AttributeError NoneType object has no attribute x Previous versions of the interpreter would point to just the line making it ambiguous which object was None These enhanced errors can also be helpful when dealing with deeply nested dict objects and multiple function calls Traceback most recent call last File query py line 37 in module magic_arithmetic foo File query py line 18 in magic_arithmetic return add_counts x 25 File query py line 24 in add_counts return 25 query_user user1 query_user user2 File query py line 32 in query_user return 1 query_count db response a b c user retry True TypeError NoneType object is not subscriptable As well as complex arithmetic expressions Traceback most recent call last File calculation py line 54 in module result x y z a b c ZeroDivisionError division by zero Additionally the information used by the enhanced traceback feature is made available via a general API that can be used to correlate bytecode instructions with source code location This information can be retrieved using The codeobject co_positions method in Python The PyCode_Addr2Location function in the C API See PEP 657 for more details Contributed by Pablo Galindo Batuhan Taskaya and Ammar Askar in bpo 43950 Note This feature requires storing column positions in Code Objects which may result in a small increase in interpreter memory usage and disk usage for compiled Python files To avoid storing the extra information and deactivate printing the extra traceback information use the X no_debug_ranges command line option or the PYTHONNODEBUGRANGES environment variable PEP 654 Exception Groups and except PEP 654 introduces language features that enable a program to raise and handle multiple unrelated exceptions simultaneously The builtin types ExceptionGroup and BaseExceptionGroup make it possible to group exceptions and raise them together and the new except syntax generalizes except to match subgroups of exception groups See PEP 654 for more details Contributed by Irit Katriel in bpo 45292 PEP written by Irit Katriel Yury Selivanov and Guido van Rossum PEP 678 Exceptions can be enriched with notes The add_note method is added to BaseException It can be used to enrich exceptions with context information that is not available at the time when the exception is raised The added notes appear in the default traceback See PEP 678 for more details Contributed by Irit Katriel in bpo 45607 PEP,en
2174, written by Zac Hatfield Dodds Windows py exe launcher improvements The copy of the Python Launcher for Windows included with Python 3 11 has been significantly updated It now supports company tag syntax as defined in PEP 514 using the V company tag argument instead of the limited major minor This allows launching distributions other than PythonCore the one hosted on python org When using V selectors either company or tag can be omitted but all installs will be searched For example V OtherPython will select the best tag registered for OtherPython while V 3 11 or V 3 11 will select the best distribution with tag 3 11 When using the legacy major major minor major bitness or major minor bitness arguments all existing behaviour should be preserved from past versions and only releases from PythonCore will be selected However the 64 suffix now implies not 32 bit not necessarily x86 64 as there are multiple supported 64 bit platforms 32 bit runtimes are detected by checking the runtime s tag for a 32 suffix All releases of Python since 3 5 have included this in their 32 bit builds New Features Related to Type Hints This section covers major changes affecting PEP 484 type hints and the typing module PEP 646 Variadic generics PEP 484 previously introduced TypeVar enabling creation of generics parameterised with a single type PEP 646 adds TypeVarTuple enabling parameterisation with an arbitrary number of types In other words a TypeVarTuple is a variadic type variable enabling variadic generics This enables a wide variety of use cases In particular it allows the type of array like structures in numerical computing libraries such as NumPy and TensorFlow to be parameterised with the array shape Static type checkers will now be able to catch shape related bugs in code that uses these libraries See PEP 646 for more details Contributed by Matthew Rahtz in bpo 43224 with contributions by Serhiy Storchaka and Jelle Zijlstra PEP written by Mark Mendoza Matthew Rahtz Pradeep Kumar Srinivasan and Vincent Siles PEP 655 Marking individual TypedDict items as required or not required Required and NotRequired provide a straightforward way to mark whether individual items in a TypedDict must be present Previously this was only possible using inheritance All fields are still required by default unless the total parameter is set to False in which case all fields are still not required by default For example the following specifies a TypedDict with one required and one not required key class Movie TypedDict title str year NotRequired int m1 Movie title Black Panther year 2018 OK m2 Movie title Star Wars OK year is not required m3 Movie year 2022 ERROR missing required field title The following definition is equivalent class Movie TypedDict total False title Required str year int See PEP 655 for more details Contributed by David Foster and Jelle Zijlstra in bpo 47087 PEP written by David Foster PEP 673 Self type The new Self annotation provides a simple and intuitive way to annotate methods that return an instance of their class This behaves the same as the TypeVar based approach specified in PEP 484 but is more concise and easier to follow Common use cases include alternative constructors provided as classmethod s and __enter__ methods that return self class MyLock def __enter__ self Self self lock return self class MyInt classmethod def fromhex cls s str Self return cls int s 16 Self can also be used to annotate method parameters or attributes of the same type as their enclosing class See PEP 673 for more details Contributed by James Hilton Balfe in bpo 46534 PEP written by Pradeep Kumar Srinivasan and James Hilton Balfe PEP 675 Arbitrary literal string type The new LiteralString annotation may be used to indicate that a function parameter can be of any literal string type This allows a function to accept arbitrary literal string types as well as strings created from other literal strings Type checkers can then enforce that sensitive functions such as those that execute SQL statements or shell commands are called only with static arguments providing,en
2175, protection against injection attacks For example a SQL query function could be annotated as follows def run_query sql LiteralString def caller arbitrary_string str query_string LiteralString table_name LiteralString None run_query SELECT FROM students ok run_query query_string ok run_query SELECT FROM table_name ok run_query arbitrary_string type checker error run_query type checker error f SELECT FROM students WHERE name arbitrary_string See PEP 675 for more details Contributed by Jelle Zijlstra in bpo 47088 PEP written by Pradeep Kumar Srinivasan and Graham Bleaney PEP 681 Data class transforms dataclass_transform may be used to decorate a class metaclass or a function that is itself a decorator The presence of dataclass_transform tells a static type checker that the decorated object performs runtime magic that transforms a class giving it dataclass like behaviors For example The create_model decorator is defined by a library typing dataclass_transform def create_model cls Type T Type T cls __init__ cls __eq__ cls __ne__ return cls The create_model decorator can now be used to create new model classes create_model class CustomerModel id int name str c CustomerModel id 327 name Eric Idle See PEP 681 for more details Contributed by Jelle Zijlstra in gh 91860 PEP written by Erik De Bonte and Eric Traut PEP 563 may not be the future PEP 563 Postponed Evaluation of Annotations the from __future__ import annotations future statement that was originally planned for release in Python 3 10 has been put on hold indefinitely See this message from the Steering Council for more information Other Language Changes Starred unpacking expressions can now be used in for statements See bpo 46725 for more details Asynchronous comprehensions are now allowed inside comprehensions in asynchronous functions Outer comprehensions implicitly become asynchronous in this case Contributed by Serhiy Storchaka in bpo 33346 A TypeError is now raised instead of an AttributeError in with statements and contextlib ExitStack enter_context for objects that do not support the context manager protocol and in async with statements and contextlib AsyncExitStack enter_async_context for objects not supporting the asynchronous context manager protocol Contributed by Serhiy Storchaka in bpo 12022 and bpo 44471 Added object __getstate__ which provides the default implementation of the __getstate__ method copy ing and pickle ing instances of subclasses of builtin types bytearray set frozenset collections OrderedDict collections deque weakref WeakSet and datetime tzinfo now copies and pickles instance attributes implemented as slots This change has an unintended side effect It trips up a small minority of existing Python projects not expecting object __getstate__ to exist See the later comments on gh 70766 for discussions of what workarounds such code may need Contributed by Serhiy Storchaka in bpo 26579 Added a P command line option and a PYTHONSAFEPATH environment variable which disable the automatic prepending to sys path of the script s directory when running a script or the current directory when using c and m This ensures only stdlib and installed modules are picked up by import and avoids unintentionally or maliciously shadowing modules with those in a local and typically user writable directory Contributed by Victor Stinner in gh 57684 A z option was added to the Format Specification Mini Language that coerces negative to positive zero after rounding to the format precision See PEP 682 for more details Contributed by John Belmonte in gh 90153 Bytes are no longer accepted on sys path Support broke sometime between Python 3 2 and 3 6 with no one noticing until after Python 3 10 0 was released In addition bringing back support would be problematic due to interactions between b and sys path_importer_cache when there is a mixture of str and bytes keys Contributed by Thomas Grainger in gh 91181 Other CPython Implementation Changes The special methods __complex__ for complex and __bytes__ for bytes are implemented to support the typing SupportsComplex and typing Sup,en
2176,portsBytes protocols Contributed by Mark Dickinson and Donghee Na in bpo 24234 siphash13 is added as a new internal hashing algorithm It has similar security properties as siphash24 but it is slightly faster for long inputs str bytes and some other types now use it as the default algorithm for hash PEP 552 hash based pyc files now use siphash13 too Contributed by Inada Naoki in bpo 29410 When an active exception is re raised by a raise statement with no parameters the traceback attached to this exception is now always sys exc_info 1 __traceback__ This means that changes made to the traceback in the current except clause are reflected in the re raised exception Contributed by Irit Katriel in bpo 45711 The interpreter state s representation of handled exceptions aka exc_info or _PyErr_StackItem now only has the exc_value field exc_type and exc_traceback have been removed as they can be derived from exc_value Contributed by Irit Katriel in bpo 45711 A new command line option AppendPath has been added for the Windows installer It behaves similarly to PrependPath but appends the install and scripts directories instead of prepending them Contributed by Bastian Neuburger in bpo 44934 The PyConfig module_search_paths_set field must now be set to 1 for initialization to use PyConfig module_search_paths to initialize sys path Otherwise initialization will recalculate the path and replace any values added to module_search_paths The output of the help option now fits in 50 lines 80 columns Information about Python environment variables and X options is now available using the respective help env and help xoptions flags and with the new help all Contributed by Éric Araujo in bpo 46142 Converting between int and str in bases other than 2 binary 4 8 octal 16 hexadecimal or 32 such as base 10 decimal now raises a ValueError if the number of digits in string form is above a limit to avoid potential denial of service attacks due to the algorithmic complexity This is a mitigation for CVE 2020 10735 This limit can be configured or disabled by environment variable command line flag or sys APIs See the integer string conversion length limitation documentation The default limit is 4300 digits in string form New Modules tomllib For parsing TOML See PEP 680 for more details Contributed by Taneli Hukkinen in bpo 40059 wsgiref types WSGI specific types for static type checking Contributed by Sebastian Rittau in bpo 42012 Improved Modules asyncio Added the TaskGroup class an asynchronous context manager holding a group of tasks that will wait for all of them upon exit For new code this is recommended over using create_task and gather directly Contributed by Yury Selivanov and others in gh 90908 Added timeout an asynchronous context manager for setting a timeout on asynchronous operations For new code this is recommended over using wait_for directly Contributed by Andrew Svetlov in gh 90927 Added the Runner class which exposes the machinery used by run Contributed by Andrew Svetlov in gh 91218 Added the Barrier class to the synchronization primitives in the asyncio library and the related BrokenBarrierError exception Contributed by Yves Duprat and Andrew Svetlov in gh 87518 Added keyword argument all_errors to asyncio loop create_connection so that multiple connection errors can be raised as an ExceptionGroup Added the asyncio StreamWriter start_tls method for upgrading existing stream based connections to TLS Contributed by Ian Good in bpo 34975 Added raw datagram socket functions to the event loop sock_sendto sock_recvfrom and sock_recvfrom_into These have implementations in SelectorEventLoop and ProactorEventLoop Contributed by Alex Grönholm in bpo 46805 Added cancelling and uncancel methods to Task These are primarily intended for internal use notably by TaskGroup contextlib Added non parallel safe chdir context manager to change the current working directory and then restore it on exit Simple wrapper around chdir Contributed by Filipe Laíns in bpo 25625 dataclasses Change field default mutability check allowing only defaults which are hashable ,en
2177,instead of any object which is not an instance of dict list or set Contributed by Eric V Smith in bpo 44674 datetime Add datetime UTC a convenience alias for datetime timezone utc Contributed by Kabir Kwatra in gh 91973 datetime date fromisoformat datetime time fromisoformat and datetime datetime fromisoformat can now be used to parse most ISO 8601 formats barring only those that support fractional hours and minutes Contributed by Paul Ganssle in gh 80010 enum Renamed EnumMeta to EnumType EnumMeta kept as an alias Added StrEnum with members that can be used as and must be strings Added ReprEnum which only modifies the __repr__ of members while returning their literal values rather than names for __str__ and __format__ used by str format and f string s Changed Enum __format__ the default for format str format and f string s to always produce the same result as Enum __str__ for enums inheriting from ReprEnum it will be the member s value for all other enums it will be the enum and member name e g Color RED Added a new boundary class parameter to Flag enums and the FlagBoundary enum with its options to control how to handle out of range flag values Added the verify enum decorator and the EnumCheck enum with its options to check enum classes against several specific constraints Added the member and nonmember decorators to ensure the decorated object is is not converted to an enum member Added the property decorator which works like property except for enums Use this instead of types DynamicClassAttribute Added the global_enum enum decorator which adjusts __repr__ and __str__ to show values as members of their module rather than the enum class For example re ASCII for the ASCII member of re RegexFlag rather than RegexFlag ASCII Enhanced Flag to support len iteration and in not in on its members For example the following now works len AFlag 3 2 and list AFlag 3 AFlag ONE AFlag TWO Changed Enum and Flag so that members are now defined before __init_subclass__ is called dir now includes methods etc from mixed in data types Changed Flag to only consider primary values power of two canonical while composite values 3 6 10 etc are considered aliases inverted flags are coerced to their positive equivalent fcntl On FreeBSD the F_DUP2FD and F_DUP2FD_CLOEXEC flags respectively are supported the former equals to dup2 usage while the latter set the FD_CLOEXEC flag in addition fractions Support PEP 515 style initialization of Fraction from string Contributed by Sergey B Kirpichev in bpo 44258 Fraction now implements an __int__ method so that an isinstance some_fraction typing SupportsInt check passes Contributed by Mark Dickinson in bpo 44547 functools functools singledispatch now supports types UnionType and typing Union as annotations to the dispatch argument from functools import singledispatch singledispatch def fun arg verbose False if verbose print Let me just say end print arg fun register def _ arg int float verbose False if verbose print Strength in numbers eh end print arg from typing import Union fun register def _ arg Union list set verbose False if verbose print Enumerate this for i elem in enumerate arg print i elem Contributed by Yurii Karabas in bpo 46014 hashlib hashlib blake2b and hashlib blake2s now prefer libb2 over Python s vendored copy Contributed by Christian Heimes in bpo 47095 The internal _sha3 module with SHA3 and SHAKE algorithms now uses tiny_sha3 instead of the Keccak Code Package to reduce code and binary size The hashlib module prefers optimized SHA3 and SHAKE implementations from OpenSSL The change affects only installations without OpenSSL support Contributed by Christian Heimes in bpo 47098 Add hashlib file_digest a helper function for efficient hashing of files or file like objects Contributed by Christian Heimes in gh 89313 IDLE and idlelib Apply syntax highlighting to pyi files Contributed by Alex Waygood and Terry Jan Reedy in bpo 45447 Include prompts when saving Shell with inputs and outputs Contributed by Terry Jan Reedy in gh 95191 inspect Add getmembers_static to return all members without trigg,en
2178,ering dynamic lookup via the descriptor protocol Contributed by Weipeng Hong in bpo 30533 Add ismethodwrapper for checking if the type of an object is a MethodWrapperType Contributed by Hakan Çelik in bpo 29418 Change the frame related functions in the inspect module to return new FrameInfo and Traceback class instances backwards compatible with the previous named tuple like interfaces that includes the extended PEP 657 position information end line number column and end column The affected functions are inspect getframeinfo inspect getouterframes inspect getinnerframes inspect stack inspect trace Contributed by Pablo Galindo in gh 88116 locale Add locale getencoding to get the current locale encoding It is similar to locale getpreferredencoding False but ignores the Python UTF 8 Mode logging Added getLevelNamesMapping to return a mapping from logging level names e g CRITICAL to the values of their corresponding Logging Levels e g 50 by default Contributed by Andrei Kulakovin in gh 88024 Added a createSocket method to SysLogHandler to match SocketHandler createSocket It is called automatically during handler initialization and when emitting an event if there is no active socket Contributed by Kirill Pinchuk in gh 88457 math Add math exp2 return 2 raised to the power of x Contributed by Gideon Mitchell in bpo 45917 Add math cbrt return the cube root of x Contributed by Ajith Ramachandran in bpo 44357 The behaviour of two math pow corner cases was changed for consistency with the IEEE 754 specification The operations math pow 0 0 math inf and math pow 0 0 math inf now return inf Previously they raised ValueError Contributed by Mark Dickinson in bpo 44339 The math nan value is now always available Contributed by Victor Stinner in bpo 46917 operator A new function operator call has been added such that operator call obj args kwargs obj args kwargs Contributed by Antony Lee in bpo 44019 os On Windows os urandom now uses BCryptGenRandom instead of CryptGenRandom which is deprecated Contributed by Donghee Na in bpo 44611 pathlib glob and rglob return only directories if pattern ends with a pathname components separator sep or altsep Contributed by Eisuke Kawasima in bpo 22276 and bpo 33392 re Atomic grouping and possessive quantifiers m n are now supported in regular expressions Contributed by Jeffrey C Jacobs and Serhiy Storchaka in bpo 433030 shutil Add optional parameter dir_fd in shutil rmtree Contributed by Serhiy Storchaka in bpo 46245 socket Add CAN Socket support for NetBSD Contributed by Thomas Klausner in bpo 30512 create_connection has an option to raise in case of failure to connect an ExceptionGroup containing all errors instead of only raising the last error Contributed by Irit Katriel in bpo 29980 sqlite3 You can now disable the authorizer by passing None to set_authorizer Contributed by Erlend E Aasland in bpo 44491 Collation name create_collation can now contain any Unicode character Collation names with invalid characters now raise UnicodeEncodeError instead of sqlite3 ProgrammingError Contributed by Erlend E Aasland in bpo 44688 sqlite3 exceptions now include the SQLite extended error code as sqlite_errorcode and the SQLite error name as sqlite_errorname Contributed by Aviv Palivoda Daniel Shahaf and Erlend E Aasland in bpo 16379 and bpo 24139 Add setlimit and getlimit to sqlite3 Connection for setting and getting SQLite limits by connection basis Contributed by Erlend E Aasland in bpo 45243 sqlite3 now sets sqlite3 threadsafety based on the default threading mode the underlying SQLite library has been compiled with Contributed by Erlend E Aasland in bpo 45613 sqlite3 C callbacks now use unraisable exceptions if callback tracebacks are enabled Users can now register an unraisable hook handler to improve their debug experience Contributed by Erlend E Aasland in bpo 45828 Fetch across rollback no longer raises InterfaceError Instead we leave it to the SQLite library to handle these cases Contributed by Erlend E Aasland in bpo 44092 Add serialize and deserialize to sqlite3 Connection for serializing and deserial,en
2179,izing databases Contributed by Erlend E Aasland in bpo 41930 Add create_window_function to sqlite3 Connection for creating aggregate window functions Contributed by Erlend E Aasland in bpo 34916 Add blobopen to sqlite3 Connection sqlite3 Blob allows incremental I O operations on blobs Contributed by Aviv Palivoda and Erlend E Aasland in bpo 24905 string Add get_identifiers and is_valid to string Template which respectively return all valid placeholders and whether any invalid placeholders are present Contributed by Ben Kehoe in gh 90465 sys sys exc_info now derives the type and traceback fields from the value the exception instance so when an exception is modified while it is being handled the changes are reflected in the results of subsequent calls to exc_info Contributed by Irit Katriel in bpo 45711 Add sys exception which returns the active exception instance equivalent to sys exc_info 1 Contributed by Irit Katriel in bpo 46328 Add the sys flags safe_path flag Contributed by Victor Stinner in gh 57684 sysconfig Three new installation schemes posix_venv nt_venv and venv were added and are used when Python creates new virtual environments or when it is running from a virtual environment The first two schemes posix_venv and nt_venv are OS specific for non Windows and Windows the venv is essentially an alias to one of them according to the OS Python runs on This is useful for downstream distributors who modify sysconfig get_preferred_scheme Third party code that creates new virtual environments should use the new venv installation scheme to determine the paths as does venv Contributed by Miro Hrončok in bpo 45413 tempfile SpooledTemporaryFile objects now fully implement the methods of io BufferedIOBase or io TextIOBase depending on file mode This lets them work correctly with APIs that expect file like objects such as compression modules Contributed by Carey Metcalfe in gh 70363 threading On Unix if the sem_clockwait function is available in the C library glibc 2 30 and newer the threading Lock acquire method now uses the monotonic clock time CLOCK_MONOTONIC for the timeout rather than using the system clock time CLOCK_REALTIME to not be affected by system clock changes Contributed by Victor Stinner in bpo 41710 time On Unix time sleep now uses the clock_nanosleep or nanosleep function if available which has a resolution of 1 nanosecond 10 9 seconds rather than using select which has a resolution of 1 microsecond 10 6 seconds Contributed by Benjamin Szőke and Victor Stinner in bpo 21302 On Windows 8 1 and newer time sleep now uses a waitable timer based on high resolution timers which has a resolution of 100 nanoseconds 10 7 seconds Previously it had a resolution of 1 millisecond 10 3 seconds Contributed by Benjamin Szőke Donghee Na Eryk Sun and Victor Stinner in bpo 21302 and bpo 45429 tkinter Added method info_patchlevel which returns the exact version of the Tcl library as a named tuple similar to sys version_info Contributed by Serhiy Storchaka in gh 91827 traceback Add traceback StackSummary format_frame_summary to allow users to override which frames appear in the traceback and how they are formatted Contributed by Ammar Askar in bpo 44569 Add traceback TracebackException print which prints the formatted TracebackException instance to a file Contributed by Irit Katriel in bpo 33809 typing For major changes see New Features Related to Type Hints Add typing assert_never and typing Never typing assert_never is useful for asking a type checker to confirm that a line of code is not reachable At runtime it raises an AssertionError Contributed by Jelle Zijlstra in gh 90633 Add typing reveal_type This is useful for asking a type checker what type it has inferred for a given expression At runtime it prints the type of the received value Contributed by Jelle Zijlstra in gh 90572 Add typing assert_type This is useful for asking a type checker to confirm that the type it has inferred for a given expression matches the given type At runtime it simply returns the received value Contributed by Jelle Zijlstra in gh 90638 typing Typ,en
2180,edDict types can now be generic Contributed by Samodya Abeysiriwardane in gh 89026 NamedTuple types can now be generic Contributed by Serhiy Storchaka in bpo 43923 Allow subclassing of typing Any This is useful for avoiding type checker errors related to highly dynamic class such as mocks Contributed by Shantanu Jain in gh 91154 The typing final decorator now sets the __final__ attributed on the decorated object Contributed by Jelle Zijlstra in gh 90500 The typing get_overloads function can be used for introspecting the overloads of a function typing clear_overloads can be used to clear all registered overloads of a function Contributed by Jelle Zijlstra in gh 89263 The __init__ method of Protocol subclasses is now preserved Contributed by Adrian Garcia Badarasco in gh 88970 The representation of empty tuple types Tuple is simplified This affects introspection e g get_args Tuple now evaluates to instead of Contributed by Serhiy Storchaka in gh 91137 Loosen runtime requirements for type annotations by removing the callable check in the private typing _type_check function Contributed by Gregory Beauregard in gh 90802 typing get_type_hints now supports evaluating strings as forward references in PEP 585 generic aliases Contributed by Niklas Rosenstein in gh 85542 typing get_type_hints no longer adds Optional to parameters with None as a default Contributed by Nikita Sobolev in gh 90353 typing get_type_hints now supports evaluating bare stringified ClassVar annotations Contributed by Gregory Beauregard in gh 90711 typing no_type_check no longer modifies external classes and functions It also now correctly marks classmethods as not to be type checked Contributed by Nikita Sobolev in gh 90729 unicodedata The Unicode database has been updated to version 14 0 0 Contributed by Benjamin Peterson in bpo 45190 unittest Added methods enterContext and enterClassContext of class TestCase method enterAsyncContext of class IsolatedAsyncioTestCase and function unittest enterModuleContext Contributed by Serhiy Storchaka in bpo 45046 venv When new Python virtual environments are created the venv sysconfig installation scheme is used to determine the paths inside the environment When Python runs in a virtual environment the same installation scheme is the default That means that downstream distributors can change the default sysconfig install scheme without changing behavior of virtual environments Third party code that also creates new virtual environments should do the same Contributed by Miro Hrončok in bpo 45413 warnings warnings catch_warnings now accepts arguments for warnings simplefilter providing a more concise way to locally ignore warnings or convert them to errors Contributed by Zac Hatfield Dodds in bpo 47074 zipfile Added support for specifying member name encoding for reading metadata in a ZipFile s directory and file headers Contributed by Stephen J Turnbull and Serhiy Storchaka in bpo 28080 Added ZipFile mkdir for creating new directories inside ZIP archives Contributed by Sam Ezeh in gh 49083 Added stem suffix and suffixes to zipfile Path Contributed by Miguel Brito in gh 88261 Optimizations This section covers specific optimizations independent of the Faster CPython project which is covered in its own section The compiler now optimizes simple printf style formatting on string literals containing only the format codes s r and a and makes it as fast as a corresponding f string expression Contributed by Serhiy Storchaka in bpo 28307 Integer division is better tuned for optimization by compilers It is now around 20 faster on x86 64 when dividing an int by a value smaller than 2 30 Contributed by Gregory P Smith and Tim Peters in gh 90564 sum is now nearly 30 faster for integers smaller than 2 30 Contributed by Stefan Behnel in gh 68264 Resizing lists is streamlined for the common case speeding up list append by 15 and simple list comprehension s by up to 20 30 Contributed by Dennis Sweeney in gh 91165 Dictionaries don t store hash values when all keys are Unicode objects decreasing dict size For example sys getsizeof dict from,en
2181,keys abcdefg is reduced from 352 bytes to 272 bytes 23 smaller on 64 bit platforms Contributed by Inada Naoki in bpo 46845 Using asyncio DatagramProtocol is now orders of magnitude faster when transferring large files over UDP with speeds over 100 times higher for a 60 MiB file Contributed by msoxzw in gh 91487 math functions comb and perm are now 10 times faster for large arguments with a larger speedup for larger k Contributed by Serhiy Storchaka in bpo 37295 The statistics functions mean variance and stdev now consume iterators in one pass rather than converting them to a list first This is twice as fast and can save substantial memory Contributed by Raymond Hettinger in gh 90415 unicodedata normalize now normalizes pure ASCII strings in constant time Contributed by Donghee Na in bpo 44987 Faster CPython CPython 3 11 is an average of 25 faster than CPython 3 10 as measured with the pyperformance benchmark suite when compiled with GCC on Ubuntu Linux Depending on your workload the overall speedup could be 10 60 This project focuses on two major areas in Python Faster Startup and Faster Runtime Optimizations not covered by this project are listed separately under Optimizations Faster Startup Frozen imports Static code objects Python caches bytecode in the __pycache__ directory to speed up module loading Previously in 3 10 Python module execution looked like this Read __pycache__ Unmarshal Heap allocated code object Evaluate In Python 3 11 the core modules essential for Python startup are frozen This means that their Code Objects and bytecode are statically allocated by the interpreter This reduces the steps in module execution process to Statically allocated code object Evaluate Interpreter startup is now 10 15 faster in Python 3 11 This has a big impact for short running programs using Python Contributed by Eric Snow Guido van Rossum and Kumar Aditya in many issues Faster Runtime Cheaper lazy Python frames Python frames holding execution information are created whenever Python calls a Python function The following are new frame optimizations Streamlined the frame creation process Avoided memory allocation by generously re using frame space on the C stack Streamlined the internal frame struct to contain only essential information Frames previously held extra debugging and memory management information Old style frame objects are now created only when requested by debuggers or by Python introspection functions such as sys _getframe and inspect currentframe For most user code no frame objects are created at all As a result nearly all Python functions calls have sped up significantly We measured a 3 7 speedup in pyperformance Contributed by Mark Shannon in bpo 44590 Inlined Python function calls During a Python function call Python will call an evaluating C function to interpret that function s code This effectively limits pure Python recursion to what s safe for the C stack In 3 11 when CPython detects Python code calling another Python function it sets up a new frame and jumps to the new code inside the new frame This avoids calling the C interpreting function altogether Most Python function calls now consume no C stack space speeding them up In simple recursive functions like fibonacci or factorial we observed a 1 7x speedup This also means recursive functions can recurse significantly deeper if the user increases the recursion limit with sys setrecursionlimit We measured a 1 3 improvement in pyperformance Contributed by Pablo Galindo and Mark Shannon in bpo 45256 PEP 659 Specializing Adaptive Interpreter PEP 659 is one of the key parts of the Faster CPython project The general idea is that while Python is a dynamic language most code has regions where objects and types rarely change This concept is known as type stability At runtime Python will try to look for common patterns and type stability in the executing code Python will then replace the current operation with a more specialized one This specialized operation uses fast paths available only to those use cases types which generally outperform their generic counter,en
2182,parts This also brings in another concept called inline caching where Python caches the results of expensive operations directly in the bytecode The specializer will also combine certain common instruction pairs into one superinstruction reducing the overhead during execution Python will only specialize when it sees code that is hot executed multiple times This prevents Python from wasting time on run once code Python can also de specialize when code is too dynamic or when the use changes Specialization is attempted periodically and specialization attempts are not too expensive allowing specialization to adapt to new circumstances PEP written by Mark Shannon with ideas inspired by Stefan Brunthaler See PEP 659 for more information Implementation by Mark Shannon and Brandt Bucher with additional help from Irit Katriel and Dennis Sweeney Operation Form Specialization Operation speedup Contributor s up to Binary x x x x x Binary add multiply and subtract for common types such 10 Mark Shannon operations x as int float and str take custom fast paths for Donghee Na Brandt their underlying types Bucher Dennis Sweeney Subscript a i Subscripting container types such as list tuple 10 25 Irit Katriel Mark and dict directly index the underlying data Shannon structures Subscripting custom __getitem__ is also inlined similar to Inlined Python function calls Store subscript a i z Similar to subscripting specialization above 10 25 Dennis Sweeney Calls f arg C arg Calls to common builtin C functions and types such as 20 Mark Shannon Ken len and str directly call their underlying C Jin version This avoids going through the internal calling convention Load global print len The object s index in the globals builtins namespace is 1 Mark Shannon variable cached Loading globals and builtins require zero namespace lookups Load attribute o attr Similar to loading global variables The attribute s 2 Mark Shannon index inside the class object s namespace is cached In most cases attribute loading will require zero namespace lookups Load methods o meth The actual address of the method is cached Method 10 20 Ken Jin Mark for call loading now has no namespace lookups even for Shannon classes with long inheritance chains Store attribute o attr z Similar to load attribute optimization 2 in pyperformance Mark Shannon Unpack Sequence seq Specialized for common containers such as list and 8 Brandt Bucher tuple Avoids internal calling convention 1 A similar optimization already existed since Python 3 8 3 11 specializes for more forms and reduces some overhead 2 A similar optimization already existed since Python 3 10 3 11 specializes for more forms Furthermore all attribute loads should be sped up by bpo 45947 Misc Objects now require less memory due to lazily created object namespaces Their namespace dictionaries now also share keys more freely Contributed Mark Shannon in bpo 45340 and bpo 40116 Zero cost exceptions are implemented eliminating the cost of try statements when no exception is raised Contributed by Mark Shannon in bpo 40222 A more concise representation of exceptions in the interpreter reduced the time required for catching an exception by about 10 Contributed by Irit Katriel in bpo 45711 re s regular expression matching engine has been partially refactored and now uses computed gotos or threaded code on supported platforms As a result Python 3 11 executes the pyperformance regular expression benchmarks up to 10 faster than Python 3 10 Contributed by Brandt Bucher in gh 91404 FAQ How should I write my code to utilize these speedups Write Pythonic code that follows common best practices you don t have to change your code The Faster CPython project optimizes for common code patterns we observe Will CPython 3 11 use more memory Maybe not we don t expect memory use to exceed 20 higher than 3 10 This is offset by memory optimizations for frame objects and object dictionaries as mentioned above I don t see any speedups in my workload Why Certain code won t have noticeable benefits If your code spends most of its time on I O operations or already doe,en
2183,s most of its computation in a C extension library like NumPy there won t be significant speedups This project currently benefits pure Python workloads the most Furthermore the pyperformance figures are a geometric mean Even within the pyperformance benchmarks certain benchmarks have slowed down slightly while others have sped up by nearly 2x Is there a JIT compiler No We re still exploring other optimizations About Faster CPython explores optimizations for CPython The main team is funded by Microsoft to work on this full time Pablo Galindo Salgado is also funded by Bloomberg LP to work on the project part time Finally many contributors are volunteers from the community CPython bytecode changes The bytecode now contains inline cache entries which take the form of the newly added CACHE instructions Many opcodes expect to be followed by an exact number of caches and instruct the interpreter to skip over them at runtime Populated caches can look like arbitrary instructions so great care should be taken when reading or modifying raw adaptive bytecode containing quickened data New opcodes ASYNC_GEN_WRAP RETURN_GENERATOR and SEND used in generators and co routines COPY_FREE_VARS which avoids needing special caller side code for closures JUMP_BACKWARD_NO_INTERRUPT for use in certain loops where handling interrupts is undesirable MAKE_CELL to create Cell Objects CHECK_EG_MATCH and PREP_RERAISE_STAR to handle the new exception groups and except added in PEP 654 PUSH_EXC_INFO for use in exception handlers RESUME a no op for internal tracing debugging and optimization checks Replaced opcodes Replaced Opcode s New Opcode s Notes BINARY_ INPLACE_ BINARY_OP Replaced all numeric binary in place opcodes with a single opcode CALL_FUNCTION CALL_FUNCTION_KW CALL KW_NAMES PRECALL Decouples argument shifting for methods CALL_METHOD PUSH_NULL from handling of keyword arguments allows better specialization of calls DUP_TOP DUP_TOP_TWO ROT_TWO COPY SWAP Stack manipulation instructions ROT_THREE ROT_FOUR ROT_N JUMP_IF_NOT_EXC_MATCH CHECK_EXC_MATCH Now performs check but doesn t jump JUMP_ABSOLUTE POP_JUMP_IF_FALSE JUMP_BACKWARD See 3 TRUE FALSE NONE and POP_JUMP_IF_TRUE POP_JUMP_BACKWARD_IF_ NOT_NONE variants for each direction POP_JUMP_FORWARD_IF_ SETUP_WITH SETUP_ASYNC_WITH BEFORE_WITH with block setup 3 All jump opcodes are now relative including the existing JUMP_IF_TRUE_OR_POP and JUMP_IF_FALSE_OR_POP The argument is now an offset from the current instruction rather than an absolute location Changed removed opcodes Changed MATCH_CLASS and MATCH_KEYS to no longer push an additional boolean value to indicate success failure Instead None is pushed on failure in place of the tuple of extracted values Changed opcodes that work with exceptions to reflect them now being represented as one item on the stack instead of three see gh 89874 Removed COPY_DICT_WITHOUT_KEYS GEN_START POP_BLOCK SETUP_FINALLY and YIELD_FROM Deprecated This section lists Python APIs that have been deprecated in Python 3 11 Deprecated C APIs are listed separately Language Builtins Chaining classmethod descriptors introduced in bpo 19072 is now deprecated It can no longer be used to wrap other descriptors such as property The core design of this feature was flawed and caused a number of downstream problems To pass through a classmethod consider using the __wrapped__ attribute that was added in Python 3 10 Contributed by Raymond Hettinger in gh 89519 Octal escapes in string and bytes literals with values larger than 0o377 255 in decimal now produce a DeprecationWarning In a future Python version they will raise a SyntaxWarning and eventually a SyntaxError Contributed by Serhiy Storchaka in gh 81548 The delegation of int to __trunc__ is now deprecated Calling int a when type a implements __trunc__ but not __int__ or __index__ now raises a DeprecationWarning Contributed by Zackery Spytz in bpo 44977 Modules PEP 594 led to the deprecations of the following modules slated for removal in Python 3 13 aifc chunk msilib pipes telnetlib audioop crypt nis sndhdr uu cgi imghdr nntplib spw,en
2184,d xdrlib cgitb mailcap ossaudiodev sunau Contributed by Brett Cannon in bpo 47061 and Victor Stinner in gh 68966 The asynchat asyncore and smtpd modules have been deprecated since at least Python 3 6 Their documentation and deprecation warnings have now been updated to note they will be removed in Python 3 12 Contributed by Hugo van Kemenade in bpo 47022 The lib2to3 package and 2to3 tool are now deprecated and may not be able to parse Python 3 10 or newer See PEP 617 introducing the new PEG parser for details Contributed by Victor Stinner in bpo 40360 Undocumented modules sre_compile sre_constants and sre_parse are now deprecated Contributed by Serhiy Storchaka in bpo 47152 Standard Library The following have been deprecated in configparser since Python 3 2 Their deprecation warnings have now been updated to note they will be removed in Python 3 12 the configparser SafeConfigParser class the configparser ParsingError filename property the configparser RawConfigParser readfp method Contributed by Hugo van Kemenade in bpo 45173 configparser LegacyInterpolation has been deprecated in the docstring since Python 3 2 and is not listed in the configparser documentation It now emits a DeprecationWarning and will be removed in Python 3 13 Use configparser BasicInterpolation or configparser ExtendedInterpolation instead Contributed by Hugo van Kemenade in bpo 46607 The older set of importlib resources functions were deprecated in favor of the replacements added in Python 3 9 and will be removed in a future Python version due to not supporting resources located within package subdirectories importlib resources contents importlib resources is_resource importlib resources open_binary importlib resources open_text importlib resources read_binary importlib resources read_text importlib resources path The locale getdefaultlocale function is deprecated and will be removed in Python 3 15 Use locale setlocale locale getpreferredencoding False and locale getlocale functions instead Contributed by Victor Stinner in gh 90817 The locale resetlocale function is deprecated and will be removed in Python 3 13 Use locale setlocale locale LC_ALL instead Contributed by Victor Stinner in gh 90817 Stricter rules will now be applied for numerical group references and group names in regular expressions Only sequences of ASCII digits will now be accepted as a numerical reference and the group name in bytes patterns and replacement strings can only contain ASCII letters digits and underscores For now a deprecation warning is raised for syntax violating these rules Contributed by Serhiy Storchaka in gh 91760 In the re module the re template function and the corresponding re TEMPLATE and re T flags are deprecated as they were undocumented and lacked an obvious purpose They will be removed in Python 3 13 Contributed by Serhiy Storchaka and Miro Hrončok in gh 92728 turtle settiltangle has been deprecated since Python 3 1 it now emits a deprecation warning and will be removed in Python 3 13 Use turtle tiltangle instead it was earlier incorrectly marked as deprecated and its docstring is now corrected Contributed by Hugo van Kemenade in bpo 45837 typing Text which exists solely to provide compatibility support between Python 2 and Python 3 code is now deprecated Its removal is currently unplanned but users are encouraged to use str instead wherever possible Contributed by Alex Waygood in gh 92332 The keyword argument syntax for constructing typing TypedDict types is now deprecated Support will be removed in Python 3 13 Contributed by Jingchen Ye in gh 90224 webbrowser MacOSX is deprecated and will be removed in Python 3 13 It is untested undocumented and not used by webbrowser itself Contributed by Donghee Na in bpo 42255 The behavior of returning a value from a TestCase and IsolatedAsyncioTestCase test methods other than the default None value is now deprecated Deprecated the following not formally documented unittest functions scheduled for removal in Python 3 13 unittest findTestCases unittest makeSuite unittest getTestCaseNames Use TestLoader methods instead,en
2185, unittest TestLoader loadTestsFromModule unittest TestLoader loadTestsFromTestCase unittest TestLoader getTestCaseNames Contributed by Erlend E Aasland in bpo 5846 unittest TestProgram usageExit is marked deprecated to be removed in 3 13 Contributed by Carlos Damázio in gh 67048 Pending Removal in Python 3 12 The following Python APIs have been deprecated in earlier Python releases and will be removed in Python 3 12 C APIs pending removal are listed separately The asynchat module The asyncore module The entire distutils package The imp module The typing io namespace The typing re namespace cgi log importlib find_loader importlib abc Loader module_repr importlib abc MetaPathFinder find_module importlib abc PathEntryFinder find_loader importlib abc PathEntryFinder find_module importlib machinery BuiltinImporter find_module importlib machinery BuiltinLoader module_repr importlib machinery FileFinder find_loader importlib machinery FileFinder find_module importlib machinery FrozenImporter find_module importlib machinery FrozenLoader module_repr importlib machinery PathFinder find_module importlib machinery WindowsRegistryFinder find_module importlib util module_for_loader importlib util set_loader_wrapper importlib util set_package_wrapper pkgutil ImpImporter pkgutil ImpLoader pathlib Path link_to sqlite3 enable_shared_cache sqlite3 OptimizedUnicode PYTHONTHREADDEBUG environment variable The following deprecated aliases in unittest Deprecated alias Method Name Deprecated in failUnless assertTrue 3 1 failIf assertFalse 3 1 failUnlessEqual assertEqual 3 1 failIfEqual assertNotEqual 3 1 failUnlessAlmostEqual assertAlmostEqual 3 1 failIfAlmostEqual assertNotAlmostEqual 3 1 failUnlessRaises assertRaises 3 1 assert_ assertTrue 3 2 assertEquals assertEqual 3 2 assertNotEquals assertNotEqual 3 2 assertAlmostEquals assertAlmostEqual 3 2 assertNotAlmostEquals assertNotAlmostEqual 3 2 assertRegexpMatches assertRegex 3 2 assertRaisesRegexp assertRaisesRegex 3 2 assertNotRegexpMatches assertNotRegex 3 5 Removed This section lists Python APIs that have been removed in Python 3 11 Removed C APIs are listed separately Removed the asyncio coroutine decorator enabling legacy generator based coroutines to be compatible with async await code The function has been deprecated since Python 3 8 and the removal was initially scheduled for Python 3 10 Use async def instead Contributed by Illia Volochii in bpo 43216 Removed asyncio coroutines CoroWrapper used for wrapping legacy generator based coroutine objects in the debug mode Contributed by Illia Volochii in bpo 43216 Due to significant security concerns the reuse_address parameter of asyncio loop create_datagram_endpoint disabled in Python 3 9 is now entirely removed This is because of the behavior of the socket option SO_REUSEADDR in UDP Contributed by Hugo van Kemenade in bpo 45129 Removed the binhex module deprecated in Python 3 9 Also removed the related similarly deprecated binascii functions binascii a2b_hqx binascii b2a_hqx binascii rlecode_hqx binascii rldecode_hqx The binascii crc_hqx function remains available Contributed by Victor Stinner in bpo 45085 Removed the distutils bdist_msi command deprecated in Python 3 9 Use bdist_wheel wheel packages instead Contributed by Hugo van Kemenade in bpo 45124 Removed the __getitem__ methods of xml dom pulldom DOMEventStream wsgiref util FileWrapper and fileinput FileInput deprecated since Python 3 9 Contributed by Hugo van Kemenade in bpo 45132 Removed the deprecated gettext functions lgettext ldgettext lngettext and ldngettext Also removed the bind_textdomain_codeset function the NullTranslations output_charset and NullTranslations set_output_charset methods and the codeset parameter of translation and install since they are only used for the l gettext functions Contributed by Donghee Na and Serhiy Storchaka in bpo 44235 Removed from the inspect module The getargspec function deprecated since Python 3 0 use inspect signature or inspect getfullargspec instead The formatargspec function deprecated since Python 3 5 use the inspect signature functio,en
2186,n or the inspect Signature object directly The undocumented Signature from_builtin and Signature from_function methods deprecated since Python 3 5 use the Signature from_callable method instead Contributed by Hugo van Kemenade in bpo 45320 Removed the __class_getitem__ method from pathlib PurePath because it was not used and added by mistake in previous versions Contributed by Nikita Sobolev in bpo 46483 Removed the MailmanProxy class in the smtpd module as it is unusable without the external mailman package Contributed by Donghee Na in bpo 35800 Removed the deprecated split method of _tkinter TkappType Contributed by Erlend E Aasland in bpo 38371 Removed namespace package support from unittest discovery It was introduced in Python 3 4 but has been broken since Python 3 7 Contributed by Inada Naoki in bpo 23882 Removed the undocumented private float __set_format__ method previously known as float __setformat__ in Python 3 7 Its docstring said You probably don t want to use this function It exists mainly to be used in Python s test suite Contributed by Victor Stinner in bpo 46852 The experimental isolated subinterpreters configure flag and corresponding EXPERIMENTAL_ISOLATED_SUBINTERPRETERS macro have been removed Pynche The Pythonically Natural Color and Hue Editor has been moved out of Tools scripts and is being developed independently from the Python source tree Porting to Python 3 11 This section lists previously described changes and other bugfixes in the Python API that may require changes to your Python code Porting notes for the C API are listed separately open io open codecs open and fileinput FileInput no longer accept U universal newline in the file mode In Python 3 universal newline mode is used by default whenever a file is opened in text mode and the U flag has been deprecated since Python 3 3 The newline parameter to these functions controls how universal newlines work Contributed by Victor Stinner in bpo 37330 ast AST node positions are now validated when provided to compile and other related functions If invalid positions are detected a ValueError will be raised Contributed by Pablo Galindo in gh 93351 Prohibited passing non concurrent futures ThreadPoolExecutor executors to asyncio loop set_default_executor following a deprecation in Python 3 8 Contributed by Illia Volochii in bpo 43234 calendar The calendar LocaleTextCalendar and calendar LocaleHTMLCalendar classes now use locale getlocale instead of using locale getdefaultlocale if no locale is specified Contributed by Victor Stinner in bpo 46659 The pdb module now reads the pdbrc configuration file with the UTF 8 encoding Contributed by Srinivas Reddy Thatiparthy శ ర న వ స ర డ డ త ట పర త in bpo 41137 The population parameter of random sample must be a sequence and automatic conversion of set s to list s is no longer supported Also if the sample size is larger than the population size a ValueError is raised Contributed by Raymond Hettinger in bpo 40465 The random optional parameter of random shuffle was removed It was previously an arbitrary random function to use for the shuffle now random random its previous default will always be used In re Regular Expression Syntax global inline flags e g i can now only be used at the start of regular expressions Using them elsewhere has been deprecated since Python 3 6 Contributed by Serhiy Storchaka in bpo 47066 In the re module several long standing bugs where fixed that in rare cases could cause capture groups to get the wrong result Therefore this could change the captured output in these cases Contributed by Ma Lin in bpo 35859 Build Changes CPython now has PEP 11 Tier 3 support for cross compiling to the WebAssembly platforms Emscripten wasm32 unknown emscripten i e Python in the browser and WebAssembly System Interface WASI wasm32 unknown wasi The effort is inspired by previous work like Pyodide These platforms provide a limited subset of POSIX APIs Python standard libraries features and modules related to networking processes threading signals mmap and users groups are not available or don t work Emscripte,en
2187,n contributed by Christian Heimes and Ethan Smith in gh 84461 and WASI contributed by Christian Heimes in gh 90473 platforms promoted in gh 95085 Building CPython now requires A C11 compiler and standard library Optional C11 features are not required Contributed by Victor Stinner in bpo 46656 bpo 45440 and bpo 46640 Support for IEEE 754 floating point numbers Contributed by Victor Stinner in bpo 46917 The Py_NO_NAN macro has been removed Since CPython now requires IEEE 754 floats NaN values are always available Contributed by Victor Stinner in bpo 46656 The tkinter package now requires Tcl Tk version 8 5 12 or newer Contributed by Serhiy Storchaka in bpo 46996 Build dependencies compiler flags and linker flags for most stdlib extension modules are now detected by configure libffi libnsl libsqlite3 zlib bzip2 liblzma libcrypt Tcl Tk and uuid flags are detected by pkg config when available tkinter now requires a pkg config command to detect development settings for Tcl Tk headers and libraries Contributed by Christian Heimes and Erlend Egeberg Aasland in bpo 45847 bpo 45747 and bpo 45763 libpython is no longer linked against libcrypt Contributed by Mike Gilbert in bpo 45433 CPython can now be built with the ThinLTO option via passing thin to with lto i e with lto thin Contributed by Donghee Na and Brett Holman in bpo 44340 Freelists for object structs can now be disabled A new configure option without freelists can be used to disable all freelists except empty tuple singleton Contributed by Christian Heimes in bpo 45522 Modules Setup and Modules makesetup have been improved and tied up Extension modules can now be built through makesetup All except some test modules can be linked statically into a main binary or library Contributed by Brett Cannon and Christian Heimes in bpo 45548 bpo 45570 bpo 45571 and bpo 43974 Note Use the environment variables TCLTK_CFLAGS and TCLTK_LIBS to manually specify the location of Tcl Tk headers and libraries The configure options with tcltk includes and with tcltk libs have been removed On RHEL 7 and CentOS 7 the development packages do not provide tcl pc and tk pc use TCLTK_LIBS ltk8 5 ltkstub8 5 ltcl8 5 The directory Misc rhel7 contains pc files and instructions on how to build Python with RHEL 7 s and CentOS 7 s Tcl Tk and OpenSSL CPython will now use 30 bit digits by default for the Python int implementation Previously the default was to use 30 bit digits on platforms with SIZEOF_VOID_P 8 and 15 bit digits otherwise It s still possible to explicitly request use of 15 bit digits via either the enable big digits option to the configure script or for Windows the PYLONG_BITS_IN_DIGIT variable in PC pyconfig h but this option may be removed at some point in the future Contributed by Mark Dickinson in bpo 45569 C API Changes New Features Add a new PyType_GetName function to get type s short name Contributed by Hai Shi in bpo 42035 Add a new PyType_GetQualName function to get type s qualified name Contributed by Hai Shi in bpo 42035 Add new PyThreadState_EnterTracing and PyThreadState_LeaveTracing functions to the limited C API to suspend and resume tracing and profiling Contributed by Victor Stinner in bpo 43760 Added the Py_Version constant which bears the same value as PY_VERSION_HEX Contributed by Gabriele N Tornetta in bpo 43931 Py_buffer and APIs are now part of the limited API and the stable ABI PyObject_CheckBuffer PyObject_GetBuffer PyBuffer_GetPointer PyBuffer_SizeFromFormat PyBuffer_ToContiguous PyBuffer_FromContiguous PyObject_CopyData PyBuffer_IsContiguous PyBuffer_FillContiguousStrides PyBuffer_FillInfo PyBuffer_Release PyMemoryView_FromBuffer bf_getbuffer and bf_releasebuffer type slots Contributed by Christian Heimes in bpo 45459 Added the PyType_GetModuleByDef function used to get the module in which a method was defined in cases where this information is not available directly via PyCMethod Contributed by Petr Viktorin in bpo 46613 Add new functions to pack and unpack C double serialize and deserialize PyFloat_Pack2 PyFloat_Pack4 PyFloat_Pack8 PyFloat_Unpack2 PyFloat_Unpack4 a,en
2188,nd PyFloat_Unpack8 Contributed by Victor Stinner in bpo 46906 Add new functions to get frame object attributes PyFrame_GetBuiltins PyFrame_GetGenerator PyFrame_GetGlobals PyFrame_GetLasti Added two new functions to get and set the active exception instance PyErr_GetHandledException and PyErr_SetHandledException These are alternatives to PyErr_SetExcInfo and PyErr_GetExcInfo which work with the legacy 3 tuple representation of exceptions Contributed by Irit Katriel in bpo 46343 Added the PyConfig safe_path member Contributed by Victor Stinner in gh 57684 Porting to Python 3 11 Some macros have been converted to static inline functions to avoid macro pitfalls The change should be mostly transparent to users as the replacement functions will cast their arguments to the expected types to avoid compiler warnings due to static type checks However when the limited C API is set to 3 11 these casts are not done and callers will need to cast arguments to their expected types See PEP 670 for more details Contributed by Victor Stinner and Erlend E Aasland in gh 89653 PyErr_SetExcInfo no longer uses the type and traceback arguments the interpreter now derives those values from the exception instance the value argument The function still steals references of all three arguments Contributed by Irit Katriel in bpo 45711 PyErr_GetExcInfo now derives the type and traceback fields of the result from the exception instance the value field Contributed by Irit Katriel in bpo 45711 _frozen has a new is_package field to indicate whether or not the frozen module is a package Previously a negative value in the size field was the indicator Now only non negative values be used for size Contributed by Kumar Aditya in bpo 46608 _PyFrameEvalFunction now takes _PyInterpreterFrame as its second parameter instead of PyFrameObject See PEP 523 for more details of how to use this function pointer type PyCode_New and PyCode_NewWithPosOnlyArgs now take an additional exception_table argument Using these functions should be avoided if at all possible To get a custom code object create a code object using the compiler then get a modified version with the replace method PyCodeObject no longer has the co_code co_varnames co_cellvars and co_freevars fields Instead use PyCode_GetCode PyCode_GetVarnames PyCode_GetCellvars and PyCode_GetFreevars respectively to access them via the C API Contributed by Brandt Bucher in bpo 46841 and Ken Jin in gh 92154 and gh 94936 The old trashcan macros Py_TRASHCAN_SAFE_BEGIN Py_TRASHCAN_SAFE_END are now deprecated They should be replaced by the new macros Py_TRASHCAN_BEGIN and Py_TRASHCAN_END A tp_dealloc function that has the old macros such as static void mytype_dealloc mytype p PyObject_GC_UnTrack p Py_TRASHCAN_SAFE_BEGIN p Py_TRASHCAN_SAFE_END should migrate to the new macros as follows static void mytype_dealloc mytype p PyObject_GC_UnTrack p Py_TRASHCAN_BEGIN p mytype_dealloc Py_TRASHCAN_END Note that Py_TRASHCAN_BEGIN has a second argument which should be the deallocation function it is in To support older Python versions in the same codebase you can define the following macros and use them throughout the code credit these were copied from the mypy codebase if PY_VERSION_HEX 0x03080000 define CPy_TRASHCAN_BEGIN op dealloc Py_TRASHCAN_BEGIN op dealloc define CPy_TRASHCAN_END op Py_TRASHCAN_END else define CPy_TRASHCAN_BEGIN op dealloc Py_TRASHCAN_SAFE_BEGIN op define CPy_TRASHCAN_END op Py_TRASHCAN_SAFE_END op endif The PyType_Ready function now raises an error if a type is defined with the Py_TPFLAGS_HAVE_GC flag set but has no traverse function PyTypeObject tp_traverse Contributed by Victor Stinner in bpo 44263 Heap types with the Py_TPFLAGS_IMMUTABLETYPE flag can now inherit the PEP 590 vectorcall protocol Previously this was only possible for static types Contributed by Erlend E Aasland in bpo 43908 Since Py_TYPE is changed to a inline static function Py_TYPE obj new_type must be replaced with Py_SET_TYPE obj new_type see the Py_SET_TYPE function available since Python 3 9 For backward compatibility this macro can be used ,en
2189,if PY_VERSION_HEX 0x030900A4 defined Py_SET_TYPE static inline void _Py_SET_TYPE PyObject ob PyTypeObject type ob ob_type type define Py_SET_TYPE ob type _Py_SET_TYPE PyObject ob type endif Contributed by Victor Stinner in bpo 39573 Since Py_SIZE is changed to a inline static function Py_SIZE obj new_size must be replaced with Py_SET_SIZE obj new_size see the Py_SET_SIZE function available since Python 3 9 For backward compatibility this macro can be used if PY_VERSION_HEX 0x030900A4 defined Py_SET_SIZE static inline void _Py_SET_SIZE PyVarObject ob Py_ssize_t size ob ob_size size define Py_SET_SIZE ob size _Py_SET_SIZE PyVarObject ob size endif Contributed by Victor Stinner in bpo 39573 Python h no longer includes the header files stdlib h stdio h errno h and string h when the Py_LIMITED_API macro is set to 0x030b0000 Python 3 11 or higher C extensions should explicitly include the header files after include Python h Contributed by Victor Stinner in bpo 45434 The non limited API files cellobject h classobject h code h context h funcobject h genobject h and longintrepr h have been moved to the Include cpython directory Moreover the eval h header file was removed These files must not be included directly as they are already included in Python h Include Files If they have been included directly consider including Python h instead Contributed by Victor Stinner in bpo 35134 The PyUnicode_CHECK_INTERNED macro has been excluded from the limited C API It was never usable there because it used internal structures which are not available in the limited C API Contributed by Victor Stinner in bpo 46007 The following frame functions and type are now directly available with include Python h it s no longer needed to add include frameobject h PyFrame_Check PyFrame_GetBack PyFrame_GetBuiltins PyFrame_GetGenerator PyFrame_GetGlobals PyFrame_GetLasti PyFrame_GetLocals PyFrame_Type Contributed by Victor Stinner in gh 93937 The PyFrameObject structure members have been removed from the public C API While the documentation notes that the PyFrameObject fields are subject to change at any time they have been stable for a long time and were used in several popular extensions In Python 3 11 the frame struct was reorganized to allow performance optimizations Some fields were removed entirely as they were details of the old implementation PyFrameObject fields f_back use PyFrame_GetBack f_blockstack removed f_builtins use PyFrame_GetBuiltins f_code use PyFrame_GetCode f_gen use PyFrame_GetGenerator f_globals use PyFrame_GetGlobals f_iblock removed f_lasti use PyFrame_GetLasti Code using f_lasti with PyCode_Addr2Line should use PyFrame_GetLineNumber instead it may be faster f_lineno use PyFrame_GetLineNumber f_locals use PyFrame_GetLocals f_stackdepth removed f_state no public API renamed to f_frame f_state f_trace no public API f_trace_lines use PyObject_GetAttrString PyObject frame f_trace_lines f_trace_opcodes use PyObject_GetAttrString PyObject frame f_trace_opcodes f_localsplus no public API renamed to f_frame localsplus f_valuestack removed The Python frame object is now created lazily A side effect is that the f_back member must not be accessed directly since its value is now also computed lazily The PyFrame_GetBack function must be called instead Debuggers that accessed the f_locals directly must call PyFrame_GetLocals instead They no longer need to call PyFrame_FastToLocalsWithError or PyFrame_LocalsToFast in fact they should not call those functions The necessary updating of the frame is now managed by the virtual machine Code defining PyFrame_GetCode on Python 3 8 and older if PY_VERSION_HEX 0x030900B1 static inline PyCodeObject PyFrame_GetCode PyFrameObject frame Py_INCREF frame f_code return frame f_code endif Code defining PyFrame_GetBack on Python 3 8 and older if PY_VERSION_HEX 0x030900B1 static inline PyFrameObject PyFrame_GetBack PyFrameObject frame Py_XINCREF frame f_back return frame f_back endif Or use the pythoncapi_compat project to get these two functions on older Python versions Changes of the PyThreadState structure members,en
2190, frame removed use PyThreadState_GetFrame function added to Python 3 9 by bpo 40429 Warning the function returns a strong reference need to call Py_XDECREF tracing changed use PyThreadState_EnterTracing and PyThreadState_LeaveTracing functions added to Python 3 11 by bpo 43760 recursion_depth removed use tstate recursion_limit tstate recursion_remaining instead stackcheck_counter removed Code defining PyThreadState_GetFrame on Python 3 8 and older if PY_VERSION_HEX 0x030900B1 static inline PyFrameObject PyThreadState_GetFrame PyThreadState tstate Py_XINCREF tstate frame return tstate frame endif Code defining PyThreadState_EnterTracing and PyThreadState_LeaveTracing on Python 3 10 and older if PY_VERSION_HEX 0x030B00A2 static inline void PyThreadState_EnterTracing PyThreadState tstate tstate tracing if PY_VERSION_HEX 0x030A00A1 tstate cframe use_tracing 0 else tstate use_tracing 0 endif static inline void PyThreadState_LeaveTracing PyThreadState tstate int use_tracing tstate c_tracefunc NULL tstate c_profilefunc NULL tstate tracing if PY_VERSION_HEX 0x030A00A1 tstate cframe use_tracing use_tracing else tstate use_tracing use_tracing endif endif Or use the pythoncapi compat project to get these functions on old Python functions Distributors are encouraged to build Python with the optimized Blake2 library libb2 The PyConfig module_search_paths_set field must now be set to 1 for initialization to use PyConfig module_search_paths to initialize sys path Otherwise initialization will recalculate the path and replace any values added to module_search_paths PyConfig_Read no longer calculates the initial search path and will not fill any values into PyConfig module_search_paths To calculate default paths and then modify them finish initialization and use PySys_GetObject to retrieve sys path as a Python list object and modify it directly Deprecated Deprecate the following functions to configure the Python initialization PySys_AddWarnOptionUnicode PySys_AddWarnOption PySys_AddXOption PySys_HasWarnOptions PySys_SetArgvEx PySys_SetArgv PySys_SetPath Py_SetPath Py_SetProgramName Py_SetPythonHome Py_SetStandardStreamEncoding _Py_SetProgramFullPath Use the new PyConfig API of the Python Initialization Configuration instead PEP 587 Contributed by Victor Stinner in gh 88279 Deprecate the ob_shash member of the PyBytesObject Use PyObject_Hash instead Contributed by Inada Naoki in bpo 46864 Pending Removal in Python 3 12 The following C APIs have been deprecated in earlier Python releases and will be removed in Python 3 12 PyUnicode_AS_DATA PyUnicode_AS_UNICODE PyUnicode_AsUnicodeAndSize PyUnicode_AsUnicode PyUnicode_FromUnicode PyUnicode_GET_DATA_SIZE PyUnicode_GET_SIZE PyUnicode_GetSize PyUnicode_IS_COMPACT PyUnicode_IS_READY PyUnicode_READY PyUnicode_WSTR_LENGTH _PyUnicode_AsUnicode PyUnicode_WCHAR_KIND PyUnicodeObject PyUnicode_InternImmortal Removed PyFrame_BlockSetup and PyFrame_BlockPop have been removed Contributed by Mark Shannon in bpo 40222 Remove the following math macros using the errno variable Py_ADJUST_ERANGE1 Py_ADJUST_ERANGE2 Py_OVERFLOWED Py_SET_ERANGE_IF_OVERFLOW Py_SET_ERRNO_ON_MATH_ERROR Contributed by Victor Stinner in bpo 45412 Remove Py_UNICODE_COPY and Py_UNICODE_FILL macros deprecated since Python 3 3 Use PyUnicode_CopyCharacters or memcpy wchar_t string and PyUnicode_Fill functions instead Contributed by Victor Stinner in bpo 41123 Remove the pystrhex h header file It only contains private functions C extensions should only include the main Python h header file Contributed by Victor Stinner in bpo 45434 Remove the Py_FORCE_DOUBLE macro It was used by the Py_IS_INFINITY macro Contributed by Victor Stinner in bpo 45440 The following items are no longer available when Py_LIMITED_API is defined PyMarshal_WriteLongToFile PyMarshal_WriteObjectToFile PyMarshal_ReadObjectFromString PyMarshal_WriteObjectToString the Py_MARSHAL_VERSION macro These are not part of the limited API Contributed by Victor Stinner in bpo 45474 Exclude PyWeakref_GET_OBJECT from the limited C API It never worked since the PyWeakReference structure,en
2191, is opaque in the limited C API Contributed by Victor Stinner in bpo 35134 Remove the PyHeapType_GET_MEMBERS macro It was exposed in the public C API by mistake it must only be used by Python internally Use the PyTypeObject tp_members member instead Contributed by Victor Stinner in bpo 40170 Remove the HAVE_PY_SET_53BIT_PRECISION macro moved to the internal C API Contributed by Victor Stinner in bpo 45412 Remove the Py_UNICODE encoder APIs as they have been deprecated since Python 3 3 are little used and are inefficient relative to the recommended alternatives The removed functions are PyUnicode_Encode PyUnicode_EncodeASCII PyUnicode_EncodeLatin1 PyUnicode_EncodeUTF7 PyUnicode_EncodeUTF8 PyUnicode_EncodeUTF16 PyUnicode_EncodeUTF32 PyUnicode_EncodeUnicodeEscape PyUnicode_EncodeRawUnicodeEscape PyUnicode_EncodeCharmap PyUnicode_TranslateCharmap PyUnicode_EncodeDecimal PyUnicode_TransformDecimalToASCII See PEP 624 for details and migration guidance Contributed by Inada Naoki in bpo 44029 Notable changes in 3 11 4 tarfile The extraction methods in tarfile and shutil unpack_archive have a new a filter argument that allows limiting tar features than may be surprising or dangerous such as creating files outside the destination directory See Extraction filters for details In Python 3 12 use without the filter argument will show a DeprecationWarning In Python 3 14 the default will switch to data Contributed by Petr Viktorin in PEP 706 Notable changes in 3 11 5 OpenSSL Windows builds and macOS installers from python org now use OpenSSL 3 0,en
2192,8 Errors and Exceptions Until now error messages haven t been more than mentioned but if you have tried out the examples you have probably seen some There are at least two distinguishable kinds of errors syntax errors and exceptions 8 1 Syntax Errors Syntax errors also known as parsing errors are perhaps the most common kind of complaint you get while you are still learning Python while True print Hello world File stdin line 1 while True print Hello world SyntaxError invalid syntax The parser repeats the offending line and displays little arrow s pointing at the token in the line where the error was detected The error may be caused by the absence of a token before the indicated token In the example the error is detected at the function print since a colon is missing before it File name and line number are printed so you know where to look in case the input came from a script 8 2 Exceptions Even if a statement or expression is syntactically correct it may cause an error when an attempt is made to execute it Errors detected during execution are called exceptions and are not unconditionally fatal you will soon learn how to handle them in Python programs Most exceptions are not handled by programs however and result in error messages as shown here 10 1 0 Traceback most recent call last File stdin line 1 in module ZeroDivisionError division by zero 4 spam 3 Traceback most recent call last File stdin line 1 in module NameError name spam is not defined 2 2 Traceback most recent call last File stdin line 1 in module TypeError can only concatenate str not int to str The last line of the error message indicates what happened Exceptions come in different types and the type is printed as part of the message the types in the example are ZeroDivisionError NameError and TypeError The string printed as the exception type is the name of the built in exception that occurred This is true for all built in exceptions but need not be true for user defined exceptions although it is a useful convention Standard exception names are built in identifiers not reserved keywords The rest of the line provides detail based on the type of exception and what caused it The preceding part of the error message shows the context where the exception occurred in the form of a stack traceback In general it contains a stack traceback listing source lines however it will not display lines read from standard input Built in Exceptions lists the built in exceptions and their meanings 8 3 Handling Exceptions It is possible to write programs that handle selected exceptions Look at the following example which asks the user for input until a valid integer has been entered but allows the user to interrupt the program using Control C or whatever the operating system supports note that a user generated interruption is signalled by raising the KeyboardInterrupt exception while True try x int input Please enter a number break except ValueError print Oops That was no valid number Try again The try statement works as follows First the try clause the statement s between the try and except keywords is executed If no exception occurs the except clause is skipped and execution of the try statement is finished If an exception occurs during execution of the try clause the rest of the clause is skipped Then if its type matches the exception named after the except keyword the except clause is executed and then execution continues after the try except block If an exception occurs which does not match the exception named in the except clause it is passed on to outer try statements if no handler is found it is an unhandled exception and execution stops with an error message A try statement may have more than one except clause to specify handlers for different exceptions At most one handler will be executed Handlers only handle exceptions that occur in the corresponding try clause not in other handlers of the same try statement An except clause may name multiple exceptions as a parenthesized tuple for example except RuntimeError TypeError NameError pass A class in an except clause is comp,en
2193,atible with an exception if it is the same class or a base class thereof but not the other way around an except clause listing a derived class is not compatible with a base class For example the following code will print B C D in that order class B Exception pass class C B pass class D C pass for cls in B C D try raise cls except D print D except C print C except B print B Note that if the except clauses were reversed with except B first it would have printed B B B the first matching except clause is triggered When an exception occurs it may have associated values also known as the exception s arguments The presence and types of the arguments depend on the exception type The except clause may specify a variable after the exception name The variable is bound to the exception instance which typically has an args attribute that stores the arguments For convenience builtin exception types define __str__ to print all the arguments without explicitly accessing args try raise Exception spam eggs except Exception as inst print type inst the exception type print inst args arguments stored in args print inst __str__ allows args to be printed directly but may be overridden in exception subclasses x y inst args unpack args print x x print y y class Exception spam eggs spam eggs x spam y eggs The exception s __str__ output is printed as the last part detail of the message for unhandled exceptions BaseException is the common base class of all exceptions One of its subclasses Exception is the base class of all the non fatal exceptions Exceptions which are not subclasses of Exception are not typically handled because they are used to indicate that the program should terminate They include SystemExit which is raised by sys exit and KeyboardInterrupt which is raised when a user wishes to interrupt the program Exception can be used as a wildcard that catches almost everything However it is good practice to be as specific as possible with the types of exceptions that we intend to handle and to allow any unexpected exceptions to propagate on The most common pattern for handling Exception is to print or log the exception and then re raise it allowing a caller to handle the exception as well import sys try f open myfile txt s f readline i int s strip except OSError as err print OS error err except ValueError print Could not convert data to an integer except Exception as err print f Unexpected err type err raise The try except statement has an optional else clause which when present must follow all except clauses It is useful for code that must be executed if the try clause does not raise an exception For example for arg in sys argv 1 try f open arg r except OSError print cannot open arg else print arg has len f readlines lines f close The use of the else clause is better than adding additional code to the try clause because it avoids accidentally catching an exception that wasn t raised by the code being protected by the try except statement Exception handlers do not handle only exceptions that occur immediately in the try clause but also those that occur inside functions that are called even indirectly in the try clause For example def this_fails x 1 0 try this_fails except ZeroDivisionError as err print Handling run time error err Handling run time error division by zero 8 4 Raising Exceptions The raise statement allows the programmer to force a specified exception to occur For example raise NameError HiThere Traceback most recent call last File stdin line 1 in module NameError HiThere The sole argument to raise indicates the exception to be raised This must be either an exception instance or an exception class a class that derives from BaseException such as Exception or one of its subclasses If an exception class is passed it will be implicitly instantiated by calling its constructor with no arguments raise ValueError shorthand for raise ValueError If you need to determine whether an exception was raised but don t intend to handle it a simpler form of the raise statement allows you to re raise the exception try raise NameError HiThere excep,en
2194,t NameError print An exception flew by raise An exception flew by Traceback most recent call last File stdin line 2 in module NameError HiThere 8 5 Exception Chaining If an unhandled exception occurs inside an except section it will have the exception being handled attached to it and included in the error message try open database sqlite except OSError raise RuntimeError unable to handle error Traceback most recent call last File stdin line 2 in module FileNotFoundError Errno 2 No such file or directory database sqlite During handling of the above exception another exception occurred Traceback most recent call last File stdin line 4 in module RuntimeError unable to handle error To indicate that an exception is a direct consequence of another the raise statement allows an optional from clause exc must be exception instance or None raise RuntimeError from exc This can be useful when you are transforming exceptions For example def func raise ConnectionError try func except ConnectionError as exc raise RuntimeError Failed to open database from exc Traceback most recent call last File stdin line 2 in module File stdin line 2 in func ConnectionError The above exception was the direct cause of the following exception Traceback most recent call last File stdin line 4 in module RuntimeError Failed to open database It also allows disabling automatic exception chaining using the from None idiom try open database sqlite except OSError raise RuntimeError from None Traceback most recent call last File stdin line 4 in module RuntimeError For more information about chaining mechanics see Built in Exceptions 8 6 User defined Exceptions Programs may name their own exceptions by creating a new exception class see Classes for more about Python classes Exceptions should typically be derived from the Exception class either directly or indirectly Exception classes can be defined which do anything any other class can do but are usually kept simple often only offering a number of attributes that allow information about the error to be extracted by handlers for the exception Most exceptions are defined with names that end in Error similar to the naming of the standard exceptions Many standard modules define their own exceptions to report errors that may occur in functions they define 8 7 Defining Clean up Actions The try statement has another optional clause which is intended to define clean up actions that must be executed under all circumstances For example try raise KeyboardInterrupt finally print Goodbye world Goodbye world Traceback most recent call last File stdin line 2 in module KeyboardInterrupt If a finally clause is present the finally clause will execute as the last task before the try statement completes The finally clause runs whether or not the try statement produces an exception The following points discuss more complex cases when an exception occurs If an exception occurs during execution of the try clause the exception may be handled by an except clause If the exception is not handled by an except clause the exception is re raised after the finally clause has been executed An exception could occur during execution of an except or else clause Again the exception is re raised after the finally clause has been executed If the finally clause executes a break continue or return statement exceptions are not re raised If the try statement reaches a break continue or return statement the finally clause will execute just prior to the break continue or return statement s execution If a finally clause includes a return statement the returned value will be the one from the finally clause s return statement not the value from the try clause s return statement For example def bool_return try return True finally return False bool_return False A more complicated example def divide x y try result x y except ZeroDivisionError print division by zero else print result is result finally print executing finally clause divide 2 1 result is 2 0 executing finally clause divide 2 0 division by zero executing finally clause divide 2 1 executing finally cl,en
2195,ause Traceback most recent call last File stdin line 1 in module File stdin line 3 in divide TypeError unsupported operand type s for str and str As you can see the finally clause is executed in any event The TypeError raised by dividing two strings is not handled by the except clause and therefore re raised after the finally clause has been executed In real world applications the finally clause is useful for releasing external resources such as files or network connections regardless of whether the use of the resource was successful 8 8 Predefined Clean up Actions Some objects define standard clean up actions to be undertaken when the object is no longer needed regardless of whether or not the operation using the object succeeded or failed Look at the following example which tries to open a file and print its contents to the screen for line in open myfile txt print line end The problem with this code is that it leaves the file open for an indeterminate amount of time after this part of the code has finished executing This is not an issue in simple scripts but can be a problem for larger applications The with statement allows objects like files to be used in a way that ensures they are always cleaned up promptly and correctly with open myfile txt as f for line in f print line end After the statement is executed the file f is always closed even if a problem was encountered while processing the lines Objects which like files provide predefined clean up actions will indicate this in their documentation 8 9 Raising and Handling Multiple Unrelated Exceptions There are situations where it is necessary to report several exceptions that have occurred This is often the case in concurrency frameworks when several tasks may have failed in parallel but there are also other use cases where it is desirable to continue execution and collect multiple errors rather than raise the first exception The builtin ExceptionGroup wraps a list of exception instances so that they can be raised together It is an exception itself so it can be caught like any other exception def f excs OSError error 1 SystemError error 2 raise ExceptionGroup there were problems excs f Exception Group Traceback most recent call last File stdin line 1 in module File stdin line 3 in f ExceptionGroup there were problems 1 OSError error 1 2 SystemError error 2 try f except Exception as e print f caught type e e caught class ExceptionGroup e By using except instead of except we can selectively handle only the exceptions in the group that match a certain type In the following example which shows a nested exception group each except clause extracts from the group exceptions of a certain type while letting all other exceptions propagate to other clauses and eventually to be reraised def f raise ExceptionGroup group1 OSError 1 SystemError 2 ExceptionGroup group2 OSError 3 RecursionError 4 try f except OSError as e print There were OSErrors except SystemError as e print There were SystemErrors There were OSErrors There were SystemErrors Exception Group Traceback most recent call last File stdin line 2 in module File stdin line 2 in f ExceptionGroup group1 1 ExceptionGroup group2 1 RecursionError 4 Note that the exceptions nested in an exception group must be instances not types This is because in practice the exceptions would typically be ones that have already been raised and caught by the program along the following pattern excs for test in tests try test run except Exception as e excs append e if excs raise ExceptionGroup Test Failures excs 8 10 Enriching Exceptions with Notes When an exception is created in order to be raised it is usually initialized with information that describes the error that has occurred There are cases where it is useful to add information after the exception was caught For this purpose exceptions have a method add_note note that accepts a string and adds it to the exception s notes list The standard traceback rendering includes all notes in the order they were added after the exception try raise TypeError bad type except Exception as e e add_note Ad,en
2196,d some information e add_note Add some more information raise Traceback most recent call last File stdin line 2 in module TypeError bad type Add some information Add some more information For example when collecting exceptions into an exception group we may want to add context information for the individual errors In the following each exception in the group has a note indicating when this error has occurred def f raise OSError operation failed excs for i in range 3 try f except Exception as e e add_note f Happened in Iteration i 1 excs append e raise ExceptionGroup We have some problems excs Exception Group Traceback most recent call last File stdin line 1 in module ExceptionGroup We have some problems 3 sub exceptions 1 Traceback most recent call last File stdin line 3 in module File stdin line 2 in f OSError operation failed Happened in Iteration 1 2 Traceback most recent call last File stdin line 3 in module File stdin line 2 in f OSError operation failed Happened in Iteration 2 3 Traceback most recent call last File stdin line 3 in module File stdin line 2 in f OSError operation failed Happened in Iteration 3,en
2197,Unix Specific Services The modules described in this chapter provide interfaces to features that are unique to the Unix operating system or in some cases to some or many variants of it Here s an overview posix The most common POSIX system calls Large File Support Notable Module Contents pwd The password database grp The group database termios POSIX style tty control Example tty Terminal control functions pty Pseudo terminal utilities Example fcntl The fcntl and ioctl system calls resource Resource usage information Resource Limits Resource Usage syslog Unix syslog library routines Examples Simple example,en
2198,tomllib Parse TOML files New in version 3 11 Source code Lib tomllib This module provides an interface for parsing TOML Tom s Obvious Minimal Language https toml io This module does not support writing TOML See also The Tomli W package is a TOML writer that can be used in conjunction with this module providing a write API familiar to users of the standard library marshal and pickle modules See also The TOML Kit package is a style preserving TOML library with both read and write capability It is a recommended replacement for this module for editing already existing TOML files This module defines the following functions tomllib load fp parse_float float Read a TOML file The first argument should be a readable and binary file object Return a dict Convert TOML types to Python using this conversion table parse_float will be called with the string of every TOML float to be decoded By default this is equivalent to float num_str This can be used to use another datatype or parser for TOML floats e g decimal Decimal The callable must not return a dict or a list else a ValueError is raised A TOMLDecodeError will be raised on an invalid TOML document tomllib loads s parse_float float Load TOML from a str object Return a dict Convert TOML types to Python using this conversion table The parse_float argument has the same meaning as in load A TOMLDecodeError will be raised on an invalid TOML document The following exceptions are available exception tomllib TOMLDecodeError Subclass of ValueError Examples Parsing a TOML file import tomllib with open pyproject toml rb as f data tomllib load f Parsing a TOML string import tomllib toml_str python version 3 11 0 python implementation CPython data tomllib loads toml_str Conversion Table TOML Python TOML document dict string str integer int float float configurable with parse_float boolean bool offset date time datetime datetime tzinfo attribute set to an instance of datetime timezone local date time datetime datetime tzinfo attribute set to None local date datetime date local time datetime time array list table dict inline table dict array of tables list of dicts,en
2199,What s New in Python 2 1 Author A M Kuchling Introduction This article explains the new features in Python 2 1 While there aren t as many changes in 2 1 as there were in Python 2 0 there are still some pleasant surprises in store 2 1 is the first release to be steered through the use of Python Enhancement Proposals or PEPs so most of the sizable changes have accompanying PEPs that provide more complete documentation and a design rationale for the change This article doesn t attempt to document the new features completely but simply provides an overview of the new features for Python programmers Refer to the Python 2 1 documentation or to the specific PEP for more details about any new feature that particularly interests you One recent goal of the Python development team has been to accelerate the pace of new releases with a new release coming every 6 to 9 months 2 1 is the first release to come out at this faster pace with the first alpha appearing in January 3 months after the final version of 2 0 was released The final release of Python 2 1 was made on April 17 2001 PEP 227 Nested Scopes The largest change in Python 2 1 is to Python s scoping rules In Python 2 0 at any given time there are at most three namespaces used to look up variable names local module level and the built in namespace This often surprised people because it didn t match their intuitive expectations For example a nested recursive function definition doesn t work def f def g value return g value 1 1 The function g will always raise a NameError exception because the binding of the name g isn t in either its local namespace or in the module level namespace This isn t much of a problem in practice how often do you recursively define interior functions like this but this also made using the lambda expression clumsier and this was a problem in practice In code which uses lambda you can often find local variables being copied by passing them as the default values of arguments def find self name Return list of any entries equal to name L filter lambda x name name x name self list_attribute return L The readability of Python code written in a strongly functional style suffers greatly as a result The most significant change to Python 2 1 is that static scoping has been added to the language to fix this problem As a first effect the name name default argument is now unnecessary in the above example Put simply when a given variable name is not assigned a value within a function by an assignment or the def class or import statements references to the variable will be looked up in the local namespace of the enclosing scope A more detailed explanation of the rules and a dissection of the implementation can be found in the PEP This change may cause some compatibility problems for code where the same variable name is used both at the module level and as a local variable within a function that contains further function definitions This seems rather unlikely though since such code would have been pretty confusing to read in the first place One side effect of the change is that the from module import and exec statements have been made illegal inside a function scope under certain conditions The Python reference manual has said all along that from module import is only legal at the top level of a module but the CPython interpreter has never enforced this before As part of the implementation of nested scopes the compiler which turns Python source into bytecodes has to generate different code to access variables in a containing scope from module import and exec make it impossible for the compiler to figure this out because they add names to the local namespace that are unknowable at compile time Therefore if a function contains function definitions or lambda expressions with free variables the compiler will flag this by raising a SyntaxError exception To make the preceding explanation a bit clearer here s an example x 1 def f The next line is a syntax error exec x 2 def g return x Line 4 containing the exec statement is a syntax error since exec would define a new local v,en
2200,ariable named x whose value should be accessed by g This shouldn t be much of a limitation since exec is rarely used in most Python code and when it is used it s often a sign of a poor design anyway Compatibility concerns have led to nested scopes being introduced gradually in Python 2 1 they aren t enabled by default but can be turned on within a module by using a future statement as described in PEP 236 See the following section for further discussion of PEP 236 In Python 2 2 nested scopes will become the default and there will be no way to turn them off but users will have had all of 2 1 s lifetime to fix any breakage resulting from their introduction See also PEP 227 Statically Nested Scopes Written and implemented by Jeremy Hylton PEP 236 __future__ Directives The reaction to nested scopes was widespread concern about the dangers of breaking code with the 2 1 release and it was strong enough to make the Pythoneers take a more conservative approach This approach consists of introducing a convention for enabling optional functionality in release N that will become compulsory in release N 1 The syntax uses a from import statement using the reserved module name __future__ Nested scopes can be enabled by the following statement from __future__ import nested_scopes While it looks like a normal import statement it s not there are strict rules on where such a future statement can be put They can only be at the top of a module and must precede any Python code or regular import statements This is because such statements can affect how the Python bytecode compiler parses code and generates bytecode so they must precede any statement that will result in bytecodes being produced See also PEP 236 Back to the __future__ Written by Tim Peters and primarily implemented by Jeremy Hylton PEP 207 Rich Comparisons In earlier versions Python s support for implementing comparisons on user defined classes and extension types was quite simple Classes could implement a __cmp__ method that was given two instances of a class and could only return 0 if they were equal or 1 or 1 if they weren t the method couldn t raise an exception or return anything other than a Boolean value Users of Numeric Python often found this model too weak and restrictive because in the number crunching programs that numeric Python is used for it would be more useful to be able to perform elementwise comparisons of two matrices returning a matrix containing the results of a given comparison for each element If the two matrices are of different sizes then the compare has to be able to raise an exception to signal the error In Python 2 1 rich comparisons were added in order to support this need Python classes can now individually overload each of the and operations The new magic method names are Operation Method name __lt__ __le__ __gt__ __ge__ __eq__ __ne__ The magic methods are named after the corresponding Fortran operators LT LE c Numeric programmers are almost certainly quite familiar with these names and will find them easy to remember Each of these magic methods is of the form method self other where self will be the object on the left hand side of the operator while other will be the object on the right hand side For example the expression A B will cause A __lt__ B to be called Each of these magic methods can return anything at all a Boolean a matrix a list or any other Python object Alternatively they can raise an exception if the comparison is impossible inconsistent or otherwise meaningless The built in cmp A B function can use the rich comparison machinery and now accepts an optional argument specifying which comparison operation to use this is given as one of the strings or If called without the optional third argument cmp will only return 1 0 or 1 as in previous versions of Python otherwise it will call the appropriate method and can return any Python object There are also corresponding changes of interest to C programmers there s a new slot tp_richcmp in type objects and an API for performing a given rich comparison I won t cover the C API here but will re,en
2201,fer you to PEP 207 or to 2 1 s C API documentation for the full list of related functions See also PEP 207 Rich Comparisons Written by Guido van Rossum heavily based on earlier work by David Ascher and implemented by Guido van Rossum PEP 230 Warning Framework Over its 10 years of existence Python has accumulated a certain number of obsolete modules and features along the way It s difficult to know when a feature is safe to remove since there s no way of knowing how much code uses it perhaps no programs depend on the feature or perhaps many do To enable removing old features in a more structured way a warning framework was added When the Python developers want to get rid of a feature it will first trigger a warning in the next version of Python The following Python version can then drop the feature and users will have had a full release cycle to remove uses of the old feature Python 2 1 adds the warning framework to be used in this scheme It adds a warnings module that provide functions to issue warnings and to filter out warnings that you don t want to be displayed Third party modules can also use this framework to deprecate old features that they no longer wish to support For example in Python 2 1 the regex module is deprecated so importing it causes a warning to be printed import regex __main__ 1 DeprecationWarning the regex module is deprecated please use the re module Warnings can be issued by calling the warnings warn function warnings warn feature X no longer supported The first parameter is the warning message an additional optional parameters can be used to specify a particular warning category Filters can be added to disable certain warnings a regular expression pattern can be applied to the message or to the module name in order to suppress a warning For example you may have a program that uses the regex module and not want to spare the time to convert it to use the re module right now The warning can be suppressed by calling import warnings warnings filterwarnings action ignore message regex module is deprecated category DeprecationWarning module __main__ This adds a filter that will apply only to warnings of the class DeprecationWarning triggered in the __main__ module and applies a regular expression to only match the message about the regex module being deprecated and will cause such warnings to be ignored Warnings can also be printed only once printed every time the offending code is executed or turned into exceptions that will cause the program to stop unless the exceptions are caught in the usual way of course Functions were also added to Python s C API for issuing warnings refer to PEP 230 or to Python s API documentation for the details See also PEP 5 Guidelines for Language Evolution Written by Paul Prescod to specify procedures to be followed when removing old features from Python The policy described in this PEP hasn t been officially adopted but the eventual policy probably won t be too different from Prescod s proposal PEP 230 Warning Framework Written and implemented by Guido van Rossum PEP 229 New Build System When compiling Python the user had to go in and edit the Modules Setup file in order to enable various additional modules the default set is relatively small and limited to modules that compile on most Unix platforms This means that on Unix platforms with many more features most notably Linux Python installations often don t contain all useful modules they could Python 2 0 added the Distutils a set of modules for distributing and installing extensions In Python 2 1 the Distutils are used to compile much of the standard library of extension modules autodetecting which ones are supported on the current machine It s hoped that this will make Python installations easier and more featureful Instead of having to edit the Modules Setup file in order to enable modules a setup py script in the top directory of the Python source distribution is run at build time and attempts to discover which modules can be enabled by examining the modules and header files on the system If a module is configured in ,en
2202,Modules Setup the setup py script won t attempt to compile that module and will defer to the Modules Setup file s contents This provides a way to specific any strange command line flags or libraries that are required for a specific platform In another far reaching change to the build mechanism Neil Schemenauer restructured things so Python now uses a single makefile that isn t recursive instead of makefiles in the top directory and in each of the Python Parser Objects and Modules subdirectories This makes building Python faster and also makes hacking the Makefiles clearer and simpler See also PEP 229 Using Distutils to Build Python Written and implemented by A M Kuchling PEP 205 Weak References Weak references available through the weakref module are a minor but useful new data type in the Python programmer s toolbox Storing a reference to an object say in a dictionary or a list has the side effect of keeping that object alive forever There are a few specific cases where this behaviour is undesirable object caches being the most common one and another being circular references in data structures such as trees For example consider a memoizing function that caches the results of another function f x by storing the function s argument and its result in a dictionary _cache def memoize x if _cache has_key x return _cache x retval f x Cache the returned object _cache x retval return retval This version works for simple things such as integers but it has a side effect the _cache dictionary holds a reference to the return values so they ll never be deallocated until the Python process exits and cleans up This isn t very noticeable for integers but if f returns an object or a data structure that takes up a lot of memory this can be a problem Weak references provide a way to implement a cache that won t keep objects alive beyond their time If an object is only accessible through weak references the object will be deallocated and the weak references will now indicate that the object it referred to no longer exists A weak reference to an object obj is created by calling wr weakref ref obj The object being referred to is returned by calling the weak reference as if it were a function wr It will return the referenced object or None if the object no longer exists This makes it possible to write a memoize function whose cache doesn t keep objects alive by storing weak references in the cache _cache def memoize x if _cache has_key x obj _cache x If weak reference object still exists return it if obj is not None return obj retval f x Cache a weak reference _cache x weakref ref retval return retval The weakref module also allows creating proxy objects which behave like weak references an object referenced only by proxy objects is deallocated but instead of requiring an explicit call to retrieve the object the proxy transparently forwards all operations to the object as long as the object still exists If the object is deallocated attempting to use a proxy will cause a weakref ReferenceError exception to be raised proxy weakref proxy obj proxy attr Equivalent to obj attr proxy meth Equivalent to obj meth del obj proxy attr raises weakref ReferenceError See also PEP 205 Weak References Written and implemented by Fred L Drake Jr PEP 232 Function Attributes In Python 2 1 functions can now have arbitrary information attached to them People were often using docstrings to hold information about functions and methods because the __doc__ attribute was the only way of attaching any information to a function For example in the Zope web application server functions are marked as safe for public access by having a docstring and in John Aycock s SPARK parsing framework docstrings hold parts of the BNF grammar to be parsed This overloading is unfortunate since docstrings are really intended to hold a function s documentation for example it means you can t properly document functions intended for private use in Zope Arbitrary attributes can now be set and retrieved on functions using the regular Python syntax def f pass f publish 1 f secure 1 f grammar A B,en
2203, C D The dictionary containing attributes can be accessed as the function s __dict__ Unlike the __dict__ attribute of class instances in functions you can actually assign a new dictionary to __dict__ though the new value is restricted to a regular Python dictionary you can t be tricky and set it to a UserDict instance or any other random object that behaves like a mapping See also PEP 232 Function Attributes Written and implemented by Barry Warsaw PEP 235 Importing Modules on Case Insensitive Platforms Some operating systems have filesystems that are case insensitive MacOS and Windows being the primary examples on these systems it s impossible to distinguish the filenames FILE PY and file py even though they do store the file s name in its original case they re case preserving too In Python 2 1 the import statement will work to simulate case sensitivity on case insensitive platforms Python will now search for the first case sensitive match by default raising an ImportError if no such file is found so import file will not import a module named FILE PY Case insensitive matching can be requested by setting the PYTHONCASEOK environment variable before starting the Python interpreter PEP 217 Interactive Display Hook When using the Python interpreter interactively the output of commands is displayed using the built in repr function In Python 2 1 the variable sys displayhook can be set to a callable object which will be called instead of repr For example you can set it to a special pretty printing function Create a recursive data structure L 1 2 3 L append L L Show Python s default output 1 2 3 Use pprint pprint as the display function import sys pprint sys displayhook pprint pprint L 1 2 3 Recursion on list with id 135143996 See also PEP 217 Display Hook for Interactive Use Written and implemented by Moshe Zadka PEP 208 New Coercion Model How numeric coercion is done at the C level was significantly modified This will only affect the authors of C extensions to Python allowing them more flexibility in writing extension types that support numeric operations Extension types can now set the type flag Py_TPFLAGS_CHECKTYPES in their PyTypeObject structure to indicate that they support the new coercion model In such extension types the numeric slot functions can no longer assume that they ll be passed two arguments of the same type instead they may be passed two arguments of differing types and can then perform their own internal coercion If the slot function is passed a type it can t handle it can indicate the failure by returning a reference to the Py_NotImplemented singleton value The numeric functions of the other type will then be tried and perhaps they can handle the operation if the other type also returns Py_NotImplemented then a TypeError will be raised Numeric methods written in Python can also return Py_NotImplemented causing the interpreter to act as if the method did not exist perhaps raising a TypeError perhaps trying another object s numeric methods See also PEP 208 Reworking the Coercion Model Written and implemented by Neil Schemenauer heavily based upon earlier work by Marc André Lemburg Read this to understand the fine points of how numeric operations will now be processed at the C level PEP 241 Metadata in Python Packages A common complaint from Python users is that there s no single catalog of all the Python modules in existence T Middleton s Vaults of Parnassus at www vex net parnassus retired in February 2009 available in the Internet Archive Wayback Machine was the largest catalog of Python modules but registering software at the Vaults is optional and many people did not bother As a first small step toward fixing the problem Python software packaged using the Distutils sdist command will include a file named PKG INFO containing information about the package such as its name version and author metadata in cataloguing terminology PEP 241 contains the full list of fields that can be present in the PKG INFO file As people began to package their software using Python 2 1 more and more packages will include metadat,en
2204,a making it possible to build automated cataloguing systems and experiment with them With the result experience perhaps it ll be possible to design a really good catalog and then build support for it into Python 2 2 For example the Distutils sdist and bdist_ commands could support an upload option that would automatically upload your package to a catalog server You can start creating packages containing PKG INFO even if you re not using Python 2 1 since a new release of the Distutils will be made for users of earlier Python versions Version 1 0 2 of the Distutils includes the changes described in PEP 241 as well as various bugfixes and enhancements It will be available from the Distutils SIG at https www python org community sigs current distutils sig See also PEP 241 Metadata for Python Software Packages Written and implemented by A M Kuchling PEP 243 Module Repository Upload Mechanism Written by Sean Reifschneider this draft PEP describes a proposed mechanism for uploading Python packages to a central server New and Improved Modules Ka Ping Yee contributed two new modules inspect py a module for getting information about live Python code and pydoc py a module for interactively converting docstrings to HTML or text As a bonus Tools scripts pydoc which is now automatically installed uses pydoc py to display documentation given a Python module package or class name For example pydoc xml dom displays the following Python Library Documentation package xml dom in xml NAME xml dom W3C Document Object Model implementation for Python FILE usr local lib python2 1 xml dom __init__ pyc DESCRIPTION The Python mapping of the Document Object Model is documented in the Python Library Reference in the section on the xml dom package This package contains the following modules pydoc also includes a Tk based interactive help browser pydoc quickly becomes addictive try it out Two different modules for unit testing were added to the standard library The doctest module contributed by Tim Peters provides a testing framework based on running embedded examples in docstrings and comparing the results against the expected output PyUnit contributed by Steve Purcell is a unit testing framework inspired by JUnit which was in turn an adaptation of Kent Beck s Smalltalk testing framework See https pyunit sourceforge net for more information about PyUnit The difflib module contains a class SequenceMatcher which compares two sequences and computes the changes required to transform one sequence into the other For example this module can be used to write a tool similar to the Unix diff program and in fact the sample program Tools scripts ndiff py demonstrates how to write such a script curses panel a wrapper for the panel library part of ncurses and of SYSV curses was contributed by Thomas Gellekum The panel library provides windows with the additional feature of depth Windows can be moved higher or lower in the depth ordering and the panel library figures out where panels overlap and which sections are visible The PyXML package has gone through a few releases since Python 2 0 and Python 2 1 includes an updated version of the xml package Some of the noteworthy changes include support for Expat 1 2 and later versions the ability for Expat parsers to handle files in any encoding supported by Python and various bugfixes for SAX DOM and the minidom module Ping also contributed another hook for handling uncaught exceptions sys excepthook can be set to a callable object When an exception isn t caught by any try except blocks the exception will be passed to sys excepthook which can then do whatever it likes At the Ninth Python Conference Ping demonstrated an application for this hook printing an extended traceback that not only lists the stack frames but also lists the function arguments and the local variables for each frame Various functions in the time module such as asctime and localtime require a floating point argument containing the time in seconds since the epoch The most common use of these functions is to work with the current time so the floating poin,en
2205,t argument has been made optional when a value isn t provided the current time will be used For example log file entries usually need a string containing the current time in Python 2 1 time asctime can be used instead of the lengthier time asctime time localtime time time that was previously required This change was proposed and implemented by Thomas Wouters The ftplib module now defaults to retrieving files in passive mode because passive mode is more likely to work from behind a firewall This request came from the Debian bug tracking system since other Debian packages use ftplib to retrieve files and then don t work from behind a firewall It s deemed unlikely that this will cause problems for anyone because Netscape defaults to passive mode and few people complain but if passive mode is unsuitable for your application or network setup call set_pasv 0 on FTP objects to disable passive mode Support for raw socket access has been added to the socket module contributed by Grant Edwards The pstats module now contains a simple interactive statistics browser for displaying timing profiles for Python programs invoked when the module is run as a script Contributed by Eric S Raymond A new implementation dependent function sys _getframe depth has been added to return a given frame object from the current call stack sys _getframe returns the frame at the top of the call stack if the optional integer argument depth is supplied the function returns the frame that is depth calls below the top of the stack For example sys _getframe 1 returns the caller s frame object This function is only present in CPython not in Jython or the NET implementation Use it for debugging and resist the temptation to put it into production code Other Changes and Fixes There were relatively few smaller changes made in Python 2 1 due to the shorter release cycle A search through the CVS change logs turns up 117 patches applied and 136 bugs fixed both figures are likely to be underestimates Some of the more notable changes are A specialized object allocator is now optionally available that should be faster than the system malloc and have less memory overhead The allocator uses C s malloc function to get large pools of memory and then fulfills smaller memory requests from these pools It can be enabled by providing the with pymalloc option to the configure script see Objects obmalloc c for the implementation details Authors of C extension modules should test their code with the object allocator enabled because some incorrect code may break causing core dumps at runtime There are a bunch of memory allocation functions in Python s C API that have previously been just aliases for the C library s malloc and free meaning that if you accidentally called mismatched functions the error wouldn t be noticeable When the object allocator is enabled these functions aren t aliases of malloc and free any more and calling the wrong function to free memory will get you a core dump For example if memory was allocated using PyMem_New it has to be freed using PyMem_Del not free A few modules included with Python fell afoul of this and had to be fixed doubtless there are more third party modules that will have the same problem The object allocator was contributed by Vladimir Marangozov The speed of line oriented file I O has been improved because people often complain about its lack of speed and because it s often been used as a naïve benchmark The readline method of file objects has therefore been rewritten to be much faster The exact amount of the speedup will vary from platform to platform depending on how slow the C library s getc was but is around 66 and potentially much faster on some particular operating systems Tim Peters did much of the benchmarking and coding for this change motivated by a discussion in comp lang python A new module and method for file objects was also added contributed by Jeff Epler The new method xreadlines is similar to the existing xrange built in xreadlines returns an opaque sequence object that only supports being iterated over reading a line on eve,en
2206,ry iteration but not reading the entire file into memory as the existing readlines method does You d use it like this for line in sys stdin xreadlines do something for each line For a fuller discussion of the line I O changes see the python dev summary for January 1 15 2001 at https mail python org pipermail python dev 2001 January A new method popitem was added to dictionaries to enable destructively iterating through the contents of a dictionary this can be faster for large dictionaries because there s no need to construct a list containing all the keys or values D popitem removes a random key value pair from the dictionary D and returns it as a 2 tuple This was implemented mostly by Tim Peters and Guido van Rossum after a suggestion and preliminary patch by Moshe Zadka Modules can now control which names are imported when from module import is used by defining an __all__ attribute containing a list of names that will be imported One common complaint is that if the module imports other modules such as sys or string from module import will add them to the importing module s namespace To fix this simply list the public names in __all__ List public names __all__ Database open A stricter version of this patch was first suggested and implemented by Ben Wolfson but after some python dev discussion a weaker final version was checked in Applying repr to strings previously used octal escapes for non printable characters for example a newline was 012 This was a vestigial trace of Python s C ancestry but today octal is of very little practical use Ka Ping Yee suggested using hex escapes instead of octal ones and using the n t r escapes for the appropriate characters and implemented this new formatting Syntax errors detected at compile time can now raise exceptions containing the filename and line number of the error a pleasant side effect of the compiler reorganization done by Jeremy Hylton C extensions which import other modules have been changed to use PyImport_ImportModule which means that they will use any import hooks that have been installed This is also encouraged for third party extensions that need to import some other module from C code The size of the Unicode character database was shrunk by another 340K thanks to Fredrik Lundh Some new ports were contributed MacOS X by Steven Majewski Cygwin by Jason Tishler RISCOS by Dietmar Schwertberger Unixware 7 by Billy G Allie And there s the usual list of minor bugfixes minor memory leaks docstring edits and other tweaks too lengthy to be worth itemizing see the CVS logs for the full details if you want them Acknowledgements The author would like to thank the following people for offering suggestions on various drafts of this article Graeme Cross David Goodger Jay Graves Michael Hudson Marc André Lemburg Fredrik Lundh Neil Schemenauer Thomas Wouters,en
2207,re Regular expression operations Source code Lib re This module provides regular expression matching operations similar to those found in Perl Both patterns and strings to be searched can be Unicode strings str as well as 8 bit strings bytes However Unicode strings and 8 bit strings cannot be mixed that is you cannot match a Unicode string with a bytes pattern or vice versa similarly when asking for a substitution the replacement string must be of the same type as both the pattern and the search string Regular expressions use the backslash character to indicate special forms or to allow special characters to be used without invoking their special meaning This collides with Python s usage of the same character for the same purpose in string literals for example to match a literal backslash one might have to write as the pattern string because the regular expression must be and each backslash must be expressed as inside a regular Python string literal Also please note that any invalid escape sequences in Python s usage of the backslash in string literals now generate a SyntaxWarning and in the future this will become a SyntaxError This behaviour will happen even if it is a valid escape sequence for a regular expression The solution is to use Python s raw string notation for regular expression patterns backslashes are not handled in any special way in a string literal prefixed with r So r n is a two character string containing and n while n is a one character string containing a newline Usually patterns will be expressed in Python code using this raw string notation It is important to note that most regular expression operations are available as module level functions and methods on compiled regular expressions The functions are shortcuts that don t require you to compile a regex object first but miss some fine tuning parameters See also The third party regex module which has an API compatible with the standard library re module but offers additional functionality and a more thorough Unicode support Regular Expression Syntax A regular expression or RE specifies a set of strings that matches it the functions in this module let you check if a particular string matches a given regular expression or if a given regular expression matches a particular string which comes down to the same thing Regular expressions can be concatenated to form new regular expressions if A and B are both regular expressions then AB is also a regular expression In general if a string p matches A and another string q matches B the string pq will match AB This holds unless A or B contain low precedence operations boundary conditions between A and B or have numbered group references Thus complex expressions can easily be constructed from simpler primitive expressions like the ones described here For details of the theory and implementation of regular expressions consult the Friedl book Frie09 or almost any textbook about compiler construction A brief explanation of the format of regular expressions follows For further information and a gentler presentation consult the Regular Expression HOWTO Regular expressions can contain both special and ordinary characters Most ordinary characters like A a or 0 are the simplest regular expressions they simply match themselves You can concatenate ordinary characters so last matches the string last In the rest of this section we ll write RE s in this special style usually without quotes and strings to be matched in single quotes Some characters like or are special Special characters either stand for classes of ordinary characters or affect how the regular expressions around them are interpreted Repetition operators or quantifiers m n etc cannot be directly nested This avoids ambiguity with the non greedy modifier suffix and with other modifiers in other implementations To apply a second repetition to an inner repetition parentheses may be used For example the expression a 6 matches any multiple of six a characters The special characters are Dot In the default mode this matches any character except a newline If the DOTAL,en
2208,L flag has been specified this matches any character including a newline Caret Matches the start of the string and in MULTILINE mode also matches immediately after each newline Matches the end of the string or just before the newline at the end of the string and in MULTILINE mode also matches before a newline foo matches both foo and foobar while the regular expression foo matches only foo More interestingly searching for foo in foo1 nfoo2 n matches foo2 normally but foo1 in MULTILINE mode searching for a single in foo n will find two empty matches one just before the newline and one at the end of the string Causes the resulting RE to match 0 or more repetitions of the preceding RE as many repetitions as are possible ab will match a ab or a followed by any number of b s Causes the resulting RE to match 1 or more repetitions of the preceding RE ab will match a followed by any non zero number of b s it will not match just a Causes the resulting RE to match 0 or 1 repetitions of the preceding RE ab will match either a or ab The and quantifiers are all greedy they match as much text as possible Sometimes this behaviour isn t desired if the RE is matched against a b c it will match the entire string and not just a Adding after the quantifier makes it perform the match in non greedy or minimal fashion as few characters as possible will be matched Using the RE will match only a Like the and quantifiers those where is appended also match as many times as possible However unlike the true greedy quantifiers these do not allow back tracking when the expression following it fails to match These are known as possessive quantifiers For example a a will match aaaa because the a will match all 4 a s but when the final a is encountered the expression is backtracked so that in the end the a ends up matching 3 a s total and the fourth a is matched by the final a However when a a is used to match aaaa the a will match all 4 a but when the final a fails to find any more characters to match the expression cannot be backtracked and will thus fail to match x x and x are equivalent to x x and x correspondingly New in version 3 11 m Specifies that exactly m copies of the previous RE should be matched fewer matches cause the entire RE not to match For example a 6 will match exactly six a characters but not five m n Causes the resulting RE to match from m to n repetitions of the preceding RE attempting to match as many repetitions as possible For example a 3 5 will match from 3 to 5 a characters Omitting m specifies a lower bound of zero and omitting n specifies an infinite upper bound As an example a 4 b will match aaaab or a thousand a characters followed by a b but not aaab The comma may not be omitted or the modifier would be confused with the previously described form m n Causes the resulting RE to match from m to n repetitions of the preceding RE attempting to match as few repetitions as possible This is the non greedy version of the previous quantifier For example on the 6 character string aaaaaa a 3 5 will match 5 a characters while a 3 5 will only match 3 characters m n Causes the resulting RE to match from m to n repetitions of the preceding RE attempting to match as many repetitions as possible without establishing any backtracking points This is the possessive version of the quantifier above For example on the 6 character string aaaaaa a 3 5 aa attempt to match 5 a characters then requiring 2 more a s will need more characters than available and thus fail while a 3 5 aa will match with a 3 5 capturing 5 then 4 a s by backtracking and then the final 2 a s are matched by the final aa in the pattern x m n is equivalent to x m n New in version 3 11 Either escapes special characters permitting you to match characters like and so forth or signals a special sequence special sequences are discussed below If you re not using a raw string to express the pattern remember that Python also uses the backslash as an escape sequence in string literals if the escape sequence isn t recognized by Python s parser the backslash and subsequent character are ,en
2209,included in the resulting string However if Python would recognize the resulting sequence the backslash should be repeated twice This is complicated and hard to understand so it s highly recommended that you use raw strings for all but the simplest expressions Used to indicate a set of characters In a set Characters can be listed individually e g amk will match a m or k Ranges of characters can be indicated by giving two characters and separating them by a for example a z will match any lowercase ASCII letter 0 5 0 9 will match all the two digits numbers from 00 to 59 and 0 9A Fa f will match any hexadecimal digit If is escaped e g a z or if it s placed as the first or last character e g a or a it will match a literal Special characters lose their special meaning inside sets For example will match any of the literal characters or Character classes such as w or S defined below are also accepted inside a set although the characters they match depend on the flags used Characters that are not within a range can be matched by complementing the set If the first character of the set is all the characters that are not in the set will be matched For example 5 will match any character except 5 and will match any character except has no special meaning if it s not the first character in the set To match a literal inside a set precede it with a backslash or place it at the beginning of the set For example both and will match a right bracket as well as left bracket braces and parentheses Support of nested sets and set operations as in Unicode Technical Standard 18 might be added in the future This would change the syntax so to facilitate this change a FutureWarning will be raised in ambiguous cases for the time being That includes sets starting with a literal or containing literal character sequences and To avoid a warning escape them with a backslash Changed in version 3 7 FutureWarning is raised if a character set contains constructs that will change semantically in the future A B where A and B can be arbitrary REs creates a regular expression that will match either A or B An arbitrary number of REs can be separated by the in this way This can be used inside groups see below as well As the target string is scanned REs separated by are tried from left to right When one pattern completely matches that branch is accepted This means that once A matches B will not be tested further even if it would produce a longer overall match In other words the operator is never greedy To match a literal use or enclose it inside a character class as in Matches whatever regular expression is inside the parentheses and indicates the start and end of a group the contents of a group can be retrieved after a match has been performed and can be matched later in the string with the number special sequence described below To match the literals or use or or enclose them inside a character class This is an extension notation a following a is not meaningful otherwise The first character after the determines what the meaning and further syntax of the construct is Extensions usually do not create a new group P name is the only exception to this rule Following are the currently supported extensions aiLmsux One or more letters from the set a i L m s u x The group matches the empty string the letters set the corresponding flags for the entire regular expression re A ASCII only matching re I ignore case re L locale dependent re M multi line re S dot matches all re U Unicode matching re X verbose The flags are described in Module Contents This is useful if you wish to include the flags as part of the regular expression instead of passing a flag argument to the re compile function Flags should be used first in the expression string Changed in version 3 11 This construction can only be used at the start of the expression A non capturing version of regular parentheses Matches whatever regular expression is inside the parentheses but the substring matched by the group cannot be retrieved after performing a match or referenced later in the pattern aiLmsux imsx Zero or more,en
2210, letters from the set a i L m s u x optionally followed by followed by one or more letters from the i m s x The letters set or remove the corresponding flags for the part of the expression re A ASCII only matching re I ignore case re L locale dependent re M multi line re S dot matches all re U Unicode matching re X verbose The flags are described in Module Contents The letters a L and u are mutually exclusive when used as inline flags so they can t be combined or follow Instead when one of them appears in an inline group it overrides the matching mode in the enclosing group In Unicode patterns a switches to ASCII only matching and u switches to Unicode matching default In bytes patterns L switches to locale dependent matching and a switches to ASCII only matching default This override is only in effect for the narrow inline group and the original matching mode is restored outside of the group New in version 3 6 Changed in version 3 7 The letters a L and u also can be used in a group Attempts to match as if it was a separate regular expression and if successful continues to match the rest of the pattern following it If the subsequent pattern fails to match the stack can only be unwound to a point before the because once exited the expression known as an atomic group has thrown away all stack points within itself Thus would never match anything because first the would match all characters possible then having nothing left to match the final would fail to match Since there are no stack points saved in the Atomic Group and there is no stack point before it the entire expression would thus fail to match New in version 3 11 P name Similar to regular parentheses but the substring matched by the group is accessible via the symbolic group name name Group names must be valid Python identifiers and in bytes patterns they can only contain bytes in the ASCII range Each group name must be defined only once within a regular expression A symbolic group is also a numbered group just as if the group were not named Named groups can be referenced in three contexts If the pattern is P quote P quote i e matching a string quoted with either single or double quotes Context of reference to group quote Ways to reference it in the same pattern itself P quote as shown 1 when processing match object m m group quote m end quote etc in a string passed to the repl g quote g 1 1 argument of re sub Changed in version 3 12 In bytes patterns group name can only contain bytes in the ASCII range b x00 b x7f P name A backreference to a named group it matches whatever text was matched by the earlier group named name A comment the contents of the parentheses are simply ignored Matches if matches next but doesn t consume any of the string This is called a lookahead assertion For example Isaac Asimov will match Isaac only if it s followed by Asimov Matches if doesn t match next This is a negative lookahead assertion For example Isaac Asimov will match Isaac only if it s not followed by Asimov Matches if the current position in the string is preceded by a match for that ends at the current position This is called a positive lookbehind assertion abc def will find a match in abcdef since the lookbehind will back up 3 characters and check if the contained pattern matches The contained pattern must only match strings of some fixed length meaning that abc or a b are allowed but a and a 3 4 are not Note that patterns which start with positive lookbehind assertions will not match at the beginning of the string being searched you will most likely want to use the search function rather than the match function import re m re search abc def abcdef m group 0 def This example looks for a word following a hyphen m re search r w spam egg m group 0 egg Changed in version 3 5 Added support for group references of fixed length Matches if the current position in the string is not preceded by a match for This is called a negative lookbehind assertion Similar to positive lookbehind assertions the contained pattern must only match strings of some fixed length Patterns which start with ,en
2211,negative lookbehind assertions may match at the beginning of the string being searched id name yes pattern no pattern Will try to match with yes pattern if the group with given id or name exists and with no pattern if it doesn t no pattern is optional and can be omitted For example w w w 1 is a poor email matching pattern which will match with user host com as well as user host com but not with user host com nor user host com Changed in version 3 12 Group id can only contain ASCII digits In bytes patterns group name can only contain bytes in the ASCII range b x00 b x7f The special sequences consist of and a character from the list below If the ordinary character is not an ASCII digit or an ASCII letter then the resulting RE will match the second character For example matches the character number Matches the contents of the group of the same number Groups are numbered starting from 1 For example 1 matches the the or 55 55 but not thethe note the space after the group This special sequence can only be used to match one of the first 99 groups If the first digit of number is 0 or number is 3 octal digits long it will not be interpreted as a group match but as the character with octal value number Inside the and of a character class all numeric escapes are treated as characters A Matches only at the start of the string b Matches the empty string but only at the beginning or end of a word A word is defined as a sequence of word characters Note that formally b is defined as the boundary between a w and a W character or vice versa or between w and the beginning or end of the string This means that r bat b matches at at at and as at ay but not attempt or atlas The default word characters in Unicode str patterns are Unicode alphanumerics and the underscore but this can be changed by using the ASCII flag Word boundaries are determined by the current locale if the LOCALE flag is used Note Inside a character range b represents the backspace character for compatibility with Python s string literals B Matches the empty string but only when it is not at the beginning or end of a word This means that r at B matches athens atom attorney but not at at or at B is the opposite of b so word characters in Unicode str patterns are Unicode alphanumerics or the underscore although this can be changed by using the ASCII flag Word boundaries are determined by the current locale if the LOCALE flag is used d For Unicode str patterns Matches any Unicode decimal digit that is any character in Unicode character category Nd This includes 0 9 and also many other digit characters Matches 0 9 if the ASCII flag is used For 8 bit bytes patterns Matches any decimal digit in the ASCII character set this is equivalent to 0 9 D Matches any character which is not a decimal digit This is the opposite of d Matches 0 9 if the ASCII flag is used s For Unicode str patterns Matches Unicode whitespace characters which includes t n r f v and also many other characters for example the non breaking spaces mandated by typography rules in many languages Matches t n r f v if the ASCII flag is used For 8 bit bytes patterns Matches characters considered whitespace in the ASCII character set this is equivalent to t n r f v S Matches any character which is not a whitespace character This is the opposite of s Matches t n r f v if the ASCII flag is used w For Unicode str patterns Matches Unicode word characters this includes all Unicode alphanumeric characters as defined by str isalnum as well as the underscore _ Matches a zA Z0 9_ if the ASCII flag is used For 8 bit bytes patterns Matches characters considered alphanumeric in the ASCII character set this is equivalent to a zA Z0 9_ If the LOCALE flag is used matches characters considered alphanumeric in the current locale and the underscore W Matches any character which is not a word character This is the opposite of w By default matches non underscore _ characters for which str isalnum returns False Matches a zA Z0 9_ if the ASCII flag is used If the LOCALE flag is used matches characters which are neither alphanumeric in the curr,en
2212,ent locale nor the underscore Z Matches only at the end of the string Most of the escape sequences supported by Python string literals are also accepted by the regular expression parser a b f n N r t u U v x Note that b is used to represent word boundaries and means backspace only inside character classes u U and N escape sequences are only recognized in Unicode str patterns In bytes patterns they are errors Unknown escapes of ASCII letters are reserved for future use and treated as errors Octal escapes are included in a limited form If the first digit is a 0 or if there are three octal digits it is considered an octal escape Otherwise it is a group reference As for string literals octal escapes are always at most three digits in length Changed in version 3 3 The u and U escape sequences have been added Changed in version 3 6 Unknown escapes consisting of and an ASCII letter now are errors Changed in version 3 8 The N name escape sequence has been added As in string literals it expands to the named Unicode character e g N EM DASH Module Contents The module defines several functions constants and an exception Some of the functions are simplified versions of the full featured methods for compiled regular expressions Most non trivial applications always use the compiled form Flags Changed in version 3 6 Flag constants are now instances of RegexFlag which is a subclass of enum IntFlag class re RegexFlag An enum IntFlag class containing the regex options listed below New in version 3 11 added to __all__ re A re ASCII Make w W b B d D s and S perform ASCII only matching instead of full Unicode matching This is only meaningful for Unicode str patterns and is ignored for bytes patterns Corresponds to the inline flag a Note The U flag still exists for backward compatibility but is redundant in Python 3 since matches are Unicode by default for str patterns and Unicode matching isn t allowed for bytes patterns UNICODE and the inline flag u are similarly redundant re DEBUG Display debug information about compiled expression No corresponding inline flag re I re IGNORECASE Perform case insensitive matching expressions like A Z will also match lowercase letters Full Unicode matching such as Ü matching ü also works unless the ASCII flag is used to disable non ASCII matches The current locale does not change the effect of this flag unless the LOCALE flag is also used Corresponds to the inline flag i Note that when the Unicode patterns a z or A Z are used in combination with the IGNORECASE flag they will match the 52 ASCII letters and 4 additional non ASCII letters İ U 0130 Latin capital letter I with dot above ı U 0131 Latin small letter dotless i ſ U 017F Latin small letter long s and K U 212A Kelvin sign If the ASCII flag is used only letters a to z and A to Z are matched re L re LOCALE Make w W b B and case insensitive matching dependent on the current locale This flag can be used only with bytes patterns Corresponds to the inline flag L Warning This flag is discouraged consider Unicode matching instead The locale mechanism is very unreliable as it only handles one culture at a time and only works with 8 bit locales Unicode matching is enabled by default for Unicode str patterns and it is able to handle different locales and languages Changed in version 3 6 LOCALE can be used only with bytes patterns and is not compatible with ASCII Changed in version 3 7 Compiled regular expression objects with the LOCALE flag no longer depend on the locale at compile time Only the locale at matching time affects the result of matching re M re MULTILINE When specified the pattern character matches at the beginning of the string and at the beginning of each line immediately following each newline and the pattern character matches at the end of the string and at the end of each line immediately preceding each newline By default matches only at the beginning of the string and only at the end of the string and immediately before the newline if any at the end of the string Corresponds to the inline flag m re NOFLAG Indicates no flag being applied the valu,en
2213,e is 0 This flag may be used as a default value for a function keyword argument or as a base value that will be conditionally ORed with other flags Example of use as a default value def myfunc text flag re NOFLAG return re match text flag New in version 3 11 re S re DOTALL Make the special character match any character at all including a newline without this flag will match anything except a newline Corresponds to the inline flag s re U re UNICODE In Python 3 Unicode characters are matched by default for str patterns This flag is therefore redundant with no effect and is only kept for backward compatibility See ASCII to restrict matching to ASCII characters instead re X re VERBOSE This flag allows you to write regular expressions that look nicer and are more readable by allowing you to visually separate logical sections of the pattern and add comments Whitespace within the pattern is ignored except when in a character class or when preceded by an unescaped backslash or within tokens like or P For example and are not allowed When a line contains a that is not in a character class and is not preceded by an unescaped backslash all characters from the leftmost such through the end of the line are ignored This means that the two following regular expression objects that match a decimal number are functionally equal a re compile r d the integral part the decimal point d some fractional digits re X b re compile r d d Corresponds to the inline flag x Functions re compile pattern flags 0 Compile a regular expression pattern into a regular expression object which can be used for matching using its match search and other methods described below The expression s behaviour can be modified by specifying a flags value Values can be any of the flags variables combined using bitwise OR the operator The sequence prog re compile pattern result prog match string is equivalent to result re match pattern string but using re compile and saving the resulting regular expression object for reuse is more efficient when the expression will be used several times in a single program Note The compiled versions of the most recent patterns passed to re compile and the module level matching functions are cached so programs that use only a few regular expressions at a time needn t worry about compiling regular expressions re search pattern string flags 0 Scan through string looking for the first location where the regular expression pattern produces a match and return a corresponding Match Return None if no position in the string matches the pattern note that this is different from finding a zero length match at some point in the string re match pattern string flags 0 If zero or more characters at the beginning of string match the regular expression pattern return a corresponding Match Return None if the string does not match the pattern note that this is different from a zero length match Note that even in MULTILINE mode re match will only match at the beginning of the string and not at the beginning of each line If you want to locate a match anywhere in string use search instead see also search vs match re fullmatch pattern string flags 0 If the whole string matches the regular expression pattern return a corresponding Match Return None if the string does not match the pattern note that this is different from a zero length match New in version 3 4 re split pattern string maxsplit 0 flags 0 Split string by the occurrences of pattern If capturing parentheses are used in pattern then the text of all groups in the pattern are also returned as part of the resulting list If maxsplit is nonzero at most maxsplit splits occur and the remainder of the string is returned as the final element of the list re split r W Words words words Words words words re split r W Words words words Words words words re split r W Words words words 1 Words words words re split a f 0a3B9 flags re IGNORECASE 0 3 9 If there are capturing groups in the separator and it matches at the start of the string the result will start with an empty string The same holds for the end of the string ,en
2214,re split r W words words words words That way separator components are always found at the same relative indices within the result list Empty matches for the pattern split the string only when not adjacent to a previous empty match re split r b Words words words Words words words re split r W words w o r d s re split r W words w o r d s Changed in version 3 1 Added the optional flags argument Changed in version 3 7 Added support of splitting on a pattern that could match an empty string re findall pattern string flags 0 Return all non overlapping matches of pattern in string as a list of strings or tuples The string is scanned left to right and matches are returned in the order found Empty matches are included in the result The result depends on the number of capturing groups in the pattern If there are no groups return a list of strings matching the whole pattern If there is exactly one group return a list of strings matching that group If multiple groups are present return a list of tuples of strings matching the groups Non capturing groups do not affect the form of the result re findall r bf a z which foot or hand fell fastest foot fell fastest re findall r w d set width 20 and height 10 width 20 height 10 Changed in version 3 7 Non empty matches can now start just after a previous empty match re finditer pattern string flags 0 Return an iterator yielding Match objects over all non overlapping matches for the RE pattern in string The string is scanned left to right and matches are returned in the order found Empty matches are included in the result Changed in version 3 7 Non empty matches can now start just after a previous empty match re sub pattern repl string count 0 flags 0 Return the string obtained by replacing the leftmost non overlapping occurrences of pattern in string by the replacement repl If the pattern isn t found string is returned unchanged repl can be a string or a function if it is a string any backslash escapes in it are processed That is n is converted to a single newline character r is converted to a carriage return and so forth Unknown escapes of ASCII letters are reserved for future use and treated as errors Other unknown escapes such as are left alone Backreferences such as 6 are replaced with the substring matched by group 6 in the pattern For example re sub r def s a zA Z_ a zA Z_0 9 s s r static PyObject npy_ 1 void n def myfunc static PyObject npy_myfunc void n If repl is a function it is called for every non overlapping occurrence of pattern The function takes a single Match argument and returns the replacement string For example def dashrepl matchobj if matchobj group 0 return else return re sub 1 2 dashrepl pro gram files pro gram files re sub r sAND s Baked Beans And Spam flags re IGNORECASE Baked Beans Spam The pattern may be a string or a Pattern The optional argument count is the maximum number of pattern occurrences to be replaced count must be a non negative integer If omitted or zero all occurrences will be replaced Empty matches for the pattern are replaced only when not adjacent to a previous empty match so sub x abxd returns a b d In string type repl arguments in addition to the character escapes and backreferences described above g name will use the substring matched by the group named name as defined by the P name syntax g number uses the corresponding group number g 2 is therefore equivalent to 2 but isn t ambiguous in a replacement such as g 2 0 20 would be interpreted as a reference to group 20 not a reference to group 2 followed by the literal character 0 The backreference g 0 substitutes in the entire substring matched by the RE Changed in version 3 1 Added the optional flags argument Changed in version 3 5 Unmatched groups are replaced with an empty string Changed in version 3 6 Unknown escapes in pattern consisting of and an ASCII letter now are errors Changed in version 3 7 Unknown escapes in repl consisting of and an ASCII letter now are errors Changed in version 3 7 Empty matches for the pattern are replaced when adjacent to a previous non empty match Changed in ver,en
2215,sion 3 12 Group id can only contain ASCII digits In bytes replacement strings group name can only contain bytes in the ASCII range b x00 b x7f re subn pattern repl string count 0 flags 0 Perform the same operation as sub but return a tuple new_string number_of_subs_made Changed in version 3 1 Added the optional flags argument Changed in version 3 5 Unmatched groups are replaced with an empty string re escape pattern Escape special characters in pattern This is useful if you want to match an arbitrary literal string that may have regular expression metacharacters in it For example print re escape https www python org https www python org legal_chars string ascii_lowercase string digits _ print s re escape legal_chars abcdefghijklmnopqrstuvwxyz0123456789 _ operators print join map re escape sorted operators reverse True This function must not be used for the replacement string in sub and subn only backslashes should be escaped For example digits_re r d sample usr sbin sendmail 0 errors 12 warnings print re sub digits_re digits_re replace r sample usr sbin sendmail d errors d warnings Changed in version 3 3 The _ character is no longer escaped Changed in version 3 7 Only characters that can have special meaning in a regular expression are escaped As a result and are no longer escaped re purge Clear the regular expression cache Exceptions exception re error msg pattern None pos None Exception raised when a string passed to one of the functions here is not a valid regular expression for example it might contain unmatched parentheses or when some other error occurs during compilation or matching It is never an error if a string contains no match for a pattern The error instance has the following additional attributes msg The unformatted error message pattern The regular expression pattern pos The index in pattern where compilation failed may be None lineno The line corresponding to pos may be None colno The column corresponding to pos may be None Changed in version 3 5 Added additional attributes Regular Expression Objects class re Pattern Compiled regular expression object returned by re compile Changed in version 3 9 re Pattern supports to indicate a Unicode str or bytes pattern See Generic Alias Type Pattern search string pos endpos Scan through string looking for the first location where this regular expression produces a match and return a corresponding Match Return None if no position in the string matches the pattern note that this is different from finding a zero length match at some point in the string The optional second parameter pos gives an index in the string where the search is to start it defaults to 0 This is not completely equivalent to slicing the string the pattern character matches at the real beginning of the string and at positions just after a newline but not necessarily at the index where the search is to start The optional parameter endpos limits how far the string will be searched it will be as if the string is endpos characters long so only the characters from pos to endpos 1 will be searched for a match If endpos is less than pos no match will be found otherwise if rx is a compiled regular expression object rx search string 0 50 is equivalent to rx search string 50 0 pattern re compile d pattern search dog Match at index 0 re Match object span 0 1 match d pattern search dog 1 No match search doesn t include the d Pattern match string pos endpos If zero or more characters at the beginning of string match this regular expression return a corresponding Match Return None if the string does not match the pattern note that this is different from a zero length match The optional pos and endpos parameters have the same meaning as for the search method pattern re compile o pattern match dog No match as o is not at the start of dog pattern match dog 1 Match as o is the 2nd character of dog re Match object span 1 2 match o If you want to locate a match anywhere in string use search instead see also search vs match Pattern fullmatch string pos endpos If the whole string matches this regular expression return a,en
2216, corresponding Match Return None if the string does not match the pattern note that this is different from a zero length match The optional pos and endpos parameters have the same meaning as for the search method pattern re compile o gh pattern fullmatch dog No match as o is not at the start of dog pattern fullmatch ogre No match as not the full string matches pattern fullmatch doggie 1 3 Matches within given limits re Match object span 1 3 match og New in version 3 4 Pattern split string maxsplit 0 Identical to the split function using the compiled pattern Pattern findall string pos endpos Similar to the findall function using the compiled pattern but also accepts optional pos and endpos parameters that limit the search region like for search Pattern finditer string pos endpos Similar to the finditer function using the compiled pattern but also accepts optional pos and endpos parameters that limit the search region like for search Pattern sub repl string count 0 Identical to the sub function using the compiled pattern Pattern subn repl string count 0 Identical to the subn function using the compiled pattern Pattern flags The regex matching flags This is a combination of the flags given to compile any inline flags in the pattern and implicit flags such as UNICODE if the pattern is a Unicode string Pattern groups The number of capturing groups in the pattern Pattern groupindex A dictionary mapping any symbolic group names defined by P id to group numbers The dictionary is empty if no symbolic groups were used in the pattern Pattern pattern The pattern string from which the pattern object was compiled Changed in version 3 7 Added support of copy copy and copy deepcopy Compiled regular expression objects are considered atomic Match Objects Match objects always have a boolean value of True Since match and search return None when there is no match you can test whether there was a match with a simple if statement match re search pattern string if match process match class re Match Match object returned by successful match es and search es Changed in version 3 9 re Match supports to indicate a Unicode str or bytes match See Generic Alias Type Match expand template Return the string obtained by doing backslash substitution on the template string template as done by the sub method Escapes such as n are converted to the appropriate characters and numeric backreferences 1 2 and named backreferences g 1 g name are replaced by the contents of the corresponding group The backreference g 0 will be replaced by the entire match Changed in version 3 5 Unmatched groups are replaced with an empty string Match group group1 Returns one or more subgroups of the match If there is a single argument the result is a single string if there are multiple arguments the result is a tuple with one item per argument Without arguments group1 defaults to zero the whole match is returned If a groupN argument is zero the corresponding return value is the entire matching string if it is in the inclusive range 1 99 it is the string matching the corresponding parenthesized group If a group number is negative or larger than the number of groups defined in the pattern an IndexError exception is raised If a group is contained in a part of the pattern that did not match the corresponding result is None If a group is contained in a part of the pattern that matched multiple times the last match is returned m re match r w w Isaac Newton physicist m group 0 The entire match Isaac Newton m group 1 The first parenthesized subgroup Isaac m group 2 The second parenthesized subgroup Newton m group 1 2 Multiple arguments give us a tuple Isaac Newton If the regular expression uses the P name syntax the groupN arguments may also be strings identifying groups by their group name If a string argument is not used as a group name in the pattern an IndexError exception is raised A moderately complicated example m re match r P first_name w P last_name w Malcolm Reynolds m group first_name Malcolm m group last_name Reynolds Named groups can also be referred to by their index m group ,en
2217,1 Malcolm m group 2 Reynolds If a group matches multiple times only the last match is accessible m re match r a1b2c3 Matches 3 times m group 1 Returns only the last match c3 Match __getitem__ g This is identical to m group g This allows easier access to an individual group from a match m re match r w w Isaac Newton physicist m 0 The entire match Isaac Newton m 1 The first parenthesized subgroup Isaac m 2 The second parenthesized subgroup Newton Named groups are supported as well m re match r P first_name w P last_name w Isaac Newton m first_name Isaac m last_name Newton New in version 3 6 Match groups default None Return a tuple containing all the subgroups of the match from 1 up to however many groups are in the pattern The default argument is used for groups that did not participate in the match it defaults to None For example m re match r d d 24 1632 m groups 24 1632 If we make the decimal place and everything after it optional not all groups might participate in the match These groups will default to None unless the default argument is given m re match r d d 24 m groups Second group defaults to None 24 None m groups 0 Now the second group defaults to 0 24 0 Match groupdict default None Return a dictionary containing all the named subgroups of the match keyed by the subgroup name The default argument is used for groups that did not participate in the match it defaults to None For example m re match r P first_name w P last_name w Malcolm Reynolds m groupdict first_name Malcolm last_name Reynolds Match start group Match end group Return the indices of the start and end of the substring matched by group group defaults to zero meaning the whole matched substring Return 1 if group exists but did not contribute to the match For a match object m and a group g that did contribute to the match the substring matched by group g equivalent to m group g is m string m start g m end g Note that m start group will equal m end group if group matched a null string For example after m re search b c cba m start 0 is 1 m end 0 is 2 m start 1 and m end 1 are both 2 and m start 2 raises an IndexError exception An example that will remove remove_this from email addresses email tony tiremove_thisger net m re search remove_this email email m start email m end tony tiger net Match span group For a match m return the 2 tuple m start group m end group Note that if group did not contribute to the match this is 1 1 group defaults to zero the entire match Match pos The value of pos which was passed to the search or match method of a regex object This is the index into the string at which the RE engine started looking for a match Match endpos The value of endpos which was passed to the search or match method of a regex object This is the index into the string beyond which the RE engine will not go Match lastindex The integer index of the last matched capturing group or None if no group was matched at all For example the expressions a b a b and ab will have lastindex 1 if applied to the string ab while the expression a b will have lastindex 2 if applied to the same string Match lastgroup The name of the last matched capturing group or None if the group didn t have a name or if no group was matched at all Match re The regular expression object whose match or search method produced this match instance Match string The string passed to match or search Changed in version 3 7 Added support of copy copy and copy deepcopy Match objects are considered atomic Regular Expression Examples Checking for a Pair In this example we ll use the following helper function to display match objects a little more gracefully def displaymatch match if match is None return None return Match r groups r match group match groups Suppose you are writing a poker program where a player s hand is represented as a 5 character string with each character representing a card a for ace k for king q for queen j for jack t for 10 and 2 through 9 representing the card with that value To see if a given string is a valid hand one could do the following valid re compile r a2 9tjqk 5 displaymatc,en
2218,h valid match akt5q Valid Match akt5q groups displaymatch valid match akt5e Invalid displaymatch valid match akt Invalid displaymatch valid match 727ak Valid Match 727ak groups That last hand 727ak contained a pair or two of the same valued cards To match this with a regular expression one could use backreferences as such pair re compile r 1 displaymatch pair match 717ak Pair of 7s Match 717 groups 7 displaymatch pair match 718ak No pairs displaymatch pair match 354aa Pair of aces Match 354aa groups a To find out what card the pair consists of one could use the group method of the match object in the following manner pair re compile r 1 pair match 717ak group 1 7 Error because re match returns None which doesn t have a group method pair match 718ak group 1 Traceback most recent call last File pyshell 23 line 1 in module re match r 1 718ak group 1 AttributeError NoneType object has no attribute group pair match 354aa group 1 a Simulating scanf Python does not currently have an equivalent to scanf Regular expressions are generally more powerful though also more verbose than scanf format strings The table below offers some more or less equivalent mappings between scanf format tokens and regular expressions scanf Token Regular Expression c 5c 5 d d e E f g d d d eE d i 0 xX dA Fa f 0 0 7 d o 0 7 s S u d x X 0 xX dA Fa f To extract the filename and numbers from a string like usr sbin sendmail 0 errors 4 warnings you would use a scanf format like s d errors d warnings The equivalent regular expression would be S d errors d warnings search vs match Python offers different primitive operations based on regular expressions re match checks for a match only at the beginning of the string re search checks for a match anywhere in the string this is what Perl does by default re fullmatch checks for entire string to be a match For example re match c abcdef No match re search c abcdef Match re Match object span 2 3 match c re fullmatch p n python Match re Match object span 0 6 match python re fullmatch r n python No match Regular expressions beginning with can be used with search to restrict the match at the beginning of the string re match c abcdef No match re search c abcdef No match re search a abcdef Match re Match object span 0 1 match a Note however that in MULTILINE mode match only matches at the beginning of the string whereas using search with a regular expression beginning with will match at the beginning of each line re match X A nB nX re MULTILINE No match re search X A nB nX re MULTILINE Match re Match object span 4 5 match X Making a Phonebook split splits a string into a list delimited by the passed pattern The method is invaluable for converting textual data into data structures that can be easily read and modified by Python as demonstrated in the following example that creates a phonebook First here is the input Normally it may come from a file here we are using triple quoted string syntax text Ross McFluff 834 345 1254 155 Elm Street Ronald Heathmore 892 345 3428 436 Finley Avenue Frank Burger 925 541 7625 662 South Dogwood Way Heather Albrecht 548 326 4584 919 Park Place The entries are separated by one or more newlines Now we convert the string into a list with each nonempty line having its own entry entries re split n text entries Ross McFluff 834 345 1254 155 Elm Street Ronald Heathmore 892 345 3428 436 Finley Avenue Frank Burger 925 541 7625 662 South Dogwood Way Heather Albrecht 548 326 4584 919 Park Place Finally split each entry into a list with first name last name telephone number and address We use the maxsplit parameter of split because the address has spaces our splitting pattern in it re split entry 3 for entry in entries Ross McFluff 834 345 1254 155 Elm Street Ronald Heathmore 892 345 3428 436 Finley Avenue Frank Burger 925 541 7625 662 South Dogwood Way Heather Albrecht 548 326 4584 919 Park Place The pattern matches the colon after the last name so that it does not occur in the result list With a maxsplit of 4 we could separate the house number from the street name re split entry 4 for entry in entrie,en
2219,s Ross McFluff 834 345 1254 155 Elm Street Ronald Heathmore 892 345 3428 436 Finley Avenue Frank Burger 925 541 7625 662 South Dogwood Way Heather Albrecht 548 326 4584 919 Park Place Text Munging sub replaces every occurrence of a pattern with a string or the result of a function This example demonstrates using sub with a function to munge text or randomize the order of all the characters in each word of a sentence except for the first and last characters def repl m inner_word list m group 2 random shuffle inner_word return m group 1 join inner_word m group 3 text Professor Abdolmalek please report your absences promptly re sub r w w w repl text Poefsrosr Aealmlobdk pslaee reorpt your abnseces plmrptoy re sub r w w w repl text Pofsroser Aodlambelk plasee reoprt yuor asnebces potlmrpy Finding all Adverbs findall matches all occurrences of a pattern not just the first one as search does For example if a writer wanted to find all of the adverbs in some text they might use findall in the following manner text He was carefully disguised but captured quickly by police re findall r w ly b text carefully quickly Finding all Adverbs and their Positions If one wants more information about all matches of a pattern than the matched text finditer is useful as it provides Match objects instead of strings Continuing with the previous example if a writer wanted to find all of the adverbs and their positions in some text they would use finditer in the following manner text He was carefully disguised but captured quickly by police for m in re finditer r w ly b text print 02d 02d s m start m end m group 0 07 16 carefully 40 47 quickly Raw String Notation Raw string notation r text keeps regular expressions sane Without it every backslash in a regular expression would have to be prefixed with another one to escape it For example the two following lines of code are functionally identical re match r W 1 W ff re Match object span 0 4 match ff re match W 1 W ff re Match object span 0 4 match ff When one wants to match a literal backslash it must be escaped in the regular expression With raw string notation this means r Without raw string notation one must use making the following lines of code functionally identical re match r r re Match object span 0 1 match re match r re Match object span 0 1 match Writing a Tokenizer A tokenizer or scanner analyzes a string to categorize groups of characters This is a useful first step in writing a compiler or interpreter The text categories are specified with regular expressions The technique is to combine those into a single master regular expression and to loop over successive matches from typing import NamedTuple import re class Token NamedTuple type str value str line int column int def tokenize code keywords IF THEN ENDIF FOR NEXT GOSUB RETURN token_specification NUMBER r d d Integer or decimal number ASSIGN r Assignment operator END r Statement terminator ID r A Za z Identifiers OP r Arithmetic operators NEWLINE r n Line endings SKIP r t Skip over spaces and tabs MISMATCH r Any other character tok_regex join P s s pair for pair in token_specification line_num 1 line_start 0 for mo in re finditer tok_regex code kind mo lastgroup value mo group column mo start line_start if kind NUMBER value float value if in value else int value elif kind ID and value in keywords kind value elif kind NEWLINE line_start mo end line_num 1 continue elif kind SKIP continue elif kind MISMATCH raise RuntimeError f value r unexpected on line line_num yield Token kind value line_num column statements IF quantity THEN total total price quantity tax price 0 05 ENDIF for token in tokenize statements print token The tokenizer produces the following output Token type IF value IF line 2 column 4 Token type ID value quantity line 2 column 7 Token type THEN value THEN line 2 column 16 Token type ID value total line 3 column 8 Token type ASSIGN value line 3 column 14 Token type ID value total line 3 column 17 Token type OP value line 3 column 23 Token type ID value price line 3 column 25 Token type OP value line 3 column 31 Token type,en
2220, ID value quantity line 3 column 33 Token type END value line 3 column 41 Token type ID value tax line 4 column 8 Token type ASSIGN value line 4 column 12 Token type ID value price line 4 column 15 Token type OP value line 4 column 21 Token type NUMBER value 0 05 line 4 column 23 Token type END value line 4 column 27 Token type ENDIF value ENDIF line 5 column 4 Token type END value line 5 column 9 Frie09 Friedl Jeffrey Mastering Regular Expressions 3rd ed O Reilly Media 2009 The third edition of the book no longer covers Python at all but the first edition covered writing good regular expression patterns in great detail,en
2221,struct Interpret bytes as packed binary data Source code Lib struct py This module converts between Python values and C structs represented as Python bytes objects Compact format strings describe the intended conversions to from Python values The module s functions and objects can be used for two largely distinct applications data exchange with external sources files or network connections or data transfer between the Python application and the C layer Note When no prefix character is given native mode is the default It packs or unpacks data based on the platform and compiler on which the Python interpreter was built The result of packing a given C struct includes pad bytes which maintain proper alignment for the C types involved similarly alignment is taken into account when unpacking In contrast when communicating data between external sources the programmer is responsible for defining byte ordering and padding between elements See Byte Order Size and Alignment for details Several struct functions and methods of Struct take a buffer argument This refers to objects that implement the Buffer Protocol and provide either a readable or read writable buffer The most common types used for that purpose are bytes and bytearray but many other types that can be viewed as an array of bytes implement the buffer protocol so that they can be read filled without additional copying from a bytes object Functions and Exceptions The module defines the following exception and functions exception struct error Exception raised on various occasions argument is a string describing what is wrong struct pack format v1 v2 Return a bytes object containing the values v1 v2 packed according to the format string format The arguments must match the values required by the format exactly struct pack_into format buffer offset v1 v2 Pack the values v1 v2 according to the format string format and write the packed bytes into the writable buffer buffer starting at position offset Note that offset is a required argument struct unpack format buffer Unpack from the buffer buffer presumably packed by pack format according to the format string format The result is a tuple even if it contains exactly one item The buffer s size in bytes must match the size required by the format as reflected by calcsize struct unpack_from format buffer offset 0 Unpack from buffer starting at position offset according to the format string format The result is a tuple even if it contains exactly one item The buffer s size in bytes starting at position offset must be at least the size required by the format as reflected by calcsize struct iter_unpack format buffer Iteratively unpack from the buffer buffer according to the format string format This function returns an iterator which will read equally sized chunks from the buffer until all its contents have been consumed The buffer s size in bytes must be a multiple of the size required by the format as reflected by calcsize Each iteration yields a tuple as specified by the format string New in version 3 4 struct calcsize format Return the size of the struct and hence of the bytes object produced by pack format corresponding to the format string format Format Strings Format strings describe the data layout when packing and unpacking data They are built up from format characters which specify the type of data being packed unpacked In addition special characters control the byte order size and alignment Each format string consists of an optional prefix character which describes the overall properties of the data and one or more format characters which describe the actual data values and padding Byte Order Size and Alignment By default C types are represented in the machine s native format and byte order and properly aligned by skipping pad bytes if necessary according to the rules used by the C compiler This behavior is chosen so that the bytes of a packed struct correspond exactly to the memory layout of the corresponding C struct Whether to use native byte ordering and padding or standard formats depends on the application Alternatively,en
2222, the first character of the format string can be used to indicate the byte order size and alignment of the packed data according to the following table Character Byte order Size Alignment native native native native standard none little endian standard none big endian standard none network big endian standard none If the first character is not one of these is assumed Note The number 1023 0x3ff in hexadecimal has the following byte representations 03 ff in big endian ff 03 in little endian Python example import struct struct pack h 1023 b x03 xff struct pack h 1023 b xff x03 Native byte order is big endian or little endian depending on the host system For example Intel x86 AMD64 x86 64 and Apple M1 are little endian IBM z and many legacy architectures are big endian Use sys byteorder to check the endianness of your system Native size and alignment are determined using the C compiler s sizeof expression This is always combined with native byte order Standard size depends only on the format character see the table in the Format Characters section Note the difference between and both use native byte order but the size and alignment of the latter is standardized The form represents the network byte order which is always big endian as defined in IETF RFC 1700 There is no way to indicate non native byte order force byte swapping use the appropriate choice of or Notes 1 Padding is only automatically added between successive structure members No padding is added at the beginning or the end of the encoded struct 2 No padding is added when using non native size and alignment e g with and 3 To align the end of a structure to the alignment requirement of a particular type end the format with the code for that type with a repeat count of zero See Examples Format Characters Format characters have the following meaning the conversion between C and Python values should be obvious given their types The Standard size column refers to the size of the packed value in bytes when using standard size that is when the format string starts with one of or When using native size the size of the packed value is platform dependent Format C Type Python type Standard size Notes x pad byte no value 7 c char bytes of length 1 1 b signed char integer 1 1 2 B unsigned char integer 1 2 _Bool bool 1 1 h short integer 2 2 H unsigned short integer 2 2 i int integer 4 2 I unsigned int integer 4 2 l long integer 4 2 L unsigned long integer 4 2 q long long integer 8 2 Q unsigned long long integer 8 2 n ssize_t integer 3 N size_t integer 3 e 6 float 2 4 f float float 4 4 d double float 8 4 s char bytes 9 p char bytes 8 P void integer 5 Changed in version 3 3 Added support for the n and N formats Changed in version 3 6 Added support for the e format Notes 1 The conversion code corresponds to the _Bool type defined by C99 If this type is not available it is simulated using a char In standard mode it is always represented by one byte 2 When attempting to pack a non integer using any of the integer conversion codes if the non integer has a __index__ method then that method is called to convert the argument to an integer before packing Changed in version 3 2 Added use of the __index__ method for non integers 3 The n and N conversion codes are only available for the native size selected as the default or with the byte order character For the standard size you can use whichever of the other integer formats fits your application 4 For the f d and e conversion codes the packed representation uses the IEEE 754 binary32 binary64 or binary16 format for f d or e respectively regardless of the floating point format used by the platform 5 The P format character is only available for the native byte ordering selected as the default or with the byte order character The byte order character chooses to use little or big endian ordering based on the host system The struct module does not interpret this as native ordering so the P format is not available 6 The IEEE 754 binary16 half precision type was introduced in the 2008 revision of the IEEE 754 standard It has a sign bit a 5 bit e,en
2223,xponent and 11 bit precision with 10 bits explicitly stored and can represent numbers between approximately 6 1e 05 and 6 5e 04 at full precision This type is not widely supported by C compilers on a typical machine an unsigned short can be used for storage but not for math operations See the Wikipedia page on the half precision floating point format for more information 7 When packing x inserts one NUL byte 8 The p format character encodes a Pascal string meaning a short variable length string stored in a fixed number of bytes given by the count The first byte stored is the length of the string or 255 whichever is smaller The bytes of the string follow If the string passed in to pack is too long longer than the count minus 1 only the leading count 1 bytes of the string are stored If the string is shorter than count 1 it is padded with null bytes so that exactly count bytes in all are used Note that for unpack the p format character consumes count bytes but that the string returned can never contain more than 255 bytes 9 For the s format character the count is interpreted as the length of the bytes not a repeat count like for the other format characters for example 10s means a single 10 byte string mapping to or from a single Python byte string while 10c means 10 separate one byte character elements e g cccccccccc mapping to or from ten different Python byte objects See Examples for a concrete demonstration of the difference If a count is not given it defaults to 1 For packing the string is truncated or padded with null bytes as appropriate to make it fit For unpacking the resulting bytes object always has exactly the specified number of bytes As a special case 0s means a single empty string while 0c means 0 characters A format character may be preceded by an integral repeat count For example the format string 4h means exactly the same as hhhh Whitespace characters between formats are ignored a count and its format must not contain whitespace though When packing a value x using one of the integer formats b B h H i I l L q Q if x is outside the valid range for that format then struct error is raised Changed in version 3 1 Previously some of the integer formats wrapped out of range values and raised DeprecationWarning instead of struct error For the format character the return value is either True or False When packing the truth value of the argument object is used Either 0 or 1 in the native or standard bool representation will be packed and any non zero value will be True when unpacking Examples Note Native byte order examples designated by the format prefix or lack of any prefix character may not match what the reader s machine produces as that depends on the platform and compiler Pack and unpack integers of three different sizes using big endian ordering from struct import pack bhl 1 2 3 b x01 x00 x02 x00 x00 x00 x03 unpack bhl b x01 x00 x02 x00 x00 x00 x03 1 2 3 calcsize bhl 7 Attempt to pack an integer which is too large for the defined field pack h 99999 Traceback most recent call last File stdin line 1 in module struct error h format requires 32768 number 32767 Demonstrate the difference between s and c format characters pack ccc b 1 b 2 b 3 b 123 pack 3s b 123 b 123 Unpacked fields can be named by assigning them to variables or by wrapping the result in a named tuple record b raymond x32 x12 x08 x01 x08 name serialnum school gradelevel unpack 10sHHb record from collections import namedtuple Student namedtuple Student name serialnum school gradelevel Student _make unpack 10sHHb record Student name b raymond serialnum 4658 school 264 gradelevel 8 The ordering of format characters may have an impact on size in native mode since padding is implicit In standard mode the user is responsible for inserting any desired padding Note in the first pack call below that three NUL bytes were added after the packed to align the following integer on a four byte boundary In this example the output was produced on a little endian machine pack ci b 0x12131415 b x00 x00 x00 x15 x14 x13 x12 pack ic 0x12131415 b b x15 x14 x13 x12 calcsi,en
2224,ze ci 8 calcsize ic 5 The following format llh0l results in two pad bytes being added at the end assuming the platform s longs are aligned on 4 byte boundaries pack llh0l 1 2 3 b x00 x00 x00 x01 x00 x00 x00 x02 x00 x03 x00 x00 See also Module array Packed binary storage of homogeneous data Module json JSON encoder and decoder Module pickle Python object serialization Applications Two main applications for the struct module exist data interchange between Python and C code within an application or another application compiled using the same compiler native formats and data interchange between applications using agreed upon data layout standard formats Generally speaking the format strings constructed for these two domains are distinct Native Formats When constructing format strings which mimic native layouts the compiler and machine architecture determine byte ordering and padding In such cases the format character should be used to specify native byte ordering and data sizes Internal pad bytes are normally inserted automatically It is possible that a zero repeat format code will be needed at the end of a format string to round up to the correct byte boundary for proper alignment of consecutive chunks of data Consider these two simple examples on a 64 bit little endian machine calcsize lhl 24 calcsize llh 18 Data is not padded to an 8 byte boundary at the end of the second format string without the use of extra padding A zero repeat format code solves that problem calcsize llh0l 24 The x format code can be used to specify the repeat but for native formats it is better to use a zero repeat format like 0l By default native byte ordering and alignment is used but it is better to be explicit and use the prefix character Standard Formats When exchanging data beyond your process such as networking or storage be precise Specify the exact byte order size and alignment Do not assume they match the native order of a particular machine For example network byte order is big endian while many popular CPUs are little endian By defining this explicitly the user need not care about the specifics of the platform their code is running on The first character should typically be or or Padding is the responsibility of the programmer The zero repeat format character won t work Instead the user must explicitly add x pad bytes where needed Revisiting the examples from the previous section we have calcsize qh6xq 24 pack qh6xq 1 2 3 pack lhl 1 2 3 True calcsize llh 18 pack llh 1 2 3 pack qqh 1 2 3 True calcsize qqh6x 24 calcsize llh0l 24 pack llh0l 1 2 3 pack qqh6x 1 2 3 True The above results executed on a 64 bit machine aren t guaranteed to match when executed on different machines For example the examples below were executed on a 32 bit machine calcsize qqh6x 24 calcsize llh0l 12 pack llh0l 1 2 3 pack qqh6x 1 2 3 False Classes The struct module also defines the following type class struct Struct format Return a new Struct object which writes and reads binary data according to the format string format Creating a Struct object once and calling its methods is more efficient than calling module level functions with the same format since the format string is only compiled once Note The compiled versions of the most recent format strings passed to the module level functions are cached so programs that use only a few format strings needn t worry about reusing a single Struct instance Compiled Struct objects support the following methods and attributes pack v1 v2 Identical to the pack function using the compiled format len result will equal size pack_into buffer offset v1 v2 Identical to the pack_into function using the compiled format unpack buffer Identical to the unpack function using the compiled format The buffer s size in bytes must equal size unpack_from buffer offset 0 Identical to the unpack_from function using the compiled format The buffer s size in bytes starting at position offset must be at least size iter_unpack buffer Identical to the iter_unpack function using the compiled format The buffer s size in bytes must be a multiple of size New,en
2225, in version 3 4 format The format string used to construct this Struct object Changed in version 3 7 The format string type is now str instead of bytes size The calculated size of the struct and hence of the bytes object produced by the pack method corresponding to format,en
2226,Functional Programming Modules The modules described in this chapter provide functions and classes that support a functional programming style and general operations on callables The following modules are documented in this chapter itertools Functions creating iterators for efficient looping Itertool Functions Itertools Recipes functools Higher order functions and operations on callable objects partial Objects operator Standard operators as functions Mapping Operators to Functions In place Operators,en
2227,2 Lexical analysis A Python program is read by a parser Input to the parser is a stream of tokens generated by the lexical analyzer This chapter describes how the lexical analyzer breaks a file into tokens Python reads program text as Unicode code points the encoding of a source file can be given by an encoding declaration and defaults to UTF 8 see PEP 3120 for details If the source file cannot be decoded a SyntaxError is raised 2 1 Line structure A Python program is divided into a number of logical lines 2 1 1 Logical lines The end of a logical line is represented by the token NEWLINE Statements cannot cross logical line boundaries except where NEWLINE is allowed by the syntax e g between statements in compound statements A logical line is constructed from one or more physical lines by following the explicit or implicit line joining rules 2 1 2 Physical lines A physical line is a sequence of characters terminated by an end of line sequence In source files and strings any of the standard platform line termination sequences can be used the Unix form using ASCII LF linefeed the Windows form using the ASCII sequence CR LF return followed by linefeed or the old Macintosh form using the ASCII CR return character All of these forms can be used equally regardless of platform The end of input also serves as an implicit terminator for the final physical line When embedding Python source code strings should be passed to Python APIs using the standard C conventions for newline characters the n character representing ASCII LF is the line terminator 2 1 3 Comments A comment starts with a hash character that is not part of a string literal and ends at the end of the physical line A comment signifies the end of the logical line unless the implicit line joining rules are invoked Comments are ignored by the syntax 2 1 4 Encoding declarations If a comment in the first or second line of the Python script matches the regular expression coding s w this comment is processed as an encoding declaration the first group of this expression names the encoding of the source code file The encoding declaration must appear on a line of its own If it is the second line the first line must also be a comment only line The recommended forms of an encoding expression are coding encoding name which is recognized also by GNU Emacs and vim fileencoding encoding name which is recognized by Bram Moolenaar s VIM If no encoding declaration is found the default encoding is UTF 8 In addition if the first bytes of the file are the UTF 8 byte order mark b xef xbb xbf the declared file encoding is UTF 8 this is supported among others by Microsoft s notepad If an encoding is declared the encoding name must be recognized by Python see Standard Encodings The encoding is used for all lexical analysis including string literals comments and identifiers 2 1 5 Explicit line joining Two or more physical lines may be joined into logical lines using backslash characters as follows when a physical line ends in a backslash that is not part of a string literal or comment it is joined with the following forming a single logical line deleting the backslash and the following end of line character For example if 1900 year 2100 and 1 month 12 and 1 day 31 and 0 hour 24 and 0 minute 60 and 0 second 60 Looks like a valid date return 1 A line ending in a backslash cannot carry a comment A backslash does not continue a comment A backslash does not continue a token except for string literals i e tokens other than string literals cannot be split across physical lines using a backslash A backslash is illegal elsewhere on a line outside a string literal 2 1 6 Implicit line joining Expressions in parentheses square brackets or curly braces can be split over more than one physical line without using backslashes For example month_names Januari Februari Maart These are the April Mei Juni Dutch names Juli Augustus September for the months Oktober November December of the year Implicitly continued lines can carry comments The indentation of the continuation lines is not important Blank continuation li,en
2228,nes are allowed There is no NEWLINE token between implicit continuation lines Implicitly continued lines can also occur within triple quoted strings see below in that case they cannot carry comments 2 1 7 Blank lines A logical line that contains only spaces tabs formfeeds and possibly a comment is ignored i e no NEWLINE token is generated During interactive input of statements handling of a blank line may differ depending on the implementation of the read eval print loop In the standard interactive interpreter an entirely blank logical line i e one containing not even whitespace or a comment terminates a multi line statement 2 1 8 Indentation Leading whitespace spaces and tabs at the beginning of a logical line is used to compute the indentation level of the line which in turn is used to determine the grouping of statements Tabs are replaced from left to right by one to eight spaces such that the total number of characters up to and including the replacement is a multiple of eight this is intended to be the same rule as used by Unix The total number of spaces preceding the first non blank character then determines the line s indentation Indentation cannot be split over multiple physical lines using backslashes the whitespace up to the first backslash determines the indentation Indentation is rejected as inconsistent if a source file mixes tabs and spaces in a way that makes the meaning dependent on the worth of a tab in spaces a TabError is raised in that case Cross platform compatibility note because of the nature of text editors on non UNIX platforms it is unwise to use a mixture of spaces and tabs for the indentation in a single source file It should also be noted that different platforms may explicitly limit the maximum indentation level A formfeed character may be present at the start of the line it will be ignored for the indentation calculations above Formfeed characters occurring elsewhere in the leading whitespace have an undefined effect for instance they may reset the space count to zero The indentation levels of consecutive lines are used to generate INDENT and DEDENT tokens using a stack as follows Before the first line of the file is read a single zero is pushed on the stack this will never be popped off again The numbers pushed on the stack will always be strictly increasing from bottom to top At the beginning of each logical line the line s indentation level is compared to the top of the stack If it is equal nothing happens If it is larger it is pushed on the stack and one INDENT token is generated If it is smaller it must be one of the numbers occurring on the stack all numbers on the stack that are larger are popped off and for each number popped off a DEDENT token is generated At the end of the file a DEDENT token is generated for each number remaining on the stack that is larger than zero Here is an example of a correctly though confusingly indented piece of Python code def perm l Compute the list of all permutations of l if len l 1 return l r for i in range len l s l i l i 1 p perm s for x in p r append l i i 1 x return r The following example shows various indentation errors def perm l error first line indented for i in range len l error not indented s l i l i 1 p perm l i l i 1 error unexpected indent for x in p r append l i i 1 x return r error inconsistent dedent Actually the first three errors are detected by the parser only the last error is found by the lexical analyzer the indentation of return r does not match a level popped off the stack 2 1 9 Whitespace between tokens Except at the beginning of a logical line or in string literals the whitespace characters space tab and formfeed can be used interchangeably to separate tokens Whitespace is needed between two tokens only if their concatenation could otherwise be interpreted as a different token e g ab is one token but a b is two tokens 2 2 Other tokens Besides NEWLINE INDENT and DEDENT the following categories of tokens exist identifiers keywords literals operators and delimiters Whitespace characters other than line terminators discussed ea,en
2229,rlier are not tokens but serve to delimit tokens Where ambiguity exists a token comprises the longest possible string that forms a legal token when read from left to right 2 3 Identifiers and keywords Identifiers also referred to as names are described by the following lexical definitions The syntax of identifiers in Python is based on the Unicode standard annex UAX 31 with elaboration and changes as defined below see also PEP 3131 for further details Within the ASCII range U 0001 U 007F the valid characters for identifiers are the same as in Python 2 x the uppercase and lowercase letters A through Z the underscore _ and except for the first character the digits 0 through 9 Python 3 0 introduces additional characters from outside the ASCII range see PEP 3131 For these characters the classification uses the version of the Unicode Character Database as included in the unicodedata module Identifiers are unlimited in length Case is significant identifier xid_start xid_continue id_start all characters in general categories Lu Ll Lt Lm Lo Nl the underscore and characters with the Other_ID_Start property id_continue all characters in id_start plus characters in the categories Mn Mc Nd Pc and others with the Other_ID_Continue property xid_start all characters in id_start whose NFKC normalization is in id_start xid_continue xid_continue all characters in id_continue whose NFKC normalization is in id_continue The Unicode category codes mentioned above stand for Lu uppercase letters Ll lowercase letters Lt titlecase letters Lm modifier letters Lo other letters Nl letter numbers Mn nonspacing marks Mc spacing combining marks Nd decimal numbers Pc connector punctuations Other_ID_Start explicit list of characters in PropList txt to support backwards compatibility Other_ID_Continue likewise All identifiers are converted into the normal form NFKC while parsing comparison of identifiers is based on NFKC A non normative HTML file listing all valid identifier characters for Unicode 15 0 0 can be found at https www unicode org Public 15 0 0 ucd DerivedCoreProperties txt 2 3 1 Keywords The following identifiers are used as reserved words or keywords of the language and cannot be used as ordinary identifiers They must be spelled exactly as written here False await else import pass None break except in raise True class finally is return and continue for lambda try as def from nonlocal while assert del global not with async elif if or yield 2 3 2 Soft Keywords New in version 3 10 Some identifiers are only reserved under specific contexts These are known as soft keywords The identifiers match case type and _ can syntactically act as keywords in certain contexts but this distinction is done at the parser level not when tokenizing As soft keywords their use in the grammar is possible while still preserving compatibility with existing code that uses these names as identifier names match case and _ are used in the match statement type is used in the type statement Changed in version 3 12 type is now a soft keyword 2 3 3 Reserved classes of identifiers Certain classes of identifiers besides keywords have special meanings These classes are identified by the patterns of leading and trailing underscore characters _ Not imported by from module import _ In a case pattern within a match statement _ is a soft keyword that denotes a wildcard Separately the interactive interpreter makes the result of the last evaluation available in the variable _ It is stored in the builtins module alongside built in functions like print Elsewhere _ is a regular identifier It is often used to name special items but it is not special to Python itself Note The name _ is often used in conjunction with internationalization refer to the documentation for the gettext module for more information on this convention It is also commonly used for unused variables __ __ System defined names informally known as dunder names These names are defined by the interpreter and its implementation including the standard library Current system names are discussed in the Special method names sectio,en
2230,n and elsewhere More will likely be defined in future versions of Python Any use of __ __ names in any context that does not follow explicitly documented use is subject to breakage without warning __ Class private names Names in this category when used within the context of a class definition are re written to use a mangled form to help avoid name clashes between private attributes of base and derived classes See section Identifiers Names 2 4 Literals Literals are notations for constant values of some built in types 2 4 1 String and Bytes literals String literals are described by the following lexical definitions stringliteral stringprefix shortstring longstring stringprefix r u R U f F fr Fr fR FR rf rF Rf RF shortstring shortstringitem shortstringitem longstring longstringitem longstringitem shortstringitem shortstringchar stringescapeseq longstringitem longstringchar stringescapeseq shortstringchar any source character except or newline or the quote longstringchar any source character except stringescapeseq any source character bytesliteral bytesprefix shortbytes longbytes bytesprefix b B br Br bR BR rb rB Rb RB shortbytes shortbytesitem shortbytesitem longbytes longbytesitem longbytesitem shortbytesitem shortbyteschar bytesescapeseq longbytesitem longbyteschar bytesescapeseq shortbyteschar any ASCII character except or newline or the quote longbyteschar any ASCII character except bytesescapeseq any ASCII character One syntactic restriction not indicated by these productions is that whitespace is not allowed between the stringprefix or bytesprefix and the rest of the literal The source character set is defined by the encoding declaration it is UTF 8 if no encoding declaration is given in the source file see section Encoding declarations In plain English Both types of literals can be enclosed in matching single quotes or double quotes They can also be enclosed in matching groups of three single or double quotes these are generally referred to as triple quoted strings The backslash character is used to give special meaning to otherwise ordinary characters like n which means newline when escaped n It can also be used to escape characters that otherwise have a special meaning such as newline backslash itself or the quote character See escape sequences below for examples Bytes literals are always prefixed with b or B they produce an instance of the bytes type instead of the str type They may only contain ASCII characters bytes with a numeric value of 128 or greater must be expressed with escapes Both string and bytes literals may optionally be prefixed with a letter r or R such strings are called raw strings and treat backslashes as literal characters As a result in string literals U and u escapes in raw strings are not treated specially Given that Python 2 x s raw unicode literals behave differently than Python 3 x s the ur syntax is not supported New in version 3 3 The rb prefix of raw bytes literals has been added as a synonym of br Support for the unicode legacy literal u value was reintroduced to simplify the maintenance of dual Python 2 x and 3 x codebases See PEP 414 for more information A string literal with f or F in its prefix is a formatted string literal see f strings The f may be combined with r but not with b or u therefore raw formatted strings are possible but formatted bytes literals are not In triple quoted literals unescaped newlines and quotes are allowed and are retained except that three unescaped quotes in a row terminate the literal A quote is the character used to open the literal i e either or 2 4 1 1 Escape sequences Unless an r or R prefix is present escape sequences in string and bytes literals are interpreted according to rules similar to those used by Standard C The recognized escape sequences are Escape Sequence Meaning Notes newline Backslash and newline ignored 1 Backslash Single quote Double quote a ASCII Bell BEL b ASCII Backspace BS f ASCII Formfeed FF n ASCII Linefeed LF r ASCII Carriage Return CR t ASCII Horizontal Tab TAB v ASCII Vertical Tab VT ooo Character with octal value ooo 2 4,en
2231, x hh Character with hex value hh 3 4 Escape sequences only recognized in string literals are Escape Sequence Meaning Notes N name Character named name in the 5 Unicode database u xxxx Character with 16 bit hex value 6 xxxx U xxxxxxxx Character with 32 bit hex value 7 xxxxxxxx Notes 1 A backslash can be added at the end of a line to ignore the newline This string will not include backslashes or newline characters This string will not include backslashes or newline characters The same result can be achieved using triple quoted strings or parentheses and string literal concatenation 2 As in Standard C up to three octal digits are accepted Changed in version 3 11 Octal escapes with value larger than 0o377 produce a DeprecationWarning Changed in version 3 12 Octal escapes with value larger than 0o377 produce a SyntaxWarning In a future Python version they will be eventually a SyntaxError 3 Unlike in Standard C exactly two hex digits are required 4 In a bytes literal hexadecimal and octal escapes denote the byte with the given value In a string literal these escapes denote a Unicode character with the given value 5 Changed in version 3 3 Support for name aliases 1 has been added 6 Exactly four hex digits are required 7 Any Unicode character can be encoded this way Exactly eight hex digits are required Unlike Standard C all unrecognized escape sequences are left in the string unchanged i e the backslash is left in the result This behavior is useful when debugging if an escape sequence is mistyped the resulting output is more easily recognized as broken It is also important to note that the escape sequences only recognized in string literals fall into the category of unrecognized escapes for bytes literals Changed in version 3 6 Unrecognized escape sequences produce a DeprecationWarning Changed in version 3 12 Unrecognized escape sequences produce a SyntaxWarning In a future Python version they will be eventually a SyntaxError Even in a raw literal quotes can be escaped with a backslash but the backslash remains in the result for example r is a valid string literal consisting of two characters a backslash and a double quote r is not a valid string literal even a raw string cannot end in an odd number of backslashes Specifically a raw literal cannot end in a single backslash since the backslash would escape the following quote character Note also that a single backslash followed by a newline is interpreted as those two characters as part of the literal not as a line continuation 2 4 2 String literal concatenation Multiple adjacent string or bytes literals delimited by whitespace possibly using different quoting conventions are allowed and their meaning is the same as their concatenation Thus hello world is equivalent to helloworld This feature can be used to reduce the number of backslashes needed to split long strings conveniently across long lines or even to add comments to parts of strings for example re compile A Za z_ letter or underscore A Za z0 9_ letter digit or underscore Note that this feature is defined at the syntactical level but implemented at compile time The operator must be used to concatenate string expressions at run time Also note that literal concatenation can use different quoting styles for each component even mixing raw strings and triple quoted strings and formatted string literals may be concatenated with plain string literals 2 4 3 f strings New in version 3 6 A formatted string literal or f string is a string literal that is prefixed with f or F These strings may contain replacement fields which are expressions delimited by curly braces While other string literals always have a constant value formatted strings are really expressions evaluated at run time Escape sequences are decoded like in ordinary string literals except when a literal is also marked as a raw string After decoding the grammar for the contents of the string is f_string literal_char replacement_field replacement_field f_expression conversion format_spec f_expression conditional_expression or_expr conditional_expression or_expr yield_ex,en
2232,pression conversion s r a format_spec literal_char NULL replacement_field literal_char any code point except or NULL The parts of the string outside curly braces are treated literally except that any doubled curly braces or are replaced with the corresponding single curly brace A single opening curly bracket marks a replacement field which starts with a Python expression To display both the expression text and its value after evaluation useful in debugging an equal sign may be added after the expression A conversion field introduced by an exclamation point may follow A format specifier may also be appended introduced by a colon A replacement field ends with a closing curly bracket Expressions in formatted string literals are treated like regular Python expressions surrounded by parentheses with a few exceptions An empty expression is not allowed and both lambda and assignment expressions must be surrounded by explicit parentheses Each expression is evaluated in the context where the formatted string literal appears in order from left to right Replacement expressions can contain newlines in both single quoted and triple quoted f strings and they can contain comments Everything that comes after a inside a replacement field is a comment even closing braces and quotes In that case replacement fields must be closed in a different line f abc a This is a comment 3 abc5 Changed in version 3 7 Prior to Python 3 7 an await expression and comprehensions containing an async for clause were illegal in the expressions in formatted string literals due to a problem with the implementation Changed in version 3 12 Prior to Python 3 12 comments were not allowed inside f string replacement fields When the equal sign is provided the output will have the expression text the and the evaluated value Spaces after the opening brace within the expression and after the are all retained in the output By default the causes the repr of the expression to be provided unless there is a format specified When a format is specified it defaults to the str of the expression unless a conversion r is declared New in version 3 8 The equal sign If a conversion is specified the result of evaluating the expression is converted before formatting Conversion s calls str on the result r calls repr and a calls ascii The result is then formatted using the format protocol The format specifier is passed to the __format__ method of the expression or conversion result An empty string is passed when the format specifier is omitted The formatted result is then included in the final value of the whole string Top level format specifiers may include nested replacement fields These nested fields may include their own conversion fields and format specifiers but may not include more deeply nested replacement fields The format specifier mini language is the same as that used by the str format method Formatted string literals may be concatenated but replacement fields cannot be split across literals Some examples of formatted string literals name Fred f He said his name is name r He said his name is Fred f He said his name is repr name repr is equivalent to r He said his name is Fred width 10 precision 4 value decimal Decimal 12 34567 f result value width precision nested fields result 12 35 today datetime year 2017 month 1 day 27 f today B d Y using date format specifier January 27 2017 f today B d Y using date format specifier and debugging today January 27 2017 number 1024 f number 0x using integer format specifier 0x400 foo bar f foo preserves whitespace foo bar line The mill s closed f line line The mill s closed f line 20 line The mill s closed f line r 20 line The mill s closed Reusing the outer f string quoting type inside a replacement field is permitted a dict x 2 f abc a x def abc 2 def Changed in version 3 12 Prior to Python 3 12 reuse of the same quoting type of the outer f string inside a replacement field was not possible Backslashes are also allowed in replacement fields and are evaluated the same way as in any other context a a b c print f List a contains n n join a L,en
2233,ist a contains a b c Changed in version 3 12 Prior to Python 3 12 backslashes were not permitted inside an f string replacement field Formatted string literals cannot be used as docstrings even if they do not include expressions def foo f Not a docstring foo __doc__ is None True See also PEP 498 for the proposal that added formatted string literals and str format which uses a related format string mechanism 2 4 4 Numeric literals There are three types of numeric literals integers floating point numbers and imaginary numbers There are no complex literals complex numbers can be formed by adding a real number and an imaginary number Note that numeric literals do not include a sign a phrase like 1 is actually an expression composed of the unary operator and the literal 1 2 4 5 Integer literals Integer literals are described by the following lexical definitions integer decinteger bininteger octinteger hexinteger decinteger nonzerodigit _ digit 0 _ 0 bininteger 0 b B _ bindigit octinteger 0 o O _ octdigit hexinteger 0 x X _ hexdigit nonzerodigit 1 9 digit 0 9 bindigit 0 1 octdigit 0 7 hexdigit digit a f A F There is no limit for the length of integer literals apart from what can be stored in available memory Underscores are ignored for determining the numeric value of the literal They can be used to group digits for enhanced readability One underscore can occur between digits and after base specifiers like 0x Note that leading zeros in a non zero decimal number are not allowed This is for disambiguation with C style octal literals which Python used before version 3 0 Some examples of integer literals 7 2147483647 0o177 0b100110111 3 79228162514264337593543950336 0o377 0xdeadbeef 100_000_000_000 0b_1110_0101 Changed in version 3 6 Underscores are now allowed for grouping purposes in literals 2 4 6 Floating point literals Floating point literals are described by the following lexical definitions floatnumber pointfloat exponentfloat pointfloat digitpart fraction digitpart exponentfloat digitpart pointfloat exponent digitpart digit _ digit fraction digitpart exponent e E digitpart Note that the integer and exponent parts are always interpreted using radix 10 For example 077e010 is legal and denotes the same number as 77e10 The allowed range of floating point literals is implementation dependent As in integer literals underscores are supported for digit grouping Some examples of floating point literals 3 14 10 001 1e100 3 14e 10 0e0 3 14_15_93 Changed in version 3 6 Underscores are now allowed for grouping purposes in literals 2 4 7 Imaginary literals Imaginary literals are described by the following lexical definitions imagnumber floatnumber digitpart j J An imaginary literal yields a complex number with a real part of 0 0 Complex numbers are represented as a pair of floating point numbers and have the same restrictions on their range To create a complex number with a nonzero real part add a floating point number to it e g 3 4j Some examples of imaginary literals 3 14j 10 j 10j 001j 1e100j 3 14e 10j 3 14_15_93j 2 5 Operators The following tokens are operators 2 6 Delimiters The following tokens serve as delimiters in the grammar The period can also occur in floating point and imaginary literals A sequence of three periods has a special meaning as an ellipsis literal The second half of the list the augmented assignment operators serve lexically as delimiters but also perform an operation The following printing ASCII characters have special meaning as part of other tokens or are otherwise significant to the lexical analyzer The following printing ASCII characters are not used in Python Their occurrence outside string literals and comments is an unconditional error Footnotes 1 https www unicode org Public 15 0 0 ucd NameAliases txt,en
2234,collections abc Abstract Base Classes for Containers New in version 3 3 Formerly this module was part of the collections module Source code Lib _collections_abc py This module provides abstract base classes that can be used to test whether a class provides a particular interface for example whether it is hashable or whether it is a mapping An issubclass or isinstance test for an interface works in one of three ways 1 A newly written class can inherit directly from one of the abstract base classes The class must supply the required abstract methods The remaining mixin methods come from inheritance and can be overridden if desired Other methods may be added as needed class C Sequence Direct inheritance def __init__ self Extra method not required by the ABC def __getitem__ self index Required abstract method def __len__ self Required abstract method def count self value Optionally override a mixin method issubclass C Sequence True isinstance C Sequence True 2 Existing classes and built in classes can be registered as virtual subclasses of the ABCs Those classes should define the full API including all of the abstract methods and all of the mixin methods This lets users rely on issubclass or isinstance tests to determine whether the full interface is supported The exception to this rule is for methods that are automatically inferred from the rest of the API class D No inheritance def __init__ self Extra method not required by the ABC def __getitem__ self index Abstract method def __len__ self Abstract method def count self value Mixin method def index self value Mixin method Sequence register D Register instead of inherit issubclass D Sequence True isinstance D Sequence True In this example class D does not need to define __contains__ __iter__ and __reversed__ because the in operator the iteration logic and the reversed function automatically fall back to using __getitem__ and __len__ 3 Some simple interfaces are directly recognizable by the presence of the required methods unless those methods have been set to None class E def __iter__ self def __next__ self issubclass E Iterable True isinstance E Iterable True Complex interfaces do not support this last technique because an interface is more than just the presence of method names Interfaces specify semantics and relationships between methods that cannot be inferred solely from the presence of specific method names For example knowing that a class supplies __getitem__ __len__ and __iter__ is insufficient for distinguishing a Sequence from a Mapping New in version 3 9 These abstract classes now support See Generic Alias Type and PEP 585 Collections Abstract Base Classes The collections module offers the following ABCs ABC Inherits from Abstract Methods Mixin Methods Container 1 __contains__ Hashable 1 __hash__ Iterable 1 2 __iter__ Iterator 1 Iterable __next__ __iter__ Reversible 1 Iterable __reversed__ Generator 1 Iterator send throw close __iter__ __next__ Sized 1 __len__ Callable 1 __call__ Collection 1 Sized Iterable __contains__ Container __iter__ __len__ Sequence Reversible __getitem__ __contains__ __iter__ __reversed__ index Collection __len__ and count MutableSequence Sequence __getitem__ Inherited Sequence methods and append clear __setitem__ reverse extend pop remove and __iadd__ __delitem__ __len__ insert ByteString Sequence __getitem__ Inherited Sequence methods __len__ Set Collection __contains__ __le__ __lt__ __eq__ __ne__ __gt__ __iter__ __len__ __ge__ __and__ __or__ __sub__ __xor__ and isdisjoint MutableSet Set __contains__ Inherited Set methods and clear pop __iter__ __len__ remove __ior__ __iand__ __ixor__ and add discard __isub__ Mapping Collection __getitem__ __contains__ keys items values get __iter__ __len__ __eq__ and __ne__ MutableMapping Mapping __getitem__ Inherited Mapping methods and pop popitem __setitem__ clear update and setdefault __delitem__ __iter__ __len__ MappingView Sized __len__ ItemsView MappingView Set __contains__ __iter__ KeysView MappingView Set __contains__ __iter__ ValuesView MappingView __contains__ __iter__ Collection Awaitable ,en
2235,1 __await__ Coroutine 1 Awaitable send throw close AsyncIterable 1 __aiter__ AsyncIterator 1 AsyncIterable __anext__ __aiter__ AsyncGenerator 1 AsyncIterator asend athrow aclose __aiter__ __anext__ Buffer 1 __buffer__ Footnotes 1 These ABCs override __subclasshook__ to support testing an interface by verifying the required methods are present and have not been set to None This only works for simple interfaces More complex interfaces require registration or direct subclassing 2 Checking isinstance obj Iterable detects classes that are registered as Iterable or that have an __iter__ method but it does not detect classes that iterate with the __getitem__ method The only reliable way to determine whether an object is iterable is to call iter obj Collections Abstract Base Classes Detailed Descriptions class collections abc Container ABC for classes that provide the __contains__ method class collections abc Hashable ABC for classes that provide the __hash__ method class collections abc Sized ABC for classes that provide the __len__ method class collections abc Callable ABC for classes that provide the __call__ method class collections abc Iterable ABC for classes that provide the __iter__ method Checking isinstance obj Iterable detects classes that are registered as Iterable or that have an __iter__ method but it does not detect classes that iterate with the __getitem__ method The only reliable way to determine whether an object is iterable is to call iter obj class collections abc Collection ABC for sized iterable container classes New in version 3 6 class collections abc Iterator ABC for classes that provide the __iter__ and __next__ methods See also the definition of iterator class collections abc Reversible ABC for iterable classes that also provide the __reversed__ method New in version 3 6 class collections abc Generator ABC for generator classes that implement the protocol defined in PEP 342 that extends iterators with the send throw and close methods New in version 3 5 class collections abc Sequence class collections abc MutableSequence class collections abc ByteString ABCs for read only and mutable sequences Implementation note Some of the mixin methods such as __iter__ __reversed__ and index make repeated calls to the underlying __getitem__ method Consequently if __getitem__ is implemented with constant access speed the mixin methods will have linear performance however if the underlying method is linear as it would be with a linked list the mixins will have quadratic performance and will likely need to be overridden Changed in version 3 5 The index method added support for stop and start arguments Deprecated since version 3 12 will be removed in version 3 14 The ByteString ABC has been deprecated For use in typing prefer a union like bytes bytearray or collections abc Buffer For use as an ABC prefer Sequence or collections abc Buffer class collections abc Set class collections abc MutableSet ABCs for read only and mutable sets class collections abc Mapping class collections abc MutableMapping ABCs for read only and mutable mappings class collections abc MappingView class collections abc ItemsView class collections abc KeysView class collections abc ValuesView ABCs for mapping items keys and values views class collections abc Awaitable ABC for awaitable objects which can be used in await expressions Custom implementations must provide the __await__ method Coroutine objects and instances of the Coroutine ABC are all instances of this ABC Note In CPython generator based coroutines generators decorated with types coroutine are awaitables even though they do not have an __await__ method Using isinstance gencoro Awaitable for them will return False Use inspect isawaitable to detect them New in version 3 5 class collections abc Coroutine ABC for coroutine compatible classes These implement the following methods defined in Coroutine Objects send throw and close Custom implementations must also implement __await__ All Coroutine instances are also instances of Awaitable Note In CPython generator based coroutines generators de,en
2236,corated with types coroutine are awaitables even though they do not have an __await__ method Using isinstance gencoro Coroutine for them will return False Use inspect isawaitable to detect them New in version 3 5 class collections abc AsyncIterable ABC for classes that provide an __aiter__ method See also the definition of asynchronous iterable New in version 3 5 class collections abc AsyncIterator ABC for classes that provide __aiter__ and __anext__ methods See also the definition of asynchronous iterator New in version 3 5 class collections abc AsyncGenerator ABC for asynchronous generator classes that implement the protocol defined in PEP 525 and PEP 492 New in version 3 6 class collections abc Buffer ABC for classes that provide the __buffer__ method implementing the buffer protocol See PEP 688 New in version 3 12 Examples and Recipes ABCs allow us to ask classes or instances if they provide particular functionality for example size None if isinstance myvar collections abc Sized size len myvar Several of the ABCs are also useful as mixins that make it easier to develop classes supporting container APIs For example to write a class supporting the full Set API it is only necessary to supply the three underlying abstract methods __contains__ __iter__ and __len__ The ABC supplies the remaining methods such as __and__ and isdisjoint class ListBasedSet collections abc Set Alternate set implementation favoring space over speed and not requiring the set elements to be hashable def __init__ self iterable self elements lst for value in iterable if value not in lst lst append value def __iter__ self return iter self elements def __contains__ self value return value in self elements def __len__ self return len self elements s1 ListBasedSet abcdef s2 ListBasedSet defghi overlap s1 s2 The __and__ method is supported automatically Notes on using Set and MutableSet as a mixin 1 Since some set operations create new sets the default mixin methods need a way to create new instances from an iterable The class constructor is assumed to have a signature in the form ClassName iterable That assumption is factored out to an internal classmethod called _from_iterable which calls cls iterable to produce a new set If the Set mixin is being used in a class with a different constructor signature you will need to override _from_iterable with a classmethod or regular method that can construct new instances from an iterable argument 2 To override the comparisons presumably for speed as the semantics are fixed redefine __le__ and __ge__ then the other operations will automatically follow suit 3 The Set mixin provides a _hash method to compute a hash value for the set however __hash__ is not defined because not all sets are hashable or immutable To add set hashability using mixins inherit from both Set and Hashable then define __hash__ Set _hash See also OrderedSet recipe for an example built on MutableSet For more about ABCs see the abc module and PEP 3119,en
2237,cgi Common Gateway Interface support Source code Lib cgi py Deprecated since version 3 11 will be removed in version 3 13 The cgi module is deprecated see PEP 594 for details and alternatives The FieldStorage class can typically be replaced with urllib parse parse_qsl for GET and HEAD requests and the email message module or multipart for POST and PUT Most utility functions have replacements Support module for Common Gateway Interface CGI scripts This module defines a number of utilities for use by CGI scripts written in Python The global variable maxlen can be set to an integer indicating the maximum size of a POST request POST requests larger than this size will result in a ValueError being raised during parsing The default value of this variable is 0 meaning the request size is unlimited Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information Introduction A CGI script is invoked by an HTTP server usually to process user input submitted through an HTML FORM or ISINDEX element Most often CGI scripts live in the server s special cgi bin directory The HTTP server places all sorts of information about the request such as the client s hostname the requested URL the query string and lots of other goodies in the script s shell environment executes the script and sends the script s output back to the client The script s input is connected to the client too and sometimes the form data is read this way at other times the form data is passed via the query string part of the URL This module is intended to take care of the different cases and provide a simpler interface to the Python script It also provides a number of utilities that help in debugging scripts and the latest addition is support for file uploads from a form if your browser supports it The output of a CGI script should consist of two sections separated by a blank line The first section contains a number of headers telling the client what kind of data is following Python code to generate a minimal header section looks like this print Content Type text html HTML is following print blank line end of headers The second section is usually HTML which allows the client software to display nicely formatted text with header in line images etc Here s Python code that prints a simple piece of HTML print TITLE CGI script output TITLE print H1 This is my first CGI script H1 print Hello world Using the cgi module Begin by writing import cgi When you write a new script consider adding these lines import cgitb cgitb enable This activates a special exception handler that will display detailed reports in the web browser if any errors occur If you d rather not show the guts of your program to users of your script you can have the reports saved to files instead with code like this import cgitb cgitb enable display 0 logdir path to logdir It s very helpful to use this feature during script development The reports produced by cgitb provide information that can save you a lot of time in tracking down bugs You can always remove the cgitb line later when you have tested your script and are confident that it works correctly To get at submitted form data use the FieldStorage class If the form contains non ASCII characters use the encoding keyword parameter set to the value of the encoding defined for the document It is usually contained in the META tag in the HEAD section of the HTML document or by the Content Type header This reads the form contents from the standard input or the environment depending on the value of various environment variables set according to the CGI standard Since it may consume standard input it should be instantiated only once The FieldStorage instance can be indexed like a Python dictionary It allows membership testing with the in operator and also supports the standard dictionary method keys and the built in function len Form fields containing empty strings are ignored and do not appear in the dictionary to keep such values provide a tru,en
2238,e value for the optional keep_blank_values keyword parameter when creating the FieldStorage instance For instance the following code which assumes that the Content Type header and blank line have already been printed checks that the fields name and addr are both set to a non empty string form cgi FieldStorage if name not in form or addr not in form print H1 Error H1 print Please fill in the name and addr fields return print p name form name value print p addr form addr value further form processing here Here the fields accessed through form key are themselves instances of FieldStorage or MiniFieldStorage depending on the form encoding The value attribute of the instance yields the string value of the field The getvalue method returns this string value directly it also accepts an optional second argument as a default to return if the requested key is not present If the submitted form data contains more than one field with the same name the object retrieved by form key is not a FieldStorage or MiniFieldStorage instance but a list of such instances Similarly in this situation form getvalue key would return a list of strings If you expect this possibility when your HTML form contains multiple fields with the same name use the getlist method which always returns a list of values so that you do not need to special case the single item case For example this code concatenates any number of username fields separated by commas value form getlist username usernames join value If a field represents an uploaded file accessing the value via the value attribute or the getvalue method reads the entire file in memory as bytes This may not be what you want You can test for an uploaded file by testing either the filename attribute or the file attribute You can then read the data from the file attribute before it is automatically closed as part of the garbage collection of the FieldStorage instance the read and readline methods will return bytes fileitem form userfile if fileitem file It s an uploaded file count lines linecount 0 while True line fileitem file readline if not line break linecount linecount 1 FieldStorage objects also support being used in a with statement which will automatically close them when done If an error is encountered when obtaining the contents of an uploaded file for example when the user interrupts the form submission by clicking on a Back or Cancel button the done attribute of the object for the field will be set to the value 1 The file upload draft standard entertains the possibility of uploading multiple files from one field using a recursive multipart encoding When this occurs the item will be a dictionary like FieldStorage item This can be determined by testing its type attribute which should be multipart form data or perhaps another MIME type matching multipart In this case it can be iterated over recursively just like the top level form object When a form is submitted in the old format as the query string or as a single data part of type application x www form urlencoded the items will actually be instances of the class MiniFieldStorage In this case the list file and filename attributes are always None A form submitted via POST that also has a query string will contain both FieldStorage and MiniFieldStorage items Changed in version 3 4 The file attribute is automatically closed upon the garbage collection of the creating FieldStorage instance Changed in version 3 5 Added support for the context management protocol to the FieldStorage class Higher Level Interface The previous section explains how to read CGI form data using the FieldStorage class This section describes a higher level interface which was added to this class to allow one to do it in a more readable and intuitive way The interface doesn t make the techniques described in previous sections obsolete they are still useful to process file uploads efficiently for example The interface consists of two simple methods Using the methods you can process form data in a generic way without the need to worry whether only one or more values were posted unde,en
2239,r one name In the previous section you learned to write following code anytime you expected a user to post more than one value under one name item form getvalue item if isinstance item list The user is requesting more than one item else The user is requesting only one item This situation is common for example when a form contains a group of multiple checkboxes with the same name input type checkbox name item value 1 input type checkbox name item value 2 In most situations however there s only one form control with a particular name in a form and then you expect and need only one value associated with this name So you write a script containing for example this code user form getvalue user upper The problem with the code is that you should never expect that a client will provide valid input to your scripts For example if a curious user appends another user foo pair to the query string then the script would crash because in this situation the getvalue user method call returns a list instead of a string Calling the upper method on a list is not valid since lists do not have a method of this name and results in an AttributeError exception Therefore the appropriate way to read form data values was to always use the code which checks whether the obtained value is a single value or a list of values That s annoying and leads to less readable scripts A more convenient approach is to use the methods getfirst and getlist provided by this higher level interface FieldStorage getfirst name default None This method always returns only one value associated with form field name The method returns only the first value in case that more values were posted under such name Please note that the order in which the values are received may vary from browser to browser and should not be counted on 1 If no such form field or value exists then the method returns the value specified by the optional parameter default This parameter defaults to None if not specified FieldStorage getlist name This method always returns a list of values associated with form field name The method returns an empty list if no such form field or value exists for name It returns a list consisting of one item if only one such value exists Using these methods you can write nice compact code import cgi form cgi FieldStorage user form getfirst user upper This way it s safe for item in form getlist item do_something item Functions These are useful if you want more control or if you want to employ some of the algorithms implemented in this module in other circumstances cgi parse fp None environ os environ keep_blank_values False strict_parsing False separator Parse a query in the environment or from a file the file defaults to sys stdin The keep_blank_values strict_parsing and separator parameters are passed to urllib parse parse_qs unchanged Deprecated since version 3 11 will be removed in version 3 13 This function like the rest of the cgi module is deprecated It can be replaced by calling urllib parse parse_qs directly on the desired query string except for multipart form data input which can be handled as described for parse_multipart cgi parse_multipart fp pdict encoding utf 8 errors replace separator Parse input of type multipart form data for file uploads Arguments are fp for the input file pdict for a dictionary containing other parameters in the Content Type header and encoding the request encoding Returns a dictionary just like urllib parse parse_qs keys are the field names each value is a list of values for that field For non file fields the value is a list of strings This is easy to use but not much good if you are expecting megabytes to be uploaded in that case use the FieldStorage class instead which is much more flexible Changed in version 3 7 Added the encoding and errors parameters For non file fields the value is now a list of strings not bytes Changed in version 3 10 Added the separator parameter Deprecated since version 3 11 will be removed in version 3 13 This function like the rest of the cgi module is deprecated It can be replaced with the functionality in th,en
2240,e email package e g email message EmailMessage email message Message which implements the same MIME RFCs or with the multipart PyPI project cgi parse_header string Parse a MIME header such as Content Type into a main value and a dictionary of parameters Deprecated since version 3 11 will be removed in version 3 13 This function like the rest of the cgi module is deprecated It can be replaced with the functionality in the email package which implements the same MIME RFCs For example with email message EmailMessage from email message import EmailMessage msg EmailMessage msg content type application json charset utf8 main params msg get_content_type msg content type params cgi test Robust test CGI script usable as main program Writes minimal HTTP headers and formats all information provided to the script in HTML format cgi print_environ Format the shell environment in HTML cgi print_form form Format a form in HTML cgi print_directory Format the current directory in HTML cgi print_environ_usage Print a list of useful used by CGI environment variables in HTML Caring about security There s one important rule if you invoke an external program via os system os popen or other functions with similar functionality make very sure you don t pass arbitrary strings received from the client to the shell This is a well known security hole whereby clever hackers anywhere on the web can exploit a gullible CGI script to invoke arbitrary shell commands Even parts of the URL or field names cannot be trusted since the request doesn t have to come from your form To be on the safe side if you must pass a string gotten from a form to a shell command you should make sure the string contains only alphanumeric characters dashes underscores and periods Installing your CGI script on a Unix system Read the documentation for your HTTP server and check with your local system administrator to find the directory where CGI scripts should be installed usually this is in a directory cgi bin in the server tree Make sure that your script is readable and executable by others the Unix file mode should be 0o755 octal use chmod 0755 filename Make sure that the first line of the script contains starting in column 1 followed by the pathname of the Python interpreter for instance usr local bin python Make sure the Python interpreter exists and is executable by others Make sure that any files your script needs to read or write are readable or writable respectively by others their mode should be 0o644 for readable and 0o666 for writable This is because for security reasons the HTTP server executes your script as user nobody without any special privileges It can only read write execute files that everybody can read write execute The current directory at execution time is also different it is usually the server s cgi bin directory and the set of environment variables is also different from what you get when you log in In particular don t count on the shell s search path for executables PATH or the Python module search path PYTHONPATH to be set to anything interesting If you need to load modules from a directory which is not on Python s default module search path you can change the path in your script before importing other modules For example import sys sys path insert 0 usr home joe lib python sys path insert 0 usr local lib python This way the directory inserted last will be searched first Instructions for non Unix systems will vary check your HTTP server s documentation it will usually have a section on CGI scripts Testing your CGI script Unfortunately a CGI script will generally not run when you try it from the command line and a script that works perfectly from the command line may fail mysteriously when run from the server There s one reason why you should still test your script from the command line if it contains a syntax error the Python interpreter won t execute it at all and the HTTP server will most likely send a cryptic error to the client Assuming your script has no syntax errors yet it does not work you have no choice but to read the next section Debugging ,en
2241,CGI scripts First of all check for trivial installation errors reading the section above on installing your CGI script carefully can save you a lot of time If you wonder whether you have understood the installation procedure correctly try installing a copy of this module file cgi py as a CGI script When invoked as a script the file will dump its environment and the contents of the form in HTML format Give it the right mode etc and send it a request If it s installed in the standard cgi bin directory it should be possible to send it a request by entering a URL into your browser of the form http yourhostname cgi bin cgi py name Joe Blow addr At Home If this gives an error of type 404 the server cannot find the script perhaps you need to install it in a different directory If it gives another error there s an installation problem that you should fix before trying to go any further If you get a nicely formatted listing of the environment and form content in this example the fields should be listed as addr with value At Home and name with value Joe Blow the cgi py script has been installed correctly If you follow the same procedure for your own script you should now be able to debug it The next step could be to call the cgi module s test function from your script replace its main code with the single statement cgi test This should produce the same results as those gotten from installing the cgi py file itself When an ordinary Python script raises an unhandled exception for whatever reason of a typo in a module name a file that can t be opened etc the Python interpreter prints a nice traceback and exits While the Python interpreter will still do this when your CGI script raises an exception most likely the traceback will end up in one of the HTTP server s log files or be discarded altogether Fortunately once you have managed to get your script to execute some code you can easily send tracebacks to the web browser using the cgitb module If you haven t done so already just add the lines import cgitb cgitb enable to the top of your script Then try running it again when a problem occurs you should see a detailed report that will likely make apparent the cause of the crash If you suspect that there may be a problem in importing the cgitb module you can use an even more robust approach which only uses built in modules import sys sys stderr sys stdout print Content Type text plain print your code here This relies on the Python interpreter to print the traceback The content type of the output is set to plain text which disables all HTML processing If your script works the raw HTML will be displayed by your client If it raises an exception most likely after the first two lines have been printed a traceback will be displayed Because no HTML interpretation is going on the traceback will be readable Common problems and solutions Most HTTP servers buffer the output from CGI scripts until the script is completed This means that it is not possible to display a progress report on the client s display while the script is running Check the installation instructions above Check the HTTP server s log files tail f logfile in a separate window may be useful Always check a script for syntax errors first by doing something like python script py If your script does not have any syntax errors try adding import cgitb cgitb enable to the top of the script When invoking external programs make sure they can be found Usually this means using absolute path names PATH is usually not set to a very useful value in a CGI script When reading or writing external files make sure they can be read or written by the userid under which your CGI script will be running this is typically the userid under which the web server is running or some explicitly specified userid for a web server s suexec feature Don t try to give a CGI script a set uid mode This doesn t work on most systems and is a security liability as well Footnotes 1 Note that some recent versions of the HTML specification do state what order the field values should be supplied in but knowing whether a reques,en
2242,t was received from a conforming browser or even from a browser at all is tedious and error prone,en
2243,xml etree ElementTree The ElementTree XML API Source code Lib xml etree ElementTree py The xml etree ElementTree module implements a simple and efficient API for parsing and creating XML data Changed in version 3 3 This module will use a fast implementation whenever available Deprecated since version 3 3 The xml etree cElementTree module is deprecated Warning The xml etree ElementTree module is not secure against maliciously constructed data If you need to parse untrusted or unauthenticated data see XML vulnerabilities Tutorial This is a short tutorial for using xml etree ElementTree ET in short The goal is to demonstrate some of the building blocks and basic concepts of the module XML tree and elements XML is an inherently hierarchical data format and the most natural way to represent it is with a tree ET has two classes for this purpose ElementTree represents the whole XML document as a tree and Element represents a single node in this tree Interactions with the whole document reading and writing to from files are usually done on the ElementTree level Interactions with a single XML element and its sub elements are done on the Element level Parsing XML We ll be using the following XML document as the sample data for this section xml version 1 0 data country name Liechtenstein rank 1 rank year 2008 year gdppc 141100 gdppc neighbor name Austria direction E neighbor name Switzerland direction W country country name Singapore rank 4 rank year 2011 year gdppc 59900 gdppc neighbor name Malaysia direction N country country name Panama rank 68 rank year 2011 year gdppc 13600 gdppc neighbor name Costa Rica direction W neighbor name Colombia direction E country data We can import this data by reading from a file import xml etree ElementTree as ET tree ET parse country_data xml root tree getroot Or directly from a string root ET fromstring country_data_as_string fromstring parses XML from a string directly into an Element which is the root element of the parsed tree Other parsing functions may create an ElementTree Check the documentation to be sure As an Element root has a tag and a dictionary of attributes root tag data root attrib It also has children nodes over which we can iterate for child in root print child tag child attrib country name Liechtenstein country name Singapore country name Panama Children are nested and we can access specific child nodes by index root 0 1 text 2008 Note Not all elements of the XML input will end up as elements of the parsed tree Currently this module skips over any XML comments processing instructions and document type declarations in the input Nevertheless trees built using this module s API rather than parsing from XML text can have comments and processing instructions in them they will be included when generating XML output A document type declaration may be accessed by passing a custom TreeBuilder instance to the XMLParser constructor Pull API for non blocking parsing Most parsing functions provided by this module require the whole document to be read at once before returning any result It is possible to use an XMLParser and feed data into it incrementally but it is a push API that calls methods on a callback target which is too low level and inconvenient for most needs Sometimes what the user really wants is to be able to parse XML incrementally without blocking operations while enjoying the convenience of fully constructed Element objects The most powerful tool for doing this is XMLPullParser It does not require a blocking read to obtain the XML data and is instead fed with data incrementally with XMLPullParser feed calls To get the parsed XML elements call XMLPullParser read_events Here is an example parser ET XMLPullParser start end parser feed mytag sometext list parser read_events start Element mytag at 0x7fa66db2be58 parser feed more text mytag for event elem in parser read_events print event print elem tag text elem text end mytag text sometext more text The obvious use case is applications that operate in a non blocking fashion where the XML data is being received from a socket or,en
2244, read incrementally from some storage device In such cases blocking reads are unacceptable Because it s so flexible XMLPullParser can be inconvenient to use for simpler use cases If you don t mind your application blocking on reading XML data but would still like to have incremental parsing capabilities take a look at iterparse It can be useful when you re reading a large XML document and don t want to hold it wholly in memory Where immediate feedback through events is wanted calling method XMLPullParser flush can help reduce delay please make sure to study the related security notes Finding interesting elements Element has some useful methods that help iterate recursively over all the sub tree below it its children their children and so on For example Element iter for neighbor in root iter neighbor print neighbor attrib name Austria direction E name Switzerland direction W name Malaysia direction N name Costa Rica direction W name Colombia direction E Element findall finds only elements with a tag which are direct children of the current element Element find finds the first child with a particular tag and Element text accesses the element s text content Element get accesses the element s attributes for country in root findall country rank country find rank text name country get name print name rank Liechtenstein 1 Singapore 4 Panama 68 More sophisticated specification of which elements to look for is possible by using XPath Modifying an XML File ElementTree provides a simple way to build XML documents and write them to files The ElementTree write method serves this purpose Once created an Element object may be manipulated by directly changing its fields such as Element text adding and modifying attributes Element set method as well as adding new children for example with Element append Let s say we want to add one to each country s rank and add an updated attribute to the rank element for rank in root iter rank new_rank int rank text 1 rank text str new_rank rank set updated yes tree write output xml Our XML now looks like this xml version 1 0 data country name Liechtenstein rank updated yes 2 rank year 2008 year gdppc 141100 gdppc neighbor name Austria direction E neighbor name Switzerland direction W country country name Singapore rank updated yes 5 rank year 2011 year gdppc 59900 gdppc neighbor name Malaysia direction N country country name Panama rank updated yes 69 rank year 2011 year gdppc 13600 gdppc neighbor name Costa Rica direction W neighbor name Colombia direction E country data We can remove elements using Element remove Let s say we want to remove all countries with a rank higher than 50 for country in root findall country using root findall to avoid removal during traversal rank int country find rank text if rank 50 root remove country tree write output xml Note that concurrent modification while iterating can lead to problems just like when iterating and modifying Python lists or dicts Therefore the example first collects all matching elements with root findall and only then iterates over the list of matches Our XML now looks like this xml version 1 0 data country name Liechtenstein rank updated yes 2 rank year 2008 year gdppc 141100 gdppc neighbor name Austria direction E neighbor name Switzerland direction W country country name Singapore rank updated yes 5 rank year 2011 year gdppc 59900 gdppc neighbor name Malaysia direction N country data Building XML documents The SubElement function also provides a convenient way to create new sub elements for a given element a ET Element a b ET SubElement a b c ET SubElement a c d ET SubElement c d ET dump a a b c d c a Parsing XML with Namespaces If the XML input has namespaces tags and attributes with prefixes in the form prefix sometag get expanded to uri sometag where the prefix is replaced by the full URI Also if there is a default namespace that full URI gets prepended to all of the non prefixed tags Here is an XML example that incorporates two namespaces one with the prefix fictional and the other serving as the default namespace xml version 1 0 actors xml,en
2245,ns fictional http characters example com xmlns http people example com actor name John Cleese name fictional character Lancelot fictional character fictional character Archie Leach fictional character actor actor name Eric Idle name fictional character Sir Robin fictional character fictional character Gunther fictional character fictional character Commander Clement fictional character actor actors One way to search and explore this XML example is to manually add the URI to every tag or attribute in the xpath of a find or findall root fromstring xml_text for actor in root findall http people example com actor name actor find http people example com name print name text for char in actor findall http characters example com character print char text A better way to search the namespaced XML example is to create a dictionary with your own prefixes and use those in the search functions ns real_person http people example com role http characters example com for actor in root findall real_person actor ns name actor find real_person name ns print name text for char in actor findall role character ns print char text These two approaches both output John Cleese Lancelot Archie Leach Eric Idle Sir Robin Gunther Commander Clement XPath support This module provides limited support for XPath expressions for locating elements in a tree The goal is to support a small subset of the abbreviated syntax a full XPath engine is outside the scope of the module Example Here s an example that demonstrates some of the XPath capabilities of the module We ll be using the countrydata XML document from the Parsing XML section import xml etree ElementTree as ET root ET fromstring countrydata Top level elements root findall All neighbor grand children of country children of the top level elements root findall country neighbor Nodes with name Singapore that have a year child root findall year name Singapore year nodes that are children of nodes with name Singapore root findall name Singapore year All neighbor nodes that are the second child of their parent root findall neighbor 2 For XML with namespaces use the usual qualified namespace tag notation All dublin core title tags in the document root findall http purl org dc elements 1 1 title Supported XPath syntax Syntax Meaning tag Selects all child elements with the given tag For example spam selects all child elements named spam and spam egg selects all grandchildren named egg in all children named spam namespace selects all tags in the given namespace spam selects tags named spam in any or no namespace and only selects tags that are not in a namespace Changed in version 3 8 Support for star wildcards was added Selects all child elements including comments and processing instructions For example egg selects all grandchildren named egg Selects the current node This is mostly useful at the beginning of the path to indicate that it s a relative path Selects all subelements on all levels beneath the current element For example egg selects all egg elements in the entire tree Selects the parent element Returns None if the path attempts to reach the ancestors of the start element the element find was called on attrib Selects all elements that have the given attribute attrib value Selects all elements for which the given attribute has the given value The value cannot contain quotes attrib value Selects all elements for which the given attribute does not have the given value The value cannot contain quotes New in version 3 10 tag Selects all elements that have a child named tag Only immediate children are supported text Selects all elements whose complete text content including descendants equals the given text New in version 3 7 text Selects all elements whose complete text content including descendants does not equal the given text New in version 3 10 tag text Selects all elements that have a child named tag whose complete text content including descendants equals the given text tag text Selects all elements that have a child named tag whose complete text content including descendants does not equal the give,en
2246,n text New in version 3 10 position Selects all elements that are located at the given position The position can be either an integer 1 is the first position the expression last for the last position or a position relative to the last position e g last 1 Predicates expressions within square brackets must be preceded by a tag name an asterisk or another predicate position predicates must be preceded by a tag name Reference Functions xml etree ElementTree canonicalize xml_data None out None from_file None options C14N 2 0 transformation function Canonicalization is a way to normalise XML output in a way that allows byte by byte comparisons and digital signatures It reduced the freedom that XML serializers have and instead generates a more constrained XML representation The main restrictions regard the placement of namespace declarations the ordering of attributes and ignorable whitespace This function takes an XML data string xml_data or a file path or file like object from_file as input converts it to the canonical form and writes it out using the out file like object if provided or returns it as a text string if not The output file receives text not bytes It should therefore be opened in text mode with utf 8 encoding Typical uses xml_data root root print canonicalize xml_data with open c14n_output xml mode w encoding utf 8 as out_file canonicalize xml_data out out_file with open c14n_output xml mode w encoding utf 8 as out_file canonicalize from_file inputfile xml out out_file The configuration options are as follows with_comments set to true to include comments default false strip_text set to true to strip whitespace before and after text content default false rewrite_prefixes set to true to replace namespace prefixes by n number default false qname_aware_tags a set of qname aware tag names in which prefixes should be replaced in text content default empty qname_aware_attrs a set of qname aware attribute names in which prefixes should be replaced in text content default empty exclude_attrs a set of attribute names that should not be serialised exclude_tags a set of tag names that should not be serialised In the option list above a set refers to any collection or iterable of strings no ordering is expected New in version 3 8 xml etree ElementTree Comment text None Comment element factory This factory function creates a special element that will be serialized as an XML comment by the standard serializer The comment string can be either a bytestring or a Unicode string text is a string containing the comment string Returns an element instance representing a comment Note that XMLParser skips over comments in the input instead of creating comment objects for them An ElementTree will only contain comment nodes if they have been inserted into to the tree using one of the Element methods xml etree ElementTree dump elem Writes an element tree or element structure to sys stdout This function should be used for debugging only The exact output format is implementation dependent In this version it s written as an ordinary XML file elem is an element tree or an individual element Changed in version 3 8 The dump function now preserves the attribute order specified by the user xml etree ElementTree fromstring text parser None Parses an XML section from a string constant Same as XML text is a string containing XML data parser is an optional parser instance If not given the standard XMLParser parser is used Returns an Element instance xml etree ElementTree fromstringlist sequence parser None Parses an XML document from a sequence of string fragments sequence is a list or other sequence containing XML data fragments parser is an optional parser instance If not given the standard XMLParser parser is used Returns an Element instance New in version 3 2 xml etree ElementTree indent tree space level 0 Appends whitespace to the subtree to indent the tree visually This can be used to generate pretty printed XML output tree can be an Element or ElementTree space is the whitespace string that will be inserted for each indentation level two space c,en
2247,haracters by default For indenting partial subtrees inside of an already indented tree pass the initial indentation level as level New in version 3 9 xml etree ElementTree iselement element Check if an object appears to be a valid element object element is an element instance Return True if this is an element object xml etree ElementTree iterparse source events None parser None Parses an XML section into an element tree incrementally and reports what s going on to the user source is a filename or file object containing XML data events is a sequence of events to report back The supported events are the strings start end comment pi start ns and end ns the ns events are used to get detailed namespace information If events is omitted only end events are reported parser is an optional parser instance If not given the standard XMLParser parser is used parser must be a subclass of XMLParser and can only use the default TreeBuilder as a target Returns an iterator providing event elem pairs it has a root attribute that references the root element of the resulting XML tree once source is fully read Note that while iterparse builds the tree incrementally it issues blocking reads on source or the file it names As such it s unsuitable for applications where blocking reads can t be made For fully non blocking parsing see XMLPullParser Note iterparse only guarantees that it has seen the character of a starting tag when it emits a start event so the attributes are defined but the contents of the text and tail attributes are undefined at that point The same applies to the element children they may or may not be present If you need a fully populated element look for end events instead Deprecated since version 3 4 The parser argument Changed in version 3 8 The comment and pi events were added xml etree ElementTree parse source parser None Parses an XML section into an element tree source is a filename or file object containing XML data parser is an optional parser instance If not given the standard XMLParser parser is used Returns an ElementTree instance xml etree ElementTree ProcessingInstruction target text None PI element factory This factory function creates a special element that will be serialized as an XML processing instruction target is a string containing the PI target text is a string containing the PI contents if given Returns an element instance representing a processing instruction Note that XMLParser skips over processing instructions in the input instead of creating PI objects for them An ElementTree will only contain processing instruction nodes if they have been inserted into to the tree using one of the Element methods xml etree ElementTree register_namespace prefix uri Registers a namespace prefix The registry is global and any existing mapping for either the given prefix or the namespace URI will be removed prefix is a namespace prefix uri is a namespace uri Tags and attributes in this namespace will be serialized with the given prefix if at all possible New in version 3 2 xml etree ElementTree SubElement parent tag attrib extra Subelement factory This function creates an element instance and appends it to an existing element The element name attribute names and attribute values can be either bytestrings or Unicode strings parent is the parent element tag is the subelement name attrib is an optional dictionary containing element attributes extra contains additional attributes given as keyword arguments Returns an element instance xml etree ElementTree tostring element encoding us ascii method xml xml_declaration None default_namespace None short_empty_elements True Generates a string representation of an XML element including all subelements element is an Element instance encoding 1 is the output encoding default is US ASCII Use encoding unicode to generate a Unicode string otherwise a bytestring is generated method is either xml html or text default is xml xml_declaration default_namespace and short_empty_elements has the same meaning as in ElementTree write Returns an optionally encoded string containing the XML data,en
2248, Changed in version 3 4 Added the short_empty_elements parameter Changed in version 3 8 Added the xml_declaration and default_namespace parameters Changed in version 3 8 The tostring function now preserves the attribute order specified by the user xml etree ElementTree tostringlist element encoding us ascii method xml xml_declaration None default_namespace None short_empty_elements True Generates a string representation of an XML element including all subelements element is an Element instance encoding 1 is the output encoding default is US ASCII Use encoding unicode to generate a Unicode string otherwise a bytestring is generated method is either xml html or text default is xml xml_declaration default_namespace and short_empty_elements has the same meaning as in ElementTree write Returns a list of optionally encoded strings containing the XML data It does not guarantee any specific sequence except that b join tostringlist element tostring element New in version 3 2 Changed in version 3 4 Added the short_empty_elements parameter Changed in version 3 8 Added the xml_declaration and default_namespace parameters Changed in version 3 8 The tostringlist function now preserves the attribute order specified by the user xml etree ElementTree XML text parser None Parses an XML section from a string constant This function can be used to embed XML literals in Python code text is a string containing XML data parser is an optional parser instance If not given the standard XMLParser parser is used Returns an Element instance xml etree ElementTree XMLID text parser None Parses an XML section from a string constant and also returns a dictionary which maps from element id s to elements text is a string containing XML data parser is an optional parser instance If not given the standard XMLParser parser is used Returns a tuple containing an Element instance and a dictionary XInclude support This module provides limited support for XInclude directives via the xml etree ElementInclude helper module This module can be used to insert subtrees and text strings into element trees based on information in the tree Example Here s an example that demonstrates use of the XInclude module To include an XML document in the current document use the http www w3 org 2001 XInclude include element and set the parse attribute to xml and use the href attribute to specify the document to include xml version 1 0 document xmlns xi http www w3 org 2001 XInclude xi include href source xml parse xml document By default the href attribute is treated as a file name You can use custom loaders to override this behaviour Also note that the standard helper does not support XPointer syntax To process this file load it as usual and pass the root element to the xml etree ElementTree module from xml etree import ElementTree ElementInclude tree ElementTree parse document xml root tree getroot ElementInclude include root The ElementInclude module replaces the http www w3 org 2001 XInclude include element with the root element from the source xml document The result might look something like this document xmlns xi http www w3 org 2001 XInclude para This is a paragraph para document If the parse attribute is omitted it defaults to xml The href attribute is required To include a text document use the http www w3 org 2001 XInclude include element and set the parse attribute to text xml version 1 0 document xmlns xi http www w3 org 2001 XInclude Copyright c xi include href year txt parse text document The result might look something like document xmlns xi http www w3 org 2001 XInclude Copyright c 2003 document Reference Functions xml etree ElementInclude default_loader href parse encoding None Default loader This default loader reads an included resource from disk href is a URL parse is for parse mode either xml or text encoding is an optional text encoding If not given encoding is utf 8 Returns the expanded resource If the parse mode is xml this is an ElementTree instance If the parse mode is text this is a Unicode string If the loader fails it can return None or raise an exception,en
2249, xml etree ElementInclude include elem loader None base_url None max_depth 6 This function expands XInclude directives elem is the root element loader is an optional resource loader If omitted it defaults to default_loader If given it should be a callable that implements the same interface as default_loader base_url is base URL of the original file to resolve relative include file references max_depth is the maximum number of recursive inclusions Limited to reduce the risk of malicious content explosion Pass a negative value to disable the limitation Returns the expanded resource If the parse mode is xml this is an ElementTree instance If the parse mode is text this is a Unicode string If the loader fails it can return None or raise an exception Changed in version 3 9 Added the base_url and max_depth parameters Element Objects class xml etree ElementTree Element tag attrib extra Element class This class defines the Element interface and provides a reference implementation of this interface The element name attribute names and attribute values can be either bytestrings or Unicode strings tag is the element name attrib is an optional dictionary containing element attributes extra contains additional attributes given as keyword arguments tag A string identifying what kind of data this element represents the element type in other words text tail These attributes can be used to hold additional data associated with the element Their values are usually strings but may be any application specific object If the element is created from an XML file the text attribute holds either the text between the element s start tag and its first child or end tag or None and the tail attribute holds either the text between the element s end tag and the next tag or None For the XML data a b 1 c 2 d 3 c b 4 a the a element has None for both text and tail attributes the b element has text 1 and tail 4 the c element has text 2 and tail None and the d element has text None and tail 3 To collect the inner text of an element see itertext for example join element itertext Applications may store arbitrary objects in these attributes attrib A dictionary containing the element s attributes Note that while the attrib value is always a real mutable Python dictionary an ElementTree implementation may choose to use another internal representation and create the dictionary only if someone asks for it To take advantage of such implementations use the dictionary methods below whenever possible The following dictionary like methods work on the element attributes clear Resets an element This function removes all subelements clears all attributes and sets the text and tail attributes to None get key default None Gets the element attribute named key Returns the attribute value or default if the attribute was not found items Returns the element attributes as a sequence of name value pairs The attributes are returned in an arbitrary order keys Returns the elements attribute names as a list The names are returned in an arbitrary order set key value Set the attribute key on the element to value The following methods work on the element s children subelements append subelement Adds the element subelement to the end of this element s internal list of subelements Raises TypeError if subelement is not an Element extend subelements Appends subelements from a sequence object with zero or more elements Raises TypeError if a subelement is not an Element New in version 3 2 find match namespaces None Finds the first subelement matching match match may be a tag name or a path Returns an element instance or None namespaces is an optional mapping from namespace prefix to full name Pass as prefix to move all unprefixed tag names in the expression into the given namespace findall match namespaces None Finds all matching subelements by tag name or path Returns a list containing all matching elements in document order namespaces is an optional mapping from namespace prefix to full name Pass as prefix to move all unprefixed tag names in the expression into the given namespace findtext ma,en
2250,tch default None namespaces None Finds text for the first subelement matching match match may be a tag name or a path Returns the text content of the first matching element or default if no element was found Note that if the matching element has no text content an empty string is returned namespaces is an optional mapping from namespace prefix to full name Pass as prefix to move all unprefixed tag names in the expression into the given namespace insert index subelement Inserts subelement at the given position in this element Raises TypeError if subelement is not an Element iter tag None Creates a tree iterator with the current element as the root The iterator iterates over this element and all elements below it in document depth first order If tag is not None or only elements whose tag equals tag are returned from the iterator If the tree structure is modified during iteration the result is undefined New in version 3 2 iterfind match namespaces None Finds all matching subelements by tag name or path Returns an iterable yielding all matching elements in document order namespaces is an optional mapping from namespace prefix to full name New in version 3 2 itertext Creates a text iterator The iterator loops over this element and all subelements in document order and returns all inner text New in version 3 2 makeelement tag attrib Creates a new element object of the same type as this element Do not call this method use the SubElement factory function instead remove subelement Removes subelement from the element Unlike the find methods this method compares elements based on the instance identity not on tag value or contents Element objects also support the following sequence type methods for working with subelements __delitem__ __getitem__ __setitem__ __len__ Caution Elements with no subelements will test as False Testing the truth value of an Element is deprecated and will raise an exception in Python 3 14 Use specific len elem or elem is None test instead element root find foo if not element careful print element not found or element has no subelements if element is None print element not found Changed in version 3 12 Testing the truth value of an Element emits DeprecationWarning Prior to Python 3 8 the serialisation order of the XML attributes of elements was artificially made predictable by sorting the attributes by their name Based on the now guaranteed ordering of dicts this arbitrary reordering was removed in Python 3 8 to preserve the order in which attributes were originally parsed or created by user code In general user code should try not to depend on a specific ordering of attributes given that the XML Information Set explicitly excludes the attribute order from conveying information Code should be prepared to deal with any ordering on input In cases where deterministic XML output is required e g for cryptographic signing or test data sets canonical serialisation is available with the canonicalize function In cases where canonical output is not applicable but a specific attribute order is still desirable on output code should aim for creating the attributes directly in the desired order to avoid perceptual mismatches for readers of the code In cases where this is difficult to achieve a recipe like the following can be applied prior to serialisation to enforce an order independently from the Element creation def reorder_attributes root for el in root iter attrib el attrib if len attrib 1 adjust attribute order e g by sorting attribs sorted attrib items attrib clear attrib update attribs ElementTree Objects class xml etree ElementTree ElementTree element None file None ElementTree wrapper class This class represents an entire element hierarchy and adds some extra support for serialization to and from standard XML element is the root element The tree is initialized with the contents of the XML file if given _setroot element Replaces the root element for this tree This discards the current contents of the tree and replaces it with the given element Use with care element is an element instance find match namespaces Non,en
2251,e Same as Element find starting at the root of the tree findall match namespaces None Same as Element findall starting at the root of the tree findtext match default None namespaces None Same as Element findtext starting at the root of the tree getroot Returns the root element for this tree iter tag None Creates and returns a tree iterator for the root element The iterator loops over all elements in this tree in section order tag is the tag to look for default is to return all elements iterfind match namespaces None Same as Element iterfind starting at the root of the tree New in version 3 2 parse source parser None Loads an external XML section into this element tree source is a file name or file object parser is an optional parser instance If not given the standard XMLParser parser is used Returns the section root element write file encoding us ascii xml_declaration None default_namespace None method xml short_empty_elements True Writes the element tree to a file as XML file is a file name or a file object opened for writing encoding 1 is the output encoding default is US ASCII xml_declaration controls if an XML declaration should be added to the file Use False for never True for always None for only if not US ASCII or UTF 8 or Unicode default is None default_namespace sets the default XML namespace for xmlns method is either xml html or text default is xml The keyword only short_empty_elements parameter controls the formatting of elements that contain no content If True the default they are emitted as a single self closed tag otherwise they are emitted as a pair of start end tags The output is either a string str or binary bytes This is controlled by the encoding argument If encoding is unicode the output is a string otherwise it s binary Note that this may conflict with the type of file if it s an open file object make sure you do not try to write a string to a binary stream and vice versa Changed in version 3 4 Added the short_empty_elements parameter Changed in version 3 8 The write method now preserves the attribute order specified by the user This is the XML file that is going to be manipulated html head title Example page title head body p Moved to a href http example org example org a or a href http example com example com a p body html Example of changing the attribute target of every link in first paragraph from xml etree ElementTree import ElementTree tree ElementTree tree parse index xhtml Element html at 0xb77e6fac p tree find body p Finds first occurrence of tag p in body p Element p at 0xb77ec26c links list p iter a Returns list of all links links Element a at 0xb77ec2ac Element a at 0xb77ec1cc for i in links Iterates through all found links i attrib target blank tree write output xhtml QName Objects class xml etree ElementTree QName text_or_uri tag None QName wrapper This can be used to wrap a QName attribute value in order to get proper namespace handling on output text_or_uri is a string containing the QName value in the form uri local or if the tag argument is given the URI part of a QName If tag is given the first argument is interpreted as a URI and this argument is interpreted as a local name QName instances are opaque TreeBuilder Objects class xml etree ElementTree TreeBuilder element_factory None comment_factory None pi_factory None insert_comments False insert_pis False Generic element structure builder This builder converts a sequence of start data end comment and pi method calls to a well formed element structure You can use this class to build an element structure using a custom XML parser or a parser for some other XML like format element_factory when given must be a callable accepting two positional arguments a tag and a dict of attributes It is expected to return a new element instance The comment_factory and pi_factory functions when given should behave like the Comment and ProcessingInstruction functions to create comments and processing instructions When not given the default factories will be used When insert_comments and or insert_pis is true comments pis will be inserted into the tr,en
2252,ee if they appear within the root element but not outside of it close Flushes the builder buffers and returns the toplevel document element Returns an Element instance data data Adds text to the current element data is a string This should be either a bytestring or a Unicode string end tag Closes the current element tag is the element name Returns the closed element start tag attrs Opens a new element tag is the element name attrs is a dictionary containing element attributes Returns the opened element comment text Creates a comment with the given text If insert_comments is true this will also add it to the tree New in version 3 8 pi target text Creates a process instruction with the given target name and text If insert_pis is true this will also add it to the tree New in version 3 8 In addition a custom TreeBuilder object can provide the following methods doctype name pubid system Handles a doctype declaration name is the doctype name pubid is the public identifier system is the system identifier This method does not exist on the default TreeBuilder class New in version 3 2 start_ns prefix uri Is called whenever the parser encounters a new namespace declaration before the start callback for the opening element that defines it prefix is for the default namespace and the declared namespace prefix name otherwise uri is the namespace URI New in version 3 8 end_ns prefix Is called after the end callback of an element that declared a namespace prefix mapping with the name of the prefix that went out of scope New in version 3 8 class xml etree ElementTree C14NWriterTarget write with_comments False strip_text False rewrite_prefixes False qname_aware_tags None qname_aware_attrs None exclude_attrs None exclude_tags None A C14N 2 0 writer Arguments are the same as for the canonicalize function This class does not build a tree but translates the callback events directly into a serialised form using the write function New in version 3 8 XMLParser Objects class xml etree ElementTree XMLParser target None encoding None This class is the low level building block of the module It uses xml parsers expat for efficient event based parsing of XML It can be fed XML data incrementally with the feed method and parsing events are translated to a push API by invoking callbacks on the target object If target is omitted the standard TreeBuilder is used If encoding 1 is given the value overrides the encoding specified in the XML file Changed in version 3 8 Parameters are now keyword only The html argument no longer supported close Finishes feeding data to the parser Returns the result of calling the close method of the target passed during construction by default this is the toplevel document element feed data Feeds data to the parser data is encoded data flush Triggers parsing of any previously fed unparsed data which can be used to ensure more immediate feedback in particular with Expat 2 6 0 The implementation of flush temporarily disables reparse deferral with Expat if currently enabled and triggers a reparse Disabling reparse deferral has security consequences please see xml parsers expat xmlparser SetReparseDeferralEnabled for details Note that flush has been backported to some prior releases of CPython as a security fix Check for availability of flush using hasattr if used in code running across a variety of Python versions New in version 3 12 3 XMLParser feed calls target s start tag attrs_dict method for each opening tag its end tag method for each closing tag and data is processed by method data data For further supported callback methods see the TreeBuilder class XMLParser close calls target s method close XMLParser can be used not only for building a tree structure This is an example of counting the maximum depth of an XML file from xml etree ElementTree import XMLParser class MaxDepth The target object of the parser maxDepth 0 depth 0 def start self tag attrib Called for each opening tag self depth 1 if self depth self maxDepth self maxDepth self depth def end self tag Called for each closing tag self depth 1 def data self data pass We,en
2253, do not need to do anything with data def close self Called when all data has been parsed return self maxDepth target MaxDepth parser XMLParser target target exampleXml a b b b c d d c b a parser feed exampleXml parser close 4 XMLPullParser Objects class xml etree ElementTree XMLPullParser events None A pull parser suitable for non blocking applications Its input side API is similar to that of XMLParser but instead of pushing calls to a callback target XMLPullParser collects an internal list of parsing events and lets the user read from it events is a sequence of events to report back The supported events are the strings start end comment pi start ns and end ns the ns events are used to get detailed namespace information If events is omitted only end events are reported feed data Feed the given bytes data to the parser flush Triggers parsing of any previously fed unparsed data which can be used to ensure more immediate feedback in particular with Expat 2 6 0 The implementation of flush temporarily disables reparse deferral with Expat if currently enabled and triggers a reparse Disabling reparse deferral has security consequences please see xml parsers expat xmlparser SetReparseDeferralEnabled for details Note that flush has been backported to some prior releases of CPython as a security fix Check for availability of flush using hasattr if used in code running across a variety of Python versions New in version 3 12 3 close Signal the parser that the data stream is terminated Unlike XMLParser close this method always returns None Any events not yet retrieved when the parser is closed can still be read with read_events read_events Return an iterator over the events which have been encountered in the data fed to the parser The iterator yields event elem pairs where event is a string representing the type of event e g end and elem is the encountered Element object or other context value as follows start end the current Element comment pi the current comment processing instruction start ns a tuple prefix uri naming the declared namespace mapping end ns None this may change in a future version Events provided in a previous call to read_events will not be yielded again Events are consumed from the internal queue only when they are retrieved from the iterator so multiple readers iterating in parallel over iterators obtained from read_events will have unpredictable results Note XMLPullParser only guarantees that it has seen the character of a starting tag when it emits a start event so the attributes are defined but the contents of the text and tail attributes are undefined at that point The same applies to the element children they may or may not be present If you need a fully populated element look for end events instead New in version 3 4 Changed in version 3 8 The comment and pi events were added Exceptions class xml etree ElementTree ParseError XML parse error raised by the various parsing methods in this module when parsing fails The string representation of an instance of this exception will contain a user friendly error message In addition it will have the following attributes available code A numeric error code from the expat parser See the documentation of xml parsers expat for the list of error codes and their meanings position A tuple of line column numbers specifying where the error occurred Footnotes 1 The encoding string included in XML output should conform to the appropriate standards For example UTF 8 is valid but UTF8 is not See https www w3 org TR 2006 REC xml11 20060816 NT EncodingDecl and https www iana org assignments character sets character sets xhtml,en
2254,os path Common pathname manipulations Source code Lib posixpath py for POSIX and Lib ntpath py for Windows This module implements some useful functions on pathnames To read or write files see open and for accessing the filesystem see the os module The path parameters can be passed as strings or bytes or any object implementing the os PathLike protocol Unlike a Unix shell Python does not do any automatic path expansions Functions such as expanduser and expandvars can be invoked explicitly when an application desires shell like path expansion See also the glob module See also The pathlib module offers high level path objects Note All of these functions accept either only bytes or only string objects as their parameters The result is an object of the same type if a path or file name is returned Note Since different operating systems have different path name conventions there are several versions of this module in the standard library The os path module is always the path module suitable for the operating system Python is running on and therefore usable for local paths However you can also import and use the individual modules if you want to manipulate a path that is always in one of the different formats They all have the same interface posixpath for UNIX style paths ntpath for Windows paths Changed in version 3 8 exists lexists isdir isfile islink and ismount now return False instead of raising an exception for paths that contain characters or bytes unrepresentable at the OS level os path abspath path Return a normalized absolutized version of the pathname path On most platforms this is equivalent to calling the function normpath as follows normpath join os getcwd path Changed in version 3 6 Accepts a path like object os path basename path Return the base name of pathname path This is the second element of the pair returned by passing path to the function split Note that the result of this function is different from the Unix basename program where basename for foo bar returns bar the basename function returns an empty string Changed in version 3 6 Accepts a path like object os path commonpath paths Return the longest common sub path of each pathname in the sequence paths Raise ValueError if paths contain both absolute and relative pathnames the paths are on the different drives or if paths is empty Unlike commonprefix this returns a valid path Availability Unix Windows New in version 3 5 Changed in version 3 6 Accepts a sequence of path like objects os path commonprefix list Return the longest path prefix taken character by character that is a prefix of all paths in list If list is empty return the empty string Note This function may return invalid paths because it works a character at a time To obtain a valid path see commonpath os path commonprefix usr lib usr local lib usr l os path commonpath usr lib usr local lib usr Changed in version 3 6 Accepts a path like object os path dirname path Return the directory name of pathname path This is the first element of the pair returned by passing path to the function split Changed in version 3 6 Accepts a path like object os path exists path Return True if path refers to an existing path or an open file descriptor Returns False for broken symbolic links On some platforms this function may return False if permission is not granted to execute os stat on the requested file even if the path physically exists Changed in version 3 3 path can now be an integer True is returned if it is an open file descriptor False otherwise Changed in version 3 6 Accepts a path like object os path lexists path Return True if path refers to an existing path Returns True for broken symbolic links Equivalent to exists on platforms lacking os lstat Changed in version 3 6 Accepts a path like object os path expanduser path On Unix and Windows return the argument with an initial component of or user replaced by that user s home directory On Unix an initial is replaced by the environment variable HOME if it is set otherwise the current user s home directory is looked up in the password directory through the b,en
2255,uilt in module pwd An initial user is looked up directly in the password directory On Windows USERPROFILE will be used if set otherwise a combination of HOMEPATH and HOMEDRIVE will be used An initial user is handled by checking that the last directory component of the current user s home directory matches USERNAME and replacing it if so If the expansion fails or if the path does not begin with a tilde the path is returned unchanged Changed in version 3 6 Accepts a path like object Changed in version 3 8 No longer uses HOME on Windows os path expandvars path Return the argument with environment variables expanded Substrings of the form name or name are replaced by the value of environment variable name Malformed variable names and references to non existing variables are left unchanged On Windows name expansions are supported in addition to name and name Changed in version 3 6 Accepts a path like object os path getatime path Return the time of last access of path The return value is a floating point number giving the number of seconds since the epoch see the time module Raise OSError if the file does not exist or is inaccessible os path getmtime path Return the time of last modification of path The return value is a floating point number giving the number of seconds since the epoch see the time module Raise OSError if the file does not exist or is inaccessible Changed in version 3 6 Accepts a path like object os path getctime path Return the system s ctime which on some systems like Unix is the time of the last metadata change and on others like Windows is the creation time for path The return value is a number giving the number of seconds since the epoch see the time module Raise OSError if the file does not exist or is inaccessible Changed in version 3 6 Accepts a path like object os path getsize path Return the size in bytes of path Raise OSError if the file does not exist or is inaccessible Changed in version 3 6 Accepts a path like object os path isabs path Return True if path is an absolute pathname On Unix that means it begins with a slash on Windows that it begins with a back slash after chopping off a potential drive letter Changed in version 3 6 Accepts a path like object os path isfile path Return True if path is an existing regular file This follows symbolic links so both islink and isfile can be true for the same path Changed in version 3 6 Accepts a path like object os path isdir path Return True if path is an existing directory This follows symbolic links so both islink and isdir can be true for the same path Changed in version 3 6 Accepts a path like object os path isjunction path Return True if path refers to an existing directory entry that is a junction Always return False if junctions are not supported on the current platform New in version 3 12 os path islink path Return True if path refers to an existing directory entry that is a symbolic link Always False if symbolic links are not supported by the Python runtime Changed in version 3 6 Accepts a path like object os path ismount path Return True if pathname path is a mount point a point in a file system where a different file system has been mounted On POSIX the function checks whether path s parent path is on a different device than path or whether path and path point to the same i node on the same device this should detect mount points for all Unix and POSIX variants It is not able to reliably detect bind mounts on the same filesystem On Windows a drive letter root and a share UNC are always mount points and for any other path GetVolumePathName is called to see if it is different from the input path New in version 3 4 Support for detecting non root mount points on Windows Changed in version 3 6 Accepts a path like object os path isdevdrive path Return True if pathname path is located on a Windows Dev Drive A Dev Drive is optimized for developer scenarios and offers faster performance for reading and writing files It is recommended for use for source code temporary build directories package caches and other IO intensive operations May raise an error ,en
2256,for an invalid path for example one without a recognizable drive but returns False on platforms that do not support Dev Drives See the Windows documentation for information on enabling and creating Dev Drives Availability Windows New in version 3 12 os path join path paths Join one or more path segments intelligently The return value is the concatenation of path and all members of paths with exactly one directory separator following each non empty part except the last That is the result will only end in a separator if the last part is either empty or ends in a separator If a segment is an absolute path which on Windows requires both a drive and a root then all previous segments are ignored and joining continues from the absolute path segment On Windows the drive is not reset when a rooted path segment e g r foo is encountered If a segment is on a different drive or is an absolute path all previous segments are ignored and the drive is reset Note that since there is a current directory for each drive os path join c foo represents a path relative to the current directory on drive C c foo not c foo Changed in version 3 6 Accepts a path like object for path and paths os path normcase path Normalize the case of a pathname On Windows convert all characters in the pathname to lowercase and also convert forward slashes to backward slashes On other operating systems return the path unchanged Changed in version 3 6 Accepts a path like object os path normpath path Normalize a pathname by collapsing redundant separators and up level references so that A B A B A B and A foo B all become A B This string manipulation may change the meaning of a path that contains symbolic links On Windows it converts forward slashes to backward slashes To normalize case use normcase Note On POSIX systems in accordance with IEEE Std 1003 1 2013 Edition 4 13 Pathname Resolution if a pathname begins with exactly two slashes the first component following the leading characters may be interpreted in an implementation defined manner although more than two leading characters shall be treated as a single character Changed in version 3 6 Accepts a path like object os path realpath path strict False Return the canonical path of the specified filename eliminating any symbolic links encountered in the path if they are supported by the operating system If a path doesn t exist or a symlink loop is encountered and strict is True OSError is raised If strict is False the path is resolved as far as possible and any remainder is appended without checking whether it exists Note This function emulates the operating system s procedure for making a path canonical which differs slightly between Windows and UNIX with respect to how links and subsequent path components interact Operating system APIs make paths canonical as needed so it s not normally necessary to call this function Changed in version 3 6 Accepts a path like object Changed in version 3 8 Symbolic links and junctions are now resolved on Windows Changed in version 3 10 The strict parameter was added os path relpath path start os curdir Return a relative filepath to path either from the current directory or from an optional start directory This is a path computation the filesystem is not accessed to confirm the existence or nature of path or start On Windows ValueError is raised when path and start are on different drives start defaults to os curdir Availability Unix Windows Changed in version 3 6 Accepts a path like object os path samefile path1 path2 Return True if both pathname arguments refer to the same file or directory This is determined by the device number and i node number and raises an exception if an os stat call on either pathname fails Availability Unix Windows Changed in version 3 2 Added Windows support Changed in version 3 4 Windows now uses the same implementation as all other platforms Changed in version 3 6 Accepts a path like object os path sameopenfile fp1 fp2 Return True if the file descriptors fp1 and fp2 refer to the same file Availability Unix Windows Changed in version 3 2 Added Windows s,en
2257,upport Changed in version 3 6 Accepts a path like object os path samestat stat1 stat2 Return True if the stat tuples stat1 and stat2 refer to the same file These structures may have been returned by os fstat os lstat or os stat This function implements the underlying comparison used by samefile and sameopenfile Availability Unix Windows Changed in version 3 4 Added Windows support Changed in version 3 6 Accepts a path like object os path split path Split the pathname path into a pair head tail where tail is the last pathname component and head is everything leading up to that The tail part will never contain a slash if path ends in a slash tail will be empty If there is no slash in path head will be empty If path is empty both head and tail are empty Trailing slashes are stripped from head unless it is the root one or more slashes only In all cases join head tail returns a path to the same location as path but the strings may differ Also see the functions dirname and basename Changed in version 3 6 Accepts a path like object os path splitdrive path Split the pathname path into a pair drive tail where drive is either a mount point or the empty string On systems which do not use drive specifications drive will always be the empty string In all cases drive tail will be the same as path On Windows splits a pathname into drive UNC sharepoint and relative path If the path contains a drive letter drive will contain everything up to and including the colon splitdrive c dir c dir If the path contains a UNC path drive will contain the host name and share splitdrive host computer dir host computer dir Changed in version 3 6 Accepts a path like object os path splitroot path Split the pathname path into a 3 item tuple drive root tail where drive is a device name or mount point root is a string of separators after the drive and tail is everything after the root Any of these items may be the empty string In all cases drive root tail will be the same as path On POSIX systems drive is always empty The root may be empty if path is relative a single forward slash if path is absolute or two forward slashes implementation defined per IEEE Std 1003 1 2017 4 13 Pathname Resolution For example splitroot home sam home sam splitroot home sam home sam splitroot home sam home sam On Windows drive may be empty a drive letter name a UNC share or a device name The root may be empty a forward slash or a backward slash For example splitroot C Users Sam C Users Sam splitroot Server Share Users Sam Server Share Users Sam New in version 3 12 os path splitext path Split the pathname path into a pair root ext such that root ext path and the extension ext is empty or begins with a period and contains at most one period If the path contains no extension ext will be splitext bar bar If the path contains an extension then ext will be set to this extension including the leading period Note that previous periods will be ignored splitext foo bar exe foo bar exe splitext foo bar exe foo bar exe Leading periods of the last component of the path are considered to be part of the root splitext cshrc cshrc splitext foo jpg foo jpg Changed in version 3 6 Accepts a path like object os path supports_unicode_filenames True if arbitrary Unicode strings can be used as file names within limitations imposed by the file system,en
2258,11 Brief Tour of the Standard Library Part II This second tour covers more advanced modules that support professional programming needs These modules rarely occur in small scripts 11 1 Output Formatting The reprlib module provides a version of repr customized for abbreviated displays of large or deeply nested containers import reprlib reprlib repr set supercalifragilisticexpialidocious a c d e f g The pprint module offers more sophisticated control over printing both built in and user defined objects in a way that is readable by the interpreter When the result is longer than one line the pretty printer adds line breaks and indentation to more clearly reveal data structure import pprint t black cyan white green red magenta yellow blue pprint pprint t width 30 black cyan white green red magenta yellow blue The textwrap module formats paragraphs of text to fit a given screen width import textwrap doc The wrap method is just like fill except that it returns a list of strings instead of one big string with newlines to separate the wrapped lines print textwrap fill doc width 40 The wrap method is just like fill except that it returns a list of strings instead of one big string with newlines to separate the wrapped lines The locale module accesses a database of culture specific data formats The grouping attribute of locale s format function provides a direct way of formatting numbers with group separators import locale locale setlocale locale LC_ALL English_United States 1252 English_United States 1252 conv locale localeconv get a mapping of conventions x 1234567 8 locale format_string d x grouping True 1 234 567 locale format_string s f conv currency_symbol conv frac_digits x grouping True 1 234 567 80 11 2 Templating The string module includes a versatile Template class with a simplified syntax suitable for editing by end users This allows users to customize their applications without having to alter the application The format uses placeholder names formed by with valid Python identifiers alphanumeric characters and underscores Surrounding the placeholder with braces allows it to be followed by more alphanumeric letters with no intervening spaces Writing creates a single escaped from string import Template t Template village folk send 10 to cause t substitute village Nottingham cause the ditch fund Nottinghamfolk send 10 to the ditch fund The substitute method raises a KeyError when a placeholder is not supplied in a dictionary or a keyword argument For mail merge style applications user supplied data may be incomplete and the safe_substitute method may be more appropriate it will leave placeholders unchanged if data is missing t Template Return the item to owner d dict item unladen swallow t substitute d Traceback most recent call last KeyError owner t safe_substitute d Return the unladen swallow to owner Template subclasses can specify a custom delimiter For example a batch renaming utility for a photo browser may elect to use percent signs for placeholders such as the current date image sequence number or file format import time os path photofiles img_1074 jpg img_1076 jpg img_1077 jpg class BatchRename Template delimiter fmt input Enter rename style d date n seqnum f format Enter rename style d date n seqnum f format Ashley_ n f t BatchRename fmt date time strftime d b y for i filename in enumerate photofiles base ext os path splitext filename newname t substitute d date n i f ext print 0 1 format filename newname img_1074 jpg Ashley_0 jpg img_1076 jpg Ashley_1 jpg img_1077 jpg Ashley_2 jpg Another application for templating is separating program logic from the details of multiple output formats This makes it possible to substitute custom templates for XML files plain text reports and HTML web reports 11 3 Working with Binary Data Record Layouts The struct module provides pack and unpack functions for working with variable length binary record formats The following example shows how to loop through header information in a ZIP file without using the zipfile module Pack codes H and I represent two and four byte unsigned num,en
2259,bers respectively The indicates that they are standard size and in little endian byte order import struct with open myfile zip rb as f data f read start 0 for i in range 3 show the first 3 file headers start 14 fields struct unpack IIIHH data start start 16 crc32 comp_size uncomp_size filenamesize extra_size fields start 16 filename data start start filenamesize start filenamesize extra data start start extra_size print filename hex crc32 comp_size uncomp_size start extra_size comp_size skip to the next header 11 4 Multi threading Threading is a technique for decoupling tasks which are not sequentially dependent Threads can be used to improve the responsiveness of applications that accept user input while other tasks run in the background A related use case is running I O in parallel with computations in another thread The following code shows how the high level threading module can run tasks in background while the main program continues to run import threading zipfile class AsyncZip threading Thread def __init__ self infile outfile threading Thread __init__ self self infile infile self outfile outfile def run self f zipfile ZipFile self outfile w zipfile ZIP_DEFLATED f write self infile f close print Finished background zip of self infile background AsyncZip mydata txt myarchive zip background start print The main program continues to run in foreground background join Wait for the background task to finish print Main program waited until background was done The principal challenge of multi threaded applications is coordinating threads that share data or other resources To that end the threading module provides a number of synchronization primitives including locks events condition variables and semaphores While those tools are powerful minor design errors can result in problems that are difficult to reproduce So the preferred approach to task coordination is to concentrate all access to a resource in a single thread and then use the queue module to feed that thread with requests from other threads Applications using Queue objects for inter thread communication and coordination are easier to design more readable and more reliable 11 5 Logging The logging module offers a full featured and flexible logging system At its simplest log messages are sent to a file or to sys stderr import logging logging debug Debugging information logging info Informational message logging warning Warning config file s not found server conf logging error Error occurred logging critical Critical error shutting down This produces the following output WARNING root Warning config file server conf not found ERROR root Error occurred CRITICAL root Critical error shutting down By default informational and debugging messages are suppressed and the output is sent to standard error Other output options include routing messages through email datagrams sockets or to an HTTP Server New filters can select different routing based on message priority DEBUG INFO WARNING ERROR and CRITICAL The logging system can be configured directly from Python or can be loaded from a user editable configuration file for customized logging without altering the application 11 6 Weak References Python does automatic memory management reference counting for most objects and garbage collection to eliminate cycles The memory is freed shortly after the last reference to it has been eliminated This approach works fine for most applications but occasionally there is a need to track objects only as long as they are being used by something else Unfortunately just tracking them creates a reference that makes them permanent The weakref module provides tools for tracking objects without creating a reference When the object is no longer needed it is automatically removed from a weakref table and a callback is triggered for weakref objects Typical applications include caching objects that are expensive to create import weakref gc class A def __init__ self value self value value def __repr__ self return str self value a A 10 create a reference d weakref WeakValueDictionary d primary a does ,en
2260,not create a reference d primary fetch the object if it is still alive 10 del a remove the one reference gc collect run garbage collection right away 0 d primary entry was automatically removed Traceback most recent call last File stdin line 1 in module d primary entry was automatically removed File C python312 lib weakref py line 46 in __getitem__ o self data key KeyError primary 11 7 Tools for Working with Lists Many data structure needs can be met with the built in list type However sometimes there is a need for alternative implementations with different performance trade offs The array module provides an array object that is like a list that stores only homogeneous data and stores it more compactly The following example shows an array of numbers stored as two byte unsigned binary numbers typecode H rather than the usual 16 bytes per entry for regular lists of Python int objects from array import array a array H 4000 10 700 22222 sum a 26932 a 1 3 array H 10 700 The collections module provides a deque object that is like a list with faster appends and pops from the left side but slower lookups in the middle These objects are well suited for implementing queues and breadth first tree searches from collections import deque d deque task1 task2 task3 d append task4 print Handling d popleft Handling task1 unsearched deque starting_node def breadth_first_search unsearched node unsearched popleft for m in gen_moves node if is_goal m return m unsearched append m In addition to alternative list implementations the library also offers other tools such as the bisect module with functions for manipulating sorted lists import bisect scores 100 perl 200 tcl 400 lua 500 python bisect insort scores 300 ruby scores 100 perl 200 tcl 300 ruby 400 lua 500 python The heapq module provides functions for implementing heaps based on regular lists The lowest valued entry is always kept at position zero This is useful for applications which repeatedly access the smallest element but do not want to run a full list sort from heapq import heapify heappop heappush data 1 3 5 7 9 2 4 6 8 0 heapify data rearrange the list into heap order heappush data 5 add a new entry heappop data for i in range 3 fetch the three smallest entries 5 0 1 11 8 Decimal Floating Point Arithmetic The decimal module offers a Decimal datatype for decimal floating point arithmetic Compared to the built in float implementation of binary floating point the class is especially helpful for financial applications and other uses which require exact decimal representation control over precision control over rounding to meet legal or regulatory requirements tracking of significant decimal places or applications where the user expects the results to match calculations done by hand For example calculating a 5 tax on a 70 cent phone charge gives different results in decimal floating point and binary floating point The difference becomes significant if the results are rounded to the nearest cent from decimal import round Decimal 0 70 Decimal 1 05 2 Decimal 0 74 round 70 1 05 2 0 73 The Decimal result keeps a trailing zero automatically inferring four place significance from multiplicands with two place significance Decimal reproduces mathematics as done by hand and avoids issues that can arise when binary floating point cannot exactly represent decimal quantities Exact representation enables the Decimal class to perform modulo calculations and equality tests that are unsuitable for binary floating point Decimal 1 00 Decimal 10 Decimal 0 00 1 00 0 10 0 09999999999999995 sum Decimal 0 1 10 Decimal 1 0 True 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 1 0 False The decimal module provides arithmetic with as much precision as needed getcontext prec 36 Decimal 1 Decimal 7 Decimal 0 142857142857142857142857142857142857,en
2261,Codec registry and support functions int PyCodec_Register PyObject search_function Part of the Stable ABI Register a new codec search function As side effect this tries to load the encodings package if not yet done to make sure that it is always first in the list of search functions int PyCodec_Unregister PyObject search_function Part of the Stable ABI since version 3 10 Unregister a codec search function and clear the registry s cache If the search function is not registered do nothing Return 0 on success Raise an exception and return 1 on error New in version 3 10 int PyCodec_KnownEncoding const char encoding Part of the Stable ABI Return 1 or 0 depending on whether there is a registered codec for the given encoding This function always succeeds PyObject PyCodec_Encode PyObject object const char encoding const char errors Return value New reference Part of the Stable ABI Generic codec based encoding API object is passed through the encoder function found for the given encoding using the error handling method defined by errors errors may be NULL to use the default method defined for the codec Raises a LookupError if no encoder can be found PyObject PyCodec_Decode PyObject object const char encoding const char errors Return value New reference Part of the Stable ABI Generic codec based decoding API object is passed through the decoder function found for the given encoding using the error handling method defined by errors errors may be NULL to use the default method defined for the codec Raises a LookupError if no encoder can be found Codec lookup API In the following functions the encoding string is looked up converted to all lower case characters which makes encodings looked up through this mechanism effectively case insensitive If no codec is found a KeyError is set and NULL returned PyObject PyCodec_Encoder const char encoding Return value New reference Part of the Stable ABI Get an encoder function for the given encoding PyObject PyCodec_Decoder const char encoding Return value New reference Part of the Stable ABI Get a decoder function for the given encoding PyObject PyCodec_IncrementalEncoder const char encoding const char errors Return value New reference Part of the Stable ABI Get an IncrementalEncoder object for the given encoding PyObject PyCodec_IncrementalDecoder const char encoding const char errors Return value New reference Part of the Stable ABI Get an IncrementalDecoder object for the given encoding PyObject PyCodec_StreamReader const char encoding PyObject stream const char errors Return value New reference Part of the Stable ABI Get a StreamReader factory function for the given encoding PyObject PyCodec_StreamWriter const char encoding PyObject stream const char errors Return value New reference Part of the Stable ABI Get a StreamWriter factory function for the given encoding Registry API for Unicode encoding error handlers int PyCodec_RegisterError const char name PyObject error Part of the Stable ABI Register the error handling callback function error under the given name This callback function will be called by a codec when it encounters unencodable characters undecodable bytes and name is specified as the error parameter in the call to the encode decode function The callback gets a single argument an instance of UnicodeEncodeError UnicodeDecodeError or UnicodeTranslateError that holds information about the problematic sequence of characters or bytes and their offset in the original string see Unicode Exception Objects for functions to extract this information The callback must either raise the given exception or return a two item tuple containing the replacement for the problematic sequence and an integer giving the offset in the original string at which encoding decoding should be resumed Return 0 on success 1 on error PyObject PyCodec_LookupError const char name Return value New reference Part of the Stable ABI Lookup the error handling callback function registered under name As a special case NULL can be passed in which case the error handling callback for strict will be returned PyObject PyCode,en
2262,c_StrictErrors PyObject exc Return value Always NULL Part of the Stable ABI Raise exc as an exception PyObject PyCodec_IgnoreErrors PyObject exc Return value New reference Part of the Stable ABI Ignore the unicode error skipping the faulty input PyObject PyCodec_ReplaceErrors PyObject exc Return value New reference Part of the Stable ABI Replace the unicode encode error with or U FFFD PyObject PyCodec_XMLCharRefReplaceErrors PyObject exc Return value New reference Part of the Stable ABI Replace the unicode encode error with XML character references PyObject PyCodec_BackslashReplaceErrors PyObject exc Return value New reference Part of the Stable ABI Replace the unicode encode error with backslash escapes x u and U PyObject PyCodec_NameReplaceErrors PyObject exc Return value New reference Part of the Stable ABI since version 3 7 Replace the unicode encode error with N escapes New in version 3 5,en
2263,code Interpreter base classes Source code Lib code py The code module provides facilities to implement read eval print loops in Python Two classes and convenience functions are included which can be used to build applications which provide an interactive interpreter prompt class code InteractiveInterpreter locals None This class deals with parsing and interpreter state the user s namespace it does not deal with input buffering or prompting or input file naming the filename is always passed in explicitly The optional locals argument specifies the dictionary in which code will be executed it defaults to a newly created dictionary with key __name__ set to __console__ and key __doc__ set to None class code InteractiveConsole locals None filename console Closely emulate the behavior of the interactive Python interpreter This class builds on InteractiveInterpreter and adds prompting using the familiar sys ps1 and sys ps2 and input buffering code interact banner None readfunc None local None exitmsg None Convenience function to run a read eval print loop This creates a new instance of InteractiveConsole and sets readfunc to be used as the InteractiveConsole raw_input method if provided If local is provided it is passed to the InteractiveConsole constructor for use as the default namespace for the interpreter loop The interact method of the instance is then run with banner and exitmsg passed as the banner and exit message to use if provided The console object is discarded after use Changed in version 3 6 Added exitmsg parameter code compile_command source filename input symbol single This function is useful for programs that want to emulate Python s interpreter main loop a k a the read eval print loop The tricky part is to determine when the user has entered an incomplete command that can be completed by entering more text as opposed to a complete command or a syntax error This function almost always makes the same decision as the real interpreter main loop source is the source string filename is the optional filename from which source was read defaulting to input and symbol is the optional grammar start symbol which should be single the default eval or exec Returns a code object the same as compile source filename symbol if the command is complete and valid None if the command is incomplete raises SyntaxError if the command is complete and contains a syntax error or raises OverflowError or ValueError if the command contains an invalid literal Interactive Interpreter Objects InteractiveInterpreter runsource source filename input symbol single Compile and run some source in the interpreter Arguments are the same as for compile_command the default for filename is input and for symbol is single One of several things can happen The input is incorrect compile_command raised an exception SyntaxError or OverflowError A syntax traceback will be printed by calling the showsyntaxerror method runsource returns False The input is incomplete and more input is required compile_command returned None runsource returns True The input is complete compile_command returned a code object The code is executed by calling the runcode which also handles run time exceptions except for SystemExit runsource returns False The return value can be used to decide whether to use sys ps1 or sys ps2 to prompt the next line InteractiveInterpreter runcode code Execute a code object When an exception occurs showtraceback is called to display a traceback All exceptions are caught except SystemExit which is allowed to propagate A note about KeyboardInterrupt this exception may occur elsewhere in this code and may not always be caught The caller should be prepared to deal with it InteractiveInterpreter showsyntaxerror filename None Display the syntax error that just occurred This does not display a stack trace because there isn t one for syntax errors If filename is given it is stuffed into the exception instead of the default filename provided by Python s parser because it always uses string when reading from a string The output is written by the write method Interact,en
2264,iveInterpreter showtraceback Display the exception that just occurred We remove the first stack item because it is within the interpreter object implementation The output is written by the write method Changed in version 3 5 The full chained traceback is displayed instead of just the primary traceback InteractiveInterpreter write data Write a string to the standard error stream sys stderr Derived classes should override this to provide the appropriate output handling as needed Interactive Console Objects The InteractiveConsole class is a subclass of InteractiveInterpreter and so offers all the methods of the interpreter objects as well as the following additions InteractiveConsole interact banner None exitmsg None Closely emulate the interactive Python console The optional banner argument specify the banner to print before the first interaction by default it prints a banner similar to the one printed by the standard Python interpreter followed by the class name of the console object in parentheses so as not to confuse this with the real interpreter since it s so close The optional exitmsg argument specifies an exit message printed when exiting Pass the empty string to suppress the exit message If exitmsg is not given or None a default message is printed Changed in version 3 4 To suppress printing any banner pass an empty string Changed in version 3 6 Print an exit message when exiting InteractiveConsole push line Push a line of source text to the interpreter The line should not have a trailing newline it may have internal newlines The line is appended to a buffer and the interpreter s runsource method is called with the concatenated contents of the buffer as source If this indicates that the command was executed or invalid the buffer is reset otherwise the command is incomplete and the buffer is left as it was after the line was appended The return value is True if more input is required False if the line was dealt with in some way this is the same as runsource InteractiveConsole resetbuffer Remove any unhandled source text from the input buffer InteractiveConsole raw_input prompt Write a prompt and read a line The returned line does not include the trailing newline When the user enters the EOF key sequence EOFError is raised The base implementation reads from sys stdin a subclass may replace this with a different implementation,en
2265,poplib POP3 protocol client Source code Lib poplib py This module defines a class POP3 which encapsulates a connection to a POP3 server and implements the protocol as defined in RFC 1939 The POP3 class supports both the minimal and optional command sets from RFC 1939 The POP3 class also supports the STLS command introduced in RFC 2595 to enable encrypted communication on an already established connection Additionally this module provides a class POP3_SSL which provides support for connecting to POP3 servers that use SSL as an underlying protocol layer Note that POP3 though widely supported is obsolescent The implementation quality of POP3 servers varies widely and too many are quite poor If your mailserver supports IMAP you would be better off using the imaplib IMAP4 class as IMAP servers tend to be better implemented Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information The poplib module provides two classes class poplib POP3 host port POP3_PORT timeout This class implements the actual POP3 protocol The connection is created when the instance is initialized If port is omitted the standard POP3 port 110 is used The optional timeout parameter specifies a timeout in seconds for the connection attempt if not specified the global default timeout setting will be used Raises an auditing event poplib connect with arguments self host port All commands will raise an auditing event poplib putline with arguments self and line where line is the bytes about to be sent to the remote host Changed in version 3 9 If the timeout parameter is set to be zero it will raise a ValueError to prevent the creation of a non blocking socket class poplib POP3_SSL host port POP3_SSL_PORT timeout None context None This is a subclass of POP3 that connects to the server over an SSL encrypted socket If port is not specified 995 the standard POP3 over SSL port is used timeout works as in the POP3 constructor context is an optional ssl SSLContext object which allows bundling SSL configuration options certificates and private keys into a single potentially long lived structure Please read Security considerations for best practices Raises an auditing event poplib connect with arguments self host port All commands will raise an auditing event poplib putline with arguments self and line where line is the bytes about to be sent to the remote host Changed in version 3 2 context parameter added Changed in version 3 4 The class now supports hostname check with ssl SSLContext check_hostname and Server Name Indication see ssl HAS_SNI Changed in version 3 9 If the timeout parameter is set to be zero it will raise a ValueError to prevent the creation of a non blocking socket Changed in version 3 12 The deprecated keyfile and certfile parameters have been removed One exception is defined as an attribute of the poplib module exception poplib error_proto Exception raised on any errors from this module errors from socket module are not caught The reason for the exception is passed to the constructor as a string See also Module imaplib The standard Python IMAP module Frequently Asked Questions About Fetchmail The FAQ for the fetchmail POP IMAP client collects information on POP3 server variations and RFC noncompliance that may be useful if you need to write an application based on the POP protocol POP3 Objects All POP3 commands are represented by methods of the same name in lowercase most return the response text sent by the server A POP3 instance has the following methods POP3 set_debuglevel level Set the instance s debugging level This controls the amount of debugging output printed The default 0 produces no debugging output A value of 1 produces a moderate amount of debugging output generally a single line per request A value of 2 or higher produces the maximum amount of debugging output logging each line sent and received on the control connection POP3 getwelcome Returns the greeting string sent by the POP3 server POP3 capa Query the se,en
2266,rver s capabilities as specified in RFC 2449 Returns a dictionary in the form name param New in version 3 4 POP3 user username Send user command response should indicate that a password is required POP3 pass_ password Send password response includes message count and mailbox size Note the mailbox on the server is locked until quit is called POP3 apop user secret Use the more secure APOP authentication to log into the POP3 server POP3 rpop user Use RPOP authentication similar to UNIX r commands to log into POP3 server POP3 stat Get mailbox status The result is a tuple of 2 integers message count mailbox size POP3 list which Request message list result is in the form response mesg_num octets octets If which is set it is the message to list POP3 retr which Retrieve whole message number which and set its seen flag Result is in form response line octets POP3 dele which Flag message number which for deletion On most servers deletions are not actually performed until QUIT the major exception is Eudora QPOP which deliberately violates the RFCs by doing pending deletes on any disconnect POP3 rset Remove any deletion marks for the mailbox POP3 noop Do nothing Might be used as a keep alive POP3 quit Signoff commit changes unlock mailbox drop connection POP3 top which howmuch Retrieves the message header plus howmuch lines of the message after the header of message number which Result is in form response line octets The POP3 TOP command this method uses unlike the RETR command doesn t set the message s seen flag unfortunately TOP is poorly specified in the RFCs and is frequently broken in off brand servers Test this method by hand against the POP3 servers you will use before trusting it POP3 uidl which None Return message digest unique id list If which is specified result contains the unique id for that message in the form response mesgnum uid otherwise result is list response mesgnum uid octets POP3 utf8 Try to switch to UTF 8 mode Returns the server response if successful raises error_proto if not Specified in RFC 6856 New in version 3 5 POP3 stls context None Start a TLS session on the active connection as specified in RFC 2595 This is only allowed before user authentication context parameter is a ssl SSLContext object which allows bundling SSL configuration options certificates and private keys into a single potentially long lived structure Please read Security considerations for best practices This method supports hostname checking via ssl SSLContext check_hostname and Server Name Indication see ssl HAS_SNI New in version 3 4 Instances of POP3_SSL have no additional methods The interface of this subclass is identical to its parent POP3 Example Here is a minimal example without error checking that opens a mailbox and retrieves and prints all messages import getpass poplib M poplib POP3 localhost M user getpass getuser M pass_ getpass getpass numMessages len M list 1 for i in range numMessages for j in M retr i 1 1 print j At the end of the module there is a test section that contains a more extensive example of usage,en
2267,runpy Locating and executing Python modules Source code Lib runpy py The runpy module is used to locate and run Python modules without importing them first Its main use is to implement the m command line switch that allows scripts to be located using the Python module namespace rather than the filesystem Note that this is not a sandbox module all code is executed in the current process and any side effects such as cached imports of other modules will remain in place after the functions have returned Furthermore any functions and classes defined by the executed code are not guaranteed to work correctly after a runpy function has returned If that limitation is not acceptable for a given use case importlib is likely to be a more suitable choice than this module The runpy module provides two functions runpy run_module mod_name init_globals None run_name None alter_sys False Execute the code of the specified module and return the resulting module globals dictionary The module s code is first located using the standard import mechanism refer to PEP 302 for details and then executed in a fresh module namespace The mod_name argument should be an absolute module name If the module name refers to a package rather than a normal module then that package is imported and the __main__ submodule within that package is then executed and the resulting module globals dictionary returned The optional dictionary argument init_globals may be used to pre populate the module s globals dictionary before the code is executed The supplied dictionary will not be modified If any of the special global variables below are defined in the supplied dictionary those definitions are overridden by run_module The special global variables __name__ __spec__ __file__ __cached__ __loader__ and __package__ are set in the globals dictionary before the module code is executed Note that this is a minimal set of variables other variables may be set implicitly as an interpreter implementation detail __name__ is set to run_name if this optional argument is not None to mod_name __main__ if the named module is a package and to the mod_name argument otherwise __spec__ will be set appropriately for the actually imported module that is __spec__ name will always be mod_name or mod_name __main__ never run_name __file__ __cached__ __loader__ and __package__ are set as normal based on the module spec If the argument alter_sys is supplied and evaluates to True then sys argv 0 is updated with the value of __file__ and sys modules __name__ is updated with a temporary module object for the module being executed Both sys argv 0 and sys modules __name__ are restored to their original values before the function returns Note that this manipulation of sys is not thread safe Other threads may see the partially initialised module as well as the altered list of arguments It is recommended that the sys module be left alone when invoking this function from threaded code See also The m option offering equivalent functionality from the command line Changed in version 3 1 Added ability to execute packages by looking for a __main__ submodule Changed in version 3 2 Added __cached__ global variable see PEP 3147 Changed in version 3 4 Updated to take advantage of the module spec feature added by PEP 451 This allows __cached__ to be set correctly for modules run this way as well as ensuring the real module name is always accessible as __spec__ name Changed in version 3 12 The setting of __cached__ __loader__ and __package__ are deprecated See ModuleSpec for alternatives runpy run_path path_name init_globals None run_name None Execute the code at the named filesystem location and return the resulting module globals dictionary As with a script name supplied to the CPython command line the supplied path may refer to a Python source file a compiled bytecode file or a valid sys path entry containing a __main__ module e g a zipfile containing a top level __main__ py file For a simple script the specified code is simply executed in a fresh module namespace For a valid sys path entry typically a zipfile or ,en
2268,directory the entry is first added to the beginning of sys path The function then looks for and executes a __main__ module using the updated path Note that there is no special protection against invoking an existing __main__ entry located elsewhere on sys path if there is no such module at the specified location The optional dictionary argument init_globals may be used to pre populate the module s globals dictionary before the code is executed The supplied dictionary will not be modified If any of the special global variables below are defined in the supplied dictionary those definitions are overridden by run_path The special global variables __name__ __spec__ __file__ __cached__ __loader__ and __package__ are set in the globals dictionary before the module code is executed Note that this is a minimal set of variables other variables may be set implicitly as an interpreter implementation detail __name__ is set to run_name if this optional argument is not None and to run_path otherwise If the supplied path directly references a script file whether as source or as precompiled byte code then __file__ will be set to the supplied path and __spec__ __cached__ __loader__ and __package__ will all be set to None If the supplied path is a reference to a valid sys path entry then __spec__ will be set appropriately for the imported __main__ module that is __spec__ name will always be __main__ __file__ __cached__ __loader__ and __package__ will be set as normal based on the module spec A number of alterations are also made to the sys module Firstly sys path may be altered as described above sys argv 0 is updated with the value of path_name and sys modules __name__ is updated with a temporary module object for the module being executed All modifications to items in sys are reverted before the function returns Note that unlike run_module the alterations made to sys are not optional in this function as these adjustments are essential to allowing the execution of sys path entries As the thread safety limitations still apply use of this function in threaded code should be either serialised with the import lock or delegated to a separate process See also Interface options for equivalent functionality on the command line python path to script New in version 3 2 Changed in version 3 4 Updated to take advantage of the module spec feature added by PEP 451 This allows __cached__ to be set correctly in the case where __main__ is imported from a valid sys path entry rather than being executed directly Changed in version 3 12 The setting of __cached__ __loader__ and __package__ are deprecated See also PEP 338 Executing modules as scripts PEP written and implemented by Nick Coghlan PEP 366 Main module explicit relative imports PEP written and implemented by Nick Coghlan PEP 451 A ModuleSpec Type for the Import System PEP written and implemented by Eric Snow Command line and environment CPython command line details The importlib import_module function,en
2269,An introduction to the ipaddress module author Peter Moody author Nick Coghlan Overview This document aims to provide a gentle introduction to the ipaddress module It is aimed primarily at users that aren t already familiar with IP networking terminology but may also be useful to network engineers wanting an overview of how ipaddress represents IP network addressing concepts Creating Address Network Interface objects Since ipaddress is a module for inspecting and manipulating IP addresses the first thing you ll want to do is create some objects You can use ipaddress to create objects from strings and integers A Note on IP Versions For readers that aren t particularly familiar with IP addressing it s important to know that the Internet Protocol IP is currently in the process of moving from version 4 of the protocol to version 6 This transition is occurring largely because version 4 of the protocol doesn t provide enough addresses to handle the needs of the whole world especially given the increasing number of devices with direct connections to the internet Explaining the details of the differences between the two versions of the protocol is beyond the scope of this introduction but readers need to at least be aware that these two versions exist and it will sometimes be necessary to force the use of one version or the other IP Host Addresses Addresses often referred to as host addresses are the most basic unit when working with IP addressing The simplest way to create addresses is to use the ipaddress ip_address factory function which automatically determines whether to create an IPv4 or IPv6 address based on the passed in value ipaddress ip_address 192 0 2 1 IPv4Address 192 0 2 1 ipaddress ip_address 2001 DB8 1 IPv6Address 2001 db8 1 Addresses can also be created directly from integers Values that will fit within 32 bits are assumed to be IPv4 addresses ipaddress ip_address 3221225985 IPv4Address 192 0 2 1 ipaddress ip_address 42540766411282592856903984951653826561 IPv6Address 2001 db8 1 To force the use of IPv4 or IPv6 addresses the relevant classes can be invoked directly This is particularly useful to force creation of IPv6 addresses for small integers ipaddress ip_address 1 IPv4Address 0 0 0 1 ipaddress IPv4Address 1 IPv4Address 0 0 0 1 ipaddress IPv6Address 1 IPv6Address 1 Defining Networks Host addresses are usually grouped together into IP networks so ipaddress provides a way to create inspect and manipulate network definitions IP network objects are constructed from strings that define the range of host addresses that are part of that network The simplest form for that information is a network address network prefix pair where the prefix defines the number of leading bits that are compared to determine whether or not an address is part of the network and the network address defines the expected value of those bits As for addresses a factory function is provided that determines the correct IP version automatically ipaddress ip_network 192 0 2 0 24 IPv4Network 192 0 2 0 24 ipaddress ip_network 2001 db8 0 96 IPv6Network 2001 db8 96 Network objects cannot have any host bits set The practical effect of this is that 192 0 2 1 24 does not describe a network Such definitions are referred to as interface objects since the ip on a network notation is commonly used to describe network interfaces of a computer on a given network and are described further in the next section By default attempting to create a network object with host bits set will result in ValueError being raised To request that the additional bits instead be coerced to zero the flag strict False can be passed to the constructor ipaddress ip_network 192 0 2 1 24 Traceback most recent call last ValueError 192 0 2 1 24 has host bits set ipaddress ip_network 192 0 2 1 24 strict False IPv4Network 192 0 2 0 24 While the string form offers significantly more flexibility networks can also be defined with integers just like host addresses In this case the network is considered to contain only the single address identified by the integer so the network prefix includes ,en
2270,the entire network address ipaddress ip_network 3221225984 IPv4Network 192 0 2 0 32 ipaddress ip_network 42540766411282592856903984951653826560 IPv6Network 2001 db8 128 As with addresses creation of a particular kind of network can be forced by calling the class constructor directly instead of using the factory function Host Interfaces As mentioned just above if you need to describe an address on a particular network neither the address nor the network classes are sufficient Notation like 192 0 2 1 24 is commonly used by network engineers and the people who write tools for firewalls and routers as shorthand for the host 192 0 2 1 on the network 192 0 2 0 24 Accordingly ipaddress provides a set of hybrid classes that associate an address with a particular network The interface for creation is identical to that for defining network objects except that the address portion isn t constrained to being a network address ipaddress ip_interface 192 0 2 1 24 IPv4Interface 192 0 2 1 24 ipaddress ip_interface 2001 db8 1 96 IPv6Interface 2001 db8 1 96 Integer inputs are accepted as with networks and use of a particular IP version can be forced by calling the relevant constructor directly Inspecting Address Network Interface Objects You ve gone to the trouble of creating an IPv 4 6 Address Network Interface object so you probably want to get information about it ipaddress tries to make doing this easy and intuitive Extracting the IP version addr4 ipaddress ip_address 192 0 2 1 addr6 ipaddress ip_address 2001 db8 1 addr6 version 6 addr4 version 4 Obtaining the network from an interface host4 ipaddress ip_interface 192 0 2 1 24 host4 network IPv4Network 192 0 2 0 24 host6 ipaddress ip_interface 2001 db8 1 96 host6 network IPv6Network 2001 db8 96 Finding out how many individual addresses are in a network net4 ipaddress ip_network 192 0 2 0 24 net4 num_addresses 256 net6 ipaddress ip_network 2001 db8 0 96 net6 num_addresses 4294967296 Iterating through the usable addresses on a network net4 ipaddress ip_network 192 0 2 0 24 for x in net4 hosts print x 192 0 2 1 192 0 2 2 192 0 2 3 192 0 2 4 192 0 2 252 192 0 2 253 192 0 2 254 Obtaining the netmask i e set bits corresponding to the network prefix or the hostmask any bits that are not part of the netmask net4 ipaddress ip_network 192 0 2 0 24 net4 netmask IPv4Address 255 255 255 0 net4 hostmask IPv4Address 0 0 0 255 net6 ipaddress ip_network 2001 db8 0 96 net6 netmask IPv6Address ffff ffff ffff ffff ffff ffff net6 hostmask IPv6Address ffff ffff Exploding or compressing the address addr6 exploded 2001 0db8 0000 0000 0000 0000 0000 0001 addr6 compressed 2001 db8 1 net6 exploded 2001 0db8 0000 0000 0000 0000 0000 0000 96 net6 compressed 2001 db8 96 While IPv4 doesn t support explosion or compression the associated objects still provide the relevant properties so that version neutral code can easily ensure the most concise or most verbose form is used for IPv6 addresses while still correctly handling IPv4 addresses Networks as lists of Addresses It s sometimes useful to treat networks as lists This means it is possible to index them like this net4 1 IPv4Address 192 0 2 1 net4 1 IPv4Address 192 0 2 255 net6 1 IPv6Address 2001 db8 1 net6 1 IPv6Address 2001 db8 ffff ffff It also means that network objects lend themselves to using the list membership test syntax like this if address in network do something Containment testing is done efficiently based on the network prefix addr4 ipaddress ip_address 192 0 2 1 addr4 in ipaddress ip_network 192 0 2 0 24 True addr4 in ipaddress ip_network 192 0 3 0 24 False Comparisons ipaddress provides some simple hopefully intuitive ways to compare objects where it makes sense ipaddress ip_address 192 0 2 1 ipaddress ip_address 192 0 2 2 True A TypeError exception is raised if you try to compare objects of different versions or different types Using IP Addresses with other modules Other modules that use IP addresses such as socket usually won t accept objects from this module directly Instead they must be coerced to an integer or string that the other module will a,en
2271,ccept addr4 ipaddress ip_address 192 0 2 1 str addr4 192 0 2 1 int addr4 3221225985 Getting more detail when instance creation fails When creating address network interface objects using the version agnostic factory functions any errors will be reported as ValueError with a generic error message that simply says the passed in value was not recognized as an object of that type The lack of a specific error is because it s necessary to know whether the value is supposed to be IPv4 or IPv6 in order to provide more detail on why it has been rejected To support use cases where it is useful to have access to this additional detail the individual class constructors actually raise the ValueError subclasses ipaddress AddressValueError and ipaddress NetmaskValueError to indicate exactly which part of the definition failed to parse correctly The error messages are significantly more detailed when using the class constructors directly For example ipaddress ip_address 192 168 0 256 Traceback most recent call last ValueError 192 168 0 256 does not appear to be an IPv4 or IPv6 address ipaddress IPv4Address 192 168 0 256 Traceback most recent call last ipaddress AddressValueError Octet 256 255 not permitted in 192 168 0 256 ipaddress ip_network 192 168 0 1 64 Traceback most recent call last ValueError 192 168 0 1 64 does not appear to be an IPv4 or IPv6 network ipaddress IPv4Network 192 168 0 1 64 Traceback most recent call last ipaddress NetmaskValueError 64 is not a valid netmask However both of the module specific exceptions have ValueError as their parent class so if you re not concerned with the particular type of error you can still write code like the following try network ipaddress IPv4Network address except ValueError print address netmask is invalid for IPv4 address,en
2272,Sequence Protocol int PySequence_Check PyObject o Part of the Stable ABI Return 1 if the object provides the sequence protocol and 0 otherwise Note that it returns 1 for Python classes with a __getitem__ method unless they are dict subclasses since in general it is impossible to determine what type of keys the class supports This function always succeeds Py_ssize_t PySequence_Size PyObject o Py_ssize_t PySequence_Length PyObject o Part of the Stable ABI Returns the number of objects in sequence o on success and 1 on failure This is equivalent to the Python expression len o PyObject PySequence_Concat PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Return the concatenation of o1 and o2 on success and NULL on failure This is the equivalent of the Python expression o1 o2 PyObject PySequence_Repeat PyObject o Py_ssize_t count Return value New reference Part of the Stable ABI Return the result of repeating sequence object o count times or NULL on failure This is the equivalent of the Python expression o count PyObject PySequence_InPlaceConcat PyObject o1 PyObject o2 Return value New reference Part of the Stable ABI Return the concatenation of o1 and o2 on success and NULL on failure The operation is done in place when o1 supports it This is the equivalent of the Python expression o1 o2 PyObject PySequence_InPlaceRepeat PyObject o Py_ssize_t count Return value New reference Part of the Stable ABI Return the result of repeating sequence object o count times or NULL on failure The operation is done in place when o supports it This is the equivalent of the Python expression o count PyObject PySequence_GetItem PyObject o Py_ssize_t i Return value New reference Part of the Stable ABI Return the i th element of o or NULL on failure This is the equivalent of the Python expression o i PyObject PySequence_GetSlice PyObject o Py_ssize_t i1 Py_ssize_t i2 Return value New reference Part of the Stable ABI Return the slice of sequence object o between i1 and i2 or NULL on failure This is the equivalent of the Python expression o i1 i2 int PySequence_SetItem PyObject o Py_ssize_t i PyObject v Part of the Stable ABI Assign object v to the i th element of o Raise an exception and return 1 on failure return 0 on success This is the equivalent of the Python statement o i v This function does not steal a reference to v If v is NULL the element is deleted but this feature is deprecated in favour of using PySequence_DelItem int PySequence_DelItem PyObject o Py_ssize_t i Part of the Stable ABI Delete the i th element of object o Returns 1 on failure This is the equivalent of the Python statement del o i int PySequence_SetSlice PyObject o Py_ssize_t i1 Py_ssize_t i2 PyObject v Part of the Stable ABI Assign the sequence object v to the slice in sequence object o from i1 to i2 This is the equivalent of the Python statement o i1 i2 v int PySequence_DelSlice PyObject o Py_ssize_t i1 Py_ssize_t i2 Part of the Stable ABI Delete the slice in sequence object o from i1 to i2 Returns 1 on failure This is the equivalent of the Python statement del o i1 i2 Py_ssize_t PySequence_Count PyObject o PyObject value Part of the Stable ABI Return the number of occurrences of value in o that is return the number of keys for which o key value On failure return 1 This is equivalent to the Python expression o count value int PySequence_Contains PyObject o PyObject value Part of the Stable ABI Determine if o contains value If an item in o is equal to value return 1 otherwise return 0 On error return 1 This is equivalent to the Python expression value in o Py_ssize_t PySequence_Index PyObject o PyObject value Part of the Stable ABI Return the first index i for which o i value On error return 1 This is equivalent to the Python expression o index value PyObject PySequence_List PyObject o Return value New reference Part of the Stable ABI Return a list object with the same contents as the sequence or iterable o or NULL on failure The returned list is guaranteed to be new This is equivalent to the Python expression list o PyObject PySequence_Tuple PyObject,en
2273, o Return value New reference Part of the Stable ABI Return a tuple object with the same contents as the sequence or iterable o or NULL on failure If o is a tuple a new reference will be returned otherwise a tuple will be constructed with the appropriate contents This is equivalent to the Python expression tuple o PyObject PySequence_Fast PyObject o const char m Return value New reference Part of the Stable ABI Return the sequence or iterable o as an object usable by the other PySequence_Fast family of functions If the object is not a sequence or iterable raises TypeError with m as the message text Returns NULL on failure The PySequence_Fast functions are thus named because they assume o is a PyTupleObject or a PyListObject and access the data fields of o directly As a CPython implementation detail if o is already a sequence or list it will be returned Py_ssize_t PySequence_Fast_GET_SIZE PyObject o Returns the length of o assuming that o was returned by PySequence_Fast and that o is not NULL The size can also be retrieved by calling PySequence_Size on o but PySequence_Fast_GET_SIZE is faster because it can assume o is a list or tuple PyObject PySequence_Fast_GET_ITEM PyObject o Py_ssize_t i Return value Borrowed reference Return the i th element of o assuming that o was returned by PySequence_Fast o is not NULL and that i is within bounds PyObject PySequence_Fast_ITEMS PyObject o Return the underlying array of PyObject pointers Assumes that o was returned by PySequence_Fast and o is not NULL Note if a list gets resized the reallocation may relocate the items array So only use the underlying array pointer in contexts where the sequence cannot change PyObject PySequence_ITEM PyObject o Py_ssize_t i Return value New reference Return the i th element of o or NULL on failure Faster form of PySequence_GetItem but without checking that PySequence_Check on o is true and without adjustment for negative indices,en
2274,email utils Miscellaneous utilities Source code Lib email utils py There are a couple of useful utilities provided in the email utils module email utils localtime dt None Return local time as an aware datetime object If called without arguments return current time Otherwise dt argument should be a datetime instance and it is converted to the local time zone according to the system time zone database If dt is naive that is dt tzinfo is None it is assumed to be in local time The isdst parameter is ignored New in version 3 3 Deprecated since version 3 12 will be removed in version 3 14 The isdst parameter email utils make_msgid idstring None domain None Returns a string suitable for an RFC 2822 compliant Message ID header Optional idstring if given is a string used to strengthen the uniqueness of the message id Optional domain if given provides the portion of the msgid after the The default is the local hostname It is not normally necessary to override this default but may be useful certain cases such as a constructing distributed system that uses a consistent domain name across multiple hosts Changed in version 3 2 Added the domain keyword The remaining functions are part of the legacy Compat32 email API There is no need to directly use these with the new API since the parsing and formatting they provide is done automatically by the header parsing machinery of the new API email utils quote str Return a new string with backslashes in str replaced by two backslashes and double quotes replaced by backslash double quote email utils unquote str Return a new string which is an unquoted version of str If str ends and begins with double quotes they are stripped off Likewise if str ends and begins with angle brackets they are stripped off email utils parseaddr address Parse address which should be the value of some address containing field such as To or Cc into its constituent realname and email address parts Returns a tuple of that information unless the parse fails in which case a 2 tuple of is returned email utils formataddr pair charset utf 8 The inverse of parseaddr this takes a 2 tuple of the form realname email_address and returns the string value suitable for a To or Cc header If the first element of pair is false then the second element is returned unmodified Optional charset is the character set that will be used in the RFC 2047 encoding of the realname if the realname contains non ASCII characters Can be an instance of str or a Charset Defaults to utf 8 Changed in version 3 3 Added the charset option email utils getaddresses fieldvalues This method returns a list of 2 tuples of the form returned by parseaddr fieldvalues is a sequence of header field values as might be returned by Message get_all Here s a simple example that gets all the recipients of a message from email utils import getaddresses tos msg get_all to ccs msg get_all cc resent_tos msg get_all resent to resent_ccs msg get_all resent cc all_recipients getaddresses tos ccs resent_tos resent_ccs email utils parsedate date Attempts to parse a date according to the rules in RFC 2822 however some mailers don t follow that format as specified so parsedate tries to guess correctly in such cases date is a string containing an RFC 2822 date such as Mon 20 Nov 1995 19 12 08 0500 If it succeeds in parsing the date parsedate returns a 9 tuple that can be passed directly to time mktime otherwise None will be returned Note that indexes 6 7 and 8 of the result tuple are not usable email utils parsedate_tz date Performs the same function as parsedate but returns either None or a 10 tuple the first 9 elements make up a tuple that can be passed directly to time mktime and the tenth is the offset of the date s timezone from UTC which is the official term for Greenwich Mean Time 1 If the input string has no timezone the last element of the tuple returned is 0 which represents UTC Note that indexes 6 7 and 8 of the result tuple are not usable email utils parsedate_to_datetime date The inverse of format_datetime Performs the same function as parsedate but on success returns a date,en
2275,time otherwise ValueError is raised if date contains an invalid value such as an hour greater than 23 or a timezone offset not between 24 and 24 hours If the input date has a timezone of 0000 the datetime will be a naive datetime and if the date is conforming to the RFCs it will represent a time in UTC but with no indication of the actual source timezone of the message the date comes from If the input date has any other valid timezone offset the datetime will be an aware datetime with the corresponding a timezone tzinfo New in version 3 3 email utils mktime_tz tuple Turn a 10 tuple as returned by parsedate_tz into a UTC timestamp seconds since the Epoch If the timezone item in the tuple is None assume local time email utils formatdate timeval None localtime False usegmt False Returns a date string as per RFC 2822 e g Fri 09 Nov 2001 01 08 47 0000 Optional timeval if given is a floating point time value as accepted by time gmtime and time localtime otherwise the current time is used Optional localtime is a flag that when True interprets timeval and returns a date relative to the local timezone instead of UTC properly taking daylight savings time into account The default is False meaning UTC is used Optional usegmt is a flag that when True outputs a date string with the timezone as an ascii string GMT rather than a numeric 0000 This is needed for some protocols such as HTTP This only applies when localtime is False The default is False email utils format_datetime dt usegmt False Like formatdate but the input is a datetime instance If it is a naive datetime it is assumed to be UTC with no information about the source timezone and the conventional 0000 is used for the timezone If it is an aware datetime then the numeric timezone offset is used If it is an aware timezone with offset zero then usegmt may be set to True in which case the string GMT is used instead of the numeric timezone offset This provides a way to generate standards conformant HTTP date headers New in version 3 3 email utils decode_rfc2231 s Decode the string s according to RFC 2231 email utils encode_rfc2231 s charset None language None Encode the string s according to RFC 2231 Optional charset and language if given is the character set name and language name to use If neither is given s is returned as is If charset is given but language is not the string is encoded using the empty string for language email utils collapse_rfc2231_value value errors replace fallback_charset us ascii When a header parameter is encoded in RFC 2231 format Message get_param may return a 3 tuple containing the character set language and value collapse_rfc2231_value turns this into a unicode string Optional errors is passed to the errors argument of str s encode method it defaults to replace Optional fallback_charset specifies the character set to use if the one in the RFC 2231 header is not known by Python it defaults to us ascii For convenience if the value passed to collapse_rfc2231_value is not a tuple it should be a string and it is returned unquoted email utils decode_params params Decode parameters list according to RFC 2231 params is a sequence of 2 tuples containing elements of the form content type string value Footnotes 1 Note that the sign of the timezone offset is the opposite of the sign of the time timezone variable for the same timezone the latter variable follows the POSIX standard while this module follows RFC 2822,en
2276,weakref Weak references Source code Lib weakref py The weakref module allows the Python programmer to create weak references to objects In the following the term referent means the object which is referred to by a weak reference A weak reference to an object is not enough to keep the object alive when the only remaining references to a referent are weak references garbage collection is free to destroy the referent and reuse its memory for something else However until the object is actually destroyed the weak reference may return the object even if there are no strong references to it A primary use for weak references is to implement caches or mappings holding large objects where it s desired that a large object not be kept alive solely because it appears in a cache or mapping For example if you have a number of large binary image objects you may wish to associate a name with each If you used a Python dictionary to map names to images or images to names the image objects would remain alive just because they appeared as values or keys in the dictionaries The WeakKeyDictionary and WeakValueDictionary classes supplied by the weakref module are an alternative using weak references to construct mappings that don t keep objects alive solely because they appear in the mapping objects If for example an image object is a value in a WeakValueDictionary then when the last remaining references to that image object are the weak references held by weak mappings garbage collection can reclaim the object and its corresponding entries in weak mappings are simply deleted WeakKeyDictionary and WeakValueDictionary use weak references in their implementation setting up callback functions on the weak references that notify the weak dictionaries when a key or value has been reclaimed by garbage collection WeakSet implements the set interface but keeps weak references to its elements just like a WeakKeyDictionary does finalize provides a straight forward way to register a cleanup function to be called when an object is garbage collected This is simpler to use than setting up a callback function on a raw weak reference since the module automatically ensures that the finalizer remains alive until the object is collected Most programs should find that using one of these weak container types or finalize is all they need it s not usually necessary to create your own weak references directly The low level machinery is exposed by the weakref module for the benefit of advanced uses Not all objects can be weakly referenced Objects which support weak references include class instances functions written in Python but not in C instance methods sets frozensets some file objects generators type objects sockets arrays deques regular expression pattern objects and code objects Changed in version 3 2 Added support for thread lock threading Lock and code objects Several built in types such as list and dict do not directly support weak references but can add support through subclassing class Dict dict pass obj Dict red 1 green 2 blue 3 this object is weak referenceable CPython implementation detail Other built in types such as tuple and int do not support weak references even when subclassed Extension types can easily be made to support weak references see Weak Reference Support When __slots__ are defined for a given type weak reference support is disabled unless a __weakref__ string is also present in the sequence of strings in the __slots__ declaration See __slots__ documentation for details class weakref ref object callback Return a weak reference to object The original object can be retrieved by calling the reference object if the referent is still alive if the referent is no longer alive calling the reference object will cause None to be returned If callback is provided and not None and the returned weakref object is still alive the callback will be called when the object is about to be finalized the weak reference object will be passed as the only parameter to the callback the referent will no longer be available It is allowable for many weak references to b,en
2277,e constructed for the same object Callbacks registered for each weak reference will be called from the most recently registered callback to the oldest registered callback Exceptions raised by the callback will be noted on the standard error output but cannot be propagated they are handled in exactly the same way as exceptions raised from an object s __del__ method Weak references are hashable if the object is hashable They will maintain their hash value even after the object was deleted If hash is called the first time only after the object was deleted the call will raise TypeError Weak references support tests for equality but not ordering If the referents are still alive two references have the same equality relationship as their referents regardless of the callback If either referent has been deleted the references are equal only if the reference objects are the same object This is a subclassable type rather than a factory function __callback__ This read only attribute returns the callback currently associated to the weakref If there is no callback or if the referent of the weakref is no longer alive then this attribute will have value None Changed in version 3 4 Added the __callback__ attribute weakref proxy object callback Return a proxy to object which uses a weak reference This supports use of the proxy in most contexts instead of requiring the explicit dereferencing used with weak reference objects The returned object will have a type of either ProxyType or CallableProxyType depending on whether object is callable Proxy objects are not hashable regardless of the referent this avoids a number of problems related to their fundamentally mutable nature and prevents their use as dictionary keys callback is the same as the parameter of the same name to the ref function Accessing an attribute of the proxy object after the referent is garbage collected raises ReferenceError Changed in version 3 8 Extended the operator support on proxy objects to include the matrix multiplication operators and weakref getweakrefcount object Return the number of weak references and proxies which refer to object weakref getweakrefs object Return a list of all weak reference and proxy objects which refer to object class weakref WeakKeyDictionary dict Mapping class that references keys weakly Entries in the dictionary will be discarded when there is no longer a strong reference to the key This can be used to associate additional data with an object owned by other parts of an application without adding attributes to those objects This can be especially useful with objects that override attribute accesses Note that when a key with equal value to an existing key but not equal identity is inserted into the dictionary it replaces the value but does not replace the existing key Due to this when the reference to the original key is deleted it also deletes the entry in the dictionary class T str pass k1 k2 T T d weakref WeakKeyDictionary d k1 1 d k1 1 d k2 2 d k1 2 del k1 d A workaround would be to remove the key prior to reassignment class T str pass k1 k2 T T d weakref WeakKeyDictionary d k1 1 d k1 1 del d k1 d k2 2 d k2 2 del k1 d k2 2 Changed in version 3 9 Added support for and operators specified in PEP 584 WeakKeyDictionary objects have an additional method that exposes the internal references directly The references are not guaranteed to be live at the time they are used so the result of calling the references needs to be checked before being used This can be used to avoid creating references that will cause the garbage collector to keep the keys around longer than needed WeakKeyDictionary keyrefs Return an iterable of the weak references to the keys class weakref WeakValueDictionary dict Mapping class that references values weakly Entries in the dictionary will be discarded when no strong reference to the value exists any more Changed in version 3 9 Added support for and operators as specified in PEP 584 WeakValueDictionary objects have an additional method that has the same issues as the WeakKeyDictionary keyrefs method WeakValueDictionary ,en
2278,valuerefs Return an iterable of the weak references to the values class weakref WeakSet elements Set class that keeps weak references to its elements An element will be discarded when no strong reference to it exists any more class weakref WeakMethod method callback A custom ref subclass which simulates a weak reference to a bound method i e a method defined on a class and looked up on an instance Since a bound method is ephemeral a standard weak reference cannot keep hold of it WeakMethod has special code to recreate the bound method until either the object or the original function dies class C def method self print method called c C r weakref ref c method r r weakref WeakMethod c method r bound method C method of __main__ C object at 0x7fc859830220 r method called del c gc collect 0 r callback is the same as the parameter of the same name to the ref function New in version 3 4 class weakref finalize obj func args kwargs Return a callable finalizer object which will be called when obj is garbage collected Unlike an ordinary weak reference a finalizer will always survive until the reference object is collected greatly simplifying lifecycle management A finalizer is considered alive until it is called either explicitly or at garbage collection and after that it is dead Calling a live finalizer returns the result of evaluating func arg kwargs whereas calling a dead finalizer returns None Exceptions raised by finalizer callbacks during garbage collection will be shown on the standard error output but cannot be propagated They are handled in the same way as exceptions raised from an object s __del__ method or a weak reference s callback When the program exits each remaining live finalizer is called unless its atexit attribute has been set to false They are called in reverse order of creation A finalizer will never invoke its callback during the later part of the interpreter shutdown when module globals are liable to have been replaced by None __call__ If self is alive then mark it as dead and return the result of calling func args kwargs If self is dead then return None detach If self is alive then mark it as dead and return the tuple obj func args kwargs If self is dead then return None peek If self is alive then return the tuple obj func args kwargs If self is dead then return None alive Property which is true if the finalizer is alive false otherwise atexit A writable boolean property which by default is true When the program exits it calls all remaining live finalizers for which atexit is true They are called in reverse order of creation Note It is important to ensure that func args and kwargs do not own any references to obj either directly or indirectly since otherwise obj will never be garbage collected In particular func should not be a bound method of obj New in version 3 4 weakref ReferenceType The type object for weak references objects weakref ProxyType The type object for proxies of objects which are not callable weakref CallableProxyType The type object for proxies of callable objects weakref ProxyTypes Sequence containing all the type objects for proxies This can make it simpler to test if an object is a proxy without being dependent on naming both proxy types See also PEP 205 Weak References The proposal and rationale for this feature including links to earlier implementations and information about similar features in other languages Weak Reference Objects Weak reference objects have no methods and no attributes besides ref __callback__ A weak reference object allows the referent to be obtained if it still exists by calling it import weakref class Object pass o Object r weakref ref o o2 r o is o2 True If the referent no longer exists calling the reference object returns None del o o2 print r None Testing that a weak reference object is still live should be done using the expression ref is not None Normally application code that needs to use a reference object should follow this pattern r is a weak reference object o r if o is None referent has been garbage collected print Object has been deallocated can t fro,en
2279,bnicate else print Object is still live o do_something_useful Using a separate test for liveness creates race conditions in threaded applications another thread can cause a weak reference to become invalidated before the weak reference is called the idiom shown above is safe in threaded applications as well as single threaded applications Specialized versions of ref objects can be created through subclassing This is used in the implementation of the WeakValueDictionary to reduce the memory overhead for each entry in the mapping This may be most useful to associate additional information with a reference but could also be used to insert additional processing on calls to retrieve the referent This example shows how a subclass of ref can be used to store additional information about an object and affect the value that s returned when the referent is accessed import weakref class ExtendedRef weakref ref def __init__ self ob callback None annotations super __init__ ob callback self __counter 0 for k v in annotations items setattr self k v def __call__ self Return a pair containing the referent and the number of times the reference has been called ob super __call__ if ob is not None self __counter 1 ob ob self __counter return ob Example This simple example shows how an application can use object IDs to retrieve objects that it has seen before The IDs of the objects can then be used in other data structures without forcing the objects to remain alive but the objects can still be retrieved by ID if they do import weakref _id2obj_dict weakref WeakValueDictionary def remember obj oid id obj _id2obj_dict oid obj return oid def id2obj oid return _id2obj_dict oid Finalizer Objects The main benefit of using finalize is that it makes it simple to register a callback without needing to preserve the returned finalizer object For instance import weakref class Object pass kenny Object weakref finalize kenny print You killed Kenny finalize object at for Object at del kenny You killed Kenny The finalizer can be called directly as well However the finalizer will invoke the callback at most once def callback x y z print CALLBACK return x y z obj Object f weakref finalize obj callback 1 2 z 3 assert f alive assert f 6 CALLBACK assert not f alive f callback not called because finalizer dead del obj callback not called because finalizer dead You can unregister a finalizer using its detach method This kills the finalizer and returns the arguments passed to the constructor when it was created obj Object f weakref finalize obj callback 1 2 z 3 f detach Object object function callback 1 2 z 3 newobj func args kwargs _ assert not f alive assert newobj is obj assert func args kwargs 6 CALLBACK Unless you set the atexit attribute to False a finalizer will be called when the program exits if it is still alive For instance obj Object weakref finalize obj print obj dead or exiting finalize object at for Object at exit obj dead or exiting Comparing finalizers with __del__ methods Suppose we want to create a class whose instances represent temporary directories The directories should be deleted with their contents when the first of the following events occurs the object is garbage collected the object s remove method is called or the program exits We might try to implement the class using a __del__ method as follows class TempDir def __init__ self self name tempfile mkdtemp def remove self if self name is not None shutil rmtree self name self name None property def removed self return self name is None def __del__ self self remove Starting with Python 3 4 __del__ methods no longer prevent reference cycles from being garbage collected and module globals are no longer forced to None during interpreter shutdown So this code should work without any issues on CPython However handling of __del__ methods is notoriously implementation specific since it depends on internal details of the interpreter s garbage collector implementation A more robust alternative can be to define a finalizer which only references the specific functions and objects that it needs rather t,en
2280,han having access to the full state of the object class TempDir def __init__ self self name tempfile mkdtemp self _finalizer weakref finalize self shutil rmtree self name def remove self self _finalizer property def removed self return not self _finalizer alive Defined like this our finalizer only receives a reference to the details it needs to clean up the directory appropriately If the object never gets garbage collected the finalizer will still be called at exit The other advantage of weakref based finalizers is that they can be used to register finalizers for classes where the definition is controlled by a third party such as running code when a module is unloaded import weakref sys def unloading_module implicit reference to the module globals from the function body weakref finalize sys modules __name__ unloading_module Note If you create a finalizer object in a daemonic thread just as the program exits then there is the possibility that the finalizer does not get called at exit However in a daemonic thread atexit register try finally and with do not guarantee that cleanup occurs either,en
2281,email charset Representing character sets Source code Lib email charset py This module is part of the legacy Compat32 email API In the new API only the aliases table is used The remaining text in this section is the original documentation of the module This module provides a class Charset for representing character sets and character set conversions in email messages as well as a character set registry and several convenience methods for manipulating this registry Instances of Charset are used in several other modules within the email package Import this class from the email charset module class email charset Charset input_charset DEFAULT_CHARSET Map character sets to their email properties This class provides information about the requirements imposed on email for a specific character set It also provides convenience routines for converting between character sets given the availability of the applicable codecs Given a character set it will do its best to provide information on how to use that character set in an email message in an RFC compliant way Certain character sets must be encoded with quoted printable or base64 when used in email headers or bodies Certain character sets must be converted outright and are not allowed in email Optional input_charset is as described below it is always coerced to lower case After being alias normalized it is also used as a lookup into the registry of character sets to find out the header encoding body encoding and output conversion codec to be used for the character set For example if input_charset is iso 8859 1 then headers and bodies will be encoded using quoted printable and no output conversion codec is necessary If input_charset is euc jp then headers will be encoded with base64 bodies will not be encoded but output text will be converted from the euc jp character set to the iso 2022 jp character set Charset instances have the following data attributes input_charset The initial character set specified Common aliases are converted to their official email names e g latin_1 is converted to iso 8859 1 Defaults to 7 bit us ascii header_encoding If the character set must be encoded before it can be used in an email header this attribute will be set to charset QP for quoted printable charset BASE64 for base64 encoding or charset SHORTEST for the shortest of QP or BASE64 encoding Otherwise it will be None body_encoding Same as header_encoding but describes the encoding for the mail message s body which indeed may be different than the header encoding charset SHORTEST is not allowed for body_encoding output_charset Some character sets must be converted before they can be used in email headers or bodies If the input_charset is one of them this attribute will contain the name of the character set output will be converted to Otherwise it will be None input_codec The name of the Python codec used to convert the input_charset to Unicode If no conversion codec is necessary this attribute will be None output_codec The name of the Python codec used to convert Unicode to the output_charset If no conversion codec is necessary this attribute will have the same value as the input_codec Charset instances also have the following methods get_body_encoding Return the content transfer encoding used for body encoding This is either the string quoted printable or base64 depending on the encoding used or it is a function in which case you should call the function with a single argument the Message object being encoded The function should then set the Content Transfer Encoding header itself to whatever is appropriate Returns the string quoted printable if body_encoding is QP returns the string base64 if body_encoding is BASE64 and returns the string 7bit otherwise get_output_charset Return the output character set This is the output_charset attribute if that is not None otherwise it is input_charset header_encode string Header encode the string string The type of encoding base64 or quoted printable will be based on the header_encoding attribute header_encode_lines string maxlengths Header encode a string by,en
2282, converting it first to bytes This is similar to header_encode except that the string is fit into maximum line lengths as given by the argument maxlengths which must be an iterator each element returned from this iterator will provide the next maximum line length body_encode string Body encode the string string The type of encoding base64 or quoted printable will be based on the body_encoding attribute The Charset class also provides a number of methods to support standard operations and built in functions __str__ Returns input_charset as a string coerced to lower case __repr__ is an alias for __str__ __eq__ other This method allows you to compare two Charset instances for equality __ne__ other This method allows you to compare two Charset instances for inequality The email charset module also provides the following functions for adding new entries to the global character set alias and codec registries email charset add_charset charset header_enc None body_enc None output_charset None Add character properties to the global registry charset is the input character set and must be the canonical name of a character set Optional header_enc and body_enc is either charset QP for quoted printable charset BASE64 for base64 encoding charset SHORTEST for the shortest of quoted printable or base64 encoding or None for no encoding SHORTEST is only valid for header_enc The default is None for no encoding Optional output_charset is the character set that the output should be in Conversions will proceed from input charset to Unicode to the output charset when the method Charset convert is called The default is to output in the same character set as the input Both input_charset and output_charset must have Unicode codec entries in the module s character set to codec mapping use add_codec to add codecs the module does not know about See the codecs module s documentation for more information The global character set registry is kept in the module global dictionary CHARSETS email charset add_alias alias canonical Add a character set alias alias is the alias name e g latin 1 canonical is the character set s canonical name e g iso 8859 1 The global charset alias registry is kept in the module global dictionary ALIASES email charset add_codec charset codecname Add a codec that map characters in the given character set to and from Unicode charset is the canonical name of a character set codecname is the name of a Python codec as appropriate for the second argument to the str s encode method,en
2283,Porting Extension Modules to Python 3 We recommend the following resources for porting extension modules to Python 3 The Migrating C extensions chapter from Supporting Python 3 An in depth guide a book on moving from Python 2 to Python 3 in general guides the reader through porting an extension module The Porting guide from the py3c project provides opinionated suggestions with supporting code The Cython and CFFI libraries offer abstractions over Python s C API Extensions generally need to be re written to use one of them but the library then handles differences between various Python versions and implementations,en
2284,xml sax handler Base classes for SAX handlers Source code Lib xml sax handler py The SAX API defines five kinds of handlers content handlers DTD handlers error handlers entity resolvers and lexical handlers Applications normally only need to implement those interfaces whose events they are interested in they can implement the interfaces in a single object or in multiple objects Handler implementations should inherit from the base classes provided in the module xml sax handler so that all methods get default implementations class xml sax handler ContentHandler This is the main callback interface in SAX and the one most important to applications The order of events in this interface mirrors the order of the information in the document class xml sax handler DTDHandler Handle DTD events This interface specifies only those DTD events required for basic parsing unparsed entities and attributes class xml sax handler EntityResolver Basic interface for resolving entities If you create an object implementing this interface then register the object with your Parser the parser will call the method in your object to resolve all external entities class xml sax handler ErrorHandler Interface used by the parser to present error and warning messages to the application The methods of this object control whether errors are immediately converted to exceptions or are handled in some other way class xml sax handler LexicalHandler Interface used by the parser to represent low frequency events which may not be of interest to many applications In addition to these classes xml sax handler provides symbolic constants for the feature and property names xml sax handler feature_namespaces value http xml org sax features namespaces true Perform Namespace processing false Optionally do not perform Namespace processing implies namespace prefixes default access parsing read only not parsing read write xml sax handler feature_namespace_prefixes value http xml org sax features namespace prefixes true Report the original prefixed names and attributes used for Namespace declarations false Do not report attributes used for Namespace declarations and optionally do not report original prefixed names default access parsing read only not parsing read write xml sax handler feature_string_interning value http xml org sax features string interning true All element names prefixes attribute names Namespace URIs and local names are interned using the built in intern function false Names are not necessarily interned although they may be default access parsing read only not parsing read write xml sax handler feature_validation value http xml org sax features validation true Report all validation errors implies external general entities and external parameter entities false Do not report validation errors access parsing read only not parsing read write xml sax handler feature_external_ges value http xml org sax features external general entities true Include all external general text entities false Do not include external general entities access parsing read only not parsing read write xml sax handler feature_external_pes value http xml org sax features external parameter entities true Include all external parameter entities including the external DTD subset false Do not include any external parameter entities even the external DTD subset access parsing read only not parsing read write xml sax handler all_features List of all features xml sax handler property_lexical_handler value http xml org sax properties lexical handler data type xml sax handler LexicalHandler not supported in Python 2 description An optional extension handler for lexical events like comments access read write xml sax handler property_declaration_handler value http xml org sax properties declaration handler data type xml sax sax2lib DeclHandler not supported in Python 2 description An optional extension handler for DTD related events other than notations and unparsed entities access read write xml sax handler property_dom_node value http xml org sax properties dom node data type org w3c dom Node not s,en
2285,upported in Python 2 description When parsing the current DOM node being visited if this is a DOM iterator when not parsing the root DOM node for iteration access parsing read only not parsing read write xml sax handler property_xml_string value http xml org sax properties xml string data type Bytes description The literal string of characters that was the source for the current event access read only xml sax handler all_properties List of all known property names ContentHandler Objects Users are expected to subclass ContentHandler to support their application The following methods are called by the parser on the appropriate events in the input document ContentHandler setDocumentLocator locator Called by the parser to give the application a locator for locating the origin of document events SAX parsers are strongly encouraged though not absolutely required to supply a locator if it does so it must supply the locator to the application by invoking this method before invoking any of the other methods in the DocumentHandler interface The locator allows the application to determine the end position of any document related event even if the parser is not reporting an error Typically the application will use this information for reporting its own errors such as character content that does not match an application s business rules The information returned by the locator is probably not sufficient for use with a search engine Note that the locator will return correct information only during the invocation of the events in this interface The application should not attempt to use it at any other time ContentHandler startDocument Receive notification of the beginning of a document The SAX parser will invoke this method only once before any other methods in this interface or in DTDHandler except for setDocumentLocator ContentHandler endDocument Receive notification of the end of a document The SAX parser will invoke this method only once and it will be the last method invoked during the parse The parser shall not invoke this method until it has either abandoned parsing because of an unrecoverable error or reached the end of input ContentHandler startPrefixMapping prefix uri Begin the scope of a prefix URI Namespace mapping The information from this event is not necessary for normal Namespace processing the SAX XML reader will automatically replace prefixes for element and attribute names when the feature_namespaces feature is enabled the default There are cases however when applications need to use prefixes in character data or in attribute values where they cannot safely be expanded automatically the startPrefixMapping and endPrefixMapping events supply the information to the application to expand prefixes in those contexts itself if necessary Note that startPrefixMapping and endPrefixMapping events are not guaranteed to be properly nested relative to each other all startPrefixMapping events will occur before the corresponding startElement event and all endPrefixMapping events will occur after the corresponding endElement event but their order is not guaranteed ContentHandler endPrefixMapping prefix End the scope of a prefix URI mapping See startPrefixMapping for details This event will always occur after the corresponding endElement event but the order of endPrefixMapping events is not otherwise guaranteed ContentHandler startElement name attrs Signals the start of an element in non namespace mode The name parameter contains the raw XML 1 0 name of the element type as a string and the attrs parameter holds an object of the Attributes interface see The Attributes Interface containing the attributes of the element The object passed as attrs may be re used by the parser holding on to a reference to it is not a reliable way to keep a copy of the attributes To keep a copy of the attributes use the copy method of the attrs object ContentHandler endElement name Signals the end of an element in non namespace mode The name parameter contains the name of the element type just as with the startElement event ContentHandler startElementNS name,en
2286, qname attrs Signals the start of an element in namespace mode The name parameter contains the name of the element type as a uri localname tuple the qname parameter contains the raw XML 1 0 name used in the source document and the attrs parameter holds an instance of the AttributesNS interface see The AttributesNS Interface containing the attributes of the element If no namespace is associated with the element the uri component of name will be None The object passed as attrs may be re used by the parser holding on to a reference to it is not a reliable way to keep a copy of the attributes To keep a copy of the attributes use the copy method of the attrs object Parsers may set the qname parameter to None unless the feature_namespace_prefixes feature is activated ContentHandler endElementNS name qname Signals the end of an element in namespace mode The name parameter contains the name of the element type just as with the startElementNS method likewise the qname parameter ContentHandler characters content Receive notification of character data The Parser will call this method to report each chunk of character data SAX parsers may return all contiguous character data in a single chunk or they may split it into several chunks however all of the characters in any single event must come from the same external entity so that the Locator provides useful information content may be a string or bytes instance the expat reader module always produces strings Note The earlier SAX 1 interface provided by the Python XML Special Interest Group used a more Java like interface for this method Since most parsers used from Python did not take advantage of the older interface the simpler signature was chosen to replace it To convert old code to the new interface use content instead of slicing content with the old offset and length parameters ContentHandler ignorableWhitespace whitespace Receive notification of ignorable whitespace in element content Validating Parsers must use this method to report each chunk of ignorable whitespace see the W3C XML 1 0 recommendation section 2 10 non validating parsers may also use this method if they are capable of parsing and using content models SAX parsers may return all contiguous whitespace in a single chunk or they may split it into several chunks however all of the characters in any single event must come from the same external entity so that the Locator provides useful information ContentHandler processingInstruction target data Receive notification of a processing instruction The Parser will invoke this method once for each processing instruction found note that processing instructions may occur before or after the main document element A SAX parser should never report an XML declaration XML 1 0 section 2 8 or a text declaration XML 1 0 section 4 3 1 using this method ContentHandler skippedEntity name Receive notification of a skipped entity The Parser will invoke this method once for each entity skipped Non validating processors may skip entities if they have not seen the declarations because for example the entity was declared in an external DTD subset All processors may skip external entities depending on the values of the feature_external_ges and the feature_external_pes properties DTDHandler Objects DTDHandler instances provide the following methods DTDHandler notationDecl name publicId systemId Handle a notation declaration event DTDHandler unparsedEntityDecl name publicId systemId ndata Handle an unparsed entity declaration event EntityResolver Objects EntityResolver resolveEntity publicId systemId Resolve the system identifier of an entity and return either the system identifier to read from as a string or an InputSource to read from The default implementation returns systemId ErrorHandler Objects Objects with this interface are used to receive error and warning information from the XMLReader If you create an object that implements this interface then register the object with your XMLReader the parser will call the methods in your object to report all warnings and errors There are three level,en
2287,s of errors available warnings possibly recoverable errors and unrecoverable errors All methods take a SAXParseException as the only parameter Errors and warnings may be converted to an exception by raising the passed in exception object ErrorHandler error exception Called when the parser encounters a recoverable error If this method does not raise an exception parsing may continue but further document information should not be expected by the application Allowing the parser to continue may allow additional errors to be discovered in the input document ErrorHandler fatalError exception Called when the parser encounters an error it cannot recover from parsing is expected to terminate when this method returns ErrorHandler warning exception Called when the parser presents minor warning information to the application Parsing is expected to continue when this method returns and document information will continue to be passed to the application Raising an exception in this method will cause parsing to end LexicalHandler Objects Optional SAX2 handler for lexical events This handler is used to obtain lexical information about an XML document Lexical information includes information describing the document encoding used and XML comments embedded in the document as well as section boundaries for the DTD and for any CDATA sections The lexical handlers are used in the same manner as content handlers Set the LexicalHandler of an XMLReader by using the setProperty method with the property identifier http xml org sax properties lexical handler LexicalHandler comment content Reports a comment anywhere in the document including the DTD and outside the document element LexicalHandler startDTD name public_id system_id Reports the start of the DTD declarations if the document has an associated DTD LexicalHandler endDTD Reports the end of DTD declaration LexicalHandler startCDATA Reports the start of a CDATA marked section The contents of the CDATA marked section will be reported through the characters handler LexicalHandler endCDATA Reports the end of a CDATA marked section,en
2288,What s New In Python 3 9 Editor Łukasz Langa This article explains the new features in Python 3 9 compared to 3 8 Python 3 9 was released on October 5 2020 For full details see the changelog See also PEP 596 Python 3 9 Release Schedule Summary Release highlights New syntax features PEP 584 union operators added to dict PEP 585 type hinting generics in standard collections PEP 614 relaxed grammar restrictions on decorators New built in features PEP 616 string methods to remove prefixes and suffixes New features in the standard library PEP 593 flexible function and variable annotations os pidfd_open added that allows process management without races and signals Interpreter improvements PEP 573 fast access to module state from methods of C extension types PEP 617 CPython now uses a new parser based on PEG a number of Python builtins range tuple set frozenset list dict are now sped up using PEP 590 vectorcall garbage collection does not block on resurrected objects a number of Python modules _abc audioop _bz2 _codecs _contextvars _crypt _functools _json _locale math operator resource time _weakref now use multiphase initialization as defined by PEP 489 a number of standard library modules audioop ast grp _hashlib pwd _posixsubprocess random select struct termios zlib are now using the stable ABI defined by PEP 384 New library modules PEP 615 the IANA Time Zone Database is now present in the standard library in the zoneinfo module an implementation of a topological sort of a graph is now provided in the new graphlib module Release process changes PEP 602 CPython adopts an annual release cycle You should check for DeprecationWarning in your code When Python 2 7 was still supported a lot of functionality in Python 3 was kept for backward compatibility with Python 2 7 With the end of Python 2 support these backward compatibility layers have been removed or will be removed soon Most of them emitted a DeprecationWarning warning for several years For example using collections Mapping instead of collections abc Mapping emits a DeprecationWarning since Python 3 3 released in 2012 Test your application with the W default command line option to see DeprecationWarning and PendingDeprecationWarning or even with W error to treat them as errors Warnings Filter can be used to ignore warnings from third party code Python 3 9 is the last version providing those Python 2 backward compatibility layers to give more time to Python projects maintainers to organize the removal of the Python 2 support and add support for Python 3 9 Aliases to Abstract Base Classes in the collections module like collections Mapping alias to collections abc Mapping are kept for one last release for backward compatibility They will be removed from Python 3 10 More generally try to run your tests in the Python Development Mode which helps to prepare your code to make it compatible with the next Python version Note a number of pre existing deprecations were removed in this version of Python as well Consult the Removed section New Features Dictionary Merge Update Operators Merge and update operators have been added to the built in dict class Those complement the existing dict update and d1 d2 methods of merging dictionaries Example x key1 value1 from x key2 value2 from x y key2 value2 from y key3 value3 from y x y key1 value1 from x key2 value2 from y key3 value3 from y y x key2 value2 from x key3 value3 from y key1 value1 from x See PEP 584 for a full description Contributed by Brandt Bucher in bpo 36144 New String Methods to Remove Prefixes and Suffixes str removeprefix prefix and str removesuffix suffix have been added to easily remove an unneeded prefix or a suffix from a string Corresponding bytes bytearray and collections UserString methods have also been added See PEP 616 for a full description Contributed by Dennis Sweeney in bpo 39939 Type Hinting Generics in Standard Collections In type annotations you can now use built in collection types such as list and dict as generic types instead of importing the corresponding capitalized types e g List or Dict from typing,en
2289, Some other types in the standard library are also now generic for example queue Queue Example def greet_all names list str None for name in names print Hello name See PEP 585 for more details Contributed by Guido van Rossum Ethan Smith and Batuhan Taşkaya in bpo 39481 New Parser Python 3 9 uses a new parser based on PEG instead of LL 1 The new parser s performance is roughly comparable to that of the old parser but the PEG formalism is more flexible than LL 1 when it comes to designing new language features We ll start using this flexibility in Python 3 10 and later The ast module uses the new parser and produces the same AST as the old parser In Python 3 10 the old parser will be deleted and so will all functionality that depends on it primarily the parser module which has long been deprecated In Python 3 9 only you can switch back to the LL 1 parser using a command line switch X oldparser or an environment variable PYTHONOLDPARSER 1 See PEP 617 for more details Contributed by Guido van Rossum Pablo Galindo and Lysandros Nikolaou in bpo 40334 Other Language Changes __import__ now raises ImportError instead of ValueError which used to occur when a relative import went past its top level package Contributed by Ngalim Siregar in bpo 37444 Python now gets the absolute path of the script filename specified on the command line ex python3 script py the __file__ attribute of the __main__ module became an absolute path rather than a relative path These paths now remain valid after the current directory is changed by os chdir As a side effect the traceback also displays the absolute path for __main__ module frames in this case Contributed by Victor Stinner in bpo 20443 In the Python Development Mode and in debug build the encoding and errors arguments are now checked for string encoding and decoding operations Examples open str encode and bytes decode By default for best performance the errors argument is only checked at the first encoding decoding error and the encoding argument is sometimes ignored for empty strings Contributed by Victor Stinner in bpo 37388 replace s n now returns s instead of an empty string for all non zero n It is now consistent with replace s There are similar changes for bytes and bytearray objects Contributed by Serhiy Storchaka in bpo 28029 Any valid expression can now be used as a decorator Previously the grammar was much more restrictive See PEP 614 for details Contributed by Brandt Bucher in bpo 39702 Improved help for the typing module Docstrings are now shown for all special forms and special generic aliases like Union and List Using help with generic alias like List int will show the help for the correspondent concrete type list in this case Contributed by Serhiy Storchaka in bpo 40257 Parallel running of aclose asend athrow is now prohibited and ag_running now reflects the actual running status of the async generator Contributed by Yury Selivanov in bpo 30773 Unexpected errors in calling the __iter__ method are no longer masked by TypeError in the in operator and functions contains indexOf and countOf of the operator module Contributed by Serhiy Storchaka in bpo 40824 Unparenthesized lambda expressions can no longer be the expression part in an if clause in comprehensions and generator expressions See bpo 41848 and bpo 43755 for details New Modules zoneinfo The zoneinfo module brings support for the IANA time zone database to the standard library It adds zoneinfo ZoneInfo a concrete datetime tzinfo implementation backed by the system s time zone data Example from zoneinfo import ZoneInfo from datetime import datetime timedelta Daylight saving time dt datetime 2020 10 31 12 tzinfo ZoneInfo America Los_Angeles print dt 2020 10 31 12 00 00 07 00 dt tzname PDT Standard time dt timedelta days 7 print dt 2020 11 07 12 00 00 08 00 print dt tzname PST As a fall back source of data for platforms that don t ship the IANA database the tzdata module was released as a first party package distributed via PyPI and maintained by the CPython core team See also PEP 615 Support for the IANA Time Zone Database in t,en
2290,he Standard Library PEP written and implemented by Paul Ganssle graphlib A new module graphlib was added that contains the graphlib TopologicalSorter class to offer functionality to perform topological sorting of graphs Contributed by Pablo Galindo Tim Peters and Larry Hastings in bpo 17005 Improved Modules ast Added the indent option to dump which allows it to produce a multiline indented output Contributed by Serhiy Storchaka in bpo 37995 Added ast unparse as a function in the ast module that can be used to unparse an ast AST object and produce a string with code that would produce an equivalent ast AST object when parsed Contributed by Pablo Galindo and Batuhan Taskaya in bpo 38870 Added docstrings to AST nodes that contains the ASDL signature used to construct that node Contributed by Batuhan Taskaya in bpo 39638 asyncio Due to significant security concerns the reuse_address parameter of asyncio loop create_datagram_endpoint is no longer supported This is because of the behavior of the socket option SO_REUSEADDR in UDP For more details see the documentation for loop create_datagram_endpoint Contributed by Kyle Stanley Antoine Pitrou and Yury Selivanov in bpo 37228 Added a new coroutine shutdown_default_executor that schedules a shutdown for the default executor that waits on the ThreadPoolExecutor to finish closing Also asyncio run has been updated to use the new coroutine Contributed by Kyle Stanley in bpo 34037 Added asyncio PidfdChildWatcher a Linux specific child watcher implementation that polls process file descriptors bpo 38692 Added a new coroutine asyncio to_thread It is mainly used for running IO bound functions in a separate thread to avoid blocking the event loop and essentially works as a high level version of run_in_executor that can directly take keyword arguments Contributed by Kyle Stanley and Yury Selivanov in bpo 32309 When cancelling the task due to a timeout asyncio wait_for will now wait until the cancellation is complete also in the case when timeout is 0 like it does with positive timeouts Contributed by Elvis Pranskevichus in bpo 32751 asyncio now raises TyperError when calling incompatible methods with an ssl SSLSocket socket Contributed by Ido Michael in bpo 37404 compileall Added new possibility to use hardlinks for duplicated pyc files hardlink_dupes parameter and hardlink dupes command line option Contributed by Lumír Frenzy Balhar in bpo 40495 Added new options for path manipulation in resulting pyc files stripdir prependdir limit_sl_dest parameters and s p e command line options Added the possibility to specify the option for an optimization level multiple times Contributed by Lumír Frenzy Balhar in bpo 38112 concurrent futures Added a new cancel_futures parameter to concurrent futures Executor shutdown that cancels all pending futures which have not started running instead of waiting for them to complete before shutting down the executor Contributed by Kyle Stanley in bpo 39349 Removed daemon threads from ThreadPoolExecutor and ProcessPoolExecutor This improves compatibility with subinterpreters and predictability in their shutdown processes Contributed by Kyle Stanley in bpo 39812 Workers in ProcessPoolExecutor are now spawned on demand only when there are no available idle workers to reuse This optimizes startup overhead and reduces the amount of lost CPU time to idle workers Contributed by Kyle Stanley in bpo 39207 curses Added curses get_escdelay curses set_escdelay curses get_tabsize and curses set_tabsize functions Contributed by Anthony Sottile in bpo 38312 datetime The isocalendar of datetime date and isocalendar of datetime datetime methods now returns a namedtuple instead of a tuple Contributed by Donghee Na in bpo 24416 distutils The upload command now creates SHA2 256 and Blake2b 256 hash digests It skips MD5 on platforms that block MD5 digest Contributed by Christian Heimes in bpo 40698 fcntl Added constants F_OFD_GETLK F_OFD_SETLK and F_OFD_SETLKW Contributed by Donghee Na in bpo 38602 ftplib FTP and FTP_TLS now raise a ValueError if the given timeout for their construct,en
2291,or is zero to prevent the creation of a non blocking socket Contributed by Donghee Na in bpo 39259 gc When the garbage collector makes a collection in which some objects resurrect they are reachable from outside the isolated cycles after the finalizers have been executed do not block the collection of all objects that are still unreachable Contributed by Pablo Galindo and Tim Peters in bpo 38379 Added a new function gc is_finalized to check if an object has been finalized by the garbage collector Contributed by Pablo Galindo in bpo 39322 hashlib The hashlib module can now use SHA3 hashes and SHAKE XOF from OpenSSL when available Contributed by Christian Heimes in bpo 37630 Builtin hash modules can now be disabled with configure without builtin hashlib hashes or selectively enabled with e g configure with builtin hashlib hashes sha3 blake2 to force use of OpenSSL based implementation Contributed by Christian Heimes in bpo 40479 http HTTP status codes 103 EARLY_HINTS 418 IM_A_TEAPOT and 425 TOO_EARLY are added to http HTTPStatus Contributed by Donghee Na in bpo 39509 and Ross Rhodes in bpo 39507 IDLE and idlelib Added option to toggle cursor blink off Contributed by Zackery Spytz in bpo 4603 Escape key now closes IDLE completion windows Contributed by Johnny Najera in bpo 38944 Added keywords to module name completion list Contributed by Terry J Reedy in bpo 37765 New in 3 9 maintenance releases Make IDLE invoke sys excepthook when started without n User hooks were previously ignored Contributed by Ken Hilton in bpo 43008 The changes above have been backported to 3 8 maintenance releases Rearrange the settings dialog Split the General tab into Windows and Shell Ed tabs Move help sources which extend the Help menu to the Extensions tab Make space for new options and shorten the dialog The latter makes the dialog better fit small screens Contributed by Terry Jan Reedy in bpo 40468 Move the indent space setting from the Font tab to the new Windows tab Contributed by Mark Roseman and Terry Jan Reedy in bpo 33962 Apply syntax highlighting to pyi files Contributed by Alex Waygood and Terry Jan Reedy in bpo 45447 imaplib IMAP4 and IMAP4_SSL now have an optional timeout parameter for their constructors Also the open method now has an optional timeout parameter with this change The overridden methods of IMAP4_SSL and IMAP4_stream were applied to this change Contributed by Donghee Na in bpo 38615 imaplib IMAP4 unselect is added imaplib IMAP4 unselect frees server s resources associated with the selected mailbox and returns the server to the authenticated state This command performs the same actions as imaplib IMAP4 close except that no messages are permanently removed from the currently selected mailbox Contributed by Donghee Na in bpo 40375 importlib To improve consistency with import statements importlib util resolve_name now raises ImportError instead of ValueError for invalid relative import attempts Contributed by Ngalim Siregar in bpo 37444 Import loaders which publish immutable module objects can now publish immutable packages in addition to individual modules Contributed by Dino Viehland in bpo 39336 Added importlib resources files function with support for subdirectories in package data matching backport in importlib_resources version 1 5 Contributed by Jason R Coombs in bpo 39791 Refreshed importlib metadata from importlib_metadata version 1 6 1 inspect inspect BoundArguments arguments is changed from OrderedDict to regular dict Contributed by Inada Naoki in bpo 36350 and bpo 39775 ipaddress ipaddress now supports IPv6 Scoped Addresses IPv6 address with suffix scope_id Scoped IPv6 addresses can be parsed using ipaddress IPv6Address If present scope zone ID is available through the scope_id attribute Contributed by Oleksandr Pavliuk in bpo 34788 Starting with Python 3 9 5 the ipaddress module no longer accepts any leading zeros in IPv4 address strings Contributed by Christian Heimes in bpo 36384 math Expanded the math gcd function to handle multiple arguments Formerly it only supported two arguments Contributed by Serhiy St,en
2292,orchaka in bpo 39648 Added math lcm return the least common multiple of specified arguments Contributed by Mark Dickinson Ananthakrishnan and Serhiy Storchaka in bpo 39479 and bpo 39648 Added math nextafter return the next floating point value after x towards y Contributed by Victor Stinner in bpo 39288 Added math ulp return the value of the least significant bit of a float Contributed by Victor Stinner in bpo 39310 multiprocessing The multiprocessing SimpleQueue class has a new close method to explicitly close the queue Contributed by Victor Stinner in bpo 30966 nntplib NNTP and NNTP_SSL now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non blocking socket Contributed by Donghee Na in bpo 39259 os Added CLD_KILLED and CLD_STOPPED for si_code Contributed by Donghee Na in bpo 38493 Exposed the Linux specific os pidfd_open bpo 38692 and os P_PIDFD bpo 38713 for process management with file descriptors The os unsetenv function is now also available on Windows Contributed by Victor Stinner in bpo 39413 The os putenv and os unsetenv functions are now always available Contributed by Victor Stinner in bpo 39395 Added os waitstatus_to_exitcode function convert a wait status to an exit code Contributed by Victor Stinner in bpo 40094 pathlib Added pathlib Path readlink which acts similarly to os readlink Contributed by Girts Folkmanis in bpo 30618 pdb On Windows now Pdb supports pdbrc Contributed by Tim Hopper and Dan Lidral Porter in bpo 20523 poplib POP3 and POP3_SSL now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non blocking socket Contributed by Donghee Na in bpo 39259 pprint pprint can now pretty print types SimpleNamespace Contributed by Carl Bordum Hansen in bpo 37376 pydoc The documentation string is now shown not only for class function method etc but for any object that has its own __doc__ attribute Contributed by Serhiy Storchaka in bpo 40257 random Added a new random Random randbytes method generate random bytes Contributed by Victor Stinner in bpo 40286 signal Exposed the Linux specific signal pidfd_send_signal for sending to signals to a process using a file descriptor instead of a pid bpo 38712 smtplib SMTP and SMTP_SSL now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non blocking socket Contributed by Donghee Na in bpo 39259 LMTP constructor now has an optional timeout parameter Contributed by Donghee Na in bpo 39329 socket The socket module now exports the CAN_RAW_JOIN_FILTERS constant on Linux 4 1 and greater Contributed by Stefan Tatschner and Zackery Spytz in bpo 25780 The socket module now supports the CAN_J1939 protocol on platforms that support it Contributed by Karl Ding in bpo 40291 The socket module now has the socket send_fds and socket recv_fds functions Contributed by Joannah Nanjekye Shinya Okano and Victor Stinner in bpo 28724 time On AIX thread_time is now implemented with thread_cputime which has nanosecond resolution rather than clock_gettime CLOCK_THREAD_CPUTIME_ID which has a resolution of 10 milliseconds Contributed by Batuhan Taskaya in bpo 40192 sys Added a new sys platlibdir attribute name of the platform specific library directory It is used to build the path of standard library and the paths of installed extension modules It is equal to lib on most platforms On Fedora and SuSE it is equal to lib64 on 64 bit platforms Contributed by Jan Matějek Matěj Cepl Charalampos Stratakis and Victor Stinner in bpo 1294959 Previously sys stderr was block buffered when non interactive Now stderr defaults to always being line buffered Contributed by Jendrik Seipp in bpo 13601 tracemalloc Added tracemalloc reset_peak to set the peak size of traced memory blocks to the current size to measure the peak of specific pieces of code Contributed by Huon Wilson in bpo 40630 typing PEP 593 introduced an typing Annotated type to decorate existing types with context specific metadata and new include_extras parameter to typing get_type_hints to access the me,en
2293,tadata at runtime Contributed by Till Varoquaux and Konstantin Kashin unicodedata The Unicode database has been updated to version 13 0 0 bpo 39926 venv The activation scripts provided by venv now all specify their prompt customization consistently by always using the value specified by __VENV_PROMPT__ Previously some scripts unconditionally used __VENV_PROMPT__ others only if it happened to be set which was the default case and one used __VENV_NAME__ instead Contributed by Brett Cannon in bpo 37663 xml White space characters within attributes are now preserved when serializing xml etree ElementTree to XML file EOLNs are no longer normalized to n This is the result of discussion about how to interpret section 2 11 of XML spec Contributed by Mefistotelis in bpo 39011 Optimizations Optimized the idiom for assignment a temporary variable in comprehensions Now for y in expr in comprehensions is as fast as a simple assignment y expr For example sums s for s in 0 for x in data for s in s x Unlike the operator this idiom does not leak a variable to the outer scope Contributed by Serhiy Storchaka in bpo 32856 Optimized signal handling in multithreaded applications If a thread different than the main thread gets a signal the bytecode evaluation loop is no longer interrupted at each bytecode instruction to check for pending signals which cannot be handled Only the main thread of the main interpreter can handle signals Previously the bytecode evaluation loop was interrupted at each instruction until the main thread handles signals Contributed by Victor Stinner in bpo 40010 Optimized the subprocess module on FreeBSD using closefrom Contributed by Ed Maste Conrad Meyer Kyle Evans Kubilay Kocak and Victor Stinner in bpo 38061 PyLong_FromDouble is now up to 1 87x faster for values that fit into long Contributed by Sergey Fedoseev in bpo 37986 A number of Python builtins range tuple set frozenset list dict are now sped up by using PEP 590 vectorcall protocol Contributed by Donghee Na Mark Shannon Jeroen Demeyer and Petr Viktorin in bpo 37207 Optimized difference_update for the case when the other set is much larger than the base set Suggested by Evgeny Kapun with code contributed by Michele Orrù in bpo 8425 Python s small object allocator obmalloc c now allows no more than one empty arena to remain available for immediate reuse without returning it to the OS This prevents thrashing in simple loops where an arena could be created and destroyed anew on each iteration Contributed by Tim Peters in bpo 37257 floor division of float operation now has a better performance Also the message of ZeroDivisionError for this operation is updated Contributed by Donghee Na in bpo 39434 Decoding short ASCII strings with UTF 8 and ascii codecs is now about 15 faster Contributed by Inada Naoki in bpo 37348 Here s a summary of performance improvements from Python 3 4 through Python 3 9 Python version 3 4 3 5 3 6 3 7 3 8 3 9 Variable and attribute read access read_local 7 1 7 1 5 4 5 1 3 9 3 9 read_nonlocal 7 1 8 1 5 8 5 4 4 4 4 5 read_global 15 5 19 0 14 3 13 6 7 6 7 8 read_builtin 21 1 21 6 18 5 19 0 7 5 7 8 read_classvar_from_class 25 6 26 5 20 7 19 5 18 4 17 9 read_classvar_from_instance 22 8 23 5 18 8 17 1 16 4 16 9 read_instancevar 32 4 33 1 28 0 26 3 25 4 25 3 read_instancevar_slots 27 8 31 3 20 8 20 8 20 2 20 5 read_namedtuple 73 8 57 5 45 0 46 8 18 4 18 7 read_boundmethod 37 6 37 9 29 6 26 9 27 7 41 1 Variable and attribute write access write_local 8 7 9 3 5 5 5 3 4 3 4 3 write_nonlocal 10 5 11 1 5 6 5 5 4 7 4 8 write_global 19 7 21 2 18 0 18 0 15 8 16 7 write_classvar 92 9 96 0 104 6 102 1 39 2 39 8 write_instancevar 44 6 45 8 40 0 38 9 35 5 37 4 write_instancevar_slots 35 6 36 1 27 3 26 6 25 7 25 8 Data structure read access read_list 24 2 24 5 20 8 20 8 19 0 19 5 read_deque 24 7 25 5 20 2 20 6 19 8 20 2 read_dict 24 3 25 7 22 3 23 0 21 0 22 4 read_strdict 22 6 24 3 19 5 21 2 18 9 21 5 Data structure write access write_list 27 1 28 5 22 5 21 6 20 0 20 0 write_deque 28 7 30 1 22 7 21 8 23 5 21 7 write_dict 31 4 33 3 29 3 29 2 24 7 25 4 write_strdi,en
2294,ct 28 4 29 9 27 5 25 2 23 1 24 5 Stack or queue operations list_append_pop 93 4 112 7 75 4 74 2 50 8 50 6 deque_append_pop 43 5 57 0 49 4 49 2 42 5 44 2 deque_append_popleft 43 7 57 3 49 7 49 7 42 8 46 4 Timing loop loop_overhead 0 5 0 6 0 4 0 3 0 3 0 3 These results were generated from the variable access benchmark script at Tools scripts var_access_benchmark py The benchmark script displays timings in nanoseconds The benchmarks were measured on an Intel Core i7 4960HQ processor running the macOS 64 bit builds found at python org Deprecated The distutils bdist_msi command is now deprecated use bdist_wheel wheel packages instead Contributed by Hugo van Kemenade in bpo 39586 Currently math factorial accepts float instances with non negative integer values like 5 0 It raises a ValueError for non integral and negative floats It is now deprecated In future Python versions it will raise a TypeError for all floats Contributed by Serhiy Storchaka in bpo 37315 The parser and symbol modules are deprecated and will be removed in future versions of Python For the majority of use cases users can leverage the Abstract Syntax Tree AST generation and compilation stage using the ast module The Public C API functions PyParser_SimpleParseStringFlags PyParser_SimpleParseStringFlagsFilename PyParser_SimpleParseFileFlags and PyNode_Compile are deprecated and will be removed in Python 3 10 together with the old parser Using NotImplemented in a boolean context has been deprecated as it is almost exclusively the result of incorrect rich comparator implementations It will be made a TypeError in a future version of Python Contributed by Josh Rosenberg in bpo 35712 The random module currently accepts any hashable type as a possible seed value Unfortunately some of those types are not guaranteed to have a deterministic hash value After Python 3 9 the module will restrict its seeds to None int float str bytes and bytearray Opening the GzipFile file for writing without specifying the mode argument is deprecated In future Python versions it will always be opened for reading by default Specify the mode argument for opening it for writing and silencing a warning Contributed by Serhiy Storchaka in bpo 28286 Deprecated the split method of _tkinter TkappType in favour of the splitlist method which has more consistent and predicable behavior Contributed by Serhiy Storchaka in bpo 38371 The explicit passing of coroutine objects to asyncio wait has been deprecated and will be removed in version 3 11 Contributed by Yury Selivanov and Kyle Stanley in bpo 34790 binhex4 and hexbin4 standards are now deprecated The binhex module and the following binascii functions are now deprecated b2a_hqx a2b_hqx rlecode_hqx rledecode_hqx Contributed by Victor Stinner in bpo 39353 ast classes slice Index and ExtSlice are considered deprecated and will be removed in future Python versions value itself should be used instead of Index value Tuple slices Load should be used instead of ExtSlice slices Contributed by Serhiy Storchaka in bpo 34822 ast classes Suite Param AugLoad and AugStore are considered deprecated and will be removed in future Python versions They were not generated by the parser and not accepted by the code generator in Python 3 Contributed by Batuhan Taskaya in bpo 39639 and bpo 39969 and Serhiy Storchaka in bpo 39988 The PyEval_InitThreads and PyEval_ThreadsInitialized functions are now deprecated and will be removed in Python 3 11 Calling PyEval_InitThreads now does nothing The GIL is initialized by Py_Initialize since Python 3 7 Contributed by Victor Stinner in bpo 39877 Passing None as the first argument to the shlex split function has been deprecated Contributed by Zackery Spytz in bpo 33262 smtpd MailmanProxy is now deprecated as it is unusable without an external module mailman Contributed by Samuel Colvin in bpo 35800 The lib2to3 module now emits a PendingDeprecationWarning Python 3 9 switched to a PEG parser see PEP 617 and Python 3 10 may include new language syntax that is not parsable by lib2to3 s LL 1 parser The lib2to3 module may be removed from the,en
2295, standard library in a future Python version Consider third party alternatives such as LibCST or parso Contributed by Carl Meyer in bpo 40360 The random parameter of random shuffle has been deprecated Contributed by Raymond Hettinger in bpo 40465 Removed The erroneous version at unittest mock __version__ has been removed nntplib NNTP xpath and xgtitle methods have been removed These methods are deprecated since Python 3 3 Generally these extensions are not supported or not enabled by NNTP server administrators For xgtitle please use nntplib NNTP descriptions or nntplib NNTP description instead Contributed by Donghee Na in bpo 39366 array array tostring and fromstring methods have been removed They were aliases to tobytes and frombytes deprecated since Python 3 2 Contributed by Victor Stinner in bpo 38916 The undocumented sys callstats function has been removed Since Python 3 7 it was deprecated and always returned None It required a special build option CALL_PROFILE which was already removed in Python 3 7 Contributed by Victor Stinner in bpo 37414 The sys getcheckinterval and sys setcheckinterval functions have been removed They were deprecated since Python 3 2 Use sys getswitchinterval and sys setswitchinterval instead Contributed by Victor Stinner in bpo 37392 The C function PyImport_Cleanup has been removed It was documented as Empty the module table For internal use only Contributed by Victor Stinner in bpo 36710 _dummy_thread and dummy_threading modules have been removed These modules were deprecated since Python 3 7 which requires threading support Contributed by Victor Stinner in bpo 37312 aifc openfp alias to aifc open sunau openfp alias to sunau open and wave openfp alias to wave open have been removed They were deprecated since Python 3 7 Contributed by Victor Stinner in bpo 37320 The isAlive method of threading Thread has been removed It was deprecated since Python 3 8 Use is_alive instead Contributed by Donghee Na in bpo 37804 Methods getchildren and getiterator of classes ElementTree and Element in the ElementTree module have been removed They were deprecated in Python 3 2 Use iter x or list x instead of x getchildren and x iter or list x iter instead of x getiterator Contributed by Serhiy Storchaka in bpo 36543 The old plistlib API has been removed it was deprecated since Python 3 4 Use the load loads dump and dumps functions Additionally the use_builtin_types parameter was removed standard bytes objects are always used instead Contributed by Jon Janzen in bpo 36409 The C function PyGen_NeedsFinalizing has been removed It was not documented tested or used anywhere within CPython after the implementation of PEP 442 Patch by Joannah Nanjekye Contributed by Joannah Nanjekye in bpo 15088 base64 encodestring and base64 decodestring aliases deprecated since Python 3 1 have been removed use base64 encodebytes and base64 decodebytes instead Contributed by Victor Stinner in bpo 39351 fractions gcd function has been removed it was deprecated since Python 3 5 bpo 22486 use math gcd instead Contributed by Victor Stinner in bpo 39350 The buffering parameter of bz2 BZ2File has been removed Since Python 3 0 it was ignored and using it emitted a DeprecationWarning Pass an open file object to control how the file is opened Contributed by Victor Stinner in bpo 39357 The encoding parameter of json loads has been removed As of Python 3 1 it was deprecated and ignored using it has emitted a DeprecationWarning since Python 3 8 Contributed by Inada Naoki in bpo 39377 with await asyncio lock and with yield from asyncio lock statements are not longer supported use async with lock instead The same is correct for asyncio Condition and asyncio Semaphore Contributed by Andrew Svetlov in bpo 34793 The sys getcounts function the X showalloccount command line option and the show_alloc_count field of the C structure PyConfig have been removed They required a special Python build by defining COUNT_ALLOCS macro Contributed by Victor Stinner in bpo 39489 The _field_types attribute of the typing NamedTuple class has been removed It was depreca,en
2296,ted since Python 3 8 Use the __annotations__ attribute instead Contributed by Serhiy Storchaka in bpo 40182 The symtable SymbolTable has_exec method has been removed It was deprecated since 2006 and only returning False when it s called Contributed by Batuhan Taskaya in bpo 40208 The asyncio Task current_task and asyncio Task all_tasks have been removed They were deprecated since Python 3 7 and you can use asyncio current_task and asyncio all_tasks instead Contributed by Rémi Lapeyre in bpo 40967 The unescape method in the html parser HTMLParser class has been removed it was deprecated since Python 3 4 html unescape should be used for converting character references to the corresponding unicode characters Porting to Python 3 9 This section lists previously described changes and other bugfixes that may require changes to your code Changes in the Python API __import__ and importlib util resolve_name now raise ImportError where it previously raised ValueError Callers catching the specific exception type and supporting both Python 3 9 and earlier versions will need to catch both using except ImportError ValueError The venv activation scripts no longer special case when __VENV_PROMPT__ is set to The select epoll unregister method no longer ignores the EBADF error Contributed by Victor Stinner in bpo 39239 The compresslevel parameter of bz2 BZ2File became keyword only since the buffering parameter has been removed Contributed by Victor Stinner in bpo 39357 Simplified AST for subscription Simple indices will be represented by their value extended slices will be represented as tuples Index value will return a value itself ExtSlice slices will return Tuple slices Load Contributed by Serhiy Storchaka in bpo 34822 The importlib module now ignores the PYTHONCASEOK environment variable when the E or I command line options are being used The encoding parameter has been added to the classes ftplib FTP and ftplib FTP_TLS as a keyword only parameter and the default encoding is changed from Latin 1 to UTF 8 to follow RFC 2640 asyncio loop shutdown_default_executor has been added to AbstractEventLoop meaning alternative event loops that inherit from it should have this method defined Contributed by Kyle Stanley in bpo 34037 The constant values of future flags in the __future__ module is updated in order to prevent collision with compiler flags Previously PyCF_ALLOW_TOP_LEVEL_AWAIT was clashing with CO_FUTURE_DIVISION Contributed by Batuhan Taskaya in bpo 39562 array u now uses wchar_t as C type instead of Py_UNICODE This change doesn t affect to its behavior because Py_UNICODE is alias of wchar_t since Python 3 3 Contributed by Inada Naoki in bpo 34538 The logging getLogger API now returns the root logger when passed the name root whereas previously it returned a non root logger named root This could affect cases where user code explicitly wants a non root logger named root or instantiates a logger using logging getLogger __name__ in some top level module called root py Contributed by Vinay Sajip in bpo 37742 Division handling of PurePath now returns NotImplemented instead of raising a TypeError when passed something other than an instance of str or PurePath This allows creating compatible classes that don t inherit from those mentioned types Contributed by Roger Aiudi in bpo 34775 Starting with Python 3 9 5 the ipaddress module no longer accepts any leading zeros in IPv4 address strings Leading zeros are ambiguous and interpreted as octal notation by some libraries For example the legacy function socket inet_aton treats leading zeros as octal notatation glibc implementation of modern inet_pton does not accept any leading zeros Contributed by Christian Heimes in bpo 36384 codecs lookup now normalizes the encoding name the same way as encodings normalize_encoding except that codecs lookup also converts the name to lower case For example latex latin1 encoding name is now normalized to latex_latin1 Contributed by Jordon Xu in bpo 37751 Changes in the C API Instances of heap allocated types such as those created with PyType_FromSpec and simila,en
2297,r APIs hold a reference to their type object since Python 3 8 As indicated in the Changes in the C API of Python 3 8 for the vast majority of cases there should be no side effect but for types that have a custom tp_traverse function ensure that all custom tp_traverse functions of heap allocated types visit the object s type Example int foo_traverse foo_struct self visitproc visit void arg Rest of the traverse function if PY_VERSION_HEX 0x03090000 This was not needed before Python 3 9 Python issue 35810 and 40217 Py_VISIT Py_TYPE self endif If your traverse function delegates to tp_traverse of its base class or another type ensure that Py_TYPE self is visited only once Note that only heap type are expected to visit the type in tp_traverse For example if your tp_traverse function includes base tp_traverse self visit arg then add if PY_VERSION_HEX 0x03090000 This was not needed before Python 3 9 bpo 35810 and bpo 40217 if base tp_flags Py_TPFLAGS_HEAPTYPE a heap type s tp_traverse already visited Py_TYPE self else Py_VISIT Py_TYPE self else See bpo 35810 and bpo 40217 for more information The functions PyEval_CallObject PyEval_CallFunction PyEval_CallMethod and PyEval_CallObjectWithKeywords are deprecated Use PyObject_Call and its variants instead See more details in bpo 29548 CPython bytecode changes The LOAD_ASSERTION_ERROR opcode was added for handling the assert statement Previously the assert statement would not work correctly if the AssertionError exception was being shadowed Contributed by Zackery Spytz in bpo 34880 The COMPARE_OP opcode was split into four distinct instructions COMPARE_OP for rich comparisons IS_OP for is and is not tests CONTAINS_OP for in and not in tests JUMP_IF_NOT_EXC_MATCH for checking exceptions in try except statements Contributed by Mark Shannon in bpo 39156 Build Changes Added with platlibdir option to the configure script name of the platform specific library directory stored in the new sys platlibdir attribute See sys platlibdir attribute for more information Contributed by Jan Matějek Matěj Cepl Charalampos Stratakis and Victor Stinner in bpo 1294959 The COUNT_ALLOCS special build macro has been removed Contributed by Victor Stinner in bpo 39489 On non Windows platforms the setenv and unsetenv functions are now required to build Python Contributed by Victor Stinner in bpo 39395 On non Windows platforms creating bdist_wininst installers is now officially unsupported See bpo 10945 for more details When building Python on macOS from source _tkinter now links with non system Tcl and Tk frameworks if they are installed in Library Frameworks as had been the case on older releases of macOS If a macOS SDK is explicitly configured by using enable universalsdk or isysroot only the SDK itself is searched The default behavior can still be overridden with with tcltk includes and with tcltk libs Contributed by Ned Deily in bpo 34956 Python can now be built for Windows 10 ARM64 Contributed by Steve Dower in bpo 33125 Some individual tests are now skipped when pgo is used The tests in question increased the PGO task time significantly and likely didn t help improve optimization of the final executable This speeds up the task by a factor of about 15x Running the full unit test suite is slow This change may result in a slightly less optimized build since not as many code branches will be executed If you are willing to wait for the much slower build the old behavior can be restored using configure PROFILE_TASK m test pgo extended We make no guarantees as to which PGO task set produces a faster build Users who care should run their own relevant benchmarks as results can depend on the environment workload and compiler tool chain See bpo 36044 and bpo 37707 for more details C API Changes New Features PEP 573 Added PyType_FromModuleAndSpec to associate a module with a class PyType_GetModule and PyType_GetModuleState to retrieve the module and its state and PyCMethod and METH_METHOD to allow a method to access the class it was defined in Contributed by Marcel Plch and Petr Viktorin in bpo 38787 Added PyFrame_G,en
2298,etCode function get a frame code Added PyFrame_GetBack function get the frame next outer frame Contributed by Victor Stinner in bpo 40421 Added PyFrame_GetLineNumber to the limited C API Contributed by Victor Stinner in bpo 40421 Added PyThreadState_GetInterpreter and PyInterpreterState_Get functions to get the interpreter Added PyThreadState_GetFrame function to get the current frame of a Python thread state Added PyThreadState_GetID function get the unique identifier of a Python thread state Contributed by Victor Stinner in bpo 39947 Added a new public PyObject_CallNoArgs function to the C API which calls a callable Python object without any arguments It is the most efficient way to call a callable Python object without any argument Contributed by Victor Stinner in bpo 37194 Changes in the limited C API if Py_LIMITED_API macro is defined Provide Py_EnterRecursiveCall and Py_LeaveRecursiveCall as regular functions for the limited API Previously there were defined as macros but these macros didn t compile with the limited C API which cannot access PyThreadState recursion_depth field the structure is opaque in the limited C API PyObject_INIT and PyObject_INIT_VAR become regular opaque function to hide implementation details Contributed by Victor Stinner in bpo 38644 and bpo 39542 The PyModule_AddType function is added to help adding a type to a module Contributed by Donghee Na in bpo 40024 Added the functions PyObject_GC_IsTracked and PyObject_GC_IsFinalized to the public API to allow to query if Python objects are being currently tracked or have been already finalized by the garbage collector respectively Contributed by Pablo Galindo Salgado in bpo 40241 Added _PyObject_FunctionStr to get a user friendly string representation of a function like object Patch by Jeroen Demeyer in bpo 37645 Added PyObject_CallOneArg for calling an object with one positional argument Patch by Jeroen Demeyer in bpo 37483 Porting to Python 3 9 PyInterpreterState eval_frame PEP 523 now requires a new mandatory tstate parameter PyThreadState Contributed by Victor Stinner in bpo 38500 Extension modules m_traverse m_clear and m_free functions of PyModuleDef are no longer called if the module state was requested but is not allocated yet This is the case immediately after the module is created and before the module is executed Py_mod_exec function More precisely these functions are not called if m_size is greater than 0 and the module state as returned by PyModule_GetState is NULL Extension modules without module state m_size 0 are not affected If Py_AddPendingCall is called in a subinterpreter the function is now scheduled to be called from the subinterpreter rather than being called from the main interpreter Each subinterpreter now has its own list of scheduled calls Contributed by Victor Stinner in bpo 39984 The Windows registry is no longer used to initialize sys path when the E option is used if PyConfig use_environment is set to 0 This is significant when embedding Python on Windows Contributed by Zackery Spytz in bpo 8901 The global variable PyStructSequence_UnnamedField is now a constant and refers to a constant string Contributed by Serhiy Storchaka in bpo 38650 The PyGC_Head structure is now opaque It is only defined in the internal C API pycore_gc h Contributed by Victor Stinner in bpo 40241 The Py_UNICODE_COPY Py_UNICODE_FILL PyUnicode_WSTR_LENGTH PyUnicode_FromUnicode PyUnicode_AsUnicode _PyUnicode_AsUnicode and PyUnicode_AsUnicodeAndSize are marked as deprecated in C They have been deprecated by PEP 393 since Python 3 3 Contributed by Inada Naoki in bpo 36346 The Py_FatalError function is replaced with a macro which logs automatically the name of the current function unless the Py_LIMITED_API macro is defined Contributed by Victor Stinner in bpo 39882 The vectorcall protocol now requires that the caller passes only strings as keyword names See bpo 37540 for more information Implementation details of a number of macros and functions are now hidden PyObject_IS_GC macro was converted to a function The PyObject_NEW macro becomes an alias t,en
2299,o the PyObject_New macro and the PyObject_NEW_VAR macro becomes an alias to the PyObject_NewVar macro They no longer access directly the PyTypeObject tp_basicsize member PyObject_GET_WEAKREFS_LISTPTR macro was converted to a function the macro accessed directly the PyTypeObject tp_weaklistoffset member PyObject_CheckBuffer macro was converted to a function the macro accessed directly the PyTypeObject tp_as_buffer member PyIndex_Check is now always declared as an opaque function to hide implementation details removed the PyIndex_Check macro The macro accessed directly the PyTypeObject tp_as_number member See bpo 40170 for more details Removed Excluded PyFPE_START_PROTECT and PyFPE_END_PROTECT macros of pyfpe h from the limited C API Contributed by Victor Stinner in bpo 38835 The tp_print slot of PyTypeObject has been removed It was used for printing objects to files in Python 2 7 and before Since Python 3 0 it has been ignored and unused Contributed by Jeroen Demeyer in bpo 36974 Changes in the limited C API if Py_LIMITED_API macro is defined Excluded the following functions from the limited C API PyThreadState_DeleteCurrent Contributed by Joannah Nanjekye in bpo 37878 _Py_CheckRecursionLimit _Py_NewReference _Py_ForgetReference _PyTraceMalloc_NewReference _Py_GetRefTotal The trashcan mechanism which never worked in the limited C API PyTrash_UNWIND_LEVEL Py_TRASHCAN_BEGIN_CONDITION Py_TRASHCAN_BEGIN Py_TRASHCAN_END Py_TRASHCAN_SAFE_BEGIN Py_TRASHCAN_SAFE_END Moved following functions and definitions to the internal C API _PyDebug_PrintTotalRefs _Py_PrintReferences _Py_PrintReferenceAddresses _Py_tracemalloc_config _Py_AddToAllObjects specific to Py_TRACE_REFS build Contributed by Victor Stinner in bpo 38644 and bpo 39542 Removed _PyRuntime getframe hook and removed _PyThreadState_GetFrame macro which was an alias to _PyRuntime getframe They were only exposed by the internal C API Removed also PyThreadFrameGetter type Contributed by Victor Stinner in bpo 39946 Removed the following functions from the C API Call PyGC_Collect explicitly to clear all free lists Contributed by Inada Naoki and Victor Stinner in bpo 37340 bpo 38896 and bpo 40428 PyAsyncGen_ClearFreeLists PyContext_ClearFreeList PyDict_ClearFreeList PyFloat_ClearFreeList PyFrame_ClearFreeList PyList_ClearFreeList PyMethod_ClearFreeList and PyCFunction_ClearFreeList the free lists of bound method objects have been removed PySet_ClearFreeList the set free list has been removed in Python 3 4 PyTuple_ClearFreeList PyUnicode_ClearFreeList the Unicode free list has been removed in Python 3 3 Removed _PyUnicode_ClearStaticStrings function Contributed by Victor Stinner in bpo 39465 Removed Py_UNICODE_MATCH It has been deprecated by PEP 393 and broken since Python 3 3 The PyUnicode_Tailmatch function can be used instead Contributed by Inada Naoki in bpo 36346 Cleaned header files of interfaces defined but with no implementation The public API symbols being removed are _PyBytes_InsertThousandsGroupingLocale _PyBytes_InsertThousandsGrouping _Py_InitializeFromArgs _Py_InitializeFromWideArgs _PyFloat_Repr _PyFloat_Digits _PyFloat_DigitsInit PyFrame_ExtendStack _PyAIterWrapper_Type PyNullImporter_Type PyCmpWrapper_Type PySortWrapper_Type PyNoArgsFunction Contributed by Pablo Galindo Salgado in bpo 39372 Notable changes in Python 3 9 1 typing The behavior of typing Literal was changed to conform with PEP 586 and to match the behavior of static type checkers specified in the PEP 1 Literal now de duplicates parameters 2 Equality comparisons between Literal objects are now order independent 3 Literal comparisons now respect types For example Literal 0 Literal False previously evaluated to True It is now False To support this change the internally used type cache now supports differentiating types 4 Literal objects will now raise a TypeError exception during equality comparisons if any of their parameters are not hashable Note that declaring Literal with mutable parameters will not throw an error from typing import Literal Literal 0 Literal 0 Literal False Traceback most recent cal,en
2300,l last File stdin line 1 in module TypeError unhashable type set Contributed by Yurii Karabas in bpo 42345 macOS 11 0 Big Sur and Apple Silicon Mac support As of 3 9 1 Python now fully supports building and running on macOS 11 0 Big Sur and on Apple Silicon Macs based on the ARM64 architecture A new universal build variant universal2 is now available to natively support both ARM64 and Intel 64 in one set of executables Binaries can also now be built on current versions of macOS to be deployed on a range of older macOS versions tested to 10 9 while making some newer OS functions and options conditionally available based on the operating system version in use at runtime weaklinking Contributed by Ronald Oussoren and Lawrence D Anna in bpo 41100 Notable changes in Python 3 9 2 collections abc collections abc Callable generic now flattens type parameters similar to what typing Callable currently does This means that collections abc Callable int str str will have __args__ of int str str previously this was int str str To allow this change types GenericAlias can now be subclassed and a subclass will be returned when subscripting the collections abc Callable type Code which accesses the arguments via typing get_args or __args__ need to account for this change A DeprecationWarning may be emitted for invalid forms of parameterizing collections abc Callable which may have passed silently in Python 3 9 1 This DeprecationWarning will become a TypeError in Python 3 10 Contributed by Ken Jin in bpo 42195 urllib parse Earlier Python versions allowed using both and as query parameter separators in urllib parse parse_qs and urllib parse parse_qsl Due to security concerns and to conform with newer W3C recommendations this has been changed to allow only a single separator key with as the default This change also affects cgi parse and cgi parse_multipart as they use the affected functions internally For more details please see their respective documentation Contributed by Adam Goldschmidt Senthil Kumaran and Ken Jin in bpo 42967 Notable changes in Python 3 9 3 A security fix alters the ftplib FTP behavior to not trust the IPv4 address sent from the remote server when setting up a passive data channel We reuse the ftp server IP address instead For unusual code requiring the old behavior set a trust_server_pasv_ipv4_address attribute on your FTP instance to True See gh 87451 Notable changes in Python 3 9 5 urllib parse The presence of newline or tab characters in parts of a URL allows for some forms of attacks Following the WHATWG specification that updates RFC 3986 ASCII newline n r and tab t characters are stripped from the URL by the parser in urllib parse preventing such attacks The removal characters are controlled by a new module level variable urllib parse _UNSAFE_URL_BYTES_TO_REMOVE See gh 88048 Notable security feature in 3 9 14 Converting between int and str in bases other than 2 binary 4 8 octal 16 hexadecimal or 32 such as base 10 decimal now raises a ValueError if the number of digits in string form is above a limit to avoid potential denial of service attacks due to the algorithmic complexity This is a mitigation for CVE 2020 10735 This limit can be configured or disabled by environment variable command line flag or sys APIs See the integer string conversion length limitation documentation The default limit is 4300 digits in string form Notable changes in 3 9 17 tarfile The extraction methods in tarfile and shutil unpack_archive have a new a filter argument that allows limiting tar features than may be surprising or dangerous such as creating files outside the destination directory See Extraction filters for details In Python 3 12 use without the filter argument will show a DeprecationWarning In Python 3 14 the default will switch to data Contributed by Petr Viktorin in PEP 706,en
2301,cgitb Traceback manager for CGI scripts Source code Lib cgitb py Deprecated since version 3 11 will be removed in version 3 13 The cgitb module is deprecated see PEP 594 for details The cgitb module provides a special exception handler for Python scripts Its name is a bit misleading It was originally designed to display extensive traceback information in HTML for CGI scripts It was later generalized to also display this information in plain text After this module is activated if an uncaught exception occurs a detailed formatted report will be displayed The report includes a traceback showing excerpts of the source code for each level as well as the values of the arguments and local variables to currently running functions to help you debug the problem Optionally you can save this information to a file instead of sending it to the browser To enable this feature simply add this to the top of your CGI script import cgitb cgitb enable The options to the enable function control whether the report is displayed in the browser and whether the report is logged to a file for later analysis cgitb enable display 1 logdir None context 5 format html This function causes the cgitb module to take over the interpreter s default handling for exceptions by setting the value of sys excepthook The optional argument display defaults to 1 and can be set to 0 to suppress sending the traceback to the browser If the argument logdir is present the traceback reports are written to files The value of logdir should be a directory where these files will be placed The optional argument context is the number of lines of context to display around the current line of source code in the traceback this defaults to 5 If the optional argument format is html the output is formatted as HTML Any other value forces plain text output The default value is html cgitb text info context 5 This function handles the exception described by info a 3 tuple containing the result of sys exc_info formatting its traceback as text and returning the result as a string The optional argument context is the number of lines of context to display around the current line of source code in the traceback this defaults to 5 cgitb html info context 5 This function handles the exception described by info a 3 tuple containing the result of sys exc_info formatting its traceback as HTML and returning the result as a string The optional argument context is the number of lines of context to display around the current line of source code in the traceback this defaults to 5 cgitb handler info None This function handles an exception using the default settings that is show a report in the browser but don t log to a file This can be used when you ve caught an exception and want to report it using cgitb The optional info argument should be a 3 tuple containing an exception type exception value and traceback object exactly like the tuple returned by sys exc_info If the info argument is not supplied the current exception is obtained from sys exc_info,en
2302,tracemalloc Trace memory allocations New in version 3 4 Source code Lib tracemalloc py The tracemalloc module is a debug tool to trace memory blocks allocated by Python It provides the following information Traceback where an object was allocated Statistics on allocated memory blocks per filename and per line number total size number and average size of allocated memory blocks Compute the differences between two snapshots to detect memory leaks To trace most memory blocks allocated by Python the module should be started as early as possible by setting the PYTHONTRACEMALLOC environment variable to 1 or by using X tracemalloc command line option The tracemalloc start function can be called at runtime to start tracing Python memory allocations By default a trace of an allocated memory block only stores the most recent frame 1 frame To store 25 frames at startup set the PYTHONTRACEMALLOC environment variable to 25 or use the X tracemalloc 25 command line option Examples Display the top 10 Display the 10 files allocating the most memory import tracemalloc tracemalloc start run your application snapshot tracemalloc take_snapshot top_stats snapshot statistics lineno print Top 10 for stat in top_stats 10 print stat Example of output of the Python test suite Top 10 frozen importlib _bootstrap 716 size 4855 KiB count 39328 average 126 B frozen importlib _bootstrap 284 size 521 KiB count 3199 average 167 B usr lib python3 4 collections __init__ py 368 size 244 KiB count 2315 average 108 B usr lib python3 4 unittest case py 381 size 185 KiB count 779 average 243 B usr lib python3 4 unittest case py 402 size 154 KiB count 378 average 416 B usr lib python3 4 abc py 133 size 88 7 KiB count 347 average 262 B frozen importlib _bootstrap 1446 size 70 4 KiB count 911 average 79 B frozen importlib _bootstrap 1454 size 52 0 KiB count 25 average 2131 B string 5 size 49 7 KiB count 148 average 344 B usr lib python3 4 sysconfig py 411 size 48 0 KiB count 1 average 48 0 KiB We can see that Python loaded 4855 KiB data bytecode and constants from modules and that the collections module allocated 244 KiB to build namedtuple types See Snapshot statistics for more options Compute differences Take two snapshots and display the differences import tracemalloc tracemalloc start start your application snapshot1 tracemalloc take_snapshot call the function leaking memory snapshot2 tracemalloc take_snapshot top_stats snapshot2 compare_to snapshot1 lineno print Top 10 differences for stat in top_stats 10 print stat Example of output before after running some tests of the Python test suite Top 10 differences frozen importlib _bootstrap 716 size 8173 KiB 4428 KiB count 71332 39369 average 117 B usr lib python3 4 linecache py 127 size 940 KiB 940 KiB count 8106 8106 average 119 B usr lib python3 4 unittest case py 571 size 298 KiB 298 KiB count 589 589 average 519 B frozen importlib _bootstrap 284 size 1005 KiB 166 KiB count 7423 1526 average 139 B usr lib python3 4 mimetypes py 217 size 112 KiB 112 KiB count 1334 1334 average 86 B usr lib python3 4 http server py 848 size 96 0 KiB 96 0 KiB count 1 1 average 96 0 KiB usr lib python3 4 inspect py 1465 size 83 5 KiB 83 5 KiB count 109 109 average 784 B usr lib python3 4 unittest mock py 491 size 77 7 KiB 77 7 KiB count 143 143 average 557 B usr lib python3 4 urllib parse py 476 size 71 8 KiB 71 8 KiB count 969 969 average 76 B usr lib python3 4 contextlib py 38 size 67 2 KiB 67 2 KiB count 126 126 average 546 B We can see that Python has loaded 8173 KiB of module data bytecode and constants and that this is 4428 KiB more than had been loaded before the tests when the previous snapshot was taken Similarly the linecache module has cached 940 KiB of Python source code to format tracebacks all of it since the previous snapshot If the system has little free memory snapshots can be written on disk using the Snapshot dump method to analyze the snapshot offline Then use the Snapshot load method reload the snapshot Get the traceback of a memory block Code to display the traceback of the biggest memory block import tracemal,en
2303,loc Store 25 frames tracemalloc start 25 run your application snapshot tracemalloc take_snapshot top_stats snapshot statistics traceback pick the biggest memory block stat top_stats 0 print s memory blocks 1f KiB stat count stat size 1024 for line in stat traceback format print line Example of output of the Python test suite traceback limited to 25 frames 903 memory blocks 870 1 KiB File frozen importlib _bootstrap line 716 File frozen importlib _bootstrap line 1036 File frozen importlib _bootstrap line 934 File frozen importlib _bootstrap line 1068 File frozen importlib _bootstrap line 619 File frozen importlib _bootstrap line 1581 File frozen importlib _bootstrap line 1614 File usr lib python3 4 doctest py line 101 import pdb File frozen importlib _bootstrap line 284 File frozen importlib _bootstrap line 938 File frozen importlib _bootstrap line 1068 File frozen importlib _bootstrap line 619 File frozen importlib _bootstrap line 1581 File frozen importlib _bootstrap line 1614 File usr lib python3 4 test support __init__ py line 1728 import doctest File usr lib python3 4 test test_pickletools py line 21 support run_doctest pickletools File usr lib python3 4 test regrtest py line 1276 test_runner File usr lib python3 4 test regrtest py line 976 display_failure not verbose File usr lib python3 4 test regrtest py line 761 match_tests ns match_tests File usr lib python3 4 test regrtest py line 1563 main File usr lib python3 4 test __main__ py line 3 regrtest main_in_temp_cwd File usr lib python3 4 runpy py line 73 exec code run_globals File usr lib python3 4 runpy py line 160 __main__ fname loader pkg_name We can see that the most memory was allocated in the importlib module to load data bytecode and constants from modules 870 1 KiB The traceback is where the importlib loaded data most recently on the import pdb line of the doctest module The traceback may change if a new module is loaded Pretty top Code to display the 10 lines allocating the most memory with a pretty output ignoring frozen importlib _bootstrap and unknown files import linecache import os import tracemalloc def display_top snapshot key_type lineno limit 10 snapshot snapshot filter_traces tracemalloc Filter False frozen importlib _bootstrap tracemalloc Filter False unknown top_stats snapshot statistics key_type print Top s lines limit for index stat in enumerate top_stats limit 1 frame stat traceback 0 print s s s 1f KiB index frame filename frame lineno stat size 1024 line linecache getline frame filename frame lineno strip if line print s line other top_stats limit if other size sum stat size for stat in other print s other 1f KiB len other size 1024 total sum stat size for stat in top_stats print Total allocated size 1f KiB total 1024 tracemalloc start run your application snapshot tracemalloc take_snapshot display_top snapshot Example of output of the Python test suite Top 10 lines 1 Lib base64 py 414 419 8 KiB _b85chars2 a b for a in _b85chars for b in _b85chars 2 Lib base64 py 306 419 8 KiB _a85chars2 a b for a in _a85chars for b in _a85chars 3 collections __init__ py 368 293 6 KiB exec class_definition namespace 4 Lib abc py 133 115 2 KiB cls super __new__ mcls name bases namespace 5 unittest case py 574 103 1 KiB testMethod 6 Lib linecache py 127 95 4 KiB lines fp readlines 7 urllib parse py 476 71 8 KiB for a in _hexdig for b in _hexdig 8 string 5 62 0 KiB 9 Lib _weakrefset py 37 60 0 KiB self data set 10 Lib base64 py 142 59 8 KiB _b32tab2 a b for a in _b32tab for b in _b32tab 6220 other 3602 8 KiB Total allocated size 5303 1 KiB See Snapshot statistics for more options Record the current and peak size of all traced memory blocks The following code computes two sums like 0 1 2 inefficiently by creating a list of those numbers This list consumes a lot of memory temporarily We can use get_traced_memory and reset_peak to observe the small memory usage after the sum is computed as well as the peak memory usage during the computations import tracemalloc tracemalloc start Example code compute a sum with a large temporary list large_sum sum list range 100,en
2304,000 first_size first_peak tracemalloc get_traced_memory tracemalloc reset_peak Example code compute a sum with a small temporary list small_sum sum list range 1000 second_size second_peak tracemalloc get_traced_memory print f first_size first_peak print f second_size second_peak Output first_size 664 first_peak 3592984 second_size 804 second_peak 29704 Using reset_peak ensured we could accurately record the peak during the computation of small_sum even though it is much smaller than the overall peak size of memory blocks since the start call Without the call to reset_peak second_peak would still be the peak from the computation large_sum that is equal to first_peak In this case both peaks are much higher than the final memory usage and which suggests we could optimise by removing the unnecessary call to list and writing sum range API Functions tracemalloc clear_traces Clear traces of memory blocks allocated by Python See also stop tracemalloc get_object_traceback obj Get the traceback where the Python object obj was allocated Return a Traceback instance or None if the tracemalloc module is not tracing memory allocations or did not trace the allocation of the object See also gc get_referrers and sys getsizeof functions tracemalloc get_traceback_limit Get the maximum number of frames stored in the traceback of a trace The tracemalloc module must be tracing memory allocations to get the limit otherwise an exception is raised The limit is set by the start function tracemalloc get_traced_memory Get the current size and peak size of memory blocks traced by the tracemalloc module as a tuple current int peak int tracemalloc reset_peak Set the peak size of memory blocks traced by the tracemalloc module to the current size Do nothing if the tracemalloc module is not tracing memory allocations This function only modifies the recorded peak size and does not modify or clear any traces unlike clear_traces Snapshots taken with take_snapshot before a call to reset_peak can be meaningfully compared to snapshots taken after the call See also get_traced_memory New in version 3 9 tracemalloc get_tracemalloc_memory Get the memory usage in bytes of the tracemalloc module used to store traces of memory blocks Return an int tracemalloc is_tracing True if the tracemalloc module is tracing Python memory allocations False otherwise See also start and stop functions tracemalloc start nframe int 1 Start tracing Python memory allocations install hooks on Python memory allocators Collected tracebacks of traces will be limited to nframe frames By default a trace of a memory block only stores the most recent frame the limit is 1 nframe must be greater or equal to 1 You can still read the original number of total frames that composed the traceback by looking at the Traceback total_nframe attribute Storing more than 1 frame is only useful to compute statistics grouped by traceback or to compute cumulative statistics see the Snapshot compare_to and Snapshot statistics methods Storing more frames increases the memory and CPU overhead of the tracemalloc module Use the get_tracemalloc_memory function to measure how much memory is used by the tracemalloc module The PYTHONTRACEMALLOC environment variable PYTHONTRACEMALLOC NFRAME and the X tracemalloc NFRAME command line option can be used to start tracing at startup See also stop is_tracing and get_traceback_limit functions tracemalloc stop Stop tracing Python memory allocations uninstall hooks on Python memory allocators Also clears all previously collected traces of memory blocks allocated by Python Call take_snapshot function to take a snapshot of traces before clearing them See also start is_tracing and clear_traces functions tracemalloc take_snapshot Take a snapshot of traces of memory blocks allocated by Python Return a new Snapshot instance The snapshot does not include memory blocks allocated before the tracemalloc module started to trace memory allocations Tracebacks of traces are limited to get_traceback_limit frames Use the nframe parameter of the start function to store more frames The tracemalloc m,en
2305,odule must be tracing memory allocations to take a snapshot see the start function See also the get_object_traceback function DomainFilter class tracemalloc DomainFilter inclusive bool domain int Filter traces of memory blocks by their address space domain New in version 3 6 inclusive If inclusive is True include match memory blocks allocated in the address space domain If inclusive is False exclude match memory blocks not allocated in the address space domain domain Address space of a memory block int Read only property Filter class tracemalloc Filter inclusive bool filename_pattern str lineno int None all_frames bool False domain int None Filter on traces of memory blocks See the fnmatch fnmatch function for the syntax of filename_pattern The pyc file extension is replaced with py Examples Filter True subprocess __file__ only includes traces of the subprocess module Filter False tracemalloc __file__ excludes traces of the tracemalloc module Filter False unknown excludes empty tracebacks Changed in version 3 5 The pyo file extension is no longer replaced with py Changed in version 3 6 Added the domain attribute domain Address space of a memory block int or None tracemalloc uses the domain 0 to trace memory allocations made by Python C extensions can use other domains to trace other resources inclusive If inclusive is True include only match memory blocks allocated in a file with a name matching filename_pattern at line number lineno If inclusive is False exclude ignore memory blocks allocated in a file with a name matching filename_pattern at line number lineno lineno Line number int of the filter If lineno is None the filter matches any line number filename_pattern Filename pattern of the filter str Read only property all_frames If all_frames is True all frames of the traceback are checked If all_frames is False only the most recent frame is checked This attribute has no effect if the traceback limit is 1 See the get_traceback_limit function and Snapshot traceback_limit attribute Frame class tracemalloc Frame Frame of a traceback The Traceback class is a sequence of Frame instances filename Filename str lineno Line number int Snapshot class tracemalloc Snapshot Snapshot of traces of memory blocks allocated by Python The take_snapshot function creates a snapshot instance compare_to old_snapshot Snapshot key_type str cumulative bool False Compute the differences with an old snapshot Get statistics as a sorted list of StatisticDiff instances grouped by key_type See the Snapshot statistics method for key_type and cumulative parameters The result is sorted from the biggest to the smallest by absolute value of StatisticDiff size_diff StatisticDiff size absolute value of StatisticDiff count_diff Statistic count and then by StatisticDiff traceback dump filename Write the snapshot into a file Use load to reload the snapshot filter_traces filters Create a new Snapshot instance with a filtered traces sequence filters is a list of DomainFilter and Filter instances If filters is an empty list return a new Snapshot instance with a copy of the traces All inclusive filters are applied at once a trace is ignored if no inclusive filters match it A trace is ignored if at least one exclusive filter matches it Changed in version 3 6 DomainFilter instances are now also accepted in filters classmethod load filename Load a snapshot from a file See also dump statistics key_type str cumulative bool False Get statistics as a sorted list of Statistic instances grouped by key_type key_type description filename filename lineno filename and line number traceback traceback If cumulative is True cumulate size and count of memory blocks of all frames of the traceback of a trace not only the most recent frame The cumulative mode can only be used with key_type equals to filename and lineno The result is sorted from the biggest to the smallest by Statistic size Statistic count and then by Statistic traceback traceback_limit Maximum number of frames stored in the traceback of traces result of the get_traceback_limit when the snapshot was taken traces Trace,en
2306,s of all memory blocks allocated by Python sequence of Trace instances The sequence has an undefined order Use the Snapshot statistics method to get a sorted list of statistics Statistic class tracemalloc Statistic Statistic on memory allocations Snapshot statistics returns a list of Statistic instances See also the StatisticDiff class count Number of memory blocks int size Total size of memory blocks in bytes int traceback Traceback where the memory block was allocated Traceback instance StatisticDiff class tracemalloc StatisticDiff Statistic difference on memory allocations between an old and a new Snapshot instance Snapshot compare_to returns a list of StatisticDiff instances See also the Statistic class count Number of memory blocks in the new snapshot int 0 if the memory blocks have been released in the new snapshot count_diff Difference of number of memory blocks between the old and the new snapshots int 0 if the memory blocks have been allocated in the new snapshot size Total size of memory blocks in bytes in the new snapshot int 0 if the memory blocks have been released in the new snapshot size_diff Difference of total size of memory blocks in bytes between the old and the new snapshots int 0 if the memory blocks have been allocated in the new snapshot traceback Traceback where the memory blocks were allocated Traceback instance Trace class tracemalloc Trace Trace of a memory block The Snapshot traces attribute is a sequence of Trace instances Changed in version 3 6 Added the domain attribute domain Address space of a memory block int Read only property tracemalloc uses the domain 0 to trace memory allocations made by Python C extensions can use other domains to trace other resources size Size of the memory block in bytes int traceback Traceback where the memory block was allocated Traceback instance Traceback class tracemalloc Traceback Sequence of Frame instances sorted from the oldest frame to the most recent frame A traceback contains at least 1 frame If the tracemalloc module failed to get a frame the filename unknown at line number 0 is used When a snapshot is taken tracebacks of traces are limited to get_traceback_limit frames See the take_snapshot function The original number of frames of the traceback is stored in the Traceback total_nframe attribute That allows to know if a traceback has been truncated by the traceback limit The Trace traceback attribute is an instance of Traceback instance Changed in version 3 7 Frames are now sorted from the oldest to the most recent instead of most recent to oldest total_nframe Total number of frames that composed the traceback before truncation This attribute can be set to None if the information is not available Changed in version 3 9 The Traceback total_nframe attribute was added format limit None most_recent_first False Format the traceback as a list of lines Use the linecache module to retrieve lines from the source code If limit is set format the limit most recent frames if limit is positive Otherwise format the abs limit oldest frames If most_recent_first is True the order of the formatted frames is reversed returning the most recent frame first instead of last Similar to the traceback format_tb function except that format does not include newlines Example print Traceback most recent call first for line in traceback print line Output Traceback most recent call first File test py line 9 obj Object File test py line 12 tb tracemalloc get_object_traceback f,en
2307,termios POSIX style tty control This module provides an interface to the POSIX calls for tty I O control For a complete description of these calls see termios 3 Unix manual page It is only available for those Unix versions that support POSIX termios style tty I O control configured during installation Availability Unix All functions in this module take a file descriptor fd as their first argument This can be an integer file descriptor such as returned by sys stdin fileno or a file object such as sys stdin itself This module also defines all the constants needed to work with the functions provided here these have the same name as their counterparts in C Please refer to your system documentation for more information on using these terminal control interfaces The module defines the following functions termios tcgetattr fd Return a list containing the tty attributes for file descriptor fd as follows iflag oflag cflag lflag ispeed ospeed cc where cc is a list of the tty special characters each a string of length 1 except the items with indices VMIN and VTIME which are integers when these fields are defined The interpretation of the flags and the speeds as well as the indexing in the cc array must be done using the symbolic constants defined in the termios module termios tcsetattr fd when attributes Set the tty attributes for file descriptor fd from the attributes which is a list like the one returned by tcgetattr The when argument determines when the attributes are changed termios TCSANOW Change attributes immediately termios TCSADRAIN Change attributes after transmitting all queued output termios TCSAFLUSH Change attributes after transmitting all queued output and discarding all queued input termios tcsendbreak fd duration Send a break on file descriptor fd A zero duration sends a break for 0 25 0 5 seconds a nonzero duration has a system dependent meaning termios tcdrain fd Wait until all output written to file descriptor fd has been transmitted termios tcflush fd queue Discard queued data on file descriptor fd The queue selector specifies which queue TCIFLUSH for the input queue TCOFLUSH for the output queue or TCIOFLUSH for both queues termios tcflow fd action Suspend or resume input or output on file descriptor fd The action argument can be TCOOFF to suspend output TCOON to restart output TCIOFF to suspend input or TCION to restart input termios tcgetwinsize fd Return a tuple ws_row ws_col containing the tty window size for file descriptor fd Requires termios TIOCGWINSZ or termios TIOCGSIZE New in version 3 11 termios tcsetwinsize fd winsize Set the tty window size for file descriptor fd from winsize which is a two item tuple ws_row ws_col like the one returned by tcgetwinsize Requires at least one of the pairs termios TIOCGWINSZ termios TIOCSWINSZ termios TIOCGSIZE termios TIOCSSIZE to be defined New in version 3 11 See also Module tty Convenience functions for common terminal control operations Example Here s a function that prompts for a password with echoing turned off Note the technique using a separate tcgetattr call and a try finally statement to ensure that the old tty attributes are restored exactly no matter what happens def getpass prompt Password import termios sys fd sys stdin fileno old termios tcgetattr fd new termios tcgetattr fd new 3 new 3 termios ECHO lflags try termios tcsetattr fd termios TCSADRAIN new passwd input prompt finally termios tcsetattr fd termios TCSADRAIN old return passwd,en
2308,xml dom minidom Minimal DOM implementation Source code Lib xml dom minidom py xml dom minidom is a minimal implementation of the Document Object Model interface with an API similar to that in other languages It is intended to be simpler than the full DOM and also significantly smaller Users who are not already proficient with the DOM should consider using the xml etree ElementTree module for their XML processing instead Warning The xml dom minidom module is not secure against maliciously constructed data If you need to parse untrusted or unauthenticated data see XML vulnerabilities DOM applications typically start by parsing some XML into a DOM With xml dom minidom this is done through the parse functions from xml dom minidom import parse parseString dom1 parse c temp mydata xml parse an XML file by name datasource open c temp mydata xml dom2 parse datasource parse an open file dom3 parseString myxml Some data empty some more data myxml The parse function can take either a filename or an open file object xml dom minidom parse filename_or_file parser None bufsize None Return a Document from the given input filename_or_file may be either a file name or a file like object parser if given must be a SAX2 parser object This function will change the document handler of the parser and activate namespace support other parser configuration like setting an entity resolver must have been done in advance If you have XML in a string you can use the parseString function instead xml dom minidom parseString string parser None Return a Document that represents the string This method creates an io StringIO object for the string and passes that on to parse Both functions return a Document object representing the content of the document What the parse and parseString functions do is connect an XML parser with a DOM builder that can accept parse events from any SAX parser and convert them into a DOM tree The name of the functions are perhaps misleading but are easy to grasp when learning the interfaces The parsing of the document will be completed before these functions return it s simply that these functions do not provide a parser implementation themselves You can also create a Document by calling a method on a DOM Implementation object You can get this object either by calling the getDOMImplementation function in the xml dom package or the xml dom minidom module Once you have a Document you can add child nodes to it to populate the DOM from xml dom minidom import getDOMImplementation impl getDOMImplementation newdoc impl createDocument None some_tag None top_element newdoc documentElement text newdoc createTextNode Some textual content top_element appendChild text Once you have a DOM document object you can access the parts of your XML document through its properties and methods These properties are defined in the DOM specification The main property of the document object is the documentElement property It gives you the main element in the XML document the one that holds all others Here is an example program dom3 parseString myxml Some data myxml assert dom3 documentElement tagName myxml When you are finished with a DOM tree you may optionally call the unlink method to encourage early cleanup of the now unneeded objects unlink is an xml dom minidom specific extension to the DOM API that renders the node and its descendants essentially useless Otherwise Python s garbage collector will eventually take care of the objects in the tree See also Document Object Model DOM Level 1 Specification The W3C recommendation for the DOM supported by xml dom minidom DOM Objects The definition of the DOM API for Python is given as part of the xml dom module documentation This section lists the differences between the API and xml dom minidom Node unlink Break internal references within the DOM so that it will be garbage collected on versions of Python without cyclic GC Even when cyclic GC is available using this can make large amounts of memory available sooner so calling this on DOM objects as soon as they are no longer needed is good practice This only nee,en
2309,ds to be called on the Document object but may be called on child nodes to discard children of that node You can avoid calling this method explicitly by using the with statement The following code will automatically unlink dom when the with block is exited with xml dom minidom parse datasource as dom Work with dom Node writexml writer indent addindent newl encoding None standalone None Write XML to the writer object The writer receives texts but not bytes as input it should have a write method which matches that of the file object interface The indent parameter is the indentation of the current node The addindent parameter is the incremental indentation to use for subnodes of the current one The newl parameter specifies the string to use to terminate newlines For the Document node an additional keyword argument encoding can be used to specify the encoding field of the XML header Similarly explicitly stating the standalone argument causes the standalone document declarations to be added to the prologue of the XML document If the value is set to True standalone yes is added otherwise it is set to no Not stating the argument will omit the declaration from the document Changed in version 3 8 The writexml method now preserves the attribute order specified by the user Changed in version 3 9 The standalone parameter was added Node toxml encoding None standalone None Return a string or byte string containing the XML represented by the DOM node With an explicit encoding 1 argument the result is a byte string in the specified encoding With no encoding argument the result is a Unicode string and the XML declaration in the resulting string does not specify an encoding Encoding this string in an encoding other than UTF 8 is likely incorrect since UTF 8 is the default encoding of XML The standalone argument behaves exactly as in writexml Changed in version 3 8 The toxml method now preserves the attribute order specified by the user Changed in version 3 9 The standalone parameter was added Node toprettyxml indent t newl n encoding None standalone None Return a pretty printed version of the document indent specifies the indentation string and defaults to a tabulator newl specifies the string emitted at the end of each line and defaults to n The encoding argument behaves like the corresponding argument of toxml The standalone argument behaves exactly as in writexml Changed in version 3 8 The toprettyxml method now preserves the attribute order specified by the user Changed in version 3 9 The standalone parameter was added DOM Example This example program is a fairly realistic example of a simple program In this particular case we do not take much advantage of the flexibility of the DOM import xml dom minidom document slideshow title Demo slideshow title slide title Slide title title point This is a demo point point Of a program for processing slides point slide slide title Another demo slide title point It is important point point To have more than point point one slide point slide slideshow dom xml dom minidom parseString document def getText nodelist rc for node in nodelist if node nodeType node TEXT_NODE rc append node data return join rc def handleSlideshow slideshow print html handleSlideshowTitle slideshow getElementsByTagName title 0 slides slideshow getElementsByTagName slide handleToc slides handleSlides slides print html def handleSlides slides for slide in slides handleSlide slide def handleSlide slide handleSlideTitle slide getElementsByTagName title 0 handlePoints slide getElementsByTagName point def handleSlideshowTitle title print f title getText title childNodes title def handleSlideTitle title print f h2 getText title childNodes h2 def handlePoints points print ul for point in points handlePoint point print ul def handlePoint point print f li getText point childNodes li def handleToc slides for slide in slides title slide getElementsByTagName title 0 print f p getText title childNodes p handleSlideshow dom minidom and the DOM standard The xml dom minidom module is essentially a DOM 1 0 compatible DOM with some DOM 2 feat,en
2310,ures primarily namespace features Usage of the DOM interface in Python is straight forward The following mapping rules apply Interfaces are accessed through instance objects Applications should not instantiate the classes themselves they should use the creator functions available on the Document object Derived interfaces support all operations and attributes from the base interfaces plus any new operations Operations are used as methods Since the DOM uses only in parameters the arguments are passed in normal order from left to right There are no optional arguments void operations return None IDL attributes map to instance attributes For compatibility with the OMG IDL language mapping for Python an attribute foo can also be accessed through accessor methods _get_foo and _set_foo readonly attributes must not be changed this is not enforced at runtime The types short int unsigned int unsigned long long and boolean all map to Python integer objects The type DOMString maps to Python strings xml dom minidom supports either bytes or strings but will normally produce strings Values of type DOMString may also be None where allowed to have the IDL null value by the DOM specification from the W3C const declarations map to variables in their respective scope e g xml dom minidom Node PROCESSING_INSTRUCTION_NODE they must not be changed DOMException is currently not supported in xml dom minidom Instead xml dom minidom uses standard Python exceptions such as TypeError and AttributeError NodeList objects are implemented using Python s built in list type These objects provide the interface defined in the DOM specification but with earlier versions of Python they do not support the official API They are however much more Pythonic than the interface defined in the W3C recommendations The following interfaces have no implementation in xml dom minidom DOMTimeStamp EntityReference Most of these reflect information in the XML document that is not of general utility to most DOM users Footnotes 1 The encoding name included in the XML output should conform to the appropriate standards For example UTF 8 is valid but UTF8 is not valid in an XML document s declaration even though Python accepts it as an encoding name See https www w3 org TR 2006 REC xml11 20060816 NT EncodingDecl and https www iana org assignments character sets character sets xhtml,en
2311,Internationalization The modules described in this chapter help you write software that is independent of language and locale by providing mechanisms for selecting a language to be used in program messages or by tailoring output to match local conventions The list of modules described in this chapter is gettext Multilingual internationalization services GNU gettext API Class based API The NullTranslations class The GNUTranslations class Solaris message catalog support The Catalog constructor Internationalizing your programs and modules Localizing your module Localizing your application Changing languages on the fly Deferred translations Acknowledgements locale Internationalization services Background details hints tips and caveats For extension writers and programs that embed Python Access to message catalogs,en
2312,What s New In Python 3 2 Author Raymond Hettinger This article explains the new features in Python 3 2 as compared to 3 1 Python 3 2 was released on February 20 2011 It focuses on a few highlights and gives a few examples For full details see the Misc NEWS file See also PEP 392 Python 3 2 Release Schedule PEP 384 Defining a Stable ABI In the past extension modules built for one Python version were often not usable with other Python versions Particularly on Windows every feature release of Python required rebuilding all extension modules that one wanted to use This requirement was the result of the free access to Python interpreter internals that extension modules could use With Python 3 2 an alternative approach becomes available extension modules which restrict themselves to a limited API by defining Py_LIMITED_API cannot use many of the internals but are constrained to a set of API functions that are promised to be stable for several releases As a consequence extension modules built for 3 2 in that mode will also work with 3 3 3 4 and so on Extension modules that make use of details of memory structures can still be built but will need to be recompiled for every feature release See also PEP 384 Defining a Stable ABI PEP written by Martin von Löwis PEP 389 Argparse Command Line Parsing Module A new module for command line parsing argparse was introduced to overcome the limitations of optparse which did not provide support for positional arguments not just options subcommands required options and other common patterns of specifying and validating options This module has already had widespread success in the community as a third party module Being more fully featured than its predecessor the argparse module is now the preferred module for command line processing The older module is still being kept available because of the substantial amount of legacy code that depends on it Here s an annotated example parser showing features like limiting results to a set of choices specifying a metavar in the help screen validating that one or more positional arguments is present and making a required option import argparse parser argparse ArgumentParser description Manage servers main description for help epilog Tested on Solaris and Linux displayed after help parser add_argument action argument name choices deploy start stop three allowed values help action on each target help msg parser add_argument targets metavar HOSTNAME var name used in help msg nargs require one or more targets help url for target machines help msg explanation parser add_argument u user u or user option required True make it a required argument help login as user Example of calling the parser on a command string cmd deploy sneezy example com sleepy example com u skycaptain result parser parse_args cmd split result action deploy result targets sneezy example com sleepy example com result user skycaptain Example of the parser s automatically generated help parser parse_args h split usage manage_cloud py h u USER deploy start stop HOSTNAME HOSTNAME Manage servers positional arguments deploy start stop action on each target HOSTNAME url for target machines optional arguments h help show this help message and exit u USER user USER login as user Tested on Solaris and Linux An especially nice argparse feature is the ability to define subparsers each with their own argument patterns and help displays import argparse parser argparse ArgumentParser prog HELM subparsers parser add_subparsers parser_l subparsers add_parser launch help Launch Control first subgroup parser_l add_argument m missiles action store_true parser_l add_argument t torpedos action store_true parser_m subparsers add_parser move help Move Vessel second subgroup aliases steer turn equivalent names parser_m add_argument c course type int required True parser_m add_argument s speed type int default 0 helm py help top level help launch and move helm py launch help help for launch options helm py launch missiles set missiles True and torpedos False helm py steer course 180 speed 5 set movement parameters See,en
2313, also PEP 389 New Command Line Parsing Module PEP written by Steven Bethard Upgrading optparse code for details on the differences from optparse PEP 391 Dictionary Based Configuration for Logging The logging module provided two kinds of configuration one style with function calls for each option or another style driven by an external file saved in a configparser format Those options did not provide the flexibility to create configurations from JSON or YAML files nor did they support incremental configuration which is needed for specifying logger options from a command line To support a more flexible style the module now offers logging config dictConfig for specifying logging configuration with plain Python dictionaries The configuration options include formatters handlers filters and loggers Here s a working example of a configuration dictionary version 1 formatters brief format levelname 8s name 15s message s full format asctime s name 15s levelname 8s message s handlers console class logging StreamHandler formatter brief level INFO stream ext sys stdout console_priority class logging StreamHandler formatter full level ERROR stream ext sys stderr root level DEBUG handlers console console_priority If that dictionary is stored in a file called conf json it can be loaded and called with code like this import json logging config with open conf json as f conf json load f logging config dictConfig conf logging info Transaction completed normally INFO root Transaction completed normally logging critical Abnormal termination 2011 02 17 11 14 36 694 root CRITICAL Abnormal termination See also PEP 391 Dictionary Based Configuration for Logging PEP written by Vinay Sajip PEP 3148 The concurrent futures module Code for creating and managing concurrency is being collected in a new top level namespace concurrent Its first member is a futures package which provides a uniform high level interface for managing threads and processes The design for concurrent futures was inspired by the java util concurrent package In that model a running call and its result are represented by a Future object that abstracts features common to threads processes and remote procedure calls That object supports status checks running or done timeouts cancellations adding callbacks and access to results or exceptions The primary offering of the new module is a pair of executor classes for launching and managing calls The goal of the executors is to make it easier to use existing tools for making parallel calls They save the effort needed to setup a pool of resources launch the calls create a results queue add time out handling and limit the total number of threads processes or remote procedure calls Ideally each application should share a single executor across multiple components so that process and thread limits can be centrally managed This solves the design challenge that arises when each component has its own competing strategy for resource management Both classes share a common interface with three methods submit for scheduling a callable and returning a Future object map for scheduling many asynchronous calls at a time and shutdown for freeing resources The class is a context manager and can be used in a with statement to assure that resources are automatically released when currently pending futures are done executing A simple of example of ThreadPoolExecutor is a launch of four parallel threads for copying files import concurrent futures shutil with concurrent futures ThreadPoolExecutor max_workers 4 as e e submit shutil copy src1 txt dest1 txt e submit shutil copy src2 txt dest2 txt e submit shutil copy src3 txt dest3 txt e submit shutil copy src3 txt dest4 txt See also PEP 3148 Futures Execute Computations Asynchronously PEP written by Brian Quinlan Code for Threaded Parallel URL reads an example using threads to fetch multiple web pages in parallel Code for computing prime numbers in parallel an example demonstrating ProcessPoolExecutor PEP 3147 PYC Repository Directories Python s scheme for caching bytecode in pyc files did not work well in environ,en
2314,ments with multiple Python interpreters If one interpreter encountered a cached file created by another interpreter it would recompile the source and overwrite the cached file thus losing the benefits of caching The issue of pyc fights has become more pronounced as it has become commonplace for Linux distributions to ship with multiple versions of Python These conflicts also arise with CPython alternatives such as Unladen Swallow To solve this problem Python s import machinery has been extended to use distinct filenames for each interpreter Instead of Python 3 2 and Python 3 3 and Unladen Swallow each competing for a file called mymodule pyc they will now look for mymodule cpython 32 pyc mymodule cpython 33 pyc and mymodule unladen10 pyc And to prevent all of these new files from cluttering source directories the pyc files are now collected in a __pycache__ directory stored under the package directory Aside from the filenames and target directories the new scheme has a few aspects that are visible to the programmer Imported modules now have a __cached__ attribute which stores the name of the actual file that was imported import collections collections __cached__ c py32 lib __pycache__ collections cpython 32 pyc The tag that is unique to each interpreter is accessible from the imp module import imp imp get_tag cpython 32 Scripts that try to deduce source filename from the imported file now need to be smarter It is no longer sufficient to simply strip the c from a pyc filename Instead use the new functions in the imp module imp source_from_cache c py32 lib __pycache__ collections cpython 32 pyc c py32 lib collections py imp cache_from_source c py32 lib collections py c py32 lib __pycache__ collections cpython 32 pyc The py_compile and compileall modules have been updated to reflect the new naming convention and target directory The command line invocation of compileall has new options i for specifying a list of files and directories to compile and b which causes bytecode files to be written to their legacy location rather than __pycache__ The importlib abc module has been updated with new abstract base classes for loading bytecode files The obsolete ABCs PyLoader and PyPycLoader have been deprecated instructions on how to stay Python 3 1 compatible are included with the documentation See also PEP 3147 PYC Repository Directories PEP written by Barry Warsaw PEP 3149 ABI Version Tagged so Files The PYC repository directory allows multiple bytecode cache files to be co located This PEP implements a similar mechanism for shared object files by giving them a common directory and distinct names for each version The common directory is pyshared and the file names are made distinct by identifying the Python implementation such as CPython PyPy Jython etc the major and minor version numbers and optional build flags such as d for debug m for pymalloc u for wide unicode For an arbitrary package foo you may see these files when the distribution package is installed usr share pyshared foo cpython 32m so usr share pyshared foo cpython 33md so In Python itself the tags are accessible from functions in the sysconfig module import sysconfig sysconfig get_config_var SOABI find the version tag cpython 32mu sysconfig get_config_var EXT_SUFFIX find the full filename extension cpython 32mu so See also PEP 3149 ABI Version Tagged so Files PEP written by Barry Warsaw PEP 3333 Python Web Server Gateway Interface v1 0 1 This informational PEP clarifies how bytes text issues are to be handled by the WSGI protocol The challenge is that string handling in Python 3 is most conveniently handled with the str type even though the HTTP protocol is itself bytes oriented The PEP differentiates so called native strings that are used for request response headers and metadata versus byte strings which are used for the bodies of requests and responses The native strings are always of type str but are restricted to code points between U 0000 through U 00FF which are translatable to bytes using Latin 1 encoding These strings are used for the keys and values in the e,en
2315,nvironment dictionary and for response headers and statuses in the start_response function They must follow RFC 2616 with respect to encoding That is they must either be ISO 8859 1 characters or use RFC 2047 MIME encoding For developers porting WSGI applications from Python 2 here are the salient points If the app already used strings for headers in Python 2 no change is needed If instead the app encoded output headers or decoded input headers then the headers will need to be re encoded to Latin 1 For example an output header encoded in utf 8 was using h encode utf 8 now needs to convert from bytes to native strings using h encode utf 8 decode latin 1 Values yielded by an application or sent using the write method must be byte strings The start_response function and environ must use native strings The two cannot be mixed For server implementers writing CGI to WSGI pathways or other CGI style protocols the users must to be able access the environment using native strings even though the underlying platform may have a different convention To bridge this gap the wsgiref module has a new function wsgiref handlers read_environ for transcoding CGI variables from os environ into native strings and returning a new dictionary See also PEP 3333 Python Web Server Gateway Interface v1 0 1 PEP written by Phillip Eby Other Language Changes Some smaller changes made to the core Python language are String formatting for format and str format gained new capabilities for the format character Previously for integers in binary octal or hexadecimal it caused the output to be prefixed with 0b 0o or 0x respectively Now it can also handle floats complex and Decimal causing the output to always have a decimal point even when no digits follow it format 20 o 0o24 format 12 34 5 0f 12 Suggested by Mark Dickinson and implemented by Eric Smith in bpo 7094 There is also a new str format_map method that extends the capabilities of the existing str format method by accepting arbitrary mapping objects This new method makes it possible to use string formatting with any of Python s many dictionary like objects such as defaultdict Shelf ConfigParser or dbm It is also useful with custom dict subclasses that normalize keys before look up or that supply a __missing__ method for unknown keys import shelve d shelve open tmp shl The project_name status is status as of date format_map d The testing project status is green as of February 15 2011 class LowerCasedDict dict def __getitem__ self key return dict __getitem__ self key lower lcd LowerCasedDict part widgets quantity 10 There are QUANTITY Part in stock format_map lcd There are 10 widgets in stock class PlaceholderDict dict def __missing__ self key return format key Hello name welcome to location format_map PlaceholderDict Hello name welcome to location Suggested by Raymond Hettinger and implemented by Eric Smith in bpo 6081 The interpreter can now be started with a quiet option q to prevent the copyright and version information from being displayed in the interactive mode The option can be introspected using the sys flags attribute python q sys flags sys flags debug 0 division_warning 0 inspect 0 interactive 0 optimize 0 dont_write_bytecode 0 no_user_site 0 no_site 0 ignore_environment 0 verbose 0 bytes_warning 0 quiet 1 Contributed by Marcin Wojdyr in bpo 1772833 The hasattr function works by calling getattr and detecting whether an exception is raised This technique allows it to detect methods created dynamically by __getattr__ or __getattribute__ which would otherwise be absent from the class dictionary Formerly hasattr would catch any exception possibly masking genuine errors Now hasattr has been tightened to only catch AttributeError and let other exceptions pass through class A property def f self return 1 0 a A hasattr a f Traceback most recent call last ZeroDivisionError integer division or modulo by zero Discovered by Yury Selivanov and fixed by Benjamin Peterson bpo 9666 The str of a float or complex number is now the same as its repr Previously the str form was shorter but that just caused confusi,en
2316,on and is no longer needed now that the shortest possible repr is displayed by default import math repr math pi 3 141592653589793 str math pi 3 141592653589793 Proposed and implemented by Mark Dickinson bpo 9337 memoryview objects now have a release method and they also now support the context management protocol This allows timely release of any resources that were acquired when requesting a buffer from the original object with memoryview b abcdefgh as v print v tolist 97 98 99 100 101 102 103 104 Added by Antoine Pitrou bpo 9757 Previously it was illegal to delete a name from the local namespace if it occurs as a free variable in a nested block def outer x def inner return x inner del x This is now allowed Remember that the target of an except clause is cleared so this code which used to work with Python 2 6 raised a SyntaxError with Python 3 1 and now works again def f def print_error print e try something except Exception as e print_error implicit del e here See bpo 4617 Struct sequence types are now subclasses of tuple This means that C structures like those returned by os stat time gmtime and sys version_info now work like a named tuple and now work with functions and methods that expect a tuple as an argument This is a big step forward in making the C structures as flexible as their pure Python counterparts import sys isinstance sys version_info tuple True Version d d d s d sys version_info Version 3 2 0 final 0 Suggested by Arfrever Frehtes Taifersar Arahesis and implemented by Benjamin Peterson in bpo 8413 Warnings are now easier to control using the PYTHONWARNINGS environment variable as an alternative to using W at the command line export PYTHONWARNINGS ignore RuntimeWarning once UnicodeWarning Suggested by Barry Warsaw and implemented by Philip Jenvey in bpo 7301 A new warning category ResourceWarning has been added It is emitted when potential issues with resource consumption or cleanup are detected It is silenced by default in normal release builds but can be enabled through the means provided by the warnings module or on the command line A ResourceWarning is issued at interpreter shutdown if the gc garbage list isn t empty and if gc DEBUG_UNCOLLECTABLE is set all uncollectable objects are printed This is meant to make the programmer aware that their code contains object finalization issues A ResourceWarning is also issued when a file object is destroyed without having been explicitly closed While the deallocator for such object ensures it closes the underlying operating system resource usually a file descriptor the delay in deallocating the object could produce various issues especially under Windows Here is an example of enabling the warning from the command line python q Wdefault f open foo wb del f __main__ 1 ResourceWarning unclosed file _io BufferedWriter name foo Added by Antoine Pitrou and Georg Brandl in bpo 10093 and bpo 477863 range objects now support index and count methods This is part of an effort to make more objects fully implement the collections Sequence abstract base class As a result the language will have a more uniform API In addition range objects now support slicing and negative indices even with values larger than sys maxsize This makes range more interoperable with lists range 0 100 2 count 10 1 range 0 100 2 index 10 5 range 0 100 2 5 10 range 0 100 2 0 5 range 0 10 2 Contributed by Daniel Stutzbach in bpo 9213 by Alexander Belopolsky in bpo 2690 and by Nick Coghlan in bpo 10889 The callable builtin function from Py2 x was resurrected It provides a concise readable alternative to using an abstract base class in an expression like isinstance x collections Callable callable max True callable 20 False See bpo 10518 Python s import mechanism can now load modules installed in directories with non ASCII characters in the path name This solved an aggravating problem with home directories for users with non ASCII characters in their usernames Required extensive work by Victor Stinner in bpo 9425 New Improved and Deprecated Modules Python s standard library has undergone significant maint,en
2317,enance efforts and quality improvements The biggest news for Python 3 2 is that the email package mailbox module and nntplib modules now work correctly with the bytes text model in Python 3 For the first time there is correct handling of messages with mixed encodings Throughout the standard library there has been more careful attention to encodings and text versus bytes issues In particular interactions with the operating system are now better able to exchange non ASCII data using the Windows MBCS encoding locale aware encodings or UTF 8 Another significant win is the addition of substantially better support for SSL connections and security certificates In addition more classes now implement a context manager to support convenient and reliable resource clean up using a with statement email The usability of the email package in Python 3 has been mostly fixed by the extensive efforts of R David Murray The problem was that emails are typically read and stored in the form of bytes rather than str text and they may contain multiple encodings within a single email So the email package had to be extended to parse and generate email messages in bytes format New functions message_from_bytes and message_from_binary_file and new classes BytesFeedParser and BytesParser allow binary message data to be parsed into model objects Given bytes input to the model get_payload will by default decode a message body that has a Content Transfer Encoding of 8bit using the charset specified in the MIME headers and return the resulting string Given bytes input to the model Generator will convert message bodies that have a Content Transfer Encoding of 8bit to instead have a 7bit Content Transfer Encoding Headers with unencoded non ASCII bytes are deemed to be RFC 2047 encoded using the unknown 8bit character set A new class BytesGenerator produces bytes as output preserving any unchanged non ASCII data that was present in the input used to build the model including message bodies with a Content Transfer Encoding of 8bit The smtplib SMTP class now accepts a byte string for the msg argument to the sendmail method and a new method send_message accepts a Message object and can optionally obtain the from_addr and to_addrs addresses directly from the object Proposed and implemented by R David Murray bpo 4661 and bpo 10321 elementtree The xml etree ElementTree package and its xml etree cElementTree counterpart have been updated to version 1 3 Several new and useful functions and methods have been added xml etree ElementTree fromstringlist which builds an XML document from a sequence of fragments xml etree ElementTree register_namespace for registering a global namespace prefix xml etree ElementTree tostringlist for string representation including all sublists xml etree ElementTree Element extend for appending a sequence of zero or more elements xml etree ElementTree Element iterfind searches an element and subelements xml etree ElementTree Element itertext creates a text iterator over an element and its subelements xml etree ElementTree TreeBuilder end closes the current element xml etree ElementTree TreeBuilder doctype handles a doctype declaration Two methods have been deprecated xml etree ElementTree getchildren use list elem instead xml etree ElementTree getiterator use Element iter instead For details of the update see Introducing ElementTree on Fredrik Lundh s website Contributed by Florent Xicluna and Fredrik Lundh bpo 6472 functools The functools module includes a new decorator for caching function calls functools lru_cache can save repeated queries to an external resource whenever the results are expected to be the same For example adding a caching decorator to a database query function can save database accesses for popular searches import functools functools lru_cache maxsize 300 def get_phone_number name c conn cursor c execute SELECT phonenumber FROM phonelist WHERE name name return c fetchone 0 for name in user_requests get_phone_number name cached lookup To help with choosing an effective cache size the wrapped function is instrumented for ,en
2318,tracking cache statistics get_phone_number cache_info CacheInfo hits 4805 misses 980 maxsize 300 currsize 300 If the phonelist table gets updated the outdated contents of the cache can be cleared with get_phone_number cache_clear Contributed by Raymond Hettinger and incorporating design ideas from Jim Baker Miki Tebeka and Nick Coghlan see recipe 498245 recipe 577479 bpo 10586 and bpo 10593 The functools wraps decorator now adds a __wrapped__ attribute pointing to the original callable function This allows wrapped functions to be introspected It also copies __annotations__ if defined And now it also gracefully skips over missing attributes such as __doc__ which might not be defined for the wrapped callable In the above example the cache can be removed by recovering the original function get_phone_number get_phone_number __wrapped__ uncached function By Nick Coghlan and Terrence Cole bpo 9567 bpo 3445 and bpo 8814 To help write classes with rich comparison methods a new decorator functools total_ordering will use existing equality and inequality methods to fill in the remaining methods For example supplying __eq__ and __lt__ will enable total_ordering to fill in __le__ __gt__ and __ge__ total_ordering class Student def __eq__ self other return self lastname lower self firstname lower other lastname lower other firstname lower def __lt__ self other return self lastname lower self firstname lower other lastname lower other firstname lower With the total_ordering decorator the remaining comparison methods are filled in automatically Contributed by Raymond Hettinger To aid in porting programs from Python 2 the functools cmp_to_key function converts an old style comparison function to modern key function locale aware sort order sorted iterable key cmp_to_key locale strcoll For sorting examples and a brief sorting tutorial see the Sorting HowTo tutorial Contributed by Raymond Hettinger itertools The itertools module has a new accumulate function modeled on APL s scan operator and Numpy s accumulate function from itertools import accumulate list accumulate 8 2 50 8 10 60 prob_dist 0 1 0 4 0 2 0 3 list accumulate prob_dist cumulative probability distribution 0 1 0 5 0 7 1 0 For an example using accumulate see the examples for the random module Contributed by Raymond Hettinger and incorporating design suggestions from Mark Dickinson collections The collections Counter class now has two forms of in place subtraction the existing operator for saturating subtraction and the new subtract method for regular subtraction The former is suitable for multisets which only have positive counts and the latter is more suitable for use cases that allow negative counts from collections import Counter tally Counter dogs 5 cats 3 tally Counter dogs 2 cats 8 saturating subtraction tally Counter dogs 3 tally Counter dogs 5 cats 3 tally subtract dogs 2 cats 8 regular subtraction tally Counter dogs 3 cats 5 Contributed by Raymond Hettinger The collections OrderedDict class has a new method move_to_end which takes an existing key and moves it to either the first or last position in the ordered sequence The default is to move an item to the last position This is equivalent of renewing an entry with od k od pop k A fast move to end operation is useful for resequencing entries For example an ordered dictionary can be used to track order of access by aging entries from the oldest to the most recently accessed from collections import OrderedDict d OrderedDict fromkeys a b X d e list d a b X d e d move_to_end X list d a b d e X Contributed by Raymond Hettinger The collections deque class grew two new methods count and reverse that make them more substitutable for list objects from collections import deque d deque simsalabim d count s 2 d reverse d deque m i b a l a s m i s Contributed by Raymond Hettinger threading The threading module has a new Barrier synchronization class for making multiple threads wait until all of them have reached a common barrier point Barriers are useful for making sure that a task with multiple preconditions does not run until all o,en
2319,f the predecessor tasks are complete Barriers can work with an arbitrary number of threads This is a generalization of a Rendezvous which is defined for only two threads Implemented as a two phase cyclic barrier Barrier objects are suitable for use in loops The separate filling and draining phases assure that all threads get released drained before any one of them can loop back and re enter the barrier The barrier fully resets after each cycle Example of using barriers from threading import Barrier Thread def get_votes site ballots conduct_election site all_polls_closed wait do not count until all polls are closed totals summarize ballots publish site totals all_polls_closed Barrier len sites for site in sites Thread target get_votes args site start In this example the barrier enforces a rule that votes cannot be counted at any polling site until all polls are closed Notice how a solution with a barrier is similar to one with threading Thread join but the threads stay alive and continue to do work summarizing ballots after the barrier point is crossed If any of the predecessor tasks can hang or be delayed a barrier can be created with an optional timeout parameter Then if the timeout period elapses before all the predecessor tasks reach the barrier point all waiting threads are released and a BrokenBarrierError exception is raised def get_votes site ballots conduct_election site try all_polls_closed wait timeout midnight time now except BrokenBarrierError lockbox seal_ballots ballots queue put lockbox else totals summarize ballots publish site totals In this example the barrier enforces a more robust rule If some election sites do not finish before midnight the barrier times out and the ballots are sealed and deposited in a queue for later handling See Barrier Synchronization Patterns for more examples of how barriers can be used in parallel computing Also there is a simple but thorough explanation of barriers in The Little Book of Semaphores section 3 6 Contributed by Kristján Valur Jónsson with an API review by Jeffrey Yasskin in bpo 8777 datetime and time The datetime module has a new type timezone that implements the tzinfo interface by returning a fixed UTC offset and timezone name This makes it easier to create timezone aware datetime objects from datetime import datetime timezone datetime now timezone utc datetime datetime 2010 12 8 21 4 2 923754 tzinfo datetime timezone utc datetime strptime 01 01 2000 12 00 0000 m d Y H M z datetime datetime 2000 1 1 12 0 tzinfo datetime timezone utc Also timedelta objects can now be multiplied by float and divided by float and int objects And timedelta objects can now divide one another The datetime date strftime method is no longer restricted to years after 1900 The new supported year range is from 1000 to 9999 inclusive Whenever a two digit year is used in a time tuple the interpretation has been governed by time accept2dyear The default is True which means that for a two digit year the century is guessed according to the POSIX rules governing the y strptime format Starting with Py3 2 use of the century guessing heuristic will emit a DeprecationWarning Instead it is recommended that time accept2dyear be set to False so that large date ranges can be used without guesswork import time warnings warnings resetwarnings remove the default warning filters time accept2dyear True guess whether 11 means 11 or 2011 time asctime 11 1 1 12 34 56 4 1 0 Warning from warnings module DeprecationWarning Century info guessed for a 2 digit year Fri Jan 1 12 34 56 2011 time accept2dyear False use the full range of allowable dates time asctime 11 1 1 12 34 56 4 1 0 Fri Jan 1 12 34 56 11 Several functions now have significantly expanded date ranges When time accept2dyear is false the time asctime function will accept any year that fits in a C int while the time mktime and time strftime functions will accept the full range supported by the corresponding operating system functions Contributed by Alexander Belopolsky and Victor Stinner in bpo 1289118 bpo 5094 bpo 6641 bpo 2706 bpo 1777412 bpo 8013 and,en
2320, bpo 10827 math The math module has been updated with six new functions inspired by the C99 standard The isfinite function provides a reliable and fast way to detect special values It returns True for regular numbers and False for Nan or Infinity from math import isfinite isfinite x for x in 123 4 56 float Nan float Inf True True False False The expm1 function computes e x 1 for small values of x without incurring the loss of precision that usually accompanies the subtraction of nearly equal quantities from math import expm1 expm1 0 013671875 more accurate way to compute e x 1 for a small x 0 013765762467652909 The erf function computes a probability integral or Gaussian error function The complementary error function erfc is 1 erf x from math import erf erfc sqrt erf 1 0 sqrt 2 0 portion of normal distribution within 1 standard deviation 0 682689492137086 erfc 1 0 sqrt 2 0 portion of normal distribution outside 1 standard deviation 0 31731050786291404 erf 1 0 sqrt 2 0 erfc 1 0 sqrt 2 0 1 0 The gamma function is a continuous extension of the factorial function See https en wikipedia org wiki Gamma_function for details Because the function is related to factorials it grows large even for small values of x so there is also a lgamma function for computing the natural logarithm of the gamma function from math import gamma lgamma gamma 7 0 six factorial 720 0 lgamma 801 0 log 800 factorial 4551 950730698041 Contributed by Mark Dickinson abc The abc module now supports abstractclassmethod and abstractstaticmethod These tools make it possible to define an abstract base class that requires a particular classmethod or staticmethod to be implemented class Temperature metaclass abc ABCMeta abc abstractclassmethod def from_fahrenheit cls t abc abstractclassmethod def from_celsius cls t Patch submitted by Daniel Urban bpo 5867 io The io BytesIO has a new method getbuffer which provides functionality similar to memoryview It creates an editable view of the data without making a copy The buffer s random access and support for slice notation are well suited to in place editing REC_LEN LOC_START LOC_LEN 34 7 11 def change_location buffer record_number location start record_number REC_LEN LOC_START buffer start start LOC_LEN location import io byte_stream io BytesIO b G3805 storeroom Main chassis b X7899 shipping Reserve cog b L6988 receiving Primary sprocket buffer byte_stream getbuffer change_location buffer 1 b warehouse change_location buffer 0 b showroom print byte_stream getvalue b G3805 showroom Main chassis b X7899 warehouse Reserve cog b L6988 receiving Primary sprocket Contributed by Antoine Pitrou in bpo 5506 reprlib When writing a __repr__ method for a custom container it is easy to forget to handle the case where a member refers back to the container itself Python s builtin objects such as list and set handle self reference by displaying in the recursive part of the representation string To help write such __repr__ methods the reprlib module has a new decorator recursive_repr for detecting recursive calls to __repr__ and substituting a placeholder string instead class MyList list recursive_repr def __repr__ self return join map repr self m MyList abc m append m m append x print m a b c x Contributed by Raymond Hettinger in bpo 9826 and bpo 9840 logging In addition to dictionary based configuration described above the logging package has many other improvements The logging documentation has been augmented by a basic tutorial an advanced tutorial and a cookbook of logging recipes These documents are the fastest way to learn about logging The logging basicConfig set up function gained a style argument to support three different types of string formatting It defaults to for traditional formatting can be set to for the new str format style or can be set to for the shell style formatting provided by string Template The following three configurations are equivalent from logging import basicConfig basicConfig style format name s levelname s message s basicConfig style format name levelname message basicConfig style format name leveln,en
2321,ame message If no configuration is set up before a logging event occurs there is now a default configuration using a StreamHandler directed to sys stderr for events of WARNING level or higher Formerly an event occurring before a configuration was set up would either raise an exception or silently drop the event depending on the value of logging raiseExceptions The new default handler is stored in logging lastResort The use of filters has been simplified Instead of creating a Filter object the predicate can be any Python callable that returns True or False There were a number of other improvements that add flexibility and simplify configuration See the module documentation for a full listing of changes in Python 3 2 csv The csv module now supports a new dialect unix_dialect which applies quoting for all fields and a traditional Unix style with n as the line terminator The registered dialect name is unix The csv DictWriter has a new method writeheader for writing out an initial row to document the field names import csv sys w csv DictWriter sys stdout name dept dialect unix w writeheader name dept w writerows name tom dept accounting name susan dept Salesl tom accounting susan sales New dialect suggested by Jay Talbot in bpo 5975 and the new method suggested by Ed Abraham in bpo 1537721 contextlib There is a new and slightly mind blowing tool ContextDecorator that is helpful for creating a context manager that does double duty as a function decorator As a convenience this new functionality is used by contextmanager so that no extra effort is needed to support both roles The basic idea is that both context managers and function decorators can be used for pre action and post action wrappers Context managers wrap a group of statements using a with statement and function decorators wrap a group of statements enclosed in a function So occasionally there is a need to write a pre action or post action wrapper that can be used in either role For example it is sometimes useful to wrap functions or groups of statements with a logger that can track the time of entry and time of exit Rather than writing both a function decorator and a context manager for the task the contextmanager provides both capabilities in a single definition from contextlib import contextmanager import logging logging basicConfig level logging INFO contextmanager def track_entry_and_exit name logging info Entering s name yield logging info Exiting s name Formerly this would have only been usable as a context manager with track_entry_and_exit widget loader print Some time consuming activity goes here load_widget Now it can be used as a decorator as well track_entry_and_exit widget loader def activity print Some time consuming activity goes here load_widget Trying to fulfill two roles at once places some limitations on the technique Context managers normally have the flexibility to return an argument usable by a with statement but there is no parallel for function decorators In the above example there is not a clean way for the track_entry_and_exit context manager to return a logging instance for use in the body of enclosed statements Contributed by Michael Foord in bpo 9110 decimal and fractions Mark Dickinson crafted an elegant and efficient scheme for assuring that different numeric datatypes will have the same hash value whenever their actual values are equal bpo 8188 assert hash Fraction 3 2 hash 1 5 hash Decimal 1 5 hash complex 1 5 0 Some of the hashing details are exposed through a new attribute sys hash_info which describes the bit width of the hash value the prime modulus the hash values for infinity and nan and the multiplier used for the imaginary part of a number sys hash_info sys hash_info width 64 modulus 2305843009213693951 inf 314159 nan 0 imag 1000003 An early decision to limit the interoperability of various numeric types has been relaxed It is still unsupported and ill advised to have implicit mixing in arithmetic expressions such as Decimal 1 1 float 1 1 because the latter loses information in the process of constructing the binary float Howev,en
2322,er since existing floating point value can be converted losslessly to either a decimal or rational representation it makes sense to add them to the constructor and to support mixed type comparisons The decimal Decimal constructor now accepts float objects directly so there in no longer a need to use the from_float method bpo 8257 Mixed type comparisons are now fully supported so that Decimal objects can be directly compared with float and fractions Fraction bpo 2531 and bpo 8188 Similar changes were made to fractions Fraction so that the from_float and from_decimal methods are no longer needed bpo 8294 from decimal import Decimal from fractions import Fraction Decimal 1 1 Decimal 1 100000000000000088817841970012523233890533447265625 Fraction 1 1 Fraction 2476979795053773 2251799813685248 Another useful change for the decimal module is that the Context clamp attribute is now public This is useful in creating contexts that correspond to the decimal interchange formats specified in IEEE 754 see bpo 8540 Contributed by Mark Dickinson and Raymond Hettinger ftp The ftplib FTP class now supports the context management protocol to unconditionally consume socket error exceptions and to close the FTP connection when done from ftplib import FTP with FTP ftp1 at proftpd org as ftp ftp login ftp dir 230 Anonymous login ok restrictions apply dr xr xr x 9 ftp ftp 154 May 6 10 43 dr xr xr x 9 ftp ftp 154 May 6 10 43 dr xr xr x 5 ftp ftp 4096 May 6 10 43 CentOS dr xr xr x 3 ftp ftp 18 Jul 10 2008 Fedora Other file like objects such as mmap mmap and fileinput input also grew auto closing context managers with fileinput input files log1 txt log2 txt as f for line in f process line Contributed by Tarek Ziadé and Giampaolo Rodolà in bpo 4972 and by Georg Brandl in bpo 8046 and bpo 1286 The FTP_TLS class now accepts a context parameter which is a ssl SSLContext object allowing bundling SSL configuration options certificates and private keys into a single potentially long lived structure Contributed by Giampaolo Rodolà bpo 8806 popen The os popen and subprocess Popen functions now support with statements for auto closing of the file descriptors Contributed by Antoine Pitrou and Brian Curtin in bpo 7461 and bpo 10554 select The select module now exposes a new constant attribute PIPE_BUF which gives the minimum number of bytes which are guaranteed not to block when select select says a pipe is ready for writing import select select PIPE_BUF 512 Available on Unix systems Patch by Sébastien Sablé in bpo 9862 gzip and zipfile gzip GzipFile now implements the io BufferedIOBase abstract base class except for truncate It also has a peek method and supports unseekable as well as zero padded file objects The gzip module also gains the compress and decompress functions for easier in memory compression and decompression Keep in mind that text needs to be encoded as bytes before compressing and decompressing import gzip s Three shall be the number thou shalt count s and the number of the counting shall be three b s encode convert to utf 8 len b 89 c gzip compress b len c 77 gzip decompress c decode 42 decompress and convert to text Three shall be the number thou shalt count Contributed by Anand B Pillai in bpo 3488 and by Antoine Pitrou Nir Aides and Brian Curtin in bpo 9962 bpo 1675951 bpo 7471 and bpo 2846 Also the zipfile ZipExtFile class was reworked internally to represent files stored inside an archive The new implementation is significantly faster and can be wrapped in an io BufferedReader object for more speedups It also solves an issue where interleaved calls to read and readline gave the wrong results Patch submitted by Nir Aides in bpo 7610 tarfile The TarFile class can now be used as a context manager In addition its add method has a new option filter that controls which files are added to the archive and allows the file metadata to be edited The new filter option replaces the older less flexible exclude parameter which is now deprecated If specified the optional filter parameter needs to be a keyword argument The user supplied filter function ,en
2323,accepts a TarInfo object and returns an updated TarInfo object or if it wants the file to be excluded the function can return None import tarfile glob def myfilter tarinfo if tarinfo isfile only save real files tarinfo uname monty redact the user name return tarinfo with tarfile open name myarchive tar gz mode w gz as tf for filename in glob glob txt tf add filename filter myfilter tf list rw r r monty 501 902 2011 01 26 17 59 11 annotations txt rw r r monty 501 123 2011 01 26 17 59 11 general_questions txt rw r r monty 501 3514 2011 01 26 17 59 11 prion txt rw r r monty 501 124 2011 01 26 17 59 11 py_todo txt rw r r monty 501 1399 2011 01 26 17 59 11 semaphore_notes txt Proposed by Tarek Ziadé and implemented by Lars Gustäbel in bpo 6856 hashlib The hashlib module has two new constant attributes listing the hashing algorithms guaranteed to be present in all implementations and those available on the current implementation import hashlib hashlib algorithms_guaranteed sha1 sha224 sha384 sha256 sha512 md5 hashlib algorithms_available md2 SHA256 SHA512 dsaWithSHA mdc2 SHA224 MD4 sha256 sha512 ripemd160 SHA1 MDC2 SHA SHA384 MD2 ecdsa with SHA1 md4 md5 sha1 DSA SHA sha224 dsaEncryption DSA RIPEMD160 sha MD5 sha384 Suggested by Carl Chenet in bpo 7418 ast The ast module has a wonderful a general purpose tool for safely evaluating expression strings using the Python literal syntax The ast literal_eval function serves as a secure alternative to the builtin eval function which is easily abused Python 3 2 adds bytes and set literals to the list of supported types strings bytes numbers tuples lists dicts sets booleans and None from ast import literal_eval request req 3 func pow args 2 0 5 literal_eval request args 2 0 5 req 3 func pow request os system do something harmful literal_eval request Traceback most recent call last ValueError malformed node or string _ast Call object at 0x101739a10 Implemented by Benjamin Peterson and Georg Brandl os Different operating systems use various encodings for filenames and environment variables The os module provides two new functions fsencode and fsdecode for encoding and decoding filenames import os filename Sehenswürdigkeiten os fsencode filename b Sehensw xc3 xbcrdigkeiten Some operating systems allow direct access to encoded bytes in the environment If so the os supports_bytes_environ constant will be true For direct access to encoded environment variables if available use the new os getenvb function or use os environb which is a bytes version of os environ Contributed by Victor Stinner shutil The shutil copytree function has two new options ignore_dangling_symlinks when symlinks False so that the function copies a file pointed to by a symlink not the symlink itself This option will silence the error raised if the file doesn t exist copy_function is a callable that will be used to copy files shutil copy2 is used by default Contributed by Tarek Ziadé In addition the shutil module now supports archiving operations for zipfiles uncompressed tarfiles gzipped tarfiles and bzipped tarfiles And there are functions for registering additional archiving file formats such as xz compressed tarfiles or custom formats The principal functions are make_archive and unpack_archive By default both operate on the current directory which can be set by os chdir and on any sub directories The archive filename needs to be specified with a full pathname The archiving step is non destructive the original files are left unchanged import shutil pprint os chdir mydata change to the source directory f shutil make_archive var backup mydata zip archive the current directory f show the name of archive var backup mydata zip os chdir tmp change to an unpacking shutil unpack_archive var backup mydata zip recover the data pprint pprint shutil get_archive_formats display known formats bztar bzip2 ed tar file gztar gzip ed tar file tar uncompressed tar file zip ZIP file shutil register_archive_format register a new archive format name xz function xz compress callable archiving function extra_args level 8 arguments to the functi,en
2324,on description xz compression Contributed by Tarek Ziadé sqlite3 The sqlite3 module was updated to pysqlite version 2 6 0 It has two new capabilities The sqlite3 Connection in_transit attribute is true if there is an active transaction for uncommitted changes The sqlite3 Connection enable_load_extension and sqlite3 Connection load_extension methods allows you to load SQLite extensions from so files One well known extension is the fulltext search extension distributed with SQLite Contributed by R David Murray and Shashwat Anand bpo 8845 html A new html module was introduced with only a single function escape which is used for escaping reserved characters from HTML markup import html html escape x 2 x 7 x gt 2 amp amp x lt 7 socket The socket module has two new improvements Socket objects now have a detach method which puts the socket into closed state without actually closing the underlying file descriptor The latter can then be reused for other purposes Added by Antoine Pitrou bpo 8524 socket create_connection now supports the context management protocol to unconditionally consume socket error exceptions and to close the socket when done Contributed by Giampaolo Rodolà bpo 9794 ssl The ssl module added a number of features to satisfy common requirements for secure encrypted authenticated internet connections A new class SSLContext serves as a container for persistent SSL data such as protocol settings certificates private keys and various other options It includes a wrap_socket for creating an SSL socket from an SSL context A new function ssl match_hostname supports server identity verification for higher level protocols by implementing the rules of HTTPS from RFC 2818 which are also suitable for other protocols The ssl wrap_socket constructor function now takes a ciphers argument The ciphers string lists the allowed encryption algorithms using the format described in the OpenSSL documentation When linked against recent versions of OpenSSL the ssl module now supports the Server Name Indication extension to the TLS protocol allowing multiple virtual hosts using different certificates on a single IP port This extension is only supported in client mode and is activated by passing the server_hostname argument to ssl SSLContext wrap_socket Various options have been added to the ssl module such as OP_NO_SSLv2 which disables the insecure and obsolete SSLv2 protocol The extension now loads all the OpenSSL ciphers and digest algorithms If some SSL certificates cannot be verified they are reported as an unknown algorithm error The version of OpenSSL being used is now accessible using the module attributes ssl OPENSSL_VERSION a string ssl OPENSSL_VERSION_INFO a 5 tuple and ssl OPENSSL_VERSION_NUMBER an integer Contributed by Antoine Pitrou in bpo 8850 bpo 1589 bpo 8322 bpo 5639 bpo 4870 bpo 8484 and bpo 8321 nntp The nntplib module has a revamped implementation with better bytes and text semantics as well as more practical APIs These improvements break compatibility with the nntplib version in Python 3 1 which was partly dysfunctional in itself Support for secure connections through both implicit using nntplib NNTP_SSL and explicit using nntplib NNTP starttls TLS has also been added Contributed by Antoine Pitrou in bpo 9360 and Andrew Vant in bpo 1926 certificates http client HTTPSConnection urllib request HTTPSHandler and urllib request urlopen now take optional arguments to allow for server certificate checking against a set of Certificate Authorities as recommended in public uses of HTTPS Added by Antoine Pitrou bpo 9003 imaplib Support for explicit TLS on standard IMAP4 connections has been added through the new imaplib IMAP4 starttls method Contributed by Lorenzo M Catucci and Antoine Pitrou bpo 4471 http client There were a number of small API improvements in the http client module The old style HTTP 0 9 simple responses are no longer supported and the strict parameter is deprecated in all classes The HTTPConnection and HTTPSConnection classes now have a source_address parameter for a host port tuple indicating where the HTTP,en
2325, connection is made from Support for certificate checking and HTTPS virtual hosts were added to HTTPSConnection The request method on connection objects allowed an optional body argument so that a file object could be used to supply the content of the request Conveniently the body argument now also accepts an iterable object so long as it includes an explicit Content Length header This extended interface is much more flexible than before To establish an HTTPS connection through a proxy server there is a new set_tunnel method that sets the host and port for HTTP Connect tunneling To match the behavior of http server the HTTP client library now also encodes headers with ISO 8859 1 Latin 1 encoding It was already doing that for incoming headers so now the behavior is consistent for both incoming and outgoing traffic See work by Armin Ronacher in bpo 10980 unittest The unittest module has a number of improvements supporting test discovery for packages easier experimentation at the interactive prompt new testcase methods improved diagnostic messages for test failures and better method names The command line call python m unittest can now accept file paths instead of module names for running specific tests bpo 10620 The new test discovery can find tests within packages locating any test importable from the top level directory The top level directory can be specified with the t option a pattern for matching files with p and a directory to start discovery with s python m unittest discover s my_proj_dir p _test py Contributed by Michael Foord Experimentation at the interactive prompt is now easier because the unittest TestCase class can now be instantiated without arguments from unittest import TestCase TestCase assertEqual pow 2 3 8 Contributed by Michael Foord The unittest module has two new methods assertWarns and assertWarnsRegex to verify that a given warning type is triggered by the code under test with self assertWarns DeprecationWarning legacy_function XYZ Contributed by Antoine Pitrou bpo 9754 Another new method assertCountEqual is used to compare two iterables to determine if their element counts are equal whether the same elements are present with the same number of occurrences regardless of order def test_anagram self self assertCountEqual algorithm logarithm Contributed by Raymond Hettinger A principal feature of the unittest module is an effort to produce meaningful diagnostics when a test fails When possible the failure is recorded along with a diff of the output This is especially helpful for analyzing log files of failed test runs However since diffs can sometime be voluminous there is a new maxDiff attribute that sets maximum length of diffs displayed In addition the method names in the module have undergone a number of clean ups For example assertRegex is the new name for assertRegexpMatches which was misnamed because the test uses re search not re match Other methods using regular expressions are now named using short form Regex in preference to Regexp this matches the names used in other unittest implementations matches Python s old name for the re module and it has unambiguous camel casing Contributed by Raymond Hettinger and implemented by Ezio Melotti To improve consistency some long standing method aliases are being deprecated in favor of the preferred names Old Name Preferred Name assert_ assertTrue assertEquals assertEqual assertNotEquals assertNotEqual assertAlmostEquals assertAlmostEqual assertNotAlmostEquals assertNotAlmostEqual Likewise the TestCase fail methods deprecated in Python 3 1 are expected to be removed in Python 3 3 Contributed by Ezio Melotti bpo 9424 The assertDictContainsSubset method was deprecated because it was misimplemented with the arguments in the wrong order This created hard to debug optical illusions where tests like TestCase assertDictContainsSubset a 1 b 2 a 1 would fail Contributed by Raymond Hettinger random The integer methods in the random module now do a better job of producing uniform distributions Previously they computed selections with int n random which had a slig,en
2326,ht bias whenever n was not a power of two Now multiple selections are made from a range up to the next power of two and a selection is kept only when it falls within the range 0 x n The functions and methods affected are randrange randint choice shuffle and sample Contributed by Raymond Hettinger bpo 9025 poplib POP3_SSL class now accepts a context parameter which is a ssl SSLContext object allowing bundling SSL configuration options certificates and private keys into a single potentially long lived structure Contributed by Giampaolo Rodolà bpo 8807 asyncore asyncore dispatcher now provides a handle_accepted method returning a sock addr pair which is called when a connection has actually been established with a new remote endpoint This is supposed to be used as a replacement for old handle_accept and avoids the user to call accept directly Contributed by Giampaolo Rodolà bpo 6706 tempfile The tempfile module has a new context manager TemporaryDirectory which provides easy deterministic cleanup of temporary directories with tempfile TemporaryDirectory as tmpdirname print created temporary dir tmpdirname Contributed by Neil Schemenauer and Nick Coghlan bpo 5178 inspect The inspect module has a new function getgeneratorstate to easily identify the current state of a generator iterator from inspect import getgeneratorstate def gen yield demo g gen getgeneratorstate g GEN_CREATED next g demo getgeneratorstate g GEN_SUSPENDED next g None getgeneratorstate g GEN_CLOSED Contributed by Rodolpho Eckhardt and Nick Coghlan bpo 10220 To support lookups without the possibility of activating a dynamic attribute the inspect module has a new function getattr_static Unlike hasattr this is a true read only search guaranteed not to change state while it is searching class A property def f self print Running return 10 a A getattr a f Running 10 inspect getattr_static a f property object at 0x1022bd788 Contributed by Michael Foord pydoc The pydoc module now provides a much improved web server interface as well as a new command line option b to automatically open a browser window to display that server pydoc3 2 b Contributed by Ron Adam bpo 2001 dis The dis module gained two new functions for inspecting code code_info and show_code Both provide detailed code object information for the supplied function method source code string or code object The former returns a string and the latter prints it import dis random dis show_code random choice Name choice Filename Library Frameworks Python framework Versions 3 2 lib python3 2 random py Argument count 2 Kw only arguments 0 Number of locals 3 Stack size 11 Flags OPTIMIZED NEWLOCALS NOFREE Constants 0 Choose a random element from a non empty sequence 1 Cannot choose from an empty sequence Names 0 _randbelow 1 len 2 ValueError 3 IndexError Variable names 0 self 1 seq 2 i In addition the dis function now accepts string arguments so that the common idiom dis compile s eval can be shortened to dis s dis 3 x 1 if x 2 1 else x 2 1 0 LOAD_NAME 0 x 3 LOAD_CONST 0 2 6 BINARY_MODULO 7 LOAD_CONST 1 1 10 COMPARE_OP 2 13 POP_JUMP_IF_FALSE 28 16 LOAD_CONST 2 3 19 LOAD_NAME 0 x 22 BINARY_MULTIPLY 23 LOAD_CONST 1 1 26 BINARY_ADD 27 RETURN_VALUE 28 LOAD_NAME 0 x 31 LOAD_CONST 0 2 34 BINARY_FLOOR_DIVIDE 35 RETURN_VALUE Taken together these improvements make it easier to explore how CPython is implemented and to see for yourself what the language syntax does under the hood Contributed by Nick Coghlan in bpo 9147 dbm All database modules now support the get and setdefault methods Suggested by Ray Allen in bpo 9523 ctypes A new type ctypes c_ssize_t represents the C ssize_t datatype site The site module has three new functions useful for reporting on the details of a given Python installation getsitepackages lists all global site packages directories getuserbase reports on the user s base directory where data can be stored getusersitepackages reveals the user specific site packages directory path import site site getsitepackages Library Frameworks Python framework Versions 3 2 lib python3 2 site packages Library Framewor,en
2327,ks Python framework Versions 3 2 lib site python Library Python 3 2 site packages site getuserbase Users raymondhettinger Library Python 3 2 site getusersitepackages Users raymondhettinger Library Python 3 2 lib python site packages Conveniently some of site s functionality is accessible directly from the command line python m site user base Users raymondhettinger local python m site user site Users raymondhettinger local lib python3 2 site packages Contributed by Tarek Ziadé in bpo 6693 sysconfig The new sysconfig module makes it straightforward to discover installation paths and configuration variables that vary across platforms and installations The module offers access simple access functions for platform and version information get_platform returning values like linux i586 or macosx 10 6 ppc get_python_version returns a Python version string such as 3 2 It also provides access to the paths and variables corresponding to one of seven named schemes used by distutils Those include posix_prefix posix_home posix_user nt nt_user os2 os2_home get_paths makes a dictionary containing installation paths for the current installation scheme get_config_vars returns a dictionary of platform specific variables There is also a convenient command line interface C Python32 python m sysconfig Platform win32 Python version 3 2 Current installation scheme nt Paths data C Python32 include C Python32 Include platinclude C Python32 Include platlib C Python32 Lib site packages platstdlib C Python32 Lib purelib C Python32 Lib site packages scripts C Python32 Scripts stdlib C Python32 Lib Variables BINDIR C Python32 BINLIBDEST C Python32 Lib EXE exe INCLUDEPY C Python32 Include LIBDEST C Python32 Lib SO pyd VERSION 32 abiflags base C Python32 exec_prefix C Python32 platbase C Python32 prefix C Python32 projectbase C Python32 py_version 3 2 py_version_nodot 32 py_version_short 3 2 srcdir C Python32 userbase C Documents and Settings Raymond Application Data Python Moved out of Distutils by Tarek Ziadé pdb The pdb debugger module gained a number of usability improvements pdb py now has a c option that executes commands as given in a pdbrc script file A pdbrc script file can contain continue and next commands that continue debugging The Pdb class constructor now accepts a nosigint argument New commands l list ll long list and source for listing source code New commands display and undisplay for showing or hiding the value of an expression if it has changed New command interact for starting an interactive interpreter containing the global and local names found in the current scope Breakpoints can be cleared by breakpoint number Contributed by Georg Brandl Antonio Cuni and Ilya Sandler configparser The configparser module was modified to improve usability and predictability of the default parser and its supported INI syntax The old ConfigParser class was removed in favor of SafeConfigParser which has in turn been renamed to ConfigParser Support for inline comments is now turned off by default and section or option duplicates are not allowed in a single configuration source Config parsers gained a new API based on the mapping protocol parser ConfigParser parser read_string DEFAULT location upper left visible yes editable no color blue main title Main Menu color green options title Options parser main color green parser main editable no section parser options section title Options section title Options editable editable s section title Options editable no The new API is implemented on top of the classical API so custom parser subclasses should be able to use it without modifications The INI file structure accepted by config parsers can now be customized Users can specify alternative option value delimiters and comment prefixes change the name of the DEFAULT section or switch the interpolation syntax There is support for pluggable interpolation including an additional interpolation handler ExtendedInterpolation parser ConfigParser interpolation ExtendedInterpolation parser read_dict buildout directory home ambv zope9 custom prefix usr local parser rea,en
2328,d_string buildout parts zope9 instance find links buildout directory downloads dist zope9 recipe plone recipe zope9install location opt zope instance recipe plone recipe zope9instance zope9 location zope9 location zope conf custom prefix etc zope conf parser buildout find links n home ambv zope9 downloads dist parser instance zope conf usr local etc zope conf instance parser instance instance zope conf usr local etc zope conf instance zope9 location opt zope A number of smaller features were also introduced like support for specifying encoding in read operations specifying fallback values for get functions or reading directly from dictionaries and strings All changes contributed by Łukasz Langa urllib parse A number of usability improvements were made for the urllib parse module The urlparse function now supports IPv6 addresses as described in RFC 2732 import urllib parse urllib parse urlparse http dead beef cafe 5417 affe 8FA3 deaf feed foo ParseResult scheme http netloc dead beef cafe 5417 affe 8FA3 deaf feed path foo params query fragment The urldefrag function now returns a named tuple r urllib parse urldefrag http python org about target r DefragResult url http python org about fragment target r 0 http python org about r fragment target And the urlencode function is now much more flexible accepting either a string or bytes type for the query argument If it is a string then the safe encoding and error parameters are sent to quote_plus for encoding urllib parse urlencode type telenovela name Dónde Está Elisa encoding latin 1 type telenovela name BFD F3nde Est E1 Elisa 3F As detailed in Parsing ASCII Encoded Bytes all the urllib parse functions now accept ASCII encoded byte strings as input so long as they are not mixed with regular strings If ASCII encoded byte strings are given as parameters the return types will also be an ASCII encoded byte strings urllib parse urlparse b http www python org 80 about ParseResultBytes scheme b http netloc b www python org 80 path b about params b query b fragment b Work by Nick Coghlan Dan Mahn and Senthil Kumaran in bpo 2987 bpo 5468 and bpo 9873 mailbox Thanks to a concerted effort by R David Murray the mailbox module has been fixed for Python 3 2 The challenge was that mailbox had been originally designed with a text interface but email messages are best represented with bytes because various parts of a message may have different encodings The solution harnessed the email package s binary support for parsing arbitrary email messages In addition the solution required a number of API changes As expected the add method for mailbox Mailbox objects now accepts binary input StringIO and text file input are deprecated Also string input will fail early if non ASCII characters are used Previously it would fail when the email was processed in a later step There is also support for binary output The get_file method now returns a file in the binary mode where it used to incorrectly set the file to text mode There is also a new get_bytes method that returns a bytes representation of a message corresponding to a given key It is still possible to get non binary output using the old API s get_string method but that approach is not very useful Instead it is best to extract messages from a Message object or to load them from binary input Contributed by R David Murray with efforts from Steffen Daode Nurpmeso and an initial patch by Victor Stinner in bpo 9124 turtledemo The demonstration code for the turtle module was moved from the Demo directory to main library It includes over a dozen sample scripts with lively displays Being on sys path it can now be run directly from the command line python m turtledemo Moved from the Demo directory by Alexander Belopolsky in bpo 10199 Multi threading The mechanism for serializing execution of concurrently running Python threads generally known as the GIL or Global Interpreter Lock has been rewritten Among the objectives were more predictable switching intervals and reduced overhead due to lock contention and the number of ensuing system calls The notion of a c,en
2329,heck interval to allow thread switches has been abandoned and replaced by an absolute duration expressed in seconds This parameter is tunable through sys setswitchinterval It currently defaults to 5 milliseconds Additional details about the implementation can be read from a python dev mailing list message however priority requests as exposed in this message have not been kept for inclusion Contributed by Antoine Pitrou Regular and recursive locks now accept an optional timeout argument to their acquire method Contributed by Antoine Pitrou bpo 7316 Similarly threading Semaphore acquire also gained a timeout argument Contributed by Torsten Landschoff bpo 850728 Regular and recursive lock acquisitions can now be interrupted by signals on platforms using Pthreads This means that Python programs that deadlock while acquiring locks can be successfully killed by repeatedly sending SIGINT to the process by pressing Ctrl C in most shells Contributed by Reid Kleckner bpo 8844 Optimizations A number of small performance enhancements have been added Python s peephole optimizer now recognizes patterns such x in 1 2 3 as being a test for membership in a set of constants The optimizer recasts the set as a frozenset and stores the pre built constant Now that the speed penalty is gone it is practical to start writing membership tests using set notation This style is both semantically clear and operationally fast extension name rpartition 2 if extension in xml html xhtml css handle name Patch and additional tests contributed by Dave Malcolm bpo 6690 Serializing and unserializing data using the pickle module is now several times faster Contributed by Alexandre Vassalotti Antoine Pitrou and the Unladen Swallow team in bpo 9410 and bpo 3873 The Timsort algorithm used in list sort and sorted now runs faster and uses less memory when called with a key function Previously every element of a list was wrapped with a temporary object that remembered the key value associated with each element Now two arrays of keys and values are sorted in parallel This saves the memory consumed by the sort wrappers and it saves time lost to delegating comparisons Patch by Daniel Stutzbach in bpo 9915 JSON decoding performance is improved and memory consumption is reduced whenever the same string is repeated for multiple keys Also JSON encoding now uses the C speedups when the sort_keys argument is true Contributed by Antoine Pitrou in bpo 7451 and by Raymond Hettinger and Antoine Pitrou in bpo 10314 Recursive locks created with the threading RLock API now benefit from a C implementation which makes them as fast as regular locks and between 10x and 15x faster than their previous pure Python implementation Contributed by Antoine Pitrou bpo 3001 The fast search algorithm in stringlib is now used by the split rsplit splitlines and replace methods on bytes bytearray and str objects Likewise the algorithm is also used by rfind rindex rsplit and rpartition Patch by Florent Xicluna in bpo 7622 and bpo 7462 Integer to string conversions now work two digits at a time reducing the number of division and modulo operations bpo 6713 by Gawain Bolton Mark Dickinson and Victor Stinner There were several other minor optimizations Set differencing now runs faster when one operand is much larger than the other patch by Andress Bennetts in bpo 8685 The array repeat method has a faster implementation bpo 1569291 by Alexander Belopolsky The BaseHTTPRequestHandler has more efficient buffering bpo 3709 by Andrew Schaaf The operator attrgetter function has been sped up bpo 10160 by Christos Georgiou And ConfigParser loads multi line arguments a bit faster bpo 7113 by Łukasz Langa Unicode Python has been updated to Unicode 6 0 0 The update to the standard adds over 2 000 new characters including emoji symbols which are important for mobile phones In addition the updated standard has altered the character properties for two Kannada characters U 0CF1 U 0CF2 and one New Tai Lue numeric character U 19DA making the former eligible for use in identifiers while disqualifying the latter For more i,en
2330,nformation see Unicode Character Database Changes Codecs Support was added for cp720 Arabic DOS encoding bpo 1616979 MBCS encoding no longer ignores the error handler argument In the default strict mode it raises an UnicodeDecodeError when it encounters an undecodable byte sequence and an UnicodeEncodeError for an unencodable character The MBCS codec supports strict and ignore error handlers for decoding and strict and replace for encoding To emulate Python3 1 MBCS encoding select the ignore handler for decoding and the replace handler for encoding On Mac OS X Python decodes command line arguments with utf 8 rather than the locale encoding By default tarfile uses utf 8 encoding on Windows instead of mbcs and the surrogateescape error handler on all operating systems Documentation The documentation continues to be improved A table of quick links has been added to the top of lengthy sections such as Built in Functions In the case of itertools the links are accompanied by tables of cheatsheet style summaries to provide an overview and memory jog without having to read all of the docs In some cases the pure Python source code can be a helpful adjunct to the documentation so now many modules now feature quick links to the latest version of the source code For example the functools module documentation has a quick link at the top labeled Source code Lib functools py Contributed by Raymond Hettinger see rationale The docs now contain more examples and recipes In particular re module has an extensive section Regular Expression Examples Likewise the itertools module continues to be updated with new Itertools Recipes The datetime module now has an auxiliary implementation in pure Python No functionality was changed This just provides an easier to read alternate implementation Contributed by Alexander Belopolsky in bpo 9528 The unmaintained Demo directory has been removed Some demos were integrated into the documentation some were moved to the Tools demo directory and others were removed altogether Contributed by Georg Brandl in bpo 7962 IDLE The format menu now has an option to clean source files by stripping trailing whitespace Contributed by Raymond Hettinger bpo 5150 IDLE on Mac OS X now works with both Carbon AquaTk and Cocoa AquaTk Contributed by Kevin Walzer Ned Deily and Ronald Oussoren bpo 6075 Code Repository In addition to the existing Subversion code repository at https svn python org there is now a Mercurial repository at https hg python org After the 3 2 release there are plans to switch to Mercurial as the primary repository This distributed version control system should make it easier for members of the community to create and share external changesets See PEP 385 for details To learn to use the new version control system see the Quick Start or the Guide to Mercurial Workflows Build and C API Changes Changes to Python s build process and to the C API include The idle pydoc and 2to3 scripts are now installed with a version specific suffix on make altinstall bpo 10679 The C functions that access the Unicode Database now accept and return characters from the full Unicode range even on narrow unicode builds Py_UNICODE_TOLOWER Py_UNICODE_ISDECIMAL and others A visible difference in Python is that unicodedata numeric now returns the correct value for large code points and repr may consider more characters as printable Reported by Bupjoe Lee and fixed by Amaury Forgeot D Arc bpo 5127 Computed gotos are now enabled by default on supported compilers which are detected by the configure script They can still be disabled selectively by specifying without computed gotos Contributed by Antoine Pitrou bpo 9203 The option with wctype functions was removed The built in unicode database is now used for all functions Contributed by Amaury Forgeot D Arc bpo 9210 Hash values are now values of a new type Py_hash_t which is defined to be the same size as a pointer Previously they were of type long which on some 64 bit operating systems is still only 32 bits long As a result of this fix set and dict can now hold more than 2 32 entries on b,en
2331,uilds with 64 bit pointers previously they could grow to that size but their performance degraded catastrophically Suggested by Raymond Hettinger and implemented by Benjamin Peterson bpo 9778 A new macro Py_VA_COPY copies the state of the variable argument list It is equivalent to C99 va_copy but available on all Python platforms bpo 2443 A new C API function PySys_SetArgvEx allows an embedded interpreter to set sys argv without also modifying sys path bpo 5753 PyEval_CallObject is now only available in macro form The function declaration which was kept for backwards compatibility reasons is now removed the macro was introduced in 1997 bpo 8276 There is a new function PyLong_AsLongLongAndOverflow which is analogous to PyLong_AsLongAndOverflow They both serve to convert Python int into a native fixed width type while providing detection of cases where the conversion won t fit bpo 7767 The PyUnicode_CompareWithASCIIString function now returns not equal if the Python string is NUL terminated There is a new function PyErr_NewExceptionWithDoc that is like PyErr_NewException but allows a docstring to be specified This lets C exceptions have the same self documenting capabilities as their pure Python counterparts bpo 7033 When compiled with the with valgrind option the pymalloc allocator will be automatically disabled when running under Valgrind This gives improved memory leak detection when running under Valgrind while taking advantage of pymalloc at other times bpo 2422 Removed the O format from the PyArg_Parse functions The format is no longer used and it had never been documented bpo 8837 There were a number of other small changes to the C API See the Misc NEWS file for a complete list Also there were a number of updates to the Mac OS X build see Mac BuildScript README txt for details For users running a 32 64 bit build there is a known problem with the default Tcl Tk on Mac OS X 10 6 Accordingly we recommend installing an updated alternative such as ActiveState Tcl Tk 8 5 9 See https www python org download mac tcltk for additional details Porting to Python 3 2 This section lists previously described changes and other bugfixes that may require changes to your code The configparser module has a number of clean ups The major change is to replace the old ConfigParser class with long standing preferred alternative SafeConfigParser In addition there are a number of smaller incompatibilities The interpolation syntax is now validated on get and set operations In the default interpolation scheme only two tokens with percent signs are valid name s and the latter being an escaped percent sign The set and add_section methods now verify that values are actual strings Formerly unsupported types could be introduced unintentionally Duplicate sections or options from a single source now raise either DuplicateSectionError or DuplicateOptionError Formerly duplicates would silently overwrite a previous entry Inline comments are now disabled by default so now the character can be safely used in values Comments now can be indented Consequently for or to appear at the start of a line in multiline values it has to be interpolated This keeps comment prefix characters in values from being mistaken as comments is now a valid value and is no longer automatically converted to an empty string For empty strings use option in a line The nntplib module was reworked extensively meaning that its APIs are often incompatible with the 3 1 APIs bytearray objects can no longer be used as filenames instead they should be converted to bytes The array tostring and array fromstring have been renamed to array tobytes and array frombytes for clarity The old names have been deprecated See bpo 8990 PyArg_Parse functions t format has been removed use s or s instead w and w formats has been removed use w instead The PyCObject type deprecated in 3 1 has been removed To wrap opaque C pointers in Python objects the PyCapsule API should be used instead the new type has a well defined interface for passing typing safety information and a less complicated signature for calling,en
2332, a destructor The sys setfilesystemencoding function was removed because it had a flawed design The random seed function and method now salt string seeds with an sha512 hash function To access the previous version of seed in order to reproduce Python 3 1 sequences set the version argument to 1 random seed s version 1 The previously deprecated string maketrans function has been removed in favor of the static methods bytes maketrans and bytearray maketrans This change solves the confusion around which types were supported by the string module Now str bytes and bytearray each have their own maketrans and translate methods with intermediate translation tables of the appropriate type Contributed by Georg Brandl bpo 5675 The previously deprecated contextlib nested function has been removed in favor of a plain with statement which can accept multiple context managers The latter technique is faster because it is built in and it does a better job finalizing multiple context managers when one of them raises an exception with open mylog txt as infile open a out w as outfile for line in infile if critical in line outfile write line Contributed by Georg Brandl and Mattias Brändström appspot issue 53094 struct pack now only allows bytes for the s string pack code Formerly it would accept text arguments and implicitly encode them to bytes using UTF 8 This was problematic because it made assumptions about the correct encoding and because a variable length encoding can fail when writing to fixed length segment of a structure Code such as struct pack 6sHHBBB GIF87a x y should be rewritten with to use bytes instead of text struct pack 6sHHBBB b GIF87a x y Discovered by David Beazley and fixed by Victor Stinner bpo 10783 The xml etree ElementTree class now raises an xml etree ElementTree ParseError when a parse fails Previously it raised an xml parsers expat ExpatError The new longer str value on floats may break doctests which rely on the old output format In subprocess Popen the default value for close_fds is now True under Unix under Windows it is True if the three standard streams are set to None False otherwise Previously close_fds was always False by default which produced difficult to solve bugs or race conditions when open file descriptors would leak into the child process Support for legacy HTTP 0 9 has been removed from urllib request and http client Such support is still present on the server side in http server Contributed by Antoine Pitrou bpo 10711 SSL sockets in timeout mode now raise socket timeout when a timeout occurs rather than a generic SSLError Contributed by Antoine Pitrou bpo 10272 The misleading functions PyEval_AcquireLock and PyEval_ReleaseLock have been officially deprecated The thread state aware APIs such as PyEval_SaveThread and PyEval_RestoreThread should be used instead Due to security risks asyncore handle_accept has been deprecated and a new function asyncore handle_accepted was added to replace it Contributed by Giampaolo Rodola in bpo 6706 Due to the new GIL implementation PyEval_InitThreads cannot be called before Py_Initialize anymore,en
2333,itertools Functions creating iterators for efficient looping This module implements a number of iterator building blocks inspired by constructs from APL Haskell and SML Each has been recast in a form suitable for Python The module standardizes a core set of fast memory efficient tools that are useful by themselves or in combination Together they form an iterator algebra making it possible to construct specialized tools succinctly and efficiently in pure Python For instance SML provides a tabulation tool tabulate f which produces a sequence f 0 f 1 The same effect can be achieved in Python by combining map and count to form map f count These tools and their built in counterparts also work well with the high speed functions in the operator module For example the multiplication operator can be mapped across two vectors to form an efficient dot product sum starmap operator mul zip vec1 vec2 strict True Infinite iterators Iterator Arguments Results Example count start step start start step start 2 step count 10 10 11 12 13 14 cycle p p0 p1 plast p0 p1 cycle ABCD A B C D A B C D repeat elem n elem elem elem endlessly or up to n times repeat 10 3 10 10 10 Iterators terminating on the shortest input sequence Iterator Arguments Results Example accumulate p func p0 p0 p1 p0 p1 p2 accumulate 1 2 3 4 5 1 3 6 10 15 batched p n p0 p1 p_n 1 batched ABCDEFG n 3 ABC DEF G chain p q p0 p1 plast q0 q1 chain ABC DEF A B C D E F chain from_iterable iterable p0 p1 plast q0 q1 chain from_iterable ABC DEF A B C D E F compress data selectors d 0 if s 0 d 1 if s 1 compress ABCDEF 1 0 1 0 1 1 A C E F dropwhile predicate seq seq n seq n 1 starting when predicate fails dropwhile lambda x x 5 1 4 6 4 1 6 4 1 filterfalse predicate seq elements of seq where predicate elem fails filterfalse lambda x x 2 range 10 0 2 4 6 8 groupby iterable key sub iterators grouped by value of key v islice seq start stop step elements from seq start stop step islice ABCDEFG 2 None C D E F G pairwise iterable p 0 p 1 p 1 p 2 pairwise ABCDEFG AB BC CD DE EF FG starmap func seq func seq 0 func seq 1 starmap pow 2 5 3 2 10 3 32 9 1000 takewhile predicate seq seq 0 seq 1 until predicate fails takewhile lambda x x 5 1 4 6 4 1 1 4 tee it n it1 it2 itn splits one iterator into n zip_longest p q p 0 q 0 p 1 q 1 zip_longest ABCD xy fillvalue Ax By C D Combinatoric iterators Iterator Arguments Results product p q repeat 1 cartesian product equivalent to a nested for loop permutations p r r length tuples all possible orderings no repeated elements combinations p r r length tuples in sorted order no repeated elements combinations_with_replacement p r r length tuples in sorted order with repeated elements Examples Results product ABCD repeat 2 AA AB AC AD BA BB BC BD CA CB CC CD DA DB DC DD permutations ABCD 2 AB AC AD BA BC BD CA CB CD DA DB DC combinations ABCD 2 AB AC AD BC BD CD combinations_with_replacement ABCD 2 AA AB AC AD BB BC BD CC CD DD Itertool Functions The following module functions all construct and return iterators Some provide streams of infinite length so they should only be accessed by functions or loops that truncate the stream itertools accumulate iterable func initial None Make an iterator that returns accumulated sums or accumulated results of other binary functions specified via the optional func argument If func is supplied it should be a function of two arguments Elements of the input iterable may be any type that can be accepted as arguments to func For example with the default operation of addition elements may be any addable type including Decimal or Fraction Usually the number of elements output matches the input iterable However if the keyword argument initial is provided the accumulation leads off with the initial value so that the output has one more element than the input iterable Roughly equivalent to def accumulate iterable func operator add initial None Return running totals accumulate 1 2 3 4 5 1 3 6 10 15 accumulate 1 2 3 4 5 initial 100 100 101 103 106 110 115 accumulate 1 2 3 4 5 operator mul 1 2 6 24 120 it iter iterable total initial if init,en
2334,ial is None try total next it except StopIteration return yield total for element in it total func total element yield total There are a number of uses for the func argument It can be set to min for a running minimum max for a running maximum or operator mul for a running product Amortization tables can be built by accumulating interest and applying payments data 3 4 6 2 1 9 0 7 5 8 list accumulate data operator mul running product 3 12 72 144 144 1296 0 0 0 0 list accumulate data max running maximum 3 4 6 6 6 9 9 9 9 9 Amortize a 5 loan of 1000 with 10 annual payments of 90 account_update lambda bal pmt round bal 1 05 pmt list accumulate repeat 90 10 account_update initial 1_000 1000 960 918 874 828 779 728 674 618 559 497 See functools reduce for a similar function that returns only the final accumulated value New in version 3 2 Changed in version 3 3 Added the optional func parameter Changed in version 3 8 Added the optional initial parameter itertools batched iterable n Batch data from the iterable into tuples of length n The last batch may be shorter than n Loops over the input iterable and accumulates data into tuples up to size n The input is consumed lazily just enough to fill a batch The result is yielded as soon as the batch is full or when the input iterable is exhausted flattened_data roses red violets blue sugar sweet unflattened list batched flattened_data 2 unflattened roses red violets blue sugar sweet for batch in batched ABCDEFG 3 print batch A B C D E F G Roughly equivalent to def batched iterable n batched ABCDEFG 3 ABC DEF G if n 1 raise ValueError n must be at least one it iter iterable while batch tuple islice it n yield batch New in version 3 12 itertools chain iterables Make an iterator that returns elements from the first iterable until it is exhausted then proceeds to the next iterable until all of the iterables are exhausted Used for treating consecutive sequences as a single sequence Roughly equivalent to def chain iterables chain ABC DEF A B C D E F for it in iterables for element in it yield element classmethod chain from_iterable iterable Alternate constructor for chain Gets chained inputs from a single iterable argument that is evaluated lazily Roughly equivalent to def from_iterable iterables chain from_iterable ABC DEF A B C D E F for it in iterables for element in it yield element itertools combinations iterable r Return r length subsequences of elements from the input iterable The combination tuples are emitted in lexicographic ordering according to the order of the input iterable So if the input iterable is sorted the output tuples will be produced in sorted order Elements are treated as unique based on their position not on their value So if the input elements are unique there will be no repeated values in each combination Roughly equivalent to def combinations iterable r combinations ABCD 2 AB AC AD BC BD CD combinations range 4 3 012 013 023 123 pool tuple iterable n len pool if r n return indices list range r yield tuple pool i for i in indices while True for i in reversed range r if indices i i n r break else return indices i 1 for j in range i 1 r indices j indices j 1 1 yield tuple pool i for i in indices The code for combinations can be also expressed as a subsequence of permutations after filtering entries where the elements are not in sorted order according to their position in the input pool def combinations iterable r pool tuple iterable n len pool for indices in permutations range n r if sorted indices list indices yield tuple pool i for i in indices The number of items returned is n r n r when 0 r n or zero when r n itertools combinations_with_replacement iterable r Return r length subsequences of elements from the input iterable allowing individual elements to be repeated more than once The combination tuples are emitted in lexicographic ordering according to the order of the input iterable So if the input iterable is sorted the output tuples will be produced in sorted order Elements are treated as unique based on their position not on their value So if the input eleme,en
2335,nts are unique the generated combinations will also be unique Roughly equivalent to def combinations_with_replacement iterable r combinations_with_replacement ABC 2 AA AB AC BB BC CC pool tuple iterable n len pool if not n and r return indices 0 r yield tuple pool i for i in indices while True for i in reversed range r if indices i n 1 break else return indices i indices i 1 r i yield tuple pool i for i in indices The code for combinations_with_replacement can be also expressed as a subsequence of product after filtering entries where the elements are not in sorted order according to their position in the input pool def combinations_with_replacement iterable r pool tuple iterable n len pool for indices in product range n repeat r if sorted indices list indices yield tuple pool i for i in indices The number of items returned is n r 1 r n 1 when n 0 New in version 3 1 itertools compress data selectors Make an iterator that filters elements from data returning only those that have a corresponding element in selectors that evaluates to True Stops when either the data or selectors iterables has been exhausted Roughly equivalent to def compress data selectors compress ABCDEF 1 0 1 0 1 1 A C E F return d for d s in zip data selectors if s New in version 3 1 itertools count start 0 step 1 Make an iterator that returns evenly spaced values starting with number start Often used as an argument to map to generate consecutive data points Also used with zip to add sequence numbers Roughly equivalent to def count start 0 step 1 count 10 10 11 12 13 14 count 2 5 0 5 2 5 3 0 3 5 n start while True yield n n step When counting with floating point numbers better accuracy can sometimes be achieved by substituting multiplicative code such as start step i for i in count Changed in version 3 1 Added step argument and allowed non integer arguments itertools cycle iterable Make an iterator returning elements from the iterable and saving a copy of each When the iterable is exhausted return elements from the saved copy Repeats indefinitely Roughly equivalent to def cycle iterable cycle ABCD A B C D A B C D A B C D saved for element in iterable yield element saved append element while saved for element in saved yield element Note this member of the toolkit may require significant auxiliary storage depending on the length of the iterable itertools dropwhile predicate iterable Make an iterator that drops elements from the iterable as long as the predicate is true afterwards returns every element Note the iterator does not produce any output until the predicate first becomes false so it may have a lengthy start up time Roughly equivalent to def dropwhile predicate iterable dropwhile lambda x x 5 1 4 6 4 1 6 4 1 iterable iter iterable for x in iterable if not predicate x yield x break for x in iterable yield x itertools filterfalse predicate iterable Make an iterator that filters elements from iterable returning only those for which the predicate is false If predicate is None return the items that are false Roughly equivalent to def filterfalse predicate iterable filterfalse lambda x x 2 range 10 0 2 4 6 8 if predicate is None predicate bool for x in iterable if not predicate x yield x itertools groupby iterable key None Make an iterator that returns consecutive keys and groups from the iterable The key is a function computing a key value for each element If not specified or is None key defaults to an identity function and returns the element unchanged Generally the iterable needs to already be sorted on the same key function The operation of groupby is similar to the uniq filter in Unix It generates a break or new group every time the value of the key function changes which is why it is usually necessary to have sorted the data using the same key function That behavior differs from SQL s GROUP BY which aggregates common elements regardless of their input order The returned group is itself an iterator that shares the underlying iterable with groupby Because the source is shared when the groupby object is advanced the previous group is no longer visible,en
2336, So if that data is needed later it should be stored as a list groups uniquekeys data sorted data key keyfunc for k g in groupby data keyfunc groups append list g Store group iterator as a list uniquekeys append k groupby is roughly equivalent to class groupby k for k g in groupby AAAABBBCCDAABBB A B C D A B list g for k g in groupby AAAABBBCCD AAAA BBB CC D def __init__ self iterable key None if key is None key lambda x x self keyfunc key self it iter iterable self tgtkey self currkey self currvalue object def __iter__ self return self def __next__ self self id object while self currkey self tgtkey self currvalue next self it Exit on StopIteration self currkey self keyfunc self currvalue self tgtkey self currkey return self currkey self _grouper self tgtkey self id def _grouper self tgtkey id while self id is id and self currkey tgtkey yield self currvalue try self currvalue next self it except StopIteration return self currkey self keyfunc self currvalue itertools islice iterable stop itertools islice iterable start stop step Make an iterator that returns selected elements from the iterable If start is non zero then elements from the iterable are skipped until start is reached Afterward elements are returned consecutively unless step is set higher than one which results in items being skipped If stop is None then iteration continues until the iterator is exhausted if at all otherwise it stops at the specified position If start is None then iteration starts at zero If step is None then the step defaults to one Unlike regular slicing islice does not support negative values for start stop or step Can be used to extract related fields from data where the internal structure has been flattened for example a multi line report may list a name field on every third line Roughly equivalent to def islice iterable args islice ABCDEFG 2 A B islice ABCDEFG 2 4 C D islice ABCDEFG 2 None C D E F G islice ABCDEFG 0 None 2 A C E G s slice args start stop step s start or 0 s stop or sys maxsize s step or 1 it iter range start stop step try nexti next it except StopIteration Consume iterable up to the start position for i element in zip range start iterable pass return try for i element in enumerate iterable if i nexti yield element nexti next it except StopIteration Consume to stop for i element in zip range i 1 stop iterable pass itertools pairwise iterable Return successive overlapping pairs taken from the input iterable The number of 2 tuples in the output iterator will be one fewer than the number of inputs It will be empty if the input iterable has fewer than two values Roughly equivalent to def pairwise iterable pairwise ABCDEFG AB BC CD DE EF FG a b tee iterable next b None return zip a b New in version 3 10 itertools permutations iterable r None Return successive r length permutations of elements in the iterable If r is not specified or is None then r defaults to the length of the iterable and all possible full length permutations are generated The permutation tuples are emitted in lexicographic order according to the order of the input iterable So if the input iterable is sorted the output tuples will be produced in sorted order Elements are treated as unique based on their position not on their value So if the input elements are unique there will be no repeated values within a permutation Roughly equivalent to def permutations iterable r None permutations ABCD 2 AB AC AD BA BC BD CA CB CD DA DB DC permutations range 3 012 021 102 120 201 210 pool tuple iterable n len pool r n if r is None else r if r n return indices list range n cycles list range n n r 1 yield tuple pool i for i in indices r while n for i in reversed range r cycles i 1 if cycles i 0 indices i indices i 1 indices i i 1 cycles i n i else j cycles i indices i indices j indices j indices i yield tuple pool i for i in indices r break else return The code for permutations can be also expressed as a subsequence of product filtered to exclude entries with repeated elements those from the same position in the input pool def permutations iterable r None pool tuple iterab,en
2337,le n len pool r n if r is None else r for indices in product range n repeat r if len set indices r yield tuple pool i for i in indices The number of items returned is n n r when 0 r n or zero when r n itertools product iterables repeat 1 Cartesian product of input iterables Roughly equivalent to nested for loops in a generator expression For example product A B returns the same as x y for x in A for y in B The nested loops cycle like an odometer with the rightmost element advancing on every iteration This pattern creates a lexicographic ordering so that if the input s iterables are sorted the product tuples are emitted in sorted order To compute the product of an iterable with itself specify the number of repetitions with the optional repeat keyword argument For example product A repeat 4 means the same as product A A A A This function is roughly equivalent to the following code except that the actual implementation does not build up intermediate results in memory def product args repeat 1 product ABCD xy Ax Ay Bx By Cx Cy Dx Dy product range 2 repeat 3 000 001 010 011 100 101 110 111 pools tuple pool for pool in args repeat result for pool in pools result x y for x in result for y in pool for prod in result yield tuple prod Before product runs it completely consumes the input iterables keeping pools of values in memory to generate the products Accordingly it is only useful with finite inputs itertools repeat object times Make an iterator that returns object over and over again Runs indefinitely unless the times argument is specified Roughly equivalent to def repeat object times None repeat 10 3 10 10 10 if times is None while True yield object else for i in range times yield object A common use for repeat is to supply a stream of constant values to map or zip list map pow range 10 repeat 2 0 1 4 9 16 25 36 49 64 81 itertools starmap function iterable Make an iterator that computes the function using arguments obtained from the iterable Used instead of map when argument parameters are already grouped in tuples from a single iterable when the data has been pre zipped The difference between map and starmap parallels the distinction between function a b and function c Roughly equivalent to def starmap function iterable starmap pow 2 5 3 2 10 3 32 9 1000 for args in iterable yield function args itertools takewhile predicate iterable Make an iterator that returns elements from the iterable as long as the predicate is true Roughly equivalent to def takewhile predicate iterable takewhile lambda x x 5 1 4 6 4 1 1 4 for x in iterable if predicate x yield x else break Note the element that first fails the predicate condition is consumed from the input iterator and there is no way to access it This could be an issue if an application wants to further consume the input iterator after takewhile has been run to exhaustion To work around this problem consider using more iterools before_and_after instead itertools tee iterable n 2 Return n independent iterators from a single iterable The following Python code helps explain what tee does although the actual implementation is more complex and uses only a single underlying FIFO first in first out queue def tee iterable n 2 it iter iterable deques collections deque for i in range n def gen mydeque while True if not mydeque when the local deque is empty try newval next it fetch a new value and except StopIteration return for d in deques load it to all the deques d append newval yield mydeque popleft return tuple gen d for d in deques Once a tee has been created the original iterable should not be used anywhere else otherwise the iterable could get advanced without the tee objects being informed tee iterators are not threadsafe A RuntimeError may be raised when simultaneously using iterators returned by the same tee call even if the original iterable is threadsafe This itertool may require significant auxiliary storage depending on how much temporary data needs to be stored In general if one iterator uses most or all of the data before another iterator starts it is faster to use list instead ,en
2338,of tee itertools zip_longest iterables fillvalue None Make an iterator that aggregates elements from each of the iterables If the iterables are of uneven length missing values are filled in with fillvalue Iteration continues until the longest iterable is exhausted Roughly equivalent to def zip_longest args fillvalue None zip_longest ABCD xy fillvalue Ax By C D iterators iter it for it in args num_active len iterators if not num_active return while True values for i it in enumerate iterators try value next it except StopIteration num_active 1 if not num_active return iterators i repeat fillvalue value fillvalue values append value yield tuple values If one of the iterables is potentially infinite then the zip_longest function should be wrapped with something that limits the number of calls for example islice or takewhile If not specified fillvalue defaults to None Itertools Recipes This section shows recipes for creating an extended toolset using the existing itertools as building blocks The primary purpose of the itertools recipes is educational The recipes show various ways of thinking about individual tools for example that chain from_iterable is related to the concept of flattening The recipes also give ideas about ways that the tools can be combined for example how starmap and repeat can work together The recipes also show patterns for using itertools with the operator and collections modules as well as with the built in itertools such as map filter reversed and enumerate A secondary purpose of the recipes is to serve as an incubator The accumulate compress and pairwise itertools started out as recipes Currently the sliding_window iter_index and sieve recipes are being tested to see whether they prove their worth Substantially all of these recipes and many many others can be installed from the more itertools project found on the Python Package Index python m pip install more itertools Many of the recipes offer the same high performance as the underlying toolset Superior memory performance is kept by processing elements one at a time rather than bringing the whole iterable into memory all at once Code volume is kept small by linking the tools together in a functional style High speed is retained by preferring vectorized building blocks over the use of for loops and generators which incur interpreter overhead import collections import functools import math import operator import random def take n iterable Return first n items of the iterable as a list return list islice iterable n def prepend value iterable Prepend a single value in front of an iterable prepend 1 2 3 4 1 2 3 4 return chain value iterable def tabulate function start 0 Return function 0 function 1 return map function count start def repeatfunc func times None args Repeat calls to func with specified arguments Example repeatfunc random random if times is None return starmap func repeat args return starmap func repeat args times def flatten list_of_lists Flatten one level of nesting return chain from_iterable list_of_lists def ncycles iterable n Returns the sequence elements n times return chain from_iterable repeat tuple iterable n def tail n iterable Return an iterator over the last n items tail 3 ABCDEFG E F G return iter collections deque iterable maxlen n def consume iterator n None Advance the iterator n steps ahead If n is None consume entirely Use functions that consume iterators at C speed if n is None feed the entire iterator into a zero length deque collections deque iterator maxlen 0 else advance to the empty slice starting at position n next islice iterator n n None def nth iterable n default None Returns the nth item or a default value return next islice iterable n None default def quantify iterable predicate bool Given a predicate that returns True or False count the True results return sum map predicate iterable def first_true iterable default False predicate None Returns the first true value or the default if there is no true value first_true a b c x a or b or c or x first_true a b x f a if f a else b if f b else x return next filter predi,en
2339,cate iterable default def all_equal iterable key None Returns True if all the elements are equal to each other return len take 2 groupby iterable key 1 def unique_justseen iterable key None List unique elements preserving order Remember only the element just seen unique_justseen AAAABBBCCDAABBB A B C D A B unique_justseen ABBcCAD str casefold A B c A D if key is None return map operator itemgetter 0 groupby iterable return map next map operator itemgetter 1 groupby iterable key def unique_everseen iterable key None List unique elements preserving order Remember all elements ever seen unique_everseen AAAABBBCCDAABBB A B C D unique_everseen ABBcCAD str casefold A B c D seen set if key is None for element in filterfalse seen __contains__ iterable seen add element yield element else for element in iterable k key element if k not in seen seen add k yield element def sliding_window iterable n Collect data into overlapping fixed length chunks or blocks sliding_window ABCDEFG 4 ABCD BCDE CDEF DEFG it iter iterable window collections deque islice it n 1 maxlen n for x in it window append x yield tuple window def grouper iterable n incomplete fill fillvalue None Collect data into non overlapping fixed length chunks or blocks grouper ABCDEFG 3 fillvalue x ABC DEF Gxx grouper ABCDEFG 3 incomplete strict ABC DEF ValueError grouper ABCDEFG 3 incomplete ignore ABC DEF iterators iter iterable n match incomplete case fill return zip_longest iterators fillvalue fillvalue case strict return zip iterators strict True case ignore return zip iterators case _ raise ValueError Expected fill strict or ignore def roundrobin iterables Visit input iterables in a cycle until each is exhausted roundrobin ABC D EF A D E B F C Algorithm credited to George Sakkis iterators map iter iterables for num_active in range len iterables 0 1 iterators cycle islice iterators num_active yield from map next iterators def partition predicate iterable Partition entries into false entries and true entries If predicate is slow consider wrapping it with functools lru_cache partition is_odd range 10 0 2 4 6 8 and 1 3 5 7 9 t1 t2 tee iterable return filterfalse predicate t1 filter predicate t2 def subslices seq Return all contiguous non empty subslices of a sequence subslices ABCD A AB ABC ABCD B BC BCD C CD D slices starmap slice combinations range len seq 1 2 return map operator getitem repeat seq slices def iter_index iterable value start 0 stop None Return indices where a value occurs in a sequence or iterable iter_index AABCADEAF A 0 1 4 7 seq_index getattr iterable index None if seq_index is None Path for general iterables it islice iterable start stop for i element in enumerate it start if element is value or element value yield i else Path for sequences with an index method stop len iterable if stop is None else stop i start try while True yield i seq_index value i stop i 1 except ValueError pass def iter_except func exception first None Call a function repeatedly until an exception is raised Converts a call until exception interface to an iterator interface iter_except d popitem KeyError non blocking dictionary iterator try if first is not None yield first while True yield func except exception pass The following recipes have a more mathematical flavor def powerset iterable powerset 1 2 3 1 2 3 1 2 1 3 2 3 1 2 3 s list iterable return chain from_iterable combinations s r for r in range len s 1 def sum_of_squares iterable Add up the squares of the input values sum_of_squares 10 20 30 1400 return math sumprod tee iterable def reshape matrix cols Reshape a 2 D matrix to have a given number of columns reshape 0 1 2 3 4 5 3 0 1 2 3 4 5 return batched chain from_iterable matrix cols def transpose matrix Swap the rows and columns of a 2 D matrix transpose 1 2 3 11 22 33 1 11 2 22 3 33 return zip matrix strict True def matmul m1 m2 Multiply two matrices matmul 7 5 3 5 2 5 7 9 49 80 41 60 n len m2 0 return batched starmap math sumprod product m1 transpose m2 n def convolve signal kernel Discrete linear convolution of two iterables Equivalent to polynomial multiplication C,en
2340,onvolutions are mathematically commutative however the inputs are evaluated differently The signal is consumed lazily and can be infinite The kernel is fully consumed before the calculations begin Article https betterexplained com articles intuitive convolution Video https www youtube com watch v KuXjwB4LzSA convolve 1 1 20 1 3 1 4 17 60 convolve data 0 25 0 25 0 25 0 25 Moving average blur convolve data 1 2 0 1 2 1st derivative estimate convolve data 1 2 1 2nd derivative estimate kernel tuple kernel 1 n len kernel padded_signal chain repeat 0 n 1 signal repeat 0 n 1 windowed_signal sliding_window padded_signal n return map math sumprod repeat kernel windowed_signal def polynomial_from_roots roots Compute a polynomial s coefficients from its roots x 5 x 4 x 3 expands to x³ 4x² 17x 60 polynomial_from_roots 5 4 3 1 4 17 60 factors zip repeat 1 map operator neg roots return list functools reduce convolve factors 1 def polynomial_eval coefficients x Evaluate a polynomial at a specific value Computes with better numeric stability than Horner s method Evaluate x³ 4x² 17x 60 at x 5 polynomial_eval 1 4 17 60 x 5 0 n len coefficients if not n return type x 0 powers map pow repeat x reversed range n return math sumprod coefficients powers def polynomial_derivative coefficients Compute the first derivative of a polynomial f x x³ 4x² 17x 60 f x 3x² 8x 17 polynomial_derivative 1 4 17 60 3 8 17 n len coefficients powers reversed range 1 n return list map operator mul coefficients powers def sieve n Primes less than n sieve 30 2 3 5 7 11 13 17 19 23 29 if n 2 yield 2 start 3 data bytearray 0 1 n 2 limit math isqrt n 1 for p in iter_index data 1 start limit yield from iter_index data 1 start p p data p p n p p bytes len range p p n p p start p p yield from iter_index data 1 start def factor n Prime factors of n factor 99 3 3 11 factor 1_000_000_000_000_007 47 59 360620266859 factor 1_000_000_000_000_403 1000000000000403 for prime in sieve math isqrt n 1 while not n prime yield prime n prime if n 1 return if n 1 yield n def totient n Count of natural numbers up to n that are coprime to n https mathworld wolfram com TotientFunction html totient 12 4 because len 1 5 7 11 4 for p in unique_justseen factor n n n p return n,en
2341,What s New In Python 3 7 Editor Elvis Pranskevichus elvis magic io This article explains the new features in Python 3 7 compared to 3 6 Python 3 7 was released on June 27 2018 For full details see the changelog Summary Release Highlights New syntax features PEP 563 postponed evaluation of type annotations Backwards incompatible syntax changes async and await are now reserved keywords New library modules contextvars PEP 567 Context Variables dataclasses PEP 557 Data Classes importlib resources New built in features PEP 553 the new breakpoint function Python data model improvements PEP 562 customization of access to module attributes PEP 560 core support for typing module and generic types the insertion order preservation nature of dict objects has been declared to be an official part of the Python language spec Significant improvements in the standard library The asyncio module has received new features significant usability and performance improvements The time module gained support for functions with nanosecond resolution CPython implementation improvements Avoiding the use of ASCII as a default text encoding PEP 538 legacy C locale coercion PEP 540 forced UTF 8 runtime mode PEP 552 deterministic pycs New Python Development Mode PEP 565 improved DeprecationWarning handling C API improvements PEP 539 new C API for thread local storage Documentation improvements PEP 545 Python documentation translations New documentation translations Japanese French and Korean This release features notable performance improvements in many areas The Optimizations section lists them in detail For a list of changes that may affect compatibility with previous Python releases please refer to the Porting to Python 3 7 section New Features PEP 563 Postponed Evaluation of Annotations The advent of type hints in Python uncovered two glaring usability issues with the functionality of annotations added in PEP 3107 and refined further in PEP 526 annotations could only use names which were already available in the current scope in other words they didn t support forward references of any kind and annotating source code had adverse effects on startup time of Python programs Both of these issues are fixed by postponing the evaluation of annotations Instead of compiling code which executes expressions in annotations at their definition time the compiler stores the annotation in a string form equivalent to the AST of the expression in question If needed annotations can be resolved at runtime using typing get_type_hints In the common case where this is not required the annotations are cheaper to store since short strings are interned by the interpreter and make startup time faster Usability wise annotations now support forward references making the following syntax valid class C classmethod def from_string cls source str C def validate_b self obj B bool class B Since this change breaks compatibility the new behavior needs to be enabled on a per module basis in Python 3 7 using a __future__ import from __future__ import annotations It will become the default in Python 3 10 See also PEP 563 Postponed evaluation of annotations PEP written and implemented by Łukasz Langa PEP 538 Legacy C Locale Coercion An ongoing challenge within the Python 3 series has been determining a sensible default strategy for handling the 7 bit ASCII text encoding assumption currently implied by the use of the default C or POSIX locale on non Windows platforms PEP 538 updates the default interpreter command line interface to automatically coerce that locale to an available UTF 8 based locale as described in the documentation of the new PYTHONCOERCECLOCALE environment variable Automatically setting LC_CTYPE this way means that both the core interpreter and locale aware C extensions such as readline will assume the use of UTF 8 as the default text encoding rather than ASCII The platform support definition in PEP 11 has also been updated to limit full text handling support to suitably configured non ASCII based locales As part of this change the default error handler for stdin and stdou,en
2342,t is now surrogateescape rather than strict when using any of the defined coercion target locales currently C UTF 8 C utf8 and UTF 8 The default error handler for stderr continues to be backslashreplace regardless of locale Locale coercion is silent by default but to assist in debugging potentially locale related integration problems explicit warnings emitted directly on stderr can be requested by setting PYTHONCOERCECLOCALE warn This setting will also cause the Python runtime to emit a warning if the legacy C locale remains active when the core interpreter is initialized While PEP 538 s locale coercion has the benefit of also affecting extension modules such as GNU readline as well as child processes including those running non Python applications and older versions of Python it has the downside of requiring that a suitable target locale be present on the running system To better handle the case where no suitable target locale is available as occurs on RHEL CentOS 7 for example Python 3 7 also implements PEP 540 Forced UTF 8 Runtime Mode See also PEP 538 Coercing the legacy C locale to a UTF 8 based locale PEP written and implemented by Nick Coghlan PEP 540 Forced UTF 8 Runtime Mode The new X utf8 command line option and PYTHONUTF8 environment variable can be used to enable the Python UTF 8 Mode When in UTF 8 mode CPython ignores the locale settings and uses the UTF 8 encoding by default The error handlers for sys stdin and sys stdout streams are set to surrogateescape The forced UTF 8 mode can be used to change the text handling behavior in an embedded Python interpreter without changing the locale settings of an embedding application While PEP 540 s UTF 8 mode has the benefit of working regardless of which locales are available on the running system it has the downside of having no effect on extension modules such as GNU readline child processes running non Python applications and child processes running older versions of Python To reduce the risk of corrupting text data when communicating with such components Python 3 7 also implements PEP 540 Forced UTF 8 Runtime Mode The UTF 8 mode is enabled by default when the locale is C or POSIX and the PEP 538 locale coercion feature fails to change it to a UTF 8 based alternative whether that failure is due to PYTHONCOERCECLOCALE 0 being set LC_ALL being set or the lack of a suitable target locale See also PEP 540 Add a new UTF 8 mode PEP written and implemented by Victor Stinner PEP 553 Built in breakpoint Python 3 7 includes the new built in breakpoint function as an easy and consistent way to enter the Python debugger Built in breakpoint calls sys breakpointhook By default the latter imports pdb and then calls pdb set_trace but by binding sys breakpointhook to the function of your choosing breakpoint can enter any debugger Additionally the environment variable PYTHONBREAKPOINT can be set to the callable of your debugger of choice Set PYTHONBREAKPOINT 0 to completely disable built in breakpoint See also PEP 553 Built in breakpoint PEP written and implemented by Barry Warsaw PEP 539 New C API for Thread Local Storage While Python provides a C API for thread local storage support the existing Thread Local Storage TLS API has used int to represent TLS keys across all platforms This has not generally been a problem for officially support platforms but that is neither POSIX compliant nor portable in any practical sense PEP 539 changes this by providing a new Thread Specific Storage TSS API to CPython which supersedes use of the existing TLS API within the CPython interpreter while deprecating the existing API The TSS API uses a new type Py_tss_t instead of int to represent TSS keys an opaque type the definition of which may depend on the underlying TLS implementation Therefore this will allow to build CPython on platforms where the native TLS key is defined in a way that cannot be safely cast to int Note that on platforms where the native TLS key is defined in a way that cannot be safely cast to int all functions of the existing TLS API will be no op and immediately return failu,en
2343,re This indicates clearly that the old API is not supported on platforms where it cannot be used reliably and that no effort will be made to add such support See also PEP 539 A New C API for Thread Local Storage in CPython PEP written by Erik M Bray implementation by Masayuki Yamamoto PEP 562 Customization of Access to Module Attributes Python 3 7 allows defining __getattr__ on modules and will call it whenever a module attribute is otherwise not found Defining __dir__ on modules is now also allowed A typical example of where this may be useful is module attribute deprecation and lazy loading See also PEP 562 Module __getattr__ and __dir__ PEP written and implemented by Ivan Levkivskyi PEP 564 New Time Functions With Nanosecond Resolution The resolution of clocks in modern systems can exceed the limited precision of a floating point number returned by the time time function and its variants To avoid loss of precision PEP 564 adds six new nanosecond variants of the existing timer functions to the time module time clock_gettime_ns time clock_settime_ns time monotonic_ns time perf_counter_ns time process_time_ns time time_ns The new functions return the number of nanoseconds as an integer value Measurements show that on Linux and Windows the resolution of time time_ns is approximately 3 times better than that of time time See also PEP 564 Add new time functions with nanosecond resolution PEP written and implemented by Victor Stinner PEP 565 Show DeprecationWarning in __main__ The default handling of DeprecationWarning has been changed such that these warnings are once more shown by default but only when the code triggering them is running directly in the __main__ module As a result developers of single file scripts and those using Python interactively should once again start seeing deprecation warnings for the APIs they use but deprecation warnings triggered by imported application library and framework modules will continue to be hidden by default As a result of this change the standard library now allows developers to choose between three different deprecation warning behaviours FutureWarning always displayed by default recommended for warnings intended to be seen by application end users e g for deprecated application configuration settings DeprecationWarning displayed by default only in __main__ and when running tests recommended for warnings intended to be seen by other Python developers where a version upgrade may result in changed behaviour or an error PendingDeprecationWarning displayed by default only when running tests intended for cases where a future version upgrade will change the warning category to DeprecationWarning or FutureWarning Previously both DeprecationWarning and PendingDeprecationWarning were only visible when running tests which meant that developers primarily writing single file scripts or using Python interactively could be surprised by breaking changes in the APIs they used See also PEP 565 Show DeprecationWarning in __main__ PEP written and implemented by Nick Coghlan PEP 560 Core Support for typing module and Generic Types Initially PEP 484 was designed in such way that it would not introduce any changes to the core CPython interpreter Now type hints and the typing module are extensively used by the community so this restriction is removed The PEP introduces two special methods __class_getitem__ and __mro_entries__ these methods are now used by most classes and special constructs in typing As a result the speed of various operations with types increased up to 7 times the generic types can be used without metaclass conflicts and several long standing bugs in typing module are fixed See also PEP 560 Core support for typing module and generic types PEP written and implemented by Ivan Levkivskyi PEP 552 Hash based pyc Files Python has traditionally checked the up to dateness of bytecode cache files i e pyc files by comparing the source metadata last modified timestamp and size with source metadata saved in the cache file header when it was generated While effective this invalidation method has its,en
2344, drawbacks When filesystem timestamps are too coarse Python can miss source updates leading to user confusion Additionally having a timestamp in the cache file is problematic for build reproducibility and content based build systems PEP 552 extends the pyc format to allow the hash of the source file to be used for invalidation instead of the source timestamp Such pyc files are called hash based By default Python still uses timestamp based invalidation and does not generate hash based pyc files at runtime Hash based pyc files may be generated with py_compile or compileall Hash based pyc files come in two variants checked and unchecked Python validates checked hash based pyc files against the corresponding source files at runtime but doesn t do so for unchecked hash based pycs Unchecked hash based pyc files are a useful performance optimization for environments where a system external to Python e g the build system is responsible for keeping pyc files up to date See Cached bytecode invalidation for more information See also PEP 552 Deterministic pycs PEP written and implemented by Benjamin Peterson PEP 545 Python Documentation Translations PEP 545 describes the process of creating and maintaining Python documentation translations Three new translations have been added Japanese https docs python org ja French https docs python org fr Korean https docs python org ko See also PEP 545 Python Documentation Translations PEP written and implemented by Julien Palard Inada Naoki and Victor Stinner Python Development Mode X dev The new X dev command line option or the new PYTHONDEVMODE environment variable can be used to enable Python Development Mode When in development mode Python performs additional runtime checks that are too expensive to be enabled by default See Python Development Mode documentation for the full description Other Language Changes An await expression and comprehensions containing an async for clause were illegal in the expressions in formatted string literals due to a problem with the implementation In Python 3 7 this restriction was lifted More than 255 arguments can now be passed to a function and a function can now have more than 255 parameters Contributed by Serhiy Storchaka in bpo 12844 and bpo 18896 bytes fromhex and bytearray fromhex now ignore all ASCII whitespace not only spaces Contributed by Robert Xiao in bpo 28927 str bytes and bytearray gained support for the new isascii method which can be used to test if a string or bytes contain only the ASCII characters Contributed by INADA Naoki in bpo 32677 ImportError now displays module name and module __file__ path when from import fails Contributed by Matthias Bussonnier in bpo 29546 Circular imports involving absolute imports with binding a submodule to a name are now supported Contributed by Serhiy Storchaka in bpo 30024 object __format__ x is now equivalent to str x rather than format str self Contributed by Serhiy Storchaka in bpo 28974 In order to better support dynamic creation of stack traces types TracebackType can now be instantiated from Python code and the tb_next attribute on tracebacks is now writable Contributed by Nathaniel J Smith in bpo 30579 When using the m switch sys path 0 is now eagerly expanded to the full starting directory path rather than being left as the empty directory which allows imports from the current working directory at the time when an import occurs Contributed by Nick Coghlan in bpo 33053 The new X importtime option or the PYTHONPROFILEIMPORTTIME environment variable can be used to show the timing of each module import Contributed by Inada Naoki in bpo 31415 New Modules contextvars The new contextvars module and a set of new C APIs introduce support for context variables Context variables are conceptually similar to thread local variables Unlike TLS context variables support asynchronous code correctly The asyncio and decimal modules have been updated to use and support context variables out of the box Particularly the active decimal context is now stored in a context variable which allows decimal operations to work ,en
2345,with the correct context in asynchronous code See also PEP 567 Context Variables PEP written and implemented by Yury Selivanov dataclasses The new dataclass decorator provides a way to declare data classes A data class describes its attributes using class variable annotations Its constructor and other magic methods such as __repr__ __eq__ and __hash__ are generated automatically Example dataclass class Point x float y float z float 0 0 p Point 1 5 2 5 print p produces Point x 1 5 y 2 5 z 0 0 See also PEP 557 Data Classes PEP written and implemented by Eric V Smith importlib resources The new importlib resources module provides several new APIs and one new ABC for access to opening and reading resources inside packages Resources are roughly similar to files inside packages but they needn t be actual files on the physical file system Module loaders can provide a get_resource_reader function which returns a importlib abc ResourceReader instance to support this new API Built in file path loaders and zip file loaders both support this Contributed by Barry Warsaw and Brett Cannon in bpo 32248 See also importlib_resources a PyPI backport for earlier Python versions Improved Modules argparse The new ArgumentParser parse_intermixed_args method allows intermixing options and positional arguments Contributed by paul j3 in bpo 14191 asyncio The asyncio module has received many new features usability and performance improvements Notable changes include The new provisional asyncio run function can be used to run a coroutine from synchronous code by automatically creating and destroying the event loop Contributed by Yury Selivanov in bpo 32314 asyncio gained support for contextvars loop call_soon loop call_soon_threadsafe loop call_later loop call_at and Future add_done_callback have a new optional keyword only context parameter Tasks now track their context automatically See PEP 567 for more details Contributed by Yury Selivanov in bpo 32436 The new asyncio create_task function has been added as a shortcut to asyncio get_event_loop create_task Contributed by Andrew Svetlov in bpo 32311 The new loop start_tls method can be used to upgrade an existing connection to TLS Contributed by Yury Selivanov in bpo 23749 The new loop sock_recv_into method allows reading data from a socket directly into a provided buffer making it possible to reduce data copies Contributed by Antoine Pitrou in bpo 31819 The new asyncio current_task function returns the currently running Task instance and the new asyncio all_tasks function returns a set of all existing Task instances in a given loop The Task current_task and Task all_tasks methods have been deprecated Contributed by Andrew Svetlov in bpo 32250 The new provisional BufferedProtocol class allows implementing streaming protocols with manual control over the receive buffer Contributed by Yury Selivanov in bpo 32251 The new asyncio get_running_loop function returns the currently running loop and raises a RuntimeError if no loop is running This is in contrast with asyncio get_event_loop which will create a new event loop if none is running Contributed by Yury Selivanov in bpo 32269 The new StreamWriter wait_closed coroutine method allows waiting until the stream writer is closed The new StreamWriter is_closing method can be used to determine if the writer is closing Contributed by Andrew Svetlov in bpo 32391 The new loop sock_sendfile coroutine method allows sending files using os sendfile when possible Contributed by Andrew Svetlov in bpo 32410 The new Future get_loop and Task get_loop methods return the instance of the loop on which a task or a future were created Server get_loop allows doing the same for asyncio Server objects Contributed by Yury Selivanov in bpo 32415 and Srinivas Reddy Thatiparthy in bpo 32418 It is now possible to control how instances of asyncio Server begin serving Previously the server would start serving immediately when created The new start_serving keyword argument to loop create_server and loop create_unix_server as well as Server start_serving and Server serve_forever can be,en
2346, used to decouple server instantiation and serving The new Server is_serving method returns True if the server is serving Server objects are now asynchronous context managers srv await loop create_server async with srv some code At this point srv is closed and no longer accepts new connections Contributed by Yury Selivanov in bpo 32662 Callback objects returned by loop call_later gained the new when method which returns an absolute scheduled callback timestamp Contributed by Andrew Svetlov in bpo 32741 The loop create_datagram_endpoint method gained support for Unix sockets Contributed by Quentin Dawans in bpo 31245 The asyncio open_connection asyncio start_server functions loop create_connection loop create_server loop create_accepted_socket methods and their corresponding UNIX socket variants now accept the ssl_handshake_timeout keyword argument Contributed by Neil Aspinall in bpo 29970 The new Handle cancelled method returns True if the callback was cancelled Contributed by Marat Sharafutdinov in bpo 31943 The asyncio source has been converted to use the async await syntax Contributed by Andrew Svetlov in bpo 32193 The new ReadTransport is_reading method can be used to determine the reading state of the transport Additionally calls to ReadTransport resume_reading and ReadTransport pause_reading are now idempotent Contributed by Yury Selivanov in bpo 32356 Loop methods which accept socket paths now support passing path like objects Contributed by Yury Selivanov in bpo 32066 In asyncio TCP sockets on Linux are now created with TCP_NODELAY flag set by default Contributed by Yury Selivanov and Victor Stinner in bpo 27456 Exceptions occurring in cancelled tasks are no longer logged Contributed by Yury Selivanov in bpo 30508 New WindowsSelectorEventLoopPolicy and WindowsProactorEventLoopPolicy classes Contributed by Yury Selivanov in bpo 33792 Several asyncio APIs have been deprecated binascii The b2a_uu function now accepts an optional backtick keyword argument When it s true zeros are represented by instead of spaces Contributed by Xiang Zhang in bpo 30103 calendar The HTMLCalendar class has new class attributes which ease the customization of CSS classes in the produced HTML calendar Contributed by Oz Tiram in bpo 30095 collections collections namedtuple now supports default values Contributed by Raymond Hettinger in bpo 32320 compileall compileall compile_dir learned the new invalidation_mode parameter which can be used to enable hash based pyc invalidation The invalidation mode can also be specified on the command line using the new invalidation mode argument Contributed by Benjamin Peterson in bpo 31650 concurrent futures ProcessPoolExecutor and ThreadPoolExecutor now support the new initializer and initargs constructor arguments Contributed by Antoine Pitrou in bpo 21423 The ProcessPoolExecutor can now take the multiprocessing context via the new mp_context argument Contributed by Thomas Moreau in bpo 31540 contextlib The new nullcontext is a simpler and faster no op context manager than ExitStack Contributed by Jesse Bakker in bpo 10049 The new asynccontextmanager AbstractAsyncContextManager and AsyncExitStack have been added to complement their synchronous counterparts Contributed by Jelle Zijlstra in bpo 29679 and bpo 30241 and by Alexander Mohr and Ilya Kulakov in bpo 29302 cProfile The cProfile command line now accepts m module_name as an alternative to script path Contributed by Sanyam Khurana in bpo 21862 crypt The crypt module now supports the Blowfish hashing method Contributed by Serhiy Storchaka in bpo 31664 The mksalt function now allows specifying the number of rounds for hashing Contributed by Serhiy Storchaka in bpo 31702 datetime The new datetime fromisoformat method constructs a datetime object from a string in one of the formats output by datetime isoformat Contributed by Paul Ganssle in bpo 15873 The tzinfo class now supports sub minute offsets Contributed by Alexander Belopolsky in bpo 5288 dbm dbm dumb now supports reading read only files and no longer writes the index file when it is not changed,en
2347, decimal The decimal module now uses context variables to store the decimal context Contributed by Yury Selivanov in bpo 32630 dis The dis function is now able to disassemble nested code objects the code of comprehensions generator expressions and nested functions and the code used for building nested classes The maximum depth of disassembly recursion is controlled by the new depth parameter Contributed by Serhiy Storchaka in bpo 11822 distutils README rst is now included in the list of distutils standard READMEs and therefore included in source distributions Contributed by Ryan Gonzalez in bpo 11913 enum The Enum learned the new _ignore_ class property which allows listing the names of properties which should not become enum members Contributed by Ethan Furman in bpo 31801 In Python 3 8 attempting to check for non Enum objects in Enum classes will raise a TypeError e g 1 in Color similarly attempting to check for non Flag objects in a Flag member will raise TypeError e g 1 in Perm RW currently both operations return False instead and are deprecated Contributed by Ethan Furman in bpo 33217 functools functools singledispatch now supports registering implementations using type annotations Contributed by Łukasz Langa in bpo 32227 gc The new gc freeze function allows freezing all objects tracked by the garbage collector and excluding them from future collections This can be used before a POSIX fork call to make the GC copy on write friendly or to speed up collection The new gc unfreeze functions reverses this operation Additionally gc get_freeze_count can be used to obtain the number of frozen objects Contributed by Li Zekun in bpo 31558 hmac The hmac module now has an optimized one shot digest function which is up to three times faster than HMAC Contributed by Christian Heimes in bpo 32433 http client HTTPConnection and HTTPSConnection now support the new blocksize argument for improved upload throughput Contributed by Nir Soffer in bpo 31945 http server SimpleHTTPRequestHandler now supports the HTTP If Modified Since header The server returns the 304 response status if the target file was not modified after the time specified in the header Contributed by Pierre Quentel in bpo 29654 SimpleHTTPRequestHandler accepts the new directory argument in addition to the new directory command line argument With this parameter the server serves the specified directory by default it uses the current working directory Contributed by Stéphane Wirtel and Julien Palard in bpo 28707 The new ThreadingHTTPServer class uses threads to handle requests using ThreadingMixin It is used when http server is run with m Contributed by Julien Palard in bpo 31639 idlelib and IDLE Multiple fixes for autocompletion Contributed by Louie Lu in bpo 15786 Module Browser on the File menu formerly called Class Browser now displays nested functions and classes in addition to top level functions and classes Contributed by Guilherme Polo Cheryl Sabella and Terry Jan Reedy in bpo 1612262 The Settings dialog Options Configure IDLE has been partly rewritten to improve both appearance and function Contributed by Cheryl Sabella and Terry Jan Reedy in multiple issues The font sample now includes a selection of non Latin characters so that users can better see the effect of selecting a particular font Contributed by Terry Jan Reedy in bpo 13802 The sample can be edited to include other characters Contributed by Serhiy Storchaka in bpo 31860 The IDLE features formerly implemented as extensions have been reimplemented as normal features Their settings have been moved from the Extensions tab to other dialog tabs Contributed by Charles Wohlganger and Terry Jan Reedy in bpo 27099 Editor code context option revised Box displays all context lines up to maxlines Clicking on a context line jumps the editor to that line Context colors for custom themes is added to Highlights tab of Settings dialog Contributed by Cheryl Sabella and Terry Jan Reedy in bpo 33642 bpo 33768 and bpo 33679 On Windows a new API call tells Windows that tk scales for DPI On Windows 8 1 or 10 with DPI compati,en
2348,bility properties of the Python binary unchanged and a monitor resolution greater than 96 DPI this should make text and lines sharper It should otherwise have no effect Contributed by Terry Jan Reedy in bpo 33656 New in 3 7 1 Output over N lines 50 by default is squeezed down to a button N can be changed in the PyShell section of the General page of the Settings dialog Fewer but possibly extra long lines can be squeezed by right clicking on the output Squeezed output can be expanded in place by double clicking the button or into the clipboard or a separate window by right clicking the button Contributed by Tal Einat in bpo 1529353 The changes above have been backported to 3 6 maintenance releases NEW in 3 7 4 Add Run Customized to the Run menu to run a module with customized settings Any command line arguments entered are added to sys argv They re appear in the box for the next customized run One can also suppress the normal Shell main module restart Contributed by Cheryl Sabella Terry Jan Reedy and others in bpo 5680 and bpo 37627 New in 3 7 5 Add optional line numbers for IDLE editor windows Windows open without line numbers unless set otherwise in the General tab of the configuration dialog Line numbers for an existing window are shown and hidden in the Options menu Contributed by Tal Einat and Saimadhav Heblikar in bpo 17535 importlib The importlib abc ResourceReader ABC was introduced to support the loading of resources from packages See also importlib resources Contributed by Barry Warsaw Brett Cannon in bpo 32248 importlib reload now raises ModuleNotFoundError if the module lacks a spec Contributed by Garvit Khatri in bpo 29851 importlib find_spec now raises ModuleNotFoundError instead of AttributeError if the specified parent module is not a package i e lacks a __path__ attribute Contributed by Milan Oberkirch in bpo 30436 The new importlib source_hash can be used to compute the hash of the passed source A hash based pyc file embeds the value returned by this function io The new TextIOWrapper reconfigure method can be used to reconfigure the text stream with the new settings Contributed by Antoine Pitrou in bpo 30526 and INADA Naoki in bpo 15216 ipaddress The new subnet_of and supernet_of methods of ipaddress IPv6Network and ipaddress IPv4Network can be used for network containment tests Contributed by Michel Albert and Cheryl Sabella in bpo 20825 itertools itertools islice now accepts integer like objects as start stop and slice arguments Contributed by Will Roberts in bpo 30537 locale The new monetary argument to locale format_string can be used to make the conversion use monetary thousands separators and grouping strings Contributed by Garvit in bpo 10379 The locale getpreferredencoding function now always returns UTF 8 on Android or when in the forced UTF 8 mode logging Logger instances can now be pickled Contributed by Vinay Sajip in bpo 30520 The new StreamHandler setStream method can be used to replace the logger stream after handler creation Contributed by Vinay Sajip in bpo 30522 It is now possible to specify keyword arguments to handler constructors in configuration passed to logging config fileConfig Contributed by Preston Landers in bpo 31080 math The new math remainder function implements the IEEE 754 style remainder operation Contributed by Mark Dickinson in bpo 29962 mimetypes The MIME type of bmp has been changed from image x ms bmp to image bmp Contributed by Nitish Chandra in bpo 22589 msilib The new Database Close method can be used to close the MSI database Contributed by Berker Peksag in bpo 20486 multiprocessing The new Process close method explicitly closes the process object and releases all resources associated with it ValueError is raised if the underlying process is still running Contributed by Antoine Pitrou in bpo 30596 The new Process kill method can be used to terminate the process using the SIGKILL signal on Unix Contributed by Vitor Pereira in bpo 30794 Non daemonic threads created by Process are now joined on process exit Contributed by Antoine Pitrou in bpo 18966 os os fwalk now,en
2349, accepts the path argument as bytes Contributed by Serhiy Storchaka in bpo 28682 os scandir gained support for file descriptors Contributed by Serhiy Storchaka in bpo 25996 The new register_at_fork function allows registering Python callbacks to be executed at process fork Contributed by Antoine Pitrou in bpo 16500 Added os preadv combine the functionality of os readv and os pread and os pwritev functions combine the functionality of os writev and os pwrite Contributed by Pablo Galindo in bpo 31368 The mode argument of os makedirs no longer affects the file permission bits of newly created intermediate level directories Contributed by Serhiy Storchaka in bpo 19930 os dup2 now returns the new file descriptor Previously None was always returned Contributed by Benjamin Peterson in bpo 32441 The structure returned by os stat now contains the st_fstype attribute on Solaris and its derivatives Contributed by Jesús Cea Avión in bpo 32659 pathlib The new Path is_mount method is now available on POSIX systems and can be used to determine whether a path is a mount point Contributed by Cooper Ry Lees in bpo 30897 pdb pdb set_trace now takes an optional header keyword only argument If given it is printed to the console just before debugging begins Contributed by Barry Warsaw in bpo 31389 pdb command line now accepts m module_name as an alternative to script file Contributed by Mario Corchero in bpo 32206 py_compile py_compile compile and by extension compileall now respects the SOURCE_DATE_EPOCH environment variable by unconditionally creating pyc files for hash based validation This allows for guaranteeing reproducible builds of pyc files when they are created eagerly Contributed by Bernhard M Wiedemann in bpo 29708 pydoc The pydoc server can now bind to an arbitrary hostname specified by the new n command line argument Contributed by Feanil Patel in bpo 31128 queue The new SimpleQueue class is an unbounded FIFO queue Contributed by Antoine Pitrou in bpo 14976 re The flags re ASCII re LOCALE and re UNICODE can be set within the scope of a group Contributed by Serhiy Storchaka in bpo 31690 re split now supports splitting on a pattern like r b or that matches an empty string Contributed by Serhiy Storchaka in bpo 25054 Regular expressions compiled with the re LOCALE flag no longer depend on the locale at compile time Locale settings are applied only when the compiled regular expression is used Contributed by Serhiy Storchaka in bpo 30215 FutureWarning is now emitted if a regular expression contains character set constructs that will change semantically in the future such as nested sets and set operations Contributed by Serhiy Storchaka in bpo 30349 Compiled regular expression and match objects can now be copied using copy copy and copy deepcopy Contributed by Serhiy Storchaka in bpo 10076 signal The new warn_on_full_buffer argument to the signal set_wakeup_fd function makes it possible to specify whether Python prints a warning on stderr when the wakeup buffer overflows Contributed by Nathaniel J Smith in bpo 30050 socket The new socket getblocking method returns True if the socket is in blocking mode and False otherwise Contributed by Yury Selivanov in bpo 32373 The new socket close function closes the passed socket file descriptor This function should be used instead of os close for better compatibility across platforms Contributed by Christian Heimes in bpo 32454 The socket module now exposes the socket TCP_CONGESTION Linux 2 6 13 socket TCP_USER_TIMEOUT Linux 2 6 37 and socket TCP_NOTSENT_LOWAT Linux 3 12 constants Contributed by Omar Sandoval in bpo 26273 and Nathaniel J Smith in bpo 29728 Support for socket AF_VSOCK sockets has been added to allow communication between virtual machines and their hosts Contributed by Cathy Avery in bpo 27584 Sockets now auto detect family type and protocol from file descriptor by default Contributed by Christian Heimes in bpo 28134 socketserver socketserver ThreadingMixIn server_close now waits until all non daemon threads complete socketserver ForkingMixIn server_close now waits until all child,en
2350, processes complete Add a new socketserver ForkingMixIn block_on_close class attribute to socketserver ForkingMixIn and socketserver ThreadingMixIn classes Set the class attribute to False to get the pre 3 7 behaviour sqlite3 sqlite3 Connection now exposes the backup method when the underlying SQLite library is at version 3 6 11 or higher Contributed by Lele Gaifax in bpo 27645 The database argument of sqlite3 connect now accepts any path like object instead of just a string Contributed by Anders Lorentsen in bpo 31843 ssl The ssl module now uses OpenSSL s builtin API instead of match_hostname to check a host name or an IP address Values are validated during TLS handshake Any certificate validation error including failing the host name check now raises SSLCertVerificationError and aborts the handshake with a proper TLS Alert message The new exception contains additional information Host name validation can be customized with SSLContext hostname_checks_common_name Contributed by Christian Heimes in bpo 31399 Note The improved host name check requires a libssl implementation compatible with OpenSSL 1 0 2 or 1 1 Consequently OpenSSL 0 9 8 and 1 0 1 are no longer supported see Platform Support Removals for more details The ssl module is mostly compatible with LibreSSL 2 7 2 and newer The ssl module no longer sends IP addresses in SNI TLS extension Contributed by Christian Heimes in bpo 32185 match_hostname no longer supports partial wildcards like www example org Contributed by Mandeep Singh in bpo 23033 and Christian Heimes in bpo 31399 The default cipher suite selection of the ssl module now uses a blacklist approach rather than a hard coded whitelist Python no longer re enables ciphers that have been blocked by OpenSSL security updates Default cipher suite selection can be configured at compile time Contributed by Christian Heimes in bpo 31429 Validation of server certificates containing internationalized domain names IDNs is now supported As part of this change the SSLSocket server_hostname attribute now stores the expected hostname in A label form xn pythn mua org rather than the U label form pythön org Contributed by Nathaniel J Smith and Christian Heimes in bpo 28414 The ssl module has preliminary and experimental support for TLS 1 3 and OpenSSL 1 1 1 At the time of Python 3 7 0 release OpenSSL 1 1 1 is still under development and TLS 1 3 hasn t been finalized yet The TLS 1 3 handshake and protocol behaves slightly differently than TLS 1 2 and earlier see TLS 1 3 Contributed by Christian Heimes in bpo 32947 bpo 20995 bpo 29136 bpo 30622 and bpo 33618 SSLSocket and SSLObject no longer have a public constructor Direct instantiation was never a documented and supported feature Instances must be created with SSLContext methods wrap_socket and wrap_bio Contributed by Christian Heimes in bpo 32951 OpenSSL 1 1 APIs for setting the minimum and maximum TLS protocol version are available as SSLContext minimum_version and SSLContext maximum_version Supported protocols are indicated by several new flags such as HAS_TLSv1_1 Contributed by Christian Heimes in bpo 32609 Added ssl SSLContext post_handshake_auth to enable and ssl SSLSocket verify_client_post_handshake to initiate TLS 1 3 post handshake authentication Contributed by Christian Heimes in gh 78851 string string Template now lets you to optionally modify the regular expression pattern for braced placeholders and non braced placeholders separately Contributed by Barry Warsaw in bpo 1198569 subprocess The subprocess run function accepts the new capture_output keyword argument When true stdout and stderr will be captured This is equivalent to passing subprocess PIPE as stdout and stderr arguments Contributed by Bo Bayles in bpo 32102 The subprocess run function and the subprocess Popen constructor now accept the text keyword argument as an alias to universal_newlines Contributed by Andrew Clegg in bpo 31756 On Windows the default for close_fds was changed from False to True when redirecting the standard handles It s now possible to set close_fds to true when redirecting the s,en
2351,tandard handles See subprocess Popen This means that close_fds now defaults to True on all supported platforms Contributed by Segev Finer in bpo 19764 The subprocess module is now more graceful when handling KeyboardInterrupt during subprocess call subprocess run or in a Popen context manager It now waits a short amount of time for the child to exit before continuing the handling of the KeyboardInterrupt exception Contributed by Gregory P Smith in bpo 25942 sys The new sys breakpointhook hook function is called by the built in breakpoint Contributed by Barry Warsaw in bpo 31353 On Android the new sys getandroidapilevel returns the build time Android API version Contributed by Victor Stinner in bpo 28740 The new sys get_coroutine_origin_tracking_depth function returns the current coroutine origin tracking depth as set by the new sys set_coroutine_origin_tracking_depth asyncio has been converted to use this new API instead of the deprecated sys set_coroutine_wrapper Contributed by Nathaniel J Smith in bpo 32591 time PEP 564 adds six new functions with nanosecond resolution to the time module time clock_gettime_ns time clock_settime_ns time monotonic_ns time perf_counter_ns time process_time_ns time time_ns New clock identifiers have been added time CLOCK_BOOTTIME Linux Identical to time CLOCK_MONOTONIC except it also includes any time that the system is suspended time CLOCK_PROF FreeBSD NetBSD and OpenBSD High resolution per process CPU timer time CLOCK_UPTIME FreeBSD OpenBSD Time whose absolute value is the time the system has been running and not suspended providing accurate uptime measurement The new time thread_time and time thread_time_ns functions can be used to get per thread CPU time measurements Contributed by Antoine Pitrou in bpo 32025 The new time pthread_getcpuclockid function returns the clock ID of the thread specific CPU time clock tkinter The new tkinter ttk Spinbox class is now available Contributed by Alan Moore in bpo 32585 tracemalloc tracemalloc Traceback behaves more like regular tracebacks sorting the frames from oldest to most recent Traceback format now accepts negative limit truncating the result to the abs limit oldest frames To get the old behaviour use the new most_recent_first argument to Traceback format Contributed by Jesse Bakker in bpo 32121 types The new WrapperDescriptorType MethodWrapperType MethodDescriptorType and ClassMethodDescriptorType classes are now available Contributed by Manuel Krebber and Guido van Rossum in bpo 29377 and Serhiy Storchaka in bpo 32265 The new types resolve_bases function resolves MRO entries dynamically as specified by PEP 560 Contributed by Ivan Levkivskyi in bpo 32717 unicodedata The internal unicodedata database has been upgraded to use Unicode 11 Contributed by Benjamin Peterson unittest The new k command line option allows filtering tests by a name substring or a Unix shell like pattern For example python m unittest k foo runs foo_tests SomeTest test_something bar_tests SomeTest test_foo but not bar_tests FooTest test_something Contributed by Jonas Haag in bpo 32071 unittest mock The sentinel attributes now preserve their identity when they are copied or pickled Contributed by Serhiy Storchaka in bpo 20804 The new seal function allows sealing Mock instances which will disallow further creation of attribute mocks The seal is applied recursively to all attributes that are themselves mocks Contributed by Mario Corchero in bpo 30541 urllib parse urllib parse quote has been updated from RFC 2396 to RFC 3986 adding to the set of characters that are never quoted by default Contributed by Christian Theune and Ratnadeep Debnath in bpo 16285 uu The uu encode function now accepts an optional backtick keyword argument When it s true zeros are represented by instead of spaces Contributed by Xiang Zhang in bpo 30103 uuid The new UUID is_safe attribute relays information from the platform about whether generated UUIDs are generated with a multiprocessing safe method Contributed by Barry Warsaw in bpo 22807 uuid getnode now prefers universally administered MAC address,en
2352,es over locally administered MAC addresses This makes a better guarantee for global uniqueness of UUIDs returned from uuid uuid1 If only locally administered MAC addresses are available the first such one found is returned Contributed by Barry Warsaw in bpo 32107 warnings The initialization of the default warnings filters has changed as follows warnings enabled via command line options including those for b and the new CPython specific X dev option are always passed to the warnings machinery via the sys warnoptions attribute warnings filters enabled via the command line or the environment now have the following order of precedence the BytesWarning filter for b or bb any filters specified with the W option any filters specified with the PYTHONWARNINGS environment variable any other CPython specific filters e g the default filter added for the new X dev mode any implicit filters defined directly by the warnings machinery in CPython debug builds all warnings are now displayed by default the implicit filter list is empty Contributed by Nick Coghlan and Victor Stinner in bpo 20361 bpo 32043 and bpo 32230 Deprecation warnings are once again shown by default in single file scripts and at the interactive prompt See PEP 565 Show DeprecationWarning in __main__ for details Contributed by Nick Coghlan in bpo 31975 xml As mitigation against DTD and external entity retrieval the xml dom minidom and xml sax modules no longer process external entities by default Contributed by Christian Heimes in gh 61441 xml etree ElementPath predicates in the find methods can now compare text of the current node with text not only text in children Predicates also allow adding spaces for better readability Contributed by Stefan Behnel in bpo 31648 xmlrpc server SimpleXMLRPCDispatcher register_function can now be used as a decorator Contributed by Xiang Zhang in bpo 7769 zipapp Function create_archive now accepts an optional filter argument to allow the user to select which files should be included in the archive Contributed by Irmen de Jong in bpo 31072 Function create_archive now accepts an optional compressed argument to generate a compressed archive A command line option compress has also been added to support compression Contributed by Zhiming Wang in bpo 31638 zipfile ZipFile now accepts the new compresslevel parameter to control the compression level Contributed by Bo Bayles in bpo 21417 Subdirectories in archives created by ZipFile are now stored in alphabetical order Contributed by Bernhard M Wiedemann in bpo 30693 C API Changes A new API for thread local storage has been implemented See PEP 539 New C API for Thread Local Storage for an overview and Thread Specific Storage TSS API for a complete reference Contributed by Masayuki Yamamoto in bpo 25658 The new context variables functionality exposes a number of new C APIs The new PyImport_GetModule function returns the previously imported module with the given name Contributed by Eric Snow in bpo 28411 The new Py_RETURN_RICHCOMPARE macro eases writing rich comparison functions Contributed by Petr Victorin in bpo 23699 The new Py_UNREACHABLE macro can be used to mark unreachable code paths Contributed by Barry Warsaw in bpo 31338 The tracemalloc now exposes a C API through the new PyTraceMalloc_Track and PyTraceMalloc_Untrack functions Contributed by Victor Stinner in bpo 30054 The new import__find__load__start and import__find__load__done static markers can be used to trace module imports Contributed by Christian Heimes in bpo 31574 The fields name and doc of structures PyMemberDef PyGetSetDef PyStructSequence_Field PyStructSequence_Desc and wrapperbase are now of type const char rather of char Contributed by Serhiy Storchaka in bpo 28761 The result of PyUnicode_AsUTF8AndSize and PyUnicode_AsUTF8 is now of type const char rather of char Contributed by Serhiy Storchaka in bpo 28769 The result of PyMapping_Keys PyMapping_Values and PyMapping_Items is now always a list rather than a list or a tuple Contributed by Oren Milman in bpo 28280 Added functions PySlice_Unpack and PySlice_AdjustIndices Contr,en
2353,ibuted by Serhiy Storchaka in bpo 27867 PyOS_AfterFork is deprecated in favour of the new functions PyOS_BeforeFork PyOS_AfterFork_Parent and PyOS_AfterFork_Child Contributed by Antoine Pitrou in bpo 16500 The PyExc_RecursionErrorInst singleton that was part of the public API has been removed as its members being never cleared may cause a segfault during finalization of the interpreter Contributed by Xavier de Gaye in bpo 22898 and bpo 30697 Added C API support for timezones with timezone constructors PyTimeZone_FromOffset and PyTimeZone_FromOffsetAndName and access to the UTC singleton with PyDateTime_TimeZone_UTC Contributed by Paul Ganssle in bpo 10381 The type of results of PyThread_start_new_thread and PyThread_get_thread_ident and the id parameter of PyThreadState_SetAsyncExc changed from long to unsigned long Contributed by Serhiy Storchaka in bpo 6532 PyUnicode_AsWideCharString now raises a ValueError if the second argument is NULL and the wchar_t string contains null characters Contributed by Serhiy Storchaka in bpo 30708 Changes to the startup sequence and the management of dynamic memory allocators mean that the long documented requirement to call Py_Initialize before calling most C API functions is now relied on more heavily and failing to abide by it may lead to segfaults in embedding applications See the Porting to Python 3 7 section in this document and the Before Python Initialization section in the C API documentation for more details The new PyInterpreterState_GetID returns the unique ID for a given interpreter Contributed by Eric Snow in bpo 29102 Py_DecodeLocale Py_EncodeLocale now use the UTF 8 encoding when the UTF 8 mode is enabled Contributed by Victor Stinner in bpo 29240 PyUnicode_DecodeLocaleAndSize and PyUnicode_EncodeLocale now use the current locale encoding for surrogateescape error handler Contributed by Victor Stinner in bpo 29240 The start and end parameters of PyUnicode_FindChar are now adjusted to behave like string slices Contributed by Xiang Zhang in bpo 28822 Build Changes Support for building without threads has been removed The threading module is now always available Contributed by Antoine Pitrou in bpo 31370 A full copy of libffi is no longer bundled for use when building the _ctypes module on non OSX UNIX platforms An installed copy of libffi is now required when building _ctypes on such platforms Contributed by Zachary Ware in bpo 27979 The Windows build process no longer depends on Subversion to pull in external sources a Python script is used to download zipfiles from GitHub instead If Python 3 6 is not found on the system via py 3 6 NuGet is used to download a copy of 32 bit Python for this purpose Contributed by Zachary Ware in bpo 30450 The ssl module requires OpenSSL 1 0 2 or 1 1 compatible libssl OpenSSL 1 0 1 has reached end of lifetime on 2016 12 31 and is no longer supported LibreSSL is temporarily not supported as well LibreSSL releases up to version 2 6 4 are missing required OpenSSL 1 0 2 APIs Optimizations The overhead of calling many methods of various standard library classes implemented in C has been significantly reduced by porting more code to use the METH_FASTCALL convention Contributed by Victor Stinner in bpo 29300 bpo 29507 bpo 29452 and bpo 29286 Various optimizations have reduced Python startup time by 10 on Linux and up to 30 on macOS Contributed by Victor Stinner INADA Naoki in bpo 29585 and Ivan Levkivskyi in bpo 31333 Method calls are now up to 20 faster due to the bytecode changes which avoid creating bound method instances Contributed by Yury Selivanov and INADA Naoki in bpo 26110 The asyncio module received a number of notable optimizations for commonly used functions The asyncio get_event_loop function has been reimplemented in C to make it up to 15 times faster Contributed by Yury Selivanov in bpo 32296 asyncio Future callback management has been optimized Contributed by Yury Selivanov in bpo 32348 asyncio gather is now up to 15 faster Contributed by Yury Selivanov in bpo 32355 asyncio sleep is now up to 2 times faster when the delay argument ,en
2354,is zero or negative Contributed by Andrew Svetlov in bpo 32351 The performance overhead of asyncio debug mode has been reduced Contributed by Antoine Pitrou in bpo 31970 As a result of PEP 560 work the import time of typing has been reduced by a factor of 7 and many typing operations are now faster Contributed by Ivan Levkivskyi in bpo 32226 sorted and list sort have been optimized for common cases to be up to 40 75 faster Contributed by Elliot Gorokhovsky in bpo 28685 dict copy is now up to 5 5 times faster Contributed by Yury Selivanov in bpo 31179 hasattr and getattr are now about 4 times faster when name is not found and obj does not override object __getattr__ or object __getattribute__ Contributed by INADA Naoki in bpo 32544 Searching for certain Unicode characters like Ukrainian capital Є in a string was up to 25 times slower than searching for other characters It is now only 3 times slower in the worst case Contributed by Serhiy Storchaka in bpo 24821 The collections namedtuple factory has been reimplemented to make the creation of named tuples 4 to 6 times faster Contributed by Jelle Zijlstra with further improvements by INADA Naoki Serhiy Storchaka and Raymond Hettinger in bpo 28638 date fromordinal and date fromtimestamp are now up to 30 faster in the common case Contributed by Paul Ganssle in bpo 32403 The os fwalk function is now up to 2 times faster thanks to the use of os scandir Contributed by Serhiy Storchaka in bpo 25996 The speed of the shutil rmtree function has been improved by 20 40 thanks to the use of the os scandir function Contributed by Serhiy Storchaka in bpo 28564 Optimized case insensitive matching and searching of regular expressions Searching some patterns can now be up to 20 times faster Contributed by Serhiy Storchaka in bpo 30285 re compile now converts flags parameter to int object if it is RegexFlag It is now as fast as Python 3 5 and faster than Python 3 6 by about 10 depending on the pattern Contributed by INADA Naoki in bpo 31671 The modify methods of classes selectors EpollSelector selectors PollSelector and selectors DevpollSelector may be around 10 faster under heavy loads Contributed by Giampaolo Rodola in bpo 30014 Constant folding has been moved from the peephole optimizer to the new AST optimizer which is able perform optimizations more consistently Contributed by Eugene Toder and INADA Naoki in bpo 29469 and bpo 11549 Most functions and methods in abc have been rewritten in C This makes creation of abstract base classes and calling isinstance and issubclass on them 1 5x faster This also reduces Python start up time by up to 10 Contributed by Ivan Levkivskyi and INADA Naoki in bpo 31333 Significant speed improvements to alternate constructors for datetime date and datetime datetime by using fast path constructors when not constructing subclasses Contributed by Paul Ganssle in bpo 32403 The speed of comparison of array array instances has been improved considerably in certain cases It is now from 10x to 70x faster when comparing arrays holding values of the same integer type Contributed by Adrian Wielgosik in bpo 24700 The math erf and math erfc functions now use the faster C library implementation on most platforms Contributed by Serhiy Storchaka in bpo 26121 Other CPython Implementation Changes Trace hooks may now opt out of receiving the line and opt into receiving the opcode events from the interpreter by setting the corresponding new f_trace_lines and f_trace_opcodes attributes on the frame being traced Contributed by Nick Coghlan in bpo 31344 Fixed some consistency problems with namespace package module attributes Namespace module objects now have an __file__ that is set to None previously unset and their __spec__ origin is also set to None previously the string namespace See bpo 32305 Also the namespace module object s __spec__ loader is set to the same value as __loader__ previously the former was set to None See bpo 32303 The locals dictionary now displays in the lexical order that variables were defined Previously the order was undefined Contributed by Raymond Hetti,en
2355,nger in bpo 32690 The distutils upload command no longer tries to change CR end of line characters to CRLF This fixes a corruption issue with sdists that ended with a byte equivalent to CR Contributed by Bo Bayles in bpo 32304 Deprecated Python Behavior Yield expressions both yield and yield from clauses are now deprecated in comprehensions and generator expressions aside from the iterable expression in the leftmost for clause This ensures that comprehensions always immediately return a container of the appropriate type rather than potentially returning a generator iterator object while generator expressions won t attempt to interleave their implicit output with the output from any explicit yield expressions In Python 3 7 such expressions emit DeprecationWarning when compiled in Python 3 8 this will be a SyntaxError Contributed by Serhiy Storchaka in bpo 10544 Returning a subclass of complex from object __complex__ is deprecated and will be an error in future Python versions This makes __complex__ consistent with object __int__ and object __float__ Contributed by Serhiy Storchaka in bpo 28894 Deprecated Python modules functions and methods aifc aifc openfp has been deprecated and will be removed in Python 3 9 Use aifc open instead Contributed by Brian Curtin in bpo 31985 asyncio Support for directly await ing instances of asyncio Lock and other asyncio synchronization primitives has been deprecated An asynchronous context manager must be used in order to acquire and release the synchronization resource Contributed by Andrew Svetlov in bpo 32253 The asyncio Task current_task and asyncio Task all_tasks methods have been deprecated Contributed by Andrew Svetlov in bpo 32250 collections In Python 3 8 the abstract base classes in collections abc will no longer be exposed in the regular collections module This will help create a clearer distinction between the concrete classes and the abstract base classes Contributed by Serhiy Storchaka in bpo 25988 dbm dbm dumb now supports reading read only files and no longer writes the index file when it is not changed A deprecation warning is now emitted if the index file is missing and recreated in the r and w modes this will be an error in future Python releases Contributed by Serhiy Storchaka in bpo 28847 enum In Python 3 8 attempting to check for non Enum objects in Enum classes will raise a TypeError e g 1 in Color similarly attempting to check for non Flag objects in a Flag member will raise TypeError e g 1 in Perm RW currently both operations return False instead Contributed by Ethan Furman in bpo 33217 gettext Using non integer value for selecting a plural form in gettext is now deprecated It never correctly worked Contributed by Serhiy Storchaka in bpo 28692 importlib Methods MetaPathFinder find_module replaced by MetaPathFinder find_spec and PathEntryFinder find_loader replaced by PathEntryFinder find_spec both deprecated in Python 3 4 now emit DeprecationWarning Contributed by Matthias Bussonnier in bpo 29576 The importlib abc ResourceLoader ABC has been deprecated in favour of importlib abc ResourceReader locale locale format has been deprecated use locale format_string instead Contributed by Garvit in bpo 10379 macpath The macpath is now deprecated and will be removed in Python 3 8 Contributed by Chi Hsuan Yen in bpo 9850 threading dummy_threading and _dummy_thread have been deprecated It is no longer possible to build Python with threading disabled Use threading instead Contributed by Antoine Pitrou in bpo 31370 socket The silent argument value truncation in socket htons and socket ntohs has been deprecated In future versions of Python if the passed argument is larger than 16 bits an exception will be raised Contributed by Oren Milman in bpo 28332 ssl ssl wrap_socket is deprecated Use ssl SSLContext wrap_socket instead Contributed by Christian Heimes in bpo 28124 sunau sunau openfp has been deprecated and will be removed in Python 3 9 Use sunau open instead Contributed by Brian Curtin in bpo 31985 sys Deprecated sys set_coroutine_wrapper and sys get_coroutine_wrapper The un,en
2356,documented sys callstats function has been deprecated and will be removed in a future Python version Contributed by Victor Stinner in bpo 28799 wave wave openfp has been deprecated and will be removed in Python 3 9 Use wave open instead Contributed by Brian Curtin in bpo 31985 Deprecated functions and types of the C API Function PySlice_GetIndicesEx is deprecated and replaced with a macro if Py_LIMITED_API is not set or set to a value in the range between 0x03050400 and 0x03060000 not inclusive or is 0x03060100 or higher Contributed by Serhiy Storchaka in bpo 27867 PyOS_AfterFork has been deprecated Use PyOS_BeforeFork PyOS_AfterFork_Parent or PyOS_AfterFork_Child instead Contributed by Antoine Pitrou in bpo 16500 Platform Support Removals FreeBSD 9 and older are no longer officially supported For full Unicode support including within extension modules nix platforms are now expected to provide at least one of C UTF 8 full locale C utf8 full locale or UTF 8 LC_CTYPE only locale as an alternative to the legacy ASCII based C locale OpenSSL 0 9 8 and 1 0 1 are no longer supported which means building CPython 3 7 with SSL TLS support on older platforms still using these versions requires custom build options that link to a more recent version of OpenSSL Notably this issue affects the Debian 8 aka jessie and Ubuntu 14 04 aka Trusty LTS Linux distributions as they still use OpenSSL 1 0 1 by default Debian 9 stretch and Ubuntu 16 04 xenial as well as recent releases of other LTS Linux releases e g RHEL CentOS 7 5 SLES 12 SP3 use OpenSSL 1 0 2 or later and remain supported in the default build configuration CPython s own CI configuration file provides an example of using the SSL compatibility testing infrastructure in CPython s test suite to build and link against OpenSSL 1 1 0 rather than an outdated system provided OpenSSL API and Feature Removals The following features and APIs have been removed from Python 3 7 The os stat_float_times function has been removed It was introduced in Python 2 3 for backward compatibility with Python 2 2 and was deprecated since Python 3 1 Unknown escapes consisting of and an ASCII letter in replacement templates for re sub were deprecated in Python 3 5 and will now cause an error Removed support of the exclude argument in tarfile TarFile add It was deprecated in Python 2 7 and 3 2 Use the filter argument instead The ntpath splitunc function was deprecated in Python 3 1 and has now been removed Use splitdrive instead collections namedtuple no longer supports the verbose parameter or _source attribute which showed the generated source code for the named tuple class This was part of an optimization designed to speed up class creation Contributed by Jelle Zijlstra with further improvements by INADA Naoki Serhiy Storchaka and Raymond Hettinger in bpo 28638 Functions bool float list and tuple no longer take keyword arguments The first argument of int can now be passed only as positional argument Removed previously deprecated in Python 2 4 classes Plist Dict and _InternalDict in the plistlib module Dict values in the result of functions readPlist and readPlistFromBytes are now normal dicts You no longer can use attribute access to access items of these dictionaries The asyncio windows_utils socketpair function has been removed Use the socket socketpair function instead it is available on all platforms since Python 3 5 asyncio windows_utils socketpair was just an alias to socket socketpair on Python 3 5 and newer asyncio no longer exports the selectors and _overlapped modules as asyncio selectors and asyncio _overlapped Replace from asyncio import selectors with import selectors Direct instantiation of ssl SSLSocket and ssl SSLObject objects is now prohibited The constructors were never documented tested or designed as public constructors Users were supposed to use ssl wrap_socket or ssl SSLContext Contributed by Christian Heimes in bpo 32951 The unused distutils install_misc command has been removed Contributed by Eric N Vander Weele in bpo 29218 Module Removals The fpectl module has been removed It was,en
2357, never enabled by default never worked correctly on x86 64 and it changed the Python ABI in ways that caused unexpected breakage of C extensions Contributed by Nathaniel J Smith in bpo 29137 Windows only Changes The python launcher py exe can accept 32 64 bit specifiers without having to specify a minor version as well So py 3 32 and py 3 64 become valid as well as py 3 7 32 also the m 64 and m n 64 forms are now accepted to force 64 bit python even if 32 bit would have otherwise been used If the specified version is not available py exe will error exit Contributed by Steve Barnes in bpo 30291 The launcher can be run as py 0 to produce a list of the installed pythons with default marked with an asterisk Running py 0p will include the paths If py is run with a version specifier that cannot be matched it will also print the short form list of available specifiers Contributed by Steve Barnes in bpo 30362 Porting to Python 3 7 This section lists previously described changes and other bugfixes that may require changes to your code Changes in Python Behavior async and await names are now reserved keywords Code using these names as identifiers will now raise a SyntaxError Contributed by Jelle Zijlstra in bpo 30406 PEP 479 is enabled for all code in Python 3 7 meaning that StopIteration exceptions raised directly or indirectly in coroutines and generators are transformed into RuntimeError exceptions Contributed by Yury Selivanov in bpo 32670 object __aiter__ methods can no longer be declared as asynchronous Contributed by Yury Selivanov in bpo 31709 Due to an oversight earlier Python versions erroneously accepted the following syntax f 1 for x in 1 class C 1 for x in 1 pass Python 3 7 now correctly raises a SyntaxError as a generator expression always needs to be directly inside a set of parentheses and cannot have a comma on either side and the duplication of the parentheses can be omitted only on calls Contributed by Serhiy Storchaka in bpo 32012 and bpo 32023 When using the m switch the initial working directory is now added to sys path rather than an empty string which dynamically denoted the current working directory at the time of each import Any programs that are checking for the empty string or otherwise relying on the previous behaviour will need to be updated accordingly e g by also checking for os getcwd or os path dirname __main__ __file__ depending on why the code was checking for the empty string in the first place Changes in the Python API socketserver ThreadingMixIn server_close now waits until all non daemon threads complete Set the new socketserver ThreadingMixIn block_on_close class attribute to False to get the pre 3 7 behaviour Contributed by Victor Stinner in bpo 31233 and bpo 33540 socketserver ForkingMixIn server_close now waits until all child processes complete Set the new socketserver ForkingMixIn block_on_close class attribute to False to get the pre 3 7 behaviour Contributed by Victor Stinner in bpo 31151 and bpo 33540 The locale localeconv function now temporarily sets the LC_CTYPE locale to the value of LC_NUMERIC in some cases Contributed by Victor Stinner in bpo 31900 pkgutil walk_packages now raises a ValueError if path is a string Previously an empty list was returned Contributed by Sanyam Khurana in bpo 24744 A format string argument for string Formatter format is now positional only Passing it as a keyword argument was deprecated in Python 3 5 Contributed by Serhiy Storchaka in bpo 29193 Attributes key value and coded_value of class http cookies Morsel are now read only Assigning to them was deprecated in Python 3 5 Use the set method for setting them Contributed by Serhiy Storchaka in bpo 29192 The mode argument of os makedirs no longer affects the file permission bits of newly created intermediate level directories To set their file permission bits you can set the umask before invoking makedirs Contributed by Serhiy Storchaka in bpo 19930 The struct Struct format type is now str instead of bytes Contributed by Victor Stinner in bpo 21071 parse_multipart now accepts the encoding and errors a,en
2358,rguments and returns the same results as FieldStorage for non file fields the value associated to a key is a list of strings not bytes Contributed by Pierre Quentel in bpo 29979 Due to internal changes in socket calling socket fromshare on a socket created by socket share in older Python versions is not supported repr for BaseException has changed to not include the trailing comma Most exceptions are affected by this change Contributed by Serhiy Storchaka in bpo 30399 repr for datetime timedelta has changed to include the keyword arguments in the output Contributed by Utkarsh Upadhyay in bpo 30302 Because shutil rmtree is now implemented using the os scandir function the user specified handler onerror is now called with the first argument os scandir instead of os listdir when listing the directory is failed Support for nested sets and set operations in regular expressions as in Unicode Technical Standard 18 might be added in the future This would change the syntax To facilitate this future change a FutureWarning will be raised in ambiguous cases for the time being That include sets starting with a literal or containing literal character sequences and To avoid a warning escape them with a backslash Contributed by Serhiy Storchaka in bpo 30349 The result of splitting a string on a regular expression that could match an empty string has been changed For example splitting on r s will now split not only on whitespaces as it did previously but also on empty strings before all non whitespace characters and just before the end of the string The previous behavior can be restored by changing the pattern to r s A FutureWarning was emitted for such patterns since Python 3 5 For patterns that match both empty and non empty strings the result of searching for all matches may also be changed in other cases For example in the string a n n the pattern r m s will not only match empty strings at positions 2 and 3 but also the string n at positions 2 3 To match only blank lines the pattern should be rewritten as r m S n re sub now replaces empty matches adjacent to a previous non empty match For example re sub x abxd returns now a b d instead of a b d the first minus between b and d replaces x and the second minus replaces an empty string between x and d Contributed by Serhiy Storchaka in bpo 25054 and bpo 32308 Change re escape to only escape regex special characters instead of escaping all characters other than ASCII letters numbers and _ Contributed by Serhiy Storchaka in bpo 29995 tracemalloc Traceback frames are now sorted from oldest to most recent to be more consistent with traceback Contributed by Jesse Bakker in bpo 32121 On OSes that support socket SOCK_NONBLOCK or socket SOCK_CLOEXEC bit flags the socket type no longer has them applied Therefore checks like if sock type socket SOCK_STREAM work as expected on all platforms Contributed by Yury Selivanov in bpo 32331 On Windows the default for the close_fds argument of subprocess Popen was changed from False to True when redirecting the standard handles If you previously depended on handles being inherited when using subprocess Popen with standard io redirection you will have to pass close_fds False to preserve the previous behaviour or use STARTUPINFO lpAttributeList importlib machinery PathFinder invalidate_caches which implicitly affects importlib invalidate_caches now deletes entries in sys path_importer_cache which are set to None Contributed by Brett Cannon in bpo 33169 In asyncio loop sock_recv loop sock_sendall loop sock_accept loop getaddrinfo loop getnameinfo have been changed to be proper coroutine methods to match their documentation Previously these methods returned asyncio Future instances Contributed by Yury Selivanov in bpo 32327 asyncio Server sockets now returns a copy of the internal list of server sockets instead of returning it directly Contributed by Yury Selivanov in bpo 32662 Struct format is now a str instance instead of a bytes instance Contributed by Victor Stinner in bpo 21071 argparse subparsers can now be made mandatory by passing required True to Argum,en
2359,entParser add_subparsers Contributed by Anthony Sottile in bpo 26510 ast literal_eval is now stricter Addition and subtraction of arbitrary numbers are no longer allowed Contributed by Serhiy Storchaka in bpo 31778 Calendar itermonthdates will now consistently raise an exception when a date falls outside of the 0001 01 01 through 9999 12 31 range To support applications that cannot tolerate such exceptions the new Calendar itermonthdays3 and Calendar itermonthdays4 can be used The new methods return tuples and are not restricted by the range supported by datetime date Contributed by Alexander Belopolsky in bpo 28292 collections ChainMap now preserves the order of the underlying mappings Contributed by Raymond Hettinger in bpo 32792 The submit method of concurrent futures ThreadPoolExecutor and concurrent futures ProcessPoolExecutor now raises a RuntimeError if called during interpreter shutdown Contributed by Mark Nemec in bpo 33097 The configparser ConfigParser constructor now uses read_dict to process the default values making its behavior consistent with the rest of the parser Non string keys and values in the defaults dictionary are now being implicitly converted to strings Contributed by James Tocknell in bpo 23835 Several undocumented internal imports were removed One example is that os errno is no longer available use import errno directly instead Note that such undocumented internal imports may be removed any time without notice even in micro version releases Changes in the C API The function PySlice_GetIndicesEx is considered unsafe for resizable sequences If the slice indices are not instances of int but objects that implement the __index__ method the sequence can be resized after passing its length to PySlice_GetIndicesEx This can lead to returning indices out of the length of the sequence For avoiding possible problems use new functions PySlice_Unpack and PySlice_AdjustIndices Contributed by Serhiy Storchaka in bpo 27867 CPython bytecode changes There are two new opcodes LOAD_METHOD and CALL_METHOD Contributed by Yury Selivanov and INADA Naoki in bpo 26110 The STORE_ANNOTATION opcode has been removed Contributed by Mark Shannon in bpo 32550 Windows only Changes The file used to override sys path is now called python executable _pth instead of sys path See Finding modules for more information Contributed by Steve Dower in bpo 28137 Other CPython implementation changes In preparation for potential future changes to the public CPython runtime initialization API see PEP 432 for an initial but somewhat outdated draft CPython s internal startup and configuration management logic has been significantly refactored While these updates are intended to be entirely transparent to both embedding applications and users of the regular CPython CLI they re being mentioned here as the refactoring changes the internal order of various operations during interpreter startup and hence may uncover previously latent defects either in embedding applications or in CPython itself Initially contributed by Nick Coghlan and Eric Snow as part of bpo 22257 and further updated by Nick Eric and Victor Stinner in a number of other issues Some known details affected PySys_AddWarnOptionUnicode is not currently usable by embedding applications due to the requirement to create a Unicode object prior to calling Py_Initialize Use PySys_AddWarnOption instead warnings filters added by an embedding application with PySys_AddWarnOption should now more consistently take precedence over the default filters set by the interpreter Due to changes in the way the default warnings filters are configured setting Py_BytesWarningFlag to a value greater than one is no longer sufficient to both emit BytesWarning messages and have them converted to exceptions Instead the flag must be set to cause the warnings to be emitted in the first place and an explicit error BytesWarning warnings filter added to convert them to exceptions Due to a change in the way docstrings are handled by the compiler the implicit return None in a function body consisting solely of a docstring,en
2360, is now marked as occurring on the same line as the docstring not on the function s header line The current exception state has been moved from the frame object to the co routine This simplified the interpreter and fixed a couple of obscure bugs caused by having swap exception state when entering or exiting a generator Contributed by Mark Shannon in bpo 25612 Notable changes in Python 3 7 1 Starting in 3 7 1 Py_Initialize now consistently reads and respects all of the same environment settings as Py_Main in earlier Python versions it respected an ill defined subset of those environment variables while in Python 3 7 0 it didn t read any of them due to bpo 34247 If this behavior is unwanted set Py_IgnoreEnvironmentFlag to 1 before calling Py_Initialize In 3 7 1 the C API for Context Variables was updated to use PyObject pointers See also bpo 34762 In 3 7 1 the tokenize module now implicitly emits a NEWLINE token when provided with input that does not have a trailing new line This behavior now matches what the C tokenizer does internally Contributed by Ammar Askar in bpo 33899 Notable changes in Python 3 7 2 In 3 7 2 venv on Windows no longer copies the original binaries but creates redirector scripts named python exe and pythonw exe instead This resolves a long standing issue where all virtual environments would have to be upgraded or recreated with each Python update However note that this release will still require recreation of virtual environments in order to get the new scripts Notable changes in Python 3 7 6 Due to significant security concerns the reuse_address parameter of asyncio loop create_datagram_endpoint is no longer supported This is because of the behavior of the socket option SO_REUSEADDR in UDP For more details see the documentation for loop create_datagram_endpoint Contributed by Kyle Stanley Antoine Pitrou and Yury Selivanov in bpo 37228 Notable changes in Python 3 7 10 Earlier Python versions allowed using both and as query parameter separators in urllib parse parse_qs and urllib parse parse_qsl Due to security concerns and to conform with newer W3C recommendations this has been changed to allow only a single separator key with as the default This change also affects cgi parse and cgi parse_multipart as they use the affected functions internally For more details please see their respective documentation Contributed by Adam Goldschmidt Senthil Kumaran and Ken Jin in bpo 42967 Notable changes in Python 3 7 11 A security fix alters the ftplib FTP behavior to not trust the IPv4 address sent from the remote server when setting up a passive data channel We reuse the ftp server IP address instead For unusual code requiring the old behavior set a trust_server_pasv_ipv4_address attribute on your FTP instance to True See gh 87451 The presence of newline or tab characters in parts of a URL allows for some forms of attacks Following the WHATWG specification that updates RFC 3986 ASCII newline n r and tab t characters are stripped from the URL by the parser urllib parse preventing such attacks The removal characters are controlled by a new module level variable urllib parse _UNSAFE_URL_BYTES_TO_REMOVE See gh 88048 Notable security feature in 3 7 14 Converting between int and str in bases other than 2 binary 4 8 octal 16 hexadecimal or 32 such as base 10 decimal now raises a ValueError if the number of digits in string form is above a limit to avoid potential denial of service attacks due to the algorithmic complexity This is a mitigation for CVE 2020 10735 This limit can be configured or disabled by environment variable command line flag or sys APIs See the integer string conversion length limitation documentation The default limit is 4300 digits in string form,en
2361,getopt C style parser for command line options Source code Lib getopt py Note The getopt module is a parser for command line options whose API is designed to be familiar to users of the C getopt function Users who are unfamiliar with the C getopt function or who would like to write less code and get better help and error messages should consider using the argparse module instead This module helps scripts to parse the command line arguments in sys argv It supports the same conventions as the Unix getopt function including the special meanings of arguments of the form and Long options similar to those supported by GNU software may be used as well via an optional third argument This module provides two functions and an exception getopt getopt args shortopts longopts Parses command line options and parameter list args is the argument list to be parsed without the leading reference to the running program Typically this means sys argv 1 shortopts is the string of option letters that the script wants to recognize with options that require an argument followed by a colon i e the same format that Unix getopt uses Note Unlike GNU getopt after a non option argument all further arguments are considered also non options This is similar to the way non GNU Unix systems work longopts if specified must be a list of strings with the names of the long options which should be supported The leading characters should not be included in the option name Long options which require an argument should be followed by an equal sign Optional arguments are not supported To accept only long options shortopts should be an empty string Long options on the command line can be recognized so long as they provide a prefix of the option name that matches exactly one of the accepted options For example if longopts is foo frob the option fo will match as foo but f will not match uniquely so GetoptError will be raised The return value consists of two elements the first is a list of option value pairs the second is the list of program arguments left after the option list was stripped this is a trailing slice of args Each option and value pair returned has the option as its first element prefixed with a hyphen for short options e g x or two hyphens for long options e g long option and the option argument as its second element or an empty string if the option has no argument The options occur in the list in the same order in which they were found thus allowing multiple occurrences Long and short options may be mixed getopt gnu_getopt args shortopts longopts This function works like getopt except that GNU style scanning mode is used by default This means that option and non option arguments may be intermixed The getopt function stops processing options as soon as a non option argument is encountered If the first character of the option string is or if the environment variable POSIXLY_CORRECT is set then option processing stops as soon as a non option argument is encountered exception getopt GetoptError This is raised when an unrecognized option is found in the argument list or when an option requiring an argument is given none The argument to the exception is a string indicating the cause of the error For long options an argument given to an option which does not require one will also cause this exception to be raised The attributes msg and opt give the error message and related option if there is no specific option to which the exception relates opt is an empty string exception getopt error Alias for GetoptError for backward compatibility An example using only Unix style options import getopt args a b cfoo d bar a1 a2 split args a b cfoo d bar a1 a2 optlist args getopt getopt args abc d optlist a b c foo d bar args a1 a2 Using long option names is equally easy s condition foo testing output file abc def x a1 a2 args s split args condition foo testing output file abc def x a1 a2 optlist args getopt getopt args x condition output file testing optlist condition foo testing output file abc def x args a1 a2 In a script typical usage is something like this import getopt ,en
2362,sys def main try opts args getopt getopt sys argv 1 ho v help output except getopt GetoptError as err print help information and exit print err will print something like option a not recognized usage sys exit 2 output None verbose False for o a in opts if o v verbose True elif o in h help usage sys exit elif o in o output output a else assert False unhandled option if __name__ __main__ main Note that an equivalent command line interface could be produced with less code and more informative help and error messages by using the argparse module import argparse if __name__ __main__ parser argparse ArgumentParser parser add_argument o output parser add_argument v dest verbose action store_true args parser parse_args do something with args output do something with args verbose See also Module argparse Alternative command line option and argument parsing library,en
2363,html HyperText Markup Language support Source code Lib html __init__ py This module defines utilities to manipulate HTML html escape s quote True Convert the characters and in string s to HTML safe sequences Use this if you need to display text that might contain such characters in HTML If the optional flag quote is true the characters and are also translated this helps for inclusion in an HTML attribute value delimited by quotes as in a href New in version 3 2 html unescape s Convert all named and numeric character references e g gt 62 x3e in the string s to the corresponding Unicode characters This function uses the rules defined by the HTML 5 standard for both valid and invalid character references and the list of HTML 5 named character references New in version 3 4 Submodules in the html package are html parser HTML XHTML parser with lenient parsing mode html entities HTML entity definitions,en
2364,ipaddress IPv4 IPv6 manipulation library Source code Lib ipaddress py ipaddress provides the capabilities to create manipulate and operate on IPv4 and IPv6 addresses and networks The functions and classes in this module make it straightforward to handle various tasks related to IP addresses including checking whether or not two hosts are on the same subnet iterating over all hosts in a particular subnet checking whether or not a string represents a valid IP address or network definition and so on This is the full module API reference for an overview and introduction see An introduction to the ipaddress module New in version 3 3 Convenience factory functions The ipaddress module provides factory functions to conveniently create IP addresses networks and interfaces ipaddress ip_address address Return an IPv4Address or IPv6Address object depending on the IP address passed as argument Either IPv4 or IPv6 addresses may be supplied integers less than 2 32 will be considered to be IPv4 by default A ValueError is raised if address does not represent a valid IPv4 or IPv6 address ipaddress ip_address 192 168 0 1 IPv4Address 192 168 0 1 ipaddress ip_address 2001 db8 IPv6Address 2001 db8 ipaddress ip_network address strict True Return an IPv4Network or IPv6Network object depending on the IP address passed as argument address is a string or integer representing the IP network Either IPv4 or IPv6 networks may be supplied integers less than 2 32 will be considered to be IPv4 by default strict is passed to IPv4Network or IPv6Network constructor A ValueError is raised if address does not represent a valid IPv4 or IPv6 address or if the network has host bits set ipaddress ip_network 192 168 0 0 28 IPv4Network 192 168 0 0 28 ipaddress ip_interface address Return an IPv4Interface or IPv6Interface object depending on the IP address passed as argument address is a string or integer representing the IP address Either IPv4 or IPv6 addresses may be supplied integers less than 2 32 will be considered to be IPv4 by default A ValueError is raised if address does not represent a valid IPv4 or IPv6 address One downside of these convenience functions is that the need to handle both IPv4 and IPv6 formats means that error messages provide minimal information on the precise error as the functions don t know whether the IPv4 or IPv6 format was intended More detailed error reporting can be obtained by calling the appropriate version specific class constructors directly IP Addresses Address objects The IPv4Address and IPv6Address objects share a lot of common attributes Some attributes that are only meaningful for IPv6 addresses are also implemented by IPv4Address objects in order to make it easier to write code that handles both IP versions correctly Address objects are hashable so they can be used as keys in dictionaries class ipaddress IPv4Address address Construct an IPv4 address An AddressValueError is raised if address is not a valid IPv4 address The following constitutes a valid IPv4 address 1 A string in decimal dot notation consisting of four decimal integers in the inclusive range 0 255 separated by dots e g 192 168 0 1 Each integer represents an octet byte in the address Leading zeroes are not tolerated to prevent confusion with octal notation 2 An integer that fits into 32 bits 3 An integer packed into a bytes object of length 4 most significant octet first ipaddress IPv4Address 192 168 0 1 IPv4Address 192 168 0 1 ipaddress IPv4Address 3232235521 IPv4Address 192 168 0 1 ipaddress IPv4Address b xC0 xA8 x00 x01 IPv4Address 192 168 0 1 Changed in version 3 8 Leading zeros are tolerated even in ambiguous cases that look like octal notation Changed in version 3 9 5 Leading zeros are no longer tolerated and are treated as an error IPv4 address strings are now parsed as strict as glibc inet_pton version The appropriate version number 4 for IPv4 6 for IPv6 max_prefixlen The total number of bits in the address representation for this version 32 for IPv4 128 for IPv6 The prefix defines the number of leading bits in an address that are compared to determin,en
2365,e whether or not an address is part of a network compressed exploded The string representation in dotted decimal notation Leading zeroes are never included in the representation As IPv4 does not define a shorthand notation for addresses with octets set to zero these two attributes are always the same as str addr for IPv4 addresses Exposing these attributes makes it easier to write display code that can handle both IPv4 and IPv6 addresses packed The binary representation of this address a bytes object of the appropriate length most significant octet first This is 4 bytes for IPv4 and 16 bytes for IPv6 reverse_pointer The name of the reverse DNS PTR record for the IP address e g ipaddress ip_address 127 0 0 1 reverse_pointer 1 0 0 127 in addr arpa ipaddress ip_address 2001 db8 1 reverse_pointer 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 8 b d 0 1 0 0 2 ip6 arpa This is the name that could be used for performing a PTR lookup not the resolved hostname itself New in version 3 5 is_multicast True if the address is reserved for multicast use See RFC 3171 for IPv4 or RFC 2373 for IPv6 is_private True if the address is allocated for private networks See iana ipv4 special registry for IPv4 or iana ipv6 special registry for IPv6 is_global True if the address is allocated for public networks See iana ipv4 special registry for IPv4 or iana ipv6 special registry for IPv6 New in version 3 4 is_unspecified True if the address is unspecified See RFC 5735 for IPv4 or RFC 2373 for IPv6 is_reserved True if the address is otherwise IETF reserved is_loopback True if this is a loopback address See RFC 3330 for IPv4 or RFC 2373 for IPv6 is_link_local True if the address is reserved for link local usage See RFC 3927 IPv4Address __format__ fmt Returns a string representation of the IP address controlled by an explicit format string fmt can be one of the following s the default option equivalent to str b for a zero padded binary string X or x for an uppercase or lowercase hexadecimal representation or n which is equivalent to b for IPv4 addresses and x for IPv6 For binary and hexadecimal representations the form specifier and the grouping option _ are available __format__ is used by format str format and f strings format ipaddress IPv4Address 192 168 0 1 192 168 0 1 b format ipaddress IPv4Address 192 168 0 1 0b11000000101010000000000000000001 f ipaddress IPv6Address 2001 db8 1000 s 2001 db8 1000 format ipaddress IPv6Address 2001 db8 1000 _X 2001_0DB8_0000_0000_0000_0000_0000_1000 _n format ipaddress IPv6Address 2001 db8 1000 0x2001_0db8_0000_0000_0000_0000_0000_1000 New in version 3 9 class ipaddress IPv6Address address Construct an IPv6 address An AddressValueError is raised if address is not a valid IPv6 address The following constitutes a valid IPv6 address 1 A string consisting of eight groups of four hexadecimal digits each group representing 16 bits The groups are separated by colons This describes an exploded longhand notation The string can also be compressed shorthand notation by various means See RFC 4291 for details For example 0000 0000 0000 0000 0000 0abc 0007 0def can be compressed to abc 7 def Optionally the string may also have a scope zone ID expressed with a suffix scope_id If present the scope ID must be non empty and may not contain See RFC 4007 for details For example fe80 1234 1 might identify address fe80 1234 on the first link of the node 2 An integer that fits into 128 bits 3 An integer packed into a bytes object of length 16 big endian ipaddress IPv6Address 2001 db8 1000 IPv6Address 2001 db8 1000 ipaddress IPv6Address ff02 5678 1 IPv6Address ff02 5678 1 compressed The short form of the address representation with leading zeroes in groups omitted and the longest sequence of groups consisting entirely of zeroes collapsed to a single empty group This is also the value returned by str addr for IPv6 addresses exploded The long form of the address representation with all leading zeroes and groups consisting entirely of zeroes included For the following attributes and methods see the corresponding documentation of the IPv4A,en
2366,ddress class packed reverse_pointer version max_prefixlen is_multicast is_private is_global is_unspecified is_reserved is_loopback is_link_local New in version 3 4 is_global is_site_local True if the address is reserved for site local usage Note that the site local address space has been deprecated by RFC 3879 Use is_private to test if this address is in the space of unique local addresses as defined by RFC 4193 ipv4_mapped For addresses that appear to be IPv4 mapped addresses starting with FFFF 96 this property will report the embedded IPv4 address For any other address this property will be None scope_id For scoped addresses as defined by RFC 4007 this property identifies the particular zone of the address s scope that the address belongs to as a string When no scope zone is specified this property will be None sixtofour For addresses that appear to be 6to4 addresses starting with 2002 16 as defined by RFC 3056 this property will report the embedded IPv4 address For any other address this property will be None teredo For addresses that appear to be Teredo addresses starting with 2001 32 as defined by RFC 4380 this property will report the embedded server client IP address pair For any other address this property will be None IPv6Address __format__ fmt Refer to the corresponding method documentation in IPv4Address New in version 3 9 Conversion to Strings and Integers To interoperate with networking interfaces such as the socket module addresses must be converted to strings or integers This is handled using the str and int builtin functions str ipaddress IPv4Address 192 168 0 1 192 168 0 1 int ipaddress IPv4Address 192 168 0 1 3232235521 str ipaddress IPv6Address 1 1 int ipaddress IPv6Address 1 1 Note that IPv6 scoped addresses are converted to integers without scope zone ID Operators Address objects support some operators Unless stated otherwise operators can only be applied between compatible objects i e IPv4 with IPv4 IPv6 with IPv6 Comparison operators Address objects can be compared with the usual set of comparison operators Same IPv6 addresses with different scope zone IDs are not equal Some examples IPv4Address 127 0 0 2 IPv4Address 127 0 0 1 True IPv4Address 127 0 0 2 IPv4Address 127 0 0 1 False IPv4Address 127 0 0 2 IPv4Address 127 0 0 1 True IPv6Address fe80 1234 IPv6Address fe80 1234 1 False IPv6Address fe80 1234 1 IPv6Address fe80 1234 2 True Arithmetic operators Integers can be added to or subtracted from address objects Some examples IPv4Address 127 0 0 2 3 IPv4Address 127 0 0 5 IPv4Address 127 0 0 2 3 IPv4Address 126 255 255 255 IPv4Address 255 255 255 255 1 Traceback most recent call last File stdin line 1 in module ipaddress AddressValueError 4294967296 2 32 is not permitted as an IPv4 address IP Network definitions The IPv4Network and IPv6Network objects provide a mechanism for defining and inspecting IP network definitions A network definition consists of a mask and a network address and as such defines a range of IP addresses that equal the network address when masked binary AND with the mask For example a network definition with the mask 255 255 255 0 and the network address 192 168 1 0 consists of IP addresses in the inclusive range 192 168 1 0 to 192 168 1 255 Prefix net mask and host mask There are several equivalent ways to specify IP network masks A prefix nbits is a notation that denotes how many high order bits are set in the network mask A net mask is an IP address with some number of high order bits set Thus the prefix 24 is equivalent to the net mask 255 255 255 0 in IPv4 or ffff ff00 in IPv6 In addition a host mask is the logical inverse of a net mask and is sometimes used for example in Cisco access control lists to denote a network mask The host mask equivalent to 24 in IPv4 is 0 0 0 255 Network objects All attributes implemented by address objects are implemented by network objects as well In addition network objects implement additional attributes All of these are common between IPv4Network and IPv6Network so to avoid duplication they are only documented for IPv4Network Network objects,en
2367, are hashable so they can be used as keys in dictionaries class ipaddress IPv4Network address strict True Construct an IPv4 network definition address can be one of the following 1 A string consisting of an IP address and an optional mask separated by a slash The IP address is the network address and the mask can be either a single number which means it s a prefix or a string representation of an IPv4 address If it s the latter the mask is interpreted as a net mask if it starts with a non zero field or as a host mask if it starts with a zero field with the single exception of an all zero mask which is treated as a net mask If no mask is provided it s considered to be 32 For example the following address specifications are equivalent 192 168 1 0 24 192 168 1 0 255 255 255 0 and 192 168 1 0 0 0 0 255 2 An integer that fits into 32 bits This is equivalent to a single address network with the network address being address and the mask being 32 3 An integer packed into a bytes object of length 4 big endian The interpretation is similar to an integer address 4 A two tuple of an address description and a netmask where the address description is either a string a 32 bits integer a 4 bytes packed integer or an existing IPv4Address object and the netmask is either an integer representing the prefix length e g 24 or a string representing the prefix mask e g 255 255 255 0 An AddressValueError is raised if address is not a valid IPv4 address A NetmaskValueError is raised if the mask is not valid for an IPv4 address If strict is True and host bits are set in the supplied address then ValueError is raised Otherwise the host bits are masked out to determine the appropriate network address Unless stated otherwise all network methods accepting other network address objects will raise TypeError if the argument s IP version is incompatible to self Changed in version 3 5 Added the two tuple form for the address constructor parameter version max_prefixlen Refer to the corresponding attribute documentation in IPv4Address is_multicast is_private is_unspecified is_reserved is_loopback is_link_local These attributes are true for the network as a whole if they are true for both the network address and the broadcast address network_address The network address for the network The network address and the prefix length together uniquely define a network broadcast_address The broadcast address for the network Packets sent to the broadcast address should be received by every host on the network hostmask The host mask as an IPv4Address object netmask The net mask as an IPv4Address object with_prefixlen compressed exploded A string representation of the network with the mask in prefix notation with_prefixlen and compressed are always the same as str network exploded uses the exploded form the network address with_netmask A string representation of the network with the mask in net mask notation with_hostmask A string representation of the network with the mask in host mask notation num_addresses The total number of addresses in the network prefixlen Length of the network prefix in bits hosts Returns an iterator over the usable hosts in the network The usable hosts are all the IP addresses that belong to the network except the network address itself and the network broadcast address For networks with a mask length of 31 the network address and network broadcast address are also included in the result Networks with a mask of 32 will return a list containing the single host address list ip_network 192 0 2 0 29 hosts IPv4Address 192 0 2 1 IPv4Address 192 0 2 2 IPv4Address 192 0 2 3 IPv4Address 192 0 2 4 IPv4Address 192 0 2 5 IPv4Address 192 0 2 6 list ip_network 192 0 2 0 31 hosts IPv4Address 192 0 2 0 IPv4Address 192 0 2 1 list ip_network 192 0 2 1 32 hosts IPv4Address 192 0 2 1 overlaps other True if this network is partly or wholly contained in other or other is wholly contained in this network address_exclude network Computes the network definitions resulting from removing the given network from this one Returns an iterator of network objects Raises ValueE,en
2368,rror if network is not completely contained in this network n1 ip_network 192 0 2 0 28 n2 ip_network 192 0 2 1 32 list n1 address_exclude n2 IPv4Network 192 0 2 8 29 IPv4Network 192 0 2 4 30 IPv4Network 192 0 2 2 31 IPv4Network 192 0 2 0 32 subnets prefixlen_diff 1 new_prefix None The subnets that join to make the current network definition depending on the argument values prefixlen_diff is the amount our prefix length should be increased by new_prefix is the desired new prefix of the subnets it must be larger than our prefix One and only one of prefixlen_diff and new_prefix must be set Returns an iterator of network objects list ip_network 192 0 2 0 24 subnets IPv4Network 192 0 2 0 25 IPv4Network 192 0 2 128 25 list ip_network 192 0 2 0 24 subnets prefixlen_diff 2 IPv4Network 192 0 2 0 26 IPv4Network 192 0 2 64 26 IPv4Network 192 0 2 128 26 IPv4Network 192 0 2 192 26 list ip_network 192 0 2 0 24 subnets new_prefix 26 IPv4Network 192 0 2 0 26 IPv4Network 192 0 2 64 26 IPv4Network 192 0 2 128 26 IPv4Network 192 0 2 192 26 list ip_network 192 0 2 0 24 subnets new_prefix 23 Traceback most recent call last File stdin line 1 in module raise ValueError new prefix must be longer ValueError new prefix must be longer list ip_network 192 0 2 0 24 subnets new_prefix 25 IPv4Network 192 0 2 0 25 IPv4Network 192 0 2 128 25 supernet prefixlen_diff 1 new_prefix None The supernet containing this network definition depending on the argument values prefixlen_diff is the amount our prefix length should be decreased by new_prefix is the desired new prefix of the supernet it must be smaller than our prefix One and only one of prefixlen_diff and new_prefix must be set Returns a single network object ip_network 192 0 2 0 24 supernet IPv4Network 192 0 2 0 23 ip_network 192 0 2 0 24 supernet prefixlen_diff 2 IPv4Network 192 0 0 0 22 ip_network 192 0 2 0 24 supernet new_prefix 20 IPv4Network 192 0 0 0 20 subnet_of other Return True if this network is a subnet of other a ip_network 192 168 1 0 24 b ip_network 192 168 1 128 30 b subnet_of a True New in version 3 7 supernet_of other Return True if this network is a supernet of other a ip_network 192 168 1 0 24 b ip_network 192 168 1 128 30 a supernet_of b True New in version 3 7 compare_networks other Compare this network to other In this comparison only the network addresses are considered host bits aren t Returns either 1 0 or 1 ip_network 192 0 2 1 32 compare_networks ip_network 192 0 2 2 32 1 ip_network 192 0 2 1 32 compare_networks ip_network 192 0 2 0 32 1 ip_network 192 0 2 1 32 compare_networks ip_network 192 0 2 1 32 0 Deprecated since version 3 7 It uses the same ordering and comparison algorithm as and class ipaddress IPv6Network address strict True Construct an IPv6 network definition address can be one of the following 1 A string consisting of an IP address and an optional prefix length separated by a slash The IP address is the network address and the prefix length must be a single number the prefix If no prefix length is provided it s considered to be 128 Note that currently expanded netmasks are not supported That means 2001 db00 0 24 is a valid argument while 2001 db00 0 ffff ff00 is not 2 An integer that fits into 128 bits This is equivalent to a single address network with the network address being address and the mask being 128 3 An integer packed into a bytes object of length 16 big endian The interpretation is similar to an integer address 4 A two tuple of an address description and a netmask where the address description is either a string a 128 bits integer a 16 bytes packed integer or an existing IPv6Address object and the netmask is an integer representing the prefix length An AddressValueError is raised if address is not a valid IPv6 address A NetmaskValueError is raised if the mask is not valid for an IPv6 address If strict is True and host bits are set in the supplied address then ValueError is raised Otherwise the host bits are masked out to determine the appropriate network address Changed in version 3 5 Added the two tuple form for the address constructor parameter ver,en
2369,sion max_prefixlen is_multicast is_private is_unspecified is_reserved is_loopback is_link_local network_address broadcast_address hostmask netmask with_prefixlen compressed exploded with_netmask with_hostmask num_addresses prefixlen hosts Returns an iterator over the usable hosts in the network The usable hosts are all the IP addresses that belong to the network except the Subnet Router anycast address For networks with a mask length of 127 the Subnet Router anycast address is also included in the result Networks with a mask of 128 will return a list containing the single host address overlaps other address_exclude network subnets prefixlen_diff 1 new_prefix None supernet prefixlen_diff 1 new_prefix None subnet_of other supernet_of other compare_networks other Refer to the corresponding attribute documentation in IPv4Network is_site_local These attribute is true for the network as a whole if it is true for both the network address and the broadcast address Operators Network objects support some operators Unless stated otherwise operators can only be applied between compatible objects i e IPv4 with IPv4 IPv6 with IPv6 Logical operators Network objects can be compared with the usual set of logical operators Network objects are ordered first by network address then by net mask Iteration Network objects can be iterated to list all the addresses belonging to the network For iteration all hosts are returned including unusable hosts for usable hosts use the hosts method An example for addr in IPv4Network 192 0 2 0 28 addr IPv4Address 192 0 2 0 IPv4Address 192 0 2 1 IPv4Address 192 0 2 2 IPv4Address 192 0 2 3 IPv4Address 192 0 2 4 IPv4Address 192 0 2 5 IPv4Address 192 0 2 6 IPv4Address 192 0 2 7 IPv4Address 192 0 2 8 IPv4Address 192 0 2 9 IPv4Address 192 0 2 10 IPv4Address 192 0 2 11 IPv4Address 192 0 2 12 IPv4Address 192 0 2 13 IPv4Address 192 0 2 14 IPv4Address 192 0 2 15 Networks as containers of addresses Network objects can act as containers of addresses Some examples IPv4Network 192 0 2 0 28 0 IPv4Address 192 0 2 0 IPv4Network 192 0 2 0 28 15 IPv4Address 192 0 2 15 IPv4Address 192 0 2 6 in IPv4Network 192 0 2 0 28 True IPv4Address 192 0 3 6 in IPv4Network 192 0 2 0 28 False Interface objects Interface objects are hashable so they can be used as keys in dictionaries class ipaddress IPv4Interface address Construct an IPv4 interface The meaning of address is as in the constructor of IPv4Network except that arbitrary host addresses are always accepted IPv4Interface is a subclass of IPv4Address so it inherits all the attributes from that class In addition the following attributes are available ip The address IPv4Address without network information interface IPv4Interface 192 0 2 5 24 interface ip IPv4Address 192 0 2 5 network The network IPv4Network this interface belongs to interface IPv4Interface 192 0 2 5 24 interface network IPv4Network 192 0 2 0 24 with_prefixlen A string representation of the interface with the mask in prefix notation interface IPv4Interface 192 0 2 5 24 interface with_prefixlen 192 0 2 5 24 with_netmask A string representation of the interface with the network as a net mask interface IPv4Interface 192 0 2 5 24 interface with_netmask 192 0 2 5 255 255 255 0 with_hostmask A string representation of the interface with the network as a host mask interface IPv4Interface 192 0 2 5 24 interface with_hostmask 192 0 2 5 0 0 0 255 class ipaddress IPv6Interface address Construct an IPv6 interface The meaning of address is as in the constructor of IPv6Network except that arbitrary host addresses are always accepted IPv6Interface is a subclass of IPv6Address so it inherits all the attributes from that class In addition the following attributes are available ip network with_prefixlen with_netmask with_hostmask Refer to the corresponding attribute documentation in IPv4Interface Operators Interface objects support some operators Unless stated otherwise operators can only be applied between compatible objects i e IPv4 with IPv4 IPv6 with IPv6 Logical operators Interface objects can be compared with the usual set of logic,en
2370,al operators For equality comparison and both the IP address and network must be the same for the objects to be equal An interface will not compare equal to any address or network object For ordering etc the rules are different Interface and address objects with the same IP version can be compared and the address objects will always sort before the interface objects Two interface objects are first compared by their networks and if those are the same then by their IP addresses Other Module Level Functions The module also provides the following module level functions ipaddress v4_int_to_packed address Represent an address as 4 packed bytes in network big endian order address is an integer representation of an IPv4 IP address A ValueError is raised if the integer is negative or too large to be an IPv4 IP address ipaddress ip_address 3221225985 IPv4Address 192 0 2 1 ipaddress v4_int_to_packed 3221225985 b xc0 x00 x02 x01 ipaddress v6_int_to_packed address Represent an address as 16 packed bytes in network big endian order address is an integer representation of an IPv6 IP address A ValueError is raised if the integer is negative or too large to be an IPv6 IP address ipaddress summarize_address_range first last Return an iterator of the summarized network range given the first and last IP addresses first is the first IPv4Address or IPv6Address in the range and last is the last IPv4Address or IPv6Address in the range A TypeError is raised if first or last are not IP addresses or are not of the same version A ValueError is raised if last is not greater than first or if first address version is not 4 or 6 ipaddr for ipaddr in ipaddress summarize_address_range ipaddress IPv4Address 192 0 2 0 ipaddress IPv4Address 192 0 2 130 IPv4Network 192 0 2 0 25 IPv4Network 192 0 2 128 31 IPv4Network 192 0 2 130 32 ipaddress collapse_addresses addresses Return an iterator of the collapsed IPv4Network or IPv6Network objects addresses is an iterator of IPv4Network or IPv6Network objects A TypeError is raised if addresses contains mixed version objects ipaddr for ipaddr in ipaddress collapse_addresses ipaddress IPv4Network 192 0 2 0 25 ipaddress IPv4Network 192 0 2 128 25 IPv4Network 192 0 2 0 24 ipaddress get_mixed_type_key obj Return a key suitable for sorting between networks and addresses Address and Network objects are not sortable by default they re fundamentally different so the expression IPv4Address 192 0 2 0 IPv4Network 192 0 2 0 24 doesn t make sense There are some times however where you may wish to have ipaddress sort these anyway If you need to do this you can use this function as the key argument to sorted obj is either a network or address object Custom Exceptions To support more specific error reporting from class constructors the module defines the following exceptions exception ipaddress AddressValueError ValueError Any value error related to the address exception ipaddress NetmaskValueError ValueError Any value error related to the net mask,en
2371,array Efficient arrays of numeric values This module defines an object type which can compactly represent an array of basic values characters integers floating point numbers Arrays are sequence types and behave very much like lists except that the type of objects stored in them is constrained The type is specified at object creation time by using a type code which is a single character The following type codes are defined Type code C Type Python Type Minimum size in bytes Notes b signed char int 1 B unsigned char int 1 u wchar_t Unicode character 2 1 h signed short int 2 H unsigned short int 2 i signed int int 2 I unsigned int int 2 l signed long int 4 L unsigned long int 4 q signed long long int 8 Q unsigned long long int 8 f float float 4 d double float 8 Notes 1 It can be 16 bits or 32 bits depending on the platform Changed in version 3 9 array u now uses wchar_t as C type instead of deprecated Py_UNICODE This change doesn t affect its behavior because Py_UNICODE is alias of wchar_t since Python 3 3 Deprecated since version 3 3 will be removed in version 4 0 The actual representation of values is determined by the machine architecture strictly speaking by the C implementation The actual size can be accessed through the array itemsize attribute The module defines the following item array typecodes A string with all available type codes The module defines the following type class array array typecode initializer A new array whose items are restricted by typecode and initialized from the optional initializer value which must be a bytes or bytearray object a Unicode string or iterable over elements of the appropriate type If given a bytes or bytearray object the initializer is passed to the new array s frombytes method if given a Unicode string the initializer is passed to the fromunicode method otherwise the initializer s iterator is passed to the extend method to add initial items to the array Array objects support the ordinary sequence operations of indexing slicing concatenation and multiplication When using slice assignment the assigned value must be an array object with the same type code in all other cases TypeError is raised Array objects also implement the buffer interface and may be used wherever bytes like objects are supported Raises an auditing event array __new__ with arguments typecode initializer typecode The typecode character used to create the array itemsize The length in bytes of one array item in the internal representation append x Append a new item with value x to the end of the array buffer_info Return a tuple address length giving the current memory address and the length in elements of the buffer used to hold array s contents The size of the memory buffer in bytes can be computed as array buffer_info 1 array itemsize This is occasionally useful when working with low level and inherently unsafe I O interfaces that require memory addresses such as certain ioctl operations The returned numbers are valid as long as the array exists and no length changing operations are applied to it Note When using array objects from code written in C or C the only way to effectively make use of this information it makes more sense to use the buffer interface supported by array objects This method is maintained for backward compatibility and should be avoided in new code The buffer interface is documented in Buffer Protocol byteswap Byteswap all items of the array This is only supported for values which are 1 2 4 or 8 bytes in size for other types of values RuntimeError is raised It is useful when reading data from a file written on a machine with a different byte order count x Return the number of occurrences of x in the array extend iterable Append items from iterable to the end of the array If iterable is another array it must have exactly the same type code if not TypeError will be raised If iterable is not an array it must be iterable and its elements must be the right type to be appended to the array frombytes buffer Appends items from the bytes like object interpreting its content as an array of machine values,en
2372, as if it had been read from a file using the fromfile method New in version 3 2 fromstring is renamed to frombytes for clarity fromfile f n Read n items as machine values from the file object f and append them to the end of the array If less than n items are available EOFError is raised but the items that were available are still inserted into the array fromlist list Append items from the list This is equivalent to for x in list a append x except that if there is a type error the array is unchanged fromunicode s Extends this array with data from the given Unicode string The array must have type code u otherwise a ValueError is raised Use array frombytes unicodestring encode enc to append Unicode data to an array of some other type index x start stop Return the smallest i such that i is the index of the first occurrence of x in the array The optional arguments start and stop can be specified to search for x within a subsection of the array Raise ValueError if x is not found Changed in version 3 10 Added optional start and stop parameters insert i x Insert a new item with value x in the array before position i Negative values are treated as being relative to the end of the array pop i Removes the item with the index i from the array and returns it The optional argument defaults to 1 so that by default the last item is removed and returned remove x Remove the first occurrence of x from the array reverse Reverse the order of the items in the array tobytes Convert the array to an array of machine values and return the bytes representation the same sequence of bytes that would be written to a file by the tofile method New in version 3 2 tostring is renamed to tobytes for clarity tofile f Write all items as machine values to the file object f tolist Convert the array to an ordinary list with the same items tounicode Convert the array to a Unicode string The array must have a type u otherwise a ValueError is raised Use array tobytes decode enc to obtain a Unicode string from an array of some other type The string representation of array objects has the form array typecode initializer The initializer is omitted if the array is empty otherwise it is a Unicode string if the typecode is u otherwise it is a list of numbers The string representation is guaranteed to be able to be converted back to an array with the same type and value using eval so long as the array class has been imported using from array import array Variables inf and nan must also be defined if it contains corresponding floating point values Examples array l array u hello u2641 array l 1 2 3 4 5 array d 1 0 2 0 3 14 inf nan See also Module struct Packing and unpacking of heterogeneous binary data Module xdrlib Packing and unpacking of External Data Representation XDR data as used in some remote procedure call systems NumPy The NumPy package defines another array type,en
2373,mailbox Manipulate mailboxes in various formats Source code Lib mailbox py This module defines two classes Mailbox and Message for accessing and manipulating on disk mailboxes and the messages they contain Mailbox offers a dictionary like mapping from keys to messages Message extends the email message module s Message class with format specific state and behavior Supported mailbox formats are Maildir mbox MH Babyl and MMDF See also Module email Represent and manipulate messages Mailbox objects class mailbox Mailbox A mailbox which may be inspected and modified The Mailbox class defines an interface and is not intended to be instantiated Instead format specific subclasses should inherit from Mailbox and your code should instantiate a particular subclass The Mailbox interface is dictionary like with small keys corresponding to messages Keys are issued by the Mailbox instance with which they will be used and are only meaningful to that Mailbox instance A key continues to identify a message even if the corresponding message is modified such as by replacing it with another message Messages may be added to a Mailbox instance using the set like method add and removed using a del statement or the set like methods remove and discard Mailbox interface semantics differ from dictionary semantics in some noteworthy ways Each time a message is requested a new representation typically a Message instance is generated based upon the current state of the mailbox Similarly when a message is added to a Mailbox instance the provided message representation s contents are copied In neither case is a reference to the message representation kept by the Mailbox instance The default Mailbox iterator iterates over message representations not keys as the default dictionary iterator does Moreover modification of a mailbox during iteration is safe and well defined Messages added to the mailbox after an iterator is created will not be seen by the iterator Messages removed from the mailbox before the iterator yields them will be silently skipped though using a key from an iterator may result in a KeyError exception if the corresponding message is subsequently removed Warning Be very cautious when modifying mailboxes that might be simultaneously changed by some other process The safest mailbox format to use for such tasks is Maildir try to avoid using single file formats such as mbox for concurrent writing If you re modifying a mailbox you must lock it by calling the lock and unlock methods before reading any messages in the file or making any changes by adding or deleting a message Failing to lock the mailbox runs the risk of losing messages or corrupting the entire mailbox Mailbox instances have the following methods add message Add message to the mailbox and return the key that has been assigned to it Parameter message may be a Message instance an email message Message instance a string a byte string or a file like object which should be open in binary mode If message is an instance of the appropriate format specific Message subclass e g if it s an mboxMessage instance and this is an mbox instance its format specific information is used Otherwise reasonable defaults for format specific information are used Changed in version 3 2 Support for binary input was added remove key __delitem__ key discard key Delete the message corresponding to key from the mailbox If no such message exists a KeyError exception is raised if the method was called as remove or __delitem__ but no exception is raised if the method was called as discard The behavior of discard may be preferred if the underlying mailbox format supports concurrent modification by other processes __setitem__ key message Replace the message corresponding to key with message Raise a KeyError exception if no message already corresponds to key As with add parameter message may be a Message instance an email message Message instance a string a byte string or a file like object which should be open in binary mode If message is an instance of the appropriate format specific Message subclass e g if it s an m,en
2374,boxMessage instance and this is an mbox instance its format specific information is used Otherwise the format specific information of the message that currently corresponds to key is left unchanged iterkeys Return an iterator over all keys keys The same as iterkeys except that a list is returned rather than an iterator itervalues __iter__ Return an iterator over representations of all messages The messages are represented as instances of the appropriate format specific Message subclass unless a custom message factory was specified when the Mailbox instance was initialized Note The behavior of __iter__ is unlike that of dictionaries which iterate over keys values The same as itervalues except that a list is returned rather than an iterator iteritems Return an iterator over key message pairs where key is a key and message is a message representation The messages are represented as instances of the appropriate format specific Message subclass unless a custom message factory was specified when the Mailbox instance was initialized items The same as iteritems except that a list of pairs is returned rather than an iterator of pairs get key default None __getitem__ key Return a representation of the message corresponding to key If no such message exists default is returned if the method was called as get and a KeyError exception is raised if the method was called as __getitem__ The message is represented as an instance of the appropriate format specific Message subclass unless a custom message factory was specified when the Mailbox instance was initialized get_message key Return a representation of the message corresponding to key as an instance of the appropriate format specific Message subclass or raise a KeyError exception if no such message exists get_bytes key Return a byte representation of the message corresponding to key or raise a KeyError exception if no such message exists New in version 3 2 get_string key Return a string representation of the message corresponding to key or raise a KeyError exception if no such message exists The message is processed through email message Message to convert it to a 7bit clean representation get_file key Return a file like representation of the message corresponding to key or raise a KeyError exception if no such message exists The file like object behaves as if open in binary mode This file should be closed once it is no longer needed Changed in version 3 2 The file object really is a binary file previously it was incorrectly returned in text mode Also the file like object now supports the context manager protocol you can use a with statement to automatically close it Note Unlike other representations of messages file like representations are not necessarily independent of the Mailbox instance that created them or of the underlying mailbox More specific documentation is provided by each subclass __contains__ key Return True if key corresponds to a message False otherwise __len__ Return a count of messages in the mailbox clear Delete all messages from the mailbox pop key default None Return a representation of the message corresponding to key and delete the message If no such message exists return default The message is represented as an instance of the appropriate format specific Message subclass unless a custom message factory was specified when the Mailbox instance was initialized popitem Return an arbitrary key message pair where key is a key and message is a message representation and delete the corresponding message If the mailbox is empty raise a KeyError exception The message is represented as an instance of the appropriate format specific Message subclass unless a custom message factory was specified when the Mailbox instance was initialized update arg Parameter arg should be a key to message mapping or an iterable of key message pairs Updates the mailbox so that for each given key and message the message corresponding to key is set to message as if by using __setitem__ As with __setitem__ each key must already correspond to a message in the mailbox or else a KeyError excepti,en
2375,on will be raised so in general it is incorrect for arg to be a Mailbox instance Note Unlike with dictionaries keyword arguments are not supported flush Write any pending changes to the filesystem For some Mailbox subclasses changes are always written immediately and flush does nothing but you should still make a habit of calling this method lock Acquire an exclusive advisory lock on the mailbox so that other processes know not to modify it An ExternalClashError is raised if the lock is not available The particular locking mechanisms used depend upon the mailbox format You should always lock the mailbox before making any modifications to its contents unlock Release the lock on the mailbox if any close Flush the mailbox unlock it if necessary and close any open files For some Mailbox subclasses this method does nothing Maildir objects class mailbox Maildir dirname factory None create True A subclass of Mailbox for mailboxes in Maildir format Parameter factory is a callable object that accepts a file like message representation which behaves as if opened in binary mode and returns a custom representation If factory is None MaildirMessage is used as the default message representation If create is True the mailbox is created if it does not exist If create is True and the dirname path exists it will be treated as an existing maildir without attempting to verify its directory layout It is for historical reasons that dirname is named as such rather than path Maildir is a directory based mailbox format invented for the qmail mail transfer agent and now widely supported by other programs Messages in a Maildir mailbox are stored in separate files within a common directory structure This design allows Maildir mailboxes to be accessed and modified by multiple unrelated programs without data corruption so file locking is unnecessary Maildir mailboxes contain three subdirectories namely tmp new and cur Messages are created momentarily in the tmp subdirectory and then moved to the new subdirectory to finalize delivery A mail user agent may subsequently move the message to the cur subdirectory and store information about the state of the message in a special info section appended to its file name Folders of the style introduced by the Courier mail transfer agent are also supported Any subdirectory of the main mailbox is considered a folder if is the first character in its name Folder names are represented by Maildir without the leading Each folder is itself a Maildir mailbox but should not contain other folders Instead a logical nesting is indicated using to delimit levels e g Archived 2005 07 colon The Maildir specification requires the use of a colon in certain message file names However some operating systems do not permit this character in file names If you wish to use a Maildir like format on such an operating system you should specify another character to use instead The exclamation point is a popular choice For example import mailbox mailbox Maildir colon The colon attribute may also be set on a per instance basis Maildir instances have all of the methods of Mailbox in addition to the following list_folders Return a list of the names of all folders get_folder folder Return a Maildir instance representing the folder whose name is folder A NoSuchMailboxError exception is raised if the folder does not exist add_folder folder Create a folder whose name is folder and return a Maildir instance representing it remove_folder folder Delete the folder whose name is folder If the folder contains any messages a NotEmptyError exception will be raised and the folder will not be deleted clean Delete temporary files from the mailbox that have not been accessed in the last 36 hours The Maildir specification says that mail reading programs should do this occasionally Some Mailbox methods implemented by Maildir deserve special remarks add message __setitem__ key message update arg Warning These methods generate unique file names based upon the current process ID When using multiple threads undetected name clashes may occur and cause corruption of t,en
2376,he mailbox unless threads are coordinated to avoid using these methods to manipulate the same mailbox simultaneously flush All changes to Maildir mailboxes are immediately applied so this method does nothing lock unlock Maildir mailboxes do not support or require locking so these methods do nothing close Maildir instances do not keep any open files and the underlying mailboxes do not support locking so this method does nothing get_file key Depending upon the host platform it may not be possible to modify or remove the underlying message while the returned file remains open See also maildir man page from Courier A specification of the format Describes a common extension for supporting folders Using maildir format Notes on Maildir by its inventor Includes an updated name creation scheme and details on info semantics mbox objects class mailbox mbox path factory None create True A subclass of Mailbox for mailboxes in mbox format Parameter factory is a callable object that accepts a file like message representation which behaves as if opened in binary mode and returns a custom representation If factory is None mboxMessage is used as the default message representation If create is True the mailbox is created if it does not exist The mbox format is the classic format for storing mail on Unix systems All messages in an mbox mailbox are stored in a single file with the beginning of each message indicated by a line whose first five characters are From Several variations of the mbox format exist to address perceived shortcomings in the original In the interest of compatibility mbox implements the original format which is sometimes referred to as mboxo This means that the Content Length header if present is ignored and that any occurrences of From at the beginning of a line in a message body are transformed to From when storing the message although occurrences of From are not transformed to From when reading the message Some Mailbox methods implemented by mbox deserve special remarks get_file key Using the file after calling flush or close on the mbox instance may yield unpredictable results or raise an exception lock unlock Three locking mechanisms are used dot locking and if available the flock and lockf system calls See also mbox man page from tin A specification of the format with details on locking Configuring Netscape Mail on Unix Why The Content Length Format is Bad An argument for using the original mbox format rather than a variation mbox is a family of several mutually incompatible mailbox formats A history of mbox variations MH objects class mailbox MH path factory None create True A subclass of Mailbox for mailboxes in MH format Parameter factory is a callable object that accepts a file like message representation which behaves as if opened in binary mode and returns a custom representation If factory is None MHMessage is used as the default message representation If create is True the mailbox is created if it does not exist MH is a directory based mailbox format invented for the MH Message Handling System a mail user agent Each message in an MH mailbox resides in its own file An MH mailbox may contain other MH mailboxes called folders in addition to messages Folders may be nested indefinitely MH mailboxes also support sequences which are named lists used to logically group messages without moving them to sub folders Sequences are defined in a file called mh_sequences in each folder The MH class manipulates MH mailboxes but it does not attempt to emulate all of mh s behaviors In particular it does not modify and is not affected by the context or mh_profile files that are used by mh to store its state and configuration MH instances have all of the methods of Mailbox in addition to the following list_folders Return a list of the names of all folders get_folder folder Return an MH instance representing the folder whose name is folder A NoSuchMailboxError exception is raised if the folder does not exist add_folder folder Create a folder whose name is folder and return an MH instance representing it remove_folder folder Delet,en
2377,e the folder whose name is folder If the folder contains any messages a NotEmptyError exception will be raised and the folder will not be deleted get_sequences Return a dictionary of sequence names mapped to key lists If there are no sequences the empty dictionary is returned set_sequences sequences Re define the sequences that exist in the mailbox based upon sequences a dictionary of names mapped to key lists like returned by get_sequences pack Rename messages in the mailbox as necessary to eliminate gaps in numbering Entries in the sequences list are updated correspondingly Note Already issued keys are invalidated by this operation and should not be subsequently used Some Mailbox methods implemented by MH deserve special remarks remove key __delitem__ key discard key These methods immediately delete the message The MH convention of marking a message for deletion by prepending a comma to its name is not used lock unlock Three locking mechanisms are used dot locking and if available the flock and lockf system calls For MH mailboxes locking the mailbox means locking the mh_sequences file and only for the duration of any operations that affect them locking individual message files get_file key Depending upon the host platform it may not be possible to remove the underlying message while the returned file remains open flush All changes to MH mailboxes are immediately applied so this method does nothing close MH instances do not keep any open files so this method is equivalent to unlock See also nmh Message Handling System Home page of nmh an updated version of the original mh MH nmh Email for Users Programmers A GPL licensed book on mh and nmh with some information on the mailbox format Babyl objects class mailbox Babyl path factory None create True A subclass of Mailbox for mailboxes in Babyl format Parameter factory is a callable object that accepts a file like message representation which behaves as if opened in binary mode and returns a custom representation If factory is None BabylMessage is used as the default message representation If create is True the mailbox is created if it does not exist Babyl is a single file mailbox format used by the Rmail mail user agent included with Emacs The beginning of a message is indicated by a line containing the two characters Control Underscore 037 and Control L 014 The end of a message is indicated by the start of the next message or in the case of the last message a line containing a Control Underscore 037 character Messages in a Babyl mailbox have two sets of headers original headers and so called visible headers Visible headers are typically a subset of the original headers that have been reformatted or abridged to be more attractive Each message in a Babyl mailbox also has an accompanying list of labels or short strings that record extra information about the message and a list of all user defined labels found in the mailbox is kept in the Babyl options section Babyl instances have all of the methods of Mailbox in addition to the following get_labels Return a list of the names of all user defined labels used in the mailbox Note The actual messages are inspected to determine which labels exist in the mailbox rather than consulting the list of labels in the Babyl options section but the Babyl section is updated whenever the mailbox is modified Some Mailbox methods implemented by Babyl deserve special remarks get_file key In Babyl mailboxes the headers of a message are not stored contiguously with the body of the message To generate a file like representation the headers and body are copied together into an io BytesIO instance which has an API identical to that of a file As a result the file like object is truly independent of the underlying mailbox but does not save memory compared to a string representation lock unlock Three locking mechanisms are used dot locking and if available the flock and lockf system calls See also Format of Version 5 Babyl Files A specification of the Babyl format Reading Mail with Rmail The Rmail manual with some information on Babyl semantics MMDF obj,en
2378,ects class mailbox MMDF path factory None create True A subclass of Mailbox for mailboxes in MMDF format Parameter factory is a callable object that accepts a file like message representation which behaves as if opened in binary mode and returns a custom representation If factory is None MMDFMessage is used as the default message representation If create is True the mailbox is created if it does not exist MMDF is a single file mailbox format invented for the Multichannel Memorandum Distribution Facility a mail transfer agent Each message is in the same form as an mbox message but is bracketed before and after by lines containing four Control A 001 characters As with the mbox format the beginning of each message is indicated by a line whose first five characters are From but additional occurrences of From are not transformed to From when storing messages because the extra message separator lines prevent mistaking such occurrences for the starts of subsequent messages Some Mailbox methods implemented by MMDF deserve special remarks get_file key Using the file after calling flush or close on the MMDF instance may yield unpredictable results or raise an exception lock unlock Three locking mechanisms are used dot locking and if available the flock and lockf system calls See also mmdf man page from tin A specification of MMDF format from the documentation of tin a newsreader MMDF A Wikipedia article describing the Multichannel Memorandum Distribution Facility Message objects class mailbox Message message None A subclass of the email message module s Message Subclasses of mailbox Message add mailbox format specific state and behavior If message is omitted the new instance is created in a default empty state If message is an email message Message instance its contents are copied furthermore any format specific information is converted insofar as possible if message is a Message instance If message is a string a byte string or a file it should contain an RFC 2822 compliant message which is read and parsed Files should be open in binary mode but text mode files are accepted for backward compatibility The format specific state and behaviors offered by subclasses vary but in general it is only the properties that are not specific to a particular mailbox that are supported although presumably the properties are specific to a particular mailbox format For example file offsets for single file mailbox formats and file names for directory based mailbox formats are not retained because they are only applicable to the original mailbox But state such as whether a message has been read by the user or marked as important is retained because it applies to the message itself There is no requirement that Message instances be used to represent messages retrieved using Mailbox instances In some situations the time and memory required to generate Message representations might not be acceptable For such situations Mailbox instances also offer string and file like representations and a custom message factory may be specified when a Mailbox instance is initialized MaildirMessage objects class mailbox MaildirMessage message None A message with Maildir specific behaviors Parameter message has the same meaning as with the Message constructor Typically a mail user agent application moves all of the messages in the new subdirectory to the cur subdirectory after the first time the user opens and closes the mailbox recording that the messages are old whether or not they ve actually been read Each message in cur has an info section added to its file name to store information about its state Some mail readers may also add an info section to messages in new The info section may take one of two forms it may contain 2 followed by a list of standardized flags e g 2 FR or it may contain 1 followed by so called experimental information Standard flags for Maildir messages are as follows Flag Meaning Explanation D Draft Under composition F Flagged Marked as important P Passed Forwarded resent or bounced R Replied Replied to S Seen Read T Trashed Marked for subsequent ,en
2379,deletion MaildirMessage instances offer the following methods get_subdir Return either new if the message should be stored in the new subdirectory or cur if the message should be stored in the cur subdirectory Note A message is typically moved from new to cur after its mailbox has been accessed whether or not the message is has been read A message msg has been read if S in msg get_flags is True set_subdir subdir Set the subdirectory the message should be stored in Parameter subdir must be either new or cur get_flags Return a string specifying the flags that are currently set If the message complies with the standard Maildir format the result is the concatenation in alphabetical order of zero or one occurrence of each of D F P R S and T The empty string is returned if no flags are set or if info contains experimental semantics set_flags flags Set the flags specified by flags and unset all others add_flag flag Set the flag s specified by flag without changing other flags To add more than one flag at a time flag may be a string of more than one character The current info is overwritten whether or not it contains experimental information rather than flags remove_flag flag Unset the flag s specified by flag without changing other flags To remove more than one flag at a time flag maybe a string of more than one character If info contains experimental information rather than flags the current info is not modified get_date Return the delivery date of the message as a floating point number representing seconds since the epoch set_date date Set the delivery date of the message to date a floating point number representing seconds since the epoch get_info Return a string containing the info for a message This is useful for accessing and modifying info that is experimental i e not a list of flags set_info info Set info to info which should be a string When a MaildirMessage instance is created based upon an mboxMessage or MMDFMessage instance the Status and X Status headers are omitted and the following conversions take place Resulting state mboxMessage or MMDFMessage state cur subdirectory O flag F flag F flag R flag A flag S flag R flag T flag D flag When a MaildirMessage instance is created based upon an MHMessage instance the following conversions take place Resulting state MHMessage state cur subdirectory unseen sequence cur subdirectory and S flag no unseen sequence F flag flagged sequence R flag replied sequence When a MaildirMessage instance is created based upon a BabylMessage instance the following conversions take place Resulting state BabylMessage state cur subdirectory unseen label cur subdirectory and S flag no unseen label P flag forwarded or resent label R flag answered label T flag deleted label mboxMessage objects class mailbox mboxMessage message None A message with mbox specific behaviors Parameter message has the same meaning as with the Message constructor Messages in an mbox mailbox are stored together in a single file The sender s envelope address and the time of delivery are typically stored in a line beginning with From that is used to indicate the start of a message though there is considerable variation in the exact format of this data among mbox implementations Flags that indicate the state of the message such as whether it has been read or marked as important are typically stored in Status and X Status headers Conventional flags for mbox messages are as follows Flag Meaning Explanation R Read Read O Old Previously detected by MUA D Deleted Marked for subsequent deletion F Flagged Marked as important A Answered Replied to The R and O flags are stored in the Status header and the D F and A flags are stored in the X Status header The flags and headers typically appear in the order mentioned mboxMessage instances offer the following methods get_from Return a string representing the From line that marks the start of the message in an mbox mailbox The leading From and the trailing newline are excluded set_from from_ time_ None Set the From line to from_ which should be specified without a leading From or traili,en
2380,ng newline For convenience time_ may be specified and will be formatted appropriately and appended to from_ If time_ is specified it should be a time struct_time instance a tuple suitable for passing to time strftime or True to use time gmtime get_flags Return a string specifying the flags that are currently set If the message complies with the conventional format the result is the concatenation in the following order of zero or one occurrence of each of R O D F and A set_flags flags Set the flags specified by flags and unset all others Parameter flags should be the concatenation in any order of zero or more occurrences of each of R O D F and A add_flag flag Set the flag s specified by flag without changing other flags To add more than one flag at a time flag may be a string of more than one character remove_flag flag Unset the flag s specified by flag without changing other flags To remove more than one flag at a time flag maybe a string of more than one character When an mboxMessage instance is created based upon a MaildirMessage instance a From line is generated based upon the MaildirMessage instance s delivery date and the following conversions take place Resulting state MaildirMessage state R flag S flag O flag cur subdirectory D flag T flag F flag F flag A flag R flag When an mboxMessage instance is created based upon an MHMessage instance the following conversions take place Resulting state MHMessage state R flag and O flag no unseen sequence O flag unseen sequence F flag flagged sequence A flag replied sequence When an mboxMessage instance is created based upon a BabylMessage instance the following conversions take place Resulting state BabylMessage state R flag and O flag no unseen label O flag unseen label D flag deleted label A flag answered label When a mboxMessage instance is created based upon an MMDFMessage instance the From line is copied and all flags directly correspond Resulting state MMDFMessage state R flag R flag O flag O flag D flag D flag F flag F flag A flag A flag MHMessage objects class mailbox MHMessage message None A message with MH specific behaviors Parameter message has the same meaning as with the Message constructor MH messages do not support marks or flags in the traditional sense but they do support sequences which are logical groupings of arbitrary messages Some mail reading programs although not the standard mh and nmh use sequences in much the same way flags are used with other formats as follows Sequence Explanation unseen Not read but previously detected by MUA replied Replied to flagged Marked as important MHMessage instances offer the following methods get_sequences Return a list of the names of sequences that include this message set_sequences sequences Set the list of sequences that include this message add_sequence sequence Add sequence to the list of sequences that include this message remove_sequence sequence Remove sequence from the list of sequences that include this message When an MHMessage instance is created based upon a MaildirMessage instance the following conversions take place Resulting state MaildirMessage state unseen sequence no S flag replied sequence R flag flagged sequence F flag When an MHMessage instance is created based upon an mboxMessage or MMDFMessage instance the Status and X Status headers are omitted and the following conversions take place Resulting state mboxMessage or MMDFMessage state unseen sequence no R flag replied sequence A flag flagged sequence F flag When an MHMessage instance is created based upon a BabylMessage instance the following conversions take place Resulting state BabylMessage state unseen sequence unseen label replied sequence answered label BabylMessage objects class mailbox BabylMessage message None A message with Babyl specific behaviors Parameter message has the same meaning as with the Message constructor Certain message labels called attributes are defined by convention to have special meanings The attributes are as follows Label Explanation unseen Not read but previously detected by MUA deleted Marked for subsequent dele,en
2381,tion filed Copied to another file or mailbox answered Replied to forwarded Forwarded edited Modified by the user resent Resent By default Rmail displays only visible headers The BabylMessage class though uses the original headers because they are more complete Visible headers may be accessed explicitly if desired BabylMessage instances offer the following methods get_labels Return a list of labels on the message set_labels labels Set the list of labels on the message to labels add_label label Add label to the list of labels on the message remove_label label Remove label from the list of labels on the message get_visible Return an Message instance whose headers are the message s visible headers and whose body is empty set_visible visible Set the message s visible headers to be the same as the headers in message Parameter visible should be a Message instance an email message Message instance a string or a file like object which should be open in text mode update_visible When a BabylMessage instance s original headers are modified the visible headers are not automatically modified to correspond This method updates the visible headers as follows each visible header with a corresponding original header is set to the value of the original header each visible header without a corresponding original header is removed and any of Date From Reply To To CC and Subject that are present in the original headers but not the visible headers are added to the visible headers When a BabylMessage instance is created based upon a MaildirMessage instance the following conversions take place Resulting state MaildirMessage state unseen label no S flag deleted label T flag answered label R flag forwarded label P flag When a BabylMessage instance is created based upon an mboxMessage or MMDFMessage instance the Status and X Status headers are omitted and the following conversions take place Resulting state mboxMessage or MMDFMessage state unseen label no R flag deleted label D flag answered label A flag When a BabylMessage instance is created based upon an MHMessage instance the following conversions take place Resulting state MHMessage state unseen label unseen sequence answered label replied sequence MMDFMessage objects class mailbox MMDFMessage message None A message with MMDF specific behaviors Parameter message has the same meaning as with the Message constructor As with message in an mbox mailbox MMDF messages are stored with the sender s address and the delivery date in an initial line beginning with From Likewise flags that indicate the state of the message are typically stored in Status and X Status headers Conventional flags for MMDF messages are identical to those of mbox message and are as follows Flag Meaning Explanation R Read Read O Old Previously detected by MUA D Deleted Marked for subsequent deletion F Flagged Marked as important A Answered Replied to The R and O flags are stored in the Status header and the D F and A flags are stored in the X Status header The flags and headers typically appear in the order mentioned MMDFMessage instances offer the following methods which are identical to those offered by mboxMessage get_from Return a string representing the From line that marks the start of the message in an mbox mailbox The leading From and the trailing newline are excluded set_from from_ time_ None Set the From line to from_ which should be specified without a leading From or trailing newline For convenience time_ may be specified and will be formatted appropriately and appended to from_ If time_ is specified it should be a time struct_time instance a tuple suitable for passing to time strftime or True to use time gmtime get_flags Return a string specifying the flags that are currently set If the message complies with the conventional format the result is the concatenation in the following order of zero or one occurrence of each of R O D F and A set_flags flags Set the flags specified by flags and unset all others Parameter flags should be the concatenation in any order of zero or more occurrences of each of R O D F and A add_,en
2382,flag flag Set the flag s specified by flag without changing other flags To add more than one flag at a time flag may be a string of more than one character remove_flag flag Unset the flag s specified by flag without changing other flags To remove more than one flag at a time flag maybe a string of more than one character When an MMDFMessage instance is created based upon a MaildirMessage instance a From line is generated based upon the MaildirMessage instance s delivery date and the following conversions take place Resulting state MaildirMessage state R flag S flag O flag cur subdirectory D flag T flag F flag F flag A flag R flag When an MMDFMessage instance is created based upon an MHMessage instance the following conversions take place Resulting state MHMessage state R flag and O flag no unseen sequence O flag unseen sequence F flag flagged sequence A flag replied sequence When an MMDFMessage instance is created based upon a BabylMessage instance the following conversions take place Resulting state BabylMessage state R flag and O flag no unseen label O flag unseen label D flag deleted label A flag answered label When an MMDFMessage instance is created based upon an mboxMessage instance the From line is copied and all flags directly correspond Resulting state mboxMessage state R flag R flag O flag O flag D flag D flag F flag F flag A flag A flag Exceptions The following exception classes are defined in the mailbox module exception mailbox Error The based class for all other module specific exceptions exception mailbox NoSuchMailboxError Raised when a mailbox is expected but is not found such as when instantiating a Mailbox subclass with a path that does not exist and with the create parameter set to False or when opening a folder that does not exist exception mailbox NotEmptyError Raised when a mailbox is not empty but is expected to be such as when deleting a folder that contains messages exception mailbox ExternalClashError Raised when some mailbox related condition beyond the control of the program causes it to be unable to proceed such as when failing to acquire a lock that another program already holds a lock or when a uniquely generated file name already exists exception mailbox FormatError Raised when the data in a file cannot be parsed such as when an MH instance attempts to read a corrupted mh_sequences file Examples A simple example of printing the subjects of all messages in a mailbox that seem interesting import mailbox for message in mailbox mbox mbox subject message subject Could possibly be None if subject and python in subject lower print subject To copy all mail from a Babyl mailbox to an MH mailbox converting all of the format specific information that can be converted import mailbox destination mailbox MH Mail destination lock for message in mailbox Babyl RMAIL destination add mailbox MHMessage message destination flush destination unlock This example sorts mail from several mailing lists into different mailboxes being careful to avoid mail corruption due to concurrent modification by other programs mail loss due to interruption of the program or premature termination due to malformed messages in the mailbox import mailbox import email errors list_names python list python dev python bugs boxes name mailbox mbox email s name for name in list_names inbox mailbox Maildir Maildir factory None for key in inbox iterkeys try message inbox key except email errors MessageParseError continue The message is malformed Just leave it for name in list_names list_id message list id if list_id and name in list_id Get mailbox to use box boxes name Write copy to disk before removing original If there s a crash you might duplicate a message but that s better than losing a message completely box lock box add message box flush box unlock Remove original message inbox lock inbox discard key inbox flush inbox unlock break Found destination so stop looking for box in boxes itervalues box close,en
2383,msilib Read and write Microsoft Installer files Source code Lib msilib __init__ py Deprecated since version 3 11 will be removed in version 3 13 The msilib module is deprecated see PEP 594 for details The msilib supports the creation of Microsoft Installer msi files Because these files often contain an embedded cabinet file cab it also exposes an API to create CAB files Support for reading cab files is currently not implemented read support for the msi database is possible This package aims to provide complete access to all tables in an msi file therefore it is a fairly low level API One primary application of this package is the creation of Python installer package itself although that currently uses a different version of msilib The package contents can be roughly split into four parts low level CAB routines low level MSI routines higher level MSI routines and standard table structures msilib FCICreate cabname files Create a new CAB file named cabname files must be a list of tuples each containing the name of the file on disk and the name of the file inside the CAB file The files are added to the CAB file in the order they appear in the list All files are added into a single CAB file using the MSZIP compression algorithm Callbacks to Python for the various steps of MSI creation are currently not exposed msilib UuidCreate Return the string representation of a new unique identifier This wraps the Windows API functions UuidCreate and UuidToString msilib OpenDatabase path persist Return a new database object by calling MsiOpenDatabase path is the file name of the MSI file persist can be one of the constants MSIDBOPEN_CREATEDIRECT MSIDBOPEN_CREATE MSIDBOPEN_DIRECT MSIDBOPEN_READONLY or MSIDBOPEN_TRANSACT and may include the flag MSIDBOPEN_PATCHFILE See the Microsoft documentation for the meaning of these flags depending on the flags an existing database is opened or a new one created msilib CreateRecord count Return a new record object by calling MSICreateRecord count is the number of fields of the record msilib init_database name schema ProductName ProductCode ProductVersion Manufacturer Create and return a new database name initialize it with schema and set the properties ProductName ProductCode ProductVersion and Manufacturer schema must be a module object containing tables and _Validation_records attributes typically msilib schema should be used The database will contain just the schema and the validation records when this function returns msilib add_data database table records Add all records to the table named table in database The table argument must be one of the predefined tables in the MSI schema e g Feature File Component Dialog Control etc records should be a list of tuples each one containing all fields of a record according to the schema of the table For optional fields None can be passed Field values can be ints strings or instances of the Binary class class msilib Binary filename Represents entries in the Binary table inserting such an object using add_data reads the file named filename into the table msilib add_tables database module Add all table content from module to database module must contain an attribute tables listing all tables for which content should be added and one attribute per table that has the actual content This is typically used to install the sequence tables msilib add_stream database name path Add the file path into the _Stream table of database with the stream name name msilib gen_uuid Return a new UUID in the format that MSI typically requires i e in curly braces and with all hexdigits in uppercase See also FCICreate UuidCreate UuidToString Database Objects Database OpenView sql Return a view object by calling MSIDatabaseOpenView sql is the SQL statement to execute Database Commit Commit the changes pending in the current transaction by calling MSIDatabaseCommit Database GetSummaryInformation count Return a new summary information object by calling MsiGetSummaryInformation count is the maximum number of updated values Database Close Close the database object through MsiCloseHandle New,en
2384, in version 3 7 See also MSIDatabaseOpenView MSIDatabaseCommit MSIGetSummaryInformation MsiCloseHandle View Objects View Execute params Execute the SQL query of the view through MSIViewExecute If params is not None it is a record describing actual values of the parameter tokens in the query View GetColumnInfo kind Return a record describing the columns of the view through calling MsiViewGetColumnInfo kind can be either MSICOLINFO_NAMES or MSICOLINFO_TYPES View Fetch Return a result record of the query through calling MsiViewFetch View Modify kind data Modify the view by calling MsiViewModify kind can be one of MSIMODIFY_SEEK MSIMODIFY_REFRESH MSIMODIFY_INSERT MSIMODIFY_UPDATE MSIMODIFY_ASSIGN MSIMODIFY_REPLACE MSIMODIFY_MERGE MSIMODIFY_DELETE MSIMODIFY_INSERT_TEMPORARY MSIMODIFY_VALIDATE MSIMODIFY_VALIDATE_NEW MSIMODIFY_VALIDATE_FIELD or MSIMODIFY_VALIDATE_DELETE data must be a record describing the new data View Close Close the view through MsiViewClose See also MsiViewExecute MSIViewGetColumnInfo MsiViewFetch MsiViewModify MsiViewClose Summary Information Objects SummaryInformation GetProperty field Return a property of the summary through MsiSummaryInfoGetProperty field is the name of the property and can be one of the constants PID_CODEPAGE PID_TITLE PID_SUBJECT PID_AUTHOR PID_KEYWORDS PID_COMMENTS PID_TEMPLATE PID_LASTAUTHOR PID_REVNUMBER PID_LASTPRINTED PID_CREATE_DTM PID_LASTSAVE_DTM PID_PAGECOUNT PID_WORDCOUNT PID_CHARCOUNT PID_APPNAME or PID_SECURITY SummaryInformation GetPropertyCount Return the number of summary properties through MsiSummaryInfoGetPropertyCount SummaryInformation SetProperty field value Set a property through MsiSummaryInfoSetProperty field can have the same values as in GetProperty value is the new value of the property Possible value types are integer and string SummaryInformation Persist Write the modified properties to the summary information stream using MsiSummaryInfoPersist See also MsiSummaryInfoGetProperty MsiSummaryInfoGetPropertyCount MsiSummaryInfoSetProperty MsiSummaryInfoPersist Record Objects Record GetFieldCount Return the number of fields of the record through MsiRecordGetFieldCount Record GetInteger field Return the value of field as an integer where possible field must be an integer Record GetString field Return the value of field as a string where possible field must be an integer Record SetString field value Set field to value through MsiRecordSetString field must be an integer value a string Record SetStream field value Set field to the contents of the file named value through MsiRecordSetStream field must be an integer value a string Record SetInteger field value Set field to value through MsiRecordSetInteger Both field and value must be an integer Record ClearData Set all fields of the record to 0 through MsiRecordClearData See also MsiRecordGetFieldCount MsiRecordSetString MsiRecordSetStream MsiRecordSetInteger MsiRecordClearData Errors All wrappers around MSI functions raise MSIError the string inside the exception will contain more detail CAB Objects class msilib CAB name The class CAB represents a CAB file During MSI construction files will be added simultaneously to the Files table and to a CAB file Then when all files have been added the CAB file can be written then added to the MSI file name is the name of the CAB file in the MSI file append full file logical Add the file with the pathname full to the CAB file under the name logical If there is already a file named logical a new file name is created Return the index of the file in the CAB file and the new name of the file inside the CAB file commit database Generate a CAB file add it as a stream to the MSI file put it into the Media table and remove the generated file from the disk Directory Objects class msilib Directory database cab basedir physical logical default componentflags Create a new directory in the Directory table There is a current component at each point in time for the directory which is either explicitly created through start_component or implicitly when files are added for the first time Files a,en
2385,re added into the current component and into the cab file To create a directory a base directory object needs to be specified can be None the path to the physical directory and a logical directory name default specifies the DefaultDir slot in the directory table componentflags specifies the default flags that new components get start_component component None feature None flags None keyfile None uuid None Add an entry to the Component table and make this component the current component for this directory If no component name is given the directory name is used If no feature is given the current feature is used If no flags are given the directory s default flags are used If no keyfile is given the KeyPath is left null in the Component table add_file file src None version None language None Add a file to the current component of the directory starting a new one if there is no current component By default the file name in the source and the file table will be identical If the src file is specified it is interpreted relative to the current directory Optionally a version and a language can be specified for the entry in the File table glob pattern exclude None Add a list of files to the current component as specified in the glob pattern Individual files can be excluded in the exclude list remove_pyc Remove pyc files on uninstall See also Directory Table File Table Component Table FeatureComponents Table Features class msilib Feature db id title desc display level 1 parent None directory None attributes 0 Add a new record to the Feature table using the values id parent id title desc display level directory and attributes The resulting feature object can be passed to the start_component method of Directory set_current Make this feature the current feature of msilib New components are automatically added to the default feature unless a feature is explicitly specified See also Feature Table GUI classes msilib provides several classes that wrap the GUI tables in an MSI database However no standard user interface is provided class msilib Control dlg name Base class of the dialog controls dlg is the dialog object the control belongs to and name is the control s name event event argument condition 1 ordering None Make an entry into the ControlEvent table for this control mapping event attribute Make an entry into the EventMapping table for this control condition action condition Make an entry into the ControlCondition table for this control class msilib RadioButtonGroup dlg name property Create a radio button control named name property is the installer property that gets set when a radio button is selected add name x y width height text value None Add a radio button named name to the group at the coordinates x y width height and with the label text If value is None it defaults to name class msilib Dialog db name x y w h attr title first default cancel Return a new Dialog object An entry in the Dialog table is made with the specified coordinates dialog attributes title name of the first default and cancel controls control name type x y width height attributes property text control_next help Return a new Control object An entry in the Control table is made with the specified parameters This is a generic method for specific types specialized methods are provided text name x y width height attributes text Add and return a Text control bitmap name x y width height text Add and return a Bitmap control line name x y width height Add and return a Line control pushbutton name x y width height attributes text next_control Add and return a PushButton control radiogroup name x y width height attributes property text next_control Add and return a RadioButtonGroup control checkbox name x y width height attributes property text next_control Add and return a CheckBox control See also Dialog Table Control Table Control Types ControlCondition Table ControlEvent Table EventMapping Table RadioButton Table Precomputed tables msilib provides a few subpackages that contain only schema and table definitions Currently these definitions are based on MSI versio,en
2386,n 2 0 msilib schema This is the standard MSI schema for MSI 2 0 with the tables variable providing a list of table definitions and _Validation_records providing the data for MSI validation msilib sequence This module contains table contents for the standard sequence tables AdminExecuteSequence AdminUISequence AdvtExecuteSequence InstallExecuteSequence and InstallUISequence msilib text This module contains definitions for the UIText and ActionText tables for the standard installer actions,en
2387,secrets Generate secure random numbers for managing secrets New in version 3 6 Source code Lib secrets py The secrets module is used for generating cryptographically strong random numbers suitable for managing data such as passwords account authentication security tokens and related secrets In particular secrets should be used in preference to the default pseudo random number generator in the random module which is designed for modelling and simulation not security or cryptography See also PEP 506 Random numbers The secrets module provides access to the most secure source of randomness that your operating system provides class secrets SystemRandom A class for generating random numbers using the highest quality sources provided by the operating system See random SystemRandom for additional details secrets choice sequence Return a randomly chosen element from a non empty sequence secrets randbelow n Return a random int in the range 0 n secrets randbits k Return an int with k random bits Generating tokens The secrets module provides functions for generating secure tokens suitable for applications such as password resets hard to guess URLs and similar secrets token_bytes nbytes None Return a random byte string containing nbytes number of bytes If nbytes is None or not supplied a reasonable default is used token_bytes 16 b xebr x17D t xae xd4 xe3S xb6 xe2 xebP1 x8b secrets token_hex nbytes None Return a random text string in hexadecimal The string has nbytes random bytes each byte converted to two hex digits If nbytes is None or not supplied a reasonable default is used token_hex 16 f9bf78b9a18ce6d46a0cd2b0b86df9da secrets token_urlsafe nbytes None Return a random URL safe text string containing nbytes random bytes The text is Base64 encoded so on average each byte results in approximately 1 3 characters If nbytes is None or not supplied a reasonable default is used token_urlsafe 16 Drmhze6EPcv0fN_81Bj nA How many bytes should tokens use To be secure against brute force attacks tokens need to have sufficient randomness Unfortunately what is considered sufficient will necessarily increase as computers get more powerful and able to make more guesses in a shorter period As of 2015 it is believed that 32 bytes 256 bits of randomness is sufficient for the typical use case expected for the secrets module For those who want to manage their own token length you can explicitly specify how much randomness is used for tokens by giving an int argument to the various token_ functions That argument is taken as the number of bytes of randomness to use Otherwise if no argument is provided or if the argument is None the token_ functions will use a reasonable default instead Note That default is subject to change at any time including during maintenance releases Other functions secrets compare_digest a b Return True if strings or bytes like objects a and b are equal otherwise False using a constant time compare to reduce the risk of timing attacks See hmac compare_digest for additional details Recipes and best practices This section shows recipes and best practices for using secrets to manage a basic level of security Generate an eight character alphanumeric password import string import secrets alphabet string ascii_letters string digits password join secrets choice alphabet for i in range 8 Note Applications should not store passwords in a recoverable format whether plain text or encrypted They should be salted and hashed using a cryptographically strong one way irreversible hash function Generate a ten character alphanumeric password with at least one lowercase character at least one uppercase character and at least three digits import string import secrets alphabet string ascii_letters string digits while True password join secrets choice alphabet for i in range 10 if any c islower for c in password and any c isupper for c in password and sum c isdigit for c in password 3 break Generate an XKCD style passphrase import secrets On standard Linux systems use a convenient dictionary file Other platforms may need to provide their own word list ,en
2388,with open usr share dict words as f words word strip for word in f password join secrets choice words for i in range 4 Generate a hard to guess temporary URL containing a security token suitable for password recovery applications import secrets url https example com reset secrets token_urlsafe,en
2389,contextlib Utilities for with statement contexts Source code Lib contextlib py This module provides utilities for common tasks involving the with statement For more information see also Context Manager Types and With Statement Context Managers Utilities Functions and classes provided class contextlib AbstractContextManager An abstract base class for classes that implement object __enter__ and object __exit__ A default implementation for object __enter__ is provided which returns self while object __exit__ is an abstract method which by default returns None See also the definition of Context Manager Types New in version 3 6 class contextlib AbstractAsyncContextManager An abstract base class for classes that implement object __aenter__ and object __aexit__ A default implementation for object __aenter__ is provided which returns self while object __aexit__ is an abstract method which by default returns None See also the definition of Asynchronous Context Managers New in version 3 7 contextlib contextmanager This function is a decorator that can be used to define a factory function for with statement context managers without needing to create a class or separate __enter__ and __exit__ methods While many objects natively support use in with statements sometimes a resource needs to be managed that isn t a context manager in its own right and doesn t implement a close method for use with contextlib closing An abstract example would be the following to ensure correct resource management from contextlib import contextmanager contextmanager def managed_resource args kwds Code to acquire resource e g resource acquire_resource args kwds try yield resource finally Code to release resource e g release_resource resource The function can then be used like this with managed_resource timeout 3600 as resource Resource is released at the end of this block even if code in the block raises an exception The function being decorated must return a generator iterator when called This iterator must yield exactly one value which will be bound to the targets in the with statement s as clause if any At the point where the generator yields the block nested in the with statement is executed The generator is then resumed after the block is exited If an unhandled exception occurs in the block it is reraised inside the generator at the point where the yield occurred Thus you can use a try except finally statement to trap the error if any or ensure that some cleanup takes place If an exception is trapped merely in order to log it or to perform some action rather than to suppress it entirely the generator must reraise that exception Otherwise the generator context manager will indicate to the with statement that the exception has been handled and execution will resume with the statement immediately following the with statement contextmanager uses ContextDecorator so the context managers it creates can be used as decorators as well as in with statements When used as a decorator a new generator instance is implicitly created on each function call this allows the otherwise one shot context managers created by contextmanager to meet the requirement that context managers support multiple invocations in order to be used as decorators Changed in version 3 2 Use of ContextDecorator contextlib asynccontextmanager Similar to contextmanager but creates an asynchronous context manager This function is a decorator that can be used to define a factory function for async with statement asynchronous context managers without needing to create a class or separate __aenter__ and __aexit__ methods It must be applied to an asynchronous generator function A simple example from contextlib import asynccontextmanager asynccontextmanager async def get_connection conn await acquire_db_connection try yield conn finally await release_db_connection conn async def get_all_users async with get_connection as conn return conn query SELECT New in version 3 7 Context managers defined with asynccontextmanager can be used either as decorators or with async with statements import time from conte,en
2390,xtlib import asynccontextmanager asynccontextmanager async def timeit now time monotonic try yield finally print f it took time monotonic now s to run timeit async def main async code When used as a decorator a new generator instance is implicitly created on each function call This allows the otherwise one shot context managers created by asynccontextmanager to meet the requirement that context managers support multiple invocations in order to be used as decorators Changed in version 3 10 Async context managers created with asynccontextmanager can be used as decorators contextlib closing thing Return a context manager that closes thing upon completion of the block This is basically equivalent to from contextlib import contextmanager contextmanager def closing thing try yield thing finally thing close And lets you write code like this from contextlib import closing from urllib request import urlopen with closing urlopen https www python org as page for line in page print line without needing to explicitly close page Even if an error occurs page close will be called when the with block is exited Note Most types managing resources support the context manager protocol which closes thing on leaving the with statement As such closing is most useful for third party types that don t support context managers This example is purely for illustration purposes as urlopen would normally be used in a context manager contextlib aclosing thing Return an async context manager that calls the aclose method of thing upon completion of the block This is basically equivalent to from contextlib import asynccontextmanager asynccontextmanager async def aclosing thing try yield thing finally await thing aclose Significantly aclosing supports deterministic cleanup of async generators when they happen to exit early by break or an exception For example from contextlib import aclosing async with aclosing my_generator as values async for value in values if value 42 break This pattern ensures that the generator s async exit code is executed in the same context as its iterations so that exceptions and context variables work as expected and the exit code isn t run after the lifetime of some task it depends on New in version 3 10 contextlib nullcontext enter_result None Return a context manager that returns enter_result from __enter__ but otherwise does nothing It is intended to be used as a stand in for an optional context manager for example def myfunction arg ignore_exceptions False if ignore_exceptions Use suppress to ignore all exceptions cm contextlib suppress Exception else Do not ignore any exceptions cm has no effect cm contextlib nullcontext with cm Do something An example using enter_result def process_file file_or_path if isinstance file_or_path str If string open file cm open file_or_path else Caller is responsible for closing file cm nullcontext file_or_path with cm as file Perform processing on the file It can also be used as a stand in for asynchronous context managers async def send_http session None if not session If no http session create it with aiohttp cm aiohttp ClientSession else Caller is responsible for closing the session cm nullcontext session async with cm as session Send http requests with session New in version 3 7 Changed in version 3 10 asynchronous context manager support was added contextlib suppress exceptions Return a context manager that suppresses any of the specified exceptions if they occur in the body of a with statement and then resumes execution with the first statement following the end of the with statement As with any other mechanism that completely suppresses exceptions this context manager should be used only to cover very specific errors where silently continuing with program execution is known to be the right thing to do For example from contextlib import suppress with suppress FileNotFoundError os remove somefile tmp with suppress FileNotFoundError os remove someotherfile tmp This code is equivalent to try os remove somefile tmp except FileNotFoundError pass try os remove someotherfile tmp except FileNotFo,en
2391,undError pass This context manager is reentrant If the code within the with block raises a BaseExceptionGroup suppressed exceptions are removed from the group If any exceptions in the group are not suppressed a group containing them is re raised New in version 3 4 Changed in version 3 12 suppress now supports suppressing exceptions raised as part of an BaseExceptionGroup contextlib redirect_stdout new_target Context manager for temporarily redirecting sys stdout to another file or file like object This tool adds flexibility to existing functions or classes whose output is hardwired to stdout For example the output of help normally is sent to sys stdout You can capture that output in a string by redirecting the output to an io StringIO object The replacement stream is returned from the __enter__ method and so is available as the target of the with statement with redirect_stdout io StringIO as f help pow s f getvalue To send the output of help to a file on disk redirect the output to a regular file with open help txt w as f with redirect_stdout f help pow To send the output of help to sys stderr with redirect_stdout sys stderr help pow Note that the global side effect on sys stdout means that this context manager is not suitable for use in library code and most threaded applications It also has no effect on the output of subprocesses However it is still a useful approach for many utility scripts This context manager is reentrant New in version 3 4 contextlib redirect_stderr new_target Similar to redirect_stdout but redirecting sys stderr to another file or file like object This context manager is reentrant New in version 3 5 contextlib chdir path Non parallel safe context manager to change the current working directory As this changes a global state the working directory it is not suitable for use in most threaded or async contexts It is also not suitable for most non linear code execution like generators where the program execution is temporarily relinquished unless explicitly desired you should not yield when this context manager is active This is a simple wrapper around chdir it changes the current working directory upon entering and restores the old one on exit This context manager is reentrant New in version 3 11 class contextlib ContextDecorator A base class that enables a context manager to also be used as a decorator Context managers inheriting from ContextDecorator have to implement __enter__ and __exit__ as normal __exit__ retains its optional exception handling even when used as a decorator ContextDecorator is used by contextmanager so you get this functionality automatically Example of ContextDecorator from contextlib import ContextDecorator class mycontext ContextDecorator def __enter__ self print Starting return self def __exit__ self exc print Finishing return False The class can then be used like this mycontext def function print The bit in the middle function Starting The bit in the middle Finishing with mycontext print The bit in the middle Starting The bit in the middle Finishing This change is just syntactic sugar for any construct of the following form def f with cm Do stuff ContextDecorator lets you instead write cm def f Do stuff It makes it clear that the cm applies to the whole function rather than just a piece of it and saving an indentation level is nice too Existing context managers that already have a base class can be extended by using ContextDecorator as a mixin class from contextlib import ContextDecorator class mycontext ContextBaseClass ContextDecorator def __enter__ self return self def __exit__ self exc return False Note As the decorated function must be able to be called multiple times the underlying context manager must support use in multiple with statements If this is not the case then the original construct with the explicit with statement inside the function should be used New in version 3 2 class contextlib AsyncContextDecorator Similar to ContextDecorator but only for asynchronous functions Example of AsyncContextDecorator from asyncio import run from contextlib import AsyncConte,en
2392,xtDecorator class mycontext AsyncContextDecorator async def __aenter__ self print Starting return self async def __aexit__ self exc print Finishing return False The class can then be used like this mycontext async def function print The bit in the middle run function Starting The bit in the middle Finishing async def function async with mycontext print The bit in the middle run function Starting The bit in the middle Finishing New in version 3 10 class contextlib ExitStack A context manager that is designed to make it easy to programmatically combine other context managers and cleanup functions especially those that are optional or otherwise driven by input data For example a set of files may easily be handled in a single with statement as follows with ExitStack as stack files stack enter_context open fname for fname in filenames All opened files will automatically be closed at the end of the with statement even if attempts to open files later in the list raise an exception The __enter__ method returns the ExitStack instance and performs no additional operations Each instance maintains a stack of registered callbacks that are called in reverse order when the instance is closed either explicitly or implicitly at the end of a with statement Note that callbacks are not invoked implicitly when the context stack instance is garbage collected This stack model is used so that context managers that acquire their resources in their __init__ method such as file objects can be handled correctly Since registered callbacks are invoked in the reverse order of registration this ends up behaving as if multiple nested with statements had been used with the registered set of callbacks This even extends to exception handling if an inner callback suppresses or replaces an exception then outer callbacks will be passed arguments based on that updated state This is a relatively low level API that takes care of the details of correctly unwinding the stack of exit callbacks It provides a suitable foundation for higher level context managers that manipulate the exit stack in application specific ways New in version 3 3 enter_context cm Enters a new context manager and adds its __exit__ method to the callback stack The return value is the result of the context manager s own __enter__ method These context managers may suppress exceptions just as they normally would if used directly as part of a with statement Changed in version 3 11 Raises TypeError instead of AttributeError if cm is not a context manager push exit Adds a context manager s __exit__ method to the callback stack As __enter__ is not invoked this method can be used to cover part of an __enter__ implementation with a context manager s own __exit__ method If passed an object that is not a context manager this method assumes it is a callback with the same signature as a context manager s __exit__ method and adds it directly to the callback stack By returning true values these callbacks can suppress exceptions the same way context manager __exit__ methods can The passed in object is returned from the function allowing this method to be used as a function decorator callback callback args kwds Accepts an arbitrary callback function and arguments and adds it to the callback stack Unlike the other methods callbacks added this way cannot suppress exceptions as they are never passed the exception details The passed in callback is returned from the function allowing this method to be used as a function decorator pop_all Transfers the callback stack to a fresh ExitStack instance and returns it No callbacks are invoked by this operation instead they will now be invoked when the new stack is closed either explicitly or implicitly at the end of a with statement For example a group of files can be opened as an all or nothing operation as follows with ExitStack as stack files stack enter_context open fname for fname in filenames Hold onto the close method but don t call it yet close_files stack pop_all close If opening any file fails all previously opened files will be closed automatically If all files,en
2393, are opened successfully they will remain open even after the with statement ends close_files can then be invoked explicitly to close them all close Immediately unwinds the callback stack invoking callbacks in the reverse order of registration For any context managers and exit callbacks registered the arguments passed in will indicate that no exception occurred class contextlib AsyncExitStack An asynchronous context manager similar to ExitStack that supports combining both synchronous and asynchronous context managers as well as having coroutines for cleanup logic The close method is not implemented aclose must be used instead coroutine enter_async_context cm Similar to ExitStack enter_context but expects an asynchronous context manager Changed in version 3 11 Raises TypeError instead of AttributeError if cm is not an asynchronous context manager push_async_exit exit Similar to ExitStack push but expects either an asynchronous context manager or a coroutine function push_async_callback callback args kwds Similar to ExitStack callback but expects a coroutine function coroutine aclose Similar to ExitStack close but properly handles awaitables Continuing the example for asynccontextmanager async with AsyncExitStack as stack connections await stack enter_async_context get_connection for i in range 5 All opened connections will automatically be released at the end of the async with statement even if attempts to open a connection later in the list raise an exception New in version 3 7 Examples and Recipes This section describes some examples and recipes for making effective use of the tools provided by contextlib Supporting a variable number of context managers The primary use case for ExitStack is the one given in the class documentation supporting a variable number of context managers and other cleanup operations in a single with statement The variability may come from the number of context managers needed being driven by user input such as opening a user specified collection of files or from some of the context managers being optional with ExitStack as stack for resource in resources stack enter_context resource if need_special_resource special acquire_special_resource stack callback release_special_resource special Perform operations that use the acquired resources As shown ExitStack also makes it quite easy to use with statements to manage arbitrary resources that don t natively support the context management protocol Catching exceptions from __enter__ methods It is occasionally desirable to catch exceptions from an __enter__ method implementation without inadvertently catching exceptions from the with statement body or the context manager s __exit__ method By using ExitStack the steps in the context management protocol can be separated slightly in order to allow this stack ExitStack try x stack enter_context cm except Exception handle __enter__ exception else with stack Handle normal case Actually needing to do this is likely to indicate that the underlying API should be providing a direct resource management interface for use with try except finally statements but not all APIs are well designed in that regard When a context manager is the only resource management API provided then ExitStack can make it easier to handle various situations that can t be handled directly in a with statement Cleaning up in an __enter__ implementation As noted in the documentation of ExitStack push this method can be useful in cleaning up an already allocated resource if later steps in the __enter__ implementation fail Here s an example of doing this for a context manager that accepts resource acquisition and release functions along with an optional validation function and maps them to the context management protocol from contextlib import contextmanager AbstractContextManager ExitStack class ResourceManager AbstractContextManager def __init__ self acquire_resource release_resource check_resource_ok None self acquire_resource acquire_resource self release_resource release_resource if check_resource_ok is None def check_resource_ok resource r,en
2394,eturn True self check_resource_ok check_resource_ok contextmanager def _cleanup_on_error self with ExitStack as stack stack push self yield The validation check passed and didn t raise an exception Accordingly we want to keep the resource and pass it back to our caller stack pop_all def __enter__ self resource self acquire_resource with self _cleanup_on_error if not self check_resource_ok resource msg Failed validation for r raise RuntimeError msg format resource return resource def __exit__ self exc_details We don t need to duplicate any of our resource release logic self release_resource Replacing any use of try finally and flag variables A pattern you will sometimes see is a try finally statement with a flag variable to indicate whether or not the body of the finally clause should be executed In its simplest form that can t already be handled just by using an except clause instead it looks something like this cleanup_needed True try result perform_operation if result cleanup_needed False finally if cleanup_needed cleanup_resources As with any try statement based code this can cause problems for development and review because the setup code and the cleanup code can end up being separated by arbitrarily long sections of code ExitStack makes it possible to instead register a callback for execution at the end of a with statement and then later decide to skip executing that callback from contextlib import ExitStack with ExitStack as stack stack callback cleanup_resources result perform_operation if result stack pop_all This allows the intended cleanup up behaviour to be made explicit up front rather than requiring a separate flag variable If a particular application uses this pattern a lot it can be simplified even further by means of a small helper class from contextlib import ExitStack class Callback ExitStack def __init__ self callback args kwds super __init__ self callback callback args kwds def cancel self self pop_all with Callback cleanup_resources as cb result perform_operation if result cb cancel If the resource cleanup isn t already neatly bundled into a standalone function then it is still possible to use the decorator form of ExitStack callback to declare the resource cleanup in advance from contextlib import ExitStack with ExitStack as stack stack callback def cleanup_resources result perform_operation if result stack pop_all Due to the way the decorator protocol works a callback function declared this way cannot take any parameters Instead any resources to be released must be accessed as closure variables Using a context manager as a function decorator ContextDecorator makes it possible to use a context manager in both an ordinary with statement and also as a function decorator For example it is sometimes useful to wrap functions or groups of statements with a logger that can track the time of entry and time of exit Rather than writing both a function decorator and a context manager for the task inheriting from ContextDecorator provides both capabilities in a single definition from contextlib import ContextDecorator import logging logging basicConfig level logging INFO class track_entry_and_exit ContextDecorator def __init__ self name self name name def __enter__ self logging info Entering s self name def __exit__ self exc_type exc exc_tb logging info Exiting s self name Instances of this class can be used as both a context manager with track_entry_and_exit widget loader print Some time consuming activity goes here load_widget And also as a function decorator track_entry_and_exit widget loader def activity print Some time consuming activity goes here load_widget Note that there is one additional limitation when using context managers as function decorators there s no way to access the return value of __enter__ If that value is needed then it is still necessary to use an explicit with statement See also PEP 343 The with statement The specification background and examples for the Python with statement Single use reusable and reentrant context managers Most context managers are written in a way that means they c,en
2395,an only be used effectively in a with statement once These single use context managers must be created afresh each time they re used attempting to use them a second time will trigger an exception or otherwise not work correctly This common limitation means that it is generally advisable to create context managers directly in the header of the with statement where they are used as shown in all of the usage examples above Files are an example of effectively single use context managers since the first with statement will close the file preventing any further IO operations using that file object Context managers created using contextmanager are also single use context managers and will complain about the underlying generator failing to yield if an attempt is made to use them a second time from contextlib import contextmanager contextmanager def singleuse print Before yield print After cm singleuse with cm pass Before After with cm pass Traceback most recent call last RuntimeError generator didn t yield Reentrant context managers More sophisticated context managers may be reentrant These context managers can not only be used in multiple with statements but may also be used inside a with statement that is already using the same context manager threading RLock is an example of a reentrant context manager as are suppress redirect_stdout and chdir Here s a very simple example of reentrant use from contextlib import redirect_stdout from io import StringIO stream StringIO write_to_stream redirect_stdout stream with write_to_stream print This is written to the stream rather than stdout with write_to_stream print This is also written to the stream print This is written directly to stdout This is written directly to stdout print stream getvalue This is written to the stream rather than stdout This is also written to the stream Real world examples of reentrancy are more likely to involve multiple functions calling each other and hence be far more complicated than this example Note also that being reentrant is not the same thing as being thread safe redirect_stdout for example is definitely not thread safe as it makes a global modification to the system state by binding sys stdout to a different stream Reusable context managers Distinct from both single use and reentrant context managers are reusable context managers or to be completely explicit reusable but not reentrant context managers since reentrant context managers are also reusable These context managers support being used multiple times but will fail or otherwise not work correctly if the specific context manager instance has already been used in a containing with statement threading Lock is an example of a reusable but not reentrant context manager for a reentrant lock it is necessary to use threading RLock instead Another example of a reusable but not reentrant context manager is ExitStack as it invokes all currently registered callbacks when leaving any with statement regardless of where those callbacks were added from contextlib import ExitStack stack ExitStack with stack stack callback print Callback from first context print Leaving first context Leaving first context Callback from first context with stack stack callback print Callback from second context print Leaving second context Leaving second context Callback from second context with stack stack callback print Callback from outer context with stack stack callback print Callback from inner context print Leaving inner context print Leaving outer context Leaving inner context Callback from inner context Callback from outer context Leaving outer context As the output from the example shows reusing a single stack object across multiple with statements works correctly but attempting to nest them will cause the stack to be cleared at the end of the innermost with statement which is unlikely to be desirable behaviour Using separate ExitStack instances instead of reusing a single instance avoids that problem from contextlib import ExitStack with ExitStack as outer_stack outer_stack callback print Callback from outer context wi,en
2396,th ExitStack as inner_stack inner_stack callback print Callback from inner context print Leaving inner context print Leaving outer context Leaving inner context Callback from inner context Leaving outer context Callback from outer context,en
2397,email mime Creating email and MIME objects from scratch Source code Lib email mime This module is part of the legacy Compat32 email API Its functionality is partially replaced by the contentmanager in the new API but in certain applications these classes may still be useful even in non legacy code Ordinarily you get a message object structure by passing a file or some text to a parser which parses the text and returns the root message object However you can also build a complete message structure from scratch or even individual Message objects by hand In fact you can also take an existing structure and add new Message objects move them around etc This makes a very convenient interface for slicing and dicing MIME messages You can create a new object structure by creating Message instances adding attachments and all the appropriate headers manually For MIME messages though the email package provides some convenient subclasses to make things easier Here are the classes class email mime base MIMEBase _maintype _subtype policy compat32 _params Module email mime base This is the base class for all the MIME specific subclasses of Message Ordinarily you won t create instances specifically of MIMEBase although you could MIMEBase is provided primarily as a convenient base class for more specific MIME aware subclasses _maintype is the Content Type major type e g text or image and _subtype is the Content Type minor type e g plain or gif _params is a parameter key value dictionary and is passed directly to Message add_header If policy is specified defaults to the compat32 policy it will be passed to Message The MIMEBase class always adds a Content Type header based on _maintype _subtype and _params and a MIME Version header always set to 1 0 Changed in version 3 6 Added policy keyword only parameter class email mime nonmultipart MIMENonMultipart Module email mime nonmultipart A subclass of MIMEBase this is an intermediate base class for MIME messages that are not multipart The primary purpose of this class is to prevent the use of the attach method which only makes sense for multipart messages If attach is called a MultipartConversionError exception is raised class email mime multipart MIMEMultipart _subtype mixed boundary None _subparts None policy compat32 _params Module email mime multipart A subclass of MIMEBase this is an intermediate base class for MIME messages that are multipart Optional _subtype defaults to mixed but can be used to specify the subtype of the message A Content Type header of multipart _subtype will be added to the message object A MIME Version header will also be added Optional boundary is the multipart boundary string When None the default the boundary is calculated when needed for example when the message is serialized _subparts is a sequence of initial subparts for the payload It must be possible to convert this sequence to a list You can always attach new subparts to the message by using the Message attach method Optional policy argument defaults to compat32 Additional parameters for the Content Type header are taken from the keyword arguments or passed into the _params argument which is a keyword dictionary Changed in version 3 6 Added policy keyword only parameter class email mime application MIMEApplication _data _subtype octet stream _encoder email encoders encode_base64 policy compat32 _params Module email mime application A subclass of MIMENonMultipart the MIMEApplication class is used to represent MIME message objects of major type application _data contains the bytes for the raw application data Optional _subtype specifies the MIME subtype and defaults to octet stream Optional _encoder is a callable i e function which will perform the actual encoding of the data for transport This callable takes one argument which is the MIMEApplication instance It should use get_payload and set_payload to change the payload to encoded form It should also add any Content Transfer Encoding or other headers to the message object as necessary The default encoding is base64 See the email encoders module for a list of ,en
2398,the built in encoders Optional policy argument defaults to compat32 _params are passed straight through to the base class constructor Changed in version 3 6 Added policy keyword only parameter class email mime audio MIMEAudio _audiodata _subtype None _encoder email encoders encode_base64 policy compat32 _params Module email mime audio A subclass of MIMENonMultipart the MIMEAudio class is used to create MIME message objects of major type audio _audiodata contains the bytes for the raw audio data If this data can be decoded as au wav aiff or aifc then the subtype will be automatically included in the Content Type header Otherwise you can explicitly specify the audio subtype via the _subtype argument If the minor type could not be guessed and _subtype was not given then TypeError is raised Optional _encoder is a callable i e function which will perform the actual encoding of the audio data for transport This callable takes one argument which is the MIMEAudio instance It should use get_payload and set_payload to change the payload to encoded form It should also add any Content Transfer Encoding or other headers to the message object as necessary The default encoding is base64 See the email encoders module for a list of the built in encoders Optional policy argument defaults to compat32 _params are passed straight through to the base class constructor Changed in version 3 6 Added policy keyword only parameter class email mime image MIMEImage _imagedata _subtype None _encoder email encoders encode_base64 policy compat32 _params Module email mime image A subclass of MIMENonMultipart the MIMEImage class is used to create MIME message objects of major type image _imagedata contains the bytes for the raw image data If this data type can be detected jpeg png gif tiff rgb pbm pgm ppm rast xbm bmp webp and exr attempted then the subtype will be automatically included in the Content Type header Otherwise you can explicitly specify the image subtype via the _subtype argument If the minor type could not be guessed and _subtype was not given then TypeError is raised Optional _encoder is a callable i e function which will perform the actual encoding of the image data for transport This callable takes one argument which is the MIMEImage instance It should use get_payload and set_payload to change the payload to encoded form It should also add any Content Transfer Encoding or other headers to the message object as necessary The default encoding is base64 See the email encoders module for a list of the built in encoders Optional policy argument defaults to compat32 _params are passed straight through to the MIMEBase constructor Changed in version 3 6 Added policy keyword only parameter class email mime message MIMEMessage _msg _subtype rfc822 policy compat32 Module email mime message A subclass of MIMENonMultipart the MIMEMessage class is used to create MIME objects of main type message _msg is used as the payload and must be an instance of class Message or a subclass thereof otherwise a TypeError is raised Optional _subtype sets the subtype of the message it defaults to rfc822 Optional policy argument defaults to compat32 Changed in version 3 6 Added policy keyword only parameter class email mime text MIMEText _text _subtype plain _charset None policy compat32 Module email mime text A subclass of MIMENonMultipart the MIMEText class is used to create MIME objects of major type text _text is the string for the payload _subtype is the minor type and defaults to plain _charset is the character set of the text and is passed as an argument to the MIMENonMultipart constructor it defaults to us ascii if the string contains only ascii code points and utf 8 otherwise The _charset parameter accepts either a string or a Charset instance Unless the _charset argument is explicitly set to None the MIMEText object created will have both a Content Type header with a charset parameter and a Content Transfer Encoding header This means that a subsequent set_payload call will not result in an encoded payload even if a charset is passed in the set_payload comman,en
2399,d You can reset this behavior by deleting the Content Transfer Encoding header after which a set_payload call will automatically encode the new payload and add a new Content Transfer Encoding header Optional policy argument defaults to compat32 Changed in version 3 5 _charset also accepts Charset instances Changed in version 3 6 Added policy keyword only parameter,en
2400,6 Modules If you quit from the Python interpreter and enter it again the definitions you have made functions and variables are lost Therefore if you want to write a somewhat longer program you are better off using a text editor to prepare the input for the interpreter and running it with that file as input instead This is known as creating a script As your program gets longer you may want to split it into several files for easier maintenance You may also want to use a handy function that you ve written in several programs without copying its definition into each program To support this Python has a way to put definitions in a file and use them in a script or in an interactive instance of the interpreter Such a file is called a module definitions from a module can be imported into other modules or into the main module the collection of variables that you have access to in a script executed at the top level and in calculator mode A module is a file containing Python definitions and statements The file name is the module name with the suffix py appended Within a module the module s name as a string is available as the value of the global variable __name__ For instance use your favorite text editor to create a file called fibo py in the current directory with the following contents Fibonacci numbers module def fib n write Fibonacci series up to n a b 0 1 while a n print a end a b b a b print def fib2 n return Fibonacci series up to n result a b 0 1 while a n result append a a b b a b return result Now enter the Python interpreter and import this module with the following command import fibo This does not add the names of the functions defined in fibo directly to the current namespace see Python Scopes and Namespaces for more details it only adds the module name fibo there Using the module name you can access the functions fibo fib 1000 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 fibo fib2 100 0 1 1 2 3 5 8 13 21 34 55 89 fibo __name__ fibo If you intend to use a function often you can assign it to a local name fib fibo fib fib 500 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 6 1 More on Modules A module can contain executable statements as well as function definitions These statements are intended to initialize the module They are executed only the first time the module name is encountered in an import statement 1 They are also run if the file is executed as a script Each module has its own private namespace which is used as the global namespace by all functions defined in the module Thus the author of a module can use global variables in the module without worrying about accidental clashes with a user s global variables On the other hand if you know what you are doing you can touch a module s global variables with the same notation used to refer to its functions modname itemname Modules can import other modules It is customary but not required to place all import statements at the beginning of a module or script for that matter The imported module names if placed at the top level of a module outside any functions or classes are added to the module s global namespace There is a variant of the import statement that imports names from a module directly into the importing module s namespace For example from fibo import fib fib2 fib 500 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 This does not introduce the module name from which the imports are taken in the local namespace so in the example fibo is not defined There is even a variant to import all names that a module defines from fibo import fib 500 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 This imports all names except those beginning with an underscore _ In most cases Python programmers do not use this facility since it introduces an unknown set of names into the interpreter possibly hiding some things you have already defined Note that in general the practice of importing from a module or package is frowned upon since it often causes poorly readable code However it is okay to use it to save typing in interactive sessions If the module name is followed by as then the name follow,en
2401,ing as is bound directly to the imported module import fibo as fib fib fib 500 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 This is effectively importing the module in the same way that import fibo will do with the only difference of it being available as fib It can also be used when utilising from with similar effects from fibo import fib as fibonacci fibonacci 500 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 Note For efficiency reasons each module is only imported once per interpreter session Therefore if you change your modules you must restart the interpreter or if it s just one module you want to test interactively use importlib reload e g import importlib importlib reload modulename 6 1 1 Executing modules as scripts When you run a Python module with python fibo py arguments the code in the module will be executed just as if you imported it but with the __name__ set to __main__ That means that by adding this code at the end of your module if __name__ __main__ import sys fib int sys argv 1 you can make the file usable as a script as well as an importable module because the code that parses the command line only runs if the module is executed as the main file python fibo py 50 0 1 1 2 3 5 8 13 21 34 If the module is imported the code is not run import fibo This is often used either to provide a convenient user interface to a module or for testing purposes running the module as a script executes a test suite 6 1 2 The Module Search Path When a module named spam is imported the interpreter first searches for a built in module with that name These module names are listed in sys builtin_module_names If not found it then searches for a file named spam py in a list of directories given by the variable sys path sys path is initialized from these locations The directory containing the input script or the current directory when no file is specified PYTHONPATH a list of directory names with the same syntax as the shell variable PATH The installation dependent default by convention including a site packages directory handled by the site module More details are at The initialization of the sys path module search path Note On file systems which support symlinks the directory containing the input script is calculated after the symlink is followed In other words the directory containing the symlink is not added to the module search path After initialization Python programs can modify sys path The directory containing the script being run is placed at the beginning of the search path ahead of the standard library path This means that scripts in that directory will be loaded instead of modules of the same name in the library directory This is an error unless the replacement is intended See section Standard Modules for more information 6 1 3 Compiled Python files To speed up loading modules Python caches the compiled version of each module in the __pycache__ directory under the name module version pyc where the version encodes the format of the compiled file it generally contains the Python version number For example in CPython release 3 3 the compiled version of spam py would be cached as __pycache__ spam cpython 33 pyc This naming convention allows compiled modules from different releases and different versions of Python to coexist Python checks the modification date of the source against the compiled version to see if it s out of date and needs to be recompiled This is a completely automatic process Also the compiled modules are platform independent so the same library can be shared among systems with different architectures Python does not check the cache in two circumstances First it always recompiles and does not store the result for the module that s loaded directly from the command line Second it does not check the cache if there is no source module To support a non source compiled only distribution the compiled module must be in the source directory and there must not be a source module Some tips for experts You can use the O or OO switches on the Python command to reduce the size of a compiled module The O switch removes assert stat,en
2402,ements the OO switch removes both assert statements and __doc__ strings Since some programs may rely on having these available you should only use this option if you know what you re doing Optimized modules have an opt tag and are usually smaller Future releases may change the effects of optimization A program doesn t run any faster when it is read from a pyc file than when it is read from a py file the only thing that s faster about pyc files is the speed with which they are loaded The module compileall can create pyc files for all modules in a directory There is more detail on this process including a flow chart of the decisions in PEP 3147 6 2 Standard Modules Python comes with a library of standard modules described in a separate document the Python Library Reference Library Reference hereafter Some modules are built into the interpreter these provide access to operations that are not part of the core of the language but are nevertheless built in either for efficiency or to provide access to operating system primitives such as system calls The set of such modules is a configuration option which also depends on the underlying platform For example the winreg module is only provided on Windows systems One particular module deserves some attention sys which is built into every Python interpreter The variables sys ps1 and sys ps2 define the strings used as primary and secondary prompts import sys sys ps1 sys ps2 sys ps1 C C print Yuck Yuck C These two variables are only defined if the interpreter is in interactive mode The variable sys path is a list of strings that determines the interpreter s search path for modules It is initialized to a default path taken from the environment variable PYTHONPATH or from a built in default if PYTHONPATH is not set You can modify it using standard list operations import sys sys path append ufs guido lib python 6 3 The dir Function The built in function dir is used to find out which names a module defines It returns a sorted list of strings import fibo sys dir fibo __name__ fib fib2 dir sys __breakpointhook__ __displayhook__ __doc__ __excepthook__ __interactivehook__ __loader__ __name__ __package__ __spec__ __stderr__ __stdin__ __stdout__ __unraisablehook__ _clear_type_cache _current_frames _debugmallocstats _framework _getframe _git _home _xoptions abiflags addaudithook api_version argv audit base_exec_prefix base_prefix breakpointhook builtin_module_names byteorder call_tracing callstats copyright displayhook dont_write_bytecode exc_info excepthook exec_prefix executable exit flags float_info float_repr_style get_asyncgen_hooks get_coroutine_origin_tracking_depth getallocatedblocks getdefaultencoding getdlopenflags getfilesystemencodeerrors getfilesystemencoding getprofile getrecursionlimit getrefcount getsizeof getswitchinterval gettrace hash_info hexversion implementation int_info intern is_finalizing last_traceback last_type last_value maxsize maxunicode meta_path modules path path_hooks path_importer_cache platform prefix ps1 ps2 pycache_prefix set_asyncgen_hooks set_coroutine_origin_tracking_depth setdlopenflags setprofile setrecursionlimit setswitchinterval settrace stderr stdin stdout thread_info unraisablehook version version_info warnoptions Without arguments dir lists the names you have defined currently a 1 2 3 4 5 import fibo fib fibo fib dir __builtins__ __name__ a fib fibo sys Note that it lists all types of names variables modules functions etc dir does not list the names of built in functions and variables If you want a list of those they are defined in the standard module builtins import builtins dir builtins ArithmeticError AssertionError AttributeError BaseException BlockingIOError BrokenPipeError BufferError BytesWarning ChildProcessError ConnectionAbortedError ConnectionError ConnectionRefusedError ConnectionResetError DeprecationWarning EOFError Ellipsis EnvironmentError Exception False FileExistsError FileNotFoundError FloatingPointError FutureWarning GeneratorExit IOError ImportError ImportWarning IndentationError IndexError InterruptedError IsADirectoryError Ke,en
2403,yError KeyboardInterrupt LookupError MemoryError NameError None NotADirectoryError NotImplemented NotImplementedError OSError OverflowError PendingDeprecationWarning PermissionError ProcessLookupError ReferenceError ResourceWarning RuntimeError RuntimeWarning StopIteration SyntaxError SyntaxWarning SystemError SystemExit TabError TimeoutError True TypeError UnboundLocalError UnicodeDecodeError UnicodeEncodeError UnicodeError UnicodeTranslateError UnicodeWarning UserWarning ValueError Warning ZeroDivisionError _ __build_class__ __debug__ __doc__ __import__ __name__ __package__ abs all any ascii bin bool bytearray bytes callable chr classmethod compile complex copyright credits delattr dict dir divmod enumerate eval exec exit filter float format frozenset getattr globals hasattr hash help hex id input int isinstance issubclass iter len license list locals map max memoryview min next object oct open ord pow print property quit range repr reversed round set setattr slice sorted staticmethod str sum super tuple type vars zip 6 4 Packages Packages are a way of structuring Python s module namespace by using dotted module names For example the module name A B designates a submodule named B in a package named A Just like the use of modules saves the authors of different modules from having to worry about each other s global variable names the use of dotted module names saves the authors of multi module packages like NumPy or Pillow from having to worry about each other s module names Suppose you want to design a collection of modules a package for the uniform handling of sound files and sound data There are many different sound file formats usually recognized by their extension for example wav aiff au so you may need to create and maintain a growing collection of modules for the conversion between the various file formats There are also many different operations you might want to perform on sound data such as mixing adding echo applying an equalizer function creating an artificial stereo effect so in addition you will be writing a never ending stream of modules to perform these operations Here s a possible structure for your package expressed in terms of a hierarchical filesystem sound Top level package __init__ py Initialize the sound package formats Subpackage for file format conversions __init__ py wavread py wavwrite py aiffread py aiffwrite py auread py auwrite py effects Subpackage for sound effects __init__ py echo py surround py reverse py filters Subpackage for filters __init__ py equalizer py vocoder py karaoke py When importing the package Python searches through the directories on sys path looking for the package subdirectory The __init__ py files are required to make Python treat directories containing the file as packages unless using a namespace package a relatively advanced feature This prevents directories with a common name such as string from unintentionally hiding valid modules that occur later on the module search path In the simplest case __init__ py can just be an empty file but it can also execute initialization code for the package or set the __all__ variable described later Users of the package can import individual modules from the package for example import sound effects echo This loads the submodule sound effects echo It must be referenced with its full name sound effects echo echofilter input output delay 0 7 atten 4 An alternative way of importing the submodule is from sound effects import echo This also loads the submodule echo and makes it available without its package prefix so it can be used as follows echo echofilter input output delay 0 7 atten 4 Yet another variation is to import the desired function or variable directly from sound effects echo import echofilter Again this loads the submodule echo but this makes its function echofilter directly available echofilter input output delay 0 7 atten 4 Note that when using from package import item the item can be either a submodule or subpackage of the package or some other name defined in the package like a function class or variable The import sta,en
2404,tement first tests whether the item is defined in the package if not it assumes it is a module and attempts to load it If it fails to find it an ImportError exception is raised Contrarily when using syntax like import item subitem subsubitem each item except for the last must be a package the last item can be a module or a package but can t be a class or function or variable defined in the previous item 6 4 1 Importing From a Package Now what happens when the user writes from sound effects import Ideally one would hope that this somehow goes out to the filesystem finds which submodules are present in the package and imports them all This could take a long time and importing sub modules might have unwanted side effects that should only happen when the sub module is explicitly imported The only solution is for the package author to provide an explicit index of the package The import statement uses the following convention if a package s __init__ py code defines a list named __all__ it is taken to be the list of module names that should be imported when from package import is encountered It is up to the package author to keep this list up to date when a new version of the package is released Package authors may also decide not to support it if they don t see a use for importing from their package For example the file sound effects __init__ py could contain the following code __all__ echo surround reverse This would mean that from sound effects import would import the three named submodules of the sound effects package Be aware that submodules might become shadowed by locally defined names For example if you added a reverse function to the sound effects __init__ py file the from sound effects import would only import the two submodules echo and surround but not the reverse submodule because it is shadowed by the locally defined reverse function __all__ echo refers to the echo py file surround refers to the surround py file reverse refers to the reverse function now def reverse msg str this name shadows the reverse py submodule return msg 1 in the case of a from sound effects import If __all__ is not defined the statement from sound effects import does not import all submodules from the package sound effects into the current namespace it only ensures that the package sound effects has been imported possibly running any initialization code in __init__ py and then imports whatever names are defined in the package This includes any names defined and submodules explicitly loaded by __init__ py It also includes any submodules of the package that were explicitly loaded by previous import statements Consider this code import sound effects echo import sound effects surround from sound effects import In this example the echo and surround modules are imported in the current namespace because they are defined in the sound effects package when the from import statement is executed This also works when __all__ is defined Although certain modules are designed to export only names that follow certain patterns when you use import it is still considered bad practice in production code Remember there is nothing wrong with using from package import specific_submodule In fact this is the recommended notation unless the importing module needs to use submodules with the same name from different packages 6 4 2 Intra package References When packages are structured into subpackages as with the sound package in the example you can use absolute imports to refer to submodules of siblings packages For example if the module sound filters vocoder needs to use the echo module in the sound effects package it can use from sound effects import echo You can also write relative imports with the from module import name form of import statement These imports use leading dots to indicate the current and parent packages involved in the relative import From the surround module for example you might use from import echo from import formats from filters import equalizer Note that relative imports are based on the name of the current module Since the name of the main mo,en
2405,dule is always __main__ modules intended for use as the main module of a Python application must always use absolute imports 6 4 3 Packages in Multiple Directories Packages support one more special attribute __path__ This is initialized to be a list containing the name of the directory holding the package s __init__ py before the code in that file is executed This variable can be modified doing so affects future searches for modules and subpackages contained in the package While this feature is not often needed it can be used to extend the set of modules found in a package Footnotes 1 In fact function definitions are also statements that are executed the execution of a module level function definition adds the function name to the module s global namespace,en
2406,Generator Objects Generator objects are what Python uses to implement generator iterators They are normally created by iterating over a function that yields values rather than explicitly calling PyGen_New or PyGen_NewWithQualName type PyGenObject The C structure used for generator objects PyTypeObject PyGen_Type The type object corresponding to generator objects int PyGen_Check PyObject ob Return true if ob is a generator object ob must not be NULL This function always succeeds int PyGen_CheckExact PyObject ob Return true if ob s type is PyGen_Type ob must not be NULL This function always succeeds PyObject PyGen_New PyFrameObject frame Return value New reference Create and return a new generator object based on the frame object A reference to frame is stolen by this function The argument must not be NULL PyObject PyGen_NewWithQualName PyFrameObject frame PyObject name PyObject qualname Return value New reference Create and return a new generator object based on the frame object with __name__ and __qualname__ set to name and qualname A reference to frame is stolen by this function The frame argument must not be NULL,en
2407,functools Higher order functions and operations on callable objects Source code Lib functools py The functools module is for higher order functions functions that act on or return other functions In general any callable object can be treated as a function for the purposes of this module The functools module defines the following functions functools cache user_function Simple lightweight unbounded function cache Sometimes called memoize Returns the same as lru_cache maxsize None creating a thin wrapper around a dictionary lookup for the function arguments Because it never needs to evict old values this is smaller and faster than lru_cache with a size limit For example cache def factorial n return n factorial n 1 if n else 1 factorial 10 no previously cached result makes 11 recursive calls 3628800 factorial 5 just looks up cached value result 120 factorial 12 makes two new recursive calls the other 10 are cached 479001600 The cache is threadsafe so that the wrapped function can be used in multiple threads This means that the underlying data structure will remain coherent during concurrent updates It is possible for the wrapped function to be called more than once if another thread makes an additional call before the initial call has been completed and cached New in version 3 9 functools cached_property func Transform a method of a class into a property whose value is computed once and then cached as a normal attribute for the life of the instance Similar to property with the addition of caching Useful for expensive computed properties of instances that are otherwise effectively immutable Example class DataSet def __init__ self sequence_of_numbers self _data tuple sequence_of_numbers cached_property def stdev self return statistics stdev self _data The mechanics of cached_property are somewhat different from property A regular property blocks attribute writes unless a setter is defined In contrast a cached_property allows writes The cached_property decorator only runs on lookups and only when an attribute of the same name doesn t exist When it does run the cached_property writes to the attribute with the same name Subsequent attribute reads and writes take precedence over the cached_property method and it works like a normal attribute The cached value can be cleared by deleting the attribute This allows the cached_property method to run again The cached_property does not prevent a possible race condition in multi threaded usage The getter function could run more than once on the same instance with the latest run setting the cached value If the cached property is idempotent or otherwise not harmful to run more than once on an instance this is fine If synchronization is needed implement the necessary locking inside the decorated getter function or around the cached property access Note this decorator interferes with the operation of PEP 412 key sharing dictionaries This means that instance dictionaries can take more space than usual Also this decorator requires that the __dict__ attribute on each instance be a mutable mapping This means it will not work with some types such as metaclasses since the __dict__ attributes on type instances are read only proxies for the class namespace and those that specify __slots__ without including __dict__ as one of the defined slots as such classes don t provide a __dict__ attribute at all If a mutable mapping is not available or if space efficient key sharing is desired an effect similar to cached_property can also be achieved by stacking property on top of lru_cache See How do I cache method calls for more details on how this differs from cached_property New in version 3 8 Changed in version 3 12 Prior to Python 3 12 cached_property included an undocumented lock to ensure that in multi threaded usage the getter function was guaranteed to run only once per instance However the lock was per property not per instance which could result in unacceptably high lock contention In Python 3 12 this locking is removed functools cmp_to_key func Transform an old style comparison function to a key funct,en
2408,ion Used with tools that accept key functions such as sorted min max heapq nlargest heapq nsmallest itertools groupby This function is primarily used as a transition tool for programs being converted from Python 2 which supported the use of comparison functions A comparison function is any callable that accepts two arguments compares them and returns a negative number for less than zero for equality or a positive number for greater than A key function is a callable that accepts one argument and returns another value to be used as the sort key Example sorted iterable key cmp_to_key locale strcoll locale aware sort order For sorting examples and a brief sorting tutorial see Sorting Techniques New in version 3 2 functools lru_cache user_function functools lru_cache maxsize 128 typed False Decorator to wrap a function with a memoizing callable that saves up to the maxsize most recent calls It can save time when an expensive or I O bound function is periodically called with the same arguments The cache is threadsafe so that the wrapped function can be used in multiple threads This means that the underlying data structure will remain coherent during concurrent updates It is possible for the wrapped function to be called more than once if another thread makes an additional call before the initial call has been completed and cached Since a dictionary is used to cache results the positional and keyword arguments to the function must be hashable Distinct argument patterns may be considered to be distinct calls with separate cache entries For example f a 1 b 2 and f b 2 a 1 differ in their keyword argument order and may have two separate cache entries If user_function is specified it must be a callable This allows the lru_cache decorator to be applied directly to a user function leaving the maxsize at its default value of 128 lru_cache def count_vowels sentence return sum sentence count vowel for vowel in AEIOUaeiou If maxsize is set to None the LRU feature is disabled and the cache can grow without bound If typed is set to true function arguments of different types will be cached separately If typed is false the implementation will usually regard them as equivalent calls and only cache a single result Some types such as str and int may be cached separately even when typed is false Note type specificity applies only to the function s immediate arguments rather than their contents The scalar arguments Decimal 42 and Fraction 42 are be treated as distinct calls with distinct results In contrast the tuple arguments answer Decimal 42 and answer Fraction 42 are treated as equivalent The wrapped function is instrumented with a cache_parameters function that returns a new dict showing the values for maxsize and typed This is for information purposes only Mutating the values has no effect To help measure the effectiveness of the cache and tune the maxsize parameter the wrapped function is instrumented with a cache_info function that returns a named tuple showing hits misses maxsize and currsize The decorator also provides a cache_clear function for clearing or invalidating the cache The original underlying function is accessible through the __wrapped__ attribute This is useful for introspection for bypassing the cache or for rewrapping the function with a different cache The cache keeps references to the arguments and return values until they age out of the cache or until the cache is cleared If a method is cached the self instance argument is included in the cache See How do I cache method calls An LRU least recently used cache works best when the most recent calls are the best predictors of upcoming calls for example the most popular articles on a news server tend to change each day The cache s size limit assures that the cache does not grow without bound on long running processes such as web servers In general the LRU cache should only be used when you want to reuse previously computed values Accordingly it doesn t make sense to cache functions with side effects functions that need to create distinct mutable objects on each call such as,en
2409, generators and async functions or impure functions such as time or random Example of an LRU cache for static web content lru_cache maxsize 32 def get_pep num Retrieve text of a Python Enhancement Proposal resource f https peps python org pep num 04d try with urllib request urlopen resource as s return s read except urllib error HTTPError return Not Found for n in 8 290 308 320 8 218 320 279 289 320 9991 pep get_pep n print n len pep get_pep cache_info CacheInfo hits 3 misses 8 maxsize 32 currsize 8 Example of efficiently computing Fibonacci numbers using a cache to implement a dynamic programming technique lru_cache maxsize None def fib n if n 2 return n return fib n 1 fib n 2 fib n for n in range 16 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 fib cache_info CacheInfo hits 28 misses 16 maxsize None currsize 16 New in version 3 2 Changed in version 3 3 Added the typed option Changed in version 3 8 Added the user_function option Changed in version 3 9 Added the function cache_parameters functools total_ordering Given a class defining one or more rich comparison ordering methods this class decorator supplies the rest This simplifies the effort involved in specifying all of the possible rich comparison operations The class must define one of __lt__ __le__ __gt__ or __ge__ In addition the class should supply an __eq__ method For example total_ordering class Student def _is_valid_operand self other return hasattr other lastname and hasattr other firstname def __eq__ self other if not self _is_valid_operand other return NotImplemented return self lastname lower self firstname lower other lastname lower other firstname lower def __lt__ self other if not self _is_valid_operand other return NotImplemented return self lastname lower self firstname lower other lastname lower other firstname lower Note While this decorator makes it easy to create well behaved totally ordered types it does come at the cost of slower execution and more complex stack traces for the derived comparison methods If performance benchmarking indicates this is a bottleneck for a given application implementing all six rich comparison methods instead is likely to provide an easy speed boost Note This decorator makes no attempt to override methods that have been declared in the class or its superclasses Meaning that if a superclass defines a comparison operator total_ordering will not implement it again even if the original method is abstract New in version 3 2 Changed in version 3 4 Returning NotImplemented from the underlying comparison function for unrecognised types is now supported functools partial func args keywords Return a new partial object which when called will behave like func called with the positional arguments args and keyword arguments keywords If more arguments are supplied to the call they are appended to args If additional keyword arguments are supplied they extend and override keywords Roughly equivalent to def partial func args keywords def newfunc fargs fkeywords newkeywords keywords fkeywords return func args fargs newkeywords newfunc func func newfunc args args newfunc keywords keywords return newfunc The partial is used for partial function application which freezes some portion of a function s arguments and or keywords resulting in a new object with a simplified signature For example partial can be used to create a callable that behaves like the int function where the base argument defaults to two from functools import partial basetwo partial int base 2 basetwo __doc__ Convert base 2 string to an int basetwo 10010 18 class functools partialmethod func args keywords Return a new partialmethod descriptor which behaves like partial except that it is designed to be used as a method definition rather than being directly callable func must be a descriptor or a callable objects which are both like normal functions are handled as descriptors When func is a descriptor such as a normal Python function classmethod staticmethod abstractmethod or another instance of partialmethod calls to __get__ are delegated to the underlying descriptor and an a,en
2410,ppropriate partial object returned as the result When func is a non descriptor callable an appropriate bound method is created dynamically This behaves like a normal Python function when used as a method the self argument will be inserted as the first positional argument even before the args and keywords supplied to the partialmethod constructor Example class Cell def __init__ self self _alive False property def alive self return self _alive def set_state self state self _alive bool state set_alive partialmethod set_state True set_dead partialmethod set_state False c Cell c alive False c set_alive c alive True New in version 3 4 functools reduce function iterable initializer Apply function of two arguments cumulatively to the items of iterable from left to right so as to reduce the iterable to a single value For example reduce lambda x y x y 1 2 3 4 5 calculates 1 2 3 4 5 The left argument x is the accumulated value and the right argument y is the update value from the iterable If the optional initializer is present it is placed before the items of the iterable in the calculation and serves as a default when the iterable is empty If initializer is not given and iterable contains only one item the first item is returned Roughly equivalent to def reduce function iterable initializer None it iter iterable if initializer is None value next it else value initializer for element in it value function value element return value See itertools accumulate for an iterator that yields all intermediate values functools singledispatch Transform a function into a single dispatch generic function To define a generic function decorate it with the singledispatch decorator When defining a function using singledispatch note that the dispatch happens on the type of the first argument from functools import singledispatch singledispatch def fun arg verbose False if verbose print Let me just say end print arg To add overloaded implementations to the function use the register attribute of the generic function which can be used as a decorator For functions annotated with types the decorator will infer the type of the first argument automatically fun register def _ arg int verbose False if verbose print Strength in numbers eh end print arg fun register def _ arg list verbose False if verbose print Enumerate this for i elem in enumerate arg print i elem types UnionType and typing Union can also be used fun register def _ arg int float verbose False if verbose print Strength in numbers eh end print arg from typing import Union fun register def _ arg Union list set verbose False if verbose print Enumerate this for i elem in enumerate arg print i elem For code which doesn t use type annotations the appropriate type argument can be passed explicitly to the decorator itself fun register complex def _ arg verbose False if verbose print Better than complicated end print arg real arg imag To enable registering lambdas and pre existing functions the register attribute can also be used in a functional form def nothing arg verbose False print Nothing fun register type None nothing The register attribute returns the undecorated function This enables decorator stacking pickling and the creation of unit tests for each variant independently fun register float fun register Decimal def fun_num arg verbose False if verbose print Half of your number end print arg 2 fun_num is fun False When called the generic function dispatches on the type of the first argument fun Hello world Hello world fun test verbose True Let me just say test fun 42 verbose True Strength in numbers eh 42 fun spam spam eggs spam verbose True Enumerate this 0 spam 1 spam 2 eggs 3 spam fun None Nothing fun 1 23 0 615 Where there is no registered implementation for a specific type its method resolution order is used to find a more generic implementation The original function decorated with singledispatch is registered for the base object type which means it is used if no better implementation is found If an implementation is registered to an abstract base class virtual subclasses of the base class w,en
2411,ill be dispatched to that implementation from collections abc import Mapping fun register def _ arg Mapping verbose False if verbose print Keys Values for key value in arg items print key value fun a b a b To check which implementation the generic function will choose for a given type use the dispatch attribute fun dispatch float function fun_num at 0x1035a2840 fun dispatch dict note default implementation function fun at 0x103fe0000 To access all registered implementations use the read only registry attribute fun registry keys dict_keys class NoneType class int class object class decimal Decimal class list class float fun registry float function fun_num at 0x1035a2840 fun registry object function fun at 0x103fe0000 New in version 3 4 Changed in version 3 7 The register attribute now supports using type annotations Changed in version 3 11 The register attribute now supports types UnionType and typing Union as type annotations class functools singledispatchmethod func Transform a method into a single dispatch generic function To define a generic method decorate it with the singledispatchmethod decorator When defining a function using singledispatchmethod note that the dispatch happens on the type of the first non self or non cls argument class Negator singledispatchmethod def neg self arg raise NotImplementedError Cannot negate a neg register def _ self arg int return arg neg register def _ self arg bool return not arg singledispatchmethod supports nesting with other decorators such as classmethod Note that to allow for dispatcher register singledispatchmethod must be the outer most decorator Here is the Negator class with the neg methods bound to the class rather than an instance of the class class Negator singledispatchmethod classmethod def neg cls arg raise NotImplementedError Cannot negate a neg register classmethod def _ cls arg int return arg neg register classmethod def _ cls arg bool return not arg The same pattern can be used for other similar decorators staticmethod abstractmethod and others New in version 3 8 functools update_wrapper wrapper wrapped assigned WRAPPER_ASSIGNMENTS updated WRAPPER_UPDATES Update a wrapper function to look like the wrapped function The optional arguments are tuples to specify which attributes of the original function are assigned directly to the matching attributes on the wrapper function and which attributes of the wrapper function are updated with the corresponding attributes from the original function The default values for these arguments are the module level constants WRAPPER_ASSIGNMENTS which assigns to the wrapper function s __module__ __name__ __qualname__ __annotations__ and __doc__ the documentation string and WRAPPER_UPDATES which updates the wrapper function s __dict__ i e the instance dictionary To allow access to the original function for introspection and other purposes e g bypassing a caching decorator such as lru_cache this function automatically adds a __wrapped__ attribute to the wrapper that refers to the function being wrapped The main intended use for this function is in decorator functions which wrap the decorated function and return the wrapper If the wrapper function is not updated the metadata of the returned function will reflect the wrapper definition rather than the original function definition which is typically less than helpful update_wrapper may be used with callables other than functions Any attributes named in assigned or updated that are missing from the object being wrapped are ignored i e this function will not attempt to set them on the wrapper function AttributeError is still raised if the wrapper function itself is missing any attributes named in updated Changed in version 3 2 The __wrapped__ attribute is now automatically added The __annotations__ attribute is now copied by default Missing attributes no longer trigger an AttributeError Changed in version 3 4 The __wrapped__ attribute now always refers to the wrapped function even if that function defined a __wrapped__ attribute see bpo 17482 functools wraps wrapped assigned WRAPPER_ASSIGNME,en
2412,NTS updated WRAPPER_UPDATES This is a convenience function for invoking update_wrapper as a function decorator when defining a wrapper function It is equivalent to partial update_wrapper wrapped wrapped assigned assigned updated updated For example from functools import wraps def my_decorator f wraps f def wrapper args kwds print Calling decorated function return f args kwds return wrapper my_decorator def example Docstring print Called example function example Calling decorated function Called example function example __name__ example example __doc__ Docstring Without the use of this decorator factory the name of the example function would have been wrapper and the docstring of the original example would have been lost partial Objects partial objects are callable objects created by partial They have three read only attributes partial func A callable object or function Calls to the partial object will be forwarded to func with new arguments and keywords partial args The leftmost positional arguments that will be prepended to the positional arguments provided to a partial object call partial keywords The keyword arguments that will be supplied when the partial object is called partial objects are like function objects in that they are callable weak referenceable and can have attributes There are some important differences For instance the __name__ and __doc__ attributes are not created automatically Also partial objects defined in classes behave like static methods and do not transform into bound methods during instance attribute look up,en
2413,Concrete Objects Layer The functions in this chapter are specific to certain Python object types Passing them an object of the wrong type is not a good idea if you receive an object from a Python program and you are not sure that it has the right type you must perform a type check first for example to check that an object is a dictionary use PyDict_Check The chapter is structured like the family tree of Python object types Warning While the functions described in this chapter carefully check the type of the objects which are passed in many of them do not check for NULL being passed instead of a valid object Allowing NULL to be passed in can cause memory access violations and immediate termination of the interpreter Fundamental Objects This section describes Python type objects and the singleton object None Type Objects Creating Heap Allocated Types The None Object Numeric Objects Integer Objects Boolean Objects Floating Point Objects Pack and Unpack functions Pack functions Unpack functions Complex Number Objects Complex Numbers as C Structures Complex Numbers as Python Objects Sequence Objects Generic operations on sequence objects were discussed in the previous chapter this section deals with the specific kinds of sequence objects that are intrinsic to the Python language Bytes Objects Byte Array Objects Type check macros Direct API functions Macros Unicode Objects and Codecs Unicode Objects Unicode Type Unicode Character Properties Creating and accessing Unicode strings Locale Encoding File System Encoding wchar_t Support Built in Codecs Generic Codecs UTF 8 Codecs UTF 32 Codecs UTF 16 Codecs UTF 7 Codecs Unicode Escape Codecs Raw Unicode Escape Codecs Latin 1 Codecs ASCII Codecs Character Map Codecs MBCS codecs for Windows Methods Slots Methods and Slot Functions Tuple Objects Struct Sequence Objects List Objects Container Objects Dictionary Objects Set Objects Function Objects Function Objects Instance Method Objects Method Objects Cell Objects Code Objects Extra information Other Objects File Objects Module Objects Initializing C modules Single phase initialization Multi phase initialization Low level module creation functions Support functions Module lookup Iterator Objects Descriptor Objects Slice Objects Ellipsis Object MemoryView objects Weak Reference Objects Capsules Frame Objects Internal Frames Generator Objects Coroutine Objects Context Variables Objects DateTime Objects Objects for Type Hinting,en
2414,The concurrent package Currently there is only one module in this package concurrent futures Launching parallel tasks,en
2415,The initialization of the sys path module search path A module search path is initialized when Python starts This module search path may be accessed at sys path The first entry in the module search path is the directory that contains the input script if there is one Otherwise the first entry is the current directory which is the case when executing the interactive shell a c command or m module The PYTHONPATH environment variable is often used to add directories to the search path If this environment variable is found then the contents are added to the module search path Note PYTHONPATH will affect all installed Python versions environments Be wary of setting this in your shell profile or global environment variables The site module offers more nuanced techniques as mentioned below The next items added are the directories containing standard Python modules as well as any extension module s that these modules depend on Extension modules are pyd files on Windows and so files on other platforms The directory with the platform independent Python modules is called prefix The directory with the extension modules is called exec_prefix The PYTHONHOME environment variable may be used to set the prefix and exec_prefix locations Otherwise these directories are found by using the Python executable as a starting point and then looking for various landmark files and directories Note that any symbolic links are followed so the real Python executable location is used as the search starting point The Python executable location is called home Once home is determined the prefix directory is found by first looking for python majorversion minorversion zip python311 zip On Windows the zip archive is searched for in home and on Unix the archive is expected to be in lib Note that the expected zip archive location is added to the module search path even if the archive does not exist If no archive was found Python on Windows will continue the search for prefix by looking for Lib os py Python on Unix will look for lib python majorversion minorversion os py lib python3 11 os py On Windows prefix and exec_prefix are the same however on other platforms lib python majorversion minorversion lib dynload lib python3 11 lib dynload is searched for and used as an anchor for exec_prefix On some platforms lib may be lib64 or another value see sys platlibdir and PYTHONPLATLIBDIR Once found prefix and exec_prefix are available at sys prefix and sys exec_prefix respectively Finally the site module is processed and site packages directories are added to the module search path A common way to customize the search path is to create sitecustomize or usercustomize modules as described in the site module documentation Note Certain command line options may further affect path calculations See E I s and S for further details Virtual environments If Python is run in a virtual environment as described at Virtual Environments and Packages then prefix and exec_prefix are specific to the virtual environment If a pyvenv cfg file is found alongside the main executable or in the directory one level above the executable the following variations apply If home is an absolute path and PYTHONHOME is not set this path is used instead of the path to the main executable when deducing prefix and exec_prefix _pth files To completely override sys path create a _pth file with the same name as the shared library or executable python _pth or python311 _pth The shared library path is always known on Windows however it may not be available on other platforms In the _pth file specify one line for each path to add to sys path The file based on the shared library name overrides the one based on the executable which allows paths to be restricted for any program loading the runtime if desired When the file exists all registry and environment variables are ignored isolated mode is enabled and site is not imported unless one line in the file specifies import site Blank paths and lines starting with are ignored Each path may be absolute or relative to the location of the file Import statements other t,en
2416,han to site are not permitted and arbitrary code cannot be specified Note that pth files without leading underscore will be processed normally by the site module when import site has been specified Embedded Python If Python is embedded within another application Py_InitializeFromConfig and the PyConfig structure can be used to initialize Python The path specific details are described at Python Path Configuration Alternatively the older Py_SetPath can be used to bypass the initialization of the module search path See also Finding modules for detailed Windows notes Using Python on Unix platforms for Unix details,en
2417,2to3 Automated Python 2 to 3 code translation 2to3 is a Python program that reads Python 2 x source code and applies a series of fixers to transform it into valid Python 3 x code The standard library contains a rich set of fixers that will handle almost all code 2to3 supporting library lib2to3 is however a flexible and generic library so it is possible to write your own fixers for 2to3 Deprecated since version 3 11 will be removed in version 3 13 The lib2to3 module was marked pending for deprecation in Python 3 9 raising PendingDeprecationWarning on import and fully deprecated in Python 3 11 raising DeprecationWarning The 2to3 tool is part of that It will be removed in Python 3 13 Using 2to3 2to3 will usually be installed with the Python interpreter as a script It is also located in the Tools scripts directory of the Python root 2to3 s basic arguments are a list of files or directories to transform The directories are recursively traversed for Python sources Here is a sample Python 2 x source file example py def greet name print Hello 0 format name print What s your name name raw_input greet name It can be converted to Python 3 x code via 2to3 on the command line 2to3 example py A diff against the original source file is printed 2to3 can also write the needed modifications right back to the source file A backup of the original file is made unless n is also given Writing the changes back is enabled with the w flag 2to3 w example py After transformation example py looks like this def greet name print Hello 0 format name print What s your name name input greet name Comments and exact indentation are preserved throughout the translation process By default 2to3 runs a set of predefined fixers The l flag lists all available fixers An explicit set of fixers to run can be given with f Likewise the x explicitly disables a fixer The following example runs only the imports and has_key fixers 2to3 f imports f has_key example py This command runs every fixer except the apply fixer 2to3 x apply example py Some fixers are explicit meaning they aren t run by default and must be listed on the command line to be run Here in addition to the default fixers the idioms fixer is run 2to3 f all f idioms example py Notice how passing all enables all default fixers Sometimes 2to3 will find a place in your source code that needs to be changed but 2to3 cannot fix automatically In this case 2to3 will print a warning beneath the diff for a file You should address the warning in order to have compliant 3 x code 2to3 can also refactor doctests To enable this mode use the d flag Note that only doctests will be refactored This also doesn t require the module to be valid Python For example doctest like examples in a reST document could also be refactored with this option The v option enables output of more information on the translation process Since some print statements can be parsed as function calls or statements 2to3 cannot always read files containing the print function When 2to3 detects the presence of the from __future__ import print_function compiler directive it modifies its internal grammar to interpret print as a function This change can also be enabled manually with the p flag Use p to run fixers on code that already has had its print statements converted Also e can be used to make exec a function The o or output dir option allows specification of an alternate directory for processed output files to be written to The n flag is required when using this as backup files do not make sense when not overwriting the input files New in version 3 2 3 The o option was added The W or write unchanged files flag tells 2to3 to always write output files even if no changes were required to the file This is most useful with o so that an entire Python source tree is copied with translation from one directory to another This option implies the w flag as it would not make sense otherwise New in version 3 2 3 The W flag was added The add suffix option specifies a string to append to all output filenames The n flag is required when specifying this as backups are n,en
2418,ot necessary when writing to different filenames Example 2to3 n W add suffix 3 example py Will cause a converted file named example py3 to be written New in version 3 2 3 The add suffix option was added To translate an entire project from one directory tree to another use 2to3 output dir python3 version mycode W n python2 version mycode Fixers Each step of transforming code is encapsulated in a fixer The command 2to3 l lists them As documented above each can be turned on and off individually They are described here in more detail apply Removes usage of apply For example apply function args kwargs is converted to function args kwargs asserts Replaces deprecated unittest method names with the correct ones From To failUnlessEqual a b assertEqual a b assertEquals a b assertEqual a b failIfEqual a b assertNotEqual a b assertNotEquals a b assertNotEqual a b failUnless a assertTrue a assert_ a assertTrue a failIf a assertFalse a failUnlessRaises exc cal assertRaises exc cal failUnlessAlmostEqual a b assertAlmostEqual a b assertAlmostEquals a b assertAlmostEqual a b failIfAlmostEqual a b assertNotAlmostEqual a b assertNotAlmostEquals a b assertNotAlmostEqual a b basestring Converts basestring to str buffer Converts buffer to memoryview This fixer is optional because the memoryview API is similar but not exactly the same as that of buffer dict Fixes dictionary iteration methods dict iteritems is converted to dict items dict iterkeys to dict keys and dict itervalues to dict values Similarly dict viewitems dict viewkeys and dict viewvalues are converted respectively to dict items dict keys and dict values It also wraps existing usages of dict items dict keys and dict values in a call to list except Converts except X T to except X as T exec Converts the exec statement to the exec function execfile Removes usage of execfile The argument to execfile is wrapped in calls to open compile and exec exitfunc Changes assignment of sys exitfunc to use of the atexit module filter Wraps filter usage in a list call funcattrs Fixes function attributes that have been renamed For example my_function func_closure is converted to my_function __closure__ future Removes from __future__ import new_feature statements getcwdu Renames os getcwdu to os getcwd has_key Changes dict has_key key to key in dict idioms This optional fixer performs several transformations that make Python code more idiomatic Type comparisons like type x is SomeClass and type x SomeClass are converted to isinstance x SomeClass while 1 becomes while True This fixer also tries to make use of sorted in appropriate places For example this block L list some_iterable L sort is changed to L sorted some_iterable import Detects sibling imports and converts them to relative imports imports Handles module renames in the standard library imports2 Handles other modules renames in the standard library It is separate from the imports fixer only because of technical limitations input Converts input prompt to eval input prompt intern Converts intern to sys intern isinstance Fixes duplicate types in the second argument of isinstance For example isinstance x int int is converted to isinstance x int and isinstance x int float int is converted to isinstance x int float itertools_imports Removes imports of itertools ifilter itertools izip and itertools imap Imports of itertools ifilterfalse are also changed to itertools filterfalse itertools Changes usage of itertools ifilter itertools izip and itertools imap to their built in equivalents itertools ifilterfalse is changed to itertools filterfalse long Renames long to int map Wraps map in a list call It also changes map None x to list x Using from future_builtins import map disables this fixer metaclass Converts the old metaclass syntax __metaclass__ Meta in the class body to the new class X metaclass Meta methodattrs Fixes old method attribute names For example meth im_func is converted to meth __func__ ne Converts the old not equal syntax to next Converts the use of iterator s next methods to the next function It also renames next methods to __next__ n,en
2419,onzero Renames definitions of methods called __nonzero__ to __bool__ numliterals Converts octal literals into the new syntax operator Converts calls to various functions in the operator module to other but equivalent function calls When needed the appropriate import statements are added e g import collections abc The following mapping are made From To operator isCallable obj callable obj operator sequenceIncludes obj operator contains obj operator isSequenceType obj isinstance obj collections abc Sequence operator isMappingType obj isinstance obj collections abc Mapping operator isNumberType obj isinstance obj numbers Number operator repeat obj n operator mul obj n operator irepeat obj n operator imul obj n paren Add extra parenthesis where they are required in list comprehensions For example x for x in 1 2 becomes x for x in 1 2 print Converts the print statement to the print function raise Converts raise E V to raise E V and raise E V T to raise E V with_traceback T If E is a tuple the translation will be incorrect because substituting tuples for exceptions has been removed in 3 0 raw_input Converts raw_input to input reduce Handles the move of reduce to functools reduce reload Converts reload to importlib reload renames Changes sys maxint to sys maxsize repr Replaces backtick repr with the repr function set_literal Replaces use of the set constructor with set literals This fixer is optional standarderror Renames StandardError to Exception sys_exc Changes the deprecated sys exc_value sys exc_type sys exc_traceback to use sys exc_info throw Fixes the API change in generator s throw method tuple_params Removes implicit tuple parameter unpacking This fixer inserts temporary variables types Fixes code broken from the removal of some members in the types module unicode Renames unicode to str urllib Handles the rename of urllib and urllib2 to the urllib package ws_comma Removes excess whitespace from comma separated items This fixer is optional xrange Renames xrange to range and wraps existing range calls with list xreadlines Changes for x in file xreadlines to for x in file zip Wraps zip usage in a list call This is disabled when from future_builtins import zip appears lib2to3 2to3 s library Source code Lib lib2to3 Deprecated since version 3 11 will be removed in version 3 13 Python 3 9 switched to a PEG parser see PEP 617 while lib2to3 is using a less flexible LL 1 parser Python 3 10 includes new language syntax that is not parsable by lib2to3 s LL 1 parser see PEP 634 The lib2to3 module was marked pending for deprecation in Python 3 9 raising PendingDeprecationWarning on import and fully deprecated in Python 3 11 raising DeprecationWarning It will be removed from the standard library in Python 3 13 Consider third party alternatives such as LibCST or parso Note The lib2to3 API should be considered unstable and may change drastically in the future,en
2420,importlib resources Package resource reading opening and access Source code Lib importlib resources __init__ py New in version 3 7 This module leverages Python s import system to provide access to resources within packages Resources are file like resources associated with a module or package in Python The resources may be contained directly in a package within a subdirectory contained in that package or adjacent to modules outside a package Resources may be text or binary As a result Python module sources py of a package and compilation artifacts pycache are technically de facto resources of that package In practice however resources are primarily those non Python artifacts exposed specifically by the package author Resources can be opened or read in either binary or text mode Resources are roughly akin to files inside directories though it s important to keep in mind that this is just a metaphor Resources and packages do not have to exist as physical files and directories on the file system for example a package and its resources can be imported from a zip file using zipimport Note This module provides functionality similar to pkg_resources Basic Resource Access without the performance overhead of that package This makes reading resources included in packages easier with more stable and consistent semantics The standalone backport of this module provides more information on using importlib resources and migrating from pkg_resources to importlib resources Loaders that wish to support resource reading should implement a get_resource_reader fullname method as specified by importlib resources abc ResourceReader class importlib resources Anchor Represents an anchor for resources either a module object or a module name as a string Defined as Union str ModuleType importlib resources files anchor Anchor None None Returns a Traversable object representing the resource container think directory and its resources think files A Traversable may contain other containers think subdirectories anchor is an optional Anchor If the anchor is a package resources are resolved from that package If a module resources are resolved adjacent to that module in the same package or the package root If the anchor is omitted the caller s module is used New in version 3 9 Changed in version 3 12 package parameter was renamed to anchor anchor can now be a non package module and if omitted will default to the caller s module package is still accepted for compatibility but will raise a DeprecationWarning Consider passing the anchor positionally or using importlib_resources 5 10 for a compatible interface on older Pythons importlib resources as_file traversable Given a Traversable object representing a file or directory typically from importlib resources files return a context manager for use in a with statement The context manager provides a pathlib Path object Exiting the context manager cleans up any temporary file or directory created when the resource was extracted from e g a zip file Use as_file when the Traversable methods read_text etc are insufficient and an actual file or directory on the file system is required New in version 3 9 Changed in version 3 12 Added support for traversable representing a directory Deprecated functions An older deprecated set of functions is still available but is scheduled for removal in a future version of Python The main drawback of these functions is that they do not support directories they assume all resources are located directly within a package importlib resources Package Whenever a function accepts a Package argument you can pass in either a module object or a module name as a string You can only pass module objects whose __spec__ submodule_search_locations is not None The Package type is defined as Union str ModuleType Deprecated since version 3 12 importlib resources Resource For resource arguments of the functions below you can pass in the name of a resource as a string or a path like object The Resource type is defined as Union str os PathLike importlib resources open_binary package resource Open for binar,en
2421,y reading the resource within package package is either a name or a module object which conforms to the Package requirements resource is the name of the resource to open within package it may not contain path separators and it may not have sub resources i e it cannot be a directory This function returns a typing BinaryIO instance a binary I O stream open for reading Deprecated since version 3 11 Calls to this function can be replaced by files package joinpath resource open rb importlib resources open_text package resource encoding utf 8 errors strict Open for text reading the resource within package By default the resource is opened for reading as UTF 8 package is either a name or a module object which conforms to the Package requirements resource is the name of the resource to open within package it may not contain path separators and it may not have sub resources i e it cannot be a directory encoding and errors have the same meaning as with built in open This function returns a typing TextIO instance a text I O stream open for reading Deprecated since version 3 11 Calls to this function can be replaced by files package joinpath resource open r encoding encoding importlib resources read_binary package resource Read and return the contents of the resource within package as bytes package is either a name or a module object which conforms to the Package requirements resource is the name of the resource to open within package it may not contain path separators and it may not have sub resources i e it cannot be a directory This function returns the contents of the resource as bytes Deprecated since version 3 11 Calls to this function can be replaced by files package joinpath resource read_bytes importlib resources read_text package resource encoding utf 8 errors strict Read and return the contents of resource within package as a str By default the contents are read as strict UTF 8 package is either a name or a module object which conforms to the Package requirements resource is the name of the resource to open within package it may not contain path separators and it may not have sub resources i e it cannot be a directory encoding and errors have the same meaning as with built in open This function returns the contents of the resource as str Deprecated since version 3 11 Calls to this function can be replaced by files package joinpath resource read_text encoding encoding importlib resources path package resource Return the path to the resource as an actual file system path This function returns a context manager for use in a with statement The context manager provides a pathlib Path object Exiting the context manager cleans up any temporary file created when the resource needs to be extracted from e g a zip file package is either a name or a module object which conforms to the Package requirements resource is the name of the resource to open within package it may not contain path separators and it may not have sub resources i e it cannot be a directory Deprecated since version 3 11 Calls to this function can be replaced using as_file as_file files package joinpath resource importlib resources is_resource package name Return True if there is a resource named name in the package otherwise False This function does not consider directories to be resources package is either a name or a module object which conforms to the Package requirements Deprecated since version 3 11 Calls to this function can be replaced by files package joinpath resource is_file importlib resources contents package Return an iterable over the named items within the package The iterable returns str resources e g files and non resources e g directories The iterable does not recurse into subdirectories package is either a name or a module object which conforms to the Package requirements Deprecated since version 3 11 Calls to this function can be replaced by resource name for resource in files package iterdir if resource is_file,en
2422,xml sax Support for SAX2 parsers Source code Lib xml sax __init__ py The xml sax package provides a number of modules which implement the Simple API for XML SAX interface for Python The package itself provides the SAX exceptions and the convenience functions which will be most used by users of the SAX API Warning The xml sax module is not secure against maliciously constructed data If you need to parse untrusted or unauthenticated data see XML vulnerabilities Changed in version 3 7 1 The SAX parser no longer processes general external entities by default to increase security Before the parser created network connections to fetch remote files or loaded local files from the file system for DTD and entities The feature can be enabled again with method setFeature on the parser object and argument feature_external_ges The convenience functions are xml sax make_parser parser_list Create and return a SAX XMLReader object The first parser found will be used If parser_list is provided it must be an iterable of strings which name modules that have a function named create_parser Modules listed in parser_list will be used before modules in the default list of parsers Changed in version 3 8 The parser_list argument can be any iterable not just a list xml sax parse filename_or_stream handler error_handler handler ErrorHandler Create a SAX parser and use it to parse a document The document passed in as filename_or_stream can be a filename or a file object The handler parameter needs to be a SAX ContentHandler instance If error_handler is given it must be a SAX ErrorHandler instance if omitted SAXParseException will be raised on all errors There is no return value all work must be done by the handler passed in xml sax parseString string handler error_handler handler ErrorHandler Similar to parse but parses from a buffer string received as a parameter string must be a str instance or a bytes like object Changed in version 3 5 Added support of str instances A typical SAX application uses three kinds of objects readers handlers and input sources Reader in this context is another term for parser i e some piece of code that reads the bytes or characters from the input source and produces a sequence of events The events then get distributed to the handler objects i e the reader invokes a method on the handler A SAX application must therefore obtain a reader object create or open the input sources create the handlers and connect these objects all together As the final step of preparation the reader is called to parse the input During parsing methods on the handler objects are called based on structural and syntactic events from the input data For these objects only the interfaces are relevant they are normally not instantiated by the application itself Since Python does not have an explicit notion of interface they are formally introduced as classes but applications may use implementations which do not inherit from the provided classes The InputSource Locator Attributes AttributesNS and XMLReader interfaces are defined in the module xml sax xmlreader The handler interfaces are defined in xml sax handler For convenience InputSource which is often instantiated directly and the handler classes are also available from xml sax These interfaces are described below In addition to these classes xml sax provides the following exception classes exception xml sax SAXException msg exception None Encapsulate an XML error or warning This class can contain basic error or warning information from either the XML parser or the application it can be subclassed to provide additional functionality or to add localization Note that although the handlers defined in the ErrorHandler interface receive instances of this exception it is not required to actually raise the exception it is also useful as a container for information When instantiated msg should be a human readable description of the error The optional exception parameter if given should be None or an exception that was caught by the parsing code and is being passed along as information This is the base class,en
2423, for the other SAX exception classes exception xml sax SAXParseException msg exception locator Subclass of SAXException raised on parse errors Instances of this class are passed to the methods of the SAX ErrorHandler interface to provide information about the parse error This class supports the SAX Locator interface as well as the SAXException interface exception xml sax SAXNotRecognizedException msg exception None Subclass of SAXException raised when a SAX XMLReader is confronted with an unrecognized feature or property SAX applications and extensions may use this class for similar purposes exception xml sax SAXNotSupportedException msg exception None Subclass of SAXException raised when a SAX XMLReader is asked to enable a feature that is not supported or to set a property to a value that the implementation does not support SAX applications and extensions may use this class for similar purposes See also SAX The Simple API for XML This site is the focal point for the definition of the SAX API It provides a Java implementation and online documentation Links to implementations and historical information are also available Module xml sax handler Definitions of the interfaces for application provided objects Module xml sax saxutils Convenience functions for use in SAX applications Module xml sax xmlreader Definitions of the interfaces for parser provided objects SAXException Objects The SAXException exception class supports the following methods SAXException getMessage Return a human readable message describing the error condition SAXException getException Return an encapsulated exception object or None,en
2424,venv Creation of virtual environments New in version 3 3 Source code Lib venv The venv module supports creating lightweight virtual environments each with their own independent set of Python packages installed in their site directories A virtual environment is created on top of an existing Python installation known as the virtual environment s base Python and may optionally be isolated from the packages in the base environment so only those explicitly installed in the virtual environment are available When used from within a virtual environment common installation tools such as pip will install Python packages into a virtual environment without needing to be told to do so explicitly A virtual environment is amongst other things Used to contain a specific Python interpreter and software libraries and binaries which are needed to support a project library or application These are by default isolated from software in other virtual environments and Python interpreters and libraries installed in the operating system Contained in a directory conventionally either named venv or venv in the project directory or under a container directory for lots of virtual environments such as virtualenvs Not checked into source control systems such as Git Considered as disposable it should be simple to delete and recreate it from scratch You don t place any project code in the environment Not considered as movable or copyable you just recreate the same environment in the target location See PEP 405 for more background on Python virtual environments See also Python Packaging User Guide Creating and using virtual environments Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information Creating virtual environments Creation of virtual environments is done by executing the command venv python m venv path to new virtual environment Running this command creates the target directory creating any parent directories that don t exist already and places a pyvenv cfg file in it with a home key pointing to the Python installation from which the command was run a common name for the target directory is venv It also creates a bin or Scripts on Windows subdirectory containing a copy symlink of the Python binary binaries as appropriate for the platform or arguments used at environment creation time It also creates an initially empty lib pythonX Y site packages subdirectory on Windows this is Lib site packages If an existing directory is specified it will be re used Changed in version 3 5 The use of venv is now recommended for creating virtual environments Deprecated since version 3 6 pyvenv was the recommended tool for creating virtual environments for Python 3 3 and 3 4 and is deprecated in Python 3 6 On Windows invoke the venv command as follows c Python35 python m venv c path to myenv Alternatively if you configured the PATH and PATHEXT variables for your Python installation c python m venv c path to myenv The command if run with h will show the available options usage venv h system site packages symlinks copies clear upgrade without pip prompt PROMPT upgrade deps ENV_DIR ENV_DIR Creates virtual Python environments in one or more target directories positional arguments ENV_DIR A directory to create the environment in optional arguments h help show this help message and exit system site packages Give the virtual environment access to the system site packages dir symlinks Try to use symlinks rather than copies when symlinks are not the default for the platform copies Try to use copies rather than symlinks even when symlinks are the default for the platform clear Delete the contents of the environment directory if it already exists before environment creation upgrade Upgrade the environment directory to use this version of Python assuming Python has been upgraded in place without pip Skips installing or upgrading pip in the virtual environment pip is bootstrapped by default prompt PROMPT Provides an alternative prompt prefix for thi,en
2425,s environment upgrade deps Upgrade core dependencies pip to the latest version in PyPI Once an environment has been created you may wish to activate it e g by sourcing an activate script in its bin directory Changed in version 3 12 setuptools is no longer a core venv dependency Changed in version 3 9 Add upgrade deps option to upgrade pip setuptools to the latest on PyPI Changed in version 3 4 Installs pip by default added the without pip and copies options Changed in version 3 4 In earlier versions if the target directory already existed an error was raised unless the clear or upgrade option was provided Note While symlinks are supported on Windows they are not recommended Of particular note is that double clicking python exe in File Explorer will resolve the symlink eagerly and ignore the virtual environment Note On Microsoft Windows it may be required to enable the Activate ps1 script by setting the execution policy for the user You can do this by issuing the following PowerShell command PS C Set ExecutionPolicy ExecutionPolicy RemoteSigned Scope CurrentUserSee About Execution Policies for more information The created pyvenv cfg file also includes the include system site packages key set to true if venv is run with the system site packages option false otherwise Unless the without pip option is given ensurepip will be invoked to bootstrap pip into the virtual environment Multiple paths can be given to venv in which case an identical virtual environment will be created according to the given options at each provided path How venvs work When a Python interpreter is running from a virtual environment sys prefix and sys exec_prefix point to the directories of the virtual environment whereas sys base_prefix and sys base_exec_prefix point to those of the base Python used to create the environment It is sufficient to check sys prefix sys base_prefix to determine if the current interpreter is running from a virtual environment A virtual environment may be activated using a script in its binary directory bin on POSIX Scripts on Windows This will prepend that directory to your PATH so that running python will invoke the environment s Python interpreter and you can run installed scripts without having to use their full path The invocation of the activation script is platform specific venv must be replaced by the path to the directory containing the virtual environment Platform Shell Command to activate virtual environment POSIX bash zsh source venv bin activate fish source venv bin activate fish csh tcsh source venv bin activate csh PowerShell venv bin Activate ps1 Windows cmd exe C venv Scripts activate bat PowerShell PS C venv Scripts Activate ps1 New in version 3 4 fish and csh activation scripts New in version 3 8 PowerShell activation scripts installed under POSIX for PowerShell Core support You don t specifically need to activate a virtual environment as you can just specify the full path to that environment s Python interpreter when invoking Python Furthermore all scripts installed in the environment should be runnable without activating it In order to achieve this scripts installed into virtual environments have a shebang line which points to the environment s Python interpreter i e path to venv bin python This means that the script will run with that interpreter regardless of the value of PATH On Windows shebang line processing is supported if you have the Python Launcher for Windows installed Thus double clicking an installed script in a Windows Explorer window should run it with the correct interpreter without the environment needing to be activated or on the PATH When a virtual environment has been activated the VIRTUAL_ENV environment variable is set to the path of the environment Since explicitly activating a virtual environment is not required to use it VIRTUAL_ENV cannot be relied upon to determine whether a virtual environment is being used Warning Because scripts installed in environments should not expect the environment to be activated their shebang lines contain the absolute paths to their environment s inte,en
2426,rpreters Because of this environments are inherently non portable in the general case You should always have a simple means of recreating an environment for example if you have a requirements file requirements txt you can invoke pip install r requirements txt using the environment s pip to install all of the packages needed by the environment If for any reason you need to move the environment to a new location you should recreate it at the desired location and delete the one at the old location If you move an environment because you moved a parent directory of it you should recreate the environment in its new location Otherwise software installed into the environment may not work as expected You can deactivate a virtual environment by typing deactivate in your shell The exact mechanism is platform specific and is an internal implementation detail typically a script or shell function will be used API The high level method described above makes use of a simple API which provides mechanisms for third party virtual environment creators to customize environment creation according to their needs the EnvBuilder class class venv EnvBuilder system_site_packages False clear False symlinks False upgrade False with_pip False prompt None upgrade_deps False The EnvBuilder class accepts the following keyword arguments on instantiation system_site_packages a Boolean value indicating that the system Python site packages should be available to the environment defaults to False clear a Boolean value which if true will delete the contents of any existing target directory before creating the environment symlinks a Boolean value indicating whether to attempt to symlink the Python binary rather than copying upgrade a Boolean value which if true will upgrade an existing environment with the running Python for use when that Python has been upgraded in place defaults to False with_pip a Boolean value which if true ensures pip is installed in the virtual environment This uses ensurepip with the default pip option prompt a String to be used after virtual environment is activated defaults to None which means directory name of the environment would be used If the special string is provided the basename of the current directory is used as the prompt upgrade_deps Update the base venv modules to the latest on PyPI Changed in version 3 4 Added the with_pip parameter Changed in version 3 6 Added the prompt parameter Changed in version 3 9 Added the upgrade_deps parameter Creators of third party virtual environment tools will be free to use the provided EnvBuilder class as a base class The returned env builder is an object which has a method create create env_dir Create a virtual environment by specifying the target directory absolute or relative to the current directory which is to contain the virtual environment The create method will either create the environment in the specified directory or raise an appropriate exception The create method of the EnvBuilder class illustrates the hooks available for subclass customization def create self env_dir Create a virtualized Python environment in a directory env_dir is the target directory to create an environment in env_dir os path abspath env_dir context self ensure_directories env_dir self create_configuration context self setup_python context self setup_scripts context self post_setup context Each of the methods ensure_directories create_configuration setup_python setup_scripts and post_setup can be overridden ensure_directories env_dir Creates the environment directory and all necessary subdirectories that don t already exist and returns a context object This context object is just a holder for attributes such as paths for use by the other methods If the EnvBuilder is created with the arg clear True contents of the environment directory will be cleared and then all necessary subdirectories will be recreated The returned context object is a types SimpleNamespace with the following attributes env_dir The location of the virtual environment Used for __VENV_DIR__ in activation scripts see install_scripts env_na,en
2427,me The name of the virtual environment Used for __VENV_NAME__ in activation scripts see install_scripts prompt The prompt to be used by the activation scripts Used for __VENV_PROMPT__ in activation scripts see install_scripts executable The underlying Python executable used by the virtual environment This takes into account the case where a virtual environment is created from another virtual environment inc_path The include path for the virtual environment lib_path The purelib path for the virtual environment bin_path The script path for the virtual environment bin_name The name of the script path relative to the virtual environment location Used for __VENV_BIN_NAME__ in activation scripts see install_scripts env_exe The name of the Python interpreter in the virtual environment Used for __VENV_PYTHON__ in activation scripts see install_scripts env_exec_cmd The name of the Python interpreter taking into account filesystem redirections This can be used to run Python in the virtual environment Changed in version 3 11 The venv sysconfig installation scheme is used to construct the paths of the created directories Changed in version 3 12 The attribute lib_path was added to the context and the context object was documented create_configuration context Creates the pyvenv cfg configuration file in the environment setup_python context Creates a copy or symlink to the Python executable in the environment On POSIX systems if a specific executable python3 x was used symlinks to python and python3 will be created pointing to that executable unless files with those names already exist setup_scripts context Installs activation scripts appropriate to the platform into the virtual environment upgrade_dependencies context Upgrades the core venv dependency packages currently pip in the environment This is done by shelling out to the pip executable in the environment New in version 3 9 Changed in version 3 12 setuptools is no longer a core venv dependency post_setup context A placeholder method which can be overridden in third party implementations to pre install packages in the virtual environment or perform other post creation steps Changed in version 3 7 2 Windows now uses redirector scripts for python w exe instead of copying the actual binaries In 3 7 2 only setup_python does nothing unless running from a build in the source tree Changed in version 3 7 3 Windows copies the redirector scripts as part of setup_python instead of setup_scripts This was not the case in 3 7 2 When using symlinks the original executables will be linked In addition EnvBuilder provides this utility method that can be called from setup_scripts or post_setup in subclasses to assist in installing custom scripts into the virtual environment install_scripts context path path is the path to a directory that should contain subdirectories common posix nt each containing scripts destined for the bin directory in the environment The contents of common and the directory corresponding to os name are copied after some text replacement of placeholders __VENV_DIR__ is replaced with the absolute path of the environment directory __VENV_NAME__ is replaced with the environment name final path segment of environment directory __VENV_PROMPT__ is replaced with the prompt the environment name surrounded by parentheses and with a following space __VENV_BIN_NAME__ is replaced with the name of the bin directory either bin or Scripts __VENV_PYTHON__ is replaced with the absolute path of the environment s executable The directories are allowed to exist for when an existing environment is being upgraded There is also a module level convenience function venv create env_dir system_site_packages False clear False symlinks False with_pip False prompt None upgrade_deps False Create an EnvBuilder with the given keyword arguments and call its create method with the env_dir argument New in version 3 3 Changed in version 3 4 Added the with_pip parameter Changed in version 3 6 Added the prompt parameter Changed in version 3 9 Added the upgrade_deps parameter An example of extending EnvBuilder The f,en
2428,ollowing script shows how to extend EnvBuilder by implementing a subclass which installs setuptools and pip into a created virtual environment import os import os path from subprocess import Popen PIPE import sys from threading import Thread from urllib parse import urlparse from urllib request import urlretrieve import venv class ExtendedEnvBuilder venv EnvBuilder This builder installs setuptools and pip so that you can pip or easy_install other packages into the created virtual environment param nodist If true setuptools and pip are not installed into the created virtual environment param nopip If true pip is not installed into the created virtual environment param progress If setuptools or pip are installed the progress of the installation can be monitored by passing a progress callable If specified it is called with two arguments a string indicating some progress and a context indicating where the string is coming from The context argument can have one of three values main indicating that it is called from virtualize itself and stdout and stderr which are obtained by reading lines from the output streams of a subprocess which is used to install the app If a callable is not specified default progress information is output to sys stderr def __init__ self args kwargs self nodist kwargs pop nodist False self nopip kwargs pop nopip False self progress kwargs pop progress None self verbose kwargs pop verbose False super __init__ args kwargs def post_setup self context Set up any packages which need to be pre installed into the virtual environment being created param context The information for the virtual environment creation request being processed os environ VIRTUAL_ENV context env_dir if not self nodist self install_setuptools context Can t install pip without setuptools if not self nopip and not self nodist self install_pip context def reader self stream context Read lines from a subprocess output stream and either pass to a progress callable if specified or write progress information to sys stderr progress self progress while True s stream readline if not s break if progress is not None progress s context else if not self verbose sys stderr write else sys stderr write s decode utf 8 sys stderr flush stream close def install_script self context name url _ _ path _ _ _ urlparse url fn os path split path 1 binpath context bin_path distpath os path join binpath fn Download script into the virtual environment s binaries folder urlretrieve url distpath progress self progress if self verbose term n else term if progress is not None progress Installing s s name term main else sys stderr write Installing s s name term sys stderr flush Install in the virtual environment args context env_exe fn p Popen args stdout PIPE stderr PIPE cwd binpath t1 Thread target self reader args p stdout stdout t1 start t2 Thread target self reader args p stderr stderr t2 start p wait t1 join t2 join if progress is not None progress done main else sys stderr write done n Clean up no longer needed os unlink distpath def install_setuptools self context Install setuptools in the virtual environment param context The information for the virtual environment creation request being processed url https bootstrap pypa io ez_setup py self install_script context setuptools url clear up the setuptools archive which gets downloaded pred lambda o o startswith setuptools and o endswith tar gz files filter pred os listdir context bin_path for f in files f os path join context bin_path f os unlink f def install_pip self context Install pip in the virtual environment param context The information for the virtual environment creation request being processed url https bootstrap pypa io get pip py self install_script context pip url def main args None import argparse parser argparse ArgumentParser prog __name__ description Creates virtual Python environments in one or more target directories parser add_argument dirs metavar ENV_DIR nargs help A directory in which to create the virtual environment parser add_argument no setuptools default False action store_true dest no,en
2429,dist help Don t install setuptools or pip in the virtual environment parser add_argument no pip default False action store_true dest nopip help Don t install pip in the virtual environment parser add_argument system site packages default False action store_true dest system_site help Give the virtual environment access to the system site packages dir if os name nt use_symlinks False else use_symlinks True parser add_argument symlinks default use_symlinks action store_true dest symlinks help Try to use symlinks rather than copies when symlinks are not the default for the platform parser add_argument clear default False action store_true dest clear help Delete the contents of the virtual environment directory if it already exists before virtual environment creation parser add_argument upgrade default False action store_true dest upgrade help Upgrade the virtual environment directory to use this version of Python assuming Python has been upgraded in place parser add_argument verbose default False action store_true dest verbose help Display the output from the scripts which install setuptools and pip options parser parse_args args if options upgrade and options clear raise ValueError you cannot supply upgrade and clear together builder ExtendedEnvBuilder system_site_packages options system_site clear options clear symlinks options symlinks upgrade options upgrade nodist options nodist nopip options nopip verbose options verbose for d in options dirs builder create d if __name__ __main__ rc 1 try main rc 0 except Exception as e print Error s e file sys stderr sys exit rc This script is also available for download online,en
2430,Module Objects PyTypeObject PyModule_Type Part of the Stable ABI This instance of PyTypeObject represents the Python module type This is exposed to Python programs as types ModuleType int PyModule_Check PyObject p Return true if p is a module object or a subtype of a module object This function always succeeds int PyModule_CheckExact PyObject p Return true if p is a module object but not a subtype of PyModule_Type This function always succeeds PyObject PyModule_NewObject PyObject name Return value New reference Part of the Stable ABI since version 3 7 Return a new module object with the __name__ attribute set to name The module s __name__ __doc__ __package__ and __loader__ attributes are filled in all but __name__ are set to None the caller is responsible for providing a __file__ attribute New in version 3 3 Changed in version 3 4 __package__ and __loader__ are set to None PyObject PyModule_New const char name Return value New reference Part of the Stable ABI Similar to PyModule_NewObject but the name is a UTF 8 encoded string instead of a Unicode object PyObject PyModule_GetDict PyObject module Return value Borrowed reference Part of the Stable ABI Return the dictionary object that implements module s namespace this object is the same as the __dict__ attribute of the module object If module is not a module object or a subtype of a module object SystemError is raised and NULL is returned It is recommended extensions use other PyModule_ and PyObject_ functions rather than directly manipulate a module s __dict__ PyObject PyModule_GetNameObject PyObject module Return value New reference Part of the Stable ABI since version 3 7 Return module s __name__ value If the module does not provide one or if it is not a string SystemError is raised and NULL is returned New in version 3 3 const char PyModule_GetName PyObject module Part of the Stable ABI Similar to PyModule_GetNameObject but return the name encoded to utf 8 void PyModule_GetState PyObject module Part of the Stable ABI Return the state of the module that is a pointer to the block of memory allocated at module creation time or NULL See PyModuleDef m_size PyModuleDef PyModule_GetDef PyObject module Part of the Stable ABI Return a pointer to the PyModuleDef struct from which the module was created or NULL if the module wasn t created from a definition PyObject PyModule_GetFilenameObject PyObject module Return value New reference Part of the Stable ABI Return the name of the file from which module was loaded using module s __file__ attribute If this is not defined or if it is not a unicode string raise SystemError and return NULL otherwise return a reference to a Unicode object New in version 3 2 const char PyModule_GetFilename PyObject module Part of the Stable ABI Similar to PyModule_GetFilenameObject but return the filename encoded to utf 8 Deprecated since version 3 2 PyModule_GetFilename raises UnicodeEncodeError on unencodable filenames use PyModule_GetFilenameObject instead Initializing C modules Modules objects are usually created from extension modules shared libraries which export an initialization function or compiled in modules where the initialization function is added using PyImport_AppendInittab See Building C and C Extensions or Extending Embedded Python for details The initialization function can either pass a module definition instance to PyModule_Create and return the resulting module object or request multi phase initialization by returning the definition struct itself type PyModuleDef Part of the Stable ABI including all members The module definition struct which holds all information needed to create a module object There is usually only one statically initialized variable of this type for each module PyModuleDef_Base m_base Always initialize this member to PyModuleDef_HEAD_INIT const char m_name Name for the new module const char m_doc Docstring for the module usually a docstring variable created with PyDoc_STRVAR is used Py_ssize_t m_size Module state may be kept in a per module memory area that can be retrieved with PyModule_GetState rather than in ,en
2431,static globals This makes modules safe for use in multiple sub interpreters This memory area is allocated based on m_size on module creation and freed when the module object is deallocated after the m_free function has been called if present Setting m_size to 1 means that the module does not support sub interpreters because it has global state Setting it to a non negative value means that the module can be re initialized and specifies the additional amount of memory it requires for its state Non negative m_size is required for multi phase initialization See PEP 3121 for more details PyMethodDef m_methods A pointer to a table of module level functions described by PyMethodDef values Can be NULL if no functions are present PyModuleDef_Slot m_slots An array of slot definitions for multi phase initialization terminated by a 0 NULL entry When using single phase initialization m_slots must be NULL Changed in version 3 5 Prior to version 3 5 this member was always set to NULL and was defined as inquiry m_reload traverseproc m_traverse A traversal function to call during GC traversal of the module object or NULL if not needed This function is not called if the module state was requested but is not allocated yet This is the case immediately after the module is created and before the module is executed Py_mod_exec function More precisely this function is not called if m_size is greater than 0 and the module state as returned by PyModule_GetState is NULL Changed in version 3 9 No longer called before the module state is allocated inquiry m_clear A clear function to call during GC clearing of the module object or NULL if not needed This function is not called if the module state was requested but is not allocated yet This is the case immediately after the module is created and before the module is executed Py_mod_exec function More precisely this function is not called if m_size is greater than 0 and the module state as returned by PyModule_GetState is NULL Like PyTypeObject tp_clear this function is not always called before a module is deallocated For example when reference counting is enough to determine that an object is no longer used the cyclic garbage collector is not involved and m_free is called directly Changed in version 3 9 No longer called before the module state is allocated freefunc m_free A function to call during deallocation of the module object or NULL if not needed This function is not called if the module state was requested but is not allocated yet This is the case immediately after the module is created and before the module is executed Py_mod_exec function More precisely this function is not called if m_size is greater than 0 and the module state as returned by PyModule_GetState is NULL Changed in version 3 9 No longer called before the module state is allocated Single phase initialization The module initialization function may create and return the module object directly This is referred to as single phase initialization and uses one of the following two module creation functions PyObject PyModule_Create PyModuleDef def Return value New reference Create a new module object given the definition in def This behaves like PyModule_Create2 with module_api_version set to PYTHON_API_VERSION PyObject PyModule_Create2 PyModuleDef def int module_api_version Return value New reference Part of the Stable ABI Create a new module object given the definition in def assuming the API version module_api_version If that version does not match the version of the running interpreter a RuntimeWarning is emitted Note Most uses of this function should be using PyModule_Create instead only use this if you are sure you need it Before it is returned from in the initialization function the resulting module object is typically populated using functions like PyModule_AddObjectRef Multi phase initialization An alternate way to specify extensions is to request multi phase initialization Extension modules created this way behave more like Python modules the initialization is split between the creation phase when the module object is created ,en
2432,and the execution phase when it is populated The distinction is similar to the __new__ and __init__ methods of classes Unlike modules created using single phase initialization these modules are not singletons if the sys modules entry is removed and the module is re imported a new module object is created and the old module is subject to normal garbage collection as with Python modules By default multiple modules created from the same definition should be independent changes to one should not affect the others This means that all state should be specific to the module object using e g using PyModule_GetState or its contents such as the module s __dict__ or individual classes created with PyType_FromSpec All modules created using multi phase initialization are expected to support sub interpreters Making sure multiple modules are independent is typically enough to achieve this To request multi phase initialization the initialization function PyInit_modulename returns a PyModuleDef instance with non empty m_slots Before it is returned the PyModuleDef instance must be initialized with the following function PyObject PyModuleDef_Init PyModuleDef def Return value Borrowed reference Part of the Stable ABI since version 3 5 Ensures a module definition is a properly initialized Python object that correctly reports its type and reference count Returns def cast to PyObject or NULL if an error occurred New in version 3 5 The m_slots member of the module definition must point to an array of PyModuleDef_Slot structures type PyModuleDef_Slot int slot A slot ID chosen from the available values explained below void value Value of the slot whose meaning depends on the slot ID New in version 3 5 The m_slots array must be terminated by a slot with id 0 The available slot types are Py_mod_create Specifies a function that is called to create the module object itself The value pointer of this slot must point to a function of the signature PyObject create_module PyObject spec PyModuleDef def The function receives a ModuleSpec instance as defined in PEP 451 and the module definition It should return a new module object or set an error and return NULL This function should be kept minimal In particular it should not call arbitrary Python code as trying to import the same module again may result in an infinite loop Multiple Py_mod_create slots may not be specified in one module definition If Py_mod_create is not specified the import machinery will create a normal module object using PyModule_New The name is taken from spec not the definition to allow extension modules to dynamically adjust to their place in the module hierarchy and be imported under different names through symlinks all while sharing a single module definition There is no requirement for the returned object to be an instance of PyModule_Type Any type can be used as long as it supports setting and getting import related attributes However only PyModule_Type instances may be returned if the PyModuleDef has non NULL m_traverse m_clear m_free non zero m_size or slots other than Py_mod_create Py_mod_exec Specifies a function that is called to execute the module This is equivalent to executing the code of a Python module typically this function adds classes and constants to the module The signature of the function is int exec_module PyObject module If multiple Py_mod_exec slots are specified they are processed in the order they appear in the m_slots array Py_mod_multiple_interpreters Specifies one of the following values Py_MOD_MULTIPLE_INTERPRETERS_NOT_SUPPORTED The module does not support being imported in subinterpreters Py_MOD_MULTIPLE_INTERPRETERS_SUPPORTED The module supports being imported in subinterpreters but only when they share the main interpreter s GIL See Isolating Extension Modules Py_MOD_PER_INTERPRETER_GIL_SUPPORTED The module supports being imported in subinterpreters even when they have their own GIL See Isolating Extension Modules This slot determines whether or not importing this module in a subinterpreter will fail Multiple Py_mod_multiple_interpreters slots may not ,en
2433,be specified in one module definition If Py_mod_multiple_interpreters is not specified the import machinery defaults to Py_MOD_MULTIPLE_INTERPRETERS_NOT_SUPPORTED New in version 3 12 See PEP 489 for more details on multi phase initialization Low level module creation functions The following functions are called under the hood when using multi phase initialization They can be used directly for example when creating module objects dynamically Note that both PyModule_FromDefAndSpec and PyModule_ExecDef must be called to fully initialize a module PyObject PyModule_FromDefAndSpec PyModuleDef def PyObject spec Return value New reference Create a new module object given the definition in def and the ModuleSpec spec This behaves like PyModule_FromDefAndSpec2 with module_api_version set to PYTHON_API_VERSION New in version 3 5 PyObject PyModule_FromDefAndSpec2 PyModuleDef def PyObject spec int module_api_version Return value New reference Part of the Stable ABI since version 3 7 Create a new module object given the definition in def and the ModuleSpec spec assuming the API version module_api_version If that version does not match the version of the running interpreter a RuntimeWarning is emitted Note Most uses of this function should be using PyModule_FromDefAndSpec instead only use this if you are sure you need it New in version 3 5 int PyModule_ExecDef PyObject module PyModuleDef def Part of the Stable ABI since version 3 7 Process any execution slots Py_mod_exec given in def New in version 3 5 int PyModule_SetDocString PyObject module const char docstring Part of the Stable ABI since version 3 7 Set the docstring for module to docstring This function is called automatically when creating a module from PyModuleDef using either PyModule_Create or PyModule_FromDefAndSpec New in version 3 5 int PyModule_AddFunctions PyObject module PyMethodDef functions Part of the Stable ABI since version 3 7 Add the functions from the NULL terminated functions array to module Refer to the PyMethodDef documentation for details on individual entries due to the lack of a shared module namespace module level functions implemented in C typically receive the module as their first parameter making them similar to instance methods on Python classes This function is called automatically when creating a module from PyModuleDef using either PyModule_Create or PyModule_FromDefAndSpec New in version 3 5 Support functions The module initialization function if using single phase initialization or a function called from a module execution slot if using multi phase initialization can use the following functions to help initialize the module state int PyModule_AddObjectRef PyObject module const char name PyObject value Part of the Stable ABI since version 3 10 Add an object to module as name This is a convenience function which can be used from the module s initialization function On success return 0 On error raise an exception and return 1 Return NULL if value is NULL It must be called with an exception raised in this case Example usage static int add_spam PyObject module int value PyObject obj PyLong_FromLong value if obj NULL return 1 int res PyModule_AddObjectRef module spam obj Py_DECREF obj return res The example can also be written without checking explicitly if obj is NULL static int add_spam PyObject module int value PyObject obj PyLong_FromLong value int res PyModule_AddObjectRef module spam obj Py_XDECREF obj return res Note that Py_XDECREF should be used instead of Py_DECREF in this case since obj can be NULL New in version 3 10 int PyModule_AddObject PyObject module const char name PyObject value Part of the Stable ABI Similar to PyModule_AddObjectRef but steals a reference to value on success if it returns 0 The new PyModule_AddObjectRef function is recommended since it is easy to introduce reference leaks by misusing the PyModule_AddObject function Note Unlike other functions that steal references PyModule_AddObject only releases the reference to value on success This means that its return value must be checked and calling code must Py_DECREF value,en
2434, manually on error Example usage static int add_spam PyObject module int value PyObject obj PyLong_FromLong value if obj NULL return 1 if PyModule_AddObject module spam obj 0 Py_DECREF obj return 1 PyModule_AddObject stole a reference to obj Py_DECREF obj is not needed here return 0 The example can also be written without checking explicitly if obj is NULL static int add_spam PyObject module int value PyObject obj PyLong_FromLong value if PyModule_AddObject module spam obj 0 Py_XDECREF obj return 1 PyModule_AddObject stole a reference to obj Py_DECREF obj is not needed here return 0 Note that Py_XDECREF should be used instead of Py_DECREF in this case since obj can be NULL int PyModule_AddIntConstant PyObject module const char name long value Part of the Stable ABI Add an integer constant to module as name This convenience function can be used from the module s initialization function Return 1 on error 0 on success int PyModule_AddStringConstant PyObject module const char name const char value Part of the Stable ABI Add a string constant to module as name This convenience function can be used from the module s initialization function The string value must be NULL terminated Return 1 on error 0 on success PyModule_AddIntMacro module macro Add an int constant to module The name and the value are taken from macro For example PyModule_AddIntMacro module AF_INET adds the int constant AF_INET with the value of AF_INET to module Return 1 on error 0 on success PyModule_AddStringMacro module macro Add a string constant to module int PyModule_AddType PyObject module PyTypeObject type Part of the Stable ABI since version 3 10 Add a type object to module The type object is finalized by calling internally PyType_Ready The name of the type object is taken from the last component of tp_name after dot Return 1 on error 0 on success New in version 3 9 Module lookup Single phase initialization creates singleton modules that can be looked up in the context of the current interpreter This allows the module object to be retrieved later with only a reference to the module definition These functions will not work on modules created using multi phase initialization since multiple such modules can be created from a single definition PyObject PyState_FindModule PyModuleDef def Return value Borrowed reference Part of the Stable ABI Returns the module object that was created from def for the current interpreter This method requires that the module object has been attached to the interpreter state with PyState_AddModule beforehand In case the corresponding module object is not found or has not been attached to the interpreter state yet it returns NULL int PyState_AddModule PyObject module PyModuleDef def Part of the Stable ABI since version 3 3 Attaches the module object passed to the function to the interpreter state This allows the module object to be accessible via PyState_FindModule Only effective on modules created using single phase initialization Python calls PyState_AddModule automatically after importing a module so it is unnecessary but harmless to call it from module initialization code An explicit call is needed only if the module s own init code subsequently calls PyState_FindModule The function is mainly intended for implementing alternative import mechanisms either by calling it directly or by referring to its implementation for details of the required state updates The caller must hold the GIL Return 0 on success or 1 on failure New in version 3 3 int PyState_RemoveModule PyModuleDef def Part of the Stable ABI since version 3 3 Removes the module object created from def from the interpreter state Return 0 on success or 1 on failure The caller must hold the GIL New in version 3 3,en
2435,Parsing arguments and building values These functions are useful when creating your own extensions functions and methods Additional information and examples are available in Extending and Embedding the Python Interpreter The first three of these functions described PyArg_ParseTuple PyArg_ParseTupleAndKeywords and PyArg_Parse all use format strings which are used to tell the function about the expected arguments The format strings use the same syntax for each of these functions Parsing arguments A format string consists of zero or more format units A format unit describes one Python object it is usually a single character or a parenthesized sequence of format units With a few exceptions a format unit that is not a parenthesized sequence normally corresponds to a single address argument to these functions In the following description the quoted form is the format unit the entry in round parentheses is the Python object type that matches the format unit and the entry in square brackets is the type of the C variable s whose address should be passed Strings and buffers These formats allow accessing an object as a contiguous chunk of memory You don t have to provide raw storage for the returned unicode or bytes area Unless otherwise stated buffers are not NUL terminated There are three ways strings and buffers can be converted to C Formats such as y and s fill a Py_buffer structure This locks the underlying buffer so that the caller can subsequently use the buffer even inside a Py_BEGIN_ALLOW_THREADS block without the risk of mutable data being resized or destroyed As a result you have to call PyBuffer_Release after you have finished processing the data or in any early abort case The es es et and et formats allocate the result buffer You have to call PyMem_Free after you have finished processing the data or in any early abort case Other formats take a str or a read only bytes like object such as bytes and provide a const char pointer to its buffer In this case the buffer is borrowed it is managed by the corresponding Python object and shares the lifetime of this object You won t have to release any memory yourself To ensure that the underlying buffer may be safely borrowed the object s PyBufferProcs bf_releasebuffer field must be NULL This disallows common mutable objects such as bytearray but also some read only objects such as memoryview of bytes Besides this bf_releasebuffer requirement there is no check to verify whether the input object is immutable e g whether it would honor a request for a writable buffer or whether another thread can mutate the data Note For all variants of formats s y etc the macro PY_SSIZE_T_CLEAN must be defined before including Python h On Python 3 9 and older the type of the length argument is Py_ssize_t if the PY_SSIZE_T_CLEAN macro is defined or int otherwise s str const char Convert a Unicode object to a C pointer to a character string A pointer to an existing string is stored in the character pointer variable whose address you pass The C string is NUL terminated The Python string must not contain embedded null code points if it does a ValueError exception is raised Unicode objects are converted to C strings using utf 8 encoding If this conversion fails a UnicodeError is raised Note This format does not accept bytes like objects If you want to accept filesystem paths and convert them to C character strings it is preferable to use the O format with PyUnicode_FSConverter as converter Changed in version 3 5 Previously TypeError was raised when embedded null code points were encountered in the Python string s str or bytes like object Py_buffer This format accepts Unicode objects as well as bytes like objects It fills a Py_buffer structure provided by the caller In this case the resulting C string may contain embedded NUL bytes Unicode objects are converted to C strings using utf 8 encoding s str read only bytes like object const char Py_ssize_t Like s except that it provides a borrowed buffer The result is stored into two C variables the first one a pointer to a C string the second one its length T,en
2436,he string may contain embedded null bytes Unicode objects are converted to C strings using utf 8 encoding z str or None const char Like s but the Python object may also be None in which case the C pointer is set to NULL z str bytes like object or None Py_buffer Like s but the Python object may also be None in which case the buf member of the Py_buffer structure is set to NULL z str read only bytes like object or None const char Py_ssize_t Like s but the Python object may also be None in which case the C pointer is set to NULL y read only bytes like object const char This format converts a bytes like object to a C pointer to a borrowed character string it does not accept Unicode objects The bytes buffer must not contain embedded null bytes if it does a ValueError exception is raised Changed in version 3 5 Previously TypeError was raised when embedded null bytes were encountered in the bytes buffer y bytes like object Py_buffer This variant on s doesn t accept Unicode objects only bytes like objects This is the recommended way to accept binary data y read only bytes like object const char Py_ssize_t This variant on s doesn t accept Unicode objects only bytes like objects S bytes PyBytesObject Requires that the Python object is a bytes object without attempting any conversion Raises TypeError if the object is not a bytes object The C variable may also be declared as PyObject Y bytearray PyByteArrayObject Requires that the Python object is a bytearray object without attempting any conversion Raises TypeError if the object is not a bytearray object The C variable may also be declared as PyObject U str PyObject Requires that the Python object is a Unicode object without attempting any conversion Raises TypeError if the object is not a Unicode object The C variable may also be declared as PyObject w read write bytes like object Py_buffer This format accepts any object which implements the read write buffer interface It fills a Py_buffer structure provided by the caller The buffer may contain embedded null bytes The caller have to call PyBuffer_Release when it is done with the buffer es str const char encoding char buffer This variant on s is used for encoding Unicode into a character buffer It only works for encoded data without embedded NUL bytes This format requires two arguments The first is only used as input and must be a const char which points to the name of an encoding as a NUL terminated string or NULL in which case utf 8 encoding is used An exception is raised if the named encoding is not known to Python The second argument must be a char the value of the pointer it references will be set to a buffer with the contents of the argument text The text will be encoded in the encoding specified by the first argument PyArg_ParseTuple will allocate a buffer of the needed size copy the encoded data into this buffer and adjust buffer to reference the newly allocated storage The caller is responsible for calling PyMem_Free to free the allocated buffer after use et str bytes or bytearray const char encoding char buffer Same as es except that byte string objects are passed through without recoding them Instead the implementation assumes that the byte string object uses the encoding passed in as parameter es str const char encoding char buffer Py_ssize_t buffer_length This variant on s is used for encoding Unicode into a character buffer Unlike the es format this variant allows input data which contains NUL characters It requires three arguments The first is only used as input and must be a const char which points to the name of an encoding as a NUL terminated string or NULL in which case utf 8 encoding is used An exception is raised if the named encoding is not known to Python The second argument must be a char the value of the pointer it references will be set to a buffer with the contents of the argument text The text will be encoded in the encoding specified by the first argument The third argument must be a pointer to an integer the referenced integer will be set to the number of bytes in the output buffer There are two modes ,en
2437,of operation If buffer points a NULL pointer the function will allocate a buffer of the needed size copy the encoded data into this buffer and set buffer to reference the newly allocated storage The caller is responsible for calling PyMem_Free to free the allocated buffer after usage If buffer points to a non NULL pointer an already allocated buffer PyArg_ParseTuple will use this location as the buffer and interpret the initial value of buffer_length as the buffer size It will then copy the encoded data into the buffer and NUL terminate it If the buffer is not large enough a ValueError will be set In both cases buffer_length is set to the length of the encoded data without the trailing NUL byte et str bytes or bytearray const char encoding char buffer Py_ssize_t buffer_length Same as es except that byte string objects are passed through without recoding them Instead the implementation assumes that the byte string object uses the encoding passed in as parameter Changed in version 3 12 u u Z and Z are removed because they used a legacy Py_UNICODE representation Numbers b int unsigned char Convert a nonnegative Python integer to an unsigned tiny int stored in a C unsigned char B int unsigned char Convert a Python integer to a tiny int without overflow checking stored in a C unsigned char h int short int Convert a Python integer to a C short int H int unsigned short int Convert a Python integer to a C unsigned short int without overflow checking i int int Convert a Python integer to a plain C int I int unsigned int Convert a Python integer to a C unsigned int without overflow checking l int long int Convert a Python integer to a C long int k int unsigned long Convert a Python integer to a C unsigned long without overflow checking L int long long Convert a Python integer to a C long long K int unsigned long long Convert a Python integer to a C unsigned long long without overflow checking n int Py_ssize_t Convert a Python integer to a C Py_ssize_t c bytes or bytearray of length 1 char Convert a Python byte represented as a bytes or bytearray object of length 1 to a C char Changed in version 3 3 Allow bytearray objects C str of length 1 int Convert a Python character represented as a str object of length 1 to a C int f float float Convert a Python floating point number to a C float d float double Convert a Python floating point number to a C double D complex Py_complex Convert a Python complex number to a C Py_complex structure Other objects O object PyObject Store a Python object without any conversion in a C object pointer The C program thus receives the actual object that was passed A new strong reference to the object is not created i e its reference count is not increased The pointer stored is not NULL O object typeobject PyObject Store a Python object in a C object pointer This is similar to O but takes two C arguments the first is the address of a Python type object the second is the address of the C variable of type PyObject into which the object pointer is stored If the Python object does not have the required type TypeError is raised O object converter anything Convert a Python object to a C variable through a converter function This takes two arguments the first is a function the second is the address of a C variable of arbitrary type converted to void The converter function in turn is called as follows status converter object address where object is the Python object to be converted and address is the void argument that was passed to the PyArg_Parse function The returned status should be 1 for a successful conversion and 0 if the conversion has failed When the conversion fails the converter function should raise an exception and leave the content of address unmodified If the converter returns Py_CLEANUP_SUPPORTED it may get called a second time if the argument parsing eventually fails giving the converter a chance to release any memory that it had already allocated In this second call the object parameter will be NULL address will have the same value as in the original call Changed in version 3 1 Py_CLEANUP_SUPPORTE,en
2438,D was added p bool int Tests the value passed in for truth a boolean p redicate and converts the result to its equivalent C true false integer value Sets the int to 1 if the expression was true and 0 if it was false This accepts any valid Python value See Truth Value Testing for more information about how Python tests values for truth New in version 3 3 items tuple matching items The object must be a Python sequence whose length is the number of format units in items The C arguments must correspond to the individual format units in items Format units for sequences may be nested It is possible to pass long integers integers whose value exceeds the platform s LONG_MAX however no proper range checking is done the most significant bits are silently truncated when the receiving field is too small to receive the value actually the semantics are inherited from downcasts in C your mileage may vary A few other characters have a meaning in a format string These may not occur inside nested parentheses They are Indicates that the remaining arguments in the Python argument list are optional The C variables corresponding to optional arguments should be initialized to their default value when an optional argument is not specified PyArg_ParseTuple does not touch the contents of the corresponding C variable s PyArg_ParseTupleAndKeywords only Indicates that the remaining arguments in the Python argument list are keyword only Currently all keyword only arguments must also be optional arguments so must always be specified before in the format string New in version 3 3 The list of format units ends here the string after the colon is used as the function name in error messages the associated value of the exception that PyArg_ParseTuple raises The list of format units ends here the string after the semicolon is used as the error message instead of the default error message and mutually exclude each other Note that any Python object references which are provided to the caller are borrowed references do not release them i e do not decrement their reference count Additional arguments passed to these functions must be addresses of variables whose type is determined by the format string these are used to store values from the input tuple There are a few cases as described in the list of format units above where these parameters are used as input values they should match what is specified for the corresponding format unit in that case For the conversion to succeed the arg object must match the format and the format must be exhausted On success the PyArg_Parse functions return true otherwise they return false and raise an appropriate exception When the PyArg_Parse functions fail due to conversion failure in one of the format units the variables at the addresses corresponding to that and the following format units are left untouched API Functions int PyArg_ParseTuple PyObject args const char format Part of the Stable ABI Parse the parameters of a function that takes only positional parameters into local variables Returns true on success on failure it returns false and raises the appropriate exception int PyArg_VaParse PyObject args const char format va_list vargs Part of the Stable ABI Identical to PyArg_ParseTuple except that it accepts a va_list rather than a variable number of arguments int PyArg_ParseTupleAndKeywords PyObject args PyObject kw const char format char keywords Part of the Stable ABI Parse the parameters of a function that takes both positional and keyword parameters into local variables The keywords argument is a NULL terminated array of keyword parameter names Empty names denote positional only parameters Returns true on success on failure it returns false and raises the appropriate exception Changed in version 3 6 Added support for positional only parameters int PyArg_VaParseTupleAndKeywords PyObject args PyObject kw const char format char keywords va_list vargs Part of the Stable ABI Identical to PyArg_ParseTupleAndKeywords except that it accepts a va_list rather than a variable number of arguments int PyArg_ValidateKeywordArgumen,en
2439,ts PyObject Part of the Stable ABI Ensure that the keys in the keywords argument dictionary are strings This is only needed if PyArg_ParseTupleAndKeywords is not used since the latter already does this check New in version 3 2 int PyArg_Parse PyObject args const char format Part of the Stable ABI Function used to deconstruct the argument lists of old style functions these are functions which use the METH_OLDARGS parameter parsing method which has been removed in Python 3 This is not recommended for use in parameter parsing in new code and most code in the standard interpreter has been modified to no longer use this for that purpose It does remain a convenient way to decompose other tuples however and may continue to be used for that purpose int PyArg_UnpackTuple PyObject args const char name Py_ssize_t min Py_ssize_t max Part of the Stable ABI A simpler form of parameter retrieval which does not use a format string to specify the types of the arguments Functions which use this method to retrieve their parameters should be declared as METH_VARARGS in function or method tables The tuple containing the actual parameters should be passed as args it must actually be a tuple The length of the tuple must be at least min and no more than max min and max may be equal Additional arguments must be passed to the function each of which should be a pointer to a PyObject variable these will be filled in with the values from args they will contain borrowed references The variables which correspond to optional parameters not given by args will not be filled in these should be initialized by the caller This function returns true on success and false if args is not a tuple or contains the wrong number of elements an exception will be set if there was a failure This is an example of the use of this function taken from the sources for the _weakref helper module for weak references static PyObject weakref_ref PyObject self PyObject args PyObject object PyObject callback NULL PyObject result NULL if PyArg_UnpackTuple args ref 1 2 object callback result PyWeakref_NewRef object callback return result The call to PyArg_UnpackTuple in this example is entirely equivalent to this call to PyArg_ParseTuple PyArg_ParseTuple args O O ref object callback Building values PyObject Py_BuildValue const char format Return value New reference Part of the Stable ABI Create a new value based on a format string similar to those accepted by the PyArg_Parse family of functions and a sequence of values Returns the value or NULL in the case of an error an exception will be raised if NULL is returned Py_BuildValue does not always build a tuple It builds a tuple only if its format string contains two or more format units If the format string is empty it returns None if it contains exactly one format unit it returns whatever object is described by that format unit To force it to return a tuple of size 0 or one parenthesize the format string When memory buffers are passed as parameters to supply data to build objects as for the s and s formats the required data is copied Buffers provided by the caller are never referenced by the objects created by Py_BuildValue In other words if your code invokes malloc and passes the allocated memory to Py_BuildValue your code is responsible for calling free for that memory once Py_BuildValue returns In the following description the quoted form is the format unit the entry in round parentheses is the Python object type that the format unit will return and the entry in square brackets is the type of the C value s to be passed The characters space tab colon and comma are ignored in format strings but not within format units such as s This can be used to make long format strings a tad more readable s str or None const char Convert a null terminated C string to a Python str object using utf 8 encoding If the C string pointer is NULL None is used s str or None const char Py_ssize_t Convert a C string and its length to a Python str object using utf 8 encoding If the C string pointer is NULL the length is ignored and None is returned y bytes c,en
2440,onst char This converts a C string to a Python bytes object If the C string pointer is NULL None is returned y bytes const char Py_ssize_t This converts a C string and its lengths to a Python object If the C string pointer is NULL None is returned z str or None const char Same as s z str or None const char Py_ssize_t Same as s u str const wchar_t Convert a null terminated wchar_t buffer of Unicode UTF 16 or UCS 4 data to a Python Unicode object If the Unicode buffer pointer is NULL None is returned u str const wchar_t Py_ssize_t Convert a Unicode UTF 16 or UCS 4 data buffer and its length to a Python Unicode object If the Unicode buffer pointer is NULL the length is ignored and None is returned U str or None const char Same as s U str or None const char Py_ssize_t Same as s i int int Convert a plain C int to a Python integer object b int char Convert a plain C char to a Python integer object h int short int Convert a plain C short int to a Python integer object l int long int Convert a C long int to a Python integer object B int unsigned char Convert a C unsigned char to a Python integer object H int unsigned short int Convert a C unsigned short int to a Python integer object I int unsigned int Convert a C unsigned int to a Python integer object k int unsigned long Convert a C unsigned long to a Python integer object L int long long Convert a C long long to a Python integer object K int unsigned long long Convert a C unsigned long long to a Python integer object n int Py_ssize_t Convert a C Py_ssize_t to a Python integer c bytes of length 1 char Convert a C int representing a byte to a Python bytes object of length 1 C str of length 1 int Convert a C int representing a character to Python str object of length 1 d float double Convert a C double to a Python floating point number f float float Convert a C float to a Python floating point number D complex Py_complex Convert a C Py_complex structure to a Python complex number O object PyObject Pass a Python object untouched but create a new strong reference to it i e its reference count is incremented by one If the object passed in is a NULL pointer it is assumed that this was caused because the call producing the argument found an error and set an exception Therefore Py_BuildValue will return NULL but won t raise an exception If no exception has been raised yet SystemError is set S object PyObject Same as O N object PyObject Same as O except it doesn t create a new strong reference Useful when the object is created by a call to an object constructor in the argument list O object converter anything Convert anything to a Python object through a converter function The function is called with anything which should be compatible with void as its argument and should return a new Python object or NULL if an error occurred items tuple matching items Convert a sequence of C values to a Python tuple with the same number of items items list matching items Convert a sequence of C values to a Python list with the same number of items items dict matching items Convert a sequence of C values to a Python dictionary Each pair of consecutive C values adds one item to the dictionary serving as key and value respectively If there is an error in the format string the SystemError exception is set and NULL returned PyObject Py_VaBuildValue const char format va_list vargs Return value New reference Part of the Stable ABI Identical to Py_BuildValue except that it accepts a va_list rather than a variable number of arguments,en
2441,1 Introduction This reference manual describes the Python programming language It is not intended as a tutorial While I am trying to be as precise as possible I chose to use English rather than formal specifications for everything except syntax and lexical analysis This should make the document more understandable to the average reader but will leave room for ambiguities Consequently if you were coming from Mars and tried to re implement Python from this document alone you might have to guess things and in fact you would probably end up implementing quite a different language On the other hand if you are using Python and wonder what the precise rules about a particular area of the language are you should definitely be able to find them here If you would like to see a more formal definition of the language maybe you could volunteer your time or invent a cloning machine It is dangerous to add too many implementation details to a language reference document the implementation may change and other implementations of the same language may work differently On the other hand CPython is the one Python implementation in widespread use although alternate implementations continue to gain support and its particular quirks are sometimes worth being mentioned especially where the implementation imposes additional limitations Therefore you ll find short implementation notes sprinkled throughout the text Every Python implementation comes with a number of built in and standard modules These are documented in The Python Standard Library A few built in modules are mentioned when they interact in a significant way with the language definition 1 1 Alternate Implementations Though there is one Python implementation which is by far the most popular there are some alternate implementations which are of particular interest to different audiences Known implementations include CPython This is the original and most maintained implementation of Python written in C New language features generally appear here first Jython Python implemented in Java This implementation can be used as a scripting language for Java applications or can be used to create applications using the Java class libraries It is also often used to create tests for Java libraries More information can be found at the Jython website Python for NET This implementation actually uses the CPython implementation but is a managed NET application and makes NET libraries available It was created by Brian Lloyd For more information see the Python for NET home page IronPython An alternate Python for NET Unlike Python NET this is a complete Python implementation that generates IL and compiles Python code directly to NET assemblies It was created by Jim Hugunin the original creator of Jython For more information see the IronPython website PyPy An implementation of Python written completely in Python It supports several advanced features not found in other implementations like stackless support and a Just in Time compiler One of the goals of the project is to encourage experimentation with the language itself by making it easier to modify the interpreter since it is written in Python Additional information is available on the PyPy project s home page Each of these implementations varies in some way from the language as documented in this manual or introduces specific information beyond what s covered in the standard Python documentation Please refer to the implementation specific documentation to determine what else you need to know about the specific implementation you re using 1 2 Notation The descriptions of lexical analysis and syntax use a modified Backus Naur form BNF grammar notation This uses the following style of definition name lc_letter lc_letter _ lc_letter a z The first line says that a name is an lc_letter followed by a sequence of zero or more lc_letter s and underscores An lc_letter in turn is any of the single characters a through z This rule is actually adhered to for the names defined in lexical and grammar rules in this document Each rule begins with a name which is the name d,en
2442,efined by the rule and A vertical bar is used to separate alternatives it is the least binding operator in this notation A star means zero or more repetitions of the preceding item likewise a plus means one or more repetitions and a phrase enclosed in square brackets means zero or one occurrences in other words the enclosed phrase is optional The and operators bind as tightly as possible parentheses are used for grouping Literal strings are enclosed in quotes White space is only meaningful to separate tokens Rules are normally contained on a single line rules with many alternatives may be formatted alternatively with each line after the first beginning with a vertical bar In lexical definitions as the example above two more conventions are used Two literal characters separated by three dots mean a choice of any single character in the given inclusive range of ASCII characters A phrase between angular brackets gives an informal description of the symbol defined e g this could be used to describe the notion of control character if needed Even though the notation used is almost the same there is a big difference between the meaning of lexical and syntactic definitions a lexical definition operates on the individual characters of the input source while a syntax definition operates on the stream of tokens generated by the lexical analysis All uses of BNF in the next chapter Lexical Analysis are lexical definitions uses in subsequent chapters are syntactic definitions,en
2443,String conversion and formatting Functions for number conversion and formatted string output int PyOS_snprintf char str size_t size const char format Part of the Stable ABI Output not more than size bytes to str according to the format string format and the extra arguments See the Unix man page snprintf 3 int PyOS_vsnprintf char str size_t size const char format va_list va Part of the Stable ABI Output not more than size bytes to str according to the format string format and the variable argument list va Unix man page vsnprintf 3 PyOS_snprintf and PyOS_vsnprintf wrap the Standard C library functions snprintf and vsnprintf Their purpose is to guarantee consistent behavior in corner cases which the Standard C functions do not The wrappers ensure that str size 1 is always 0 upon return They never write more than size bytes including the trailing 0 into str Both functions require that str NULL size 0 format NULL and size INT_MAX Note that this means there is no equivalent to the C99 n snprintf NULL 0 which would determine the necessary buffer size The return value rv for these functions should be interpreted as follows When 0 rv size the output conversion was successful and rv characters were written to str excluding the trailing 0 byte at str rv When rv size the output conversion was truncated and a buffer with rv 1 bytes would have been needed to succeed str size 1 is 0 in this case When rv 0 something bad happened str size 1 is 0 in this case too but the rest of str is undefined The exact cause of the error depends on the underlying platform The following functions provide locale independent string to number conversions unsigned long PyOS_strtoul const char str char ptr int base Part of the Stable ABI Convert the initial part of the string in str to an unsigned long value according to the given base which must be between 2 and 36 inclusive or be the special value 0 Leading white space and case of characters are ignored If base is zero it looks for a leading 0b 0o or 0x to tell which base If these are absent it defaults to 10 Base must be 0 or between 2 and 36 inclusive If ptr is non NULL it will contain a pointer to the end of the scan If the converted value falls out of range of corresponding return type range error occurs errno is set to ERANGE and ULONG_MAX is returned If no conversion can be performed 0 is returned See also the Unix man page strtoul 3 New in version 3 2 long PyOS_strtol const char str char ptr int base Part of the Stable ABI Convert the initial part of the string in str to an long value according to the given base which must be between 2 and 36 inclusive or be the special value 0 Same as PyOS_strtoul but return a long value instead and LONG_MAX on overflows See also the Unix man page strtol 3 New in version 3 2 double PyOS_string_to_double const char s char endptr PyObject overflow_exception Part of the Stable ABI Convert a string s to a double raising a Python exception on failure The set of accepted strings corresponds to the set of strings accepted by Python s float constructor except that s must not have leading or trailing whitespace The conversion is independent of the current locale If endptr is NULL convert the whole string Raise ValueError and return 1 0 if the string is not a valid representation of a floating point number If endptr is not NULL convert as much of the string as possible and set endptr to point to the first unconverted character If no initial segment of the string is the valid representation of a floating point number set endptr to point to the beginning of the string raise ValueError and return 1 0 If s represents a value that is too large to store in a float for example 1e500 is such a string on many platforms then if overflow_exception is NULL return Py_HUGE_VAL with an appropriate sign and don t set any exception Otherwise overflow_exception must point to a Python exception object raise that exception and return 1 0 In both cases set endptr to point to the first character after the converted value If any other error occurs during the conversion for example an out of memory,en
2444, error set the appropriate Python exception and return 1 0 New in version 3 1 char PyOS_double_to_string double val char format_code int precision int flags int ptype Part of the Stable ABI Convert a double val to a string using supplied format_code precision and flags format_code must be one of e E f F g G or r For r the supplied precision must be 0 and is ignored The r format code specifies the standard repr format flags can be zero or more of the values Py_DTSF_SIGN Py_DTSF_ADD_DOT_0 or Py_DTSF_ALT or ed together Py_DTSF_SIGN means to always precede the returned string with a sign character even if val is non negative Py_DTSF_ADD_DOT_0 means to ensure that the returned string will not look like an integer Py_DTSF_ALT means to apply alternate formatting rules See the documentation for the PyOS_snprintf specifier for details If ptype is non NULL then the value it points to will be set to one of Py_DTST_FINITE Py_DTST_INFINITE or Py_DTST_NAN signifying that val is a finite number an infinite number or not a number respectively The return value is a pointer to buffer with the converted string or NULL if the conversion failed The caller is responsible for freeing the returned string by calling PyMem_Free New in version 3 1 int PyOS_stricmp const char s1 const char s2 Case insensitive comparison of strings The function works almost identically to strcmp except that it ignores the case int PyOS_strnicmp const char s1 const char s2 Py_ssize_t size Case insensitive comparison of strings The function works almost identically to strncmp except that it ignores the case,en
2445,Descriptor Guide Author Raymond Hettinger Contact python at rcn dot com Contents Descriptor Guide Primer Simple example A descriptor that returns a constant Dynamic lookups Managed attributes Customized names Closing thoughts Complete Practical Example Validator class Custom validators Practical application Technical Tutorial Abstract Definition and introduction Descriptor protocol Overview of descriptor invocation Invocation from an instance Invocation from a class Invocation from super Summary of invocation logic Automatic name notification ORM example Pure Python Equivalents Properties Functions and methods Kinds of methods Static methods Class methods Member objects and __slots__ Descriptors let objects customize attribute lookup storage and deletion This guide has four major sections 1 The primer gives a basic overview moving gently from simple examples adding one feature at a time Start here if you re new to descriptors 2 The second section shows a complete practical descriptor example If you already know the basics start there 3 The third section provides a more technical tutorial that goes into the detailed mechanics of how descriptors work Most people don t need this level of detail 4 The last section has pure Python equivalents for built in descriptors that are written in C Read this if you re curious about how functions turn into bound methods or about the implementation of common tools like classmethod staticmethod property and __slots__ Primer In this primer we start with the most basic possible example and then we ll add new capabilities one by one Simple example A descriptor that returns a constant The Ten class is a descriptor whose __get__ method always returns the constant 10 class Ten def __get__ self obj objtype None return 10 To use the descriptor it must be stored as a class variable in another class class A x 5 Regular class attribute y Ten Descriptor instance An interactive session shows the difference between normal attribute lookup and descriptor lookup a A Make an instance of class A a x Normal attribute lookup 5 a y Descriptor lookup 10 In the a x attribute lookup the dot operator finds x 5 in the class dictionary In the a y lookup the dot operator finds a descriptor instance recognized by its __get__ method Calling that method returns 10 Note that the value 10 is not stored in either the class dictionary or the instance dictionary Instead the value 10 is computed on demand This example shows how a simple descriptor works but it isn t very useful For retrieving constants normal attribute lookup would be better In the next section we ll create something more useful a dynamic lookup Dynamic lookups Interesting descriptors typically run computations instead of returning constants import os class DirectorySize def __get__ self obj objtype None return len os listdir obj dirname class Directory size DirectorySize Descriptor instance def __init__ self dirname self dirname dirname Regular instance attribute An interactive session shows that the lookup is dynamic it computes different updated answers each time s Directory songs g Directory games s size The songs directory has twenty files 20 g size The games directory has three files 3 os remove games chess Delete a game g size File count is automatically updated 2 Besides showing how descriptors can run computations this example also reveals the purpose of the parameters to __get__ The self parameter is size an instance of DirectorySize The obj parameter is either g or s an instance of Directory It is the obj parameter that lets the __get__ method learn the target directory The objtype parameter is the class Directory Managed attributes A popular use for descriptors is managing access to instance data The descriptor is assigned to a public attribute in the class dictionary while the actual data is stored as a private attribute in the instance dictionary The descriptor s __get__ and __set__ methods are triggered when the public attribute is accessed In the following example age is the public attribute and _age is the private attribute When the public a,en
2446,ttribute is accessed the descriptor logs the lookup or update import logging logging basicConfig level logging INFO class LoggedAgeAccess def __get__ self obj objtype None value obj _age logging info Accessing r giving r age value return value def __set__ self obj value logging info Updating r to r age value obj _age value class Person age LoggedAgeAccess Descriptor instance def __init__ self name age self name name Regular instance attribute self age age Calls __set__ def birthday self self age 1 Calls both __get__ and __set__ An interactive session shows that all access to the managed attribute age is logged but that the regular attribute name is not logged mary Person Mary M 30 The initial age update is logged INFO root Updating age to 30 dave Person David D 40 INFO root Updating age to 40 vars mary The actual data is in a private attribute name Mary M _age 30 vars dave name David D _age 40 mary age Access the data and log the lookup INFO root Accessing age giving 30 30 mary birthday Updates are logged as well INFO root Accessing age giving 30 INFO root Updating age to 31 dave name Regular attribute lookup isn t logged David D dave age Only the managed attribute is logged INFO root Accessing age giving 40 40 One major issue with this example is that the private name _age is hardwired in the LoggedAgeAccess class That means that each instance can only have one logged attribute and that its name is unchangeable In the next example we ll fix that problem Customized names When a class uses descriptors it can inform each descriptor about which variable name was used In this example the Person class has two descriptor instances name and age When the Person class is defined it makes a callback to __set_name__ in LoggedAccess so that the field names can be recorded giving each descriptor its own public_name and private_name import logging logging basicConfig level logging INFO class LoggedAccess def __set_name__ self owner name self public_name name self private_name _ name def __get__ self obj objtype None value getattr obj self private_name logging info Accessing r giving r self public_name value return value def __set__ self obj value logging info Updating r to r self public_name value setattr obj self private_name value class Person name LoggedAccess First descriptor instance age LoggedAccess Second descriptor instance def __init__ self name age self name name Calls the first descriptor self age age Calls the second descriptor def birthday self self age 1 An interactive session shows that the Person class has called __set_name__ so that the field names would be recorded Here we call vars to look up the descriptor without triggering it vars vars Person name public_name name private_name _name vars vars Person age public_name age private_name _age The new class now logs access to both name and age pete Person Peter P 10 INFO root Updating name to Peter P INFO root Updating age to 10 kate Person Catherine C 20 INFO root Updating name to Catherine C INFO root Updating age to 20 The two Person instances contain only the private names vars pete _name Peter P _age 10 vars kate _name Catherine C _age 20 Closing thoughts A descriptor is what we call any object that defines __get__ __set__ or __delete__ Optionally descriptors can have a __set_name__ method This is only used in cases where a descriptor needs to know either the class where it was created or the name of class variable it was assigned to This method if present is called even if the class is not a descriptor Descriptors get invoked by the dot operator during attribute lookup If a descriptor is accessed indirectly with vars some_class descriptor_name the descriptor instance is returned without invoking it Descriptors only work when used as class variables When put in instances they have no effect The main motivation for descriptors is to provide a hook allowing objects stored in class variables to control what happens during attribute lookup Traditionally the calling class controls what happens during lookup Descriptors invert that relationship and allow the data being l,en
2447,ooked up to have a say in the matter Descriptors are used throughout the language It is how functions turn into bound methods Common tools like classmethod staticmethod property and functools cached_property are all implemented as descriptors Complete Practical Example In this example we create a practical and powerful tool for locating notoriously hard to find data corruption bugs Validator class A validator is a descriptor for managed attribute access Prior to storing any data it verifies that the new value meets various type and range restrictions If those restrictions aren t met it raises an exception to prevent data corruption at its source This Validator class is both an abstract base class and a managed attribute descriptor from abc import ABC abstractmethod class Validator ABC def __set_name__ self owner name self private_name _ name def __get__ self obj objtype None return getattr obj self private_name def __set__ self obj value self validate value setattr obj self private_name value abstractmethod def validate self value pass Custom validators need to inherit from Validator and must supply a validate method to test various restrictions as needed Custom validators Here are three practical data validation utilities 1 OneOf verifies that a value is one of a restricted set of options 2 Number verifies that a value is either an int or float Optionally it verifies that a value is between a given minimum or maximum 3 String verifies that a value is a str Optionally it validates a given minimum or maximum length It can validate a user defined predicate as well class OneOf Validator def __init__ self options self options set options def validate self value if value not in self options raise ValueError f Expected value r to be one of self options r class Number Validator def __init__ self minvalue None maxvalue None self minvalue minvalue self maxvalue maxvalue def validate self value if not isinstance value int float raise TypeError f Expected value r to be an int or float if self minvalue is not None and value self minvalue raise ValueError f Expected value r to be at least self minvalue r if self maxvalue is not None and value self maxvalue raise ValueError f Expected value r to be no more than self maxvalue r class String Validator def __init__ self minsize None maxsize None predicate None self minsize minsize self maxsize maxsize self predicate predicate def validate self value if not isinstance value str raise TypeError f Expected value r to be an str if self minsize is not None and len value self minsize raise ValueError f Expected value r to be no smaller than self minsize r if self maxsize is not None and len value self maxsize raise ValueError f Expected value r to be no bigger than self maxsize r if self predicate is not None and not self predicate value raise ValueError f Expected self predicate to be true for value r Practical application Here s how the data validators can be used in a real class class Component name String minsize 3 maxsize 10 predicate str isupper kind OneOf wood metal plastic quantity Number minvalue 0 def __init__ self name kind quantity self name name self kind kind self quantity quantity The descriptors prevent invalid instances from being created Component Widget metal 5 Blocked Widget is not all uppercase Traceback most recent call last ValueError Expected method isupper of str objects to be true for Widget Component WIDGET metle 5 Blocked metle is misspelled Traceback most recent call last ValueError Expected metle to be one of metal plastic wood Component WIDGET metal 5 Blocked 5 is negative Traceback most recent call last ValueError Expected 5 to be at least 0 Component WIDGET metal V Blocked V isn t a number Traceback most recent call last TypeError Expected V to be an int or float c Component WIDGET metal 5 Allowed The inputs are valid Technical Tutorial What follows is a more technical tutorial for the mechanics and details of how descriptors work Abstract Defines descriptors summarizes the protocol and shows how descriptors are called Provides an example showing how object rel,en
2448,ational mappings work Learning about descriptors not only provides access to a larger toolset it creates a deeper understanding of how Python works Definition and introduction In general a descriptor is an attribute value that has one of the methods in the descriptor protocol Those methods are __get__ __set__ and __delete__ If any of those methods are defined for an attribute it is said to be a descriptor The default behavior for attribute access is to get set or delete the attribute from an object s dictionary For instance a x has a lookup chain starting with a __dict__ x then type a __dict__ x and continuing through the method resolution order of type a If the looked up value is an object defining one of the descriptor methods then Python may override the default behavior and invoke the descriptor method instead Where this occurs in the precedence chain depends on which descriptor methods were defined Descriptors are a powerful general purpose protocol They are the mechanism behind properties methods static methods class methods and super They are used throughout Python itself Descriptors simplify the underlying C code and offer a flexible set of new tools for everyday Python programs Descriptor protocol descr __get__ self obj type None descr __set__ self obj value descr __delete__ self obj That is all there is to it Define any of these methods and an object is considered a descriptor and can override default behavior upon being looked up as an attribute If an object defines __set__ or __delete__ it is considered a data descriptor Descriptors that only define __get__ are called non data descriptors they are often used for methods but other uses are possible Data and non data descriptors differ in how overrides are calculated with respect to entries in an instance s dictionary If an instance s dictionary has an entry with the same name as a data descriptor the data descriptor takes precedence If an instance s dictionary has an entry with the same name as a non data descriptor the dictionary entry takes precedence To make a read only data descriptor define both __get__ and __set__ with the __set__ raising an AttributeError when called Defining the __set__ method with an exception raising placeholder is enough to make it a data descriptor Overview of descriptor invocation A descriptor can be called directly with desc __get__ obj or desc __get__ None cls But it is more common for a descriptor to be invoked automatically from attribute access The expression obj x looks up the attribute x in the chain of namespaces for obj If the search finds a descriptor outside of the instance __dict__ its __get__ method is invoked according to the precedence rules listed below The details of invocation depend on whether obj is an object class or instance of super Invocation from an instance Instance lookup scans through a chain of namespaces giving data descriptors the highest priority followed by instance variables then non data descriptors then class variables and lastly __getattr__ if it is provided If a descriptor is found for a x then it is invoked with desc __get__ a type a The logic for a dotted lookup is in object __getattribute__ Here is a pure Python equivalent def find_name_in_mro cls name default Emulate _PyType_Lookup in Objects typeobject c for base in cls __mro__ if name in vars base return vars base name return default def object_getattribute obj name Emulate PyObject_GenericGetAttr in Objects object c null object objtype type obj cls_var find_name_in_mro objtype name null descr_get getattr type cls_var __get__ null if descr_get is not null if hasattr type cls_var __set__ or hasattr type cls_var __delete__ return descr_get cls_var obj objtype data descriptor if hasattr obj __dict__ and name in vars obj return vars obj name instance variable if descr_get is not null return descr_get cls_var obj objtype non data descriptor if cls_var is not null return cls_var class variable raise AttributeError name Note there is no __getattr__ hook in the __getattribute__ code That is why calling __getattribute__ directly or with super __g,en
2449,etattribute__ will bypass __getattr__ entirely Instead it is the dot operator and the getattr function that are responsible for invoking __getattr__ whenever __getattribute__ raises an AttributeError Their logic is encapsulated in a helper function def getattr_hook obj name Emulate slot_tp_getattr_hook in Objects typeobject c try return obj __getattribute__ name except AttributeError if not hasattr type obj __getattr__ raise return type obj __getattr__ obj name __getattr__ Invocation from a class The logic for a dotted lookup such as A x is in type __getattribute__ The steps are similar to those for object __getattribute__ but the instance dictionary lookup is replaced by a search through the class s method resolution order If a descriptor is found it is invoked with desc __get__ None A The full C implementation can be found in type_getattro and _PyType_Lookup in Objects typeobject c Invocation from super The logic for super s dotted lookup is in the __getattribute__ method for object returned by super A dotted lookup such as super A obj m searches obj __class__ __mro__ for the base class B immediately following A and then returns B __dict__ m __get__ obj A If not a descriptor m is returned unchanged The full C implementation can be found in super_getattro in Objects typeobject c A pure Python equivalent can be found in Guido s Tutorial Summary of invocation logic The mechanism for descriptors is embedded in the __getattribute__ methods for object type and super The important points to remember are Descriptors are invoked by the __getattribute__ method Classes inherit this machinery from object type or super Overriding __getattribute__ prevents automatic descriptor calls because all the descriptor logic is in that method object __getattribute__ and type __getattribute__ make different calls to __get__ The first includes the instance and may include the class The second puts in None for the instance and always includes the class Data descriptors always override instance dictionaries Non data descriptors may be overridden by instance dictionaries Automatic name notification Sometimes it is desirable for a descriptor to know what class variable name it was assigned to When a new class is created the type metaclass scans the dictionary of the new class If any of the entries are descriptors and if they define __set_name__ that method is called with two arguments The owner is the class where the descriptor is used and the name is the class variable the descriptor was assigned to The implementation details are in type_new and set_names in Objects typeobject c Since the update logic is in type __new__ notifications only take place at the time of class creation If descriptors are added to the class afterwards __set_name__ will need to be called manually ORM example The following code is a simplified skeleton showing how data descriptors could be used to implement an object relational mapping The essential idea is that the data is stored in an external database The Python instances only hold keys to the database s tables Descriptors take care of lookups or updates class Field def __set_name__ self owner name self fetch f SELECT name FROM owner table WHERE owner key self store f UPDATE owner table SET name WHERE owner key def __get__ self obj objtype None return conn execute self fetch obj key fetchone 0 def __set__ self obj value conn execute self store value obj key conn commit We can use the Field class to define models that describe the schema for each table in a database class Movie table Movies Table name key title Primary key director Field year Field def __init__ self key self key key class Song table Music key title artist Field year Field genre Field def __init__ self key self key key To use the models first connect to the database import sqlite3 conn sqlite3 connect entertainment db An interactive session shows how data is retrieved from the database and how it can be updated Movie Star Wars director George Lucas jaws Movie Jaws f Released in jaws year by jaws director Released in 1975 by Steven Spielberg Song Country Ro,en
2450,ads artist John Denver Movie Star Wars director J J Abrams Movie Star Wars director J J Abrams Pure Python Equivalents The descriptor protocol is simple and offers exciting possibilities Several use cases are so common that they have been prepackaged into built in tools Properties bound methods static methods class methods and __slots__ are all based on the descriptor protocol Properties Calling property is a succinct way of building a data descriptor that triggers a function call upon access to an attribute Its signature is property fget None fset None fdel None doc None property The documentation shows a typical use to define a managed attribute x class C def getx self return self __x def setx self value self __x value def delx self del self __x x property getx setx delx I m the x property To see how property is implemented in terms of the descriptor protocol here is a pure Python equivalent class Property Emulate PyProperty_Type in Objects descrobject c def __init__ self fget None fset None fdel None doc None self fget fget self fset fset self fdel fdel if doc is None and fget is not None doc fget __doc__ self __doc__ doc self _name def __set_name__ self owner name self _name name def __get__ self obj objtype None if obj is None return self if self fget is None raise AttributeError f property self _name r of type obj __name__ r object has no getter return self fget obj def __set__ self obj value if self fset is None raise AttributeError f property self _name r of type obj __name__ r object has no setter self fset obj value def __delete__ self obj if self fdel is None raise AttributeError f property self _name r of type obj __name__ r object has no deleter self fdel obj def getter self fget prop type self fget self fset self fdel self __doc__ prop _name self _name return prop def setter self fset prop type self self fget fset self fdel self __doc__ prop _name self _name return prop def deleter self fdel prop type self self fget self fset fdel self __doc__ prop _name self _name return prop The property builtin helps whenever a user interface has granted attribute access and then subsequent changes require the intervention of a method For instance a spreadsheet class may grant access to a cell value through Cell b10 value Subsequent improvements to the program require the cell to be recalculated on every access however the programmer does not want to affect existing client code accessing the attribute directly The solution is to wrap access to the value attribute in a property data descriptor class Cell property def value self Recalculate the cell before returning value self recalc return self _value Either the built in property or our Property equivalent would work in this example Functions and methods Python s object oriented features are built upon a function based environment Using non data descriptors the two are merged seamlessly Functions stored in class dictionaries get turned into methods when invoked Methods only differ from regular functions in that the object instance is prepended to the other arguments By convention the instance is called self but could be called this or any other variable name Methods can be created manually with types MethodType which is roughly equivalent to class MethodType Emulate PyMethod_Type in Objects classobject c def __init__ self func obj self __func__ func self __self__ obj def __call__ self args kwargs func self __func__ obj self __self__ return func obj args kwargs To support automatic creation of methods functions include the __get__ method for binding methods during attribute access This means that functions are non data descriptors that return bound methods during dotted lookup from an instance Here s how it works class Function def __get__ self obj objtype None Simulate func_descr_get in Objects funcobject c if obj is None return self return MethodType self obj Running the following class in the interpreter shows how the function descriptor works in practice class D def f self x return x The function has a qualified name attribute to support introspection D f __qualname__ ,en
2451,D f Accessing the function through the class dictionary does not invoke __get__ Instead it just returns the underlying function object D __dict__ f function D f at 0x00C45070 Dotted access from a class calls __get__ which just returns the underlying function unchanged D f function D f at 0x00C45070 The interesting behavior occurs during dotted access from an instance The dotted lookup calls __get__ which returns a bound method object d D d f bound method D f of __main__ D object at 0x00B18C90 Internally the bound method stores the underlying function and the bound instance d f __func__ function D f at 0x00C45070 d f __self__ __main__ D object at 0x00B18C90 If you have ever wondered where self comes from in regular methods or where cls comes from in class methods this is it Kinds of methods Non data descriptors provide a simple mechanism for variations on the usual patterns of binding functions into methods To recap functions have a __get__ method so that they can be converted to a method when accessed as attributes The non data descriptor transforms an obj f args call into f obj args Calling cls f args becomes f args This chart summarizes the binding and its two most useful variants Transformation Called from an object Called from a class function f obj args f args staticmethod f args f args classmethod f type obj args f cls args Static methods Static methods return the underlying function without changes Calling either c f or C f is the equivalent of a direct lookup into object __getattribute__ c f or object __getattribute__ C f As a result the function becomes identically accessible from either an object or a class Good candidates for static methods are methods that do not reference the self variable For instance a statistics package may include a container class for experimental data The class provides normal methods for computing the average mean median and other descriptive statistics that depend on the data However there may be useful functions which are conceptually related but do not depend on the data For instance erf x is handy conversion routine that comes up in statistical work but does not directly depend on a particular dataset It can be called either from an object or the class s erf 1 5 9332 or Sample erf 1 5 9332 Since static methods return the underlying function with no changes the example calls are unexciting class E staticmethod def f x return x 10 E f 3 30 E f 3 30 Using the non data descriptor protocol a pure Python version of staticmethod would look like this import functools class StaticMethod Emulate PyStaticMethod_Type in Objects funcobject c def __init__ self f self f f functools update_wrapper self f def __get__ self obj objtype None return self f def __call__ self args kwds return self f args kwds The functools update_wrapper call adds a __wrapped__ attribute that refers to the underlying function Also it carries forward the attributes necessary to make the wrapper look like the wrapped function __name__ __qualname__ __doc__ and __annotations__ Class methods Unlike static methods class methods prepend the class reference to the argument list before calling the function This format is the same for whether the caller is an object or a class class F classmethod def f cls x return cls __name__ x F f 3 F 3 F f 3 F 3 This behavior is useful whenever the method only needs to have a class reference and does not rely on data stored in a specific instance One use for class methods is to create alternate class constructors For example the classmethod dict fromkeys creates a new dictionary from a list of keys The pure Python equivalent is class Dict dict classmethod def fromkeys cls iterable value None Emulate dict_fromkeys in Objects dictobject c d cls for key in iterable d key value return d Now a new dictionary of unique keys can be constructed like this d Dict fromkeys abracadabra type d is Dict True d a None b None r None c None d None Using the non data descriptor protocol a pure Python version of classmethod would look like this import functools class ClassMethod Emulate PyClassMethod_Type in Obj,en
2452,ects funcobject c def __init__ self f self f f functools update_wrapper self f def __get__ self obj cls None if cls is None cls type obj if hasattr type self f __get__ This code path was added in Python 3 9 and was deprecated in Python 3 11 return self f __get__ cls cls return MethodType self f cls The code path for hasattr type self f __get__ was added in Python 3 9 and makes it possible for classmethod to support chained decorators For example a classmethod and property could be chained together In Python 3 11 this functionality was deprecated class G classmethod property def __doc__ cls return f A doc for cls __name__ r G __doc__ A doc for G The functools update_wrapper call in ClassMethod adds a __wrapped__ attribute that refers to the underlying function Also it carries forward the attributes necessary to make the wrapper look like the wrapped function __name__ __qualname__ __doc__ and __annotations__ Member objects and __slots__ When a class defines __slots__ it replaces instance dictionaries with a fixed length array of slot values From a user point of view that has several effects 1 Provides immediate detection of bugs due to misspelled attribute assignments Only attribute names specified in __slots__ are allowed class Vehicle __slots__ id_number make model auto Vehicle auto id_nubmer VYE483814LQEX Traceback most recent call last AttributeError Vehicle object has no attribute id_nubmer 2 Helps create immutable objects where descriptors manage access to private attributes stored in __slots__ class Immutable __slots__ _dept _name Replace the instance dictionary def __init__ self dept name self _dept dept Store to private attribute self _name name Store to private attribute property Read only descriptor def dept self return self _dept property def name self Read only descriptor return self _name mark Immutable Botany Mark Watney mark dept Botany mark dept Space Pirate Traceback most recent call last AttributeError property dept of Immutable object has no setter mark location Mars Traceback most recent call last AttributeError Immutable object has no attribute location 3 Saves memory On a 64 bit Linux build an instance with two attributes takes 48 bytes with __slots__ and 152 bytes without This flyweight design pattern likely only matters when a large number of instances are going to be created 4 Improves speed Reading instance variables is 35 faster with __slots__ as measured with Python 3 10 on an Apple M1 processor 5 Blocks tools like functools cached_property which require an instance dictionary to function correctly from functools import cached_property class CP __slots__ Eliminates the instance dict cached_property Requires an instance dict def pi self return 4 sum 1 0 n 2 0 n 1 0 for n in reversed range 100_000 CP pi Traceback most recent call last TypeError No __dict__ attribute on CP instance to cache pi property It is not possible to create an exact drop in pure Python version of __slots__ because it requires direct access to C structures and control over object memory allocation However we can build a mostly faithful simulation where the actual C structure for slots is emulated by a private _slotvalues list Reads and writes to that private structure are managed by member descriptors null object class Member def __init__ self name clsname offset Emulate PyMemberDef in Include structmember h Also see descr_new in Objects descrobject c self name name self clsname clsname self offset offset def __get__ self obj objtype None Emulate member_get in Objects descrobject c Also see PyMember_GetOne in Python structmember c if obj is None return self value obj _slotvalues self offset if value is null raise AttributeError self name return value def __set__ self obj value Emulate member_set in Objects descrobject c obj _slotvalues self offset value def __delete__ self obj Emulate member_delete in Objects descrobject c value obj _slotvalues self offset if value is null raise AttributeError self name obj _slotvalues self offset null def __repr__ self Emulate member_repr in Objects descrobject c return f Member self name r,en
2453, of self clsname r The type __new__ method takes care of adding member objects to class variables class Type type Simulate how the type metaclass adds member objects for slots def __new__ mcls clsname bases mapping kwargs Emulate type_new in Objects typeobject c type_new calls PyTypeReady which calls add_methods slot_names mapping get slot_names for offset name in enumerate slot_names mapping name Member name clsname offset return type __new__ mcls clsname bases mapping kwargs The object __new__ method takes care of creating instances that have slots instead of an instance dictionary Here is a rough simulation in pure Python class Object Simulate how object __new__ allocates memory for __slots__ def __new__ cls args kwargs Emulate object_new in Objects typeobject c inst super __new__ cls if hasattr cls slot_names empty_slots null len cls slot_names object __setattr__ inst _slotvalues empty_slots return inst def __setattr__ self name value Emulate _PyObject_GenericSetAttrWithDict Objects object c cls type self if hasattr cls slot_names and name not in cls slot_names raise AttributeError f cls __name__ r object has no attribute name r super __setattr__ name value def __delattr__ self name Emulate _PyObject_GenericSetAttrWithDict Objects object c cls type self if hasattr cls slot_names and name not in cls slot_names raise AttributeError f cls __name__ r object has no attribute name r super __delattr__ name To use the simulation in a real class just inherit from Object and set the metaclass to Type class H Object metaclass Type Instance variables stored in slots slot_names x y def __init__ self x y self x x self y y At this point the metaclass has loaded member objects for x and y from pprint import pp pp dict vars H __module__ __main__ __doc__ Instance variables stored in slots slot_names x y __init__ function H __init__ at 0x7fb5d302f9d0 x Member x of H y Member y of H When instances are created they have a slot_values list where the attributes are stored h H 10 20 vars h _slotvalues 10 20 h x 55 vars h _slotvalues 55 20 Misspelled or unassigned attributes will raise an exception h xz Traceback most recent call last AttributeError H object has no attribute xz,en
2454,Python C API Reference Manual This manual documents the API used by C and C programmers who want to write extension modules or embed Python It is a companion to Extending and Embedding the Python Interpreter which describes the general principles of extension writing but does not document the API functions in detail Introduction Coding standards Include Files Useful macros Objects Types and Reference Counts Exceptions Embedding Python Debugging Builds C API Stability Unstable C API Stable Application Binary Interface Platform Considerations Contents of Limited API The Very High Level Layer Reference Counting Exception Handling Printing and clearing Raising exceptions Issuing warnings Querying the error indicator Signal Handling Exception Classes Exception Objects Unicode Exception Objects Recursion Control Standard Exceptions Standard Warning Categories Utilities Operating System Utilities System Functions Process Control Importing Modules Data marshalling support Parsing arguments and building values String conversion and formatting PyHash API Reflection Codec registry and support functions Support for Perf Maps Abstract Objects Layer Object Protocol Call Protocol Number Protocol Sequence Protocol Mapping Protocol Iterator Protocol Buffer Protocol Old Buffer Protocol Concrete Objects Layer Fundamental Objects Numeric Objects Sequence Objects Container Objects Function Objects Other Objects Initialization Finalization and Threads Before Python Initialization Global configuration variables Initializing and finalizing the interpreter Process wide parameters Thread State and the Global Interpreter Lock Sub interpreter support Asynchronous Notifications Profiling and Tracing Advanced Debugger Support Thread Local Storage Support Python Initialization Configuration Example PyWideStringList PyStatus PyPreConfig Preinitialize Python with PyPreConfig PyConfig Initialization with PyConfig Isolated Configuration Python Configuration Python Path Configuration Py_RunMain Py_GetArgcArgv Multi Phase Initialization Private Provisional API Memory Management Overview Allocator Domains Raw Memory Interface Memory Interface Object allocators Default Memory Allocators Customize Memory Allocators Debug hooks on the Python memory allocators The pymalloc allocator tracemalloc C API Examples Object Implementation Support Allocating Objects on the Heap Common Object Structures Type Objects Number Object Structures Mapping Object Structures Sequence Object Structures Buffer Object Structures Async Object Structures Slot Type typedefs Examples Supporting Cyclic Garbage Collection API and ABI Versioning,en
2455,Built in Functions The Python interpreter has a number of functions and types built into it that are always available They are listed here in alphabetical order Built in Functions A abs aiter E enumerate L len list R range repr all anext any eval exec locals M reversed round ascii B bin F filter map max S set setattr bool breakpoint float format memoryview min slice sorted bytearray bytes frozenset G N next O staticmethod str C callable getattr globals object oct sum super T chr classmethod H hasattr open ord P tuple type V compile complex hash help pow print vars Z zip D delattr hex I id property _ __import__ dict dir input int divmod isinstance issubclass iter abs x Return the absolute value of a number The argument may be an integer a floating point number or an object implementing __abs__ If the argument is a complex number its magnitude is returned aiter async_iterable Return an asynchronous iterator for an asynchronous iterable Equivalent to calling x __aiter__ Note Unlike iter aiter has no 2 argument variant New in version 3 10 all iterable Return True if all elements of the iterable are true or if the iterable is empty Equivalent to def all iterable for element in iterable if not element return False return True awaitable anext async_iterator awaitable anext async_iterator default When awaited return the next item from the given asynchronous iterator or default if given and the iterator is exhausted This is the async variant of the next builtin and behaves similarly This calls the __anext__ method of async_iterator returning an awaitable Awaiting this returns the next value of the iterator If default is given it is returned if the iterator is exhausted otherwise StopAsyncIteration is raised New in version 3 10 any iterable Return True if any element of the iterable is true If the iterable is empty return False Equivalent to def any iterable for element in iterable if element return True return False ascii object As repr return a string containing a printable representation of an object but escape the non ASCII characters in the string returned by repr using x u or U escapes This generates a string similar to that returned by repr in Python 2 bin x Convert an integer number to a binary string prefixed with 0b The result is a valid Python expression If x is not a Python int object it has to define an __index__ method that returns an integer Some examples bin 3 0b11 bin 10 0b1010 If the prefix 0b is desired or not you can use either of the following ways format 14 b format 14 b 0b1110 1110 f 14 b f 14 b 0b1110 1110 See also format for more information class bool x False Return a Boolean value i e one of True or False x is converted using the standard truth testing procedure If x is false or omitted this returns False otherwise it returns True The bool class is a subclass of int see Numeric Types int float complex It cannot be subclassed further Its only instances are False and True see Boolean Type bool Changed in version 3 7 x is now a positional only parameter breakpoint args kws This function drops you into the debugger at the call site Specifically it calls sys breakpointhook passing args and kws straight through By default sys breakpointhook calls pdb set_trace expecting no arguments In this case it is purely a convenience function so you don t have to explicitly import pdb or type as much code to enter the debugger However sys breakpointhook can be set to some other function and breakpoint will automatically call that allowing you to drop into the debugger of choice If sys breakpointhook is not accessible this function will raise RuntimeError By default the behavior of breakpoint can be changed with the PYTHONBREAKPOINT environment variable See sys breakpointhook for usage details Note that this is not guaranteed if sys breakpointhook has been replaced Raises an auditing event builtins breakpoint with argument breakpointhook New in version 3 7 class bytearray source b class bytearray source encoding class bytearray source encoding errors Return a new array of bytes The bytearray class is a mutable sequence of ,en
2456,integers in the range 0 x 256 It has most of the usual methods of mutable sequences described in Mutable Sequence Types as well as most methods that the bytes type has see Bytes and Bytearray Operations The optional source parameter can be used to initialize the array in a few different ways If it is a string you must also give the encoding and optionally errors parameters bytearray then converts the string to bytes using str encode If it is an integer the array will have that size and will be initialized with null bytes If it is an object conforming to the buffer interface a read only buffer of the object will be used to initialize the bytes array If it is an iterable it must be an iterable of integers in the range 0 x 256 which are used as the initial contents of the array Without an argument an array of size 0 is created See also Binary Sequence Types bytes bytearray memoryview and Bytearray Objects class bytes source b class bytes source encoding class bytes source encoding errors Return a new bytes object which is an immutable sequence of integers in the range 0 x 256 bytes is an immutable version of bytearray it has the same non mutating methods and the same indexing and slicing behavior Accordingly constructor arguments are interpreted as for bytearray Bytes objects can also be created with literals see String and Bytes literals See also Binary Sequence Types bytes bytearray memoryview Bytes Objects and Bytes and Bytearray Operations callable object Return True if the object argument appears callable False if not If this returns True it is still possible that a call fails but if it is False calling object will never succeed Note that classes are callable calling a class returns a new instance instances are callable if their class has a __call__ method New in version 3 2 This function was first removed in Python 3 0 and then brought back in Python 3 2 chr i Return the string representing a character whose Unicode code point is the integer i For example chr 97 returns the string a while chr 8364 returns the string This is the inverse of ord The valid range for the argument is from 0 through 1 114 111 0x10FFFF in base 16 ValueError will be raised if i is outside that range classmethod Transform a method into a class method A class method receives the class as an implicit first argument just like an instance method receives the instance To declare a class method use this idiom class C classmethod def f cls arg1 arg2 The classmethod form is a function decorator see Function definitions for details A class method can be called either on the class such as C f or on an instance such as C f The instance is ignored except for its class If a class method is called for a derived class the derived class object is passed as the implied first argument Class methods are different than C or Java static methods If you want those see staticmethod in this section For more information on class methods see The standard type hierarchy Changed in version 3 9 Class methods can now wrap other descriptors such as property Changed in version 3 10 Class methods now inherit the method attributes __module__ __name__ __qualname__ __doc__ and __annotations__ and have a new __wrapped__ attribute Changed in version 3 11 Class methods can no longer wrap other descriptors such as property compile source filename mode flags 0 dont_inherit False optimize 1 Compile the source into a code or AST object Code objects can be executed by exec or eval source can either be a normal string a byte string or an AST object Refer to the ast module documentation for information on how to work with AST objects The filename argument should give the file from which the code was read pass some recognizable value if it wasn t read from a file string is commonly used The mode argument specifies what kind of code must be compiled it can be exec if source consists of a sequence of statements eval if it consists of a single expression or single if it consists of a single interactive statement in the latter case expression statements that evaluate to something other than None,en
2457, will be printed The optional arguments flags and dont_inherit control which compiler options should be activated and which future features should be allowed If neither is present or both are zero the code is compiled with the same flags that affect the code that is calling compile If the flags argument is given and dont_inherit is not or is zero then the compiler options and the future statements specified by the flags argument are used in addition to those that would be used anyway If dont_inherit is a non zero integer then the flags argument is it the flags future features and compiler options in the surrounding code are ignored Compiler options and future statements are specified by bits which can be bitwise ORed together to specify multiple options The bitfield required to specify a given future feature can be found as the compiler_flag attribute on the _Feature instance in the __future__ module Compiler flags can be found in ast module with PyCF_ prefix The argument optimize specifies the optimization level of the compiler the default value of 1 selects the optimization level of the interpreter as given by O options Explicit levels are 0 no optimization __debug__ is true 1 asserts are removed __debug__ is false or 2 docstrings are removed too This function raises SyntaxError if the compiled source is invalid and ValueError if the source contains null bytes If you want to parse Python code into its AST representation see ast parse Raises an auditing event compile with arguments source and filename This event may also be raised by implicit compilation Note When compiling a string with multi line code in single or eval mode input must be terminated by at least one newline character This is to facilitate detection of incomplete and complete statements in the code module Warning It is possible to crash the Python interpreter with a sufficiently large complex string when compiling to an AST object due to stack depth limitations in Python s AST compiler Changed in version 3 2 Allowed use of Windows and Mac newlines Also input in exec mode does not have to end in a newline anymore Added the optimize parameter Changed in version 3 5 Previously TypeError was raised when null bytes were encountered in source New in version 3 8 ast PyCF_ALLOW_TOP_LEVEL_AWAIT can now be passed in flags to enable support for top level await async for and async with class complex real 0 imag 0 class complex string Return a complex number with the value real imag 1j or convert a string or number to a complex number If the first parameter is a string it will be interpreted as a complex number and the function must be called without a second parameter The second parameter can never be a string Each argument may be any numeric type including complex If imag is omitted it defaults to zero and the constructor serves as a numeric conversion like int and float If both arguments are omitted returns 0j For a general Python object x complex x delegates to x __complex__ If __complex__ is not defined then it falls back to __float__ If __float__ is not defined then it falls back to __index__ Note When converting from a string the string must not contain whitespace around the central or operator For example complex 1 2j is fine but complex 1 2j raises ValueError The complex type is described in Numeric Types int float complex Changed in version 3 6 Grouping digits with underscores as in code literals is allowed Changed in version 3 8 Falls back to __index__ if __complex__ and __float__ are not defined delattr object name This is a relative of setattr The arguments are an object and a string The string must be the name of one of the object s attributes The function deletes the named attribute provided the object allows it For example delattr x foobar is equivalent to del x foobar name need not be a Python identifier see setattr class dict kwarg class dict mapping kwarg class dict iterable kwarg Create a new dictionary The dict object is the dictionary class See dict and Mapping Types dict for documentation about this class For other containers see the built in l,en
2458,ist set and tuple classes as well as the collections module dir dir object Without arguments return the list of names in the current local scope With an argument attempt to return a list of valid attributes for that object If the object has a method named __dir__ this method will be called and must return the list of attributes This allows objects that implement a custom __getattr__ or __getattribute__ function to customize the way dir reports their attributes If the object does not provide __dir__ the function tries its best to gather information from the object s __dict__ attribute if defined and from its type object The resulting list is not necessarily complete and may be inaccurate when the object has a custom __getattr__ The default dir mechanism behaves differently with different types of objects as it attempts to produce the most relevant rather than complete information If the object is a module object the list contains the names of the module s attributes If the object is a type or class object the list contains the names of its attributes and recursively of the attributes of its bases Otherwise the list contains the object s attributes names the names of its class s attributes and recursively of the attributes of its class s base classes The resulting list is sorted alphabetically For example import struct dir show the names in the module namespace __builtins__ __name__ struct dir struct show the names in the struct module Struct __all__ __builtins__ __cached__ __doc__ __file__ __initializing__ __loader__ __name__ __package__ _clearcache calcsize error pack pack_into unpack unpack_from class Shape def __dir__ self return area perimeter location s Shape dir s area location perimeter Note Because dir is supplied primarily as a convenience for use at an interactive prompt it tries to supply an interesting set of names more than it tries to supply a rigorously or consistently defined set of names and its detailed behavior may change across releases For example metaclass attributes are not in the result list when the argument is a class divmod a b Take two non complex numbers as arguments and return a pair of numbers consisting of their quotient and remainder when using integer division With mixed operand types the rules for binary arithmetic operators apply For integers the result is the same as a b a b For floating point numbers the result is q a b where q is usually math floor a b but may be 1 less than that In any case q b a b is very close to a if a b is non zero it has the same sign as b and 0 abs a b abs b enumerate iterable start 0 Return an enumerate object iterable must be a sequence an iterator or some other object which supports iteration The __next__ method of the iterator returned by enumerate returns a tuple containing a count from start which defaults to 0 and the values obtained from iterating over iterable seasons Spring Summer Fall Winter list enumerate seasons 0 Spring 1 Summer 2 Fall 3 Winter list enumerate seasons start 1 1 Spring 2 Summer 3 Fall 4 Winter Equivalent to def enumerate iterable start 0 n start for elem in iterable yield n elem n 1 eval expression globals None locals None The arguments are a string and optional globals and locals If provided globals must be a dictionary If provided locals can be any mapping object The expression argument is parsed and evaluated as a Python expression technically speaking a condition list using the globals and locals dictionaries as global and local namespace If the globals dictionary is present and does not contain a value for the key __builtins__ a reference to the dictionary of the built in module builtins is inserted under that key before expression is parsed That way you can control what builtins are available to the executed code by inserting your own __builtins__ dictionary into globals before passing it to eval If the locals dictionary is omitted it defaults to the globals dictionary If both dictionaries are omitted the expression is executed with the globals and locals in the environment where eval is called Note eval does not have access ,en
2459,to the nested scopes non locals in the enclosing environment The return value is the result of the evaluated expression Syntax errors are reported as exceptions Example x 1 eval x 1 2 This function can also be used to execute arbitrary code objects such as those created by compile In this case pass a code object instead of a string If the code object has been compiled with exec as the mode argument eval s return value will be None Hints dynamic execution of statements is supported by the exec function The globals and locals functions return the current global and local dictionary respectively which may be useful to pass around for use by eval or exec If the given source is a string then leading and trailing spaces and tabs are stripped See ast literal_eval for a function that can safely evaluate strings with expressions containing only literals Raises an auditing event exec with the code object as the argument Code compilation events may also be raised exec object globals None locals None closure None This function supports dynamic execution of Python code object must be either a string or a code object If it is a string the string is parsed as a suite of Python statements which is then executed unless a syntax error occurs 1 If it is a code object it is simply executed In all cases the code that s executed is expected to be valid as file input see the section File input in the Reference Manual Be aware that the nonlocal yield and return statements may not be used outside of function definitions even within the context of code passed to the exec function The return value is None In all cases if the optional parts are omitted the code is executed in the current scope If only globals is provided it must be a dictionary and not a subclass of dictionary which will be used for both the global and the local variables If globals and locals are given they are used for the global and local variables respectively If provided locals can be any mapping object Remember that at the module level globals and locals are the same dictionary If exec gets two separate objects as globals and locals the code will be executed as if it were embedded in a class definition If the globals dictionary does not contain a value for the key __builtins__ a reference to the dictionary of the built in module builtins is inserted under that key That way you can control what builtins are available to the executed code by inserting your own __builtins__ dictionary into globals before passing it to exec The closure argument specifies a closure a tuple of cellvars It s only valid when the object is a code object containing free variables The length of the tuple must exactly match the number of free variables referenced by the code object Raises an auditing event exec with the code object as the argument Code compilation events may also be raised Note The built in functions globals and locals return the current global and local dictionary respectively which may be useful to pass around for use as the second and third argument to exec Note The default locals act as described for function locals below modifications to the default locals dictionary should not be attempted Pass an explicit locals dictionary if you need to see effects of the code on locals after function exec returns Changed in version 3 11 Added the closure parameter filter function iterable Construct an iterator from those elements of iterable for which function is true iterable may be either a sequence a container which supports iteration or an iterator If function is None the identity function is assumed that is all elements of iterable that are false are removed Note that filter function iterable is equivalent to the generator expression item for item in iterable if function item if function is not None and item for item in iterable if item if function is None See itertools filterfalse for the complementary function that returns elements of iterable for which function is false class float x 0 0 Return a floating point number constructed from a number or string x If the argument is a string it s,en
2460,hould contain a decimal number optionally preceded by a sign and optionally embedded in whitespace The optional sign may be or a sign has no effect on the value produced The argument may also be a string representing a NaN not a number or positive or negative infinity More precisely the input must conform to the floatvalue production rule in the following grammar after leading and trailing whitespace characters are removed sign infinity Infinity inf nan nan digit a Unicode decimal digit i e characters in Unicode general category Nd digitpart digit _ digit number digitpart digitpart digitpart exponent e E digitpart floatnumber number exponent floatvalue sign floatnumber infinity nan Case is not significant so for example inf Inf INFINITY and iNfINity are all acceptable spellings for positive infinity Otherwise if the argument is an integer or a floating point number a floating point number with the same value within Python s floating point precision is returned If the argument is outside the range of a Python float an OverflowError will be raised For a general Python object x float x delegates to x __float__ If __float__ is not defined then it falls back to __index__ If no argument is given 0 0 is returned Examples float 1 23 1 23 float 12345 n 12345 0 float 1e 003 0 001 float 1E6 1000000 0 float Infinity inf The float type is described in Numeric Types int float complex Changed in version 3 6 Grouping digits with underscores as in code literals is allowed Changed in version 3 7 x is now a positional only parameter Changed in version 3 8 Falls back to __index__ if __float__ is not defined format value format_spec Convert a value to a formatted representation as controlled by format_spec The interpretation of format_spec will depend on the type of the value argument however there is a standard formatting syntax that is used by most built in types Format Specification Mini Language The default format_spec is an empty string which usually gives the same effect as calling str value A call to format value format_spec is translated to type value __format__ value format_spec which bypasses the instance dictionary when searching for the value s __format__ method A TypeError exception is raised if the method search reaches object and the format_spec is non empty or if either the format_spec or the return value are not strings Changed in version 3 4 object __format__ format_spec raises TypeError if format_spec is not an empty string class frozenset iterable set Return a new frozenset object optionally with elements taken from iterable frozenset is a built in class See frozenset and Set Types set frozenset for documentation about this class For other containers see the built in set list tuple and dict classes as well as the collections module getattr object name getattr object name default Return the value of the named attribute of object name must be a string If the string is the name of one of the object s attributes the result is the value of that attribute For example getattr x foobar is equivalent to x foobar If the named attribute does not exist default is returned if provided otherwise AttributeError is raised name need not be a Python identifier see setattr Note Since private name mangling happens at compilation time one must manually mangle a private attribute s attributes with two leading underscores name in order to retrieve it with getattr globals Return the dictionary implementing the current module namespace For code within functions this is set when the function is defined and remains the same regardless of where the function is called hasattr object name The arguments are an object and a string The result is True if the string is the name of one of the object s attributes False if not This is implemented by calling getattr object name and seeing whether it raises an AttributeError or not hash object Return the hash value of the object if it has one Hash values are integers They are used to quickly compare dictionary keys during a dictionary lookup Numeric values that compare equal have the same hash value even if the,en
2461,y are of different types as is the case for 1 and 1 0 Note For objects with custom __hash__ methods note that hash truncates the return value based on the bit width of the host machine help help request Invoke the built in help system This function is intended for interactive use If no argument is given the interactive help system starts on the interpreter console If the argument is a string then the string is looked up as the name of a module function class method keyword or documentation topic and a help page is printed on the console If the argument is any other kind of object a help page on the object is generated Note that if a slash appears in the parameter list of a function when invoking help it means that the parameters prior to the slash are positional only For more info see the FAQ entry on positional only parameters This function is added to the built in namespace by the site module Changed in version 3 4 Changes to pydoc and inspect mean that the reported signatures for callables are now more comprehensive and consistent hex x Convert an integer number to a lowercase hexadecimal string prefixed with 0x If x is not a Python int object it has to define an __index__ method that returns an integer Some examples hex 255 0xff hex 42 0x2a If you want to convert an integer number to an uppercase or lower hexadecimal string with prefix or not you can use either of the following ways x 255 x 255 X 255 0xff ff FF format 255 x format 255 x format 255 X 0xff ff FF f 255 x f 255 x f 255 X 0xff ff FF See also format for more information See also int for converting a hexadecimal string to an integer using a base of 16 Note To obtain a hexadecimal string representation for a float use the float hex method id object Return the identity of an object This is an integer which is guaranteed to be unique and constant for this object during its lifetime Two objects with non overlapping lifetimes may have the same id value CPython implementation detail This is the address of the object in memory Raises an auditing event builtins id with argument id input input prompt If the prompt argument is present it is written to standard output without a trailing newline The function then reads a line from input converts it to a string stripping a trailing newline and returns that When EOF is read EOFError is raised Example s input Monty Python s Flying Circus s Monty Python s Flying Circus If the readline module was loaded then input will use it to provide elaborate line editing and history features Raises an auditing event builtins input with argument prompt before reading input Raises an auditing event builtins input result with the result after successfully reading input class int x 0 class int x base 10 Return an integer object constructed from a number or string x or return 0 if no arguments are given If x defines __int__ int x returns x __int__ If x defines __index__ it returns x __index__ If x defines __trunc__ it returns x __trunc__ For floating point numbers this truncates towards zero If x is not a number or if base is given then x must be a string bytes or bytearray instance representing an integer in radix base Optionally the string can be preceded by or with no space in between have leading zeros be surrounded by whitespace and have single underscores interspersed between digits A base n integer string contains digits each representing a value from 0 to n 1 The values 0 9 can be represented by any Unicode decimal digit The values 10 35 can be represented by a to z or A to Z The default base is 10 The allowed bases are 0 and 2 36 Base 2 8 and 16 strings can be optionally prefixed with 0b 0B 0o 0O or 0x 0X as with integer literals in code For base 0 the string is interpreted in a similar way to an integer literal in code in that the actual base is 2 8 10 or 16 as determined by the prefix Base 0 also disallows leading zeros int 010 0 is not legal while int 010 and int 010 8 are The integer type is described in Numeric Types int float complex Changed in version 3 4 If base is not an instance of int and the base object has a base __ind,en
2462,ex__ method that method is called to obtain an integer for the base Previous versions used base __int__ instead of base __index__ Changed in version 3 6 Grouping digits with underscores as in code literals is allowed Changed in version 3 7 x is now a positional only parameter Changed in version 3 8 Falls back to __index__ if __int__ is not defined Changed in version 3 11 The delegation to __trunc__ is deprecated Changed in version 3 11 int string inputs and string representations can be limited to help avoid denial of service attacks A ValueError is raised when the limit is exceeded while converting a string x to an int or when converting an int into a string would exceed the limit See the integer string conversion length limitation documentation isinstance object classinfo Return True if the object argument is an instance of the classinfo argument or of a direct indirect or virtual subclass thereof If object is not an object of the given type the function always returns False If classinfo is a tuple of type objects or recursively other such tuples or a Union Type of multiple types return True if object is an instance of any of the types If classinfo is not a type or tuple of types and such tuples a TypeError exception is raised TypeError may not be raised for an invalid type if an earlier check succeeds Changed in version 3 10 classinfo can be a Union Type issubclass class classinfo Return True if class is a subclass direct indirect or virtual of classinfo A class is considered a subclass of itself classinfo may be a tuple of class objects or recursively other such tuples or a Union Type in which case return True if class is a subclass of any entry in classinfo In any other case a TypeError exception is raised Changed in version 3 10 classinfo can be a Union Type iter object iter object sentinel Return an iterator object The first argument is interpreted very differently depending on the presence of the second argument Without a second argument object must be a collection object which supports the iterable protocol the __iter__ method or it must support the sequence protocol the __getitem__ method with integer arguments starting at 0 If it does not support either of those protocols TypeError is raised If the second argument sentinel is given then object must be a callable object The iterator created in this case will call object with no arguments for each call to its __next__ method if the value returned is equal to sentinel StopIteration will be raised otherwise the value will be returned See also Iterator Types One useful application of the second form of iter is to build a block reader For example reading fixed width blocks from a binary database file until the end of file is reached from functools import partial with open mydata db rb as f for block in iter partial f read 64 b process_block block len s Return the length the number of items of an object The argument may be a sequence such as a string bytes tuple list or range or a collection such as a dictionary set or frozen set CPython implementation detail len raises OverflowError on lengths larger than sys maxsize such as range 2 100 class list class list iterable Rather than being a function list is actually a mutable sequence type as documented in Lists and Sequence Types list tuple range locals Update and return a dictionary representing the current local symbol table Free variables are returned by locals when it is called in function blocks but not in class blocks Note that at the module level locals and globals are the same dictionary Note The contents of this dictionary should not be modified changes may not affect the values of local and free variables used by the interpreter map function iterable iterables Return an iterator that applies function to every item of iterable yielding the results If additional iterables arguments are passed function must take that many arguments and is applied to the items from all iterables in parallel With multiple iterables the iterator stops when the shortest iterable is exhausted For cases where the function inputs are a,en
2463,lready arranged into argument tuples see itertools starmap max iterable key None max iterable default key None max arg1 arg2 args key None Return the largest item in an iterable or the largest of two or more arguments If one positional argument is provided it should be an iterable The largest item in the iterable is returned If two or more positional arguments are provided the largest of the positional arguments is returned There are two optional keyword only arguments The key argument specifies a one argument ordering function like that used for list sort The default argument specifies an object to return if the provided iterable is empty If the iterable is empty and default is not provided a ValueError is raised If multiple items are maximal the function returns the first one encountered This is consistent with other sort stability preserving tools such as sorted iterable key keyfunc reverse True 0 and heapq nlargest 1 iterable key keyfunc Changed in version 3 4 Added the default keyword only parameter Changed in version 3 8 The key can be None class memoryview object Return a memory view object created from the given argument See Memory Views for more information min iterable key None min iterable default key None min arg1 arg2 args key None Return the smallest item in an iterable or the smallest of two or more arguments If one positional argument is provided it should be an iterable The smallest item in the iterable is returned If two or more positional arguments are provided the smallest of the positional arguments is returned There are two optional keyword only arguments The key argument specifies a one argument ordering function like that used for list sort The default argument specifies an object to return if the provided iterable is empty If the iterable is empty and default is not provided a ValueError is raised If multiple items are minimal the function returns the first one encountered This is consistent with other sort stability preserving tools such as sorted iterable key keyfunc 0 and heapq nsmallest 1 iterable key keyfunc Changed in version 3 4 Added the default keyword only parameter Changed in version 3 8 The key can be None next iterator next iterator default Retrieve the next item from the iterator by calling its __next__ method If default is given it is returned if the iterator is exhausted otherwise StopIteration is raised class object Return a new featureless object object is a base for all classes It has methods that are common to all instances of Python classes This function does not accept any arguments Note object does not have a __dict__ so you can t assign arbitrary attributes to an instance of the object class oct x Convert an integer number to an octal string prefixed with 0o The result is a valid Python expression If x is not a Python int object it has to define an __index__ method that returns an integer For example oct 8 0o10 oct 56 0o70 If you want to convert an integer number to an octal string either with the prefix 0o or not you can use either of the following ways o 10 o 10 0o12 12 format 10 o format 10 o 0o12 12 f 10 o f 10 o 0o12 12 See also format for more information open file mode r buffering 1 encoding None errors None newline None closefd True opener None Open file and return a corresponding file object If the file cannot be opened an OSError is raised See Reading and Writing Files for more examples of how to use this function file is a path like object giving the pathname absolute or relative to the current working directory of the file to be opened or an integer file descriptor of the file to be wrapped If a file descriptor is given it is closed when the returned I O object is closed unless closefd is set to False mode is an optional string that specifies the mode in which the file is opened It defaults to r which means open for reading in text mode Other common values are w for writing truncating the file if it already exists x for exclusive creation and a for appending which on some Unix systems means that all writes append to the end of the file regardless of the current,en
2464, seek position In text mode if encoding is not specified the encoding used is platform dependent locale getencoding is called to get the current locale encoding For reading and writing raw bytes use binary mode and leave encoding unspecified The available modes are Character Meaning r open for reading default w open for writing truncating the file first x open for exclusive creation failing if the file already exists a open for writing appending to the end of file if it exists b binary mode t text mode default open for updating reading and writing The default mode is r open for reading text a synonym of rt Modes w and w b open and truncate the file Modes r and r b open the file with no truncation As mentioned in the Overview Python distinguishes between binary and text I O Files opened in binary mode including b in the mode argument return contents as bytes objects without any decoding In text mode the default or when t is included in the mode argument the contents of the file are returned as str the bytes having been first decoded using a platform dependent encoding or using the specified encoding if given Note Python doesn t depend on the underlying operating system s notion of text files all the processing is done by Python itself and is therefore platform independent buffering is an optional integer used to set the buffering policy Pass 0 to switch buffering off only allowed in binary mode 1 to select line buffering only usable when writing in text mode and an integer 1 to indicate the size in bytes of a fixed size chunk buffer Note that specifying a buffer size this way applies for binary buffered I O but TextIOWrapper i e files opened with mode r would have another buffering To disable buffering in TextIOWrapper consider using the write_through flag for io TextIOWrapper reconfigure When no buffering argument is given the default buffering policy works as follows Binary files are buffered in fixed size chunks the size of the buffer is chosen using a heuristic trying to determine the underlying device s block size and falling back on io DEFAULT_BUFFER_SIZE On many systems the buffer will typically be 4096 or 8192 bytes long Interactive text files files for which isatty returns True use line buffering Other text files use the policy described above for binary files encoding is the name of the encoding used to decode or encode the file This should only be used in text mode The default encoding is platform dependent whatever locale getencoding returns but any text encoding supported by Python can be used See the codecs module for the list of supported encodings errors is an optional string that specifies how encoding and decoding errors are to be handled this cannot be used in binary mode A variety of standard error handlers are available listed under Error Handlers though any error handling name that has been registered with codecs register_error is also valid The standard names include strict to raise a ValueError exception if there is an encoding error The default value of None has the same effect ignore ignores errors Note that ignoring encoding errors can lead to data loss replace causes a replacement marker such as to be inserted where there is malformed data surrogateescape will represent any incorrect bytes as low surrogate code units ranging from U DC80 to U DCFF These surrogate code units will then be turned back into the same bytes when the surrogateescape error handler is used when writing data This is useful for processing files in an unknown encoding xmlcharrefreplace is only supported when writing to a file Characters not supported by the encoding are replaced with the appropriate XML character reference nnn backslashreplace replaces malformed data by Python s backslashed escape sequences namereplace also only supported when writing replaces unsupported characters with N escape sequences newline determines how to parse newline characters from the stream It can be None n r and r n It works as follows When reading input from the stream if newline is None universal newlines mode is enabled Lines in the input,en
2465, can end in n r or r n and these are translated into n before being returned to the caller If it is universal newlines mode is enabled but line endings are returned to the caller untranslated If it has any of the other legal values input lines are only terminated by the given string and the line ending is returned to the caller untranslated When writing output to the stream if newline is None any n characters written are translated to the system default line separator os linesep If newline is or n no translation takes place If newline is any of the other legal values any n characters written are translated to the given string If closefd is False and a file descriptor rather than a filename was given the underlying file descriptor will be kept open when the file is closed If a filename is given closefd must be True the default otherwise an error will be raised A custom opener can be used by passing a callable as opener The underlying file descriptor for the file object is then obtained by calling opener with file flags opener must return an open file descriptor passing os open as opener results in functionality similar to passing None The newly created file is non inheritable The following example uses the dir_fd parameter of the os open function to open a file relative to a given directory import os dir_fd os open somedir os O_RDONLY def opener path flags return os open path flags dir_fd dir_fd with open spamspam txt w opener opener as f print This will be written to somedir spamspam txt file f os close dir_fd don t leak a file descriptor The type of file object returned by the open function depends on the mode When open is used to open a file in a text mode w r wt rt etc it returns a subclass of io TextIOBase specifically io TextIOWrapper When used to open a file in a binary mode with buffering the returned class is a subclass of io BufferedIOBase The exact class varies in read binary mode it returns an io BufferedReader in write binary and append binary modes it returns an io BufferedWriter and in read write mode it returns an io BufferedRandom When buffering is disabled the raw stream a subclass of io RawIOBase io FileIO is returned See also the file handling modules such as fileinput io where open is declared os os path tempfile and shutil Raises an auditing event open with arguments file mode flags The mode and flags arguments may have been modified or inferred from the original call Changed in version 3 3 The opener parameter was added The x mode was added IOError used to be raised it is now an alias of OSError FileExistsError is now raised if the file opened in exclusive creation mode x already exists Changed in version 3 4 The file is now non inheritable Changed in version 3 5 If the system call is interrupted and the signal handler does not raise an exception the function now retries the system call instead of raising an InterruptedError exception see PEP 475 for the rationale The namereplace error handler was added Changed in version 3 6 Support added to accept objects implementing os PathLike On Windows opening a console buffer may return a subclass of io RawIOBase other than io FileIO Changed in version 3 11 The U mode has been removed ord c Given a string representing one Unicode character return an integer representing the Unicode code point of that character For example ord a returns the integer 97 and ord Euro sign returns 8364 This is the inverse of chr pow base exp mod None Return base to the power exp if mod is present return base to the power exp modulo mod computed more efficiently than pow base exp mod The two argument form pow base exp is equivalent to using the power operator base exp The arguments must have numeric types With mixed operand types the coercion rules for binary arithmetic operators apply For int operands the result has the same type as the operands after coercion unless the second argument is negative in that case all arguments are converted to float and a float result is delivered For example pow 10 2 returns 100 but pow 10 2 returns 0 01 For a negative base of type int or float an,en
2466,d a non integral exponent a complex result is delivered For example pow 9 0 5 returns a value close to 3j For int operands base and exp if mod is present mod must also be of integer type and mod must be nonzero If mod is present and exp is negative base must be relatively prime to mod In that case pow inv_base exp mod is returned where inv_base is an inverse to base modulo mod Here s an example of computing an inverse for 38 modulo 97 pow 38 1 mod 97 23 23 38 97 1 True Changed in version 3 8 For int operands the three argument form of pow now allows the second argument to be negative permitting computation of modular inverses Changed in version 3 8 Allow keyword arguments Formerly only positional arguments were supported print objects sep end n file None flush False Print objects to the text stream file separated by sep and followed by end sep end file and flush if present must be given as keyword arguments All non keyword arguments are converted to strings like str does and written to the stream separated by sep and followed by end Both sep and end must be strings they can also be None which means to use the default values If no objects are given print will just write end The file argument must be an object with a write string method if it is not present or None sys stdout will be used Since printed arguments are converted to text strings print cannot be used with binary mode file objects For these use file write instead Output buffering is usually determined by file However if flush is true the stream is forcibly flushed Changed in version 3 3 Added the flush keyword argument class property fget None fset None fdel None doc None Return a property attribute fget is a function for getting an attribute value fset is a function for setting an attribute value fdel is a function for deleting an attribute value And doc creates a docstring for the attribute A typical use is to define a managed attribute x class C def __init__ self self _x None def getx self return self _x def setx self value self _x value def delx self del self _x x property getx setx delx I m the x property If c is an instance of C c x will invoke the getter c x value will invoke the setter and del c x the deleter If given doc will be the docstring of the property attribute Otherwise the property will copy fget s docstring if it exists This makes it possible to create read only properties easily using property as a decorator class Parrot def __init__ self self _voltage 100000 property def voltage self Get the current voltage return self _voltage The property decorator turns the voltage method into a getter for a read only attribute with the same name and it sets the docstring for voltage to Get the current voltage getter setter deleter A property object has getter setter and deleter methods usable as decorators that create a copy of the property with the corresponding accessor function set to the decorated function This is best explained with an example class C def __init__ self self _x None property def x self I m the x property return self _x x setter def x self value self _x value x deleter def x self del self _x This code is exactly equivalent to the first example Be sure to give the additional functions the same name as the original property x in this case The returned property object also has the attributes fget fset and fdel corresponding to the constructor arguments Changed in version 3 5 The docstrings of property objects are now writeable class range stop class range start stop step 1 Rather than being a function range is actually an immutable sequence type as documented in Ranges and Sequence Types list tuple range repr object Return a string containing a printable representation of an object For many types this function makes an attempt to return a string that would yield an object with the same value when passed to eval otherwise the representation is a string enclosed in angle brackets that contains the name of the type of the object together with additional information often including the name and address of the object A class can control what ,en
2467,this function returns for its instances by defining a __repr__ method If sys displayhook is not accessible this function will raise RuntimeError This class has a custom representation that can be evaluated class Person def __init__ self name age self name name self age age def __repr__ self return f Person self name self age reversed seq Return a reverse iterator seq must be an object which has a __reversed__ method or supports the sequence protocol the __len__ method and the __getitem__ method with integer arguments starting at 0 round number ndigits None Return number rounded to ndigits precision after the decimal point If ndigits is omitted or is None it returns the nearest integer to its input For the built in types supporting round values are rounded to the closest multiple of 10 to the power minus ndigits if two multiples are equally close rounding is done toward the even choice so for example both round 0 5 and round 0 5 are 0 and round 1 5 is 2 Any integer value is valid for ndigits positive zero or negative The return value is an integer if ndigits is omitted or None Otherwise the return value has the same type as number For a general Python object number round delegates to number __round__ Note The behavior of round for floats can be surprising for example round 2 675 2 gives 2 67 instead of the expected 2 68 This is not a bug it s a result of the fact that most decimal fractions can t be represented exactly as a float See Floating Point Arithmetic Issues and Limitations for more information class set class set iterable Return a new set object optionally with elements taken from iterable set is a built in class See set and Set Types set frozenset for documentation about this class For other containers see the built in frozenset list tuple and dict classes as well as the collections module setattr object name value This is the counterpart of getattr The arguments are an object a string and an arbitrary value The string may name an existing attribute or a new attribute The function assigns the value to the attribute provided the object allows it For example setattr x foobar 123 is equivalent to x foobar 123 name need not be a Python identifier as defined in Identifiers and keywords unless the object chooses to enforce that for example in a custom __getattribute__ or via __slots__ An attribute whose name is not an identifier will not be accessible using the dot notation but is accessible through getattr etc Note Since private name mangling happens at compilation time one must manually mangle a private attribute s attributes with two leading underscores name in order to set it with setattr class slice stop class slice start stop step None Return a slice object representing the set of indices specified by range start stop step The start and step arguments default to None start stop step Slice objects have read only data attributes start stop and step which merely return the argument values or their default They have no other explicit functionality however they are used by NumPy and other third party packages Slice objects are also generated when extended indexing syntax is used For example a start stop step or a start stop i See itertools islice for an alternate version that returns an iterator Changed in version 3 12 Slice objects are now hashable provided start stop and step are hashable sorted iterable key None reverse False Return a new sorted list from the items in iterable Has two optional arguments which must be specified as keyword arguments key specifies a function of one argument that is used to extract a comparison key from each element in iterable for example key str lower The default value is None compare the elements directly reverse is a boolean value If set to True then the list elements are sorted as if each comparison were reversed Use functools cmp_to_key to convert an old style cmp function to a key function The built in sorted function is guaranteed to be stable A sort is stable if it guarantees not to change the relative order of elements that compare equal this is helpful for sorting in multip,en
2468,le passes for example sort by department then by salary grade The sort algorithm uses only comparisons between items While defining an __lt__ method will suffice for sorting PEP 8 recommends that all six rich comparisons be implemented This will help avoid bugs when using the same data with other ordering tools such as max that rely on a different underlying method Implementing all six comparisons also helps avoid confusion for mixed type comparisons which can call reflected the __gt__ method For sorting examples and a brief sorting tutorial see Sorting Techniques staticmethod Transform a method into a static method A static method does not receive an implicit first argument To declare a static method use this idiom class C staticmethod def f arg1 arg2 argN The staticmethod form is a function decorator see Function definitions for details A static method can be called either on the class such as C f or on an instance such as C f Moreover they can be called as regular functions such as f Static methods in Python are similar to those found in Java or C Also see classmethod for a variant that is useful for creating alternate class constructors Like all decorators it is also possible to call staticmethod as a regular function and do something with its result This is needed in some cases where you need a reference to a function from a class body and you want to avoid the automatic transformation to instance method For these cases use this idiom def regular_function class C method staticmethod regular_function For more information on static methods see The standard type hierarchy Changed in version 3 10 Static methods now inherit the method attributes __module__ __name__ __qualname__ __doc__ and __annotations__ have a new __wrapped__ attribute and are now callable as regular functions class str object class str object b encoding utf 8 errors strict Return a str version of object See str for details str is the built in string class For general information about strings see Text Sequence Type str sum iterable start 0 Sums start and the items of an iterable from left to right and returns the total The iterable s items are normally numbers and the start value is not allowed to be a string For some use cases there are good alternatives to sum The preferred fast way to concatenate a sequence of strings is by calling join sequence To add floating point values with extended precision see math fsum To concatenate a series of iterables consider using itertools chain Changed in version 3 8 The start parameter can be specified as a keyword argument Changed in version 3 12 Summation of floats switched to an algorithm that gives higher accuracy on most builds class super class super type object_or_type None Return a proxy object that delegates method calls to a parent or sibling class of type This is useful for accessing inherited methods that have been overridden in a class The object_or_type determines the method resolution order to be searched The search starts from the class right after the type For example if __mro__ of object_or_type is D B C A object and the value of type is B then super searches C A object The __mro__ attribute of the object_or_type lists the method resolution search order used by both getattr and super The attribute is dynamic and can change whenever the inheritance hierarchy is updated If the second argument is omitted the super object returned is unbound If the second argument is an object isinstance obj type must be true If the second argument is a type issubclass type2 type must be true this is useful for classmethods There are two typical use cases for super In a class hierarchy with single inheritance super can be used to refer to parent classes without naming them explicitly thus making the code more maintainable This use closely parallels the use of super in other programming languages The second use case is to support cooperative multiple inheritance in a dynamic execution environment This use case is unique to Python and is not found in statically compiled languages or languages that only support single i,en
2469,nheritance This makes it possible to implement diamond diagrams where multiple base classes implement the same method Good design dictates that such implementations have the same calling signature in every case because the order of calls is determined at runtime because that order adapts to changes in the class hierarchy and because that order can include sibling classes that are unknown prior to runtime For both use cases a typical superclass call looks like this class C B def method self arg super method arg This does the same thing as super C self method arg In addition to method lookups super also works for attribute lookups One possible use case for this is calling descriptors in a parent or sibling class Note that super is implemented as part of the binding process for explicit dotted attribute lookups such as super __getitem__ name It does so by implementing its own __getattribute__ method for searching classes in a predictable order that supports cooperative multiple inheritance Accordingly super is undefined for implicit lookups using statements or operators such as super name Also note that aside from the zero argument form super is not limited to use inside methods The two argument form specifies the arguments exactly and makes the appropriate references The zero argument form only works inside a class definition as the compiler fills in the necessary details to correctly retrieve the class being defined as well as accessing the current instance for ordinary methods For practical suggestions on how to design cooperative classes using super see guide to using super class tuple class tuple iterable Rather than being a function tuple is actually an immutable sequence type as documented in Tuples and Sequence Types list tuple range class type object class type name bases dict kwds With one argument return the type of an object The return value is a type object and generally the same object as returned by object __class__ The isinstance built in function is recommended for testing the type of an object because it takes subclasses into account With three arguments return a new type object This is essentially a dynamic form of the class statement The name string is the class name and becomes the __name__ attribute The bases tuple contains the base classes and becomes the __bases__ attribute if empty object the ultimate base of all classes is added The dict dictionary contains attribute and method definitions for the class body it may be copied or wrapped before becoming the __dict__ attribute The following two statements create identical type objects class X a 1 X type X dict a 1 See also Type Objects Keyword arguments provided to the three argument form are passed to the appropriate metaclass machinery usually __init_subclass__ in the same way that keywords in a class definition besides metaclass would See also Customizing class creation Changed in version 3 6 Subclasses of type which don t override type __new__ may no longer use the one argument form to get the type of an object vars vars object Return the __dict__ attribute for a module class instance or any other object with a __dict__ attribute Objects such as modules and instances have an updateable __dict__ attribute however other objects may have write restrictions on their __dict__ attributes for example classes use a types MappingProxyType to prevent direct dictionary updates Without an argument vars acts like locals Note the locals dictionary is only useful for reads since updates to the locals dictionary are ignored A TypeError exception is raised if an object is specified but it doesn t have a __dict__ attribute for example if its class defines the __slots__ attribute zip iterables strict False Iterate over several iterables in parallel producing tuples with an item from each one Example for item in zip 1 2 3 sugar spice everything nice print item 1 sugar 2 spice 3 everything nice More formally zip returns an iterator of tuples where the i th tuple contains the i th element from each of the argument iterables Another way to think of zip is that it turns ,en
2470,rows into columns and columns into rows This is similar to transposing a matrix zip is lazy The elements won t be processed until the iterable is iterated on e g by a for loop or by wrapping in a list One thing to consider is that the iterables passed to zip could have different lengths sometimes by design and sometimes because of a bug in the code that prepared these iterables Python offers three different approaches to dealing with this issue By default zip stops when the shortest iterable is exhausted It will ignore the remaining items in the longer iterables cutting off the result to the length of the shortest iterable list zip range 3 fee fi fo fum 0 fee 1 fi 2 fo zip is often used in cases where the iterables are assumed to be of equal length In such cases it s recommended to use the strict True option Its output is the same as regular zip list zip a b c 1 2 3 strict True a 1 b 2 c 3 Unlike the default behavior it raises a ValueError if one iterable is exhausted before the others for item in zip range 3 fee fi fo fum strict True print item 0 fee 1 fi 2 fo Traceback most recent call last ValueError zip argument 2 is longer than argument 1 Without the strict True argument any bug that results in iterables of different lengths will be silenced possibly manifesting as a hard to find bug in another part of the program Shorter iterables can be padded with a constant value to make all the iterables have the same length This is done by itertools zip_longest Edge cases With a single iterable argument zip returns an iterator of 1 tuples With no arguments it returns an empty iterator Tips and tricks The left to right evaluation order of the iterables is guaranteed This makes possible an idiom for clustering a data series into n length groups using zip iter s n strict True This repeats the same iterator n times so that each output tuple has the result of n calls to the iterator This has the effect of dividing the input into n length chunks zip in conjunction with the operator can be used to unzip a list x 1 2 3 y 4 5 6 list zip x y 1 4 2 5 3 6 x2 y2 zip zip x y x list x2 and y list y2 True Changed in version 3 10 Added the strict argument __import__ name globals None locals None fromlist level 0 Note This is an advanced function that is not needed in everyday Python programming unlike importlib import_module This function is invoked by the import statement It can be replaced by importing the builtins module and assigning to builtins __import__ in order to change semantics of the import statement but doing so is strongly discouraged as it is usually simpler to use import hooks see PEP 302 to attain the same goals and does not cause issues with code which assumes the default import implementation is in use Direct use of __import__ is also discouraged in favor of importlib import_module The function imports the module name potentially using the given globals and locals to determine how to interpret the name in a package context The fromlist gives the names of objects or submodules that should be imported from the module given by name The standard implementation does not use its locals argument at all and uses its globals only to determine the package context of the import statement level specifies whether to use absolute or relative imports 0 the default means only perform absolute imports Positive values for level indicate the number of parent directories to search relative to the directory of the module calling __import__ see PEP 328 for the details When the name variable is of the form package module normally the top level package the name up till the first dot is returned not the module named by name However when a non empty fromlist argument is given the module named by name is returned For example the statement import spam results in bytecode resembling the following code spam __import__ spam globals locals 0 The statement import spam ham results in this call spam __import__ spam ham globals locals 0 Note how __import__ returns the toplevel module here because this is the object that is bound to a name by the import stateme,en
2471,nt On the other hand the statement from spam ham import eggs sausage as saus results in _temp __import__ spam ham globals locals eggs sausage 0 eggs _temp eggs saus _temp sausage Here the spam ham module is returned from __import__ From this object the names to import are retrieved and assigned to their respective names If you simply want to import a module potentially within a package by name use importlib import_module Changed in version 3 3 Negative values for level are no longer supported which also changes the default value to 0 Changed in version 3 9 When the command line options E or I are being used the environment variable PYTHONCASEOK is now ignored Footnotes 1 Note that the parser only accepts the Unix style end of line convention If you are reading the code from a file make sure to use newline conversion mode to convert Windows or Mac style newlines,en
2472,Futures Source code Lib asyncio futures py Lib asyncio base_futures py Future objects are used to bridge low level callback based code with high level async await code Future Functions asyncio isfuture obj Return True if obj is either of an instance of asyncio Future an instance of asyncio Task a Future like object with a _asyncio_future_blocking attribute New in version 3 5 asyncio ensure_future obj loop None Return obj argument as is if obj is a Future a Task or a Future like object isfuture is used for the test a Task object wrapping obj if obj is a coroutine iscoroutine is used for the test in this case the coroutine will be scheduled by ensure_future a Task object that would await on obj if obj is an awaitable inspect isawaitable is used for the test If obj is neither of the above a TypeError is raised Important See also the create_task function which is the preferred way for creating new Tasks Save a reference to the result of this function to avoid a task disappearing mid execution Changed in version 3 5 1 The function accepts any awaitable object Deprecated since version 3 10 Deprecation warning is emitted if obj is not a Future like object and loop is not specified and there is no running event loop asyncio wrap_future future loop None Wrap a concurrent futures Future object in a asyncio Future object Deprecated since version 3 10 Deprecation warning is emitted if future is not a Future like object and loop is not specified and there is no running event loop Future Object class asyncio Future loop None A Future represents an eventual result of an asynchronous operation Not thread safe Future is an awaitable object Coroutines can await on Future objects until they either have a result or an exception set or until they are cancelled A Future can be awaited multiple times and the result is same Typically Futures are used to enable low level callback based code e g in protocols implemented using asyncio transports to interoperate with high level async await code The rule of thumb is to never expose Future objects in user facing APIs and the recommended way to create a Future object is to call loop create_future This way alternative event loop implementations can inject their own optimized implementations of a Future object Changed in version 3 7 Added support for the contextvars module Deprecated since version 3 10 Deprecation warning is emitted if loop is not specified and there is no running event loop result Return the result of the Future If the Future is done and has a result set by the set_result method the result value is returned If the Future is done and has an exception set by the set_exception method this method raises the exception If the Future has been cancelled this method raises a CancelledError exception If the Future s result isn t yet available this method raises a InvalidStateError exception set_result result Mark the Future as done and set its result Raises a InvalidStateError error if the Future is already done set_exception exception Mark the Future as done and set an exception Raises a InvalidStateError error if the Future is already done done Return True if the Future is done A Future is done if it was cancelled or if it has a result or an exception set with set_result or set_exception calls cancelled Return True if the Future was cancelled The method is usually used to check if a Future is not cancelled before setting a result or an exception for it if not fut cancelled fut set_result 42 add_done_callback callback context None Add a callback to be run when the Future is done The callback is called with the Future object as its only argument If the Future is already done when this method is called the callback is scheduled with loop call_soon An optional keyword only context argument allows specifying a custom contextvars Context for the callback to run in The current context is used when no context is provided functools partial can be used to pass parameters to the callback e g Call print Future fut when fut is done fut add_done_callback functools partial print Future Changed in version 3 7,en
2473, The context keyword only parameter was added See PEP 567 for more details remove_done_callback callback Remove callback from the callbacks list Returns the number of callbacks removed which is typically 1 unless a callback was added more than once cancel msg None Cancel the Future and schedule callbacks If the Future is already done or cancelled return False Otherwise change the Future s state to cancelled schedule the callbacks and return True Changed in version 3 9 Added the msg parameter exception Return the exception that was set on this Future The exception or None if no exception was set is returned only if the Future is done If the Future has been cancelled this method raises a CancelledError exception If the Future isn t done yet this method raises an InvalidStateError exception get_loop Return the event loop the Future object is bound to New in version 3 7 This example creates a Future object creates and schedules an asynchronous Task to set result for the Future and waits until the Future has a result async def set_after fut delay value Sleep for delay seconds await asyncio sleep delay Set value as a result of fut Future fut set_result value async def main Get the current event loop loop asyncio get_running_loop Create a new Future object fut loop create_future Run set_after coroutine in a parallel Task We are using the low level loop create_task API here because we already have a reference to the event loop at hand Otherwise we could have just used asyncio create_task loop create_task set_after fut 1 world print hello Wait until fut has a result 1 second and print it print await fut asyncio run main Important The Future object was designed to mimic concurrent futures Future Key differences include unlike asyncio Futures concurrent futures Future instances cannot be awaited asyncio Future result and asyncio Future exception do not accept the timeout argument asyncio Future result and asyncio Future exception raise an InvalidStateError exception when the Future is not done Callbacks registered with asyncio Future add_done_callback are not called immediately They are scheduled with loop call_soon instead asyncio Future is not compatible with the concurrent futures wait and concurrent futures as_completed functions asyncio Future cancel accepts an optional msg argument but concurrent futures Future cancel does not,en
2474,Curses Programming with Python Author A M Kuchling Eric S Raymond Release 2 04 Abstract This document describes how to use the curses extension module to control text mode displays What is curses The curses library supplies a terminal independent screen painting and keyboard handling facility for text based terminals such terminals include VT100s the Linux console and the simulated terminal provided by various programs Display terminals support various control codes to perform common operations such as moving the cursor scrolling the screen and erasing areas Different terminals use widely differing codes and often have their own minor quirks In a world of graphical displays one might ask why bother It s true that character cell display terminals are an obsolete technology but there are niches in which being able to do fancy things with them are still valuable One niche is on small footprint or embedded Unixes that don t run an X server Another is tools such as OS installers and kernel configurators that may have to run before any graphical support is available The curses library provides fairly basic functionality providing the programmer with an abstraction of a display containing multiple non overlapping windows of text The contents of a window can be changed in various ways adding text erasing it changing its appearance and the curses library will figure out what control codes need to be sent to the terminal to produce the right output curses doesn t provide many user interface concepts such as buttons checkboxes or dialogs if you need such features consider a user interface library such as Urwid The curses library was originally written for BSD Unix the later System V versions of Unix from AT T added many enhancements and new functions BSD curses is no longer maintained having been replaced by ncurses which is an open source implementation of the AT T interface If you re using an open source Unix such as Linux or FreeBSD your system almost certainly uses ncurses Since most current commercial Unix versions are based on System V code all the functions described here will probably be available The older versions of curses carried by some proprietary Unixes may not support everything though The Windows version of Python doesn t include the curses module A ported version called UniCurses is available The Python curses module The Python module is a fairly simple wrapper over the C functions provided by curses if you re already familiar with curses programming in C it s really easy to transfer that knowledge to Python The biggest difference is that the Python interface makes things simpler by merging different C functions such as addstr mvaddstr and mvwaddstr into a single addstr method You ll see this covered in more detail later This HOWTO is an introduction to writing text mode programs with curses and Python It doesn t attempt to be a complete guide to the curses API for that see the Python library guide s section on ncurses and the C manual pages for ncurses It will however give you the basic ideas Starting and ending a curses application Before doing anything curses must be initialized This is done by calling the initscr function which will determine the terminal type send any required setup codes to the terminal and create various internal data structures If successful initscr returns a window object representing the entire screen this is usually called stdscr after the name of the corresponding C variable import curses stdscr curses initscr Usually curses applications turn off automatic echoing of keys to the screen in order to be able to read keys and only display them under certain circumstances This requires calling the noecho function curses noecho Applications will also commonly need to react to keys instantly without requiring the Enter key to be pressed this is called cbreak mode as opposed to the usual buffered input mode curses cbreak Terminals usually return special keys such as the cursor keys or navigation keys such as Page Up and Home as a multibyte escape sequence While you could write your application,en
2475, to expect such sequences and process them accordingly curses can do it for you returning a special value such as curses KEY_LEFT To get curses to do the job you ll have to enable keypad mode stdscr keypad True Terminating a curses application is much easier than starting one You ll need to call curses nocbreak stdscr keypad False curses echo to reverse the curses friendly terminal settings Then call the endwin function to restore the terminal to its original operating mode curses endwin A common problem when debugging a curses application is to get your terminal messed up when the application dies without restoring the terminal to its previous state In Python this commonly happens when your code is buggy and raises an uncaught exception Keys are no longer echoed to the screen when you type them for example which makes using the shell difficult In Python you can avoid these complications and make debugging much easier by importing the curses wrapper function and using it like this from curses import wrapper def main stdscr Clear screen stdscr clear This raises ZeroDivisionError when i 10 for i in range 0 11 v i 10 stdscr addstr i 0 10 divided by is format v 10 v stdscr refresh stdscr getkey wrapper main The wrapper function takes a callable object and does the initializations described above also initializing colors if color support is present wrapper then runs your provided callable Once the callable returns wrapper will restore the original state of the terminal The callable is called inside a try except that catches exceptions restores the state of the terminal and then re raises the exception Therefore your terminal won t be left in a funny state on exception and you ll be able to read the exception s message and traceback Windows and Pads Windows are the basic abstraction in curses A window object represents a rectangular area of the screen and supports methods to display text erase it allow the user to input strings and so forth The stdscr object returned by the initscr function is a window object that covers the entire screen Many programs may need only this single window but you might wish to divide the screen into smaller windows in order to redraw or clear them separately The newwin function creates a new window of a given size returning the new window object begin_x 20 begin_y 7 height 5 width 40 win curses newwin height width begin_y begin_x Note that the coordinate system used in curses is unusual Coordinates are always passed in the order y x and the top left corner of a window is coordinate 0 0 This breaks the normal convention for handling coordinates where the x coordinate comes first This is an unfortunate difference from most other computer applications but it s been part of curses since it was first written and it s too late to change things now Your application can determine the size of the screen by using the curses LINES and curses COLS variables to obtain the y and x sizes Legal coordinates will then extend from 0 0 to curses LINES 1 curses COLS 1 When you call a method to display or erase text the effect doesn t immediately show up on the display Instead you must call the refresh method of window objects to update the screen This is because curses was originally written with slow 300 baud terminal connections in mind with these terminals minimizing the time required to redraw the screen was very important Instead curses accumulates changes to the screen and displays them in the most efficient manner when you call refresh For example if your program displays some text in a window and then clears the window there s no need to send the original text because they re never visible In practice explicitly telling curses to redraw a window doesn t really complicate programming with curses much Most programs go into a flurry of activity and then pause waiting for a keypress or some other action on the part of the user All you have to do is to be sure that the screen has been redrawn before pausing to wait for user input by first calling stdscr refresh or the refresh method of some other relevant window A ,en
2476,pad is a special case of a window it can be larger than the actual display screen and only a portion of the pad displayed at a time Creating a pad requires the pad s height and width while refreshing a pad requires giving the coordinates of the on screen area where a subsection of the pad will be displayed pad curses newpad 100 100 These loops fill the pad with letters addch is explained in the next section for y in range 0 99 for x in range 0 99 pad addch y x ord a x x y y 26 Displays a section of the pad in the middle of the screen 0 0 coordinate of upper left corner of pad area to display 5 5 coordinate of upper left corner of window area to be filled with pad content 20 75 coordinate of lower right corner of window area to be filled with pad content pad refresh 0 0 5 5 20 75 The refresh call displays a section of the pad in the rectangle extending from coordinate 5 5 to coordinate 20 75 on the screen the upper left corner of the displayed section is coordinate 0 0 on the pad Beyond that difference pads are exactly like ordinary windows and support the same methods If you have multiple windows and pads on screen there is a more efficient way to update the screen and prevent annoying screen flicker as each part of the screen gets updated refresh actually does two things 1 Calls the noutrefresh method of each window to update an underlying data structure representing the desired state of the screen 2 Calls the function doupdate function to change the physical screen to match the desired state recorded in the data structure Instead you can call noutrefresh on a number of windows to update the data structure and then call doupdate to update the screen Displaying Text From a C programmer s point of view curses may sometimes look like a twisty maze of functions all subtly different For example addstr displays a string at the current cursor location in the stdscr window while mvaddstr moves to a given y x coordinate first before displaying the string waddstr is just like addstr but allows specifying a window to use instead of using stdscr by default mvwaddstr allows specifying both a window and a coordinate Fortunately the Python interface hides all these details stdscr is a window object like any other and methods such as addstr accept multiple argument forms Usually there are four different forms Form Description str or ch Display the string str or character ch at the current position str or ch attr Display the string str or character ch using attribute attr at the current position y x str or ch Move to position y x within the window and display str or ch y x str or ch attr Move to position y x within the window and display str or ch using attribute attr Attributes allow displaying text in highlighted forms such as boldface underline reverse code or in color They ll be explained in more detail in the next subsection The addstr method takes a Python string or bytestring as the value to be displayed The contents of bytestrings are sent to the terminal as is Strings are encoded to bytes using the value of the window s encoding attribute this defaults to the default system encoding as returned by locale getencoding The addch methods take a character which can be either a string of length 1 a bytestring of length 1 or an integer Constants are provided for extension characters these constants are integers greater than 255 For example ACS_PLMINUS is a symbol and ACS_ULCORNER is the upper left corner of a box handy for drawing borders You can also use the appropriate Unicode character Windows remember where the cursor was left after the last operation so if you leave out the y x coordinates the string or character will be displayed wherever the last operation left off You can also move the cursor with the move y x method Because some terminals always display a flashing cursor you may want to ensure that the cursor is positioned in some location where it won t be distracting it can be confusing to have the cursor blinking at some apparently random location If your application doesn t need a blinking cursor at all you can call curs_,en
2477,set False to make it invisible For compatibility with older curses versions there s a leaveok bool function that s a synonym for curs_set When bool is true the curses library will attempt to suppress the flashing cursor and you won t need to worry about leaving it in odd locations Attributes and Color Characters can be displayed in different ways Status lines in a text based application are commonly shown in reverse video or a text viewer may need to highlight certain words curses supports this by allowing you to specify an attribute for each cell on the screen An attribute is an integer each bit representing a different attribute You can try to display text with multiple attribute bits set but curses doesn t guarantee that all the possible combinations are available or that they re all visually distinct That depends on the ability of the terminal being used so it s safest to stick to the most commonly available attributes listed here Attribute Description A_BLINK Blinking text A_BOLD Extra bright or bold text A_DIM Half bright text A_REVERSE Reverse video text A_STANDOUT The best highlighting mode available A_UNDERLINE Underlined text So to display a reverse video status line on the top line of the screen you could code stdscr addstr 0 0 Current mode Typing mode curses A_REVERSE stdscr refresh The curses library also supports color on those terminals that provide it The most common such terminal is probably the Linux console followed by color xterms To use color you must call the start_color function soon after calling initscr to initialize the default color set the curses wrapper function does this automatically Once that s done the has_colors function returns TRUE if the terminal in use can actually display color Note curses uses the American spelling color instead of the Canadian British spelling colour If you re used to the British spelling you ll have to resign yourself to misspelling it for the sake of these functions The curses library maintains a finite number of color pairs containing a foreground or text color and a background color You can get the attribute value corresponding to a color pair with the color_pair function this can be bitwise OR ed with other attributes such as A_REVERSE but again such combinations are not guaranteed to work on all terminals An example which displays a line of text using color pair 1 stdscr addstr Pretty text curses color_pair 1 stdscr refresh As I said before a color pair consists of a foreground and background color The init_pair n f b function changes the definition of color pair n to foreground color f and background color b Color pair 0 is hard wired to white on black and cannot be changed Colors are numbered and start_color initializes 8 basic colors when it activates color mode They are 0 black 1 red 2 green 3 yellow 4 blue 5 magenta 6 cyan and 7 white The curses module defines named constants for each of these colors curses COLOR_BLACK curses COLOR_RED and so forth Let s put all this together To change color 1 to red text on a white background you would call curses init_pair 1 curses COLOR_RED curses COLOR_WHITE When you change a color pair any text already displayed using that color pair will change to the new colors You can also display new text in this color with stdscr addstr 0 0 RED ALERT curses color_pair 1 Very fancy terminals can change the definitions of the actual colors to a given RGB value This lets you change color 1 which is usually red to purple or blue or any other color you like Unfortunately the Linux console doesn t support this so I m unable to try it out and can t provide any examples You can check if your terminal can do this by calling can_change_color which returns True if the capability is there If you re lucky enough to have such a talented terminal consult your system s man pages for more information User Input The C curses library offers only very simple input mechanisms Python s curses module adds a basic text input widget Other libraries such as Urwid have more extensive collections of widgets There are two methods for getting input from a ,en
2478,window getch refreshes the screen and then waits for the user to hit a key displaying the key if echo has been called earlier You can optionally specify a coordinate to which the cursor should be moved before pausing getkey does the same thing but converts the integer to a string Individual characters are returned as 1 character strings and special keys such as function keys return longer strings containing a key name such as KEY_UP or G It s possible to not wait for the user using the nodelay window method After nodelay True getch and getkey for the window become non blocking To signal that no input is ready getch returns curses ERR a value of 1 and getkey raises an exception There s also a halfdelay function which can be used to in effect set a timer on each getch if no input becomes available within a specified delay measured in tenths of a second curses raises an exception The getch method returns an integer if it s between 0 and 255 it represents the ASCII code of the key pressed Values greater than 255 are special keys such as Page Up Home or the cursor keys You can compare the value returned to constants such as curses KEY_PPAGE curses KEY_HOME or curses KEY_LEFT The main loop of your program may look something like this while True c stdscr getch if c ord p PrintDocument elif c ord q break Exit the while loop elif c curses KEY_HOME x y 0 The curses ascii module supplies ASCII class membership functions that take either integer or 1 character string arguments these may be useful in writing more readable tests for such loops It also supplies conversion functions that take either integer or 1 character string arguments and return the same type For example curses ascii ctrl returns the control character corresponding to its argument There s also a method to retrieve an entire string getstr It isn t used very often because its functionality is quite limited the only editing keys available are the backspace key and the Enter key which terminates the string It can optionally be limited to a fixed number of characters curses echo Enable echoing of characters Get a 15 character string with the cursor on the top line s stdscr getstr 0 0 15 The curses textpad module supplies a text box that supports an Emacs like set of keybindings Various methods of the Textbox class support editing with input validation and gathering the edit results either with or without trailing spaces Here s an example import curses from curses textpad import Textbox rectangle def main stdscr stdscr addstr 0 0 Enter IM message hit Ctrl G to send editwin curses newwin 5 30 2 1 rectangle stdscr 1 0 1 5 1 1 30 1 stdscr refresh box Textbox editwin Let the user edit until Ctrl G is struck box edit Get resulting contents message box gather See the library documentation on curses textpad for more details For More Information This HOWTO doesn t cover some advanced topics such as reading the contents of the screen or capturing mouse events from an xterm instance but the Python library page for the curses module is now reasonably complete You should browse it next If you re in doubt about the detailed behavior of the curses functions consult the manual pages for your curses implementation whether it s ncurses or a proprietary Unix vendor s The manual pages will document any quirks and provide complete lists of all the functions attributes and ACS_ characters available to you Because the curses API is so large some functions aren t supported in the Python interface Often this isn t because they re difficult to implement but because no one has needed them yet Also Python doesn t yet support the menu library associated with ncurses Patches adding support for these would be welcome see the Python Developer s Guide to learn more about submitting patches to Python Writing Programs with NCURSES a lengthy tutorial for C programmers The ncurses man page The ncurses FAQ Use curses don t swear video of a PyCon 2013 talk on controlling terminals using curses or Urwid Console Applications with Urwid video of a PyCon CA 2012 talk demonstrating some applications written using ,en
2479,Urwid,cy
2480,The None Object Note that the PyTypeObject for None is not directly exposed in the Python C API Since None is a singleton testing for object identity using in C is sufficient There is no PyNone_Check function for the same reason PyObject Py_None The Python None object denoting lack of value This object has no methods and is immortal Changed in version 3 12 Py_None is immortal Py_RETURN_NONE Return Py_None from a function,en
2481,pydoc Documentation generator and online help system Source code Lib pydoc py The pydoc module automatically generates documentation from Python modules The documentation can be presented as pages of text on the console served to a web browser or saved to HTML files For modules classes functions and methods the displayed documentation is derived from the docstring i e the __doc__ attribute of the object and recursively of its documentable members If there is no docstring pydoc tries to obtain a description from the block of comment lines just above the definition of the class function or method in the source file or at the top of the module see inspect getcomments The built in function help invokes the online help system in the interactive interpreter which uses pydoc to generate its documentation as text on the console The same text documentation can also be viewed from outside the Python interpreter by running pydoc as a script at the operating system s command prompt For example running python m pydoc sys at a shell prompt will display documentation on the sys module in a style similar to the manual pages shown by the Unix man command The argument to pydoc can be the name of a function module or package or a dotted reference to a class method or function within a module or module in a package If the argument to pydoc looks like a path that is it contains the path separator for your operating system such as a slash in Unix and refers to an existing Python source file then documentation is produced for that file Note In order to find objects and their documentation pydoc imports the module s to be documented Therefore any code on module level will be executed on that occasion Use an if __name__ __main__ guard to only execute code when a file is invoked as a script and not just imported When printing output to the console pydoc attempts to paginate the output for easier reading If the PAGER environment variable is set pydoc will use its value as a pagination program Specifying a w flag before the argument will cause HTML documentation to be written out to a file in the current directory instead of displaying text on the console Specifying a k flag before the argument will search the synopsis lines of all available modules for the keyword given as the argument again in a manner similar to the Unix man command The synopsis line of a module is the first line of its documentation string You can also use pydoc to start an HTTP server on the local machine that will serve documentation to visiting web browsers python m pydoc p 1234 will start a HTTP server on port 1234 allowing you to browse the documentation at http localhost 1234 in your preferred web browser Specifying 0 as the port number will select an arbitrary unused port python m pydoc n hostname will start the server listening at the given hostname By default the hostname is localhost but if you want the server to be reached from other machines you may want to change the host name that the server responds to During development this is especially useful if you want to run pydoc from within a container python m pydoc b will start the server and additionally open a web browser to a module index page Each served page has a navigation bar at the top where you can Get help on an individual item Search all modules with a keyword in their synopsis line and go to the Module index Topics and Keywords pages When pydoc generates documentation it uses the current environment and path to locate modules Thus invoking pydoc spam documents precisely the version of the module you would get if you started the Python interpreter and typed import spam Module docs for core modules are assumed to reside in https docs python org X Y library where X and Y are the major and minor version numbers of the Python interpreter This can be overridden by setting the PYTHONDOCS environment variable to a different URL or to a local directory containing the Library Reference Manual pages Changed in version 3 2 Added the b option Changed in version 3 3 The g command line option was removed Changed in versi,en
2482,on 3 4 pydoc now uses inspect signature rather than inspect getfullargspec to extract signature information from callables Changed in version 3 7 Added the n option,en
2483,Dictionary Objects type PyDictObject This subtype of PyObject represents a Python dictionary object PyTypeObject PyDict_Type Part of the Stable ABI This instance of PyTypeObject represents the Python dictionary type This is the same object as dict in the Python layer int PyDict_Check PyObject p Return true if p is a dict object or an instance of a subtype of the dict type This function always succeeds int PyDict_CheckExact PyObject p Return true if p is a dict object but not an instance of a subtype of the dict type This function always succeeds PyObject PyDict_New Return value New reference Part of the Stable ABI Return a new empty dictionary or NULL on failure PyObject PyDictProxy_New PyObject mapping Return value New reference Part of the Stable ABI Return a types MappingProxyType object for a mapping which enforces read only behavior This is normally used to create a view to prevent modification of the dictionary for non dynamic class types void PyDict_Clear PyObject p Part of the Stable ABI Empty an existing dictionary of all key value pairs int PyDict_Contains PyObject p PyObject key Part of the Stable ABI Determine if dictionary p contains key If an item in p is matches key return 1 otherwise return 0 On error return 1 This is equivalent to the Python expression key in p PyObject PyDict_Copy PyObject p Return value New reference Part of the Stable ABI Return a new dictionary that contains the same key value pairs as p int PyDict_SetItem PyObject p PyObject key PyObject val Part of the Stable ABI Insert val into the dictionary p with a key of key key must be hashable if it isn t TypeError will be raised Return 0 on success or 1 on failure This function does not steal a reference to val int PyDict_SetItemString PyObject p const char key PyObject val Part of the Stable ABI This is the same as PyDict_SetItem but key is specified as a const char UTF 8 encoded bytes string rather than a PyObject int PyDict_DelItem PyObject p PyObject key Part of the Stable ABI Remove the entry in dictionary p with key key key must be hashable if it isn t TypeError is raised If key is not in the dictionary KeyError is raised Return 0 on success or 1 on failure int PyDict_DelItemString PyObject p const char key Part of the Stable ABI This is the same as PyDict_DelItem but key is specified as a const char UTF 8 encoded bytes string rather than a PyObject PyObject PyDict_GetItem PyObject p PyObject key Return value Borrowed reference Part of the Stable ABI Return the object from dictionary p which has a key key Return NULL if the key key is not present but without setting an exception Note Exceptions that occur while this calls __hash__ and __eq__ methods are silently ignored Prefer the PyDict_GetItemWithError function instead Changed in version 3 10 Calling this API without GIL held had been allowed for historical reason It is no longer allowed PyObject PyDict_GetItemWithError PyObject p PyObject key Return value Borrowed reference Part of the Stable ABI Variant of PyDict_GetItem that does not suppress exceptions Return NULL with an exception set if an exception occurred Return NULL without an exception set if the key wasn t present PyObject PyDict_GetItemString PyObject p const char key Return value Borrowed reference Part of the Stable ABI This is the same as PyDict_GetItem but key is specified as a const char UTF 8 encoded bytes string rather than a PyObject Note Exceptions that occur while this calls __hash__ and __eq__ methods or while creating the temporary str object are silently ignored Prefer using the PyDict_GetItemWithError function with your own PyUnicode_FromString key instead PyObject PyDict_SetDefault PyObject p PyObject key PyObject defaultobj Return value Borrowed reference This is the same as the Python level dict setdefault If present it returns the value corresponding to key from the dictionary p If the key is not in the dict it is inserted with value defaultobj and defaultobj is returned This function evaluates the hash function of key only once instead of evaluating it independently for the lookup and the insertion Ne,en
2484,w in version 3 4 PyObject PyDict_Items PyObject p Return value New reference Part of the Stable ABI Return a PyListObject containing all the items from the dictionary PyObject PyDict_Keys PyObject p Return value New reference Part of the Stable ABI Return a PyListObject containing all the keys from the dictionary PyObject PyDict_Values PyObject p Return value New reference Part of the Stable ABI Return a PyListObject containing all the values from the dictionary p Py_ssize_t PyDict_Size PyObject p Part of the Stable ABI Return the number of items in the dictionary This is equivalent to len p on a dictionary int PyDict_Next PyObject p Py_ssize_t ppos PyObject pkey PyObject pvalue Part of the Stable ABI Iterate over all key value pairs in the dictionary p The Py_ssize_t referred to by ppos must be initialized to 0 prior to the first call to this function to start the iteration the function returns true for each pair in the dictionary and false once all pairs have been reported The parameters pkey and pvalue should either point to PyObject variables that will be filled in with each key and value respectively or may be NULL Any references returned through them are borrowed ppos should not be altered during iteration Its value represents offsets within the internal dictionary structure and since the structure is sparse the offsets are not consecutive For example PyObject key value Py_ssize_t pos 0 while PyDict_Next self dict pos key value do something interesting with the values The dictionary p should not be mutated during iteration It is safe to modify the values of the keys as you iterate over the dictionary but only so long as the set of keys does not change For example PyObject key value Py_ssize_t pos 0 while PyDict_Next self dict pos key value long i PyLong_AsLong value if i 1 PyErr_Occurred return 1 PyObject o PyLong_FromLong i 1 if o NULL return 1 if PyDict_SetItem self dict key o 0 Py_DECREF o return 1 Py_DECREF o int PyDict_Merge PyObject a PyObject b int override Part of the Stable ABI Iterate over mapping object b adding key value pairs to dictionary a b may be a dictionary or any object supporting PyMapping_Keys and PyObject_GetItem If override is true existing pairs in a will be replaced if a matching key is found in b otherwise pairs will only be added if there is not a matching key in a Return 0 on success or 1 if an exception was raised int PyDict_Update PyObject a PyObject b Part of the Stable ABI This is the same as PyDict_Merge a b 1 in C and is similar to a update b in Python except that PyDict_Update doesn t fall back to the iterating over a sequence of key value pairs if the second argument has no keys attribute Return 0 on success or 1 if an exception was raised int PyDict_MergeFromSeq2 PyObject a PyObject seq2 int override Part of the Stable ABI Update or merge into dictionary a from the key value pairs in seq2 seq2 must be an iterable object producing iterable objects of length 2 viewed as key value pairs In case of duplicate keys the last wins if override is true else the first wins Return 0 on success or 1 if an exception was raised Equivalent Python except for the return value def PyDict_MergeFromSeq2 a seq2 override for key value in seq2 if override or key not in a a key value int PyDict_AddWatcher PyDict_WatchCallback callback Register callback as a dictionary watcher Return a non negative integer id which must be passed to future calls to PyDict_Watch In case of error e g no more watcher IDs available return 1 and set an exception New in version 3 12 int PyDict_ClearWatcher int watcher_id Clear watcher identified by watcher_id previously returned from PyDict_AddWatcher Return 0 on success 1 on error e g if the given watcher_id was never registered New in version 3 12 int PyDict_Watch int watcher_id PyObject dict Mark dictionary dict as watched The callback granted watcher_id by PyDict_AddWatcher will be called when dict is modified or deallocated Return 0 on success or 1 on error New in version 3 12 int PyDict_Unwatch int watcher_id PyObject dict Mark dictionary dict as no longer watched The c,en
2485,allback granted watcher_id by PyDict_AddWatcher will no longer be called when dict is modified or deallocated The dict must previously have been watched by this watcher Return 0 on success or 1 on error New in version 3 12 type PyDict_WatchEvent Enumeration of possible dictionary watcher events PyDict_EVENT_ADDED PyDict_EVENT_MODIFIED PyDict_EVENT_DELETED PyDict_EVENT_CLONED PyDict_EVENT_CLEARED or PyDict_EVENT_DEALLOCATED New in version 3 12 typedef int PyDict_WatchCallback PyDict_WatchEvent event PyObject dict PyObject key PyObject new_value Type of a dict watcher callback function If event is PyDict_EVENT_CLEARED or PyDict_EVENT_DEALLOCATED both key and new_value will be NULL If event is PyDict_EVENT_ADDED or PyDict_EVENT_MODIFIED new_value will be the new value for key If event is PyDict_EVENT_DELETED key is being deleted from the dictionary and new_value will be NULL PyDict_EVENT_CLONED occurs when dict was previously empty and another dict is merged into it To maintain efficiency of this operation per key PyDict_EVENT_ADDED events are not issued in this case instead a single PyDict_EVENT_CLONED is issued and key will be the source dictionary The callback may inspect but must not modify dict doing so could have unpredictable effects including infinite recursion Do not trigger Python code execution in the callback as it could modify the dict as a side effect If event is PyDict_EVENT_DEALLOCATED taking a new reference in the callback to the about to be destroyed dictionary will resurrect it and prevent it from being freed at this time When the resurrected object is destroyed later any watcher callbacks active at that time will be called again Callbacks occur before the notified modification to dict takes place so the prior state of dict can be inspected If the callback sets an exception it must return 1 this exception will be printed as an unraisable exception using PyErr_WriteUnraisable Otherwise it should return 0 There may already be a pending exception set on entry to the callback In this case the callback should return 0 with the same exception still set This means the callback may not call any other API that can set an exception unless it saves and clears the exception state first and restores it before returning New in version 3 12,en
2486,xml dom The Document Object Model API Source code Lib xml dom __init__ py The Document Object Model or DOM is a cross language API from the World Wide Web Consortium W3C for accessing and modifying XML documents A DOM implementation presents an XML document as a tree structure or allows client code to build such a structure from scratch It then gives access to the structure through a set of objects which provided well known interfaces The DOM is extremely useful for random access applications SAX only allows you a view of one bit of the document at a time If you are looking at one SAX element you have no access to another If you are looking at a text node you have no access to a containing element When you write a SAX application you need to keep track of your program s position in the document somewhere in your own code SAX does not do it for you Also if you need to look ahead in the XML document you are just out of luck Some applications are simply impossible in an event driven model with no access to a tree Of course you could build some sort of tree yourself in SAX events but the DOM allows you to avoid writing that code The DOM is a standard tree representation for XML data The Document Object Model is being defined by the W3C in stages or levels in their terminology The Python mapping of the API is substantially based on the DOM Level 2 recommendation DOM applications typically start by parsing some XML into a DOM How this is accomplished is not covered at all by DOM Level 1 and Level 2 provides only limited improvements There is a DOMImplementation object class which provides access to Document creation methods but no way to access an XML reader parser Document builder in an implementation independent way There is also no well defined way to access these methods without an existing Document object In Python each DOM implementation will provide a function getDOMImplementation DOM Level 3 adds a Load Store specification which defines an interface to the reader but this is not yet available in the Python standard library Once you have a DOM document object you can access the parts of your XML document through its properties and methods These properties are defined in the DOM specification this portion of the reference manual describes the interpretation of the specification in Python The specification provided by the W3C defines the DOM API for Java ECMAScript and OMG IDL The Python mapping defined here is based in large part on the IDL version of the specification but strict compliance is not required though implementations are free to support the strict mapping from IDL See section Conformance for a detailed discussion of mapping requirements See also Document Object Model DOM Level 2 Specification The W3C recommendation upon which the Python DOM API is based Document Object Model DOM Level 1 Specification The W3C recommendation for the DOM supported by xml dom minidom Python Language Mapping Specification This specifies the mapping from OMG IDL to Python Module Contents The xml dom contains the following functions xml dom registerDOMImplementation name factory Register the factory function with the name name The factory function should return an object which implements the DOMImplementation interface The factory function can return the same object every time or a new one for each call as appropriate for the specific implementation e g if that implementation supports some customization xml dom getDOMImplementation name None features Return a suitable DOM implementation The name is either well known the module name of a DOM implementation or None If it is not None imports the corresponding module and returns a DOMImplementation object if the import succeeds If no name is given and if the environment variable PYTHON_DOM is set this variable is used to find the implementation If name is not given this examines the available implementations to find one with the required feature set If no implementation can be found raise an ImportError The features list must be a sequence of feature version pairs which are passed to th,en
2487,e hasFeature method on available DOMImplementation objects Some convenience constants are also provided xml dom EMPTY_NAMESPACE The value used to indicate that no namespace is associated with a node in the DOM This is typically found as the namespaceURI of a node or used as the namespaceURI parameter to a namespaces specific method xml dom XML_NAMESPACE The namespace URI associated with the reserved prefix xml as defined by Namespaces in XML section 4 xml dom XMLNS_NAMESPACE The namespace URI for namespace declarations as defined by Document Object Model DOM Level 2 Core Specification section 1 1 8 xml dom XHTML_NAMESPACE The URI of the XHTML namespace as defined by XHTML 1 0 The Extensible HyperText Markup Language section 3 1 1 In addition xml dom contains a base Node class and the DOM exception classes The Node class provided by this module does not implement any of the methods or attributes defined by the DOM specification concrete DOM implementations must provide those The Node class provided as part of this module does provide the constants used for the nodeType attribute on concrete Node objects they are located within the class rather than at the module level to conform with the DOM specifications Objects in the DOM The definitive documentation for the DOM is the DOM specification from the W3C Note that DOM attributes may also be manipulated as nodes instead of as simple strings It is fairly rare that you must do this however so this usage is not yet documented Interface Section Purpose DOMImplementation DOMImplementation Objects Interface to the underlying implementation Node Node Objects Base interface for most objects in a document NodeList NodeList Objects Interface for a sequence of nodes DocumentType DocumentType Objects Information about the declarations needed to process a document Document Document Objects Object which represents an entire document Element Element Objects Element nodes in the document hierarchy Attr Attr Objects Attribute value nodes on element nodes Comment Comment Objects Representation of comments in the source document Text Text and CDATASection Objects Nodes containing textual content from the document ProcessingInstruction ProcessingInstruction Objects Processing instruction representation An additional section describes the exceptions defined for working with the DOM in Python DOMImplementation Objects The DOMImplementation interface provides a way for applications to determine the availability of particular features in the DOM they are using DOM Level 2 added the ability to create new Document and DocumentType objects using the DOMImplementation as well DOMImplementation hasFeature feature version Return True if the feature identified by the pair of strings feature and version is implemented DOMImplementation createDocument namespaceUri qualifiedName doctype Return a new Document object the root of the DOM with a child Element object having the given namespaceUri and qualifiedName The doctype must be a DocumentType object created by createDocumentType or None In the Python DOM API the first two arguments can also be None in order to indicate that no Element child is to be created DOMImplementation createDocumentType qualifiedName publicId systemId Return a new DocumentType object that encapsulates the given qualifiedName publicId and systemId strings representing the information contained in an XML document type declaration Node Objects All of the components of an XML document are subclasses of Node Node nodeType An integer representing the node type Symbolic constants for the types are on the Node object ELEMENT_NODE ATTRIBUTE_NODE TEXT_NODE CDATA_SECTION_NODE ENTITY_NODE PROCESSING_INSTRUCTION_NODE COMMENT_NODE DOCUMENT_NODE DOCUMENT_TYPE_NODE NOTATION_NODE This is a read only attribute Node parentNode The parent of the current node or None for the document node The value is always a Node object or None For Element nodes this will be the parent element except for the root element in which case it will be the Document object For Attr nodes this is always None This is a read only,en
2488, attribute Node attributes A NamedNodeMap of attribute objects Only elements have actual values for this others provide None for this attribute This is a read only attribute Node previousSibling The node that immediately precedes this one with the same parent For instance the element with an end tag that comes just before the self element s start tag Of course XML documents are made up of more than just elements so the previous sibling could be text a comment or something else If this node is the first child of the parent this attribute will be None This is a read only attribute Node nextSibling The node that immediately follows this one with the same parent See also previousSibling If this is the last child of the parent this attribute will be None This is a read only attribute Node childNodes A list of nodes contained within this node This is a read only attribute Node firstChild The first child of the node if there are any or None This is a read only attribute Node lastChild The last child of the node if there are any or None This is a read only attribute Node localName The part of the tagName following the colon if there is one else the entire tagName The value is a string Node prefix The part of the tagName preceding the colon if there is one else the empty string The value is a string or None Node namespaceURI The namespace associated with the element name This will be a string or None This is a read only attribute Node nodeName This has a different meaning for each node type see the DOM specification for details You can always get the information you would get here from another property such as the tagName property for elements or the name property for attributes For all node types the value of this attribute will be either a string or None This is a read only attribute Node nodeValue This has a different meaning for each node type see the DOM specification for details The situation is similar to that with nodeName The value is a string or None Node hasAttributes Return True if the node has any attributes Node hasChildNodes Return True if the node has any child nodes Node isSameNode other Return True if other refers to the same node as this node This is especially useful for DOM implementations which use any sort of proxy architecture because more than one object can refer to the same node Note This is based on a proposed DOM Level 3 API which is still in the working draft stage but this particular interface appears uncontroversial Changes from the W3C will not necessarily affect this method in the Python DOM interface though any new W3C API for this would also be supported Node appendChild newChild Add a new child node to this node at the end of the list of children returning newChild If the node was already in the tree it is removed first Node insertBefore newChild refChild Insert a new child node before an existing child It must be the case that refChild is a child of this node if not ValueError is raised newChild is returned If refChild is None it inserts newChild at the end of the children s list Node removeChild oldChild Remove a child node oldChild must be a child of this node if not ValueError is raised oldChild is returned on success If oldChild will not be used further its unlink method should be called Node replaceChild newChild oldChild Replace an existing node with a new node It must be the case that oldChild is a child of this node if not ValueError is raised Node normalize Join adjacent text nodes so that all stretches of text are stored as single Text instances This simplifies processing text from a DOM tree for many applications Node cloneNode deep Clone this node Setting deep means to clone all child nodes as well This returns the clone NodeList Objects A NodeList represents a sequence of nodes These objects are used in two ways in the DOM Core recommendation an Element object provides one as its list of child nodes and the getElementsByTagName and getElementsByTagNameNS methods of Node return objects with this interface to represent query results The DOM Level 2 recommendation defines one method,en
2489, and one attribute for these objects NodeList item i Return the i th item from the sequence if there is one or None The index i is not allowed to be less than zero or greater than or equal to the length of the sequence NodeList length The number of nodes in the sequence In addition the Python DOM interface requires that some additional support is provided to allow NodeList objects to be used as Python sequences All NodeList implementations must include support for __len__ and __getitem__ this allows iteration over the NodeList in for statements and proper support for the len built in function If a DOM implementation supports modification of the document the NodeList implementation must also support the __setitem__ and __delitem__ methods DocumentType Objects Information about the notations and entities declared by a document including the external subset if the parser uses it and can provide the information is available from a DocumentType object The DocumentType for a document is available from the Document object s doctype attribute if there is no DOCTYPE declaration for the document the document s doctype attribute will be set to None instead of an instance of this interface DocumentType is a specialization of Node and adds the following attributes DocumentType publicId The public identifier for the external subset of the document type definition This will be a string or None DocumentType systemId The system identifier for the external subset of the document type definition This will be a URI as a string or None DocumentType internalSubset A string giving the complete internal subset from the document This does not include the brackets which enclose the subset If the document has no internal subset this should be None DocumentType name The name of the root element as given in the DOCTYPE declaration if present DocumentType entities This is a NamedNodeMap giving the definitions of external entities For entity names defined more than once only the first definition is provided others are ignored as required by the XML recommendation This may be None if the information is not provided by the parser or if no entities are defined DocumentType notations This is a NamedNodeMap giving the definitions of notations For notation names defined more than once only the first definition is provided others are ignored as required by the XML recommendation This may be None if the information is not provided by the parser or if no notations are defined Document Objects A Document represents an entire XML document including its constituent elements attributes processing instructions comments etc Remember that it inherits properties from Node Document documentElement The one and only root element of the document Document createElement tagName Create and return a new element node The element is not inserted into the document when it is created You need to explicitly insert it with one of the other methods such as insertBefore or appendChild Document createElementNS namespaceURI tagName Create and return a new element with a namespace The tagName may have a prefix The element is not inserted into the document when it is created You need to explicitly insert it with one of the other methods such as insertBefore or appendChild Document createTextNode data Create and return a text node containing the data passed as a parameter As with the other creation methods this one does not insert the node into the tree Document createComment data Create and return a comment node containing the data passed as a parameter As with the other creation methods this one does not insert the node into the tree Document createProcessingInstruction target data Create and return a processing instruction node containing the target and data passed as parameters As with the other creation methods this one does not insert the node into the tree Document createAttribute name Create and return an attribute node This method does not associate the attribute node with any particular element You must use setAttributeNode on the appropriate Element object to use the newly crea,en
2490,ted attribute instance Document createAttributeNS namespaceURI qualifiedName Create and return an attribute node with a namespace The tagName may have a prefix This method does not associate the attribute node with any particular element You must use setAttributeNode on the appropriate Element object to use the newly created attribute instance Document getElementsByTagName tagName Search for all descendants direct children children s children etc with a particular element type name Document getElementsByTagNameNS namespaceURI localName Search for all descendants direct children children s children etc with a particular namespace URI and localname The localname is the part of the namespace after the prefix Element Objects Element is a subclass of Node so inherits all the attributes of that class Element tagName The element type name In a namespace using document it may have colons in it The value is a string Element getElementsByTagName tagName Same as equivalent method in the Document class Element getElementsByTagNameNS namespaceURI localName Same as equivalent method in the Document class Element hasAttribute name Return True if the element has an attribute named by name Element hasAttributeNS namespaceURI localName Return True if the element has an attribute named by namespaceURI and localName Element getAttribute name Return the value of the attribute named by name as a string If no such attribute exists an empty string is returned as if the attribute had no value Element getAttributeNode attrname Return the Attr node for the attribute named by attrname Element getAttributeNS namespaceURI localName Return the value of the attribute named by namespaceURI and localName as a string If no such attribute exists an empty string is returned as if the attribute had no value Element getAttributeNodeNS namespaceURI localName Return an attribute value as a node given a namespaceURI and localName Element removeAttribute name Remove an attribute by name If there is no matching attribute a NotFoundErr is raised Element removeAttributeNode oldAttr Remove and return oldAttr from the attribute list if present If oldAttr is not present NotFoundErr is raised Element removeAttributeNS namespaceURI localName Remove an attribute by name Note that it uses a localName not a qname No exception is raised if there is no matching attribute Element setAttribute name value Set an attribute value from a string Element setAttributeNode newAttr Add a new attribute node to the element replacing an existing attribute if necessary if the name attribute matches If a replacement occurs the old attribute node will be returned If newAttr is already in use InuseAttributeErr will be raised Element setAttributeNodeNS newAttr Add a new attribute node to the element replacing an existing attribute if necessary if the namespaceURI and localName attributes match If a replacement occurs the old attribute node will be returned If newAttr is already in use InuseAttributeErr will be raised Element setAttributeNS namespaceURI qname value Set an attribute value from a string given a namespaceURI and a qname Note that a qname is the whole attribute name This is different than above Attr Objects Attr inherits from Node so inherits all its attributes Attr name The attribute name In a namespace using document it may include a colon Attr localName The part of the name following the colon if there is one else the entire name This is a read only attribute Attr prefix The part of the name preceding the colon if there is one else the empty string Attr value The text value of the attribute This is a synonym for the nodeValue attribute NamedNodeMap Objects NamedNodeMap does not inherit from Node NamedNodeMap length The length of the attribute list NamedNodeMap item index Return an attribute with a particular index The order you get the attributes in is arbitrary but will be consistent for the life of a DOM Each item is an attribute node Get its value with the value attribute There are also experimental methods that give this class more mapping behavior You can use them or you can,en
2491, use the standardized getAttribute family of methods on the Element objects Comment Objects Comment represents a comment in the XML document It is a subclass of Node but cannot have child nodes Comment data The content of the comment as a string The attribute contains all characters between the leading and trailing but does not include them Text and CDATASection Objects The Text interface represents text in the XML document If the parser and DOM implementation support the DOM s XML extension portions of the text enclosed in CDATA marked sections are stored in CDATASection objects These two interfaces are identical but provide different values for the nodeType attribute These interfaces extend the Node interface They cannot have child nodes Text data The content of the text node as a string Note The use of a CDATASection node does not indicate that the node represents a complete CDATA marked section only that the content of the node was part of a CDATA section A single CDATA section may be represented by more than one node in the document tree There is no way to determine whether two adjacent CDATASection nodes represent different CDATA marked sections ProcessingInstruction Objects Represents a processing instruction in the XML document this inherits from the Node interface and cannot have child nodes ProcessingInstruction target The content of the processing instruction up to the first whitespace character This is a read only attribute ProcessingInstruction data The content of the processing instruction following the first whitespace character Exceptions The DOM Level 2 recommendation defines a single exception DOMException and a number of constants that allow applications to determine what sort of error occurred DOMException instances carry a code attribute that provides the appropriate value for the specific exception The Python DOM interface provides the constants but also expands the set of exceptions so that a specific exception exists for each of the exception codes defined by the DOM The implementations must raise the appropriate specific exception each of which carries the appropriate value for the code attribute exception xml dom DOMException Base exception class used for all specific DOM exceptions This exception class cannot be directly instantiated exception xml dom DomstringSizeErr Raised when a specified range of text does not fit into a string This is not known to be used in the Python DOM implementations but may be received from DOM implementations not written in Python exception xml dom HierarchyRequestErr Raised when an attempt is made to insert a node where the node type is not allowed exception xml dom IndexSizeErr Raised when an index or size parameter to a method is negative or exceeds the allowed values exception xml dom InuseAttributeErr Raised when an attempt is made to insert an Attr node that is already present elsewhere in the document exception xml dom InvalidAccessErr Raised if a parameter or an operation is not supported on the underlying object exception xml dom InvalidCharacterErr This exception is raised when a string parameter contains a character that is not permitted in the context it s being used in by the XML 1 0 recommendation For example attempting to create an Element node with a space in the element type name will cause this error to be raised exception xml dom InvalidModificationErr Raised when an attempt is made to modify the type of a node exception xml dom InvalidStateErr Raised when an attempt is made to use an object that is not defined or is no longer usable exception xml dom NamespaceErr If an attempt is made to change any object in a way that is not permitted with regard to the Namespaces in XML recommendation this exception is raised exception xml dom NotFoundErr Exception when a node does not exist in the referenced context For example NamedNodeMap removeNamedItem will raise this if the node passed in does not exist in the map exception xml dom NotSupportedErr Raised when the implementation does not support the requested type of object or operation exception xml dom N,en
2492,oDataAllowedErr This is raised if data is specified for a node which does not support data exception xml dom NoModificationAllowedErr Raised on attempts to modify an object where modifications are not allowed such as for read only nodes exception xml dom SyntaxErr Raised when an invalid or illegal string is specified exception xml dom WrongDocumentErr Raised when a node is inserted in a different document than it currently belongs to and the implementation does not support migrating the node from one document to the other The exception codes defined in the DOM recommendation map to the exceptions described above according to this table Constant Exception DOMSTRING_SIZE_ERR DomstringSizeErr HIERARCHY_REQUEST_ERR HierarchyRequestErr INDEX_SIZE_ERR IndexSizeErr INUSE_ATTRIBUTE_ERR InuseAttributeErr INVALID_ACCESS_ERR InvalidAccessErr INVALID_CHARACTER_ERR InvalidCharacterErr INVALID_MODIFICATION_ERR InvalidModificationErr INVALID_STATE_ERR InvalidStateErr NAMESPACE_ERR NamespaceErr NOT_FOUND_ERR NotFoundErr NOT_SUPPORTED_ERR NotSupportedErr NO_DATA_ALLOWED_ERR NoDataAllowedErr NO_MODIFICATION_ALLOWED_ERR NoModificationAllowedErr SYNTAX_ERR SyntaxErr WRONG_DOCUMENT_ERR WrongDocumentErr Conformance This section describes the conformance requirements and relationships between the Python DOM API the W3C DOM recommendations and the OMG IDL mapping for Python Type Mapping The IDL types used in the DOM specification are mapped to Python types according to the following table IDL Type Python Type boolean bool or int int int long int int unsigned int int DOMString str or bytes null None Accessor Methods The mapping from OMG IDL to Python defines accessor functions for IDL attribute declarations in much the way the Java mapping does Mapping the IDL declarations readonly attribute string someValue attribute string anotherValue yields three accessor functions a get method for someValue _get_someValue and get and set methods for anotherValue _get_anotherValue and _set_anotherValue The mapping in particular does not require that the IDL attributes are accessible as normal Python attributes object someValue is not required to work and may raise an AttributeError The Python DOM API however does require that normal attribute access work This means that the typical surrogates generated by Python IDL compilers are not likely to work and wrapper objects may be needed on the client if the DOM objects are accessed via CORBA While this does require some additional consideration for CORBA DOM clients the implementers with experience using DOM over CORBA from Python do not consider this a problem Attributes that are declared readonly may not restrict write access in all DOM implementations In the Python DOM API accessor functions are not required If provided they should take the form defined by the Python IDL mapping but these methods are considered unnecessary since the attributes are accessible directly from Python Set accessors should never be provided for readonly attributes The IDL definitions do not fully embody the requirements of the W3C DOM API such as the notion of certain objects such as the return value of getElementsByTagName being live The Python DOM API does not require implementations to enforce such requirements,en
2493,nis Interface to Sun s NIS Yellow Pages Deprecated since version 3 11 will be removed in version 3 13 The nis module is deprecated see PEP 594 for details The nis module gives a thin wrapper around the NIS library useful for central administration of several hosts Because NIS exists only on Unix systems this module is only available for Unix Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information The nis module defines the following functions nis match key mapname domain default_domain Return the match for key in map mapname or raise an error nis error if there is none Both should be strings key is 8 bit clean Return value is an arbitrary array of bytes may contain NULL and other joys Note that mapname is first checked if it is an alias to another name The domain argument allows overriding the NIS domain used for the lookup If unspecified lookup is in the default NIS domain nis cat mapname domain default_domain Return a dictionary mapping key to value such that match key mapname value Note that both keys and values of the dictionary are arbitrary arrays of bytes Note that mapname is first checked if it is an alias to another name The domain argument allows overriding the NIS domain used for the lookup If unspecified lookup is in the default NIS domain nis maps domain default_domain Return a list of all valid maps The domain argument allows overriding the NIS domain used for the lookup If unspecified lookup is in the default NIS domain nis get_default_domain Return the system default NIS domain The nis module defines the following exception exception nis error An error raised when a NIS function returns an error code,en
2494,collections Container datatypes Source code Lib collections __init__ py This module implements specialized container datatypes providing alternatives to Python s general purpose built in containers dict list set and tuple namedtuple factory function for creating tuple subclasses with named fields deque list like container with fast appends and pops on either end ChainMap dict like class for creating a single view of multiple mappings Counter dict subclass for counting hashable objects OrderedDict dict subclass that remembers the order entries were added defaultdict dict subclass that calls a factory function to supply missing values UserDict wrapper around dictionary objects for easier dict subclassing UserList wrapper around list objects for easier list subclassing UserString wrapper around string objects for easier string subclassing ChainMap objects New in version 3 3 A ChainMap class is provided for quickly linking a number of mappings so they can be treated as a single unit It is often much faster than creating a new dictionary and running multiple update calls The class can be used to simulate nested scopes and is useful in templating class collections ChainMap maps A ChainMap groups multiple dicts or other mappings together to create a single updateable view If no maps are specified a single empty dictionary is provided so that a new chain always has at least one mapping The underlying mappings are stored in a list That list is public and can be accessed or updated using the maps attribute There is no other state Lookups search the underlying mappings successively until a key is found In contrast writes updates and deletions only operate on the first mapping A ChainMap incorporates the underlying mappings by reference So if one of the underlying mappings gets updated those changes will be reflected in ChainMap All of the usual dictionary methods are supported In addition there is a maps attribute a method for creating new subcontexts and a property for accessing all but the first mapping maps A user updateable list of mappings The list is ordered from first searched to last searched It is the only stored state and can be modified to change which mappings are searched The list should always contain at least one mapping new_child m None kwargs Returns a new ChainMap containing a new map followed by all of the maps in the current instance If m is specified it becomes the new map at the front of the list of mappings if not specified an empty dict is used so that a call to d new_child is equivalent to ChainMap d maps If any keyword arguments are specified they update passed map or new empty dict This method is used for creating subcontexts that can be updated without altering values in any of the parent mappings Changed in version 3 4 The optional m parameter was added Changed in version 3 10 Keyword arguments support was added parents Property returning a new ChainMap containing all of the maps in the current instance except the first one This is useful for skipping the first map in the search Use cases are similar to those for the nonlocal keyword used in nested scopes The use cases also parallel those for the built in super function A reference to d parents is equivalent to ChainMap d maps 1 Note the iteration order of a ChainMap is determined by scanning the mappings last to first baseline music bach art rembrandt adjustments art van gogh opera carmen list ChainMap adjustments baseline music art opera This gives the same ordering as a series of dict update calls starting with the last mapping combined baseline copy combined update adjustments list combined music art opera Changed in version 3 9 Added support for and operators specified in PEP 584 See also The MultiContext class in the Enthought CodeTools package has options to support writing to any mapping in the chain Django s Context class for templating is a read only chain of mappings It also features pushing and popping of contexts similar to the new_child method and the parents property The Nested Contexts recipe has options to control whether writes and oth,en
2495,er mutations apply only to the first mapping or to any mapping in the chain A greatly simplified read only version of Chainmap ChainMap Examples and Recipes This section shows various approaches to working with chained maps Example of simulating Python s internal lookup chain import builtins pylookup ChainMap locals globals vars builtins Example of letting user specified command line arguments take precedence over environment variables which in turn take precedence over default values import os argparse defaults color red user guest parser argparse ArgumentParser parser add_argument u user parser add_argument c color namespace parser parse_args command_line_args k v for k v in vars namespace items if v is not None combined ChainMap command_line_args os environ defaults print combined color print combined user Example patterns for using the ChainMap class to simulate nested contexts c ChainMap Create root context d c new_child Create nested child context e c new_child Child of c independent from d e maps 0 Current context dictionary like Python s locals e maps 1 Root context like Python s globals e parents Enclosing context chain like Python s nonlocals d x 1 Set value in current context d x Get first key in the chain of contexts del d x Delete from current context list d All nested values k in d Check all nested values len d Number of nested values d items All nested items dict d Flatten into a regular dictionary The ChainMap class only makes updates writes and deletions to the first mapping in the chain while lookups will search the full chain However if deep writes and deletions are desired it is easy to make a subclass that updates keys found deeper in the chain class DeepChainMap ChainMap Variant of ChainMap that allows direct updates to inner scopes def __setitem__ self key value for mapping in self maps if key in mapping mapping key value return self maps 0 key value def __delitem__ self key for mapping in self maps if key in mapping del mapping key return raise KeyError key d DeepChainMap zebra black elephant blue lion yellow d lion orange update an existing key two levels down d snake red new keys get added to the topmost dict del d elephant remove an existing key one level down d display result DeepChainMap zebra black snake red lion orange Counter objects A counter tool is provided to support convenient and rapid tallies For example Tally occurrences of words in a list cnt Counter for word in red blue red green blue blue cnt word 1 cnt Counter blue 3 red 2 green 1 Find the ten most common words in Hamlet import re words re findall r w open hamlet txt read lower Counter words most_common 10 the 1143 and 966 to 762 of 669 i 631 you 554 a 546 my 514 hamlet 471 in 451 class collections Counter iterable or mapping A Counter is a dict subclass for counting hashable objects It is a collection where elements are stored as dictionary keys and their counts are stored as dictionary values Counts are allowed to be any integer value including zero or negative counts The Counter class is similar to bags or multisets in other languages Elements are counted from an iterable or initialized from another mapping or counter c Counter a new empty counter c Counter gallahad a new counter from an iterable c Counter red 4 blue 2 a new counter from a mapping c Counter cats 4 dogs 8 a new counter from keyword args Counter objects have a dictionary interface except that they return a zero count for missing items instead of raising a KeyError c Counter eggs ham c bacon count of a missing element is zero 0 Setting a count to zero does not remove an element from a counter Use del to remove it entirely c sausage 0 counter entry with a zero count del c sausage del actually removes the entry New in version 3 1 Changed in version 3 7 As a dict subclass Counter inherited the capability to remember insertion order Math operations on Counter objects also preserve order Results are ordered according to when an element is first encountered in the left operand and then by the order encountered in the right operand Counter objects support additional m,en
2496,ethods beyond those available for all dictionaries elements Return an iterator over elements repeating each as many times as its count Elements are returned in the order first encountered If an element s count is less than one elements will ignore it c Counter a 4 b 2 c 0 d 2 sorted c elements a a a a b b most_common n Return a list of the n most common elements and their counts from the most common to the least If n is omitted or None most_common returns all elements in the counter Elements with equal counts are ordered in the order first encountered Counter abracadabra most_common 3 a 5 b 2 r 2 subtract iterable or mapping Elements are subtracted from an iterable or from another mapping or counter Like dict update but subtracts counts instead of replacing them Both inputs and outputs may be zero or negative c Counter a 4 b 2 c 0 d 2 d Counter a 1 b 2 c 3 d 4 c subtract d c Counter a 3 b 0 c 3 d 6 New in version 3 2 total Compute the sum of the counts c Counter a 10 b 5 c 0 c total 15 New in version 3 10 The usual dictionary methods are available for Counter objects except for two which work differently for counters fromkeys iterable This class method is not implemented for Counter objects update iterable or mapping Elements are counted from an iterable or added in from another mapping or counter Like dict update but adds counts instead of replacing them Also the iterable is expected to be a sequence of elements not a sequence of key value pairs Counters support rich comparison operators for equality subset and superset relationships All of those tests treat missing elements as having zero counts so that Counter a 1 Counter a 1 b 0 returns true Changed in version 3 10 Rich comparison operations were added Changed in version 3 10 In equality tests missing elements are treated as having zero counts Formerly Counter a 3 and Counter a 3 b 0 were considered distinct Common patterns for working with Counter objects c total total of all counts c clear reset all counts list c list unique elements set c convert to a set dict c convert to a regular dictionary c items convert to a list of elem cnt pairs Counter dict list_of_pairs convert from a list of elem cnt pairs c most_common n 1 1 n least common elements c remove zero and negative counts Several mathematical operations are provided for combining Counter objects to produce multisets counters that have counts greater than zero Addition and subtraction combine counters by adding or subtracting the counts of corresponding elements Intersection and union return the minimum and maximum of corresponding counts Equality and inclusion compare corresponding counts Each operation can accept inputs with signed counts but the output will exclude results with counts of zero or less c Counter a 3 b 1 d Counter a 1 b 2 c d add two counters together c x d x Counter a 4 b 3 c d subtract keeping only positive counts Counter a 2 c d intersection min c x d x Counter a 1 b 1 c d union max c x d x Counter a 3 b 2 c d equality c x d x False c d inclusion c x d x False Unary addition and subtraction are shortcuts for adding an empty counter or subtracting from an empty counter c Counter a 2 b 4 c Counter a 2 c Counter b 4 New in version 3 3 Added support for unary plus unary minus and in place multiset operations Note Counters were primarily designed to work with positive integers to represent running counts however care was taken to not unnecessarily preclude use cases needing other types or negative values To help with those use cases this section documents the minimum range and type restrictions The Counter class itself is a dictionary subclass with no restrictions on its keys and values The values are intended to be numbers representing counts but you could store anything in the value field The most_common method requires only that the values be orderable For in place operations such as c key 1 the value type need only support addition and subtraction So fractions floats and decimals would work and negative values are supported The same is also true for update and subtract which allow negative a,en
2497,nd zero values for both inputs and outputs The multiset methods are designed only for use cases with positive values The inputs may be negative or zero but only outputs with positive values are created There are no type restrictions but the value type needs to support addition subtraction and comparison The elements method requires integer counts It ignores zero and negative counts See also Bag class in Smalltalk Wikipedia entry for Multisets C multisets tutorial with examples For mathematical operations on multisets and their use cases see Knuth Donald The Art of Computer Programming Volume II Section 4 6 3 Exercise 19 To enumerate all distinct multisets of a given size over a given set of elements see itertools combinations_with_replacement map Counter combinations_with_replacement ABC 2 AA AB AC BB BC CC deque objects class collections deque iterable maxlen Returns a new deque object initialized left to right using append with data from iterable If iterable is not specified the new deque is empty Deques are a generalization of stacks and queues the name is pronounced deck and is short for double ended queue Deques support thread safe memory efficient appends and pops from either side of the deque with approximately the same O 1 performance in either direction Though list objects support similar operations they are optimized for fast fixed length operations and incur O n memory movement costs for pop 0 and insert 0 v operations which change both the size and position of the underlying data representation If maxlen is not specified or is None deques may grow to an arbitrary length Otherwise the deque is bounded to the specified maximum length Once a bounded length deque is full when new items are added a corresponding number of items are discarded from the opposite end Bounded length deques provide functionality similar to the tail filter in Unix They are also useful for tracking transactions and other pools of data where only the most recent activity is of interest Deque objects support the following methods append x Add x to the right side of the deque appendleft x Add x to the left side of the deque clear Remove all elements from the deque leaving it with length 0 copy Create a shallow copy of the deque New in version 3 5 count x Count the number of deque elements equal to x New in version 3 2 extend iterable Extend the right side of the deque by appending elements from the iterable argument extendleft iterable Extend the left side of the deque by appending elements from iterable Note the series of left appends results in reversing the order of elements in the iterable argument index x start stop Return the position of x in the deque at or after index start and before index stop Returns the first match or raises ValueError if not found New in version 3 5 insert i x Insert x into the deque at position i If the insertion would cause a bounded deque to grow beyond maxlen an IndexError is raised New in version 3 5 pop Remove and return an element from the right side of the deque If no elements are present raises an IndexError popleft Remove and return an element from the left side of the deque If no elements are present raises an IndexError remove value Remove the first occurrence of value If not found raises a ValueError reverse Reverse the elements of the deque in place and then return None New in version 3 2 rotate n 1 Rotate the deque n steps to the right If n is negative rotate to the left When the deque is not empty rotating one step to the right is equivalent to d appendleft d pop and rotating one step to the left is equivalent to d append d popleft Deque objects also provide one read only attribute maxlen Maximum size of a deque or None if unbounded New in version 3 1 In addition to the above deques support iteration pickling len d reversed d copy copy d copy deepcopy d membership testing with the in operator and subscript references such as d 0 to access the first element Indexed access is O 1 at both ends but slows to O n in the middle For fast random access use lists instead Starting in version 3 5 deques supp,en
2498,ort __add__ __mul__ and __imul__ Example from collections import deque d deque ghi make a new deque with three items for elem in d iterate over the deque s elements print elem upper G H I d append j add a new entry to the right side d appendleft f add a new entry to the left side d show the representation of the deque deque f g h i j d pop return and remove the rightmost item j d popleft return and remove the leftmost item f list d list the contents of the deque g h i d 0 peek at leftmost item g d 1 peek at rightmost item i list reversed d list the contents of a deque in reverse i h g h in d search the deque True d extend jkl add multiple elements at once d deque g h i j k l d rotate 1 right rotation d deque l g h i j k d rotate 1 left rotation d deque g h i j k l deque reversed d make a new deque in reverse order deque l k j i h g d clear empty the deque d pop cannot pop from an empty deque Traceback most recent call last File pyshell 6 line 1 in toplevel d pop IndexError pop from an empty deque d extendleft abc extendleft reverses the input order d deque c b a deque Recipes This section shows various approaches to working with deques Bounded length deques provide functionality similar to the tail filter in Unix def tail filename n 10 Return the last n lines of a file with open filename as f return deque f n Another approach to using deques is to maintain a sequence of recently added elements by appending to the right and popping to the left def moving_average iterable n 3 moving_average 40 30 50 46 39 44 40 0 42 0 45 0 43 0 https en wikipedia org wiki Moving_average it iter iterable d deque itertools islice it n 1 d appendleft 0 s sum d for elem in it s elem d popleft d append elem yield s n A round robin scheduler can be implemented with input iterators stored in a deque Values are yielded from the active iterator in position zero If that iterator is exhausted it can be removed with popleft otherwise it can be cycled back to the end with the rotate method def roundrobin iterables roundrobin ABC D EF A D E B F C iterators deque map iter iterables while iterators try while True yield next iterators 0 iterators rotate 1 except StopIteration Remove an exhausted iterator iterators popleft The rotate method provides a way to implement deque slicing and deletion For example a pure Python implementation of del d n relies on the rotate method to position elements to be popped def delete_nth d n d rotate n d popleft d rotate n To implement deque slicing use a similar approach applying rotate to bring a target element to the left side of the deque Remove old entries with popleft add new entries with extend and then reverse the rotation With minor variations on that approach it is easy to implement Forth style stack manipulations such as dup drop swap over pick rot and roll defaultdict objects class collections defaultdict default_factory None Return a new dictionary like object defaultdict is a subclass of the built in dict class It overrides one method and adds one writable instance variable The remaining functionality is the same as for the dict class and is not documented here The first argument provides the initial value for the default_factory attribute it defaults to None All remaining arguments are treated the same as if they were passed to the dict constructor including keyword arguments defaultdict objects support the following method in addition to the standard dict operations __missing__ key If the default_factory attribute is None this raises a KeyError exception with the key as argument If default_factory is not None it is called without arguments to provide a default value for the given key this value is inserted in the dictionary for the key and returned If calling default_factory raises an exception this exception is propagated unchanged This method is called by the __getitem__ method of the dict class when the requested key is not found whatever it returns or raises is then returned or raised by __getitem__ Note that __missing__ is not called for any operations besides __getitem__ This means that get will like n,en
2499,ormal dictionaries return None as a default rather than using default_factory defaultdict objects support the following instance variable default_factory This attribute is used by the __missing__ method it is initialized from the first argument to the constructor if present or to None if absent Changed in version 3 9 Added merge and update operators specified in PEP 584 defaultdict Examples Using list as the default_factory it is easy to group a sequence of key value pairs into a dictionary of lists s yellow 1 blue 2 yellow 3 blue 4 red 1 d defaultdict list for k v in s d k append v sorted d items blue 2 4 red 1 yellow 1 3 When each key is encountered for the first time it is not already in the mapping so an entry is automatically created using the default_factory function which returns an empty list The list append operation then attaches the value to the new list When keys are encountered again the look up proceeds normally returning the list for that key and the list append operation adds another value to the list This technique is simpler and faster than an equivalent technique using dict setdefault d for k v in s d setdefault k append v sorted d items blue 2 4 red 1 yellow 1 3 Setting the default_factory to int makes the defaultdict useful for counting like a bag or multiset in other languages s mississippi d defaultdict int for k in s d k 1 sorted d items i 4 m 1 p 2 s 4 When a letter is first encountered it is missing from the mapping so the default_factory function calls int to supply a default count of zero The increment operation then builds up the count for each letter The function int which always returns zero is just a special case of constant functions A faster and more flexible way to create constant functions is to use a lambda function which can supply any constant value not just zero def constant_factory value return lambda value d defaultdict constant_factory missing d update name John action ran name s action s to object s d John ran to missing Setting the default_factory to set makes the defaultdict useful for building a dictionary of sets s red 1 blue 2 red 3 blue 4 red 1 blue 4 d defaultdict set for k v in s d k add v sorted d items blue 2 4 red 1 3 namedtuple Factory Function for Tuples with Named Fields Named tuples assign meaning to each position in a tuple and allow for more readable self documenting code They can be used wherever regular tuples are used and they add the ability to access fields by name instead of position index collections namedtuple typename field_names rename False defaults None module None Returns a new tuple subclass named typename The new subclass is used to create tuple like objects that have fields accessible by attribute lookup as well as being indexable and iterable Instances of the subclass also have a helpful docstring with typename and field_names and a helpful __repr__ method which lists the tuple contents in a name value format The field_names are a sequence of strings such as x y Alternatively field_names can be a single string with each fieldname separated by whitespace and or commas for example x y or x y Any valid Python identifier may be used for a fieldname except for names starting with an underscore Valid identifiers consist of letters digits and underscores but do not start with a digit or underscore and cannot be a keyword such as class for return global pass or raise If rename is true invalid fieldnames are automatically replaced with positional names For example abc def ghi abc is converted to abc _1 ghi _3 eliminating the keyword def and the duplicate fieldname abc defaults can be None or an iterable of default values Since fields with a default value must come after any fields without a default the defaults are applied to the rightmost parameters For example if the fieldnames are x y z and the defaults are 1 2 then x will be a required argument y will default to 1 and z will default to 2 If module is defined the __module__ attribute of the named tuple is set to that value Named tuple instances do not have per instance dictionaries so they are lightw,en
2500,eight and require no more memory than regular tuples To support pickling the named tuple class should be assigned to a variable that matches typename Changed in version 3 1 Added support for rename Changed in version 3 6 The verbose and rename parameters became keyword only arguments Changed in version 3 6 Added the module parameter Changed in version 3 7 Removed the verbose parameter and the _source attribute Changed in version 3 7 Added the defaults parameter and the _field_defaults attribute Basic example Point namedtuple Point x y p Point 11 y 22 instantiate with positional or keyword arguments p 0 p 1 indexable like the plain tuple 11 22 33 x y p unpack like a regular tuple x y 11 22 p x p y fields also accessible by name 33 p readable __repr__ with a name value style Point x 11 y 22 Named tuples are especially useful for assigning field names to result tuples returned by the csv or sqlite3 modules EmployeeRecord namedtuple EmployeeRecord name age title department paygrade import csv for emp in map EmployeeRecord _make csv reader open employees csv rb print emp name emp title import sqlite3 conn sqlite3 connect companydata cursor conn cursor cursor execute SELECT name age title department paygrade FROM employees for emp in map EmployeeRecord _make cursor fetchall print emp name emp title In addition to the methods inherited from tuples named tuples support three additional methods and two attributes To prevent conflicts with field names the method and attribute names start with an underscore classmethod somenamedtuple _make iterable Class method that makes a new instance from an existing sequence or iterable t 11 22 Point _make t Point x 11 y 22 somenamedtuple _asdict Return a new dict which maps field names to their corresponding values p Point x 11 y 22 p _asdict x 11 y 22 Changed in version 3 1 Returns an OrderedDict instead of a regular dict Changed in version 3 8 Returns a regular dict instead of an OrderedDict As of Python 3 7 regular dicts are guaranteed to be ordered If the extra features of OrderedDict are required the suggested remediation is to cast the result to the desired type OrderedDict nt _asdict somenamedtuple _replace kwargs Return a new instance of the named tuple replacing specified fields with new values p Point x 11 y 22 p _replace x 33 Point x 33 y 22 for partnum record in inventory items inventory partnum record _replace price newprices partnum timestamp time now somenamedtuple _fields Tuple of strings listing the field names Useful for introspection and for creating new named tuple types from existing named tuples p _fields view the field names x y Color namedtuple Color red green blue Pixel namedtuple Pixel Point _fields Color _fields Pixel 11 22 128 255 0 Pixel x 11 y 22 red 128 green 255 blue 0 somenamedtuple _field_defaults Dictionary mapping field names to default values Account namedtuple Account type balance defaults 0 Account _field_defaults balance 0 Account premium Account type premium balance 0 To retrieve a field whose name is stored in a string use the getattr function getattr p x 11 To convert a dictionary to a named tuple use the double star operator as described in Unpacking Argument Lists d x 11 y 22 Point d Point x 11 y 22 Since a named tuple is a regular Python class it is easy to add or change functionality with a subclass Here is how to add a calculated field and a fixed width print format class Point namedtuple Point x y __slots__ property def hypot self return self x 2 self y 2 0 5 def __str__ self return Point x 6 3f y 6 3f hypot 6 3f self x self y self hypot for p in Point 3 4 Point 14 5 7 print p Point x 3 000 y 4 000 hypot 5 000 Point x 14 000 y 0 714 hypot 14 018 The subclass shown above sets __slots__ to an empty tuple This helps keep memory requirements low by preventing the creation of instance dictionaries Subclassing is not useful for adding new stored fields Instead simply create a new named tuple type from the _fields attribute Point3D namedtuple Point3D Point _fields z Docstrings can be customized by making direct assignments to the __doc__ fields Book na,en
2501,medtuple Book id title authors Book __doc__ Hardcover book in active collection Book id __doc__ 13 digit ISBN Book title __doc__ Title of first printing Book authors __doc__ List of authors sorted by last name Changed in version 3 5 Property docstrings became writeable See also See typing NamedTuple for a way to add type hints for named tuples It also provides an elegant notation using the class keyword class Component NamedTuple part_number int weight float description Optional str None See types SimpleNamespace for a mutable namespace based on an underlying dictionary instead of a tuple The dataclasses module provides a decorator and functions for automatically adding generated special methods to user defined classes OrderedDict objects Ordered dictionaries are just like regular dictionaries but have some extra capabilities relating to ordering operations They have become less important now that the built in dict class gained the ability to remember insertion order this new behavior became guaranteed in Python 3 7 Some differences from dict still remain The regular dict was designed to be very good at mapping operations Tracking insertion order was secondary The OrderedDict was designed to be good at reordering operations Space efficiency iteration speed and the performance of update operations were secondary The OrderedDict algorithm can handle frequent reordering operations better than dict As shown in the recipes below this makes it suitable for implementing various kinds of LRU caches The equality operation for OrderedDict checks for matching order A regular dict can emulate the order sensitive equality test with p q and all k1 k2 for k1 k2 in zip p q The popitem method of OrderedDict has a different signature It accepts an optional argument to specify which item is popped A regular dict can emulate OrderedDict s od popitem last True with d popitem which is guaranteed to pop the rightmost last item A regular dict can emulate OrderedDict s od popitem last False with k next iter d d pop k which will return and remove the leftmost first item if it exists OrderedDict has a move_to_end method to efficiently reposition an element to an endpoint A regular dict can emulate OrderedDict s od move_to_end k last True with d k d pop k which will move the key and its associated value to the rightmost last position A regular dict does not have an efficient equivalent for OrderedDict s od move_to_end k last False which moves the key and its associated value to the leftmost first position Until Python 3 8 dict lacked a __reversed__ method class collections OrderedDict items Return an instance of a dict subclass that has methods specialized for rearranging dictionary order New in version 3 1 popitem last True The popitem method for ordered dictionaries returns and removes a key value pair The pairs are returned in LIFO last in first out order if last is true or FIFO first in first out order if false move_to_end key last True Move an existing key to either end of an ordered dictionary The item is moved to the right end if last is true the default or to the beginning if last is false Raises KeyError if the key does not exist d OrderedDict fromkeys abcde d move_to_end b join d acdeb d move_to_end b last False join d bacde New in version 3 2 In addition to the usual mapping methods ordered dictionaries also support reverse iteration using reversed Equality tests between OrderedDict objects are order sensitive and are implemented as list od1 items list od2 items Equality tests between OrderedDict objects and other Mapping objects are order insensitive like regular dictionaries This allows OrderedDict objects to be substituted anywhere a regular dictionary is used Changed in version 3 5 The items keys and values views of OrderedDict now support reverse iteration using reversed Changed in version 3 6 With the acceptance of PEP 468 order is retained for keyword arguments passed to the OrderedDict constructor and its update method Changed in version 3 9 Added merge and update operators specified in PEP 584 OrderedDict Examples and Recipes It,en
2502, is straightforward to create an ordered dictionary variant that remembers the order the keys were last inserted If a new entry overwrites an existing entry the original insertion position is changed and moved to the end class LastUpdatedOrderedDict OrderedDict Store items in the order the keys were last added def __setitem__ self key value super __setitem__ key value self move_to_end key An OrderedDict would also be useful for implementing variants of functools lru_cache from collections import OrderedDict from time import time class TimeBoundedLRU LRU Cache that invalidates and refreshes old entries def __init__ self func maxsize 128 maxage 30 self cache OrderedDict args timestamp result self func func self maxsize maxsize self maxage maxage def __call__ self args if args in self cache self cache move_to_end args timestamp result self cache args if time timestamp self maxage return result result self func args self cache args time result if len self cache self maxsize self cache popitem 0 return result class MultiHitLRUCache LRU cache that defers caching a result until it has been requested multiple times To avoid flushing the LRU cache with one time requests we don t cache until a request has been made more than once def __init__ self func maxsize 128 maxrequests 4096 cache_after 1 self requests OrderedDict uncached_key request_count self cache OrderedDict cached_key function_result self func func self maxrequests maxrequests max number of uncached requests self maxsize maxsize max number of stored return values self cache_after cache_after def __call__ self args if args in self cache self cache move_to_end args return self cache args result self func args self requests args self requests get args 0 1 if self requests args self cache_after self requests move_to_end args if len self requests self maxrequests self requests popitem 0 else self requests pop args None self cache args result if len self cache self maxsize self cache popitem 0 return result UserDict objects The class UserDict acts as a wrapper around dictionary objects The need for this class has been partially supplanted by the ability to subclass directly from dict however this class can be easier to work with because the underlying dictionary is accessible as an attribute class collections UserDict initialdata Class that simulates a dictionary The instance s contents are kept in a regular dictionary which is accessible via the data attribute of UserDict instances If initialdata is provided data is initialized with its contents note that a reference to initialdata will not be kept allowing it to be used for other purposes In addition to supporting the methods and operations of mappings UserDict instances provide the following attribute data A real dictionary used to store the contents of the UserDict class UserList objects This class acts as a wrapper around list objects It is a useful base class for your own list like classes which can inherit from them and override existing methods or add new ones In this way one can add new behaviors to lists The need for this class has been partially supplanted by the ability to subclass directly from list however this class can be easier to work with because the underlying list is accessible as an attribute class collections UserList list Class that simulates a list The instance s contents are kept in a regular list which is accessible via the data attribute of UserList instances The instance s contents are initially set to a copy of list defaulting to the empty list list can be any iterable for example a real Python list or a UserList object In addition to supporting the methods and operations of mutable sequences UserList instances provide the following attribute data A real list object used to store the contents of the UserList class Subclassing requirements Subclasses of UserList are expected to offer a constructor which can be called with either no arguments or one argument List operations which return a new sequence attempt to create an instance of the actual implementation class To do so it assumes that the con,en
2503,structor can be called with a single parameter which is a sequence object used as a data source If a derived class does not wish to comply with this requirement all of the special methods supported by this class will need to be overridden please consult the sources for information about the methods which need to be provided in that case UserString objects The class UserString acts as a wrapper around string objects The need for this class has been partially supplanted by the ability to subclass directly from str however this class can be easier to work with because the underlying string is accessible as an attribute class collections UserString seq Class that simulates a string object The instance s content is kept in a regular string object which is accessible via the data attribute of UserString instances The instance s contents are initially set to a copy of seq The seq argument can be any object which can be converted into a string using the built in str function In addition to supporting the methods and operations of strings UserString instances provide the following attribute data A real str object used to store the contents of the UserString class Changed in version 3 5 New methods __getnewargs__ __rmod__ casefold format_map isprintable and maketrans,en
2504,Support for Perf Maps On supported platforms as of this writing only Linux the runtime can take advantage of perf map files to make Python functions visible to an external profiling tool such as perf A running process may create a file in the tmp directory which contains entries that can map a section of executable code to a name This interface is described in the documentation of the Linux Perf tool In Python these helper APIs can be used by libraries and features that rely on generating machine code on the fly Note that holding the Global Interpreter Lock GIL is not required for these APIs int PyUnstable_PerfMapState_Init void This is Unstable API It may change without warning in minor releases Open the tmp perf pid map file unless it s already opened and create a lock to ensure thread safe writes to the file provided the writes are done through PyUnstable_WritePerfMapEntry Normally there s no need to call this explicitly just use PyUnstable_WritePerfMapEntry and it will initialize the state on first call Returns 0 on success 1 on failure to create open the perf map file or 2 on failure to create a lock Check errno for more information about the cause of a failure int PyUnstable_WritePerfMapEntry const void code_addr unsigned int code_size const char entry_name This is Unstable API It may change without warning in minor releases Write one single entry to the tmp perf pid map file This function is thread safe Here is what an example entry looks like address size name 7f3529fcf759 b py bar run t py Will call PyUnstable_PerfMapState_Init before writing the entry if the perf map file is not already opened Returns 0 on success or the same error codes as PyUnstable_PerfMapState_Init on failure void PyUnstable_PerfMapState_Fini void This is Unstable API It may change without warning in minor releases Close the perf map file opened by PyUnstable_PerfMapState_Init This is called by the runtime itself during interpreter shut down In general there shouldn t be a reason to explicitly call this except to handle specific scenarios such as forking,en
2505,ftplib FTP protocol client Source code Lib ftplib py This module defines the class FTP and a few related items The FTP class implements the client side of the FTP protocol You can use this to write Python programs that perform a variety of automated FTP jobs such as mirroring other FTP servers It is also used by the module urllib request to handle URLs that use FTP For more information on FTP File Transfer Protocol see internet RFC 959 The default encoding is UTF 8 following RFC 2640 Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information Here s a sample session using the ftplib module from ftplib import FTP ftp FTP ftp us debian org connect to host default port ftp login user anonymous passwd anonymous 230 Login successful ftp cwd debian change into debian directory 250 Directory successfully changed ftp retrlines LIST list directory contents rw rw r 1 1176 1176 1063 Jun 15 10 18 README drwxr sr x 5 1176 1176 4096 Dec 19 2000 pool drwxr sr x 4 1176 1176 4096 Nov 17 2008 project drwxr xr x 3 1176 1176 4096 Oct 10 2012 tools 226 Directory send OK with open README wb as fp ftp retrbinary RETR README fp write 226 Transfer complete ftp quit 221 Goodbye Reference FTP objects class ftplib FTP host user passwd acct timeout None source_address None encoding utf 8 Return a new instance of the FTP class Parameters host str The hostname to connect to If given connect host is implicitly called by the constructor user str The username to log in with default anonymous If given login host passwd acct is implicitly called by the constructor passwd str The password to use when logging in If not given and if passwd is the empty string or a password will be automatically generated acct str Account information to be used for the ACCT FTP command Few systems implement this See RFC 959 for more details timeout float None A timeout in seconds for blocking operations like connect default the global default timeout setting source_address tuple None A 2 tuple host port for the socket to bind to as its source address before connecting encoding str The encoding for directories and filenames default utf 8 The FTP class supports the with statement e g from ftplib import FTP with FTP ftp1 at proftpd org as ftp ftp login ftp dir 230 Anonymous login ok restrictions apply dr xr xr x 9 ftp ftp 154 May 6 10 43 dr xr xr x 9 ftp ftp 154 May 6 10 43 dr xr xr x 5 ftp ftp 4096 May 6 10 43 CentOS dr xr xr x 3 ftp ftp 18 Jul 10 2008 Fedora Changed in version 3 2 Support for the with statement was added Changed in version 3 3 source_address parameter was added Changed in version 3 9 If the timeout parameter is set to be zero it will raise a ValueError to prevent the creation of a non blocking socket The encoding parameter was added and the default was changed from Latin 1 to UTF 8 to follow RFC 2640 Several FTP methods are available in two flavors one for handling text files and another for binary files The methods are named for the command which is used followed by lines for the text version or binary for the binary version FTP instances have the following methods set_debuglevel level Set the instance s debugging level as an int This controls the amount of debugging output printed The debug levels are 0 default No debug output 1 Produce a moderate amount of debug output generally a single line per request 2 or higher Produce the maximum amount of debugging output logging each line sent and received on the control connection connect host port 0 timeout None source_address None Connect to the given host and port This function should be called only once for each instance it should not be called if a host argument was given when the FTP instance was created All other FTP methods can only be called after a connection has successfully been made Parameters host str The host to connect to port int The TCP port to connect to default 21 as specified by the FTP protocol specification It is rarely needed to specify a different port number timeo,en
2506,ut float None A timeout in seconds for the connection attempt default the global default timeout setting source_address tuple None A 2 tuple host port for the socket to bind to as its source address before connecting Raises an auditing event ftplib connect with arguments self host port Changed in version 3 3 source_address parameter was added getwelcome Return the welcome message sent by the server in reply to the initial connection This message sometimes contains disclaimers or help information that may be relevant to the user login user anonymous passwd acct Log on to the connected FTP server This function should be called only once for each instance after a connection has been established it should not be called if the host and user arguments were given when the FTP instance was created Most FTP commands are only allowed after the client has logged in Parameters user str The username to log in with default anonymous passwd str The password to use when logging in If not given and if passwd is the empty string or a password will be automatically generated acct str Account information to be used for the ACCT FTP command Few systems implement this See RFC 959 for more details abort Abort a file transfer that is in progress Using this does not always work but it s worth a try sendcmd cmd Send a simple command string to the server and return the response string Raises an auditing event ftplib sendcmd with arguments self cmd voidcmd cmd Send a simple command string to the server and handle the response Return the response string if the response code corresponds to success codes in the range 200 299 Raise error_reply otherwise Raises an auditing event ftplib sendcmd with arguments self cmd retrbinary cmd callback blocksize 8192 rest None Retrieve a file in binary transfer mode Parameters cmd str An appropriate STOR command STOR filename callback callable A single parameter callable that is called for each block of data received with its single argument being the data as bytes blocksize int The maximum chunk size to read on the low level socket object created to do the actual transfer This also corresponds to the largest size of data that will be passed to callback Defaults to 8192 rest int A REST command to be sent to the server See the documentation for the rest parameter of the transfercmd method retrlines cmd callback None Retrieve a file or directory listing in the encoding specified by the encoding parameter at initialization cmd should be an appropriate RETR command see retrbinary or a command such as LIST or NLST usually just the string LIST LIST retrieves a list of files and information about those files NLST retrieves a list of file names The callback function is called for each line with a string argument containing the line with the trailing CRLF stripped The default callback prints the line to sys stdout set_pasv val Enable passive mode if val is true otherwise disable passive mode Passive mode is on by default storbinary cmd fp blocksize 8192 callback None rest None Store a file in binary transfer mode Parameters cmd str An appropriate STOR command STOR filename fp file object A file object opened in binary mode which is read until EOF using its read method in blocks of size blocksize to provide the data to be stored blocksize int The read block size Defaults to 8192 callback callable A single parameter callable that is called for each block of data sent with its single argument being the data as bytes rest int A REST command to be sent to the server See the documentation for the rest parameter of the transfercmd method Changed in version 3 2 The rest parameter was added storlines cmd fp callback None Store a file in line mode cmd should be an appropriate STOR command see storbinary Lines are read until EOF from the file object fp opened in binary mode using its readline method to provide the data to be stored callback is an optional single parameter callable that is called on each line after it is sent transfercmd cmd rest None Initiate a transfer over the data connection If the transfer is active send an EPRT o,en
2507,r PORT command and the transfer command specified by cmd and accept the connection If the server is passive send an EPSV or PASV command connect to it and start the transfer command Either way return the socket for the connection If optional rest is given a REST command is sent to the server passing rest as an argument rest is usually a byte offset into the requested file telling the server to restart sending the file s bytes at the requested offset skipping over the initial bytes Note however that the transfercmd method converts rest to a string with the encoding parameter specified at initialization but no check is performed on the string s contents If the server does not recognize the REST command an error_reply exception will be raised If this happens simply call transfercmd without a rest argument ntransfercmd cmd rest None Like transfercmd but returns a tuple of the data connection and the expected size of the data If the expected size could not be computed None will be returned as the expected size cmd and rest means the same thing as in transfercmd mlsd path facts List a directory in a standardized format by using MLSD command RFC 3659 If path is omitted the current directory is assumed facts is a list of strings representing the type of information desired e g type size perm Return a generator object yielding a tuple of two elements for every file found in path First element is the file name the second one is a dictionary containing facts about the file name Content of this dictionary might be limited by the facts argument but server is not guaranteed to return all requested facts New in version 3 3 nlst argument Return a list of file names as returned by the NLST command The optional argument is a directory to list default is the current server directory Multiple arguments can be used to pass non standard options to the NLST command Note If your server supports the command mlsd offers a better API dir argument Produce a directory listing as returned by the LIST command printing it to standard output The optional argument is a directory to list default is the current server directory Multiple arguments can be used to pass non standard options to the LIST command If the last argument is a function it is used as a callback function as for retrlines the default prints to sys stdout This method returns None Note If your server supports the command mlsd offers a better API rename fromname toname Rename file fromname on the server to toname delete filename Remove the file named filename from the server If successful returns the text of the response otherwise raises error_perm on permission errors or error_reply on other errors cwd pathname Set the current directory on the server mkd pathname Create a new directory on the server pwd Return the pathname of the current directory on the server rmd dirname Remove the directory named dirname on the server size filename Request the size of the file named filename on the server On success the size of the file is returned as an integer otherwise None is returned Note that the SIZE command is not standardized but is supported by many common server implementations quit Send a QUIT command to the server and close the connection This is the polite way to close a connection but it may raise an exception if the server responds with an error to the QUIT command This implies a call to the close method which renders the FTP instance useless for subsequent calls see below close Close the connection unilaterally This should not be applied to an already closed connection such as after a successful call to quit After this call the FTP instance should not be used any more after a call to close or quit you cannot reopen the connection by issuing another login method FTP_TLS objects class ftplib FTP_TLS host user passwd acct context None timeout None source_address None encoding utf 8 An FTP subclass which adds TLS support to FTP as described in RFC 4217 Connect to port 21 implicitly securing the FTP control connection before authenticating Note The user must explicitly secure the data connec,en
2508,tion by calling the prot_p method Parameters host str The hostname to connect to If given connect host is implicitly called by the constructor user str The username to log in with default anonymous If given login host passwd acct is implicitly called by the constructor passwd str The password to use when logging in If not given and if passwd is the empty string or a password will be automatically generated acct str Account information to be used for the ACCT FTP command Few systems implement this See RFC 959 for more details context ssl SSLContext An SSL context object which allows bundling SSL configuration options certificates and private keys into a single potentially long lived structure Please read Security considerations for best practices timeout float None A timeout in seconds for blocking operations like connect default the global default timeout setting source_address tuple None A 2 tuple host port for the socket to bind to as its source address before connecting encoding str The encoding for directories and filenames default utf 8 New in version 3 2 Changed in version 3 3 Added the source_address parameter Changed in version 3 4 The class now supports hostname check with ssl SSLContext check_hostname and Server Name Indication see ssl HAS_SNI Changed in version 3 9 If the timeout parameter is set to be zero it will raise a ValueError to prevent the creation of a non blocking socket The encoding parameter was added and the default was changed from Latin 1 to UTF 8 to follow RFC 2640 Changed in version 3 12 The deprecated keyfile and certfile parameters have been removed Here s a sample session using the FTP_TLS class ftps FTP_TLS ftp pureftpd org ftps login 230 Anonymous user logged in ftps prot_p 200 Data protection level set to private ftps nlst 6jack OpenBSD antilink blogbench bsdcam clockspeed djbdns jedi docs eaccelerator jedi favicon ico francotone fugu ignore libpuzzle metalog minidentd misc mysql udf global user variables php jenkins hash php skein hash php webdav phpaudit phpbench pincaster ping posto pub public public_keys pure ftpd qscan qtc sharedance skycache sound tmp ucarp FTP_TLS class inherits from FTP defining these additional methods and attributes ssl_version The SSL version to use defaults to ssl PROTOCOL_SSLv23 auth Set up a secure control connection by using TLS or SSL depending on what is specified in the ssl_version attribute Changed in version 3 4 The method now supports hostname check with ssl SSLContext check_hostname and Server Name Indication see ssl HAS_SNI ccc Revert control channel back to plaintext This can be useful to take advantage of firewalls that know how to handle NAT with non secure FTP without opening fixed ports New in version 3 3 prot_p Set up secure data connection prot_c Set up clear text data connection Module variables exception ftplib error_reply Exception raised when an unexpected reply is received from the server exception ftplib error_temp Exception raised when an error code signifying a temporary error response codes in the range 400 499 is received exception ftplib error_perm Exception raised when an error code signifying a permanent error response codes in the range 500 599 is received exception ftplib error_proto Exception raised when a reply is received from the server that does not fit the response specifications of the File Transfer Protocol i e begin with a digit in the range 1 5 ftplib all_errors The set of all exceptions as a tuple that methods of FTP instances may raise as a result of problems with the FTP connection as opposed to programming errors made by the caller This set includes the four exceptions listed above as well as OSError and EOFError See also Module netrc Parser for the netrc file format The file netrc is typically used by FTP clients to load user authentication information before prompting the user,en
2509,Runners Source code Lib asyncio runners py This section outlines high level asyncio primitives to run asyncio code They are built on top of an event loop with the aim to simplify async code usage for common wide spread scenarios Running an asyncio Program Runner context manager Handling Keyboard Interruption Running an asyncio Program asyncio run coro debug None loop_factory None Execute the coroutine coro and return the result This function runs the passed coroutine taking care of managing the asyncio event loop finalizing asynchronous generators and closing the executor This function cannot be called when another asyncio event loop is running in the same thread If debug is True the event loop will be run in debug mode False disables debug mode explicitly None is used to respect the global Debug Mode settings If loop_factory is not None it is used to create a new event loop otherwise asyncio new_event_loop is used The loop is closed at the end This function should be used as a main entry point for asyncio programs and should ideally only be called once It is recommended to use loop_factory to configure the event loop instead of policies The executor is given a timeout duration of 5 minutes to shutdown If the executor hasn t finished within that duration a warning is emitted and the executor is closed Example async def main await asyncio sleep 1 print hello asyncio run main New in version 3 7 Changed in version 3 9 Updated to use loop shutdown_default_executor Changed in version 3 10 debug is None by default to respect the global debug mode settings Changed in version 3 12 Added loop_factory parameter Runner context manager class asyncio Runner debug None loop_factory None A context manager that simplifies multiple async function calls in the same context Sometimes several top level async functions should be called in the same event loop and contextvars Context If debug is True the event loop will be run in debug mode False disables debug mode explicitly None is used to respect the global Debug Mode settings loop_factory could be used for overriding the loop creation It is the responsibility of the loop_factory to set the created loop as the current one By default asyncio new_event_loop is used and set as current event loop with asyncio set_event_loop if loop_factory is None Basically asyncio run example can be rewritten with the runner usage async def main await asyncio sleep 1 print hello with asyncio Runner as runner runner run main New in version 3 11 run coro context None Run a coroutine coro in the embedded loop Return the coroutine s result or raise its exception An optional keyword only context argument allows specifying a custom contextvars Context for the coro to run in The runner s default context is used if None This function cannot be called when another asyncio event loop is running in the same thread close Close the runner Finalize asynchronous generators shutdown default executor close the event loop and release embedded contextvars Context get_loop Return the event loop associated with the runner instance Note Runner uses the lazy initialization strategy its constructor doesn t initialize underlying low level structures Embedded loop and context are created at the with body entering or the first call of run or get_loop Handling Keyboard Interruption New in version 3 11 When signal SIGINT is raised by Ctrl C KeyboardInterrupt exception is raised in the main thread by default However this doesn t work with asyncio because it can interrupt asyncio internals and can hang the program from exiting To mitigate this issue asyncio handles signal SIGINT as follows 1 asyncio Runner run installs a custom signal SIGINT handler before any user code is executed and removes it when exiting from the function 2 The Runner creates the main task for the passed coroutine for its execution 3 When signal SIGINT is raised by Ctrl C the custom signal handler cancels the main task by calling asyncio Task cancel which raises asyncio CancelledError inside the main task This causes the Python stack to unwind try except and try final,en
2510,ly blocks can be used for resource cleanup After the main task is cancelled asyncio Runner run raises KeyboardInterrupt 4 A user could write a tight loop which cannot be interrupted by asyncio Task cancel in which case the second following Ctrl C immediately raises the KeyboardInterrupt without cancelling the main task,en
2511,Abstract Objects Layer The functions in this chapter interact with Python objects regardless of their type or with wide classes of object types e g all numerical types or all sequence types When used on object types for which they do not apply they will raise a Python exception It is not possible to use these functions on objects that are not properly initialized such as a list object that has been created by PyList_New but whose items have not been set to some non NULL value yet Object Protocol Call Protocol The tp_call Protocol The Vectorcall Protocol Recursion Control Vectorcall Support API Object Calling API Call Support API Number Protocol Sequence Protocol Mapping Protocol Iterator Protocol Buffer Protocol Buffer structure Buffer request types request independent fields readonly format shape strides suboffsets contiguity requests compound requests Complex arrays NumPy style shape and strides PIL style shape strides and suboffsets Buffer related functions Old Buffer Protocol,en
2512,Multimedia Services The modules described in this chapter implement various algorithms or interfaces that are mainly useful for multimedia applications They are available at the discretion of the installation Here s an overview wave Read and write WAV files Wave_read Objects Wave_write Objects colorsys Conversions between color systems,en
2513,14 Interactive Input Editing and History Substitution Some versions of the Python interpreter support editing of the current input line and history substitution similar to facilities found in the Korn shell and the GNU Bash shell This is implemented using the GNU Readline library which supports various styles of editing This library has its own documentation which we won t duplicate here 14 1 Tab Completion and History Editing Completion of variable and module names is automatically enabled at interpreter startup so that the Tab key invokes the completion function it looks at Python statement names the current local variables and the available module names For dotted expressions such as string a it will evaluate the expression up to the final and then suggest completions from the attributes of the resulting object Note that this may execute application defined code if an object with a __getattr__ method is part of the expression The default configuration also saves your history into a file named python_history in your user directory The history will be available again during the next interactive interpreter session 14 2 Alternatives to the Interactive Interpreter This facility is an enormous step forward compared to earlier versions of the interpreter however some wishes are left It would be nice if the proper indentation were suggested on continuation lines the parser knows if an indent token is required next The completion mechanism might use the interpreter s symbol table A command to check or even suggest matching parentheses quotes etc would also be useful One alternative enhanced interactive interpreter that has been around for quite some time is IPython which features tab completion object exploration and advanced history management It can also be thoroughly customized and embedded into other applications Another similar enhanced interactive environment is bpython,en
2514,File Objects These APIs are a minimal emulation of the Python 2 C API for built in file objects which used to rely on the buffered I O FILE support from the C standard library In Python 3 files and streams use the new io module which defines several layers over the low level unbuffered I O of the operating system The functions described below are convenience C wrappers over these new APIs and meant mostly for internal error reporting in the interpreter third party code is advised to access the io APIs instead PyObject PyFile_FromFd int fd const char name const char mode int buffering const char encoding const char errors const char newline int closefd Return value New reference Part of the Stable ABI Create a Python file object from the file descriptor of an already opened file fd The arguments name encoding errors and newline can be NULL to use the defaults buffering can be 1 to use the default name is ignored and kept for backward compatibility Return NULL on failure For a more comprehensive description of the arguments please refer to the io open function documentation Warning Since Python streams have their own buffering layer mixing them with OS level file descriptors can produce various issues such as unexpected ordering of data Changed in version 3 2 Ignore name attribute int PyObject_AsFileDescriptor PyObject p Part of the Stable ABI Return the file descriptor associated with p as an int If the object is an integer its value is returned If not the object s fileno method is called if it exists the method must return an integer which is returned as the file descriptor value Sets an exception and returns 1 on failure PyObject PyFile_GetLine PyObject p int n Return value New reference Part of the Stable ABI Equivalent to p readline n this function reads one line from the object p p may be a file object or any object with a readline method If n is 0 exactly one line is read regardless of the length of the line If n is greater than 0 no more than n bytes will be read from the file a partial line can be returned In both cases an empty string is returned if the end of the file is reached immediately If n is less than 0 however one line is read regardless of length but EOFError is raised if the end of the file is reached immediately int PyFile_SetOpenCodeHook Py_OpenCodeHookFunction handler Overrides the normal behavior of io open_code to pass its parameter through the provided handler The handler is a function of type type Py_OpenCodeHookFunction Equivalent of PyObject PyObject path void userData where path is guaranteed to be PyUnicodeObject The userData pointer is passed into the hook function Since hook functions may be called from different runtimes this pointer should not refer directly to Python state As this hook is intentionally used during import avoid importing new modules during its execution unless they are known to be frozen or available in sys modules Once a hook has been set it cannot be removed or replaced and later calls to PyFile_SetOpenCodeHook will fail On failure the function returns 1 and sets an exception if the interpreter has been initialized This function is safe to call before Py_Initialize Raises an auditing event setopencodehook with no arguments New in version 3 8 int PyFile_WriteObject PyObject obj PyObject p int flags Part of the Stable ABI Write object obj to file object p The only supported flag for flags is Py_PRINT_RAW if given the str of the object is written instead of the repr Return 0 on success or 1 on failure the appropriate exception will be set int PyFile_WriteString const char s PyObject p Part of the Stable ABI Write string s to file object p Return 0 on success or 1 on failure the appropriate exception will be set,en
2515,Objects for Type Hinting Various built in types for type hinting are provided Currently two types exist GenericAlias and Union Only GenericAlias is exposed to C PyObject Py_GenericAlias PyObject origin PyObject args Part of the Stable ABI since version 3 9 Create a GenericAlias object Equivalent to calling the Python class types GenericAlias The origin and args arguments set the GenericAlias s __origin__ and __args__ attributes respectively origin should be a PyTypeObject and args can be a PyTupleObject or any PyObject If args passed is not a tuple a 1 tuple is automatically constructed and __args__ is set to args Minimal checking is done for the arguments so the function will succeed even if origin is not a type The GenericAlias s __parameters__ attribute is constructed lazily from __args__ On failure an exception is raised and NULL is returned Here s an example of how to make an extension type generic static PyMethodDef my_obj_methods Other methods __class_getitem__ Py_GenericAlias METH_O METH_CLASS See PEP 585 See also The data model method __class_getitem__ New in version 3 9 PyTypeObject Py_GenericAliasType Part of the Stable ABI since version 3 9 The C type of the object returned by Py_GenericAlias Equivalent to types GenericAlias in Python New in version 3 9,en
2516,pwd The password database This module provides access to the Unix user account and password database It is available on all Unix versions Availability Unix not Emscripten not WASI Password database entries are reported as a tuple like object whose attributes correspond to the members of the passwd structure Attribute field below see pwd h Index Attribute Meaning 0 pw_name Login name 1 pw_passwd Optional encrypted password 2 pw_uid Numerical user ID 3 pw_gid Numerical group ID 4 pw_gecos User name or comment field 5 pw_dir User home directory 6 pw_shell User command interpreter The uid and gid items are integers all others are strings KeyError is raised if the entry asked for cannot be found Note In traditional Unix the field pw_passwd usually contains a password encrypted with a DES derived algorithm see module crypt However most modern unices use a so called shadow password system On those unices the pw_passwd field only contains an asterisk or the letter x where the encrypted password is stored in a file etc shadow which is not world readable Whether the pw_passwd field contains anything useful is system dependent If available the spwd module should be used where access to the encrypted password is required It defines the following items pwd getpwuid uid Return the password database entry for the given numeric user ID pwd getpwnam name Return the password database entry for the given user name pwd getpwall Return a list of all available password database entries in arbitrary order See also Module grp An interface to the group database similar to this Module spwd An interface to the shadow password database similar to this,en
2517,Exception Handling The functions described in this chapter will let you handle and raise Python exceptions It is important to understand some of the basics of Python exception handling It works somewhat like the POSIX errno variable there is a global indicator per thread of the last error that occurred Most C API functions don t clear this on success but will set it to indicate the cause of the error on failure Most C API functions also return an error indicator usually NULL if they are supposed to return a pointer or 1 if they return an integer exception the PyArg_ functions return 1 for success and 0 for failure Concretely the error indicator consists of three object pointers the exception s type the exception s value and the traceback object Any of those pointers can be NULL if non set although some combinations are forbidden for example you can t have a non NULL traceback if the exception type is NULL When a function must fail because some function it called failed it generally doesn t set the error indicator the function it called already set it It is responsible for either handling the error and clearing the exception or returning after cleaning up any resources it holds such as object references or memory allocations it should not continue normally if it is not prepared to handle the error If returning due to an error it is important to indicate to the caller that an error has been set If the error is not handled or carefully propagated additional calls into the Python C API may not behave as intended and may fail in mysterious ways Note The error indicator is not the result of sys exc_info The former corresponds to an exception that is not yet caught and is therefore still propagating while the latter returns an exception after it is caught and has therefore stopped propagating Printing and clearing void PyErr_Clear Part of the Stable ABI Clear the error indicator If the error indicator is not set there is no effect void PyErr_PrintEx int set_sys_last_vars Part of the Stable ABI Print a standard traceback to sys stderr and clear the error indicator Unless the error is a SystemExit in that case no traceback is printed and the Python process will exit with the error code specified by the SystemExit instance Call this function only when the error indicator is set Otherwise it will cause a fatal error If set_sys_last_vars is nonzero the variable sys last_exc is set to the printed exception For backwards compatibility the deprecated variables sys last_type sys last_value and sys last_traceback are also set to the type value and traceback of this exception respectively Changed in version 3 12 The setting of sys last_exc was added void PyErr_Print Part of the Stable ABI Alias for PyErr_PrintEx 1 void PyErr_WriteUnraisable PyObject obj Part of the Stable ABI Call sys unraisablehook using the current exception and obj argument This utility function prints a warning message to sys stderr when an exception has been set but it is impossible for the interpreter to actually raise the exception It is used for example when an exception occurs in an __del__ method The function is called with a single argument obj that identifies the context in which the unraisable exception occurred If possible the repr of obj will be printed in the warning message If obj is NULL only the traceback is printed An exception must be set when calling this function Changed in version 3 4 Print a traceback Print only traceback if obj is NULL Changed in version 3 8 Use sys unraisablehook void PyErr_DisplayException PyObject exc Part of the Stable ABI since version 3 12 Print the standard traceback display of exc to sys stderr including chained exceptions and notes New in version 3 12 Raising exceptions These functions help you set the current thread s error indicator For convenience some of these functions will always return a NULL pointer for use in a return statement void PyErr_SetString PyObject type const char message Part of the Stable ABI This is the most common way to set the error indicator The first argument specifies the exception type it is n,en
2518,ormally one of the standard exceptions e g PyExc_RuntimeError You need not create a new strong reference to it e g with Py_INCREF The second argument is an error message it is decoded from utf 8 void PyErr_SetObject PyObject type PyObject value Part of the Stable ABI This function is similar to PyErr_SetString but lets you specify an arbitrary Python object for the value of the exception PyObject PyErr_Format PyObject exception const char format Return value Always NULL Part of the Stable ABI This function sets the error indicator and returns NULL exception should be a Python exception class The format and subsequent parameters help format the error message they have the same meaning and values as in PyUnicode_FromFormat format is an ASCII encoded string PyObject PyErr_FormatV PyObject exception const char format va_list vargs Return value Always NULL Part of the Stable ABI since version 3 5 Same as PyErr_Format but taking a va_list argument rather than a variable number of arguments New in version 3 5 void PyErr_SetNone PyObject type Part of the Stable ABI This is a shorthand for PyErr_SetObject type Py_None int PyErr_BadArgument Part of the Stable ABI This is a shorthand for PyErr_SetString PyExc_TypeError message where message indicates that a built in operation was invoked with an illegal argument It is mostly for internal use PyObject PyErr_NoMemory Return value Always NULL Part of the Stable ABI This is a shorthand for PyErr_SetNone PyExc_MemoryError it returns NULL so an object allocation function can write return PyErr_NoMemory when it runs out of memory PyObject PyErr_SetFromErrno PyObject type Return value Always NULL Part of the Stable ABI This is a convenience function to raise an exception when a C library function has returned an error and set the C variable errno It constructs a tuple object whose first item is the integer errno value and whose second item is the corresponding error message gotten from strerror and then calls PyErr_SetObject type object On Unix when the errno value is EINTR indicating an interrupted system call this calls PyErr_CheckSignals and if that set the error indicator leaves it set to that The function always returns NULL so a wrapper function around a system call can write return PyErr_SetFromErrno type when the system call returns an error PyObject PyErr_SetFromErrnoWithFilenameObject PyObject type PyObject filenameObject Return value Always NULL Part of the Stable ABI Similar to PyErr_SetFromErrno with the additional behavior that if filenameObject is not NULL it is passed to the constructor of type as a third parameter In the case of OSError exception this is used to define the filename attribute of the exception instance PyObject PyErr_SetFromErrnoWithFilenameObjects PyObject type PyObject filenameObject PyObject filenameObject2 Return value Always NULL Part of the Stable ABI since version 3 7 Similar to PyErr_SetFromErrnoWithFilenameObject but takes a second filename object for raising errors when a function that takes two filenames fails New in version 3 4 PyObject PyErr_SetFromErrnoWithFilename PyObject type const char filename Return value Always NULL Part of the Stable ABI Similar to PyErr_SetFromErrnoWithFilenameObject but the filename is given as a C string filename is decoded from the filesystem encoding and error handler PyObject PyErr_SetFromWindowsErr int ierr Return value Always NULL Part of the Stable ABI on Windows since version 3 7 This is a convenience function to raise WindowsError If called with ierr of 0 the error code returned by a call to GetLastError is used instead It calls the Win32 function FormatMessage to retrieve the Windows description of error code given by ierr or GetLastError then it constructs a tuple object whose first item is the ierr value and whose second item is the corresponding error message gotten from FormatMessage and then calls PyErr_SetObject PyExc_WindowsError object This function always returns NULL Availability Windows PyObject PyErr_SetExcFromWindowsErr PyObject type int ierr Return value Always NULL Part of the Stable ABI on Wi,en
2519,ndows since version 3 7 Similar to PyErr_SetFromWindowsErr with an additional parameter specifying the exception type to be raised Availability Windows PyObject PyErr_SetFromWindowsErrWithFilename int ierr const char filename Return value Always NULL Part of the Stable ABI on Windows since version 3 7 Similar to PyErr_SetFromWindowsErr with the additional behavior that if filename is not NULL it is decoded from the filesystem encoding os fsdecode and passed to the constructor of OSError as a third parameter to be used to define the filename attribute of the exception instance Availability Windows PyObject PyErr_SetExcFromWindowsErrWithFilenameObject PyObject type int ierr PyObject filename Return value Always NULL Part of the Stable ABI on Windows since version 3 7 Similar to PyErr_SetExcFromWindowsErr with the additional behavior that if filename is not NULL it is passed to the constructor of OSError as a third parameter to be used to define the filename attribute of the exception instance Availability Windows PyObject PyErr_SetExcFromWindowsErrWithFilenameObjects PyObject type int ierr PyObject filename PyObject filename2 Return value Always NULL Part of the Stable ABI on Windows since version 3 7 Similar to PyErr_SetExcFromWindowsErrWithFilenameObject but accepts a second filename object Availability Windows New in version 3 4 PyObject PyErr_SetExcFromWindowsErrWithFilename PyObject type int ierr const char filename Return value Always NULL Part of the Stable ABI on Windows since version 3 7 Similar to PyErr_SetFromWindowsErrWithFilename with an additional parameter specifying the exception type to be raised Availability Windows PyObject PyErr_SetImportError PyObject msg PyObject name PyObject path Return value Always NULL Part of the Stable ABI since version 3 7 This is a convenience function to raise ImportError msg will be set as the exception s message string name and path both of which can be NULL will be set as the ImportError s respective name and path attributes New in version 3 3 PyObject PyErr_SetImportErrorSubclass PyObject exception PyObject msg PyObject name PyObject path Return value Always NULL Part of the Stable ABI since version 3 6 Much like PyErr_SetImportError but this function allows for specifying a subclass of ImportError to raise New in version 3 6 void PyErr_SyntaxLocationObject PyObject filename int lineno int col_offset Set file line and offset information for the current exception If the current exception is not a SyntaxError then it sets additional attributes which make the exception printing subsystem think the exception is a SyntaxError New in version 3 4 void PyErr_SyntaxLocationEx const char filename int lineno int col_offset Part of the Stable ABI since version 3 7 Like PyErr_SyntaxLocationObject but filename is a byte string decoded from the filesystem encoding and error handler New in version 3 2 void PyErr_SyntaxLocation const char filename int lineno Part of the Stable ABI Like PyErr_SyntaxLocationEx but the col_offset parameter is omitted void PyErr_BadInternalCall Part of the Stable ABI This is a shorthand for PyErr_SetString PyExc_SystemError message where message indicates that an internal operation e g a Python C API function was invoked with an illegal argument It is mostly for internal use Issuing warnings Use these functions to issue warnings from C code They mirror similar functions exported by the Python warnings module They normally print a warning message to sys stderr however it is also possible that the user has specified that warnings are to be turned into errors and in that case they will raise an exception It is also possible that the functions raise an exception because of a problem with the warning machinery The return value is 0 if no exception is raised or 1 if an exception is raised It is not possible to determine whether a warning message is actually printed nor what the reason is for the exception this is intentional If an exception is raised the caller should do its normal exception handling for example Py_DECREF owned references and return an error value ,en
2520,int PyErr_WarnEx PyObject category const char message Py_ssize_t stack_level Part of the Stable ABI Issue a warning message The category argument is a warning category see below or NULL the message argument is a UTF 8 encoded string stack_level is a positive number giving a number of stack frames the warning will be issued from the currently executing line of code in that stack frame A stack_level of 1 is the function calling PyErr_WarnEx 2 is the function above that and so forth Warning categories must be subclasses of PyExc_Warning PyExc_Warning is a subclass of PyExc_Exception the default warning category is PyExc_RuntimeWarning The standard Python warning categories are available as global variables whose names are enumerated at Standard Warning Categories For information about warning control see the documentation for the warnings module and the W option in the command line documentation There is no C API for warning control int PyErr_WarnExplicitObject PyObject category PyObject message PyObject filename int lineno PyObject module PyObject registry Issue a warning message with explicit control over all warning attributes This is a straightforward wrapper around the Python function warnings warn_explicit see there for more information The module and registry arguments may be set to NULL to get the default effect described there New in version 3 4 int PyErr_WarnExplicit PyObject category const char message const char filename int lineno const char module PyObject registry Part of the Stable ABI Similar to PyErr_WarnExplicitObject except that message and module are UTF 8 encoded strings and filename is decoded from the filesystem encoding and error handler int PyErr_WarnFormat PyObject category Py_ssize_t stack_level const char format Part of the Stable ABI Function similar to PyErr_WarnEx but use PyUnicode_FromFormat to format the warning message format is an ASCII encoded string New in version 3 2 int PyErr_ResourceWarning PyObject source Py_ssize_t stack_level const char format Part of the Stable ABI since version 3 6 Function similar to PyErr_WarnFormat but category is ResourceWarning and it passes source to warnings WarningMessage New in version 3 6 Querying the error indicator PyObject PyErr_Occurred Return value Borrowed reference Part of the Stable ABI Test whether the error indicator is set If set return the exception type the first argument to the last call to one of the PyErr_Set functions or to PyErr_Restore If not set return NULL You do not own a reference to the return value so you do not need to Py_DECREF it The caller must hold the GIL Note Do not compare the return value to a specific exception use PyErr_ExceptionMatches instead shown below The comparison could easily fail since the exception may be an instance instead of a class in the case of a class exception or it may be a subclass of the expected exception int PyErr_ExceptionMatches PyObject exc Part of the Stable ABI Equivalent to PyErr_GivenExceptionMatches PyErr_Occurred exc This should only be called when an exception is actually set a memory access violation will occur if no exception has been raised int PyErr_GivenExceptionMatches PyObject given PyObject exc Part of the Stable ABI Return true if the given exception matches the exception type in exc If exc is a class object this also returns true when given is an instance of a subclass If exc is a tuple all exception types in the tuple and recursively in subtuples are searched for a match PyObject PyErr_GetRaisedException void Return value New reference Part of the Stable ABI since version 3 12 Return the exception currently being raised clearing the error indicator at the same time Return NULL if the error indicator is not set This function is used by code that needs to catch exceptions or code that needs to save and restore the error indicator temporarily For example PyObject exc PyErr_GetRaisedException code that might produce other errors PyErr_SetRaisedException exc See also PyErr_GetHandledException to save the exception currently being handled New in version 3 12 void PyErr_SetRaisedE,en
2521,xception PyObject exc Part of the Stable ABI since version 3 12 Set exc as the exception currently being raised clearing the existing exception if one is set Warning This call steals a reference to exc which must be a valid exception New in version 3 12 void PyErr_Fetch PyObject ptype PyObject pvalue PyObject ptraceback Part of the Stable ABI Deprecated since version 3 12 Use PyErr_GetRaisedException instead Retrieve the error indicator into three variables whose addresses are passed If the error indicator is not set set all three variables to NULL If it is set it will be cleared and you own a reference to each object retrieved The value and traceback object may be NULL even when the type object is not Note This function is normally only used by legacy code that needs to catch exceptions or save and restore the error indicator temporarily For example PyObject type value traceback PyErr_Fetch type value traceback code that might produce other errors PyErr_Restore type value traceback void PyErr_Restore PyObject type PyObject value PyObject traceback Part of the Stable ABI Deprecated since version 3 12 Use PyErr_SetRaisedException instead Set the error indicator from the three objects type value and traceback clearing the existing exception if one is set If the objects are NULL the error indicator is cleared Do not pass a NULL type and non NULL value or traceback The exception type should be a class Do not pass an invalid exception type or value Violating these rules will cause subtle problems later This call takes away a reference to each object you must own a reference to each object before the call and after the call you no longer own these references If you don t understand this don t use this function I warned you Note This function is normally only used by legacy code that needs to save and restore the error indicator temporarily Use PyErr_Fetch to save the current error indicator void PyErr_NormalizeException PyObject exc PyObject val PyObject tb Part of the Stable ABI Deprecated since version 3 12 Use PyErr_GetRaisedException instead to avoid any possible de normalization Under certain circumstances the values returned by PyErr_Fetch below can be unnormalized meaning that exc is a class object but val is not an instance of the same class This function can be used to instantiate the class in that case If the values are already normalized nothing happens The delayed normalization is implemented to improve performance Note This function does not implicitly set the __traceback__ attribute on the exception value If setting the traceback appropriately is desired the following additional snippet is needed if tb NULL PyException_SetTraceback val tb PyObject PyErr_GetHandledException void Part of the Stable ABI since version 3 11 Retrieve the active exception instance as would be returned by sys exception This refers to an exception that was already caught not to an exception that was freshly raised Returns a new reference to the exception or NULL Does not modify the interpreter s exception state Note This function is not normally used by code that wants to handle exceptions Rather it can be used when code needs to save and restore the exception state temporarily Use PyErr_SetHandledException to restore or clear the exception state New in version 3 11 void PyErr_SetHandledException PyObject exc Part of the Stable ABI since version 3 11 Set the active exception as known from sys exception This refers to an exception that was already caught not to an exception that was freshly raised To clear the exception state pass NULL Note This function is not normally used by code that wants to handle exceptions Rather it can be used when code needs to save and restore the exception state temporarily Use PyErr_GetHandledException to get the exception state New in version 3 11 void PyErr_GetExcInfo PyObject ptype PyObject pvalue PyObject ptraceback Part of the Stable ABI since version 3 7 Retrieve the old style representation of the exception info as known from sys exc_info This refers to an exception that was already caught not to an exc,en
2522,eption that was freshly raised Returns new references for the three objects any of which may be NULL Does not modify the exception info state This function is kept for backwards compatibility Prefer using PyErr_GetHandledException Note This function is not normally used by code that wants to handle exceptions Rather it can be used when code needs to save and restore the exception state temporarily Use PyErr_SetExcInfo to restore or clear the exception state New in version 3 3 void PyErr_SetExcInfo PyObject type PyObject value PyObject traceback Part of the Stable ABI since version 3 7 Set the exception info as known from sys exc_info This refers to an exception that was already caught not to an exception that was freshly raised This function steals the references of the arguments To clear the exception state pass NULL for all three arguments This function is kept for backwards compatibility Prefer using PyErr_SetHandledException Note This function is not normally used by code that wants to handle exceptions Rather it can be used when code needs to save and restore the exception state temporarily Use PyErr_GetExcInfo to read the exception state New in version 3 3 Changed in version 3 11 The type and traceback arguments are no longer used and can be NULL The interpreter now derives them from the exception instance the value argument The function still steals references of all three arguments Signal Handling int PyErr_CheckSignals Part of the Stable ABI This function interacts with Python s signal handling If the function is called from the main thread and under the main Python interpreter it checks whether a signal has been sent to the processes and if so invokes the corresponding signal handler If the signal module is supported this can invoke a signal handler written in Python The function attempts to handle all pending signals and then returns 0 However if a Python signal handler raises an exception the error indicator is set and the function returns 1 immediately such that other pending signals may not have been handled yet they will be on the next PyErr_CheckSignals invocation If the function is called from a non main thread or under a non main Python interpreter it does nothing and returns 0 This function can be called by long running C code that wants to be interruptible by user requests such as by pressing Ctrl C Note The default Python signal handler for SIGINT raises the KeyboardInterrupt exception void PyErr_SetInterrupt Part of the Stable ABI Simulate the effect of a SIGINT signal arriving This is equivalent to PyErr_SetInterruptEx SIGINT Note This function is async signal safe It can be called without the GIL and from a C signal handler int PyErr_SetInterruptEx int signum Part of the Stable ABI since version 3 10 Simulate the effect of a signal arriving The next time PyErr_CheckSignals is called the Python signal handler for the given signal number will be called This function can be called by C code that sets up its own signal handling and wants Python signal handlers to be invoked as expected when an interruption is requested for example when the user presses Ctrl C to interrupt an operation If the given signal isn t handled by Python it was set to signal SIG_DFL or signal SIG_IGN it will be ignored If signum is outside of the allowed range of signal numbers 1 is returned Otherwise 0 is returned The error indicator is never changed by this function Note This function is async signal safe It can be called without the GIL and from a C signal handler New in version 3 10 int PySignal_SetWakeupFd int fd This utility function specifies a file descriptor to which the signal number is written as a single byte whenever a signal is received fd must be non blocking It returns the previous such file descriptor The value 1 disables the feature this is the initial state This is equivalent to signal set_wakeup_fd in Python but without any error checking fd should be a valid file descriptor The function should only be called from the main thread Changed in version 3 5 On Windows the function now also supports socket handles,en
2523, Exception Classes PyObject PyErr_NewException const char name PyObject base PyObject dict Return value New reference Part of the Stable ABI This utility function creates and returns a new exception class The name argument must be the name of the new exception a C string of the form module classname The base and dict arguments are normally NULL This creates a class object derived from Exception accessible in C as PyExc_Exception The __module__ attribute of the new class is set to the first part up to the last dot of the name argument and the class name is set to the last part after the last dot The base argument can be used to specify alternate base classes it can either be only one class or a tuple of classes The dict argument can be used to specify a dictionary of class variables and methods PyObject PyErr_NewExceptionWithDoc const char name const char doc PyObject base PyObject dict Return value New reference Part of the Stable ABI Same as PyErr_NewException except that the new exception class can easily be given a docstring If doc is non NULL it will be used as the docstring for the exception class New in version 3 2 Exception Objects PyObject PyException_GetTraceback PyObject ex Return value New reference Part of the Stable ABI Return the traceback associated with the exception as a new reference as accessible from Python through the __traceback__ attribute If there is no traceback associated this returns NULL int PyException_SetTraceback PyObject ex PyObject tb Part of the Stable ABI Set the traceback associated with the exception to tb Use Py_None to clear it PyObject PyException_GetContext PyObject ex Return value New reference Part of the Stable ABI Return the context another exception instance during whose handling ex was raised associated with the exception as a new reference as accessible from Python through the __context__ attribute If there is no context associated this returns NULL void PyException_SetContext PyObject ex PyObject ctx Part of the Stable ABI Set the context associated with the exception to ctx Use NULL to clear it There is no type check to make sure that ctx is an exception instance This steals a reference to ctx PyObject PyException_GetCause PyObject ex Return value New reference Part of the Stable ABI Return the cause either an exception instance or None set by raise from associated with the exception as a new reference as accessible from Python through the __cause__ attribute void PyException_SetCause PyObject ex PyObject cause Part of the Stable ABI Set the cause associated with the exception to cause Use NULL to clear it There is no type check to make sure that cause is either an exception instance or None This steals a reference to cause The __suppress_context__ attribute is implicitly set to True by this function PyObject PyException_GetArgs PyObject ex Return value New reference Part of the Stable ABI since version 3 12 Return args of exception ex void PyException_SetArgs PyObject ex PyObject args Part of the Stable ABI since version 3 12 Set args of exception ex to args PyObject PyUnstable_Exc_PrepReraiseStar PyObject orig PyObject excs This is Unstable API It may change without warning in minor releases Implement part of the interpreter s implementation of except orig is the original exception that was caught and excs is the list of the exceptions that need to be raised This list contains the unhandled part of orig if any as well as the exceptions that were raised from the except clauses so they have a different traceback from orig and those that were reraised and have the same traceback as orig Return the ExceptionGroup that needs to be reraised in the end or None if there is nothing to reraise New in version 3 12 Unicode Exception Objects The following functions are used to create and modify Unicode exceptions from C PyObject PyUnicodeDecodeError_Create const char encoding const char object Py_ssize_t length Py_ssize_t start Py_ssize_t end const char reason Return value New reference Part of the Stable ABI Create a UnicodeDecodeError object with the attributes encoding object len,en
2524,gth start end and reason encoding and reason are UTF 8 encoded strings PyObject PyUnicodeDecodeError_GetEncoding PyObject exc PyObject PyUnicodeEncodeError_GetEncoding PyObject exc Return value New reference Part of the Stable ABI Return the encoding attribute of the given exception object PyObject PyUnicodeDecodeError_GetObject PyObject exc PyObject PyUnicodeEncodeError_GetObject PyObject exc PyObject PyUnicodeTranslateError_GetObject PyObject exc Return value New reference Part of the Stable ABI Return the object attribute of the given exception object int PyUnicodeDecodeError_GetStart PyObject exc Py_ssize_t start int PyUnicodeEncodeError_GetStart PyObject exc Py_ssize_t start int PyUnicodeTranslateError_GetStart PyObject exc Py_ssize_t start Part of the Stable ABI Get the start attribute of the given exception object and place it into start start must not be NULL Return 0 on success 1 on failure int PyUnicodeDecodeError_SetStart PyObject exc Py_ssize_t start int PyUnicodeEncodeError_SetStart PyObject exc Py_ssize_t start int PyUnicodeTranslateError_SetStart PyObject exc Py_ssize_t start Part of the Stable ABI Set the start attribute of the given exception object to start Return 0 on success 1 on failure int PyUnicodeDecodeError_GetEnd PyObject exc Py_ssize_t end int PyUnicodeEncodeError_GetEnd PyObject exc Py_ssize_t end int PyUnicodeTranslateError_GetEnd PyObject exc Py_ssize_t end Part of the Stable ABI Get the end attribute of the given exception object and place it into end end must not be NULL Return 0 on success 1 on failure int PyUnicodeDecodeError_SetEnd PyObject exc Py_ssize_t end int PyUnicodeEncodeError_SetEnd PyObject exc Py_ssize_t end int PyUnicodeTranslateError_SetEnd PyObject exc Py_ssize_t end Part of the Stable ABI Set the end attribute of the given exception object to end Return 0 on success 1 on failure PyObject PyUnicodeDecodeError_GetReason PyObject exc PyObject PyUnicodeEncodeError_GetReason PyObject exc PyObject PyUnicodeTranslateError_GetReason PyObject exc Return value New reference Part of the Stable ABI Return the reason attribute of the given exception object int PyUnicodeDecodeError_SetReason PyObject exc const char reason int PyUnicodeEncodeError_SetReason PyObject exc const char reason int PyUnicodeTranslateError_SetReason PyObject exc const char reason Part of the Stable ABI Set the reason attribute of the given exception object to reason Return 0 on success 1 on failure Recursion Control These two functions provide a way to perform safe recursive calls at the C level both in the core and in extension modules They are needed if the recursive code does not necessarily invoke Python code which tracks its recursion depth automatically They are also not needed for tp_call implementations because the call protocol takes care of recursion handling int Py_EnterRecursiveCall const char where Part of the Stable ABI since version 3 9 Marks a point where a recursive C level call is about to be performed If USE_STACKCHECK is defined this function checks if the OS stack overflowed using PyOS_CheckStack If this is the case it sets a MemoryError and returns a nonzero value The function then checks if the recursion limit is reached If this is the case a RecursionError is set and a nonzero value is returned Otherwise zero is returned where should be a UTF 8 encoded string such as in instance check to be concatenated to the RecursionError message caused by the recursion depth limit Changed in version 3 9 This function is now also available in the limited API void Py_LeaveRecursiveCall void Part of the Stable ABI since version 3 9 Ends a Py_EnterRecursiveCall Must be called once for each successful invocation of Py_EnterRecursiveCall Changed in version 3 9 This function is now also available in the limited API Properly implementing tp_repr for container types requires special recursion handling In addition to protecting the stack tp_repr also needs to track objects to prevent cycles The following two functions facilitate this functionality Effectively these are the C equivalent to reprlib recursive_repr,en
2525, int Py_ReprEnter PyObject object Part of the Stable ABI Called at the beginning of the tp_repr implementation to detect cycles If the object has already been processed the function returns a positive integer In that case the tp_repr implementation should return a string object indicating a cycle As examples dict objects return and list objects return The function will return a negative integer if the recursion limit is reached In that case the tp_repr implementation should typically return NULL Otherwise the function returns zero and the tp_repr implementation can continue normally void Py_ReprLeave PyObject object Part of the Stable ABI Ends a Py_ReprEnter Must be called once for each invocation of Py_ReprEnter that returns zero Standard Exceptions All standard Python exceptions are available as global variables whose names are PyExc_ followed by the Python exception name These have the type PyObject they are all class objects For completeness here are all the variables C Name Python Name Notes PyExc_BaseException BaseException 1 PyExc_Exception Exception 1 PyExc_ArithmeticError ArithmeticError 1 PyExc_AssertionError AssertionError PyExc_AttributeError AttributeError PyExc_BlockingIOError BlockingIOError PyExc_BrokenPipeError BrokenPipeError PyExc_BufferError BufferError PyExc_ChildProcessError ChildProcessError PyExc_ConnectionAbortedError ConnectionAbortedError PyExc_ConnectionError ConnectionError PyExc_ConnectionRefusedError ConnectionRefusedError PyExc_ConnectionResetError ConnectionResetError PyExc_EOFError EOFError PyExc_FileExistsError FileExistsError PyExc_FileNotFoundError FileNotFoundError PyExc_FloatingPointError FloatingPointError PyExc_GeneratorExit GeneratorExit PyExc_ImportError ImportError PyExc_IndentationError IndentationError PyExc_IndexError IndexError PyExc_InterruptedError InterruptedError PyExc_IsADirectoryError IsADirectoryError PyExc_KeyError KeyError PyExc_KeyboardInterrupt KeyboardInterrupt PyExc_LookupError LookupError 1 PyExc_MemoryError MemoryError PyExc_ModuleNotFoundError ModuleNotFoundError PyExc_NameError NameError PyExc_NotADirectoryError NotADirectoryError PyExc_NotImplementedError NotImplementedError PyExc_OSError OSError 1 PyExc_OverflowError OverflowError PyExc_PermissionError PermissionError PyExc_ProcessLookupError ProcessLookupError PyExc_RecursionError RecursionError PyExc_ReferenceError ReferenceError PyExc_RuntimeError RuntimeError PyExc_StopAsyncIteration StopAsyncIteration PyExc_StopIteration StopIteration PyExc_SyntaxError SyntaxError PyExc_SystemError SystemError PyExc_SystemExit SystemExit PyExc_TabError TabError PyExc_TimeoutError TimeoutError PyExc_TypeError TypeError PyExc_UnboundLocalError UnboundLocalError PyExc_UnicodeDecodeError UnicodeDecodeError PyExc_UnicodeEncodeError UnicodeEncodeError PyExc_UnicodeError UnicodeError PyExc_UnicodeTranslateError UnicodeTranslateError PyExc_ValueError ValueError PyExc_ZeroDivisionError ZeroDivisionError New in version 3 3 PyExc_BlockingIOError PyExc_BrokenPipeError PyExc_ChildProcessError PyExc_ConnectionError PyExc_ConnectionAbortedError PyExc_ConnectionRefusedError PyExc_ConnectionResetError PyExc_FileExistsError PyExc_FileNotFoundError PyExc_InterruptedError PyExc_IsADirectoryError PyExc_NotADirectoryError PyExc_PermissionError PyExc_ProcessLookupError and PyExc_TimeoutError were introduced following PEP 3151 New in version 3 5 PyExc_StopAsyncIteration and PyExc_RecursionError New in version 3 6 PyExc_ModuleNotFoundError These are compatibility aliases to PyExc_OSError C Name Notes PyExc_EnvironmentError PyExc_IOError PyExc_WindowsError 2 Changed in version 3 3 These aliases used to be separate exception types Notes 1 This is a base class for other standard exceptions 2 Only defined on Windows protect code that uses this by testing that the preprocessor macro MS_WINDOWS is defined Standard Warning Categories All standard Python warning categories are available as global variables whose names are PyExc_ followed by the Python exception name These have the type PyObject they are all class objects For completeness here are al,en
2526,l the variables C Name Python Name Notes PyExc_Warning Warning 3 PyExc_BytesWarning BytesWarning PyExc_DeprecationWarning DeprecationWarning PyExc_FutureWarning FutureWarning PyExc_ImportWarning ImportWarning PyExc_PendingDeprecationWarning PendingDeprecationWarning PyExc_ResourceWarning ResourceWarning PyExc_RuntimeWarning RuntimeWarning PyExc_SyntaxWarning SyntaxWarning PyExc_UnicodeWarning UnicodeWarning PyExc_UserWarning UserWarning New in version 3 2 PyExc_ResourceWarning Notes 3 This is a base class for other standard warning categories,en
2527,How to port Python 2 Code to Python 3 author Brett Cannon Python 2 reached its official end of life at the start of 2020 This means that no new bug reports fixes or changes will be made to Python 2 it s no longer supported see PEP 373 and status of Python versions If you are looking to port an extension module instead of pure Python code please see Porting Extension Modules to Python 3 The archived python porting mailing list may contain some useful guidance Since Python 3 13 the original porting guide was discontinued You can find the old guide in the archive Third party guides There are also multiple third party guides that might be useful Guide by Fedora PyCon 2020 tutorial Guide by DigitalOcean Guide by ActiveState,en
2528,Python Development Mode New in version 3 7 The Python Development Mode introduces additional runtime checks that are too expensive to be enabled by default It should not be more verbose than the default if the code is correct new warnings are only emitted when an issue is detected It can be enabled using the X dev command line option or by setting the PYTHONDEVMODE environment variable to 1 See also Python debug build Effects of the Python Development Mode Enabling the Python Development Mode is similar to the following command but with additional effects described below PYTHONMALLOC debug PYTHONASYNCIODEBUG 1 python W default X faulthandler Effects of the Python Development Mode Add default warning filter The following warnings are shown DeprecationWarning ImportWarning PendingDeprecationWarning ResourceWarning Normally the above warnings are filtered by the default warning filters It behaves as if the W default command line option is used Use the W error command line option or set the PYTHONWARNINGS environment variable to error to treat warnings as errors Install debug hooks on memory allocators to check for Buffer underflow Buffer overflow Memory allocator API violation Unsafe usage of the GIL See the PyMem_SetupDebugHooks C function It behaves as if the PYTHONMALLOC environment variable is set to debug To enable the Python Development Mode without installing debug hooks on memory allocators set the PYTHONMALLOC environment variable to default Call faulthandler enable at Python startup to install handlers for the SIGSEGV SIGFPE SIGABRT SIGBUS and SIGILL signals to dump the Python traceback on a crash It behaves as if the X faulthandler command line option is used or if the PYTHONFAULTHANDLER environment variable is set to 1 Enable asyncio debug mode For example asyncio checks for coroutines that were not awaited and logs them It behaves as if the PYTHONASYNCIODEBUG environment variable is set to 1 Check the encoding and errors arguments for string encoding and decoding operations Examples open str encode and bytes decode By default for best performance the errors argument is only checked at the first encoding decoding error and the encoding argument is sometimes ignored for empty strings The io IOBase destructor logs close exceptions Set the dev_mode attribute of sys flags to True The Python Development Mode does not enable the tracemalloc module by default because the overhead cost to performance and memory would be too large Enabling the tracemalloc module provides additional information on the origin of some errors For example ResourceWarning logs the traceback where the resource was allocated and a buffer overflow error logs the traceback where the memory block was allocated The Python Development Mode does not prevent the O command line option from removing assert statements nor from setting __debug__ to False The Python Development Mode can only be enabled at the Python startup Its value can be read from sys flags dev_mode Changed in version 3 8 The io IOBase destructor now logs close exceptions Changed in version 3 9 The encoding and errors arguments are now checked for string encoding and decoding operations ResourceWarning Example Example of a script counting the number of lines of the text file specified in the command line import sys def main fp open sys argv 1 nlines len fp readlines print nlines The file is closed implicitly if __name__ __main__ main The script does not close the file explicitly By default Python does not emit any warning Example using README txt which has 269 lines python script py README txt 269 Enabling the Python Development Mode displays a ResourceWarning warning python X dev script py README txt 269 script py 10 ResourceWarning unclosed file _io TextIOWrapper name README rst mode r encoding UTF 8 main ResourceWarning Enable tracemalloc to get the object allocation traceback In addition enabling tracemalloc shows the line where the file was opened python X dev X tracemalloc 5 script py README rst 269 script py 10 ResourceWarning unclosed file _io TextIOWrapper name README rst mode r,en
2529, encoding UTF 8 main Object allocated at most recent call last File script py lineno 10 main File script py lineno 4 fp open sys argv 1 The fix is to close explicitly the file Example using a context manager def main Close the file explicitly when exiting the with block with open sys argv 1 as fp nlines len fp readlines print nlines Not closing a resource explicitly can leave a resource open for way longer than expected it can cause severe issues upon exiting Python It is bad in CPython but it is even worse in PyPy Closing resources explicitly makes an application more deterministic and more reliable Bad file descriptor error example Script displaying the first line of itself import os def main fp open __file__ firstline fp readline print firstline rstrip os close fp fileno The file is closed implicitly main By default Python does not emit any warning python script py import os The Python Development Mode shows a ResourceWarning and logs a Bad file descriptor error when finalizing the file object python X dev script py import os script py 10 ResourceWarning unclosed file _io TextIOWrapper name script py mode r encoding UTF 8 main ResourceWarning Enable tracemalloc to get the object allocation traceback Exception ignored in _io TextIOWrapper name script py mode r encoding UTF 8 Traceback most recent call last File script py line 10 in module main OSError Errno 9 Bad file descriptor os close fp fileno closes the file descriptor When the file object finalizer tries to close the file descriptor again it fails with the Bad file descriptor error A file descriptor must be closed only once In the worst case scenario closing it twice can lead to a crash see bpo 18748 for an example The fix is to remove the os close fp fileno line or open the file with closefd False,en
2530,Descriptor Objects Descriptors are objects that describe some attribute of an object They are found in the dictionary of type objects PyTypeObject PyProperty_Type Part of the Stable ABI The type object for the built in descriptor types PyObject PyDescr_NewGetSet PyTypeObject type struct PyGetSetDef getset Return value New reference Part of the Stable ABI PyObject PyDescr_NewMember PyTypeObject type struct PyMemberDef meth Return value New reference Part of the Stable ABI PyObject PyDescr_NewMethod PyTypeObject type struct PyMethodDef meth Return value New reference Part of the Stable ABI PyObject PyDescr_NewWrapper PyTypeObject type struct wrapperbase wrapper void wrapped Return value New reference PyObject PyDescr_NewClassMethod PyTypeObject type PyMethodDef method Return value New reference Part of the Stable ABI int PyDescr_IsData PyObject descr Return non zero if the descriptor objects descr describes a data attribute or 0 if it describes a method descr must be a descriptor object there is no error checking PyObject PyWrapper_New PyObject PyObject Return value New reference Part of the Stable ABI,en
2531,Platform Support The asyncio module is designed to be portable but some platforms have subtle differences and limitations due to the platforms underlying architecture and capabilities All Platforms loop add_reader and loop add_writer cannot be used to monitor file I O Windows Source code Lib asyncio proactor_events py Lib asyncio windows_events py Lib asyncio windows_utils py Changed in version 3 8 On Windows ProactorEventLoop is now the default event loop All event loops on Windows do not support the following methods loop create_unix_connection and loop create_unix_server are not supported The socket AF_UNIX socket family is specific to Unix loop add_signal_handler and loop remove_signal_handler are not supported SelectorEventLoop has the following limitations SelectSelector is used to wait on socket events it supports sockets and is limited to 512 sockets loop add_reader and loop add_writer only accept socket handles e g pipe file descriptors are not supported Pipes are not supported so the loop connect_read_pipe and loop connect_write_pipe methods are not implemented Subprocesses are not supported i e loop subprocess_exec and loop subprocess_shell methods are not implemented ProactorEventLoop has the following limitations The loop add_reader and loop add_writer methods are not supported The resolution of the monotonic clock on Windows is usually around 15 6 milliseconds The best resolution is 0 5 milliseconds The resolution depends on the hardware availability of HPET and on the Windows configuration Subprocess Support on Windows On Windows the default event loop ProactorEventLoop supports subprocesses whereas SelectorEventLoop does not The policy set_child_watcher function is also not supported as ProactorEventLoop has a different mechanism to watch child processes macOS Modern macOS versions are fully supported macOS 10 8 On macOS 10 6 10 7 and 10 8 the default event loop uses selectors KqueueSelector which does not support character devices on these versions The SelectorEventLoop can be manually configured to use SelectSelector or PollSelector to support character devices on these older versions of macOS Example import asyncio import selectors selector selectors SelectSelector loop asyncio SelectorEventLoop selector asyncio set_event_loop loop,en
2532,random Generate pseudo random numbers Source code Lib random py This module implements pseudo random number generators for various distributions For integers there is uniform selection from a range For sequences there is uniform selection of a random element a function to generate a random permutation of a list in place and a function for random sampling without replacement On the real line there are functions to compute uniform normal Gaussian lognormal negative exponential gamma and beta distributions For generating distributions of angles the von Mises distribution is available Almost all module functions depend on the basic function random which generates a random float uniformly in the half open range 0 0 X 1 0 Python uses the Mersenne Twister as the core generator It produces 53 bit precision floats and has a period of 2 19937 1 The underlying implementation in C is both fast and threadsafe The Mersenne Twister is one of the most extensively tested random number generators in existence However being completely deterministic it is not suitable for all purposes and is completely unsuitable for cryptographic purposes The functions supplied by this module are actually bound methods of a hidden instance of the random Random class You can instantiate your own instances of Random to get generators that don t share state Class Random can also be subclassed if you want to use a different basic generator of your own devising see the documentation on that class for more details The random module also provides the SystemRandom class which uses the system function os urandom to generate random numbers from sources provided by the operating system Warning The pseudo random generators of this module should not be used for security purposes For security or cryptographic uses see the secrets module See also M Matsumoto and T Nishimura Mersenne Twister A 623 dimensionally equidistributed uniform pseudorandom number generator ACM Transactions on Modeling and Computer Simulation Vol 8 No 1 January pp 3 30 1998 Complementary Multiply with Carry recipe for a compatible alternative random number generator with a long period and comparatively simple update operations Bookkeeping functions random seed a None version 2 Initialize the random number generator If a is omitted or None the current system time is used If randomness sources are provided by the operating system they are used instead of the system time see the os urandom function for details on availability If a is an int it is used directly With version 2 the default a str bytes or bytearray object gets converted to an int and all of its bits are used With version 1 provided for reproducing random sequences from older versions of Python the algorithm for str and bytes generates a narrower range of seeds Changed in version 3 2 Moved to the version 2 scheme which uses all of the bits in a string seed Changed in version 3 11 The seed must be one of the following types None int float str bytes or bytearray random getstate Return an object capturing the current internal state of the generator This object can be passed to setstate to restore the state random setstate state state should have been obtained from a previous call to getstate and setstate restores the internal state of the generator to what it was at the time getstate was called Functions for bytes random randbytes n Generate n random bytes This method should not be used for generating security tokens Use secrets token_bytes instead New in version 3 9 Functions for integers random randrange stop random randrange start stop step Return a randomly selected element from range start stop step This is roughly equivalent to choice range start stop step but supports arbitrarily large ranges and is optimized for common cases The positional argument pattern matches the range function Keyword arguments should not be used because they can be interpreted in unexpected ways For example randrange start 100 is interpreted as randrange 0 100 1 Changed in version 3 2 randrange is more sophisticated about producing equally distributed values Fo,en
2533,rmerly it used a style like int random n which could produce slightly uneven distributions Changed in version 3 12 Automatic conversion of non integer types is no longer supported Calls such as randrange 10 0 and randrange Fraction 10 1 now raise a TypeError random randint a b Return a random integer N such that a N b Alias for randrange a b 1 random getrandbits k Returns a non negative Python integer with k random bits This method is supplied with the Mersenne Twister generator and some other generators may also provide it as an optional part of the API When available getrandbits enables randrange to handle arbitrarily large ranges Changed in version 3 9 This method now accepts zero for k Functions for sequences random choice seq Return a random element from the non empty sequence seq If seq is empty raises IndexError random choices population weights None cum_weights None k 1 Return a k sized list of elements chosen from the population with replacement If the population is empty raises IndexError If a weights sequence is specified selections are made according to the relative weights Alternatively if a cum_weights sequence is given the selections are made according to the cumulative weights perhaps computed using itertools accumulate For example the relative weights 10 5 30 5 are equivalent to the cumulative weights 10 15 45 50 Internally the relative weights are converted to cumulative weights before making selections so supplying the cumulative weights saves work If neither weights nor cum_weights are specified selections are made with equal probability If a weights sequence is supplied it must be the same length as the population sequence It is a TypeError to specify both weights and cum_weights The weights or cum_weights can use any numeric type that interoperates with the float values returned by random that includes integers floats and fractions but excludes decimals Weights are assumed to be non negative and finite A ValueError is raised if all weights are zero For a given seed the choices function with equal weighting typically produces a different sequence than repeated calls to choice The algorithm used by choices uses floating point arithmetic for internal consistency and speed The algorithm used by choice defaults to integer arithmetic with repeated selections to avoid small biases from round off error New in version 3 6 Changed in version 3 9 Raises a ValueError if all weights are zero random shuffle x Shuffle the sequence x in place To shuffle an immutable sequence and return a new shuffled list use sample x k len x instead Note that even for small len x the total number of permutations of x can quickly grow larger than the period of most random number generators This implies that most permutations of a long sequence can never be generated For example a sequence of length 2080 is the largest that can fit within the period of the Mersenne Twister random number generator Changed in version 3 11 Removed the optional parameter random random sample population k counts None Return a k length list of unique elements chosen from the population sequence Used for random sampling without replacement Returns a new list containing elements from the population while leaving the original population unchanged The resulting list is in selection order so that all sub slices will also be valid random samples This allows raffle winners the sample to be partitioned into grand prize and second place winners the subslices Members of the population need not be hashable or unique If the population contains repeats then each occurrence is a possible selection in the sample Repeated elements can be specified one at a time or with the optional keyword only counts parameter For example sample red blue counts 4 2 k 5 is equivalent to sample red red red red blue blue k 5 To choose a sample from a range of integers use a range object as an argument This is especially fast and space efficient for sampling from a large population sample range 10000000 k 60 If the sample size is larger than the population size a ValueError is raised Change,en
2534,d in version 3 9 Added the counts parameter Changed in version 3 11 The population must be a sequence Automatic conversion of sets to lists is no longer supported Discrete distributions The following function generates a discrete distribution random binomialvariate n 1 p 0 5 Binomial distribution Return the number of successes for n independent trials with the probability of success in each trial being p Mathematically equivalent to sum random p for i in range n The number of trials n should be a non negative integer The probability of success p should be between 0 0 p 1 0 The result is an integer in the range 0 X n New in version 3 12 Real valued distributions The following functions generate specific real valued distributions Function parameters are named after the corresponding variables in the distribution s equation as used in common mathematical practice most of these equations can be found in any statistics text random random Return the next random floating point number in the range 0 0 X 1 0 random uniform a b Return a random floating point number N such that a N b for a b and b N a for b a The end point value b may or may not be included in the range depending on floating point rounding in the expression a b a random random triangular low high mode Return a random floating point number N such that low N high and with the specified mode between those bounds The low and high bounds default to zero and one The mode argument defaults to the midpoint between the bounds giving a symmetric distribution random betavariate alpha beta Beta distribution Conditions on the parameters are alpha 0 and beta 0 Returned values range between 0 and 1 random expovariate lambd 1 0 Exponential distribution lambd is 1 0 divided by the desired mean It should be nonzero The parameter would be called lambda but that is a reserved word in Python Returned values range from 0 to positive infinity if lambd is positive and from negative infinity to 0 if lambd is negative Changed in version 3 12 Added the default value for lambd random gammavariate alpha beta Gamma distribution Not the gamma function The shape and scale parameters alpha and beta must have positive values Calling conventions vary and some sources define beta as the inverse of the scale The probability distribution function is x alpha 1 math exp x beta pdf x math gamma alpha beta alpha random gauss mu 0 0 sigma 1 0 Normal distribution also called the Gaussian distribution mu is the mean and sigma is the standard deviation This is slightly faster than the normalvariate function defined below Multithreading note When two threads call this function simultaneously it is possible that they will receive the same return value This can be avoided in three ways 1 Have each thread use a different instance of the random number generator 2 Put locks around all calls 3 Use the slower but thread safe normalvariate function instead Changed in version 3 11 mu and sigma now have default arguments random lognormvariate mu sigma Log normal distribution If you take the natural logarithm of this distribution you ll get a normal distribution with mean mu and standard deviation sigma mu can have any value and sigma must be greater than zero random normalvariate mu 0 0 sigma 1 0 Normal distribution mu is the mean and sigma is the standard deviation Changed in version 3 11 mu and sigma now have default arguments random vonmisesvariate mu kappa mu is the mean angle expressed in radians between 0 and 2 pi and kappa is the concentration parameter which must be greater than or equal to zero If kappa is equal to zero this distribution reduces to a uniform random angle over the range 0 to 2 pi random paretovariate alpha Pareto distribution alpha is the shape parameter random weibullvariate alpha beta Weibull distribution alpha is the scale parameter and beta is the shape parameter Alternative Generator class random Random seed Class that implements the default pseudo random number generator used by the random module Changed in version 3 11 Formerly the seed could be any hashable object Now it is limited to Non,en
2535,e int float str bytes or bytearray Subclasses of Random should override the following methods if they wish to make use of a different basic generator seed a None version 2 Override this method in subclasses to customise the seed behaviour of Random instances getstate Override this method in subclasses to customise the getstate behaviour of Random instances setstate state Override this method in subclasses to customise the setstate behaviour of Random instances random Override this method in subclasses to customise the random behaviour of Random instances Optionally a custom generator subclass can also supply the following method getrandbits k Override this method in subclasses to customise the getrandbits behaviour of Random instances class random SystemRandom seed Class that uses the os urandom function for generating random numbers from sources provided by the operating system Not available on all systems Does not rely on software state and sequences are not reproducible Accordingly the seed method has no effect and is ignored The getstate and setstate methods raise NotImplementedError if called Notes on Reproducibility Sometimes it is useful to be able to reproduce the sequences given by a pseudo random number generator By reusing a seed value the same sequence should be reproducible from run to run as long as multiple threads are not running Most of the random module s algorithms and seeding functions are subject to change across Python versions but two aspects are guaranteed not to change If a new seeding method is added then a backward compatible seeder will be offered The generator s random method will continue to produce the same sequence when the compatible seeder is given the same seed Examples Basic examples random Random float 0 0 x 1 0 0 37444887175646646 uniform 2 5 10 0 Random float 2 5 x 10 0 3 1800146073117523 expovariate 1 5 Interval between arrivals averaging 5 seconds 5 148957571865031 randrange 10 Integer from 0 to 9 inclusive 7 randrange 0 101 2 Even integer from 0 to 100 inclusive 26 choice win lose draw Single random element from a sequence draw deck ace two three four split shuffle deck Shuffle a list deck four two ace three sample 10 20 30 40 50 k 4 Four samples without replacement 40 10 50 30 Simulations Six roulette wheel spins weighted sampling with replacement choices red black green 18 18 2 k 6 red green black black red black Deal 20 cards without replacement from a deck of 52 playing cards and determine the proportion of cards with a ten value ten jack queen or king deal sample tens low cards counts 16 36 k 20 deal count tens 20 0 15 Estimate the probability of getting 5 or more heads from 7 spins of a biased coin that settles on heads 60 of the time sum binomialvariate n 7 p 0 6 5 for i in range 10_000 10_000 0 4169 Probability of the median of 5 samples being in middle two quartiles def trial return 2_500 sorted choices range 10_000 k 5 2 7_500 sum trial for i in range 10_000 10_000 0 7958 Example of statistical bootstrapping using resampling with replacement to estimate a confidence interval for the mean of a sample https www thoughtco com example of bootstrapping 3126155 from statistics import fmean as mean from random import choices data 41 50 29 37 81 30 73 63 20 35 68 22 60 31 95 means sorted mean choices data k len data for i in range 100 print f The sample mean of mean data 1f has a 90 confidence f interval from means 5 1f to means 94 1f Example of a resampling permutation test to determine the statistical significance or p value of an observed difference between the effects of a drug versus a placebo Example from Statistics is Easy by Dennis Shasha and Manda Wilson from statistics import fmean as mean from random import shuffle drug 54 73 53 70 73 68 52 65 65 placebo 54 51 58 44 55 52 42 47 58 46 observed_diff mean drug mean placebo n 10_000 count 0 combined drug placebo for i in range n shuffle combined new_diff mean combined len drug mean combined len drug count new_diff observed_diff print f n label reshufflings produced only count instances with a difference print f at least ,en
2536,as extreme as the observed difference of observed_diff 1f print f The one sided p value of count n 4f leads us to reject the null print f hypothesis that there is no difference between the drug and the placebo Simulation of arrival times and service deliveries for a multiserver queue from heapq import heapify heapreplace from random import expovariate gauss from statistics import mean quantiles average_arrival_interval 5 6 average_service_time 15 0 stdev_service_time 3 5 num_servers 3 waits arrival_time 0 0 servers 0 0 num_servers time when each server becomes available heapify servers for i in range 1_000_000 arrival_time expovariate 1 0 average_arrival_interval next_server_available servers 0 wait max 0 0 next_server_available arrival_time waits append wait service_duration max 0 0 gauss average_service_time stdev_service_time service_completed arrival_time wait service_duration heapreplace servers service_completed print f Mean wait mean waits 1f Max wait max waits 1f print Quartiles round q 1 for q in quantiles waits See also Statistics for Hackers a video tutorial by Jake Vanderplas on statistical analysis using just a few fundamental concepts including simulation sampling shuffling and cross validation Economics Simulation a simulation of a marketplace by Peter Norvig that shows effective use of many of the tools and distributions provided by this module gauss uniform sample betavariate choice triangular and randrange A Concrete Introduction to Probability using Python a tutorial by Peter Norvig covering the basics of probability theory how to write simulations and how to perform data analysis using Python Recipes These recipes show how to efficiently make random selections from the combinatoric iterators in the itertools module def random_product args repeat 1 Random selection from itertools product args kwds pools tuple pool for pool in args repeat return tuple map random choice pools def random_permutation iterable r None Random selection from itertools permutations iterable r pool tuple iterable r len pool if r is None else r return tuple random sample pool r def random_combination iterable r Random selection from itertools combinations iterable r pool tuple iterable n len pool indices sorted random sample range n r return tuple pool i for i in indices def random_combination_with_replacement iterable r Choose r elements with replacement Order the result to match the iterable Result will be in set itertools combinations_with_replacement iterable r pool tuple iterable n len pool indices sorted random choices range n k r return tuple pool i for i in indices The default random returns multiples of 2 ⁵³ in the range 0 0 x 1 0 All such numbers are evenly spaced and are exactly representable as Python floats However many other representable floats in that interval are not possible selections For example 0 05954861408025609 isn t an integer multiple of 2 ⁵³ The following recipe takes a different approach All floats in the interval are possible selections The mantissa comes from a uniform distribution of integers in the range 2⁵² mantissa 2⁵³ The exponent comes from a geometric distribution where exponents smaller than 53 occur half as often as the next larger exponent from random import Random from math import ldexp class FullRandom Random def random self mantissa 0x10_0000_0000_0000 self getrandbits 52 exponent 53 x 0 while not x x self getrandbits 32 exponent x bit_length 32 return ldexp mantissa exponent All real valued distributions in the class will use the new method fr FullRandom fr random 0 05954861408025609 fr expovariate 0 25 8 87925541791544 The recipe is conceptually equivalent to an algorithm that chooses from all the multiples of 2 ¹⁰⁷⁴ in the range 0 0 x 1 0 All such numbers are evenly spaced but most have to be rounded down to the nearest representable Python float The value 2 ¹⁰⁷⁴ is the smallest positive unnormalized float and is equal to math ulp 0 0 See also Generating Pseudo random Floating Point Values a paper by Allen B Downey describing ways to generate more fine grained floats than normally gen,en
2537,erated by random,en
2538,Reference Counting The functions and macros in this section are used for managing reference counts of Python objects Py_ssize_t Py_REFCNT PyObject o Get the reference count of the Python object o Note that the returned value may not actually reflect how many references to the object are actually held For example some objects are immortal and have a very high refcount that does not reflect the actual number of references Consequently do not rely on the returned value to be accurate other than a value of 0 or 1 Use the Py_SET_REFCNT function to set an object reference count Changed in version 3 10 Py_REFCNT is changed to the inline static function Changed in version 3 11 The parameter type is no longer const PyObject void Py_SET_REFCNT PyObject o Py_ssize_t refcnt Set the object o reference counter to refcnt Note that this function has no effect on immortal objects New in version 3 9 Changed in version 3 12 Immortal objects are not modified void Py_INCREF PyObject o Indicate taking a new strong reference to object o indicating it is in use and should not be destroyed This function is usually used to convert a borrowed reference to a strong reference in place The Py_NewRef function can be used to create a new strong reference When done using the object release it by calling Py_DECREF The object must not be NULL if you aren t sure that it isn t NULL use Py_XINCREF Do not expect this function to actually modify o in any way For at least some objects this function has no effect Changed in version 3 12 Immortal objects are not modified void Py_XINCREF PyObject o Similar to Py_INCREF but the object o can be NULL in which case this has no effect See also Py_XNewRef PyObject Py_NewRef PyObject o Part of the Stable ABI since version 3 10 Create a new strong reference to an object call Py_INCREF on o and return the object o When the strong reference is no longer needed Py_DECREF should be called on it to release the reference The object o must not be NULL use Py_XNewRef if o can be NULL For example Py_INCREF obj self attr obj can be written as self attr Py_NewRef obj See also Py_INCREF New in version 3 10 PyObject Py_XNewRef PyObject o Part of the Stable ABI since version 3 10 Similar to Py_NewRef but the object o can be NULL If the object o is NULL the function just returns NULL New in version 3 10 void Py_DECREF PyObject o Release a strong reference to object o indicating the reference is no longer used Once the last strong reference is released i e the object s reference count reaches 0 the object s type s deallocation function which must not be NULL is invoked This function is usually used to delete a strong reference before exiting its scope The object must not be NULL if you aren t sure that it isn t NULL use Py_XDECREF Do not expect this function to actually modify o in any way For at least some objects this function has no effect Warning The deallocation function can cause arbitrary Python code to be invoked e g when a class instance with a __del__ method is deallocated While exceptions in such code are not propagated the executed code has free access to all Python global variables This means that any object that is reachable from a global variable should be in a consistent state before Py_DECREF is invoked For example code to delete an object from a list should copy a reference to the deleted object in a temporary variable update the list data structure and then call Py_DECREF for the temporary variable Changed in version 3 12 Immortal objects are not modified void Py_XDECREF PyObject o Similar to Py_DECREF but the object o can be NULL in which case this has no effect The same warning from Py_DECREF applies here as well void Py_CLEAR PyObject o Release a strong reference for object o The object may be NULL in which case the macro has no effect otherwise the effect is the same as for Py_DECREF except that the argument is also set to NULL The warning for Py_DECREF does not apply with respect to the object passed because the macro carefully uses a temporary variable and sets the argument to NULL before releasing the reference ,en
2539,It is a good idea to use this macro whenever releasing a reference to an object that might be traversed during garbage collection Changed in version 3 12 The macro argument is now only evaluated once If the argument has side effects these are no longer duplicated void Py_IncRef PyObject o Part of the Stable ABI Indicate taking a new strong reference to object o A function version of Py_XINCREF It can be used for runtime dynamic embedding of Python void Py_DecRef PyObject o Part of the Stable ABI Release a strong reference to object o A function version of Py_XDECREF It can be used for runtime dynamic embedding of Python Py_SETREF dst src Macro safely releasing a strong reference to object dst and setting dst to src As in case of Py_CLEAR the obvious code can be deadly Py_DECREF dst dst src The safe way is Py_SETREF dst src That arranges to set dst to src _before_ releasing the reference to the old value of dst so that any code triggered as a side effect of dst getting torn down no longer believes dst points to a valid object New in version 3 6 Changed in version 3 12 The macro arguments are now only evaluated once If an argument has side effects these are no longer duplicated Py_XSETREF dst src Variant of Py_SETREF macro that uses Py_XDECREF instead of Py_DECREF New in version 3 6 Changed in version 3 12 The macro arguments are now only evaluated once If an argument has side effects these are no longer duplicated,en
2540,calendar General calendar related functions Source code Lib calendar py This module allows you to output calendars like the Unix cal program and provides additional useful functions related to the calendar By default these calendars have Monday as the first day of the week and Sunday as the last the European convention Use setfirstweekday to set the first day of the week to Sunday 6 or to any other weekday Parameters that specify dates are given as integers For related functionality see also the datetime and time modules The functions and classes defined in this module use an idealized calendar the current Gregorian calendar extended indefinitely in both directions This matches the definition of the proleptic Gregorian calendar in Dershowitz and Reingold s book Calendrical Calculations where it s the base calendar for all computations Zero and negative years are interpreted as prescribed by the ISO 8601 standard Year 0 is 1 BC year 1 is 2 BC and so on class calendar Calendar firstweekday 0 Creates a Calendar object firstweekday is an integer specifying the first day of the week MONDAY is 0 the default SUNDAY is 6 A Calendar object provides several methods that can be used for preparing the calendar data for formatting This class doesn t do any formatting itself This is the job of subclasses Calendar instances have the following methods iterweekdays Return an iterator for the week day numbers that will be used for one week The first value from the iterator will be the same as the value of the firstweekday property itermonthdates year month Return an iterator for the month month 1 12 in the year year This iterator will return all days as datetime date objects for the month and all days before the start of the month or after the end of the month that are required to get a complete week itermonthdays year month Return an iterator for the month month in the year year similar to itermonthdates but not restricted by the datetime date range Days returned will simply be day of the month numbers For the days outside of the specified month the day number is 0 itermonthdays2 year month Return an iterator for the month month in the year year similar to itermonthdates but not restricted by the datetime date range Days returned will be tuples consisting of a day of the month number and a week day number itermonthdays3 year month Return an iterator for the month month in the year year similar to itermonthdates but not restricted by the datetime date range Days returned will be tuples consisting of a year a month and a day of the month numbers New in version 3 7 itermonthdays4 year month Return an iterator for the month month in the year year similar to itermonthdates but not restricted by the datetime date range Days returned will be tuples consisting of a year a month a day of the month and a day of the week numbers New in version 3 7 monthdatescalendar year month Return a list of the weeks in the month month of the year as full weeks Weeks are lists of seven datetime date objects monthdays2calendar year month Return a list of the weeks in the month month of the year as full weeks Weeks are lists of seven tuples of day numbers and weekday numbers monthdayscalendar year month Return a list of the weeks in the month month of the year as full weeks Weeks are lists of seven day numbers yeardatescalendar year width 3 Return the data for the specified year ready for formatting The return value is a list of month rows Each month row contains up to width months defaulting to 3 Each month contains between 4 and 6 weeks and each week contains 1 7 days Days are datetime date objects yeardays2calendar year width 3 Return the data for the specified year ready for formatting similar to yeardatescalendar Entries in the week lists are tuples of day numbers and weekday numbers Day numbers outside this month are zero yeardayscalendar year width 3 Return the data for the specified year ready for formatting similar to yeardatescalendar Entries in the week lists are day numbers Day numbers outside this month are zero class calendar TextCalendar firstweekda,en
2541,y 0 This class can be used to generate plain text calendars TextCalendar instances have the following methods formatmonth theyear themonth w 0 l 0 Return a month s calendar in a multi line string If w is provided it specifies the width of the date columns which are centered If l is given it specifies the number of lines that each week will use Depends on the first weekday as specified in the constructor or set by the setfirstweekday method prmonth theyear themonth w 0 l 0 Print a month s calendar as returned by formatmonth formatyear theyear w 2 l 1 c 6 m 3 Return a m column calendar for an entire year as a multi line string Optional parameters w l and c are for date column width lines per week and number of spaces between month columns respectively Depends on the first weekday as specified in the constructor or set by the setfirstweekday method The earliest year for which a calendar can be generated is platform dependent pryear theyear w 2 l 1 c 6 m 3 Print the calendar for an entire year as returned by formatyear class calendar HTMLCalendar firstweekday 0 This class can be used to generate HTML calendars HTMLCalendar instances have the following methods formatmonth theyear themonth withyear True Return a month s calendar as an HTML table If withyear is true the year will be included in the header otherwise just the month name will be used formatyear theyear width 3 Return a year s calendar as an HTML table width defaulting to 3 specifies the number of months per row formatyearpage theyear width 3 css calendar css encoding None Return a year s calendar as a complete HTML page width defaulting to 3 specifies the number of months per row css is the name for the cascading style sheet to be used None can be passed if no style sheet should be used encoding specifies the encoding to be used for the output defaulting to the system default encoding formatmonthname theyear themonth withyear True Return a month name as an HTML table row If withyear is true the year will be included in the row otherwise just the month name will be used HTMLCalendar has the following attributes you can override to customize the CSS classes used by the calendar cssclasses A list of CSS classes used for each weekday The default class list is cssclasses mon tue wed thu fri sat sun more styles can be added for each day cssclasses mon text bold tue wed thu fri sat sun red Note that the length of this list must be seven items cssclass_noday The CSS class for a weekday occurring in the previous or coming month New in version 3 7 cssclasses_weekday_head A list of CSS classes used for weekday names in the header row The default is the same as cssclasses New in version 3 7 cssclass_month_head The month s head CSS class used by formatmonthname The default value is month New in version 3 7 cssclass_month The CSS class for the whole month s table used by formatmonth The default value is month New in version 3 7 cssclass_year The CSS class for the whole year s table of tables used by formatyear The default value is year New in version 3 7 cssclass_year_head The CSS class for the table head for the whole year used by formatyear The default value is year New in version 3 7 Note that although the naming for the above described class attributes is singular e g cssclass_month cssclass_noday one can replace the single CSS class with a space separated list of CSS classes for example text bold text red Here is an example how HTMLCalendar can be customized class CustomHTMLCal calendar HTMLCalendar cssclasses style text nowrap for style in calendar HTMLCalendar cssclasses cssclass_month_head text center month head cssclass_month text center month cssclass_year text italic lead class calendar LocaleTextCalendar firstweekday 0 locale None This subclass of TextCalendar can be passed a locale name in the constructor and will return month and weekday names in the specified locale class calendar LocaleHTMLCalendar firstweekday 0 locale None This subclass of HTMLCalendar can be passed a locale name in the constructor and will return month and weekday names in the specified local,en
2542,e Note The constructor formatweekday and formatmonthname methods of these two classes temporarily change the LC_TIME locale to the given locale Because the current locale is a process wide setting they are not thread safe For simple text calendars this module provides the following functions calendar setfirstweekday weekday Sets the weekday 0 is Monday 6 is Sunday to start each week The values MONDAY TUESDAY WEDNESDAY THURSDAY FRIDAY SATURDAY and SUNDAY are provided for convenience For example to set the first weekday to Sunday import calendar calendar setfirstweekday calendar SUNDAY calendar firstweekday Returns the current setting for the weekday to start each week calendar isleap year Returns True if year is a leap year otherwise False calendar leapdays y1 y2 Returns the number of leap years in the range from y1 to y2 exclusive where y1 and y2 are years This function works for ranges spanning a century change calendar weekday year month day Returns the day of the week 0 is Monday for year 1970 month 1 12 day 1 31 calendar weekheader n Return a header containing abbreviated weekday names n specifies the width in characters for one weekday calendar monthrange year month Returns weekday of first day of the month and number of days in month for the specified year and month calendar monthcalendar year month Returns a matrix representing a month s calendar Each row represents a week days outside of the month are represented by zeros Each week begins with Monday unless set by setfirstweekday calendar prmonth theyear themonth w 0 l 0 Prints a month s calendar as returned by month calendar month theyear themonth w 0 l 0 Returns a month s calendar in a multi line string using the formatmonth of the TextCalendar class calendar prcal year w 0 l 0 c 6 m 3 Prints the calendar for an entire year as returned by calendar calendar calendar year w 2 l 1 c 6 m 3 Returns a 3 column calendar for an entire year as a multi line string using the formatyear of the TextCalendar class calendar timegm tuple An unrelated but handy function that takes a time tuple such as returned by the gmtime function in the time module and returns the corresponding Unix timestamp value assuming an epoch of 1970 and the POSIX encoding In fact time gmtime and timegm are each others inverse The calendar module exports the following data attributes calendar day_name An array that represents the days of the week in the current locale calendar day_abbr An array that represents the abbreviated days of the week in the current locale calendar MONDAY calendar TUESDAY calendar WEDNESDAY calendar THURSDAY calendar FRIDAY calendar SATURDAY calendar SUNDAY Aliases for the days of the week where MONDAY is 0 and SUNDAY is 6 New in version 3 12 class calendar Day Enumeration defining days of the week as integer constants The members of this enumeration are exported to the module scope as MONDAY through SUNDAY New in version 3 12 calendar month_name An array that represents the months of the year in the current locale This follows normal convention of January being month number 1 so it has a length of 13 and month_name 0 is the empty string calendar month_abbr An array that represents the abbreviated months of the year in the current locale This follows normal convention of January being month number 1 so it has a length of 13 and month_abbr 0 is the empty string calendar JANUARY calendar FEBRUARY calendar MARCH calendar APRIL calendar MAY calendar JUNE calendar JULY calendar AUGUST calendar SEPTEMBER calendar OCTOBER calendar NOVEMBER calendar DECEMBER Aliases for the months of the year where JANUARY is 1 and DECEMBER is 12 New in version 3 12 class calendar Month Enumeration defining months of the year as integer constants The members of this enumeration are exported to the module scope as JANUARY through DECEMBER New in version 3 12 The calendar module defines the following exceptions exception calendar IllegalMonthError month A subclass of ValueError raised when the given month number is outside of the range 1 12 inclusive month The invalid month number exception calendar Ill,en
2543,egalWeekdayError weekday A subclass of ValueError raised when the given weekday number is outside of the range 0 6 inclusive weekday The invalid weekday number See also Module datetime Object oriented interface to dates and times with similar functionality to the time module Module time Low level time related functions Command Line Usage New in version 2 5 The calendar module can be executed as a script from the command line to interactively print a calendar python m calendar h L LOCALE e ENCODING t text html w WIDTH l LINES s SPACING m MONTHS c CSS year month For example to print a calendar for the year 2000 python m calendar 2000 2000 January February March Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su 1 2 1 2 3 4 5 6 1 2 3 4 5 3 4 5 6 7 8 9 7 8 9 10 11 12 13 6 7 8 9 10 11 12 10 11 12 13 14 15 16 14 15 16 17 18 19 20 13 14 15 16 17 18 19 17 18 19 20 21 22 23 21 22 23 24 25 26 27 20 21 22 23 24 25 26 24 25 26 27 28 29 30 28 29 27 28 29 30 31 31 April May June Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su 1 2 1 2 3 4 5 6 7 1 2 3 4 3 4 5 6 7 8 9 8 9 10 11 12 13 14 5 6 7 8 9 10 11 10 11 12 13 14 15 16 15 16 17 18 19 20 21 12 13 14 15 16 17 18 17 18 19 20 21 22 23 22 23 24 25 26 27 28 19 20 21 22 23 24 25 24 25 26 27 28 29 30 29 30 31 26 27 28 29 30 July August September Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su 1 2 1 2 3 4 5 6 1 2 3 3 4 5 6 7 8 9 7 8 9 10 11 12 13 4 5 6 7 8 9 10 10 11 12 13 14 15 16 14 15 16 17 18 19 20 11 12 13 14 15 16 17 17 18 19 20 21 22 23 21 22 23 24 25 26 27 18 19 20 21 22 23 24 24 25 26 27 28 29 30 28 29 30 31 25 26 27 28 29 30 31 October November December Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su 1 1 2 3 4 5 1 2 3 2 3 4 5 6 7 8 6 7 8 9 10 11 12 4 5 6 7 8 9 10 9 10 11 12 13 14 15 13 14 15 16 17 18 19 11 12 13 14 15 16 17 16 17 18 19 20 21 22 20 21 22 23 24 25 26 18 19 20 21 22 23 24 23 24 25 26 27 28 29 27 28 29 30 25 26 27 28 29 30 31 30 31 The following options are accepted help h Show the help message and exit locale LOCALE L LOCALE The locale to use for month and weekday names Defaults to English encoding ENCODING e ENCODING The encoding to use for output encoding is required if locale is set type text html t text html Print the calendar to the terminal as text or as an HTML document year The year to print the calendar for Must be a number between 1 and 9999 Defaults to the current year month The month of the specified year to print the calendar for Must be a number between 1 and 12 and may only be used in text mode Defaults to printing a calendar for the full year Text mode options width WIDTH w WIDTH The width of the date column in terminal columns The date is printed centred in the column Any value lower than 2 is ignored Defaults to 2 lines LINES l LINES The number of lines for each week in terminal rows The date is printed top aligned Any value lower than 1 is ignored Defaults to 1 spacing SPACING s SPACING The space between months in columns Any value lower than 2 is ignored Defaults to 6 months MONTHS m MONTHS The number of months printed per row Defaults to 3 HTML mode options css CSS c CSS The path of a CSS stylesheet to use for the calendar This must either be relative to the generated HTML or an absolute HTTP or file URL,en
2544,json JSON encoder and decoder Source code Lib json __init__ py JSON JavaScript Object Notation specified by RFC 7159 which obsoletes RFC 4627 and by ECMA 404 is a lightweight data interchange format inspired by JavaScript object literal syntax although it is not a strict subset of JavaScript 1 Warning Be cautious when parsing JSON data from untrusted sources A malicious JSON string may cause the decoder to consume considerable CPU and memory resources Limiting the size of data to be parsed is recommended json exposes an API familiar to users of the standard library marshal and pickle modules Encoding basic Python object hierarchies import json json dumps foo bar baz None 1 0 2 foo bar baz null 1 0 2 print json dumps foo bar foo bar print json dumps u1234 u1234 print json dumps print json dumps c 0 b 0 a 0 sort_keys True a 0 b 0 c 0 from io import StringIO io StringIO json dump streaming API io io getvalue streaming API Compact encoding import json json dumps 1 2 3 4 5 6 7 separators 1 2 3 4 5 6 7 Pretty printing import json print json dumps 4 5 6 7 sort_keys True indent 4 4 5 6 7 Decoding JSON import json json loads foo bar baz null 1 0 2 foo bar baz None 1 0 2 json loads foo bar foo x08ar from io import StringIO io StringIO streaming API json load io streaming API Specializing JSON object decoding import json def as_complex dct if __complex__ in dct return complex dct real dct imag return dct json loads __complex__ true real 1 imag 2 object_hook as_complex 1 2j import decimal json loads 1 1 parse_float decimal Decimal Decimal 1 1 Extending JSONEncoder import json class ComplexEncoder json JSONEncoder def default self obj if isinstance obj complex return obj real obj imag Let the base class default method raise the TypeError return super default obj json dumps 2 1j cls ComplexEncoder 2 0 1 0 ComplexEncoder encode 2 1j 2 0 1 0 list ComplexEncoder iterencode 2 1j 2 0 1 0 Using json tool from the shell to validate and pretty print echo json obj python m json tool json obj echo 1 2 3 4 python m json tool Expecting property name enclosed in double quotes line 1 column 2 char 1 See Command Line Interface for detailed documentation Note JSON is a subset of YAML 1 2 The JSON produced by this module s default settings in particular the default separators value is also a subset of YAML 1 0 and 1 1 This module can thus also be used as a YAML serializer Note This module s encoders and decoders preserve input and output order by default Order is only lost if the underlying containers are unordered Basic Usage json dump obj fp skipkeys False ensure_ascii True check_circular True allow_nan True cls None indent None separators None default None sort_keys False kw Serialize obj as a JSON formatted stream to fp a write supporting file like object using this conversion table If skipkeys is true default False then dict keys that are not of a basic type str int float bool None will be skipped instead of raising a TypeError The json module always produces str objects not bytes objects Therefore fp write must support str input If ensure_ascii is true the default the output is guaranteed to have all incoming non ASCII characters escaped If ensure_ascii is false these characters will be output as is If check_circular is false default True then the circular reference check for container types will be skipped and a circular reference will result in a RecursionError or worse If allow_nan is false default True then it will be a ValueError to serialize out of range float values nan inf inf in strict compliance of the JSON specification If allow_nan is true their JavaScript equivalents NaN Infinity Infinity will be used If indent is a non negative integer or string then JSON array elements and object members will be pretty printed with that indent level An indent level of 0 negative or will only insert newlines None the default selects the most compact representation Using a positive integer indent indents that many spaces per level If indent is a string such as t that string is used to indent each level Changed in version 3 2 Allow strings for indent,en
2545, in addition to integers If specified separators should be an item_separator key_separator tuple The default is if indent is None and otherwise To get the most compact JSON representation you should specify to eliminate whitespace Changed in version 3 4 Use as default if indent is not None If specified default should be a function that gets called for objects that can t otherwise be serialized It should return a JSON encodable version of the object or raise a TypeError If not specified TypeError is raised If sort_keys is true default False then the output of dictionaries will be sorted by key To use a custom JSONEncoder subclass e g one that overrides the default method to serialize additional types specify it with the cls kwarg otherwise JSONEncoder is used Changed in version 3 6 All optional parameters are now keyword only Note Unlike pickle and marshal JSON is not a framed protocol so trying to serialize multiple objects with repeated calls to dump using the same fp will result in an invalid JSON file json dumps obj skipkeys False ensure_ascii True check_circular True allow_nan True cls None indent None separators None default None sort_keys False kw Serialize obj to a JSON formatted str using this conversion table The arguments have the same meaning as in dump Note Keys in key value pairs of JSON are always of the type str When a dictionary is converted into JSON all the keys of the dictionary are coerced to strings As a result of this if a dictionary is converted into JSON and then back into a dictionary the dictionary may not equal the original one That is loads dumps x x if x has non string keys json load fp cls None object_hook None parse_float None parse_int None parse_constant None object_pairs_hook None kw Deserialize fp a read supporting text file or binary file containing a JSON document to a Python object using this conversion table object_hook is an optional function that will be called with the result of any object literal decoded a dict The return value of object_hook will be used instead of the dict This feature can be used to implement custom decoders e g JSON RPC class hinting object_pairs_hook is an optional function that will be called with the result of any object literal decoded with an ordered list of pairs The return value of object_pairs_hook will be used instead of the dict This feature can be used to implement custom decoders If object_hook is also defined the object_pairs_hook takes priority Changed in version 3 1 Added support for object_pairs_hook parse_float if specified will be called with the string of every JSON float to be decoded By default this is equivalent to float num_str This can be used to use another datatype or parser for JSON floats e g decimal Decimal parse_int if specified will be called with the string of every JSON int to be decoded By default this is equivalent to int num_str This can be used to use another datatype or parser for JSON integers e g float Changed in version 3 11 The default parse_int of int now limits the maximum length of the integer string via the interpreter s integer string conversion length limitation to help avoid denial of service attacks parse_constant if specified will be called with one of the following strings Infinity Infinity NaN This can be used to raise an exception if invalid JSON numbers are encountered Changed in version 3 1 parse_constant doesn t get called on null true false anymore To use a custom JSONDecoder subclass specify it with the cls kwarg otherwise JSONDecoder is used Additional keyword arguments will be passed to the constructor of the class If the data being deserialized is not a valid JSON document a JSONDecodeError will be raised Changed in version 3 6 All optional parameters are now keyword only Changed in version 3 6 fp can now be a binary file The input encoding should be UTF 8 UTF 16 or UTF 32 json loads s cls None object_hook None parse_float None parse_int None parse_constant None object_pairs_hook None kw Deserialize s a str bytes or bytearray instance containing a JSON document to a Python object using this conver,en
2546,sion table The other arguments have the same meaning as in load If the data being deserialized is not a valid JSON document a JSONDecodeError will be raised Changed in version 3 6 s can now be of type bytes or bytearray The input encoding should be UTF 8 UTF 16 or UTF 32 Changed in version 3 9 The keyword argument encoding has been removed Encoders and Decoders class json JSONDecoder object_hook None parse_float None parse_int None parse_constant None strict True object_pairs_hook None Simple JSON decoder Performs the following translations in decoding by default JSON Python object dict array list string str number int int number real float true True false False null None It also understands NaN Infinity and Infinity as their corresponding float values which is outside the JSON spec object_hook if specified will be called with the result of every JSON object decoded and its return value will be used in place of the given dict This can be used to provide custom deserializations e g to support JSON RPC class hinting object_pairs_hook if specified will be called with the result of every JSON object decoded with an ordered list of pairs The return value of object_pairs_hook will be used instead of the dict This feature can be used to implement custom decoders If object_hook is also defined the object_pairs_hook takes priority Changed in version 3 1 Added support for object_pairs_hook parse_float if specified will be called with the string of every JSON float to be decoded By default this is equivalent to float num_str This can be used to use another datatype or parser for JSON floats e g decimal Decimal parse_int if specified will be called with the string of every JSON int to be decoded By default this is equivalent to int num_str This can be used to use another datatype or parser for JSON integers e g float parse_constant if specified will be called with one of the following strings Infinity Infinity NaN This can be used to raise an exception if invalid JSON numbers are encountered If strict is false True is the default then control characters will be allowed inside strings Control characters in this context are those with character codes in the 0 31 range including t tab n r and 0 If the data being deserialized is not a valid JSON document a JSONDecodeError will be raised Changed in version 3 6 All parameters are now keyword only decode s Return the Python representation of s a str instance containing a JSON document JSONDecodeError will be raised if the given JSON document is not valid raw_decode s Decode a JSON document from s a str beginning with a JSON document and return a 2 tuple of the Python representation and the index in s where the document ended This can be used to decode a JSON document from a string that may have extraneous data at the end class json JSONEncoder skipkeys False ensure_ascii True check_circular True allow_nan True sort_keys False indent None separators None default None Extensible JSON encoder for Python data structures Supports the following objects and types by default Python JSON dict object list tuple array str string int float int float derived Enums number True true False false None null Changed in version 3 4 Added support for int and float derived Enum classes To extend this to recognize other objects subclass and implement a default method with another method that returns a serializable object for o if possible otherwise it should call the superclass implementation to raise TypeError If skipkeys is false the default a TypeError will be raised when trying to encode keys that are not str int float or None If skipkeys is true such items are simply skipped If ensure_ascii is true the default the output is guaranteed to have all incoming non ASCII characters escaped If ensure_ascii is false these characters will be output as is If check_circular is true the default then lists dicts and custom encoded objects will be checked for circular references during encoding to prevent an infinite recursion which would cause a RecursionError Otherwise no such check takes place If allow_nan is true the,en
2547, default then NaN Infinity and Infinity will be encoded as such This behavior is not JSON specification compliant but is consistent with most JavaScript based encoders and decoders Otherwise it will be a ValueError to encode such floats If sort_keys is true default False then the output of dictionaries will be sorted by key this is useful for regression tests to ensure that JSON serializations can be compared on a day to day basis If indent is a non negative integer or string then JSON array elements and object members will be pretty printed with that indent level An indent level of 0 negative or will only insert newlines None the default selects the most compact representation Using a positive integer indent indents that many spaces per level If indent is a string such as t that string is used to indent each level Changed in version 3 2 Allow strings for indent in addition to integers If specified separators should be an item_separator key_separator tuple The default is if indent is None and otherwise To get the most compact JSON representation you should specify to eliminate whitespace Changed in version 3 4 Use as default if indent is not None If specified default should be a function that gets called for objects that can t otherwise be serialized It should return a JSON encodable version of the object or raise a TypeError If not specified TypeError is raised Changed in version 3 6 All parameters are now keyword only default o Implement this method in a subclass such that it returns a serializable object for o or calls the base implementation to raise a TypeError For example to support arbitrary iterators you could implement default like this def default self o try iterable iter o except TypeError pass else return list iterable Let the base class default method raise the TypeError return super default o encode o Return a JSON string representation of a Python data structure o For example json JSONEncoder encode foo bar baz foo bar baz iterencode o Encode the given object o and yield each string representation as available For example for chunk in json JSONEncoder iterencode bigobject mysocket write chunk Exceptions exception json JSONDecodeError msg doc pos Subclass of ValueError with the following additional attributes msg The unformatted error message doc The JSON document being parsed pos The start index of doc where parsing failed lineno The line corresponding to pos colno The column corresponding to pos New in version 3 5 Standard Compliance and Interoperability The JSON format is specified by RFC 7159 and by ECMA 404 This section details this module s level of compliance with the RFC For simplicity JSONEncoder and JSONDecoder subclasses and parameters other than those explicitly mentioned are not considered This module does not comply with the RFC in a strict fashion implementing some extensions that are valid JavaScript but not valid JSON In particular Infinite and NaN number values are accepted and output Repeated names within an object are accepted and only the value of the last name value pair is used Since the RFC permits RFC compliant parsers to accept input texts that are not RFC compliant this module s deserializer is technically RFC compliant under default settings Character Encodings The RFC requires that JSON be represented using either UTF 8 UTF 16 or UTF 32 with UTF 8 being the recommended default for maximum interoperability As permitted though not required by the RFC this module s serializer sets ensure_ascii True by default thus escaping the output so that the resulting strings only contain ASCII characters Other than the ensure_ascii parameter this module is defined strictly in terms of conversion between Python objects and Unicode strings and thus does not otherwise directly address the issue of character encodings The RFC prohibits adding a byte order mark BOM to the start of a JSON text and this module s serializer does not add a BOM to its output The RFC permits but does not require JSON deserializers to ignore an initial BOM in their input This module s deserializer raises a ValueError when,en
2548, an initial BOM is present The RFC does not explicitly forbid JSON strings which contain byte sequences that don t correspond to valid Unicode characters e g unpaired UTF 16 surrogates but it does note that they may cause interoperability problems By default this module accepts and outputs when present in the original str code points for such sequences Infinite and NaN Number Values The RFC does not permit the representation of infinite or NaN number values Despite that by default this module accepts and outputs Infinity Infinity and NaN as if they were valid JSON number literal values Neither of these calls raises an exception but the results are not valid JSON json dumps float inf Infinity json dumps float nan NaN Same when deserializing json loads Infinity inf json loads NaN nan In the serializer the allow_nan parameter can be used to alter this behavior In the deserializer the parse_constant parameter can be used to alter this behavior Repeated Names Within an Object The RFC specifies that the names within a JSON object should be unique but does not mandate how repeated names in JSON objects should be handled By default this module does not raise an exception instead it ignores all but the last name value pair for a given name weird_json x 1 x 2 x 3 json loads weird_json x 3 The object_pairs_hook parameter can be used to alter this behavior Top level Non Object Non Array Values The old version of JSON specified by the obsolete RFC 4627 required that the top level value of a JSON text must be either a JSON object or array Python dict or list and could not be a JSON null boolean number or string value RFC 7159 removed that restriction and this module does not and has never implemented that restriction in either its serializer or its deserializer Regardless for maximum interoperability you may wish to voluntarily adhere to the restriction yourself Implementation Limitations Some JSON deserializer implementations may set limits on the size of accepted JSON texts the maximum level of nesting of JSON objects and arrays the range and precision of JSON numbers the content and maximum length of JSON strings This module does not impose any such limits beyond those of the relevant Python datatypes themselves or the Python interpreter itself When serializing to JSON beware any such limitations in applications that may consume your JSON In particular it is common for JSON numbers to be deserialized into IEEE 754 double precision numbers and thus subject to that representation s range and precision limitations This is especially relevant when serializing Python int values of extremely large magnitude or when serializing instances of exotic numerical types such as decimal Decimal Command Line Interface Source code Lib json tool py The json tool module provides a simple command line interface to validate and pretty print JSON objects If the optional infile and outfile arguments are not specified sys stdin and sys stdout will be used respectively echo json obj python m json tool json obj echo 1 2 3 4 python m json tool Expecting property name enclosed in double quotes line 1 column 2 char 1 Changed in version 3 5 The output is now in the same order as the input Use the sort keys option to sort the output of dictionaries alphabetically by key Command line options infile The JSON file to be validated or pretty printed python m json tool mp_films json title And Now for Something Completely Different year 1971 title Monty Python and the Holy Grail year 1975 If infile is not specified read from sys stdin outfile Write the output of the infile to the given outfile Otherwise write it to sys stdout sort keys Sort the output of dictionaries alphabetically by key New in version 3 5 no ensure ascii Disable escaping of non ascii characters see json dumps for more information New in version 3 9 json lines Parse every input line as separate JSON object New in version 3 8 indent tab no indent compact Mutually exclusive options for whitespace control New in version 3 9 h help Show the help message Footnotes 1 As noted in the errata for RFC 7159 JSON,en
2549, permits literal U 2028 LINE SEPARATOR and U 2029 PARAGRAPH SEPARATOR characters in strings whereas JavaScript as of ECMAScript Edition 5 1 does not,en
2550,urllib URL handling modules Source code Lib urllib urllib is a package that collects several modules for working with URLs urllib request for opening and reading URLs urllib error containing the exceptions raised by urllib request urllib parse for parsing URLs urllib robotparser for parsing robots txt files,en
2551,marshal Internal Python object serialization This module contains functions that can read and write Python values in a binary format The format is specific to Python but independent of machine architecture issues e g you can write a Python value to a file on a PC transport the file to a Sun and read it back there Details of the format are undocumented on purpose it may change between Python versions although it rarely does 1 This is not a general persistence module For general persistence and transfer of Python objects through RPC calls see the modules pickle and shelve The marshal module exists mainly to support reading and writing the pseudo compiled code for Python modules of pyc files Therefore the Python maintainers reserve the right to modify the marshal format in backward incompatible ways should the need arise If you re serializing and de serializing Python objects use the pickle module instead the performance is comparable version independence is guaranteed and pickle supports a substantially wider range of objects than marshal Warning The marshal module is not intended to be secure against erroneous or maliciously constructed data Never unmarshal data received from an untrusted or unauthenticated source Not all Python object types are supported in general only objects whose value is independent from a particular invocation of Python can be written and read by this module The following types are supported booleans integers floating point numbers complex numbers strings bytes bytearrays tuples lists sets frozensets dictionaries and code objects where it should be understood that tuples lists sets frozensets and dictionaries are only supported as long as the values contained therein are themselves supported The singletons None Ellipsis and StopIteration can also be marshalled and unmarshalled For format version lower than 3 recursive lists sets and dictionaries cannot be written see below There are functions that read write files as well as functions operating on bytes like objects The module defines these functions marshal dump value file version Write the value on the open file The value must be a supported type The file must be a writeable binary file If the value has or contains an object that has an unsupported type a ValueError exception is raised but garbage data will also be written to the file The object will not be properly read back by load The version argument indicates the data format that dump should use see below Raises an auditing event marshal dumps with arguments value version marshal load file Read one value from the open file and return it If no valid value is read e g because the data has a different Python version s incompatible marshal format raise EOFError ValueError or TypeError The file must be a readable binary file Raises an auditing event marshal load with no arguments Note If an object containing an unsupported type was marshalled with dump load will substitute None for the unmarshallable type Changed in version 3 10 This call used to raise a code __new__ audit event for each code object Now it raises a single marshal load event for the entire load operation marshal dumps value version Return the bytes object that would be written to a file by dump value file The value must be a supported type Raise a ValueError exception if value has or contains an object that has an unsupported type The version argument indicates the data format that dumps should use see below Raises an auditing event marshal dumps with arguments value version marshal loads bytes Convert the bytes like object to a value If no valid value is found raise EOFError ValueError or TypeError Extra bytes in the input are ignored Raises an auditing event marshal loads with argument bytes Changed in version 3 10 This call used to raise a code __new__ audit event for each code object Now it raises a single marshal loads event for the entire load operation In addition the following constants are defined marshal version Indicates the format that the module uses Version 0 is the historical format version 1 shares interned strings,en
2552, and version 2 uses a binary format for floating point numbers Version 3 adds support for object instancing and recursion The current version is 4 Footnotes 1 The name of this module stems from a bit of terminology used by the designers of Modula 3 amongst others who use the term marshalling for shipping of data around in a self contained form Strictly speaking to marshal means to convert some data from internal to external form in an RPC buffer for instance and unmarshalling for the reverse process,en
2553,What s New in Python 2 2 Author A M Kuchling Introduction This article explains the new features in Python 2 2 2 released on October 14 2002 Python 2 2 2 is a bugfix release of Python 2 2 originally released on December 21 2001 Python 2 2 can be thought of as the cleanup release There are some features such as generators and iterators that are completely new but most of the changes significant and far reaching though they may be are aimed at cleaning up irregularities and dark corners of the language design This article doesn t attempt to provide a complete specification of the new features but instead provides a convenient overview For full details you should refer to the documentation for Python 2 2 such as the Python Library Reference and the Python Reference Manual If you want to understand the complete implementation and design rationale for a change refer to the PEP for a particular new feature PEPs 252 and 253 Type and Class Changes The largest and most far reaching changes in Python 2 2 are to Python s model of objects and classes The changes should be backward compatible so it s likely that your code will continue to run unchanged but the changes provide some amazing new capabilities Before beginning this the longest and most complicated section of this article I ll provide an overview of the changes and offer some comments A long time ago I wrote a web page listing flaws in Python s design One of the most significant flaws was that it s impossible to subclass Python types implemented in C In particular it s not possible to subclass built in types so you can t just subclass say lists in order to add a single useful method to them The UserList module provides a class that supports all of the methods of lists and that can be subclassed further but there s lots of C code that expects a regular Python list and won t accept a UserList instance Python 2 2 fixes this and in the process adds some exciting new capabilities A brief summary You can subclass built in types such as lists and even integers and your subclasses should work in every place that requires the original type It s now possible to define static and class methods in addition to the instance methods available in previous versions of Python It s also possible to automatically call methods on accessing or setting an instance attribute by using a new mechanism called properties Many uses of __getattr__ can be rewritten to use properties instead making the resulting code simpler and faster As a small side benefit attributes can now have docstrings too The list of legal attributes for an instance can be limited to a particular set using slots making it possible to safeguard against typos and perhaps make more optimizations possible in future versions of Python Some users have voiced concern about all these changes Sure they say the new features are neat and lend themselves to all sorts of tricks that weren t possible in previous versions of Python but they also make the language more complicated Some people have said that they ve always recommended Python for its simplicity and feel that its simplicity is being lost Personally I think there s no need to worry Many of the new features are quite esoteric and you can write a lot of Python code without ever needed to be aware of them Writing a simple class is no more difficult than it ever was so you don t need to bother learning or teaching them unless they re actually needed Some very complicated tasks that were previously only possible from C will now be possible in pure Python and to my mind that s all for the better I m not going to attempt to cover every single corner case and small change that were required to make the new features work Instead this section will paint only the broad strokes See section Related Links Related Links for further sources of information about Python 2 2 s new object model Old and New Classes First you should know that Python 2 2 really has two kinds of classes classic or old style classes and new style classes The old style class model is exactly the same as the class model in e,en
2554,arlier versions of Python All the new features described in this section apply only to new style classes This divergence isn t intended to last forever eventually old style classes will be dropped possibly in Python 3 0 So how do you define a new style class You do it by subclassing an existing new style class Most of Python s built in types such as integers lists dictionaries and even files are new style classes now A new style class named object the base class for all built in types has also been added so if no built in type is suitable you can just subclass object class C object def __init__ self This means that class statements that don t have any base classes are always classic classes in Python 2 2 Actually you can also change this by setting a module level variable named __metaclass__ see PEP 253 for the details but it s easier to just subclass object The type objects for the built in types are available as built ins named using a clever trick Python has always had built in functions named int float and str In 2 2 they aren t functions any more but type objects that behave as factories when called int type int int 123 123 To make the set of types complete new type objects such as dict and file have been added Here s a more interesting example adding a lock method to file objects class LockableFile file def lock self operation length 0 start 0 whence 0 import fcntl return fcntl lockf self fileno operation length start whence The now obsolete posixfile module contained a class that emulated all of a file object s methods and also added a lock method but this class couldn t be passed to internal functions that expected a built in file something which is possible with our new LockableFile Descriptors In previous versions of Python there was no consistent way to discover what attributes and methods were supported by an object There were some informal conventions such as defining __members__ and __methods__ attributes that were lists of names but often the author of an extension type or a class wouldn t bother to define them You could fall back on inspecting the __dict__ of an object but when class inheritance or an arbitrary __getattr__ hook were in use this could still be inaccurate The one big idea underlying the new class model is that an API for describing the attributes of an object using descriptors has been formalized Descriptors specify the value of an attribute stating whether it s a method or a field With the descriptor API static methods and class methods become possible as well as more exotic constructs Attribute descriptors are objects that live inside class objects and have a few attributes of their own __name__ is the attribute s name __doc__ is the attribute s docstring __get__ object is a method that retrieves the attribute value from object __set__ object value sets the attribute on object to value __delete__ object value deletes the value attribute of object For example when you write obj x the steps that Python actually performs are descriptor obj __class__ x descriptor __get__ obj For methods descriptor __get__ returns a temporary object that s callable and wraps up the instance and the method to be called on it This is also why static methods and class methods are now possible they have descriptors that wrap up just the method or the method and the class As a brief explanation of these new kinds of methods static methods aren t passed the instance and therefore resemble regular functions Class methods are passed the class of the object but not the object itself Static and class methods are defined like this class C object def f arg1 arg2 f staticmethod f def g cls arg1 arg2 g classmethod g The staticmethod function takes the function f and returns it wrapped up in a descriptor so it can be stored in the class object You might expect there to be special syntax for creating such methods def static f defstatic f or something like that but no such syntax has been defined yet that s been left for future versions of Python More new features such as slots and properties are also implemented as new kinds ,en
2555,of descriptors and it s not difficult to write a descriptor class that does something novel For example it would be possible to write a descriptor class that made it possible to write Eiffel style preconditions and postconditions for a method A class that used this feature might be defined like this from eiffel import eiffelmethod class C object def f self arg1 arg2 The actual function def pre_f self Check preconditions def post_f self Check postconditions f eiffelmethod f pre_f post_f Note that a person using the new eiffelmethod doesn t have to understand anything about descriptors This is why I think the new features don t increase the basic complexity of the language There will be a few wizards who need to know about it in order to write eiffelmethod or the ZODB or whatever but most users will just write code on top of the resulting libraries and ignore the implementation details Multiple Inheritance The Diamond Rule Multiple inheritance has also been made more useful through changing the rules under which names are resolved Consider this set of classes diagram taken from PEP 253 by Guido van Rossum class A def save self class B class C def save self class D The lookup rule for classic classes is simple but not very smart the base classes are searched depth first going from left to right A reference to D save will search the classes D B and then A where save would be found and returned C save would never be found at all This is bad because if C s save method is saving some internal state specific to C not calling it will result in that state never getting saved New style classes follow a different algorithm that s a bit more complicated to explain but does the right thing in this situation Note that Python 2 3 changes this algorithm to one that produces the same results in most cases but produces more useful results for really complicated inheritance graphs 1 List all the base classes following the classic lookup rule and include a class multiple times if it s visited repeatedly In the above example the list of visited classes is D B A C A 2 Scan the list for duplicated classes If any are found remove all but one occurrence leaving the last one in the list In the above example the list becomes D B C A after dropping duplicates Following this rule referring to D save will return C save which is the behaviour we re after This lookup rule is the same as the one followed by Common Lisp A new built in function super provides a way to get at a class s superclasses without having to reimplement Python s algorithm The most commonly used form will be super class obj which returns a bound superclass object not the actual class object This form will be used in methods to call a method in the superclass for example D s save method would look like this class D B C def save self Call superclass save super D self save Save D s private information here super can also return unbound superclass objects when called as super class or super class1 class2 but this probably won t often be useful Attribute Access A fair number of sophisticated Python classes define hooks for attribute access using __getattr__ most commonly this is done for convenience to make code more readable by automatically mapping an attribute access such as obj parent into a method call such as obj get_parent Python 2 2 adds some new ways of controlling attribute access First __getattr__ attr_name is still supported by new style classes and nothing about it has changed As before it will be called when an attempt is made to access obj foo and no attribute named foo is found in the instance s dictionary New style classes also support a new method __getattribute__ attr_name The difference between the two methods is that __getattribute__ is always called whenever any attribute is accessed while the old __getattr__ is only called if foo isn t found in the instance s dictionary However Python 2 2 s support for properties will often be a simpler way to trap attribute references Writing a __getattr__ method is complicated because to avoid recursion you can t use regular attri,en
2556,bute accesses inside them and instead have to mess around with the contents of __dict__ __getattr__ methods also end up being called by Python when it checks for other methods such as __repr__ or __coerce__ and so have to be written with this in mind Finally calling a function on every attribute access results in a sizable performance loss property is a new built in type that packages up three functions that get set or delete an attribute and a docstring For example if you want to define a size attribute that s computed but also settable you could write class C object def get_size self result computation return result def set_size self size compute something based on the size and set internal state appropriately Define a property The delete this attribute method is defined as None so the attribute can t be deleted size property get_size set_size None Storage size of this instance That is certainly clearer and easier to write than a pair of __getattr__ __setattr__ methods that check for the size attribute and handle it specially while retrieving all other attributes from the instance s __dict__ Accesses to size are also the only ones which have to perform the work of calling a function so references to other attributes run at their usual speed Finally it s possible to constrain the list of attributes that can be referenced on an object using the new __slots__ class attribute Python objects are usually very dynamic at any time it s possible to define a new attribute on an instance by just doing obj new_attr 1 A new style class can define a class attribute named __slots__ to limit the legal attributes to a particular set of names An example will make this clear class C object __slots__ template name obj C print obj template None obj template Test print obj template Test obj newattr None Traceback most recent call last File stdin line 1 in AttributeError C object has no attribute newattr Note how you get an AttributeError on the attempt to assign to an attribute not listed in __slots__ Related Links This section has just been a quick overview of the new features giving enough of an explanation to start you programming but many details have been simplified or ignored Where should you go to get a more complete picture The Descriptor Guide is a lengthy tutorial introduction to the descriptor features written by Guido van Rossum If my description has whetted your appetite go read this tutorial next because it goes into much more detail about the new features while still remaining quite easy to read Next there are two relevant PEPs PEP 252 and PEP 253 PEP 252 is titled Making Types Look More Like Classes and covers the descriptor API PEP 253 is titled Subtyping Built in Types and describes the changes to type objects that make it possible to subtype built in objects PEP 253 is the more complicated PEP of the two and at a few points the necessary explanations of types and meta types may cause your head to explode Both PEPs were written and implemented by Guido van Rossum with substantial assistance from the rest of the Zope Corp team Finally there s the ultimate authority the source code Most of the machinery for the type handling is in Objects typeobject c but you should only resort to it after all other avenues have been exhausted including posting a question to python list or python dev PEP 234 Iterators Another significant addition to 2 2 is an iteration interface at both the C and Python levels Objects can define how they can be looped over by callers In Python versions up to 2 1 the usual way to make for item in obj work is to define a __getitem__ method that looks something like this def __getitem__ self index return next item __getitem__ is more properly used to define an indexing operation on an object so that you can write obj 5 to retrieve the sixth element It s a bit misleading when you re using this only to support for loops Consider some file like object that wants to be looped over the index parameter is essentially meaningless as the class probably assumes that a series of __getitem__ calls will be made with index ,en
2557,incrementing by one each time In other words the presence of the __getitem__ method doesn t mean that using file 5 to randomly access the sixth element will work though it really should In Python 2 2 iteration can be implemented separately and __getitem__ methods can be limited to classes that really do support random access The basic idea of iterators is simple A new built in function iter obj or iter C sentinel is used to get an iterator iter obj returns an iterator for the object obj while iter C sentinel returns an iterator that will invoke the callable object C until it returns sentinel to signal that the iterator is done Python classes can define an __iter__ method which should create and return a new iterator for the object if the object is its own iterator this method can just return self In particular iterators will usually be their own iterators Extension types implemented in C can implement a tp_iter function in order to return an iterator and extension types that want to behave as iterators can define a tp_iternext function So after all this what do iterators actually do They have one required method next which takes no arguments and returns the next value When there are no more values to be returned calling next should raise the StopIteration exception L 1 2 3 i iter L print i iterator object at 0x8116870 i next 1 i next 2 i next 3 i next Traceback most recent call last File stdin line 1 in StopIteration In 2 2 Python s for statement no longer expects a sequence it expects something for which iter will return an iterator For backward compatibility and convenience an iterator is automatically constructed for sequences that don t implement __iter__ or a tp_iter slot so for i in 1 2 3 will still work Wherever the Python interpreter loops over a sequence it s been changed to use the iterator protocol This means you can do things like this L 1 2 3 i iter L a b c i a b c 1 2 3 Iterator support has been added to some of Python s basic types Calling iter on a dictionary will return an iterator which loops over its keys m Jan 1 Feb 2 Mar 3 Apr 4 May 5 Jun 6 Jul 7 Aug 8 Sep 9 Oct 10 Nov 11 Dec 12 for key in m print key m key Mar 3 Feb 2 Aug 8 Sep 9 May 5 Jun 6 Jul 7 Jan 1 Apr 4 Nov 11 Dec 12 Oct 10 That s just the default behaviour If you want to iterate over keys values or key value pairs you can explicitly call the iterkeys itervalues or iteritems methods to get an appropriate iterator In a minor related change the in operator now works on dictionaries so key in dict is now equivalent to dict has_key key Files also provide an iterator which calls the readline method until there are no more lines in the file This means you can now read each line of a file using code like this for line in file do something for each line Note that you can only go forward in an iterator there s no way to get the previous element reset the iterator or make a copy of it An iterator object could provide such additional capabilities but the iterator protocol only requires a next method See also PEP 234 Iterators Written by Ka Ping Yee and GvR implemented by the Python Labs crew mostly by GvR and Tim Peters PEP 255 Simple Generators Generators are another new feature one that interacts with the introduction of iterators You re doubtless familiar with how function calls work in Python or C When you call a function it gets a private namespace where its local variables are created When the function reaches a return statement the local variables are destroyed and the resulting value is returned to the caller A later call to the same function will get a fresh new set of local variables But what if the local variables weren t thrown away on exiting a function What if you could later resume the function where it left off This is what generators provide they can be thought of as resumable functions Here s the simplest example of a generator function def generate_ints N for i in range N yield i A new keyword yield was introduced for generators Any function containing a yield statement is a generator function this is detected by Python s bytecode comp,en
2558,iler which compiles the function specially as a result Because a new keyword was introduced generators must be explicitly enabled in a module by including a from __future__ import generators statement near the top of the module s source code In Python 2 3 this statement will become unnecessary When you call a generator function it doesn t return a single value instead it returns a generator object that supports the iterator protocol On executing the yield statement the generator outputs the value of i similar to a return statement The big difference between yield and a return statement is that on reaching a yield the generator s state of execution is suspended and local variables are preserved On the next call to the generator s next method the function will resume executing immediately after the yield statement For complicated reasons the yield statement isn t allowed inside the try block of a try finally statement read PEP 255 for a full explanation of the interaction between yield and exceptions Here s a sample usage of the generate_ints generator gen generate_ints 3 gen generator object at 0x8117f90 gen next 0 gen next 1 gen next 2 gen next Traceback most recent call last File stdin line 1 in File stdin line 2 in generate_ints StopIteration You could equally write for i in generate_ints 5 or a b c generate_ints 3 Inside a generator function the return statement can only be used without a value and signals the end of the procession of values afterwards the generator cannot return any further values return with a value such as return 5 is a syntax error inside a generator function The end of the generator s results can also be indicated by raising StopIteration manually or by just letting the flow of execution fall off the bottom of the function You could achieve the effect of generators manually by writing your own class and storing all the local variables of the generator as instance variables For example returning a list of integers could be done by setting self count to 0 and having the next method increment self count and return it However for a moderately complicated generator writing a corresponding class would be much messier Lib test test_generators py contains a number of more interesting examples The simplest one implements an in order traversal of a tree using generators recursively A recursive generator that generates Tree leaves in in order def inorder t if t for x in inorder t left yield x yield t label for x in inorder t right yield x Two other examples in Lib test test_generators py produce solutions for the N Queens problem placing N queens on an NxN chess board so that no queen threatens another and the Knight s Tour a route that takes a knight to every square of an NxN chessboard without visiting any square twice The idea of generators comes from other programming languages especially Icon https www2 cs arizona edu icon where the idea of generators is central In Icon every expression and function call behaves like a generator One example from An Overview of the Icon Programming Language at https www2 cs arizona edu icon docs ipd266 htm gives an idea of what this looks like sentence Store it in the neighboring harbor if i find or sentence 5 then write i In Icon the find function returns the indexes at which the substring or is found 3 23 33 In the if statement i is first assigned a value of 3 but 3 is less than 5 so the comparison fails and Icon retries it with the second value of 23 23 is greater than 5 so the comparison now succeeds and the code prints the value 23 to the screen Python doesn t go nearly as far as Icon in adopting generators as a central concept Generators are considered a new part of the core Python language but learning or using them isn t compulsory if they don t solve any problems that you have feel free to ignore them One novel feature of Python s interface as compared to Icon s is that a generator s state is represented as a concrete object the iterator that can be passed around to other functions or stored in a data structure See also PEP 255 Simple Generators Written by Neil,en
2559, Schemenauer Tim Peters Magnus Lie Hetland Implemented mostly by Neil Schemenauer and Tim Peters with other fixes from the Python Labs crew PEP 237 Unifying Long Integers and Integers In recent versions the distinction between regular integers which are 32 bit values on most machines and long integers which can be of arbitrary size was becoming an annoyance For example on platforms that support files larger than 2 32 bytes the tell method of file objects has to return a long integer However there were various bits of Python that expected plain integers and would raise an error if a long integer was provided instead For example in Python 1 5 only regular integers could be used as a slice index and abc 1L would raise a TypeError exception with the message slice index must be int Python 2 2 will shift values from short to long integers as required The L suffix is no longer needed to indicate a long integer literal as now the compiler will choose the appropriate type Using the L suffix will be discouraged in future 2 x versions of Python triggering a warning in Python 2 4 and probably dropped in Python 3 0 Many operations that used to raise an OverflowError will now return a long integer as their result For example 1234567890123 1234567890123L 2 64 18446744073709551616L In most cases integers and long integers will now be treated identically You can still distinguish them with the type built in function but that s rarely needed See also PEP 237 Unifying Long Integers and Integers Written by Moshe Zadka and Guido van Rossum Implemented mostly by Guido van Rossum PEP 238 Changing the Division Operator The most controversial change in Python 2 2 heralds the start of an effort to fix an old design flaw that s been in Python from the beginning Currently Python s division operator behaves like C s division operator when presented with two integer arguments it returns an integer result that s truncated down when there would be a fractional part For example 3 2 is 1 not 1 5 and 1 2 is 1 not 0 5 This means that the results of division can vary unexpectedly depending on the type of the two operands and because Python is dynamically typed it can be difficult to determine the possible types of the operands The controversy is over whether this is really a design flaw and whether it s worth breaking existing code to fix this It s caused endless discussions on python dev and in July 2001 erupted into a storm of acidly sarcastic postings on comp lang python I won t argue for either side here and will stick to describing what s implemented in 2 2 Read PEP 238 for a summary of arguments and counter arguments Because this change might break code it s being introduced very gradually Python 2 2 begins the transition but the switch won t be complete until Python 3 0 First I ll borrow some terminology from PEP 238 True division is the division that most non programmers are familiar with 3 2 is 1 5 1 4 is 0 25 and so forth Floor division is what Python s operator currently does when given integer operands the result is the floor of the value returned by true division Classic division is the current mixed behaviour of it returns the result of floor division when the operands are integers and returns the result of true division when one of the operands is a floating point number Here are the changes 2 2 introduces A new operator is the floor division operator Yes we know it looks like C s comment symbol always performs floor division no matter what the types of its operands are so 1 2 is 0 and 1 0 2 0 is also 0 0 is always available in Python 2 2 you don t need to enable it using a __future__ statement By including a from __future__ import division in a module the operator will be changed to return the result of true division so 1 2 is 0 5 Without the __future__ statement still means classic division The default meaning of will not change until Python 3 0 Classes can define methods called __truediv__ and __floordiv__ to overload the two division operators At the C level there are also slots in the PyNumberMethods structure so extension types can defi,en
2560,ne the two operators Python 2 2 supports some command line arguments for testing whether code will work with the changed division semantics Running python with Q warn will cause a warning to be issued whenever division is applied to two integers You can use this to find code that s affected by the change and fix it By default Python 2 2 will simply perform classic division without a warning the warning will be turned on by default in Python 2 3 See also PEP 238 Changing the Division Operator Written by Moshe Zadka and Guido van Rossum Implemented by Guido van Rossum Unicode Changes Python s Unicode support has been enhanced a bit in 2 2 Unicode strings are usually stored as UCS 2 as 16 bit unsigned integers Python 2 2 can also be compiled to use UCS 4 32 bit unsigned integers as its internal encoding by supplying enable unicode ucs4 to the configure script It s also possible to specify disable unicode to completely disable Unicode support When built to use UCS 4 a wide Python the interpreter can natively handle Unicode characters from U 000000 to U 110000 so the range of legal values for the unichr function is expanded accordingly Using an interpreter compiled to use UCS 2 a narrow Python values greater than 65535 will still cause unichr to raise a ValueError exception This is all described in PEP 261 Support for wide Unicode characters consult it for further details Another change is simpler to explain Since their introduction Unicode strings have supported an encode method to convert the string to a selected encoding such as UTF 8 or Latin 1 A symmetric decode encoding method has been added to 8 bit strings though not to Unicode strings in 2 2 decode assumes that the string is in the specified encoding and decodes it returning whatever is returned by the codec Using this new feature codecs have been added for tasks not directly related to Unicode For example codecs have been added for uu encoding MIME s base64 encoding and compression with the zlib module s Here is a lengthy piece of redundant overly verbose and repetitive text data s encode zlib data x x9c r xc9 xc1 r x80 x10 x04 xc0 Ul data decode zlib Here is a lengthy piece of redundant overly verbose nand repetitive text n print s encode uu begin 666 data M2 5R92 I R A QE F T D EE8V4 V8 F5D 6YD86YT O F5R D F5R8F S92P 86YD E 5T 71I F4 5X X end sheesh encode rot 13 furrfu To convert a class instance to Unicode a __unicode__ method can be defined by a class analogous to __str__ encode decode and __unicode__ were implemented by Marc André Lemburg The changes to support using UCS 4 internally were implemented by Fredrik Lundh and Martin von Löwis See also PEP 261 Support for wide Unicode characters Written by Paul Prescod PEP 227 Nested Scopes In Python 2 1 statically nested scopes were added as an optional feature to be enabled by a from __future__ import nested_scopes directive In 2 2 nested scopes no longer need to be specially enabled and are now always present The rest of this section is a copy of the description of nested scopes from my What s New in Python 2 1 document if you read it when 2 1 came out you can skip the rest of this section The largest change introduced in Python 2 1 and made complete in 2 2 is to Python s scoping rules In Python 2 0 at any given time there are at most three namespaces used to look up variable names local module level and the built in namespace This often surprised people because it didn t match their intuitive expectations For example a nested recursive function definition doesn t work def f def g value return g value 1 1 The function g will always raise a NameError exception because the binding of the name g isn t in either its local namespace or in the module level namespace This isn t much of a problem in practice how often do you recursively define interior functions like this but this also made using the lambda expression clumsier and this was a problem in practice In code which uses lambda you can often find local variables being copied by passing them as the default values of arguments def find self name Return list of any,en
2561, entries equal to name L filter lambda x name name x name self list_attribute return L The readability of Python code written in a strongly functional style suffers greatly as a result The most significant change to Python 2 2 is that static scoping has been added to the language to fix this problem As a first effect the name name default argument is now unnecessary in the above example Put simply when a given variable name is not assigned a value within a function by an assignment or the def class or import statements references to the variable will be looked up in the local namespace of the enclosing scope A more detailed explanation of the rules and a dissection of the implementation can be found in the PEP This change may cause some compatibility problems for code where the same variable name is used both at the module level and as a local variable within a function that contains further function definitions This seems rather unlikely though since such code would have been pretty confusing to read in the first place One side effect of the change is that the from module import and exec statements have been made illegal inside a function scope under certain conditions The Python reference manual has said all along that from module import is only legal at the top level of a module but the CPython interpreter has never enforced this before As part of the implementation of nested scopes the compiler which turns Python source into bytecodes has to generate different code to access variables in a containing scope from module import and exec make it impossible for the compiler to figure this out because they add names to the local namespace that are unknowable at compile time Therefore if a function contains function definitions or lambda expressions with free variables the compiler will flag this by raising a SyntaxError exception To make the preceding explanation a bit clearer here s an example x 1 def f The next line is a syntax error exec x 2 def g return x Line 4 containing the exec statement is a syntax error since exec would define a new local variable named x whose value should be accessed by g This shouldn t be much of a limitation since exec is rarely used in most Python code and when it is used it s often a sign of a poor design anyway See also PEP 227 Statically Nested Scopes Written and implemented by Jeremy Hylton New and Improved Modules The xmlrpclib module was contributed to the standard library by Fredrik Lundh providing support for writing XML RPC clients XML RPC is a simple remote procedure call protocol built on top of HTTP and XML For example the following snippet retrieves a list of RSS channels from the O Reilly Network and then lists the recent headlines for one channel import xmlrpclib s xmlrpclib Server http www oreillynet com meerkat xml rpc server php channels s meerkat getChannels channels is a list of dictionaries like this id 4 title Freshmeat Daily News id 190 title 32Bits Online id 4549 title 3DGamers Get the items for one channel items s meerkat getItems channel 4 items is another list of dictionaries like this link http freshmeat net releases 52719 description A utility which converts HTML to XSL FO title html2fo 0 3 Default The SimpleXMLRPCServer module makes it easy to create straightforward XML RPC servers See http xmlrpc scripting com for more information about XML RPC The new hmac module implements the HMAC algorithm described by RFC 2104 Contributed by Gerhard Häring Several functions that originally returned lengthy tuples now return pseudo sequences that still behave like tuples but also have mnemonic attributes such as memberst_mtime or tm_year The enhanced functions include stat fstat statvfs and fstatvfs in the os module and localtime gmtime and strptime in the time module For example to obtain a file s size using the old tuples you d end up writing something like file_size os stat filename stat ST_SIZE but now this can be written more clearly as file_size os stat filename st_size The original patch for this feature was contributed by Nick Mathewson The Python profiler has been ,en
2562,extensively reworked and various errors in its output have been corrected Contributed by Fred L Drake Jr and Tim Peters The socket module can be compiled to support IPv6 specify the enable ipv6 option to Python s configure script Contributed by Jun ichiro itojun Hagino Two new format characters were added to the struct module for 64 bit integers on platforms that support the C long long type q is for a signed 64 bit integer and Q is for an unsigned one The value is returned in Python s long integer type Contributed by Tim Peters In the interpreter s interactive mode there s a new built in function help that uses the pydoc module introduced in Python 2 1 to provide interactive help help object displays any available help text about object help with no argument puts you in an online help utility where you can enter the names of functions classes or modules to read their help text Contributed by Guido van Rossum using Ka Ping Yee s pydoc module Various bugfixes and performance improvements have been made to the SRE engine underlying the re module For example the re sub and re split functions have been rewritten in C Another contributed patch speeds up certain Unicode character ranges by a factor of two and a new finditer method that returns an iterator over all the non overlapping matches in a given string SRE is maintained by Fredrik Lundh The BIGCHARSET patch was contributed by Martin von Löwis The smtplib module now supports RFC 2487 Secure SMTP over TLS so it s now possible to encrypt the SMTP traffic between a Python program and the mail transport agent being handed a message smtplib also supports SMTP authentication Contributed by Gerhard Häring The imaplib module maintained by Piers Lauder has support for several new extensions the NAMESPACE extension defined in RFC 2342 SORT GETACL and SETACL Contributed by Anthony Baxter and Michel Pelletier The rfc822 module s parsing of email addresses is now compliant with RFC 2822 an update to RFC 822 The module s name is not going to be changed to rfc2822 A new package email has also been added for parsing and generating e mail messages Contributed by Barry Warsaw and arising out of his work on Mailman The difflib module now contains a new Differ class for producing human readable lists of changes a delta between two sequences of lines of text There are also two generator functions ndiff and restore which respectively return a delta from two sequences or one of the original sequences from a delta Grunt work contributed by David Goodger from ndiff py code by Tim Peters who then did the generatorization New constants ascii_letters ascii_lowercase and ascii_uppercase were added to the string module There were several modules in the standard library that used string letters to mean the ranges A Za z but that assumption is incorrect when locales are in use because string letters varies depending on the set of legal characters defined by the current locale The buggy modules have all been fixed to use ascii_letters instead Reported by an unknown person fixed by Fred L Drake Jr The mimetypes module now makes it easier to use alternative MIME type databases by the addition of a MimeTypes class which takes a list of filenames to be parsed Contributed by Fred L Drake Jr A Timer class was added to the threading module that allows scheduling an activity to happen at some future time Contributed by Itamar Shtull Trauring Interpreter Changes and Fixes Some of the changes only affect people who deal with the Python interpreter at the C level because they re writing Python extension modules embedding the interpreter or just hacking on the interpreter itself If you only write Python code none of the changes described here will affect you very much Profiling and tracing functions can now be implemented in C which can operate at much higher speeds than Python based functions and should reduce the overhead of profiling and tracing This will be of interest to authors of development environments for Python Two new C functions were added to Python s API PyEval_SetProfile and PyEval_SetTrace The exist,en
2563,ing sys setprofile and sys settrace functions still exist and have simply been changed to use the new C level interface Contributed by Fred L Drake Jr Another low level API primarily of interest to implementors of Python debuggers and development tools was added PyInterpreterState_Head and PyInterpreterState_Next let a caller walk through all the existing interpreter objects PyInterpreterState_ThreadHead and PyThreadState_Next allow looping over all the thread states for a given interpreter Contributed by David Beazley The C level interface to the garbage collector has been changed to make it easier to write extension types that support garbage collection and to debug misuses of the functions Various functions have slightly different semantics so a bunch of functions had to be renamed Extensions that use the old API will still compile but will not participate in garbage collection so updating them for 2 2 should be considered fairly high priority To upgrade an extension module to the new API perform the following steps Rename Py_TPFLAGS_GC to Py_TPFLAGS_HAVE_GC Use PyObject_GC_New or PyObject_GC_NewVar to allocate objects and PyObject_GC_Del to deallocate them Rename PyObject_GC_Init to PyObject_GC_Track and PyObject_GC_Fini to PyObject_GC_UnTrack Remove PyGC_HEAD_SIZE from object size calculations Remove calls to PyObject_AS_GC and PyObject_FROM_GC A new et format sequence was added to PyArg_ParseTuple et takes both a parameter and an encoding name and converts the parameter to the given encoding if the parameter turns out to be a Unicode string or leaves it alone if it s an 8 bit string assuming it to already be in the desired encoding This differs from the es format character which assumes that 8 bit strings are in Python s default ASCII encoding and converts them to the specified new encoding Contributed by M A Lemburg and used for the MBCS support on Windows described in the following section A different argument parsing function PyArg_UnpackTuple has been added that s simpler and presumably faster Instead of specifying a format string the caller simply gives the minimum and maximum number of arguments expected and a set of pointers to PyObject variables that will be filled in with argument values Two new flags METH_NOARGS and METH_O are available in method definition tables to simplify implementation of methods with no arguments or a single untyped argument Calling such methods is more efficient than calling a corresponding method that uses METH_VARARGS Also the old METH_OLDARGS style of writing C methods is now officially deprecated Two new wrapper functions PyOS_snprintf and PyOS_vsnprintf were added to provide cross platform implementations for the relatively new snprintf and vsnprintf C lib APIs In contrast to the standard sprintf and vsprintf functions the Python versions check the bounds of the buffer used to protect against buffer overruns Contributed by M A Lemburg The _PyTuple_Resize function has lost an unused parameter so now it takes 2 parameters instead of 3 The third argument was never used and can simply be discarded when porting code from earlier versions to Python 2 2 Other Changes and Fixes As usual there were a bunch of other improvements and bugfixes scattered throughout the source tree A search through the CVS change logs finds there were 527 patches applied and 683 bugs fixed between Python 2 1 and 2 2 2 2 1 applied 139 patches and fixed 143 bugs 2 2 2 applied 106 patches and fixed 82 bugs These figures are likely to be underestimates Some of the more notable changes are The code for the MacOS port for Python maintained by Jack Jansen is now kept in the main Python CVS tree and many changes have been made to support MacOS X The most significant change is the ability to build Python as a framework enabled by supplying the enable framework option to the configure script when compiling Python According to Jack Jansen This installs a self contained Python installation plus the OS X framework glue into Library Frameworks Python framework or another location of choice For now there is little immedia,en
2564,te added benefit to this actually there is the disadvantage that you have to change your PATH to be able to find Python but it is the basis for creating a full blown Python application porting the MacPython IDE possibly using Python as a standard OSA scripting language and much more Most of the MacPython toolbox modules which interface to MacOS APIs such as windowing QuickTime scripting etc have been ported to OS X but they ve been left commented out in setup py People who want to experiment with these modules can uncomment them manually Keyword arguments passed to built in functions that don t take them now cause a TypeError exception to be raised with the message function takes no keyword arguments Weak references added in Python 2 1 as an extension module are now part of the core because they re used in the implementation of new style classes The ReferenceError exception has therefore moved from the weakref module to become a built in exception A new script Tools scripts cleanfuture py by Tim Peters automatically removes obsolete __future__ statements from Python source code An additional flags argument has been added to the built in function compile so the behaviour of __future__ statements can now be correctly observed in simulated shells such as those presented by IDLE and other development environments This is described in PEP 264 Contributed by Michael Hudson The new license introduced with Python 1 6 wasn t GPL compatible This is fixed by some minor textual changes to the 2 2 license so it s now legal to embed Python inside a GPLed program again Note that Python itself is not GPLed but instead is under a license that s essentially equivalent to the BSD license same as it always was The license changes were also applied to the Python 2 0 1 and 2 1 1 releases When presented with a Unicode filename on Windows Python will now convert it to an MBCS encoded string as used by the Microsoft file APIs As MBCS is explicitly used by the file APIs Python s choice of ASCII as the default encoding turns out to be an annoyance On Unix the locale s character set is used if locale nl_langinfo CODESET is available Windows support was contributed by Mark Hammond with assistance from Marc André Lemburg Unix support was added by Martin von Löwis Large file support is now enabled on Windows Contributed by Tim Peters The Tools scripts ftpmirror py script now parses a netrc file if you have one Contributed by Mike Romberg Some features of the object returned by the xrange function are now deprecated and trigger warnings when they re accessed they ll disappear in Python 2 3 xrange objects tried to pretend they were full sequence types by supporting slicing sequence multiplication and the in operator but these features were rarely used and therefore buggy The tolist method and the start stop and step attributes are also being deprecated At the C level the fourth argument to the PyRange_New function repeat has also been deprecated There were a bunch of patches to the dictionary implementation mostly to fix potential core dumps if a dictionary contains objects that sneakily changed their hash value or mutated the dictionary they were contained in For a while python dev fell into a gentle rhythm of Michael Hudson finding a case that dumped core Tim Peters fixing the bug Michael finding another case and round and round it went On Windows Python can now be compiled with Borland C thanks to a number of patches contributed by Stephen Hansen though the result isn t fully functional yet But this is progress Another Windows enhancement Wise Solutions generously offered PythonLabs use of their InstallerMaster 8 1 system Earlier PythonLabs Windows installers used Wise 5 0a which was beginning to show its age Packaged up by Tim Peters Files ending in pyw can now be imported on Windows pyw is a Windows only thing used to indicate that a script needs to be run using PYTHONW EXE instead of PYTHON EXE in order to prevent a DOS console from popping up to display the output This patch makes it possible to import such scripts in case they re also usable as ,en
2565,modules Implemented by David Bolen On platforms where Python uses the C dlopen function to load extension modules it s now possible to set the flags used by dlopen using the sys getdlopenflags and sys setdlopenflags functions Contributed by Bram Stolk The pow built in function no longer supports 3 arguments when floating point numbers are supplied pow x y z returns x y z but this is never useful for floating point numbers and the final result varies unpredictably depending on the platform A call such as pow 2 0 8 0 7 0 will now raise a TypeError exception Acknowledgements The author would like to thank the following people for offering suggestions corrections and assistance with various drafts of this article Fred Bremmer Keith Briggs Andrew Dalke Fred L Drake Jr Carel Fellinger David Goodger Mark Hammond Stephen Hansen Michael Hudson Jack Jansen Marc André Lemburg Martin von Löwis Fredrik Lundh Michael McLay Nick Mathewson Paul Moore Gustavo Niemeyer Don O Donnell Joonas Paalasma Tim Peters Jens Quade Tom Reinhardt Neil Schemenauer Guido van Rossum Greg Ward Edward Welbourne,en
2566,codecs Codec registry and base classes Source code Lib codecs py This module defines base classes for standard Python codecs encoders and decoders and provides access to the internal Python codec registry which manages the codec and error handling lookup process Most standard codecs are text encodings which encode text to bytes and decode bytes to text but there are also codecs provided that encode text to text and bytes to bytes Custom codecs may encode and decode between arbitrary types but some module features are restricted to be used specifically with text encodings or with codecs that encode to bytes The module defines the following functions for encoding and decoding with any codec codecs encode obj encoding utf 8 errors strict Encodes obj using the codec registered for encoding Errors may be given to set the desired error handling scheme The default error handler is strict meaning that encoding errors raise ValueError or a more codec specific subclass such as UnicodeEncodeError Refer to Codec Base Classes for more information on codec error handling codecs decode obj encoding utf 8 errors strict Decodes obj using the codec registered for encoding Errors may be given to set the desired error handling scheme The default error handler is strict meaning that decoding errors raise ValueError or a more codec specific subclass such as UnicodeDecodeError Refer to Codec Base Classes for more information on codec error handling The full details for each codec can also be looked up directly codecs lookup encoding Looks up the codec info in the Python codec registry and returns a CodecInfo object as defined below Encodings are first looked up in the registry s cache If not found the list of registered search functions is scanned If no CodecInfo object is found a LookupError is raised Otherwise the CodecInfo object is stored in the cache and returned to the caller class codecs CodecInfo encode decode streamreader None streamwriter None incrementalencoder None incrementaldecoder None name None Codec details when looking up the codec registry The constructor arguments are stored in attributes of the same name name The name of the encoding encode decode The stateless encoding and decoding functions These must be functions or methods which have the same interface as the encode and decode methods of Codec instances see Codec Interface The functions or methods are expected to work in a stateless mode incrementalencoder incrementaldecoder Incremental encoder and decoder classes or factory functions These have to provide the interface defined by the base classes IncrementalEncoder and IncrementalDecoder respectively Incremental codecs can maintain state streamwriter streamreader Stream writer and reader classes or factory functions These have to provide the interface defined by the base classes StreamWriter and StreamReader respectively Stream codecs can maintain state To simplify access to the various codec components the module provides these additional functions which use lookup for the codec lookup codecs getencoder encoding Look up the codec for the given encoding and return its encoder function Raises a LookupError in case the encoding cannot be found codecs getdecoder encoding Look up the codec for the given encoding and return its decoder function Raises a LookupError in case the encoding cannot be found codecs getincrementalencoder encoding Look up the codec for the given encoding and return its incremental encoder class or factory function Raises a LookupError in case the encoding cannot be found or the codec doesn t support an incremental encoder codecs getincrementaldecoder encoding Look up the codec for the given encoding and return its incremental decoder class or factory function Raises a LookupError in case the encoding cannot be found or the codec doesn t support an incremental decoder codecs getreader encoding Look up the codec for the given encoding and return its StreamReader class or factory function Raises a LookupError in case the encoding cannot be found codecs getwriter encoding Look up the codec for the give,en
2567,n encoding and return its StreamWriter class or factory function Raises a LookupError in case the encoding cannot be found Custom codecs are made available by registering a suitable codec search function codecs register search_function Register a codec search function Search functions are expected to take one argument being the encoding name in all lower case letters with hyphens and spaces converted to underscores and return a CodecInfo object In case a search function cannot find a given encoding it should return None Changed in version 3 9 Hyphens and spaces are converted to underscore codecs unregister search_function Unregister a codec search function and clear the registry s cache If the search function is not registered do nothing New in version 3 10 While the builtin open and the associated io module are the recommended approach for working with encoded text files this module provides additional utility functions and classes that allow the use of a wider range of codecs when working with binary files codecs open filename mode r encoding None errors strict buffering 1 Open an encoded file using the given mode and return an instance of StreamReaderWriter providing transparent encoding decoding The default file mode is r meaning to open the file in read mode Note If encoding is not None then the underlying encoded files are always opened in binary mode No automatic conversion of n is done on reading and writing The mode argument may be any binary mode acceptable to the built in open function the b is automatically added encoding specifies the encoding which is to be used for the file Any encoding that encodes to and decodes from bytes is allowed and the data types supported by the file methods depend on the codec used errors may be given to define the error handling It defaults to strict which causes a ValueError to be raised in case an encoding error occurs buffering has the same meaning as for the built in open function It defaults to 1 which means that the default buffer size will be used Changed in version 3 11 The U mode has been removed codecs EncodedFile file data_encoding file_encoding None errors strict Return a StreamRecoder instance a wrapped version of file which provides transparent transcoding The original file is closed when the wrapped version is closed Data written to the wrapped file is decoded according to the given data_encoding and then written to the original file as bytes using file_encoding Bytes read from the original file are decoded according to file_encoding and the result is encoded using data_encoding If file_encoding is not given it defaults to data_encoding errors may be given to define the error handling It defaults to strict which causes ValueError to be raised in case an encoding error occurs codecs iterencode iterator encoding errors strict kwargs Uses an incremental encoder to iteratively encode the input provided by iterator This function is a generator The errors argument as well as any other keyword argument is passed through to the incremental encoder This function requires that the codec accept text str objects to encode Therefore it does not support bytes to bytes encoders such as base64_codec codecs iterdecode iterator encoding errors strict kwargs Uses an incremental decoder to iteratively decode the input provided by iterator This function is a generator The errors argument as well as any other keyword argument is passed through to the incremental decoder This function requires that the codec accept bytes objects to decode Therefore it does not support text to text encoders such as rot_13 although rot_13 may be used equivalently with iterencode The module also provides the following constants which are useful for reading and writing to platform dependent files codecs BOM codecs BOM_BE codecs BOM_LE codecs BOM_UTF8 codecs BOM_UTF16 codecs BOM_UTF16_BE codecs BOM_UTF16_LE codecs BOM_UTF32 codecs BOM_UTF32_BE codecs BOM_UTF32_LE These constants define various byte sequences being Unicode byte order marks BOMs for several encodings They are used in UTF 16 and UTF 32 data str,en
2568,eams to indicate the byte order used and in UTF 8 as a Unicode signature BOM_UTF16 is either BOM_UTF16_BE or BOM_UTF16_LE depending on the platform s native byte order BOM is an alias for BOM_UTF16 BOM_LE for BOM_UTF16_LE and BOM_BE for BOM_UTF16_BE The others represent the BOM in UTF 8 and UTF 32 encodings Codec Base Classes The codecs module defines a set of base classes which define the interfaces for working with codec objects and can also be used as the basis for custom codec implementations Each codec has to define four interfaces to make it usable as codec in Python stateless encoder stateless decoder stream reader and stream writer The stream reader and writers typically reuse the stateless encoder decoder to implement the file protocols Codec authors also need to define how the codec will handle encoding and decoding errors Error Handlers To simplify and standardize error handling codecs may implement different error handling schemes by accepting the errors string argument German ß encode encoding ascii errors backslashreplace b German xdf u266c German ß encode encoding ascii errors xmlcharrefreplace b German 223 9836 The following error handlers can be used with all Python Standard Encodings codecs Value Meaning strict Raise UnicodeError or a subclass this is the default Implemented in strict_errors ignore Ignore the malformed data and continue without further notice Implemented in ignore_errors replace Replace with a replacement marker On encoding use ASCII character On decoding use U FFFD the official REPLACEMENT CHARACTER Implemented in replace_errors backslashreplace Replace with backslashed escape sequences On encoding use hexadecimal form of Unicode code point with formats x hh u xxxx U xxxxxxxx On decoding use hexadecimal form of byte value with format x hh Implemented in backslashreplace_errors surrogateescape On decoding replace byte with individual surrogate code ranging from U DC80 to U DCFF This code will then be turned back into the same byte when the surrogateescape error handler is used when encoding the data See PEP 383 for more The following error handlers are only applicable to encoding within text encodings Value Meaning xmlcharrefreplace Replace with XML HTML numeric character reference which is a decimal form of Unicode code point with format num Implemented in xmlcharrefreplace_errors namereplace Replace with N escape sequences what appears in the braces is the Name property from Unicode Character Database Implemented in namereplace_errors In addition the following error handler is specific to the given codecs Value Codecs Meaning surrogatepass utf 8 utf 16 utf 32 Allow encoding and decoding surrogate code utf 16 be utf 16 le point U D800 U DFFF as normal code utf 32 be utf 32 le point Otherwise these codecs treat the presence of surrogate code point in str as an error New in version 3 1 The surrogateescape and surrogatepass error handlers Changed in version 3 4 The surrogatepass error handler now works with utf 16 and utf 32 codecs New in version 3 5 The namereplace error handler Changed in version 3 5 The backslashreplace error handler now works with decoding and translating The set of allowed values can be extended by registering a new named error handler codecs register_error name error_handler Register the error handling function error_handler under the name name The error_handler argument will be called during encoding and decoding in case of an error when name is specified as the errors parameter For encoding error_handler will be called with a UnicodeEncodeError instance which contains information about the location of the error The error handler must either raise this or a different exception or return a tuple with a replacement for the unencodable part of the input and a position where encoding should continue The replacement may be either str or bytes If the replacement is bytes the encoder will simply copy them into the output buffer If the replacement is a string the encoder will encode the replacement Encoding continues on original input at the specified position Negative pos,en
2569,ition values will be treated as being relative to the end of the input string If the resulting position is out of bound an IndexError will be raised Decoding and translating works similarly except UnicodeDecodeError or UnicodeTranslateError will be passed to the handler and that the replacement from the error handler will be put into the output directly Previously registered error handlers including the standard error handlers can be looked up by name codecs lookup_error name Return the error handler previously registered under the name name Raises a LookupError in case the handler cannot be found The following standard error handlers are also made available as module level functions codecs strict_errors exception Implements the strict error handling Each encoding or decoding error raises a UnicodeError codecs ignore_errors exception Implements the ignore error handling Malformed data is ignored encoding or decoding is continued without further notice codecs replace_errors exception Implements the replace error handling Substitutes ASCII character for encoding errors or U FFFD the official REPLACEMENT CHARACTER for decoding errors codecs backslashreplace_errors exception Implements the backslashreplace error handling Malformed data is replaced by a backslashed escape sequence On encoding use the hexadecimal form of Unicode code point with formats x hh u xxxx U xxxxxxxx On decoding use the hexadecimal form of byte value with format x hh Changed in version 3 5 Works with decoding and translating codecs xmlcharrefreplace_errors exception Implements the xmlcharrefreplace error handling for encoding within text encoding only The unencodable character is replaced by an appropriate XML HTML numeric character reference which is a decimal form of Unicode code point with format num codecs namereplace_errors exception Implements the namereplace error handling for encoding within text encoding only The unencodable character is replaced by a N escape sequence The set of characters that appear in the braces is the Name property from Unicode Character Database For example the German lowercase letter ß will be converted to byte sequence N LATIN SMALL LETTER SHARP S New in version 3 5 Stateless Encoding and Decoding The base Codec class defines these methods which also define the function interfaces of the stateless encoder and decoder class codecs Codec encode input errors strict Encodes the object input and returns a tuple output object length consumed For instance text encoding converts a string object to a bytes object using a particular character set encoding e g cp1252 or iso 8859 1 The errors argument defines the error handling to apply It defaults to strict handling The method may not store state in the Codec instance Use StreamWriter for codecs which have to keep state in order to make encoding efficient The encoder must be able to handle zero length input and return an empty object of the output object type in this situation decode input errors strict Decodes the object input and returns a tuple output object length consumed For instance for a text encoding decoding converts a bytes object encoded using a particular character set encoding to a string object For text encodings and bytes to bytes codecs input must be a bytes object or one which provides the read only buffer interface for example buffer objects and memory mapped files The errors argument defines the error handling to apply It defaults to strict handling The method may not store state in the Codec instance Use StreamReader for codecs which have to keep state in order to make decoding efficient The decoder must be able to handle zero length input and return an empty object of the output object type in this situation Incremental Encoding and Decoding The IncrementalEncoder and IncrementalDecoder classes provide the basic interface for incremental encoding and decoding Encoding decoding the input isn t done with one call to the stateless encoder decoder function but with multiple calls to the encode decode method of the incremental encoder decoder The incremental enco,en
2570,der decoder keeps track of the encoding decoding process during method calls The joined output of calls to the encode decode method is the same as if all the single inputs were joined into one and this input was encoded decoded with the stateless encoder decoder IncrementalEncoder Objects The IncrementalEncoder class is used for encoding an input in multiple steps It defines the following methods which every incremental encoder must define in order to be compatible with the Python codec registry class codecs IncrementalEncoder errors strict Constructor for an IncrementalEncoder instance All incremental encoders must provide this constructor interface They are free to add additional keyword arguments but only the ones defined here are used by the Python codec registry The IncrementalEncoder may implement different error handling schemes by providing the errors keyword argument See Error Handlers for possible values The errors argument will be assigned to an attribute of the same name Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the IncrementalEncoder object encode object final False Encodes object taking the current state of the encoder into account and returns the resulting encoded object If this is the last call to encode final must be true the default is false reset Reset the encoder to the initial state The output is discarded call encode object final True passing an empty byte or text string if necessary to reset the encoder and to get the output getstate Return the current state of the encoder which must be an integer The implementation should make sure that 0 is the most common state States that are more complicated than integers can be converted into an integer by marshaling pickling the state and encoding the bytes of the resulting string into an integer setstate state Set the state of the encoder to state state must be an encoder state returned by getstate IncrementalDecoder Objects The IncrementalDecoder class is used for decoding an input in multiple steps It defines the following methods which every incremental decoder must define in order to be compatible with the Python codec registry class codecs IncrementalDecoder errors strict Constructor for an IncrementalDecoder instance All incremental decoders must provide this constructor interface They are free to add additional keyword arguments but only the ones defined here are used by the Python codec registry The IncrementalDecoder may implement different error handling schemes by providing the errors keyword argument See Error Handlers for possible values The errors argument will be assigned to an attribute of the same name Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the IncrementalDecoder object decode object final False Decodes object taking the current state of the decoder into account and returns the resulting decoded object If this is the last call to decode final must be true the default is false If final is true the decoder must decode the input completely and must flush all buffers If this isn t possible e g because of incomplete byte sequences at the end of the input it must initiate error handling just like in the stateless case which might raise an exception reset Reset the decoder to the initial state getstate Return the current state of the decoder This must be a tuple with two items the first must be the buffer containing the still undecoded input The second must be an integer and can be additional state info The implementation should make sure that 0 is the most common additional state info If this additional state info is 0 it must be possible to set the decoder to the state which has no input buffered and 0 as the additional state info so that feeding the previously buffered input to the decoder returns it to the previous state without producing any output Additional state info that is more complicated than integers can be converted into an integer by marshaling pickling the info and enco,en
2571,ding the bytes of the resulting string into an integer setstate state Set the state of the decoder to state state must be a decoder state returned by getstate Stream Encoding and Decoding The StreamWriter and StreamReader classes provide generic working interfaces which can be used to implement new encoding submodules very easily See encodings utf_8 for an example of how this is done StreamWriter Objects The StreamWriter class is a subclass of Codec and defines the following methods which every stream writer must define in order to be compatible with the Python codec registry class codecs StreamWriter stream errors strict Constructor for a StreamWriter instance All stream writers must provide this constructor interface They are free to add additional keyword arguments but only the ones defined here are used by the Python codec registry The stream argument must be a file like object open for writing text or binary data as appropriate for the specific codec The StreamWriter may implement different error handling schemes by providing the errors keyword argument See Error Handlers for the standard error handlers the underlying stream codec may support The errors argument will be assigned to an attribute of the same name Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the StreamWriter object write object Writes the object s contents encoded to the stream writelines list Writes the concatenated iterable of strings to the stream possibly by reusing the write method Infinite or very large iterables are not supported The standard bytes to bytes codecs do not support this method reset Resets the codec buffers used for keeping internal state Calling this method should ensure that the data on the output is put into a clean state that allows appending of new fresh data without having to rescan the whole stream to recover state In addition to the above methods the StreamWriter must also inherit all other methods and attributes from the underlying stream StreamReader Objects The StreamReader class is a subclass of Codec and defines the following methods which every stream reader must define in order to be compatible with the Python codec registry class codecs StreamReader stream errors strict Constructor for a StreamReader instance All stream readers must provide this constructor interface They are free to add additional keyword arguments but only the ones defined here are used by the Python codec registry The stream argument must be a file like object open for reading text or binary data as appropriate for the specific codec The StreamReader may implement different error handling schemes by providing the errors keyword argument See Error Handlers for the standard error handlers the underlying stream codec may support The errors argument will be assigned to an attribute of the same name Assigning to this attribute makes it possible to switch between different error handling strategies during the lifetime of the StreamReader object The set of allowed values for the errors argument can be extended with register_error read size 1 chars 1 firstline False Decodes data from the stream and returns the resulting object The chars argument indicates the number of decoded code points or bytes to return The read method will never return more data than requested but it might return less if there is not enough available The size argument indicates the approximate maximum number of encoded bytes or code points to read for decoding The decoder can modify this setting as appropriate The default value 1 indicates to read and decode as much as possible This parameter is intended to prevent having to decode huge files in one step The firstline flag indicates that it would be sufficient to only return the first line if there are decoding errors on later lines The method should use a greedy read strategy meaning that it should read as much data as is allowed within the definition of the encoding and the given size e g if optional encoding endings or state markers are available on the,en
2572, stream these should be read too readline size None keepends True Read one line from the input stream and return the decoded data size if given is passed as size argument to the stream s read method If keepends is false line endings will be stripped from the lines returned readlines sizehint None keepends True Read all lines available on the input stream and return them as a list of lines Line endings are implemented using the codec s decode method and are included in the list entries if keepends is true sizehint if given is passed as the size argument to the stream s read method reset Resets the codec buffers used for keeping internal state Note that no stream repositioning should take place This method is primarily intended to be able to recover from decoding errors In addition to the above methods the StreamReader must also inherit all other methods and attributes from the underlying stream StreamReaderWriter Objects The StreamReaderWriter is a convenience class that allows wrapping streams which work in both read and write modes The design is such that one can use the factory functions returned by the lookup function to construct the instance class codecs StreamReaderWriter stream Reader Writer errors strict Creates a StreamReaderWriter instance stream must be a file like object Reader and Writer must be factory functions or classes providing the StreamReader and StreamWriter interface resp Error handling is done in the same way as defined for the stream readers and writers StreamReaderWriter instances define the combined interfaces of StreamReader and StreamWriter classes They inherit all other methods and attributes from the underlying stream StreamRecoder Objects The StreamRecoder translates data from one encoding to another which is sometimes useful when dealing with different encoding environments The design is such that one can use the factory functions returned by the lookup function to construct the instance class codecs StreamRecoder stream encode decode Reader Writer errors strict Creates a StreamRecoder instance which implements a two way conversion encode and decode work on the frontend the data visible to code calling read and write while Reader and Writer work on the backend the data in stream You can use these objects to do transparent transcodings e g from Latin 1 to UTF 8 and back The stream argument must be a file like object The encode and decode arguments must adhere to the Codec interface Reader and Writer must be factory functions or classes providing objects of the StreamReader and StreamWriter interface respectively Error handling is done in the same way as defined for the stream readers and writers StreamRecoder instances define the combined interfaces of StreamReader and StreamWriter classes They inherit all other methods and attributes from the underlying stream Encodings and Unicode Strings are stored internally as sequences of code points in range U 0000 U 10FFFF See PEP 393 for more details about the implementation Once a string object is used outside of CPU and memory endianness and how these arrays are stored as bytes become an issue As with other codecs serialising a string into a sequence of bytes is known as encoding and recreating the string from the sequence of bytes is known as decoding There are a variety of different text serialisation codecs which are collectivity referred to as text encodings The simplest text encoding called latin 1 or iso 8859 1 maps the code points 0 255 to the bytes 0x0 0xff which means that a string object that contains code points above U 00FF can t be encoded with this codec Doing so will raise a UnicodeEncodeError that looks like the following although the details of the error message may differ UnicodeEncodeError latin 1 codec can t encode character u1234 in position 3 ordinal not in range 256 There s another group of encodings the so called charmap encodings that choose a different subset of all Unicode code points and how these code points are mapped to the bytes 0x0 0xff To see how this is done simply open e g encodings cp1252 py which is an encod,en
2573,ing that is used primarily on Windows There s a string constant with 256 characters that shows you which character is mapped to which byte value All of these encodings can only encode 256 of the 1114112 code points defined in Unicode A simple and straightforward way that can store each Unicode code point is to store each code point as four consecutive bytes There are two possibilities store the bytes in big endian or in little endian order These two encodings are called UTF 32 BE and UTF 32 LE respectively Their disadvantage is that if e g you use UTF 32 BE on a little endian machine you will always have to swap bytes on encoding and decoding UTF 32 avoids this problem bytes will always be in natural endianness When these bytes are read by a CPU with a different endianness then bytes have to be swapped though To be able to detect the endianness of a UTF 16 or UTF 32 byte sequence there s the so called BOM Byte Order Mark This is the Unicode character U FEFF This character can be prepended to every UTF 16 or UTF 32 byte sequence The byte swapped version of this character 0xFFFE is an illegal character that may not appear in a Unicode text So when the first character in a UTF 16 or UTF 32 byte sequence appears to be a U FFFE the bytes have to be swapped on decoding Unfortunately the character U FEFF had a second purpose as a ZERO WIDTH NO BREAK SPACE a character that has no width and doesn t allow a word to be split It can e g be used to give hints to a ligature algorithm With Unicode 4 0 using U FEFF as a ZERO WIDTH NO BREAK SPACE has been deprecated with U 2060 WORD JOINER assuming this role Nevertheless Unicode software still must be able to handle U FEFF in both roles as a BOM it s a device to determine the storage layout of the encoded bytes and vanishes once the byte sequence has been decoded into a string as a ZERO WIDTH NO BREAK SPACE it s a normal character that will be decoded like any other There s another encoding that is able to encode the full range of Unicode characters UTF 8 UTF 8 is an 8 bit encoding which means there are no issues with byte order in UTF 8 Each byte in a UTF 8 byte sequence consists of two parts marker bits the most significant bits and payload bits The marker bits are a sequence of zero to four 1 bits followed by a 0 bit Unicode characters are encoded like this with x being payload bits which when concatenated give the Unicode character Range Encoding U 00000000 U 0000007F 0xxxxxxx U 00000080 U 000007FF 110xxxxx 10xxxxxx U 00000800 U 0000FFFF 1110xxxx 10xxxxxx 10xxxxxx U 00010000 U 0010FFFF 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx The least significant bit of the Unicode character is the rightmost x bit As UTF 8 is an 8 bit encoding no BOM is required and any U FEFF character in the decoded string even if it s the first character is treated as a ZERO WIDTH NO BREAK SPACE Without external information it s impossible to reliably determine which encoding was used for encoding a string Each charmap encoding can decode any random byte sequence However that s not possible with UTF 8 as UTF 8 byte sequences have a structure that doesn t allow arbitrary byte sequences To increase the reliability with which a UTF 8 encoding can be detected Microsoft invented a variant of UTF 8 that Python calls utf 8 sig for its Notepad program Before any of the Unicode characters is written to the file a UTF 8 encoded BOM which looks like this as a byte sequence 0xef 0xbb 0xbf is written As it s rather improbable that any charmap encoded file starts with these byte values which would e g map to LATIN SMALL LETTER I WITH DIAERESIS RIGHT POINTING DOUBLE ANGLE QUOTATION MARK INVERTED QUESTION MARK in iso 8859 1 this increases the probability that a utf 8 sig encoding can be correctly guessed from the byte sequence So here the BOM is not used to be able to determine the byte order used for generating the byte sequence but as a signature that helps in guessing the encoding On encoding the utf 8 sig codec will write 0xef 0xbb 0xbf as the first three bytes to the file On decoding utf 8 sig will skip those three bytes if they,en
2574, appear as the first three bytes in the file In UTF 8 the use of the BOM is discouraged and should generally be avoided Standard Encodings Python comes with a number of codecs built in either implemented as C functions or with dictionaries as mapping tables The following table lists the codecs by name together with a few common aliases and the languages for which the encoding is likely used Neither the list of aliases nor the list of languages is meant to be exhaustive Notice that spelling alternatives that only differ in case or use a hyphen instead of an underscore are also valid aliases therefore e g utf 8 is a valid alias for the utf_8 codec CPython implementation detail Some common encodings can bypass the codecs lookup machinery to improve performance These optimization opportunities are only recognized by CPython for a limited set of case insensitive aliases utf 8 utf8 latin 1 latin1 iso 8859 1 iso8859 1 mbcs Windows only ascii us ascii utf 16 utf16 utf 32 utf32 and the same using underscores instead of dashes Using alternative aliases for these encodings may result in slower execution Changed in version 3 6 Optimization opportunity recognized for us ascii Many of the character sets support the same languages They vary in individual characters e g whether the EURO SIGN is supported or not and in the assignment of characters to code positions For the European languages in particular the following variants typically exist an ISO 8859 codeset a Microsoft Windows code page which is typically derived from an 8859 codeset but replaces control characters with additional graphic characters an IBM EBCDIC code page an IBM PC code page which is ASCII compatible Codec Aliases Languages ascii 646 us ascii English big5 big5 tw csbig5 Traditional Chinese big5hkscs big5 hkscs hkscs Traditional Chinese cp037 IBM037 IBM039 English cp273 273 IBM273 csIBM273 German New in version 3 4 cp424 EBCDIC CP HE IBM424 Hebrew cp437 437 IBM437 English cp500 EBCDIC CP BE EBCDIC CP CH Western Europe IBM500 cp720 Arabic cp737 Greek cp775 IBM775 Baltic languages cp850 850 IBM850 Western Europe cp852 852 IBM852 Central and Eastern Europe cp855 855 IBM855 Bulgarian Byelorussian Macedonian Russian Serbian cp856 Hebrew cp857 857 IBM857 Turkish cp858 858 IBM858 Western Europe cp860 860 IBM860 Portuguese cp861 861 CP IS IBM861 Icelandic cp862 862 IBM862 Hebrew cp863 863 IBM863 Canadian cp864 IBM864 Arabic cp865 865 IBM865 Danish Norwegian cp866 866 IBM866 Russian cp869 869 CP GR IBM869 Greek cp874 Thai cp875 Greek cp932 932 ms932 mskanji ms kanji Japanese cp949 949 ms949 uhc Korean cp950 950 ms950 Traditional Chinese cp1006 Urdu cp1026 ibm1026 Turkish cp1125 1125 ibm1125 cp866u ruscii Ukrainian New in version 3 4 cp1140 ibm1140 Western Europe cp1250 windows 1250 Central and Eastern Europe cp1251 windows 1251 Bulgarian Byelorussian Macedonian Russian Serbian cp1252 windows 1252 Western Europe cp1253 windows 1253 Greek cp1254 windows 1254 Turkish cp1255 windows 1255 Hebrew cp1256 windows 1256 Arabic cp1257 windows 1257 Baltic languages cp1258 windows 1258 Vietnamese euc_jp eucjp ujis u jis Japanese euc_jis_2004 jisx0213 eucjis2004 Japanese euc_jisx0213 eucjisx0213 Japanese euc_kr euckr korean ksc5601 Korean ks_c 5601 ks_c 5601 1987 ksx1001 ks_x 1001 gb2312 chinese csiso58gb231280 euc Simplified Chinese cn euccn eucgb2312 cn gb2312 1980 gb2312 80 iso ir 58 gbk 936 cp936 ms936 Unified Chinese gb18030 gb18030 2000 Unified Chinese hz hzgb hz gb hz gb 2312 Simplified Chinese iso2022_jp csiso2022jp iso2022jp Japanese iso 2022 jp iso2022_jp_1 iso2022jp 1 iso 2022 jp 1 Japanese iso2022_jp_2 iso2022jp 2 iso 2022 jp 2 Japanese Korean Simplified Chinese Western Europe Greek iso2022_jp_2004 iso2022jp 2004 iso 2022 jp 2004 Japanese iso2022_jp_3 iso2022jp 3 iso 2022 jp 3 Japanese iso2022_jp_ext iso2022jp ext iso 2022 jp ext Japanese iso2022_kr csiso2022kr iso2022kr Korean iso 2022 kr latin_1 iso 8859 1 iso8859 1 8859 Western Europe cp819 latin latin1 L1 iso8859_2 iso 8859 2 latin2 L2 Central and Eastern Europe iso8859_3 iso 8859 3 latin3 L3 Esperanto Maltese iso8859_4 i,en
2575,so 8859 4 latin4 L4 Baltic languages iso8859_5 iso 8859 5 cyrillic Bulgarian Byelorussian Macedonian Russian Serbian iso8859_6 iso 8859 6 arabic Arabic iso8859_7 iso 8859 7 greek greek8 Greek iso8859_8 iso 8859 8 hebrew Hebrew iso8859_9 iso 8859 9 latin5 L5 Turkish iso8859_10 iso 8859 10 latin6 L6 Nordic languages iso8859_11 iso 8859 11 thai Thai languages iso8859_13 iso 8859 13 latin7 L7 Baltic languages iso8859_14 iso 8859 14 latin8 L8 Celtic languages iso8859_15 iso 8859 15 latin9 L9 Western Europe iso8859_16 iso 8859 16 latin10 L10 South Eastern Europe johab cp1361 ms1361 Korean koi8_r Russian koi8_t Tajik New in version 3 5 koi8_u Ukrainian kz1048 kz_1048 strk1048_2002 rk1048 Kazakh New in version 3 5 mac_cyrillic maccyrillic Bulgarian Byelorussian Macedonian Russian Serbian mac_greek macgreek Greek mac_iceland maciceland Icelandic mac_latin2 maclatin2 maccentraleurope Central and Eastern Europe mac_centeuro mac_roman macroman macintosh Western Europe mac_turkish macturkish Turkish ptcp154 csptcp154 pt154 cp154 Kazakh cyrillic asian shift_jis csshiftjis shiftjis sjis Japanese s_jis shift_jis_2004 shiftjis2004 sjis_2004 Japanese sjis2004 shift_jisx0213 shiftjisx0213 sjisx0213 Japanese s_jisx0213 utf_32 U32 utf32 all languages utf_32_be UTF 32BE all languages utf_32_le UTF 32LE all languages utf_16 U16 utf16 all languages utf_16_be UTF 16BE all languages utf_16_le UTF 16LE all languages utf_7 U7 unicode 1 1 utf 7 all languages utf_8 U8 UTF utf8 cp65001 all languages utf_8_sig all languages Changed in version 3 4 The utf 16 and utf 32 encoders no longer allow surrogate code points U D800 U DFFF to be encoded The utf 32 decoders no longer decode byte sequences that correspond to surrogate code points Changed in version 3 8 cp65001 is now an alias to utf_8 Python Specific Encodings A number of predefined codecs are specific to Python so their codec names have no meaning outside Python These are listed in the tables below based on the expected input and output types note that while text encodings are the most common use case for codecs the underlying codec infrastructure supports arbitrary data transforms rather than just text encodings For asymmetric codecs the stated meaning describes the encoding direction Text Encodings The following codecs provide str to bytes encoding and bytes like object to str decoding similar to the Unicode text encodings Codec Aliases Meaning idna Implement RFC 3490 see also encodings idna Only errors strict is supported mbcs ansi Windows only Encode the dbcs operand according to the ANSI codepage CP_ACP oem Windows only Encode the operand according to the OEM codepage CP_OEMCP New in version 3 6 palmos Encoding of PalmOS 3 5 punycode Implement RFC 3492 Stateful codecs are not supported raw_unicode_escape Latin 1 encoding with u XXXX and U XXXXXXXX for other code points Existing backslashes are not escaped in any way It is used in the Python pickle protocol undefined Raise an exception for all conversions even empty strings The error handler is ignored unicode_escape Encoding suitable as the contents of a Unicode literal in ASCII encoded Python source code except that quotes are not escaped Decode from Latin 1 source code Beware that Python source code actually uses UTF 8 by default Changed in version 3 8 unicode_internal codec is removed Binary Transforms The following codecs provide binary transforms bytes like object to bytes mappings They are not supported by bytes decode which only produces str output Codec Aliases Meaning Encoder decoder base64_codec 1 base64 base_64 Convert the operand to base64 encodebytes multiline MIME base64 the base64 decodebytes result always includes a trailing n Changed in version 3 4 accepts any bytes like object as input for encoding and decoding bz2_codec bz2 Compress the operand using bz2 compress bz2 bz2 decompress hex_codec hex Convert the operand to binascii b2a_hex hexadecimal representation binascii a2b_hex with two digits per byte quopri_codec quopri Convert the operand to MIME quopri encode with quotedprintable quoted printable quotetabs True quoted_pr,en
2576,intable quopri decode uu_codec uu Convert the operand using uu encode uu decode uuencode Note uu is deprecated zlib_codec zip zlib Compress the operand using zlib compress gzip zlib decompress 1 In addition to bytes like objects base64_codec also accepts ASCII only instances of str for decoding New in version 3 2 Restoration of the binary transforms Changed in version 3 4 Restoration of the aliases for the binary transforms Text Transforms The following codec provides a text transform a str to str mapping It is not supported by str encode which only produces bytes output Codec Aliases Meaning rot_13 rot13 Return the Caesar cypher encryption of the operand New in version 3 2 Restoration of the rot_13 text transform Changed in version 3 4 Restoration of the rot13 alias encodings idna Internationalized Domain Names in Applications This module implements RFC 3490 Internationalized Domain Names in Applications and RFC 3492 Nameprep A Stringprep Profile for Internationalized Domain Names IDN It builds upon the punycode encoding and stringprep If you need the IDNA 2008 standard from RFC 5891 and RFC 5895 use the third party idna module These RFCs together define a protocol to support non ASCII characters in domain names A domain name containing non ASCII characters such as www Alliancefrançaise nu is converted into an ASCII compatible encoding ACE such as www xn alliancefranaise npb nu The ACE form of the domain name is then used in all places where arbitrary characters are not allowed by the protocol such as DNS queries HTTP Host fields and so on This conversion is carried out in the application if possible invisible to the user The application should transparently convert Unicode domain labels to IDNA on the wire and convert back ACE labels to Unicode before presenting them to the user Python supports this conversion in several ways the idna codec performs conversion between Unicode and ACE separating an input string into labels based on the separator characters defined in section 3 1 of RFC 3490 and converting each label to ACE as required and conversely separating an input byte string into labels based on the separator and converting any ACE labels found into unicode Furthermore the socket module transparently converts Unicode host names to ACE so that applications need not be concerned about converting host names themselves when they pass them to the socket module On top of that modules that have host names as function parameters such as http client and ftplib accept Unicode host names http client then also transparently sends an IDNA hostname in the Host field if it sends that field at all When receiving host names from the wire such as in reverse name lookup no automatic conversion to Unicode is performed applications wishing to present such host names to the user should decode them to Unicode The module encodings idna also implements the nameprep procedure which performs certain normalizations on host names to achieve case insensitivity of international domain names and to unify similar characters The nameprep functions can be used directly if desired encodings idna nameprep label Return the nameprepped version of label The implementation currently assumes query strings so AllowUnassigned is true encodings idna ToASCII label Convert a label to ASCII as specified in RFC 3490 UseSTD3ASCIIRules is assumed to be false encodings idna ToUnicode label Convert a label to Unicode as specified in RFC 3490 encodings mbcs Windows ANSI codepage This module implements the ANSI codepage CP_ACP Availability Windows Changed in version 3 2 Before 3 2 the errors argument was ignored replace was always used to encode and ignore to decode Changed in version 3 3 Support any error handler encodings utf_8_sig UTF 8 codec with BOM signature This module implements a variant of the UTF 8 codec On encoding a UTF 8 encoded BOM will be prepended to the UTF 8 encoded bytes For the stateful encoder this is only done once on the first write to the byte stream On decoding an optional UTF 8 encoded BOM at the start of the data will be skipped,en
2577,curses panel A panel stack extension for curses Panels are windows with the added feature of depth so they can be stacked on top of each other and only the visible portions of each window will be displayed Panels can be added moved up or down in the stack and removed Functions The module curses panel defines the following functions curses panel bottom_panel Returns the bottom panel in the panel stack curses panel new_panel win Returns a panel object associating it with the given window win Be aware that you need to keep the returned panel object referenced explicitly If you don t the panel object is garbage collected and removed from the panel stack curses panel top_panel Returns the top panel in the panel stack curses panel update_panels Updates the virtual screen after changes in the panel stack This does not call curses doupdate so you ll have to do this yourself Panel Objects Panel objects as returned by new_panel above are windows with a stacking order There s always a window associated with a panel which determines the content while the panel methods are responsible for the window s depth in the panel stack Panel objects have the following methods Panel above Returns the panel above the current panel Panel below Returns the panel below the current panel Panel bottom Push the panel to the bottom of the stack Panel hidden Returns True if the panel is hidden not visible False otherwise Panel hide Hide the panel This does not delete the object it just makes the window on screen invisible Panel move y x Move the panel to the screen coordinates y x Panel replace win Change the window associated with the panel to the window win Panel set_userptr obj Set the panel s user pointer to obj This is used to associate an arbitrary piece of data with the panel and can be any Python object Panel show Display the panel which might have been hidden Panel top Push panel to the top of the stack Panel userptr Returns the user pointer for the panel This might be any Python object Panel window Returns the window object associated with the panel,en
2578,Allocating Objects on the Heap PyObject _PyObject_New PyTypeObject type Return value New reference PyVarObject _PyObject_NewVar PyTypeObject type Py_ssize_t size Return value New reference PyObject PyObject_Init PyObject op PyTypeObject type Return value Borrowed reference Part of the Stable ABI Initialize a newly allocated object op with its type and initial reference Returns the initialized object If type indicates that the object participates in the cyclic garbage detector it is added to the detector s set of observed objects Other fields of the object are not affected PyVarObject PyObject_InitVar PyVarObject op PyTypeObject type Py_ssize_t size Return value Borrowed reference Part of the Stable ABI This does everything PyObject_Init does and also initializes the length information for a variable size object PyObject_New TYPE typeobj Allocate a new Python object using the C structure type TYPE and the Python type object typeobj PyTypeObject Fields not defined by the Python object header are not initialized The caller will own the only reference to the object i e its reference count will be one The size of the memory allocation is determined from the tp_basicsize field of the type object PyObject_NewVar TYPE typeobj size Allocate a new Python object using the C structure type TYPE and the Python type object typeobj PyTypeObject Fields not defined by the Python object header are not initialized The allocated memory allows for the TYPE structure plus size Py_ssize_t fields of the size given by the tp_itemsize field of typeobj This is useful for implementing objects like tuples which are able to determine their size at construction time Embedding the array of fields into the same allocation decreases the number of allocations improving the memory management efficiency void PyObject_Del void op Releases memory allocated to an object using PyObject_New or PyObject_NewVar This is normally called from the tp_dealloc handler specified in the object s type The fields of the object should not be accessed after this call as the memory is no longer a valid Python object PyObject _Py_NoneStruct Object which is visible in Python as None This should only be accessed using the Py_None macro which evaluates to a pointer to this object See also PyModule_Create To allocate and create extension modules,en
2579,xmlrpc XMLRPC server and client modules XML RPC is a Remote Procedure Call method that uses XML passed via HTTP as a transport With it a client can call methods with parameters on a remote server the server is named by a URI and get back structured data xmlrpc is a package that collects server and client modules implementing XML RPC The modules are xmlrpc client xmlrpc server,en
2580,The Python Language Reference This reference manual describes the syntax and core semantics of the language It is terse but attempts to be exact and complete The semantics of non essential built in object types and of the built in functions and modules are described in The Python Standard Library For an informal introduction to the language see The Python Tutorial For C or C programmers two additional manuals exist Extending and Embedding the Python Interpreter describes the high level picture of how to write a Python extension module and the Python C API Reference Manual describes the interfaces available to C C programmers in detail 1 Introduction 1 1 Alternate Implementations 1 2 Notation 2 Lexical analysis 2 1 Line structure 2 2 Other tokens 2 3 Identifiers and keywords 2 4 Literals 2 5 Operators 2 6 Delimiters 3 Data model 3 1 Objects values and types 3 2 The standard type hierarchy 3 3 Special method names 3 4 Coroutines 4 Execution model 4 1 Structure of a program 4 2 Naming and binding 4 3 Exceptions 5 The import system 5 1 importlib 5 2 Packages 5 3 Searching 5 4 Loading 5 5 The Path Based Finder 5 6 Replacing the standard import system 5 7 Package Relative Imports 5 8 Special considerations for __main__ 5 9 References 6 Expressions 6 1 Arithmetic conversions 6 2 Atoms 6 3 Primaries 6 4 Await expression 6 5 The power operator 6 6 Unary arithmetic and bitwise operations 6 7 Binary arithmetic operations 6 8 Shifting operations 6 9 Binary bitwise operations 6 10 Comparisons 6 11 Boolean operations 6 12 Assignment expressions 6 13 Conditional expressions 6 14 Lambdas 6 15 Expression lists 6 16 Evaluation order 6 17 Operator precedence 7 Simple statements 7 1 Expression statements 7 2 Assignment statements 7 3 The assert statement 7 4 The pass statement 7 5 The del statement 7 6 The return statement 7 7 The yield statement 7 8 The raise statement 7 9 The break statement 7 10 The continue statement 7 11 The import statement 7 12 The global statement 7 13 The nonlocal statement 7 14 The type statement 8 Compound statements 8 1 The if statement 8 2 The while statement 8 3 The for statement 8 4 The try statement 8 5 The with statement 8 6 The match statement 8 7 Function definitions 8 8 Class definitions 8 9 Coroutines 8 10 Type parameter lists 9 Top level components 9 1 Complete Python programs 9 2 File input 9 3 Interactive input 9 4 Expression input 10 Full Grammar specification,en
2581,Iterator Protocol There are two functions specifically for working with iterators int PyIter_Check PyObject o Part of the Stable ABI since version 3 8 Return non zero if the object o can be safely passed to PyIter_Next and 0 otherwise This function always succeeds int PyAIter_Check PyObject o Part of the Stable ABI since version 3 10 Return non zero if the object o provides the AsyncIterator protocol and 0 otherwise This function always succeeds New in version 3 10 PyObject PyIter_Next PyObject o Return value New reference Part of the Stable ABI Return the next value from the iterator o The object must be an iterator according to PyIter_Check it is up to the caller to check this If there are no remaining values returns NULL with no exception set If an error occurs while retrieving the item returns NULL and passes along the exception To write a loop which iterates over an iterator the C code should look something like this PyObject iterator PyObject_GetIter obj PyObject item if iterator NULL propagate error while item PyIter_Next iterator do something with item release reference when done Py_DECREF item Py_DECREF iterator if PyErr_Occurred propagate error else continue doing useful work type PySendResult The enum value used to represent different results of PyIter_Send New in version 3 10 PySendResult PyIter_Send PyObject iter PyObject arg PyObject presult Part of the Stable ABI since version 3 10 Sends the arg value into the iterator iter Returns PYGEN_RETURN if iterator returns Return value is returned via presult PYGEN_NEXT if iterator yields Yielded value is returned via presult PYGEN_ERROR if iterator has raised and exception presult is set to NULL New in version 3 10,en
2582,List Objects type PyListObject This subtype of PyObject represents a Python list object PyTypeObject PyList_Type Part of the Stable ABI This instance of PyTypeObject represents the Python list type This is the same object as list in the Python layer int PyList_Check PyObject p Return true if p is a list object or an instance of a subtype of the list type This function always succeeds int PyList_CheckExact PyObject p Return true if p is a list object but not an instance of a subtype of the list type This function always succeeds PyObject PyList_New Py_ssize_t len Return value New reference Part of the Stable ABI Return a new list of length len on success or NULL on failure Note If len is greater than zero the returned list object s items are set to NULL Thus you cannot use abstract API functions such as PySequence_SetItem or expose the object to Python code before setting all items to a real object with PyList_SetItem Py_ssize_t PyList_Size PyObject list Part of the Stable ABI Return the length of the list object in list this is equivalent to len list on a list object Py_ssize_t PyList_GET_SIZE PyObject list Similar to PyList_Size but without error checking PyObject PyList_GetItem PyObject list Py_ssize_t index Return value Borrowed reference Part of the Stable ABI Return the object at position index in the list pointed to by list The position must be non negative indexing from the end of the list is not supported If index is out of bounds 0 or len list return NULL and set an IndexError exception PyObject PyList_GET_ITEM PyObject list Py_ssize_t i Return value Borrowed reference Similar to PyList_GetItem but without error checking int PyList_SetItem PyObject list Py_ssize_t index PyObject item Part of the Stable ABI Set the item at index index in list to item Return 0 on success If index is out of bounds return 1 and set an IndexError exception Note This function steals a reference to item and discards a reference to an item already in the list at the affected position void PyList_SET_ITEM PyObject list Py_ssize_t i PyObject o Macro form of PyList_SetItem without error checking This is normally only used to fill in new lists where there is no previous content Note This macro steals a reference to item and unlike PyList_SetItem does not discard a reference to any item that is being replaced any reference in list at position i will be leaked int PyList_Insert PyObject list Py_ssize_t index PyObject item Part of the Stable ABI Insert the item item into list list in front of index index Return 0 if successful return 1 and set an exception if unsuccessful Analogous to list insert index item int PyList_Append PyObject list PyObject item Part of the Stable ABI Append the object item at the end of list list Return 0 if successful return 1 and set an exception if unsuccessful Analogous to list append item PyObject PyList_GetSlice PyObject list Py_ssize_t low Py_ssize_t high Return value New reference Part of the Stable ABI Return a list of the objects in list containing the objects between low and high Return NULL and set an exception if unsuccessful Analogous to list low high Indexing from the end of the list is not supported int PyList_SetSlice PyObject list Py_ssize_t low Py_ssize_t high PyObject itemlist Part of the Stable ABI Set the slice of list between low and high to the contents of itemlist Analogous to list low high itemlist The itemlist may be NULL indicating the assignment of an empty list slice deletion Return 0 on success 1 on failure Indexing from the end of the list is not supported int PyList_Sort PyObject list Part of the Stable ABI Sort the items of list in place Return 0 on success 1 on failure This is equivalent to list sort int PyList_Reverse PyObject list Part of the Stable ABI Reverse the items of list in place Return 0 on success 1 on failure This is the equivalent of list reverse PyObject PyList_AsTuple PyObject list Return value New reference Part of the Stable ABI Return a new tuple object containing the contents of list equivalent to tuple list,en
2583,Common Object Structures There are a large number of structures which are used in the definition of object types for Python This section describes these structures and how they are used Base object types and macros All Python objects ultimately share a small number of fields at the beginning of the object s representation in memory These are represented by the PyObject and PyVarObject types which are defined in turn by the expansions of some macros also used whether directly or indirectly in the definition of all other Python objects Additional macros can be found under reference counting type PyObject Part of the Limited API Only some members are part of the stable ABI All object types are extensions of this type This is a type which contains the information Python needs to treat a pointer to an object as an object In a normal release build it contains only the object s reference count and a pointer to the corresponding type object Nothing is actually declared to be a PyObject but every pointer to a Python object can be cast to a PyObject Access to the members must be done by using the macros Py_REFCNT and Py_TYPE type PyVarObject Part of the Limited API Only some members are part of the stable ABI This is an extension of PyObject that adds the ob_size field This is only used for objects that have some notion of length This type does not often appear in the Python C API Access to the members must be done by using the macros Py_REFCNT Py_TYPE and Py_SIZE PyObject_HEAD This is a macro used when declaring new types which represent objects without a varying length The PyObject_HEAD macro expands to PyObject ob_base See documentation of PyObject above PyObject_VAR_HEAD This is a macro used when declaring new types which represent objects with a length that varies from instance to instance The PyObject_VAR_HEAD macro expands to PyVarObject ob_base See documentation of PyVarObject above int Py_Is PyObject x PyObject y Part of the Stable ABI since version 3 10 Test if the x object is the y object the same as x is y in Python New in version 3 10 int Py_IsNone PyObject x Part of the Stable ABI since version 3 10 Test if an object is the None singleton the same as x is None in Python New in version 3 10 int Py_IsTrue PyObject x Part of the Stable ABI since version 3 10 Test if an object is the True singleton the same as x is True in Python New in version 3 10 int Py_IsFalse PyObject x Part of the Stable ABI since version 3 10 Test if an object is the False singleton the same as x is False in Python New in version 3 10 PyTypeObject Py_TYPE PyObject o Get the type of the Python object o Return a borrowed reference Use the Py_SET_TYPE function to set an object type Changed in version 3 11 Py_TYPE is changed to an inline static function The parameter type is no longer const PyObject int Py_IS_TYPE PyObject o PyTypeObject type Return non zero if the object o type is type Return zero otherwise Equivalent to Py_TYPE o type New in version 3 9 void Py_SET_TYPE PyObject o PyTypeObject type Set the object o type to type New in version 3 9 Py_ssize_t Py_SIZE PyVarObject o Get the size of the Python object o Use the Py_SET_SIZE function to set an object size Changed in version 3 11 Py_SIZE is changed to an inline static function The parameter type is no longer const PyVarObject void Py_SET_SIZE PyVarObject o Py_ssize_t size Set the object o size to size New in version 3 9 PyObject_HEAD_INIT type This is a macro which expands to initialization values for a new PyObject type This macro expands to _PyObject_EXTRA_INIT 1 type PyVarObject_HEAD_INIT type size This is a macro which expands to initialization values for a new PyVarObject type including the ob_size field This macro expands to _PyObject_EXTRA_INIT 1 type size Implementing functions and methods type PyCFunction Part of the Stable ABI Type of the functions used to implement most Python callables in C Functions of this type take two PyObject parameters and return one such value If the return value is NULL an exception shall have been set If not NULL the return value is interpreted as the re,en
2584,turn value of the function as exposed in Python The function must return a new reference The function signature is PyObject PyCFunction PyObject self PyObject args type PyCFunctionWithKeywords Part of the Stable ABI Type of the functions used to implement Python callables in C with signature METH_VARARGS METH_KEYWORDS The function signature is PyObject PyCFunctionWithKeywords PyObject self PyObject args PyObject kwargs type _PyCFunctionFast Type of the functions used to implement Python callables in C with signature METH_FASTCALL The function signature is PyObject _PyCFunctionFast PyObject self PyObject const args Py_ssize_t nargs type _PyCFunctionFastWithKeywords Type of the functions used to implement Python callables in C with signature METH_FASTCALL METH_KEYWORDS The function signature is PyObject _PyCFunctionFastWithKeywords PyObject self PyObject const args Py_ssize_t nargs PyObject kwnames type PyCMethod Type of the functions used to implement Python callables in C with signature METH_METHOD METH_FASTCALL METH_KEYWORDS The function signature is PyObject PyCMethod PyObject self PyTypeObject defining_class PyObject const args Py_ssize_t nargs PyObject kwnames New in version 3 9 type PyMethodDef Part of the Stable ABI including all members Structure used to describe a method of an extension type This structure has four fields const char ml_name Name of the method PyCFunction ml_meth Pointer to the C implementation int ml_flags Flags bits indicating how the call should be constructed const char ml_doc Points to the contents of the docstring The ml_meth is a C function pointer The functions may be of different types but they always return PyObject If the function is not of the PyCFunction the compiler will require a cast in the method table Even though PyCFunction defines the first parameter as PyObject it is common that the method implementation uses the specific C type of the self object The ml_flags field is a bitfield which can include the following flags The individual flags indicate either a calling convention or a binding convention There are these calling conventions METH_VARARGS This is the typical calling convention where the methods have the type PyCFunction The function expects two PyObject values The first one is the self object for methods for module functions it is the module object The second parameter often called args is a tuple object representing all arguments This parameter is typically processed using PyArg_ParseTuple or PyArg_UnpackTuple METH_KEYWORDS Can only be used in certain combinations with other flags METH_VARARGS METH_KEYWORDS METH_FASTCALL METH_KEYWORDS and METH_METHOD METH_FASTCALL METH_KEYWORDS METH_VARARGS METH_KEYWORDS Methods with these flags must be of type PyCFunctionWithKeywords The function expects three parameters self args kwargs where kwargs is a dictionary of all the keyword arguments or possibly NULL if there are no keyword arguments The parameters are typically processed using PyArg_ParseTupleAndKeywords METH_FASTCALL Fast calling convention supporting only positional arguments The methods have the type _PyCFunctionFast The first parameter is self the second parameter is a C array of PyObject values indicating the arguments and the third parameter is the number of arguments the length of the array New in version 3 7 Changed in version 3 10 METH_FASTCALL is now part of the stable ABI METH_FASTCALL METH_KEYWORDS Extension of METH_FASTCALL supporting also keyword arguments with methods of type _PyCFunctionFastWithKeywords Keyword arguments are passed the same way as in the vectorcall protocol there is an additional fourth PyObject parameter which is a tuple representing the names of the keyword arguments which are guaranteed to be strings or possibly NULL if there are no keywords The values of the keyword arguments are stored in the args array after the positional arguments New in version 3 7 METH_METHOD Can only be used in the combination with other flags METH_METHOD METH_FASTCALL METH_KEYWORDS METH_METHOD METH_FASTCALL METH_KEYWORDS Extension of METH_FASTCALL METH_KEYWORDS ,en
2585,supporting the defining class that is the class that contains the method in question The defining class might be a superclass of Py_TYPE self The method needs to be of type PyCMethod the same as for METH_FASTCALL METH_KEYWORDS with defining_class argument added after self New in version 3 9 METH_NOARGS Methods without parameters don t need to check whether arguments are given if they are listed with the METH_NOARGS flag They need to be of type PyCFunction The first parameter is typically named self and will hold a reference to the module or object instance In all cases the second parameter will be NULL The function must have 2 parameters Since the second parameter is unused Py_UNUSED can be used to prevent a compiler warning METH_O Methods with a single object argument can be listed with the METH_O flag instead of invoking PyArg_ParseTuple with a O argument They have the type PyCFunction with the self parameter and a PyObject parameter representing the single argument These two constants are not used to indicate the calling convention but the binding when use with methods of classes These may not be used for functions defined for modules At most one of these flags may be set for any given method METH_CLASS The method will be passed the type object as the first parameter rather than an instance of the type This is used to create class methods similar to what is created when using the classmethod built in function METH_STATIC The method will be passed NULL as the first parameter rather than an instance of the type This is used to create static methods similar to what is created when using the staticmethod built in function One other constant controls whether a method is loaded in place of another definition with the same method name METH_COEXIST The method will be loaded in place of existing definitions Without METH_COEXIST the default is to skip repeated definitions Since slot wrappers are loaded before the method table the existence of a sq_contains slot for example would generate a wrapped method named __contains__ and preclude the loading of a corresponding PyCFunction with the same name With the flag defined the PyCFunction will be loaded in place of the wrapper object and will co exist with the slot This is helpful because calls to PyCFunctions are optimized more than wrapper object calls PyObject PyCMethod_New PyMethodDef ml PyObject self PyObject module PyTypeObject cls Return value New reference Part of the Stable ABI since version 3 9 Turn ml into a Python callable object The caller must ensure that ml outlives the callable Typically ml is defined as a static variable The self parameter will be passed as the self argument to the C function in ml ml_meth when invoked self can be NULL The callable object s __module__ attribute can be set from the given module argument module should be a Python string which will be used as name of the module the function is defined in If unavailable it can be set to None or NULL See also function __module__ The cls parameter will be passed as the defining_class argument to the C function Must be set if METH_METHOD is set on ml ml_flags New in version 3 9 PyObject PyCFunction_NewEx PyMethodDef ml PyObject self PyObject module Return value New reference Part of the Stable ABI Equivalent to PyCMethod_New ml self module NULL PyObject PyCFunction_New PyMethodDef ml PyObject self Return value New reference Part of the Stable ABI since version 3 4 Equivalent to PyCMethod_New ml self NULL NULL Accessing attributes of extension types type PyMemberDef Part of the Stable ABI including all members Structure which describes an attribute of a type which corresponds to a C struct member When defining a class put a NULL terminated array of these structures in the tp_members slot Its fields are in order const char name Name of the member A NULL value marks the end of a PyMemberDef array The string should be static no copy is made of it int type The type of the member in the C struct See Member types for the possible values Py_ssize_t offset The offset in bytes that the member is located on the type ,en
2586,s object struct int flags Zero or more of the Member flags combined using bitwise OR const char doc The docstring or NULL The string should be static no copy is made of it Typically it is defined using PyDoc_STR By default when flags is 0 members allow both read and write access Use the Py_READONLY flag for read only access Certain types like Py_T_STRING imply Py_READONLY Only Py_T_OBJECT_EX and legacy T_OBJECT members can be deleted For heap allocated types created using PyType_FromSpec or similar PyMemberDef may contain a definition for the special member __vectorcalloffset__ corresponding to tp_vectorcall_offset in type objects These must be defined with Py_T_PYSSIZET and Py_READONLY for example static PyMemberDef spam_type_members __vectorcalloffset__ Py_T_PYSSIZET offsetof Spam_object vectorcall Py_READONLY NULL Sentinel You may need to include stddef h for offsetof The legacy offsets tp_dictoffset and tp_weaklistoffset can be defined similarly using __dictoffset__ and __weaklistoffset__ members but extensions are strongly encouraged to use Py_TPFLAGS_MANAGED_DICT and Py_TPFLAGS_MANAGED_WEAKREF instead Changed in version 3 12 PyMemberDef is always available Previously it required including structmember h PyObject PyMember_GetOne const char obj_addr struct PyMemberDef m Part of the Stable ABI Get an attribute belonging to the object at address obj_addr The attribute is described by PyMemberDef m Returns NULL on error Changed in version 3 12 PyMember_GetOne is always available Previously it required including structmember h int PyMember_SetOne char obj_addr struct PyMemberDef m PyObject o Part of the Stable ABI Set an attribute belonging to the object at address obj_addr to object o The attribute to set is described by PyMemberDef m Returns 0 if successful and a negative value on failure Changed in version 3 12 PyMember_SetOne is always available Previously it required including structmember h Member flags The following flags can be used with PyMemberDef flags Py_READONLY Not writable Py_AUDIT_READ Emit an object __getattr__ audit event before reading Py_RELATIVE_OFFSET Indicates that the offset of this PyMemberDef entry indicates an offset from the subclass specific data rather than from PyObject Can only be used as part of Py_tp_members slot when creating a class using negative basicsize It is mandatory in that case This flag is only used in PyType_Slot When setting tp_members during class creation Python clears it and sets PyMemberDef offset to the offset from the PyObject struct Changed in version 3 10 The RESTRICTED READ_RESTRICTED and WRITE_RESTRICTED macros available with include structmember h are deprecated READ_RESTRICTED and RESTRICTED are equivalent to Py_AUDIT_READ WRITE_RESTRICTED does nothing Changed in version 3 12 The READONLY macro was renamed to Py_READONLY The PY_AUDIT_READ macro was renamed with the Py_ prefix The new names are now always available Previously these required include structmember h The header is still available and it provides the old names Member types PyMemberDef type can be one of the following macros corresponding to various C types When the member is accessed in Python it will be converted to the equivalent Python type When it is set from Python it will be converted back to the C type If that is not possible an exception such as TypeError or ValueError is raised Unless marked D attributes defined this way cannot be deleted using e g del or delattr Macro name C type Python type Py_T_BYTE char int Py_T_SHORT short int Py_T_INT int int Py_T_LONG long int Py_T_LONGLONG long long int Py_T_UBYTE unsigned char int Py_T_UINT unsigned int int Py_T_USHORT unsigned short int Py_T_ULONG unsigned long int Py_T_ULONGLONG unsigned long long int Py_T_PYSSIZET Py_ssize_t int Py_T_FLOAT float float Py_T_DOUBLE double float Py_T_BOOL char written as 0 or 1 bool Py_T_STRING const char str RO Py_T_STRING_INPLACE const char str RO Py_T_CHAR char 0 127 str Py_T_OBJECT_EX PyObject object D Zero terminated UTF8 encoded C string With Py_T_STRING the C representation is a pointer with Py_T_STRING_INPLACE,en
2587, the string is stored directly in the structure String of length 1 Only ASCII is accepted RO Implies Py_READONLY D Can be deleted in which case the pointer is set to NULL Reading a NULL pointer raises AttributeError New in version 3 12 In previous versions the macros were only available with include structmember h and were named without the Py_ prefix e g as T_INT The header is still available and contains the old names along with the following deprecated types T_OBJECT Like Py_T_OBJECT_EX but NULL is converted to None This results in surprising behavior in Python deleting the attribute effectively sets it to None T_NONE Always None Must be used with Py_READONLY Defining Getters and Setters type PyGetSetDef Part of the Stable ABI including all members Structure to define property like access for a type See also description of the PyTypeObject tp_getset slot const char name attribute name getter get C function to get the attribute setter set Optional C function to set or delete the attribute If NULL the attribute is read only const char doc optional docstring void closure Optional user data pointer providing additional data for getter and setter typedef PyObject getter PyObject void Part of the Stable ABI The get function takes one PyObject parameter the instance and a user data pointer the associated closure It should return a new reference on success or NULL with a set exception on failure typedef int setter PyObject PyObject void Part of the Stable ABI set functions take two PyObject parameters the instance and the value to be set and a user data pointer the associated closure In case the attribute should be deleted the second parameter is NULL Should return 0 on success or 1 with a set exception on failure,en
2588,Python Setup and Usage This part of the documentation is devoted to general information on the setup of the Python environment on different platforms the invocation of the interpreter and things that make working with Python easier 1 Command line and environment 1 1 Command line 1 1 1 Interface options 1 1 2 Generic options 1 1 3 Miscellaneous options 1 1 4 Options you shouldn t use 1 2 Environment variables 1 2 1 Debug mode variables 2 Using Python on Unix platforms 2 1 Getting and installing the latest version of Python 2 1 1 On Linux 2 1 2 On FreeBSD and OpenBSD 2 2 Building Python 2 3 Python related paths and files 2 4 Miscellaneous 2 5 Custom OpenSSL 3 Configure Python 3 1 Build Requirements 3 2 Generated files 3 2 1 configure script 3 3 Configure Options 3 3 1 General Options 3 3 2 WebAssembly Options 3 3 3 Install Options 3 3 4 Performance options 3 3 5 Python Debug Build 3 3 6 Debug options 3 3 7 Linker options 3 3 8 Libraries options 3 3 9 Security Options 3 3 10 macOS Options 3 3 11 Cross Compiling Options 3 4 Python Build System 3 4 1 Main files of the build system 3 4 2 Main build steps 3 4 3 Main Makefile targets 3 4 4 C extensions 3 5 Compiler and linker flags 3 5 1 Preprocessor flags 3 5 2 Compiler flags 3 5 3 Linker flags 4 Using Python on Windows 4 1 The full installer 4 1 1 Installation steps 4 1 2 Removing the MAX_PATH Limitation 4 1 3 Installing Without UI 4 1 4 Installing Without Downloading 4 1 5 Modifying an install 4 2 The Microsoft Store package 4 2 1 Known issues 4 2 1 1 Redirection of local data registry and temporary paths 4 3 The nuget org packages 4 4 The embeddable package 4 4 1 Python Application 4 4 2 Embedding Python 4 5 Alternative bundles 4 6 Configuring Python 4 6 1 Excursus Setting environment variables 4 6 2 Finding the Python executable 4 7 UTF 8 mode 4 8 Python Launcher for Windows 4 8 1 Getting started 4 8 1 1 From the command line 4 8 1 2 Virtual environments 4 8 1 3 From a script 4 8 1 4 From file associations 4 8 2 Shebang Lines 4 8 3 Arguments in shebang lines 4 8 4 Customization 4 8 4 1 Customization via INI files 4 8 4 2 Customizing default Python versions 4 8 5 Diagnostics 4 8 6 Dry Run 4 8 7 Install on demand 4 8 8 Return codes 4 9 Finding modules 4 10 Additional modules 4 10 1 PyWin32 4 10 2 cx_Freeze 4 11 Compiling Python on Windows 4 12 Other Platforms 5 Using Python on a Mac 5 1 Getting and Installing Python 5 1 1 How to run a Python script 5 1 2 Running scripts with a GUI 5 1 3 Configuration 5 2 The IDE 5 3 Installing Additional Python Packages 5 4 GUI Programming 5 5 Distributing Python Applications 5 6 Other Resources 6 Editors and IDEs,en
2589,MemoryView objects A memoryview object exposes the C level buffer interface as a Python object which can then be passed around like any other object PyObject PyMemoryView_FromObject PyObject obj Return value New reference Part of the Stable ABI Create a memoryview object from an object that provides the buffer interface If obj supports writable buffer exports the memoryview object will be read write otherwise it may be either read only or read write at the discretion of the exporter PyBUF_READ Flag to request a readonly buffer PyBUF_WRITE Flag to request a writable buffer PyObject PyMemoryView_FromMemory char mem Py_ssize_t size int flags Return value New reference Part of the Stable ABI since version 3 7 Create a memoryview object using mem as the underlying buffer flags can be one of PyBUF_READ or PyBUF_WRITE New in version 3 3 PyObject PyMemoryView_FromBuffer const Py_buffer view Return value New reference Part of the Stable ABI since version 3 11 Create a memoryview object wrapping the given buffer structure view For simple byte buffers PyMemoryView_FromMemory is the preferred function PyObject PyMemoryView_GetContiguous PyObject obj int buffertype char order Return value New reference Part of the Stable ABI Create a memoryview object to a contiguous chunk of memory in either C or F ortran order from an object that defines the buffer interface If memory is contiguous the memoryview object points to the original memory Otherwise a copy is made and the memoryview points to a new bytes object buffertype can be one of PyBUF_READ or PyBUF_WRITE int PyMemoryView_Check PyObject obj Return true if the object obj is a memoryview object It is not currently allowed to create subclasses of memoryview This function always succeeds Py_buffer PyMemoryView_GET_BUFFER PyObject mview Return a pointer to the memoryview s private copy of the exporter s buffer mview must be a memoryview instance this macro doesn t check its type you must do it yourself or you will risk crashes PyObject PyMemoryView_GET_BASE PyObject mview Return either a pointer to the exporting object that the memoryview is based on or NULL if the memoryview has been created by one of the functions PyMemoryView_FromMemory or PyMemoryView_FromBuffer mview must be a memoryview instance,en
2590,http server HTTP servers Source code Lib http server py This module defines classes for implementing HTTP servers Warning http server is not recommended for production It only implements basic security checks Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information One class HTTPServer is a socketserver TCPServer subclass It creates and listens at the HTTP socket dispatching the requests to a handler Code to create and run the server looks like this def run server_class HTTPServer handler_class BaseHTTPRequestHandler server_address 8000 httpd server_class server_address handler_class httpd serve_forever class http server HTTPServer server_address RequestHandlerClass This class builds on the TCPServer class by storing the server address as instance variables named server_name and server_port The server is accessible by the handler typically through the handler s server instance variable class http server ThreadingHTTPServer server_address RequestHandlerClass This class is identical to HTTPServer but uses threads to handle requests by using the ThreadingMixIn This is useful to handle web browsers pre opening sockets on which HTTPServer would wait indefinitely New in version 3 7 The HTTPServer and ThreadingHTTPServer must be given a RequestHandlerClass on instantiation of which this module provides three different variants class http server BaseHTTPRequestHandler request client_address server This class is used to handle the HTTP requests that arrive at the server By itself it cannot respond to any actual HTTP requests it must be subclassed to handle each request method e g GET or POST BaseHTTPRequestHandler provides a number of class and instance variables and methods for use by subclasses The handler will parse the request and the headers then call a method specific to the request type The method name is constructed from the request For example for the request method SPAM the do_SPAM method will be called with no arguments All of the relevant information is stored in instance variables of the handler Subclasses should not need to override or extend the __init__ method BaseHTTPRequestHandler has the following instance variables client_address Contains a tuple of the form host port referring to the client s address server Contains the server instance close_connection Boolean that should be set before handle_one_request returns indicating if another request may be expected or if the connection should be shut down requestline Contains the string representation of the HTTP request line The terminating CRLF is stripped This attribute should be set by handle_one_request If no valid request line was processed it should be set to the empty string command Contains the command request type For example GET path Contains the request path If query component of the URL is present then path includes the query Using the terminology of RFC 3986 path here includes hier part and the query request_version Contains the version string from the request For example HTTP 1 0 headers Holds an instance of the class specified by the MessageClass class variable This instance parses and manages the headers in the HTTP request The parse_headers function from http client is used to parse the headers and it requires that the HTTP request provide a valid RFC 2822 style header rfile An io BufferedIOBase input stream ready to read from the start of the optional input data wfile Contains the output stream for writing a response back to the client Proper adherence to the HTTP protocol must be used when writing to this stream in order to achieve successful interoperation with HTTP clients Changed in version 3 6 This is an io BufferedIOBase stream BaseHTTPRequestHandler has the following attributes server_version Specifies the server software version You may want to override this The format is multiple whitespace separated strings where each string is of the form name version For example BaseHTTP 0 2 sys_version Contains the Python ,en
2591,system version in a form usable by the version_string method and the server_version class variable For example Python 1 4 error_message_format Specifies a format string that should be used by send_error method for building an error response to the client The string is filled by default with variables from responses based on the status code that passed to send_error error_content_type Specifies the Content Type HTTP header of error responses sent to the client The default value is text html protocol_version Specifies the HTTP version to which the server is conformant It is sent in responses to let the client know the server s communication capabilities for future requests If set to HTTP 1 1 the server will permit HTTP persistent connections however your server must then include an accurate Content Length header using send_header in all of its responses to clients For backwards compatibility the setting defaults to HTTP 1 0 MessageClass Specifies an email message Message like class to parse HTTP headers Typically this is not overridden and it defaults to http client HTTPMessage responses This attribute contains a mapping of error code integers to two element tuples containing a short and long message For example code shortmessage longmessage The shortmessage is usually used as the message key in an error response and longmessage as the explain key It is used by send_response_only and send_error methods A BaseHTTPRequestHandler instance has the following methods handle Calls handle_one_request once or if persistent connections are enabled multiple times to handle incoming HTTP requests You should never need to override it instead implement appropriate do_ methods handle_one_request This method will parse and dispatch the request to the appropriate do_ method You should never need to override it handle_expect_100 When an HTTP 1 1 conformant server receives an Expect 100 continue request header it responds back with a 100 Continue followed by 200 OK headers This method can be overridden to raise an error if the server does not want the client to continue For e g server can choose to send 417 Expectation Failed as a response header and return False New in version 3 2 send_error code message None explain None Sends and logs a complete error reply to the client The numeric code specifies the HTTP error code with message as an optional short human readable description of the error The explain argument can be used to provide more detailed information about the error it will be formatted using the error_message_format attribute and emitted after a complete set of headers as the response body The responses attribute holds the default values for message and explain that will be used if no value is provided for unknown codes the default value for both is the string The body will be empty if the method is HEAD or the response code is one of the following 1 xx 204 No Content 205 Reset Content 304 Not Modified Changed in version 3 4 The error response includes a Content Length header Added the explain argument send_response code message None Adds a response header to the headers buffer and logs the accepted request The HTTP response line is written to the internal buffer followed by Server and Date headers The values for these two headers are picked up from the version_string and date_time_string methods respectively If the server does not intend to send any other headers using the send_header method then send_response should be followed by an end_headers call Changed in version 3 3 Headers are stored to an internal buffer and end_headers needs to be called explicitly send_header keyword value Adds the HTTP header to an internal buffer which will be written to the output stream when either end_headers or flush_headers is invoked keyword should specify the header keyword with value specifying its value Note that after the send_header calls are done end_headers MUST BE called in order to complete the operation Changed in version 3 2 Headers are stored in an internal buffer send_response_only code message None Sends the response header only,en
2592, used for the purposes when 100 Continue response is sent by the server to the client The headers not buffered and sent directly the output stream If the message is not specified the HTTP message corresponding the response code is sent New in version 3 2 end_headers Adds a blank line indicating the end of the HTTP headers in the response to the headers buffer and calls flush_headers Changed in version 3 2 The buffered headers are written to the output stream flush_headers Finally send the headers to the output stream and flush the internal headers buffer New in version 3 3 log_request code size Logs an accepted successful request code should specify the numeric HTTP code associated with the response If a size of the response is available then it should be passed as the size parameter log_error Logs an error when a request cannot be fulfilled By default it passes the message to log_message so it takes the same arguments format and additional values log_message format Logs an arbitrary message to sys stderr This is typically overridden to create custom error logging mechanisms The format argument is a standard printf style format string where the additional arguments to log_message are applied as inputs to the formatting The client ip address and current date and time are prefixed to every message logged version_string Returns the server software s version string This is a combination of the server_version and sys_version attributes date_time_string timestamp None Returns the date and time given by timestamp which must be None or in the format returned by time time formatted for a message header If timestamp is omitted it uses the current date and time The result looks like Sun 06 Nov 1994 08 49 37 GMT log_date_time_string Returns the current date and time formatted for logging address_string Returns the client address Changed in version 3 3 Previously a name lookup was performed To avoid name resolution delays it now always returns the IP address class http server SimpleHTTPRequestHandler request client_address server directory None This class serves files from the directory directory and below or the current directory if directory is not provided directly mapping the directory structure to HTTP requests Changed in version 3 7 Added the directory parameter Changed in version 3 9 The directory parameter accepts a path like object A lot of the work such as parsing the request is done by the base class BaseHTTPRequestHandler This class implements the do_GET and do_HEAD functions The following are defined as class level attributes of SimpleHTTPRequestHandler server_version This will be SimpleHTTP __version__ where __version__ is defined at the module level extensions_map A dictionary mapping suffixes into MIME types contains custom overrides for the default system mappings The mapping is used case insensitively and so should contain only lower cased keys Changed in version 3 9 This dictionary is no longer filled with the default system mappings but only contains overrides The SimpleHTTPRequestHandler class defines the following methods do_HEAD This method serves the HEAD request type it sends the headers it would send for the equivalent GET request See the do_GET method for a more complete explanation of the possible headers do_GET The request is mapped to a local file by interpreting the request as a path relative to the current working directory If the request was mapped to a directory the directory is checked for a file named index html or index htm in that order If found the file s contents are returned otherwise a directory listing is generated by calling the list_directory method This method uses os listdir to scan the directory and returns a 404 error response if the listdir fails If the request was mapped to a file it is opened Any OSError exception in opening the requested file is mapped to a 404 File not found error If there was a If Modified Since header in the request and the file was not modified after this time a 304 Not Modified response is sent Otherwise the content type is guessed by calling the guess_type me,en
2593,thod which in turn uses the extensions_map variable and the file contents are returned A Content type header with the guessed content type is output followed by a Content Length header with the file s size and a Last Modified header with the file s modification time Then follows a blank line signifying the end of the headers and then the contents of the file are output If the file s MIME type starts with text the file is opened in text mode otherwise binary mode is used For example usage see the implementation of the test function in Lib http server py Changed in version 3 7 Support of the If Modified Since header The SimpleHTTPRequestHandler class can be used in the following manner in order to create a very basic webserver serving files relative to the current directory import http server import socketserver PORT 8000 Handler http server SimpleHTTPRequestHandler with socketserver TCPServer PORT Handler as httpd print serving at port PORT httpd serve_forever SimpleHTTPRequestHandler can also be subclassed to enhance behavior such as using different index file names by overriding the class attribute index_pages http server can also be invoked directly using the m switch of the interpreter Similar to the previous example this serves files relative to the current directory python m http server The server listens to port 8000 by default The default can be overridden by passing the desired port number as an argument python m http server 9000 By default the server binds itself to all interfaces The option b bind specifies a specific address to which it should bind Both IPv4 and IPv6 addresses are supported For example the following command causes the server to bind to localhost only python m http server bind 127 0 0 1 Changed in version 3 4 Added the bind option Changed in version 3 8 Support IPv6 in the bind option By default the server uses the current directory The option d directory specifies a directory to which it should serve the files For example the following command uses a specific directory python m http server directory tmp Changed in version 3 7 Added the directory option By default the server is conformant to HTTP 1 0 The option p protocol specifies the HTTP version to which the server is conformant For example the following command runs an HTTP 1 1 conformant server python m http server protocol HTTP 1 1 Changed in version 3 11 Added the protocol option class http server CGIHTTPRequestHandler request client_address server This class is used to serve either files or output of CGI scripts from the current directory and below Note that mapping HTTP hierarchic structure to local directory structure is exactly as in SimpleHTTPRequestHandler Note CGI scripts run by the CGIHTTPRequestHandler class cannot execute redirects HTTP code 302 because code 200 script output follows is sent prior to execution of the CGI script This pre empts the status code The class will however run the CGI script instead of serving it as a file if it guesses it to be a CGI script Only directory based CGI are used the other common server configuration is to treat special extensions as denoting CGI scripts The do_GET and do_HEAD functions are modified to run CGI scripts and serve the output instead of serving files if the request leads to somewhere below the cgi_directories path The CGIHTTPRequestHandler defines the following data member cgi_directories This defaults to cgi bin htbin and describes directories to treat as containing CGI scripts The CGIHTTPRequestHandler defines the following method do_POST This method serves the POST request type only allowed for CGI scripts Error 501 Can only POST to CGI scripts is output when trying to POST to a non CGI url Note that CGI scripts will be run with UID of user nobody for security reasons Problems with the CGI script will be translated to error 403 CGIHTTPRequestHandler can be enabled in the command line by passing the cgi option python m http server cgi Warning CGIHTTPRequestHandler and the cgi command line option are not intended for use by untrusted clients and may be vulnerable to exploitatio,en
2594,n Always use within a secure environment Security Considerations SimpleHTTPRequestHandler will follow symbolic links when handling requests this makes it possible for files outside of the specified directory to be served Earlier versions of Python did not scrub control characters from the log messages emitted to stderr from python m http server or the default BaseHTTPRequestHandler log_message implementation This could allow remote clients connecting to your server to send nefarious control codes to your terminal Changed in version 3 12 Control characters are scrubbed in stderr logs,en
2595,Data Compression and Archiving The modules described in this chapter support data compression with the zlib gzip bzip2 and lzma algorithms and the creation of ZIP and tar format archives See also Archiving operations provided by the shutil module zlib Compression compatible with gzip gzip Support for gzip files Examples of usage Command Line Interface Command line options bz2 Support for bzip2 compression De compression of files Incremental de compression One shot de compression Examples of usage lzma Compression using the LZMA algorithm Reading and writing compressed files Compressing and decompressing data in memory Miscellaneous Specifying custom filter chains Examples zipfile Work with ZIP archives ZipFile Objects Path Objects PyZipFile Objects ZipInfo Objects Command Line Interface Command line options Decompression pitfalls From file itself File System limitations Resources limitations Interruption Default behaviors of extraction tarfile Read and write tar archive files TarFile Objects TarInfo Objects Extraction filters Default named filters Filter errors Hints for further verification Supporting older Python versions Stateful extraction filter example Command Line Interface Command line options Examples Supported tar formats Unicode issues,en
2596,stat Interpreting stat results Source code Lib stat py The stat module defines constants and functions for interpreting the results of os stat os fstat and os lstat if they exist For complete details about the stat fstat and lstat calls consult the documentation for your system Changed in version 3 4 The stat module is backed by a C implementation The stat module defines the following functions to test for specific file types stat S_ISDIR mode Return non zero if the mode is from a directory stat S_ISCHR mode Return non zero if the mode is from a character special device file stat S_ISBLK mode Return non zero if the mode is from a block special device file stat S_ISREG mode Return non zero if the mode is from a regular file stat S_ISFIFO mode Return non zero if the mode is from a FIFO named pipe stat S_ISLNK mode Return non zero if the mode is from a symbolic link stat S_ISSOCK mode Return non zero if the mode is from a socket stat S_ISDOOR mode Return non zero if the mode is from a door New in version 3 4 stat S_ISPORT mode Return non zero if the mode is from an event port New in version 3 4 stat S_ISWHT mode Return non zero if the mode is from a whiteout New in version 3 4 Two additional functions are defined for more general manipulation of the file s mode stat S_IMODE mode Return the portion of the file s mode that can be set by os chmod that is the file s permission bits plus the sticky bit set group id and set user id bits on systems that support them stat S_IFMT mode Return the portion of the file s mode that describes the file type used by the S_IS functions above Normally you would use the os path is functions for testing the type of a file the functions here are useful when you are doing multiple tests of the same file and wish to avoid the overhead of the stat system call for each test These are also useful when checking for information about a file that isn t handled by os path like the tests for block and character devices Example import os sys from stat import def walktree top callback recursively descend the directory tree rooted at top calling the callback function for each regular file for f in os listdir top pathname os path join top f mode os lstat pathname st_mode if S_ISDIR mode It s a directory recurse into it walktree pathname callback elif S_ISREG mode It s a file call the callback function callback pathname else Unknown file type print a message print Skipping s pathname def visitfile file print visiting file if __name__ __main__ walktree sys argv 1 visitfile An additional utility function is provided to convert a file s mode in a human readable string stat filemode mode Convert a file s mode to a string of the form rwxrwxrwx New in version 3 3 Changed in version 3 4 The function supports S_IFDOOR S_IFPORT and S_IFWHT All the variables below are simply symbolic indexes into the 10 tuple returned by os stat os fstat or os lstat stat ST_MODE Inode protection mode stat ST_INO Inode number stat ST_DEV Device inode resides on stat ST_NLINK Number of links to the inode stat ST_UID User id of the owner stat ST_GID Group id of the owner stat ST_SIZE Size in bytes of a plain file amount of data waiting on some special files stat ST_ATIME Time of last access stat ST_MTIME Time of last modification stat ST_CTIME The ctime as reported by the operating system On some systems like Unix is the time of the last metadata change and on others like Windows is the creation time see platform documentation for details The interpretation of file size changes according to the file type For plain files this is the size of the file in bytes For FIFOs and sockets under most flavors of Unix including Linux in particular the size is the number of bytes waiting to be read at the time of the call to os stat os fstat or os lstat this can sometimes be useful especially for polling one of these special files after a non blocking open The meaning of the size field for other character and block devices varies more depending on the implementation of the underlying system call The variables below define the flags used in the ST_MODE f,en
2597,ield Use of the functions above is more portable than use of the first set of flags stat S_IFSOCK Socket stat S_IFLNK Symbolic link stat S_IFREG Regular file stat S_IFBLK Block device stat S_IFDIR Directory stat S_IFCHR Character device stat S_IFIFO FIFO stat S_IFDOOR Door New in version 3 4 stat S_IFPORT Event port New in version 3 4 stat S_IFWHT Whiteout New in version 3 4 Note S_IFDOOR S_IFPORT or S_IFWHT are defined as 0 when the platform does not have support for the file types The following flags can also be used in the mode argument of os chmod stat S_ISUID Set UID bit stat S_ISGID Set group ID bit This bit has several special uses For a directory it indicates that BSD semantics is to be used for that directory files created there inherit their group ID from the directory not from the effective group ID of the creating process and directories created there will also get the S_ISGID bit set For a file that does not have the group execution bit S_IXGRP set the set group ID bit indicates mandatory file record locking see also S_ENFMT stat S_ISVTX Sticky bit When this bit is set on a directory it means that a file in that directory can be renamed or deleted only by the owner of the file by the owner of the directory or by a privileged process stat S_IRWXU Mask for file owner permissions stat S_IRUSR Owner has read permission stat S_IWUSR Owner has write permission stat S_IXUSR Owner has execute permission stat S_IRWXG Mask for group permissions stat S_IRGRP Group has read permission stat S_IWGRP Group has write permission stat S_IXGRP Group has execute permission stat S_IRWXO Mask for permissions for others not in group stat S_IROTH Others have read permission stat S_IWOTH Others have write permission stat S_IXOTH Others have execute permission stat S_ENFMT System V file locking enforcement This flag is shared with S_ISGID file record locking is enforced on files that do not have the group execution bit S_IXGRP set stat S_IREAD Unix V7 synonym for S_IRUSR stat S_IWRITE Unix V7 synonym for S_IWUSR stat S_IEXEC Unix V7 synonym for S_IXUSR The following flags can be used in the flags argument of os chflags stat UF_NODUMP Do not dump the file stat UF_IMMUTABLE The file may not be changed stat UF_APPEND The file may only be appended to stat UF_OPAQUE The directory is opaque when viewed through a union stack stat UF_NOUNLINK The file may not be renamed or deleted stat UF_COMPRESSED The file is stored compressed macOS 10 6 stat UF_HIDDEN The file should not be displayed in a GUI macOS 10 5 stat SF_ARCHIVED The file may be archived stat SF_IMMUTABLE The file may not be changed stat SF_APPEND The file may only be appended to stat SF_NOUNLINK The file may not be renamed or deleted stat SF_SNAPSHOT The file is a snapshot file See the BSD or macOS systems man page chflags 2 for more information On Windows the following file attribute constants are available for use when testing bits in the st_file_attributes member returned by os stat See the Windows API documentation for more detail on the meaning of these constants stat FILE_ATTRIBUTE_ARCHIVE stat FILE_ATTRIBUTE_COMPRESSED stat FILE_ATTRIBUTE_DEVICE stat FILE_ATTRIBUTE_DIRECTORY stat FILE_ATTRIBUTE_ENCRYPTED stat FILE_ATTRIBUTE_HIDDEN stat FILE_ATTRIBUTE_INTEGRITY_STREAM stat FILE_ATTRIBUTE_NORMAL stat FILE_ATTRIBUTE_NOT_CONTENT_INDEXED stat FILE_ATTRIBUTE_NO_SCRUB_DATA stat FILE_ATTRIBUTE_OFFLINE stat FILE_ATTRIBUTE_READONLY stat FILE_ATTRIBUTE_REPARSE_POINT stat FILE_ATTRIBUTE_SPARSE_FILE stat FILE_ATTRIBUTE_SYSTEM stat FILE_ATTRIBUTE_TEMPORARY stat FILE_ATTRIBUTE_VIRTUAL New in version 3 5 On Windows the following constants are available for comparing against the st_reparse_tag member returned by os lstat These are well known constants but are not an exhaustive list stat IO_REPARSE_TAG_SYMLINK stat IO_REPARSE_TAG_MOUNT_POINT stat IO_REPARSE_TAG_APPEXECLINK New in version 3 8,en
2598,traceback Print or retrieve a stack traceback Source code Lib traceback py This module provides a standard interface to extract format and print stack traces of Python programs It exactly mimics the behavior of the Python interpreter when it prints a stack trace This is useful when you want to print stack traces under program control such as in a wrapper around the interpreter The module uses traceback objects these are objects of type types TracebackType which are assigned to the __traceback__ field of BaseException instances See also Module faulthandler Used to dump Python tracebacks explicitly on a fault after a timeout or on a user signal Module pdb Interactive source code debugger for Python programs The module defines the following functions traceback print_tb tb limit None file None Print up to limit stack trace entries from traceback object tb starting from the caller s frame if limit is positive Otherwise print the last abs limit entries If limit is omitted or None all entries are printed If file is omitted or None the output goes to sys stderr otherwise it should be an open file or file like object to receive the output Changed in version 3 5 Added negative limit support traceback print_exception exc value tb limit None file None chain True Print exception information and stack trace entries from traceback object tb to file This differs from print_tb in the following ways if tb is not None it prints a header Traceback most recent call last it prints the exception type and value after the stack trace if type value is SyntaxError and value has the appropriate format it prints the line where the syntax error occurred with a caret indicating the approximate position of the error Since Python 3 10 instead of passing value and tb an exception object can be passed as the first argument If value and tb are provided the first argument is ignored in order to provide backwards compatibility The optional limit argument has the same meaning as for print_tb If chain is true the default then chained exceptions the __cause__ or __context__ attributes of the exception will be printed as well like the interpreter itself does when printing an unhandled exception Changed in version 3 5 The etype argument is ignored and inferred from the type of value Changed in version 3 10 The etype parameter has been renamed to exc and is now positional only traceback print_exc limit None file None chain True This is a shorthand for print_exception sys exception limit file chain traceback print_last limit None file None chain True This is a shorthand for print_exception sys last_exc limit file chain In general it will work only after an exception has reached an interactive prompt see sys last_exc traceback print_stack f None limit None file None Print up to limit stack trace entries starting from the invocation point if limit is positive Otherwise print the last abs limit entries If limit is omitted or None all entries are printed The optional f argument can be used to specify an alternate stack frame to start The optional file argument has the same meaning as for print_tb Changed in version 3 5 Added negative limit support traceback extract_tb tb limit None Return a StackSummary object representing a list of pre processed stack trace entries extracted from the traceback object tb It is useful for alternate formatting of stack traces The optional limit argument has the same meaning as for print_tb A pre processed stack trace entry is a FrameSummary object containing attributes filename lineno name and line representing the information that is usually printed for a stack trace traceback extract_stack f None limit None Extract the raw traceback from the current stack frame The return value has the same format as for extract_tb The optional f and limit arguments have the same meaning as for print_stack traceback format_list extracted_list Given a list of tuples or FrameSummary objects as returned by extract_tb or extract_stack return a list of strings ready for printing Each string in the resulting list corresponds to the item with the same index i,en
2599,n the argument list Each string ends in a newline the strings may contain internal newlines as well for those items whose source text line is not None traceback format_exception_only exc value Format the exception part of a traceback using an exception value such as given by sys last_value The return value is a list of strings each ending in a newline The list contains the exception s message which is normally a single string however for SyntaxError exceptions it contains several lines that when printed display detailed information about where the syntax error occurred Following the message the list contains the exception s notes Since Python 3 10 instead of passing value an exception object can be passed as the first argument If value is provided the first argument is ignored in order to provide backwards compatibility Changed in version 3 10 The etype parameter has been renamed to exc and is now positional only Changed in version 3 11 The returned list now includes any notes attached to the exception traceback format_exception exc value tb limit None chain True Format a stack trace and the exception information The arguments have the same meaning as the corresponding arguments to print_exception The return value is a list of strings each ending in a newline and some containing internal newlines When these lines are concatenated and printed exactly the same text is printed as does print_exception Changed in version 3 5 The etype argument is ignored and inferred from the type of value Changed in version 3 10 This function s behavior and signature were modified to match print_exception traceback format_exc limit None chain True This is like print_exc limit but returns a string instead of printing to a file traceback format_tb tb limit None A shorthand for format_list extract_tb tb limit traceback format_stack f None limit None A shorthand for format_list extract_stack f limit traceback clear_frames tb Clears the local variables of all the stack frames in a traceback tb by calling the clear method of each frame object New in version 3 4 traceback walk_stack f Walk a stack following f f_back from the given frame yielding the frame and line number for each frame If f is None the current stack is used This helper is used with StackSummary extract New in version 3 5 traceback walk_tb tb Walk a traceback following tb_next yielding the frame and line number for each frame This helper is used with StackSummary extract New in version 3 5 The module also defines the following classes TracebackException Objects New in version 3 5 TracebackException objects are created from actual exceptions to capture data for later printing in a lightweight fashion class traceback TracebackException exc_type exc_value exc_traceback limit None lookup_lines True capture_locals False compact False max_group_width 15 max_group_depth 10 Capture an exception for later rendering limit lookup_lines and capture_locals are as for the StackSummary class If compact is true only data that is required by TracebackException s format method is saved in the class attributes In particular the __context__ field is calculated only if __cause__ is None and __suppress_context__ is false Note that when locals are captured they are also shown in the traceback max_group_width and max_group_depth control the formatting of exception groups see BaseExceptionGroup The depth refers to the nesting level of the group and the width refers to the size of a single exception group s exceptions array The formatted output is truncated when either limit is exceeded Changed in version 3 10 Added the compact parameter Changed in version 3 11 Added the max_group_width and max_group_depth parameters __cause__ A TracebackException of the original __cause__ __context__ A TracebackException of the original __context__ exceptions If self represents an ExceptionGroup this field holds a list of TracebackException instances representing the nested exceptions Otherwise it is None New in version 3 11 __suppress_context__ The __suppress_context__ value from the original exception __notes__ The __note,en
2600,s__ value from the original exception or None if the exception does not have any notes If it is not None is it formatted in the traceback after the exception string New in version 3 11 stack A StackSummary representing the traceback exc_type The class of the original traceback filename For syntax errors the file name where the error occurred lineno For syntax errors the line number where the error occurred end_lineno For syntax errors the end line number where the error occurred Can be None if not present New in version 3 10 text For syntax errors the text where the error occurred offset For syntax errors the offset into the text where the error occurred end_offset For syntax errors the end offset into the text where the error occurred Can be None if not present New in version 3 10 msg For syntax errors the compiler error message classmethod from_exception exc limit None lookup_lines True capture_locals False Capture an exception for later rendering limit lookup_lines and capture_locals are as for the StackSummary class Note that when locals are captured they are also shown in the traceback print file None chain True Print to file default sys stderr the exception information returned by format New in version 3 11 format chain True Format the exception If chain is not True __cause__ and __context__ will not be formatted The return value is a generator of strings each ending in a newline and some containing internal newlines print_exception is a wrapper around this method which just prints the lines to a file format_exception_only Format the exception part of the traceback The return value is a generator of strings each ending in a newline The generator emits the exception s message followed by its notes if it has any The exception message is normally a single string however for SyntaxError exceptions it consists of several lines that when printed display detailed information about where the syntax error occurred Changed in version 3 11 The exception s notes are now included in the output StackSummary Objects New in version 3 5 StackSummary objects represent a call stack ready for formatting class traceback StackSummary classmethod extract frame_gen limit None lookup_lines True capture_locals False Construct a StackSummary object from a frame generator such as is returned by walk_stack or walk_tb If limit is supplied only this many frames are taken from frame_gen If lookup_lines is False the returned FrameSummary objects will not have read their lines in yet making the cost of creating the StackSummary cheaper which may be valuable if it may not actually get formatted If capture_locals is True the local variables in each FrameSummary are captured as object representations Changed in version 3 12 Exceptions raised from repr on a local variable when capture_locals is True are no longer propagated to the caller classmethod from_list a_list Construct a StackSummary object from a supplied list of FrameSummary objects or old style list of tuples Each tuple should be a 4 tuple with filename lineno name line as the elements format Returns a list of strings ready for printing Each string in the resulting list corresponds to a single frame from the stack Each string ends in a newline the strings may contain internal newlines as well for those items with source text lines For long sequences of the same frame and line the first few repetitions are shown followed by a summary line stating the exact number of further repetitions Changed in version 3 6 Long sequences of repeated frames are now abbreviated format_frame_summary frame_summary Returns a string for printing one of the frames involved in the stack This method is called for each FrameSummary object to be printed by StackSummary format If it returns None the frame is omitted from the output New in version 3 11 FrameSummary Objects New in version 3 5 A FrameSummary object represents a single frame in a traceback class traceback FrameSummary filename lineno name lookup_line True locals None line None Represents a single frame in the traceback or stack that is being formatted or pr,en
2601,inted It may optionally have a stringified version of the frame s locals included in it If lookup_line is False the source code is not looked up until the FrameSummary has the line attribute accessed which also happens when casting it to a tuple line may be directly provided and will prevent line lookups happening at all locals is an optional local variable dictionary and if supplied the variable representations are stored in the summary for later display FrameSummary instances have the following attributes filename The filename of the source code for this frame Equivalent to accessing f f_code co_filename on a frame object f lineno The line number of the source code for this frame name Equivalent to accessing f f_code co_name on a frame object f line A string representing the source code for this frame with leading and trailing whitespace stripped If the source is not available it is None Traceback Examples This simple example implements a basic read eval print loop similar to but less useful than the standard Python interactive interpreter loop For a more complete implementation of the interpreter loop refer to the code module import sys traceback def run_user_code envdir source input try exec source envdir except Exception print Exception in user code print 60 traceback print_exc file sys stdout print 60 envdir while True run_user_code envdir The following example demonstrates the different ways to print and format the exception and traceback import sys traceback def lumberjack bright_side_of_life def bright_side_of_life return tuple 0 try lumberjack except IndexError exc sys exception print print_tb traceback print_tb exc __traceback__ limit 1 file sys stdout print print_exception traceback print_exception exc limit 2 file sys stdout print print_exc traceback print_exc limit 2 file sys stdout print format_exc first and last line formatted_lines traceback format_exc splitlines print formatted_lines 0 print formatted_lines 1 print format_exception print repr traceback format_exception exc print extract_tb print repr traceback extract_tb exc __traceback__ print format_tb print repr traceback format_tb exc __traceback__ print tb_lineno exc __traceback__ tb_lineno The output for the example would look similar to this print_tb File doctest line 10 in module lumberjack print_exception Traceback most recent call last File doctest line 10 in module lumberjack File doctest line 4 in lumberjack bright_side_of_life IndexError tuple index out of range print_exc Traceback most recent call last File doctest line 10 in module lumberjack File doctest line 4 in lumberjack bright_side_of_life IndexError tuple index out of range format_exc first and last line Traceback most recent call last IndexError tuple index out of range format_exception Traceback most recent call last n File doctest default 0 line 10 in module n lumberjack n File doctest default 0 line 4 in lumberjack n bright_side_of_life n File doctest default 0 line 7 in bright_side_of_life n return tuple 0 n n IndexError tuple index out of range n extract_tb FrameSummary file doctest line 10 in module FrameSummary file doctest line 4 in lumberjack FrameSummary file doctest line 7 in bright_side_of_life format_tb File doctest default 0 line 10 in module n lumberjack n File doctest default 0 line 4 in lumberjack n bright_side_of_life n File doctest default 0 line 7 in bright_side_of_life n return tuple 0 n n tb_lineno 10 The following example shows the different ways to print and format the stack import traceback def another_function lumberstack def lumberstack traceback print_stack print repr traceback extract_stack print repr traceback format_stack another_function File doctest line 10 in module another_function File doctest line 3 in another_function lumberstack File doctest line 6 in lumberstack traceback print_stack doctest 10 module another_function doctest 3 another_function lumberstack doctest 7 lumberstack print repr traceback extract_stack File doctest line 10 in module n another_function n File doctest line 3 in another_function n lumberstack n File doctest line 8 in ,en
2602,lumberstack n print repr traceback format_stack n This last example demonstrates the final few formatting functions import traceback traceback format_list spam py 3 module spam eggs eggs py 42 eggs return bacon File spam py line 3 in module n spam eggs n File eggs py line 42 in eggs n return bacon n an_error IndexError tuple index out of range traceback format_exception_only type an_error an_error IndexError tuple index out of range n,en
2603,Data Persistence The modules described in this chapter support storing Python data in a persistent form on disk The pickle and marshal modules can turn many Python data types into a stream of bytes and then recreate the objects from the bytes The various DBM related modules support a family of hash based file formats that store a mapping of strings to other strings The list of modules described in this chapter is pickle Python object serialization Relationship to other Python modules Comparison with marshal Comparison with json Data stream format Module Interface What can be pickled and unpickled Pickling Class Instances Persistence of External Objects Dispatch Tables Handling Stateful Objects Custom Reduction for Types Functions and Other Objects Out of band Buffers Provider API Consumer API Example Restricting Globals Performance Examples copyreg Register pickle support functions Example shelve Python object persistence Restrictions Example marshal Internal Python object serialization dbm Interfaces to Unix databases dbm gnu GNU database manager dbm ndbm New Database Manager dbm dumb Portable DBM implementation sqlite3 DB API 2 0 interface for SQLite databases Tutorial Reference Module functions Module constants Connection objects Cursor objects Row objects Blob objects PrepareProtocol objects Exceptions SQLite and Python types Default adapters and converters deprecated Command line interface How to guides How to use placeholders to bind values in SQL queries How to adapt custom Python types to SQLite values How to write adaptable objects How to register adapter callables How to convert SQLite values to custom Python types Adapter and converter recipes How to use connection shortcut methods How to use the connection context manager How to work with SQLite URIs How to create and use row factories How to handle non UTF 8 text encodings Explanation Transaction control Transaction control via the autocommit attribute Transaction control via the isolation_level attribute,en
2604,Streams Source code Lib asyncio streams py Streams are high level async await ready primitives to work with network connections Streams allow sending and receiving data without using callbacks or low level protocols and transports Here is an example of a TCP echo client written using asyncio streams import asyncio async def tcp_echo_client message reader writer await asyncio open_connection 127 0 0 1 8888 print f Send message r writer write message encode await writer drain data await reader read 100 print f Received data decode r print Close the connection writer close await writer wait_closed asyncio run tcp_echo_client Hello World See also the Examples section below Stream Functions The following top level asyncio functions can be used to create and work with streams coroutine asyncio open_connection host None port None limit None ssl None family 0 proto 0 flags 0 sock None local_addr None server_hostname None ssl_handshake_timeout None ssl_shutdown_timeout None happy_eyeballs_delay None interleave None Establish a network connection and return a pair of reader writer objects The returned reader and writer objects are instances of StreamReader and StreamWriter classes limit determines the buffer size limit used by the returned StreamReader instance By default the limit is set to 64 KiB The rest of the arguments are passed directly to loop create_connection Note The sock argument transfers ownership of the socket to the StreamWriter created To close the socket call its close method Changed in version 3 7 Added the ssl_handshake_timeout parameter Changed in version 3 8 Added the happy_eyeballs_delay and interleave parameters Changed in version 3 10 Removed the loop parameter Changed in version 3 11 Added the ssl_shutdown_timeout parameter coroutine asyncio start_server client_connected_cb host None port None limit None family socket AF_UNSPEC flags socket AI_PASSIVE sock None backlog 100 ssl None reuse_address None reuse_port None ssl_handshake_timeout None ssl_shutdown_timeout None start_serving True Start a socket server The client_connected_cb callback is called whenever a new client connection is established It receives a reader writer pair as two arguments instances of the StreamReader and StreamWriter classes client_connected_cb can be a plain callable or a coroutine function if it is a coroutine function it will be automatically scheduled as a Task limit determines the buffer size limit used by the returned StreamReader instance By default the limit is set to 64 KiB The rest of the arguments are passed directly to loop create_server Note The sock argument transfers ownership of the socket to the server created To close the socket call the server s close method Changed in version 3 7 Added the ssl_handshake_timeout and start_serving parameters Changed in version 3 10 Removed the loop parameter Changed in version 3 11 Added the ssl_shutdown_timeout parameter Unix Sockets coroutine asyncio open_unix_connection path None limit None ssl None sock None server_hostname None ssl_handshake_timeout None ssl_shutdown_timeout None Establish a Unix socket connection and return a pair of reader writer Similar to open_connection but operates on Unix sockets See also the documentation of loop create_unix_connection Note The sock argument transfers ownership of the socket to the StreamWriter created To close the socket call its close method Availability Unix Changed in version 3 7 Added the ssl_handshake_timeout parameter The path parameter can now be a path like object Changed in version 3 10 Removed the loop parameter Changed in version 3 11 Added the ssl_shutdown_timeout parameter coroutine asyncio start_unix_server client_connected_cb path None limit None sock None backlog 100 ssl None ssl_handshake_timeout None ssl_shutdown_timeout None start_serving True Start a Unix socket server Similar to start_server but works with Unix sockets See also the documentation of loop create_unix_server Note The sock argument transfers ownership of the socket to the server created To close the socket call the server s close method Availabilit,en
2605,y Unix Changed in version 3 7 Added the ssl_handshake_timeout and start_serving parameters The path parameter can now be a path like object Changed in version 3 10 Removed the loop parameter Changed in version 3 11 Added the ssl_shutdown_timeout parameter StreamReader class asyncio StreamReader Represents a reader object that provides APIs to read data from the IO stream As an asynchronous iterable the object supports the async for statement It is not recommended to instantiate StreamReader objects directly use open_connection and start_server instead feed_eof Acknowledge the EOF coroutine read n 1 Read up to n bytes from the stream If n is not provided or set to 1 read until EOF then return all read bytes If EOF was received and the internal buffer is empty return an empty bytes object If n is 0 return an empty bytes object immediately If n is positive return at most n available bytes as soon as at least 1 byte is available in the internal buffer If EOF is received before any byte is read return an empty bytes object coroutine readline Read one line where line is a sequence of bytes ending with n If EOF is received and n was not found the method returns partially read data If EOF is received and the internal buffer is empty return an empty bytes object coroutine readexactly n Read exactly n bytes Raise an IncompleteReadError if EOF is reached before n can be read Use the IncompleteReadError partial attribute to get the partially read data coroutine readuntil separator b n Read data from the stream until separator is found On success the data and separator will be removed from the internal buffer consumed Returned data will include the separator at the end If the amount of data read exceeds the configured stream limit a LimitOverrunError exception is raised and the data is left in the internal buffer and can be read again If EOF is reached before the complete separator is found an IncompleteReadError exception is raised and the internal buffer is reset The IncompleteReadError partial attribute may contain a portion of the separator New in version 3 5 2 at_eof Return True if the buffer is empty and feed_eof was called StreamWriter class asyncio StreamWriter Represents a writer object that provides APIs to write data to the IO stream It is not recommended to instantiate StreamWriter objects directly use open_connection and start_server instead write data The method attempts to write the data to the underlying socket immediately If that fails the data is queued in an internal write buffer until it can be sent The method should be used along with the drain method stream write data await stream drain writelines data The method writes a list or any iterable of bytes to the underlying socket immediately If that fails the data is queued in an internal write buffer until it can be sent The method should be used along with the drain method stream writelines lines await stream drain close The method closes the stream and the underlying socket The method should be used though not mandatory along with the wait_closed method stream close await stream wait_closed can_write_eof Return True if the underlying transport supports the write_eof method False otherwise write_eof Close the write end of the stream after the buffered write data is flushed transport Return the underlying asyncio transport get_extra_info name default None Access optional transport information see BaseTransport get_extra_info for details coroutine drain Wait until it is appropriate to resume writing to the stream Example writer write data await writer drain This is a flow control method that interacts with the underlying IO write buffer When the size of the buffer reaches the high watermark drain blocks until the size of the buffer is drained down to the low watermark and writing can be resumed When there is nothing to wait for the drain returns immediately coroutine start_tls sslcontext server_hostname None ssl_handshake_timeout None ssl_shutdown_timeout None Upgrade an existing stream based connection to TLS Parameters sslcontext a configured instance of SSLContex,en
2606,t server_hostname sets or overrides the host name that the target server s certificate will be matched against ssl_handshake_timeout is the time in seconds to wait for the TLS handshake to complete before aborting the connection 60 0 seconds if None default ssl_shutdown_timeout is the time in seconds to wait for the SSL shutdown to complete before aborting the connection 30 0 seconds if None default New in version 3 11 Changed in version 3 12 Added the ssl_shutdown_timeout parameter is_closing Return True if the stream is closed or in the process of being closed New in version 3 7 coroutine wait_closed Wait until the stream is closed Should be called after close to wait until the underlying connection is closed ensuring that all data has been flushed before e g exiting the program New in version 3 7 Examples TCP echo client using streams TCP echo client using the asyncio open_connection function import asyncio async def tcp_echo_client message reader writer await asyncio open_connection 127 0 0 1 8888 print f Send message r writer write message encode await writer drain data await reader read 100 print f Received data decode r print Close the connection writer close await writer wait_closed asyncio run tcp_echo_client Hello World See also The TCP echo client protocol example uses the low level loop create_connection method TCP echo server using streams TCP echo server using the asyncio start_server function import asyncio async def handle_echo reader writer data await reader read 100 message data decode addr writer get_extra_info peername print f Received message r from addr r print f Send message r writer write data await writer drain print Close the connection writer close await writer wait_closed async def main server await asyncio start_server handle_echo 127 0 0 1 8888 addrs join str sock getsockname for sock in server sockets print f Serving on addrs async with server await server serve_forever asyncio run main See also The TCP echo server protocol example uses the loop create_server method Get HTTP headers Simple example querying HTTP headers of the URL passed on the command line import asyncio import urllib parse import sys async def print_http_headers url url urllib parse urlsplit url if url scheme https reader writer await asyncio open_connection url hostname 443 ssl True else reader writer await asyncio open_connection url hostname 80 query f HEAD url path or HTTP 1 0 r n f Host url hostname r n f r n writer write query encode latin 1 while True line await reader readline if not line break line line decode latin1 rstrip if line print f HTTP header line Ignore the body close the socket writer close await writer wait_closed url sys argv 1 asyncio run print_http_headers url Usage python example py http example com path page html or with HTTPS python example py https example com path page html Register an open socket to wait for data using streams Coroutine waiting until a socket receives data using the open_connection function import asyncio import socket async def wait_for_data Get a reference to the current event loop because we want to access low level APIs loop asyncio get_running_loop Create a pair of connected sockets rsock wsock socket socketpair Register the open socket to wait for data reader writer await asyncio open_connection sock rsock Simulate the reception of data from the network loop call_soon wsock send abc encode Wait for data data await reader read 100 Got data we are done close the socket print Received data decode writer close await writer wait_closed Close the second socket wsock close asyncio run wait_for_data See also The register an open socket to wait for data using a protocol example uses a low level protocol and the loop create_connection method The watch a file descriptor for read events example uses the low level loop add_reader method to watch a file descriptor,en
2607,netrc netrc file processing Source code Lib netrc py The netrc class parses and encapsulates the netrc file format used by the Unix ftp program and other FTP clients class netrc netrc file A netrc instance or subclass instance encapsulates data from a netrc file The initialization argument if present specifies the file to parse If no argument is given the file netrc in the user s home directory as determined by os path expanduser will be read Otherwise a FileNotFoundError exception will be raised Parse errors will raise NetrcParseError with diagnostic information including the file name line number and terminating token If no argument is specified on a POSIX system the presence of passwords in the netrc file will raise a NetrcParseError if the file ownership or permissions are insecure owned by a user other than the user running the process or accessible for read or write by any other user This implements security behavior equivalent to that of ftp and other programs that use netrc Changed in version 3 4 Added the POSIX permission check Changed in version 3 7 os path expanduser is used to find the location of the netrc file when file is not passed as argument Changed in version 3 10 netrc try UTF 8 encoding before using locale specific encoding The entry in the netrc file no longer needs to contain all tokens The missing tokens value default to an empty string All the tokens and their values now can contain arbitrary characters like whitespace and non ASCII characters If the login name is anonymous it won t trigger the security check exception netrc NetrcParseError Exception raised by the netrc class when syntactical errors are encountered in source text Instances of this exception provide three interesting attributes msg Textual explanation of the error filename The name of the source file lineno The line number on which the error was found netrc Objects A netrc instance has the following methods netrc authenticators host Return a 3 tuple login account password of authenticators for host If the netrc file did not contain an entry for the given host return the tuple associated with the default entry If neither matching host nor default entry is available return None netrc __repr__ Dump the class data as a string in the format of a netrc file This discards comments and may reorder the entries Instances of netrc have public instance variables netrc hosts Dictionary mapping host names to login account password tuples The default entry if any is represented as a pseudo host by that name netrc macros Dictionary mapping macro names to string lists,en
2608,email header Internationalized headers Source code Lib email header py This module is part of the legacy Compat32 email API In the current API encoding and decoding of headers is handled transparently by the dictionary like API of the EmailMessage class In addition to uses in legacy code this module can be useful in applications that need to completely control the character sets used when encoding headers The remaining text in this section is the original documentation of the module RFC 2822 is the base standard that describes the format of email messages It derives from the older RFC 822 standard which came into widespread use at a time when most email was composed of ASCII characters only RFC 2822 is a specification written assuming email contains only 7 bit ASCII characters Of course as email has been deployed worldwide it has become internationalized such that language specific character sets can now be used in email messages The base standard still requires email messages to be transferred using only 7 bit ASCII characters so a slew of RFCs have been written describing how to encode email containing non ASCII characters into RFC 2822 compliant format These RFCs include RFC 2045 RFC 2046 RFC 2047 and RFC 2231 The email package supports these standards in its email header and email charset modules If you want to include non ASCII characters in your email headers say in the Subject or To fields you should use the Header class and assign the field in the Message object to an instance of Header instead of using a string for the header value Import the Header class from the email header module For example from email message import Message from email header import Header msg Message h Header p xf6stal iso 8859 1 msg Subject h msg as_string Subject iso 8859 1 q p F6stal n n Notice here how we wanted the Subject field to contain a non ASCII character We did this by creating a Header instance and passing in the character set that the byte string was encoded in When the subsequent Message instance was flattened the Subject field was properly RFC 2047 encoded MIME aware mail readers would show this header using the embedded ISO 8859 1 character Here is the Header class description class email header Header s None charset None maxlinelen None header_name None continuation_ws errors strict Create a MIME compliant header that can contain strings in different character sets Optional s is the initial header value If None the default the initial header value is not set You can later append to the header with append method calls s may be an instance of bytes or str but see the append documentation for semantics Optional charset serves two purposes it has the same meaning as the charset argument to the append method It also sets the default character set for all subsequent append calls that omit the charset argument If charset is not provided in the constructor the default the us ascii character set is used both as s s initial charset and as the default for subsequent append calls The maximum line length can be specified explicitly via maxlinelen For splitting the first line to a shorter value to account for the field header which isn t included in s e g Subject pass in the name of the field in header_name The default maxlinelen is 76 and the default value for header_name is None meaning it is not taken into account for the first line of a long split header Optional continuation_ws must be RFC 2822 compliant folding whitespace and is usually either a space or a hard tab character This character will be prepended to continuation lines continuation_ws defaults to a single space character Optional errors is passed straight through to the append method append s charset None errors strict Append the string s to the MIME header Optional charset if given should be a Charset instance see email charset or the name of a character set which will be converted to a Charset instance A value of None the default means that the charset given in the constructor is used s may be an instance of bytes or str If it is an instance of bytes then charset is th,en
2609,e encoding of that byte string and a UnicodeError will be raised if the string cannot be decoded with that character set If s is an instance of str then charset is a hint specifying the character set of the characters in the string In either case when producing an RFC 2822 compliant header using RFC 2047 rules the string will be encoded using the output codec of the charset If the string cannot be encoded using the output codec a UnicodeError will be raised Optional errors is passed as the errors argument to the decode call if s is a byte string encode splitchars t maxlinelen None linesep n Encode a message header into an RFC compliant format possibly wrapping long lines and encapsulating non ASCII parts in base64 or quoted printable encodings Optional splitchars is a string containing characters which should be given extra weight by the splitting algorithm during normal header wrapping This is in very rough support of RFC 2822 s higher level syntactic breaks split points preceded by a splitchar are preferred during line splitting with the characters preferred in the order in which they appear in the string Space and tab may be included in the string to indicate whether preference should be given to one over the other as a split point when other split chars do not appear in the line being split Splitchars does not affect RFC 2047 encoded lines maxlinelen if given overrides the instance s value for the maximum line length linesep specifies the characters used to separate the lines of the folded header It defaults to the most useful value for Python application code n but r n can be specified in order to produce headers with RFC compliant line separators Changed in version 3 2 Added the linesep argument The Header class also provides a number of methods to support standard operators and built in functions __str__ Returns an approximation of the Header as a string using an unlimited line length All pieces are converted to unicode using the specified encoding and joined together appropriately Any pieces with a charset of unknown 8bit are decoded as ASCII using the replace error handler Changed in version 3 2 Added handling for the unknown 8bit charset __eq__ other This method allows you to compare two Header instances for equality __ne__ other This method allows you to compare two Header instances for inequality The email header module also provides the following convenient functions email header decode_header header Decode a message header value without converting the character set The header value is in header This function returns a list of decoded_string charset pairs containing each of the decoded parts of the header charset is None for non encoded parts of the header otherwise a lower case string containing the name of the character set specified in the encoded string Here s an example from email header import decode_header decode_header iso 8859 1 q p F6stal b p xf6stal iso 8859 1 email header make_header decoded_seq maxlinelen None header_name None continuation_ws Create a Header instance from a sequence of pairs as returned by decode_header decode_header takes a header value string and returns a sequence of pairs of the format decoded_string charset where charset is the name of the character set This function takes one of those sequence of pairs and returns a Header instance Optional maxlinelen header_name and continuation_ws are as in the Header constructor,en
2610,File Formats The modules described in this chapter parse various miscellaneous file formats that aren t markup languages and are not related to e mail csv CSV File Reading and Writing Module Contents Dialects and Formatting Parameters Reader Objects Writer Objects Examples configparser Configuration file parser Quick Start Supported Datatypes Fallback Values Supported INI File Structure Interpolation of values Mapping Protocol Access Customizing Parser Behaviour Legacy API Examples ConfigParser Objects RawConfigParser Objects Exceptions tomllib Parse TOML files Examples Conversion Table netrc netrc file processing netrc Objects plistlib Generate and parse Apple plist files Examples,en
2611,urllib error Exception classes raised by urllib request Source code Lib urllib error py The urllib error module defines the exception classes for exceptions raised by urllib request The base exception class is URLError The following exceptions are raised by urllib error as appropriate exception urllib error URLError The handlers raise this exception or derived exceptions when they run into a problem It is a subclass of OSError reason The reason for this error It can be a message string or another exception instance Changed in version 3 3 URLError used to be a subtype of IOError which is now an alias of OSError exception urllib error HTTPError url code msg hdrs fp Though being an exception a subclass of URLError an HTTPError can also function as a non exceptional file like return value the same thing that urlopen returns This is useful when handling exotic HTTP errors such as requests for authentication url Contains the request URL An alias for filename attribute code An HTTP status code as defined in RFC 2616 This numeric value corresponds to a value found in the dictionary of codes as found in http server BaseHTTPRequestHandler responses reason This is usually a string explaining the reason for this error An alias for msg attribute headers The HTTP response headers for the HTTP request that caused the HTTPError An alias for hdrs attribute New in version 3 4 fp A file like object where the HTTP error body can be read from exception urllib error ContentTooShortError msg content This exception is raised when the urlretrieve function detects that the amount of the downloaded data is less than the expected amount given by the Content Length header content The downloaded and supposedly truncated data,en
2612,Frame Objects type PyFrameObject Part of the Limited API as an opaque struct The C structure of the objects used to describe frame objects There are no public members in this structure Changed in version 3 11 The members of this structure were removed from the public C API Refer to the What s New entry for details The PyEval_GetFrame and PyThreadState_GetFrame functions can be used to get a frame object See also Reflection PyTypeObject PyFrame_Type The type of frame objects It is the same object as types FrameType in the Python layer Changed in version 3 11 Previously this type was only available after including frameobject h int PyFrame_Check PyObject obj Return non zero if obj is a frame object Changed in version 3 11 Previously this function was only available after including frameobject h PyFrameObject PyFrame_GetBack PyFrameObject frame Get the frame next outer frame Return a strong reference or NULL if frame has no outer frame New in version 3 9 PyObject PyFrame_GetBuiltins PyFrameObject frame Get the frame s f_builtins attribute Return a strong reference The result cannot be NULL New in version 3 11 PyCodeObject PyFrame_GetCode PyFrameObject frame Part of the Stable ABI since version 3 10 Get the frame code Return a strong reference The result frame code cannot be NULL New in version 3 9 PyObject PyFrame_GetGenerator PyFrameObject frame Get the generator coroutine or async generator that owns this frame or NULL if this frame is not owned by a generator Does not raise an exception even if the return value is NULL Return a strong reference or NULL New in version 3 11 PyObject PyFrame_GetGlobals PyFrameObject frame Get the frame s f_globals attribute Return a strong reference The result cannot be NULL New in version 3 11 int PyFrame_GetLasti PyFrameObject frame Get the frame s f_lasti attribute Returns 1 if frame f_lasti is None New in version 3 11 PyObject PyFrame_GetVar PyFrameObject frame PyObject name Get the variable name of frame Return a strong reference to the variable value on success Raise NameError and return NULL if the variable does not exist Raise an exception and return NULL on error name type must be a str New in version 3 12 PyObject PyFrame_GetVarString PyFrameObject frame const char name Similar to PyFrame_GetVar but the variable name is a C string encoded in UTF 8 New in version 3 12 PyObject PyFrame_GetLocals PyFrameObject frame Get the frame s f_locals attribute dict Return a strong reference New in version 3 11 int PyFrame_GetLineNumber PyFrameObject frame Part of the Stable ABI since version 3 10 Return the line number that frame is currently executing Internal Frames Unless using PEP 523 you will not need this struct _PyInterpreterFrame The interpreter s internal frame representation New in version 3 11 PyObject PyUnstable_InterpreterFrame_GetCode struct _PyInterpreterFrame frame This is Unstable API It may change without warning in minor releases Return a strong reference to the code object for the frame New in version 3 12 int PyUnstable_InterpreterFrame_GetLasti struct _PyInterpreterFrame frame This is Unstable API It may change without warning in minor releases Return the byte offset into the last executed instruction New in version 3 12 int PyUnstable_InterpreterFrame_GetLine struct _PyInterpreterFrame frame This is Unstable API It may change without warning in minor releases Return the currently executing line number or 1 if there is no line number New in version 3 12,en
2613,What s New In Python 3 1 Author Raymond Hettinger This article explains the new features in Python 3 1 compared to 3 0 Python 3 1 was released on June 27 2009 PEP 372 Ordered Dictionaries Regular Python dictionaries iterate over key value pairs in arbitrary order Over the years a number of authors have written alternative implementations that remember the order that the keys were originally inserted Based on the experiences from those implementations a new collections OrderedDict class has been introduced The OrderedDict API is substantially the same as regular dictionaries but will iterate over keys and values in a guaranteed order depending on when a key was first inserted If a new entry overwrites an existing entry the original insertion position is left unchanged Deleting an entry and reinserting it will move it to the end The standard library now supports use of ordered dictionaries in several modules The configparser module uses them by default This lets configuration files be read modified and then written back in their original order The _asdict method for collections namedtuple now returns an ordered dictionary with the values appearing in the same order as the underlying tuple indices The json module is being built out with an object_pairs_hook to allow OrderedDicts to be built by the decoder Support was also added for third party tools like PyYAML See also PEP 372 Ordered Dictionaries PEP written by Armin Ronacher and Raymond Hettinger Implementation written by Raymond Hettinger Since an ordered dictionary remembers its insertion order it can be used in conjunction with sorting to make a sorted dictionary regular unsorted dictionary d banana 3 apple 4 pear 1 orange 2 dictionary sorted by key OrderedDict sorted d items key lambda t t 0 OrderedDict apple 4 banana 3 orange 2 pear 1 dictionary sorted by value OrderedDict sorted d items key lambda t t 1 OrderedDict pear 1 orange 2 banana 3 apple 4 dictionary sorted by length of the key string OrderedDict sorted d items key lambda t len t 0 OrderedDict pear 1 apple 4 orange 2 banana 3 The new sorted dictionaries maintain their sort order when entries are deleted But when new keys are added the keys are appended to the end and the sort is not maintained PEP 378 Format Specifier for Thousands Separator The built in format function and the str format method use a mini language that now includes a simple non locale aware way to format a number with a thousands separator That provides a way to humanize a program s output improving its professional appearance and readability format 1234567 d 1 234 567 format 1234567 89 2f 1 234 567 89 format 12345 6 8901234 12j f 12 345 600000 8 901 234 120000j format Decimal 1234567 89 f 1 234 567 89 The supported types are int float complex and decimal Decimal Discussions are underway about how to specify alternative separators like dots spaces apostrophes or underscores Locale aware applications should use the existing n format specifier which already has some support for thousands separators See also PEP 378 Format Specifier for Thousands Separator PEP written by Raymond Hettinger and implemented by Eric Smith and Mark Dickinson Other Language Changes Some smaller changes made to the core Python language are Directories and zip archives containing a __main__ py file can now be executed directly by passing their name to the interpreter The directory zipfile is automatically inserted as the first entry in sys path Suggestion and initial patch by Andy Chu revised patch by Phillip J Eby and Nick Coghlan bpo 1739468 The int type gained a bit_length method that returns the number of bits necessary to represent its argument in binary n 37 bin 37 0b100101 n bit_length 6 n 2 123 1 n bit_length 123 n 1 bit_length 124 Contributed by Fredrik Johansson Victor Stinner Raymond Hettinger and Mark Dickinson bpo 3439 The fields in format strings can now be automatically numbered Sir of format Gallahad Camelot Sir Gallahad of Camelot Formerly the string would have required numbered fields such as Sir 0 of 1 Contributed by Eric Smith bpo 5237 The string ,en
2614,maketrans function is deprecated and is replaced by new static methods bytes maketrans and bytearray maketrans This change solves the confusion around which types were supported by the string module Now str bytes and bytearray each have their own maketrans and translate methods with intermediate translation tables of the appropriate type Contributed by Georg Brandl bpo 5675 The syntax of the with statement now allows multiple context managers in a single statement with open mylog txt as infile open a out w as outfile for line in infile if critical in line outfile write line With the new syntax the contextlib nested function is no longer needed and is now deprecated Contributed by Georg Brandl and Mattias Brändström appspot issue 53094 round x n now returns an integer if x is an integer Previously it returned a float round 1123 2 1100 Contributed by Mark Dickinson bpo 4707 Python now uses David Gay s algorithm for finding the shortest floating point representation that doesn t change its value This should help mitigate some of the confusion surrounding binary floating point numbers The significance is easily seen with a number like 1 1 which does not have an exact equivalent in binary floating point Since there is no exact equivalent an expression like float 1 1 evaluates to the nearest representable value which is 0x1 199999999999ap 0 in hex or 1 100000000000000088817841970012523233890533447265625 in decimal That nearest value was and still is used in subsequent floating point calculations What is new is how the number gets displayed Formerly Python used a simple approach The value of repr 1 1 was computed as format 1 1 17g which evaluated to 1 1000000000000001 The advantage of using 17 digits was that it relied on IEEE 754 guarantees to assure that eval repr 1 1 would round trip exactly to its original value The disadvantage is that many people found the output to be confusing mistaking intrinsic limitations of binary floating point representation as being a problem with Python itself The new algorithm for repr 1 1 is smarter and returns 1 1 Effectively it searches all equivalent string representations ones that get stored with the same underlying float value and returns the shortest representation The new algorithm tends to emit cleaner representations when possible but it does not change the underlying values So it is still the case that 1 1 2 2 3 3 even though the representations may suggest otherwise The new algorithm depends on certain features in the underlying floating point implementation If the required features are not found the old algorithm will continue to be used Also the text pickle protocols assure cross platform portability by using the old algorithm Contributed by Eric Smith and Mark Dickinson bpo 1580 New Improved and Deprecated Modules Added a collections Counter class to support convenient counting of unique items in a sequence or iterable Counter red blue red green blue blue Counter blue 3 red 2 green 1 Contributed by Raymond Hettinger bpo 1696199 Added a new module tkinter ttk for access to the Tk themed widget set The basic idea of ttk is to separate to the extent possible the code implementing a widget s behavior from the code implementing its appearance Contributed by Guilherme Polo bpo 2983 The gzip GzipFile and bz2 BZ2File classes now support the context management protocol Automatically close file after writing with gzip GzipFile filename wb as f f write b xxx Contributed by Antoine Pitrou The decimal module now supports methods for creating a decimal object from a binary float The conversion is exact but can sometimes be surprising Decimal from_float 1 1 Decimal 1 100000000000000088817841970012523233890533447265625 The long decimal result shows the actual binary fraction being stored for 1 1 The fraction has many digits because 1 1 cannot be exactly represented in binary Contributed by Raymond Hettinger and Mark Dickinson The itertools module grew two new functions The itertools combinations_with_replacement function is one of four for generating combinatorics including permutations and Car,en
2615,tesian products The itertools compress function mimics its namesake from APL Also the existing itertools count function now has an optional step argument and can accept any type of counting sequence including fractions Fraction and decimal Decimal p q for p q in combinations_with_replacement LOVE 2 LL LO LV LE OO OV OE VV VE EE list compress data range 10 selectors 0 0 1 1 0 1 0 1 0 0 2 3 5 7 c count start Fraction 1 2 step Fraction 1 6 next c next c next c next c Fraction 1 2 Fraction 2 3 Fraction 5 6 Fraction 1 1 Contributed by Raymond Hettinger collections namedtuple now supports a keyword argument rename which lets invalid fieldnames be automatically converted to positional names in the form _0 _1 etc This is useful when the field names are being created by an external source such as a CSV header SQL field list or user input query input SELECT region dept count FROM main GROUPBY region dept cursor execute query query_fields desc 0 for desc in cursor description UserQuery namedtuple UserQuery query_fields rename True pprint pprint UserQuery row for row in cursor UserQuery region South dept Shipping _2 185 UserQuery region North dept Accounting _2 37 UserQuery region West dept Sales _2 419 Contributed by Raymond Hettinger bpo 1818 The re sub re subn and re split functions now accept a flags parameter Contributed by Gregory Smith The logging module now implements a simple logging NullHandler class for applications that are not using logging but are calling library code that does Setting up a null handler will suppress spurious warnings such as No handlers could be found for logger foo h logging NullHandler logging getLogger foo addHandler h Contributed by Vinay Sajip bpo 4384 The runpy module which supports the m command line switch now supports the execution of packages by looking for and executing a __main__ submodule when a package name is supplied Contributed by Andi Vajda bpo 4195 The pdb module can now access and display source code loaded via zipimport or any other conformant PEP 302 loader Contributed by Alexander Belopolsky bpo 4201 functools partial objects can now be pickled Suggested by Antoine Pitrou and Jesse Noller Implemented by Jack Diederich bpo 5228 Add pydoc help topics for symbols so that help works as expected in the interactive environment Contributed by David Laban bpo 4739 The unittest module now supports skipping individual tests or classes of tests And it supports marking a test as an expected failure a test that is known to be broken but shouldn t be counted as a failure on a TestResult class TestGizmo unittest TestCase unittest skipUnless sys platform startswith win requires Windows def test_gizmo_on_windows self unittest expectedFailure def test_gimzo_without_required_library self Also tests for exceptions have been builtout to work with context managers using the with statement def test_division_by_zero self with self assertRaises ZeroDivisionError x 0 In addition several new assertion methods were added including assertSetEqual assertDictEqual assertDictContainsSubset assertListEqual assertTupleEqual assertSequenceEqual assertRaisesRegexp assertIsNone and assertIsNotNone Contributed by Benjamin Peterson and Antoine Pitrou The io module has three new constants for the seek method SEEK_SET SEEK_CUR and SEEK_END The sys version_info tuple is now a named tuple sys version_info sys version_info major 3 minor 1 micro 0 releaselevel alpha serial 2 Contributed by Ross Light bpo 4285 The nntplib and imaplib modules now support IPv6 Contributed by Derek Morr bpo 1655 and bpo 1664 The pickle module has been adapted for better interoperability with Python 2 x when used with protocol 2 or lower The reorganization of the standard library changed the formal reference for many objects For example __builtin__ set in Python 2 is called builtins set in Python 3 This change confounded efforts to share data between different versions of Python But now when protocol 2 or lower is selected the pickler will automatically use the old Python 2 names for both loading and dumping This remapping is turned on by defau,en
2616,lt but can be disabled with the fix_imports option s 1 2 3 pickle dumps s protocol 0 b c__builtin__ nset np0 n lp1 nL1L naL2L naL3L natp2 nRp3 n pickle dumps s protocol 0 fix_imports False b cbuiltins nset np0 n lp1 nL1L naL2L naL3L natp2 nRp3 n An unfortunate but unavoidable side effect of this change is that protocol 2 pickles produced by Python 3 1 won t be readable with Python 3 0 The latest pickle protocol protocol 3 should be used when migrating data between Python 3 x implementations as it doesn t attempt to remain compatible with Python 2 x Contributed by Alexandre Vassalotti and Antoine Pitrou bpo 6137 A new module importlib was added It provides a complete portable pure Python reference implementation of the import statement and its counterpart the __import__ function It represents a substantial step forward in documenting and defining the actions that take place during imports Contributed by Brett Cannon Optimizations Major performance enhancements have been added The new I O library as defined in PEP 3116 was mostly written in Python and quickly proved to be a problematic bottleneck in Python 3 0 In Python 3 1 the I O library has been entirely rewritten in C and is 2 to 20 times faster depending on the task at hand The pure Python version is still available for experimentation purposes through the _pyio module Contributed by Amaury Forgeot d Arc and Antoine Pitrou Added a heuristic so that tuples and dicts containing only untrackable objects are not tracked by the garbage collector This can reduce the size of collections and therefore the garbage collection overhead on long running programs depending on their particular use of datatypes Contributed by Antoine Pitrou bpo 4688 Enabling a configure option named with computed gotos on compilers that support it notably gcc SunPro icc the bytecode evaluation loop is compiled with a new dispatch mechanism which gives speedups of up to 20 depending on the system the compiler and the benchmark Contributed by Antoine Pitrou along with a number of other participants bpo 4753 The decoding of UTF 8 UTF 16 and LATIN 1 is now two to four times faster Contributed by Antoine Pitrou and Amaury Forgeot d Arc bpo 4868 The json module now has a C extension to substantially improve its performance In addition the API was modified so that json works only with str not with bytes That change makes the module closely match the JSON specification which is defined in terms of Unicode Contributed by Bob Ippolito and converted to Py3 1 by Antoine Pitrou and Benjamin Peterson bpo 4136 Unpickling now interns the attribute names of pickled objects This saves memory and allows pickles to be smaller Contributed by Jake McGuire and Antoine Pitrou bpo 5084 IDLE IDLE s format menu now provides an option to strip trailing whitespace from a source file Contributed by Roger D Serwy bpo 5150 Build and C API Changes Changes to Python s build process and to the C API include Integers are now stored internally either in base 2 15 or in base 2 30 the base being determined at build time Previously they were always stored in base 2 15 Using base 2 30 gives significant performance improvements on 64 bit machines but benchmark results on 32 bit machines have been mixed Therefore the default is to use base 2 30 on 64 bit machines and base 2 15 on 32 bit machines on Unix there s a new configure option enable big digits that can be used to override this default Apart from the performance improvements this change should be invisible to end users with one exception for testing and debugging purposes there s a new sys int_info that provides information about the internal format giving the number of bits per digit and the size in bytes of the C type used to store each digit import sys sys int_info sys int_info bits_per_digit 30 sizeof_digit 4 Contributed by Mark Dickinson bpo 4258 The PyLong_AsUnsignedLongLong function now handles a negative pylong by raising OverflowError instead of TypeError Contributed by Mark Dickinson and Lisandro Dalcrin bpo 5175 Deprecated PyNumber_Int Use PyNumber_Long instead Contributed b,en
2617,y Mark Dickinson bpo 4910 Added a new PyOS_string_to_double function to replace the deprecated functions PyOS_ascii_strtod and PyOS_ascii_atof Contributed by Mark Dickinson bpo 5914 Added PyCapsule as a replacement for the PyCObject API The principal difference is that the new type has a well defined interface for passing typing safety information and a less complicated signature for calling a destructor The old type had a problematic API and is now deprecated Contributed by Larry Hastings bpo 5630 Porting to Python 3 1 This section lists previously described changes and other bugfixes that may require changes to your code The new floating point string representations can break existing doctests For example def e Compute the base of natural logarithms e 2 7182818284590451 return sum 1 math factorial x for x in reversed range 30 doctest testmod Failed example e Expected 2 7182818284590451 Got 2 718281828459045 The automatic name remapping in the pickle module for protocol 2 or lower can make Python 3 1 pickles unreadable in Python 3 0 One solution is to use protocol 3 Another solution is to set the fix_imports option to False See the discussion above for more details,en
2618,cmd Support for line oriented command interpreters Source code Lib cmd py The Cmd class provides a simple framework for writing line oriented command interpreters These are often useful for test harnesses administrative tools and prototypes that will later be wrapped in a more sophisticated interface class cmd Cmd completekey tab stdin None stdout None A Cmd instance or subclass instance is a line oriented interpreter framework There is no good reason to instantiate Cmd itself rather it s useful as a superclass of an interpreter class you define yourself in order to inherit Cmd s methods and encapsulate action methods The optional argument completekey is the readline name of a completion key it defaults to Tab If completekey is not None and readline is available command completion is done automatically The optional arguments stdin and stdout specify the input and output file objects that the Cmd instance or subclass instance will use for input and output If not specified they will default to sys stdin and sys stdout If you want a given stdin to be used make sure to set the instance s use_rawinput attribute to False otherwise stdin will be ignored Cmd Objects A Cmd instance has the following methods Cmd cmdloop intro None Repeatedly issue a prompt accept input parse an initial prefix off the received input and dispatch to action methods passing them the remainder of the line as argument The optional argument is a banner or intro string to be issued before the first prompt this overrides the intro class attribute If the readline module is loaded input will automatically inherit bash like history list editing e g Control P scrolls back to the last command Control N forward to the next one Control F moves the cursor to the right non destructively Control B moves the cursor to the left non destructively etc An end of file on input is passed back as the string EOF An interpreter instance will recognize a command name foo if and only if it has a method do_foo As a special case a line beginning with the character is dispatched to the method do_help As another special case a line beginning with the character is dispatched to the method do_shell if such a method is defined This method will return when the postcmd method returns a true value The stop argument to postcmd is the return value from the command s corresponding do_ method If completion is enabled completing commands will be done automatically and completing of commands args is done by calling complete_foo with arguments text line begidx and endidx text is the string prefix we are attempting to match all returned matches must begin with it line is the current input line with leading whitespace removed begidx and endidx are the beginning and ending indexes of the prefix text which could be used to provide different completion depending upon which position the argument is in Cmd do_help arg All subclasses of Cmd inherit a predefined do_help This method called with an argument bar invokes the corresponding method help_bar and if that is not present prints the docstring of do_bar if available With no argument do_help lists all available help topics that is all commands with corresponding help_ methods or commands that have docstrings and also lists any undocumented commands Cmd onecmd str Interpret the argument as though it had been typed in response to the prompt This may be overridden but should not normally need to be see the precmd and postcmd methods for useful execution hooks The return value is a flag indicating whether interpretation of commands by the interpreter should stop If there is a do_ method for the command str the return value of that method is returned otherwise the return value from the default method is returned Cmd emptyline Method called when an empty line is entered in response to the prompt If this method is not overridden it repeats the last nonempty command entered Cmd default line Method called on an input line when the command prefix is not recognized If this method is not overridden it prints an error message and returns Cmd completedefault text ,en
2619,line begidx endidx Method called to complete an input line when no command specific complete_ method is available By default it returns an empty list Cmd columnize list displaywidth 80 Method called to display a list of strings as a compact set of columns Each column is only as wide as necessary Columns are separated by two spaces for readability Cmd precmd line Hook method executed just before the command line line is interpreted but after the input prompt is generated and issued This method is a stub in Cmd it exists to be overridden by subclasses The return value is used as the command which will be executed by the onecmd method the precmd implementation may re write the command or simply return line unchanged Cmd postcmd stop line Hook method executed just after a command dispatch is finished This method is a stub in Cmd it exists to be overridden by subclasses line is the command line which was executed and stop is a flag which indicates whether execution will be terminated after the call to postcmd this will be the return value of the onecmd method The return value of this method will be used as the new value for the internal flag which corresponds to stop returning false will cause interpretation to continue Cmd preloop Hook method executed once when cmdloop is called This method is a stub in Cmd it exists to be overridden by subclasses Cmd postloop Hook method executed once when cmdloop is about to return This method is a stub in Cmd it exists to be overridden by subclasses Instances of Cmd subclasses have some public instance variables Cmd prompt The prompt issued to solicit input Cmd identchars The string of characters accepted for the command prefix Cmd lastcmd The last nonempty command prefix seen Cmd cmdqueue A list of queued input lines The cmdqueue list is checked in cmdloop when new input is needed if it is nonempty its elements will be processed in order as if entered at the prompt Cmd intro A string to issue as an intro or banner May be overridden by giving the cmdloop method an argument Cmd doc_header The header to issue if the help output has a section for documented commands Cmd misc_header The header to issue if the help output has a section for miscellaneous help topics that is there are help_ methods without corresponding do_ methods Cmd undoc_header The header to issue if the help output has a section for undocumented commands that is there are do_ methods without corresponding help_ methods Cmd ruler The character used to draw separator lines under the help message headers If empty no ruler line is drawn It defaults to Cmd use_rawinput A flag defaulting to true If true cmdloop uses input to display a prompt and read the next command if false sys stdout write and sys stdin readline are used This means that by importing readline on systems that support it the interpreter will automatically support Emacs like line editing and command history keystrokes Cmd Example The cmd module is mainly useful for building custom shells that let a user work with a program interactively This section presents a simple example of how to build a shell around a few of the commands in the turtle module Basic turtle commands such as forward are added to a Cmd subclass with method named do_forward The argument is converted to a number and dispatched to the turtle module The docstring is used in the help utility provided by the shell The example also includes a basic record and playback facility implemented with the precmd method which is responsible for converting the input to lowercase and writing the commands to a file The do_playback method reads the file and adds the recorded commands to the cmdqueue for immediate playback import cmd sys from turtle import class TurtleShell cmd Cmd intro Welcome to the turtle shell Type help or to list commands n prompt turtle file None basic turtle commands def do_forward self arg Move the turtle forward by the specified distance FORWARD 10 forward parse arg def do_right self arg Turn turtle right by given number of degrees RIGHT 20 right parse arg def do_left self arg Turn turtle l,en
2620,eft by given number of degrees LEFT 90 left parse arg def do_goto self arg Move turtle to an absolute position with changing orientation GOTO 100 200 goto parse arg def do_home self arg Return turtle to the home position HOME home def do_circle self arg Draw circle with given radius an options extent and steps CIRCLE 50 circle parse arg def do_position self arg Print the current turtle position POSITION print Current position is d d n position def do_heading self arg Print the current turtle heading in degrees HEADING print Current heading is d n heading def do_color self arg Set the color COLOR BLUE color arg lower def do_undo self arg Undo repeatedly the last turtle action s UNDO def do_reset self arg Clear the screen and return turtle to center RESET reset def do_bye self arg Stop recording close the turtle window and exit BYE print Thank you for using Turtle self close bye return True record and playback def do_record self arg Save future commands to filename RECORD rose cmd self file open arg w def do_playback self arg Playback commands from a file PLAYBACK rose cmd self close with open arg as f self cmdqueue extend f read splitlines def precmd self line line line lower if self file and playback not in line print line file self file return line def close self if self file self file close self file None def parse arg Convert a series of zero or more numbers to an argument tuple return tuple map int arg split if __name__ __main__ TurtleShell cmdloop Here is a sample session with the turtle shell showing the help functions using blank lines to repeat commands and the simple record and playback facility Welcome to the turtle shell Type help or to list commands turtle Documented commands type help topic bye color goto home playback record right circle forward heading left position reset undo turtle help forward Move the turtle forward by the specified distance FORWARD 10 turtle record spiral cmd turtle position Current position is 0 0 turtle heading Current heading is 0 turtle reset turtle circle 20 turtle right 30 turtle circle 40 turtle right 30 turtle circle 60 turtle right 30 turtle circle 80 turtle right 30 turtle circle 100 turtle right 30 turtle circle 120 turtle right 30 turtle circle 120 turtle heading Current heading is 180 turtle forward 100 turtle turtle right 90 turtle forward 100 turtle turtle right 90 turtle forward 400 turtle right 90 turtle forward 500 turtle right 90 turtle forward 400 turtle right 90 turtle forward 300 turtle playback spiral cmd Current position is 0 0 Current heading is 0 Current heading is 180 turtle bye Thank you for using Turtle,en
2621,Argparse Tutorial author Tshepang Mbambo This tutorial is intended to be a gentle introduction to argparse the recommended command line parsing module in the Python standard library Note There are two other modules that fulfill the same task namely getopt an equivalent for getopt from the C language and the deprecated optparse Note also that argparse is based on optparse and therefore very similar in terms of usage Concepts Let s show the sort of functionality that we are going to explore in this introductory tutorial by making use of the ls command ls cpython devguide prog py pypy rm unused function patch ls pypy ctypes_configure demo dotviewer include lib_pypy lib python ls l total 20 drwxr xr x 19 wena wena 4096 Feb 18 18 51 cpython drwxr xr x 4 wena wena 4096 Feb 8 12 04 devguide rwxr xr x 1 wena wena 535 Feb 19 00 05 prog py drwxr xr x 14 wena wena 4096 Feb 7 00 59 pypy rw r r 1 wena wena 741 Feb 18 01 01 rm unused function patch ls help Usage ls OPTION FILE List information about the FILEs the current directory by default Sort entries alphabetically if none of cftuvSUX nor sort is specified A few concepts we can learn from the four commands The ls command is useful when run without any options at all It defaults to displaying the contents of the current directory If we want beyond what it provides by default we tell it a bit more In this case we want it to display a different directory pypy What we did is specify what is known as a positional argument It s named so because the program should know what to do with the value solely based on where it appears on the command line This concept is more relevant to a command like cp whose most basic usage is cp SRC DEST The first position is what you want copied and the second position is where you want it copied to Now say we want to change behaviour of the program In our example we display more info for each file instead of just showing the file names The l in that case is known as an optional argument That s a snippet of the help text It s very useful in that you can come across a program you have never used before and can figure out how it works simply by reading its help text The basics Let us start with a very simple example which does almost nothing import argparse parser argparse ArgumentParser parser parse_args Following is a result of running the code python prog py python prog py help usage prog py h options h help show this help message and exit python prog py verbose usage prog py h prog py error unrecognized arguments verbose python prog py foo usage prog py h prog py error unrecognized arguments foo Here is what is happening Running the script without any options results in nothing displayed to stdout Not so useful The second one starts to display the usefulness of the argparse module We have done almost nothing but already we get a nice help message The help option which can also be shortened to h is the only option we get for free i e no need to specify it Specifying anything else results in an error But even then we do get a useful usage message also for free Introducing Positional arguments An example import argparse parser argparse ArgumentParser parser add_argument echo args parser parse_args print args echo And running the code python prog py usage prog py h echo prog py error the following arguments are required echo python prog py help usage prog py h echo positional arguments echo options h help show this help message and exit python prog py foo foo Here is what s happening We ve added the add_argument method which is what we use to specify which command line options the program is willing to accept In this case I ve named it echo so that it s in line with its function Calling our program now requires us to specify an option The parse_args method actually returns some data from the options specified in this case echo The variable is some form of magic that argparse performs for free i e no need to specify which variable that value is stored in You will also notice that its name matches the string argument given to the method echo Note however that a,en
2622,lthough the help display looks nice and all it currently is not as helpful as it can be For example we see that we got echo as a positional argument but we don t know what it does other than by guessing or by reading the source code So let s make it a bit more useful import argparse parser argparse ArgumentParser parser add_argument echo help echo the string you use here args parser parse_args print args echo And we get python prog py h usage prog py h echo positional arguments echo echo the string you use here options h help show this help message and exit Now how about doing something even more useful import argparse parser argparse ArgumentParser parser add_argument square help display a square of a given number args parser parse_args print args square 2 Following is a result of running the code python prog py 4 Traceback most recent call last File prog py line 5 in module print args square 2 TypeError unsupported operand type s for or pow str and int That didn t go so well That s because argparse treats the options we give it as strings unless we tell it otherwise So let s tell argparse to treat that input as an integer import argparse parser argparse ArgumentParser parser add_argument square help display a square of a given number type int args parser parse_args print args square 2 Following is a result of running the code python prog py 4 16 python prog py four usage prog py h square prog py error argument square invalid int value four That went well The program now even helpfully quits on bad illegal input before proceeding Introducing Optional arguments So far we have been playing with positional arguments Let us have a look on how to add optional ones import argparse parser argparse ArgumentParser parser add_argument verbosity help increase output verbosity args parser parse_args if args verbosity print verbosity turned on And the output python prog py verbosity 1 verbosity turned on python prog py python prog py help usage prog py h verbosity VERBOSITY options h help show this help message and exit verbosity VERBOSITY increase output verbosity python prog py verbosity usage prog py h verbosity VERBOSITY prog py error argument verbosity expected one argument Here is what is happening The program is written so as to display something when verbosity is specified and display nothing when not To show that the option is actually optional there is no error when running the program without it Note that by default if an optional argument isn t used the relevant variable in this case args verbosity is given None as a value which is the reason it fails the truth test of the if statement The help message is a bit different When using the verbosity option one must also specify some value any value The above example accepts arbitrary integer values for verbosity but for our simple program only two values are actually useful True or False Let s modify the code accordingly import argparse parser argparse ArgumentParser parser add_argument verbose help increase output verbosity action store_true args parser parse_args if args verbose print verbosity turned on And the output python prog py verbose verbosity turned on python prog py verbose 1 usage prog py h verbose prog py error unrecognized arguments 1 python prog py help usage prog py h verbose options h help show this help message and exit verbose increase output verbosity Here is what is happening The option is now more of a flag than something that requires a value We even changed the name of the option to match that idea Note that we now specify a new keyword action and give it the value store_true This means that if the option is specified assign the value True to args verbose Not specifying it implies False It complains when you specify a value in true spirit of what flags actually are Notice the different help text Short options If you are familiar with command line usage you will notice that I haven t yet touched on the topic of short versions of the options It s quite simple import argparse parser argparse ArgumentParser parser add_argument v verbose help increase out,en
2623,put verbosity action store_true args parser parse_args if args verbose print verbosity turned on And here goes python prog py v verbosity turned on python prog py help usage prog py h v options h help show this help message and exit v verbose increase output verbosity Note that the new ability is also reflected in the help text Combining Positional and Optional arguments Our program keeps growing in complexity import argparse parser argparse ArgumentParser parser add_argument square type int help display a square of a given number parser add_argument v verbose action store_true help increase output verbosity args parser parse_args answer args square 2 if args verbose print f the square of args square equals answer else print answer And now the output python prog py usage prog py h v square prog py error the following arguments are required square python prog py 4 16 python prog py 4 verbose the square of 4 equals 16 python prog py verbose 4 the square of 4 equals 16 We ve brought back a positional argument hence the complaint Note that the order does not matter How about we give this program of ours back the ability to have multiple verbosity values and actually get to use them import argparse parser argparse ArgumentParser parser add_argument square type int help display a square of a given number parser add_argument v verbosity type int help increase output verbosity args parser parse_args answer args square 2 if args verbosity 2 print f the square of args square equals answer elif args verbosity 1 print f args square 2 answer else print answer And the output python prog py 4 16 python prog py 4 v usage prog py h v VERBOSITY square prog py error argument v verbosity expected one argument python prog py 4 v 1 4 2 16 python prog py 4 v 2 the square of 4 equals 16 python prog py 4 v 3 16 These all look good except the last one which exposes a bug in our program Let s fix it by restricting the values the verbosity option can accept import argparse parser argparse ArgumentParser parser add_argument square type int help display a square of a given number parser add_argument v verbosity type int choices 0 1 2 help increase output verbosity args parser parse_args answer args square 2 if args verbosity 2 print f the square of args square equals answer elif args verbosity 1 print f args square 2 answer else print answer And the output python prog py 4 v 3 usage prog py h v 0 1 2 square prog py error argument v verbosity invalid choice 3 choose from 0 1 2 python prog py 4 h usage prog py h v 0 1 2 square positional arguments square display a square of a given number options h help show this help message and exit v 0 1 2 verbosity 0 1 2 increase output verbosity Note that the change also reflects both in the error message as well as the help string Now let s use a different approach of playing with verbosity which is pretty common It also matches the way the CPython executable handles its own verbosity argument check the output of python help import argparse parser argparse ArgumentParser parser add_argument square type int help display the square of a given number parser add_argument v verbosity action count help increase output verbosity args parser parse_args answer args square 2 if args verbosity 2 print f the square of args square equals answer elif args verbosity 1 print f args square 2 answer else print answer We have introduced another action count to count the number of occurrences of specific options python prog py 4 16 python prog py 4 v 4 2 16 python prog py 4 vv the square of 4 equals 16 python prog py 4 verbosity verbosity the square of 4 equals 16 python prog py 4 v 1 usage prog py h v square prog py error unrecognized arguments 1 python prog py 4 h usage prog py h v square positional arguments square display a square of a given number options h help show this help message and exit v verbosity increase output verbosity python prog py 4 vvv 16 Yes it s now more of a flag similar to action store_true in the previous version of our script That should explain the complaint It also behaves similar to store_true action No,en
2624,w here s a demonstration of what the count action gives You ve probably seen this sort of usage before And if you don t specify the v flag that flag is considered to have None value As should be expected specifying the long form of the flag we should get the same output Sadly our help output isn t very informative on the new ability our script has acquired but that can always be fixed by improving the documentation for our script e g via the help keyword argument That last output exposes a bug in our program Let s fix import argparse parser argparse ArgumentParser parser add_argument square type int help display a square of a given number parser add_argument v verbosity action count help increase output verbosity args parser parse_args answer args square 2 bugfix replace with if args verbosity 2 print f the square of args square equals answer elif args verbosity 1 print f args square 2 answer else print answer And this is what it gives python prog py 4 vvv the square of 4 equals 16 python prog py 4 vvvv the square of 4 equals 16 python prog py 4 Traceback most recent call last File prog py line 11 in module if args verbosity 2 TypeError not supported between instances of NoneType and int First output went well and fixes the bug we had before That is we want any value 2 to be as verbose as possible Third output not so good Let s fix that bug import argparse parser argparse ArgumentParser parser add_argument square type int help display a square of a given number parser add_argument v verbosity action count default 0 help increase output verbosity args parser parse_args answer args square 2 if args verbosity 2 print f the square of args square equals answer elif args verbosity 1 print f args square 2 answer else print answer We ve just introduced yet another keyword default We ve set it to 0 in order to make it comparable to the other int values Remember that by default if an optional argument isn t specified it gets the None value and that cannot be compared to an int value hence the TypeError exception And python prog py 4 16 You can go quite far just with what we ve learned so far and we have only scratched the surface The argparse module is very powerful and we ll explore a bit more of it before we end this tutorial Getting a little more advanced What if we wanted to expand our tiny program to perform other powers not just squares import argparse parser argparse ArgumentParser parser add_argument x type int help the base parser add_argument y type int help the exponent parser add_argument v verbosity action count default 0 args parser parse_args answer args x args y if args verbosity 2 print f args x to the power args y equals answer elif args verbosity 1 print f args x args y answer else print answer Output python prog py usage prog py h v x y prog py error the following arguments are required x y python prog py h usage prog py h v x y positional arguments x the base y the exponent options h help show this help message and exit v verbosity python prog py 4 2 v 4 2 16 Notice that so far we ve been using verbosity level to change the text that gets displayed The following example instead uses verbosity level to display more text instead import argparse parser argparse ArgumentParser parser add_argument x type int help the base parser add_argument y type int help the exponent parser add_argument v verbosity action count default 0 args parser parse_args answer args x args y if args verbosity 2 print f Running __file__ if args verbosity 1 print f args x args y end print answer Output python prog py 4 2 16 python prog py 4 2 v 4 2 16 python prog py 4 2 vv Running prog py 4 2 16 Specifying ambiguous arguments When there is ambiguity in deciding whether an argument is positional or for an argument can be used to tell parse_args that everything after that is a positional argument parser argparse ArgumentParser prog PROG parser add_argument n nargs parser add_argument args nargs ambiguous so parse_args assumes it s an option parser parse_args f usage PROG h n N N args PROG error unrecognized arguments f parser parse_args f Name,en
2625,space args f n None ambiguous so the n option greedily accepts arguments parser parse_args n 1 2 3 Namespace args n 1 2 3 parser parse_args n 1 2 3 Namespace args 2 3 n 1 Conflicting options So far we have been working with two methods of an argparse ArgumentParser instance Let s introduce a third one add_mutually_exclusive_group It allows for us to specify options that conflict with each other Let s also change the rest of the program so that the new functionality makes more sense we ll introduce the quiet option which will be the opposite of the verbose one import argparse parser argparse ArgumentParser group parser add_mutually_exclusive_group group add_argument v verbose action store_true group add_argument q quiet action store_true parser add_argument x type int help the base parser add_argument y type int help the exponent args parser parse_args answer args x args y if args quiet print answer elif args verbose print f args x to the power args y equals answer else print f args x args y answer Our program is now simpler and we ve lost some functionality for the sake of demonstration Anyways here s the output python prog py 4 2 4 2 16 python prog py 4 2 q 16 python prog py 4 2 v 4 to the power 2 equals 16 python prog py 4 2 vq usage prog py h v q x y prog py error argument q quiet not allowed with argument v verbose python prog py 4 2 v quiet usage prog py h v q x y prog py error argument q quiet not allowed with argument v verbose That should be easy to follow I ve added that last output so you can see the sort of flexibility you get i e mixing long form options with short form ones Before we conclude you probably want to tell your users the main purpose of your program just in case they don t know import argparse parser argparse ArgumentParser description calculate X to the power of Y group parser add_mutually_exclusive_group group add_argument v verbose action store_true group add_argument q quiet action store_true parser add_argument x type int help the base parser add_argument y type int help the exponent args parser parse_args answer args x args y if args quiet print answer elif args verbose print f args x to the power args y equals answer else print f args x args y answer Note that slight difference in the usage text Note the v q which tells us that we can either use v or q but not both at the same time python prog py help usage prog py h v q x y calculate X to the power of Y positional arguments x the base y the exponent options h help show this help message and exit v verbose q quiet How to translate the argparse output The output of the argparse module such as its help text and error messages are all made translatable using the gettext module This allows applications to easily localize messages produced by argparse See also Internationalizing your programs and modules For instance in this argparse output python prog py help usage prog py h v q x y calculate X to the power of Y positional arguments x the base y the exponent options h help show this help message and exit v verbose q quiet The strings usage positional arguments options and show this help message and exit are all translatable In order to translate these strings they must first be extracted into a po file For example using Babel run this command pybabel extract o messages po usr lib python3 12 argparse py This command will extract all translatable strings from the argparse module and output them into a file named messages po This command assumes that your Python installation is in usr lib You can find out the location of the argparse module on your system using this script import argparse print argparse __file__ Once the messages in the po file are translated and the translations are installed using gettext argparse will be able to display the translated messages To translate your own strings in the argparse output use gettext Conclusion The argparse module offers a lot more than shown here Its docs are quite detailed and thorough and full of examples Having gone through this tutorial you should easily digest them without feeling overwhelmed,en
2626,Event Loop Source code Lib asyncio events py Lib asyncio base_events py Preface The event loop is the core of every asyncio application Event loops run asynchronous tasks and callbacks perform network IO operations and run subprocesses Application developers should typically use the high level asyncio functions such as asyncio run and should rarely need to reference the loop object or call its methods This section is intended mostly for authors of lower level code libraries and frameworks who need finer control over the event loop behavior Obtaining the Event Loop The following low level functions can be used to get set or create an event loop asyncio get_running_loop Return the running event loop in the current OS thread Raise a RuntimeError if there is no running event loop This function can only be called from a coroutine or a callback New in version 3 7 asyncio get_event_loop Get the current event loop When called from a coroutine or a callback e g scheduled with call_soon or similar API this function will always return the running event loop If there is no running event loop set the function will return the result of the get_event_loop_policy get_event_loop call Because this function has rather complex behavior especially when custom event loop policies are in use using the get_running_loop function is preferred to get_event_loop in coroutines and callbacks As noted above consider using the higher level asyncio run function instead of using these lower level functions to manually create and close an event loop Deprecated since version 3 12 Deprecation warning is emitted if there is no current event loop In some future Python release this will become an error asyncio set_event_loop loop Set loop as the current event loop for the current OS thread asyncio new_event_loop Create and return a new event loop object Note that the behaviour of get_event_loop set_event_loop and new_event_loop functions can be altered by setting a custom event loop policy Contents This documentation page contains the following sections The Event Loop Methods section is the reference documentation of the event loop APIs The Callback Handles section documents the Handle and TimerHandle instances which are returned from scheduling methods such as loop call_soon and loop call_later The Server Objects section documents types returned from event loop methods like loop create_server The Event Loop Implementations section documents the SelectorEventLoop and ProactorEventLoop classes The Examples section showcases how to work with some event loop APIs Event Loop Methods Event loops have low level APIs for the following Running and stopping the loop Scheduling callbacks Scheduling delayed callbacks Creating Futures and Tasks Opening network connections Creating network servers Transferring files TLS Upgrade Watching file descriptors Working with socket objects directly DNS Working with pipes Unix signals Executing code in thread or process pools Error Handling API Enabling debug mode Running Subprocesses Running and stopping the loop loop run_until_complete future Run until the future an instance of Future has completed If the argument is a coroutine object it is implicitly scheduled to run as a asyncio Task Return the Future s result or raise its exception loop run_forever Run the event loop until stop is called If stop is called before run_forever is called the loop will poll the I O selector once with a timeout of zero run all callbacks scheduled in response to I O events and those that were already scheduled and then exit If stop is called while run_forever is running the loop will run the current batch of callbacks and then exit Note that new callbacks scheduled by callbacks will not run in this case instead they will run the next time run_forever or run_until_complete is called loop stop Stop the event loop loop is_running Return True if the event loop is currently running loop is_closed Return True if the event loop was closed loop close Close the event loop The loop must not be running when this function is called Any pending callbacks will be ,en
2627,discarded This method clears all queues and shuts down the executor but does not wait for the executor to finish This method is idempotent and irreversible No other methods should be called after the event loop is closed coroutine loop shutdown_asyncgens Schedule all currently open asynchronous generator objects to close with an aclose call After calling this method the event loop will issue a warning if a new asynchronous generator is iterated This should be used to reliably finalize all scheduled asynchronous generators Note that there is no need to call this function when asyncio run is used Example try loop run_forever finally loop run_until_complete loop shutdown_asyncgens loop close New in version 3 6 coroutine loop shutdown_default_executor timeout None Schedule the closure of the default executor and wait for it to join all of the threads in the ThreadPoolExecutor Once this method has been called using the default executor with loop run_in_executor will raise a RuntimeError The timeout parameter specifies the amount of time in float seconds the executor will be given to finish joining With the default None the executor is allowed an unlimited amount of time If the timeout is reached a RuntimeWarning is emitted and the default executor is terminated without waiting for its threads to finish joining Note Do not call this method when using asyncio run as the latter handles default executor shutdown automatically New in version 3 9 Changed in version 3 12 Added the timeout parameter Scheduling callbacks loop call_soon callback args context None Schedule the callback callback to be called with args arguments at the next iteration of the event loop Return an instance of asyncio Handle which can be used later to cancel the callback Callbacks are called in the order in which they are registered Each callback will be called exactly once The optional keyword only context argument specifies a custom contextvars Context for the callback to run in Callbacks use the current context when no context is provided Unlike call_soon_threadsafe this method is not thread safe loop call_soon_threadsafe callback args context None A thread safe variant of call_soon When scheduling callbacks from another thread this function must be used since call_soon is not thread safe Raises RuntimeError if called on a loop that s been closed This can happen on a secondary thread when the main application is shutting down See the concurrency and multithreading section of the documentation Changed in version 3 7 The context keyword only parameter was added See PEP 567 for more details Note Most asyncio scheduling functions don t allow passing keyword arguments To do that use functools partial will schedule print Hello flush True loop call_soon functools partial print Hello flush True Using partial objects is usually more convenient than using lambdas as asyncio can render partial objects better in debug and error messages Scheduling delayed callbacks Event loop provides mechanisms to schedule callback functions to be called at some point in the future Event loop uses monotonic clocks to track time loop call_later delay callback args context None Schedule callback to be called after the given delay number of seconds can be either an int or a float An instance of asyncio TimerHandle is returned which can be used to cancel the callback callback will be called exactly once If two callbacks are scheduled for exactly the same time the order in which they are called is undefined The optional positional args will be passed to the callback when it is called If you want the callback to be called with keyword arguments use functools partial An optional keyword only context argument allows specifying a custom contextvars Context for the callback to run in The current context is used when no context is provided Changed in version 3 7 The context keyword only parameter was added See PEP 567 for more details Changed in version 3 8 In Python 3 7 and earlier with the default event loop implementation the delay could not exceed one day This has been fixed in Python 3 8 l,en
2628,oop call_at when callback args context None Schedule callback to be called at the given absolute timestamp when an int or a float using the same time reference as loop time This method s behavior is the same as call_later An instance of asyncio TimerHandle is returned which can be used to cancel the callback Changed in version 3 7 The context keyword only parameter was added See PEP 567 for more details Changed in version 3 8 In Python 3 7 and earlier with the default event loop implementation the difference between when and the current time could not exceed one day This has been fixed in Python 3 8 loop time Return the current time as a float value according to the event loop s internal monotonic clock Note Changed in version 3 8 In Python 3 7 and earlier timeouts relative delay or absolute when should not exceed one day This has been fixed in Python 3 8 See also The asyncio sleep function Creating Futures and Tasks loop create_future Create an asyncio Future object attached to the event loop This is the preferred way to create Futures in asyncio This lets third party event loops provide alternative implementations of the Future object with better performance or instrumentation New in version 3 5 2 loop create_task coro name None context None Schedule the execution of coroutine coro Return a Task object Third party event loops can use their own subclass of Task for interoperability In this case the result type is a subclass of Task If the name argument is provided and not None it is set as the name of the task using Task set_name An optional keyword only context argument allows specifying a custom contextvars Context for the coro to run in The current context copy is created when no context is provided Changed in version 3 8 Added the name parameter Changed in version 3 11 Added the context parameter loop set_task_factory factory Set a task factory that will be used by loop create_task If factory is None the default task factory will be set Otherwise factory must be a callable with the signature matching loop coro context None where loop is a reference to the active event loop and coro is a coroutine object The callable must return a asyncio Future compatible object loop get_task_factory Return a task factory or None if the default one is in use Opening network connections coroutine loop create_connection protocol_factory host None port None ssl None family 0 proto 0 flags 0 sock None local_addr None server_hostname None ssl_handshake_timeout None ssl_shutdown_timeout None happy_eyeballs_delay None interleave None all_errors False Open a streaming transport connection to a given address specified by host and port The socket family can be either AF_INET or AF_INET6 depending on host or the family argument if provided The socket type will be SOCK_STREAM protocol_factory must be a callable returning an asyncio protocol implementation This method will try to establish the connection in the background When successful it returns a transport protocol pair The chronological synopsis of the underlying operation is as follows 1 The connection is established and a transport is created for it 2 protocol_factory is called without arguments and is expected to return a protocol instance 3 The protocol instance is coupled with the transport by calling its connection_made method 4 A transport protocol tuple is returned on success The created transport is an implementation dependent bidirectional stream Other arguments ssl if given and not false a SSL TLS transport is created by default a plain TCP transport is created If ssl is a ssl SSLContext object this context is used to create the transport if ssl is True a default context returned from ssl create_default_context is used See also SSL TLS security considerations server_hostname sets or overrides the hostname that the target server s certificate will be matched against Should only be passed if ssl is not None By default the value of the host argument is used If host is empty there is no default and you must pass a value for server_hostname If server_hostname is an empty string hostna,en
2629,me matching is disabled which is a serious security risk allowing for potential man in the middle attacks family proto flags are the optional address family protocol and flags to be passed through to getaddrinfo for host resolution If given these should all be integers from the corresponding socket module constants happy_eyeballs_delay if given enables Happy Eyeballs for this connection It should be a floating point number representing the amount of time in seconds to wait for a connection attempt to complete before starting the next attempt in parallel This is the Connection Attempt Delay as defined in RFC 8305 A sensible default value recommended by the RFC is 0 25 250 milliseconds interleave controls address reordering when a host name resolves to multiple IP addresses If 0 or unspecified no reordering is done and addresses are tried in the order returned by getaddrinfo If a positive integer is specified the addresses are interleaved by address family and the given integer is interpreted as First Address Family Count as defined in RFC 8305 The default is 0 if happy_eyeballs_delay is not specified and 1 if it is sock if given should be an existing already connected socket socket object to be used by the transport If sock is given none of host port family proto flags happy_eyeballs_delay interleave and local_addr should be specified Note The sock argument transfers ownership of the socket to the transport created To close the socket call the transport s close method local_addr if given is a local_host local_port tuple used to bind the socket locally The local_host and local_port are looked up using getaddrinfo similarly to host and port ssl_handshake_timeout is for a TLS connection the time in seconds to wait for the TLS handshake to complete before aborting the connection 60 0 seconds if None default ssl_shutdown_timeout is the time in seconds to wait for the SSL shutdown to complete before aborting the connection 30 0 seconds if None default all_errors determines what exceptions are raised when a connection cannot be created By default only a single Exception is raised the first exception if there is only one or all errors have same message or a single OSError with the error messages combined When all_errors is True an ExceptionGroup will be raised containing all exceptions even if there is only one Changed in version 3 5 Added support for SSL TLS in ProactorEventLoop Changed in version 3 6 The socket option socket TCP_NODELAY is set by default for all TCP connections Changed in version 3 7 Added the ssl_handshake_timeout parameter Changed in version 3 8 Added the happy_eyeballs_delay and interleave parameters Happy Eyeballs Algorithm Success with Dual Stack Hosts When a server s IPv4 path and protocol are working but the server s IPv6 path and protocol are not working a dual stack client application experiences significant connection delay compared to an IPv4 only client This is undesirable because it causes the dual stack client to have a worse user experience This document specifies requirements for algorithms that reduce this user visible delay and provides an algorithm For more information https datatracker ietf org doc html rfc6555 Changed in version 3 11 Added the ssl_shutdown_timeout parameter Changed in version 3 12 all_errors was added See also The open_connection function is a high level alternative API It returns a pair of StreamReader StreamWriter that can be used directly in async await code coroutine loop create_datagram_endpoint protocol_factory local_addr None remote_addr None family 0 proto 0 flags 0 reuse_port None allow_broadcast None sock None Create a datagram connection The socket family can be either AF_INET AF_INET6 or AF_UNIX depending on host or the family argument if provided The socket type will be SOCK_DGRAM protocol_factory must be a callable returning a protocol implementation A tuple of transport protocol is returned on success Other arguments local_addr if given is a local_host local_port tuple used to bind the socket locally The local_host and local_port are looked up using getaddrin,en
2630,fo remote_addr if given is a remote_host remote_port tuple used to connect the socket to a remote address The remote_host and remote_port are looked up using getaddrinfo family proto flags are the optional address family protocol and flags to be passed through to getaddrinfo for host resolution If given these should all be integers from the corresponding socket module constants reuse_port tells the kernel to allow this endpoint to be bound to the same port as other existing endpoints are bound to so long as they all set this flag when being created This option is not supported on Windows and some Unixes If the socket SO_REUSEPORT constant is not defined then this capability is unsupported allow_broadcast tells the kernel to allow this endpoint to send messages to the broadcast address sock can optionally be specified in order to use a preexisting already connected socket socket object to be used by the transport If specified local_addr and remote_addr should be omitted must be None Note The sock argument transfers ownership of the socket to the transport created To close the socket call the transport s close method See UDP echo client protocol and UDP echo server protocol examples Changed in version 3 4 4 The family proto flags reuse_address reuse_port allow_broadcast and sock parameters were added Changed in version 3 8 Added support for Windows Changed in version 3 8 1 The reuse_address parameter is no longer supported as using socket SO_REUSEADDR poses a significant security concern for UDP Explicitly passing reuse_address True will raise an exception When multiple processes with differing UIDs assign sockets to an identical UDP socket address with SO_REUSEADDR incoming packets can become randomly distributed among the sockets For supported platforms reuse_port can be used as a replacement for similar functionality With reuse_port socket SO_REUSEPORT is used instead which specifically prevents processes with differing UIDs from assigning sockets to the same socket address Changed in version 3 11 The reuse_address parameter disabled since Python 3 8 1 3 7 6 and 3 6 10 has been entirely removed coroutine loop create_unix_connection protocol_factory path None ssl None sock None server_hostname None ssl_handshake_timeout None ssl_shutdown_timeout None Create a Unix connection The socket family will be AF_UNIX socket type will be SOCK_STREAM A tuple of transport protocol is returned on success path is the name of a Unix domain socket and is required unless a sock parameter is specified Abstract Unix sockets str bytes and Path paths are supported See the documentation of the loop create_connection method for information about arguments to this method Availability Unix Changed in version 3 7 Added the ssl_handshake_timeout parameter The path parameter can now be a path like object Changed in version 3 11 Added the ssl_shutdown_timeout parameter Creating network servers coroutine loop create_server protocol_factory host None port None family socket AF_UNSPEC flags socket AI_PASSIVE sock None backlog 100 ssl None reuse_address None reuse_port None ssl_handshake_timeout None ssl_shutdown_timeout None start_serving True Create a TCP server socket type SOCK_STREAM listening on port of the host address Returns a Server object Arguments protocol_factory must be a callable returning a protocol implementation The host parameter can be set to several types which determine where the server would be listening If host is a string the TCP server is bound to a single network interface specified by host If host is a sequence of strings the TCP server is bound to all network interfaces specified by the sequence If host is an empty string or None all interfaces are assumed and a list of multiple sockets will be returned most likely one for IPv4 and another one for IPv6 The port parameter can be set to specify which port the server should listen on If 0 or None the default a random unused port will be selected note that if host resolves to multiple network interfaces a different random port will be selected for each interface family can be set,en
2631, to either socket AF_INET or AF_INET6 to force the socket to use IPv4 or IPv6 If not set the family will be determined from host name defaults to AF_UNSPEC flags is a bitmask for getaddrinfo sock can optionally be specified in order to use a preexisting socket object If specified host and port must not be specified Note The sock argument transfers ownership of the socket to the server created To close the socket call the server s close method backlog is the maximum number of queued connections passed to listen defaults to 100 ssl can be set to an SSLContext instance to enable TLS over the accepted connections reuse_address tells the kernel to reuse a local socket in TIME_WAIT state without waiting for its natural timeout to expire If not specified will automatically be set to True on Unix reuse_port tells the kernel to allow this endpoint to be bound to the same port as other existing endpoints are bound to so long as they all set this flag when being created This option is not supported on Windows ssl_handshake_timeout is for a TLS server the time in seconds to wait for the TLS handshake to complete before aborting the connection 60 0 seconds if None default ssl_shutdown_timeout is the time in seconds to wait for the SSL shutdown to complete before aborting the connection 30 0 seconds if None default start_serving set to True the default causes the created server to start accepting connections immediately When set to False the user should await on Server start_serving or Server serve_forever to make the server to start accepting connections Changed in version 3 5 Added support for SSL TLS in ProactorEventLoop Changed in version 3 5 1 The host parameter can be a sequence of strings Changed in version 3 6 Added ssl_handshake_timeout and start_serving parameters The socket option socket TCP_NODELAY is set by default for all TCP connections Changed in version 3 11 Added the ssl_shutdown_timeout parameter See also The start_server function is a higher level alternative API that returns a pair of StreamReader and StreamWriter that can be used in an async await code coroutine loop create_unix_server protocol_factory path None sock None backlog 100 ssl None ssl_handshake_timeout None ssl_shutdown_timeout None start_serving True Similar to loop create_server but works with the AF_UNIX socket family path is the name of a Unix domain socket and is required unless a sock argument is provided Abstract Unix sockets str bytes and Path paths are supported See the documentation of the loop create_server method for information about arguments to this method Availability Unix Changed in version 3 7 Added the ssl_handshake_timeout and start_serving parameters The path parameter can now be a Path object Changed in version 3 11 Added the ssl_shutdown_timeout parameter coroutine loop connect_accepted_socket protocol_factory sock ssl None ssl_handshake_timeout None ssl_shutdown_timeout None Wrap an already accepted connection into a transport protocol pair This method can be used by servers that accept connections outside of asyncio but that use asyncio to handle them Parameters protocol_factory must be a callable returning a protocol implementation sock is a preexisting socket object returned from socket accept Note The sock argument transfers ownership of the socket to the transport created To close the socket call the transport s close method ssl can be set to an SSLContext to enable SSL over the accepted connections ssl_handshake_timeout is for an SSL connection the time in seconds to wait for the SSL handshake to complete before aborting the connection 60 0 seconds if None default ssl_shutdown_timeout is the time in seconds to wait for the SSL shutdown to complete before aborting the connection 30 0 seconds if None default Returns a transport protocol pair New in version 3 5 3 Changed in version 3 7 Added the ssl_handshake_timeout parameter Changed in version 3 11 Added the ssl_shutdown_timeout parameter Transferring files coroutine loop sendfile transport file offset 0 count None fallback True Send a file over a transport Return the tota,en
2632,l number of bytes sent The method uses high performance os sendfile if available file must be a regular file object opened in binary mode offset tells from where to start reading the file If specified count is the total number of bytes to transmit as opposed to sending the file until EOF is reached File position is always updated even when this method raises an error and file tell can be used to obtain the actual number of bytes sent fallback set to True makes asyncio to manually read and send the file when the platform does not support the sendfile system call e g Windows or SSL socket on Unix Raise SendfileNotAvailableError if the system does not support the sendfile syscall and fallback is False New in version 3 7 TLS Upgrade coroutine loop start_tls transport protocol sslcontext server_side False server_hostname None ssl_handshake_timeout None ssl_shutdown_timeout None Upgrade an existing transport based connection to TLS Create a TLS coder decoder instance and insert it between the transport and the protocol The coder decoder implements both transport facing protocol and protocol facing transport Return the created two interface instance After await the protocol must stop using the original transport and communicate with the returned object only because the coder caches protocol side data and sporadically exchanges extra TLS session packets with transport In some situations e g when the passed transport is already closing this may return None Parameters transport and protocol instances that methods like create_server and create_connection return sslcontext a configured instance of SSLContext server_side pass True when a server side connection is being upgraded like the one created by create_server server_hostname sets or overrides the host name that the target server s certificate will be matched against ssl_handshake_timeout is for a TLS connection the time in seconds to wait for the TLS handshake to complete before aborting the connection 60 0 seconds if None default ssl_shutdown_timeout is the time in seconds to wait for the SSL shutdown to complete before aborting the connection 30 0 seconds if None default New in version 3 7 Changed in version 3 11 Added the ssl_shutdown_timeout parameter Watching file descriptors loop add_reader fd callback args Start monitoring the fd file descriptor for read availability and invoke callback with the specified arguments once fd is available for reading loop remove_reader fd Stop monitoring the fd file descriptor for read availability Returns True if fd was previously being monitored for reads loop add_writer fd callback args Start monitoring the fd file descriptor for write availability and invoke callback with the specified arguments once fd is available for writing Use functools partial to pass keyword arguments to callback loop remove_writer fd Stop monitoring the fd file descriptor for write availability Returns True if fd was previously being monitored for writes See also Platform Support section for some limitations of these methods Working with socket objects directly In general protocol implementations that use transport based APIs such as loop create_connection and loop create_server are faster than implementations that work with sockets directly However there are some use cases when performance is not critical and working with socket objects directly is more convenient coroutine loop sock_recv sock nbytes Receive up to nbytes from sock Asynchronous version of socket recv Return the received data as a bytes object sock must be a non blocking socket Changed in version 3 7 Even though this method was always documented as a coroutine method releases before Python 3 7 returned a Future Since Python 3 7 this is an async def method coroutine loop sock_recv_into sock buf Receive data from sock into the buf buffer Modeled after the blocking socket recv_into method Return the number of bytes written to the buffer sock must be a non blocking socket New in version 3 7 coroutine loop sock_recvfrom sock bufsize Receive a datagram of up to bufsize from sock Asynchronous version of,en
2633, socket recvfrom Return a tuple of received data remote address sock must be a non blocking socket New in version 3 11 coroutine loop sock_recvfrom_into sock buf nbytes 0 Receive a datagram of up to nbytes from sock into buf Asynchronous version of socket recvfrom_into Return a tuple of number of bytes received remote address sock must be a non blocking socket New in version 3 11 coroutine loop sock_sendall sock data Send data to the sock socket Asynchronous version of socket sendall This method continues to send to the socket until either all data in data has been sent or an error occurs None is returned on success On error an exception is raised Additionally there is no way to determine how much data if any was successfully processed by the receiving end of the connection sock must be a non blocking socket Changed in version 3 7 Even though the method was always documented as a coroutine method before Python 3 7 it returned a Future Since Python 3 7 this is an async def method coroutine loop sock_sendto sock data address Send a datagram from sock to address Asynchronous version of socket sendto Return the number of bytes sent sock must be a non blocking socket New in version 3 11 coroutine loop sock_connect sock address Connect sock to a remote socket at address Asynchronous version of socket connect sock must be a non blocking socket Changed in version 3 5 2 address no longer needs to be resolved sock_connect will try to check if the address is already resolved by calling socket inet_pton If not loop getaddrinfo will be used to resolve the address See also loop create_connection and asyncio open_connection coroutine loop sock_accept sock Accept a connection Modeled after the blocking socket accept method The socket must be bound to an address and listening for connections The return value is a pair conn address where conn is a new socket object usable to send and receive data on the connection and address is the address bound to the socket on the other end of the connection sock must be a non blocking socket Changed in version 3 7 Even though the method was always documented as a coroutine method before Python 3 7 it returned a Future Since Python 3 7 this is an async def method See also loop create_server and start_server coroutine loop sock_sendfile sock file offset 0 count None fallback True Send a file using high performance os sendfile if possible Return the total number of bytes sent Asynchronous version of socket sendfile sock must be a non blocking socket SOCK_STREAM socket file must be a regular file object open in binary mode offset tells from where to start reading the file If specified count is the total number of bytes to transmit as opposed to sending the file until EOF is reached File position is always updated even when this method raises an error and file tell can be used to obtain the actual number of bytes sent fallback when set to True makes asyncio manually read and send the file when the platform does not support the sendfile syscall e g Windows or SSL socket on Unix Raise SendfileNotAvailableError if the system does not support sendfile syscall and fallback is False sock must be a non blocking socket New in version 3 7 DNS coroutine loop getaddrinfo host port family 0 type 0 proto 0 flags 0 Asynchronous version of socket getaddrinfo coroutine loop getnameinfo sockaddr flags 0 Asynchronous version of socket getnameinfo Changed in version 3 7 Both getaddrinfo and getnameinfo methods were always documented to return a coroutine but prior to Python 3 7 they were in fact returning asyncio Future objects Starting with Python 3 7 both methods are coroutines Working with pipes coroutine loop connect_read_pipe protocol_factory pipe Register the read end of pipe in the event loop protocol_factory must be a callable returning an asyncio protocol implementation pipe is a file like object Return pair transport protocol where transport supports the ReadTransport interface and protocol is an object instantiated by the protocol_factory With SelectorEventLoop event loop the pipe is set to non blocking mode corou,en
2634,tine loop connect_write_pipe protocol_factory pipe Register the write end of pipe in the event loop protocol_factory must be a callable returning an asyncio protocol implementation pipe is file like object Return pair transport protocol where transport supports WriteTransport interface and protocol is an object instantiated by the protocol_factory With SelectorEventLoop event loop the pipe is set to non blocking mode Note SelectorEventLoop does not support the above methods on Windows Use ProactorEventLoop instead for Windows See also The loop subprocess_exec and loop subprocess_shell methods Unix signals loop add_signal_handler signum callback args Set callback as the handler for the signum signal The callback will be invoked by loop along with other queued callbacks and runnable coroutines of that event loop Unlike signal handlers registered using signal signal a callback registered with this function is allowed to interact with the event loop Raise ValueError if the signal number is invalid or uncatchable Raise RuntimeError if there is a problem setting up the handler Use functools partial to pass keyword arguments to callback Like signal signal this function must be invoked in the main thread loop remove_signal_handler sig Remove the handler for the sig signal Return True if the signal handler was removed or False if no handler was set for the given signal Availability Unix See also The signal module Executing code in thread or process pools awaitable loop run_in_executor executor func args Arrange for func to be called in the specified executor The executor argument should be an concurrent futures Executor instance The default executor is used if executor is None Example import asyncio import concurrent futures def blocking_io File operations such as logging can block the event loop run them in a thread pool with open dev urandom rb as f return f read 100 def cpu_bound CPU bound operations will block the event loop in general it is preferable to run them in a process pool return sum i i for i in range 10 7 async def main loop asyncio get_running_loop Options 1 Run in the default loop s executor result await loop run_in_executor None blocking_io print default thread pool result 2 Run in a custom thread pool with concurrent futures ThreadPoolExecutor as pool result await loop run_in_executor pool blocking_io print custom thread pool result 3 Run in a custom process pool with concurrent futures ProcessPoolExecutor as pool result await loop run_in_executor pool cpu_bound print custom process pool result if __name__ __main__ asyncio run main Note that the entry point guard if __name__ __main__ is required for option 3 due to the peculiarities of multiprocessing which is used by ProcessPoolExecutor See Safe importing of main module This method returns a asyncio Future object Use functools partial to pass keyword arguments to func Changed in version 3 5 3 loop run_in_executor no longer configures the max_workers of the thread pool executor it creates instead leaving it up to the thread pool executor ThreadPoolExecutor to set the default loop set_default_executor executor Set executor as the default executor used by run_in_executor executor must be an instance of ThreadPoolExecutor Changed in version 3 11 executor must be an instance of ThreadPoolExecutor Error Handling API Allows customizing how exceptions are handled in the event loop loop set_exception_handler handler Set handler as the new event loop exception handler If handler is None the default exception handler will be set Otherwise handler must be a callable with the signature matching loop context where loop is a reference to the active event loop and context is a dict object containing the details of the exception see call_exception_handler documentation for details about context If the handler is called on behalf of a Task or Handle it is run in the contextvars Context of that task or callback handle Changed in version 3 12 The handler may be called in the Context of the task or handle where the exception originated loop get_exception_handler Return the current,en
2635, exception handler or None if no custom exception handler was set New in version 3 5 2 loop default_exception_handler context Default exception handler This is called when an exception occurs and no exception handler is set This can be called by a custom exception handler that wants to defer to the default handler behavior context parameter has the same meaning as in call_exception_handler loop call_exception_handler context Call the current event loop exception handler context is a dict object containing the following keys new keys may be introduced in future Python versions message Error message exception optional Exception object future optional asyncio Future instance task optional asyncio Task instance handle optional asyncio Handle instance protocol optional Protocol instance transport optional Transport instance socket optional socket socket instance asyncgen optional Asynchronous generator that caused the exception Note This method should not be overloaded in subclassed event loops For custom exception handling use the set_exception_handler method Enabling debug mode loop get_debug Get the debug mode bool of the event loop The default value is True if the environment variable PYTHONASYNCIODEBUG is set to a non empty string False otherwise loop set_debug enabled bool Set the debug mode of the event loop Changed in version 3 7 The new Python Development Mode can now also be used to enable the debug mode loop slow_callback_duration This attribute can be used to set the minimum execution duration in seconds that is considered slow When debug mode is enabled slow callbacks are logged Default value is 100 milliseconds See also The debug mode of asyncio Running Subprocesses Methods described in this subsections are low level In regular async await code consider using the high level asyncio create_subprocess_shell and asyncio create_subprocess_exec convenience functions instead Note On Windows the default event loop ProactorEventLoop supports subprocesses whereas SelectorEventLoop does not See Subprocess Support on Windows for details coroutine loop subprocess_exec protocol_factory args stdin subprocess PIPE stdout subprocess PIPE stderr subprocess PIPE kwargs Create a subprocess from one or more string arguments specified by args args must be a list of strings represented by str or bytes encoded to the filesystem encoding The first string specifies the program executable and the remaining strings specify the arguments Together string arguments form the argv of the program This is similar to the standard library subprocess Popen class called with shell False and the list of strings passed as the first argument however where Popen takes a single argument which is list of strings subprocess_exec takes multiple string arguments The protocol_factory must be a callable returning a subclass of the asyncio SubprocessProtocol class Other parameters stdin can be any of these a file like object an existing file descriptor a positive integer for example those created with os pipe the subprocess PIPE constant default which will create a new pipe and connect it the value None which will make the subprocess inherit the file descriptor from this process the subprocess DEVNULL constant which indicates that the special os devnull file will be used stdout can be any of these a file like object the subprocess PIPE constant default which will create a new pipe and connect it the value None which will make the subprocess inherit the file descriptor from this process the subprocess DEVNULL constant which indicates that the special os devnull file will be used stderr can be any of these a file like object the subprocess PIPE constant default which will create a new pipe and connect it the value None which will make the subprocess inherit the file descriptor from this process the subprocess DEVNULL constant which indicates that the special os devnull file will be used the subprocess STDOUT constant which will connect the standard error stream to the process standard output stream All other keyword arguments are passed to subprocess Popen withou,en
2636,t interpretation except for bufsize universal_newlines shell text encoding and errors which should not be specified at all The asyncio subprocess API does not support decoding the streams as text bytes decode can be used to convert the bytes returned from the stream to text If a file like object passed as stdin stdout or stderr represents a pipe then the other side of this pipe should be registered with connect_write_pipe or connect_read_pipe for use with the event loop See the constructor of the subprocess Popen class for documentation on other arguments Returns a pair of transport protocol where transport conforms to the asyncio SubprocessTransport base class and protocol is an object instantiated by the protocol_factory coroutine loop subprocess_shell protocol_factory cmd stdin subprocess PIPE stdout subprocess PIPE stderr subprocess PIPE kwargs Create a subprocess from cmd which can be a str or a bytes string encoded to the filesystem encoding using the platform s shell syntax This is similar to the standard library subprocess Popen class called with shell True The protocol_factory must be a callable returning a subclass of the SubprocessProtocol class See subprocess_exec for more details about the remaining arguments Returns a pair of transport protocol where transport conforms to the SubprocessTransport base class and protocol is an object instantiated by the protocol_factory Note It is the application s responsibility to ensure that all whitespace and special characters are quoted appropriately to avoid shell injection vulnerabilities The shlex quote function can be used to properly escape whitespace and special characters in strings that are going to be used to construct shell commands Callback Handles class asyncio Handle A callback wrapper object returned by loop call_soon loop call_soon_threadsafe get_context Return the contextvars Context object associated with the handle New in version 3 12 cancel Cancel the callback If the callback has already been canceled or executed this method has no effect cancelled Return True if the callback was cancelled New in version 3 7 class asyncio TimerHandle A callback wrapper object returned by loop call_later and loop call_at This class is a subclass of Handle when Return a scheduled callback time as float seconds The time is an absolute timestamp using the same time reference as loop time New in version 3 7 Server Objects Server objects are created by loop create_server loop create_unix_server start_server and start_unix_server functions Do not instantiate the Server class directly class asyncio Server Server objects are asynchronous context managers When used in an async with statement it s guaranteed that the Server object is closed and not accepting new connections when the async with statement is completed srv await loop create_server async with srv some code At this point srv is closed and no longer accepts new connections Changed in version 3 7 Server object is an asynchronous context manager since Python 3 7 Changed in version 3 11 This class was exposed publicly as asyncio Server in Python 3 9 11 3 10 3 and 3 11 close Stop serving close listening sockets and set the sockets attribute to None The sockets that represent existing incoming client connections are left open The server is closed asynchronously use the wait_closed coroutine to wait until the server is closed and no more connections are active get_loop Return the event loop associated with the server object New in version 3 7 coroutine start_serving Start accepting connections This method is idempotent so it can be called when the server is already serving The start_serving keyword only parameter to loop create_server and asyncio start_server allows creating a Server object that is not accepting connections initially In this case Server start_serving or Server serve_forever can be used to make the Server start accepting connections New in version 3 7 coroutine serve_forever Start accepting connections until the coroutine is cancelled Cancellation of serve_forever task causes the server to be closed This met,en
2637,hod can be called if the server is already accepting connections Only one serve_forever task can exist per one Server object Example async def client_connected reader writer Communicate with the client with reader writer streams For example await reader readline async def main host port srv await asyncio start_server client_connected host port await srv serve_forever asyncio run main 127 0 0 1 0 New in version 3 7 is_serving Return True if the server is accepting new connections New in version 3 7 coroutine wait_closed Wait until the close method completes and all active connections have finished sockets List of socket like objects asyncio trsock TransportSocket which the server is listening on Changed in version 3 7 Prior to Python 3 7 Server sockets used to return an internal list of server sockets directly In 3 7 a copy of that list is returned Event Loop Implementations asyncio ships with two different event loop implementations SelectorEventLoop and ProactorEventLoop By default asyncio is configured to use SelectorEventLoop on Unix and ProactorEventLoop on Windows class asyncio SelectorEventLoop An event loop based on the selectors module Uses the most efficient selector available for the given platform It is also possible to manually configure the exact selector implementation to be used import asyncio import selectors class MyPolicy asyncio DefaultEventLoopPolicy def new_event_loop self selector selectors SelectSelector return asyncio SelectorEventLoop selector asyncio set_event_loop_policy MyPolicy Availability Unix Windows class asyncio ProactorEventLoop An event loop for Windows that uses I O Completion Ports IOCP Availability Windows See also MSDN documentation on I O Completion Ports class asyncio AbstractEventLoop Abstract base class for asyncio compliant event loops The Event Loop Methods section lists all methods that an alternative implementation of AbstractEventLoop should have defined Examples Note that all examples in this section purposefully show how to use the low level event loop APIs such as loop run_forever and loop call_soon Modern asyncio applications rarely need to be written this way consider using the high level functions like asyncio run Hello World with call_soon An example using the loop call_soon method to schedule a callback The callback displays Hello World and then stops the event loop import asyncio def hello_world loop A callback to print Hello World and stop the event loop print Hello World loop stop loop asyncio new_event_loop Schedule a call to hello_world loop call_soon hello_world loop Blocking call interrupted by loop stop try loop run_forever finally loop close See also A similar Hello World example created with a coroutine and the run function Display the current date with call_later An example of a callback displaying the current date every second The callback uses the loop call_later method to reschedule itself after 5 seconds and then stops the event loop import asyncio import datetime def display_date end_time loop print datetime datetime now if loop time 1 0 end_time loop call_later 1 display_date end_time loop else loop stop loop asyncio new_event_loop Schedule the first call to display_date end_time loop time 5 0 loop call_soon display_date end_time loop Blocking call interrupted by loop stop try loop run_forever finally loop close See also A similar current date example created with a coroutine and the run function Watch a file descriptor for read events Wait until a file descriptor received some data using the loop add_reader method and then close the event loop import asyncio from socket import socketpair Create a pair of connected file descriptors rsock wsock socketpair loop asyncio new_event_loop def reader data rsock recv 100 print Received data decode We are done unregister the file descriptor loop remove_reader rsock Stop the event loop loop stop Register the file descriptor for read event loop add_reader rsock reader Simulate the reception of data from the network loop call_soon wsock send abc encode try Run the event loop loop run_forever finally We are done,en
2638, Close sockets and the event loop rsock close wsock close loop close See also A similar example using transports protocols and the loop create_connection method Another similar example using the high level asyncio open_connection function and streams Set signal handlers for SIGINT and SIGTERM This signals example only works on Unix Register handlers for signals SIGINT and SIGTERM using the loop add_signal_handler method import asyncio import functools import os import signal def ask_exit signame loop print got signal s exit signame loop stop async def main loop asyncio get_running_loop for signame in SIGINT SIGTERM loop add_signal_handler getattr signal signame functools partial ask_exit signame loop await asyncio sleep 3600 print Event loop running for 1 hour press Ctrl C to interrupt print f pid os getpid send SIGINT or SIGTERM to exit asyncio run main,en
2639,msvcrt Useful routines from the MS VC runtime These functions provide access to some useful capabilities on Windows platforms Some higher level modules use these functions to build the Windows implementations of their services For example the getpass module uses this in the implementation of the getpass function Further documentation on these functions can be found in the Platform API documentation The module implements both the normal and wide char variants of the console I O api The normal API deals only with ASCII characters and is of limited use for internationalized applications The wide char API should be used where ever possible Changed in version 3 3 Operations in this module now raise OSError where IOError was raised File Operations msvcrt locking fd mode nbytes Lock part of a file based on file descriptor fd from the C runtime Raises OSError on failure The locked region of the file extends from the current file position for nbytes bytes and may continue beyond the end of the file mode must be one of the LK_ constants listed below Multiple regions in a file may be locked at the same time but may not overlap Adjacent regions are not merged they must be unlocked individually Raises an auditing event msvcrt locking with arguments fd mode nbytes msvcrt LK_LOCK msvcrt LK_RLCK Locks the specified bytes If the bytes cannot be locked the program immediately tries again after 1 second If after 10 attempts the bytes cannot be locked OSError is raised msvcrt LK_NBLCK msvcrt LK_NBRLCK Locks the specified bytes If the bytes cannot be locked OSError is raised msvcrt LK_UNLCK Unlocks the specified bytes which must have been previously locked msvcrt setmode fd flags Set the line end translation mode for the file descriptor fd To set it to text mode flags should be os O_TEXT for binary it should be os O_BINARY msvcrt open_osfhandle handle flags Create a C runtime file descriptor from the file handle handle The flags parameter should be a bitwise OR of os O_APPEND os O_RDONLY and os O_TEXT The returned file descriptor may be used as a parameter to os fdopen to create a file object Raises an auditing event msvcrt open_osfhandle with arguments handle flags msvcrt get_osfhandle fd Return the file handle for the file descriptor fd Raises OSError if fd is not recognized Raises an auditing event msvcrt get_osfhandle with argument fd Console I O msvcrt kbhit Return True if a keypress is waiting to be read msvcrt getch Read a keypress and return the resulting character as a byte string Nothing is echoed to the console This call will block if a keypress is not already available but will not wait for Enter to be pressed If the pressed key was a special function key this will return 000 or xe0 the next call will return the keycode The Control C keypress cannot be read with this function msvcrt getwch Wide char variant of getch returning a Unicode value msvcrt getche Similar to getch but the keypress will be echoed if it represents a printable character msvcrt getwche Wide char variant of getche returning a Unicode value msvcrt putch char Print the byte string char to the console without buffering msvcrt putwch unicode_char Wide char variant of putch accepting a Unicode value msvcrt ungetch char Cause the byte string char to be pushed back into the console buffer it will be the next character read by getch or getche msvcrt ungetwch unicode_char Wide char variant of ungetch accepting a Unicode value Other Functions msvcrt heapmin Force the malloc heap to clean itself up and return unused blocks to the operating system On failure this raises OSError msvcrt CRT_ASSEMBLY_VERSION The CRT Assembly version from the crtassem h header file msvcrt VC_ASSEMBLY_PUBLICKEYTOKEN The VC Assembly public key token from the crtassem h header file msvcrt LIBRARIES_ASSEMBLY_NAME_PREFIX The Libraries Assembly name prefix from the crtassem h header file,en
2640,Capsules Refer to Providing a C API for an Extension Module for more information on using these objects New in version 3 1 type PyCapsule This subtype of PyObject represents an opaque value useful for C extension modules who need to pass an opaque value as a void pointer through Python code to other C code It is often used to make a C function pointer defined in one module available to other modules so the regular import mechanism can be used to access C APIs defined in dynamically loaded modules type PyCapsule_Destructor Part of the Stable ABI The type of a destructor callback for a capsule Defined as typedef void PyCapsule_Destructor PyObject See PyCapsule_New for the semantics of PyCapsule_Destructor callbacks int PyCapsule_CheckExact PyObject p Return true if its argument is a PyCapsule This function always succeeds PyObject PyCapsule_New void pointer const char name PyCapsule_Destructor destructor Return value New reference Part of the Stable ABI Create a PyCapsule encapsulating the pointer The pointer argument may not be NULL On failure set an exception and return NULL The name string may either be NULL or a pointer to a valid C string If non NULL this string must outlive the capsule Though it is permitted to free it inside the destructor If the destructor argument is not NULL it will be called with the capsule as its argument when it is destroyed If this capsule will be stored as an attribute of a module the name should be specified as modulename attributename This will enable other modules to import the capsule using PyCapsule_Import void PyCapsule_GetPointer PyObject capsule const char name Part of the Stable ABI Retrieve the pointer stored in the capsule On failure set an exception and return NULL The name parameter must compare exactly to the name stored in the capsule If the name stored in the capsule is NULL the name passed in must also be NULL Python uses the C function strcmp to compare capsule names PyCapsule_Destructor PyCapsule_GetDestructor PyObject capsule Part of the Stable ABI Return the current destructor stored in the capsule On failure set an exception and return NULL It is legal for a capsule to have a NULL destructor This makes a NULL return code somewhat ambiguous use PyCapsule_IsValid or PyErr_Occurred to disambiguate void PyCapsule_GetContext PyObject capsule Part of the Stable ABI Return the current context stored in the capsule On failure set an exception and return NULL It is legal for a capsule to have a NULL context This makes a NULL return code somewhat ambiguous use PyCapsule_IsValid or PyErr_Occurred to disambiguate const char PyCapsule_GetName PyObject capsule Part of the Stable ABI Return the current name stored in the capsule On failure set an exception and return NULL It is legal for a capsule to have a NULL name This makes a NULL return code somewhat ambiguous use PyCapsule_IsValid or PyErr_Occurred to disambiguate void PyCapsule_Import const char name int no_block Part of the Stable ABI Import a pointer to a C object from a capsule attribute in a module The name parameter should specify the full name to the attribute as in module attribute The name stored in the capsule must match this string exactly Return the capsule s internal pointer on success On failure set an exception and return NULL Changed in version 3 3 no_block has no effect anymore int PyCapsule_IsValid PyObject capsule const char name Part of the Stable ABI Determines whether or not capsule is a valid capsule A valid capsule is non NULL passes PyCapsule_CheckExact has a non NULL pointer stored in it and its internal name matches the name parameter See PyCapsule_GetPointer for information on how capsule names are compared In other words if PyCapsule_IsValid returns a true value calls to any of the accessors any function starting with PyCapsule_Get are guaranteed to succeed Return a nonzero value if the object is valid and matches the name passed in Return 0 otherwise This function will not fail int PyCapsule_SetContext PyObject capsule void context Part of the Stable ABI Set the context pointer inside capsule to co,en
2641,ntext Return 0 on success Return nonzero and set an exception on failure int PyCapsule_SetDestructor PyObject capsule PyCapsule_Destructor destructor Part of the Stable ABI Set the destructor inside capsule to destructor Return 0 on success Return nonzero and set an exception on failure int PyCapsule_SetName PyObject capsule const char name Part of the Stable ABI Set the name inside capsule to name If non NULL the name must outlive the capsule If the previous name stored in the capsule was not NULL no attempt is made to free it Return 0 on success Return nonzero and set an exception on failure int PyCapsule_SetPointer PyObject capsule void pointer Part of the Stable ABI Set the void pointer inside capsule to pointer The pointer may not be NULL Return 0 on success Return nonzero and set an exception on failure,en
2642,ossaudiodev Access to OSS compatible audio devices Deprecated since version 3 11 will be removed in version 3 13 The ossaudiodev module is deprecated see PEP 594 for details This module allows you to access the OSS Open Sound System audio interface OSS is available for a wide range of open source and commercial Unices and is the standard audio interface for Linux and recent versions of FreeBSD Changed in version 3 3 Operations in this module now raise OSError where IOError was raised See also Open Sound System Programmer s Guide the official documentation for the OSS C API The module defines a large number of constants supplied by the OSS device driver see sys soundcard h on either Linux or FreeBSD for a listing ossaudiodev defines the following variables and functions exception ossaudiodev OSSAudioError This exception is raised on certain errors The argument is a string describing what went wrong If ossaudiodev receives an error from a system call such as open write or ioctl it raises OSError Errors detected directly by ossaudiodev result in OSSAudioError For backwards compatibility the exception class is also available as ossaudiodev error ossaudiodev open mode ossaudiodev open device mode Open an audio device and return an OSS audio device object This object supports many file like methods such as read write and fileno although there are subtle differences between conventional Unix read write semantics and those of OSS audio devices It also supports a number of audio specific methods see below for the complete list of methods device is the audio device filename to use If it is not specified this module first looks in the environment variable AUDIODEV for a device to use If not found it falls back to dev dsp mode is one of r for read only record access w for write only playback access and rw for both Since many sound cards only allow one process to have the recorder or player open at a time it is a good idea to open the device only for the activity needed Further some sound cards are half duplex they can be opened for reading or writing but not both at once Note the unusual calling syntax the first argument is optional and the second is required This is a historical artifact for compatibility with the older linuxaudiodev module which ossaudiodev supersedes ossaudiodev openmixer device Open a mixer device and return an OSS mixer device object device is the mixer device filename to use If it is not specified this module first looks in the environment variable MIXERDEV for a device to use If not found it falls back to dev mixer Audio Device Objects Before you can write to or read from an audio device you must call three methods in the correct order 1 setfmt to set the output format 2 channels to set the number of channels 3 speed to set the sample rate Alternately you can use the setparameters method to set all three audio parameters at once This is more convenient but may not be as flexible in all cases The audio device objects returned by open define the following methods and read only attributes oss_audio_device close Explicitly close the audio device When you are done writing to or reading from an audio device you should explicitly close it A closed device cannot be used again oss_audio_device fileno Return the file descriptor associated with the device oss_audio_device read size Read size bytes from the audio input and return them as a Python string Unlike most Unix device drivers OSS audio devices in blocking mode the default will block read until the entire requested amount of data is available oss_audio_device write data Write a bytes like object data to the audio device and return the number of bytes written If the audio device is in blocking mode the default the entire data is always written again this is different from usual Unix device semantics If the device is in non blocking mode some data may not be written see writeall Changed in version 3 5 Writable bytes like object is now accepted oss_audio_device writeall data Write a bytes like object data to the audio device waits until the audio device is able to a,en
2643,ccept data writes as much data as it will accept and repeats until data has been completely written If the device is in blocking mode the default this has the same effect as write writeall is only useful in non blocking mode Has no return value since the amount of data written is always equal to the amount of data supplied Changed in version 3 5 Writable bytes like object is now accepted Changed in version 3 2 Audio device objects also support the context management protocol i e they can be used in a with statement The following methods each map to exactly one ioctl system call The correspondence is obvious for example setfmt corresponds to the SNDCTL_DSP_SETFMT ioctl and sync to SNDCTL_DSP_SYNC this can be useful when consulting the OSS documentation If the underlying ioctl fails they all raise OSError oss_audio_device nonblock Put the device into non blocking mode Once in non blocking mode there is no way to return it to blocking mode oss_audio_device getfmts Return a bitmask of the audio output formats supported by the soundcard Some of the formats supported by OSS are Format Description AFMT_MU_LAW a logarithmic encoding used by Sun au files and dev audio AFMT_A_LAW a logarithmic encoding AFMT_IMA_ADPCM a 4 1 compressed format defined by the Interactive Multimedia Association AFMT_U8 Unsigned 8 bit audio AFMT_S16_LE Signed 16 bit audio little endian byte order as used by Intel processors AFMT_S16_BE Signed 16 bit audio big endian byte order as used by 68k PowerPC Sparc AFMT_S8 Signed 8 bit audio AFMT_U16_LE Unsigned 16 bit little endian audio AFMT_U16_BE Unsigned 16 bit big endian audio Consult the OSS documentation for a full list of audio formats and note that most devices support only a subset of these formats Some older devices only support AFMT_U8 the most common format used today is AFMT_S16_LE oss_audio_device setfmt format Try to set the current audio format to format see getfmts for a list Returns the audio format that the device was set to which may not be the requested format May also be used to return the current audio format do this by passing an audio format of AFMT_QUERY oss_audio_device channels nchannels Set the number of output channels to nchannels A value of 1 indicates monophonic sound 2 stereophonic Some devices may have more than 2 channels and some high end devices may not support mono Returns the number of channels the device was set to oss_audio_device speed samplerate Try to set the audio sampling rate to samplerate samples per second Returns the rate actually set Most sound devices don t support arbitrary sampling rates Common rates are Rate Description 8000 default rate for dev audio 11025 speech recording 22050 44100 CD quality audio at 16 bits sample and 2 channels 96000 DVD quality audio at 24 bits sample oss_audio_device sync Wait until the sound device has played every byte in its buffer This happens implicitly when the device is closed The OSS documentation recommends closing and re opening the device rather than using sync oss_audio_device reset Immediately stop playing or recording and return the device to a state where it can accept commands The OSS documentation recommends closing and re opening the device after calling reset oss_audio_device post Tell the driver that there is likely to be a pause in the output making it possible for the device to handle the pause more intelligently You might use this after playing a spot sound effect before waiting for user input or before doing disk I O The following convenience methods combine several ioctls or one ioctl and some simple calculations oss_audio_device setparameters format nchannels samplerate strict False Set the key audio sampling parameters sample format number of channels and sampling rate in one method call format nchannels and samplerate should be as specified in the setfmt channels and speed methods If strict is true setparameters checks to see if each parameter was actually set to the requested value and raises OSSAudioError if not Returns a tuple format nchannels samplerate indicating the parameter values that were actu,en
2644,ally set by the device driver i e the same as the return values of setfmt channels and speed For example fmt channels rate dsp setparameters fmt channels rate is equivalent to fmt dsp setfmt fmt channels dsp channels channels rate dsp rate rate oss_audio_device bufsize Returns the size of the hardware buffer in samples oss_audio_device obufcount Returns the number of samples that are in the hardware buffer yet to be played oss_audio_device obuffree Returns the number of samples that could be queued into the hardware buffer to be played without blocking Audio device objects also support several read only attributes oss_audio_device closed Boolean indicating whether the device has been closed oss_audio_device name String containing the name of the device file oss_audio_device mode The I O mode for the file either r rw or w Mixer Device Objects The mixer object provides two file like methods oss_mixer_device close This method closes the open mixer device file Any further attempts to use the mixer after this file is closed will raise an OSError oss_mixer_device fileno Returns the file handle number of the open mixer device file Changed in version 3 2 Mixer objects also support the context management protocol The remaining methods are specific to audio mixing oss_mixer_device controls This method returns a bitmask specifying the available mixer controls Control being a specific mixable channel such as SOUND_MIXER_PCM or SOUND_MIXER_SYNTH This bitmask indicates a subset of all available mixer controls the SOUND_MIXER_ constants defined at module level To determine if for example the current mixer object supports a PCM mixer use the following Python code mixer ossaudiodev openmixer if mixer controls 1 ossaudiodev SOUND_MIXER_PCM PCM is supported code For most purposes the SOUND_MIXER_VOLUME master volume and SOUND_MIXER_PCM controls should suffice but code that uses the mixer should be flexible when it comes to choosing mixer controls On the Gravis Ultrasound for example SOUND_MIXER_VOLUME does not exist oss_mixer_device stereocontrols Returns a bitmask indicating stereo mixer controls If a bit is set the corresponding control is stereo if it is unset the control is either monophonic or not supported by the mixer use in combination with controls to determine which See the code example for the controls function for an example of getting data from a bitmask oss_mixer_device reccontrols Returns a bitmask specifying the mixer controls that may be used to record See the code example for controls for an example of reading from a bitmask oss_mixer_device get control Returns the volume of a given mixer control The returned volume is a 2 tuple left_volume right_volume Volumes are specified as numbers from 0 silent to 100 full volume If the control is monophonic a 2 tuple is still returned but both volumes are the same Raises OSSAudioError if an invalid control is specified or OSError if an unsupported control is specified oss_mixer_device set control left right Sets the volume for a given mixer control to left right left and right must be ints and between 0 silent and 100 full volume On success the new volume is returned as a 2 tuple Note that this may not be exactly the same as the volume specified because of the limited resolution of some soundcard s mixers Raises OSSAudioError if an invalid mixer control was specified or if the specified volumes were out of range oss_mixer_device get_recsrc This method returns a bitmask indicating which control s are currently being used as a recording source oss_mixer_device set_recsrc bitmask Call this function to specify a recording source Returns a bitmask indicating the new recording source or sources if successful raises OSError if an invalid source was specified To set the current recording source to the microphone input mixer setrecsrc 1 ossaudiodev SOUND_MIXER_MIC,en
2645,sys monitoring Execution event monitoring New in version 3 12 Note sys monitoring is a namespace within the sys module not an independent module so there is no need to import sys monitoring simply import sys and then use sys monitoring This namespace provides access to the functions and constants necessary to activate and control event monitoring As programs execute events occur that might be of interest to tools that monitor execution The sys monitoring namespace provides means to receive callbacks when events of interest occur The monitoring API consists of three components Tool identifiers Events Callbacks Tool identifiers A tool identifier is an integer and the associated name Tool identifiers are used to discourage tools from interfering with each other and to allow multiple tools to operate at the same time Currently tools are completely independent and cannot be used to monitor each other This restriction may be lifted in the future Before registering or activating events a tool should choose an identifier Identifiers are integers in the range 0 to 5 inclusive Registering and using tools sys monitoring use_tool_id tool_id int name str None Must be called before tool_id can be used tool_id must be in the range 0 to 5 inclusive Raises a ValueError if tool_id is in use sys monitoring free_tool_id tool_id int None Should be called once a tool no longer requires tool_id Note free_tool_id will not disable global or local events associated with tool_id nor will it unregister any callback functions This function is only intended to be used to notify the VM that the particular tool_id is no longer in use sys monitoring get_tool tool_id int str None Returns the name of the tool if tool_id is in use otherwise it returns None tool_id must be in the range 0 to 5 inclusive All IDs are treated the same by the VM with regard to events but the following IDs are pre defined to make co operation of tools easier sys monitoring DEBUGGER_ID 0 sys monitoring COVERAGE_ID 1 sys monitoring PROFILER_ID 2 sys monitoring OPTIMIZER_ID 5 There is no obligation to set an ID nor is there anything preventing a tool from using an ID even it is already in use However tools are encouraged to use a unique ID and respect other tools Events The following events are supported sys monitoring events BRANCH A conditional branch is taken or not sys monitoring events CALL A call in Python code event occurs before the call sys monitoring events C_RAISE An exception raised from any callable except for Python functions event occurs after the exit sys monitoring events C_RETURN Return from any callable except for Python functions event occurs after the return sys monitoring events EXCEPTION_HANDLED An exception is handled sys monitoring events INSTRUCTION A VM instruction is about to be executed sys monitoring events JUMP An unconditional jump in the control flow graph is made sys monitoring events LINE An instruction is about to be executed that has a different line number from the preceding instruction sys monitoring events PY_RESUME Resumption of a Python function for generator and coroutine functions except for throw calls sys monitoring events PY_RETURN Return from a Python function occurs immediately before the return the callee s frame will be on the stack sys monitoring events PY_START Start of a Python function occurs immediately after the call the callee s frame will be on the stack sys monitoring events PY_THROW A Python function is resumed by a throw call sys monitoring events PY_UNWIND Exit from a Python function during exception unwinding sys monitoring events PY_YIELD Yield from a Python function occurs immediately before the yield the callee s frame will be on the stack sys monitoring events RAISE An exception is raised except those that cause a STOP_ITERATION event sys monitoring events RERAISE An exception is re raised for example at the end of a finally block sys monitoring events STOP_ITERATION An artificial StopIteration is raised see the STOP_ITERATION event More events may be added in the future These events are attributes of the sys monito,en
2646,ring events namespace Each event is represented as a power of 2 integer constant To define a set of events simply bitwise or the individual events together For example to specify both PY_RETURN and PY_START events use the expression PY_RETURN PY_START sys monitoring events NO_EVENTS An alias for 0 so users can do explict comparisions like if get_events DEBUGGER_ID NO_EVENTS Events are divided into three groups Local events Local events are associated with normal execution of the program and happen at clearly defined locations All local events can be disabled The local events are PY_START PY_RESUME PY_RETURN PY_YIELD CALL LINE INSTRUCTION JUMP BRANCH STOP_ITERATION Ancillary events Ancillary events can be monitored like other events but are controlled by another event C_RAISE C_RETURN The C_RETURN and C_RAISE events are controlled by the CALL event C_RETURN and C_RAISE events will only be seen if the corresponding CALL event is being monitored Other events Other events are not necessarily tied to a specific location in the program and cannot be individually disabled The other events that can be monitored are PY_THROW PY_UNWIND RAISE EXCEPTION_HANDLED The STOP_ITERATION event PEP 380 specifies that a StopIteration exception is raised when returning a value from a generator or coroutine However this is a very inefficient way to return a value so some Python implementations notably CPython 3 12 do not raise an exception unless it would be visible to other code To allow tools to monitor for real exceptions without slowing down generators and coroutines the STOP_ITERATION event is provided STOP_ITERATION can be locally disabled unlike RAISE Turning events on and off In order to monitor an event it must be turned on and a corresponding callback must be registered Events can be turned on or off by setting the events either globally or for a particular code object Setting events globally Events can be controlled globally by modifying the set of events being monitored sys monitoring get_events tool_id int int Returns the int representing all the active events sys monitoring set_events tool_id int event_set int None Activates all events which are set in event_set Raises a ValueError if tool_id is not in use No events are active by default Per code object events Events can also be controlled on a per code object basis sys monitoring get_local_events tool_id int code CodeType int Returns all the local events for code sys monitoring set_local_events tool_id int code CodeType event_set int None Activates all the local events for code which are set in event_set Raises a ValueError if tool_id is not in use Local events add to global events but do not mask them In other words all global events will trigger for a code object regardless of the local events Disabling events sys monitoring DISABLE A special value that can be returned from a callback function to disable events for the current code location Local events can be disabled for a specific code location by returning sys monitoring DISABLE from a callback function This does not change which events are set or any other code locations for the same event Disabling events for specific locations is very important for high performance monitoring For example a program can be run under a debugger with no overhead if the debugger disables all monitoring except for a few breakpoints sys monitoring restart_events None Enable all the events that were disabled by sys monitoring DISABLE for all tools Registering callback functions To register a callable for events call sys monitoring register_callback tool_id int event int func Callable None Callable None Registers the callable func for the event with the given tool_id If another callback was registered for the given tool_id and event it is unregistered and returned Otherwise register_callback returns None Functions can be unregistered by calling sys monitoring register_callback tool_id event None Callback functions can be registered and unregistered at any time Registering or unregistering a callback function will generate a sys audit event Callba,en
2647,ck function arguments sys monitoring MISSING A special value that is passed to a callback function to indicate that there are no arguments to the call When an active event occurs the registered callback function is called Different events will provide the callback function with different arguments as follows PY_START and PY_RESUME func code CodeType instruction_offset int DISABLE Any PY_RETURN and PY_YIELD func code CodeType instruction_offset int retval object DISABLE Any CALL C_RAISE and C_RETURN func code CodeType instruction_offset int callable object arg0 object MISSING DISABLE Any If there are no arguments arg0 is set to sys monitoring MISSING RAISE RERAISE EXCEPTION_HANDLED PY_UNWIND PY_THROW and STOP_ITERATION func code CodeType instruction_offset int exception BaseException DISABLE Any LINE func code CodeType line_number int DISABLE Any BRANCH and JUMP func code CodeType instruction_offset int destination_offset int DISABLE Any Note that the destination_offset is where the code will next execute For an untaken branch this will be the offset of the instruction following the branch INSTRUCTION func code CodeType instruction_offset int DISABLE Any,en
2648,logging config Logging configuration Source code Lib logging config py Important This page contains only reference information For tutorials please see Basic Tutorial Advanced Tutorial Logging Cookbook This section describes the API for configuring the logging module Configuration functions The following functions configure the logging module They are located in the logging config module Their use is optional you can configure the logging module using these functions or by making calls to the main API defined in logging itself and defining handlers which are declared either in logging or logging handlers logging config dictConfig config Takes the logging configuration from a dictionary The contents of this dictionary are described in Configuration dictionary schema below If an error is encountered during configuration this function will raise a ValueError TypeError AttributeError or ImportError with a suitably descriptive message The following is a possibly incomplete list of conditions which will raise an error A level which is not a string or which is a string not corresponding to an actual logging level A propagate value which is not a boolean An id which does not have a corresponding destination A non existent handler id found during an incremental call An invalid logger name Inability to resolve to an internal or external object Parsing is performed by the DictConfigurator class whose constructor is passed the dictionary used for configuration and has a configure method The logging config module has a callable attribute dictConfigClass which is initially set to DictConfigurator You can replace the value of dictConfigClass with a suitable implementation of your own dictConfig calls dictConfigClass passing the specified dictionary and then calls the configure method on the returned object to put the configuration into effect def dictConfig config dictConfigClass config configure For example a subclass of DictConfigurator could call DictConfigurator __init__ in its own __init__ then set up custom prefixes which would be usable in the subsequent configure call dictConfigClass would be bound to this new subclass and then dictConfig could be called exactly as in the default uncustomized state New in version 3 2 logging config fileConfig fname defaults None disable_existing_loggers True encoding None Reads the logging configuration from a configparser format file The format of the file should be as described in Configuration file format This function can be called several times from an application allowing an end user to select from various pre canned configurations if the developer provides a mechanism to present the choices and load the chosen configuration It will raise FileNotFoundError if the file doesn t exist and RuntimeError if the file is invalid or empty Parameters fname A filename or a file like object or an instance derived from RawConfigParser If a RawConfigParser derived instance is passed it is used as is Otherwise a ConfigParser is instantiated and the configuration read by it from the object passed in fname If that has a readline method it is assumed to be a file like object and read using read_file otherwise it is assumed to be a filename and passed to read defaults Defaults to be passed to the ConfigParser can be specified in this argument disable_existing_loggers If specified as False loggers which exist when this call is made are left enabled The default is True because this enables old behaviour in a backward compatible way This behaviour is to disable any existing non root loggers unless they or their ancestors are explicitly named in the logging configuration encoding The encoding used to open file when fname is filename Changed in version 3 4 An instance of a subclass of RawConfigParser is now accepted as a value for fname This facilitates Use of a configuration file where logging configuration is just part of the overall application configuration Use of a configuration read from a file and then modified by the using application e g based on command line parameters or other aspects of the runtime e,en
2649,nvironment before being passed to fileConfig Changed in version 3 10 Added the encoding parameter Changed in version 3 12 An exception will be thrown if the provided file doesn t exist or is invalid or empty logging config listen port DEFAULT_LOGGING_CONFIG_PORT verify None Starts up a socket server on the specified port and listens for new configurations If no port is specified the module s default DEFAULT_LOGGING_CONFIG_PORT is used Logging configurations will be sent as a file suitable for processing by dictConfig or fileConfig Returns a Thread instance on which you can call start to start the server and which you can join when appropriate To stop the server call stopListening The verify argument if specified should be a callable which should verify whether bytes received across the socket are valid and should be processed This could be done by encrypting and or signing what is sent across the socket such that the verify callable can perform signature verification and or decryption The verify callable is called with a single argument the bytes received across the socket and should return the bytes to be processed or None to indicate that the bytes should be discarded The returned bytes could be the same as the passed in bytes e g when only verification is done or they could be completely different perhaps if decryption were performed To send a configuration to the socket read in the configuration file and send it to the socket as a sequence of bytes preceded by a four byte length string packed in binary using struct pack L n Note Because portions of the configuration are passed through eval use of this function may open its users to a security risk While the function only binds to a socket on localhost and so does not accept connections from remote machines there are scenarios where untrusted code could be run under the account of the process which calls listen Specifically if the process calling listen runs on a multi user machine where users cannot trust each other then a malicious user could arrange to run essentially arbitrary code in a victim user s process simply by connecting to the victim s listen socket and sending a configuration which runs whatever code the attacker wants to have executed in the victim s process This is especially easy to do if the default port is used but not hard even if a different port is used To avoid the risk of this happening use the verify argument to listen to prevent unrecognised configurations from being applied Changed in version 3 4 The verify argument was added Note If you want to send configurations to the listener which don t disable existing loggers you will need to use a JSON format for the configuration which will use dictConfig for configuration This method allows you to specify disable_existing_loggers as False in the configuration you send logging config stopListening Stops the listening server which was created with a call to listen This is typically called before calling join on the return value from listen Security considerations The logging configuration functionality tries to offer convenience and in part this is done by offering the ability to convert text in configuration files into Python objects used in logging configuration for example as described in User defined objects However these same mechanisms importing callables from user defined modules and calling them with parameters from the configuration could be used to invoke any code you like and for this reason you should treat configuration files from untrusted sources with extreme caution and satisfy yourself that nothing bad can happen if you load them before actually loading them Configuration dictionary schema Describing a logging configuration requires listing the various objects to create and the connections between them for example you may create a handler named console and then say that the logger named startup will send its messages to the console handler These objects aren t limited to those provided by the logging module because you might write your own formatter or handler class The parameters t,en
2650,o these classes may also need to include external objects such as sys stderr The syntax for describing these objects and connections is defined in Object connections below Dictionary Schema Details The dictionary passed to dictConfig must contain the following keys version to be set to an integer value representing the schema version The only valid value at present is 1 but having this key allows the schema to evolve while still preserving backwards compatibility All other keys are optional but if present they will be interpreted as described below In all cases below where a configuring dict is mentioned it will be checked for the special key to see if a custom instantiation is required If so the mechanism described in User defined objects below is used to create an instance otherwise the context is used to determine what to instantiate formatters the corresponding value will be a dict in which each key is a formatter id and each value is a dict describing how to configure the corresponding Formatter instance The configuring dict is searched for the following optional keys which correspond to the arguments passed to create a Formatter object format datefmt style validate since version 3 8 defaults since version 3 12 An optional class key indicates the name of the formatter s class as a dotted module and class name The instantiation arguments are as for Formatter thus this key is most useful for instantiating a customised subclass of Formatter For example the alternative class might present exception tracebacks in an expanded or condensed format If your formatter requires different or extra configuration keys you should use User defined objects filters the corresponding value will be a dict in which each key is a filter id and each value is a dict describing how to configure the corresponding Filter instance The configuring dict is searched for the key name defaulting to the empty string and this is used to construct a logging Filter instance handlers the corresponding value will be a dict in which each key is a handler id and each value is a dict describing how to configure the corresponding Handler instance The configuring dict is searched for the following keys class mandatory This is the fully qualified name of the handler class level optional The level of the handler formatter optional The id of the formatter for this handler filters optional A list of ids of the filters for this handler Changed in version 3 11 filters can take filter instances in addition to ids All other keys are passed through as keyword arguments to the handler s constructor For example given the snippet handlers console class logging StreamHandler formatter brief level INFO filters allow_foo stream ext sys stdout file class logging handlers RotatingFileHandler formatter precise filename logconfig log maxBytes 1024 backupCount 3 the handler with id console is instantiated as a logging StreamHandler using sys stdout as the underlying stream The handler with id file is instantiated as a logging handlers RotatingFileHandler with the keyword arguments filename logconfig log maxBytes 1024 backupCount 3 loggers the corresponding value will be a dict in which each key is a logger name and each value is a dict describing how to configure the corresponding Logger instance The configuring dict is searched for the following keys level optional The level of the logger propagate optional The propagation setting of the logger filters optional A list of ids of the filters for this logger Changed in version 3 11 filters can take filter instances in addition to ids handlers optional A list of ids of the handlers for this logger The specified loggers will be configured according to the level propagation filters and handlers specified root this will be the configuration for the root logger Processing of the configuration will be as for any logger except that the propagate setting will not be applicable incremental whether the configuration is to be interpreted as incremental to the existing configuration This value defaults to False which means that the specified c,en
2651,onfiguration replaces the existing configuration with the same semantics as used by the existing fileConfig API If the specified value is True the configuration is processed as described in the section on Incremental Configuration disable_existing_loggers whether any existing non root loggers are to be disabled This setting mirrors the parameter of the same name in fileConfig If absent this parameter defaults to True This value is ignored if incremental is True Incremental Configuration It is difficult to provide complete flexibility for incremental configuration For example because objects such as filters and formatters are anonymous once a configuration is set up it is not possible to refer to such anonymous objects when augmenting a configuration Furthermore there is not a compelling case for arbitrarily altering the object graph of loggers handlers filters formatters at run time once a configuration is set up the verbosity of loggers and handlers can be controlled just by setting levels and in the case of loggers propagation flags Changing the object graph arbitrarily in a safe way is problematic in a multi threaded environment while not impossible the benefits are not worth the complexity it adds to the implementation Thus when the incremental key of a configuration dict is present and is True the system will completely ignore any formatters and filters entries and process only the level settings in the handlers entries and the level and propagate settings in the loggers and root entries Using a value in the configuration dict lets configurations to be sent over the wire as pickled dicts to a socket listener Thus the logging verbosity of a long running application can be altered over time with no need to stop and restart the application Object connections The schema describes a set of logging objects loggers handlers formatters filters which are connected to each other in an object graph Thus the schema needs to represent connections between the objects For example say that once configured a particular logger has attached to it a particular handler For the purposes of this discussion we can say that the logger represents the source and the handler the destination of a connection between the two Of course in the configured objects this is represented by the logger holding a reference to the handler In the configuration dict this is done by giving each destination object an id which identifies it unambiguously and then using the id in the source object s configuration to indicate that a connection exists between the source and the destination object with that id So for example consider the following YAML snippet formatters brief configuration for formatter with id brief goes here precise configuration for formatter with id precise goes here handlers h1 This is an id configuration of handler with id h1 goes here formatter brief h2 This is another id configuration of handler with id h2 goes here formatter precise loggers foo bar baz other configuration for logger foo bar baz handlers h1 h2 Note YAML used here because it s a little more readable than the equivalent Python source form for the dictionary The ids for loggers are the logger names which would be used programmatically to obtain a reference to those loggers e g foo bar baz The ids for Formatters and Filters can be any string value such as brief precise above and they are transient in that they are only meaningful for processing the configuration dictionary and used to determine connections between objects and are not persisted anywhere when the configuration call is complete The above snippet indicates that logger named foo bar baz should have two handlers attached to it which are described by the handler ids h1 and h2 The formatter for h1 is that described by id brief and the formatter for h2 is that described by id precise User defined objects The schema supports user defined objects for handlers filters and formatters Loggers do not need to have different types for different instances so there is no support in this configuration schema for user defined logge,en
2652,r classes Objects to be configured are described by dictionaries which detail their configuration In some places the logging system will be able to infer from the context how an object is to be instantiated but when a user defined object is to be instantiated the system will not know how to do this In order to provide complete flexibility for user defined object instantiation the user needs to provide a factory a callable which is called with a configuration dictionary and which returns the instantiated object This is signalled by an absolute import path to the factory being made available under the special key Here s a concrete example formatters brief format message s default format asctime s levelname 8s name 15s message s datefmt Y m d H M S custom my package customFormatterFactory bar baz spam 99 9 answer 42 The above YAML snippet defines three formatters The first with id brief is a standard logging Formatter instance with the specified format string The second with id default has a longer format and also defines the time format explicitly and will result in a logging Formatter initialized with those two format strings Shown in Python source form the brief and default formatters have configuration sub dictionaries format message s and format asctime s levelname 8s name 15s message s datefmt Y m d H M S respectively and as these dictionaries do not contain the special key the instantiation is inferred from the context as a result standard logging Formatter instances are created The configuration sub dictionary for the third formatter with id custom is my package customFormatterFactory bar baz spam 99 9 answer 42 and this contains the special key which means that user defined instantiation is wanted In this case the specified factory callable will be used If it is an actual callable it will be used directly otherwise if you specify a string as in the example the actual callable will be located using normal import mechanisms The callable will be called with the remaining items in the configuration sub dictionary as keyword arguments In the above example the formatter with id custom will be assumed to be returned by the call my package customFormatterFactory bar baz spam 99 9 answer 42 Warning The values for keys such as bar spam and answer in the above example should not be configuration dictionaries or references such as cfg foo or ext bar because they will not be processed by the configuration machinery but passed to the callable as is The key has been used as the special key because it is not a valid keyword parameter name and so will not clash with the names of the keyword arguments used in the call The also serves as a mnemonic that the corresponding value is a callable Changed in version 3 11 The filters member of handlers and loggers can take filter instances in addition to ids You can also specify a special key whose value is a dictionary is a mapping of attribute names to values If found the specified attributes will be set on the user defined object before it is returned Thus with the following configuration my package customFormatterFactory bar baz spam 99 9 answer 42 foo bar baz bozz the returned formatter will have attribute foo set to bar and attribute baz set to bozz Warning The values for attributes such as foo and baz in the above example should not be configuration dictionaries or references such as cfg foo or ext bar because they will not be processed by the configuration machinery but set as attribute values as is Handler configuration order Handlers are configured in alphabetical order of their keys and a configured handler replaces the configuration dictionary in a working copy of the handlers dictionary in the schema If you use a construct such as cfg handlers foo then initially handlers foo points to the configuration dictionary for the handler named foo and later once that handler has been configured it points to the configured handler instance Thus cfg handlers foo could resolve to either a dictionary or a handler instance In general it is wise to name handlers in a way such that dependent ha,en
2653,ndlers are configured _after_ any handlers they depend on that allows something like cfg handlers foo to be used in configuring a handler that depends on handler foo If that dependent handler were named bar problems would result because the configuration of bar would be attempted before that of foo and foo would not yet have been configured However if the dependent handler were named foobar it would be configured after foo with the result that cfg handlers foo would resolve to configured handler foo and not its configuration dictionary Access to external objects There are times where a configuration needs to refer to objects external to the configuration for example sys stderr If the configuration dict is constructed using Python code this is straightforward but a problem arises when the configuration is provided via a text file e g JSON YAML In a text file there is no standard way to distinguish sys stderr from the literal string sys stderr To facilitate this distinction the configuration system looks for certain special prefixes in string values and treat them specially For example if the literal string ext sys stderr is provided as a value in the configuration then the ext will be stripped off and the remainder of the value processed using normal import mechanisms The handling of such prefixes is done in a way analogous to protocol handling there is a generic mechanism to look for prefixes which match the regular expression P prefix a z P suffix whereby if the prefix is recognised the suffix is processed in a prefix dependent manner and the result of the processing replaces the string value If the prefix is not recognised then the string value will be left as is Access to internal objects As well as external objects there is sometimes also a need to refer to objects in the configuration This will be done implicitly by the configuration system for things that it knows about For example the string value DEBUG for a level in a logger or handler will automatically be converted to the value logging DEBUG and the handlers filters and formatter entries will take an object id and resolve to the appropriate destination object However a more generic mechanism is needed for user defined objects which are not known to the logging module For example consider logging handlers MemoryHandler which takes a target argument which is another handler to delegate to Since the system already knows about this class then in the configuration the given target just needs to be the object id of the relevant target handler and the system will resolve to the handler from the id If however a user defines a my package MyHandler which has an alternate handler the configuration system would not know that the alternate referred to a handler To cater for this a generic resolution system allows the user to specify handlers file configuration of file handler goes here custom my package MyHandler alternate cfg handlers file The literal string cfg handlers file will be resolved in an analogous way to strings with the ext prefix but looking in the configuration itself rather than the import namespace The mechanism allows access by dot or by index in a similar way to that provided by str format Thus given the following snippet handlers email class logging handlers SMTPHandler mailhost localhost fromaddr my_app domain tld toaddrs support_team domain tld dev_team domain tld subject Houston we have a problem in the configuration the string cfg handlers would resolve to the dict with key handlers the string cfg handlers email would resolve to the dict with key email in the handlers dict and so on The string cfg handlers email toaddrs 1 would resolve to dev_team domain tld and the string cfg handlers email toaddrs 0 would resolve to the value support_team domain tld The subject value could be accessed using either cfg handlers email subject or equivalently cfg handlers email subject The latter form only needs to be used if the key contains spaces or non alphanumeric characters If an index value consists only of decimal digits access will be attempted using the cor,en
2654,responding integer value falling back to the string value if needed Given a string cfg handlers myhandler mykey 123 this will resolve to config_dict handlers myhandler mykey 123 If the string is specified as cfg handlers myhandler mykey 123 the system will attempt to retrieve the value from config_dict handlers myhandler mykey 123 and fall back to config_dict handlers myhandler mykey 123 if that fails Import resolution and custom importers Import resolution by default uses the builtin __import__ function to do its importing You may want to replace this with your own importing mechanism if so you can replace the importer attribute of the DictConfigurator or its superclass the BaseConfigurator class However you need to be careful because of the way functions are accessed from classes via descriptors If you are using a Python callable to do your imports and you want to define it at class level rather than instance level you need to wrap it with staticmethod For example from importlib import import_module from logging config import BaseConfigurator BaseConfigurator importer staticmethod import_module You don t need to wrap with staticmethod if you re setting the import callable on a configurator instance Configuring QueueHandler and QueueListener If you want to configure a QueueHandler noting that this is normally used in conjunction with a QueueListener you can configure both together After the configuration the QueueListener instance will be available as the listener attribute of the created handler and that in turn will be available to you using getHandlerByName and passing the name you have used for the QueueHandler in your configuration The dictionary schema for configuring the pair is shown in the example YAML snippet below handlers qhand class logging handlers QueueHandler queue my module queue_factory listener my package CustomListener handlers hand_name_1 hand_name_2 The queue and listener keys are optional If the queue key is present the corresponding value can be one of the following An actual instance of queue Queue or a subclass thereof This is of course only possible if you are constructing or modifying the configuration dictionary in code A string that resolves to a callable which when called with no arguments returns the queue Queue instance to use That callable could be a queue Queue subclass or a function which returns a suitable queue instance such as my module queue_factory A dict with a key which is constructed in the usual way as discussed in User defined objects The result of this construction should be a queue Queue instance If the queue key is absent a standard unbounded queue Queue instance is created and used If the listener key is present the corresponding value can be one of the following A subclass of logging handlers QueueListener This is of course only possible if you are constructing or modifying the configuration dictionary in code A string which resolves to a class which is a subclass of QueueListener such as my package CustomListener A dict with a key which is constructed in the usual way as discussed in User defined objects The result of this construction should be a callable with the same signature as the QueueListener initializer If the listener key is absent logging handlers QueueListener is used The values under the handlers key are the names of other handlers in the configuration not shown in the above snippet which will be passed to the queue listener Any custom queue handler and listener classes will need to be defined with the same initialization signatures as QueueHandler and QueueListener New in version 3 12 Configuration file format The configuration file format understood by fileConfig is based on configparser functionality The file must contain sections called loggers handlers and formatters which identify by name the entities of each type which are defined in the file For each such entity there is a separate section which identifies how that entity is configured Thus for a logger named log01 in the loggers section the relevant configuration details are held in a section logg,en
2655,er_log01 Similarly a handler called hand01 in the handlers section will have its configuration held in a section called handler_hand01 while a formatter called form01 in the formatters section will have its configuration specified in a section called formatter_form01 The root logger configuration must be specified in a section called logger_root Note The fileConfig API is older than the dictConfig API and does not provide functionality to cover certain aspects of logging For example you cannot configure Filter objects which provide for filtering of messages beyond simple integer levels using fileConfig If you need to have instances of Filter in your logging configuration you will need to use dictConfig Note that future enhancements to configuration functionality will be added to dictConfig so it s worth considering transitioning to this newer API when it s convenient to do so Examples of these sections in the file are given below loggers keys root log02 log03 log04 log05 log06 log07 handlers keys hand01 hand02 hand03 hand04 hand05 hand06 hand07 hand08 hand09 formatters keys form01 form02 form03 form04 form05 form06 form07 form08 form09 The root logger must specify a level and a list of handlers An example of a root logger section is given below logger_root level NOTSET handlers hand01 The level entry can be one of DEBUG INFO WARNING ERROR CRITICAL or NOTSET For the root logger only NOTSET means that all messages will be logged Level values are evaluated in the context of the logging package s namespace The handlers entry is a comma separated list of handler names which must appear in the handlers section These names must appear in the handlers section and have corresponding sections in the configuration file For loggers other than the root logger some additional information is required This is illustrated by the following example logger_parser level DEBUG handlers hand01 propagate 1 qualname compiler parser The level and handlers entries are interpreted as for the root logger except that if a non root logger s level is specified as NOTSET the system consults loggers higher up the hierarchy to determine the effective level of the logger The propagate entry is set to 1 to indicate that messages must propagate to handlers higher up the logger hierarchy from this logger or 0 to indicate that messages are not propagated to handlers up the hierarchy The qualname entry is the hierarchical channel name of the logger that is to say the name used by the application to get the logger Sections which specify handler configuration are exemplified by the following handler_hand01 class StreamHandler level NOTSET formatter form01 args sys stdout The class entry indicates the handler s class as determined by eval in the logging package s namespace The level is interpreted as for loggers and NOTSET is taken to mean log everything The formatter entry indicates the key name of the formatter for this handler If blank a default formatter logging _defaultFormatter is used If a name is specified it must appear in the formatters section and have a corresponding section in the configuration file The args entry when evaluated in the context of the logging package s namespace is the list of arguments to the constructor for the handler class Refer to the constructors for the relevant handlers or to the examples below to see how typical entries are constructed If not provided it defaults to The optional kwargs entry when evaluated in the context of the logging package s namespace is the keyword argument dict to the constructor for the handler class If not provided it defaults to handler_hand02 class FileHandler level DEBUG formatter form02 args python log w handler_hand03 class handlers SocketHandler level INFO formatter form03 args localhost handlers DEFAULT_TCP_LOGGING_PORT handler_hand04 class handlers DatagramHandler level WARN formatter form04 args localhost handlers DEFAULT_UDP_LOGGING_PORT handler_hand05 class handlers SysLogHandler level ERROR formatter form05 args localhost handlers SYSLOG_UDP_PORT handlers SysLogHandler LOG_USER handler_hand,en
2656,06 class handlers NTEventLogHandler level CRITICAL formatter form06 args Python Application Application handler_hand07 class handlers SMTPHandler level WARN formatter form07 args localhost from abc user1 abc user2 xyz Logger Subject kwargs timeout 10 0 handler_hand08 class handlers MemoryHandler level NOTSET formatter form08 target args 10 ERROR handler_hand09 class handlers HTTPHandler level NOTSET formatter form09 args localhost 9022 log GET kwargs secure True Sections which specify formatter configuration are typified by the following formatter_form01 format F1 asctime s levelname s message s customfield s datefmt style validate True defaults customfield defaultvalue class logging Formatter The arguments for the formatter configuration are the same as the keys in the dictionary schema formatters section The defaults entry when evaluated in the context of the logging package s namespace is a dictionary of default values for custom formatting fields If not provided it defaults to None Note Due to the use of eval as described above there are potential security risks which result from using the listen to send and receive configurations via sockets The risks are limited to where multiple users with no mutual trust run code on the same machine see the listen documentation for more information See also Module logging API reference for the logging module Module logging handlers Useful handlers included with the logging module,en
2657,gc Garbage Collector interface This module provides an interface to the optional garbage collector It provides the ability to disable the collector tune the collection frequency and set debugging options It also provides access to unreachable objects that the collector found but cannot free Since the collector supplements the reference counting already used in Python you can disable the collector if you are sure your program does not create reference cycles Automatic collection can be disabled by calling gc disable To debug a leaking program call gc set_debug gc DEBUG_LEAK Notice that this includes gc DEBUG_SAVEALL causing garbage collected objects to be saved in gc garbage for inspection The gc module provides the following functions gc enable Enable automatic garbage collection gc disable Disable automatic garbage collection gc isenabled Return True if automatic collection is enabled gc collect generation 2 With no arguments run a full collection The optional argument generation may be an integer specifying which generation to collect from 0 to 2 A ValueError is raised if the generation number is invalid The number of unreachable objects found is returned The free lists maintained for a number of built in types are cleared whenever a full collection or collection of the highest generation 2 is run Not all items in some free lists may be freed due to the particular implementation in particular float The effect of calling gc collect while the interpreter is already performing a collection is undefined gc set_debug flags Set the garbage collection debugging flags Debugging information will be written to sys stderr See below for a list of debugging flags which can be combined using bit operations to control debugging gc get_debug Return the debugging flags currently set gc get_objects generation None Returns a list of all objects tracked by the collector excluding the list returned If generation is not None return only the objects tracked by the collector that are in that generation Changed in version 3 8 New generation parameter Raises an auditing event gc get_objects with argument generation gc get_stats Return a list of three per generation dictionaries containing collection statistics since interpreter start The number of keys may change in the future but currently each dictionary will contain the following items collections is the number of times this generation was collected collected is the total number of objects collected inside this generation uncollectable is the total number of objects which were found to be uncollectable and were therefore moved to the garbage list inside this generation New in version 3 4 gc set_threshold threshold0 threshold1 threshold2 Set the garbage collection thresholds the collection frequency Setting threshold0 to zero disables collection The GC classifies objects into three generations depending on how many collection sweeps they have survived New objects are placed in the youngest generation generation 0 If an object survives a collection it is moved into the next older generation Since generation 2 is the oldest generation objects in that generation remain there after a collection In order to decide when to run the collector keeps track of the number object allocations and deallocations since the last collection When the number of allocations minus the number of deallocations exceeds threshold0 collection starts Initially only generation 0 is examined If generation 0 has been examined more than threshold1 times since generation 1 has been examined then generation 1 is examined as well With the third generation things are a bit more complicated see Collecting the oldest generation for more information gc get_count Return the current collection counts as a tuple of count0 count1 count2 gc get_threshold Return the current collection thresholds as a tuple of threshold0 threshold1 threshold2 gc get_referrers objs Return the list of objects that directly refer to any of objs This function will only locate those containers which support garbage collection extension types which do refer to ,en
2658,other objects but do not support garbage collection will not be found Note that objects which have already been dereferenced but which live in cycles and have not yet been collected by the garbage collector can be listed among the resulting referrers To get only currently live objects call collect before calling get_referrers Warning Care must be taken when using objects returned by get_referrers because some of them could still be under construction and hence in a temporarily invalid state Avoid using get_referrers for any purpose other than debugging Raises an auditing event gc get_referrers with argument objs gc get_referents objs Return a list of objects directly referred to by any of the arguments The referents returned are those objects visited by the arguments C level tp_traverse methods if any and may not be all objects actually directly reachable tp_traverse methods are supported only by objects that support garbage collection and are only required to visit objects that may be involved in a cycle So for example if an integer is directly reachable from an argument that integer object may or may not appear in the result list Raises an auditing event gc get_referents with argument objs gc is_tracked obj Returns True if the object is currently tracked by the garbage collector False otherwise As a general rule instances of atomic types aren t tracked and instances of non atomic types containers user defined objects are However some type specific optimizations can be present in order to suppress the garbage collector footprint of simple instances e g dicts containing only atomic keys and values gc is_tracked 0 False gc is_tracked a False gc is_tracked True gc is_tracked False gc is_tracked a 1 False gc is_tracked a True New in version 3 1 gc is_finalized obj Returns True if the given object has been finalized by the garbage collector False otherwise x None class Lazarus def __del__ self global x x self lazarus Lazarus gc is_finalized lazarus False del lazarus gc is_finalized x True New in version 3 9 gc freeze Freeze all the objects tracked by the garbage collector move them to a permanent generation and ignore them in all the future collections If a process will fork without exec avoiding unnecessary copy on write in child processes will maximize memory sharing and reduce overall memory usage This requires both avoiding creation of freed holes in memory pages in the parent process and ensuring that GC collections in child processes won t touch the gc_refs counter of long lived objects originating in the parent process To accomplish both call gc disable early in the parent process gc freeze right before fork and gc enable early in child processes New in version 3 7 gc unfreeze Unfreeze the objects in the permanent generation put them back into the oldest generation New in version 3 7 gc get_freeze_count Return the number of objects in the permanent generation New in version 3 7 The following variables are provided for read only access you can mutate the values but should not rebind them gc garbage A list of objects which the collector found to be unreachable but could not be freed uncollectable objects Starting with Python 3 4 this list should be empty most of the time except when using instances of C extension types with a non NULL tp_del slot If DEBUG_SAVEALL is set then all unreachable objects will be added to this list rather than freed Changed in version 3 2 If this list is non empty at interpreter shutdown a ResourceWarning is emitted which is silent by default If DEBUG_UNCOLLECTABLE is set in addition all uncollectable objects are printed Changed in version 3 4 Following PEP 442 objects with a __del__ method don t end up in gc garbage anymore gc callbacks A list of callbacks that will be invoked by the garbage collector before and after collection The callbacks will be called with two arguments phase and info phase can be one of two values start The garbage collection is about to start stop The garbage collection has finished info is a dict providing more information for the callback The following keys are curr,en
2659,ently defined generation The oldest generation being collected collected When phase is stop the number of objects successfully collected uncollectable When phase is stop the number of objects that could not be collected and were put in garbage Applications can add their own callbacks to this list The primary use cases are Gathering statistics about garbage collection such as how often various generations are collected and how long the collection takes Allowing applications to identify and clear their own uncollectable types when they appear in garbage New in version 3 3 The following constants are provided for use with set_debug gc DEBUG_STATS Print statistics during collection This information can be useful when tuning the collection frequency gc DEBUG_COLLECTABLE Print information on collectable objects found gc DEBUG_UNCOLLECTABLE Print information of uncollectable objects found objects which are not reachable but cannot be freed by the collector These objects will be added to the garbage list Changed in version 3 2 Also print the contents of the garbage list at interpreter shutdown if it isn t empty gc DEBUG_SAVEALL When set all unreachable objects found will be appended to garbage rather than being freed This can be useful for debugging a leaking program gc DEBUG_LEAK The debugging flags necessary for the collector to print information about a leaking program equal to DEBUG_COLLECTABLE DEBUG_UNCOLLECTABLE DEBUG_SAVEALL,en
2660,The Python Profilers Source code Lib profile py and Lib pstats py Introduction to the profilers cProfile and profile provide deterministic profiling of Python programs A profile is a set of statistics that describes how often and for how long various parts of the program executed These statistics can be formatted into reports via the pstats module The Python standard library provides two different implementations of the same profiling interface 1 cProfile is recommended for most users it s a C extension with reasonable overhead that makes it suitable for profiling long running programs Based on lsprof contributed by Brett Rosen and Ted Czotter 2 profile a pure Python module whose interface is imitated by cProfile but which adds significant overhead to profiled programs If you re trying to extend the profiler in some way the task might be easier with this module Originally designed and written by Jim Roskind Note The profiler modules are designed to provide an execution profile for a given program not for benchmarking purposes for that there is timeit for reasonably accurate results This particularly applies to benchmarking Python code against C code the profilers introduce overhead for Python code but not for C level functions and so the C code would seem faster than any Python one Instant User s Manual This section is provided for users that don t want to read the manual It provides a very brief overview and allows a user to rapidly perform profiling on an existing application To profile a function that takes a single argument you can do import cProfile import re cProfile run re compile foo bar Use profile instead of cProfile if the latter is not available on your system The above action would run re compile and print profile results like the following 214 function calls 207 primitive calls in 0 002 seconds Ordered by cumulative time ncalls tottime percall cumtime percall filename lineno function 1 0 000 0 000 0 002 0 002 built in method builtins exec 1 0 000 0 000 0 001 0 001 string 1 module 1 0 000 0 000 0 001 0 001 __init__ py 250 compile 1 0 000 0 000 0 001 0 001 __init__ py 289 _compile 1 0 000 0 000 0 000 0 000 _compiler py 759 compile 1 0 000 0 000 0 000 0 000 _parser py 937 parse 1 0 000 0 000 0 000 0 000 _compiler py 598 _code 1 0 000 0 000 0 000 0 000 _parser py 435 _parse_sub The first line indicates that 214 calls were monitored Of those calls 207 were primitive meaning that the call was not induced via recursion The next line Ordered by cumulative time indicates the output is sorted by the cumtime values The column headings include ncalls for the number of calls tottime for the total time spent in the given function and excluding time made in calls to sub functions percall is the quotient of tottime divided by ncalls cumtime is the cumulative time spent in this and all subfunctions from invocation till exit This figure is accurate even for recursive functions percall is the quotient of cumtime divided by primitive calls filename lineno function provides the respective data of each function When there are two numbers in the first column for example 3 1 it means that the function recursed The second value is the number of primitive calls and the former is the total number of calls Note that when the function does not recurse these two values are the same and only the single figure is printed Instead of printing the output at the end of the profile run you can save the results to a file by specifying a filename to the run function import cProfile import re cProfile run re compile foo bar restats The pstats Stats class reads profile results from a file and formats them in various ways The files cProfile and profile can also be invoked as a script to profile another script For example python m cProfile o output_file s sort_order m module myscript py o writes the profile results to a file instead of to stdout s specifies one of the sort_stats sort values to sort the output by This only applies when o is not supplied m specifies that a module is being profiled instead of a script New in version 3 7 Added the m opt,en
2661,ion to cProfile New in version 3 8 Added the m option to profile The pstats module s Stats class has a variety of methods for manipulating and printing the data saved into a profile results file import pstats from pstats import SortKey p pstats Stats restats p strip_dirs sort_stats 1 print_stats The strip_dirs method removed the extraneous path from all the module names The sort_stats method sorted all the entries according to the standard module line name string that is printed The print_stats method printed out all the statistics You might try the following sort calls p sort_stats SortKey NAME p print_stats The first call will actually sort the list by function name and the second call will print out the statistics The following are some interesting calls to experiment with p sort_stats SortKey CUMULATIVE print_stats 10 This sorts the profile by cumulative time in a function and then only prints the ten most significant lines If you want to understand what algorithms are taking time the above line is what you would use If you were looking to see what functions were looping a lot and taking a lot of time you would do p sort_stats SortKey TIME print_stats 10 to sort according to time spent within each function and then print the statistics for the top ten functions You might also try p sort_stats SortKey FILENAME print_stats __init__ This will sort all the statistics by file name and then print out statistics for only the class init methods since they are spelled with __init__ in them As one final example you could try p sort_stats SortKey TIME SortKey CUMULATIVE print_stats 5 init This line sorts statistics with a primary key of time and a secondary key of cumulative time and then prints out some of the statistics To be specific the list is first culled down to 50 re 5 of its original size then only lines containing init are maintained and that sub sub list is printed If you wondered what functions called the above functions you could now p is still sorted according to the last criteria do p print_callers 5 init and you would get a list of callers for each of the listed functions If you want more functionality you re going to have to read the manual or guess what the following functions do p print_callees p add restats Invoked as a script the pstats module is a statistics browser for reading and examining profile dumps It has a simple line oriented interface implemented using cmd and interactive help profile and cProfile Module Reference Both the profile and cProfile modules provide the following functions profile run command filename None sort 1 This function takes a single argument that can be passed to the exec function and an optional file name In all cases this routine executes exec command __main__ __dict__ __main__ __dict__ and gathers profiling statistics from the execution If no file name is present then this function automatically creates a Stats instance and prints a simple profiling report If the sort value is specified it is passed to this Stats instance to control how the results are sorted profile runctx command globals locals filename None sort 1 This function is similar to run with added arguments to supply the globals and locals dictionaries for the command string This routine executes exec command globals locals and gathers profiling statistics as in the run function above class profile Profile timer None timeunit 0 0 subcalls True builtins True This class is normally only used if more precise control over profiling is needed than what the cProfile run function provides A custom timer can be supplied for measuring how long code takes to run via the timer argument This must be a function that returns a single number representing the current time If the number is an integer the timeunit specifies a multiplier that specifies the duration of each unit of time For example if the timer returns times measured in thousands of seconds the time unit would be 001 Directly using the Profile class allows formatting profile results without writing the profile data to a file import cProfile pstats io from pstats imp,en
2662,ort SortKey pr cProfile Profile pr enable do something pr disable s io StringIO sortby SortKey CUMULATIVE ps pstats Stats pr stream s sort_stats sortby ps print_stats print s getvalue The Profile class can also be used as a context manager supported only in cProfile module see Context Manager Types import cProfile with cProfile Profile as pr do something pr print_stats Changed in version 3 8 Added context manager support enable Start collecting profiling data Only in cProfile disable Stop collecting profiling data Only in cProfile create_stats Stop collecting profiling data and record the results internally as the current profile print_stats sort 1 Create a Stats object based on the current profile and print the results to stdout dump_stats filename Write the results of the current profile to filename run cmd Profile the cmd via exec runctx cmd globals locals Profile the cmd via exec with the specified global and local environment runcall func args kwargs Profile func args kwargs Note that profiling will only work if the called command function actually returns If the interpreter is terminated e g via a sys exit call during the called command function execution no profiling results will be printed The Stats Class Analysis of the profiler data is done using the Stats class class pstats Stats filenames or profile stream sys stdout This class constructor creates an instance of a statistics object from a filename or list of filenames or from a Profile instance Output will be printed to the stream specified by stream The file selected by the above constructor must have been created by the corresponding version of profile or cProfile To be specific there is no file compatibility guaranteed with future versions of this profiler and there is no compatibility with files produced by other profilers or the same profiler run on a different operating system If several files are provided all the statistics for identical functions will be coalesced so that an overall view of several processes can be considered in a single report If additional files need to be combined with data in an existing Stats object the add method can be used Instead of reading the profile data from a file a cProfile Profile or profile Profile object can be used as the profile data source Stats objects have the following methods strip_dirs This method for the Stats class removes all leading path information from file names It is very useful in reducing the size of the printout to fit within close to 80 columns This method modifies the object and the stripped information is lost After performing a strip operation the object is considered to have its entries in a random order as it was just after object initialization and loading If strip_dirs causes two function names to be indistinguishable they are on the same line of the same filename and have the same function name then the statistics for these two entries are accumulated into a single entry add filenames This method of the Stats class accumulates additional profiling information into the current profiling object Its arguments should refer to filenames created by the corresponding version of profile run or cProfile run Statistics for identically named re file line name functions are automatically accumulated into single function statistics dump_stats filename Save the data loaded into the Stats object to a file named filename The file is created if it does not exist and is overwritten if it already exists This is equivalent to the method of the same name on the profile Profile and cProfile Profile classes sort_stats keys This method modifies the Stats object by sorting it according to the supplied criteria The argument can be either a string or a SortKey enum identifying the basis of a sort example time name SortKey TIME or SortKey NAME The SortKey enums argument have advantage over the string argument in that it is more robust and less error prone When more than one key is provided then additional keys are used as secondary criteria when there is equality in all keys selected before them For example sort_stat,en
2663,s SortKey NAME SortKey FILE will sort all the entries according to their function name and resolve all ties identical function names by sorting by file name For the string argument abbreviations can be used for any key names as long as the abbreviation is unambiguous The following are the valid string and SortKey Valid String Arg Valid enum Arg Meaning calls SortKey CALLS call count cumulative SortKey CUMULATIVE cumulative time cumtime N A cumulative time file N A file name filename SortKey FILENAME file name module N A file name ncalls N A call count pcalls SortKey PCALLS primitive call count line SortKey LINE line number name SortKey NAME function name nfl SortKey NFL name file line stdname SortKey STDNAME standard name time SortKey TIME internal time tottime N A internal time Note that all sorts on statistics are in descending order placing most time consuming items first where as name file and line number searches are in ascending order alphabetical The subtle distinction between SortKey NFL and SortKey STDNAME is that the standard name is a sort of the name as printed which means that the embedded line numbers get compared in an odd way For example lines 3 20 and 40 would if the file names were the same appear in the string order 20 3 and 40 In contrast SortKey NFL does a numeric compare of the line numbers In fact sort_stats SortKey NFL is the same as sort_stats SortKey NAME SortKey FILENAME SortKey LINE For backward compatibility reasons the numeric arguments 1 0 1 and 2 are permitted They are interpreted as stdname calls time and cumulative respectively If this old style format numeric is used only one sort key the numeric key will be used and additional arguments will be silently ignored New in version 3 7 Added the SortKey enum reverse_order This method for the Stats class reverses the ordering of the basic list within the object Note that by default ascending vs descending order is properly selected based on the sort key of choice print_stats restrictions This method for the Stats class prints out a report as described in the profile run definition The order of the printing is based on the last sort_stats operation done on the object subject to caveats in add and strip_dirs The arguments provided if any can be used to limit the list down to the significant entries Initially the list is taken to be the complete set of profiled functions Each restriction is either an integer to select a count of lines or a decimal fraction between 0 0 and 1 0 inclusive to select a percentage of lines or a string that will interpreted as a regular expression to pattern match the standard name that is printed If several restrictions are provided then they are applied sequentially For example print_stats 1 foo would first limit the printing to first 10 of list and then only print functions that were part of filename foo In contrast the command print_stats foo 1 would limit the list to all functions having file names foo and then proceed to only print the first 10 of them print_callers restrictions This method for the Stats class prints a list of all functions that called each function in the profiled database The ordering is identical to that provided by print_stats and the definition of the restricting argument is also identical Each caller is reported on its own line The format differs slightly depending on the profiler that produced the stats With profile a number is shown in parentheses after each caller to show how many times this specific call was made For convenience a second non parenthesized number repeats the cumulative time spent in the function at the right With cProfile each caller is preceded by three numbers the number of times this specific call was made and the total and cumulative times spent in the current function while it was invoked by this specific caller print_callees restrictions This method for the Stats class prints a list of all function that were called by the indicated function Aside from this reversal of direction of calls re called vs was called by the arguments and ordering are identical to the prin,en
2664,t_callers method get_stats_profile This method returns an instance of StatsProfile which contains a mapping of function names to instances of FunctionProfile Each FunctionProfile instance holds information related to the function s profile such as how long the function took to run how many times it was called etc New in version 3 9 Added the following dataclasses StatsProfile FunctionProfile Added the following function get_stats_profile What Is Deterministic Profiling Deterministic profiling is meant to reflect the fact that all function call function return and exception events are monitored and precise timings are made for the intervals between these events during which time the user s code is executing In contrast statistical profiling which is not done by this module randomly samples the effective instruction pointer and deduces where time is being spent The latter technique traditionally involves less overhead as the code does not need to be instrumented but provides only relative indications of where time is being spent In Python since there is an interpreter active during execution the presence of instrumented code is not required in order to do deterministic profiling Python automatically provides a hook optional callback for each event In addition the interpreted nature of Python tends to add so much overhead to execution that deterministic profiling tends to only add small processing overhead in typical applications The result is that deterministic profiling is not that expensive yet provides extensive run time statistics about the execution of a Python program Call count statistics can be used to identify bugs in code surprising counts and to identify possible inline expansion points high call counts Internal time statistics can be used to identify hot loops that should be carefully optimized Cumulative time statistics should be used to identify high level errors in the selection of algorithms Note that the unusual handling of cumulative times in this profiler allows statistics for recursive implementations of algorithms to be directly compared to iterative implementations Limitations One limitation has to do with accuracy of timing information There is a fundamental problem with deterministic profilers involving accuracy The most obvious restriction is that the underlying clock is only ticking at a rate typically of about 001 seconds Hence no measurements will be more accurate than the underlying clock If enough measurements are taken then the error will tend to average out Unfortunately removing this first error induces a second source of error The second problem is that it takes a while from when an event is dispatched until the profiler s call to get the time actually gets the state of the clock Similarly there is a certain lag when exiting the profiler event handler from the time that the clock s value was obtained and then squirreled away until the user s code is once again executing As a result functions that are called many times or call many functions will typically accumulate this error The error that accumulates in this fashion is typically less than the accuracy of the clock less than one clock tick but it can accumulate and become very significant The problem is more important with profile than with the lower overhead cProfile For this reason profile provides a means of calibrating itself for a given platform so that this error can be probabilistically on the average removed After the profiler is calibrated it will be more accurate in a least square sense but it will sometimes produce negative numbers when call counts are exceptionally low and the gods of probability work against you Do not be alarmed by negative numbers in the profile They should only appear if you have calibrated your profiler and the results are actually better than without calibration Calibration The profiler of the profile module subtracts a constant from each event handling time to compensate for the overhead of calling the time function and socking away the results By default the constant is 0 The following procedure can b,en
2665,e used to obtain a better constant for a given platform see Limitations import profile pr profile Profile for i in range 5 print pr calibrate 10000 The method executes the number of Python calls given by the argument directly and again under the profiler measuring the time for both It then computes the hidden overhead per profiler event and returns that as a float For example on a 1 8Ghz Intel Core i5 running macOS and using Python s time process_time as the timer the magical number is about 4 04e 6 The object of this exercise is to get a fairly consistent result If your computer is very fast or your timer function has poor resolution you might have to pass 100000 or even 1000000 to get consistent results When you have a consistent answer there are three ways you can use it import profile 1 Apply computed bias to all Profile instances created hereafter profile Profile bias your_computed_bias 2 Apply computed bias to a specific Profile instance pr profile Profile pr bias your_computed_bias 3 Specify computed bias in instance constructor pr profile Profile bias your_computed_bias If you have a choice you are better off choosing a smaller constant and then your results will less often show up as negative in profile statistics Using a custom timer If you want to change how current time is determined for example to force use of wall clock time or elapsed process time pass the timing function you want to the Profile class constructor pr profile Profile your_time_func The resulting profiler will then call your_time_func Depending on whether you are using profile Profile or cProfile Profile your_time_func s return value will be interpreted differently profile Profile your_time_func should return a single number or a list of numbers whose sum is the current time like what os times returns If the function returns a single time number or the list of returned numbers has length 2 then you will get an especially fast version of the dispatch routine Be warned that you should calibrate the profiler class for the timer function that you choose see Calibration For most machines a timer that returns a lone integer value will provide the best results in terms of low overhead during profiling os times is pretty bad as it returns a tuple of floating point values If you want to substitute a better timer in the cleanest fashion derive a class and hardwire a replacement dispatch method that best handles your timer call along with the appropriate calibration constant cProfile Profile your_time_func should return a single number If it returns integers you can also invoke the class constructor with a second argument specifying the real duration of one unit of time For example if your_integer_time_func returns times measured in thousands of seconds you would construct the Profile instance as follows pr cProfile Profile your_integer_time_func 0 001 As the cProfile Profile class cannot be calibrated custom timer functions should be used with care and should be as fast as possible For the best results with a custom timer it might be necessary to hard code it in the C source of the internal _lsprof module Python 3 3 adds several new functions in time that can be used to make precise measurements of process or wall clock time For example see time perf_counter,en
2666,ssl TLS SSL wrapper for socket objects Source code Lib ssl py This module provides access to Transport Layer Security often known as Secure Sockets Layer encryption and peer authentication facilities for network sockets both client side and server side This module uses the OpenSSL library It is available on all modern Unix systems Windows macOS and probably additional platforms as long as OpenSSL is installed on that platform Note Some behavior may be platform dependent since calls are made to the operating system socket APIs The installed version of OpenSSL may also cause variations in behavior For example TLSv1 3 comes with OpenSSL version 1 1 1 Warning Don t use this module without reading the Security considerations Doing so may lead to a false sense of security as the default settings of the ssl module are not necessarily appropriate for your application Availability not Emscripten not WASI This module does not work or is not available on WebAssembly platforms wasm32 emscripten and wasm32 wasi See WebAssembly platforms for more information This section documents the objects and functions in the ssl module for more general information about TLS SSL and certificates the reader is referred to the documents in the See Also section at the bottom This module provides a class ssl SSLSocket which is derived from the socket socket type and provides a socket like wrapper that also encrypts and decrypts the data going over the socket with SSL It supports additional methods such as getpeercert which retrieves the certificate of the other side of the connection and cipher which retrieves the cipher being used for the secure connection For more sophisticated applications the ssl SSLContext class helps manage settings and certificates which can then be inherited by SSL sockets created through the SSLContext wrap_socket method Changed in version 3 5 3 Updated to support linking with OpenSSL 1 1 0 Changed in version 3 6 OpenSSL 0 9 8 1 0 0 and 1 0 1 are deprecated and no longer supported In the future the ssl module will require at least OpenSSL 1 0 2 or 1 1 0 Changed in version 3 10 PEP 644 has been implemented The ssl module requires OpenSSL 1 1 1 or newer Use of deprecated constants and functions result in deprecation warnings Functions Constants and Exceptions Socket creation Instances of SSLSocket must be created using the SSLContext wrap_socket method The helper function create_default_context returns a new context with secure default settings Client socket example with default context and IPv4 IPv6 dual stack import socket import ssl hostname www python org context ssl create_default_context with socket create_connection hostname 443 as sock with context wrap_socket sock server_hostname hostname as ssock print ssock version Client socket example with custom context and IPv4 hostname www python org PROTOCOL_TLS_CLIENT requires valid cert chain and hostname context ssl SSLContext ssl PROTOCOL_TLS_CLIENT context load_verify_locations path to cabundle pem with socket socket socket AF_INET socket SOCK_STREAM 0 as sock with context wrap_socket sock server_hostname hostname as ssock print ssock version Server socket example listening on localhost IPv4 context ssl SSLContext ssl PROTOCOL_TLS_SERVER context load_cert_chain path to certchain pem path to private key with socket socket socket AF_INET socket SOCK_STREAM 0 as sock sock bind 127 0 0 1 8443 sock listen 5 with context wrap_socket sock server_side True as ssock conn addr ssock accept Context creation A convenience function helps create SSLContext objects for common purposes ssl create_default_context purpose Purpose SERVER_AUTH cafile None capath None cadata None Return a new SSLContext object with default settings for the given purpose The settings are chosen by the ssl module and usually represent a higher security level than when calling the SSLContext constructor directly cafile capath cadata represent optional CA certificates to trust for certificate verification as in SSLContext load_verify_locations If all three are None this function can choose to trust the system s de,en
2667,fault CA certificates instead The settings are PROTOCOL_TLS_CLIENT or PROTOCOL_TLS_SERVER OP_NO_SSLv2 and OP_NO_SSLv3 with high encryption cipher suites without RC4 and without unauthenticated cipher suites Passing SERVER_AUTH as purpose sets verify_mode to CERT_REQUIRED and either loads CA certificates when at least one of cafile capath or cadata is given or uses SSLContext load_default_certs to load default CA certificates When keylog_filename is supported and the environment variable SSLKEYLOGFILE is set create_default_context enables key logging Note The protocol options cipher and other settings may change to more restrictive values anytime without prior deprecation The values represent a fair balance between compatibility and security If your application needs specific settings you should create a SSLContext and apply the settings yourself Note If you find that when certain older clients or servers attempt to connect with a SSLContext created by this function that they get an error stating Protocol or cipher suite mismatch it may be that they only support SSL3 0 which this function excludes using the OP_NO_SSLv3 SSL3 0 is widely considered to be completely broken If you still wish to continue to use this function but still allow SSL 3 0 connections you can re enable them using ctx ssl create_default_context Purpose CLIENT_AUTH ctx options ssl OP_NO_SSLv3 New in version 3 4 Changed in version 3 4 4 RC4 was dropped from the default cipher string Changed in version 3 6 ChaCha20 Poly1305 was added to the default cipher string 3DES was dropped from the default cipher string Changed in version 3 8 Support for key logging to SSLKEYLOGFILE was added Changed in version 3 10 The context now uses PROTOCOL_TLS_CLIENT or PROTOCOL_TLS_SERVER protocol instead of generic PROTOCOL_TLS Exceptions exception ssl SSLError Raised to signal an error from the underlying SSL implementation currently provided by the OpenSSL library This signifies some problem in the higher level encryption and authentication layer that s superimposed on the underlying network connection This error is a subtype of OSError The error code and message of SSLError instances are provided by the OpenSSL library Changed in version 3 3 SSLError used to be a subtype of socket error library A string mnemonic designating the OpenSSL submodule in which the error occurred such as SSL PEM or X509 The range of possible values depends on the OpenSSL version New in version 3 3 reason A string mnemonic designating the reason this error occurred for example CERTIFICATE_VERIFY_FAILED The range of possible values depends on the OpenSSL version New in version 3 3 exception ssl SSLZeroReturnError A subclass of SSLError raised when trying to read or write and the SSL connection has been closed cleanly Note that this doesn t mean that the underlying transport read TCP has been closed New in version 3 3 exception ssl SSLWantReadError A subclass of SSLError raised by a non blocking SSL socket when trying to read or write data but more data needs to be received on the underlying TCP transport before the request can be fulfilled New in version 3 3 exception ssl SSLWantWriteError A subclass of SSLError raised by a non blocking SSL socket when trying to read or write data but more data needs to be sent on the underlying TCP transport before the request can be fulfilled New in version 3 3 exception ssl SSLSyscallError A subclass of SSLError raised when a system error was encountered while trying to fulfill an operation on a SSL socket Unfortunately there is no easy way to inspect the original errno number New in version 3 3 exception ssl SSLEOFError A subclass of SSLError raised when the SSL connection has been terminated abruptly Generally you shouldn t try to reuse the underlying transport when this error is encountered New in version 3 3 exception ssl SSLCertVerificationError A subclass of SSLError raised when certificate validation has failed New in version 3 7 verify_code A numeric error number that denotes the verification error verify_message A human readable string of the verificat,en
2668,ion error exception ssl CertificateError An alias for SSLCertVerificationError Changed in version 3 7 The exception is now an alias for SSLCertVerificationError Random generation ssl RAND_bytes num Return num cryptographically strong pseudo random bytes Raises an SSLError if the PRNG has not been seeded with enough data or if the operation is not supported by the current RAND method RAND_status can be used to check the status of the PRNG and RAND_add can be used to seed the PRNG For almost all applications os urandom is preferable Read the Wikipedia article Cryptographically secure pseudorandom number generator CSPRNG to get the requirements of a cryptographically strong generator New in version 3 3 ssl RAND_status Return True if the SSL pseudo random number generator has been seeded with enough randomness and False otherwise You can use ssl RAND_egd and ssl RAND_add to increase the randomness of the pseudo random number generator ssl RAND_add bytes entropy Mix the given bytes into the SSL pseudo random number generator The parameter entropy a float is a lower bound on the entropy contained in string so you can always use 0 0 See RFC 1750 for more information on sources of entropy Changed in version 3 5 Writable bytes like object is now accepted Certificate handling ssl cert_time_to_seconds cert_time Return the time in seconds since the Epoch given the cert_time string representing the notBefore or notAfter date from a certificate in b d H M S Y Z strptime format C locale Here s an example import ssl timestamp ssl cert_time_to_seconds Jan 5 09 34 43 2018 GMT timestamp 1515144883 from datetime import datetime print datetime utcfromtimestamp timestamp 2018 01 05 09 34 43 notBefore or notAfter dates must use GMT RFC 5280 Changed in version 3 5 Interpret the input time as a time in UTC as specified by GMT timezone in the input string Local timezone was used previously Return an integer no fractions of a second in the input format ssl get_server_certificate addr ssl_version PROTOCOL_TLS_CLIENT ca_certs None timeout Given the address addr of an SSL protected server as a hostname port number pair fetches the server s certificate and returns it as a PEM encoded string If ssl_version is specified uses that version of the SSL protocol to attempt to connect to the server If ca_certs is specified it should be a file containing a list of root certificates the same format as used for the cafile parameter in SSLContext load_verify_locations The call will attempt to validate the server certificate against that set of root certificates and will fail if the validation attempt fails A timeout can be specified with the timeout parameter Changed in version 3 3 This function is now IPv6 compatible Changed in version 3 5 The default ssl_version is changed from PROTOCOL_SSLv3 to PROTOCOL_TLS for maximum compatibility with modern servers Changed in version 3 10 The timeout parameter was added ssl DER_cert_to_PEM_cert DER_cert_bytes Given a certificate as a DER encoded blob of bytes returns a PEM encoded string version of the same certificate ssl PEM_cert_to_DER_cert PEM_cert_string Given a certificate as an ASCII PEM string returns a DER encoded sequence of bytes for that same certificate ssl get_default_verify_paths Returns a named tuple with paths to OpenSSL s default cafile and capath The paths are the same as used by SSLContext set_default_verify_paths The return value is a named tuple DefaultVerifyPaths cafile resolved path to cafile or None if the file doesn t exist capath resolved path to capath or None if the directory doesn t exist openssl_cafile_env OpenSSL s environment key that points to a cafile openssl_cafile hard coded path to a cafile openssl_capath_env OpenSSL s environment key that points to a capath openssl_capath hard coded path to a capath directory New in version 3 4 ssl enum_certificates store_name Retrieve certificates from Windows system cert store store_name may be one of CA ROOT or MY Windows may provide additional cert stores too The function returns a list of cert_bytes encoding_type trust tuples The encoding_type sp,en
2669,ecifies the encoding of cert_bytes It is either x509_asn for X 509 ASN 1 data or pkcs_7_asn for PKCS 7 ASN 1 data Trust specifies the purpose of the certificate as a set of OIDS or exactly True if the certificate is trustworthy for all purposes Example ssl enum_certificates CA b data x509_asn 1 3 6 1 5 5 7 3 1 1 3 6 1 5 5 7 3 2 b data x509_asn True Availability Windows New in version 3 4 ssl enum_crls store_name Retrieve CRLs from Windows system cert store store_name may be one of CA ROOT or MY Windows may provide additional cert stores too The function returns a list of cert_bytes encoding_type trust tuples The encoding_type specifies the encoding of cert_bytes It is either x509_asn for X 509 ASN 1 data or pkcs_7_asn for PKCS 7 ASN 1 data Availability Windows New in version 3 4 Constants All constants are now enum IntEnum or enum IntFlag collections New in version 3 6 ssl CERT_NONE Possible value for SSLContext verify_mode Except for PROTOCOL_TLS_CLIENT it is the default mode With client side sockets just about any cert is accepted Validation errors such as untrusted or expired cert are ignored and do not abort the TLS SSL handshake In server mode no certificate is requested from the client so the client does not send any for client cert authentication See the discussion of Security considerations below ssl CERT_OPTIONAL Possible value for SSLContext verify_mode In client mode CERT_OPTIONAL has the same meaning as CERT_REQUIRED It is recommended to use CERT_REQUIRED for client side sockets instead In server mode a client certificate request is sent to the client The client may either ignore the request or send a certificate in order perform TLS client cert authentication If the client chooses to send a certificate it is verified Any verification error immediately aborts the TLS handshake Use of this setting requires a valid set of CA certificates to be passed to SSLContext load_verify_locations ssl CERT_REQUIRED Possible value for SSLContext verify_mode In this mode certificates are required from the other side of the socket connection an SSLError will be raised if no certificate is provided or if its validation fails This mode is not sufficient to verify a certificate in client mode as it does not match hostnames check_hostname must be enabled as well to verify the authenticity of a cert PROTOCOL_TLS_CLIENT uses CERT_REQUIRED and enables check_hostname by default With server socket this mode provides mandatory TLS client cert authentication A client certificate request is sent to the client and the client must provide a valid and trusted certificate Use of this setting requires a valid set of CA certificates to be passed to SSLContext load_verify_locations class ssl VerifyMode enum IntEnum collection of CERT_ constants New in version 3 6 ssl VERIFY_DEFAULT Possible value for SSLContext verify_flags In this mode certificate revocation lists CRLs are not checked By default OpenSSL does neither require nor verify CRLs New in version 3 4 ssl VERIFY_CRL_CHECK_LEAF Possible value for SSLContext verify_flags In this mode only the peer cert is checked but none of the intermediate CA certificates The mode requires a valid CRL that is signed by the peer cert s issuer its direct ancestor CA If no proper CRL has been loaded with SSLContext load_verify_locations validation will fail New in version 3 4 ssl VERIFY_CRL_CHECK_CHAIN Possible value for SSLContext verify_flags In this mode CRLs of all certificates in the peer cert chain are checked New in version 3 4 ssl VERIFY_X509_STRICT Possible value for SSLContext verify_flags to disable workarounds for broken X 509 certificates New in version 3 4 ssl VERIFY_ALLOW_PROXY_CERTS Possible value for SSLContext verify_flags to enables proxy certificate verification New in version 3 10 ssl VERIFY_X509_TRUSTED_FIRST Possible value for SSLContext verify_flags It instructs OpenSSL to prefer trusted certificates when building the trust chain to validate a certificate This flag is enabled by default New in version 3 4 4 ssl VERIFY_X509_PARTIAL_CHAIN Possible value for SSLContext verify_flags It ,en
2670,instructs OpenSSL to accept intermediate CAs in the trust store to be treated as trust anchors in the same way as the self signed root CA certificates This makes it possible to trust certificates issued by an intermediate CA without having to trust its ancestor root CA New in version 3 10 class ssl VerifyFlags enum IntFlag collection of VERIFY_ constants New in version 3 6 ssl PROTOCOL_TLS Selects the highest protocol version that both the client and server support Despite the name this option can select both SSL and TLS protocols New in version 3 6 Deprecated since version 3 10 TLS clients and servers require different default settings for secure communication The generic TLS protocol constant is deprecated in favor of PROTOCOL_TLS_CLIENT and PROTOCOL_TLS_SERVER ssl PROTOCOL_TLS_CLIENT Auto negotiate the highest protocol version that both the client and server support and configure the context client side connections The protocol enables CERT_REQUIRED and check_hostname by default New in version 3 6 ssl PROTOCOL_TLS_SERVER Auto negotiate the highest protocol version that both the client and server support and configure the context server side connections New in version 3 6 ssl PROTOCOL_SSLv23 Alias for PROTOCOL_TLS Deprecated since version 3 6 Use PROTOCOL_TLS instead ssl PROTOCOL_SSLv3 Selects SSL version 3 as the channel encryption protocol This protocol is not available if OpenSSL is compiled with the no ssl3 option Warning SSL version 3 is insecure Its use is highly discouraged Deprecated since version 3 6 OpenSSL has deprecated all version specific protocols Use the default protocol PROTOCOL_TLS_SERVER or PROTOCOL_TLS_CLIENT with SSLContext minimum_version and SSLContext maximum_version instead ssl PROTOCOL_TLSv1 Selects TLS version 1 0 as the channel encryption protocol Deprecated since version 3 6 OpenSSL has deprecated all version specific protocols ssl PROTOCOL_TLSv1_1 Selects TLS version 1 1 as the channel encryption protocol Available only with openssl version 1 0 1 New in version 3 4 Deprecated since version 3 6 OpenSSL has deprecated all version specific protocols ssl PROTOCOL_TLSv1_2 Selects TLS version 1 2 as the channel encryption protocol Available only with openssl version 1 0 1 New in version 3 4 Deprecated since version 3 6 OpenSSL has deprecated all version specific protocols ssl OP_ALL Enables workarounds for various bugs present in other SSL implementations This option is set by default It does not necessarily set the same flags as OpenSSL s SSL_OP_ALL constant New in version 3 2 ssl OP_NO_SSLv2 Prevents an SSLv2 connection This option is only applicable in conjunction with PROTOCOL_TLS It prevents the peers from choosing SSLv2 as the protocol version New in version 3 2 Deprecated since version 3 6 SSLv2 is deprecated ssl OP_NO_SSLv3 Prevents an SSLv3 connection This option is only applicable in conjunction with PROTOCOL_TLS It prevents the peers from choosing SSLv3 as the protocol version New in version 3 2 Deprecated since version 3 6 SSLv3 is deprecated ssl OP_NO_TLSv1 Prevents a TLSv1 connection This option is only applicable in conjunction with PROTOCOL_TLS It prevents the peers from choosing TLSv1 as the protocol version New in version 3 2 Deprecated since version 3 7 The option is deprecated since OpenSSL 1 1 0 use the new SSLContext minimum_version and SSLContext maximum_version instead ssl OP_NO_TLSv1_1 Prevents a TLSv1 1 connection This option is only applicable in conjunction with PROTOCOL_TLS It prevents the peers from choosing TLSv1 1 as the protocol version Available only with openssl version 1 0 1 New in version 3 4 Deprecated since version 3 7 The option is deprecated since OpenSSL 1 1 0 ssl OP_NO_TLSv1_2 Prevents a TLSv1 2 connection This option is only applicable in conjunction with PROTOCOL_TLS It prevents the peers from choosing TLSv1 2 as the protocol version Available only with openssl version 1 0 1 New in version 3 4 Deprecated since version 3 7 The option is deprecated since OpenSSL 1 1 0 ssl OP_NO_TLSv1_3 Prevents a TLSv1 3 connection This option is only applicable in conj,en
2671,unction with PROTOCOL_TLS It prevents the peers from choosing TLSv1 3 as the protocol version TLS 1 3 is available with OpenSSL 1 1 1 or later When Python has been compiled against an older version of OpenSSL the flag defaults to 0 New in version 3 6 3 Deprecated since version 3 7 The option is deprecated since OpenSSL 1 1 0 It was added to 2 7 15 and 3 6 3 for backwards compatibility with OpenSSL 1 0 2 ssl OP_NO_RENEGOTIATION Disable all renegotiation in TLSv1 2 and earlier Do not send HelloRequest messages and ignore renegotiation requests via ClientHello This option is only available with OpenSSL 1 1 0h and later New in version 3 7 ssl OP_CIPHER_SERVER_PREFERENCE Use the server s cipher ordering preference rather than the client s This option has no effect on client sockets and SSLv2 server sockets New in version 3 3 ssl OP_SINGLE_DH_USE Prevents re use of the same DH key for distinct SSL sessions This improves forward secrecy but requires more computational resources This option only applies to server sockets New in version 3 3 ssl OP_SINGLE_ECDH_USE Prevents re use of the same ECDH key for distinct SSL sessions This improves forward secrecy but requires more computational resources This option only applies to server sockets New in version 3 3 ssl OP_ENABLE_MIDDLEBOX_COMPAT Send dummy Change Cipher Spec CCS messages in TLS 1 3 handshake to make a TLS 1 3 connection look more like a TLS 1 2 connection This option is only available with OpenSSL 1 1 1 and later New in version 3 8 ssl OP_NO_COMPRESSION Disable compression on the SSL channel This is useful if the application protocol supports its own compression scheme New in version 3 3 class ssl Options enum IntFlag collection of OP_ constants ssl OP_NO_TICKET Prevent client side from requesting a session ticket New in version 3 6 ssl OP_IGNORE_UNEXPECTED_EOF Ignore unexpected shutdown of TLS connections This option is only available with OpenSSL 3 0 0 and later New in version 3 10 ssl OP_ENABLE_KTLS Enable the use of the kernel TLS To benefit from the feature OpenSSL must have been compiled with support for it and the negotiated cipher suites and extensions must be supported by it a list of supported ones may vary by platform and kernel version Note that with enabled kernel TLS some cryptographic operations are performed by the kernel directly and not via any available OpenSSL Providers This might be undesirable if for example the application requires all cryptographic operations to be performed by the FIPS provider This option is only available with OpenSSL 3 0 0 and later New in version 3 12 ssl OP_LEGACY_SERVER_CONNECT Allow legacy insecure renegotiation between OpenSSL and unpatched servers only New in version 3 12 ssl HAS_ALPN Whether the OpenSSL library has built in support for the Application Layer Protocol Negotiation TLS extension as described in RFC 7301 New in version 3 5 ssl HAS_NEVER_CHECK_COMMON_NAME Whether the OpenSSL library has built in support not checking subject common name and SSLContext hostname_checks_common_name is writeable New in version 3 7 ssl HAS_ECDH Whether the OpenSSL library has built in support for the Elliptic Curve based Diffie Hellman key exchange This should be true unless the feature was explicitly disabled by the distributor New in version 3 3 ssl HAS_SNI Whether the OpenSSL library has built in support for the Server Name Indication extension as defined in RFC 6066 New in version 3 2 ssl HAS_NPN Whether the OpenSSL library has built in support for the Next Protocol Negotiation as described in the Application Layer Protocol Negotiation When true you can use the SSLContext set_npn_protocols method to advertise which protocols you want to support New in version 3 3 ssl HAS_SSLv2 Whether the OpenSSL library has built in support for the SSL 2 0 protocol New in version 3 7 ssl HAS_SSLv3 Whether the OpenSSL library has built in support for the SSL 3 0 protocol New in version 3 7 ssl HAS_TLSv1 Whether the OpenSSL library has built in support for the TLS 1 0 protocol New in version 3 7 ssl HAS_TLSv1_1 Whether the OpenSSL library has bui,en
2672,lt in support for the TLS 1 1 protocol New in version 3 7 ssl HAS_TLSv1_2 Whether the OpenSSL library has built in support for the TLS 1 2 protocol New in version 3 7 ssl HAS_TLSv1_3 Whether the OpenSSL library has built in support for the TLS 1 3 protocol New in version 3 7 ssl CHANNEL_BINDING_TYPES List of supported TLS channel binding types Strings in this list can be used as arguments to SSLSocket get_channel_binding New in version 3 3 ssl OPENSSL_VERSION The version string of the OpenSSL library loaded by the interpreter ssl OPENSSL_VERSION OpenSSL 1 0 2k 26 Jan 2017 New in version 3 2 ssl OPENSSL_VERSION_INFO A tuple of five integers representing version information about the OpenSSL library ssl OPENSSL_VERSION_INFO 1 0 2 11 15 New in version 3 2 ssl OPENSSL_VERSION_NUMBER The raw version number of the OpenSSL library as a single integer ssl OPENSSL_VERSION_NUMBER 268443839 hex ssl OPENSSL_VERSION_NUMBER 0x100020bf New in version 3 2 ssl ALERT_DESCRIPTION_HANDSHAKE_FAILURE ssl ALERT_DESCRIPTION_INTERNAL_ERROR ALERT_DESCRIPTION_ Alert Descriptions from RFC 5246 and others The IANA TLS Alert Registry contains this list and references to the RFCs where their meaning is defined Used as the return value of the callback function in SSLContext set_servername_callback New in version 3 4 class ssl AlertDescription enum IntEnum collection of ALERT_DESCRIPTION_ constants New in version 3 6 Purpose SERVER_AUTH Option for create_default_context and SSLContext load_default_certs This value indicates that the context may be used to authenticate web servers therefore it will be used to create client side sockets New in version 3 4 Purpose CLIENT_AUTH Option for create_default_context and SSLContext load_default_certs This value indicates that the context may be used to authenticate web clients therefore it will be used to create server side sockets New in version 3 4 class ssl SSLErrorNumber enum IntEnum collection of SSL_ERROR_ constants New in version 3 6 class ssl TLSVersion enum IntEnum collection of SSL and TLS versions for SSLContext maximum_version and SSLContext minimum_version New in version 3 7 TLSVersion MINIMUM_SUPPORTED TLSVersion MAXIMUM_SUPPORTED The minimum or maximum supported SSL or TLS version These are magic constants Their values don t reflect the lowest and highest available TLS SSL versions TLSVersion SSLv3 TLSVersion TLSv1 TLSVersion TLSv1_1 TLSVersion TLSv1_2 TLSVersion TLSv1_3 SSL 3 0 to TLS 1 3 Deprecated since version 3 10 All TLSVersion members except TLSVersion TLSv1_2 and TLSVersion TLSv1_3 are deprecated SSL Sockets class ssl SSLSocket socket socket SSL sockets provide the following methods of Socket Objects accept bind close connect detach fileno getpeername getsockname getsockopt setsockopt gettimeout settimeout setblocking listen makefile recv recv_into but passing a non zero flags argument is not allowed send sendall with the same limitation sendfile but os sendfile will be used for plain text sockets only else send will be used shutdown However since the SSL and TLS protocol has its own framing atop of TCP the SSL sockets abstraction can in certain respects diverge from the specification of normal OS level sockets See especially the notes on non blocking sockets Instances of SSLSocket must be created using the SSLContext wrap_socket method Changed in version 3 5 The sendfile method was added Changed in version 3 5 The shutdown does not reset the socket timeout each time bytes are received or sent The socket timeout is now the maximum total duration of the shutdown Deprecated since version 3 6 It is deprecated to create a SSLSocket instance directly use SSLContext wrap_socket to wrap a socket Changed in version 3 7 SSLSocket instances must to created with wrap_socket In earlier versions it was possible to create instances directly This was never documented or officially supported Changed in version 3 10 Python now uses SSL_read_ex and SSL_write_ex internally The functions support reading and writing of data larger than 2 GB Writing zero length data no longer fails with a protocol violation error,en
2673, SSL sockets also have the following additional methods and attributes SSLSocket read len 1024 buffer None Read up to len bytes of data from the SSL socket and return the result as a bytes instance If buffer is specified then read into the buffer instead and return the number of bytes read Raise SSLWantReadError or SSLWantWriteError if the socket is non blocking and the read would block As at any time a re negotiation is possible a call to read can also cause write operations Changed in version 3 5 The socket timeout is no longer reset each time bytes are received or sent The socket timeout is now the maximum total duration to read up to len bytes Deprecated since version 3 6 Use recv instead of read SSLSocket write buf Write buf to the SSL socket and return the number of bytes written The buf argument must be an object supporting the buffer interface Raise SSLWantReadError or SSLWantWriteError if the socket is non blocking and the write would block As at any time a re negotiation is possible a call to write can also cause read operations Changed in version 3 5 The socket timeout is no longer reset each time bytes are received or sent The socket timeout is now the maximum total duration to write buf Deprecated since version 3 6 Use send instead of write Note The read and write methods are the low level methods that read and write unencrypted application level data and decrypt encrypt it to encrypted wire level data These methods require an active SSL connection i e the handshake was completed and SSLSocket unwrap was not called Normally you should use the socket API methods like recv and send instead of these methods SSLSocket do_handshake Perform the SSL setup handshake Changed in version 3 4 The handshake method also performs match_hostname when the check_hostname attribute of the socket s context is true Changed in version 3 5 The socket timeout is no longer reset each time bytes are received or sent The socket timeout is now the maximum total duration of the handshake Changed in version 3 7 Hostname or IP address is matched by OpenSSL during handshake The function match_hostname is no longer used In case OpenSSL refuses a hostname or IP address the handshake is aborted early and a TLS alert message is sent to the peer SSLSocket getpeercert binary_form False If there is no certificate for the peer on the other end of the connection return None If the SSL handshake hasn t been done yet raise ValueError If the binary_form parameter is False and a certificate was received from the peer this method returns a dict instance If the certificate was not validated the dict is empty If the certificate was validated it returns a dict with several keys amongst them subject the principal for which the certificate was issued and issuer the principal issuing the certificate If a certificate contains an instance of the Subject Alternative Name extension see RFC 3280 there will also be a subjectAltName key in the dictionary The subject and issuer fields are tuples containing the sequence of relative distinguished names RDNs given in the certificate s data structure for the respective fields and each RDN is a sequence of name value pairs Here is a real world example issuer countryName IL organizationName StartCom Ltd organizationalUnitName Secure Digital Certificate Signing commonName StartCom Class 2 Primary Intermediate Server CA notAfter Nov 22 08 15 19 2013 GMT notBefore Nov 21 03 09 52 2011 GMT serialNumber 95F0 subject description 571208 SLe257oHY9fVQ07Z countryName US stateOrProvinceName California localityName San Francisco organizationName Electronic Frontier Foundation Inc commonName eff org emailAddress hostmaster eff org subjectAltName DNS eff org DNS eff org version 3 If the binary_form parameter is True and a certificate was provided this method returns the DER encoded form of the entire certificate as a sequence of bytes or None if the peer did not provide a certificate Whether the peer provides a certificate depends on the SSL socket s role for a client SSL socket the server will always provide a certificate regardless o,en
2674,f whether validation was required for a server SSL socket the client will only provide a certificate when requested by the server therefore getpeercert will return None if you used CERT_NONE rather than CERT_OPTIONAL or CERT_REQUIRED See also SSLContext check_hostname Changed in version 3 2 The returned dictionary includes additional items such as issuer and notBefore Changed in version 3 4 ValueError is raised when the handshake isn t done The returned dictionary includes additional X509v3 extension items such as crlDistributionPoints caIssuers and OCSP URIs Changed in version 3 9 IPv6 address strings no longer have a trailing new line SSLSocket cipher Returns a three value tuple containing the name of the cipher being used the version of the SSL protocol that defines its use and the number of secret bits being used If no connection has been established returns None SSLSocket shared_ciphers Return the list of ciphers available in both the client and server Each entry of the returned list is a three value tuple containing the name of the cipher the version of the SSL protocol that defines its use and the number of secret bits the cipher uses shared_ciphers returns None if no connection has been established or the socket is a client socket New in version 3 5 SSLSocket compression Return the compression algorithm being used as a string or None if the connection isn t compressed If the higher level protocol supports its own compression mechanism you can use OP_NO_COMPRESSION to disable SSL level compression New in version 3 3 SSLSocket get_channel_binding cb_type tls unique Get channel binding data for current connection as a bytes object Returns None if not connected or the handshake has not been completed The cb_type parameter allow selection of the desired channel binding type Valid channel binding types are listed in the CHANNEL_BINDING_TYPES list Currently only the tls unique channel binding defined by RFC 5929 is supported ValueError will be raised if an unsupported channel binding type is requested New in version 3 3 SSLSocket selected_alpn_protocol Return the protocol that was selected during the TLS handshake If SSLContext set_alpn_protocols was not called if the other party does not support ALPN if this socket does not support any of the client s proposed protocols or if the handshake has not happened yet None is returned New in version 3 5 SSLSocket selected_npn_protocol Return the higher level protocol that was selected during the TLS SSL handshake If SSLContext set_npn_protocols was not called or if the other party does not support NPN or if the handshake has not yet happened this will return None New in version 3 3 Deprecated since version 3 10 NPN has been superseded by ALPN SSLSocket unwrap Performs the SSL shutdown handshake which removes the TLS layer from the underlying socket and returns the underlying socket object This can be used to go from encrypted operation over a connection to unencrypted The returned socket should always be used for further communication with the other side of the connection rather than the original socket SSLSocket verify_client_post_handshake Requests post handshake authentication PHA from a TLS 1 3 client PHA can only be initiated for a TLS 1 3 connection from a server side socket after the initial TLS handshake and with PHA enabled on both sides see SSLContext post_handshake_auth The method does not perform a cert exchange immediately The server side sends a CertificateRequest during the next write event and expects the client to respond with a certificate on the next read event If any precondition isn t met e g not TLS 1 3 PHA not enabled an SSLError is raised Note Only available with OpenSSL 1 1 1 and TLS 1 3 enabled Without TLS 1 3 support the method raises NotImplementedError New in version 3 8 SSLSocket version Return the actual SSL protocol version negotiated by the connection as a string or None if no secure connection is established As of this writing possible return values include SSLv2 SSLv3 TLSv1 TLSv1 1 and TLSv1 2 Recent OpenSSL versions may define more return va,en
2675,lues New in version 3 5 SSLSocket pending Returns the number of already decrypted bytes available for read pending on the connection SSLSocket context The SSLContext object this SSL socket is tied to New in version 3 2 SSLSocket server_side A boolean which is True for server side sockets and False for client side sockets New in version 3 2 SSLSocket server_hostname Hostname of the server str type or None for server side socket or if the hostname was not specified in the constructor New in version 3 2 Changed in version 3 7 The attribute is now always ASCII text When server_hostname is an internationalized domain name IDN this attribute now stores the A label form xn pythn mua org rather than the U label form pythön org SSLSocket session The SSLSession for this SSL connection The session is available for client and server side sockets after the TLS handshake has been performed For client sockets the session can be set before do_handshake has been called to reuse a session New in version 3 6 SSLSocket session_reused New in version 3 6 SSL Contexts New in version 3 2 An SSL context holds various data longer lived than single SSL connections such as SSL configuration options certificate s and private key s It also manages a cache of SSL sessions for server side sockets in order to speed up repeated connections from the same clients class ssl SSLContext protocol None Create a new SSL context You may pass protocol which must be one of the PROTOCOL_ constants defined in this module The parameter specifies which version of the SSL protocol to use Typically the server chooses a particular protocol version and the client must adapt to the server s choice Most of the versions are not interoperable with the other versions If not specified the default is PROTOCOL_TLS it provides the most compatibility with other versions Here s a table showing which versions in a client down the side can connect to which versions in a server along the top client server SSLv2 SSLv3 TLS 3 TLSv1 TLSv1 1 TLSv1 2 SSLv2 yes no no 1 no no no SSLv3 no yes no 2 no no no TLS SSLv23 3 no 1 no 2 yes yes yes yes TLSv1 no no yes yes no no TLSv1 1 no no yes no yes no TLSv1 2 no no yes no no yes Footnotes 1 SSLContext disables SSLv2 with OP_NO_SSLv2 by default 2 SSLContext disables SSLv3 with OP_NO_SSLv3 by default 3 TLS 1 3 protocol will be available with PROTOCOL_TLS in OpenSSL 1 1 1 There is no dedicated PROTOCOL constant for just TLS 1 3 See also create_default_context lets the ssl module choose security settings for a given purpose Changed in version 3 6 The context is created with secure default values The options OP_NO_COMPRESSION OP_CIPHER_SERVER_PREFERENCE OP_SINGLE_DH_USE OP_SINGLE_ECDH_USE OP_NO_SSLv2 and OP_NO_SSLv3 except for PROTOCOL_SSLv3 are set by default The initial cipher suite list contains only HIGH ciphers no NULL ciphers and no MD5 ciphers Deprecated since version 3 10 SSLContext without protocol argument is deprecated The context class will either require PROTOCOL_TLS_CLIENT or PROTOCOL_TLS_SERVER protocol in the future Changed in version 3 10 The default cipher suites now include only secure AES and ChaCha20 ciphers with forward secrecy and security level 2 RSA and DH keys with less than 2048 bits and ECC keys with less than 224 bits are prohibited PROTOCOL_TLS PROTOCOL_TLS_CLIENT and PROTOCOL_TLS_SERVER use TLS 1 2 as minimum TLS version SSLContext objects have the following methods and attributes SSLContext cert_store_stats Get statistics about quantities of loaded X 509 certificates count of X 509 certificates flagged as CA certificates and certificate revocation lists as dictionary Example for a context with one CA cert and one other cert context cert_store_stats crl 0 x509_ca 1 x509 2 New in version 3 4 SSLContext load_cert_chain certfile keyfile None password None Load a private key and the corresponding certificate The certfile string must be the path to a single file in PEM format containing the certificate as well as any number of CA certificates needed to establish the certificate s authenticity The keyfile string if present must p,en
2676,oint to a file containing the private key Otherwise the private key will be taken from certfile as well See the discussion of Certificates for more information on how the certificate is stored in the certfile The password argument may be a function to call to get the password for decrypting the private key It will only be called if the private key is encrypted and a password is necessary It will be called with no arguments and it should return a string bytes or bytearray If the return value is a string it will be encoded as UTF 8 before using it to decrypt the key Alternatively a string bytes or bytearray value may be supplied directly as the password argument It will be ignored if the private key is not encrypted and no password is needed If the password argument is not specified and a password is required OpenSSL s built in password prompting mechanism will be used to interactively prompt the user for a password An SSLError is raised if the private key doesn t match with the certificate Changed in version 3 3 New optional argument password SSLContext load_default_certs purpose Purpose SERVER_AUTH Load a set of default certification authority CA certificates from default locations On Windows it loads CA certs from the CA and ROOT system stores On all systems it calls SSLContext set_default_verify_paths In the future the method may load CA certificates from other locations too The purpose flag specifies what kind of CA certificates are loaded The default settings Purpose SERVER_AUTH loads certificates that are flagged and trusted for TLS web server authentication client side sockets Purpose CLIENT_AUTH loads CA certificates for client certificate verification on the server side New in version 3 4 SSLContext load_verify_locations cafile None capath None cadata None Load a set of certification authority CA certificates used to validate other peers certificates when verify_mode is other than CERT_NONE At least one of cafile or capath must be specified This method can also load certification revocation lists CRLs in PEM or DER format In order to make use of CRLs SSLContext verify_flags must be configured properly The cafile string if present is the path to a file of concatenated CA certificates in PEM format See the discussion of Certificates for more information about how to arrange the certificates in this file The capath string if present is the path to a directory containing several CA certificates in PEM format following an OpenSSL specific layout The cadata object if present is either an ASCII string of one or more PEM encoded certificates or a bytes like object of DER encoded certificates Like with capath extra lines around PEM encoded certificates are ignored but at least one certificate must be present Changed in version 3 4 New optional argument cadata SSLContext get_ca_certs binary_form False Get a list of loaded certification authority CA certificates If the binary_form parameter is False each list entry is a dict like the output of SSLSocket getpeercert Otherwise the method returns a list of DER encoded certificates The returned list does not contain certificates from capath unless a certificate was requested and loaded by a SSL connection Note Certificates in a capath directory aren t loaded unless they have been used at least once New in version 3 4 SSLContext get_ciphers Get a list of enabled ciphers The list is in order of cipher priority See SSLContext set_ciphers Example ctx ssl SSLContext ssl PROTOCOL_SSLv23 ctx set_ciphers ECDHE AESGCM ECDSA ctx get_ciphers aead True alg_bits 256 auth auth rsa description ECDHE RSA AES256 GCM SHA384 TLSv1 2 Kx ECDH Au RSA Enc AESGCM 256 Mac AEAD digest None id 50380848 kea kx ecdhe name ECDHE RSA AES256 GCM SHA384 protocol TLSv1 2 strength_bits 256 symmetric aes 256 gcm aead True alg_bits 128 auth auth rsa description ECDHE RSA AES128 GCM SHA256 TLSv1 2 Kx ECDH Au RSA Enc AESGCM 128 Mac AEAD digest None id 50380847 kea kx ecdhe name ECDHE RSA AES128 GCM SHA256 protocol TLSv1 2 strength_bits 128 symmetric aes 128 gcm New in version 3 6 SSLContext set_default_verify_paths ,en
2677,Load a set of default certification authority CA certificates from a filesystem path defined when building the OpenSSL library Unfortunately there s no easy way to know whether this method succeeds no error is returned if no certificates are to be found When the OpenSSL library is provided as part of the operating system though it is likely to be configured properly SSLContext set_ciphers ciphers Set the available ciphers for sockets created with this context It should be a string in the OpenSSL cipher list format If no cipher can be selected because compile time options or other configuration forbids use of all the specified ciphers an SSLError will be raised Note when connected the SSLSocket cipher method of SSL sockets will give the currently selected cipher TLS 1 3 cipher suites cannot be disabled with set_ciphers SSLContext set_alpn_protocols protocols Specify which protocols the socket should advertise during the SSL TLS handshake It should be a list of ASCII strings like http 1 1 spdy 2 ordered by preference The selection of a protocol will happen during the handshake and will play out according to RFC 7301 After a successful handshake the SSLSocket selected_alpn_protocol method will return the agreed upon protocol This method will raise NotImplementedError if HAS_ALPN is False New in version 3 5 SSLContext set_npn_protocols protocols Specify which protocols the socket should advertise during the SSL TLS handshake It should be a list of strings like http 1 1 spdy 2 ordered by preference The selection of a protocol will happen during the handshake and will play out according to the Application Layer Protocol Negotiation After a successful handshake the SSLSocket selected_npn_protocol method will return the agreed upon protocol This method will raise NotImplementedError if HAS_NPN is False New in version 3 3 Deprecated since version 3 10 NPN has been superseded by ALPN SSLContext sni_callback Register a callback function that will be called after the TLS Client Hello handshake message has been received by the SSL TLS server when the TLS client specifies a server name indication The server name indication mechanism is specified in RFC 6066 section 3 Server Name Indication Only one callback can be set per SSLContext If sni_callback is set to None then the callback is disabled Calling this function a subsequent time will disable the previously registered callback The callback function will be called with three arguments the first being the ssl SSLSocket the second is a string that represents the server name that the client is intending to communicate or None if the TLS Client Hello does not contain a server name and the third argument is the original SSLContext The server name argument is text For internationalized domain name the server name is an IDN A label xn pythn mua org A typical use of this callback is to change the ssl SSLSocket s SSLSocket context attribute to a new object of type SSLContext representing a certificate chain that matches the server name Due to the early negotiation phase of the TLS connection only limited methods and attributes are usable like SSLSocket selected_alpn_protocol and SSLSocket context The SSLSocket getpeercert SSLSocket cipher and SSLSocket compression methods require that the TLS connection has progressed beyond the TLS Client Hello and therefore will not return meaningful values nor can they be called safely The sni_callback function must return None to allow the TLS negotiation to continue If a TLS failure is required a constant ALERT_DESCRIPTION_ can be returned Other return values will result in a TLS fatal error with ALERT_DESCRIPTION_INTERNAL_ERROR If an exception is raised from the sni_callback function the TLS connection will terminate with a fatal TLS alert message ALERT_DESCRIPTION_HANDSHAKE_FAILURE This method will raise NotImplementedError if the OpenSSL library had OPENSSL_NO_TLSEXT defined when it was built New in version 3 7 SSLContext set_servername_callback server_name_callback This is a legacy API retained for backwards compatibility When possible you should use,en
2678, sni_callback instead The given server_name_callback is similar to sni_callback except that when the server hostname is an IDN encoded internationalized domain name the server_name_callback receives a decoded U label pythön org If there is an decoding error on the server name the TLS connection will terminate with an ALERT_DESCRIPTION_INTERNAL_ERROR fatal TLS alert message to the client New in version 3 4 SSLContext load_dh_params dhfile Load the key generation parameters for Diffie Hellman DH key exchange Using DH key exchange improves forward secrecy at the expense of computational resources both on the server and on the client The dhfile parameter should be the path to a file containing DH parameters in PEM format This setting doesn t apply to client sockets You can also use the OP_SINGLE_DH_USE option to further improve security New in version 3 3 SSLContext set_ecdh_curve curve_name Set the curve name for Elliptic Curve based Diffie Hellman ECDH key exchange ECDH is significantly faster than regular DH while arguably as secure The curve_name parameter should be a string describing a well known elliptic curve for example prime256v1 for a widely supported curve This setting doesn t apply to client sockets You can also use the OP_SINGLE_ECDH_USE option to further improve security This method is not available if HAS_ECDH is False New in version 3 3 See also SSL TLS Perfect Forward Secrecy Vincent Bernat SSLContext wrap_socket sock server_side False do_handshake_on_connect True suppress_ragged_eofs True server_hostname None session None Wrap an existing Python socket sock and return an instance of SSLContext sslsocket_class default SSLSocket The returned SSL socket is tied to the context its settings and certificates sock must be a SOCK_STREAM socket other socket types are unsupported The parameter server_side is a boolean which identifies whether server side or client side behavior is desired from this socket For client side sockets the context construction is lazy if the underlying socket isn t connected yet the context construction will be performed after connect is called on the socket For server side sockets if the socket has no remote peer it is assumed to be a listening socket and the server side SSL wrapping is automatically performed on client connections accepted via the accept method The method may raise SSLError On client connections the optional parameter server_hostname specifies the hostname of the service which we are connecting to This allows a single server to host multiple SSL based services with distinct certificates quite similarly to HTTP virtual hosts Specifying server_hostname will raise a ValueError if server_side is true The parameter do_handshake_on_connect specifies whether to do the SSL handshake automatically after doing a socket connect or whether the application program will call it explicitly by invoking the SSLSocket do_handshake method Calling SSLSocket do_handshake explicitly gives the program control over the blocking behavior of the socket I O involved in the handshake The parameter suppress_ragged_eofs specifies how the SSLSocket recv method should signal unexpected EOF from the other end of the connection If specified as True the default it returns a normal EOF an empty bytes object in response to unexpected EOF errors raised from the underlying socket if False it will raise the exceptions back to the caller session see session To wrap an SSLSocket in another SSLSocket use SSLContext wrap_bio Changed in version 3 5 Always allow a server_hostname to be passed even if OpenSSL does not have SNI Changed in version 3 6 session argument was added Changed in version 3 7 The method returns an instance of SSLContext sslsocket_class instead of hard coded SSLSocket SSLContext sslsocket_class The return type of SSLContext wrap_socket defaults to SSLSocket The attribute can be overridden on instance of class in order to return a custom subclass of SSLSocket New in version 3 7 SSLContext wrap_bio incoming outgoing server_side False server_hostname None session None Wrap the BIO objects incoming ,en
2679,and outgoing and return an instance of SSLContext sslobject_class default SSLObject The SSL routines will read input data from the incoming BIO and write data to the outgoing BIO The server_side server_hostname and session parameters have the same meaning as in SSLContext wrap_socket Changed in version 3 6 session argument was added Changed in version 3 7 The method returns an instance of SSLContext sslobject_class instead of hard coded SSLObject SSLContext sslobject_class The return type of SSLContext wrap_bio defaults to SSLObject The attribute can be overridden on instance of class in order to return a custom subclass of SSLObject New in version 3 7 SSLContext session_stats Get statistics about the SSL sessions created or managed by this context A dictionary is returned which maps the names of each piece of information to their numeric values For example here is the total number of hits and misses in the session cache since the context was created stats context session_stats stats hits stats misses 0 0 SSLContext check_hostname Whether to match the peer cert s hostname in SSLSocket do_handshake The context s verify_mode must be set to CERT_OPTIONAL or CERT_REQUIRED and you must pass server_hostname to wrap_socket in order to match the hostname Enabling hostname checking automatically sets verify_mode from CERT_NONE to CERT_REQUIRED It cannot be set back to CERT_NONE as long as hostname checking is enabled The PROTOCOL_TLS_CLIENT protocol enables hostname checking by default With other protocols hostname checking must be enabled explicitly Example import socket ssl context ssl SSLContext ssl PROTOCOL_TLSv1_2 context verify_mode ssl CERT_REQUIRED context check_hostname True context load_default_certs s socket socket socket AF_INET socket SOCK_STREAM ssl_sock context wrap_socket s server_hostname www verisign com ssl_sock connect www verisign com 443 New in version 3 4 Changed in version 3 7 verify_mode is now automatically changed to CERT_REQUIRED when hostname checking is enabled and verify_mode is CERT_NONE Previously the same operation would have failed with a ValueError SSLContext keylog_filename Write TLS keys to a keylog file whenever key material is generated or received The keylog file is designed for debugging purposes only The file format is specified by NSS and used by many traffic analyzers such as Wireshark The log file is opened in append only mode Writes are synchronized between threads but not between processes New in version 3 8 SSLContext maximum_version A TLSVersion enum member representing the highest supported TLS version The value defaults to TLSVersion MAXIMUM_SUPPORTED The attribute is read only for protocols other than PROTOCOL_TLS PROTOCOL_TLS_CLIENT and PROTOCOL_TLS_SERVER The attributes maximum_version minimum_version and SSLContext options all affect the supported SSL and TLS versions of the context The implementation does not prevent invalid combination For example a context with OP_NO_TLSv1_2 in options and maximum_version set to TLSVersion TLSv1_2 will not be able to establish a TLS 1 2 connection New in version 3 7 SSLContext minimum_version Like SSLContext maximum_version except it is the lowest supported version or TLSVersion MINIMUM_SUPPORTED New in version 3 7 SSLContext num_tickets Control the number of TLS 1 3 session tickets of a PROTOCOL_TLS_SERVER context The setting has no impact on TLS 1 0 to 1 2 connections New in version 3 8 SSLContext options An integer representing the set of SSL options enabled on this context The default value is OP_ALL but you can specify other options such as OP_NO_SSLv2 by ORing them together Changed in version 3 6 SSLContext options returns Options flags ssl create_default_context options Options OP_ALL OP_NO_SSLv3 OP_NO_SSLv2 OP_NO_COMPRESSION 2197947391 Deprecated since version 3 7 All OP_NO_SSL and OP_NO_TLS options have been deprecated since Python 3 7 Use SSLContext minimum_version and SSLContext maximum_version instead SSLContext post_handshake_auth Enable TLS 1 3 post handshake client authentication Post handshake auth is disabled by default a,en
2680,nd a server can only request a TLS client certificate during the initial handshake When enabled a server may request a TLS client certificate at any time after the handshake When enabled on client side sockets the client signals the server that it supports post handshake authentication When enabled on server side sockets SSLContext verify_mode must be set to CERT_OPTIONAL or CERT_REQUIRED too The actual client cert exchange is delayed until SSLSocket verify_client_post_handshake is called and some I O is performed New in version 3 8 SSLContext protocol The protocol version chosen when constructing the context This attribute is read only SSLContext hostname_checks_common_name Whether check_hostname falls back to verify the cert s subject common name in the absence of a subject alternative name extension default true New in version 3 7 Changed in version 3 10 The flag had no effect with OpenSSL before version 1 1 1l Python 3 8 9 3 9 3 and 3 10 include workarounds for previous versions SSLContext security_level An integer representing the security level for the context This attribute is read only New in version 3 10 SSLContext verify_flags The flags for certificate verification operations You can set flags like VERIFY_CRL_CHECK_LEAF by ORing them together By default OpenSSL does neither require nor verify certificate revocation lists CRLs New in version 3 4 Changed in version 3 6 SSLContext verify_flags returns VerifyFlags flags ssl create_default_context verify_flags VerifyFlags VERIFY_X509_TRUSTED_FIRST 32768 SSLContext verify_mode Whether to try to verify other peers certificates and how to behave if verification fails This attribute must be one of CERT_NONE CERT_OPTIONAL or CERT_REQUIRED Changed in version 3 6 SSLContext verify_mode returns VerifyMode enum ssl create_default_context verify_mode VerifyMode CERT_REQUIRED 2 Certificates Certificates in general are part of a public key private key system In this system each principal which may be a machine or a person or an organization is assigned a unique two part encryption key One part of the key is public and is called the public key the other part is kept secret and is called the private key The two parts are related in that if you encrypt a message with one of the parts you can decrypt it with the other part and only with the other part A certificate contains information about two principals It contains the name of a subject and the subject s public key It also contains a statement by a second principal the issuer that the subject is who they claim to be and that this is indeed the subject s public key The issuer s statement is signed with the issuer s private key which only the issuer knows However anyone can verify the issuer s statement by finding the issuer s public key decrypting the statement with it and comparing it to the other information in the certificate The certificate also contains information about the time period over which it is valid This is expressed as two fields called notBefore and notAfter In the Python use of certificates a client or server can use a certificate to prove who they are The other side of a network connection can also be required to produce a certificate and that certificate can be validated to the satisfaction of the client or server that requires such validation The connection attempt can be set to raise an exception if the validation fails Validation is done automatically by the underlying OpenSSL framework the application need not concern itself with its mechanics But the application does usually need to provide sets of certificates to allow this process to take place Python uses files to contain certificates They should be formatted as PEM see RFC 1422 which is a base 64 encoded form wrapped with a header line and a footer line BEGIN CERTIFICATE certificate in base64 PEM encoding END CERTIFICATE Certificate chains The Python files which contain certificates can contain a sequence of certificates sometimes called a certificate chain This chain should start with the specific certificate for the principal who is the client or se,en
2681,rver and then the certificate for the issuer of that certificate and then the certificate for the issuer of that certificate and so on up the chain till you get to a certificate which is self signed that is a certificate which has the same subject and issuer sometimes called a root certificate The certificates should just be concatenated together in the certificate file For example suppose we had a three certificate chain from our server certificate to the certificate of the certification authority that signed our server certificate to the root certificate of the agency which issued the certification authority s certificate BEGIN CERTIFICATE certificate for your server END CERTIFICATE BEGIN CERTIFICATE the certificate for the CA END CERTIFICATE BEGIN CERTIFICATE the root certificate for the CA s issuer END CERTIFICATE CA certificates If you are going to require validation of the other side of the connection s certificate you need to provide a CA certs file filled with the certificate chains for each issuer you are willing to trust Again this file just contains these chains concatenated together For validation Python will use the first chain it finds in the file which matches The platform s certificates file can be used by calling SSLContext load_default_certs this is done automatically with create_default_context Combined key and certificate Often the private key is stored in the same file as the certificate in this case only the certfile parameter to SSLContext load_cert_chain needs to be passed If the private key is stored with the certificate it should come before the first certificate in the certificate chain BEGIN RSA PRIVATE KEY private key in base64 encoding END RSA PRIVATE KEY BEGIN CERTIFICATE certificate in base64 PEM encoding END CERTIFICATE Self signed certificates If you are going to create a server that provides SSL encrypted connection services you will need to acquire a certificate for that service There are many ways of acquiring appropriate certificates such as buying one from a certification authority Another common practice is to generate a self signed certificate The simplest way to do this is with the OpenSSL package using something like the following openssl req new x509 days 365 nodes out cert pem keyout cert pem Generating a 1024 bit RSA private key writing new private key to cert pem You are about to be asked to enter information that will be incorporated into your certificate request What you are about to enter is what is called a Distinguished Name or a DN There are quite a few fields but you can leave some blank For some fields there will be a default value If you enter the field will be left blank Country Name 2 letter code AU US State or Province Name full name Some State MyState Locality Name eg city Some City Organization Name eg company Internet Widgits Pty Ltd My Organization Inc Organizational Unit Name eg section My Group Common Name eg YOUR name myserver mygroup myorganization com Email Address ops myserver mygroup myorganization com The disadvantage of a self signed certificate is that it is its own root certificate and no one else will have it in their cache of known and trusted root certificates Examples Testing for SSL support To test for the presence of SSL support in a Python installation user code should use the following idiom try import ssl except ImportError pass else do something that requires SSL support Client side operation This example creates a SSL context with the recommended security settings for client sockets including automatic certificate verification context ssl create_default_context If you prefer to tune security settings yourself you might create a context from scratch but beware that you might not get the settings right context ssl SSLContext ssl PROTOCOL_TLS_CLIENT context load_verify_locations etc ssl certs ca bundle crt this snippet assumes your operating system places a bundle of all CA certificates in etc ssl certs ca bundle crt if not you ll get an error and have to adjust the location The PROTOCOL_TLS_CLIENT protocol configures the context for cert v,en
2682,alidation and hostname verification verify_mode is set to CERT_REQUIRED and check_hostname is set to True All other protocols create SSL contexts with insecure defaults When you use the context to connect to a server CERT_REQUIRED and check_hostname validate the server certificate it ensures that the server certificate was signed with one of the CA certificates checks the signature for correctness and verifies other properties like validity and identity of the hostname conn context wrap_socket socket socket socket AF_INET server_hostname www python org conn connect www python org 443 You may then fetch the certificate cert conn getpeercert Visual inspection shows that the certificate does identify the desired service that is the HTTPS host www python org pprint pprint cert OCSP http ocsp digicert com caIssuers http cacerts digicert com DigiCertSHA2ExtendedValidationServerCA crt crlDistributionPoints http crl3 digicert com sha2 ev server g1 crl http crl4 digicert com sha2 ev server g1 crl issuer countryName US organizationName DigiCert Inc organizationalUnitName www digicert com commonName DigiCert SHA2 Extended Validation Server CA notAfter Sep 9 12 00 00 2016 GMT notBefore Sep 5 00 00 00 2014 GMT serialNumber 01BB6F00122B177F36CAB49CEA8B6B26 subject businessCategory Private Organization 1 3 6 1 4 1 311 60 2 1 3 US 1 3 6 1 4 1 311 60 2 1 2 Delaware serialNumber 3359300 streetAddress 16 Allen Rd postalCode 03894 4801 countryName US stateOrProvinceName NH localityName Wolfeboro organizationName Python Software Foundation commonName www python org subjectAltName DNS www python org DNS python org DNS pypi org DNS docs python org DNS testpypi org DNS bugs python org DNS wiki python org DNS hg python org DNS mail python org DNS packaging python org DNS pythonhosted org DNS www pythonhosted org DNS test pythonhosted org DNS us pycon org DNS id python org version 3 Now the SSL channel is established and the certificate verified you can proceed to talk with the server conn sendall b HEAD HTTP 1 0 r nHost linuxfr org r n r n pprint pprint conn recv 1024 split b r n b HTTP 1 1 200 OK b Date Sat 18 Oct 2014 18 27 20 GMT b Server nginx b Content Type text html charset utf 8 b X Frame Options SAMEORIGIN b Content Length 45679 b Accept Ranges bytes b Via 1 1 varnish b Age 2188 b X Served By cache lcy1134 LCY b X Cache HIT b X Cache Hits 11 b Vary Cookie b Strict Transport Security max age 63072000 includeSubDomains b Connection close b b See the discussion of Security considerations below Server side operation For server operation typically you ll need to have a server certificate and private key each in a file You ll first create a context holding the key and the certificate so that clients can check your authenticity Then you ll open a socket bind it to a port call listen on it and start waiting for clients to connect import socket ssl context ssl create_default_context ssl Purpose CLIENT_AUTH context load_cert_chain certfile mycertfile keyfile mykeyfile bindsocket socket socket bindsocket bind myaddr example com 10023 bindsocket listen 5 When a client connects you ll call accept on the socket to get the new socket from the other end and use the context s SSLContext wrap_socket method to create a server side SSL socket for the connection while True newsocket fromaddr bindsocket accept connstream context wrap_socket newsocket server_side True try deal_with_client connstream finally connstream shutdown socket SHUT_RDWR connstream close Then you ll read data from the connstream and do something with it till you are finished with the client or the client is finished with you def deal_with_client connstream data connstream recv 1024 empty data means the client is finished with us while data if not do_something connstream data we ll assume do_something returns False when we re finished with client break data connstream recv 1024 finished with client And go back to listening for new client connections of course a real server would probably handle each client connection in a separate thread or put the sockets in non blocking mode and use an ,en
2683,event loop Notes on non blocking sockets SSL sockets behave slightly different than regular sockets in non blocking mode When working with non blocking sockets there are thus several things you need to be aware of Most SSLSocket methods will raise either SSLWantWriteError or SSLWantReadError instead of BlockingIOError if an I O operation would block SSLWantReadError will be raised if a read operation on the underlying socket is necessary and SSLWantWriteError for a write operation on the underlying socket Note that attempts to write to an SSL socket may require reading from the underlying socket first and attempts to read from the SSL socket may require a prior write to the underlying socket Changed in version 3 5 In earlier Python versions the SSLSocket send method returned zero instead of raising SSLWantWriteError or SSLWantReadError Calling select tells you that the OS level socket can be read from or written to but it does not imply that there is sufficient data at the upper SSL layer For example only part of an SSL frame might have arrived Therefore you must be ready to handle SSLSocket recv and SSLSocket send failures and retry after another call to select Conversely since the SSL layer has its own framing a SSL socket may still have data available for reading without select being aware of it Therefore you should first call SSLSocket recv to drain any potentially available data and then only block on a select call if still necessary of course similar provisions apply when using other primitives such as poll or those in the selectors module The SSL handshake itself will be non blocking the SSLSocket do_handshake method has to be retried until it returns successfully Here is a synopsis using select to wait for the socket s readiness while True try sock do_handshake break except ssl SSLWantReadError select select sock except ssl SSLWantWriteError select select sock See also The asyncio module supports non blocking SSL sockets and provides a higher level API It polls for events using the selectors module and handles SSLWantWriteError SSLWantReadError and BlockingIOError exceptions It runs the SSL handshake asynchronously as well Memory BIO Support New in version 3 5 Ever since the SSL module was introduced in Python 2 6 the SSLSocket class has provided two related but distinct areas of functionality SSL protocol handling Network IO The network IO API is identical to that provided by socket socket from which SSLSocket also inherits This allows an SSL socket to be used as a drop in replacement for a regular socket making it very easy to add SSL support to an existing application Combining SSL protocol handling and network IO usually works well but there are some cases where it doesn t An example is async IO frameworks that want to use a different IO multiplexing model than the select poll on a file descriptor readiness based model that is assumed by socket socket and by the internal OpenSSL socket IO routines This is mostly relevant for platforms like Windows where this model is not efficient For this purpose a reduced scope variant of SSLSocket called SSLObject is provided class ssl SSLObject A reduced scope variant of SSLSocket representing an SSL protocol instance that does not contain any network IO methods This class is typically used by framework authors that want to implement asynchronous IO for SSL through memory buffers This class implements an interface on top of a low level SSL object as implemented by OpenSSL This object captures the state of an SSL connection but does not provide any network IO itself IO needs to be performed through separate BIO objects which are OpenSSL s IO abstraction layer This class has no public constructor An SSLObject instance must be created using the wrap_bio method This method will create the SSLObject instance and bind it to a pair of BIOs The incoming BIO is used to pass data from Python to the SSL protocol instance while the outgoing BIO is used to pass data the other way around The following methods are available context server_side server_hostname session session_reused read,en
2684, write getpeercert selected_alpn_protocol selected_npn_protocol cipher shared_ciphers compression pending do_handshake verify_client_post_handshake unwrap get_channel_binding version When compared to SSLSocket this object lacks the following features Any form of network IO recv and send read and write only to the underlying MemoryBIO buffers There is no do_handshake_on_connect machinery You must always manually call do_handshake to start the handshake There is no handling of suppress_ragged_eofs All end of file conditions that are in violation of the protocol are reported via the SSLEOFError exception The method unwrap call does not return anything unlike for an SSL socket where it returns the underlying socket The server_name_callback callback passed to SSLContext set_servername_callback will get an SSLObject instance instead of a SSLSocket instance as its first parameter Some notes related to the use of SSLObject All IO on an SSLObject is non blocking This means that for example read will raise an SSLWantReadError if it needs more data than the incoming BIO has available Changed in version 3 7 SSLObject instances must be created with wrap_bio In earlier versions it was possible to create instances directly This was never documented or officially supported An SSLObject communicates with the outside world using memory buffers The class MemoryBIO provides a memory buffer that can be used for this purpose It wraps an OpenSSL memory BIO Basic IO object class ssl MemoryBIO A memory buffer that can be used to pass data between Python and an SSL protocol instance pending Return the number of bytes currently in the memory buffer eof A boolean indicating whether the memory BIO is current at the end of file position read n 1 Read up to n bytes from the memory buffer If n is not specified or negative all bytes are returned write buf Write the bytes from buf to the memory BIO The buf argument must be an object supporting the buffer protocol The return value is the number of bytes written which is always equal to the length of buf write_eof Write an EOF marker to the memory BIO After this method has been called it is illegal to call write The attribute eof will become true after all data currently in the buffer has been read SSL session New in version 3 6 class ssl SSLSession Session object used by session id time timeout ticket_lifetime_hint has_ticket Security considerations Best defaults For client use if you don t have any special requirements for your security policy it is highly recommended that you use the create_default_context function to create your SSL context It will load the system s trusted CA certificates enable certificate validation and hostname checking and try to choose reasonably secure protocol and cipher settings For example here is how you would use the smtplib SMTP class to create a trusted secure connection to a SMTP server import ssl smtplib smtp smtplib SMTP mail python org port 587 context ssl create_default_context smtp starttls context context 220 b 2 0 0 Ready to start TLS If a client certificate is needed for the connection it can be added with SSLContext load_cert_chain By contrast if you create the SSL context by calling the SSLContext constructor yourself it will not have certificate validation nor hostname checking enabled by default If you do so please read the paragraphs below to achieve a good security level Manual settings Verifying certificates When calling the SSLContext constructor directly CERT_NONE is the default Since it does not authenticate the other peer it can be insecure especially in client mode where most of time you would like to ensure the authenticity of the server you re talking to Therefore when in client mode it is highly recommended to use CERT_REQUIRED However it is in itself not sufficient you also have to check that the server certificate which can be obtained by calling SSLSocket getpeercert matches the desired service For many protocols and applications the service can be identified by the hostname This common check is automatically performed when SSLContext check_host,en
2685,name is enabled Changed in version 3 7 Hostname matchings is now performed by OpenSSL Python no longer uses match_hostname In server mode if you want to authenticate your clients using the SSL layer rather than using a higher level authentication mechanism you ll also have to specify CERT_REQUIRED and similarly check the client certificate Protocol versions SSL versions 2 and 3 are considered insecure and are therefore dangerous to use If you want maximum compatibility between clients and servers it is recommended to use PROTOCOL_TLS_CLIENT or PROTOCOL_TLS_SERVER as the protocol version SSLv2 and SSLv3 are disabled by default client_context ssl SSLContext ssl PROTOCOL_TLS_CLIENT client_context minimum_version ssl TLSVersion TLSv1_3 client_context maximum_version ssl TLSVersion TLSv1_3 The SSL context created above will only allow TLSv1 3 and later if supported by your system connections to a server PROTOCOL_TLS_CLIENT implies certificate validation and hostname checks by default You have to load certificates into the context Cipher selection If you have advanced security requirements fine tuning of the ciphers enabled when negotiating a SSL session is possible through the SSLContext set_ciphers method Starting from Python 3 2 3 the ssl module disables certain weak ciphers by default but you may want to further restrict the cipher choice Be sure to read OpenSSL s documentation about the cipher list format If you want to check which ciphers are enabled by a given cipher list use SSLContext get_ciphers or the openssl ciphers command on your system Multi processing If using this module as part of a multi processed application using for example the multiprocessing or concurrent futures modules be aware that OpenSSL s internal random number generator does not properly handle forked processes Applications must change the PRNG state of the parent process if they use any SSL feature with os fork Any successful call of RAND_add or RAND_bytes is sufficient TLS 1 3 New in version 3 7 The TLS 1 3 protocol behaves slightly differently than previous version of TLS SSL Some new TLS 1 3 features are not yet available TLS 1 3 uses a disjunct set of cipher suites All AES GCM and ChaCha20 cipher suites are enabled by default The method SSLContext set_ciphers cannot enable or disable any TLS 1 3 ciphers yet but SSLContext get_ciphers returns them Session tickets are no longer sent as part of the initial handshake and are handled differently SSLSocket session and SSLSession are not compatible with TLS 1 3 Client side certificates are also no longer verified during the initial handshake A server can request a certificate at any time Clients process certificate requests while they send or receive application data from the server TLS 1 3 features like early data deferred TLS client cert request signature algorithm configuration and rekeying are not supported yet See also Class socket socket Documentation of underlying socket class SSL TLS Strong Encryption An Introduction Intro from the Apache HTTP Server documentation RFC 1422 Privacy Enhancement for Internet Electronic Mail Part II Certificate Based Key Management Steve Kent RFC 4086 Randomness Requirements for Security Donald E Jeffrey I Schiller RFC 5280 Internet X 509 Public Key Infrastructure Certificate and Certificate Revocation List CRL Profile D Cooper RFC 5246 The Transport Layer Security TLS Protocol Version 1 2 T Dierks et al RFC 6066 Transport Layer Security TLS Extensions D Eastlake IANA TLS Transport Layer Security TLS Parameters IANA RFC 7525 Recommendations for Secure Use of Transport Layer Security TLS and Datagram Transport Layer Security DTLS IETF Mozilla s Server Side TLS recommendations Mozilla,en
2686,Why is Python Installed on my Computer FAQ What is Python Python is a programming language It s used for many different applications It s used in some high schools and colleges as an introductory programming language because Python is easy to learn but it s also used by professional software developers at places such as Google NASA and Lucasfilm Ltd If you wish to learn more about Python start with the Beginner s Guide to Python Why is Python installed on my machine If you find Python installed on your system but don t remember installing it there are several possible ways it could have gotten there Perhaps another user on the computer wanted to learn programming and installed it you ll have to figure out who s been using the machine and might have installed it A third party application installed on the machine might have been written in Python and included a Python installation There are many such applications from GUI programs to network servers and administrative scripts Some Windows machines also have Python installed At this writing we re aware of computers from Hewlett Packard and Compaq that include Python Apparently some of HP Compaq s administrative tools are written in Python Many Unix compatible operating systems such as macOS and some Linux distributions have Python installed by default it s included in the base installation Can I delete Python That depends on where Python came from If someone installed it deliberately you can remove it without hurting anything On Windows use the Add Remove Programs icon in the Control Panel If Python was installed by a third party application you can also remove it but that application will no longer work You should use that application s uninstaller rather than removing Python directly If Python came with your operating system removing it is not recommended If you remove it whatever tools were written in Python will no longer run and some of them might be important to you Reinstalling the whole system would then be required to fix things again,en
2687,Installing Python Modules Email distutils sig python org As a popular open source development project Python has an active supporting community of contributors and users that also make their software available for other Python developers to use under open source license terms This allows Python users to share and collaborate effectively benefiting from the solutions others have already created to common and sometimes even rare problems as well as potentially contributing their own solutions to the common pool This guide covers the installation part of the process For a guide to creating and sharing your own Python projects refer to the Python packaging user guide Note For corporate and other institutional users be aware that many organisations have their own policies around using and contributing to open source software Please take such policies into account when making use of the distribution and installation tools provided with Python Key terms pip is the preferred installer program Starting with Python 3 4 it is included by default with the Python binary installers A virtual environment is a semi isolated Python environment that allows packages to be installed for use by a particular application rather than being installed system wide venv is the standard tool for creating virtual environments and has been part of Python since Python 3 3 Starting with Python 3 4 it defaults to installing pip into all created virtual environments virtualenv is a third party alternative and predecessor to venv It allows virtual environments to be used on versions of Python prior to 3 4 which either don t provide venv at all or aren t able to automatically install pip into created environments The Python Package Index is a public repository of open source licensed packages made available for use by other Python users the Python Packaging Authority is the group of developers and documentation authors responsible for the maintenance and evolution of the standard packaging tools and the associated metadata and file format standards They maintain a variety of tools documentation and issue trackers on GitHub distutils is the original build and distribution system first added to the Python standard library in 1998 While direct use of distutils is being phased out it still laid the foundation for the current packaging and distribution infrastructure and it not only remains part of the standard library but its name lives on in other ways such as the name of the mailing list used to coordinate Python packaging standards development Changed in version 3 5 The use of venv is now recommended for creating virtual environments See also Python Packaging User Guide Creating and using virtual environments Basic usage The standard packaging tools are all designed to be used from the command line The following command will install the latest version of a module and its dependencies from the Python Package Index python m pip install SomePackage Note For POSIX users including macOS and Linux users the examples in this guide assume the use of a virtual environment For Windows users the examples in this guide assume that the option to adjust the system PATH environment variable was selected when installing Python It s also possible to specify an exact or minimum version directly on the command line When using comparator operators such as or some other special character which get interpreted by shell the package name and the version should be enclosed within double quotes python m pip install SomePackage 1 0 4 specific version python m pip install SomePackage 1 0 4 minimum version Normally if a suitable module is already installed attempting to install it again will have no effect Upgrading existing modules must be requested explicitly python m pip install upgrade SomePackage More information and resources regarding pip and its capabilities can be found in the Python Packaging User Guide Creation of virtual environments is done through the venv module Installing packages into an active virtual environment uses the commands shown above See also Python Packaging ,en
2688,User Guide Installing Python Distribution Packages How do I These are quick answers or links for some common tasks install pip in versions of Python prior to Python 3 4 Python only started bundling pip with Python 3 4 For earlier versions pip needs to be bootstrapped as described in the Python Packaging User Guide See also Python Packaging User Guide Requirements for Installing Packages install packages just for the current user Passing the user option to python m pip install will install a package just for the current user rather than for all users of the system install scientific Python packages A number of scientific Python packages have complex binary dependencies and aren t currently easy to install using pip directly At this point in time it will often be easier for users to install these packages by other means rather than attempting to install them with pip See also Python Packaging User Guide Installing Scientific Packages work with multiple versions of Python installed in parallel On Linux macOS and other POSIX systems use the versioned Python commands in combination with the m switch to run the appropriate copy of pip python2 m pip install SomePackage default Python 2 python2 7 m pip install SomePackage specifically Python 2 7 python3 m pip install SomePackage default Python 3 python3 4 m pip install SomePackage specifically Python 3 4 Appropriately versioned pip commands may also be available On Windows use the py Python launcher in combination with the m switch py 2 m pip install SomePackage default Python 2 py 2 7 m pip install SomePackage specifically Python 2 7 py 3 m pip install SomePackage default Python 3 py 3 4 m pip install SomePackage specifically Python 3 4 Common installation issues Installing into the system Python on Linux On Linux systems a Python installation will typically be included as part of the distribution Installing into this Python installation requires root access to the system and may interfere with the operation of the system package manager and other components of the system if a component is unexpectedly upgraded using pip On such systems it is often better to use a virtual environment or a per user installation when installing packages with pip Pip not installed It is possible that pip does not get installed by default One potential fix is python m ensurepip default pip There are also additional resources for installing pip Installing binary extensions Python has typically relied heavily on source based distribution with end users being expected to compile extension modules from source as part of the installation process With the introduction of support for the binary wheel format and the ability to publish wheels for at least Windows and macOS through the Python Package Index this problem is expected to diminish over time as users are more regularly able to install pre built extensions rather than needing to build them themselves Some of the solutions for installing scientific software that are not yet available as pre built wheel files may also help with obtaining other binary extensions without needing to build them locally See also Python Packaging User Guide Binary Extensions,en
2689,Call Protocol CPython supports two different calling protocols tp_call and vectorcall The tp_call Protocol Instances of classes that set tp_call are callable The signature of the slot is PyObject tp_call PyObject callable PyObject args PyObject kwargs A call is made using a tuple for the positional arguments and a dict for the keyword arguments similarly to callable args kwargs in Python code args must be non NULL use an empty tuple if there are no arguments but kwargs may be NULL if there are no keyword arguments This convention is not only used by tp_call tp_new and tp_init also pass arguments this way To call an object use PyObject_Call or another call API The Vectorcall Protocol New in version 3 9 The vectorcall protocol was introduced in PEP 590 as an additional protocol for making calls more efficient As rule of thumb CPython will prefer the vectorcall for internal calls if the callable supports it However this is not a hard rule Additionally some third party extensions use tp_call directly rather than using PyObject_Call Therefore a class supporting vectorcall must also implement tp_call Moreover the callable must behave the same regardless of which protocol is used The recommended way to achieve this is by setting tp_call to PyVectorcall_Call This bears repeating Warning A class supporting vectorcall must also implement tp_call with the same semantics Changed in version 3 12 The Py_TPFLAGS_HAVE_VECTORCALL flag is now removed from a class when the class s __call__ method is reassigned This internally sets tp_call only and thus may make it behave differently than the vectorcall function In earlier Python versions vectorcall should only be used with immutable or static types A class should not implement vectorcall if that would be slower than tp_call For example if the callee needs to convert the arguments to an args tuple and kwargs dict anyway then there is no point in implementing vectorcall Classes can implement the vectorcall protocol by enabling the Py_TPFLAGS_HAVE_VECTORCALL flag and setting tp_vectorcall_offset to the offset inside the object structure where a vectorcallfunc appears This is a pointer to a function with the following signature typedef PyObject vectorcallfunc PyObject callable PyObject const args size_t nargsf PyObject kwnames Part of the Stable ABI since version 3 12 callable is the object being called args is a C array consisting of the positional arguments followed by the values of the keyword arguments This can be NULL if there are no arguments nargsf is the number of positional arguments plus possibly the PY_VECTORCALL_ARGUMENTS_OFFSET flag To get the actual number of positional arguments from nargsf use PyVectorcall_NARGS kwnames is a tuple containing the names of the keyword arguments in other words the keys of the kwargs dict These names must be strings instances of str or a subclass and they must be unique If there are no keyword arguments then kwnames can instead be NULL PY_VECTORCALL_ARGUMENTS_OFFSET Part of the Stable ABI since version 3 12 If this flag is set in a vectorcall nargsf argument the callee is allowed to temporarily change args 1 In other words args points to argument 1 not 0 in the allocated vector The callee must restore the value of args 1 before returning For PyObject_VectorcallMethod this flag means instead that args 0 may be changed Whenever they can do so cheaply without additional allocation callers are encouraged to use PY_VECTORCALL_ARGUMENTS_OFFSET Doing so will allow callables such as bound methods to make their onward calls which include a prepended self argument very efficiently New in version 3 8 To call an object that implements vectorcall use a call API function as with any other callable PyObject_Vectorcall will usually be most efficient Note In CPython 3 8 the vectorcall API and related functions were available provisionally under names with a leading underscore _PyObject_Vectorcall _Py_TPFLAGS_HAVE_VECTORCALL _PyObject_VectorcallMethod _PyVectorcall_Function _PyObject_CallOneArg _PyObject_CallMethodNoArgs _PyObject_CallMethodOneArg Additionally PyObj,en
2690,ect_VectorcallDict was available as _PyObject_FastCallDict The old names are still defined as aliases of the new non underscored names Recursion Control When using tp_call callees do not need to worry about recursion CPython uses Py_EnterRecursiveCall and Py_LeaveRecursiveCall for calls made using tp_call For efficiency this is not the case for calls done using vectorcall the callee should use Py_EnterRecursiveCall and Py_LeaveRecursiveCall if needed Vectorcall Support API Py_ssize_t PyVectorcall_NARGS size_t nargsf Part of the Stable ABI since version 3 12 Given a vectorcall nargsf argument return the actual number of arguments Currently equivalent to Py_ssize_t nargsf PY_VECTORCALL_ARGUMENTS_OFFSET However the function PyVectorcall_NARGS should be used to allow for future extensions New in version 3 8 vectorcallfunc PyVectorcall_Function PyObject op If op does not support the vectorcall protocol either because the type does not or because the specific instance does not return NULL Otherwise return the vectorcall function pointer stored in op This function never raises an exception This is mostly useful to check whether or not op supports vectorcall which can be done by checking PyVectorcall_Function op NULL New in version 3 9 PyObject PyVectorcall_Call PyObject callable PyObject tuple PyObject dict Part of the Stable ABI since version 3 12 Call callable s vectorcallfunc with positional and keyword arguments given in a tuple and dict respectively This is a specialized function intended to be put in the tp_call slot or be used in an implementation of tp_call It does not check the Py_TPFLAGS_HAVE_VECTORCALL flag and it does not fall back to tp_call New in version 3 8 Object Calling API Various functions are available for calling a Python object Each converts its arguments to a convention supported by the called object either tp_call or vectorcall In order to do as little conversion as possible pick one that best fits the format of data you have available The following table summarizes the available functions please see individual documentation for details Function callable args kwargs PyObject_Call PyObject tuple dict NULL PyObject_CallNoArgs PyObject PyObject_CallOneArg PyObject 1 object PyObject_CallObject PyObject tuple NULL PyObject_CallFunction PyObject format PyObject_CallMethod obj char format PyObject_CallFunctionObjArgs PyObject variadic PyObject_CallMethodObjArgs obj name variadic PyObject_CallMethodNoArgs obj name PyObject_CallMethodOneArg obj name 1 object PyObject_Vectorcall PyObject vectorcall vectorcall PyObject_VectorcallDict PyObject vectorcall dict NULL PyObject_VectorcallMethod arg name vectorcall vectorcall PyObject PyObject_Call PyObject callable PyObject args PyObject kwargs Return value New reference Part of the Stable ABI Call a callable Python object callable with arguments given by the tuple args and named arguments given by the dictionary kwargs args must not be NULL use an empty tuple if no arguments are needed If no named arguments are needed kwargs can be NULL Return the result of the call on success or raise an exception and return NULL on failure This is the equivalent of the Python expression callable args kwargs PyObject PyObject_CallNoArgs PyObject callable Return value New reference Part of the Stable ABI since version 3 10 Call a callable Python object callable without any arguments It is the most efficient way to call a callable Python object without any argument Return the result of the call on success or raise an exception and return NULL on failure New in version 3 9 PyObject PyObject_CallOneArg PyObject callable PyObject arg Return value New reference Call a callable Python object callable with exactly 1 positional argument arg and no keyword arguments Return the result of the call on success or raise an exception and return NULL on failure New in version 3 9 PyObject PyObject_CallObject PyObject callable PyObject args Return value New reference Part of the Stable ABI Call a callable Python object callable with arguments given by the tuple args If no arguments are needed then args,en
2691, can be NULL Return the result of the call on success or raise an exception and return NULL on failure This is the equivalent of the Python expression callable args PyObject PyObject_CallFunction PyObject callable const char format Return value New reference Part of the Stable ABI Call a callable Python object callable with a variable number of C arguments The C arguments are described using a Py_BuildValue style format string The format can be NULL indicating that no arguments are provided Return the result of the call on success or raise an exception and return NULL on failure This is the equivalent of the Python expression callable args Note that if you only pass PyObject args PyObject_CallFunctionObjArgs is a faster alternative Changed in version 3 4 The type of format was changed from char PyObject PyObject_CallMethod PyObject obj const char name const char format Return value New reference Part of the Stable ABI Call the method named name of object obj with a variable number of C arguments The C arguments are described by a Py_BuildValue format string that should produce a tuple The format can be NULL indicating that no arguments are provided Return the result of the call on success or raise an exception and return NULL on failure This is the equivalent of the Python expression obj name arg1 arg2 Note that if you only pass PyObject args PyObject_CallMethodObjArgs is a faster alternative Changed in version 3 4 The types of name and format were changed from char PyObject PyObject_CallFunctionObjArgs PyObject callable Return value New reference Part of the Stable ABI Call a callable Python object callable with a variable number of PyObject arguments The arguments are provided as a variable number of parameters followed by NULL Return the result of the call on success or raise an exception and return NULL on failure This is the equivalent of the Python expression callable arg1 arg2 PyObject PyObject_CallMethodObjArgs PyObject obj PyObject name Return value New reference Part of the Stable ABI Call a method of the Python object obj where the name of the method is given as a Python string object in name It is called with a variable number of PyObject arguments The arguments are provided as a variable number of parameters followed by NULL Return the result of the call on success or raise an exception and return NULL on failure PyObject PyObject_CallMethodNoArgs PyObject obj PyObject name Call a method of the Python object obj without arguments where the name of the method is given as a Python string object in name Return the result of the call on success or raise an exception and return NULL on failure New in version 3 9 PyObject PyObject_CallMethodOneArg PyObject obj PyObject name PyObject arg Call a method of the Python object obj with a single positional argument arg where the name of the method is given as a Python string object in name Return the result of the call on success or raise an exception and return NULL on failure New in version 3 9 PyObject PyObject_Vectorcall PyObject callable PyObject const args size_t nargsf PyObject kwnames Part of the Stable ABI since version 3 12 Call a callable Python object callable The arguments are the same as for vectorcallfunc If callable supports vectorcall this directly calls the vectorcall function stored in callable Return the result of the call on success or raise an exception and return NULL on failure New in version 3 9 PyObject PyObject_VectorcallDict PyObject callable PyObject const args size_t nargsf PyObject kwdict Call callable with positional arguments passed exactly as in the vectorcall protocol but with keyword arguments passed as a dictionary kwdict The args array contains only the positional arguments Regardless of which protocol is used internally a conversion of arguments needs to be done Therefore this function should only be used if the caller already has a dictionary ready to use for the keyword arguments but not a tuple for the positional arguments New in version 3 9 PyObject PyObject_VectorcallMethod PyObject name PyObject const args size_t nargsf PyObje,en
2692,ct kwnames Part of the Stable ABI since version 3 12 Call a method using the vectorcall calling convention The name of the method is given as a Python string name The object whose method is called is args 0 and the args array starting at args 1 represents the arguments of the call There must be at least one positional argument nargsf is the number of positional arguments including args 0 plus PY_VECTORCALL_ARGUMENTS_OFFSET if the value of args 0 may temporarily be changed Keyword arguments can be passed just like in PyObject_Vectorcall If the object has the Py_TPFLAGS_METHOD_DESCRIPTOR feature this will call the unbound method object with the full args vector as arguments Return the result of the call on success or raise an exception and return NULL on failure New in version 3 9 Call Support API int PyCallable_Check PyObject o Part of the Stable ABI Determine if the object o is callable Return 1 if the object is callable and 0 otherwise This function always succeeds,en
2693,Annotations Best Practices author Larry Hastings Abstract This document is designed to encapsulate the best practices for working with annotations dicts If you write Python code that examines __annotations__ on Python objects we encourage you to follow the guidelines described below The document is organized into four sections best practices for accessing the annotations of an object in Python versions 3 10 and newer best practices for accessing the annotations of an object in Python versions 3 9 and older other best practices for __annotations__ that apply to any Python version and quirks of __annotations__ Note that this document is specifically about working with __annotations__ not uses for annotations If you re looking for information on how to use type hints in your code please see the typing module Accessing The Annotations Dict Of An Object In Python 3 10 And Newer Python 3 10 adds a new function to the standard library inspect get_annotations In Python versions 3 10 and newer calling this function is the best practice for accessing the annotations dict of any object that supports annotations This function can also un stringize stringized annotations for you If for some reason inspect get_annotations isn t viable for your use case you may access the __annotations__ data member manually Best practice for this changed in Python 3 10 as well as of Python 3 10 o __annotations__ is guaranteed to always work on Python functions classes and modules If you re certain the object you re examining is one of these three specific objects you may simply use o __annotations__ to get at the object s annotations dict However other types of callables for example callables created by functools partial may not have an __annotations__ attribute defined When accessing the __annotations__ of a possibly unknown object best practice in Python versions 3 10 and newer is to call getattr with three arguments for example getattr o __annotations__ None Before Python 3 10 accessing __annotations__ on a class that defines no annotations but that has a parent class with annotations would return the parent s __annotations__ In Python 3 10 and newer the child class s annotations will be an empty dict instead Accessing The Annotations Dict Of An Object In Python 3 9 And Older In Python 3 9 and older accessing the annotations dict of an object is much more complicated than in newer versions The problem is a design flaw in these older versions of Python specifically to do with class annotations Best practice for accessing the annotations dict of other objects functions other callables and modules is the same as best practice for 3 10 assuming you aren t calling inspect get_annotations you should use three argument getattr to access the object s __annotations__ attribute Unfortunately this isn t best practice for classes The problem is that since __annotations__ is optional on classes and because classes can inherit attributes from their base classes accessing the __annotations__ attribute of a class may inadvertently return the annotations dict of a base class As an example class Base a int 3 b str abc class Derived Base pass print Derived __annotations__ This will print the annotations dict from Base not Derived Your code will have to have a separate code path if the object you re examining is a class isinstance o type In that case best practice relies on an implementation detail of Python 3 9 and before if a class has annotations defined they are stored in the class s __dict__ dictionary Since the class may or may not have annotations defined best practice is to call the get method on the class dict To put it all together here is some sample code that safely accesses the __annotations__ attribute on an arbitrary object in Python 3 9 and before if isinstance o type ann o __dict__ get __annotations__ None else ann getattr o __annotations__ None After running this code ann should be either a dictionary or None You re encouraged to double check the type of ann using isinstance before further examination Note that some exotic or malformed type objects m,en
2694,ay not have a __dict__ attribute so for extra safety you may also wish to use getattr to access __dict__ Manually Un Stringizing Stringized Annotations In situations where some annotations may be stringized and you wish to evaluate those strings to produce the Python values they represent it really is best to call inspect get_annotations to do this work for you If you re using Python 3 9 or older or if for some reason you can t use inspect get_annotations you ll need to duplicate its logic You re encouraged to examine the implementation of inspect get_annotations in the current Python version and follow a similar approach In a nutshell if you wish to evaluate a stringized annotation on an arbitrary object o If o is a module use o __dict__ as the globals when calling eval If o is a class use sys modules o __module__ __dict__ as the globals and dict vars o as the locals when calling eval If o is a wrapped callable using functools update_wrapper functools wraps or functools partial iteratively unwrap it by accessing either o __wrapped__ or o func as appropriate until you have found the root unwrapped function If o is a callable but not a class use o __globals__ as the globals when calling eval However not all string values used as annotations can be successfully turned into Python values by eval String values could theoretically contain any valid string and in practice there are valid use cases for type hints that require annotating with string values that specifically can t be evaluated For example PEP 604 union types using before support for this was added to Python 3 10 Definitions that aren t needed at runtime only imported when typing TYPE_CHECKING is true If eval attempts to evaluate such values it will fail and raise an exception So when designing a library API that works with annotations it s recommended to only attempt to evaluate string values when explicitly requested to by the caller Best Practices For __annotations__ In Any Python Version You should avoid assigning to the __annotations__ member of objects directly Let Python manage setting __annotations__ If you do assign directly to the __annotations__ member of an object you should always set it to a dict object If you directly access the __annotations__ member of an object you should ensure that it s a dictionary before attempting to examine its contents You should avoid modifying __annotations__ dicts You should avoid deleting the __annotations__ attribute of an object __annotations__ Quirks In all versions of Python 3 function objects lazy create an annotations dict if no annotations are defined on that object You can delete the __annotations__ attribute using del fn __annotations__ but if you then access fn __annotations__ the object will create a new empty dict that it will store and return as its annotations Deleting the annotations on a function before it has lazily created its annotations dict will throw an AttributeError using del fn __annotations__ twice in a row is guaranteed to always throw an AttributeError Everything in the above paragraph also applies to class and module objects in Python 3 10 and newer In all versions of Python 3 you can set __annotations__ on a function object to None However subsequently accessing the annotations on that object using fn __annotations__ will lazy create an empty dictionary as per the first paragraph of this section This is not true of modules and classes in any Python version those objects permit setting __annotations__ to any Python value and will retain whatever value is set If Python stringizes your annotations for you using from __future__ import annotations and you specify a string as an annotation the string will itself be quoted In effect the annotation is quoted twice For example from __future__ import annotations def foo a str pass print foo __annotations__ This prints a str This shouldn t really be considered a quirk it s mentioned here simply because it might be surprising,en
2695,Coroutine Objects New in version 3 5 Coroutine objects are what functions declared with an async keyword return type PyCoroObject The C structure used for coroutine objects PyTypeObject PyCoro_Type The type object corresponding to coroutine objects int PyCoro_CheckExact PyObject ob Return true if ob s type is PyCoro_Type ob must not be NULL This function always succeeds PyObject PyCoro_New PyFrameObject frame PyObject name PyObject qualname Return value New reference Create and return a new coroutine object based on the frame object with __name__ and __qualname__ set to name and qualname A reference to frame is stolen by this function The frame argument must not be NULL,en
2696,Buffer Protocol Certain objects available in Python wrap access to an underlying memory array or buffer Such objects include the built in bytes and bytearray and some extension types like array array Third party libraries may define their own types for special purposes such as image processing or numeric analysis While each of these types have their own semantics they share the common characteristic of being backed by a possibly large memory buffer It is then desirable in some situations to access that buffer directly and without intermediate copying Python provides such a facility at the C level in the form of the buffer protocol This protocol has two sides on the producer side a type can export a buffer interface which allows objects of that type to expose information about their underlying buffer This interface is described in the section Buffer Object Structures on the consumer side several means are available to obtain a pointer to the raw underlying data of an object for example a method parameter Simple objects such as bytes and bytearray expose their underlying buffer in byte oriented form Other forms are possible for example the elements exposed by an array array can be multi byte values An example consumer of the buffer interface is the write method of file objects any object that can export a series of bytes through the buffer interface can be written to a file While write only needs read only access to the internal contents of the object passed to it other methods such as readinto need write access to the contents of their argument The buffer interface allows objects to selectively allow or reject exporting of read write and read only buffers There are two ways for a consumer of the buffer interface to acquire a buffer over a target object call PyObject_GetBuffer with the right parameters call PyArg_ParseTuple or one of its siblings with one of the y w or s format codes In both cases PyBuffer_Release must be called when the buffer isn t needed anymore Failure to do so could lead to various issues such as resource leaks Buffer structure Buffer structures or simply buffers are useful as a way to expose the binary data from another object to the Python programmer They can also be used as a zero copy slicing mechanism Using their ability to reference a block of memory it is possible to expose any data to the Python programmer quite easily The memory could be a large constant array in a C extension it could be a raw block of memory for manipulation before passing to an operating system library or it could be used to pass around structured data in its native in memory format Contrary to most data types exposed by the Python interpreter buffers are not PyObject pointers but rather simple C structures This allows them to be created and copied very simply When a generic wrapper around a buffer is needed a memoryview object can be created For short instructions how to write an exporting object see Buffer Object Structures For obtaining a buffer see PyObject_GetBuffer type Py_buffer Part of the Stable ABI including all members since version 3 11 void buf A pointer to the start of the logical structure described by the buffer fields This can be any location within the underlying physical memory block of the exporter For example with negative strides the value may point to the end of the memory block For contiguous arrays the value points to the beginning of the memory block PyObject obj A new reference to the exporting object The reference is owned by the consumer and automatically released i e reference count decremented and set to NULL by PyBuffer_Release The field is the equivalent of the return value of any standard C API function As a special case for temporary buffers that are wrapped by PyMemoryView_FromBuffer or PyBuffer_FillInfo this field is NULL In general exporting objects MUST NOT use this scheme Py_ssize_t len product shape itemsize For contiguous arrays this is the length of the underlying memory block For non contiguous arrays it is the length that the logical structure would have if it were copied to a c,en
2697,ontiguous representation Accessing char buf 0 up to char buf len 1 is only valid if the buffer has been obtained by a request that guarantees contiguity In most cases such a request will be PyBUF_SIMPLE or PyBUF_WRITABLE int readonly An indicator of whether the buffer is read only This field is controlled by the PyBUF_WRITABLE flag Py_ssize_t itemsize Item size in bytes of a single element Same as the value of struct calcsize called on non NULL format values Important exception If a consumer requests a buffer without the PyBUF_FORMAT flag format will be set to NULL but itemsize still has the value for the original format If shape is present the equality product shape itemsize len still holds and the consumer can use itemsize to navigate the buffer If shape is NULL as a result of a PyBUF_SIMPLE or a PyBUF_WRITABLE request the consumer must disregard itemsize and assume itemsize 1 const char format A NUL terminated string in struct module style syntax describing the contents of a single item If this is NULL B unsigned bytes is assumed This field is controlled by the PyBUF_FORMAT flag int ndim The number of dimensions the memory represents as an n dimensional array If it is 0 buf points to a single item representing a scalar In this case shape strides and suboffsets MUST be NULL The maximum number of dimensions is given by PyBUF_MAX_NDIM Py_ssize_t shape An array of Py_ssize_t of length ndim indicating the shape of the memory as an n dimensional array Note that shape 0 shape ndim 1 itemsize MUST be equal to len Shape values are restricted to shape n 0 The case shape n 0 requires special attention See complex arrays for further information The shape array is read only for the consumer Py_ssize_t strides An array of Py_ssize_t of length ndim giving the number of bytes to skip to get to a new element in each dimension Stride values can be any integer For regular arrays strides are usually positive but a consumer MUST be able to handle the case strides n 0 See complex arrays for further information The strides array is read only for the consumer Py_ssize_t suboffsets An array of Py_ssize_t of length ndim If suboffsets n 0 the values stored along the nth dimension are pointers and the suboffset value dictates how many bytes to add to each pointer after de referencing A suboffset value that is negative indicates that no de referencing should occur striding in a contiguous memory block If all suboffsets are negative i e no de referencing is needed then this field must be NULL the default value This type of array representation is used by the Python Imaging Library PIL See complex arrays for further information how to access elements of such an array The suboffsets array is read only for the consumer void internal This is for use internally by the exporting object For example this might be re cast as an integer by the exporter and used to store flags about whether or not the shape strides and suboffsets arrays must be freed when the buffer is released The consumer MUST NOT alter this value Constants PyBUF_MAX_NDIM The maximum number of dimensions the memory represents Exporters MUST respect this limit consumers of multi dimensional buffers SHOULD be able to handle up to PyBUF_MAX_NDIM dimensions Currently set to 64 Buffer request types Buffers are usually obtained by sending a buffer request to an exporting object via PyObject_GetBuffer Since the complexity of the logical structure of the memory can vary drastically the consumer uses the flags argument to specify the exact buffer type it can handle All Py_buffer fields are unambiguously defined by the request type request independent fields The following fields are not influenced by flags and must always be filled in with the correct values obj buf len itemsize ndim readonly format PyBUF_WRITABLE Controls the readonly field If set the exporter MUST provide a writable buffer or else report failure Otherwise the exporter MAY provide either a read only or writable buffer but the choice MUST be consistent for all consumers PyBUF_FORMAT Controls the format field If set this field MUST b,en
2698,e filled in correctly Otherwise this field MUST be NULL PyBUF_WRITABLE can be d to any of the flags in the next section Since PyBUF_SIMPLE is defined as 0 PyBUF_WRITABLE can be used as a stand alone flag to request a simple writable buffer PyBUF_FORMAT can be d to any of the flags except PyBUF_SIMPLE The latter already implies format B unsigned bytes shape strides suboffsets The flags that control the logical structure of the memory are listed in decreasing order of complexity Note that each flag contains all bits of the flags below it Request shape strides suboffsets PyBUF_INDIRECT yes yes if needed PyBUF_STRIDES yes yes NULL PyBUF_ND yes NULL NULL PyBUF_SIMPLE NULL NULL NULL contiguity requests C or Fortran contiguity can be explicitly requested with and without stride information Without stride information the buffer must be C contiguous Request shape strides suboffsets contig PyBUF_C_CONTIGUOUS yes yes NULL C PyBUF_F_CONTIGUOUS yes yes NULL F PyBUF_ANY_CONTIGUOUS yes yes NULL C or F PyBUF_ND yes NULL NULL C compound requests All possible requests are fully defined by some combination of the flags in the previous section For convenience the buffer protocol provides frequently used combinations as single flags In the following table U stands for undefined contiguity The consumer would have to call PyBuffer_IsContiguous to determine contiguity Request shape strides suboffsets contig readonly format PyBUF_FULL yes yes if needed U 0 yes PyBUF_FULL_RO yes yes if needed U 1 or 0 yes PyBUF_RECORDS yes yes NULL U 0 yes PyBUF_RECORDS_RO yes yes NULL U 1 or 0 yes PyBUF_STRIDED yes yes NULL U 0 NULL PyBUF_STRIDED_RO yes yes NULL U 1 or 0 NULL PyBUF_CONTIG yes NULL NULL C 0 NULL PyBUF_CONTIG_RO yes NULL NULL C 1 or 0 NULL Complex arrays NumPy style shape and strides The logical structure of NumPy style arrays is defined by itemsize ndim shape and strides If ndim 0 the memory location pointed to by buf is interpreted as a scalar of size itemsize In that case both shape and strides are NULL If strides is NULL the array is interpreted as a standard n dimensional C array Otherwise the consumer must access an n dimensional array as follows ptr char buf indices 0 strides 0 indices n 1 strides n 1 item typeof item ptr As noted above buf can point to any location within the actual memory block An exporter can check the validity of a buffer with this function def verify_structure memlen itemsize ndim shape strides offset Verify that the parameters represent a valid array within the bounds of the allocated memory char mem start of the physical memory block memlen length of the physical memory block offset char buf mem if offset itemsize return False if offset 0 or offset itemsize memlen return False if any v itemsize for v in strides return False if ndim 0 return ndim 0 and not shape and not strides if 0 in shape return True imin sum strides j shape j 1 for j in range ndim if strides j 0 imax sum strides j shape j 1 for j in range ndim if strides j 0 return 0 offset imin and offset imax itemsize memlen PIL style shape strides and suboffsets In addition to the regular items PIL style arrays can contain pointers that must be followed in order to get to the next element in a dimension For example the regular three dimensional C array char v 2 2 3 can also be viewed as an array of 2 pointers to 2 two dimensional arrays char v 2 2 3 In suboffsets representation those two pointers can be embedded at the start of buf pointing to two char x 2 3 arrays that can be located anywhere in memory Here is a function that returns a pointer to the element in an N D array pointed to by an N dimensional index when there are both non NULL strides and suboffsets void get_item_pointer int ndim void buf Py_ssize_t strides Py_ssize_t suboffsets Py_ssize_t indices char pointer char buf int i for i 0 i ndim i pointer strides i indices i if suboffsets i 0 pointer char pointer suboffsets i return void pointer Buffer related functions int PyObject_CheckBuffer PyObject obj Part of the Stable ABI since version 3 11 Return 1 if obj supports the buffer interface otherwise ,en
2699,0 When 1 is returned it doesn t guarantee that PyObject_GetBuffer will succeed This function always succeeds int PyObject_GetBuffer PyObject exporter Py_buffer view int flags Part of the Stable ABI since version 3 11 Send a request to exporter to fill in view as specified by flags If the exporter cannot provide a buffer of the exact type it MUST raise BufferError set view obj to NULL and return 1 On success fill in view set view obj to a new reference to exporter and return 0 In the case of chained buffer providers that redirect requests to a single object view obj MAY refer to this object instead of exporter See Buffer Object Structures Successful calls to PyObject_GetBuffer must be paired with calls to PyBuffer_Release similar to malloc and free Thus after the consumer is done with the buffer PyBuffer_Release must be called exactly once void PyBuffer_Release Py_buffer view Part of the Stable ABI since version 3 11 Release the buffer view and release the strong reference i e decrement the reference count to the view s supporting object view obj This function MUST be called when the buffer is no longer being used otherwise reference leaks may occur It is an error to call this function on a buffer that was not obtained via PyObject_GetBuffer Py_ssize_t PyBuffer_SizeFromFormat const char format Part of the Stable ABI since version 3 11 Return the implied itemsize from format On error raise an exception and return 1 New in version 3 9 int PyBuffer_IsContiguous const Py_buffer view char order Part of the Stable ABI since version 3 11 Return 1 if the memory defined by the view is C style order is C or Fortran style order is F contiguous or either one order is A Return 0 otherwise This function always succeeds void PyBuffer_GetPointer const Py_buffer view const Py_ssize_t indices Part of the Stable ABI since version 3 11 Get the memory area pointed to by the indices inside the given view indices must point to an array of view ndim indices int PyBuffer_FromContiguous const Py_buffer view const void buf Py_ssize_t len char fort Part of the Stable ABI since version 3 11 Copy contiguous len bytes from buf to view fort can be C or F for C style or Fortran style ordering 0 is returned on success 1 on error int PyBuffer_ToContiguous void buf const Py_buffer src Py_ssize_t len char order Part of the Stable ABI since version 3 11 Copy len bytes from src to its contiguous representation in buf order can be C or F or A for C style or Fortran style ordering or either one 0 is returned on success 1 on error This function fails if len src len int PyObject_CopyData PyObject dest PyObject src Part of the Stable ABI since version 3 11 Copy data from src to dest buffer Can convert between C style and or Fortran style buffers 0 is returned on success 1 on error void PyBuffer_FillContiguousStrides int ndims Py_ssize_t shape Py_ssize_t strides int itemsize char order Part of the Stable ABI since version 3 11 Fill the strides array with byte strides of a contiguous C style if order is C or Fortran style if order is F array of the given shape with the given number of bytes per element int PyBuffer_FillInfo Py_buffer view PyObject exporter void buf Py_ssize_t len int readonly int flags Part of the Stable ABI since version 3 11 Handle buffer requests for an exporter that wants to expose buf of size len with writability set according to readonly buf is interpreted as a sequence of unsigned bytes The flags argument indicates the request type This function always fills in view as specified by flags unless buf has been designated as read only and PyBUF_WRITABLE is set in flags On success set view obj to a new reference to exporter and return 0 Otherwise raise BufferError set view obj to NULL and return 1 If this function is used as part of a getbufferproc exporter MUST be set to the exporting object and flags must be passed unmodified Otherwise exporter MUST be NULL,en
2700,signal Set handlers for asynchronous events Source code Lib signal py This module provides mechanisms to use signal handlers in Python General rules The signal signal function allows defining custom handlers to be executed when a signal is received A small number of default handlers are installed SIGPIPE is ignored so write errors on pipes and sockets can be reported as ordinary Python exceptions and SIGINT is translated into a KeyboardInterrupt exception if the parent process has not changed it A handler for a particular signal once set remains installed until it is explicitly reset Python emulates the BSD style interface regardless of the underlying implementation with the exception of the handler for SIGCHLD which follows the underlying implementation On WebAssembly platforms wasm32 emscripten and wasm32 wasi signals are emulated and therefore behave differently Several functions and signals are not available on these platforms Execution of Python signal handlers A Python signal handler does not get executed inside the low level C signal handler Instead the low level signal handler sets a flag which tells the virtual machine to execute the corresponding Python signal handler at a later point for example at the next bytecode instruction This has consequences It makes little sense to catch synchronous errors like SIGFPE or SIGSEGV that are caused by an invalid operation in C code Python will return from the signal handler to the C code which is likely to raise the same signal again causing Python to apparently hang From Python 3 3 onwards you can use the faulthandler module to report on synchronous errors A long running calculation implemented purely in C such as regular expression matching on a large body of text may run uninterrupted for an arbitrary amount of time regardless of any signals received The Python signal handlers will be called when the calculation finishes If the handler raises an exception it will be raised out of thin air in the main thread See the note below for a discussion Signals and threads Python signal handlers are always executed in the main Python thread of the main interpreter even if the signal was received in another thread This means that signals can t be used as a means of inter thread communication You can use the synchronization primitives from the threading module instead Besides only the main thread of the main interpreter is allowed to set a new signal handler Module contents Changed in version 3 5 signal SIG handler SIG_DFL SIG_IGN and sigmask SIG_BLOCK SIG_UNBLOCK SIG_SETMASK related constants listed below were turned into enums Signals Handlers and Sigmasks respectively getsignal pthread_sigmask sigpending and sigwait functions return human readable enums as Signals objects The signal module defines three enums class signal Signals enum IntEnum collection of SIG constants and the CTRL_ constants New in version 3 5 class signal Handlers enum IntEnum collection the constants SIG_DFL and SIG_IGN New in version 3 5 class signal Sigmasks enum IntEnum collection the constants SIG_BLOCK SIG_UNBLOCK and SIG_SETMASK Availability Unix See the man page sigprocmask 2 and pthread_sigmask 3 for further information New in version 3 5 The variables defined in the signal module are signal SIG_DFL This is one of two standard signal handling options it will simply perform the default function for the signal For example on most systems the default action for SIGQUIT is to dump core and exit while the default action for SIGCHLD is to simply ignore it signal SIG_IGN This is another standard signal handler which will simply ignore the given signal signal SIGABRT Abort signal from abort 3 signal SIGALRM Timer signal from alarm 2 Availability Unix signal SIGBREAK Interrupt from keyboard CTRL BREAK Availability Windows signal SIGBUS Bus error bad memory access Availability Unix signal SIGCHLD Child process stopped or terminated Availability Unix signal SIGCLD Alias to SIGCHLD Availability not macOS signal SIGCONT Continue the process if it is currently stopped Availability Unix signal SIGFPE Floating point,en
2701, exception For example division by zero See also ZeroDivisionError is raised when the second argument of a division or modulo operation is zero signal SIGHUP Hangup detected on controlling terminal or death of controlling process Availability Unix signal SIGILL Illegal instruction signal SIGINT Interrupt from keyboard CTRL C Default action is to raise KeyboardInterrupt signal SIGKILL Kill signal It cannot be caught blocked or ignored Availability Unix signal SIGPIPE Broken pipe write to pipe with no readers Default action is to ignore the signal Availability Unix signal SIGSEGV Segmentation fault invalid memory reference signal SIGSTKFLT Stack fault on coprocessor The Linux kernel does not raise this signal it can only be raised in user space Availability Linux On architectures where the signal is available See the man page signal 7 for further information New in version 3 11 signal SIGTERM Termination signal signal SIGUSR1 User defined signal 1 Availability Unix signal SIGUSR2 User defined signal 2 Availability Unix signal SIGWINCH Window resize signal Availability Unix SIG All the signal numbers are defined symbolically For example the hangup signal is defined as signal SIGHUP the variable names are identical to the names used in C programs as found in signal h The Unix man page for signal lists the existing signals on some systems this is signal 2 on others the list is in signal 7 Note that not all systems define the same set of signal names only those names defined by the system are defined by this module signal CTRL_C_EVENT The signal corresponding to the Ctrl C keystroke event This signal can only be used with os kill Availability Windows New in version 3 2 signal CTRL_BREAK_EVENT The signal corresponding to the Ctrl Break keystroke event This signal can only be used with os kill Availability Windows New in version 3 2 signal NSIG One more than the number of the highest signal number Use valid_signals to get valid signal numbers signal ITIMER_REAL Decrements interval timer in real time and delivers SIGALRM upon expiration signal ITIMER_VIRTUAL Decrements interval timer only when the process is executing and delivers SIGVTALRM upon expiration signal ITIMER_PROF Decrements interval timer both when the process executes and when the system is executing on behalf of the process Coupled with ITIMER_VIRTUAL this timer is usually used to profile the time spent by the application in user and kernel space SIGPROF is delivered upon expiration signal SIG_BLOCK A possible value for the how parameter to pthread_sigmask indicating that signals are to be blocked New in version 3 3 signal SIG_UNBLOCK A possible value for the how parameter to pthread_sigmask indicating that signals are to be unblocked New in version 3 3 signal SIG_SETMASK A possible value for the how parameter to pthread_sigmask indicating that the signal mask is to be replaced New in version 3 3 The signal module defines one exception exception signal ItimerError Raised to signal an error from the underlying setitimer or getitimer implementation Expect this error if an invalid interval timer or a negative time is passed to setitimer This error is a subtype of OSError New in version 3 3 This error used to be a subtype of IOError which is now an alias of OSError The signal module defines the following functions signal alarm time If time is non zero this function requests that a SIGALRM signal be sent to the process in time seconds Any previously scheduled alarm is canceled only one alarm can be scheduled at any time The returned value is then the number of seconds before any previously set alarm was to have been delivered If time is zero no alarm is scheduled and any scheduled alarm is canceled If the return value is zero no alarm is currently scheduled Availability Unix See the man page alarm 2 for further information signal getsignal signalnum Return the current signal handler for the signal signalnum The returned value may be a callable Python object or one of the special values signal SIG_IGN signal SIG_DFL or None Here signal SIG_IGN means that the signal was pr,en
2702,eviously ignored signal SIG_DFL means that the default way of handling the signal was previously in use and None means that the previous signal handler was not installed from Python signal strsignal signalnum Returns the description of signal signalnum such as Interrupt for SIGINT Returns None if signalnum has no description Raises ValueError if signalnum is invalid New in version 3 8 signal valid_signals Return the set of valid signal numbers on this platform This can be less than range 1 NSIG if some signals are reserved by the system for internal use New in version 3 8 signal pause Cause the process to sleep until a signal is received the appropriate handler will then be called Returns nothing Availability Unix See the man page signal 2 for further information See also sigwait sigwaitinfo sigtimedwait and sigpending signal raise_signal signum Sends a signal to the calling process Returns nothing New in version 3 8 signal pidfd_send_signal pidfd sig siginfo None flags 0 Send signal sig to the process referred to by file descriptor pidfd Python does not currently support the siginfo parameter it must be None The flags argument is provided for future extensions no flag values are currently defined See the pidfd_send_signal 2 man page for more information Availability Linux 5 1 New in version 3 9 signal pthread_kill thread_id signalnum Send the signal signalnum to the thread thread_id another thread in the same process as the caller The target thread can be executing any code Python or not However if the target thread is executing the Python interpreter the Python signal handlers will be executed by the main thread of the main interpreter Therefore the only point of sending a signal to a particular Python thread would be to force a running system call to fail with InterruptedError Use threading get_ident or the ident attribute of threading Thread objects to get a suitable value for thread_id If signalnum is 0 then no signal is sent but error checking is still performed this can be used to check if the target thread is still running Raises an auditing event signal pthread_kill with arguments thread_id signalnum Availability Unix See the man page pthread_kill 3 for further information See also os kill New in version 3 3 signal pthread_sigmask how mask Fetch and or change the signal mask of the calling thread The signal mask is the set of signals whose delivery is currently blocked for the caller Return the old signal mask as a set of signals The behavior of the call is dependent on the value of how as follows SIG_BLOCK The set of blocked signals is the union of the current set and the mask argument SIG_UNBLOCK The signals in mask are removed from the current set of blocked signals It is permissible to attempt to unblock a signal which is not blocked SIG_SETMASK The set of blocked signals is set to the mask argument mask is a set of signal numbers e g signal SIGINT signal SIGTERM Use valid_signals for a full mask including all signals For example signal pthread_sigmask signal SIG_BLOCK reads the signal mask of the calling thread SIGKILL and SIGSTOP cannot be blocked Availability Unix See the man page sigprocmask 2 and pthread_sigmask 3 for further information See also pause sigpending and sigwait New in version 3 3 signal setitimer which seconds interval 0 0 Sets given interval timer one of signal ITIMER_REAL signal ITIMER_VIRTUAL or signal ITIMER_PROF specified by which to fire after seconds float is accepted different from alarm and after that every interval seconds if interval is non zero The interval timer specified by which can be cleared by setting seconds to zero When an interval timer fires a signal is sent to the process The signal sent is dependent on the timer being used signal ITIMER_REAL will deliver SIGALRM signal ITIMER_VIRTUAL sends SIGVTALRM and signal ITIMER_PROF will deliver SIGPROF The old values are returned as a tuple delay interval Attempting to pass an invalid interval timer will cause an ItimerError Availability Unix signal getitimer which Returns current value of a given interval timer specified by ,en
2703,which Availability Unix signal set_wakeup_fd fd warn_on_full_buffer True Set the wakeup file descriptor to fd When a signal is received the signal number is written as a single byte into the fd This can be used by a library to wakeup a poll or select call allowing the signal to be fully processed The old wakeup fd is returned or 1 if file descriptor wakeup was not enabled If fd is 1 file descriptor wakeup is disabled If not 1 fd must be non blocking It is up to the library to remove any bytes from fd before calling poll or select again When threads are enabled this function can only be called from the main thread of the main interpreter attempting to call it from other threads will cause a ValueError exception to be raised There are two common ways to use this function In both approaches you use the fd to wake up when a signal arrives but then they differ in how they determine which signal or signals have arrived In the first approach we read the data out of the fd s buffer and the byte values give you the signal numbers This is simple but in rare cases it can run into a problem generally the fd will have a limited amount of buffer space and if too many signals arrive too quickly then the buffer may become full and some signals may be lost If you use this approach then you should set warn_on_full_buffer True which will at least cause a warning to be printed to stderr when signals are lost In the second approach we use the wakeup fd only for wakeups and ignore the actual byte values In this case all we care about is whether the fd s buffer is empty or non empty a full buffer doesn t indicate a problem at all If you use this approach then you should set warn_on_full_buffer False so that your users are not confused by spurious warning messages Changed in version 3 5 On Windows the function now also supports socket handles Changed in version 3 7 Added warn_on_full_buffer parameter signal siginterrupt signalnum flag Change system call restart behaviour if flag is False system calls will be restarted when interrupted by signal signalnum otherwise system calls will be interrupted Returns nothing Availability Unix See the man page siginterrupt 3 for further information Note that installing a signal handler with signal will reset the restart behaviour to interruptible by implicitly calling siginterrupt with a true flag value for the given signal signal signal signalnum handler Set the handler for signal signalnum to the function handler handler can be a callable Python object taking two arguments see below or one of the special values signal SIG_IGN or signal SIG_DFL The previous signal handler will be returned see the description of getsignal above See the Unix man page signal 2 for further information When threads are enabled this function can only be called from the main thread of the main interpreter attempting to call it from other threads will cause a ValueError exception to be raised The handler is called with two arguments the signal number and the current stack frame None or a frame object for a description of frame objects see the description in the type hierarchy or see the attribute descriptions in the inspect module On Windows signal can only be called with SIGABRT SIGFPE SIGILL SIGINT SIGSEGV SIGTERM or SIGBREAK A ValueError will be raised in any other case Note that not all systems define the same set of signal names an AttributeError will be raised if a signal name is not defined as SIG module level constant signal sigpending Examine the set of signals that are pending for delivery to the calling thread i e the signals which have been raised while blocked Return the set of the pending signals Availability Unix See the man page sigpending 2 for further information See also pause pthread_sigmask and sigwait New in version 3 3 signal sigwait sigset Suspend execution of the calling thread until the delivery of one of the signals specified in the signal set sigset The function accepts the signal removes it from the pending list of signals and returns the signal number Availability Unix See the man page sigwait 3 for fu,en
2704,rther information See also pause pthread_sigmask sigpending sigwaitinfo and sigtimedwait New in version 3 3 signal sigwaitinfo sigset Suspend execution of the calling thread until the delivery of one of the signals specified in the signal set sigset The function accepts the signal and removes it from the pending list of signals If one of the signals in sigset is already pending for the calling thread the function will return immediately with information about that signal The signal handler is not called for the delivered signal The function raises an InterruptedError if it is interrupted by a signal that is not in sigset The return value is an object representing the data contained in the siginfo_t structure namely si_signo si_code si_errno si_pid si_uid si_status si_band Availability Unix See the man page sigwaitinfo 2 for further information See also pause sigwait and sigtimedwait New in version 3 3 Changed in version 3 5 The function is now retried if interrupted by a signal not in sigset and the signal handler does not raise an exception see PEP 475 for the rationale signal sigtimedwait sigset timeout Like sigwaitinfo but takes an additional timeout argument specifying a timeout If timeout is specified as 0 a poll is performed Returns None if a timeout occurs Availability Unix See the man page sigtimedwait 2 for further information See also pause sigwait and sigwaitinfo New in version 3 3 Changed in version 3 5 The function is now retried with the recomputed timeout if interrupted by a signal not in sigset and the signal handler does not raise an exception see PEP 475 for the rationale Examples Here is a minimal example program It uses the alarm function to limit the time spent waiting to open a file this is useful if the file is for a serial device that may not be turned on which would normally cause the os open to hang indefinitely The solution is to set a 5 second alarm before opening the file if the operation takes too long the alarm signal will be sent and the handler raises an exception import signal os def handler signum frame signame signal Signals signum name print f Signal handler called with signal signame signum raise OSError Couldn t open device Set the signal handler and a 5 second alarm signal signal signal SIGALRM handler signal alarm 5 This open may hang indefinitely fd os open dev ttyS0 os O_RDWR signal alarm 0 Disable the alarm Note on SIGPIPE Piping output of your program to tools like head 1 will cause a SIGPIPE signal to be sent to your process when the receiver of its standard output closes early This results in an exception like BrokenPipeError Errno 32 Broken pipe To handle this case wrap your entry point to catch this exception as follows import os import sys def main try simulate large output your code replaces this loop for x in range 10000 print y flush output here to force SIGPIPE to be triggered while inside this try block sys stdout flush except BrokenPipeError Python flushes standard streams on exit redirect remaining output to devnull to avoid another BrokenPipeError at shutdown devnull os open os devnull os O_WRONLY os dup2 devnull sys stdout fileno sys exit 1 Python exits with error code 1 on EPIPE if __name__ __main__ main Do not set SIGPIPE s disposition to SIG_DFL in order to avoid BrokenPipeError Doing that would cause your program to exit unexpectedly whenever any socket connection is interrupted while your program is still writing to it Note on Signal Handlers and Exceptions If a signal handler raises an exception the exception will be propagated to the main thread and may be raised after any bytecode instruction Most notably a KeyboardInterrupt may appear at any point during execution Most Python code including the standard library cannot be made robust against this and so a KeyboardInterrupt or any other exception resulting from a signal handler may on rare occasions put the program in an unexpected state To illustrate this issue consider the following code class SpamContext def __init__ self self lock threading Lock def __enter__ self If KeyboardInterrupt occurs here every,en
2705,thing is fine self lock acquire If KeyboardInterrupt occurs here __exit__ will not be called KeyboardInterrupt could occur just before the function returns def __exit__ self exc_type exc_val exc_tb self lock release For many programs especially those that merely want to exit on KeyboardInterrupt this is not a problem but applications that are complex or require high reliability should avoid raising exceptions from signal handlers They should also avoid catching KeyboardInterrupt as a means of gracefully shutting down Instead they should install their own SIGINT handler Below is an example of an HTTP server that avoids KeyboardInterrupt import signal import socket from selectors import DefaultSelector EVENT_READ from http server import HTTPServer SimpleHTTPRequestHandler interrupt_read interrupt_write socket socketpair def handler signum frame print Signal handler called with signal signum interrupt_write send b 0 signal signal signal SIGINT handler def serve_forever httpd sel DefaultSelector sel register interrupt_read EVENT_READ sel register httpd EVENT_READ while True for key _ in sel select if key fileobj interrupt_read interrupt_read recv 1 return if key fileobj httpd httpd handle_request print Serving on port 8000 httpd HTTPServer 8000 SimpleHTTPRequestHandler serve_forever httpd print Shutdown,en
2706,email headerregistry Custom Header Objects Source code Lib email headerregistry py New in version 3 6 1 Headers are represented by customized subclasses of str The particular class used to represent a given header is determined by the header_factory of the policy in effect when the headers are created This section documents the particular header_factory implemented by the email package for handling RFC 5322 compliant email messages which not only provides customized header objects for various header types but also provides an extension mechanism for applications to add their own custom header types When using any of the policy objects derived from EmailPolicy all headers are produced by HeaderRegistry and have BaseHeader as their last base class Each header class has an additional base class that is determined by the type of the header For example many headers have the class UnstructuredHeader as their other base class The specialized second class for a header is determined by the name of the header using a lookup table stored in the HeaderRegistry All of this is managed transparently for the typical application program but interfaces are provided for modifying the default behavior for use by more complex applications The sections below first document the header base classes and their attributes followed by the API for modifying the behavior of HeaderRegistry and finally the support classes used to represent the data parsed from structured headers class email headerregistry BaseHeader name value name and value are passed to BaseHeader from the header_factory call The string value of any header object is the value fully decoded to unicode This base class defines the following read only properties name The name of the header the portion of the field before the This is exactly the value passed in the header_factory call for name that is case is preserved defects A tuple of HeaderDefect instances reporting any RFC compliance problems found during parsing The email package tries to be complete about detecting compliance issues See the errors module for a discussion of the types of defects that may be reported max_count The maximum number of headers of this type that can have the same name A value of None means unlimited The BaseHeader value for this attribute is None it is expected that specialized header classes will override this value as needed BaseHeader also provides the following method which is called by the email library code and should not in general be called by application programs fold policy Return a string containing linesep characters as required to correctly fold the header according to policy A cte_type of 8bit will be treated as if it were 7bit since headers may not contain arbitrary binary data If utf8 is False non ASCII data will be RFC 2047 encoded BaseHeader by itself cannot be used to create a header object It defines a protocol that each specialized header cooperates with in order to produce the header object Specifically BaseHeader requires that the specialized class provide a classmethod named parse This method is called as follows parse string kwds kwds is a dictionary containing one pre initialized key defects defects is an empty list The parse method should append any detected defects to this list On return the kwds dictionary must contain values for at least the keys decoded and defects decoded should be the string value for the header that is the header value fully decoded to unicode The parse method should assume that string may contain content transfer encoded parts but should correctly handle all valid unicode characters as well so that it can parse un encoded header values BaseHeader s __new__ then creates the header instance and calls its init method The specialized class only needs to provide an init method if it wishes to set additional attributes beyond those provided by BaseHeader itself Such an init method should look like this def init self args kw self _myattr kw pop myattr super init args kw That is anything extra that the specialized class puts in to the kwds dictionary should be r,en
2707,emoved and handled and the remaining contents of kw and args passed to the BaseHeader init method class email headerregistry UnstructuredHeader An unstructured header is the default type of header in RFC 5322 Any header that does not have a specified syntax is treated as unstructured The classic example of an unstructured header is the Subject header In RFC 5322 an unstructured header is a run of arbitrary text in the ASCII character set RFC 2047 however has an RFC 5322 compatible mechanism for encoding non ASCII text as ASCII characters within a header value When a value containing encoded words is passed to the constructor the UnstructuredHeader parser converts such encoded words into unicode following the RFC 2047 rules for unstructured text The parser uses heuristics to attempt to decode certain non compliant encoded words Defects are registered in such cases as well as defects for issues such as invalid characters within the encoded words or the non encoded text This header type provides no additional attributes class email headerregistry DateHeader RFC 5322 specifies a very specific format for dates within email headers The DateHeader parser recognizes that date format as well as recognizing a number of variant forms that are sometimes found in the wild This header type provides the following additional attributes datetime If the header value can be recognized as a valid date of one form or another this attribute will contain a datetime instance representing that date If the timezone of the input date is specified as 0000 indicating it is in UTC but contains no information about the source timezone then datetime will be a naive datetime If a specific timezone offset is found including 0000 then datetime will contain an aware datetime that uses datetime timezone to record the timezone offset The decoded value of the header is determined by formatting the datetime according to the RFC 5322 rules that is it is set to email utils format_datetime self datetime When creating a DateHeader value may be datetime instance This means for example that the following code is valid and does what one would expect msg Date datetime 2011 7 15 21 Because this is a naive datetime it will be interpreted as a UTC timestamp and the resulting value will have a timezone of 0000 Much more useful is to use the localtime function from the utils module msg Date utils localtime This example sets the date header to the current time and date using the current timezone offset class email headerregistry AddressHeader Address headers are one of the most complex structured header types The AddressHeader class provides a generic interface to any address header This header type provides the following additional attributes groups A tuple of Group objects encoding the addresses and groups found in the header value Addresses that are not part of a group are represented in this list as single address Groups whose display_name is None addresses A tuple of Address objects encoding all of the individual addresses from the header value If the header value contains any groups the individual addresses from the group are included in the list at the point where the group occurs in the value that is the list of addresses is flattened into a one dimensional list The decoded value of the header will have all encoded words decoded to unicode idna encoded domain names are also decoded to unicode The decoded value is set by joining the str value of the elements of the groups attribute with A list of Address and Group objects in any combination may be used to set the value of an address header Group objects whose display_name is None will be interpreted as single addresses which allows an address list to be copied with groups intact by using the list obtained from the groups attribute of the source header class email headerregistry SingleAddressHeader A subclass of AddressHeader that adds one additional attribute address The single address encoded by the header value If the header value actually contains more than one address which would be a violation of the RFC under t,en
2708,he default policy accessing this attribute will result in a ValueError Many of the above classes also have a Unique variant for example UniqueUnstructuredHeader The only difference is that in the Unique variant max_count is set to 1 class email headerregistry MIMEVersionHeader There is really only one valid value for the MIME Version header and that is 1 0 For future proofing this header class supports other valid version numbers If a version number has a valid value per RFC 2045 then the header object will have non None values for the following attributes version The version number as a string with any whitespace and or comments removed major The major version number as an integer minor The minor version number as an integer class email headerregistry ParameterizedMIMEHeader MIME headers all start with the prefix Content Each specific header has a certain value described under the class for that header Some can also take a list of supplemental parameters which have a common format This class serves as a base for all the MIME headers that take parameters params A dictionary mapping parameter names to parameter values class email headerregistry ContentTypeHeader A ParameterizedMIMEHeader class that handles the Content Type header content_type The content type string in the form maintype subtype maintype subtype class email headerregistry ContentDispositionHeader A ParameterizedMIMEHeader class that handles the Content Disposition header content_disposition inline and attachment are the only valid values in common use class email headerregistry ContentTransferEncoding Handles the Content Transfer Encoding header cte Valid values are 7bit 8bit base64 and quoted printable See RFC 2045 for more information class email headerregistry HeaderRegistry base_class BaseHeader default_class UnstructuredHeader use_default_map True This is the factory used by EmailPolicy by default HeaderRegistry builds the class used to create a header instance dynamically using base_class and a specialized class retrieved from a registry that it holds When a given header name does not appear in the registry the class specified by default_class is used as the specialized class When use_default_map is True the default the standard mapping of header names to classes is copied in to the registry during initialization base_class is always the last class in the generated class s __bases__ list The default mappings are subject UniqueUnstructuredHeader date UniqueDateHeader resent date DateHeader orig date UniqueDateHeader sender UniqueSingleAddressHeader resent sender SingleAddressHeader to UniqueAddressHeader resent to AddressHeader cc UniqueAddressHeader resent cc AddressHeader bcc UniqueAddressHeader resent bcc AddressHeader from UniqueAddressHeader resent from AddressHeader reply to UniqueAddressHeader mime version MIMEVersionHeader content type ContentTypeHeader content disposition ContentDispositionHeader content transfer encoding ContentTransferEncodingHeader message id MessageIDHeader HeaderRegistry has the following methods map_to_type self name cls name is the name of the header to be mapped It will be converted to lower case in the registry cls is the specialized class to be used along with base_class to create the class used to instantiate headers that match name __getitem__ name Construct and return a class to handle creating a name header __call__ name value Retrieves the specialized header associated with name from the registry using default_class if name does not appear in the registry and composes it with base_class to produce a class calls the constructed class s constructor passing it the same argument list and finally returns the class instance created thereby The following classes are the classes used to represent data parsed from structured headers and can in general be used by an application program to construct structured values to assign to specific headers class email headerregistry Address display_name username domain addr_spec None The class used to represent an email address The general form of an address is display_name usernam,en
2709,e domain or username domain where each part must conform to specific syntax rules spelled out in RFC 5322 As a convenience addr_spec can be specified instead of username and domain in which case username and domain will be parsed from the addr_spec An addr_spec must be a properly RFC quoted string if it is not Address will raise an error Unicode characters are allowed and will be property encoded when serialized However per the RFCs unicode is not allowed in the username portion of the address display_name The display name portion of the address if any with all quoting removed If the address does not have a display name this attribute will be an empty string username The username portion of the address with all quoting removed domain The domain portion of the address addr_spec The username domain portion of the address correctly quoted for use as a bare address the second form shown above This attribute is not mutable __str__ The str value of the object is the address quoted according to RFC 5322 rules but with no Content Transfer Encoding of any non ASCII characters To support SMTP RFC 5321 Address handles one special case if username and domain are both the empty string or None then the string value of the Address is class email headerregistry Group display_name None addresses None The class used to represent an address group The general form of an address group is display_name address list As a convenience for processing lists of addresses that consist of a mixture of groups and single addresses a Group may also be used to represent single addresses that are not part of a group by setting display_name to None and providing a list of the single address as addresses display_name The display_name of the group If it is None and there is exactly one Address in addresses then the Group represents a single address that is not in a group addresses A possibly empty tuple of Address objects representing the addresses in the group __str__ The str value of a Group is formatted according to RFC 5322 but with no Content Transfer Encoding of any non ASCII characters If display_name is none and there is a single Address in the addresses list the str value will be the same as the str of that single Address Footnotes 1 Originally added in 3 3 as a provisional module,en
2710,html entities Definitions of HTML general entities Source code Lib html entities py This module defines four dictionaries html5 name2codepoint codepoint2name and entitydefs html entities html5 A dictionary that maps HTML5 named character references 1 to the equivalent Unicode character s e g html5 gt Note that the trailing semicolon is included in the name e g gt however some of the names are accepted by the standard even without the semicolon in this case the name is present with and without the See also html unescape New in version 3 3 html entities entitydefs A dictionary mapping XHTML 1 0 entity definitions to their replacement text in ISO Latin 1 html entities name2codepoint A dictionary that maps HTML4 entity names to the Unicode code points html entities codepoint2name A dictionary that maps Unicode code points to HTML4 entity names Footnotes 1 See https html spec whatwg org multipage named characters html named character references,en
2711,Enum HOWTO An Enum is a set of symbolic names bound to unique values They are similar to global variables but they offer a more useful repr grouping type safety and a few other features They are most useful when you have a variable that can take one of a limited selection of values For example the days of the week from enum import Enum class Weekday Enum MONDAY 1 TUESDAY 2 WEDNESDAY 3 THURSDAY 4 FRIDAY 5 SATURDAY 6 SUNDAY 7 Or perhaps the RGB primary colors from enum import Enum class Color Enum RED 1 GREEN 2 BLUE 3 As you can see creating an Enum is as simple as writing a class that inherits from Enum itself Note Case of Enum MembersBecause Enums are used to represent constants and to help avoid issues with name clashes between mixin class methods attributes and enum names we strongly recommend using UPPER_CASE names for members and will be using that style in our examples Depending on the nature of the enum a member s value may or may not be important but either way that value can be used to get the corresponding member Weekday 3 Weekday WEDNESDAY 3 As you can see the repr of a member shows the enum name the member name and the value The str of a member shows only the enum name and member name print Weekday THURSDAY Weekday THURSDAY The type of an enumeration member is the enum it belongs to type Weekday MONDAY enum Weekday isinstance Weekday FRIDAY Weekday True Enum members have an attribute that contains just their name print Weekday TUESDAY name TUESDAY Likewise they have an attribute for their value Weekday WEDNESDAY value 3 Unlike many languages that treat enumerations solely as name value pairs Python Enums can have behavior added For example datetime date has two methods for returning the weekday weekday and isoweekday The difference is that one of them counts from 0 6 and the other from 1 7 Rather than keep track of that ourselves we can add a method to the Weekday enum to extract the day from the date instance and return the matching enum member classmethod def from_date cls date return cls date isoweekday The complete Weekday enum now looks like this class Weekday Enum MONDAY 1 TUESDAY 2 WEDNESDAY 3 THURSDAY 4 FRIDAY 5 SATURDAY 6 SUNDAY 7 classmethod def from_date cls date return cls date isoweekday Now we can find out what today is Observe from datetime import date Weekday from_date date today Weekday TUESDAY 2 Of course if you re reading this on some other day you ll see that day instead This Weekday enum is great if our variable only needs one day but what if we need several Maybe we re writing a function to plot chores during a week and don t want to use a list we could use a different type of Enum from enum import Flag class Weekday Flag MONDAY 1 TUESDAY 2 WEDNESDAY 4 THURSDAY 8 FRIDAY 16 SATURDAY 32 SUNDAY 64 We ve changed two things we re inherited from Flag and the values are all powers of 2 Just like the original Weekday enum above we can have a single selection first_week_day Weekday MONDAY first_week_day Weekday MONDAY 1 But Flag also allows us to combine several members into a single variable weekend Weekday SATURDAY Weekday SUNDAY weekend Weekday SATURDAY SUNDAY 96 You can even iterate over a Flag variable for day in weekend print day Weekday SATURDAY Weekday SUNDAY Okay let s get some chores set up chores_for_ethan feed the cat Weekday MONDAY Weekday WEDNESDAY Weekday FRIDAY do the dishes Weekday TUESDAY Weekday THURSDAY answer SO questions Weekday SATURDAY And a function to display the chores for a given day def show_chores chores day for chore days in chores items if day in days print chore show_chores chores_for_ethan Weekday SATURDAY answer SO questions In cases where the actual values of the members do not matter you can save yourself some work and use auto for the values from enum import auto class Weekday Flag MONDAY auto TUESDAY auto WEDNESDAY auto THURSDAY auto FRIDAY auto SATURDAY auto SUNDAY auto WEEKEND SATURDAY SUNDAY Programmatic access to enumeration members and their attributes Sometimes it s useful to access members in enumerations programmatically i e situations where Color RED,en
2712, won t do because the exact color is not known at program writing time Enum allows such access Color 1 Color RED 1 Color 3 Color BLUE 3 If you want to access enum members by name use item access Color RED Color RED 1 Color GREEN Color GREEN 2 If you have an enum member and need its name or value member Color RED member name RED member value 1 Duplicating enum members and values Having two enum members with the same name is invalid class Shape Enum SQUARE 2 SQUARE 3 Traceback most recent call last TypeError SQUARE already defined as 2 However an enum member can have other names associated with it Given two entries A and B with the same value and A defined first B is an alias for the member A By value lookup of the value of A will return the member A By name lookup of A will return the member A By name lookup of B will also return the member A class Shape Enum SQUARE 2 DIAMOND 1 CIRCLE 3 ALIAS_FOR_SQUARE 2 Shape SQUARE Shape SQUARE 2 Shape ALIAS_FOR_SQUARE Shape SQUARE 2 Shape 2 Shape SQUARE 2 Note Attempting to create a member with the same name as an already defined attribute another member a method etc or attempting to create an attribute with the same name as a member is not allowed Ensuring unique enumeration values By default enumerations allow multiple names as aliases for the same value When this behavior isn t desired you can use the unique decorator from enum import Enum unique unique class Mistake Enum ONE 1 TWO 2 THREE 3 FOUR 3 Traceback most recent call last ValueError duplicate values found in enum Mistake FOUR THREE Using automatic values If the exact value is unimportant you can use auto from enum import Enum auto class Color Enum RED auto BLUE auto GREEN auto member value for member in Color 1 2 3 The values are chosen by _generate_next_value_ which can be overridden class AutoName Enum staticmethod def _generate_next_value_ name start count last_values return name class Ordinal AutoName NORTH auto SOUTH auto EAST auto WEST auto member value for member in Ordinal NORTH SOUTH EAST WEST Note The _generate_next_value_ method must be defined before any members Iteration Iterating over the members of an enum does not provide the aliases list Shape Shape SQUARE 2 Shape DIAMOND 1 Shape CIRCLE 3 list Weekday Weekday MONDAY 1 Weekday TUESDAY 2 Weekday WEDNESDAY 4 Weekday THURSDAY 8 Weekday FRIDAY 16 Weekday SATURDAY 32 Weekday SUNDAY 64 Note that the aliases Shape ALIAS_FOR_SQUARE and Weekday WEEKEND aren t shown The special attribute __members__ is a read only ordered mapping of names to members It includes all names defined in the enumeration including the aliases for name member in Shape __members__ items name member SQUARE Shape SQUARE 2 DIAMOND Shape DIAMOND 1 CIRCLE Shape CIRCLE 3 ALIAS_FOR_SQUARE Shape SQUARE 2 The __members__ attribute can be used for detailed programmatic access to the enumeration members For example finding all the aliases name for name member in Shape __members__ items if member name name ALIAS_FOR_SQUARE Note Aliases for flags include values with multiple flags set such as 3 and no flags set i e 0 Comparisons Enumeration members are compared by identity Color RED is Color RED True Color RED is Color BLUE False Color RED is not Color BLUE True Ordered comparisons between enumeration values are not supported Enum members are not integers but see IntEnum below Color RED Color BLUE Traceback most recent call last File stdin line 1 in module TypeError not supported between instances of Color and Color Equality comparisons are defined though Color BLUE Color RED False Color BLUE Color RED True Color BLUE Color BLUE True Comparisons against non enumeration values will always compare not equal again IntEnum was explicitly designed to behave differently see below Color BLUE 2 False Warning It is possible to reload modules if a reloaded module contains enums they will be recreated and the new members may not compare identical equal to the original members Allowed members and attributes of enumerations Most of the examples above use integers for enumeration values Using integers is short and handy,en
2713, and provided by default by the Functional API but not strictly enforced In the vast majority of use cases one doesn t care what the actual value of an enumeration is But if the value is important enumerations can have arbitrary values Enumerations are Python classes and can have methods and special methods as usual If we have this enumeration class Mood Enum FUNKY 1 HAPPY 3 def describe self self is the member here return self name self value def __str__ self return my custom str 0 format self value classmethod def favorite_mood cls cls here is the enumeration return cls HAPPY Then Mood favorite_mood Mood HAPPY 3 Mood HAPPY describe HAPPY 3 str Mood FUNKY my custom str 1 The rules for what is allowed are as follows names that start and end with a single underscore are reserved by enum and cannot be used all other attributes defined within an enumeration will become members of this enumeration with the exception of special methods __str__ __add__ etc descriptors methods are also descriptors and variable names listed in _ignore_ Note if your enumeration defines __new__ and or __init__ any value s given to the enum member will be passed into those methods See Planet for an example Note The __new__ method if defined is used during creation of the Enum members it is then replaced by Enum s __new__ which is used after class creation for lookup of existing members See When to use __new__ vs __init__ for more details Restricted Enum subclassing A new Enum class must have one base enum class up to one concrete data type and as many object based mixin classes as needed The order of these base classes is class EnumName mix in data type base enum pass Also subclassing an enumeration is allowed only if the enumeration does not define any members So this is forbidden class MoreColor Color PINK 17 Traceback most recent call last TypeError enum MoreColor cannot extend enum Color But this is allowed class Foo Enum def some_behavior self pass class Bar Foo HAPPY 1 SAD 2 Allowing subclassing of enums that define members would lead to a violation of some important invariants of types and instances On the other hand it makes sense to allow sharing some common behavior between a group of enumerations See OrderedEnum for an example Dataclass support When inheriting from a dataclass the __repr__ omits the inherited class name For example from dataclasses import dataclass field dataclass class CreatureDataMixin size str legs int tail bool field repr False default True class Creature CreatureDataMixin Enum BEETLE small 6 DOG medium 4 Creature DOG Creature DOG size medium legs 4 Use the dataclass argument repr False to use the standard repr Changed in version 3 12 Only the dataclass fields are shown in the value area not the dataclass name Pickling Enumerations can be pickled and unpickled from test test_enum import Fruit from pickle import dumps loads Fruit TOMATO is loads dumps Fruit TOMATO True The usual restrictions for pickling apply picklable enums must be defined in the top level of a module since unpickling requires them to be importable from that module Note With pickle protocol version 4 it is possible to easily pickle enums nested in other classes It is possible to modify how enum members are pickled unpickled by defining __reduce_ex__ in the enumeration class The default method is by value but enums with complicated values may want to use by name import enum class MyEnum enum Enum __reduce_ex__ enum pickle_by_enum_name Note Using by name for flags is not recommended as unnamed aliases will not unpickle Functional API The Enum class is callable providing the following functional API Animal Enum Animal ANT BEE CAT DOG Animal enum Animal Animal ANT Animal ANT 1 list Animal Animal ANT 1 Animal BEE 2 Animal CAT 3 Animal DOG 4 The semantics of this API resemble namedtuple The first argument of the call to Enum is the name of the enumeration The second argument is the source of enumeration member names It can be a whitespace separated string of names a sequence of names a sequence of 2 tuples with key value pairs or a mapping e g dictionary ,en
2714,of names to values The last two options enable assigning arbitrary values to enumerations the others auto assign increasing integers starting with 1 use the start parameter to specify a different starting value A new class derived from Enum is returned In other words the above assignment to Animal is equivalent to class Animal Enum ANT 1 BEE 2 CAT 3 DOG 4 The reason for defaulting to 1 as the starting number and not 0 is that 0 is False in a boolean sense but by default enum members all evaluate to True Pickling enums created with the functional API can be tricky as frame stack implementation details are used to try and figure out which module the enumeration is being created in e g it will fail if you use a utility function in a separate module and also may not work on IronPython or Jython The solution is to specify the module name explicitly as follows Animal Enum Animal ANT BEE CAT DOG module __name__ Warning If module is not supplied and Enum cannot determine what it is the new Enum members will not be unpicklable to keep errors closer to the source pickling will be disabled The new pickle protocol 4 also in some circumstances relies on __qualname__ being set to the location where pickle will be able to find the class For example if the class was made available in class SomeData in the global scope Animal Enum Animal ANT BEE CAT DOG qualname SomeData Animal The complete signature is Enum value NewEnumName names module qualname type mixed in class start 1 value What the new enum class will record as its name names The enum members This can be a whitespace or comma separated string values will start at 1 unless otherwise specified RED GREEN BLUE RED GREEN BLUE RED GREEN BLUE or an iterator of names RED GREEN BLUE or an iterator of name value pairs CYAN 4 MAGENTA 5 YELLOW 6 or a mapping CHARTREUSE 7 SEA_GREEN 11 ROSEMARY 42 module name of module where new enum class can be found qualname where in module new enum class can be found type type to mix in to new enum class start number to start counting at if only names are passed in Changed in version 3 5 The start parameter was added Derived Enumerations IntEnum The first variation of Enum that is provided is also a subclass of int Members of an IntEnum can be compared to integers by extension integer enumerations of different types can also be compared to each other from enum import IntEnum class Shape IntEnum CIRCLE 1 SQUARE 2 class Request IntEnum POST 1 GET 2 Shape 1 False Shape CIRCLE 1 True Shape CIRCLE Request POST True However they still can t be compared to standard Enum enumerations class Shape IntEnum CIRCLE 1 SQUARE 2 class Color Enum RED 1 GREEN 2 Shape CIRCLE Color RED False IntEnum values behave like integers in other ways you d expect int Shape CIRCLE 1 a b c Shape CIRCLE b i for i in range Shape SQUARE 0 1 StrEnum The second variation of Enum that is provided is also a subclass of str Members of a StrEnum can be compared to strings by extension string enumerations of different types can also be compared to each other New in version 3 11 IntFlag The next variation of Enum provided IntFlag is also based on int The difference being IntFlag members can be combined using the bitwise operators and the result is still an IntFlag member if possible Like IntEnum IntFlag members are also integers and can be used wherever an int is used Note Any operation on an IntFlag member besides the bit wise operations will lose the IntFlag membership Bit wise operations that result in invalid IntFlag values will lose the IntFlag membership See FlagBoundary for details New in version 3 6 Changed in version 3 11 Sample IntFlag class from enum import IntFlag class Perm IntFlag R 4 W 2 X 1 Perm R Perm W Perm R W 6 Perm R Perm W 6 RW Perm R Perm W Perm R in RW True It is also possible to name the combinations class Perm IntFlag R 4 W 2 X 1 RWX 7 Perm RWX Perm RWX 7 Perm RWX Perm 0 Perm 7 Perm RWX 7 Note Named combinations are considered aliases Aliases do not show up during iteration but can be returned from by value lookups Changed in version 3 11 Another important difference betwe,en
2715,en IntFlag and Enum is that if no flags are set the value is 0 its boolean evaluation is False Perm R Perm X Perm 0 bool Perm R Perm X False Because IntFlag members are also subclasses of int they can be combined with them but may lose IntFlag membership Perm X 4 Perm R X 5 Perm X 8 9 Note The negation operator always returns an IntFlag member with a positive value Perm X value Perm R Perm W value 6 True IntFlag members can also be iterated over list RW Perm R 4 Perm W 2 New in version 3 11 Flag The last variation is Flag Like IntFlag Flag members can be combined using the bitwise operators Unlike IntFlag they cannot be combined with nor compared against any other Flag enumeration nor int While it is possible to specify the values directly it is recommended to use auto as the value and let Flag select an appropriate value New in version 3 6 Like IntFlag if a combination of Flag members results in no flags being set the boolean evaluation is False from enum import Flag auto class Color Flag RED auto BLUE auto GREEN auto Color RED Color GREEN Color 0 bool Color RED Color GREEN False Individual flags should have values that are powers of two 1 2 4 8 while combinations of flags will not class Color Flag RED auto BLUE auto GREEN auto WHITE RED BLUE GREEN Color WHITE Color WHITE 7 Giving a name to the no flags set condition does not change its boolean value class Color Flag BLACK 0 RED auto BLUE auto GREEN auto Color BLACK Color BLACK 0 bool Color BLACK False Flag members can also be iterated over purple Color RED Color BLUE list purple Color RED 1 Color BLUE 2 New in version 3 11 Note For the majority of new code Enum and Flag are strongly recommended since IntEnum and IntFlag break some semantic promises of an enumeration by being comparable to integers and thus by transitivity to other unrelated enumerations IntEnum and IntFlag should be used only in cases where Enum and Flag will not do for example when integer constants are replaced with enumerations or for interoperability with other systems Others While IntEnum is part of the enum module it would be very simple to implement independently class IntEnum int Enum pass This demonstrates how similar derived enumerations can be defined for example a FloatEnum that mixes in float instead of int Some rules 1 When subclassing Enum mix in types must appear before Enum itself in the sequence of bases as in the IntEnum example above 2 Mix in types must be subclassable For example bool and range are not subclassable and will throw an error during Enum creation if used as the mix in type 3 While Enum can have members of any type once you mix in an additional type all the members must have values of that type e g int above This restriction does not apply to mix ins which only add methods and don t specify another type 4 When another data type is mixed in the value attribute is not the same as the enum member itself although it is equivalent and will compare equal 5 A data type is a mixin that defines __new__ or a dataclass 6 style formatting s and r call the Enum class s __str__ and __repr__ respectively other codes such as i or h for IntEnum treat the enum member as its mixed in type 7 Formatted string literals str format and format will use the enum s __str__ method Note Because IntEnum IntFlag and StrEnum are designed to be drop in replacements for existing constants their __str__ method has been reset to their data types __str__ method When to use __new__ vs __init__ __new__ must be used whenever you want to customize the actual value of the Enum member Any other modifications may go in either __new__ or __init__ with __init__ being preferred For example if you want to pass several items to the constructor but only want one of them to be the value class Coordinate bytes Enum Coordinate with binary codes that can be indexed by the int code def __new__ cls value label unit obj bytes __new__ cls value obj _value_ value obj label label obj unit unit return obj PX 0 P X km PY 1 P Y km VX 2 V X km s VY 3 V Y km s print Coordinate PY Coordinate PY print Coordinate 3 Coordinate VY Warning,en
2716, Do not call super __new__ as the lookup only __new__ is the one that is found instead use the data type directly Finer Points Supported __dunder__ names __members__ is a read only ordered mapping of member_name member items It is only available on the class __new__ if specified must create and return the enum members it is also a very good idea to set the member s _value_ appropriately Once all the members are created it is no longer used Supported _sunder_ names _name_ name of the member _value_ value of the member can be set modified in __new__ _missing_ a lookup function used when a value is not found may be overridden _ignore_ a list of names either as a list or a str that will not be transformed into members and will be removed from the final class _order_ used in Python 2 3 code to ensure member order is consistent class attribute removed during class creation _generate_next_value_ used by the Functional API and by auto to get an appropriate value for an enum member may be overridden Note For standard Enum classes the next value chosen is the last value seen incremented by one For Flag classes the next value chosen will be the next highest power of two regardless of the last value seen New in version 3 6 _missing_ _order_ _generate_next_value_ New in version 3 7 _ignore_ To help keep Python 2 Python 3 code in sync an _order_ attribute can be provided It will be checked against the actual order of the enumeration and raise an error if the two do not match class Color Enum _order_ RED GREEN BLUE RED 1 BLUE 3 GREEN 2 Traceback most recent call last TypeError member order does not match _order_ RED BLUE GREEN RED GREEN BLUE Note In Python 2 code the _order_ attribute is necessary as definition order is lost before it can be recorded _Private__names Private names are not converted to enum members but remain normal attributes Changed in version 3 11 Enum member type Enum members are instances of their enum class and are normally accessed as EnumClass member In certain situations such as writing custom enum behavior being able to access one member directly from another is useful and is supported however in order to avoid name clashes between member names and attributes methods from mixed in classes upper case names are strongly recommended Changed in version 3 5 Creating members that are mixed with other data types When subclassing other data types such as int or str with an Enum all values after the are passed to that data type s constructor For example class MyEnum IntEnum help int int x base 10 integer example 11 16 so x 11 and base 16 MyEnum example value and hex 11 is 17 Boolean value of Enum classes and members Enum classes that are mixed with non Enum types such as int str etc are evaluated according to the mixed in type s rules otherwise all members evaluate as True To make your own enum s boolean evaluation depend on the member s value add the following to your class def __bool__ self return bool self value Plain Enum classes always evaluate as True Enum classes with methods If you give your enum subclass extra methods like the Planet class below those methods will show up in a dir of the member but not of the class dir Planet EARTH JUPITER MARS MERCURY NEPTUNE SATURN URANUS VENUS __class__ __doc__ __members__ __module__ dir Planet EARTH __class__ __doc__ __module__ mass name radius surface_gravity value Combining members of Flag Iterating over a combination of Flag members will only return the members that are comprised of a single bit class Color Flag RED auto GREEN auto BLUE auto MAGENTA RED BLUE YELLOW RED GREEN CYAN GREEN BLUE Color 3 named combination Color YELLOW 3 Color 7 not named combination Color RED GREEN BLUE 7 Flag and IntFlag minutia Using the following snippet for our examples class Color IntFlag BLACK 0 RED 1 GREEN 2 BLUE 4 PURPLE RED BLUE WHITE RED GREEN BLUE the following are true single bit flags are canonical multi bit and zero bit flags are aliases only canonical flags are returned during iteration list Color WHITE Color RED 1 Color GREEN 2 Color BLUE 4 negating a flag or flag set returns a,en
2717, new flag flag set with the corresponding positive integer value Color BLUE Color BLUE 4 Color BLUE Color RED GREEN 3 names of pseudo flags are constructed from their members names Color RED Color GREEN name RED GREEN multi bit flags aka aliases can be returned from operations Color RED Color BLUE Color PURPLE 5 Color 7 or Color 1 Color WHITE 7 Color 0 Color BLACK 0 membership containment checking zero valued flags are always considered to be contained Color BLACK in Color WHITE True otherwise only if all bits of one flag are in the other flag will True be returned Color PURPLE in Color WHITE True Color GREEN in Color PURPLE False There is a new boundary mechanism that controls how out of range invalid bits are handled STRICT CONFORM EJECT and KEEP STRICT raises an exception when presented with invalid values CONFORM discards any invalid bits EJECT lose Flag status and become a normal int with the given value KEEP keep the extra bits keeps Flag status and extra bits extra bits do not show up in iteration extra bits do show up in repr and str The default for Flag is STRICT the default for IntFlag is EJECT and the default for _convert_ is KEEP see ssl Options for an example of when KEEP is needed How are Enums and Flags different Enums have a custom metaclass that affects many aspects of both derived Enum classes and their instances members Enum Classes The EnumType metaclass is responsible for providing the __contains__ __dir__ __iter__ and other methods that allow one to do things with an Enum class that fail on a typical class such as list Color or some_enum_var in Color EnumType is responsible for ensuring that various other methods on the final Enum class are correct such as __new__ __getnewargs__ __str__ and __repr__ Flag Classes Flags have an expanded view of aliasing to be canonical the value of a flag needs to be a power of two value and not a duplicate name So in addition to the Enum definition of alias a flag with no value a k a 0 or with more than one power of two value e g 3 is considered an alias Enum Members aka instances The most interesting thing about enum members is that they are singletons EnumType creates them all while it is creating the enum class itself and then puts a custom __new__ in place to ensure that no new ones are ever instantiated by returning only the existing member instances Flag Members Flag members can be iterated over just like the Flag class and only the canonical members will be returned For example list Color Color RED 1 Color GREEN 2 Color BLUE 4 Note that BLACK PURPLE and WHITE do not show up Inverting a flag member returns the corresponding positive value rather than a negative value for example Color RED Color GREEN BLUE 6 Flag members have a length corresponding to the number of power of two values they contain For example len Color PURPLE 2 Enum Cookbook While Enum IntEnum StrEnum Flag and IntFlag are expected to cover the majority of use cases they cannot cover them all Here are recipes for some different types of enumerations that can be used directly or as examples for creating one s own Omitting values In many use cases one doesn t care what the actual value of an enumeration is There are several ways to define this type of simple enumeration use instances of auto for the value use instances of object as the value use a descriptive string as the value use a tuple as the value and a custom __new__ to replace the tuple with an int value Using any of these methods signifies to the user that these values are not important and also enables one to add remove or reorder members without having to renumber the remaining members Using auto Using auto would look like class Color Enum RED auto BLUE auto GREEN auto Color GREEN Color GREEN 3 Using object Using object would look like class Color Enum RED object GREEN object BLUE object Color GREEN Color GREEN object object at 0x This is also a good example of why you might want to write your own __repr__ class Color Enum RED object GREEN object BLUE object def __repr__ self return s s self __class__ __name__ self _name_ Color GREEN Col,en
2718,or GREEN Using a descriptive string Using a string as the value would look like class Color Enum RED stop GREEN go BLUE too fast Color GREEN Color GREEN go Using a custom __new__ Using an auto numbering __new__ would look like class AutoNumber Enum def __new__ cls value len cls __members__ 1 obj object __new__ cls obj _value_ value return obj class Color AutoNumber RED GREEN BLUE Color GREEN Color GREEN 2 To make a more general purpose AutoNumber add args to the signature class AutoNumber Enum def __new__ cls args this is the only change from above value len cls __members__ 1 obj object __new__ cls obj _value_ value return obj Then when you inherit from AutoNumber you can write your own __init__ to handle any extra arguments class Swatch AutoNumber def __init__ self pantone unknown self pantone pantone AUBURN 3497 SEA_GREEN 1246 BLEACHED_CORAL New color no Pantone code yet Swatch SEA_GREEN Swatch SEA_GREEN 2 Swatch SEA_GREEN pantone 1246 Swatch BLEACHED_CORAL pantone unknown Note The __new__ method if defined is used during creation of the Enum members it is then replaced by Enum s __new__ which is used after class creation for lookup of existing members Warning Do not call super __new__ as the lookup only __new__ is the one that is found instead use the data type directly e g obj int __new__ cls value OrderedEnum An ordered enumeration that is not based on IntEnum and so maintains the normal Enum invariants such as not being comparable to other enumerations class OrderedEnum Enum def __ge__ self other if self __class__ is other __class__ return self value other value return NotImplemented def __gt__ self other if self __class__ is other __class__ return self value other value return NotImplemented def __le__ self other if self __class__ is other __class__ return self value other value return NotImplemented def __lt__ self other if self __class__ is other __class__ return self value other value return NotImplemented class Grade OrderedEnum A 5 B 4 C 3 D 2 F 1 Grade C Grade A True DuplicateFreeEnum Raises an error if a duplicate member value is found instead of creating an alias class DuplicateFreeEnum Enum def __init__ self args cls self __class__ if any self value e value for e in cls a self name e cls self value name raise ValueError aliases not allowed in DuplicateFreeEnum r r a e class Color DuplicateFreeEnum RED 1 GREEN 2 BLUE 3 GRENE 2 Traceback most recent call last ValueError aliases not allowed in DuplicateFreeEnum GRENE GREEN Note This is a useful example for subclassing Enum to add or change other behaviors as well as disallowing aliases If the only desired change is disallowing aliases the unique decorator can be used instead Planet If __new__ or __init__ is defined the value of the enum member will be passed to those methods class Planet Enum MERCURY 3 303e 23 2 4397e6 VENUS 4 869e 24 6 0518e6 EARTH 5 976e 24 6 37814e6 MARS 6 421e 23 3 3972e6 JUPITER 1 9e 27 7 1492e7 SATURN 5 688e 26 6 0268e7 URANUS 8 686e 25 2 5559e7 NEPTUNE 1 024e 26 2 4746e7 def __init__ self mass radius self mass mass in kilograms self radius radius in meters property def surface_gravity self universal gravitational constant m3 kg 1 s 2 G 6 67300E 11 return G self mass self radius self radius Planet EARTH value 5 976e 24 6378140 0 Planet EARTH surface_gravity 9 802652743337129 TimePeriod An example to show the _ignore_ attribute in use from datetime import timedelta class Period timedelta Enum different lengths of time _ignore_ Period i Period vars for i in range 367 Period day_ d i i list Period 2 Period day_0 datetime timedelta 0 Period day_1 datetime timedelta days 1 list Period 2 Period day_365 datetime timedelta days 365 Period day_366 datetime timedelta days 366 Subclassing EnumType While most enum needs can be met by customizing Enum subclasses either with class decorators or custom functions EnumType can be subclassed to provide a different Enum experience,en
2719,Exceptions Source code Lib asyncio exceptions py exception asyncio TimeoutError A deprecated alias of TimeoutError raised when the operation has exceeded the given deadline Changed in version 3 11 This class was made an alias of TimeoutError exception asyncio CancelledError The operation has been cancelled This exception can be caught to perform custom operations when asyncio Tasks are cancelled In almost all situations the exception must be re raised Changed in version 3 8 CancelledError is now a subclass of BaseException rather than Exception exception asyncio InvalidStateError Invalid internal state of Task or Future Can be raised in situations like setting a result value for a Future object that already has a result value set exception asyncio SendfileNotAvailableError The sendfile syscall is not available for the given socket or file type A subclass of RuntimeError exception asyncio IncompleteReadError The requested read operation did not complete fully Raised by the asyncio stream APIs This exception is a subclass of EOFError expected The total number int of expected bytes partial A string of bytes read before the end of stream was reached exception asyncio LimitOverrunError Reached the buffer size limit while looking for a separator Raised by the asyncio stream APIs consumed The total number of to be consumed bytes,en
2720,Set Objects This section details the public API for set and frozenset objects Any functionality not listed below is best accessed using either the abstract object protocol including PyObject_CallMethod PyObject_RichCompareBool PyObject_Hash PyObject_Repr PyObject_IsTrue PyObject_Print and PyObject_GetIter or the abstract number protocol including PyNumber_And PyNumber_Subtract PyNumber_Or PyNumber_Xor PyNumber_InPlaceAnd PyNumber_InPlaceSubtract PyNumber_InPlaceOr and PyNumber_InPlaceXor type PySetObject This subtype of PyObject is used to hold the internal data for both set and frozenset objects It is like a PyDictObject in that it is a fixed size for small sets much like tuple storage and will point to a separate variable sized block of memory for medium and large sized sets much like list storage None of the fields of this structure should be considered public and all are subject to change All access should be done through the documented API rather than by manipulating the values in the structure PyTypeObject PySet_Type Part of the Stable ABI This is an instance of PyTypeObject representing the Python set type PyTypeObject PyFrozenSet_Type Part of the Stable ABI This is an instance of PyTypeObject representing the Python frozenset type The following type check macros work on pointers to any Python object Likewise the constructor functions work with any iterable Python object int PySet_Check PyObject p Return true if p is a set object or an instance of a subtype This function always succeeds int PyFrozenSet_Check PyObject p Return true if p is a frozenset object or an instance of a subtype This function always succeeds int PyAnySet_Check PyObject p Return true if p is a set object a frozenset object or an instance of a subtype This function always succeeds int PySet_CheckExact PyObject p Return true if p is a set object but not an instance of a subtype This function always succeeds New in version 3 10 int PyAnySet_CheckExact PyObject p Return true if p is a set object or a frozenset object but not an instance of a subtype This function always succeeds int PyFrozenSet_CheckExact PyObject p Return true if p is a frozenset object but not an instance of a subtype This function always succeeds PyObject PySet_New PyObject iterable Return value New reference Part of the Stable ABI Return a new set containing objects returned by the iterable The iterable may be NULL to create a new empty set Return the new set on success or NULL on failure Raise TypeError if iterable is not actually iterable The constructor is also useful for copying a set c set s PyObject PyFrozenSet_New PyObject iterable Return value New reference Part of the Stable ABI Return a new frozenset containing objects returned by the iterable The iterable may be NULL to create a new empty frozenset Return the new set on success or NULL on failure Raise TypeError if iterable is not actually iterable The following functions and macros are available for instances of set or frozenset or instances of their subtypes Py_ssize_t PySet_Size PyObject anyset Part of the Stable ABI Return the length of a set or frozenset object Equivalent to len anyset Raises a SystemError if anyset is not a set frozenset or an instance of a subtype Py_ssize_t PySet_GET_SIZE PyObject anyset Macro form of PySet_Size without error checking int PySet_Contains PyObject anyset PyObject key Part of the Stable ABI Return 1 if found 0 if not found and 1 if an error is encountered Unlike the Python __contains__ method this function does not automatically convert unhashable sets into temporary frozensets Raise a TypeError if the key is unhashable Raise SystemError if anyset is not a set frozenset or an instance of a subtype int PySet_Add PyObject set PyObject key Part of the Stable ABI Add key to a set instance Also works with frozenset instances like PyTuple_SetItem it can be used to fill in the values of brand new frozensets before they are exposed to other code Return 0 on success or 1 on failure Raise a TypeError if the key is unhashable Raise a MemoryError if there is no room to grow Raise a System,en
2721,Error if set is not an instance of set or its subtype The following functions are available for instances of set or its subtypes but not for instances of frozenset or its subtypes int PySet_Discard PyObject set PyObject key Part of the Stable ABI Return 1 if found and removed 0 if not found no action taken and 1 if an error is encountered Does not raise KeyError for missing keys Raise a TypeError if the key is unhashable Unlike the Python discard method this function does not automatically convert unhashable sets into temporary frozensets Raise SystemError if set is not an instance of set or its subtype PyObject PySet_Pop PyObject set Return value New reference Part of the Stable ABI Return a new reference to an arbitrary object in the set and removes the object from the set Return NULL on failure Raise KeyError if the set is empty Raise a SystemError if set is not an instance of set or its subtype int PySet_Clear PyObject set Part of the Stable ABI Empty an existing set of all elements Return 0 on success Return 1 and raise SystemError if set is not an instance of set or its subtype,en